Solar flares are one of the strongest outbursts of solar activity,posing a serious threat to Earth’s critical infrastructure,such as communications,navigation,power,and aviation.Therefore,it is essential to accuratel...Solar flares are one of the strongest outbursts of solar activity,posing a serious threat to Earth’s critical infrastructure,such as communications,navigation,power,and aviation.Therefore,it is essential to accurately predict solar flares in order to ensure the safety of human activities.Currently,the research focuses on two directions:first,identifying predictors with more physical information and higher prediction accuracy,and second,building flare prediction models that can effectively handle complex observational data.In terms of flare observability and predictability,this paper analyses multiple dimensions of solar flare observability and evaluates the potential of observational parameters in prediction.In flare prediction models,the paper focuses on data-driven models and physical models,with an emphasis on the advantages of deep learning techniques in dealing with complex and high-dimensional data.By reviewing existing traditional machine learning,deep learning,and fusion methods,the key roles of these techniques in improving prediction accuracy and efficiency are revealed.Regarding prevailing challenges,this study discusses the main challenges currently faced in solar flare prediction,such as the complexity of flare samples,the multimodality of observational data,and the interpretability of models.The conclusion summarizes these findings and proposes future research directions and potential technology advancement.展开更多
Major solar plasma disturbances are subjected to Lomb-Scargle periodogram and wavelet analysis to determine the occurrence frequency.These disruptions include interplanetary coronal mass ejection,sudden storm commence...Major solar plasma disturbances are subjected to Lomb-Scargle periodogram and wavelet analysis to determine the occurrence frequency.These disruptions include interplanetary coronal mass ejection,sudden storm commencement,high-speed streams,corotating interaction regions,interplanetary shocks and Forbush decreases.We included information on all of the aforementioned solar disturbances for the last six solar cycles,from 1965 to 2023,for this study.Our findings reveal some intriguing and noteworthy results that clearly distinguish between even and odd-numbered solar cycles.The study suggests that the Sun behaves differently in odd and even-numbered solar cycles as it comes from the massive solar eruptions.During even-numbered solar cycles,variations with a period of∼44 days are prominently observed in addition to solar rotation(∼27 days)and extended solar(∼36 days)rotation.However,in addition to solar rotation,prolonged solar rotation,and periods of around 44 days,we also detect a number of intermittent changes with nearly comparable amplitude during the oddnumbered solar cycles.The findings also demonstrate that,in contrast to odd-numbered solar cycles,the emissions rate of these disruptions is more distinct and predictable during even-numbered solar cycles.展开更多
Solar activities have a great impact on modern high-tech systems,such as human aerospace activities,satellite communication and navigation,deep space exploration,and related scientific research.Therefore,studying the ...Solar activities have a great impact on modern high-tech systems,such as human aerospace activities,satellite communication and navigation,deep space exploration,and related scientific research.Therefore,studying the long-term evolution trend of solar activity and accurately predicting the future solar cycles are highly anticipated.Based on the wavelet transform and empirical function fitting of the longest recorded data of the annual average relative sunspot number(ASN)series of 323 yr to date,this work decisively verifies the existence of the solar century cycles and confirms that its length is about 104.0 yr,and the magnitude has a slightly increasing trend on the timescale of several hundred years.Based on this long-term evolutionary trend,we predict solar cycles 25 and26 by using phase similar prediction methods.As for solar cycle 25,its maximum ASN will be about146.7±33.40,obviously stronger than solar cycle 24.The peak year will occur approximately in 2024,and the period will be about 11±1 yr.As for solar cycle 26,it will start around 2030,and reach its maximum between2035 and 2036,with maximum ASN of about 133.0±3.200,and period of about 10 yr.展开更多
In this present study,we have analyzed different types of X-ray solar flares(C,M,and X classes)coming out from different classes of sunspot groups(SSGs).The data which we have taken under this study cover the duration...In this present study,we have analyzed different types of X-ray solar flares(C,M,and X classes)coming out from different classes of sunspot groups(SSGs).The data which we have taken under this study cover the duration of 24 yr from 1996 to 2019.During this,we observed a total of 15015 flares(8417 in SC-23 and 6598 in SC-24)emitted from a total of 33780 active regions(21746 in SC-23 and 12034 in SC-24)with sunspot only.We defined the flaring potential or flare-production potential as the ratio of the total number of flares produced from a particular type of SSG to the total number of the same-class SSGs observed on the solar surface.Here we studied yearly changes in the flaring potential of different McIntosh class groups of sunspots in different phases of SC-23 and 24.In addition,we investigated yearly variations in the potential of producing flares by different SSGs(A,B,C,D,E,F,and H)during different phases(ascending,maximum,descending,and minimum)of SC-23 and 24.These are our findings:(1)D,E,and F SSGs have the potential of producing flares≥8 times greater than A,B,C and H SSGs;(2)The larger and more complex D,E,and F SSGs produced nearly 80%of flares in SC-23 and 24;(3)The A,B,C and H SSGs,which are smaller and simpler,produced only 20%of flares in SC-23 and 24;(4)The biggest and most complex SSGs of F-class have flaring potential 1.996 and 3.443 per SSG in SC-23 and 24,respectively.