The occurrence of midnight Equatorial Plasma Bubbles(EPBs)during the June solstice period of the ascending phase of solar cycle 24,from 2010 to 2014,was studied using data from the 47 MHz Equatorial Atmosphere Radar(E...The occurrence of midnight Equatorial Plasma Bubbles(EPBs)during the June solstice period of the ascending phase of solar cycle 24,from 2010 to 2014,was studied using data from the 47 MHz Equatorial Atmosphere Radar(EAR)at Kototabang,Indonesia.The analysis shows that the occurrence of midnight hour EPBs was at its maximum during the low solar activity year 2010 and monotonically decreased thereafter with increasing solar activity.Details of the dependence of midnight hour EPB occurrence on solar activity were investigated using SAMI2 model simulation with a realistic input of E×B drift velocity data obtained from the CINDI-IVM onboard the C/NOFS satellite.Results obtained from term-by-term analysis of the flux tube integrated linear growth rate of RT instability indicate that the formation of a high flux tube electron content height gradient(steep vertical gradient)region at higher altitudes,due to the elevated F layer,is the key factor enhancing the growth rate of RT instability during low solar activity June solstices.Other factors are discussed in light of the relatively weak westward zonal electric field in the presence of the equatorward neutral wind and north-to-south transequatorial wind around the midnight hours of low solar activity June solstices.Also discussed are the initial seeding of RT instability by MSTIDs and how the threshold height required for EPB development varies with solar activity.展开更多
OI 630.0 nm airglow observations,from a new observatory at Bom Jesus de Lapa,were used to study the interaction between EPBs(Equatorial Plasma Bubbles)and the MSTID(Medium-Scale Traveling Ionospheric Disturbance)over ...OI 630.0 nm airglow observations,from a new observatory at Bom Jesus de Lapa,were used to study the interaction between EPBs(Equatorial Plasma Bubbles)and the MSTID(Medium-Scale Traveling Ionospheric Disturbance)over the Northeast region in Brazil.On the night of September 16 to 17,2020,an EPB was observed propagating eastward,in an apparent fossil stage,until it interacted with a dark band electrified MSTID(e MSTID).After the interaction,four EPBs merged,followed by an abrupt southward development and bifurcations.Analysis of the data suggests that an eastward polarization electric field,induced by the dark band e MSTID,forced the EPB into an upward drift,growing latitudinally along the magnetic field lines and then bifurcating.展开更多
Branching structure(BS)is a very important phenomenon in the evolution of equatorial plasma bubbles(EPBs),the mechanism of which is widely studied from observation and from simulation.However,occurrence characteristic...Branching structure(BS)is a very important phenomenon in the evolution of equatorial plasma bubbles(EPBs),the mechanism of which is widely studied from observation and from simulation.However,occurrence characteristics of branching structure of equatorial plasma bubbles(BSEPBs)have not been well addressed.In this work,we used seven-years(2012-2018)of observations from two all-sky imagers to study occurrence of BSEPBs in detail.These data reveal a high incidence of BS in EPB cases;in particular,most EPBs occurring on days with geomagnetic disturbances exhibited BS.Periods when all EPBs exhibited BS increased significantly in the 2014 solar maximum.Occurrence times of BSEPBs varied with local time;most of the BSEPBs began to appear between 21:00 and 22:00 LT.During the solar maximum,some BSEPBs were observed after midnight.The data also reveal that BSEPBs are characterized primarily by two branches or three branches.Multi-branching appeared only in the solar maximum.EPB events with different coexisting branching structures increased from 2012 to 2014 and decreased from 2014 to 2018.These results strongly suggest that BSEPB occurrence is related to solar activity and geomagnetic activity,and thus provide a new perspective for future studies of EPBs as well as enriching our understanding of ionospheric irregularity.展开更多
During a long-term Equatorial Plasma Bubbles(EPBs)occurrence between October 2020 and March 2021,a significant EPB suppression event was identified on November 22 and the observations from multi-instrument have been u...During a long-term Equatorial Plasma Bubbles(EPBs)occurrence between October 2020 and March 2021,a significant EPB suppression event was identified on November 22 and the observations from multi-instrument have been utilized to investigate this event.Global-scale Observations of the Limb and Disk(GOLD)satellite observed prominent EPBs between 23:40 UT and 23:55 UT during the long-term occurrence days.However,no dark stripes representing EPBs were observed on November 22,and the Equatorial Ionization Anomaly(EIA)structure remained intact.The Total Electron Content(TEC)maps show that these EPBs appeared in the region between 35°W and 65°W longitudes and the magnitudes of the TEC loss in EPBs regions were about 20 TECU.Except for 22 November,the S4 index was consistently greater than 0.6 throughout November,indicating significant ionospheric scintillation.The Rate Of TEC Index(ROTI)maps revealed that the spatial extent and intensity of EPBs increased after their suppression,and the EPBs were locally generated.The swarm electron density measurements indicated that the variation amplitudes of EPBs at 510 km altitude were approximately 3 to 5 times larger than that at 460 km altitude.The impact region of EPBs at 510 km was between 15°S and 20°N latitudes,while at 460 km,it was between 0°and 17°N latitudes.During the period of EPB suppression,the average h’f at three ionosonde stations decreased by about 50 km,and the vertical drift velocity(V z)approached~0 m/s while it was more than 20 m/s during the long-term occurrence.展开更多
Detecting and characterizing Total Electron Content(TEC)depletion is important for studying the ionospheric threat due to the Equatorial Plasma Bubble(EPB)when applying the Ground-Based Augmentation System(GBAS)at low...Detecting and characterizing Total Electron Content(TEC)depletion is important for studying the ionospheric threat due to the Equatorial Plasma Bubble(EPB)when applying the Ground-Based Augmentation System(GBAS)at low latitudes.This paper develops a robust method to automatically identify TEC depletion and derive its parameters.The rolling barrel algorithm is used to automatically identify the TEC depletion candidate and its parameters.Then,the depletion candidates are screened by several improved techniques to distinguish actual depletions from other phenomena such as Traveling Ionospheric Disturbance(TID)or abnormal data.Next,based on the depletion signals from three triangular receivers,the method derives EPB parameters such as velocity,width and gradient.The time lag and front velocity are calculated based on crosscorrelation using TEC depletions and the geometrical distribution of three triangular receivers.The width and gradient of slope are then determined by using TEC depletion from a single receiver.By comparison,both the station-pair method and proposed method depend on the assumption that the EPB morphology is frozen during the short time when the plasma bubble moves between the receivers.However,our method relaxes the restriction that the baseline length should be shorter than the width of slope required by the station-pair.This relaxation is favorable for studying small-scale slope of depletions using stations of a longer baseline.In addition,the accuracy of the width and gradient is free of impact from hardware biases and small-scale disturbance,as it is based only on the relative TEC variation.The method is demonstrated by processing Global Positioning System(GPS)and Bei Dou Navigation Satellite System(BDS)data on 15 August,2018,in a solar minimum cycle.展开更多
