scholarly journals Discovering the Low-Latitude Ionospheric Trough Associated With the Inner Radiation Belt

2021 ◽  
Author(s):  
Alexander Karpachev
Keyword(s):  
Geomagnetic Storm ◽  
Radiation Belt ◽  
Ring Current ◽  
Recovery Phase ◽  
Low Latitude ◽  
Champ Satellite ◽  
Main Ionospheric Trough ◽  
Long Time ◽  
Late Recovery ◽  
First Time

Abstract The dynamics of ionospheric troughs during great geomagnetic storm on April 11–13, 2001 is considered. An analysis is based on measurements of electron density at altitudes of the CHAMP satellite 410–465 km. The subauroral, mid-latitude and low-latitude troughs were observed at nighttime, sometimes simultaneously. The subauroral trough is usually defined as the main ionospheric trough. The mid-latitude trough is associated with the magnetospheric ring current. It appears at the beginning of the storm recovery phase at latitudes of 40–45° GMLat (L=1.7–2.0) and exists for a long time at the late recovery phase at latitudes of the residual ring current 50–55° GMLat (L~2.4–3.0). The low-latitude trough was revealed for the first time. It is developed at the latitudes of the inner radiation belt 34–45° GMLat (L=1.45–2.00). This trough is associated with the precipitation of energetic particles from the inner radiation belt.

scholarly journals Discovery of a low-latitude ionospheric trough associated with the inner radiation belt

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
A. T. Karpachev
Keyword(s):  
Geomagnetic Storm ◽  
Radiation Belt ◽  
Ring Current ◽  
Recovery Phase ◽  
Low Latitude ◽  
Champ Satellite ◽  
Long Period ◽  
Main Ionospheric Trough ◽  
Late Recovery ◽  
First Time

AbstractThe dynamics of ionospheric troughs that developed during a great geomagnetic storm on 11–13 April 2001 are studied using measurements of electron density obtained by the CHAMP satellite at an altitude of 410–465 km. Subauroral, mid-latitude and low-latitude troughs were observed at nighttime, sometimes simultaneously. The subauroral trough is usually defined as the main ionospheric trough, whereas the mid-latitude trough is associated with the magnetospheric ring current. It appeared at the beginning of the storm recovery phase around latitudes of 40°–45° GMLat (L = 1.7–2.0) and existed for a long period of time throughout the late recovery phase of the residual ring current at latitudes of 50°–55° GMLat (L ~ 2.4–3.0). For the first time, a low-latitude trough was revealed. It developed at latitudes of 34°–45° GMLat (L = 1.45–2.00) in association with the precipitation of energetic particles from the inner radiation belt.

scholarly journals Sub-Auroral, Mid-Latitude, and Low-Latitude Troughs during Severe Geomagnetic Storms

2021 ◽  
Vol 13 (3) ◽  
pp. 534
Author(s):  
Alexander Karpachev
Keyword(s):  
Radiation Belt ◽  
Ring Current ◽  
Geomagnetic Storms ◽  
Recovery Phase ◽  
Internal Radiation ◽  
Low Latitude ◽  
Champ Satellite ◽  
Main Ionospheric Trough ◽  
Long Time ◽  
First Time

The dynamics of ionospheric troughs during intense geomagnetic storms is considered in this paper. The study is based on electron density measurements at CHAMP satellite altitudes of 405–465 km in the period from 2000 to 2002. A detailed analysis of four storms with Kp from 5+ to 9− is presented. Three troughs were identified: sub-auroral, mid-latitude, and low-latitude. The sub-auroral trough is usually defined as the main ionospheric trough (MIT). The mid-latitude trough is observed equatorward of the MIT and is associated with the magnetospheric ring current; therefore, it is named the ring ionospheric trough (RIT). The RIT appears at the beginning of the storm recovery phase at geomagnetic latitudes of 40–45° GMLat (L = 1.75–2.0) and exists, for a long time, at the late stage of the recovery phase at latitudes of the residual ring current 50–55° GMLat (L ~ 2.5–3.0). The low-latitude trough (LLT) is discovered for the first time. It forms only during great storms at the latitudes of the internal radiation belt (IRB), 34–45° GMLat (L = 1.45–2.0). The LLT’s lowest latitude of 34° GMLat was recorded in the night sector (2–3 LT). The occurrence probability and position of the RIT and LLT depend on the hemisphere and longitude.

