University of Oulu

W. Xu et al., "VLF Measurements and Modeling of the D-Region Response to the 2017 Total Solar Eclipse," in IEEE Transactions on Geoscience and Remote Sensing, vol. 57, no. 10, pp. 7613-7622, Oct. 2019. doi: 10.1109/TGRS.2019.2914920

VLF measurements and modeling of the D-region response to the 2017 total solar eclipse

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Author: Xu, Wei1; Marshall, Robert A.2; Kero, Antti3;
Organizations: 1Department of Aerospace Engineering Sciences, University of Colorado Boulder, Boulder, CO 80309 USA
2Department of Aerospace Engineering Sciences, University of Colorado Boulder, Boulder, CO 80309 USA
3Sodankylä Geophysical Observatory, University of Oulu, 90014 Oulu, Finland
4Space Science Division, Naval Research Laboratory, Washington, DC 20375 USA
5Center for Atmospheric and Space Sciences, Utah State University, Logan, UT 84322 USA
Format: article
Version: accepted version
Access: open
Online Access: PDF Full Text (PDF, 13.4 MB)
Persistent link:
Language: English
Published: Institute of Electrical and Electronics Engineers, 2019
Publish Date: 2019-09-25


In this paper, we report measurements in Colorado and Utah of the disturbed very-low-frequency (VLF) signals from the NML Navy transmitter in North Dakota during the 2017 solar eclipse. Using an occultation mask of solar fluxes together with detailed chemistry and VLF propagation simulations, we quantify the D-region response to the eclipse, in terms of electron density variation, as well as the expected signatures of VLF transmitter signals. The VLF measurements, including an anomalous amplitude enhancement recorded in UT, can be quantitatively explained using the Wait and Spies ionospheric profile with a sharpness parameter of β = 0.3 km⁻¹ above ~55 km and an increase in the D-region ionosphere height of Δh′ ≃ 8 km. This sharpness parameter is consistent with previously reported rocket measurements and first-principles calculations. The best-fit results suggest a reduction of D-region electron density by ~90% during the eclipse in the D-region, implying an occultation of Lyman by nearly 99%. This finding agrees with detailed calculations of time-dependent obscuration factors utilizing the He 30.4-nm images from Solar Dynamics Observatory as a proxy for the distribution of Lyman across the solar disk and limb. Moreover, the present results show that subionospheric VLF propagation is sensitive to the sharpness parameter of the electron density profile in the D-region. Previously reported first-principles simulations have shown that the sharpness parameter is mostly controlled by the background concentration of minor neutral species. Thus, the VLF technique can be likely used to remotely sense these neutral species at and below the effective reflection altitudes of VLF waves.

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Series: IEEE transactions on geoscience and remote sensing
ISSN: 0196-2892
ISSN-E: 1558-0644
ISSN-L: 0196-2892
Volume: 57
Issue: 10
Pages: 7613 - 7622
DOI: 10.1109/TGRS.2019.2914920
Type of Publication: A1 Journal article – refereed
Field of Science: 115 Astronomy and space science
114 Physical sciences
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