Author name code: doyle ADS astronomy entries on 2022-09-14 author:"Doyle, J.G." ------------------------------------------------------------------------ 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: Detection of spicules termed rapid blueshifted excursions as seen in the chromosphere via H α and the transition region via Si IV 1394 Å line emission Authors: Vilangot Nhalil, Nived; Shetye, Juie; Doyle, J. Gerry Bibcode: 2022MNRAS.515.2672V Altcode: 2022arXiv220701415V; 2022MNRAS.tmp.1929N We show signatures of spicules termed rapid blueshifted excursions (RBEs) in the Si IV 1394 Å emission line using a semi-automated detection approach. We use the H α filtergrams obtained by the CRISP imaging spectropolarimeter on the Swedish 1-m Solar Telescope and co-aligned Interface Region Imaging Spectrograph data using the SJI 1400 Å channel to study the spatiotemporal signature of the RBEs in the transition region. The detection of RBEs is carried out using an oriented coronal loop tracing algorithm on H α Dopplergrams at ±35 km s-1. We find that the number of detected features is significantly impacted by the time-varying contrast values of the detection images, which are caused by the changes in the atmospheric seeing conditions. We detect 407 events with lifetime greater than 32 s. This number is further reduced to 168 RBEs based on the H α profile and the proximity of RBEs to the large-scale flow. Of these 168 RBEs, 89 of them display a clear spatiotemporal signature in the SJI 1400 Å channel, indicating that a total of $\sim 53{{\ \rm per\ cent}}$ are observed to have co-spatial signatures between the chromosphere and the transition region. Title: Doubling of minute-long quasi-periodic pulsations from super-flares on a low-mass star Authors: Doyle, J. Gerry; Irawati, Puji; Kolotkov, Dmitrii Y.; Ramsay, Gavin; Nhalil, Nived Vilangot; Dhillon, Vik S.; Marsh, Tom R.; Yadav, Ram Kesh Bibcode: 2022MNRAS.514.5178D Altcode: 2022MNRAS.tmp.1673D; 2022arXiv220608070D Using the ULTRASPEC instrument mounted on the 2.4-m Thai National Telescope, we observed two large flares, each with a total energy close to 1034 erg with sub-second cadence. A combination of a wavelet analysis, a Fourier transform plus an empirical mode decomposition, reveals quasi-periodic pulsations (QPPs) that exhibit an apparent doubling of the oscillation period. Both events showed oscillations of a few minutes over a interval of several minutes, and despite the availability of sub-second cadence, there was no evidence of sub-minute oscillations. The doubling of the QPP periods and shorter lifetime of shorter-period QPP modes strongly favour resonant dynamics of magnetohydrodynamic waves in a coronal loop. We estimate loop lengths to be 0.2-0.7 R⋆, in agreement with a typical length of solar coronal loops. These observations presents rare and compelling evidence for the presence of compact plasma loops in a stellar corona. Title: The puzzling story of flare inactive ultra fast rotating M dwarfs - I. Exploring their magnetic fields Authors: Doyle, Lauren; Bagnulo, Stefano; Ramsay, Gavin; Doyle, J. Gerry; Hakala, Pasi Bibcode: 2022MNRAS.512..979D Altcode: 2022arXiv220206889D; 2022MNRAS.tmp..468D Stars which are rapidly rotating are expected to show high levels of activity according to the activity-rotation relation. However, previous TESS studies have found ultra fast rotating (UFR) M dwarfs with periods less than 1 d displaying low levels of flaring activity. As a result, in this study, we utilize VLT/FORS2 spectro-polarimetric data of 10 M dwarf UFR stars between spectral types ~M2-M6 all with Prot < 1, to detect the presence of a magnetic field. We divide our sample into rotation period bins of equal size, with one star having many more flares in the TESS light curve than the other. We also provide an analysis of the long-term variability within our sample using TESS light curves taken during Cycles 1 and 3 (up to 3 yr apart). We identify 605 flares from our sample which have energies between 2.0 × 1031 and 5.4 × 1034 erg. Although we find no significant difference in the flare rate between the Cycles, two of our targets display changes in their light-curve morphology, potentially caused by a difference in the spot distribution. Overall, we find five stars (50 per cent) in our sample have a detectable magnetic field with strengths ~1-2 kG. Of these five, four were the more flare active stars within the period bins with one being the less flare active star. It would appear the magnetic field strength may not be the answer to the lack of flaring activity and supersaturation or magnetic field configuration may play a role. However, it is clear the relationship between rotation and activity is more complex than a steady decrease over time. Title: The puzzling story of flare inactive ultra fast rotating M dwarfs. II. Searching for radial velocity variations Authors: Ramsay, Gavin; Hakala, Pasi; Doyle, J. Gerry; Doyle, Lauren; Bagnulo, Stefano Bibcode: 2022MNRAS.511.2755R Altcode: 2022MNRAS.tmp..250R; 2022arXiv220206888R Observations made using TESS revealed a sample of low-mass stars which show a periodic modulation on a period <0.2 d. Surprisingly, many of these ultra fast rotating (UFR) stars showed no evidence of flare activity which would be expected from such rapidly rotating stars. We present results from a spectroscopic survey of UFRs using the Nordic Optical Telescope to search for radial velocity variations which could reveal evidence for binarity. Our sample of 29 sources have a photometric period between 0.1-0.2 d, cover spectral classes of M0-4V, and show no evidence for flares. We detect only one source with clear radial velocity shifts, with another two having Gaia RUWE values which suggests they are binaries. Further observations reveal the former star possibly contains a brown dwarf companion with a mass of M2 > 58 MJup and probability P(M2 < 90 MJup) = 50 per cent. There is no evidence for the companion in our spectra, strengthening the case for a brown dwarf companion. We also examine the folded TESS light curves of all our targets, finding at least two are eclipsing binaries and one which has been contaminated by a spatially nearby δ Sct star. We estimate that around 1/4 of our targets may have been contaminated by short period variable stars. However, the majority of our targets are consistent with being single, low mass stars whose variability is due to starspots. We outline the possible reasons why they are not flare active despite being such rapid rotators. Title: Implications of spicule activity on coronal loop heating and catastrophic cooling Authors: Nived, V. N.; Scullion, E.; Doyle, J. G.; Susino, R.; Antolin, P.; Spadaro, D.; Sasso, C.; Sahin, S.; Mathioudakis, M. Bibcode: 2022MNRAS.509.5523N Altcode: 2021arXiv211107967N; 2021MNRAS.tmp.3004N We report on the properties of coronal loop foot-point heating with observations at the highest resolution, from the CRisp Imaging Spectro-Polarimeter located at the Swedish 1-m Solar Telescope and co-aligned NASA Solar Dynamics Observatory observations, of Type II spicules in the chromosphere and their signatures in the extreme ultraviolet (EUV) corona. Here, we address one important issue, as to why there is not always a one-to-one correspondence, between Type II spicules and hot coronal plasma signatures, i.e. beyond TR temperatures. We do not detect any difference in their spectral properties in a quiet Sun region compared to a region dominated by coronal loops. On the other hand, the number density close to the foot-points in the active region is found to be an order of magnitude higher than in the quiet Sun case. A differential emission measure analysis reveals a peak at ~5 × 105 K of the order of 1022 cm-5 K-1. Using this result as a constraint, we conduct numerical simulations and show that with an energy input of 1.25 × 1024 erg (corresponding to ~10 RBEs contributing to the burst) we manage to reproduce the observation very closely. However, simulation runs with lower thermal energy input do not reproduce the synthetic AIA 171 Å signatures, indicating that there is a critical number of spicules required in order to account for the AIA 171 Å signatures in the simulation. Furthermore, the higher energy (1.25 × 1024 erg) simulations reproduce catastrophic cooling with a cycle duration of ~5 h, matching a periodicity we observe in the EUV observations. Title: The Nature of High-frequency Oscillations Associated with Short-lived Spicule-type Events Authors: Shetye, Juie; Verwichte, Erwin; Stangalini, Marco; Doyle, J. G. Bibcode: 2021arXiv211214486S Altcode: We investigate high resolution spectroscopic and imaging observations from the CRisp Imaging SpectroPolarimeter (CRISP) instrument to study the dynamics of chromospheric spicule type events. It is widely accepted that chromospheric fine structures are waveguides for several types of magnetohydrodynamic (MHD) oscillations, which can transport energy from the lower to upper layers of the Sun. We provide a statistical study of 30 high frequency waves associated with spicule type events. These high frequency oscillations have two components of transverse motions: the plane of sky (POS) motion and the line of sight (LOS) motion. We focus on single isolated spicules and track the POS using time distance analysis and in the LOS direction using Doppler information. We use moment analysis to find the relation between the two motions. The composition of these two motions suggests that the wave has a helical structure. The oscillations do not have phase differences between points along the structure. This may be the result of the oscillation being a standing mode, or that propagation is mostly in the perpendicular direction. There is evidence of fast magnetoacoustic wave fronts propagating across these structures. To conclude, we hypothesize that the compression and rarefaction of passing magnetoacoustic waves may influence the appearance of spicule type events, not only by contributing to moving them in and out of the wing of the spectral line but also through the creation of density enhancements and an increase in opacity in the Halpha line. 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: The Nature of High-frequency Oscillations Associated with Short-lived Spicule-type Events Authors: Shetye, Juie; Verwichte, Erwin; Stangalini, Marco; Doyle, J. G. Bibcode: 2021ApJ...921...30S Altcode: We investigate high-resolution spectroscopic and imaging observations from the CRisp Imaging SpectroPolarimeter (CRISP) instrument to study the dynamics of chromospheric spicule-type events. It is widely accepted that chromospheric fine structures are waveguides for several types of magnetohydrodynamic (MHD) oscillations, which can transport energy from the lower to upper layers of the Sun. We provide a statistical study of 30 high-frequency waves associated with spicule-type events. These high-frequency oscillations have two components of transverse motions: the plane-of-sky (POS) motion and the line-of-sight (LOS) motion. We focus on single isolated spicules and track the POS using time-distance analysis and in the LOS direction using Doppler information. We use moment analysis to find the relation between the two motions. The composition of these two motions suggests that the wave has a helical structure. The oscillations do not have phase differences between points along the structure. This may be the result of the oscillation being a standing mode, or that propagation is mostly in the perpendicular direction. There is evidence of fast magnetoacoustic wave fronts propagating across these structures. To conclude, we hypothesize that the compression and rarefaction of passing magnetoacoustic waves may influence the appearance of spicule-type events, not only by contributing to moving them in and out of the wing of the spectral line but also through the creation of density enhancements and an increase in opacity in the Hα line. Title: Transiting Exoplanet Survey Satellite (TESS) Observations of Flares and Quasi-Periodic Pulsations from Low-Mass Stars and Potential Impact on Exoplanets Authors: Ramsay, Gavin; Kolotkov, Dmitrii; Doyle, J. Gerry; Doyle, Lauren Bibcode: 2021SoPh..296..162R Altcode: 2021arXiv210810670R We have performed a search for flares and quasi-periodic pulsations (QPPs) from low-mass M-dwarf stars using Transient Exoplanet Survey Satellite (TESS) two-minute cadence data. We find seven stars that show evidence of QPPs. Using Fourier and empirical mode decomposition techniques, we confirm the presence of 11 QPPs in these seven stars with a period between 10.2 and 71.9 minutes, including an oscillation with strong drift in the period and a double-mode oscillation. The fraction of flares that showed QPPs (7%) is higher than other studies of stellar flares, but it is very similar to the fraction of solar C-class flares. Based on the stellar parameters taken from the TESS Input Catalog, we determine the lengths and magnetic-field strengths of the flare coronal loops using the period of the QPPs and various assumptions about the origin of the QPPs. We also use a scaling relationship based on flares from the Sun and solar-type stars and the observed energy, plus the duration of the flares, finding that the different approaches predict loop lengths that are consistent to within a factor of about two. We also discuss the flare frequency of the seven stars determining whether this could result in ozone depletion or abiogenesis in any orbiting exoplanet. Three of our stars have a sufficiently high rate of energetic flares, which are likely to cause abiogenesis. However, two of these stars are also in the range where ozone depletion is likely to occur. We speculate on the implications of the flare rates, loop lengths, and QPPs for life on potential exoplanets orbiting in their host star's habitable zone. Title: Searching for Quasi Periodic Pulsations in flares from low mass stars using TESS data Authors: Ramsay, Gavin; Kolotkov, Dmitrii; Doyle, J. Gerry; Doyle, L., Bibcode: 2021tsc2.confE..74R Altcode: We have searched the light curves of low mass stars with TESS 2 min cadence data in Cycles 1 & 2 for Quasi Periodic Pulsations (QPPs) in stellar flares. We identified 11 flares from 7 stars which have QPPs with periods ranging from ~10 min to 70 min. We use several methods for determining the loop length of the flares and find they can extend to a handful of stellar radius. Based on scaling relationships we determine the magnetic field strength in the coronal loops and compare the loop lengths to distance to the habitable zone for the host star. Title: The AstroPath Image Acquisition and Segmentation Workflow Authors: Green, Benjamin; Berry, Sneha; Giraldo, Nicolas; Cottrell, Tricia; Engle, Elizabeth; Xu, Haiyang; Ogurtsova, Aleksandra; Wang, Daphne; Nguyen, Peter; Soto-Diaz, Sigfredo; Loyola, Jose; Doyle, Joshua; Wilton, Richard; Eminizer, Margaret; Roskes, Jeffrey; Szalay, Alexander; Taube, Janis Bibcode: 2021wems.confE..12G Altcode: Multidimensional, spatially resolved analyses of cells from pathology slides are of great diagnostic and prognostic interest. New multispectral, multiplex immunofluorescence microscopy platforms have the potential to facilitate such analyses, and here, we further improve and standardize the image acquisition and cell classification workflow. Studies to date on this emerging technology have typically assessed ~10 operator-dependent high power fields (HPFs) per slide, which represents a fraction of the tissue available for study. Standard cell segmentation and classification algorithms often oversegment larger cells, when they are segmented at the same time as smaller cells. Here we describe our AstroPath imaging platform, which addresses each of these considerations. In our study, slides from formalin-fixed paraffin embedded tissue specimens were stained with an optimized 6-plex multiplex immunofluorescence (mIF) assay. The slides were then scanned at 35 unique wavelengths using a multispectral microscope (Vectra 3.0 or Vectra Polaris) with 20% overlap of HPFs in an operator-independent fashion. An average of 1300 HPFs per slide was required to image the entire tissue, and each microscope scanned between 2 to 3 slides per day with this approach. After the images were captured and organized, overlaps were used to measure, quantify and correct systematics in the imagery (see Eminizer abstract). The central parts of the images were used to create a set of seamless "primary" tiles, similar to the strategy of the Sloan Digital Sky Survey, for a statistically fair pixel coverage of the whole tissue area (see Roskes abstract). Images were then linearly unmixed from the 35 wavelengths to 8 component layers (DAPI, tissue auto-fluorescence, and the 6 added fluorescent dyes) using inForm Cell Analysis Title: Power-law energy distributions of small-scale impulsive events on the active Sun: results from IRIS Authors: Vilangot Nhalil, Nived; Nelson, Chris J.; Mathioudakis, Mihalis; Doyle, J. Gerry; Ramsay, Gavin Bibcode: 2020MNRAS.499.1385V Altcode: 2020MNRAS.tmp.2719N; 2020arXiv200903123V Numerous studies have analysed inferred power-law distributions between frequency and energy of impulsive events in the outer solar atmosphere in an attempt to understand the predominant energy supply mechanism in the corona. Here, we apply a burst detection algorithm to high-resolution imaging data obtained by the Interface Region Imaging Spectrograph to further investigate the derived power-law index, γ, of bright impulsive events in the transition region. Applying the algorithm with a constant minimum event lifetime (of either 60 s or 110 s) indicated that the target under investigation, such as Plage and Sunspot, has an influence on the observed power-law index. For regions dominated by sunspots, we always find γ < 2; however, for data sets where the target is a plage region, we often find that γ > 2 in the energy range (~1023, ~1026) erg. Applying the algorithm with a minimum event lifetime of three time-steps indicated that cadence was another important factor, with the highest cadence data sets returning γ > 2 values. The estimated total radiative power obtained for the observed energy distributions is typically 10-25 per cent of what would be required to sustain the corona indicating that impulsive events in this energy range are not sufficient to solve coronal heating. If we were to extend the power-law distribution down to an energy of 1021 erg, and assume parity between radiative energy release and the deposition of thermal energy, then such bursts could provide 25-50 per cent of the required energy to account for the coronal heating problem. Title: TESS observations of southern ultrafast rotating low-mass stars Authors: Ramsay, Gavin; Doyle, J. Gerry; Doyle, Lauren Bibcode: 2020MNRAS.497.2320R Altcode: 2020MNRAS.tmp.2138R; 2020arXiv200704071R In our previous study of low-mass stars using TESS, we found a handful that show a periodic modulation on a period <1 d but also displayed no flaring activity. Here we present the results of a systematic search for ultrafast rotators (UFRs) in the Southern ecliptic hemisphere, which were observed in 2-min cadence with TESS. Using data from Gaia DR2, we obtain a sample of over 13 000 stars close to the lower main sequence. Of these, we identify 609 stars that lie on the lower main sequence and have a periodic modulation <1 d. The fraction of stars that show flares appears to drop significantly at periods <0.2 d. If the periods are a signature of the rotation rate, this would be a surprise, since faster rotators would be expected to have a stronger magnetic field and, therefore, produce more flares. We explore possible reasons for our finding: The flare inactive stars are members of binaries, in which case the stars rotation rate could have increased as the binary orbital separation reduced due to angular momentum loss over time, or that enhanced emission occurs at blue wavelengths beyond the pass band of TESS. Follow-up spectroscopy and flare monitoring at blue/ultraviolet wavelengths of these flare inactive stars are required to resolve this question. Title: Velocity Response of the Observed Explosive Events in the Lower Solar Atmosphere. I. Formation of the Flowing Cool-loop System Authors: Srivastava, A. K.; Rao, Yamini K.; Konkol, P.; Murawski, K.; Mathioudakis, M.; Tiwari, Sanjiv K.; Scullion, E.; Doyle, J. G.; Dwivedi, B. N. Bibcode: 2020ApJ...894..155S Altcode: 2020arXiv200402775S We observe plasma flows in cool loops using the Slit-Jaw Imager on board the Interface Region Imaging Spectrometer (IRIS). Huang et al. observed unusually broadened Si IV 1403 Šline profiles at the footpoints of such loops that were attributed to signatures of explosive events (EEs). We have chosen one such unidirectional flowing cool-loop system observed by IRIS where one of the footpoints is associated with significantly broadened Si IV line profiles. The line-profile broadening indirectly indicates the occurrence of numerous EEs below the transition region (TR), while it directly infers a large velocity enhancement/perturbation, further causing the plasma flows in the observed loop system. The observed features are implemented in a model atmosphere in which a low-lying bipolar magnetic field system is perturbed in the chromosphere by a velocity pulse with a maximum amplitude of 200 km s-1. The data-driven 2D numerical simulation shows that the plasma motions evolve in a similar manner as observed by IRIS in the form of flowing plasma filling the skeleton of a cool-loop system. We compare the spatio-temporal evolution of the cool-loop system in the framework of our model with the observations, and conclude that their formation is mostly associated with the velocity response of the transient energy release above their footpoints in the chromosphere/TR. Our observations and modeling results suggest that the velocity responses most likely associated to the EEs could be one of the main candidates for the dynamics and energetics of the flowing cool-loop systems in the lower solar atmosphere. Title: Superflares and variability in solar-type stars with TESS in the Southern hemisphere Authors: Doyle, L.; Ramsay, G.; Doyle, J. G. Bibcode: 2020MNRAS.494.3596D Altcode: 2020MNRAS.tmp.1151D; 2020arXiv200314410D Superflares on solar-type stars have been a rapidly developing field ever since the launch of Kepler. Over the years, there have been several studies investigating the statistics of these explosive events. In this study, we present a statistical analysis of stellar flares on solar-type stars made using photometric data in 2-min cadence from Transiting Exoplanet Survey Satellite of the whole Southern hemisphere (sectors 1-13). We derive rotational periods for all the stars in our sample from rotational modulations present in the light curve as a result of large star-spot(s) on the surface. We identify 1980 stellar flares from 209 solar-type stars with energies in the range of 1031-1036 erg (using the solar flare classification, this corresponds to X1-X100 000) and conduct an analysis into their properties. We investigate the rotational phase of the flares and find no preference for any phase, suggesting the flares are randomly distributed. As a benchmark, we use GOES data of solar flares to detail the close relationship between solar flares and sunspots. In addition, we also calculate approximate spot areas for each of our stars and compare this to flare number, rotational phase, and flare energy. Additionally, two of our stars were observed in the continuous viewing zone with light-curves spanning 1 yr; as a result we examine the stellar variability of these stars in more detail. Title: Exploring Flaring Behaviour on Low Mass Stars, Solar-type Stars and the Sun Authors: Doyle, L.; Ramsay, G.; Doyle, J. G.; Wyper, P. F.; Scullion, E.; Wu, K.; McLaughlin, J. A. Bibcode: 2020IAUS..354..384D Altcode: We report on our project to study the activity in both the Sun and low mass stars. Utilising high cadence, Hα observations of a filament eruption made using the CRISP spectropolarimeter mounted on the Swedish Solar Telescope has allowed us to determine 3D velocity maps of the event. To gain insight into the physical mechanism which drives the event we have qualitatively compared our observation to a 3D MHD reconnection model. Solar-type and low mass stars can be highly active producing flares with energies exceeding erg. Using K2 and TESS data we find no correlation between the number of flares and the rotation phase which is surprising. Our solar flare model can be used to aid our understanding of the origin of flares in other stars. By scaling up our solar model to replicate observed stellar flare energies, we investigate the conditions needed for such high energy flares. Title: On the Observations of Rapid Forced Reconnection in the Solar Corona Authors: Srivastava, A. K.; Mishra, S. K.; Jelínek, P.; Samanta, Tanmoy; Tian, Hui; Pant, Vaibhav; Kayshap, P.; Banerjee, Dipankar; Doyle, J. G.; Dwivedi, B. N. Bibcode: 2019ApJ...887..137S Altcode: 2019arXiv190107971S Using multiwavelength imaging observations from the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory on 2012 May 3, we present a novel physical scenario for the formation of a temporary X-point in the solar corona, where plasma dynamics are forced externally by a moving prominence. Natural diffusion was not predominant; however, a prominence driven inflow occurred first, forming a thin current sheet, thereafter enabling a forced magnetic reconnection at a considerably high rate. Observations in relation to the numerical model reveal that forced reconnection may rapidly and efficiently occur at higher rates in the solar corona. This physical process may also heat the corona locally even without establishing a significant and self-consistent diffusion region. Using a parametric numerical study, we demonstrate that the implementation of the external driver increases the rate of the reconnection even when the resistivity required for creating normal diffusion region decreases at the X-point. We conjecture that the appropriate external forcing can bring the oppositely directed field lines into the temporarily created diffusion region first via the plasma inflows as seen in the observations. The reconnection and related plasma outflows may occur thereafter at considerably larger rates. Title: Observations and 3D Magnetohydrodynamic Modeling of a Confined Helical Jet Launched by a Filament Eruption Authors: Doyle, Lauren; Wyper, Peter F.; Scullion, Eamon; McLaughlin, James A.; Ramsay, Gavin; Doyle, J. Gerard Bibcode: 2019ApJ...887..246D Altcode: 2019arXiv191202133D We present a detailed analysis of a confined filament eruption and jet associated with a C1.5 class solar flare. Multi-wavelength observations from the Global Oscillations Network Group and Solar Dynamics Observatory reveal the filament forming over several days following the emergence and then partial cancellation of a minority polarity spot within a decaying bipolar active region. The emergence is also associated with the formation of a 3D null point separatrix that surrounds the minority polarity. The filament eruption occurs concurrently with brightenings adjacent to and below the filament, suggestive of breakout and flare reconnection, respectively. The erupting filament material becomes partially transferred into a strong outflow jet (∼60 km s-1) along coronal loops, becoming guided back toward the surface. Utilizing high-resolution Hα observations from the Swedish Solar Telescope/CRisp Imaging SpectroPolarimeter, we construct velocity maps of the outflows, demonstrating their highly structured but broadly helical nature. We contrast the observations with a 3D magnetohydrodynamic simulation of a breakout jet in a closed-field background and find close qualitative agreement. We conclude that the suggested model provides an intuitive mechanism for transferring twist/helicity in confined filament eruptions, thus validating the applicability of the breakout model not only to jets and coronal mass ejections but also to confined eruptions and flares. Title: Probing the origin of stellar flares on M dwarfs using TESS data sectors 1-3 Authors: Doyle, L.; Ramsay, G.; Doyle, J. G.; Wu, K. Bibcode: 2019MNRAS.489..437D Altcode: 2019arXiv190802698D; 2019MNRAS.tmp.2115D Detailed studies of the Sun have shown that sunspots and solar flares are closely correlated. Photometric data from Kepler/K2 has allowed similar studies to be carried out on other stars. Here, we utilize Transiting Exoplanet Survey Satellite (TESS) photometric 2-min cadence of 167 low-mass stars from Sectors 1 to 3 to investigate the relationship between star-spots and stellar flares. From our sample, 90 per cent show clear rotational modulation likely due to the presence of a large, dominant star-spot and we use this to determine a rotational period for each star. Additionally, each low-mass star shows one or more flares in its light curve and using Gaia Data Release 2 parallaxes and SkyMapper magnitudes we can estimate the energy of the flares in the TESS band-pass. Overall, we have 1834 flares from the 167 low-mass stars with energies from 6.0 × 1029 to 2.4 × 1035 erg. We find none of the stars in our sample show any preference for rotational phase, suggesting the lack of a correlation between the large, dominant star-spot, and flare number. We discuss this finding in greater detail and present further scenarios to account for the origin of flares on these low-mass stars. Title: VizieR Online Data Catalog: Stellar parameters of M and K dwarfs (Houdebine+, 2019) Authors: Houdebine, E. R.; Mullan, D. J.; Doyle, J. G.; de La Vieuville, G.; Butler, C. J.; Paletou, F. Bibcode: 2019yCat..51580056H Altcode: Observations of (R-I)C (Cousin's photometric system) or (R-I)<SU photometric system) for our samples of K and M dwarfs were taken from several papers. We selected eight samples of K and M dwarfs according to their (R-I)C colors. This represents a total sample of 2765 K and M dwarfs. Most stars in this sample are nearby or large proper motion stars. We also completed these samples of stars with a ninth sample of stars: the M0-M1 sample, which includes some stars from the samples of stars from B12 and M15 (see Table 1), as well as several stars initially from the M2 sample, which were found to have higher temperatures (we included in the M0-M1 sample stars down to the spectral type dM1.5).

(3 data files). Title: The Mass-Activity Relationships in M and K Dwarfs. I. Stellar Parameters of Our Sample of M and K Dwarfs Authors: Houdebine, Éric R.; Mullan, D. J.; Doyle, J. G.; de La Vieuville, Geoffroy; Butler, C. J.; Paletou, F. Bibcode: 2019AJ....158...56H Altcode: 2019arXiv190507921H Empirical correlations between stellar parameters such as rotation or radius and magnetic activity diagnostics require estimates of the effective temperatures and the stellar radii. The aim of this study is to propose simple methods that can be applied to large samples of stars in order to derive estimates of the stellar parameters. Good empirical correlations between red/infrared colors (e.g., (R - I) C ) and effective temperatures have been well established for a long time. The more recent (R - I) C color-T eff correlation using the data of Mann et al. (hereafter M15) and Boyajian et al. (hereafter B12) shows that this color can be applied as a temperature estimate for large samples of stars. We find that the mean scatter in T eff relative to the (R - I) C -T eff relationship of B12 and M15 data is only ±3σ = 44.6 K for K dwarfs and ±3σ = 39.4 K for M dwarfs. These figures are small and show that the (R - I) C color can be used as a first-guess effective temperature estimator for K and M dwarfs. We derive effective temperatures for about 1910 K and M dwarfs using the calibration of (R - I) C color-T eff from B12 and M15 data. We also compiled T eff and metallicity measurements available in the literature using the VizieR database. We determine T eff for 441 stars with previously unknown effective temperatures. We also identified 21 new spectroscopic binaries and one triple system from our high-resolution spectra.

Based on Gaia DR2 and Hipparcos parallax measurements. Title: Multiwavelength High-resolution Observations of Chromospheric Swirls in the Quiet Sun Authors: Shetye, Juie; Verwichte, Erwin; Stangalini, Marco; Judge, Philip G.; Doyle, J. G.; Arber, Tony; Scullion, Eamon; Wedemeyer, Sven Bibcode: 2019ApJ...881...83S Altcode: We report observations of small-scale swirls seen in the solar chromosphere. They are typically 2 Mm in diameter and last around 10 minutes. Using spectropolarimetric observations obtained by the CRisp Imaging Spectro-Polarimeter at the Swedish 1 m Solar Telescope, we identify and study a set of swirls in chromospheric Ca II 8542 Å and Hα lines as well as in the photospheric Fe I line. We have three main areas of focus. First, we compare the appearance, morphology, dynamics, and associated plasma parameters between the Ca II and Hα channels. Rotation and expansion of the chromospheric swirl pattern are explored using polar plots. Second, we explore the connection to underlying photospheric magnetic concentration (MC) dynamics. MCs are tracked using the SWAMIS tracking code. The swirl center and MC remain cospatial and share similar periods of rotation. Third, we elucidate the role swirls play in modifying chromospheric acoustic oscillations and found a temporary reduction in wave period during swirls. We use cross-correlation wavelets to examine the change in period and phase relations between different wavelengths. The physical picture that emerges is that a swirl is a flux tube that extends above an MC in a downdraft region in an intergranular lane. The rotational motion of the MC matches the chromospheric signatures. We could not determine whether a swirl is a gradual response to the photospheric motion or an actual propagating Alfvénic wave. Title: Confined pseudo-shocks as an energy source for the active solar corona Authors: Srivastava, Abhishek Kumar; Murawski, Krzysztof; Kuźma, BlaŻej; Wójcik, Dariusz Patryk; Zaqarashvili, Teimuraz V.; Stangalini, Marco; Musielak, Zdzislaw E.; Doyle, John Gerard; Kayshap, Pradeep; Dwivedi, Bhola N. Bibcode: 2018NatAs...2..951S Altcode: 2018NatAs.tmp..138S The Sun's active corona requires an energy flux of 103 W m-2 to compensate for radiative losses and to maintain its high temperature1. Plasma moves in the corona through magnetic loops2,3, which may be connected with the flows in and around sunspots4-6. Global energizing processes (for example, reconnection) play an important part in heating the corona7-9; however, energy and mass transport may also occur via shocks, waves or flows5,10,11. A full picture and the influence of such localized events, which significantly couple with various layers of the solar upper atmosphere, is still not clear. Using the Interface Region Imaging Spectrograph temporal image data of C uc(ii) 1,330 Å, we observed the presence of pseudo-shocks around a sunspot. Unlike shocks12, pseudo-shocks exhibit discontinuities only in the mass density. A two-fluid numerical simulation reproduces such confined pseudo-shocks with rarefied plasma regions lagging behind them. We find that these pseudo-shocks carry an energy of 103 W m-2, which is enough to locally power the inner corona and also generate bulk flows ( 10-5 kg m-2 s-1), contributing to the localized mass transport. If they are ubiquitous, such energized and bulky pseudo-shocks above active regions could provide an important contribution to the heating and mass transport in the overlying solar corona. Title: A persistent quiet-Sun small-scale tornado. I. Characteristics and dynamics Authors: Tziotziou, K.; Tsiropoula, G.; Kontogiannis, I.; Scullion, E.; Doyle, J. G. Bibcode: 2018A&A...618A..51T Altcode: Context. Vortex flows have been extensively observed over a wide range of spatial and temporal scales in different spectral lines, and thus layers of the solar atmosphere, and have been widely found in numerical simulations. However, signatures of vortex flows have only recently been reported in the wings of the Hα, but never so far in the Hα line centre.
Aims: We investigate the appearance, characteristics, substructure, and dynamics of a 1.7 h persistent vortex flow observed from the ground and from space in a quiet-Sun region in several lines/channels covering all atmospheric layers from the photosphere up to the low corona.
Methods: We use high spatial and temporal resolution CRisp Imaging SpectroPolarimeter (CRISP) observations in several wavelengths along the Hα and Ca II 8542 Å line profiles, simultaneous Atmospheric Imaging Assembly (AIA) observations in several Ultraviolet (UV) and Extreme ultraviolet (EUV) channels and Helioseismic and Magnetic Imager (HMI) magnetograms to study a persistent vortex flow located at the south solar hemisphere. Doppler velocities were derived from the Hα line profiles. Our analysis involves visual inspection and comparison of all available simultaneous/near-simultaneous observations and detailed investigation of the vortex appearance, characteristics and dynamics using time slices along linear and circular slits.
Results: The most important characteristic of the analysed clockwise rotating vortex flow is its long duration (at least 1.7 h) and its large radius ( 3″). The vortex flow shows different behaviours in the different wavelengths along the Hα and Ca II 8542 Å profiles reflecting the different formation heights and mechanisms of the two lines. Ground-based observations combined with AIA observations reveal the existence of a funnel-like structure expanding with height, possibly rotating rigidly or quasi-rigidly. However, there is no clear evidence that the flow is magnetically driven as no associated magnetic bright points have been observed in the photosphere. Hα and Ca II 8542 Å observations also reveal significant substructure within the flow, manifested as several individual intermittent chromospheric swirls with typical sizes and durations. They also exhibit a wide range of morphological patterns, appearing as dark absorbing features, associated mostly with mean upwards velocities around 3 km s-1 and up to 8 km s-1, and occupying on average 25% of the total vortex area. The radial expansion of the spiral flow occurs with a mean velocity of 3 km s-1, while its dynamics can be related to the dynamics of a clockwise rigidly rotating logarithmic spiral with a swinging motion that is, however, highly perturbed by nearby flows associated with fibril-like structures. A first rough estimate of the rotational period of the vortex falls in the range of 200-300 s.
Conclusions: The vortex flow resembles a small-scale tornado in contrast to previously reported short-lived swirls and in analogy to persistent giant tornadoes. It is unclear whether the observed substructure is indeed due to the physical presence of individual intermittent, recurring swirls or a manifestation of wave-related instabilities within a large vortex flow. Moreover, we cannot conclusively demonstrate that the long duration of the observed vortex is the result of a central swirl acting as an "engine" for the vortex flow, although there is significant supporting evidence inferred from its dynamics. It also cannot be excluded that this persistent vortex results from the combined action of several individual smaller swirls further assisted by nearby flows or that this is a new case in the literature of a hydrodynamically driven vortex flow.

The movie associated to Fig. 4 is available at https://www.aanda.org Title: Investigating the rotational phase of stellar flares on M dwarfs using K2 short cadence data Authors: Doyle, L.; Ramsay, G.; Doyle, J. G.; Wu, K.; Scullion, E. Bibcode: 2018MNRAS.480.2153D Altcode: 2018MNRAS.tmp.1870D; 2018arXiv180708592D We present an analysis of K2 short cadence data of 34 M dwarfs which have spectral types in the range M0-L1. Of these stars, 31 showed flares with a duration between ∼10 and 90min. Using distances obtained from Gaia DR2 parallaxes, we determined the energy of the flares to be in the range ∼1.2 × 1029-6 × 1034 erg. In agreement with previous studies we find rapidly rotating stars tend to show more flares, with evidence for a decline in activity in stars with rotation periods longer than ∼10 d. The rotational modulation seen in M dwarf stars is widely considered to result from a starspot which rotates in and out of view. Flux minimum is therefore the rotation phase where we view the main starspot close to the stellar disc centre. Surprisingly, having determined the rotational phase of each flare in our study we find none show any preference for rotational phase. We outline three scenarios which could account for this unexpected finding. The relationship between rotation phase and flare rate will be explored further using data from wide surveys such as NGTS and TESS. Title: Signatures of quiet Sun reconnection events in Ca II, Hα, and Fe I Authors: Shetye, J.; Shelyag, S.; Reid, A. L.; Scullion, E.; Doyle, J. G.; Arber, T. D. Bibcode: 2018MNRAS.479.3274S Altcode: 2018MNRAS.tmp.1509S; 2017arXiv170310968S We use observations of quiet Sun (QS) regions in the Hα 6563 Å, Ca II 8542 Å, and Fe I 6302 Å lines. We observe brightenings in the wings of the Hα and Ca II combined with observations of the interacting magnetic concentrations observed in the Stokes signals of Fe I. These brightenings are similar to Ellerman bombs (EBs), i.e. impulsive bursts in the wings of the Balmer lines that leave the line cores unaffected. Such enhancements suggest that these events have similar formation mechanisms to the classical EBs found in active regions, with the reduced intensity enhancements found in the QS regions due to a weaker feeding magnetic flux. The observations also show that the quiet Sun Ellerman bombs are formed at a higher height in the upper photosphere than the photospheric continuum level. Using simulations, we investigate the formation mechanism associated with the events and suggest that these events are driven by the interaction of magnetic field lines in the upper photospheric regions. The results of the simulation are in agreement with observations when comparing the light curves, and in most cases, we found that the peak in the Ca II 8542 Å wing occurred before the peak in Hα wing. Moreover, in some cases, the line profiles observed in Ca II are asymmetrical with a raised core profile. The source of heating in these events is shown by the MURaM simulations and is suggested to occur 430 km above the photosphere. Title: Searching for the Origin of Flares in M dwarfs Authors: Doyle, Lauren; Ramsay, Gavin; Doyle, John G. Bibcode: 2018csss.confE..81D Altcode: 2018arXiv181106594D We present an overview of K2 short cadence observations for 34 M dwarfs observed in Campaigns 1 - 9 which have spectral types between M0 - L1. All of the stars in our sample showed flares with the most energetic reaching 3×10(34) ergs. As previous studies have found, we find rapidly rotating stars tend to show more flares, with evidence for a decline in activity in stars with rotation periods longer than approximately 10 days. We determined the rotational phase of each flare and performed a simple statistical test on our sample to determine whether the phase distribution of the flares is random or if there is a preference for phase. We find, with the exception of one star which is in a known binary system, that none show a preference for the rotational phase of the flares. This is unexpected and all stars in our sample show flares at all rotational phases, suggesting these flares are not all originating from one dominant starspot on the surface of the stars. We outline three scenarios which could explain the lack of a correlation between the number of flares and the stellar rotation phase. In addition we also highlight preliminary observations of DP Cnc, observed in campaigns 16 and 18, and is one of the stars in our extended sample from K2Campaigns 10 -18 which are still to be examined. Title: Energetics of Hi-C EUV brightenings Authors: Subramanian, Srividya; Kashyap, Vinay L.; Tripathi, Durgesh; Madjarska, Maria S.; Doyle, John G. Bibcode: 2018A&A...615A..47S Altcode: 2018arXiv180309505S We study the thermal structure and energetics of the point-like extreme ultraviolet (EUV) brightenings within a system of fan loops observed in the active region AR 11520. These brightenings were simultaneously observed on 2012 July 11 by the High-resolution Coronal (Hi-C) imager and the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory (SDO). We identified 27 brightenings by automatically determining intensity enhancements in both Hi-C and AIA 193 Å light curves. The energetics of these brightenings were studied using the Differential Emission Measure (DEM) diagnostics. The DEM weighted temperatures of these transients are in the range log T(K) = 6.2-6.6 with radiative energies ≈1024-25 ergs and densities approximately equal to a few times 109 cm-3. To the best of our knowledge, these are the smallest brightenings in EUV ever detected. We used these results to determine the mechanism of energy loss in these brightenings. Our analysis reveals that the dominant mechanism of energy loss for all the identified brightenings is conduction rather than radiation. Title: First Evidence of the Frequency Filtering of Magnetoacoustic Waves in the Flaring Star EK Dra Authors: Srivastava, A. K.; Pandey, J. C.; Karmakar, Subhajeet; Chowdhury, Partha; Moon, Y. -J.; Goossens, Marcel; Jelínek, P.; Mathioudakis, M.; Doyle, J. G.; Dwivedi, B. N. Bibcode: 2018arXiv180408858S Altcode: Using the data obtained from XMM-Newton, we show the gradual evolution of two periodicities of ~4500 s and ~2200 s in the decay phase of the flare observed in a solar analog EK Dra. The longer period evolves firstly for first 14 ks, while the shorter period evolves for next 10 ks in the decay phase. We find that these two periodicities are associated with the magnetoacoustic waves triggered in the flaring region. The flaring loop system shows cooling and thus it is subjected to the change in the scale height and the acoustic cut-off period. This serves to filter the longer period magnetoacoustic waves and enables the propagation of the shorter period waves in the later phase of the flare. We provide the first clues of the dynamic behaviour of EK Dra's corona which affects the propagation of waves and causes their filtering. Title: Stellar flare oscillations: evidence for oscillatory reconnection and evolution of MHD modes Authors: Doyle, J. G.; Shetye, J.; Antonova, A. E.; Kolotkov, D. Y.; Srivastava, A. K.; Stangalini, M.; Gupta, G. R.; Avramova, A.; Mathioudakis, M. Bibcode: 2018MNRAS.475.2842D Altcode: 2018MNRAS.tmp...77D Here, we report on the detection of a range of quasi-periodic pulsations (20-120 s; QPPs) observed during flaring activity of several magnetically active dMe stars, namely AF Psc, CR Dra, GJ 3685A, Gl 65, SDSS J084425.9+513830, and SDSS J144738.47+035312.1 in the GALEX NUV filter. Based on a solar analogy, this work suggests that many of these flares may be triggered by external drivers creating a periodic reconnection in the flare current sheet or an impulsive energy release giving rise to an avalanche of periodic bursts that occur at time intervals that correspond to the detected periods, thus generating QPPs in their rising and peak phases. Some of these flares also show fast QPPs in their decay phase, indicating the presence of fast sausage mode oscillations either driven externally by periodic reconnection or intrinsically in the post-flare loop system during the flare energy release. Title: Photospheric Observations of Surface and Body Modes in Solar Magnetic Pores Authors: Keys, Peter H.; Morton, Richard J.; Jess, David B.; Verth, Gary; Grant, Samuel D. T.; Mathioudakis, Mihalis; Mackay, Duncan H.; Doyle, John G.; Christian, Damian J.; Keenan, Francis P.; Erdélyi, Robertus Bibcode: 2018ApJ...857...28K Altcode: 2018arXiv180301859K Over the past number of years, great strides have been made in identifying the various low-order magnetohydrodynamic wave modes observable in a number of magnetic structures found within the solar atmosphere. However, one aspect of these modes that has remained elusive, until now, is their designation as either surface or body modes. This property has significant implications for how these modes transfer energy from the waveguide to the surrounding plasma. Here, for the first time to our knowledge, we present conclusive, direct evidence of these wave characteristics in numerous pores that were observed to support sausage modes. As well as outlining methods to detect these modes in observations, we make estimates of the energies associated with each mode. We find surface modes more frequently in the data, as well as that surface modes appear to carry more energy than those displaying signatures of body modes. We find frequencies in the range of ∼2-12 mHz, with body modes as high as 11 mHz, but we do not find surface modes above 10 mHz. It is expected that the techniques we have applied will help researchers search for surface and body signatures in other modes and in differing structures from those presented here. Title: Origin of impulsive plasma outflows due to magnetoacoustic shocks Authors: Rao, Y. K.; Srivastava, A. K.; Doyle, J. G.; Dwivedi, B. N. Bibcode: 2017MNRAS.470.2449R Altcode: We study an impulsive plasma outflow in the quiet-Sun using multiwavelength observations from the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory (SDO) on 2011 March 30. The outflow rises to the upper solar atmosphere with a high terminal speed of 1250 km s- 1. Emissions from multiple SDO/AIA channels (log T (K) = 4.7 to log T (K) = 7.0), peak at the same time indicating its highly impulsive origin. We obtain the line-of-sight differential emission measure maps and find that the outflow is made up of multitemperature plasma. Investigation of SDO/HMI magnetic field data at its footpoint shows that the emerging flux of negative polarity is oscillating at the period of 442 s. The oscillations are also observed in the intensity of 1600 Å almost co-temporally at the base of the outflow with the almost same period (≈416 s). The ∼7.0 min periodicity in the magnetic flux and 1600 Å flux is present both prior to and during the onset, and even after the outflows for the duration of ≈1 h. This indicates that the magnetoacoustic waves are generated and present at the base of the outflow and interact with the localized small-scale current sheet and associated X-point. Magnetoacoustic waves encounter with the discontinuity at the X-point that may further develop into the fast magnetic shocks leading to the formation of the observed shock cusp and triggering of the impulsive plasma outflows. Title: Chromospheric Inversions of a Micro-flaring Region Authors: Reid, A.; Henriques, V.; Mathioudakis, M.; Doyle, J. G.; Ray, T. Bibcode: 2017ApJ...845..100R Altcode: 2017arXiv170700029R We use spectropolarimetric observations of the Ca II 8542 Å line, taken from the Swedish 1 m Solar Telescope, in an attempt to recover dynamic activity in a micro-flaring region near a sunspot via inversions. These inversions show localized mean temperature enhancements of ∼1000 K in the chromosphere and upper photosphere, along with co-spatial bi-directional Doppler shifting of 5-10 km s-1. This heating also extends along a nearby chromospheric fibril, which is co-spatial to 10-15 km s-1 downflows. Strong magnetic flux cancellation is also apparent in one of the footpoints, and is concentrated in the chromosphere. This event more closely resembles that of an Ellerman Bomb, though placed slightly higher in the atmosphere than what is typically observed. Title: High-frequency torsional Alfvén waves as an energy source for coronal heating Authors: Srivastava, Abhishek Kumar; Shetye, Juie; Murawski, Krzysztof; Doyle, John Gerard; Stangalini, Marco; Scullion, Eamon; Ray, Tom; Wójcik, Dariusz Patryk; Dwivedi, Bhola N. Bibcode: 2017NatSR...743147S Altcode: The existence of the Sun’s hot atmosphere and the solar wind acceleration continues to be an outstanding problem in solar-astrophysics. Although magnetohydrodynamic (MHD) modes and dissipation of magnetic energy contribute to heating and the mass cycle of the solar atmosphere, yet direct evidence of such processes often generates debate. Ground-based 1-m Swedish Solar Telescope (SST)/CRISP, Hα 6562.8 Å observations reveal, for the first time, the ubiquitous presence of high frequency (~12-42 mHz) torsional motions in thin spicular-type structures in the chromosphere. We detect numerous oscillating flux tubes on 10 June 2014 between 07:17 UT to 08:08 UT in a quiet-Sun field-of-view of 60” × 60” (1” = 725 km). Stringent numerical model shows that these observations resemble torsional Alfvén waves associated with high frequency drivers which contain a huge amount of energy (~105 W m-2) in the chromosphere. Even after partial reflection from the transition region, a significant amount of energy (~103 W m-2) is transferred onto the overlying corona. We find that oscillating tubes serve as substantial sources of Alfvén wave generation that provide sufficient Poynting flux not only to heat the corona but also to originate the supersonic solar wind. Title: Modelling the environment around five ultracool dwarfs via the radio domain Authors: Metodieva, Y. T.; Kuznetsov, A. A.; Antonova, A. E.; Doyle, J. G.; Ramsay, G.; Wu, K. Bibcode: 2017MNRAS.465.1995M Altcode: 2016arXiv161002989M We present the results of a series of short radio observations of six ultracool dwarfs made using the upgraded Very Large Array in S (2-4GHz) and C (4-7GHz) bands. LSR J1835+3259 exhibits a 100 per cent right-hand circularly polarized burst that shows intense narrow-band features with a fast negative frequency drift of about -30 MHz s-1. They are superimposed on a fainter broad-band emission feature with a total duration of about 20 min, bandwidth of about 1 GHz, centred at about 3.5 GHz, and a slow positive frequency drift of about 1 MHz s-1. This makes it the first such event detected below 4 GHz and the first one exhibiting both positive and negative frequency drifts. Polarized radio emission is also seen in 2MASS J00361617+1821104 and NLTT 33370, while LP 349-25 and TVLM 513-46546 have unpolarized emission and BRI B0021-0214 was not detected. We can reproduce the main characteristics of the burst from LSR J1835+3259 using a model describing the magnetic field of the dwarf as a tilted dipole. We also analyse the origins of the quiescent radio emission and estimate the required parameters of the magnetic field and energetic electrons. Although our results are non-unique, we find a set of models that agree well with the observations. Title: Solar Ellerman Bombs in 1D Radiative Hydrodynamics Authors: Reid, A.; Mathioudakis, M.; Kowalski, A.; Doyle, J. G.; Allred, J. C. Bibcode: 2017ApJ...835L..37R Altcode: 2017arXiv170104213R Recent observations from the Interface Region Imaging Spectrograph appear to show impulsive brightenings in high temperature lines, which when combined with simultaneous ground-based observations in Hα, appear co-spatial to Ellerman Bombs (EBs). We use the RADYN one-dimensional radiative transfer code in an attempt to try and reproduce the observed line profiles and simulate the atmospheric conditions of these events. Combined with the MULTI/RH line synthesis codes, we compute the Hα, Ca II 8542 Å, and Mg II h and k lines for these simulated events and compare them to previous observations. Our findings hint that the presence of superheated regions in the photosphere (>10,000 K) is not a plausible explanation for the production of EB signatures. While we are able to recreate EB-like line profiles in Hα, Ca II 8542 Å, and Mg II h and k, we cannot achieve agreement with all of these simultaneously. Title: Explosive events in active region observed by IRIS and SST/CRISP Authors: Huang, Z.; Madjarska, M. S.; Scullion, E. M.; Xia, L. -D.; Doyle, J. G.; Ray, T. Bibcode: 2017MNRAS.464.1753H Altcode: 2016arXiv160907698H Transition-region explosive events (EEs) are characterized by non-Gaussian line profiles with enhanced wings at Doppler velocities of 50-150 km s-1. They are believed to be the signature of solar phenomena that are one of the main contributors to coronal heating. The aim of this study is to investigate the link of EEs to dynamic phenomena in the transition region and chromosphere in an active region. We analyse observations simultaneously taken by the Interface Region Imaging Spectrograph (IRIS) in the Si IV 1394 Å line and the slit-jaw (SJ) 1400 Å images, and the Swedish 1-m Solar Telescope in the Hα line. In total 24 events were found. They are associated with small-scale loop brightenings in SJ 1400 Å images. Only four events show a counterpart in the Hα-35 km s-1 and Hα+35 km s-1 images. Two of them represent brightenings in the conjunction region of several loops that are also related to a bright region (granular lane) in the Hα-35 km s-1 and Hα+35 km s-1 images. 16 are general loop brightenings that do not show any discernible response in the Hα images. Six EEs appear as propagating loop brightenings, from which two are associated with dark jet-like features clearly seen in the Hα-35 km s-1 images. We found that chromospheric events with jet-like appearance seen in the wings of the Hα line can trigger EEs in the transition region and in this case the IRIS Si IV 1394 Å line profiles are seeded with absorption components resulting from Fe II and Ni II. Our study indicates that EEs occurring in active regions have mostly upper-chromosphere/transition-region origin. We suggest that magnetic reconnection resulting from the braidings of small-scale transition region loops is one of the possible mechanisms of energy release that are responsible for the EEs reported in this paper. Title: On the relationship between magnetic cancellation and UV burst formation Authors: Nelson, C. J.; Doyle, J. G.; Erdélyi, R. Bibcode: 2016MNRAS.463.2190N Altcode: 2016arXiv160806505N; 2016MNRAS.tmp.1156N Burst-like events with signatures in the UV are often observed co-spatial to strong line-of-sight photospheric magnetic fields. Several authors, for example, have noted the spatial relationship between Ellerman bombs (EBs) and moving magnetic features (MMFs), regions of flux which disconnect from a sunspot or pore before propagating away in the moat flow and often displaying evidence of cancellation. In this article, data collected by the Solar Dynamics Observatory's Helioseismic and Magnetic Imager and Atmospheric Imaging Assembly are analysed in an attempt to understand the potential links between such cancellation and UV burst formation. Two MMFs from AR 11579, three bi-poles from AR 11765, and six bi-poles (four of which were co-spatial to Interface Region Imaging Spectrograph bursts) in AR 11850 were identified for analysis. All of these cancellation features were found to have lifetimes of the order hours and cancellation rates of the order 1014-1015 Mx s-1. Hα line wing data from the Dunn Solar Telescope's Interferometric BIdimensional Spectrometer were also available for AR 11579 facilitating a discussion of links between MMFs and EBs. Using an algebraic model of photospheric magnetic reconnection, the measured cancellation rates are then used to ascertain estimates of certain quantities (such as upflow speeds, jet extents, and potential energy releases), which compared reasonably to the properties of EBs reported within the literature. Our results suggest that cancellation rates of the order measured here are capable of supplying enough energy to drive certain UV bursts (including EBs), however, they are not a guaranteeing condition for burst formation. Title: A prototype of the NFIRAOS to instrument thermo-mechanical interface Authors: Hill, Alexis; Byrnes, Peter; Fitzsimmons, Joeleff; Herriot, Glen; Reshetov, Vlad; Szeto, Kei; Winter, Calvin; Pennec, Yan; Lambert, Sam; Poulton, Evan; Doyle, Jeffrey Bibcode: 2016SPIE.9912E..02H Altcode: NFIRAOS is the first light adaptive optics system for the Thirty Meter Telescope (TMT). NFIRAOS components are maintained at a stable -30°C +/-0.5°C by embedding an actively cooled refrigeration system in the walls of the NFIRAOS enclosure. Three instruments are attached to interface ports in the NFIRAOS enclosure and are required to be thermally stable while the instrument rotates in place. Additionally, instruments must be installed and removed while NFIRAOS is cold to avoid lengthy cool-down cycles. A portion of the actively cooled enclosure system and the interface has been prototyped at NRC-Herzberg. We present a description of the design of the interface and results of testing so far and lessons learned. Title: Magnetic Flux Cancellation in Ellerman Bombs Authors: Reid, A.; Mathioudakis, M.; Doyle, J. G.; Scullion, E.; Nelson, C. J.; Henriques, V.; Ray, T. Bibcode: 2016ApJ...823..110R Altcode: 2016arXiv160307100R Ellerman Bombs (EBs) are often found to be co-spatial with bipolar photospheric magnetic fields. We use Hα imaging spectroscopy along with Fe I 6302.5 Å spectropolarimetry from the Swedish 1 m Solar Telescope (SST), combined with data from the Solar Dynamic Observatory, to study EBs and the evolution of the local magnetic fields at EB locations. EBs are found via an EB detection and tracking algorithm. Using NICOLE inversions of the spectropolarimetric data, we find that, on average, (3.43 ± 0.49) × 1024 erg of stored magnetic energy disappears from the bipolar region during EB burning. The inversions also show flux cancellation rates of 1014-1015 Mx s-1 and temperature enhancements of 200 K at the detection footpoints. We investigate the near-simultaneous flaring of EBs due to co-temporal flux emergence from a sunspot, which shows a decrease in transverse velocity when interacting with an existing, stationary area of opposite polarity magnetic flux, resulting in the formation of the EBs. We also show that these EBs can be fueled further by additional, faster moving, negative magnetic flux regions. Title: High-cadence observations of spicular-type events on the Sun Authors: Shetye, J.; Doyle, J. G.; Scullion, E.; Nelson, C. J.; Kuridze, D.; Henriques, V.; Woeger, F.; Ray, T. Bibcode: 2016A&A...589A...3S Altcode: 2016arXiv160108087S Context. Chromospheric observations taken at high-cadence and high-spatial resolution show a range of spicule-like features, including Type-I, Type-II (as well as rapid blue-shifted excursions (RBEs) and rapid red-shifted excursions (RREs) which are thought to be on-disk counterparts of Type-II spicules) and those which seem to appear within a few seconds, which if interpreted as flows would imply mass flow velocities in excess of 1000 km s-1.
Aims: This article seeks to quantify and study rapidly appearing spicular-type events. We also compare the multi-object multi-frame blind deconvolution (MOMFBD) and speckle reconstruction techniques to understand if these spicules are more favourably observed using a particular technique.
Methods: We use spectral imaging observations taken with the CRisp Imaging SpectroPolarimeter (CRISP) on the Swedish 1-m Solar Telescope. Data was sampled at multiple positions within the Hα line profile for both an on-disk and limb location.
Results: The data is host to numerous rapidly appearing features which are observed at different locations within the Hα line profile. The feature's durations vary between 10-20 s and lengths around 3500 km. Sometimes, a time delay in their appearance between the blue and red wings of 3-5 s is evident, whereas, sometimes they are near simultaneous. In some instances, features are observed to fade and then re-emerge at the same location several tens of seconds later.
Conclusions: We provide the first statistical analysis of these spicules and suggest that these observations can be interpreted as the line-of-sight (LOS) movement of highly dynamic spicules moving in and out of the narrow 60 mÅ transmission filter that is used to observe in different parts of the Hα line profile. The LOS velocity component of the observed fast chromospheric features, manifested as Doppler shifts, are responsible for their appearance in the red and blue wings of Hα line. Additional work involving data at other wavelengths is required to investigate the nature of their possible wave-like activity. Title: High Cadence Observations and Analysis of Spicular-type Events Using CRISP Onboard SST Authors: Shetye, J.; Doyle, J. G.; Scullion, E.; Nelson, C. J.; Kuridze, D. Bibcode: 2016ASPC..504..115S Altcode: We present spectroscopic and imaging observations of apparent ultra-fast spicule-like features observed with CRisp Imaging SpectroPolarimeter (CRISP) at the Swedish 1-m Solar Telescope (SST). The data shows spicules with an apparent velocity above 500 km s-1, very short lifetimes of up to 20 s and length/height around 3500 km. The spicules are seen as dark absorption structures in the Hα wings ±516 mÅ, ±774 mÅ and ±1032 mÅ which suddenly appear and disappear from the FOV. These features show a time delay in their appearance in the blue and red wings by 3-5 s. We suggest that their appearance/disappearance is due to their Doppler motion in and out of the 60 mÅ filter. See Fig. 1 for the evolution of the event at two line positions. Title: Solar Science with the Atacama Large Millimeter/Submillimeter Array—A New View of Our Sun Authors: Wedemeyer, S.; Bastian, T.; Brajša, R.; Hudson, H.; Fleishman, G.; Loukitcheva, M.; Fleck, B.; Kontar, E. P.; De Pontieu, B.; Yagoubov, P.; Tiwari, S. K.; Soler, R.; Black, J. H.; Antolin, P.; Scullion, E.; Gunár, S.; Labrosse, N.; Ludwig, H. -G.; Benz, A. O.; White, S. M.; Hauschildt, P.; Doyle, J. G.; Nakariakov, V. M.; Ayres, T.; Heinzel, P.; Karlicky, M.; Van Doorsselaere, T.; Gary, D.; Alissandrakis, C. E.; Nindos, A.; Solanki, S. K.; Rouppe van der Voort, L.; Shimojo, M.; Kato, Y.; Zaqarashvili, T.; Perez, E.; Selhorst, C. L.; Barta, M. Bibcode: 2016SSRv..200....1W Altcode: 2015SSRv..tmp..118W; 2015arXiv150406887W The Atacama Large Millimeter/submillimeter Array (ALMA) is a new powerful tool for observing the Sun at high spatial, temporal, and spectral resolution. These capabilities can address a broad range of fundamental scientific questions in solar physics. The radiation observed by ALMA originates mostly from the chromosphere—a complex and dynamic region between the photosphere and corona, which plays a crucial role in the transport of energy and matter and, ultimately, the heating of the outer layers of the solar atmosphere. Based on first solar test observations, strategies for regular solar campaigns are currently being developed. State-of-the-art numerical simulations of the solar atmosphere and modeling of instrumental effects can help constrain and optimize future observing modes for ALMA. Here we present a short technical description of ALMA and an overview of past efforts and future possibilities for solar observations at submillimeter and millimeter wavelengths. In addition, selected numerical simulations and observations at other wavelengths demonstrate ALMA's scientific potential for studying the Sun for a large range of science cases. Title: Evolutionary tradeoffs in cellular composition across diverse bacteria Authors: Kempes, Christopher P.; Wang, Lawrence; Amend, Jan P.; Doyle, John; Hoehler, Tori Bibcode: 2016ISME...10.2145K Altcode: One of the most important classic and contemporary interests in biology is the connection between cellular composition and physiological function. Decades of research have allowed us to understand the detailed relationship between various cellular components and processes for individual species, and have uncovered common functionality across diverse species. However, there still remains the need for frameworks that can mechanistically predict the tradeoffs between cellular functions and elucidate and interpret average trends across species. Here we provide a comprehensive analysis of how cellular composition changes across the diversity of bacteria as connected with physiological function and metabolism, spanning five orders of magnitude in body size. We present an analysis of the trends with cell volume that covers shifts in genomic, protein, cellular envelope, RNA and ribosomal content. We show that trends in protein content are more complex than a simple proportionality with the overall genome size, and that the number of ribosomes is simply explained by cross-species shifts in biosynthesis requirements. Furthermore, we show that the largest and smallest bacteria are limited by physical space requirements. At the lower end of size, cell volume is dominated by DNA and protein content—the requirement for which predicts a lower limit on cell size that is in good agreement with the smallest observed bacteria. At the upper end of bacterial size, we have identified a point at which the number of ribosomes required for biosynthesis exceeds available cell volume. Between these limits we are able to discuss systematic and dramatic shifts in cellular composition. Much of our analysis is connected with the basic energetics of cells where we show that the scaling of metabolic rate is surprisingly superlinear with all cellular components. Title: First simultaneous SST/CRISP and IRIS observations of a small-scale quiet Sun vortex Authors: Park, S. -H.; Tsiropoula, G.; Kontogiannis, I.; Tziotziou, K.; Scullion, E.; Doyle, J. G. Bibcode: 2016A&A...586A..25P Altcode: 2015arXiv151206032P Context. Ubiquitous small-scale vortices have recently been found in the lower atmosphere of the quiet Sun in state-of-the-art solar observations and in numerical simulations.
Aims: We investigate the characteristics and temporal evolution of a granular-scale vortex and its associated upflows through the photosphere and chromosphere of a quiet Sun internetwork region.
Methods: We analyzed high spatial and temporal resolution ground- and spaced-based observations of a quiet Sun region. The observations consist of high-cadence time series of wideband and narrowband images of both Hα 6563 Å and Ca II 8542 Å lines obtained with the CRisp Imaging SpectroPolarimeter (CRISP) instrument at the Swedish 1-m Solar Telescope (SST), as well as ultraviolet imaging and spectral data simultaneously obtained by the Interface Region Imaging Spectrograph (IRIS).
Results: A small-scale vortex is observed for the first time simultaneously in Hα, Ca II 8542 Å, and Mg II k lines. During the evolution of the vortex, Hα narrowband images at -0.77 Å and Ca II 8542 Å narrowband images at -0.5 Å, and their corresponding Doppler signal maps, clearly show consecutive high-speed upflow events in the vortex region. These high-speed upflows with a size of 0.5-1 Mm appear in the shape of spiral arms and exhibit two distinctive apparent motions in the plane of sky for a few minutes: (1) a swirling motion with an average speed of 13 km s-1 and (2) an expanding motion at a rate of 4-6 km s-1. Furthermore, the spectral analysis of Mg II k and Mg II subordinate lines in the vortex region indicates an upward velocity of up to ~8 km s-1 along with a higher temperature compared to the nearby quiet Sun chromosphere.
Conclusions: The consecutive small-scale vortex events can heat the upper chromosphere by driving continuous high-speed upflows through the lower atmosphere.

