Kinetic Alfvén waves at the magnetopause-mode conversion, transport and formation of LLBL

Jay R. Johnson, Chio-Zong Cheng

Research output: Chapter in Book/Report/Conference proceedingChapter

2 Citations (Scopus)

Abstract

At the magnetopause, large amplitude, low frequency (ULF), transverse MHD waves are nearly always observed. These waves likely result from mode conversion of compressional MHD waves observed in the magnetosheath to kinetic Alfven waves at the magnetopause where there is a steep gradient in the Alfven velocity [Johnson and Cheng, Geophys. Res. Lett., 24, 1423, (1997)]. The mode conversion process can explain the following wave observations typically found during satellite crossings of the magnetopause: (1) a dramatic change in wave polarization from compressional in the magnetosheath to transverse at the magnetopause, (2) an amplification of wave amplitude at the magnetopause, (3) a change in Poynting flux from crossfield in the magnetosheath to field-aligned at the magnetopause, and (4) a steepening in the wave power spectrum at the magnetopause. We examine magnetic field data from a set of ISEE1, ISEE2, and WIND magnetopause crossings and compare with the predictions of theoretical wave solutions based on the kinetic-fluid model with particular attention to the role of magnetic field rotation across the magnetopause. The results of the study suggest a good qualitative agreement between the observations and the theory of mode conversion to kinetic Alfven waves. Because mode converted kinetic Alfven waves readily decouple particles from the magnetic field lines, efficient quasilinear transport (D ~ 109m2/s) can occur. Moreover, if the wave amplitude is sufficiently large (Bwave/B0 > 0.2) stochastic particle transport also occurs. This wave induced transport can lead to significant heating and particle entry into the low latitude boundary layer across closed field lines.

Original languageEnglish
Title of host publicationEarth?s Low-Latitude Boundary Layer, 2003
EditorsPatrick T. Newell, Terry Onsager
PublisherBlackwell Publishing Ltd
Pages211-221
Number of pages11
ISBN (Electronic)9781118668566
ISBN (Print)9780875909929
DOIs
Publication statusPublished - 2002 Jan 1

Publication series

NameGeophysical Monograph Series
Volume133
ISSN (Print)0065-8448
ISSN (Electronic)2328-8779

Fingerprint

magnetopause
kinetics
magnetosheath
magnetohydrodynamic waves
magnetic field
magnetic fields
polarization (waves)
transverse waves
tropical regions
wave power
entry
power spectra
boundary layers
low frequencies
amplification
gradients
heating
polarization
boundary layer
fluids

All Science Journal Classification (ASJC) codes

  • Geophysics

Cite this

Johnson, J. R., & Cheng, C-Z. (2002). Kinetic Alfvén waves at the magnetopause-mode conversion, transport and formation of LLBL. In P. T. Newell, & T. Onsager (Eds.), Earth?s Low-Latitude Boundary Layer, 2003 (pp. 211-221). (Geophysical Monograph Series; Vol. 133). Blackwell Publishing Ltd. https://doi.org/10.1029/133GM21
Johnson, Jay R. ; Cheng, Chio-Zong. / Kinetic Alfvén waves at the magnetopause-mode conversion, transport and formation of LLBL. Earth?s Low-Latitude Boundary Layer, 2003. editor / Patrick T. Newell ; Terry Onsager. Blackwell Publishing Ltd, 2002. pp. 211-221 (Geophysical Monograph Series).
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Johnson, JR & Cheng, C-Z 2002, Kinetic Alfvén waves at the magnetopause-mode conversion, transport and formation of LLBL. in PT Newell & T Onsager (eds), Earth?s Low-Latitude Boundary Layer, 2003. Geophysical Monograph Series, vol. 133, Blackwell Publishing Ltd, pp. 211-221. https://doi.org/10.1029/133GM21

Kinetic Alfvén waves at the magnetopause-mode conversion, transport and formation of LLBL. / Johnson, Jay R.; Cheng, Chio-Zong.

