The Temperature Anisotropy and Helium Abundance Features of Alfvénic Slow Solar Wind Observed by Parker Solar Probe, Helios, and Wind Missions
Slow solar wind is typically characterized as having low Alfvénicity, but the occasional occurrence of highly Alfvénic slow solar wind (HASSW) raises questions about its source regions and evolution. In this work, we conduct a statistical analysis of temperature anisotropy and helium abundance in HA...
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2025-01-01
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| author | Jia Huang Davin E. Larson Tamar Ervin Mingzhe Liu Oscar Ortiz Mihailo M. Martinović Zhenguang Huang Alexandros Chasapis Xiangning Chu B. L. Alterman Zesen Huang Wenwen Wei J. L. Verniero Lan K. Jian Adam Szabo Orlando Romeo Ali Rahmati Roberto Livi Phyllis Whittlesey Samer T. Alnussirat Justin C. Kasper Michael Stevens Stuart D. Bale |
| author_facet | Jia Huang Davin E. Larson Tamar Ervin Mingzhe Liu Oscar Ortiz Mihailo M. Martinović Zhenguang Huang Alexandros Chasapis Xiangning Chu B. L. Alterman Zesen Huang Wenwen Wei J. L. Verniero Lan K. Jian Adam Szabo Orlando Romeo Ali Rahmati Roberto Livi Phyllis Whittlesey Samer T. Alnussirat Justin C. Kasper Michael Stevens Stuart D. Bale |
| author_sort | Jia Huang |
| collection | DOAJ |
| description | Slow solar wind is typically characterized as having low Alfvénicity, but the occasional occurrence of highly Alfvénic slow solar wind (HASSW) raises questions about its source regions and evolution. In this work, we conduct a statistical analysis of temperature anisotropy and helium abundance in HASSW using data from the Parker Solar Probe (PSP) within 0.25 au, Helios between 0.3 au and 1 au, and Wind near 1 au. Our findings reveal that HASSW is prevalent close to the Sun, with PSP observations displaying a distinct “U-shaped” Alfvénicity distribution with respect to increasing solar wind speed, unlike the monotonic increase trend seen in Helios and Wind data. This highlights a previously unreported population of unusually low-speed HASSW, which is found in both sub-Alfvénic and super-Alfvénic regimes. The observed decreasing overlap in temperature anisotropy between HASSW and fast solar wind (FSW) with increasing heliocentric distance suggests different underlying heating processes. Additionally, HASSW exhibits two distinct helium abundance populations, particularly evident in PSP data, with generally higher helium abundance compared to less Alfvénic slow solar wind. Moreover, the decreasing overlap in temperature anisotropy versus helium abundance distributions between HASSW and FSW with decreasing radial distance implies that not all HASSW originates from the same source region as FSW. |
| format | Article |
| id | doaj-art-b1a12b7b0bf74a2884f3ebef8bf06af3 |
| institution | OA Journals |
| issn | 2041-8205 |
| language | English |
| publishDate | 2025-01-01 |
| publisher | IOP Publishing |
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| series | The Astrophysical Journal Letters |
| spelling | doaj-art-b1a12b7b0bf74a2884f3ebef8bf06af32025-08-20T02:23:57ZengIOP PublishingThe Astrophysical Journal Letters2041-82052025-01-019862L2810.3847/2041-8213/ade0acThe Temperature Anisotropy and Helium Abundance Features of Alfvénic Slow Solar Wind Observed by Parker Solar Probe, Helios, and Wind MissionsJia Huang0https://orcid.org/0000-0002-9954-4707Davin E. Larson1https://orcid.org/0000-0001-5030-6030Tamar Ervin2https://orcid.org/0000-0002-8475-8606Mingzhe Liu3https://orcid.org/0000-0003-2981-0544Oscar Ortiz4Mihailo M. Martinović5https://orcid.org/0000-0002-7365-0472Zhenguang Huang6https://orcid.org/0000-0003-1674-0647Alexandros Chasapis7https://orcid.org/0000-0001-8478-5797Xiangning Chu8https://orcid.org/0000-0003-4109-0770B. L. Alterman9https://orcid.org/0000-0001-6673-3432Zesen Huang10https://orcid.org/0000-0001-9570-5975Wenwen Wei11https://orcid.org/0000-0001-8495-9179J. L. Verniero12https://orcid.org/0000-0003-1138-652XLan K. Jian13https://orcid.org/0000-0002-6849-5527Adam Szabo14https://orcid.org/0000-0003-3255-9071Orlando Romeo15https://orcid.org/0000-0002-4559-2199Ali Rahmati16https://orcid.org/0000-0003-0519-6498Roberto Livi17https://orcid.org/0000-0002-0396-0547Phyllis Whittlesey18https://orcid.org/0000-0002-7287-5098Samer T. Alnussirat19https://orcid.org/0000-0001-6125-6411Justin C. Kasper20https://orcid.org/0000-0002-7077-930XMichael Stevens21https://orcid.org/0000-0002-7728-0085Stuart D. Bale22https://orcid.org/0000-0002-1989-3596Space Sciences Laboratory, University of California , Berkeley, CA 94720, USA ; huangjia.sky@gmail.com, huangjia@berkeley.eduSpace Sciences Laboratory, University of California , Berkeley, CA 94720, USA ; huangjia.sky@gmail.com, huangjia@berkeley.eduSpace Sciences Laboratory, University of California , Berkeley, CA 94720, USA ; huangjia.sky@gmail.com, huangjia@berkeley.edu; Department of Physics, University of California , Berkeley, Berkeley, CA 94720, USASpace Sciences Laboratory, University of California , Berkeley, CA 94720, USA ; huangjia.sky@gmail.com, huangjia@berkeley.eduSpace Sciences Laboratory, University of California , Berkeley, CA 