HR: 1340h
AN: SM43C-1233    [Abstracts]
TI: High time resolution density measurements by Cluster at the Earth's bow shock
AU: * Masson, A
EM: Arnaud.Masson@esa.int
AF: SCI-SH, RSSD, ESA/ESTEC, Keplerlaan 1, Noordwijk, 2201AZ Netherlands
AU: Laakso, H
EM: Harri.Laakso@esa.int
AF: SCI-SH, RSSD, ESA/ESTEC, Keplerlaan 1, Noordwijk, 2201AZ Netherlands
AU: Décreau, P
EM: pdecreau@cnrs-orleans.fr
AF: LPCE, CNRS and Université d'Orléans, 3A, avenue de la recherche scientifique, Orleans, 45071 France
AU: Andre, M
EM: ma@irfu.se
AF: IRF Uppsala, Angström Laboratory, Lägerhyddsv„gen 1 , Uppsala, 75121 Sweden
AU: Bale, S
EM: bale@ssl.berkeley.edu
AF: Space Science Laboratory, Berkeley University, Berkeley, CA 94720 United States
AU: Saxena, R
EM: rsaxena@hermes.ssl.berkeley.edu
AF: Space Science Laboratory, Berkeley University, Berkeley, CA 94720 United States
AU: Escoubet, P
EM: Philippe.Escoubet@esa.int
AF: SCI-SH, RSSD, ESA/ESTEC, Keplerlaan 1, Noordwijk, 2201AZ Netherlands
AU: Taylor, M
SM43C-1233 AF: SCI-SH, RSSD, ESA/ESTEC, Keplerlaan 1, Noordwijk, 2201AZ Netherlands
AU: Opgenoorth, H
EM: Hermann.Opgenoorth@esa.int
AF: SCI-SH, RSSD, ESA/ESTEC, Keplerlaan 1, Noordwijk, 2201AZ Netherlands
AB: In most of the regions crossed by the Cluster mission, the active sounding of the WHISPER experiment provides accurate electron density data on all four spacecraft. These measurements are performed every 28 s in normal mode. In some plasma conditions, the WHISPER passive VLF spectra can also be used to extract the electron density, but only when a clear plasma frequency cut-off is observed. The time resolution of these measurements is 2.2s in normal mode. The potential difference between one EFW probe and the spacecraft, usually called spacecraft potential, is measured every 0.2 s. Its variation is strongly dependent on the electron density but also on the photoelectron temperature, the plasma composition, the bias current and the radius of the sphere for a double probe experiment. Properly calibrating the s/c potential on Cluster is necessary to provide reliable electron density data with a time resolution up to 140 times better than the WHISPER active sounding data in normal mode. Results related to the calibration of the s/c potential at the Earth's bow shock will be presented. S/c potential versus density relationship with error bar is proposed, for each bias current applied to the probes. This analysis is based on tens of bow shock crossings by Cluster. Comparison with recent numerical simulations dedicated to the behaviour of the spacecraft potential measurements on Cluster will also be presented.
DE: 7894 Instruments and techniques
SC: SPA-Magnetospheric Physics [SM]
MN: Fall Meeting 2005