The 2 nd Equatorial Plasma Bubble(EPB)workshop,funded by the Institute of Geology and Geophysics,Chinese Academy of Sciences,and the National Natural Science Foundation of China,took place in Beijing,China during Sept...The 2 nd Equatorial Plasma Bubble(EPB)workshop,funded by the Institute of Geology and Geophysics,Chinese Academy of Sciences,and the National Natural Science Foundation of China,took place in Beijing,China during September 13–15,2019.The EPB workshop belongs to a conference series that began in 2016 in Nagoya,Japan at the Institute for Space-Earth Environmental Research,Nagoya University,resulting in a special issue of Progress in Earth and Planetary Science that focused on EPBs.The main goal of the series is to organize in-depth discussion by scientists working on ionospheric irregularities,and solve the scientific challenges in EPB and ionospheric scintillation forecasting.The 2 nd EPB workshop gathered almost 60 scientists from seven countries.A total of 20 invited and contributing papers focusing on ionospheric irregularities and scintillations were presented.Here we briefly comment on 10 papers included in this special issue.展开更多
The all-sky meteor radars are primarily designed for observations of mesospheric neutral wind.Recently,the capability of all-sky radars in investigating ionospheric irregularities of the Bragg scales has been develope...The all-sky meteor radars are primarily designed for observations of mesospheric neutral wind.Recently,the capability of all-sky radars in investigating ionospheric irregularities of the Bragg scales has been developed.However,limited by the relatively small range gate span of the all-sky radar,this capability is mainly constrained to the observations of irregularities at lower altitudes,e.g.,E-region irregularities.The F-region irregularities at higher altitudes up to hundreds of kilometers,e.g.,equatorial plasma bubbles(EPBs),are usually considered beyond the detection range of all-sky radars.In this paper,we try to extend the capability of a conventional interferometric all-sky meteor radar located at Sanya(18.4°N,109.7°E)for investigating the spatial features of EPBs.Based on the arriving angles of irregularity backscatter echoes obtained by the radar interferometry technique,and according to the magnetic sensitivity of the EPB field-aligned irregularities,the true ranges of the irregularity structures could be determined to further reveal the spatial features of EPB structures.The results are confirmed by the collocated narrow-beam very high frequency(VHF)radar and the Low lAtitude long Range Ionospheric raDar(LARID).It is revealed that the all-sky radar could be employed to investigate EPB irregularities in a larger zonal region than narrow-beam VHF radars,which could be up to~2000 km.The observations could well cover the blind area of the LARID field-of-view,and thus could be employed to continuously trace EPB occurrences and evolutions over thousands of kilometers by combining with LARID in future studies.展开更多
Using the observations of the 630-nm all-sky imagers(ASIs)located in the geomagnetic conjugate points in the American sector from 2014 to 2017,this study statistically analyzed the features of conjugate equatorial pla...Using the observations of the 630-nm all-sky imagers(ASIs)located in the geomagnetic conjugate points in the American sector from 2014 to 2017,this study statistically analyzed the features of conjugate equatorial plasma bubbles(EPBs),including their occurrence rate,zonal width,location and zonal drift velocity.The results show that the occurrence rate of the EPBs that occur simultaneously at geomagnetic conjugate points is~84%.The zonal widths of the EPBs are mainly~100 km,and the width differences of EPBs between the northern and southern hemispheres are mainly within±30 km.The zonal displacements of the center locations of the northern and southern EPBs are within±50 km.The zonal drift velocities of the northern and southern EPBs are nearly equal.However,it should be noted that the velocity of the EPBs in the northern hemisphere is 10%faster than that in the southern hemisphere.The results suggest that conjugate EPBs are common.Moreover,the non-conjugate EPBs in the northern and southern hemisphere can occur occasionally,which is probably associated with the different ionospheric backgrounds between the two hemispheres.The features of the conjugate EPBs as shown in this study provides support for the nowcasting of EPBs in the conjugate hemispheres.展开更多
This paper highlights the crucial role of Indonesia’s GNSS receiver network in advancing Equatorial Plasma Bubble(EPB)studies in Southeast and East Asia,as ionospheric irregularities within EPB can disrupt GNSS signa...This paper highlights the crucial role of Indonesia’s GNSS receiver network in advancing Equatorial Plasma Bubble(EPB)studies in Southeast and East Asia,as ionospheric irregularities within EPB can disrupt GNSS signals and degrade positioning accuracy.Managed by the Indonesian Geospatial Information Agency(BIG),the Indonesia Continuously Operating Reference Station(Ina-CORS)network comprises over 300 GNSS receivers spanning equatorial to southern low-latitude regions.Ina-CORS is uniquely situated to monitor EPB generation,zonal drift,and dissipation across Southeast Asia.We provide a practical tool for EPB research,by sharing two-dimensional rate of Total Electron Content(TEC)change index(ROTI)derived from this network.We generate ROTI maps with a 10-minute resolution,and samples from May 2024 are publicly available for further scientific research.Two preliminary findings from the ROTI maps of Ina-CORS are noteworthy.First,the Ina-CORS ROTI maps reveal that the irregularities within a broader EPB structure persist longer,increasing the potential for these irregularities to migrate farther eastward.Second,we demonstrate that combined ROTI maps from Ina-CORS and GNSS receivers in East Asia and Australia can be used to monitor the development of ionospheric irregularities in Southeast and East Asia.We have demonstrated the combined ROTI maps to capture the development of ionospheric irregularities in the Southeast/East Asian sector during the G5 Geomagnetic Storm on May 11,2024.We observed simultaneous ionospheric irregularities in Japan and Australia,respectively propagating northwestward and southwestward,before midnight,whereas Southeast Asia’s equatorial and low-latitude regions exhibited irregularities post-midnight.By sharing ROTI maps from Indonesia and integrating them with regional GNSS networks,researchers can conduct comprehensive EPB studies,enhancing the understanding of EPB behavior across Southeast and East Asia and contributing significantly to ionospheric research.展开更多
The significance of laser-driven polarized beam acceleration has been increasingly recognized in recent years.We propose an efficient method for generating polarized proton beams from a pre-polarized hydrogen halide g...The significance of laser-driven polarized beam acceleration has been increasingly recognized in recent years.We propose an efficient method for generating polarized proton beams from a pre-polarized hydrogen halide gas jet,utilizing magnetic vortex acceleration enhanced by a laser-driven plasma bubble.When a petawatt laser pulse passes through a pre-polarized gas jet,a bubble-like ultra-nonlinear plasma wave is formed.As a portion of the particles constituting this wave,background protons are swept by the acceleration field of the bubble and oscillate significantly along the laser propagation axis.Some of the pre-accelerated protons in the plasma wave are trapped by the acceleration field at the rear side of the target.This acceleration field is intensified by the transverse expansion of the laser-driven magnetic vortex,resulting in energetic polarized proton beams.The spin of energetic protons is determined by their precession within the electromagnetic field,which is described using the Thomas-Bargmann-Michel-Telegdi equation in analytical models and particle-in-cell simulations.Multidimensional simulations reveal that monoenergetic proton beams with an energy of hundreds of MeV,a beam charge of hundreds of pC,and a beam polarization of tens of percent can be produced at laser powers of several petawatts.Such laser-driven polarized proton beams have promise for application in polarized beam colliders,where they can be utilized to investigate particle interactions and to explore the properties of matter under extreme conditions.展开更多
