Hot Plasma Research Articles

Short-term anticorrelations between in situ averaged charge states of Fe and O in the solar wind

Observations of the Fe and O charge states in the solar wind and interplanetary coronal mass ejections (ICMEs) generally exhibit a positive correlation between the average charge states of Fe and O ($ avQ Fe $ and $ avQ O $). Because Fe and O charge states freeze at different heights in the corona, this positive correlation indicates that conditions at different heights in the corona vary as a whole. We identify short time periods in the solar wind that exhibit anticorrelations between the average Fe and O charge states and investigate their properties. We aim to distinguish whether these anticorrelations are due to the related solar sources or to transport effects (e.g., differential streaming). We study kinetic properties of the solar wind related to these anticorrelated structures as well as heavy ion differential streaming in order to infer a possible relationship between conditions in coronal source regions and the reported in situ measurements. We employed a recently developed sliding-window cross-correlation method to locate anticorrelated structures in the solar wind composition measurements between 2001 and 2010 from the Advanced Composition Explorer (ACE). To account for fluctuations and measurement uncertainties, we varied the timescales and temporal lags. We determined the onset and end times of the gradual increases or decreases in the average charge states of O and Fe and analyzed the kinetic and plasma properties of the anticorrelated structures. We identified 103 anticorrelated structures both in the solar wind and in ICMEs. The behavior of $ avQ Fe $ is strongly related to solar wind kinetic properties, including proton speed, proton temperature, and the proton-proton collisional age. We find that the anticorrelation of $ avQ Fe $ and $ avQ O $ during these time periods cannot be explained by differential streaming nor by unrecorded hot plasma ejections. Thus, the measured anticorrelated variations in $ avQ Fe $ and $ avQ O $ probably indicate that changes in coronal conditions at different freeze-in heights may follow opposite monotonic trends.

New purely damped pairs of quasinormal modes in a hot and dense strongly-coupled plasma

Abstract Perturbed black holes exhibit damped oscillations whose eigenfrequencies define their quasinormal modes (QNMs). In the case of asymptotically Anti-de Sitter (AdS) black holes, the spectra of QNMs are related to the near-equilibrium behavior of specific strongly interacting quantum field theories via the holographic gauge-gravity duality. In the present work, we numerically obtain the spectra of homogeneous non-hydrodynamic QNMs of a top-down holographic construction called the 2 R-Charge Black Hole (2RCBH) model, which describes a hot and dense strongly-coupled plasma. The main result is the discovery of a new structure of pairs of purely imaginary QNMs. Those new purely damped QNMs dominate the late time equilibration of the strongly-coupled plasma at large values of the chemical potential, while at lower values the fundamental QNMs are instead ordinary poles with imaginary and real parts describing oscillatory decaying perturbations. We also observe a new phenomenon of asymptotic pole fusion for different pairs of purely imaginary QNMs at asymptotically large values of the chemical potential. This phenomenon corresponds to the asymptotic merging of the two poles within each pair of purely imaginary QNMs, with the different pairs of merged poles being evenly spaced by a constant value of 4π in all the different perturbation channels associated to different irreducible representations of the spatial SO(3) rotation symmetry of the medium. In particular, this indicates that characteristic equilibration times for the plasma develop upper bounds that cannot be surpassed by further doping the medium with increasing values of the chemical potential.

Electrical conductivity of hot relativistic plasma in a strong magnetic field

We employ first-principles quantum field theoretical methods to investigate the longitudinal and transverse electrical conductivities of a strongly magnetized hot quantum electrodynamics (QED) plasma at the leading order in coupling. The analysis employs the fermion damping rate in the Landau-level representation, calculated with full kinematics and exact amplitudes of one-to-two and two-to-one QED processes. In the relativistic regime, both conductivities exhibit an approximate scaling behavior described by σ∥,⊥=Tσ˜∥,⊥, where σ˜∥,⊥ are functions of the dimensionless ratio |eB|/T2 (with T denoting temperature and B magnetic field strength). We argue that the mechanisms for the transverse and longitudinal conductivities differ significantly, leading to a strong suppression of the former in comparison to the latter. Published by the American Physical Society 2024