(5)The potential for producing flares in each SSG is higher in SC-24 than in SC-23,although SC-24 is a weaker cycle than SC-23.(6)The alterations in the number of flares(C+M+X)show different time profiles than the alterations in sunspot numbers during SC-23 and 24,with several peaks.(7)The SSGs of C,D,E,and H-class have the highest flaring potential in the descending phase of both SC-23 and 24.(8)F-class SSGs have the highest flaring potential in the descending phase of SC-23 but also in the maximum phase of SC-24.展开更多
The time series of daily data on solar activity proxies, namely the sunspot number(SSN), sunspot area(SSA), solar radio flux(F10.7), modified coronal index(MCI), solar flare index(FI), and cosmic ray intensity(CRI), w...The time series of daily data on solar activity proxies, namely the sunspot number(SSN), sunspot area(SSA), solar radio flux(F10.7), modified coronal index(MCI), solar flare index(FI), and cosmic ray intensity(CRI), were analyzed to understand the solar activity modulations and short-term periodicities therein. Rieger-type and other short-term periods include the solar rotational period that covers the maximum activity phase period(maximum phase of solar cycle 24). The wavelet power spectra and Periodogram of SSN, SSA, F10.7, MCI, FI, and CRI exhibited a significant short-term period. The heliospheric effects exist for a particular period(~27 days) and they are related to the solar activity phenomena. The cross-correlation coefficients and time lags between the CRI and solar activity parameters were estimated to be ~200, 46, 281, 39, and 47 days for SSN, SSA, F10.7, MCI, and FI respectively during the time series 2012–2015(maximum phase of solar cycle 24).展开更多
An extreme ultraviolet(EUV) close-up view of the Sun offers unprecedented detail of heating events in the solar corona. Enhanced temporal and spatial images obtained by the Solar Orbiter during its first science perih...An extreme ultraviolet(EUV) close-up view of the Sun offers unprecedented detail of heating events in the solar corona. Enhanced temporal and spatial images obtained by the Solar Orbiter during its first science perihelion enabled us to identify clustered EUV bright tadpoles(CEBTs) occurring near the footpoints of coronal loops.Combining SDO/AIA observations, we determine the altitudes of six distinct CEBTs by stereoscopy, ranging from ~1300 to 3300 km. We then notice a substantial presence of dark, cooler filamentary structures seemingly beneath the CEBTs, displaying periodic up-and-down motions lasting 3–5 minutes. This periodic behavior suggests an association of the majority of CEBTs with Type I spicules. Out of the ten selected CEBTs with fast downward velocity, six exhibit corrected velocities close to or exceeding 50 km s^(-1). These velocities notably surpass the typical speeds of Type I spicules. We explore the generation of such velocities. It indicates that due to the previous limited observations of spicules in the EUV wavelengths, they may reveal novel observational features beyond our current understanding. Gaining insights into these features contributes to a better comprehension of small-scale coronal heating dynamics.展开更多
We investigate the oscillations in active region(AR)NOAA 12891,which produces a C2.0 three-ribbon flare accompanying a jet on 2021 November 2.Using the data from the Atmospheric Imaging Assembly onboard the Solar Dyna...We investigate the oscillations in active region(AR)NOAA 12891,which produces a C2.0 three-ribbon flare accompanying a jet on 2021 November 2.Using the data from the Atmospheric Imaging Assembly onboard the Solar Dynamics Observatory,the 5 minutes decayless kink oscillations of coronal loops were detected and they are independent of the solar flare.Based on the observed oscillations and seismological diagnostics,we estimate that the Alfvén speed and magnetic field in these coronal loops are around 466 kms^(-1) sand 7.6 G,respectively.Additionally,the flare-related jet shows its plasmoids with 1 minute periodicity same as the intensity fluctuation of nearby flare ribbon.The correlation between the intensity fluctuation of jet and that of flare ribbon indicates that their 1 minute oscillations should originate from the same reconnection process.展开更多
