Cyclotron maser emission: Stars, planets, and laboratory

Vorgul, I.; Kellett, B. J.; Cairns, R. A.; Bingham, R.; Ronald, K.; Speirs, D. C.; McConville, S. L.; Gillespie, K. M.; Phelps, A. D. R.

doi:10.1063/1.3567420

Cited by 21 publications

(18 citation statements)

References 28 publications

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“…Shifting the electron energy too far will result in electron synchrotron emission, and will thus remove the CME. More intense CME's are best explained by a greater number of keV electrons (Vorgul et al 2011). On this basis, and the observed CME intensity from LSR-J1835, we simply take the flux for the auroral electron beam for Jupiter (Gerard & Singh 1982), and multiply it by 10 5 .…”

Section: (C) Mechanism For Generating H 3 + By Electron Beammentioning

confidence: 99%

Lightning and charge processes in brown dwarf and exoplanet atmospheres

Helling

Rimmer

2019

Phil. Trans. R. Soc. A.

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The study of the composition of brown dwarf atmospheres helped to understand their formation and evolution. Similarly, the study of exoplanet atmospheres is expected to constrain their formation and evolutionary states. We use results from three-dimensional simulations, kinetic cloud formation and kinetic ion-neutral chemistry to investigate ionization processes that will affect their atmosphere chemistry: the dayside of super-hot Jupiters is dominated by atomic hydrogen, and not H 2 O. Such planetary atmospheres exhibit a substantial degree of thermal ionization and clouds only form on the nightside where lightning leaves chemical tracers (e.g. HCN) for possibly long enough to be detectable. External radiation may cause exoplanets to be enshrouded in a shell of highly ionized, H 3 + -forming gas and a weather-driven aurora may emerge. Brown dwarfs enable us to study the role of electron beams for the emergence of an extrasolar, weather system-driven aurora-like chemistry, and the effect of strong magnetic fields on cold atmospheric gases. Electron beams trigger the formation of H 3 + in the upper atmosphere of a brown dwarf (e.g. LSR-J1835), which may react with it to form hydronium, H 3 O + , as a longer lived chemical tracer. Brown dwarfs and super-hot gas giants may be excellent candidates to search for H 3 O + as an H 3 + product. This article is part of a discussion meeting issue ‘Advances in hydrogen molecular ions: H 3 + , H 5 + and beyond’.

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Section: (C) Mechanism For Generating H 3 + By Electron Beammentioning

confidence: 99%

Lightning and charge processes in brown dwarf and exoplanet atmospheres

Helling

Rimmer

2019

Phil. Trans. R. Soc. A.

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“…For hotter stars than M-dwarfs and brown dwarfs, coronal mass ejections are the sources of accelerated electrons like for example on the radio emitting flare stars like UV Ceti or the magnetic chemically peculiar, extremely fast rotating radio pulsar CU Virginis (Bingham, Cairns & Kellett 2001;Vorgul et al 2011). The solar wind provides the majority of electrons for planetary cyclotron radio emission (Zarka et al 2008) for most of the solar system planets 2 .…”

Section: Introductionmentioning

confidence: 99%

Flash ionization signature in coherent cyclotron emission from brown dwarfs

Vorgul

Helling

2016

Mon. Not. R. Astron. Soc.

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Brown dwarfs form mineral clouds in their atmospheres, where charged particles can produce large-scale discharges in form of lightning resulting in substantial sudden increase of local ionisation. Brown dwarfs are observed to emit cyclotron radio emission. We show that signatures of strong transient atmospheric ionisation events (flash ionisation) can be imprinted on a pre-existing radiation. Detection of such flash ionisation events will open investigations into the ionisation state and atmospheric dynamics. Such events can also result from explosion shock waves, material outbursts or (volcanic) eruptions. We present an analytical model that describes the modulation of a pre-existing electromagnetic radiation by a time-dependent (flash) conductivity that is characteristic for flash ionisation events like lightning. Our conductivity model reproduces the conductivity function derived from observations of Terrestrial Gamma Ray Flashes, and is applicable to astrophysical objects with strong temporal variations in the local ionization, as in planetary atmospheres and protoplanetary disks. We show that the field responds with a characteristic flash-shaped pulse to a conductivity flash of intermediate intensity. More powerful ionisation events result in smaller variations of the initial radiation, or in its damping. We show that the characteristic damping of the response field for high-power initial radiation carries information about the ionisation flash magnitude and duration. The duration of the pulse amplification or the damping is consistently shorter for larger conductivity variations and can be used to evaluate the intensity of the flash ionisation. Our work suggests that cyclotron emission could be probe signals for electrification processes inside BD atmosphere.

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“…These properties suggest that the source of the radio emission is the electron cyclotron maser instability (CMI; Wu and Lee 1979). The electron cyclotron maser mechanism has been shown to be responsible for the auroral kilometric radiation on Earth (see, Trakhtengerts and Rycroft 2008;Speirs et al 2008;Vorgul et al 2011). Figure 13 shows a light curve of a M-dwarf (TVLM 513-46546) of spectral type M9.5 which shows clear and periodically repeating emission peaks at 8.44 GHz.…”

Section: Multi-wavelength Observations Of Activity On Ultracool Dwarfsmentioning

confidence: 99%

Atmospheric Electrification in Dusty, Reactive Gases in the Solar System and Beyond

et al. 2016

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Detailed observations of the solar system planets reveal a wide variety of local atmospheric conditions. Astronomical observations have revealed a variety of extrasolar planets none of which resembles any of the solar system planets in full. Instead, the most massive amongst the extrasolar planets, the gas giants, appear very similar to the class of (young) brown dwarfs which are amongst the oldest objects in the Universe. Despite this diversity, solar system planets, extrasolar planets and brown dwarfs have broadly similar global temperatures between 300 and 2500 K. In consequence, clouds of different chemical species form in their atmospheres. While the details of these clouds differ, the fundamental physical processes are the same. Further to this, all these objects were observed to produce radio and X-ray emissions. While both kinds of radiation are well studied on Earth and to a lesser extent on the solar system planets, the occurrence of emissions that potentially originate from accelerated electrons on brown dwarfs, extrasolar planets and protoplanetary disks is not well understood yet. This paper offers an interdisciplinary view on electrification processes and their feedback on their hosting environment in meteorology, volcanology, planetology and research on extrasolar planets and planet formation.

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Cyclotron maser emission: Stars, planets, and laboratory

Cited by 21 publications

References 28 publications

Lightning and charge processes in brown dwarf and exoplanet atmospheres

Lightning and charge processes in brown dwarf and exoplanet atmospheres

Flash ionization signature in coherent cyclotron emission from brown dwarfs

Atmospheric Electrification in Dusty, Reactive Gases in the Solar System and Beyond

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