PROBLEMS OF THE OUTER RADIATION BELT FORMATION AND TOPOLOGICAL FEATURES OF HIGH LATITUDE MAGNETOSPHERE

2021 ◽  
Vol 44 ◽  
pp. 7-11
Author(s):  
Elena Antonova ◽  
Keyword(s):  
Geomagnetic Storm ◽  
High Latitude ◽  
Radiation Belt ◽  
Ring Current ◽  
Outer Part ◽  
Auroral Oval ◽  
Plasma Pressure ◽  
Relativistic Electrons ◽  
Outer Radiation Belt ◽  
Topological Features

We analyzed the problems of formation of the outer radiation belt (ORB) taking into consideration the latest changes in our understanding of the high-latitude magnetospheric topology. This includes strong evidence that the auroral oval maps to the outer part of the ring current, meanwhile the ORB polar boundary maps inside the auroral oval. Our analysis also includes the variation of the plasma pressure distribution and the time of the acceleration of relativistic electrons during geomagnetic storm. It is shown that the maximum of ORB is formed after the geomagnetic storm in the region of plasma pressure maximum. The position of this maximum agrees with the prediction of the ORB formation theory based on the analysis of ring current development during storm. We emphasize the role of adiabatic processes in the ORB dynamics and the importance of the substorm injections during storm recovery phase for the formation of enhanced fluxes of ORB electrons after the storm.

The dynamics of the inner boundary of the outer radiation belt during geomagnetic storms

2020 ◽  
Author(s):  
Xiaofei Shi ◽  
Jie Ren ◽  
Qiugang Zong
Keyword(s):  
Radiation Belt ◽  
Electron Flux ◽  
Geomagnetic Storms ◽  
Minimum Energy ◽  
Onset Time ◽  
Recovery Phase ◽  
Outer Radiation Belt ◽  
H Index ◽  
Late Recovery ◽  
Energy Dependent

<p>We present a statistical study of energy-dependent and L shell-dependent inner boundary of the outer radiation belt during 37 isolated geomagnetic storms using observations from Van Allen Probes from 2013 to 2017. There are mutual transformations between "V-shaped" and "S-shaped" inner boundaries during different storm phases, resulting from the competition among electron loss, radial transport and local acceleration. The radial position, onset time, E<sub>st</sub> (the minimum energy at L<sub>st</sub> where the inner boundary starts to exhibit an S-shaped form), and the radial width of S-shaped boundary (ΔL) are quantitatively defined according to the formation of a reversed energy spectrum (electron flux going up with increasing energies from hundreds of keV to ~1 MeV) from a kappa-like spectrum (electron flux steeply falling with increasing energies). The case and statistical results present that (1) The inner boundary has repeatable features associated with storms: the inner boundary is transformed from S-shaped to V-shaped form in several hours during the storm commencement and main phase, and retains in the V-shaped form for several days until it evolves into S-shaped during late recovery phase; (2) ΔL shows positive correlation with SYM-H index; (3) The duration of the V-shaped form is positively correlated with the storm intensity and the duration of the recovery phase; (4) The minimum energy E<sub>st</sub> are mainly distributed in the range of 100-550 keV. All these findings have important implications for understanding the dynamics of energetic electrons in the slot region and the outer radiation belt during geomagnetic storms.</p>

scholarly journals Statistical properties of substorms during different storm and solar cycle phases

2013 ◽  
Vol 31 (2) ◽  
pp. 349-358 ◽  
Author(s):  
N. Partamies ◽  
L. Juusola ◽  
E. Tanskanen ◽  
K. Kauristie
Keyword(s):  
Ring Current ◽  
Solar Maximum ◽  
Recovery Phase ◽  
Growth Phases ◽  
Single Cycle ◽  
Phase Duration ◽  
Automated Recognition ◽  
Long Time ◽  
Storms And Substorms ◽  
Average Behaviour

