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), Antoinette Galvin (University of New Hampshire, Durham, New Hampshire, United States)

Between January 2022 and July 2024, we analyzed coronal mass ejections (CMEs) observed simulta-
neously by the STEREO-A and L1 spacecraft, during a period when their angular separation ranged
from 35◦ east to 20◦ west of the Sun–Earth line. Of 87 identified CMEs, only 36 were detected by both
spacecraft, indicating the limited longitudinal extent or asymmetry of many events. We statistically
examined the properties of these 2-spacecraft (2-SC) CMEs, including their magnetic field strength,
proton speed, spatial sizes, and the characteristics of associated shocks and sheaths. These multi-
point measurements allowed us to assess variations between local and global CME structures and to
constrain the geometry of the magnetic ejecta and the shock front.
To complement the statistical analysis, we conducted a detailed case study of one well-observed
event. We applied a spatial interpolation technique to reconstruct the magnetic field between the two
spacecraft, enabling us to visualize the CME structure across the intervening space. We then employed
the Grad–Shafranov reconstruction method to determine the orientation of the magnetic ejecta axis.
By combining interpolation and magnetic field fitting, we constructed a physical sketch of the CME’s
three-dimensional configuration in interplanetary space.
Our findings provide new insights into the spatial structure and evolution of CMEs, highlighting
the importance of multi-spacecraft observations in resolving their geometry and propagation character-
istics. The results have implications for understanding CME-driven space weather and for improving
forecasting models that rely on accurate knowledge of CME shapes, sizes, and orientations.