In early 2014, continuous monitoring with the Hisaki satellite discovered transient auroral emission at Jupiter during a period when the solar wind was relatively quiet for a few days. Simultaneous imaging made by the Hubble Space Telescope (HST) suggested that the transient aurora is associated with a global magnetospheric disturbance that spans from the inner to outer magnetosphere. However, the temporal and spatial evolutions of the magnetospheric disturbance were not resolved because of the lack of continuous monitoring of the transient aurora simultaneously with the imaging. Here we report the coordinated observation of the aurora and plasma torus made by Hisaki and HST during the approach phase of the Juno spacecraft in mid‐2016. On day 142, Hisaki detected a transient aurora with a maximum total H2 emission power of ~8.5 TW. The simultaneous HST imaging was indicative of a large “dawn storm,” which is associated with tail reconnection, at the onset of the transient aurora. The outer emission, which is associated with hot plasma injection in the inner magnetosphere, followed the dawn storm within less than two Jupiter rotations. The monitoring of the torus with Hisaki indicated that the hot plasma population increased in the torus during the transient aurora. These results imply that the magnetospheric disturbance is initiated via the tail reconnection and rapidly expands toward the inner magnetosphere, followed by the hot plasma injection reaching the plasma torus. This corresponds to the radially inward transport of the plasma and/or energy from the outer to the inner magnetosphere.

We compare Chandra and XMM-Newton X-ray observations of Jupiter during 2007 with a rich multi-instrument data set including upstream in situ solar wind measurements from the New Horizons spacecraft, radio emissions from the Nançay Decametric Array and Wind/Waves, and ultraviolet (UV) observations from the Hubble Space Telescope. New Horizons data revealed two corotating interaction regions (CIRs) impacted Jupiter during these observations. Non-Io decametric bursts and UV emissions brightened together and varied in phase with the CIRs. We characterize three types of X-ray aurorae: hard X-ray bremsstrahlung main emission, pulsed/flared soft X-ray emissions, and a newly identified dim flickering (varying on short time scales, but quasi-continuously present) aurora. For most observations, the X-ray aurorae were dominated by pulsed/flaring emissions, with ion spectral lines that were best fit by iogenic plasma. However, the brightest X-ray aurora was coincident with a magnetosphere expansion. For this observation, the aurorae were produced by both flickering emission and erratic pulses/flares. Auroral spectral models for this observation required the addition of solar wind ions to attain good fits, suggesting solar wind entry into the outer magnetosphere or directly into the pole for this particularly bright observation. X-ray bremsstrahlung from high energy electrons was only bright for one observation, which was during a forward shock. This bremsstrahlung was spatially coincident with bright UV main emission (power > 1 TW) and X-ray ion spectral line dusk emission, suggesting closening of upward and downward current systems during the shock. Otherwise, the bremsstrahlung was dim, and UV main emission power was also lower (<700 GW), suggesting their power scaled together.

The influence of the surface application of active elements on the composition, morphology, adherence, and growth rate of oxide scales formed during high temperature exposure has been investigated. The active elements were applied as aqueous solutions of nitrate salts that were subsequently transformed into oxide. The active elements used were: Y, Ce, La, Hf, Ca, and Zr. The chromia-forming substrates used were AISI 304 and 310 stainless steels and IN 738, a nickel base alloy. To determine the effect of the minor alloying elements in stainless steels on the surface doping effect, Y was applied to three alloy modifications of AISI 304. The effect of the presence or absence of Mn and Si in the alloy on high temperature corrosion behavior was determined. Several different application techniques were used to determine which technique was most beneficial to the behavior of the oxide barrier scale.The application of Y, Ce, and La was found to enhance the oxidation resistance of the commercial stainless steels whereas no benefits were found for alloys with Hf, Ca, and Zr added to their surfaces. It was determined that Si had to be present in AISI 304 stainless steel for the enhancement of its oxidation resistance. There was no beneficial effect for modified 304 containing only Mn or neither Mn nor Si. The yttrium added and the untreated, modified AISI 304 with Si only showed more resistance to scale spallation than any other 304 alloy tested, modified or commercial. AbstractThe polarization behavior of various pure zinc, AI-Zn, and Zn-Ni coatings was studied to evaluate electrochemical methods for use in testing the performance of such coatings on sheet steel. Behavior in deaerated chloride solutions was found to simulate more nearly the good performance of pure zinc (galvanized) coatings in service. AI-Zn coatings exhibited low corrosion rates in both aerated and deaerated chioride solutions, yet they maintained active corrosion potentials and conferred galvanic cathodic protection to bare steel exposed in a scribe through the coating. The galvanic current, which provides cathodic protection for the steel in a scribe, was measured successfuly using the polarization resistance technique.( 1) Pyrex is a registered tradename of Coming Glass, Inc., Corning, New York.

In January 2014 Jupiter's FUV main auroral oval decreased its emitted power by 70% and shifted equatorward by ∼1°. Intense, low‐latitude features were also detected. The decrease in emitted power is attributed to a decrease in auroral current density rather than electron energy. This could be caused by a decrease in the source electron density, an order of magnitude increase in the source electron thermal energy, or a combination of these. Both can be explained either by expansion of the magnetosphere or by an increase in the inward transport of hot plasma through the middle magnetosphere and its interchange with cold flux tubes moving outward. In the latter case the hot plasma could have increased the electron temperature in the source region and produced the intense, low‐latitude features, while the increased cold plasma transport rate produced the shift of the main oval.

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.

