Persistent Link:
http://hdl.handle.net/10150/280630
Title:
Acceleration of interstellar helium in the inner heliosphere
Author:
Moise, Elena
Issue Date:
2004
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
The heliosphere, the volume inflated by the solar wind, is impenetrable to inter-stellar plasma, except for high-energy galactic cosmic rays. Neutral components of the local interstellar medium (LISM), however, do enter at the speed of Sun's relative motion to LISM. On their journey through the heliosphere, interstellar neutrals are subject to ionization by solar wind protons and electrons, solar photons, and also the gravitational pull of the Sun. Once ionized, the newly created ions, called "pickup ions" (PUIs), are swept out by the solar wind toward the termination shock (TS). Helium atoms, having a higher ionization potential, penetrate deeper into the solar system, with their trajectories gravitational focused to form a cone of high concentration of LISM He in the wake of the Sun's motion through LISM. This He cone provides a rich source of He⁺ PUIs. Recent theories suggest that PUIs are the seed particles for the detected anomalous cosmic rays (ACRs)--singly-charged ions highly enriched in He, N, O, and Ne, and with energies < 50 MeV/nuc after solar modulation. To reach such high energies, it would be necessary that the PUIs be pre-accelerated before reaching the TS, where the ions are finally accelerated to become ACRs. This thesis investigates two aspects of the PUIs life cycle by using the data gathered by Solar Wind Composition Spectrometer (SWICS) on the Advance Composition Explorer (ACE). The first is a study of pre-acceleration of He⁺ PUIs up to 100 KeV, by shocks generated by coronal mass ejecta. Our result implies that quasi-parallel shocks are more efficient at accelerating He⁺ PUIs in this energy interval than quasi-perpendicular shocks. The second is a study of time-variability of the gravitationally focused He cone. Our results suggest that the most likely cause of observed variability is due to the changing ionization rate of He over the solar cycle.
Type:
text; Dissertation-Reproduction (electronic)
Keywords:
Physics, Astronomy and Astrophysics.
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Graduate College; Physics
Degree Grantor:
University of Arizona
Advisor:
Hsieh, K. C.

Full metadata record

DC FieldValue Language
dc.language.isoen_USen_US
dc.titleAcceleration of interstellar helium in the inner heliosphereen_US
dc.creatorMoise, Elenaen_US
dc.contributor.authorMoise, Elenaen_US
dc.date.issued2004en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractThe heliosphere, the volume inflated by the solar wind, is impenetrable to inter-stellar plasma, except for high-energy galactic cosmic rays. Neutral components of the local interstellar medium (LISM), however, do enter at the speed of Sun's relative motion to LISM. On their journey through the heliosphere, interstellar neutrals are subject to ionization by solar wind protons and electrons, solar photons, and also the gravitational pull of the Sun. Once ionized, the newly created ions, called "pickup ions" (PUIs), are swept out by the solar wind toward the termination shock (TS). Helium atoms, having a higher ionization potential, penetrate deeper into the solar system, with their trajectories gravitational focused to form a cone of high concentration of LISM He in the wake of the Sun's motion through LISM. This He cone provides a rich source of He⁺ PUIs. Recent theories suggest that PUIs are the seed particles for the detected anomalous cosmic rays (ACRs)--singly-charged ions highly enriched in He, N, O, and Ne, and with energies < 50 MeV/nuc after solar modulation. To reach such high energies, it would be necessary that the PUIs be pre-accelerated before reaching the TS, where the ions are finally accelerated to become ACRs. This thesis investigates two aspects of the PUIs life cycle by using the data gathered by Solar Wind Composition Spectrometer (SWICS) on the Advance Composition Explorer (ACE). The first is a study of pre-acceleration of He⁺ PUIs up to 100 KeV, by shocks generated by coronal mass ejecta. Our result implies that quasi-parallel shocks are more efficient at accelerating He⁺ PUIs in this energy interval than quasi-perpendicular shocks. The second is a study of time-variability of the gravitationally focused He cone. Our results suggest that the most likely cause of observed variability is due to the changing ionization rate of He over the solar cycle.en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.subjectPhysics, Astronomy and Astrophysics.en_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.disciplinePhysicsen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorHsieh, K. C.en_US
dc.identifier.proquest3145103en_US
dc.identifier.bibrecord.b47209884en_US
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