EGU2020-21075, updated on 16 May 2023
EGU General Assembly 2020
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.

Stream Interaction Regions in the Inner Heliosphere: Insights from the First Four Orbits of Parker Solar Probe

Robert Allen1, George Ho1, Lan Jian2, David Lario2, Dusan Odstrcil2, Charles Arge2, Sam Badman3,4, Stuart Bale3,4,5, Anthony Case6, Eric Christian2, Christina Cohen7, Carl Henney8, Matthew Hill1, Shaela Jones2, Justin Kasper6,9, Kelly Korreck6, David Malaspina10, David McComas11, Nour Raouafi1, and Michael Stevens6
Robert Allen et al.
  • 1Johns Hopkins Applied Physics Laboratory, Laurel, MD 20723, USA (
  • 2NASA/Goddard Space Flight Center, Greenbelt, MD 20771, USA
  • 3Physics Department, University of California, Berkeley, CA 94720-7300, USA
  • 4Space Sciences Laboratory, University of California, Berkeley, CA 94720-7450, USA
  • 5The Blackett Laboratory, Imperial College London, London, SW7 2AZ, UK
  • 6Smithsonian Astrophysical Observatory, Cambridge, MA 02138, USA
  • 7California Institute of Technology, Pasadena, CA 91125, USA
  • 8Air Force Research Laboratory, Space Vehicles Directorate, Kirtland AFB, NM 87117, USA
  • 9Climate and Space Sciences and Engineering, University of Michigan, Ann Arbor, MI 48109, USA
  • 10Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, CO 80303, USA
  • 11Princeton University, Department of Astrophysical Sciences, Princeton, NJ, USA

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.

How to cite: Allen, R., Ho, G., Jian, L., Lario, D., Odstrcil, D., Arge, C., Badman, S., Bale, S., Case, A., Christian, E., Cohen, C., Henney, C., Hill, M., Jones, S., Kasper, J., Korreck, K., Malaspina, D., McComas, D., Raouafi, N., and Stevens, M.: Stream Interaction Regions in the Inner Heliosphere: Insights from the First Four Orbits of Parker Solar Probe, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21075,, 2020.


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