arXiv subjects

Hirohisa Hara

Publications and source records attributed to Hirohisa Hara.

At least 19 recordsLinked to original sources

arXiv2026

Cause of chromospheric opposite polarity intrusions discovered in Sunrise III/SCIP data: MURaM-ChE simulations point to twisted flux ropes

The Sunrise Chromospheric Infrared spectroPolarimeter (SCIP) instrument onboard the balloon-borne Sunrise III observatory provided new high-resolution observations of the solar chromosphere in the Ca II 854.2 nm line. The Stokes-V signal in magnetic network regions was found to show fine-structured details, which suggests the magnetic field above the network elements does not simply expand as a unipolar feature but displays opposite-polarity-intrusions (OPIs). These features appear as elongated structures in Stokes-V observations. In this work, we demonstrate that such features appear ubiquitously in a numerical simulation of the solar chromosphere. We use a simulation that is computed with the recently developed chromospheric extension of MURaM (MURaM-ChE) and resembles an enhanced network region. We find that OPIs appear ubiquitously in the vertical component of the magnetic field at around 1 Mm above the surface and are visible in the synthetic Stokes-V signal of the Ca II 854.2 nm line. The structures have lengths of 2 Mm to 7 Mm and widths of approximately 1 Mm. The magnetic field configurations associated with the OPI features appear to belong to twisted flux ropes (TFRs) and are visible for most of the time in the presented 21 min time series. Our results show that the magnetic structure of the chromosphere is more complex than previously thought, with even seemingly simple flux tubes showing embedded twisted fields pointing in the opposite direction. This may help in explaining new high-resolution observations from the Sunrise III mission.

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arXiv2026

Science operation, data handling, and ground support system of the SOLAR-C mission

SOLAR-C is an international solar-observing satellite mission led by Japan Aerospace Exploration Agency (JAXA). It aims to elucidate mass and energy transport in solar atmospheres through extreme ultraviolet (EUV) spectroscopy. The mission carries the EUV High-throughput Spectroscopic Telescope (EUVST) and the Solar Spectral Irradiance Monitor (SoSpIM), enabling comprehensive observations across a wide temperature range (10^4 K to 10^7 K) with minimum temperature gaps and high spatial and temporal resolution. To achieve its science objectives regarding atmospheric heating and solar flare eruptions, SOLAR-C implements a flexible and responsive operational procedure and a data processing system, while building on the heritage of the Hinode and IRIS satellites. The Chief Observer creates observation timelines that include core observation plans and approved proposed plans while taking into account the solar activity levels. A SpaceWire communication architecture is employed onboard the spacecraft, and a method is implemented in which the mission instrument temporarily acts as the network master during data transfer to support the high data rate requirements. Telemetry is downlinked at ground stations worldwide and gathered at the Institute of Space and Astronautical Science, JAXA. The EUVST data are calibrated at the SOLAR-C Science Center at Nagoya University, while the SoSpIM data are calibrated at the Processing and Archiving Facility before being integrated into the science data products. The data will be made publicly available immediately. The integrated operational scheme for this mission is expected to advance our understanding of solar atmospheric heating and flare processes.

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arXiv2026

High-order Paschen emission from the quiet-Sun off-limb chromosphere

We report the detection of high-order hydrogen Paschen emission lines (Pa~15, Pa~16, and Pa~17) in the quiet-Sun chromosphere off the solar limb using the Chromospheric Infrared SpectroPolarimeter (SCIP) on board the {\sc Sunrise~iii} balloon telescope. These lines reveal thread-like structures resembling spicules and exhibit systematically smaller Doppler velocities than Ca~II~854.2~nm, suggesting that they are optically thinner and more affected by line-of-sight averaging, especially near the limb. Non-LTE radiative transfer synthesis using the spherically symmetric one-dimensional code \texttt{rhsphere} reproduces the overall spectral properties. The observed ratios among three Paschen lines show systematic deviations from synthetic and theoretical results, suggesting that additional physical effects may influence the formation of high-order Paschen lines. The study demonstrates the potential of high-order Paschen lines as a new diagnostic of optically thin plasma in the off-limb chromosphere.