Movies associated to Figs. 2 and 3 are available at http://www.aanda.org Title: SSALMON - The Solar Simulations for the Atacama Large Millimeter Observatory Network Authors: Wedemeyer, S.; Bastian, T.; Brajša, R.; Barta, M.; Hudson, H.; Fleishman, G.; Loukitcheva, M.; Fleck, B.; Kontar, E.; De Pontieu, B.; Tiwari, S.; Kato, Y.; Soler, R.; Yagoubov, P.; Black, J. H.; Antolin, P.; Gunár, S.; Labrosse, N.; Benz, A. O.; Nindos, A.; Steffen, M.; Scullion, E.; Doyle, J. G.; Zaqarashvili, T.; Hanslmeier, A.; Nakariakov, V. M.; Heinzel, P.; Ayres, T.; Karlicky, M. Bibcode: 2015AdSpR..56.2679W Altcode: 2015arXiv150205601W The Solar Simulations for the Atacama Large Millimeter Observatory Network (SSALMON) was initiated in 2014 in connection with two ALMA development studies. The Atacama Large Millimeter/submillimeter Array (ALMA) is a powerful new tool, which can also observe the Sun at high spatial, temporal, and spectral resolution. The international SSALMONetwork aims at co-ordinating the further development of solar observing modes for ALMA and at promoting scientific opportunities for solar physics with particular focus on numerical simulations, which can provide important constraints for the observing modes and can aid the interpretation of future observations. The radiation detected by ALMA originates mostly in the solar chromosphere - a complex and dynamic layer between the photosphere and corona, which plays an important role in the transport of energy and matter and the heating of the outer layers of the solar atmosphere. Potential targets include active regions, prominences, quiet Sun regions, flares. Here, we give a brief overview over the network and potential science cases for future solar observations with ALMA. Title: Active region upflows. I. Multi-instrument observations Authors: Vanninathan, K.; Madjarska, M. S.; Galsgaard, K.; Huang, Z.; Doyle, J. G. Bibcode: 2015A&A...584A..38V Altcode: 2015arXiv150905624V Context. We study upflows at the edges of active regions, called AR outflows, using multi-instrument observations.
Aims: This study intends to provide the first direct observational evidence of whether chromospheric jets play an important role in furnishing mass that could sustain coronal upflows. The evolution of the photospheric magnetic field, associated with the footpoints of the upflow region and the plasma properties of active region upflows is investigated with the aim of providing information for benchmarking data-driven modelling of this solar feature.
Methods: We spatially and temporally combine multi-instrument observations obtained with the Extreme-ultraviolet Imaging Spectrometer on board the Hinode, the Atmospheric Imaging Assembly and the Helioseismic Magnetic Imager instruments on board the Solar Dynamics Observatory and the Interferometric BI-dimensional Spectro-polarimeter installed at the National Solar Observatory, Sac Peak, to study the plasma parameters of the upflows and the impact of the chromosphere on active region upflows.
Results: Our analysis shows that the studied active region upflow presents similarly to those studied previously, i.e. it displays blueshifted emission of 5-20 kms-1 in Fe xii and Fe xiii and its average electron density is 1.8 × 109 cm-3 at 1 MK. The time variation of the density is obtained showing no significant change (in a 3σ error). The plasma density along a single loop is calculated revealing a drop of 50% over a distance of ~20 000 km along the loop. We find a second velocity component in the blue wing of the Fe xii and Fe xiii lines at 105 kms-1 reported only once before. For the first time we study the time evolution of this component at high cadence and find that it is persistent during the whole observing period of 3.5 h with variations of only ±15 kms-1. We also, for the first time, study the evolution of the photospheric magnetic field at high cadence and find that magnetic flux diffusion is responsible for the formation of the upflow region. High cadence Hα observations are used to study the chromosphere at the footpoints of the upflow region. We find no significant jet-like (spicule/rapid blue excursion) activity to account for several hours/days of plasma upflow. The jet-like activity in this region is not continuous and blueward asymmetries are a bare minimum. Using an image enhancement technique for imaging and spectral data, we show that the coronal structures seen in the AIA 193 Å channel are comparable to the EIS Fe xii images, while images in the AIA 171 Å channel reveal additional loops that are a result of contribution from cooler emission to this channel.
Conclusions: Our results suggest that at chromospheric heights there are no signatures that support the possible contribution of spicules to active region upflows. We suggest that magnetic flux diffusion is responsible for the formation of the coronal upflows. The existence of two velocity components possibly indicates the presence of two different flows, which are produced by two different physical mechanisms, e.g. magnetic reconnection and pressure-driven jets.

Movies associated to Figs. A.1-A.3 are available in electronic form at http://www.aanda.org Title: Searching for I-band variability in stars in the M/L spectral transition region Authors: Ramsay, Gavin; Hakala, Pasi; Doyle, J. Gerry Bibcode: 2015MNRAS.453.1484R Altcode: 2015arXiv150707784R We report on I-band photometric observations of 21 stars with spectral types between M8 and L4 made using the Isaac Newton Telescope. The total amount of time for observations which had a cadence of <2.3 min was 58.5 h, with additional data with lower cadence. We test for photometric variability using the Kruskal-Wallis H-test and find that four sources (2MASS J10224821+5825453, 2MASS J07464256+2000321, 2MASS J16262034+3925190 and 2MASS J12464678+4027150) were found to be significantly variable at least on one epoch. Three of these sources are reported as photometrically variable for the first time. If we include sources which were deemed marginally variable, the number of variable sources is 6 (29 per cent). No flares were detected from any source. The percentage of sources which we found were variable is similar to previous studies. We summarize the mechanisms which have been put forward to explain the light curves of brown dwarfs. Title: Magnetospherically driven optical and radio aurorae at the end of the stellar main sequence Authors: Hallinan, G.; Littlefair, S. P.; Cotter, G.; Bourke, S.; Harding, L. K.; Pineda, J. S.; Butler, R. P.; Golden, A.; Basri, G.; Doyle, J. G.; Kao, M. M.; Berdyugina, S. V.; Kuznetsov, A.; Rupen, M. P.; Antonova, A. Bibcode: 2015Natur.523..568H Altcode: 2015arXiv150708739H Aurorae are detected from all the magnetized planets in our Solar System, including Earth. They are powered by magnetospheric current systems that lead to the precipitation of energetic electrons into the high-latitude regions of the upper atmosphere. In the case of the gas-giant planets, these aurorae include highly polarized radio emission at kilohertz and megahertz frequencies produced by the precipitating electrons, as well as continuum and line emission in the infrared, optical, ultraviolet and X-ray parts of the spectrum, associated with the collisional excitation and heating of the hydrogen-dominated atmosphere. Here we report simultaneous radio and optical spectroscopic observations of an object at the end of the stellar main sequence, located right at the boundary between stars and brown dwarfs, from which we have detected radio and optical auroral emissions both powered by magnetospheric currents. Whereas the magnetic activity of stars like our Sun is powered by processes that occur in their lower atmospheres, these aurorae are powered by processes originating much further out in the magnetosphere of the dwarf star that couple energy into the lower atmosphere. The dissipated power is at least four orders of magnitude larger than what is produced in the Jovian magnetosphere, revealing aurorae to be a potentially ubiquitous signature of large-scale magnetospheres that can scale to luminosities far greater than those observed in our Solar System. These magnetospheric current systems may also play a part in powering some of the weather phenomena reported on brown dwarfs. 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: The view from K2: questioning the traditional view of flaring on early dM stars Authors: Ramsay, Gavin; Doyle, J. Gerry Bibcode: 2015MNRAS.449.3015R Altcode: 2015arXiv150302696R We use K2 short cadence data obtained over a duration of 50 d during Campaign 0 to observe two M1V dwarf stars, TYC 1330-879-1 and RXJ 0626+2349. We provide an overview of our data analysis, in particular, making a comparison between using a fixed set of pixels and an aperture which follows the position of the source. We find that this moving aperture approach can give fewer non-astrophysical features compared to a fixed aperture. Both sources shows flares as energetic as observed from several M4V stars using both Kepler and ground-based telescopes. We find that the flare energy distribution of the sources shown here are very similar to the less active M3-M5 stars but are ∼8 times less likely to produce a flare of a comparable energy to the more active M0-M5 stars. We discuss the biases and sources of systematic errors when comparing the activity of stars derived from different instruments. We conclude that K2 observations will provide an excellent opportunity to perform a census of flare activity across the full range of M dwarf spectral class and hence the physical mechanisms which power them. Title: New Upper Limit on the Electron's Electric Dipole Moment Authors: Doyle, John Bibcode: 2015APS..APR.B8003D Altcode: The ACME collaboration has measured the electron's electric dipole moment (eEDM) to be de =(- 2 . 1 +/- 3 .7stat +/- 2 .5syst) ×10-29 e .cm. This corresponds to an upper limit of | de | < 8 . 7 × 10-29 e .cm with 90 percent confidence, which represents an order of magnitude improvement on the previous best limit. We describe our method of measuring the eEDM using a buffer gas cooled beam of thorium monoxide (ThO) and discuss our approach to finding and quantifying systematic effects. This results constrains T-violating physics at the TeV energy scale.

This project is supported by NSF.</p> Title: A coronal wave and an asymmetric eruptive filament in SUMER, CDS, EIT, and TRACE co-observations Authors: Madjarska, M. S.; Doyle, J. G.; Shetye, J. Bibcode: 2015A&A...575A..39M Altcode: 2014arXiv1412.1984M Context. The investigation covers the complex subject of coronal waves and the phenomena contributing to and/or causing their formation.
Aims: The objectives of the present study is to provide a better physical understanding of the complex inter-relation and evolution of several solar coronal features comprising a double-peak flare, a coronal dimming caused by a coronal mass ejection (CME), a CME-driven compression, and a fast-mode wave. For the first time, the evolution of an asymmetric eruptive filament is analysed in simultaneous Solar Ultraviolet Measurement of Emitted Radiation (SUMER) spectroscopic and Transition Region and Coronal Explorer (TRACE) and Extreme-ultraviolet Imaging Telescope (EIT) imaging data.
Methods: We use imaging observations from EIT and TRACE in the 195 Å channel and spectroscopic observations from the Coronal Diagnostic Spectrometer (CDS) in a rastering and SUMER in a sit-and-stare observing mode. The SUMER spectra cover spectral lines with formation temperatures from log T(K) ~ 4.0 to 6.1.
Results: Although the event was already analysed in two previous studies, our analysis brings a wealth of new information on the dynamics and physical properties of the observed phenomena. We found that the dynamic event is related to a complex flare with two distinct impulsive peaks, one according to the Geostationary Operational Environmental Satellite (GOES) classification as C1.1 and the second - C1.9. The first energy release triggers a fast-mode wave and a CME with a clear CME driven compression ahead of it. This activity is related to, or possibly caused, by an asymmetric filament eruption. The filament is observed to rise with its leading edge moving at a speed of ~300 kms-1 detected both in the SUMER and CDS data. The rest of the filament body moves at only ~150 kms-1 while untwisting. No signature is found of the fast-mode wave in the SUMER data, suggesting that the plasma disturbed by the wave had temperatures above 600 000 K. The erupting filament material is found to emit only in spectral lines at transition region temperatures. Earlier identification of a coronal response detected in the Mg x 609.79 Å line is found to be caused by a blend from the O iv 609.83 Å line.
Conclusions: We present a unique analysis of the complex phenomenon called "EIT/coronal wave", confirming its bimodal nature. We suggest that the disintegration of the dimming/CME and the CME-driven compression are either caused by a CME-CME interaction taking place in the low solar atmosphere or by an impulsive CME cavity overexpansion in the low solar atmosphere.

A movie associated to Fig. A.1 is available in electronic form at http://www.aanda.org Title: Low-resolution optical spectra of ultracool dwarfs with OSIRIS/GTC Authors: Metodieva, Y.; Antonova, A.; Golev, V.; Dimitrov, D.; García-Álvarez, D.; Doyle, J. G. Bibcode: 2015MNRAS.446.3878M Altcode: 2014arXiv1412.2736M We present the results of low-resolution optical spectroscopy with OSIRIS/GTC (Optical System for Imaging and Low Resolution Integrated Spectroscopy/Gran Telescopio Canarias) for a sample of ultracool dwarfs. For a subsample of seven objects, based on 2 Micron Sky Survey (2MASS) NIR photometric colours, a `photometric' spectral type is determined and compared to the results of the optical spectroscopy. For the stars, showing Hα line in emission, equivalent widths were measured, and the ratio of Hα to bolometric luminosity were calculated. We find that two dwarfs show the presence of magnetic activity over long periods, LP 326-21 - quasi-constant-like, and 2MASS J17071830+6439331 - variable. Title: A multiwavelength study of the M dwarf binary YY Geminorum Authors: Butler, C. J.; Erkan, N.; Budding, E.; Doyle, J. G.; Foing, B.; Bromage, G. E.; Kellett, B. J.; Frueh, M.; Huovelin, J.; Brown, A.; Neff, J. E. Bibcode: 2015MNRAS.446.4205B Altcode: 2015arXiv150103930B We review the results of the 1988 multiwavelength campaign on the late-type eclipsing binary YY Geminorum. Observations include: broad-band optical and near-infrared photometry, simultaneous optical and ultraviolet (IUE) spectroscopy, X-ray (Ginga) and radio (VLA) data. From models fitted to the optical light curves, fundamental physical parameters have been determined together with evidence for transient maculations (spots) located near quadrature longitudes and intermediate latitudes. Eclipses were observed at optical, ultraviolet and radio wavelengths. Significant drops in 6 cm radio emission near the phases of both primary and secondary eclipse indicate relatively compact radio emitting volumes that may lie between the binary components. IUE observations during secondary eclipse are indicative of a uniform chromosphere saturated with Mg II emission and an extended volume of Lyα emission. Profile fitting of high-dispersion Hα spectra confirms the chromospheric saturation and indicates significant Hα opacity to heights of a few per cent of the photospheric radius. There is evidence for an enhanced Hα emission region visible near phase 0.25-0.35 which may be associated with a large spot on the primary and with two small optical flares which were also observed at other wavelengths: one in microwave radiation and the other in X-rays. For both flares, LX/Lopt is consistent with energy release in closed magnetic structures. Title: Stellar flares observed by LOFT: implications for the physics of coronae and for the "space weather" environment of extrasolar planets Authors: Drake, S. A.; Behar, E.; Doyle, J. G.; Güdel, M.; Hamaguchi, K.; Kowalski, A. F.; Maccarone, T.; Osten, R. A.; Peretz, U.; Wolk, S. J. Bibcode: 2015arXiv150102771D Altcode: This is a White Paper in support of the mission concept of the Large Observatory for X-ray Timing (LOFT), proposed as a medium-sized ESA mission. We discuss the potential of LOFT for the study of stellar flares. For a summary, we refer to the paper. Title: Small-scale Structuring of Ellerman Bombs at the Solar Limb Authors: Nelson, C. J.; Scullion, E. M.; Doyle, J. G.; Freij, N.; Erdélyi, R. Bibcode: 2015ApJ...798...19N Altcode: 2014arXiv1410.5715N Ellerman bombs (EBs) have been widely studied in recent years due to their dynamic, explosive nature and apparent links to the underlying photospheric magnetic field implying that they may be formed by magnetic reconnection in the photosphere. Despite a plethora of researches discussing the morphologies of EBs, there has been a limited investigation of how these events appear at the limb, specifically, whether they manifest as vertical extensions away from the disk. In this article, we make use of high-resolution, high-cadence observations of an Active Region at the solar limb, collected by the CRisp Imaging SpectroPolarimeter (CRISP) instrument, to identify EBs and infer their physical properties. The upper atmosphere is also probed using the Solar Dynamic Observatory's Atmospheric Imaging Assembly (SDO/AIA). We analyze 22 EB events evident within these data, finding that 20 appear to follow a parabolic path away from the solar surface at an average speed of 9 km s-1, extending away from their source by 580 km, before retreating back at a similar speed. These results show strong evidence of vertical motions associated with EBs, possibly explaining the dynamical "flaring" (changing in area and intensity) observed in on-disk events. Two in-depth case studies are also presented that highlight the unique dynamical nature of EBs within the lower solar atmosphere. The viewing angle of these observations allows for a direct linkage between these EBs and other small-scale events in the Hα line wings, including a potential flux emergence scenario. The findings presented here suggest that EBs could have a wider-reaching influence on the solar atmosphere than previously thought, as we reveal a direct linkage between EBs and an emerging small-scale loop, and other near-by small-scale explosive events. However, as previous research found, these extensions do not appear to impact upon the Hα line core, and are not observed by the SDO/AIA EUV filters. Title: Erratum: Erratum to: Off-limb (Spicule) DEM Distribution from SoHO/SUMER Observations Authors: Vanninathan, K.; Madjarska, M. S.; Scullion, E.; Doyle, J. G. Bibcode: 2014SoPh..289.4749V Altcode: 2014SoPh..tmp..127V No abstract at ADS Title: Explosive Events on a Subarcsecond Scale in IRIS Observations: A Case Study Authors: Huang, Zhenghua; Madjarska, Maria S.; Xia, Lidong; Doyle, J. G.; Galsgaard, Klaus; Fu, Hui Bibcode: 2014ApJ...797...88H Altcode: 2014arXiv1409.6425H We present a study of a typical explosive event (EE) at subarcsecond scale witnessed by strong non-Gaussian profiles with blue- and redshifted emission of up to 150 km s-1 seen in the transition region Si IV 1402.8 Å, and the chromospheric Mg II k 2796.4 Å and C II 1334.5 Å observed by the Interface Region Imaging Spectrograph (IRIS) at unprecedented spatial and spectral resolution. For the first time an EE is found to be associated with very small-scale (~120 km wide) plasma ejection followed by retraction in the chromosphere. These small-scale jets originate from a compact bright-point-like structure of ~1.''5 size as seen in the IRIS 1330 Å images. SDO/AIA and SDO/HMI co-observations show that the EE lies in the footpoint of a complex loop-like brightening system. The EE is detected in the higher temperature channels of AIA 171 Å, 193 Å, and 131 Å, suggesting that it reaches a higher temperature of log T = 5.36 ± 0.06 (K). Brightenings observed in the AIA channels with durations 90-120 s are probably caused by the plasma ejections seen in the chromosphere. The wings of the C II line behave in a similar manner to the Si IV'S, indicating close formation temperatures, while the Mg II k wings show additional Doppler-shifted emission. Magnetic convergence or emergence followed by cancellation at a rate of 5 × 1014 Mx s-1 is associated with the EE region. The combined changes of the locations and the flux of different magnetic patches suggest that magnetic reconnection must have taken place. Our results challenge several theories put forward in the past to explain non-Gaussian line profiles, i.e., EEs. Our case study on its own, however, cannot reject these theories; thus, further in-depth studies on the phenomena producing EEs are required. Title: The M4.5V flare star AF Psc as seen in K2 engineering data Authors: Ramsay, Gavin; Doyle, J. Gerry Bibcode: 2014MNRAS.442.2926R Altcode: 2014arXiv1405.7318R We present the light curve of the little studied flare star AF Psc (M4.5V) obtained using engineering data from the K2 mission. Data were obtained in long-cadence mode giving an effective exposure of 29 min and nearly 9 d of coverage. A clear modulation on a period of 1.08 d was seen which is the signature of the stellar rotation period. We identify 14 flares in the light curve, with the most luminous flares apparently coming from the same active region. We compare the flare characteristics of AF Psc to two M4V flare stars studied using Kepler data. The K2 mission will present a unique opportunity to study the rotation and flare properties of late-type dwarf stars with different ages and mass. Title: Hα spectroscopy and multiwavelength imaging of a solar flare caused by filament eruption Authors: Huang, Z.; Madjarska, M. S.; Koleva, K.; Doyle, J. G.; Duchlev, P.; Dechev, M.; Reardon, K. Bibcode: 2014A&A...566A.148H Altcode: 2014arXiv1405.2194H Context. We study a sequence of eruptive events including filament eruption, a GOES C4.3 flare, and a coronal mass ejection.
Aims: We aim to identify the possible trigger(s) and precursor(s) of the filament destabilisation, investigate flare kernel characteristics, flare ribbons/kernels formation and evolution, study the interrelation of the filament-eruption/flare/coronal-mass-ejection phenomena as part of the integral active-region magnetic field configuration, and determine Hα line profile evolution during the eruptive phenomena.
Methods: Multi-instrument observations are analysed including Hα line profiles, speckle images at Hα - 0.8 Å and Hα + 0.8 Å from IBIS at DST/NSO, EUV images and magnetograms from the SDO, coronagraph images from STEREO, and the X-ray flux observations from Fermi and GOES.
Results: We establish that the filament destabilisation and eruption are the main triggers for the flaring activity. A surge-like event with a circular ribbon in one of the filament footpoints is determined as the possible trigger of the filament destabilisation. Plasma draining in this footpoint is identified as the precursor for the filament eruption. A magnetic flux emergence prior to the filament destabilisation followed by a high rate of flux cancellation of 1.34 × 1016 Mx s-1 is found during the flare activity. The flare X-ray lightcurves reveal three phases that are found to be associated with three different ribbons occurring consecutively. A kernel from each ribbon is selected and analysed. The kernel lightcurves and Hα line profiles reveal that the emission increase in the line centre is stronger than that in the line wings. A delay of around 5-6 min is found between the increase in the line centre and the occurrence of red asymmetry. Only red asymmetry is observed in the ribbons during the impulsive phases. Blue asymmetry is only associated with the dynamic filament.

Appendix A and movie associated to Fig. A.4 are available in electronic form at http://www.aanda.org Title: Intensity Enhancement of O VI Ultraviolet Emission Lines in Solar Spectra due to Opacity Authors: Keenan, F. P.; Doyle, J. G.; Madjarska, M. S.; Rose, S. J.; Bowler, L. A.; Britton, J.; McCrink, L.; Mathioudakis, M. Bibcode: 2014ApJ...784L..39K Altcode: 2014arXiv1403.1470K Opacity is a property of many plasmas. It is normally expected that if an emission line in a plasma becomes optically thick, then its intensity ratio to that of another transition that remains optically thin should decrease. However, radiative transfer calculations undertaken both by ourselves and others predict that under certain conditions the intensity ratio of an optically thick to an optically thin line can show an increase over the optically thin value, indicating an enhancement in the former. These conditions include the geometry of the emitting plasma and its orientation to the observer. A similar effect can take place between lines of differing optical depths. While previous observational studies have focused on stellar point sources, here we investigate the spatially resolved solar atmosphere using measurements of the I(1032 Å)/I(1038 Å) intensity ratio of O VI in several regions obtained with the Solar Ultraviolet Measurements of Emitted Radiation instrument on board the Solar and Heliospheric Observatory satellite. We find several I(1032 Å)/I(1038 Å) ratios observed on the disk to be significantly larger than the optically thin value of 2.0, providing the first detection (to our knowledge) of intensity enhancement in the ratio arising from opacity effects in the solar atmosphere. The agreement between observation and theory is excellent and confirms that the O VI emission originates from a slab-like geometry in the solar atmosphere, rather than from cylindrical structures. Title: Excitation of an outflow from the lower solar atmosphere and a co-temporal EUV transient brightening Authors: Nelson, C. J.; Doyle, J. G. Bibcode: 2013A&A...560A..31N Altcode: 2013arXiv1310.8490N
Aims: We analyse an absorption event within the Hα line wings, which has been identified as a surge, and the co-spatial evolution of an EUV brightening, with spatial and temporal scales analogous to a small blinker.
Methods: We conduct a multi-wavelength, multi-instrument analysis using high-cadence, high-resolution data, collected by the Interferometric BIdimensional Spectrometer on the Dunn Solar Telescope, as well as the space-borne Atmospheric Imaging Assembly and Helioseismic and Magnetic Imager instruments on board the Solar Dynamics Observatory.
Results: One large absorption event situated within the plage region trailing the lead sunspot of AR 11579 is identified within the Hα line wings. This event is found to be co-spatially linked to a medium-scale (around 4'' in diameter) brightening within the transition region and corona. This ejection appears to have a parabolic evolution, first forming in the Hα blue wing before fading and reappearing in the Hα red wing, and comprises a number of smaller fibril events. The line-of-sight photospheric magnetic field shows no evidence of cancellation leading to this event.
Conclusions: Our research has identified clear evidence that at least a subset of transient brightening events in the transition region is linked to the influx of cooler plasma from the lower solar atmosphere during large eruptive events, such as surges. These observations agree with previous numerical researches on the nature of blinkers and, therefore, suggest that magnetic reconnection is the driver of the analysed surge events; however, further research is required to confirm this.

A movie attached to Fig. 2 is available in electronic form at http://www.aanda.org Title: Ellerman Bombs—Evidence for Magnetic Reconnection in the Lower Solar Atmosphere Authors: Nelson, C. J.; Shelyag, S.; Mathioudakis, M.; Doyle, J. G.; Madjarska, M. S.; Uitenbroek, H.; Erdélyi, R. Bibcode: 2013ApJ...779..125N Altcode: 2013arXiv1310.7756N The presence of photospheric magnetic reconnection has long been thought to give rise to short and impulsive events, such as Ellerman bombs (EBs) and Type II spicules. In this article, we combine high-resolution, high-cadence observations from the Interferometric BIdimensional Spectrometer and Rapid Oscillations in the Solar Atmosphere instruments at the Dunn Solar Telescope, National Solar Observatory, New Mexico, with co-aligned Solar Dynamics Observatory Atmospheric Imaging Assembly and Hinode Solar Optical Telescope (SOT) data to observe small-scale events situated within an active region. These data are then compared with state-of-the-art numerical simulations of the lower atmosphere made using the MURaM code. It is found that brightenings, in both the observations and the simulations, of the wings of the Hα line profile, interpreted as EBs, are often spatially correlated with increases in the intensity of the Fe I λ6302.5 line core. Bipolar regions inferred from Hinode/SOT magnetic field data show evidence of flux cancellation associated, co-spatially, with these EBs, suggesting that magnetic reconnection could be a driver of these high-energy events. Through the analysis of similar events in the simulated lower atmosphere, we are able to infer that line profiles analogous to the observations occur co-spatially with regions of strong opposite-polarity magnetic flux. These observed events and their simulated counterparts are interpreted as evidence of photospheric magnetic reconnection at scales observable using current observational instrumentation. Title: Short-duration high-amplitude flares detected on the M dwarf star KIC 5474065 Authors: Ramsay, Gavin; Doyle, J. Gerry; Hakala, Pasi; Garcia-Alvarez, David; Brooks, Adam; Barclay, Thomas; Still, Martin Bibcode: 2013MNRAS.434.2451R Altcode: 2013MNRAS.tmp.1831R; 2013arXiv1306.5938R Using data obtained during the RATS-Kepler project, we identified one short-duration flare in a 1 h sequence of ground-based photometry of the dwarf star KIC 5474065. Observations made using Gran Telescopio Canarias show that it is a star with an M4V spectral type. Kepler observations made using 1 min sampling show that KIC 5474065 exhibits large-amplitude (δF/F > 0.4) optical flares which have a duration as short as 10 min. We compare the energy distribution of flares from KIC 5474065 with that of KIC 9726699, which has also been observed using 1-min sampling, and ground-based observations of other M dwarf stars in the literature. We discuss the possible implications these short-duration, relatively low-energy flares would have on the atmosphere of exoplanets orbiting in the habitable zone of these flare stars. Title: Diagnosing transient ionization in dynamic events Authors: Doyle, J. G.; Giunta, A.; Madjarska, M. S.; Summers, H.; O'Mullane, M.; Singh, A. Bibcode: 2013A&A...557L...9D Altcode: 2013arXiv1307.8251D
Aims: The present study aims to provide a diagnostic line ratio that will enable the observer to determine whether a plasma is in a state of transient ionization.
Methods: We use the Atomic Data and Analysis Structure (ADAS) to calculate line contribution functions for two lines, Si iv 1394 Å and O iv 1401 Å, formed in the solar transition region. The generalized collisional-radiative theory is used. It includes all radiative and electron collisional processes, except for photon-induced processes. State-resolved direct ionization and recombination to and from the next ionization stage are also taken into account.
Results: For dynamic bursts with a decay time of a few seconds, the Si iv 1394 Å line can be enhanced by a factor of 2-4 in the first fraction of a second with the peak in the line contribution function occurring initially at a higher electron temperature due to transient ionization compared to ionization equilibrium conditions. On the other hand, the O iv 1401 Å does not show such any enhancement. Thus the ratio of these two lines, which can be observed with the Interface Region Imaging Spectrograph, can be used as a diagnostic of transient ionization.
Conclusions: We show that simultaneous high-cadence observations of two lines formed in the solar transition region may be used as a direct diagnostic of whether the observed plasma is in transient ionization. The ratio of these two lines can change by a factor of four in a few seconds owing to transient ionization alone. Title: Measurement of the Electron's Electric Dipole Moment in Thorium Monoxide Authors: Baron, J.; Demille, D.; Doyle, J.; Gabrielse, G.; Hess, P.; Hutzler, N.; Oleary, B.; Panda, C.; Petrik, E.; Spaun, B. Bibcode: 2013mss..confETF06B Altcode: Some polar diatomic molecules have large effective internal electric fields ({E}_{eff}∼10^{11} V/cm that can be used to make measurements of the electron's electric dipole moment (eEDM) with unprecedented sensitivity. By performing precision spectroscopy on the metastable H ^{3}Δ_{1} state of ThO in a cryogenic buffer gas beam, we have demonstrated a statistical sensitivity to the eEDM of δ d_{e}≈1×10^{-28} e\cdot cm/√{T/{days}}, which is competitive with the current experimental limit, |d_{e}|<1.05×10^{-27}e\cdot cm. The existence of a non-zero eEDM on this level would be evidence for the existence of interactions that violate parity and time-reversal symmetries that are not included in the Standard Model. Many extensions to the Standard Model (in particular supersymmetric theories) predict the eEDM to be very close to the current experimental limit. We present an overview and discuss the characterization of systematic errors in this experiment.

E. R. Meyer and J. L. Bohn, Phys. Rev. A 78, 010502 (2008)

J. Hudson, D. Kara, J. Smallman, B. Sauer, M. Tarbutt, E. Hinds, Nature 473 493 (2011)

This work is supported by the NSF. Title: VizieR Online Data Catalog: Radio survey of ultracool dwarfs (Antonova+, 2013) Authors: Antonova, A.; Hallinan, G.; Doyle, J. G.; Yu, S.; Kuznetsov, A.; Metodieva, Y.; Golden, A.; Cruz, K. L. Bibcode: 2013yCat..35490131A Altcode: 2013yCat..35499131A The observations were conducted with the NRAO Very Large Array in the period 09 August-09 September 2009 using the standard continuum mode with 2x50MHz contiguous bands.

(1 data file). Title: Statistical Analysis of Small Ellerman Bomb Events Authors: Nelson, C. J.; Doyle, J. G.; Erdélyi, R.; Huang, Z.; Madjarska, M. S.; Mathioudakis, M.; Mumford, S. J.; Reardon, K. Bibcode: 2013SoPh..283..307N Altcode: 2013arXiv1301.1351N The properties of Ellerman bombs (EBs), small-scale brightenings in the Hα line wings, have proved difficult to establish because their size is close to the spatial resolution of even the most advanced telescopes. Here, we aim to infer the size and lifetime of EBs using high-resolution data of an emerging active region collected using the Interferometric BIdimensional Spectrometer (IBIS) and Rapid Oscillations of the Solar Atmosphere (ROSA) instruments as well as the Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamics Observatory (SDO). We develop an algorithm to track EBs through their evolution, finding that EBs can often be much smaller (around 0.3″) and shorter-lived (less than one minute) than previous estimates. A correlation between G-band magnetic bright points and EBs is also found. Combining SDO/HMI and G-band data gives a good proxy of the polarity for the vertical magnetic field. It is found that EBs often occur both over regions of opposite polarity flux and strong unipolar fields, possibly hinting at magnetic reconnection as a driver of these events.The energetics of EB events is found to follow a power-law distribution in the range of a nanoflare (1022−25 ergs). Title: Looking for a Pulse: A Search for Rotationally Modulated Radio Emission from the Hot Jupiter, τ Boötis b Authors: Hallinan, G.; Sirothia, S. K.; Antonova, A.; Ishwara-Chandra, C. H.; Bourke, S.; Doyle, J. G.; Hartman, J.; Golden, A. Bibcode: 2013ApJ...762...34H Altcode: 2012arXiv1210.8259H Hot Jupiters have been proposed as a likely population of low-frequency radio sources due to electron cyclotron maser emission of similar nature to that detected from the auroral regions of magnetized solar system planets. Such emission will likely be confined to specific ranges of orbital/rotational phase due to a narrowly beamed radiation pattern. We report on GMRT 150 MHz radio observations of the hot Jupiter τ Boötis b, consisting of 40 hr carefully scheduled to maximize coverage of the planet's 79.5 hr orbital/rotational period in an effort to detect such rotationally modulated emission. The resulting image is the deepest yet published at these frequencies and leads to a 3σ upper limit on the flux density from the planet of 1.2 mJy, two orders of magnitude lower than predictions derived from scaling laws based on solar system planetary radio emission. This represents the most stringent upper limits for both quiescent and rotationally modulated radio emission from a hot Jupiter yet achieved and suggests that either (1) the magnetic dipole moment of τ Boötis b is insufficient to generate the surface field strengths of >50 G required for detection at 150 MHz or (2) Earth lies outside the beaming pattern of the radio emission from the planet. Title: Ellerman bombs: small-scale brightenings in the photosphere Authors: Nelson, C. J.; Doyle, J. G.; Erdélyi, R.; Madjarska, M.; Mumford, S. J. Bibcode: 2013MmSAI..84..436N Altcode: Observations of small-scale events in the solar atmosphere are limited by the spatial and temporal resolutions of the current crop of observational instruments. Both high-cadence and high-resolution observations of the photosphere have shown the continued dynamics to extremely small-scales. Ellerman bombs, brightening events in the wings of the Halpha line profile, are one example of small-scale, short-lived events which have been widely studied due to their fast dynamics in recent years. By combining the Interferometric BIdimensional Spectrometer (IBIS) instrument with the Helioseismic and Magnetic Imager (HMI/SDO), we show the small-scale nature of these events, as well as their link to the background magnetic field. It is found that EBs can be much smaller and shorter-lived than previous estimates have stated, implying the continued dynamics of the solar atmosphere below current observational limits. Title: Volume-limited radio survey of ultracool dwarfs Authors: Antonova, A.; Hallinan, G.; Doyle, J. G.; Yu, S.; Kuznetsov, A.; Metodieva, Y.; Golden, A.; Cruz, K. L. Bibcode: 2013A&A...549A.131A Altcode: 2012arXiv1212.3464A
Aims: We aim to increase the sample of ultracool dwarfs studied in the radio domain to allow a more statistically significant understanding of the physical conditions associated with these magnetically active objects.
Methods: We conducted a volume-limited survey at 4.9 GHz of 32 nearby ultracool dwarfs with spectral types covering the range M7-T8. A statistical analysis was performed on the combined data from the present survey and previous radio observations of ultracool dwarfs.
Results: Whilst no radio emission was detected from any of the targets, significant upper limits were placed on the radio luminosities that are below the luminosities of previously detected ultracool dwarfs. Combining our results with those from the literature gives a detection rate for dwarfs in the spectral range M7-L3.5 of ~9%. In comparison, only one dwarf later than L3.5 is detected in 53 observations. We report the observed detection rate as a function of spectral type and the number distribution of the dwarfs as a function of spectral type and rotation velocity.
Conclusions: The radio observations to date point to a drop in the detection rate toward the ultracool dwarfs. However, the emission levels of detected ultracool dwarfs are comparable to those of earlier type active M dwarfs, which may imply that a mildly relativistic electron beam or a strong magnetic field can exist in ultracool dwarfs. Fast rotation may be a sufficient condition to produce magnetic fields strengths of several hundred Gauss to several kilo Gauss, as suggested by the data for the active ultracool dwarfs with known rotation rates. A possible reason for the non-detection of radio emission from some dwarfs is that maybe the centrifugal acceleration mechanism in these dwarfs is weak (due to a low rotation rate) and thus cannot provide the necessary density and/or energy of accelerated electrons. An alternative explanation could be long-term variability, as is the case for several ultracool dwarfs whose radio emission varies considerably over long periods with emission levels dropping below the detection limit in some instances. Title: Nature of Quiet Sun Oscillations Using Data from the Hinode, TRACE, and SOHO Spacecraft Authors: Gupta, G. R.; Subramanian, S.; Banerjee, D.; Madjarska, M. S.; Doyle, J. G. Bibcode: 2013SoPh..282...67G Altcode: 2012arXiv1209.5252G; 2012SoPh..tmp..247G We study the nature of quiet-Sun oscillations using multi-wavelength observations from TRACE, Hinode, and SOHO. The aim is to investigate the existence of propagating waves in the solar chromosphere and the transition region by analyzing the statistical distribution of power in different locations, e.g. in bright magnetic (network), bright non-magnetic and dark non-magnetic (inter-network) regions, separately. We use Fourier power and phase-difference techniques combined with a wavelet analysis. Two-dimensional Fourier power maps were constructed in the period bands 2 - 4 minutes, 4 - 6 minutes, 6 - 15 minutes, and beyond 15 minutes. We detect the presence of long-period oscillations with periods between 15 and 30 minutes in bright magnetic regions. These oscillations were detected from the chromosphere to the transition region. The Fourier power maps show that short-period powers are mainly concentrated in dark regions whereas long-period powers are concentrated in bright magnetic regions. This is the first report of long-period waves in quiet-Sun network regions. We suggest that the observed propagating oscillations are due to magnetoacoustic waves, which can be important for the heating of the solar atmosphere. Title: Coronal hole boundaries at small scales. IV. SOT view. Magnetic field properties of small-scale transient brightenings in coronal holes Authors: Huang, Z.; Madjarska, M. S.; Doyle, J. G.; Lamb, D. A. Bibcode: 2012A&A...548A..62H Altcode: 2012arXiv1210.2009H Context. We study the magnetic properties of small-scale transients in coronal holes and a few in the quiet Sun identified in X-ray observations and spectroscopic data in two previous papers.
Aims: We aim to investigate the role of small-scale transients in the evolution of the magnetic field in an equatorial coronal hole.
Methods: Two sets of observations of an equatorial coronal hole and another two in quiet-Sun regions were analysed using longitudinal magnetograms taken by the Solar Optical Telescope. An automatic feature tracking program, SWAMIS, was used to identify and track the magnetic features. Each event was then visually analysed in detail.
Results: In both coronal holes and quiet-Sun regions, all brightening events are associated with bipolar regions and are caused by magnetic flux emergence followed by cancellation with the pre-existing and/or newly emerging magnetic flux. In the coronal hole, 19 of 22 events have a single stable polarity which does not change its position in time. In eleven cases this is the dominant polarity. In the coronal hole, the magnetic features with the largest flux are those of the dominant polarity, while the opposite polarity is distributed in weaker features. The number of magnetic features of the dominant polarity is four times grater than the opposite polarity. The supergranulation configuration appears to preserve its general shape during approximately nine hours of observations although the large concentrations (the dominant polarity) in the network did evolve and/or were slightly displaced, and their strength either increased or decreased. The emission fluctuations/radiance oscillations seen in the X-ray bright points are associated with recurring magnetic cancellation in the footpoints. Unique observations of an X-ray jet reveal similar magnetic behaviour in the footpoints, i.e. cancellation of the opposite polarity magnetic flux. We find that the magnetic flux cancellation rate during the jet is much higher than in bright points. Not all magnetic cancellations result in an X-ray enhancement, suggesting that there is a threshold of the amount of magnetic flux involved in a cancellation above which brightening would occur at X-ray temperatures.
Conclusions: Our study demonstrates that the magnetic flux in coronal holes is continuously processed through magnetic reconnection which is responsible for the formation of numerous small-scale transient events. The open magnetic flux forming the coronal-hole phenomenon is largely involved in these transient features. The question of whether this open flux is transported as a result of the formation and evolution of these transient events, however, still remains open.

Three movies and Appendix A are available in electronic form at http://www.aanda.org Title: Off-limb (Spicule) DEM Distribution from SoHO/SUMER Observations Authors: Vanninathan, K.; Madjarska, M. S.; Scullion, E.; Doyle, J. G. Bibcode: 2012SoPh..280..425V Altcode: 2012SoPh..tmp...88V; 2012arXiv1203.2073V In the present work we derive a Differential Emission Measure (DEM) distribution from a region dominated by spicules. We use spectral data from the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) spectrometer on-board the Solar Heliospheric Observatory (SoHO) covering the entire SUMER wavelength range taken off-limb in the Northern polar coronal hole to construct this DEM distribution using the CHIANTI atomic database. This distribution is then used to study the thermal properties of the emission contributing to the 171 Å channel in the Atmospheric Imaging Assembly (AIA) on-board the Solar Dynamics Observatory (SDO). From our off-limb DEM we found that the radiance in the AIA 171 Å channel is dominated by emission from the Fe IX 171.07 Å line and has sparingly little contribution from other lines. The product of the Fe IX 171.07 Å line contribution function with the off-limb DEM was found to have a maximum at logTmax (K)=5.8 indicating that during spicule observations the emission in this line comes from plasma at transition region temperatures rather than coronal. For comparison, the same product with a quiet Sun and prominence DEM were found to have a maximum at logTmax (K)=5.9 and logTmax (K)=5.7, respectively. We point out that the interpretation of data obtained from the AIA 171 Å filter should be done with foreknowledge of the thermal nature of the observed phenomenon. For example, with an off-limb DEM we find that only 3.6 % of the plasma is above a million degrees, whereas using a quiet Sun DEM, this contribution rises to 15 %. Title: Coronal hole boundaries evolution at small scales. III. EIS and SUMER views Authors: Madjarska, M. S.; Huang, Z.; Doyle, J. G.; Subramanian, S. Bibcode: 2012A&A...545A..67M Altcode: 2012arXiv1207.1281M Context. We report on the plasma properties of small-scale transient events identified in the quiet Sun, coronal holes and their boundaries.
Aims: We aim at deriving the physical characteristics of events that were identified as small-scale transient brightenings in XRT images.
Methods: We used spectroscopic co-observations from SUMER/SoHO and EIS/Hinode combined with high-cadence imaging data from XRT/Hinode. We measured Doppler shifts using single and multiple Gaussian fits of the transition region and coronal lines as well as electron densities and temperatures. We combined co-temporal imaging and spectroscopy to separate brightening expansions from plasma flows.
Results: The transient brightening events in coronal holes and their boundaries were found to be very dynamical, producing high-density outflows at high speeds. Most of these events represent X-ray jets from pre-existing or newly emerging coronal bright points at X-ray temperatures. The average electron density of the jets is log10 Ne ≈ 8.76 cm-3 while in the flaring site it is log10 Ne ≈ 9.51 cm-3. The jet temperatures reach a maximum of 2.5 MK but in the majority of the cases the temperatures do not exceed 1.6 MK. The footpoints of jets have maximum temperatures of 2.5 MK, though in a single event scanned a minute after the flaring the measured temperature was 12 MK. The jets are produced by multiple microflaring in the transition region and corona. Chromospheric emission was only detected in their footpoints and was only associated with downflows. The Doppler shift measurements in the quiet Sun transient brightenings confirmed that these events do not produce jet-like phenomena. The plasma flows in these phenomena remain trapped in closed loops.
Conclusions: We can conclude that the dynamic day-by-day and even hour-by-hour small-scale evolution of coronal hole boundaries reported in Paper I is indeed related to coronal bright points. The XRT observations reported in Paper II revealed that these changes are associated with the dynamic evolution of coronal bright points producing multiple jets during their lifetime until their full disappearance. We demonstrate here through spectroscopic EIS and SUMER co-observations combined with high-cadence imaging information that the co-existence of open and closed magnetic fields results in multiple energy depositions, which propel high-density plasma along open magnetic field lines. We conclude from the physical characteristics obtained in this study that X-ray jets are important candidates for the source of the slow solar wind. This, however, does not exclude the possibility that these jets are also the microstreams observed in the fast solar wind, as recently suggested.

Figures A.1, A.2, and movies are available in electronic form at http://www.aanda.org Title: Solar Fine-Scale Structures. I. Spicules and Other Small-Scale, Jet-Like Events at the Chromospheric Level: Observations and Physical Parameters Authors: Tsiropoula, G.; Tziotziou, K.; Kontogiannis, I.; Madjarska, M. S.; Doyle, J. G.; Suematsu, Y. Bibcode: 2012SSRv..169..181T Altcode: 2012SSRv..tmp...65T; 2012arXiv1207.3956T Over the last two decades the uninterrupted, high resolution observations of the Sun, from the excellent range of telescopes aboard many spacecraft complemented with observations from sophisticated ground-based telescopes have opened up a new world producing significantly more complete information on the physical conditions of the solar atmosphere than before. The interface between the lower solar atmosphere where energy is generated by subsurface convection and the corona comprises the chromosphere, which is dominated by jet-like, dynamic structures, called mottles when found in quiet regions, fibrils when found in active regions and spicules when observed at the solar limb. Recently, space observations with Hinode have led to the suggestion that there should exist two different types of spicules called Type I and Type II which have different properties. Ground-based observations in the Ca ii H and K filtergrams reveal the existence of long, thin emission features called straws in observations close to the limb, and a class of short-lived events called rapid blue-shifted excursions characterized by large Doppler shifts that appear only in the blue wing of the Ca ii infrared line. It has been suggested that the key to understanding how the solar plasma is accelerated and heated may well be found in the studies of these jet-like, dynamic events. However, while these structures are observed and studied for more than 130 years in the visible, but also in the UV and EUV emission lines and continua, there are still many questions to be answered. Thus, despite their importance and a multitude of observations performed and theoretical models proposed, questions regarding their origin, how they are formed, their physical parameters, their association with the underlying photospheric magnetic field, how they appear in the different spectral lines, and the interrelationship between structures observed in quiet and active regions on the disk and at the limb, as well as their role in global processes has not yet received definitive answers. In addition, how they affect the coronal heating and solar wind need to be further explored. In this review we present observations and physical properties of small-scale jet-like chromospheric events observed in active and quiet regions, on the disk and at the limb and discuss their interrelationship. Title: The Diagnostic Potential of Transition Region Lines Undergoing Transient Ionization in Dynamic Events Authors: Doyle, J. G.; Giunta, A.; Singh, A.; Madjarska, M. S.; Summers, H.; Kellett, B. J.; O'Mullane, M. Bibcode: 2012SoPh..280..111D Altcode: 2012SoPh..tmp..118D; 2012arXiv1204.6598D We discuss the diagnostic potential of high cadence UV spectral data when transient ionization is considered. For this we use high cadence UV spectra taken during the impulsive phase of a solar flare (observed with instruments on-board the Solar Maximum Mission) which showed excellent correspondence with hard X-ray pulses. The ionization fraction of the transition region ion O V and, in particular, the contribution function for the O V 1371 Å line are computed within the Atomic Data and Analysis Structure, which is a collection of fundamental and derived atomic data and codes to manipulate them. Due to transient ionization, the O V 1371 Å line is enhanced in the first fraction of a second with the peak in the line contribution function occurring initially at a higher electron temperature than in ionization equilibrium. The rise time and enhancement factor depend mostly on the electron density. The fractional increase in the O V 1371 Å emissivity due to transient ionization can reach a factor of two-four and can explain the fast response in the line flux of transition regions ions during the impulsive phase of flares solely as a result of transient ionization. This technique can be used to diagnose the electron temperature and density of solar flares observed with the forthcoming Interface Region Imaging Spectrograph. Title: Electron-beam-induced Radio Emission from Ultracool Dwarfs Authors: Yu, S.; Doyle, J. G.; Kuznetsov, A.; Hallinan, G.; Antonova, A.; MacKinnon, A. L.; Golden, A. Bibcode: 2012ApJ...752...60Y Altcode: 2012arXiv1204.2261Y We present the numerical simulations for an electron-beam-driven and loss-cone-driven electron-cyclotron maser (ECM) with different plasma parameters and different magnetic field strengths for a relatively small region and short timescale in an attempt to interpret the recent discovered intense radio emission from ultracool dwarfs. We find that a large amount of electromagnetic (EM) field energy can be effectively released from the beam-driven ECM, which rapidly heats the surrounding plasma. A rapidly developed high-energy tail of electrons in velocity space (resulting from the heating process of the ECM) may produce the radio continuum depending on the initial strength of the external magnetic field and the electron beam current. Both significant linear polarization and circular polarization of EM waves can be obtained from the simulations. The spectral energy distributions of the simulated radio waves show that harmonics may appear from 10 to 70νpe (νpe is the electron plasma frequency) in the non-relativistic case and from 10 to 600νpe in the relativistic case, which makes it difficult to find the fundamental cyclotron frequency in the observed radio frequencies. A wide frequency band should therefore be covered by future radio observations. Title: Coronal hole boundaries and the slow solar wind from Hinode/EIS/XRT/SOT and SUMER/SoHO Authors: Madjarska, M. S.; Huang, Zh.; Doyle, J. G.; Subramanian, S. Bibcode: 2012decs.confE..16M Altcode: We present a statistical study on outflows at coronal hole boundaries and inside coronal holes and discuss their role in the slow solar wind formation in the low solar corona. The outflows are studied in XRT/Hinode image data taken with the Al_poly filter using an automatic identification method. A spectroscopic analysis is made using EIS and SUMER data of spectral lines with formation temperatures in the range from 10 000 K to 12 MK. The derived plasma parameters of about 60 phenomena will be reported. The longitudinal magnetic field data for each feature falling in the SOT/Hinode field-of-view (more than 25) are studied using a magnetic feature tracking procedure and a visual inspection. The mechanism of the outflow formation and acceleration will be discussed. 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: Comparative Analysis of Two Formation Scenarios of Bursty Radio Emission from Ultracool Dwarfs Authors: Kuznetsov, A. A.; Doyle, J. G.; Yu, S.; Hallinan, G.; Antonova, A.; Golden, A. Bibcode: 2012ApJ...746...99K Altcode: 2011arXiv1111.7019K Recently, a number of ultracool dwarfs have been found to produce periodic radio bursts with high brightness temperature and polarization degree; the emission properties are similar to the auroral radio emissions of the magnetized planets of the solar system. We simulate the dynamic spectra of radio emission from ultracool dwarfs. The emission is assumed to be generated due to the electron-cyclotron maser instability. We consider two source models: the emission caused by interaction with a satellite and the emission from a narrow sector of active longitudes; the stellar magnetic field is modeled by a tilted dipole. We have found that for the dwarf TVLM 513-46546, the model of the satellite-induced emission is inconsistent with observations. On the other hand, the model of emission from an active sector is able to reproduce qualitatively the main features of the radio light curves of this dwarf; the magnetic dipole seems to be highly tilted (by about 60°) with respect to the rotation axis. Title: The Response of A Three-dimensional Solar Atmosphere to Wave-driven Jets Authors: Scullion, E.; Erdélyi, R.; Fedun, V.; Doyle, J. G. Bibcode: 2011ApJ...743...14S Altcode: Global oscillations from the solar interior are, mainly, pressure-driven (p-modes) oscillations with a peak power of a five-minute period. These oscillations are considered to manifest in many phenomena in the lower solar atmosphere, most notably, in spicules. These small-scale jets may provide the key to understanding the powering mechanisms of the transition region (TR) and lower corona. Here, we simulate the formation of wave-driven (type-I) spicule phenomena in three dimensions and the transmission of acoustic waves from the lower chromosphere and into the corona. The outer atmosphere oscillates in response to the jet formation, and in turn, we reveal the formation of a circular seismic surface wave, which we name as a Transition Region Quake (TRQ). The TRQ forms as a consequence of an upward propelling spicular wave train that repeatedly punctures and energizes the TR. The steep density gradient enables the TRQ to develop and radially fan outward from the location where the spicular plasma column impinges the TR. We suggest the TRQ formation as a formidable mechanism in continuously sustaining part of the energy budget of the TR. We present a supporting numerical model which allow us to determine the level of energy dumping at the TR by upward-propagating p-modes. Upon applying a wavelet analysis on our simulations we identify the presence of a chromospheric cavity which resonates with the jet propagation and leaves behind an oscillatory wake with a distinctive periodicity. Through our numerical analysis we also discover type-I spicule turbulence leading to a convection-based motion in the low corona. Title: Overview of the Southern Andes - ANtarctic GRavity wave InitiAtive (SAANGRIA) Authors: Doyle, J.; Fritts, D. C.; Smith, R. B.; Eckermann, S. D.; Taylor, M. J. Bibcode: 2011AGUFM.A52B..05D Altcode: An overview of the Southern Andes - ANtarctic GRavity wave InitiAtive (SAANGRIA) will be presented, which is a comprehensive, airborne and ground-based measurement and modeling program focused on providing a new understanding of gravity wave (GW) dynamics and impacts from the troposphere through the mesosphere and lower thermosphere (MLT). This program will employ the new NSF/NCAR GV (NGV) research aircraft from a base near the southern tip of South America in a 10-week field measurement campaign from late June to early September 2013. The region, spanning the southern Andes, Drake Passage, and Antarctic Peninsula, is chosen since all the relevant GW sources occur strongly here and satellite observations suggest this region in winter contains the largest GW amplitudes on the planet. Given large-amplitude GWs that propagate routinely into the MLT, the region offers an ideal natural laboratory for studying these important GW dynamics and effects impacting weather and climate over a much deeper atmospheric layer than previous campaigns have attempted (0-100 km altitude). An overview will be provided of the airborne and ground based instrumentation and the suite of GW-focused forecasting and modeling tools that will be used to guide the NGV. Title: Magnetic reconnection resulting from flux emergence: implications for jet formation in the lower solar atmosphere? Authors: Ding, J. Y.; Madjarska, M. S.; Doyle, J. G.; Lu, Q. M.; Vanninathan, K.; Huang, Z. Bibcode: 2011A&A...535A..95D Altcode: 2011arXiv1109.5606D
Aims: We aim at investigating the formation of jet-like features in the lower solar atmosphere, e.g. chromosphere and transition region, as a result of magnetic reconnection.
Methods: Magnetic reconnection as occurring at chromospheric and transition regions densities and triggered by magnetic flux emergence is studied using a 2.5D MHD code. The initial atmosphere is static and isothermal, with a temperature of 2 × 104 K. The initial magnetic field is uniform and vertical. Two physical environments with different magnetic field strength (25 G and 50 G) are presented. In each case, two sub-cases are discussed, where the environments have different initial mass density.
Results: In the case where we have a weaker magnetic field (25 G) and higher plasma density (Ne = 2 × 1011 cm-3), valid for the typical quiet Sun chromosphere, a plasma jet would be observed with a temperature of 2-3 × 104 K and a velocity as high as 40 kms-1. The opposite case of a medium with a lower electron density (Ne = 2 × 1010 cm-3), i.e. more typical for the transition region, and a stronger magnetic field of 50 G, up-flows with line-of-sight velocities as high as ~90 kms-1 and temperatures of 6 × 105 K, i.e. upper transition region - low coronal temperatures, are produced. Only in the latter case, the low corona Fe ix 171 Å shows a response in the jet which is comparable to the O v increase.
Conclusions: The results show that magnetic reconnection can be an efficient mechanism to drive plasma outflows in the chromosphere and transition region. The model can reproduce characteristics, such as temperature and velocity for a range of jet features like a fibril, a spicule, a hot X-ray jet or a transition region jet by changing either the magnetic field strength or the electron density, i.e. where in the atmosphere the reconnection occurs. Title: Simulation of the rotation-modulated and satellite-induced radio emissions from brown dwarfs Authors: Kuznetsov, A. A.; Doyle, J. G.; Yu, S. Bibcode: 2011epsc.conf...90K Altcode: 2011DPS....43...90K We simulate the dynamic spectra of the radio emission from a brown dwarf. The emission is produced due to the electron-cyclotron maser instability. Two source models are considered: the emission caused by interaction with a satellite and the emission from a sector of active longitudes. We have found that for the dwarf TVLM513 the model of an active sector (with a highly tilted magnetic dipole) fits the observations better. Title: Starspots on the fastest rotators in the β Pictoris moving group Authors: García-Alvarez, D.; Lanza, A. F.; Messina, S.; Drake, J. J.; van Wyk, F.; Shobbrook, R. R.; Butler, C. J.; Kilkenny, D.; Doyle, J. G.; Kashyap, V. L. Bibcode: 2011A&A...533A..30G Altcode: 2011arXiv1107.5688G
Aims: We carried out high-resolution spectroscopy and BV(I)C photometric monitoring of the two fastest late-type rotators in the nearby β Pictoris moving group, HD 199143 (F7V) and CD-64°1208 (K7V). The motivation for this work is to investigate the rotation periods and photospheric spot patterns of these very young stars, with a longer term view to probing the evolution of rotation and magnetic activity during the early phases of main-sequence evolution. We also aim to derive information on key physical parameters, such as rotational velocity and rotation period.
Methods: We applied maximum entropy (ME) and Tikhonov regularizing (TR) criteria to derive the surface spot map distributions of the optical modulation observed in HD 199143 (F7 V) and CD-64°1208 (K7 V). We also used cross-correlation techniques to determine stellar parameters such as radial velocities and rotational velocities. Lomb-Scargle periodograms were used to obtain the rotational periods from differential magnitude time series.
Results: We find periods and inclinations of 0.356 days and 21.5 deg for HD 199143, and 0.355 days and 50.1 deg for CD-64°1208. The spot maps of HD 199143 obtained from the ME and TR methods are very similar, although the latter gives a smoother distribution of the filling factor. Maps obtained at two different epochs three weeks apart show a remarkable increase in spot coverage amounting to ~7% of the surface of the photosphere over a time period of only ~20 days. The spot maps of CD-64°1208 from the two methods show good longitudinal agreement, whereas the latitude range of the spots is extended to cover the whole visible hemisphere in the TR map. The distributions obtained from the first light curve of HD 199143 show the presence of an extended and asymmetric active longitude with the maximum filling factor at longitude ~325°. A secondary active longitude is present at ~100°. The spotted area distributions on CD-64°1208 show two active longitudes separated by about 180°, which is not unusual on such very active stars.

Figures 7-10 are available in electronic form at http://www.aanda.org Title: Can coronal hole spicules reach coronal temperatures? Authors: Madjarska, M. S.; Vanninathan, K.; Doyle, J. G. Bibcode: 2011A&A...532L...1M Altcode: 2011arXiv1105.1296M
Aims: The present study aims to provide observational evidence of whether coronal hole spicules reach coronal temperatures.
Methods: We combine multi-instrument co-observations obtained with the SUMER/SoHO and with the EIS/SOT/XRT/Hinode.
Results: The analysed three large spicules were found to be comprised of numerous thin spicules that rise, rotate, and descend simultaneously forming a bush-like feature. Their rotation resembles the untwisting of a large flux rope. They show velocities ranging from 50 to 250 kms-1. We clearly associated the red- and blue-shifted emissions in transition region lines not only with rotating but also with rising and descending plasmas. Our main result is that these spicules although very large and dynamic, are not present in the spectral lines formed at temperatures above 300 000 K.
Conclusions: In this paper we present the analysis of three Ca ii H large spicules that are composed of numerous dynamic thin spicules but appear as macrospicules in lower resolution EUV images. We found no coronal counterpart of these and smaller spicules. We believe that the identification of phenomena that have very different origins as macrospicules is due to the interpretation of the transition region emission, and especially the He ii emission, wherein both chromospheric large spicules and coronal X-ray jets are present. We suggest that the recent observation of spicules in the coronal AIA/SDO 171 Å and 211 Å channels probably comes from the existence of transition region emission there.

Movie is available in electronic form at http://www.aanda.org Title: Mapping radio emitting-region on low-mass stars and brown dwarfs Authors: Yu, S.; Doyle, J. G.; Hallinan, G.; MacKinnon, A. L. Bibcode: 2011EPJWC..1606013Y Altcode: Strong magnetic activity in ultracool dwarfs (UCDs, spectral classes later than M7) have emerged from a number of radio observations, including the periodic beams. The highly (up to 100%) circularly polarized nature of the emission point to an effective amplification mechanism of the high-frequency electromagnetic waves - the electron cyclotron maser (ECM) instability. Several anisotropic velocity distibution models of electrons, including the horseshoe distribution, ring shell distribution and the loss-cone distribution, are able to generate the ECM instability. A magnetic-field-aligned electric potential would play an significant role in the ECM process. We are developing a theoretical model in order to simulate ECM and apply this model to map the radio-emitting region on low-mass stars and brown dwarfs. Title: Water vapor intrusions into the High Arctic during winter Authors: Doyle, J. G.; Lesins, G.; Thackray, C. P.; Perro, C.; Nott, G. J.; Duck, T. J.; Damoah, R.; Drummond, J. R. Bibcode: 2011GeoRL..3812806D Altcode: The meridional transport of water vapor into the High Arctic, accompanied by dry enthalpy and clouds, impacts the surface radiative forcing. The evolution of one such moist intrusion over 9-11 February 2010 is presented. The event is analyzed using a unique blend of measurements including a new pan-Arctic retrieval of column water vapor from the Microwave Humidity Sounders, water vapor profiles from a Raman lidar and a ground-based microwave radiometer at the Polar Environment Atmospheric Research Laboratory (PEARL), in Eureka (80°N, 86°W), on Ellesmere Island in the Canadian High Arctic. A radiation model reveals the intrusion is associated with a 17 W m-2 average increase in downwelling longwave irradiance. Optically thin clouds, as observed by the lidar, contribute a further 20 W m-2 to the downwelling longwave irradiance at their peak. Intrusion events are shown to be a regular occurrence in the Arctic winter with implications for the understanding of the mechanisms driving Arctic Amplification. Title: Modelling the radio pulses of an ultracool dwarf Authors: Yu, S.; Hallinan, G.; Doyle, J. G.; MacKinnon, A. L.; Antonova, A.; Kuznetsov, A.; Golden, A.; Zhang, Z. H. Bibcode: 2011A&A...525A..39Y Altcode: 2010arXiv1009.1548Y Context. Recently, unanticipated magnetic activity in ultracool dwarfs (UCDs, spectral classes later than M7) has emerged from a number of radio observations. The highly (up to 100%) circularly polarized nature and high brightness temperature of the emission have been interpreted as requiring an effective amplification mechanism of the high-frequency electromagnetic waves - the electron cyclotron maser instability (ECMI).
Aims: We aim to understand the magnetic topology and the properties of the radio emitting region and associated plasmas in these ultracool dwarfs, interpreting the origin of radio pulses and their radiation mechanism.
Methods: An active region model was built, based on the rotation of the UCD and the ECMI mechanism.
Results: The high degree of variability in the brightness and the diverse profile of pulses can be interpreted in terms of a large-scale hot active region with extended magnetic structure existing in the magnetosphere of TVLM 513-46546. We suggest the time profile of the radio light curve is in the form of power law in the model. Combining the analysis of the data and our simulation, we can determine the loss-cone electrons have a density in the range of 1.25 × 105 -5 × 105 cm-3 and temperature between 107 and 5 × 107 K. The active region has a size < 1RJup, while the pulses produced by the ECMI mechanism are from a much more compact region (e.g. ~0.007 RJup). A surface magnetic field strength of ≈7000 G is predicted.
Conclusions: The active region model is applied to the radio emission from TVLM 513-46546, in which the ECMI mechanism is responsible for the radio bursts from the magnetic tubes and the rotation of the dwarf can modulate the integral of flux with respect to time. The radio emitting region consists of complicated substructures. With this model, we can determine the nature (e.g. size, temperature, density) of the radio emitting region and plasma. The magnetic topology can also be constrained. We compare our predicted X-ray flux with Chandra X-ray observation of TVLM 513-46546. Although the X-ray detection is only marginally significant, our predicted flux is significantly lower than the observed flux. Further multi-wavelength observations will help us better understand the magnetic field structure and plasma behavior on the ultracool dwarf. Title: Phase connecting multi-epoch radio data for the ultracool dwarf TVLM 513-46546 Authors: Doyle, J. G.; Antonova, A.; Marsh, M. S.; Hallinan, G.; Yu, S.; Golden, A. Bibcode: 2010A&A...524A..15D Altcode: Context. Radio data obtained for the ultracool dwarf TVLM 513-46546 has indicated a rotation period of ≈1.96 h via regular radio pulses, but how stable is this period. This has major implications regarding the stability of the magnetic field structures responsible for the radio emission from the ultracool dwarf.
Aims: The aim of the present work is to investigate the stability of this rotation period using two datasets taken ≈40 days apart, some 12 months after the first report of periodical pulses in the radio data.
Methods: Here we use a Bayesian analysis method which is a statistical procedure that endeavours to estimate the parameters of an underlying model probability distribution based on the observed data.
Results: Periodical pulses are detected in datasets taken in April and June 2007, with the pulses being confined to a narrow range in the rotation period. This is in contradiction to a previous report of only aperiodic activity in the April 2007 dataset, while in fact both datasets have a periodic signal with a false alarm probability ≪ 10-12. These two datasets are then used to derive a more accurate period (previously determined to be 1.96 h) of 1.96733 ± 0.00002 h.
Conclusions: The similarly in the burst structure in datasets taken several weeks apart point towards the stability of an electric field structure which is somehow generated and sustained within the magnetosphere of the ultracool dwarf. The derived period of 1.96733 h is consistent with the period derived via radio and optical data taken some 12 months prior to the present observations and implies the near phase constancy of the pulsed emission. This suggest the presence of stable large-scale magnetic fields on timescales of more than 1 year. The characteristics of the pulses suggest that they are produced by the electron cyclotron maser (ECM) instability. Title: A permanently-acting NEA damage mitigation technique via the Yarkovsky effect Authors: Hyland, D. C.; Altwaijry, H. A.; Ge, S.; Margulieux, R.; Doyle, J.; Sandberg, J.; Young, B.; Bai, X.; Lopez, J.; Satak, N. Bibcode: 2010CosRe..48..430H Altcode: In the later stages of a combined mission of exploration and damage mitigation of a hazardous Near Earth Asteroid (NEA), sufficiently detailed tracking, orbit prediction, mass distribution, and physical properties data have been accumulated. It may be desirable to implement a “slow push” damage mitigation technique that is capable of altering the NEA orbit continuously and permanently. This possibility was suggested in a companion paper that outlined an archetypal exploration/mitigation mission to the NEA 99942 Apophis, which is achieved using a novel albedo change approach. The details and apparatus used in the albedo modification technique are described in the paper. We describe the design details and the constraints on particle size (to prevent electrostatic levitation and escape) and on the dispensing speed (to achieve the desired coverage zone and prevent particles from orbiting or escaping). Title: A mission template for exploration and damage mitigation of potential hazard of Near Earth Asteroids Authors: Hyland, D. C.; Altwaijry, H. A.; Margulieux, R.; Doyle, J.; Sandberg, J.; Young, B.; Satak, N.; Lopez, J.; Ge, S.; Bai, X. Bibcode: 2010CosRe..48..437H Altcode: The Apophis Exploratory and Mitigation Platform (AEMP) concept was developed as a prototype mission to explore and potentially deflect the Near Earth Asteroid (NEA) 99942 Apophis. Deflection of the asteroid from the potential 2036 impact will be achieved using a gravity tractor technique, while a permanent deflection, eliminating future threats, will be imparted using a novel albedo manipulation technique. This mission will serve as an archetypal template for future missions to small NEAs and could be adapted to mitigate the threat of collision with other potential Earth-crossing objects. Title: Looking for a Radio Pulse from Hot Jupiters Authors: Hallinan, G.; Sirothia, S.; Chandra, I.; Doyle, J. G.; Antonova, A.; Golden, A. Bibcode: 2010epsc.conf..413H Altcode: No abstract at ADS Title: Investigating Magnetic Field Strengths and Topologies for Pulsing Ultracool Dwarfs: The M8.5 Dwarf TVLM 513-46546 Authors: Antonova, A.; Hallinan, G.; Doyle, J. G.; Golden, A. Bibcode: 2010POBeo..90..117A Altcode: The detection of both quiescent and flaring nonthermal radio emission from a number of late M-, L-type dwarfs indicates the presence of magnetic activity in the ultracool dwarf domain. What is more, four of those dwarfs show periodic, highly circularly polarized pulsing signatures consistent with electron cyclotron maser emission. The pulsing emission can be used as a powerful diagnostic of magnetic field strengths and topologies of very low-mass stars and brown dwarfs. Here we present our results from multi-epoch VLA observations of the M8.5 dwarf TVLM 513-46546 which provide evidence of the presence of stable large-scale magnetic fields with kilogaus strengths, as well as broadband dynamic spectra of the individual pulses in the emission of the dwarf obtained using the Arecibo Observatory. We discuss how such observations can be used for mapping the radio coronae of UCDs. Title: Coronal hole boundaries evolution at small scales. II. XRT view. Can small-scale outflows at CHBs be a source of the slow solar wind Authors: Subramanian, S.; Madjarska, M. S.; Doyle, J. G. Bibcode: 2010A&A...516A..50S Altcode: 2010arXiv1002.1675S
Aims: We aim to further explore the small-scale evolution of coronal hole boundaries using X-ray high-resolution and high-cadence images. We intend to determine the fine structure and dynamics of the events causing changes of coronal hole boundaries and to explore the possibility that these events are the source of the slow solar wind.
Methods: We developed an automated procedure for the identification of transient brightenings in images from the X-ray telescope on-board Hinode taken with an Al Poly filter in the equatorial coronal holes, polar coronal holes, and the quiet Sun with and without transient coronal holes.
Results: We found that in comparison to the quiet Sun, the boundaries of coronal holes are abundant with brightening events including areas inside the coronal holes where closed magnetic field structures are present. The visual analysis of these brightenings revealed that around 70% of them in equatorial, polar and transient coronal holes and their boundaries show expanding loop structures and/or collimated outflows. In the quiet Sun only 30% of the brightenings show flows with most of them appearing to be contained in the solar corona by closed magnetic field lines. This strongly suggests that magnetic reconnection of co-spatial open and closed magnetic field lines creates the necessary conditions for plasma outflows to large distances. The ejected plasma always originates from pre-existing or newly emerging (at X-ray temperatures) bright points.
Conclusions: The present study confirms our findings that the evolution of loop structures known as coronal bright points is associated with the small-scale changes of coronal hole boundaries. The loop structures show an expansion and eruption with the trapped plasma consequently escaping along the “quasi” open magnetic field lines. These ejections appear to be triggered by magnetic reconnection, e.g. the so-called interchange reconnection between the closed magnetic field lines (BPs) and the open magnetic field lines of the coronal holes. We suggest that these plasma outflows are possibly one of the sources of the slow solar wind.

