TY - JOUR

T1 - Auroral signatures of transient processes in the outer magnetosphere

AU - Popescu, D.

AU - Sauvaud, J. A.

AU - Stenuit, H.

AU - Delcourt, D. C.

AU - Sergeev, V. A.

AU - Brittnacher, M.

AU - Parks, G. K.

AU - Mukai, T.

AU - Kokubun, S.

AU - Kovrazhkin, R. A.

PY - 2002/12

Y1 - 2002/12

N2 - We present an analysis of sporadic and recurrent injections of magnetospheric ions in the midnight auroral oval during substorms and of the associated ionospheric ion outflows. The source of plasma sheet precipitating ions is determined using a simple method, based on the measured relation between the ion inverse velocity and time (l = v × t). This method is applied here to two typical passes of the Interball-Auroral (IA) satellite at distances of ∼ 3 R E above the auroral regions. Substorm related ion injections are shown to be mainly due to time of flight effects. In contrast with particle trajectory computations (Sauvaud et al., 1999), the im,erse velocity method does not require magnetic and electric field models and can thus be used systematically for the detection of time of flight dispersed ion structures (TDIS). This allowed us to build a large database of TDIS events and to perform a statistical analysis of their spatial distribution. For the cases presented here the source region of the injected ions is found at radial distances from 18 to 30 RE near the equatorial magnetosphere. At Interball altitudes (∼ 3 R E ), ion injections detected at the poleward boundary of the nighside auroral oval are associated with shear Alfvén waves superimposed over large-scale quasi-static current structures. We show that the most poleward TDIS are collocated with a large outflow of ionospheric H + and O + displaying pitch-angle distributions peaked in the pitch-angle range 90°-120°. These ions are thus accelerated perpendicularly to the magnetic field not only in the main auroral acceleration region but also up to at least 3 R E . The expanding auroral bulge thus constitutes a significant source of H + and O + ions for the mid-tail magnetosphere.

AB - We present an analysis of sporadic and recurrent injections of magnetospheric ions in the midnight auroral oval during substorms and of the associated ionospheric ion outflows. The source of plasma sheet precipitating ions is determined using a simple method, based on the measured relation between the ion inverse velocity and time (l = v × t). This method is applied here to two typical passes of the Interball-Auroral (IA) satellite at distances of ∼ 3 R E above the auroral regions. Substorm related ion injections are shown to be mainly due to time of flight effects. In contrast with particle trajectory computations (Sauvaud et al., 1999), the im,erse velocity method does not require magnetic and electric field models and can thus be used systematically for the detection of time of flight dispersed ion structures (TDIS). This allowed us to build a large database of TDIS events and to perform a statistical analysis of their spatial distribution. For the cases presented here the source region of the injected ions is found at radial distances from 18 to 30 RE near the equatorial magnetosphere. At Interball altitudes (∼ 3 R E ), ion injections detected at the poleward boundary of the nighside auroral oval are associated with shear Alfvén waves superimposed over large-scale quasi-static current structures. We show that the most poleward TDIS are collocated with a large outflow of ionospheric H + and O + displaying pitch-angle distributions peaked in the pitch-angle range 90°-120°. These ions are thus accelerated perpendicularly to the magnetic field not only in the main auroral acceleration region but also up to at least 3 R E . The expanding auroral bulge thus constitutes a significant source of H + and O + ions for the mid-tail magnetosphere.

KW - SHEET ION INJECTIONS

KW - PLASMA SHEET

KW - FIELD

KW - BULGE

KW - SPACECRAFT

KW - EXPANSION

KW - SUBSTORMS

KW - BOUNDARY

KW - DYNAMICS

KW - REGION

UR - http://www.scopus.com/inward/record.url?scp=0036944701&partnerID=8YFLogxK

U2 - 10.1016/S0273-1177(02)80388-X

DO - 10.1016/S0273-1177(02)80388-X

M3 - Article

VL - 30

SP - 2701

EP - 2711

JO - Advances in Space Research

JF - Advances in Space Research

SN - 0273-1177

IS - 12

T2 - D3 5/PSRBI Symposium of the COSPAR Scientific Commission D held at the 33rd COSPAR Assembly

Y2 - 1 July 2000

ER -