Abstract. Substorm properties during different storm phases have been studied using an automated recognition of substorm and storm phases in the auroral electrojet (AL) and ring current (Dst) index data from 1995–2009. The large number of events (about 500 storms and 15 000 substorms) provides statistically reliable distributions, average behaviour and long time series of simple parameters, such as durations and intensities. The phases of storms and substorms have been examined independently. Substorm phases have been further combined to single and multi-cycle events. The former consist of one growth, one expansion and one recovery phase, while the latter include multiple expansion and recovery phases after one growth phase. Our findings show that most substorms take place during non-storm times, and substorms during storm initial phases resemble isolated non-storm time substorms. Both during storm initial phases and non-storm times, the substorm growth phases may last longer than the other substorm phases. Substorm recovery phase is typically the longest phase but its duration also varies most. The longest substorm recovery phase duration was observed during multi-cycle substorms. The longest substorm expansion and storm main phases were found during the years close to the solar maximum. The shortest substorm events (the shortest phase durations) are the single-cycle substorms. The period of expansion onsets during multi-cycle substorms varied hugely for events with a small number of expansion phases. For events with a larger number of expansions, a clearer periodicity of about one hour (median value) was suggested.

Evolution of the low-latitude geomagnetic storm field and the importance of turbulent diffusion for ring current particle losses

1996 ◽  
Vol 101 (A11) ◽  
pp. 24689-24706 ◽  
Author(s):  
A. Grafe ◽  
V. Y. Trakhtengerts ◽  
P. A. Bespalov ◽  
A. G. Demekhov
Keyword(s):  
Geomagnetic Storm ◽  
Turbulent Diffusion ◽  
Ring Current ◽  
Low Latitude

scholarly journals PENGARUH ORIENTASI MEDAN MAGNET ANTARPLANET PADA GANGGUAN GEOMAGNET DI LINTANG RENDAH

2016 ◽  
Vol 13 (2) ◽  
pp. 73
Author(s):  
Anton Winarko ◽  
Anwar Santoso
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Interplanetary Magnetic Field ◽  
Geomagnetic Storm ◽  
Interplanetary Space ◽  
Recovery Phase ◽  
Geomagnetic Disturbance ◽  
Wind Condition ◽  
Low Latitude ◽  
Sudden Impulse

Interplanetary Magnetic Field (IMF) is a part of the Solar magnetic field that is carried into interplanetary space by the solar wind. Based on previous study it is known that solar wind condition when reconnection occurs has important role on geomagnetic disturbance. This paper discusses low-latitude geomagnetic field responses to various condition of reconnection, i.e. when north-south component of Interplanetary Magnetic Field (IMF Bz) was south-directed (<0) in long duration, IMF Bz switch to opposite direction after reconnection, and neutral IMF Bz (~0). Case studies show that precondition which IMF Bz<0 prompt more intense geomagnetic storm compared to IMF Bz ~0. At low latitude, precondition of IMF Bz <0 tend to trigger disturbance in the form of geomagnetic storm, while the IMF Bz~0 one could trigger Sudden Impulse. Change of IMF Bz direction after reconnection affected recovery phase acceleration, that was on IMF Bz>0, recovery phase  took less time compared to IMF Bz<0. AbstrakMedan magnet antarplanet (Interplanetary Magnetic Field/IMF) adalah medan magnet matahari yang dibawa oleh angin surya dan menjalar dalam ruang antarplanet. Berdasarkan studi sebelumnya diketahui bahwa kondisi angin surya saat terjadi rekoneksi amat berpengaruh terhadap gangguan geomagnet yang terjadi. Pada makalah ini dibahas respons medan geomagnet di lintang rendah pada berbagai kondisi rekoneksi yaitu pada saat komponen utara-selatan medan magnet antarplanet (IMF Bz) dominan selatan (IMF Bz<0) dalam durasi panjang, IMF Bz berbalik arah setelah rekoneksi, dan  IMF Bz cenderung netral (IMF Bz~0). Dari studi kasus menunjukkan bahwa prakondisi IMF Bz <0 mengakibatkan badai geomagnet yang lebih intens dibandingkan IMF Bz~0. Di lintang rendah, prakondisi IMF Bz<0 cenderung mengakibatkan gangguan berupa badai geomagnet sedangkan IMF Bz~0 dapat memicu Sudden Impulse. Perubahan arah IMF Bz yang terjadi setelah rekoneksi mempengaruhi laju fase pemulihan (recovery phase), yaitu pada IMF Bz>0, fase pemulihannya cenderung berlangsung lebih cepat dibandingkan saat IMF Bz<0.

