Worst‐Case Severe Environments for Surface Charging Observed at LANL Satellites as Dependent on Solar Wind and Geomagnetic Conditions

Abstract

The 400 worst‐case severe environments for surface charging detected at Los Alamos National Laboratory satellites during the years of 1990–2005 as binned by the definitions of four criteria developed by Matéo‐Vélez et al. (2018, https://doi.org/10.1002/2017sw001689) and the solar wind and Interplanetary Magnetic Field (IMF) parameters and geomagnetic activity indices are analyzed. The conducted analysis shows that only Auroral Electrojet/Auroral Lower index determines the highest risk for severe environments for surface charging to happen. The presence of a substorm with the southward turning pattern in IMF Bz indicates that the environment can be severe for surface charging to occur but this environment will not depend on whether a substorm was moderate or intense. No clear dependence on IMF Bz is found for risk to a severe environment to occur. Appearances of severe environments for surface charging do not necessarily require high values of Kp (Planetarische Kennziffer) and no storm is needed for such an event to be detected. Among solar wind parameters, solar wind velocity Vsw is directly related to the highest risk of severe environments, dependent on the Vsw value; and number density Nsw is of no importance. Two criteria for severe environment events based on the enhancements of low energy particle fluxes exhibit clearer dependencies on the solar wind and IMF parameters and geomagnetic activity indices with more distinct patterns in their time history.

Using ARMAX Models to Determine the Drivers of 40–150 keV GOES Electron Fluxes

“…A number of variables show high simple (single variable) correlations with keV electron flux, but by using an ARMAX analysis, which removes the confounding effect of diurnal cyclicity and allows assessment of each parameter independently, we show more definitively that substorms (measured by AE ) are the most influential process at 40 and 75 keV. This accords with previous work that found substorms to be an important correlate with both keV (Ganushkina et al., 2021) and MeV electrons (Simms, Engebretson, Clilverd, Rodger, Lessard, et al., 2018).…”

“…For this reason, daily/orbit averaging misses much of the behavior of these electrons. Moreover, even moderate storms are not necessary for electron enhancements in this energy range, with many surface charging events detected during low to moderate substorm activity and no direct dependence on substorm strength (Ganushkina et al., 2021; Matéo‐Vélez et al., 2018).…”

“…The effects of multiplicative combinations of parameters such as -V SW B z (Denton et al, 2016) were not studied and it is possible that not a single parameter but the combined effect of multiple driving parameters that result in the observed fast variations of the keV electrons. Ganushkina et al (2021) discovered that the AE/AL (Auroral Electrojet/Auroral Lower) indices, together with solar wind speed, provide a better model of the severe environments related to surface charging of satellites by keV electrons measured by LANL (1990LANL ( -2005 than do IMFB z , Kp, and solar wind number density. Based on integral electron fluxes, among 400 events of worst-case severe environments (categorized based on four criteria (Matéo-Vélez et al, 2018) of the solar wind and IMF parameters and geomagnetic indices), 100 were in one criterion based on the measured spacecraft potential and 300 in the other 3 criteria based on these electron flux measurements.…”

Energetic Electron Flux Predictions in the Near‐Earth Plasma Sheet From Solar Wind Driving

“…Suprathermal electrons (∼1 to 100 keV) in the near‐Earth plasma sheet have particular effectiveness at altering the inner magnetosphere (e.g., Garrett, 1979; Turner & Li, 2008; Yu et al., 2019), and they are the seed population for radiation belt MeV electrons (e.g., Allison et al., 2019; Chen et al., 2007; Fu et al., 2011; Horne et al., 2005; Jaynes et al., 2015; Kennel & Petschek, 1966; Kennel & Thorne, 1967; Li et al., 2008, 2012; Malykhin et al., 2021). They contribute to spacecraft surface charging environments (e.g., Davis et al., 2008; Garrett, 1981; Koons et al., 1999), posing a space weather hazard to satellites at geosynchronous orbit (GEO; e.g., Choi et al., 2011; Ganushkina et al., 2021; Matéo‐Vélez et al., 2018; Thomsen et al., 2013); and, they can penetrate deep inside GEO to medium Earth orbit (MEO; Motoba et al., 2021; Turner et al., 2015).…”

Forecast of the Energetic Electron Environment of the Radiation Belts

“…The type of problem and its severity is dependant upon the energy of the incident particles. Electrons with energies of the order of ∼100 keV cause surface charging of the satellite body (Ganushkina et al., 2021). The resulting discharges may damage the outer skin and solar cells of a satellite.…”