Effect of Rapid Changes of Solar Wind Conditions on the Pickup Ion Velocity Distribution.
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| Title: | Effect of Rapid Changes of Solar Wind Conditions on the Pickup Ion Velocity Distribution. |
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| Authors: | Bower, J. S.1 jonathan.bower@unh.edu, Moebius, E.1, Berger, L.2, Farrugia, C.1, Keilbach, D.2, Lee, M. A.1, Quinn, P. R.1, Schwadron, N.1, Taut, A.2 |
| Source: | Journal of Geophysical Research. Space Physics. Aug2019, Vol. 124 Issue 8, p6418-6437. 20p. |
| Subject Terms: | Solar wind, Velocity distribution (Statistical mechanics), Ions, Magnetic flux density, Meteorological observations |
| Abstract: | We performed the first systematic analysis of pickup ion (PUI) cutoff speed variations, across compression regions and due to fast fluctuations in solar wind (SW) speed and magnetic field strength. This study is motivated by the need to remove or correct for systematic effects on the determination of the interstellar flow longitude based on the longitudinal variation of the PUI cutoff. Using 2007–2014 STEREO A PLASTIC observations, we identified SW compression regions and accumulated the contained PUI velocity distributions in a superposed epoch analysis. The shift of the cutoff in velocity, interpreted as PUI energization, varies systematically across the compression region and increases approximately linearly with the speed gradient of the compression. Additionally, the shift remains positive into the negative speed gradient at the beginning of the rarefaction region. A similar response is found when PUI distributions are sorted according to the strength of fast fluctuations in SW speed, density, and magnetic field strength. These parameters remain high in the first part of the rarefaction region, suggesting a possible PUI energization through compressive turbulence. Based on these results, we removed the strongest compression regions from the interstellar flow analysis, finding no significant change in direction or uncertainty. Thus, we have revealed the influence of adiabatic compression and compressive turbulence, increasing the PUI cutoff energy, and we have demonstrated that the determination of the interstellar inflow direction via analysis of PUI distributions is robust for a multiyear data set, even in the presence of SW interaction regions. Key Points: The cutoff speed of the pickup ion helium distribution function is shown to systematically increase in solar wind compression regionsThe magnitude of the pickup ion cutoff shift scales approximately linearly with the solar wind speed gradient in the compression regionThe interstellar flow longitude obtained from the pickup ion cutoff is largely unaffected by compressions, when using multiyear data sets [ABSTRACT FROM AUTHOR] |
| Copyright of Journal of Geophysical Research. Space Physics is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.) | |
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| FullText | Text: Availability: 0 |
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| Header | DbId: 8gh DbLabel: GreenFILE An: 138895463 AccessLevel: 6 PubType: Academic Journal PubTypeId: academicJournal PreciseRelevancyScore: 0 |
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| Items | – Name: Title Label: Title Group: Ti Data: Effect of Rapid Changes of Solar Wind Conditions on the Pickup Ion Velocity Distribution. – Name: Author Label: Authors Group: Au Data: <searchLink fieldCode="AR" term="%22Bower%2C+J%2E+S%2E%22">Bower, J. S.</searchLink><relatesTo>1</relatesTo><i> jonathan.bower@unh.edu</i><br /><searchLink fieldCode="AR" term="%22Moebius%2C+E%2E%22">Moebius, E.</searchLink><relatesTo>1</relatesTo><br /><searchLink fieldCode="AR" term="%22Berger%2C+L%2E%22">Berger, L.</searchLink><relatesTo>2</relatesTo><br /><searchLink fieldCode="AR" term="%22Farrugia%2C+C%2E%22">Farrugia, C.</searchLink><relatesTo>1</relatesTo><br /><searchLink fieldCode="AR" term="%22Keilbach%2C+D%2E%22">Keilbach, D.</searchLink><relatesTo>2</relatesTo><br /><searchLink fieldCode="AR" term="%22Lee%2C+M%2E+A%2E%22">Lee, M. A.</searchLink><relatesTo>1</relatesTo><br /><searchLink fieldCode="AR" term="%22Quinn%2C+P%2E+R%2E%22">Quinn, P. R.</searchLink><relatesTo>1</relatesTo><br /><searchLink fieldCode="AR" term="%22Schwadron%2C+N%2E%22">Schwadron, N.</searchLink><relatesTo>1</relatesTo><br /><searchLink fieldCode="AR" term="%22Taut%2C+A%2E%22">Taut, A.