The Significant Enhanced Quiet-Time Equatorial Ionization Anomaly by the Intense Solar Flare on 06 September 2017

Abstract

On 06 September 2017, two X-class intense solar flare cases (X2.2 and X9.3) are observed. The X2.2/X9.3 case starts at 0857/1153 UT and peaks at 0910/1202 UT. The latter one is the most powerful event in recent decades and the more “geoeffective.” Using the total electron content (TEC) from the Global Navigation Satellite System, the Thermosphere-Ionosphere Electrodynamic General Circulation Model, the enhanced equatorial ionization anomaly (EIA) during the intense “geoeffective” X9.3 solar flare are investigated in this work. The observed and modeled TEC indicate that the daytime plasma is obviously enhanced by the solar flares. The model results show that the significant enhancement in EIA due to solar flare has a maximum density of 6.63 × 10¹¹ m⁻³ at pre-noon sector. It has a maximum increase in the percentage of 26.59%. Four areas of enhanced and two areas of reduced electron density are found, forming a butterfly-like structure. Based on the term analysis of ion continuity equation, the rate of chemical production during daytime is considerably strengthened, with an average magnitude of 7.37 cm⁻³s⁻¹. The roles of ambipolar diffusion are positive at almost all local time (LT) of EIA, except for the post-dusk sector. The daytime eastward electric field is weakened by an average intensity of 0.12 mV/m, preventing the formation of enhanced EIA. The effects of the disturbed horizontal winds (major: meridional winds) have an obvious hemispheric asymmetry.