Dependence of the open-closed field line boundary in Saturn's ionosphere on both the IMF and solar wind dynamic pressure:comparison with the UV auroral oval observed by the HST

We model the open magnetic field region in Saturn's southern polar ionosphere during two compression regions observed by the Cassini spacecraft upstream of Saturn in January 2004, and compare these with the auroral ovals observed simultaneously in ultraviolet images obtained by the Hubble Space Telescope. The modelling employs the paraboloid model of Saturn's magnetospheric magnetic field, whose parameters are varied according to the observed values of both the solar wind dynamic pressure and the interplanetary magnetic field (IMF) vector. It is shown that the open field area responds strongly to the IMF vector for both expanded and compressed magnetic models, corresponding to low and high dynamic pressure, respectively. It is also shown that the computed open field region agrees with the poleward boundary of the auroras as well as or better than those derived previously from a model in which only the variation of the IMF vector was taken into account. The results again support the hypothesis that the auroral oval at Saturn is associated with the open-closed field line boundary and hence with the solar wind interaction

Cluster spacecraft observations of a ULF wave enhanced by Space Plasma Exploration by Active Radar (SPEAR)

Space Plasma Exploration by Active Radar (SPEAR) is a high-latitude ionospheric heating facility capable of exciting ULF waves on local magnetic field lines. We examine an interval from 1 February 2006 when SPEAR was transmitting a 1 Hz modulation signal with a 10 min on-off cycle. Ground magnetometer data indicated that SPEAR modulated currents in the local ionosphere at 1 Hz, and enhanced a natural field line resonance with a 10 min period. During this interval the Cluster spacecraft passed over the heater site. Signatures of the SPEAR-enhanced field line resonance were present in the magnetic field data measured by the magnetometer on-board Cluster-2. These are the first joint ground- and space-based detections of field line tagging by SPEAR

Energy-banded ions in Saturn's magnetosphere

Using data from the Cassini Plasma Spectrometer ion mass spectrometer, we report the first observation of energy-banded ions at Saturn. Observed near midnight at relatively high magnetic latitudes, the banded ions are dominantly H+, and they occupy the range of energies typically associated with the thermal pickup distribution in the inner magnetosphere (L < 10), but their energies decline monotonically with increasing radial distance (or time or decreasing latitude). Their pitch angle distribution suggests a source at low (or slightly southern) latitudes. The band energies, including their pitch angle dependence, are consistent with a bounce-resonant interaction between thermal H+ ions and the standing wave structure of a field line resonance. There is additional evidence in the pitch angle dependence of the band energies that the particles in each band may have a common time of flight from their most recent interaction with the wave, which may have been at slightly southern latitudes. Thus, while the particles are basically bounce resonant, their energization may be dominated by their most recent encounter with the standing wave

Energy-banded ions in Saturn's magnetosphere

Using data from the Cassini Plasma Spectrometer ion mass spectrometer, we report the first observation of energy-banded ions at Saturn. Observed near midnight at relatively high magnetic latitudes, the banded ions are dominantly H+, and they occupy the range of energies typically associated with the thermal pickup distribution in the inner magnetosphere (L < 10), but their energies decline monotonically with increasing radial distance (or time or decreasing latitude). Their pitch angle distribution suggests a source at low (or slightly southern) latitudes. The band energies, including their pitch angle dependence, are consistent with a bounce-resonant interaction between thermal H+ ions and the standing wave structure of a field line resonance. There is additional evidence in the pitch angle dependence of the band energies that the particles in each band may have a common time of flight from their most recent interaction with the wave, which may have been at slightly southern latitudes. Thus, while the particles are basically bounce resonant, their energization may be dominated by their most recent encounter with the standing wave

Simultaneous Cassini VIMS and UVIS observations of Saturn's southern aurora: Comparing emissions from H, H-2 and H-3(+) at a high spatial resolution

Here, for the first time, temporally coincident and spatially overlapping Cassini VIMS and UVIS observations of Saturn's southern aurora are presented. Ultraviolet auroral H and H-2 emissions from UVIS are compared to infrared H-3(+) emission from VIMS. The auroral emission is structured into three arcs - H, H-2 and H-3(+) are morphologically identical in the bright main auroral oval (similar to 73 degrees S), but there is an equatorward arc that is seen predominantly in H (similar to 70 degrees S), and a poleward arc (similar to 74 degrees S) that is seen mainly in H-2 and H-3(+). These observations indicate that, for the main auroral oval, UV emission is a good proxy for the infrared H-3(+) morphology (and vice versa), but for emission either poleward or equatorward this is no longer true. Hence, simultaneous UV/IR observations are crucial for completing the picture of how the atmosphere interacts with the magnetosphere

