The aurorae of Uranus past equinox

Lamy, Laurent; Prangé, Renée; Hansen, K. C.; Tao, Chihiro; Cowley, S. W. H.; Stallard, T.; Melin, Henrik; Achilleos, N.; Guio, P.; Badman, S. V.; Kim, T.; Pogorelov, N. V.

doi:10.1002/2017ja023918

Cited by 29 publications

(42 citation statements)

References 25 publications

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“…We also note that the northern auroral C 2 H 6 emission weakened during periods of low solar activity in previous work, which similarly suggests a connection with solar-wind conditions on longer timescales 13 .…”

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confidence: 79%

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A brightening of Jupiter’s auroral 7.8-μm CH4 emission during a solar-wind compression

et al. 2019

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Enhanced mid-infrared emission from CH 4 and other stratospheric hydrocarbons have been observed coincident with Jupiter's ultraviolet auroral emission 1-3 , which demonstrates that auroral processes and the neutral stratosphere of Jupiter are coupled. However, the exact nature of this coupling has remained an open question. Here, we present a time series of Subaru-COMICS images of Jupiter at 7.80 µm measured between January 11-14th, February 4-5th and May 17-20th (UT) 2017, which show both the morphology and magnitude of the auroral CH 4 emission to vary on daily timescales in relation to external solar-wind conditions. The southern auroral CH 4 emission increased in brightness temperature (T b) by ∆T b = 3.8 ± 0.9 K between January 11th 15:50 UT-12th 12:57 UT during a predicted solarwind compression. During the same compression, the northern auroral emission exhibited a dusk-side brightening, which mimicks the morphology observed in the ultraviolet auroral emission during periods of enhanced solar-wind pressures 4, 5. These results suggest that changes in external solar wind conditions perturb the jovian magnetosphere such that ener

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supporting

confidence: 79%

“…impinging on Jupiter's magnetosphere. This model is used extensively by the outer planets magnetosphere community [11][12][13] in the absence of in-situ measurements of the solar-wind conditions.…”

Section: Methodsmentioning

confidence: 99%

A brightening of Jupiter’s auroral 7.8-μm CH4 emission during a solar-wind compression

et al. 2019

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“…Figure 2 shows these data projected for different geometries. These observations appear consistent with more recent ultraviolet observations obtained with the Hubble Space Telescope [9,[31][32][33] and show emission in the form of discrete faint spots. At Neptune, no unambiguous detection of auroral emission made [13]-the only magnetized planet in our solar system without a single observation of its auroral emissions.…”

Section: The Voyager 2 Flybyssupporting

confidence: 93%

“…The HST observations of auroral emissions from Uranus [31][32][33] show relatively weak auroral spots on the body of the planet, similar to Voyager 2 observed in 1986 (figure 2). Lamy et al [31] was the first to coordinate the observations with the arrival of a coronal mass ejection (CME) at the planet, which likely produced enhanced auroral emission.…”

Section: (A) Uranussupporting

confidence: 65%

The upper atmospheres of Uranus and Neptune

Melin

2020

Phil. Trans. R. Soc. A.

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We review the current understanding of the upper atmospheres of Uranus and Neptune, and explore the upcoming opportunities available to study these exciting planets. The ice giants are the least understood planets in the solar system, having been only visited by a single spacecraft, in 1986 and 1989, respectively. The upper atmosphere plays a critical role in connecting the atmosphere to the forces and processes contained within the magnetic field. For example, auroral current systems can drive charged particles into the atmosphere, heating it by way of Joule heating. Ground-based observations of H 3 + provides a powerful remote diagnostic of the physical properties and processes that occur within the upper atmosphere, and a rich dataset exists for Uranus. These observations span almost three decades and have revealed that the upper atmosphere has continuously cooled between 1992 and 2018 at about 8 K/year, from approximately 750 K to approximately 500 K. The reason for this trend remain unclear, but could be related to seasonally driven changes in the Joule heating rates due to the tilted and offset magnetic field, or could be related to changing vertical distributions of hydrocarbons. H 3 + has not yet been detected at Neptune, but this discovery provides low-hanging fruit for upcoming facilities such as the James Webb Space Telescope and the next generation of 30 m telescopes. Detecting H 3 + at Neptune would enable the characterization of its upper atmosphere for the first time since 1989. To fully understand the ice giants, we need dedicated orbital missions, in the same way the Cassini spacecraft explored Saturn. Only by combining in situ observations of the magnetic field with in-orbit remote sensing can we get the complete picture of how energy moves between the atmosphere and the magnetic field. This article is part of a discussion meeting issue ‘Future exploration of ice giant systems’.

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“…These maps have been available online 2 since the beginning of the SOHO mission and extend to Carrington rotation 2168 (Sep-Oct 2015) as of this writing. They provide a concise visualization of the evolution of the coronal structure, in white light, and have been used for CME detection and measurements (e.g., Lamy et al 2017, and references therein).…”

Section: Sbos In Carrington Mapsmentioning

confidence: 99%

Streamer-blowout Coronal Mass Ejections: Their Properties and Relation to the Coronal Magnetic Field Structure

Vourlidas

Webb

2018

ApJ

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We present a comprehensive analysis of a particular class of coronal mass ejection (CME) event, called streamer-blowout CME (SBOs). The events are characterized by a gradual swelling of the overlying streamer, lasting hours to days, followed by a slow, wide CME, generally exhibiting a 3-part structure, which leaves the streamer significantly depleted in its wake. We identify 909 SBO events in the LASCO/C2 observations between 1996 and 2015. The average blowout lasts for 40.5 hours but the evacuation can take days for some events. SBO-CMEs are wider and more massive than the average CME. Their properties generally vary during and between solar cycles. Their minimum (maximum) monthly occurrence rate of one (six) events in cycle 23 has doubled in cycle 24---a probable manifestation of the weaker global fields in the current cycle. The locations of SBOs follow the tilt of the global dipole (but not from 2014 onwards), do not correlate with sunspot numbers and exhibit flux rope morphology at a much higher rate (61%) than regular CMEs (40%). We propose that these characteristics are consistent with SBOs arising from extended polarity inversion lines outside active regions (e.g. quiet sun and polar crown filaments) through the release, via reconnection, of magnetic energy, likely accumulated via differential rotation.

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The aurorae of Uranus past equinox

Cited by 29 publications

References 25 publications

A brightening of Jupiter’s auroral 7.8-μm CH4 emission during a solar-wind compression

A brightening of Jupiter’s auroral 7.8-μm CH4 emission during a solar-wind compression

The upper atmospheres of Uranus and Neptune

Streamer-blowout Coronal Mass Ejections: Their Properties and Relation to the Coronal Magnetic Field Structure

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