We observed an Hα surge that occurred in NOAA Active Region 12401 on 2015 August 17, and we discuss its trigger mechanism, and kinematic and thermal properties. It is suggested that this surge was caused by a chromos...We observed an Hα surge that occurred in NOAA Active Region 12401 on 2015 August 17, and we discuss its trigger mechanism, and kinematic and thermal properties. It is suggested that this surge was caused by a chromospheric reconnection which ejected cool and dense material with transverse velocity of about 21–28 km s-1 and initial Doppler velocity of 12 km s^-1. This surge is similar to the injection of newly formed filament materials from their footpoints, except that the surge here occurred in a relatively weak magnetic environment of 100 G. Thus, we discuss the possibility of filament material replenishment via the erupting mass in such a weak magnetic field, which is often associated with quiescent filaments. It is found that the local plasma can be heated up to about 1.3 times the original temperature, which results in an acceleration of about –0.017 km s^-2. It can lift the dense material up to 10 Mm and higher with an inclination angle smaller than 50°, namely the typical height of active region filaments, but it can hardly inject the material up to those filaments higher than 25 Mm, like some quiescent filaments. Thus, we think that the injection model does not work well in describing the formation of quiescent filaments.展开更多
With an extensive analysis,we study the temporal evolution of magnetic flux during three successive M-class flares in two adjacent active regions：NOAA 10039 and 10044.The primary data are full disk longitudinal magne...With an extensive analysis,we study the temporal evolution of magnetic flux during three successive M-class flares in two adjacent active regions：NOAA 10039 and 10044.The primary data are full disk longitudinal magnetograms observed by SOHO/MDI.All three flares are observed to be accompanied by magnetic flux changes.The changes occurred immediately or within 1 ～ 10 minutes after the starting time of the flares,indicating that the changes are obvious consequences of the solar flares.Although changes in many points are intrinsic in magnetic flux,for some sites,it is caused by a rapid expansion motion of magnetic flux.For the second flare,the associated change is more gradual compared with the ＇step-function＇ reported in literature.Furthermore,we use the data observed by the Imaging Vector Magnetograph（IVM） at Mees Solar Observatory to check possible line profile changes during the flares.The results from the IVM data confirm the flux changes obtained from the MDI data.A series of line profiles were obtained from the IVM＇s observations and analyzed for flux change sites.We find that the fluctuations in the width,depth and central wavelength of the lines are less than 5.0 even at the flare＇s core.No line profile change is observed during or after the flare.We conclude that the magnetic field changes associated with the three solar flares are not caused by flare emission.展开更多
We have obtained 2D spectra of Ha and CaII λ8542A for the flare of 1998 November 11, and derived its 2D velocity field and integrated intensity field. The velocity distribution shows that the red-shift and blue-shift...We have obtained 2D spectra of Ha and CaII λ8542A for the flare of 1998 November 11, and derived its 2D velocity field and integrated intensity field. The velocity distribution shows that the red-shift and blue-shift velocities lie respectively in the northern and southern parts of the flare and that the maximum velocity seems to be located in two footpoints of the flare loop system. The integrated intensity distribution shows that the CaIIλ8542A line is formed at a lower height than the Ha line, we used 'multi-cloud model' (MCM) to obtain four parameters for the two lines (Doppler width, △λD, Doppler shift, △λ0, line source function, S, and optical depth at the line center, TO). We also estimated the column number densities of hydrogen at the second level, N2, and of the ionized calcium at the third level, N3, as well as the kinetic temperature, Tc. The wide Hα profile at the loop top may be explained by an overlapping of two or more elementary profiles. It is shown that the uncertainty in calibration does not affect the derived Doppler shift and line broadening, only the source function and optical depth.展开更多
Fast electron beams(FEBs) are one of the main products of various active events and are ubiquitous in solar,space and cosmic plasmas.They reveal themselves in hard X-ray and radio emissions.The observed characteristic...Fast electron beams(FEBs) are one of the main products of various active events and are ubiquitous in solar,space and cosmic plasmas.They reveal themselves in hard X-ray and radio emissions.The observed characteristics of X-ray and radio emissions sensitively depend on the energy distribution of FEBs,which usually have a power-law energy spectrum.As FEBs travel in the solar atmosphere,their energy distribution can considerably vary due to the interaction with ambient plasmas.Tang et al.investigated the evolution of the energy spectrum of the FEBs traveling along a flare loop and discussed the possible effects on associated hard X-ray(HXR) and radio emissions.Considering the ubiquitous coronal loops in active regions,in the present paper,we investigate the parametric evolution of the energy spectra of FEBs when propagating along coronal loops.Here,we take the sunpot atmospheric model as an approximate coronal loop atmosphere model.The results show that the energy loss has an important impact on the cutoff behavior and energy spectra of FEBs when precipitating in a coronal loop with density ratio n_(b)/n_(e)= 0.01.The initially single power-law spectrum with a steepness cutoff can evolve into a more complex double power-law spectrum or two “knees” power-law spectrum with a flattened steepness cutoff behavior or saturation cutoff behavior.Our calculations also demonstrate that the energy spectrum evolution is not obvious if n_(b)/n_(0)= 0.001 as Tang et al.asserted.The present results are helpful for a more comprehensive understanding of the dynamic spectra of HXR and radio emissions from FEBs.展开更多
