Representation of the measured geosynchronous plasma environment in spacecraft charging calculations

Abstract

1] Historically, the characterization of the magnetospheric environment has limited our ability to determine spacecraft surface charging levels. One difficulty lies in the common practice of fitting the plasma data to a Maxwellian or Double Maxwellian distribution function, which may not represent the data well for use in spacecraft charging simulations. We use electron and ion flux spectra measured by the Los Alamos National Laboratory (LANL) Magnetospheric Plasma Analyzer (MPA) during eclipse in September 2001 to examine how the use of different spectral representations of the charged particle environment in computations of spacecraft potentials during magnetospheric substorms affects the accuracy of the results. We examine charging and noncharging flux spectra and the relationships between the density and temperature moments. We then calculate the spacecraft potential (zero net current) using both the measured fluxes and several different fits to these fluxes. The potential computed using the measured fluxes and secondary and backscattered fluxes computed for graphite carbon, with a constant fraction of 81% of secondary electrons escaping, is within a factor of three of the measured potential for 87% of the data. Potentials calculated using a Kappa function fit to the electron flux and a Maxwellian function fit to the ion flux agree with measured potentials nearly as well. Alternative spectral representations give less accurate estimates. The use of all the components of the net flux, along with spacecraft specific average material properties, gives a better estimate of the spacecraft potential than the measured flux from a single high-energy channel.Citation: Davis, V. A., M.

Iron-Based Microbial Ecosystem on and Below the Seafloor: A Case Study of Hydrothermal Fields of the Southern Mariana Trough

“…Analysis of the collected fluids from the boreholes can provide valuable information about the geochemical conditions and microbiological activities of the sub-seafloor aquifers. Davis and Moyer (2008) first reported the presence of the Zetaproteobacteria in iron-rich mats in the SMT. Sequentially, comprehensive microbiological analyses of the various samples from the SMT hydrothermal fields have been done (Kato et al, 2009a,b, 2010).…”

Space Weather Effects Produced by the Ring Current Particles

“…They can be responsible for surface charging effects which is a serious risk for satellites (e.g., Garrett 1981;Lanzerotti et al 1998;Koons et al 1999;Whipple 1981;Davis et al 2008). The electrons with energies of 10's of keV do not penetrate deep into the satellite materials but stay near the surface.…”

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.…”