Heterogeneous Online Computational Platform for GEM-Based Plasma Impurity Monitoring Systems

The fusion energy research field presents many intricate challenges that require resolution. Many diagnostic systems employed in experiments are approaching the limits of current technology. Implementing efficient measurements requires using an appropriate set of tools to facilitate the optimal utilization of hardware. Fusion energy measurements must provide low latency processing with the capacity for future improvements and the ability to handle complex data flows efficiently. The presented work addresses these requirements and describes the implementation of a high-performance, low-latency software platform with convenient development for soft X-ray (SXR) plasma impurities emission tracing—the Asynchronous Complex Computation Platform (AC2P). This article presents the architectural design, implementation details, and performance and latency measurements based on the raw data acquired from the WEST tokamak and laboratory tests. AC2P provides the tools to develop low-latency, multi-core, multi-device complex data flow graph scale-up solutions for measuring impurities in hot plasmas. The system has been designed to operate online during experiments, calculate the energy distribution, position and occurrence time of SXR photons, monitor the data stream’s quality and archive any abnormalities for subsequent offline verification and algorithm improvement. This article presents AC2P, which operates as part of the SXR measurement system on the WEST tokamak.

The baryon census and the mass-density of stars, neutral gas, and hot gas as a function of halo mass

Abstract We study the stellar, neutral gas content within halos over a halo mass range 1010to1015.5M⊙ and hot X-ray gas content over a halo mass range 1012.8to1015.5M⊙ in the local universe. We combine various empirical datasets of stellar, H i and X-ray observations of galaxies, groups and clusters to establish fundamental baryonic mass vs halo mass scaling relations. These scaling relations are combined with halo mass function to obtain the baryon densities of stars, neutral gas and hot gas (T > 106K), as a function of halo mass. We calculate the contributions of the individual baryonic components to the cosmic baryon fraction. Cosmic stellar mass density ($\Omega _\text{star}=2.09^{+0.21}_{-0.18} \times 10^{-3}$), cosmic H i mass density ($\Omega _\rm{H\,{\small I}}=0.49^{+0.25}_{-0.12} \times 10^{-3}$) and cosmic neutral gas mass density ($\Omega _\text{neutral gas}=0.71^{+0.39}_{-0.18} \times 10^{-3}$) estimates are consistent with previous more direct method measurements of these values, thereby establishing the veracity of our method. We also give an estimate of the cosmic hot plasma density ($\Omega _\text{hot gas}=2.58^{+2.1}_{-0.66} \times 10^{-3}$).

NGC 7314: X-Ray Study of the Evolving Accretion Properties

We present a comprehensive analysis of the timing and spectral properties of NGC 7314, a Seyfert 1.9 galaxy, using X-ray observations from XMM-Newton, NuSTAR, and RXTE/proportional counter array (PCA). The timing analysis reveals significant variability across different energy bands, with fractional variability values consistent with previous studies. The highly variable soft photons and comparatively less variable high-energy photons imply different origins of these two types. The soft energy photons come from a hot corona near the center, while the high-energy photons are produced by inverse Compton scattering of these primary X-ray photons in a hot plasma away from the central region. The spectral analysis employs various models to characterize the emission components. The results indicate the presence of a soft energy bump, Fe Kα line emission, and a prominent reflection component. The long-term RXTE/PCA data analysis reveals temporal variations in the photon index (Γ) and power-law flux, suggesting evolving emission properties over time. The signature of both broad and narrow Fe Kα emission line features suggested the broad, variable one coming from the accretion disk (∼10−5 pc), while the nonevolving narrow line cannot be well constrained. The absorption feature could originate in a highly ionized region, possibly closer to the broad-line region. The evolution of the inner accretion properties indicates that NGC 7314 could be a potential changing-state active galactic nucleus.

