Electron Wing‐Like Structures Formed at a Negatively Charged Spacecraft Moving in a Magnetized Plasma

Abstract

Spacecraft‐plasma interactions are studied with self‐consistent numerical simulations of magnetized plasmas, where electrons are strongly magnetized whereas ions are weakly magnetized. It is found that for a spacecraft in such a magnetized plasma corresponding to a low Earth orbit, electrons can be reflected from a negatively charged spacecraft and then guided by geomagnetic field lines. The reflected electrons can leave a sharp trail like wings if the spacecraft size is greater than an average electron gyroradius of the environment. Such an electron wing‐like structure is associated with propagating Langmuir waves. This results in nontrivial asymmetric electrostatic potentials close to the spacecraft and even farther than the Debye screening distance. The convective electric field also gives rise to a differential potential of the spacecraft with respect to the plasma, resulting in yet another asymmetry in the plasma dynamics and the potential distribution around the spacecraft. These asymmetries in the plasma dynamics can significantly influence in‐situ measurements of space plasma. The results show a good qualitative agreement with actual measurements by a satellite in the polar regions.

Particle-In-Cell Simulations of the Cassini Spacecraft's Interaction with Saturn's Ionosphere during the Grand Finale

“…Electron-wings associated with propagating Langmuir waves were also identified around the spacecraft which produced a sharp enhancements to the in-flowing electrons. Similar electron-wings were previously identified in simulations of spacecraft moving through the polar regions of the Earth's ionosphere [Miyake et al, 2020] and these simulations indicate this phenomena occurred at Cassini too.…”

“…Similar wing-like structures have been identified at moving bodies produced by Alfvén and whistler waves [Drell et al, 1965, Neuebauer, 1980, Stenzel and Urrutia, 1989, which propagate at characteristic velocities associated with their relative speed to the spacecraft such that they advect downstream. Electron-wing structures, similar to these reported herein, have been identified as consisting of propagating Langmuir waves [Miyake et al, 2020] produced by electrons reflected from a negatively charged spacecraft which are then guided by the magnetic field lines. Calculation of the Langmuir Probe group velocity, c L = √ 3k B T e m e ∼ = 1,200 km s −1 , and the angle to the magnetic field, θ = arctan(v f low /c L ) ≈ 2 • , confirms this mode propagates at small angles to the magnetic field in the spacecraft frame, as can be seen in Figure 2.…”

The Spacecraft Wake: Interference With Electric Field Observations and a Possibility to Detect Cold Ions

“…The small Debye length in LEO gives large wake potentials, which further concentrated early studies to low altitudes. Observations (Ferguson et al, 2013;Katz et al, 1998) and recent simulations of wakes and related effects include the geomagnetic field for orbiting spacecraft in LEO (Miyake et al, 2020), while other simulation studies consider slower sounding rockets (Darian et al, 2017), and their booms of a few meters (Paulsson et al, 2018(Paulsson et al, , 2019. Wakes in LEO can also be of practical interest for close-proximity formation flying (Maxwell & Schaub, 2019;Maxwell et al, 2021).…”

Evidence that Interaction with the Spacecraft Plasma Wake Generates Plasma Waves Close to the Electron Cyclotron Frequency in the Near-Sun Solar Wind

“…Many prior studies have reported data analysis and/or simulation results demonstrating the generation of plasma waves by interaction between a spacecraft and a flowing plasma (e.g., Keller et al 1997;Singh 2000;Guio & Pécseli 2005;Endo et al 2015;Miyake et al 2020). Some of these studies have specifically identified wake-driven waves near the electron cycltron frequency (Singh 2000;Endo et al 2015).…”