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arXiv2026

Magnetoacoustic Portals in Quiet-Sun Fluxtubes Revealed by Chromospheric Spectropolarimetry with SUNRISE III/SCIP

Acoustic waves propagate into the chromosphere, contributing to energy transport and their dynamics. Their upward propagation is restricted to frequencies above the acoustic cutoff frequency. The magnetic field configuration plays a key role in determining whether acoustic waves can propagate upward because the cutoff frequency is reduced in regions where the field is inclined with respect to gravity, forming so-called magnetoacoustic portals. Previous studies linked magnetic fields and oscillations in quiet regions, but these analyses were based on photospheric magnetic field information, leaving chromospheric structure unconstrained. This study investigates the coupling between acoustic waves and magnetic topology using photospheric and, for the first time, chromospheric spectropolarimetry in a quiet region, obtained with the Sunrise Chromospheric Infrared SpectroPolarimeter (SCIP) aboard the Sunrise iii balloon-borne solar observatory launched in 2024. The SCIP sit-and-stare observations sampled magnetic features in which the line-of-sight field strength exhibits multiple sharp spatial peaks in the photosphere while becoming broader and weaker at two heights in the chromosphere, indicating expanding fluxtubes. The chromospheric velocity field in these fluxtubes exhibits strong 5-minute oscillations, while the surrounding regions show weak 3-minute oscillations. In these fluxtubes, sawtooth temporal velocity variations are associated with intensity enhancements, suggesting steepened shocks. Fluxtubes with low-frequency oscillations are identified not only in network regions but also in weak internetwork regions. These results provide observational evidence that fluxtubes expanding into the chromosphere act as magnetoacoustic portals, in both network and internetwork regions, allowing low-frequency waves to propagate upward and driving chromospheric dynamics via shocks.

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arXiv2026

Chromospheric Dynamics of an Umbral Flare Kernel - Based on Coordinated SUNRISE III SCIP and Domeless Solar Telescope Observations

We report imaging spectroscopic observations of an M1.4 solar flare obtained during a coordinated observation between the infrared spectropolarimeter SCIP onboard the SUNRISE-III balloon mission and Domeless Solar Telescope (DST) at Hida Observatory, Kyoto University. The flare that occurred on 2024 July 13 in NOAA Active Region 13738 exhibited a compact flare kernel located within a sunspot umbra. SCIP performed rapid slit-scan observations over a field of view of 58" x 58" around the umbra with a cadence of 40 s, covering infrared chromospheric and upper-photospheric lines including Ca II 8498/8542 A and K I D1. At the same time, DST observed a wider surrounding region with a cadence of 25 s in H-alpha, Ca II 8542 A, and Na I D1/D2. Clear flare-related brightenings are detected in all chromospheric lines observed by SCIP and DST, while no significant enhancement is found in photospheric lines. The high spatial resolution of SCIP reveals fine substructures within the kernel on spatial scales of order 1000 km, which appear smeared in ground-based observations. The spectral profiles exhibit temporally and spatially varying Doppler shifts and line broadenings, indicating complex, fine-scale plasma motions in the chromosphere. These results suggest that the observed red asymmetry arises from the temporal succession of multiple fine-scale kernels, as revealed by SCIP, rather than from a single continuous process.

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arXiv2026

Horizontal Magnetic Fields Dominate the Quiet Sun Internetwork in Sunrise III Observations. Evidence from Traditional and Transformer-Based Inversions

The relative prevalence of horizontal and vertical magnetic fields in the quiet-Sun internetwork remains debated, owing to the weak linear polarisation signals that make the inferred magnetic inclination distributions sensitive to observational quality and inversion methodology. We investigate the magnetic topology of the quiet-Sun internetwork in {\sc Sunrise~iii} observations by independently applying transformer-based and traditional inversion techniques to the same spectropolarimetric dataset. We analyse observations obtained with the Sunrise Chromospheric Infrared spectroPolarimeter (SCIP). Transformer-based inversions (SINN), trained exclusively on synthetic Stokes profiles generated from a large radiative magnetohydrodynamic simulation, are compared with independent inversions performed using the \textsc{DeSIRe} code. Both inversion methods recover a quiet-Sun magnetic topology in which internetwork fields are strongly dominated by the horizontal component, whereas network fields exhibit a substantially more balanced topology. At $\logτ=-1.2$, the median horizontal and unsigned line-of-sight field components in the internetwork are 64 and 7G with \textsc{DeSIRe}, and 71 and 8G with SINN, respectively, corresponding to a horizontal-to-line-of-sight ratio of approximately nine for both methods. The agreement between the two fundamentally different inversion methodologies indicates that the quiet-Sun internetwork is characterised by a substantially stronger horizontal than vertical magnetic field component. These results demonstrate that transformer-based inversions can be successfully transferred from synthetic training data to real spectropolarimetric observations, while providing inference orders of magnitude faster than traditional inversion techniques.

