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| Titel |
Low-frequency ionospheric sounding with Narrow Bipolar Event lightning radio emissions: regular variabilities and solar-X-ray responses |
| VerfasserIn |
A. R. Jacobson, R. Holzworth, E. Lay, M. Heavner, D. A. Smith |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
0992-7689
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| Digitales Dokument |
URL |
| Erschienen |
In: Annales Geophysicae ; 25, no. 10 ; Nr. 25, no. 10 (2007-11-06), S.2175-2184 |
| Datensatznummer |
250015932
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| Publikation (Nr.) |
 copernicus.org/angeo-25-2175-2007.pdf |
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| Zusammenfassung |
| We present refinements of a method of ionospheric D-region sounding that
makes opportunistic use of powerful (109–1011 W) broadband
lightning radio emissions in the low-frequency (LF; 30–300 kHz) band. Such
emissions are from "Narrow Bipolar Event" (NBE) lightning, and they are
characterized by a narrow (10-μs), simple emission waveform. These
pulses can be used to perform time-delay reflectometry (or "sounding") of
the D-region underside, at an effective LF radiated power exceeding by
orders-of-magnitude that from man-made sounders. We use this opportunistic
sounder to retrieve instantaneous LF ionospheric-reflection height whenever
a suitable lightning radio pulse from a located NBE is recorded. We show how
to correct for three sources of "regular" variability, namely solar zenith
angle, radio-propagation range, and radio-propagation azimuth. The residual
median magnitude of the noise in reflection height, after applying the
regression corrections for the three regular variabilities, is on the order
of 1 km. This noise level allows us to retrieve the
D-region-reflector-height variation with solar X-ray flux density for
intensity levels at and above an M-1 flare. The instantaneous time response
is limited by the occurrence rate of NBEs, and the noise level in the height
determination is typically in the range ±1 km. |
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