Following our previous work,we studied the partial eruption of a large-scale horse-shoe-like filament that had beenobserved in a decaying active region on the solar disk for more than 4.5 days.The filament became acti...Following our previous work,we studied the partial eruption of a large-scale horse-shoe-like filament that had beenobserved in a decaying active region on the solar disk for more than 4.5 days.The filament became active after itwas broken into two pieces,P1 and P2 seen in Hα,by magnetic reconnection between the magnetic field around itand that of a newly emerging active region nearby.P1 eventually erupted 13 hr after the breaking and escaped fromthe Sun,developing to a fast coronal mass ejection,and P2 stayed.But the mass in P1 falling down to P2 in theeruption suggests that the global magnetic fields over P1 and P2 were still connected to each other prior to theeruption.The reconnection process breaking the filament occurred outside the filament,and P1 and P2 were locatedalmost at the same altitude,so the fashion of the filament partial eruption studied here differs from that of the“double-decker model”and that of reconnection inside the filament.Analyzing the decay indices of thebackground fields above P1 and P2,n_(1)and n_(2),showed that the altitude where n_(1)exceeds the critical value of n_(c)=1.5 for the loss of equilibrium or the torus instability is lower than that where n_(2)>nc,and that n_(1)>n_(2) alwaysholds at all altitudes.Combining this fact with that the eruption occurred 13 hr after filament was broken byreconnection,we conclude that the eruption of P1 was triggered by the loss of equilibrium or the torus instability inthe configuration,and magnetic reconnection breaking the filament helped weaken the confinement of thebackground field on P1,allowing P1 to erupt.Detailed features of the eruption and the corresponding physicalscenario were also discussed.展开更多
Light bridges(LBs)are bright lanes that divide one sunspot umbra into two or more parts.Though frequently observed in sunspots,their formation mechanisms have rarely been studied and thus are not well understood.Here ...Light bridges(LBs)are bright lanes that divide one sunspot umbra into two or more parts.Though frequently observed in sunspots,their formation mechanisms have rarely been studied and thus are not well understood.Here we present results from the first statistical investigation on the formation of LBs.Using observations with the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory,we identified 144 LBs within 71 active regions(ARs)over the whole year of 2014.The formation processes of these LBs can be categorized into three groups:penumbral intrusion(type-A),sunspot merging(typeB)and umbral-dot emergence(type-C).The numbers of events in these three categories are 74,57 and 13,respectively.The duration of the LB formation process is mostly less than 40 hours,with an average of~20 hours.Most LBs have a maximum length of less than 20.For type-A LBs,we found a positive correlation between the LB length and the duration of the LB formation process,suggesting a similar speed of penumbral intrusion in different sunspots.展开更多
We report detailed observation of the“herringbone”of a Type II solar radio burst that occurred on 2010 November 3rd.Data from the Space Weather Prediction Center,National Oceanic and Atmospheric Administration,e-CAL...We report detailed observation of the“herringbone”of a Type II solar radio burst that occurred on 2010 November 3rd.Data from the Space Weather Prediction Center,National Oceanic and Atmospheric Administration,e-CALLISTO,and Nan?ay Radio Heliograph are analyzed.We determine the brightness temperature and degree of circular polarization of the“herringbone”burst.Correlations between the physical parameters and the“herringbone”are examined.Based on the relationship,this is the first study that suggested this“herringbone”was generated through fundamental plasma.展开更多
A combined uniform and long-time series of Ca-K images from the Kodaikanal Observatory,Mount Wilson Observatory and Mauna Loa Solar Observatory was used to identify and study the Ca-K small-scale features and their so...A combined uniform and long-time series of Ca-K images from the Kodaikanal Observatory,Mount Wilson Observatory and Mauna Loa Solar Observatory was used to identify and study the Ca-K small-scale features and their solar cycle variations over a century.The small scale features are classified into three distinct categories:enhanced network,active network and quiet network.All these features show that their areas vary according to the11 yr solar cycle.The relative amplitude of the Ca-K network variations agrees with that of the sunspot cycle.The total area of these small-scale features varies from about 5%during the minimum phase of the solar cycle to about20%during its maximum phase.展开更多
基金supported by the National Key Research and Development Program of China(grant No.2022YFF0503600)the National Natural Science Foundation of China(NSFC,grant No.42130202).
