[P-EM11] Heliosphere and Interplanetary Space

[PEM11-01] Stream Interaction Regions in the Inner Heliosphere: Insights from the First Four Orbits of Parker Solar Probe

★Invited Papers

*Robert Colby Allen¹, George Ho¹, Lan K Jian², David Lario², Dusan Odstrcil², Charles Nick Arge², Sam T Badman^4,5, Steward D Bale^4,5,7,8, John W Bonnell⁵, Anthony W Case⁹, Eric R Christian², Christina M. S. Cohen³, Thierry Dundok de Wit¹⁰, Keith Goetz¹¹, Peter R Harvey⁵, Carl J Henney¹², Matt E Hill¹, Shaela I Jones^2,6, Justin C Kasper^13,9, Kelly E Korreck⁹, Davin Larson⁵, Roberto Livi⁵, Robert J MacDowall², David M Malaspina¹⁴, Glenn M Mason¹, M Leila Mays², David J McComas¹⁵, Ralph McNutt Jr.¹, Don G Mitchell¹, Marc Pulupa⁵, Nour Raouafi¹, Nathon Schwadron¹⁶, Michael L Stevens⁹, Sarah K Vines¹, Phyllis L Whittlesey⁵, Mark Wiedenbeck¹⁷ (1.Johns Hopkins University Applied Physics Laboratory, 2.NASA/Goddard Space Flight Center, 3.California Institute of Technology, 4.Physics Department, University of California Berkeley, 5.Space Sciences Laboratory, University of California Berkeley, 6.Catholic University of America, 7.The Blackett Laboratory, Imperial College London, 8.School of Physics and Astronomy, Queen Mary University of London, 9.Smithsonian Astrophysical Observatory, 10.LPC2E, CNRS, 11.School of Physics and Astronomy, University of Minnesota, 12.Air Force Research Laboratory, Space Vehicles Directorate, 13.Climate and Space Sciences and Engineering, University of Michigan, 14.Laboratory for Atmospheric and Space Physics, University of Colorado Boulder, 15.Princeton University, Department of Astrophysical Sciences, 16.University of New Hampshire, Space Science Center, 17.Jet Propulsion Laboratory)

Keywords:Stream Interaction Regions, Corotating Interaction Regions, Solar Wind, Acceleration

The first four orbits of Parker Solar Probe (PSP) consists of many observations of stream interaction regions (SIRs), which form when fast solar wind streams overtake slower solar wind. While it is known that SIRs accelerate ions in the heliosphere and can trigger geomagnetic storms, the temporal and radial evolution of SIRs is still an active topic of research. During the first four orbits of PSP, SIRs were observed by PSP at small heliospheric distances, as well as at 1 au by the Advanced Composition Explorer (ACE), Wind, and Solar Terrestrial Relations Observatory (STEREO) missions. These SIRs are observed not only at different heliospheric distances, but also at different points in the temporal development of the stream interface. Through analyzing the various SIRs together, insight can be gained in regards to the spatial and temporal evolution of SIR characteristics, as well as to the mechanisms of particle acceleration and transport along the SIR interface. The general characteristics of SIRs observed by PSP during the first four orbits are presented, and an in-depth comparison of a few of the SIR events is conducted to further analyze the evolution of SIR streams in the inner heliosphere. These observations show examples of a fast solar wind stream steepening into an SIR, with evidence of locally accelerated particles via compressive mechanisms at the interface distinguishable from observations of particles likely accelerated at shocks formed at larger heliospheric distances.