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Identifying the sources of the solar wind at the Sun with total solar eclipse observations

Presentation #303.01 in the session Solar and Atmospheric Science with Eclipses.

Published onOct 20, 2022
Identifying the sources of the solar wind at the Sun with total solar eclipse observations

The remarkable quality of total solar observations in the visible and near IR range of the coronal spectrum has recently culminated in the unambiguous identification of the sources of fast, intermediate and slow speed solar wind streams at the Sun [Habbal et al., ApJ 911, L4, 2021]. The uniqueness of these observations is based on (1) multi-wavelength images of the corona of emission from different ionization states of Fe spanning over a solar cycle, (2) their spatial coverage starting from the solar surface out to 3 — 5 Rs, (3) the outstanding diagnostic capabilities of coronal emission lines for inferring fundamental plasma properties, and (4) the availability of in-situ Fe charge states in the ecliptic over the same time period. This complement of observations established the ubiquity of open coronal structures associated with continual solar wind streams, ranging from 300 to 700 km/s, albeit with in situ Fe charge state clustered around Fe10+, regardless of phase within a solar cycle. This charge state is characteristic of 1.2 MK plasmas in the corona. On the other hand, the eclipse observations show that the distribution of the higher Fe13+ charge state in the corona changes with solar cycle, while the sporadic appearance of solar wind streams with in situ charge states > Fe11+ exhibits no cycle dependence, regardless of speed. The discovery of continual streams of slow, intermediate, and fast solar wind, characterized by the same electron temperature at their sources at the Sun, places new constraints on the physical processes shaping the solar wind. On the other hand, streams associated with charge states exceeding Fe11+, are conjectured to be released from hot coronal plasmas at temperatures exceeding 1.8 MK from streamers and active regions driven by the dynamics of prominences which are magnetically linked to them.

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