Solar Activity Dependence of Night Side Aurora in Winter/Dark Conditions

Abstract:

The dependence of the night side auroral energy flux on solar activity is quantitatively studied for winter/dark and geomagnetically quiet conditions of Kp 1-3. With data combined from TIMED/GUVI and DMSP/SSUSI observations, we first separate the effects of geomagnetic activity from those of solar flux on the auroral precipitation. Our results showed that, the solar flux dependence of both the diffuse and discrete auroral power, changed with the geomagnetic activity. This phenomenon might be associated with increasing background ionospheric ionization as the geomagnetic activity increases, which consequently changes the ionospheric conductivity and limites the plasma density gradient along the magnetic field line. Different solar activity dependent rate is also found between pre-midnight and post-midnight diffuse auroral precipitation. All these results indicate effects from conjugate summer hemisphere.