Author name code: bewsher ADS astronomy entries on 2022-09-14 author:"Bewsher, Danielle" ------------------------------------------------------------------------ Title: Evidence for conservative mass transfer in the classical Algol system δ Librae from its surface carbon-to-nitrogen abundance ratio Authors: Dervişoǧlu, A.; Pavlovski, K.; Lehmann, H.; Southworth, J.; Bewsher, D. Bibcode: 2018MNRAS.481.5660D Altcode: 2018MNRAS.tmp.2565D; 2018arXiv181001465D Algol-type binary systems are the product of rapid mass transfer between the initially more massive component to its companion. It is still unknown whether the process is conservative, or whether substantial mass is lost from the system. The history of a system prior to mass exchange is imprinted in the photospheric chemical composition, in particular in the carbon-to-nitrogen (C/N) ratio. We use this to trace the efficiency of mass-transfer processes in the components of a classical Algol-type system, δ Librae. The present analysis is based on new spectroscopic data (ground-based high-resolution échelle spectra) and extracted archival photometric observations (space-based measurements from the STEREO satellites). In the orbital solution, non-Keplerian effects on the radial-velocity variations were taken into account. This reduces the primary's mass by 1.1 M_⊙ (∼23 per cent) significantly in comparison to previous studies, and removes a long-standing discrepancy between the radius and effective temperature. A spectral disentangling technique is applied to the échelle observations and the spectra of the individual components are separated. Atmospheric and abundance analyses are performed for the mass-gaining component and we found C/N =1.55 ± 0.40 for this star. An extensive set of evolutionary models (3.5 × 106) for both components are calculated from which the best-fitting model is derived. It is found that β, the parameter that quantifies the efficiency of mass-loss from a binary system, is close to zero. This means that the mass transfer in δ Lib is mostly conservative with little mass-loss from the system. Title: The first study of 54 new eccentric eclipsing binaries in our Galaxy Authors: Zasche, P.; Wolf, M.; Uhlař, R.; Cagaš, P.; Juryšek, J.; Mašek, M.; Hoňková, K.; Kučáková, H.; Lehký, M.; Kotková, L.; White, G. J.; Bewsher, D.; Tylšar, M.; Jelínek, M.; Paschke, A. Bibcode: 2018A&A...619A..85Z Altcode: 2018arXiv181108471Z We present an analysis of the apsidal motion and light curve parameters of 54 never-before-studied galactic Algol-type binaries. This is the first analysis of such a large sample of eccentric eclipsing binaries in our Galaxy, and has enabled us to identify several systems that are worthy of further study. Bringing together data from various databases and surveys, supplemented with new observations, we have been able to trace the long-term evolution of the eccentric orbit over durations extending back up to several decades. Our present study explores a rather different sample of stars to those presented in the previously published catalogue of eccentric eclipsing binaries, sampling to fainter magnitudes, covering later spectral types, sensitive to different orbital periods with more than 50% of our systems having periods longer than six days. The typical apsidal motion in the sample is rather slow (mostly of order of centuries long), although in some cases this is less than 50 yr. All of the systems, except one, have eccentricities less than 0.5, with an average value of 0.23. Several of the stars also show evidence for additional period variability. In particular we can identify three systems in the sample, HD 44093, V611 Pup, and HD 313631, which likely represent relativistic apsidal rotators.

The full Table 1 is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/619/A85 Title: VizieR Online Data Catalog: 54 new eccentric galactic eclipsing binaries (Zasche+, 2018) Authors: Zasche, P.; Wolf, M.; Uhlar, R.; Cagas, P.; Jurysek, J.; Masek, M.; Honkova, K.; Kucakova, H.; Lehky, M.; Kotkova, L.; White, G. J.; Bewsher, D.; Tylsar, M.; Jelinek, M.; Paschke, A. Bibcode: 2018yCat..36190085Z Altcode: We have derived the preliminary apsidal motion and light curve parameters for 54 Algol-type binaries. This is the first time any such analysis of such a large sample of eccentric eclipsing binaries has been studied in our Galaxy using different sources of photometry. Bringing together data from various databases and surveys has facilitated estimation of the long-term evolution of the orbit and the apsidal precession of our sample.

(2 data files). Title: Temporal resolution of a pre-maximum halt in a classical nova: V5589 Sgr observed with STEREO HI-1B Authors: Eyres, S. P. S.; Bewsher, D.; Hillman, Y.; Holdsworth, D. L.; Rushton, M. T.; Bresnahan, D.; Evans, A.; Mróz, P. Bibcode: 2017MNRAS.467.2684E Altcode: 2017arXiv170109026E Classical novae show a rapid rise in optical brightness over a few hours. Until recently the rise phase, particularly the phenomenon of a pre-maximum halt, was observed sporadically. Solar observation satellites observing coronal mass ejections enable us to observe the pre-maximum phase in unprecedented temporal resolution. We present observations of V5589 Sgr with STEREO HI-1B at a cadence of 40 min, the highest to date. We temporally resolve a pre-maximum halt for the first time, with two examples each rising over 40 min then declining within 80 min. Comparison with a grid of outburst models suggests that this double peak, and the overall rise time-scale, is consistent with a white dwarf mass, central temperature and accretion rate close to 1.0 M⊙, 5 × 107 K and 10-10 M⊙ yr-1, respectively. The modelling formally predicts mass-loss onset at JD 245 6038.2391 ± 0.0139, 12 h before the optical maximum. The model assumes a main-sequence donor. Observational evidence is for a subgiant companion, meaning that the accretion rate is underestimated. Post-maximum, we see erratic variations commonly associated with much slower novae. Estimating the decline rate is difficult, but we place the time to decline two magnitudes as 2.1 < t2(d) < 3.9, making V5589 Sgr a 'very fast' nova. The brightest point defines 'day 0' as JD 245 6038.8224 ± 0.0139, although at this high cadence the meaning of the observed maximum becomes difficult to define. We suggest that such erratic variability normally goes undetected in faster novae due to the low cadence of typical observations, implying that erratic behaviour is not necessarily related to the rate of decline. Title: Mapping the circumsolar dust ring near the orbit of Venus Authors: Jones, M. H.; Bewsher, D.; Brown, D. S. Bibcode: 2017Icar..288..172J Altcode: Synoptic images obtained from the HI-2 instrument on STEREO-A and -B between 2007 and 2014 have been used to further investigate the circumsolar dust ring at the orbit of Venus that was reported by Jones et al. (2013). The analysis is based on high signal-to-noise ratio photometry of the zodiacal light, using data acquired over 10-day intervals, followed by a process of extracting spatial variability on scales up to about 6.5°. The resulting images provide information about the structure of the ring at the location where it is viewed tangentially. We identify 65 usable data sets that comprise about 11% of the available HI-2 data. Analysis of these images show that the orientation of the ring appears to be different to that of the orbit of Venus, with an inclination of 2.1° and longitude of ascending node of 68.5°. We map the variation of ring density parameters in a frame of reference that is co-rotating with Venus and find a pattern suggestive of dust in a 3: 2 orbital resonance. However, the location of the maxima of dust densities is not as expected from theoretical models, and there is some evidence that the dust density distribution in the ring has a pattern speed that differs from the mean motion of Venus. Title: Nova Light Curves From The Solar Mass Ejection Imager (SMEI) - II. The extended catalog Authors: Hounsell, R.; Darnley, M. J.; Bode, M. F.; Harman, D. J.; Surina, F.; Starrfield, S.; Holdsworth, D. L.; Bewsher, D.; Hick, P. P.; Jackson, B. V.; Buffington, A.; Clover, J. M.; Shafter, A. W. Bibcode: 2016ApJ...820..104H Altcode: 2015arXiv151203321H We present the results from observing nine Galactic novae in eruption with the Solar Mass Ejection Imager (SMEI) between 2004 and 2009. While many of these novae reached peak magnitudes that were either at or approaching the detection limits of SMEI, we were still able to produce light curves that in many cases contained more data at and around the initial rise, peak, and decline than those found in other variable star catalogs. For each nova, we obtained a peak time, maximum magnitude, and for several an estimate of the decline time ({t}{{2}}). Interestingly, although of lower quality than those found in Hounsell et al., two of the light curves may indicate the presence of a pre-maximum halt. In addition, the high cadence of the SMEI instrument has allowed the detection of low-amplitude variations in at least one of the nova light curves. Title: Imaging and mapping the circumsolar dust ring near the orbit of Venus Authors: Jones, M.; Bewsher, D.; Brown, D. Bibcode: 2014acm..conf..250J Altcode: Asteroids and comets are the dominant source of dust feeding the zodiacal cloud [1,2]. The orbits of grains of size 10--100 microns are expected to decay by Poynting-Robertson drag [3], but in the vicinity of planetary orbits dust may get trapped into exterior mean motion resonances [4] to form a circumsolar dust ring. It has long been known that such a ring exists close to the Earth's orbit [5], but even now, little is known about its detailed structure. No such ring or associated resonance feature has been detected at the orbits of Mars or Jupiter [6]. While re-analysis of photometry data from the Helios mission provided some evidence of a ring associated with Venus [7], the existence of such a ring could not be conclusively demonstrated.