文摘Solar flares are one of the strongest outbursts of solar activity,posing a serious threat to Earth’s critical infrastructure,such as communications,navigation,power,and aviation.Therefore,it is essential to accurately predict solar flares in order to ensure the safety of human activities.Currently,the research focuses on two directions:first,identifying predictors with more physical information and higher prediction accuracy,and second,building flare prediction models that can effectively handle complex observational data.In terms of flare observability and predictability,this paper analyses multiple dimensions of solar flare observability and evaluates the potential of observational parameters in prediction.In flare prediction models,the paper focuses on data-driven models and physical models,with an emphasis on the advantages of deep learning techniques in dealing with complex and high-dimensional data.By reviewing existing traditional machine learning,deep learning,and fusion methods,the key roles of these techniques in improving prediction accuracy and efficiency are revealed.Regarding prevailing challenges,this study discusses the main challenges currently faced in solar flare prediction,such as the complexity of flare samples,the multimodality of observational data,and the interpretability of models.The conclusion summarizes these findings and proposes future research directions and potential technology advancement.
文摘Major solar plasma disturbances are subjected to Lomb-Scargle periodogram and wavelet analysis to determine the occurrence frequency.These disruptions include interplanetary coronal mass ejection,sudden storm commencement,high-speed streams,corotating interaction regions,interplanetary shocks and Forbush decreases.We included information on all of the aforementioned solar disturbances for the last six solar cycles,from 1965 to 2023,for this study.Our findings reveal some intriguing and noteworthy results that clearly distinguish between even and odd-numbered solar cycles.The study suggests that the Sun behaves differently in odd and even-numbered solar cycles as it comes from the massive solar eruptions.During even-numbered solar cycles,variations with a period of∼44 days are prominently observed in addition to solar rotation(∼27 days)and extended solar(∼36 days)rotation.However,in addition to solar rotation,prolonged solar rotation,and periods of around 44 days,we also detect a number of intermittent changes with nearly comparable amplitude during the oddnumbered solar cycles.The findings also demonstrate that,in contrast to odd-numbered solar cycles,the emissions rate of these disruptions is more distinct and predictable during even-numbered solar cycles.
基金supported by the National Key R&D Program of China 2021YFA1600503 and 2022YFF0503001the Strategic Priority Research Program of the Chinese Academy of Sciences XDB0560302+1 种基金the National Natural Science Foundation of China(NSFC,grant No.11973057)the International Partnership Program of Chinese Academy of Sciences 183311KYSB20200003。
文摘Solar activities have a great impact on modern high-tech systems,such as human aerospace activities,satellite communication and navigation,deep space exploration,and related scientific research.Therefore,studying the long-term evolution trend of solar activity and accurately predicting the future solar cycles are highly anticipated.Based on the wavelet transform and empirical function fitting of the longest recorded data of the annual average relative sunspot number(ASN)series of 323 yr to date,this work decisively verifies the existence of the solar century cycles and confirms that its length is about 104.0 yr,and the magnitude has a slightly increasing trend on the timescale of several hundred years.Based on this long-term evolutionary trend,we predict solar cycles 25 and26 by using phase similar prediction methods.As for solar cycle 25,its maximum ASN will be about146.7±33.40,obviously stronger than solar cycle 24.The peak year will occur approximately in 2024,and the period will be about 11±1 yr.As for solar cycle 26,it will start around 2030,and reach its maximum between2035 and 2036,with maximum ASN of about 133.0±3.200,and period of about 10 yr.
基金partially supported by the Institute of Eminence(Io E)Program(Scheme No:6031)of BHU,Varanasi。
文摘In this present study,we have analyzed different types of X-ray solar flares(C,M,and X classes)coming out from different classes of sunspot groups(SSGs).The data which we have taken under this study cover the duration of 24 yr from 1996 to 2019.During this,we observed a total of 15015 flares(8417 in SC-23 and 6598 in SC-24)emitted from a total of 33780 active regions(21746 in SC-23 and 12034 in SC-24)with sunspot only.We defined the flaring potential or flare-production potential as the ratio of the total number of flares produced from a particular type of SSG to the total number of the same-class SSGs observed on the solar surface.Here we studied yearly changes in the flaring potential of different McIntosh class groups of sunspots in different phases of SC-23 and 24.In addition,we investigated yearly variations in the potential of producing flares by different SSGs(A,B,C,D,E,F,and H)during different phases(ascending,maximum,descending,and minimum)of SC-23 and 24.These are our findings:(1)D,E,and F SSGs have the potential of producing flares≥8 times greater than A,B,C and H SSGs;(2)The larger and more complex D,E,and F SSGs produced nearly 80%of flares in SC-23 and 24;(3)The A,B,C and H SSGs,which are smaller and simpler,produced only 20%of flares in SC-23 and 24;(4)The biggest and most complex SSGs of F-class have flaring potential 1.996 and 3.443 per SSG in SC-23 and 24,respectively.(5)The potential for producing flares in each SSG is higher in SC-24 than in SC-23,although SC-24 is a weaker cycle than SC-23.(6)The alterations in the number of flares(C+M+X)show different time profiles than the alterations in sunspot numbers during SC-23 and 24,with several peaks.(7)The SSGs of C,D,E,and H-class have the highest flaring potential in the descending phase of both SC-23 and 24.(8)F-class SSGs have the highest flaring potential in the descending phase of SC-23 but also in the maximum phase of SC-24.
