PUI Heating in the Supersonic Solar Wind
The outer heliosphere is profoundly influenced by nonthermal energetic pickup ions (PUIs), which dominate the internal pressure of the solar wind beyond ~10 au, surpassing both solar wind and magnetic pressures. PUIs are formed mostly through charge exchange between interstellar neutral atoms and so...
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IOP Publishing
2025-01-01
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| Series: | The Astrophysical Journal |
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| Online Access: | https://doi.org/10.3847/1538-4357/ada891 |
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| author | Parisa Mostafavi Laxman Adhikari Bishwas L. Shrestha Gary P. Zank Merav Opher Matthew E. Hill Heather A. Elliott Pontus C. Brandt Ralph L. McNutt David J. McComas Andrew R. Poppe Elena Provornikova Romina Nikoukar Peter Kollmann S. Alan Stern Kelsi N. Singer Anne Verbiscer Joel Parker |
| author_facet | Parisa Mostafavi Laxman Adhikari Bishwas L. Shrestha Gary P. Zank Merav Opher Matthew E. Hill Heather A. Elliott Pontus C. Brandt Ralph L. McNutt David J. McComas Andrew R. Poppe Elena Provornikova Romina Nikoukar Peter Kollmann S. Alan Stern Kelsi N. Singer Anne Verbiscer Joel Parker |
| author_sort | Parisa Mostafavi |
| collection | DOAJ |
| description | The outer heliosphere is profoundly influenced by nonthermal energetic pickup ions (PUIs), which dominate the internal pressure of the solar wind beyond ~10 au, surpassing both solar wind and magnetic pressures. PUIs are formed mostly through charge exchange between interstellar neutral atoms and solar wind ions. This study examines the apparent heating of PUIs in the distant supersonic solar wind before reaching the heliospheric termination shock. New Horizons’ SWAP observations reveal an unexpected PUI temperature change between 2015 and 2020, with a notable bump in PUI temperature. Concurrent observations from the ACE and Wind spacecraft at 1 au indicate a ~50% increase in solar wind dynamic pressure at the end of 2014. Our simulation suggests that the bump observed in the PUI temperature by New Horizons is largely associated with the enhanced solar wind dynamic pressure observed at 1 au. Additional PUI temperature enhancements imply the involvement of other heating mechanisms. Analysis of New Horizons data reveals a correlation between shocks and PUI heating during the declining phase of the solar cycle. Using a PUI-mediated plasma model, we explore shock structures and PUI heating, finding that shocks preferentially heat PUIs over the thermal solar wind in the outer heliosphere. We also show that the broad shock thickness observed by New Horizons is due to the large diffusion coefficient associated with PUIs. Shocks and compression regions in the distant supersonic solar wind lead to elevated PUI temperatures and thus they can increase the production of energetic neutral atoms with large energy. |
| format | Article |
| id | doaj-art-6af96e8fb64a426391338cdc88dff8a5 |
| institution | DOAJ |
| issn | 1538-4357 |
| language | English |
| publishDate | 2025-01-01 |
| publisher | IOP Publishing |
| record_format | Article |
| series | The Astrophysical Journal |
| spelling | doaj-art-6af96e8fb64a426391338cdc88dff8a52025-08-20T03:09:28ZengIOP PublishingThe Astrophysical Journal1538-43572025-01-01979222210.3847/1538-4357/ada891PUI Heating in the Supersonic Solar WindParisa Mostafavi0https://orcid.org/0000-0002-3808-3580Laxman Adhikari1https://orcid.org/0000-0003-1549-5256Bishwas L. Shrestha2https://orcid.org/0000-0002-5247-4107Gary P. Zank3https://orcid.org/0000-0002-4642-6192Merav Opher4https://orcid.org/0000-0002-8767-8273Matthew E. Hill5https://orcid.org/0000-0002-5674-4936Heather A. Elliott6https://orcid.org/0000-0003-2297-3922Pontus C. Brandt7https://orcid.org/0000-0002-4644-0306Ralph L. McNutt8https://orcid.org/0000-0002-4722-9166David J. McComas9https://orcid.org/0000-0001-6160-1158Andrew R. Poppe10https://orcid.org/0000-0001-8137-8176Elena Provornikova11https://orcid.org/0000-0001-8875-7478Romina Nikoukar12https://orcid.org/0000-0002-8608-2822Peter Kollmann13https://orcid.org/0000-0002-4274-9760S. Alan Stern14https://orcid.org/0000-0001-5018-7537Kelsi N. Singer15https://orcid.org/0000-0003-3045-8445Anne