Authors: Sahanaj Aktar Banu (University of New Hampshire, Durham, New Hampshire, United States), Noé Lugaz(University of New Hampshire, Durham, New Hampshire, United States), Nada AlHaddad (University of New Hampshire, Durham, New Hampshire, United States), Bin Zhuang (University of New Hampshire, Durham, New Hampshire, United States), Charles J Farrugia (University of New Hampshire, Durham, New Hampshire, United States), Camilla Scolini (Solar Physics & Space weather, Royal Observatory of Belgium), Wenyuan Yu (University of New Hampshire, Durham, New Hampshire, United States), Antoinette Galvin (University of New Hampshire, Durham, New Hampshire, United States)

In this work, we study coronal mass ejections (CMEs) observed by Wind and STEREO-A between January 2022 and August 2023, utilizing in-situ measurements of magnetic fields and plasma parameters to identify CMEs measured simultaneously by both spacecraft. This timeframe is chosen due to the preferred proximity of STEREO-A to the L1 point, with spacecraft separation decreasing from approximately 35° to 0°. An increase in multi-point CME detections is anticipated as the spacecraft angular separation approaches zero and the activity of solar cycle 25 increases. However, our analysis reveals significant discrepancies in CME detections and in-situ signatures of CMEs between the two closely positioned spacecraft. We find that out of 49 CMEs measured by Wind or STEREO-A, only 14 are observed by both spacecraft. A detailed analysis of the 14 simultaneously measured CMEs indicates that even within a small angular separation (10–15°), CMEs’ properties vary noticeably. This study raises numerous questions about our knowledge of CME properties.