Author name code: gaizauskas ADS astronomy entries on 2022-09-14 author:"Gaizauskas, V." ------------------------------------------------------------------------ Title: Where Do Solar Filaments Form? Authors: Mackay, Duncan H.; Gaizauskas, Victor; Yeates, Anthony R. Bibcode: 2014IAUS..300..445M Altcode: In the present study, we consider where large, stable solar filaments form relative to underlying magnetic polarities. We find that 92% of all large stable filaments form in magnetic configurations involving the interaction of two or more bipoles. Only 7% form above the Polarity Inversion Line (PIL) of a single bipole. This indicates that a key element in the formation of large-scale stable filaments is the convergence of magnetic flux, resulting in either flux cancellation or coronal reconnection. Title: The Grand Schism in Canadian Astronomy III: Exploring the Origins of the Conflict Authors: Gaizauskas, Victor Bibcode: 2012JRASC.106..230G Altcode: No abstract at ADS Title: The Grand Schism in Canadian Astronomy II: Exploring the Origins of the Conflict Authors: Gaizauskas, Victor Bibcode: 2012JRASC.106..190G Altcode: No abstract at ADS Title: The Grand Schism in Canadian Astronomy I: The Rise and Fall of Mount Kobau Authors: Gaizauskas, Victor Bibcode: 2011JRASC.105...95G Altcode: No abstract at ADS Title: Jack Lambourne Locke (1921-2010) Authors: Gaizauskas, Victor Bibcode: 2010JRASC.104..253G Altcode: No abstract at ADS Title: Early Years at the David Dunlap Observatory Authors: Gaizauskas, Victor Bibcode: 2008JRASC.102..222G Altcode: No abstract at ADS Title: Development of Flux Imbalances in Solar Activity Nests and the Evolution of Filament Channels Authors: Gaizauskas, V. Bibcode: 2008ApJ...686.1432G Altcode: Bipolar active regions tend to emerge in tight clusters that persist at the same location in so-called activity nests. This study examines how flux evolves inside three different arrangements of interacting nests. Each contains ~2 × 1023 Mx, and each develops local flux imbalances that interact to form filaments and filament channels. They include: a pair of isolated closely packed nests; a pair of widely spaced nests with neighboring nests on their outer flanks; and a chain of three closely packed nests. These cases result in flux imbalances that are, respectively: large and concentrated on the outer edges of the nests; large and concentrated between the nests; and weak and concentrated on the outer edges of the nests. An amount of flux equivalent to a single large sunspot pair, but composed entirely of weaker flux densities (<mid 50mid G), is representative of the net fluxes measured for all three examples of multiple activity nests. In the majority of cases, the pools of net flux form filament channels, i.e., configurations with a clear horizontal component of the magnetic field directed along a polarity inversion line (PIL). This study proposes that large quiescent filaments and their channels are natural storehouses of magnetic energy constructed by surface flows out of slowly reconnecting pools of "orphaned" magnetic flux that originate at outer boundaries of decaying activity nests. Title: Where Do Solar Filaments Form?: Consequences for Theoretical Models Authors: Mackay, Duncan H.; Gaizauskas, Victor; Yeates, Anthony R. Bibcode: 2008SoPh..248...51M Altcode: 2008SoPh..tmp...25M This paper examines the locations where large, stable solar filaments form relative to magnetic bipoles lying underneath them. The study extends the earlier work of F. Tang to include two additional classification categories for stable filaments and to consider their population during four distinct phases of the solar cycle. With this new classification scheme, results show that over 92% of filaments form in flux distributions that are nonbipolar in nature where the filament lies either fully (79%) or partially (13%) above a polarity inversion line (PIL) external to any single bipole. Filaments that form within a single bipole (traditionally called Type A) are not as common as previously thought. These results are a significant departure from those of F. Tang. Consistency with the earlier work is shown when our data are regrouped to conform to the two-category classification scheme for filaments adopted by F. Tang. We also demonstrate that only filaments that form along the external PIL lying between two bipoles (62% of the full sample, traditionally called Type B) show any form of solar cycle dependence, where their number significantly increases