Solar Origins of August 26, 2018 Geomagnetic Storm: Responses of the Interplanetary Medium and Equatorial/Low‐Latitude Ionosphere to the Storm

Abstract

Perturbations in the solar atmosphere are the major origins of geomagnetic storms. Reconfiguration of magnetic fields in the solar atmosphere causes uplift of materials from the solar chromosphere into the corona. These relatively cool, but dense materials are suspended against gravity at greater heights by magnetic tension in the dips of the field lines, appearing by absorption against the hotter and brighter background (Carlyle, 2016). These materials could be elongated in structures, to the order of thousands of kilometers in length to form filaments, which could, in turn erupt from the solar coronal surface as Coronal Mass Ejection (CME). CMEs, particularly the Earth-directed ones are the sources of space weather events (e.g., geomagnetic storms) on the Earth. High Speed Streams (HSSs) from the Sun's coronal holes are the sources of the Corotating Interaction Regions (CIRs) which also known to cause geomagnetic storms (Burlaga & Lepping, 1977;Gosling, 1993). The occurrences of geomagnetic storms do influence the electrodynamics of

African and American Equatorial Ionization Anomaly (EIA) Responses to 2013 SSW Event

“…As shown by our results, following the arguments recently advanced by Akala et al. (2021) and Oyedokun et al. (2021), the corresponding local time of the main phase of the minor storm was at evening time in the American sector and at post‐midnight period in the African sector.…”

“…In the American sector, daytime eastward PPEF at sunset could have increased vertical E × B drift, leading to overall intensification of plasma forward fountain and consequently, enhancements in TEC (Akala et al., 2020; Arowolo et al., 2021; Tsurutani et al., 2008). On the other hand, in the African sector, the negative TEC response can be attributed to the downward direction of E × B drift caused by the nighttime westward PPEF (Akala et al., 2021; Tsurutani et al., 2008). Also, the effect of solar flux on 10 January 2013 to TEC value at both longitudes was minimal, compared to that of the effect of SSW forcing (16 January 2013) We observed a simultaneous occurrence of well‐developed two‐peak EIA signatures in the African and American sectors during the peak phase of January 2013 SSW.…”

“…The uplifted plasma diffuses along the magnetic field lines in a forward fountain manner (Kelley, 2009) to create a pair of well-developed two peaks of plasma ionization at about ±15° of the magnetic equator, and a reduced ionization at the magnetic equator (trough). When there is additional forcing arising from disturbances like SSW (strengthening) or geomagnetic storms on the ionosphere at daytime, plasma forward fountain mechanism could be intensified to a level of a super fountain, in which case, EIA crests locations could expand pole-ward to about ±30° of the magnetic equator, depending on the strength of the forcing (Akala et al, 2020(Akala et al, , 2021. On the other hand, if the forcing manifests at night, the usual daytime plasma fountain is reversed, causing equator-ward compression of plasma from their daytime crests locations (Arowolo et al, 2021).…”

“…The lesser cases of irregularities occurrences recorded in the African sector could be due to longitudinal differences in the distribution of evening-time eastward electric field (Fejer et al, 1999(Fejer et al, , 2008. It is known that during geomagnetic storm, around sunset hours (PRE time), the combined effect of eastward PPEF and PRE intensifies fountain effect (Tsurutani et al, 2008) to create suitable conditions for generation of irregularities (Akala et al, 2021). As shown by our results, following the arguments recently advanced by Akala et al (2021) and Oyedokun et al (2021), the corresponding local time of the main phase of the minor storm was at evening time in the American sector and at post-midnight period in the African sector.…”

“…It is known that during geomagnetic storm, around sunset hours (PRE time), the combined effect of eastward PPEF and PRE intensifies fountain effect (Tsurutani et al, 2008) to create suitable conditions for generation of irregularities (Akala et al, 2021). As shown by our results, following the arguments recently advanced by Akala et al (2021) and Oyedokun et al (2021), the corresponding local time of the main phase of the minor storm was at evening time in the American sector and at post-midnight period in the African sector. For this reason, on the day of the moderate storm's main phase (17th January), irregularities were present in the American sector, and absent in the African sector.…”