The driving and excitation mechanisms of decay-less kink oscillations in coronal loops remain under debate. We aim to quantify and provide simple observational constraints on the photospheric driving of oscillating coronal loops in a few typical active region configurations: sunspot, plage, pores and enhanced-network regions. We then aim to investigate the possible interplay between photospheric driving and properties of kink oscillations in connected coronal loops. We analyse two unique datasets of the corona and photosphere taken at a high resolution during the first coordinated observation campaign between Solar Orbiter and the Swedish 1-m Solar Telescope (SST). A local correlation tracking method is applied on the SST/CRISP data to quantify the photospheric motions at the base of coronal loops. The same loops are then analysed in the corona by exploiting data from the Extreme Ultraviolet Imager on Solar Orbiter, and by using a wavelet analysis to characterize the kink oscillations. Each photospheric region shows dynamics with an overall increase in strength going from pore, plage, enhanced-network to sunspot regions. Differences are also seen in the kink-mode amplitudes of the corresponding coronal loops. This suggests the photosphere is involved in the driving of coronal kink oscillations. However, the few samples available does not allow to further establish the excitation mechanism yet. Despite oscillating coronal loops being anchored in seemingly "static" strong magnetic field regions as seen from coronal EUV observations, photospheric observations provide evidence for a continuous and significant driving at their base. The precise connection between photospheric driving and coronal kink oscillations remains to be further investigated. This study finally provides critical constraints on photospheric driving that can be tested in existing numerical models of coronal loops.

Context. The Polarimetric and Helioseismic Imager (SO/PHI), on board the Solar Orbiter mission, is the first photospheric magnetograph and tachograph to observe the Sun from outside the Sun-Earth line. The Full Disc Telescope (FDT) of SO/PHI, images the whole solar disk with a spatial resolution that varies with the distance between the Sun and the spacecraft. Aims. We check for consistency between the magnetic field strength (B), the field inclination (gamma), the line-of-sight (LoS) magnetic component (B-LoS) and the field azimuth (phi), inferred by SO/PHI-FDT and the Helioseismic and Magnetic Imager (HMI), on board Solar Dynamics Observatory (SDO), and obtain linear correlation coefficients among them. Methods. We use data from both instruments obtained on 8 March 2022, when the angle between SDO and Solar Orbiter was 3.4 degrees and the solar disk showed four developed active regions. Before comparing the magnetic field products of both instruments we perform a precise alignment of the data, including a matching of the plate scale. Further, in order to improve the homogeneity of the compared data products, the SDO/HMI data were convolved with the SO/PHI-FDT point spread function (PSF). The linear correlation coefficients are obtained through a linear regression of SDO/HMI to SO/PHI-FDT. Results. The two instruments yield comparable magnetic field data products. The slope coefficients for a linear fit are 1.37 for B, 1.11 for gamma, 1.35 for B-LoS and 1 for the azimuth. The corresponding fit offsets are -94 G, -9.8 degrees, 5.2 G and 0.1 degrees, respectively. The agreement between both instruments is significantly better when we take into account the different spatial resolution of both instruments. The fitting results vary slightly depending on the analyzed active region except for one of the four active regions, which shows larger differences and has been excluded from the comparison. The comparison of the LoS magnetic field products from SDO/HMI at 45 s and 720 s with SO/PHI-FDT shows a slope value of 1.17, with the offset less than 6 G, in both cases.

