Formation of H+ PUI Tails Downstream of Distant Interplanetary Shocks
New Horizons’ Solar Wind Around Pluto (SWAP) instrument has observed interplanetary shocks from ∼20 to 60 au from the Sun. Different studies have analyzed the effects of these shocks on the solar wind ion (SWI) and interstellar pickup ion (PUI) distributions. A key finding includes the observation o...
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2025-01-01
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| Online Access: | https://doi.org/10.3847/1538-4357/addf45 |
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| author | E. J. Zirnstein D. J. McComas B. L. Shrestha H. A. Elliott P. C. Brandt S. A. Stern A. R. Poppe J. Parker E. Provornikova K. Singer A. Verbiscer New Horizons Heliophysics Team |
| author_facet | E. J. Zirnstein D. J. McComas B. L. Shrestha H. A. Elliott P. C. Brandt S. A. Stern A. R. Poppe J. Parker E. Provornikova K. Singer A. Verbiscer New Horizons Heliophysics Team |
| author_sort | E. J. Zirnstein |
| collection | DOAJ |
| description | New Horizons’ Solar Wind Around Pluto (SWAP) instrument has observed interplanetary shocks from ∼20 to 60 au from the Sun. Different studies have analyzed the effects of these shocks on the solar wind ion (SWI) and interstellar pickup ion (PUI) distributions. A key finding includes the observation of PUI tails downstream of some shocks. However, PUI tails have only been observed when SWAP was measuring 24 hr averages of the count rate histograms. After a software change in 2021 February, SWAP’s measurement resolution was improved to ∼30 minutes averages, but no PUI tails have been observed since this change. In this study, we use a test particle code to simulate the downstream SWI and PUI distributions to study the possible existence and formation of PUI tails, using the shock compression ratio, shock thickness, and turbulence as free parameters. We find that in most cases, a suprathermal tail does not develop downstream of interplanetary shocks, but a persistent hump and PUI cutoff exists at energies above the PUI injection energy. The extent of the hump largely depends on the shock compression ratio. We find PUI tails do form when turbulence is included in the model. After we convert our distributions to count rates in the spacecraft frame, the results show similar structure to the data. We conclude that significant H ^+ PUI tails can form downstream of distant interplanetary shocks if there is a relatively large compression ratio (>2) and significant turbulence present. |
| format | Article |
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| institution | OA Journals |
| issn | 1538-4357 |
| language | English |
| publishDate | 2025-01-01 |
| publisher | IOP Publishing |
| record_format | Article |
| series | The Astrophysical Journal |
| spelling | doaj-art-704fc48e1cd648439d8328d6b2f71c862025-08-20T02:37:05ZengIOP PublishingThe Astrophysical Journal1538-43572025-01-01986220510.3847/1538-4357/addf45Formation of H+ PUI Tails Downstream of Distant Interplanetary ShocksE. J. Zirnstein0https://orcid.org/0000-0001-7240-0618D. J. McComas1https://orcid.org/0000-0001-6160-1158B. L. Shrestha2https://orcid.org/0000-0002-5247-4107H. A. Elliott3https://orcid.org/0000-0003-2297-3922P. C. Brandt4https://orcid.org/0000-0002-4644-0306S. A. Stern5https://orcid.org/0000-0001-5018-7537A. R. Poppe6https://orcid.org/0000-0001-8137-8176J. Parker7https://orcid.org/0000-0002-3672-0603E. Provornikova8https://orcid.org/0000-0001-8875-7478K. Singer9https://orcid.org/0000-0003-3045-8445A. Verbiscer10https://orcid.org/0000-0002-3323-9304New Horizons Heliophysics TeamDepartment of Astrophysical Sciences, Princeton University , Princeton, NJ 08544, USA ; ejz@princeton.eduDepartment of Astrophysical Sciences, Princeton University , Princeton, NJ 08544, USA ; ejz@princeton.eduDepartment of Astrophysical Sciences, Princeton University , Princeton, NJ 08544, USA ; ejz@princeton.eduSouthwest Research Institute, San Antonio , TX 78228, USAJohns Hopkins University Applied Physics Laboratory, Laurel, MD 20723, USASouthwest Research Institute, Boulder, CO 80302, USASpace Sciences Laboratory, University of California at Berkley , Berkley, CA 94720, USASouthwest Research Institute, Boulder, CO 80302, USAJohns Hopkins University Applied Physics Laboratory, Laurel, MD 20723, USASouthwest Research Institute, Boulder, CO 80302, USADepartment of Astronomy, University of Virginia , Charlottesville, VA 22904, USANew Horizons’ Solar Wind Around Pluto (SWAP) instrument has observed interplanetary shocks from ∼20 to 60 au from the Sun. Different studies have analyzed the effects of these shocks on the solar wind ion (SWI) and interstellar pickup ion (PUI) distributions. A key finding includes the observation of PUI tails downstream of some shocks. However, PUI tails have only been observed when SWAP was measuring 24 hr averages of the count rate histograms. After a software change in 2021 February, SWAP’s measurement resolution was improved to ∼30 minutes averages, but no PUI tails have been observed since this change. In this study, we use a test particle code to simulate the downstream SWI and PUI distributions to study the possible existence and formation of PUI tails, using the shock compression ratio, shock thickness, and turbulence as free parameters. We find that in most cases, a suprathermal tail does not develop downstream of interplanetary shocks, but a persistent hump and PUI cutoff exists at energies above the PUI injection energy. The extent of the hump largely depends on the shock compression ratio. We find PUI tails do form when turbulence is included in the model. After we convert our distributions to count rates in the spacecraft frame, the results show similar structure to the data. We conclude that significant H ^+ PUI tails can form downstream of distant interplanetary shocks if there is a relatively large compression ratio (>2) and significant turbulence present.https://doi.org/10.3847/1538-4357/addf45HeliosphereSolar windInterplanetary shocksParticle physicsInterplanetary turbulence |
| spellingShingle | E. J. Zirnstein D. J. McComas B. L. Shrestha H. A. Elliott P. C. Brandt S. A. Stern A. R. Poppe J. Parker E. Provornikova K. Singer A. Verbiscer New Horizons Heliophysics Team Formation of H+ PUI Tails Downstream of Distant Interplanetary Shocks The Astrophysical Journal Heliosphere Solar wind Interplanetary shocks Particle physics Interplanetary turbulence |
| title | Formation of H+ PUI Tails Downstream of Distant Interplanetary Shocks |
| title_full | Formation of H+ PUI Tails Downstream of Distant Interplanetary Shocks |
| title_fullStr | Formation of H+ PUI Tails Downstream of Distant Interplanetary Shocks |
| title_full_unstemmed | Formation of H+ PUI Tails Downstream of Distant Interplanetary Shocks |
| title_short | Formation of H+ PUI Tails Downstream of Distant Interplanetary Shocks |
| title_sort | formation of h pui tails downstream of distant interplanetary shocks |
| topic | Heliosphere Solar wind Interplanetary shocks Particle physics Interplanetary turbulence |
| url | https://doi.org/10.3847/1538-4357/addf45 |
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