VLF signal phase variations due to annular solar eclipses of May 20-21, 2012 and December 26, 2019

摘要

For the VLF propagation path NWC - Yakutsk the maximum increases of the signal phase delay were 0.652 and 0.48 radians for the annular solar eclipses of May 20, 2012 at 22:07:12 UT and December 26, 2019 at 06:07:30 UT respectively. Based on the solar eclipse circumstances and the Bessel elements the distributions of the eclipse linear phase and the ratio of open solar area to the full one along the propagation path NWC - Yakutsk are defined with a step 200 km and 126 seconds resolution for each distant element. The normalization coefficients relating the effective height changes of the Earth-ionosphere waveguide and the logarithm of the ratio of a solar radiation flux during the eclipse to a total radiation flux for the daytime are 2.597 ± 0.136 and 2.284 ± 0.178 km for the eclipses of May 20-21, 2012 and December 26, 2019 respectively. During the maximum shadowing of the NWC - Yakutsk radio path due to the solar eclipse of May 20, 2012 the maximum change of the effective height of the Earth-ionosphere waveguide is 4.71 km at 22:13:30 UT (for the segment 27° N 120° E, the eclipse linear phase is 0.953). For the eclipse of December 26, 2019, the maximum change of the effective height of the Earth-ionosphere waveguide is 4.29 km at 06:09:36 UT (for the segment 2° N 117° E, the eclipse linear phase is 0.962).