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| Titel |
Alfvénic intervals in the solar wind at 1 AU 1995-2011 |
| VerfasserIn |
Kristian Snekvik, Eija Tanskanen, Emilia Kilpua, David Pérez-Suárez |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250078989
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| Zusammenfassung |
| We have done a statistical study of alfvénic intervals in the solar wind based on ACE
and Wind measurements. During alfvénic intervals, the magnetic field exhibits
alfvénic fluctuations with periods around 1 hour. The magnetic fluctuations are
typically 2-4Â nT, and the solar wind speed is mostly above 400 km/s. The effect is
moderate and regular energy transfer from the solar wind to the magnetosphere in
periods up to 8 days, but 1-3 days is most common. Our statistics show that alvénic
fluctuations are the most important drivers of geomagnetic activity in the trailing
parts of high-speed streams, while non-alfvenic fluctuations are more important
when the solar wind speed is increasing, which typically correspond to the stream
interaction region. From 1995 to 2011 there were 738 alfvénic intervals, each lasting
more than 12 hours. The occurrence rate of such intervals has a strong solar cycle
dependence, with a peak in the early declining phase of the sunspot cycle. In the year of
maximum occurrence (2003), the total duration of alfvénic intervals was more
than 180 days, while on average the total duration is 73 days per year. The list of
alfvenic intervals will be provided for the community in a paper under preparation. |
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