Mars Global Surveyor Measurements of the Martian Solar Wind Interaction

Abstract

The solar wind at Mars interacts with the extended atmosphere and small-scale crustal magnetic fields. This interaction shares elements with a variety of solar system bodies, and has direct bearing on studies of the long-term evolution of the Martian atmosphere, the structure of the upper atmosphere, and fundamental plasma processes. The magnetometer (MAG) and electron reflectometer (ER) on Mars Global Surveyor (MGS) continue to make many contributions toward understanding the plasma environment, thanks in large part to a spacecraft orbit that had low periapsis, had good coverage of the interaction region, and has been long-lived in its mapping orbit. The crustal magnetic fields discovered using MGS data perturb plasma boundaries on timescales associated with Mars' rotation and enable a complex magnetic field topology near the planet. Every portion of the plasma environment has been sampled by MGS, confirming previous measurements and making new discoveries in each region. The entire system is highly variable, and responds to changes in solar EUV flux, upstream pressure, IMF direction, and the orientation of Mars with respect to the Sun and solar wind flow. New insights from MGS should come from future analysis of new and existing data, as well as multi-spacecraft observations.

The MAVEN Magnetic Field Investigation

“…2). The characteristics of the solar wind interaction with a weakly magnetized, or unmagnetized body are in some regards similar to the flow about a magnetized planet (Luhmann et al 1992;Brain 2006), but for the lack of a global-scale magnetosphere within which the motion of charged particles is governed by an intrinsic planetary magnetic field.…”

Interplanetary Space Weather: A New Paradigm

“…Mars has a unique response to solar storms shaped by the planet's strange magnetic topology [ Brain , 2007]. Instead of a global magnetic field like that of Earth, Mars is patchily covered by dozens of magnetic "umbrellas."…”

Access of solar wind electrons into the Martian magnetosphere

“…Figure 2 shows maps of electron fluxes for the Northern dayside Hemisphere (where effects of crustal fields are small) for different signs of the B y component of the IMF. A proxy direction of the B yIMF component was inferred from the MGS observations assuming that the magnetic field at middle latitudes of the Northern Hemisphere is primarily of induced origin (Brain et al, 2006b;Dubinin et al, 2006;Fedorov et al, 2006). A positive sign corresponds to the case when piled up magnetic field is expected to be higher in the Northern Hemisphere.…”

“…Electrons which penetrate to altitudes h≤400 km in the regions of strong crustal fields form a spatially well organized pattern with bands stretched in the longitudinal direction (see also Brain, 2006c). Figure 12 shows maps of electron fluxes in the energy range 30-80 eV and 100-300 eV measured on the MGS spacecraft by the MAG/ER instrument at h∼400 km in the night sector (∼02:00 LT).…”