Auroral Beads in Conjunction With Kinetic Alfvén Waves in the Equatorial Inner-Magnetosphere

Sheng Tian; L. R. Lyons; Y. Nishimura; J. R. Wygant; Robert L Lysak; C. P. Ferradas; X. An; A. B. Igl; G. D. Reeves; B. A. Larsen; D. Ma

doi:10.1029/2022GL098457

Auroral Beads in Conjunction With Kinetic Alfvén Waves in the Equatorial Inner-Magnetosphere

Sheng Tian, L. R. Lyons, Y. Nishimura, J. R. Wygant, Robert L Lysak, C. P. Ferradas, X. An, A. B. Igl, G. D. Reeves, B. A. Larsen, D. Ma

Physics and Astronomy (Twin Cities)

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

3 Scopus citations

Abstract

Auroral beads are spatially wavy forms routinely seen before the onset of auroral substorms and are closely related to the onset-related instabilities. To date, the acceleration mechanism of electrons that create auroral beads is not fully determined. Here, we present a fortuitous event when the Van Allen Probe A (RBSP-A) was in magnetic conjunction with auroral beads. RBSP-A observed Alfvén waves, locally generated kinetic Alfvén waves (KAWs) and Alfvénic accelerated electrons at several 100 eV. The Alfvén waves and KAWs carried sufficient Poynting flux to power visible aurora and may control the beads' motion. These observations and previous simulations support that the Alfvénic acceleration is the acceleration mechanism of the auroral beads. Specifically, KAWs are generated around the equator and accelerate local cold electrons to several 100 eV. The waves are suggested to propagate to both hemispheres and accelerate electrons to several keV, which directly account for the auroral beads.

Original language	English (US)
Article number	e2022GL098457
Journal	Geophysical Research Letters
Volume	49
Issue number	9
DOIs	https://doi.org/10.1029/2022GL098457
State	Published - May 16 2022

Bibliographical note

Funding Information:
The authors thank the following funding sources, including the NSF Grant 2108582, NASA grants 80NSSC19K0306, 80NSSC20K1314, 80NSSC20K1269, and NASA prime contract NAS5‐01072.

Publisher Copyright:
© 2022. The Authors.

Keywords

Landau resonance
Poynting flux
auroral beads
instability
kinetic Alfven wave
magnetosphere-ionosphere coupling

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10.1029/2022GL098457

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@article{b3637b00cfc243d894569f39cfe93337,

title = "Auroral Beads in Conjunction With Kinetic Alfv{\'e}n Waves in the Equatorial Inner-Magnetosphere",

abstract = "Auroral beads are spatially wavy forms routinely seen before the onset of auroral substorms and are closely related to the onset-related instabilities. To date, the acceleration mechanism of electrons that create auroral beads is not fully determined. Here, we present a fortuitous event when the Van Allen Probe A (RBSP-A) was in magnetic conjunction with auroral beads. RBSP-A observed Alfv{\'e}n waves, locally generated kinetic Alfv{\'e}n waves (KAWs) and Alfv{\'e}nic accelerated electrons at several 100 eV. The Alfv{\'e}n waves and KAWs carried sufficient Poynting flux to power visible aurora and may control the beads' motion. These observations and previous simulations support that the Alfv{\'e}nic acceleration is the acceleration mechanism of the auroral beads. Specifically, KAWs are generated around the equator and accelerate local cold electrons to several 100 eV. The waves are suggested to propagate to both hemispheres and accelerate electrons to several keV, which directly account for the auroral beads.",

keywords = "Landau resonance, Poynting flux, auroral beads, instability, kinetic Alfven wave, magnetosphere-ionosphere coupling",

author = "Sheng Tian and Lyons, {L. R.} and Y. Nishimura and Wygant, {J. R.} and Lysak, {Robert L} and Ferradas, {C. P.} and X. An and Igl, {A. B.} and Reeves, {G. D.} and Larsen, {B. A.} and D. Ma",

note = "Funding Information: The authors thank the following funding sources, including the NSF Grant 2108582, NASA grants 80NSSC19K0306, 80NSSC20K1314, 80NSSC20K1269, and NASA prime contract NAS5‐01072. Publisher Copyright: {\textcopyright} 2022. The Authors.",

year = "2022",

month = may,

day = "16",

doi = "10.1029/2022GL098457",

language = "English (US)",

volume = "49",

journal = "Geophysical Research Letters",

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TY - JOUR

T1 - Auroral Beads in Conjunction With Kinetic Alfvén Waves in the Equatorial Inner-Magnetosphere

AU - Tian, Sheng

AU - Lyons, L. R.

AU - Nishimura, Y.

AU - Wygant, J. R.

AU - Lysak, Robert L

AU - Ferradas, C. P.

AU - An, X.

AU - Igl, A. B.

AU - Reeves, G. D.

AU - Larsen, B. A.

AU - Ma, D.

N1 - Funding Information: The authors thank the following funding sources, including the NSF Grant 2108582, NASA grants 80NSSC19K0306, 80NSSC20K1314, 80NSSC20K1269, and NASA prime contract NAS5‐01072. Publisher Copyright: © 2022. The Authors.

PY - 2022/5/16

Y1 - 2022/5/16

N2 - Auroral beads are spatially wavy forms routinely seen before the onset of auroral substorms and are closely related to the onset-related instabilities. To date, the acceleration mechanism of electrons that create auroral beads is not fully determined. Here, we present a fortuitous event when the Van Allen Probe A (RBSP-A) was in magnetic conjunction with auroral beads. RBSP-A observed Alfvén waves, locally generated kinetic Alfvén waves (KAWs) and Alfvénic accelerated electrons at several 100 eV. The Alfvén waves and KAWs carried sufficient Poynting flux to power visible aurora and may control the beads' motion. These observations and previous simulations support that the Alfvénic acceleration is the acceleration mechanism of the auroral beads. Specifically, KAWs are generated around the equator and accelerate local cold electrons to several 100 eV. The waves are suggested to propagate to both hemispheres and accelerate electrons to several keV, which directly account for the auroral beads.

AB - Auroral beads are spatially wavy forms routinely seen before the onset of auroral substorms and are closely related to the onset-related instabilities. To date, the acceleration mechanism of electrons that create auroral beads is not fully determined. Here, we present a fortuitous event when the Van Allen Probe A (RBSP-A) was in magnetic conjunction with auroral beads. RBSP-A observed Alfvén waves, locally generated kinetic Alfvén waves (KAWs) and Alfvénic accelerated electrons at several 100 eV. The Alfvén waves and KAWs carried sufficient Poynting flux to power visible aurora and may control the beads' motion. These observations and previous simulations support that the Alfvénic acceleration is the acceleration mechanism of the auroral beads. Specifically, KAWs are generated around the equator and accelerate local cold electrons to several 100 eV. The waves are suggested to propagate to both hemispheres and accelerate electrons to several keV, which directly account for the auroral beads.

KW - Landau resonance

KW - Poynting flux

KW - auroral beads

KW - instability

KW - kinetic Alfven wave

KW - magnetosphere-ionosphere coupling

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JF - Geophysical Research Letters

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ER -

Auroral Beads in Conjunction With Kinetic Alfvén Waves in the Equatorial Inner-Magnetosphere

Abstract

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