Speaker
Description
The dynamics and turbulent features of the Earth’s magnetosheath (MSH) are greatly affected by the angle between the interplanetary magnetic field (IMF) and the shock normal direction. Generally, behind a quasi-parallel shock, strong turbulence and high magnetic field fluctuations are generated (often seen in the dawn flank) while a quasi-perpendicular shock (more often found in the dusk flank) is easily distinguished by sharp transitions from the solar wind to the MSH.
Asymmetries between the two flanks of the MSH can be investigated either statistically, through observations collected by single spacecrafts, or, ideally, through simultaneous observations of the MSH performed by pairs of spacecrafts. Using a combination of both approaches, we compile a database of simultaneous observations of the Earth's MSH by ESA's Cluster and NASA's MMS missions, that enables both an instantaneous assessment of the dawn-dusk state of the MSH and a statistical evaluation of simultaneous dawn-dusk MSH observations. The database includes 117 events when Cluster 4 and MMS 4 crossed simultaneously the magnetosheath between January–April, 2017–2021. For each event, the geometry of the bow shock and MSH is determined through two common approaches: a minimum variance analysis of in‐situ magnetic field measurements, and a geometrical approach which considers a parameterized bow shock model. We will describe the database and how the selection of the events was performed, along with the determination of the MSH geometry configuration. We find that both methods estimate the same bow shock geometry in about 75% of the cases, and that the quasi-perpendicular geometry seems to be more often observed, with a good agreement between the two methods. Further, turbulence features of the MSH captured during events included in the database are analyzed and discussed with respect to the bow-shock geometry and shape, their flank distribution or distance from the bow-shock. ODYN, an open-source software analysis tool dedicated to the analysis of turbulence and intermittency is primarily used for the investigations and will be briefly introduced.
