On the feasibility of detecting the ionospheric effects of solar energetic particle events at Mars using spacecraft‐spacecraft radio links

Abstract

AbstractIndirect evidence and theoretical modeling suggests that the effects of solar energetic particle (SEP) events on the ionosphere of Mars are substantial, but observations have not yet provided quantitative information on the magnitude or vertical distribution of the plasma produced below 100 km by SEP events. Strong radio wave absorption is anticipated during a SEP event due to the production of plasma at low altitudes where the neutral atmosphere is relatively dense. Here we test the feasibility of measuring the ionospheric effects of SEP events using power losses in spacecraft‐spacecraft UHF radio links. Both lander‐orbiter and orbiter‐orbiter cases are considered for the UHF radio frequency of 400 MHz. A large SEP event should cause an ionospheric power loss at 400 MHz of 1.5 dB in lander‐orbiter communications and, due to the longer path length, a larger power loss of 35 dB in orbiter‐orbiter communications. Multiple SEP events occur each year that can cause a lander‐orbiter power loss of 0.1 dB, which is shown to be theoretically detectable by current instrumentation, and an orbiter‐orbiter power loss of 2 dB. The vertical profile of electron density at low altitudes can be determined from orbiter‐orbiter power losses.