Influence of geomagnetic storms on the mid latitude D and F2 regions

Pyla Naidu,Malladi Devi,Tirumalaraju Madhavilatha

doi:10.4401/ag-8127

Abstract

The signal amplitude of 22.1 kHz Very Low Frequency (VLF) waves, transmitted from the radio station Skelton, UK (GQD at 54.7 0 N, 2.8 0 W) and received at South France station (SID, Sudden Ionospheric Disturbance monitoring station at 46 0 N, 2 0 E) is studied for the effect of geomagnetic storms on the lower ionosphere. The VLF parameters, D-Layer Preparation Time (DLPT) depth and Mid-Day Peak (MDP) have been used to study the response of D-region to the geomagnetic storms occurred during the equinox months of 2012-2015. The two parameters recorded enhancement on the storm day and subsequent days. A shift in the sunrise Terminator Time is observed for the geomagnetic storms for which Sudden Commencement (SC) occurred during the day lit hours on the previous day. The observed effect of the geomagnetic storms on the mid latitude D-region is due to the precipitation of high energy particles. The response of F 2 -region to geomagnetic storms is studied using the f o F 2 data at Dourbes (50.1 0 N, 4.6 0 E), Belgium which is near the mid-point of the GQD-South France VLF path. The percentage of deviation of f o F 2 from the quiet day values, Df o F 2 is found to undergo positive and negative changes. The positive storm effect during daytime is mainly due to the penetration electric field and strong negative phase during both day time and night time is due to depleted [O]/[N 2 ] ratios.

Highlights

The Very Low Frequency (VLF) signals (3-30 kHz) have been used for investigating the response of the lower ionospheric D-region to solar events like X-ray flares and geomagnetic storms [Kumar et al, 2015; Selvakumaran et al, 2015; Kumar and Kumar, 2018]
The response of mid latitude D and F2 regions to intense geomagnetic storms which occurred during equinox months of 2012-2015 has been studied using the VLF amplitude data of Skelton (GQD) U.K -South France SID station path and frequency of F2-region (foF2) data at Dourbes
The D-Layer Preparation Time (DLPT) depth evaluated using the VLF amplitude of 22.1 kHz waves propagating over the path of GQD (UK) and South France station showed an increase on the storm day (Dst minimum)

Summary

Introduction

The Very Low Frequency (VLF) signals (3-30 kHz) have been used for investigating the response of the lower ionospheric D-region to solar events like X-ray flares and geomagnetic storms [Kumar et al, 2015; Selvakumaran et al, 2015; Kumar and Kumar, 2018]. These waves propagate in the earth-ionosphere waveguide and their propagation path completely lies in the D-region. Their propagation characteristics are sensitive to changes in the electron density and conductivity of the D-region. The space weather events like geomagnetic storms modify the high latitude ionosphere through solar wind driven particle precipitation, Joule heating and thermospheric circulation [Venkatesh et al, 2017]

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