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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 36, issue 1 | Copyright
Ann. Geophys., 36, 71-79, 2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Regular paper 19 Jan 2018

Regular paper | 19 Jan 2018

Unexpected Southern Hemisphere ionospheric response to geomagnetic storm of 15 August 2015

Ilya Edemskiy1, Jan Lastovicka2, Dalia Buresova2, John Bosco Habarulema3, and Ivan Nepomnyashchikh4 Ilya Edemskiy et al.
  • 1Institute of Solar-Terrestrial Physics, SB RAS, Irkutsk, Russia
  • 2Institute of Atmospheric Physics CAS, Prague, Czech Republic
  • 3South African National Space Agency (SANSA) Space Science, Hermanus, South Africa
  • 4Irkutsk State Technical University, Irkutsk, Russia

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 05:00UT near the southwestern coast of Australia. The southern plume was associated with local time slightly after noontime (1–2h after local noon). The plumes moved with the Sun. They peaked near 13:00UT southward of South Africa. The southern plume kept constant geomagnetic latitude (63–64°S); it persisted for about 10h, whereas the northern plume persisted for about 2h 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.

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Short summary
An unusual geomagnetic storm effect on the ionosphere in the form of localized enhancement of total electron content southward of South Africa is investigated using data from different ionosphere sounding facilities. Global ionospheric maps allow us to get the occurrence rate of such irregularities over the period of 2002–2016 and to see its correlation with solar cycle. The events we detected occur during geomagnetic storms, but not every geomagnetic storm produces such an effect.
An unusual geomagnetic storm effect on the ionosphere in the form of localized enhancement of...