Long-term determination of energetic electron precipitation

Details of Research

TitleLong-term determination of energetic electron precipitation into the atmosphere from AARDDVARK subionospheric VLF observationsAbstractWe 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 SodankylÃ¤, Finland (SodankylÃ¤ 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 693days 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. Key Points Subionospheric VLF used to detect energetic electron precipitation Magnitudes agree with satellite observations but with higher sensitivity Variation agrees well with that of lower band chorus Â©2015. American Geophysical Union. All Rights Reserved.

Details

1st AuthorNeal, J. AuthorNeal, J.Rodger, C.Clilverd, M.Thomson, N.Raita, T.Ulich, T.Year2015JournalJournal of Geophysical Research: Space PhysicsVolume120Number3Pages2194-2211DOI10.1002/2014JA020689URLhttps://www.scopus.com/inward/recor.....e8384c949d8d3eb44adac1ff9PublisherBlackwell Publishing LtdAuthor KeywordsAARDDVARK networkelectron precipitationradiation beltssubionospheric VLF propagation

Other

CitationNeal, J., Rodger, C., Clilverd, M., Thomson, N., Raita, T. and Ulich, T. (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

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