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arXiv2026

Expanding magnetic canopy structure and parasitic polarities in a quiet-Sun network element observed by Sunrise III/SCIP

We present high-resolution multi-line spectropolarimetric observations of a quiet-Sun network element obtained with the {\sc Sunrise~iii} Chromospheric Infrared SpectroPolarimeter. The observations combine photospheric, upper-photospheric, and chromospheric diagnostics at a spatial resolution and polarimetric sensitivity that allow the transverse magnetic structure of the network boundary to be examined directly. We find that the strongest linear polarisation is concentrated in a narrow ridge around the edge of the magnetic element, co-spatial with enhanced transverse magnetic field inferred from multiline inversions. The magnetic azimuth exhibits a coherent, predominantly radial organisation around a more vertical core, consistent with an expanding magnetic canopy. An azimuth proxy derived directly from the observed Fe~\textsc{i} and K~\textsc{i} linear polarisation reproduces the same large-scale organisation, showing that this structure is encoded in the Stokes profiles rather than imposed by the inversion. Response functions and a MURaM-based forward-synthesis test indicate that the Fe~\textsc{i}~8468~Å linear polarisation is sensitive to magnetic azimuth in the upper photosphere, with the closest proxy agreement occurring near $\logτ\approx-3$. We find no evidence for strong azimuthal shear between the Fe- and K-sensitive diagnostics. At the network boundary, we also identify localised parasitic-polarity patches associated with complex, multi-lobed Stokes $V$ profiles, and one case in which the Stokes $V$ polarity reverses between photospheric Fe~\textsc{i} and chromospheric Ca~\textsc{ii} lines. These results demonstrate that quiet-Sun network boundaries contain organised upper-photospheric canopy fields together with small-scale mixed-polarity structure, providing new constraints on the three-dimensional magnetic structure of network elements.

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arXiv2026

Three-dimensional Magnetic Field Structure of a Quiet-Sun Region Revealed by Sunrise III/SCIP

The balloon-borne stratospheric solar observatory Sunrise III successfully completed 6.5 days of observations in July 2024. One of its focal-plane instruments, the Sunrise Chromospheric Infrared spectroPolarimeter (SCIP), is a slit-scanning spectropolarimeter that simultaneously measures full Stokes profiles of multiple spectral lines in the 850 nm and 770 nm bands. SCIP obtained an unprecedented data set of a quiet-sun region near disk center, covering a $58'' \times 58''$ field of view. With an integration time of 10 s per slit position, the scan was completed in 107 minutes without interruption, achieving remarkably stable polarimetric precision of 0.03-0.04% (1$σ$) of the continuum level. The multi-wavelength SCIP observations reveal that the chromospheric line-of-sight (LOS) magnetic field exhibits thread-like, elongated structures over the internetwork regions, with no obvious photospheric counterpart directly below. These threads are typically narrower than $1''$ and are embedded within the canopy fields extending from the network regions. Their LOS field strengths derived from the weak-field approximation are typically 10-20 G weaker than the surrounding canopy. In particularly clear cases, the magnetic polarity of the threads is opposite to that of the adjacent canopy. These findings suggest that the canopy field is not simply an expanding structure originating from network regions, but instead has a complex three-dimensional configuration containing numerous localized substructures. These observations provide new constraints on the quiet-sun magnetic topology from the photosphere to the chromosphere.

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arXiv2026

Three-dimensional Magnetic Structures of Ellerman Bombs revealed by SUNRISE III/SCIP

Ellerman bombs (EBs) are widely recognized as photospheric and chromospheric signatures of magnetic reconnection. However, the three-dimensional (3D) magnetic topology has remained elusive due to the lack of seamless height coverage in observations. Here, we present initial results from the SUNRISE III/SCIP (Sunrise Chromospheric Infrared spectroPolarimeter) observations of an emerging flux region. Exploiting the seeing-free, high-spatial-resolution observations provided by the 1-meter balloon-borne telescope, SCIP achieved seamless multi-line spectropolarimetry from the photosphere to the lower chromosphere. We analyzed the multi-line Stokes profiles of the photospheric Fe I and K I lines and the chromospheric Ca II lines, and applied the Weak Field Approximation to the K I and Ca II lines to reconstruct the 3D magnetic field structure. The blue- and red-wing brightenings of the Ca II 8542 Å line appear at spatially offset locations, indicating bi-directional reconnection flows. The reconstructed 3D magnetic field reveals that the opposite-polarity field structure reaches different heights in the two events analyzed. In one event, it is confined to the lower layers and is absent at the formation height of Ca II 8542 Å core, which shows no intensity enhancement, whereas in the other event it extends up to the Ca II 8542 Å core formation height, where enhanced line-core intensity is also observed. We interpret this as the reconnection current sheet reaching different altitudes. These results demonstrate that SCIP has successfully resolved the 3D structure of EBs, distinguishing magnetic reconnection events occurring at different atmospheric heights.

