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Solar activity dependence of nightside aurora in winter conditions
Author(s) -
Zhou Su,
Luan Xiaoli,
Dou Xiankang
Publication year - 2016
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
eISSN - 2169-9402
pISSN - 2169-9380
DOI - 10.1002/2015ja021865
Subject(s) - physics , earth's magnetic field , thermosphere , atmospheric sciences , solar maximum , ionosphere , flux (metallurgy) , satellite , solar cycle , solar minimum , quiet , solar wind , astrophysics , environmental science , geophysics , plasma , astronomy , magnetic field , chemistry , organic chemistry , quantum mechanics
The dependence of the nightside (21:00–03:00 MLT; magnetic local time) auroral energy flux on solar activity was quantitatively studied for winter/dark and geomagnetically quiet conditions. Using data combined from Thermosphere, Ionosphere, Mesosphere Energetics and Dynamics/Global Ultraviolet Imager and Defense Meteorological Satellite Program/Special Sensor Ultraviolet Spectrographic Imager observations, we separated the effects of geomagnetic activity from those of solar flux on the nightside auroral precipitation. The results showed that the nightside auroral power was reduced by ~42% in solar maximum ( F 10.7 = 200 sfu; solar flux unit 1 sfu = 10 −22 W m −2 Hz −1 ) with respect to that under solar minimum ( F 10.7 = 70 sfu) for the Kp = 1 condition, and this change rate became less (~21%) for the Kp = 3 condition. In addition, the solar cycle dependence of nightside auroral power was similar with that from both the premidnight (21:00–23:00 MLT) and postmidnight (01:00–03:00 MLT) sectors. These results indicated that as the ionospheric ionization increases with the enhanced auroral and geomagnetic activities, the solar activity dependences of nightside auroral power become weaker, at least under geomagnetically quiet conditions.