Auroral magnetospheric cyclotron emission processes

numerical and experimental simulations

K. Ronald, D. C. Speirs, S. L. McConville, Karen Gillespie, A. D. R. Phelps, R. Bingham, I. Vorgul, R. A. Cairns, A. W. Cross, Craig Robertson, C. G. Whyte, W. He, B. J. Kellett

Research output: Contribution to journalArticle

14 Citations (Scopus)

Abstract

Satellites have observed powerful radio waves (up to 1 GW peaked at 300 kHz) radiating from regions of reduced plasma density about 3200 km above the Earth's surface in the polar magnetosphere. The emission is associated with the observation of horseshoe or 'shell' distributions in the velocity space of the Earthbound flux of electrons, arising from magnetic compression. It has been postulated that this distribution holds the free energy required to explain the radiation emission. To verify this proposition, a series of numerical and experimental simulations of the mechanism scaled to microwave frequencies have been conducted in concert with a theoretical analysis of the growth rate and propagation of the resultant radiation. The numerical simulations were conducted with electron beams of 75 keV and currents of 18 and 34 A gyrating in a magnetic field of 0.18 T, and 85 keV and 18 A in a magnetic field of 0.48 T. The simulations predicted that the radiation would be emitted close to the cyclotron frequency (4.42 and 11.7 GHz) in near cut-off TE modes (TE0,1 and TE0,3/TE2,3, respectively) with efficiencies of 2% and 1.3%. The experimental measurements demonstrated mode content very close to that predicted by the simulations with output powers of 19 kW and 35 kW from electron beams of 75 keV energy and 12 A and 34 A of current, respectively, at 4.42 GHz. Powers of 9.4 kW and 30 kW from 85 keV electron beams of 12 and 30 A were observed at 11.7 GHz. The spectral, polarization and propagation properties of the radiation are similar to those observed in the magnetosphere. A scheme will be outlined for introducing a background plasma into the apparatus, with omega(pe) < omega(ce)/10 to enhance the comparison with the auroral magnetosphere.

Original languageEnglish
Article number074015
Number of pages11
JournalPlasma Physics and Controlled Fusion
Volume53
Issue number7
DOIs
Publication statusPublished - Jul 2011

Fingerprint

Cyclotrons
Magnetosphere
cyclotrons
magnetospheres
Radiation
Electron beams
electron beams
radiation
simulation
magnetic compression
Magnetic fields
Radio waves
propagation
Plasma density
Microwave frequencies
radio waves
cyclotron frequency
Earth surface
microwave frequencies
magnetic fields

Keywords

  • terrestrial kilometric radiation
  • maser instability
  • laboratory plasmas
  • space
  • distributions
  • generation
  • driven

Cite this

@article{57618c71bcc0471bb52abf75bf0113ff,
title = "Auroral magnetospheric cyclotron emission processes: numerical and experimental simulations",
abstract = "Satellites have observed powerful radio waves (up to 1 GW peaked at 300 kHz) radiating from regions of reduced plasma density about 3200 km above the Earth's surface in the polar magnetosphere. The emission is associated with the observation of horseshoe or 'shell' distributions in the velocity space of the Earthbound flux of electrons, arising from magnetic compression. It has been postulated that this distribution holds the free energy required to explain the radiation emission. To verify this proposition, a series of numerical and experimental simulations of the mechanism scaled to microwave frequencies have been conducted in concert with a theoretical analysis of the growth rate and propagation of the resultant radiation. The numerical simulations were conducted with electron beams of 75 keV and currents of 18 and 34 A gyrating in a magnetic field of 0.18 T, and 85 keV and 18 A in a magnetic field of 0.48 T. The simulations predicted that the radiation would be emitted close to the cyclotron frequency (4.42 and 11.7 GHz) in near cut-off TE modes (TE0,1 and TE0,3/TE2,3, respectively) with efficiencies of 2{\%} and 1.3{\%}. The experimental measurements demonstrated mode content very close to that predicted by the simulations with output powers of 19 kW and 35 kW from electron beams of 75 keV energy and 12 A and 34 A of current, respectively, at 4.42 GHz. Powers of 9.4 kW and 30 kW from 85 keV electron beams of 12 and 30 A were observed at 11.7 GHz. The spectral, polarization and propagation properties of the radiation are similar to those observed in the magnetosphere. A scheme will be outlined for introducing a background plasma into the apparatus, with omega(pe) < omega(ce)/10 to enhance the comparison with the auroral magnetosphere.",
keywords = "terrestrial kilometric radiation, maser instability, laboratory plasmas, space, distributions, generation, driven",
author = "K. Ronald and Speirs, {D. C.} and McConville, {S. L.} and Karen Gillespie and Phelps, {A. D. R.} and R. Bingham and I. Vorgul and Cairns, {R. A.} and Cross, {A. W.} and Craig Robertson and Whyte, {C. G.} and W. He and Kellett, {B. J.}",
year = "2011",
month = "7",
doi = "10.1088/0741-3335/53/7/074015",
language = "English",
volume = "53",
journal = "Plasma Physics and Controlled Fusion",
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Auroral magnetospheric cyclotron emission processes : numerical and experimental simulations. / Ronald, K.; Speirs, D. C.; McConville, S. L.; Gillespie, Karen; Phelps, A. D. R.; Bingham, R.; Vorgul, I.; Cairns, R. A.; Cross, A. W.; Robertson, Craig; Whyte, C. G.; He, W.; Kellett, B. J.

