Longitudinal Differences in Electron Temperature on Both Sides of Zero Declination Line in the Mid-latitude Topside Ionosphere

In this study, electron temperature (Te) observations from the Defense Meteorological Satellite Program F17 and F18 spacecraft during 2010-2017 are analyzed to explore the longitudinal differences of Te in the topside ionosphere on both sides of zero geomagnetic declination lines in the northern mid-latitude under geomagnetically weak activities (Kp <= 3). Te in the North American sector (45oW-135oW) has prominent longitudinal differences on sector scale. Te increases from the west side to east side in the morning, but vice versa in the afternoon. The relative value of longitudinal differences in Te peaks in May to August. The East Asian sector (45oE-135oE) of similar geomagnetic field configurations is selected for verification. There are similar local time and seasonal dependencies in the two sectors, while the intensity of longitudinal differences of Te weakens in the latter sector. The estimation of contributions to the longitudinal difference of Te from thermosphere winds provided by the empirical horizontal wind model (HWM14), peak height (hmF2) and peak density (NmF2) of the F2 layer indicates that the magnetic declination modulation effect of neutral winds at mid-latitudes changes electron density (Ne), which indirectly changes the longitudinal difference in Te. Furthermore, the zonal wind at different local times and the seasonal variation of meridional winds may be the main effect factors of dependencies in Te longitudinal differences. The sector longitudinal differences of both geomagnetic declination and horizontal winds are possibly major reasons causing the different intensity of this characteristic in the two sectors.

Automated summary

This study analyzed electron temperature observations from 2010 to 2017 to explore longitudinal differences in the topside ionosphere in the northern mid-latitudes. The North American sector showed prominent longitudinal differences in Te, while the East Asian sector exhibited weaker differences, possibly due to factors such as geomagnetic activity and horizontal winds.