Abstract Details


Name: Anjali Agarwal
Affiliation: Indian Institute of Astrophysics
Conference ID: TVS202510163
Title: Dissecting Magnetic Clouds: Instantaneous Expansion, Compression, and Mesoscale Inhomogeneities
Authors and Co-Authors: Anjali Agarwal
Abstract Type: Contributory Presentation
Abstract: Coronal mass ejections (CMEs) are the huge expulsions of coronal plasma and magnetic flux from the Sun into the heliosphere and are major drivers of geomagnetic disturbances. The duration of such disturbances can depend on the CME’s instantaneous expansion speed. In contrast to the conventional approach, we propose and validate a novel Constant Acceleration Accounted Perspective (CAAP) method to estimate the CME’s instantaneous expansion speed from single-point in situ observations. To demonstrate our method, we select a unique 2021 November 3-5 CME for which the simultaneous speed measurements of its center by Solar Orbiter and trailing edge (TE) by Wind enable the measurement of its instantaneous expansion speed. Interestingly, the magnetic cloud (MC) shows an unexpected increase in its magnetic flux with distance, along with the notable discrepancies--likely influenced by the ambient medium or possibly the presence of inherent MC inhomogeneities. Dissecting MCs across different scales and perspectives at different distances from the Sun is crucial. Therefore, to examine properties at mesoscales within an MC, we selected another event of 2023 September 24-26, uniquely observed in situ by STEREO-A and Wind when these spacecraft are marginally separated at 1 AU. Using our novel method to identify the compressed region of an MC, we find that the MC is compressed at its TE; however, the compression is more pronounced at STEREO-A. Our detailed analysis casts doubt on whether a CME can truly be regarded as coherent across its angular span. Our findings underscore the importance of accurately determining the instantaneous expansion speed of CMEs and identifying which part of an MC is likely to impact Earth, in order to improve space weather forecasting.