Earth?s Low-Latitude Boundary Layer, 2003. ed. / Patrick T. Newell; Terry Onsager. Blackwell Publishing Ltd, 2002. p. 211-221 (Geophysical Monograph Series; Vol. 133).

Research output: Chapter in Book/Report/Conference proceedingChapter

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T1 - Kinetic Alfvén waves at the magnetopause-mode conversion, transport and formation of LLBL

AU - Johnson, Jay R.

AU - Cheng, Chio-Zong

PY - 2002/1/1

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N2 - At the magnetopause, large amplitude, low frequency (ULF), transverse MHD waves are nearly always observed. These waves likely result from mode conversion of compressional MHD waves observed in the magnetosheath to kinetic Alfven waves at the magnetopause where there is a steep gradient in the Alfven velocity [Johnson and Cheng, Geophys. Res. Lett., 24, 1423, (1997)]. The mode conversion process can explain the following wave observations typically found during satellite crossings of the magnetopause: (1) a dramatic change in wave polarization from compressional in the magnetosheath to transverse at the magnetopause, (2) an amplification of wave amplitude at the magnetopause, (3) a change in Poynting flux from crossfield in the magnetosheath to field-aligned at the magnetopause, and (4) a steepening in the wave power spectrum at the magnetopause. We examine magnetic field data from a set of ISEE1, ISEE2, and WIND magnetopause crossings and compare with the predictions of theoretical wave solutions based on the kinetic-fluid model with particular attention to the role of magnetic field rotation across the magnetopause. The results of the study suggest a good qualitative agreement between the observations and the theory of mode conversion to kinetic Alfven waves. Because mode converted kinetic Alfven waves readily decouple particles from the magnetic field lines, efficient quasilinear transport (D ~ 109m2/s) can occur. Moreover, if the wave amplitude is sufficiently large (Bwave/B0 > 0.2) stochastic particle transport also occurs. This wave induced transport can lead to significant heating and particle entry into the low latitude boundary layer across closed field lines.

AB - At the magnetopause, large amplitude, low frequency (ULF), transverse MHD waves are nearly always observed. These waves likely result from mode conversion of compressional MHD waves observed in the magnetosheath to kinetic Alfven waves at the magnetopause where there is a steep gradient in the Alfven velocity [Johnson and Cheng, Geophys. Res. Lett., 24, 1423, (1997)]. The mode conversion process can explain the following wave observations typically found during satellite crossings of the magnetopause: (1) a dramatic change in wave polarization from compressional in the magnetosheath to transverse at the magnetopause, (2) an amplification of wave amplitude at the magnetopause, (3) a change in Poynting flux from crossfield in the magnetosheath to field-aligned at the magnetopause, and (4) a steepening in the wave power spectrum at the magnetopause. We examine magnetic field data from a set of ISEE1, ISEE2, and WIND magnetopause crossings and compare with the predictions of theoretical wave solutions based on the kinetic-fluid model with particular attention to the role of magnetic field rotation across the magnetopause. The results of the study suggest a good qualitative agreement between the observations and the theory of mode conversion to kinetic Alfven waves. Because mode converted kinetic Alfven waves readily decouple particles from the magnetic field lines, efficient quasilinear transport (D ~ 109m2/s) can occur. Moreover, if the wave amplitude is sufficiently large (Bwave/B0 > 0.2) stochastic particle transport also occurs. This wave induced transport can lead to significant heating and particle entry into the low latitude boundary layer across closed field lines.

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Johnson JR, Cheng C-Z. Kinetic Alfvén waves at the magnetopause-mode conversion, transport and formation of LLBL. In Newell PT, Onsager T, editors, Earth?s Low-Latitude Boundary Layer, 2003. Blackwell Publishing Ltd. 2002. p. 211-221. (Geophysical Monograph Series). https://doi.org/10.1029/133GM21