This paper reports that plasma density depletions appearing at middle latitudes near sunrise survived until afternoon on 29 May 2017 during the recovery phase of a geomagnetic storm.By analyzing GPS data collected in ...This paper reports that plasma density depletions appearing at middle latitudes near sunrise survived until afternoon on 29 May 2017 during the recovery phase of a geomagnetic storm.By analyzing GPS data collected in Japan,we investigate temporal variations in the horizontal two-dimensional distribution of total electron content(TEC)during the geomagnetic storm.The SYM-H index reached-142 n T around 08 UT on 28 May 2017.TEC depletions extending up to approximately 38°N along the meridional direction appeared over Japan around 05 LT(LT=UT+9 hours)on 29 May 2017,when TEC rapidly increased at sunrise due to the solar extreme ultraviolet(EUV)radiation.The TEC depletions appeared sequentially over Japan for approximately 8 hours in sunlit conditions.At 06 LT on 29 May,when the plasma depletions first appeared over Japan,the background TEC was enhanced to approximately 17 TECU,and then decreased to approximately 80%of the TEC typical of magnetically quiet conditions.We conclude that this temporal variation of background plasma density in the ionosphere was responsible for the persistence of these plasma depletions for so long in daytime.By using the Naval Research Laboratory:Sami2 is Another Model of the Ionosphere(SAMI2),we have evaluated how plasma production and ambipolar diffusion along the magnetic field may affect the rate of plasma depletion disappearance.Simulation shows that the plasma density increases at the time of plasma depletion appearance;subsequent decreases in the plasma density appear to be responsible for the long-lasting persistence of plasma depletions during daytime.The plasma density depletion in the top side ionosphere is not filled by the plasma generated by the solar EUV productions because plasma production occurs mainly at the bottom side of the ionosphere.展开更多
Observational evidence is insufficient to understand how equatorial plasma bubbles(EPBs)form over low latitudes.The mechanism of plasma-density enhancement(formation of"plasma blobs")at low latitudes is in d...Observational evidence is insufficient to understand how equatorial plasma bubbles(EPBs)form over low latitudes.The mechanism of plasma-density enhancement(formation of"plasma blobs")at low latitudes is in dispute.In this paper,we use data from multiple ground-based instruments(one all-sky airglow imager,five digisondes,and one Fabry–Perot interferometer)to investigate the evolution of an EPB event that occurred at low latitudes over China on the night of 06 December 2015(06-Dec-2015).We provide observational evidence that an enhanced equatorward wind most likely induced by a substorm could have initiated the Rayleigh–Taylor instability(RTI)that destabilized several EPB depletions in an upwelling region of a large-scale wave-like structure(LSWS)in the bottomside ionosphere.Those EPB depletions were forced to surge poleward,from nearly 10°to 19°magnetic latitude,two hours before midnight.Smaller-scale bifurcations evolved rapidly from tips of airglow depletions by a secondary E×B instability when the aforementioned substorm-induced southwestward wind blew through.During the growth phase of the EPB depletions,a westward polarization electric field inside the LSWS is likely to have compressed plasma downward,inducing the two airglow-type blobs observed in the bottomside ionosphere,by a mechanism of LSWS-blob connection that we propose.We also provide observational evidence of brightness airglow depletions.We find that an enhanced poleward wind associated with a passing-by brightness wave(BW)is likely to have transported plasma to fill the airglow depletions,which finally evolved into brightness airglow structures.This study investigates the physical processes accompanied by the EPB event and those two-airglow blobs observed at low-latitudes over China.展开更多
Large Scale Wave Structures(LSWS)in the equatorial ionospheric F-region were observed by measuring spatial and temporal variations within detrended total electron content(dTEC)data obtained by ground-based GNSS receiv...Large Scale Wave Structures(LSWS)in the equatorial ionospheric F-region were observed by measuring spatial and temporal variations within detrended total electron content(dTEC)data obtained by ground-based GNSS receivers over the South American continent.By using dTEC-maps,we have been able to produce,for the first-time,two-dimensional representations of LSWS.During the period from September to December,the LSWS frequently occurred starting a few hours prior to Equatorial Plasma Bubble(EPB)development.From 17 events of LSWS observed in 2014 and 2015,wave characteristics were obtained:the observed wavelengths,periods,and the phase speeds are respectively,~900 km,~41 min and~399 m/s;the waves propagated from the northeast to southeast.In some cases the front of the oscillation was meridionally aligned,extending to more than 1600 km,the first time such large extension of the wavefront has been reported.From F-layer bottom height oscillation data,measured by ionosonde,LSWS exhibit two different vertical phase propagation modes,in-phase and downward phase.The former mode indicates the presence of a polarization electric field in the F-layer bottom side;the latter suggests propagation of atmospheric gravity waves.The presence of LSWS near the solar terminator,followed by the development of EPBs,suggests that the upwelling of the F-layer bottom height produces a condition favorable to the development of Rayleigh–Taylor instability.展开更多
Bubble core fields as well bubble shape modification due to the nondepleted electrons inside the bubble is investigated theoretically. It is found that the Mope of transverse fields are reduced significantly, however,...Bubble core fields as well bubble shape modification due to the nondepleted electrons inside the bubble is investigated theoretically. It is found that the Mope of transverse fields are reduced significantly, however, the slope of longitudinal electric field, which plays a key role on electrons acceleration in bubble, changes little. Moreover a modified longitudinal compressed bubble shape leads to a shorter dephasing distance which makes the electrons acceleration energy reduced to some extent. As a comparison we perform particle-in-cell simulations whose results are consistent with that of our theoretical consideration.展开更多
