Auroral Processes at the Giant Planets: Energy Deposition, Emission Mechanisms, Morphology and Spectra

Badman, S. V.; Branduardi‐Raymont, G.; Galand, M.; Hess, S.; Krupp, N.; Lamy, Laurent; Melin, Henrik; Tao, Chihiro

doi:10.1007/s11214-014-0042-x

Cited by 101 publications

(70 citation statements)

References 361 publications

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“…The auroral FUV emission in brown dwarfs has not yet been discovered, but would be an important confirmation of the effects of auroral electron beams in brown dwarf atmospheres. Moreover, following the Jovian example, this FUV emission would be diagnostic of the total auroral energy and is sensitive to the auroral electron energy distribution (Bhardwaj & Gladstone 2000;Badman et al 2015; J. S. Pineda et al 2017, in preparation).…”

Section: Emission Line Featuresmentioning

confidence: 99%

“…ECM radio emission has been observed in the magnetized planets of the solar system, signaling the presence of non-thermal energetic electron distributions in the regions around the planetary magnetic poles, near the top of the atmosphere (e.g., Zarka 1998). The energetic electron beams responsible for the radio emission precipitate into the atmosphere and generate a cascade of additional auroral emission processes (see Badman et al 2015 and references therein). In Jupiter and Saturn, where the atmospheres are predominantly hydrogen, the collision of the energetic electrons with the atmospheric gas leads to the excitation and ionization of H/H 2 and subsequent emissions at UV and optical wavelengths, including Lyman and Balmer line emissions (Perry et al 1999;Vasavada et al 1999;Grodent et al 2003;Gustin et al 2013;Dyudina et al 2016).…”

Section: Auroral Processes In Planetary Magnetospheresmentioning

confidence: 99%

“…The de-excitation and recombination of hydrogen will lead to considerable Balmer and Lyman series emission, as well as UV emission in the Lyman and Werner bands (Badman et al 2015). Consequently, brown dwarfs hosting auroral radio emission are likely to generate surface features that are bright in Hα, Lyα, and the FUV.…”

Section: Emission Line Featuresmentioning

confidence: 99%

“…H 3 + , however, is sensitive to the conditions in the atmosphere, and could be an important diagnostic with strong emission features at 2 μm and 4 μm (Tao et al 2011(Tao et al , 2012Badman et al 2015). The ro-vibrational features are thermally excited and depend on the atmospheric temperature.…”

Section: Emission Line Featuresmentioning

confidence: 99%

“…The ro-vibrational features are thermally excited and depend on the atmospheric temperature. Additionally, the presence of H 3 + is limited by the electron number density and the concentration of gas species, like CH 4 and H 2 O, that act to destroy the ion (Badman et al 2015). Interestingly, although auroral electron beams in brown dwarfs are likely to create H 3 + , the concentration may not build up significantly if the ion is quickly destroyed.…”

Section: Emission Line Featuresmentioning

confidence: 99%

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A Panchromatic View of Brown Dwarf Aurorae

Pineda

Hallinan

Kao

2017

ApJ

118

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Stellar coronal activity has been shown to persist into the low-mass star regime, down to late M-dwarf spectral types. However, there is now an accumulation of evidence suggesting that at the end of the main sequence, there is a transition in the nature of the magnetic activity from chromospheric and coronal to planet-like and auroral, from local impulsive heating via flares and MHD wave dissipation to energy dissipation from strong large-scale magnetospheric current systems. We examine this transition and the prevalence of auroral activity in brown dwarfs through a compilation of multiwavelength surveys of magnetic activity, including radio, X-ray, and optical. We compile the results of those surveys and place their conclusions in the context of auroral emission as a consequence of large-scale magnetospheric current systems that accelerate energetic electron beams and drive the particles to impact the cool atmospheric gas. We explore the different manifestations of auroral phenomena, like Hα, in brown dwarf atmospheres and define their distinguishing characteristics. We conclude that large-amplitude photometric variability in the near-infrared is most likely a consequence of clouds in brown dwarf atmospheres, but that auroral activity may be responsible for long-lived stable surface features. We report a connection between auroral Hα emission and quiescent radio emission in electron cyclotron maser instability pulsing brown dwarfs, suggesting a potential underlying physical connection between quiescent and auroral emissions. We also discuss the electrodynamic engines powering brown dwarf aurorae and the possible role of satellites around these systems both to power the aurorae and seed the magnetosphere with plasma.

