Long-term determination of energetic electron precipitation into the atmosphere from AARDDVARK subionospheric VLF observations

Neal, Jason J.; Rodger, Craig J.; Clilverd, Mark A. ORCID: https://orcid.org/0000-0002-7388-1529; Thomson, Neil R.; Raita, Tero; Ulich, Thomas. 2015 Long-term determination of energetic electron precipitation into the atmosphere from AARDDVARK subionospheric VLF observations. Journal of Geophysical Research: Space Physics, 120 (3). 2194-2211. 10.1002/2014JA020689

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Abstract/Summary

We analyze observations of subionospherically propagating very low frequency (VLF) radio waves to determine outer radiation belt energetic electron precipitation (EEP) flux magnitudes. The radio wave receiver in Sodankylä, Finland (Sodankylä Geophysical Observatory) observes signals from the transmitter with call sign NAA (Cutler, Maine). The receiver is part of the Antarctic-Arctic Radiation-belt Dynamic Deposition VLF Atmospheric Research Konsortia (AARDDVARK). We use a near-continuous data set spanning November 2004 until December 2013 to determine the long time period EEP variations. We determine quiet day curves over the entire period and use these to identify propagation disturbances caused by EEP. Long Wave Propagation Code radio wave propagation modeling is used to estimate the precipitating electron flux magnitudes from the observed amplitude disturbances, allowing for solar cycle changes in the ambient D region and dynamic variations in the EEP energy spectra. Our method performs well during the summer months when the daylit ionosphere is most stable but fails during the winter. From the summer observations, we have obtained 693 days worth of hourly EEP flux magnitudes over the 2004–2013 period. These AARDDVARK-based fluxes agree well with independent satellite precipitation measurements during high-intensity events. However, our method of EEP detection is 10–50 times more sensitive to low flux levels than the satellite measurements. Our EEP variations also show good agreement with the variation in lower band chorus wave powers, providing some confidence that chorus is the primary driver for the outer belt precipitation we are monitoring.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	10.1002/2014JA020689
Programmes:	BAS Programmes > BAS Programmes 2015 > Space Weather and Atmosphere
ISSN:	21699380
Additional Keywords:	electron precipitation, radiation belts, subionospheric VLF propagation, AARDDVARK network
Date made live:	19 May 2015 10:37 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/510826

Item Type:

Publication - Article

Digital Object Identifier (DOI):

10.1002/2014JA020689

Programmes:

BAS Programmes > BAS Programmes 2015 > Space Weather and Atmosphere

ISSN:

21699380

Additional Keywords:

electron precipitation, radiation belts, subionospheric VLF propagation, AARDDVARK network

Date made live:

19 May 2015 10:37 +0 (UTC)