Storm-time ionization enhancements at the topside low-latitude ionosphere

Abstract. Ion density enhancements at the topside low-latitude ionosphere during a Bastille storm on 15–16 July 2000 and Halloween storms on 29–31 October 2003 were studied using data from ROCSAT-1/IPEI experiment. Prominent ion density enhancements demonstrate similar temporal dynamics both in the sunlit and in the nightside hemispheres. The ion density increases dramatically (up to two orders of magnitude) during the main phase of the geomagnetic storms and reaches peak values at the storm maximum. The density enhancements are mostly localized in the region of a South Atlantic Anomaly (SAA), which is characterized by very intense fluxes of energetic particles. The dynamics of near-Earth radiation was studied using SAMPEX/LEICA data on >0.6 MeV electrons and >0.8 MeV protons at around 600 km altitude. During the magnetic storms the energetic particle fluxes in the SAA region and in its vicinity increase more than three orders of magnitude. The location of increased fluxes overlaps well with the regions of ion density enhancements. Two mechanisms were considered to be responsible for the generation of storm-time ion density enhancements: prompt penetration of the interplanetary electric field and abundant ionization of the ionosphere by enhanced precipitation of energetic particles from the radiation belt.

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The impact of intense fluxes of energetic protons on the low-latitude ionosphere

E3S Web of Conferences ◽

10.1051/e3sconf/202019601011 ◽

2020 ◽

Vol 196 ◽

pp. 01011

Author(s):

Alla Suvorova ◽

Alexei Dmitriev

Keyword(s):

Radiation Belt ◽

Energetic Particles ◽

Low Earth Orbit ◽

Ion Concentration ◽

Low Latitude ◽

Simultaneous Observation ◽

Low Earth Orbit Satellites ◽

Low Latitude Ionosphere ◽

The Impact ◽

Earth’S Radiation Belt

Experiments on board low-Earth orbit satellites show that energetic particles (tens of keV) of the Earth’s radiation belt can penetrate to the equatorial ionosphere. Impact of the energetic particles on the upper atmosphere and ionosphere was studied for the case of the geomagnetic storm on 22 July 2009. We present changes of local ion concentration in the low-latitude ionosphere at night measured by the C/NOFS satellite at heights 400-800 km during the magnetic storm and quiet days. The ionospheric density during the storm was compared with a simultaneous observation of enhancements of 30-80 keV proton fluxes measured by the NOAA/POES satellites near the equator at height ~850 km. We suggest that ionospheric irregularities at night can be caused by effect of energetic protons.

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Changes in the longitudinal structure of the low-latitude ionosphere during the July 2004 sequence of geomagnetic storms

Journal of Geophysical Research Atmospheres ◽

10.1029/2008ja013539 ◽

2008 ◽

Vol 113 (A11) ◽

pp. n/a-n/a ◽

Cited By ~ 9

Author(s):

N. M. Pedatella ◽

J. M. Forbes ◽

J. Lei ◽

J. P. Thayer ◽

K. M. Larson

Keyword(s):

Geomagnetic Storms ◽

Low Latitude ◽

Longitudinal Structure ◽

Low Latitude Ionosphere

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How Coherent are Flux Variations in the Outer Van Allen Radiation Belt?

10.5194/egusphere-egu2020-20204 ◽

2020 ◽

Author(s):

Samuel Walton ◽

Colin Forsyth ◽

Iain Jonathan Rae ◽

Clare Watt ◽

Richard Horne ◽

...

Keyword(s):

Geomagnetic Activity ◽

Radiation Belt ◽

Geomagnetic Storms ◽

Outer Boundary ◽

Radial Distance ◽

Radiation Belts ◽

Outer Radiation Belt ◽

Electron Population ◽

Storms And Substorms ◽

Using Data

The electron population inside Earth&#8217;s outer radiation belt is highly variable and typically linked to geomagnetic activity such as storms and substorms. These variations can differ with radial distance, such that the fluxes at the outer boundary are different from those in the heart of the belt. Using data from the Proton Electron Telescope (PET) on board NASA&#8217;s Solar Anomalous Magnetospheric Particle Explorer (SAMPEX), we have examined the correlation between electron fluxes at all L's within the radiation belts for a range of geomagnetic conditions, as well as longer-term averages. Our analysis shows that fluxes at L&#8776;2-4 and L&#8776;4-10 are well correlated within these regions, with coefficients in excess of 80%, however, the correlation between these two regions is low. These correlations vary between storm-times and quiet-times. We examine whether, and to what extent this correlation is related to the level of enhancement of the outer radiation belt during geomagnetic storms, and whether the plasmapause plays any role defining the different regions of correlated flux.

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Effects of strong IMF Bz southward events on the equatorial and mid-latitude ionosphere

Annales Geophysicae ◽

10.5194/angeo-27-1175-2009 ◽

2009 ◽

Vol 27 (3) ◽

pp. 1175-1187 ◽

Cited By ~ 31

Author(s):

E. Astafyeva

Keyword(s):

Electric Fields ◽

Geomagnetic Storms ◽

The Other ◽

Negative Events ◽

Equatorial Anomaly ◽

Low Latitude ◽

Sudden Drop ◽

Ionospheric Response ◽

Peak Structure ◽

Low Latitude Ionosphere

Abstract. Dayside ionospheric response to five intense geomagnetic storms (Dst<−120 nT) that occurred in 2001–2005 was investigated by use of simultaneous TEC measurements by the CHAMP, SAC-C, TOPEX/Jason-1 satellites. Since the satellites passed over different longitudinal sectors and measured TEC in different range of altitudes, it was possible to obtain information about altitudinal and longitudinal ionosphere redistribution during these storms. Severe enhancements (up to ~350%) of the equatorial and mid-latitude TEC above ~430 km with concurrent traveling of the equatorial anomaly crests for a distance of 10–15° of latitude were observed during two of the five events analyzed here (6 November 2001 and 8 November 2004). This phenomenon, known as the dayside ionosphere uplift, or the "daytime super-fountain effect", occurred after sudden drop in IMF Bz and consequent penetration of the electric fields to the low-latitude ionosphere. However, the same order Bz negative events caused comparatively weak changes in the dayside TEC (up to ~80 TECU) during the other three events of 18 June 2003, 11 February 2004 and 24 August 2005. At the main phase of these storms there were mostly observed formation of the "typical" dual peak structure of the equatorial anomaly rather than the reinforcement of the fountain effect and the anomaly itself. Possible reasons and factors responsible for the development of the extreme ionosphere effects are discussed in the paper.

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

Remote Sensing ◽

10.3390/rs13030534 ◽

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.

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