Fluctuations Driven by Multicomponent Pickup Ion Distributions in the Outer Heliosheath
The stability of a realistic multicomponent pickup ion (PUI) velocity distribution derived from a global model of neutral atoms in the heliosphere, which treats hydrogen and helium atoms self-consistently and includes equations for electrons and helium ions, is investigated using linear instability...
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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/adaaf4 |
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| author | Ameneh Mousavi Vadim Roytershteyn Federico Fraternale Nikolai Pogorelov |
| author_facet | Ameneh Mousavi Vadim Roytershteyn Federico Fraternale Nikolai Pogorelov |
| author_sort | Ameneh Mousavi |
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| description | The stability of a realistic multicomponent pickup ion (PUI) velocity distribution derived from a global model of neutral atoms in the heliosphere, which treats hydrogen and helium atoms self-consistently and includes equations for electrons and helium ions, is investigated using linear instability analysis and hybrid simulations. Linear instability analysis shows that the excited oblique mirror waves and the parallel/quasi-parallel Alfvén-cyclotron (AC) waves have lower growth rates than those obtained previously by A. Mousavi et al. for the PUI velocity distributions given by J. Heerikhuisen et al. The PUI scattering by each of the two modes alone is studied. In contrast to the previous investigations, our current simulations using the updated realistic distributions indicate that mirror waves alone do not effectively scatter PUIs in pitch angle. Instead, they primarily contribute to reducing the thermal spread anisotropy of the PUIs originating from the neutral solar wind. The unstable AC waves exhibit lower growth rates but higher saturation levels than the mirror waves. Two-dimensional (2D) simulation results show that when all unstable waves are present, the predominant contributor to the fluctuating magnetic field energy is the AC mode. The AC waves quickly scatter the PUIs with pitch angles away from 90 ^∘ toward isotropy, while the PUIs near 90 ^∘ pitch angle maintain a degree of anisotropy within our simulation timeframe. Moreover, several 1D and 2D hybrid simulations with different numbers of particles per cell are performed to examine the impact of numerical noise on PUI scattering. Finally, the implications of these results for the Interstellar Boundary Explorer energetic neutral atom ribbon are discussed. |
| format | Article |
| id | doaj-art-796e229e72fc427d93f9ff2e1b434664 |
| institution | Kabale University |
| issn | 1538-4357 |
| language | English |
| publishDate | 2025-01-01 |
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| series | The Astrophysical Journal |
| spelling | doaj-art-796e229e72fc427d93f9ff2e1b4346642025-02-06T16:17:32ZengIOP PublishingThe Astrophysical Journal1538-43572025-01-0198019510.3847/1538-4357/adaaf4Fluctuations Driven by Multicomponent Pickup Ion Distributions in the Outer HeliosheathAmeneh Mousavi0Vadim Roytershteyn1Federico Fraternale2https://orcid.org/0000-0002-4700-2762Nikolai Pogorelov3https://orcid.org/0000-0002-6409-2392Space Science Institute , Boulder, CO 80301, USA ; amousavi@spacescience.orgSpace Science Institute , Boulder, CO 80301, USA ; amousavi@spacescience.orgCenter for Space Plasma and Aeronomic Research, The University of Alabama in Huntsville , Huntsville, AL 35899, USACenter for Space Plasma and Aeronomic Research, The University of Alabama in Huntsville , Huntsville, AL 35899, USAThe stability of a realistic multicomponent pickup ion (PUI) velocity distribution derived from a global model of neutral atoms in the heliosphere, which treats hydrogen and helium atoms self-consistently and includes equations for electrons and helium ions, is investigated using linear instability analysis and hybrid simulations. Linear instability analysis shows that the excited oblique mirror waves and the parallel/quasi-parallel Alfvén-cyclotron (AC) waves have lower growth rates than those obtained previously by A. Mousavi et al. for the PUI velocity distributions given by J. Heerikhuisen et al. The PUI scattering by each of the two modes alone is studied. In contrast to the previous investigations, our current simulations using the updated realistic distributions indicate that mirror waves alone do not effectively scatter PUIs in pitch angle. Instead, they primarily contribute to reducing the thermal spread anisotropy of the PUIs originating from the neutral solar wind. The unstable AC waves exhibit lower growth rates but higher saturation levels than the mirror waves. Two-dimensional (2D) simulation results show that when all unstable waves are present, the predominant contributor to the fluctuating magnetic field energy is the AC mode. The AC waves quickly scatter the PUIs with pitch angles away from 90 ^∘ toward isotropy, while the PUIs near 90 ^∘ pitch angle maintain a degree of anisotropy within our simulation timeframe. Moreover, several 1D and 2D hybrid simulations with different numbers of particles per cell are performed to examine the impact of numerical noise on PUI scattering. Finally, the implications of these results for the Interstellar Boundary Explorer energetic neutral atom ribbon are discussed.https://doi.org/10.3847/1538-4357/adaaf4Pickup ions |
| spellingShingle | Ameneh Mousavi Vadim Roytershteyn Federico Fraternale Nikolai Pogorelov Fluctuations Driven by Multicomponent Pickup Ion Distributions in the Outer Heliosheath The Astrophysical Journal Pickup ions |
| title | Fluctuations Driven by Multicomponent Pickup Ion Distributions in the Outer Heliosheath |
| title_full | Fluctuations Driven by Multicomponent Pickup Ion Distributions in the Outer Heliosheath |
| title_fullStr | Fluctuations Driven by Multicomponent Pickup Ion Distributions in the Outer Heliosheath |
| title_full_unstemmed | Fluctuations Driven by Multicomponent Pickup Ion Distributions in the Outer Heliosheath |
| title_short | Fluctuations Driven by Multicomponent Pickup Ion Distributions in the Outer Heliosheath |
| title_sort | fluctuations driven by multicomponent pickup ion distributions in the outer heliosheath |
| topic | Pickup ions |
| url | https://doi.org/10.3847/1538-4357/adaaf4 |
| work_keys_str_mv | AT amenehmousavi fluctuationsdrivenbymulticomponentpickupiondistributionsintheouterheliosheath AT vadimroytershteyn fluctuationsdrivenbymulticomponentpickupiondistributionsintheouterheliosheath AT federicofraternale fluctuationsdrivenbymulticomponentpickupiondistributionsintheouterheliosheath AT nikolaipogorelov fluctuationsdrivenbymulticomponentpickupiondistributionsintheouterheliosheath |