Low-energy electron current in the Martian tail due to reconnection of draped interplanetary magnetic field and crustal magnetic fields

We observe seasonal, nighttime clustering of significant enhancements in the Mars Global Surveyor electron omnidirectional flux data at low-energy levels over a specific geographical region at the west edge of the crustal fields (at around 70 degrees S and between 30 degrees E and 150 degrees E). We propose that photoelectrons generated over the crustal sources on the Martian dayside are transported along lines of the reconnected interplanetary magnetic field to the nightside and populate currents formed in the magnetotail. Comparison of the draping direction (estimated from the dayside data between 50 degrees and 60 degrees N latitude band over the northern hemisphere) at the closest time of the enhancements with the crustal fields at similar to 150 degrees E and similar to 65 degrees S shows the existence of favorable conditions for the reconnection. Seasonal variation observed in the draping direction accounts for the seasonal nature of the phenomenon. Moreover, a nearly 25 d periodic variation of the draping direction, due to solar rotation, strictly coincides with the periodic variation observed in the strength of the enhancements. We also demonstrate the effect of the Sun on the electron flux variations over two regions: (1) closed crustal fields and (2) the enhancement clustering region. Finally, we propose a model for the distribution of current sources on the nightside that accounts for the perturbations observed in the magnetic field data.