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Coronal loops are the fundamental building blocks of the solar corona. Therefore, comprehending their properties is essential in unraveling the dynamics of the upper solar atmosphere. In this study, we conduct a comparative analysis of the morphology and dynamics of a coronal loop observed from two different spacecraft: the High Resolution Imager (HRIEUV) of the Extreme Ultraviolet Imager on board the Solar Orbiter, and the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory. These spacecraft were separated by 43° during this observation. The main findings of this study are that (1) the observed loop exhibits similar widths in both the HRIEUV and AIA data, suggesting that the cross-sectional shape of the loop is circular; (2) the loop maintains a uniform width along its entire length, supporting the notion that coronal loops do not exhibit expansion; and (3) notably, the loop undergoes unconventional dynamics, including thread separation and abrupt downward movement. Intriguingly, these dynamic features also appear similar in data from both spacecraft. Although based on observation of a single loop, these results raise questions about the validity of the coronal-veil hypothesis and underscore the intricate and diverse nature of the complexity within coronal loops. [ABSTRACT FROM AUTHOR]

Author(s): James A. Klimchuk [1] Journey From the Center of the Sun by Jack B. Zirker Princeton University Press: 2002. 312 pp. $29.95, £19.95 The Sun has been a source [...]

Occurrences of explosive energy releases are fairly common on the Sun where temperatures rise above its surface temperature, and a magnetic field is often the only source of energy to power such explosions. The reasons for a sudden release of solar magnetism continue to be debated, with the process of magnetic reconnection seen as the most widely accepted explanation. A new report by D.E. Innes and colleagues provides evidence of bi-directional outflow jets, which are part of the reconnection process theory, as seen in the ultraviolet spectra from the ESA-NASA Solar and Heliospheric Observatory. The case for magnetic reconnection has also been reinforced by recent observations from the Yohkoh satellite.

Commission 10 of the International Astronomical Union has more than 650 members who study a wide range of activity phenomena produced by our nearest star, the Sun. Solar activity is intrinsically related to solar magnetic fields and encompasses events from the smallest energy releases (nano- or even picoflares) to the largest eruptions in the Solar System, coronal mass ejections (CMEs), which propagate into the Heliosphere reaching the Earth and beyond. Solar activity is manifested in the appearance of sunspot groups or active regions, which are the principal sources of activity phenomena from the emergence of their magnetic flux through their dispersion and decay. The period 2008–2009 saw an unanticipated extended solar cycle minimum and unprecedentedly weak polar-cap and heliospheric field. Associated with that was the 2009 historical maximum in galactic cosmic rays flux since measurements begun in the middle of the 20th Century. Since then Cycle 24 has re-started solar activity producing some spectacular eruptions observed with a fleet of spacecraft and ground-based facilities. In the last triennium major advances in our knowledge and understanding of solar activity were due to continuing success of space missions as SOHO, Hinode, RHESSI and the twin STEREO spacecraft, further enriched by the breathtaking images of the solar atmosphere produced by the Solar Dynamic Observatory (SDO) launched on 11 February 2010 in the framework of NASA's Living with a Star program. In August 2012, at the time of the IAU General Assembly in Beijing when the mandate of this Commission ends, we will be in the unique position to have for the first time a full 3-D view of the Sun and solar activity phenomena provided by the twin STEREO missions about 120 degrees behind and ahead of Earth and other spacecraft around the Earth and ground-based observatories. These new observational insights are continuously posing new questions, inspiring and advancing theoretical analysis and modelling, improving our understanding of the physics underlying magnetic activity phenomena. Commission 10 reports on a vigorously evolving field of research produced by a large community. The number of refereed publications containing ‘Sun’, ‘heliosphere’, or a synonym in their abstracts continued the steady growth seen over the preceding decades, reaching about 2000 in the years 2008–2010, with a total of close to 4000 unique authors. This report, however, has its limitations and it is inherently incomplete, as it was prepared jointly by the members of the Organising Committee of Commission 10 (see the names of the primary contributors to the sections indicated in parentheses) reflecting their fields of expertise and interest. Nevertheless, we believe that it is a representative sample of significant new results obtained during the last triennium in the field of solar activity. [ABSTRACT FROM PUBLISHER]

The solar activity cycle entered a prolonged quiet phase that started in 2008 and ended in 2010. This minimum lasted for a year longer than expected and all activity proxies, as measured from Earth and from Space, reached minimum values never observed before (de Toma, 2012). The number of spotless days from 2006 to 2009 totals 800, the largest ever recorded in modern times. Solar irradiance was at historic minimums. The interplanetary magnetic field was measured at values as low as 2.9 nT and the cosmic rays were observed at records-high. While rumors spread that the Sun could be entering a grand minimum quiet phase (such as the Maunder minimum of the XVII century), activity took over in 2010 and we are now well into Solar Cycle 24 (albeit, probably, a low intensity cycle), approaching towards a maximum due by mid 2013. In addition to bringing us the possibility to observe a quiet state of the Sun and of the Heliosphere that was previously not recorded with modern instruments, the Sun has also shown us how little we know about the dynamo mechanism that drives its activity as all solar cycle predictions failed to see this extended minimum coming. [ABSTRACT FROM PUBLISHER]

