Identifying the Coronal Source Regions of Solar Wind Streams from Total Solar Eclipse Observations and in situ Measurements Extending Over a Solar Cycle

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 (${\mathrm{T}}_{\mathrm{fexi}}$ = $1.2\pm 0.1$ MK) and Fe XIV 530.3 nm (${\mathrm{T}}_{\mathrm{fexiv}}$ = $1.8\pm 0.1$ MK) emission, complemented by in situ Fe charge state and proton speed measurements from ACE/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 $\mathrm{F}{\mathrm{e}}^{10+}$, hence a constant electron temperature, ${\mathrm{T}}_{\mathrm{c}}$ = ${\mathrm{T}}_{\mathrm{fexi}}$, in the expanding corona. The in situ Fe charge states are found to cluster around $\mathrm{F}{\mathrm{e}}^{10+}$, independently of the 300 to 700 km ${\mathrm{s}}^{-1}$ stream speeds, referred to as the continual solar wind. $\mathrm{F}{\mathrm{e}}^{10+}$ thus yields the fiducial link between the continual solar wind and its ${\mathrm{T}}_{\mathrm{fexi}}$ sources at the Sun. While the spatial distribution of Fe XIV emission, from $\mathrm{F}{\mathrm{e}}^{13+}$, associated with streamers, changes throughout the solar cycle, the sporadic appearance of charge states $>\mathrm{F}{\mathrm{e}}^{11+}$, in situ, exhibits no cycle dependence regardless of speed. These latter streams are conjectured to be released from hot coronal plasmas at temperatures $\ge {\mathrm{T}}_{\mathrm{fexiv}}$ 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 ${\mathrm{T}}_{\mathrm{fexi}}$ in the expanding corona, places new constraints on the physical processes shaping the solar wind.

arXiv comment18 pages, 9 figures, accepted for publication in ApJ Letters

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• The Solar Minimum Eclipse of 2019 July 2. III. Inferring the Coronal $T_e$ with a Radiative Differential Emission Measure Inversion
• New Observations of the IR Emission Corona from the July 2, 2019 Eclipse Flight of the Airborne Infrared Spectrometer
• Total Solar Eclipse White Light Images as a Benchmark for PFSS Coronal Magnetic Field Models: An In-Depth Analysis over a Solar Cycle
• The Double-Bubble CME of the 2020 December 14 Total Solar Eclipse
• Enhanced Non-Thermal Line Broadening inside Coronal Cavities above Solar Prominences revealed by Spectral Imaging CoronaGraph
• What Determines the Brightness of the Magnetically Open Solar Corona?: Insights from Three-dimensional Radiative Magnetohydrodynamic Simulations and Observations
• Polarization of the Corona Observed During the 2017 and 2019 Total Solar Eclipses