Induced magnetospheres form around planetary bodies with atmospheres through the interaction of the solar wind with their ionosphere. Induced magnetospheres are highly dependent on the solar wind conditions and have only been studied with single spacecraft missions in the past. Without simultaneous measurements of solar wind variations and phenomena in the magnetosphere, establishing a link between both can only be done indirectly, using statistics over a large set of measurements. This gap in knowledge could be addressed by a multi -spacecraft plasma mission, optimized for studying global spatial and temporal variations in the magnetospheric system around Venus, which hosts the most prominent example of an induced magnetosphere in our solar system. The MVSE mission comprises four satellites, of which three are identical scientific spacecraft, carrying the same suite of instruments probing different regions of the induced magnetosphere and the solar wind simultaneously. The fourth spacecraft is the transfer vehicle which acts as a relay satellite for communications at Venus. In this way, changes in the solar wind conditions and extreme solar events can be observed, and their effects can be quantified as they propagate through the Venusian induced magnetosphere. Additionally, energy transfer in the Venusian induced magnetosphere can be investigated. The scientific payload includes instrumentation to measure the magnetic field, electric field, and ion-electron velocity distributions. This study presents the scientific motivation for the mission as well as requirements and the resulting mission design. Concretely, a mission timeline along with a complete spacecraft design, including mass, power, communication, propulsion and thermal budgets are given. This mission was initially conceived at the Alpbach Summer School 2022 and refined during a week-long study at ESA's Concurrent Design Facility in Redu, Belgium.

Traditionally, the observation time needed to build synoptic maps of the solar magnetic field is bound to the 27 days of a full Carrington rotation due to the single viewpoint from Earth. Our aim is to reduce this observation time to 13.5 days by combining magnetograms from two vantage points, 180 degrees apart in longitude in the ideal case. We combined observations taken by the Polarimetric and Helioseismic Imager ( during the superior conjunction of the Solar Orbiter in February 2021 with data from the Helioseismic and Magnetic Imager ( and constructed a synoptic map of the line-of-sight magnetic field of CR 2240. The result is the first multi-view synoptic map using and data from an observing period of only 16 days. Comparing the multi-view synoptic map to the standard synoptic map of shows a significant amount of magnetic evolution between the dates on which the two instruments observed the same solar longitudes. The changed magnetic field was caught by the multi-view synoptic map but would have been missed by a standard synoptic map. Our results demonstrate that multi-view synoptic maps provide a new method to obtain a more instantaneous map of the magnetic field over the entire solar surface.

The Polarimetric and Helioseismic Imager on board the Solar Orbiter mission (SO/PHI) offers refocusing capabilities to cope with the strongly varying thermal environment of the optical system along the spacecraft's elliptical orbit. The series of images recorded during in-flight focus calibrations can be employed for phase diversity analyses. In this work we infer the wavefront degradation caused by the thermo-optical effects in the High Resolution Telescope (HRT) from images taken during the fine and coarse focus scans performed in the commissioning phase of the instrument. The difference between these two series of images are mainly related to the employed defocused step (smaller for the fine scans) and the signal-to-noise ratio (higher for the coarse scans). We use the retrieved wavefronts to reconstruct the original scene observed during the calibration of the instrument. We applied a generalized phase diversity algorithm that allowed us to use several images taken with different amounts of defocus to sense the wavefront degradation caused by the instrument. The algorithm also uses information from both the inferred wavefront and the series of images to restore the solar scene We find that most of the retrieved Zernike coefficients tend to converge to the same value when increasing the number of images employed for PD for both the fine and the coarse focusing scans. The restored scenes also show signs of convergence, and the merit function is minimized more as $K$ increases. Apart from a defocus, the inferred wavefronts are consistent for the two datasets ($ For the fine scan images, the quiet-sun contrast improves from $4.5\,$ for the original focused image up to about $10\,$. For the coarse scan images, the contrast of the restored scene is as high as $11\,$.

