Correlation of very low and low frequency signal variations at mid-latitudes with magnetic activity and outer-zone particles

Abstract

Abstract. The disturbances of very low and low frequency signals in the lower mid-latitude ionosphere caused by magnetic storms, proton bursts and relativistic electron fluxes are investigated on the basis of VLF-LF measurements obtained in the Far East and European networks. We have found that magnetic storm (−150 < Dst < −100 nT) influence is not strong on variations of VLF-LF signals. The anomalies with negative amplitude were registered during the main and recovery phases for several magnetic storms (mainly for three northernmost paths). The correlation between VLF-LF signals and geomagnetic activity is rather weak even for these paths (≈ 12-18 %). Also, the correlation between magnetic activity and VLF signal variations recorded onboard the DEMETER satellite is not found. The significant influence of outer-zone particles (energetic particle sensor on board/Geostationary Operational Environmental Satellite (GOES) measurements) on the VLF-LF signal variations is found for almost half of the sub-ionospheric paths.

The Behavior of VLF/LF Variations Associated with Geomagnetic Activity, Earthquakes, and the Quiet Condition Using a Neural Network Approach

“…In one case of the five, the disturbances in the signals caused by magnetic storms were not detected absolutely. These results corresponded to the conclusions that had been obtained in previous work [ 10 , 11 , 12 ].…”

“…We can see that the magnetic storm-induced disturbances in the signals arose on the very day of the magnetic activation ( Figure 5 a), and in addition, a few days after it or after the day of the onset of magnetic activation ( Figure 5 b). Indeed, the disturbance in the signal occurred not only on the day of the magnetic storm, but also the day after it [ 10 , 11 , 12 ]. For example, if a magnetic storm began in the daytime, then as a rule, the disturbance in the signal occurred only the next day.…”

“…It was previously established that magnetic storms and solar energetic particle fluxes can induce phase and amplitude variations in the VLF signal [ 6 , 7 , 8 , 9 ]. The correlation of the phase and amplitude variations in the LF signal to the disturbance storm time (DST) index, as well as the correlation of the outer-zone particles (protons and electrons) to the high-pitch angle was revealed in [ 10 , 11 , 12 ]. In this work, we applied a neural network method for estimating the VLF/LF signal sensitivity to geomagnetic and seismic activity.…”

Effect of the total solar eclipse of March 20, 2015, on VLF/LF propagation

“…The storm recovery phase continued for more than a week, and an intense flux of relativistic electrons was registered during that period. Although geomagnetic activity affects only the behavior of a nighttime signal on midlatitude paths (e.g., (Rozhnoi et al, 2014)) and the eclipse was observed during the daytime, this made it difficult to select quiet undisturbed days as a control for the observations. Fifteen of the 22 paths crossed the region where the occultation was 40-90%.…”