Perpendicular transport of solar energetic particles in heliospheric magnetic fields

Ming Zhang, J. Randy Jokipii, R. B. Mckibben

Research output: Contribution to journalArticle

49 Citations (Scopus)

Abstract

This paper presents direct observational evidence for large perpendicular diffusive flows of solar energetic particles in heliospheric magnetic fields. Using anisotropy measurements of 40-92 MeV protons obtained by the High-Energy Telescope of the COSPIN consortium on Ulysses at high heliographic latitudes, we find that during several gradual solar particle events, for periods of many hours, the observed particle flow is directed at significant angles to the measured local magnetic field direction, which can only be explained by cross-field diffusion. The variation of the particle flow direction with the magnetic field direction seen in the 2000 July 14 solar energetic particle event has allowed us to derive a large κ ratio of 0.25 with an error bar of less than 0.05. An upper limit κA ≪ 0.17 is also found by analyzing the dependence of the particle anisotropy on the magnetic field polarity. The observation suggests that perpendicular diffusion of solar energetic particles cannot be neglected even in the early phase of a solar particle event.

Original languageEnglish (US)
Pages (from-to)493-499
Number of pages7
JournalAstrophysical Journal
Volume595
Issue number1 I
DOIs
StatePublished - Sep 20 2003

Fingerprint

energetic particles
energetics
magnetic field
magnetic fields
anisotropy
polar regions
polarity
particle
telescopes
protons
energy

Keywords

  • Diffusion
  • Solar-terrestrial relations
  • Sun: magnetic fields
  • Sun: particle emission

ASJC Scopus subject areas

  • Space and Planetary Science

Cite this

Perpendicular transport of solar energetic particles in heliospheric magnetic fields. / Zhang, Ming; Jokipii, J. Randy; Mckibben, R. B.

In: Astrophysical Journal, Vol. 595, No. 1 I, 20.09.2003, p. 493-499.

Research output: Contribution to journalArticle

@article{d833e740f39a4f7d8bbb4b1eb82e14cc,
title = "Perpendicular transport of solar energetic particles in heliospheric magnetic fields",
abstract = "This paper presents direct observational evidence for large perpendicular diffusive flows of solar energetic particles in heliospheric magnetic fields. Using anisotropy measurements of 40-92 MeV protons obtained by the High-Energy Telescope of the COSPIN consortium on Ulysses at high heliographic latitudes, we find that during several gradual solar particle events, for periods of many hours, the observed particle flow is directed at significant angles to the measured local magnetic field direction, which can only be explained by cross-field diffusion. The variation of the particle flow direction with the magnetic field direction seen in the 2000 July 14 solar energetic particle event has allowed us to derive a large κ⊥/κ ∥ ratio of 0.25 with an error bar of less than 0.05. An upper limit κA/κ⊥ ≪ 0.17 is also found by analyzing the dependence of the particle anisotropy on the magnetic field polarity. The observation suggests that perpendicular diffusion of solar energetic particles cannot be neglected even in the early phase of a solar particle event.",
keywords = "Diffusion, Solar-terrestrial relations, Sun: magnetic fields, Sun: particle emission",
author = "Ming Zhang and Jokipii, {J. Randy} and Mckibben, {R. B.}",
year = "2003",
month = "9",
day = "20",
doi = "10.1086/377301",
language = "English (US)",
volume = "595",
pages = "493--499",
journal = "Astrophysical Journal",
issn = "0004-637X",
publisher = "IOP Publishing Ltd.",
number = "1 I",

}

TY - JOUR

T1 - Perpendicular transport of solar energetic particles in heliospheric magnetic fields

AU - Zhang, Ming

AU - Jokipii, J. Randy

AU - Mckibben, R. B.

PY - 2003/9/20

Y1 - 2003/9/20

N2 - This paper presents direct observational evidence for large perpendicular diffusive flows of solar energetic particles in heliospheric magnetic fields. Using anisotropy measurements of 40-92 MeV protons obtained by the High-Energy Telescope of the COSPIN consortium on Ulysses at high heliographic latitudes, we find that during several gradual solar particle events, for periods of many hours, the observed particle flow is directed at significant angles to the measured local magnetic field direction, which can only be explained by cross-field diffusion. The variation of the particle flow direction with the magnetic field direction seen in the 2000 July 14 solar energetic particle event has allowed us to derive a large κ⊥/κ ∥ ratio of 0.25 with an error bar of less than 0.05. An upper limit κA/κ⊥ ≪ 0.17 is also found by analyzing the dependence of the particle anisotropy on the magnetic field polarity. The observation suggests that perpendicular diffusion of solar energetic particles cannot be neglected even in the early phase of a solar particle event.

AB - This paper presents direct observational evidence for large perpendicular diffusive flows of solar energetic particles in heliospheric magnetic fields. Using anisotropy measurements of 40-92 MeV protons obtained by the High-Energy Telescope of the COSPIN consortium on Ulysses at high heliographic latitudes, we find that during several gradual solar particle events, for periods of many hours, the observed particle flow is directed at significant angles to the measured local magnetic field direction, which can only be explained by cross-field diffusion. The variation of the particle flow direction with the magnetic field direction seen in the 2000 July 14 solar energetic particle event has allowed us to derive a large κ⊥/κ ∥ ratio of 0.25 with an error bar of less than 0.05. An upper limit κA/κ⊥ ≪ 0.17 is also found by analyzing the dependence of the particle anisotropy on the magnetic field polarity. The observation suggests that perpendicular diffusion of solar energetic particles cannot be neglected even in the early phase of a solar particle event.

KW - Diffusion

KW - Solar-terrestrial relations

KW - Sun: magnetic fields

KW - Sun: particle emission

UR - http://www.scopus.com/inward/record.url?scp=0141484375&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0141484375&partnerID=8YFLogxK

U2 - 10.1086/377301

DO - 10.1086/377301

M3 - Article

AN - SCOPUS:0141484375

VL - 595

SP - 493

EP - 499

JO - Astrophysical Journal

JF - Astrophysical Journal

SN - 0004-637X

IS - 1 I

ER -