The Influence of the Inner Magnetospheric Electric Field on Plasma Sheet Access

AbstractThis study presents observations of the large‐scale electric field and H+ fluxes over the entire Van Allen Probes mission duration. These observations are used to determine the spatial distributions of the azimuthal component of the ExB drift velocity and the plasma sheet H+ pressure, and their geomagnetic activity dependence. To investigate the influence of the inner magnetospheric electric field on H+ plasma sheet access, the boundary of zero azimuthal ExB drift velocity (BZEB) is identified as a proxy of the inner extent of the convection electric field and its characteristics are compared with that of the inner edge of the H+ plasma sheet (H+ IEPS). We find that the large‐scale convection electric field has a dominant role on H+ plasma sheet access. This is evidenced by the good correlation between the BZEB and the H+ IEPS. Both boundaries present overall deeper access with increasing Kp. Moreover, both boundaries exhibit a similar deeper access on the evening sector compared to the afternoon sector, and both boundaries are more closely collocated in L for moderate and high Kp, while for low Kp the H+ IEPS is located at lower L than the BZEB. Furthermore, the collocation of both boundaries in L is better in the evening sector than in the afternoon sector, where the H+ IEPS lies farther inward in the afternoon sector for all Kp levels. This implies that the afternoon sector is the preferred region of the overlap between the hot ion plasma sheet and the cold plasmasphere.

Statistical Properties of Quasi‐Periodic Electromagnetic Ion Cyclotron Waves: ULF Modulation Effects

AbstractElectromagnetic ion cyclotron (EMIC) waves effectively scatter relativistic electrons in Earth's radiation belts and energetic ions in the ring current. Empirical models parameterizing the EMIC wave characteristics are important elements of inner magnetosphere simulations. Two main EMIC wave populations included in such simulations are the population generated by plasma sheet injections and another population generated by magnetospheric compression due to the solar wind. In this study, we investigate a third class of EMIC waves, generated by hot plasma sheet ions modulated by compressional ultra‐low frequency (ULF) waves. Such ULF‐modulated EMIC waves are mostly observed on the dayside, between magnetopause and the outer radiation belt edge. We show that ULF‐modulated EMIC waves are weakly oblique (with a wave normal angle ) and narrow‐banded (with a spectral width of of the mean frequency). We construct an empirical model of the EMIC wave characteristics as a function of ‐shell and MLT. The low ratio of electron plasma frequency to electron gyrofrequency around the EMIC wave generation region does not allow these waves to scatter energetic electrons. However, these waves provide very effective (comparable to strong diffusion) quasi‐periodic precipitation of plasma sheet protons.

Spatially resolved plasma composition evolution in a solar flare – The effect of reconnection outflow

Context. Solar flares exhibit complex variations in elemental abundances compared to photospheric values. These abundance variations, characterized by the first ionization potential (FIP) bias, remain challenging to interpret. Aims. We aim to (1) examine the spatial and temporal evolution of coronal abundances in the X8.2 flare on 2017 September 10, and (2) provide a new scenario to interpret the often observed high FIP bias loop top, and provide further insight into differences between spatially resolved and Sun-as-a-star flare composition measurements. Methods. We analyzed 12 Hinode/Extreme-ultraviolet Imaging Spectrometer (EIS) raster scans spanning 3.5 hours, employing both Ca XIV 193.87 Å/Ar XIV 194.40 Å and Fe XVI 262.98 Å/S XIII 256.69 Å composition diagnostics to derive FIP bias values. We used the Markov Chain Monte Carlo (MCMC) differential emission measure (DEM) method to obtain the distribution of plasma temperatures, which forms the basis for the FIP bias calculations. Results. Both the Ca/Ar and Fe/S composition diagnostics consistently show that flare loop tops maintain high FIP bias values of > 2–6, with peak phase values exceeding 4, over the extended duration, while footpoints exhibit photospheric FIP bias of ∼1. The consistency between these two diagnostics forms the basis for our interpretation of the abundance variations. Conclusions. We propose that this variation arises from a combination of two distinct processes: high FIP bias plasma downflows from the plasma sheet confined to loop tops, and chromospheric evaporation filling the loop footpoints with low FIP bias plasma. Mixing between these two sources produces the observed gradient. Our observations show that the localized high FIP bias signature at loop tops is likely diluted by the bright footpoint emission in spatially averaged measurements. The spatially resolved spectroscopic observations enabled by EIS prove critical for revealing this complex abundance variation in loops. Furthermore, our observations show clear evidence that the origin of hot flare plasma in flaring loops consists of a combination of both directly heated plasma in the corona and from ablated chromospheric material; and our results provide valuable insights into the formation and composition of loop top brightenings, also known as EUV knots, which are a common feature at the tops of flare loops.

