Numerical analysis of electron density and response time delay during solar flares in mid-latitudinal lower ionosphere
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ORIGINAL ARTICLE
Numerical analysis of electron density and response time delay during solar flares in mid-latitudinal lower ionosphere Sayak Chakraborty1 · Tamal Basak1
Received: 21 June 2020 / Accepted: 7 December 2020 © The Author(s), under exclusive licence to Springer Nature B.V. part of Springer Nature 2020
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 (χ(t))’ profile over ionosphere. We numerically solve the ‘electron continuity equation’ to obtain the lower ionospheric electron density profile (Ne (t)). The electron production rate (q(t)) is governed by the (i) X-ray profile (φ(t)) of the flare, (ii) χ(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 Ne (t)-profile computation. We observe that temporal Ne (t)-profiles differ when computed for lower ionosphere over different discrete latitudes. Further, we compute the spatial Ne (t)-profile across mid-latitude at the time when φ(t) = φmax . Now we assume that, these flares repeat themselves every day of a year (DoY ) at the same time of a day and we compute Ne (t)profiles for each day. We found a seasonal effect on Ne (t)profile due to solar flare. Further, we investigate the response time delay (t) of the lower ionosphere, which is the time difference between incidence of X-ray and the respective change in Ne (t)-profiles during solar flares. Strong seasonal effects on Ne (t)-profile and t are the unique results of this work. Keywords Solar flares · Electron continuity equation of lower ionosphere
B T. Basak
[email protected]
1
Amity University Kolkata, Major Arterial Road, Action Area II, Rajarhat, New Town, Kolkata 700135, India
1 Introduction Solar-ionosphere interaction during solar flares causes sudden enhancements and thereafter a gradual decay of the ionospheric electron density (Ne (t)). Since, the degree of ionization varies widely from layer to layer, it causes a wide variation in the altitude profile of Ne (t). The impact of a solar flare is different at different layers. Le et al. (2012) reported that the Extreme Ultra Violet (EUV) response of a flare is better correlated than X-ray response with Total Electron Content (TEC) of the ionosphere. From SROSS-C2 satellite data analysis, Sharma et al. (2004) reported that the temperature enhancement of ions and electron of ionosphere take place during a flare. Berdermann et al. (2018) reported an overall ionospheric response to an X9.3-class flare and it’s consequences on navigation systems. The systematic enhancement of lower ionospheric parameters during a set of solar flares is reported by
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