Coronal Mass Ejection Distortion at 0.1 au Observed by WISPR
Abstract
Although many coronal mass ejections (CMEs) are modeled using geometric models expanding self-similarly, various numerical MHD simulations, imaging, and in situ observations suggest that CMEs become distorted. Common distortions descriptions are "pancaking", front flattering, and rotational skew. Many distortions are associated with spatial and temporal changes in CME background solar wind conditions. Other studies suggest that distortion happens because CMEs lose coherence over their full angular extend once portions of plasma separate exceeding the Alfven speed, which can occur between 0.1 and 0.2 au. We present evidence of one CME becoming distorted while WISPR observed it and explore possible explanations. The inner and outer cameras observe the CME on January 20-22, 2021, while it propagates almost through the entire field-of-view, extending 95 degrees radially. We derive the CME kinematics using multiple techniques, and reconstruct it using WISPR and coronagraph observations. We find that up to ~0.08 au, the CME follows the graduated cylindrical shell (GCS) model well and expands approximately self-similarly. After this period in which WISPR observes a circular-like front profile, it becomes concave. By projecting the GCS model over WISPR images, we are unable to reproduce the profile change observed. As projection effects cannot explain the concave profile, our interpretation is that the CME becomes distorted by ~0.1 au. The CME seems to expand more at higher latitudes, where the solar wind speed is likely higher. We also discuss CME plasma conditions necessary for loss of coherence at ~0.1 au, which occurs when the relative separation speed between CME plasma parcels becomes higher than the Alfven speed.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2021
- Bibcode:
- 2021AGUFMSH42A..09B