with magnetic activity over the solar cycle. Finally, current observations and theoretical models for the formation of filaments are discussed in the context of the present results. We conclude that key elements in the formation of the majority of filaments considered within this study must be the convergence of magnetic flux resulting in either flux cancellation or coronal reconnection. Title: Helicity as a Component of Filament Formation Authors: Mackay, D. H.; Gaizauskas, V. Bibcode: 2003SoPh..216..121M Altcode: In this paper we seek the origin of the axial component of the magnetic field in filaments by adapting theory to observations. A previous paper (Mackay, Gaizauskas, and van Ballegooijen, 2000) showed that surface flows acting on potential magnetic fields for 27 days - the maximum time between the emergence of magnetic flux and the formation of large filaments between the resulting activity complexes - cannot explain the chirality or inverse polarity nature of the observed filaments. We show that the inclusion of initial helicity, for which there is observational evidence, in the flux transport model results in sufficiently strong dextral fields of inverse polarity to account for the existence and length of an observed filament within the allotted time. The simulations even produce a large length of dextral chirality when just small amounts of helicity are included in the initial configuration. The modeling suggests that the axial field component in filaments can result from a combination of surface (flux transport) and sub-surface (helicity) effects acting together. Here surface effects convert the large-scale helicity emerging in active regions into a smaller-scale magnetic-field component parallel to the polarity inversion line so as to form a magnetic configuration suitable for a filament. Title: Formation of a Switchback During the Rising Phase of Solar Cycle 21 Authors: Gaizauskas, V. Bibcode: 2002SoPh..211..179G Altcode: The customary notion that high-latitude filaments arise from magnetic flux originating in the active-region belts finds its modern expression in numerical models that generate filament channels from flux patterns migrating from active latitudes to the polar caps. Polarity inversions underlying high-latitude filament channels are swept into distinct patterns called `switchbacks' under the joint influence of differential rotation, supergranular diffusion, and meridional flow. The numerical model of Mackay and van Ballegooijen (2001) predicts a heretofore unsuspected solar-cycle dependence to the hemispheric pattern of filament magnetic fields. Observations presented here of a switchback formed early in cycle 21 confirm some key aspects of their model. In this remarkable example the flux diffusing out of the source region migrates to the opposite side of the Sun before it encounters another active region with which to create the quadrupolar field configuration wherein a return arm forms to complete the switchback. Title: Obituary: Arthur Edwin Covington, 1913-2001 Authors: Gaizauskas, Victor Bibcode: 2002BAAS...34.1357G Altcode: No abstract at ADS Title: Evolution of Solar Filament Channels Observed during a Major Poleward Surge of Photospheric Magnetic Flux Authors: Gaizauskas, V.; Mackay, D. H.; Harvey, K. L. Bibcode: 2001ApJ...558..888G Altcode: We describe the evolution of a solar filament channel marked by extremes: a length near one solar radius, and a duration of a year. Its genesis centers on an episode of flux emergence so powerful that it launched a surge of photospheric magnetic flux almost to the northern polar cap. This extraordinary injection of new flux at the solar surface occurred in midterm of the longest lived activity complex of cycle 21 (~20 rotations). The new flux emerged just north of the equator as a pair of adjacent activity complexes-a ``supercluster'' of sunspots-remote from other active regions in a longitude band spanning ~90°. Channels quickly formed along separate polarity inversion lines in this large-scale quadrupolar configuration. None of the initial channels survived more than two solar rotations; none merged to form a greater whole. As individual bipoles within and between the activity complexes expanded, fragmented, and cancelled, only flux at the outermost edges of the adjacent complexes survived, thanks to the remoteness of other strong concentrations of magnetic flux. The result, after three solar rotations, was a simplified bipolar pattern of poleward-streaming