Verbiscer16https://orcid.org/0000-0002-3323-9304Joel Parker17https://orcid.org/0000-0002-3672-0603Johns Hopkins Applied Physics Laboratory , Laurel, MD 20723, USA ; parisa.mostafavi@jhuapl.eduDepartment of Space Science, University of Alabama in Huntsville , Huntsville, AL 35899, USADepartment of Astrophysical Sciences, Princeton University , Princeton, NJ 08544, USADepartment of Space Science, University of Alabama in Huntsville , Huntsville, AL 35899, USA; Center for Space Plasma and Aeronomic Research (CSPAR), University of Alabama in Huntsville , Huntsville, AL 35899, USAAstronomy Department, Boston University , Boston, MA, USAJohns Hopkins Applied Physics Laboratory , Laurel, MD 20723, USA ; parisa.mostafavi@jhuapl.eduSouthwest Research Institute , San Antonio, TX, USAJohns Hopkins Applied Physics Laboratory , Laurel, MD 20723, USA ; parisa.mostafavi@jhuapl.eduJohns Hopkins Applied Physics Laboratory , Laurel, MD 20723, USA ; parisa.mostafavi@jhuapl.eduDepartment of Astrophysical Sciences, Princeton University , Princeton, NJ 08544, USAUniversity of California Berkeley , Berkeley, CA, USAJohns Hopkins Applied Physics Laboratory , Laurel, MD 20723, USA ; parisa.mostafavi@jhuapl.eduJohns Hopkins Applied Physics Laboratory , Laurel, MD 20723, USA ; parisa.mostafavi@jhuapl.eduJohns Hopkins Applied Physics Laboratory , Laurel, MD 20723, USA ; parisa.mostafavi@jhuapl.eduSouthwest Research Institute , Boulder, CO, USASouthwest Research Institute , Boulder, CO, USASpace Sciences Laboratory, University of California , Berkeley, CA 94720, USA; Department of Astronomy, University of Virginia , Charlottesville, VA, USASouthwest Research Institute , Boulder, CO, USAThe outer heliosphere is profoundly influenced by nonthermal energetic pickup ions (PUIs), which dominate the internal pressure of the solar wind beyond ~10 au, surpassing both solar wind and magnetic pressures. PUIs are formed mostly through charge exchange between interstellar neutral atoms and solar wind ions. This study examines the apparent heating of PUIs in the distant supersonic solar wind before reaching the heliospheric termination shock. New Horizons’ SWAP observations reveal an unexpected PUI temperature change between 2015 and 2020, with a notable bump in PUI temperature. Concurrent observations from the ACE and Wind spacecraft at 1 au indicate a ~50% increase in solar wind dynamic pressure at the end of 2014. Our simulation suggests that the bump observed in the PUI temperature by New Horizons is largely associated with the enhanced solar wind dynamic pressure observed at 1 au. Additional PUI temperature enhancements imply the involvement of other heating mechanisms. Analysis of New Horizons data reveals a correlation between shocks and PUI heating during the declining phase of the solar cycle. Using a PUI-mediated plasma model, we explore shock structures and PUI heating, finding that shocks preferentially heat PUIs over the thermal solar wind in the outer heliosphere. We also show that the broad shock thickness observed by New Horizons is due to the large diffusion coefficient associated with PUIs. Shocks and compression regions in the distant supersonic solar wind lead to elevated PUI temperatures and thus they can increase the production of energetic neutral atoms with large energy.https://doi.org/10.3847/1538-4357/ada891HeliospherePickup ionsShocksSolar wind |
| spellingShingle | Parisa Mostafavi Laxman Adhikari Bishwas L. Shrestha Gary P. Zank Merav Opher Matthew E. Hill Heather A. Elliott Pontus C. Brandt Ralph L. McNutt David J. McComas Andrew R. Poppe Elena Provornikova Romina Nikoukar Peter Kollmann S. Alan Stern Kelsi N. Singer Anne Verbiscer Joel Parker PUI Heating in the Supersonic Solar Wind The Astrophysical Journal Heliosphere Pickup ions Shocks Solar wind |
| title | PUI Heating in the Supersonic Solar Wind |
| title_full | PUI Heating in the Supersonic Solar Wind |
| title_fullStr | PUI Heating in the Supersonic Solar Wind |
| title_full_unstemmed | PUI Heating in the Supersonic Solar Wind |
| title_short | PUI Heating in the Supersonic Solar Wind |
| title_sort | pui heating in the supersonic solar wind |
| topic | Heliosphere Pickup ions Shocks Solar wind |
| url | https://doi.org/10.3847/1538-4357/ada891 |
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