文摘The time series of daily data on solar activity proxies, namely the sunspot number(SSN), sunspot area(SSA), solar radio flux(F10.7), modified coronal index(MCI), solar flare index(FI), and cosmic ray intensity(CRI), were analyzed to understand the solar activity modulations and short-term periodicities therein. Rieger-type and other short-term periods include the solar rotational period that covers the maximum activity phase period(maximum phase of solar cycle 24). The wavelet power spectra and Periodogram of SSN, SSA, F10.7, MCI, FI, and CRI exhibited a significant short-term period. The heliospheric effects exist for a particular period(~27 days) and they are related to the solar activity phenomena. The cross-correlation coefficients and time lags between the CRI and solar activity parameters were estimated to be ~200, 46, 281, 39, and 47 days for SSN, SSA, F10.7, MCI, and FI respectively during the time series 2012–2015(maximum phase of solar cycle 24).
基金supported by National Key R&D Program of China Nos. 2022YFF0503800 and 2021YFA0718600the Strategic Priority Research Program of the Chinese Academy of Sciences (No. XDB0560000)+1 种基金National Natural Science Foundation of China (NSFC, Grant Nos. 12073032, 42274201, 42150105, and 42204176)the Specialized Research Fund for State Key Laboratories of China。
文摘An extreme ultraviolet(EUV) close-up view of the Sun offers unprecedented detail of heating events in the solar corona. Enhanced temporal and spatial images obtained by the Solar Orbiter during its first science perihelion enabled us to identify clustered EUV bright tadpoles(CEBTs) occurring near the footpoints of coronal loops.Combining SDO/AIA observations, we determine the altitudes of six distinct CEBTs by stereoscopy, ranging from ~1300 to 3300 km. We then notice a substantial presence of dark, cooler filamentary structures seemingly beneath the CEBTs, displaying periodic up-and-down motions lasting 3–5 minutes. This periodic behavior suggests an association of the majority of CEBTs with Type I spicules. Out of the ten selected CEBTs with fast downward velocity, six exhibit corrected velocities close to or exceeding 50 km s^(-1). These velocities notably surpass the typical speeds of Type I spicules. We explore the generation of such velocities. It indicates that due to the previous limited observations of spicules in the EUV wavelengths, they may reveal novel observational features beyond our current understanding. Gaining insights into these features contributes to a better comprehension of small-scale coronal heating dynamics.
基金funded by NSFC under Grant Nos.12073081,11973092 and 11790302CAS Strategic Pioneer Program on Space Science under Grant Nos.XDA15052200 and XDA15320301supported by Surface Project of Jiangsu No.BK20211402。
文摘We investigate the oscillations in active region(AR)NOAA 12891,which produces a C2.0 three-ribbon flare accompanying a jet on 2021 November 2.Using the data from the Atmospheric Imaging Assembly onboard the Solar Dynamics Observatory,the 5 minutes decayless kink oscillations of coronal loops were detected and they are independent of the solar flare.Based on the observed oscillations and seismological diagnostics,we estimate that the Alfvén speed and magnetic field in these coronal loops are around 466 kms^(-1) sand 7.6 G,respectively.Additionally,the flare-related jet shows its plasmoids with 1 minute periodicity same as the intensity fluctuation of nearby flare ribbon.The correlation between the intensity fluctuation of jet and that of flare ribbon indicates that their 1 minute oscillations should originate from the same reconnection process.
