Energetic Particles in the Heliosphere: from the Sun to Planetary Atmospheres
The radiation belt slot region: A source of energetic electron precipitation in the southern hemisphere polar vortex.
Andrew J. Kavanagh
Neil Cobbett, Peter Kirsch, Tracy Moffat-Griffin
British Antarctic Survey
Energetic electron precipitation at mid-magnetic latitudes in the southern winter hemisphere has the potential to influence regional climate variability. The offset of the magnetic pole in the southern hemisphere means that the footprint of the radiation belt slot region crosses the winter polar vortex; during large geomagnetic storms the slot region can be filled by electrons, some of which precipitate into the atmosphere. Energetic electron precipitation changes the ion chemistry, generating species that impact the heat balance of the middle atmosphere and potentially influence regional climate variability when transported in the polar vortex. Energetic precipitation also leads to increased ionization in the mesosphere, which in turn attenuates high frequency radio waves that pass through the region. We present observations of the attenuation of a transmitted signal at 1.96 MHz under the Antarctic footprint of the radiation belt slot-region. We show that increased electron fluxes measured by NOAA POES satellites correlates with changes in the received signal that one would expect from increased ionization in the mesosphere. An epoch analysis of the largest of these slot-region filling events shows a clear response to the precipitating electron flux suggesting that the slot region is a source of precipitation that has the potential to impact on the heat balance of the middle atmosphere and below.


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