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Section: Emission Line Featuresmentioning

confidence: 99%

Section: Auroral Processes In Planetary Magnetospheresmentioning

confidence: 99%

Section: Emission Line Featuresmentioning

confidence: 99%

Section: Emission Line Featuresmentioning

confidence: 99%

Section: Emission Line Featuresmentioning

confidence: 99%

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A Panchromatic View of Brown Dwarf Aurorae

Pineda

Hallinan

Kao

2017

ApJ

118

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The brightness ratio of H Lyman‐α/H₂ bands in FUV auroral emissions: A diagnosis for the energy of precipitating electrons and associated magnetospheric acceleration processes applied to Saturn

Tao

Lamy

Prangé

2014

Geophysical Research Letters

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We propose that the ratio of the auroral brightness of H Lyman-α to that of far ultraviolet H 2 and the absolute value of the H 2 brightness provide good indicators of the acceleration versus nonacceleration processes for field-aligned auroral electron precipitation in the Saturn magnetosphere-ionosphere coupled system. This finding is based on model results indicating that this ratio is a decreasing function of the auroral electron energy over the whole auroral energy range, as previously suggested by Cassini observations. For electron energies above 5 keV, the results agree with the Knight relation, as in the environments of the Earth and Jupiter. On the other hand, decreasing electron flux with increasing electron energies below a few keV is also found and alternately explained as a nonacceleration reflecting the magnetospheric plasma distribution and/or wave-particle interactions.

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Vertical emissivity profiles of Jupiter's northern H₃⁺ and H₂ infrared auroras observed by Subaru/IRCS

et al. 2014

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We resolved the vertical emissivity profiles of H 3 + overtone, H 3 + hot overtone, and H 2 emission lines of the Jovian northern auroras in K band obtained in December 2011 observed by the IR Camera and Spectrograph of the Subaru 8.2 m telescope with the adaptive optics system (AO188). The spatial resolution achieved was~0.2 arcsec, corresponding to~600 km at Jupiter. We derived the vertical emissivity profiles at three polar regions close to the Jovian limb. The H 3 + overtone and H 3 + hot overtone lines had similar peak altitudes of 700-900 km and 680-950 km above the 1 bar level, which were 100-300 km and 150-420 km lower, respectively, than the model values. On the contrary, the H 2 peak emission altitude was high, 590-720 km above the 1 bar level. It was consistent with the value expected for precipitation of~1 keV electron, which favors a higher-altitude emissivity profile. We concluded that the lower peak altitudes of H 3 + overtone and hot overtone lines were caused by the nonlocal thermodynamic equilibrium effect stronger than the model assumption. We could reproduce the observational emissivity profiles from the model by including this effect. It has been proposed that neutral H 2 and ionized H 3 + emissions can have different source altitudes because of their different morphologies and velocities; however, our observed results with a general circulation model show that the peak emission altitudes of H 3 + and H 2 can be similar even with different velocities.

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Auroral Processes at the Giant Planets: Energy Deposition, Emission Mechanisms, Morphology and Spectra

Cited by 101 publications

References 361 publications

A Panchromatic View of Brown Dwarf Aurorae

A Panchromatic View of Brown Dwarf Aurorae

The brightness ratio of H Lyman‐α/H₂ bands in FUV auroral emissions: A diagnosis for the energy of precipitating electrons and associated magnetospheric acceleration processes applied to Saturn

Vertical emissivity profiles of Jupiter's northern H₃⁺ and H₂ infrared auroras observed by Subaru/IRCS

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Auroral Processes at the Giant Planets: Energy Deposition, Emission Mechanisms, Morphology and Spectra

Cited by 101 publications

References 361 publications

A Panchromatic View of Brown Dwarf Aurorae

A Panchromatic View of Brown Dwarf Aurorae

The brightness ratio of H Lyman‐α/H2 bands in FUV auroral emissions: A diagnosis for the energy of precipitating electrons and associated magnetospheric acceleration processes applied to Saturn

Vertical emissivity profiles of Jupiter's northern H3+ and H2 infrared auroras observed by Subaru/IRCS

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Product

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The brightness ratio of H Lyman‐α/H₂ bands in FUV auroral emissions: A diagnosis for the energy of precipitating electrons and associated magnetospheric acceleration processes applied to Saturn

Vertical emissivity profiles of Jupiter's northern H₃⁺ and H₂ infrared auroras observed by Subaru/IRCS