基金supported by the National Natural Science Foundation of China (41731067 and 41822404)Shenzhen Technology Project (JCYJ20170307150645407)+6 种基金the Fundamental Research Funds for the Central Universities (Grant No. HIT.BRETV.201901)the support by China Postdoctoral Science Foundation (2018M641812)support of the US NSF (AGS-1821294)the National Natural Science Foundation of China (11729301)supported by NJIT and US NSF AGS 1821294 grantpartly supported by the Korea Astronomy and Space Science Institute and Seoul National Universitythe strategic priority research program of Chinese Academy of Science (CAS) (Grant No. XDB09000000)
文摘We observed an Hα surge that occurred in NOAA Active Region 12401 on 2015 August 17, and we discuss its trigger mechanism, and kinematic and thermal properties. It is suggested that this surge was caused by a chromospheric reconnection which ejected cool and dense material with transverse velocity of about 21–28 km s-1 and initial Doppler velocity of 12 km s^-1. This surge is similar to the injection of newly formed filament materials from their footpoints, except that the surge here occurred in a relatively weak magnetic environment of 100 G. Thus, we discuss the possibility of filament material replenishment via the erupting mass in such a weak magnetic field, which is often associated with quiescent filaments. It is found that the local plasma can be heated up to about 1.3 times the original temperature, which results in an acceleration of about –0.017 km s^-2. It can lift the dense material up to 10 Mm and higher with an inclination angle smaller than 50°, namely the typical height of active region filaments, but it can hardly inject the material up to those filaments higher than 25 Mm, like some quiescent filaments. Thus, we think that the injection model does not work well in describing the formation of quiescent filaments.
基金Supported by the National Natural Science Foundation of China (Grants Nos. 10833007,10933003 and 10928307)the National Basic Research Program of China (973 Program) under grant 2011CB811402
文摘With an extensive analysis,we study the temporal evolution of magnetic flux during three successive M-class flares in two adjacent active regions：NOAA 10039 and 10044.The primary data are full disk longitudinal magnetograms observed by SOHO/MDI.All three flares are observed to be accompanied by magnetic flux changes.The changes occurred immediately or within 1 ～ 10 minutes after the starting time of the flares,indicating that the changes are obvious consequences of the solar flares.Although changes in many points are intrinsic in magnetic flux,for some sites,it is caused by a rapid expansion motion of magnetic flux.For the second flare,the associated change is more gradual compared with the ＇step-function＇ reported in literature.Furthermore,we use the data observed by the Imaging Vector Magnetograph（IVM） at Mees Solar Observatory to check possible line profile changes during the flares.The results from the IVM data confirm the flux changes obtained from the MDI data.A series of line profiles were obtained from the IVM＇s observations and analyzed for flux change sites.We find that the fluctuations in the width,depth and central wavelength of the lines are less than 5.0 even at the flare＇s core.No line profile change is observed during or after the flare.We conclude that the magnetic field changes associated with the three solar flares are not caused by flare emission.
文摘We have obtained 2D spectra of Ha and CaII λ8542A for the flare of 1998 November 11, and derived its 2D velocity field and integrated intensity field. The velocity distribution shows that the red-shift and blue-shift velocities lie respectively in the northern and southern parts of the flare and that the maximum velocity seems to be located in two footpoints of the flare loop system. The integrated intensity distribution shows that the CaIIλ8542A line is formed at a lower height than the Ha line, we used 'multi-cloud model' (MCM) to obtain four parameters for the two lines (Doppler width, △λD, Doppler shift, △λ0, line source function, S, and optical depth at the line center, TO). We also estimated the column number densities of hydrogen at the second level, N2, and of the ionized calcium at the third level, N3, as well as the kinetic temperature, Tc. The wide Hα profile at the loop top may be explained by an overlapping of two or more elementary profiles. It is shown that the uncertainty in calibration does not affect the derived Doppler shift and line broadening, only the source function and optical depth.
基金supported by the National Natural Science Foundation of China(NSFC,Grant Nos.12173076,42174195,11873018 and 41531071)by Lishui University Initial Funding under grant QD2182by NSF of Jiangsu Province under grant BK20191513。
文摘Fast electron beams(FEBs) are one of the main products of various active events and are ubiquitous in solar,space and cosmic plasmas.They reveal themselves in hard X-ray and radio emissions.The observed characteristics of X-ray and radio emissions sensitively depend on the energy distribution of FEBs,which usually have a power-law energy spectrum.As FEBs travel in the solar atmosphere,their energy distribution can considerably vary due to the interaction with ambient plasmas.Tang et al.investigated the evolution of the energy spectrum of the FEBs traveling along a flare loop and discussed the possible effects on associated hard X-ray(HXR) and radio emissions.Considering the ubiquitous coronal loops in active regions,in the present paper,we investigate the parametric evolution of the energy spectra of FEBs when propagating along coronal loops.Here,we take the sunpot atmospheric model as an approximate coronal loop atmosphere model.The results show that the energy loss has an important impact on the cutoff behavior and energy spectra of FEBs when precipitating in a coronal loop with density ratio n_(b)/n_(e)= 0.01.The initially single power-law spectrum with a steepness cutoff can evolve into a more complex double power-law spectrum or two “knees” power-law spectrum with a flattened steepness cutoff behavior or saturation cutoff behavior.Our calculations also demonstrate that the energy spectrum evolution is not obvious if n_(b)/n_(0)= 0.001 as Tang et al.asserted.The present results are helpful for a more comprehensive understanding of the dynamic spectra of HXR and radio emissions from FEBs.