We estimate the zonal drift velocity of small-scale ionospheric irregularities at low latitude by leveraging the spaced-receivers technique applied to two GNSS receivers for scintillation monitoring installed along th...We estimate the zonal drift velocity of small-scale ionospheric irregularities at low latitude by leveraging the spaced-receivers technique applied to two GNSS receivers for scintillation monitoring installed along the magnetic parallel passing in Presidente Prudente(Brazil,magnetic latitude 12.8°S).The investigated ionospheric sector is ideal to study small-scale irregularities,being located close to the expected position of the southern crest of the equatorial ionospheric anomaly.The measurement campaign took place between September 2013 and February 2014,i.e.equinox and summer solstice seasons under solar maximum,during which the probability of formation of small-scale irregularities is expected to maximize.We found that the hourly average of the velocity increases up to 135 m/s right after the local sunset at ionospheric altitudes and then smoothly decreases in the next hours.Such measurements are in agreement with independent estimations of the velocity made by the Incoherent Scatter Radar located at the Jicamarca Radio Observatory(magnetic latitude 0.1°N),by the Boa Vista Ionosonde(magnetic latitude 12.0°N),and by applying a recently-developed empirical regional short-term forecasting model.Additionally,we investigated the relationship with the percentage occurrence of amplitude scintillation;we report that it is exponentially dependent on the zonal velocity of the irregularities that cause it.展开更多
The propagation of an intense laser pulse in an under-dense plasma induces a plasma wake that is suitable for the acceleration of electrons to relativistic energies. For an ultra-intense laser pulse which has a longit...The propagation of an intense laser pulse in an under-dense plasma induces a plasma wake that is suitable for the acceleration of electrons to relativistic energies. For an ultra-intense laser pulse which has a longitudinal size shorter than the plasma wavelength, λp, instead of a periodic plasma wave, a cavity free from cold plasma electrons, called a bubble, is formed behind the laser pulse. An intense charge separation electric field inside the moving bubble can capture the electrons at the base of the bubble and accelerate them with a narrow energy spread. In the nonlinear bubble regime, due to localized depletion at the front of the pulse during its propagation through the plasma, the phase shift between carrier waves and pulse envelope plays an important role in plasma response. The carrier–envelope phase（CEP） breaks down the symmetric transverse ponderomotive force of the laser pulse that makes the bubble structure unstable. Our studies using a series of two-dimensional（2D） particle-in-cell（PIC） simulations show that the frequency-chirped laser pulses are more effective in controlling the pulse depletion rate and consequently the effect of the CEP in the bubble regime. The results indicate that the utilization of a positively chirped laser pulse leads to an increase in rate of erosion of the leading edge of the pulse that rapidly results in the formation of a steep intensity gradient at the front of the pulse. A more unstable bubble structure, the self-injections in different positions, and high dark current are the results of using a positively chirped laser pulse. For a negatively chirped laser pulse, the pulse depletion process is compensated during the propagation of the pulse in plasma in such a way that results in a more stable bubble shape and therefore, a localized electron bunch is produced during the acceleration process. As a result, by the proper choice of chirping, one can tune the number of self-injected electrons, the size of accelerated bunch and its energy spectrum to the values required for practical applications.展开更多
The spatial gradient induced by the Equatorial Plasma Bubble(EPB)in low latitude regions is a major challenge for the Ground Based Augmentation System(GBAS).To facilitate the implementation and operation of GBAS Appro...The spatial gradient induced by the Equatorial Plasma Bubble(EPB)in low latitude regions is a major challenge for the Ground Based Augmentation System(GBAS).To facilitate the implementation and operation of GBAS Approach Service Type(GAST)-D at Hong Kong International Airport,the impact of EPB induced spatial gradients needs to be analyzed.Previous simulations using a two-dimensional trapezoid model neglected the three-dimen-sional structure of the EPB,assuming ionospheric delay on a thin shell at a specific altitude.To address this limitation,this paper adopts a cube above the magnetic equator to characterize the EPB threat model.The ionospheric delay difference between satellite signals passing through the EPB model is limited by the upper bound spatial gradi-ent derived with the data collected from Hong Kong Satellite Positioning Reference Station Network.The simula-tion results reveal that ionospheric monitors in GAST D can satisfy the Category Il/ll approach requirement,i.e.,the probability of missed detection PMp for the diferential range error E,larger than 2.75 m is lower than1×10^(-9).The potentially hazardous event with the largest E,of 2.47 m and PmD of1.86×10^(-9) occurs when the satelite signal moves parallel to the equator near the Equatorial lonization Anomaly(ElA)region,and its significant portion traverses in the EPBdepletion region.展开更多
The vertical profile of the ionosphere density plays a significant role in the development of low-latitude Equatorial Plasma Bubbles(EPBs),that in turn lead to ionospheric scintillation which can severely degrade prec...The vertical profile of the ionosphere density plays a significant role in the development of low-latitude Equatorial Plasma Bubbles(EPBs),that in turn lead to ionospheric scintillation which can severely degrade precision and availability of critical users of the Global Navigation Satellite System(GNSS).Accurate estimation of ionospheric delays through vertical electron density profiles is vital for mitigating GNSS errors and enhancing location-based services.The objective of this study is to propose a neural network,trained with radio occultation data from the COSMIC-1 mission,that generates average ionospheric electron density profiles during dusk,focusing on the pre-reversal enhancement of the zonal electric field.Results show that the estimated profiles exhibit a clear seasonal pattern,and reproduce adequately the climatological behavior of the ionosphere,thus presenting strong appeal on ionospheric error attenuation.展开更多
基金partly supported by the National Natural Science Foundation of China(42020104002)by a Postdoctoral Fellowship at the Institute of Geology and Geophysics,Chinese Academy of Sciences(IGGCAS)partially supported by JSPS KAKENHI Grant Number 20H00197。
文摘The occurrence of midnight Equatorial Plasma Bubbles(EPBs)during the June solstice period of the ascending phase of solar cycle 24,from 2010 to 2014,was studied using data from the 47 MHz Equatorial Atmosphere Radar(EAR)at Kototabang,Indonesia.The analysis shows that the occurrence of midnight hour EPBs was at its maximum during the low solar activity year 2010 and monotonically decreased thereafter with increasing solar activity.Details of the dependence of midnight hour EPB occurrence on solar activity were investigated using SAMI2 model simulation with a realistic input of E×B drift velocity data obtained from the CINDI-IVM onboard the C/NOFS satellite.Results obtained from term-by-term analysis of the flux tube integrated linear growth rate of RT instability indicate that the formation of a high flux tube electron content height gradient(steep vertical gradient)region at higher altitudes,due to the elevated F layer,is the key factor enhancing the growth rate of RT instability during low solar activity June solstices.Other factors are discussed in light of the relatively weak westward zonal electric field in the presence of the equatorward neutral wind and north-to-south transequatorial wind around the midnight hours of low solar activity June solstices.Also discussed are the initial seeding of RT instability by MSTIDs and how the threshold height required for EPB development varies with solar activity.
