Author name code: gallagher ADS astronomy entries on 2022-09-14 author:"Gallagher, Peter T." ------------------------------------------------------------------------ Title: Searching for stellar flares from low-mass stars using ASKAP and TESS Authors: Rigney, Jeremy; Ramsay, Gavin; Carley, Eoin P.; Doyle, J. Gerry; Gallagher, Peter T.; Wang, Yuanming; Pritchard, Joshua; Murphy, Tara; Lenc, Emil; Kaplan, David L. Bibcode: 2022MNRAS.516..540R Altcode: 2022MNRAS.tmp.2052R; 2022arXiv220700405R Solar radio emission at low frequencies (<1 GHz) can provide valuable information on processes driving flares and coronal mass ejections (CMEs). Radio emission has been detected from active M dwarf stars, suggestive of much higher levels of activity than previously thought. Observations of active M dwarfs at low frequencies can provide information on the emission mechanism for high energy flares and possible stellar CMEs. Here, we conducted two observations with the Australian Square Kilometre Array Pathfinder Telescope totalling 26 h and scheduled to overlap with the Transiting Exoplanet Survey Satellite Sector 36 field, utilizing the wide fields of view of both telescopes to search for multiple M dwarfs. We detected variable radio emission in Stokes I centred at 888 MHz from four known active M dwarfs. Two of these sources were also detected with Stokes V circular polarization. When examining the detected radio emission characteristics, we were not able to distinguish between the models for either electron cyclotron maser or gyrosynchrotron emission. These detections add to the growing number of M dwarfs observed with variable low-frequency emission. Title: Excitation of Langmuir waves at shocks and solar type II radio bursts Authors: Mann, G.; Vocks, C.; Warmuth, A.; Magdalenic, J.; Bisi, M.; Carley, E.; Dabrowski, B.; Gallagher, P.; Krankowski, A.; Matyjasiak, B.; Rotkaehl, H.; Zucca, P. Bibcode: 2022A&A...660A..71M Altcode: Context. In the solar corona, shocks can be generated due to the pressure pulse of a flare and/or driven by a rising coronal mass ejection (CME). Coronal shock waves can be observed as solar type II radio bursts in the Sun's radio radiation. In dynamic radio spectra, they appear as stripes of an enhanced radio emission slowly drifting from high to low frequencies. The radio emission is thought to be plasma emission, that is to say the emission happens near the electron plasma frequency and/or its harmonics. Plasma emission means that energetic electrons excite Langmuir waves, which convert into radio waves via non-linear plasma processes. Thus, energetic electrons are necessary for plasma emission. In the case of type II radio bursts, the energetic electrons are considered to be shock accelerated.
Aims: Shock drift acceleration (SDA) is regarded as the mechanism for producing energetic electrons in the foreshock region. SDA delivers a shifted loss-cone velocity distribution function (VDF) for the energetic electrons. The aim of the paper is to study in which way and under which conditions a shifted loss-cone VDF of electrons excites Langmuir waves in an efficient way in the corona.
Methods: By means of the results of SDA, the shape of the resulted VDF was derived. It is a shifted loss-cone VDF showing both a loss-cone and a beam-like component. The growth rates for exciting Langmuir waves were calculated in the framework of Maxwell-Vlasov equations. The results are discussed by employing plasma and shock parameters usually found in the corona at the 25 MHz level.
Results: We have found that moderate coronal shocks with an Alfven-Mach number in the range 1.59 < MA < 2.53 are able to accelerate electrons up to energies sufficient enough to excite Langmur waves, which convert into radio waves seen as solar type II radio bursts. Title: Tracking a beam of electrons from the low solar corona into interplanetary space with the Low Frequency Array, Parker Solar Probe and 1 au spacecraft Authors: Badman, Samuel T.; Carley, Eoin P.; Cañizares, Luis Alberto; Dresing, Nina; Jian, Lan K.; Lario, David; Gallagher, Peter T.; Martínez-Oliveros, Juan C.; Pulupa, Marc; Bale, Stuart D. Bibcode: 2022arXiv220408497B Altcode: Type III radio bursts are the result of plasma emission from mildly relativistic electron beams propagating from the low solar corona into the heliosphere where they can eventually be detected in situ if they align with the location of a heliospheric spacecraft. Here we observe a type III radio burst from 0.1-16 MHz using the Parker Solar Probe (PSP) FIELDS Radio Frequency Spectrometer (RFS), and from 10-80 MHz using the Low Frequency Array (LOFAR). This event was not associated with any detectable flare activity but was part of an ongoing noise storm that occurred during PSP encounter 2. A deprojection of the LOFAR radio sources into 3D space shows that the type III radio burst sources were located on open magnetic field from 1.6-3 $R_\odot$ and originated from a specific active region near the East limb. Combining PSP/RFS observations with WIND/WAVES and Solar Terrestrial Relations Observatory (STEREO)/WAVES, we reconstruct the type III radio source trajectory in the heliosphere interior to PSP's position, assuming ecliptic confinement. An energetic electron enhancement is subsequently detected in situ at the STEREO-A spacecraft at compatible times although the onset and duration suggests the individual burst contributes a subset of the enhancement. This work shows relatively small-scale flux emergence in the corona can cause the injection of electron beams from the low corona into the heliosphere, without needing a strong solar flare. The complementary nature of combined ground and space-based radio observations, especially in the era of PSP, is also clearly highlighted by this study. Title: Comparing the Heliospheric Cataloging, Analysis, and Techniques Service (HELCATS) Manual and Automatic Catalogues of Coronal Mass Ejections Using Solar Terrestrial Relations Observatory/Heliospheric Imager (STEREO/HI) Data Authors: Rodriguez, L.; Barnes, D.; Hosteaux, S.; Davies, J. A.; Willems, S.; Pant, V.; Harrison, R. A.; Berghmans, D.; Bothmer, V.; Eastwood, J. P.; Gallagher, P. T.; Kilpua, E. K. J.; Magdalenic, J.; Mierla, M.; Möstl, C.; Rouillard, A. P.; Odstrčil, D.; Poedts, S. Bibcode: 2022SoPh..297...23R Altcode: 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. Title: LOFAR4SpaceWeather (LOFAR4SW) Increasing European Space-Weather Capability with Europes Largest Radio Telescope: Completing the Critical Design Review (CDR) Authors: Bisi, Mario; Fallows, Richard; Vermeulen, Rene; Robertson, Stuart; Ruiter, Mark; Vilmer, Nicole; Rothkaehl, Hanna; Matyjasiak, Barbara; Verbiest, Joris; Carley, Eoin; Gallagher, Peter; Carozzi, Tobia; Lindqvist, Michael; Olberg, Michael; Kruger, Paulus; Mevius, Maaijke; Barnes, David; Chang, Oyuki; Baldovin, Carla Bibcode: 2021AGUFMSH45E2412B Altcode: Space Weather research, monitoring, and operations are a very important topics from the scientific, operational, and societal-impacts points of view. Knowledge of interactions in the Sun-Earth system, the physics behind observed space-weather phenomena, and its direct impact on modern technologies are key areas of interest. This involves all aspects of political, user, forecaster, and scientific engagement with various stakeholders with the full recognition that space weather is a worldwide threat with varied local, regional, continent-wide impacts, and global impacts. The LOFAR For Space Weather (LOFAR4SW) project (see: http://lofar4sw.eu/) is a Horizon 2020 (H2020) INFRADEV design study to undertake investigations and perform a design study into the upgrading of the Low Frequency Array (LOFAR). The project aims to prepare a novel design pathway which can bring new capabilities into the space-weather domain. LOFAR is presently the world's largest low frequency radio telescope consisting of a dense core of 24 stations near Exloo in The Netherlands, an additional 14 stations spread across the northeast Netherlands, and a further 14 stations based internationally across Europe. These international stations are six across Germany, three in northern Poland, and one each in France, Ireland, Latvia, Sweden, and the UK. Further sites are being planned across Europe. The final design of LOFAR4SW will provide a comprehensive conceptual and technical description of the necessary LOFAR upgrades needed to enable simultaneous operation as a radio telescope for astronomical research as well as an infrastructure working for space-weather studies and monitoring. In this work we present the overview of the LOFAR4SW project, examples of its capabilities and will summarise the outcomes of the Critical Design Review (CDR) planned to be held virtually 21-23 September 2021. A fully-envisage longer-term goal of enable a LOFAR4SW update would make LOFAR one of Europes most-comprehensive space-weather observing systems capable of shedding new light on several aspects of the space-weather system, from the Sun to the solar wind to Jupiter and Earths ionosphere. Title: STIX X-ray microflare observations during the Solar Orbiter commissioning phase Authors: Battaglia, Andrea Francesco; Saqri, Jonas; Massa, Paolo; Perracchione, Emma; Dickson, Ewan C. M.; Xiao, Hualin; Veronig, Astrid M.; Warmuth, Alexander; Battaglia, Marina; Hurford, Gordon J.; Meuris, Aline; Limousin, Olivier; Etesi, László; Maloney, Shane A.; Schwartz, Richard A.; Kuhar, Matej; Schuller, Frederic; Senthamizh Pavai, Valliappan; Musset, Sophie; Ryan, Daniel F.; Kleint, Lucia; Piana, Michele; Massone, Anna Maria; Benvenuto, Federico; Sylwester, Janusz; Litwicka, Michalina; Stȩślicki, Marek; Mrozek, Tomasz; Vilmer, Nicole; Fárník, František; Kašparová, Jana; Mann, Gottfried; Gallagher, Peter T.; Dennis, Brian R.; Csillaghy, André; Benz, Arnold O.; Krucker, Säm Bibcode: 2021A&A...656A...4B Altcode: 2021arXiv210610058B Context. The Spectrometer/Telescope for Imaging X-rays (STIX) is the hard X-ray instrument onboard Solar Orbiter designed to observe solar flares over a broad range of flare sizes.
Aims: We report the first STIX observations of solar microflares recorded during the instrument commissioning phase in order to investigate the STIX performance at its detection limit.
Methods: STIX uses hard X-ray imaging spectroscopy in the range between 4-150 keV to diagnose the hottest flare plasma and related nonthermal electrons. This first result paper focuses on the temporal and spectral evolution of STIX microflares occuring in the Active Region (AR) AR12765 in June 2020, and compares the STIX measurements with Earth-orbiting observatories such as the X-ray Sensor of the Geostationary Operational Environmental Satellite (GOES/XRS), the Atmospheric Imaging Assembly of the Solar Dynamics Observatory, and the X-ray Telescope of the Hinode mission.
Results: For the observed microflares of the GOES A and B class, the STIX peak time at lowest energies is located in the impulsive phase of the flares, well before the GOES peak time. Such a behavior can either be explained by the higher sensitivity of STIX to higher temperatures compared to GOES, or due to the existence of a nonthermal component reaching down to low energies. The interpretation is inconclusive due to limited counting statistics for all but the largest flare in our sample. For this largest flare, the low-energy peak time is clearly due to thermal emission, and the nonthermal component seen at higher energies occurs even earlier. This suggests that the classic thermal explanation might also be favored for the majority of the smaller flares. In combination with EUV and soft X-ray observations, STIX corroborates earlier findings that an isothermal assumption is of limited validity. Future diagnostic efforts should focus on multi-wavelength studies to derive differential emission measure distributions over a wide range of temperatures to accurately describe the energetics of solar flares.
Conclusions: Commissioning observations confirm that STIX is working as designed. As a rule of thumb, STIX detects flares as small as the GOES A class. For flares above the GOES B class, detailed spectral and imaging analyses can be performed. Title: First results from the REAL-time Transient Acquisition backend (REALTA) at the Irish LOFAR station Authors: Murphy, P. C.; Callanan, P.; McCauley, J.; McKenna, D. J.; Fionnagáin, D. Ó.; Louis, C. K.; Redman, M. P.; Cañizares, L. A.; Carley, E. P.; Maloney, S. A.; Coghlan, B.; Daly, M.; Scully, J.; Dooley, J.; Gajjar, V.; Giese, C.; Brennan, A.; Keane, E. F.; Maguire, C. A.; Quinn, J.; Mooney, S.; Ryan, A. M.; Walsh, J.; Jackman, C. M.; Golden, A.; Ray, T. P.; Doyle, J. G.; Rigney, J.; Burton, M.; Gallagher, P. T. Bibcode: 2021A&A...655A..16M Altcode: 2021arXiv210811251M Modern radio interferometers such as the LOw Frequency ARray (LOFAR) are capable of producing data at hundreds of gigabits to terabits per second. This high data rate makes the analysis of radio data cumbersome and computationally expensive. While high performance computing facilities exist for large national and international facilities, that may not be the case for instruments operated by a single institution or a small consortium. Data rates for next generation radio telescopes are set to eclipse those currently in operation, hence local processing of data will become all the more important. Here, we introduce the REAL-time Transient Acquisition backend (REALTA), a computing backend at the Irish LOFAR station (I-LOFAR) which facilitates the recording of data in near real-time and post-processing. We also present first searches and scientific results of a number of radio phenomena observed by I-LOFAR and REALTA, including pulsars, fast radio bursts, rotating radio transients, the search for extraterrestrial intelligence, Jupiter, and the Sun. Title: Observing Jupiter's radio emissions using multiple LOFAR stations: a first case study of the Io-decametric emission using the Irish IE613, French FR606 and German DE604 stations Authors: Louis, Corentin K.; Jackman, Caitriona M.; Griessmeier, Jean-Mathias; Wucknitz, Olaf; McKenna, David J.; Murphy, Pearse; Gallagher, Peter T.; Carley, Eoin; Fionnagáin, Dúalta Ó; Golden, Aaron; McCauley, Joe; Callanan, Paul; Redman, Matt; Vocks, Christian Bibcode: 2021arXiv211109599L Altcode: The Low Frequency Array (LOFAR) is an international radio telescope array, consisting of 38 stations in the Netherlands and 14 international stations spread over Europe. Here we present an observation method to study the jovian decametric radio emissions from several LOFAR stations (here DE604, FR606 and IE613), at high temporal and spectral resolution. This method is based on prediction tools, such as radio emission simulations and probability maps, and data processing. We report an observation of Io-induced decametric emission from June 2021, and a first case study of the substructures that compose the macroscopic emissions (called millisecond bursts). The study of these bursts make it possible to determine the electron populations at the origin of these emissions. We then present several possible future avenues for study based on these observations. The methodology and study perspectives described in this paper can be applied to new observations of jovian radio emissions induced by Io, but also by Ganymede or Europa, or jovian auroral radio emissions. Title: Solar Flare Effects on the Earth's Lower Ionosphere Authors: Hayes, Laura A.; O'Hara, Oscar S. D.; Murray, Sophie A.; Gallagher, Peter T. Bibcode: 2021SoPh..296..157H Altcode: 2021arXiv210906558H Solar flares significantly impact the conditions of the Earth's ionosphere. In particular, the sudden increase in X-ray flux during a flare penetrates down to the lowest-lying D-region and dominates ionization at these altitudes (≈60 - 100 km). Measurements of very low frequency (VLF: 3 - 30 kHz) radio waves that reflect at D-region altitudes provide a unique remote-sensing probe to investigate the D-region response to solar-flare emissions. Here, using a combination of VLF amplitude measurements at 24 kHz together with X-ray observations from the Geostationary Operational Environment Satellite (GOES) X-ray sensor, we present a large-scale statistical study of 334 solar-flare events and their impacts on the D-region over the past solar cycle. Focusing on both GOES broadband X-ray channels, we investigate how the flare peak fluxes and position on the solar disk dictate an ionospheric response and extend this to investigate the characteristic time delay between incident X-ray flux and the D-region response. We show that the VLF amplitude linearly correlates with both the 1 - 8 Å and 0.5 - 4 Å channels, with correlation coefficients of 0.80 and 0.79, respectively. For the two X-class flares in our sample, however, there appears to be a turnover in the linear relationship, similar to previous works. Unlike higher altitude ionospheric regions for which the location of the flare on the solar disk affects the ionospheric response, we find that the D-region response to solar flares does not depend on the flare location. By comparing the time delays between the peak X-ray fluxes in both GOES channels and VLF amplitudes, we find that there is an important difference between the D-region response and the X-ray spectral band. We also demonstrate for several flare events that show a negative time delay, the peak VLF amplitude matches with the impulsive 25 - 50 keV hard X-ray fluxes measured by the Ramaty High Energy Solar Spectroscopic Imager (RHESSI). These results highlight the importance of performing full spectral analysis when studying the ionospheric responses to solar flares. Title: Quasi-Periodic Particle Acceleration in a Solar Flare Authors: Clarke, B. P.; Hayes, L. A.; Gallagher, P. T.; Maloney, S. A.; Carley, E. P. Bibcode: 2021AAS...23830303C Altcode: A common feature of electromagnetic emission from solar flares is the presence of intensity pulsations that vary as a function of time. Known as quasi-periodic pulsations (QPPs), these variations in flux appear to include periodic components and characteristic time-scales. Here, we analyse a GOES M3.7 class flare exhibiting pronounced QPPs across a broad band of wavelengths using imaging and timeseries analysis. We identify QPPs in the timeseries of X-ray, low frequency radio and EUV wavelengths using wavelet analysis, and localise the region of the flare site from which the QPPs originate via X-ray and EUV imaging. It was found that the pulsations within the 171 A, 1600 A, soft X-ray (SXR), and hard X-ray (HXR) light curves yielded similar periods of ~122 s, ~131 s, ~123 s, and ~137 s, respectively, indicating a common progenitor. The low frequency radio emission at 2.5 MHz contained a longer period of ∼231 s. Imaging analysis indicates that the location of the X-ray and EUV pulsations originates from a HXR footpoint linked to a system of nearby open magnetic field lines. Our results suggest that intermittent particle acceleration, likely due to 'bursty' magnetic reconnection, is responsible for the QPPs. The precipitating electrons accelerated towards the chromosphere produce the X-ray and EUV pulsations, while the escaping electrons result in low frequency radio pulses in the form of type III radio bursts. The modulation of the reconnection process, resulting in episodic particle acceleration, explains the presence of these QPPs across the entire spatial range of flaring emission. Title: The flare likelihood and region eruption forecasting (FLARECAST) project: flare forecasting in the big data & machine learning era Authors: Georgoulis, Manolis K.; Bloomfield, D. Shaun; Piana, Michele; Massone, Anna Maria; Soldati, Marco; Gallagher, Peter T.; Pariat, Etienne; Vilmer, Nicole; Buchlin, Eric; Baudin, Frederic; Csillaghy, Andre; Sathiapal, Hanna; Jackson, David R.; Alingery, Pablo; Benvenuto, Federico; Campi, Cristina; Florios, Konstantinos; Gontikakis, Constantinos; Guennou, Chloe; Guerra, Jordan A.; Kontogiannis, Ioannis; Latorre, Vittorio; Murray, Sophie A.; Park, Sung-Hong; von Stachelski, Samuelvon; Torbica, Aleksandar; Vischi, Dario; Worsfold, Mark Bibcode: 2021JSWSC..11...39G Altcode: 2021arXiv210505993G The European Union funded the FLARECAST project, that ran from January 2015 until February 2018. FLARECAST had a research-to-operations (R2O) focus, and accordingly introduced several innovations into the discipline of solar flare forecasting. FLARECAST innovations were: first, the treatment of hundreds of physical properties viewed as promising flare predictors on equal footing, extending multiple previous works; second, the use of fourteen (14) different machine learning techniques, also on equal footing, to optimize the immense Big Data parameter space created by these many predictors; third, the establishment of a robust, three-pronged communication effort oriented toward policy makers, space-weather stakeholders and the wider public. FLARECAST pledged to make all its data, codes and infrastructure openly available worldwide. The combined use of 170+ properties (a total of 209 predictors are now available) in multiple machine-learning algorithms, some of which were designed exclusively for the project, gave rise to changing sets of best-performing predictors for the forecasting of different flaring levels, at least for major flares. At the same time, FLARECAST reaffirmed the importance of rigorous training and testing practices to avoid overly optimistic pre-operational prediction performance. In addition, the project has (a) tested new and revisited physically intuitive flare predictors and (b) provided meaningful clues toward the transition from flares to eruptive flares, namely, events associated with coronal mass ejections (CMEs). These leads, along with the FLARECAST data, algorithms and infrastructure, could help facilitate integrated space-weather forecasting efforts that take steps to avoid effort duplication. In spite of being one of the most intensive and systematic flare forecasting efforts to-date, FLARECAST has not managed to convincingly lift the barrier of stochasticity in solar flare occurrence and forecasting: solar flare prediction thus remains inherently probabilistic. Title: Type III solar radio burst detection and classification: A deep learning approach Authors: Scully, Jeremiah; Flynn, Ronan; Carley, Eoin; Gallagher, Peter; Daly, Mark Bibcode: 2021arXiv210513387S Altcode: Solar Radio Bursts (SRBs) are generally observed in dynamic spectra and have five major spectral classes, labelled Type I to Type V depending on their shape and extent in frequency and time. Due to their complex characterisation, a challenge in solar radio physics is the automatic detection and classification of such radio bursts. Classification of SRBs has become fundamental in recent years due to large data rates generated by advanced radio telescopes such as the LOw-Frequency ARray, (LOFAR). Current state-of-the-art algorithms implement the Hough or Radon transform as a means of detecting predefined parametric shapes in images. These algorithms achieve up to 84% accuracy, depending on the Type of radio burst being classified. Other techniques include procedures that rely on Constant-FalseAlarm-Rate detection, which is essentially detection of radio bursts using a de-noising and adaptive threshold in dynamic spectra. It works well for a variety of different Types of radio bursts and achieves an accuracy of up to 70%. In this research, we are introducing a methodology named You Only Look Once v2 (YOLOv2) for solar radio burst classification. By using Type III simulation methods we can train the algorithm to classify real Type III solar radio bursts in real-time at an accu Title: Failure to forecast: A case study in nowcasting and forecasting the eruption of a coronal mass ejection and its geomagnetic impacts on Dec 7-10, 2020. Authors: Gallagher, Peter; Murray, Sophie; Malone-Leigh, John; Campanyà, Joan; Cañizares, Alberto; Carley, Eoin; Blake, Seán Bibcode: 2021EGUGA..2315520G Altcode: Forecasting solar flares based on while-light images and photospheric magnetograms of sunspots is notoriously challenging, while accurate forecasting of coronal mass ejections (CME) is still in its infancy. That said, the chances of a CME being launched is more likely following a flare. CMEs launched from the western hemisphere and "halo" CMEs are the most likely to be geomagnetically impactful, but forecasting their arrival and impact at Earth depends on how well their velocity is known near the Sun, the solar wind conditions between the Sun and the Earth, the accuracy of theoretical models and on the orientation of the CME magnetic field. In this presentation, we describe a well observed active region, flare, CME, radio burst and sudden geomagnetic impulse that was observed on December 7-10, 2020 by a slew of instruments (SDO, ACE, DSCOVR, PSP, US and European magnetometers). This was a solar eruption that was not expected, but the CME and resulting geomagnetic impact should have been straight-forward to model and forecast. What can we learn from our failure to forecast this simple event and its impacts at Earth? Title: LOFAR observations of a jet-driven piston shock in the low solar corona Authors: Maguire, Ciara; Carley, Eoin; Zucca, Pietro; Vilmer, Nicole; Gallagher, Peter Bibcode: 2021EGUGA..23.7602M Altcode: The Sun produces highly dynamic and eruptive events that can drive shocks through the corona. These shocks can accelerate electrons, which result in plasma emission in the form of a type II radio burst. Despite a large number of type II radio bursts observations, the precise origin of coronal shocks is still subject to investigation. Here we present a well-observed solar eruptive event that occurred on 16 October 2015, focusing on a jet observed in the extreme ultraviolet by the SDO Atmospheric Imaging Assembly, a streamer observed in white-light by the Large Angle and Spectrometric Coronagraph, and a metric type II radio burst observed by the LOw-Frequency Array (LOFAR) radio telescope. For the first time, LOFAR has interferometrically imaged the fundamental and harmonic sources of a type II radio burst and revealed that the sources did not appear to be co-spatial, as would be expected from the plasma emission mechanism. We correct for the separation between the fundamental and harmonic using a model which accounts for the scattering of radio waves by electron density fluctuations in a turbulent plasma. This allows us to show the type II radio sources were located ∼0.5 Rsun above the jet and propagated at a speed of ∼1000 km s-1, which was significantly faster than the jet speed of ∼200 km s-1. This suggests that the type II burst was generated by a piston shock driven by the jet in the low corona. Title: LOFAR4SW - Space Weather Science and Operations with LOFAR Authors: Rothkaehl, Hanna; Matyjasiak, Barbara; Baldovin, Carla; Bisi, Mario; Barnes, David; Carley, Eoin; Carozzi, Tobia; Fallows, Richard A.; Gallagher, Peter T.; Mevius, Maaijke; Robertson, Stuart C.; Ruiter, Mark; Verbiest, Joris; Vermeulen, Renne; Vilmer, Nicole Bibcode: 2021EGUGA..23.6455R Altcode: Space Weather (SW) research is a very important topic from the scientific, operational and civic society point of view. Knowledge of interactions in the Sun-Earth system, the physics behind observed SW phenomena, and its direct impact on modern technologies were and will be key areas of interest. The LOFAR for Space Weather (LOFAR4SW) project aim is to prepare a novel tool which can bring new capabilities into this domain. The project is realised in the frame of a Horizon 2020 INFRADEV call. The base for the project is the Low Frequency Array (LOFAR) - the worlds largest low frequency radio telescope, with a dense core near Exloo in The Netherlands and many stations distributed both in the Netherlands and Europe wide with baselines up to 2000 km. The final design of LOFAR4SW will provide a full conceptual and technical description of the LOFAR upgrade, to enable simultaneous operation as a radio telescope for astronomical research as well as an infrastructure working for Space Weather studies. In this work we present the current status of the project, including examples of the capabilities of LOFAR4SW and the project timeline as we plan for the Critical Design Review later in 2021. Title: LOFAR Imaging of the Solar Corona during the 2015 March 20 Solar Eclipse Authors: Ryan, Aoife Maria; Gallagher, Peter T.; Carley, Eoin P.; Brentjens, Michiel A.; Murphy, Pearse C.; Vocks, Christian; Morosan, Diana E.; Reid, Hamish; Magdalenic, Jasmina; Breitling, Frank; Zucca, Pietro; Fallows, Richard; Mann, Gottfried; Kerdraon, Alain; Halfwerk, Ronald Bibcode: 2021EGUGA..2311094R Altcode: The solar corona is a highly-structured plasma which can reach temperatures of more than 2 MK. At low frequencies (decimetric and metric wavelengths), scattering and refraction of electromagnetic waves are thought to considerably increase the imaged radio source sizes (up to a few arcminutes). However, exactly how source size relates to scattering due to turbulence is still subject to investigation. The theoretical predictions relating source broadening to propagation effects have not been fully confirmed by observations, due to the rarity of high spatial resolution observations of the solar corona at low frequencies. Here, the LOw Frequency ARray (LOFAR) was used to observe the solar corona at 120-180 MHz using baselines of up to 3.5 km (corresponding to a resolution of 1-2") during the partial solar eclipse of 2015 March 20. A lunar de-occultation technique was used to achieve higher spatial resolution (0.6") than that attainable via standard interferometric imaging (2.4"). This provides a means of studying the contribution of scattering to apparent source size broadening. This study shows that the de-occultation technique can reveal a more structured quiet corona that is not resolved from standard imaging, implying scattering may be overestimated in this region when using standard imaging techniques. However, an active region source was measured to be 4" using both de-occultation and standard imaging. This may be explained by increased scattering of radio waves by turbulent density fluctuations in active regions, which is more severe than in the quiet Sun. Title: LOFAR imaging of the solar corona during the 2015 March 20 solar eclipse Authors: Ryan, A. M.; Gallagher, P. T.; Carley, E. P.; Brentjens, M. A.; Murphy, P. C.; Vocks, C.; Morosan, D. E.; Reid, H.; Magdalenic, J.; Breitling, F.; Zucca, P.; Fallows, R.; Mann, G.; Kerdraon, A.; Halfwerk, R. Bibcode: 2021A&A...648A..43R Altcode: 2021arXiv210205552R The solar corona is a highly-structured plasma which can reach temperatures of more than ∼2 MK. At low frequencies (decimetric and metric wavelengths), scattering and refraction of electromagnetic waves are thought to considerably increase the imaged radio source sizes (up to a few arcminutes). However, exactly how source size relates to scattering due to turbulence is still subject to investigation. The theoretical predictions relating source broadening to propagation effects have not been fully confirmed by observations due to the rarity of high spatial resolution observations of the solar corona at low frequencies. Here, the LOw Frequency ARray (LOFAR) was used to observe the solar corona at 120−180 MHz using baselines of up to ∼3.5 km (corresponding to a resolution of ∼1−2') during the partial solar eclipse of 2015 March 20. A lunar de-occultation technique was used to achieve higher spatial resolution (∼0.6') than that attainable via standard interferometric imaging (∼2.4'). This provides a means of studying the contribution of scattering to apparent source size broadening. It was found that the de-occultation technique reveals a more structured quiet corona that is not resolved from standard imaging, implying scattering may be overestimated in this region when using standard imaging techniques. However, an active region source was measured to be ∼4' using both de-occultation and standard imaging. This may be explained by the increased scattering of radio waves by turbulent density fluctuations in active regions, which is more severe than in the quiet Sun. Title: Quasi-periodic Particle Acceleration in a Solar Flare Authors: Clarke, Brendan P.; Hayes, Laura A.; Gallagher, Peter T.; Maloney, Shane A.; Carley, Eoin P. Bibcode: 2021ApJ...910..123C Altcode: 2021arXiv210204267C A common feature of electromagnetic emission from solar flares is the presence of intensity pulsations that vary as a function of time. Known as quasi-periodic pulsations (QPPs), these variations in flux appear to include periodic components and characteristic timescales. Here, we analyze a GOES M3.7 class flare exhibiting pronounced QPPs across a broad band of wavelengths using imaging and time series analysis. We identify QPPs in the time series of X-ray, low-frequency radio, and extreme ultraviolet (EUV) wavelengths using wavelet analysis, and localize the region of the flare site from which the QPPs originate via X-ray and EUV imaging. It was found that the pulsations within the 171 Å, 1600 Å, soft X-ray, and hard X-ray light curves yielded similar periods of ${122}_{-22}^{+26}$ <!-- --> s, ${131}_{-27}^{+36}$ <!-- --> s, ${123}_{-26}^{+11}$ <!-- --> s, and ${137}_{-56}^{+49}$ <!-- --> s, respectively, indicating a common progenitor. The low-frequency radio emission at 2.5 MHz contained a longer period of ∼231 s. Imaging analysis indicates that the location of the X-ray and EUV pulsations originates from a hard X-ray footpoint linked to a system of nearby open magnetic field lines. Our results suggest that intermittent particle acceleration, likely due to "bursty" magnetic reconnection, is responsible for the QPPs. The precipitating electrons accelerated toward the chromosphere produce the X-ray and EUV pulsations, while the escaping electrons result in low-frequency radio pulses in the form of type III radio bursts. The modulation of the reconnection process, resulting in episodic particle acceleration, explains the presence of these QPPs across the entire spatial range of flaring emission. Title: LOFAR Observations of a Jet-driven Piston Shock in the Low Solar Corona Authors: Maguire, Ciara A.; Carley, Eoin P.; Zucca, Pietro; Vilmer, Nicole; Gallagher, Peter T. Bibcode: 2021ApJ...909....2M Altcode: 2021arXiv210105569M The Sun produces highly dynamic and eruptive events that can drive shocks through the corona. These shocks can accelerate electrons, which result in plasma emission in the form of a type II radio burst. Despite the large number of type II radio burst observations, the precise origin of coronal shocks is still subject to investigation. Here, we present a well-observed solar eruptive event that occurred on 2015 October 16, focusing on a jet observed in the extreme ultraviolet by the Atmospheric Imaging Assembly (SDO/AIA), a streamer observed in white light by the Large Angle and Spectrometric Coronagraph (SOHO/LASCO), and a metric type II radio burst observed by the LOw Frequency Array (LOFAR). LOFAR interferometrically imaged the fundamental and harmonic sources of a type II radio burst and revealed that the sources did not appear to be cospatial, as would be expected from the plasma emission mechanism. We correct for the separation between the fundamental and harmonic using a model that accounts for scattering of radio waves by electron density fluctuations in a turbulent plasma. This allows us to show the type II radio sources were located ∼0.5R⊙ above the jet and propagated at a speed of ∼1000 km s-1, which was significantly faster than the jet speed of ∼200 km s-1. This suggests that the type II burst was generated by a piston shock driven by the jet in the low corona. Title: Nonthermal electrons revealed by LOFAR Authors: Zucca, Pietro; Pellizzoni, Alberto; Krankowski, Andrzej; Rothkaehl, Hanna; Mann, Gottfried; Vocks, Christian; Magdalenic, Jasmina; Marque, Christophe; Jackson, Bernard; Fallows, Richard; Tomasik, Lukasz; Hamish; Reid, A. S.; Gallagher, Peter; Vourlidas, Angelos; Bisi, Mario M.; Carley, Eoin; Matyjasiak, Barbara; Kozarev, Kamen; Dabrowski, Bartosz; Morosan, Diana; Tiburzi, Caterina; Chang, Peijin Bibcode: 2021cosp...43E1065Z Altcode: During solar flares and CMEs, the corona is heated, plasma motion, waves and shocks are ignited, and particles are accelerated. The accelerated particles propagate through the solar corona causing a variety of plasma instabilities that lead to enhanced non-thermal radio emission, known as "radio bursts". By studying radio-bursts' characteristics we can gain insight into the properties of energetic particles and the ambient coronal plasma, and the properties of particle acceleration mechanisms, such as magnetic reconnection and/or shocks in the solar atmosphere. The Low Frequency aRray (LOFAR) can be used to study the fundamental plasma physics of solar radio bursts with unprecedented time resolution in dynamic spectra, as well as with both interferometric imaging and tied array imaging. In this talk, an overview of recent results obtained with the LOFAR telescope will be given, including observations of a different variety of radio bursts such as type II, III and IV. These observations were performed with simultaneous beam formed and interferometric imaging, resulting in unprecedented special resolution with baselines up to ~120 km. Finally, we will present the plan for future observations and the remaining challenges of solar-heliospheric low-frequency observations. Title: Results from the LOFAR coordination with PSP Authors: Zucca, Pietro; Pellizzoni, Alberto; Krankowski, Andrzej; Rothkaehl, Hanna; Mann, Gottfried; Vocks, Christian; Magdalenic, Jasmina; Marque, Christophe; Jackson, Bernard; Fallows, Richard; Tomasik, Lukasz; Miteva, Rositsa; Hamish; Reid, A. S.; Gallagher, Peter; Vourlidas, Angelos; Bisi, Mario M.; Carley, Eoin; Matyjasiak, Barbara; Kozarev, Kamen; Dabrowski, Bartosz; Morosan, Diana; Tiburzi, Caterina; Zhabngm, Peijin Bibcode: 2021cosp...43E.945Z Altcode: Understanding and modelling the complex state of the Sun-solar wind-magnetosphere-ionosphere-thermosphere system, requires a comprehensive set of multiwavelength observations. LOFAR has unique capabilities in the radio domain. Some examples of these include: a) the ability to take high-resolution solar dynamic spectra and radio images of the Sun; b) observing the scintillation (interplanetary scintillation - IPS) of distant, compact, astronomical radio sources to determine the density, velocity and turbulence structure of the solar wind; and c) the use of Faraday rotation as a tool to probe the interplanetary magnetic-field strength and direction. However, to better understand and predict how the Sun, its atmosphere, and more in general the Heliosphere works and impacts Earth, the combination of in-situ spacecraft measurements and ground-based remote-sensing observations of coronal and heliospheric plasma parameters is extremely useful. Ground-based observations can be used to infer a global picture of the inner heliosphere, providing the essential context into which in-situ measurements from spacecraft can be placed. Conversely, remote-sensing observations usually contain information from extended lines of sight, with some deconvolution and modelling necessary to build up a three-dimensional (3-D) picture. Precise spacecraft measurements, when calibrated, can provide ground truth to constrain these models. The PSP mission is observing the solar corona and near-Sun interplanetary space. It has a highly-elliptical orbit taking the spacecraft as close as nearly 36 solar radii from the Sun centre on its first perihelion passage, and subsequent passages ultimately reaching as close as 9.8 solar radii. Four instruments are on the spacecraft's payload: FIELDS measuring the radio emission, electric and magnetic fields, Poynting flux, and plasma waves as well as the electron density and temperature; ISOIS measuring energetic electrons, protons, and heavy ions in the energy range 10 keV-100 MeV; SWEAP measuring the density, temperature, and flow speed of electrons, protons, and alphas in the solar wind; and finally, WISPR imaging coronal streamers, coronal mass ejections (CMEs), their associated shocks, and other solar wind structures in the corona and near-Sun interplanetary space, and provide context for the other three in-situ instruments. In this talk, several results of the joint LOFAR/PSP campaign will be presented, including fine structures of radio bursts, localization and kinematics of propagating radio sources in the heliosphere, and the challenges and plans for future observing campaigns including PSP and Solar Orbiter. Title: LOFAR observations of radio burst source sizes and scattering in the solar corona Authors: Murphy, Pearse C.; Carley, Eoin P.; Ryan, Aoife Maria; Zucca, Pietro; Gallagher, Peter T. Bibcode: 2021A&A...645A..11M Altcode: 2020arXiv201113735M Low frequency radio wave scattering and refraction can have a dramatic effect on the observed size and position of radio sources in the solar corona. The scattering and refraction is thought to be due to fluctuations in electron density caused by turbulence. Hence, determining the true radio source size can provide information on the turbulence in coronal plasma. However, the lack of high spatial resolution radio interferometric observations at low frequencies, such as with the LOw Frequency ARray (LOFAR), has made it difficult to determine the true radio source size and level of radio wave scattering. Here we directly fit the visibilities of a LOFAR observation of a Type IIIb radio burst with an elliptical Gaussian to determine its source size and position. This circumvents the need to image the source and then de-convolve LOFAR's point spread function, which can introduce spurious effects to the source size and shape. For a burst at 34.76 MHz, we find full width at half maximum (FWHM) heights along the major and minor axes to be 18.8' ± 0.1' and 10.2' ± 0.1', respectively, at a plane of sky heliocentric distance of 1.75 R⊙. Our results suggest that the level of density fluctuations in the solar corona is the main cause of the scattering of radio waves, resulting in large source sizes. However, the magnitude of ɛ may be smaller than what has been previously derived in observations of radio wave scattering in tied-array images. Title: LOFAR4SpaceWeather (LOFAR4SW) - Increasing European Space-Weather Capability with Europe's Largest Radio Telescope: Preparing for the Critical Design Review (CDR) Authors: Bisi, M. M.; Fallows, R. A.; Vermeulen, R.; Robertson, S. C.; Ruiter, M.; Vilmer, N.; Rothkaehl, H.; Matyjasiak, B.; Verbiest, J.; Carley, E.; Gallagher, P.; Carozzi, T.; Lindqvist, M.; Olberg, M.; Kruger, P.; Mevius, M.; Barnes, D.; Chang, O.; Baldovin, C. Bibcode: 2020AGUFMSH0030021B Altcode: The Low Frequency Array (LOFAR) consists of a dense core of 24 stations near Exloo in The Netherlands, an additional 14 stations spread across the northeast Netherlands, and a further 14 stations based internationally across Europe. These international stations are six in Germany, three in northern Poland, and one each in France, Ireland, Latvia, Sweden, and the UK. LOFAR can observe over a wide bandwidth of radio frequencies (~10-250 MHz) at high spatial/temporal resolutions. It has capabilities that enable studies of several aspects of space weather to be progressed well beyond today's state-of-the-art. However, with its present governance it can only be used for space-weather campaign studies. This severely limits LOFAR's ability to contribute to space-weather monitoring/forecast beyond its core strength of enabling world-leading scientific research.

The LOFAR For Space Weather (LOFAR4SW) project (see: http://lofar4sw.eu/) is a Horizon 2020 (H2020) INFRADEV design study to undertake investigations into upgrading LOFAR to allow for regular space-weather science/monitoring observations in parallel with normal radio-astronomy/scientific operations. This involves all aspects of political, user, forecaster, and scientific engagement with various stakeholders with the full recognition that space weather is a worldwide threat with varied local, regional, continent-wide impacts, and global impacts.

Here, we summarise the most-recent key aspects of the LOFAR4SW progress including outputs/progress following the Detailed Design Review (DDR) and User Workshop, and particularly our plans for the Critical Design Review (CDR) which is now delayed due to COVID-19 effects on project progress.