Study of the excitation of large-amplitude oscillations in a prominence by nearby flares

Large-amplitude oscillations are a common occurrence in solar prominences. These oscillations are triggered by energetic phenomena such as jets and flares. On March 14-15, 2015, a filament partially erupted in two stages, leading to oscillations in different parts of it. In this study, we aim to explore the longitudinal oscillations resulting from the eruption, with special focus on unravelling the underlying mechanisms responsible for their initiation. We pay special attention to the huge oscillation on March 15. The oscillations and jets were analysed using the time-distance technique. For the study of flares and their interaction with the filament, we analysed the different AIA channels in detail and used the differential-emission-measure (DEM) technique. In the initial phase of the event, a jet induces the fragmentation of the filament, which causes it to split into two segments. One of the segments remains in the same position, while the other is detached and moves to a different location. This causes oscillations in both segments: (a) the change of position apparently causes the detached segment to oscillate longitudinally with a period of periodlalofirstphaseDF ; (b) the jet flows reach the remaining filament also producing longitudinal oscillations with a period of periodlalofirstphaseRF . In the second phase, on March 15 another jet seemingly activates the detached filament eruption. After the eruption, there is an associated flare. A large longitudinal oscillation is produced in the remnant segment with a period of periodlalosecondphase and a velocity amplitude of velocitylalosecondphase . During the triggering of the oscillation, bright field lines connect the flare with the filament. These only appear in the AIA 131 and 94 channels, indicating that they contain very hot plasma. The DEM analysis also confirms this result. Both indicate that a plasma of around 10 MK pushes the prominence from its south-eastern side, displacing it along the field lines and initiating the oscillation. From this evidence, the flare and not the preceding jet initiates the oscillation. The hot plasma from the flare escapes and flows into the filament channel structure. In this paper, we shed light on how flares can initiate the huge oscillations in filaments. We propose an explanation in which part of the post-flare loops reconnect with the filament channel's magnetic-field lines that host the prominence.

Analysis and implementation of the equivalent load circuit for switching performance of hot cathode plasma switch developed

Analysis and implementation of the equivalent load circuit for switching performance of hot cathode plasma switch developed

Impact of hot plasma effects on electron cyclotron current drive in tokamak plasmas

Abstract Focusing on the impact of hot plasma effects on electron cyclotron current drive (ECCD), this paper presents the numerical results of top launch ECCD (TL-ECCD) and outside midplane or equatorial-plane launch ECCD (EL-ECCD) in the HL-3-like tokamak plasmas. For EL-ECCD, there is little difference in the calculated results under the cold and hot plasma propagation models, and the results are not affected by the dominant current drive mechanism of EC waves. In the cases of TL-ECCD, the large initial parallel refraction makes the influence of hot plasma effects on ECCD become significant. In the range of toroidal magnetic fields BT discussed in this paper, the difference between the calculated results under the two propagation models rapidly decreases as the value of BT decreases, and the difference between the two is already very small in the range of 1.8 T ≤ BT ≤ 2.0 T. Therefore, the influence of hot plasma effects can also be neglected for TL-ECCD, and the cold plasma propagation model can be directly adopted. For the HL-3-like tokamak equipped with a dual-frequency EC wave system at 140 GHz and 105 GHz, if the addition of a TL-ECCD is considered in the existing outside midplane and upper launch manners, through appropriate combination of 140 GHz TL-ECCD and dual-frequency outside EL-ECCD, the ECCD can be used in a larger BT window (1.8 T ≤ BT ≤ 2.25 T) and a wider radial range (0.1 ≤ ρ ≤ 0.8 ~ 0.9) to generate current efficiently. The normalized current drive efficiency of the TL-ECCD is nonlinear with the injected EC power, it reaches the maximum at the injected power of 6 ~ 8 MW. This is of significance for the stable operation of HL-3-like tokamak with high plasma current above 1 MA.