基金supported by Coordenacao de Aperfeicoamento de Pessoal de Nível Superior(CAPES)by Conselho Nacional de Desenvolvimento Científico e Tecnológico(CNPq),under the processes 470589/2012-4,305461/2015-0,303511/2017-6,307653/2017-0,and 169815/2017-0the Fundacao de AmparoàPesquisa do Estado de Sao Paulo(FAPESP)under the process 2018/09066-8。
文摘OI 630.0 nm airglow observations,from a new observatory at Bom Jesus de Lapa,were used to study the interaction between EPBs(Equatorial Plasma Bubbles)and the MSTID(Medium-Scale Traveling Ionospheric Disturbance)over the Northeast region in Brazil.On the night of September 16 to 17,2020,an EPB was observed propagating eastward,in an apparent fossil stage,until it interacted with a dark band electrified MSTID(e MSTID).After the interaction,four EPBs merged,followed by an abrupt southward development and bifurcations.Analysis of the data suggests that an eastward polarization electric field,induced by the dark band e MSTID,forced the EPB into an upward drift,growing latitudinally along the magnetic field lines and then bifurcating.
基金supported by the Youth Science and Technology Innovation Foundation of NSSCthe International Partnership Program of Chinese Academy of Sciences(183311KYSB20200003)+1 种基金the National Natural Science Foundation of China(41831073 and 42004138)the Open Research Project of Large Research Infrastructures of CAS–“Study on the interaction between low/mid-latitude atmosphere and ionosphere based on the Chinese Meridian Project”。
文摘Branching structure(BS)is a very important phenomenon in the evolution of equatorial plasma bubbles(EPBs),the mechanism of which is widely studied from observation and from simulation.However,occurrence characteristics of branching structure of equatorial plasma bubbles(BSEPBs)have not been well addressed.In this work,we used seven-years(2012-2018)of observations from two all-sky imagers to study occurrence of BSEPBs in detail.These data reveal a high incidence of BS in EPB cases;in particular,most EPBs occurring on days with geomagnetic disturbances exhibited BS.Periods when all EPBs exhibited BS increased significantly in the 2014 solar maximum.Occurrence times of BSEPBs varied with local time;most of the BSEPBs began to appear between 21:00 and 22:00 LT.During the solar maximum,some BSEPBs were observed after midnight.The data also reveal that BSEPBs are characterized primarily by two branches or three branches.Multi-branching appeared only in the solar maximum.EPB events with different coexisting branching structures increased from 2012 to 2014 and decreased from 2014 to 2018.These results strongly suggest that BSEPB occurrence is related to solar activity and geomagnetic activity,and thus provide a new perspective for future studies of EPBs as well as enriching our understanding of ionospheric irregularity.
基金National Natural Science Foundation of China(No.42104009)China Postdoctoral Science Foundation(No.2022M720988)Postgraduate Research&Practice Innovation Program of Jiangsu Province(No.KYCX22_0663)。
文摘During a long-term Equatorial Plasma Bubbles(EPBs)occurrence between October 2020 and March 2021,a significant EPB suppression event was identified on November 22 and the observations from multi-instrument have been utilized to investigate this event.Global-scale Observations of the Limb and Disk(GOLD)satellite observed prominent EPBs between 23:40 UT and 23:55 UT during the long-term occurrence days.However,no dark stripes representing EPBs were observed on November 22,and the Equatorial Ionization Anomaly(EIA)structure remained intact.The Total Electron Content(TEC)maps show that these EPBs appeared in the region between 35°W and 65°W longitudes and the magnitudes of the TEC loss in EPBs regions were about 20 TECU.Except for 22 November,the S4 index was consistently greater than 0.6 throughout November,indicating significant ionospheric scintillation.The Rate Of TEC Index(ROTI)maps revealed that the spatial extent and intensity of EPBs increased after their suppression,and the EPBs were locally generated.The swarm electron density measurements indicated that the variation amplitudes of EPBs at 510 km altitude were approximately 3 to 5 times larger than that at 460 km altitude.The impact region of EPBs at 510 km was between 15°S and 20°N latitudes,while at 460 km,it was between 0°and 17°N latitudes.During the period of EPB suppression,the average h’f at three ionosonde stations decreased by about 50 km,and the vertical drift velocity(V z)approached~0 m/s while it was more than 20 m/s during the long-term occurrence.
基金financial support from National Key Research and Development Program of China(No.2017YFB0503404)the National Natural Science Foundation of China(Nos.61871012,U1833125)+2 种基金Open fund project of Intelligent Operation Key Laboratory of Civil Aviation Airport Group(No.KLAGIO20180405)The National Key Research and Development Program of China(No.2018YFB0505105)Beijing Nova Program of Science and Technology(No.Z191100001119134)。
文摘Detecting and characterizing Total Electron Content(TEC)depletion is important for studying the ionospheric threat due to the Equatorial Plasma Bubble(EPB)when applying the Ground-Based Augmentation System(GBAS)at low latitudes.This paper develops a robust method to automatically identify TEC depletion and derive its parameters.The rolling barrel algorithm is used to automatically identify the TEC depletion candidate and its parameters.Then,the depletion candidates are screened by several improved techniques to distinguish actual depletions from other phenomena such as Traveling Ionospheric Disturbance(TID)or abnormal data.Next,based on the depletion signals from three triangular receivers,the method derives EPB parameters such as velocity,width and gradient.The time lag and front velocity are calculated based on crosscorrelation using TEC depletions and the geometrical distribution of three triangular receivers.The width and gradient of slope are then determined by using TEC depletion from a single receiver.By comparison,both the station-pair method and proposed method depend on the assumption that the EPB morphology is frozen during the short time when the plasma bubble moves between the receivers.However,our method relaxes the restriction that the baseline length should be shorter than the width of slope required by the station-pair.This relaxation is favorable for studying small-scale slope of depletions using stations of a longer baseline.In addition,the accuracy of the width and gradient is free of impact from hardware biases and small-scale disturbance,as it is based only on the relative TEC variation.The method is demonstrated by processing Global Positioning System(GPS)and Bei Dou Navigation Satellite System(BDS)data on 15 August,2018,in a solar minimum cycle.