A fully-envisage longer-term goal of enable a LOFAR4SW update would make LOFAR one of Europe's most-comprehensive space-weather observing systems capable of shedding new light on several aspects of the space-weather system, from the Sun to the solar wind to Jupiter and Earth's ionosphere. Title: CMEs in the Heliosphere: III. A Statistical Analysis of the Kinematic Properties Derived from Stereoscopic Geometrical Modelling Techniques Applied to CMEs Detected in the Heliosphere from 2008 to 2014 by STEREO/HI-1 Authors: Barnes, D.; Davies, J. A.; Harrison, R. A.; Byrne, J. P.; Perry, C. H.; Bothmer, V.; Eastwood, J. P.; Gallagher, P. T.; Kilpua, E. K. J.; Möstl, C.; Rodriguez, L.; Rouillard, A. P.; Odstrčil, D. Bibcode: 2020SoPh..295..150B Altcode: 2020arXiv200614879B We present an analysis of coronal mass ejections (CMEs) observed by the Heliospheric Imagers (HIs) onboard NASA's Solar Terrestrial Relations Observatory (STEREO) spacecraft. Between August 2008 and April 2014 we identify 273 CMEs that are observed simultaneously, by the HIs on both spacecraft. For each CME, we track the observed leading edge, as a function of time, from both vantage points, and apply the Stereoscopic Self-Similar Expansion (SSSE) technique to infer their propagation throughout the inner heliosphere. The technique is unable to accurately locate CMEs when their observed leading edge passes between the spacecraft; however, we are able to successfully apply the technique to 151, most of which occur once the spacecraft-separation angle exceeds 180∘, during solar maximum. We find that using a small half-width to fit the CME can result in inferred acceleration to unphysically high velocities and that using a larger half-width can fail to accurately locate the CMEs close to the Sun because the method does not account for CME over-expansion in this region. Observed velocities from SSSE are found to agree well with single-spacecraft (SSEF) analysis techniques applied to the same events. CME propagation directions derived from SSSE and SSEF analysis agree poorly because of known limitations present in the latter. Title: The Spectrometer/Telescope for Imaging X-rays (STIX) Authors: Krucker, Säm; Hurford, G. J.; Grimm, O.; Kögl, S.; Gröbelbauer, H. -P.; Etesi, L.; Casadei, D.; Csillaghy, A.; Benz, A. O.; Arnold, N. G.; Molendini, F.; Orleanski, P.; Schori, D.; Xiao, H.; Kuhar, M.; Hochmuth, N.; Felix, S.; Schramka, F.; Marcin, S.; Kobler, S.; Iseli, L.; Dreier, M.; Wiehl, H. J.; Kleint, L.; Battaglia, M.; Lastufka, E.; Sathiapal, H.; Lapadula, K.; Bednarzik, M.; Birrer, G.; Stutz, St.; Wild, Ch.; Marone, F.; Skup, K. R.; Cichocki, A.; Ber, K.; Rutkowski, K.; Bujwan, W.; Juchnikowski, G.; Winkler, M.; Darmetko, M.; Michalska, M.; Seweryn, K.; Białek, A.; Osica, P.; Sylwester, J.; Kowalinski, M.; Ścisłowski, D.; Siarkowski, M.; Stęślicki, M.; Mrozek, T.; Podgórski, P.; Meuris, A.; Limousin, O.; Gevin, O.; Le Mer, I.; Brun, S.; Strugarek, A.; Vilmer, N.; Musset, S.; Maksimović, M.; Fárník, F.; Kozáček, Z.; Kašparová, J.; Mann, G.; Önel, H.; Warmuth, A.; Rendtel, J.; Anderson, J.; Bauer, S.; Dionies, F.; Paschke, J.; Plüschke, D.; Woche, M.; Schuller, F.; Veronig, A. M.; Dickson, E. C. M.; Gallagher, P. T.; Maloney, S. A.; Bloomfield, D. S.; Piana, M.; Massone, A. M.; Benvenuto, F.; Massa, P.; Schwartz, R. A.; Dennis, B. R.; van Beek, H. F.; Rodríguez-Pacheco, J.; Lin, R. P. Bibcode: 2020A&A...642A..15K Altcode:
Aims: The Spectrometer Telescope for Imaging X-rays (STIX) on Solar Orbiter is a hard X-ray imaging spectrometer, which covers the energy range from 4 to 150 keV. STIX observes hard X-ray bremsstrahlung emissions from solar flares and therefore provides diagnostics of the hottest (⪆10 MK) flare plasma while quantifying the location, spectrum, and energy content of flare-accelerated nonthermal electrons.
Methods: To accomplish this, STIX applies an indirect bigrid Fourier imaging technique using a set of tungsten grids (at pitches from 0.038 to 1 mm) in front of 32 coarsely pixelated CdTe detectors to provide information on angular scales from 7 to 180 arcsec with 1 keV energy resolution (at 6 keV). The imaging concept of STIX has intrinsically low telemetry and it is therefore well-suited to the limited resources available to the Solar Orbiter payload. To further reduce the downlinked data volume, STIX data are binned on board into 32 selectable energy bins and dynamically-adjusted time bins with a typical duration of 1 s during flares.
Results: Through hard X-ray diagnostics, STIX provides critical information for understanding the acceleration of electrons at the Sun and their transport into interplanetary space and for determining the magnetic connection of Solar Orbiter back to the Sun. In this way, STIX serves to link Solar Orbiter's remote and in-situ measurements. Title: Statistical Study of GOES X-Ray Quasi-periodic Pulsations in Solar Flares Authors: Hayes, L.; Inglis, A.; Christe, S.; Dennis, B.; Gallagher, P. Bibcode: 2020SPD....5121114H Altcode: Small-amplitude quasi-periodic pulsations (QPPs) detected in soft X-ray emission are commonplace in many flares. To date, the underpinning processes resulting in the QPPs are unknown. In this paper, we attempt to constrain the prevalence of stationary QPPs in the largest statistical study to date, including a study of the relationship of QPP periods to the properties of the flaring active region, flare ribbons, and coronal mass ejection (CME) affiliation. We build upon the work of Inglis et al. and use a model comparison test to search for significant power in the Fourier spectra of lightcurves of the GOES 1-8 Å channel. We analyze all X-, M- and C-class flares of the past solar cycle, a total of 5519 flares, and search for periodicity in the 6-300 s timescale range. Approximately 46% of X-class, 29% of M-class, and 7% of C-class flares show evidence of stationary QPPs, with periods that follow a log-normal distribution peaked at 20 s. The QPP periods were found to be independent of flare magnitude; however, a positive correlation was found between QPP period and flare duration. No dependence of the QPP periods on the global active region properties was identified. A positive correlation was found between QPPs and ribbon properties, including unsigned magnetic flux, ribbon area, and ribbon separation distance. We found that both flares with and without an associated CME can host QPPs. Furthermore, we demonstrate that for X- and M-class flares, decay-phase QPPs have statistically longer periods than impulsive-phase QPPs. Title: Ensemble forecasting of major solar flares: methods for combining models Authors: Guerra, Jordan A.; Murray, Sophie A.; Shaun Bloomfield, D.; Gallagher, Peter T. Bibcode: 2020JSWSC..10...38G Altcode: 2020arXiv200800382G One essential component of operational space weather forecasting is the prediction of solar flares. With a multitude of flare forecasting methods now available online it is still unclear which of these methods performs best, and none are substantially better than climatological forecasts. Space weather researchers are increasingly looking towards methods used by the terrestrial weather community to improve current forecasting techniques. Ensemble forecasting has been used in numerical weather prediction for many years as a way to combine different predictions in order to obtain a more accurate result. Here we construct ensemble forecasts for major solar flares by linearly combining the full-disk probabilistic forecasts from a group of operational forecasting methods (ASAP, ASSA, MAG4, MOSWOC, NOAA, and MCSTAT). Forecasts from each method are weighted by a factor that accounts for the method's ability to predict previous events, and several performance metrics (both probabilistic and categorical) are considered. It is found that most ensembles achieve a better skill metric (between 5% and 15%) than any of the members alone. Moreover, over 90% of ensembles perform better (as measured by forecast attributes) than a simple equal-weights average. Finally, ensemble uncertainties are highly dependent on the internal metric being optimized and they are estimated to be less than 20% for probabilities greater than 0.2. This simple multi-model, linear ensemble technique can provide operational space weather centres with the basis for constructing a versatile ensemble forecasting system - an improved starting point to their forecasts that can be tailored to different end-user needs. Title: A New Facility for Airborne Solar Astronomy: NASA's WB-57 at the 2017 Total Solar Eclipse Authors: Caspi, Amir; Seaton, Daniel B.; Tsang, Constantine C. C.; DeForest, Craig E.; Bryans, Paul; DeLuca, Edward E.; Tomczyk, Steven; Burkepile, Joan T.; Casey, Thomas "Tony"; Collier, John; Darrow, Donald "DD"; Del Rosso, Dominic; Durda, Daniel D.; Gallagher, Peter T.; Golub, Leon; Jacyna, Matthew; Johnson, David "DJ"; Judge, Philip G.; Klemm, Cary "Diddle"; Laurent, Glenn T.; Lewis, Johanna; Mallini, Charles J.; Parent, Thomas "Duster"; Propp, Timothy; Steffl, Andrew J.; Warner, Jeff; West, Matthew J.; Wiseman, John; Yates, Mallory; Zhukov, Andrei N.; NASA WB-57 2017 Eclipse Observing Team Bibcode: 2020ApJ...895..131C Altcode: 2020arXiv200409658C NASA's WB-57 High Altitude Research Program provides a deployable, mobile, and stratospheric platform for scientific research. Airborne platforms are of particular value for making coronal observations during total solar eclipses because of their ability both to follow the Moon's shadow and to get above most of the atmospheric air mass that can interfere with astronomical observations. We used the 2017 August 21 eclipse as a pathfinding mission for high-altitude airborne solar astronomy, using the existing high-speed visible-light and near/midwave infrared imaging suite mounted in the WB-57 nose cone. In this paper, we describe the aircraft, the instrument, and the 2017 mission; operations and data acquisition; and preliminary analysis of data quality from the existing instrument suite. We describe benefits and technical limitations of this platform for solar and other astronomical observations. We present a preliminary analysis of the visible-light data quality and discuss the limiting factors that must be overcome with future instrumentation. We conclude with a discussion of lessons learned from this pathfinding mission and prospects for future research at upcoming eclipses, as well as an evaluation of the capabilities of the WB-57 platform for future solar astronomy and general astronomical observation. Title: Imaging the Solar Corona during the 2015 March 20 Eclipse using LOFAR Authors: Ryan, Aoife Maria; Gallagher, Peter T.; Carley, Eoin P.; Morosan, Diana E.; Brentjens, Michiel A.; Zucca, Pietro; Fallows, Richard; Vocks, Christian; Mann, Gottfried; Breitling, Frank; Magdalenic, Jasmina; Kerdraon, Alain; Reid, Hamish Bibcode: 2020EGUGA..2218173R Altcode: The solar corona is a highly-structured plasma which reaches temperatures of more than ~2MK. At low radio frequencies (≤ 400 MHz), scattering and refraction of electromagnetic waves are thought to broaden sources to several arcminutes. However, exactly how source size relates to scattering due to turbulence is still subject to investigation. This is mainly due to the lack of high spatial resolution observations of the solar corona at low frequencies. Here, we use the LOw Frequency ARray (LOFAR) to observe the solar corona at 120-180 MHz using baselines of up to ~3.5 km (~1--2') during a partial solar eclipse of 2015 March 20. We use a lunar de-occultation technique to achieve higher spatial resolution than that attainable via traditional interferometric imaging. This provides a means of studying source sizes in the corona that are smaller than the angular width of the interferometric point spread function. Title: Interferometric Observations of the Active Regions in Radio Domain Before and After the Total Solar Eclipse on 21 August 2017 Authors: Dabrowski, Bartosz; Flisek, Paweł; Vocks, Christian; Morosan, Diana; Zhang, Peijin; Zucca, Pietro; Magdalenic, Jasmina; Fallows, Richard; Krankowski, Andrzej; Mann, Gottfried; Blaszkiewicz, Leszek; Rudawy, Pawel; Hajduk, Marcin; Fron, Adam; Gallagher, Peter; Ryan, Aoife Maria; Kotulak, Kacper; Matyjasiak, Barbara Bibcode: 2020EGUGA..22.7374D Altcode: We hereby present the interferometric LOFAR observations made before and after the total solar eclipse on 21 August 2017, during which the type III radio bursts have been detected.The LOw-Frequency ARray (LOFAR) is a large radio interferometer operating in the frequency range of 10-240 MHz, designed and constructed by ASTRON (the Netherlands Institute for Radio Astronomy). The LOFAR telescope is an array of stations distributed throughout the Netherlands and other parts of Europe. Currently the system consist of 52 LOFAR stations located in Europe. Apart from the high time and frequency resolution of the dynamic spectra, LOFAR allows also a 2D imaging of the radio sources and tracking of their positions through the solar corona.In this work we present a preliminary analysis of the dynamic spectra of type III radio bursts with radio images. Title: Type III Radio Bursts and Langmuir Wave Excitation Authors: Mann, Gottfried; Vocks, Christian; Bisi, Mario; Carley, Eoin; Dabrowski, Bartosz; Fallows, Richard; Gallagher, Peter; Krankowski, Andrzej; Magdalenic, Jasmina; Marque, Christophe; Morosan, Diana; Rothkaehl, Hanna; Zucca, Pietro Bibcode: 2020EGUGA..22.7595M Altcode: Type III radio bursts are a common phenomenon the Sun's nonthermal radio radiation. They appear as stripes of enhanced radio emission with a rapid drift from high to low frequencies in dynamic radio spectra. They are considered as the radio signatures of beams of energetic electrons travelling along magnetic field lines from the solar corona into the interplanetary space. With the ground based radio interferometer LOFAR and the instrument FIELDS onboard NASA's "Parker Solar Probe" (PSP), type III radio bursts can be observed simultaneously from high (10-240 MHz) to low frequencies (0.01-20 MHz) with LOFAR and PSP's FIELDs, respectively. That allows to track these electron beams from the corona up to the interplanetary space. Assuming that a population of energetic electrons is initially injected, the velocity distribution function of these electrons evolves into a beam like one. Such distribution function leads to the excitation of Langmuir waves which convert into radio waves finally observed as type II radio bursts. Numerical calculations of the electron-beam-plasma interaction reveal that the Langmuir waves are excited by different parts of the energetic electrons at different distances in the corona and interplanetary space. This result is compared with special type III radio bursts observed with LOFAR and PSP's FIELDS. Title: Evolution of the Alfvén Mach number associated with a coronal mass ejection shock Authors: Maguire, Ciara; Carley, Eoin; McCauley, Joseph; Gallagher, Peter Bibcode: 2020EGUGA..2211425M Altcode: The Sun regularly produces large-scale eruptive events, such as coronal mass ejections (CMEs) that can drive shock waves through the solar corona. Such shocks can result in electron acceleration and subsequent radio emission in the form of a type II radio burst. However, the early-phase evolution of shock properties and its relationship to type II burst evolution is still subject to investigation. Here we study the evolution of a CME-driven shock by comparing three commonly used methods of calculating the Alfvén Mach number (MA), namely: shock geometry, a comparison of CME speed to a model of the coronal Alfvén speed, and the type II band-splitting method. We applied the three methods to the 2017 September 2 event, focusing on the shock wave observed in extreme ultraviolet (EUV) by the Solar Ultraviolet Imager (SUVI) on board GOES-16, in white-light by the Large Angle and Spectrometric Coronagraph (LASCO) on board SOHO, and the type II radio burst observed by the Irish Low Frequency Array (I-LOFAR). We show that the three different methods of estimating shock MA yield consistent results and provide a means of relating shock property evolution to the type II emission duration. The type II radio emission emerged from near the nose of the CME when MA was in the range 1.4-2.4 at a heliocentric distance of ∼1.6 R⊙. The emission ceased when the CME nose reached ∼2.4 R⊙, despite an increasing Alfvén Mach number (up to 4). We suggest the radio emission cessation is due to the lack of quasi-perpendicular geometry at this altitude, which inhibits efficient electron acceleration and subsequent radio emission. Title: Statistical Study of GOES X-Ray Quasi-periodic Pulsations in Solar Flares Authors: Hayes, Laura A.; Inglis, Andrew R.; Christe, Steven; Dennis, Brian; Gallagher, Peter T. Bibcode: 2020ApJ...895...50H Altcode: 2020arXiv200411775H Small-amplitude quasi-periodic pulsations (QPPs) detected in soft X-ray emission are commonplace in many flares. To date, the underpinning processes resulting in the QPPs are unknown. In this paper, we attempt to constrain the prevalence of stationary QPPs in the largest statistical study to date, including a study of the relationship of QPP periods to the properties of the flaring active region, flare ribbons, and coronal mass ejection (CME) affiliation. We build upon the work of Inglis et al. and use a model comparison test to search for significant power in the Fourier spectra of lightcurves of the GOES 1-8 Å channel. We analyze all X-, M- and C-class flares of the past solar cycle, a total of 5519 flares, and search for periodicity in the 6-300 s timescale range. Approximately 46% of X-class, 29% of M-class, and 7% of C-class flares show evidence of stationary QPPs, with periods that follow a log-normal distribution peaked at 20 s. The QPP periods were found to be independent of flare magnitude; however, a positive correlation was found between QPP period and flare duration. No dependence of the QPP periods on the global active region properties was identified. A positive correlation was found between QPPs and ribbon properties, including unsigned magnetic flux, ribbon area, and ribbon separation distance. We found that both flares with and without an associated CME can host QPPs. Furthermore, we demonstrate that for X- and M-class flares, decay-phase QPPs have statistically longer periods than impulsive-phase QPPs. Title: LOFAR4SpaceWeather (LOFAR4SW) - Increasing European Space-Weather Capability with Europe's Largest Radio Telescope: Beyond the Detailed Design Review (DDR) Authors: Bisi, Mario M.; Ruiter, Mark; Fallows, Richard A.; Vermeulen, René; Robertson, Stuart C.; Vilmer, Nicole; Rothkaehl, Hanna; Matyjasiak, Barbara; Verbiest, Joris; Gallagher, Peter T.; Olberg, Michael; Carozzi, Tobia; Lindqvist, Michael; Carley, Eoin; Krüger, Paulus; Mevius, Maaijke; Baldovin, Carla; Barnes, David Bibcode: 2020EGUGA..2214948B Altcode: The Low Frequency Array (LOFAR) is an advanced phased-array radio-telescope system based across Europe. It is capable of observing over a wide radio bandwidth of ~10-250 MHz at both high spatial and temporal resolutions. LOFAR has capabilities that enable studies of many aspects of what we class as space weather (from the Sun to the Earth and afar) to be progressed beyond today's state-of-the-art. However, with the present setup and organisation behind the operations of the telescope, it can only be used for space-weather campaign studies with limited triggering availability. This severely limits our ability to effectively use LOFAR to contribute to space-weather monitoring/forecast beyond its core strength of enabling world-leading scientific research. LOFAR itself is made up of a dense core of 24 stations near Exloo in The Netherlands with an additional 14 stations spread across the northeast Netherlands. In addition to those, there are a further 13 stations based internationally across Europe. These international stations are, currently, six in Germany, three in northern Poland, and one each in France, Ireland, Latvia, Sweden, and the UK. Further sites are under preparations (for example, in Italy). We are undertaking a Horizon 2020 (H2020) INFRADEV design study to undertake investigations into upgrading LOFAR to allow for regular space-weather science/monitoring observations in parallel with normal radio-astronomy/scientific operations. This project is called the LOFAR For Space Weather (LOFAR4SW) project (see: http://lofar4sw.eu/). Our work involves all aspects of scientific and engineering work along with end-user and political engagements with various stakeholders. This is with the full recognition that space weather is a worldwide threat with varying local, regional, continent-wide impacts, and also global impacts - and hence is a global concern. Here, we summarise the most-recent key aspects of the LOFAR4SW progress including outputs/progress following the Detailed Design Review (DDR) that took place at ASTRON, The Netherlands, in March 2020, as well as the implementation of recommendations from the earlier Preliminary Design Review (PDR) with an outlook to the LOFAR4SW User Workshop the week following EGU 2020. We also aim to briefly summarise a key set of the longer-term goals envisaged for LOFAR to become one of Europe's most-comprehensive space-weather observing systems capable of shedding new light on several aspects of the space-weather system, from the Sun to the solar wind to Jupiter and Earth's ionosphere. Title: A Comparison of Flare Forecasting Methods. IV. Evaluating Consecutive-day Forecasting Patterns Authors: Park, Sung-Hong; Leka, K. D.; Kusano, Kanya; Andries, Jesse; Barnes, Graham; Bingham, Suzy; Bloomfield, D. Shaun; McCloskey, Aoife E.; Delouille, Veronique; Falconer, David; Gallagher, Peter T.; Georgoulis, Manolis K.; Kubo, Yuki; Lee, Kangjin; Lee, Sangwoo; Lobzin, Vasily; Mun, JunChul; Murray, Sophie A.; Hamad Nageem, Tarek A. M.; Qahwaji, Rami; Sharpe, Michael; Steenburgh, R. A.; Steward, Graham; Terkildsen, Michael Bibcode: 2020ApJ...890..124P Altcode: 2020arXiv200102808P A crucial challenge to successful flare prediction is forecasting periods that transition between "flare-quiet" and "flare-active." Building on earlier studies in this series in which we describe the methodology, details, and results of flare forecasting comparison efforts, we focus here on patterns of forecast outcomes (success and failure) over multiday periods. A novel analysis is developed to evaluate forecasting success in the context of catching the first event of flare-active periods and, conversely, correctly predicting declining flare activity. We demonstrate these evaluation methods graphically and quantitatively as they provide both quick comparative evaluations and options for detailed analysis. For the testing interval 2016-2017, we determine the relative frequency distribution of two-day dichotomous forecast outcomes for three different event histories (I.e., event/event, no-event/event, and event/no-event) and use it to highlight performance differences between forecasting methods. A trend is identified across all forecasting methods that a high/low forecast probability on day 1 remains high/low on day 2, even though flaring activity is transitioning. For M-class and larger flares, we find that explicitly including persistence or prior flare history in computing forecasts helps to improve overall forecast performance. It is also found that using magnetic/modern data leads to improvement in catching the first-event/first-no-event transitions. Finally, 15% of major (I.e., M-class or above) flare days over the testing interval were effectively missed due to a lack of observations from instruments away from the Earth-Sun line. Title: The Effect of the 21 August 2017 Total Solar Eclipse on the Phase of VLF/LF Signals Authors: Rozhnoi, A.; Solovieva, M.; Shalimov, S.; Ouzounov, D.; Gallagher, P.; Verth, G.; McCauley, J.; Shelyag, S.; Fedun, V. Bibcode: 2020E&SS....700839R Altcode: An experimental study of the phase and amplitude observations of sub-ionospheric very low and low frequency (VLF/LF) signals is performed to analyze the response of the lower ionosphere during the 21 August 2017 total solar eclipse in the United States of America. Three different sub-ionospheric wave paths are investigated. The length of the paths varies from 2,200 to 6,400 km, and the signal frequencies are 21.4, 25.2, and 40.75 kHz. The two paths cross the region of the total eclipse, and the third path is in the region of 40-60% of obscuration. None of the signals reveal any noticeable amplitude changes during the eclipse, while negative phase anomalies (from -33° to -95°) are detected for all three paths. It is shown that the effective reflection height of the ionosphere in low and middle latitudes is increased by about 3-5 km during the eclipse. Estimation of the electron density change in the lower ionosphere caused by the eclipse, using linear recombination law, shows that the average decrease is by 2.1 to 4.5 times. Title: Evolution of the Alfvén Mach number associated with a coronal mass ejection shock Authors: Maguire, Ciara A.; Carley, Eoin P.; McCauley, Joseph; Gallagher, Peter T. Bibcode: 2020A&A...633A..56M Altcode: 2019arXiv191201863M The Sun regularly produces large-scale eruptive events, such as coronal mass ejections (CMEs) that can drive shock waves through the solar corona. Such shocks can result in electron acceleration and subsequent radio emission in the form of a type II radio burst. However, the early-phase evolution of shock properties and its relationship to type II burst evolution is still subject to investigation. Here we study the evolution of a CME-driven shock by comparing three commonly used methods of calculating the Alfvén Mach number (MA), namely: shock geometry, a comparison of CME speed to a model of the coronal Alfvén speed, and the type II band-splitting method. We applied the three methods to the 2017 September 2 event, focusing on the shock wave observed in extreme ultraviolet by the Solar Ultraviolet Imager on board GOES-16, in white-light by the Large Angle and Spectrometric Coronagraph on board SOHO, and the type II radio burst observed by the Irish Low Frequency Array. We show that the three different methods of estimating shock MA yield consistent results and provide a means of relating shock property evolution to the type II emission duration. The type II radio emission emerged from near the nose of the CME when MA was in the range 1.4-2.4 at a heliocentric distance of ∼1.6 R⊙. The emission ceased when the CME nose reached ∼2.4 R⊙, despite an increasing Alfvén Mach number (up to 4). We suggest the radio emission cessation is due to the lack of quasi-perpendicular geometry at this altitude, which inhibits efficient electron acceleration and subsequent radio emission. Title: Radio observatories and instrumentation used in space weather science and operations Authors: Carley, Eoin P.; Baldovin, Carla; Benthem, Pieter; Bisi, Mario M.; Fallows, Richard A.; Gallagher, Peter T.; Olberg, Michael; Rothkaehl, Hanna; Vermeulen, Rene; Vilmer, Nicole; Barnes, David Bibcode: 2020JSWSC..10....7C Altcode: The low frequency array (LOFAR) is a phased array interferometer currently consisting of 13 international stations across Europe and 38 stations surrounding a central hub in the Netherlands. The instrument operates in the frequency range of ~10-240 MHz and is used for a variety of astrophysical science cases. While it is not heliophysics or space weather dedicated, a new project entitled "LOFAR for Space Weather" (LOFAR4SW) aims at designing a system upgrade to allow the entire array to observe the Sun, heliosphere, Earth's ionosphere, and Jupiter throughout its observing window. This will allow the instrument to operate as a space weather observing platform, facilitating both space weather science and operations. Part of this design study aims to survey the existing space weather infrastructure operating at radio frequencies and show how LOFAR4SW can advance the current state-of-the-art in this field. In this paper, we survey radio instrumentation and facilities that currently operate in space weather science and/or operations, including instruments involved in solar, heliospheric, and ionospheric studies. We furthermore include an overview of the major space weather service providers in operation today and the current state-of-the-art in the radio data they use and provide routinely. The aim is to compare LOFAR4SW to the existing radio research infrastructure in space weather and show how it may advance both space weather science and operations in the radio domain in the near future. Title: Novel observations of the middle corona during the 2017 total solar eclipse Authors: Caspi, A.; Seaton, D. B.; Tsang, C.; DeForest, C.; Bryans, P.; Samra, J.; DeLuca, E.; Tomczyk, S.; Burkepile, J.; Gallagher, P.; Golub, L.; Judge, P. G.; Laurent, G. T.; West, M.; Zhukov, A. Bibcode: 2019AGUFMSH13A..10C Altcode: Total solar eclipses offer rare opportunities to study the middle corona. This intriguing region contains complex interfaces and transitions between physical regimes, but has historically been under-observed due to the challenges of observing its dim emission so close to the bright inner corona and blinding solar disk. The unique circumstances of a total solar eclipse coupled with a high-altitude observing platform provide nearly space-quality observing conditions, including for wavelengths inaccessible by ground-based observatories, but with availability of ground-quality resources, including high-speed, high-resolution, wide-field coronography typically inaccessible from space. We used the 2017 August 21 "Great American" total solar eclipse to observe the solar corona from ~1.02 to ~3 RSun in both visible (533.9 ± 4.75 nm) and medium-wave infrared (3-5 μm) light using stabilized telescopes on two of NASA's WB-57F high-altitude research aircraft. This pathfinding mission utilized existing instrumentation to evaluate the platform performance, guide instrumentation development, and explore new discovery space for future studies of the middle corona.

We present the high-speed (30 Hz), high-resolution (3 arcsec/pixel) visible and IR observations obtained during the eclipse, and analysis of these observations in the context of coronal structure and dynamics. We discuss the limitations of the prototype data and pathways forward for future instrumentation and missions optimized for the range of observable parameters in the middle corona. We also discuss the benefits of such eclipse studies to an understanding of the corona as a single, unified system, from its origins at the solar surface to its extension into the heliosphere, particularly within the context of a developing multi- and inter-disciplinary research collaboration, COHERENT (the "Corona as a Holistic Environment" Research Network). Title: The Breakthrough Listen Search for Extraterrestrial Intelligence Authors: Gajjar, Vishal; Siemion, Andrew; Croft, Steve; Brzycki, Bryan; Burgay, Marta; Carozzi, Tobia; Concu, Raimondo; Czech, Daniel; DeBoer, David; DeMarines, Julia; Drew, Jamie; Enriquez, J. Emilio; Fawcett, James; Gallagher, Peter; Gerret, Michael; Gizani, Nectaria; Hellbourg, Greg; Holder, Jamie; Isaacson, Howard; Kudale, Sanjay; Lacki, Brian; Lebofsky, Matthew; Li, Di; MacMahon, David H. E.; McCauley, Joe; Melis, Andrea; Molinari, Emilio; Murphy, Pearse; Perrodin, Delphine; Pilia, Maura; Price, Danny C.; Webb, Claire; Werthimer, Dan; Williams, David; Worden, Pete; Zarka, Philippe; Zhang, Yunfan Gerry Bibcode: 2019BAAS...51g.223G Altcode: 2019astro2020U.223G; 2019arXiv190705519G In this white paper, we outline the status of the on-going observing campaign with our primary and collaborative observing facilities, as well as planned activities with these instruments over the next few years with the Breakthrough Listen program for the technosignature searches. Title: A Comparison of Flare Forecasting Methods. III. Systematic Behaviors of Operational Solar Flare Forecasting Systems Authors: Leka, K. D.; Park, Sung-Hong; Kusano, Kanya; Andries, Jesse; Barnes, Graham; Bingham, Suzy; Bloomfield, D. Shaun; McCloskey, Aoife E.; Delouille, Veronique; Falconer, David; Gallagher, Peter T.; Georgoulis, Manolis K.; Kubo, Yuki; Lee, Kangjin; Lee, Sangwoo; Lobzin, Vasily; Mun, JunChul; Murray, Sophie A.; Hamad Nageem, Tarek A. M.; Qahwaji, Rami; Sharpe, Michael; Steenburgh, Robert A.; Steward, Graham; Terkildsen, Michael Bibcode: 2019ApJ...881..101L Altcode: 2019arXiv190702909L A workshop was recently held at Nagoya University (2017 October 31-November 2), sponsored by the Center for International Collaborative Research, at the Institute for Space-Earth Environmental Research, Nagoya University, Japan, to quantitatively compare the performance of today’s operational solar flare forecasting facilities. Building upon Paper I of this series, in Paper II we described the participating methods for this latest comparison effort, the evaluation methodology, and presented quantitative comparisons. In this paper, we focus on the behavior and performance of the methods when evaluated in the context of broad implementation differences. Acknowledging the short testing interval available and the small number of methods available, we do find that forecast performance: (1) appears to improve by including persistence or prior flare activity, region evolution, and a human “forecaster in the loop” (2) is hurt by restricting data to disk-center observations; (3) may benefit from long-term statistics but mostly when then combined with modern data sources and statistical approaches. These trends are arguably weak and must be viewed with numerous caveats, as discussed both here and in Paper II. Following this present work, in Paper IV (Park et al. 2019) we will present a novel analysis method to evaluate temporal patterns of forecasting errors of both types (i.e., misses and false alarms). Hence, most importantly, with this series of papers, we demonstrate the techniques for facilitating comparisons in the interest of establishing performance-positive methodologies. Title: A Comparison of Flare Forecasting Methods. II. Benchmarks, Metrics, and Performance Results for Operational Solar Flare Forecasting Systems Authors: Leka, K. D.; Park, Sung-Hong; Kusano, Kanya; Andries, Jesse; Barnes, Graham; Bingham, Suzy; Bloomfield, D. Shaun; McCloskey, Aoife E.; Delouille, Veronique; Falconer, David; Gallagher, Peter T.; Georgoulis, Manolis K.; Kubo, Yuki; Lee, Kangjin; Lee, Sangwoo; Lobzin, Vasily; Mun, JunChul; Murray, Sophie A.; Hamad Nageem, Tarek A. M.; Qahwaji, Rami; Sharpe, Michael; Steenburgh, Robert A.; Steward, Graham; Terkildsen, Michael Bibcode: 2019ApJS..243...36L Altcode: 2019arXiv190702905L Solar flares are extremely energetic phenomena in our solar system. Their impulsive and often drastic radiative increases, particularly at short wavelengths, bring immediate impacts that motivate solar physics and space weather research to understand solar flares to the point of being able to forecast them. As data and algorithms improve dramatically, questions must be asked concerning how well the forecasting performs; crucially, we must ask how to rigorously measure performance in order to critically gauge any improvements. Building upon earlier-developed methodology of Paper I (Barnes et al. 2016), international representatives of regional warning centers and research facilities assembled in 2017 at the Institute for Space-Earth Environmental Research, Nagoya University, Japan to, for the first time, directly compare the performance of operational solar flare forecasting methods. Multiple quantitative evaluation metrics are employed, with the focus and discussion on evaluation methodologies given the restrictions of operational forecasting. Numerous methods performed consistently above the “no-skill” level, although which method scored top marks is decisively a function of flare event definition and the metric used; there was no single winner. Following in this paper series, we ask why the performances differ by examining implementation details (Leka et al. 2019), and then we present a novel analysis method to evaluate temporal patterns of forecasting errors in Paper IV (Park et al. 2019). With these works, this team presents a well-defined and robust methodology for evaluating solar flare forecasting methods in both research and operational frameworks and today’s performance benchmarks against which improvements and new methods may be compared. Title: Temporal, Spectral and Spatial Analysis of Flaring Quasi-Periodic Pulsations Authors: Hayes, Laura A.; Gallagher, Peter; Christe, Steven; Dennis, Brian R. Bibcode: 2019AAS...23422505H Altcode: One of the key observational features in flaring emission associated with accelerated electrons is the presence of pronounced modulations and oscillatory signatures known as quasi-periodic pulsations (QPPs). To date, the underpinning mechanisms resulting in the emission modulation remains unknown, and detailed multi-wavelength investigations of flaring QPP events are required to identify the modulation process. Here we will present a detailed temporal, spectral and spatially-resolved investigation of the X1.2 solar flare from May 15 2013 that demonstrate large modulations in its emission. During the impulsive phase, pronounced QPPs with a period of 50s are observed across multiple wavebands including hard and soft X-rays, microwave, UV, EUV - essentially across the whole flaring region. We examine the modulation amplitudes of the different emissions, and in particular focus on the hard X-ray and microwave spectral indices and on the modulation of the degree of polarization of the radio emissions. To further constrain the potential QPP mechanism, we analyse spatially resolved observations of the non-thermal pulsations using both RHESSI and Nobeyama RadioHeliograph data to probe the locations of where the QPP emission is occurring. The results are suggestive of a trap-plus-precipitation model. We will also discuss the QPP modulation in relation to the observed CME eruption. The current theories to explain the presence of QPPs in the context of this event will be presented, along with a discussion of how this type of analysis can be further utilized to probe the mechanisms for electron acceleration and plasma heating. Title: CMEs in the Heliosphere: II. A Statistical Analysis of the Kinematic Properties Derived from Single-Spacecraft Geometrical Modelling Techniques Applied to CMEs Detected in the Heliosphere from 2007 to 2017 by STEREO/HI-1 Authors: Barnes, D.; Davies, J. A.; Harrison, R. A.; Byrne, J. P.; Perry, C. H.; Bothmer, V.; Eastwood, J. P.; Gallagher, P. T.; Kilpua, E. K. J.; Möstl, C.; Rodriguez, L.; Rouillard, A. P.; Odstrčil, D. Bibcode: 2019SoPh..294...57B Altcode: Recent observations with the Heliospheric Imagers (HIs) onboard the twin NASA Solar Terrestrial Relations Observatory (STEREO) spacecraft have provided unprecedented observations of a large number of coronal mass ejections (CMEs) in the inner heliosphere. In this article we discuss the generation of the HIGeoCAT CME catalogue and perform a statistical analysis of its events. The catalogue was generated as part of the EU FP7 HELCATS (Heliospheric Cataloguing, Analysis and Techniques Service) project (www.helcats-fp7.eu/). It is created by generating time/elongation maps for CMEs using observations from the inner (HI-1) and outer (HI-2) cameras along a position angle close to the CME apex. Next, we apply single-spacecraft geometric-fitting techniques to determine the kinematic properties of these CMEs, including their speeds, propagation directions, and launch times. The catalogue contains a total of 1455 events (801 from STEREO-A and 654 from STEREO-B) from April 2007 to the end of August 2017. We perform a statistical analysis of the properties of CMEs in HIGeoCAT and compare the results with those from the Large Angle Spectrometric Coronagraph (LASCO) CDAW catalogues (Yashiro et al.J. Geophys. Res. Space Phys.109, A07105, 2004) and the COR-2 catalogue of Vourlidas et al. (Astrophys. J.838, 141, 2004) during the same period. We find that the distributions of both speeds and latitudes for the HIGeoCAT CMEs correlate with the sunspot number over the solar cycle. We also find that the HI-derived CME speed distributions are generally consistent with coronagraph catalogues over the solar cycle, albeit with greater absolute speeds due to the differing methods with which each is derived. Title: LOFAR For Space Weather (LOFAR4SW): Increasing European Space-Weather Capability with Europe's Largest Radio Telescope Authors: Bisi, Mario M.; Vermeulen, René; Fallows, Richard A.; Benthem, Pieter; Vilmer, Nicole; Rothkaehl, Hanna; Matyjasiak, Barbara; Verbiest, Joris; Gallagher, Peter T.; Carley, Eoin; Olberg, Michael; Mevius, Maaijke; Robertson, Stuart C.; Barnes, David Bibcode: 2019shin.confE.229B Altcode: The Low Frequency Array (LOFAR) consists of a dense core of 24 stations within a 4km diameter, 14 stations spread further afield across the northeast area of The Netherlands, and a further 13 stations spread internationally (six across Germany, three in northern Poland, and one each in France, Ireland, Sweden, and the UK). Further international expansion is under way. LOFAR observes over a wide bandwidth in radio frequencies (10-250 MHz) with both a high temporal and spatial resolution. LOFAR is one of the world’s most-flexible radio instruments with capabilities that enable studies of several aspects of space weather to be progressed beyond today’s state-of-the-art.

However, in its present setup, LOFAR can only be used for space-weather purposes on a campaign bases of observations. This is where observing time has to be competed for alongside astronomy and all other types of radio observations requested.

The LOFAR For Space Weather (LOFAR4SW) project is a Horizon 2020 (H2020) INFRADEV design study undertaking investigations/design steps into upgrading LOFAR to allow for regular space-weather monitoring observations in parallel with normal radio-astronomy and scientific operations. A fully-implemented LOFAR4SW system would include a wide range of observational capabilities covering the Sun, corona, inner heliosphere, Earth’s ionosphere, Jupiter, heliosphere-planetary interactions, and potentially extra-solar space weather on a routine/regular basis adding to our knowledge, understanding, and prediction capabilities of space weather - a global threat.

In this presentation, we summarise the LOFAR4SW design study, progress to date post-Preliminary Design Review and pre-Mid-Term Review, and some of the longer-term goals envisaged for LOFAR to become one of Europe’s most-comprehensive space-weather observatories, shedding new light on several aspects of the space-weather system, from the Sun to the solar wind to the ionosphere. Title: Loss-cone instability modulation due to a magnetohydrodynamic sausage mode oscillation in the solar corona Authors: Carley, Eoin P.; Hayes, Laura A.; Murray, Sophie A.; Morosan, Diana E.; Shelley, Warren; Vilmer, Nicole; Gallagher, Peter T. Bibcode: 2019NatCo..10.2276C Altcode: Solar flares often involve the acceleration of particles to relativistic energies and the generation of high-intensity bursts of radio emission. In some cases, the radio bursts can show periodic or quasiperiodic intensity pulsations. However, precisely how these pulsations are generated is still subject to debate. Prominent theories employ mechanisms such as periodic magnetic reconnection, magnetohydrodynamic (MHD) oscillations, or some combination of both. Here we report on high-cadence (0.25 s) radio imaging of a 228 MHz radio source pulsating with a period of 2.3 s during a solar flare on 2014-April-18. The pulsating source is due to an MHD sausage mode oscillation periodically triggering electron acceleration in the corona. The periodic electron acceleration results in the modulation of a loss-cone instability, ultimately resulting in pulsating plasma emission. The results show that a complex combination of MHD oscillations and plasma instability modulation can lead to pulsating radio emission in astrophysical environments. Title: Persistent Quasi-periodic Pulsations during a Large X-class Solar Flare Authors: Hayes, Laura A.; Gallagher, Peter T.; Dennis, Brian R.; Ireland, Jack; Inglis, Andrew; Morosan, Diana E. Bibcode: 2019ApJ...875...33H Altcode: 2019arXiv190301328H Solar flares often display pulsating and oscillatory signatures in the emission, known as quasi-periodic pulsations (QPP). QPP are typically identified during the impulsive phase of flares, yet in some cases, their presence is detected late into the decay phase. Here, we report extensive fine structure QPP that are detected throughout the large X8.2 flare from 2017 September 10. Following the analysis of the thermal pulsations observed in the Geostationary Operational Environmental Satellite/X-ray sensor and the 131 Å channel of Solar Dynamics Observatory/Atmospheric Imaging Assembly, we find a pulsation period of ∼65 s during the impulsive phase followed by lower amplitude QPP with a period of ∼150 s in the decay phase, up to three hours after the peak of the flare. We find that during the time of the impulsive QPP, the soft X-ray source observed with the Reuven Ramaty High Energy Solar Spectroscopic Imager rapidly rises at a velocity of approximately 17 km s-1 following the plasmoid/coronal mass ejection eruption. We interpret these QPP in terms of a manifestation of the reconnection dynamics in the eruptive event. During the long-duration decay phase lasting several hours, extended downward contractions of collapsing loops/plasmoids that reach the top of the flare arcade are observed in EUV. We note that the existence of persistent QPP into the decay phase of this flare are most likely related to these features. The QPP during this phase are discussed in terms of magnetohydrodynamic wave modes triggered in the post-flaring loops. Title: LOFAR4SW: New capability for Space Weather science by radio diagnostic. Authors: Rothkaehl, Hanna; Vermeulen, Rene; Fallows, Richard; Verbiest, Joris; Vilmer, Nicole; Olberg, Michael; Bisi, Mario; Gallagher, Peter; Matyjasiak, Barbara; Carley, Eoin; Carozzi, Tobia; Robertson, Stuart Bibcode: 2019EGUGA..21.7679R Altcode: The Low Frequency Array (LOFAR) telescope is one of the world's leading radio astronomical instruments which advantage was already proven by many key science findings. Its wide application in many domains, not limited only to astronomy, is used by scientists around the world. LOFAR covers a wide range of low radio frequencies, between 10 and 250 MHz, and has a spatial resolution better than 1 arcsec. The construction of the telescope enables both interferometric imaging as well as observations using the formation of multiple sensitive, narrow beams. The current LOFAR infrastructure, however, allows only to monitor and investigate the Space Weather conditions. A step towards preparing the instrument for full Space weather services and providing high-quality data for forecasting is the LOFAR for Space Weather (LOFAR4SW) project. LOFAR4SW is an international Horizon 2020 (H2020) INFRADEV design study, started December 2017 the aim of which is to deliver the full conceptual and technical design for creating a new leading-edge European research facility for space weather science. A fully-implemented LOFAR4SW system will enable a wide range of solar and space weather research topics to be tackled and have unique strengths in several high-impact science areas: tracing the initial launch of a CME; detailed tracking of the solar wind and CMEs through interplanetary space; in-depth studies of micro- structure in the Earth's ionosphere. This facility will uniquely provide the missing link of measurements of the interplanetary magnetic field on global scales - a key parameter in forecasting the severity of geomagnetic storm on Earth. The aim of the presentation is to show the science cases on which emphasis will be placed in the designed LOFAR4SW facility. Title: Multiple regions of shock-accelerated particles during a solar coronal mass ejection Authors: Morosan, Diana E.; Carley, Eoin P.; Hayes, Laura A.; Murray, Sophie A.; Zucca, Pietro; Fallows, Richard A.; McCauley, Joe; Kilpua, Emilia K. J.; Mann, Gottfried; Vocks, Christian; Gallagher, Peter T. Bibcode: 2019NatAs...3..452M Altcode: 2019NatAs.tmp..210M; 2019arXiv190811743M; 2019NatAs.tmp..252M The Sun is an active star that can launch large eruptions of magnetized plasma into the heliosphere, known as coronal mass ejections (CMEs). These can drive shocks that accelerate particles to high energies, often resulting in radio emission at low frequencies (<200 MHz). So far, the relationship between the expansion of CMEs, shocks and particle acceleration is not well understood, partly due to the lack of radio imaging at low frequencies during the onset of shock-producing CMEs. Here, we report multi-instrument radio, white-light and ultraviolet imaging of the second largest flare in solar cycle 24 (2008-present) and its associated fast CME (3,038 ± 288 km s-1). We identify the location of a multitude of radio shock signatures, called herringbones, and find evidence for shock-accelerated electron beams at multiple locations along the expanding CME. These observations support theories of non-uniform, rippled shock fronts driven by an expanding CME in the solar corona. Title: Properties and magnetic origins of solar S-bursts Authors: Clarke, Brendan P.; Morosan, Diana E.; Gallagher, Peter T.; Dorovskyy, Vladimir V.; Konovalenko, Alexander A.; Carley, Eoin P. Bibcode: 2019A&A...622A.204C Altcode: 2019arXiv190107424C Context. Solar activity is often accompanied by solar radio emission, consisting of numerous types of solar radio bursts. At low frequencies (<100 MHz) radio bursts with short durations of milliseconds, such as solar S-bursts, have been identified. To date, their origin and many of their characteristics remain unclear.
Aims: We report observations from the Ukrainian T-shaped Radio telescope, (UTR-2), and the LOw Frequency ARray (LOFAR) which give us new insight into their nature.
Methods: Over 3000 S-bursts were observed on 9 July 2013 at frequencies of 17.4-83.1 MHz during a period of low solar activity. Leading models of S-burst generation were tested by analysing the spectral properties of S-bursts and estimating coronal magnetic field strengths.
Results: S-bursts were found to have short durations of 0.5-0.9 s. Multiple instruments were used to measure the dependence of drift rate on frequency which is represented by a power law with an index of 1.57. For the first time, we show a linear relation between instantaneous bandwidth and frequency over a wide frequency band. The flux calibration and high sensitivity of UTR-2 enabled measurements of their fluxes, which yielded 11 ± 3 solar flux units (1 SFU ≡ 104 Jy). The source particle velocities of S-bursts were found to be ∼0.07 c. S-burst source heights were found to range from 1.3 R⊙ to 2 R⊙. Furthermore, a contemporary theoretical model of S-burst generation was used to conduct remote sensing of the coronal magnetic field at these heights which yielded values of 0.9-5.8 G. Within error, these values are comparable to those predicted by various relations between magnetic field strength and height in the corona. Title: Expansion of High-speed Solar Wind Streams from Coronal Holes through the Inner Heliosphere Authors: Garton, Tadhg M.; Murray, Sophie A.; Gallagher, Peter T. Bibcode: 2018ApJ...869L..12G Altcode: 2018arXiv181111605G Coronal holes (CHs) are regions of open magnetic flux that are the source of high-speed solar wind (HSSW) streams. To date, it is not clear which aspects of CHs exert the most influence on the properties of the solar wind as it expands through the Heliosphere. Here, we study the relationship between CH properties extracted from Atmospheric Imaging Assembly images using the Coronal Hole Identification via Multi-thermal Emission Recognition Algorithm and HSSW measurements from Advanced Composition Explorer at L1. For CH longitudinal widths Δθ CH < 67°, the peak solar wind velocity (v max) is found to scale as v max ≈ 330.8 + 5.7 Δθ CH km s-1. For larger longitudinal widths (Δθ CH > 67°), v max is found to tend to a constant value (∼710 km s-1). Furthermore, we find that the duration of HSSW streams (Δt) are directly related to the longitudinal width of CHs (Δt SW ≈ 0.09Δθ CH) and that their longitudinal expansion factor is f SW ≈ 1.2 ± 0.1. We also derive an expression for the CH flux-tube expansion factor, f FT, which varies as f SW ≳ f FT ≳ 0.8. These results enable us to estimate the peak speeds and durations of HSSW streams at L1 using the properties of CHs identified in the solar corona. Title: Sunspot Group Classification using Neural Networks Authors: Maloney, S. A.; Gallagher, P. T. Bibcode: 2018csc..confE..92M Altcode: Sunspots are the sources of the most extreme and potentially adverse solar events such as flares and CMEs. As such many forecasting systems have been developed to predict these events, a number of which rely on sunspot group classifications. The classifications are manually produced so are subject to human errors and biases. Additionally, as the classifications are only produced on a daily basis this limits the time resolution of some forecasting methods. Further with the imaging cadence of SDO HMI, it would be impossible for a human to produce classifications for every observation. As such the development of an automated classification system would provide many benefits.

Neural networks (NNs) have proven to be powerful tools for solving many complex problems such as classification, regression, and optimisation. In particular, the application of convolutional neural networks (CNNs) to image classification has greatly improved the performance of such systems. The first example of this, in the 1990s, was the identification of handwritten digits from 646 checks an 82% accuracy was achieved. Since then there have been numerous advances in both the network architectures and the underlying components. Recently an accuracy rate of 97.75% was achieved, identifying 1000 classes in 150,000 images for the ILSVRC2017 challenge. We applied a number of modern CNN architectures to the problem of classifying sunspots groups in SDO HMI observations. The input data consisted of SDO HMI SHARPs magnetograms and the daily McIntosh or Mount Wilson sunspot classifications provided by the USAF/NOAA. The entire dataset (2011-2018) was randomly split into three sets, train, test and validate. The train and test sets were used to optimise the parameters and hyperparameters of the chosen network architectures to achieve optimal performance. Once the all the parameters were fixed the accuracy of the networks were determined using the validation set containing only unseen data. We present the results of this work together with some issues encountered and avenues of further research. Title: Three-dimensional magnetic reconnection in a collapsing coronal loop system Authors: O'Flannagain, Aidan M.; Maloney, Shane A.; Gallagher, Peter T.; Browning, Philippa; Refojo, Jose Bibcode: 2018A&A...617A...9O Altcode: 2018arXiv180609365O Context. Magnetic reconnection is believed to be the primary mechanism by which non-potential energy stored in coronal magnetic fields is rapidly released during solar eruptive events. Unfortunately, owing to the small spatial scales on which reconnection is thought to occur, it is not directly observable in the solar corona. However, larger scale processes, such as associated inflow and outflow, and signatures of accelerated particles have been put forward as evidence of reconnection.
Aims: Using a combination of observations we explore the origin of a persistent Type I radio source that accompanies a coronal X-shaped structure during its passage across the disk. Of particular interest is the time range around a partial collapse of the structure that is associated with inflow, outflow, and signatures of particle acceleration.
Methods: Imaging radio observations from the Nançay Radioheliograph were used to localise the radio source. Solar Dynamics Observatory (SDO) AIA extreme ultraviolet (EUV) observations from the same time period were analysed, looking for evidence of inflows and outflows. Further mpole magnetic reconstructions using SDO HMI observations allowed the magnetic connectivity associated with the radio source to be determined.
Results: The Type I radio source was well aligned with a magnetic separator identified in the extrapolations. During the partial collapse, gradual (1 km s-1) and fast (5 km s-1) inflow phases and fast (30 km s-1) and rapid (80-100 km s-1) outflow phases were observed, resulting in an estimated reconnection rate of ∼0.06. The radio source brightening and dimming was found to be co-temporal with increased soft X-ray emission observed in both Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) and Geostationary Operational Environmental Satellite (GOES).
Conclusions: We interpret the brightening and dimming of the radio emission as evidence for accelerated electrons in the reconnection region responding to a gradual fall and rapid rise in electric drift velocity, in response to the inflowing and outflowing field lines. These results present a comprehensive example of 3D null-point reconnection.

The movies associated to Figs. 2 and 3 are available at https://www.aanda.org/ Title: Photospheric Shear Flows in Solar Active Regions and Their Relation to Flare Occurrence Authors: Park, Sung-Hong; Guerra, Jordan A.; Gallagher, Peter T.; Georgoulis, Manolis K.; Bloomfield, D. Shaun Bibcode: 2018SoPh..293..114P Altcode: 2018arXiv180707714P Solar active regions (ARs) that produce major flares typically exhibit strong plasma shear flows around photospheric magnetic polarity inversion lines (MPILs). It is therefore important to quantitatively measure such photospheric shear flows in ARs for a better understanding of their relation to flare occurrence. Photospheric flow fields were determined by applying the Differential Affine Velocity Estimator for Vector Magnetograms (DAVE4VM) method to a large data set of 2548 coaligned pairs of AR vector magnetograms with 12-min separation over the period 2012 - 2016. From each AR flow-field map, three shear-flow parameters were derived corresponding to the mean («S »), maximum (Smax) and integral (Ssum) shear-flow speeds along strong-gradient, strong-field MPIL segments. We calculated flaring rates within 24 h as a function of each shear-flow parameter and we investigated the relation between the parameters and the waiting time (τ ) until the next major flare (class M1.0 or above) after the parameter observation. In general, it is found that the larger Ssum an AR has, the more likely it is for the AR to produce flares within 24 h. It is also found that among ARs which produce major flares, if one has a larger value of Ssum then τ generally gets shorter. These results suggest that large ARs with widespread and/or strong shear flows along MPILs tend to not only be more flare productive, but also produce major flares within 24 h or less. Title: LOFAR4SpaceWeather (LOFAR4SW): Increasing European Space-Weather Capability with Europe's Largest Radio Telescope Authors: Bisi, Mario Mark; Vermeulen, René; Fallows, Richard A.; Vilmer, Nicole; Rothkaehl, Hanna; Verbiest, Joris; Gallagher, Peter T.; Olberg, Michael; Mevius, Maaijke; Robertson, Stuart C. Bibcode: 2018shin.confE.268B Altcode: The Low Frequency Array (LOFAR) is one of a relatively-new breed of radio-astronomy instruments. It covers a wide bandwidth in radio frequencies (10-250 MHz) with both a high temporal and spatial resolution using a large number of stations distributed across Europe. LOFAR consists of a dense core of 24 stations within a 4km diameter, 14 stations spread further afield across the northeast area of The Netherlands, and a further 13 stations spread internationally (six across Germany, three in northern Poland, and one each in France, Ireland, Sweden, and the UK). Further international sites are under preparations, which will then expand LOFAR even further across Europe. LOFAR is one of the world's most-flexible radio instruments with capabilities that enable studies of several aspects of space weather to be progressed beyond today's state-of-the-art. However, in its present setup, it can only be used for space-weather purposes on a campaign bases. This is where observing time has to be competed for alongside astronomy and all other types of radio observations requested. Title: Radio observations of energetic electrons in association with coronal mass ejections in the solar corona Authors: Carley, Eoin; Vilmer, Nicole; Gallagher, Peter Bibcode: 2018cosp...42E.514C Altcode: Coronal mass ejections are large eruptions of plasma and magnetic field from the low solar corona into the heliosphere. These eruptions are often associated with energetic electrons that produce various kinds of radio emission. However, there is ongoing investigation into exactly where, when and how the electron acceleration occurs during flaring and eruption, and how the radio emission can be exploited as a diagnostic of the particle acceleration and CME plasma properties. In this talk I will firstly present recent observations from the Nançay Radioheliograph (NRH) that show the sites and kinds of electron acceleration that take place during flaring and eruption, from the destabilisation of a flux rope to development of a CME. This shows evidence for the tether-cutting model and numerous sites of electron acceleration both external and internal to the CME during its development. Secondly, using an analysis of gyrosynchrotron radiation from NRH and a non-thermal electron diagnostic using X-ray observations, I show that radio emission can be produced internal to the CME from non-thermal electrons of energies >1MeV in a CME core magnetic field strength of 4.4G. Overall, this reveals how different types of radio observations can be used as a diagnostic of the locations and kinds of electron acceleration during an eruptive event, and also how radio may be used to both image CMEs and give new insight into their dynamics and internal plasma properties. Title: Shock location and CME 3D reconstruction of a solar type II radio burst with LOFAR Authors: Zucca, P.; Morosan, D. E.; Rouillard, A. P.; Fallows, R.; Gallagher, P. T.; Magdalenic, J.; Klein, K. -L.; Mann, G.; Vocks, C.; Carley, E. P.; Bisi, M. M.; Kontar, E. P.; Rothkaehl, H.; Dabrowski, B.; Krankowski, A.; Anderson, J.; Asgekar, A.; Bell, M. E.; Bentum, M. J.; Best, P.; Blaauw, R.; Breitling, F.; Broderick, J. W.; Brouw, W. N.; Brüggen, M.; Butcher, H. R.; Ciardi, B.; de Geus, E.; Deller, A.; Duscha, S.; Eislöffel, J.; Garrett, M. A.; Grießmeier, J. M.; Gunst, A. W.; Heald, G.; Hoeft, M.; Hörandel, J.; Iacobelli, M.; Juette, E.; Karastergiou, A.; van Leeuwen, J.; McKay-Bukowski, D.; Mulder, H.; Munk, H.; Nelles, A.; Orru, E.; Paas, H.; Pandey, V. N.; Pekal, R.; Pizzo, R.; Polatidis, A. G.; Reich, W.; Rowlinson, A.; Schwarz, D. J.; Shulevski, A.; Sluman, J.; Smirnov, O.; Sobey, C.; Soida, M.; Thoudam, S.; Toribio, M. C.; Vermeulen, R.; van Weeren, R. J.; Wucknitz, O.; Zarka, P. Bibcode: 2018A&A...615A..89Z Altcode: 2018arXiv180401025Z Context. Type II radio bursts are evidence of shocks in the solar atmosphere and inner heliosphere that emit radio waves ranging from sub-meter to kilometer lengths. These shocks may be associated with coronal mass ejections (CMEs) and reach speeds higher than the local magnetosonic speed. Radio imaging of decameter wavelengths (20-90 MHz) is now possible with the Low Frequency Array (LOFAR), opening a new radio window in which to study coronal shocks that leave the inner solar corona and enter the interplanetary medium and to understand their association with CMEs.
Aims: To this end, we study a coronal shock associated with a CME and type II radio burst to determine the locations at which the radio emission is generated, and we investigate the origin of the band-splitting phenomenon.
Methods: Thetype II shock source-positions and spectra were obtained using 91 simultaneous tied-array beams of LOFAR, and the CME was observed by the Large Angle and Spectrometric Coronagraph (LASCO) on board the Solar and Heliospheric Observatory (SOHO) and by the COR2A coronagraph of the SECCHI instruments on board the Solar Terrestrial Relation Observatory(STEREO). The 3D structure was inferred using triangulation of the coronographic observations. Coronal magnetic fields were obtained from a 3D magnetohydrodynamics (MHD) polytropic model using the photospheric fields measured by the Heliospheric Imager (HMI) on board the Solar Dynamic Observatory (SDO) as lower boundary.
Results: The type II radio source of the coronal shock observed between 50 and 70 MHz was found to be located at the expanding flank of the CME, where the shock geometry is quasi-perpendicular with θBn 70°. The type II radio burst showed first and second harmonic emission; the second harmonic source was cospatial with the first harmonic source to within the observational uncertainty. This suggests that radio wave propagation does not alter the apparent location of the harmonic source. The sources of the two split bands were also found to be cospatial within the observational uncertainty, in agreement with the interpretation that split bands are simultaneous radio emission from upstream and downstream of the shock front. The fast magnetosonic Mach number derived from this interpretation was found to lie in the range 1.3-1.5. The fast magnetosonic Mach numbers derived from modelling the CME and the coronal magnetic field around the type II source were found to lie in the range 1.4-1.6. Title: LOFAR network, new tool for Space Weather Program in the frame of H2020 action LOFAR4SW Authors: Rothkaehl, Hanna; Vilmer, Nicole; Fallows, Richard; Gallagher, Peter; Bisi, Mario M.; Vermeulen, Rene; Verbiest, Joris; Lindqvist, Michael Bibcode: 2018cosp...42E2892R Altcode: The LOFAR for Space Weather (LOFAR4SW) is an international project the aim of which is to deliver the full conceptual and technical design for creating a new leading-edge European research facility for space weather science. The project will engage with stakeholders to prepare a facility which produces unique research data with key impact on advance predictions of space weather events affecting crucial technologicalinfrastructures of today's society.The objective of LOFAR4SW is to prepare for a large scale high-end research facility in which completely simultaneous, independent observing modes and signal paths provide continuous access to two research communities: radio astronomy and space weather research.Space weather science aims, through observation, monitoring, analysis and modelling, at understanding and ultimately predicting the complex state of the solar wind - magnetosphere - ionosphere - thermosphere system, and the potential impact on biological and technological systems on Earth. Increased fundamental knowledge, coupled to large-scale monitoring programs, is needed for much more advanced predictions of the impact of space weather events on Earth.A fully-implemented LOFAR4SW system will enable a wide range of solar and space weather research topics to be tackled and have unique strengths in several high-impact science areas: tracing the initial launch of a CME; detailed tracking of the solar wind and CMEs through interplanetary space; in-depth studies of micro-structure in the Earth's ionosphere. This facility will uniquely provide the missing link of measurements of the interplanetary magnetic field on global scales - a key parameter in forecasting the severity of geomagnetic storm on Earth. The LOFAR4SW will allow scientists to to answer many important questions with regard to the solar corona, the heliosphere, and Earth's ionosphere.The action was started on December 2017 and the aim of this presentation is to show the main goals of the project and the initiated activities Title: Flare forecasting using the evolution of McIntosh sunspot classifications Authors: McCloskey, Aoife E.; Gallagher, Peter T.; Bloomfield, D. Shaun Bibcode: 2018JSWSC...8A..34M Altcode: 2018arXiv180500919M Most solar flares originate in sunspot groups, where magnetic field changes lead to energy build-up and release. However, few flare-forecasting methods use information of sunspot-group evolution, instead focusing on static point-in-time observations. Here, a new forecast method is presented based upon the 24-h evolution in McIntosh classification of sunspot groups. Evolution-dependent ≥C1.0 and ≥M1.0 flaring rates are found from NOAA-numbered sunspot groups over December 1988-June 1996 (Solar Cycle 22; SC22) before converting to probabilities assuming Poisson statistics. These flaring probabilities are used to generate operational forecasts for sunspot groups over July 1996-December 2008 (SC23), with performance studied by verification metrics. Major findings are: (i) considering Brier skill score (BSS) for ≥C1.0 flares, the evolution-dependent McIntosh-Poisson method (BSSevolution = 0.09) performs better than the static McIntosh-Poisson method (BSSstatic = - 0.09); (ii) low BSS values arise partly from both methods over-forecasting SC23 flares from the SC22 rates, symptomatic of ≥C1.0 rates in SC23 being on average ≈80% of those in SC22 (with ≥M1.0 being ≈50%); (iii) applying a bias-correction factor to reduce the SC22 rates used in forecasting SC23 flares yields modest improvement in skill relative to climatology for both methods (BSSstaticcorr = 0.09 and BSSevolutioncorr = 0.0.20) and improved forecast reliability diagrams. Title: LOFAR observations of the quiet solar corona Authors: Vocks, C.; Mann, G.; Breitling, F.; Bisi, M. M.; Dąbrowski, B.; Fallows, R.; Gallagher, P. T.; Krankowski, A.; Magdalenić, J.; Marqué, C.; Morosan, D.; Rucker, H. Bibcode: 2018A&A...614A..54V Altcode: 2018arXiv180300453V Context. The quiet solar corona emits meter-wave thermal bremsstrahlung. Coronal radio emission can only propagate above that radius, Rω, where the local plasma frequency equals the observing frequency. The radio interferometer LOw Frequency ARray (LOFAR) observes in its low band (10-90 MHz) solar radio emission originating from the middle and upper corona.
Aims: We present the first solar aperture synthesis imaging observations in the low band of LOFAR in 12 frequencies each separated by 5 MHz. From each of these radio maps we infer Rω, and a scale height temperature, T. These results can be combined into coronal density and temperature profiles.
Methods: We derived radial intensity profiles from the radio images. We focus on polar directions with simpler, radial magnetic field structure. Intensity profiles were modeled by ray-tracing simulations, following wave paths through the refractive solar corona, and including free-free emission and absorption. We fitted model profiles to observations with Rω and T as fitting parameters.
Results: In the low corona, Rω < 1.5 solar radii, we find high scale height temperatures up to 2.2 × 106 K, much more than the brightness temperatures usually found there. But if all Rω values are combined into a density profile, this profile can be fitted by a hydrostatic model with the same temperature, thereby confirming this with two independent methods. The density profile deviates from the hydrostatic model above 1.5 solar radii, indicating the transition into the solar wind.
Conclusions: These results demonstrate what information can be gleaned from solar low-frequency radio images. The scale height temperatures we find are not only higher than brightness temperatures, but also than temperatures derived from coronograph or extreme ultraviolet (EUV) data. Future observations will provide continuous frequency coverage. This continuous coverage eliminates the need for local hydrostatic density models in the data analysis and enables the analysis of more complex coronal structures such as those with closed magnetic fields. Title: Eclipse Science from 50,000 Feet: New Coronal Results from NASA WB-57F High-Altitude Aircraft Observations of the 2017 Total Solar Eclipse Authors: Caspi, Amir; Tsang, Constantine; Seaton, Daniel B.; DeForest, Craig; Bryans, Paul; DeLuca, Edward; Tomczyk, Steven; Burkepile, Joan; Casey, Thomas Anthony; Collier, John; Darrow, Donald DD; Del Rosso, Dominic; Durda, Daniel D.; Gallagher, Peter; Gascar, Jasmine; Golub, Leon; Jacyna, Matthew; Johnson, David DJ; Judge, Philip G.; Klemm, Cary; Laurent, Glenn Thomas; Lewis, Johanna; Mallini, Charles; Parent, Thomas Duster; Propp, Timothy; Steffl, Andrew; Warner, Jeff; West, Matthew John; Wiseman, John; Yates, Mallory; Zhukov, Andrei Bibcode: 2018tess.conf31302C Altcode: Total solar eclipses present rare opportunities to study the complex solar corona, down to altitudes of just a few percent of a solar radius above the surface. Studying the corona is critical to gaining a better understanding of the dominant driver of space weather that affects human assets on Earth and elsewhere. For example, it is still poorly understood how the corona is heated to temperatures of 1-2 MK globally and up to 5-10 MK above active regions, while the underlying chromosphere is 100 times cooler. The stability of large-scale coronal structures and the extent of their reach to the middle and outer corona are also not well known, limited in large part by sensitivities and fields of view of existing observations.