Context. The amount of magnetic flux passing through the solar surface is an important parameter determining solar activity and the heliospheric magnetic field. It is usually determined from line-of-sight magnetograms. Aims. We aim to test the reliability of determining the line-of-sight magnetic field from 3D MHD (magnetohydrodynamic) simulations of unipolar regions. In contrast to earlier similar studies, we consider the full solar disk, by considering the full centre-to-limb variation, as well as regions with different averaged field strengths. Methods. We synthesised Stokes profiles from MURaM MHD simulations of unipolar regions with varying mean vertical magnetic flux densities, ranging from quiet Sun to active region plage. We did this for a comprehensive range of heliocentric angles: from mu = 1 to mu = 0.15, and for two commonly used photospheric spectral lines: Fe I 6173.3 and Fe I 5250.2 & Aring;. The synthesised profiles were spatially foreshortened and binned to different spatial resolutions characteristic of space-based magnetographs currently in operation. The line-of-sight magnetic field was derived with a Milne-Eddington Inversion as well as with other commonly used methods. Results. The inferred spatially averaged < B-LOS > is always lower than that present in the MHD simulations, with the exception of mu approximate to 1 and sufficiently high spatial resolution. It is also generally inconsistent with a linear dependence on mu. Above mu = 0.5 the spatial resolution greatly impacts the retrieved line-of-sight magnetic field. For mu <= 0.5 the retrieved B-LOS is nearly independent of resolution, but is always lower than expected from the simulation. These trends persist regardless of the mean vertical magnetic field in the MHD simulations and are independent of the B-LOS retrieval method. For mu <= 0.5, a larger < B-LOS > is inferred for the 5250.2 & Aring; spectral line than 6173.3 & Aring;, but the converse is true at higher mu. Conclusions. The obtained results show that with high spatial resolution observations, for instance those achieved with SO/PHI-HRT (High Resolution Telescope of the Polarimetric and Helioseismic Imager on Solar Orbiter) at close perihelion, the magnetic flux can be reliably retrieved at high mu values, whereas in lower resolution observations, as well as at lower mu, a significant fraction of the magnetic flux is missed. The results found here raise some doubts of the reliability of determining the radial field by dividing the line-of-sight field by mu and are of considerable importance for deducing the total magnetic flux of the Sun. They may also contribute to the resolution of the open flux problem.

Context. The relationship between UV bursts and solar surges is complex, with these events sometimes being observed together and sometimes being observed independently. Why this sporadic association exists is unknown; however, it likely relates to the physical conditions at the site of the energy release that drives these events. Aims. Here, we aim to better understand the relationship between UV bursts and solar surges through a multi-instrument analysis of several associated events that occurred around the trailing sunspot in AR 12957. Methods. We used data from Solar Orbiter, the Solar Dynamics Observatory (SDO), and the Interface Region Imaging Spectrograph (IRIS) to achieve our aims. These data were sampled on 3 March 2022 between 09:30:30 UT and 11:00:00 UT, during which time a coordinated observing campaign associated with the Slow Solar Wind Connection Solar Orbiter Observing Plan (SOOP) took place. Results. Numerous small-scale negative polarity magnetic magnetic features (MMFs) were observed to move quickly (potentially up to 3.3 km s-1) away from a sunspot until they collided with a more stable positive polarity plage region around 7 Mm away. Several UV bursts were identified in IRIS slit-jaw imager (SJI) 1400 & Aring; data co-spatial to where these opposite polarity fields interacted, with spatial scales (< 2 Mm) and lifetimes (< 20 minutes) larger than typical values for such events. Two surges were also observed to occur at these locations, with one being short (5 Mm) and hot (bright in the IRIS SJI images), whilst the other was a cooler (dark in coronal imaging channels), longer surge that appeared to fill an active region loop. Conclusions. Magnetic reconnection between the negative polarity MMFs around the sunspot and the positive polarity plage region appears to be the driver of these events. Both the speed of the MMFs and the locally open magnetic topology of the plage region could possibly have been important for forming the surges.

Solar irradiance variability has been monitored almost exclusively from the Earth’s perspective. We present a method to combine the unprecedented observations of the photospheric magnetic field and continuum intensity from outside the Sun-Earth line, which is being recorded by the Polarimetric and Helioseismic Imager on board the Solar Orbiter mission (SO/PHI), with solar observations recorded from the Earth’s perspective to examine the solar irradiance variability from both perspectives simultaneously. Taking SO/PHI magnetograms and continuum intensity images from the cruise phase of the Solar Orbiter mission and concurrent observations from the Helioseismic and Magnetic Imager onboard the Solar Dynamics Observatory (SDO/HMI) as input into the SATIRE-S model, we successfully reconstructed the total solar irradiance variability as apparent from both perspectives. In later stages of the SO mission, the orbital plane will tilt in such a way as to bring the spacecraft away from the ecliptic to heliographic latitudes of up to 33°. The current study sets the template for the reconstruction of solar irradiance variability as seen from outside the ecliptic from data that SO/PHI is expected to collect from such positions. Such a reconstruction will be beneficial to factoring inclination into how the brightness variations of the Sun compare to those of other cool stars, whose rotation axes are randomly inclined.