4 movies are only available in electronic form at http://www.aanda.org Title: Chromospheric magnetic reconnection caused by photospheric flux emergence: implications for jet-like events formation Authors: Ding, J. Y.; Madjarska, M. S.; Doyle, J. G.; Lu, Q. M. Bibcode: 2010A&A...510A.111D Altcode: 2009arXiv0912.4449D Magnetic reconnection in the low atmosphere, e.g. chromosphere, is investigated in various physical environments. Its implications for the origination of explosive events (small-scale jets) are discussed. A 2.5-dimensional resistive magnetohydrodynamic (MHD) model in Cartesian coordinates is used. It is found that the temperature and velocity of the outflow jets as a result of magnetic reconnection are strongly dependent on the physical environments, e.g. the magnitude of the magnetic field strength and the plasma density. If the magnetic field strength is weak and the density is high, the temperature of the jets is very low (~104 K) as well as its velocity (~40 km s-1). However, if environments with stronger magnetic field strength (40 G) and smaller density (electron density N_e=2× 1010 cm-3) are considered, the outflow jets reach higher temperatures of up to 6× 10^5 K and a line-of-sight velocity of up to 130 km s-1 which is comparable with the observational values of jet-like events. Title: A spectroscopic analysis of macrospicules . Authors: Scullion, E.; Doyle, J. G.; Erdélyi, R. Bibcode: 2010MmSAI..81..737S Altcode: We explore the nature of macrospicule structures, both off-limb and on-disk, and their possible relation to explosive events in the mid-solar atmosphere. We use high resolution spectroscopy obtained with the SoHO/SUMER instrument. We present a highly resolved spectroscopic analysis and line parameter study of time series data for such jets. We focus on two interesting off-limb events which rapidly propagate between the mid-transition region N IV 765 Å line formation (140 000 K) and the lower corona Ne VIII 770 Å line formation (630 000 K). In one example, a strong jet-like event is associated with a cool feature not present in the Ne VIII 770 Å line radiance or Doppler velocity maps. Our data reveals fast, repetitive plasma outflows with blue-shift velocities of ≈ 145 km s-1 in the lower solar atmosphere. The data suggests a strong role for smaller jets (spicules), as a precursor to macrospicule formation, which may have a common origin with explosive events. Title: Statistical Detection of Propagating Waves in a Polar Coronal Hole Authors: Gupta, G. R.; O'Shea, E.; Banerjee, D.; Popescu, M.; Doyle, J. G. Bibcode: 2010ASSP...19..433G Altcode: 2009arXiv0902.4333G; 2010mcia.conf..433G Waves are important in the heating of the solar corona and the acceleration of the solar wind. We have examined a long spectral time series sampling a southern coronal hole, observed on the 25 February 1997 using the SUMER spectrometer onboard SoHO. The observations used the spectra lines NIV 765Å, formed in the transition region, and Ne VIII 770Å, formed in the low corona. The spectra indicate the presence of compressional waves with periods of about 18 min, and also significant power at shorter periods. Using Fourier techniques, we measured the phase delays between the intensity as well as the velocity oscillations in the two lines as a function of frequency. From these measurements we derive the travel time of the propagating oscillations and so the propagation speeds of the waves producing the oscillations. As the measured propagation speeds are subsonic, we conclude that the observed waves are slow magneto-acoustic ones. Title: Deriving the coronal hole electron temperature: electron density dependent ionization / recombination considerations Authors: Doyle, John Gerard; Chapman, Steven; Bryans, Paul; Pérez-Suárez, David; Singh, Avninda; Summers, Hugh; Savin, Daniel Wolf Bibcode: 2010RAA....10...91D Altcode: 2009arXiv0909.3195D Comparison of appropriate theoretically derived line ratios with observational data can yield estimates of a plasma's physical parameters, such as electron density or temperature. The usual practice in the calculation of the line ratio is the assumption of excitation by electrons/protons followed by radiative decay. Furthermore, it is normal to use the so-called coronal approximation, i.e. one only considers ionization and recombination to and from the ground-state. A more accurate treatment is to include ionization/recombination to and from metastable levels. Here, we apply this to two lines from adjacent ionization stages, Mg IX 368 Å and Mg X 625 Å, which has been shown to be a very useful temperature diagnostic. At densities typical of coronal hole conditions, the difference between the electron temperature derived assuming the zero density limit compared with the electron density dependent ionization/recombination is small. This, however, is not the case for flares where the electron density is orders of magnitude larger. The derived temperature for the coronal hole at solar maximum is around 1.04 MK compared to just below 0.82 MK at solar minimum. Title: Multi-frequency long-term monitoring of the ultracool dwarf TVLM 513-46546 Authors: Antonova, Antoaneta; Doyle, John Gerard; Hallinan, Gregg; Golden, Aaron; Bourke, Stephen Bibcode: 2010BlgAJ..14...58A Altcode: Recently, observations of three ultracool dwarfs have shown that the emission is in fact due to the electron cyclotron maser instability operating in the low plasma density, high magnetic field strength regions above the poles of a large-scale magnetic field, i.e. it is similar to that of the magnetized planets in the Solar system. The M8.5 dwarf TVLM 513-46546 is one of the most studied radio emitting dwarfs. It has been found to display periodic pulses of 100% circularly polarized radio emission, the periodicity of the bursts being consistent with the rotational period of the dwarf as confirmed by optical I band observations . Here we present a systematic review and analysis of all observations of TVLM 513-46546 conducted in the radio X and C bands, including our latest VLA and Arecibo observations. Title: Waves in the Transition Region Authors: Scullion, E.; Erdélyi, R.; Doyle, J. G. Bibcode: 2010ASSP...19..426S Altcode: 2010mcia.conf..426S Fundamental questions concerning coronal heating and the origin of the fast solar wind may be answered through greater understanding of fine structures in the lower solar atmosphere. We present results from a 2.5-D ideal-MHD simulation from a new numerical code, plus new supportive observational material. The simulation was run with the Sheffield Advanced Code (SAC, Shelyag et al. 2008, A&A, 486, 655) and is supported by multi-instrument evidence of a surface wave obtained from co-alignment of observations with Hinode/EIS and SoHO/MDI. Title: Fine Structure of a Coronal Bright Point as Seen with SoHO, TRACE, and Hinode Authors: Pérez-Suárez, D.; Maclean, R. C.; Doyle, J. G.; Madjarska, M. S. Bibcode: 2009ASPC..415..140P Altcode: We present a study of a Coronal Bright Point (BPs) where data from Hinode, SoHO and TRACE are analyzed. Covering a large temperature range, we study the variation of the BP from the surface to the corona investigating both the morphology and variation in physical parameters, such as electron density, Doppler-shift and magnetic field variability. We obtain excellent correlation between the X-ray light curve with the positive magnetic flux; also a good agreement is found between a potential extrapolated magnetic field and the loops seen in the X-ray images. Title: Jets in Polar Coronal Holes Authors: Scullion, E.; Popescu, M. D.; Banerjee, D.; Doyle, J. G.; Erdélyi, R. Bibcode: 2009ApJ...704.1385S Altcode: Here, we explore the nature of small-scale jet-like structures and their possible relation to explosive events and other known transient features, like spicules and macrospicules, using high-resolution spectroscopy obtained with the Solar and Heliospheric Observatory/Solar Ultraviolet Measurements of Emitted Radiation instrument. We present a highly resolved spectroscopic analysis and line parameter study of time-series data for jets occurring on-disk and off-limb in both a northern and a southern coronal hole. The analysis reveals many small-scale transients which rapidly propagate between the mid-transition region (N IV 765 Å line formation: 140,000 K) and the lower corona (Ne VIII 770 Å line formation: 630,000 K). In one example, a strong jet-like event is associated with a cool feature not present in the Ne VIII 770 Å line radiance or Doppler velocity maps. Another similar event is observed, but with a hot component, which could be perceived as a blinker. Our data reveal fast, repetitive plasma outflows with blueshift velocities of ≈145 km s-1 in the lower solar atmosphere. The data suggest a strong role for smaller jets (spicules), as a precursor to macrospicule formation, which may have a common origin with explosive events. Title: Explosive Events Associated with a Surge Authors: Madjarska, M. S.; Doyle, J. G.; de Pontieu, B. Bibcode: 2009ApJ...701..253M Altcode: 2009arXiv0906.2544M The solar atmosphere contains a wide variety of small-scale transient features. Here, we explore the interrelation between some of them such as surges, explosive events, and blinkers via simultaneous spectral and imaging data taken with the TRACE imager, the SUMER and Coronal Diagnostics Spectrometer (CDS) on board SOHO, and Swedish Vacuum Solar Telescope La Palma. The features were observed in spectral lines with formation temperatures from 10,000 K to 1 MK and with the TRACE Fe IX/X 171 Å filter. The Hα filtergrams were taken in the wings of the Hα 6365 Å line at ±700 mÅ and ±350 mÅ. The alignment of all data in both time and solar XY shows that SUMER line profiles, which are attributed to explosive events, are due to a surge phenomenon. The surge's up- and downflows, which often appear simultaneously, correspond to the blue- and redshifted emission of the transition region N V 1238.82 Å and O V 629.77 Å lines as well as radiance increases of the C I, S I, and S II and Si II chromospheric lines. Some parts of the surge are also visible in the TRACE 171 Å images which could suggest heating to coronal temperatures. The surge is triggered, most probably, by one or more Elerman bombs which are best visible in Hα ± 350 Å but were also registered by TRACE Fe IX/X 171 Å and correspond to a strong radiance increase in the CDS Mg IX 368.07 Å line. With the present study, we demonstrate that the division of small-scale transient events into a number of different subgroups, for instance explosive events, blinkers, spicules, surges or just brightenings, is ambiguous, implying that the definition of a feature based only on either spectroscopic or imaging characteristics as well as insufficient spectral and spatial resolution can be incomplete. Title: Signatures of Alfvén waves in the polar coronal holes as seen by EIS/Hinode Authors: Banerjee, D.; Pérez-Suárez, D.; Doyle, J. G. Bibcode: 2009A&A...501L..15B Altcode: 2009arXiv0906.4600B Context: We diagnose the properties of the plume and interplume regions in a polar coronal hole and the role of waves in the acceleration of the solar wind.
Aims: We attempt to detect whether Alfvén waves are present in the polar coronal holes through variations in EUV line widths.
Methods: Using spectral observations performed over a polar coronal hole region with the EIS spectrometer on Hinode, we study the variation in the line width and electron density as a function of height. We use the density sensitive line pairs of Fe xii 186.88 Å and 195.119 Å and Fe xiii 203.82 Å and 202.04 Å.
Results: For the polar region, the line width data show that the nonthermal line-of-sight velocity increases from 26~km s-1 at 10´´ above the limb to 42~km s-1 some 150´´ (i.e. ~110 000 km) above the limb. The electron density shows a decrease from 3.3 × 10^9~cm-3 to 1.9 × 10^8~cm-3 over the same distance.
Conclusions: These results imply that the nonthermal velocity is inversely proportional to the quadratic root of the electron density, in excellent agreement with what is predicted for undamped radially propagating linear Alfvén waves. Our data provide signatures of Alfvén waves in the polar coronal hole regions, which could be important for the acceleration of the solar wind.

Table [see full textsee full textsee full text] and Fig. [see full textsee full textsee full text] are only available in electronic form at http://www.aanda.org Title: Stellar and galactic environment survey (SAGE) Authors: Barstow, M. A.; Burleigh, M. R.; Bannister, N. J.; Lapington, J. S.; Kowalski, M. P.; Cruddace, R. G.; Wood, K. S.; Auchere, F.; Bode, M. F.; Bromage, G. E.; Gibson, B.; Collier Cameron, A.; Cassatella, A.; Delmotte, F.; Ravet, M. -F.; Doyle, J. G.; Jeffery, C. S.; Gaensicke, B.; Jordan, C.; Kappelmann, N.; Werner, K.; Lallement, R.; de Martino, D.; Matthews, S. A.; Phillips, K. J. H.; Del Zanna, G.; Orio, M.; Pace, E.; Pagano, I.; Schmitt, J. H. M. M.; Welsh, B. Y. Bibcode: 2009Ap&SS.320..231B Altcode: 2008Ap&SS.tmp..161B This paper describes a proposed high resolution soft X-ray and Extreme Ultraviolet (EUV) spectroscopy mission to carry out a survey of Stellar and Galactic Environments (SAGE). The payload is based on novel diffraction grating technology which has already been proven in a sub-orbital space mission and which is ready to fly on a satellite platform with minimal development. Much of the technical detail of the instrumentation has been reported elsewhere and we concentrate our discussion here on the scientific goals of a SAGE base-line mission, demonstrating the scientific importance of high resolution spectroscopy in the Extreme Ultraviolet for the study of stars and the local interstellar medium. Title: Stellar And Galactic Environment survey (SAGE) Authors: Barstow, M. A.; Kowalski, M. P.; Cruddace, R. G.; Wood, K. S.; Auchere, F.; Bannister, N. J.; Bode, M. F.; Bromage, G. E.; Burleigh, M. R.; Collier Cameron, A.; Cassatella, A.; Delmotte, F.; Doyle, J. G.; Gaensicke, B.; Gibson, B.; Jeffery, C. S.; Jordan, C.; Kappelmann, N.; Lallement, R.; Lapington, J. S.; de Martino, D.; Matthews, S. A.; Orio, M.; Pace, E.; Pagano, I.; Phillips, K. J. H.; Ravet, M. -F.; Schmitt, J. H. M. M.; Welsh, B. Y.; Werner, K.; Del Zanna, G. Bibcode: 2009ExA....23..169B Altcode: 2008ExA...tmp...25B This paper describes a proposed high resolution soft X-ray and Extreme Ultraviolet spectroscopy mission to carry out a survey of Stellar and Galactic Environments (SAGE). The payload is based on novel diffraction grating technology which has already been proven in a sub-orbital space mission and which is ready to fly on a satellite platform with minimal development. We discuss the goals of a SAGE base-line mission and demonstrate the scientific importance of high resolution spectroscopy in the Extreme Ultraviolet for the study of stars and the local interstellar medium. Title: On the statistical detection of propagating waves in polar coronal holes Authors: Gupta, G. R.; O'Shea, E.; Banerjee, D.; Popescu, M.; Doyle, J. G. Bibcode: 2009A&A...493..251G Altcode: 2009arXiv0902.2676G Context: Waves are important to the study of dynamical processes in coronal holes and the acceleration of the fast solar wind. A spectral time series was taken with the SUMER spectrometer on-board SoHO on 20 October 1996. The observations were obtained in the N iv 765 Å transition region line and the Ne viii 770 Å line of the low corona.
Aims: We detect the presence of waves and study their characteristic properties in terms of their propagation speeds and direction. Previous statistical studies, undertaken with data from the CDS spectrometer, report the presence of waves in these regions. We extend this analysis using SUMER observations.
Methods: Using Fourier techniques, we measured the phase delays between intensity oscillations, as well as between velocity oscillations, in our two lines over the full range of available frequencies. From this, we were able to measure the travel time of the propagating oscillations, hence the propagation speeds of the waves that produce the oscillations.
Results: We detect the long period oscillations in polar coronal holes on the disc. For network bright locations within coronal holes, our results indicate the presence of compressional waves with a dominant period of ≈25 min. However, we also find power at many other different frequencies, so we are able to study oscillations over a full range of frequencies. We find evidence of propagating waves with a fixed time delay in the coronal hole. We find, moreover, that there is a difference in the nature of the wave propagation in the bright (“network”), as opposed to the dark (“internetwork”) regions, with the latter sometimes showing evidence of downwardly propagating waves that are not seen in the former. From a measurement of propagation speeds, we find that all measured waves are subsonic in nature.
Conclusions: Waves with different characteristics are found to be present at different locations in the observed coronal hole. The measured propagation speeds are subsonic, indicating that the majority of them are slow magneto-acoustic in nature. These waves, measured in the lower atmosphere, could accelerate farther at higher altitudes and may be important for the acceleration of the fast solar wind. Title: On oscillations found in an active region with EIS on Hinode Authors: O'Shea, E.; Doyle, J. G. Bibcode: 2009A&A...494..355O Altcode: Aims: Using temporal series (40'' slot) data in the ion{Fe}{xii} 195 Å line from the extreme-ultraviolet imaging spectrometer (EIS) on board the Hinode satellite, we seek to carry out a statistical study of oscillations in an active region.
Methods: Using wavelet techniques, we measure the frequency and duration of oscillations found in the time series data. Stokes I and V data from Hinode's SOT are used to measure photospheric magnetic fields, while an EIS raster is used to provide estimates of LOS velocity and electron density. The measured frequencies are displayed as maps in different bands to aid their analysis.
Results: Oscillations over a broad range of frequencies (2-154 mHz) are found throughout the active region at the temperature of ion{Fe}{xii} (log T=6.1 K). Oscillations with frequencies between 2-8 mHz are concentrated in bright plage areas, while oscillations of higher frequency preferentially group at the edges of these areas. Evidence is found for harmonics on the boundary of the active region loop, indicating the presence of standing waves. From a measurement of the lengths and electron density of loops appearing in our active region field-of-view (FOV), together with a knowledge of the periods (frequencies) of the oscillations within the area of these loops, we find a magnetic field value of between 12.2±2.08-18.9±3.40 G, assuming standing fast kink waves.
Conclusions: We conclude that waves, which the observed oscillations are signatures of, are common in the active region studied, over a broad range of frequencies. The change in the distribution of the oscillations present at frequencies less than 8 mHz and those at all frequencies above this indicates a variation of the wave mode with frequency, e.g., possibly from slow magnetoacoustic waves in the bright plage regions to fast magnetoacoustic waves at the boundaries of these regions. The preference for higher frequency oscillations to cluster on the edges of regions of high magnetic field is considered indicative of resonant absorption. Based on our measurements of magnetic field, we conclude that the oscillations found by us in the active region loop are fast kink waves. Title: The structure and dynamics of a bright point as seen with Hinode, SoHO and TRACE Authors: Pérez-Suárez, D.; Maclean, R. C.; Doyle, J. G.; Madjarska, M. S. Bibcode: 2008A&A...492..575P Altcode: 2008arXiv0810.1020P Context: Solar coronal bright points have been studied for more than three decades, but some fundamental questions about their formation and evolution still remain unanswered.
Aims: Our aim is to determine the plasma properties of a coronal bright point and compare its magnetic topology extrapolated from magnetogram data with its appearance in X-ray images.
Methods: We analyse spectroscopic data obtained with EIS/Hinode, Ca ii H and G-band images from SOT/Hinode, UV images from TRACE, X-ray images from XRT/Hinode and high-resolution/high-cadence magnetogram data from MDI/SoHO.
Results: The BP comprises several coronal loops as seen in the X-ray images, while the chromospheric structure consists of tens of small bright points as seen in Ca ii H. An excellent correlation exists between the Ca ii H bright points and increases in the magnetic field strength, implying that the Ca ii H passband is a good indicator for the concentration of magnetic flux. Furthermore, some of the Ca ii H bright points are the locations of the loop foot-points as determined from a comparison between the extrapolated magnetic field configuration and the X-ray images. Doppler velocities between 6 and 15 km s-1 are derived from the Fe xii and Fe xiii lines for the bright point region, while for Fe xiv and Si vii they are in the range from -15 to +15 km s-1. The coronal electron density is 3.7 × 109 cm-3. An excellent correlation is found between the positive magnetic flux and the X-ray light-curves.
Conclusions: The remarkable agreement between the extrapolated magnetic field configuration and some of the loops composing the bright point as seen in the X-ray images suggests that a large fraction of the magnetic field in the bright point is close to potential. However, some loops in the X-ray images do not have a counterpart in the extrapolated magnetic field configuration implying a non-potential component. The close correlation between the positive magnetic flux and the X-ray emission suggests that energy released by magnetic reconnection is stimulated by flux emergence or cancellation. Title: Lidar Observations of Volcanic Aerosol Layers Over Halifax, Canada Authors: Bitar, L.; Duck, T. J.; Doyle, J.; Perro, C. Bibcode: 2008AGUFM.A53B0272B Altcode: Lidar measurements of vertical aerosol distributions from late summer 2008 indicate the presence of unusual aerosol layers in the upper troposphere and lower stratosphere over Halifax, Nova Scotia in Eastern Canada (44.64°N, 63.59°W). Trajectory analyses indicate that the sources of the aerosol layers were the explosive 7-8 August eruptions of Kasatochi volcano in the Aleutian Volcanic Arc (52.17°N, 175.51°W). The aerosol plumes were detected on multiple days throughout August and September by the Dalhousie Raman Lidar. A new high-altitude receiver addition to the lidar system is being used to enhance investigation of the optical characteristics as well as the vertical and temporal structures of the observed volcanic aerosol layers. Title: Study of Transition Region Transient Events with Hinode Authors: Subramanian, S.; Madjarska, M.; Doyle, J. G. Bibcode: 2008ASPC..397..194S Altcode: We present preliminary results of a study of transient events in the solar transition region (TR), using observations taken at disk centre on 9 April, 2007 with SOT, XRT and EIS on-board Hinode; CDS and MDI on-board SoHO, plus TRACE covering the photosphere to corona. Title: Confirmation of the Electron Cyclotron Maser Instability as the Dominant Source of Radio Emission from Very Low Mass Stars and Brown Dwarfs Authors: Hallinan, G.; Antonova, A.; Doyle, J. G.; Bourke, S.; Lane, C.; Golden, A. Bibcode: 2008ApJ...684..644H Altcode: 2008arXiv0805.4010H We report on radio observations of the M8.5 dwarf LSR J1835+3259 and the L3.5 dwarf 2MASS J00361617+1821104, which provide the strongest evidence to date that the electron cyclotron maser instability is the dominant mechanism producing radio emission in the magnetospheres of ultracool dwarfs. As has previously been reported for the M9 dwarf TVLM 513-46546, periodic pulses of 100% circularly polarized, coherent radio emission are detected from both dwarfs with periods of 2.84 +/- 0.01 and 3.08 +/- 0.05 hr, respectively, for LSR J1835+3259 and 2MASS J00361617+1821104. Importantly, periodic unpolarized radio emission is also detected from 2MASS J00361617+1821104, and brightness temperature limitations rule out gyrosynchrotron radiation as a source of this radio emission. The unpolarized emission from this and other ultracool dwarfs is also attributed to electron cyclotron maser emission, which has become depolarized on traversing the ultracool dwarf magnetosphere, possibly due to propagations effects such as scattering. Based on available vsin i data in the literature and rotation periods derived from the periodic radio data for the three confirmed sources of electron cyclotron maser emission, TVLM 513-46546, LSR J1835+3259, and 2MASS J00361617+1821104, we determine that the rotation axes of all three dwarfs are close to perpendicular to our line of sight. This suggests a possible geometrical selection effect due to the inherent directivity of electron cyclotron maser emission, that may account for the previously reported relationship between radio activity and vsin i observed for ultracool dwarfs. We also determine the radius of the dwarf LSR J1835+3259 to be >=0.117 +/- 0.012 R⊙. The implied size of the radius, together with the bolometric luminosity of the dwarf, suggests that either LSR J1835 is a young- or intermediate-age brown dwarf, or that current theoretical models underestimate the radii of ultracool dwarfs. 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: Magnetic Variability of an XRT Bright Point Authors: Maclean, R. C.; Owens, B. J.; Pérez Suárez, D.; Doyle, J. G. Bibcode: 2008ASPC..397..178M Altcode: Solar coronal bright points display complex internal structure when viewed at the high spatial resolutions provided by the instruments onboard Hinode and SoHO. We study the magnetic evolution of a newly formed bright point on the 6th of April 2007, using high-resolution SoHO/MDI magnetogram data as a basis for topological reconstruction of the 3D magnetic field in the corona. A dynamic network of magnetic connections exists both within the bright point itself and linking it with the surrounding magnetic features. When these changes in magnetic connectivity are compared with Hinode/XRT observations of X-ray loops and brightenings, we can gain new insights into how changes in the coronal magnetic field configuration lead to brightenings of magnetic structures within the bright point, with possible implications for coronal heating. Title: A mini-survey of ultracool dwarfs at 4.9 GHz Authors: Antonova, A.; Doyle, J. G.; Hallinan, G.; Bourke, S.; Golden, A. Bibcode: 2008A&A...487..317A Altcode: 2008arXiv0805.4574A Context: A selection of ultracool dwarfs are known to be radio active, with both gyrosynchrotron emission and the electron cyclotron maser instability being given as likely emission mechanisms.
Aims: We explore whether ultracool dwarfs previously undetected at 8.5 GHz may be detectable at a lower frequency.
Methods: We select a sample of fast rotating ultracool dwarfs with no detectable radio activity at 8.5 GHz, observing each of them at 4.9 GHz.
Results: From the 8 dwarfs in our sample, we detect emission from 2MASS J07464256+2000321, with a mean flux level of 286 ± 24 μJy. The light-curve of 2MASS J07464256+2000321, is dominated towards the end of the observation by a very bright, ≈ 100% left circularly polarized burst during which the flux reached 2.4 mJy. The burst was preceded by a raise in the level of activity, with the average flux being ≈160 μJy in the first hour of observation rising to ≈400 μJy in the 40 min before the burst. During both periods, there is significant variability.
Conclusions: The detection of 100% circular polarization in the emission at 4.9 GHz points towards the electron cyclotron maser as the emission mechanism. However, the observations at 4.9 GHz and 8.5 GHz were not simultaneous, thus the actual fraction of dwarfs capable of producing radio emission, as well as the fraction of those that show periodic pulsations is still unclear, as indeed are the relative roles played by the electron cyclotron maser instability versus gyrosynchrotron emission, therefore we cannot assert if the previous non-detection at 8.5 GHz was due to a cut-off in emission between 4.9 and 8.4 GHz, or due to long term variability. Title: Small-scale flows in SUMER and TRACE high-cadence co-observations Authors: Madjarska, M. S.; Doyle, J. G. Bibcode: 2008A&A...482..273M Altcode: 2008arXiv0802.2477M Context: We report on the physical properties of small-scale transient flows observed simultaneously at high cadence with the SUMER spectrometer and the TRACE imager in the plage area of an active region.
Aims: Our major objective is to provide a better understanding of the nature of transient phenomena in the solar atmosphere by using high-cadence imager and spectrometer co-observations at similar spatial and temporal resolution.
Methods: A sequence of TRACE Fe IX/X λ171 Å and high-resolution MDI images were analysed together with simultaneously obtained SUMER observations in spectral lines covering a temperature range from 10 000 K to 1 MK.
Results: We reveal the existence of numerous transient flows in small-scale loops (up to 30 Mm) observed in the plage area of an active region. These flows have temperatures from 10 000 K (the low temperature limit of our observations) to 250 000 K. The coronal response of these features is uncertain due to a blending of the observed coronal line Mg x λ624.85 Å. The duration of the events ranges from 60 s to 19 min depending on the loop size. Some of the flows reach supersonic velocities.
Conclusions: The Doppler shifts often associated with explosive events or bi-directional jets can actually be identified with flows (some of them reaching supersonic velocities) in small-scale loops. Additionally, we demonstrate how a line-of-sight effect can give misleading information on the nature of the observed phenomena if only either an imager or a spectrometer is used.

An animation of the TRACE λ171 Å images is only available in electronic form at http://www.aanda.org Title: Jets or High-Velocity Flows Revealed in High-Cadence Spectrometer and Imager Co-observations? Authors: Madjarska, M. S.; Doyle, J. G.; Innes, D. E.; Curdt, W. Bibcode: 2007ApJ...670L..57M Altcode: 2007arXiv0710.2199M We report on active region EUV dynamic events observed simultaneously at high cadence with SOHO SUMER and TRACE. Although the features appear in the TRACE Fe IX/X 171 Å images as jets seen in projection on the solar disk, the SUMER spectral line profiles suggest that the plasma has been driven along a curved large-scale magnetic structure, a preexisting loop. The SUMER observations were carried out in spectral lines covering a large temperature range from 104 to 106 K. The spectral analysis revealed that a sudden heating from an energy deposition is followed by a high-velocity plasma flow. The Doppler velocities were found to be in the range from 90 to 160 km s-1. The heating process has a duration which is below the SUMER exposure time of 25 s while the lifetime of the events is from 5 to 15 minutes. The additional check on soft X-ray Yohkoh images shows that the features most probably reach 3 MK (X-ray) temperatures. The spectroscopic analysis showed no existence of cold material during the events. Title: Plasma condensation in coronal loops Authors: O'Shea, E.; Banerjee, D.; Doyle, J. G. Bibcode: 2007A&A...475L..25O Altcode: Aims:Using temporal series data from the Coronal Diagnostic Spectrometer (CDS) on SOHO, we seek to investigate plasma condensation through the use of spectroscopic analysis.
Methods: Using a space-time (X-T) type plot we show, for a number of transition region (TR) and coronal lines, the variation of intensity (radiant flux) with time in an off-limb loop system. Noting a number of pixels where the intensity shows a sharp jump in value for the TR lines and a corresponding sharp decrease for the coronal lines, we investigate further and plot the intensity and velocity for these pixels as a function of time. Using standard Fourier techniques, together with a pre-whitening method, we measure all statistically significant frequencies present in the time series so created.
Results: We find that, for the cooler lines of He I 584 Å and O V 629 Å, there are sharp increases in intensity, accompanied by large blueshifted velocities. In the case of O V there is a substantial rebound to redshifted velocities when the strong brightening fades. The sharp increase in intensity and blueshifted velocity in the cooler lines is accompanied by a corresponding decrease in the intensity of the coronal lines (Mg X 624 Å, Fe XVI 360 Å, Si XII 520 Å), but with no corresponding change in their velocity values implying an evacuation of plasma. From the Fourier analysis, evidence is found for possible 1st and 2nd harmonics in the He I and O V lines, indicative of standing waves in loops.
Conclusions: We conclude that what we are seeing is the first spectroscopic evidence of plasma condensation taking place in coronal loops.