This report is on activities of the Division at the General Assembly in Rio de Janeiro. Summaries of scientific activities over the past triennium have been published in Transactions A, see Melrose et al. (2008), Klimchuk et al. (2008), Martinez Pillet et al. (2008) and Bougeret et al. (2008). The business meeting of the three Commissions were incorporated into the business meeting of the Division. This report is based in part on minutes of the business meeting, provided by the Secretary of the Division, Lidia van Driel-Gesztelyi, and it also includes reports provided by the Presidents of the Commissions (C10, C12, C49) and of the Working Groups (WGs) in the Division. [ABSTRACT FROM PUBLISHER]

This report is on activities of the Division at the General Assembly in Rio de Janeiro. Summaries of scientific activities over the past triennium have been published in Transactions A, see Melrose et al. (2008), Klimchuk et al. (2008), Martinez Pillet et al. (2008) and Bougeret et al. (2008). The business meeting of the three Commissions were incorporated into the business meeting of the Division. This report is based in part on minutes of the business meeting, provided by the Secretary of the Division, Lidia van Driel-Gesztelyi, and it also includes reports provided by the Presidents of the Commissions (C10, C12, C49) and of the Working Groups (WGs) in the Division. [ABSTRACT FROM PUBLISHER]

Commission 10 deals with solar activity in all of its forms, ranging from the smallest nanoflares to the largest coronal mass ejections. This report reviews scientific progress over the roughly two-year period ending in the middle of 2008. This has been an exciting time in solar physics, highlighted by the launches of the Hinode and STEREO missions late in 2006. The report is reasonably comprehensive, though it is far from exhaustive. Limited space prevents the inclusion of many significant results. The report is divided into the following sections: Photosphere and chromosphere; Transition region; Corona and coronal heating; Coronal jets; flares; Coronal mass ejection initiation; Global coronal waves and shocks; Coronal dimming; The link between low coronal CME signatures and magnetic clouds; Coronal mass ejections in the heliosphere; and Coronal mass ejections and space weather. Primary authorship is indicated at the beginning of each section. [ABSTRACT FROM PUBLISHER]

Division II of the IAU provides a forum for astronomers and astrophysicists studying a wide range of phenomena related to the structure, radiation and activity of the Sun, and its interaction with the Earth and the rest of the solar system. Division II encompasses three Commissions, 10, 12 and 49, and four Working Groups. [ABSTRACT FROM PUBLISHER]

Division II provides a forum for astronomers studying a wide range of problems related to the structure, radiation and activity of the Sun, and its interaction with the Earth and the rest of the solar system. [ABSTRACT FROM PUBLISHER]

Commission 10 aims at the study of various forms of solar activity, including networks, plages, pores, spots, fibrils, surges, jets, filaments/prominences, coronal loops, flares, coronal mass ejections (CMEs), solar cycle, microflares, nanoflares, coronal heating etc., which are all manifestation of the interplay of magnetic fields and solar plasma. Increasingly important is the study of solar activities as sources of various disturbances in the interplanetary space and near-Earth “space weather”.Over the past three years a major component of research on the active Sun has involved data from the RHESSI spacecraft. This review starts with an update on current and planned solar observations from spacecraft. The discussion of solar flares gives emphasis to new results from RHESSI, along with updates on other aspects of flares. Recent progress on two theoretical concepts, magnetic reconnection and magnetic helicity is then summarized, followed by discussions of coronal loops and heating, the magnetic carpet and filaments. The final topic discussed is coronal mass ejections and space weather.The discussions on each topic is relatively brief, and intended as an outline to put the extensive list of references in context.The review was prepared jointly by the members of the Organizing Committee, and the names of the primary contributors to the various sections are indicated in parentheses. [ABSTRACT FROM PUBLISHER]

Division II of the IAU provides a forum for astronomers studying a wide range of phenomena related to the structure, radiation and activity of the Sun, and its interaction with the Earth and the rest of the solar system. Division II encompasses three Commissions, 10, 12 and 49, and four working groups. During the last triennia the activities of the division involved some reorganization of the division and its working groups, developing new procedures for election of division and commission officers, promoting annual meetings from within the division and evaluating all the proposed meetings, evaluating the division's representatives for the IAU to international scientific organizations, and participating in general IAU business. [ABSTRACT FROM PUBLISHER]

The Business Meeting of Commission 10 was held as part of the Business Meeting of Division II (Sun and Heliosphere), chaired by Valentin Martínez-Pillet, the President of the Division. The President of Commission 10 (C10; Solar activity), Lidia van Driel-Gesztelyi, took the chair for the business meeting of C10. She summarised the activities of C10 over the triennium and the election of the incoming OC. [ABSTRACT FROM AUTHOR]

Hinode is Japan's third solar mission following Hinotori (1981–1982) and Yohkoh (1991–2001): it was launched on 2006 September 22 and is in operation currently. Hinode carries three instruments: the Solar Optical Telescope, the X-Ray Telescope, and the EUV Imaging Spectrometer. These instruments were built under international collaboration with the National Aeronautics and Space Administration and the UK Science and Technology Facilities Council, and its operation has been contributed to by the European Space Agency and the Norwegian Space Center. After describing the satellite operations and giving a performance evaluation of the three instruments, reviews are presented on major scientific discoveries by Hinode in the first eleven years (one solar cycle long) of its operation. This review article concludes with future prospects for solar physics research based on the achievements of Hinode. [ABSTRACT FROM AUTHOR]