When: Friday, March 1, 2024, 2:30 PM - 3:30 PMWhere: GO Jones 610
The fate of solar energetic particles in Mars' atmosphere and ionosphere
Solar energetic particles (SEPs) are known to be absorbed by the atmosphere thereby ionizing different layers of the Martian atmosphere and producing auroras, with only the most energetic protons able to reach the surface of Mars. We can track the fate of the ionizing particles by analysing their space weather effects, such as the attenuation produced by these new layers on the HF radio signal propagating through the atmosphere with the two HF radars currently in operation at Mars, i.e., the MARSIS radar onboard Mars Express and the SHARAD radar onboard Mars Reconnaissance Orbiter.
One of the largest widespread SEP events of the current solar cycle was the one that occurred on 15 February 2022, observed by almost all missions deployed in the inner solar system. In particular, the SEP event was detected by BepiColombo and Parker Solar Probe, which were radially separated by only 0.03 au and extremely well-aligned along the Parker spiral interplanetary magnetic field line, which was also fairly well (within 30°) connected to Mars. The proton-rich SEP event was observed by MAVEN and Mars Odyssey in orbit around Mars and was able to penetrate down to the surface of the planet, producing one of the largest ground level enhancements ever observed at the surface of Mars by the Radiation Assessment Detector (RAD) onboard the Curiosity rover of the Mars Science Laboratory (MSL) mission. Both radars, MARSIS and SHARAD, observed signs of signal attenuation during this event. MARSIS, which operates at lower frequencies, experienced a blackout during the entirety of the SEP event, while SHARAD, which operates at a higher frequency, was only affected by partial attenuation. This indicates that despite the proton event being one of the more significant events ever measured at Mars, the new ionospheric layers at low altitude did not absorb as much HF radio signals as in principle would be expected for an event of this magnitude, giving new clues regarding the response of the middle-upper atmosphere to the impact of large SEP events.
This seminar will focus on this event and other similar cases at Mars to show that thanks to the coordination of missions, for the first time, we can to track the fate of SEP particles (both ions and electrons) in Mars’ atmosphere by having upstream observations in the solar wind, upstream observations within the magnetosheath of Mars, in-situ upper-atmosphere data, remote observations in the middle atmosphere, and data at the surface of Mars. This is a feasibility case for the systematic exploration of the red planet, as currently proposed to ESA with the mission concept M-MATISSE (M7 candidate in Phase-A).