Effect of Magnetic Storm Related Thermospheric Changes on the Evolution of Equatorial Plasma Bubbles

Abstract

Past efforts to predict scintillations on VHF and L-band radio signals recorded at equatorial and low-latitude stations have been mostly based on a theoretical linear growth rate of Rayleigh-Taylor instability on the bottomside of the post-sunset equatorial F layer, which is responsible for the generation of an equatorial plasma bubble (EPB). However, it is the maximum height that an EPB reaches above the dip equator and development of intermediate scale irregularities within the EPB, in its nonlinear phase of evolution that determines the latitudinal distribution of scintillations. Amplitude scintillations recorded by a network of VHF and L-band receivers on a quiet day, 13 March 2015 and on 20 March 2015, a few days after the 17 March 2015 magnetic storm, show that latitudinal extent of scintillations caused by EPB irregularities is lesser on 20 March than on 13 March. Geomagnetic and ionosonde data from an equatorial station, and vertical total electron content distributions obtained from Global Navigation Satellite Systems observations, indicate that the equatorial ionospheric conditions are approximately same on these 2 days. Simulation of thermospheric conditions for these 2 days is carried out using the Coupled Thermosphere, Ionosphere, Plasmasphere, and Electrodynamics model. It is found that thermospheric atomic oxygen density is enhanced in the aftermath of the major magnetic storm of 17 March 2015, resulting in enhanced ion-neutral collision frequencies over the dip equator on 20 March. This limits the height to which an EPB rises over the dip equator on this day, and thus impacts the latitudinal distribution of scintillations.

Intensification and Weakening of Equatorial Plasma Bubble Development Observed by GOLD During Different Phases of a Geomagnetic Storm

“…The response of EPB development to geomagnetic storms has been widely investigated using different techniques including the use of ionosondes (Abdu et al., 2003; Santos et al., 2012; Sripathi et al., 2018), TEC derived from the Global Navigation Satellite Systems (GNSS) (Cherniak et al., 2019; de Paula et al., 2019; F. Huang et al., 2021; Picanço et al., 2022), low‐earth orbiting (LEO) satellites (Chang et al., 2022; Wan et al., 2022; Zakharenkova et al., 2019), ground‐ and space‐based imagers (Ghodpage et al., 2018; Karan et al., 2023; Wu et al., 2020) and numerical models (Bhattacharyya et al., 2019; Blanc & Richmond, 1980; Carter et al., 2014, 2016). Four important deductions from these studies are (a) The influence of disturbance electric fields on ESF/EPB development is a function of local time.…”

Ground‐Based GNSS and C/NOFS Observations of Ionospheric Irregularities Over Africa: A Case Study of the 2013 St. Patrick’s Day Geomagnetic Storm

“…The formation of EPBs can be significantly altered during geomagnetic storm mostly by the Prompt Penetration Electric Field (PPEF) (Nishida et al., 1966), the disturbance dynamo electric field (DDEF) (Blanc & Richmond, 1980) and trans‐equatorial neutral wind (Maruyama & Matuura, 1984; Mendillo et al., 1992). For example, the regular pre‐reversal enhancement (PRE) in the vertical E × B drift which is responsible for the uplift of the equatorial F‐layer can be enhanced (reduced) by eastward (westward) PPEF (DDEF) in the postsunset period thereby, promoting the generation (inhibition) of EPBs (A. O. Akala et al., 2020; Amaechi et al, 2020a; Bhattacharyya et al., 2019; Dungey, 1956; B. J. Fejer et al., 1999; X. Luo et al., 2019; Tulasi Ram et al., 2006; Whalen, 2002).…”

“…For example, the regular pre-reversal enhancement (PRE) in the vertical E × B drift which is responsible for the uplift of the equatorial F-layer can be enhanced (reduced) by eastward (westward) PPEF (DDEF) in the postsunset period thereby, promoting the generation (inhibition) of EPBs (A. O. Akala et al, 2020;Amaechi et al, 2020a;Bhattacharyya et al, 2019;Dungey, 1956;B. J. Fejer et al, 1999;X.…”

Active (Evolving) Phase of Equatorial Plasma Bubbles Observed Over Tirunelveli

“…Various ambient ionospheric conditions like strength of pre‐reversal enhancement (PRE) of the eastward electric field, vertical density gradient at the bottom side of F region, ion‐neutral collisions, horizontal conductivities in E region, alignment of sunset terminator and magnetic meridian, neutral winds, and strength of ambient magnetic field play an important role in deciding the genesis of EPBs (Abdu et al, 2008; Basu et al, 1996; Bhattacharyya, 2004; Patra et al, 1997; Tsunoda, 1985). Worldwide efforts have led to a situation where we have gathered fairly good understanding about EPBs through theory, observations, and simulations (Bhattacharyya et al, 2019; Burke et al, 2004; Carter et al, 2014; Engavale & Bhattacharyya, 2005; Fejer, 1997; Navarro et al, 2019; Ossakow, 1981; Retterer, 2010; Sultan, 1996; Yokoyama et al, 2014). But day‐to‐day generation of scintillation producing irregularities in the low‐latitude ionosphere is still a challenging question from the prediction point of view.…”