Here we report on recent work that confirms the existence of a circumsolar ring at Venus from sensitive optical photometry of the zodiacal cloud [8]. Our analysis uses synoptic images from the HI-2 instrument on STEREO [9]. We discuss the techniques that we have developed to extract images of the Venus ring, and describe the approach taken towards creating a simple parametric model of the ring. We note that the maximum over-density in the ring is about 10% that of the smooth zodiacal cloud, and we highlight other aspects of the ring structure that we have already determined. We demonstrate that the STEREO HI-2 data allow the density structure of the Venus ring to be mapped in much greater detail than the Earth ring. Thus the Venus ring has the potential to provide a stringent test of models of resonance ring formation. Not only is this relevant to understanding the structure of the zodiacal cloud, it is of importance in the context of exoplanetary systems which are also expected to display analogous circumstellar dust rings [10,11]. We conclude by discussing current progress in mapping the density distribution of the Venus circumsolar ring. Title: STEREO/HI and optical observations of the classical nova V5583 Sagittarii Authors: Holdsworth, Daniel L.; Rushton, M. T.; Bewsher, D.; Walter, F. M.; Eyres, S. P. S.; Hounsell, R.; Darnley, M. J. Bibcode: 2014MNRAS.438.3483H Altcode: 2014MNRAS.tmp..110H; 2013arXiv1312.5235H The classical nova V5583 Sgr (Nova Sagittarii 2009 No 3) has been observed during the rise phase and shortly after by NASA's Solar TErrestrial RElations Observatory/Heliospheric Imager (STEREO/HI) instruments, with later optical spectroscopy obtained with the R-C Spectrograph at Cerro Tololo Inter-American Observatory, Chile. The time of peak in the STEREO passband has been constrained to within 4 h, as a result of the high cadence data obtained by STEREO/HI. The optical spectra show the nova evolving from the permitted to the nebular phases. The neon abundance in the ejecta is [Ne/O] ≳ +1.0, which suggests that V5583 Sgr was most likely a neon nova. Title: VizieR Online Data Catalog: STEREO non-magnetic chemically peculiar stars (Paunzen+, 2013) Authors: Paunzen, E.; Wraight, K. T.; Fossati, L.; Netopil, M.; White, G. J.; Bewsher, D. Bibcode: 2014yCat..74290119P Altcode: We have analysed the photometric data obtained with the STEREO spacecraft for 558 non-magnetic chemically peculiar (CP) stars to search for rotational and pulsational variability. Applying the Lomb-Scargle and the phase dispersion minimization methods, we have detected photometric variability for 44 objects from which 35 were previously unknown. The new objects are all bright stars on the ecliptic plane (magnitude range 4.7<V<11.7) and will therefore be of great interest to studies of stellar structure and evolution. In particular, several show multiple signals consistent with hybrid δ Scuti and γ Doradus pulsation, with different periodicities allowing very different regions of the stellar interior to be studied. There are two subgroups of stars in our sample: the cool metallic line Am (CP1) and the hot HgMn (CP3) stars. These objects fall well inside the classical instability strip where δ Scuti, γ Doradus and slowly pulsating B-type stars are located. We also expect to find periods correlated to the orbital period for CP1 objects as they are mostly members of binary systems. For CP3 stars, rotationally induced variability is still a matter of debate. Although surface spots were detected, they are believed to produce only marginal photometric amplitudes. So, periods from several hours to a few days were expected for these two star groups. The STEREO/HI-1 data are well matched to studies of this frequency domain, owing to the cadence of approximately 40-min and multiple epochs over four and a half years. The remaining 514 stars are likely to be constant in the investigated range from 0.1 to 10d. In some cases, the presence of blending or systematic effects prevented us from detecting any reliable variability and in those cases we classified the star as constant. We discuss our results in comparison to already published ones and find a very good agreement. Finally, we have calibrated the variable stars in terms of the effective temperature and luminosity in order to estimate masses and ages. For this purpose, we used specifically developed calibrations for CP stars and, when available, Hipparcos parallaxes. All but two objects cover the stellar mass range from 1.5 to 5M⊙ and are located between the zero- and terminal-age main sequence.

(3 data files). Title: VizieR Online Data Catalog: STEREO magnetic chemically peculiar stars (Wraight+, 2012) Authors: Wraight, K. T.; Fossati, L.; Netopil, M.; Paunzen, E.; Rode-Paunzen, M.; Bewsher, D.; Norton, A. J.; White, G. J. Bibcode: 2014yCat..74200757W Altcode: The stars were observed with the STEREO/HI-1 imager, on board of the Stereo satellites, launched primarily to observe the coronal mass ejections. The field of view is 20x20°, with a resolution of 70arcsec/pix. mostly in the 630-730nm wavelength range. Over the course of an orbit, almost 900,000 stars of 12th magnitude and brighter are imaged within 10° of the ecliptic plane, at a cadence of about 40min.

(3 data files). Title: Imaging of a Circumsolar Dust Ring Near the Orbit of Venus Authors: Jones, M. H.; Bewsher, D.; Brown, D. S. Bibcode: 2013Sci...342..960J Altcode: The gravitational interaction of dust in the zodiacal cloud with individual planets is expected to give rise to ringlike features: Such a circumsolar ring has been observed associated with Earth, but such resonance rings have not been confirmed to exist for other planets. Here, we report on sensitive photometric observations, based on imaging from the STEREO mission, that confirm the existence of a dust ring at the orbit of Venus. The maximum overdensity of dust in this ring, compared to the zodiacal cloud, is ~10%. The radial density profile of this ring differs from the model used to describe Earth’s ring in that it has two distinct steplike components, with one step being interior and the other exterior to the orbit of Venus. Title: On-Orbit Degradation of Solar Instruments Authors: BenMoussa, A.; Gissot, S.; Schühle, U.; Del Zanna, G.; Auchère, F.; Mekaoui, S.; Jones, A. R.; Walton, D.; Eyles, C. J.; Thuillier, G.; Seaton, D.; Dammasch, I. E.; Cessateur, G.; Meftah, M.; Andretta, V.; Berghmans, D.; Bewsher, D.; Bolsée, D.; Bradley, L.; Brown, D. S.; Chamberlin, P. C.; Dewitte, S.; Didkovsky, L. V.; Dominique, M.; Eparvier, F. G.; Foujols, T.; Gillotay, D.; Giordanengo, B.; Halain, J. P.; Hock, R. A.; Irbah, A.; Jeppesen, C.; Judge, D. L.; Kretzschmar, M.; McMullin, D. R.; Nicula, B.; Schmutz, W.; Ucker, G.; Wieman, S.; Woodraska, D.; Woods, T. N. Bibcode: 2013SoPh..288..389B Altcode: 2013arXiv1304.5488B We present the lessons learned about the degradation observed in several space solar missions, based on contributions at the Workshop about On-Orbit Degradation of Solar and Space Weather Instruments that took place at the Solar Terrestrial Centre of Excellence (Royal Observatory of Belgium) in Brussels on 3 May 2012. The aim of this workshop was to open discussions related to the degradation observed in Sun-observing instruments exposed to the effects of the space environment. This article summarizes the various lessons learned and offers recommendations to reduce or correct expected degradation with the goal of increasing the useful lifespan of future and ongoing space missions. Title: A photometric study of chemically peculiar stars with the STEREO satellites - II. Non-magnetic chemically peculiar stars Authors: Paunzen, E.; Wraight, K. T.; Fossati, L.; Netopil, M.; White, G. J.; Bewsher, D. Bibcode: 2013MNRAS.429..119P Altcode: 2012arXiv1211.1535P We have analysed the photometric data obtained with the STEREO spacecraft for 558 non-magnetic chemically peculiar (CP) stars to search for rotational and pulsational variability. Applying the Lomb-Scargle and the phase dispersion minimization methods, we have detected photometric variability for 44 objects from which 35 were previously unknown. The new objects are all bright stars on the ecliptic plane (magnitude range 4.7 < V < 11.7) and will therefore be of great interest to studies of stellar structure and evolution. In particular, several show multiple signals consistent with hybrid δ Scuti and γ Doradus pulsation, with different periodicities allowing very different regions of the stellar interior to be studied. There are two subgroups of stars in our sample: the cool metallic line Am (CP1) and the hot HgMn (CP3) stars. These objects fall well inside the classical instability strip where δ Scuti, γ Doradus and slowly pulsating B-type stars are located. We also expect to find periods correlated to the orbital period for CP1 objects as they are mostly members of binary systems. For CP3 stars, rotationally induced variability is still a matter of debate. Although surface spots were detected, they are believed to produce only marginal photometric amplitudes. So, periods from several hours to a few days were expected for these two star groups. The STEREO/HI-1 data are well matched to studies of this frequency domain, owing to the cadence of approximately 40 min and multiple epochs over four and a half years. The remaining 514 stars are likely to be constant in the investigated range from 0.1 to 10 d. In some cases, the presence of blending or systematic effects prevented us from detecting any reliable variability and in those cases we classified the star as constant. We discuss our results in comparison to already published ones and find a very good agreement. Finally, we have calibrated the variable stars in terms of the effective temperature and luminosity in order to estimate masses and ages. For this purpose, we used specifically developed calibrations for CP stars and, when available, Hipparcos parallaxes. All but two objects cover the stellar mass range from 1.5 to 5 M⊙ and are located between the zero- and terminal-age main sequence. Title: Bright low mass eclipsing binary candidates observed by STEREO Authors: Wraight, K. T.; Fossati, L.; White, Glenn J.; Norton, A. J.; Bewsher, D. Bibcode: 2012MNRAS.427.2298W Altcode: 2012arXiv1209.2014W Observations from the Heliospheric Imagers (HI-1) on both the STEREO spacecraft have been analysed to search for bright low mass eclipsing binaries (EBs) and potential brown dwarf transits and to determine the radii of the