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

A Rozhnoi,M Hayakawa,K Schwingenschuh,M Solovieva,B Levin,V Fedun

doi:10.5194/angeo-32-1455-2014

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.

Highlights

The measurements of sub-ionospheric very low and low frequency radio signals in the mid-latitude paths in the range of 15–50 kHz are broadly used for the identification of earthquake electromagnetic precursors
Our results indicate that the influence of particle fluxes on VLF–LF signals at midlatitudes is stronger than magnetic activity (Dst > −150 nT) influence
We investigated the response of the lower midlatitude ionosphere on magnetic activity and outer-zone particle fluxes

Summary

Introduction

The measurements of sub-ionospheric very low and low frequency radio signals in the mid-latitude paths in the range of 15–50 kHz are broadly used for the identification of earthquake electromagnetic precursors (see, e.g., Molchanov and Hayakawa, 2008; Hayakawa et al, 2010; Hayakawa, 2011; Biagi et al, 2004, 2007; Rozhnoi et al, 2004, 2009). The new receivers were installed in Yuzhno-Sakhalinsk and YuzhnoKurilsk (Russia), Graz (Austria) and Sheffield (UK) This improvement and the following study are essential for (i) a better identification of electromagnetic precursors of earthquakes and (ii) for finding the lower ionosphere response to tsunamis and volcano eruptions. Besides ground-based observations, the correlation method is used to analyse the VLF variations recorded onboard the DEMETER satellite

Source data

Correlation with magnetic activity

Correlation with proton bursts and relativistic electron fluxes

Discussion and conclusions