A corrector for spacecraft calculated electron moments

Abstract

Abstract. We present the application of a numerical method to correct electron moments calculated on-board spacecraft from the effects of potential broadening and energy range truncation. Assuming a shape for the natural distribution of the ambient plasma and employing the scalar approximation, the on-board moments can be represented as non-linear integral functions of the underlying distribution. We have implemented an algorithm which inverts this system successfully over a wide range of parameters for an assumed underlying drifting Maxwellian distribution. The outputs of the solver are the corrected electron plasma temperature T e , density N e and velocity vector V e . We also make an estimation of the temperature anisotropy A of the distribution. We present corrected moment data from Cluster's PEACE experiment for a range of plasma environments and make comparisons with electron and ion data from other Cluster instruments, as well as the equivalent ground-based calculations using full 3-D distribution PEACE telemetry.

Impact of plasma sheath on rocket-based E-region ion measurements

“…Corrected values are obtained from the spacecraft floating potential and detector limits. The corrected moments show good agreement with data from other Cluster instruments, as well as ground based calculation using 3D distribution PEACE telemetry Geach et al (2005). Such sensors are part of many satellites recently deployed, or scheduled for launch.…”

“…Measurements of three-dimensional particle velocity distributions in the magnetosphere are also reported by many authors Carlson et al (2001), Ogilvie et al (1995), Pfaff et al (2001). Geach et al (2005) computed the corrected moments of data obtained from Cluster's PEACE experiment in different plasma environments. The correction accounts for the effects of potential broadening and energy range truncation.…”

Quantified energy dissipation rates in the terrestrial bow shock: 1. Analysis techniques and methodology

“…Onboard particle distribution moments (or moments calculated from telemetered particle distributions) can suffer from inaccuracies due to spacecraft charging [e.g., Génot and Schwartz, 2004;Geach et al, 2005;Davis et al, 2008], multiple species [e.g., Paschmann and Daly, 1998], multiple components [e.g., Wüest et al, 2007], and limited energy ranges (e.g., V Ti ≳ V bulk ). In the following we discuss how we accounted for these potential inaccuracies when examining moments of the velocity distribution functions.…”

Electron velocity distribution and lion roars in the magnetosheath

“…With the help of background magnetic field, we can also determine the electron pitch angle velocity distribution and hence also the temperature anisotropy. We have used the truncated corrector electron moments (Geach et al, 2005) of the Cluster PEACE (Plasma Electron and Current Experiment) data to analyse the electron distribution in the magnetosheath environment. The two PEACE sensors on board each Cluster spacecraft sample the electron velocity distribution across the full 4π solid angle and the energy range 0.7 ev to 26kev with a time resolution of 4 s (Johnstone et al, 1997).…”

“…The reason for using the truncated corrector electron moments is that the moments calculated on-board spacecraft typically over or under-estimate the values of the 'true' moments, because they convolve effects caused by the presence of a potential (from the spacecraft itself) and lower and upper energy truncation imposed by the detector. Furthermore, the spacecraft environment includes photo and secondary electrons, which can return to the spacecraft and enter the detector, therefore contaminating the measured moments (Szita et al, 2001;Génot and Schwartz, 2004;Geach et al, 2005). Pitch angle distributions derived from the electron data are also studied.…”