companions. A total of nine EB candidates have been found, ranging in brightness from V = 6.59 to 11.3 mag, where the radius of the companion appears to be less than 0.4 R⊙, with a diverse range of host temperatures, from 4074 to 6925 K. Both components of one candidate, BD-07 3648, appear to be less than 0.4 R⊙ and this represents a particularly interesting system for further study. The shapes of the eclipses in some cases are not clear enough to be certain they are total and the corresponding radii found should therefore be considered as lower limits. The EBs reported in this paper have either been newly found by the present analysis or previously reported to be eclipsing by our earlier STEREO/HI-1 results. One of the new objects has subsequently been confirmed using archival SuperWASP data. This study was made possible by using an improved matched filter extraction algorithm, which is described in this paper. Title: STEREO observations of long period variables Authors: Wraight, K. T.; Bewsher, D.; White, Glenn J.; Nowotny, W.; Norton, A. J.; Paladini, C. Bibcode: 2012MNRAS.426..816W Altcode: 2012arXiv1206.1485W Observations from the Heliospheric Imagers (HI-1) on both the STEREO spacecrafts have been analysed to search for very long period large amplitude stellar variability, finding six new candidates. A total of 85 objects, mostly previously known Mira variables, were found to show convincing variability on time-scales of over a 100 days. These objects range in peak brightness from about fourth magnitude to 10th magnitude in R and have periods between about 170 and 490 d. There is a period gap between 200 and 300 d where no objects were found and this is discussed. 15 of the Miras in the sample are previously recorded as having variable periods and the possibility for these and two other stars to have undergone a period change or to be irregular is discussed. In addition to the six stars in the sample not previously recorded as variable, another seven are recorded as variable but with no classification. Our period determination is the first to be made for 19 of these 85 stars. The sample represents a set of very long period variables that would be challenging to monitor from the Earth, or even from Earth orbit, owing to their position on the ecliptic plane and that their periods are often close to a year or an integer fraction thereof. The possibility for the new candidates to possess circumstellar shells is discussed. Title: Long-Term Evolution of the Photometric Calibration of the STEREO Heliospheric Imagers: I. HI-1 Authors: Bewsher, D.; Brown, D. S.; Eyles, C. J. Bibcode: 2012SoPh..276..491B Altcode: The aim of this paper is to determine whether the photometric response of the STEREO HI-1A and HI-1B Heliospheric Imagers has evolved or degraded during the mission to date. This is done using the methodology of Bewsher et al. (Solar Phys.264, 433, 2010) to calculate the photometric calibration factor, μ, over the four complete STEREO heliocentric orbits between the start of the science mission operations in April 2007 and June 2011, and to evaluate whether this parameter has undergone any significant variation. It is shown that the photometric response of the instruments has remained stable to within ∼ 1%. The value of μ across different parts of the field of view is also determined to evaluate the validity of the calibrated large-scale flatfield determined by Bewsher et al. (Solar Phys.264, 433, 2010). Based on the results, new revised values for the photometric calibration factor and conversion factors for diffuse sources are presented. Title: A photometric study of chemically peculiar stars with the STEREO satellites - I. Magnetic chemically peculiar stars Authors: Wraight, K. T.; Fossati, L.; Netopil, M.; Paunzen, E.; Rode-Paunzen, M.; Bewsher, D.; Norton, A. J.; White, Glenn J. Bibcode: 2012MNRAS.420..757W Altcode: 2011MNRAS.tmp.2052W; 2011arXiv1110.6283W About 10 per cent of upper main-sequence stars are characterized by the presence of chemical peculiarities, often found together with a structured magnetic field. The atmospheres of most of those chemically peculiar stars present surface spots, leading to photometric variability caused by rotational modulation. The study of the light curves of those stars therefore permits a precise measurement of their rotational period, which is important to study stellar evolution and to plan further detailed observations. We analysed the light curves of 1028 chemically peculiar stars obtained with the STEREO spacecraft. We present here the results obtained for the 337 magnetic chemically peculiar stars in our sample. Thanks to the cadence and stability of the photometry, STEREO data are perfectly suitable to study variability signals with a periodicity typical of magnetic chemically peculiar stars. Using a matched filter algorithm and then two different period searching algorithms, we compiled a list of 82 magnetic chemically peculiar stars for which we measured a reliable rotational period; for 48 of them, this is the first measurement of their rotational period. The remaining 255 stars are likely to be constant, although we cannot exclude the presence of long-period variability. In some cases, the presence of blending or systematic effects prevented us from detecting any reliable variability and in those cases we classified the star as constant. For each star we classified as variable, we determined temperature, luminosity, mass and fractional age, but the limited statistics, biased towards the shorter periods, prevented us from finding any evolutionary trend of the rotational period. For a few stars, the comparison between their projected rotational velocity and equatorial velocity let us believe that their real rotational period might be longer than that found here and previously obtained. For the 82 stars identified as variable, we give all necessary information needed to plan further phase-dependent observations. Data obtained with the Heliospheric Imager instruments on board the STEREO spacecraft. Title: What is the true nature of blinkers? Authors: Subramanian, S.; Madjarska, M. S.; Doyle, J. G.; Bewsher, D. Bibcode: 2012A&A...538A..50S Altcode: 2011arXiv1111.2149S
Aims: The aim of this work is to identify the true nature of the transient EUV brightenings, called blinkers.
Methods: Co-spatial and co-temporal multi-instrument data, including imaging (EUVI/STEREO, XRT and SOT/Hinode), spectroscopic (CDS/SoHO and EIS/Hinode) and magnetogram (SOT/Hinode) data, of an isolated equatorial coronal hole were used. An automatic program for identifying transient brightenings in CDS O v 629 Å, EUVI 171 Å and XRT was applied.
Results: We identified 28 blinker groups in the CDS O v 629 Å raster images. All CDS O v 629 Å blinkers showed counterparts in EUVI 171 Å and 304 Å images. We classified these blinkers into two categories, one associated with coronal counterparts and other with no coronal counterparts as seen in XRT images and EIS Fe xii 195.12 Å raster images. Around two-thirds of the blinkers show coronal counterparts and correspond to various events like EUV/X-ray jets, brightenings in coronal bright points or foot-point brightenings of larger loops. These brightenings occur repetitively and have a lifetime of around 40 min at transition region temperatures. The remaining blinker groups with no coronal counterpart in XRT and EIS Fe xii 195.12 Å appear as point-like brightenings and have chromospheric/transition region origin. They take place only once and have a lifetime of around 20 min. In general, lifetimes of blinkers are different at different wavelengths, i.e. different temperatures, decreasing from the chromosphere to the corona.
Conclusions: This work shows that the term blinker covers a range of phenomena. Blinkers are the EUV response of various transient events originating at coronal, transition region and chromospheric heights. Hence, events associated with blinkers contribute to the formation and maintenance of the temperature gradient in the transition region and the corona. Title: STEREO observations of stars and the search for exoplanets Authors: Wraight, K. T.; White, Glenn J.; Bewsher, D.; Norton, A. J. Bibcode: 2011MNRAS.416.2477W Altcode: 2011arXiv1103.0911W; 2011MNRAS.tmp.1348W The feasibility of using data from the NASA STEREO mission for variable star and asteroseismology studies has been examined. A data analysis pipeline has been developed that is able to apply selected algorithms to the entire data base of nearly a million stars to search for signs of variability. An analysis limited to stars of magnitude 10.5 has been carried out, which has resulted in the extraction of 263 eclipsing binaries (EBs), of which 122 are not recorded as such in the SIMBAD online data base. The characteristics of the STEREO observations are shown to be extremely well suited to variable star studies with the ability to provide continuous phase coverage for extended periods as well as repeated visits that allow both short- and long-term variability to be observed. This will greatly inform studies of particular stars, such as the pre-cataclysmic variable V471 Tau, as well as the entire classes of stars, including many forms of rotational variability. The high-precision photometry has also revealed a potentially substellar companion to a bright (R= 7.5 mag) nearby star (HD 213597), detected with 5σ significance. This would provide a significant contribution to the exoplanet research if follow-up observations ascertain the mass to be within the planetary domain. Some particularly unusual EBs from the recovered sample are discussed, including a possible reclassification of a well-known star as an EB rather than a rotational variable (HR 7355) and several particularly eccentric systems, including very long period EBs. Title: VizieR Online Data Catalog: STEREO observations of variable stars (Wraight+, 2011) Authors: Wraight, K. T.; White, G. J.; Bewsher, D.; Norton, A. J. . Bibcode: 2011yCat..74162477W Altcode: Description of the analysis of stars brighter than R=10.5mag from the Heliospheric Imager on the STEREO-Ahead spacecraft (STEREO/HI-1A). Analysis of the effectiveness of the different algorithms used. Analysis of different trends amongst the sample of EBs detected. Photometric lightcurves of several individual stars of interest given, including all measurably eccentric EBs detected. Statistics for 263 eclipsing binaries. Lightcurves for all EBs provided in supporting information in the electronic version of the paper.