In: Plasma Physics and Controlled Fusion, Vol. 53, No. 7, 074015, 07.2011.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Auroral magnetospheric cyclotron emission processes

T2 - numerical and experimental simulations

AU - Ronald, K.

AU - Speirs, D. C.

AU - McConville, S. L.

AU - Gillespie, Karen

AU - Phelps, A. D. R.

AU - Bingham, R.

AU - Vorgul, I.

AU - Cairns, R. A.

AU - Cross, A. W.

AU - Robertson, Craig

AU - Whyte, C. G.

AU - He, W.

AU - Kellett, B. J.

PY - 2011/7

Y1 - 2011/7

N2 - Satellites have observed powerful radio waves (up to 1 GW peaked at 300 kHz) radiating from regions of reduced plasma density about 3200 km above the Earth's surface in the polar magnetosphere. The emission is associated with the observation of horseshoe or 'shell' distributions in the velocity space of the Earthbound flux of electrons, arising from magnetic compression. It has been postulated that this distribution holds the free energy required to explain the radiation emission. To verify this proposition, a series of numerical and experimental simulations of the mechanism scaled to microwave frequencies have been conducted in concert with a theoretical analysis of the growth rate and propagation of the resultant radiation. The numerical simulations were conducted with electron beams of 75 keV and currents of 18 and 34 A gyrating in a magnetic field of 0.18 T, and 85 keV and 18 A in a magnetic field of 0.48 T. The simulations predicted that the radiation would be emitted close to the cyclotron frequency (4.42 and 11.7 GHz) in near cut-off TE modes (TE0,1 and TE0,3/TE2,3, respectively) with efficiencies of 2% and 1.3%. The experimental measurements demonstrated mode content very close to that predicted by the simulations with output powers of 19 kW and 35 kW from electron beams of 75 keV energy and 12 A and 34 A of current, respectively, at 4.42 GHz. Powers of 9.4 kW and 30 kW from 85 keV electron beams of 12 and 30 A were observed at 11.7 GHz. The spectral, polarization and propagation properties of the radiation are similar to those observed in the magnetosphere. A scheme will be outlined for introducing a background plasma into the apparatus, with omega(pe) < omega(ce)/10 to enhance the comparison with the auroral magnetosphere.

AB - Satellites have observed powerful radio waves (up to 1 GW peaked at 300 kHz) radiating from regions of reduced plasma density about 3200 km above the Earth's surface in the polar magnetosphere. The emission is associated with the observation of horseshoe or 'shell' distributions in the velocity space of the Earthbound flux of electrons, arising from magnetic compression. It has been postulated that this distribution holds the free energy required to explain the radiation emission. To verify this proposition, a series of numerical and experimental simulations of the mechanism scaled to microwave frequencies have been conducted in concert with a theoretical analysis of the growth rate and propagation of the resultant radiation. The numerical simulations were conducted with electron beams of 75 keV and currents of 18 and 34 A gyrating in a magnetic field of 0.18 T, and 85 keV and 18 A in a magnetic field of 0.48 T. The simulations predicted that the radiation would be emitted close to the cyclotron frequency (4.42 and 11.7 GHz) in near cut-off TE modes (TE0,1 and TE0,3/TE2,3, respectively) with efficiencies of 2% and 1.3%. The experimental measurements demonstrated mode content very close to that predicted by the simulations with output powers of 19 kW and 35 kW from electron beams of 75 keV energy and 12 A and 34 A of current, respectively, at 4.42 GHz. Powers of 9.4 kW and 30 kW from 85 keV electron beams of 12 and 30 A were observed at 11.7 GHz. The spectral, polarization and propagation properties of the radiation are similar to those observed in the magnetosphere. A scheme will be outlined for introducing a background plasma into the apparatus, with omega(pe) < omega(ce)/10 to enhance the comparison with the auroral magnetosphere.

KW - terrestrial kilometric radiation

KW - maser instability

KW - laboratory plasmas

KW - space

KW - distributions

KW - generation

KW - driven

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DO - 10.1088/0741-3335/53/7/074015

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