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SUMMARY:The big geomagnetic storm of 17 March 2015: measurements from the 
 EPT/PROBA-V as well as their interpretation
DTSTART;VALUE=DATE-TIME:20161011T053000Z
DTEND;VALUE=DATE-TIME:20161011T060000Z
DTSTAMP;VALUE=DATE-TIME:20261014T232428Z
UID:indico-contribution-761@cern.ch
DESCRIPTION:Speakers: Jsoeph Lemaire (BIRA-IASB & CSR-UCL)\nV. Pierrard (1
 \, 2) \, G. Lopez-Rosson (1) \, J.  Lemaire (1\, 2)\n(1) BIRA-IASB\, Bruss
 els\; (2) CSR/UCL\, Louvain-La-Neuve\n\nSince May 2013\, the Electron Prot
 on Telescope (EPT) orbits at 820 km altitude on a polar LEO track (Cyamuku
 ngo et al. 2014\; Pierrard et al. 2014).  \nThe fluxes of trapped electron
 s ranging from 0.5 MeV to 20 MeV are measured by the EPT in 7 energy chann
 els. We present and discuss here the observations collected during the per
 iod of the 17 March 2015 geomagnetic storm (Dst: -231 nT).\n\nAfter the so
 uthward turning of the IMF\, during the main phase of this large geomagnet
 ic storm\, an important dropout was observed at low altitudes in all energ
 y channels of the EPT\, for all drift shells of the outer Radiation Belt (
 L > 4). \nPenetration of relativistic electrons down to L = 2\, into the i
 nner Radiation Belt\, was then also observed in the SAA at low altitudes (
 820 km). This strong injection event filled up the slot region between the
  inner and outer Radiation Belts\, for a period lasting a few days. \n\nTh
 e (L-t) maps of the fluxes measured indicate that the outer belt electron 
 fluxes finally became significantly larger after the geomagnetic storm tha
 n before this event.  It was also observed simultaneously by the MAGEIS/VA
 P-B detector along the highly excentric equatorial orbit of the Van Allen 
 Probes B.  Similar post-storm enhancements of energetic electrons fluxes i
 n the outer radiation belt have often been observed and reported earlier\,
  but never simultaneously (i) at low altitudes (along a LEO alike that of 
 EPT/PROBA-V) and (ii) at large radial distances in the equatorial region (
 along a GTO orbit alike that of MAGEIS/VAP-B). The time variations of the 
 energy spectra\, made at both altitudes along the same drift shells\, have
  been compared to each other during the different phases of this geomagnet
 ic storm.  \n\nWe show how Betatron deceleration and the uplift of mirror 
 points (during the storm main phase)\, and Betatron acceleration and downw
 ard motion of mirror points (during the recovery phase) can explain the ob
 served flux variations (i.e. the flux dropouts followed by the flux enhanc
 ements). Both at low altitude and at high altitude\,  these flux variation
 s are due to Betatron deceleration and acceleration (the Dst-effect) induc
 ed by the initial built up of the Ring Current intensity\, and subsequentl
 y by its decay\, during the slower recovery phase.\n\nWe also pointed out 
 how the effects of a concomitant interaction of outer belt electrons with 
 whistler and ULF waves\, during main phases and recovery phases can accoun
 t for observed post-storm flux enhancements (or decreases) of outer belt e
 lectron population\, often observed after geomagnetic storm events.\n\nhtt
 ps://indico.particle.mephi.ru/event/4/contributions/761/
LOCATION:Milan Hotel Rossini
URL:https://indico.particle.mephi.ru/event/4/contributions/761/
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