The Slow Solar Wind Connection Solar Orbiter Observing Plan (Slow Wind SOOP) was developed to utilise the extensive suite of remote sensing and in situ instruments on board the ESA/NASA Solar Orbiter mission to answer significant outstanding questions regarding the origin and formation of the slow solar wind. The Slow Wind SOOP was designed to link remote sensing and in situ measurements of slow wind originating at open-closed field boundaries. The SOOP ran just prior to Solar Orbiter's first close perihelion passage during two remote sensing windows (RSW1 and RSW2) between 2022 March 3-6 and 2022 March 17-22, while Solar Orbiter was at a heliocentric distance of 0.55-0.51 and 0.38-0.34 au from the Sun, respectively. Coordinated observation campaigns were also conducted by Hinode and IRIS. The magnetic connectivity tool was used, along with low latency in situ data, and full-disk remote sensing observations, to guide the target pointing of Solar Orbiter. Solar Orbiter targeted an active region complex during RSW1, the boundary of a coronal hole, and the periphery of a decayed active region during RSW2. Post-observation analysis using the magnetic connectivity tool along with in situ measurements from MAG and SWA/PAS, show that slow solar wind, with velocities between 210 and 600 km/s, arrived at the spacecraft originating from two out of the three of the target regions. The Slow Wind SOOP, despite presenting many challenges, was very successful, providing a blueprint for planning future observation campaigns that rely on the magnetic connectivity of Solar Orbiter.

Context. Earth-side observations of solar p modes can be used to image and monitor magnetic activity on the Sun's far side. In this work, we use magnetograms of the far side obtained by the Polarimetric and Helioseismic Imager (PHI) on board Solar Orbiter (SO) to directly assess the validity of far-side helioseismic holography for the first time.Aims. We wish to co-locate the positions of active regions in helioseismic images and magnetograms and to calibrate the helioseismic measurements in terms of the magnetic field strength.Methods. We identified three magnetograms displaying a total of six active regions on the far side from 18 November 2020, 3 October 2021, and 3 February 2022. The first two dates are from the SO cruise phase and the third is from the beginning of the nominal operation phase. We computed contemporaneous seismic phase maps for these three dates using helioseismic holography applied to the time series of Dopplergrams from the Helioseismic and Magnetic Imager (HMI) at the Solar Dynamics Observatory (SDO).Results. Among the six active regions seen in SO/PHI magnetograms, five of them are identified on the seismic maps at almost the same positions as on the magnetograms. One region is too weak to be detected above the seismic noise. To calibrate the seismic maps, we fit a linear relationship between the seismic phase shifts and the unsigned line-of-sight magnetic field averaged over the active region areas extracted from the SO/PHI magnetograms.Conclusions. SO/PHI provides the strongest evidence so far that helioseismic imaging is able to provide reliable information on active regions on the far side, including their positions, areas, and the mean unsigned magnetic field.