Key Points: 22 • Jupiter's equatorial X-ray emission varies in accordance with solar cycle 24 but 23 auroral power can be comparably bright at solar min & max 24 • Charge Exchange models provide good fits to aurora spectra retrieving S:O ra-25 tios of 0.4-1.3 agreeing with in-situ magnetosphere measurements 26 • We report systematic differences between Chandra ACIS and XMM-Newton EPIC-27 pn Jovian spectra and the impact of these on opacity and quenching 28 Corresponding author: William R Dunn, w.dunn@ucl.ac.uk -1-Abstract 29The 2007-2009 solar minimum was the longest of the space age. We present the first of 30 two companion papers on Chandra and XMM-Newton X-ray campaigns of Jupiter through 31 February-March 2007. We find that low solar X-ray flux during solar minimum causes 32 Jupiter's equatorial regions to be exceptionally X-ray dim (0.21GW at minimum; 0.76GW 33 at maximum). While the Jovian equatorial emission varies with solar cycle, the auro-34 rae have comparably bright intervals at solar minimum and maximum. We apply atomic 35 charge exchange models to auroral spectra and find that iogenic plasma of sulphur and 36 oxygen ions provides excellent fits for XMM-Newton observations. The fitted spectral 37 S:O ratios of 0.4-1.3 are in good agreement with in-situ magnetospheric S:O measure-38 ments of 0.3-1.5, suggesting that the ions that produce Jupiter's X-ray aurora predom-39 inantly originate inside the magnetosphere. The aurorae were particularly bright on Feb 40 24-25 and March 8-9, but these two observations exhibit very different spatial, spectral 41 and temporal behaviour. 24-25 Feb was the only observation in this campaign with sig-42 nificant hard X-ray bremsstrahlung from precipitating electrons, suggesting this may be 43 rare. For 8-9 March, a bremsstrahlung component was absent, but bright oxygen O 6+ 44 lines and best-fit models containing carbon, point to contributions from solar wind ions. 45This contribution is absent in the other observations. Comparing simultaneous Chan-46 dra ACIS and XMM-Newton EPIC spectra showed that ACIS systematically under-reported 47 0.45-0.6keV Jovian emission, suggesting quenching may be less important for Jupiter's 48 atmosphere than previously thought. We therefore recommend XMM-Newton for spec-49 tral analyses and quantifying opacity/quenching effects. 50 1 Introduction 51 With their launch in 1999, the XMM-Newton and Chandra X-ray Observatories 52 ushered in a revolution in X-ray astronomy, providing a paradigm-shift in our understand-53 ing of Jupiter's X-ray (0.2 -10 keV) emissions. The combination of these two comple-54 mentary observatories have permitted an array of invaluable research on Jupiter's au-55 rorae. So far, these studies have identified two dominant sources of Jupiter's X-ray emis-56 sion: a) scattering and fluorescence of solar photons in Jupiter's atmosphere across the 57 planet's Sun-lit face [Branduardi-Raymont et al., 2004; Bhardwaj et al., 2005, 2006; Branduardi-58 Raymont et al., 2007a; Cravens et al., 2006] and b) dynamic auroral emiss...

Saturn's dayside aurora displays a number of morphological features poleward of the main emission region. We present an unusual morphology captured by the Hubble Space Telescope on 14 June 2014 (day 165), where for 2 h, Saturn's FUV aurora faded almost entirely, with the exception of a distinct emission spot at high latitude. The spot remained fixed in local time between 10 and 15 LT and moved poleward to a minimum colatitude of ~4°. It was bright and persistent, displaying intensities of up to 49 kR over a lifetime of 2 h. Interestingly, the spot constituted the entirety of the northern auroral emission, with no emissions present at any other local time—including Saturn's characteristic dawn arc, the complete absence of which is rarely observed. Solar wind parameters from propagation models, together with a Cassini magnetopause crossing and solar wind encounter, indicate that Saturn's magnetosphere was likely to have been embedded in a rarefaction region, resulting in an expanded magnetosphere configuration during the interval. We infer that the spot was sustained by reconnection either poleward of the cusp or at low latitudes under a strong component of interplanetary magnetic field transverse to the solar wind flow. The subsequent poleward motion could then arise from either reconfiguration of successive open field lines across the polar cap or convection of newly opened field lines. We also consider the possible modulation of the feature by planetary period rotating current systems.

Saturn's morningside auroras consist mainly of rotating, transient emission patches, following periodic reconnection in the magnetotail. Simultaneous responses in global energetic neutral atom (ENA) emissions have been observed at similar local times, suggesting a link between the auroras and large‐scale injections of hot ions in the outer magnetosphere. In this study, we use Cassini's remote sensing instruments to observe multiple plasma injection signatures within coincident auroral and ENA imagery, captured during 9 April 2014. Kilometric radio emissions also indicate clear injection activity. We track the motion of rotating signatures in the auroras and ENAs to test their local time relationship. Two successive auroral signatures—separated by ~4 hr UT—form postmidnight before rotating to the dayside while moving equatorward. The first has a clear ENA counterpart, maintaining a similar local time mapping throughout ~9 hr observation. Mapping of the ionospheric equatorward motion post‐dawn indicates a factor ~5 reduction of the magnetospheric source region's radial speed at a distance of ~14‐20 RS, possibly a plasma or magnetic boundary. The second auroral signature has no clear ENA counterpart; viewing geometry was relatively unchanged, so the ENAs were likely too weak to detect by this time. A third, older injection signature, seen in both auroral and ENA imagery on the nightside, may have been sustained by field‐aligned currents linked with the southern planetary period oscillation system, or the re‐energization of ENAs around midnight local times. The ENA injection signatures form near magnetic longitudes associated with magnetotail thinning.