(1 data file). Title: Straylight-Rejection Performance of the STEREO HI Instruments Authors: Halain, J. -P.; Eyles, C. J.; Mazzoli, A.; Bewsher, D.; Davies, J. A.; Mazy, E.; Rochus, P.; Defise, J. M.; Davis, C. J.; Harrison, R. A.; Crothers, S. R.; Brown, D. S.; Korendyke, C.; Moses, J. D.; Socker, D. G.; Howard, R. A.; Newmark, J. S. Bibcode: 2011SoPh..271..197H Altcode: 2011SoPh..tmp..189H; 2011SoPh..tmp..132H; 2011SoPh..tmp..258H The SECCHI Heliospheric Imager (HI) instruments on-board the STEREO spacecraft have been collecting images of solar wind transients, including coronal mass ejections, as they propagate through the inner heliosphere since the beginning of 2007. Title: The UCLan SDO Data Hub Authors: Dalla, S.; Walsh, R. W.; Chapman, S. A.; Marsh, M.; Regnier, S.; Bewsher, D.; Brown, D. S.; Kelly, J.; Laitinen, T.; Alexander, C. Bibcode: 2010AGUFMSH23C1876D Altcode: A data pipeline for the distribution of SDO data products has been developed throughout a number of countries in the US, Europe and Asia. The UK node within this pipeline is at the University of Central Lancashire (UCLan), where a data center has been established to host a rolling AIA and HMI archive, aimed at supplying data to the country's large solar scientific community. This presentation will describe the hardware and software structures of the archive, as well as the best practice identified and feedback received from users of the facility. We will also discuss algorithms that are run locally in order to identify solar features and events. Title: Determination of the Photometric Calibration and Large-Scale Flatfield of the STEREO Heliospheric Imagers: I. HI-1 Authors: Bewsher, D.; Brown, D. S.; Eyles, C. J.; Kellett, B. J.; White, G. J.; Swinyard, B. Bibcode: 2010SoPh..264..433B Altcode: 2010SoPh..tmp..105B The aim of this paper is to calculate an accurate large-scale flatfield for the STEREO HI-1 instruments. This is done by analysing the variation in intensity of stars in the background starfield as they pass across the CCD. In order to use the background starfield, a photometric calibration is performed which defines a HI magnitude scale and a conversion between this scale and measured intensity. The photometric calibration uses stellar spectra folded through the instrument response to make initial intensity predictions. However, a secondary prediction method based on the photometric calibration, which blends the R-, V- and B-magnitudes of a star, is derived for stars with no spectral information. Title: Intermittent release of transients in the slow solar wind: 1. Remote sensing observations Authors: Rouillard, A. P.; Davies, J. A.; Lavraud, B.; Forsyth, R. J.; Savani, N. P.; Bewsher, D.; Brown, D. S.; Sheeley, N. R.; Davis, C. J.; Harrison, R. A.; Howard, R. A.; Vourlidas, A.; Lockwood, M.; Crothers, S. R.; Eyles, C. J. Bibcode: 2010JGRA..115.4103R Altcode: 2010JGRA..11504103R The Heliospheric Imager (HI) instruments on board the STEREO spacecraft are used to analyze the solar wind during August and September 2007. We show how HI can be used to image the streamer belt and, in particular, the variability of the slow solar wind which originates inside and in the vicinity of the streamer belt. Intermittent mass flows are observed in HI difference images, streaming out along the extension of helmet streamers. These flows can appear very differently in images: plasma distributed on twisted flux ropes, V-shaped structures, or “blobs.” The variety of these transient features may highlight the richness of phenomena that could occur near helmet streamers: emergence of flux ropes, reconnection of magnetic field lines at the tip of helmet streamers, or disconnection of open magnetic field lines. The plasma released with these transient events forms part of the solar wind in the higher corona; HI observations show that these transients are frequently entrained by corotating interaction regions (CIRs), leading to the formation of larger, brighter plasma structures in HI images. This entrainment is used to estimate the trajectory of these plasma ejecta. In doing so, we demonstrate that successive transients can be entrained by the same CIR in the high corona if they emanate from the same corotating source. Some parts of the streamers are more effective sources of transients than others. Surprisingly, evidence is given for the outflow of a recurring twisted magnetic structure, suggesting that the emergence of flux ropes can be recurrent. Title: Coronal mass ejections in the heliosphere Authors: Harrison, R. A.; Davis, C. J.; Bewsher, D.; Davies, J. A.; Eyles, C. J.; Crothers, S. R. Bibcode: 2010AdSpR..45....1H Altcode: With the advent of the NASA STEREO mission, we are in a position to perform unique investigations of the evolution of coronal mass ejections (CMEs) as they propagate through the heliosphere, and thus can investigate the relationship between CMEs and their interplanetary counterparts, so-called interplanetary CMEs (ICMEs). ICME studies have been principally limited to single-point, in-situ observations; interpretation of the in-situ characteristics of ICMEs has been used to derive a range of ICME properties which we can now confirm or refute using the STEREO imaging data. This paper is a review of early STEREO CME observations and how they relate to our currently understanding of ICMEs based on in-situ observations. In that sense, it is a first glance at the applications of the new data-sets to this topic and provides pointers to more detailed analyses. We find good agreement with in-situ-based interpretations, but this in turn leads to an anomaly regarding the final stages of a CME event that we investigate briefly to identify directions for future study. Title: A solar storm observed from the Sun to Venus using the STEREO, Venus Express, and MESSENGER spacecraft Authors: Rouillard, A. P.; Davies, J. A.; Forsyth, R. J.; Savani, N. P.; Sheeley, N. R.; Thernisien, A.; Zhang, T. -L.; Howard, R. A.; Anderson, B.; Carr, C. M.; Tsang, S.; Lockwood, M.; Davis, C. J.; Harrison, R. A.; Bewsher, D.; Fränz, M.; Crothers, S. R.; Eyles, C. J.; Brown, D. S.; Whittaker, I.; Hapgood, M.; Coates, A. J.; Jones, G. H.; Grande, M.; Frahm, R. A.; Winningham, J. D. Bibcode: 2009JGRA..114.7106R Altcode: 2009JGRA..11407106R The suite of SECCHI optical imaging instruments on the STEREO-A spacecraft is used to track a solar storm, consisting of several coronal mass ejections (CMEs) and other coronal loops, as it propagates from the Sun into the heliosphere during May 2007. The 3-D propagation path of the largest interplanetary CME (ICME) is determined from the observations made by the SECCHI Heliospheric Imager (HI) on STEREO-A (HI-1/2A). Two parts of the CME are tracked through the SECCHI images, a bright loop and a V-shaped feature located at the rear of the event. We show that these two structures could be the result of line-of-sight integration of the light scattered by electrons located on a single flux rope. In addition to being imaged by HI, the CME is observed simultaneously by the plasma and magnetic field experiments on the Venus Express and MESSENGER spacecraft. The imaged loop and V-shaped structure bound, as expected, the flux rope observed in situ. The SECCHI images reveal that the leading loop-like structure propagated faster than the V-shaped structure, and a decrease in in situ CME speed occurred during the passage of the flux rope. We interpret this as the result of the continuous radial expansion of the flux rope as it progressed outward through the interplanetary medium. An expansion speed in the radial direction of ∼30 km s-1 is obtained directly from the SECCHI-HI images and is in agreement with the difference in speed of the two structures observed in situ. This paper shows that the flux rope location can be determined from white light images, which could have important space weather applications. Title: A Multispacecraft Analysis of a Small-Scale Transient Entrained by Solar Wind Streams Authors: Rouillard, A. P.; Savani, N. P.; Davies, J. A.; Lavraud, B.; Forsyth, R. J.; Morley, S. K.; Opitz, A.; Sheeley, N. R.; Burlaga, L. F.; Sauvaud, J. -A.; Simunac, K. D. C.; Luhmann, J. G.; Galvin, A. B.; Crothers, S. R.; Davis, C. J.; Harrison, R. A.; Lockwood, M.; Eyles, C. J.; Bewsher, D.; Brown, D. S. Bibcode: 2009SoPh..256..307R Altcode: The images taken by the Heliospheric Imagers (HIs), part of the SECCHI imaging package onboard the pair of STEREO spacecraft, provide information on the radial and latitudinal evolution of the plasma compressed inside corotating interaction regions (CIRs). A plasma density wave imaged by the HI instrument onboard STEREO-B was found to propagate towards STEREO-A, enabling a comparison between simultaneous remote-sensing and in situ observations of its structure to be performed. In situ measurements made by STEREO-A show that the plasma density wave is associated with the passage of a CIR. The magnetic field compressed after the CIR stream interface (SI) is found to have a planar distribution. Minimum variance analysis of the magnetic field vectors shows that the SI is inclined at 54° to the orbital plane of the STEREO-A spacecraft. This inclination of the CIR SI is comparable to the inclination of the associated plasma density wave observed by HI. A small-scale magnetic cloud with a flux rope topology and radial extent of 0.08 AU is also embedded prior to the SI. The pitch-angle distribution of suprathermal electrons measured by the STEREO-A SWEA instrument shows that an open magnetic field topology in the cloud replaced the heliospheric current sheet locally. These observations confirm that HI observes CIRs in difference images when a small-scale transient is caught up in the compression region. Title: Two Years of the STEREO