Study in the Extreme UV Range of the Spectral Transmission of Nickel Plasma Created under the Effect of an X-Ray Pulse of the Z-Pinch

Spectral properties of the high-temperature plasma obtained by exposing a nickel layer to a source of high-power X-ray radiation (a power of 6–10 TW with a duration of 7–10 ns) based on a Z-pinch, formed during implosion of tungsten multi-wire arrays at the Angara-5-1 facility, are studied. In this case, the Z-pinch radiation heats the target and turns it into the hot plasma, and the same radiation probes the target plasma to determine the spectral dependence of the transmission of this plasma. An original scheme is proposed for measuring the incident, transmitted and self-emission of a target simultaneously in one experiment in the frame mode using a grazing incidence diffraction spectrograph. Using laser shadow imaging, experimental data are obtained on the velocity of the plasma expansion on the irradiated and back sides of the target, which reached 100 km/s. Targets made of thin Ni layers deposited on a mylar film are studied. An irradiationinduced multiple increase in the transmission of the target plasma in the EUV range is observed compared to the transmittance of the target in the cold state. The dependence of the absorption spectrum of the plasma and the accompanying self-radiation of the target on the power and shape of the heating pulse is studied. The measurement results are compared with numerical calculations performed using the RALEF-2D two-dimensional radiation code, which has been repeatedly used previously to simulate similar experiments. The shape of the spectral dependence of the transmission in the experiment and calculation is similar in the range of ∼30–200 Å, but the model plasma transmission (∼0.8–0.9) is higher than that obtained using a spectrograph and X-ray multi-frame photography (∼0.5–0.6).

The SRG/eROSITA diffuse soft X-ray background

Context. The SRG/eROSITA All-Sky Surveys (eRASSs) combine the advantages of complete sky coverage and the energy resolution provided by the charge couple device and offer the most holistic and detailed view of the diffuse soft X-ray background (SXRB) to date. The first eRASS (eRASSl) was completed at solar minimum, when solar wind charge exchange emission was minimal, providing the clearest view of the SXRB. Aims. We aim to extract spatial and spectral information from each constituent of the SXRB in the western Galactic hemisphere, focusing on the local hot bubble (LHB). Methods. We extracted and analysed eRASSl spectra from almost all directions in the western Galactic hemisphere by dividing the sky into equal signal-to-noise bins. We fitted all bins with fixed spectral templates of known background constituents. Results. We find the temperature of the LHB exhibits a north-south dichotomy at high latitudes (|b| > 30°), with the south being hotter, with a mean temperature at kT = 121.8 ± 0.6 eV and the north at kT = 100.8 ± 0.5 eV. At low latitudes, the LHB temperature increases towards the Galactic plane, especially towards the inner Galaxy. The LHB emission measure (EMLHB) enhances approximately towards the Galactic poles. The EMLHB map shows clear anti-correlation with the local dust column density. In particular, we found tunnels of dust cavities filled with hot plasma, potentially forming a wider network of hot interstellar medium. We also constructed a three-dimensional LHB model from EMLHB, assuming constant density. The average thermal pressure of the LHB is Pthermal/k = 10100−1500+1200 cm−3 K, a lower value than typical supernova remnants and wind-blown bubbles. This could be an indication of the LHB being open towards high Galactic latitudes.

Characterizing the Magnetic and Plasma Environment Upstream of Ganymede

AbstractWe present an application of the latest UCL‐AGA magnetodisc model (MDISC) to the study of the magnetic and plasma conditions in the near‐Ganymede space. By doing this, we provide a comparison with measurements from Juno's most recent flyby of the Jovian moon, perijove 34 (PJ34). We find good agreement between the model results and the magnetometer data, pointing toward a hot plasma index value (2.7190.024)107 Pa m T−1 and an effective magnetodisc radius (79.51.1) Jupiter radii for the Jovian magnetosphere, for the duration of the trajectory, suggesting a configuration with middling levels of expansion. We also predict the plasma conditions observed by Juno during the same flight‐path, as well as the typical conditions over the orbit of Ganymede, with the magnetic and hot plasma pressures assuming dominant roles. Finally, these results are compared with functional fits of a compilation of Galileo flyby data obtained in the vicinity of Ganymede's orbit, suggesting Juno experienced somewhat similar conditions, despite a systematic overestimation in magnetic field intensity in the near‐Ganymede space.

