Lugaz N, Farrugia C J, Winslow R M, Al-Haddad N, Kilpua E K J, Riley P
Space Science Center, University of New Hampshire, Durham, NH, USA.
Department of Physics, University of New Hampshire, Durham, NH, USA.
J Geophys Res Space Phys. 2016 Nov;121(11):10861-10879. doi: 10.1002/2016JA023100. Epub 2016 Oct 29.
We identify all fast-mode forward shocks, whose sheath regions resulted in a moderate (56 cases) or intense (38 cases) geomagnetic storm during 18.5 years from January 1997 to June 2015. We study their main properties, interplanetary causes and geo-effects. We find that half (49/94) such shocks are associated with interacting coronal mass ejections (CMEs), as they are either shocks propagating into a preceding CME (35 cases) or a shock propagating into the sheath region of a preceding shock (14 cases). About half (22/45) of the shocks driven by isolated transients and which have geo-effective sheaths compress pre-existing southward . Most of the remaining sheaths appear to have planar structures with southward magnetic fields, including some with planar structures consistent with field line draping ahead of the magnetic ejecta. A typical (median) geo-effective shock-sheath structure drives a geomagnetic storm with peak Dst of -88 nT, pushes the subsolar magnetopause location to 6.3 R, i.e. below geosynchronous orbit and is associated with substorms with a peak AL-index of -1350 nT. There are some important differences between sheaths associated with CME-CME interaction (stronger storms) and those associated with isolated CMEs (stronger compression of the magnetosphere). We detail six case studies of different types of geo-effective shock-sheaths, as well as two events for which there was no geomagnetic storm but other magnetospheric effects. Finally, we discuss our results in terms of space weather forecasting, and potential effects on Earth's radiation belts.
我们识别出了所有快速模式正向激波，在1997年1月至2015年6月的18.5年期间，其鞘区引发了中度（56例）或强烈（38例）的地磁风暴。我们研究了它们的主要特性、行星际成因和地球效应。我们发现，其中一半（49/94）的此类激波与相互作用的日冕物质抛射（CME）有关，因为它们要么是传播到先前CME中的激波（35例），要么是传播到先前激波鞘区中的激波（14例）。由孤立瞬变驱动且具有地球效应鞘区的激波中，约一半（22/45）会压缩先前存在的南向 。其余大多数鞘区似乎具有南向磁场的平面结构，包括一些具有与磁 ejecta 前方场线悬垂一致的平面结构。典型（中位数）的地球效应激波 - 鞘区结构驱动的地磁风暴Dst峰值为 -88 nT，将日下磁层顶位置推至6.3 R，即低于地球同步轨道，并与峰值AL指数为 -1350 nT的亚暴相关。与CME - CME相互作用相关的鞘区（更强的风暴）和与孤立CME相关的鞘区（对磁层更强的压缩）之间存在一些重要差异。我们详细介绍了六种不同类型的地球效应激波 - 鞘区的案例研究，以及两个没有地磁风暴但有其他磁层效应的事件。最后，我们从空间天气预报以及对地球辐射带的潜在影响方面讨论了我们的结果。