A movie is only available in electronic form at http://www.aanda.org Title: Evidence for wave harmonics in cool loops Authors: O'Shea, E.; Srivastava, A. K.; Doyle, J. G.; Banerjee, D. Bibcode: 2007A&A...473L..13O Altcode: Aims:Using temporal series image data from the Coronal Diagnostic Spectrometer (CDS) on SOHO, we study oscillations found in intensity (radiance) measurements from the transition region O v 629 line with the aim of finding evidence of wave harmonics in cool loops.
Methods: Using standard Fourier techniques, together with a pre-whitening method, we measure all statistically significant frequencies present in oscillations found in flaring active region loops at the temperature of O v. By measuring the distances travelled by three Propagating Disturbances (PDs), estimates of their propagation speeds are calculated.
Results: Evidence is found for harmonics in the measured oscillations suggesting the presence of standing waves in the loops. We find that PDs in cool O v active region loops have sub-sonic velocities of between 12-24 km s-1, suggesting they are moved either by slow mode (acoustic or slow magnetoacoustic) wave propagation or by bulk flows along the loops triggered by the flaring that also produces the PDs.
Conclusions: We find evidence that standing waves are present in flaring cool transition region loops. This evidence comes in the form of oscillations showing harmonic frequencies that match those expected for standing fast kink waves. Title: Rotational Modulation of M/L Dwarfs due to Magnetic Spots Authors: Lane, C.; Hallinan, G.; Zavala, R. T.; Butler, R. F.; Boyle, R. P.; Bourke, S.; Antonova, A.; Doyle, J. G.; Vrba, F. J.; Golden, A. Bibcode: 2007ApJ...668L.163L Altcode: 2007arXiv0709.1045L We find periodic I-band variability in two ultracool dwarfs, TVLM 513-46546 and 2MASS J00361617+1821104, on either side of the M/L dwarf boundary. Both of these targets are short-period radio transients, with the detected I-band periods matching those found at radio wavelengths (P=1.96 hr for TVLM 513-46546 and P=3 hr for 2MASS J00361617+1821104). We attribute the detected I-band periodicities to the periods of rotation of the dwarfs, supported by radius estimates and measured vsini values for the objects. Based on the detected period of rotation of TVLM 513-46546 (M9) in the I band, along with confirmation of strong magnetic fields from recent radio observations, we argue for magnetically induced spots as the cause of this periodic variability. The I-band rotational modulation of the L3.5 dwarf 2MASS J00361617+1821104 appeared to vary in amplitude with time. We conclude that the most likely cause of the I-band variability for this object is magnetic spots, possibly coupled with time-evolving features such as dust clouds. Title: Sporadic long-term variability in radio activity from a brown dwarf Authors: Antonova, A.; Doyle, J. G.; Hallinan, G.; Golden, A.; Koen, C. Bibcode: 2007A&A...472..257A Altcode: 2007arXiv0707.0634A Context: Radio activity has been observed in a large variety of stellar objects, including in the last few years, ultra-cool dwarfs.
Aims: To explore the extent of long-term radio activity in ultra-cool dwarfs.
Methods: We use data taken over an extended period of 9 hr from the Very Large Array of the source 2MASS J05233822-1403022 in September 2006, plus data taken in 2004.
Results: The observation taken in September 2006 failed to detect any radio activity at 8.46 GHz. A closer inspection of earlier data reveals that the source varied from a null detection on 3 May 2004, to ≈95 μJy on 17 May 2004, to 230 μJy on 18 June 2004. The lack of detection in September 2006 suggests at least a factor of ten flux variability at 8.46 GHz. Three short photometric runs did not reveal any optical variability.
Conclusions: In addition to the observed pulsing nature of the radio flux from another ultra-cool source, the present observations suggests that ultra-cool dwarfs may not just be pulsing but can also display long-term sporadic variability in their levels of quiescent radio emission. The lack of optical photometric variability suggests an absence of large-scale spots at the time of the latest VLA observations, although small very high latitude spots combined with a low inclination could cause very low amplitude rotational modulation which may not be measurable. We discuss this large variability in the radio emission within the context of both gyrosynchrotron emission and the electron-cyclotron maser, favoring the latter mechanism. Title: Periodic Bursts of Coherent Radio Emission from an Ultracool Dwarf Authors: Hallinan, G.; Bourke, S.; Lane, C.; Antonova, A.; Zavala, R. T.; Brisken, W. F.; Boyle, R. P.; Vrba, F. J.; Doyle, J. G.; Golden, A. Bibcode: 2007ApJ...663L..25H Altcode: 2007arXiv0705.2054H We report the detection of periodic (p=1.96 hr) bursts of extremely bright, 100% circularly polarized, coherent radio emission from the M9 dwarf TVLM 513-46546. Simultaneous photometric monitoring observations have established this periodicity to be the rotation period of the dwarf. These bursts, which were not present in previous observations of this target, confirm that ultracool dwarfs can generate persistent levels of broadband, coherent radio emission, associated with the presence of kG magnetic fields in a large-scale, stable configuration. Compact sources located at the magnetic polar regions produce highly beamed emission generated by the electron cyclotron maser instability, the same mechanism known to generate planetary coherent radio emission in our solar system. The narrow beams of radiation pass our line of sight as the dwarf rotates, producing the associated periodic bursts. The resulting radio light curves are analogous to the periodic light curves associated with pulsar radio emission highlighting TVLM 513-46546 as the prototype of a new class of transient radio source. Title: On the Signature of MHD Waves in Coronal Holes Authors: Srivastava, A. K.; Doyle, J. G.; O'Shea, E. Bibcode: 2007nam7.conf...87S Altcode: Polar coronal holes are the open magnetic field regions of strongly-reduced emissions at various wavelengths. Recent spectroscopic analysis provides an evidence for the presence of MHD waves, which may be one of the possible energy sources in polar coronal holes. We present our some recent findings which interestedly engaged with the presence of MHD waves, and discuss their possible roles in polar coronal holes. Title: A statistical study of wave propagation in coronal holes Authors: O'Shea, E.; Banerjee, D.; Doyle, J. G. Bibcode: 2007A&A...463..713O Altcode: Aims:To find evidence for propagating magnetoacoustic waves in equatorial and polar coronal hole locations.
Methods: Using temporal series data from the Coronal Diagnostic Spectrometer (CDS) on SOHO, we study oscillations found in radiant flux and velocity measurements from transition region (O V 629) and coronal lines (Mg X 624, Si XII 520). We use Fourier techniques to measure phase delays between flux ("intensity") oscillations and between velocity oscillations of different transition region-corona and corona-corona line pairs. We also measure the phase delays between flux and velocity oscillations (I-V) in the three spectral lines investigated.
Results: We find outwardly propagating slow magnetoacoustic waves in both of the coronal hole regions studied. The propagation speeds are found to be lower than those found in off-limb locations. We find evidence for a resonant cavity or "Doppler" effect, whereby the measured phases are present at fixed integer intervals of f/4 (90° of phase) and 3f/8 (135° of phase) instead of the expected interval of f or 360°. We find, in addition, from the I-V phases, evidence for standing waves at coronal temperatures in the lines of Mg X 624 and Si XII 520. Correlations are found between the locations where the phases are measured and localised brightenings in both equatorial and polar coronal holes. This suggests that the slow magnetoacoustic waves are originating preferentially from bright areas within the coronal holes which we take to be the locations of concentrated magnetic field (loops, bright points). Finally, we find evidence that in these bright regions along the slit, the measured phases tend to occur at a spectrum of frequencies, perhaps suggesting the presence of discrete propagating wave packets.
Conclusions: .We conclude that propagating slow magnetoacoustic waves are present in equatorial and polar coronal hole locations and that they occur preferentially in bright regions that are associated with magnetic field concentrations in the form of loops or bright points. In addition, we conclude that some resonant cavity effect is affecting the propagating waves, perhaps resulting in the standing waves that are found at coronal temperatures. Title: A study of a macro-spicule and a transition region explosive event in a solar coronal hole Authors: Popescu, M. D.; Xia, L. D.; Banerjee, D.; Doyle, J. G. Bibcode: 2007AdSpR..40.1021P Altcode: AimsSpicules and the higher macro-spicules (jet-like structures seen at the solar limb) are believed to be the dominant mechanism for mass ejection in the higher solar atmosphere outside active regions. But what is the connection between them and other small-scale structures in the Sun's atmosphere, like for example transition region explosive events, is not known yet. MethodsOur data are temporal series spectroheliograms of EUV emission lines from two ions (N IV 765 Å and Ne VIII 770 Å), taken with the SUMER (Solar UV Measurements of Emitted Radiation) spectrograph on SoHO (the Solar and Heliospheric Observatory). SUMER's good spatial, spectral and temporal resolution allowed us to have one of the most detailed studies of these small-scale structures over a range of transition region temperatures. ResultsOur study reveals that a macro-spicule seen off-limb looks similar to a transition region explosive event, especially in the map of the lines' full-width-at-half-maximum (FWHM). The macro-spicule seen in the low transition region N IV line (≈140,000 K) is also visible in the higher temperature Ne VIII line (≈630,000 K). Also, the jet seen on-disk in the N IV line heats and accelerates plasma to the higher Ne VIII temperature, traveling probably along the local (presumably open) magnetic field line. Title: Analysis of power spectra of Doppler shift time series as a diagnostic tool for quiescent coronal loops Authors: Taroyan, Y.; Erdélyi, R.; Doyle, J. G.; Bradshaw, S. J. Bibcode: 2007A&A...462..331T Altcode: Context: Analysing the structure of solar coronal loops is crucial to our understanding of the processes which heat and maintain the coronal plasma at multimillion degree temperatures. The determination of the physical parameters of the loops remains both an observational and theoretical challenge.
Aims: The present work is aimed at tackling some of these challenges such as the determination of the average loop temperature and its distribution along a given loop.
Methods: A novel diagnostic technique for quiescent coronal loops based on the analysis of power spectra of Doppler shift time series is proposed. It is assumed that the loop is heated randomly both in space and time by small-scale discrete impulsive events of unspecified nature. The loop evolution is characterised by longitudinal motions caused by the random heating events. These random motions can be represented as a superposition of the normal modes of the loop, i.e., its standing acoustic wave harmonics. The idea is borrowed from helioseismology where a similar approach resulted in a deep understanding of the solar interior.
Results: It is shown that depending on the heliographic position of the loop and its geometrical orientation, various harmonics can be identified in the power spectra of the line shift time series. The highest power peak corresponds to the fundamental mode. The peaks become smaller as the frequency increases. The frequencies of the harmonics are determined by the loop length and temperature and thus are suggested to be used as a temperature diagnostic tool. It is demonstrated that the analysis of the power spectra allows the distinction between uniformly heated loops from loops heated near their footpoints and to estimate the average energy of a single heating event. The proposed new method could in principle be used to study the multithermal structure of coronal loops.
Conclusions: .The power spectrum analysis is a potentially powerful technique for coronal loop diagnostics. Title: Rotational Modulation of the Radio Emission from the M9 Dwarf TVLM 513-46546: Broadband Coherent Emission at the Substellar Boundary? Authors: Hallinan, G.; Antonova, A.; Doyle, J. G.; Bourke, S.; Brisken, W. F.; Golden, A. Bibcode: 2006ApJ...653..690H Altcode: 2006astro.ph..8556H The Very Large Array was used to observe the ultracool rapidly rotating M9 dwarf TVLM 513-46546 simultaneously at 4.88 and 8.44 GHz. The radio emission was determined to be persistent, variable, and periodic at both frequencies with a period of ~2 hr. This periodicity is in excellent agreement with the estimated period of rotation of the dwarf based on its vsini of ~60 km s-1. This rotational modulation places strong constraints on the source size of the radio-emitting region and hence the brightness temperature of the associated emission. We find the resulting high brightness temperature, together with the inherent directivity of the rotationally modulated component of the emission, difficult to reconcile with incoherent gyrosynchrotron radiation. We conclude that a more likely source is coherent, electron cyclotron maser emission from the low-density regions above the magnetic poles. This model requires the magnetic field of TVLM 513-46546 to take the form of a large-scale, stable dipole or multipole with surface field strengths up to at least 3 kG. We discuss a mechanism by which broadband, persistent electron cyclotron maser emission can be sustained in the low-density regions of the magnetospheres of ultracool dwarfs. A second nonvarying, unpolarized component of the emission may be due to depolarization of the coherent electron cyclotron maser emission or, alternatively, incoherent gyrosynchrotron or synchrotron radiation from a population of electrons trapped in the large-scale magnetic field. Title: Transition region counterpart of a moving magnetic feature Authors: Lin, C. -H.; Banerjee, D.; O'Shea, E.; Doyle, J. G. Bibcode: 2006A&A...460..597L Altcode: Context: .While moving magnetic features have been studied extensively at the photospheric level, the effect they have on the upper atmosphere remains largely unknown, and it is this which we seek to address in this work.
Aims: .In this work we aim to investigate the chromospheric and transition-region dynamics associated with a moving magnetic monopole by using spectral time-series and images.
Methods: .Cross correlation was applied to images taken by different instruments and at different times in order to spatially correlate brightenings seen at transition region temperatures with moving magnetic features seen in magnetograms. We used wavelet analysis to examine and compare the periodicities of time-series signals in different regions.
Results: .Oscillations with a multitude of frequencies are found in the chromospheric and transition-region brightenings associated with a moving magnetic monopole. The region of the brightenings shows a tendency to be blue-shifted when compared to the average motion of the entire field of view. The results indicate the presence of waves and/or flows carrying energy from the monopole to the higher atmosphere.
Conclusions: .We studied the influence of a moving magnetic monopole, as recorded by magnetograms, up to transition region temperatures. This suggests that the magnetic monopole, despite being small, can influence dynamics in the upper atmospheric layers. Title: GALEX high time-resolution ultraviolet observations of dMe flare events Authors: Welsh, B. Y.; Wheatley, J.; Browne, S. E.; Siegmund, O. H. W.; Doyle, J. G.; O'Shea, E.; Antonova, A.; Forster, K.; Seibert, M.; Morrissey, P.; Taroyan, Y. Bibcode: 2006A&A...458..921W Altcode: 2006astro.ph..8254W Aims.We present near ultraviolet (NUV: 1750-2800 Å) and far ultraviolet (FUV: 1350-1750 Å) light-curves for flares on 4 nearby dMe-type stars (GJ 3685A, CR Dra, AF Psc and SDSS J084425.9+513830.5) observed with the GALEX satellite.
Methods: .Taking advantage of the time-tagged events recorded with the GALEX photon counting detectors, we present high temporal resolution (<0.01 s) analysis of these UV flare data.
Results: .A statistical analysis of 700 s of pre-flare quiescence data for both CR Dra and SDSS J084425.9+513830.5 failed to reveal the presence of significant micro-flare activity in time bins of 0.2, 1 and 10 s intervals. Using an appropriate differential emission measure for both the quiescent and flaring state, it is possible to reproduce the observed FUV:NUV flux ratios. A major determinant in reproducing this flux ratio is found to be the value of plasma electron density during the flare. We also searched the count rate data recorded during each of the four flare events for periodicity associated with magneto-hydrodynamic oscillations in the active region coronal loops. Significant oscillations were detected during the flare events observed on all 4 stars, with periodicities found in the 30 to 40 s range. Flare oscillations with this periodicity can be explained as acoustic waves in a coronal loop of length of ≈109 cm for an assumed plasma temperature of 5-20 × 106 K. This suggests a loop length for these M-dwarf flares of less than 1/10th of the stellar radii. We believe that this is the first detection of non-solar coronal loop flare oscillations observed at ultraviolet wavelengths.
Title: Observational Clues to the Origin of the Fast Solar Wind Authors: Popescu, M. D.; Doyle, J. G.; Banerjee, D. Bibcode: 2006ihy..workE..43P Altcode: It is well known that the fast solar wind originates from coronal holes, but its source close to the solar 'surface' has been a matter of debate even in today's era of modern solar observations. Recently, it has been suggested that the fast solar wind outflow starts at about 10 kilometers per second in coronal funnels, which are located at the edges of the chromospheric magnetic network inside coronal holes. We present further evidence that the outflow might also originate from above 'explosive event' sites. These jets have a lifetime of about 5 minutes and are often seen reoccurring at the same location over intervals of typically 20-30 minutes. Although the expelled jets might actually extend high in the Sun's atmosphere, they are not seen in the intensity on the disk. Some of the transparent features might nevertheless appear as macrospicules at the Sun's edge. This observation itself is shedding new light onto another long- standing question regarding the nature of macrospicules. These results about the small-scale structures of coronal holes and their consequence on explaining the nature of the fast solar wind have been derived due to an innovative way of extracting information from the spectral data offered by SOHO’s highest resolution detector, SUMER. The 'secret' of our technique lies in understanding plasma properties from the signature it leaves in the shape and widths of the spectral lines. Title: Line Broadening of EUV Lines at the Solar Limb Observed with SUMER/SoHO. Relation to Spicules Authors: Giannikakis, J.; Tsiropoula, G.; Tziotziou, K.; Antonopoulou, E.; Doyle, J. G. Bibcode: 2006AIPC..848..115G Altcode: We study the broadening of EUV line widths as we move from the disk through and off the solar limb. This broadening maximizes at approximately 10 Mm above the limb. We use one raster scan and two time series obtained by SUMER/SoHO to examine a possible correlation between this phenomenon and spicule activity. It appears that spicule presence leads to even wider profiles whereas the appearance of macrospicules extends the broadening to even greater distances above the limb. We suggest that this correlation might imply that spicules are responsible for this disk-to-limb behavior even in regions where they cannot be observed. Title: Off-Limb Coronal Loop Dynamics as Seen from CDS, EIT and TRACE Authors: Banerjee, D.; O'Shea, E.; Doyle, J. G. Bibcode: 2006ESASP.617E..83B Altcode: 2006soho...17E..83B No abstract at ADS Title: The Signature of Moving Magnetic Feature in the Solar Atmosphere Authors: Lin, C. -H.; Banerjee, D.; O'Shea, E.; Doyle, J. G. Bibcode: 2006ESASP.617E..97L Altcode: 2006soho...17E..97L No abstract at ADS Title: Dynamic features in the solar atmosphere with unusual spectral line enhancements and Doppler-shifts Authors: Doyle, J. G.; Ishak, B.; Madjarska, M. S.; O'Shea, E.; Dzifćáková, E. Bibcode: 2006A&A...451L..35D Altcode: Context.The solar atmosphere contains a wide variety of transient features, here, we discuss data relating to one such feature.
Aims.To explore via simultaneous spectral and imaging data the nature of high-velocity flow events in the solar transition region.
Methods.High spectral and temporal resolution data from SUMER/SoHO plus high resolution images from TRACE are used.
Results.In the transient feature discussed, we see a factor of two enhancement in N v 1238, coupled with a factor of two decrease in O v 629 visible over 3''-4'' along the slit. Furthermore, the O v line shows a secondary component with a down-flow of ≈75 km s-1, while the N v line shows only a small additional broadening of the line.
Conclusions.Inclusion of an electron density dependent ionization calculation will increase the N v radiance over that of O v at large electron densities. We suggest this feature can be explained via a highly focused jet at the O v/Ovi formation temperature resulting from reconnection. Also, we believe that this event is not unique but that their detection depends on the availability of simultaneous spectral and imaging data of comparable spatial and temporal resolution. Title: Magnetoacoustic wave propagation in off-limb polar regions Authors: O'Shea, E.; Banerjee, D.; Doyle, J. G. Bibcode: 2006A&A...452.1059O Altcode: Aims.To find evidence of magnetoacoustic waves in off-limb polar regions.
Methods: .Using temporal series data from the Coronal Diagnostic Spectrometer (CDS) on SOHO, we study oscillations found in radiant flux and velocity measurements from transition region and coronal spectral lines. We use Fourier techniques to measure phase delays between flux (“intensity”) oscillations and between velocity oscillations of different transition region-corona and corona-corona line pairs. We also measure the phase delays between flux and velocity oscillations (I-V).
Results: .The phase delays measured between different line pairs, when plotted over a -180 ° to +180 ° range, line up along diagonal lines corresponding to measurable and fixed time delays. The slopes of these diagonal lines suggest the outward propagation of waves. Using the measured time delays, we estimate propagation speeds for the different line pairs that indicate that the waves producing the observed phase delays are magnetoacoustic waves propagating at speeds close to the sound speed. In addition, we find that the phases occur at fixed integer frequencies of f/4 (90 °) and 3f/16 (67.5 °), instead of the expected interval of f (360 °), indicating that a “Doppler effect” is acting on the waves.
Conclusions: .From I-V measurements, we find evidence for fast magnetoacoustic waves to be predominantly present at coronal temperatures, while at transition region temperatures slow magnetoacoustic waves are more common. We find strong evidence for outwardly propagating slow magnetoacostic waves in off-limb polar regions and an indication that these propagating waves are influenced by some form of resonant cavity through which they pass. Title: Study of a transient siphon flow in a cold loop Authors: Doyle, J. G.; Taroyan, Y.; Ishak, B.; Madjarska, M. S.; Bradshaw, S. J. Bibcode: 2006A&A...452.1075D Altcode: Context: .The nature of loops is still a matter of debate with several explanations having been put forward. Simultaneous spectral and imaging data have the capacity to provide a new insight into mass motions, dynamics and energetics of loops.
Aims: .We report on spectral data taken with the Solar Ultraviolet Measurements of Emitted Radiation spectrograph (SUMER) and imaging data from the Transition Region and Coronal Explorer (TRACE) of a transient event which occurred in a cold loop, lasting a few minutes.
Methods: .A sequence of TRACE images in the 1550 Å and 171 Å filters show a disturbance which originated at one foot-point and propagates along the loop. The SUMER slit was placed at the other foot-point of the loop. In order to interpret the results, numerical simulations were performed with the results then converted into observable quantities and compared with the data.
Results: .During the event a radiance increase and a relative red shift of ≈ 20~km s-1 was detected in the N v 1238.82 Å line. 1D numerical simulations are performed and observable quantities derived from the results of the simulations. The observed dynamic behaviour of the N v 1238.82 Å line profiles was recovered.
Conclusions: .The results suggest that the observations could be interpreted in terms of a short-lived siphon flow reaching a speed of 120~km s-1 and driven by a nonlinear heating pulse. The energies required to drive the observed red-shifts are estimated to be about 1025 erg. The absence of a significant blue-shift caused by the return flow is explained. Title: Macrospicules and blinkers as seen in Shutterless EIT 304 Å Authors: Madjarska, M. S.; Doyle, J. G.; Hochedez, J. -F.; Theissen, A. Bibcode: 2006A&A...452L..11M Altcode: Aims.Small-scale transient phenomena in the solar atmosphere are believed to play a crucial role in the coronal heating and solar wind generation. This study aims at providing new observational evidence on blinkers and macrospicules appearance in imager data and in doing so, establish the long disputed relationship between these phenomena.
Methods: .We analyse unique high-cadence images in the transition region He ii 304 Å line obtained in a shutterless mode of the Extreme-ultraviolet Imaging Telescope on board the Solar and Heliospheric Observatory. The data have a cadence of approximately 68 s and a pixel size of 2.62 arcsec. The events are identified through an automatic brightenings identification procedure. Features showing a jet-like structure seen in projection on the disk were selected and their light-curve further analysed.
Results: .The temporal evolution of the intensity in three events is shown, two of them seen on-disk as jet-like features and one above the limb. The flux increase, size and duration derived from the light-curve of the on-disk events show an identity with the blinker phenomenon.
Conclusions: .The light curves of these events suggest that the off-limb and on-disk features are in fact one and the same phenomenon and therefore that some blinkers are the on-disk counterparts of macrospicules. Title: Multi-wavelength study of a high velocity event near a sunspot Authors: Lin, Chia-Hsien; Banerjee, D.; O'Shea, E.; Doyle, J. G. Bibcode: 2006A&A...450.1181L Altcode: Context: .Jets with velocities higher than 200 km s-1 are often observed in the X-ray spectral range in the solar atmosphere, however, very few such objects are observed in the EUV range.
Aims: .We report on an eruptive event observed in the south-west side of a sunspot, within active region, AR0554, in a range of spectral lines formed in the transition region and corona.
Methods: .The main data were time-series observations obtained with the Coronal Diagnostic Spectrometer (CDS), in addition to images from the Michelson Doppler Imager (MDI) and Extreme ultraviolet Imaging Telescope (EIT) on board the Solar and Heliospheric Observatory. Additional high resolution images from the Transition Region and Coronal Explorer (TRACE) were also used.
Results: .The event brightened a loop connecting the sunspot and a bright-point structure, triggering both a high-speed flow in the loop and a transient, low-speed ambient flow into the sunspot. The energy released is quickly conducted to the chromosphere, as deduced from the TRACE 1600 Å images and the light curve of He i 522 Å as seen by CDS. The results from our multi-wavelength study further indicates that the effect of the eruptive event may have reached temperatures higher than 2 × 106 K. Relative Doppler velocities of over 300 km s-1 were detected in the transition region line, O v 629 Å.
Conclusions: .The multi-wavelength analysis indicates that the event is likely due to fast magnetic reconnection in the transition region. The velocities detected are consistent with the results obtained by the evaporation jet model. Title: Where Are the Roots of the Fast Solar Wind? . Authors: Popescu, Miruna Daniela; Doyle, John Gerard Bibcode: 2006RoAJ...16S.195P Altcode: 2006RoAJS..16..195P No abstract at ADS Title: Repetitive occurrence of explosive events at a coronal hole boundary Authors: Doyle, J. G.; Popescu, M. D.; Taroyan, Y. Bibcode: 2006A&A...446..327D Altcode: SUMER/SoHO data taken at a coronal hole boundary show a repetitive explosive event occurrence rate of around 3 min increasing to over 5 min towards the end of the activity. We suggest that the neighbouring oppositely directed closed and open field lines at the coronal hole boundary undergo repetitive reconnection seen as a sequence of explosive events. The repetitive reconnection may be triggered by transverse oscillations of the flux tubes in the closed field line region. These oscillations periodically separate and bring together the closed and open field lines on the two sides of the coronal hole boundary. An important indicator favouring the interpretation in terms of a kink mode is the observed increase in the oscillation period. Title: Off-limb coronal loop dynamics as seen from CDS, EIT and TRACE Authors: Banerjee, D.; O'Shea, E.; Doyle, J. G. Bibcode: 2006cosp...36..780B Altcode: 2006cosp.meet..780B Observations have revealed the existence of weak transient disturbances in extended coronal loop systems These propagating disturbances PDs originate from small scale brightenings at the footpoints of the loops and propagate upward along the loops In all cases observed the projected propagation speed is close to but below the expected sound speed in the loops This suggest that the PDs could be interpreted as slow mode MHD waves Interpreting the oscillation in terms of different wave modes and or plasma motions always depend on the line of sight as we observe in the limb or on the center of the disk The JOP 165 campaign will address some of these questions MDI and TRACE photospheric and UV imaging of TRACE and SPIRIT have been acquired simultaneously with high temporal and spatial coverage along with the spectroscopic data from CDS EIT was operated in the shutterless mode to achieve high Cadence Some of the off-limb active region dynamics and oscillations observed during this JOP campaign will be focussed in this presentation Plasma condensations and temporal variations in active region loops will be also addressed Title: Polar and equatorial Coronal holes and the solar wind Authors: Banerjee, D.; O'Shea, E.; Doyle, J. G. Bibcode: 2006cosp...36..771B Altcode: 2006cosp.meet..771B Coronal holes are low density regions where the solar magnetic field is open to interplanetary space thus provides the sun s magnetic connection to the heliosphere The fast solar wind is believed to be originating from coronal holes We study the variation of the line width and electron density as a function of height above coronal holes from forbidden spectral lines of Si VIII The spectra were obtained with the Solar Ultraviolet Measurements of Emitted Radiation spectrometer flown on the it Solar and Heliospheric Observatory spacecraft The observations concentrate on the dark regions outside the plumes which are believed to be the locations where the fast solar wind originates We also examine long spectral time series with the Coronal Diagnostic Spectrometer CDS on-board SoHO The observations were obtained with several transition region and coronal lines We study the dynamics of coronal holes in the polar regions and also in the equatorial regions on the disk From a study of the phase delays between flux and velocity measurements I-V we find evidence for magnetoacoustic waves Measurements of phase delays between different line pairs reveals that the measured phases tend to line up along diagonal lines corresponding to fixed time delays From the orientation of the slopes of these diagonal lines we can infer that the higher temperature lines lag the cooler temperature lines suggesting the outward propagation of waves From estimates of the formation heights of the lines and using the measured time delays we estimate Title: Nanoflare heating of coronal loops: hydrodynamic response and observational consequences Authors: Taroyan, Y.; Bradshaw, S. J.; Doyle, J. G. Bibcode: 2006A&A...446..315T Altcode: The plasma response inside a semicircular coronal loop heated by nanoflares is examined. The loop is thermally and gravitationally stratified. The losses due to thermal conduction and radiation are balanced by localised energy pulses randomly deposited along the loop. The initial stage of the loop evolution during which the temperature along the loop gradually increases from chromospheric to coronal values is completed about 20 minutes after the start of the heating. The random heating produces a thin transition region which is in a continuous motion. The profiles of the C IV, O VI, Ne VIII and Mg X resonance lines, which have peak formation temperatures covering the upper transition region and lower corona, are synthesised. The line shifts and the average shifts are calculated and compared with the observations. It is shown that the nanoflare heating mechanism may reproduce the observed dynamics of the transition region lines. The calculated and previously measured average Doppler shift values are in good agreement for the studied spectral lines except for the C IV line. Possible reasons for this discrepancy are discussed. The study also shows that the nanoflares could contribute to the oscillation power often seen in the mHz ranges. The power peak of the resulting oscillations is near 2 mHz. Title: The extent of 3-min oscillations in regions other than sunspot plumes Authors: Lin, C. -H.; Banerjee, D.; Doyle, J. G.; O'Shea, E. Bibcode: 2005A&A...444..585L Altcode: The active region, AR0554, was observed with NIS/CDS on board SoHO to examine the extent and range of oscillations from a range of features. Among all the NIS spectral lines analysed, significant oscillations were found in Si xii 520 Å, Mg x 625 Å, O v 629 Å, and He i 522 Å. The periods of the strongest oscillations in these lines were ≈10-20 min. After the dominant 10-20 min oscillations were filtered out from these lines, only O v 629 Å showed significant (i.e. above the 95% significance level) shorter-period oscillations. Specifically, we found that weak but significant 3-min oscillations are not confined to the umbra/plume but can be seen in many bright locations. The duration of these non-umbral 3-min oscillations is mostly ≈20 min. In contrast, the 3-min oscillations within the umbra are strong and stable for longer than 50 min. The duration could be related to the size of the oscillating source region, rather than the lifetime of the oscillation. To find the possible sources of these 3-min oscillations outside of the umbra, we compared the oscillations of single pixels in different regions. The results of our comparison indicate a possible connection between the magnetic fields and the oscillations. Therefore, we suggest that 3-min oscillations may exist in many magnetic structures, but are often too weak to be seen in an unfiltered signal. Title: Variation of Line Widths in Polar Off-Limb Regions Authors: Banerjee, D.; O'Shea, E.; Doyle, J. G. Bibcode: 2005ESASP.600E..43B Altcode: 2005dysu.confE..43B; 2005ESPM...11...43B No abstract at ADS Title: Study of a Transient Siphon Flow in a Cold Loop Authors: Taroyan, Y.; Doyle, J. G.; Ishak, B.; Madjarska, M. S.; Bradshaw, S. J. Bibcode: 2005ESASP.600E..25T Altcode: 2005ESPM...11...25T; 2005dysu.confE..25T No abstract at ADS Title: Optical and EUV observations of solar flare kernels Authors: García-Alvarez, D.; Johns-Krull, C. M.; Doyle, J. G.; Ugarte-Urra, I.; Madjarska, M. S.; Butler, C. J. Bibcode: 2005A&A...444..593G Altcode: We present high-resolution spectral observations, covering the entire optical region (3800-9000 Å), of a solar flare observed during a multi-wavelength campaign. The flare, recorded on 2002 January 11, was a medium solar flare event (GOES class C7.5). The spectral observations were carried out using the Hamilton echelle spectrograph on the coudé auxiliary telescope at Lick Observatory and with the Coronal Diagnostic Spectrometer (CDS) on board SoHO. The high signal-to-noise optical spectra are analysed using the same techniques as we applied to stellar flare data. Hα images obtained at Big Bear Solar Observatory (BBSO), plus magnetograms obtained with the Michelson Doppler Imager (MDI) on board SoHO and Transition Region And Coronal Explorer (TRACE) 1600 Å were used in the flare analysis. We observe stellar-like behaviour in the main solar chromospheric activity indicators, which show either filling-in or emission during the flare. We find that the Balmer and Ca II lines show asymmetric profiles, with red-shifted wings and blue-shifted cores. This behaviour could be explained by material expanding. During the flare, the Mg i and Fe i lines show a filling-in of the line profile indicating that the flare affected the lower atmosphere. There is some evidence for pre-flare heating as seen in Fe xix 592 Å. Furthermore, O v 629 Å shows an increase in flux some 10 min. before the coronal lines, perhaps indicating particle beam heating in the initial stages of the flare. We have also determined the main physical parameters at flare maximum. The electron densities and electron temperatures found for the flare imply that the Balmer emitting plasma originates in the chromosphere. The physical parameters obtained for the modelled flare are consistent with previously derived values for solar flares. Title: Very long period activity at the base of solar wind streams Authors: Popescu, M. D.; Banerjee, D.; O'Shea, E.; Doyle, J. G.; Xia, L. D. Bibcode: 2005A&A...442.1087P Altcode: Using time series data of spectral lines originating from a wide range of temperatures in the solar transition region, above a polar coronal hole, from SUMER (Solar Ultraviolet Measurements of Emitted Radiation) on SoHO (Solar and Heliospheric Observatory), we report on the detection of very long (≈170 min) periodic intensity fluctuations, above the limb. Our data also reveal long periodicities (10 90 min), previously observed with other SoHO instruments. With the acoustic cut-off frequency implying a maximum allowable period of ≈90 min, it is unclear whether these intensity fluctuations are due to waves or are the result of a recurrent magnetic reconnection process. Title: Detection of Waves in the Equatorial Coronal Holes Authors: Banerjee, D.; O'Shea, E.; Doyle, J. G. Bibcode: 2005ESASP.596E..41B Altcode: 2005ccmf.confE..41B No abstract at ADS Title: Spicules and Blinkers as Seen in Shutterless EIT 304 Å Authors: Madjarska, M. S.; Doyle, J. G.; Hochedez, J. F.; Theissen, A. Bibcode: 2005ESASP.596E..73M Altcode: 2005ccmf.confE..73M No abstract at ADS Title: Evidence for explosive event activity originating in the chromosphere Authors: Doyle, J. G.; Ishak, B.; Ugarte-Urra, I.; Bryans, P.; Summers, H. P. Bibcode: 2005A&A...439.1183D Altcode: We report on a joint SUMER, CDS, TRACE study, concentrating on a region which shows prolonged EUV explosive event (EE) activity in the transition region line N v 1238 Å, yet little evidence of such activity in another transition region line O v 629 Å (formed at a similar temperature) which was observed simultaneously. A possible explanation for the lack of major activity in the O v line in several explosive events could be that they originate in the lower chromosphere. This is consistent with the enhancements in the C i 1249 Å line and with the findings of another study which reported time delays between the chromospheric and transition region lines in some EE's using high cadence observations (10 s exposure time) obtained with the SUMER spectrometer in H i Ly 6 (20 000 K) and S vi (200 000 K). Using the generalized collisional-radiative picture, including the population of metastable levels, we derive the density dependent contribution function for both N v 1238 and O v 629 for four values of the electron density; 106 cm-3 representing the low density limit, 109 cm-3 for a typical quiet Sun electron density plus 1011 cm-3 and 1012 cm-3 for an active region. These calculations show that with increasing electron density, both lines shift to slightly lower temperatures. However, the major difference is in the relative increase in the line flux with increasing density. For N v, increasing the density to 1011 cm-3 results in a 60% increase in the line flux, while O v shows a 30% decrease. Increasing the electron density to 1012 cm-3 results in a factor of two decrease in the O v flux, thus making it difficult to detect explosive event activity in this line if the event is formed in the chromosphere. Other explosive events which show simultaneous activity in both lines are probably formed in the transition region. In one such event, activity is observed in both N v and O v, yet nothing in C i. In this event we also observe an increase in the TRACE 173 emission, delayed by ≈40 s compared to the transition region lines. Title: On the Connection Between the Disk and Limb Events Observed by Soho Authors: Xia, L. D.; Popescu, M. D.; Chen, Y.; Doyle, J. G. Bibcode: 2005ESASP.592..575X Altcode: 2005soho...16E.110X; 2005ESASP.592E.110X No abstract at ADS Title: Electron density along a coronal loop observed with CDS/SOHO Authors: Ugarte-Urra, I.; Doyle, J. G.; Walsh, R. W.; Madjarska, M. S. Bibcode: 2005A&A...439..351U Altcode: The analysis of a coronal loop observed by CDS and EIT on board SOHO is presented. The loop was situated above the North-East limb at a latitude of ~48°, being clearly visible in the hottest lines of the dataset, Fe xvi 360.76 Å, i.e. greater than 2 000 000 K. The cooler lines in the sample (i.e. O v 629.73 Å and He i 584.35 Å) showed only a brightening at the footpoints location. Based on the Fe xiv 353.84/334.17 line ratio, the electron density along the loop was determined following three different approaches for the background subtraction. No differences, within the error bars, can be found between the three methods. At the apex, the density is 0.9×109 cm-3, while at the footpoint it is 50% greater, i.e. 1.4×109 cm-3. The inferred filling factor values along the loop, at the formation temperature of the lines, are in the range 0.2-0.9. One dimensional hydrodynamic modelling of the loop along a given field line, gravity neglected, was performed. A minimum χ2 analysis results in a best fit case where the total energy input is directed preferentially to the loop footpoint (the heating rate is three times larger at the base than at the apex). An isochoric solution can not be ruled out completely. The exercise illustrates the necessity of accurate spectral diagnostics in order to derive definite conclusions from theoretical models and suggests the need for simultaneous density and temperature diagnostics. Title: Time series study of EUV spicules observed by SUMER/SoHO Authors: Xia, L. D.; Popescu, M. D.; Doyle, J. G.; Giannikakis, J. Bibcode: 2005A&A...438.1115X Altcode: Here we study the dynamic properties of EUV spicules seen at the solar limb. The selected data were obtained as time series in polar coronal holes by SUMER/SoHO. The short exposure time and the almost fixed position of the spectrometer's slit allow the analysis of spicule properties such as occurrence, lifetime and Doppler velocity. Our data reveal that spicules occur repeatedly at the same location with a birth rate of around 0.16/min as estimated at 10´´ above the limb and a lifetime ranging from 15 down to ≈3 min. We are able to see some spicules showing a process of “falling after rising” indicated by the sudden change of the Doppler velocity sign. A periodicity of ≈5 min is sometimes discernible in their occurrence. Most spicules have a height between 10´´ and 20´´ above the limb. Some can stretch up to 40´´; these “long macro-spicules” seem to be comprised of a group of high spicules. Some of them have an obvious periodicity in the radiance of ≈5 min. Title: Footpoint excitation of standing acoustic waves in coronal loops Authors: Taroyan, Y.; Erdélyi, R.; Doyle, J. G.; Bradshaw, S. J. Bibcode: 2005A&A...438..713T Altcode: A new theoretical model for the study of slow standing sausage mode oscillations in hot (T > 6 MK) active region coronal loops is presented. These oscillations are observed by the SUMER spectrometer on board the SoHO satellite. The model contains the transition region and the upper chromosphere which enables us to study the entire process of hot loop oscillations - from the impulsive footpoint excitation phase to the rapid damping phase. It is shown that standing acoustic waves can be excited by an impulsive heat deposition at the chromospheric footpoint of a loop if the duration of the pulse matches the fundamental mode period. The pulse is immediately followed by a standing wave consistent with the SUMER observations in hot loops. The amount of released energy determines the oscillation amplitude. The combined effects of thermal conduction and radiation on the behaviour of the standing acoustic waves in hot gravitationally stratified loops are investigated. In addition to damping, these effects lead to downflows which are superimposed on the oscillations. The implications of the results in coronal seismology are discussed. Title: Comparison Between Explosive Events of Two Transition Region Lines of Similar Temperatures Authors: Ishak, B.; Doyle, J. G.; Ugarte-Urra, I. Bibcode: 2005PADEU..15...21I Altcode: We present the difference in behavior of two transition region lines at very close temperatures, observed with SUMER/SoHO. N v 1238.82 A shows a series of explosive events with broadenings mostly shifted to the blue. This is not seen in O v 629.73 A, the behavior of which remains "quiet" throughout most of the time series. Title: Electron densities in EUV coronal bright points Authors: Ugarte-Urra, I.; Doyle, J. G.; Del Zanna, G. Bibcode: 2005A&A...435.1169U Altcode: Electron density measurements of six coronal bright points have been obtained using line ratio diagnostics of four ions in the temperature range 1.3-2.0 × 106 K. The results suggest that BP plasma has more similarities to active region plasma than to quiet Sun plasma. Nevertheless, they do not show the exact same behaviour: the increase of electron density at temperatures over log~Te ~ 6.2, observed in the core of active regions, has not been detected. The Fe XII results based on new atomic data, although in better agreement decreasing more than a factor of two the densities obtained with older calculations, are still in some instances higher than those from Si X. This could be a consequence of the inhomogeneity of the plasma in the observed volume. New measurements with a better constriction of the volumetric properties seem necessary to rule out the influence of other factors and confirm whether there is an inconsistency between the ions, perhaps due to line blending problems in the Fe XII lines. Title: On the widths and ratios of Mg X 609.79 and 624.94 Å lines in polar off-limb regions Authors: O'Shea, E.; Banerjee, D.; Doyle, J. G. Bibcode: 2005A&A...436L..35O Altcode: Using measurements of Mg X 609.78 and 624.94 Å lines from the Coronal Diagnostic Spectrometer (CDS) on board SOHO, we seek to examine the variation of line width and line ratio in regions far off-limb at the Northern pole of the Sun. It is found that above ≈1150´´ the ratio of the two coronal Mg X resonance lines reduces to values that might be expected for a more radiatively dominant excitation mode. A comparison of the line widths with these ratios indicates that the line widths start to show a decrease in their values at the location where the dominant excitation changes from being collisionally to radiatively dominant, that is, at ≈1150´´. We suggest that the decrease in the line widths above ≈1150´´ is likely to be due to a reduction in the non-thermal component of the line widths caused by a damping of upwardly propagating Alfvén waves. Title: Blinker/macro-spicule activity in an off-limb polar region Authors: O'Shea, E.; Banerjee, D.; Doyle, J. G. Bibcode: 2005A&A...436L..43O Altcode: Using measurements of O V 629.73 Å from the Coronal Diagnostic Spectrometer (CDS) on board SOHO we report on blinker activity in off-limb regions above the Northern pole of the Sun. The blinkers are found to be occurring above a region showing strong dynamic activity, with evidence for evacuation of plasma. The presence of blinkers is discussed in terms of the heating of spicular material. Title: Coronal oscillations in the vicinity of a sunspot as observed by GIS/CDS Authors: Lin, C. -H.; Banerjee, D.; Doyle, J. G.; O'Shea, E.; Foley, C. R. Bibcode: 2005A&A...434..751L Altcode: In this paper, we present results from a time series analysis of data from the Grazing Incidence Spectrometer (GIS), onboard SoHO. Our observations were concentrated at the boundary between the quiet Sun and an active region, close to a sunspot plume. The dominant oscillations in all the lines studied are of periods longer than 5 min. Although our observations were not taken directly above the sunspot, the 3-min oscillations, which are normally associated with the umbra, are seen in several spectral lines, suggesting some leakage perhaps via plume structures. The oscillations of coronal lines form wavepackets, and are intermittent with no obvious decay. The average time scale of the intermittence is of the order of 20 min, which would correspond to a source size of 2 arcsec. Title: Northern Adriatic Response to a Wintertime Bora Wind Event Authors: Lee, Craig M.; Askari, Farid; Book, Jeff; Carniel, Sandro; Cushman-Roisin, Benoit; Dorman, Clive; Doyle, James; Flament, Pierre; Harris, Courtney K.; Jones, Burton H.; Kuzmic, Milivoj; Martin, Paul; Ogston, Andrea; Orlic, Mirko; Perkins, Henry; Poulain, Pierre-Marie; Pullen, Julie; Russo, Aniello; Sherwood, Christopher; Signell, Richard P.; Thaler, Dietmar Bibcode: 2005EOSTr..86..157L Altcode: During winters, the northern Adriatic Sea experiences frequent, intense cold-air outbreaks that drive oceanic heat loss and imprint complex but predictable patterns in the underlying waters. This strong, reliable forcing makes this region an excellent laboratory for observational and numerical investigations of air-sea interaction, sediment and biological transport, and mesoscale wind-driven flow. Narrow sea surface wind jets, commonly known as ``bora,'' occur when cold, dry air spills through gaps in the Dinaric Alps (the mountain range situated along the Adriatic's eastern shore). Horizontal variations in these winds drive a mosaic of oceanic cyclonic and anticyclonic cells that draw coastal waters far into the middle basin. The winds also drive intense cooling and overturning, producing a sharp front between dense, vertically homogenous waters (North Adriatic Dense Water, or NAdDW) in the north and the lighter (colder, fresher), stratified waters of the Po River plume. Once subducted at the front, the NAdDW flows southward in a narrow vein following the isobaths (contours of constant depth) of the Italian coast. In addition to governing the basin's general circulation, these processes also influence sediment transport and modulate biological and optical variability. Title: Line broadening of EUV lines across the Solar limb: A spicule contribution? Authors: Doyle, J. G.; Giannikakis, J.; Xia, L. D.; Madjarska, M. S. Bibcode: 2005A&A...431L..17D Altcode: Spectral lines formed in the solar transition region show an increase in the line width, peaking at ≈10 000 km above the limb. Looking at a region off-limb with no obvious spicules, the non-spicule region has a significantly smaller line width above 6000 km compared those taken in a spicule region. We suggest that this increase in line broadening is not due to small scale random motions but rather to unresolved line shifts due to spicules and/or macro-spicules activity. Title: Searching for the Origins of the Fast Solar Wind Authors: Popescu, M. D.; Doyle, J. G. Bibcode: 2005ASSL..320..235P Altcode: 2005smp..conf..235P No abstract at ADS Title: The effect of metastable level populations on the ionization fraction of Li-like ions Authors: Doyle, J. G.; Summers, H. P.; Bryans, P. Bibcode: 2005A&A...430L..29D Altcode: Lines from Li-like ions have been known to produce theoretical intensities under-estimated compared to lines of a similar formation temperature. Here we investigate this anomalous behaviour whereby the ionization fractions are calculated using the ADAS code considering the electron density dependence of dielectronic recombination coupled with collisional ionization from metastable levels. For the lines investigated, the line contribution functions show a clear dependence with increasing electron density. For example, C IV 1548 Å shows over a factor of three enhancement for Ne = 1012 cm-3. The increase in the higher temperature lines is lower, but are still in the range of 30 to 60%. Furthermore, all the lines have their peak contribution shifted to lower temperature. Calculating the total radiative power output at an electron density of 1011 cm-3, we find that the difference in the transition region is 10-15% while above 106 K the difference is around 30% compared to the low density value. Title: Impulse Excitation and Damping of Slow Standing Mode Oscillations in Hot Coronal Loops Authors: Taroyan, Y.; Erdélyi, R.; Doyle, J. G. Bibcode: 2004ESASP.575..443T Altcode: 2004soho...15..443T No abstract at ADS Title: Detection of Long Periodwaves in the Polar Coronal Holes Authors: Banerjee, D.; O'Shea, E.; Doyle, J. G.; Poedts, S. Bibcode: 2004ESASP.575..136B Altcode: 2004soho...15..136B No abstract at ADS Title: Temporal Evolution of the Magnetic Network in Polar Coronal Holes Authors: Popescu, M. D.; Xia, L. D.; Doyle, J. G. Bibcode: 2004ESASP.575..513P Altcode: 2004soho...15..513P No abstract at ADS Title: Joint Observing Program 166: Multi-Instrumental Study of Extreme-Ultraviolet Coronal Bright Points Authors: Ugarte-Urra, I.; Doyle, J. G. Bibcode: 2004ESASP.575..535U Altcode: 2004soho...15..535U No abstract at ADS Title: Coronal Oscillations in the Vicinity of a Sunspot as Observed by GIS/CDS Authors: Lin, C. H.; Banerjee, D.; Doyle, J. G.; O'Shea, E. Bibcode: 2004ESASP.575..416L Altcode: 2004soho...15..416L No abstract at ADS Title: Determining the Temperature Profile Along a Plasma Loop Iii: Spectrometers Verus Imagers Authors: Walsh, R. W.; Ugarte-Urra, I.; Doyle, J. G.; Noglik, J. B. Bibcode: 2004ESASP.575..567W Altcode: 2004soho...15..567W No abstract at ADS Title: Dynamic Properties of Solar Spicules Observed by SUMER/SOHO Authors: Xia, L. D.; Popescu, M. D.; Doyle, J. G. Bibcode: 2004ESASP.575..362X Altcode: 2004soho...15..362X No abstract at ADS Title: Transition region small-scale dynamics as seen by SUMER on SOHO Authors: Teriaca, L.; Banerjee, D.; Falchi, A.; Doyle, J. G.; Madjarska, M. S. Bibcode: 2004A&A...427.1065T Altcode: High spectral, spatial and temporal resolution UV observations of the quiet Sun transition region show a highly structured and dynamical environment where transient supersonic flows are commonly observed. Strongly non-Gaussian line profiles are the spectral signatures of these flows and are known in the literature as explosive events. In this paper we present a high spatial resolution (≈ 1'') spectroheliogram of a 273''× 291'' area of the quiet Sun acquired with SUMER/SOHO in the O VI spectral line at λ103.193 nm. The extremely high quality of these observations allows us to identify tens of explosive events from which we estimate an average size of 1800 km and a birthrate of 2500 s-1 over the entire Sun. Estimates of the kinetic and enthalpy fluxes associated with these events show that explosive events are not important as far as solar coronal heating is concerned. The relationship with the underlying photospheric magnetic field is also studied, revealing that explosive events generally occur in regions with weak (and, very likely, mixed polarity) magnetic flux. By studying the structure of upward and downward flows exceeding those associated to average quiet Sun profiles, we find a clear correlation between the ``excess'' flows and the magnetic network. However, although explosive events are always associated with flow patterns often covering areas larger than the explosive event itself, the contrary is not true. In particular, almost all flows associated with the stronger concentrations of photospheric magnetic flux do not show non-Gaussian line profiles. In some cases, non-Gaussian line profiles are associated with supersonic flows in small magnetic loops. The case of a small loop showing a supersonic siphon-like flow of ≈130 km s-1 is studied in detail. This is, to our knowledge, the first detection of a supersonic siphon-like flow in a quiet Sun loop. In other cases, the flow patterns associated with explosive events may suggest a relation with UV spicules. Title: CDS wide slit time-series of EUV coronal bright points Authors: Ugarte-Urra, I.; Doyle, J. G.; Nakariakov, V. M.; Foley, C. R. Bibcode: 2004A&A...425.1083U Altcode: Wide slit (90''×240'') movies of four Extreme Ultraviolet coronal bright points (BPs) obtained with the Coronal Diagnostic Spectrometer (CDS) on board the Solar and Heliospheric Observatory (SoHO) have been inspected. The wavelet analysis of the He I 584.34 Å, O V 629.73 Å and Mg VII/IX 368 Å time-series confirms the oscillating nature of the BPs, with periods ranging between 600 and 1100 s. In one case we detect periods as short as 236 s. We suggest that these oscillations are the same as those seen in the chromospheric network and that a fraction of the network bright points are most likely the cool footpoints of the loops comprising coronal bright points. These oscillations are interpreted in terms of global acoustic modes of the closed magnetic structures associated with BPs. Title: Network boundary origins of fast solar wind seen in the low transition region? Authors: Popescu, M. D.; Doyle, J. G.; Xia, L. D. Bibcode: 2004A&A...421..339P Altcode: We present a study of a high spatial resolution raster acquired on-disk with the SUMER (Solar Ultraviolet Measurements of Emitted Radiation) grating spectrograph on SoHO (the Solar and Heliospheric Observatory) in a polar Coronal Hole (CH) region. We analyse two EUV emission lines, representing the properties of solar plasma in the low transition region (TR), O III 703.87 Å (maximum electron temperature, Te≈ 8× 104 K), as well as in the corona, Mg IX 706.02 Å (Te≈ 106 K). For Mg IX, we find that low CH intensities correspond to negative Doppler velocities (outflows) of ≈5 km s-1. Along the quiet Sun (QS)/CH boundaries, the coronal plasma begins to be more red-shifted. A coronal bright point (BP) located within the CH is blue-shifted in the coronal line. In the TR line, the outer region of the BP is red-shifted at ≈5 km s-1, but, towards its middle, the shift is around zero. The O III line, although it shows predominant downward motion of ≈5.5 km s-1 in the CH and ≈6 km s-1 in the QS, it also has blue-shifts arranged in a small-scale network pattern with average negative values of 3.5 km s-1 in CH and 3 km s-1 in the QS. The blue-shifts are caused either by plasma outflows of a few km s-1, or by transient events such as bi-directional jets which dislocate plasma to upward velocities even higher than 100 km s-1. The outflows originate predominantly from the intersection between the magnetic network and the inter-network cells (network boundaries). The bi-directional jets are found along the CH/QS boundaries, and, moreover, in locations where the plasma seen in the Mg IX line is blue-shifted, but very close to small red-shifted regions. Another interesting change in behaviour is observed at the QS/CH boundaries, in the O III line, where plasma from the network changes its velocity sign, becoming red-shifted. Our results constitute the lowest-in-altitude observed signature of plasma outflows from the chromospheric network boundaries inside a CH. We have derived this conclusion from direct correlation between Doppler velocity and the intensity of the O III 702.87 Åline. Title: Solar Oscillations and the Magnetic Atmosphere Authors: Taroyan, Y.; Doyle, J. G. Bibcode: 2004PADEU..14..129T Altcode: With the launch of the SOHO and TRACE satellites two new branches of solar physics have emerged: time-distance helioseismology and coronal seismology. In time-distance helioseismology the travel time of the acoustic waves between different points on the solar surface is measured to infer the local structure and properties of the subsurface layers of the Sun. The travel time changes due to the atmospheric magnetic field are evaluated theoretically. Coronal seismology utilises MHD waves in solar coronal structures as a tool to diagnose the physical parameters of the coronal plasma. Theoretical modelling of recently observed slow standing mode oscillations in stratified loops is presented. It is shown that large-amplitude resonant standing waves can be driven by small-amplitude oscillations at the chromospheric footpoints of the loops. The periods and the behaviour of these waves are different from those predicted by the classical theory of isothermal loop oscillations. The possible relationsheep between the oscillations studied in time-distance helioseismology and in coronal seismology is addressed. Title: Coronal response of Bi-directional Jets Authors: Doyle, J. G.; Madjarska, M. S.; DzifČÁkovÁ, E.; Dammasch, I. E. Bibcode: 2004SoPh..221...51D Altcode: EUV bi-directional jets are a prominent class of phenomena characterizing the solar transition region. Using simultaneously obtained SUMER observations in the chromospheric Si ii 1251.16 Å and C i 1251.17 Å, transition region N v 1238.8 Å and coronal Mg x 625 Å lines we show an example of a bi-directional jet observed in the chromospheric and the transition region lines but not showing any detectable signature in the coronal line. The phenomenon, however, was also clearly detected by the TRACE imager with the 171 Å filter. This discrepancy is explained here with a non-Maxwellian electron distribution which makes a significant fraction of the plasma in the TRACE 171 Å pass-band to be derived from temperatures around ≈ 300 000 K, as opposed to ≈ 800 000 K. This could have implications for other phenomena observed in the TRACE pass-bands, including the transition region `moss' and the 3- and 5-min oscillations. Title: New insight into the blinker phenomenon and the dynamics of the solar transition region Authors: Doyle, J. G.; Roussev, I. I.; Madjarska, M. S. Bibcode: 2004A&A...418L...9D Altcode: We present, for the first time, blinker phenomena being associated with brightenings in pre-existing coronal loops registered by the Extreme-ultraviolet Imaging Telescope (EIT) in Fe XII 195 Å. The brightenings occur during the emergence of new magnetic flux as registered by the Big Bear Solar Observatory (BBSO) magnetograph. The blinkers were identified using simultaneous observations obtained with the Coronal Diagnostic Spectrometer (CDS) and Solar Ultraviolet Measurements of Emitted Radiation (SUMER) spectrograph. In light of the new observational results, we present one possible theoretical interpretation of the blinker phenomenon. We suggest that the blinker activity we observe is triggered by interchange reconnection, serving to provide topological connectivity between newly emerging flux and pre-existing flux. The EIT images show the existence of loop structures prior to the onset of the blinker activity. Based on the available spatial resolution the blinker occurs within, or nearby, an existing coronal loop. The temperature interfaces created in the reconnection process between the cool plasma of the newly emerging loop and the hot plasma of the existing loop are what we suggest to causes the observed activity seen in both the SUMER and CDS data. As the temperature interfaces propagate with the characteristic speed of a conduction front, they heat up the cool chromospheric plasma to coronal temperatures, an increasing volume of which brightens at transition region temperatures. We believe this new interpretation gives further qualitative understanding about the evolution of newly emerging flux on the Sun. This also provides new insight into the dynamic nature of the solar transition region. Title: Signature of oscillations in coronal bright points Authors: Ugarte-Urra, I.; Doyle, J. G.; Madjarska, M. S.; O'Shea, E. Bibcode: 2004A&A...418..313U Altcode: A detailed study of two consecutive bright points observed simultaneously with the Coronal Diagnostic Spectrometer (CDS), the Extreme ultraviolet Imaging Telescope (EIT) and the Michelson Doppler Imager (MDI) onboard the Solar and Heliospheric Observatory (SOHO) is presented. The analysis of the evolution of the photospheric magnetic features and their coronal counterpart shows that there is a linear dependence between the EIT Fe XII 195 Å flux and the total magnetic flux of the photospheric bipolarity. The appearance of the coronal emission is associated with the emergence of new magnetic flux and the disappearance of coronal emission is associated with the cancellation of one of the polarities. In one of the cases the disappearance takes place ∼3-4 h before the full cancellation of the weakest polarity.

The spectral data obtained with CDS show that one of the bright points experienced short time variations in the flux on a time scale of 420-650 s, correlated in the transition region lines (O V 629.73 Å and O III 599.60 Å) and also the He I 584.34 Å line. The coronal line (Mg IX 368.07 Å) undergoes changes as well, but on a longer scale. The wavelet analysis of the temporal series reveals that many of these events appear in a random fashion and sometimes after periods of quietness. However, we have found two cases of an oscillatory behaviour. A sub-section of the O V temporal series of the second bright point shows a damped oscillation of five cycles peaking in the wavelet spectrum at 546 s, but showing in the latter few cycles a lengthening of that period. The period compares well with that detected in the S VI 933.40 Å oscillations seen in another bright point observed with the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) spectrometer, which has a period of 491 s. The derived electron density in the transition region was 3×1010 cm-3 with some small variability, while the coronal electron density was 5×108 cm-3. Title: Evidence of Magnetic Reconnection along Coronal Hole Boundaries Authors: Madjarska, M. S.; Doyle, J. G.; van Driel-Gesztelyi, L. Bibcode: 2004ApJ...603L..57M Altcode: The present study reveals for the first time the existence of bidirectional jets, which are a signature of magnetic reconnection, occurring along coronal hole boundaries. The Solar Ultraviolet Measurement of Emitted Radiation spectrometer observations obtained in the N IV 765.15 Å (1.3×105 K) and Ne VIII 770.42 Å (6×105 K) emission lines in an equatorial extension of a polar coronal hole, known as the ``Elephant's Trunk'' coronal hole, show small regions of a few arcseconds size with strong blue- and redshifted emission reaching Doppler shifts of up to 150 km s-1, i.e., bidirectional jets. The jets' number density along coronal hole boundaries was found to be about 4-5 times higher with respect to the quiet Sun. Title: Bi-Directional Jets at Coronal Hole Boundaries Authors: Madjarska, M. S.; Doyle, J. G.; van Driel-Gesztelyi, L. Bibcode: 2004ESASP.547..397M Altcode: 2004soho...13..397M Our study reveals, for the first time, the presence of bi-directional jets which are considered to be signatures of magnetic reconnection occurring along coronal hole boundaries. The SUMER observations obtained in Ne VIII 770.42 Å (6 10 K) and N IV 765.15 Å (1.3 10 K) show small regions of a few arcsec size with strong blueand red-shifted emission reaching Doppler shifts up to 150 km s which appear along the coronal hole boundaries where evolving loop systems are present. Title: A Study of Transition Region and Coronal Doppler Shifts in a Solar Coronal Hole Authors: Popescu, M. D.; Doyle, J. G. Bibcode: 2004ESASP.547..363P Altcode: 2004soho...13..363P We present a study of a high spatial resolution raster scan taken on-disk with the SoHO/SUMER spectrograph in a solar polar Coronal Hole (CH) region. We have analysed the line shifts and widths of two EUV emitting ions, O III 703.87 Å and Mg IX 706.02 Å. Our results confirm plasma outflows from CHs. In particular, the correlation between the intensity and the Doppler velocity in the case of the O III line constitute the lowest precise indication of fast wind streams seen originating from the network boundaries in the transition region. Title: Time-Distance Helioseismology and the Magnetic Atmosphere of the Sun Authors: Taroyan, Y.; Erdélyi, R.; Doyle, J. G. Bibcode: 2004ESASP.547...33T Altcode: 2004soho...13...33T No abstract at ADS Title: Oscillations in Coronal Bright Points Authors: Ugarte-Urra, I.; Doyle, J. G.; Madjarska, M. S.; O'Shea, E. Bibcode: 2004ESASP.547..329U Altcode: 2004soho...13..329U No abstract at ADS Title: Coronal Oscillations above Sunspots? Authors: Doyle, J. G.; Dzifćáková, E.; Madjarska, M. S. Bibcode: 2003SoPh..218...79D Altcode: Observational data clearly indicate the presence of 3-min oscillations in sunspots in spectral lines covering a vast temperature range from the low chromosphere to those lines normally associated with coronal temperatures. We show that after folding in the sunspot plume emission measure distribution, the contribution functions for lines normally formed just below 1×106 K are shifted to lower temperatures. For example, the Fe ix 171 Å line is shifted to 6×105 K for a Maxwellian distribution and to less than 5×105 K with a non-Maxwellian distribution. Other lines such as Mg ix 368 Å will also be affected. This then questions some previous work regarding the suggested detection of 3-min oscillations in the corona above sunspots. Title: MUSICOS 1998: Observations of Rotational Modulation and Flares on the RS CVn Binary HR1099 Authors: García-Alvarez, D.; Foing, B. H.; Montes, D.; Oliveira, J.; Doyle, J. G.; MUSICOS 98 Collaboration Bibcode: 2003csss...12..958G Altcode: 2001astro.ph..9235G We present simultaneous and continuous observations of Hα, Hβ, ion{Na}{1} D1, D2, ion{He}{1} D3 and ion{Ca}{2} H & K lines of the chromospherically active binary HR 1099. We have observed HR 1099 for more than 3 weeks almost continuously and monitored two flares. An increase in Hα and ion{Ca}{2} H & K, Hβ and ion{He}{1} D3 and a strong filling-in of the ion{Na}{1} D1, D2 during the flares are observed. We have found that the flares took place at the same phase (0.85) of the binary orbit, and both of them seems to occur near the limb. Title: Line Shift Variations in Solar Transition Region Lines Authors: Doyle, J. G.; Madjarska, M.; Giamikakis, J.; Teriaca, L.; Roussev, I. Bibcode: 2003csss...12..619D Altcode: Two high time cadence datasets, taken in C III 977Å and O VI 1032Å were analysed in an effort to establish the extent of the variability in the Doppler-shift of typical mid-transition region lines. In C III, the shortest time-scale variability seems to occur in the network boundary regions where the line-shift can vary by 7-8 km s-1 in less than 1 min. The internetwork region also shows variability although this tends to be longer lived, ∼2-3 mins. The average C III line-shift in all regions is for a red-shift of ∼ 8 km s-1 in very good agreement with that derived by others. Furthermore, there does not seem to be any obvious difference in the average line-shift in network and internetwork regions. On a few rare occasions, the C III line was blue-shifted. The O VI line was also red-shifted with the network region showing evidence for a periodicity. These observations were compared to model line profiles based on the response of a 2D MHD environment representing the solar transition region to micro-scale energy depositions. A variety of temperatures at which the energy deposition takes place as well as the amount of energy deposited was examined. Title: Sunspot plume observations in the EUV. The gas pressure differential between the umbra and surrounding region Authors: Doyle, J. G.; Madjarska, M. S. Bibcode: 2003A&A...407L..29D Altcode: The electron density over a bright sunspot plume region was evaluated using lines within the O V 760 Å multiplet. The plume showed an intensity enhancement factor of ~9 in the O V lines compared to regions outside the sunspot umbra. Internal agreement between the various ratios is excellent which would suggest that the O V lines do not suffer from blending problems. The derived mean electron densities for the sunspot plume is log Ne/cm-3 ~ 9.9 compared to log Ne/cm-3 ~ 10.20-10.45 in the surrounding area. The derived gas pressure in the plume compared to that outside leads weight to the suggestion that it is plasma flowing from outside the spot into the umbra at transition region temperatures that is the main cause of the down-flows. The plume non-thermal velocities are 5 to 10 km ; s-1 smaller than those measured in regions external to the spot, suggesting significantly less turbulence within the umbra. Title: Simultaneous observations of solar transition region blinkers and explosive events by SUMER, CDS and BBSO. Are blinkers, explosive events and spicules the same phenomenon? Authors: Madjarska, M. S.; Doyle, J. G. Bibcode: 2003A&A...403..731M Altcode: The SoHO discovery of the new ``blinker'' phenomena focused our study on the search of its relation to already known phenomena such as explosive events and spicules. The study was performed using a specially planned joint observing program involving the Coronal Diagnostic Spectrometer (CDS), Solar Ultraviolet Measurements of Emitted Radiation spectrograph (SUMER) and Big Bear Solar Observatory (BBSO) magnetograph. Within each blinker, the SUMER data reveal the presence of small-scale (3 arcsec-5 arcsec), short-lived (2-3 min) bright features not seen in the CDS data which has sometimes being interpreted as oscillations in SUMER data. With this data we have clearly identified UV explosive events in CDS data. The explosive events show a size close to the small-scale brightenings forming the blinker core. However, they appear in the SUMER data with their typical strong blue and red wings while the blinker shows at best only a small increase in the emission of the blue and red wings and in most instances the typical transition region red-shift in the center of the line. In all cases the explosive events cover one pixel in CDS corresponding to a size of 4arcsec x 4arcsec -6arcsec . All identified explosive events were located at the border of the bright network i.e. the blinker, in the network or even in the internetwork. From this data, we believe that blinkers and explosive events are two separate phenomena not directly related or triggering each other. In this study, the Doppler shift was derived in a blinker phenomenon for the first time. It ranges from -5 to 25 km ; s-1 and is predominantly red-shifted. The observed magnetic flux increase during the blinker phenomena seems to play a crucial role in the development of this event. We suggest that ``blinkers'' maybe the on-disk signature of spicules. Title: Doppler images of the RS CVn binary HR 1099 (V711 Tau) from the MUSICOS 1998 campaign Authors: García-Alvarez, D.; Barnes, J. R.; Collier Cameron, A.; Doyle, J. G.; Messina, S.; Lanza, A. F.; Rodonò, M. Bibcode: 2003A&A...402.1073G Altcode: 2003astro.ph..3154G We present Doppler Images of the RS CVn binary system HR 1099 (V711 Tau) from spectra taken in two different sites, KPNO and MSO, during the MUSICOS 1998 campaign. Contemporaneous APT photometry is used to constrain the Doppler Images. The resulting maximum entropy reconstructions based on the least-squares deconvolved profiles, derived from ~ 2000 photospheric absorption lines, reveal the presence of starspots at medium-high latitudes. We have obtained maps for both components of the binary system for the first time. The predominant structure in the primary component is an off-centered polar spot, confirming previous works on the same target by using independent codes. The result is verified by using both data sets independently. The lower spectral resolution data set gives a less detailed map for the MSO data set. The images obtained for the secondary component show a low latitude spot around orbital phase 0.7. This spot seems to mirror the structure seen on the primary. It might suggest that tidal forces may influence the spot distribution on this binary system.

Based on observations obtained during the MUSICOS 98 MUlti-SIte COntinuous Spectroscopic campaign from Kitt Peak National Observatory, USA, and Mt. Stromlo Observatory, Australia. Title: An EUV Bright Point as seen by SUMER, CDS, MDI and EIT on-board SoHO Authors: Madjarska, M. S.; Doyle, J. G.; Teriaca, L.; Banerjee, D. Bibcode: 2003A&A...398..775M Altcode: This paper presents the formation, evolution and decay of a coronal bright point via a spectroscopic analysis of its transition region counterpart and the evolution of the underlying magnetic bipole during 3 days of almost continuous observations. The data were obtained with various instruments on-board SoHO, including the SUMER spectrograph in the transition region line S VI 933.40 Å, CDS in the He I 584.33, O V 629.73 and Mg IX 368.06 Å lines, plus MDI and EIT. The existence of the coronal feature is strongly correlated with the evolution of the underlying bipolar region. The lifetime of the bright point from the moment when it was first visible in the EIT images until its complete disappearance was ~ 18 hrs. Furthermore, the bright point only became visible at coronal temperatures when the two converging opposite magnetic polarities were ~ 7000 km apart. As far as the temporal coverage of the data permits, we found that the bright point disappeared at coronal temperatures after a full cancellation of one of the magnetic polarities. The spectroscopic analysis reveals the presence of small-scale ( ~ 6 arcsec) transient brightenings within the bright point with a periodicity of ~ 6 min. The Doppler shift in the bright point was found to be in the range of -10 to 10 km ; s-1 although it is dominated by a red-shifted emission which is associated with regions characterized by stronger ``quiet'' Sun photospheric magnetic flux. Small-scale brightenings within the bright point show velocity variations in the range 3-6 km ; s-1. In general the bright point has a radiance ~ 4 times higher than that of the network. No relation was found between the bright point and the UV explosive event phenomena. Title: Simultaneous optical and X-ray observations of flares and rotational modulation on the RS CVn binary HR 1099 (V711 Tau) from the MUSICOS 1998 campaign Authors: García-Alvarez, D.; Foing, B. H.; Montes, D.; Oliveira, J.; Doyle, J. G.; Messina, S.; Lanza, A. F.; Rodonò, M.; Abbott, J.; Ash, T. D. C.; Baldry, I. K.; Bedding, T. R.; Buckley, D. A. H.; Cami, J.; Cao, H.; Catala, C.; Cheng, K. P.; Domiciano de Souza, A., Jr.; Donati, J. -F.; Hubert, A. -M.; Janot-Pacheco, E.; Hao, J. X.; Kaper, L.; Kaufer, A.; Leister, N. V.; Neff, J. E.; Neiner, C.; Orlando, S.; O'Toole, S. J.; Schäfer, D.; Smartt, S. J.; Stahl, O.; Telting, J.; Tubbesing, S. Bibcode: 2003A&A...397..285G Altcode: 2002astro.ph.10230G We present simultaneous and continuous observations of the Hα, Hβ, He I D3, Na I D1, D2 doublet and the Ca II H & K lines for the RS CVn system HR 1099. The spectroscopic observations were obtained during the MUSICOS 1998 campaign involving several observatories and instruments, both echelle and long-slit spectrographs. During this campaign, HR 1099 was observed almost continuously for more than 8 orbits of 2.8 deg. Two large optical flares were observed, both showing an increase in the emission of Hα, Ca II H & K, Hβ and He I D3 and a strong filling-in of the Na I D1, D2 doublet. Contemporary photometric observations were carried out with the robotic telescopes APT-80 of Catania and Phoenix-25 of Fairborn Observatories. Maps of the distribution of the spotted regions on the photosphere of the binary components were derived using the Maximum Entropy and Tikhonov photometric regularization criteria. Rotational modulation was observed in Hα and He I D3 in anti-correlation with the photometric light curves. Both flares occurred at the same binary phase (0.85), suggesting that these events took place in the same active region. Simultaneous X-ray observations, performed by ASM on board RXTE, show several flare-like events, some of which correlate well with the observed optical flares. Rotational modulation in the X-ray light curve has been detected with minimum flux when the less active G5 V star was in front. A possible periodicity in the X-ray flare-like events was also found.

