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| Titel |
Solar Wind Energy Input during Prolonged, Intense Northward Interplanetary Magnetic Fields: A New Coupling Function |
| VerfasserIn |
A. M. Du, B. T. Tsurutani, W. Sun |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250062773
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| Zusammenfassung |
| Sudden energy release (ER) events in the midnight sector at auroral zone latitudes during
intense (B > 10 nT), long-duration (T > 3 hr), northward (Bz > 0 nT = N) IMF magnetic
clouds (MCs) during solar cycle 23 (SC23) have been examined in detail. The MCs with
northward-then-southward (NS) IMFs were analyzed separately from MCs with
southward-then-northward (SN) configurations. It is found that there is a lack of substorms
during the N field intervals of NS clouds. In sharp contrast, ER events do occur during
the N field portions of SN MCs. From the above two results it is reasonable to
conclude that the latter ER events represent residual energy remaining from the
preceding S portions of the SN MCs. We derive a new solar wind-magnetosphere
coupling function during northward IMFs: ENIMF = α N-1-12V 7-3B1-2 + β
V |Dstmin|. The first term on the right-hand side of the equation represents the energy
input via “viscous interaction”, and the second term indicates the residual energy
stored in the magnetotail. It is empirically found that the magnetosphere/magnetotail
can store energy for a maximum of ~ 4 hrs before it has dissipated away. This
concept is defining one for ER/substorm energy storage. Our scenario indicates
that the rate of solar wind energy injection into the magnetosphere/magnetotail
determines the form of energy release into the magnetosphere/ionosphere. This may be
more important than the dissipation mechanism itself (in understanding the form
of the release). The concept of short-term energy storage is applied for the solar
case. It is argued that it may be necessary to identify the rate of energy input into
solar magnetic loop systems to be able to predict the occurrence of solar flares. |
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