Tomer et al.

processes and external solar wind activities (Clarke et al. 2002; Yoshikawa et al. 2014).

While the solar irradiation of the upper Jovian atmosphere causes primary UV emission, X-ray aurorae, on the other hand, provide complex diagnostics by probing the composition of the magnetospheric plasma and its coupling to the solar wind.

Theoretical studies over the past decades have established that Jovian X-ray emission originates from multiple physical mechanisms operating in both the auroral and low-latitude atmosphere.

For example, X-ray emissions originating from equatorial/disk region are largely controlled by scattering and fluorescence of solar X-rays (Cravens et al. 2006; Bhardwaj et al. 2005; McEntee et al. 2022; Wibisono et al. 2023).

Early models by Cravens et al. (1995) demonstrated that energetic precipitation of highly ionised oxygen and sulfur ions from the magnetosphere into the polar atmosphere can produce soft X-ray aurorae through charge exchange, electron capture, and subsequent line emission.

Later work by Cravens et al. (2003) further connected these auroral X-rays to magnetosphere-ionosphere coupling processes, including field-aligned acceleration, plasma transport, and reconnection-driven particle injections.

In contrast, non-auroral disk X-rays are understood to arise mainly from scattering and fluorescence of incident solar X-rays in Jupiter’s upper atmosphere, as modelled by Cravens et al. (2006), explaining the observed correlation between disk X-ray brightness and solar activity.

More recently, Ozak, Cravens, & Schultz (2013) developed detailed auroral ion precipitation models for Jupiter and predicted characteristic X-ray signatures expected from precipitating heavy ions observed by JUNO, reinforcing the view that Jovian auroral X-rays are primarily controlled by magnetospheric ion dynamics rather than direct solar forcing.

Jupiter’s X-ray emissions were first detected with the Einstein Observatory (Metzger et al. 1983) and subsequently investigated in greater detail with ROSAT, Chandra and XMM-Newton revealing their spatial, spectral, and temporal properties (Waite et al. 1994; Gladstone, Waite, & Lewis 1998; Gladstone et al. 2002; Branduardi-Raymont et al. 2004; Elsner et al. 2005; Bhardwaj et al. 2006; Branduardi-Raymont et al. 2007, 2008; Dunn et al. 2020a; Jackman et al. 2018).

Auroral X-rays are spatially concentrated in the polar zones and are spectrally complex: the soft X-ray band (<2 keV) is dominated by line emission produced by charge exchange of highly charged heavy ions (notably Ovii/Oviii features in the ∼0.5–0.8 keV range and putative S/C features at ∼0.25–0.35 keV), while emission above 2 keV is primarily a continuum from energeticelectron bremsstrahlung (Elsner et al. 2005; Branduardi-Raymont et al. 2007, 2008; Mori et al. 2022).

Reviews and targeted campaigns (e.g., Bhardwaj & Gladstone 2000; Branduardi-Raymont et al. 2004, 2007) emphasise that while solar-wind compressions can trigger enhancements, internal drivers-particularly ion mass loading from Io and magnetospheric injections play a major role in powering auroral Xrays (Wibisono et al. 2020).

Observationally, the northern auroral region often exhibits stronger and more persistent X-ray hot spots (e.g., the pulsating northern hot spot discovered by Chandra (Gladstone et al. 2002), a dominance linked to asymmetric magnetospheric topology and the preferential mapping of certain field-aligned current systems into
the northern polar cap (Gladstone et al. 2002; Elsner et al. 2005).

Missions such as IUE, HST, and Hisaki have each provided valuable insights into energetic activities of the Jovian surface and poles.

For example, Dunn et al. (2022) analysed 14 simultaneous Chandra and HST observations of Jupiter’s northern aurora (2016-2019) and found that the dark polar region (DPR), already known to be UV-faint, also produces almost no intrinsic X-ray emission.

X-ray observations with Chandra and XMM-Newton have revealed rich auroral dynamics, pulsations (Dunn et al. 2016), and ion line features, but analyses have typically focused on individual observing windows or coordinated campaigns.