Airborne observations during a total eclipse provide unique advantages. By flying in the stratosphere at altitudes of 50 kft or higher, they avoid all weather, the seeing quality is enormously improved, and additional wavelengths such as near-IR also become available due to significantly reduced water absorption. An airborne observatory can also follow the Moon's shadow, increasing the total observing time by 50% or more.

We present current results of solar coronal measurements from airborne observations of the 2017 Great American Total Solar Eclipse using two of NASA's WB-57 high-altitude research aircraft, each equipped with two 8.7-inch telescopes feeding high-sensitivity visible (green line and nearby continuum) and medium-wave IR (3-5 μm) cameras operating at high cadence (30 Hz) with ∼3 arcsec/pixel platescale and ±3 Rsun fields of view. The two aircraft flew along the eclipse path, separated by ∼110 km, to observe a total of ∼7.5 minutes of totality in both visible and MWIR. These observations enable groundbreaking studies of high-speed coherent motion - including possible Alfvén waves and nanojets - in the lower and middle corona that could shed light on coronal heating processes and the formation and stability of coronal structures. Our MWIR observations of a cool prominence and hot coronal active region plasma will be combined with spectra from the AIR-Spec instrument, flown concurrently on NCAR's HIAPER GV. We review the WB-57 eclipse mission and the current results of analysis on the visible and IR coronal measurements, along with an outlook for future analysis and missions. Title: CMEs in the Heliosphere: I. A Statistical Analysis of the Observational Properties of CMEs Detected in the Heliosphere from 2007 to 2017 by STEREO/HI-1 Authors: Harrison, R. A.; Davies, J. A.; Barnes, D.; Byrne, J. P.; Perry, C. H.; Bothmer, V.; Eastwood, J. P.; Gallagher, P. T.; Kilpua, E. K. J.; Möstl, C.; Rodriguez, L.; Rouillard, A. P.; Odstrčil, D. Bibcode: 2018SoPh..293...77H Altcode: 2018arXiv180402320H We present a statistical analysis of coronal mass ejections (CMEs) imaged by the Heliospheric Imager (HI) instruments on board NASA's twin-spacecraft STEREO mission between April 2007 and August 2017 for STEREO-A and between April 2007 and September 2014 for STEREO-B. The analysis exploits a catalogue that was generated within the FP7 HELCATS project. Here, we focus on the observational characteristics of CMEs imaged in the heliosphere by the inner (HI-1) cameras, while following papers will present analyses of CME propagation through the entire HI fields of view. More specifically, in this paper we present distributions of the basic observational parameters - namely occurrence frequency, central position angle (PA) and PA span - derived from nearly 2000 detections of CMEs in the heliosphere by HI-1 on STEREO-A or STEREO-B from the minimum between Solar Cycles 23 and 24 to the maximum of Cycle 24; STEREO-A analysis includes a further 158 CME detections from the descending phase of Cycle 24, by which time communication with STEREO-B had been lost. We compare heliospheric CME characteristics with properties of CMEs observed at coronal altitudes, and with sunspot number. As expected, heliospheric CME rates correlate with sunspot number, and are not inconsistent with coronal rates once instrumental factors/differences in cataloguing philosophy are considered. As well as being more abundant, heliospheric CMEs, like their coronal counterparts, tend to be wider during solar maximum. Our results confirm previous coronagraph analyses suggesting that CME launch sites do not simply migrate to higher latitudes with increasing solar activity. At solar minimum, CMEs tend to be launched from equatorial latitudes, while at maximum, CMEs appear to be launched over a much wider latitude range; this has implications for understanding the CME/solar source association. Our analysis provides some supporting evidence for the systematic dragging of CMEs to lower latitude as they propagate outwards. Title: LOFAR for Space Weather (LOFAR4SW) H2020 program Authors: Rothkaehl, Hanna; Vermeulen, René; Fallows, Richard; Verbiest, Joris; Vilmer, Nicole; Olberg, Michael; Bisi, Mario; Gallagher, Peter Bibcode: 2018EGUGA..2018974R Altcode: The LOFAR for Space Weather (LOFAR4SW) is an international project the aim of which is to deliver the full conceptual and technical design for creating a new leading-edge European research facility for space weather science. The project will engage with stakeholders to prepare a facility which produces unique research data with key impact on advance predictions of space weather events affecting crucial technological infrastructures of today's society. The objective of LOFAR4SW is to prepare for a large scale high-end research facility in which completely simultaneous, independent observing modes and signal paths provide continuous access to two research communities: radio astronomy and space weather research. Space weather science aims, through observation, monitoring, analysis and modelling, at understanding and ultimately predicting the complex state of the solar wind - magnetosphere - ionosphere - thermosphere system, and the potential impact on biological and technological systems on Earth. Increased fundamental knowledge, coupled to large-scale monitoring programs, is needed for much more advanced predictions of the impact of space weather events on Earth. A fully-implemented LOFAR4SW system will enable a wide range of solar and space weather research topics to be tackled and have unique strengths in several high-impact science areas: tracing the initial launch of a CME; detailed tracking of the solar wind and CMEs through interplanetary space; in-depth studies of micro-structure in the Earth's ionosphere. This facility will uniquely provide the missing link of measurements of the interplanetary magnetic field on global scales - a key parameter in forecasting the severity of geomagnetic storm on Earth. The LOFAR4SW will allow scientists to to answer many important questions with regard to the solar corona, the heliosphere, and Earth's ionosphere. The action was started on December 2017 and the aim of this presentation is to show the main goals of the project and the initiated activities Title: VizieR Online Data Catalog: Quasi-periodic pulsations in solar flares (Inglis+, 2016) Authors: Inglis, A. R.; Ireland, J.; Dennis, B. R.; Hayes, L.; Gallagher, P. Bibcode: 2018yCat..18330284I Altcode: We have used data from the Geostationary Operational Environmental Satellite (GOES) instrument series, and from Fermi/Gamma-ray Burst Monitor (GBM). For this reason, we choose the interval 2011 February 1 - 2015 December 31, as it not only coincides with the availability of GOES-15 satellite data, but also includes regular solar observations by GBM.

GOES satellites are equipped with solar X-ray detectors that record the incident flux in the 0.5-4Å and 1-8Å wavelength ranges. Solar X-ray data from the most recent satellite, GOES-15, has been available since 2010 at a nominal 2s cadence. To access the GOES catalog, we use the Heliophysics Event Knowledgebase (HEK).

Fermi/GBM operates in the 8keV-40MeV range and regularly observes emission from solar flares, with a solar duty cycle of ~60%, similar to the solar-dedicated Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI). To accumulate the database of Fermi/GBM events, we use the GBM trigger catalog produced by the instrument team, selecting all events marked as flares.

(2 data files). Title: Connecting Coronal Mass Ejections to Their Solar Active Region Sources: Combining Results from the HELCATS and FLARECAST Projects Authors: Murray, Sophie A.; Guerra, Jordan A.; Zucca, Pietro; Park, Sung-Hong; Carley, Eoin P.; Gallagher, Peter T.; Vilmer, Nicole; Bothmer, Volker Bibcode: 2018SoPh..293...60M Altcode: 2018arXiv180306529M Coronal mass ejections (CMEs) and other solar eruptive phenomena can be physically linked by combining data from a multitude of ground-based and space-based instruments alongside models; however, this can be challenging for automated operational systems. The EU Framework Package 7 HELCATS project provides catalogues of CME observations and properties from the Heliospheric Imagers on board the two NASA/STEREO spacecraft in order to track the evolution of CMEs in the inner heliosphere. From the main HICAT catalogue of over 2,000 CME detections, an automated algorithm has been developed to connect the CMEs observed by STEREO to any corresponding solar flares and active-region (AR) sources on the solar surface. CME kinematic properties, such as speed and angular width, are compared with AR magnetic field properties, such as magnetic flux, area, and neutral line characteristics. The resulting LOWCAT catalogue is also compared to the extensive AR property database created by the EU Horizon 2020 FLARECAST project, which provides more complex magnetic field parameters derived from vector magnetograms. Initial statistical analysis has been undertaken on the new data to provide insight into the link between flare and CME events, and characteristics of eruptive ARs. Warning thresholds determined from analysis of the evolution of these parameters is shown to be a useful output for operational space weather purposes. Parameters of particular interest for further analysis include total unsigned flux, vertical current, and current helicity. The automated method developed to create the LOWCAT catalogue may also be useful for future efforts to develop operational CME forecasting. Title: Tracking of an electron beam through the solar corona with LOFAR Authors: Mann, G.; Breitling, F.; Vocks, C.; Aurass, H.; Steinmetz, M.; Strassmeier, K. G.; Bisi, M. M.; Fallows, R. A.; Gallagher, P.; Kerdraon, A.; Mackinnon, A.; Magdalenic, J.; Rucker, H.; Anderson, J.; Asgekar, A.; Avruch, I. M.; Bell, M. E.; Bentum, M. J.; Bernardi, G.; Best, P.; Bîrzan, L.; Bonafede, A.; Broderick, J. W.; Brüggen, M.; Butcher, H. R.; Ciardi, B.; Corstanje, A.; de Gasperin, F.; de Geus, E.; Deller, A.; Duscha, S.; Eislöffel, J.; Engels, D.; Falcke, H.; Fender, R.; Ferrari, C.; Frieswijk, W.; Garrett, M. A.; Grießmeier, J.; Gunst, A. W.; van Haarlem, M.; Hassall, T. E.; Heald, G.; Hessels, J. W. T.; Hoeft, M.; Hörandel, J.; Horneffer, A.; Juette, E.; Karastergiou, A.; Klijn, W. F. A.; Kondratiev, V. I.; Kramer, M.; Kuniyoshi, M.; Kuper, G.; Maat, P.; Markoff, S.; McFadden, R.; McKay-Bukowski, D.; McKean, J. P.; Mulcahy, D. D.; Munk, H.; Nelles, A.; Norden, M. J.; Orru, E.; Paas, H.; Pandey-Pommier, M.; Pandey, V. N.; Pizzo, R.; Polatidis, A. G.; Rafferty, D.; Reich, W.; Röttgering, H.; Scaife, A. M. M.; Schwarz, D. J.; Serylak, M.; Sluman, J.; Smirnov, O.; Stappers, B. W.; Tagger, M.; Tang, Y.; Tasse, C.; ter Veen, S.; Thoudam, S.; Toribio, M. C.; Vermeulen, R.; van Weeren, R. J.; Wise, M. W.; Wucknitz, O.; Yatawatta, S.; Zarka, P.; Zensus, J. A. Bibcode: 2018A&A...611A..57M Altcode: The Sun's activity leads to bursts of radio emission, among other phenomena. An example is type-III radio bursts. They occur frequently and appear as short-lived structures rapidly drifting from high to low frequencies in dynamic radio spectra. They are usually interpreted as signatures of beams of energetic electrons propagating along coronal magnetic field lines. Here we present novel interferometric LOFAR (LOw Frequency ARray) observations of three solar type-III radio bursts and their reverse bursts with high spectral, spatial, and temporal resolution. They are consistent with a propagation of the radio sources along the coronal magnetic field lines with nonuniform speed. Hence, the type-III radio bursts cannot be generated by a monoenergetic electron beam, but by an ensemble of energetic electrons with a spread distribution in velocity and energy. Additionally, the density profile along the propagation path is derived in the corona. It agrees well with three-fold coronal density model by (1961, ApJ, 133, 983). Title: Active Region Photospheric Magnetic Properties Derived from Line-of-Sight and Radial Fields Authors: Guerra, J. A.; Park, S. -H.; Gallagher, P. T.; Kontogiannis, I.; Georgoulis, M. K.; Bloomfield, D. S. Bibcode: 2018SoPh..293....9G Altcode: 2017arXiv171206902G The effect of using two representations of the normal-to-surface magnetic field to calculate photospheric measures that are related to the active region (AR) potential for flaring is presented. Several AR properties were computed using line-of-sight (Blos) and spherical-radial (Br) magnetograms from the Space-weather HMI Active Region Patch (SHARP) products of the Solar Dynamics Observatory, characterizing the presence and features of magnetic polarity inversion lines, fractality, and magnetic connectivity of the AR photospheric field. The data analyzed correspond to ≈4 ,000 AR observations, achieved by randomly selecting 25% of days between September 2012 and May 2016 for analysis at 6-hr cadence. Results from this statistical study include: i) the Br component results in a slight upwards shift of property values in a manner consistent with a field-strength underestimation by the Blos component; ii) using the Br component results in significantly lower inter-property correlation in one-third of the cases, implying more independent information as regards the state of the AR photospheric magnetic field; iii) flaring rates for each property vary between the field components in a manner consistent with the differences in property-value ranges resulting from the components; iv) flaring rates generally increase for higher values of properties, except the Fourier spectral power index that has flare rates peaking around a value of 5 /3 . These findings indicate that there may be advantages in using Br rather than Blos in calculating flare-related AR magnetic properties, especially for regions located far from central meridian. Title: Automated coronal hole identification via multi-thermal intensity segmentation Authors: Garton, Tadhg M.; Gallagher, Peter T.; Murray, Sophie A. Bibcode: 2018JSWSC...8A...2G Altcode: 2017arXiv171111476G; 2018JSWSC...8A..02G Coronal holes (CH) are regions of open magnetic fields that appear as dark areas in the solar corona due to their low density and temperature compared to the surrounding quiet corona. To date, accurate identification and segmentation of CHs has been a difficult task due to their comparable intensity to local quiet Sun regions. Current segmentation methods typically rely on the use of single Extreme Ultra-Violet passband and magnetogram images to extract CH information. Here, the coronal hole identification via multi-thermal emission recognition algorithm (CHIMERA) is described, which analyses multi-thermal images from the atmospheric image assembly (AIA) onboard the solar dynamics observatory (SDO) to segment coronal hole boundaries by their intensity ratio across three passbands (171 Å, 193 Å, and 211 Å). The algorithm allows accurate extraction of CH boundaries and many of their properties, such as area, position, latitudinal and longitudinal width, and magnetic polarity of segmented CHs. From these properties, a clear linear relationship was identified between the duration of geomagnetic storms and coronal hole areas. CHIMERA can therefore form the basis of more accurate forecasting of the start and duration of geomagnetic storms. Title: Chasing the Great American 2017 Total Solar Eclipse: Coronal Results from NASA's WB-57F High-Altitude Research Aircraft Authors: Caspi, A.; Tsang, C.; DeForest, C. E.; Seaton, D. B.; Bryans, P.; Burkepile, J.; Casey, T. A.; Collier, J.; Darrow, D.; DeLuca, E.; Durda, D. D.; Gallagher, P.; Golub, L.; Judge, P. G.; Laurent, G. T.; Lewis, J.; Mallini, C.; Parent, T.; Propp, T.; Steffl, A.; Tomczyk, S.; Warner, J.; West, M. J.; Wiseman, J.; Zhukov, A. Bibcode: 2017AGUFMSH24A..05C Altcode: Total solar eclipses present rare opportunities to study the complex solar corona, down to altitudes of just a few percent of a solar radius above the surface, using ground-based and airborne observatories that would otherwise be dominated by the intense solar disk and high sky brightness. Studying the corona is critical to gaining a better understanding of physical processes that occur on other stars and astrophysical objects, as well as understanding the dominant driver of space weather that affects human assets at Earth and elsewhere. For example, it is still poorly understood how the corona is heated to temperatures of 1-2 MK globally and up to 5-10 MK above active regions, while the underlying chromosphere is 100 times cooler; numerous theories abound, but are difficult to constrain due to the limited sensitivities and cadences of prior measurements. The origins and stability of coronal fans, and the extent of their reach to the middle and outer corona, are also not well known, limited in large part by sensitivities and fields of view of existing observations. Airborne observations during the eclipse provide unique advantages; by flying in the stratosphere at altitudes of 50 kft or higher, they avoid all weather, the seeing quality is enormously improved, and additional wavelengths such as near- IR also become available due to significantly reduced water absorption. For an eclipse, an airborne observatory can also follow the shadow, increasing the total observing time by 50% or more. We present results of solar coronal measurements from airborne observations of the 2017 Great American Total Solar Eclipse using two of NASA's WB-57 high-altitude research aircraft, each equipped with two 8.7" telescopes feeding high-sensitivity visible (green-line) and medium-wave IR (3-5 μm) cameras operating at high cadence (30 Hz) with 3 arcsec/pixel platescale and ±3 R_sun fields of view. The aircraft flew along the eclipse path, separated by 110 km, to observe a summed 7.5 minutes of totality in both visible and NIR, enabling groundbreaking studies of high-speed wave motions and nanojets in the lower corona, the structure and extent of coronal fans, and constraints on a potential primordial dust ring around the Sun. We review the mission, and the results of analysis on the visible and IR coronal measurements. Title: Quasi-Periodic Pulsations in the Earth's Ionosphere Synchronized with Solar Flare Emission Authors: Hayes, L.; Gallagher, P.; McCauley, J.; Dennis, B. R.; Ireland, J.; Inglis, A. R. Bibcode: 2017AGUFMSH51C2514H Altcode: Solar flare activity is a powerful factor affecting the geophysical processes in the Earth's ionosphere. In particular, X-ray photons with wavelength < 10 A can penetrate down to the D-region ( 60-90 km in altitude) resulting in a dramatic increase of ionization in this lowest lying region of the Earth's ionosphere. This manifests as a substantial enhancement of electron density height profile at these altitudes to extents large enough to change the propagation conditions for Very Low Frequency (VLF 3-30 kHz) radio waves that travel in the waveguide formed by the Earth and the lower ionosphere. Recently, it has become clear that flares exhibit quasi-periodic pulsations with periods of seconds to minutes at EUV, X-ray and gamma-ray wavelengths. To date, it has not been known if the Earth's ionosphere is sensitive to these dynamic solar pulsations. Here, we report ionospheric pulsations with periods of 20 minutes that are synchronized with a set of pulsating flare loops using VLF observations of the ionospheric D-layer together with X-ray and EUV observations of a solar flare from the NOAA/GOES and NASA/SDO satellites. Modeling of the ionosphere show that the D-region electron density varies by up to an order of magnitude over the timescale of the pulsations. Our results show that the Earth's ionosphere is more sensitive to small-scale changes in solar activity than previously thought. Title: The Next Level in Automated Solar Flare Forecasting: the EU FLARECAST Project Authors: Georgoulis, M. K.; Bloomfield, D.; Piana, M.; Massone, A. M.; Gallagher, P.; Vilmer, N.; Pariat, E.; Buchlin, E.; Baudin, F.; Csillaghy, A.; Soldati, M.; Sathiapal, H.; Jackson, D.; Alingery, P.; Argoudelis, V.; Benvenuto, F.; Campi, C.; Florios, K.; Gontikakis, C.; Guennou, C.; Guerra, J. A.; Kontogiannis, I.; Latorre, V.; Murray, S.; Park, S. H.; Perasso, A.; Sciacchitano, F.; von Stachelski, S.; Torbica, A.; Vischi, D. Bibcode: 2017AGUFMSA21C..07G Altcode: We attempt an informative description of the Flare Likelihood And Region Eruption Forecasting (FLARECAST) project, European Commission's first large-scale investment to explore the limits of reliability and accuracy achieved for the forecasting of major solar flares. We outline the consortium, top-level objectives and first results of the project, highlighting the diversity and fusion of expertise needed to deliver what was promised. The project's final product, featuring an openly accessible, fully modular and free to download flare forecasting facility will be delivered in early 2018. The project's three objectives, namely, science, research-to-operations and dissemination / communication, are also discussed: in terms of science, we encapsulate our close-to-final assessment on how close (or far) are we from a practically exploitable solar flare forecasting. In terms of R2O, we briefly describe the architecture of the FLARECAST infrastructure that includes rigorous validation for each forecasting step. From the three different communication levers of the project we finally focus on lessons learned from the two-way interaction with the community of stakeholders and governmental organizations. The FLARECAST project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No. 640216. Title: The Heliospheric Cataloguing, Analysis and Techniques Service (HELCATS) project Authors: Barnes, D.; Harrison, R. A.; Davies, J. A.; Perry, C. H.; Moestl, C.; Rouillard, A.; Bothmer, V.; Rodriguez, L.; Eastwood, J. P.; Kilpua, E.; Gallagher, P.; Odstrcil, D. Bibcode: 2017AGUFMSH31A2713B Altcode: Understanding solar wind evolution is fundamental to advancing our knowledge of energy and mass transport in the solar system, whilst also being crucial to space weather and its prediction. The advent of truly wide-angle heliospheric imaging has revolutionised the study of solar wind evolution, by enabling direct and continuous observation of both transient and background components of the solar wind as they propagate from the Sun to 1 AU and beyond. The recently completed, EU-funded FP7 Heliospheric Cataloguing, Analysis and Techniques Service (HELCATS) project (1st May 2014 - 30th April 2017) combined European expertise in heliospheric imaging, built up over the last decade in particular through leadership of the Heliospheric Imager (HI) instruments aboard NASA's STEREO mission, with expertise in solar and coronal imaging as well as the interpretation of in-situ and radio diagnostic measurements of solar wind phenomena. HELCATS involved: (1) the cataloguing of transient (coronal mass ejections) and background (stream/corotating interaction regions) solar wind structures observed by the STEREO/HI instruments, including estimates of their kinematic properties based on a variety of modelling techniques; (2) the verification of these kinematic properties through comparison with solar source observations and in-situ measurements at multiple points throughout the heliosphere; (3) the assessment of the potential for initialising numerical models based on the derived kinematic properties of transient and background solar wind components; and (4) the assessment of the complementarity of radio observations (Type II radio bursts and interplanetary scintillation) in the detection and analysis of heliospheric structure in combination with heliospheric imaging observations. In this presentation, we provide an overview of the HELCATS project emphasising, in particular, the principal achievements and legacy of this unprecedented project. Title: Pulsations in the Earth's Lower Ionosphere Synchronized With Solar Flare Emission Authors: Hayes, Laura A.; Gallagher, Peter T.; McCauley, Joseph; Dennis, Brian R.; Ireland, Jack; Inglis, Andrew Bibcode: 2017JGRA..122.9841H Altcode: 2017arXiv171001725H Solar flare emission at X-ray and extreme ultraviolet (EUV) energies can cause substantial enhancements in the electron density in the Earth's lower ionosphere. It has now become clear that flares exhibit quasi-periodic pulsations with timescales of minutes at X-ray energies, but to date, it has not been known if the ionosphere is sensitive to this variability. Here using a combination of very low frequency (24 kHz) measurement together with space-based X-ray and EUV observations, we report pulsations of the ionospheric D region, which are synchronized with a set of pulsating flare loops. Modeling of the ionosphere show that the D region electron density varies by up to an order of magnitude over the timescale of the pulsations (∼ 20 min). Our results reveal that the Earth's ionosphere is more sensitive to small-scale changes in solar soft X-ray flux than previously thought and implies that planetary ionospheres are closely coupled to small-scale changes in solar/stellar activity. Title: The association of a J-burst with a solar jet Authors: Morosan, D. E.; Gallagher, P. T.; Fallows, R. A.; Reid, H.; Mann, G.; Bisi, M. M.; Magdalenić, J.; Rucker, H. O.; Thidé, B.; Vocks, C.; Anderson, J.; Asgekar, A.; Avruch, I. M.; Bell, M. E.; Bentum, M. J.; Best, P.; Blaauw, R.; Bonafede, A.; Breitling, F.; Broderick, J. W.; Brüggen, M.; Cerrigone, L.; Ciardi, B.; de Geus, E.; Duscha, S.; Eislöffel, J.; Falcke, H.; Garrett, M. A.; Grießmeier, J. M.; Gunst, A. W.; Hoeft, M.; Iacobelli, M.; Juette, E.; Kuper, G.; McFadden, R.; McKay-Bukowski, D.; McKean, J. P.; Mulcahy, D. D.; Munk, H.; Nelles, A.; Orru, E.; Paas, H.; Pandey-Pommier, M.; Pandey, V. N.; Pizzo, R.; Polatidis, A. G.; Reich, W.; Schwarz, D. J.; Sluman, J.; Smirnov, O.; Steinmetz, M.; Tagger, M.; ter Veen, S.; Thoudam, S.; Toribio, M. C.; Vermeulen, R.; van Weeren, R. J.; Wucknitz, O.; Zarka, P. Bibcode: 2017A&A...606A..81M Altcode: 2017arXiv170703428M Context. The Sun is an active star that produces large-scale energetic events such as solar flares and coronal mass ejections, and numerous smaller scale events such as solar jets. These events are often associated with accelerated particles that can cause emission at radio wavelengths. The reconfiguration of the solar magnetic field in the corona is believed to be the cause of the majority of solar energetic events and accelerated particles.
Aims: Here, we investigate a bright J-burst that was associated with a solar jet and the possible emission mechanism causing these two phenomena.
Methods: We used data from the Solar Dynamics Observatory (SDO) to observe a solar jet and radio data from the Low Frequency Array (LOFAR) and the Nançay Radioheliograph (NRH) to observe a J-burst over a broad frequency range (33-173 MHz) on 9 July 2013 at 11:06 UT.
Results: The J-burst showed fundamental and harmonic components and was associated with a solar jet observed at extreme ultraviolet wavelengths with SDO. The solar jet occurred in the northern hemisphere at a time and location coincident with the radio burst and not inside a group of complex active regions in the southern hemisphere. The jet occurred in the negative polarity region of an area of bipolar plage. Newly emerged positive flux in this region appeared to be the trigger of the jet.
Conclusions: Magnetic reconnection between the overlying coronal field lines and the newly emerged positive field lines is most likely the cause of the solar jet. Radio imaging provides a clear association between the jet and the J-burst, which shows the path of the accelerated electrons. These electrons travelled from a region in the vicinity of the solar jet along closed magnetic field lines up to the top of a closed magnetic loop at a height of 360 Mm. Such small-scale complex eruptive events arising from magnetic reconnection could facilitate accelerated electrons to produce continuously the large numbers of Type III bursts observed at low frequencies, in a similar way to the J-burst analysed here.

The movie attached to Fig. 4 is available at http://www.aanda.org Title: Searching for evidence of quasi-periodic pulsations in solar flares using the AFINO code Authors: Inglis, Andrew; Ireland, Jack; Dennis, Brian R.; Hayes, Laura Ann; Gallagher, Peter T. Bibcode: 2017SPD....4840005I Altcode: The AFINO (Automated Flare Inference of Oscillations) code is a new tool to allow analysis of temporal solar data in search of oscillatory signatures. Using AFINO, we carry out a large-scale search for evidence of signals consistent with quasi-periodic pulsations (QPP) in solar flares, focusing on the 1-300 s timescale. We analyze 675 M- and X-class flares observed by GOES in 1-8 Å soft X-rays between 2011 February 1 and 2015 December 31. Additionally, over the same era we analyze Fermi/GBM 15-25 keV X-ray data for each of these flares associated with a GBM solar flare trigger, a total of 261 events. Using a model comparison method and the Bayesian Information Criterion statistic, we determine whether there is evidence for a substantial enhancement in the Fourier power spectrum that may be consistent with a QPP-like signature.Quasi-steady periodic signatures appear more prevalently in thermal soft X-ray data than in the counterpart hard X-ray emission: according to AFINO ~30% of GOES flares but only ~8% of the same flares observed by GBM show strong signatures consistent with classical interpretations of QPP, which include MHD wave processes and oscillatory reconnection events. For both datasets, preferred characteristic timescales of ~5-30 s were found in the QPP-like events, with no clear dependence on flare magnitude. Individual events in the sample also show similar characteristic timescales in both GBM and GOES data sets, indicating that the same phenomenon is sometimes observed simultaneously in soft and hard X-rays. We discuss the implications of these survey results, and future developments of the analysis method. AFINO continues to run daily on new flares observed by GOES, and the full AFINO catalogue is made available online. Title: First results from the NASA WB-57 airborne observations of the Great American 2017 Total Solar Eclipse Authors: Caspi, Amir; Tsang, Constantine; DeForest, Craig; Seaton, Daniel B.; Bryans, Paul; Tomczyk, Steven; Burkepile, Joan; Judge, Phil; DeLuca, Edward E.; Golub, Leon; Gallagher, Peter T.; Zhukov, Andrei; West, Matthew; Durda, Daniel D.; Steffl, Andrew J. Bibcode: 2017SPD....4810701C Altcode: Total solar eclipses present rare opportunities to study the complex solar corona, down to altitudes of just a few percent of a solar radius above the surface, using ground-based and airborne observatories that would otherwise be dominated by the intense solar disk and high sky brightness. Studying the corona is critical to gaining a better understanding of physical processes that occur on other stars and astrophysical objects, as well as understanding the dominant driver of space weather that affects human assets at Earth and elsewhere. For example, it is still poorly understood how the corona is heated to temperatures of 1-2 MK globally and up to 5-10 MK above active regions, while the underlying chromosphere is 100 times cooler; numerous theories abound, but are difficult to constrain due to the limited sensitivities and cadences of prior measurements. The origins and stability of coronal fans, and the extent of their reach to the middle and outer corona, are also not well known, limited in large part by sensitivities and fields of view of existing observations.Airborne observations during the eclipse provide unique advantages; by flying in the stratosphere at altitudes of 50 kft or higher, they avoid all weather, the seeing quality is enormously improved, and additional wavelengths such as near-IR also become available due to significantly reduced water absorption. For an eclipse, an airborne observatory can also follow the shadow, increasing the total observing time by 50% or more.We present the first results from airborne observations of the 2017 Great American Total Solar Eclipse using two of NASA's WB-57 research aircraft, each equipped with two 8.7" telescopes feeding high-sensitivity visible (green-line) and near-IR (3-5 µm) cameras operating at high cadence (30 Hz) with ~3 arcsec/pixel platescale and ±3 R_sun fields of view. The aircraft will fly along the eclipse path, separated by ~90 km, to observe a summed ~8 minutes of totality in both visible and NIR, enabling groundbreaking studies of high-speed wave motions and nanojets in the lower corona, the structure and extent of coronal fans, and constraints on a potential primordial dust ring around the Sun. Title: Kinematics and shock locations of a spatial resolved solar type II radio burst with LOFAR Authors: Zucca, Pietro; Morosan, Diana; Gallagher, Peter T.; Fallows, Richard; Rouillard, Alexis; Magdalenic, Jasmina; Vocks, Christian; Marqué, Christophe; Klein, Karl-Ludwig; Mann, Gottfried Bibcode: 2017shin.confE..14Z Altcode: Type II radio bursts are evidence of shocks in the solar atmosphere emitting radio waves ranging from metric to kilometric lengths. These shocks may be associated with coronal mass ejections (CMEs) reaching super-Alfvénic speeds. Radio imaging of the decameter wavelengths is now possible with the Low Frequency Array (LOFAR), opening a new radio window to study coronal radio shocks leaving the inner solar corona and entering the interplanetary medium and understand their association with CMEs.

Here, we study a coronal shock associated with a CME and type II radio burst to determine the location where the shock is triggered in relation to the propagating CME, the ambient medium Alfvén speed and the orientation of the coronal magnetic field. The type II shock imaging and spectra were obtained using 91 simultaneous tied-array beams of LOFAR while the CME was observed by the Large Angle and Spectrometric Coronagraph (LASCO) on board the Solar and Heliospheric Observatory (SOHO).

