Detection of the infrared aurora at Uranus with Keck-NIRSPEC

Near infrared (NIR) wavelength observations of Uranus have been unable to locate any infrared aurorae, despite many attempts to do so since the 1990s. While at Jupiter and Saturn, NIR investigations have redefined our understanding of magnetosphere ionosphere thermosphere coupling, the lack of NIR auroral detection at Uranus means that we have lacked a window through which to study these processes at Uranus. Here we present NIR Uranian observations with the Keck II telescope taken on the 5 September 2006 and detect enhanced $\text{H}_{\text{3}}^{\text{+}}$ emissions. Analysing temperatures and column densities, we identify an 88\% increase in localized $\text{H}_{\text{3}}^{\text{+}}$ column density, with no significant temperature increases, consistent with auroral activity generating increased ionization. By comparing these structures against the $\text{Q}_{\text{3}}^{\text{mp}}$ magnetic field model and the Voyager 2 ultraviolet observations, we suggest that these regions make up sections of the northern aurora.Comment: 12 pages, 3 main figures, 2 extended data figures. Nat Astron (2023

Ground-based observations of Saturn’s auroral ionosphere over three days:trends in H3+ temperature, density and emission with Saturn local time and planetary period oscillation

On 19–21 April 2013, the ground-based 10-m W.M. Keck II telescope was used to simultaneously measure View the MathML sourceH3+ emissions from four regions of Saturn’s auroral ionosphere: (1) the northern noon region of the main auroral oval; (2) the northern midnight main oval; (3) the northern polar cap and (4) the southern noon main oval. The View the MathML sourceH3+ emission from these regions was captured in the form of high resolution spectral images as the planet rotated. The results herein contain twenty-three View the MathML sourceH3+ temperatures, column densities and total emissions located in the aforementioned regions – ninety-two data points in total, spread over timescales of both hours and days. Thermospheric temperatures in the spring-time northern main oval are found to be cooler than their autumn-time southern counterparts by tens of K, consistent with the hypothesis that the total thermospheric heating rate is inversely proportional to magnetic field strength. The main oval View the MathML sourceH3+ density and emission is lower at northern midnight than it is at noon, in agreement with a nearby peak in the electron influx in the post-dawn sector and a minimum flux at midnight. Finally, when arranging the northern main oval View the MathML sourceH3+ parameters as a function of the oscillation period seen in Saturn’s magnetic field – the planetary period oscillation (PPO) phase – we see a large peak in View the MathML sourceH3+ density and emission at ∼115° northern phase, with a full-width at half-maximum (FWHM) of ∼44°. This seems to indicate that the influx of electrons associated with the PPO phase at 90° is responsible at least in part for the behavior of all View the MathML sourceH3+ parameters. A combination of the View the MathML sourceH3+ production and loss timescales and the ±10° uncertainty in the location of a given PPO phase are likely, at least in part, to be responsible for the observed peaks in View the MathML sourceH3+ density and emission occurring at a later time than the peak precipitation expected at 90° PPO phase

Experimental evaluation of the wake characteristics of cross flow turbine arrays

One key factor in the exploitation of tidal energy is the study of interactions of turbines when working in tidal turbine farms. The Momentum Reversal and Lift (MRL) turbine is a novel cross flow turbine. The three blades rotate around a common central horizontal axis which is parallel to their own axis and perpendicular to the flow. The novelty of the MRL turbine is that it relies on the combination of both lift and momentum reversal (drag) for energy extraction. Scaled MRL turbine models of 0.164 m in diameter were used to characterise the flow in three different tidal array settings. Detailed maps of axial velocity profiles and velocity deficits downstream of the turbine are presented, enabling the visualisation of characteristic flow patterns. The results show that the MRL generates lower velocity deficits and turbulence intensities in the near wake than those associated with horizontal axis turbines. The downstream wake was not completely symmetrical which was related to the geometry of the device but also due to the flow developed in the flume. Amongst the three array configurations studied, a fence of turbines with the lowest separation provided the highest power output

Cassini VIMS observations of H3+ emission on the nightside of Jupiter

We present the first detailed analysis of H3+ nightside emission from Jupiter, using Visual and Infrared Mapping Spectrometer (VIMS) data from the Cassini flyby in 2000–2001, producing the first Jovian maps of nightside H3+ emission, temperature, and column density. Using these, we identify and characterize regions of H3+ nightside emission, compared against past observations of H3+ emission on the dayside. We focus our investigation on the region previously described as “mid-to-low latitude emission,” the source for which has been controversial. We find that the brightest of this emission is generated at Jovigraphic latitudes similar to the most equatorward extent of the main auroral emission but concentrated at longitudes eastward of this emission. The emission is produced by enhanced H3+ density, with temperatures dropping away in this region. This emission has a loose association with the predicted location of diffuse aurora produced by pitch angle scattering in the north, but not in the south. This emission also lays in the path of subrotating winds flowing from the aurora, suggesting a transport origin. Some differences are seen between dayside and nightside subauroral emissions, with dayside emission extending more equatorward, perhaps caused by the lack of sunlight ionization on the nightside, and unmeasured changes in temperature. Ionospheric temperatures are hotter in the polar region (~1100–1500 K), dropping away toward the equator (as low as 750 K), broadly similar to values on the dayside, highlighting the dominance of auroral effects in the polar region. No equatorial emission is observed, suggesting that very little particle precipitation occurs away from the polar regions

Why is the H3+ hot spot above Jupiter's Great Red Spot so hot?

