Are 3‐D coronal mass ejection parameters from single‐view observations consistent with multiview ones?

Abstract

To prepare for when only single‐view observations are available, we have made a test whether the 3‐D parameters (radial velocity, angular width, and source location) of halo coronal mass ejections (HCMEs) from single‐view observations are consistent with those from multiview observations. For this test, we select 44 HCMEs from December 2010 to June 2011 with the following conditions: partial and full HCMEs by SOHO and limb CMEs by twin STEREO spacecraft when they were approximately in quadrature. In this study, we compare the 3‐D parameters of the HCMEs from three different methods: (1) a geometrical triangulation method, the STEREO CAT tool developed by NASA/CCMC, for multiview observations using STEREO/SECCHI and SOHO/LASCO data, (2) the graduated cylindrical shell (GCS) flux rope model for multiview observations using STEREO/SECCHI data, and (3) an ice cream cone model for single‐view observations using SOHO/LASCO data. We find that the radial velocities and the source locations of the HCMEs from three methods are well consistent with one another with high correlation coefficients (≥0.9). However, the angular widths by the ice cream cone model are noticeably underestimated for broad CMEs larger than 100° and several partial HCMEs. A comparison between the 3‐D CME parameters directly measured from twin STEREO spacecraft and the above 3‐D parameters shows that the parameters from multiview are more consistent with the STEREO measurements than those from single view.

Which Bow Shock Theory, Gasdynamic or Magnetohydrodynamic, Better Explains CME Stand-off Distance Ratios from LASCO-C2 Observations ?

“…We assume that the measurement uncertainty of CME speeds due to the projection effects is about 15%, which is taken from Lee et al (2015), who examined the relationships between 2D CME speeds from the SOHO/LASCO CME catalog and 3D CME speeds from stereoscopic methods such as the geometrical triangulation method and the GCS model. It is noted that the projection effects only result in the underestimation of CME speeds.…”

How Reliable Are the Properties of Coronal Mass Ejections Measured from a Single Viewpoint?

“…Naturally, there have been several efforts to assess the reliability of single-viewpoint measurements by exploiting the multi-viewpoint observations from STEREO. The majority were focused on deprojection of quantities derived from a single viewpoint via various 3D reconstruction methodologies (e.g., Temmer et al 2009;Shen et al 2013;Lee et al 2015;Wood et al 2017). They showed that projection effects can indeed be corrected by means of multi-viewpoint measurements and/or 3D forward modeling.…”

Coronal electron density distributions estimated from CMEs, DH type II radio bursts, and polarized brightness measurements

“…First, the measurement uncertainties for the determination of lowest frequencies and the heights of CME leading edges are about ± 0.6-fold and ± 0.2-fold N Saito (r), respectively. Second, the uncertainty due to the projection effects is about 0.7-fold N Saito (r) if we assume a half angular width of a CME is about 41 ∘ , which is an average value of halo CMEs by Lee et al [2015]. The positive sign of this uncertainty is caused by the fact that the projection effects only result in the underestimation of heights.…”