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arXiv2026

Pre-flare and active region plasma flows and structure seen by the short wavelength camera on SOLAR-C/EUVST

The mechanisms triggering solar flares and driving coronal heating occur across wide temperature ranges on small spatial scales and short timescales, making them difficult to observe with current instrumentation. The upcoming SOLAR-C mission, launching in the late 2020s, will provide unprecedented plasma diagnostic capability with its high-throughput extreme-ultraviolet (EUV) spectroscopic telescope (EUVST), capable of ~0.2 arcsec/pix spatial sampling (~0.4 arcsec resolution), continuous temperature coverage from 0.02-15 MK, and exposure times down to 0.5 seconds. We present forward modelling of the spectrograph's short wavelength camera (170-210 Å; SOLAR-C/EUVST-SW) and its response to log T~6.2 coronal plasma in a three-dimensional MHD-simulated pre-flare active region. We compare this performance to that of the previous-generation EUV Imaging Spectrometer (EIS) on Hinode (SOLAR-B). Our results demonstrate that SOLAR-C/EUVST can distinguish individual flux tubes in simulated active region loops which Hinode/EIS cannot resolve. In simulated pre-flare plasma, SOLAR-C/EUVST captures sharp velocity gradients between adjacent upflowing and downflowing plasma which Hinode/EIS is unable to resolve. Doppler velocity measurement accuracy will reach better than 1 km/s in active regions. We show that this next-generation spectrograph can be expected to directly observe processes potentially related to flare triggering, such as plasma flows from low-altitude reconnection linked to emerging flux, and determine whether active region loops consist of a small number of strands or the hundreds predicted by magnetic reconnection-induced nanoflare heating models.

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arXiv2026

Vector Magnetic Field associated with an Active Region Filament Observed by SUNRISE III/SCIP in the Ca II 8542 Å Line

We report high-spatial-resolution spectropolarimetric observations spatially associated with a solar filament, obtained with the SUNRISE Chromospheric Infrared spectro-Polarimeter (SCIP) onboard the SUNRISE III balloon-borne solar observatory on 15 July 2024. The observed filament was located near the solar disk center, adjacent to an active region, and remained quiescent for at least two hours during the observing period. SCIP recorded full Stokes profiles in the Ca II 8542 Å line, revealing clear signatures of linear polarization produced by the transverse Zeeman effect. The detected linear polarization signals within the filament region exceeded the 2$σ$ noise level and exhibited a characteristic Zeeman double-lobe spectral shape that distinguishes them from polarization due to scattering. The magnetic field strength derived using the weak field approximation is approximately -80 G along the line of sight and 300-500 G in the transverse direction. These values likely reflect the magnetic properties of the filament and its supporting chromospheric environment. The orientation of the magnetic field vector is nearly parallel to the filament axis in its northeastern portion, while the southeastern part of the filament extends outside the field of view. To our knowledge, this is the first unambiguous detection of linear polarization associated with a solar filament with the Ca II 8542 Å line. Our results open a new diagnostic window on the vector magnetic structure of solar filaments in the lower chromosphere, complementing existing He I based diagnostics that probe the upper chromosphere.

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arXiv2026

Sunrise III: Instrument, mission, data, and first results

Sunrise III is a stratospheric balloon-borne solar observatory with a 1-m diameter telescope and three post-focus instruments, along with an image stabilisation system, all within a protective gondola. It samples the lower solar atmosphere, from the solar surface to the middle chromosphere, at a resolution approaching 50~km on the Sun. Sunrise III flew successfully for 6.5 days suspended from a zero-pressure stratospheric balloon from northern Sweden to north-western Canada in July 2024, gathering around 200 TB of data. The present issue of ApJL focuses on the first scientific results from the data collected during that flight. This paper introduces this Focus Issue, providing a very brief overview of the capabilities of the instrumentation, the flight and of the gathered data. Challenges for the measurements, data reduction and interpretation are also briefly touched upon. The paper ends with an overview of the first set of science results obtained from these data, as presented in the current Focus Issue.