flux subject to global processes of flux transport that sustained and extended it for up to a year. The long and long-lived filament channel formed in the shape of a ``switchback'' along the polarity inversion between the converging streams of opposite polarity flux, continuing along the polarity inversion between the migrating flux and the flux in the polar cap. Our observations reveal large-scale swirled patterns of chromospheric fibrils from which we infer that substantial negative helicity was built up across both adjacent activity complexes during their emergence. The patterns were still detectable in the migrating flux after the source regions had disappeared. Convergence of opposite polarity fluxes with negative helicity leads naturally to dextral filaments and filament channels, consistent with the chirality rule for the northern hemisphere found by Martin, Bilimoria, & Tracadas. We measured the chiralities of 10 filament channels associated with the initial massive emergence of magnetic flux and its subsequent surge poleward. Implications of our findings on models for forming filaments and filament channels are discussed. Title: Comparison of Theory and Observations of the Chirality of Filaments within a Dispersing Activity Complex Authors: Mackay, D. H.; Gaizauskas, V.; van Ballegooijen, A. A. Bibcode: 2000ApJ...544.1122M Altcode: We investigate the origin of the hemispheric pattern of filaments and filament channels by comparing theoretical predictions with observations of the chirality of filament channels within a dispersing activity complex. Our aim is to determine how the chirality of each specific channel arises so that general principles underlying the hemispheric pattern can be recognized. We simulate the field lines representing the filaments in the activity complex by applying a model of global flux transport to an initial magnetic configuration. The model combines the surface effects of differential rotation, meridional flows, and supergranular diffusion along with a magnetofrictional relaxation method in the overlying corona. The simulations are run with and without injecting axial magnetic fields at polarity inversion lines in the dispersing activity complex for four successive solar rotations. When the initial magnetic configuration, based on synoptic magnetic maps, is set to a potential field at the beginning of each rotation, the simulations poorly predict the chirality of the filament channels and filaments. The cases that predict the correct chirality correspond to an initial polarity inversion line, which is north-south the wrong chirality arises when the initial polarity inversion lines lie east-west. Results improve when field-line connectivities at low latitudes are retained and allowed to propagate to higher latitudes without resetting the field to a potential configuration between each rotation. When axial flux emergence exceeding 1×1019 Mx day-1 is included at the location of each filament, an excellent agreement is obtained between the theory and observations. In additon to predicting the correct chirality in all cases, axial flux emergence allows more readily the production of inverse-polarity dipped field lines needed to support filamentary mass. An origin for the hemispheric pattern as a result of the combined effects of flux transport, axial flux emergence, and magnetic helicity is then discussed. Title: Solar Activity Complexes Authors: Gaizauskas, V. Bibcode: 2000eaa..bookE2273G Altcode: SOLAR ACTIVE REGIONS tend to cluster in space and time by emerging in or beside an existing active region or at the site of a previous one. Whereas an individual bipolar sunspot region (see SUNSPOT CLASSIFICATION) typically lasts from a few days to a few weeks—rarely as long as a few solar rotations—a cluster may survive for over a year, kept alive by fresh bipolar regions repeatedly emerging wit... Title: Solar Filament Channels Authors: Gaizauskas, V. Bibcode: 2000eaa..bookE2278G Altcode: A filament channel is a magnetic rift that runs through the chromosphere along the base of a solar filament and beyond either end. Because the filament and its channel separate magnetic fields of opposite magnetic polarity at the solar surface, field lines will cross over them at some height as an arcade of closed loops. A channel is a rift in the sense that it partitions positive and negative fi... Title: Commission 12: Solar Radiation and Structure (Radiation et Structure Solaires) Authors: