Magnetosphere Seminars

MAVEN observations of solar wind driven magnetosonic waves heating the Martian dayside ionosphere

Speaker:Chris Fowler [LASP]
Date:Tuesday, Feb 13, 2018
Time:3:30 pm
Location:LASP Space Science Building, room N100 (1st floor)

Seminar Abstract:

The nature of the solar wind interaction with unmagnetized bodies can be very different to that at magnetized planets such as Earth. At unmagnetized bodies, the lack of a significant, global dipole magnetic field typically leads to an induced magnetosphere forming at the body. The solar wind stand-off distance is subsequently usually located much closer to the unmagnetized body than at magnetized equivalents. At Mars (an unmagnetized body), this solar wind stand-off distance typically lies at around 1.6 Mars radii upstream of the planet. This distance is comparable to the typical proton gyro radius in the solar wind and subsequently it is expected that particles and waves generated by the solar wind-Mars interaction may interact directly with the upper ionosphere of the planet. We present observations from NASA’s Mars Atmosphere and Volatile EvolutioN (MAVEN) mission demonstrating the effects on the ionosphere of such interactions. Magnetosonic waves are observed propagating into the upper ionosphere close to the sub-solar point, driving large amplitude (~20-100%) variations in various plasma species densities and temperatures. These waves also drive significant ion heating down to altitudes just above the exobase region; the observed ions can be energized to energies greater than escape energy and this energy deposition appears to drive substantial ion outflow. This supports the idea that such waves may play an important role in driving ionospheric escape to space at Mars, and possibly at other unmagnetized bodies exposed to the solar wind as well.