Heliospheric Imagers. Invited Review Authors: Harrison, Richard A.; Davies, Jackie A.; Rouillard, Alexis P.; Davis, Christopher J.; Eyles, Christopher J.; Bewsher, Danielle; Crothers, Steve R.; Howard, Russell A.; Sheeley, Neil R.; Vourlidas, Angelos; Webb, David F.; Brown, Daniel S.; Dorrian, Gareth D. Bibcode: 2009SoPh..256..219H Altcode: Imaging of the heliosphere is a burgeoning area of research. As a result, it is awash with new results, using novel applications, and is demonstrating great potential for future research in a wide range of topical areas. The STEREO (Solar TErrestrial RElations Observatory) Heliospheric Imager (HI) instruments are at the heart of this new development, building on the pioneering observations of the SMEI (Solar Mass Ejection Imager) instrument aboard the Coriolis spacecraft. Other earlier heliospheric imaging systems have included ground-based interplanetary scintillation (IPS) facilities and the photometers on the Helios spacecraft. With the HI instruments, we now have routine wide-angle imaging of the inner heliosphere, from vantage points outside the Sun-Earth line. HI has been used to investigate the development of coronal mass ejections (CMEs) as they pass through the heliosphere to 1 AU and beyond. Synoptic mapping has also allowed us to see graphic illustrations of the nature of mass outflow as a function of distance from the Sun - in particular, stressing the complexity of the near-Sun solar wind. The instruments have also been used to image co-rotating interaction regions (CIRs), to study the interaction of comets with the solar wind and CMEs, and to witness the impact of CMEs and CIRs on planets. The very nature of this area of research - which brings together aspects of solar physics, space-environment physics, and solar-terrestrial physics - means that the research papers are spread among a wide range of journals from different disciplines. Thus, in this special issue, it is timely and appropriate to provide a review of the results of the first two years of the HI investigations. Title: Magnetic coupling in the solar system Authors: Matthews, Sarah; Bewsher, Danielle; Davis, Chris Bibcode: 2009A&G....50b..31M Altcode: On 10 October 2008, UK solar, solar-terrestrial and planetary scientists hosted a meeting at the RAS on the theme of ``Magnetic coupling in the solar system - from the Sun into the heliosphere''. This meeting was proposed in order to stimulate discussion on how the variations of the solar magnetic field influence other solar system bodies such as comets, planets (including our own) and their moons. Energy from within the convection zone is transferred through magnetic coupling into the corona and the heliosphere beyond on a wide range of spatial and temporal scales that are related to the different types of magnetic field emergence at the solar surface. Thus in order to understand the global heliospheric magnetic field and its influence throughout the solar system, we have to understand the role that flux emergence on all scales plays in structuring in the global field and the associated solar wind. With the successful launch of two major new space-based missions, Hinode and STEREO (Solar Terrestrial Relations Observatory), scientists are well placed to study the emergence of the Sun's magnetic field and track it into the heliosphere. Title: The Heliospheric Imagers Onboard the STEREO Mission Authors: Eyles, C. J.; Harrison, R. A.; Davis, C. J.; Waltham, N. R.; Shaughnessy, B. M.; Mapson-Menard, H. C. A.; Bewsher, D.; Crothers, S. R.; Davies, J. A.; Simnett, G. M.; Howard, R. A.; Moses, J. D.; Newmark, J. S.; Socker, D. G.; Halain, J. -P.; Defise, J. -M.; Mazy, E.; Rochus, P. Bibcode: 2009SoPh..254..387E Altcode: 2008SoPh..tmp..193E Mounted on the sides of two widely separated spacecraft, the two Heliospheric Imager (HI) instruments onboard NASA's STEREO mission view, for the first time, the space between the Sun and Earth. These instruments are wide-angle visible-light imagers that incorporate sufficient baffling to eliminate scattered light to the extent that the passage of solar coronal mass ejections (CMEs) through the heliosphere can be detected. Each HI instrument comprises two cameras, HI-1 and HI-2, which have 20° and 70° fields of view and are off-pointed from the Sun direction by 14.0° and 53.7°, respectively, with their optical axes aligned in the ecliptic plane. This arrangement provides coverage over solar elongation angles from 4.0° to 88.7° at the viewpoints of the two spacecraft, thereby allowing the observation of Earth-directed CMEs along the Sun - Earth line to the vicinity of the Earth and beyond. Given the two separated platforms, this also presents the first opportunity to view the structure and evolution of CMEs in three dimensions. The STEREO spacecraft were launched from Cape Canaveral Air Force Base in late October 2006, and the HI instruments have been performing scientific observations since early 2007. The design, development, manufacture, and calibration of these unique instruments are reviewed in this paper. Mission operations, including the initial commissioning phase and the science operations phase, are described. Data processing and analysis procedures are briefly discussed, and ground-test results and in-orbit observations are used to demonstrate that the performance of the instruments meets the original scientific requirements. Title: Calibrating the Pointing and Optical Parameters of the STEREO Heliospheric Imagers Authors: Brown, D. S.; Bewsher, D.; Eyles, C. J. Bibcode: 2009SoPh..254..185B Altcode: 2008SoPh..tmp..181B The Heliospheric Imager (HI) instruments on the Solar TErrestrial RElations Observatory (STEREO) observe solar plasma as it streams out from the Sun and into the heliosphere. The telescopes point off-limb (from about 4° to 90° elongation) and so the Sun is not in the field of view. Hence, the Sun cannot be used to confirm the instrument pointing. Until now, the pointing of the instruments have been calculated using the nominal preflight instrument offsets from the STEREO spacecraft together with the spacecraft attitude data. This paper develops a new method for deriving the instrument pointing solutions, along with other optical parameters, by comparing the locations of stars identified in each HI image with the known star positions predicted from a star catalogue. The pointing and optical parameters are varied in an autonomous manner to minimise the discrepancy between the predicted and observed positions of the stars. This method is applied to all HI observations from the beginning of the mission to the end of April 2008. For the vast majority of images a good attitude solution has been obtained with a mean-squared deviation between the observed and predicted star positions of one image pixel or less. Updated values have been obtained for the instrument offsets relative to the spacecraft, and for the optical parameters of the HI cameras. With this method the HI images can be considered as "self-calibrating," with the actual instrument offsets calculated as a byproduct. The updated pointing results and their by-products have been implemented in SolarSoft. Title: A synoptic view of solar transient evolution in the inner heliosphere using the Heliospheric Imagers on STEREO Authors: Davies, J. A.; Harrison, R. A.; Rouillard, A. P.; Sheeley, N. R.; Perry, C. H.; Bewsher, D.; Davis, C. J.; Eyles, C. J.; Crothers, S. R.; Brown, D. S. Bibcode: 2009GeoRL..36.2102D Altcode: By exploiting data from the STEREO/heliospheric imagers (HI) we extend a well-established technique developed for coronal analysis by producing time-elongation plots that reveal the nature of solar transient activity over a far more extensive region of the heliosphere than previously possible from coronagraph images. Despite the simplicity of these plots, their power in demonstrating how the plethora of ascending coronal features observed near the Sun evolve as they move antisunward is obvious. The time-elongation profile of a transient tracked by HI can, moreover, be used to establish its angle out of the plane-of-the-sky an illustration of such analysis reveals coronal mass ejection material that can be clearly observed propagating out to distances beyond 1AU. This work confirms the value of the time-elongation format in identifying/characterising transient activity in the inner heliosphere, whilst also validating the ability of HI to continuously monitor solar ejecta out to and beyond 1AU. Title: Explosive Events in the Quiet Sun as Seen by EIS and SUMER Authors: Madjarska, M. S.; Boutry, C.; Bewsher, D. Bibcode: 2008ASPC..397..180M Altcode: We present preliminary results on the capabilities of EIS to register explosive events in the quiet Sun. The events were registered with EIS/Hinode and SUMER/SoHO during the Hinode/SoHO observing campaign in April 2007. First results on the coronal response of these events are shown. Both SUMER and EIS were observing spectral lines from the widest possible temperature range from a few thousand to a few million degrees Kelvin. Title: Magnetic topology of blinkers Authors: Subramanian, S.; Madjarska, M. S.; Maclean, R. C.; Doyle, J. G.; Bewsher, D. Bibcode: 2008A&A...488..323S Altcode: Context: Co-spatial and co-temporal spectroscopic, imaging and magnetogram data enable us to better understand various solar transient phenomena. Here, we study brightening events in the transition region of the quiet Sun, also called “blinkers”.
Aims: We aim to investigate the physical mechanism responsible for blinkers.
Methods: An automated blinker identification procedure (BLIP) is used to identify blinker events in SoHO/CDS data. The 3D magnetic topology of the magnetic field in the blinker region is reconstructed based on SoHO/MDI magnetogram data.
