HR: 08:45h
AN: SM41B-02    [Abstracts]
TI: 3D Ring current mapping based on ENA image inversions and the curlometer technique, using IMAGE/ HENA and Cluster/FGM/CIS data.
AU: * Vallat, C
EM: vallat@cesr.fr
AF: CESR/CNRS, 9 avenue du colonel Roche, BP4346, Toulouse, 31028 France
AU: Dandouras, I
EM: dandouras@cesr.fr
AF: CESR/CNRS, 9 avenue du colonel Roche, BP4346, Toulouse, 31028 France
AU: C:Son Brandt, P
EM: pontus.brandt@jhuapl.edu
AF: APL/JHU, 11100 Johns Hopkins Rd., Laurel, MD 20723-6099 United States
AU: Roelof, E
EM: ed.roelof@jhuapl.edu
AF: APL/JHU, 11100 Johns Hopkins Rd., Laurel, MD 20723-6099 United States
AU: Mitchell, D
EM: Donald.G.Mitchell@jhuapl.edu
AF: APL/JHU, 11100 Johns Hopkins Rd., Laurel, MD 20723-6099 United States
AU: Dunlop, M
EM: M.W.Dunlop@rl.ac.uk
AF: RAL, Chilton, Didcot, OX11 0QX United Kingdom
AU: Lucek, E
EM: e.lucek@ic.ac.uk
AF: Blackett Laboratory Imperial College, Prince Consort Road, London, SW7 2AZ United Kingdom
AU: Balogh, A
EM: a.balogh@imperial.ac.uk
AF: Blackett Laboratory Imperial College, Prince Consort Road, London, SW7 2AZ United Kingdom
AU: RŠme, H
EM: reme@cesr.fr
AF: CESR/CNRS, 9 avenue du colonel Roche, BP4346, Toulouse, 31028 France
AB: The inner magnetosphere's electric currents configuration and mapping is one of the keys for understanding current loop closure inside the whole magnetosphere. Development of the ring current as a function of geomagnetic activity is still one of the most interesting aspects about this region. A method for directly computing current is the multi-spacecraft curlometer technique, which is based on Maxwell-Ampere's law application. This requires the use of four point magnetic field high resolution measurements. The FGM experiment on board the four Cluster spacecraft allows for the first time an instantaneous calculation of the magnetic field gradients and thus a measurement of the local current density. Moreover, ENA image inversions can provide a mapping of the equatorial ion distribution. The HENA/IMAGE neutral atom image inversions allow thus the estimation of pressure gradient values, and the computation of the equatorial ring current distribution. Using these two complementary methods (curlometer technique using in-situ measurements and neutral atom image inversion using remote sensing data), an instantaneous 3D mapping of the current can be made. The ring current distribution has been studied for the 20 April 2002 storm-time event (Dst~ - 101 nT; Kp=6). During this period, Cluster was crossing perigee at R~ 4 RE in the evening sector (MLT~21), while situated inside the HENA/IMAGE field-of view. The Cluster constellation provided a direct measure of the local current density, by applying the curlometer technique. Furthermore, the CIS experiment onboard Cluster allowed a validation of the ion fluxes obtained from HENA/IMAGE data. Our analysis reveals the existence of an important local current density (~ 30 nA/m2) in this MLT sector, even if the Cluster spacecraft are situated eastward of the ring current bulk, as shown by the HENA image inversion. The curlometer results reveal also the existence of an asymmetry between the two hemispheres, characterized by a southward orientation of the current at the equator.
DE: 2409 Current systems (2708)
DE: 2730 Magnetosphere--inner
DE: 2736 Magnetosphere/ionosphere interactions
DE: 2778 Ring current
SC: SPA-Magnetospheric Physics [SM]
MN: 2005 Joint Assembly