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Over the last 10–20 years there has been an ever-increasing international awareness of risks to modern society from adverse and potentially harmful – and in extreme cases even disastrous – space weather events. Many individual countries and even international organisations like the United Nations (UN) have begun to increase their activities in preparing for and mitigating effects of adverse space weather. As in the rest of the world there is also in Europe an urgent need for coordination of Space Weather efforts in individual countries as well as in and among European organisations such as the European Space Agency (ESA) and the European Union (EU). This coordination should not only improve our ability to meet space weather risks, but also enable Europe to contribute to on-going global space weather efforts. While space weather is a global threat, which needs a global response, it also requires tailored regional and trans-regional responses that require coordination at all levels. Commissioned by the European Space Science Committee (ESSC) of the European Science Foundation, the authors – together with ex-officio advice from ESA and the EU – have over two years assessed European activities in the realm of space weather and formulated a set of recommendations to ESA, the EU and their respective member states, about how to prepare Europe for the increasing impact of adverse space weather effects on man-made infrastructure and our society as a whole. We have also analysed parallel international activities worldwide, and we give advice how Europe could incorporate its future activities into a global scheme.

Lagrange eUv Coronal Imager (LUCI) is a solar imager in the Extreme UltraViolet (EUV) that is being developed as part of the Lagrange mission, a mission designed to be positioned at the L5 Lagrangian point to monitor space weather from its source on the Sun, through the heliosphere, to the Earth. LUCI will use an off-axis two mirror design equipped with an EUV enhanced active pixel sensor. This type of detector has advantages that promise to be very beneficial for monitoring the source of space weather in the EUV. LUCI will also have a novel off-axis wide field-of-view, designed to observe the solar disk, the lower corona, and the extended solar atmosphere close to the Sun–Earth line. LUCI will provide solar coronal images at a 2–3 min cadence in a pass-band centred on 19.5. Observations made through this pass-band allow for the detection and monitoring of semi-static coronal structures such as coronal holes, prominences, and active regions; as well as transient phenomena such as solar flares, limb coronal mass ejections (CMEs), EUV waves, and coronal dimmings. The LUCI data will complement EUV solar observations provided by instruments located along the Sun–Earth line such as PROBA2-SWAP, SUVI-GOES and SDO-AIA, as well as provide unique observations to improve space weather forecasts. Together with a suite of other remote-sensing and in-situ instruments onboard Lagrange, LUCI will provide science quality operational observations for space weather monitoring.

Aims. To better understand the radiation environment in low Earth orbit (LEO), the analysis of in-situ observations of a variety of particles, at different atmospheric heights, and in a wide range of energies, is needed. Methods. We present an analysis of energetic particles, indirectly detected by the large yield radiometer (LYRA) instrument on board ESA's project for on-board autonomy 2 (PROBA2) satellite as background signal. Combining energetic particle telescope (EPT) observations with LYRA data for an overlapping period of time, we identified these particles as electrons with an energy range of 2 to 8 MeV. Results. The observed events are strongly correlated to geo-magnetic activity and appear even during modest disturbances. They are also well confined geographically within the L = 4–6 McIlwain zone, which makes it possible to identify their source. Conclusions. Although highly energetic particles are commonly perturbing data acquisition of space instruments, we show in this work that ultra-relativistic electrons with energies in the range of 2–8 MeV are detected only at high latitudes, while not present in the South Atlantic Anomaly region.

On August 14, 2010 a wide-angled coronal mass ejection (CME) was observed. This solar eruption originated from a destabilized filament that connected two active regions and the unwinding of this filament gave the eruption an untwisting motion that drew the attention of many observers. In addition to the erupting filament and the associated CME, several other low-coronal signatures that typically indicate the occurrence of a solar eruption were associated with this event. However, contrary to what was expected, the fast CME (v > 900 km s−1) was accompanied by only a weak C4.4 flare. We investigate the various eruption signatures that were observed for this event and focus on the kinematic evolution of the filament in order to determine its eruption mechanism. Had this solar eruption occurred just a few days earlier, it could have been a significant event for space weather. The risk of underestimating the strength of this eruption based solely on the C4.4 flare illustrates the need to include all eruption signatures in event analyses in order to obtain a complete picture of a solar eruption and assess its possible space weather impact.

