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.

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.

ULF waves and their influence on radiation belt dynamics in Earth's magnetosphere

2020 ◽  
Author(s):  
Robert Rankin ◽  
Alexander Degeling
Keyword(s):  
Radiation Belt ◽  
Geomagnetic Storms ◽  
Low Frequency ◽  
Recovery Phase ◽  
Ulf Waves ◽  
Wave Source ◽  
Initial Plasma ◽  
Plasma State ◽  
Van Allen Probes ◽  
Geomagnetic Fields

<p>Recent observations from the Van Allen Probes mission have established that Pc3-5 ultra-low-frequency (ULF) waves can energize ions and electrons via drift-resonance and drift-bounce resonance. The extent to which these waves contribute to the space weather of the belts is relatively poorly understood and requires sophisticated modelling and characterization of the dominant wave modes that arise in the development and recovery phase of geomagnetic storms. Despite more than four decades of observations and theoretical analysis of ULF waves, there is no framework for accurately assessing the global distribution of ULF waves and their influence on the ring current. <br>In this presentation, we describe a new global model of ULF waves that incorporates non-dipolar geomagnetic fields. The model is constrained using the GCPM of cold plasma density model and a specification of the ionosphere using the IRI and MSIS models. An algorithm is applied to adjust the initial plasma state to a quasi-static equilibrium that is then driven by a global convection electric field and ULF wave source. For specific observations by the Van Allen Probes and ARASE mission, the effect of these ULF waves on radiation belt ions and electrons is evaluated utilizing test-particle methodology and Liouville's theorem, which enables the phase space density to be followed and compared one-for-one with the satellite observations.  </p>

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 The HIA instrument on board the Tan Ce 1 Double Star near-equatorial spacecraft and its first results

2005 ◽  
Vol 23 (8) ◽  
pp. 2757-2774 ◽  
Author(s):  
H. Rème ◽  
I. Dandouras ◽  
C. Aoustin ◽  
J. M. Bosqued ◽  
J. A. Sauvaud ◽  
...  
Keyword(s):  
Solar Wind ◽  
Ring Current ◽  
Geomagnetic Storms ◽  
Distribution Functions ◽  
Double Star ◽  
Magnetospheric Substorms ◽  
Scientific Cooperation ◽  
Low Latitude ◽  
First Results ◽  
Academy Of Sciences

Abstract. On 29 December 2003, the Chinese spacecraft Tan Ce 1 (TC-1), the first component of the Double Star mission, was successfully launched within a low-latitude eccentric orbit. In the framework of the scientific cooperation between the Academy of Sciences of China and ESA, several European instruments, identical to those developed for the Cluster spacecraft, were installed on board this spacecraft. The HIA (Hot Ion Analyzer) instrument on board the TC-1 spacecraft is an ion spectrometer nearly identical to the HIA sensor of the CIS instrument on board the 4 Cluster spacecraft. This instrument has been specially adapted for TC-1. It measures the 3-D distribution functions of the ions between 5 eV/q and 32 keV/q without mass discrimination. TC-1 is like a fifth Cluster spacecraft to study the interaction of the solar wind with the magnetosphere and to study geomagnetic storms and magnetospheric substorms in the near equatorial plane. HIA was commissioned in February 2004. Due to the 2 RE higher apogee than expected, some in-flight improvements were needed in order to use HIA in the solar wind in the initial phase of the mission. Since this period HIA has obtained very good measurements in the solar wind, the magnetosheath, the dayside and nightside plasma sheet, the ring current and the radiation belts. We present here the first results in the different regions of the magnetosphere and in the solar wind. Some of them are very new and include, for example, ion dispersion structures in the bow shock and ion beams close to the magnetopause. The huge interest in the orbit of TC-1 is strongly demonstrated.

scholarly journals Predicting geomagnetic storms from solar-wind data using time-delay neural networks

1996 ◽  
Vol 14 (7) ◽  
pp. 679-686 ◽  
Author(s):  
H. Gleisner ◽  
H. Lundstedt ◽  
P. Wintoft
Keyword(s):  
Neural Networks ◽  
Solar Wind ◽  
Time Delay ◽  
Input Data ◽  
Ring Current ◽  
Geomagnetic Storms ◽  
Time History ◽  
Recovery Phase ◽  
Wind Data ◽  
Data Sequence

Abstract. We have used time-delay feed-forward neural networks to compute the geomagnetic-activity index Dst one hour ahead from a temporal sequence of solar-wind data. The input data include solar-wind density n, velocity V and the southward component Bz of the interplanetary magnetic field. Dst is not included in the input data. The networks implement an explicit functional relationship between the solar wind and the geomagnetic disturbance, including both direct and time-delayed non-linear relations. In this study we especially consider the influence of varying the temporal size of the input-data sequence. The networks are trained on data covering 6600 h, and tested on data covering 2100 h. It is found that the initial and main phases of geomagnetic storms are well predicted, almost independent of the length of the input-data sequence. However, to predict the recovery phase, we have to use up to 20 h of solar-wind input data. The recovery phase is mainly governed by the ring-current loss processes, and is very much dependent on the ring-current history, and thus also the solar-wind history. With due consideration of the time history when optimizing the networks, we can reproduce 84% of the Dst variance.