Results: During 3 h of SoHO/CDS observations on 2006 January 18, 66 blinkers were identified in the O v 629 Å emission line. Out of them, a group comprising of 16 events were modelled here. They were found to be associated with the emergence of magnetic flux which gave rise to the appearance of, and multiple magnetic reconnection events across, an upper atmosphere (coronal) magnetic null point, along with a loop structure as observed with TRACE.
Conclusions: This blinker group results from the release of energy that was accumulated during flux emergence, although whether all blinkers follow the same formation scenario requires further investigation using additional multi-instrument/multi-mission studies.

2 movies are only available in electronic form at http://star.arm.ac.uk/preprints/ and http://www.aanda.org Title: First imaging of corotating interaction regions using the STEREO spacecraft Authors: Rouillard, A. P.; Davies, J. A.; Forsyth, R. J.; Rees, A.; Davis, C. J.; Harrison, R. A.; Lockwood, M.; Bewsher, D.; Crothers, S. R.; Eyles, C. J.; Hapgood, M.; Perry, C. H. Bibcode: 2008GeoRL..3510110R Altcode: Plasma parcels are observed propagating from the Sun out to the large coronal heights monitored by the Heliospheric Imagers (HI) instruments onboard the NASA STEREO spacecraft during September 2007. The source region of these out-flowing parcels is found to corotate with the Sun and to be rooted near the western boundary of an equatorial coronal hole. These plasma enhancements evolve during their propagation through the HI cameras' fields of view and only becoming fully developed in the outer camera field of view. We provide evidence that HI is observing the formation of a Corotating Interaction Region (CIR) where fast solar wind from the equatorial coronal hole is interacting with the slow solar wind of the streamer belt located on the western edge of that coronal hole. A dense plasma parcel is also observed near the footpoint of the observed CIR at a distance less than 0.1AU from the Sun where fast wind would have not had time to catch up slow wind. We suggest that this low-lying plasma enhancement is a plasma parcel which has been disconnected from a helmet streamer and subsequently becomes embedded inside the corotating interaction region. Title: Observations of corotating interaction regions in the inner heliosphere by the STEREO spacecraft. Authors: Rouillard, A. P.; Rees, A.; Forsyth, R. J.; Davies, J. A.; Davis, C. J.; Bewsher, D. Bibcode: 2008AGUSMSH43A..02R Altcode: The images taken by the Heliospheric Imagers (HI) onboard the STEREO spacecraft provide information on the latitudinal distribution of the plasma compressed inside CIRs. In this study, the size and orientation of the plasma waves associated with these CIRs are compared to in-situ observations of density increase, non-radial flows and the orientation of the stream interface. The implications of this study for forecasting the magneto- hydrodynamic properties of CIRs impinging on the Earth's magnetosphere are discussed. Title: The relationship between EUV dimming and coronal mass ejections. I. Statistical study and probability model Authors: Bewsher, D.; Harrison, R. A.; Brown, D. S. Bibcode: 2008A&A...478..897B Altcode: Aims:There have been many studies of extreme-ultraviolet (EUV) dimming in association with coronal mass ejection (CME) onsets. However, there has never been a thorough statistical study of this association, covering appropriate temperature ranges. Thus, we make use of a large campaign database utilising the Coronal Diagnostic Spectrometer (CDS) and the Large Angle and Spectrometric COronagraph (LASCO) both on the SOlar and Heliospheric Observatory (SOHO) to associate dimming events detected at 1 and 2 million K with CME activity. The aim is to confirm whether the dimming-CME association is real or not. This in turn will confirm whether special attention should be paid to the EUV dimming in the pre-eruption and eruption periods to study the CME onset process itself.
Methods: The CDS CME onset campaign data for Mg IX and FE XVI observations on the solar limb are used to compare to LASCO event lists over a period from 1998 to 2005. Dimming events are identified and the physical extent explored, whilst comparing the events to overlying CME activity.
Results: For the identified dimming regions we have shown strong associations with CME onsets, with up to 55% of the dimming events being associated with CME activity. This is compared to the random case where up to 47% of the dimming regions are expected to be associated with CMEs. We have also shown that up to 84% of CMEs associated with our data can be tracked back to dimming regions. This compares to a random case of up to 58%.
Conclusions: These results confirm the CME-EUV dimming association, using a statistical analysis for the first time. We discuss the repercussions for the study of CME onsets, i.e. analysis of the dimming regions and the periods up to such dimming may be key to understanding the pre-CME onset plasma processes. The results stress that one emission line may not be sufficient for associating dimming regions with CMEs.

Appendix A is only available in electronic form at http://www.aanda.org Title: First Imaging of Coronal Mass Ejections in the Heliosphere Viewed from Outside the Sun Earth Line Authors: Harrison, Richard A.; Davis, Christopher J.; Eyles, Christopher J.; Bewsher, Danielle; Crothers, Steve R.; Davies, Jackie A.; Howard, Russell A.; Moses, Daniel J.; Socker, Dennis G.; Newmark, Jeffrey S.; Halain, Jean-Philippe; Defise, Jean-Marc; Mazy, Emmanuel; Rochus, Pierre; Webb, David F.; Simnett, George M. Bibcode: 2008SoPh..247..171H Altcode: We show for the first time images of solar coronal mass ejections (CMEs) viewed using the Heliospheric Imager (HI) instrument aboard the NASA STEREO spacecraft. The HI instruments are wide-angle imaging systems designed to detect CMEs in the heliosphere, in particular, for the first time, observing the propagation of such events along the Sun - Earth line, that is, those directed towards Earth. At the time of writing the STEREO spacecraft are still close to the Earth and the full advantage of the HI dual-imaging has yet to be realised. However, even these early results show that despite severe technical challenges in their design and implementation, the HI instruments can successfully detect CMEs in the heliosphere, and this is an extremely important milestone for CME research. For the principal event being analysed here we demonstrate an ability to track a CME from the corona to over 40 degrees. The time - altitude history shows a constant speed of ascent over at least the first 50 solar radii and some evidence for deceleration at distances of over 20 degrees. Comparisons of associated coronagraph data and the HI images show that the basic structure of the CME remains clearly intact as it propagates from the corona into the heliosphere. Extracting the CME signal requires a consideration of the F-coronal intensity distribution, which can be identified from the HI data. Thus we present the preliminary results on this measured F-coronal intensity and compare these to the modelled F-corona of Koutchmy and Lamy (IAU Colloq.85, 63, 1985). This analysis demonstrates that CME material some two orders of magnitude weaker than the F-corona can be detected; a specific example at 40 solar radii revealed CME intensities as low as 1.7×10−14 of the solar brightness. These observations herald a new era in CME research as we extend our capability for tracking, in particular, Earth-directed CMEs into the heliosphere. Title: Solar Mass Ejection Studies - Coordinated Investigation Programme 1 Authors: Harrison, Richard; Bewsher, Danielle; Davis, Chris; Breen, Andy; Webb, David Bibcode: 2008cosp...37.1181H Altcode: 2008cosp.meet.1181H IHY Coordinated Investigation Programme number 1 is concerned with solar coronal mass ejections (CMEs). It has two parts, specifically, (i) studies of the onset of CMEs through multispacecraft observations of the source regions of CMEs, in particular including the development of spectroscopic observations in the extreme-ultraviolet, and (ii) studies of interplanetary CMEs, especially those directed towards Earth utilising multiple spacecraft including the new STEREO mission. The effort has been done in hindsight, i.e. ‘post-event' campaigns are defined based on particular observation scenarios or on the acquisition of good quality data-sets and a range of research topics have been addressed. Here, we summarise the sub-campaigns and their results - but we also ask how these efforts have been enhanced by the IHY activities. Title: Interplanetary Coronal Mass Ejections Authors: Harrison, Richard; Davis, Chris; Davies, Jackie; Eyles, Chris; Crothers, Steve; Bewsher, Danielle Bibcode: 2008cosp...37.1182H Altcode: 2008cosp.meet.1182H With the new STEREO spacecraft and the Heliospheric Imager instruments we are now able to make the most basic observations of ICMEs, in particular those directed towards Earth and to make comparisons to the interpretations of in-situ data which have been used over the years to investigate the structure and evolution of ICMEs and of their connectivity to the Sun. Thus, we present evidence which confirms the magnetic structure of ICMEs as they propagate to Earth-like distances, and discuss how that structure evolves with time. We also consider how ICMEs are connected to the Sun and in particular investigate the view that interchange reconnection represents the ‘end game' of a CME. Title: Discovery of Accelerating Plasmoids in the Tail of Comet Encke Authors: Kellett, B.; Bingham, R.; Davies, J. A.; Bewsher, D.; Harrison, R. A.; Davis, C. J.; Eyles, C. J.; Crothers, S. R. Bibcode: 2007AGUFMSH33A1087K Altcode: Comet 2P/Encke was the second comet to have its return correctly predicted (in 1819). Encke is a Jupiter-family comet with a period of 3.30 years and a perihelion distance of 0.338 AU. The interaction between cometary plasma and the solar wind plasma provides the potential for remote monitoring of the solar wind. In this regard comet Encke is potentially a very useful probe of the solar wind because of its very short orbital period and therefore large number of close approaches to the Sun. However, for