TY - JOUR

T1 - Multi-spacecraft observation of plasma dipolarization/injection in the inner magnetosphere

AU - Apatenkov, S. V.

AU - Sergeev, V. A.

AU - Kubyshkina, M. V.

AU - Nakamura, R.

AU - Baumjohann, W.

AU - Runov, A.

AU - Alexeev, I.

AU - Fazakerley, A.

AU - Frey, H.

AU - Muhlbachler, S.

AU - Daly, P. W.

AU - Sauvaud, J. A.

AU - Ganushkina, N.

AU - Pulkkinen, T.

AU - Reeves, G. D.

AU - Khotyaintsev, Y.

PY - 2007

Y1 - 2007

N2 - Addressing the origin of the energetic particle injections into the inner magnetosphere, we investigate the 23 February 2004 substorm using a favorable constellation of four Cluster (near perigee), LANL and Geotail spacecraft. Both an energy-dispersed and a dispersionless injection were observed by Cluster crossing the plasma sheet horn, which mapped to 9–12 R E in the equatorial plane close to the midnight meridian. Two associated narrow equatorward auroral tongues/streamers propagating from the oval poleward boundary could be discerned in the global images obtained by IMAGE/WIC. As compared to the energy-dispersed event, the dispersionless injection front has important distinctions consequently repeated at 4 spacecraft: a simultaneous increase in electron fluxes at energies ∼1..300 keV, ∼25 nT increase in BZ and a local increase by a factor 1.5–1.7 in plasma pressure. The injected plasma was primarily of solar wind origin. We evaluated the change in the injected flux tube configuration during the dipolarization by fitting flux increases observed by the PEACE and RAPID instruments, assuming adiabatic heating and the Liouville theorem. Mapping the locations of the injection front detected by the four spacecraft to the equatorial plane, we estimated the injection front thickness to be ∼1 RE and the earthward propagation speed to be ∼200–400 km/s (at 9–12 RE). Based on observed injection properties, we suggest that it is the underpopulated flux tubes (bubbles with enhanced magnetic field and sharp inner front propagating earthward), which accelerate and transport particles into the strong-field dipolar region.

AB - Addressing the origin of the energetic particle injections into the inner magnetosphere, we investigate the 23 February 2004 substorm using a favorable constellation of four Cluster (near perigee), LANL and Geotail spacecraft. Both an energy-dispersed and a dispersionless injection were observed by Cluster crossing the plasma sheet horn, which mapped to 9–12 R E in the equatorial plane close to the midnight meridian. Two associated narrow equatorward auroral tongues/streamers propagating from the oval poleward boundary could be discerned in the global images obtained by IMAGE/WIC. As compared to the energy-dispersed event, the dispersionless injection front has important distinctions consequently repeated at 4 spacecraft: a simultaneous increase in electron fluxes at energies ∼1..300 keV, ∼25 nT increase in BZ and a local increase by a factor 1.5–1.7 in plasma pressure. The injected plasma was primarily of solar wind origin. We evaluated the change in the injected flux tube configuration during the dipolarization by fitting flux increases observed by the PEACE and RAPID instruments, assuming adiabatic heating and the Liouville theorem. Mapping the locations of the injection front detected by the four spacecraft to the equatorial plane, we estimated the injection front thickness to be ∼1 RE and the earthward propagation speed to be ∼200–400 km/s (at 9–12 RE). Based on observed injection properties, we suggest that it is the underpopulated flux tubes (bubbles with enhanced magnetic field and sharp inner front propagating earthward), which accelerate and transport particles into the strong-field dipolar region.

UR - http://www.scopus.com/inward/record.url?scp=34047186386&partnerID=8YFLogxK

U2 - 10.5194/angeo-25-801-2007

DO - 10.5194/angeo-25-801-2007

M3 - Article

AN - SCOPUS:34047186386

VL - 25

SP - 801

EP - 814

JO - Annales Geophysicae

JF - Annales Geophysicae

SN - 0992-7689

IS - 3

ER -