基金the support from National Natural Science Foundation of China(42020104002)。
文摘The 2 nd Equatorial Plasma Bubble(EPB)workshop,funded by the Institute of Geology and Geophysics,Chinese Academy of Sciences,and the National Natural Science Foundation of China,took place in Beijing,China during September 13–15,2019.The EPB workshop belongs to a conference series that began in 2016 in Nagoya,Japan at the Institute for Space-Earth Environmental Research,Nagoya University,resulting in a special issue of Progress in Earth and Planetary Science that focused on EPBs.The main goal of the series is to organize in-depth discussion by scientists working on ionospheric irregularities,and solve the scientific challenges in EPB and ionospheric scintillation forecasting.The 2 nd EPB workshop gathered almost 60 scientists from seven countries.A total of 20 invited and contributing papers focusing on ionospheric irregularities and scintillations were presented.Here we briefly comment on 10 papers included in this special issue.
基金supported by the National Natural Science Foundation of China(Grant Nos.42020104002,42404180)the Project of Stable Support for Youth Team in Basic Research Field,Chinese Academy of Sciences(Grant No.YSBR-018)+7 种基金the Solar-Terrestrial Environment Research Network(STERN)of Chinese Academy of Sciences,the International Partnership Program of CAS(Grant No.183311KYSB20200003)the CAS-JSPS Joint Research Project(Grant No.178GJHZ2023180MI)the Chinese Meridian Projectsupported by the National Natural Science Foundation of China(Grant No.41727803)partially supported by the JSPS KAKENHI(Grant Nos.22K21345,21H04518,20H00197,18KK0099,23K22555,24K07112,24K00898)the JSPS Bilateral Joint Research(Grant No.JPJSBP120247202)the JSPS Core-to-Core ProgramB.Asia-Africa Science Platforms。
文摘The all-sky meteor radars are primarily designed for observations of mesospheric neutral wind.Recently,the capability of all-sky radars in investigating ionospheric irregularities of the Bragg scales has been developed.However,limited by the relatively small range gate span of the all-sky radar,this capability is mainly constrained to the observations of irregularities at lower altitudes,e.g.,E-region irregularities.The F-region irregularities at higher altitudes up to hundreds of kilometers,e.g.,equatorial plasma bubbles(EPBs),are usually considered beyond the detection range of all-sky radars.In this paper,we try to extend the capability of a conventional interferometric all-sky meteor radar located at Sanya(18.4°N,109.7°E)for investigating the spatial features of EPBs.Based on the arriving angles of irregularity backscatter echoes obtained by the radar interferometry technique,and according to the magnetic sensitivity of the EPB field-aligned irregularities,the true ranges of the irregularity structures could be determined to further reveal the spatial features of EPB structures.The results are confirmed by the collocated narrow-beam very high frequency(VHF)radar and the Low lAtitude long Range Ionospheric raDar(LARID).It is revealed that the all-sky radar could be employed to investigate EPB irregularities in a larger zonal region than narrow-beam VHF radars,which could be up to~2000 km.The observations could well cover the blind area of the LARID field-of-view,and thus could be employed to continuously trace EPB occurrences and evolutions over thousands of kilometers by combining with LARID in future studies.
基金supported by the National Natural Science Foundation of China(Grant Nos.41874185,41574147,41904142,42104165)the West Light Cross-Disciplinary Innovation team of Chinese Academy of Sciences(Grant No.E1294301)。
文摘Using the observations of the 630-nm all-sky imagers(ASIs)located in the geomagnetic conjugate points in the American sector from 2014 to 2017,this study statistically analyzed the features of conjugate equatorial plasma bubbles(EPBs),including their occurrence rate,zonal width,location and zonal drift velocity.The results show that the occurrence rate of the EPBs that occur simultaneously at geomagnetic conjugate points is~84%.The zonal widths of the EPBs are mainly~100 km,and the width differences of EPBs between the northern and southern hemispheres are mainly within±30 km.The zonal displacements of the center locations of the northern and southern EPBs are within±50 km.The zonal drift velocities of the northern and southern EPBs are nearly equal.However,it should be noted that the velocity of the EPBs in the northern hemisphere is 10%faster than that in the southern hemisphere.The results suggest that conjugate EPBs are common.Moreover,the non-conjugate EPBs in the northern and southern hemisphere can occur occasionally,which is probably associated with the different ionospheric backgrounds between the two hemispheres.The features of the conjugate EPBs as shown in this study provides support for the nowcasting of EPBs in the conjugate hemispheres.
基金JSPS KAKENHI Grant Number16H06286 supports global GNSS ionospheric maps (TEC,ROTI,and detrended TEC maps) developed by the Institute for SpaceEarth Environmental Research (ISEE) of Nagoya Universitysupport of the 2024 JASSO Follow-up Research Fellowship Program for a 90-day visiting research at the Institute for Space-Earth Environmental Research (ISEE),Nagoya University+3 种基金the support received from Telkom University under the“Skema Penelitian Terapan Periode I Tahun Anggaran 2024”the Memorandum of Understanding for Research Collaboration on Regional Ionospheric Observation (No:092/SAM3/TE-DEK/2021)the National Institute of Information and Communications Technology (NICT) International Exchange Program 2024-2025(No.2024-007)support for a one-year visiting research at Hokkaido University
文摘This paper highlights the crucial role of Indonesia’s GNSS receiver network in advancing Equatorial Plasma Bubble(EPB)studies in Southeast and East Asia,as ionospheric irregularities within EPB can disrupt GNSS signals and degrade positioning accuracy.Managed by the Indonesian Geospatial Information Agency(BIG),the Indonesia Continuously Operating Reference Station(Ina-CORS)network comprises over 300 GNSS receivers spanning equatorial to southern low-latitude regions.Ina-CORS is uniquely situated to monitor EPB generation,zonal drift,and dissipation across Southeast Asia.We provide a practical tool for EPB research,by sharing two-dimensional rate of Total Electron Content(TEC)change index(ROTI)derived from this network.We generate ROTI maps with a 10-minute resolution,and samples from May 2024 are publicly available for further scientific research.Two preliminary findings from the ROTI maps of Ina-CORS are noteworthy.First,the Ina-CORS ROTI maps reveal that the irregularities within a broader EPB structure persist longer,increasing the potential for these irregularities to migrate farther eastward.Second,we demonstrate that combined ROTI maps from Ina-CORS and GNSS receivers in East Asia and Australia can be used to monitor the development of ionospheric irregularities in Southeast and East Asia.We have demonstrated the combined ROTI maps to capture the development of ionospheric irregularities in the Southeast/East Asian sector during the G5 Geomagnetic Storm on May 11,2024.We observed simultaneous ionospheric irregularities in Japan and Australia,respectively propagating northwestward and southwestward,before midnight,whereas Southeast Asia’s equatorial and low-latitude regions exhibited irregularities post-midnight.By sharing ROTI maps from Indonesia and integrating them with regional GNSS networks,researchers can conduct comprehensive EPB studies,enhancing the understanding of EPB behavior across Southeast and East Asia and contributing significantly to ionospheric research.
