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Substorm occurrence during quiet solar wind driving

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dc.contributor Aalto-yliopisto fi
dc.contributor Aalto University en
dc.contributor.author Pulkkinen, Tuija I.
dc.contributor.author Partamies, N.
dc.contributor.author Kilpua, E. K. J.
dc.date.accessioned 2015-03-30T09:00:33Z
dc.date.available 2015-03-30T09:00:33Z
dc.date.issued 2014
dc.identifier.citation Pulkkinen, Tuija I. & Partamies, N. & Kilpua, E. K. J.. 2014. Substorm occurrence during quiet solar wind driving. Journal of Geophysical Research: Space physics, Vol. 119, nro 4. pp. 2978-2989. ISSN 2169-9402 (electronic). ISSN 2169-9380 (printed). DOI: 10.1002/2013JA019503. en
dc.identifier.issn 2169-9402 (electronic)
dc.identifier.issn 2169-9380 (printed)
dc.identifier.uri https://aaltodoc.aalto.fi/handle/123456789/15434
dc.description.abstract We examine the OMNI database and International Monitor for Auroral Geomagnetic Effects (IMAGE) magnetometer chain records to study the substorm occurrence and characteristics during quiet solar driving periods, especially during the solar minimum period in 2009. We define substorm-like activations as periods where the hourly average AL is below −200 nT. Using the OMNI data set, we demonstrate that there are limiting solar wind speed, interplanetary magnetic field magnitude, and driving electric field values below which substorm-like activations (AL < 200 nT, intensification and decay of the electrojet) do not occur. These minimum parameter values are V < 266 km/s, B < 1.4 nT, and E < 0.025 mV/m; such low values are observed less than 1% of the time. We also show that for the same level of driving solar wind electric field, the electrojet intensity is smaller (by few tens of nT), and the electrojet resides farther poleward (by over 1°) during extended quiet solar driving in 2009 than during average solar activity conditions. During the solar minimum period in 2009, we demonstrate that substorm-like activations can be identified from the IMAGE magnetometer chain observations during periods when the hourly average IL index is below −100 nT. When the hourly IL activity is smaller than that, which covers 87% of the nighttime observations, the electrojet does not show coherent behavior. We thus conclude that substorm recurrence time during very quiet solar wind driving conditions is about 5–8 h, which is almost double that of the average solar activity conditions. en
dc.format.extent pp. 2978-2989
dc.format.mimetype application/pdf en
dc.language.iso en en
dc.publisher American Geophysical Union. Wiley en
dc.relation.ispartofseries Journal of Geophysical Research: Space physics, Vol. 119, nro 4 en
dc.rights © 2014. The Authors. This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made. en
dc.subject.other Space technology en
dc.title Substorm occurrence during quiet solar wind driving en
dc.type A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä fi
dc.description.version Peer reviewed en
dc.rights.holder Authors
dc.contributor.school Sähkötekniikan korkeakoulu fi
dc.contributor.school School of Electrical Engineering en
dc.subject.keyword auroral electrojets en
dc.subject.keyword solar wind-magnetosphere coupling en
dc.subject.keyword substorms en
dc.identifier.urn URN:NBN:fi:aalto-201503252091
dc.type.dcmitype text en
dc.identifier.doi 10.1002/2013JA019503
dc.type.version Final published version en

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