PROGRAM: S-7

Title:

A COMPARISON BETWEEN THE GEOEFECTIVENESS OF NORTH-SOUTH AND SOUTH-NORTH MAGNETIC CLOUD, AND AN ASSOCIATED PREDICTION

Chin-Chun Wu¹* , Ronald P. Lepping² , D. B. Berdichevsky³ and Kan Liou⁴

¹*Naval Research Laboratory, Washington, DC, 20375, USA
²Emeritus, GSFC/NASA, Greenbelt, Maryland, USA
³College Park, Maryland, USA
⁴Applied Physics Laboratory, Johns Hopkins University, Laurel, Maryland, USA

Abstract:

Using 1995-2015 Wind in-situ solar wind plasma and magnetic field data, 217 magnetic clouds (MCs) were identified. The following pertinent results were found. (i) 120 MCs were N-S type (northward→southward, magnetic field, B rotated from northward to southward), and 97 MCs are S-N type. (ii) S-N MC S-N dominated N-S MC N-S in the periods of 1995-1999, 2001-2002, and 2014-2015. In contrast, N-S MC N-S dominated S-N MC S-N in the periods of 2000, and 2003-2013. (iii) The averages of storm intensity (<Dst_min>) were -69, -57, and -84 nT for “All 217 MCs”, “120 N-S MCs”, and “97 S-N MCs” types, respectively. (iv) Confirmed with observations, that MC type depends on the phase of the magnetic solar cycle. Hence, on average, the S-N types trigger more severe storms (i.e., Dst_min < -100 nT). Also, from 1995 to 2009 the percentage of N-S types of MCs keeps increasing, and the percentage of S-N types decreasing. The percentage of S-N MCs starts increasing in the interval 2010-2015. Therefore, we expect to see a predominance of the S-N types of MCs for the coming few years. This means on average that more severe geomagnetic storms are expected in the near future. This is an interesting solar wind feature, and to be stressed in its application to “Space Weather Predictions”.

Acknowledgements:

We are grateful to the Wind SWE and MFI teams, and Kyoto University (Dst data). This study is supported by the Chief of Naval Research (CCW).

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