A selection of highlights culled from publications by HAO staff.
Steven Cranmer, Rohit Chhiber, Chris Gilly, Iver Cairns, Robin Colaninno, David McComas, Nour Raouafi, Arcadi Usmanov, Sarah Gibson, Craig DeForest review the properties of Alfvén surface and discuss its importance in models of solar wind acceleration, angular momentum transport, MHD waves and turbulence, and the geometry of closed coronal loops. Simulations results and data analysis techniques are used to determine the location of the Alfvén surface.
B. Raphaldini, M. Dikpati, A. A. Norton, A. S. W. Teruya, S. W. McIntosh, C. B. Prior, and D. MacTaggart investigate how global toroid patterns and local magnetic field topology of solar active region AR12673 together can hindcast occurrence of the biggest X-flare of cycle 24. We infer that minimum-phase storms can be forecast only hours ahead, while flare-prone active regions in peak-phase can be anticipated at least a month ahead from global toroid patterns.
Comprehensive Radiative MHD Simulations of Eruptive Flares above Collisional Polarity Inversion Lines
Matthias Rempel, Georgios Chintzoglou, Mark C. M. Cheung, Yuhong Fan, and Lucia Kleint—Solar flares are bursts of high-energy radiation that are associated with sunspots. NOVA highlights this newly published research that uses models to study what happens when sunspots collide and under what conditions these collisions cause solar flares.
Philip Judge evaluates images from the Solar Orbiter spacecraft to determine the steadiness of coronal heating. The widely-held belief that the outer atmosphere of the Sun is in a continuous state of magnetic turmoil is pitted against the EUI data with very illuminating results.
This fascinating memoir covers the scientific life of Dr. Andrew Skumanich, starting with his family’s background and their immigration to the US. It continues with Andy's childhood, early education, his influential introduction to science, and finally his illuminating career, which started at Los Alamos Scientific Laboratory in the 1950s and then continued in solar physics at the High Altitude Observatory (National Center for Atmospheric Research).
Magnetic field and plasma diagnostics for solar coronal mass ejections: A case study using the forward modeling approach
X. Liu, H. Tian, T. Toeroek, S. Gibson, Z. Yang, W. Li, and T. Samanta show results that the COronal Solar Magnetism Observatory (COSMO) Large Coronagraph (LC) can provide magnetic field measurements of CME progenitors with a high spatial resolution (2′′ pixels). By using a worse resolution (6′′ pixels), the COSMO LC observation may also be used to qualitatively study the evolution of magnetic field during the CME eruption.
This new book, by Phil Judge et al., offers a critical overview of the field of research, including a dive into methodologies to understand the nature of this recalcitrant problem. Armed with an up-to-date understanding of theory, instrumentation, and the developing field of machine learning, the authors offer suggestions for new, stronger methodologies aimed to generate measurable progress.
Philip Judge, Lucia Klient, Roberto Casini, Alfred de Wijn, Tom Schad, and Ali Tritschler uniquely connect magnetic fields threading the chromosphere to the overlying corona and other heated plasmas. They found no correlations between heated plasma and properties of chromospheric magnetic fields on scales below supergranules.
Holly Gilbert notes that sunspot observations have been recorded for over 400 years, and eclipses were first documented thousands of years ago. Although the Sun is no longer a complete mystery, the way we observe it continues to develop, as continued technological advances uncover new mysteries for future generations to solve.