基金supported by the National Key R&D Program of China No.2022YFF0503804the Strategic Priority Research Programme of the Chinese Academy of Sciences with grant XDA17040507+1 种基金the National Natural Science Foundation of China (NSFC) grant 11 933 009grants associated with the Yunling Scholar Project of Yunnan Province,the Yunnan Province Scientist Workshop of Solar Physics.
文摘Following our previous work,we studied the partial eruption of a large-scale horse-shoe-like filament that had beenobserved in a decaying active region on the solar disk for more than 4.5 days.The filament became active after itwas broken into two pieces,P1 and P2 seen in Hα,by magnetic reconnection between the magnetic field around itand that of a newly emerging active region nearby.P1 eventually erupted 13 hr after the breaking and escaped fromthe Sun,developing to a fast coronal mass ejection,and P2 stayed.But the mass in P1 falling down to P2 in theeruption suggests that the global magnetic fields over P1 and P2 were still connected to each other prior to theeruption.The reconnection process breaking the filament occurred outside the filament,and P1 and P2 were locatedalmost at the same altitude,so the fashion of the filament partial eruption studied here differs from that of the“double-decker model”and that of reconnection inside the filament.Analyzing the decay indices of thebackground fields above P1 and P2,n_(1)and n_(2),showed that the altitude where n_(1)exceeds the critical value of n_(c)=1.5 for the loss of equilibrium or the torus instability is lower than that where n_(2)>nc,and that n_(1)>n_(2) alwaysholds at all altitudes.Combining this fact with that the eruption occurred 13 hr after filament was broken byreconnection,we conclude that the eruption of P1 was triggered by the loss of equilibrium or the torus instability inthe configuration,and magnetic reconnection breaking the filament helped weaken the confinement of thebackground field on P1,allowing P1 to erupt.Detailed features of the eruption and the corresponding physicalscenario were also discussed.
基金supported by the National Natural Science Foundation of China(Grant Nos.11803002,11825301 and 11790304)the Strategic Priority Research Program of Chinese Academy of Sciences(XDA17040507)。
文摘Light bridges(LBs)are bright lanes that divide one sunspot umbra into two or more parts.Though frequently observed in sunspots,their formation mechanisms have rarely been studied and thus are not well understood.Here we present results from the first statistical investigation on the formation of LBs.Using observations with the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory,we identified 144 LBs within 71 active regions(ARs)over the whole year of 2014.The formation processes of these LBs can be categorized into three groups:penumbral intrusion(type-A),sunspot merging(typeB)and umbral-dot emergence(type-C).The numbers of events in these three categories are 74,57 and 13,respectively.The duration of the LB formation process is mostly less than 40 hours,with an average of~20 hours.Most LBs have a maximum length of less than 20.For type-A LBs,we found a positive correlation between the LB length and the duration of the LB formation process,suggesting a similar speed of penumbral intrusion in different sunspots.
基金the Faculty of Science,University of Malaya(grant No.GPF081-2020)for their funding。
文摘We report detailed observation of the“herringbone”of a Type II solar radio burst that occurred on 2010 November 3rd.Data from the Space Weather Prediction Center,National Oceanic and Atmospheric Administration,e-CALLISTO,and Nan?ay Radio Heliograph are analyzed.We determine the brightness temperature and degree of circular polarization of the“herringbone”burst.Correlations between the physical parameters and the“herringbone”are examined.Based on the relationship,this is the first study that suggested this“herringbone”was generated through fundamental plasma.
基金supported by the International Space Science Institute (ISSI),Bern,Switzerland and ISSI-Beijing,China。
文摘A combined uniform and long-time series of Ca-K images from the Kodaikanal Observatory,Mount Wilson Observatory and Mauna Loa Solar Observatory was used to identify and study the Ca-K small-scale features and their solar cycle variations over a century.The small scale features are classified into three distinct categories:enhanced network,active network and quiet network.All these features show that their areas vary according to the11 yr solar cycle.The relative amplitude of the Ca-K network variations agrees with that of the sunspot cycle.The total area of these small-scale features varies from about 5%during the minimum phase of the solar cycle to about20%during its maximum phase.
