Do we understand what creates 150-km echoes and gives them their distinct structure?
Abstract
Researchers first discovered 150-km echoes over 50 years ago using the first large VHF radars near the geomagnetic equator. However, the underlying mechanism that creates and modulates them remains largely a mystery. Despite this lack of understanding the aeronomy community uses them to monitor daytime vertical plasma drifts between 130 and 160 km altitude. In a 2016 paper, Oppenheim and Dimant used simulations to show that photoelectrons can generate the type of echoes seen by the radars but this theory doesn't explain any of the detailed structures. This paper will show the modern observations of 150 km echoes using simultaneous radar and ionosonde measurements. It will then describe the latest analysis to attempt to explain these features using large-scale kinetic simulations of photoelectrons interacting with the ambient ionospheric plasma under a range of conditions.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2017
- Bibcode:
- 2017AGUFMSA32A..08O
- Keywords:
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- 2415 Equatorial ionosphere;
- IONOSPHERE;
- 2427 Ionosphere/atmosphere interactions;
- IONOSPHERE;
- 2736 Magnetosphere/ionosphere interactions;
- MAGNETOSPHERIC PHYSICS