A total solar eclipse occurred on 20 March 2015, with a totality path passing mostly above the North Atlantic Ocean, which resulted in a partial solar eclipse over Belgium and large parts of Europe. In anticipation of this event, a dedicated observational campaign was set up at the Belgian Solar-Terrestrial Centre of Excellence (STCE). The objective was to perform high-quality observations of the eclipse and the associated effects on the geospace environment by utilising the advanced space- and ground-based instrumentation available to the STCE in order to further our understanding of these effects, particularly on the ionosphere. The study highlights the crucial importance of taking into account the eclipse geometry when analysing the ionospheric behaviour during eclipses and interpreting the eclipse effects. A detailed review of the eclipse geometry proves that considering the actual obscuration level and solar zenith angle at ionospheric heights is much more important for the analysis than at the commonly referenced Earth’s surface or at the plasmaspheric heights. The eclipse occurred during the recovery phase of a strong geomagnetic storm which certainly had an impact on (some of) the ionospheric characteristics and perhaps caused the omission of some “low-profile” effects. However, the analysis of the ionosonde measurements, carried out at unprecedented high rates during the eclipse, suggests the occurrence of travelling ionospheric disturbances (TIDs). Also, the high temporal and spatial resolution measurements proved very important in revealing and estimating some finer details of the delay in the ionospheric reaction and the ionospheric disturbances.

Aims: Knowledge of properties of the Earth’s upper atmosphere is important for predicting the lifetime of low-orbit spacecraft as well as for planning operation of space instruments whose data may be distorted by atmospheric effects. The accuracy of the models commonly used for simulating the structure of the atmosphere is limited by the scarcity of the observations they are based on, so improvement of these models requires validation under different atmospheric conditions. Measurements of the absorption of the solar extreme ultraviolet (EUV) radiation in the upper atmosphere below 500 km by instruments operating on low-Earth orbits (LEO) satellites provide efficient means for such validation as well as for continuous monitoring of the upper atmosphere and for studying its response to the solar and geomagnetic activity. Method: This paper presents results of measurements of the solar EUV radiation in the 17 nm wavelength band made with the SPIRIT and TESIS telescopes on board the CORONAS satellites and the SWAP telescope on board the PROBA2 satellite in the occulted parts of the satellite orbits. The transmittance profiles of the atmosphere at altitudes between 150 and 500 km were derived from different phases of solar activity during solar cycles 23 and 24 in the quiet state of the magnetosphere and during the development of a geomagnetic storm. We developed a mathematical procedure based on the Tikhonov regularization method for solution of ill-posed problems in order to retrieve extinction coefficients from the transmittance profiles. The transmittance profiles derived from the data and the retrieved extinction coefficients are compared with simulations carried out with the NRLMSISE-00 atmosphere model maintained by Naval Research Laboratory (USA) and the DTM-2013 model developed at CNES in the framework of the FP7 project ATMOP. Results: Under quiet and slightly disturbed magnetospheric conditions during high and low solar activity the extinction coefficients calculated by both models agreed with the measurements within the data errors. The NRLMSISE-00 model was not able to predict the enhancement of extinction above 300 km observed after 14 h from the beginning of a geomagnetic storm whereas the DTM-2013 model described this variation with good accuracy.

We report on one of the first solar-eruptive events that was simultaneously observed by three of the remote-sensing instruments onboard Solar Orbiter during the cruise phase. The Extreme Ultraviolet Imager (EUI) observed an eruption on 22 April 2021. The corresponding CME was recorded by the coronagraph Metis. Finally, the Spectrometer/Telescope for Imaging X-rays (STIX) sampled the associated X-ray flare, which was partially occulted. From the Earth, the eruption-source region was observed close to disk center. We provide an analysis of the eruption as observed by these various instruments. In particular, we show that in this eruption, continuous magnetic reconnection and heating have to be present even well after the impulsive phase. The need for this is derived from multiple independent lines of evidence – using both flare and CME observations – that have not been reported before for a single event. The combination of data from Solar Orbiter, as well as other space-based assets, clearly showcases the scientific potential for the science phase of Solar Orbiter, and the unique observations available. [ABSTRACT FROM AUTHOR]