this reason it is likely to have exhausted most of its reserves of ice and therefore possess a less dense plasma tail. The comet could therefore respond faster and more dynamically to solar wind variations than the tail of a more active or higher gas production comet. The Heliospheric Imager (HI) of STEREO-A (HI-1A), observed comet 2P/Encke during April, 2007. The comet was predicted to have reached perihelion on April 19th 0 UT. This paper will only consider the observations obtained by HI-1A on April 25th to 27th, 2007. At this time the comet was around 0.63 AU from Earth and 0.39 AU from the Sun. The comet was seen to exhibit a distinct "flick" of its plasma tail on April 26th and a series of "whiplash" events. However, the most interest phenomena seen was a whole series of "plasmoids" that were observed to break off from the brighter part of the tail near the nucleus and accelerate along the tail for 4-5 million kilometres down-wind of the nucleus. Title: A Coronal Mass Ejection at Venus observed with STEREO HI and Venus Express Authors: Davies, J. A.; Rouillard, A.; Bewsher, D.; Hapgood, M. A.; Lockwood, M. Bibcode: 2007AGUFMSH52B..06D Altcode: Observations of a CME interacting with comet Encke were made by the STEREO HI cameras in April 2007. The position of the comet allowed the direction of the CME to be determined even though it had only been observed with one STEREO spacecraft. An examination of the planetary positions indicated that the CME would intersect with Venus. Data from the Venus Express spacecraft show the passage of a CME front at the time predicted by the HI data. Title: Imaging Coronal Mass Ejections in the Heliosphere using the STEREO Heliospheric Imagers Authors: Harrison, R. A.; Davis, C. J.; Eyles, C. J.; Bewsher, D.; Crothers, S.; Davies, J. A.; Howard, R. A.; Moses, D. J.; Halain, J. Bibcode: 2007AGUFMSH42A..05H Altcode: We present images of Coronal Mass Ejections in the heliosphere, tracked from the outer corona to Earth-like distances, from the first months of the scientific operation of the Heliospheric Imagers (HI) aboard the NASA STEREO spacecraft. The HI instruments are wide-angle imaging systems designed to detect CMEs in the heliosphere, in particular, for the first time, observing the propagation of such events along the Sun-Earth line. These early results show that despite severe technical challenges in their design and implementation, the HI instruments can successfully detect CMEs in the heliosphere and this is an extremely important milestone for CME research. Among the early results, we show a number of CME events, demonstrating the ability to extract the F-coronal intensity distribution, and to track a CME from the corona to the Earth. Early investigations of the velocity profiles of CMEs as they propagate through the heliosphere and of their basic structure will be presented. Title: Solar effects at Earth as observed by the STEREO Heliospheric Imagers Authors: Rouillard, A.; Davis, C. J.; Harrison, R. A.; Davies, J. A.; Bewsher, D.; Crothers, S. R.; Eyles, C. J. Bibcode: 2007AGUFMSH51B..05R Altcode: The twin STEREO spacecraft each carry a Heliospheric Imager. These wide angle cameras have provided the first ever observations of Earth directed events from a position outside the Sun-Earth line. We present combined observations taken with the instruments onboard STEREO, SOHO and ACE spacecraft as we track the progress of material through the heliosphere. At Earth, the impact of the solar wind on the Earth's atmosphere is tracked by the Cluster satellites and EISCAT radars. Title: Solar physics in STEREO Authors: Davis, Chris; Bewsher, Danielle Bibcode: 2007A&G....48c..12D Altcode: NASA's STEREO mission uses twin spacecraft observing the Sun and solar neighbourhood from increasingly distant viewpoints to give a stereo view of the solar chromosphere and corona, including coronal mass ejections. UK researchers have provided the Heliospheric Imagers on each spacecraft, comprising sensitive wide-field cameras able to track coronal mass ejections right out to Earth's orbit. Here we describe the instruments, data-handling procedures and results obtained so far. We finish with a discussion of the potential of these instruments for a wide range of astronomical observations during the two-and-a-half-year mission. Title: A benchmark event sequence for mass ejection onset studies. A flare associated CME with coronal dimming, ascending pre-flare loops and a transient cool loop Authors: Harrison, R. A.; Bewsher, D. Bibcode: 2007A&A...461.1155H Altcode: Aims:In this study, we report on the spectroscopic observations of a particularly well-observed flare and coronal mass ejection (CME) event sequence which we feel can be used as a benchmark study for CME onsets.
Methods: Specifically, we report on a set of extreme-ultraviolet (EUV) spectroscopic observations using the Solar and Heliospheric Observatory (SOHO) to determine features of the CME onset process revealed through the analysis of plasma at different temperatures.
Results: The flare which occurred on the north-western limb was associated with a large CME. The event in question showed evidence for pre-flare ascending loops containing 1-2 million K plasma, which disappeared just prior to the flare. This disappearance is interpreted as coronal dimming, and it appears to coincide with the projected mass ejection onset time. In addition, a discrete, short-lived coronal loop containing plasma at transition region temperatures was detected just prior to this eruption. This loop displayed mass motion, along flux tubes, with oppositely directed flows. The nature and timing of this transient loop suggest a close relationship between it and the eruption process. Examinations of the timing and topology, which extend previous studies considerably, are found to be consistent with the mass ejection onset interpretation of Zhang and co-workers.
Conclusions: .The clarity of this event sequence suggests that we should regard it as a benchmark in studies of the mass ejection onset process. Title: 10 Years of CME Onset Studies with SOHO/CDS Authors: Bewsher, D.; Harrison, R. A. Bibcode: 2006ESASP.617E..21B Altcode: 2006soho...17E..21B No abstract at ADS Title: On Deriving Plasma Velocity Information from CDS/NIS Observations: Application to the Dynamics of Blinkers Authors: Brooks, David Hamilton; Bewsher, Danielle Bibcode: 2006SoPh..234..257B Altcode: Using standard instrument software and two independently developed data reduction and analysis procedures, we re-examine the accuracy of plasma velocity information derived from data obtained by the Solar and Heliospheric Observatory (SOHO)-Coronal Diagnostic Spectrometer (CDS). We discuss only the Ov 629 Å line data obtained by the Normal Incidence Spectrometer (NIS) and analyse a quiet Sun (QS) and active region (AR) dataset. Using the QS data, we demonstrate that the well-known North-South tilt in wavelength along the NIS slit varies significantly with time, which is not accounted for in the standard CDS correction procedures. In addition, when residual N - S trends exist in the data after processing, they may not be detected, nor removed, using the standard analysis software. This underscores the need for careful analysis of velocity results for individual datasets when using standard correction procedures. Furthermore, even when the results obtained by the two independent methods are well correlated (coefficients greater than 0.9), discrepancies in the values of the derived Doppler velocities can remain (95% within ±5 km s−1). Therefore, we apply the results to examine the velocities obtained for EUV blinkers by previous authors. It is found that a strong correlation exists in the patterns of variation of the blinker velocities (> 0.98), even though there may be differences in their magnitudes. That is, in a clear majority of cases, the methods agree that a blinker is red-shifted or blue-shifted, although the uncertainty in the absolute velocity may be large. Title: Statistics of the Quiet Sun Intensity Distribution Authors: Young, C. A.; Ireland, J.; Bewsher, D. Bibcode: 2005ESASP.600E..75Y Altcode: 2005ESPM...11...75Y; 2005dysu.confE..75Y No abstract at ADS Title: Statistics of the quiet Sun intensity distribution. Authors: Ireland, J.; Young, C.; Bewsher, D. Bibcode: 2005AGUSMSP21B..11I Altcode: The statistics of the quiet Sun intensity distribution present an interesting challenge. Some authors find that the observed distribution is adequately represented by a two component model, which seems to fit well with the notion of a network and internetwork being physically distinct. Other authors find that a single component model fits the intensity distribution data well, which seems to suggest that the network and internetwork emission may in fact be due to the same process. This paper examines the evidence for both these points of view, using CDS EUV data and a mixture modeling technique. Some comments are also made on the nature of the mechanism which may create the observed distributions. Title: Comparison of blinkers and explosive events: A case study Authors: Bewsher, D.; Innes, D. E.; Parnell, C. E.; Brown, D. S. Bibcode: 2005A&A...432..307B Altcode: Blinkers are brightenings at network cell junctions that are traditionally identified with SOHO/CDS and explosive events or high velocity events are identified in high resolution UV spectra obtained from HRTS and SOHO/SUMER. Criteria are determined to facilitate objective automatic identification of both blinkers and explosive events in both SOHO/CDS and SOHO/SUMER data. Blinkers are identified in SUMER data, if the temporal resolution of the data is reduced to that of CDS. Otherwise short lived, localised intensity enhancements that make up the blinker are identified. Explosive events are identified in CDS data when the line width is significantly increased, and occasionally if there is an enhancement in the wing of the line profile. A theoretical statistical model is presented which hypothesises that blinkers and explosive events are random and not connected in any way. The results given in this paper suggest that this hypothesis can not be rejected and our probability interpretation of the recent results of Brković & Peter (2004, A&A, 422, 709) are inconclusive.