基金supported by the National Natural Science Foundation of China(Grant Nos.12075081 and 12404395)the Innovation Group Project of the Natural Science Foundation of Hubei Province of China(Grant No.2024AFA038)Bin Liu acknowledges the support of Guangdong High Level Innovation Research Institute Project,Grant No.2021B0909050006.
文摘The significance of laser-driven polarized beam acceleration has been increasingly recognized in recent years.We propose an efficient method for generating polarized proton beams from a pre-polarized hydrogen halide gas jet,utilizing magnetic vortex acceleration enhanced by a laser-driven plasma bubble.When a petawatt laser pulse passes through a pre-polarized gas jet,a bubble-like ultra-nonlinear plasma wave is formed.As a portion of the particles constituting this wave,background protons are swept by the acceleration field of the bubble and oscillate significantly along the laser propagation axis.Some of the pre-accelerated protons in the plasma wave are trapped by the acceleration field at the rear side of the target.This acceleration field is intensified by the transverse expansion of the laser-driven magnetic vortex,resulting in energetic polarized proton beams.The spin of energetic protons is determined by their precession within the electromagnetic field,which is described using the Thomas-Bargmann-Michel-Telegdi equation in analytical models and particle-in-cell simulations.Multidimensional simulations reveal that monoenergetic proton beams with an energy of hundreds of MeV,a beam charge of hundreds of pC,and a beam polarization of tens of percent can be produced at laser powers of several petawatts.Such laser-driven polarized proton beams have promise for application in polarized beam colliders,where they can be utilized to investigate particle interactions and to explore the properties of matter under extreme conditions.
基金supported by the Japan Society for the Promotion of Science,KAKENHI Grants,16H06286 and 20H00197supported by NASA(NNH17ZDA001N07)NSF(AGS-1931415)grants(JDH)。
文摘This paper reports that plasma density depletions appearing at middle latitudes near sunrise survived until afternoon on 29 May 2017 during the recovery phase of a geomagnetic storm.By analyzing GPS data collected in Japan,we investigate temporal variations in the horizontal two-dimensional distribution of total electron content(TEC)during the geomagnetic storm.The SYM-H index reached-142 n T around 08 UT on 28 May 2017.TEC depletions extending up to approximately 38°N along the meridional direction appeared over Japan around 05 LT(LT=UT+9 hours)on 29 May 2017,when TEC rapidly increased at sunrise due to the solar extreme ultraviolet(EUV)radiation.The TEC depletions appeared sequentially over Japan for approximately 8 hours in sunlit conditions.At 06 LT on 29 May,when the plasma depletions first appeared over Japan,the background TEC was enhanced to approximately 17 TECU,and then decreased to approximately 80%of the TEC typical of magnetically quiet conditions.We conclude that this temporal variation of background plasma density in the ionosphere was responsible for the persistence of these plasma depletions for so long in daytime.By using the Naval Research Laboratory:Sami2 is Another Model of the Ionosphere(SAMI2),we have evaluated how plasma production and ambipolar diffusion along the magnetic field may affect the rate of plasma depletion disappearance.Simulation shows that the plasma density increases at the time of plasma depletion appearance;subsequent decreases in the plasma density appear to be responsible for the long-lasting persistence of plasma depletions during daytime.The plasma density depletion in the top side ionosphere is not filled by the plasma generated by the solar EUV productions because plasma production occurs mainly at the bottom side of the ionosphere.
基金supported by the National Natural Science Foundation of China(Grants No.41831073 and No.41804146)the Open Research Project of Large Research Infrastructures of Chinese Acadamy of Sciences—"Study on the interaction between low/midlatitude atmosphere and ionosphere based on the Chinese Meridian Project”+2 种基金the Youth Innovation Promotion Association of the Chinese Academy of Sciences(Grant No.2020156)the Project of Stable Support for Youth Team in Basic Research Field,CAS(Grant No.YSBR-018)the International Partnership Program of the Chinese Academy of Sciences(Grant No.183311KYSB20200003)。
文摘Observational evidence is insufficient to understand how equatorial plasma bubbles(EPBs)form over low latitudes.The mechanism of plasma-density enhancement(formation of"plasma blobs")at low latitudes is in dispute.In this paper,we use data from multiple ground-based instruments(one all-sky airglow imager,five digisondes,and one Fabry–Perot interferometer)to investigate the evolution of an EPB event that occurred at low latitudes over China on the night of 06 December 2015(06-Dec-2015).We provide observational evidence that an enhanced equatorward wind most likely induced by a substorm could have initiated the Rayleigh–Taylor instability(RTI)that destabilized several EPB depletions in an upwelling region of a large-scale wave-like structure(LSWS)in the bottomside ionosphere.Those EPB depletions were forced to surge poleward,from nearly 10°to 19°magnetic latitude,two hours before midnight.Smaller-scale bifurcations evolved rapidly from tips of airglow depletions by a secondary E×B instability when the aforementioned substorm-induced southwestward wind blew through.During the growth phase of the EPB depletions,a westward polarization electric field inside the LSWS is likely to have compressed plasma downward,inducing the two airglow-type blobs observed in the bottomside ionosphere,by a mechanism of LSWS-blob connection that we propose.We also provide observational evidence of brightness airglow depletions.We find that an enhanced poleward wind associated with a passing-by brightness wave(BW)is likely to have transported plasma to fill the airglow depletions,which finally evolved into brightness airglow structures.This study investigates the physical processes accompanied by the EPB event and those two-airglow blobs observed at low-latitudes over China.
基金supported by CNPq(Conselho Nacional de Pesquisa e desenvolvimento)under the grant,310927/2020-0the Sao Paulo Research Foundation(FAPESP)for its grant 2018/09066-8+2 种基金CAPES(Coordenacao de Aperfeicoamento de Pessoal de Nível Superior)the JSPS(Japan Society for Promotion of Science)KAKENHI for its support(grant JP 15H05815)the National Natural Science Foundation of China for its support(Grant No.42020104002)。
文摘Large Scale Wave Structures(LSWS)in the equatorial ionospheric F-region were observed by measuring spatial and temporal variations within detrended total electron content(dTEC)data obtained by ground-based GNSS receivers over the South American continent.By using dTEC-maps,we have been able to produce,for the first-time,two-dimensional representations of LSWS.During the period from September to December,the LSWS frequently occurred starting a few hours prior to Equatorial Plasma Bubble(EPB)development.From 17 events of LSWS observed in 2014 and 2015,wave characteristics were obtained:the observed wavelengths,periods,and the phase speeds are respectively,~900 km,~41 min and~399 m/s;the waves propagated from the northeast to southeast.In some cases the front of the oscillation was meridionally aligned,extending to more than 1600 km,the first time such large extension of the wavefront has been reported.From F-layer bottom height oscillation data,measured by ionosonde,LSWS exhibit two different vertical phase propagation modes,in-phase and downward phase.The former mode indicates the presence of a polarization electric field in the F-layer bottom side;the latter suggests propagation of atmospheric gravity waves.The presence of LSWS near the solar terminator,followed by the development of EPBs,suggests that the upwelling of the F-layer bottom height produces a condition favorable to the development of Rayleigh–Taylor instability.