In-situ relative calibration of Bragg crystals with Monte Carlo line ratio analysis.

X-ray line emission spectra can thoroughly characterize hot plasmas, especially when line shapes and ratios convey distinct aspects of plasma conditions. However, the high spectral resolution required for observing line shapes is often at odds with the large bandwidth required to observe many line ratios across a wide spectral range. One strategy to obtain high spectral resolution over a wide bandwidth is to use multiple crystals with calibrated reflectivity so that line intensities across different crystals can be compared. Here, we explore the use of a low-resolution, wide-bandwidth mica survey spectrometer to infer relative reflectivity of two high-resolution, narrow-bandwidth quartz crystals. A Monte Carlo error analysis determines comparable x-ray line ratios measured from both spectrometers, resulting in an in situ calibration factor and associated uncertainty for the relative reflectivity of the high-resolution crystals.

Ion Diffusive Transport Across the Separatrix Between the Low‐Latitude Mantle and the Plasma Sheet by Kinetic Alfvén Waves: MMS Observation

AbstractTo understand the entry of the cool low‐latitude mantle ions into the tail plasma sheet near the flanks under persistent interplanetary magnetic field By, we evaluate the role of the cross‐field diffusive transport by kinetic Alfvén waves (KAWs) by investigating two events observed by multiscale (MMS) spacecraft. Around the separatrix between the open and closed field‐line regions, a two‐component mixing of hot plasma sheet ions of a few keV with cool mantle ions of a few hundred eV was observed, indicating transport across the separatrix. The waves observed between 0.01 and 10 Hz around the separatrix had characteristics consistent with those of KAWs. The consistency allowed us to estimate the wave vectors as a function of frequency by fitting KAW dispersion to the observations. Using the observed wave powers, plasma moments, and the estimated wave vectors, we computed the cross‐field diffusion rates associated with KAWs. The diffusion rates were found to be comparable to or larger than the Bohm diffusion rates during the intervals when the two‐component mixing was observed, indicating that the KAW diffusive transport can play a role in the entry of low‐latitude mantle ions into the plasma sheet.

EWOCS-II: X-ray properties of the Wolf–Rayet stars in the young Galactic super star cluster Westerlund 1

Context. Wolf–Rayet (WR) stars are massive evolved stars that exhibit particularly fast and dense stellar winds. Although they constitute a very short phase near the end of a massive star’s life, they play a crucial role in the evolution of massive stars and have a substantial impact on their surrounding environment. Aims. We present the most comprehensive and deepest X-ray study to date of the properties of the richest Wolf–Rayet population observed in a single stellar cluster, Westerlund 1 (Wd1). By examining the X-ray signatures of WR stars, we aim to shed light on the hottest plasma in their stellar winds and gain insights into whether they exist as single stars or within binary systems. Methods. This work is based on 36 Chandra observations obtained from the “Extended Westerlund 1 and 2 Open Clusters Survey” (EWOCS) project, plus 8 archival Chandra observations. The overall exposure depth Ms) and baseline of the EWOCS observations extending over more than one year enable us to perform a detailed photometric, colour, and spectral analysis, as well as to search for short- and long-term periodicity. Results. In X-rays, we detect 20 out of the 24 known Wolf–Rayet stars in Wd1 down to an observed luminosity of ~7 × 1029 erg s−1 (assuming a distance of 4.23 kpc to Wd1), with 8 WR stars being detected in X-rays for the first time. Nine stars show clear evidence of variability over the year-long baseline, with clear signs of periodicity. The X-ray colours and spectral analysis reveal that the vast majority of the WR stars are hard X-ray sources (kT≥2.0 keV). The Fe XXV emission line at ~6.7 keV, which commonly originates from the wind–wind collision zone in binary systems, is detected for the first time in the spectra of 17 WR stars in Wd1. In addition the ~6.4 keV fluorescent line is observed in the spectra of three stars, which are among the very few massive stars exhibiting this line, indicating that dense cold material coexists with the hot gas in these systems. Overall, our X-ray results alone suggest a very high binary fraction (≥80%) for the WR star population in Wd1. When combining our results with properties of the WR population from other wavelengths, we estimate a binary fraction of ≥92%, which could even reach unity. This suggests that either all the most massive stars are found in binary systems within Wd1, or that binarity is essential for the formation of such a rich population of WR stars.

