Jupiter's auroral X-rays have been observed for 40 years with an unknown driver producing quasiperiodic emission, concentrated into auroral hot spots. In this study we analyze an ∼ 10-hr Chandra observation from 18:56 on 18 June 2017. We use a new Python pipeline to analyze the auroral morphology, perform timing analysis by incorporating Rayleigh testing, and use in situ Juno observations to infer the magnetosphere that was compressed during the Chandra interval. During this time Juno was near its apojove position of ∼112 R J , on the dawn flank of the magnetosphere near the nominal magnetopause position. We present new dynamical polar plots showing an extended X-ray hot spot in the northern auroral region traversing across the Jovian disk. From this morphology, we propose setting a numerical threshold of >7 photons per 5 • System III longitude × 5 • latitude to define a photon concentration of the northern hot spot region. Our timing analysis finds two significant quasiperiodic oscillations (QPOs) of ∼37 and ∼26 min within the extended northern hot spot. No statistically significant QPOs were found in the southern X-ray auroral emission. The Rayleigh test is combined with Monte Carlo simulation to find the statistical significance of any QPOs found. We use a flux equivalence mapping model to trace the possible origin of the QPOs, and thus the driver, to the dayside magnetopause boundary.
We report the temporal and spectral results of the first XMM-Newton observation of Jupiter's X-ray auroras during a clear magnetospheric compression event on June 2017 as confirmed by data from the Jovian Auroral Distributions Experiment (JADE) instrument onboard Juno. The northern and southern auroras were visible twice and thrice respectively as they rotated in and out of view during the ∼23-hr (almost 2.5 Jupiter rotations) long XMM-Newton Jovian-observing campaign. Previous auroral observations by Chandra and XMM-Newton have shown that the X-ray auroras sometimes pulse with a regular period. We applied wavelet and fast Fourier transforms (FFTs) on the auroral light curves to show that, following the compression event, the X-ray auroras exhibited a recurring 23-to 27-min periodicity that lasted over 12.5 hr (longer than a Jupiter rotation). This periodicity was observed from both the northern and southern auroras, suggesting that the emission from both poles was caused by a shared driver. The soft X-ray component of the auroras is due to charge exchange processes between precipitating ions and neutrals in Jupiter's atmosphere. We utilized the Atomic Charge Exchange (ACX) spectral package to produce solar wind and iogenic plasma models to fit the auroral spectra in order to identify the origins of these ions. For this observation, the iogenic model gave the best fit, which suggests that the precipitating ions are from iogenic plasma in Jupiter's magnetosphere. Plain Language SummaryThe solar wind is a continuous stream of charged particles released by the Sun that flows out toward the edge of the Solar System. It meets obstacles along the way, such as the magnetic fields of planets like the Earth to create a magnetic bubble around them called a magnetosphere. The magnetosphere prevents most of these charged particles from reaching the Earth's atmosphere. Those that make their way through interact with the gas molecules in the atmosphere above the polar regions and cause them to glow to produce the auroras or the northern and southern lights. Jupiter's auroras are much more powerful than the Earth's, and they emit different types of radiation, including X-rays. It is currently unclear as to what causes Jupiter's X-ray auroras. Its moon, Io, spews volcanic material into the magnetosphere that can be accelerated into the planet's atmosphere. We created models that consisted of the particles found in the solar wind and in the material from Io's volcanoes to see which one was responsible for Jupiter's X-ray auroras. In this case, it was Io's volcanoes. We also found that the auroras pulsate every ∼23-27 min in the north and ∼23-33 min in the south.
To help understand and determine the driver of jovian auroral X‐rays, we present the first statistical study to focus on the morphology and dynamics of the jovian northern hot spot (NHS) using Chandra data. The catalog we explore dates from December 18, 2000 up to and including September 8, 2019. Using a numerical criterion, we characterize the typical and extreme behavior of the concentrated NHS emissions across the catalog. The mean power of the NHS is found to be 1.91 GW with a maximum brightness of 2.02 Rayleighs (R), representing by far the brightest parts of the jovian X‐ray spectrum. We report a statistically significant region of emissions at the NHS center which is always present, the averaged hot spot nucleus (AHSNuc), with mean power of 0.57 GW and inferred average brightness of ∼1.2 R. We use a flux equivalence mapping model to link this distinct region of X‐ray output to a likely source location and find that the majority of mappable NHS photons emanate from the pre‐dusk to pre‐midnight sector, coincident with the dusk flank boundary. A smaller cluster maps to the noon magnetopause boundary, dominated by the AHSNuc, suggesting that there may be multiple drivers of X‐ray emissions. On application of timing analysis techniques (Rayleigh, Monte Carlo, Jackknife), we identify several instances of statistically significant quasi‐periodic oscillations (QPOs) in the NHS photons ranging from ∼2.3 to 36.4 min, suggesting possible links with ultra‐low frequency activity on the magnetopause boundary (e.g., dayside reconnection, Kelvin‐Helmholtz instabilities).
<p>During its 53-day polar orbit around Jupiter, Juno often crosses the boundaries of the Jovian magnetosphere, namely the magnetopause and bow shock, as well as the plasma disc (located at the centrifugal equator). The positions of the magnetopause and bow shock allow us to determine the dynamic pressure of the solar wind (using both the updated model of Joy et al. 2002 by Ranquist et al., 2020 and/or in situ data) which allows us to infer magnetospheric compression or relaxation, while the observations of plasma disc perturbations allows us to infer magnetospheric reconfigurations.</p> <p>The aim of this study is to examine Jovian radio emissions during magnetospheric perturbations. We then use our analysis to determine the relationship between the solar wind and Jovian radio emissions (observed and emitted from different regions of the magnetosphere, from different mechanisms, and at different wavelengths from kilometers to decameters).</p> <p>In this presentation, we show case studies for each typical case (bow shock, magnetopause and plasma disk crossings) and show that the activation of new radio sources is related to magnetospheric disturbances. By performing a statistical study of these crossings, we hope to be able to show the relationship between the activation of new radio sources (emission intensity and extension, source positions) and the solar wind (dynamic pressure, magnetic intensity, ...), with the aim of being able to use observations of planetary radio emission as a proxy for the solar wind.</p>
We present a statistical study of Jupiter’s disk X‐ray emissions using 19 years of Chandra X‐Ray Observatory (CXO) observations. Previous work has suggested that these emissions are consistent with solar X‐rays elastically scattered from Jupiter’s upper atmosphere. We showcase a new pulse invariant (PI) filtering method that minimizes instrumental effects which may produce unphysical trends in photon counts across the nearly two‐decade span of the observations. We compare the CXO results with solar X‐ray flux data from the Geostationary Operational Environmental Satellites X‐ray Sensor for the wavelength band 1–8 Å (long channel), to quantify the correlation between solar activity and Jovian disk counts. We find a statistically significant Pearson’s Correlation Coefficient of 0.9, which confirms that emitted Jovian disk X‐rays are predominantly governed by solar activity. We also utilize the high spatial resolution of the High Resolution Camera Instrument on‐board the CXO to map the disk photons to their positions on Jupiter’s surface. Voronoi tessellation diagrams were constructed with the Juno Reference Model through Perijove 9 internal field model overlaid to identify any spatial preference of equatorial photons. After accounting for area and scattering across the curved surface of the planet, we find a preference of Jovian disk emission at 2–3.5 Gauss surface magnetic field strength. This suggests that a portion of the disk X‐rays may be linked to processes other than solar scattering: the spatial preference associated with magnetic field strength may imply increased precipitation from the radiation belts, as previously postulated.
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