Using the tied array beam observing mode of LOFAR we were able to locate the type II radio shock position between 45 and 75 MHz and relate it to the expanding flank of a CME leaving the inner corona. The radio emission associated with the type II shock was found to be located at the flank of the CME in a region where the mach number is between 1.5 to 2.0 and the shock geometry is quasi-perpendicular. Title: Modeling observations of solar coronal mass ejections with heliospheric imagers verified with the Heliophysics System Observatory Authors: Möstl, C.; Isavnin, A.; Boakes, P. D.; Kilpua, E. K. J.; Davies, J. A.; Harrison, R. A.; Barnes, D.; Krupar, V.; Eastwood, J. P.; Good, S. W.; Forsyth, R. J.; Bothmer, V.; Reiss, M. A.; Amerstorfer, T.; Winslow, R. M.; Anderson, B. J.; Philpott, L. C.; Rodriguez, L.; Rouillard, A. P.; Gallagher, P.; Nieves-Chinchilla, T.; Zhang, T. L. Bibcode: 2017SpWea..15..955M Altcode: 2017arXiv170300705M We present an advance toward accurately predicting the arrivals of coronal mass ejections (CMEs) at the terrestrial planets, including Earth. For the first time, we are able to assess a CME prediction model using data over two thirds of a solar cycle of observations with the Heliophysics System Observatory. We validate modeling results of 1337 CMEs observed with the Solar Terrestrial Relations Observatory (STEREO) heliospheric imagers (HI) (science data) from 8 years of observations by five in situ observing spacecraft. We use the self-similar expansion model for CME fronts assuming 60° longitudinal width, constant speed, and constant propagation direction. With these assumptions we find that 23%-35% of all CMEs that were predicted to hit a certain spacecraft lead to clear in situ signatures, so that for one correct prediction, two to three false alarms would have been issued. In addition, we find that the prediction accuracy does not degrade with the HI longitudinal separation from Earth. Predicted arrival times are on average within 2.6 ± 16.6 h difference of the in situ arrival time, similar to analytical and numerical modeling, and a true skill statistic of 0.21. We also discuss various factors that may improve the accuracy of space weather forecasting using wide-angle heliospheric imager observations. These results form a first-order approximated baseline of the prediction accuracy that is possible with HI and other methods used for data by an operational space weather mission at the Sun-Earth L5 point. Title: Kinematics and shock locations of a spatial resolved solar type II radio burst with LOFAR. Authors: Zucca, Pietro; Morosan, Diana; Gallagher, Peter T.; Fallows, Richard; Rouillard, Alexis; Magdalenić, Jasmina; Vocks, Christian; Marqué, Christophe; Klein, Karl-Ludwig; Mann, Gottfried Bibcode: 2017EGUGA..1915801Z Altcode: Type II radio bursts are evidence of shocks in the solar atmosphere emitting radio waves ranging from metric to kilometric lengths. These shocks may be associated with coronal mass ejections (CMEs) reaching super-Alfvènic speeds. Radio imaging of the decameter wavelengths is now possible with the Low Frequency Array (LOFAR), opening a new radio window to study coronal radio shocks leaving the inner solar corona and entering the interplanetary medium and understand their association with CMEs. Here, we study a coronal shock associated with a CME and type II radio burst to determine the location where the shock is triggered in relation to the propagating CME, the ambient medium Alfvèn speed and the orientation of the coronal magnetic field. The type II shock imaging and spectra were obtained using 91 simultaneous tied-array beams of LOFAR while the CME was observed by the Large Angle and Spectrometric Coronagraph (LASCO) on board the Solar and Heliospheric Observatory (SOHO). Using the tied array beam observing mode of LOFAR we were able to locate the type II radio shock position between 45 and 75 MHz and relate it to the expanding flank of a CME leaving the inner corona. The radio emission associated with the type II shock was found to be located at the flank of the CME in a region where the mach number is between 1.5 to 2.0 and the shock geometry is quasi-perpendicular. Title: CME properties and solar source region characteristics - HELCATS results Authors: Bothmer, Volker; Mrotzek, Niclas; Murray, Sophie; Gallagher, Peter; Barnes, David; Davies, Jackie; Harrison, Richard Bibcode: 2017EGUGA..19.5107B Altcode: One objective of the EU FP7 project HELCATS is to derive and catalogue the characteristics of CMEs observed with the STEREO/COR2 & HI imagers based on geometrical and forward modelling. Here we present the results of the analysis of a subset of the 122 CME events that have been dynamically modelled with the GCS-method in the COR2 field of view and which are compiled in the KINCAT database at http://www.affects-fp7.eu/helcats-database/database.php. The CME properties, such as speeds, masses, angular widths, as derived from modelling, are compared with magnetic field properties of the corresponding solar source active region, such as magnetic flux, area, and polarity line characteristics. The results show which solar parameters define the structure of CMEs at distances around 12 solar radii and how they can be used for space weather forecast services. Title: Connecting Coronal Mass Ejections to their Solar Active Region Sources Authors: Murray, Sophie; Gallagher, Peter; Carley, Eoin; Zucca, Pietro Bibcode: 2017EGUGA..19.4923M Altcode: Severe space weather events have the potential to significantly impact a range of vital technologies on Earth and in near-Earth space. Understanding the processes involved in the solar eruptions that cause these events is imperative to provide accurate space weather forecasts. Coronal mass ejections (CMEs) and other solar eruptive phenomena can be physically linked by combining data from a multitude of ground-based and space-based instruments as well as models, however this can be challenging for automated operational systems. The EU FP7 HELCATS project provides data from heliospheric imaging onboard the two NASA/STEREO spacecraft in order to track the evolution of CMEs in the inner heliosphere. From a catalogue of nearly 2,000 CME events, an automated algorithm has been developed to connect the CMEs observed by STEREO to any corresponding solar flares and active region sources on the solar surface. CME kinematic properties, such as speed and angular width, are compared with active region magnetic field properties, such as magnetic flux, area, and polarity line characteristics. This large database provides insight into the link between CME and flare events, as well as characteristics of eruptive active regions. The automated method may prove useful for future operational CME forecasting efforts. Title: A Catalogue of Coronal Mass Ejections Observed by the STEREO Heliospheric Imagers: Results from HELCATS Authors: Barnes, David; Davies, Jackie; Harrison, Richard; Perry, Chris; Möstl, Christian; Rouillard, Alexis; Bothmer, Volker; Rodriguez, Luciano; Eastwood, Jonathan; Kilpua, Emilia; Gallagher, Peter Bibcode: 2017EGUGA..19.8160B Altcode: The wide fields of view provided by the STEREO Heliospheric Imagers (HIs) allow far greater coverage of Coronal Mass Ejections (CMEs) than are typically available from coronagraph observations. As part of the EU FP7 HELCATS (Heliospheric Cataloguing, Analysis and Techniques Service) project we present a comprehensive catalogue of CMEs that are observed in HI data, throughout the lifetime of the instruments. This spans the period from April 2007 to September 2014 for both STEREO-A and -B, with additional STEREO-A observations continuing from October 2015 to present, covering the majority of solar cycle 24. A subset of these CMEs are tracked through the HI fields of view, to which we apply both single-spacecraft and stereoscopic models to determine CME kinematic properties such as propagation directions, speeds and accelerations. The statistical properties of these results are discussed and they are compared with coronagraph observations during the same period. Title: Long-Term Tracking of Corotating Density Structures Using Heliospheric Imaging (catalogue of CIRs during 2007-2014) Authors: Plotnikov, Illya; Rouillard, Alexis P.; Davies, Jackie; Botmer, Volker; Eastwood, Jonathan; Gallagher, Peter; Harrison, Richard; Kilpua, Emilia; Möstl, Christian C.; Perry, Chris; Rodriguez, Luciano; Lavraud, Benoit; Genot, Vincent; Pinto, Rui; Sanchez-Diaz, Eduardo Bibcode: 2017EGUGA..19.4486P Altcode: The systematic monitoring of the solar wind in high-cadence and high-resolution heliospheric images taken by the Solar-Terrestrial Relation Observatory (STEREO) spacecraft permits the study of the spatial and temporal evolution of variable solar wind flows from the Sun out to 1 AU, and beyond. As part of the EU Framework 7 (FP7) Heliospheric Cataloguing, Analysis and Techniques Service (HELCATS) project, we have generated a catalogue listing the properties of more than 190 corotating structures well-observed in images taken by the Heliospheric Imager (HI) instruments on-board STEREO-A (ST-A). Based on this catalogue, we present here one of very few long-term analyses of solar wind structures advected by the background solar wind. We concentrate on the subset of plasma density structures clearly identified inside corotating structures. This analysis confirms that most of the corotating density structures detected by the heliospheric imagers comprises a series of density inhomogeneities advected by the slow solar wind that eventually become entrained by stream interaction regions. We have derived the spatial-temporal evolution of each of these corotating density structures by using a well-established fitting technique. The mean radial propagation speed of the corotating structures is found to be 311 ± 31 km s-1. We show that the speeds of the corotating density structures derived using our fitting technique track well the long-term variation of the radial speed of the slow solar wind during solar minimum years (2007-2008). Furthermore, we demonstrate that these features originate near the coronal neutral line that eventually becomes the heliospheric current sheet. Title: Overview of the HELCATS project Authors: Harrison, Richard; Davies, Jackie; Perry, Chris; Moestl, Christian; Rouillard, Alexis; Bothmer, Volker; Rodriguez, Luciano; Eastwood, Jonathan; Kilpua, Emilia; Gallagher, Peter; Odstrcil, Dusan Bibcode: 2017EGUGA..19.5296H Altcode: Understanding solar wind evolution is fundamental to advancing our knowledge of energy and mass transport in the solar system, whilst also being crucial to space weather and its prediction. The advent of truly wide-angle heliospheric imaging has revolutionised the study of solar wind evolution, by enabling direct and continuous observation of both transient and background components of the solar wind as they propagate from the Sun to 1 AU and beyond. The EU-funded FP7 Heliospheric Cataloguing, Analysis and Techniques Service (HELCATS) project combines European expertise in heliospheric imaging, built up over the last decade in particular through lead involvement in NASA's STEREO mission, with expertise in solar and coronal imaging as well as the interpretation of in-situ and radio diagnostic measurements of solar wind phenomena. HELCATS involves: (1) cataloguing of transient (coronal mass ejections) and background (stream/corotating interaction regions) solar wind structures observed by the STEREO/Heliospheric Imagers, including estimates of their kinematic properties based on a variety of modelling techniques; (2) verifying these kinematic properties through comparison with solar source observations and in-situ measurements at multiple points throughout the heliosphere; (3) assessing the potential for initialising numerical models based on the derived kinematic properties of transient and background solar wind components; (4) assessing the complementarity of radio observations (Type II radio bursts and interplanetary scintillation) in the detection and analysis of heliospheric structure in combination with heliospheric imaging observations. We provide an overview of the achievements of the HELCATS project, as it reaches its conclusion, and present selected results that seek to illustrate the value and legacy of this unprecedented, coordinated study of structures in the heliosphere. Title: Detection and Interpretation of Long-lived X-Ray Quasi-periodic Pulsations in the X-class Solar Flare on 2013 May 14 Authors: Dennis, Brian R.; Tolbert, Anne K.; Inglis, Andrew; Ireland, Jack; Wang, Tongjiang; Holman, Gordon D.; Hayes, Laura A.; Gallagher, Peter T. Bibcode: 2017ApJ...836...84D Altcode: 2017arXiv170603689D Quasi-periodic pulsations (QPP) seen in the time derivative of the GOES soft X-ray light curves are analyzed for the X3.2 event on 2013 May 14. The pulsations are apparent for a total of at least two hours from the impulsive phase to well into the decay phase, with a total of 163 distinct pulses evident to the naked eye. A wavelet analysis shows that the characteristic timescale of these pulsations increases systematically from ∼25 s at 01:10 UT, the time of the GOES peak, to ∼100 s at 02:00 UT. A second “ridge” in the wavelet power spectrum, most likely associated with flaring emission from a different active region, shows an increase from ∼40 s at 01:40 UT to ∼100 s at 03:10 UT. We assume that the QPP that produced the first ridge result from vertical kink-mode oscillations of the newly formed loops following magnetic reconnection in the coronal current sheet. This allows us to estimate the magnetic field strength as a function of altitude given the density, loop length, and QPP timescale as functions of time determined from the GOES light curves and Ramaty High Energy Solar Spectroscopic Imager (RHESSI) images. The calculated magnetic field strength of the newly formed loops ranges from ∼500 G at an altitude of 24 Mm to a low value of ∼10 G at 60 Mm, in general agreement with the expected values at these altitudes. Fast sausage-mode oscillations are also discussed and cannot be ruled out as an alternate mechanism for producing the QPP. Title: Characteristics of type III radio bursts and solar S bursts Authors: Morosan, D. E.; Gallagher, P. T. Bibcode: 2017pre8.conf..357M Altcode: 2018arXiv180210460M The Sun is an active source of radio emission which is often associated with the acceleration of electrons arising from processes such as solar flares and coronal mass ejections (CMEs). At low radio frequencies (<100 MHz), numerous solar S bursts (where S stands for short) and storms of type III radio bursts have been observed, that are not directly relates to flares and CMEs. Here, we expand our understanding on the spectral characteristic of these two different types of radio bursts based on observations from the Low Frequency Array (LOFAR). On 9 July 2013, over 3000 solar S bursts accompanied by over 800 type III radio bursts were observed over a time period of 8 hours. The characteristics of type III radio bursts presented here are consistent with previous studies. S bursts are shown to be different compared to type III bursts: they show narrow bandwidths, short durations and drift rates of about 1/2 the drift rate of type III bursts. Both type III bursts and solar S bursts occur in a region in the corona where plasma emission is the dominant emission mechanism as determined by data constrained density and magnetic field models. Title: Understanding the Physical Nature of Coronal "EIT Waves" Authors: Long, D. M.; Bloomfield, D. S.; Chen, P. F.; Downs, C.; Gallagher, P. T.; Kwon, R. -Y.; Vanninathan, K.; Veronig, A. M.; Vourlidas, A.; Vršnak, B.; Warmuth, A.; Žic, T. Bibcode: 2017SoPh..292....7L Altcode: 2016arXiv161105505L For almost 20 years the physical nature of globally propagating waves in the solar corona (commonly called "EIT waves") has been controversial and subject to debate. Additional theories have been proposed over the years to explain observations that did not agree with the originally proposed fast-mode wave interpretation. However, the incompatibility of observations made using the Extreme-ultraviolet Imaging Telescope (EIT) onboard the Solar and Heliospheric Observatory with the fast-mode wave interpretation was challenged by differing viewpoints from the twin Solar Terrestrial Relations Observatory spacecraft and data with higher spatial and temporal resolution from the Solar Dynamics Observatory. In this article, we reexamine the theories proposed to explain EIT waves to identify measurable properties and behaviours that can be compared to current and future observations. Most of us conclude that the so-called EIT waves are best described as fast-mode large-amplitude waves or shocks that are initially driven by the impulsive expansion of an erupting coronal mass ejection in the low corona. Title: Observing the Formation of Flare-driven Coronal Rain Authors: Scullion, E.; Rouppe van der Voort, L.; Antolin, P.; Wedemeyer, S.; Vissers, G.; Kontar, E. P.; Gallagher, P. T. Bibcode: 2016ApJ...833..184S Altcode: 2016arXiv161009255S Flare-driven coronal rain can manifest from rapidly cooled plasma condensations near coronal loop tops in thermally unstable postflare arcades. We detect five phases that characterize the postflare decay: heating, evaporation, conductive cooling dominance for ∼120 s, radiative/enthalpy cooling dominance for ∼4700 s, and finally catastrophic cooling occurring within 35-124 s, leading to rain strands with a periodicity of 55-70 s. We find an excellent agreement between the observations and model predictions of the dominant cooling timescales and the onset of catastrophic cooling. At the rain-formation site, we detect comoving, multithermal rain clumps that undergo catastrophic cooling from ∼1 MK to ∼22,000 K. During catastrophic cooling, the plasma cools at a maximum rate of 22,700 K s-1 in multiple loop-top sources. We calculated the density of the extreme-ultraviolet (EUV) plasma from the differential emission measure of the multithermal source employing regularized inversion. Assuming a pressure balance, we estimate the density of the chromospheric component of rain to be 9.21 × 1011 ± 1.76 × 1011 cm-3, which is comparable with quiescent coronal rain densities. With up to eight parallel strands in the EUV loop cross section, we calculate the mass loss rate from the postflare arcade to be as much as 1.98 × 1012 ± 4.95 × 1011 g s-1. Finally, we reveal a close proximity between the model predictions of {10}5.8 K and the observed properties between {10}5.9 and {10}6.2 K, which defines the temperature onset of catastrophic cooling. The close correspondence between the observations and numerical models suggests that indeed acoustic waves (with a sound travel time of 68 s) could play an important role in redistributing energy and sustaining the enthalpy-based radiative cooling. Title: A Large-Scale Search for Evidence of Quasi-Periodic Pulsations in Solar Flare X-ray Emission Authors: Inglis, A. R.; Ireland, J.; Dennis, B. R.; Hayes, L.; Gallagher, P. Bibcode: 2016AGUFMSH21E2563I Altcode: The nature of quasi-periodic pulsations in solar flares is poorly constrained, and critically the general prevalence of such signals in solar flares is unknown. We present the results of a large-scale, statistically robust search for evidence of signals consistent with quasi-periodic pulsations in solar flares, focusing on the 1 - 300s timescale. We analyse 675 M- and X-class flares observed by GOES in 1-8A soft X-rays between 2011 February 1 and 2015 December 31. Additionally, we analyse 209 events in the same time interval observed by Fermi/GBM in 15-25 keV X-rays. We use a novel model comparison approach, testing three models applied to the Fourier power spectra of each flare. From this we determine whether there is evidence for a substantial enhancement in the Fourier domain that may be consistent with a QPP signature. Our findings are that 30% of GOES events and 16% of Fermi/GBM events show signatures consistent with classical interpretations of QPP. The remaining events are adequately described by single power-law or broken power-law Fourier power spectra. For both instruments, a preferred characteristic timescale of 5-30 s was found, with no dependence on flare magnitude in GOES, and weak dependence in GBM. We also show that, for events where a detection occurred in both Fermi/GBM and GOES datasets, similar characteristic timescales were found with both instruments. We discuss the implications of these results for our understanding of solar flares and possible QPP mechanisms. Title: Solar Magnetic Data Analysis for the FLARECAST Project Authors: Guerra, J. A.; Park, S. H.; Kontogiannis, I.; Bloomfield, D.; Gallagher, P.; Georgoulis, M. K. Bibcode: 2016AGUFMSH11C2234G Altcode: The Flare Likelihood And Region Eruption foreCASTing (FLARECAST) project is an EU H2020-funded consortium project aiming to develop an advanced solar flare forecasting system by implementing state-of-the-art solar data analysis and flare prediction algorithms. The Solar Physics Group at Trinity College Dublin is in charge of the analysis of observational data to extract solar active region properties that serve as input for the prediction algorithms. The calculated active region properties correspond to a non-exhaustive list of parameters that have demonstrated a strong flare association, such as Schrijver's R-value, the Fourier power spectrum exponent, the effective connected magnetic field (Beff), the horizontal field decay index, and the weighted length of strong-gradient polarity inversion lines (WLSG). Parameters were calculated from Spaceweather HMI Active Region Patch (SHARP) magnetograms, a data product of the Helioseismic and Magnetic Imager (HMI) magnetograph on the Solar Dynamics Observatory (SDO). SHARPs provide photospheric vector-magnetic field (B) images in near-realtime. For this study, results from a statistical study performed on a robust subsample of the entire SHARP dataset will be presented. In the framework of the FLARECAST predictor component, this study focuses, for the first time, on differences between parameter values found when the radial magnetic field component, Br, is used instead of the line-of-sight component, Blos. The effect of active region longitudinal position is discussed, as well as the flare association of the properties. Title: Radio Diagnostics of Electron Acceleration Sites During the Eruption of a Flux Rope in the Solar Corona Authors: Carley, Eoin P.; Vilmer, Nicole; Gallagher, Peter T. Bibcode: 2016ApJ...833...87C Altcode: 2016arXiv160901463C Electron acceleration in the solar corona is often associated with flares and the eruption of twisted magnetic structures known as flux ropes. However, the locations and mechanisms of such particle acceleration during the flare and eruption are still subject to much investigation. Observing the exact sites of particle acceleration can help confirm how the flare and eruption are initiated and how they evolve. Here we use the Atmospheric Imaging Assembly to analyze a flare and erupting flux rope on 2014 April 18, while observations from the Nançay Radio Astronomy Facility allow us to diagnose the sites of electron acceleration during the eruption. Our analysis shows evidence of a pre-formed flux rope that slowly rises and becomes destabilized at the time of a C-class flare, plasma jet, and the escape of ≳75 keV electrons from the rope center into the corona. As the eruption proceeds, continued acceleration of electrons with energies of ∼5 keV occurs above the flux rope for a period over 5 minutes. At the flare peak, one site of electron acceleration is located close to the flare site, while another is driven by the erupting flux rope into the corona at speeds of up to 400 km s-1. Energetic electrons then fill the erupting volume, eventually allowing the flux rope legs to be clearly imaged from radio sources at 150-445 MHz. Following the analysis of Joshi et al. (2015), we conclude that the sites of energetic electrons are consistent with flux rope eruption via a tether cutting or flux cancellation scenario inside a magnetic fan-spine structure. In total, our radio observations allow us to better understand the evolution of a flux rope eruption and its associated electron acceleration sites, from eruption initiation to propagation into the corona. Title: Geomagnetically induced currents in the Irish power network during geomagnetic storms Authors: Blake, Seán. P.; Gallagher, Peter T.; McCauley, Joe; Jones, Alan G.; Hogg, Colin; Campanyà, Joan; Beggan, Ciarán. D.; Thomson, Alan W. P.; Kelly, Gemma S.; Bell, David Bibcode: 2016SpWea..14.1136B Altcode: 2016arXiv161108587B Geomagnetically induced currents (GICs) are a well-known terrestrial space weather hazard. They occur in power transmission networks and are known to have adverse effects in both high-latitude and midlatitude countries. Here we study GICs in the Irish power transmission network (geomagnetic latitude 54.7-58.5°N) during five geomagnetic storms (6-7 March 2016, 20-21 December 2015, 17-18 March 2015, 29-31 October 2003, and 13-14 March 1989). We simulate electric fields using a plane wave method together with two ground resistivity models, one of which is derived from magnetotelluric measurements (magnetotelluric (MT) model). We then calculate GICs in the 220, 275, and 400 kV transmission network. During the largest of the storm periods studied, the peak electric field was calculated to be as large as 3.8 V km-1, with associated GICs of up to 23 A using our MT model. Using our homogenous resistivity model, those peak values were 1.46 V km-1 and 25.8 A. We find that three 400 and 275 kV substations are the most likely locations for the Irish transformers to experience large GICs. Title: A Large-scale Search for Evidence of Quasi-periodic Pulsations in Solar Flares Authors: Inglis, A. R.; Ireland, J.; Dennis, B. R.; Hayes, L.; Gallagher, P. Bibcode: 2016ApJ...833..284I Altcode: 2016arXiv161007454I The nature of quasi-periodic pulsations (QPP) in solar flares is poorly constrained, and critically the general prevalence of such signals in solar flares is unknown. Therefore, we perform a large-scale search for evidence of signals consistent with QPP in solar flares, focusing on the 1-300 s timescale. We analyze 675 M- and X-class flares observed by the Geostationary Operational Environmental Satellite (GOES) series in 1-8 Å soft X-rays between 2011 February 1 and 2015 December 31. Additionally, over the same era we analyze Fermi/Gamma-ray Burst Monitor (GBM) 15-25 keV X-ray data for each of these flares associated with a Fermi/GBM solar flare trigger, a total of 261 events. Using a model comparison method, we determine whether there is evidence for a substantial enhancement in the Fourier power spectrum that may be consistent with a QPP signature, based on three tested models; a power-law plus a constant, a broken power-law plus constant, and a power-law-plus-constant with an additional QPP signature component. From this, we determine that ∼30% of GOES events and ∼8% of Fermi/GBM events show strong signatures consistent with classical interpretations of QPP. For the remaining events either two or more tested models cannot be strongly distinguished from each other, or the events are well-described by single power-law or broken power-law Fourier power spectra. For both instruments, a preferred characteristic timescale of ∼5-30 s was found in the QPP-like events, with no dependence on flare magnitude in either GOES or GBM data. We also show that individual events in the sample show similar characteristic timescales in both GBM and GOES data sets. We discuss the implications of these results for our understanding of solar flares and possible QPP mechanisms. Title: A Catalogue of Geometrically-Modelled Coronal Mass Ejections Observed by the STEREO Heliospheric Imagers Authors: Barnes, D.; Davies, J. A.; Harrison, R. A.; Perry, C. H.; Moestl, C.; Rouillard, A.; Bothmer, V.; Rodriguez, L.; Eastwood, J. P.; Kilpua, E.; Gallagher, P. Bibcode: 2016AGUFMSH31B2588B Altcode: We present a catalogue of Coronal Mass Ejections (CMEs) observed by the Heliospheric Imagers (HIs) onboard the two NASA STEREO spacecraft. This catalogue contains all CMEs observed during the operational phase of the STEREO mission, April 2007 to September 2014, for both spacecraft and resumes from November 2015 for STEREO-A. These CMEs are tracked using time-elongation plots through the HI-1 and HI-2 fields of view and to them we apply geometric models to determine their kinematic properties, such as speed, propagation direction and launch time. A subset of these CMEs, which are observed simultaneously by both spacecraft, are identified and to which stereoscopic modelling techniques are applied. The statistical properties of these catalogues are discussed as are their results compared to existing CME catalogues covering the same periods. This work is carried out as part of the EU FP7 HELCATS (Heliospheric Cataloguing, Analysis and Techniques Service) project. Title: A Comparison of Flare Forecasting Methods. I. Results from the “All-Clear” Workshop Authors: Barnes, G.; Leka, K. D.; Schrijver, C. J.; Colak, T.; Qahwaji, R.; Ashamari, O. W.; Yuan, Y.; Zhang, J.; McAteer, R. T. J.; Bloomfield, D. S.; Higgins, P. A.; Gallagher, P. T.; Falconer, D. A.; Georgoulis, M. K.; Wheatland, M. S.; Balch, C.; Dunn, T.; Wagner, E. L. Bibcode: 2016ApJ...829...89B Altcode: 2016arXiv160806319B Solar flares produce radiation that can have an almost immediate effect on the near-Earth environment, making it crucial to forecast flares in order to mitigate their negative effects. The number of published approaches to flare forecasting using photospheric magnetic field observations has proliferated, with varying claims about how well each works. Because of the different analysis techniques and data sets used, it is essentially impossible to compare the results from the literature. This problem is exacerbated by the low event rates of large solar flares. The challenges of forecasting rare events have long been recognized in the meteorology community, but have yet to be fully acknowledged by the space weather community. During the interagency workshop on “all clear” forecasts held in Boulder, CO in 2009, the performance of a number of existing algorithms was compared on common data sets, specifically line-of-sight magnetic field and continuum intensity images from the Michelson Doppler Imager, with consistent definitions of what constitutes an event. We demonstrate the importance of making such systematic comparisons, and of using standard verification statistics to determine what constitutes a good prediction scheme. When a comparison was made in this fashion, no one method clearly outperformed all others, which may in part be due to the strong correlations among the parameters used by different methods to characterize an active region. For M-class flares and above, the set of methods tends toward a weakly positive skill score (as measured with several distinct metrics), with no participating method proving substantially better than climatological forecasts. Title: Understanding the Physical Nature of Coronal "EIT Waves" Authors: Long, D. M.; Bloomfield, D. S.; Chen, P. -F.; Downs, C.; Gallagher, P. T.; Kwon, R. -Y.; Vanninathan, K.; Veronig, A.; Vourlidas, A.; Vrsnak, B.; Warmuth, A.; Zic, T. Bibcode: 2016usc..confE..24L Altcode: For almost 20 years the physical nature of globally-propagating waves in the solar corona (commonly called "EIT waves") has been controversial and subject to debate. Additional theories have been proposed throughout the years to explain observations that did not fit with the originally proposed fast-mode wave interpretation. However, the incompatibility of observations made using the Extreme-ultraviolet Imaging Telescope (EIT) on the Solar and Heliospheric Observatory with the fast-mode wave interpretation have been challenged by differing viewpoints from the Solar Terrestrial Relations Observatory spacecraft and higher spatial/temporal resolution data from the Solar Dynamics Observatory. In this paper, we reexamine the theories proposed to explain "EIT waves" to identify measurable properties and behaviours that can be compared to current and future observations. Most of us conclude that "EIT waves" are best described as fast-mode large-amplitude waves/shocks, which are initially driven by the impulsive expansion of an erupting coronal mass ejection in the low corona. Title: Flaring Rates and the Evolution of Sunspot Group McIntosh Classifications Authors: McCloskey, Aoife E.; Gallagher, Peter T.; Bloomfield, D. Shaun Bibcode: 2016SoPh..291.1711M Altcode: 2016arXiv160700903M; 2016SoPh..tmp..116M Sunspot groups are the main source of solar flares, with the energy to power them being supplied by magnetic-field evolution (e.g. flux emergence or twisting/shearing). To date, few studies have investigated the statistical relation between sunspot-group evolution and flaring, with none considering evolution in the McIntosh classification scheme. Here we present a statistical analysis of sunspot groups from Solar Cycle 22, focusing on 24-hour changes in the three McIntosh classification components. Evolution-dependent ≥C 1.0 , ≥M 1.0 , and ≥X 1.0 flaring rates are calculated, leading to the following results: i) flaring rates become increasingly higher for greater degrees of upward evolution through the McIntosh classes, with the opposite found for downward evolution; ii) the highest flaring rates are found for upward evolution from larger, more complex, classes (e.g. Zurich D- and E-classes evolving upward to F-class produce ≥C 1.0 rates of 2.66 ±0.28 and 2.31 ±0.09 flares per 24 hours, respectively); iii) increasingly complex classes give higher rates for all flare magnitudes, even when sunspot groups do not evolve over 24 hours. These results support the hypothesis that injection of magnetic energy by flux emergence (i.e. increasing in Zurich or compactness classes) leads to a higher frequency and magnitude of flaring. Title: Quasi-periodic Pulsations during the Impulsive and Decay phases of an X-class Flare Authors: Hayes, L. A.; Gallagher, P. T.; Dennis, B. R.; Ireland, J.; Inglis, A. R.; Ryan, D. F. Bibcode: 2016ApJ...827L..30H Altcode: 2016arXiv160706957H Quasi-periodic pulsations (QPPs) are often observed in X-ray emission from solar flares. To date, it is unclear what their physical origins are. Here, we present a multi-instrument investigation of the nature of QPP during the impulsive and decay phases of the X1.0 flare of 2013 October 28. We focus on the character of the fine structure pulsations evident in the soft X-ray (SXR) time derivatives and compare this variability with structure across multiple wavelengths including hard X-ray and microwave emission. We find that during the impulsive phase of the flare, high correlations between pulsations in the thermal and non-thermal emissions are seen. A characteristic timescale of ∼20 s is observed in all channels and a second timescale of ∼55 s is observed in the non-thermal emissions. SXR pulsations are seen to persist into the decay phase of this flare, up to 20 minutes after the non-thermal emission has ceased. We find that these decay phase thermal pulsations have very small amplitude and show an increase in characteristic timescale from ∼40 s up to ∼70 s. We interpret the bursty nature of the co-existing multi-wavelength QPPs during the impulsive phase in terms of episodic particle acceleration and plasma heating. The persistent thermal decay phase QPPs are most likely connected with compressive magnetohydrodynamic processes in the post-flare loops such as the fast sausage mode or the vertical kink mode. Title: Long-Term Tracking of Corotating Density Structures Using Heliospheric Imaging Authors: Plotnikov, I.; Rouillard, A. P.; Davies, J. A.; Bothmer, V.; Eastwood, J. P.; Gallagher, P.; Harrison, R. A.; Kilpua, E.; Möstl, C.; Perry, C. H.; Rodriguez, L.; Lavraud, B.; Génot, V.; Pinto, R. F.; Sanchez-Diaz, E. Bibcode: 2016SoPh..291.1853P Altcode: 2016SoPh..tmp..118P; 2016arXiv160601127P The systematic monitoring of the solar wind in high-cadence and high-resolution heliospheric images taken by the Solar-Terrestrial Relation Observatory (STEREO) spacecraft permits the study of the spatial and temporal evolution of variable solar wind flows from the Sun out to 1 AU, and beyond. As part of the EU Framework 7 (FP7) Heliospheric Cataloguing, Analysis and Techniques Service (HELCATS) project, we have generated a catalog listing the properties of 190 corotating structures well-observed in images taken by the Heliospheric Imager (HI) instruments onboard STEREO-A (ST-A). Based on this catalog, we present here one of very few long-term analyses of solar wind structures advected by the background solar wind. We concentrate on the subset of plasma density structures clearly identified inside corotating structures. This analysis confirms that most of the corotating density structures detected by the heliospheric imagers comprises a series of density inhomogeneities advected by the slow solar wind that eventually become entrained by stream interaction regions. We have derived the spatial-temporal evolution of each of these corotating density structures by using a well-established fitting technique. The mean radial propagation speed of the corotating structures is found to be 311 ±31 kms−1. Such a low mean value corresponds to the terminal speed of the slow solar wind rather than the speed of stream interfaces, which is typically intermediate between the slow and fast solar wind speeds (∼400 kms−1). Using our fitting technique, we predicted the arrival time of each corotating density structure at different probes in the inner heliosphere. We find that our derived speeds are systematically lower by ∼100 kms−1 than those measured in situ at the predicted impact times. Moreover, for cases when a stream interaction region is clearly detected in situ at the estimated impact time, we find that our derived speeds are lower than the speed of the stream interface measured in situ by an average of 55 kms−1 at ST-A and 84 kms−1 at STEREO-B (ST-B). We show that the speeds of the corotating density structures derived using our fitting technique track well the long-term variation of the radial speed of the slow solar wind during solar minimum years (2007 - 2008). Furthermore, we demonstrate that these features originate near the coronal neutral line that eventually becomes the heliospheric current sheet. Title: Enabling Solar Flare Forecasting at an Unprecedented Level: the FLARECAST Project Authors: Georgoulis, Manolis K.; Pariat, Etienne; Massone, Anna Maria; Vilmer, Nicole; Jackson, David; Buchlin, Eric; Csillaghy, Andre; Bommier, Veronique; Kontogiannis, Ioannis; Gallagher, Peter; Gontikakis, Costis; Guennou, Chloé; Murray, Sophie; Bloomfield, D. Shaun; Alingery, Pablo; Baudin, Frederic; Benvenuto, Federico; Bruggisser, Florian; Florios, Konstantinos; Guerra, Jordan; Park, Sung-Hong; Perasso, Annalisa; Piana, Michele; Sathiapal, Hanna; Soldati, Marco; Von Stachelski, Samuel; Argoudelis, Vangelis; Caminade, Stephane Bibcode: 2016cosp...41E.657G Altcode: We attempt a brief but informative description of the Flare Likelihood And Region Eruption Forecasting (FLARECAST) project, European Commission's first large-scale investment to explore the limits of reliability and accuracy for the forecasting of major solar flares. The consortium, objectives, and first results of the project - featuring an openly accessible, interactive flare forecasting facility by the end of 2017 - will be outlined. In addition, we will refer to the so-called "explorative research" element of project, aiming to connect solar flares with coronal mass ejections (CMEs) and possibly pave the way for CME, or eruptive flare, prediction. We will also emphasize the FLARECAST modus operandi, namely the diversity of expertise within the consortium that independently aims to science, infrastructure development and dissemination, both to stakeholders and to the general public. Concluding, we will underline that the FLARECAST project responds squarely to the joint COSPAR - ILWS Global Roadmap to shield society from the adversities of space weather, addressing its primary goal and, in particular, its Research Recommendations 1, 2 and 4, Teaming Recommendations II and III, and Collaboration Recommendations A, B, and D. The FLARECAST project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No. 640216. Title: Conditions for electron-cyclotron maser emission in the solar corona Authors: Morosan, D. E.; Zucca, P.; Bloomfield, D. S.; Gallagher, P. T. Bibcode: 2016A&A...589L...8M Altcode: 2016arXiv160404788M Context. The Sun is an active source of radio emission ranging from long duration radio bursts associated with solar flares and coronal mass ejections to more complex, short duration radio bursts such as solar S bursts, radio spikes and fibre bursts. While plasma emission is thought to be the dominant emission mechanism for most radio bursts, the electron-cyclotron maser (ECM) mechanism may be responsible for more complex, short-duration bursts as well as fine structures associated with long-duration bursts.
Aims: We investigate the conditions for ECM in the solar corona by considering the ratio of the electron plasma frequency ωp to the electron-cyclotron frequency Ωe. The ECM is theoretically possible when ωp/ Ωe< 1.
Methods: Two-dimensional electron density, magnetic field, plasma frequency, and electron cyclotron frequency maps of the off-limb corona were created using observations from SDO/AIA and SOHO/LASCO, together with potential field extrapolations of the magnetic field. These maps were then used to calculate ωp/Ωe and Alfvén velocity maps of the off-limb corona.
Results: We found that the condition for ECM emission (ωp/ Ωe< 1) is possible at heights <1.07 R⊙ in an active region near the limb; that is, where magnetic field strengths are >40 G and electron densities are >3 × 108 cm-3. In addition, we found comparatively high Alfvén velocities (>0.02c or >6000 km s-1) at heights <1.07 R⊙ within the active region.
Conclusions: This demonstrates that the condition for ECM emission is satisfied within areas of the corona containing large magnetic fields, such as the core of a large active region. Therefore, ECM could be a possible emission mechanism for high-frequency radio and microwave bursts. Title: Quasi-Periodic Pulsations (QPP) in a Long-Duration Flare Authors: Dennis, Brian R.; Tolbert, Anne K.; Inglis, Andrew R.; Ireland, Jack; Wang, Tongjiang; Holman, Gordon D.; Hayes, Laura Ann; Gallagher, Peter T. Bibcode: 2016SPD....47.0605D Altcode: We have detected 163 distinct peaks in the time derivative of the GOES light curve of the X-class flare on 2013 May 14. QPP were detected for the first two hours of this 8-hour event. The thermal X-ray source revealed in RHESSI 6 - 12 keV images eventually rose to an altitude of over 60 km at a rate of 1.6 km/s. The mean QPP time scale increased from ~10 s during the impulsive phase to ~100 s some two hours later. Interpreting the QPP as being produced by vertical kink mode oscillations has allowed estimates to be made of the coronal magnetic field strength as a function of altitude. This uses the measured QPP time scales with the length and densities of the oscillating loops determined from the emission measure and source volume given by the RHESSI imaging spectroscopy observations. Applying this analysis to other events will further test the idea that vertical kink-mode oscillations are the source of QPP during both the impulsive and decay phases. If this origin is established, then QPP can be used as a diagnostic of the conditions in the corona close to the energy release site. In particular, it should be possible to obtain estimates of the Alfven speed, density, beta value, and magnetic field strength in the region of the soft X-ray emitting plasma. During the impulsive phase, other processes, presumably connected to the energy release process itself, can dominate to produce the more chaotic impulsive nature of the emission light curve. Title: HELCATS - Heliospheric Cataloguing, Analysis and Techniques Service Authors: Harrison, Richard; Davies, Jackie; Perry, Chris; Moestl, Christian; Rouillard, Alexis; Bothmer, Volker; Rodriguez, Luciano; Eastwood, Jonathan; Kilpua, Emilia; Gallagher, Peter Bibcode: 2016EGUGA..1810220H Altcode: Understanding the evolution of the solar wind is fundamental to advancing our knowledge of energy and mass transport in the solar system, rendering it crucial to space weather and its prediction. The advent of truly wide-angle heliospheric imaging has revolutionised the study of both transient (CMEs) and background (SIRs/CIRs) solar wind plasma structures, by enabling their direct and continuous observation out to 1 AU and beyond. The EU-funded FP7 HELCATS project combines European expertise in heliospheric imaging, built up in particular through lead involvement in NASA's STEREO mission, with expertise in solar and coronal imaging as well as in-situ and radio measurements of solar wind phenomena, in a programme of work that will enable a much wider exploitation and understanding of heliospheric imaging observations. With HELCATS, we are (1.) cataloguing transient and background solar wind structures imaged in the heliosphere by STEREO/HI, since launch in late October 2006 to date, including estimates of their kinematic properties based on a variety of established techniques and more speculative, approaches; (2.) evaluating these kinematic properties, and thereby the validity of these techniques, through comparison with solar source observations and in-situ measurements made at multiple points throughout the heliosphere; (3.) appraising the potential for initialising advanced numerical models based on these kinematic properties; (4.) assessing the complementarity of radio observations (in particular of Type II radio bursts and interplanetary scintillation) in combination with heliospheric imagery. We will, in this presentation, provide an overview of progress from the first 18 months of the HELCATS project. Title: Performance of Major Flare Watches from the Max Millennium Program (2001 - 2010) Authors: Bloomfield, D. S.; Gallagher, P. T.; Marquette, W. H.; Milligan, R. O.; Canfield, R. C. Bibcode: 2016SoPh..291..411B Altcode: 2015arXiv151204518B; 2016SoPh..tmp....1B The physical processes that trigger solar flares are not well understood, and significant debate remains around processes governing particle acceleration, energy partition, and particle and energy transport. Observations at high resolution in energy, time, and space are required in multiple energy ranges over the whole course of many flares to build an understanding of these processes. Obtaining high-quality, co-temporal data from ground- and space- based instruments is crucial to achieving this goal and was the primary motivation for starting the Max Millennium program and Major Flare Watch (MFW) alerts, aimed at coordinating observations of all flares ≥ X1 GOES X-ray classification (including those partially occulted by the limb). We present a review of the performance of MFWs from 1 February 2001 to 31 May 2010, inclusive, which finds that (1) 220 MFWs were issued in 3407 days considered (6.5 % duty cycle), with these occurring in 32 uninterrupted periods that typically last 2 - 8 days; (2) 56% of flares ≥ X1 were caught, occurring in 19 % of MFW days; (3) MFW periods ended at suitable times, but substantial gain could have been achieved in percentage of flares caught if periods had started 24 h earlier; (4) MFWs successfully forecast X-class flares with a true skill statistic (TSS) verification metric score of 0.500, that is comparable to a categorical flare/no-flare interpretation of the NOAA Space Weather Prediction Centre probabilistic forecasts (TSS = 0.488). Title: Automatic Detection of Magnetic δ in Sunspot Groups Authors: Padinhatteeri, Sreejith; Higgins, Paul A.; Shaun Bloomfield, D.; Gallagher, Peter T. Bibcode: 2016SoPh..291...41P Altcode: 2015arXiv151006413P; 2015SoPh..tmp..184P Large and magnetically complex sunspot groups are known to be associated with flares. To date, the Mount Wilson scheme has been used to classify sunspot groups based on their morphological and magnetic properties. The most flare-prolific class, the δ sunspot group, is characterised by opposite-polarity umbrae within a common penumbra, separated by less than 2∘. In this article, we present a new system, called the Solar Monitor Active Region Tracker-Delta Finder (SMART-DF), which can be used to automatically detect and classify magnetic δ s in near-realtime. Using continuum images and magnetograms from the Helioseismic and Magnetic Imager (HMI) onboard NASA's Solar Dynamics Observatory (SDO), we first estimate distances between opposite-polarity umbrae. Opposite-polarity pairs with distances of less that 2∘ are then identified, and if these pairs are found to share a common penumbra, they are identified as a magnetic δ configuration. The algorithm was compared to manual δ detections reported by the Space Weather Prediction Center (SWPC), operated by the National Oceanic and Atmospheric Administration (NOAA). SMART-DF detected 21 out of 23 active regions (ARs) that were marked as δ spots by NOAA during 2011 - 2012 (within ±60∘ longitude). SMART-DF in addition detected five ARs that were not announced as δ spots by NOAA. The near-realtime operation of SMART-DF resulted in many δ s being identified in advance of NOAA's daily notification. SMART-DF will be integrated into SolarMonitor (www.solarmonitor.org) and the near-realtime information will be available to the public. Title: Low Frequency Radio Observations of Bi-directional Electron Beams in the Solar Corona Authors: Carley, E.; Reid, H.; Vilmer, N.; Gallagher, P. Bibcode: 2015AGUFMSH22B..01C Altcode: The radio signature of a shock travelling through the solar corona is known as a type II solar radio burst. In rare cases, these bursts can exhibit a fine structure known as 'herringbones' which are a direct indicator of particle acceleration occurring at the shock front. However, few studies have been performed on herringbones and the details of the underlying particle acceleration processes are unknown. Here, we use an image processing technique known as the Hough transform to statistically analyse the herringbone fine structure in a radio burst at 20-90MHz observed from the Rosse Solar-Terrestrial Observatory on 2011 September 22. We identify 188 individual bursts which are signatures of bi-directional electron beams continuously accelerated to speeds of 0.16 c. This occurs at a shock acceleration site initially at a constant altitude of 0.6 Rsun in the corona, followed by a shift to 0.5 Rsun. The anti-sunward beams travel a distance of 170 Mm (and possibly further) away from the acceleration site, while those travelling toward the sun come to a stop sooner, reaching a smaller distance of 112 Mm. We show that the stopping distance for the sunward beams may depend on the total number density and the velocity of the beam. Our study concludes that a detailed statistical analysis of herringbone fine structure can provide information on the physical properties of the corona which lead to these relatively rare radio bursts. Title: HELCATS - Heliospheric Cataloguing, Analysis and Techniques Service Authors: Barnes, D.; Harrison, R. A.; Davies, J. A.; Byrne, J.; Perry, C. H.; Moestl, C.; Rouillard, A. P.; Bothmer, V.; Rodriguez, L.; Eastwood, J. P.; Kilpua, E.; Odstrcil, D.; Gallagher, P. Bibcode: 2015AGUFMSH21B2410B Altcode: Understanding the evolution of the solar wind is fundamental to advancing our knowledge of energy and mass transport in the Solar System, making it crucial to space weather and its prediction. The advent of truly wide-angle heliospheric imaging has revolutionised the study of both transient (CMEs) and background (IRs) solar wind plasma structures, by enabling their direct and continuous observation out to 1 AU and beyond. The EU-funded FP7 HELCATS project combines European expertise in heliospheric imaging, built up in particular through lead involvement in NASA's STEREO mission, with expertise in solar and coronal imaging as well as in-situ and radio measurements of solar wind phenomena, in a programme of work that will enable a much wider exploitation and understanding of heliospheric imaging observations. The HELCATS project endeavors to catalogue transient and background solar wind structures imaged by STEREO/HI throughout the duration of the mission. This catalogue will include estimates of their kinematic properties using a variety of established and more speculative approaches, which are to be evaluated through comparisons with solar source and in-situ measurements. The potential for driving numerical models from these kinematic properties is to be assessed, as is their complementarity to radio observations, specifically Type II bursts and interplanetary scintillation. This presentation provides an overview of the HELCATS project and its progress in first 18 months of operations. Title: Low frequency radio observations of bi-directional electron beams in the solar corona Authors: Carley, Eoin P.; Reid, Hamish; Vilmer, Nicole; Gallagher, Peter T. Bibcode: 2015A&A...581A.100C Altcode: 2015arXiv150801065C The radio signature of a shock travelling through the solar corona is known as a type II solar radio burst. In rare cases these bursts can exhibit a fine structure known as "herringbones", which are a direct indicator of particle acceleration occurring at the shock front. However, few studies have been performed on herringbones and the details of the underlying particle acceleration processes are unknown. Here, we use an image processing technique known as the Hough transform to statistically analyse the herringbone fine structure in a radio burst at ~20-90 MHz observed from the Rosse Solar-Terrestrial Observatory on 2011 September 22. We identify 188 individual bursts which are signatures of bi-directional electron beams continuously accelerated to speeds of 0.16-0.10+0.11 c. This occurs at a shock acceleration site initially at a constant altitude of ~0.6 R⊙ in the corona, followed by a shift to ~0.5 R⊙. The anti-sunward beams travel a distance of 170-97+174 Mm (and possibly further) away from the acceleration site, while those travelling toward the Sun come to a stop sooner, reaching a smaller distance of 112-76+84 Mm. We show that the stopping distance for the sunward beams may depend on the total number density and the velocity of the beam. Our study concludes that a detailed statistical analysis of herringbone fine structure can provide information on the physical properties of the corona which lead to these relatively rare radio bursts. Title: LOFAR tied-array imaging and spectroscopy of solar S bursts Authors: Morosan, D. E.; Gallagher, P. T.; Zucca, P.; O'Flannagain, A.; Fallows, R.; Reid, H.; Magdalenić, J.; Mann, G.; Bisi, M. M.; Kerdraon, A.; Konovalenko, A. A.; MacKinnon, A. L.; Rucker, H. O.; Thidé, B.; Vocks, C.; Alexov, A.; Anderson, J.; Asgekar, A.; Avruch, I. M.; Bentum, M. J.; Bernardi, G.; Bonafede, A.; Breitling, F.; Broderick, J. W.; Brouw, W. N.; Butcher, H. R.; Ciardi, B.; de Geus, E.; Eislöffel, J.; Falcke, H.; Frieswijk, W.; Garrett, M. A.; Grießmeier, J.; Gunst, A. W.; Hessels, J. W. T.; Hoeft, M.; Karastergiou, A.; Kondratiev, V. I.; Kuper, G.; van Leeuwen, J.; McKay-Bukowski, D.; McKean, J. P.; Munk, H.; Orru, E.; Paas, H.; Pizzo, R.; Polatidis, A. G.; Scaife, A. M. M.; Sluman, J.; Tasse, C.; Toribio, M. C.; Vermeulen, R.; Zarka, P. Bibcode: 2015A&A...580A..65M Altcode: 2015arXiv150707496M Context. The Sun is an active source of radio emission that is often associated with energetic phenomena ranging from nanoflares to coronal mass ejections (CMEs). At low radio frequencies (<100 MHz), numerous millisecond duration radio bursts have been reported, such as radio spikes or solar S bursts (where S stands for short). To date, these have neither been studied extensively nor imaged because of the instrumental limitations of previous radio telescopes.
Aims: Here, LOw Frequency ARray (LOFAR) observations were used to study the spectral and spatial characteristics of a multitude of S bursts, as well as their origin and possible emission mechanisms.
Methods: We used 170 simultaneous tied-array beams for spectroscopy and imaging of S bursts. Since S bursts have short timescales and fine frequency structures, high cadence (~50 ms) tied-array images were used instead of standard interferometric imaging, that is currently limited to one image per second.
Results: On 9 July 2013, over 3000 S bursts were observed over a time period of ~8 h. S bursts were found to appear as groups of short-lived (<1 s) and narrow-bandwidth (~2.5 MHz) features, the majority drifting at ~3.5 MHz s-1 and a wide range of circular polarisation degrees (2-8 times more polarised than the accompanying Type III bursts). Extrapolation of the photospheric magnetic field using the potential field source surface (PFSS) model suggests that S bursts are associated with a trans-equatorial loop system that connects an active region in the southern hemisphere to a bipolar region of plage in the northern hemisphere.
Conclusions: We have identified polarised, short-lived solar radio bursts that have never been imaged before. They are observed at a height and frequency range where plasma emission is the dominant emission mechanism, however, they possess some of the characteristics of electron-cyclotron maser emission.

A movie associated to Fig. 3 is available in electronic form at http://www.aanda.org Title: Ellerman Bombs with Jets: Cause and Effect Authors: Reid, A.; Mathioudakis, M.; Scullion, E.; Doyle, J. G.; Shelyag, S.; Gallagher, P. Bibcode: 2015ApJ...805...64R Altcode: 2015arXiv150305359R Ellerman Bombs (EBs) are thought to arise as a result of photospheric magnetic reconnection. We use data from the Swedish 1 m Solar Telescope to study EB events on the solar disk and at the limb. Both data sets show that EBs are connected to the foot points of forming chromospheric jets. The limb observations show that a bright structure in the Hα blue wing connects to the EB initially fueling it, leading to the ejection of material upwards. The material moves along a loop structure where a newly formed jet is subsequently observed in the red wing of Hα. In the disk data set, an EB initiates a jet which propagates away from the apparent reconnection site within the EB flame. The EB then splits into two, with associated brightenings in the inter-granular lanes. Micro-jets are then observed, extending to 500 km with a lifetime of a few minutes. Observed velocities of the micro-jets are approximately 5-10 km s-1, while their chromospheric counterparts range from 50 to 80 km s-1. MURaM simulations of quiet Sun reconnection show that micro-jets with properties similar to those of the observations follow the line of reconnection in the photosphere, with associated Hα brightening at the location of increased temperature. Title: Solar and Heliospheric Physics with the Square Kilometre Array Authors: Nakariakov, V.; Bisi, M. M.; Browning, P. K.; Maia, D.; Kontar, E. P.; Oberoi, D.; Gallagher, P. T.; Cairns, I. H.; Ratcliffe, H. Bibcode: 2015aska.confE.169N Altcode: 2015PoS...215E.169N; 2015arXiv150700516N The fields of solar radiophysics and solar system radio physics, or radio heliophysics, will benefit immensely from an instrument with the capabilities projected for SKA. Potential applications include interplanetary scintillation (IPS), radio-burst tracking, and solar spectral radio imaging with a superior sensitivity. These will provide breakthrough new insights and results in topics of fundamental importance, such as the physics of impulsive energy releases, magnetohydrodynamic oscillations and turbulence, the dynamics of post-eruptive processes, energetic particle acceleration, the structure of the solar wind and the development and evolution of solar wind transients at distances up to and beyond the orbit of the Earth. The combination of the high spectral, time and spatial resolution and the unprecedented sensitivity of the SKA will radically advance our understanding of basic physical processes operating in solar and heliospheric plasmas and provide a solid foundation for the forecasting of space weather events. Title: The energetics of a global shock wave in the low solar corona Authors: Long, David; Baker, Deborah; Williams, David; Carley, Eoin; Gallagher, Peter; Zucca, Pietro Bibcode: 2015TESS....140706L Altcode: As the most energetic eruptions in the solar system, coronal mass ejections (CMEs) can produce shock waves at both their front and flanks as they erupt from the Sun into the heliosphere. However, the amount of energy produced in these eruptions, and the proportion of their energy required to produce the waves, is not well characterised. Here we use observations of a solar eruption from 2014 February 25 to estimate the energy budget of an erupting CME and the globally-propagating "EIT wave" produced by the rapid expansion of the CME flanks in the low solar corona. The "EIT wave" is shown using a combination of radio spectra and extreme ultraviolet images to be a shock front with a Mach number greater than one. Its initial energy is then calculated using the Sedov-Taylor blast-wave approximation, which provides an approximation for a shock front propagating through a region of variable density. This approach provides an initial energy estimate of ~2.8 x 10^31 ergs to produce the "EIT wave", which is approximately 10% the kinetic energy of the associated CME (shown to be ~2.5 x 10^32 ergs). These results indicate that the energy of the "EIT wave" may be significant and must be considered when estimating the total energy budget of solar eruptions. Title: Stable umbral chromospheric structures Authors: Henriques, V. M. J.; Scullion, E.; Mathioudakis, M.; Kiselman, D.; Gallagher, P. T.; Keenan, F. P. Bibcode: 2015A&A...574A.131H Altcode: 2014arXiv1412.6100H
Aims: We seek to understand the morphology of the chromosphere in sunspot umbra. We investigate if the horizontal structures observed in the spectral core of the Ca II H line are ephemeral visuals caused by the shock dynamics of more stable structures, and examine their relationship with observables in the H-alpha line.
Methods: Filtergrams in the core of the Ca II H and H-alpha lines as observed with the Swedish 1-m Solar Telescope are employed. We utilise a technique that creates composite images and tracks the flash propagation horizontally.
Results: We find 0.̋15 wide horizontal structures, in all of the three target sunspots, for every flash where the seeing is moderate to good. Discrete dark structures are identified that are stable for at least two umbral flashes, as well as systems of structures that live for up to 24 min. We find cases of extremely extended structures with similar stability, with one such structure showing an extent of 5''. Some of these structures have a correspondence in H-alpha, but we were unable to find a one-to-one correspondence for every occurrence. If the dark streaks are formed at the same heights as umbral flashes, there are systems of structures with strong departures from the vertical for all three analysed sunspots.
Conclusions: Long-lived Ca II H filamentary horizontal structures are a common and likely ever-present feature in the umbra of sunspots. If the magnetic field in the chromosphere of the umbra is indeed aligned with the structures, then the present theoretical understanding of the typical umbra needs to be revisited.

Movies associated to Figs. 3 and 4 are available in electronic form at http://www.aanda.org Title: The Energetics of a Global Shock Wave in the Low Solar Corona Authors: Long, David M.; Baker, Deborah; Williams, David R.; Carley, Eoin P.; Gallagher, Peter T.; Zucca, Pietro Bibcode: 2015ApJ...799..224L Altcode: 2014arXiv1412.2964L As the most energetic eruptions in the solar system, coronal mass ejections (CMEs) can produce shock waves at both their front and flanks as they erupt from the Sun into the heliosphere. However, the amount of energy produced in these eruptions, and the proportion of their energy required to produce the waves, is not well characterized. Here we use observations of a solar eruption from 2014 February 25 to estimate the energy budget of an erupting CME and the globally propagating "EIT wave" produced by the rapid expansion of the CME flanks in the low solar corona. The "EIT wave" is shown using a combination of radio spectra and extreme ultraviolet images to be a shock front with a Mach number greater than one. Its initial energy is then calculated using the Sedov-Taylor blast-wave approximation, which provides an approximation for a shock front propagating through a region of variable density. This approach provides an initial energy estimate of ≈2.8 × 1031 erg to produce the "EIT wave," which is approximately 10% the kinetic energy of the associated CME (shown to be ≈2.5 × 1032 erg). These results indicate that the energy of the "EIT wave" may be significant and must be considered when estimating the total energy budget of solar eruptions. Title: Solar Hard X-Ray Source Sizes in a Beam-heated and Ionized Chromosphere Authors: O'Flannagain, Aidan M.; Brown, John C.; Gallagher, Peter T. Bibcode: 2015ApJ...799..127O Altcode: Solar flare hard X-rays (HXRs) are produced as bremsstrahlung when an accelerated population of electrons interacts with the dense chromospheric plasma. HXR observations presented by Kontar et al. using the Ramaty High-Energy Solar Spectroscopic Imager have shown that HXR source sizes are three to six times more extended in height than those predicted by the standard collisional thick target model (CTTM). Several possible explanations have been put forward including the multi-threaded nature of flare loops, pitch-angle scattering, and magnetic mirroring. However, the nonuniform ionization (NUI) structure along the path of the electron beam has not been fully explored as a solution to this problem. Ionized plasma is known to be less effective at producing nonthermal bremsstrahlung HXRs when compared to neutral plasma. If the peak HXR emission was produced in a locally ionized region within the chromosphere, the intensity of emission will be preferentially reduced around this peak, resulting in a more extended source. Due to this effect, along with the associated density enhancement in the upper chromosphere, injection of a beam of electrons into a partially ionized plasma should result in an HXR source that is substantially more vertically extended relative to that for a neutral target. Here we present the results of a modification to the CTTM, which takes into account both a localized form of chromospheric NUI and an increased target density. We find 50 keV HXR source widths, with and without the inclusion of a locally ionized region, of ~3 Mm and ~0.7 Mm, respectively. This helps to provide a theoretical solution to the currently open question of overly extended HXR sources. Title: Simulating Geomagnetically Induced Currents in the Irish Power Network Authors: Jones, A. G.; Blake, S. P.; Gallagher, P.; McCauley, J.; Hogg, C.; Beggan, C.; Thomson, A. W. P.; Kelly, G.; Walsh, S. Bibcode: 2014AGUFMSM31A4179J Altcode: Geomagnetic storms are known to cause geomagnetically induced currents (GICs) which can damage or destroy transformers on power grids. Previous studies have examined the vulnerability of power networks in countries such as the UK, New Zealand, Canada and South Africa. Here we describe the application of a British Geological Survey (BGS) thin-sheet conductivity model to compute the geo-electric field from the variation of the magnetic field, in order to better quantify the risk of space weather to Ireland's power network. This was achieved using DIAS magnetotelluric data from across Ireland. As part of a near-real-time warning package for Eirgrid (who oversee Ireland's transmission network), severe storm events such as the Halloween 2003 storm and the corresponding GIC flows at transformers are simulated. Title: The HELCATS Project: Characterising the Evolution of Coronal Mass Ejections Observed During Solar Cycle 24 Authors: Bisi, M. M.; Harrison, R. A.; Davies, J. A.; Perry, C. H.; Moestl, C.; Rouillard, A. P.; Bothmer, V.; Rodriguez, L.; Eastwood, J. P.; Kilpua, E.; Gallagher, P.; Odstrcil, D. Bibcode: 2014AGUFMSH43B4214B Altcode: Understanding the evolution of coronal mass ejections (CMEs) is fundamental to advancing our knowledge of energy and mass transport in the solar system, thus also rendering it crucial to space weather and its prediction. The advent of truly wide-angle heliospheric imaging has revolutionised the study of CMEs, by enabling their direct and continuous observation as they propagate from the Sun out to 1 AU and beyond. The recently initiated EU-funded FP7 Heliospheric Cataloguing, Analysis and Technique Service (HELCATS) project combines European expertise in the field of heliospheric imaging, built up over the last decade in particular through lead involvement in NASA's STEREO mission, with expertise in such areas as solar and coronal imaging as well as the interpretation of in-situ and radio diagnostic measurements of solar wind phenomena. The goals of HELCATS include the cataloguing of CMEs observed in the heliosphere by the Heliospheric Imager (HI) instruments on the STEREO spacecraft, since their launch in late October 2006 to date, an interval that covers much of the historically weak solar cycle 24. Included in the catalogue will be estimates of the kinematic properties of the imaged CMEs, based on a variety of established, and some more speculative, modelling approaches (geometrical, forward, inverse, magneto-hydrodynamic); these kinematic properties will be verified through comparison with solar disc and coronal imaging observations, as well as through comparison with radio diagnostic and in-situ measurements made at multiple points throughout the heliosphere. We will provide an overview of the HELCATS project, and present initial results that will seek to illuminate the unusual nature of solar cycle 24. Title: Solar Hard X-ray Source Sizes in a Beam-Heated and Ionised Chromosphere Authors: O'Flannagain, A.; Brown, J. C.; Gallagher, P. T. Bibcode: 2014arXiv1411.5168O Altcode: Solar flare hard X-rays (HXRs) are produced as bremsstrahlung when an accelerated population of electrons interacts with the dense chromospheric plasma. HXR observations presented by using the Ramaty High-Energy Solar Spectroscopic Imager (RHESSI) have shown that HXR source sizes are 3-6 times more extended in height than those predicted by the standard collisional thick target model (CTTM). Several possible explanations have been put forward including the multi-threaded nature of flare loops, pitch-angle scattering, and magnetic mirroring. However, the nonuniform ionisation (NUI) structure along the path of the electron beam has not been fully explored as a solution to this problem. Ionised plasma is known to be less effective at producing nonthermal bremsstrahlung HXRs when compared to neutral plasma. If the peak HXR emission was produced in a locally ionised region within the chromosphere, the intensity of emission will be preferentially reduced around this peak, resulting in a more extended source. Due to this effect, along with the associated density enhancement in the upper chromosphere, injection of a beam of electrons into a partially ionised plasma should result in a HXR source which is substantially more vertically extended relative to that for a neutral target. Here we present the results of a modification to the CTTM which takes into account both a localised form of chromospheric NUI and an increased target density. We find 50 keV HXR source widths, with and without the inclusion of a locally ionised region, of ~3 Mm and ~0.7 Mm, respectively. This helps to provide a theoretical solution to the currently open question of overly-extended HXR sources. Title: Understanding Coronal Mass Ejections and Associated Shocks in the Solar Corona by Merging Multiwavelength Observations Authors: Zucca, P.; Pick, M.; Démoulin, P.; Kerdraon, A.; Lecacheux, A.; Gallagher, P. T. Bibcode: 2014ApJ...795...68Z Altcode: 2014arXiv1409.3691Z Using multiwavelength imaging observations, in EUV, white light and radio, and radio spectral data over a large frequency range, we analyzed the triggering and development of a complex eruptive event. This one includes two components, an eruptive jet and a coronal mass ejection (CME), which interact during more than 30 minutes, and can be considered as physically linked. This was an unusual event. The jet is generated above a typical complex magnetic configuration that has been investigated in many former studies related to the build-up of eruptive jets; this configuration includes fan-field lines originating from a corona null point above a parasitic polarity, which is embedded in one polarity region of a large active region. The initiation and development of the CME, observed first in EUV, does not show usual signatures. In this case, the eruptive jet is the main actor of this event. The CME appears first as a simple loop system that becomes destabilized by magnetic reconnection between the outer part of the jet and the ambient medium. The progression of the CME is closely associated with the occurrence of two successive type II bursts from a distinct origin. An important part of this study is the first radio type II burst for which the joint spectral and imaging observations were allowed: (1) to follow, step by step, the evolution of the spectrum and of the trajectory of the radio burst, in relationship with the CME evolution and (2) to obtain, without introducing an electronic density model, the B field and the Alfvén speed. Title: CorPITA: An Automated Algorithm for the Identification and Analysis of Coronal "EIT Waves" Authors: Long, D. M.; Bloomfield, D. S.; Gallagher, P. T.; Pérez-Suárez, D. Bibcode: 2014SoPh..289.3279L Altcode: 2014arXiv1403.6722L; 2014SoPh..tmp...66L The continuous stream of data available from the Atmospheric Imaging Assembly (AIA) telescopes onboard the Solar Dynamics Observatory (SDO) spacecraft has allowed a deeper understanding of the Sun. However, the sheer volume of data has necessitated the development of automated techniques to identify and analyse various phenomena. In this article, we describe the Coronal Pulse Identification and Tracking Algorithm (CorPITA) for the identification and analysis of coronal "EIT waves". CorPITA uses an intensity-profile technique to identify the propagating pulse, tracking it throughout its evolution before returning estimates of its kinematics. The algorithm is applied here to a data set from February 2011, allowing its capabilities to be examined and critiqued. This algorithm forms part of the SDO Feature Finding Team initiative and will be implemented as part of the Heliophysics Event Knowledgebase (HEK). This is the first fully automated algorithm to identify and track the propagating "EIT wave" rather than any associated phenomenon and will allow a deeper understanding of this controversial phenomenon. Title: LOFAR tied-array imaging of Type III solar radio bursts Authors: Morosan, D. E.; Gallagher, P. T.; Zucca, P.; Fallows, R.; Carley, E. P.; Mann, G.; Bisi, M. M.; Kerdraon, A.; Konovalenko, A. A.; MacKinnon, A. L.; Rucker, H. O.; Thidé, B.; Magdalenić, J.; Vocks, C.; Reid, H.; Anderson, J.; Asgekar, A.; Avruch, I. M.; Bentum, M. J.; Bernardi, G.; Best, P.; Bonafede, A.; Bregman, J.; Breitling, F.; Broderick, J.; Brüggen, M.; Butcher, H. R.; Ciardi, B.; Conway, J. E.; de Gasperin, F.; de Geus, E.; Deller, A.; Duscha, S.; Eislöffel, J.; Engels, D.; Falcke, H.; Ferrari, C.; Frieswijk, W.; Garrett, M. A.; Grießmeier, J.; Gunst, A. W.; Hassall, T. E.; Hessels, J. W. T.; Hoeft, M.; Hörandel, J.; Horneffer, A.; Iacobelli, M.; Juette, E.; Karastergiou, A.; Kondratiev, V. I.; Kramer, M.; Kuniyoshi, M.; Kuper, G.; Maat, P.; Markoff, S.; McKean, J. P.; Mulcahy, D. D.; Munk, H.; Nelles, A.; Norden, M. J.; Orru, E.; Paas, H.; Pandey-Pommier, M.; Pandey, V. N.; Pietka, G.; Pizzo, R.; Polatidis, A. G.; Reich, W.; Röttgering, H.; Scaife, A. M. M.; Schwarz, D.; Serylak, M.; Smirnov, O.; Stappers, B. W.; Stewart, A.; Tagger, M.; Tang, Y.; Tasse, C.; Thoudam, S.; Toribio, C.; Vermeulen, R.; van Weeren, R. J.; Wucknitz, O.; Yatawatta, S.; Zarka, P. Bibcode: 2014A&A...568A..67M Altcode: 2014arXiv1407.4385M Context. The Sun is an active source of radio emission which is often associated with energetic phenomena such as solar flares and coronal mass ejections (CMEs). At low radio frequencies (<100 MHz), the Sun has not been imaged extensively because of the instrumental limitations of previous radio telescopes.
Aims: Here, the combined high spatial, spectral, and temporal resolution of the LOw Frequency ARray (LOFAR) was used to study solar Type III radio bursts at 30-90 MHz and their association with CMEs.
Methods: The Sun was imaged with 126 simultaneous tied-array beams within ≤5 R⊙ of the solar centre. This method offers benefits over standard interferometric imaging since each beam produces high temporal (~83 ms) and spectral resolution (12.5 kHz) dynamic spectra at an array of spatial locations centred on the Sun. LOFAR's standard interferometric output is currently limited to one image per second.
Results: Over a period of 30 min, multiple Type III radio bursts were observed, a number of which were found to be located at high altitudes (~4 R⊙ from the solar center at 30 MHz) and to have non-radial trajectories. These bursts occurred at altitudes in excess of values predicted by 1D radial electron density models. The non-radial high altitude Type III bursts were found to be associated with the expanding flank of a CME.
Conclusions: The CME may have compressed neighbouring streamer plasma producing larger electron densities at high altitudes, while the non-radial burst trajectories can be explained by the deflection of radial magnetic fields as the CME expanded in the low corona.

Movie associated to Fig. 2 is available in electronic form at http://www.aanda.org Title: The Compatibility of Flare Temperatures Observed with AIA, GOES, and RHESSI Authors: Ryan, Daniel F.; O'Flannagain, Aidan M.; Aschwanden, Markus J.; Gallagher, Peter T. Bibcode: 2014SoPh..289.2547R Altcode: 2014SoPh..tmp...31R; 2014arXiv1401.4098R We test the compatibility and biases of multi-thermal flare DEM (differential emission measure) peak temperatures determined with AIA with those determined by GOES and RHESSI using the isothermal assumption. In a set of 149 M- and X-class flares observed during the first two years of the SDO mission, AIA finds DEM peak temperatures at the time of the peak GOES 1 - 8 Å flux to have an average of Tp=12.0±2.9 MK and Gaussian DEM widths of log10(σT)=0.50±0.13. From GOES observations of the same 149 events, a mean temperature of Tp=15.6±2.4 MK is inferred, which is systematically higher by a factor of TGOES/TAIA=1.4±0.4. We demonstrate that this discrepancy results from the isothermal assumption in the inversion of the GOES filter ratio. From isothermal fits to photon spectra at energies of ϵ≈6 - 12 keV of 61 of these events, RHESSI finds the temperature to be higher still by a factor of TRHESSI/TAIA=1.9±1.0. We find that this is partly a consequence of the isothermal assumption. However, RHESSI is not sensitive to the low-temperature range of the DEM peak, and thus RHESSI samples only the high-temperature tail of the DEM function. This can also contribute to the discrepancy between AIA and RHESSI temperatures. The higher flare temperatures found by GOES and RHESSI imply correspondingly lower emission measures. We conclude that self-consistent flare DEM temperatures and emission measures require simultaneous fitting of EUV (AIA) and soft X-ray (GOES and RHESSI) fluxes. Title: a Workflow-Oriented Approach to Propagation Models in Heliophysics Authors: Pierantoni, Gabriele; Carley, Eoin P.; Byrne, Jason P.; Perez-Suarez, David; Gallagher, Peter T. Bibcode: 2014ComSc..15..271P Altcode: The Sun is responsible for the eruption of billions of tons of plasma andthe generation of near light-speed particles that propagate throughout the solarsystem and beyond. If directed towards Earth, these events can be damaging toour tecnological infrastructure. Hence there is an effort to understand the causeof the eruptive events and how they propagate from Sun to Earth. However, thephysics governing their propagation is not well understood, so there is a need todevelop a theoretical description of their propagation, known as a PropagationModel, in order to predict when they may impact Earth. It is often difficultto define a single propagation model that correctly describes the physics ofsolar eruptive events, and even more difficult to implement models capable ofcatering for all these complexities and to validate them using real observational data.