Based on observations obtained during the MUSICOS 98 MUlti-SIte COntinuous Spectroscopic campaign from Observatoire de Haute-Provence, France, Kitt Peak National Observatory, USA, ESO La Silla, Chile, Mt. Stromlo Observatory, Australia, Xinglong National Observatory, China, Isaac Newton Telescope, Spain, Laboratório Nacional de Astrofísica, Brazil, and South African Astronomical Observatory, South Africa. Contemporaneous observations from Catania, Italy and Fairborn Observatories, USA, and on data obtained with the Rossi X-ray Timing Explorer. Title: Transition region small-scale dynamics: UV explosive events Authors: Teriaca, L.; Falchi, A.; Doyle, J. G.; Madjarska, M. S.; Banerjee, D. Bibcode: 2002ESASP.506..777T Altcode: 2002ESPM...10..777T; 2002svco.conf..777T High spectral, spatial and temporal resolution UV observations of the quiet Sun transition region show a highly structured and dynamical environment where transient events such as brightenings, blinkers and explosive events occur continuously. In particular explosive events are characterized by strongly non-Gaussian line profiles witnessing velocities up to 200 km s-1. The high kinetic and enthalpy fluxes associated with these events could be important in the energy balance of the transition region and, perhaps, of the whole corona. In this paper we present a high spatial resolution (~1") spectroheliogram of a 270×290 arcsec2 wide area of the quiet Sun acquired with SUMER/SoHO in the O VI 1032 spectral line. The extremely high quality of these observations allows us to identify tens of explosive events and to study their relationship with the underlying photospheric magnetic field. Moreover, the behaviour of lines emitted by plasma at chromospheric (2×104K) and coronal (106K) temperatures during transition region explosive events is investigated. We conclude that those events do not contribute significantly to the energy balance of the corona and seems typical of structure not obviously connected to the T≥106K corona. Title: Temporal variability in the Doppler-shift of solar transition region lines Authors: Doyle, J. G.; Madjarska, M. S.; Roussev, I.; Teriaca, L.; Giannikakis, J. Bibcode: 2002A&A...396..255D Altcode: High cadence datasets taken in C III 977 Å, O VI 1032 Å and Ne VIII 720 Å were analysed in an effort to establish the extent of the variability in the Doppler-shift of typical mid-transition region lines. The shortest time-scale variability seems to occur in the network boundary regions where the line-shift can vary by 7-8 km s-1 in less than 1 min. The internetwork region also shows variability although this tends to be longer lived, ~ 2-3 min. The average line-shift in C III is a red-shift which ranges from ~ 2 km s-1 to ~ 20 km s-1 with an average value for all regions selected being around 10 km s-1 in very good agreement with that derived by others. The red-shift values indicate a clear difference between network and internetwork regions, with the largest red-shift being present at the network boundary. For O VI, this gives an average red-shift ranging from 5 to 10 km s-1. For Ne VIII, there is a 13 km s-1 difference between internetwork and bright network plasma with the bright network being more red-shifted. This could imply that the bright network regions are dominated by spicule down-flow.\ In the second part we present results from 2-dimensional (2D) dissipative magnetohydrodynamic (MHD) simulations of the response of the solar transition region to micro-scale energy depositions. A variety of temperatures at which the energy deposition takes place as well as the amount of energy deposited are examined. This work is a continuation of previous related simulations where small-scale energy depositions were modelled in 1D hydrodynamics. The observable consequences of such transient events are then computed for three transition region lines, namely C IV 1548 Å, O VI 1032 Å, and Ne VIII 770 Å, under the consideration of non-equilibrium ionization. Title: On the nature of umbral oscillations: theory and observation by CDS/SoHO Authors: Banerjee, D.; O'Shea, E.; Goossens, M.; Poedts, S.; Doyle, J. G. Bibcode: 2002ESASP.506..427B Altcode: 2002ESPM...10..427B; 2002svco.conf..427B We will present solutions for magneto-acoustic-gravity (or MAG) waves. The possible wave modes in the 3-5 min range will be discussed. We will then present observations of sunspots performed in the EUV wavelength range with the Coronal Diagnostic Spectrometer (CDS) on SoHO. We examine the time series for the line intensities and relative velocities and calculate their power spectrum using wavelet transforms. We find oscillations in the chromosphere and transition region above the sunspots in the temperature range logT = 4.6 -5.4. Most of the spectral power above the umbra is contained in the 5-7 mHz frequency range. When the CDS slit crosses the sunspot plume a clear 3 min oscillation is observed. The observations are interpreted in terms of slow magnetoacoustic waves propagating upwards. Title: MUSICOS 1998: Optical and X-rays Observations of Flares on the RS CVn Binary HR 1099 Authors: García-Alvarez, D.; Doyle, J. G.; Foing, B. H.; Oliveira, J. M.; Montes, D. Bibcode: 2002ASPC..277..479G Altcode: 2001astro.ph.10305G; 2002sccx.conf..479G We present simultaneous and continuous observations of H_alpha, H_beta, NaI D_1, D_2 and HeI D_3 lines of the chromospherically active binary HR 1099. We have observed HR 1099 for more than 3 weeks almost continuously and monitored two flares. An increase in H_alpha, CaII H & K, H_beta, HeI D_3 and HeI lambda6678 and a strong filling-in of the NaI D_1, D_2 and MgI b triplet during one of the flares are observed. We have found that the flares took place at the same phase (0.85) of the binary orbit, and both of them seems to occur near the limb. Several X-rays flares were also detected by ASM on board RXTE. Rotational modulation in the X-rays light curve has been detected with maximum flux when the active K1IV star is in front. Title: The OIV and SIV intercombination lines in the ultraviolet spectra of astrophysical sources Authors: Keenan, F. P.; Ahmed, S.; Brage, T.; Doyle, J. G.; Espey, B. R.; Exter, K. M.; Hibbert, A.; Keenan, M. T. C.; Madjarska, M. S.; Mathioudakis, M.; Pollacco, D. L. Bibcode: 2002MNRAS.337..901K Altcode: New electron density diagnostic line ratios are presented for the OIV 2s22p 2P-2s2p24P and SIV 3s23p 2P-3s3p24P intercombination lines around 1400Å. A comparison of these with observational data for the symbiotic star RR Telescopii (RR Tel), obtained with the Space Telescope Imaging Spectrograph (STIS), reveals generally very good agreement between theory and observation. However the SIV2P3/2-4P1/2 transition at 1423.824Å is found to be blended with an unknown feature at 1423.774Å. The linewidth for the latter indicates that the feature arises from a species with a large ionization potential. In addition, the SIV2P1/2-4P3/2 transition at 1398.044Å is identified for the first time (to our knowledge) in an astrophysical source other than the Sun, and an improved wavelength of 1397.166 Å is measured for the OIV2P1/2-4P3/2 line. The OIV and SIV line ratios in a sunspot plume spectrum, obtained with the Solar Ultraviolet Measurements of the Emitted Radiation (SUMER) instrument on the Solar and Heliospheric Observatory, are found to be consistent, and remove discrepancies noted in previous comparisons of these two ions. Title: On the theory of MAG waves and a comparison with sunspot observations from CDS/SoHO Authors: Banerjee, D.; O'Shea, E.; Goossens, M.; Doyle, J. G.; Poedts, S. Bibcode: 2002A&A...395..263B Altcode: We examine the influence of non-adiabatic effects on the modes of an isothermal stratified magnetic atmosphere. We present new solutions for magneto-acoustic-gravity (or MAG) waves in the presence of a radiative heat exchange based on Newton's law of cooling. An analytic expression for the dispersion relation is derived, which allows the effect of a weak magnetic field on the modes to be studied. The insight so gained proves useful in extending the computations to the moderate-high field case. In the second part we present observations of two sunspots obtained in the EUV wavelength range with the Coronal Diagnostic Spectrometer (CDS) on SoHO. We examine the time series for the line intensities and relative velocities and calculate their power spectra using wavelet transforms. We find oscillations in the chromosphere and transition region above the sunspots in the temperature range log T = 4.6-5.4 K. Most of the spectral power above the umbra is contained in the 5-7 mHz frequency range. When the CDS slit crosses the sunspot umbra a clear 3 min oscillation is observed. The observed oscillation frequencies are compared with the computed frequencies and the observations are interpreted in terms of the slow magneto-acoustic waves. Title: Magnetic properties of ultraviolet transient phenomena. Are blinkers and explosive events the same phenomenon? Authors: Madjarska, M. S.; Doyle, J. G. Bibcode: 2002ESASP.505..489M Altcode: 2002solm.conf..489M; 2002IAUCo.188..489M Simultaneous 'quiet' Sun observations were performed on 2001 October 23 with the SUMER and CDS spectrometers on-board SoHO together with the Big Bear Solar Observatory magnetograph. The aim was to study the magnetic properties and distinct nature of the transition region phenomena such as explosive events and blinkers. The different appearance of the two phenomena in both spectrometer observations was analysed. Blinker phenomena were clearly associated with bipolar magnetic regions with always one polarity stronger than the other one. Higher resolution observations are needed in order to associate explosive events with any particular magnetic field changes. Title: Electron density variation in off-limb solar corona structures Authors: Ugarte-Urra, I.; Doyle, J. G.; Madjarska, M. S. Bibcode: 2002ESASP.505..595U Altcode: 2002IAUCo.188..595U; 2002solm.conf..595U We present a study of the electron density variation for off limb observations with the Coronal Diagnostic Spectrometer (CDS) on board SoHO using the density sensitive coronal line ratio Si X (356.0/347.4). The analysis is divided into three parts: the latitudinal variation from 1.01 < r/Rsolar < 1.09, the temporal variation in successive rasters, and the electron density along a hot coronal loop found in one of the rasters. Title: Explosive events and associated periodicities Authors: Giannikakis, I.; Doyle, J. G.; Antonopoulou, E. Bibcode: 2002ESASP.505..413G Altcode: 2002IAUCo.188..413G; 2002solm.conf..413G We studied an explosive event which occurred in the transition region line O VI, in particular we investigate whether this event produced periodicities in the line intensity during its evolution. Title: Slow MAG waves in the sunspot umbra as observed by CDS/SOHO Authors: Banerjee, D.; O'Shea, E.; Doyle, J. G.; Goossens, M.; Poedts, S. Bibcode: 2002ESASP.505..187B Altcode: 2002solm.conf..187B; 2002IAUCo.188..187B We present observations, in the EUV wavelength range, of two sunspots, carried out by the Coronal Diagostic Spectrometer (CDS) on SoHO. We examine the time series for the line intensities and relative velocities and calculate their power spectrum using wavelet transforms. We find oscillations in the chromosphere and transition region above the sunspots in the temperature range logT = 4.6 - 5.4. Most of the spectral power above the umbra are contained in the 5 - 7 mHz frequency range. When the CDS slit croses the sunspot plume a clear 3 in oscillation is observed. We also present new solutions for magnetic-acoustic-gravity (or MAG) waves in the presence of radiative heat exchange based on Newton's law of cooling. The observed oscillation frequencies are compared with the computed frequencies. The observations are interpreted in terms of slow magnetoacoustic waves propagating upwards. Title: Transition region explosive events: Do they have a coronal counterpart? Authors: Teriaca, L.; Madjarska, M. S.; Doyle, J. G. Bibcode: 2002A&A...392..309T Altcode: EUV explosive events are a prominent class of phenomena characterizing the solar transition region. Their correct location in the wider frame-work of the outer solar atmosphere can provide important insight on the nature of the transition region itself and its relationship with the hotter corona and the cooler chromosphere. In this paper we present new high-cadence SUMER observations of the ``quiet'' Sun obtained simultaneously in the mid-transition region N V 1238.8 Å line (1.8x 105 K) and in the coronal Mg X 625 Å line (1.1x 106 K). These observations are aimed at providing information on the behaviour of the coronal plasma during EUV transition region explosive events detected in N V 1238.8 Å. None of the events observed in N V shows any detectable signature in the Mg X line profile or in its integrated intensity. The analysis of 1996 observations obtained simultaneously in N V 1238.8 Å and S II 1253.8 Å (3.5x 104 K) shows, instead, a weak but clear presence of enhanced wings in the S II line profile during a series of events observed in N V. These results suggest that EUV explosive events are not directly relevant in heating the corona and are characteristic of structures not obviously connected with the upper corona. The evidence of a chromospheric response suggests that, contrary to some previous suggestions, explosive events have a chromospheric origin. Title: Transition region counterpart of X-ray/EUV coronal bright points registered by SUMER, CDS, EIT and MDI/SOHO Authors: Madjarska, M. S.; Doyle, J. G. Bibcode: 2002ESASP.508..311M Altcode: 2002soho...11..311M We present a spectroscopic analysis of the transition region counterpart of Coronal Bright Points (BPs). Simultaneous observations obtained with the SUMER spectrometer in the S VI 933.38 Å and Ly 6 930.75 &Aring lines, CDS in the He I 584.33, O V 629.73 and Mg IX 368.06 Å MDI and EIT Fe XII 195 Å on-board SoHO were analysed. The dataset obtained on 1996 October 16, 17 & 18 reveals a complete picture of the formation, temporal evolution and decay of a bright point. The nature of the intensity variations in a BP, its Doppler velocities and its relation to transient phenomena such as explosive events and blinkers are discussed. Title: Observations and modelling of a large optical flare on AT Microscopii Authors: García-Alvarez, D.; Jevremović, D.; Doyle, J. G.; Butler, C. J. Bibcode: 2002A&A...383..548G Altcode: 2001astro.ph.12224G Spectroscopic observations covering the wavelength range 3600-4600 Å are presented for a large flare on the late type M dwarf AT Mic (dM4.5e). A procedure to estimate the physical parameters of the flaring plasma has been used which assumes a simplified slab model of the flare based on a comparison of observed and computed Balmer decrements. With this procedure we have determined the electron density, electron temperature, optical thickness and temperature of the underlying source for the impulsive and gradual phases of the flare. The magnitude and duration of the flare allows us to trace the physical parameters of the response of the lower atmosphere. In order to check our derived values we have compared them with other methods. In addition, we have also applied our procedure to a stellar and a solar flare for which parameters have been obtained using other techniques. Title: Dynamics and Diagnostics of Explosive Events and Blinkers Authors: Madjarska, M. S.; Doyle, J. G.; Teriaca, L. Bibcode: 2002mwoc.conf...69M Altcode: The knowledge of the main physical parameters of UV explosive events and blinkers, such as density and temperature, is of great importance for the better understanding of the true nature of these transient events. In this context, density and temperature diagnostics based on lines belonging to O iv 1400Å and O iii multiplets is presented for both kind of events. The dynamics of the solar transient phenomena is revealed through their temporal and spatial evolution as observed in spectral lines covering a wide temperature range. The results are obtained using SUMER, CDS, MDI and EIT aboard SoHO, TRACE and Big Bear Solar Observatory observations and are aimed to give more information about the main properties of these phenomena. The events are also studied in connection with the evolution of the underlying magnetic field, searching for observational evidences of their further propagation higher in the solar corona. Title: Temporal evolution of different temperature plasma during explosive events Authors: Madjarska, M. S.; Doyle, J. G. Bibcode: 2002A&A...382..319M Altcode: High cadence observations (10 s exposure time) obtained with the SUMER spectrometer on-board SoHO in the Ly 6 (20 000 K) and S VI (200 000 K) lines reveal new insight on the nature of explosive events. A time delay in the response of the S VI line with respect to the Ly 6 line has been observed, with the Ly 6 line responding with about 20-40 s earlier. A temporal series obtained with 30 s exposure time and covering the entire Lyman series plus O I, C II and S VI (temperature range from 15 000 to 200 000 K) has also been explored showing the response of all these lines during transient phenomena. New common features linking explosive events and blinkers were found. During explosive events, the central intensity increases between 1.6 and 2.0 times the pre-event value while the same range of intensity increase was already reported during blinker phenomena. On the other hand the maximum intensity increase in Ly 6 was only 13%. Title: Long-Period Oscillations in Polar Coronal Holes as Observed by CDS on SOHO Authors: Banerjee, D.; O'Shea, E.; Doyle, J. G.; Goossens, M. Bibcode: 2002mwoc.conf...19B Altcode: We examine spectral time series of the coronal line Mg ix 368Å, the transition region line O v 629Å, and the chromospheric line He i 584Å observed during several periods of 2000, with the Coronal Diagnostic Spectrometer (CDS) onboard the SoHO spacecraft. We study different parts of coronal holes, plumes and inter-plumes (off-limb) as a separate study. We report here on a time series analysis, using wavelet methods, of small individual regions in the polar coronal hole. The wavelet analysis allows us to derive the duration as well as the periods of the oscillations. The statistical significance of the oscillations was estimated by using a randomisation method. Our observations indicate the presence of compressional waves with periods of 20-30 minutes or longer. These slow magneto-acoustic waves may provide enough energy flux for the acceleration of the fast solar wind. Title: Signatures of very long period waves in the polar coronal holes Authors: Banerjee, D.; O'Shea, E.; Doyle, J. G.; Goossens, M. Bibcode: 2001A&A...380L..39B Altcode: We examine long spectral time series of a coronal hole observed on the 7th March 2000 with the Coronal Diagnostic Spectrometer (CDS) on-board SoHO. The observations were obtained in the chromospheric He I, and a series of higher temperature oxygen lines. In this letter we report on the presence of long period oscillations in a polar coronal hole region on the disk. Our observations indicate the presence of compressional waves with periods of 20-30 min or longer. Title: Modelling of solar explosive events in 2D environments. III. Observable consequences Authors: Roussev, I.; Doyle, J. G.; Galsgaard, K.; Erdélyi, R. Bibcode: 2001A&A...380..719R Altcode: We examine the response via line synthesis of two representative transition region lines, namely C IV 1548.2 Å and O VI 1031.9 Å, in various physical environments representing the ``quiet'' Sun to magnetic reconnection events. Our calculations of ion populations allow for departures from equilibrium ionization (EI), which is critical in studies of transient events. Both lines reveal highly blue- and red-shifted Doppler components, and some of the results are examined in the context of solar explosive events. The observable consequences of magnetic reconnection are subtle in the various physical circumstances examined here and differ from one emission line to another, because of the difference in their formation temperatures. Title: Oxygen abundance in polar coronal holes Authors: Teriaca, L.; Poletto, G.; Falchi, A.; Doyle, J. G. Bibcode: 2001AIPC..598...65T Altcode: 2001sgc..conf...65T Fast solar wind is known to emanate from polar coronal holes. However, only recently attention has been given to the problem of where, within coronal holes, fast wind originates. Information on whether the fast solar wind originates from plumes or interplume regions may be obtained by comparing the elemental abundances in these regions with those characterizing the fast wind. Here we present a first attempt to determine the oxygen abundance in the interplume regions by using spectra taken at times of minimum in the solar cycle (when it is easier to identify these structures) by the SUMER spectrograph aboard SoHO. To this end, we analyze spectra taken in 1996 in polar regions, at altitudes ranging between 1.05 and 1.3 Rsolar, finding a value >=8.5 for the oxygen abundance in the interplume regions. From the analysis of the O VI 1032 to 1037 line intensity ratio we also find no evidence of outflow velocities below 1.2 solar radii in interplume regions, while there are indications that outflow motions start to be significant above 1.5 solar radii. The method used and the assumptions made are discussed in light of the derived values. Our values are compared with previous determinations in the corona and solar wind. . Title: Long period oscillations in the inter-plume regions of the Sun Authors: Banerjee, D.; O'Shea, E.; Doyle, J. G.; Goossens, M. Bibcode: 2001A&A...377..691B Altcode: We examine long spectral time series of inter-plume lanes observed on the 14th and 15th March 2000 with the Coronal Diagnostic Spectrometer (CDS) on-board SoHO. The observations were obtained in lines over a wide temperature range, from the chromosphere to the corona. The statistical significance of the oscillations was estimated by using a randomisation method. Our observations indicate the presence of compressional waves with periods of 20-50 min or longer, both off-limb and on-disk and up to 70 min further out to at least 25 arcsec off-limb. To our knowledge this is the first time that long period oscillations in the inter-plume regions close to the limb of the Sun have been detected. We interpret these oscillations as outward propagating slow magneto-acoustic waves which may contribute significantly to the heating of the lower corona by compressive dissipation and which may also provide some of the enough energy flux required for the acceleration of the fast solar wind. These slow waves may have been produced at the network boundaries in the coronal hole. Title: Temporal evolution of explosive events as observed in Lyman and S VI lines Authors: Madjarska, M. S.; Doyle, J. G. Bibcode: 2001ESASP.493..279M Altcode: 2001sefs.work..279M No abstract at ADS Title: Temporal Variability in Transition Region Line . Authors: Giannikakis, I.; Doyle, J. G.; Antonopoulou, E.; Madjarska, M. Bibcode: 2001hell.confE..41G Altcode: No abstract at ADS Title: Explosive Events and associated Periodicities Authors: Giannikakis, I.; Doyle, J. G.; Antonopoulou, E. Bibcode: 2001hell.confE..20G Altcode: No abstract at ADS Title: Modelling of explosive events in the solar transition region in a 2D environment. II. Various MHD experiments Authors: Roussev, I.; Galsgaard, K.; Erdélyi, R.; Doyle, J. G. Bibcode: 2001A&A...375..228R Altcode: We examine the response of various physical environments representing the solar atmosphere to a magnetic reconnection event. The reconnection is driven by a localized increase of the magnetic diffusivity in the current concentration formed between two magnetic fluxes of opposite polarity. The time dependent evolution is then followed by numerically solving the 2-dimensional (2D) dissipative magnetohydrodynamic (MHD) equations, including also effects of thermal conduction, radiative losses, and volumetric heating.\ This work continues a previous related study (Roussev et al. 2001a), and compares results obtained from exploring different initial states. The choice of the initial states is found to be crucial to the dynamics of the reconnection jets. The numerical experiments are aimed at modelling transient events on the quiet Sun, with an emphasis on explosive events. The 2D reconnection experiments presented in this paper are the basis for a detailed analysis on the line synthesis in transition region resonant lines, presented by Roussev et al. (\cite{rou01b}). Title: The nature of network oscillations Authors: Banerjee, D.; O'Shea, E.; Doyle, J. G.; Goossens, M. Bibcode: 2001A&A...371.1137B Altcode: We examine time-series of spectral data obtained from the Coronal Diagnostic Spectrometer (CDS) and the Solar Ultraviolet Measurements of Emitted Radiation instrument (SUMER) onboard the Solar Heliospheric Observatory (SOHO) spacecraft, in the period 30-31 July 1996. The observations were obtained in lines, ranging in temperature from 12 000 K to 106 K, covering the low chromosphere to the corona. We report here on a time series analysis, using wavelet methods, of small individual network regions in the quiet Sun. The wavelet analysis allows us to derive the duration as well as the periods of the oscillations. The statistical significance of the oscillations was estimated by using a randomisation method. The oscillations are considered to be due to waves, which are produced in short bursts with coherence times of about 10-20 min. The low chromospheric and transition region lines show intensity and velocity power in the 2-4 mHz range. The coronal line Mg x does not show any statistically significant power in this range. In general, it is thought likely that the chromosphere and possibly the transition region oscillates in response to forcing by the p-modes, but they are also influenced strongly by the presence of magnetic fields. The observed 2-4 mHz network oscillations can thus be interpreted in terms of kink and sausage waves propagating upwards along thin magnetic flux tubes. We perform a linear numerical computation comparing the results with our observations. Title: Electron density variations during ultraviolet transient events Authors: Teriaca, L.; Madjarska, M. S.; Doyle, J. G. Bibcode: 2001SoPh..200...91T Altcode: % High-resolution temporal observations performed with the SUMER spectrometer on SOHO provide an opportunity to investigate the electron density variations in the `quiet-Sun' solar transition region due to UV transient events. Two datasets obtained in the density sensitive lines belonging to the O iv 1400 Å multiplet were searched for such events, leading to the identification of two explosive events, on 10 July 1996 and 31 May 1997. In both cases, the O iv 1401.16/1404.81 density-sensitive line intensity ratio shows a clear variation, corresponding to enhancements in the electron density by factors of ∼3. This is fully consistent with recent 2.5D MHD simulations. The 10 July 1996 dataset also provided us with the opportunity to monitor the behavior of the electron density through an UV blinker. Despite an increase of a factor of two in the line intensities, no variation of the electron density was found. This suggests that the intensity enhancement is due to an increase in the filling factor. Title: Numerical Modeling of the Transition Region Dynamics Authors: Teriaca, L.; Doyle, J. G. Bibcode: 2001ASSL..259..307T Altcode: 2001dysu.conf..307T We explore the idea that the occurrence of nano-flares in a magnetic loop around the O VI formation temperature could explain the observed red-shift of mid-low transition region lines as well as the blue-shift observed in low coronal lines (T > 6 times 105 K). Observations are compared to numerical simulations of the response of the solar atmosphere to an energy perturbation of 4 times 1024 ergs representing an energy release during magnetic reconnection in a 1-D semi-circular flux tube. The temporal evolution of the thermodynamic state of the loop is finally converted into C III 977, C IV 1548, O V 630, O VI 1032, Ne VII 465 and Ne VIII 770 line profiles in non-equilibrium ionization. Performing an integration over the entire period of simulation, redshifts of 8.5, 6.1 and 1.7 km s-1, are found in C III, C IV, and O V while blue-shifts of -1.8, -3.9 and -10.7 km s-1 were derived for O VI, Ne VII and Ne VIII respectively, in good agreement with observations. Title: Modelling of explosive events in the solar transition region in a 2D environment. I. General reconnection jet dynamics Authors: Roussev, I.; Galsgaard, K.; Erdélyi, R.; Doyle, J. G. Bibcode: 2001A&A...370..298R Altcode: The aim of the present study is to investigate the reconnection jets formed during the process of magnetic flux cancellation in the physical environment of the solar transition region. The emission properties of these jets are then computed for two resonance transition region lines, C iv 1548.2 Å and O vi 1031.9 Å, under the assumption of non-equilibrium ionization. The numerical modelling involves 2-dimensional (2D) dissipative, radiative, nonlinear magnetohydrodynamics. The nonlinear anisotropic thermal conduction, radiative losses, and volumetric heating are taken into account in order to assess their role in the physical situation examined. This work is a continuation of previous related simulations where small-scale energy depositions were modelled in 1D radiative hydrodynamics. Having an X-point reconnection in the mid-transition region gives blue-shifts of the order of ~ 100 km s-1, however, the red-shift can be up to one order of magnitude less. Title: Solar Mn I 5432/5395 Å line formation explained Authors: Doyle, J. G.; Jevremović, D.; Short, C. I.; Hauschildt, P. H.; Livingston, W.; Vince, I. Bibcode: 2001A&A...369L..13D Altcode: We present a solution for the long standing problem concerning the ``chromospheric'' behaviour of the Mn i 5395/5432 Å lines in the solar spectrum using multi-line/multi-species NLTE modelling. Using comprehensive spectral line formation modelling, we show that the Mn i lines are very sensitive to optical pumping in a transition which overlaps with Mg ii k. It therefore follows that one has to be careful with the choice of lines as temperature indicators and for the determination of the Mn abundances although on the other hand, due to the formation process of these lines they may be useful as a solar and stellar activity diagnostic. Title: Active region oscillations Authors: O'Shea, E.; Banerjee, D.; Doyle, J. G.; Fleck, B.; Murtagh, F. Bibcode: 2001A&A...368.1095O Altcode: We report here on an investigation of high frequency oscillations in active regions, carried out using high cadence observations of O V 629 Å, Mg Ix 368 Å and Fe Xvi 335 Å, with the Coronal Diagnostic Spectrometer (cds) on soho. Using the techniques of wavelet analysis on various temporal series datasets, we find that certain oscillation frequencies are favoured for each line. We find furthermore that a ~ 5 min oscillation signature is commonly present in all lines, suggesting a coupling of the photospheric driver with the transition region and coronal loop modes. We report on the tendency for higher frequency oscillations to be present at lower intensity values, suggesting that higher frequency oscillations occur in interloop regions or at loop boundaries, possibly as a result of some resonant absorption process. In addition, we find that the coronal lines of Fe Xvi and Mg Ix show more significant oscillations in the velocity than in the intensity, which suggests that in the velocity we measure additional non-compressive wave modes not visible in the intensity. As this effect is not seen in the transition region line of O V it would seem that these additional non-compressive modes are produced in and limited to the corona. We suggest that there are two main mechanisms responsible for the observed oscillations; either resonant Alfvén and/or fast kink waves or propagating slow magnetoacoustic waves, both present in coronal loops. Title: On the nature of network oscillations Authors: Banerjee, D.; O'Shea, E.; Doyle, J. G.; Goossens, M.; Fleck, B. Bibcode: 2001ESASP.464..175B Altcode: 2001soho...10..175B We examine time-series of spectral data obtained from the Solar Ultraviolet Measurements of Emitted Radiation instrument (SUMER), on board SOHO in the period 10-31 July 1996. Observations were obtained in lines, ranging in temperature from 12,000 K to 106K, covering the low chromosphere to the corona. In this short contribution we report on the time series analysis on one of these dataset, using wavelet methods, of small individual network regions in the quiet Sun. The wavelet analysis allows us to derive the duration as well as the periods of the oscillations. The statistical significance of the oscillations was estimated by using a randomisation method. The oscillations are considered to be due to waves, which are produced in short bursts with coherence times of about 10-20 minutes. The low chromospheric and transition region lines show intensity and velocity power in the 2.4 mHz range. The observed 2-4 mHz network oscillations can be interpreted in terms of kink and sausage waves propagating upwards along thin magnetic flux tubes. The kink waves can be generated by random foot-point motions, e.g. by exploding granules, at the photospheric level. As they propagate within flux tubes, their amplitude grows exponentially with height and becomes non-linear. The waves can thereby undergo a mode transformation and become sausage type waves, which are more easily detected on the disk. Title: Electron Density Enhancement During an UV Explosive Event Authors: Madjarska, M. S.; Doyle, J. G.; Teriaca, L. Bibcode: 2001IAUS..203..407M Altcode: High resolution temporal observations performed with the SUMER spectrometer on SOHO provide us the opportunity to investigate the electron density variations in the solar mid transition region due to explosive event-like phenomena. The O IV 1401.16/1404.81 density sensitive line intensity ratio shows a clear increase during a strong explosive event, corresponding to an electron density enhancement of a factor of ~ 3.5 respect to pre-event values. This is consistent with recent MHD simulations (2.5 D) carried out by Karpen et al. (1998). Karpen J. T., Antiochos S. K., DeVore C. R. and Golub L., 1998, ApJ 495, 491. Title: SUMER Observations of the Solar Transition Region: Spatial and Temporal Behaviour Authors: Teriaca, L.; Doyle, J. G.; Banerjee, D. Bibcode: 2001IAUS..203..425T Altcode: In this paper we examine the spatial and temporal behaviour of the quiet Sun transition region using high resolution SUMER observations in O VI 1032. The observations are devoted to the study of the variability in the transition region and consists of four raster scans of the same area followed by a long series of spectra taken in the same position with high temporal cadence. A detailed study of the raster images allows us to differentiate the network and internetwork through Doppler shift and line width measurements. We have also identified several explosive-events like phenomena toghether with an UV bright point. We also show evidence for a possible formation of a shock front after one partcular bright point appearence. The oscillatory nature of the transition region is finally investigated using the wavelet analysis and particular attention has been paid to the effect due to the occurrence of explosive events. Title: Long Period Oscillations in Polar Plumes as observed by CDS on SoHO Authors: Banerjee, D.; O'Shea, E.; Doyle, J. G.; Goossens, M. Bibcode: 2001IAUS..203..244B Altcode: We examine spectral time series of coronal line Mg IX 368 Å and transition region line O V 629 Å, observed with the Coronal Diagnostic Spectrometer (CDS) onboard the SOHO spacecraft. Primarily we were looking for intensity and velocity oscillations in polar plumes, however by chance we detected a giant macro-spicule at the limb and were able to follow its dynamical structure. Blue and red-shifted emission in the O V line indicates that it is probably a rotating twisted magnetic jet. Emission is also detected in the Mg IX 368 Å line, at a temperature of 1 million K. Both Fourier and wavelet transforms have been applied independently to the analysis of the oscillations in order to find the most reliable periods. We report here on the existence of long period oscillations in the polar plumes as observed in the O V 629 Å line. Our observations indicate the presence of compressional waves with periods of 20-25 minutes. Title: Environment of Two RS CVn Stars (CD-ROM Directory: contribs/ozeren) Authors: Özeren, F. F.; Doyle, J. G.; Jevromovic, D.; Gunn, A. G. Bibcode: 2001ASPC..223.1036O Altcode: 2001csss...11.1036O No abstract at ADS Title: A spectroscopic study of the eclipsing binaries SV Camelopardalis and XY Ursae Majoris Authors: Özeren, F. F.; Gunn, A. G.; Doyle, J. G.; Jevremović, D. Bibcode: 2001A&A...366..202O Altcode: High-resolution spectroscopic observations of the eclipsing RS CVn-type active close binaries SV Camelopardalis and XY Ursae Majoris reveal excess emission components in the Hα and Hβ lines. We have used the spectral subtraction technique to separate the excess emission from the photospheric background and find that in both stars the excess emission is associated with the secondary, cooler component. Analysis of the EWHα/EWHβ ratio indicates that in both cases the emission is probably associated with surface plage regions or prominences viewed against the stellar disks. We find no evidence of excess absorption features associated with extended prominence-like material in these systems. Based on observations made at Observatoire de Haute Provence (CNRS), France. Title: A Quiescent Atmosphere of AD Leo (CD-ROM Directory: contribs/jevrem2) Authors: Jevremović, D.; Doyle, J. G.; Butler, C. J. Bibcode: 2001ASPC..223..815J Altcode: 2001csss...11..815J No abstract at ADS Title: Active region oscillations Authors: O'Shea, E.; Banerjee, D.; Doyle, J. G.; Fleck, B.; Murtagh, F. Bibcode: 2001ESASP.464..223O Altcode: 2001soho...10..223O We report here on an investigation of high frequency oscillations in active regions, carried out using high cadence observations of O V 629 Å, Mg IX 368 Å and Fe XVI 335 Å with the Coronal Diagnostic Spectrometer (CDS) on SoHO. Using the techniques of wavelet analysis on various temporal series datasets, we find that certain bands of oscillation frequency are favoured for each line. We report on the tendency for higher frequency oscillations to correspond to lower intensity values, suggesting that higher frequency oscillations occur in inter-loop regions or at loop boundaries, and further that some resonant absorption process is perhaps at work at these locations. We suggest that there are two possible mechanisms for the observed oscillations; either resonant Alfvén waves or resonant fast kink waves in coronal loops. Title: A Role of Isotropic Turbulence in Atmospheres of Late Type Stars (CD-ROM Directory: contribs/jevrem1) Authors: Jevremović, D.; Doyle, J. G.; Short, C. I. Bibcode: 2001ASPC..223..809J Altcode: 2001csss...11..809J No abstract at ADS Title: Electron density diagnostics for solar ultraviolet lines of O V Authors: O'Shea, E.; O'Neill, T.; Keenan, F. P.; Doyle, J. G. Bibcode: 2000SoPh..196..321O Altcode: We determine the electron densities for a range of solar features using new calculations for the O v line ratio, R=I(λ761.1)/I(λ760.4), in conjunction with observational data obtained with the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) instrument on the Solar and Heliospheric Observatory (SOHO). The densities obtained from this diagnostic are in good agreement with earlier measured values. This provides support for the theoretical diagnostics presented in this paper, and hence the atomic data used in their derivation. We conclude from these results that this particular O v ratio is a useful diagnostic for many types of solar features. Title: Long period oscillations in the polar plumes Authors: Banerjee, D.; O'Shea, E.; Doyle, J. G.; Goossens, M. Bibcode: 2000AIPC..537..160B Altcode: 2000wdss.conf..160B We examine spectral time series of the transition region line O v 629 Å, observed with the Coronal Diagnostic Spectrometer (CDS) on the SoHO spacecraft. Both Fourier and wavelet transforms have been applied independently to the analysis of plume oscillations in order to find the most reliable periods. The wavelet analysis enables us to derive the duration as well as the periods of the oscillations. Our observations indicate the presence of compressional waves with periods of 10-20 minutes. We have also detected a 10+/-2 minute periodicity in the network regions of the north polar coronal hole. The waves are produced in short bursts with coherence times of about 20-30 minutes. We interpret these oscillations as outward propagating slow magneto-acoustic waves, which may contribute significantly to the heating of the lower corona by compressive dissipation and which may also provide enough energy flux for the acceleration of the fast solar wind. The data support the idea that the same driver is responsible for the network and plume oscillations with the network providing the magnetic channel through which the waves propagate upwards from the lower atmosphere to the plumes. . Title: Long-Period Oscillations in Polar Plumes as Observed by cds on Soho Authors: Banerjee, D.; O'Shea, E.; Doyle, J. G. Bibcode: 2000SoPh..196...63B Altcode: We examine spectral time series of the transition region line O v 629Å, observed with the Coronal Diagnostic Spectrometer (CDS) on the SOHO spacecraft in July 1997. Both Fourier and wavelet transforms have been applied independently to the analysis of plume oscillations in order to find the most reliable periods. The wavelet analysis allows us to derive the duration as well as the periods of the oscillations. Our observations indicate the presence of compressional waves with periods of 10-25 min. We have also detected a 11±1 min periodicity in the network regions of the north polar coronal hole. The waves are produced in short bursts with coherence times of about 30 min. We interpret these oscillations as outward propagating slow magneto-acoustic waves, which may contribute significantly to the heating of the lower corona by compressive dissipation and which may also provide enough energy flux for the acceleration of the fast solar wind. The data support the idea that the same driver is responsible for the network and plume oscillations with the network providing the magnetic channel through which the waves propagate upwards from the lower atmosphere to the plumes. Title: Modelling near-IR spectra and mid-IR dust emission of Mira variables at different phases Authors: Lobel, A.; Bagnulo, S.; Doyle, J. G.; Power, C. Bibcode: 2000MNRAS.317..391L Altcode: We model the spectral changes of late oxygen-rich Miras observed in different pulsation phases. From a combination of variable near-IR spectra and UKIRT spectro-photometry of the 9.7-μm silicate dust emission feature in different phases we study the influence of the changing atmospheric circumstances on the conditions in the circumstellar dust shell. From a detailed modelling of TiO and VO bands in the near-IR spectra, we determine changes of the effective temperature and the effective atmospheric acceleration of the central star. The corresponding model spectral energy distribution is redistributed through the dust shell by means of radiative transfer calculations in order to perform a detailed modelling of shape changes observed in the silicate feature. We show that the latter are mainly caused by changes in the flux distribution of the incident radiation field with stellar pulsation, whereas intensity changes of the dust emission result from stellar luminosity changes as they are enshrouded by very optically thin dust shells. In the case of the Mira o Cet we compute that the effective temperature increases from Teff=2400K in the minimum phase to 3000K (+/-100K) around the maximum phase. The amplified momentum transfer around maximum light enhances the acceleration of the dust outflow near the dust condensation radius of ~6R*. This produces variations of the terminal dust outflow velocity with phase (Δv∞~=5kms-1) at larger distance from the star. The corresponding small changes in flux mean opacity and gas mass-loss rates (from 2.8 to 3.2×10-7Msolaryr-1) are sufficient to model the shape changes observed in the dust emission feature. A comparison with the modelling results for another long period Mira, U Ori, is also provided. Title: Physical parameters of EUV explosive events Authors: Pérez, M. E.; Doyle, J. G. Bibcode: 2000A&A...360..331P Altcode: Previously published results of EUV explosive events and electron density enhancements in the solar transition region are revised. An attempt has been made to correlate both observational phenomena, and to associate the observed density enhancements to magnetic reconnection sites. The corresponding local magnetic field strength in these sites is estimated. These values are of the same order as previously measured in photospheric cancelling flux regions. Title: Rotational modulation and flares on RS CVn and BY Dra stars. XX. Photometry and spectroscopy of CC Eri in late 1989 Authors: Amado, P. J.; Doyle, J. G.; Byrne, P. B.; Cutispoto, G.; Kilkenny, D.; Mathioudakis, M.; Neff, J. E. Bibcode: 2000A&A...359..159A Altcode: The active flaring binary CC Eri was studied via multi-wavelength observations involving multi-based photometry and ground- and space-based spectroscopy. Combining early spectroscopic data with the present implies an orbital period of P=1.5615 days. Furthermore, the spectroscopic data suggests spectral types of K7 and M3 for the system. The optical photometry indicated a small spot coverage in late 1989, consistent with data taken a year later which showed CC Eri entering its brightest-to-date phase. Two flares were detected in the ultraviolet spectral data. These flares radiated 2.7 1031 erg and 1.6 1031 erg in the C Iv line alone, each with a total estimated radiative energy budget of ~ 1036 erg. For the higher-temperature lines, such as C Iv, there was no systematic variability with phase. The lower-temperature lines show a slight indication of rotational modulation. However, there is a much larger scatter in the individual measurements of the Mg Ii and C Iv fluxes than would be expected from measurement errors alone, consistent with an atmosphere showing continual small-scale activity. Title: The contribution of the micro-turbulent velocity on the modelling of chromospheric lines in late type dwarfs Authors: Jevremović, D.; Doyle, J. G.; Short, C. I. Bibcode: 2000A&A...358..575J Altcode: We discuss the influence of the non-thermal velocity (micro-turbulence) on the formation of chromospheric lines in the atmospheres of late type dwarfs. A review of previous work shows a variety of different approaches to the problem leading to different atmospheric structures and consequently different computed line profiles. In that light, we re-examine the formation of the Hydrogen Balmer lines and Na i D lines using twelve different distributions of the micro-turbulent velocity throughout the atmosphere. Our results show a wide range of possible line shapes. Using the analogy with the solar case and the latest results of the non-thermal component widths as derived from instruments on-board SOHO we model Hα and the Na i D lines in an active dMe star Gl 616.2. Based in part on observations made at Observatoire de Haute Provence (CNRS), France and SOHO Title: Polar Plumes and Inter-plume regions as observed by SUMER on SOHO Authors: Banerjee, D.; Teriaca, L.; Doyle, J. G.; Lemaire, P. Bibcode: 2000SoPh..194...43B Altcode: We present observations of O vi 1032 Å line profiles obtained with the SUMER instrument on SOHO extending from the solar disk to 1.5 R⊙ above the limb in the north polar coronal hole. Variations of the intensity and linewidth in the polar plume and inter-plume regions are investigated. We find an anti-correlation between the intensity and the linewidth in the plume and inter-plume regions with detailed plume structures been seen out to 1.5 R⊙. Possible implications regarding the magnetic topologies of these two regions and related heating mechanisms are discussed. The O vi linewidth measurements are combined with UVCS output to provide an overview of its variations with height extending up to 3.5 R⊙. We find a linear increase of the linewidth from 1 to 1.2 R⊙, then a plateau followed by a sharp increase around 1.5 R⊙. Title: Photometric modelling of starspots - II. The fortran code spotpic Authors: Amado, P. J.; Doyle, J. G.; Byrne, P. B. Bibcode: 2000MNRAS.314..489A Altcode: A fortran code which computes synthetic light and colour curves of active, spotted stars has been developed. The main feature of this code is that it can simultaneously model the V light curve and the (V-R)c, (V-I)c, (V-K) colour data. It also uses new effective temperature-colour and Barnes-Evans-like calibrations, temperature and gravity-dependent limb darkening coefficients and different effective surface gravities for the spotted and unspotted photosphere. The code allows for two-component spots, i.e. spots with umbral and penumbral components. Various problematic spot configurations were investigated and we conclude that, in order to be able to differentiate spots with various thermal structures (umbrae, penumbrae, faculae) or polar spots from equatorial bands, the modelling of the infrared colours, especially (V-I)c and (V-K), is needed. Title: Solar transition region line broadening: Limb to limb measurements Authors: Doyle, J. G.; Teriaca, L.; Banerjee, D. Bibcode: 2000A&A...356..335D Altcode: Full disk images from SUMER/SoHO taken in He I, C IV and Ne VIII are used to investigate whether there exists a center-to-limb variation in the line width. Both C IV and He I show such a variation but the higher temperature Ne VIII line is relatively constant. For C IV, this corresponds to ~ 3 km s-1 difference while He I is significantly larger particularly at the limb. This work may suggest that the non-thermal motions are slightly non-isotropic in the transition region and upper chromosphere, with the horizontal unresolved motions exceeding those in the vertical plane however a more probable explanation is that the lines are broadened due to opacity effects. The more slower variation in the C IV 1548 Ä line width could be explained by increasing the opacity from zero at disk center to ~ 1 at the limb. For He I the opacity is significantly grater than unity at the limb. This therefore implying all mass motions in the chromosphere, transition region and corona are isotropic. Title: Giant macro-spicule as observed by CDS on SOHO Authors: Banerjee, D.; O'Shea, E.; Doyle, J. G. Bibcode: 2000A&A...355.1152B Altcode: We examine spectral time series of coronal line Mg ix 368 Ä and transition region line O v 629 Ä, observed with the Coronal Diagnostic Spectrometer (CDS) onboard the SOHO spacecraft. Primarily we were looking for intensity and velocity oscillations in polar plumes, however by chance we detected a giant macro-spicule at the limb and were able to follow its dynamical structure. Blue and red-shifted emission in the O v line indicates that it is probably a rotating twisted magnetic jet. Emission is also detected in the Mg ix 368 Ä line, at a temperature of 1 million K. Both Fourier and wavelet transforms have been applied independently to the analysis of the oscillations in order to find the most reliable periods. We report here on the existence of long period oscillations in the polar plumes as observed in the O v 629 Ä line. Our observations indicate the presence of compressional waves with periods of 20-25 minutes. Title: Modelling of Explosive Events in the Solar Transition Region: Importance of Radiative Losses and Thermal Conduction Authors: Roussev, I.; Erdélyi, R.; Doyle, J. G.; Galsgaard, K. Bibcode: 1999ESASP.448..641R Altcode: 1999mfsp.conf..641R; 1999ESPM....9..641R No abstract at ADS Title: New Insight in Transition Region Dynamics as Derived from SUMER Observations and Numerical Modelling Authors: Teriaca, L.; Doyle, J. G.; Erdélyi, R.; Sarro, L. M.; Banerjee, D. Bibcode: 1999ESASP.448..379T Altcode: 1999ESPM....9..379T; 1999mfsp.conf..379T No abstract at ADS Title: New insight into transition region dynamics via SUMER observations and numerical modelling Authors: Teriaca, L.; Doyle, J. G.; Erdélyi, R.; Sarro, L. M. Bibcode: 1999A&A...352L..99T Altcode: We explore the idea that the occurrence of nano-flares in a magnetic loop around the O vi formation temperature could explain the observed red-shift of mid-low transition region lines as well as the blue-shift observed in low coronal lines (T > 6x 105\ K). Observations are compared to numerical simulations of the response of the solar atmosphere to an energy perturbation of 4x 1024 ergs representing an energy release during magnetic reconnection in a 1-D semi-circular flux tube. The temporal evolution of the thermodynamic state of the loop is converted into C iv 1548, O vi 1032 and Ne viii 770 line profiles in non-equilibrium ionization. Performing an integration over the entire period of simulations, a redshift of ~ 6\ km\ s-1 is found in C iv, while a blue-shift of ~ 2\ km\ s-1 and ~ 10\ km\ s-1 were derived for O vi and Ne viii, respectively, in reasonable agreement with observations. Title: SUMER Measurements of Electron Density Enhancements in the Solar Transition Region Authors: Pérez, M. E.; Doyle, J. G.; O'Shea, E.; Keenan, F. Bibcode: 1999ESASP.448..629P Altcode: 1999mfsp.conf..629P; 1999ESPM....9..629P No abstract at ADS Title: Temporal variability in the electron density at the solar transition region Authors: Pérez, M. E.; Doyle, J. G.; O'Shea, E.; Keenan, F. P. Bibcode: 1999A&A...351.1139P Altcode: The electron density as measured in the transition region of a coronal hole, a `quiet' Sun region at disk center plus an active region shows variations of up to a factor of two at T_e ~ 1.5 105 K, lasting at most only a few minutes. There is remarkable agreement between the number of such variations, their temporal variability and duration in the coronal hole and `quiet' Sun datasets, consistent with an earlier bright point study. There appears to be evidence of super-granular cells, with the increases in electron density occurring along the network boundaries. At some locations, periodicities of between 8 and 16 min are visible in the electron density variations. We associate these variations with the sites of explosive events. Title: Modelling explosive events in the solar atmosphere Authors: Sarro, L. M.; Erdélyi, R.; Doyle, J. G.; Pérez, M. E. Bibcode: 1999A&A...351..721S Altcode: High-resolution ultraviolet (UV) spectra of the outer solar atmosphere show transient brightenings often referred to as explosive events. These are localized regions of small spatial extent that show sudden enhancements in the intensities of lines formed between 20,000 and 200,000 K, accompanied by strong non-gaussian profiles. The present work is an attempt to extract observational consequences from computational simulations of the dynamic response of a coronal loop to energy perturbations. Explosive events are simulated in semi-circular magnetic flux tubes. Thermal energy perturbations drive flows along the flux tube giving rise to thermodynamic phenomena. The temporal evolution of the thermodynamic state of the loop is converted into C iv lambda 1548.2 Ä line profiles in (non)-equilibrium ionization. Time dependent carbon ion populations are obtained in the non-equilibrium conditions derived from the thermodynamic variables by means of an adaptive grid code. Most important, departures from ionization equilibrium are assessed for the first time under conditions such as those encountered in explosive events. Title: The Wilson-Bappu relation for RS CVn stars Authors: Özeren, F. F.; Doyle, J. G.; Jevremovic, D. Bibcode: 1999A&A...350..635O Altcode: We investigate the extent to which the Wilson-Bappu relationship holds for chromospherically active binaries using the Mg ii h&k lines of 41 RS CVn stars observed with IUE. The resulting fits are different from the relationships obtained for single, less active stars. The parallax used were those from the hipparcos catalogue, these give a much better correlation than the magnitudes taken from CABS. Within a particular luminosity class the relationship is good, however it tends to break down when we incorporate objects ranging in luminosity from class i to v. From model calculations there is very little dependence of the Mg ii line width on effective temperature. The line width does however depend on the column mass at the transition region boundary showing increased line width at lower column mass. There is also a dependence on the column mass adopted for the temperature minimum, however, the major and dominant parameter is the surface gravity scaling as g(-1/4) . Within a luminosity class more active objects will show larger lines widths reflecting a higher column mass deeper in the atmosphere, e.g. at the temperature minimum level. Title: SUMER Observations of Line Shifts in the Quiet Sun and in an Active Region Authors: Teriaca, L.; Banerjee, D.; Doyle, J. G.; Erdély, R. Bibcode: 1999ESASP.446..645T Altcode: 1999soho....8..645T The UV spectral lines formed at transition region temperatures in the solar atmosphere, shows a prevailing redshifted emission. Using the Solar Ultraviolet Measurements of Emitted Radiation spectrometer flown on the Solar and Heliospheric Observatory spacecraft, we measure the amount of line shift as a function of the temperature for several spectral lines formed in the range between 104 and 106 K. We analyze spectrograms relative to the quiet Sun and to the active region NOAA 7946. The velocities derived are increasing from a redshift of ~ 0 km/s at ~ 20000 K to 10 km/s at 1.9x105 K for the quiet Sun, and to ~ 15 km/s at 105 K for the active region. At higher temperature an opposite behaviour is observed. In the quiet Sun a blueshift of ~ -2 km/s is observed at the Ne viii formation temperature (6x105 K), while in the active region, a blue-shifted value around -8 km/s is observed for the same spectral line. By 106 K the blueshift is ~ -10 km/s in the active region as measured by Fe xii 1242. Title: The Nature Of Network Oscillations In The Solar Chromosphere Authors: Banerjee, D.; Doyle, J. G.; O'Shea, E. Bibcode: 1999ESASP.446..161B Altcode: 1999soho....8..161B We examine the simultaneous time-series spectral data for NI 1319 deg and CII 1335 deg and CII and OVI obtained from the SUMER instrument on the SOHO spacecraft. The observed 4-5 min network oscillations can be interpreted in terms of kink and sausage waves propagating upwards along thin magnetic flux tubes. Transverse kink waves can be generated by random foot-point motions driven by exploding granules at the photospheric level. As they propagate within flux tubes, their amplitude grows exponentially with height and become non-linear, thereby undergoing a mode transformation becomes longitudinal sausage type. We propose that for the network bright regions these sausage waves are responsible for the 3.5 mHz power peak. Numerical results based on thin flux tube equations will be compared with observations. Our two layer isothermal atmospheric model predicts a coupled oscillator frquency which matches fairly well with the network observations. Title: Coronal Hole Diagnostics out to 8 solar radii Authors: Doyle, J. G.; Teriaca, L.; Banerjee, D.; Fludra, A. Bibcode: 1999ESASP.446..281D Altcode: 1999soho....8..281D The line width measurements (from Si VIII) and Ne estimates (from Si VIII and Si IX) based on SUMER and CDS observations are combined with LASCO and UVCS output to provide an overview of its variations with height above a polar coronal hole. From the combined dataset we find a radial dependence of the electron density, in the range 1-2 solar radii as r-8, from 2 to 4 solar radii as r-4 and then as r-2. Combining the Si VIII half width at 1/e of the peak intensity with the UVCS O VI half width, we find a small increase of the half width from 1 to 1.2 solar radii, then a plateau until 1.5 solar radii, thereafter a sharp increase until 2 solar radii, finally a more gradual increase reaching 550 km/s at 3.5 solar radii. Our data suggests that the MHD waves responsible for the excess line broadening tends to become non-linear as it reaches 1.2 solar radii. Title: SUMER observations of Doppler shift in the quiet Sun and in an active region Authors: Teriaca, L.; Banerjee, D.; Doyle, J. G. Bibcode: 1999A&A...349..636T Altcode: The UV spectral lines formed at transition region temperatures in the solar atmosphere, show a prevailing redshifted emission. Using the Solar Ultraviolet Measurements of Emitted Radiation spectrometer flown on the Solar and Heliospheric Observatory spacecraft, we measure the amount of line shift as a function of the temperature for several spectral lines formed in the range between 10(4) and 10(6) \ K. We analyze spectrograms relative to the quiet Sun and to the active region NOAA\ 7946. The velocities derived are increasing from a redshift of ~ \ 0 \ km ; s(-1) at ~ 20000\ K to 10\ km ; s(-1) at 1.9\ 10(5) \ K for the quiet Sun, and to ~ 15 \ km ; s(-1) at 10(5) \ K for the active region. At higher temperature an opposite behaviour is observed. In the quiet Sun a blueshift of ~ \ -2 \ km ; s(-1) is observed at the Ne viii formation temperature (6.3\ 10(5) \ K), while in the active region, a blue-shifted value around -8\ km ; s(-1) is observed for the same spectral line. The finding of blueshift in Ne viii is due to the adoption of a new rest wavelength of 770.428 Ä. By 10(6) \ K the blueshift is ~ \ -10 \ km ; s(-1) in the active region as measured by Fe xii 1242. Title: Coronal hole diagnostics out to 8Rsun Authors: Doyle, J. G.; Teriaca, L.; Banerjee, D. Bibcode: 1999A&A...349..956D Altcode: The Si viii line width measurements and N_e estimates based on SUMER observations are combined with LASCO and UVCS output to provide an overview of its variations with height above a polar coronal hole. From the combined dataset we find a radial dependence of the electron density, in the range 1-2 Rsun as r(-8) , from 2 to 4 Rsun as r(-4) and then as r(-2) . Combining the Si viii half width at 1/e of the peak intensity with the UVCS O vi half width, we find a small increase of the half width from 1 to 1.2 Rsun, then a plateau until 1.5 Rsun, thereafter a sharp increase until 2 Rsun, finally a more gradual increase reaching 550 km s(-1) at 3.5 Rsun. Our data suggests that the MHD waves responsible for the excess line broadening tends to become non-linear as it reaches 1.2 Rsun. Title: Electron densities above a polar coronal hole based on improved SI IX density diagnostics Authors: Doyle, J. G.; Keenan, F. P.; Ryans, R. S. I.; Aggarwal, K. M.; Fludra, A. Bibcode: 1999SoPh..188...73D Altcode: Using new close-coupling excitation rates for the C-like ion Si ix, density-diagnostic ratios based on Si ix lines have been re-evaluated and applied to a sequence of CDS observations taken above a polar coronal hole. The derived electron densities are in excellent agreement with previous values of Neestimated from the N-like ion Si viii for another coronal hole. The confirmed trend is for a fall-off of one order of magnitude within the first 0.3 R⊙above the limb. These densities are well fitted with an analytic formula for the density profile out to at least 8 R⊙, by which stage the electron density has fallen to ∼4×103 cm−3, from 1.5×108 cm−3at 1.0 R⊙. Title: Exploring the dynamical nature of the lower solar chromosphere Authors: Doyle, J. G.; van den Oord, G. H. J.; O'Shea, E.; Banerjee, D. Bibcode: 1999A&A...347..335D Altcode: We examine spectral time-series of two lower-chromospheric lines (N i 1319 Ä and C ii 1335 Ä) observed with the SUMER instrument on the SOHO spacecraft. We point out differences between (intensity and velocity) power spectra of network and internetwork regions and argue that the behaviour resembles that of Ca ii power spectra. No significant phase differences are found between the intensities of both lines. However, when phase spectra are averaged along the slit there is some evidence that the C ii intensity lags that of N i by 16 sec near 3 mHz. Intensity power spectra of C ii are affected at higher frequencies by streams of emitting structures. Using contrast-enhanced time slices we show that 1) there exists a grain-like pattern which is found in both network and internetwork regions; 2) streams of supersonically moving structures probably outline a wave interference pattern; 3) the sizes of structures observed in N i are smaller than when observed in C ii. At various points our findings disagree with earlier results from SUMER. A cookbook formalism is presented to derive confidence levels for power, phase, gain and coherency spectra. Title: Alfvén waves in the solar polar coronal holes Authors: Banerjee, D.; Teriaca, L.; Doyle, J. G.; Wilhelm, K. Bibcode: 1999AIPC..471..289B Altcode: 1999sowi.conf..289B We study the variation of the line width and electron density as a function of height above two coronal holes from forbidden spectral lines of Si VIII. The spectra were obtained with the Solar Ultraviolet Measurements of Emitted Radiation spectrometer flown on the Solar and Heliospheric Observatory spacecraft. The observations concentrate on the dark regions outside the plumes, which are believed to be the location, where the fast solar wind originates. The line width data show that the non-thermal line-of-sight velocity increases from 20 km s-1 at 27 arc sec above the limb to 37 km s-1 some 370 arc sec (i.e. ~1.38 Rsolar) above the limb. The electron density shows a decrease from 3.5 108 cm-3 to 1.6 107 cm-3 over the same distance. This data implies that the non-thermal velocity is inversely proportional to the quadratic root of the electron density in the range 1-1.2 Rsolar, in excellent agreement with that predicted for undamped radially propagating Alfvén waves. Beyond 1.2 Rsolar our data suggests an effective breakdown of linear theory for the propagation of Alfvén waves. Title: Eclipsing behaviour of the radio emission in the Algol system V505 Sagittarii Authors: Gunn, A. G.; Brady, P. A.; Migenes, V.; Spencer, R. E.; Doyle, J. G. Bibcode: 1999MNRAS.304..611G Altcode: We present radio interferometric observations of the EA2 Algol-type binary system V505 Sagittarii made with the ATNF Compact Array at 6 and 3.6 cm over one orbital cycle (1.18 d). We have obtained a strong detection of the source (1.5 mJy at 6 cm and 1.4 mJy at 3.6 cm) and derive a brightness temperature for the emitting region of T_b ~ 2.7 x 10_9 K, a magnetic field strength of 17 < B < 170 G and an electron density of N_e ~ 3.7 x 10_8 cm_-3. The radio flux density levels show a clear modulation with evidence of eclipses of the emission region at both conjunctions of the binary. The form of the light curve implies that the radio source involves at least some enhanced emission in the intra-binary region. This has important consequences for the details of coronal formation and field interaction in active close binary stars. We discuss some scenarios for the formation of intra-binary active regions in Algol-type binary systems. Title: Modelling the spectral energy distribution and SED variability of the Carbon Mira R Fornacis Authors: Lobel, A.; Doyle, J. G.; Bagnulo, S. Bibcode: 1999A&A...343..466L Altcode: We have developed a new method to determine the physical properties and the local circumstances of dust shells surrounding Carbon- and Oxygen-rich stars for a given pulsation phase. The observed mid-IR dust emission feature(s), in conjunction with IRAS BB photometry and coeval optical and near-IR BB photometry, are modelled from radiative transport calculations through the dust shell using a grid of detailed synthetic model input spectra for M-S-C giants. From its application to the optical Carbon Mira R For we find that the temperature of the inner shell boundary exceeds 1000 K, ranging between 1200 K and 1400 K. The optical depth of the shell at 11.3 mu m is determined at tau_ {11 microns }=0.105 with T_eff=3200+/-200 K for the central star in the considered phase of variability. By-products of the analysis are the shell composition of 90% amorphous carbon and only 10% SiC grains with rather small average radii of 0.05+/-0.02 mu m. The dust density distribution assumes a power law of r(-2) for a steady-state wind with a geometrical thickness ranging between 10(4) and 5 10(4) times the inner boundary shell radius and with a high gas mass-loss rate of 3-4 10(-6) Msun y(-1) derived by radiation pressure onto the dust. We show that the optical and near-IR light curves are strongly affected by small changes of T_eff and of the shell optical depth with pulsation. A comparison of high resolution optical spectra of R For and medium/low resolution spectra of other carbon stars with the selected model input spectrum is also provided. Based on observations taken at UKIRT, CST, JCMT, SAAO, AAO and the IRAS Pointsource Catalogue Title: Explosive events in the solar atmosphere Authors: Pérez, M. E.; Doyle, J. G.; Erdélyi, R.; Sarro, L. M. Bibcode: 1999A&A...342..279P Altcode: Two examples of explosive events observed with SUMER in transition region spectral lines are reported here; one detected in C iv 1548 Angstroms, in a region within the northern polar coronal hole, and the other in O vi 1032 Angstroms, in an active region. The event measured in C iv lasted ~ 3 min and extended approximately a region of 8 arc sec along the slit (N-S) and 8 arc sec in the E-W direction. Velocities reached around 150 km s(-1) in the blue wing and 100 km s(-1) in the red wing. The active region events were more energetic and in total lasted ~ 6 min. At the point of maximum activity, a region of 8 arc sec along the slit is covered by one explosive event located in the northern section of the observed region, while in the southern section we observe two events very closely located and extended over a maximum of 14 arc sec along the slit. More precisely, in the northern section we have at least two consecutive events occurring in a short time interval ( ~ 12 min) separated by ~ 3 arc sec. In the E-W direction the raster length covered by each of these events was approximately 4 arc sec. The explosive events seen in O vi showed a very complex structure of subsonic and supersonic velocity flows, both red-shifted and blue-shifted. The apparent maximum velocity reached in the blue wing was approximately 250 km s(-1) and 215 km s(-1) in the red wing. Title: Line Width Variations above a Coronal Hole: Implications for Heating Authors: Doyle, J. G.; Teriaca, L.; Banerjee, D. Bibcode: 1999ASPC..158..366D Altcode: 1999ssa..conf..366D No abstract at ADS Title: Solar and Stellar Activity: Similarities and Differences Authors: Butler, C. J.; Doyle, J. G. Bibcode: 1999ASPC..158.....B Altcode: 1999ssa..conf.....B No abstract at ADS Title: Turbulent Bursts in the Solar Transition Region Authors: O'Shea, E.; Doyle, J. G. Bibcode: 1999ASPC..158..383O Altcode: 1999ssa..conf..383O No abstract at ADS Title: Observations of Explosive Events in the Solar Atmosphere Authors: Pérez, M. E.; Doyle, J. G. Bibcode: 1999ASPC..158..387P Altcode: 1999ssa..conf..387P No abstract at ADS Title: Oscillations in Chromospheric Network Bright Points Authors: Banerjee, D.; Doyle, J. G.; O'Shea, E. Bibcode: 1999ASPC..158..297B Altcode: 1999ssa..conf..297B No abstract at ADS Title: Observations and Modelling of a Flare on AD Leo Authors: Jevremovic, D.; Butler, C. J.; Doyle, J. G. Bibcode: 1999ASPC..158..222J Altcode: 1999ssa..conf..222J No abstract at ADS Title: SUMER Observations of Doppler Shifts in the Quiet Sun and an Active Region Authors: Teriaca, L.; Doyle, J. G.; Banerjee, D. Bibcode: 1999ASPC..158..362T Altcode: 1999ssa..conf..362T No abstract at ADS Title: Dynamical Nature of the Quiet Solar Outer Atmosphere Authors: Banerjee, D.; Doyle, J.; O'Shea, E.; van den Oord, G. Bibcode: 1999ASPC..183..389B Altcode: 1999hrsp.conf..389B No abstract at ADS Title: Modelling of Explosive Events in the Solar Transition Region Authors: Roussev, I.; Erdélyi, S.; Doyle, J. G.; Galsgaard, K. Bibcode: 1999RoAJ....9S..57R Altcode: We present preliminary results of modelling 2D magnetic reconnection in the solar transition region environment. Compressible magnetohydrodynamic (MHD) simulations are performed by using a 2D MHD code based on staggered meshes. The present work is an attempt to numerically simulate magnetic reconnection that occurs between newly emerging magnetic flux and the pre-existing network field, which is widely believed to cause explosive events observed in the solar atmosphere. The formation of asymmetric reconnection jets is demonstrated in this study. Nonlinear anisotropic thermal conduction, radiative losses, and volumetric heating are included in the energy equation in order to investigate the formation of reconnection jets more precisely, as these processes are of fundamental importance at that region. The role of both nonlinear anisotropic thermal conduction and radiative losses is found to be significant in the solar transition region. Title: The Wilson-Bappu Relation for RS CVn Stars Authors: Özeren, F. F.; Doyle, J. G. Bibcode: 1999ASPC..158..315O Altcode: 1999ssa..conf..315O No abstract at ADS Title: The oscillatory nature of the upper solar atmosphere. Authors: O'Shea, E.; Doyle, J. G.; Banerjee, D.; van den Oord, G. H. J. Bibcode: 1999joso.proc..128O Altcode: The authors examine time series spectral data obtained by the SUMER instrument onboard SOHO. Lines of N V 1242 Å, Si II 1533 Å, C IV 1548 Å, C II 1037 Å and O VI 1037.6 Å were measured and found to show intensity oscillations. The oscillations were usually observed to occur in small regions along the slit, limited to a few arcsec. N V 1242 Å typically showed frequencies of between 1 - 2 mHz. The Si II and C IV lines observed simultaneously were found to have differing oscillation frequency ranges of 2 - 8 mHz and 2 - 4 mHz respectively. The C II and O VI lines also measured simultaneously were both found to have oscillation frequency ranges of 2 - 4 mHz. In addition a time lag of ≡50 seconds was measured between the intensity oscillations in these two lines, perhaps signifying a propagating wave from the low temperature C II line region to the higher temperature O VI region of the atmosphere. Title: Observations of explosive events in the solar atmosphere. Authors: Pèrez, M. E.; Doyle, J. G. Bibcode: 1999joso.proc..178P Altcode: Two examples of explosive events observed with SUMER in transition region spectral lines are reported here; one detected in C IV 1548 Å, in a region within the northern polar coronal hole, and the other in O VI 1032 Å, in an active region located in the solar disk. The event measured in C IV lasts over 3 min and extends approximately over a region of 8 arcsec along the slit (N-S) and 8 arcsec in the E-W direction. Velocities reach values of around 150 km s-1 in the blue wing and 100 km s-1 in the red wing. The active region events are more energetic and in total they last over 6 minutes. These explosive events seen in O VI showed a very complex structure of subsonic and supersonic velocity flows, both redshifted and blueshifted. The largest apparent maximum velocity reached in the blue wing was approximately 250 km s-1 and 215 km s-1 in the red wing. Title: Solar and Stellar Activity: Similarities and Differences Authors: Butler, C. J.; Doyle, J. G.; Bailey, M. E. Bibcode: 1998PASP..110.1513B Altcode: Conference was held in Armagh, Northern Ireland, in 1998 September. Proceedings will be edited by C. J. Butler and J. G. Doyle and published in the ASP Conference Series. Title: Broadening of SI VIII lines observed in the solar polar coronal holes Authors: Banerjee, D.; Teriaca, L.; Doyle, J. G.; Wilhelm, K. Bibcode: 1998A&A...339..208B Altcode: We study the variation of the line width and electron density as a function of height above two coronal holes from forbidden spectral lines of Si viii. The spectra were obtained with the Solar Ultraviolet Measurements of Emitted Radiation spectrometer flown on the Solar and Heliospheric Observatory spacecraft. The observations concentrate on the dark regions outside the plumes, which are believed to be the locations, where the fast solar wind originates. The line width data show that the non-thermal line-of-sight velocity increases from 27 {km s}(-1) at 27 arc sec above the limb to 46 {km s}(-1) some 250 arc sec ({i.e. } ~ 180,000 km) above the limb. The electron density shows a decrease from 1.1 10(8) {cm}(-3) to 1.6 10(7) {cm}(-3) over the same distance. This data implies that the non-thermal velocity is inversely proportional to the quadratic root of the electron density, in excellent agreement with that predicted for undamped radially propagating Alfven waves. We show that the energy flux associated with these hydromagnetic waves is sufficient to drive the high speed solar wind streams. Title: The solar transition region: a time-varying interface between the chromosphere and corona? Authors: O'Shea, E.; Doyle, J. G.; Keenan, F. P. Bibcode: 1998A&A...338.1102O Altcode: Using joint observations taken with the CDS and SUMER instruments onboard SOHO, we re-examine the solar transition region in an attempt to determine whether it is de-coupled from the over-lying coronal region. Line ratios calculated from temporal series observations of O iv and Fe xiii spectral lines were converted to electron density, and hence electron pressure using theoretical line ratios. Little or no evidence was found to support the constant electron density assumption, and instead a constant electron pressure is found between the transition region and corona. This lends support to the idea that the transition region is a time varying interface between the chromosphere and corona, and is not formed in unresolved fine-structures that are disconnected from the corona. Title: Center-to-limb line width measurements of solar chromospheric, transition region and coronal lines Authors: Erdelyi, R.; Doyle, J. G.; Perez, M. E.; Wilhelm, K. Bibcode: 1998A&A...337..287E Altcode: Line widths derived from observational data obtained by SUMER onboard SOHO in August 1996 at disk center and at the limb are used to confront those derived via assuming Alfven and/or magneto-acoustic wave heating. The observational data clearly shows a center-to-limb variation in the upper chromospheric and transition region lines, with only a marginal difference in the coronal lines in the sense of additional broadening further from disk center. Numerical estimations based on linear MHD, favour the existence of Alfven wave heating over magneto-acoustic heating, although further calculations are required. For example, non-linear effects could change the wave characteristics which in turn can have a major effect on the overall line broadening. Title: Chromospheric modelling of the Hα and NA I D lines in five M dwarfs of low to high activity level Authors: Short, C. I.; Doyle, J. G. Bibcode: 1998A&A...336..613S Altcode: We have obtained simultaneous high resolution Hα and Na I D spectra of five dwarf M stars that span a wide range in chromospheric activity level. The observed Na I D lines exhibit behavior that is qualitatively similar to that of more well established diagnostics such as the Ca II HK lines: as the activity level, as indicated by the Hα line, increases, the absorption core brightens and then develops an emission reversal. We compare the observed profiles with computed non-LTE profiles from a grid of chromospheric/transition region models. We find that the Hα and Na I D lines tend to be in general agreement as indicators of approximate chromospheric activity level. However, the Hα line systematically indicates a value for the mass loading at the onset of the Transition Region and the location of T_min that is 0.4 dex lower in column mass density than that indicated by Na I D. Therefore, the profile of both lines cannot be simultaneously well fit for all but one of our stars. We also find, in agreement with the pioneering study of Andretta et al. (\cite{adb}), that for dMe stars the shape of the Na I D emission cores is a much more sensitive indicator of chromospheric thickness (or, equivalently, chromospheric steepness) than is Hα , and, therefore, provides a powerful diagnostic complement to Hα . Finally, we investigate the dependence of the predicted line profiles on the values of the stellar parameters and conclude that the inferred chromospheric pressure is sensitive to the choice of T_eff and log g, especially among dMe stars. Specifically, among dMe stars, a model in which the value of T_eff is too small or too large by approximately 200 K, or in which the value of log g is too large or too small by 0.5 dex, will give rise to closest fit values of the column mass density at the location of the Transition Region and T_min that are too small or too large, respectively, by approximately 0.3 dex. As a result, discrepancies between the stellar parameters of our photospheric model and those of the program objects allow us to extract only upper or lower limits for the values of the column mass density at critical points in the chromospheric structure Title: Waves in the solar transition region Authors: Doyle, J. G.; van den Oord, G. H. J.; O'Shea, E.; Banerjee, D. Bibcode: 1998SoPh..181...51D Altcode: The power spectra for line intensities of several lines formed in the upper transition region around 100000 to 250000 K are presented. A period of ∼5 min is clearly present in lines due to Oiii, Oiv, and Ov. In one dataset a period approaching 10 min is present for ∼40 min. The size of the emitting features is limited to ∼7 arc sec squared. In all datasets examined, there is excess power below 4 mHz everywhere along the slit, although the observed periods do not always come from the most intense regions. In ∼40% of instances clear periods are observable in the 2-5 mHz range with the largest power peak at 3.0 mHz. In all regions, the 5.0 mHz power peak is smaller. For the frequencies investigated there are no significant time delays in any of the datasets examined. This finding may not be entirely unexpected as the formation temperatures of Oiii (∼100000 K) and Ov (∼250000 K) may be too close in order to result in an observable phase shift. Title: Coronal line-width variations Authors: Doyle, J. G.; Banerjee, D.; Perez, M. E. Bibcode: 1998SoPh..181...91D Altcode: Line-width measurements of the coronal ion Siviii confirm earlier observations which show an increase in the non-thermal velocity above the solar limb. The present data, taken at the equatorial limb, show an increase from 24 km s-1 at the limb to 28 km s-1 some 25000 km above the limb. The electron density as measured from the Siviii line pair shows a decrease from 3.5 × 108 cm-3 to 1.8 × 108 cm-3 over the same distance. These data imply that the non-thermal velocity is inversely proportional to the quadratic root of the electron density, in excellent agreement with that predicted for undamped radially propagating Alfvén waves. Title: Observations and modelling of spectral energy distributions of carbon stars with optically thin envelopes Authors: Bagnulo, S.; Doyle, J. G.; Andretta, V. Bibcode: 1998MNRAS.296..545B Altcode: We present broad-band photometry in the optical, near-infrared and submillimetre, and mid-infrared spectrophotometry of a selection of carbon stars with optically thin envelopes. Most of the observations were carried out simultaneously. Beside the emission feature at 11.3mum due to silicon carbide grains in the circumstellar environment, many of our mid-infrared spectra show an emission feature at 8.6mum. All the observed spectral energy distributions exhibit a very large far-infrared flux excess. Both these features are indeed common to many carbon stars surrounded by optically thin envelopes. We have modelled the observed spectral energy distributions by means of a full radiative transfer treatment, paying particular attention to the features quoted above. The peak at 8.6mum is usually ascribed to the presence of hydrogenated amorphous carbon grains. We find also that the feature at 8.6mum might be reproduced by assuming that the stars have a circumstellar environment formed of both carbon- and oxygen-rich dust grains, although this is in contrast with what one should expect in a carbon-rich environment. The far-infrared flux excess is usually explained by the presence of a cool detached dust shell. Following this hypothesis, our models suggest a time-scale for the modulation of the mass-loss rate of the order of some 10^3yr. Title: On the rotation-activity correlation for active binary stars Authors: Gunn, A. G.; Mitrou, C. K.; Doyle, J. G. Bibcode: 1998MNRAS.296..150G Altcode: We present an investigation of rotation-activity correlations using International Ultraviolet Explorer (IUE) SWP measurements of the Civ emission line at 1550Angstroms for 72 active binary systems. We use a standard stellar evolution code to derive non-empirical Rossby numbers, R_0, for each star in our sample and compare the resulting Civ rotation-activity correlation to that found for empirically derived values of the Rossby number and that based on rotation alone. For dwarf stars our values of R_0 do not differ greatly from empirical ones and we find a corresponding lack of improvement in correlation. Only a marginal improvement in correlation is found for evolved components in our sample. We discuss possible additional factors, other than rotation or convection, that may influence the activity levels in active binaries. Our observational data imply, in contrast to the theoretical predictions of convective motions, that activity is only weakly related to mass in evolved stars. We conclude that current dynamo theory is limited in its application to the study of active stars because of the uncertainty in the angular velocity-depth profile in stellar interiors and the unknown effects of binarity and surface gravity. Title: Pa-beta as a chromospheric diagnostic in M dwarfs Authors: Short, C. I.; Doyle, J. G. Bibcode: 1998A&A...331L...5S Altcode: We have obtained, for the first time, a high resolution near-infrared spectrum in the region of Pabeta of a chromospherically active M dwarf (AU Mic). We demonstrate that both Pabeta and Hα can be fit with a model of large chromospheric pressure, but that the two lines indicate clearly different values of the exact pressure. There are several important types of missing physics that need to be included in the calculations before the importance of this apparent discrepancy can be assessed. Nevertheless, the approximate agreement of the two lines lends support to an earlier theoretical result that the Paschen series is a useful chromospheric diagnostic in M dwarfs. Title: The photosphere and chromosphere of the RS Canum Venaticorum star, II Pegasi. II. A multi-wavelength campaign in August/September 1992 Authors: Byrne, P. B.; Abdul Aziz, H.; Amado, P. J.; Arevalo, M. J.; Avgoloupis, S.; Doyle, J. G.; Eibe, M. T.; Elliott, K. H.; Jeffries, R. D.; Lanzafame, A. C.; Lazaro, C.; Murphy, H. M.; Neff, J. E.; Panov, K. P.; Sarro, L. M.; Seiradakis, J. H.; Spencer, R. E. Bibcode: 1998A&AS..127..505B Altcode: We describe multi-wavelength, simultaneous observations of the RS CVn star, II Pegasi, most of which were obtained during the first three weeks of September 1992. These observations were made using optical and infra-red broad-band photometry, ultraviolet and optical spectroscopy and microwave monitoring. We have detected photospheric spots and chromospheric flares, as well as deriving a description of mean conditions in the quiet chromosphere. One of the flares, observed in optical photometry and ultraviolet spectroscopy is one of the most energetic ever observed on this star. We demonstrate that in its ``quiescent'' state II Peg is continually variable in most of its chromospheric emissions, as well as in its coronal output. Title: Explosive events modelled in the view of SOHO observations Authors: Erdélyi, R.; Sarro, L. B.; Doyle, J. G. Bibcode: 1998ESASP.421..207E Altcode: 1998sjcp.conf..207E No abstract at ADS Title: Chromospheric and coronal activity levels in the nearby faint M dwarf GL 105B Authors: Doyle, J. G.; Short, C. I.; Byrne, P. B.; Amado, P. J. Bibcode: 1998A&A...329..229D Altcode: Monitoring with the HRI onboard ROSAT failed to detect the nearby faint M dwarf star Gl 105B (a star of anomalously low chromospheric and coronal activity), implying log L_x < 26.1. High resolution optical data for Caii HK indicate a surface flux of ~ 6.5 \ 10(3) \ erg \ cm(-2) \ s(-1) , in good agreement with the previously measured Mg ii hk flux. Based on chromospheric modelling, both the Hα and Caii K line profiles indicate an atmospheric structure which is intermediate between that of an intermediate dM chromosphere and a basal chromosphere. Also, the modelling indicates that a better fit is obtained using a model atmosphere which has Tmin less than 2650 K, and a thin, steep chromosphere. Furthermore, the Caii HK radiative losses may only be ~ 5% of the radiative losses in the UV continuum, implying total chromospheric losses in excess of 10(5) erg cm(-2) s(-1) . Title: Observations of Explosive Events in the Solar Atmosphere Authors: Perez, E. P.; Doyle, J. G.; Erdelyi, R. Bibcode: 1998ASPC..154..666P Altcode: 1998csss...10..666P Two ultraviolet explosive events are reported here; one which lasted over 2 mins and was detected in a region within the northern polar coronal hole and a second event which lasted over 4 mins and was detected within an active region. The coronal hole event first showed a mass upflow, followed by blue and red-shifted plasma, then finally a red-shifted plasma. Velocities reached ~120 km s^{-1}. The active region event was more energetic, showing a second injection after about 2 mins. The maximum velocity reached 300 km s^{-1}. Towards the end of each of these events, the location of the mass upflow/downflow had shifted by 3-4 arcsec compared to the initial location. Title: In Memoriam of P. Brendan Byrne Authors: Doyle, J. G. Bibcode: 1998ASPC..154..127D Altcode: 1998csss...10..127D No abstract at ADS Title: Modeling of Explosive Events in the Solar Atmosphere Authors: Sarro, L. M.; Doyle, J. G.; Montesinos, B.; Erdelyi, R.; de Sterck, H. Bibcode: 1998ASPC..154..693S Altcode: 1998csss...10..693S High-resolution ultraviolet (UV) spectra show transient brightenings --- often referred to as explosive events --- in the solar atmosphere. The present work describes the progress made on their numerical simulations. Using semi-circular magnetic flux tubes we find that thermal energy perturbations drive flows along the flux tube. The time evolution of our simulations first shows a sudden rise in temperature at the perturbation site followed by the ejection of cool dense gas bullets and the generation of sound waves. This is then followed by the appearance of ``new'' transition regions moving at different velocities. Our computational results are converted into UV line profiles in (non)-equilibrium ionization. Observational signatures (e.g., emission measures) are calculated as a function of time at different locations on the solar disk. Title: Modelling the Spectral Energy Distribution of Carbon and Oxygen-rich stars from stellar model spectra Authors: Lobel, A.; Doyle, J. G.; Bagnulo, S. Bibcode: 1998IAUS..191P.307L Altcode: We have developed a new method to determine the physical properties and the local circumstances of dust shells surrounding Carbon- and Oxygen-rich stars for a given pulsation phase. The observed mid-IR dust emission feature(s), in conjunction with IRAS BB photometry and coeval optical and near-IR BB photometry, are modelled from radiative transport calculations through the dust shell using a grid of detailed synthetic model input spectra for M-S-C giants to the DUSTY code. From its application to the optical Carbon Mira R For we find that the temperature of the inner shell boundary exceeds 1000 K, ranging between 1200 K and 1400 K. The optical depth of the shell at 11.3 microns is determined at tau11 = 0.105 with Teff = 3200 +- 200 K for the central star in the considered phase of variability (Jul.