Abstract | Energetic electrons at Mercury are abundant from the lowest energies (<10 keV) to energies of hundreds of keV as shown by the MESSENGER data. In particular the low-energy (1-10 keV) suprathermal electrons were present at all local times. When the measured locations of these suprathermal electrons are plotted in simplified B versus L coordinates (where B is the magnitude of the magnetic field, L defines an axisymmetric surface of those lines of magnetic force from the dipole component of Mercury’s internal field that intersect the magnetic equator at a distance L RM from the dipole center, and RM is Mercury’s radius), several distinct clusters of events can be seen. The majority were near the planet’s magnetic equator on the nightside of the planet, and a dawn–dusk asymmetry is clearly seen in the data. We infer all of these are signatures of accelerated electrons being injected from Mercury’s tail region through reconnection and/or depolarization events and then drift around the planet to form a quasi-trapped electron distribution at Mercury. |