In this paper, we envisage that workflows offer both a theoretical andpractical framerwork for a novel approach to propagation models. We definea mathematical framework that aims at encompassing the different modalitieswith which workflows can be used, and provide a set of generic building blockswritten in the TAVERNA workflow language that users can use to build theirown propagation models. Finally we test both the theoretical model and thecomposite building blocks of the workflow with a real Science Use Case that wasdiscussed during the 4th CDAW (Coordinated Data Analysis Workshop) eventheld by the HELIO project. We show that generic workflow building blocks canbe used to construct a propagation model that succesfully describes the transitof solar eruptive events toward Earth and predict a correct Earth-impact time Title: A study of sympathetic eruptions using the Heliophysics Events Knowledgebase Authors: Higgins, Paul A.; Schrijver, Carolus J.; Title, Alan M.; Bloomfield, D. Shaun; Gallagher, Peter T Bibcode: 2014AAS...22412316H Altcode: Over the past few decades there have been a number of papers investigating the connection between flares occurring in succession. Statistically, any connection that affects the timing of successive flares that exists is found to be weak. However, the majority of previous investigations has been limited by only considering the causal connection between soft X-ray flares. More recent case studies have shown convincing evidence that large eruptions cause a global reorganization of overlying magnetic fields that can result in the eruption of both flares and filaments at large distances from the original event. In this work, the connection between GOES X-ray flares (C-, M-, and X-class) and filament eruptions occurring in succession in two different active regions is considered statistically. The filament eruptions are recorded in the Heliophysics Events Knowledgebase by observers using SDO/AIA data. A significant causal connection is found between the two event types, such that large flares are followed by filament eruptions within 24 hours much more often than they are preceded by filament eruptions. This stipulates that the flares either cause the filaments to erupt or affect the eruption timing such that the filament eruptions follow the flares more closely in time. Title: The Compatibility of Flare Temperatures Observed with AIA, GOES, and RHESSI Authors: Ryan, Daniel; Aschwanden, Markus J.; O'Flannagain, Aidan M; Gallagher, Peter T Bibcode: 2014AAS...22412337R Altcode: In this talk we compare multi-thermal flare DEM peak temperatures determined with SDO/AIA with those determined by GOES/XRS and RHESSI using the isothermal assumption. In a set of 149 M- and X-class flares, AIA finds an average DEM peak temperature at the time of the GOES long channel peak of 12.0±2.9 MK and Gaussian DEM widths of log10(σT ) = 0.50±0.13. From GOES observations of the same 149 events, a mean temperature of 15.6±2.4 MK is inferred, which is higher by a factor of TGOES/TAIA = 1.4±0.4. We demonstrate that this discrepancy results from the isothermal assumption in the inversion of the GOES filter ratio. From isothermal fits to photon spectra at energies of 6-12 keV of 61 of these events, RHESSI finds the temperature to be higher (TRHESSI/TAIA = 1.9±1.0). We find that this is partly a consequence of the isothermal assumption. However, RHESSI is not sensitive to the low-temperature range of the DEM peak, and thus only samples the DEM’s high-temperature tail. This is expected to be the cause of further discrepancies. We conclude that self-consistent flare DEM temperatures require simultaneous fitting of EUV and SXR fluxes. Title: Sunspotter: Using Citizen Science to Determine the Complexity of Sunspots Authors: Higgins, Paul A.; Perez-Suarez, David; Parrish, Michael; O'Callaghan, David; Leka, K D.; Barnes, Graham; Roche, Joseph; Gallagher, Peter T Bibcode: 2014AAS...22411203H Altcode: It is well known that sunspot groups with large, complex magnetic field configurations and strong, sheared polarity separation lines produce the largest flares. While methods for determining certain physical properties, such as total magnetic flux and polarity-separation-line length have been successfully developed for characterizing sunspot groups, a reliable automated method for determining sunspot complexity has never been developed. Since complexity can only be measured in a relative sense, we have used crowd-sourcing methods to allow human observers to compare the complexity of pairs of sunspot groups. This allows a large dataset to be ranked in terms of complexity. Sunspotter.org uses the Zooniverse platform and allows the general public to contribute comparisons using a web-browser interface. The results of this project will help to establish the true relationship between sunspot group complexity and flares, which has been discussed in the solar physics community for many decades. Title: Decay-phase Cooling and Inferred Heating of M- and X-class Solar Flares Authors: Ryan, Daniel; Chamberlin, Phillip C.; Milligan, Ryan O.; Gallagher, Peter T Bibcode: 2014AAS...22412315R Altcode: Hydrodynamic modelling is a well established and important field in understanding the evolution of solar flares. However, in order to be of greatest use the results of such models must be compared to statistically significant samples of flare observations. In this talk we observationally investigate the hydrodynamic decay phase evolution of 72 M- and X-class flares using GOES/XRS, SDO/EVE and Hinode/XRT and quantify their cooling rates. The results are then compared to the predictions of an analytical zero-dimensional hydrodynamic model. We find that the model does not fit the observations well, but does provide a well-defined lower limit on a flare's total cooling time. The discrepancy between observations and the model is then assumed to be primarily due to heating during the decay phase. The decay-phase heating necessary to account for the discrepancy is quantified and found be ~50% of the total thermally radiated energy, as calculated with GOES/XRS. This suggests that the energy released during the decay phase may be as significant as that released during the rise phase. Title: The formation heights of coronal shocks from 2D density and Alfvén speed maps Authors: Zucca, Pietro; Carley, Eoin P.; Bloomfield, D. Shaun; Gallagher, Peter T. Bibcode: 2014A&A...564A..47Z Altcode: 2014arXiv1402.4051Z Context. Super-Alfvénic shocks associated with coronal mass ejections (CMEs) can produce radio emission known as Type II bursts. In the absence of direct imaging, accurate estimates of coronal electron densities, magnetic field strengths, and Alfvén speeds are required to calculate the kinematics of shocks. To date, 1D radial models have been used, but these are not appropriate for shocks propagating in non-radial directions.
Aims: Here, we study a coronal shock wave associated with a CME and Type II radio burst using 2D electron density and Alfvén speed maps to determine the locations that shocks are excited as the CME expands through the corona.
Methods: Coronal density maps were obtained from emission measures derived from the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamic Observatory (SDO) and polarized brightness measurements from the Large Angle and Spectrometric Coronagraph (LASCO) on board the Solar and Heliospheric Observatory (SOHO). Alfvén speed maps were calculated using these density maps and magnetic field extrapolations from the Helioseismic and Magnetic Imager (SDO/HMI). The computed density and Alfvén speed maps were then used to calculate the shock kinematics in non-radial directions.
Results: Using the kinematics of the Type II burst and associated shock, we find our observations to be consistent with the formation of a shock located at the CME flanks where the Alfvén speed has a local minimum.
Conclusions: The 1D density models are not appropriate for shocks that propagate non-radially along the flanks of a CME. Rather, the 2D density, magnetic field and Alfvén speed maps described here give a more accurate method for determining the fundamental properties of shocks and their relation to CMEs. Title: Automated Detection, Characterisation and Tracking of Solar Coronal Mass Ejections Authors: Gallagher, Peter; Carley, Eoin; Byrne, Jason; Morgan, Huw; Refojo, Jose Bibcode: 2014cosp...40E.923G Altcode: Coronal mass ejections (CMEs) are large eruptions of plasma and magnetic flux from the Sun through interplanetary space. If they impact the Earth, they can cause space weather effects that are detrimental to technological systems upon which society is highly dependent. It is therefore important to automatically identify and track CMEs in near-realtime in order to better forecast their possible arrival at Earth. Due to the diffuse nature and comparatively high speeds of CMEs, it is computationally challenging to automatically identify, characterise and track them as they move through the solar corona and inner heliosphere. Here, we review and discuss current state-of-the-art image processing techniques, and how they are being used to automatically generate catalogues of CME properties in near-realtime and for space weather purposes. Furthermore, we discus recent advances in the reconstruction and visualisation of CMEs in 3D, which is crucial to our understanding of their detailed structure and resulting evolution through space. Title: The Relationship between Coronal Mass Ejections and Low Frequency Radio Bursts in the Low Corona Authors: Gallagher, Peter; Carley, Eoin; Byrne, Jason; Long, David; Zucca, Pietro; Bloomfield, Shaun; McCauley, Joseph Bibcode: 2014cosp...40E.924G Altcode: Cosmic rays and solar energetic particles may be accelerated to relativistic energies by shock waves in astrophysical plasmas. On the Sun, shocks and particle acceleration are often associated with the eruption of coronal mass ejections (CMEs). However, the physical relationship between CMEs and shock particle acceleration is not well understood. Here, we use extreme ultraviolet, radio and white-light imaging of a solar eruptive event on 22 September 2011 to show that a CME-induced shock was coincident with a coronal wave and an intense metric radio burst generated by intermittent acceleration of electrons to kinetic energies of 2-46 keV (0.1-0.4 c). Our observations show that plasmoid-driven quasiperpendicular shocks are capable of producing quasiperiodic acceleration of electrons, an effect consistent with a turbulent or rippled plasma shock surface. Title: Quasiperiodic acceleration of electrons by a plasmoid-driven shock in the solar atmosphere Authors: Carley, Eoin P.; Long, David M.; Byrne, Jason P.; Zucca, Pietro; Bloomfield, D. Shaun; McCauley, Joseph; Gallagher, Peter T. Bibcode: 2013NatPh...9..811C Altcode: 2014arXiv1406.0743C Cosmic rays and solar energetic particles may be accelerated to relativistic energies by shock waves in astrophysical plasmas. On the Sun, shocks and particle acceleration are often associated with the eruption of magnetized plasmoids, called coronal mass ejections (CMEs). However, the physical relationship between CMEs and shock particle acceleration is not well understood. Here, we use extreme ultraviolet, radio and white-light imaging of a solar eruptive event on 22 September 2011 to show that a CME-induced shock (Alfvén Mach number ) was coincident with a coronal wave and an intense metric radio burst generated by intermittent acceleration of electrons to kinetic energies of 2-46keV (0.1-0.4c). Our observations show that plasmoid-driven quasiperpendicular shocks are capable of producing quasiperiodic acceleration of electrons, an effect consistent with a turbulent or rippled plasma shock surface. Title: Decay-phase Cooling and Inferred Heating of M- and X-class Solar Flares Authors: Ryan, Daniel F.; Chamberlin, Phillip C.; Milligan, Ryan O.; Gallagher, Peter T. Bibcode: 2013ApJ...778...68R Altcode: 2014arXiv1401.4079R In this paper, the cooling of 72 M- and X-class flares is examined using GOES/XRS and SDO/EVE. The observed cooling rates are quantified and the observed total cooling times are compared with the predictions of an analytical zero-dimensional hydrodynamic model. We find that the model does not fit the observations well, but does provide a well-defined lower limit on a flare's total cooling time. The discrepancy between observations and the model is then assumed to be primarily due to heating during the decay phase. The decay-phase heating necessary to account for the discrepancy is quantified and found be ~50% of the total thermally radiated energy, as calculated with GOES. This decay-phase heating is found to scale with the observed peak thermal energy. It is predicted that approximating the total thermal energy from the peak is minimally affected by the decay-phase heating in small flares. However, in the most energetic flares the decay-phase heating inferred from the model can be several times greater than the peak thermal energy. Title: Improved methods for determining the kinematics of coronal mass ejections and coronal waves Authors: Byrne, J. P.; Long, D. M.; Gallagher, P. T.; Bloomfield, D. S.; Maloney, S. A.; McAteer, R. T. J.; Morgan, H.; Habbal, S. R. Bibcode: 2013A&A...557A..96B Altcode: 2013arXiv1307.8155B Context. The study of solar eruptive events and associated phenomena is of great importance in the context of solar and heliophysics. Coronal mass ejections (CMEs) and coronal waves are energetic manifestations of the restructuring of the solar magnetic field and mass motion of the plasma. Characterising this motion is vital for deriving the dynamics of these events and thus understanding the physics driving their initiation and propagation. The development and use of appropriate methods for measuring event kinematics is therefore imperative.
Aims: Traditional approaches to the study of CME and coronal wave kinematics do not return wholly accurate nor robust estimates of the true event kinematics and associated uncertainties. We highlight the drawbacks of these approaches, and demonstrate improved methods for accurate and reliable determination of the kinematics.
Methods: The Savitzky-Golay filter is demonstrated as a more appropriate fitting technique for CME and coronal wave studies, and a residual resampling bootstrap technique is demonstrated as a statistically rigorous method for the determination of kinematic error estimates and goodness-of-fit tests.
Results: It is shown that the scatter on distance-time measurements of small sample size can significantly limit the ability to derive accurate and reliable kinematics. This may be overcome by (i) increasing measurement precision and sampling cadence; and (ii) applying robust methods for deriving the kinematics and reliably determining their associated uncertainties. If a priori knowledge exists and a pre-determined model form for the kinematics is available (or indeed any justified fitting-form to be tested against the data), then its precision can be examined using a bootstrapping technique to determine the confidence interval associated with the model/fitting parameters.
Conclusions: Improved methods for determining the kinematics of CMEs and coronal waves are demonstrated to great effect, overcoming many issues highlighted in traditional numerical differencing and error propagation techniques. Title: HELIO - Discovering solar effects in all the heliosphere Authors: Pérez-Suárez, D.; Bentley, R. D.; Aboudarham, J.; Brooke, J.; Csillaghy, A.; Gallagher, P. T.; Jacquey, C.; Messerotti, M.; Pierantoni, G. Bibcode: 2013EPSC....8..328P Altcode: HELIO, the HELiophysics Integrated Observatory, consists of a set of integrated software tools developed by an international consortium under the European Commission's Seventh Framework Programme (FP7). HELIO is designed to help scientists easily search heliophysical data and discover any possible connections. This is achieved by merging information from feature and event catalogues and services that know about the locations and capabilities of instruments to find all the data available that contain information on a certain event by propagating it through the whole solar system. There are then tools to access data archives and processing tools that allow the users to create their own workflows.

HELIO is definitely making the research in heliophysics more accessible to different scientists [1] but it capabilities goes further than this. It can be adapted to other fields in science, where multiple observations in different observatories are used to study a particular event. The interfaces of the HELIO services are based onWeb services and, as far as possible, are compliant with IVOA standards. This simplifies access to the capabilities via different tools like Web browsers, scripting languages (IDL, Python, etc.), and workflow tools (Taverna, Kepler, etc.). The overall capabilities of the system can greatly increased when the services are combined using workflows or scripting languages. While we try to hide the use of these tools for most users, those who choose to gain familiarity with such tools can address more complex problems.

A brief introduction to HELIO services and a use case demonstration will be presented. Title: The SWAP EUV Imaging Telescope Part I: Instrument Overview and Pre-Flight Testing Authors: Seaton, D. B.; Berghmans, D.; Nicula, B.; Halain, J. -P.; De Groof, A.; Thibert, T.; Bloomfield, D. S.; Raftery, C. L.; Gallagher, P. T.; Auchère, F.; Defise, J. -M.; D'Huys, E.; Lecat, J. -H.; Mazy, E.; Rochus, P.; Rossi, L.; Schühle, U.; Slemzin, V.; Yalim, M. S.; Zender, J. Bibcode: 2013SoPh..286...43S Altcode: 2012SoPh..tmp..217S; 2012arXiv1208.4631S The Sun Watcher with Active Pixels and Image Processing (SWAP) is an EUV solar telescope onboard 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 54×54 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. Title: The Projects for Onboard Autonomy (PROBA2) Science Centre: Sun Watcher Using APS Detectors and Image Processing (SWAP) and Large-Yield Radiometer (LYRA) Science Operations and Data Products Authors: Zender, J.; Berghmans, D.; Bloomfield, D. S.; Cabanas Parada, C.; Dammasch, I.; De Groof, A.; D'Huys, E.; Dominique, M.; Gallagher, P.; Giordanengo, B.; Higgins, P. A.; Hochedez, J. -F.; Yalim, M. S.; Nicula, B.; Pylyser, E.; Sanchez-Duarte, L.; Schwehm, G.; Seaton, D. B.; Stanger, A.; Stegen, K.; Willems, S. Bibcode: 2013SoPh..286...93Z Altcode: 2012SoPh..tmp..142Z The PROBA2 Science Centre (P2SC) is a small-scale science operations centre supporting the Sun observation instruments onboard PROBA2: the EUV imager Sun Watcher using APS detectors and image Processing (SWAP) and Large-Yield Radiometer (LYRA). PROBA2 is one of ESA's small, low-cost Projects for Onboard Autonomy (PROBA) and part of ESA's In-Orbit Technology Demonstration Programme. The P2SC is hosted at the Royal Observatory of Belgium, co-located with both Principal Investigator teams. The P2SC tasks cover science planning, instrument commanding, instrument monitoring, data processing, support of outreach activities, and distribution of science data products. PROBA missions aim for a high degree of autonomy at mission and system level, including the science operations centre. The autonomy and flexibility of the P2SC is reached by a set of web-based interfaces allowing the operators as well as the instrument teams to monitor quasi-continuously the status of the operations, allowing a quick reaction to solar events. In addition, several new concepts are implemented at instrument, spacecraft, and ground-segment levels allowing a high degree of flexibility in the operations of the instruments. This article explains the key concepts of the P2SC, emphasising the automation and the flexibility achieved in the commanding as well as the data-processing chain. Title: Temperature Response of the 171 Å Passband of the SWAP Imager on PROBA2, with a Comparison to TRACE, SOHO, STEREO, and SDO Authors: Raftery, Claire L.; Bloomfield, D. Shaun; Gallagher, Peter T.; Seaton, Daniel B.; Berghmans, David; De Groof, Anik Bibcode: 2013SoPh..286..111R Altcode: We calculated the temperature response of the 171 Å passbands of the Sun Watcher using APS detectors and image Processing (SWAP) instrument onboard the PRoject for OnBoard Autonomy 2 (PROBA2) satellite. These results were compared to the temperature responses of the Extreme Ultraviolet Imaging Telescope (EIT) onboard the Solar and Heliospheric Observatory (SOHO), the Transition Region and Coronal Explorer (TRACE), the twin Extreme Ultraviolet Imagers (EUVI) onboard the Solar TErrestrial RElations Observatory (STEREO) A and B spacecraft, and the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory (SDO). Multiplying the wavelength-response functions for each instrument by a series of isothermal synthetic spectra and integrating over the range 165 - 195 Å produced temperature-response functions for the six instruments. Each temperature response was then multiplied by sample differential emission-measure functions for four different solar conditions. For any given plasma condition (e.g. quiet Sun, active region), it was found that the overall variation with temperature agreed remarkably well across the six instruments, although the wavelength responses for each instrument have some distinctly different features. Deviations were observed, however, when we compared the response of any one instrument to different solar conditions, particularly for the case of solar flares. Title: Solar flare X-ray source motion as a response to electron spectral hardening Authors: O'Flannagain, A. M.; Gallagher, P. T.; Brown, J. C.; Milligan, R. O.; Holman, G. D. Bibcode: 2013A&A...555A..21O Altcode: 2013arXiv1305.1574O Context. Solar flare hard X-rays (HXRs) are thought to be produced by nonthermal coronal electrons stopping in the chromosphere or remaining trapped in the corona. The collisional thick target model (CTTM) predicts that more energetic electrons penetrate to greater column depths along the flare loop. This requires that sources produced by harder power-law injection spectra should appear further down the legs or footpoints of a flareloop. Therefore, the frequently observed hardening of the injected power-law electron spectrum during flare onset should be concurrent with a descending hard X-ray source.
Aims: We test this implication of the CTTM by comparing its predicted HXR source locations with those derived from observations of a solar flare which exhibits a nonthermally-dominated spectrum before the peak in HXRs, known as an early impulsive event.
Methods: The HXR images and spectra of an early impulsive C-class flare were obtained using the Ramaty High-Energy Solar Spectroscopic Imager (RHESSI). Images were reconstructed to produce HXR source height evolutions for three energy bands. Spatially integrated spectral analysis was performed to isolate nonthermal emission and to determine the power-law index of the electron injection spectrum. The observed height-time evolutions were then fitted with CTTM-based simulated heights for each energy, using the electron spectral indices derived from the RHESSI spectra.
Results: The flare emission was found to be dominantly nonthermal above ~7 keV, with emission of thermal and nonthermal X-rays likely to be simultaneously observable below that energy. The density structure required for a good match between model and observed source heights agreed with previous studies of flare loop densities.
Conclusions: The CTTM has been used to produce a descent of model HXR source heights that compares well with observations of this event. Based on this interpretation, downward motion of nonthermal sources should occur in any flare where there is spectral hardening in the electron distribution during a flare. However, this is often masked by thermal emission associated with flare plasma preheating. To date, flare models that predict transfer of energy from the corona to the chromosphere by means other than a flux of nonthermal electrons do not predict this observed source descent. Therefore, flares such as this will be key in explaining this elusive energy transfer process. Title: SHILLELAgh: A data-driven solar wind model for studying solar energetic particle events Authors: Higgins, Paul Anthony; Perez-Suarez, David; Nitta, Nariaki; Gallagher, Peter T. Bibcode: 2013shin.confE.140H Altcode: A method for estimating the properties of the solar wind in the equatorial plane is presented. OMNI and STEREO in situ solar wind data is used as input. The solar wind is assumed to propagate radially at a constant velocity and the corona is assumed to remain static. An empirical density model is applied to the ballistically propagated solar wind. A 2D map of solar wind properties is obtained that is well suited for use in investigations of heliospheric features (e.g., co-rotating interaction regions). In this work, the propagation of solar energetic particle (SEP) events is investigated using the model. Our method provides a convenient vehicle for assessing the directionality and hence, the geo-effectiveness of SEP events. Title: Measuring the Diffusion of Solar Magnetic Flux on Large Spatio-Temporal Scales Authors: Higgins, Paul Anthony; Bloomfield, D. Shaun; Gallagher, Peter T. Bibcode: 2013shin.confE..91H Altcode: We present an investigation of the large-scale flows that influence magnetic fields at the solar surface. The aim of this work is to accurately characterise the supergranular diffusion coefficient, D, that governs the dispersal rate of magnetic features in the photosphere. There is a disconnect between the measured rate of magnetic field dispersal ( 50 - 300 km2/s) and the value of D used in global simulations of solar magnetic field evolution ( 500 - 600 km2/s). We track the poleward motion of magnetic features in a latitude-time map and compare the poleward progression to a data-driven simulation that includes differential rotation, the meridional flow, and supergranular diffusion. We find that over a time scale of months, setting D = 100 km2/s matches observations, but over a time scale of years, setting D = 500 km2/s is a better match. This supports the idea that observational time scale causes the disconnect in D values, which leads us to the conclusion that the present magnetic surface flux transport model is not adequate to explain the observed evolution of the solar surface magnetic field. Title: Advanced Techniques for Studying Coronal Mass Ejections in Three-Dimensions Authors: Byrne, Jason P.; Morgan, Huw; Habbal, Shadia; Gallagher, Peter Bibcode: 2013shin.confE.161B Altcode: As the STEREO mission progresses into 2013, the spacecrafts have moved into quadrature on the far side of the Sun - a unique perspective in the context of solar physics. This year also heralds the arrival of solar maximum, when the solar activity cycle should peak and a multitude of eruptive events may be observed. Therefore, methods for studying the dynamical evolution of such phenomena as coronal mass ejections (CMEs) are crucial for revealing the physics at play in these unique observations. To this end, we present advanced image processing and stereoscopic techniques for studying CMEs in an effort to determine their true 3D nature as they propagate through the solar corona. This is achieved by first performing a dynamic/quiescent signal separation to remove the static corona in SECCHI images and applying multiscale filtering techniques to enhance the observed structures. Then an elliptical tie-pointing technique is used to generate a 3D surface characterisation of the observed CME front, in order to reveal its true morphology as it evolves. A model flux-rope was generated in order to prove the optimal use of this 3D reconstruction technique, especially while the spacecraft are in quadrature; and is being used to determine the uncertainties involved in kinematic and morphological analyses of candidate events observed during this phase of the STEREO mission. Title: SHEBA - HELIO's propagation model: a walk through its possibilities Authors: Pérez-Suárez, David; Pierantoni, Gabriele; Maloney, Shane A.; Higgins, Paul A.; Gallagher, Peter T.; Bentley, Robert D. Bibcode: 2013EGUGA..1513919P Altcode: The Heliophysics Integrated Observatory (HELIO) is a software infrastructure involving a collection of web services, heliospheric data sources (e.g., solar, planetary, etc.), and event catalogues - all of which are accessible through a unified front end. HELIO brings to the scientist the possibility to search an event occurred in the heliosphere and find out which other events are linked with the one under study. To get the relation between events HELIO uses SHEBA (Solar-Heliospheric Event Ballistic Algorithm), a simple propagation model for Coronal Mass Ejections, Solar Energetic Particle and Co-rotating Interaction Regions. This poster explains the basics of SHEBA and it walks through real-case scenarios of its use. Title: Observational Calculation of Flare Filling Factors Using GOES/XRS, SDO/EVE and SDO/AIA Authors: Ryan, Daniel F.; Bowen, Trevor A.; Chamberlin, Philip C.; Milligan, Ryan O.; Gallagher, Peter T. Bibcode: 2013enss.confE.133R Altcode: A solar flare's filling factor is the fraction of its total volume which is occupied by high density emitting plasma. This is a completely unknown factor and a major source of uncertainty in many studies requiring density calculations. While the filling factor is usually assumed to be unity, tentative observational evidence suggests it may be orders of magnitude less than that. This would have significant consequences on past and future flare density and emission measure analyses. In this poster we examine several C-class events and present the first observational calculations of flare filling factors using GOES/XRS, SDO/EVE and SDO/AIA. We find that filling factors are indeed orders of magnitude less than unity. The sample in this study ranges from 10-1 - 10-6, with a mean of 10-2.4 and a median of 10-3.4. Title: An Examination of Flare Cooling Using SDO/EVE Authors: Ryan, Daniel F.; Chamberlin, Phil C.; Gallagher, Peter T.; Milligan, Ryan O. Bibcode: 2013enss.confE.144R Altcode: The processes by which solar flares cool have been modeled many times using magnetohydrodynamic simulations. However, few studies have tried to compare the results of such models to observations of large numbers of flares. A better observational understanding of flare cooling would help us to better constrain initial flare energy inputs and better understand how potentially harmful radiation is released into the solar system. The advent of SDO/EVE allows us to observe flare cooling more directly than before while making fewer assumptions (e.g. the isothermal assumption). This is done by charting the temporal evolution from several temperature sensitive lines within the EVE spectral range. In this poster we have used SDO/EVE and GOES/XRS to calculate flare cooling profiles of 72 M- and X-class flares. The observed cooling times have been compared to those predicted by the simple and highly idealized Cargill et al. (1995) model. We find that although the model does not accurately fit the distribution, the agreement is still better than expected, particularly at shorter cooling times. Title: Solar Flare Prediction Using Advanced Feature Extraction, Machine Learning, and Feature Selection Authors: Ahmed, Omar W.; Qahwaji, Rami; Colak, Tufan; Higgins, Paul A.; Gallagher, Peter T.; Bloomfield, D. Shaun Bibcode: 2013SoPh..283..157A Altcode: 2011SoPh..tmp..404A Novel machine-learning and feature-selection algorithms have been developed to study: i) the flare-prediction-capability of magnetic feature (MF) properties generated by the recently developed Solar Monitor Active Region Tracker (SMART); ii) SMART's MF properties that are most significantly related to flare occurrence. Spatiotemporal association algorithms are developed to associate MFs with flares from April 1996 to December 2010 in order to differentiate flaring and non-flaring MFs and enable the application of machine-learning and feature-selection algorithms. A machine-learning algorithm is applied to the associated datasets to determine the flare-prediction-capability of all 21 SMART MF properties. The prediction performance is assessed using standard forecast-verification measures and compared with the prediction measures of one of the standard technologies for flare-prediction that is also based on machine-learning: Automated Solar Activity Prediction (ASAP). The comparison shows that the combination of SMART MFs with machine-learning has the potential to achieve more accurate flare-prediction than ASAP. Feature-selection algorithms are then applied to determine the MF properties that are most related to flare occurrence. It is found that a reduced set of six MF properties can achieve a similar degree of prediction accuracy as the full set of 21 SMART MF properties. Title: TEBBS: A New Automatic Method for Calculating Background-Subtracted Thermal Flare Properties Using GOES/XRS Authors: Ryan, Daniel F.; Milligan, Ryan O.; Gallagher, Peter T.; Dennis, Brian R.; Tolbert, A. Kim; Schwartz, Richard A.; Young, C. Alex Bibcode: 2013enss.confE.143R Altcode: The GOES/XRS has become a "standard candle" by which flare observations from other satellites are compared. It is increasingly being used alongside SDO to help us better understand solar flares. In addition, the longevity of GOES makes it uniquely suited to the study of large numbers of flares over multiple solar cycles. However, in order to use the GOES/XRS to accurately derive flare thermal properties, it is essential to adequately subtract emission from non-flaring plasma. To date, the potential of the GOES/XRS has been limited by the lack of standard background subtraction method, capable of being quickly and automatically applied to any number of flares. In this poster we present just such a method, the Temperature and Emission measure-Based Background Subtraction (TEBBS; Ryan et al. 2012). This method calculates a flare's thermal properties (temperature, emission measure etc.) by first automatically determining a suitable background subtraction based on the physical credibility of the results it produces. This method increases the GOES/XRS's potential both as a stand-alone instrument as well as in complimenting observations made by SDO and other solar observatories. Title: The Coronal Pulse Identification and Tracking Algorithm (CorPITA) Authors: Long, David M.; Bloomfield, D. Shaun; Feeney-Barry, R.; Gallagher, Peter T.; Pérez-Suárez, David Bibcode: 2013enss.confE..68L Altcode: The Coronal Pulse Identification and Tracking Algorithm (CorPITA) is an automated technique for detecting and analysing "EIT Waves" in data from the Solar Dynamics Observatory (SDO) spacecraft. CorPITA will operate as part of the Heliophysics Event Knowledgebase (HEK), providing unbiased, near-real-time identification of coronal pulses. When triggered by the start of a solar flare, the algorithm uses an intensity profile technique radiating from the source of the flare to examine the entire solar disk. If a pulse is identified, the kinematics and morphological variation of the pulse are determined for all directions along the solar surface. Here, CorPITA is applied to a test data-set encompassing a series of solar flares of different classes from 13-20 February 2011. This allows the effectiveness of the algorithm in dealing with the varied morphology of different eruptions to be characterised. The automated nature of this approach will enable an unbiased examination of "EIT Waves" and their relationship to coronal mass ejections. Title: Evidence for partial Taylor relaxation from changes in magnetic geometry and energy during a solar flare Authors: Murray, S. A.; Bloomfield, D. S.; Gallagher, P. T. Bibcode: 2013A&A...550A.119M Altcode: 2012arXiv1212.5906M Context. Solar flares are powered by energy stored in the coronal magnetic field, a portion of which is released when the field reconfigures into a lower energy state. Investigation of sunspot magnetic field topology during flare activity is useful to improve our understanding of flaring processes.
Aims: Here we investigate the deviation of the non-linear field configuration from that of the linear and potential configurations, and study the free energy available leading up to and after a flare.
Methods: The evolution of the magnetic field in NOAA region 10953 was examined using data from Hinode/SOT-SP, over a period of 12 h leading up to and after a GOES B1.0 flare. Previous work on this region found pre- and post-flare changes in photospheric vector magnetic field parameters of flux elements outside the primary sunspot. 3D geometry was thus investigated using potential, linear force-free, and non-linear force-free field extrapolations in order to fully understand the evolution of the field lines.
Results: Traced field line geometrical and footpoint orientation differences show that the field does not completely relax to a fully potential or linear force-free state after the flare. Magnetic and free magnetic energies increase significantly ~6.5-2.5 h before the flare by ~1031 erg. After the flare, the non-linear force-free magnetic energy and free magnetic energies decrease but do not return to pre-flare "quiet" values.
Conclusions: The post-flare non-linear force-free field configuration is closer (but not equal) to that of the linear force-free field configuration than a potential one. However, the small degree of similarity suggests that partial Taylor relaxation has occurred over a time scale of ~3-4 h. Title: Spectrometer Telescope for Imaging X-rays (STIX) Authors: Benz, A. O.; Gallagher, P.; Veronig, A.; Grimm, O.; Sylwester, J.; Orleanski, P.; Arnold, N.; Bednarzik, M.; Farnik, F.; Hurford, G.; Krucker, S.; Limousin, O.; Mann, G.; Vilmer, N. Bibcode: 2012IAUSS...6E.509B Altcode: The Solar Orbiter Mission has been confirmed within ESA's M-class Cosmic Vision plan. Launch date is January 2017 into an orbit that reaches nearly one quarter AU in the perihelion. STIX is one of the 10 instruments selected for close cooperation. STIX applies a Fourier-imaging technique using shading tungsten grids. A total of 32 pixelized CdTe detectors will permit high resolution imaging spectroscopy. The design has passed ESA's Preliminary Design Review and will be finalized by the end of 2012. The instrument specification will be presented and its scientific potential discussed. Title: The Thermal Properties of Solar Flares over Three Solar Cycles Using GOES X-Ray Observations Authors: Ryan, Daniel F.; Milligan, Ryan O.; Gallagher, Peter T.; Dennis, Brian R.; Tolbert, A. Kim; Schwartz, Richard A.; Young, C. Alex Bibcode: 2012ApJS..202...11R Altcode: 2012arXiv1206.1005R Solar flare X-ray emission results from rapidly increasing temperatures and emission measures in flaring active region loops. To date, observations from the X-Ray Sensor (XRS) on board the Geostationary Operational Environmental Satellite (GOES) have been used to derive these properties, but have been limited by a number of factors, including the lack of a consistent background subtraction method capable of being automatically applied to large numbers of flares. In this paper, we describe an automated Temperature and Emission measure-Based Background Subtraction method (TEBBS), that builds on the methods of Bornmann. Our algorithm ensures that the derived temperature is always greater than the instrumental limit and the pre-flare background temperature, and that the temperature and emission measure are increasing during the flare rise phase. Additionally, TEBBS utilizes the improved estimates of GOES temperatures and emission measures from White et al. TEBBS was successfully applied to over 50,000 solar flares occurring over nearly three solar cycles (1980-2007), and used to create an extensive catalog of the solar flare thermal properties. We confirm that the peak emission measure and total radiative losses scale with background subtracted GOES X-ray flux as power laws, while the peak temperature scales logarithmically. As expected, the peak emission measure shows an increasing trend with peak temperature, although the total radiative losses do not. While these results are comparable to previous studies, we find that flares of a given GOES class have lower peak temperatures and higher peak emission measures than previously reported. The TEBBS database of flare thermal plasma properties is publicly available at http://www.SolarMonitor.org/TEBBS/. Title: LEMUR: Large European module for solar Ultraviolet Research. European contribution to JAXA's Solar-C mission Authors: Teriaca, Luca; Andretta, Vincenzo; Auchère, Frédéric; Brown, Charles M.; Buchlin, Eric; Cauzzi, Gianna; Culhane, J. Len; Curdt, Werner; Davila, Joseph M.; Del Zanna, Giulio; Doschek, George A.; Fineschi, Silvano; Fludra, Andrzej; Gallagher, Peter T.; Green, Lucie; Harra, Louise K.; Imada, Shinsuke; Innes, Davina; Kliem, Bernhard; Korendyke, Clarence; Mariska, John T.; Martínez-Pillet, Valentin; Parenti, Susanna; Patsourakos, Spiros; Peter, Hardi; Poletto, Luca; Rutten, Robert J.; Schühle, Udo; Siemer, Martin; Shimizu, Toshifumi; Socas-Navarro, Hector; Solanki, Sami K.; Spadaro, Daniele; Trujillo-Bueno, Javier; Tsuneta, Saku; Dominguez, Santiago Vargas; Vial, Jean-Claude; Walsh, Robert; Warren, Harry P.; Wiegelmann, Thomas; Winter, Berend; Young, Peter Bibcode: 2012ExA....34..273T Altcode: 2011ExA...tmp..135T; 2011arXiv1109.4301T The solar outer atmosphere is an extremely dynamic environment characterized by the continuous interplay between the plasma and the magnetic field that generates and permeates it. Such interactions play a fundamental role in hugely diverse astrophysical systems, but occur at scales that cannot be studied outside the solar system. Understanding this complex system requires concerted, simultaneous solar observations from the visible to the vacuum ultraviolet (VUV) and soft X-rays, at high spatial resolution (between 0.1'' and 0.3''), at high temporal resolution (on the order of 10 s, i.e., the time scale of chromospheric dynamics), with a wide temperature coverage (0.01 MK to 20 MK, from the chromosphere to the flaring corona), and the capability of measuring magnetic fields through spectropolarimetry at visible and near-infrared wavelengths. Simultaneous spectroscopic measurements sampling the entire temperature range are particularly important. These requirements are fulfilled by the Japanese Solar-C mission (Plan B), composed of a spacecraft in a geosynchronous orbit with a payload providing a significant improvement of imaging and spectropolarimetric capabilities in the UV, visible, and near-infrared with respect to what is available today and foreseen in the near future. The Large European Module for solar Ultraviolet Research (LEMUR), described in this paper, is a large VUV telescope feeding a scientific payload of high-resolution imaging spectrographs and cameras. LEMUR consists of two major components: a VUV solar telescope with a 30 cm diameter mirror and a focal length of 3.6 m, and a focal-plane package composed of VUV spectrometers covering six carefully chosen wavelength ranges between 170 Å and 1270 Å. The LEMUR slit covers 280'' on the Sun with 0.14'' per pixel sampling. In addition, LEMUR is capable of measuring mass flows velocities (line shifts) down to 2 km s - 1 or better. LEMUR has been proposed to ESA as the European contribution to the Solar C mission. Title: Studying Sun-Planet Connections Using the Heliophysics Integrated Observatory (HELIO) Authors: Pérez-Suárez, D.; Maloney, S. A.; Higgins, P. A.; Bloomfield, D. S.; Gallagher, P. T.; Pierantoni, G.; Bonnin, X.; Cecconi, B.; Alberti, V.; Bocchialini, K.; Dierckxsens, M.; Opitz, A.; Le Blanc, A.; Aboudarham, J.; Bentley, R. B.; Brooke, J.; Coghlan, B.; Csillaghy, A.; Jacquey, C.; Lavraud, B.; Messerotti, M. Bibcode: 2012SoPh..280..603P Altcode: 2012SoPh..tmp..215P The Heliophysics Integrated Observatory (HELIO) is a software infrastructure involving a collection of web services, heliospheric data sources (e.g., solar, planetary, etc.), and event catalogues - all of which are accessible through a unified front end. In this paper we use the HELIO infrastructure to perform three case studies based on solar events that propagate through the heliosphere. These include a coronal mass ejection that intersects both Earth and Mars, a solar energetic particle event that crosses the orbit of Earth, and a high-speed solar wind stream, produced by a coronal hole, that is observed in situ at Earth (L1). A ballistic propagation model is run as one of the HELIO services and used to model these events, predicting if they will interact with a spacecraft or planet and determining the associated time of arrival. The HELIO infrastructure streamlines the method used to perform these kinds of case study by centralising the process of searching for and visualising data, indicating interesting features on the solar disk, and finally connecting remotely observed solar features with those detected by in situ solar wind and energetic particle instruments. HELIO represents an important leap forward in European heliophysics infrastructure by bridging the boundaries of traditional scientific domains. Title: Observations of Low Frequency Solar Radio Bursts from the Rosse Solar-Terrestrial Observatory Authors: Zucca, P.; Carley, E. P.; McCauley, J.; Gallagher, P. T.; Monstein, C.; McAteer, R. T. J. Bibcode: 2012SoPh..280..591Z Altcode: 2012SoPh..tmp...94Z; 2012arXiv1204.0943Z The Rosse Solar-Terrestrial Observatory (RSTO; www.rosseobservatory.ie) was established at Birr Castle, Co. Offaly, Ireland (53°05'38.9″, 7°55'12.7″) in 2010 to study solar radio bursts and the response of the Earth's ionosphere and geomagnetic field. To date, three Compound Astronomical Low-cost Low-frequency Instrument for Spectroscopy in Transportable Observatory (CALLISTO) spectrometers have been installed, with the capability of observing in the frequency range of 10 - 870 MHz. The receivers are fed simultaneously by biconical and log-periodic antennas. Nominally, frequency spectra in the range of 10 - 400 MHz are obtained with four sweeps per second over 600 channels. Here, we describe the RSTO solar radio spectrometer set-up, and present dynamic spectra of samples of type II, III and IV radio bursts. In particular, we describe the fine-scale structure observed in type II bursts, including band splitting and rapidly varying herringbone features. Title: The spectrometer telescope for imaging x-rays on board the Solar Orbiter mission Authors: Benz, A. O.; Krucker, S.; Hurford, G. J.; Arnold, N. G.; Orleanski, P.; Gröbelbauer, H. -P.; Klober, S.; Iseli, L.; Wiehl, H. J.; Csillaghy, A.; Etesi, L.; Hochmuth, N.; Battaglia, M.; Bednarzik, M.; Resanovic, R.; Grimm, O.; Viertel, G.; Commichau, V.; Meuris, A.; Limousin, O.; Brun, S.; Vilmer, N.; Skup, K. R.; Graczyk, R.; Stolarski, M.; Michalska, M.; Nowosielski, W.; Cichocki, A.; Mosdorf, M.; Seweryn, K.; Przepiórka, A.; Sylwester, J.; Kowalinski, M.; Mrozek, T.; Podgorski, P.; Mann, G.; Aurass, H.; Popow, E.; Onel, H.; Dionies, F.; Bauer, S.; Rendtel, J.; Warmuth, A.; Woche, M.; Plüschke, D.; Bittner, W.; Paschke, J.; Wolker, D.; Van Beek, H. F.; Farnik, F.; Kasparova, J.; Veronig, A. M.; Kienreich, I. W.; Gallagher, P. T.; Bloomfield, D. S.; Piana, M.; Massone, A. M.; Dennis, B. R.; Schwarz, R. A.; Lin, R. P. Bibcode: 2012SPIE.8443E..3LB Altcode: The Spectrometer Telescope for Imaging X-rays (STIX) is one of 10 instruments on board Solar Orbiter, a confirmed Mclass mission of the European Space Agency (ESA) within the Cosmic Vision program scheduled to be launched in 2017. STIX applies a Fourier-imaging technique using a set of tungsten grids (at pitches from 0.038 to 1 mm) in front of 32 pixelized CdTe detectors to provide imaging spectroscopy of solar thermal and non-thermal hard X-ray emissions from 4 to 150 keV. The status of the instrument reviewed in this paper is based on the design that passed the Preliminary Design Review (PDR) in early 2012. Particular emphasis is given to the first light of the detector system called Caliste-SO. Title: Investigating the Driving Mechanisms of Coronal Mass Ejections Authors: Lin, C.; Gallagher, P. T.; Raftery, C. L. Bibcode: 2012ASPC..454..403L Altcode: The objective of this investigation was to first examine the kinematics of coronal mass ejections (CMEs) using EUV and coronagraph images, and then to make a comparison with theoretical models in the hope to identify the driving mechanisms of the CMEs. We have studied two CMEs which occurred on 2006 Dec. 17 (CME06) and 2007 Dec. 31 (CME07). The models studied in this work were catastrophe, breakout, and toroidal instability models. We found that after the eruption, the accelerations of both events exhibited a drop before increasing again. Our comparisons with the theories suggested that CME06 can be best described by a hybrid of the catastrophe and breakout models while CME07 is most consistent with the breakout model. Based on the catastrophe model, we deduced that the reconnection rate in the current sheet for CME06 was intermediate, the onset of its eruption occurred at a height of ∼200 Mm, and the Alfvén speed and the magnetic field strength at this height were ∼130-250 km s-1 and 7 Gauss, respectively. Title: CORIMP CME Catalogue: Automatically Detecting & Tracking CMEs in Coronagraph Data Authors: Byrne, Jason Phelim; Morgan, Huw; Habbal, Shadia; Gallagher, Peter Bibcode: 2012shin.confE..91B Altcode: With the large amounts of CME image data available from the SOHO and STEREO coronagraphs, manual cataloguing of events can be tedious and subject to user bias. Therefore automated catalogues, such as CACTus and SEEDS, have been developed in an effort to produce a robust method of detection and analysis of events. Here we present the development of a new CORIMP (coronal image processing) CME detection and tracking technique that overcomes many of the drawbacks of previous methods. It works by first employing a dynamic CME separation technique to remove the static background, and then characterizing CMEs via a multiscale edge-detection algorithm. This allows the inherent structure of the CMEs to be revealed in each image, which is usually prone to spatiotemporal crosstalk as a result of traditional image-differencing techniques. Thus the kinematic and morphological information on each event is resolved with higher accuracy than previous catalogues, revealing CME acceleration and expansion profiles otherwise undetected, and enabling a determination of the varying speeds attained across the span of the CME. The potential for a 3D characterization of the internal structure of CMEs is also demonstrated. Title: Automatic Detection and Tracking of Coronal Mass Ejections. II. Multiscale Filtering of Coronagraph Images Authors: Byrne, Jason P.; Morgan, Huw; Habbal, Shadia R.; Gallagher, Peter T. Bibcode: 2012ApJ...752..145B Altcode: 2012arXiv1207.6125B Studying coronal mass ejections (CMEs) in coronagraph data can be challenging due to their diffuse structure and transient nature, and user-specific biases may be introduced through visual inspection of the images. The large amount of data available from the Solar and Heliospheric Observatory (SOHO), Solar TErrestrial RElations Observatory (STEREO), and future coronagraph missions also makes manual cataloging of CMEs tedious, and so a robust method of detection and analysis is required. This has led to the development of automated CME detection and cataloging packages such as CACTus, SEEDS, and ARTEMIS. Here, we present the development of a new CORIMP (coronal image processing) CME detection and tracking technique that overcomes many of the drawbacks of current catalogs. It works by first employing the dynamic CME separation technique outlined in a companion paper, and then characterizing CME structure via a multiscale edge-detection algorithm. The detections are chained through time to determine the CME kinematics and morphological changes as it propagates across the plane of sky. The effectiveness of the method is demonstrated by its application to a selection of SOHO/LASCO and STEREO/SECCHI images, as well as to synthetic coronagraph images created from a model corona with a variety of CMEs. The algorithms described in this article are being applied to the whole LASCO and SECCHI data sets, and a catalog of results will soon be available to the public. Title: Coronal Mass Ejection Mass, Energy, and Force Estimates Using STEREO Authors: Carley, Eoin P.; McAteer, R. T. James; Gallagher, Peter T. Bibcode: 2012ApJ...752...36C Altcode: 2012arXiv1204.4601C Understanding coronal mass ejection (CME) energetics and dynamics has been a long-standing problem, and although previous observational estimates have been made, such studies have been hindered by large uncertainties in CME mass. Here, the two vantage points of the Solar Terrestrial Relations Observatory (STEREO) COR1 and COR2 coronagraphs were used to accurately estimate the mass of the 2008 December 12 CME. Acceleration estimates derived from the position of the CME front in three dimensions were combined with the mass estimates to calculate the magnitude of the kinetic energy and driving force at different stages of the CME evolution. The CME asymptotically approaches a mass of 3.4 ± 1.0 × 1015 g beyond ~10 R ⊙. The kinetic energy shows an initial rise toward 6.3 ± 3.7 × 1029 erg at ~3 R ⊙, beyond which it rises steadily to 4.2 ± 2.5 × 1030 erg at ~18 R ⊙. The dynamics are described by an early phase of strong acceleration, dominated by a force of peak magnitude of 3.4 ± 2.2 × 1014 N at ~3 R ⊙, after which a force of 3.8 ± 5.4 × 1013 N takes effect between ~7 and 18 R ⊙. These results are consistent with magnetic (Lorentz) forces acting at heliocentric distances of lsim7 R ⊙, while solar wind drag forces dominate at larger distances (gsim7 R ⊙). Title: HELIO - A Research Environment for Heliophysics Authors: Bentley, R. D.; Abourdarham, J.; Csillaghy, A.; Messerotti, M.; Gallagher, P.; Bocchialini, K.; Jacquey, C.; Hapgood, M. Bibcode: 2012EGUGA..1411634B Altcode: HELIO, the Heliophysics Integrated Observatory, is a research infrastructure funded under Capacities programme of the EC's 7th Framework Programme (FP7). It provides a collaborative environment where scientists can discover, understand and model the connection between solar phenomena, interplanetary disturbances and their effects on the planets. The project is designed around a service-oriented architecture with needed capabilities that support metadata curation and search, data location and retrieval, and data processing and storage being established as independent services. HELIO provides integrated access to the data and metadata from the domains that constitute heliophysics - solar, heliospheric, geophysics and planetary. More than 50 event catalogues can be used in the search, together with just under 10 feature catalogues; data from more than 150 instruments from nearly 50 observatories can be accessed. A comprehensive user interface is available and the serves can also be accessed through IDL; a workflow tool provides the ability to combine services together and it is possible to execute programmes on demand including propagation models. We will report on the status of HELIO and the services that are available and demonstrate how these resources can be used to address use cases involving multiple spacecraft and modelling. We will also describe how we hope to combine the tools developed by HELIO into a Collaborative Research Environment for Heliophysics. We have been holding a series of Coordinated Data Analysis Workshops (CDAW) in which we demonstrate the capabilities of the project and participants are able to use them to address science use cases. Two CDAWs have been held so far, in Dublin and Trieste; a third will be held in February 2012 in Orsay, and a fourth is planned in May/June 2012. Typical use cases relate to phenomena propagating from the Sun and being observed by at least two observatories in different parts of the inner Solar System. The HELIO Consortium includes thirteen groups from the UK, France, Ireland, Italy, Switzerland, Spain and the US; the project started in June 2009 and has a duration of 36 months Title: Toward Reliable Benchmarking of Solar Flare Forecasting Methods Authors: Bloomfield, D. Shaun; Higgins, Paul A.; McAteer, R. T. James; Gallagher, Peter T. Bibcode: 2012ApJ...747L..41B Altcode: 2012arXiv1202.5995B Solar flares occur in complex sunspot groups, but it remains unclear how the probability of producing a flare of a given magnitude relates to the characteristics of the sunspot group. Here, we use Geostationary Operational Environmental Satellite X-ray flares and McIntosh group classifications from solar cycles 21 and 22 to calculate average flare rates for each McIntosh class and use these to determine Poisson probabilities for different flare magnitudes. Forecast verification measures are studied to find optimum thresholds to convert Poisson flare probabilities into yes/no predictions of cycle 23 flares. A case is presented to adopt the true skill statistic (TSS) as a standard for forecast comparison over the commonly used Heidke skill score (HSS). In predicting flares over 24 hr, the maximum values of TSS achieved are 0.44 (C-class), 0.53 (M-class), 0.74 (X-class), 0.54 (>=M1.0), and 0.46 (>=C1.0). The maximum values of HSS are 0.38 (C-class), 0.27 (M-class), 0.14 (X-class), 0.28 (>=M1.0), and 0.41 (>=C1.0). These show that Poisson probabilities perform comparably to some more complex prediction systems, but the overall inaccuracy highlights the problem with using average values to represent flaring rate distributions. Title: The Evolution of Sunspot Magnetic Fields Associated with a Solar Flare Authors: Murray, Sophie A.; Bloomfield, D. Shaun; Gallagher, Peter T. Bibcode: 2012SoPh..277...45M Altcode: 2011arXiv1105.1978M; 2011SoPh..tmp..129M; 2011SoPh..tmp..185M; 2011SoPh..tmp..254M Solar flares occur due to the sudden release of energy stored in active-region magnetic fields. To date, the precursors to flaring are still not fully understood, although there is evidence that flaring is related to changes in the topology or complexity of an active-region's magnetic field. Here, the evolution of the magnetic field in active region NOAA 10953 was examined using Hinode/SOT-SP data over a period of 12 hours leading up to and after a GOES B1.0 flare. A number of magnetic-field properties and low-order aspects of magnetic-field topology were extracted from two flux regions that exhibited increased Ca II H emission during the flare. Pre-flare increases in vertical field strength, vertical current density, and inclination angle of ≈ 8° toward the vertical were observed in flux elements surrounding the primary sunspot. The vertical field strength and current density subsequently decreased in the post-flare state, with the inclination becoming more horizontal by ≈ 7°. This behavior of the field vector may provide a physical basis for future flare-forecasting efforts. Title: Automated detection and tracking of solar and heliospheric features in the frame of the European project HELIO Authors: Bonnin, X.; Aboudarham, J.; Fuller, N.; Renie, C.; Perez-Suarez, D.; Gallagher, P.; Higgins, P.; Krista, L.; Csillaghy, A.; Bentley, R. Bibcode: 2011sf2a.conf..373B Altcode: In the frame of the European project HELIO, the Observatoire de Paris-Meudon is in charge of the Heliophysics Feature Catalogue (HFC), a service which provides access to existing solar and heliospheric feature data. In order to create a catalogue as exhaustive as possible, recognition codes are developed to automatically detect and track features. At the time, HFC contains data of filaments, active regions, coronal holes, sunspots and type III radio bursts for a full solar cycle. The insertion of prominences and type II radio bursts should be done in the short term. We present here an overview of some of the algorithms used to populate HFC. The development of such fast and robust techniques also addresses the needs of the Space Weather community in terms of near real-time monitoring capabilities. Title: Active Regions and the Global Magnetic Field of the Sun Authors: Higgins, P. A.; Bloomfield, D. S.; Gallagher, P. T. Bibcode: 2011AGUFMSH43B1940H Altcode: The Sun follows an 11 year activity cycle, over which the global magnetic field begins highly dipolar, and becomes more complex at cycle maximum, until reverting back to a dipole state, but with reversed polarity. Many magnetic structures of varying complexity (active regions) are observed to emerge, evolve, and decay over the cycle. Beyond location and orientation, the dependence of active region magnetic properties on the phase of the solar cycle is not well known. Here, we use automated feature detection methods to detect and characterize thousands of active region detections and statistically investigate their physical properties. We find that the mean size and flux of magnetic features on the solar disk is dependent on the phase of the cycle. We establish a direct connection between the spatial distribution of active regions on the solar disk and the configuration of the global solar magnetic field by investigating the polarity imbalance of feature magnetic flux. Using a global potential field source surface model, we find that the shape of the global field is strongly dependent on the large scale distribution of imbalanced flux. Title: Propagation of Coronal Mass Ejections in 3D and the Structure of the Inner Heliosphere Authors: Gallagher, P. T.; Byrne, J. P.; Maloney, S. A.; McAteer, J. Bibcode: 2011AGUFMSH34C..02G Altcode: Solar coronal mass ejections (CMEs) are the most significant drivers of adverse space weather on Earth, but the physics governing their propagation through the heliosphere is not well understood. Although stereoscopic imaging of CMEs with NASA's Solar Terrestrial Relations Observatory (STEREO) has provided some insight into their three-dimensional (3D) propagation, the mechanisms governing their evolution remain unclear because of difficulties in reconstructing their true 3D structure. In this talk I will describe the use of an elliptical tie-pointing technique to reconstruct a CME front in 3D, enabling us to quantify its deflected trajectory from high latitudes along the ecliptic, and measure its increasing angular width and propagation. At large distances from the Sun (>7 R_sun), I will describe how its motion is determined by drag effects in the solar wind, using ENLIL simulations of the inner heliosphere. By combining a 3D reconstruction with modelling of the solar wind, we predict an arrival time within 30 mins of the in-situ detection of the CME at ACE Title: The Wave Properties of Coronal Bright Fronts Observed Using SDO/AIA Authors: Long, David M.; DeLuca, Edward E.; Gallagher, Peter T. Bibcode: 2011ApJ...741L..21L Altcode: 2011arXiv1109.5897L Coronal bright fronts (CBFs) are large-scale wavefronts that propagate through the solar corona at hundreds of kilometers per second. While their kinematics have been studied in detail, many questions remain regarding the temporal evolution of their amplitude and pulse width. Here, contemporaneous high cadence, multi-thermal observations of the solar corona from the Solar Dynamic Observatory (SDO) and Solar TErrestrial RElations Observatory (STEREO) spacecraft are used to determine the kinematics and expansion rate of a CBF wavefront observed on 2010 August 14. The CBF was found to have a lower initial velocity with weaker deceleration in STEREO observations compared to SDO observations (~340 km s-1 and -72 m s-2 as opposed to ~410 km s-1 and -279 m s-2). The CBF kinematics from SDO were found to be highly passband-dependent, with an initial velocity ranging from 379 ± 12 km s-1 to 460 ± 28 km s-1 and acceleration ranging from -128 ± 28 m s-2 to -431 ± 86 m s-2 in the 335 Å and 304 Å passbands, respectively. These kinematics were used to estimate a quiet coronal magnetic field strength range of ~1-2 G. Significant pulse broadening was also observed, with expansion rates of ~130 km s-1 (STEREO) and ~220 km s-1 (SDO). By treating the CBF as a linear superposition of sinusoidal waves within a Gaussian envelope, the resulting dispersion rate of the pulse was found to be ~8-13 Mm2 s-1. These results are indicative of a fast-mode magnetoacoustic wave pulse propagating through an inhomogeneous medium. Title: An Observational Overview of Solar Flares Authors: Fletcher, L.; Dennis, B. R.; Hudson, H. S.; Krucker, S.; Phillips, K.; Veronig, A.; Battaglia, M.; Bone, L.; Caspi, A.; Chen, Q.; Gallagher, P.; Grigis, P. T.; Ji, H.; Liu, W.; Milligan, R. O.; Temmer, M. Bibcode: 2011SSRv..159...19F Altcode: 2011SSRv..tmp..261F; 2011arXiv1109.5932F We present an overview of solar flares and associated phenomena, drawing upon a wide range of observational data primarily from the RHESSI era. Following an introductory discussion and overview of the status of observational capabilities, the article is split into topical sections which deal with different areas of flare phenomena (footpoints and ribbons, coronal sources, relationship to coronal mass ejections) and their interconnections. We also discuss flare soft X-ray spectroscopy and the energetics of the process. The emphasis is to describe the observations from multiple points of view, while bearing in mind the models that link them to each other and to theory. The present theoretical and observational understanding of solar flares is far from complete, so we conclude with a brief discussion of models, and a list of missing but important observations. Title: STEREO Direct Imaging of a Coronal Mass Ejection-driven Shock to 0.5 AU Authors: Maloney, Shane A.; Gallagher, Peter T. Bibcode: 2011ApJ...736L...5M Altcode: 2011arXiv1106.1593M Fast coronal mass ejections (CMEs) generate standing or bow shocks as they propagate through the corona and solar wind. Although CME shocks have previously been detected indirectly via their emission at radio frequencies, direct imaging has remained elusive due to their low contrast at optical wavelengths. Here we report the first images of a CME-driven shock as it propagates through interplanetary space from 8 R sun to 120 R sun (0.5 AU), using observations from the STEREO Heliospheric Imager. The CME was measured to have a velocity of ~1000 km s-1 and a Mach number of 4.1 ± 1.2, while the shock front standoff distance (Δ) was found to increase linearly to ~20 R sun at 0.5 AU. The normalized standoff distance (Δ/DO ) showed reasonable agreement with semi-empirical relations, where DO is the CME radius. However, when normalized using the radius of curvature, Δ/RO did not agree well with theory, implying that RO was underestimated by a factor of ≈3-8. This is most likely due to the difficulty in estimating the larger radius of curvature along the CME axis from the observations, which provide only a cross-sectional view of the CME. Title: Deceleration and dispersion of large-scale coronal bright fronts Authors: Long, D. M.; Gallagher, P. T.; McAteer, R. T. J.; Bloomfield, D. S. Bibcode: 2011A&A...531A..42L Altcode: 2011arXiv1104.4334L Context. One of the most dramatic manifestations of solar activity are large-scale coronal bright fronts (CBFs) observed in extreme ultraviolet (EUV) images of the solar atmosphere. To date, the energetics and kinematics of CBFs remain poorly understood, due to the low image cadence and sensitivity of previous EUV imagers and the limited methods used to extract the features.
Aims: In this paper, the trajectory and morphology of CBFs was determined in order to investigate the varying properties of a sample of CBFs, including their kinematics and pulse shape, dispersion, and dissipation.
Methods: We have developed a semi-automatic intensity profiling technique to extract the morphology and accurate positions of CBFs in 2.5-10 min cadence images from STEREO/EUVI. The technique was applied to sequences of 171 Å and 195 Å images from STEREO/EUVI in order to measure the wave properties of four separate CBF events.
Results: Following launch at velocities of ~240-450 km s-1 each of the four events studied showed significant negative acceleration ranging from ~-290 to -60 m s-2. The CBF spatial and temporal widths were found to increase from ~50 Mm to ~200 Mm and ~100 s to ~1500 s respectively, suggesting that they are dispersive in nature. The variation in position-angle averaged pulse-integrated intensity with propagation shows no clear trend across the four events studied. These results are most consistent with CBFs being dispersive magnetoacoustic waves.

