Solar Wind Heating Near the Sun: A Radial Evolution Approach
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| Autores principales: | , , , , , , , , , , , , , , , , , , , , , |
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| Formato: | Preprint |
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2026
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| author | Yogesh Ofman, Leon Klein, Kristopher Shankarappa, Niranjana Martinović, Mihailo M. Howes, Gregory G. Mostafavi, Parisa Boardsen, Scott A Sadykov, Viacheslav M Pal, Sanchita Jian, Lan K Gupta, Aakash Chakrabarty, D. Alterman, B. L. Verniero, Jaye L Paulson, K. W. Huang, Jia Livi, Roberto Larson, Davin E. Möstl, Christian Davies, Emma E. Weiler, Eva |
| author_facet | Yogesh Ofman, Leon Klein, Kristopher Shankarappa, Niranjana Martinović, Mihailo M. Howes, Gregory G. Mostafavi, Parisa Boardsen, Scott A Sadykov, Viacheslav M Pal, Sanchita Jian, Lan K Gupta, Aakash Chakrabarty, D. Alterman, B. L. Verniero, Jaye L Paulson, K. W. Huang, Jia Livi, Roberto Larson, Davin E. Möstl, Christian Davies, Emma E. Weiler, Eva |
| contents | Characterizing the plasma state in the near-Sun environment is essential to constrain the mechanisms that heat and accelerate the solar wind. In this study, we use Parker Solar Probe (PSP) observations from Encounters 1 through 24 to investigate the radial evolution of solar wind plasma and magnetic field properties in this region. Using intervals with high field-of-view ($>85\%$) coverage, we derive the radial profiles of magnetic field strength ($|B|$), proton density ($N$), bulk speed ($V$), total proton temperature ($T$), parallel ($T_\parallel$) and perpendicular ($T_\perp$) temperatures, temperature anisotropy ($T_\perp/T_\parallel$), plasma beta ($β$), Alfvén Mach number ($M_A$), and magnetic field fluctuations ($δB/B$) for sub and super-Alfvénic regions. In super-Alfvénic regions, power-law of $|B|$, $N$, $V$, and $T$ as a function of heliocentric distance are broadly consistent with previous \textit{Helios} results at $>0.3$ AU. The radial evolution of the components of the temperature tensor reveals distinct behavior: $T_\perp$ decreases monotonically with distance, whereas $T_\parallel$ exhibits a non-monotonic trend -- decreasing in the sub-Alfvénic region, increasing just beyond the Alfvén surface. We interpret the increase in $T_\parallel$ as a proxy for proton beam occurrence. We further examine the evolution of magnetic field fluctuations, finding decreasing radial/parallel fluctuations but enhanced tangential/normal/perpendicular fluctuations in sunward direction. These fluctuations may provide free energy for beam generation and particle heating via wave-particle interactions. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2602_10275 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Solar Wind Heating Near the Sun: A Radial Evolution Approach Yogesh Ofman, Leon Klein, Kristopher Shankarappa, Niranjana Martinović, Mihailo M. Howes, Gregory G. Mostafavi, Parisa Boardsen, Scott A Sadykov, Viacheslav M Pal, Sanchita Jian, Lan K Gupta, Aakash Chakrabarty, D. Alterman, B. L. Verniero, Jaye L Paulson, K. W. Huang, Jia Livi, Roberto Larson, Davin E. Möstl, Christian Davies, Emma E. Weiler, Eva Solar and Stellar Astrophysics Space Physics Characterizing the plasma state in the near-Sun environment is essential to constrain the mechanisms that heat and accelerate the solar wind. In this study, we use Parker Solar Probe (PSP) observations from Encounters 1 through 24 to investigate the radial evolution of solar wind plasma and magnetic field properties in this region. Using intervals with high field-of-view ($>85\%$) coverage, we derive the radial profiles of magnetic field strength ($|B|$), proton density ($N$), bulk speed ($V$), total proton temperature ($T$), parallel ($T_\parallel$) and perpendicular ($T_\perp$) temperatures, temperature anisotropy ($T_\perp/T_\parallel$), plasma beta ($β$), Alfvén Mach number ($M_A$), and magnetic field fluctuations ($δB/B$) for sub and super-Alfvénic regions. In super-Alfvénic regions, power-law of $|B|$, $N$, $V$, and $T$ as a function of heliocentric distance are broadly consistent with previous \textit{Helios} results at $>0.3$ AU. The radial evolution of the components of the temperature tensor reveals distinct behavior: $T_\perp$ decreases monotonically with distance, whereas $T_\parallel$ exhibits a non-monotonic trend -- decreasing in the sub-Alfvénic region, increasing just beyond the Alfvén surface. We interpret the increase in $T_\parallel$ as a proxy for proton beam occurrence. We further examine the evolution of magnetic field fluctuations, finding decreasing radial/parallel fluctuations but enhanced tangential/normal/perpendicular fluctuations in sunward direction. These fluctuations may provide free energy for beam generation and particle heating via wave-particle interactions. |
| title | Solar Wind Heating Near the Sun: A Radial Evolution Approach |
| topic | Solar and Stellar Astrophysics Space Physics |
| url | https://arxiv.org/abs/2602.10275 |