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arXiv2025

Sunrise III: Overview of Observatory and Instruments

In July 2024, Sunrise completed its third successful science flight. The Sunrise III observatory had been upgraded significantly after the two previous successful flights in 2009 and 2013. Three completely new instruments focus on the small-scale physical processes and their complex interaction from the deepest observable layers in the photosphere up to chromospheric heights. Previously poorly explored spectral regions and lines are exploited to paint a three-dimensional picture of the solar atmosphere with unprecedented completeness and level of detail. The full polarimetric information is captured by all three instruments to reveal the interaction between the magnetic fields and the hydrodynamic processes. Two slit-based spectropolarimeters, the Sunrise UV Spectropolarimeter and Imager (SUSI) and the Sunrise Chromospheric Infrared spectro-Polarimeter (SCIP), focus on the near-ultraviolet and the near-infrared regions respectively, and the imaging spectropolarimeter Tunable Magnetograph (TuMag) simultaneously obtains maps of the full field-of-view of $46 \times 46$ Mm$^2$ in the photosphere and the chromosphere in the visible. The instruments are operated in an orchestrated mode, benefiting from a new Image Stabilization and Light Distribution unit (ISLiD), with the Correlating Wavefront Sensor (CWS) providing the autofocus control and an image stability with a root-mean-square value smaller than 0.005''. A new gondola was constructed to significantly improve the telescope pointing stability, required to achieve uninterrupted observations over many hours. Sunrise III was launched successfully on July 10, 2024, from the Esrange Space Center near Kiruna (Sweden). It reached the landing site between the Mackenzie River and the Great Bear Lake in Canada after a flight duration of 6.5 days. In this paper, we give an overview of the Sunrise III observatory and its instruments.

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arXiv2022

Development of Fast and Precise Scan Mirror Mechanism for an Airborne Solar Telescope

We developed a scan mirror mechanism (SMM) that enable a slit-based spectrometer or spectropolarimeter to precisely and quickly map an astronomical object. The SMM, designed to be installed in the optical path preceding the entrance slit, tilts a folding mirror and then moves the reflected image laterally on the slit plane, thereby feeding a different one-dimensional image to be dispersed by the spectroscopic equipment. In general, the SMM is required to scan quickly and broadly while precisely placing the slit position across the field-of-view (FOV). These performances are highly in demand for near-future observations, such as studies on the magnetohydrodynamics of the photosphere and the chromosphere. Our SMM implements a closed-loop control system by installing electromagnetic actuators and gap-based capacitance sensors. Our optical test measurements confirmed that the SMM fulfils the following performance criteria: i) supreme scan-step uniformity (linearity of 0.08%) across the wide scan range (${\pm}$1005 arcsec), ii) high stability (3$σ$ = 0.1 arcsec), where the angles are expressed in mechanical angle, and iii) fast stepping speed (26 ms). The excellent capability of the SMM will be demonstrated soon in actual use by installing the mechanism for a near-infrared spectropolarimeter onboard the balloon-borne solar observatory for the third launch, Sunrise III.

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arXiv2021

Probing Upflowing Regions in the Quiet Sun and Coronal Holes

Recent observations from Parker Solar Probe have revealed that the solar wind has a highly variable structure. How this complex behaviour is formed in the solar corona is not yet known, since it requires omnipresent fluctuations, which constantly emit material to feed the wind. In this article we analysed 14 upflow regions in the solar corona to find potential sources for plasma flow. The upflow regions were derived from spectroscopic data from the EUV Imaging Spectrometer (EIS) onboard Hinode determining their Doppler velocity and defining regions which have blueshifts stronger than $-6\,km\,s^{-1}$. To identify the sources of this blueshift data from the Atmospheric Imaging Assembly (AIA) and the Helioseismic and Magnetic Imager (HMI), onboard the Solar Dynamics Observatory (SDO), and the X-ray Telescope (XRT), onboard Hinode, were used. The analysis revealed that only 5 out of 14 of the upflows were associated with frequent transients, like obvious jets or bright points. In contrast to that, seven events were associated with small-scale features, which show a large variety of dynamics. Some resemble small bright points, while others show an eruptive nature, all of which are faint and only live for a few minutes; we can not rule out that several of these sources may be fainter and, hence, less obvious jets. Since the complex structure of the solar wind is known, this suggests that new sources have to be considered or better methods used to analyse the known sources. This work shows that small and frequent features, which were previously neglected, can cause strong upflows in the solar corona. These results emphasise the importance of the first observations from the Extreme-Ultraviolet Imager (EUI) onboard Solar Orbiter, which revealed complex small-scale coronal structures.