Figures 3-8, 10, 11, 13-15, 17, 18 and the movie are available in electronic form at http://www.aanda.org Title: Large-scale Bright Fronts in the Solar Corona: A Review of "EIT waves" Authors: Gallagher, Peter T.; Long, David M. Bibcode: 2011SSRv..158..365G Altcode: 2010SSRv..tmp..184G; 2010arXiv1006.0140G "EIT waves" are large-scale coronal bright fronts (CBFs) that were first observed in 195 Å images obtained using the Extreme-ultraviolet Imaging Telescope (EIT) onboard the Solar and Heliospheric Observatory ( SOHO). Commonly called "EIT waves", CBFs typically appear as diffuse fronts that propagate pseudo-radially across the solar disk at velocities of 100-700 km s-1 with front widths of 50-100 Mm. As their speed is greater than the quiet coronal sound speed ( c s ≤200 km s-1) and comparable to the local Alfvén speed ( v A ≤1000 km s-1), they were initially interpreted as fast-mode magnetoacoustic waves (vf=(cs2 + vA2)^{1/2}). Their propagation is now known to be modified by regions where the magnetosonic sound speed varies, such as active regions and coronal holes, but there is also evidence for stationary CBFs at coronal hole boundaries. The latter has led to the suggestion that they may be a manifestation of a processes such as Joule heating or magnetic reconnection, rather than a wave-related phenomena. While the general morphological and kinematic properties of CBFs and their association with coronal mass ejections have now been well described, there are many questions regarding their excitation and propagation. In particular, the theoretical interpretation of these enigmatic events as magnetohydrodynamic waves or due to changes in magnetic topology remains the topic of much debate. Title: The Evolution and Space Weather Effects of Solar Coronal Holes Authors: Krista, Larisza Diana; Gallagher, Peter T. Bibcode: 2011shin.confE.163K Altcode: As solar activity is the foremost important aspect of space weather, the forecasting of flare and CME related transient geomagnetic storms has become a primary initiative. Minor magnetic storms caused by coronal holes (CHs) have also proven to be important due to their long-lasting and recurrent geomagnetic effects. In order to forecast CH related geomagnetic storms, the author developed the Coronal Hole Automated Recognition and Monitoring (CHARM) algorithm to replace the user-dependent CH detection methods commonly used. CHARM uses an intensity thresholding method to identify low intensity regions in EUV or X-ray images. Since CHs are regions of 'open' magnetic field and predominant polarity, magnetograms were used to differentiate CHs from other low intensity regions. The Coronal Hole Evolution (CHEVOL) algorithm was developed and used in conjunction with CHARM to study the boundary evolution of CHs. It is widely accepted that the short-term changes in CH boundaries are due to the interchange reconnection between the CH open field lines and small loops. We determined the magnetic reconnection rate and the diffusion coefficient at CH boundaries in order to test the interchange reconnection model. The author also developed the Minor Storm (MIST) package to link CHs to high-speed solar wind (HSSW) periods detected at Earth. Using the algorithm the relationship between CHs, the corresponding HSSW properties, and geomagnetic indices were studied between 2000-2009. The results showed a strong correlation between the velocity and HSSW proton plasma temperature, which indicates that the heating and acceleration of the solar wind plasma in CHs are closely related, and perhaps caused by the same mechanism. The research presented here includes analysis of CHs on small and large spatial/temporal scales, allowing us to further our understanding of CHs as a whole. Title: Solar magnetic feature detection and tracking for space weather monitoring Authors: Higgins, P. A.; Gallagher, P. T.; McAteer, R. T. J.; Bloomfield, D. S. Bibcode: 2011AdSpR..47.2105H Altcode: 2010arXiv1006.5898H We present an automated system for detecting, tracking, and cataloging emerging active regions throughout their evolution and decay using SOHO Michelson Doppler Interferometer (MDI) magnetograms. The SolarMonitor Active Region Tracking (SMART) algorithm relies on consecutive image differencing to remove both quiet-Sun and transient magnetic features, and region-growing techniques to group flux concentrations into classifiable features. We determine magnetic properties such as region size, total flux, flux imbalance, flux emergence rate, Schrijver’s R-value, R∗ (a modified version of R), and Falconer’s measurement of non-potentiality. A persistence algorithm is used to associate developed active regions with emerging flux regions in previous measurements, and to track regions beyond the limb through multiple solar rotations. We find that the total number and area of magnetic regions on disk vary with the sunspot cycle. While sunspot numbers are a proxy to the solar magnetic field, SMART offers a direct diagnostic of the surface magnetic field and its variation over timescale of hours to years. SMART will form the basis of the active region extraction and tracking algorithm for the Heliophysics Integrated Observatory (HELIO). Title: HELIO: The Heliophysics Integrated Observatory Authors: Bentley, R. D.; Csillaghy, A.; Aboudarham, J.; Jacquey, C.; Hapgood, M. A.; Bocchialini, K.; Messerotti, M.; Brooke, J.; Gallagher, P.; Fox, P.; Hurlburt, N.; Roberts, D. A.; Duarte, L. Sanchez Bibcode: 2011AdSpR..47.2235B Altcode: Heliophysics is a new research field that explores the Sun-Solar System Connection; it requires the joint exploitation of solar, heliospheric, magnetospheric and ionospheric observations.HELIO, the Heliophysics Integrated Observatory, will facilitate this study by creating an integrated e-Infrastructure that has no equivalent anywhere else. It will be a key component of a worldwide effort to integrate heliophysics data and will coordinate closely with international organizations to exploit synergies with complementary domains.HELIO was proposed under a Research Infrastructure call in the Capacities Programme of the European Commission’s 7th Framework Programme (FP7). The project was selected for negotiation in January 2009; following a successful conclusion to these, the project started on 1 June 2009 and will last for 36 months. Title: Coronal mass ejection detection using wavelets, curvelets and ridgelets: Applications for space weather monitoring Authors: Gallagher, P. T.; Young, C. A.; Byrne, J. P.; McAteer, R. T. J. Bibcode: 2011AdSpR..47.2118G Altcode: 2010arXiv1012.1901G Coronal mass ejections (CMEs) are large-scale eruptions of plasma and magnetic field that can produce adverse space weather at Earth and other locations in the Heliosphere. Due to the intrinsic multiscale nature of features in coronagraph images, wavelet and multiscale image processing techniques are well suited to enhancing the visibility of CMEs and suppressing noise. However, wavelets are better suited to identifying point-like features, such as noise or background stars, than to enhancing the visibility of the curved form of a typical CME front. Higher order multiscale techniques, such as ridgelets and curvelets, were therefore explored to characterise the morphology (width, curvature) and kinematics (position, velocity, acceleration) of CMEs. Curvelets in particular were found to be well suited to characterising CME properties in a self-consistent manner. Curvelets are thus likely to be of benefit to autonomous monitoring of CME properties for space weather applications. Title: The Evolution and Space Weather Effects of Solar Coronal Holes Authors: Krista, Larisza; Gallagher, P. Bibcode: 2011SPD....42.0705K Altcode: 2011BAAS..43S.0705K As solar activity is the foremost important aspect of space weather, the forecasting of flare and CME related transient geomagnetic storms has become a primary initiative. Minor magnetic storms caused by coronal holes (CHs) have also proven to be important due to their long-lasting and recurrent geomagnetic effects. In order to forecast CH related geomagnetic storms, the author developed the Coronal Hole Automated Recognition and Monitoring (CHARM) algorithm to replace the user-dependent CH detection methods commonly used. CHARM uses an intensity thresholding method to identify low intensity regions in EUV or X-ray images. Since CHs are regions of "open” magnetic field and predominant polarity, magnetograms were used to differentiate CHs from other low intensity regions. The Coronal Hole Evolution (CHEVOL) algorithm was developed and used in conjunction with CHARM to study the boundary evolution of CHs. It is widely accepted that the short-term changes in CH boundaries are due to the interchange reconnection between the CH open field lines and small loops. We determined the magnetic reconnection rate and the diffusion coefficient at CH boundaries in order to test the interchange reconnection model. The author also developed the Minor Storm (MIST) package to link CHs to high-speed solar wind (HSSW) periods detected at Earth. Using the algorithm the relationship between CHs, the corresponding HSSW properties, and geomagnetic indices were studied between 2000-2009. The results showed a strong correlation between the velocity and HSSW proton plasma temperature, which indicates that the heating and acceleration of the solar wind plasma in CHs are closely related, and perhaps caused by the same mechanism. The research presented here includes analysis of CHs on small and large spatial/temporal scales, allowing us to further our understanding of CHs as a whole. Title: Wavefront Expansion and Dispersion of Coronal Bright Fronts Authors: Long, David; DeLuca, E.; Gallagher, P. Bibcode: 2011SPD....42.0505L Altcode: 2011BAAS..43S.0505L The true nature of Coronal Bright Fronts (CBFs; commonly called "EIT Waves") remains enigmatic despite more than ten years of research. High cadence contemporaneous observations from the Solar Dynamic Observatory (SDO) and Solar TErrestrial RElations Observatory (STEREO) spacecraft are used here to determine the kinematics and dispersion of a CBF pulse observed on 2010 August 14. The CBF exhibited clear deceleration with propagation, with lower initial velocity and weaker deceleration in STEREO observations compared to SDO. The kinematics of the CBF were found to be highly passband dependent, with the pulse exhibiting higher initial velocity and stronger deceleration in cooler passbands. Significant pulse broadening was also measured using both STEREO ( 55 km/s) andSDO ( 65 km/s) observations. The dispersion rate of the pulse was derived by modeling the CBF as a linear superposition of sinusoidal waves within a Gaussian envelope. These results imply that the observed CBF is a fast-mode magnetoacoustic wave, and allowed the quiet coronal magnetic field strength to be estimated at 1-2 G. Title: Short-term Evolution of Coronal Hole Boundaries Authors: Krista, Larisza D.; Gallagher, Peter T.; Bloomfield, D. Shaun Bibcode: 2011ApJ...731L..26K Altcode: 2011arXiv1103.2660K The interaction of open and closed field lines at coronal hole (CH) boundaries is widely accepted to be due to interchange magnetic reconnection. To date, it is unclear how the boundaries vary on short timescales and at what velocity this occurs. Here, we describe an automated boundary tracking method used to determine CH boundary displacements on short timescales. The boundary displacements were found to be isotropic and to have typical expansion/contraction speeds of <=2 km s-1, which indicate magnetic reconnection rates of <=3 × 10-3. The observed displacements were used in conjunction with the interchange reconnection model to derive typical diffusion coefficients of <=3 × 1013 cm2 s-1. These results are consistent with an interchange reconnection process in the low corona driven by the random granular motions of open and closed fields in the photosphere. Title: Automated Solar Feature Detection for Space Weather Applications Authors: Pérez-Suárez, David; Higgins, Paul A.; Bloomfield, D. Shaun; McAteer, R. T. James; Krista, Larisza D.; Byrne, Jason P.; Gallagher, Peter. T. Bibcode: 2011asip.book..207P Altcode: 2011arXiv1109.6922P The solar surface and atmosphere are highly dynamic plasma environments, which evolve over a wide range of temporal and spatial scales. Large-scale eruptions, such as coronal mass ejections, can be accelerated to millions of kilometres per hour in a matter of minutes, making their automated detection and characterisation challenging. Additionally, there are numerous faint solar features, such as coronal holes and coronal dimmings, which are important for space weather monitoring and forecasting, but their low intensity and sometimes transient nature makes them problematic to detect using traditional image processing techniques. These difficulties are compounded by advances in ground- and space- based instrumentation, which have increased the volume of data that solar physicists are confronted with on a minute-by-minute basis; NASA's Solar Dynamics Observatory for example is returning many thousands of images per hour (~1.5 TB/day). This chapter reviews recent advances in the application of images processing techniques to the automated detection of active regions, coronal holes, filaments, CMEs, and coronal dimmings for the purposes of space weather monitoring and prediction. Title: A Bayesian approach to comparing theoretic models to observational data: A case study from solar flare physics Authors: Adamakis, S.; Raftery, C. L.; Walsh, R. W.; Gallagher, P. T. Bibcode: 2011arXiv1102.0242A Altcode: Solar flares are large-scale releases of energy in the solar atmosphere, which are characterised by rapid changes in the hydrodynamic properties of plasma from the photosphere to the corona. Solar physicists have typically attempted to understand these complex events using a combination of theoretical models and observational data. From a statistical perspective, there are many challenges associated with making accurate and statistically significant comparisons between theory and observations, due primarily to the large number of free parameters associated with physical models. This class of ill-posed statistical problem is ideally suited to Bayesian methods. In this paper, the solar flare studied by Raftery et al. (2009) is reanalysed using a Bayesian framework. This enables us to study the evolution of the flare's temperature, emission measure and energy loss in a statistically self-consistent manner. The Bayesian-based model selection techniques imply that no decision can be made regarding which of the conductive or non-thermal beam heating play the most important role in heating the flare plasma during the impulsive phase of this event. Title: The Solar Cycle Dependence of Active Region Properties Authors: Higgins, P.; Gallagher, P. T.; Bloomfield, D. Bibcode: 2010AGUFMSH53B..01H Altcode: The solar cycle dependence of global active region (AR) emergence and dynamics is analysed using the SolarMonitor Active Region Tracker (SMART), which automatically detects and characterises magnetic flux concentrations using full-disk magnetograms. SMART is run on a magnetogram data set ranging from 1997 to 2009, resulting in measurements of each AR on disk each day. AR properties such as heliographic location, orientation, magnetic flux, flux imbalance, Schrijver's R value, Falconer's WLSG proxy for non-potentiality, and flare productivity are compared over cycle 23. We find several solar cycle modulations in the globally summed AR flux which may help to characterize the subsurface solar dynamo as well as global magnetic flux transport. The global flare index is better correlated to the global R value than WLSG or magnetic flux. Also, the emergence of highly non-potential, flare-productive ARs is found to be more confined in latitude than ARs in general, with little dependence on the phase of the solar cycle. Title: Solar Wind Drag and the Kinematics of Interplanetary Coronal Mass Ejections Authors: Maloney, Shane A.; Gallagher, Peter T. Bibcode: 2010ApJ...724L.127M Altcode: 2010arXiv1010.0192M Coronal mass ejections (CMEs) are large-scale ejections of plasma and magnetic field from the solar corona, which propagate through interplanetary space at velocities of ~100-2500 km s-1. Although plane-of-sky coronagraph measurements have provided some insight into their kinematics near the Sun (<32 R sun), it is still unclear what forces govern their evolution during both their early acceleration and later propagation. Here, we use the dual perspectives of the STEREO spacecraft to derive the three-dimensional kinematics of CMEs over a range of heliocentric distances (~2-250 R sun). We find evidence for solar wind (SW) drag forces acting in interplanetary space, with a fast CME decelerated and a slow CME accelerated toward typical SW velocities. We also find that the fast CME showed linear (δ = 1) dependence on the velocity difference between the CME and the SW, while the slow CME showed a quadratic (δ = 2) dependence. The differing forms of drag for the two CMEs indicate the forces responsible for their acceleration may be different. Title: Observations of Coronal Bright Fronts using SDO/AIA Authors: Long, D.; Deluca, E. E.; Gallagher, P. T. Bibcode: 2010AGUFMSH23A1825L Altcode: Coronal bright fronts (CBFs; commonly called ``EIT waves'') have been studied in detail for over ten years but remain a source of much debate. We present the first observations of a CBF using the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamic Observatory (SDO). An intensity profiling technique is used to automatically identify the position of the CBF. The resulting kinematics of the pulse are studied in detail, with the CBF exhibiting clear deceleration with propagation. The multi-wavelength capabilities of SDO/AIA are also used to examine the CBF across multiple passbands. The CBF is evident in both the 193 and 211~Å passbands, with the 171~Å passband showing no clear CBF signal in contrast to previous observations from other space-based instruments. Comparing these results with similar observations from STEREO/EUVI, we suggest that CBFs may best be approximated as freely-propagating magneto-acoustic waves. Title: Quantifying the Evolving Magnetic Structure of Active Regions Authors: Conlon, Paul A.; McAteer, R. T. James; Gallagher, Peter T.; Fennell, Linda Bibcode: 2010ApJ...722..577C Altcode: The topical and controversial issue of parameterizing the magnetic structure of solar active regions has vital implications in the understanding of how these structures form, evolve, produce solar flares, and decay. This interdisciplinary and ill-constrained problem of quantifying complexity is addressed by using a two-dimensional wavelet transform modulus maxima (WTMM) method to study the multifractal properties of active region photospheric magnetic fields. The WTMM method provides an adaptive space-scale partition of a fractal distribution, from which one can extract the multifractal spectra. The use of a novel segmentation procedure allows us to remove the quiet Sun component and reliably study the evolution of active region multifractal parameters. It is shown that prior to the onset of solar flares, the magnetic field undergoes restructuring as Dirac-like features (with a Hölder exponent, h = -1) coalesce to form step functions (where h = 0). The resulting configuration has a higher concentration of gradients along neutral line features. We propose that when sufficient flux is present in an active region for a period of time, it must be structured with a fractal dimension greater than 1.2, and a Hölder exponent greater than -0.7, in order to produce M- and X-class flares. This result has immediate applications in the study of the underlying physics of active region evolution and space weather forecasting. Title: Evidence for Internal Tether-cutting in a Flare/Coronal Mass Ejection Observed by MESSENGER, RHESSI, and STEREO Authors: Raftery, Claire L.; Gallagher, Peter T.; McAteer, R. T. James; Lin, Chia-Hsien; Delahunt, Gareth Bibcode: 2010ApJ...721.1579R Altcode: The relationship between eruptive flares and coronal mass ejections (CMEs) is a topic of ongoing debate, especially regarding the possibility of a common initiation mechanism. We studied the kinematic and hydrodynamic properties of a well-observed event that occurred on 2007 December 31 using data from MESSENGER, RHESSI, and STEREO in order to gain new physical insight into the evolution of the flare and CME. The initiation mechanism was determined by comparing observations to the internal tether-cutting, breakout, and ideal magnetohydrodynamic (MHD) models. Evidence of pre-eruption reconnection immediately eliminated the ideal MHD model. The timing and location of the soft and hard X-ray sources led to the conclusion that the event was initiated by the internal tether-cutting mechanism. In addition, a thermal source was observed to move in a downward direction during the impulsive phase of the event, followed by upward motion during the decay phase, providing evidence for X- to Y-type magnetic reconnection. Title: Propagation of an Earth-directed coronal mass ejection in three dimensions Authors: Byrne, Jason P.; Maloney, Shane A.; McAteer, R. T. James; Refojo, Jose M.; Gallagher, Peter T. Bibcode: 2010NatCo...1...74B Altcode: 2010NatCo...1E..74B; 2010arXiv1010.0643B Solar coronal mass ejections (CMEs) are the most significant drivers of adverse space weather on Earth, but the physics governing their propagation through the heliosphere is not well understood. Although stereoscopic imaging of CMEs with NASA's Solar Terrestrial Relations Observatory (STEREO) has provided some insight into their three-dimensional (3D) propagation, the mechanisms governing their evolution remain unclear because of difficulties in reconstructing their true 3D structure. In this paper, we use a new elliptical tie-pointing technique to reconstruct a full CME front in 3D, enabling us to quantify its deflected trajectory from high latitudes along the ecliptic, and measure its increasing angular width and propagation from 2 to 46 (~0.2 AU). Beyond 7 , we show that its motion is determined by an aerodynamic drag in the solar wind and, using our reconstruction as input for a 3D magnetohydrodynamic simulation, we determine an accurate arrival time at the Lagrangian L1 point near Earth. Title: Characterizing complexity in solar magnetogram data using a wavelet-based segmentation method Authors: Kestener, Pierre; Khalil, André; Arneodo, Alain; Conlon, P.; McAteer, J.; Gallagher, P. Bibcode: 2010ada..confE..24K Altcode: 2010arXiv1005.1536K The multifractal nature of solar photospheric magnetic structures are studied using the 2D wavelet transform modulus maxima (WTMM) method. This relies on computing partition functions from the wavelet transform skeleton defined by the WTMM method. This skeleton provides an adaptive space-scale partition of the fractal distribution under study, from which one can extract the multifractal singularity spectrum. We describe the implementation of a multiscale image processing segmentation procedure based on the partitioning of the WT skeleton which allows the disentangling of the information concerning the multifractal properties of active regions from the surrounding quiet-Sun field. The quiet Sun exhibits a average Hölder exponent $\sim -0.75$, with observed multifractal properties due to the supergranular structure. On the other hand, active region multifractal spectra exhibit an average Hölder exponent $\sim 0.38$ similar to those found when studying experimental data from turbulent flows. Title: Characterizing Complexity in Solar Magnetogram Data Using a Wavelet-based Segmentation Method Authors: Kestener, P.; Conlon, P. A.; Khalil, A.; Fennell, L.; McAteer, R. T. J.; Gallagher, P. T.; Arneodo, A. Bibcode: 2010ApJ...717..995K Altcode: The multifractal nature of solar photospheric magnetic structures is studied using the two-dimensional wavelet transform modulus maxima (WTMM) method. This relies on computing partition functions from the wavelet transform skeleton defined by the WTMM method. This skeleton provides an adaptive space-scale partition of the fractal distribution under study, from which one can extract the multifractal singularity spectrum. We describe the implementation of a multiscale image processing segmentation procedure based on the partitioning of the WT skeleton, which allows the disentangling of the information concerning the multifractal properties of active regions from the surrounding quiet-Sun field. The quiet Sun exhibits an average Hölder exponent ~-0.75, with observed multifractal properties due to the supergranular structure. On the other hand, active region multifractal spectra exhibit an average Hölder exponent ~0.38, similar to those found when studying experimental data from turbulent flows. Title: Investigating the driving mechanisms of coronal mass ejections Authors: Lin, C. -H.; Gallagher, P. T.; Raftery, C. L. Bibcode: 2010A&A...516A..44L Altcode: 2010arXiv1003.5035L
Aims: The objective of this study was to examine the kinematics of coronal mass ejections (CMEs) using EUV and coronagraph images, and to make a quantitative comparison with a number of theoretical models. One particular aim was to investigate the acceleration profile of CMEs in the low corona.
Methods: We selected two CME events for this study, which occurred on 2006 December 17 (CME06) and 2007 December 31 (CME07). CME06 was observed using the EIT and LASCO instruments on-board SOHO, while CME07 was observed using the SECCHI imaging suite on STEREO. The first step of the analysis was to track the motion of each CME front and derive its velocity and acceleration. We then compared the observational kinematics, along with the information of the associated X-ray emissions from GOES and RHESSI, with the kinematics proposed by three CME models (catastrophe, breakout and toroidal instability).
Results: We found that CME06 lasted over eight hours while CME07 released its energy in less than three hours. After the eruption, both CMEs were briefly slowed down before being accelerated again. The peak accelerations during the re-acceleration phase coincided with the peak soft X-ray emissions for both CMEs. Their values were ~60 m s-2 for CME06 and ~600 m s-2 for CME07. CME07 reached a maximum speed of over 1000 km s-1 before being slowed down to propagate away at a constant, final speed of ~700 km s-1. CME06 did not reach a constant speed but was moving at a small acceleration by the end of the observation. Our comparison with the theories suggested that CME06 can be best described by a hybrid of the catastrophe model and breakout model while the characteristics of CME07 were most consistent with the breakout model. Based on the catastrophe model, we deduced that the reconnection rate in the current sheet for CME06 was intermediate, the onset of its eruption occurred at a height of ~200 Mm, and the Alfvén speed and the magnetic field strength at this height were approximately 130-250 km s-1 and 7 Gauss, respectively. Title: Propagation of an Earth-Directed Coronal Mass Ejection in 3D Authors: Byrne, Jason; Gallagher, P. T.; Maloney, S. A.; McAteer, J. Bibcode: 2010AAS...21631405B Altcode: 2010BAAS...41..894B We have developed a new method to reconstruct the 3D evolution of a CME front using the Sun Earth Connection Coronal and Heliospheric Investigation (SECCHI) onboard the Solar Terrestrial Relations Observatory (STEREO). On 12 December 2008 an Earth-directed CME was observed by STEREO while the spacecraft were in near quadrature at 86.7 degrees separation. This positioning presents an ideal case for observing its propagation through the combined SECCHI instrument fields-of-view and applying our technique to reconstruct the CME front in 3D. The reconstruction allows us to determine the true CME front kinematics and morphology, and we measure three important dynamic effects at play: deflection from a high latitude source region; an increasing angular width; and interplanetary drag. Title: Turbulence, complexity, and solar flares Authors: McAteer, R. T. James; Gallagher, Peter T.; Conlon, Paul A. Bibcode: 2010AdSpR..45.1067M Altcode: 2009arXiv0909.5636M The issue of predicting solar flares is one of the most fundamental in physics, addressing issues of plasma physics, high-energy physics, and modelling of complex systems. It also poses societal consequences, with our ever-increasing need for accurate space weather forecasts. Solar flares arise naturally as a competition between an input (flux emergence and rearrangement) in the photosphere and an output (electrical current build up and resistive dissipation) in the corona. Although initially localised, this redistribution affects neighbouring regions and an avalanche occurs resulting in large scale eruptions of plasma, particles, and magnetic field. As flares are powered from the stressed field rooted in the photosphere, a study of the photospheric magnetic complexity can be used to both predict activity and understand the physics of the magnetic field. The magnetic energy spectrum and multifractal spectrum are highlighted as two possible approaches to this. Title: Evidence For Internal Tether-cutting in a Flare/CME Event. Authors: Raftery, Claire; Gallagher, P. T.; McAteer, R. T. J.; Lin, C. H.; Delahunt, G. Bibcode: 2010AAS...21631403R Altcode: 2010BAAS...41..894R The relationship between eruptive flares and CMEs is a topic of ongoing debate, especially regarding the possibility of a common initiation mechanism. In order to gain new physical insight into this problem, the kinematic and hydrodynamic properties of a well-observed event were studied using data from MESSENGER, RHESSI and STEREO/Secchi. These data were compared to three theoretical models to determine the event's initiation mechanism. The timing and positioning of EUV and X-ray sources along with evidence for pre-eruption particle acceleration led to the conclusion that the event was initiated by the internal tether-cutting mechanism and was followed by breakout reconnection some 10 minutes after launch. Title: A Method to Calculate Background-Subtracted Flare Plasma Parameters Using GOES Over Three Solar Cycles Authors: Ryan, Daniel; Gallagher, P. T.; Milligan, R. O.; Young, C. A. Bibcode: 2010AAS...21640436R Altcode: The GOES solar flare catalogue is the largest, self-consistent listing currently available covering three solar cycles - #21, 22, and 23 - from 1974 to the present. Solar X-ray flux integrated over the full solar disk is recorded every 3s in each of the two GOES channels (long; 1-8Å and short; 0.5-4Å). By taking the ratio of the flux in the two passbands, parameters of the SXR-emitting plasma (e.g. temperature, emission measure, radiative loss rate etc.) can be derived, as well as the timescales over which they change. In doing so, it is vital to perform a suitable background subtraction to remove the influence of flux not associated with the flaring plasma. Using the method outlined in Bornmann 1990, we have developed a technique to systematically derive the flare parameters for all GOES flares from 1980 to present after accounting for background emission. This then allows us to make statistically meaningful comparisons between events observed over the course of the past three solar cycles.

