Signatures of wedgelets over Fennoscandia during the St Patrick s Day Storm 2015

During the long main phase of the St Patrick's Day storm on March 17, 2015, we found three separate enhancements of the westward electrojet. These enhancements are observed in the ionospheric equivalent currents computed using geomagnetic data over Fennoscandia. Using data from the IMAGE magnet...

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Bibliographic Details
Published in:Journal of Space Weather and Space Climate
Main Authors: Schillings, Audrey, Palin, Laurianne, Bower, Gemma E., Opgenoorth, Hermann J., Milan, Steve E., Kauristie, Kirsti, Juusola, Liisa, Reeves, Geoff D., Henderson, Mike G., Paxton, Larry J., Lester, Mark, Hamrin, Maria, Van De Kamp, Max
Format: Article in Journal/Newspaper
Language:English
Published: Umeå universitet, Institutionen för fysik 2023
Subjects:
Ionospheric equivalent currents
St Patrick s Day storm
Substorm
Wedgelets
Westward electrojet
Fusion
Plasma and Space Physics
plasma och rymdfysik
Abisko
Kevo
Fennoscandia
Online Access:http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-212096
https://doi.org/10.1051/swsc/2023018
Description
Summary:During the long main phase of the St Patrick's Day storm on March 17, 2015, we found three separate enhancements of the westward electrojet. These enhancements are observed in the ionospheric equivalent currents computed using geomagnetic data over Fennoscandia. Using data from the IMAGE magnetometer network, we identified localised field-aligned current (FAC) systems superimposed on the pre-existing ionospheric current system. We suggest that these localised current systems are wedgelets and that they can potentially contribute to a larger-scale structure of a substorm current wedge (SCW). Each wedgelet is associated with a negative BX spike. Each spike is recorded at a higher latitude than the former one and all three are very localised over Fennoscandia. The first spike occurred at 17:34 UT and was observed at Lycksele, R rvik and Nurmij rvi, the second spike was recorded at 17:41 UT and located at Lycksele and R rvik, whereas the last spike occurred at 17:47 UT and was observed at Kevo and Abisko. Simultaneous optical auroral data and electron injections at the geosynchronous orbit indicate that one or more substorms took place in the polar ionosphere at the time of the wedgelets. This study demonstrates the occurrence of small and short-lived structures such as wedgelets at different locations over a short time scale, 15 min in this case.

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