Hemispheric Asymmetry of Pre-Midnight Topside Ionospheric Vertical Flow Velocities Observed at Midlatitudes by FORMOSAT-5 During Equinoxes
Abstract
FORMOSAT-5 (FS-5) satellite orbiting at 720 km altitude measured the pre-midnight topside ionospheric properties at 2230 LT sector during the solar minimum year of 2018. The latitudinal variations of ion density for March and September equinoxes are observed to be almost identical to each other at different longitudes along the FS-5 orbits. They indicate a hemispheric symmetrical variation with respect to the density value near the equator. However, a hemispheric asymmetry in the vertical flow velocities has been observed at midlatitudes for both equinoxes. The vertical flow velocities in the northern hemisphere indicate a persistent negative (downward) value. While in the southern hemisphere, the vertical flow velocities vary around the zero value with frequent positive (upward) value observed. This north-south hemispheric asymmetry of vertical flow velocity variations apparently does not correlate with the density variations, but is closely related to a south-to-north inter-hemispheric transport of plasma flows. The persistent hemispheric asymmetry of vertical flow velocities observed at midlatitudes during both equinoctial seasons is probably caused by the different pace in the diurnal variations of vertical ionospheric movement in the two hemispheres from the heat capacity effect in the northern hemispheric land mass verses the southern hemispheric ocean water.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMSA13B3236S
- Keywords:
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- 0355 Thermosphere: composition and chemistry;
- ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 0358 Thermosphere: energy deposition;
- ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 3369 Thermospheric dynamics;
- ATMOSPHERIC PROCESSES;
- 7949 Ionospheric storms;
- SPACE WEATHER