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| Titel |
Solar wind control of the local time of substorm onset |
| VerfasserIn |
Adrian Grocott, Nathan Case, Karl Laundal, Hannah Laurens, Steve Milan |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250153763
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| Publikation (Nr.) |
 EGU/EGU2017-18779.pdf |
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| Zusammenfassung |
| We use solar wind and interplanetary magnetic field data, along with satellite global
auroral imagery, to investigate what controls the magnetic local time (MLT) of
substorm onset. We find that substorm onsets occur over a wide range of MLTs
(18 – 4 hrs), with a typical MLT (mode) of 23 hrs. In agreement with previous
studies, IMF BY , acts to move the onset to an earlier/later local time in the northern
hemisphere and a later/earlier local time in the southern hemisphere, depending
on the sign of BY , consistent with a twist of the conjugate magnetic field line.
This effect explains a small fraction of the observed MLT variation (∼ 1 hr), but
cannot account for the tendency of onset to be often displaced to earlier (< 23 hrs)
or later (> 23 hrs) MLTs in both hemispheres. We also inspect the relationship
between solar wind V Y and onset MLT, which also has a small, but measurable
effect on the local time of substorm onset. This effect acts in the same sense in
the northern and southern hemispheres, moving onset to earlier times for positive
V Y and later times for negative V Y . We find that a function relating both BY and
V Y to onset MLT produces a better fit than a function based on either parameter
alone. |
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