基金Supported by the National Natural Science Foundation of China(NNSFC)under Grant Nos.11175023,10834008the Fundamental Research Funds for the Central Universities(FRFCU)
文摘Bubble core fields as well bubble shape modification due to the nondepleted electrons inside the bubble is investigated theoretically. It is found that the Mope of transverse fields are reduced significantly, however, the slope of longitudinal electric field, which plays a key role on electrons acceleration in bubble, changes little. Moreover a modified longitudinal compressed bubble shape leads to a shorter dephasing distance which makes the electrons acceleration energy reduced to some extent. As a comparison we perform particle-in-cell simulations whose results are consistent with that of our theoretical consideration.
基金funded by FAPESP(Process 06/04008-2)funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Sk?odowska-Curie Actions grant agreement No 722023。
文摘We estimate the zonal drift velocity of small-scale ionospheric irregularities at low latitude by leveraging the spaced-receivers technique applied to two GNSS receivers for scintillation monitoring installed along the magnetic parallel passing in Presidente Prudente(Brazil,magnetic latitude 12.8°S).The investigated ionospheric sector is ideal to study small-scale irregularities,being located close to the expected position of the southern crest of the equatorial ionospheric anomaly.The measurement campaign took place between September 2013 and February 2014,i.e.equinox and summer solstice seasons under solar maximum,during which the probability of formation of small-scale irregularities is expected to maximize.We found that the hourly average of the velocity increases up to 135 m/s right after the local sunset at ionospheric altitudes and then smoothly decreases in the next hours.Such measurements are in agreement with independent estimations of the velocity made by the Incoherent Scatter Radar located at the Jicamarca Radio Observatory(magnetic latitude 0.1°N),by the Boa Vista Ionosonde(magnetic latitude 12.0°N),and by applying a recently-developed empirical regional short-term forecasting model.Additionally,we investigated the relationship with the percentage occurrence of amplitude scintillation;we report that it is exponentially dependent on the zonal velocity of the irregularities that cause it.
文摘The propagation of an intense laser pulse in an under-dense plasma induces a plasma wake that is suitable for the acceleration of electrons to relativistic energies. For an ultra-intense laser pulse which has a longitudinal size shorter than the plasma wavelength, λp, instead of a periodic plasma wave, a cavity free from cold plasma electrons, called a bubble, is formed behind the laser pulse. An intense charge separation electric field inside the moving bubble can capture the electrons at the base of the bubble and accelerate them with a narrow energy spread. In the nonlinear bubble regime, due to localized depletion at the front of the pulse during its propagation through the plasma, the phase shift between carrier waves and pulse envelope plays an important role in plasma response. The carrier–envelope phase（CEP） breaks down the symmetric transverse ponderomotive force of the laser pulse that makes the bubble structure unstable. Our studies using a series of two-dimensional（2D） particle-in-cell（PIC） simulations show that the frequency-chirped laser pulses are more effective in controlling the pulse depletion rate and consequently the effect of the CEP in the bubble regime. The results indicate that the utilization of a positively chirped laser pulse leads to an increase in rate of erosion of the leading edge of the pulse that rapidly results in the formation of a steep intensity gradient at the front of the pulse. A more unstable bubble structure, the self-injections in different positions, and high dark current are the results of using a positively chirped laser pulse. For a negatively chirped laser pulse, the pulse depletion process is compensated during the propagation of the pulse in plasma in such a way that results in a more stable bubble shape and therefore, a localized electron bunch is produced during the acceleration process. As a result, by the proper choice of chirping, one can tune the number of self-injected electrons, the size of accelerated bunch and its energy spectrum to the values required for practical applications.
基金supported by grants from the Research Grants Council of the Hong Kong Special Administrative Region,China (Project No.25202520,15214523)the National Natural Science Foundation of China (Grant No.42004029)。
文摘The spatial gradient induced by the Equatorial Plasma Bubble(EPB)in low latitude regions is a major challenge for the Ground Based Augmentation System(GBAS).To facilitate the implementation and operation of GBAS Approach Service Type(GAST)-D at Hong Kong International Airport,the impact of EPB induced spatial gradients needs to be analyzed.Previous simulations using a two-dimensional trapezoid model neglected the three-dimen-sional structure of the EPB,assuming ionospheric delay on a thin shell at a specific altitude.To address this limitation,this paper adopts a cube above the magnetic equator to characterize the EPB threat model.The ionospheric delay difference between satellite signals passing through the EPB model is limited by the upper bound spatial gradi-ent derived with the data collected from Hong Kong Satellite Positioning Reference Station Network.The simula-tion results reveal that ionospheric monitors in GAST D can satisfy the Category Il/ll approach requirement,i.e.,the probability of missed detection PMp for the diferential range error E,larger than 2.75 m is lower than1×10^(-9).The potentially hazardous event with the largest E,of 2.47 m and PmD of1.86×10^(-9) occurs when the satelite signal moves parallel to the equator near the Equatorial lonization Anomaly(ElA)region,and its significant portion traverses in the EPBdepletion region.
基金CAPES scholarships 88887.570088/2020-00 and 88887.634447/2021-00 and worked on this research in collaboration to the framework CNPq 465648/2014-2 and FAPESP 2017/01150-0.GSFAOM are supported by CNPq awards 165561/2023-8 and 309389/2021-6 respectively+1 种基金PRPS and JS were supported by CAPES awards 850937/2023-00 and 88887.901203/2023-00 respectivelyJS also acknowledges FAPESP 2018/06158-9.
文摘The vertical profile of the ionosphere density plays a significant role in the development of low-latitude Equatorial Plasma Bubbles(EPBs),that in turn lead to ionospheric scintillation which can severely degrade precision and availability of critical users of the Global Navigation Satellite System(GNSS).Accurate estimation of ionospheric delays through vertical electron density profiles is vital for mitigating GNSS errors and enhancing location-based services.The objective of this study is to propose a neural network,trained with radio occultation data from the COSMIC-1 mission,that generates average ionospheric electron density profiles during dusk,focusing on the pre-reversal enhancement of the zonal electric field.Results show that the estimated profiles exhibit a clear seasonal pattern,and reproduce adequately the climatological behavior of the ionosphere,thus presenting strong appeal on ionospheric error attenuation.
