Substorm Manifestations at Radio Paths of Oblique Ionospheric Sounding in the Arctic

Abstract

The impact of geomagnetic substorms on radio propagation within the high-frequency (HF) range was analyzed using oblique ionospheric sounding data. These data were obtained from the unique system of radio paths that covers the whole region of the Russian Arctic. The study focused on the effects of two substorms with a twofold difference in intensity. Variations of four radio propagation parameters were studied: the maximum and lowest observed frequencies of the F2 ionospheric layer (F2MOF and F2LOF), and the same frequencies of the sporadic Es layer (EsMOF and EsLOF). Even the weak geomagnetic substorm (AEmax ~ 500 nT) significantly changed the ionosphere state and, consequently, the character of radio propagation at paths. The absorption of signals was more pronounced during a more intense substorm which resulted in loss of information during the transmissions through HF channels. The variations of propagation parameters (ΔMOF and ΔLOF) depend more on the path reflection point location and on the intensity of a substorm. Two substorms with a twofold difference in intensity had similar effects on ΔMOF, except for (a) the more pronounced smoothing of the Main Effect and (b) the higher ΔEsMOF amplitude during the intense substorm. Both issues are explained by more intense particle precipitations during the more intense disturbance.