Filamentary Currents and Alfvénic Vortices in the Inner Magnetosphere

C. C. Chaston; J. W. Bonnell; J. R. Wygant; G. D. Reeves; D. N. Baker

doi:10.1029/2019GL086318

Filamentary Currents and Alfvénic Vortices in the Inner Magnetosphere

C. C. Chaston, J. W. Bonnell, J. R. Wygant, G. D. Reeves, D. N. Baker

Physics and Astronomy (Twin Cities)

Research output: Contribution to journal › Article › peer-review

8 Scopus citations

Abstract

We show that broadband low-frequency Alfvénic field variations observed in the inner-magnetosphere from the Van Allen Probes during geomagnetically disturbed intervals are composed of multiscale current sheets, current filaments, flow shears, and vortices. These observations pertain to spacecraft frame frequencies (f_sc) over the range 0.1 < f_sc < 10 Hz and correspond to structure advected over the spacecraft on scales (λ) over the range 0.1 ≲ λ/ρ_i ≲ 10. where ρ_i is the average ion gyroradius. The topology of the current and flow is derived via time domain and spectral approaches adapted for the interpretation of advected structure. The results reveal the action of magnetic and convective nonlinearities in the generation of broadband Alfvénic fluctuations prevalent in the inner magnetosphere during active times. The observed current filamentation and rotational vorticity is suggestive of how broadband Alfvénic field variations on kinetic scales are driven and support geophysically significant particle acceleration in the inner magnetosphere.

Original language	English (US)
Article number	e2019GL086318
Journal	Geophysical Research Letters
Volume	47
Issue number	4
DOIs	https://doi.org/10.1029/2019GL086318
State	Published - Feb 28 2020

Bibliographical note

Funding Information:
This research was supported by the NASA Grants NNX15AF57G, NNX16AG69G, NNX17AD36G, and NNX17AI55G and Van Allen Probes (RBSP) funding provided under NASA prime contract NAS5-01072; including the EFW and EMFISIS investigations under JHU/APL Contract 921647, RBSP-ECT under JHU/APL Contract 967399. Van Allen Probes measurements used in this study can be obtained from the following data repositories: EFW (http://www.space.umn.edu/rbspefw-data/); EMFISIS (http://emfisis.physics.uiowa.edu/data/index; HOPE/MAGEIS/REPT https://www.rbsp-ect.lanl.gov/science/DataDirectories.php); RBSPICE (http://rbspice.ftecs.com/Data.html); and/or by directly contacting the first author.

Publisher Copyright:
©2020. American Geophysical Union. All Rights Reserved.

Keywords

Alfven waves
geomagnetic stormsVan Allen Probes
radiation belts
ring current
turbulence

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@article{b546268e37464814a80937ef1ffd6219,

title = "Filamentary Currents and Alfv{\'e}nic Vortices in the Inner Magnetosphere",

abstract = "We show that broadband low-frequency Alfv{\'e}nic field variations observed in the inner-magnetosphere from the Van Allen Probes during geomagnetically disturbed intervals are composed of multiscale current sheets, current filaments, flow shears, and vortices. These observations pertain to spacecraft frame frequencies (fsc) over the range 0.1 < fsc < 10 Hz and correspond to structure advected over the spacecraft on scales (λ) over the range 0.1 ≲ λ/ρi ≲ 10. where ρi is the average ion gyroradius. The topology of the current and flow is derived via time domain and spectral approaches adapted for the interpretation of advected structure. The results reveal the action of magnetic and convective nonlinearities in the generation of broadband Alfv{\'e}nic fluctuations prevalent in the inner magnetosphere during active times. The observed current filamentation and rotational vorticity is suggestive of how broadband Alfv{\'e}nic field variations on kinetic scales are driven and support geophysically significant particle acceleration in the inner magnetosphere.",

keywords = "Alfven waves, geomagnetic stormsVan Allen Probes, radiation belts, ring current, turbulence",

author = "Chaston, {C. C.} and Bonnell, {J. W.} and Wygant, {J. R.} and Reeves, {G. D.} and Baker, {D. N.}",

