7 December 2023We present key results of a case study of an M4-class flare on March 28, 2022, seen by STIX and EUI/FSI onboard Solar Orbiter, and SDO/AIA. An interesting aspect of this flare was the change in the non-thermal hard X-ray (HXR) source configuration during a late HXR peak, changing from the classical two footpoints at the ends of the flaring loops...

7 December 2023EUV waves are large-scale wave-like coronal disturbances visible in extreme ultraviolet (EUV) light. EUV waves arise from active regions (ARs) and are almost always associated with Coronal Mass Ejections (CMEs). The nature of EUV waves and their interrelation with CMEs is still debated. In the following, we investigate the nature of these...

16 November 2023In recent years, a consensus seems to have arisen that coronal heating is a dynamic process. For example, in De Moortel and Browning (2015) we read “coronal heating is intrinsically non-steady”. This point is not contested here, for it is well known that the energy input must be variable, being driven by granulation, emerging magnetic flux and...

9 November 2023Zeeman spectropolarimetry provides a method to infer the properties of the photospheric magnetic field, however, this is method is hampered by the 180°-ambiguity in the orientation of the transverse component: specifically two equally-intense, oppositely-directed transverse fields produce the very same spectro-polarimetric signal. The removal of...

2 November 2023The photosphere exists at a temperature of around 6000 degrees. In the 1940s, following correct interpretation of solar spectra it was discovered that the temperature of the corona is instead about 150 times hotter, reaching one million degrees (coronal temperatures can even be an order of magnitude higher during high-energy events such as...

25 October 2023Solar eruptive activities, including flares, eruptive filaments, CMEs, and coronal jets, are widely distributed in energy scales. The observed solar eruptions span a range of at least a factor of 10⁸ in energy. Large, highly energetic “X-class” eruptions can release energy substantially exceeding ∼ 10³³ ergs. Coronal...

18 October 2023The solar corona is built by arch-like loop structures filled with million Kelvin hot plasma. The so-called active corona follows the 11-year solar activity cycle and is governed by strong magnetic concentrations in active regions including sunspots and plages. Powerful flares and coronal mass ejections are some of the transient signatures of...

11 October 2023On the 9th of April 2022 Solar Orbiter observed a virtually scatter-free solar particle event with an unusually long magnetic connection while immersed in a magnetic cloud. It was observed both in energetic electrons and ions while Solar Orbiter was at 0.43 au from the Sun. The length of the magnetic field line was inferred to be about three...

27 September 2023The coupling mechanism of the ubiquitous proton beams with fields is a cutting-edge scientific question in the solar wind wavelike turbulence. Using Solar Orbiter's high-quality measurements, it is found that the proton beam is not strictly parallel to the local magnetic field, exhibiting an intriguing feature of non-field-alignment. This...

20 September 2023The unequivocal and persistently growing interest in studying wave and oscillatory phenomena in the corona is motivated by their use for plasma diagnostics, and for their potential contribution to the enigmatic coronal heating. Recently discovered low-amplitude decayless kink oscillations are among the most promising candidates for both those...