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New kinetic cyclotron instability for electron beam in time-changing magnetic fields

Published online by Cambridge University Press:  18 May 2020

Irena Vorgul Open the ORCID record for Irena Vorgul [Opens in a new window] ,
M. Ayling Open the ORCID record for M. Ayling [Opens in a new window] ,
C. R. Straub Open the ORCID record for C. R. Straub [Opens in a new window] ,
D. M. MacKay Open the ORCID record for D. M. MacKay [Opens in a new window] ,
J. D. Houghton Open the ORCID record for J. D. Houghton [Opens in a new window]  and
G. A. Lamb Open the ORCID record for G. A. Lamb [Opens in a new window]
Irena Vorgul*
Affiliation:
SUPA, School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews KY16 9SS, UK
M. Ayling
Affiliation:
SUPA, School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews KY16 9SS, UK
C. R. Straub
Affiliation:
SUPA, School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews KY16 9SS, UK
D. M. MacKay
Affiliation:
SUPA, School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews KY16 9SS, UK
J. D. Houghton
Affiliation:
SUPA, School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews KY16 9SS, UK
G. A. Lamb
Affiliation:
SUPA, School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews KY16 9SS, UK
*
†Email address for correspondence: [email protected]
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Abstract

This paper examines the velocity distribution function and cyclotron resonance conditions for a beam of electrons moving in a magnetic field which gradually changes with time. A spatial gradient of magnetic field is known to result in an unstable horseshoe distribution of electrons. The field gradient in time adds additional effects due to an induced electric field. The resultant anisotropic velocity distribution function, which we call a Luvdisk distribution, has some distinctive properties when compared to the horseshoe. Fitting the cyclotron resonance condition circle shows that the frequency of the resultant emission is under the local cyclotron frequency. While the spatial gradient results in the emission coming almost perpendicularly to the field, the direction of the radiation under a time-changing field has more variability. The Luvdisk distribution also arises when the magnetic field has a gradient both in space and time. The beam can be unstable if those gradients are added or subtracted from each other (if the gradients are of equal or different sign), which occurs even when the total change of magnetic field is negative. While the frequency of the emission is related to the final magnetic field value, its direction is indicative of the field’s history which produced the instability.

Keywords

astrophysical plasmasintense particle beamsplasma instabilities
Type
Research Article
Information
Journal of Plasma Physics , Volume 86 , Issue 3 , June 2020 , 905860303
Copyright
© The Author(s), 2020. Published by Cambridge University Press

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References

Bingham, R. & Cairns, R. A. 2000 Generation of auroral kilometric radiation by electron horseshoe distributions. Phys. Plasmas 7, 3089.CrossRefGoogle Scholar
Bingham, R., Cairns, R. A. & Kellett, B. J. 2001 Coherent cyclotron maser radiation from UV Ceti. Astron. Astrophys. 370, 1000.CrossRefGoogle Scholar
Cairns, R. A., Vorgul, I. & Bingham, R. 2008 Cyclotron maser radiation from an inhomogeneous plasma. Phys. Rev. Lett. 101, 215003.CrossRefGoogle ScholarPubMed
Cairns, R. A., Vorgul, I., Bingham, R., Ronald, K., Speirs, D. C., McConville, S. L., Gillespie, K. M., Bryson, R., Phelps, A. D. R., Kellett, B. J. et al. 2011 Cyclotron maser radiation from inhomogeneous plasmas. Phys. Plasmas 18 (2), 022902.CrossRefGoogle Scholar
Ergun, R. E., Carlson, C. W., McFadden, J. P., Delory, G. T., Strangeway, R. J. & Pritchett, P. L. 2000 Electron-cyclotron maser driven by charged-particle acceleration from magnetic field-aligned electric fields. Astrophys. J. 538, 456.CrossRefGoogle Scholar
Gary, S. P., McKean, M. E., Winske, D., Anderson, B. J., Denton, R. E. & Fuselier, S. A. 1994 The proton cyclotron instability and the anisotropy/$\unicode[STIX]{x1D6FD}$ inverse correlation. J. Geophys. Res. 99 (A4), 5903–5914.CrossRefGoogle Scholar
Harding, L. K., Hallinan, G., Boyle, R. P., Golden, A., Singh, N., Sheehan, B., Zavala, R. T. & Butler, R. F. 2013 Periodic optical variability of radio-detected ultracool dwarfs. Astrophys. J. 779, 101.CrossRefGoogle Scholar
Kellett, B. J., Graffagnino, V., Bingham, R., Muxlow, T. W. B. & Gunn, A. G. 2007 CU virginis – the first stellar pulsar. Astrophys., e-prints, arXiv:astro-ph/0701214.Google Scholar
Lamy, L., Zarka, P., Cecconi, B., Prangé, R., Kurth, W. S., Hospodarsky, G., Persoon, A., Morooka, M., Wahlund, J.-E. & Hunt, G. J. 2018 The low-frequency source of Saturn’s kilometric radiation. Science 362 (6410), eaat2027.CrossRefGoogle ScholarPubMed
Qin, H. & Davidson, R. C. 2006 An exact magnetic-moment invariant of charged-particle gyromotion. Phys. Rev. Lett. 96, 085003.CrossRefGoogle ScholarPubMed
Speirs, D. C., Bingham, R., Cairns, R. A., Vorgul, I., Kellett, B. J., Phelps, A. D. R. & Ronald, K. 2014 Backward wave cyclotron-maser emission in the auroral magnetosphere. Phys. Rev. Lett. 113 (15), 155002–155007.CrossRefGoogle ScholarPubMed
Trigilio, C., Leto, P., Umana, G., Buemi, C. S. & Leone, F. 2008 The radio lighthouse cu virginis: the spin-down of a single main-sequence star. Mon. Not. R. Astron. Soc. 384 (4), 1437–1443.CrossRefGoogle Scholar
Vorgul, I., Cairns, R. A. & Bingham, R. 2005 Radiation modes growth rate in cylindrical geometry with application to space and laboratory plasmas with a horseshoe-type cyclotron maser instability. Phys. Plasmas 12, 122903.Google Scholar
Vorgul, I., Kellet, B. J., Cairns, R. A., Bingham, R., Ronald, K., Speirs, D. C., McConville, S. L., Gillespie, K. M. & Phelps, A. D. R. 2011 Cyclotron maser emission: stars, planets, and laboratory. Phys. Plasmas 18, 5.CrossRefGoogle Scholar