94720, USA ; huangjia.sky@gmail.com, huangjia@berkeley.eduLunar and Planetary Laboratory, University of Arizona , Tucson, AZ 85719, USAClimate and Space Sciences and Engineering, University of Michigan , Ann Arbor, MI 48109, USALaboratory for Atmospheric and Space Physics, University of Colorado Boulder , Boulder, CO 80303, USALaboratory for Atmospheric and Space Physics, University of Colorado Boulder , Boulder, CO 80303, USASouthwest Research Institute , San Antonio, TX 78238, USADepartment of Earth, Planetary, and Space Sciences, University of California , Los Angeles, CA 90095, USASpace Sciences Laboratory, University of California , Berkeley, CA 94720, USA ; huangjia.sky@gmail.com, huangjia@berkeley.eduHeliophysics Science Division , NASA Goddard Space Flight Center, Greenbelt, MD 20771, USAHeliophysics Science Division , NASA Goddard Space Flight Center, Greenbelt, MD 20771, USAHeliophysics Science Division , NASA Goddard Space Flight Center, Greenbelt, MD 20771, USASpace Sciences Laboratory, University of California , Berkeley, CA 94720, USA ; huangjia.sky@gmail.com, huangjia@berkeley.eduSpace Sciences Laboratory, University of California , Berkeley, CA 94720, USA ; huangjia.sky@gmail.com, huangjia@berkeley.eduSpace Sciences Laboratory, University of California , Berkeley, CA 94720, USA ; huangjia.sky@gmail.com, huangjia@berkeley.eduSpace Sciences Laboratory, University of California , Berkeley, CA 94720, USA ; huangjia.sky@gmail.com, huangjia@berkeley.eduSpace Sciences Laboratory, University of California , Berkeley, CA 94720, USA ; huangjia.sky@gmail.com, huangjia@berkeley.eduBWX Technologies , Inc., Washington, DC 20001, USASmithsonian Astrophysical Observatory , Cambridge, MA 02138, USASpace Sciences Laboratory, University of California , Berkeley, CA 94720, USA ; huangjia.sky@gmail.com, huangjia@berkeley.edu; Department of Physics, University of California , Berkeley, Berkeley, CA 94720, USASlow solar wind is typically characterized as having low Alfvénicity, but the occasional occurrence of highly Alfvénic slow solar wind (HASSW) raises questions about its source regions and evolution. In this work, we conduct a statistical analysis of temperature anisotropy and helium abundance in HASSW using data from the Parker Solar Probe (PSP) within 0.25 au, Helios between 0.3 au and 1 au, and Wind near 1 au. Our findings reveal that HASSW is prevalent close to the Sun, with PSP observations displaying a distinct “U-shaped” Alfvénicity distribution with respect to increasing solar wind speed, unlike the monotonic increase trend seen in Helios and Wind data. This highlights a previously unreported population of unusually low-speed HASSW, which is found in both sub-Alfvénic and super-Alfvénic regimes. The observed decreasing overlap in temperature anisotropy between HASSW and fast solar wind (FSW) with increasing heliocentric distance suggests different underlying heating processes. Additionally, HASSW exhibits two distinct helium abundance populations, particularly evident in PSP data, with generally higher helium abundance compared to less Alfvénic slow solar wind. Moreover, the decreasing overlap in temperature anisotropy versus helium abundance distributions between HASSW and FSW with decreasing radial distance implies that not all HASSW originates from the same source region as FSW.https://doi.org/10.3847/2041-8213/ade0acSlow solar windSpace plasmasInterplanetary magnetic fields |
| spellingShingle | Jia Huang Davin E. Larson Tamar Ervin Mingzhe Liu Oscar Ortiz Mihailo M. Martinović Zhenguang Huang Alexandros Chasapis Xiangning Chu B. L. Alterman Zesen Huang Wenwen Wei J. L. Verniero Lan K. Jian Adam Szabo Orlando Romeo Ali Rahmati Roberto Livi Phyllis Whittlesey Samer T. Alnussirat Justin C. Kasper Michael Stevens Stuart D. Bale The Temperature Anisotropy and Helium Abundance Features of Alfvénic Slow Solar Wind Observed by Parker Solar Probe, Helios, and Wind Missions The Astrophysical Journal Letters Slow solar wind Space plasmas Interplanetary magnetic fields |
| title | The Temperature Anisotropy and Helium Abundance Features of Alfvénic Slow Solar Wind Observed by Parker Solar Probe, Helios, and Wind Missions |
| title_full | The Temperature Anisotropy and Helium Abundance Features of Alfvénic Slow Solar Wind Observed by Parker Solar Probe, Helios, and Wind Missions |
| title_fullStr | The Temperature Anisotropy and Helium Abundance Features of Alfvénic Slow Solar Wind Observed by Parker Solar Probe, Helios, and Wind Missions |
| title_full_unstemmed | The Temperature Anisotropy and Helium Abundance Features of Alfvénic Slow Solar Wind Observed by Parker Solar Probe, Helios, and Wind Missions |
| title_short | The Temperature Anisotropy and Helium Abundance Features of Alfvénic Slow Solar Wind Observed by Parker Solar Probe, Helios, and Wind Missions |
| title_sort | temperature anisotropy and helium abundance features of alfvenic slow solar wind observed by parker solar probe helios and wind missions |
| topic | Slow solar wind Space plasmas Interplanetary magnetic fields |
| url | https://doi.org/10.3847/2041-8213/ade0ac |
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