Experimental Investigation of the Secondary and Backscatter Electron Emission from Spacecraft Materials

Parker Solar Probe FIELDS Instrument Charging in the Near Sun Environment: Part 2: Comparison of In‐Flight Data and Modeling Results

“…The space potential at the antenna (with respect to infinity) is ∼ −5V, described by the first elbow of the I–V curve, and the saturated current is −53 µA, shown as the current plateau of the I–V curve as the voltage decreases. The modeled resulting photocurrent of the antenna is −60 µA (Diaz‐Aguado et al., 2020).…”

“…Material Properties Used in Surface Charging Calculations(Diaz-Aguado et al, 2020; Donegan et al, 2014 c ;Thiebault 2013) …”

Parker Solar Probe FIELDS Instrument Charging in the Near Sun Environment: Part 1: Computational Model

“…Note that past studies of the SE yield of conductive materials at temperatures greater than 600 K, have shown a decrease in yield on the order of 0.05%/K (Michizono et al., 2004; Sternglass, 1954; Warnecke, 1936). For the first perihelia the predicted antenna surface temperatures are ∼885 K, and the yield reduced by 44% relative to results at 270–300 K; for the closest perihelia, the expected decrease in SE yield is even greater, on the order of 79% (Diaz‐Aguado et al., 2020). These temperature‐dependent effects were not modeled in this analysis as photocurrent dominated the current balance by an order of magnitude.…”

“…A finer mesh, as seen in Table 5, was used for 9.5 Rs to ensure that the Debye length was greater than the mesh cell near the spacecraft, ensuring that the grid was less than half the Debye length in the sheath. (Diaz-Aguado et al, 2020;Donegan et al, 2014;Thiebault, 2013) The ion SE yield properties of Nb-C103 were not known at the time of publishing, instead the properties of Aluminum were used. Given that the ion current is small, this assumption has no significant effect on the modeling results.…”

“…SE can be approximated by an isotropic Maxwellian distribution, with a characteristic energy of T se ∼2 eV (Hachenberg & Brauer,1959;Lai, 2012Lai, , 2013. Estimates of the SE yield due to electrons have been difficult to predict theoretically, but by knowing that the yield is strictly dependent on the incoming energy and angle, we can look at J e /n e and material dependent J se /n e (T e ) figures to predict at what ambient electron temperatures the SE currents are greater than the electron current (Diaz-Aguado et al, 2020).…”