Electron precipitation caused by chaotic motion in the magnetosphere due to large-amplitude whistler waves

James Faith, Spencer Kuo, Joe Huang

Research output: Contribution to journalArticle

Abstract

In the magnetosphere, energetic electrons in the radiation belts are trapped by Earth's magnetic field and undergo bounce motion about the geomagnetic equator. When a large-amplitude whistler wave is present, the motion of the electrons becomes perturbed. It is shown that the nonlinear interaction due to the spatial dependence of the field quantities causes the motion of some of the trapped particles to become chaotic. Contrary to considering a gyroresonant interaction, this chaotic scattering does not have a directional preference and may therefore offer a plausible explanation of the simultaneous observation of the electron precipitation into the upper atmosphere at geomagnetically conjugate regions due to a single lightning flash [Burgess and Inan, 1990]. After simplifying the dipole configuration of the geomagnetic field, a Hamiltonian formulation is used to study the dynamics of a single, trapped electron on the L=3 shell, subjected to a large amplitude 13.7 kHz whistler wave. A canonical transformation is introduced to remove the time dependence from the test electron's Hamiltonian. The chaotic behavior of the electron motion is investigated with surface of section and Lyapunov exponent techniques. To show that this chaotic behavior can lead to particle precipitation, the temporal evolution of the equatorial pitch angle of the electron is computed. Considering electrons with an initial pitch angle of 88°, the results are found to be qualitatively independent of the bounce frequency. They show that the equatorial pitch angle of a chaotic electron varies wildly and often dips below 25°, the minimum loss cone angle one would expect to find for a charged particle in the magnetosphere. Therefore the electrons may escape the geomagnetic trap and be precipitated into the upper atmosphere.

Original languageEnglish (US)
Article number96JA01968
Pages (from-to)2233-2241
Number of pages9
JournalJournal of Geophysical Research: Space Physics
Volume102
Issue numberA2
StatePublished - 1997

Fingerprint

Magnetosphere
electron precipitation
magnetospheres
magnetosphere
electron
Electrons
electrons
pitch (inclination)
Hamiltonians
upper atmosphere
Upper atmosphere
Radiation belts
particle precipitation
magnetic equator
radiation belts
trapped particles
lightning
geomagnetism
Precipitation (meteorology)
Lightning

ASJC Scopus subject areas

  • Oceanography
  • Astronomy and Astrophysics
  • Atmospheric Science
  • Space and Planetary Science
  • Earth and Planetary Sciences (miscellaneous)
  • Geophysics
  • Geochemistry and Petrology

Cite this

Electron precipitation caused by chaotic motion in the magnetosphere due to large-amplitude whistler waves. / Faith, James; Kuo, Spencer; Huang, Joe.

In: Journal of Geophysical Research: Space Physics, Vol. 102, No. A2, 96JA01968, 1997, p. 2233-2241.

Research output: Contribution to journalArticle

@article{6ca927ebdc014db18145264c94e9df06,
title = "Electron precipitation caused by chaotic motion in the magnetosphere due to large-amplitude whistler waves",
abstract = "In the magnetosphere, energetic electrons in the radiation belts are trapped by Earth's magnetic field and undergo bounce motion about the geomagnetic equator. When a large-amplitude whistler wave is present, the motion of the electrons becomes perturbed. It is shown that the nonlinear interaction due to the spatial dependence of the field quantities causes the motion of some of the trapped particles to become chaotic. Contrary to considering a gyroresonant interaction, this chaotic scattering does not have a directional preference and may therefore offer a plausible explanation of the simultaneous observation of the electron precipitation into the upper atmosphere at geomagnetically conjugate regions due to a single lightning flash [Burgess and Inan, 1990]. After simplifying the dipole configuration of the geomagnetic field, a Hamiltonian formulation is used to study the dynamics of a single, trapped electron on the L=3 shell, subjected to a large amplitude 13.7 kHz whistler wave. A canonical transformation is introduced to remove the time dependence from the test electron's Hamiltonian. The chaotic behavior of the electron motion is investigated with surface of section and Lyapunov exponent techniques. To show that this chaotic behavior can lead to particle precipitation, the temporal evolution of the equatorial pitch angle of the electron is computed. Considering electrons with an initial pitch angle of 88°, the results are found to be qualitatively independent of the bounce frequency. They show that the equatorial pitch angle of a chaotic electron varies wildly and often dips below 25°, the minimum loss cone angle one would expect to find for a charged particle in the magnetosphere. Therefore the electrons may escape the geomagnetic trap and be precipitated into the upper atmosphere.",
author = "James Faith and Spencer Kuo and Joe Huang",
year = "1997",
language = "English (US)",
volume = "102",
pages = "2233--2241",
journal = "Journal of Geophysical Research: Space Physics",
issn = "0148-0227",
number = "A2",