This research is generously funded by the Irish Research Council for Science, Engineering and Technology (IRCSET). Title: Constraining Three-Dimensional Magnetic Field Extrapolations Using the Twin Perspectives of STEREO Authors: Conlon, Paul A.; Gallagher, Peter T. Bibcode: 2010ApJ...715...59C Altcode: 2010arXiv1004.1330C The three-dimensional magnetic topology of a solar active region (NOAA 10956) was reconstructed using a linear force-free field extrapolation constrained using the twin perspectives of STEREO. A set of coronal field configurations was initially generated from extrapolations of the photospheric magnetic field observed by the Michelson Doppler Imager on SOHO. Using an EUV intensity-based cost function, the extrapolated field lines that were most consistent with 171 Å passband images from the Extreme UltraViolet Imager on STEREO were identified. This facilitated quantitative constraints to be placed on the twist (α) of the extrapolated field lines, where ∇ × B = αB. Using the constrained values of α, the evolution in time of twist, connectivity, and magnetic energy were then studied. A flux emergence event was found to result in significant changes in the magnetic topology and total magnetic energy of the region. Title: CME Kinematics and Dynamics Authors: Lin, C. -H.; Gallagher, P. T. Bibcode: 2010ASSP...19..530L Altcode: 2010mcia.conf..530L The goal of this study is to investigate the driving mechanisms of CMEs and to infer the magnetic field properties at the onset of the instability. We use EIT 195 Å images and LASCO white-light coronagraph data of a CME event that occurred on 17 December 2006. It was a long-duration event, and was associated with an occulted C2.1 class flare. To determine the driving mechanism, we quantitatively and qualitatively compared the observationally obtained kinematic evolution with that predicted by three CME models: the breakout model (BO, see Antiochos et al. 1999; Lynch et al. 2008; DeVore and Antiochos 2008), the catastrophe model (CM, see Priest and Forbes 2000), and the toroidal instability model (TI, see Chen 1989; Kliem and Török 2006). Our results indicate that this CME is best represented by the CM model. We infer that, at the onset of the instability, the Alfvén speed is approximately 120 km s-1 and the height of the flux rope is roughly 100-200Mm. These parameter values are related to the magnetic environment and the loop geometry and can be used to infer the magnetic condition at the onset of the eruption.We intend to submit the full analysis to A&A. Title: The propagation of a CME front in 3D Authors: Maloney, Shane; Byrne, Jason; Gallagher, Peter T.; McAteer, R. T. James Bibcode: 2010cosp...38.1867M Altcode: 2010cosp.meet.1867M We present a new three-dimensional (3D) reconstruction of an Earth-directed coronal mass ejec-tion (CME), providing new insight into the processes that control its evolution and propagation. Previously limited fields-of-view and single vantage point observations made it impossible to confidently describe CMEs in 3D. This uncertainty in a CME's position and geometry made comparison to theory difficult and hindered progress. Our 3D reconstruction unambiguously shows three effects at play on the CME: deflection from a high latitude source region, angular width expansion, and interplanetary drag. The CME undergoes a deflection of ∼20° degrees below 10 RSun and slowly tends towards the ecliptic throughout its subsequent propagation. We interpret this deflection as a direct result of the interplay between the CME and the drawn-out dipolar topology of the (solar minimum) coronal magnetic field. The increasing angular width is in excess of that due to simple spherical expansion in the diverging solar wind so an additional source of expansion must be present. The additional source is inferred to be a pressure gradient between the internal pressure (magnetic and gas) of the flux rope relative to the ambient solar wind pressure. Low in the corona there is rapid expansion due to a large pressure difference, but further out the CME approaches equilibrium with the solar wind, and the angular width tends to a constant. The 3D reconstruction allows us to accurately determine the CME kinematics, and we show unambiguously that the interplanetary acceleration is due to aerodynamic drag. Furthermore we derive parameters from our reconstruction that act as inputs to an ENLIL model of the CME's propagation to Earth. The results show the CME undergoes a significant degrease in velocity where it encounters a slow-speed solar wind stream ahead of it (>50 RSun ). This lower velocity agrees with the derived velocity from in-situ data at the L1 point and predicts the correct arrival time, to within minutes. In our ever-increasingly technological society, the accurate prediction of adverse space weather is of paramount impor-tance and to achieve this we must understand the basic processes that govern CMEs. Our 3D reconstruction has allowed us to gain some novel insights into these processes, and emphasises the dynamic interplay between CMEs and solar wind. Title: Using HELIO to study cross-disiplinary science problems using data from multiple spacecraft Authors: Bentley, Robert; Aboudarham, Jean; Messerotti, Mauro; Jacquey, Christian; Gallagher, Peter T.; Hapgood, Mike; Bocchialini, Karine Bibcode: 2010cosp...38.1917B Altcode: 2010cosp.meet.1917B The Heliophysics Integrated Observatory, HELIO, is creating a collaborative environment where scientists can discover, understand and model the connection between solar phenomena, inter-planetary disturbances and their effects on the planets. HELIO will provide integrated access to data from the solar, heliospheric, geophysics and plan-etary domains and allow the user to undertake a search for interesting events and phenomena based solely on metadata and data products. The HELIO infrastructure will provide services to support the search that can either be used independently or as part of a work flow. The services include event and feature catalogues derived from data from all the domains and a processing capability that will use models to relate observations made in different part of the solar system. We will describe how HELIO can be used to address science problems that span the domains by allowing the user to track phenomena as they propagate through the solar system and report on progress to date. HELIO is a research infrastructure funded under Capacities programme of the EC's 7th Frame-work Programme (FP7); the project started in June 2009 and has a duration of 36 months. The HELIO Consortium includes thirteen groups from the UK, France, Ireland, Italy, Switzerland, Spain and the US. Title: On the 3-D reconstruction of Coronal Mass Ejections using coronagraph data Authors: Mierla, M.; Inhester, B.; Antunes, A.; Boursier, Y.; Byrne, J. P.; Colaninno, R.; Davila, J.; de Koning, C. A.; Gallagher, P. T.; Gissot, S.; Howard, R. A.; Howard, T. A.; Kramar, M.; Lamy, P.; Liewer, P. C.; Maloney, S.; Marqué, C.; McAteer, R. T. J.; Moran, T.; Rodriguez, L.; Srivastava, N.; St. Cyr, O. C.; Stenborg, G.; Temmer, M.; Thernisien, A.; Vourlidas, A.; West, M. J.; Wood, B. E.; Zhukov, A. N. Bibcode: 2010AnGeo..28..203M Altcode: Coronal Mass ejections (CMEs) are enormous eruptions of magnetized plasma expelled from the Sun into the interplanetary space, over the course of hours to days. They can create major disturbances in the interplanetary medium and trigger severe magnetic storms when they collide with the Earth's magnetosphere. It is important to know their real speed, propagation direction and 3-D configuration in order to accurately predict their arrival time at the Earth. Using data from the SECCHI coronagraphs onboard the STEREO mission, which was launched in October 2006, we can infer the propagation direction and the 3-D structure of such events. In this review, we first describe different techniques that were used to model the 3-D configuration of CMEs in the coronagraph field of view (up to 15 R⊙). Then, we apply these techniques to different CMEs observed by various coronagraphs. A comparison of results obtained from the application of different reconstruction algorithms is presented and discussed. Title: Addressing Science Use Cases with HELIO Authors: Bentley, R. D.; Aboudarham, J.; Csillaghy, A.; Jacquey, C.; Hapgood, M. A.; Messerotti, M.; Gallagher, P.; Bocchialini, K.; Hurlburt, N. E.; Roberts, D.; Sanchez Duarte, L. Bibcode: 2009AGUFMSH54A..06B Altcode: The Heliophysics Integrated Observatory (HELIO) is a new VO project funded under the EC's Seventh Framework Programme (FP7). It includes thirteen partners scattered over six countries and is led by University College London. HELIO is designed to support the heliophysics community and is based on a Service Oriented Architecture. The services developed by and integrated into HELIO can be used to address a wide range of science problems; they can be used individually or as part of a work-flow driven search engine that can use a propagation (or other) model to help locate obervations that describe interesting phenomena. We will describe and discuss how the components of HELIO could be used to address science use cases, particularly how a user can adapt the work flow to their own science interests. Networking is one of the three Activities of the HELIO Integrated Infrastructure Initiatives (I3) project. Within this activity we plan to involve the community in all aspects of the design and testing of the HELIO system, including determining which data and metadata should be included, how the quality and content of metadata can be included, etc. We are investigating ways of making HELIO "domain-aware" so that researchers who are specialists in one of the communities that constitute heliophysics can easily identify, access and use data they need from the other communities. We will discuss how the community can help us develop this capability. Title: The SolarMonitor Active Region Tracking (SMART) Algorithm: Variation of magnetic feature properties through solar cycle 23 Authors: Higgins, P.; Gallagher, P.; McAteer, R.; Bloomfield, D. Bibcode: 2009AGUFMSH51B1278H Altcode: The SolarMonitor Active Region Tracking (SMART) algorithm is an automated system for detecting, tracking, and cataloging magnetic features throughout their evolution and decay. The SMART method will form the basis of active region extraction and tracking within the Heliophysics Integrated Observatory (HELIO). Magnetic properties such as total flux, flux imbalance, flux emergence rate, Schrijver's R-value, R* (a modified version of R), and Falconer's measurement of non-potentiality are determined for individual features throughout solar cycle 23. The variation of these feature property distributions with progression through the solar cycle is presented. Feature detections using the SMART algorithm for line-of-sight level 1.8 SOHO/MDI magnetogram taken 22 October 2003 at 12:47. Active region candidates are denoted "AR", emerging flux concentrations are denoted "EF", plage regions are denoted "PL" and other flux concentrations are labeled "NF". Title: Automated Coronal Hole Detection Using Local Intensity Thresholding Techniques Authors: Krista, Larisza D.; Gallagher, Peter T. Bibcode: 2009SoPh..256...87K Altcode: 2009arXiv0905.1814K We identify coronal holes using a histogram-based intensity thresholding technique and compare their properties to fast solar wind streams at three different points in the heliosphere. The thresholding technique was tested on EUV and X-ray images obtained using instruments onboard STEREO, SOHO and Hinode. The full-disk images were transformed into Lambert equal-area projection maps and partitioned into a series of overlapping sub-images from which local histograms were extracted. The histograms were used to determine the threshold for the low intensity regions, which were then classified as coronal holes or filaments using magnetograms from the SOHO/MDI. For all three instruments, the local thresholding algorithm was found to successfully determine coronal hole boundaries in a consistent manner. Coronal hole properties extracted using the segmentation algorithm were then compared with in situ measurements of the solar wind at ∼ 1 AU from ACE and STEREO. Our results indicate that flux tubes rooted in coronal holes expand super-radially within 1 AU and that larger (smaller) coronal holes result in longer (shorter) duration high-speed solar wind streams. Title: Reconstructing the 3-D Trajectories of CMEs in the Inner Heliosphere Authors: Maloney, Shane A.; Gallagher, Peter T.; McAteer, R. T. James Bibcode: 2009SoPh..256..149M Altcode: 2009arXiv0905.2153M A method for the full three-dimensional (3-D) reconstruction of the trajectories of coronal mass ejections (CMEs) using Solar TErrestrial RElations Observatory (STEREO) data is presented. Four CMEs that were simultaneously observed by the inner and outer coronagraphs (COR1 and 2) of the Ahead and Behind STEREO satellites were analysed. These observations were used to derive CME trajectories in 3-D out to ∼ 15 R⊙. The reconstructions using COR1/2 data support a radial propagation model. Assuming pseudo-radial propagation at large distances from the Sun (15 - 240 R⊙), the CME positions were extrapolated into the Heliospheric Imager (HI) field-of-view. We estimated the CME velocities in the different fields-of-view. It was found that CMEs slower than the solar wind were accelerated, while CMEs faster than the solar wind were decelerated, with both tending to the solar wind velocity. Title: The Flare-CME Connection Authors: Raftery, Claire; Gallagher, P. T.; Lin, C. Bibcode: 2009SPD....40.3701R Altcode: The connection between flares and CMEs has long been hypothesized and modelled. However, a full understanding of the processes at work remains ambiguous. A detailed study of the kinematical evolution of a CME was conducted using instruments on STEREO. Flare parameters, such as the motion of soft X-ray sources, imaged using RHESSI, and emission measure and plasma temperature measured from Mercury MESSENGER are presented in conjunction with the CME data to explain the evolution of the entire system. These results are then compared to a number of theoretical models to determine which of the many hypotheses are most probable for this event. CLR is supported by an SPD studentship and the ESA/Prodex grant administered by Enterprise Ireland. Title: Magnetic Fields, Flares & Forecasts Authors: Conlon, Paul A.; Kestener, P.; McAteer, R.; Gallagher, P. Bibcode: 2009SPD....40.1602C Altcode: A 2D wavelet transform modulus maxima (WTMM) method is used to characterise the complexity of the distribution of the photospheric magnetic field of active regions. The WTMM method offers increased accuracy and reliability over previous fractal and multifractal methods. The multifractal spectrum of both quiet Sun and active region magnetic features are presented. It is shown that the multifractal nature of the quiet Sun is significantly different from that of an active region. As such, a method is proposed to seperate the information corresponding to the multifractal spectrum of an active region from the surrounding quite Sun texture. The WTMM method and segmentation procedure are shown to detect the internal restructuring of active region magnetic features prior to flaring. We detect two thresholds (Haussdorf dimension > 1.2 and Holder Exponent > -0.7) as possible indicators for conditions favourable to flaring. Title: The Temperature Response of EUV Imagers Authors: Raftery, Claire; Bloomfield, D. Shaun; Gallagher, P. Bibcode: 2009SPD....40.1213R Altcode: The temperature response of an EUV imager provides the user with the temperature range over which the instrument or passband is sensitive. These response curves appear to be highly peaked, implying a narrow range of temperature sensitivity. However, in the past, these response functions have been calculated using quiet sun spectra or constant density, assumptions which are relevant only in specific circumstances. The multithermal response of the EUV imagers - TRACE, SOHO/EIT, STEREO/EUVI, PROBA2/SWAP and SDO/AIA were investigated. It was found that a highly peaked response curve is only appropriate when looking at cooler material. However, studying higher temperature emission from e.g. active regions and flares produces a very broad, almost flat response between 105 and 107 K for all instruments. CLR is supported by an SPD studentship and the ESA/Prodex grant administered by Enterprise Ireland. Title: The kinematics of coronal mass ejections using multiscale methods Authors: Byrne, J. P.; Gallagher, P. T.; McAteer, R. T. J.; Young, C. A. Bibcode: 2009A&A...495..325B Altcode: 2009arXiv0901.3392B Aims: The diffuse morphology and transient nature of coronal mass ejections (CMEs) make them difficult to identify and track using traditional image processing techniques. We apply multiscale methods to enhance the visibility of the faint CME front. This enables an ellipse characterisation to objectively study the changing morphology and kinematics of a sample of events imaged by the Large Angle Spectrometric Coronagraph (LASCO) onboard the Solar and Heliospheric Observatory (SOHO) and the Sun Earth Connection Coronal and Heliospheric Investigation (SECCHI) onboard the Solar Terrestrial Relations Observatory (STEREO). The accuracy of these methods allows us to test the CMEs for non-constant acceleration and expansion.
Methods: We exploit the multiscale nature of CMEs to extract structure with a multiscale decomposition, akin to a Canny edge detector. Spatio-temporal filtering highlights the CME front as it propagates in time. We apply an ellipse parameterisation of the front to extract the kinematics (height, velocity, acceleration) and changing morphology (width, orientation).
Results: The kinematic evolution of the CMEs discussed in this paper have been shown to differ from existing catalogues. These catalogues are based upon running-difference techniques that can lead to over-estimating CME heights. Our resulting kinematic curves are not well-fitted with the constant acceleration model. It is shown that some events have high acceleration below ~5 R⊙. Furthermore, we find that the CME angular widths measured by these catalogues are over-estimated, and indeed for some events our analysis shows non-constant CME expansion across the plane-of-sky. Title: Multi-wavelength observations and modelling of a canonical solar flare Authors: Raftery, C. L.; Gallagher, P. T.; Milligan, R. O.; Klimchuk, J. A. Bibcode: 2009A&A...494.1127R Altcode: 2008arXiv0812.0311R Aims: We investigate the temporal evolution of temperature, emission measure, energy loss, and velocity in a C-class solar flare from both observational and theoretical perspectives.
Methods: The properties of the flare were derived by following the systematic cooling of the plasma through the response functions of a number of instruments - the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI; >5 MK), GOES-12 (5-30 MK), the Transition Region and Coronal Explorer (TRACE 171 Å; 1 MK), and the Coronal Diagnostic Spectrometer (CDS; ~0.03-8 MK). These measurements were studied in combination with simulations from the 0-D enthalpy based thermal evolution of loops (EBTEL) model.
Results: At the flare onset, upflows of ~90 km s-1 and low-level emission were observed in Fe XIX, consistent with pre-flare heating and gentle chromospheric evaporation. During the impulsive phase, upflows of ~80 km s-1 in Fe XIX and simultaneous downflows of ~20 km s-1 in He I and O V were observed, indicating explosive chromospheric evaporation. The plasma was subsequently found to reach a peak temperature of ⪆13 MK in approximately 10 min. Using EBTEL, conduction was found to be the dominant loss mechanism during the initial ~300 s of the decay phase. It was also found to be responsible for driving gentle chromospheric evaporation during this period. As the temperature fell below ~8 MK, and for the next ~4000 s, radiative losses were determined to dominate over conductive losses. The radiative loss phase was accompanied by significant downflows of ≤40 km s-1 in O V.
Conclusions: This is the first extensive study of the evolution of a canonical solar flare using both spectroscopic and broad-band instruments in conjunction with a 0-D hydrodynamic model. While our results are in broad agreement with the standard flare model, the simulations suggest that both conductive and non-thermal beam heating play important roles in heating the flare plasma during the impulsive phase of at least this event. Title: Multiresolution Analysis of Active Region Magnetic Structure and its Correlation with the Mount Wilson Classification and Flaring Activity Authors: Ireland, J.; Young, C. A.; McAteer, R. T. J.; Whelan, C.; Hewett, R. J.; Gallagher, P. T. Bibcode: 2008SoPh..252..121I Altcode: 2008arXiv0805.0101I; 2008SoPh..tmp..134I Two different multiresolution analyses are used to decompose the structure of active-region magnetic flux into concentrations of different size scales. Lines separating these opposite polarity regions of flux at each size scale are found. These lines are used as a mask on a map of the magnetic field gradient to sample the local gradient between opposite polarity regions of given scale sizes. It is shown that the maximum, average, and standard deviation of the magnetic flux gradient for α,β,βγ, and βγδ active-regions increase in the order listed, and that the order is maintained over all length scales. Since magnetic flux gradient is strongly linked to active-region activity, such as flares, this study demonstrates that, on average, the Mt. Wilson classification encodes the notion of activity over all length scales in the active-region, and not just those length scales at which the strongest flux gradients are found. Further, it is also shown that the average gradients in the field, and the average length-scale at which they occur, also increase in the same order. Finally, there are significant differences in the gradient distribution, between flaring and non-flaring active regions, which are maintained over all length scales. It is also shown that the average gradient content of active-regions that have large flares (GOES class "M" and above) is larger than that for active regions containing flares of all flare sizes; this difference is also maintained at all length scales. All of the reported results are independent of the multiresolution transform used. The implications for the Mt. Wilson classification of active-regions in relation to the multiresolution gradient content and flaring activity are discussed. Title: IDL Object Oriented Software for Hinode/XRT Image Analysis Authors: Higgins, P. A.; Gallagher, P. T. Bibcode: 2008ASPC..397..171H Altcode: We have developed a set of object oriented IDL routines that enable users to search, download and analyse images from the X-Ray Telescope (XRT) on-board Hinode. In this paper, we give specific examples of how the object can be used and how multi-instrument data analysis can be performed. The XRT object is a highly versatile and powerful IDL object, which will prove to be a useful tool for solar researchers. This software utilizes the generic Framework object available within the GEN branch of SolarSoft. Title: Flare Cooling and Implications for Hinode/EIS Authors: Raftery, C. L.; Gallagher, P. T.; Milligan, R. O. Bibcode: 2008ASPC..397..184R Altcode: The cooling of a post-flare loop system as observed by TRACE and SOHO/CDS, SOHO/EIT, GOES and RHESSI is studied and compared to the predictions of recent solar flare models. The observed C-class flare cools from ≥ 10 MK to ∼ 0.25 MK in approximately 45 mins via conduction and radiation. Using theoretical modelling, conduction was found to dominate during the first 3 min of the decay phase, after which radiation became the dominant loss mechanism (∼ 30 min). We aim to study the flare cooling process using high resolution observations from Hinode/EIS. Title: Coronal Hole Identification and Characterisation Using Automated Image Processing Techniques Authors: Krista, L. D.; Gallagher, P. T. Bibcode: 2008ASPC..397..176K Altcode: We investigate the properties of coronal holes using a histogram-based intensity thresholding technique. The area and the coordinates of the centroid were determined for a coronal hole observed by SOHO/EIT and Hinode/XRT on 20-26 May 2007. This hole was also associated with a significant increase in the mean solar wind speed measured by ACE at L1. Title: Multiscale Characterization of Eruptive Events Authors: Byrne, J. P.; Young, C. A.; Gallagher, P. T.; McAteer, R. T. J. Bibcode: 2008ASPC..397..162B Altcode: Image processing plays an important role in the analysis of data from space-based instruments. With the large volumes of information currently available from missions such as Hinode and STEREO, our aim is to produce computationally fast methods for extracting features of interest (e.g. loops, filaments, waves and eruptions). Multiscale image processing methods enable us to study these features as a function of scale. Here we describe these methods, and use them to study the multiscale properties of a coronal mass ejection (CME) observed by SOHO/LASCO, and briefly discuss the implications for Hinode. Title: The Kinematics of a Globally Propagating Disturbance in the Solar Corona Authors: Long, David M.; Gallagher, Peter T.; McAteer, R. T. James; Bloomfield, D. Shaun Bibcode: 2008ApJ...680L..81L Altcode: 2008arXiv0805.2023L The kinematics of a globally propagating disturbance (also known as an "EIT wave") is discussed using Extreme UltraViolet Imager (EUVI) data from the Solar Terrestrial Relations Observatory (STEREO). We show for the first time that an impulsively generated propagating disturbance has similar kinematics in all four EUVI passbands (304, 171, 195, and 284 Å). In the 304 Å passband the disturbance shows a velocity peak of 238 ± 20 km s-1 within ~28 minutes of its launch, varying in acceleration from 76 to -102 m s-2. This passband contains a strong contribution from a Si XI line (303.32 Å) with a peak formation temperature of ~1.6 MK. The 304 Å emission may therefore be coronal rather than chromospheric in origin. Comparable velocities and accelerations are found in the coronal 195 Å passband, while lower values are found in the lower cadence 284 Å passband. In the higher cadence 171 Å passband the velocity varies significantly, peaking at 475 ± 47 km s-1 within ~20 minutes of launch, with a variation in acceleration from 816 to -413 m s-2. The high image cadence of the 171 Å passband (2.5 minutes compared to 10 minutes for the similar temperature response 195 Å passband) is found to have a major effect on the measured velocity and acceleration of the pulse, which increase by factors of ~2 and ~10, respectively. This implies that previously measured values (e.g., using EIT) may have been underestimated. We also note that the disturbance shows strong reflection from a coronal hole in both the 171 and 195 Å passbands. The observations are consistent with an impulsively generated fast-mode magnetoacoustic wave. Title: Automated Detection and Characterisation of Coronal Holes Authors: Krista, L. D.; Gallagher, P. T. Bibcode: 2008AGUSMSP51A..13K Altcode: We investigate the physical properties of coronal holes using a histogram-based intensity thresholding technique. The method was tested on coronal holes observed by the SOHO/EIT and the Hinode/XRT instruments. The full-disk images were first transformed using the Carrington projection, which has the effect of removing off-limb pixels and preserving coronal hole areas at high latitudes. The maps were then decomposed into a series of overlapping sub-images from which histograms were extracted. The sub-images containing only quiet-sun regions showed a unimodal distribution, while those containing part of a coronal hole as well as quite Sun regions had bimodal intensity distributions. The latter distributions were modelled as the sum of two frequency distributions, representing contributions from quiet-sun and coronal hole pixels. The local minimum between the two intensity distributions was then used to identify the boundary between coronal hole and quiet-sun regions. This model was tested on a large number of EIT (19.5nm) and Hinode/XRT images obtained in Jan-Feb 2008. For both instruments, the local thresholding algorithm was found to successfully determine coronal hole boundaries in a consistent manner. This therefore enabled us to investigate the relationship between coronal holes and the solar wind at 1AU during this sample period. Title: Multi-scale structure of active region magnetic fields correlated with flaring activity Authors: Ireland, J.; Young, C. A.; McAteer, R. J.; Whelan, C. M.; Hewett, R.; Gallagher, P. T. Bibcode: 2008AGUSMSH43B..03I Altcode: Two multi-scale analyses are used to decompose active region magnetic fields into objects of different size scales, allowing one to examine the structure of the active region field at different size scales. Lines separating opposite polarity groupings of flux at different size scales are found. It is shown that the magnetic field gradients for α, β, βγ, and βγδ active regions increases in the order listed, and that the order is maintained over all object size scales. Hence for a given Mt. Wilson classification, essentially the same field gradient information is present at all size scales, when compared to any other Mt. Wilson classification. It is also shown that on average, flaring and non-flaring active regions have a different field gradient content, and that the difference between the flaring and non-flaring active regions is size scale dependent. This suggests that the gradient distribution on smaller size scales is a better indicator of flaring activity when compared to larger size scales. Title: Hydrodynamics of Cooling Solar Flare Plasmas Authors: Raftery, C. L.; Gallagher, P. T.; Milligan, R. O. Bibcode: 2008AGUSMSP51C..17R Altcode: The temperature and emission measure evolution of a cooling post-flare arcade are investigated using images and spectra from the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI). This C-class flare, observed on 2006 December 17, occurred on the west limb and lasted approximately 8-hours. It is therefore ideally suited for studying how the temperature and emission measure change during a flare. Observable parameters such as temperature and emission measure are compared to theoretical hydrodynamic models to constrain parameters such as the direct and non-thermal heating. Comparing these results to those of a flare with decay time of approximately 1-hour highlights the energies required to sustain such a long duration event. The high time resolution of RHESSI combined with the long duration of the observations are ideal for making a detailed comparison with the predictions of theory. Title: Multiscale Analysis of Active Region Evolution Authors: Hewett, R. J.; Gallagher, P. T.; McAteer, R. T. J.; Young, C. A.; Ireland, J.; Conlon, P. A.; Maguire, K. Bibcode: 2008SoPh..248..311H Altcode: Flows in the photosphere of solar active regions are turbulent in nature. Because magnetic fields are frozen into the plasma on the solar surface, magnetograms can be used to investigate the processes responsible for structuring active regions. Here, a continuous wavelet technique is developed, analyzed, and used to investigate the multiscale structure of an evolving active region using magnetograms obtained by the Michelson Doppler Imager (MDI) onboard the Solar and Heliospheric Observatory (SOHO). The multiscale structure was measured using a 2D continuous wavelet technique to extract the energy spectrum of the region over the time scale of 13 days. Preliminary evidence of an inverse cascade in active region NOAA 10488 is presented as well as a potential relationship between energy scaling and flare productivity. Title: Multiscale Edge Detection in the Corona Authors: Young, C. Alex; Gallagher, Peter T. Bibcode: 2008SoPh..248..457Y Altcode: 2008SoPh..tmp...76Y; 2008arXiv0804.1964Y Coronal Mass Ejections (CMEs) are challenging objects to detect using automated techniques, due to their high velocity and diffuse, irregular morphology. A necessary step to automating the detection process is to first remove the subjectivity introduced by the observer used in the current, standard, CME detection and tracking method. Here we describe and demonstrate a multiscale edge detection technique that addresses this step and could serve as one part of an automated CME detection system. This method provides a way to objectively define a CME front with associated error estimates. These fronts can then be used to extract CME morphology and kinematics. We apply this technique to a CME observed on 18 April 2000 by the Large Angle Solar COronagraph experiment (LASCO) C2/C3 and a CME observed on 21 April 2002 by LASCO C2/C3 and the Transition Region and Coronal Explorer (TRACE). For the two examples in this work, the heights determined by the standard manual method are larger than those determined with the multiscale method by ≈10% using LASCO data and ≈20% using TRACE data. Title: Multifractal Properties of Evolving Active Regions Authors: Conlon, P. A.; Gallagher, P. T.; McAteer, R. T. J.; Ireland, J.; Young, C. A.; Kestener, P.; Hewett, R. J.; Maguire, K. Bibcode: 2008SoPh..248..297C Altcode: Magnetohydrodynamic turbulence is thought to be responsible for producing complex, multiscale magnetic field distributions in solar active regions. Here we explore the multiscale properties of a number of evolving active regions using magnetograms from the Michelson Doppler Imager (MDI) on the Solar and Heliospheric Observatory (SOHO). The multifractal spectrum was obtained by using a modified box-counting method to study the relationship between magnetic-field multifractality and region evolution and activity. The initial emergence of each active region was found to be accompanied by characteristic changes in the multifractal spectrum. Specifically, the range of multifractal structures (Ddiv) was found to increase during emergence, as was their significance or support (Cdiv). Following this, a decrease in the range in multifractal structures occurred as the regions evolved to become large-scale, coherent structures. From the small sample considered, evidence was found for a direct relationship between the multifractal properties of the flaring regions and their flaring rate. Title: Correlation of multi-resolution analyses of active region magnetic field structure with flare activity Authors: Ireland, J.; Young, A.; McAteer, J.; Whelan, C.; Hewett, R. J.; Gallagher, P. T. Bibcode: 2007AGUFMSH13A1094I Altcode: Two multi-resolution analyses are used to decompose active region magnetic fields into objects of different lengthscales, allowing one to examine the structure of the active region field at different lengthscales. Lines separating opposite polarity groupings of flux at different lengthscales are found (a generalization of the notion of a magnetic neutral line). It is shown that the average magnetic field gradient for alpha, beta, beta-gamma, and beta-gamma-delta active regions increases in the order listed, and that the order is maintained over all length-scales. Since magnetic field gradient is strongly linked to active region activity, such as flares, this study demonstrates that, on average, the Mt. Wilson classification encodes the notion of activity over all lengthscales in the active region, and not just those lengthscales at which the strongest field gradients are found. Properties of these generalized neutral lines are also correlated with GOES flare activity in a search for an indicator of flare activity. Title: Multi-scale Tools for Solar Image Processing Authors: Young, C.; Ireland, J.; McAteer, R.; Gallagher, P. T.; Byrne, J. Bibcode: 2007AGUFMSH13A1093Y Altcode: The important information contained in solar image data exists on many different time and spatial scales. This makes multi-scale transforms such as wavelets and curvelets very appropriate tools. These and other multi- scale transforms are used in several different types of image processing including image enhancement, feature detection, deconvolution and noise reduction. We present an overview of multi-scale transforms and show some of their applications to solar image data. Title: The Bursty Nature of Solar Flare X-Ray Emission Authors: McAteer, R. T. James; Young, C. Alex; Ireland, Jack; Gallagher, Peter T. Bibcode: 2007ApJ...662..691M Altcode: The complex and highly varying temporal nature of emission from an X4.8 flare is studied across seven X-ray energy bands. A wavelet transform modulus maxima method is used to obtain the multifractal spectra of the temporal variation of the X-ray emission. As expected from the Neupert effect, the time series of the emission at low energies (3-6, 6-12 keV; thermal) is smooth. The peak Hölder exponent, around 1.2, for this low-energy emission is indicative of a signal with a high degree of memory and suggestive of a smooth chromospheric evaporation process. The more bursty emission at higher energies (100-300, 300-800 keV; nonthermal) is described by a multifractal spectrum that peaks at a smaller Hölder exponent (less than 0.5 for the largest singularities), indicative of a signal with a low degree of memory. This describes an antipersistent walk and indicates an impulsive, incoherent driving source. We suggest that this may arise from bursty reconnection, with each reconnection event producing a different and uncorrelated nonthermal particle source. The existence of a power-law scaling of wavelet coefficients across timescales is in agreement with the creation of a fractal current sheet diffusion region. Title: Wavelet Analysis of Active Region Magnetic Structure Authors: Ireland, Jack; Young, C. A.; Gallagher, P. T.; McAteer, R. T. James; Whelan, C.; Hewett, R. J. Bibcode: 2007AAS...210.9322I Altcode: 2007BAAS...39..214I A wavelet analysis is used to decompose active region magnetic fields into regions of different lengthscales, allowing one to examine the structure of the active region field at different lengthscales. Linesseparating opposite polarity groupings of flux at different lengthscales are found; these lines can be seen as a generalization of the notion of a magnetic neutral line. It is shown that the average magnetic field gradient for alpha, beta, beta-gamma, and beta-gamma-delta active regions increases in the order listed, and that the order is maintained over all length-scales. Further, the standard deviation and maximum of the magnetic field gradient, as well as the length of these generalized neutral lines, all share the same property. Since magnetic field gradient is strongly linked to active region activity, such as flares, this study demonstrates that, on average, the Mt. Wilson classification encodes the notion of activity over all lengthscales in the active region, and not just those lengthscales at which the strongest field gradients are found. This study uses the multiscale analysis toolkit Mkit developed by C. A. Young and presented elsewhere at this meeting. Title: Solar Activity Monitoring Authors: Gallagher, Peter T.; McAteer, R. T. James; Young, C. Alex; Ireland, Jack; Hewett, Russell J.; Conlon, Paul Bibcode: 2007ASSL..344...15G Altcode: No abstract at ADS Title: Multiscale Solar Image Processing Authors: Young, C. B.; Byrne, J.; Ireland, J.; Gallagher, P. T.; McAteer, R. J. Bibcode: 2006AGUFMSH23B0369Y Altcode: Wavelets have been very successfully used as a tool for noise reduction and general processing of images. Despite this, wavelets have inherent limitations with 2-D data. Wavelets are well suited for describing point singularities but much of the interesting information in images is described by edges, lines or curves. Newly developed multiscale transforms address some of these issues. The ridgelet transform takes the multiscale concept of wavelets but applies it to 1-D objects (lines) instead of 0-D objects (points). The curvelet transform likewise applies to multiscale curves. We present a preliminary study of the use of these new multiscale transforms with solar image data. These data include TRACE EUV images and LASCO coronagraph images. Title: The Complex Sun: Turbulence and Complexity of the Solar atmosphere Authors: McAteer, R. T. James; Gallagher, Peter T.; Ireland, J.; Young, C Alex; Hewett, Russell J.; Conlon, P. Bibcode: 2006ESASP.617E.137M Altcode: 2006soho...17E.137M No abstract at ADS Title: Observational Evidence of Gentle and Explosive Chromospheric Evaporation Authors: Milligan, R. O.; Gallagher, P. T.; Mathioudakis, M.; Keenan, F. P. Bibcode: 2006ESASP.617E.138M Altcode: 2006soho...17E.138M No abstract at ADS Title: Observational Evidence of Chromospheric Evaporation Authors: Milligan, Ryan O.; Gallagher, P. T.; Mathioudakis, M.; Keenan, F. P. Bibcode: 2006SPD....37.0828M Altcode: 2006BAAS...38R.662M Observational evidence for chromospheric evaporation during the impulsive phase of two solar flares is presented using data from the Reuven Ramaty High-Energy Solar Spectroscopic Imager (RHESSI) and the Coronal Diagnostic Spectrometer (CDS) on board SOHO. For the first time, co-spatial imaging and spectroscopy have been used to observe both gentle and explosive evaporation processes within HXR emitting regions. For a GOES C9.1 flare, a low flux of non-thermal electrons was found to produce low-velocity upflows in the cool He I and O V emission lines and moderate upflows in the 8 MK Fe XIX line indicative of gentle evaporation. An M2.2 flare, on the other hand, showed low-velocity downflows in the He I and O V lines and high-velocity upflows in the Fe XIX line, for an electron flux value which was an order of magnitude higher, indicative of an explosive process. These findings confirm that the dynamic response of the solar atmosphere is sensitively dependent on the flux of incident electrons as predicted by current hydrodynamical simulations. Title: How Complex Are Solar Flare Hrx Lightcurves? A Multiscalar Multifractal Approach. Authors: McAteer, R. T. J.; Young, C.; Ireland, J.; Gallagher, P. T. Bibcode: 2006SPD....37.0824M Altcode: 2006BAAS...38..235M A wavelet transform modulus maxima approach to the calculation of the singularity spectrum is applied to hard X-ray (7 energy bands from 3--800keV) lightcurves from an X4.8 flare on 23 July 2002. The multifractality of each lightcurve is discussed in terms of the Hausdorff dimension, D, of the Holder exponent, h, of each detected singularity. In addition to a general discussion of the technique, we show results showing a general increase in complexity of lightcurves at higher energies Title: Multiscale Structure of Active Region Magnetic Fields Authors: Hewett, Russell J.; Gallagher, P. T.; McAteer, R.; Young, C.; Ireland, J. Bibcode: 2006SPD....37.0301H Altcode: 2006BAAS...38..222H Flows in the photosphere of solar active regions are in a state ofhighly developed turbulence. As magnetic fields are frozen into theplasma in the solar surface, magnetograms can therefore be used toinvestigate the processes responsible for structuring active regions.Here, the multiscale structure of a large sample of active regionmagnetograms from the Michelson Doppler Imager (MDI) onboard theSolar and Heliospheric Observatory (SOHO) are investigated. Initialresults regarding the relationship between multiscale structuring andactive region evolution and flaring activity is discussed. Title: Multifractal Analysis of Solar Magnetograms Authors: Conlon, Paul; McAteer, R. T.; Gallagher, P. T.; Ireland, J.; Young, C. A.; Young, C. A. Bibcode: 2006SPD....37.0303C Altcode: 2006BAAS...38Q.222C Magnetohydrodynamic turbulence is thought to be responsible for structuring sunspot magnetic fields. Here we explore the selfsimilar and multi-scaling properties of this turbulence using multi-fractal methods. The multi-fractal spectrum was obtained from full disk Michelos Doppler Imager magnetograms, to study the relationship between magnetic field multifractality and flaring and non-flaring regions. In particular, box counting and wavelet based techniques where investigated. The discrete box counting method was found to be inadequate for these purposes, primarily due to discretization errors. Wavelet based methods, on the other hand, where found to be more stable for diagnosing turbulence in active region magnetic fields. Title: Observational Evidence of Gentle Chromospheric Evaporation during the Impulsive Phase of a Solar Flare Authors: Milligan, Ryan O.; Gallagher, Peter T.; Mathioudakis, Mihalis; Keenan, Francis P. Bibcode: 2006ApJ...642L.169M Altcode: 2006astro.ph..3652M Observational evidence of gentle chromospheric evaporation during the impulsive phase of a C9.1 solar flare is presented using data from the Reuven Ramaty High-Energy Solar Spectroscopic Imager and the Coronal Diagnostic Spectrometer on board the Solar and Heliospheric Observatory. Until now, evidence of gentle evaporation has often been reported during the decay phase of solar flares, where thermal conduction is thought to be the driving mechanism. Here we show that the chromospheric response to a low flux of nonthermal electrons (>=5×109 ergs cm-2 s-1) results in plasma upflows of 13+/-16, 16+/-18, and 110+/-58 km s-1 in the cool He I and O V emission lines and the 8 MK Fe XIX line, respectively. These findings, in conjunction with other recently reported work, now confirm that the dynamic response of the solar atmosphere is sensitively dependent on the flux of incident electrons. Title: RHESSI and SOHO CDS Observations of Explosive Chromospheric Evaporation Authors: Milligan, Ryan O.; Gallagher, Peter T.; Mathioudakis, Mihalis; Bloomfield, D. Shaun; Keenan, Francis P.; Schwartz, Richard A. Bibcode: 2006ApJ...638L.117M Altcode: 2005astro.ph..9664M Simultaneous observations of explosive chromospheric evaporation are presented using data from the Reuven Ramaty High-Energy Solar Spectroscopic Imager (RHESSI) and the Coronal Diagnostic Spectrometer (CDS) on board the Solar and Heliospheric Observatory. For the first time, cospatial imaging and spectroscopy have been used to observe explosive evaporation within a hard X-ray emitting region. RHESSI X-ray images and spectra were used to determine the flux of nonthermal electrons accelerated during the impulsive phase of an M2.2 flare. When we assumed a thick-target model, the injected electron spectrum was found to have a spectral index of ~7.3, a low-energy cutoff of ~20 keV, and a resulting flux of >=4×1010 ergs cm-2 s-1. The dynamic response of the atmosphere was determined using CDS spectra; we found a mean upflow velocity of 230+/-38 km s-1 in Fe XIX (592.23 Å) and associated downflows of 36+/-16 and 43+/-22 km s-1 at chromospheric and transition region temperatures, respectively, relative to an averaged quiet-Sun spectra. The errors represent a 1 σ dispersion. The properties of the accelerated electron spectrum and the corresponding evaporative velocities were found to be consistent with the predictions of theory. Title: Wavelet analysis of Active Region structure Authors: Ireland, J.; Young, C. A.; Whelan, C.; Gallagher, P. T.; McAteer, R. T. J.; Hewett, R. J. Bibcode: 2006cosp...36.2595I Altcode: 2006cosp.meet.2595I Active regions are known to consist of complex magnetic fields as evinced by both fractal and multifractal studies In contrast the Mt Wilson classification of active regions is relatively simple yet is useful in predicting the likelihood of flaring events since it considers the overall geometrical structure of the active region In particular neutral lines are especially important in evaluating the likelihood of flare events occurring Wavelet analysis techniques in conjunction with edge detection methods are applied to the problem of diagnosing the gross geometrical structure of active region magnetic field Active region fields are decomposed into their constituent parts using wavelet techniques and edge detection methods are used to characterize the neutral lines present A statistical analysis is presented outlining the utility of this approach in automatically generating a Mt Wilson classification for a given active region Title: Plasma diagnostics of active-region evolution and implications for coronal heating Authors: Milligan, R. O.; Gallagher, P. T.; Mathioudakis, M.; Keenan, F. P.; Bloomfield, D. S. Bibcode: 2005MNRAS.363..259M Altcode: 2005MNRAS.tmp..764M; 2005astro.ph..9219M A detailed study is presented of the decaying solar-active region NOAA 10103 observed with the Coronal Diagnostic Spectrometer (CDS), the Michelson Doppler Imager (MDI) and the Extreme-ultraviolet Imaging Telescope (EIT) onboard the Solar and Heliospheric Observatory (SOHO). Electron-density maps formed using SiX (356.03 Å/347.41 Å) show that the density varies from ~1010cm-3 in the active-region core to ~7 × 108cm-3 at the region boundaries. Over the 5d of observations, the average electron density fell by ~30 per cent. Temperature maps formed using FeXVI (335.41 Å)/FeXIV (334.18 Å) show electron temperatures of ~2.34 × 106 K in the active-region core and ~2.10 × 106 K at the region boundaries. Similarly to the electron density, there was a small decrease in the average electron temperature over the 5-d period. The radiative, conductive and mass-flow losses were calculated and used to determine the resultant heating rate (PH). Radiative losses were found to dominate the active-region cooling process. As the region decayed, the heating rate decreased by almost a factor of 5 between the first and last day of observations. The heating rate was then compared to the total unsigned magnetic flux , yielding a power law of the form PH~Φ0.81+/-0.32tot. This result suggests that waves rather than nanoflares may be the dominant heating mechanism in this active region. Title: Statistics of Active Region Complexity: A Large-Scale Fractal Dimension Survey Authors: McAteer, R. T. James; Gallagher, Peter T.; Ireland, Jack Bibcode: 2005ApJ...631..628M Altcode: A quantification of the magnetic complexity of active regions using a fractal dimension measure is presented. This fully automated approach uses full-disk MDI magnetograms of active regions from a large data set (2742 days of the SOHO mission, 9342 active region images) to compare the calculated fractal dimension of each region to both its Mount Wilson classification and flare rate. Each Mount Wilson class exhibits a similar fractal dimension frequency distribution, possibly suggesting a self-similar nature of all active regions. Solar flare productivity exhibits an increase in both the frequency and GOES X-ray magnitude of flares from regions with higher fractal dimension. Specifically, a lower threshold fractal dimension of 1.2 and 1.25 exists as a necessary, but not sufficient, requirement for an active region to produce M- and X-class flares, respectively, within 24 hr of the observation. Title: Foreword Authors: Gallagher, Peter; Berghmans, David; Aschwanden, Markus Bibcode: 2005SoPh..228....1G Altcode: No abstract at ADS Title: Automated Boundary-extraction And Region-growing Techniques Applied To Solar Magnetograms Authors: McAteer, R. T. James; Gallagher, Peter T.; Ireland, Jack; Young, C. Alex Bibcode: 2005SoPh..228...55M Altcode: We present an automated approach to active region extraction from full-disc MDI longitudinal magnetograms. This uses a region-growing technique in conjunction with boundary-extraction to define a number of enclosed contours as belonging to separate regions of magnetic significance on the solar disc. This provides an objective definition of active regions and areas of plage on the Sun. A number of parameters relating to the flare potential of each region are discussed. Title: Chromospheric Response to Non-Thermal Electrons During Flares Using RHESSI and SOHO/CDS Authors: Milligan, R. O.; Gallagher, P. T.; Mathioudakis, M.; Keenan, F. P. Bibcode: 2005AGUSMSP52A..04M Altcode: Many current solar flare models predict a relationship between the amount of energy deposited in the chromospheric and transition region layers of the solar atmosphere by non-thermal electrons, and the velocity at which this superheated material rises. For the first time, we present findings from simultaneous observations of loop footpoints using RHESSI and SOHO/CDS. RHESSI HXR images and spectra are used to determine the flux of non-thermal electrons using the thick-target bremsstrahlung model, while upflow velocities in the Fe XIX emission line are observed using CDS. Title: From Raw Data to Flare Predictions: A Fully Automated Technique Authors: McAteer, R. T.; Gallagher, P. T.; Ireland, J.; Young, A. Bibcode: 2005AGUSMSP42A..06M Altcode: With the large volume of solar data which already exists, and expected in the near future with SDO, automated techniques are becoming increasingly vital. We present a fully automated active region extraction routine based on boundary extraction and region growing techniques applied to full disc MDI longitudinal magnetograms. Once extracted, any number of image processing techniques can be applied to the data leading to the possibility of automated classification. We discuss a large scale (9 years of MDI data, ~10,000 active region images) fractal survey of this data. This quantifies the meaning of magnetic complexity, relating lower threshold fractal dimension to the onset of large flares. Title: Representation of Sun Spots with Shapelets Authors: Young, C.; Gallagher, P. T.; Ireland, J.; McAteer, R. Bibcode: 2005AGUSMSP11A..07Y Altcode: Shapelets are complete set of orthonormal functions that can be used to represent most images. These functions are Gauss-Hermite polynomials and are the eigenfunctions of the 2D harmonic oscillator. They were first used in image processing to study the shape of galaxies. Shapelets have properties that allow one to compute quantities such as chirality, shear and asymmetry in images. We use these functions to represent magnetograms of sunspots, allowing us to calculate a large set of descriptive quantities including those previously mentioned. These quantities are then correlated with the current classification schemes used to type sunspots. Title: Observations of Hα Intensity Oscillations in a Flare Ribbon Authors: McAteer, R. T. James; Gallagher, Peter T.; Brown, Daniel S.; Bloomfield, D. Shaun; Moore, Ruth; Williams, David R.; Mathioudakis, Mihalis; Katsiyannis, A.; Keenan, Francis P. Bibcode: 2005ApJ...620.1101M Altcode: High-cadence Hα blue wing observations of a C9.6 solar flare obtained at Big Bear Solar Observatory using the Rapid Dual Imager are presented. Wavelet and time-distance methods were used to study oscillatory power along the ribbon, finding periods of 40-80 s during the impulsive phase of the flare. A parametric study found statistically significant intensity oscillations with amplitudes of 3% of the peak flare amplitude, periods of 69 s (14.5 mHz) and oscillation decay times of 500 s. These measured properties are consistent with the existence of flare-induced acoustic waves within the overlying loops. Title: Energy partition in two solar flare/CME events Authors: Emslie, A. G.; Kucharek, H.; Dennis, B. R.; Gopalswamy, N.; Holman, G. D.; Share, G. H.; Vourlidas, A.; Forbes, T. G.; Gallagher, P. T.; Mason, G. M.; Metcalf, T. R.; Mewaldt, R. A.; Murphy, R. J.; Schwartz, R. A.; Zurbuchen, T. H. Bibcode: 2004JGRA..10910104E Altcode: Using coordinated observations from instruments on the Advanced Composition Explorer (ACE), the Solar and Heliospheric Observatory (SOHO), and the Ramaty High Energy Solar Spectroscopic Imager (RHESSI), we have evaluated the energetics of two well-observed flare/CME events on 21 April 2002 and 23 July 2002. For each event, we have estimated the energy contents (and the likely uncertainties) of (1) the coronal mass ejection, (2) the thermal plasma at the Sun, (3) the hard X-ray producing accelerated electrons, (4) the gamma-ray producing ions, and (5) the solar energetic particles. The results are assimilated and discussed relative to the probable amount of nonpotential magnetic energy available in a large active region. Title: Active Region Evolution and Activity During the Storms of Halloween 2003 Authors: Gallagher, P. T. Bibcode: 2004AAS...204.4702G Altcode: 2004BAAS...36..737G The three week period around Halloween 2003 was characterized by some of the largest and most energetic flares and CMEs observed in recent years (e.g., see http://beauty.nascom.nasa.gov/ ptg/oct-nov-2003-xflares.html for details of the 12 X-class flares). This increased activity resulted from the almost simultaneous formation of three complex beta-gamma-delta regions: NOAA 0484, 0486, and 0488. In this talk, the distinctive characteristics, rapid evolution, and extreme activity of the these regions will be reviewed in light of the multitude of observations from SOHO, RHESSI, TRACE, BBSO, and other ground- and space-based observatories. Our current understanding of the mechanisms involved in forming such regions, and the processes involved in storing and releasing such numerous and energetic events will also be discussed. Title: Optical Observations of Flare-Induced Oscillations Authors: McATeer, R. T. J.; Gallagher, P. T.; Brown, D. S. Bibcode: 2004AAS...204.9806M Altcode: 2004BAAS...36..985M We present high-cadence H alpha blue wing observations of a C9.6 solar flare. Oscillations (period 40-80s) are shown to be present in the post-flare section of lightcurves from a short-lived flare ribbon. Wavelet analysis is used to show the excellent agreement of oscillatory power at 52.4s with a distance-time plot along one half of the ribbon. A best-fit of an oscillation to the curve shows oscillatory amplitude ∼ 0.03% flare ampltiude, period ∼ 69s and decay time ∼ 500s. These parameters are in good agreement with the formation of a second harmonic acoustic wave. A study of loop lengths along the ribbon also agrees with the presence of a ∼ 50s period

JMA is funded by a NRC Research Associateship. Observations were carried out via a Leverhulme Trust Fellowship. Title: Plasma Diagnostics of Active Region Evolution and Implications for Coronal Heating Authors: Milligan, R. O.; Gallagher, P. T.; Mathioudakis, M.; Bloomfield, D. S.; Keenan, F. P. Bibcode: 2004AAS...204.9803M Altcode: 2004BAAS...36..984M The decaying solar active region NOAA 10103 was observed during 2002 September 10--14 using the Coronal Diagnostic Spectrometer (CDS) onboard the Solar and Heliospheric Observatory (SOHO). Electron density maps were created using the Si X (356Å/347Å) ratio, which show densities of ∼1010cm-3 in the active region core, and ∼7x108cm-3 in the region boundaries. Over the five days of observations, the average electron density fell by approximately a factor of two. Temperature maps were created using the Fe XVI (335.4Å)/Fe XIV (334.2Å) ratio, which show electron temperatures of ∼2.2x106K in the active region core, and ∼2.0x106K in the region boundaries. Similarly to the electron density, the average electron temperature decreased over the five days, but by only ∼3%. The radiative and conductive losses, and resultant heating rate, were then calculated and compared to the total unsigned magnetic flux (Φ tot = ∫ dA |Bz|) from Michelson Doppler Interferometer (MDI) magnetograms. Losses due to radiation were found to exceed conductive losses by a factor of ten. As the region decayed, the heating rate decreased by close to an order of magnitiude between the first and last day of observations. In line with several coronal heating theories, a power-law relationship of the form Ptot} ∼Φ {tot0.95±0.07 was found between the heating rate and the unsigned magnetic flux. This result provides further observational evidence for wave rather than nanoflare heating of solar active regions.

Ryan Milligan would like to thank the Solar Physics Division for being awarded an SPD Studentship. Title: Search for 1-10 Hz modulations in coronal emission with SECIS during the August 11, 1999 eclipse Authors: Rudawy, P.; Phillips, K. J. H.; Gallagher, P. T.; Williams, D. R.; Rompolt, B.; Keenan, F. P. Bibcode: 2004A&A...416.1179R Altcode: Results of the search of the periodic changes of the 530.3 nm line intensity emitted by selected structures of the solar corona in the frequency range 1-10 Hz are presented. A set of 12 728 images of the section of the solar corona extending from near the north pole to the south-west were taken simultaneously in the 530.3 nm (``green'') line and white-light with the Solar Eclipse Coronal Imaging System (SECIS) during the 143-seconds-long totality of the 1999 August 11 solar eclipse observed in Shabla, Bulgaria. The time resolution of the collected data is better than 0.05 s and the pixel size is approximately 4 arcsec. Using classical Fourier spectral analysis tools, we investigated temporal changes of the local 530.3 nm coronal line brightness in the frequency range 1-10 Hz of thousands of points within the field of view. The various photometric and instrumental effects have been extensively considered. We did not find any indisputable, statistically significant evidence of periodicities in any of the investigated points (at significance level α=0.05). Title: Ultraviolet Oscillations in the Chromosphere of the Quiet Sun Authors: McAteer, R. T. James; Gallagher, Peter T.; Bloomfield, D. Shaun; Williams, David R.; Mathioudakis, Mihalis; Keenan, Francis P. Bibcode: 2004ApJ...602..436M Altcode: Quiet-Sun oscillations in the four Transition Region and Coronal Explorer (TRACE) ultraviolet passbands centered on 1700, 1600, 1216, and 1550 Å are studied using a wavelet-based technique. Both network and internetwork regions show oscillations with a variety of periods and lifetimes in all passbands. The most frequent network oscillation has a period of 283 s, with a lifetime of 2-3 cycles in all passbands. These oscillations are discussed in terms of upwardly propagating magnetohydrodynamic wave models. The most frequent internetwork oscillation has a period of 252 s, again with a lifetime of 2-3 cycles, in all passbands. The tendency for these oscillations to recur in the same position is discussed in terms of ``persistent flashers.'' The network contains greater oscillatory power than the internetwork at periods longer than 300 s in the low chromosphere. This value is shown to decrease to 250 s in the high chromosphere. The internetwork also displays a larger number of short-lifetime, long-period oscillations than the network, especially in the low chromosphere. Both network and internetwork regions contain a small number of nonrecurring long-lifetime oscillations. Title: An Automated Wavelet Analysis Approach to TRACE Quiet Sun Oscillations Authors: McAteer, R. T. J.; Gallagher, P. T.; Williams, D. R. Williams D. R.; Bloomfield, D. S.; Mathioudakis, M.; Keenan, F. P. Bibcode: 2004ESASP.547..139M Altcode: 2004soho...13..139M An automated wavelet analysis approach to TRACE UV quiet Sun datasets is discussed. Periodicity and lifetime of oscillations present in the network and internetwork are compared and contrasted. This provides a means of extending previous Fourier results into the time-localised domain. The longest lifetime oscillations occur around the acoustic band and the network tends to dominate over the internetwork at periods 4 mins. However, it is shown that the internetwork can dominate over the network at long periods (7 - 20 mins), but only for short lifetimes ( 3 complete oscillations). These results are discussed in terms of chromospheric heating theories. Title: Physics of superfast coronal mass ejections observed during cycle 23 Authors: Lawrence, G.; Gallagher, P.; Leamon, R.; Stenborg, G. Bibcode: 2004cosp...35.2882L Altcode: 2004cosp.meet.2882L Between January 1996 and the present time the Large Angle Spectrometric Coronagraphs (LASCO) onboard the Solar and Heliospheric Observatory (SOHO) have observed over 6000 coronal mass ejections (CMEs). The typical speed of these CMEs has been found to vary between 400-500 km/s during the present solar cycle, and the vast majority of all CMEs are found to have speeds below 1,000 km/s. However, a high-speed tail to the distribution is clearly present, and a small fraction of all CMEs, 20 events in total, are found to have speeds in the range 2,000 - 2,500 km/s. This category of 'superfast CMEs' is doubly significant because they appear to correspond the extreme limits of physics involved in the initiation and acceleration processes, and because such events when directed earthwards have characteristically short transit times and hence leave little reaction/assessment time for potentially sensitive systems. The superfast CMEs are all associated with significant solar flares, and the large flare/very fast CME paradigm is studied. Of particular interest is the acceleration of such very fast CMEs and the nature, magnitude and timing of the acceleration process is characterised within the limits of the observations. Title: Initial Results from SECIS Observations of the 2001 Eclipse Authors: Katsiyannis, A. C.; McAteer, R. T. J.; Williams, D. R.; Gallagher, P. T.; Keenan, F. P. Bibcode: 2004ESASP.547..459K Altcode: 2004astro.ph.11722K; 2004soho...13..459K SECIS observations of the June 2001 total solar eclipse were taken using an Fe XIV 5303 Å filter. Existing software was modified and new code was developed for the reduction and analysis of these data. The observations, data reduction, study of the atmospheric and instrumental effects, together with some preliminary results are discussed. Emphasis is given to the techniques used for the automated alignment of the 8000 images, the application of the `a Trous algorithm for noise filtering and the software developed for the automated detection of intensity oscillations using wavelet analysis. In line with findings from the 1999 SECIS total eclipse observations, intensity oscillations with periods in the range of 20-30 s, both inside and just outside coronal loops are also presented. Title: The Relationship Between Large Solar Flares and Very Fast Coronal Mass Ejections - Physics and Causality Authors: Lawrence, G.; Gallagher, P.; Dennis, B. Bibcode: 2003AGUFMSH21C..07L Altcode: The fastest coronal mass ejection observed to date by the LASCO coronagrph onboard SOHO was also the best observed thanks to the Max Millenium co-ordinated observation campaign running at the time. Data from RHESSI, TRACE and SOHO from April 21 2002 are presented which yield a clear timeline of the physical processes involved and their relationships to each other. The causality of the solar flare-CME system is discussed and implications for theory and modelling are presented. Other large flare/very fast CME events are analysed and agreement with the paradigm is studied. Particular attention is paid to the acceleration of such very fast CMEs and the nature, magnitude and timing of the acceleration process is characterised within the limits of the observations. Title: The Polar Crown Filament Eruption and Associated CME of 2003 February 18 Authors: Hill, S. M.; Christopher, B. C.; Burkepile, J.; Gallagher, P. T.; Detoma, G. Bibcode: 2003AGUFMSH21C..04H Altcode: On 2003 February 18, a polar crown filament dramatically erupted, becoming the core of a classic three part Coronal Mass Ejection (CME). The event was well observed from the disk to 30 solar radii in multiple bands, some of which were at high cadence. Phenomena observed include: high-latitude filament eruption, the formation of two bright ribbons, soft X-ray coronal dimmings, post-eruption arcade evolution, and a classical three-part CME. Specifically, the filament eruption was seen on the disk and out to ~1.3 solar radii in soft X-rays, extreme ultraviolet, H-alpha, and He I 1083 nm. The CME was visible in white light coronagraph images from 1.08 to 30 solar radii. Though post CME reconnection arcades reached only the B5 level in GOES XRS measurements, they were observed in hard X-rays (at energies less than 12 keV), soft X-rays, extreme ultraviolet, and a two-ribbon flare structure was seen in H-alpha and in He I 1083 nm. The observations were conducted using GOES SXI, SOHO EIT and LASCO, RHESSI, and the MLSO ACOS suite. We present the results of our initial timing, height vs. time, and light curve analyses of this event. The timing results address issues of the simultaneity and sequence of filament motion, coronal dimming, CME 'launch', and arcade formation. The height versus time results are presented for both the filament/CME core and the CME front to provide observational constraints for CME acceleration models. Finally, the arcade light curve results support estimation of the magnetic reconnection rate for further discrimination between model predictions. Title: Multiscale Feature Identification in the Solar Atmosphere Authors: Young, C.; Gallagher, P. T.; Myers, D. C. Bibcode: 2003AGUFMSH42B0543Y Altcode: Multiscale methods offer a powerful approach to solar image processing and analysis. In this paper, wavelet-based methods are applied to a sequence of TRACE 195 passband images and LASCO C2/C3 white-light images to unambiguously identify faint features associated with the 2002 April 21 X-class flare and CME. Morphological properties, such as feature width, height, velocity and acceleration are then extracted, and compared to recent results from traditional image processing techniques. Title: Eclipse observations of high-frequency oscillations in active region coronal loops Authors: Katsiyannis, A. C.; Williams, D. R.; McAteer, R. T. J.; Gallagher, P. T.; Keenan, F. P.; Murtagh, F. Bibcode: 2003A&A...406..709K Altcode: 2003astro.ph..5225K One of the mechanisms proposed for heating the corona above solar active regions is the damping of magnetohydrodynamic (MHD) waves. Continuing on previous work, we provide observational evidence for the existence of high-frequency MHD waves in coronal loops observed during the August 1999 total solar eclipse. A wavelet analysis is used to identify twenty 4x4 arcsec2 areas showing intensity oscillations. All detections lie in the frequency range 0.15-0.25 Hz (7-4 s), last for at least 3 periods at a confidence level of more than 99% and arise just outside known coronal loops. This leads us to suggest that they occur in low emission-measure or different temperature loops associated with the active region. Title: Large solar energetic particle events of cycle 23: A global view Authors: Gopalswamy, N.; Yashiro, S.; Lara, A.; Kaiser, M. L.; Thompson, B. J.; Gallagher, P. T.; Howard, R. A. Bibcode: 2003GeoRL..30.8015G Altcode: 2003GeoRL..30lSEP3G We report on a study of all the large solar energetic particle (SEP) events that occurred during the minimum to maximum interval of solar cycle 23. The main results are: 1. The occurrence rate of the SEP events, long-wavelength type II bursts and the fast and wide frontside western hemispheric CMEs is quite similar, consistent with the scenario that CME-driven shocks accelerate both protons and electrons; major flares have a much higher rate. 2. The SEP intensity is better correlated with the CME speed than with the X-ray flare class. 3. CMEs associated with high-intensity SEPs are about 4 times more likely to be preceded by wide CMEs from the same solar source region, suggesting the importance of the preconditioning of the eruption region. We use a specific event to demonstrate that preceding eruption from a nearby source can significantly affect the properties of SEPs and type II radio bursts. Title: Multiscale Feature Identification in Solar Flares and CMEs Authors: Myers, D. C.; Gallagher, P. T.; Young, C. A. Bibcode: 2003SPD....34.0307M Altcode: 2003BAAS...35Q.809M Multiscale methods offer a powerful approach to solar image processing and analysis. In this paper, wavelet-based methods are applied to a sequence of TRACE 195 Å passband images to unambiguously identify faint features associated with the 2002 April 21 X-class flare and CME. Morphological properties, such as feature width, height, velocity and acceleration are then extracted, and compared to recent results from traditional image processing techniques. Title: Rapid Acceleration of a Coronal Mass Ejection in the Low Corona and Implications for Propagation Authors: Gallagher, Peter T.; Lawrence, Gareth R.; Dennis, Brian R. Bibcode: 2003ApJ...588L..53G Altcode: A high-velocity coronal mass ejection (CME) associated with the 2002 April 21 X1.5 flare is studied using a unique set of observations from the Transition Region and Coronal Explorer (TRACE), the Ultraviolet Coronagraph Spectrometer (UVCS), and the Large Angle and Spectroscopic Coronagraph (LASCO). The event is first observed as a rapid rise in GOES X-rays, followed by two simultaneous brightenings that appear to be connected by an ascending looplike feature. While expanding, the appearance of the feature remains remarkably constant as it passes through the TRACE 195 Å passband and LASCO fields of view, allowing its height-time behavior to be accurately determined. The acceleration is consistent with an exponential rise with an e-folding time of ~138 s and peaks at ~1500 m s-2 when the leading edge is at ~1.7 Rsolar from Sun center. The acceleration subsequently falls off with an e-folding time of over 1000 s. At distances beyond ~3.4 Rsolar, the height-time profile is approximately linear with a constant velocity of ~2500 km s-1. These results are briefly discussed in light of recent kinematic models of CMEs. Title: RHESSI, TRACE, and the Spatial Neupert Effect Authors: Zarro, D. M.; Dennis, B. R.; Gallagher, P.; Tolbert, A. K.; Myers, D. C. Bibcode: 2003SPD....34.1804Z Altcode: 2003BAAS...35..840Z We combine RHESSI and TRACE observations to investigate the spatial and temporal associations between hard X-ray (HXR) and extreme ultraviolet (EUV) emissions in impulsive bursts observed during the GOES X flare of April 21, 2002. The RHESSI HXR (above 25 keV) time profile for this event is in general agreement with the time derivative of the GOES soft X-ray (1 to 8-A) flux. This temporal correlation - the Neupert Effect - is consistent with nonthermal thick-target electrons being the primary source of heating of the soft X-ray emitting thermal plasma during the flare impulsive phase.

To further investigate the link between nonthermal electrons and thermal soft X-ray emission, we examine the spatial and temporal behavior of HXR emission in high-resolution (2-3 arcsecs) RHESSI images. Specifically, we identify regions of enhanced HXR emission and compare their lightcurves with corresponding lightcurves observed simultaneously with the TRACE 195-A filter at 1-arcsec spatial resolution. The TRACE 195-A bandpass contains contributions from Fe XII and Fe XXIV lines which are sensitive to plasmas at temperatures of near 1.5 MK and 15-20 MK, respectively. Consequently, when used in conjunction with GOES, the TRACE 195-A flux provides a useful proxy for investigating the spatial properties of flare-heated thermal plasma. Title: Rapid Acceleration of a Coronal Mass Ejection in the Low Corona and Implications for Propagation Authors: Gallagher, P.; Lawrence, G.; Dennis, B. Bibcode: 2003SPD....34.0515G Altcode: 2003BAAS...35..816G A high-velocity Coronal Mass Ejection (CME) associated with the 2002 April 21 X1.5 flare is studied using a unique set of observations from the Transition Region and Coronal Explorer (TRACE), the Ultraviolet Coronagraph Spectrometer (UVCS), and the Large-Angle Spectrometric Coronagraph (LASCO). The event is first observed as a rapid rise in GOES X-rays, followed by two simultaneous brightenings which appear to be connected by an ascending loop-like feature. While expanding, the appearance of the feature remains remarkably constant as it passes through the TRACE 195 Å passband and LASCO fields-of-view, allowing its height-time behaviour to be acurately determined. The acceleration is consistent with an exponential rise with an e-folding time of ∼138 s and peaks at ∼1500 m s-2 when the leading-edge is at ∼1.7 R⊙ from Sun center. The acceleration subsequently falls off with an e-folding time of over 1000 s. At distances beyond ∼3.4 R⊙ , the height-time profile is approximately linear with a constant velocity of ∼2500 km s-1. These results are briefly discussed in light of recent kinematic models of CMEs. Title: Hα , EUV, and Microwave Observations of a Large Flare as Evidence for Spontaneous Magnetic Reconnection Authors: Lee, J.; Gallagher, P. T.; Gary, D. E.; Nita, G. M.; Choe, G. S. Bibcode: 2003SPD....34.1604L Altcode: 2003BAAS...35Q.833L The large solar flare with GOES class X1.1 occurred on 2000 March 22 is observed with the Owens Valley Solar Array (OVSA), Hα filtergram of Big Bear Solar observatory (bbso), the Transition region and Coronal Explorer (trace), and the Michelson Doppler Imager (mdi) onboard Solar and Heliospheric Observatory (SOHO). During the impulsive phase a set of EUV loops are visible in a small volume confined to the center of the large β γ δ -type active region. Radio emission at 5 GHz appears as a single source encompassing multiple Hα ribbons, and radio emissions at other frequencies also appear within the central core region. We interpret these observations under the idea of the confined flare in contrast with the more commonly cited, eruptive flare, using a schematic magnetic reconnection geometry based on the mdi magnetogram. It is suggested that the EUV loops represent a separatrix in part, and that the radio and Hα sources coincide with the whole part of the separatrix and its footpoints, respectively. In addition, a Coronal Mass Ejection (CME) as detected in the LASCO coronagraph after this flare is briefly discussed in relation to the above idea of magnetic reconnection.

