The SWAP EUV Imaging Telescope Part I: Instrument Overview and Pre-Flight Testing

The Sun Watcher with Active Pixels and Image Processing (SWAP) is an EUV solar telescope on board ESA's Project for Onboard Autonomy 2 (PROBA2) mission launched on 2 November 2009. SWAP has a spectral bandpass centered on 17.4 nm and provides images of the low solar corona over a 54x54 arcmin field-of-view with 3.2 arcsec pixels and an imaging cadence of about two minutes. SWAP is designed to monitor all space-weather-relevant events and features in the low solar corona. Given the limited resources of the PROBA2 microsatellite, the SWAP telescope is designed with various innovative technologies, including an off-axis optical design and a CMOS-APS detector. This article provides reference documentation for users of the SWAP image data.Comment: 26 pages, 9 figures, 1 movi

Prominence eruption observed in He II 304 Å up to >6 R⊙ by EUI/FSI aboard Solar Orbiter⋆

Aims. We report observations of a unique, large prominence eruption that was observed in the He II 304 Å passband of the Extreme Ultraviolet Imager/Full Sun Imager telescope aboard Solar Orbiter on 15–16 February 2022. Methods. Observations from several vantage points – Solar Orbiter, the Solar-Terrestrial Relations Observatory, the Solar and Heliospheric Observatory, and Earth-orbiting satellites – were used to measure the kinematics of the erupting prominence and the associated coronal mass ejection. Three-dimensional reconstruction was used to calculate the deprojected positions and speeds of different parts of the prominence. Observations in several passbands allowed us to analyse the radiative properties of the erupting prominence. Results. The leading parts of the erupting prominence and the leading edge of the corresponding coronal mass ejection propagate at speeds of around 1700 km s−1 and 2200 km s−1, respectively, while the trailing parts of the prominence are significantly slower (around 500 km s−1). Parts of the prominence are tracked up to heights of over 6 R⊙. The He II emission is probably produced via collisional excitation rather than scattering. Surprisingly, the brightness of a trailing feature increases with height. Conclusions. The reported prominence is the first observed in He II 304 Å emission at such a great height (above 6 R⊙)

Study of the propagation, in situ signatures, and geoeffectiveness of shear-induced coronal mass ejections in different solar winds

Aims. Our goal is to propagate multiple eruptions –obtained through numerical simulations performed in a previous study– to 1 AU and to analyse the effects of different background solar winds on their dynamics and structure at Earth. We also aim to improve the understanding of why some consecutive eruptions do not result in the expected geoeffectiveness, and how a secondary coronal mass ejection (CME) can affect the configuration of the preceding one. Methods. Using the 2.5D magnetohydrodynamics package of the code MPI-AMRVAC, we numerically modelled consecutive CMEs inserted in two different solar winds by imposing shearing motions onto the inner boundary, which in our case represents the low corona. In one of the simulations, the secondary CME was a stealth ejecta resulting from the reconfiguration of the coronal field. The initial magnetic configuration depicts a triple arcade structure shifted southward, and embedded into a bimodal solar wind. We triggered eruptions by imposing shearing motions along the southernmost polarity inversion line, and the computational mesh tracks them via a refinement method that applies to current-carrying structures, and is continuously adapted throughout the simulations. We also compared the signatures of some of our eruptions with those of a multiple CME event that occurred in September 2009 using data from spacecraft around Mercury and Earth. Furthermore, we computed and analysed the Dst index for all the simulations performed. Results. The observed event fits well at 1 AU with two of our simulations, one with a stealth CME and the other without. This highlights the difficulty of attempting to use in situ observations to distinguish whether or not the second eruption was stealthy, because of the processes the flux ropes undergo during their propagation in the interplanetary space. We simulate the CMEs propagated in two different solar winds, one slow and another faster one. In the first case, plasma blobs arise in the trail of eruptions. The faster solar wind simulations create no plasma blobs in the aftermath of the eruptions, and therefore we interpret them as possible indicators of the initial magnetic configuration, which changes along with the background wind. Interestingly, the Dst computation results in a reduced geoeffectiveness in the case of consecutive CMEs when the flux ropes arrive with a leading positive Bz. When the Bz component is reversed, the geoeffectiveness increases, meaning that the magnetic reconnections with the trailing blobs and eruptions strongly affect the impact of the arriving interplanetary CME