Numerical analysis of electron density and response time delay during solar flares in mid-latitudinal lower ionosphere

Abstract

Impacts of solar flare vary at different parts of the lower ionosphere depending on it’s proximity to the direct exposure of incoming solar radiation. The quantitative analysis of this phenomena can be attributed to ‘solar zenith angle ( $\chi (t)$ )’ profile over ionosphere. We numerically solve the ‘electron continuity equation’ to obtain the lower ionospheric electron density profile ( $N_{e}(t)$ ). The electron production rate ( $q(t)$ ) is governed by the (i) X-ray profile ( $\phi (t)$ ) of the flare, (ii) $\chi (t)$ -values during the flare occurrence etc. For analyzing the X-ray profile during flares, we use the GOES-15 satellite observations. Since we’re working on electron continuity equation based simplified ionospheric model, we confined our analysis for comparatively stable mid-latitude ionosphere only. We choose three flares each from C, M and X-classes for $N_{e}(t)$ -profile computation. We observe that temporal $N_{e}(t)$ -profiles differ when computed for lower ionosphere over different discrete latitudes. Further, we compute the spatial $N_{e}(t)$ -profile across mid-latitude at the time when $\phi (t)=\phi _{max}$ . Now we assume that, these flares repeat themselves every day of a year ( $DoY$ ) at the same time of a day and we compute $N_{e}(t)$ -profiles for each day. We found a seasonal effect on $N_{e}(t)$ -profile due to solar flare. Further, we investigate the response time delay ( $\Delta t$ ) of the lower ionosphere, which is the time difference between incidence of X-ray and the respective change in $N_{e}(t)$ -profiles during solar flares. Strong seasonal effects on $N_{e}(t)$ -profile and $\Delta t$ are the unique results of this work.