scholarly journals Are our ideas about <i>Dst</i> correct?

1999 ◽  
Vol 17 (1) ◽  
pp. 1-10 ◽  
Author(s):  
A. Grafe
Keyword(s):  
Geomagnetic Field ◽  
Ring Current ◽  
Recovery Phase ◽  
Main Phase ◽  
Local Times ◽  
Moderate Intensity ◽  
Start Time ◽  
Low Latitude ◽  
Magnetospheric Configuration And Dynamics ◽  
Phase Asymmetry

Abstract. The idea of two separate storm time ring currents, a symmetric and an asymmetric one has accepted since the 1960s. The existence of a symmetric equatorial ring current was concluded from Dst. However, the asymmetric development of the low-latitude geomagnetic disturbance field during storms lead to the assumption of the real existence of an asymmetric ring current. I think it is time to inquire whether this conception is correct. Thus, I have investigated the development of the low-latitude geomagnetic field during all the magnetic local times under disturbed and quiet conditions. The storm on February 6–9, 1986 and a statistical analysis of many storms has shown that the asymmetry does not vanish during the storm recovery phase. The ratio between the recovery phase asymmetry and the main phase asymmetry is low only for powerful storms. Storms of moderate intensity show the opposite. The global picture of the field evolution of the February storm shows clear differences at different local times. For instance the main phase and recovery phase start time does not coincide with Dst. Also the ring current decay is not the same at different local times. Therefore, Dst gives an incorrect picture of the field development. Moreover, asymmetry does not disappear during international quiet days as the investigation of the low-latitude geomagnetic field shows. Considering all these observations, I think we must revise our ideas about the ring current. In my opinion only one ring current exists and this is an asymmetric one. This asymmetry increases during storms and develops rather fast to more or less symmetric conditions. However, in no case is it justified to conclude from Dst that a symmetric ring current exists.Key words. Magnetospheric physics (current systems; magnetospheric configuration and dynamics; storms and substorms)

Chorus acceleration of relativistic electrons in extremely low L-shell during geomagnetic storm

2020 ◽  
Author(s):  
Zhenxia Zhang ◽  
Lunjin Chen ◽  
Si Liu ◽  
Ying Xiong ◽  
Xinqiao Li ◽  
...  
Keyword(s):  
Geomagnetic Storm ◽  
Radiation Belt ◽  
Electron Acceleration ◽  
Acceleration Process ◽  
Relativistic Electrons ◽  
Chorus Waves ◽  
Van Allen Probes ◽  
New Finding ◽  
First Time ◽  
Shell Region

&lt;p&gt;Based on data from the Van Allen Probes and ZH-1 satellites, relativistic electron enhancements in extremely low L-shell Regions (reaching L~3) were observed during major geomagnetic storm (minimum Dst`-190 nT). &amp;#160;Contrary to what occurs in the outer belt, such an intense and deep electron penetration event is rare and more interesting. Strong whistler-mode (chorus and hiss) waves, with amplitudes 81-126 pT, were also observed in the extremely low L-shell simultaneously (reaching L~2.5) where the plasmapause was suppressed. The bounce-averaged diffusion coefficient calculations support that the chorus waves can play a significantly important role in diffusing and accelerating the 1-3 MeV electrons even in such low L-shells during storms. This is the first time that the electron acceleration induced by chorus waves in the extremely low L-shell region is reported. This new finding will help to deeply understand the electron acceleration process in radiation belt physics.&lt;/p&gt;

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