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Dependence of Geomagnetic Storms on Their Associated Halo CME Parameters |
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| Authors: | Jae-Ok Lee Y-J Moon Kyoung-Sun Lee R-S Kim |
| Institution: | 1. School of Space Research, Kyung Hee University, Yongin, Korea 2. Astronomy and Space Science, Kyung Hee University, Yongin, Korea 3. Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Sagamihara, Japan 4. Korea Astronomy and Space Science Institute, Daejeon, Korea |
| Abstract: | We compare the geoeffective parameters of halo coronal mass ejections (CMEs). We consider 50 front-side full-halo CMEs (FFH CMEs), which are from the list of Michalek, Gopalswamy, and Yashiro (Solar Phys. 246, 399, 2007), whose asymmetric-cone model parameters and earthward-direction parameter were available. For each CME we use its projected velocity V p], radial velocity V r], angle between cone axis and sky plane γ] from the cone model, earthward-direction parameter D], source longitude L], and magnetic-field orientation M] of its CME source region. We make a simple linear-regression analysis to find out the relationship between CME parameters and Dst index. The main results are as follows: i) The combined parameters (V r D)1/2 and V r γ] have higher correlation coefficients cc] with the Dst index than the other parameters V p and V r]: cc=0.76 for (V r D)1/2, cc=0.70 for V r γ, cc=0.55 for V r, and cc=0.17 for V p. ii) Correlation coefficients between V r γ and Dst index depend on L and M; cc=0.59 for 21 eastern events E], cc=0.80 for 29 western events W], cc=0.49 for 17 northward magnetic-field events N], and cc=0.69 for 33 southward magnetic-field events S]. iii) Super geomagnetic storms (Dst≤?200 nT) only appear in the western and southward magnetic-field events. The mean absolute Dst values of geomagnetic storms (Dst≤?50 nT) increase with an order of E+N, E+S, W+N, and W+S events; the mean absolute Dst value (169 nT) of W+S events is significantly larger than that (75 nT) of E+N events. Our results demonstrate that not only do the cone-model parameters together with the earthward-direction parameter improve the relationship between CME parameters and Dst index, but also the longitude and the magnetic-field orientation of a FFH CME source region play a significant role in predicting geomagnetic storms. |
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