Abstract
Abstract. Geomagnetic storms are the most pronounced phenomenon of space weather. When studying ionospheric response to a storm of 15 August 2015, an unexpected phenomenon was observed at higher middle latitudes of the Southern Hemisphere. This phenomenon was a localized total electron content (TEC) enhancement (LTE) in the form of two separated plumes, which peaked southward of South Africa. The plumes were first observed at 05:00 UT near the southwestern coast of Australia. The southern plume was associated with local time slightly after noontime (1–2 h after local noon). The plumes moved with the Sun. They peaked near 13:00 UT southward of South Africa. The southern plume kept constant geomagnetic latitude (63–64° S); it persisted for about 10 h, whereas the northern plume persisted for about 2 h more. Both plumes disappeared over the South Atlantic Ocean. No similar LTE event was observed during the prolonged solar activity minimum period of 2006–2009. In 2012–2016 we detected altogether 26 LTEs and all of them were associated with the southward excursion of Bz. The negative Bz excursion is a necessary but not sufficient condition for the LTE occurrence as during some geomagnetic storms associated with negative Bz excursions the LTE events did not appear.
Highlights
The ionospheric variability is to a large extent driven by the solar and geomagnetic activity and is influenced by plasma transport, electric fields and currents, and neutral winds and atmospheric waves (e.g., Prolss, 2004; Kelley, 2009; Rishbeth and Mendillo, 2001)
We shall focus on the event of 15 August, because it was accompanied by an unexpected phenomenon in the Southern Hemisphere (SH) ionosphere
Solar data confirm the existence of a coronal mass ejections (CMEs) probably responsible for the 15 August geomagnetic storm
Summary
The ionospheric variability is to a large extent driven by the solar and geomagnetic activity and is influenced by plasma transport, electric fields and currents, and neutral winds and atmospheric waves (e.g., Prolss, 2004; Kelley, 2009; Rishbeth and Mendillo, 2001). I. Edemskiy et al.: Unexpected SH ionospheric response to storm of 15 August 2015 magnetic field intensity variations for the period range of 30–60 min correlated well with TEC variations on the same timescale. The event of 15 August 2015, revealed strong and unexpected localized enhancement of TEC observed near local noon in a region between Africa and Antarctica – i.e., at southern higher midlatitudes. This was a by-product of the requested analysis but a scientifically interesting puzzle.
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