Global magnetohydrodynamic simulation of the 15 March 2013 coronal mass ejection eventInterpretation of the 30-80MeV proton flux

Details

• Journal Title:
  Journal of Geophysical Research: Space Physics
• Personal Author:
  Wu, Chin‐Chun ; Liou, Kan ; Vourlidas, Angelos ; Plunkett, Simon ; Dryer, Murray ; Wu, S. T. ; Mewaldt, Richard A.
• NOAA Program & Office:
  SWPC (Space Weather Prediction Center) ; NWS (National Weather Service)
• Description:
  The coronal mass ejection (CME) event on 15 March 2013 is one of the few solar events in Cycle 24 that produced a large solar energetic particle (SEP) event and severe geomagnetic activity. Observations of SEP from the ACE spacecraft show a complex time-intensity SEP profile that is not easily understood with current empirical SEP models. In this study, we employ a global three-dimensional (3-D) magnetohydrodynamic (MHD) simulation to help interpret the observations. The simulation is based on the H3DMHD code and incorporates extrapolations of photospheric magnetic field as the inner boundary condition at a solar radial distance (r) of 2.5 solar radii. A Gaussian-shaped velocity pulse is imposed at the inner boundary as a proxy for the complex physical conditions that initiated the CME. It is found that the time-intensity profile of the high-energy (>10MeV) SEPs can be explained by the evolution of the CME-driven shock and its interaction with the heliospheric current sheet and the nonuniform solar wind. We also demonstrate in more detail that the simulated fast-mode shock Mach number at the magnetically connected shock location is well correlated (r(cc)0.7) with the concurrent 30-80MeV proton flux. A better correlation occurs when the 30-80MeV proton flux is scaled by r(-1.4)(r(cc)=0.87). When scaled by r(-2.8), the correlation for 10-30MeV proton flux improves significantly from r(cc)=0.12 to r(cc)=0.73, with 1h delay. The present study suggests that (1) sector boundary can act as an obstacle to the propagation of SEPs; (2) the background solar wind is an important factor in the variation of IP shock strength and thus plays an important role in manipulation of SEP flux; (3) at least 50% of the variance in SEP flux can be explained by the fast-mode shock Mach number. This study demonstrates that global MHD simulation, despite the limitation implied by its physics-based ideal fluid continuum assumption, can be a viable tool for SEP data analysis.
• Source:
  Journal of Geophysical Research-Space Physics, 121(1), 56-76.
• DOI:
  https://doi.org/10.1002/2015ja021051
• Document Type:
  Journal Article
• Rights Information:
  Other
• Compliance:
  Library
• Main Document Checksum:
  urn:sha256:ebc5f1c6ab0c46ba4a6a9dc337f8e37f9e396314dc36549cd91827189998036c
• Download URL:
  https://repository.library.noaa.gov/view/noaa/15232/noaa_15232_DS1.pdf
• File Type:
  [PDF - 6.26 MB ]