The Plasmasphere During Major Geomagnetic Storms: Analysis Of Trapped Particles In The Outer Radiation Belt

2020 ◽  
Author(s):  
Jessy Matar ◽  
Benoit Hubert ◽  
Stan Cowley ◽  
Steve Milan ◽  
Zhonghua Yao ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Electric Field ◽  
Geomagnetic Field ◽  
Radiation Belt ◽  
Ring Current ◽  
Geomagnetic Storms ◽  
Outer Radiation Belt ◽  
Trapped Particles ◽  
The Earth ◽  
Field Lines

<p> The coupling between the Earth’s magnetic field and the interplanetary magnetic field (IMF) transported by the solar wind results in a cycle of magnetic field lines opening and closing generally known as the Dungey substorm cycle, mostly governed by the process of magnetic reconnection. The geomagnetic field lines can therefore have either a closed or an open topology, i.e. lower latitude field lines are closed (map from southern ionosphere to the northern), while higher latitude field lines are open (map from one polar ionosphere into interplanetary space). Closed field lines can trap electrically charged particles that bounce between mirror points located in the North and South hemispheres while drifting in longitude around the Earth, forming the plasmasphere, the radiation belts and the ring current. The outer boundary of the plasmasphere is the plasmapause. Its location is mostly driven by the interplay of the corotation electric field of ionospheric origin, and the convection electric field that results from the interaction between the IMF and the geomagnetic field. At times of prolonged intense coupling between these fields, the response of the magnetosphere becomes global and a geomagnetic storm develops. The ring current created by the motion of the trapped energetic particles intensifies and then decays as the storm abates. This study aims to find a possible relationship between the evolution of the trapped population and the process of magnetic reconnection during storm times. The EUV instrument on board the NASA-IMAGE spacecraft observed the distribution of the trapped helium ions (He+) in the plasmasphere. We consider several cases of intense geomagnetic storms observed by the IMAGE satellite. We identify the plasmapause location (Lpp) during those cases. We find a strong correlation between the Dst index and Lpp. The ring current and the trapped particles are expected to vary during storms. We use the Tsyganenko magnetic field model to map the electric potential between the Heppner-Maynard boundary (HMB) in the ionosphere and the magnetosphere and estimate the voltage and electric field in the vicinity of the plasmapause. The ionospheric electric field is deduced from the ionospheric convection velocity measured by the SuperDARN (SD) radar network at high latitudes. The tangential electric field component of the moving plasmapause boundary is estimated from IMAGE-EUV observations of the plasmasphere and is compared with expectations based on the SD data. We combine measurements of the trapped population from IMAGE-EUV and IMAGE-FUV observations of the aurora to better understand and quantify the variability of the Earth's outer radiation belt during strong storms. The auroral precipitation at ionospheric latitude is studied using FUV imaging and compared to the He+ response during the storms.</p>

scholarly journals Relationships between the AE, ap and Dst indices near solar minimum (1974) and at solar maximum (1979)

1997 ◽  
Vol 15 (10) ◽  
pp. 1265-1270 ◽  
Author(s):  
M. M. Fares Saba ◽  
W. D. Gonzalez ◽  
A. L. Clúa de Gonzalez
Keyword(s):  
Seasonal Variation ◽  
Solar Minimum ◽  
Ring Current ◽  
Geomagnetic Storms ◽  
Solar Maximum ◽  
Correlation Coefficients ◽  
The Sun ◽  
Yearly Average ◽  
First Time ◽  
Activity Indices

Abstract. Three-hourly average values of the Dst, AE and ap geomagnetic activity indices have been studied for 1 year's duration near the solar minimum (1974) and also at the solar maximum (1979). In 1979 seven intense geomagnetic storms (Dst <–100 nT) occurred, whereas in 1974 only three were reported. This study reveals: (1) the yearly average of AE is greater in 1974 than in 1979, whereas the inverse seems to be true for the yearly average of Dst, when a higher number of intense storms is present. These averages indicate the kind of activity occurring on the sun as shown in earlier work. (2) The seasonal variation of Dst is higher than that of ap and is almost negligible in AE. (3) The correlation coefficient of ap × AE is in general the highest, as the magnetometers that monitor both indices are close, and is surpassed only by the ap × Dst correlation during geomagnetic storms, when the influence of the ring current is dominant. The correlation of ap × Dst also shows a seasonal variability. (4) For the first time a study of correlation between ap and a linear combination of AE and Dst has also been made. We found higher correlation coefficients in this case as compared to those between ap × Dst and ap × AE.

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