This work has been supported by NASA grants NAG 5-10891 and NAG-11875. Title: Observational Evidence for Mode Coupling in the Chromospheric Network Authors: McAteer, R. T. James; Gallagher, Peter T.; Williams, David R.; Mathioudakis, Mihalis; Bloomfield, D. Shaun; Phillips, Kenneth J. H.; Keenan, Francis P. Bibcode: 2003ApJ...587..806M Altcode: Oscillations in network bright points (NBPs) are studied at a variety of chromospheric heights. In particular, the three-dimensional variation of NBP oscillations is studied using image segmentation and cross-correlation analysis between images taken in light of Ca II K3, Hα core, Mg I b2, and Mg I b1-0.4 Å. Wavelet analysis is used to isolate wave packets in time and to search for height-dependent time delays that result from upward- or downward-directed traveling waves. In each NBP studied, we find evidence for kink-mode waves (1.3, 1.9 mHz), traveling up through the chromosphere and coupling with sausage-mode waves (2.6, 3.8 mHz). This provides a means for depositing energy in the upper chromosphere. We also find evidence for other upward- and downward-propagating waves in the 1.3-4.6 mHz range. Some oscillations do not correspond to traveling waves, and we attribute these to waves generated in neighboring regions. Title: Hα, Extreme-Ultraviolet, and Microwave Observations of the 2000 March 22 Solar Flare and Spontaneous Magnetic Reconnection Authors: Lee, Jeongwoo; Gallagher, Peter T.; Gary, Dale E.; Nita, Gelu M.; Choe, G. S.; Bong, Su-Chan; Yun, Hong Sik Bibcode: 2003ApJ...585..524L Altcode: The evolution of a GOES class X1.1 solar flare, which occurred in NOAA Active Region 8910 on 2000 March 22, is discussed using observations from the Owens Valley Solar Array (OVSA), Big Bear Solar observatory (BBSO), Transition Region and Coronal Explorer (TRACE), and the Michelson Doppler Imager (MDI) on board Solar and Heliospheric Observatory (SOHO). During the impulsive phase, a set of coronal loops are visible in the TRACE 171 Å (~1×106 K) wavelength band, which is confined to a small volume in the center of the large βγδ-type active region. This is rapidly followed by the emergence of bright Hα ribbons that coincide with the EUV emission. Radio images show a single source encompassing the Hα ribbons at 5 GHz, but at higher frequencies a double source is seen within the area bounded by the compact Hα and EUV emissions. We interpret the observation under the idea of the confined flare in contrast with the more commonly cited, eruptive flare. We use a schematic magnetic reconnection geometry based on the MDI magnetogram to suggest that the EUV loops show some parts of a separatrix, and that the radio and Hα sources coincide with the whole part of the separatrix and its footpoints, respectively. First of all, it explains why this flare lacks the separating motion of Hα ribbons, a signature for eruptive flares. Second, the very short duration of microwave bursts in spite of the large amount of soft X-ray flux is explicable under this scenario, since energy release via spontaneous reconnection in a confined magnetic structure can be very rapid. Third, the confined magnetic geometry is also considered favorable for preserving chromospheric evaporation and plasma turbulence as inferred from the OVSA microwave spectrum. In addition, a coronal mass ejection as detected in the LASCO coronagraph after this flare is briefly discussed in relation to the above flare model. Title: Search for short period coronal plasma oscillations. SECIS results from 1999 and 2001 total eclipses Authors: Rudawy, P.; Phillips, K. J. H.; Read, P.; Gallagher, P. T.; Rompolt, B.; Berlicki, A.; Williams, D.; Keenan, F. P.; Buczylko, A. Bibcode: 2002ESASP.506..967R Altcode: 2002ESPM...10..967R; 2002svco.conf..967R Results of the analysis of the high-cadence observations of the solar corona, taken with the Solar Eclipse Coronal Imaging System instrument during joint British-Polish expeditions during the total solar eclipses of 1999 August 11 in Bulgaria (12768 images) and 2001 June 21 in Zambia (16000 images) are presented. Using data collected during the both solar eclipses we searched for possible periodic changes of the 530.3 nm line intensity emitted by the selected points of the solar corona in the frequency range up to 10 Hz. The time resolution of the collected data is close to 0.05 sec and the pixel size is approximately 4 seconds of arc. The standard photometric processing and correction of the image motions caused by temporal drifts of the instrument pointing were made. Using classical Fourier spectral analysis and wavelet analysis tools we investigated temporal changes of the 530.3 nm coronal line brightness of many thousands of points at various heights and position angles above the solar limb. We did not find any statistically important evidence of periodicity in the frequency range from 1 to 10 Hz in any of the investigated points. Title: RHESSI Observations of Flares During the Storms Period from 14 to 24 April 2002 Authors: Dennis, B. R.; Gallagher, P. T. Bibcode: 2002AGUFMSA12A..01D Altcode: The Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) observes X-rays and gamma rays from solar flares in the energy range from 3 keV to 17 MeV with a duty cycle of about 50%. The RHESSI observations of the flares during the Storms Workshop period from 14 to 24 April, 2002, will be reviewed. Many GOES C- and M-class flares were observed including the M2.6 flare on 17 April that was followed by a CME. The X1.5 flare on 21 April was particularly well observed with RHESSI in X-rays from its start at 00:40 UT until 01:33 UT on the first orbit, just before the soft X-ray peak. Footpoint emission was detected to energies as high as 200 keV, and a spatially-separated coronal source was identified at energies below about 30 keV. The coronal X-ray source was followed for over 12 more hours on subsequent orbits as it gradually rose to over 130,000 km above the limb. The X-ray images and spectra of this flare will be presented in relation to the TRACE images in the 195-angstrom band and the LASCO images of the associated CME. Title: An observational study of a magneto-acoustic wave in the solar corona Authors: Williams, D. R.; Mathioudakis, M.; Gallagher, P. T.; Phillips, K. J. H.; McAteer, R. T. J.; Keenan, F. P.; Rudawy, P.; Katsiyannis, A. C. Bibcode: 2002MNRAS.336..747W Altcode: The Solar Eclipse Corona Imaging System (SECIS) observed a strong 6-s oscillation in an active region coronal loop, during the 1999 August 11 total solar eclipse. In the present paper we show that this oscillation is associated with a fast-mode magneto-acoustic wave that travels through the loop apex with a velocity of 2100 km s-1. We use near-simultaneous SOHO observations to calculate the parameters of the loop and its surroundings such as density, temperature and their spatial variation. We find that the temporal evolution of the intensity is in agreement with the model of an impulsively generated, fast-mode wave. Title: Rhessi and Trace Observations of the 21 April 2002 x1.5 Flare Authors: Gallagher, Peter T.; Dennis, Brian R.; Krucker, Säm; Schwartz, Richard A.; Tolbert, A. Kimberley Bibcode: 2002SoPh..210..341G Altcode: Observations of the X1.5 flare on 21 April 2002 are reviewed using the Reuven Ramaty High-Energy Solar Spectroscopic Imager (RHESSI) and the Transition Region and Coronal Explorer (TRACE). The major findings are as follows: (1) The 3-25 keV X-rays started < 4 min before the EUV (195 Å) emission suggesting that the initial energy release heated plasma directly to ≳20 MK, well above the 1.6 MK needed to produce the Fe xii (195 Å) line. (2) Using coaligned 12-25 keV RHESSI and TRACE images, further evidence is found for the existence of hot (15-20 MK) plasma in the 195 Å passband. This hot, diffuse emission is attributed to the presence of the Fe xxiv (192 Å) line within the TRACE 195 Å passband. (3) The 12-25 keV source centroid moves away from the limb with an apparent velocity of ∼ 9.9 km s−1, slowing to ∼ 1.7 km s−1 after 3 hours, its final altitude being ∼ 140 Mm after ∼ 12 hours. This suggests that the energy release site moves to higher altitudes in agreement with classical flare models. (4) The 50-100 keV emission correlates well with EUV flare ribbons, suggesting thick-target interactions at the footpoints of the magnetic arcade. The 50-100 keV time profile matches the time derivative of the GOES light curve (Neupert effect), which suggests that the same electrons that produced the thick-target hard X-ray emission also heat the plasma seen in soft X-rays. (5) X-ray footpoint emission has an E−3 spectrum down to ∼ 10 keV suggesting a lower electron cutoff energy than previously thought. (6) The hard X-ray (25-200 keV) peaks have FWHM durations of ∼ 1 min suggesting a more gradual energy release process than expected. (7) The TRACE images reveal a bright symmetric front propagating away from the main flare site at speeds of ≥ 120 km s−1. This may be associated with the fast CME observed several minutes later by LASCO. (8) Dark sinuous lanes are observed in the TRACE images that extend almost radially from the post-flare loop system. This `fan of spines' becomes visible well into the decay phase of the flare and shows evidence for both lateral and downward motions. Title: Detections of high-frequency oscillations in solar active region coronal loops Authors: Katsiyannis, Athanassios C.; Williams, David R.; McAteer, R. T. James; Gallagher, Peter T.; Mathioudakis, Mihalis; Keenan, Francis P. Bibcode: 2002ESASP.505..441K Altcode: 2002IAUCo.188..441K; 2002solm.conf..441K One of the mechanisms proposed as a possible solution to the Sun's coronal heating problem is the damping of energy carried by magnetohydrodynamic (MHD) waves that are expected to be present in active regions. Continuing previous work on total solar eclipse data, we provide further obervational evidence for the existence of high-frequency MHD waves in coronal loops. Wavelet analysis is used to identify 21 areas of 4×4 arcsec2 with periodic intensity oscillations. The frequency range of these detections was 0.2-0.3 Hz and all last for at least 3 periods at a confidence level of more than 99%. All of the above detections are made just outside known coronal loops, leading us to suggest a possible, unconventional mechanism. Title: Detection of propagating waves throughout the chromosphere in network bright points Authors: McAteer, R. T. James; Gallagher, Peter T.; Williams, David R.; Mathioudakis, Mihalis; Phillips, Kenneth J. H.; Keenan, Francis P. Bibcode: 2002ESASP.505..305M Altcode: 2002IAUCo.188..305M; 2002solm.conf..305M We analysed oscillations in individual Network Bright Points (NBPs) in Ca II K3, Hα core, Mg I b2, and Mg I b1-0.4 Å giving us a range of heights from the upper to the lower chromosphere. Lightcurves, and hence power spectra, were created by isolating distinct regions of the NBP via a simple intensity thresholding technique. Using this technique, it was possible to identify peaks in the power spectra with particular spatial positions within the NBPs. This was extended into the time domain by means of wavelet analysis. We track the temporal evolution of power in particular frequency bands by creating power curves. These are then cross-correlated across all observed wavelengths to search for propagating waves. In particular, long-period waves with periods of 4-15 minutes (1-4 mHz) were found in the central portion of each NBP, indicating that these waves are certainly not acoustic, but possibly due to magneto-acoustic or magneto-gravity wave modes. We note the possible existence of fast-mode MHD waves in the lower chromosphere, coupling and transferring power top higher-frequency slow-mode MHD waves in the upper chromosphere. Title: Observations of a high-frequency, fast-mode wave in a coronal loop Authors: Williams, David R.; Mathioudakis, Mihalis; Gallagher, Peter T.; Phillips, Kenneth J. H.; McAteer, R. T. James; Keenan, Francis P.; Katsiyannis, Athanassios C. Bibcode: 2002ESASP.505..615W Altcode: 2002IAUCo.188..615W; 2002solm.conf..615W The high-cadence Solar Eclipse Corona Imaging System (SECIS) observed a strong 6-second oscillation in an active region coronal loop, during the 1999 August 11 total solar eclipse. In the present paper we show that this oscillation is associated with a fast-mode wave that travels through the loop apex with a velocity of ~2000 km s-1. We use near-simultaneous SoHO/CDS obervations to calculate the parameters of the loop and its surroundings such as density, temperature and their spatial variation. We also calculate radiative losses from the loop in the temperature range 105.8 - 106.4K, and compare these losses with the wave energy density. Although the wave travels a distance greater than λ/4π and therefore meets a necessary criterion for slow dissipation, the dissipation length is well in excess of the loop length. The temporal evolution of the intensity is found to be in agreement with the model of an impulsively generated, fast-mode wave. Title: Active-Region Monitoring and Flare Forecasting I. Data Processing and First Results Authors: Gallagher, Peter T.; Moon, Y. -J.; Wang, Haimin Bibcode: 2002SoPh..209..171G Altcode: This paper discusses a near real-time approach to solar active-region monitoring and flare prediction using the Big Bear Solar Observatory Active Region Monitor (ARM). Every hour, ARM reads, calibrates, and analyses a variety of data including: full-disk Hα images from the Global Hα Network; EUV, continuum, and magnetogram data from the Solar and Heliospheric Observatory (SOHO); and full-disk magnetograms from the Global Oscillation Network Group (GONG). For the first time, magnetic gradient maps derived from GONG longitudinal magnetograms are now available on-line and are found to be a useful diagnostic of flare activity. ARM also includes a variety of active-region properties from the National Oceanic and Atmospheric Administration's Space Environment Center, such as up-to-date active-region positions, GOES 5-min X-ray data, and flare-to-region identifications. Furthermore, we have developed a Flare Prediction System which estimates the probability for each region to produce C-, M-, or X-class flares based on nearly eight years of NOAA data from cycle 22. This, in addition to BBSO's daily solar activity reports, has proven a useful resource for activity forecasting. Title: Solar Submillimeter and Gamma-Ray Burst Emission Authors: Kaufmann, P.; Raulin, J. -P.; Melo, A. M.; Correia, E.; Costa, J. E. R.; de Castro, C. G. Giménez; Silva, A. V. R.; Yoshimori, M.; Hudson, H. S.; Gan, W. Q.; Gary, D. E.; Gallagher, P. T.; Levato, H.; Marun, A.; Rovira, M. Bibcode: 2002ApJ...574.1059K Altcode: Solar flare emission was measured at 212 GHz in the submillimeter range by the Submillimeter Solar Telescope in the 1.2-18 GHz microwave range by the Owens Valley Solar Array and in the gamma-ray energy range (continuum) by experiments on board the Yohkoh (>1.2 MeV) and Shenzhou 2 (>0.2 MeV) satellites. At the burst onset, the submillimeter and microwave time profiles were well correlated with gamma rays to the limit of the temporal resolution (<=10 s). At 212 GHz, fast pulses (<1 s), defined as time structures in excess of the bulk emission, were identified as the flux increased. Their spatial positions were scattered by tens of arcseconds with respect to the main burst emission position. Correlation of submillimeter emission with gamma-ray fast time structures shorter than 500 ms is suggested at the gamma-ray maximum. The time variation of the rate of occurrence of the submillimeter rapid pulses was remarkably well correlated with gamma-ray intensities in the energy range (>1.2 MeV), attaining nearly 50 pulses per minute at the maximum. These results suggest that gamma rays might be the response to multiple rapid pulses at 212 GHz and might be produced at different sites within the flaring region. Title: Statistical Evidence for Sympathetic Flares Authors: Moon, Y. -J.; Choe, G. S.; Park, Y. D.; Wang, Haimin; Gallagher, Peter T.; Chae, Jongchul; Yun, H. S.; Goode, Philip R. Bibcode: 2002ApJ...574..434M Altcode: Sympathetic flares are a pair of flares that occur almost simultaneously in different active regions, not by chance, but because of some physical connection. In this paper statistical evidence for the existence of sympathetic flares is presented. From GOES X-ray flare data, we have collected 48 pairs of near simultaneous flares whose positional information and Yohkoh soft X-ray telescope images are available. To select the active regions that probably have sympathetic flares, we have estimated the ratio R of actual flaring overlap time to random-coincidence overlap time for 38 active region pairs. We have then compared the waiting-time distributions for the two different groups of active region pairs (R>1 and R<1) with corresponding nonstationary Poisson distributions. As a result, we find a remarkable overabundance of short waiting times for the group with R>1. This is the first time such strong statistical evidence has been found for the existence of sympathetic flares. To examine the role of interconnecting coronal loops, we have also conducted the same analysis for two subgroups of the R>1 group: one with interconnecting X-ray loops and the other without. We do not find any statistical evidence that the subgroup with interconnecting coronal loops is more likely to produce sympathetic flares than the subgroup without. For the subgroup with loops, we find that sympathetic flares favor active region pairs with transequatorial loops. Title: Solar activity monitoring and forecasting capabilities at Big Bear Solar Observatory Authors: Gallagher, P. T.; Denker, C.; Yurchyshyn, V.; Spirock, T.; Qiu, J.; Wang, H.; Goode, P. R. Bibcode: 2002AnGeo..20.1105G Altcode: The availability of full-disk, high-resolution Ha Title: Electron Transport during the 1999 August 20 Flare Inferred from Microwave and Hard X-Ray Observations Authors: Lee, Jeongwoo; Gary, Dale E.; Qiu, Jiong; Gallagher, Peter T. Bibcode: 2002ApJ...572..609L Altcode: We discuss injection and transport of high-energy electrons during a GOES X-ray class M9.8 flare observed in microwaves with the Owens Valley Solar Array (OVSA) and in hard X-rays (HXRs) with the hard X-ray telescope (HXT) on board Yohkoh. Observed at 1 s timescales or better in both wavelength regimes, the event shows (1) a large difference in scale between the microwave source and the HXR source; (2) an unusually hard HXR spectrum (maximum spectral index ~-1.6), followed by rapid spectral softening; and (3) a microwave light curve containing both impulsive peaks (3 s rise time) simultaneous with those of the HXRs and a long, extended tail with a uniform decay rate (2.3 minutes). We analyze the observations within the framework of the electron trap-and-precipitation model, allowing a time-dependent injection energy spectrum. Assuming thick-target bremsstrahlung for the HXRs, we infer the electron injection function in the form Q(E,t)~(E/E0)-δ(t), where the timescale for δ(t) to change by unity is ~7 s. This injection function can account for the characteristics of the impulsive part of the microwave burst by considering the bulk of the electrons to be directly precipitating without trapping. The same injection function also accounts for the gradual part of the microwave emission by convolving the injection function with a kernel representing the trapping process, which at late times gives N(E,t)~e-νt(E/E0)-b. We require b~1.4 and ν~6×10-3β s-1, where β is the electron speed divided by the speed of light. Therefore, the derived form of the precipitation rate ν itself indicates strong pitch-angle diffusion, but the slow decay of the microwave radiation requires a small loss cone (~4°) and a low ambient density in the coronal trap. Also, the numbers of electrons needed to account for the two components of the microwave emission differ by an order of magnitude. We estimate that the >=100 keV number of the directly precipitating electrons is ~1033, while the trapped population requires ~1032 electrons. This leads us to a model of two interacting loops, the larger of which serves as an efficient trap while the smaller provides the impulsive source. These characteristics are consistent with the spatially resolved observations. Title: Solar Flare Spectroscopy and Imaging with CDS and TRACE Authors: Gallagher, P. T. Bibcode: 2002AAS...200.6807G Altcode: 2002BAAS...34..756G In this poster we discuss recent CDS and TRACE observations of a number of small and intermediate magnitude solar flares. In particular, we focus on a C3.0 flare which occurred on 26 March 2002 peaking at 15:21 UT. The event is first observed as two simultaneous foot-point brightenings in He I (584.33 A), followed by distinct loop-top emission visible in Fe XIX (592.16 A), which has a formation temperature of close to 10,000,000 K. As this high-temperature emission begins to cool, a cusp-shaped feature then becomes visible in Mg X (624.94 A) and Fe XVI (360.76 A). In addition to the morphology of the event seen in CDS and TRACE (171 A) images, a detailed analysis of CDS line parameters such as line position, width, and intensity is discussed in light of current solar flare models. Title: Core and Large-Scale Structure of the 2000 November 24 X-Class Flare and Coronal Mass Ejection Authors: Wang, Haimin; Gallagher, Peter; Yurchyshyn, Vasyl; Yang, Guo; Goode, Philip R. Bibcode: 2002ApJ...569.1026W Altcode: In this paper, we present three important aspects of the X1.8 flare and the associated coronal mass ejection (CME) that occurred on 2000 November 24: (1) The source of the flare is clearly associated with a magnetic channel structure, as was noted in a study by Zirin & Wang , which is due to a combination of flux emergence inside the leading edge of the penumbra of the major leading sunspot and proper motion of the sunspot group. The channel structure provides evidence for twisted flux ropes that can erupt, forming the core of a CME, and may be a common property of several superactive regions that have produced multiple X-class flares in the past. (2) There are actually three flare ribbons visible. The first can be seen moving away from the flare site, while the second and third make up a stationary ribbon near the leader spot. The moving ribbons could be due to a shock associated with the erupting flux rope or due to the interaction of erupting rope and the surrounding magnetic fields. In either case, the ribbon motion does not fit the classical Kopp-Pneuman model, in which the separation of ribbons is due to magnetic reconnection at successively higher and higher coronal altitudes. (3) From the coronal dimming observed with the EUV Imaging Telescope (EIT), the CME involved a much larger region than the initial X-class flare. By comparing high-resolution full-disk Hα and EIT observations, we found that a remote dimming area is cospatial with the enhanced Hα emission. This result is consistent with the recent model of Yokoyama & Shibata that some dimming areas near footpoints may be due to chromospheric evaporation. Title: Long-Period Chromospheric Oscillations in Network Bright Points Authors: McAteer, R. T. James; Gallagher, Peter T.; Williams, David R.; Mathioudakis, Mihalis; Phillips, Kenneth J. H.; Keenan, Francis P. Bibcode: 2002ApJ...567L.165M Altcode: The spatial variation of chromospheric oscillations in network bright points (NBPs) is studied using high-resolution observations in Ca II K3. Light curves and hence power spectra were created by isolating distinct regions of the NBP via a simple intensity thresholding technique. Using this technique, it was possible to identify peaks in the power spectra with particular spatial positions within the NBPs. In particular, long-period waves with periods of 4-15 minutes (1-4 mHz) were found in the central portions of each NBP, indicating that these waves are certainly not acoustic but possibly due to magnetoacoustic or magnetogravity wave modes. We also show that spatially averaged or low spatial resolution power spectra can lead to an inability to detect such long-period waves. Title: RHESSI and TRACE Observations of an X-class Flare Authors: Hudson, H.; Dennis, B.; Gallagher, P.; Krucker, S.; Reeves, K.; Warren, H. Bibcode: 2002cosp...34E3101H Altcode: 2002cosp.meetE3101H RHESSI and TRACE both obtained excellent observations of an X1.5 flare on April 21, 2002. In this paper we provide an overview of the flare and discuss the high- energy imaging and spectra in detail. The TRACE images in the 195A passband (Fe XII and FeXXIV) reveal this flare to have a spiky arcade with post-flare flow field in the "supra-arcade downflow" pattern discovered by Yohkoh. Below the spikes, but above the FeXII loops, TRACE observes a region with complex motions and fine structure. We confirm with RHESSI that this region has an elevated temperature and discuss the transition between thermal and non-thermal sources. RHESSI also observes footpoint emission distributed along the flare ribbons. Title: Space Weather: The Scientific Forecast Authors: Wang, H.; Gallagher, P. T.; Yurchyshyn, V. Bibcode: 2002stma.conf..375W Altcode: No abstract at ADS Title: Impulsive Events and Coronal Loop Cooling Observed with TRACE Authors: Seaton, D. B.; DeLuca, E. E.; Golub, L.; Reeves, K. K.; Winebarger, A. R.; Gallagher, P. T. Bibcode: 2001AGUFMSH11A0705S Altcode: Nearly every active region imaged by TRACE contains sporadic brightenings in coronal loops. Many of these ubiquitous, short-lived events appear nearly simultaneously in the Fe IX/X (log T e≈ 6.0) and the C IV channel (log T≈ 5.0); hence, we interpret them as the rapid cooling of a multifilament loops. A particularly good example of such an event was observed on 21, June 2001, as part of an hour long active region observation; a total of 52 of the TRACE 171 Å and 68 TRACE 1600 Å images have been analyzed from that sequence, as well as 35 images provided by the MDI aboard SOHO. In this poster, we will discuss the analysis of the events and the implications of our cooling model. Title: Active Region Transient Events Observed with TRACE Authors: Seaton, Daniel B.; Winebarger, Amy R.; DeLuca, Edward E.; Golub, Leon; Reeves, Katharine K.; Gallagher, Peter T. Bibcode: 2001ApJ...563L.173S Altcode: Nearly all active region observations made by the Transition Region and Coronal Explorer (TRACE) contain seemingly spontaneous, short-lived brightenings in small-scale loops. In this paper, we present an analysis of these brightenings using high-cadence TRACE observations of Active Region 9506 on 2001 June 21 from 15:17:00 to 15:46:00 UT. During this time frame, several brightenings were observed over a neutral line in a region of emerging flux that had intensity signatures in both the 171 Å (logTe~6.0) and 1600 Å (logTe~4.0-5.0) channels. The events had a cross-sectional diameter of approximately 2" and a length of 25". We interpret these as reconnection events associated with flux emergence, possible EUV counterparts to active region transient brightenings. Title: Electron Densities in the Coronae of the Sun and Procyon from Extreme-Ultraviolet Emission Line Ratios in Fe XI Authors: Pinfield, D. J.; Keenan, F. P.; Mathioudakis, M.; Widing, K. G.; Gallagher, P. T.; Gupta, G. P.; Tayal, S. S.; Thomas, R. J.; Brosius, J. W. Bibcode: 2001ApJ...562..566P Altcode: New R-matrix calculations of electron impact excitation rates for Fe XI are used to determine theoretical emission line ratios applicable to solar and stellar coronal observations. These are subsequently compared to solar spectra of the quiet Sun and an active region made by the Solar EUV Rocket Telescope and Spectrograph (SERTS-95), as well as Skylab observations of two flares. Line blending is identified, and electron densities of 109.3, 109.7, >=1010.8, and >=1011.3 cm-3 are found for the quiet Sun, active region, and the two flares, respectively. Observations of the F5 IV-V star Procyon, made with the Extreme Ultraviolet Explorer (EUVE) satellite, are compared and contrasted with the solar observations. It is confirmed that Procyon's average coronal conditions are very similar to those seen in the quiet Sun, with Ne=109.4 cm-3. In addition, although the quiet Sun is the closest solar analog to Procyon, we conclude that Procyon's coronal temperatures are slightly hotter than solar. A filling factor of 25+38-12% was derived for the corona of Procyon. Title: High-frequency oscillations in a solar active region coronal loop Authors: Williams, D. R.; Phillips, K. J. H.; Rudawy, P.; Mathioudakis, M.; Gallagher, P. T.; O'Shea, E.; Keenan, F. P.; Read, P.; Rompolt, B. Bibcode: 2001MNRAS.326..428W Altcode: The Solar Eclipse Corona Imaging System (SECIS) was used to record high-cadence observations of the solar corona during the total solar eclipse of 1999 August 11. During the 2min 23.5s of totality, 6364 images were recorded simultaneously in each of the two channels: a white light channel, and the Fexiv (5303Å) `green line' channel (T~2MK). Here we report initial results from the SECIS experiment, including the discovery of a 6-s intensity oscillation in an active region coronal loop. Title: The Extreme-Ultraviolet Structure and Properties of a Newly Emerged Active Region Authors: Gallagher, Peter T.; Phillips, Kenneth J. H.; Lee, Jeongwoo; Keenan, Francis P.; Pinfield, David J. Bibcode: 2001ApJ...558..411G Altcode: The structure and properties of a newly emerged solar active region (NOAA Active Region 7985) are discussed using the Coronal Diagnostic Spectrometer (CDS) and the Extreme-Ultraviolet Imaging Telescope (EIT) on board the Solar and Heliospheric Observatory. CDS obtained high-resolution EUV spectra in the 308-381 Å and 513-633 Å wavelength ranges, while EIT recorded full-disk EUV images in the He II (304 Å), Fe IX/X (171 Å), Fe XII (195 Å), and Fe XV (284 Å) bandpasses. Electron density measurements from Si IX, Si X, Fe XII, Fe XIII, and Fe XIV line ratios indicate that the region consists of a central high-density core with peak densities of the order of 1.2×1010 cm-3, which decrease monotonically to ~5.0×108 cm-3 at the active region boundary. The derived electron densities also vary systematically with temperature. Electron pressures as a function of both active region position and temperature were estimated using the derived electron densities and ion formation temperatures, and the constant pressure assumption was found to be an unrealistic simplification. Indeed, the active region is found to have a high-pressure core (1.3×1016 cm-3 K) that falls to 6.0×1014 cm-3 K just outside the region. CDS line ratios from different ionization stages of iron, specifically Fe XVI (335.4 Å) and Fe XIV (334.4 Å), were used to diagnose plasma temperatures within the active region. Using this method, peak temperatures of 2.1×106 K were identified. This is in good agreement with electron temperatures derived using EIT filter ratios and the two-temperature model of Zhang et al. The high-temperature emission is confined to the active region core, while emission from cooler (1-1.6)×106 K lines originates in a system of loops visible in EIT 171 and 195 Å images. Finally, the three-dimensional geometry of the active region is investigated using potential field extrapolations from a Kitt Peak magnetogram. The combination of EUV and magnetic field extrapolations extends the ``core-halo'' picture of active region structure to one in which the core is composed of a number of compact coronal loops that confine the hot, dense, high-pressure core plasma while the halo emission emerges from a system of cooler and more extended loops. Title: Asymmetric Behavior of Hα Footpoint Emission during the Early Phase of an Impulsive Flare Authors: Qiu, Jiong; Ding, Ming D.; Wang, Haimin; Gallagher, Peter T.; Sato, Jun; Denker, Carsten; Goode, Philip R. Bibcode: 2001ApJ...554..445Q Altcode: We study the impulsive phase of a C9.0 solar flare using high temporal and spatial resolution Hα images from Big Bear Solar Observatory (BBSO) in conjunction with high-cadence hard X-ray (HXR) observations from Yohkoh. During the early impulsive phase, HXR emission emerged from two kernels K1 and K2 which were connected by coronal loops observed in soft X-ray (SXR) images from Yohkoh. In Hα, the initial rise was observed in one flare kernel K2, which was followed within 10 s by enhanced emission in the associated kernel K1. Such a significant asymmetry was not observed at HXR wavelengths. Our analysis shows that the asymmetric Hα footpoint emission cannot be explained by the magnetic mirroring effect in which strong field footpoints show lower precipitation rates. Instead, we study this phenomenon by investigating the atmospheric response of the lower chromosphere to nonthermal beam heating. From numerical simulations, it is suggested that a cool atmosphere does not respond rapidly to beam impact, which may explain the missing Hα emission at K1 during the early impulsive phase. At K2, the early-phase atmosphere may be preferentially heated resulting in the Hα emission rapidly following the HXR emission. This is due to the fact that K2 is a compact source which received persistent energy deposition and consequent heating in a confined area during the early phase. K1, on the other hand, is a diffused source which therefore experienced a lower heating rate per unity area. We propose a scenario in which the flare loop consists of multiple magnetic ``threads'' connecting the compact footpoint K2 with the diffuse footpoint K1. Title: Optical, EUV, and Microwave Observations of the March 22, 2000 X-class Flare. Authors: Gallagher, P. T.; Gary, D. E.; Lee, J. Bibcode: 2001AGUSM..SP42A08G Altcode: The evolution of an X-class flare which occured in NOAA 8910 on March 22, 2000 is discussed using observations from the Owens Valley Solar Array (ovsa), Big Bear Solar Observatory (bbso), the Transition Region and Coronal Explorer (trace), and the Michelson Doppler Imager (mdi). The main energy release occurs in a set of coronal loops visible in the trace 171 Å (1 x 106~K) wavelength band, which is rapidly followed by the emergence of two bright Hα ribbons. High-cadence radio images at around 5 GHz obtained using the ovsa appears in the middle of two Hα ribbons, which thus indicates presence of energetic electrons flowing across the two ribbons. During the impulsive phase, short-lived (τ <= 30 s), narrow-band (BW <= 500 MHz), and highly polarized microwave emission is observed in radio images in the 1-2 GHz frequency range, which is possibly due to plasma radiation. At optically-thin, high frequencies ovsa total power spectra also show a typical soft-hard-soft evolution indicative of highly efficient nonthermal electron acceleration during the impulsive phase. The microwave emission from this flare is surprisingly short considering that active region is large (> 200 arc sec in diameter) and the flare is energetic (GOES X class). We consider that the compact magnetic field geometry in the flaring region and subsequent strong chromospheric evaporation into it may have limited life of high energy electrons trapped in the loops to such a short duration. Title: Radio and X ray Observations of a Limb Flare during the Max Millennium Campaign Authors: Lee, J.; Gallagher, P. T.; Gary, D. E.; Harra, L. K. Bibcode: 2001AGUSM..SP51A03L Altcode: A powerful (GOES Class M9.8), limb flare was observed on 1999 August 20 above AR 8673 during the second Max Millennium campaign. Due to its location on the limb as well as its strength, the flare observation provides an ideal case of studying vertical structure of electron acceleration and its transport. The hard X ray images from Yohkoh/HXT along with EUV images from SoHO/EIT show an impulsive, compact double brightening in the lower atmosphere and a hypothesis of footpoint emission from a compact loop seems likely. In contrast, microwave visibilities obtained using the Owens Valley Solar Array (OVSA) suggest a region of high energy electrons high in the corona (2x 105 km), requiring large loops that can act as a good trap of electrons. The duration of radio emission is also much extended compared with the hard X ray emission. We present this set of observations as a good example of the trap-plus-precipitation hypothesis, and derive numbers of electrons emitting the microwaves and hard X rays, respectively, as a measure for the trap vs. precipitation. The derived time evolution of electron numbers in energy space is not compatible with a simple hypothesis of energy-independent acceleration solely under Coulomb collisions, but instead requires an acceleration or transport process that is highly energy-dependent. Title: Results from the Big Bear Solar Observatory's New Digital Vector Magnetograph Authors: Spirock, T. J.; Denker, C.; Varsik, J.; Shumko, S.; Qiu, J.; Gallagher, P.; Chae, J.; Goode, P.; Wang, H. Bibcode: 2001AGUSM..SP51B06S Altcode: During the past several years the Big Bear Solar Observatory has been involved in an aggressive program to modernize the observatory's instrumentation. At the forefront of this effort has been the upgrade of the observatory's digital vector magnetograph (DVMG), which has been recently integrated into the observatory's daily observing program. The DVMG, which is mounted on the observatory's 25 cm vacuum refractor, is a highly sensitive, high cadence magnetograph which studies the FeI line at 630.1 nm. An easy to use GUI observing tool has been written to aid instrument development and data acquisition. This tool automatically calibrates the data and generates near real-time vector magnetograms which will aid space weather forecasting and the support of space weather missions. Also, our plan is to integrate the DVMG data into the HESSI Synoptic Archive. The very sensitive quiet Sun magnetograms, produced by the DVMG, will aid the study of small scale magnetic reconnection at the intranetwork level and its possible contribution to the coronal heating problem. Quiet sun longitudinal and active region vector magnetograms will be presented. Image quality, such as bias, cross-talk, noise levels and sensitivity, will be discussed in addition to the improvements gained in post processing such as image selection and image alignment. Title: Cornoal Heating by MHD Waves: Results from the SECIS Instrument during the 1999 Eclipse Authors: Phillip, K. J. H.; Gallagher, P. T.; Williams, D. R.; Keenan, F. P.; Rudawy, P.; Rompolt, B.; Berlicki, A. Bibcode: 2001IAUS..203..467P Altcode: We report on observational evidence for the rôles that small flare-like events and short-period MHD waves play in the heating of the solar corona. In several studies of SOHO and Yohkoh data, we examine the numbers and energies of small events in the EUV and in soft X-rays can account for the necessary energetics of the quiet-Sun corona, finding that EUV events at least might be sufficient to provide the heating, at least in closed-field regions. Results will be summarized in this paper. However, MHD waves may still play an important part, and in a separate investigation we have used fast-cadence imaging of the white-light and green-line corona during the total eclipse of 1999 August 11 to search for short-period modulations. The imaging system is the Solar Eclipse Coronal Imaging System (SECIS), and consists of a pair of CCD cameras and an adapted PC to form images of the corona at a frame rate of 44 s-1. Preliminary analysis of the data suggests the presence of fast changes over the 2-minute-long period of eclipse totality. This paper will also report on the SECIS data. Title: Characteristics of quiet Sun cell and network brightenings Authors: Harra, L. K.; Gallagher, P. T.; Phillips, K. J. H. Bibcode: 2000A&A...362..371H Altcode: Extreme ultraviolet observations of the quiet Sun are made with the Coronal Diagnostic Spectrometer (cds) on board the Solar and Heliospheric Observatory (soho). It has been previously noted that frequent transition region brightenings occur in both the bright network and dark cell regions. Analysing 1125 events, we determined the characteristics of the brightenings in the cell and network regions which include the duration, energy, and intensity increase above the background. Network brightenings are found to be larger than cell events occurring with a mean duration of 150 s and releasing an average of 1026.9 ergs per event. Cell brightenings, on the other hand, last for an average of 96 s and release 1025.8 ergs per event. It has also been found that the distribution of energy is a power-law which is different in the cell (gamma =2.5) and network (gamma =1.5) regions. When the entire quiet Sun region is analysed the value of gamma is 1.7. The number of events per cds pixel is approximately the same, and a histogram of the ratio ([peak value - background]/background) shows similar values for both the cell and network. It is important to analyse the cell and network regions separately in the context of coronal heating by such small flare-like events. Title: The Radial and Angular Variation of Electron Density in the Solar Corona. Authors: Gallagher, P. T.; Mathioudakis, M.; Phillips, K. J. H.; Tsinganos, K.; Keenan, F. P. Bibcode: 2000SPD....31.0234G Altcode: 2000BAAS...32.1290G We derive, for the first time, electron densities as a function of both radius (R) and position angle (θ ) for the south-west quadrant of the off-limb corona, using the density-sensitive Si ix (349.9 Å/341.9 Å) and Si x (356.0 Å/347.7 Å) extreme ultraviolet line ratios. The observations were made with the Coronal Diagnostic Spectrometer (cds) on board the Solar and Heliospheric Observatory (soho), over the range 1.00R⊙ < R < 1.20R⊙ and 180° < θ < 270° . Within the south polar coronal hole, the density varies from 2.3 x 108 cm-3 at 1.0R⊙ to 8.3x 107 cm-3 at 1.20R⊙ , while at the equator the density varies from 6.3 x 108 cm-3 at 1.0R⊙ to 1.6x 108 cm-3 at 1.20R⊙ . The density falloff with height is therefore faster in the equatorial region. We also find that electron densities are, on average, a factor of 2.7 larger in the equatorial regions than in the polar coronal hole at a given radial distance. Finally, we find remarkable agreement between our measured densities as a function of radius and position angle and those predicted by a recent analytic MHD model of the solar wind, strongly supporting its basic premises. Title: Multi-wavelength observations of the 1998 September 27 flare spray Authors: Gallagher, Peter T.; Williams, David R.; Phillips, Kenneth J. H.; Mathioudakis, Mihalis; Smartt, Raymond N.; Keenan, Francis P. Bibcode: 2000SoPh..195..367G Altcode: We report on observations of a large eruptive event associated with a flare that occurred on 27 September 1998 made with the Richard B. Dunn Solar Telescope at Sacramento Peak Observatory (several wave bands including off-line-center Hα), in soft and hard X-rays (GOES and BATSE), and in several TRACE wave bands (including Fe ix/x 171 Å, Fe xii 195 Å, and C iv 1550 Å). The flare initiation is signaled by two Hα foot-point brightenings which are closely followed by a hard X-ray burst and a subsequent gradual increase in other wavelengths. The flare light curves show a complicated, three-component structure which includes two minor maxima before the main GOES class C5.2 peak after which there is a characteristic exponential decline. During the initial stages, a large spray event is observed within seconds of the hard X-ray burst which can be directly associated with a two-ribbon flare in Hα. The emission returns to pre-flare levels after about 35 min, by which time a set of bright post-flare loops have begun to form at temperatures of about 1.0-1.5 MK. Part of the flare plasma also intrudes into the penumbra of a large sunspot, generally a characteristic of very powerful flares, but the flare importance in GOES soft X-rays is in fact relatively modest. Much of the energy appears to be in the form of a second ejection which is observed in optical and ultraviolet bands, traveling out via several magnetic flux tubes from the main flare site (about 60° from Sun center) to beyond the limb. Title: Transition region and coronal structuring Authors: O'Shea, E.; Gallagher, P. T.; Mathioudakis, M.; Phillips, K. J. H.; Keenan, F. P.; Katsiyannis, A. C. Bibcode: 2000A&A...358..741O Altcode: In this paper we examine regions of internetwork, network and bright network emission, observed in the quiet Sun with the Coronal Diagnostic Spectrometer (cds) onboard SoHO. The slopes of the emission measure distributions, between 5.4 <= log Te <= 6.0, are found to differ in each region, suggesting the presence of different atmospheric structures. From an analysis of emission area the network is shown to have two populations of structures, a low transition region group and a coronal group. Using mdi magnetograms the bright network emission is shown to originate from regions of strong magnetic field composed of bipolar loops and unipolar funnels, that extend from the low transition region up to the corona. Up to 30% of all radiative losses between 5.7 <= log Te <= 6.3 are found to come from these continuous bright network structures. Cross-sectional areas calculated from redshift values suggest that the area expansion seen in the bright network emission is the result of flux tube expansion into the corona, accompanied by either a downflow or upflow of material. Title: First results from the upgraded Owens Valley Solar Array. Authors: Gary, D. E.; Hurford, G. J.; Lee, J.; Gallagher, P. T. Bibcode: 2000BAAS...32..818G Altcode: No abstract at ADS Title: Magnetic Reconnection and Energetics of the 2000 March 22 Solar Flare Authors: Gallagher, P. T.; Gary, D. E.; Lee, J. Bibcode: 2000SPD....31.0260G Altcode: 2000BAAS...32..821G The evolution and properties of the 2000 March 22 X--class flare from the β δ active region NOAA 8910 are discussed using high resolution radio observations from the Owen's Valley Solar Array, TRACE UV and EUV filtergrams, GOES soft X-rays, and magnetograms from MDI on board SOHO. The episodic flare evolution is found to be extremely complicated at all observed wavelengths and releases a large amount of both thermal and non--thermal energy. From the UV and EUV observations, the flare is shown to be consistent with the model in which the release of energy is caused by several, successive loop interactions while the radio observations identify multiple non--thermal electron acceleration sites. The final stage of the flare is then characterised by the emergence of a set of post--flare loops parallel to the magnetic neutral line as the system relaxes. Title: Electron Acceleration During the 1999 August 20 Flare Authors: Lee, J.; Gary, D. E.; Gallagher, P. T. Bibcode: 2000SPD....31.0250L Altcode: 2000BAAS...32..820L A powerful flare (GOES SX class of M9.8) occurred on 1999 August 20 at 23:06 UT near the eastern limb during a Max Millennium campaign. The Owens Valley Solar Array (OVSA) at the time was operating in a high time resolution (1 s) mode to observe an impulsive microwave burst rising very rapidly (within 3 s) at all observing frequencies in the range of 1.4 to 18 GHz. As a main characteristic of the burst, the microwave spectrum decays in a remarkably well-defined exponential profile with a timescale varying in the range of ~ 30 s to ~ 4 min, in proportion to the wavelength. The accompanying hard X ray emission from the BATSE DISCLA data is confined to a short time interval ( ~ 30 s), and its light curve is very similar to that of the high-frequency (15--18 GHz) microwaves. Our analysis is therefore focused on whether these observartions are consistent with theoretical predictions for the microwave emission from trapped electrons in the corona and thick target X-ray emission from the electrons precipitating into the chromosphere. In addition, we infer the magnetic reconnection geometry from EUV images obtained from SoHO/EIT which is used as another constraint to study the property of the acceleration. The OVSA is supported by NSF grants ATM-9796213 and AST-9796238 and NASA grant NAG5-6381 to New Jersey Institute of Technology. Title: First Results from the Upgraded Owens Valley Solar Array Authors: Gary, D. E.; Hurford, G. J.; Lee, Jeongwoo; Gallagher, P. T. Bibcode: 2000SPD....31.0244G Altcode: The Owens Valley Solar Array (OVSA) has undergone extensive hardware and software upgrades in preparation for the current solar maximum and the launch of HESSI. We present an overview of the now completed upgrade from 5 to 6 antennas, and show first results from the newly expanded instrument. We show results from several recent flares, as well as multi-frequency maps of active region coronal structure, to demonstrate the improvements now possible with the instrument. The data and analysis software are freely available on the web, and we invite all who are interested in working with these data to contact the associated website. Title: SECIS: The Solar Eclipse Coronal Eclipse Imaging System Authors: Phillips, K. J. H.; Read, P. D.; Gallagher, P. T.; Keenan, F. P.; Rudawy, P.; Rompolt, B.; Berlicki, A.; Buczylko, A.; Diego, F.; Barnsley, R.; Smartt, R. N.; Pasachoff, J. M.; Babcock, B. A. Bibcode: 2000SoPh..193..259P Altcode: The Solar Eclipse Coronal Imaging System (SECIS) is an instrument designed to search for short-period modulations in the solar corona seen either during a total eclipse or with a coronagraph. The CCD cameras used in SECIS have the capability of imaging the corona at a rate of up to 70 frames a second, with the intensities in each pixel digitised in 12-bit levels. The data are captured and stored on a modified PC. With suitable optics it is thus possible to search for fast changes or short-period wave motions in the corona that will have important implications for the coronal heating mechanism. The equipment has been successfully tested using the Evans Solar Facility coronagraph at National Solar Observatory/Sacramento Peak and during the 11 August 1999 eclipse at a site in north-eastern Bulgaria. The instrument is described and preliminary results are outlined. Title: Optical and EUV Observations of the Solar Atmosphere Authors: Gallagher, P. T. Bibcode: 2000PhDT.........2G Altcode: This thesis presents the results of optical and EUV observations of the solar atmosphere ranging in height from the photosphere to the corona. In the first sections, the morphology and dynamics of the photosphere, chromosphere, transition region and corona are studied with the Coronal Diagnostic Spectrometer (CDS) and the Michelson Doppler Imager (MDI) onboard the Solar and Heliospheric Observatory (SOHO). These results are compared to, and found to be consistent with, current solar atmospheric models. We also use the density sensitive Si IX (349.9 A/341.9 A) and Si X (356.0 A/347.7 A) line ratios, observed with CDS, to study the radial and angular variation of electron density in the corona. These observations are found to agree extremely well with recent magnetohydrodynamical models of the corona and solar wind. The design and testing of the Solar Eclipse Coronal Imaging System (SECIS) is also described in the final section. This instrument was designed to search for short-period modulations in the Fe XIV (5303 A) solar corona seen either during a total eclipse or with a coronagraph. Initial results from SECIS observing programs at the John W. Evans Solar Facility coronagraph in New Mexico, and from the 1999 August 11 total solar eclipse are also discussed. Title: OVRO Solar Array Analysis Software in Support of HESSI Authors: Gallagher, P. T.; Gary, D. E.; Lee, J. Bibcode: 2000ASPC..206..363G Altcode: 2000hesp.conf..363G No abstract at ADS Title: The Quiet Sun Atmosphere as Seen by Soho Authors: Phillips, K. J. H.; Gallagher, P. T.; Harra-Murnion, L. K.; Keenan, F. P.; Pres, P. Bibcode: 2000AdSpR..25.1747P Altcode: The recent solar minimum has allowed studies to be made of quiet-Sun structures with SOHO instruments with better resolution than before. This paper reports on the morphology and dynamics of the EUV emission, including the chromospheric and transition-region network and coronal features, and how the photospheric magnetic field and coronal bright points are related Title: A New Study of the Quiet Sun Authors: O'Shea, E.; Gallagher, P. T.; Mathioudakis, M.; Phillips, K. J. H.; Keenan, F. P. Bibcode: 1999ESASP.446..519O Altcode: 1999soho....8..519O In this paper we present results of an emission measure analysis performed on regions of cell, network and bright network emission which were observed in the quiet Sun at Sun centre with the Coronal Diagnostic Spectrometer (CDS) on board SOHO. Seperate emission from the three regions was obtained by a method of image segmentation using a histogram modification technique. From the averaged emission it was possible to produce emission measures over a broad temperature range. These emission measures were then used to produce estimates of radiative and conductive losses in the three regions considered. Using a magnetogram obtained from the MDI instrument on SOHO we show that the bright network emission originates from bipolar magnetic loops and from what appear to be monopole regions, which could be the remains of footpoints of larger loops. The bright network emission shows significantly higher mean magnetic field strength as well as significantly larger radiative energy losses than either of the other two regions. We find some evidence suggesting the presence of cool loops. The process of image segmentation also enabled us to obtain the relative areas of the cell, network and bright network emission as a function of temperature. We found that only the bright network emission showed an expansion in area with temperature and therefore height. Fitting this area curve with the functional form suggested by Rabin (1991),i.e A(T)/A(Th) = [1 + (Gamma2 - 1)(T/Th)nu]1/2/Gamma , for the cross-sectional area of a flux tube, we obtain a value of Gamma=7.1 and nu=2.5 for the constriction and shape factors respectively. Title: The Radial and Angular Variation of the Electron Density in the Solar Corona Authors: Gallagher, P. T.; Mathioudakis, M.; Keenan, F. P.; Phillips, K. J. H.; Tsinganos, K. Bibcode: 1999ApJ...524L.133G Altcode: We derive, for the first time, electron densities as a function of both radius (R) and position angle (θ) for the southwest quadrant of the off-limb corona, using the density-sensitive Si IX λ349.9/λ341.9 and Si X λ356.0/λ347.7 extreme-ultraviolet line ratios. The observations were made with the coronal diagnostic spectrometer on board the Solar and Heliospheric Observatory over the ranges of 1.00 Rsolar<R<1.20 Rsolar and 180deg<θ<270deg. Within the south polar coronal hole, the density varies from 2.3×108 cm-3 at 1.0 Rsolar to 8.3×107 cm-3 at 1.20 Rsolar, while at the equator, the density varies from 6.3×108 cm-3 at 1.0 Rsolar to 1.6×108 cm-3 at 1.20 Rsolar. The density falloff with height is therefore faster in the equatorial region. We also find that electron densities are, on average, a factor of 2.7 larger in the equatorial regions than in the polar coronal hole at a given radial distance. Finally, we find remarkable agreement between our measured densities as a function of radius and position angle and those predicted by a recent analytic MHD model of the solar wind, strongly supporting its basic premises. Title: Transient events in the EUV transition region and chromosphere Authors: Gallagher, P. T.; Phillips, K. J. H.; Harra-Murnion, L. K.; Baudin, F.; Keenan, F. P. Bibcode: 1999A&A...348..251G Altcode: Rapid time cadence observations of the quiet Sun extreme ultraviolet emission, observed by the cds instrument on soho, are discussed. Numerous transient brightenings are observed in network features in both a transition region line (O V 629.73 Ä) and a chromospheric line (He I 584.33 Ä), indicating a dynamic coupling between the chromospheric and transition region network. Their durations are between 80 and 200 s and dimensions 6 000-10 000 km. A wavelet analysis reveals a tendency for semi-periodic behaviour, with excess power at a frequency of about 4 mHz. The variations are much less evident in the internetwork or cell regions, although they are again semi-periodic. Relative line-of-sight velocities have also been derived from the data, the cds spectral resolution allowing a precision of between 4.7 and 6 km s(-1) . There is a clear association of brightenings in the network with downflows of ~ 13 km s(-1) at 250 000 K with some events having velocities of up to ~ 20 km s(-1) , these being measured relative to the average quiet Sun emission. Within the internetwork, we also find a weak correlation between events seen in the He I (584.33 Ä) and the O V (629.73 Ä) lines. In this case, the events have a smaller size (<= 2 000 km), amplitude (both in terms of their intensity and velocity), and also show a higher frequency of about 6 mHz. The apparent differing properties of network and internetwork events implies that both these regions are heated by two distinct mechanisms. In the case of the internetwork, these results further confirm that acoustic waves propagating up from the photosphere and forming shocks in the overlying atmosphere are the most likely heating mechanism. For the network, it is apparent that the heating required must be in excess of that supplied by acoustic shocks. Our view is that the network events are produced by nanoflare-like magnetic reconnections in the corona, or possibly excitation due to a spicule-type event in which there is a repeated rebound. Title: Book Review: The sun in eclipse / Springer, 1997 & 1998 Authors: Gallagher, P. T.; Keenan, F. P.; Phillips, K. J. H.; Read, P. D.; Rudawy, P.; Mpolt, B. Ro Bibcode: 1999IrAJ...26..115G Altcode: The Solar Eclipse Coronal Imaging System (SECIS) is an instrument designed to search for short-period modulations in the solar corona seen either during a total eclipse or with a coronagraph. The CCD cameras used in SECIS have the capability of imaging a selected portion of the corona at a rate of 50 frames per second, with the intensities in each pixel digitised in 12-bit levels. The data are captured and stored on a modified PC. It will thus be possible to search for fast changes or short-period wave motions in the corona that will have important implications for the coronal heating mechanism. Tests have been carried out during the 1998 total solar eclipse visible in Guadeloupe (French West Indies) and with the Evans Solar Facility coronagraph at the National Solar Observatory, Sacramento Peak, with scientifically useful results obtained from the latter. Title: Quiet Sun Bright Point Dynamics and Energetics as seen by SOHO and Yohkoh Authors: Gallagher, P.; Keenan, F.; Phillips, K.; Prés, P.; Harra-Murnion, L. Bibcode: 1999ASPC..183..405G Altcode: 1999hrsp.conf..405G No abstract at ADS Title: Properties of the quiet Sun EUV network Authors: Gallagher, P. T.; Phillips, K. J. H.; Harra-Murnion, L. K.; Keenan, F. P. Bibcode: 1998A&A...335..733G Altcode: Observations of the quiet Sun network in a small region at Sun centre taken with the Coronal Diagnostic Spectrometer (CDS) on board SOHO are reported for EUV lines with T_e between ~ 10(4) and 10(6) K. The changing structure of the network in the upper chromosphere, transition region, up to the corona was examined using intensity distributions which were decomposed into two normal components using a mixture-modelling technique. This enabled areas of high and low intensities to be separated, and hence averaged network properties including area, intensity, contrast, and fractal dimension to be derived as a function of ion temperature. The network area and emission were found to be more concentrated in the transition region than in the chromosphere and in the corona, although the results for the chromospheric He lines appear to be affected by resonance scattering. At ~ 10(6) K, the area and emission of bright structures dramatically increase, partly due to the appearance of small coronal loops. There is also a discrete change in the fractal dimension at coronal temperatures, signifying a change from network to simpler coronal structures. Furthermore, the contrast of bright to dark regions is at a maximum for T_e ~ 2.5x 10(5) K and falls to its lowest values for coronal temperatures. The properties of several individual network structures were found to follow the same general behaviour as in the statistical analysis. Our results including physical dimensions are broadly consistent with the transition region model of Gabriel, although we cannot exclude the existence of low-lying loops as in the model of Dowdy et al. Title: CDS observations of the quiet Sun EUV network Authors: Gallagher, P. T.; Phillips, K. J. H.; Harra-Murnion, L. K.; Keenan, F. P. Bibcode: 1998ESASP.421..365G Altcode: 1998sjcp.conf..365G No abstract at ADS Title: The Structural Variability of the Solar EUV Network Authors: Gallagher, P. T.; Phillips, K. J. H.; Harra-Murnion, L. K.; Keenan, F. P. Bibcode: 1998ASPC..154..612G Altcode: 1998csss...10..612G Observations of the quiet Sun with the Coronal Diagnostic Spectrometer (CDS) on board the Solar and Heliospheric Observatory (SOHO) are reported for the upper chromosphere, transition region, and corona. The changing structure of the EUV network is examined over a temperature range of 1.5 x 10^4 K to 1.2 x 10^6 K using a variety of properties of the characteristic intensity distributions. The distribution of intensity in small (4 x 4 arcmins^2) areas of the quiet Sun at Sun centre has been examined. These distributions were found to consist of both a low intensity core distribution combined with an extended tail associated with the transition region EUV network. Network properties such as relative area, emission, contrast, and fractal dimension have been derived by fitting two Gaussians (one representing the cell distribution, the other the network) to each frequency histogram and then using the cross-over point of the two Gaussians as a boundary point between the two components. The integrity of the network displays a well defined relationship with temperature showing a noticeable structural enhancement in the temperature range 1.1 x 10^5 K to 2.5 x 10^5 K together with a dramatic change in integrity at coronal (>= 10^6 K) temperatures. Title: CDS Observations of the Quiet Sun EUV Network Authors: Gallagher, P. T.; Phillips, K. J. H.; Harra-Murnion, L. K.; Keenan, F. P. Bibcode: 1997ESASP.404..395G Altcode: 1997cswn.conf..395G No abstract at ADS