Context. The brightness of faculae and network depends on the angle at which they are observed and the magnetic flux density. Close to the limb, the assessment of this relationship has until now been hindered by the increasingly lower signal in magnetograms. Aims. This preliminary study aims to highlight the potential of using simultaneous observations from different vantage points to better determine the properties of faculae close to the limb. Methods. We used data from the Solar Orbiter/Polarimetric and Helioseismic Imager (SO/PHI), and the Solar Dynamics Observatory/Helioseismic and Magnetic Imager (SDO/HMI), recorded at an ∼60° angular separation of their lines of sight at the Sun. We used the continuum intensity observed close to the limb by SO/PHI and complemented it with the co-observed BLOS from SDO/HMI, originating closer to disc centre (as seen by SDO/HMI), thus avoiding the degradation of the magnetic field signal near the limb. Results. We derived the dependence of facular brightness in the continuum on disc position and magnetic flux density from the combined observations of SO/PHI and SDO/HMI. Compared with a single point of view, we were able to obtain contrast values reaching closer to the limb and to lower field strengths. We find the general dependence of the limb distance at which the contrast is maximum on the flux density to be at large in line with single viewpoint observations, in that the higher the flux density is, the closer the turning point lies to the limb. There is a tendency, however, for the maximum to be reached closer to the limb when determined from two vantage points. We note that due to the preliminary nature of this study, these results must be taken with caution. Conclusions. Our analysis shows that studies involving two viewpoints can significantly improve the detection of faculae near the solar limb and the determination of their brightness contrast relative to the quiet Sun.

Context. The High Resolution Telescope (HRT) of the Polarimetric and Helioseismic Imager on board the Solar Orbiter spacecraft (SO/PHI) and the Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory (SDO) both infer the photospheric magnetic field from polarised light images. SO/PHI is the first magnetograph to move out of the Sun–Earth line and will provide unprecedented access to the Sun’s poles. This provides excellent opportunities for new research wherein the magnetic field maps from both instruments are used simultaneously. Aims. We aim to compare the magnetic field maps from these two instruments and discuss any possible differences between them. Methods. We used data from both instruments obtained during Solar Orbiter’s inferior conjunction on 7 March 2022. The HRT data were additionally treated for geometric distortion and degraded to the same resolution as HMI. The HMI data were re-projected to correct for the 3° separation between the two observatories. Results. SO/PHI-HRT and HMI produce remarkably similar line-of-sight magnetograms, with a slope coefficient of 0.97, an offset below 1 G, and a Pearson correlation coefficient of 0.97. However, SO/PHI-HRT infers weaker line-of-sight fields for the strongest fields. As for the vector magnetic field, SO/PHI-HRT was compared to both the 720-second and 90-second HMI vector magnetic field: SO/PHI-HRT has a closer alignment with the 90-second HMI vector. In the weak signal regime (< 600 G), SO/PHI-HRT measures stronger and more horizontal fields than HMI, very likely due to the greater noise in the SO/PHI-HRT data. In the strong field regime (≳600 G), HRT infers lower field strengths but with similar inclinations (a slope of 0.92) and azimuths (a slope of 1.02). The slope values are from the comparison with the HMI 90-second vector. Possible reasons for the differences found between SO/PHI-HRT and HMI magnetic field parameters are discussed.

We use wavefront sensing to characterise the image quality of the the High Resolution Telescope (HRT) of the Polarimetric and Helioseismic Imager (SO/PHI) data products during the second remote sensing window of the Solar Orbiter (SO) nominal mission phase. Our ultimate aims are to reconstruct the HRT data by deconvolving with the HRT point spread function (PSF) and to correct for the effects of optical aberrations on the data. We use a pair of focused--defocused images to compute the wavefront error and derive the PSF of HRT by means of a phase diversity (PD) analysis. The wavefront error of HRT depends on the orbital distance of SO to the Sun. At distances $>0.5$\,au, the wavefront error is small, and stems dominantly from the inherent optical properties of HRT. At distances $<0.5$\,au, the thermo-optical effect of the Heat Rejection Entrance Window (HREW) becomes noticeable. We develop an interpolation scheme for the wavefront error that depends on the thermal variation of the HREW with the distance of SO to the Sun. We also introduce a new level of image reconstruction, termed `aberration correction', which is designed to reduce the noise caused by image deconvolution while removing the aberrations caused by the HREW. The computed PSF via phase diversity significantly reduces the degradation caused by the HREW in the near-perihelion HRT data. In addition, the aberration correction increases the noise by a factor of only $1.45$ compared to the factor of $3$ increase that results from the usual PD reconstructions.