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arXiv2021

Mapping Solar Magnetic Fields from the Photosphere to the Base of the Corona

Routine ultraviolet imaging of the Sun's upper atmosphere shows the spectacular manifestation of solar activity; yet we remain blind to its main driver, the magnetic field. Here we report unprecedented spectropolarimetric observations of an active region plage and its surrounding enhanced network, showing circular polarization in ultraviolet (Mg II $h$ & $k$ and Mn I) and visible (Fe I) lines. We infer the longitudinal magnetic field from the photosphere to the very upper chromosphere. At the top of the plage chromosphere the field strengths reach more than 300 gauss, strongly correlated with the Mg II $k$ line core intensity and the electron pressure. This unique mapping shows how the magnetic field couples the different atmospheric layers and reveals the magnetic origin of the heating in the plage chromosphere.

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arXiv2020

A Solar Magnetic-fan Flaring Arch Heated by Non-thermal Particles and Hot Plasma from an X-ray Jet Eruption

We have investigated an M1.3 limb flare, which develops as a magnetic loop/arch that fans out from an X-ray jet. Using Hinode/EIS, we found that the temperature increases with height to a value of over 10$^{7}$ K at the loop-top during the flare. The measured Doppler velocity (redshifts of 100$-$500 km s$^{-1}$) and the non-thermal velocity ($\geq$100 km s$^{-1}$) from Fe XXIV also increase with loop height. The electron density increases from $0.3\times10^{9}$ cm$^{-3}$ early in the flare rise to $1.3\times10^{9}$ cm$^{-3}$ after the flare peak. The 3-D structure of the loop derived with STEREO/EUVI indicates that the strong redshift in the loop-top region is due to upflowing plasma originating from the jet. Both hard X-ray and soft X-ray emission from RHESSI were only seen as footpoint brightenings during the impulsive phase of the flare, then, soft X-ray emission moves to the loop-top in the decay phase. Based on the temperature and density measurements and theoretical cooling models, the temperature evolution of the flare arch is consistent with impulsive heating during the jet eruption followed by conductive cooling via evaporation and minor prolonged heating in the top of the fan loop. Investigating the magnetic field topology and squashing factor map from SDO/HMI, we conclude that the observed magnetic-fan flaring arch is mostly heated from low atmospheric reconnection accompanying the jet ejection, instead of from reconnection above the arch as expected in the standard flare model.

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arXiv2020

Locating Hot Plasma in Small Flares using Spectroscopic Overlappogram Data from the Hinode {\it EUV} Imaging Spectrometer

One of the key processes associated with the "standard" flare model is chromospheric evaporation, a process where plasma heated to high temperatures by energy deposition at the flare footpoints is driven upwards into the corona. Despite several decades of study, a number of open questions remain, including the relationship between plasma produced during this process and observations of earlier "superhot" plasma. Hinode/EIS has a wide slot often used as a flare trigger in the He II emission line band. Once the intensity passes a threshold level, the study switches to one focussed on the flaring region. However, when the intensity is not high enough to reach the flare trigger threshold, these datasets are available during the entire flare period and provide high-cadence spectroscopic observations over a large field of view. We use one-minute cadence data from two such studies of a C4.7 flare and a C1.6 flare to probe the relationship between hot Fe XXIV plasma and plasmas observed by RHESSI and XRT to track where the emission comes from, and when it begins. Although the spatial and spectral information are merged in the wide-slot data, it is still possible to extract when the hot plasma appears using the Fe XXIV spectral image. It is also possible to derive spectrally pure Fe XXIV light curves from the EIS data, and compare them with those derived from hard X-rays, enabling a full exploration of the evolution of hot emission. The Fe XXIV emission peaks just after the peak in the hard X-ray lightcurve; consistent with an origin in the evaporation of heated plasma following the transfer of energy to the lower atmosphere. A peak was also found for the C4.7 flare in the RHESSI peak temperature, which occurred before the hard X-rays peaked. This suggests that the first peak in hot-plasma emission is likely directly related to the energy-release process.

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