Comparing Jupiter’s Equatorial X‐Ray Emissions With Solar X‐Ray Flux Over 19 Years of the Chandra Mission

Abstract

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.

Long Exposure Chandra X‐Ray Observation of Jupiter's Auroral Emissions During Juno Plasmasheet Encounters in September 2021

“…A detailed description of the methods for photon selection, pulse‐invariant filtering, and correction of mapping to account for Jupiter as an oblate spheroid are described in detail in McEntee et al. (2022). The mapping algorithm assumes that the full width at half maximum (FWHM) of the HRC‐I PSF is 0.8 arcsec, with an assumed PSF of 25 arcsec.…”

“…Figures S4-S13 in Supporting Information S1 present the outputs of the Rayleigh test in the same manner as shown in Figure 3, for each of the remaining time intervals listed in Table 1. Analysis was also conducted on the southern envelope (SE) emissions, which are visible in the CML range 270-165° (Jackman et al, 2018), and have SIII lat < −55° (McEntee et al, 2022). No statistically significant QPPs were found in any of the SE viewings.…”

“…These observations have revealed distinct X‐ray emissions from Jupiter's equatorial disk region and polar auroral regions. The disk emission results from elastic and fluorescent scattering of solar X‐ray photons in Jupiter's upper atmosphere, meaning that this emission is largely governed by solar activity (Bhardwaj et al., 2005, 2006; Branduardi‐Raymont et al., 2007, 2010; Cravens et al., 2006; Dunn, Branduardi‐Raymont, et al., 2020; Elsner et al., 2005a, 2005b; McEntee et al., 2022; Wibisono et al., 2023). Jupiter's auroral emissions can be further split into two components: hard X‐rays (HXRs, photons energy >2 keV) and soft X‐rays (SXRs, photon energy <2 keV).…”

Identifying the Variety of Jovian X‐Ray Auroral Structures: Tying the Morphology of X‐Ray Emissions to Associated Magnetospheric Dynamics

“…Using this new distribution, known as the Pulse Invariant (PI) distribution, we select the PI channel range where the source signal dominates the background and remove any other instrumental effects (e.g., potential build-up of instrumental noise). Using the fact that Jupiter occults any X-rays that may be behind it and the position of the planet on the detector, we can select the planet-sized region such that much of the remaining background is removed and that we only analyze Jovian photons (McEntee et al, 2022;Weigt et al, 2022). Here our focus is on the brightest and most concentrated X-ray northern auroral emissions, located using the Weigt et al (2020) numerical criterion of >7 photons per 5° SIII longitude × 5° latitude over ∼10 hr (the average duration of the observations of the catalog, around a Jovian rotation).…”

“…These observations include those taken during Juno's approach to Jupiter (in the solar wind), while Juno was at apojove (near the dawn magnetopause), during several perijoves and intervals when Juno was inside and crossed the Jovian plasmasheet. We then correct the Chandra observations using the updated mapping algorithm (assuming the altitude of X-ray emissions is 400 km above the 1-bar atmosphere) described in McEntee et al (2022), to account for the decreasing HRC gain and instrument degradation over time. This consists of applying a multiplicative gain correction factor to the X-ray signal to convert the distribution as if it were unaffected by these issues (i.e., correct the distribution as if it were observed in the year 2000, when the gain was stable).…”