The magnetic activity of the Sun directly impacts the Earth and human life. Likewise, other stars will have an impact on the habitability of planets orbiting these host stars. Although the magnetic field at the surface of the Sun is reasonably well characterised by observations, the information on the magnetic field in the higher atmospheric layers is mainly indirect. This lack of information hampers our progress in understanding solar magnetic activity. Overcoming this limitation would allow us to address four paramount long-standing questions: (1) How does the magnetic field couple the different layers of the atmosphere, and how does it transport energy? (2) How does the magnetic field structure, drive and interact with the plasma in the chromosphere and upper atmosphere? (3) How does the magnetic field destabilise the outer solar atmosphere and thus affect the interplanetary environment? (4) How do magnetic processes accelerate particles to high energies? New ground-breaking observations are needed to address these science questions. We suggest a suite of three instruments that far exceed current capabilities in terms of spatial resolution, light-gathering power, and polarimetric performance: (a) A large-aperture UV-to-IR telescope of the 1-3 m class aimed mainly to measure the magnetic field in the chromosphere by combining high spatial resolution and high sensitivity. (b) An extreme-UV-to-IR coronagraph that is designed to measure the large-scale magnetic field in the corona with an aperture of about 40 cm. (c) An extreme-UV imaging polarimeter based on a 30 cm telescope that combines high throughput in the extreme UV with polarimetry to connect the magnetic measurements of the other two instruments. Placed in a near-Earth orbit, the data downlink would be maximised, while a location at L4 or L5 would provide stereoscopic observations of the Sun in combination with Earth-based observatories. This mission to measure the magnetic field will finally unlock the driver of the dynamics in the outer solar atmosphere and thereby will greatly advance our understanding of the Sun and the heliosphere. [ABSTRACT FROM AUTHOR]

We present the results of a comparative study between automatic and manually compiled coronal mass ejection (CME) catalogues based on observations from the Heliospheric Imagers (HIs) onboard NASA's Solar Terrestrial Relations Observatory (STEREO) spacecraft. Using the Computer Aided CME Tracking software(CACTus), CMEs are identified in HI data using an automatic feature-detection algorithm, while the Heliospheric Imagers Catalogue(HICAT) includes CMEs that are detected by visual inspection of HI images. Both catalogues were compiled as part of the EU FP7 Heliospheric Cataloguing, Analysis and Techniques Service (HELCATS) project (www.helcats-fp7.eu). We compare observational parameters of the CMEs from CACTus to those listed in HICAT, such as CME frequency, position angle (PA), and PA-width. We also compare CACTus-derived speeds to speeds derived from applying geometric modelling to the majority of the HICAT CMEs, the results of which are listed in the HELCATS Heliospheric Imagers Geometric Catalogue(HIGeoCAT). We find that both CACTus and HICAT catalogues contain a similar number of events when we exclude events narrower than 20∘, which are not included in the HICAT catalogue but are found to be identified by CACTus. PA-distributions are strongly peaked around 90∘ and 270∘, with a slightly larger CME frequency northwards of the equatorial plane (particularly for the STEREO-A versions of both catalogues). The CME PA-widths in both HICAT and CACTus catalogues peak at approximately 60∘. Manually derived speeds from HIGeoCAT and automatically derived speeds by CACTus correlate well for values lower than 1000 km s−1, in particular when CMEs are propagating close to the plane of the sky. [ABSTRACT FROM AUTHOR]

Decayless kink oscillations of plasma loops in the solar corona may contain an answer to the enigmatic problem of solar and stellar coronal heating. The polarisation of the oscillations gives us a unique information about their excitation mechanisms and energy supply. However, unambiguous determination of the polarisation has remained elusive. Here, we show simultaneous detection of a 4-min decayless kink oscillation from two non-parallel lines-of-sights, separated by about 104 ∘ , provided by unique combination of the High Resolution Imager on Solar Orbiter and the Atmospheric Imaging Assembly on Solar Dynamics Observatory. The observations reveal a horizontal or weakly oblique linear polarisation of the oscillation. This conclusion is based on the comparison of observational results with forward modelling of the observational manifestation of various kinds of polarisation of kink oscillations. The revealed polarisation favours the sustainability of these oscillations by quasi-steady flows which may hence supply the energy for coronal heating., (© 2023. Springer Nature Limited.)

Coronal holes are areas on the Sun with open magnetic field lines. They are a source region of the solar wind, but how the wind emerges from coronal holes is not known. We observed a coronal hole using the Extreme Ultraviolet Imager on the Solar Orbiter spacecraft. We identified jets on scales of a few hundred kilometers, which last 20 to 100 seconds and reach speeds of ~100 kilometers per second. The jets are powered by magnetic reconnection and have kinetic energy in the picoflare range. They are intermittent but widespread within the observed coronal hole. We suggest that such picoflare jets could produce enough high-temperature plasma to sustain the solar wind and that the wind emerges from coronal holes as a highly intermittent outflow at small scales.