Appendices A and B are only available in electronic form at http://www.edpscienc es.org Title: Probability Analysis of Coincident Blinkers and Explosive Events Authors: Bewsher, D.; Brown, D.; Innes, D.; Parnell, C. Bibcode: 2004ESASP.575..465B Altcode: 2004soho...15..465B No abstract at ADS Title: Dynamics of Transition Region Blinkers Authors: Bewsher, D.; Parnell, C.; Pike, D.; Harrison, R. Bibcode: 2004ESASP.547..267B Altcode: 2004soho...13..267B Analysis of CDS data has shown that transition region blinkers and the chromosphere directly below, are preferentially more redshifted and have larger non-thermal velocities than the normal transition region and chromospheric plasma. The ranges of these enhanced velocities, however, are no larger than the typical spread of Doppler and non-thermal velocities in these regions. An overview of the Doppler and non-thermal velocities of blinkers found with CDS in the quiet Sun and active region are presented. The anticipated range of Doppler velocities of blinkers are 10 - 15 km s-1 in the quiet-Sun (10 - 20 km s-1 in active-regions) in the chromosphere (He I) and 25 - 30 km s-1 in the quiet-Sun (20 - 40 km s-1 in activeregions) in the transition region (O V). The range of non-thermal velocities of blinkers in both the quiet- Sun and active-regions are estimated to be 15 - 25 km s-1 in He I and 30 - 45 km s-1 in O V. There are more blinkers with larger Doppler and non-thermal velocities than would be expected in the whole of the chromosphere and transition region. Title: Dynamics of Blinkers Authors: Bewsher, D.; Parnell, C. E.; Pike, C. D.; Harrison, R. A. Bibcode: 2003SoPh..215..217B Altcode: The relative Doppler and non-thermal velocities of quiet-Sun and active-region blinkers identified in O v with CDS are calculated. Relative velocities for the corresponding chromospheric plasma below are also determined using the He i line. O v blinkers and the chromosphere directly below, have a preference to be more red-shifted than the normal transition region and chromospheric plasma. The ranges of these enhanced velocities, however, are no larger than the typical spread of Doppler velocities in these regions. The anticipated ranges of Doppler velocities of blinkers are 10-15 km s−1 in the quiet Sun (10-20 km s−1 in active regions) for He i and 25-30 km s−1 in the quiet Sun (20-40 km s−1 in active regions) for O v. Blinkers and the chromosphere below also have preferentially larger non-thermal velocities than the typical background chromosphere and transition region. Again the increase in magnitude of these non-thermal velocities is no greater than the typical ranges of non-thermal velocities. The ranges of non-thermal velocities of blinkers in both the quiet Sun and active regions are estimated to be 15-25 km s−1 in He i and 30-45 km s−1 in O v. There are more blinkers with larger Doppler and non-thermal velocities than would be expected in the whole of the chromosphere and transition region. The recently suggested mechanisms for blinkers are revisited and discussed further in light of the new results. Title: Comparison of Blinkers and Explosive Events Authors: Bewsher, D.; Innes, D.; Parnell, C. E. Bibcode: 2003SPD....34.1617B Altcode: 2003BAAS...35Q.836B There has been much speculation over recent years as to whether blinkers and explosive events are the same phenomena observed with different instruments.

Blinkers were first observed by Harrison (1997) by eye using SOHO/CDS, but more recently Brković et al. (2001) and Bewsher et al. (2002) have developed automated methods of identifying these events. Blinkers are small scale intensity enhancements seen in the transition region, with a mean area of 3 x 107 km2 and a mean lifetime of 16 minutes. The Doppler velocities of blinkers are preferentially more red-shifted than the typical transition region plasma. The range of these enhanced velocities, however, are no larger than the typical spread of Doppler velocities in these regions.

Explosive events were first observed using HRTS (Bruckener and Bartoe, 1983) as high energy turbulent events and jets. More recently, they have been observed using SOHO/SUMER. They have a typical size of 2" - 4" and have an average lifetime of 60 seconds. Line profiles of explosive events show strong non-Gaussian enhancements of both wings of the profile, and velocities associated with them range from +/- 50 - +/- 250 km s-1.

Examples will be presented showing (i) a co-spatial and co-incident blinker and explosive event; (ii) a blinker with no associated explosive event; and (iii) an explosive event with no associated blinker. We investigate the lightcurves and line profiles of the regions to explain the relationship, if any, between blinkers and explosive events. Title: Magnetic structure of transition region blinkers Authors: Bewsher, D.; Parnell, C. E.; Brown, D. S.; Hood, A. W. Bibcode: 2002ESASP.505..239B Altcode: 2002IAUCo.188..239B; 2002solm.conf..239B Analysis of the photospheric magnetic field has shown that the majority of blinkers, small-scale intensity enhancements seen in the transition region, occur above single fragments. We investigate the relationship between the strength of these single magnetic fragments or the ratio of any mixed magnetic fields beneath blinkers and blinker characteristics. In all cases, no correlation is found between the strength of the magnetic field and the blinker properties. We suggest, therefore, that blinkers are not caused by reconnection and that other mechanisms should be explored further. Title: Transition-Region Blinkers - II. Active-Region Properties Authors: Parnell, C. E.; Bewsher, D.; Harrison, R. A. Bibcode: 2002SoPh..206..249P Altcode: The distribution and general properties of events identified in an active region that have the same characteristics as quiet-Sun blinkers are discussed and named `active-region blinkers'. The events are identified using an automated scheme `BLinker Identification Program' (BLIP) which was designed for and tested on quiet-Sun blinkers. Like quiet-Sun blinkers, the active-region events are most easily identified in the 629 Å emission line from O v although evidence for them is also found in other extreme UV lines emitted from He i, O iii and O iv. Unlike quiet-Sun blinkers, however, they may also have coronal signatures in the lines Mg ix and Mg x. Their properties are very similar to those of quiet-Sun blinkers with mean lifetimes of 16-19 min, mean areas of 2.4-4.3×107 km2 and mean intensity enhancements factors of 1.8-3.3. Their global frequency of 7-28 s−1 is about 42%-700% higher than that for quiet-Sun blinkers. The blinkers discussed here are found above both active-region (plage) magnetic fields, as well as above the umbra and penumbra of a sunspot. Title: Transition Region Blinkers I. Quiet-Sun Properties Authors: Bewsher, D.; Parnell, C. E.; Harrison, R. A. Bibcode: 2002SoPh..206...21B Altcode: An automated method of identifying transition region blinkers is presented. The distribution and general properties of blinkers identified in the quiet Sun are discussed. The blinkers are seen most clearly in the O v (629 Å) transition region emission line, but they also have strong signatures in O iv (554 Å), and the chromospheric line, He i (584 Å). The strongest O v blinkers can also be identified in O iii (599 Å). No significant signatures are found for blinkers in the Mg ix (368 Å) and Mg x (624 Å) coronal lines. A few hundred O v blinkers are analyzed. Their global frequency is between 1 and 20 s−1 depending on how significant the peaks of the blinkers are. They have a typical area of 3×107 km2, a typical lifetime of 16 min and a typical intensity enhancement factor of 1.8. We find the ratios of the oxygen lines to be flat confirming the result that blinkers are not temperature events, but are density enhancements or due to increases in filling factor. Blinkers are found to occur preferentially over regions of enhanced chromospheric or transition region emission such as network boundaries, however, it is not so clear that they appear below the brightest coronal regions. A rough analysis of the magnetic fragments show that blinkers preferentially occur above regions where there are large or strong magnetic fragments with 75% occurring in regions where one polarity dominates. Title: The Nature of Blinkers and the Solar Transition Region Authors: Priest, E. R.; Hood, A. W.; Bewsher, D. Bibcode: 2002SoPh..205..249P Altcode: Solar plasma that exists at around 105 K, which has traditionally been referred to as the solar transition region, is probably in a dynamic and fibril state with a small filling factor. Its origin is as yet unknown, but we suggest that it may be produced primarily by one of five different physical mechanisms, namely: the heating of cool spicular material; the containment of plasma in low-lying loops in the network; the thermal linking of cool and hot plasma at the feet of coronal loops; the heating and evaporating of chromospheric plasma in response to a coronal heating event; and the cooling and draining of hot coronal plasma when coronal heating is switched off. We suggest that, in each case, a blinker could be produced by the granular compression of a network junction, causing subtelescopic fibril flux tubes to spend more of their time at transition-region temperatures and so to increase the filling factor temporarily. Title: Transition region blinkers Authors: Bewsher, Danielle Bibcode: 2002PhDT.......234B Altcode: No abstract at ADS Title: Transition Region Blinkers Authors: Parnell, C. E.; Bewsher, D.; Harrison, R. A.; Hood, A. W. Bibcode: 2001IAUS..203..359P Altcode: Blinkers are small bright emission events observed best in the O V transition region line that occur above the supergranular network. They were first observed using SoHO/CDS data and were identified manually by Harrison (1997). They are believed to be density enhancements, but how they are created and what their properties are is not well known. We have developed the first program to automatically identify blinkers and their characteristics. The evolution of the magnetic field observed by SoHO/MDI below these blinkers has then be analysed to determine what magnetic field configuration is required for a blinker to occur. Also, the coronal emission above has been investigated using SoHO/CDS and TRACE data to determine the relation between blinkers, x-ray bright points and nanoflares. All three of these events are known to occur at the network, but as yet the relation between them is not understood. Putting together the results from these multi-wave length studies we have been able to determine a model for how blinkers occur and what their effect is on the transition region around and the corona above.