Auroral evidence of radial transport at Jupiter during January 2014

We present Jovian auroral observations from the 2014 January Hubble Space Telescope (HST) campaign and investigate the auroral signatures of radial transport in the magnetosphere alongside contemporaneous radio and Hisaki EUV data. HST FUV auroral observations on day 11 show, for the first time, a significantly superrotating polar spot poleward of the main emission on the dawnside. The spot transitions from the polar to main emission region in the presence of a locally broad, bright dawnside main emission feature and two large equatorward emission features. Such a configuration of the main emission region is also unreported to date. We interpret the signatures as part of a sequence of inward radial transport processes. Hot plasma inflows from tail reconnection are thought to flow planetward and could generate the superrotating spot. The main emission feature could be the result of flow shears from prior hot inflows. Equatorward emissions are observed. These are evidence of hot plasma injections in the inner magnetosphere. The images are thought to be part of a prolonged period of reconnection. Radio emissions measured by Wind suggest that hectometric (HOM) and non-Io decametric (DAM) signatures are associated with the sequence of auroral signatures, which implies a global magnetospheric disturbance. The reconnection and injection interval can continue for several hours

Vertical emissivity profiles of Jupiter's northern H-3(+) and H-2 infrared auroras observed by Subaru/IRCS

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 8.2m telescope with the adaptive optics system (AO188). The spatial resolution achieved was similar to 0.2 arcsec, corresponding to similar 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 similar to 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

Cassini observations of ion and electron beams at Saturn and their relationship to infrared auroral arcs

We present Cassini Visual and Infrared Mapping Spectrometer observations of infrared auroral emissions from the noon sector of Saturn's ionosphere revealing multiple intense auroral arcs separated by dark regions poleward of the main oval. The arcs are interpreted as the ionospheric signatures of bursts of reconnection occurring at the dayside magnetopause. The auroral arcs were associated with upward field-aligned currents, the magnetic signatures of which were detected by Cassini at high planetary latitudes. Magnetic field and particle observations in the adjacent downward current regions showed upward bursts of 100–360 keV light ions in addition to energetic (hundreds of keV) electrons, which may have been scattered from upward accelerated beams carrying the downward currents. Broadband, upward propagating whistler waves were detected simultaneously with the ion beams. The acceleration of the light ions from low altitudes is attributed to wave-particle interactions in the downward current regions. Energetic (600 keV) oxygen ions were also detected, suggesting the presence of ambient oxygen at altitudes within the acceleration region. These simultaneous in situ and remote observations reveal the highly energetic magnetospheric dynamics driving some of Saturn's unusual auroral features. This is the first in situ identification of transient reconnection events at regions magnetically conjugate to Saturn's magnetopause

Short-Term Clinical Outcomes and Comparison of Ultrasound Versus Magnetic Resonance Imaging of Superior Capsular Reconstruction

Purpose To evaluate the short-term outcomes of 10 patients with irreparable massive rotator cuff tears treated with arthroscopic superior capsular reconstruction (SCR) using dermal allograft. Methods Between 2016 and 2018, patients with symptomatic irreparable rotator cuff tears were prospectively enrolled for treatment with arthroscopic SCR. Investigational review board approval was achieved. All patients were treated by a single fellowship-trained shoulder surgeon. Minimum follow-up was 1 year. Range of motion and functional outcome according to visual analog scale pain, American Shoulder and Elbow Surgeons, and Simple Shoulder Test scores were assessed preoperatively and at routine follow-up intervals. Magnetic resonance imaging (MRI) and ultrasound were obtained at a minimum of 1 year to assess graft integrity and to correlate clinical outcomes. Results Ten patients with a mean age of 58.6 years had a minimum follow-up of 1 year. In all patients, preoperatively to postoperatively, mean forward flexion improved from 141° to 173° (P = .018), mean visual analog scale pain score decreased from 6.5 to 1 (P = .004), and mean American Shoulder and Elbow Surgeons score improved from 43 to 87 (P = .005). At 1 year, ultrasound evaluation identified graft failure in 1 patient (10%), whereas MRI diagnosed graft failure in 7 patients (70%). Of the 7 failures diagnosed by MRI, 4 failed at the level of the glenoid, 2 failed mid-graft, and 1 failed at the humerus. Conclusions Although clinical outcomes are statistically improved following arthroscopic SCR using a dermal allograft, the early high failure rates of the graft raise concerns about the long-term outcomes of the procedure. Furthermore, the use of ultrasound alone to validate an intact graft should be used with caution, as failures can occur at the glenoid and can be missed without MRI correlation. Level of Evidence Level IV, Therapeutic case serie