Magnetic reconnection is a key mechanism involved in solar eruptions and is also a prime possibility to heat the low corona to millions of degrees. Here, we present ultra-high-resolution extreme ultraviolet observations of persistent null-point reconnection in the corona at a scale of about 390 km over one hour observations of the Extreme-Ultraviolet Imager on board Solar Orbiter spacecraft. The observations show formation of a null-point configuration above a minor positive polarity embedded within a region of dominant negative polarity near a sunspot. The gentle phase of the persistent null-point reconnection is evidenced by sustained point-like high-temperature plasma (about 10 MK) near the null-point and constant outflow blobs not only along the outer spine but also along the fan surface. The blobs appear at a higher frequency than previously observed with an average velocity of about 80 km s -1 and life-times of about 40 s. The null-point reconnection also occurs explosively but only for 4 minutes, its coupling with a mini-filament eruption generates a spiral jet. These results suggest that magnetic reconnection, at previously unresolved scales, proceeds continually in a gentle and/or explosive way to persistently transfer mass and energy to the overlying corona., (© 2023. The Author(s).)

We present the SWAP Filter: an azimuthally varying, radial normalizing filter specifically developed for EUV images of the solar corona, named for the Sun Watcher with Active Pixels and Image Processing (SWAP) instrument on the Project for On-Board Autonomy 2 (PROBA2) spacecraft. We discuss the origins of our technique, its implementation and key user-configurable parameters, and highlight its effects on data via a series of examples. We discuss the filter's strengths in a data environment in which wide field-of-view observations that specifically target the low signal-to-noise middle corona are newly available and expected to grow in the coming years., Supplementary Information: The online version contains supplementary material available at 10.1007/s11207-023-02183-w., Competing Interests: Competing interestsThe authors declare no competing interests., (© The Author(s) 2023.)

The middle corona, the region roughly spanning heliocentric distances from 1.5 to 6 solar radii, encompasses almost all of the influential physical transitions and processes that govern the behavior of coronal outflow into the heliosphere. The solar wind, eruptions, and flows pass through the region, and they are shaped by it. Importantly, the region also modulates inflow from above that can drive dynamic changes at lower heights in the inner corona. Consequently, the middle corona is essential for comprehensively connecting the corona to the heliosphere and for developing corresponding global models. Nonetheless, because it is challenging to observe, the region has been poorly studied by both major solar remote-sensing and in-situ missions and instruments, extending back to the Solar and Heliospheric Observatory (SOHO) era. Thanks to recent advances in instrumentation, observational processing techniques, and a realization of the importance of the region, interest in the middle corona has increased. Although the region cannot be intrinsically separated from other regions of the solar atmosphere, there has emerged a need to define the region in terms of its location and extension in the solar atmosphere, its composition, the physical transitions that it covers, and the underlying physics believed to shape the region. This article aims to define the middle corona, its physical characteristics, and give an overview of the processes that occur there., Competing Interests: Competing interestsThe authors declare no competing interests., (© The Author(s) 2023.)

The High Resolution Imager (HRI EUV ) telescope of the Extreme Ultraviolet Imager (EUI) instrument onboard Solar Orbiter has observed EUV brightenings, so-called campfires, as fine-scale structures at coronal temperatures. The goal of this paper is to compare the basic geometrical (size, orientation) and physical (intensity, lifetime) properties of the EUV brightenings with regions of energy dissipation in a nonpotential coronal magnetic-field simulation. In the simulation, HMI line-of-sight magnetograms are used as input to drive the evolution of solar coronal magnetic fields and energy dissipation. We applied an automatic EUV-brightening detection method to EUV images obtained on 30 May 2020 by the HRI EUV telescope. We applied the same detection method to the simulated energy dissipation maps from the nonpotential simulation to detect simulated brightenings. We detected EUV brightenings with a density of 1.41 × 10 - 3 brightenings/Mm 2 in the EUI observations and simulated brightenings between 2.76 × 10 - 2 - 4.14 × 10 - 2 brightenings/Mm 2 in the simulation, for the same time range. Although significantly more brightenings were produced in the simulations, the results show similar distributions of the key geometrical and physical properties of the observed and simulated brightenings. We conclude that the nonpotential simulation can successfully reproduce statistically the characteristic properties of the EUV brightenings (typically with more than 85% similarity); only the duration of the events is significantly different between observations and simulation. Further investigations based on high-cadence and high-resolution magnetograms from Solar Orbiter are under consideration to improve the agreement between observation and simulation., Competing Interests: Competing interestsThe authors declare no competing interests., (© The Author(s) 2022.)

