MAVEN observations of small scale magnetic structures embedded within larger scale magnetic field depletions in the Martian ionosphere

Abstract:

Unmagnetized bodies, such as Mars and Venus, do not possess a dipole magnetic field and subsequently the gravitationally bound conducting ionospheres act to stand off the incident solar wind via electromagnetic forces and the generation of electrical currents. A result of this interaction between the solar wind and ionospheres is the “entrainment” of the solar wind interplanetary magnetic field (IMF) within the dayside ionospheres of these bodies in the form of flux ropes. Flux ropes have been observed in relatively high abundance via in-situ magnetometer measurements in the lower ionospheres of Venus and Titan, in the form of small scale (~< few 10’s km) magnetic structures embedded within a weak background magnetic field. Contrary to this, at Mars, the strong crustal magnetic fields, and magnetized state of the ionosphere, have precluded the observation of similar flux rope structures within the lower ionosphere on a frequent basis. We present here MAVEN observations of small scale magnetic structures embedded within larger scale magnetic depletions in the dayside ionosphere below altitudes of ~300 km. The characteristics of these events are similar to flux ropes observed at Venus and Titan, suggesting that under certain conditions flux ropes are also observable within the Martian ionosphere. This presentation will discuss the conditions under which these magnetic depletions and small scale magnetic structures are observed, along with the ionospheric plasma properties within these events.