Abstract
AbstractThe addition of Parker Solar Probe (PSP) to the Heliophysics System Observatory has allowed for the unprecedented ability to study Corotating Interaction Regions (CIRs) at multiple radial distances without significant temporal/longitudinal variations. On September 19, 2019, PSP observed a CIR at ∼0.5 au when it was nearly radially aligned with the Solar Terrestrial Relations Observatory‐Ahead (STEREO‐A) spacecraft at ∼1 au, allowing for an unambiguous assessment of the radial evolution of a single CIR. Bulk plasma and magnetic field signatures of the CIR evolve in a fashion characteristic to previous observations; however, the suprathermal ions are enhanced over a larger longitudinal range at PSP than at STEREO‐A, although at much lower intensities. The longitudinal spread appears to be largely a consequence of magnetic field line topology at CIRs between the compressed slow solar wind upstream and high‐speed stream following the CIR, underscoring the importance of the large‐scale topology of these structures.
Highlights
Corotating Interaction Regions (CIRs) form where corotating high-speed streams, originating from coronal holes, overtake slower-speed solar wind (Belcher & Davis, 1971; for a recent review, see Richardson, 2018)
On September 19, 2019, Parker Solar Probe (PSP) observed a CIR at ∼0.5 au when it was nearly radially aligned with the Solar Terrestrial Relations Observatory-Ahead (STEREO-A) spacecraft at ∼1 au, allowing for an unambiguous assessment of the radial evolution of a single CIR
We investigate a conjunction between PSP and STEREO-A, when the two spacecraft were nearly radially aligned
Summary
Corotating Interaction Regions (CIRs) form where corotating high-speed streams, originating from coronal holes, overtake slower-speed solar wind (Belcher & Davis, 1971; for a recent review, see Richardson, 2018). In the modern era of the Heliophysics System Observatory, Parker Solar Probe (PSP), in combination with observations at 1 au, allows for an unprecedented opportunity to disentangle the radial and temporal evolution of CIRs. During the first orbit of PSP, several studies investigated CIRs in the inner heliosphere (Allen et al, 2020a; Cohen et al, 2020; Desai et al, 2020; Joyce et al, 2020; McComas et al, 2019). Allen et al (2020a) matched CIRs observed at PSP during its first orbit with observations at 1 au from the Solar Terrestrial Relations Observatory-Ahead (STEREO-A), ACE, and wind missions While this provided insight into possible differences in the energization of suprathermal ions in the inner heliosphere and their connectivity to shocks further out in the heliosphere, the conjunction geometry did not allow for the ability to differentiate between temporal and radial evolution. Discussion and summary of the conclusions of this work are given in Sections 4 and 5, respectively
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