</searchLink><relatesTo>2</relatesTo> – Name: TitleSource Label: Source Group: Src Data: <searchLink fieldCode="JN" term="%22Journal+of+Geophysical+Research%2E+Space+Physics%22">Journal of Geophysical Research. Space Physics</searchLink>. Aug2019, Vol. 124 Issue 8, p6418-6437. 20p. – Name: Subject Label: Subject Terms Group: Su Data: <searchLink fieldCode="DE" term="%22Solar+wind%22">Solar wind</searchLink><br /><searchLink fieldCode="DE" term="%22Velocity+distribution+%28Statistical+mechanics%29%22">Velocity distribution (Statistical mechanics)</searchLink><br /><searchLink fieldCode="DE" term="%22Ions%22">Ions</searchLink><br /><searchLink fieldCode="DE" term="%22Magnetic+flux+density%22">Magnetic flux density</searchLink><br /><searchLink fieldCode="DE" term="%22Meteorological+observations%22">Meteorological observations</searchLink> – Name: Abstract Label: Abstract Group: Ab Data: We performed the first systematic analysis of pickup ion (PUI) cutoff speed variations, across compression regions and due to fast fluctuations in solar wind (SW) speed and magnetic field strength. This study is motivated by the need to remove or correct for systematic effects on the determination of the interstellar flow longitude based on the longitudinal variation of the PUI cutoff. Using 2007–2014 STEREO A PLASTIC observations, we identified SW compression regions and accumulated the contained PUI velocity distributions in a superposed epoch analysis. The shift of the cutoff in velocity, interpreted as PUI energization, varies systematically across the compression region and increases approximately linearly with the speed gradient of the compression. Additionally, the shift remains positive into the negative speed gradient at the beginning of the rarefaction region. A similar response is found when PUI distributions are sorted according to the strength of fast fluctuations in SW speed, density, and magnetic field strength. These parameters remain high in the first part of the rarefaction region, suggesting a possible PUI energization through compressive turbulence. Based on these results, we removed the strongest compression regions from the interstellar flow analysis, finding no significant change in direction or uncertainty. Thus, we have revealed the influence of adiabatic compression and compressive turbulence, increasing the PUI cutoff energy, and we have demonstrated that the determination of the interstellar inflow direction via analysis of PUI distributions is robust for a multiyear data set, even in the presence of SW interaction regions. Key Points: The cutoff speed of the pickup ion helium distribution function is shown to systematically increase in solar wind compression regionsThe magnitude of the pickup ion cutoff shift scales approximately linearly with the solar wind speed gradient in the compression regionThe interstellar flow longitude obtained from the pickup ion cutoff is largely unaffected by compressions, when using multiyear data sets [ABSTRACT FROM AUTHOR] – Name: AbstractSuppliedCopyright Label: Group: Ab Data: <i>Copyright of Journal of Geophysical Research. Space Physics is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract.</i> (Copyright applies to all Abstracts.) |
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| RecordInfo | BibRecord: BibEntity: Identifiers: – Type: doi Value: 10.1029/2019JA026781 Languages: – Code: eng Text: English PhysicalDescription: Pagination: PageCount: 20 StartPage: 6418 Subjects: – SubjectFull: Solar wind Type: general – SubjectFull: Velocity distribution (Statistical mechanics) Type: general – SubjectFull: Ions Type: general – SubjectFull: Magnetic flux density Type: general – SubjectFull: Meteorological observations Type: general Titles: – TitleFull: Effect of Rapid Changes of Solar Wind Conditions on the Pickup Ion Velocity Distribution. Type: main BibRelationships: HasContributorRelationships: – PersonEntity: Name: NameFull: Bower, J. S. – PersonEntity: Name: NameFull: Moebius, E. – PersonEntity: Name: NameFull: Berger, L. – PersonEntity: Name: NameFull: Farrugia, C. – PersonEntity: Name: NameFull: Keilbach, D. – PersonEntity: Name: NameFull: Lee, M. A. – PersonEntity: Name: NameFull: Quinn, P. R. – PersonEntity: Name: NameFull: Schwadron, N. – PersonEntity: Name: NameFull: Taut, A. IsPartOfRelationships: – BibEntity: Dates: – D: 01 M: 08 Text: Aug2019 Type: published Y: 2019 Identifiers: – Type: issn-print Value: 21699380 Numbering: – Type: volume Value: 124 – Type: issue Value: 8 Titles: – TitleFull: Journal of Geophysical Research. Space Physics Type: main |
| ResultId | 1 |