-Aug. '95). By-products of the analysis are the shell composition of 90% amorphous carbon and only 10% SiC grains with rather small average radii of 0.05 +- 0.02 microns. The dust density distribution follows a power law of r^{-2} for a steady-state wind with a geometrical thickness ranging between 10^4 and 5 10^4 times the inner boundary shell radius. The density gradient of r^{-2} results from the full dynamic radiative transport calculations which include the momentum transfer from the radiation field. This elaborate method enables the modelling of the variable shape of the silicate feature of o Cet and other oxygen-rich stars in conjunction with the SED observed at various pulsation phases. We discuss the changes in the CSE and the related ranges of the mass-loss rate and terminal outflow velocity. A brief comparison of high-resolution optical spectra of R For, o Cet and spectra of other carbon- and oxygen-rich stars, with the selected model input spectra is also provided. Title: The Dynamical Nature of the Chromosphere Authors: Banerjee, D.; Doyle, J. G.; O'Shea, E. Bibcode: 1998ESASP.417..333B Altcode: 1998cesh.conf..333B No abstract at ADS Title: Transition Region Variability: Evidence for Oscillation Authors: O'Shea, E.; Doyle, J. G. Bibcode: 1998ASPC..154..798O Altcode: 1998csss...10..798O The data reported here was obtained with the Coronal Diagnostic Spectrometer (CDS) in a sit-and-stare mode using a 4 x 240 arcsec slit. Using integration times ranging from 15 to 20 sec, two different types of observing sequences were obtained, the first involved the observation of three oxygen lines due to O 3 599 AA, O 4 554 AA and O 5 630 AA. These lines have temperature of formation ranging from 100,000 K to 250,000 K. The second type of sequence involved four lines, He 1 584 AA formed below 100,000 K, O 4 554 AA and O 5 630 AA formed between 150,000 K to 250,000 K, and Mg 10 610 AA formed at 1,000,000 K. Using a FFT technique, the resulting power spectra reveals periods ranging from 4 to 10 minutes for plasma around the 150,000 to 250,000 K region. These periods were present for ~40 minutes covering a region of ~7 arcsec^2. Excess power was present below 5 mHz in most datasets in He 1 line data. For about 10-15% of the slit a single period was detected. No periods were found in the Mg 10 line, although this may be related to the fact that Mg 10 was rather weak in our data. Title: On the Rotation-Activity Correlation in Active Binaries Authors: Gunn, A. G.; Mitrou, C. K.; Doyle, J. G. Bibcode: 1998ASPC..154.1257G Altcode: 1998csss...10.1257G We present an investigation of rotation-activity correlations using IUE SWP measurements of the C 4 emission line at 1550 AA for 72 active binary systems. We use a standard stellar evolution code to derive non-empirical Rossby numbers for each star in our sample and compare the resulting C 4 rotation-activity correlation to that found for empirically derived values of Rossby number. We find only a marginal improvement in the correlation which suggests an additional factor other than rotation or convective motion influencing the activity levels in evolved stars. We conclude that current dynamo theory is limited in its application to the study of active stars because of the uncertainty in the angular velocity-depth profile in stellar interiors and the unknown effects of binarity and surface gravity. Title: Chromospheric Line Blanketing and the H I Spectrum in dM Stars Authors: Short, C. I.; Doyle, J. G. Bibcode: 1998ASPC..154..865S Altcode: 1998csss...10..865S We present non-LTE calculations of the H 1 spectrum in a grid of chromospheric models that represents a dM0 star in which the activity level ranges from quiescent to very active. We investigate three different treatments of the background opacity: 1) continuous opacity only, 2) blanketing due to lines that form in the photosphere below T_min, and 3) blanketing by lines that form throughout the entire outer atmosphere. We show that the predicted peak flux of Hα in very active (dMe) stars is reduced by ~15% by the inclusion of background line opacity. We compare the synthetic Hα profiles with observed Hα spectra of six early dM stars that span a range of activity level. A consistent treatment of line blanketing that includes the effect of the chromospheric and transition region temperature structure in the calculation of background line opacity is necessary for the accurate calculation of Hα in high activity stars. Title: Line Width Variations in the Solar Polar Coronal Holes Authors: Teriaca, L.; Banerjee, D.; Doyle, J. G. Bibcode: 1998ESASP.417..329T Altcode: 1998cesh.conf..329T No abstract at ADS Title: Randomly sampling the chromospheric peak power distribution. Authors: Doyle, J. G.; van den Oord, G. H. J.; O'Shea, E. Bibcode: 1997A&A...327..365D Altcode: We have analyzed the UV continuum light curves of 2535 pixels obtained during fifteen separate observations of active regions with the Ultraviolet Spectrometer and Polarimeter (UVSP) on board the solar maximum mission in 1989. Specifically we have looked for periodicities. In the power spectra of 738 light curves (i.e., 29%), evidence was found for periodicities at multiple frequencies. For each power spectrum, containing significant power, we determined the frequency at which the maximum power is found. The distribution N(ν), which describes the number of pixels having maximum power at frequency ν, is strongly concentrated in the 2-5mHz band with a distinct maximum at 3-3.5mHz. No pixels had their maximum power above 10mHz and only a few had their maximum power in the 5-10mHz range. The oscillations in the 2-5mHz range are probably related to evanescent acoustic waves driven by the photospheric five minute oscillations. In the 2-5mHz band, the distribution N(ν) resembles very much the power spectra as have been observed near the temperature minimum. This suggests that the photospheric power distribution can be interpreted as a probability distribution for finding a given frequency in the UV continuum light curves. In the 2-5mHz band the spread of the maximum powers and the spread of the count rates, at any frequency, is much larger than above 5mHz where both are relatively constant. No clear correlation is found between the maximum power and the count rate in a pixel. Furthermore, no evidence is found for emission from the shocks which have recently been invoked to explain the formation of CaII grains. Whether this is due to temperature effects is unclear. Our general procedure adopted to estimate the confidence level in the power spectrum of a light curve containing photon noise can be equally applied to SUMER and CDS data from SOHO. Title: Chromospheric line blanketing and the hydrogen spectrum in M dwarfs. Authors: Short, C. I.; Doyle, J. G. Bibcode: 1997A&A...326..287S Altcode: We present non-LTE calculations of the HI spectrum in a grid of chromospheric models that represents a dM0 star in which the activity level ranges from quiescent to very active. We investigate three different treatments of the background opacity: 1) continuous opacity only, 2) blanketing due to lines that form in the photosphere below T_min_, and 3) blanketing by lines that form throughout the entire outer atmosphere. We show that the predicted Wlambda_ of Lyα in all models is reduced by as much as a factor of =~4, and that of Hα in very active (dMe) stars is enhanced by a factor of about two by the inclusion of background line opacity. A consistent treatment of line blanketing that includes the effect of the chromospheric and transition region temperature structure in the calculation of background line opacity is necessary for the accurate calculation of Lyα, and in some cases Hα, in these stars. The Hα line in less active models, and the Paβ line in all models, is negligibly affected by the treatment of background opacity. We also show that, in addition to the expected suppression of emergent flux in the visible by line blanketing, the broad-band continuum flux in regions where λ<2000A is increased by as much as a factor of three in some models by the inclusion of line blanketing. This reduces the equivalent width of the Lyman series by a factor of four and is due to the veil of background lines going into emission in the UV, and to the stronger coupling of the background source function to the Planck function in the presence of blanketing by thermal lines. We confirm the results of earlier calculations that suggest the dominance of the continuum emission in the radiative cooling of the chromosphere. Therefore, any proposed heating mechanisms must supply at least an order of magnitude more non-radiative heating than would be required on the basis of an analysis in which only emission line cooling is considered. We also include a preliminary assessment of non-LTE effects in the background opacity on the emergent UV continua. Title: The CaI 4227 line as a chromospheric diagnostic for M dwarfs. Authors: Short, C. I.; Doyle, J. G.; Byrne, P. B. Bibcode: 1997A&A...324..196S Altcode: In M dwarfs the CaI 4227 line is saturated, therefore, the line core forms at a relatively small column mass density. As a result, the line is a potential diagnostic of chromospheric structure in these stars. We have calculated line profiles out of LTE for a grid of early M dwarf atmospheric models that spans the range from low to high chromospheric pressure and covers a range of observed activity levels. We have found that this line is sensitive to the detailed structure of the chromosphere in the same way as well studied strong lines such as Hα and CaII HK: as the chromospheric pressure increases, the line changes from absorption to strong emission with a central double reversal. Therefore, observations of the CaI 4227 line in M dwarfs would provide a useful additional constraint on the structure of the outer atmosphere. We also calculate consistently the line blanketing in the upper atmosphere of models with a chromosphere and transition region and investigate the effect of its inclusion on CaI 4227. Finally, we demonstrate that the effects of Partial Frequency Redistribution must be taken into account if the CaI 4227 is to be used as an accurate diagnostic of the T_min_ region in dMe stars. Title: Nonthermal Velocities in the Solar Transition Zone and Corona Authors: Doyle, J. G.; O'Shea, E.; Erdélyi, R.; Dere, K. P.; Socker, D. G.; Keenan, F. P. Bibcode: 1997SoPh..173..243D Altcode: Nonthermal velocities are presented for spectral lines covering the temperature range 10 4-10 6 K, measured from high-spectral-resolution data for several solar features observed at the limb by the high resolution telescope and spectrograph (HRTS), including a coronal hole, `quiescent regions' and several small-scale active regions. These results are compared with predictions based on acoustic waves and heating via Alfvén waves. It is likely that more than one mechanism is operating simultaneously, in particular, resonant Alfvén wave heating, which is very sensitive to background plasma motions. Title: Observations and Modelling of Spectral Energy Distributions of Asymptotic Giant Branch Stars Authors: Bagnulo, S.; Doyle, J. G. Bibcode: 1997Ap&SS.251..177B Altcode: No abstract at ADS Title: The NaI λλ5890,5896 resonance doublet as chromospheric diagnostics in M dwarfs. Authors: Andretta, V.; Doyle, J. G.; Byrne, P. B. Bibcode: 1997A&A...322..266A Altcode: The Nai D lines at 5890/5896Å are very prominent features in the spectrum of late-type stars. Nevertheless, little attention has been devoted to the potential use of those lines as chromospheric diagnostics. As a case study, we explore the dependence on chromospheric activity of the D lines in a star with T_eff_=3700K, logg=4.7 and solar metallicity. The results are compared with the better studied hydrogen spectrum. We find that the D lines seem to be a promising diagnostic of the lower-middle chromosphere, that can complement the information given by lines like Hα. We also find that, for detailed quantitative studies, it is necessary to include a proper treatment of the background opacities. Less important, instead, is the need of careful treatment of transitions induced by collisions with hydrogen atoms. Finally, our calculations make it clear that, for the most active stars, the level of coronal emission should also be taken into account. Title: Carbon stars with detached dust shells: the circumstellar envelope of UU Aurigae. Authors: Bagnulo, S.; Skinner, C. J.; Doyle, J. G.; Camphens, M. Bibcode: 1997A&A...321..605B Altcode: We have modelled the spectral energy distribution of the carbon-rich star UU Aurigae, which shows an excess flux in the far infrared and sub-millimeter regions, in terms of a detached shell generated by an episode of higher (than the current) mass loss rate. Two different compositions for the detached shell were used: oxygen-rich and carbon-rich dust grains. By assuming that at longer wavelengths the extinction coefficients of the oxygen-rich grains follow a λ^-2^ law, and those of the amorphous carbon follow a λ^-1.3^ law, we show that the model including a detached carbon-rich shell produces a more satisfactory fit to the observational data compared to the model with a detached oxygen-rich shell. Moreover, we derived a relatively small value for the distance of the detached shell from the central star, which implies that the episode of high mass loss rate ended only few hundred years ago. The results of our analysis are consistent with the scenario for the stellar evolution on the asymptotic giant branch which predicts a short time-scale modulation of the mass loss rate induced by repeated Helium shell-flashes. Title: Radio and extreme-ultraviolet observations of CF Tucanae Authors: Gunn, A. G.; Migenes, V.; Doyle, J. G.; Spencer, R. E.; Mathioudakis, M. Bibcode: 1997MNRAS.287..199G Altcode: We present contemporaneous EUV and radio observations obtained for the totally eclipsing chromospherically active RS CVn-type binary CF Tucanae. Observations were made with the ATNF Compact Array at 6 and 3.6cm over one complete orbital cycle of the system, and with the EUVE Deep Survey/Spectrometer telescope over five orbital cycles. We obtained a strong detection of the source (1.9mJy at 6cm and 1.1mJy at 3.6cm) in the radio. Both EUV and radio flux levels appear to show a clear modulation at the orbital period with a maximum at phase 0.5 which indicates the existence of an intra-binary region of activity. This has important consequences for the details of coronal formation and field interaction in active close binary stars. We interpret the EUV emission as an isotropically radiating thermal source; on the other hand, the radio emission shows evidence of intrinsic gyromagnetic directivity. We also demonstrate that contemporaneous EUV and radio observations are not sufficient to determine the characteristics of the gyro-emission electron population. Title: Constraints on mass loss from dMe stars: theory and observations. Authors: van den Oord, G. H. J.; Doyle, J. G. Bibcode: 1997A&A...319..578V Altcode: We show that the flux distribution of a wind from a cool star differs considerably from what is predicted by the theory for mass loss from hot stars. The differences are caused by the facts that 1) the mass loss rates are lower, resulting in smaller optical depths in the wind, and 2) for winds from cool stars the temperature of the wind is higher than the temperature of the star while for winds from hot stars the reverse holds. These differences result in substantial modifications of the flux distribution and imply that care must be exercised when applying the flux predictions by e.g. Wright and Barlow (1975MNRAS.170...41W) to winds from cool stars. By using observational constraints we show that the mass loss from cool dwarf stars equals at most 10^-12^Msun_/yr. This is a factor hundred lower than previous estimates. At this rate the mass loss from dMe stars is of little importance for the enrichment of the interstellar medium. By solving the radiative transfer equations for stellar winds from dMe stars, we show that the inferred power-law flux distributions, based on radio, JCMT and IRAS data, cannot be reconciled with the flux distributions from a stellar wind of 10^-10^Msun_/yr as was previously assumed. The maximum allowable mass loss rate is at most a few times 10^-12^Msun_/yr which implies that the fluxes observed with JCMT, IRAS, and in the future with ISO, require a different interpretation than free-free emission from a stellar wind. Title: Environments of active close binaries. II. GK Hydrae and TY Pyxidis. Authors: Gunn, A. G.; Doyle, J. G.; Houdebine, E. R. Bibcode: 1997A&A...319..211G Altcode: High-resolution spectroscopic observations were obtained for two eclipsing active close binary systems, GK Hydrae and TY Pyxidis. For GK Hya excess emission was observed in the Balmer lines and Mg I b lines while TY Pyx showed excess emission in the Balmer lines and Ca ii H&K lines. The emission from GK Hya arises from a global phenomenon associated solely with the secondary component. The lack of significant He I D_3_ excess absorption and an analysis of the flux ratio in the Balmer lines suggest that the emission originates in prominence-like material seen off the limb of the star. A marginal broad excess absorption band centered around the Balmer emission peaks may be caused by this material absorbing the stellar continuum against the disk with high (350km/s) line-of-sight turbulent velocities. The inference that plage-like regions and associated star-spots are not substantial on this star is in agreement with the lack of spot modulation in the photometric light curve. For TY Pyx the majority of the Hβ excess and a larger proportion of the Ca ii core emission could be attributed to a global phenomenon on the primary. Analysis suggests that very large volumes are responsible for the emission, however, there is no observational evidence for the existence of discrete extended structures around TY Pyx. Title: M VIII Diagnostic Line Ratios in SKYLAB Solar Observations Authors: Foster, V. J.; Keenan, F. P.; Reid, R. H. G.; Doyle, J. G.; Zhang, H. L.; Pradhan, A. K.; Widing, K. G. Bibcode: 1997SoPh..170..217F Altcode: Recent calculations of Mgviii electron and proton impact excitations rates are used to derive theoretical electron temperature (Te)- and density (Ne)-sensitive emission line ratios involving transitions in the 315-782 Å wavelength range. Some of these ratios are presented in the form of ratio-ratio diagrams, which should in principle allow both Ne and Te to be deduced. These results are compared with solar observational data from Skylab, but agreement between theory and observation is very poor, probably due to blending. Title: The intrinsic LY α to H α ratio in M dwarf stars. Authors: Doyle, J. G.; Mathioudakis, M.; Andretta, V.; Short, C. I.; Jelinsky, P. Bibcode: 1997A&A...318..835D Altcode: Using Ly α line profiles generated from a grid of M dwarf model atmospheres we calculate the attenuation factor [i.e. Lyα(obs)/Lyα(intrin)] due to the interstellar medium as a function of hydrogen column density. Then using selected model atmospheres, attenuation factors were calculated for those M dwarfs with available Ly α observations. The prime motivation in this work has been to look afresh at the intrinsic Ly α to H α flux ratio, an important constraint in the radiative transfer modelling of M dwarfs. For those active dMe stars where both lines were observed, the intrinsic ratio is ~3-5 (with ~50% variation). The major uncertainty in this work has been the interstellar hydrogen column density, emphasizing the need for further work in this area and in particular an accurate model of its variation in all directions. Title: An active K0 IV-V star and a hot white dwarf (EUVE J0702+129) in a wide binary. Authors: Vennes, S.; Christian, D. J.; Mathioudakis, M.; Doyle, J. G. Bibcode: 1997A&A...318L...9V Altcode: We present far ultraviolet and optical spectroscopy of the Extreme Ultraviolet Explorer (EUVE) survey source EUVE J0702+129 revealing a composite K0 star plus DA white dwarf spectrum. The International Ultraviolet Explorer spectra show continuum emission from a hot white dwarf (Teff=30-40,000K) and a rising contribution from the K0 star at λ>2500Å. High resolution optical spectroscopy uncovers a high level of activity with strong Hα and Ca H&K emission; application of the Wilson-Bappu relation indicates that the secondary star is slightly above the main sequence (K0 IV-V). Both objects are found at a distance of ~130pc and they likely constitute a physical pair. The EUV emission is dominated by the white dwarf, but the late-type star certainly contributes at higher energy. An interesting parallel is drawn with other DA+K0 pairs with moderately active secondaries such as HD 18131 and HR 1608. The present discovery as well as other recent ones demonstrate the existence of a large population of white dwarfs hidden by evolved companions (III-IV). Title: EUV Emission from RS Canum Venaticorum binaries. Authors: Mitrou, C. K.; Mathioudakis, M.; Doyle, J. G.; Antonopoulou, E. Bibcode: 1997A&A...317..776M Altcode: We performed a study of 104 RS CVn systems in the extreme ultraviolet (EUV) using the all-sky survey data obtained by the Extreme Ultraviolet Explorer (EUVE). The present sample includes several new RS CVn detections; 11 more than in the published EUVE catalogs, and 8 more than in the ROSAT Wide Field Camera catalog. The ratio of detections to non-detections remained constant throughout the sky, implying that our detections are not limited by the exposure time but are most likely limited by absorption from the interstellar medium. A general trend of increasing Lex/B (50-180Å) flux with decreasing rotational period is clear. The dwarf systems exhibit a leveling-off for the faster rotators. In contrast, the evolved systems exhibit no such effect. For the RS CVn systems the losses in the EUV represent a smaller fraction of the coronal radiative losses, as compared to active late-type dwarfs. Title: Environments of active close binaries. I. ER Vulpeculae. Authors: Gunn, A. G.; Doyle, J. G. Bibcode: 1997A&A...318...60G Altcode: High-resolution observations of the eclipsing active close binary system ER Vulpeculae have revealed excess emission in the Hα, the Ca II IRT and the Mg I b lines and excess absorption in the He I D_3_ line. The emission appears to be from a global phenomenon with the secondary component the more active. Analysis has revealed that the emission arises in plage-like material covering perhaps half of the secondary's surface. This gives credence to X-ray and UV studies which have indicated that ER Vul is near the saturation limit for dynamo-induced activity. No firm spectroscopic evidence for the existence of extended material around ER Vul was found. A consistent velocity offset of ~10km/s was observed in the excess Hα emission from the secondary component which may be associated with active regions such as spicules. If so this represents the first observation of the equivalent of solar spicule emission in a stellar system other than the Sun. Title: MHD Waves Observed (?) by SOHO: MHD Wave Heating Authors: Erdélyi, R.; Perez, E. P.; Doyle, J. G. Bibcode: 1997ESASP.404..357E Altcode: 1997cswn.conf..357E No abstract at ADS Title: Chromospheric line blanketing and the CA I 4227 line in M dwarfs Authors: Short, C. I.; Doyle, J. G. Bibcode: 1997IrAJ...24...35S Altcode: In M dwarfs the Ca I 4227 line is saturated, therefore, the line core forms at a relatively small column mass density. As a result, the line is a potential diagnostic of chromospheric structure in these stars. We have calculated line profiles out of LTE for a grid of early M dwarf atmospheric models that spans the range from low to high chromospheric pressure and covers a range of observed activity levels. We have found that this line is sensitive to the detailed structure of the chromosphere in the same way as well studied strong lines such as H alpha and Ca II HK: as the chromospheric pressure increases, the line changes from absorption to strong emission with a central double reversal. Therefore, observations of the Ca I 4227 line in M dwarfs would provide a useful additional constraint on the structure of the outer atmosphere. We also calculate consistently the line blanketing in the upper atmosphere of models with a chromosphere and transition region and investigate the effect of its inclusion on Ca I 4227. Title: Explosive Events Observed by SOHO Authors: Erdélyi, R.; Perez, E. P.; Doyle, J. G. Bibcode: 1997ESASP.404..353E Altcode: 1997cswn.conf..353E No abstract at ADS Title: Modelling of Explosive Events in the Solar Atmosphere Authors: Sarro, I. M.; de Sterk, H.; Erdélyi, R.; Montesinos, B.; Doyle, J. G. Bibcode: 1997ESASP.404..657S Altcode: 1997cswn.conf..657S No abstract at ADS Title: In memorian: Patrick Brendan Byrne (28 September 1947 - 16 September 1997) Authors: Doyle, J. G.; Butler, C. J.; Bailey, M. E. Bibcode: 1997MmSAI..68..945D Altcode: No abstract at ADS Title: A non-empirical rotation--activity correlation for active binaries Authors: Gunn, A. G.; Mitrou, C. K.; Doyle, J. G. Bibcode: 1997jena.confE.145G Altcode: We present an investigation of rotation-activity correlations using IUE SWP measurements of the CIV emission line at 1550AA for 72 active binary systems. We use a standard stellar evolution code to derive non-empirical Rossby numbers for each system. We compare the resulting rotation--CIV activity correlation to that found for empirically derived Rossby numbers and to the one based on period only. The marginal only improvement in the correlation that we find, is surprising considering that the empirically derived Rossby numbers were for main-sequence stars and should not be appropriate for evolved stars. This suggests an additional factor (other than rotation and convective motion) influencing the activity levels. Our observational data imply that activity is only weakly related to mass in evolved stars, in contrast to the theoretical predictions of convection zone motions. We conclude that current dynamo theory is limited in its application to the study of active stars, because of the uncertainty in the angular velocity--depth profile in stellar interiors and the unknown effects of binarity and surface gravity. Title: Chromospheric Line Blanketing and the Hydrogen Spectrum of dM Stars Authors: Short, C. I.; Doyle, J. G. Bibcode: 1996AAS...189.8109S Altcode: 1996BAAS...28.1383S We present non-LTE calculations of the Hi spectrum in a grid of chromospheric models that represents a dM0 star in which the activity level ranges from quiescent to very active. We investigate three different treatments of the background opacity: 1) continuous opacity only, 2) blanketing due to lines that form in the photosphere below Tmin, and 3) blanketing by lines that form throughout the entire outer atmosphere. We show that the predicted W_lambda of Lyalpha in all models, and of Hα in very active (dMe) stars, is reduced by as much as a factor of ~ 4 by the inclusion of background line opacity. A consistent treatment of line blanketing that includes the effect of the chromospheric and transition region temperature structure in the calculation of background line opacity is necessary for the accurate calculation of Lyalpha , and in some cases Hα , in thes e stars. The Hα line in less active models, and the Pabeta line in all models, is negligibly affected by the treatment of background opacity. We also show that the broad-band continuum flux in regions where lambda < 2000 A is increased by as much as a factor of ~ 3 in some models by the inclusion of chromospheric line blanketing. Title: Comprehensive Multiwavelength Observations of the 1992 January 7 Solar Flare Authors: Silva, Adriana V. R.; White, Stephen M.; Lin, Robert P.; de Pater, Imke; Gary, Dale E.; McTiernan, James M.; Hudson, Hugh S.; Doyle, J. Gerry; Hagyard, Mona J.; Kundu, Mukul R. Bibcode: 1996ApJS..106..621S Altcode: Observations of a solar flare that occurred at 2022 UT on 1992 January 7, during the 1991 December/1992 January Max `91 campaign, are presented. This flare was observed simultaneously in Hα, radio (at microwave and millimeter wavelengths), and soft and hard X-rays (by the Yohkoh spacecraft) with high spatial and moderate spectral resolution. A comparison of magneto grams before and after the flare shows evidence of the emergence of new magnetic flux of opposite polarity at the flare site. Although this flare was only of moderate size (GOES classification C8.9 and Hα importance SF), it exhibited several distinct bursts and at least 10 spatially distinct hard/soft X-ray sources. Cospatial Hα brightenings suggest that most of the X-ray sources are located at footpoints of magnetic loops. Two of the hard X-ray sources have no Hα counterparts and are therefore believed to be located at loop tops. The flare consisted of three bursts of particle acceleration followed by a purely thermal phase. High spectral resolution Ca XIX line profiles indicate upflows shortly after the second acceleration phase. Analysis of the microwave/hard X-ray/soft X-ray emission from individual sources provides information on the radio emission mechanisms, the energetic electron population, the magnetic field strength, and the plasma density. These parameters were estimated for the two microwave sources observed during the third acceleration burst; these sources were simultaneously detected in soft X-rays, and one of the sources is also seen in hard X-ray maps. Although the microwave emission is consistent with the gyro synchrotron mechanism, the millimeter emission, which peaks during the thermal phase when all nonthermal activity has ceased, is likely due to thermal bremsstrahlung from the soft X-ray emitting hot plasma. The energy lost to collisions by the energetic (>15 keV) electrons and the energy contained in the thermal plasma are calculated for each source. The energy injected by the nonthermal electrons from all sources is estimated to be 1030 ergs. Only the soft X-ray sources with gradual time profiles seem to show the Neupert effect. Title: Flare energetics: analysis of a large flare on YZ Canis Minoris observed simultaneously in the ultraviolet, optical and radio. Authors: van den Oord, G. H. J.; Doyle, J. G.; Rodono, M.; Gary, D. E.; Henry, G. W.; Byrne, P. B.; Linsky, J. L.; Haisch, B. M.; Pagano, I.; Leto, G. Bibcode: 1996A&A...310..908V Altcode: The results of coordinated observations of the dMe star YZ CMi at optical, UV and radio wavelengths during 3-7 February 1983 are presented. YZ CMi showed repeated optical flaring with the largest flare having a magnitude of 3.8 in the U-band. This flare coincided with an IUE exposure which permits a comparison of the emission measure curves of YZ CMi in its flaring and quiescent state. During the flare a downward shift of the transition zone is observed while the radiative losses in the range 10^4^-10^7^K strongly increase. The optical flare is accompanied with a radio flare at 6cm, while at 20cm no emission is detected. The flare is interpreted in terms of optically thick synchrotron emission. We present a combined interpretation of the optical/radio flare and show that the flare can be interpreted within the context of solar two-ribbon/white-light flares. Special attention is paid to the bombardment of dMe atmospheres by particle beams. We show that the characteristic temperature of the heated atmosphere is almost independent of the beam flux and lies within the range of solar white-light flare temperatures. We also show that it is unlikely that stellar flares emit black-body spectra. The fraction of accelerated particles, as follows from our combined optical/radio interpretation is in good agreement with the fraction determined by two-ribbon flare reconnection models. Title: Estimating the total radiative power output from the hot outer layers of late-type stellar atmospheres: how many lines are required? Authors: Doyle, J. G. Bibcode: 1996A&A...307..162D Altcode: The total radiative power output from the hot outer layers of six late-type stars (of different spectral types and luminosity class) is derived via an emission measure technique. This analysis was based on observational data from the spectral range 100A to 3000A obtained as a result of three separate satellite missions, i.e. Hubble Space Telescope, International Ultraviolet Explorer and the Extreme Ultraviolet Explorer. Solar observational data of active regions, coronal holes, sunspots, `quiescent' regions and flares were also used. Based on the derived total power output from all of these different plasma, it is shown that a linear relationship involving a single transition region line can be used to provide an accurate estimate of the total power output as previously shown for the Sun. The derived relationship does not include losses due to hydrogen, nor the UV continuum which can be a large contributor, particularly for very active stars. Title: EUV emission lines of O IV observed in solar spectra by the S-055 instrument on Skylab. Authors: O'Shea, E.; Foster, V. J.; Keenan, F. P.; Doyle, J. G.; Reid, R. H. G.; Zhang, H. L.; Pradhan, A. K. Bibcode: 1996A&A...306..621O Altcode: Recent calculations of electron and proton impact excitation rates in O IV are used to derive the intensity ratios of lines in the ~340-1350A wavelength range as a function of electron temperature (T_e_) and density (N_e_). These results are presented in the form of ratio-ratio diagrams, which should in principle allow both N_e_ and T_e_ to be deduced for the O IV line emitting region of a plasma. Electron temperatures derived from ratio-ratio diagrams involving the 790A/554A ratio, in conjunction with observational data for several solar features obtained with the Harvard S-055 spectrometer on board Skylab, are found to be in reasonable agreement with the value of T_e_ expected from ionization equilibrium calculations. This provides some support for the theoretical diagnostics presented in this paper, and hence the atomic data used in their derivation. However other temperature and density sensitive ratios involving the O IV multiplets at 609A, 625A and 787A could not be used to derive plasma parameters from the ratio-ratio diagrams, due to blending with lines of Mg X and S V. Title: Basic Stellar Parameter Determination for Active Cool Eclipsing Binaries Authors: Budding, E.; Butler, C. J.; Doyle, J. G.; Etzel, P. B.; Oláh, K.; Zeilik, M.; Brown, D. Bibcode: 1996Ap&SS.236..215B Altcode: We examine procedures for the determination of reliable parameter sets characterizing stars in short period eclipsing binary systems of later dwarf, generally sunlike, spectral types. These stars have magnetodynamically active components and form a useful “extension to the solar laboratory”. Their much more rapid rotation than that of the Sun implies correspondingly enhanced indications of activity-particularly with relatively large maculation effects in broadband data. We concentrate on five such systems, for which we discuss new data and analyses-CG Cyg, ER Vul, YY Gem, BH Vir and UV Psc. Our main aim is to enable more reliable absolute comparisons between the basic properties of such stars and the Sun. Some indications of the ages of these binaries can also provide further pointers to the relative importance of different parameters (e.g. rotation, age, etc.), in determining stellar activity. Title: On IV diagnostic line ratios in solar EUV spectra. Authors: Foster, V. J.; O'Shea, E.; Keenan, F. P.; Doyle, J. G.; Reid, R. H. G.; Zhang, H. L.; Pradhan, A. K. Bibcode: 1996uxsa.conf..425F Altcode: 1996uxsa.coll..425F Recent calculations of electron and proton impact excitation rates in O IV are used to derive the intensity ratios of lines in the ≡340 - 1350 Å wavelength range as a function of electron temperature (Te) and density (Ne). These results are presented in the form of ratio-ratio diagrams, which should in principle allow both Ne and Te to be deduced for the O IV line emitting region of a plasma. Electron temperatures derived from ratio-ratio diagrams involving the 790 Å/554 Å ratio, in conjunction with observational data for several solar features obtained with the Harvard S-055 spectrometer on board Skylab, are found to be in reasonable agreement with the value of Te expected from ionization equilibrium calculations. This provides some support for the theoretical diagnostics presented in this paper, and hence the atomic data used in their derivation. Title: Cross-correlation radial velocity measurements of chromospherically active binaries. Authors: Gunn, A. G.; Hall, J. C.; Lockwood, G. W.; Doyle, J. G. Bibcode: 1996A&A...305..146G Altcode: We present observational radial velocity curves for 12 chromospherically active binary systems and individual measurements for a further 5 systems. These binaries are LX Per, V 471 Tau, EI Eri, OU Gem, GK Hya, TY Pyx, Z Her, MM Her, V772 Her, ER Vul, BD-004234, MY Cyg, AR Lac, KZ And, RT And, SZ Psc and EZ Peg. Six of our target binaries do not agree with published ephemerides or orbital parameters. We also present a rigorous derivation of the resolution limit for binary star cross-correlation radial velocities. Using synthetic spectral data we investigate the errors induced by rotational broadening, signal-to-noise ratio, spectral-type mismatch and luminosity ratio. Title: On the diagnostic contents of NA I lines in M dwarfs Authors: Andretta, V.; Byrne, P. B.; Doyle, J. G. Bibcode: 1996ASPC..109..559A Altcode: 1996csss....9..559A No abstract at ADS Title: Environments of active binaries Authors: Gunn, A. G.; Doyle, J. G. Bibcode: 1996ASPC..109..649G Altcode: 1996csss....9..649G No abstract at ADS Title: Observation and modelling of main sequence star chromospheres. V. Ultraviolet excess emission in active M dwarfs. Authors: Houdebine, E. R.; Mathioudakis, M.; Doyle, J. G.; Foing, B. H. Bibcode: 1996A&A...305..209H Altcode: The variation in the continuum intensity (50-5000nm) of late-type M dwarfs is investigated via two grids of model atmospheres with different temperature minima. It is shown that the (E)UV intensity is mostly dependent on the transition region pressure, although the temperature minimum also plays an important role. We also observe a significant frequency redistribution of the photospheric flux when changing the minimum temperature, and a black-body type of emission from the lower chromosphere. We examine the formation of the continuum and point out that, although some differences appear for very low or very high activity levels, in general the global picture is much alike the Sun. We show that the UV continua are very good diagnostics of cool dwarf atmospheres, from the temperature minimum to the transition region. Our calculations give a good overview of the domains where physical parameters and spectral signatures are most likely observed. We compute the UBV(RIJKL)_J_ broad band fluxes for our models and conclude that the chromospheric contribution should be detectable in the U band and possibly also in the B band. We compare our calculations to recent high resolution observations for selected stars in a narrow spectral range ((R-I)_K_=0.875+/-0.05); we show that Hα line profiles behave as expected, with a tight correlation between the line width and equivalent width. Hα emission line stars show an excess in U-B color but not in B-V. They are also more luminous than their less active absorption line counterparts, which indicates that active dwarfs have not yet reached the main sequence and are intermediate between T Tauri stars and main sequence stars. The anomalously large proportion of active stars towards late spectral types is attributed to the very slow contraction phase for low mass stars. We calculate the fluxes in the Extreme Ultraviolet Explorer Sn/SiO band (500-740A) and show that they are compatible with observed upper limits. We further compare our results for the upper activity range to pre-main sequence models and observations. They strongly support the case for a chromospheric contribution to Hα and the blue/UV excess for those objects (T Tauris, naked T Tauris, YSOs). An important conclusion is that at high pressures, corresponding to active dMe stellar atmospheres, the chromosphere becomes a very efficient radiator at continuum wavelengths. From log(M)~-5 (column mass), radiative losses in the continuum rise exponentially and faster than in Hydrogen spectral lines because of their larger optical depths. As a consequence, Hi spectral lines have a small or negligible contribution to the total Hi (lines and continua) and white light radiative budget. We show that the hydrogen series dominate the radiative cooling in spectral lines (from 40% to 90%) for Hα emission line stars. The cooling in the (E)UV continuum overwhelms the total radiative budget and is much larger than that in outstanding chromospheric and transition region lines (e.g. CaII, MgII, HI Lyman and Balmer). We propose this as a possible contribution for the apparent saturation observed in some spectral lines, therefore questioning the suggestion of saturation in magnetic activity levels. Title: Radio Eclipse Imaging of CF Tucanae Authors: Gunn, A. G.; Doyle, J. G.; Migenes, V.; Spencer, R. E. Bibcode: 1996ASPC...93..321G Altcode: 1996ress.conf..321G No abstract at ADS Title: Nonthermal velocities in the solar transition and coronal region observed with the high-resolution telescope and spectrograph Authors: O'Shea, E.; Doyle, J. G.; Dere, K. P.; Keenan, F. P. Bibcode: 1996ASPC..109..145O Altcode: 1996csss....9..145O No abstract at ADS Title: The silicate-like mid-infrared spectrum of the C-rich star R SCULPTORIS Authors: Bagnulo, S.; Doyle, J. G.; Barlow, M. J.; Skinner, C. J. Bibcode: 1996ASPC..109..517B Altcode: 1996csss....9..517B No abstract at ADS Title: Accumulative coronal, chromospheric and transition region radiative power output from late-type stars Authors: Doyle, J. G. Bibcode: 1996ASPC..109..601D Altcode: 1996csss....9..601D No abstract at ADS Title: Surface inhomogeneities on YY Geminorum Authors: Butler, C. J.; Doyle, J. G.; Budding, E. Bibcode: 1996ASPC..109..589B Altcode: 1996csss....9..589B No abstract at ADS Title: The RS CVn binaries seen through the Eye of IRAS Authors: Mitrou, C. K.; Doyle, J. G.; Mathioudakis, M.; Antonopoulou, E. Bibcode: 1996hell.conf..301M Altcode: No abstract at ADS Title: EM distribution and radiative losses of II Peg and lambda And Authors: Mitrou, C. K.; Doyle, J. G.; Mathioudakis, M.; Antonopoulou, B. Bibcode: 1996ASPC..109..275M Altcode: 1996csss....9..275M No abstract at ADS Title: SKYLAB Observations of Temperature and Density Sensitive Emission Line Ratios in NE VI Authors: Greer, C. J.; Foster, V. J.; Keenan, F. P.; Reid, R. H. G.; Doyle, J. G.; Zhang, H. L.; Pradhan, A. K. Bibcode: 1996aeu..conf..537G Altcode: 1996IAUCo.152..537G No abstract at ADS Title: The emission of the RS CVn binaries in the IRAS passbands. Authors: Mitrou, C. K.; Doyle, J. G.; Mathioudakis, M.; Antonopoulou, E. Bibcode: 1996A&AS..115...61M Altcode: In the literature, there is an ambiguity pertaining to the existence of a far-IR excess in RS CVn systems. In the current paper we undertook a study of the behaviour of 103 such systems in the IRAS passbands. We found 72 acceptable detections in the 12μm band, and 40 in the 25μm band (50% more than the IRAS Point Source Catalog). Although our findings may be interpreted as indicating towards the existence of an excess beyond 12μm for some systems, the evidence is not conclusive in all but two cases. These are systems GX Lib and HR 7428, with Capella being the only system where the IRAS fluxes in all four bands originate from the stellar photosphere. Given the accuracy of the data we did not find 12μm excess for any system. We argue that the IRAS data alone cannot settle the issue, as their uncertainty is, in many cases, higher than what the Signal-to-Noise ratio of each observation implies. Furthermore, at the higher wavelength bands the IRAS angular resolution drops from 0.5' at 12μm to 2' at 100μm and the background becomes very complex, so one cannot be certain about the origin of the observed flux. The existence of IR excess in the RS CVn stars is important as far as the evolutionary scenarios for these systems are concerned. Future missions such as the Infrared Space Observatory will return more sensitive and accurate measurements and the ambiguity can be removed. The fluxes we quote will be helpful when planning these future observations, as we provide more accurate photometry and for a larger selection of sources than the IRAS Point Source Catalog. Title: Evolution of two small solar flares. Authors: Fludra, A.; Doyle, J. G.; Metcalf, T.; Lemen, J. R.; Phillips, K. J. H.; Culhane, J. L.; Kosugi, T. Bibcode: 1995A&A...303..914F Altcode: Data from the YOHKOH satellite have been analysed for two small flares (GOES class C) of total duration of 10 and 60 minutes. Upflows in S XV, Ca XIX and Fe XXV lines were compared and the presence of a range of upflow velocities was found. Emission from flare loop footpoints corresponding to plasma moving with a typical velocity of 200-400km/s is seen in soft X-ray images. In one of these events (23 June 1992), which occurred in sheared loops being part of a sparse magnetic arcade, with initial energy release taking place near one of the footpoints, a large proportion of upflowing plasma was seen at least 1 minute before the first peak in hard X-rays. In the second event (13 July 1992), the increase of soft X-ray emission began more than 3 minutes before, and weak mass upflows one minute before the rapid increase of temperature and the onset of the detectable hard X-ray emission. This event was probably triggered by emerging magnetic flux and accompanied by heating and restructuring of two nearby magnetic loops. In both events the emission measure of upflowing plasma is present simultaneously to, and is very well correlated in time with the hard X-ray flux in the 14-23keV band. Differential emission measure in the temperature range 5-60x10^6^K was derived from S XV, Ca XIX and Fe XXV line and continuum fluxes, and from images in two broad band soft X-ray filters, and used to analyse the thermal contribution to the hard X-ray emission. A non-thermal component of the hard X-ray emission is found at the peak of the 23 June 1992 flare. The hard X-ray emission in the 13 July 1992 flare is primarily thermal, however, a possibility of an enhanced tail of the electron energy distribution above 14keV is also indicated. The chromospheric evaporation in these flares was driven both by electron beams and thermal conduction, with conduction predominating during most of the rise phase of the 13 July 1992 flare. In both events, the soft X-ray emission measure at flare maximum was a few times 10^48^cm^-3^ with an electron temperature 19 and 24x10^6^K; the estimated lower limit of the electron density is ~10^11^cm^-3^. The broadening of Ca XIX spectral lines in the decay phase of these flares indicates persisting random motions with a velocity of 60km/s, which is very similar to the non-thermal broadening observed previously by SMM in M and X class flares. Title: Optical identification of EUV sources: the secrets of EUVE J2056-17.1. Authors: Mathioudakis, M.; Drake, J. J.; Craig, N.; Kilkenny, D.; Doyle, J. G.; Sirk, M. M.; Dupuis, J.; Fruscione, A.; Christian, C. A.; Abbott, M. J. Bibcode: 1995A&A...302..422M Altcode: We present optical, ultraviolet (UV), and extreme ultraviolet (EUV) results for a new active late-type dwarf star discovered by the Extreme Ultraviolet Explorer (EUVE). A large flare with an energy in excess of 10^35^erg and duration of ~1.1 days was detected in the EUVE Lex/B band (60-200A). The energetics of the event indicate that radiative losses in the EUV are a significant contributor to the energy budget in stellar flares. The "quiescent" EUV emission of the source is similar to the most active flare stars with the "quiescent" optical spectrum showing strong Hα, Ca II H & K, and Mg II h & k emission. A strong Li I 6707.8A absorption line is also present in the spectrum. We have estimated a Li abundance of log N(Li)=2.5+/-0.4. Although the high Li abundance suggests that EUVE J2056-17.1 is a young object having recently arrived on the main sequence; the high flare activity favours an interpretation where the enhanced Li is sustained by spallation reactions. Title: Observation and modelling of main sequence star chromospheres. IV. The chromospheric contribution to LiI lines in active dwarfs. Authors: Houdebine, E. R.; Doyle, J. G. Bibcode: 1995A&A...302..861H Altcode: In magnetically active stars, non-thermal heating and magnetic fields result in inhomogeneous outer atmospheres (plages) and photospheres (dark and bright spots). So as to gauge the importance of these phenomena on "normal photospheric lines", we investigate the influence of the chromosphere on the Lithium I lines in M dwarfs. We choose this element because LiI 6708A is often used as an age indicator. Solving the NLTE-radiation transfer problem for a grid of model atmospheres that mimic the effect of magnetic activity (from basal to saturated chromospheres), we show that the Lithium lines are in fact activity sensitive. This dependence commences at rather high activity levels, i.e. when Halpha_ goes into emission. As in the solar case, this chromospheric plage effect weakens the line equivalent widths and may cancel the photospheric spot effect on disc integrated measurements. The ionisation balance and line formation remain photoionisation controlled throughout the known pressure range in M star chromospheres. Changes in the line profiles and equivalent widths are due to the non-photospheric UV continuum that further ionises neutral lithium and depletes the line optical depths, whereas in solar plages collisional ionisation is the driving mechanism. In K dwarfs, both would compete to yield a similar effect. Therefore, great care must be exercised in the use of Li 6708A in both abundance and age calculations for active stars. We found that the 6708A to 6104A line ratio is less sensitive to magnetic activity than the line equivalent widths and should be a better age indicator. Title: A study of the size and composition of dust grains in the circumsteller envelope of IRC +10 216. Authors: Bagnulo, S.; Doyle, J. G.; Griffin, I. P. Bibcode: 1995A&A...301..501B Altcode: We utilise a modelling technique in which a generalised two-stream Eddington approximation is applied to the problem of the radiative transfer in a spherically symmetric dust shell. We calculate the emerging flux taking into account the effect of non-isotropic scattering, absorption and thermal reemission for a multiple grain size, multiple grain component distribution. We have applied our technique to the well known carbon-rich star IRC +10 216; we have considered a model with grains of amorphous carbon and silicon carbide, and we have studied how different grain size distributions affect the transport coefficients and the calculated flux. In agreement with previous works, we reproduce quite well the general spectral characteristics, spanning from λ=0.55μm to 2cm, assuming the dust envelope composed of small grains (with radius ~10^-2mum) of amorphous carbons. The presence of silicon carbide cannot be excluded, but it is not required to explain the feature at 11.4μm observed in the IRAS Low Resolution Spectrum: a one-component model including only amorphous carbons fits both the general characteristics and the feature at 11.4μm Title: Theoretical emission line intensity ratios for NE ^44^Sc VI compared to EUV solar observations. Authors: Keenan, F. P.; Foster, V. J.; Reid, R. H. G.; Doyle, J. G.; Zhang, H. L.; Pradhan, A. K. Bibcode: 1995A&A...300..534K Altcode: Recent calculations of electron and proton impact excitation rates in Ne ^44^Sc VI are used to derive the intensity ratios of lines in the ~402-1006A wavelength range as a function of electron temperature (T_e_) and density (N_e_). These results are presented in the form of ratio-ratio diagrams, which should in principle allow both N_e_ and T_e_ to be deduced for the Ne ^44^Sc VI line emitting region of a plasma. Electron temperatures and densities derived from ratio-ratio diagrams involving the 562.7, 997.4, 999.6 and 1006.1A lines, in conjunction with observational data for a sunspot obtained with the Harvard S-055 spectrometer on board Skylab, are found to be compatible, and in good agreement with plasma parameters determined using other methods. This provides some support for the diagnostic calculations presented in this paper, and hence the atomic data used in their derivation. However agreement between theory and observation is very poor for other Ne ^44^Sc VI lines in the sunspot spectrum, and for most transitions observed in S-055 active region and flare data, which is probably due to blending with lines from N ^44^Sc III, Mg ^44^Sc VI and Mg ^44^Sc VII. Title: Discovery of a white dwarf companion (EUVE J0254-053) to the K0 IV star HD18131 Authors: Vennes, S.; Mathioudakis, M.; Doyle, J. G.; Thorstensen, J. R.; Byrne, P. B. Bibcode: 1995A&A...299L..29V Altcode: New ultraviolet (UV) observations of late-type stars detected in the Extreme Ultraviolet Explorer (EUVE) all-sky survey revealed an unsuspected white dwarf companion to the K0 star HD18131. The International Ultraviolet Explorer (IUE) spectrum show a composite of a white dwarf and a late-type star. The white dwarf dominates the emission below 2000A while the K0 star prevails at longer wavelengths. A model atmosphere analysis of the new ultraviolet spectrophotometry and of the extreme ultraviolet (EUV) photometry reveals a hot, hydrogen-rich (DA) white dwarf (Teff~30000K) that is the most likely source of the EUV emission (EUVE J0254-053). We estimate a distance to the white dwarf of 70-90pc. The K0 star shows a modest level of chromospheric activity with the detection of Mg II h and k emission in the IUE spectrum. Optical spectroscopy revealed that the K0 star is a subgiant (K0 IV). The star is located at a distance of ~70pc, consistent with the estimated distance of the white dwarf. Therefore, it most likely constitutes a physical pair with the white dwarf. Until results of a radial velocity study are made available we cannot establish whether the pair is wide or close. In earlier works the strong EUV emission was attributed to the K0 star; however, our multiwavelength observations show the white dwarf as the most likely source. This discovery has important implications for the EUV white dwarf population survey and, in particular, for the binary frequency. Title: The O IV and S IV Intercombination Lines in Solar and Stellar Ultraviolet Spectra Authors: Cook, J. W.; Keenan, F. P.; Dufton, P. L.; Kingston, A. E.; Pradhan, A. K.; Zhang, H. L.; Doyle, J. G.; Hayes, M. A. Bibcode: 1995ApJ...444..936C Altcode: New calculations of O IV electron density diagnostic emission-line ratios involving the 1399.8, 1401.2, 1404.8, and 14076.4 A transitions are presented. A comparison of these calculations with observational data from a quiet solar region, a sunspot, and an active region obtained with the High Resolution Telescope and Spectrograph (HRTS), two flares observed with the SO82B spectrograph on board Skylab, and Hubble Space Telescope (HST) observations by the Goddard High Resolution Spectrograph (GHRS) of Capella, gives good results using the ratio R1 = I(1407.4 A)/I(1401.2 A). However, the electron density obtained using the ratio R2 = I(1407.4 A)/I(1404.8 A) is often an order of magnitude smaller. The O IV 1404.8 A line is blended with the S IV 1404.8 A line, and we investigate whether this ratio may still be used as a density diagnostic if the S IV 1406.1 A line intensity is used to correct for the presence of S IV 1404.8 A, using previous S IV calculations by Dufton et al. We still find systematic differences compared to density determinations from line ratios that do not involve the O IV 1404.8 A line, which we suggest are due to errors in earlier theoretical calculations of the S IV atomic data, and also possibly to previously unconsidered fluorescent pumping of the upper level of the S IV 1404.8 A transition. Title: Book-Review - Discovering the Secrets of the Sun Authors: Kippenhahn, R.; Doyle, J. G. Bibcode: 1995Obs...115...96K Altcode: No abstract at ADS Title: Which size distribution is best for IRC +10°216? Authors: Bagnulo, S.; Doyle, J. G.; Griffin, I. P. Bibcode: 1995Ap&SS.224..425B Altcode: A generalized two-streamed Eddington aproximation is applied to the problem of radiative transfer in a spherically symmetric dust shell. We investigate whether our technique allows us to draw conclusions about the size distribution of the grains. Title: Observation and modelling of main sequence star chromospheres. III. Differential analysis of hydrogen lines versus activity level in M dwarfs. Authors: Houdebine, E. R.; Doyle, J. G.; Koscielecki, M. Bibcode: 1995A&A...294..773H Altcode: In two previous papers we investigated in detail the formation of hydrogen lines in high pressure dMe stellar chromospheres, constraining the possible structures over a two orders of magnitude pressure range. In another study, we modeled the low activity M dwarf spectra. Here, we use these constraints at the extremes in magnetic activity level to simulate the effect of varying magnetic non-thermal heating in dM and dMe chromospheres by varying the transition region pressure and temperature minimum. We built four grids of model atmospheres with temperature minimum either at 2,660K or 3,000K, and a range of transition region pressure. We found that when decreasing the transition region pressure (i.e. the chromospheric temperature gradient), the Balmer lines change rapidly from emission to strong absorption, then the profiles weaken and become narrower until they disappear totally (zero Halpha_ stars). The Paschen and Brackett series exhibit a qualitatively similar behaviour, but the "emission domain" is at a higher column mass: log(M)>-4.4gcm^-2^, log(M)>-4.2gcm^-2^ and log(M)>-3.8gcm^-2^ respectively for the Balmer, Paschen and Brackett series. The Brackett lines never really develop a strong absorption. In opposition with other series, the Lyman lines show a monotonous decrease and even change to absorption for very low density models. These differences are useful spectral diagnostics for M dwarf atmospheres. All hydrogen series, except the Lyman series for intermediate and high pressures, are sensitive to the temperature minimum when large changes are considered. We also investigated the effect of the temperature break zone and found it is important only for high pressure atmospheres. We show that the continuum emission shortward of 4000A is highly dependent on the atmospheric pressure and rises sharply in the Balmer emission domain. Our grids of models successfully reproduce all types of observed Halpha_ profiles: (i) high activity with strong emission and weak self-reversal, (ii) filled in intermediate activity with inner wings in emission and the core in absorption, (iii) intermediate activity with strong and broad absorption, (iv) low activity with weak and narrow absorption, (v) "zero activity" with an undetectable profile. We discuss the line characteristics over this wide range of physical conditions. We analyse the ionisation fraction and electron density for our series of chromospheres. Changes in the ionisation fraction are important throughout the pressure range. Heavy elements are the main electron donor in the photosphere for all models, and in the chromosphere for low pressure models. Back-ionisation by the chromospheric continuum emission and direct ionisation by the photospheric radiation field are taking place at about the temperature minimum. Finally, we compare the chromospheric density regimes for main sequence stars (M, K and G dwarfs) for the quiescent and flare states. Title: Determination of the neutron lifetime using magnetically trapped neutrons Authors: Doyle, J. Bibcode: 1995dmcc.conf..519D Altcode: No abstract at ADS Title: An Energetic Flare on at Microscopium Authors: Gunn, A. G.; Doyle, J. G. Bibcode: 1995IrAJ...22...31G Altcode: In this paper we present and discuss observations of an energetic mass flow event associated with a chromospheric flare on AT Mic. AT Mic is a dM4.5e star at 8.8 pc. The spectroscopic observations were made in May 1992 using the SAAO 1.9m telescope. The useful wavelength range covered was 3750 Angstroms to 4150 Angstroms incorporating the higher Balmer lines and Ca II H and K lines. Simple models were applied to derive order of magnitude estimates for the mass and kinetic energy budget of the flare for assumed electron density, ionization fraction and temperature values. It is found that the kinetic energy of the flare plasma is two orders of magnitude less than the radiative energy release. Title: Models for M-Dwarf Basal Atmospheres Authors: Houdebine, E. R.; Doyle, J. G. Bibcode: 1995IrAJ...22...25H Altcode: We performed NLTE-radiation transfer calculations in an attempt to reproduce M dwarf spectra with zero H alpha and low Ca II emission lines. We found that zero H alpha can be produced by a range of models and that the Ca II flux is dramatically affected by the temperature minimum value. We show that it is possible to reproduce the observations with low pressure transition region and low temperature minimum models. Such models provide important constraints for modelling acoustic heating mechanisms. Title: Quaternionic generalisation of the Mandelbrot set. Authors: Gomatam, J.; Doyle, J.; Steves, B. Bibcode: 1995ASIB..336..557G Altcode: 1995fntc.conf..557G The complex quadratic map leading to the celebrated Mandelbrot set is generalised in a natural way to R4 using the framework of quaternions. Calculations are presented with the aid of Pauli spin matrices. Stability analyses of 3-cycles are summarised, with explicit expressions for generalised Mandelbrot domains in R4. It is conjectured that similar expressions hold for stability domains of k-cycles. Title: An orbital period study of SZ Piscium. Authors: Kalimeris, A.; Mitrou, C. K.; Doyle, J. G.; Antonopoulou, E.; Rovithis-Livaniou, H. Bibcode: 1995A&A...293..371K Altcode: The variations of the orbital period of the RS CVn-type binary system SZ Psc are examined through a detailed description of the O-C diagram and the use of a new analysis technique. Continuous changes of very large magnitude have been found. They are considered as short-timescale variations whose character is investigated for periodicity or as short-timescale variation of periodic or non-periodic behaviour eventually carried by an underlying long-timescale variation. The prospective physical mechanisms that could have modulated the orbital period in the observed way, have been examined for both cases. A combination of a magnetic activity cycle mechanism and an enhanced stellar wind are found to reproduce satisfactorily the period changes. Title: On the Power Output from Late-Type Stars Authors: Doyle, J. G. Bibcode: 1995IrAJ...22...29D Altcode: No abstract at ADS Title: UV Observations of Selected EUV Late-Type Objects Authors: Doyle, J. G. Bibcode: 1995iue..prop.4997D Altcode: No abstract at ADS Title: A multi-wavelength campaign on YY Geminorum. Authors: Butler, C. J.; Doyle, J. G.; Budding, E.; Foing, B. Bibcode: 1995mscs.conf..207B Altcode: No abstract at ADS Title: Surface inhomogeneities on SZ Piscium. Authors: Doyle, J. G.; Mitrou, C. K.; Mathioudakis, M.; Avgoloupis, S.; Mavridis, L. N.; Varvoglis, P. P.; Graos, F.; Antonopoulou, E. Bibcode: 1994A&A...291..135D Altcode: Ultraviolet and optical data are used to look at surface inhomogeneities on the active close binary system SZ Piscium. Lower chromospheric emission lines such as Mg II h&k, and to a lesser extend the upper chromospheric/lower transition region lines of O I 1305A and C II 1335A show a pronounced decrease when the F star is eclipsing the K sub-giant. However, higher temperature lines such as the resonance line of C IV 1550A do not show any change in flux. This suggests the presence of a plage with a high contrast at lower temperatures with a Mg II plage-to-K-star ratio of 5. Alternative explanations are explored. Monitoring of this system in the optical U-band and the ultraviolet lines such as C IV 1550A, indicates frequent high energy (10^35^-10^36^erg) flares. Title: Interferometer observations of RS Canum Venaticorum binaries. Authors: Gunn, A. G.; Spencer, R. E.; Abdul Aziz, H.; Doyle, J. G.; Davis, R. J.; Pavelin, P. E. Bibcode: 1994A&A...291..847G Altcode: We present radio flux measurements at 5 GHz for a sample of RS CVn-type chromospherically active binary systems made from 1988 to 1992 using the NRAL broad-band interferometer (BBI). The derived radio luminosities are consistent with previous observations but show that radio flaring is a common feature which will affect the results of rotation-activity studies. The mean brightness temperature for our sample, assuming a radio source size equal to twice the radius of the active stellar component, is consistent with a gyrosynchrotron emission process from mildly relativistic electrons. Title: Observation and modelling of main sequence star chromospheres I. Modelling of the hydrogen spectrum in dMe stars. Authors: Houdebine, E. R.; Doyle, J. G. Bibcode: 1994A&A...289..169H Altcode: In this new series we present observations and modelling of spectral lines formed in main sequence star chromospheres (from G0 to M8). In this paper, we discuss the Hydrogen line formations in very active dMe stellar chromospheres. We present the conclusions drawn from our modelling approach to the AU Mic (dM2e) spectrum. Our final model atmosphere is described in detail in the next paper in this series. Here, we investigate the effects of some stellar (T_eff_, vsin i) and atmospheric (turbulence, temperature structure) parameters on the line formation. We found that observations are best reproduced by a chromospheric structure including a constant temperature gradient (in a log(M) scale) in the chromosphere and transition region. We show that a very thin transition region is required to account for the observed Lyalpha_ to Halpha_ surface flux ratio. Then, to drive the Balmer lines into emission and reproduce the Halpha_ and Hbeta_ self-reversal and FWHM, the chromospheric gradient and transition region pressure must be quite high for the most active stars. We put forward a complete set of important constraints on the possible structures of such active region atmospheres from 5,000 K to 50,000 K. Notably we show that: (i) the chromosphere/transition region temperature break zone must be located at about 8,200 +/-~200 K, implying that there is rather little plasma above this temperature, (ii) the temperature break zone is central to the formation of Lyman and Balmer lines, it should be smooth and contained in a small column mass domain, (iii) the transition region must be very thin and at a high column mass, log(M)~-3, (iv) the temperature break demarcates the temperature domains of formation of Lyman and other Hydrogen series, (v) backwarming due to the Lyman and Balmer radiation fields occurs at the top of the chromosphere, (vi) turbulence and rotational broadening have little effect on the line profiles and fluxes, (vii) rotational broadening should not however be neglected because Halpha_ self-reversal is a major constraint to the modelling, (viii) the profiles are weakly dependant on the stellar effective temperature whose uncertainties can be neglected in first approximation. Finally, we further compare our results to observations and propose some general properties that could be tested with future observations. Title: Modelling of the atmospheric environment on and around cool M giants and dwarfs Authors: Doyle, J. G.; Griffin, I. P. Bibcode: 1994IrAJ...21..255D Altcode: A numerical method involving radiative transfer techniques has been developed to model the gas/dust environment around cool red giants. The method provides a large amount of information as to the physical conditions within the model dust shell, such as the temperature gradient and intensity distributions throughout the shell, as well as predicting the emergent fluxes. Although the method has so far been applied only to a few examples of carbon-rich and oxygen-rich stars, it is apparent from the results that they are an improvement upon previous work. We suggest here where further enhancements in the technique are possible. Title: Observation and modelling of main sequence star chromospheres II. Modelling of the AU MIC (dM2.5e) hydrogen spectrum. Authors: Houdebine, E. R.; Doyle, J. G. Bibcode: 1994A&A...289..185H Altcode: We present the first successful attempt in modelling simultaneously the Halpha_ and Hbeta_ high resolution profiles and the Halpha_ to Lyalpha_ flux ratio for a dMe star (AU Mic, dM2.5e). We show that a very high transition region pressure and a thin transition region are simultaneously required to reproduce our observations. We give evidence that lower pressure model chromospheres can also reproduce the Balmer line profiles, but give Lyman surface fluxes overestimated by more than an order of magnitude. Our model also reproduces the Balmer decrements, the Lyalpha_ full width half maximum (upper limit) and the Balmer jump which is weak. Discrepancies in the profiles between observations and our model point to possible systematic upward flows in active stellar chromospheres. We obtain the Paschen lines in emission and Paschen decrements as large as 41 for Pabeta_. For our model, we obtain a transition region column mass of 1.2610^-3^g/cm^2^ (log(M)=~-2.9) which should be a lower limit (with the present modelling approximations). This large pressure chromosphere yields too large equivalent widths by a factor of 3.3. We believe that this points to the inhomogeneous character of the star's chromosphere. In this context, the plage filling factor is about 30%. This disagrees with the concept of homogeneous atmospheres back-heated by large coronal X-ray radiation and suggests that additional non-thermal heating is taking place in active regions. The electron density at the top of the chromosphere is in the 10^12^-5 10^12^ cm^-3^ range, in agreement with previous estimates based on the Balmer decrements. The pressure is 6.3 Pa, of the same order as the current estimates for coronal pressures (~10 Pa). Discordant results for the HI Lyman and the HeI lines for our model atmosphere imply conflicting filling factors for these lines which indicates that, like the Sun, stellar transition regions are quite inhomogeneous. Formation of all Hydrogen series is collisionally controlled and takes place in a rather thin layer at the top of the chromosphere (Balmer, Paschen, and Brackett) or in the transition region (Lyman). The temperature break acts as a disjunction in the domains of formation of the Lyman and other series. High electron density and collisional control is a necessary condition to drive the Balmer lines into emission in M dwarf atmospheres. Because of particularly low electron temperature and density in the middle chromosphere down to the photosphere, the Balmer, Paschen and Brackett source functions are photoionisation controlled in this region. We compare our model to other dMe, dKe and solar model chromospheres. It shares common physical properties with solar flare models, thus implying a large and continuous chromospheric heating rate. The temperature break at 8200 K is very close to values obtained for the quiet Sun, plages, flares and other stellar models. This emphasizes that this temperature is constrained by the plasma ability to radiate in the Hydrogen lines, over a wide range of the plasma and stellar parameters. The total radiative cooling in the Hydrogen lines and continua is about 1.22x10^8^erg/m^2^/s, of which 66% arise from the Balmer series and continuum. The radiative cooling is dominated by the Lyman series and the Balmer series respectively in the transition region and the chromosphere. Cooling is dominated by the Paschen lines in the lower chromosphere. The short penetration of the Lyman radiation field produces a net backwarming in the upper chromosphere, while other series penetrate deeper and backwarm the lower chromosphere and the temperature minimum. Title: BD +22 4409 : a rapidly rotating, low-mass member of the Local Association. Authors: Jeffries, R. D.; Byrne, P. B.; Doyle, J. G.; Anders, G. J.; James, D. J.; Lanzafame, A. C. Bibcode: 1994MNRAS.270..153J Altcode: We present spectroscopic and photometric observations of BD +2204409, a nearby, low-mass star which, on the basis of its Galactic space motions and high EUV-tobolometric luminosity ratio, has been previously assigned membership of the young kinematic group known as the Local Association. Our observations show that BD +2204409 is a single, K5V-K7V, chromospherically active ultrafast rotator, with a probable period of 10.1710.10 h and a projected equatorial velocity of 691 1 km 1 It has a comparatively high photo spheric lithium abundance of N(Li) = 1.3010.25, and this, combined with our photometry and a trigonometric parallax, leads to the conclusion that the star is young, although probably no younger than 20-30 Myr, and is a prime Local Association candidate in all respects. Considerable variability is seen in the rotationally broadened H a emission line, and can be interpreted in terms of transient flare activity at very high latitudes or the combination of a rotationally modulated, high-latitude active region and a rather smaller flare at an unconstrained latitude. In either case, the flare radiative losses in the H a line are at least 2 x 1032 erg. There is no evidence for the corotating cool prominences that have been seen at some distance from the surfaces of other late-type rapid rotators. This may be interpreted as a geometric effect, whereby the low inclination deduced for BD +2204409, of 5001 100, combined with a centrifugal flattening of any cloud system towards the equatorial plane, renders clouds unobservable as Ha absorption transients. Spot modelling of the photometric light curves yields an asymmetric spot component, covering at least 4 per cent of the total stellar surface. Variability of 1013 per cent is seen in the strength of the Lii 6708-A line over 7 h of a rotation period, in the sense that the peak Li I equivalent width correlates with the time of maximum spot coverage deduced from the shapes of photospheric line profiles. This result is consistent with calculations of the effect of starspots on the Li I equivalent width, once projection effects and limb-darkening are taken into account. Enhanced molecular bands may also play a role, but very cool atmospheric models are required to investigate this question fully. Key words: stars: abundances - stars: activity - stars: individual: BD +2204409 - stars: late-type - stars: rotation - open clusters and associations: general. Title: Multiwavelength Observations of a Solar Flare Authors: White, S. M.; Silva, A.; de Pater, I.; Lin, R. P.; Gary, D. E.; Hudson, H. S.; Doyle, J. G.; Hagyard, M. J.; Kundu, M. R. Bibcode: 1994kofu.symp..203W Altcode: No abstract at ADS Title: Lower chromospheric activity in low activity M dwarfs Authors: Doyle, J. G.; Houdebine, E. R.; Mathioudakis, M.; Panagi, P. M. Bibcode: 1994A&A...285..233D Altcode: Four low activity dM(e) stars Gl 105B, Gl 643, Gl 813 and Gl 821 were observed spectroscopically in the optical and ultraviolet regions. Despite relatively long integrations, only one of the four had detectable Ca II K&H emission, Gl 821, which had an observed flux of 9 10^-15^ erg/cm2/s, giving a surface flux of only 0.8 10^4^ erg/cm2/s. Similarly, the IUE observations implied very weak Mg II emission. In one of these stars, Gl 813, the Mg II h&k surface flux was less than 0.4 10^4^ erg/cm2/s, which is a factor of two less than the previous known weakest dM(e) star, Gl 105B. Using radiative transfer techniques the Ca II H&K fluxes have been derived for a range of model atmospheres. The zero Hα flux can be produced by a range of models, this line is therefore a rather poor constraint for the lower atmosphere. On the other hand, the Ca II K flux can be dramatically effected by simply varying the temperature minimum. Comparing our calculations to the observational data, we find that the Ca II H&K surface fluxes cannot be reproduced with T_min_ 3000K. However, decreasing the temperature minimum by less than 400K produces Ca II H&K fluxes of the order of 10^3^ erg/cm2/s, in very good agreement with the weakest dM(e) stars. Title: High-velocity evaporation during a flare on AT Microscopii Authors: Gunn, A. G.; Doyle, J. G.; Mathioudakis, M.; Houdebine, E. R.; Avgoloupis, S. Bibcode: 1994A&A...285..489G Altcode: We present and discuss observations of a flare event on the dM4.5e star AT Mic (Gl 799AB). These data show evidence of an energetic flare with a radiated energy of 3 10^31^erg in the range 3600-4200A. The Balmer emission lines display a prominent blue asymmetry which has been used to constrain the velocity of the associated bulk plasma motion. Simple models were applied to derive order of magnitude estimates for the mass and kinetic energy budget of the flare for assumed electron density, ionization fraction and temperature values. It is found that the kinetic energy of the flare plasma is two orders of magnitude less than the radiative energy release. The chromospheric Ca II H & K lines are also observed to have a blue-shifted component which has not been observed prior to these results. We suggest that this is evidence of a very energetic particle beam penetrating to the cooler atmospheric layers where Ca II H & K is formed. Title: An optical flare on YZ Canis Minoris Authors: Gunn, A. G.; Doyle, J. G.; Mathioudakis, M.; Avgoloupis, S. Bibcode: 1994A&A...285..157G Altcode: We present and discuss observations of an energetic optical flare on the dM4.5e star YZ CMi (Gl 285). The flux-time variations and energy release of the flare are fully consistent with previous observations of this star. The observations have also revealed a symmetric excess emission in the bases of the chromospheric Balmer lines. If due to a bulk plasma motion event, the maximum extension in the Balmer wings represents a Doppler velocity of ~ 250 km/s. Title: Theoretical Emission Line Strengths for OV Compared to Extreme Ultraviolet Solar Observations Authors: Keenan, F. P.; Warren, G. A.; Doyle, J. G.; Berrington, K. A.; Kingston, A. E. Bibcode: 1994SoPh..150...61K Altcode: Recent R-matrix calculations of electron impact excitation rates in OV are used to derive the emission line intensity ratios (in energy units) R1 = I(2s2p3P - 2p23P)/I(2s21S0 - 2s2p1P1 = I(761.1 A)/I(629.7 A), R2 = I(2s21S0 - 2s2p3P1/I(2s21S0 - 2s2p1P1 = I(1218.4 A)/I(629.7 A), and R3 = I(2s2p1)P1 - 2p21S0/I(2s21S0 - 2s2p1P1) = I(774.5 A)/I(629.7 A) as a function of electron temperature (Te) and density (Ne). These results are presented as plots of R1 vsR2, andR1 vsR3, which should allowboth Ne andTe to be deduced for the OV line emitting region of a plasma. Electron densities derived from the (R1,R2) and (R1,R3) diagrams in conjunction with observational data for several solar features obtained with the Harvard S-055 spectrometer on boardSkylab are found to be compatible, and in good agreement with values ofNe estimated from line ratios in species formed at similar electron temperatures to OV. In addition, values ofTe determined from (R1,R2) and (R1,R3) are generally close to that expected theoretically. These results provide experimental support for the accuracy of the diagnostic calculations presented in this paper, and hence the atomic data used in their derivation. Title: Ultraviolet flare activity on the eclipsing binary SZ Piscium. Authors: Doyle, J. G.; Mitrou, C. K.; Mathioudakis, M.; Antonopoulou, E. Bibcode: 1994A&A...283..522D Altcode: The estimated total chromospheric, transition region and coronal losses for a flare observed on the eclipsing binary SZ Psc with the International Ultraviolet Explorer (IUE) satellite on 6 July 1990 is of the order of 4.5 1036 ergs. This estimate is similar to that derived by Doyle et al. (1989) for an ultraviolet flare on another RS CVn star, II Peg, and is a substantial fraction of the total amount that is possible to store on these stars without having to evoke the presence of kiloGauss fields. Title: NLTE-Radiation Transfer Modelling of Li I Lines in dM Atmospheres Authors: Houdebine, E. R.; Doyle, J. G. Bibcode: 1994ASPC...64..285H Altcode: 1994csss....8..285H No abstract at ADS Title: Effect of the Star Effective Temperature on the Hydrogen and Calcium Spectra in M-G Dwarfs Authors: Houdebine, E. R.; Doyle, J. G. Bibcode: 1994ASPC...64..423H Altcode: 1994csss....8..423H No abstract at ADS Title: Circumstellar Material in the RS CVn System SZ Psc Authors: Doyle, J. G. Bibcode: 1994iue..prop.4926D Altcode: No abstract at ADS Title: Dynamics of a Low Energetic Solar Flare Authors: Doyle, J. G.; Fludra, A.; Bentley, R. D.; Culhane, J. L.; Metcalf, T.; Lemen, J. R.; Kosugi, T. Bibcode: 1994ASPC...64..402D Altcode: 1994csss....8..402D No abstract at ADS Title: Ultraviolet Spectroscopy of the DA + dM Binary Feige 24 Near Inferior Conjunction: Authors: Doyle, J. G. Bibcode: 1994iue..prop.4927D Altcode: No abstract at ADS Title: Eclipse Observations of Active Binary Systems Authors: Gunn, A. G.; Doyle, J. G.; Houdebine, E. R. Bibcode: 1994ASPC...64..702G Altcode: 1994csss....8..702G No abstract at ADS Title: Coordinated HST-EUVE-IUE Observations of YZ Cmi Authors: Doyle, J. G. Bibcode: 1994iue..prop.4871D Altcode: No abstract at ADS Title: Models for M Dwarf Basal Atmospheres Authors: Houdebine, E. R.; Doyle, J. G. Bibcode: 1994ASPC...64..420H Altcode: 1994csss....8..420H No abstract at ADS Title: Low Activity M Dwarfs Authors: Doyle, J. G.; Houdebine, E. R.; Mathioudakis, M. Bibcode: 1994ASPC...64..557D Altcode: 1994csss....8..557D No abstract at ADS Title: Far infrared properties of late type dwarfs. Infrared fluxes of K and M dwarfs. Authors: Mathioudakis, M.; Doyle, J. G. Bibcode: 1993A&A...280..181M Altcode: IRAS fluxes/upper limits are presented for a large sample of K and M dwarfs. Good agreement is found between the 12 micrometer fluxes and those derived from the photospheric models of Mould (1976). Relationships between the optical and infrared colors are derived. The active dMe/dKe stars appear systematically brighter in the infrared compared with the less active dM/dK stars, which could be attributed to more efficient nonradiative heating in their atmosphere. Any systematic differences found in our results when compared with those obtained from previous studies are attributed to the different analysis packages used. Title: Rotational modulation and flares on the RS Canum Venaticorum binary II Pagasi in July/September 1990 : spots and flares on II Peg. Authors: Doyle, J. G.; Mathioudakis, M.; Murphy, H. M.; Avgoloupis, S.; Mavridis, L. N.; Seiradakis, J. H. Bibcode: 1993A&A...278..499D Altcode: During ultraviolet spectroscopic observations of the RS CVn star II Peg in September 1990 a long duration (greater than or = 3 hrs.) flare was observed. During the early stage of the event, a feature at 1354 A was present, however, within the spectral resolution of the data it is not possible to identify this line. A contribution from the hot coronal ion Fe XXI is suspected. From line diagnostic ratios, the electron pressure at flare peak was estimated to be 1017/cu cm K, decreasing to 1016/cu cm K towards the end of the flare. One other flare was observed with IUE, and three optical flares (unfortunately none of these were observed simultaneously). The chromospheric and transition region losses from the larger of the two IUE flares was approx. 3 x 1031 erg/s at flare maximum, with total chromospheric/transition region radiative losses over the duration of the event being approx. 1.5 x 1035 erg. Continuum radiative losses over the wavelength region 1150A to 1950A were approximately 3% of the above figure. At flare maximum, the N V 1240 A line showed an enhancement factor of approx. 3 over the preflare value compared to 9 for the C IV 1550 A line. We interpret this difference as due to an underabundance of nitrogen during the flare, possibly related to photoionization of lower chromospheric material by soft X-ray photons sometime prior to the flare. No evidence of rotational modulation was present in any of the transition region lines, although the chromospheric lines did show a phase variation. However, these lines (H-alpha, Ca II K and Mg II h&k) were not consistent with one another although it is clear that the H-alpha equivalent width showed variations faster than the star's rotation period, being perhaps related to the decay/activation of individual active regions. Title: Dynamics of flares on late-type dMe stars. III. Kinetic energy and mass momentum budget of a flare on AD Leonis. Authors: Houdebine, E. R.; Foing, B. H.; Doyle, J. G.; Rodono, M. Bibcode: 1993A&A...278..109H Altcode: In two previous publications (Paper I and II in this series), we described the spectral line Doppler shifts and asymmetries observed during a large flare on AD Leo, and interpreted those in terms of mass motions. Here, in order to further constrain the plasma physical properties and estimate the amount of energy released under mass motions, we developed simple methods so as to infer lower limits to the plasma cross-section, volume, column density, mass, average emissivity and optical depth. This allows us to derive the first kinetic energy and momentum budget of a stellar flare spectral signatures at visible wavelengths. The investigation of the line flux variation along the Balmer series indicates that up to 40% or more of the CaII H emission is likely to arise from radiative pumping by the Balmer H-epsilon line. For the preflare motion of the solar like 'dark filament', we estimate that its minimum mass, kinetic energy and radius are respectively about 6.4 1013 kg, 2.7 1032 erg and 5 107 m. The impulsive phase downward motion which attains deep photospheric layers in 'kernels' is believed to carry a mass of only 1.3 1013 kg and energy 2.4 1032 erg. The area/extent values we inferred from the Balmer and the CaII lines using escape probability methods agree well with NLTE-radiation transfer modelling. We obtain a minimum kernel area of approximately 6 1013 sq m and an estimated area of approximately 1014 sq m. A flaring prominence whose spectral signature is oscillatory Doppler shifts has an estimated mass and radius of respectively 1.2 1013 kg and 2 107 m. The minimum kinetic energy associated with its motion is about 2.9 1031 erg. We find that the kinetic energy associated with the detected mass motions strongly depends on the localization of the flare on the stellar disc. Ignoring or taking into account this possible projection factor for the velocities gives a total kinetic energy of respectively approximately 3 1030 erg and approximately 6 1032 erg (without the impulsive phase CME). The latter figure is about a factor of 3 times more than the energy radiated in the U-band and 2.3 times less than the 'missing energy' in the K band. This points to an interesting aspect of stellar flare energetics, that is, for this flare the kinetic energy may be a significant fraction of the total energy budget. Along the same lines, our results also indicate that possibly only a small fraction of the kinetic energy is carried by cool plasmas and that most mass motions may occur in coronal plasmas at a higher temperature regime. This important aspect of flare energetics should be assessed by simultaneous observations in optical and UV/EUV spectroscopy with a higher time resolution. Title: Effect of interstellar absorption on the MG II H & K profiles and fluxes of RS CVn stars Authors: Houdebine, E. R.; Doyle, J. G.; Butler, C. J. Bibcode: 1993IrAJ...21..102H Altcode: No abstract at ADS Title: Tuned Solar and Stellar Oscillations? Authors: Andrews, A. D.; Doyle, J. G. Bibcode: 1993IrAJ...21...83A Altcode: No abstract at ADS Title: Productivity of Armagh Observatory Compared to a Range of Institutions in the USA Authors: Doyle, J. G. Bibcode: 1993IrAJ...21..153D Altcode: No abstract at ADS Title: Dynamics of flares on late type dMe stars. II. Mass motions and prominence oscillations during a flare on AD Leonis. Authors: Houdebine, E. R.; Foing, B. H.; Doyle, J. G.; Rodono, M. Bibcode: 1993A&A...274..245H Altcode: On 28 March 1984 at 3:22 UT, a 2.1 magnitude flare in the U-band was observed simultaneously in several wavelength regions, including low resolution spectrophotometry in the wavelength range 3600-4400Å. This flare displayed enhanced emission in chromospheric lines for a duration of about 50 min. By studying in detail the emission line centroid displacements and asymmetries, we discovered several new exciting phenomena. In this paper we present evidence for complex velocity fields. A deeper investigation of the plasma physical parameters and the kinetic energy associated with these mass motions is discussed by Houdebine et al. (1993).

