SOLAR WIND HEATING OBSERVED BY SOLAR ORBITER

Abstract: In this project, we investigate the plasma heating associated with coherent structures, such as current sheets and vortices, in different solar wind conditions: slow solar wind, stream interaction regions, and heliospheric current sheets, observed by the Solar Or- biter mission. To unravel this mystery, we first use the Partial Variance of Increment method [1] to locate these coherent structures. We then employ correlation functions to determine the coexistence of these structures and investigate the global elevation of plasma temperature [2]. Additionally, we employ a quantitative analysis of conditioned PVI [3] to examine the local increase in plasma temperature [4]. The results clearly indicate that plasma heating takes place at and near these struc- tures. Specifically, current sheets locally heat the plasma, while plasma vortices have a global impact on heating. A characteristic timescale of approximately 200 seconds emerges, separating the local heating of coherent structures from other heating sources. In slow solar wind and stream interaction regions, we observe clusters of coherent structures with sizes ranging from 4 to 6 hours, underlain by a scale of 1 to 2 hours. The heliospheric current sheet does not exhibit such modulation. These coherent struc- ture clusters are embedded within larger macroscopic structures spanning 12 to 24 hours.