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Electrodynamics of degenerate induced magnetospheres

Presentation #211.07 in the session Planetary Space Physics (Poster)

Published onOct 23, 2023
Electrodynamics of degenerate induced magnetospheres

Induced magnetospheres of non-magnetized atmospheric planets like Mars and Venus are formed by magnetic fields of ionospheric currents induced by the convective electric field E = - V x B/c of the solar wind. When the interplanetary magnetic field is mostly radial (the cone angle is around 10°, an uncertainty defined by the solar wind ion temperature) the convective electric field is very small, and induced magnetospheres degenerate. Such cases are rare, 1-2% of all induced magnetosphere crossing cases per year as observed by Mars Express and Venus Express. The electrodynamics of degenerate induced magnetospheres is much different from the case of an induced magnetosphere proper. A weak magnetic barrier forms at lower altitudes that, due to relatively stronger ambipolar field, results in significantly higher escape rate. The planetary ions experience E x B drift with the dominant component across the solar wind. That causes a large cross flow plume. The drift velocity along the solar wind flow is very small and lower than the velocity gained in the ambipolar field that guides planetary ions far upstream. The bow shock at degenerate magnetospheres is quasi-parallel up to high solar zenith angles that results in strong turbulence, wave-particle interaction and planetary ion heating over almost entire day side. We illustrate the description of the degenerate induced magnetosphere electrodynamics by hybrid simulations and examples of the Mars Express and MAVEN observations.

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