Statistical Analysis of Throat Aurora Using Long Term DMSP/SSUSI Observation

Throat aurora is believed to be associated with magnetopause indentations and has direct implications on magnetopause reconnection. In this study, for the first time, we use Defense Meteorological Satellite Program/Special Sensor Ultraviolet Spectrographic Imager observations over ∼14 years to characterize the throat aurora occurrence, latitudinal extent, seasonal, and its solar cycle dependence. We identified 386 throat aurora cases during the different passes of the satellite over the northern hemisphere. The latitudinal extent of these throat aurorae are estimated and are divided into small, medium, and large categories. The small and medium latitudinal extent throat aurorae account for about 91\% of the total cases. The throat aurorae are found to occur most frequently in the post-noon hours. The throat aurorae were also observed more frequently during winter, likely due to summer-winter asymmetry in the ionospheric conductance. The occurrence of the throat aurora is also found to be anti-correlated with the solar cycle, likely because low solar activity gives good chances for sporadic reconnection that favors the occurrence of throat aurora. The dependence on interplanetary magnetic field reveals positive Bx favoring the occurrence of throat aurora. It also shows positive Bx (negative By) supports pre-noon (post-noon) occurrence. The difference in the trend and average values of background interplanetary magnetic field conditions with the throat aurora confirms the favorable conditions for the occurrence of throat aurora.