Ground‐based observations of VLF waves as a proxy for satellite observations: Development of models including the influence of solar illumination and geomagnetic disturbance levels

Simms, Laura E.; Engebretson, Mark J.; Clilverd, Mark ORCID: https://orcid.org/0000-0002-7388-1529; Rodger, Craig. 2019 Ground‐based observations of VLF waves as a proxy for satellite observations: Development of models including the influence of solar illumination and geomagnetic disturbance levels. Journal of Geophysical Research: Space Physics, 124 (4). 2682-2696. https://doi.org/10.1029/2018JA026407

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Official URL: https://agupubs.onlinelibrary.wiley.com/doi/abs/10...

Abstract/Summary

Ground VLF observations have often been used to infer VLF activity in the magnetosphere, however, they are not an unbiased measure of activity at satellite altitudes due to transionospheric absorption and subionospheric attenuation. We propose several empirical models that control for these effects. VLF power spectral density (PSD) from the VLF/ELF Logger Experiment (VELOX, L=4.6, Halley, Antarctica) is used to predict DEMETER low Earth orbit VLF PSD. Validation correlations of these models are as high as 0.764, thus ground VLF receivers spaced around the Earth could provide complete coverage of outer radiation belt lower band chorus over the latitudinal limits of this model (±45‐75°). Correlations of four frequency bands (centered at 0.5 kHz, 1.0 kHz, 2.0 kHz, and 4.25 kHz) are compared. The simple linear correlation between ground and satellite VLF PSD in the 1.0 kHz channel was 0.606 (at dawn). A cubic model resulted in higher correlation (0.638). VLF penetration to the ground is reduced by ionospheric absorption during solar illumination and by disruption of ducting field lines during disturbed conditions. Subionospheric attenuation also reduces VLF observations from distant field lines. Addition of these covariates improved predictions. Both solar illumination and disturbed conditions reduced ground observation of VLF PSD, with higher power waves penetrating to the ground proportionately less than lower power waves. The effect of illumination in reducing wave penetration was more pronounced at higher frequency (4.25 kHz), with the effect at a mid‐range frequency (2.0 kHz) falling between these two extremes.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	https://doi.org/10.1029/2018JA026407
ISSN:	0148-0227
Additional Keywords:	Ground VLF observations, Outer radiation belt VLF waves, Prediction models
Date made live:	25 Mar 2019 16:35 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/522647

Item Type:

Publication - Article

Digital Object Identifier (DOI):

https://doi.org/10.1029/2018JA026407

ISSN:

0148-0227

Additional Keywords:

Ground VLF observations, Outer radiation belt VLF waves, Prediction models

Date made live:

25 Mar 2019 16:35 +0 (UTC)

URI:

https://nora.nerc.ac.uk/id/eprint/522647