}

TY - JOUR

T1 - Electron precipitation caused by chaotic motion in the magnetosphere due to large-amplitude whistler waves

AU - Faith, James

AU - Kuo, Spencer

AU - Huang, Joe

PY - 1997

Y1 - 1997

N2 - In the magnetosphere, energetic electrons in the radiation belts are trapped by Earth's magnetic field and undergo bounce motion about the geomagnetic equator. When a large-amplitude whistler wave is present, the motion of the electrons becomes perturbed. It is shown that the nonlinear interaction due to the spatial dependence of the field quantities causes the motion of some of the trapped particles to become chaotic. Contrary to considering a gyroresonant interaction, this chaotic scattering does not have a directional preference and may therefore offer a plausible explanation of the simultaneous observation of the electron precipitation into the upper atmosphere at geomagnetically conjugate regions due to a single lightning flash [Burgess and Inan, 1990]. After simplifying the dipole configuration of the geomagnetic field, a Hamiltonian formulation is used to study the dynamics of a single, trapped electron on the L=3 shell, subjected to a large amplitude 13.7 kHz whistler wave. A canonical transformation is introduced to remove the time dependence from the test electron's Hamiltonian. The chaotic behavior of the electron motion is investigated with surface of section and Lyapunov exponent techniques. To show that this chaotic behavior can lead to particle precipitation, the temporal evolution of the equatorial pitch angle of the electron is computed. Considering electrons with an initial pitch angle of 88°, the results are found to be qualitatively independent of the bounce frequency. They show that the equatorial pitch angle of a chaotic electron varies wildly and often dips below 25°, the minimum loss cone angle one would expect to find for a charged particle in the magnetosphere. Therefore the electrons may escape the geomagnetic trap and be precipitated into the upper atmosphere.

AB - In the magnetosphere, energetic electrons in the radiation belts are trapped by Earth's magnetic field and undergo bounce motion about the geomagnetic equator. When a large-amplitude whistler wave is present, the motion of the electrons becomes perturbed. It is shown that the nonlinear interaction due to the spatial dependence of the field quantities causes the motion of some of the trapped particles to become chaotic. Contrary to considering a gyroresonant interaction, this chaotic scattering does not have a directional preference and may therefore offer a plausible explanation of the simultaneous observation of the electron precipitation into the upper atmosphere at geomagnetically conjugate regions due to a single lightning flash [Burgess and Inan, 1990]. After simplifying the dipole configuration of the geomagnetic field, a Hamiltonian formulation is used to study the dynamics of a single, trapped electron on the L=3 shell, subjected to a large amplitude 13.7 kHz whistler wave. A canonical transformation is introduced to remove the time dependence from the test electron's Hamiltonian. The chaotic behavior of the electron motion is investigated with surface of section and Lyapunov exponent techniques. To show that this chaotic behavior can lead to particle precipitation, the temporal evolution of the equatorial pitch angle of the electron is computed. Considering electrons with an initial pitch angle of 88°, the results are found to be qualitatively independent of the bounce frequency. They show that the equatorial pitch angle of a chaotic electron varies wildly and often dips below 25°, the minimum loss cone angle one would expect to find for a charged particle in the magnetosphere. Therefore the electrons may escape the geomagnetic trap and be precipitated into the upper atmosphere.

UR - http://www.scopus.com/inward/record.url?scp=37149049654&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=37149049654&partnerID=8YFLogxK

M3 - Article

VL - 102

SP - 2233

EP - 2241

JO - Journal of Geophysical Research: Space Physics

JF - Journal of Geophysical Research: Space Physics

SN - 0148-0227

IS - A2

M1 - 96JA01968

ER -