High-energy insights from an escaping coronal mass ejection with Solar Orbiter/STIX observations

Solar eruptive events, including solar flares and coronal mass ejections (CMEs), are typically characterised by energetically significant X-ray emissions from flare-accelerated electrons and hot thermal plasmas. However, the intense brightness of solar flares often overshadows high-coronal X-ray emissions from the associated eruptions due to the limited dynamic range of current instrumentation. Occulted events, where the main flare is blocked by the solar limb, provide an opportunity to observe and analyse the X-ray emissions specifically associated with CMEs. This study investigates the X-ray and extreme ultraviolet (EUV) emissions associated with a large filament eruption and CME that occurred on February 15, 2022. This event was highly occulted from the three vantage points of Solar Orbiter (sim 45$^ circ $ behind the limb), Solar–TErrestrial RElations Observatory (STEREO-A), and Earth. We utilised X-ray observations from the Spectrometer/Telescope for Imaging X-rays (STIX) and EUV observations from the Full Sun Imager (FSI) of the Extreme Ultraviolet Imager (EUI) on board Solar Orbiter, supplemented by multi-viewpoint observations from STEREO-A/Extreme-UltraViolet Imager (EUVI). This enabled a comprehensive analysis of the X-ray emissions in relation to the filament structure observed in the EUV. We used STIX's imaging and spectroscopy capabilities to characterise the X-ray source associated with the eruption. Our analysis reveals that the X-ray emissions associated with the occulted eruption originate from an altitude exceeding 0.3 \(R_ above the main flare site. The X-ray time profile shows a sharp increase and exponential decay, and consists of both a hot thermal component at 17pm 2 MK and non-thermal emissions ($>11.4 keV) characterised by an electron spectral index of 3.9pm 0.2. Imaging analysis shows an extended X-ray source that coincides with the EUV emission as observed from EUI, and was imaged until the source grew to a size exceeding the STIX imaging limit (180 arcsec). Filament eruptions and associated CMEs have hot and non-thermal components, and the associated X-ray emissions are energetically significant. Our findings demonstrate that STIX combined with EUI provides a unique and powerful tool for examining the energetic properties of the CME component of solar energetic eruptions. Multi-viewpoint and multi-instrument observations are crucial for revealing such energetically significant sources in solar eruptions that might otherwise remain obscured.

Microwave-Assisted Oxidation of N2 into NOx over a La-Ce-Mn-O Perovskite Yielding Plasmas in a Quartz Flow Reactor at Atmospheric Pressure

N2 oxidation to NOx is a challenging reaction, and alternative routes to the industrial Ostwald process are of interest. A perovskite under flowing O2-N2 mixtures at atmospheric pressure in a quartz tube reactor was irradiated by microwaves (MW), leading to the formation of hot spots and plasmas within the catalyst bed. NOx concentrations up to 2.5 vol.% in one pass were obtained at 600 W. Using a lower MW power of 100 W led to a pulsed mode yielding lower NOx concentrations and no noticeable damage to the quartz reactor. The formation of plasma was strongly dependent on the perovskite bed packing. The perovskite acted primarily as a susceptor and likely also as a catalyst, although the proportion of heterogeneous and homogenous reactions could not be determined in the present study. The simple reactor layout allowing operation at atmospheric pressure is promising for the development of practical MW-assisted N2 fixation technologies.