Abstract
Abstract This letter capitalizes on a unique set of total solar eclipse observations acquired between 2006 and 2020 in white light, Fe xi 789.2 nm (T fexi = 1.2 ± 0.1 MK), and Fe xiv 530.3 nm (T fexiv = 1.8 ± 0.1 MK) emission complemented by in situ Fe charge state and proton speed measurements from Advanced Composition Explorer/SWEPAM-SWICS to identify the source regions of different solar wind streams. The eclipse observations reveal the ubiquity of open structures invariably associated with Fe xi emission from Fe10+ and hence a constant electron temperature, T c = T fexi, in the expanding corona. The in situ Fe charge states are found to cluster around Fe10+, independently of the 300–700 km s−1 stream speeds, referred to as the continual solar wind. Thus, Fe10+ yields the fiducial link between the continual solar wind and its T fexi sources at the Sun. While the spatial distribution of Fe xiv emission from Fe13+ associated with streamers changes throughout the solar cycle, the sporadic appearance of charge states >Fe11+ in situ exhibits no cycle dependence regardless of speed. These latter streams are conjectured to be released from hot coronal plasmas at temperatures ≥T fexiv within the bulge of streamers and from active regions, driven by the dynamic behavior of prominences magnetically linked to them. The discovery of continual streams of slow, intermediate, and fast solar wind characterized by the same T fexi in the expanding corona places new constraints on the physical processes shaping the solar wind.
Highlights
To identify the sources of different solar wind streams at the Sun, the topology of expanding coronal structures, as well as the link between their plasma parameters and corresponding in situ values, need to be established
These data are complemented by in situ Fe charge state and solar wind speed measurements from Advanced Composition Explorer (ACE) covering the same time period. We show how this complementary set of observations covering 14 years yields a link between the prevalence of Fe XI emission from Fe10+, characterized by Tfexi = 1.2 ± 0.1 MK, in the expanding corona and the in situ presence of continual solar wind streams clustering around Fe10+ with speeds ranging from ≈300 to 700 km s−1
Given that the Fe10+ and Fe13+ charge states, corresponding respectively to Fe XI and Fe XIV emission in the corona, are frozen in within the field of view of the eclipse images, their spatial distribution in the corona is directly correlated with their corresponding charge state distribution in situ
Summary
To identify the sources of different solar wind streams at the Sun, the topology of expanding coronal structures, as well as the link between their plasma parameters and corresponding in situ values, need to be established. The coronal observations consist of a unique set of simultaneous white light, Fe XI, and Fe XIV total solar eclipse observations acquired between 2006 and 2020 from the descending phase of SC 23 to the beginning of SC 25 These data are complemented by in situ Fe charge state and solar wind speed measurements from ACE covering the same time period. We show how this complementary set of observations covering 14 years yields a link between the prevalence of Fe XI emission from Fe10+, characterized by Tfexi = 1.2 ± 0.1 MK, in the expanding corona and the in situ presence of continual solar wind streams clustering around Fe10+ with speeds ranging from ≈300 to 700 km s−1. These observations suggest that the sporadic appearance of high Fe charge states in situ can be attributed to the dynamics of prominences at the base of streamers driving CMEs, as well as the more variable solar wind streams
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