J. Space Weather Space Clim.
Volume 7, 2017
|Number of page(s)||20|
|Published online||27 November 2017|
Variations of topside ionospheric electron density near the dawn terminator in relation to geomagnetic activity
Institute of Space and Plasma Sciences, National Cheng Kung University,
2 Now at National Property Administration, Ministry of Finance, Taiwan
3 Department of Aerospace Engineering, Tamkang University, New Taipei City, Taiwan
* Corresponding author: email@example.com
Accepted: 20 October 2017
A statistical study to determine the influence of geomagnetic disturbances on the ionosphere across the dawn terminator at subauroral and middle latitudes is performed, based on the vertical electron density profiles measured by the GPS Occultation Experiment aboard the FORMOSAT-3/COSMIC satellites from August 2006 to July 2009. Three ranges of solar zenith angles are adopted to characterize transitions between the pre- and post-dawn ionosphere. Results indicate opposing plasma density effects at the darkened and sunlit locations between 50° and 65° magnetic latitude (λm). The darkened topside ionosphere features density increases associated with geomagnetic activity, while density reductions mark its sunlit counterpart. The average electron peak density in the F2 region can increase by up to 44% in the darkened ionosphere and decrease by up to 20% in the sunlit ionosphere as Kp changes from 0–1 to 4–5. In the λm = 55°–65° range, the dominant contributors to the density perturbation are auroral electron precipitation for the darkened region and enhanced penetration electric fields for the sunlit region, with the transition occurring across the terminator local times. Dominance shifts first to electric fields at 50°–55°, then to aurora-induced neutral wind at 45°–50°, suggesting that during disturbed times electric fields seldom penetrate below λm = 50°. Findings presented in this statistical study should contribute to the study of space weather and the understanding of non-local influences of geomagnetic disturbances on topside dynamics.
Key words: solar zenith angle / penetration electric fields / auroral electron precipitation / neutral wind / dawnside ionosphere
© S.W.Y. Tam et al., Published by EDP Sciences 2017
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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