Prior to the flare onset, weak P-Cygni profiles were observed in the Call resonance lines which we interpret as evidence for the preflare motion of a solar like "dark filament". The loop radius is estimated to be of the order of 5 1O7 m. During the impulsive phase, a high velocity mass ejection was observed (Houdebine et al. 1990, Paper I) with red-shifts in the Balmer line cores, the CaII K and HeI 4026Å. This latter event is interpreted as the downward motion of chromospheric condensations initiated by highly energetic particle beams (in the MeV range) and a subsequent chromospheric evaporation. The inferred minimum energy flux deposited by the beam in the transition region is about 9 1010 which corresponds to the energy of a large flare on the Sun. Later during the flare, a 2.68 min periodic oscillation occurred in the line centroids with a peak to peak amplitude up to ∼ 95 km s-1. We show that it is most likely the signature of periodic motions in a prominence that may have been initiated by flare-born disturbances. This prominence (whose minimum radius and apex magnetic field strength are 2 1O7m and 20G respectively) expanded slowly during the gradual phase, and finally disrupted, ejecting part of its mass higher in the corona. The loop disruption signatures are well defined reversed P-Cygni profiles that are sustained for several minutes. During the post-flare stage, we found clues for clouds of plasma spread across the stellar disc with a minimum filling factor of 17%. Title: Rotational modulation and flares on RS Canum Venaticorum and BY Draconis stars. XVII. UV spectroscopy and optical photometry of AU Microscopii in 1986. Authors: Quin, D. A.; Doyle, J. G.; Butler, C. J.; Byrne, P. B.; Swank, J. H. Bibcode: 1993A&A...272..477Q Altcode: We present IUE spectroscopy and optical photometry of the active late type star AU Mic. The UV spectroscopy allow us to measure the chromospheric and transition region line fluxes. No detectable variations attributable to rotational modulation were evident in either the chromospheric lines or optical bands. We have produced an emission measure curve for the quiescent state of AU Mic, which spans a temperature range 4.0 ≤ log Te ≤ 7.6 when coupled with previous X-ray flux measurements. The quiescent radiative losses per unit surface area over the above temperature range is ≍8 1O7 erg cm-2 s-1 Title: Chromospheric Heating in K &M Dwarfs Authors: Doyle, J. G.; Mathioudakis, M. Bibcode: 1993ASSL..183..471D Altcode: 1993pssc.symp..471D No abstract at ADS Title: Emission up to 18 ke V in the Quiescent X-ray Spectrum of II Peg Authors: Doyle, J. G.; van den Oord, G. H. J.; Kellett, B. J. Bibcode: 1993ASSL..183..311D Altcode: 1993pssc.symp..311D No abstract at ADS Title: The Nature of M Dwarfs with a Zero H Alpha Flux Authors: Doyle, J. G. Bibcode: 1993iue..prop.4657D Altcode: No abstract at ADS Title: Solar O IV and S IV lines from the High Resolution Telescope and Spectrograph (HRTS) and the S082B spectrograph on board Skylab. Authors: Keenan, F. P.; Cook, J. W.; Doyle, J. G.; Dufton, P. L.; Hayes, M. A.; Kingston, A. E. Bibcode: 1993uxrs.conf..345K Altcode: 1993uxsa.conf..345K A comparison of theoretical O IV electron density diagnostics with observational data from a quiet solar region, a sunspot and an active region obtained with the High Resolution Telescope and Spectrograph (HRTS), and a flare observed with the S082B instrument on board Skylab, reveals that the O IV 1404.8 Å line is not only blended with the S IV 1404.8 Å transition, but also with an unknown feature that contributes a significant amount to the blend. It is therefore suggested that line ratios which include the O IV 1404.8 Å transition should not be employed as density diagnostics. Title: Mass Loss from Cool Dwarfs: Limits on Detectability Authors: Doyle, J. G.; Mullan, D. J. Bibcode: 1993ASSL..183..401D Altcode: 1993pssc.symp..401D No abstract at ADS Title: Dynamic phenomena on the RS Canum Venaticorum binary II Pegasi in August 1989. I. Observational data. Authors: Doyle, J. G.; Kellett, B. J.; Butler, C. J.; Byrne, P. B.; Neff, J. E.; Brown, A.; Fox, D.; Linsky, J. L.; Bromage, G. E.; Avgoloupis, S.; Mavridis, L. N.; Seiradakis, J. H.; Mathioudakis, M.; Murphy, H. M.; Krzesinski, J.; Pajdosz, G.; Dadonas, V.; Sperauskas, J.; van Wyk, F.; Marang, F.; Olah, K.; Collier Cameron, A.; Antonomoulos, E.; Rovithis, P.; Rovithis-Livaniou, H. Bibcode: 1992A&AS...96..351D Altcode: Observational results are given for two flares in Pi Pegasi that were detected by the GINGA and IUE satellites, as well as by ground-based Johnson U-band photometry and optical spectroscopy. The best-fitting results were obtained for a combination of a single-temperature plasma together with a power law; for a two-temperature model, the temperature of the second component was very high due to the tail in the photon distribution. Title: A recalculation of the line emissivities for the strongest UV and extreme-UV lines in the 400-2800 A wavelength range Authors: Doyle, J. G.; Keenan, F. P. Bibcode: 1992A&A...264..173D Altcode: Using the most recent atomic data we re-calculate line emissivities for the strongest transitions in the 400-2800 A region. These line emissivities may be used to construct emission measure curves for either observed ultraviolet/extreme ultraviolet solar features or ultraviolet observations of stellar sources. The new tables contain several lines not in the original Raymond and Doyle tables. Title: Limits on Detectability of Mass Loss from Cool Dwarfs Authors: Mullan, D. J.; Doyle, J. G.; Redman, R. O.; Mathioudakis, M. Bibcode: 1992ApJ...397..225M Altcode: Recent spectroscopic evidence supports the theoretical expectation that certain cool dwarfs may have stellar winds with M-dot values several orders of magnitude larger than the solar rate. For large enough values of M-dot, the emission from the wind is expected to have a spectrum which, at low enough frequencies, becomes a power law, S(v) about v exp alpha with alpha about 0.7. Data from IRAS and VLA suggest that such a spectrum may in fact occur in certain M dwarfs: a key test of the wind spectrum would be provided if the stars could be detected at lambda about 1 mm. We show that the M-dot required to ensure power-law emission is a few times 10 exp -10 solar mass/yr. With M-dot of this order, fluxes at lambda about 1 mm would be tens of mJy. Using the James Clerk Maxwell Telescope, we have tested this prediction on several stars: the data are suggestive but are near the limits of detection. Confirmation of our estimates will be important for evolution and for interstellar medium (ISM) physics: if even a few percent of all M dwarfs are losing mass at the above rates, the mass balance of the ISM will be dominated by M dwarfs. Title: Chromspheric diagnostics in M dwarfs Authors: Mathioudakis, M.; Doyle, J. G. Bibcode: 1992IrAJ...20..272M Altcode: No abstract at ADS Title: Chromospheric heating in late-type dwarfs : acoustic or magnetic ? Authors: Mathioudakis, M.; Doyle, J. G. Bibcode: 1992A&A...262..523M Altcode: Mg II h and k fluxes for 69 K and 88 M dwarfs have been analyzed. An empirical lower limit is found in the Mg II flux, extended down to the latest spectral types. Based on the data presented here it is the magnetic component that dominates the emission from the atmosphere of cool dwarfs, especially the M dwarfs. It, however, coexists with an acoustically heated component, which can only be identified in the stars with the lowest fluxes in the flux-color diagram, these stars possibly being the slowest rotators. Data for the dM(e) stars, i.e., those stars with zero H-alpha, show that these are divided into two classes: (1) an inactive M dwarf star with very weak chromospheric heating, perhaps only by acoustic waves; and (2) an intermediate chromospheric activity star dominated by magnetic heating. Title: Dynamic phenomena on the RS Canum Venaticorum binary II Pegasi in August 1989. II. an interpretation. Authors: Doyle, J. G.; van den Oord, G. H. J.; Kellett, B. J. Bibcode: 1992A&A...262..533D Altcode: An analysis of the quiescent X-ray and radio observations and of the X-ray observations of a major flare of II Pegasi is presented. For both the flare and the quiescent emission, photometric, and spectroscopic optical data are also discussed. The quiescent X-ray emission shows a power-law tail up to 18 keV. It is shown that an interpretation in terms of free-free emission by nonthernal particles requires unrealistically large values for the number of particles involved and for the energy input required to maintain the population. Basic flare parameters like volume, loop length, and typical magnetic field strength are derived. The observed flare decay on II Peg is compared with the observed flare decay on Sigma CrB and Algol. It is shown that the behavior of the temperature and emission measure during the II Peg flare differs significantly from the observed behavior during the Algol/sigma CrB flares. Title: AI II as an electron density diagnostic for the upper chromosphere/lower transition region in late-type stars. Authors: Doyle, J. G.; Keenan, F. P.; Harra, L. K.; Aggarwal, K. M.; Tayal, S. S. Bibcode: 1992A&A...261..285D Altcode: The ratio of the Al II resonance line 3s2 1S-3sp 1P1 at 1670 A to the inter-system line 3s2 1S-3s3p 3P1 at 2669 A is a useful electron density diagnostic for N(e) greater than 10 exp 10/cu cm. However, it is also sensitive to the adopted electron temperature, and, in fact, should be a useful electron temperature diagnostic when Ne is not greater than 10 exp 9/cu cm. In particular, we present observational data for the RS CVn star II Peg and show that this ratio implies an electron pressure substantially less than that implied from other diagnostic line ratios but in good agreement with the pressure derived from the C III 1176/C III 1908 ratio. We suggest additional observational and theoretical work that may be required. Title: Book Review: The sun and cool stars: activity, magnetism, dynamos / Springer-Verlag, 1991 Authors: Doyle, J. G. Bibcode: 1992Obs...112..133D Altcode: No abstract at ADS Title: Limits on detectability of mass loss from cool dwarfs Authors: Mullan, D. J.; Doyle, J. G.; Mathioudakis, M.; Redman, R. O. Bibcode: 1992AAS...180.6006M Altcode: 1992BAAS...24..826M Recent spectroscopic evidence supports the theoretical expectation that certain cool dwarfs may have stellar winds with dot {M} values several orders of magnitude larger than the solar rate. For large enough values of dot {M}, the emission from the wind is expected to have a spectrum which, at low enough frequencies, becomes a power law, S_ν ~ nu (alpha ) with alpha ~ 0.7. Data from IRAS and VLA suggest that such a spectrum may in fact occur in certain M dwarfs: a key test of the wind spectrum would be provided if the stars could be detected at lambda ~ 1 mm. We show that the dot {M} required to ensure power law emission is a few times 10(-10) Msun \ yr(-1) . With dot {M} of this order, fluxes at lambda ~ 1 mm would be tens of mJy. Using the James Clerk Maxwell Telescope, we have tested this prediction on several stars: the data are suggestive but are near the limits of detection. Confirmation of our estimates will be important for studies of evolution of low mass stars and for interstellar medium (ISM) physics: if even a few percent of all M dwarfs are losing mass at the above rates, the mass balance of the ISM will be dominated by M dwarfs. Moreover, if flares on these stars are accompanied by mass ejecta, the ISM may become contaminated with deuterium produced in the surface layers of the star by energetic protons. Title: The Sun as a Star: High Spectral Resolution Solar Data Degraded to Low-Dispersion IUE Resolution Authors: Doyle, J. G.; Cook, J. W. Bibcode: 1992ApJ...391..393D Altcode: High spectral resolution (about 0.06 A) solar data for an active region and a large two-ribbon flare degraded to the typical resolution of low-dispersion (about 5 A) spectra of the IUE satellite are presented. This clearly shows the amount of detail yet to be acquired in stellar spectra and indicates the main spectral regions where line blending is a problem. Title: Excitation of the solar flare far-ultraviolet continuum by line irradiation Authors: Doyle, J. G.; Phillips, K. J. H. Bibcode: 1992A&A...257..773D Altcode: Observations of the FUV (wavelength less than 1682 A) continuum by Skylab during an intense solar flare confirm previous calculations that the excitation of this continuum is due to the ionization of neutral silicon atoms near the temperature minimum region irradiated by UV line radiation emitted by the upper chromosphere or transition region. The evidence is an observed proportionality of the continuum intensity with the intensities of C IV (1548/51 A) and C II (1335/36 A) lines. Title: Who Needs an X-Ray Satellite when we have IUE Authors: Doyle, J. G. Bibcode: 1992IrAJ...20..209D Altcode: No abstract at ADS Title: So you Think Solar Abundances are Constant Authors: Doyle, J. G. Bibcode: 1992IrAJ...20..208D Altcode: No abstract at ADS Title: Optical flares on the RS CVn binary II Peg. Authors: Mathioudakis, M.; Doyle, J. G.; Avgoloupis, V.; Mavridis, L. N.; Seiradakis, J. H. Bibcode: 1992MNRAS.255...48M Altcode: During 57.4 hr of optical monitoring in the Johnson U- and B-bands of the RS CVn binary II Peg, 10 flares were detected. The absolute energies of these events are in the range 1-180 x 10 exp 33 erg. This implies a flare activity in the U-band of 0.17 flares per hour, compared with 0.12 flares per hour from UV C IV data. A double power-law distribution is required to fit the cumulative flare-frequency distribution of the U-band flares. Title: The Origin of the Far-Ultraviolet Continuum in Solar and Stellar Flares Authors: Phillips, K. J. H.; Bromage, G. E.; Doyle, J. G. Bibcode: 1992ApJ...385..731P Altcode: A continuum in the far-ultraviolet region observed in IUE spectra of dMe stars in a flaring state is discussed and compared with that observed in solar flares. Similar continuous emission observed in solar flare far-ultraviolet spectra has been identified with neutral silicon recombination radiation excited by intense lines. This also appears to be the case for stellar flares, as is deduced here from the proportionality of far-ultraviolet line and continuum power for several flares on dMe stars, two flares on an RS CVn star (II Peg), and the spotted active binary BY Dra. The only solar flare observation available, from Skylab, obeys this same linear relation. Other emission mechanisms are considered, but they are unlikely to give the observed continuum flux. Title: High Spectral Resolution Solar Data Degraded to Low Dispersion lUE Resolution Authors: Doyle, J. G.; Cook, J. W. Bibcode: 1992ASPC...26...49D Altcode: 1992csss....7...49D No abstract at ADS Title: A MN I Emission Line at 4032 A During a Flare on the RS CVn Star II Peg Authors: Doyle, J. G.; Panagi, P. M.; Butler, C. J. Bibcode: 1992ASPC...26..300D Altcode: 1992csss....7..300D No abstract at ADS Title: The Quiescent X-ray Spectrum of the RS CVn Binary II Peg in August 1989 Authors: Doyle, J. G.; Byrne, P. B.; van den Oord, G. H. J.; Kellett, B. J.; Bromage, G. E. Bibcode: 1992ASPC...26..356D Altcode: 1992csss....7..356D No abstract at ADS Title: Millimeter; Sub-Millimeter Emission from Flare Stars Authors: Mullan, D. J.; Doyle, J. G.; Mathioudakis, M.; Redman, R. O. Bibcode: 1992ASPC...26..328M Altcode: 1992csss....7..328M No abstract at ADS Title: GL 890 - The Magnetic Brake? Authors: Byrne, P. B.; Doyle, J. G.; Mathioudakis, M. Bibcode: 1992ASPC...26..438B Altcode: 1992csss....7..438B No abstract at ADS Title: Modelling of the Large X-ray Flare on II Peg Observed with GINGA Authors: Kellett, B. E.; Doyle, J. G.; Bromage, G. E.; Byrne, P. B. Bibcode: 1992LNP...397..289K Altcode: 1992sils.conf..289K No abstract at ADS Title: Optical Flares on II Peg Authors: Mathioudakis, M.; Doyle, J. G.; Avgoloupis, S.; Mavridis, L. N.; Seiradakis, J. H. Bibcode: 1992ASPC...26..303M Altcode: 1992csss....7..303M No abstract at ADS Title: The Nature of M Dwarfs with a Zero H Alpha Flux Authors: Doyle, J. Bibcode: 1992iue..prop.4345D Altcode: No abstract at ADS Title: The August 1989 Spot Lightcurve of II Peg and Related Flare Activity Authors: Avgoloupis, S.; Doyle, J. G.; Mavridis, L. N.; Seiradakis, J. H.; Mathioudakis, M. Bibcode: 1992LNP...397..247A Altcode: 1992sils.conf..247A No abstract at ADS Title: Short Time-scale Changes in the V-band Light Curve of II Peg: Flare Companion or Prominence? Authors: Doyle, J. G.; Bromage, G. E.; Collier Cameron, A.; Kilkenny, D. W.; Krzesinski, J.; Murphy, H. M.; Neff, J. E.; Pajdosz, G.; van Wyk, F. Bibcode: 1992LNP...397..276D Altcode: 1992sils.conf..276D No abstract at ADS Title: A study of the flaring and quiscent X-ray and UV emission from II Pegasi. Authors: Tagliaferri, G.; White, N. E.; Doyle, J. G.; Culhane, J. L.; Hassall, B. J. M.; Swank, J. H. Bibcode: 1991A&A...251..161T Altcode: An investigation has been conducted of the rotational modulation of the transition-region UV and coronal X-ray emission for the RS CVn system II Pegasi. The X-ray light curve is dominated by a strong flare detected at orbital phase, where the minimum of the photometric wave occurred. The flare parameters derived show that the flare originates with a height greater than half the stellar radius. The characteristics of the flare are similar to those of a solar two-ribbon flare; a comparison of the midtransition region density with that in the coronal region shows a very steep pressure gradient. Title: A comparison of theoretical Fe xii emission line strengths with EUV observations of a solar active region Authors: Keenan, F. P.; Doyle, J. G.; Tayal, S. S.; Henry, R. J. W. Bibcode: 1991SoPh..135..353K Altcode: New theoretical electron-density-sensitive Fe XII emission line ratios R1 = I(3s23p34S3/2 - 3s3p44P5/2)/I(3s23p32P3/2 - 3s3p4D5/2 and R2 = I(3s23p32P3/2 - 3s3p42D5/2)/I(3s23p34S3/2 - 3s3p2P3/2) are derived using R-matrix electron impact excitation rate calculations. We have identified the FeXII and transitions in an active region spectrum obtained with the Harvard S-055 spectrometer on board Skylab at wavelengths of 364.0, 382.8, 1241.7, and 1349.4 Å, respectively. Electron densities determined from the observed values of R1 (log Ne ≃ 11.0) and R2(log Ne ≃ 11.4) are significantly larger than the typical active region measurements, but are similar to those derived from some active region spectra observed with the Skylab 2082A instrument, which provides observational support for the atomic data adopted in the line ratio calculations, and also for the identification of the Fe XII transitions in the S-055 spectrum. However the observed value of R3 = I(1349.4 Å)/I(1241.7 Å) is approximately a factor of two larger than one would expect from theory which, considering that the 1349.4 Å line lies at the edge of the S-055 wavelength coverage, may reflect errors in the instrument efficiency curve. Another possibility is that the 1349.4 Å transition is blended, probably with Si II 1350.1 Å. Title: The Sun as a Star - High Spectral Resolution Solar Data Degraded to Low Dispersion IUE Resolution Authors: Doyle, J. G. Bibcode: 1991IrAJ...20...95D Altcode: No abstract at ADS Title: The Sun as a Star: High Spectral Resolution Solar Data Degraded to Low Dispersion IUE Resolution Authors: Cook, J. W.; Doyle, J. G. Bibcode: 1991BAAS...23.1384C Altcode: No abstract at ADS Title: A gas-dynamic model for a flare on YZ CMi : interpretation of high-temporal-resolution spectroscopic data. Authors: Katsova, M. M.; Livshits, M. A.; Butler, C. J.; Doyle, J. G. Bibcode: 1991MNRAS.250..402K Altcode: The 3600-4400 A spectra obtained for the March 4, 1985 flare spectra of YZ CMi are analyzed on the basis of a gasdynamic model whose U-band optical radiation is generated by a condensation formed during the gasdynamic process. The source of the optical radiation is a dense, cool plasma with small height; this source is responsible for the radiation from the higher Balmer lines when they are at maximum intensity, as presently demonstrated by the hydrogen plasma kinetics of an 'eight-levels-plus-continuum' model atom. It is demonstrated that the low slope of the Balmer decrement is due to a combination of a large population in the second level of the hydrogen atom, in conjunction with a photon escape probability decrease from the medium, at the higher Balmer line frequencies. Title: Rotationalmodulation and flares on RS Canum Venaticorum and BY Draconis stars. XVI. IUE spectroscopy and VLA observations of GL 182 (=V 1005 Orionis) in October 1983. Authors: Mathioudakis, M.; Doyle, J. G.; Rodono, M.; Gibson, D. M.; Byrne, P. B.; Avgoloupis, S.; Linsky, J. L.; Gary, D.; Mavridis, L. N.; Varvoglis, P. Bibcode: 1991A&A...244..155M Altcode: A large flare was detected simultaneously with IUE and VLA on Gl 182 on October 5, 1983, this event showing the largest C IV flare enhancement yet observed by IUE. A smaller flare was also detected on October 4, although only with the IUE satellite. Line ratio and emission measure techniques are used to derive various physical parameters of the flares. The radiative losses in the temperature region log T(e) = 4.3-5.4 in the two flares are 2.9 x 10 to the 33rd and 8.4 x 10 to the 32nd ergs, respectively. Total radiative losses over the whole temperature range log T(e) = 4.0-8.0 are estimated to be of the order of 6.4 x 10 to the 34th and 1.1 x 10 to the 34th ergs, respectively. In the October 5, flare, a very strong ultraviolet continuum is present with a total energy of 1.9 x 10 to the 33rd ergs over the wavelength range 1250-1950 A. Title: Active M-type stars from the ultraviolet to the infrared. Authors: Mathioudakis, M.; Doyle, J. G. Bibcode: 1991A&A...244..433M Altcode: Fluxes at 12 microns are presented for a group of seven active dMe stars. Five of these stars are considered as significant detections at 25 microns, while only two stars were detected at 60 microns and only one at 100 microns. Comparing with previous results it is found that the fluxes are systematically lower by 7-50 percent depending on the band. Above 60 microns there is a definite excess over a blackbody radiation curve. Title: Chromospheric diagnostics in late-type stars. Authors: Mathioudakis, M.; Doyle, J. G. Bibcode: 1991A&A...244..409M Altcode: Moderate and low resolution spectroscopic observations of late type dwarfs covering a broad range of activity are presented. The strength of the TiO band in 4762 A is used for spectral classification. Calibrated fluxes for the Balmer and the Ca II H and K lines are derived. H-alpha equivalent widths are given for those stars where the line is in absorption as well as those in emission. It is confirmed that stars with no detectable or very weak H-alpha do exist. It is also shown that stars with very weak or no detectable emission in Ca II H and K also exist, this occurring preferentially in late M dwarfs. Although this can be explained in terms of reduced nonradiative heating in the chromosphere, the results cannot be conclusive due to the limited resolution of the data. Title: Book-Review - the Sun - an Introduction Authors: Stix, M.; Doyle, J. G. Bibcode: 1991IrAJ...20...49S Altcode: No abstract at ADS Title: Millimetre Continuum Emission from Flare Stars Authors: Doyle, J. G. Bibcode: 1991IrAJ...20Q..47D Altcode: No abstract at ADS Title: Book-Review - Introduction to Stellar Astrophysics - VOL.1 - Basic Stellar Observations and Data Authors: Bohm-Vitense, E.; Doyle, J. G. Bibcode: 1991IrAJ...20...50B Altcode: No abstract at ADS Title: A Mni Emission Line at 4032A during a Flare on the Rs-Canum Star II-Pegasi Authors: Doyle, J. G. Bibcode: 1991IrAJ...20R..47D Altcode: No abstract at ADS Title: Simultaneous detection of a large flare in the X-ray and optical regions on the RS CVn-type star II Peg. Authors: Doyle, J. G.; Kellett, B. J.; Byrne, P. B.; Avgoloupis, S.; Mavridis, L. N.; Seiradakis, J. H.; Bromage, G. E.; Tsuru, T.; Makishima, K.; Makishima, K.; McHardy, I. M. Bibcode: 1991MNRAS.248..503D Altcode: Results are presented for a large flare detected simultaneously on the RS CVn star II Peg by the X-ray satellite GINGA and from ground-based Johnson U-band measurements. The total U-band flare energy is estimated to be at least 6.6 x 10 to the 34th erg. This compares with at least 4.6 x 10 to 34th erg in the 1-10 keV energy range. These values are lower limits to the true radiative output, since the U-band data relates only to the rise phase of the flare, while the X-ray data were obtained during part of the decay phase. Using a 'smooth-burst model', the combined U-band plus X-ray radiative output is estimated to be about 3 x 10 to the 34th erg. Title: Millimeter continuum emission from flare stars. Authors: Doyle, J. G.; Mathioudakis, M. Bibcode: 1991A&A...241L..41D Altcode: The first detection of continuum emission in the millimeter region for two dwarf M flare stars is reported. The observed flux at 1.1 and 2 mm is weak, being just above background, but above that based on a black-body curve. This confirms the impression gained from infrared fluxes at 60 and 100 microns, which indicated excess emission at these wavelengths. Title: Multiwavelength Observations of Stellar Flares Authors: Doyle, J. Bibcode: 1991iue..prop.4064D Altcode: No abstract at ADS Title: Comparison of solar and stellar flare ultraviolet continua Authors: Phillips, K. J. H.; Bromage, G. E.; Doyle, J. G. Bibcode: 1991VA.....34..277P Altcode: It is proposed that there is a strong connection between the continua formed in the ultraviolet spectra of stellar flares with that seen in solar spectra, and that the mechanism of formation believed to occur in the latter — silicon recombination radiation excited by photo-ionization due to ultraviolet line emission — is the same as in stellar flares. Title: The Nature of M Dwarfs with a Zero H Alpha Flux Authors: Doyle, J. Bibcode: 1991iue..prop.4059D Altcode: No abstract at ADS Title: Chrpmosphere Radiative Losses in M Dwarfs Authors: Doyle, J. Bibcode: 1991iue..prop.4126D Altcode: No abstract at ADS Title: Chromospheric/Coronal Emission Correlations in 'Quiescent' and Eruptive Phenomena in M-Dwarf Stars (With 1 Figure) Authors: Mathioudakis, M.; Doyle, J. G. Bibcode: 1991mcch.conf..279M Altcode: No abstract at ADS Title: Discovery of flare activity on the dwarf M stars, GL 375 and GL 431. Authors: Doyle, J. G.; Mathioudakis, M.; Panagi, P. M.; Butler, C. J. Bibcode: 1990A&AS...86..403D Altcode: Optical and infrared photometry plus spectroscopic data is present for two new flare stars, Gl 375 and Gl 431. Both of these stars have the hydrogen Balmer lines strongly in emission. Several flares were detected on Gl 375 implying a high level of flare activity. The H-alpha surface flux of 1.0 x 10 to the 6th erg/sq cm per sec for both stars is similar to that of other active flare stars. Fluxes are given for several of the higher Balmer lines. Title: Chromospheric/coronal emission correlations in "quiscent" and eruptive phenomena in M-dwarf stars. Authors: Mathioudakis, M.; Doyle, J. G. Bibcode: 1990A&A...240..357M Altcode: A power correlation between 'quiescent' and flaring H-gamma and X-ray emission is presented for a group of active dwarf M stars. The relationship holds for both 'quiescent' and flaring conditions for several orders of magnitude change in energy. Explanations in terms of X-ray back-heating and microflaring are discussed. Title: Activity in late-type stars. VII. Chromospheric and transition region line fluxes in 2 dM and dM(e) stars. Authors: Byrne, P. B.; Doyle, J. G. Bibcode: 1990A&A...238..221B Altcode: Ultraviolet spectra of the two dM stars Gl380 and Gl411 and the dM(e) Gl900 are presented. The dM stars show mean surface fluxes in a variety of emission lines arising throughout the chromosphere and the lower transition region which are very similar to those of the quiet sun. In the one star in which it could be determined the electron density at log T(e) was roughly 4.75, also within a factor of roughly 2.5 that of the solar value. Results for a single dM(e) star indicate higher mean surface fluxes in these same lines, consistent with the view that they are intermediate between the dM and the dMe stars. Title: A Giant X-ray/optical Flare on II Peg Authors: Byrne, P. B.; Doyle, J. G.; Tsuru, T.; Avgoloupis, S.; Mavridis, L. N.; Seiridakis, J. H.; Kilkenny, D. W.; Laing, J. D.; Marang, F. Bibcode: 1990IrAJ...19..150B Altcode: The paper presents a preliminary account of a large X-ray flare recorded by an X-ray satellite (it was also recorded in broadband optical light and in hydrogen Balmer emission) as a part of a campaign to monitor the RS CVn system II Peg with ground-based optical photometry and spectroscopy and satellite ultraviolet and X-ray spectroscopy. Two X-ray flares observed are described: the first one is relatively weak in X-rays, while the second flare which is the subject of the discussion, was present when the source was reacquired after earth occultation on August 17, 1989. Flare energy, temperature, and emission measure and volume are analyzed, and emphasis is placed on the observation of a line feature at approximately 6.8 keV, coinciding in energy to the position of the H-like FeXXVI line at 1.79 A. Title: Ultraviolet continuum in solar and dMe star flares Authors: Phillips, K. J. H.; Bromage, G. E.; Doyle, J. G. Bibcode: 1990ESASP.310..427P Altcode: 1990eaia.conf..427P No abstract at ADS Title: Optical and infrared photometry of dwarf M and K stars. Authors: Doyle, J. G.; Butler, C. J. Bibcode: 1990A&A...235..335D Altcode: Absolute U, B, V, R, I, J, H, K, and L photometry are given for a group of dwarf M and K stars. Using black-body fits to the data, bolometric luminosities and radii are derived. The derived bolometric luminosities are good to + or - 10 percent and the effective temperatures to + or - 100 K. A comparison is made with the values derived by other authors. The derived radii are 14 percent smaller than those derived from the revised Barnes et al. (1978) relation involving (V - R). Title: A Comparison of Theoretical SV Emission Line Strengths with Extreme Ultraviolet Observations of a Sunspot Authors: Keenan, F. P.; Doyle, J. G. Bibcode: 1990SoPh..128..345K Altcode: 1990IAUCo.121P.345K Electron impact excitation rates for transitions in the S v ion, calculated with theR-matrix code, are used to derive the electron temperature sensitive emission line ratiosR1 =I(854.8 Å)/I(786.9 Å),R2 =I(852.2 Å)/I(786.9 Å),R3 =I(849.2 Å)/I(786.9 Å), andR4 =I(1199.1 Å)/I(786.9 Å), which are found to be significantly different from previous estimates. A comparison of the present results with observational data for a sunspot obtained with the Harvard S-055 spectrometer on boardSkylab reveals generally good agreement between theory and experiment, except in the case ofR1, which is probably due to blending in the 854.8 Å feature. The possible effects of Lyman continuum absorption on the observed line ratios is briefly discussed. Title: A periodicity in the flaring rate on the eclipsing binary YY Geminorum. Authors: Doyle, J. G.; Butler, C. J.; van den Oord, G. H. J.; Kiang, T. Bibcode: 1990A&A...232...83D Altcode: Five flares were observed on the late-type binary YY Gem in March 1988 during a total monitoring time of 408 min. The flares were unusual in that there is a periodicity in the occurrence of four of them, these being separated by 48 + or - 3 min. Considering the flares to be formed as a stochastic process, it is found that the probability of these events occurring by chance is 0.5 percent. Modeling indicates that for quite reasonable input parameters, the flare periodicity can be explained in terms of filament oscillations. The only requirement is that there should be a filament at these heights where the magnetic field drops inversely proportional to the height. Title: IUE observations of GL 644 AB (=Wolf 630) in the wavelength region 1150-1950 A, in June 1981. Authors: Mathioudakis, M.; Doyle, J. G. Bibcode: 1990A&A...232..114M Altcode: IUE short wavelength observations of the flare star Gl 644, obtained in June 1981 are presented. A flare was detected in one of the spectra as a strong increase in C IV, He II, and continuum fluxes. The electron density of the flaring plasma, determined using line ratio techniques, is 4 x 10 to the 10th/cu cm, which is an increase by a factor of 2.7 above the quiescent. The radiative losses of the flare are at least 1.3 x 10 to the 32nd erg and 4.0 x 10 to the 33rd erg over the temperature range log Te between 4.3 and 5.4 and log Te between 4.0 and 8.0, respectively. This compares with continuum losses of 8.1 x 10 to the 31st erg over the wavelength region 1250-1950 A. Title: An X-ray flare observed from van Biesbroeck 8. Authors: Tagliaferri, G.; Doyle, J. G.; Giommi, P. Bibcode: 1990A&A...231..131T Altcode: An X-ray flare was detected on the previously unknown flare-star van Biesbroeck 8 ( = Gl 644 C). The total energy of the event in the 0.05-2 keV energy range was 8 x 10 to the 31st erg/s with a mean luminosity of 1.8 x 10 to 28th erg/s. This implies an emission measure of about 6 x 10 to the 50th/cu cm, and adopting a simple loop model an electron density of 10 to the 11th/cu cm or greater. It is estimated that the flare covered 1-4 percent of the stellar surface. Quiescent X-ray emission from VB 8 was detected during an Einstein-HRI observation. These properties of VB 8 suggest that stars later than M 5 can be very active X-ray emitters. Title: Mass ejections from the rapidly rotating M dwarf star GL 890. Authors: Doyle, J. G.; Collier Cameron, A. Bibcode: 1990MNRAS.244..291D Altcode: Mg II line fluxes from the rapidly rotating single M dwarf Gliese 890 show a 'dip' lasting less than 120 min. H-alpha spectra obtained simultaneously show systematic profile changes during the Mg II 'dip': the line bisector of the H-alpha emission feature shows at first a red then a blue displacement. The behavior of both the H-alpha line bisector and the Mg II emission 'dip' is consistent with a model in which a cloud of mainly neutral hydrogen passes in front of the disk of the star. Similar behavior has been observed in the rapidly rotating single K dwarf AB Doradus. The projected area of the Gl 890 cloud is 0.25-0.40 times that of the stellar disk. Title: 1973 September 7 Two-Ribbon Flare. I. Morphology and Loop Expansion Authors: Doyle, J. G.; Widing, K. G. Bibcode: 1990ApJ...352..754D Altcode: XUV data are presented for a two-ribbon flare of H-alpha class 2B and X-ray class X1 which occurred on September 7, 1973. The morphology and loop expansion rates observed in coronal lines of Fe XIV and Ca XVII are compared with data from the chromospheric line H-alpha. The loop arcades at different temperatures and different loops in a given arcade show different expansion rates. Consideration is given to the relationship of the observed arcade loop system to various surface features. The loop aspect ratio and electron density are derived as a function of position along the loop for the coronal plasma. These values are used to derive the energy density and to discuss scaling laws relating loop length, temperature, and pressure. The observed radiative cooling times for individual loops are compared to times calculated from radiative conductive and enthalpy cooling times. Also, the observed energy density is compared with that calculated from a reconnection model. Title: 1973 September 7 Two-Ribbon Flare. II. Physical Properties of the Loops in the Arcade Authors: Widing, K. G.; Doyle, J. G. Bibcode: 1990ApJ...352..760W Altcode: Spectral data of selected lines between 170 and 340 Å for a large two-ribbon flare of 1973 September 7 are presented. The flare arcade consisted of four prominent loops. Loop intensities and densities decreased by approximately a factor of 2 during one hour of observations, beginning 15 minutes after Solrad flux maximum suggesting that the mass and energy supply are strongly maintained during the early hours of the gradual phase. Observed emission measures in Ca XVII loops give Ne = 7 × 1010 cm-3 compared with 2 × 1010 cm-3 in Fe XIV loops. The Fe XIV density sensitive 219/211 line ratio gives similar densities implying a filling factor of ≍50% near flare maximum to unity 1 hour later. These results imply that the upper and outer parts of the rising loop system are hotter and denser than the lower and inner parts of the arcade. Electron densities at the loop apex were ∼50% greater than those at the loop footpoints. The loop aspect ratio (i.e., the ratio of the loop cross section diameter to the loop foot-point separation) varies from 0.1 to 0.3, being largest for the higher temperature lines. The derived loop parameters are compared with scaling laws. Loop cooling rates are calculated and compared with observed cooling times. Finally, the observed energy density is compared with that calculated from a reconnection model. Title: Lyman-alpha and MG II H and K fluxes in a sample of dwarf M stars. Authors: Doyle, J. G.; Panagi, P.; Byrne, P. B. Bibcode: 1990A&A...228..443D Altcode: Ly-alpha and Mg II fluxes are given for a group of M dwarfs. The Ly-alpha and Mg II lines were extracted from low resolution spectra taken with the IUE satellite. The Ly-alpha line is shown to be an important source of radiative losses in dMe chromospheres, being at least a factor of two more important than Mg II. Overall it contributes approximately 25 percent of the total chromospheric losses, about the same as the more commonly observed H-alpha line. In order to have approximately equal contributions from these lines, one requires either a plateau region in the lower transition region or different filling factors for the two lines. In dM stars, Ly-alpha is approximately the same magnitude as Mg II. Title: Flare activity and orbital rotation of YY Geminorum. Authors: Doyle, J. G.; Mathioudakis, M. Bibcode: 1990A&A...227..130D Altcode: The observed flare activity on the eclipsing binary star YY Geminorum, as determined by the time-average flare energy, is more than as order of magnitude greater out-of-eclipse than that during eclipses. The out-of-eclipse value is however, heavily biased by four large flares. In the cumulative distribution diagram these larger flares have a substantially different statistical occurrence rate than the remainder of the flares. It is suggested that the small separation between the two stars leads to significantly enhanced magnetic field between the two components and thus to the occurrence of energetic flares, observable when the stars are out of eclipse. Title: A Model for the Observed Periodicity in the Flaring Rate on Yy-Geminorum Authors: Doyle, J. G.; van den Oord, G. H. J.; Butler, C. J.; Kiang, T. Bibcode: 1990IAUS..137..325D Altcode: No abstract at ADS Title: Optical spectroscopy of nova LMC 1988 No 2 during its early decline stage. Authors: Sekiguchi, K.; Kilkenny, D.; Winkler, H.; Doyle, J. G. Bibcode: 1989MNRAS.241..827S Altcode: This paper presents the results obtained from optical spectroscopy of Nova LMC 1988 No. 2 made at the SAAO. It was a very fast nova (t_2_=5d) of large amplitude ({DELTA}m>11.2 mag) and the visual maximum reached m_V_=10.3 on 1988 October 13.75 UT. A spectrogram taken 1.34d after the maximum showed strong Balmer, He I and Fe II lines with P Cyg profiles. The broad (FWZI>4000 km s^-1^) emission features extend to +3000 km s^-1^. Two principle absorption systems at ~-1700 km s^-1^ and ~-2500 km s^-1^ and higher velocity diffuse-enhanced absorption systems extending to -4000 km s^-1^ were seen. By 1988 December 2 (50d after the maximum) the nova had developed into the early nebular phase and showed very strong [Ne III] emissions. The characteristics of the nova closely resemble those of V1500 Cyg and V1370 Aql. Title: Flux-flux relation : MG II H and K versus X-rays in dwarf M and K stars. Authors: Mathioudakis, M.; Doyle, J. G. Bibcode: 1989A&A...224..179M Altcode: Surface X-ray and Mg II h and k fluxes are presented for a group of dMe, dKe, dM, and dK stars. No correlation is apparent between the fluxes for the group of stars as a whole, although a good correlation is present for a subgroup, i.e., the dMe/dKe's. The Mg II and X-ray luminosities for these active stars define an upper boundary, which is dependent upon the stellar radii. The Mg II luminosity from the less active dM/dK stars are also radii-dependent, but this is not the case for the X-ray luminosity. This may indicate a difference in the heating mechanisms for the chromosphere and corona, with acoustic wave heating being an important contributor in the chromosphere and/or a difference in the plage filling factors in the two regions. Title: Ultraviolet flares on II Pegasi. Authors: Doyle, J. G.; Byrne, P. B.; van den Oord, G. H. J. Bibcode: 1989A&A...224..153D Altcode: UV spectroscopic observations of the RS CVn star, II Peg, were obtained in February 1983. The observations show evidence for flare activity in greatly enhanced chromospheric and transition region emission lines. The flare radiation is isolated and the electron pressures of the mean quiescent atmosphere and the two flares are derived from the intersystem line flux ratios. Estimates are given of the total flare power output over the whole atmosphere and the surface filling factor for the flares. The implications of the observations for studies of flares on RS CVn stars are considered. Title: Rotational modulation and flares on RS CVn and BY Draconis stars. XIII. IUE spectroscopy and photometry of II Pegasi during September 1986. Authors: Doyle, J. G.; Butler, C. J.; Byrne, P. B.; Rodono, M.; Swank, J.; Fowles, W. Bibcode: 1989A&A...223..219D Altcode: UV spectroscopy obtained for the RS CVn star II Pegasi in September, 1986, indicates the presence of a rotational modulation effect for the Mg II h and k and O I 1305 A lines; the largest flux is observed when the primary spot concentration is nearly on the opposite hemisphere, and the rotational modulation is noted to be of opposite sense to that observed in 1981. Optical photometry shows the largest concentration of spots on one hemisphere ever observed on II Peg, implying a spot group covering over 50 percent of the projected area of one hemisphere. Title: H-alpha versus X-ray luminosity in dwarf M stars. Authors: Doyle, J. G. Bibcode: 1989A&A...218..195D Altcode: A power-law correlation is presented between the excess chromospheric H-alpha emission and the coronal X-ray emission for a group of dM and dMe stars. This excess emission was calculated by subtracting the maximum (i.e., saturated) observed H-alpha absorption equivalent width for a star of a similar color. Heating of the chromosphere through X-ray back-heating is not the dominant component of chromospheric heating in dM stars, although in the very active late-type stars its contribution could be about 50 percent. Title: An estimate of the total chromospheric, transition region and coronalradiative losses in late-type stars. Authors: Doyle, J. G. Bibcode: 1989A&A...214..258D Altcode: An estimate is made of the total radiative losses between 10,000 and 100 million K in several late-type stars. Using a relationship between the CIV 1548-A line flux and the total power losses in the atmosphere above 10,000 K developed for solar plasmas, it is shown that this relation also holds for these stars. For the active dMe and dKe stars, total radiative losses of 30-40 Merg/sq cm sec above 10,000 K are calculated, being slightly greater than that calculated for the sun if it were covered by active regions. Title: Rotational modulation and flares on RS Canum Venaticorum and BY Draconis stars. XII. Near-to-simultaneous high resolution UV and optical observations of II Pegasi during July 1984. Authors: Byrne, P. B.; Panagi, P.; Doyle, J. G.; Englebrecht, C. A.; McMahan, R.; Marang, F.; Wegner, G. Bibcode: 1989A&A...214..227B Altcode: Nearly simultaneous high resolution ground-based optical and IUE satellite UV spectroscopy and an optical light curve of the RS CVn star II Peg are presented. It is shown that the chromospheric and transition region radiative losses of the star in July 1984 are lower than previously recorded means. The flux in the Lyman-alpha line is estimated and evidence is given for variability in all of the emission lines. This variability appears to be correlated with the optical spots. Line profiles at two rotational phases for the principal UV emission lines show an excess broadening over and above the combined instrumental plus Doppler broadening. Title: Spectroscopic and photometric observations of SN 1987A- V. Days 386-616. Authors: Catchpole, R. M.; Whitelock, P. A.; Menzies, J. W.; Feast, M. W.; Marang, F.; Sekiguchi, K.; van Wyk, F.; Roberts, G.; Balona, L. A.; Egan, J. M.; Carter, B. S.; Laney, C. D.; Laing, J. D.; Spencer Jones, J. H.; Glass, I. S.; Winkler, H.; Fairall, A. P.; Lloyd Evans, T. H. H.; Cropper, M. S.; Shenton, M.; Hill, P. W.; Payne, P.; Jones, K. N.; Wargau, W.; Mason, K. O.; Jeffery, C. S.; Hellier, C.; Parker, Q. A.; Chini, R.; James, P. A.; Doyle, J. G.; Butler, C. J.; Bromage, G. Bibcode: 1989MNRAS.237P..55C Altcode: We present spectroscopic and UBV(RI)_c_JHKLM photometric observations of SN 19S7A in the Large Magellanic Cloud made at the Sutherland observatory of the SAAO between days 386 and 616 after the Kamiokande-II neutrino event. During this period the bolometric flux from the supernova measured over the U to M wavelength range has continued to decline faster than the ^56^Co decay rate. By day 56O the flux in this wavelength range accounts for only half of that expected from ^56^Co decay. The estimated total flux (including X-ray and γ-ray data) is consistent with ^56^Co remaining the sole energy source of the supernova over the period considered. Title: Activity in late-type dwarfs. III. Chromospheric and transition region line fluxes for two dM stars. Authors: Byrne, P. B.; Doyle, J. G. Bibcode: 1989A&A...208..159B Altcode: Weak upper-chromospheric and transition-region emission from two dM stars (Gl 784 and Gl 825) has been observed using deep UV spectroscopy. Ly-alpha fluxes for the two stars were also determined for the first time. Using these results it is shown that the transition from weakly active dM to active dMe star is probably due to increasing surface coverage by solarlike active regions. Also discussed are the relative importance of Ly-alpha and Mg II as chromospheric coolants in the M dwarfs and how this changes between dM and dMe stars. The interrelationship between X-ray, He II (1640-A) and C IV (1550-A) fluxes is discussed in the light of these results, and it is shown that all three are tightly related over three orders of magnitude in each. Several flux-period relationships are used to predict the rotation periods of the two stars. Title: Flares on RS CVn Stars Authors: Doyle, J. Bibcode: 1989iue..prop.3519D Altcode: No abstract at ADS Title: Optical flares from the dwarf M star V577 MON (Gliese 234 AB = Ross 614). Authors: Doyle, J. G.; van den Oord, G. H. J.; Butler, C. J. Bibcode: 1989A&A...208..208D Altcode: The paper describes a search for flaring on the Balmer emission line star, Gliese 234 AB. Ten flares were detected in a total monitoring time of 4.6 h, implying a very high level of activity. The time-averaged flare energy in the Johnson U-band is slightly greater than measured previously but due to the small number of hours of observations it is best to use the mean of these two measurements. Relative energies are given for the U, B, V, R, and I bands for a 3.8 mag U-band flare which had a 45 s rise time and 20 min decay time. Of the various models fitted to the flare data, bound-free emission seems the most promising. Title: September 7, 1973 two-ribbon flare. Authors: Doyle, J. G.; Widing, K. G. Bibcode: 1989sasf.confP.199D Altcode: 1988sasf.conf..199D; 1989IAUCo.104P.199D The flare images show a compact, nearly cylindrical arcade centered along the filament channel and composed of 4 prominent loops. The loop systems of Fe XII (Te = 1.7×106K) and Fe XIV (Te = 2.3×106K) are smaller than, and lie nested within, the arcades of Fe XVI (Te = 3×106K) and Ca XVII (Te = 5×106K). The loop arcades at different temperatures, as well as different loops within a given arcade, show different expansion rates. These vary from 6 - 8 km s-1 for Fe XIV shortly after flare maximum to 0.5 - 1 km s-1 late in the decay phase. For hotter ions, such as Ca XVII, the velocities are approximately constant at 2 - 3 km s-1 during the whole of the observations. Title: Flare energetics. Authors: Wu, S. T.; de Jager, C.; Dennis, B. R.; Hudson, H. S.; Simnett, G. M.; Strong, K. T.; Bentley, R. D.; Bornmann, P. L.; Bruner, M. E.; Cargill, P. J.; Crannell, C. J.; Doyle, J. G.; Hyder, C. L.; Kopp, R. A.; Lemen, J. R.; Martin, S. F.; Pallavicini, R.; Peres, G.; Serio, S.; Sylwester, J.; Veck, N. J. Bibcode: 1989epos.conf..377W Altcode: The authors have sought to establish a comprehensive and self-consistent picture of the sources and transport of energy within a flare. To achieve this goal, they chose five flares in 1980 that were well observed with instruments on the Solar Maximum Mission, and with other space-borne and ground-based instruments. The events were chosen to represent various types of flares. Details of the observations available for them and the corresponding physical parameters derived from these data are presented. The flares were studied from two perspectives, the impulsive and gradual phases, and then the results were compared to obtain the overall picture of the energetics of these flares. The authors also discuss the role that modeling can play in estimating the total energy of a flare when the observationally determined parameters are used as the input to a numerical model. Finally, a critique of our current understanding of flare energetics and the methods used to determine various energetics terms is outlined, and possible future directions of research in this area are suggested. Title: High Velocity MgII Wings in II Peg Authors: Doyle, J. Bibcode: 1989iue..prop.3582D Altcode: No abstract at ADS Title: An analysis of the continuum light in the 3500 - 8500 Å region from a flare observed on the dwarf M star Gliese 234AB (= V577 Mon). Authors: Doyle, J. G.; van den Oord, G. H. J.; Butler, C. J. Bibcode: 1989sasf.confP..91D Altcode: 1989IAUCo.104P..91D; 1988sasf.conf...91D Relative energies are given for the U,B,V,R and I bands for a 3.8 magnitude U-band flare observed on the dwarf dMe star Gl 234 AB on 28 Feb. 1985. This flare had a 45 second rise time and 20 minute decay time. The total flare energy from all five bands during the flare was 7×1031erg, 34% of this total was from the U-band and 20% from the two near infrared R and I bands. The energy density (per frequency interval) implied a rising continuum towards the red, however this only lasted for approximately 20 - 40 seconds, i.e. during the impulsive phase, afterwhich the excess flare emission could not be detected in the near infrared bands. Of the various models fitted to the flare data (i.e. optical synchrotron, bound-free emission and free-free emission), bound-free emission seems the most promising. Title: Multiwavelength Observations of Stellar Flares Authors: Doyle, J. Bibcode: 1989iue..prop.3633D Altcode: No abstract at ADS Title: Energetic flares on RS CVn stars. Authors: Doyle, J. G.; Byrne, P. B.; van den Oord, G. H. J. Bibcode: 1989sasf.confP.115D Altcode: 1988sasf.conf..115D; 1989IAUCo.104P.115D Ultraviolet spectroscopic observations of the RS CVn star II Peg in February 1983 show evidence for flare activity in greatly enhanced chromospheric and transition region emission lines. The total radiative losses from the chromosphere and transition region during the flare is 3.1×1035erg. Over the whole atmosphere the authors estimate total radiative losses of 2.4×1036erg, (excluding hydrogen line radiation). At flare peak, the flare radiated 1.5×1032erg s-1. Adopting a two-ribbon flare model, where the filament is located between the two stars of the system, one can have 1039(l/Rsun) erg of magnetic energy available, where l is the filament length. Therefore, only a small fraction of this magnetic energy need be converted into heating of the flare plasma. Title: A gas-dynamic model for a flare on YZ CMi: interpretation of spectroscopic observations with high temporal resolution. Authors: Katsova, M. M.; Livshits, M. A.; Butler, C. J.; Doyle, J. G. Bibcode: 1989sasf.confP..87K Altcode: 1989IAUCo.104P..87K; 1988sasf.conf...87K The spectra of a flare on YZ CMi, obtained with a temporal resolution of 60 seconds on March 4, 1985 and over the range 3600 - 4400 Å, are analysed using a gas-dynamic model. In this model, the optical radiation in the U-band, outside of flare maximum, is produced by a condensation formed during the gas-dynamic process. With the optical continuum described by a Planck function for a temperature of T ≍ 104K, the emitting source area S ≥ 5×1017cm2. The hydrogen plasma kinetics of an "8 levels plus continuum" model atom are calculated, and it is shown that the low slope of the Balmer decrement, just after the flare maximum, is connected with a large population in the second level of the hydrogen atom. Title: X-Ray/Optical Flares on RS CVn Stars Authors: Doyle, J. G. Bibcode: 1988IBVS.3250....1D Altcode: No abstract at ADS Title: Theoretical Si iv line ratios compared to extreme ultraviolet solar observations Authors: Keenan, F. P.; Doyle, J. G. Bibcode: 1988SoPh..115..229K Altcode: New theoretical electron temperature sensitive emission line ratios in SiIV involving the 3d2D − 3p2P and 4s2S − 3p2P multiplets at ∼1125 and 816 Å, respectively, are derived using recent R-matrix electron excitation rate calculations. A comparison of these with observational data for a solar active region at the limb obtained with the Harvard S-055 spectrometer on board Skylab reveals that there is good agreement between theory and observation for ratios that include the 2D3/2, 5/2 − 2P3/2 transition at 1128.3 Å. This is in contrast to the findings of Keenan, Dufton, and Kingston (1986) and provides support for the atomic data adopted in the calculations. However, the 2D3/2 − 2P1/2 line at 1122.5 Å appears to be severely blended, as suggested previously by Burton and Ridgeley (1970) and Feldman and Doschek (1977), as it leads to electron temperature estimates that differ significantly from that expected in ionisation equilibrium. The fact that the I(1122.5 Å)/I(1128.3 Å) intensity ratios determined from several flare spectra are closer to theory than that for the active region indicates that the blending is probably due to species with relatively low ionization potentials, as noted by Flower and Nussbaumer (1975). Electron temperatures deduced for a sunspot are much lower than that predicted from ionisation balance calculations, in agreement with earlier results, and imply that a cooling flow may be present. Title: The Mechanical Energy Budget in Stellar Flares Authors: Doyle, J. G. Bibcode: 1988IBVS.3244....1D Altcode: No abstract at ADS Title: Transition regions of dM stars Authors: Byrne, P. B.; Doyle, J. G. Bibcode: 1988ESASP.281a.319B Altcode: 1988uvai....1..319B; 1988IUE88...1..319B Weak upper-chromospheric and transition region (TR) emission from two dM stars (Gl784 and Gl825) were observed using deep IUE SWP exposures. In addition to the usual TR lines, Lyman alpha fluxes for the two stars were also determined. The relative importance of Lyman alpha and Mg II as chromospheric coolants in the M dwarfs and the status of the X-ray/He II (1640A) relationship in the light of these results are discussed. Title: UV flares on II Peg Authors: Doyle, J. G.; Byrne, P. B. Bibcode: 1988ESASP.281a.307D Altcode: 1988uvai....1..307D; 1988IUE88...1..307D Observations by IUE of the RS CVn star II Peg in the upper chromospheric and transition regions lines Mg II k, C IV, and He II in Feb. 1983 show evidence for flare activity. The electron pressure derived from the mean of two different line ratios produces good agreement between the allowed and intersystem lines in the differential emission measure curves. The total radiative losses from the chromosphere and transition region for the first flare on Feb. 2 is 2.46 times 10 to the 35th power erg, and at least 1.91 times 10 to the 34th power erg, for the flare on Feb. 4. Title: EUV emission line ratios for Si IV in the solar transition region. Authors: Keenan, F. P.; Doyle, J. G. Bibcode: 1988JPhys..49..227K Altcode: 1988IAUCo.102..227K Theoretical electron temperature sensitive emission line ratios in Si IV involving the 3d 2D - 3p 2P and 4s 2S - 3p 2P multiplets at ≡1125 Å and 816 Å respectively are derived using R-matrix electron excitation rate calculations. A comparison of these with observational data for a solar active region obtained with the Harvard S-055 spectrometer on board Skylab reveals that there is good agreement between theory and observation for the ratio that includes the 2D3/2,5/2 - 2P3/2 transition at 1128.3 Å. Title: Rotational modulation and flares on RS CVn and BY DRA systems. VII. simultaneous X-ray, radio and optical data for the dMe star YZ CMi on 4/5 March 1985. Authors: Doyle, J. G.; Butler, C. J.; Bryne, P. B.; van den Oord, G. H. J. Bibcode: 1988A&A...193..229D Altcode: Broad-band photometric observations of YZ CMi show a 1.2mag U-band flare at 19:55 UT on 4 March 1985, however, simultaneous X-ray observations from EXOSAT show no detectable increase. Two possible explanations for the lack of an X-ray flare may be i) a flare occurring low in the chromosphere, where the chromosphere may not have been coupled to the transition region and therefore the corona via magnetic fields or ii) proton beam heating as opposed to electron beams. During the flare, optical spectra show excess emission in the wings of all the hydrogen Balmer lines. Interpreted in terms of mass flows would imply material moving at ∼300 km s-1 simultaneously to the blue and red or alternatively random mass motions with a velocity of a similar magnitude. At flare maximum, all the Balmer lines show excess emission in the wings with Hγ and Hσ showing symmetrically broadened lines while higher members of the series such as Hζ and Hη show predominately red shifted material. Assuming a single loop flare, an interpretation in terms of directed mass flows would imply a loop of length ∼2-3 109 cm, however this would place the material in the corona where we should have observed it in X-rays. An alternative explanation, also assuming directed mass flows could involve several small flare kernels, which brighten successively, thus producing a broadened profile. An explanation similar to this has been suggested to explain the excess emission seen in the wings of Hα during solar flares. The total optical flare energy was ∼6 1031 erg in this event, with the Balmer lines contributing ∼10% to the energy in the U-band during the flare. Many short-lived bursts or micro-flares were detected in both the Johnson U-band and the Balmer emission lines. The probability for a correlation between these two data-sets to have occurred by chance was less than 10-5 . The coronal X-ray flux show only a moderate dependence on Balmer line emission and none on the U-band variations. Thus for YZ CMi not only does the large optical flare at 19:55 UT produce no significant X-ray emission but also the low level optical flares, which are seen almost continuously, are similarly absent in soft X-rays. Several X-ray flares/micro-flares were observed, however the majority of these did not show an optical counter-part. The largest of these X-ray events were at 18:00 UT and 23:30 UT, lasting an hour and 1 1/2 h respectively. Their energy in the 0.02-2 keV range were 9.1 1031 erg and 2.1 1032 erg respectively. No optical data was available for the first large X-ray flare, while the second event had only limited coverage. The photometric data implied an optical energy of at least 2.6 1031 erg. The Balmer line contribute at least 10% to the U-band energy in both the 19:55 UT and 23:30 UT flares. Radio observations at 326 MHz give an