Science Seminars

6/11/2015 – The Mars discrete aurora: Mars Express observations and modeling

Speaker: Jean-Claude Gerard (Univ. of Liege)
Date: Friday, Jun 11, 2021
Time: 4:00 PM
Location: SPSC W120

Seminar Abstract:

The Mars ultraviolet aurora was discovered in 2005 when observing the nightside limb with the SPICAM UV spectrometer on board ESA’s Mars Express (MEx) satellite. It was characterized by the transient presence of the CO Cameron bands between 140 and 180 nm and the CO2+ doublet near 289 nm which are normally absent on the nightside. This event was associated with the detection of bursts of peaked electron energy distributions in regions of residual magnetic field made earlier with particle detectors on board Mars Global Surveyor and MEx. Later, parallel observations confirmed the association between ultraviolet aurorae and enhanced downward fluxes of energetic electrons in regions showing cusp-like magnetic structures.

In this talk, we describe the methodology adopted to identify UV auroral events. We then present recent results based on detection of additional auroral signatures simultaneously observed with SPICAM and ASPERA-3 on board MEx. We confirm that all these discrete auroral events occur in regions near open-closed field line boundaries in the southern hemisphere as shown in the figure. They are confined in latitude but a shift is frequently observed between the UV aurora at the nadir and the peak of the electron flux at the spacecraft altitude. The relation between the measured electron flux and the brightness of the aurora is studied with an electron transport code. The altitude of the auroral emissions observed at the limb is consistent with precipitation of auroral electrons with a mean energy of a few hundred eV, suggesting acceleration in the Mars mini-magnetosphere.