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
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
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(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.