Objective: To investigate the effect of a quality improvement project that resulted in an infection control bundle to reduce the number of spinal cord stimulator (SCS) infections., Materials and Methods: The study was performed in a single center for neuromodulation from January 1, 2014, through May 31, 2016. In response to a high number of surgical site infections (SSIs) after SCS surgery, a multidisciplinary team analyzed the surgical process and developed an infection prevention bundle consisting of five items: 1) showering and decolonization for five days prior to surgery and showering in the hospital on the morning of surgery; 2) performing the SCS implantation as the first in the daily operating room (OR) program; 3) maintaining a minimal number of people in the OR; 4) providing home care nurses with a folder with SCS wound care instructions including pictures; 5) giving oral specific wound care instructions to patients. The number of infections was calculated for the baseline, implementation, and sustainability phases., Results: A total of 410 SCS surgeries were performed during the study period. In the preintervention phase, 26/249 (10.4%) SCS surgeries were infected. During the implementation and sustainability phase, 2/59 (3.4%) and 1/102 (1.0%) SCS surgeries were infected, respectively. The reduction in the number of infections in pre and postintervention phase was statistically significant (p = 0.003)., Conclusion: Multidisciplinary measures to reduce SSIs reduced the number of SCS associated infections in our study setting., (© 2017 International Neuromodulation Society.)

Objective: To compare the efficacy and safety of adjusted-dose unfractionated heparin with that of regional citrate anticoagulation in intensive care patients treated by continuous venovenous hemofiltration (CVVH)., Design and Setting: Prospective, randomized, clinical trial in a 32-bed medical and surgical ICU in a university teaching hospital., Patients: ICU patients with acute renal failure requiring continuous renal replacement therapy, without cirrhosis, severe coagulopathy, or known sensitivity to heparin., Interventions: Before the first CVVH run patients were randomized to receive anticoagulation with heparin or trisodium citrate. Patients eligible for another CVVH run received the other study medication in a cross-over fashion until the fourth circuit., Measurements and Results: Forty-nine circuits (hemofilters) were analyzed: 23 with heparin and 26 with citrate. The median lifetime of hemofilters was 70 h (interquartile range 44-140) with citrate anticoagulation and 40 h (17-48) with heparin (p=0.0007). One major bleeding occurred during heparin anticoagulation and one metabolic alkalosis (pH=7.60) was noted with citrate after a protocol violation. Transfusion rates (units of red cells per day of CVVH) were, respectively, 0.2 (0.0-0.4) with citrate and 1.0 (0.0-2.0) with heparin (p=0.0008)., Conclusions: Regional citrate anticoagulation seems superior to heparin for the filter lifetime and transfusion requirements in ICU patients treated by continuous renal replacement therapy.

Study Design: In 100 consecutive patients who underwent surgery because of soft cervical disc herniation, the sagittal and transverse diameters, the area of the bony cervical spinal canal, the sagittal diameter of the hernia, and the minimal bony intervertebral foramen diameter were measured by computed tomography. The data were compared with measurements from a control group of 35 matched healthy individuals., Objectives: To evaluate the relation between the severity of concurrent neurologic symptoms and the sagittal and transverse diameters, the cross-sectional area of the bony spinal canal, the sagittal diameter of the hernia, and diameter of the minimal bony intervertebral foramen in patients with soft cervical disc herniation., Summary of Background Data: Traumatic injury and spondylotic changes have a far greater impact on the spinal cord and nerve roots if the sagittal diameter of the bony cervical spinal canal is small. However, in the case of soft cervical disc herniation, no computer tomographic measurements are available for sagittal and transverse diameters, cross-sectional area of the bony spinal canal, sagittal diameter of the hernia, and diameter of the minimal bony intervertebral foramen in relation to the severity of concurrent neurologic symptoms., Methods: Computed tomography was used to measure sagittal and transverse diameters, cross-sectional area of the bony cervical spinal canal, sagittal diameter of the hernia, and diameter of the minimal bony intervertebral foramen in 100 patients with symptomatic monosegmental cervical soft disc herniation. All patients had undergone an anterior discectomy with removal of the hernia and subsequent interbody fusion using an autologous bone graft taken from the iliac crest., Results: A mean sagittal diameter of the bony cervical spinal canal of 12.9 mm was found, indicating a certain degree of developmental stenosis. Patients with motor disturbances had a significantly smaller sagittal diameter of the bony spinal canal than did patients without motor disturbances. There was a linear correlation between the sagittal diameter of the bony cervical spinal canal and that of the hernia. The sagittal diameter, the area of the bony spinal canal, and diameter of the minimal bony intervertebral foramen were significantly smaller in patients with soft cervical disc herniation than in the control group., Conclusions: Results from this study strongly suggest that the degree and severity of neurologic symptoms accompanying cervical soft disc herniation are inversely related to the sagittal diameter and the area of the bony cervical spinal canal. The latter area is reduced in cases of developmental stenosis or because of soft disc herniation. Moreover, patients with soft cervical disc herniation have a significantly smaller sagittal diameter of the bony spinal canal, a significantly smaller minimal bony intervertebral foramen diameter, and a significantly smaller cross-sectional area of the bony cervical canal than do healthy matched individuals.