Context. Extreme ultraviolet (EUV) observations of the quiet solar atmosphere reveal extended regions of weak emission compared to the ambient quiescent corona. The magnetic nature of these coronal features is not well understood. Aims. We study the magnetic properties of the weakly emitting extended regions, which we name coronal voids. In particular, we aim to understand whether these voids result from a reduced heat input into the corona or if they are associated with mainly unipolar and possibly open magnetic fields, similar to coronal holes. Methods. We defined the coronal voids via an intensity threshold of 75% of the mean quiet-Sun (QS) EUV intensity observed by the high-resolution EUV channel (HRI EUV ) of the Extreme Ultraviolet Imager on Solar Orbiter. The line-of-sight magnetograms of the same solar region recorded by the High Resolution Telescope of the Polarimetric and Helioseismic Imager allowed us to compare the photospheric magnetic field beneath the coronal voids with that in other parts of the QS. Results. The coronal voids studied here range in size from a few granules to a few supergranules and on average exhibit a reduced intensity of 67% of the mean value of the entire field of view. The magnetic flux density in the photosphere below the voids is 76% (or more) lower than in the surrounding QS. Specifically, the coronal voids show much weaker or no network structures. The detected flux imbalances fall in the range of imbalances found in QS areas of the same size. Conclusions. We conclude that coronal voids form because of locally reduced heating of the corona due to reduced magnetic flux density in the photosphere. This makes them a distinct class of (dark) structure, different from coronal holes.

&lt;p&gt;As part of the Alpbach Summer School, a collaboration between FFG, ESA and ISSI, a team of students developed the F-class CASPER mission concept to investigate Transient Luminous Events (TLEs) and Terrestrial Gamma Ray Flashes (TGFs). These lightning-related plasma phenomena, first detected on Earth in 1989, typically occur in the mesosphere at an altitude between 50-100 km. The UVS instrument onboard the JUNO mission detected several similar events on Jupiter, and they are expected to also occur on other planets.&lt;/p&gt; &lt;p&gt;The CASPER mission consists of two identical spacecraft, each of which will be equipped with three cameras in different wavelengths and four high speed sensors, the latter will function as triggers to start the data acquisition of higher resolution images. A system chosen to combat the transient characteristic of the events (lifetime &lt; 300 ms). While three sensors will be taking measurements of photons, one will quantify the electron flux in order to constrain the role of TLEs and TGFs in the global electric circuit.&lt;/p&gt; &lt;p&gt;The second great area of interest is the vertical structure of TLEs as well as their global distribution and occurrence rates. To achieve this, data will be captured using a two-satellite train in a sun-synchronous low earth orbit. The orbit is inclined at 98&amp;#176; and the satellites are phased at an angle of 5.2&amp;#176; to observe these events from two points of view simultaneously. The operational mission lifetime is five years, with a possible extension.&lt;/p&gt;

Onboard the Solar Orbiter spacecraft is the Polarimetric and Helioseismic Imager (SO/PHI), which has two telescopes, a high resolution telescope (HRT) and the full disk telescope (FDT). The instrument is designed to infer the photospheric magnetic field through differential imaging of the polarised light emitted from the Sun. It is the first magnetograph to move out of the Sun-Earth Line, providing excellent stereoscopic opportunities with other ground and space based instruments. Of particular interest is the comparison between SO/PHI-HRT and the Helioseismic and Magnetic Imager onboard the Solar Dynamics Observatory (SDO/HMI). They probe the same magnetically sensitive line of Fe1: 6173 Å and have the same aperture diameter. In March 2022 Solar Orbiter crossed the Sun-Earth line, providing an excellent opportunity for a comparison. Here a comparison between the magnetic fields, both line-of-sight and all three vector components, inferred by SDO/HMI and SO/PHI-HRT during the conjunction, are presented.

