Solar flares and D-region ionization sources at high zenith angles.
Abstract
VLF phase measurements were made at three locations along the same great circle path of propagation during a solar flare which occurred on 29 June 1973. The termination for the solar flare effect on the ionosphere at VLF reflecting heights occurred between solar zenith angles 84 and 87, considerably less than the sunset zenith angle of 94 for this height. Ionization production is considered for the various ionization sources as a function of zenith angle. The measurement is consistent with the electron density at VLF reflecting heights being primarily controlled by solar photo-detachment but at zenith angles greater than 76 the ionization available for photo-detachment is produced by scattered Lyman-alpha as the direct Lyman-alpha becomes too heavily absorbed.
- Publication:
-
Journal of Atmospheric and Terrestrial Physics
- Pub Date:
- October 1974
- DOI:
- 10.1016/0021-9169(74)90207-4
- Bibcode:
- 1974JATP...36.1695G
- Keywords:
-
- Atmospheric Ionization;
- D Region;
- Ionospheric Propagation;
- Solar Activity Effects;
- Solar Flares;
- Zenith;
- Ion Production Rates;
- Ionospheric Electron Density;
- Ionospheric Sounding;
- Lyman Alpha Radiation;
- Phase Shift;
- Photodetachment;
- Radio Observation;
- Signal Measurement;
- Very Low Frequencies;
- Geophysics