Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
1776472 | Journal of Atmospheric and Solar-Terrestrial Physics | 2014 | 38 Pages |
Abstract
The July 23, 2012 CME was an extremely fast backside event, reaching â¼1 AU (STEREO-A) within 20 h as compared to â¼3-6 days for typical CME events. Here, we present results from a simulation study of the CME and its driven shock using a combined kinematic and magnetohydrodynamic (MHD) simulation model, H3DMHD. In general, the model results match well with in situ measurements in the arrival time of the CME-driven shock and the total magnetic field strength, assuming an initial CME speed of 3100 km/s. Based on extrapolation of an empirical model, the fast CME and its large magnetic field (|B|â¼120 nT) are capable of producing an extremely large geomagnetic storm (Dstâ¼â545 nT), comparable to the well-known Halloween storm in 2003, if the CME had made a direct impact to the Earth. We investigated the effect of the adiabatic index (γ). It is found that the shock tends to arrive slightly later for a smaller γ value, and γ=5/3 provides the best agreement for the shock arrival time. We also demonstrate that the strength (the Mach number) of the CME-driven fast-mode shock is not the largest at the “nose” of the CME. This is mainly due to the manifestation of fast-mode wave speed upstream of the shock.
Keywords
Related Topics
Physical Sciences and Engineering
Earth and Planetary Sciences
Geophysics
Authors
Kan Liou, Chin-Chun Wu, Murray Dryer, Shi-Tsan Wu, Nathan Rich, Simon Plunkett, Lynn Simpson, Craig D. Fry, Kevin Schenk,