In November 2021, Solar Orbiter started its nominal mission phase. The remote-sensing instruments on board the spacecraft acquired scientific data during three observing windows surrounding the perihelion of the first orbit of this phase. The aim of the analysis is the detection of magnetohydrodynamic (MHD) wave modes in an active region by exploiting the capabilities of spectropolarimetric measurements. The High Resolution Telescope (HRT) of the Polarimetric and Helioseismic Imager (SO/PHI) on board the Solar Orbiter acquired a high-cadence data set of an active region. This is studied in the paper. B-ω and phase-difference analyses are applied on line-of-sight velocity and circular polarization maps and other averaged quantities. We find that several MHD modes at different frequencies are excited in all analysed structures. The leading sunspot shows a linear dependence of the phase lag on the angle between the magnetic field and the line of sight of the observer in its penumbra. The magnetic pore exhibits global resonances at several frequencies, which are also excited by different wave modes. The SO/PHI measurements clearly confirm the presence of magnetic and velocity oscillations that are compatible with one or more MHD wave modes in pores and a sunspot. Improvements in modelling are still necessary to interpret the relation between the fluctuations of different diagnostics.

Context. The Solar Orbiter mission completed its first remote-sensing observation windows in the spring of 2022. On 2 April 2022, an M-class flare followed by a filament eruption was seen both by the instruments on board the mission and from several observatories in Earth's orbit, providing an unprecedented view of a flaring region with a large range of observations.Aims. We aim to understand the nature of the flaring and filament eruption events via the analysis of the available dataset. The complexity of the observed features is compared with the predictions given by the standard flare model in 3D.Methods. In this paper, we use the observations from a multi-view dataset, which includes extreme ultraviolet (EUV) imaging to spectroscopy and magnetic field measurements. These data come from the Interface Region Imaging Spectrograph, the Solar Dynamics Observatory, Hinode, as well as several instruments on Solar Orbiter.Results. The large temporal coverage of the region allows us to analyse the whole sequence of the filament eruption starting with its pre-eruptive state. Information given by spectropolarimetry from SDO/HMI and Solar Orbiter PHI/HRT shows that a parasitic polarity emerging underneath the filament is responsible for bringing the flux rope to an unstable state. As the flux rope erupts, Hinode EIS captures blue-shifted emission in the transition region and coronal lines in the northern leg of the flux rope prior to the flare peak. This may be revealing the unwinding of one of the flux rope legs. At the same time, Solar Orbiter SPICE captures the whole region, complementing the Doppler diagnostics of the filament eruption. Analyses of the formation and evolution of a complex set of flare ribbons and loops, of the hard and soft X-ray emissions with STIX, show that the parasitic emerging bipole plays an important role in the evolution of the flaring region.Conclusions. The extensive dataset covering this M-class flare event demonstrates how important multiple viewpoints and varied observations are in order to understand the complexity of flaring regions. While the analysed data are overall consistent with the standard flare model, the present particular magnetic configuration shows that surrounding magnetic activity such as nearby emergence needs to be taken into account to fully understand the processes at work. This filament eruption is the first to be covered from different angles by spectroscopic instruments, and provides an unprecedented diagnostic of the multi-thermal structures present before and during the flare. This complete dataset of an eruptive event showcases the capabilities of coordinated observations with the Solar Orbiter mission.

In order to make accurate inferences about the solar interior using helioseismology, it is essential to understand all the relevant physical effects on the observations. One effect to understand is the (complex-valued) ratio of the horizontal to vertical displacement of the p- and f-modes at the height at which they are observed. Unfortunately, it is impossible to measure this ratio directly from a single vantage point, and it has been difficult to disentangle observationally from other effects. In this paper we attempt to measure the ratio directly using 7.5 hours of simultaneous observations from the Polarimetric and Helioseismic Imager on board Solar Orbiter and the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory. While image geometry problems make it difficult to determine the exact ratio, it appears to agree well with that expected from adiabatic oscillations in a standard solar model. On the other hand it does not agree with a commonly used approximation, indicating that this approximation should not be used in helioseismic analyses. In addition, the ratio appears to be real-valued.