Magnetic Field Strength in the Upper Solar Corona Using White-light Shock Structures Surrounding Coronal Mass Ejections

Abstract

To measure the magnetic field strength in the solar corona, we examined 10 fast (> 1000 km/s) limb CMEs which show clear shock structures in SOHO/LASCO images. By applying piston-shock relationship to the observed CME's standoff distance and electron density compression ratio, we estimated the Mach number, Alfven speed, and magnetic field strength in the height range 3 to 15 solar radii (Rs). Main results from this study are: (1) the standoff distance observed in solar corona is consistent with those from a magnetohydrodynamic (MHD) model and near-Earth observations; (2) the Mach number as a shock strength is in the range 1.49 to 3.43 from the standoff distance ratio, but when we use the density compression ratio, the Mach number is in the range 1.47 to 1.90, implying that the measured density compression ratio is likely to be underestimated due to observational limits; (3) the Alfven speed ranges from 259 to 982 km/s and the magnetic field strength is in the range 6 to 105 mG when the standoff distance is used; (4) if we multiply the density compression ratio by a factor of 2, the Alfven speeds and the magnetic field strengths are consistent in both methods; (5) the magnetic field strengths derived from the shock parameters are similar to those of empirical models and previous estimates.

Accepted for publication in ApJ, 11 Figures, 1 Table

References in corpus (7)

• Observations and Interpretation of a Low Coronal Shock Wave Observed in the EUV by the SDO/AIA
• Nonlinear force-free modeling of the solar coronal magnetic field
• Coronal Magnetic Field Measurement from EUV Images made by the Solar Dynamics Observatory
• The Strength and Radial Profile of Coronal Magnetic Field from the Standoff Distance of a CME-driven Shock
• Off-limb Solar Coronal Wavefronts From SDO/AIA EUV Observations - Implications For Particle Production
• Probing the Large Scale Plasma Structure of the Solar Corona with Faraday Rotation Measurements
• STEREO Direct Imaging of a CME-driven Shock to 0.5AU

Cited by in corpus (15)

• How Many CMEs Have Flux Ropes? Deciphering the Signatures of Shocks, Flux Ropes, and Prominences in Coronagraph Observations of CMEs
• Catastrophic Evaporation of Rocky Planets
• Strength of the Solar Coronal Magnetic field - A Comparison of Independent Estimates Using Contemporaneous Radio and White-light Observations
• Plasma physical parameters along Coronal Mass Ejection-driven shocks: I observations
• The radial profile of the inner heliospheric magnetic field as deduced from Faraday rotation observations
• A study of the Heliocentric dependence of Shock Standoff Distance and Geometry using 2.5D MHD Simulations of CME-driven shocks
• Solar type II radio bursts associated with CME expansions as shown by EUV waves
• Near-Sun and 1 AU magnetic field of coronal mass ejections: A parametric study
• Solar coronal density turbulence and magnetic field strength at the source regions of two successive metric type II radio bursts
• The Wave-Driver System of the Off-Disk Coronal Wave 17 January 2010
• Determination of the Coronal and Interplanetary Magnetic-Field Strength and Radial Profiles from the Large-Scale Photospheric Magnetic Fields
• Three-dimensional analyses of an aspherical coronal mass ejection and its driven shock
• Origin of a CME-related shock within the LASCO C3 field-of-view
• Formation of Isolated Radio Type II Bursts at Low Frequencies
• Measuring coronal magnetic fields with remote sensing observations of shock waves