| タイトル | Comparisons of Characteristics of Magnetic Clouds and Cloud-Like Structures During 1995-2012 |
| 本文（外部サイト） | http://hdl.handle.net/2060/20150007933 |
| 著者（英） | Wu, Chin-Chun; Lepping, Ronald P. |
| 著者所属（英） | NASA Goddard Space Flight Center |
| 発行日 | 2015-04-01 |
| 言語 | eng |
| 内容記述 | Using eighteen years (1995 - 2012) of solar wind plasma and magnetic field data (observed by the Wind spacecraft), solar activity (e.g. sunspot number: SSN), and the geomagnetic activity index (Dst), we have identified 168 magnetic clouds (MCs) and 197 magnetic cloud - like structures (MCLs), and we have made relevant comparisons. The following features are found during seven different periods (TP: Total period during 1995 - 2012, P1 and P2: first and second half period during 1995 - 2003 and 2004 - 2012, Q1 and Q2: quiet periods during 1995 - 1997 and 2007 - 2009, A1 and A2: active periods during 1998 - 2006 and 2010 - 2012). (1) During the total period the yearly occurrence frequency is 9.3 for MCs and 10.9 for MCLs. (2) In the quiet periods <NMCs>Q1 > <NMCLs>Q1 and <NMCs>Q2 > <NMCLs>Q2, but in the active periods <NMCs>A1 < <NMCLs>A1 and <NMCs>A2 < <NMCLs>A2. (3) The minimum Bz (Bzmin) inside of a MC is well correlated with the intensity of geomagnetic activity, Dstmin (minimum Dst found within a storm event) for MCs (with a Pearson correlation coefficient, c.c. = 0.75, and the fitting function is Dstmin = 0.90+7.78Bzmin), but Bzmin for MCLs is not well correlated with the Dst index (c.c. = 0.56, and the fitting function is Dstmin = -9.40+ 4.58 Bzmin). (4) MCs play a major role in producing geomagnetic storms: the absolute value of the average Dstmin (<Dstmin>MC = -70 nT) for MCs associated geomagnetic storms is two times stronger than that for MCLs (<Dstmin>MCL = -35 nT), due to the difference in the IMF (interplanetary magnetic field) strength. (5) The SSN is not correlated with MCs (<NMCs>TP, c.c. = 0.27), but is well associated with MCLs (<NMCLs>TP, c.c. = 0.85). Note that the c.c. for SSN vs. <NMCs>P2 is higher than that for SSN vs. <NMCLs>P2. (6) Averages of IMF, solar wind speed, and density inside of the MCs are higher than those inside of the MCLs. (7) The average of MC duration (approx. = 18.82 hours) is approx. = 20 % longer than the average of MCL duration (approx. = 15.69 hours). (8) There are more MCs than MCLs in the quiet solar period, and more MCLs than MCs in the active solar period, probably due to the interaction between a MC and another significant interplanetary disturbance (including another MC) which could obviously change the character of a MC, but we speculate that some MCLs are no doubt due to other factors such as complex birth conditions at the Sun. |
| NASA分類 | Solar Physics |
| レポートNO | GSFC-E-DAA-TN20351 |
| 権利 | Copyright, Distribution as joint owner in the copyright |
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