Temporal Variation of Solar Wind in Controlling Solar Wind‐Magnetosphere‐Ionosphere Energy Budget

Abstract

Periodic oscillations associated with Alfven waves with periods ranging from several tens of minutes to several hours are commonly seen in the solar wind. It is not yet known how the solar wind oscillation frequency, and thus its temporal variation, regulates the energy flow through the coupled solar wind‐magnetosphere‐ionosphere‐thermosphere system. Utilizing the Coupled Magnetosphere‐Ionosphere‐Thermosphere Model driven by solar wind and interplanetary magnetic field (IMF), we have analyzed the magnetosphere‐ionosphere‐thermosphere system response to IMF Bz oscillations with periods of 10, 30, and 60 min from the perspective of energy budget. Our results indicate that the energy flow from the solar wind to geospace depends on the IMF Bz oscillation frequency. The energy coupling efficiency, defined as the ratio of the globally integrated joule heating to Akasofu's Epsilon function, is higher for lower frequency IMF Bz oscillations. Joule heating in the upper atmosphere depends not only on directly driven processes due to solar wind variability but also on the intrinsic dynamics of the magnetosphere (i.e., loading‐unloading process). This work highlights the critical role of solar wind and IMF temporal variation and the inductive inertia and resistance of coupled magnetosphere‐ionosphere system in controlling the energy transfer in the coupled solar wind‐geospace system, which has not been explored before.

The Effects of IMF Bz Periodic Oscillations on Thermospheric Meridional Winds

“…The equatorward wind disturbances are, in general, stronger for low‐frequency oscillations, indicating more energy and momentum inputs at high latitudes and thus stronger wind drivers in these cases. This is consistent with larger PEEF and CPCP for the 30‐ and 60‐min oscillating conditions shown in Figure , and the results reported by Liu, Wang, Zhang, et al ().…”

“…As shown in Figure a (10‐min case), there are no obvious periodic Vn disturbances occurring at all latitudes, whereas notable periodic disturbances appear in the 30‐ and 60‐min cases (Figures b and c), respectively. This indicates that the global MIT system needs more than 10 min to respond fully to IMF B z variations, demonstrating the low‐pass filter nature of the coupled MIT system, which is consistent with the results of Liu, Wang, Zhang, et al (). Liu, Wang, Zhang, et al () studied the low‐pass filter character of the MIT system from the aspect of energy releasing into the ionosphere.…”

“…This indicates that the global MIT system needs more than 10 min to respond fully to IMF B z variations, demonstrating the low‐pass filter nature of the coupled MIT system, which is consistent with the results of Liu, Wang, Zhang, et al (). Liu, Wang, Zhang, et al () studied the low‐pass filter character of the MIT system from the aspect of energy releasing into the ionosphere. In our work, we focus on the responses of the MIT system to periodic IMF B z oscillations, and specifically, on studying the wind responses to the periodic variations in IMF B z .…”

“…Particle precipitation also contributes to the energy transfer from the solar wind into the upper thermosphere. Under the periodic temporal variations of IMF B z conditions, energy deposition and particle precipitation are changed periodically as well (Liu, Wang, Zhang, et al, , also seen Figure ). In the nighttime and Southern Hemisphere daytime, the effects of pressure gradient are more important than that of ion drag since the electron density is relatively low.…”

WITHDRAWN: Longitudinal Variations of Noontime Thermospheric Winds in Response to IMF Bz Temporal Oscillations: Broken Mean Circulation and Standing Feature

“…The thermospheric winds are important factors in the understanding of changes in ionosphere-thermosphere coupling system. In addition, the periodic oscillations of IMF Bz are a common phenomenon seen in the solar wind, which can produce periodic oscillations in the energy and momentum deposition in the upper atmosphere and TADs (e.g., Liu et al, 2018a;Zhang et al, 2019). Taking the abovementioned into consideration, the present work is to study the longitudinal and hemispheric patterns of the meridional wind changes at a xed local time, which…”