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Ann. Geophys., 24, 3383-3389, 2006
www.ann-geophys.net/24/3383/2006/
© European Geosciences Union 2006
Solar cycle effect on geomagnetic storms caused by interplanetary magnetic clouds
C.-C. Wu1,2,3 and R. P. Lepping3
1CSPAR/The University of Alabama in Huntsville, Huntsville, AL 35899, USA
2also at: Key State of Laboratory for Space Weather, Chinese Academy of Sciences, Beijing 100080, China
3Heliophysics Science Division, NASA/GSFC, Greenbelt, MD 20771, USA
Abstract. We investigated geomagnetic activity which was induced by interplanetary
magnetic clouds during the past four solar cycles, 1965–1998.
We have found that the intensity of such geomagnetic storms is more severe
in solar maximum than in solar minimum.
In addition, we affirm that the average solar wind speed of magnetic clouds is
faster in solar maximum than in solar minimum.
In this study, we find that
solar activity level plays a major role on the intensity of geomagnetic storms.
In particular, some new statistical results are found and listed as follows.
(1) The intensity of a geomagnetic storm in a solar active period is
stronger than in a solar quiet period.
(2) The magnitude of negative Bzmin is larger in a solar active
period than in a quiet period.
(3) Solar wind speed in an active period is faster than in a quiet period.
(4) VBsmax in an active period is much larger than in a quiet period.
(5) Solar wind parameters, Bzmin, Vmax and VBsmax are
correlated well with geomagnetic storm intensity, Dstmin during
a solar active period.
(6) Solar wind parameters, Bzmin, and VBsmax are not correlated
well (very poorly for Vmax) with geomagnetic storm intensity during
a solar quiet period.
(7) The speed of the solar wind plays a key role in the correlation of
solar wind parameters vs. the intensity of a geomagnetic storm.
(8) More severe storms with Dstmin≤−100 nT caused by MCs
occurred in the solar active period than in the solar quiet period.
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