Influence of solar X-ray flares on the earth-ionosphere waveguide

Abstract

A simultaneous analysis of solar are X-ray irradiance and VLF signal amplitude on the GQD/22.1 kHz trace was carried out. Solar are data were taken from GOES 12 satellite listings. The VLF amplitude data were recorded by means of the AbsPAL (Absolute Phase and Amplitude Logger) at the Institute of Physics, Belgrade, Serbia. It was found that solar are events from class C to class X affect the VLF signal amplitude in various ways and can be classified according to the type of effect produced in the Earth-ionosphere waveguide on the VLF propagation.

Classification of X-ray solar flares regarding their effects on the lower ionosphere electron density profile

“…Over 150 flare events, VLF-detected through May to August in the years 2004-2007, have been analyzed. Though apparently different depending on the path, the flareinduced VLF disturbances show stable patterns: while both phase and amplitude enhancement on long NAA and NWC paths are regularly detected, VLF perturbations on the short (1982 km in length) GQD path display more complexity, including both an decrease and increase, as well as oscillations, depending on the flare intensity (Grubor et al, 2005). Therefore, it is precisely the phase and amplitude perturbation of the GQD signal that we are concerned with in the present work.…”

Space weather effects on the low latitude D-region ionosphere during solar minimum

“…By extrapolating the phase profiles during the strong solar flares, Thomson et al (2005) estimated the peak value of the X-ray flux that corresponded to solar flare of X45 class. Grubor et al (2005) from measurement of GQD, Anthon (54°53′ N, 17°W, 22.1 kHz) transmitter signal at Belgrade (44°51′ N, 20°23′ E) for the solar flare events that occurred during 2004 and 2005, a low solar activity period, found that flares with classes C to X can perturb the amplitude of VLF signals propagating in the EIWG. Recently, Raulin et al (2013) examined the effects of Lyman-α excess during solar flares on the D-region ionosphere using the VLF phase measurements.…”

Initial results on solar flare effect on 24.8 kHz subionospheric propagation over long path to Suva

“…The enhancement in the amplitude of NLK signal with the increase in the solar flare intensity can be explained qualitatively as follows. As the flare flux increases, two phenomena might take place, 1) the increase in the D-region electron density and 2) redistribution of the electron density with height which lowers the D-region (Grubor et al 2005). The upper boundary of the waveguide might become more sharp and lower and as a result, VLF signal is reflected at sharp boundary with comparatively less penetration into the D-region and hence undergoes less attenuation/absorption than under the normal propagation conditions.…”

“…Researchers have reported changes in the ionospheric parameters, H' and β as a function of solar X-ray flux (Thomson et al , 2005Grubor et al 2005;Zigman et al 2007). The increase in the D-region electron density can produce significant perturbations in the phase and the amplitude of VLF signals propagating in the Earthionosphere waveguide.…”