note = "Funding Information: This research was supported by the NASA Grants NNX15AF57G, NNX16AG69G, NNX17AD36G, and NNX17AI55G and Van Allen Probes (RBSP) funding provided under NASA prime contract NAS5-01072; including the EFW and EMFISIS investigations under JHU/APL Contract 921647, RBSP-ECT under JHU/APL Contract 967399. Van Allen Probes measurements used in this study can be obtained from the following data repositories: EFW (http://www.space.umn.edu/rbspefw-data/); EMFISIS (http://emfisis.physics.uiowa.edu/data/index; HOPE/MAGEIS/REPT https://www.rbsp-ect.lanl.gov/science/DataDirectories.php); RBSPICE (http://rbspice.ftecs.com/Data.html); and/or by directly contacting the first author. Publisher Copyright: {\textcopyright}2020. American Geophysical Union. All Rights Reserved.",

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doi = "10.1029/2019GL086318",

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AU - Bonnell, J. W.

AU - Wygant, J. R.

AU - Reeves, G. D.

AU - Baker, D. N.

N1 - Funding Information: This research was supported by the NASA Grants NNX15AF57G, NNX16AG69G, NNX17AD36G, and NNX17AI55G and Van Allen Probes (RBSP) funding provided under NASA prime contract NAS5-01072; including the EFW and EMFISIS investigations under JHU/APL Contract 921647, RBSP-ECT under JHU/APL Contract 967399. Van Allen Probes measurements used in this study can be obtained from the following data repositories: EFW (http://www.space.umn.edu/rbspefw-data/); EMFISIS (http://emfisis.physics.uiowa.edu/data/index; HOPE/MAGEIS/REPT https://www.rbsp-ect.lanl.gov/science/DataDirectories.php); RBSPICE (http://rbspice.ftecs.com/Data.html); and/or by directly contacting the first author. Publisher Copyright: ©2020. American Geophysical Union. All Rights Reserved.

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N2 - We show that broadband low-frequency Alfvénic field variations observed in the inner-magnetosphere from the Van Allen Probes during geomagnetically disturbed intervals are composed of multiscale current sheets, current filaments, flow shears, and vortices. These observations pertain to spacecraft frame frequencies (fsc) over the range 0.1 < fsc < 10 Hz and correspond to structure advected over the spacecraft on scales (λ) over the range 0.1 ≲ λ/ρi ≲ 10. where ρi is the average ion gyroradius. The topology of the current and flow is derived via time domain and spectral approaches adapted for the interpretation of advected structure. The results reveal the action of magnetic and convective nonlinearities in the generation of broadband Alfvénic fluctuations prevalent in the inner magnetosphere during active times. The observed current filamentation and rotational vorticity is suggestive of how broadband Alfvénic field variations on kinetic scales are driven and support geophysically significant particle acceleration in the inner magnetosphere.

AB - We show that broadband low-frequency Alfvénic field variations observed in the inner-magnetosphere from the Van Allen Probes during geomagnetically disturbed intervals are composed of multiscale current sheets, current filaments, flow shears, and vortices. These observations pertain to spacecraft frame frequencies (fsc) over the range 0.1 < fsc < 10 Hz and correspond to structure advected over the spacecraft on scales (λ) over the range 0.1 ≲ λ/ρi ≲ 10. where ρi is the average ion gyroradius. The topology of the current and flow is derived via time domain and spectral approaches adapted for the interpretation of advected structure. The results reveal the action of magnetic and convective nonlinearities in the generation of broadband Alfvénic fluctuations prevalent in the inner magnetosphere during active times. The observed current filamentation and rotational vorticity is suggestive of how broadband Alfvénic field variations on kinetic scales are driven and support geophysically significant particle acceleration in the inner magnetosphere.

KW - Alfven waves

KW - geomagnetic stormsVan Allen Probes

KW - radiation belts

KW - ring current

KW - turbulence

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JO - Geophysical Research Letters

JF - Geophysical Research Letters

IS - 4

M1 - e2019GL086318

ER -

Filamentary Currents and Alfvénic Vortices in the Inner Magnetosphere

Abstract

Bibliographical note

Keywords

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