Recent observations of Jupiter's Great Red Spot indicate that the thermosphere above the storm is hotter than its surroundings by more than 700 K. Possible suggested sources for this heating have thus far included atmospheric gravity waves and lightning-driven acoustic waves. Here, we propose that Joule heating, driven by Great Red Spot vorticity penetrating up into the lower stratosphere and coupling to the thermosphere, may contribute to the large observed temperatures. The strength of Joule heating will depend on the local inclination angle of the magnetic field and thus the observed emissions and inferred temperatures should vary with planetary longitude as the Great Red Spot tracks across the planet. This article is part of a discussion meeting issue ‘Advances in hydrogen molecular ions: H3+, H5+ and beyond’

Asymmetric Ionospheric Jets in Jupiter's Aurora

Simultaneous infrared observations of (Formula presented.) and H2 emissions from Jupiter's northern aurora using the Near Infrared Spectrograph at Keck Observatory were used to measure the ionospheric and thermospheric wind velocities. (Formula presented.) ions supercorotate near the dawn auroral oval and subcorotate across the dusk sector and in the dawn polar region relative to the planetary rotation rate, broadly in agreement with past observations and models. An anticyclonic vortex is discovered in H2 flows, closely matching the mean magnetospheric subcorotation when the observed magnetospheric flows are averaged azimuthally. In comparing ion and neutral winds, we measure the line-of-sight effective ion drift in the neutral reference frame for the first time, revealing two blue-shifted sunward flows of ∼2 km/s. Observed (Formula presented.) and H2 emissions overlap with predictions of the Pedersen conductivity layer, suggesting two different regions of the ionosphere: (a) a deep layer, where neutral forces dominate the thermosphere and symmetric breakdown-in-corotation currents can close, and (b) a higher layer, where the observed effective ion drift allows dawn-to-dusk Pedersen currents within the upper atmosphere, in turn closing asymmetric currents within the magnetosphere. This ionospheric structure aligns well with recent Juno observations of Jupiter's aurora. The detected thermospheric vortex implies the driving of neutral flows by the momentum from the magnetosphere within the thermosphere and deeper in the atmosphere to potentially 20 mbar. Jovian neutral thermosphere might bridge the gap between current observations and modelings and perhaps be significant to the dynamics of aurora on Earth and other outer planets

Jupiter’s auroras during the Juno approach phase as observed by the Hubble Space Telescope

We present movies of the Hubble Space Telescope (HST) observations of Jupiter’s FUV auroras observed during the Juno approach phase and first capture orbit, and compare with Juno observations of the interplanetary medium near Jupiter and inside the magnetosphere. Jupiter’s FUV auroras indicate the nature of the dynamic processes occurring in Jupiter’s magnetosphere, and the approach phase provided a unique opportunity to obtain a full set of interplanetary data near to Jupiter at the time of a program of HST observations, along with the first simultaneous with Juno observations inside the magnetosphere. The overall goal was to determine the nature of the solar wind effect on Jupiter’s magnetosphere. HST observations were obtained with typically 1 orbit per day over three intervals: 16 May – 7 June, 22-30 June and 11-18 July, i.e. while Juno was in the solar wind, around the bow shock and magnetosphere crossings, and in the mid-latitude middle-outer magnetospheres. We show that these intervals are characterised by particularly dynamic polar auroras, and significant variations in the auroral power output caused by e.g. dawn storms, intense main emission and poleward forms. We compare the variation of these features with Juno observations of interplanetary compression regions and the magnetospheric environment during the intervals of these observations

Subacromial balloon spacer for irreparable rotator cuff tears of the shoulder (START:REACTS) : a group-sequential, double-blind, multicentre randomised controlled trial

Background New surgical procedures can expose patients to harm and should be carefully evaluated before widespread use. The InSpace balloon (Stryker, USA) is an innovative surgical device used to treat people with rotator cuff tears that cannot be repaired. We aimed to determine the effectiveness of the InSpace balloon for people with irreparable rotator cuff tears. Methods We conducted a double-blind, group-sequential, adaptive randomised controlled trial in 24 hospitals in the UK, comparing arthroscopic debridement of the subacromial space with biceps tenotomy (debridement only group) with the same procedure but including insertion of the InSpace balloon (debridement with device group). Participants had an irreparable rotator cuff tear, which had not resolved with conservative treatment, and they had symptoms warranting surgery. Eligibility was confirmed intraoperatively before randomly assigning (1:1) participants to a treatment group using a remote computer system. Participants and assessors were masked to group assignment. Masking was achieved by using identical incisions for both procedures, blinding the operation note, and a consistent rehabilitation programme was offered regardless of group allocation. The primary outcome was the Oxford Shoulder Score at 12 months. Pre-trial simulations using data from early and late timepoints informed stopping boundaries for two interim analyses. The primary analysis was on a modified intention-to-treat basis, adjusted for the planned interim analysis. The trial was registered with ISRCTN, ISRCTN17825590. Findings Between June 1, 2018, and July 30, 2020, we assessed 385 people for eligibility, of which 317 were eligible. 249 (79%) people consented for inclusion in the study. 117 participants were randomly allocated to a treatment group, 61 participants to the debridement only group and 56 to the debridement with device group. A predefined stopping boundary was met at the first interim analysis and recruitment stopped with 117 participants randomised. 43% of participants were female, 57% were male. We obtained primary outcome data for 114 (97%) participants. The mean Oxford Shoulder Score at 12 months was 34·3 (SD 11·1) in the debridement only group and 30·3 (10·9) in the debridement with device group (mean difference adjusted for adaptive design –4·2 [95% CI –8·2 to –0·26];p=0·037) favouring control. There was no difference in adverse events between the two groups. Interpretation In an efficient, adaptive trial design, our results favoured the debridement only group. We do not recommend the InSpace balloon for the treatment of irreparable rotator cuff tears