- 1Mullard Space Science Laboratory, University College London, London, United Kingdom (n.prado@ucl.ac.uk)
- 2Department of Physical Sciences, Embry-Riddle Aeronautical University, Daytona Beach, United States of America
- 3University of Michigan, Ann Arbor, United States of America
- 4NASA Goddard Space Flight Center, Greenbelt, United States of America
- 5Northumbria University, Newcastle, United Kingdom
Mesoscale structures in the solar wind offer unique insights into its formation, retaining signatures of heating, release mechanisms, and acceleration processes. Plasma heavy ion composition and charge states are critical observables for studying these structures. These properties, established within about 5 solar radii, are preserved as the solar wind propagates, enabling the connection between in situ measurements and their solar sources. Elevated abundance ratios of low first ionization potential (FIP) elements (e.g., Fe/O) and higher charge states are indicative of solar wind originating from active regions and quiet Sun magnetic fields, in contrast to coronal holes. These properties are often structured on mesoscales and can exhibit quasi-periodic behavior, associated with interchange reconnection at the Sun’s open-closed magnetic boundary.
We investigate a multi-day interval from March 4–9, 2022, during which Solar Orbiter’s Heavy Ion Sensor (HIS) observed mesoscale solar wind structures at ~0.49 AU. These structures were confirmed to persist to L1 via ACE and Wind observations, with similar variability in Fe/O and O7+/O6+. Spectral analysis revealed quasi-periodic signals (~30-minute periodicities) in O7+/O6+ ratios during four of the six days analyzed. To link these observations to their solar origins, we used the Wang-Sheeley Arge (WSA) model driven by ADAPT synoptic maps. The model determined solar sources were characterized by parameters empirically related to solar wind formation, such as expansion and squashing factors.
A key feature of this interval was a small stream interaction region (SIR) observed at Solar Orbiter on March 8, coinciding with a connectivity change to a new open-field region bordering a compact active region. This event, confirmed through WSA modeling, corresponded to significant enhancements in Fe/O and O7+/O6+, providing evidence of mesoscale structures linked to active region dynamics. The FIP bias observed in situ (Fe/O) was compared to remote SPICE observations (S/O) at the modeled solar source locations, highlighting challenges in reconciling in situ and remote measurements due to differences in abundance ratio derivations.
Our results demonstrate that mesoscale structures form in active regions via interchange reconnection and survive through the heliosphere, maintaining their composition signatures. This study underscores the value of combining multi-messenger observations and physics-based modeling to trace solar wind origins and reveals the need for enhanced coordination in future heliophysics missions. These findings advance our understanding of solar wind structuring and dynamics, providing a framework for future studies of mesoscale phenomena.
How to cite: Zambrana Prado, N., Wallace, S., Gershkovich, I., Viall, N., Kucera, T., Young, P., Lepri, S., and Yardley, S.: Mesoscale Dynamics in the Solar Wind: Insights from Solar Orbiter and L1 Observations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18482, https://doi.org/10.5194/egusphere-egu25-18482, 2025.