upper limit of 4 mJy for the flux. Title: An active hemisphere on II Peg. Authors: Doyle, J. G. Bibcode: 1988A&A...192..281D Altcode: IUE observations of the RS CVn star II Peg in the upper chromospheric and transition regions lines Mg II k, C IV, and He II in 1981, 1983 and 1985 shows evidence for increased activity at certain phases. The Mg II k line flux shows an above average value between phases 0.0 and 0.5. This is largely biased by the 1981 and 1983 data-sets, although the 1985 data is consistent with a flux increase in this phase interval. The C IV and He II flux show quite clear evidence of an active hemisphere, although the 1985 data is less convincing than the combined 1981 and 1983. This is perhaps explained by the reduced number of observations in 1985, although an alternative explanation may be a more even distribution of plages during 1985. The above would therefore imply the presence of a long-lived plage region. The optical spot migration rate from late 1981 to early 1986 was only 0.03 rotations per year. The increase in the ultraviolet emission level occurs at the time of the minimum in the optical light curve, therefore implying a hot plage region overlying one of the cool optical spots. Title: Large photometric variations on II Peg in Sept/Nov 1986 : implications for the starspot hypothesis. Authors: Doyle, J. G.; Butler, C. J.; Morrison, L. V.; Gibbs, P. Bibcode: 1988A&A...192..275D Altcode: Large cyclic photometric variations of ΔV= 0.5 mag are observed on II Peg in late 1986. Modelled in terms of starspots, this implies a large spot group covering at least 40% (and perhaps as much as 55%) of the projected area of one hemisphere. Title: Rotational modulation and flares on RS CVn and BY DRA systems. VIII. Simultaneous EXOSAT and H alpha observations of a flare on the dMe star GL 644 AB (Wolf 630) on 24/25 August 1985. Authors: Doyle, J. G.; Butler, C. J.; Callanan, P. J.; Tagliaferri, G.; de La Reza, R.; White, N. E.; Torres, C. A.; Quast, G. Bibcode: 1988A&A...191...79D Altcode: A large flare was detected simultaneously in X-rays and H-alpha on the visual binary Gl 644 AB at about 00:15 UT on August 25, 1985. The flare was detected with both the low (0.05-2 keV) and medium energy (2-7 keV) experiments onboard Exosat, with the flare rise time being similar in both the low and medium energy ranges, although in the low energy the peak occurred about 30 s later. This was followed a few minutes later by a second burst. The flare decay time lasted about 10 minutes longer in the low energy band than in the medium energy. The integrated flare energy detected was 11.9 x 10 to the 32nd and 4.15 x 10 to the 32nd erg respectively in the low and medium energy X-rays and 7 x 10 to the 31st erg in H-alpha. This gives an H-alpha flux of approximately 4 percent of the total X-ray flux detected from the flare or 6 percent of the low X-ray flare energy, similar to that observed in a compact solar flare. Based on the observed cooling time, the flare was estimated to have 2-3 loops of height about 10 to the 9th cm and electron density of about 10 to the 12th/cu cm. Title: Coordinated photometry, spectroscopy and X-ray observations of flare stars Authors: Butler, C. J.; Doyle, J. G.; Foing, B. H.; Rodono, M. Bibcode: 1988ASSL..143..167B Altcode: 1988acse.conf..167B The authors have compared the characteristics of flare activity in UV Ceti and YZ CMi. Almost continuous variability is seen in Hγ and U-band flux in both stars but only in UV Ceti does this correlate strongly with soft X-rays. The relative fluxes in the Balmer emission lines indicates higher densities in the chromospheres of these two dMe stars as compared to the Sun. Title: Activity in late-type dwarfs. II. Flares and SPOT variations on GL 867A (=FK Aqr) in 1981. Authors: Byrne, P. B.; Doyle, J. G. Bibcode: 1987A&A...186..268B Altcode: We present optical photometry of flares and spot variations on the flare/BY Draconis star G1 867A (= FK Aqr). Time-integrated rates of energy lost by optical flaring are derived and compared with previously published results. No evidence of season-to-season changes are evident. No spot variations were detected but there is an unusually large scatter in the mean light curve. Title: Rotational modulation and flares on RS CVn and BY Dra-type stars. V. EXOSAT and IUE observations of a flare on EQ Pegasi. Authors: Haisch, B. M.; Butler, C. J.; Doyle, J. G.; Rodono, M. Bibcode: 1987A&A...181...96H Altcode: Time-trailed UV spectra and a soft X-ray lightcurve were obtained during a flare on the binary dMe star EQ Peg AB. On the basis of solar flare Mg II surface fluxes and an about 70-percent enhancement in the disk-integrated flux during the flare on EQ Peg, it is estimated that the chromospheric flare covered about 1.5 percent of the stellar surface. The size scale is estimated to be comparable to that of a solar two-ribbon flare. This unusual flare is noted to exhibit a low-energy soft X-ray rise phase which is longer than that of most flares; it is longer than the decay phase and peaks much later than the medium energy light curve. Evidence of variable Fe II emission and variable continuum emission in select UV bands during the flare is noted. Title: Rotational modulation and flares on RS CVn and BY DRA stars. VI. Physical parameters of the chromospheres/transition regions of V711 Tau (HR 1099), II Peg and AR Lac during october 1981. Authors: Byrne, P. B.; Doyle, J. G.; Brown, A.; Linsky, J. L.; Rodono, M. Bibcode: 1987A&A...180..172B Altcode: Ground-based optical and IUE satellite-ultraviolet observations of three RS CVn stars are combined with density sensitive line ratios and differential emission measure curves to describe the physical conditions in their outer atmospheres. Solar-like densities are found to be representative of average conditions on two of the stars, V 711 Tau and AR Lac. The total radiative losses from these two stars are estimated and found to be larger than the sun by at least two orders of magnitude. Consideration of the volume emitting in two of the principal transition region lines suggests a possible relation between the disk 'filling factor' for these two lines and the dynamo-related Rossby number. Only one hemisphere of the star II Peg, the one showing least evidence of starspots, is similar. On the opposite hemisphere the presence of a discrete emitting region is deduced which is almost coincident in phase with the passage of the dominant optical spot group across the visible disk. The dimensions of this region, and an illustrative interpretation in terms of a large emitting magnetic loop, are discussed. It is compared to large active region loops on the sun. Title: A rotational modulation effect in the flare frequency on EV Lac. Authors: Doyle, J. G. Bibcode: 1987A&A...177..201D Altcode: Flare monitoring data in the Johnson B-band for the years 1973 to 1982 are discussed in terms of a rotational modulation effect. For the period from 1973 to 1976, a correlation between flare frequency and rotation period is evident, in the sense that a larger than expected number of flares occurs on one hemisphere and a smaller than expected on the other. This correlation is not evident in later years. Photometric observations carried out during the years 1974/76 did not show any evidence of a wavelike variation in the light-curve, which was apparent in later years. Title: Rotational modulation and flares on RS CVn and BY DRA stars. III. IUEobserations of V711 Tau = (HR 1099), II Peg and AR Lac. Authors: Rodono, M.; Byrne, P. B.; Neff, J. E.; Linsky, J. L.; Simon, T.; Butler, C. J.; Catalano, S.; Cutispoto, G.; Doyle, J. G.; Andrews, A. D.; Gibson, D. M. Bibcode: 1987A&A...176..267R Altcode: The authors present observations of three RS CVn stars, which were obtained over the stellar rotation cycles with the IUE satellite. Emission lines from high-temperature transition regions and chromospheres analogous to those observed in the solar spectrum were observed. However, the stellar line surface fluxes are hundreds of times the solar values. The only visible component of II Peg and both components of V711 Tau and AR Lac appear to be chromospherically active. The emission line fluxes for II Peg and, marginally, for the other two systems were observed to vary in anti-phase with the optical varations at the time of the authors' IUE observations. By comparing the results of two-spot models from Paper I with the variation of UV line flux, the authors find evidence of a close spatial correlation between spot and plage-like features. They interpret these correlations in terms of large spot areas in the stellar photospheres with overlying magnetic loops, which form plages in the outer atmosphere. Title: A 155-DAY Period in Solar Flare Frequency Authors: Doyle, J. G. Bibcode: 1987IrAJ...18...55D Altcode: No abstract at ADS Title: Rotational modulation and flares on RS CVn and BY DRA systems. II. IUE observations of BY Draconis and AU Microscopii. Authors: Butler, C. J.; Doyle, J. G.; Andrews, A. D.; Byrne, P. B.; Linsky, J. L.; Bornmann, P. L.; Rodono, M.; Pazzani, V.; Simon, T. Bibcode: 1987A&A...174..139B Altcode: The modulation of the strong chromospheric and transition region lines over one cycle of the optical light curves of BY Dra and AU Mic is studied using IUE observations. The IUE observations were made from October 2-5, 1981 and include 7 short wavelength (SW) spectra and 13 long wavelength (LW) spectra. The integrated line flux data reveal that for BY Dra in the SW spectra there is modulation in the C IV, C II, O I, and He II lines and nonflare surface fluxes; and in the LW spectra, flares are detected in the Mg II and Fe II bands. It is observed that there is no modulation in AU Mic, and the optical photometry data reveal a poor correlation between optical flare strength and UV emission line enhancements. The differential emission measure curves for BY Dra and AU Mic are compared with solar curves. It is noted that both stars show the presence of hot material throughout their rotation period. Title: Identification of forbidden lines from the N I-like ions SI VIII, S X and AR XII Authors: Doyle, J. G. Bibcode: 1987A&A...173..408D Altcode: Line identification are given for several forbidden lines from ions in the N I isoelectronic sequence, in particular Si VIII, S X and Ar XII. Ratios for several of the observed lines were compared with predicated values derived from the best atomic data currently available. Due to the rather poor spectral resolution of the data, the wavelengths cannot be considered better than ±0.5 Å. Title: An activity-rotation relationship in F-M dwarfs from MG II H and K flux. Authors: Doyle, J. G. Bibcode: 1987MNRAS.224P...1D Altcode: Mg II h and k fluxes are given for late-type dwarfs whose rotation periods are known. A good correlation between an activity parameter Rhk (represented by the ratio of Mg II h and k luminosity to bolometric luminosity) versus the Rossby-number is found for main-sequence stars F to late M. Both single and binary stars are found to follow the same relation. A saturation of Rhk occurs at rotation periods of approximately 4 day, it is suggested that stars whose rotation period is close to or shorter than this value are completely covered by active plage regions, although an alternative explanation may be saturation of the dynamo itself. Title: Proton Excitation Rate Coefficients and Cross Sections among the Fine-Structure Levels of the (2s2p)3 P State in Be-like Ions Authors: Doyle, J. G. Bibcode: 1987ADNDT..37..441D Altcode: Proton excitation cross sections and rate coefficients are given for the fine-structure transitions in the (2 s2 p) 3P state in the Be-like ions C III, N IV, O V, F VI, Ne VII, Mg IX, Si XI, S XIII, Ar XV, Ca XVII, and Fe XXIII. In the low-energy region we used the semiclassical Coulomb excitation method, while for the intermediate-energy range, we used a close-coupling impact parameter method. For the temperatures tabulated here, the rate coefficients for all the transitions are better than 5%. Title: X-ray and optical observations of the flare star Wolf 630 AB and of VB 8 G. Authors: Tagliaferri, G.; White, N. E.; Giommi, P.; Doyle, J. G. Bibcode: 1987LNP...291..176T Altcode: 1987LNP87.291..176T; 1987csss....5..176T Results from three EXOSAT observations of Wolf 630 AB are reported. Two X-ray flares have been detected, one simultaneous with an Hα flare. During the second observation a large increase in the X-ray flux from the nearby star VB 8 was also detected. Title: Evidence for an Additional Source of Opacity During the Impulsive Phase of Stellar Flares Authors: Murphy, M.; Doyle, J. G.; Byrne, P. B. Bibcode: 1987LNP...291..170M Altcode: 1987LNP87.291..170M; 1987csss....5..170M Broad-band photometric observations of YZ CMi show a 1.2 magnitude U-band flare at 19:55 UT on 4 March 1985. During the flare the Ca I feature at 4227A changed dramatically. In the spectrum taken during the rise phase, Ca I was both narrower and weaker than that of either the preflare spectrum or spectra taken later in the flare. We interpret this as evidence that the photospheric flare continuum observed here is a combination of a normal dM4.5e continuum plus an overlying continuum with a temperature of less than 4000 - 5000 K and a pressure of at least an order of magnitude less than the photosphere of a dM4.5e star. Title: A Survey of Ly Alpha and Mg II Fluxes for a Sample of Dwarf M Stars Authors: Doyle, J. Bibcode: 1987iue..prop.3009D Altcode: No abstract at ADS Title: Broadening of Hydrogen Balmer Lines During a Flare on the dMe Star YZ CMi Authors: Doyle, J. G.; Byrne, P. B. Bibcode: 1987LNP...291..173D Altcode: 1987csss....5..173D; 1987LNP87.291..173D Broad-band photometric observations of YZ CMi show a 1.2 magnitude U-band flare at 19:55 UT on 4 March 1985. During the flare, optical spectra show excess emission in the wings of all the hydrogen Balmer lines. Interpreted in terms of mass flows would imply material moving at ∼300 km s-1 simultaneously to the blue and red or alternatively random mass motions with a velocity of a similar magnitude. At flare maximum, all the Balmer lines show excess emission in the wings with H α and 11 δ showing symmetrically broadened lines while higher members of the series such as H ζ and H η show predominately red shifted material. Title: Active Phases on II Peg Authors: Panagi, P.; Doyle, J. G. Bibcode: 1987LNP...291..488P Altcode: 1987csss....5..488P; 1987LNP87.291..488P Analysis of HE data for 1981, 1983 and 1985 II Peg show evidence of a long-lived plage region in Mg II k, C IV and He II. This UV enhancement is in anti-correlation with the maximum spot visibility and would imply a hot plage region overlying the cool photospheric spot. The optical spot migration rate from late 1981 to early 1986 was only 0.03 rotations per year. Title: Characterization of the Total Flare Energy Authors: Wu, S. T.; de Jager, C.; Dennis, B. R.; Hudson, H. S.; Simnett, G. M.; Strong, K. T.; Bentley, R. D.; Bornmann, P. L.; Bruner, M. E.; Cargill, P. J.; Crannell, C. J.; Doyle, J. G.; Hyder, C. L.; Kopp, R. A.; Lemen, J. R.; Martin, S. F.; Pallavicini, R.; Peres, G.; Serio, S.; Sylwester, J.; Veek, N. J. Bibcode: 1986epos.conf.5.41W Altcode: 1986epos.confE..41W No abstract at ADS Title: Energetics of the Impulsive Phase Authors: Wu, S. T.; de Jager, C.; Dennis, B. R.; Hudson, H. S.; Simnett, G. M.; Strong, K. T.; Bentley, R. D.; Bornmann, P. L.; Bruner, M. E.; Cargill, P. J.; Crannell, C. J.; Doyle, J. G.; Hyder, C. L.; Kopp, R. A.; Lemen, J. R.; Martin, S. F.; Pallavicini, R.; Peres, G.; Serio, S.; Sylwester, J.; Veek, N. J. Bibcode: 1986epos.conf..5.5W Altcode: 1986epos.confE...5W No abstract at ADS Title: Energetics of the Gradual Phase Authors: Wu, S. T.; de Jager, C.; Dennis, B. R.; Hudson, H. S.; Simnett, G. M.; Strong, K. T.; Bentley, R. D.; Bornmann, P. L.; Bruner, M. E.; Cargill, P. J.; Crannell, C. J.; Doyle, J. G.; Hyder, C. L.; Kopp, R. A.; Lemen, J. R.; Martin, S. F.; Pallavicini, R.; Peres, G.; Serio, S.; Sylwester, J.; Veek, N. J. Bibcode: 1986epos.conf.5.20W Altcode: 1986epos.confE..20W No abstract at ADS Title: Review of Impulsive Phase Phenomena Authors: Wu, S. T.; de Jager, C.; Dennis, B. R.; Hudson, H. S.; Simnett, G. M.; Strong, K. T.; Bentley, R. D.; Bornmann, P. L.; Bruner, M. E.; Cargill, P. J.; Crannell, C. J.; Doyle, J. G.; Hyder, C. L.; Kopp, R. A.; Lemen, J. R.; Martin, S. F.; Pallavicini, R.; Peres, G.; Serio, S.; Sylwester, J.; Veek, N. J. Bibcode: 1986epos.conf.5.60W Altcode: 1986epos.confE..60W No abstract at ADS Title: Flares Chosen for Energetics Study Authors: Wu, S. T.; de Jager, C.; Dennis, B. R.; Hudson, H. S.; Simnett, G. M.; Strong, K. T.; Bentley, R. D.; Bornmann, P. L.; Bruner, M. E.; Cargill, P. J.; Crannell, C. J.; Doyle, J. G.; Hyder, C. L.; Kopp, R. A.; Lemen, J. R.; Martin, S. F.; Pallavicini, R.; Peres, G.; Serio, S.; Sylwester, J.; Veek, N. J. Bibcode: 1986epos.conf.5.47W Altcode: 1986epos.confE..47W No abstract at ADS Title: Relationships among the Phases Authors: Wu, S. T.; de Jager, C.; Dennis, B. R.; Hudson, H. S.; Simnett, G. M.; Strong, K. T.; Bentley, R. D.; Bornmann, P. L.; Bruner, M. E.; Cargill, P. J.; Crannell, C. J.; Doyle, J. G.; Hyder, C. L.; Kopp, R. A.; Lemen, J. R.; Martin, S. F.; Pallavicini, R.; Peres, G.; Serio, S.; Sylwester, J.; Veek, N. J. Bibcode: 1986epos.conf.5.39W Altcode: 1986epos.confE..39W No abstract at ADS Title: Simultaneous X-ray and optical monitoring of the flare star YZ CMi. Authors: Doyle, J. G.; Butler, C. J.; Haisch, B. M.; Rodono, M. Bibcode: 1986MNRAS.223P...1D Altcode: Broad-band photometric observations of YZ CMi show a 1.2 mag U-band flare, however, simultaneous X-ray observations from EXOSAT show no detectable increase. It is suggested that the event could have occurred low down in a part of the chromosphere, which may not have been coupled to the transition region and corona via magnetic fields. However, a more plausible explanation may have been absorption of the X-rays by an over-lying dense prominence. Several short-lived enhancements (micro-flares) were detected in both the Johnson U-band and the Balmer emission lines. Title: Rotational modulation and flares on RS CVn and BY Dra-type stars. I. Photometry and SPOT models for BY Dra, AU Mic, AR Lac, II Peg and V711 Tau (=HR 1099). Authors: Rodono, M.; Cutispoto, G.; Pazzani, V.; Catalano, S.; Byrne, P. B.; Doyle, J. G.; Butler, C. J.; Andrews, A. D.; Blanco, C.; Marilli, E.; Linsky, J. L.; Scaltriti, F.; Busso, M.; Cellino, A.; Hopkins, J. L.; Okazaki, A.; Hayashi, S. S.; Zeilik, M.; Helston, R.; Henson, G.; Smith, P.; Simon, T. Bibcode: 1986A&A...165..135R Altcode: Multicolor wide-band photometry of five active stars is presented. The observations were carried out at several places before, during and after the period of IUE observations for the purpose of determining the location, sizes, and evolution of photospheric spots at the time when chromospheric, transition region, and coronal activity data were obtained from UV and radio observations. II Peg, BY Dra, and AU Mic show fairly stable quasi-sinusoidal light curves, while AR Lac and V 711 Tau show double-peaked light curves. For V 711 Tau, a remarkable evolution of the spotted area extent and/or longitude distribution is found. Small, but definite color variations that are consistent with the cool spot hypothesis have also been detected for BY Dra, II Peg and V 711 Tau. Title: Optical photometry and spectroscopy for five dwarf M stars. Authors: Doyle, J. G.; Byrne, P. B.; Menzies, J. W. Bibcode: 1986MNRAS.220..223D Altcode: The authors report on a search for flaring and BY Dra (spotted) variations on five M-dwarf stars, Gliese 1, 461, 825, 899 and 908. The results for Gl 461 and 825 are compared with predictions of activity levels based on the measured quiescent X-ray flux. The chromospheric radiative loss rate in the Ca H and K lines are determined for Gl 461. Title: Plasma densities from the He-like ion NE IX Authors: Doyle, J. G.; Keenan, F. P. Bibcode: 1986A&A...157..116D Altcode: The authors present line emissivity data for the three principal lines of the He-like ion Ne IX. This data is compared with high resolution solar flare observations from the Solar Maximum Mission. During the rise phase of flares it is shown that the forbidden line is blended with a high temperature line, as opposed to the intercombination line suggested by McKenzie (1985). It is suggested that the electron density during the rise phase of flares be determined from the intercombination to resonance line ratio which the authors have integrated over a multi-thermal plasma and is shown to be only slightly dependent on the assumed differential emission measure distribution. Scattering of resonance line photons from the line-of-sight is shown to be unimportant. Title: Coordinated IUE and ground-based observations of stellar flares: YZ CMi, Proxima Cen and AD Leo. Authors: Foing, B. H.; Rodono, M.; Cutispoto, G.; Catalano, S.; Linsky, J. L.; Gibson, D. M.; Brown, A.; Haisch, B. M.; Butler, C. J.; Byrne, P. B.; Andrews, A. D.; Doyle, J. G.; Gary, D. E.; Henry, G. W.; Russo, G.; Vittone, A.; Scaltriti, F. Bibcode: 1986RMxAA..12..213F Altcode: Coordinated observations of stellar flares were obtained with lUE and several ground-based facilities in March 1984.The simultaneous observations allowed it to cover a wide range of wavelengths from ii5nm to 6cm.We intend to study the effect ofthe observed flares at different atmospheric heights in order to estimate the energy budget,the time scales and the cooling processes.Our observations includetime-resolved IUE spectroscopy at SWP(115-195nm) and LWP(190-320nm),optical spectroscopy at the ESO 3.6m+IDS (355-440nm),high resolution spectroscopy at the ESO 1.4m CAT+CES(653-659nm),narrow band H alpha and wide band optical photometry, infrared photometry at 2.2microns and microwave observations at 2,6 and 20 cm We present for some flare events,among the results,the first detection of infrared flux decrease -or "negative flare"-in coincidence with the flux increase at the other wavelengths:the broadening and changes of the Balmer H lines,He and high excitation lines;the appearance of higher members of the Balmer serie;the enhancements of Mg II doublet and Fe II blend (260nm);and the flare detection at 2cm and 6cm Title: Broadening of soft X-ray lines during the impulsive phase of solar flares - Random or directed mass motions? Authors: Doyle, J. G.; Bentley, R. D. Bibcode: 1986A&A...155..278D Altcode: The authors present spectroscopic data for three flares obtained with the Bent Crystal Spectrometer flown in the Solar Maximum Mission in 1980. This data is concerned with the structure of the Ca XIX resonance line at 3.176 Å during the impulsive phase of flares. On the basis of high time resolution (6s.) data, the authors suggest that the previous published results concerned with the excess broadening of the resonance line being due to bulk random mass motions may give an over-simplified picture. Instead the authors suggest that during this stage of the flare, the resonance line consists of many discrete features, which are interpreted as mass flows. Title: Trajectory Determinations and Collection of Micrometeoroids on the Space Station Authors: Doyle, J. G.; Byrne, P. B.; Butler, C. J. Bibcode: 1986A&A...156..283D Altcode: We report on a search for flaring and BY Draconis type variability on the M-dwarf Balmer emission line star, Gliese 867 B. The time-averaged flare energy in the Johnson U-band is similar to that measured in 1977 and 1978. A typical wave4ike variation of 0.15 magnitudes, seemingly due to rotational modulation of large spotted areas, was observed in the V-band with a period 1.95 days. Title: Correlation of the Mg II h & k flux versus rotational period in late-type stars Authors: Doyle, J. G. Bibcode: 1986LNP...254...33D Altcode: 1986csss....4...33D A correlation between the Mg h & k flux and the rotation period for main-sequence F to K stars has been extended to include all dMe stars with known rotational periods. It is shown that the relationship proposed by Hartmann et al for F to K stars does extend to the dMe stars, although there is more scatter. This is in part due to our inability to use the parameter representing the convective-overturn time. Title: Faint optical flares from the dwarf M star Gliese 812 (Ross 193). Authors: Doyle, J. G.; Byrne, P. B. Bibcode: 1986A&A...154..370D Altcode: The authors report on a search for flaring on the Balmer emission line star, Gliese 812. Three flares were detected in a total monitoring time of 11.66 h. The time-averaged flare energy in the Johnson U-band is substantially smaller than in other stars of similar absolute U magnitude, such as AD Leo, EQ Peg and EV Lac. Title: Flare activity and by-Draconis type variability on the late-type dMe star gliese 867B Authors: Doyle, J. G.; Byrne, P. B.; Butler, C. J. Bibcode: 1986LNP...254..231D Altcode: 1986csss....4..231D We report on an analysis of flaring and BY-Draconis type variability on the Balmer emission line star, Gliese 867B. The time-averaged flare energy in the Johnson 1-band is similar to that measured in 1977 and 1978. A variation of 0.15 magnitudes was observed in the V-band with a period l.95 days. Title: Simultaneous X-Ray and Photometric Observations of the Flare Star YZ CMi Authors: Doyle, J. G.; Butler, C. J. Bibcode: 1986LNP...254..228D Altcode: 1986csss....4..228D Broad-band photometric observations of YZ CMi show a 1.2 magnitude U-band flare, however, simultaneous X-ray observations from EXOSAT show no detectable increase. It is suggested that the energy was dissipated before reaching the corona. Two long duration U-band enhancements detected during the optical monitoring may have been the result of back-heating from an enhanced coronal X-ray flux. Title: IUE Observations of Surface Structures on II PEG Authors: Doyle, J. Bibcode: 1986iue..prop.2681D Altcode: No abstract at ADS Title: Flare energetics. Authors: Wu, S. T.; de Jager, C.; Dennis, B. R.; Hudson, H. S.; Simnett, G. M.; Strong, K. T.; Bentley, R. D.; Bornmann, P. L.; Bruner, M. E.; Cargill, P. J.; Crannell, C. J.; Doyle, J. G.; Hyder, C. L.; Kopp, R. A.; Lemen, J. R.; Martin, S. F.; Pallavicini, R.; Peres, G.; Serio, S.; Sylwester, J.; Veck, N. J. Bibcode: 1986NASCP2439....5W Altcode: In this investigation of flare energetics, the authors establish a comprehensive and self-consistent picture of the sources and transport of energy within a flare. They chose five flares in 1980 that were well observed with instruments on the SMM, and with other space-borne and ground-based instruments. Details of the observations available for them and the corresponding physical parameters derived from these data are presented. The flares were studied from two perspectives, the impulsive and gradual phases, and then the results were compared to obtain the overall picture of the energetics of these flares. The authors also discuss the role that modeling can play in estimating the total energy of a flare when the observationally determined parameters are used as the input to a numerical model. Title: The extreme ultraviolet spectrum of sunspot plumes. I - Observations Authors: Noyes, R. W.; Raymond, J. C.; Doyle, J. G.; Kingston, A. E. Bibcode: 1985ApJ...297..805N Altcode: A complete extreme ultraviolet spectrum of a sunspot plume by the Skylab S-055 spectroheliometer is presented, and the relevant observational details are discussed. Identifications and intensities are given for emission lines and continua in the 303-1343 A range. The emission from lines found between 100,000 and a million K are enhanced by up to a factor of 40 compared with quiet and active region spectra. The emission measure curve for the mean spectrum shows a high double peak at log T = 5.7 and 6.0, reflecting the very inhomogeneous spatial structure of the sunspot plumes. The extremely high signal to noise of the spectrum is used to investigate the electron density and ionization stage of the gas based on line ratio techniques. A model of line emission from a gas cooling by radiation alone at constant density is presented, and the observations are compared with various semiempirical and theoretical models. Title: The Extreme Ultraviolet Spectrum of Sunspot Plumes - Part Two - Spectral Diagnostics and Implications for Cooling Authors: Doyle, J. G.; Raymond, J. C.; Noyes, R. W.; Kingston, A. E. Bibcode: 1985ApJ...297..816D Altcode: The extreme ultraviolet emission-line spectrum of very intense sunspot plumes is analyzed. Several of the standard density diagnostics suggest a constant density, rather than constant pressure, emitting region. Temperature diagnostic line ratios of several ions yield temperatures below those expected in ionization equilibrium (and observed in the quiet Sun). This provides strong evidence for the suggestion that the internal energy of cooling, falling gas accounts for the observed radiation. The lack of such departures from equilibrium in the quiet Sun demonstrates that downflows are not the dominant source of energy at transition region temperatures. We assess the accuracy of several atomic rate coefficients. Title: Interpretation of EUV spectra from loop structures in an active region at the limb Authors: Doyle, J. G.; Mason, H. E.; Vernazza, J. E. Bibcode: 1985A&A...150...69D Altcode: EUV spectral scans and rasters of an active region observed at the limb are analyzed. These were obtained with the Harvard EUV spectroheliometer on the Apollo Telescope Mount. The spectra were taken following a small flare and an H-alpha surge. Diagnostic line ratios are used to determine electron densities and temperatures from the spectral scans. An electron pressure of 10 to the 15th/cu cm K is derived at 200,000 K. The temperatures derived from the diagnostic ratios indicate that the plasma is in ionization equilibrium, although mass flows of a few kilometers per s could be present. Rasters of the active region taken later show well defined loop structures. The parameters derived from the low temperature lines (100,000 K) and the rasters are inconsistent with those inferred from scaling laws based on static loop models. However, better agreement between the derived parameters and the models is achieved if use is made of the electron density derived from the emission measure of Mg X, and it is assumed that it remains constant up to 5-million K. Title: Flare Activity and the Quiescent X-ray Emission in dMe Stars Authors: Doyle, J. G.; Butler, C. J. Bibcode: 1985ASSL..116..237D Altcode: 1985rst..conf..237D Einstein observations of the X-ray flux of quiescent dwarf Me stars are correlated with the time-averaged energy emitted by flares in the Johnson U band. It is shown that the energy emitted by the coronae of these stars in X-rays is about an order of magnitude greater than the U band flare energy. From an estimate of the ratio of the total radiation emitted to the U band flux, it seems possible that if a similar amount of mechanical energy was dissipated in the stellar atmosphere, then the observed flare events can provide sufficient energy to heat the coronae of these stars. Title: Energetics of a double flare on November 8, 1980 Authors: Doyle, J. G.; Byrne, P. B.; Dennis, B. R.; Emslie, A. G.; Poland, A. I.; Simnett, G. M. Bibcode: 1985SoPh...98..141D Altcode: Here we complete an energy balance analysis of a double impulsive hard X-ray flare. From spatial observations, we deduce both flares probably occur in the same loop within the resolution of the data. For the first flare, the energy in the fast electrons (assuming a thick-target model) is comparable to the convective up-flow energy, suggesting that these are related successive modes of energy storage and transfer. The total energy lost through radiation and conduction, 2.0 × 1028 erg, is comparable to the energy in fast electrons 2.5 × 1028 erg. For the second flare, the energy in the fast electrons is more than one order of magnitude greater than the energy of the convective up-flow. Total energy losses are within a factor of two lower than the calculated fast electron energy. We interpret the observations as showing that the first flare occurred in a small loop with fast electrons heating the chromosphere and resulting in chromospheric evaporation increasing the density in the loop. For the second flare most of the heating occurred at the electron acceleration site. The two symmetrical components of the Ca XIX resonance line and a high velocity down-flow of 115 km s −1 observed at the end of the second hard X-ray burst are consistent with the flare eruption (reconnection) region being high in the flare loop. The estimated altitude of the acceleration site is 5500 km above the photosphere. Title: Optical photometry and spectroscopy of the flare star Gliese 229 (=HD42581). Authors: Byrne, P. B.; Doyle, J. G.; Menzies, J. W. Bibcode: 1985MNRAS.214..119B Altcode: The authors present optical flare photometry and a search for spotted variations on the star Gl 229. These results rule out the presence of a large-scale asymmetric spot distribution and indicate a low level of flare activity. This is in agreement with other indicators of stellar activity including coronal X-ray emission and radiative losses from the lower chromosphere as gauged from the strength of Ca H and K and the Balmer lines. Title: Ultrviolet Radiation from Stellar Flares and its Relation to the Coronal X-Ray Emission for dMe Stars Authors: Doyle, J. G.; Butler, C. J. Bibcode: 1985IrAJ...17...19D Altcode: No abstract at ADS Title: Ultraviolet radiation from stellar flares and the coronal X-ray emission for dwarf-Me stars Authors: Doyle, J. G.; Butler, C. J. Bibcode: 1985Natur.313..378D Altcode: The origin of chromospheric and coronal emission is thought to derive ultimately from magnetic fields generated by a dynamo mechanism involving the interaction of rotation and convection1. Although these magnetic fields are difficult to detect directly, the dramatic stellar flares, believed to be the result of magnetic reconnection, have been observed for many years on dwarf Me (dMe) stars. Here we correlate Einstein observations of the X-ray flux of quiescent dMe stars with the time-averaged energy emitted by flares in the Johnson-U band, showing that the X-ray energy emitted by the coronae of these stars is about an order of magnitude greater than the U-band flare energy. From our estimate of the ratio of the total radiation emitted to the U-band flux, it is possible that, if a similar amount of energy were dissipated in the stellar atmosphere, then the observed flare events could heat the coronae of these stars. Title: Optical photometry and UV spectroscopy of the flare star GL 735 (=V1285 Aql). Authors: Byrne, P. B.; Doyle, J. G.; Butler, C. J.; Andrews, A. D. Bibcode: 1984MNRAS.211..607B Altcode: The authors present optical photometry of flares and possible spot variations on the star Gl 735. Consideration of the energetics of the optical flares suggests that the star may be underactive when compared to other flare stars of the same spectral type. This conclusion is not supported however by an estimate of the radiative loss rate from the lower chromosphere due to Mg II h and k. Radiative losses from the upper chromosphere, transition zone and corona are also normal for a flare star of its spectral type. Title: Erratum - Solar Maximum Mission Observations of a Compact Flare - Interpretation and Theoretical Implications for Flare Theory Authors: Doyle, J. G.; Byrne, P. B. Bibcode: 1984IrAJ...16..286D Altcode: No abstract at ADS Title: Mg ix and Si xi line ratios in the sun Authors: Keenan, F. P.; Kingston, A. E.; Dufton, P. L.; Doyle, J. G.; Widing, K. G. Bibcode: 1984SoPh...94...91K Altcode: New theoretical emission line ratios for the Be-sequence ions MgIX and SiXI are presented. A comparison with observational data for two solar flares and an active region loop obtained with the Harvard EUV spectrometer and NRL XUV spectroheliograph aboard Skylab reveals that these plasmas are in ionization equilibrium at coronal temperatures. Unfortunately most of the density diagnostics are not particularly useful under solar plasma conditions, as they vary only slightly over the electron density range 108-1013cm−3. However the SiXI ratioI(3Pe2 -3Po2)/I(3Po1 -1Se0) is density sensitive in the range 108 to 1010cm−3, which is representative of electron densities found in solar active regions or small flares. Title: Rotational modulation of spots and plages on RS CVn stars. Authors: Byrne, P. B.; Doyle, J. G.; Andrews, A. D.; Butler, C. J.; Marstad, N.; Linsky, J. L.; Simon, T.; Rodono, M.; Catalano, S.; Blanco, C.; Marilli, E.; Pazzani, V. Bibcode: 1984ESASP.218..343B Altcode: 1984iue..conf..343B Observations of three RS CVn stars made with the IUE satellite are presented. Emission line fluxes are found to vary in anti-phase with the stars' optical variations. The authors interpret these correlations in terms of large-scale spots in the stellar photospheres with overlying magnetic loops, giving rise to non-thermal heating of the layers above the spots. Evidence of nonthermal gas motions is also presented which appear to be associated with the most active regions of the stars. Title: Atmospheric Structure of RS CVN Stars Authors: Doyle, J. Bibcode: 1984iue..prop.2022D Altcode: No abstract at ADS Title: Coordinated IUE and ground-based observations of active stars: flare events on YZ CMi, V1005 Ori, AD Leo and AR Lac. Authors: Rodonò, M.; Cutispoto, G.; Catalano, S.; Linsky, J. L.; Gibson, D. M.; Brown, A.; Haisch, B. M.; Butler, C. J.; Byrne, P. B.; Andrews, A. D.; Doyle, J. G.; Gary, D. E.; Henry, G. W.; Russo, G.; Vittone, A.; Scaltriti, F.; Foing, B. Bibcode: 1984ESASP.218..247R Altcode: 1984iue..conf..247R Observations of stellar flares were obtained with IUE and ground-based facilities simultaneously over a wide range of wavelengths in order to study the effect of the flare radiation at different atmospheric levels. Observations include time-resolved IUE and optical spectroscopy, narrow and wide-band optical photometry, IR photometry, and microwave observations. Results include detection of IR flux decrease, or negative flare, in coincidence with flux increase at all other wavelengths. Title: IUE observations of BY Draconis. Authors: Butler, C. J.; Doyle, J. G.; Andrews, A. D.; Byrne, P. B.; Linsky, J. L.; Simon, T.; Marstad, N. C.; Rodono, M.; Pazzani, V.; Cutispoto, C. Bibcode: 1984ESASP.218..243B Altcode: 1984iue..conf..243B Phased IUE low resolution observations of BY Draconis are discussed. They show no significant modulation of the prominent SWP emission lines over one rotation period. However a marginally significant anticorrelation of the MgII flux, and the flux in the LWR continuum, with the V light curve is observed, and is interpreted as due to plage type areas over the photospheric spots. Two SWP spectra show sporadic enhancements of the emission lines, as seen in other IUE spectra of flares. Title: Derivation of ionization balance for calcium XVIII/XIX using XRP solar X-ray data Authors: Antonucci, E.; Gabriel, A. H.; Doyle, J. G.; Dubau, J.; Faucher, P.; Jordan, C.; Veck, N. Bibcode: 1984A&A...133..239A Altcode: Spectra of calcium from solar flares are used in an attempt to derive an ionization balance for Ca XVIII/Ca XIX. The isothermal assumption inherent in this derivation is shown not to introduce errors, by modelling a number of hypothetical nonisothermal plasmas. The unresolved blend of calcium and argon lines prevents a definitive determination of the results, owing to uncertainties in the ratio of abundances of these elements. The resulting ionization balance curves are presented as a function of the solar argon/calcium abundance ratio. The theoretical ionization balance of Doyle and Raymond is consistent with the data. To within the expected accuracy of the atomic theories, there is no reason to assume that the flare plasma is other than close to steady-state ionization balance. Title: SMM Observations of a Compact Flare.Interpretation and Theoretical Implications of Flare Theory Authors: Doyle, J. G.; Byrne, P. B. Bibcode: 1984IrAJ...16..226D Altcode: In the present completion of an energy balance analysis for a double impulsive, hard X-ray flare, it is deduced on the basis of spatial observations that both flares occurred in the same loop. From observations of the Ca XIX resonance line during the second flare's hard X-ray burst, it appears that two symmetrically displaced components are moving apart at thermal velocities of about 60 km/sec. These are interpretable in terms of in situ heating, where most of the fast electrons are stopped in the loop close to the site of the acceleration (and long before they reach the chromosphere) to produce the 'evaporated' up-flow. The two symmetrical components, and a high velocity downflow of 115 km/sec observed at the end of the second hard X-ray burst, are consistent with the flare eruption region's location high in the flare loop. Title: Optical photometry and ultraviolet spectroscopy of the flare/BY DRA star GL 182(V 1005 Ori). Authors: Byrne, P. B.; Doyle, J. G.; Butler, C. J. Bibcode: 1984MNRAS.206..907B Altcode: G1 182 was previously reported to be a rapidly rotating BY Dra star which flares at an anomalously high rate. The present observations confirm its BY Dra nature but revise the rotation period, such that it is shown to rotate much more slowly. The time-averaged energy output in flares is shown to be normal for a flare star of its spectral type, and its rate of flaring is normal. IUE spectra show chromospheric features whose surface fluxes compare with those of BY Dra itself. Title: Flare parameters for the 7 September, 1973 two-ribbon flare Authors: Doyle, J. G.; Raymond, J. C. Bibcode: 1984SoPh...90...97D Altcode: A study is made of the relative importance of the various energy loss mechanisms for the long-decay event of 7 September, 1973, using spectral scans in the 400 Å-1335 Å range. This spectral range contains many of the important electron density and temperature diagnostic line ratios for the solar transition zone. We refine earlier analyses of the flare energy budget using more detailed emission measure curves and density diagnostics. We examine the constant pressure assumptions used in both coronal loop models and in the interpretation of observations in terms of flare energetics. We find that much of the upper transition region emission originates in cooling loops. Radiative losses are found to dominate. Title: Compte rendu du Symposium de l'I. U. A. A. à Charleroi, 18-20 février 1983 Authors: Doyle, J. Bibcode: 1984C&T...100...34D Altcode: No abstract at ADS Title: Line ratios for solar ultra-violet lines of O v Authors: Doyle, J. G.; Dufton, P. L.; Keenan, F. P.; Kingston, A. E. Bibcode: 1983SoPh...89..243D Altcode: New O V rate coefficients are used to calculate the ratio of the intensity of the 760 Å multiplet to that of the 630 Å line. Results are given for a range of electron densities and temperatures. The theoretical ratios are compared with observed line ratios for different solar regions. Title: A line identification list for the solar flare of 7 September, 1973 in the wavelength range 1335 Å 380 Å Authors: Doyle, J. G. Bibcode: 1983SoPh...89..115D Altcode: A wavelength list is presented for the solar flare of 7 September, 1973 in the spectral range 1335 Å-380 Å. The ions observed suggest a range of temperatures in the flare plasma from 8 × 103 K to 107 K. This wavelength range contains many of the important electron density diagnostics lines for the solar transition zone and corona. The line list should also be of potential use in the identification and comparison with stellar spectra. Title: CA XVII line ratios in solar flares Authors: Dufton, P. L.; Kingston, A. E.; Doyle, J. G.; Widing, K. G. Bibcode: 1983MNRAS.205...81D Altcode: New electron impact collision rates are presented for transitions between the 10 lowest states of Ca XVII. These data are then used to predict Ca XVII level populations and emission-line intensity ratios for electron densities and temperatures appropriate to solar flares. A comparison is made with observations obtained with the NRL spectroheliograph aboard Skylab. For the intercombination to resonance line ratio the agreement is good. For other triplet to singlet ratios agreement is less satisfactory, possibly due to uncertainties in the observational data. Title: X-ray line ratios from helium-like ions - Updated theory and SMM flare observations Authors: Wolfson, C. J.; Leibacher, J. W.; Doyle, J. G.; Phillips, K. J. H. Bibcode: 1983ApJ...269..319W Altcode: The potential which the conduction of measurements of the three principal lines emitted from helium-like ions has for the determination of plasma electron density was initially pointed out by Gabriel and Jordan (1969). The diagnostic technique is based on the fact that the ratio, R, of the intensity of a forbidden line to the intensity of an intercombination line decreases as electron density increases due to collisional excitation of levels. In the present investigation a further refinement of this procedure is provided by specifically calculating the effects of cascades from levels with principal quantum numbers up to n=6. Two improved spectrometers recently placed in operation include the SOLEX instrument on the satellite P78-1 and the X-ray Polychromator (XRP) instrument on the NASA Solar Maximum Mission satellite. Measurements obtained with one of the spectrometers making up the XRP are presented, taking into account the emission from Ne IX ions. Title: Line ratios for O VII Authors: Doyle, J. G.; Tayal, S. S.; Kingston, A. E. Bibcode: 1983MNRAS.203P..31D Altcode: New theoretical rates for electron excitation of the transitions 11S-23S and 11S-23P in O VII are used to calculate the line ratios R0 (forbidden line to intercombination line) and G0 (forbidden plus intercombination lines to resonance line). The authors' theoretical value of R0 are slightly larger than earlier calculations but their values of G0 are significantly lower than the earlier calculations. With their results the value of G0 = 1.0, from the solar observations of McKenzie & Landecker, would predict an electron temperature of 2.0×106K, which is in good agreement with the temperature of 1.8×106K predicted by recombination-ionization equilibrium calculations. Title: IUE spectra of the BY Dra/flarestar AU MIC Authors: Butler, C. J.; Andrews, A. D.; Doyle, J. G.; Byrne, P. B.; Linsky, J. L.; Simon, T.; Marstad, N.; Rodono, M.; Pazzani, V. Bibcode: 1983ASSL..102..249B Altcode: 1983ards.proc..249B; 1983IAUCo..71..249B Ground-based optical and IUE observations of BY Dra variables undertaken to follow the spectral variation of these stars over one cycle are discussed. It is noted that in the first series, 20 LWR and 19 SWP trailed spectra were taken of AU Mic over a three-day period, August 4-6, 1980. The mean integrated flux are shown here for the strong emission lines in th SWP spectra of AU Mic over the observed phase interval of 0.14 to 0.8, together with an approximate V light curve determined by the FES and IUE. Several points emerge from comparing the emission line intensities and FES magnitudes. The first is that the light curve at this time had at least three and possibly four minima. If this is to be interpreted as deriving from the rotation of a spotted star, several spotted regions would be required, distributed in stellar longitude. The second point is that repeated flaring of AU Mic makes it difficult to perceive any clearly defined modulation of the emission line intensities owing to plage regions in the vicinity of the spots. The third point is that following flare activity during SWP 9695 and WP 9698, it appears that the intensity of the HeII and SiII lines has remained high for some time after the drop in intensity of the CIV line. Title: The interpretation of EUV spectra of sunspots Authors: Doyle, J. G.; Raymond, J. C.; Noyes, R. W.; Kingston, A. E. Bibcode: 1983ASSL..102..325D Altcode: 1983ards.proc..325D; 1983IAUCo..71..325D EUV observations of a sunspot made on Skylab are discussed. For the 60,000-300,000 K temperature range, a constant electron density of 10 billion/cu cm fits the data, while for the million K plasma the density decreases by an order of magnitude and a constant pressure approximation. Temperature diagnostic line ratios show temperatures lower than the equilibrium temperature and lower than the temperatures observed in the averaged quiet sun. The observed departure from ionization equilibrium is consistent with those expected for a radiatively cooling gas. A model which assumes a constant density and a constant velocity flow of 7 km/s beginning in ionization equilibrium at log T = 5.8 matches the overall energetic needs for the transition region and accounts for the observed shift away from ionization equilibrium. Title: An Emission Measure Analysis of Two Sunspots Observed by the UVSP Instrument on the SMM Spacecraft Authors: Kingston, A. E.; Doyle, J. G.; Dufton, P. L.; Gurman, J. B. Bibcode: 1982SoPh...81...47K Altcode: The EUV observations from the SMM satellite of two sunspots are presented here. These observations show the sunspots (a) to be regions of lower intensity than the surrounding plage, contrary to that found by previous authors, and (b) to have line intensities which vary little over a period of several hours. An upper limit to mass flows of 2km s-1 is derived, indicating a relatively simple energy balance for the chromosphere-corona transition zone with thermal conduction being balanced by radiative losses. Electron densities derived from NIV to CIV line ratios imply electron pressures (log NeTe) of 15.0 to 15.3. Title: Solar Maximum Mission Workshops Authors: Doyle, J. G. Bibcode: 1982IrAJ...15..338D Altcode: No abstract at ADS Title: Observations of the occultation of HD 197999 by the Minor planet 105 Artenis. Authors: Byrne, P. B.; Coulson, I. M.; Doyle, J. G.; Taylor, G. E. Bibcode: 1982MNRAS.200P..65B Altcode: A minimum value of 110 km for the diameter Artemis is derived from observations of its occultation of a star. Title: Electron density diagnostic line ratios from the N = 3 lines of O V Authors: Widing, K. G.; Doyle, J. G.; Dufton, P. L.; Kingston, E. A. Bibcode: 1982ApJ...257..913W Altcode: New atomic physics calculations are presented for electron excitation rates for transitions between the n = 2 and n = 3 levels of O v. These are used to calculate theoretical line intensity ratios for the 192 A, 215 A, 220 A, and 248 A lines of O v. These line intensity ratios are electron density sensitive and provide valuable diagnostics at an electron temperature of approximately 200,000 for small impulsive flare events in which the transition zone ions are enhanced relative to the coronal ions. Two flares observed by the NRL spectroheliograph on Skylab, on December 22, 1973, and January 21, 1974, are studied, with electron densities of approximately 3 x 10 to the 11th per cu cm being deduced. Title: Impulsive Phase of Flares in Soft X-Ray Emission Authors: Antonucci, E.; Gabriel, A. H.; Acton, L. W.; Culhane, J. L.; Doyle, J. G.; Leibacher, J. W.; Machado, M. E.; Orwig, L. E.; Rapley, C. G. Bibcode: 1982SoPh...78..107A Altcode: Observations using the Bent Crystal Spectrometer instrument on the Solar Maximum Mission show that turbulence and blue-shifted motions are characteristic of the soft X-ray plasma during the impulsive phase of flares, and are coincident with the hard X-ray bursts observed by the Hard X-ray Burst Spectrometer. A method for analysing the Ca XIX and Fe XXV spectra characteristic of the impulsive phase is presented. Non-thermal widths and blue-shifted components in the spectral lines of Ca XIX and Fe XXV indicate the presence of turbulent velocities exceeding 100 km s-1 and upward motions of 300-400 km s-1. Title: Cercle Scientifique de Charleroi: Journées de l'astronomie Authors: Doyle, J. Bibcode: 1982C&T....98..305D Altcode: No abstract at ADS Title: I. U. A. A.: une invitation Authors: Doyle, J. Bibcode: 1982C&T....98..303D Altcode: No abstract at ADS Title: IUE Spectra of Active Stars in Binary Systems. Authors: Butler, C. J.; Andrews, A. D.; Byrne, P. B.; Doyle, J. G.; Linsky, J. L.; Marstad, N.; Simon, T.; Rodono, M.; Blanco, C.; Catalano, S.; Pazzani, E.; Marilli, V. Bibcode: 1982uxsa.coll...14B Altcode: 1982IAUCo..73...14B No abstract at ADS Title: Ultraviolet spectra of dwarf solar neighbourhood stars. I. Authors: Butler, C. J.; Byrne, P. B.; Andrews, A. D.; Doyle, J. G. Bibcode: 1981MNRAS.197..815B Altcode: Short-wavelength IUE spectra of three nearby M-type dwarfs are presented. Two of these stars, Gliese 867 A and AU Mic, are active UV Ceti flare stars and their UV spectra exhibit strong emission lines, characteristic of active chromospheres. The third star, Gliese 825, is a low-activity flare star and its spectrum reveals no chromospheric lines. A strong UV continuum exists in one of the spectra of Gliese 867 A and it is deduced that a flare took place during the exposure. A spectrum of the flare light is extracted and compared with the predictions of various flare models. Title: New ionization fractions for the lithium- and helium-like ionization stages of calcium and iron Authors: Doyle, J. G.; Raymond, J. C. Bibcode: 1981MNRAS.196..907D Altcode: A reinterpretation of the high resolution X-ray spectra of Ca XIX and Fe XXV, observed during a solar flare on March 25, 1979, is presented. New ionization fractions for Ca XVIII, Ca XIX, Fe XXIV, and Fe XXV are used, and it is shown that the new calculations substantially change the interpretation of the spectra. It is implied that the flare plasma was ionizing during the early phases of the flare, and recombining during the decay phase. Title: The energy balance in coronal holes and average quiet-sun regions Authors: Raymond, J. C.; Doyle, J. G. Bibcode: 1981ApJ...247..686R Altcode: Emission measure curves are presented for average coronal hole and quiet-sun spectra taken during the Skylab mission by Vernazza and Reeves (1978), and the curves are used to discuss the energy balance in each region. Close-coupling calculations are used for the Be sequence, assuming a 10 level ion; for B sequence ions mainly distorted wave calculations in an 11 level ion are used, but close-coupling cross sections are used for some ions; for C and Mg sequence ions, distorted wave calculations are used with 15 and 10 level ions, respectively, and close-coupling results are used for Li-like ions with two levels. Results are presented and include the following: the coronal hole spectrum shows a smaller slope in the emission measure distribution, consistent with the expected outflow effects. It is concluded that the simple constant pressure models of static coronal loops of constant cross section are basically able to match the observed emission measure distribution of the average quiet sun between 1,000,000 and 10,000,000 K. However, the cell center and network distributions are respectively steeper and shallower than predicted by the detailed cooling curve. Title: Emissivities of strong ultraviolet lines Authors: Raymond, J. C.; Doyle, J. G. Bibcode: 1981ApJ...245.1141R Altcode: Using atomic data published during the last few years for Li to Mg sequence ions, we have carried out multilevel calculations over a range of electron pressures to obtain absolute intensities for spectral lines in the UV and EUV regions of the electromagnetic spectrum. Both the pressure dependence of the ionization balance and the dependence of line emissivities on the populations of metastable levels are taken into account. These line emissivities may be used to obtain plane-parallel model atmospheres for different solar transition region structures, and in general for other late-type stars which have observable lines over a wide range of excitation potentials. Title: Transition probabilities and line intensity ratios of transitions within the ground-state configuration of O III Authors: Baluja, K. L.; Doyle, J. G. Bibcode: 1981JPhB...14L..11B Altcode: No abstract at ADS Title: An approximate calculation of the effect of opacity in the solar spectral lines of C III Authors: Doyle, J. G.; McWhirter, R. W. P. Bibcode: 1980MNRAS.193..947D Altcode: The paper applies the fact that the intensity ratio between two spectral lines arising from the same upper level can depend on opacity, to determine the optical thickness of the solar atmosphere to C III radiation. The analysis is based on observations taken near the sun's limb during the Skylab mission with the Naval Research Laboratory's spectrograph. By introducing the measured abundance of carbon and the results of ionization balance calculations, an estimate is made of the line-of-sight physical thickness of the regions emitting C III lines at the disk center. Title: Proton excitation rates for fine structure transitions in C III, O V, and NE VII in the sun Authors: Doyle, J. G.; Kingston, A. E.; Reid, R. H. Bibcode: 1980A&A....90...97D Altcode: The close-coupled impact parameter method is used to calculate the proton excitation rates for fine structure transitions in the levels (2s, 2p) 3P and (2p)2 3P of the ions C III, O V, and Ne VII. By the use of these proton rates and recently calculated electron collision rates, the effect of these proton rates on line ratios involving these fine structure levels has been studied at electron temperatures and densities appropriate to the solar transition region. Theoretical estimates of the strength of the (2s, 2p) 3P (2s)2 1S line are only slightly affected by the inclusion of proton rates. The estimate of the strength of the multiplet is decreased by 10% in the case of O V and Ne VII at the temperature of maximum abundance and 25% for higher temperatures. Title: Soft X-ray Emission During the Impulsive Phase of a Flare Authors: Antonucci, E.; Gabriel, A. H.; Doyle, J. G. Bibcode: 1980BAAS...12..900A Altcode: No abstract at ADS Title: Coronal Flare Densities Authors: Wolfson, C. J.; Doyle, J. G.; Phillips, K. J. H. Bibcode: 1980BAAS...12..912W Altcode: No abstract at ADS Title: The interpretation of C V and O VII emission line ratios in the sun Authors: Doyle, J. G. Bibcode: 1980A&A....87..183D Altcode: Recent theoretical atomic data for the collisional and radiative rates is used in a reinterpretation of the observed C V and O VII emission line ratios in the solar corona/transition region. In the calculations, transitions between the five lowest states of the He-like ion are considered. From C V an electron density of 4.5 x 10 to the 9th power per cu cm, and an electron temperature of 3.0 x 10 to the 5th power K are derived, while in the region of O VII emission lines, an upper limit of 2.0 x 10 to the 9th power per cu cm is found for the electron density, and an upper limit of 1.6 x 10 to the 15th power per cu cm K is derived for the electron pressure. Title: A study of solar ultraviolet and X-ray spectra Authors: Doyle, John Gerard Gerry Bibcode: 1980PhDT.......157D Altcode: No abstract at ADS Title: The interpretation of N IV and Ne VII emission line ratios in the sun. Authors: Dufton, P. L.; Doyle, J. G.; Kingston, A. E. Bibcode: 1979A&A....78..318D Altcode: Summary. Using new atomic data -for electron impact collision rates, the observed N Iv and Ne vIl emission line ratios in the solar transition region have been interpreted. For N Iv, the ratio I(3Pe 3P0)/I(1P0 1S ) indicates an electron density of 1.51010 for the quiet sun, while the active region results are anomalous, possibly due to blending. From the ratio !(` D `P0)/I(3Pj0 -1 1S ) in N Iv, an electron temperature of 1.0 l0 K is deduced for the quiet sun, in agreement with that expected in steady-state ionization equilibrium. For Ne vII, the ratio I(3Pj-1 lSe)!i(1F0 1S ) is an excellent electron temperature diagnostic. For the quiet sun a value of 5 10 K is found, again in agreement with that expected in steady state ionization equilibrium while higher electron temperatures are found for coronal holes (8 l0 K) and active regions (1.2 106 K). Key words: collision rates - transition region - Be sequence - plasma diagnostics -