Foukal, Peter; Solanki, Sami; Mariska, J.; Baliunas, S.; Dravins, D.; Duvall, T.; Fang, C.; Gaizauskas, V.; Heinzel, P.; Kononovich, E.; Koutchmy, S.; Melrose, D.; Stix, M.; Suematsu, Y.; Deubner, F. Bibcode: 2000IAUTA..24...73F Altcode: No abstract at ADS Title: On the Comparison of Filament Chirality and Axial Magnetic Fields Deduced from a Flux Transport Model Authors: Mackay, D. H.; Gaizauskas, V.; van Ballegooijen, A. A. Bibcode: 1999ESASP.448..507M Altcode: 1999mfsp.conf..507M; 1999ESPM....9..507M No abstract at ADS Title: Role of Helicity in the Formation of Intermediate Filaments Authors: Mackay, D. H.; Priest, E. R.; Gaizauskas, V.; van Ballegooijen, A. A. Bibcode: 1998SoPh..180..299M Altcode: In the last few years new observations have shown that solar filaments and filament channels have a surprising hemispheric pattern. To explain this pattern, a new theory for filament channel and filament formation is put forward. The theory describes the formation of a specific type of filament, namely the `intermediate filament' which forms either between active regions or at the boundary of an active region. It describes the formation in terms of the emergence of a sheared activity complex. The complex then interacts with remnant flux and, after convergence and flux cancellation, the filament forms in the channel. A key feature of the model is the net magnetic helicity of the complex. With the correct sign a filament channel can form, but with the opposite sign no filament channel forms after convergence. It is shown how the hemispheric pattern of helicity in emerging flux regions produces the observed hemispheric pattern for filaments. Title: Interactions between nested sunspots. II. A confined X1 flare in a delta-type sunspot Authors: Gaizauskas, V.; Mandrini, C. H.; Demoulin, P.; Luoni, M. L.; Rovira, M. G. Bibcode: 1998A&A...332..353G Altcode: We study the flaring activity in a nest of sunspots in which two bipolar regions emerge inside a third one. These bipolar regions belong to a large complex of activity (McMath 15314) formed by five bipoles on its May 1978 rotation. The usual spreading action during the growth of the bipoles leads to the formation of a $Delta lta-configuration: the preceding and following spots of the two interior regions overlap (p-f collision) into a single penumbra. While Delta lta-configurations created in this way normally favor strong flaring activity, only very small flares occur during 5 days. Only when the following umbra in the Delta lta$-spot breaks into pieces, accompanied by rapid photospheric motions, do intense flares occur. The largest and best observed one in this sequence, a class 1B/X1 flare on 28 May 1978, is remarkable for the absence of ejecta and for the concentration of its emission in three widely spaced sites, a pattern which holds in general over two days for lesser flares. We take this pattern as evidence that the flare is confined to the low corona. We first compute the coronal magnetic field using subphotospheric sources to model the observed magnetic data and derive the location of separatrices. In this case the magnetic field topology is defined by the link between these discrete sources. The relevant generalization of separatrices in any kind of magnetic configuration are `quasi-separatrix layers' (QSLs). We calculate them using the previous model, but also for a model obtained with a more classical extrapolation technique based on the fast Fourier transform method. We show, with both approaches, that the plage brightenings during the quiescent phase of the region and the flare kernels are located at the intersection of separatrices and QSLs with the photosphere. Moreover, they are magnetically linked. Bright and dark `post'-flare loops which form in the maximum and gradual phases of the 1B/X1 flare also highlight the location of the separatrices and the QSLs. This confirms previous studies on the importance of the magnetic field topology for flares and, with this study, we further constrain the underlying physical mechanism. We draw some conclusions about the role of magnetic reconnection in the solar corona; depending on the photospheric conditions that we identify, reconnection can lead to steady heating or flaring. Title: Are All Prominences Either Sinistral or Dextral? Authors: Zirker, J. B.; Leroy, J. -L.; Gaizauskas, V. Bibcode: 1998ASPC..150..439Z Altcode: 1998IAUCo.167..439Z; 1998npsp.conf..439Z No abstract at ADS Title: Force-Free Models of a Filament Channel in Which a Filament Forms Authors: Mackay, D. H.; Gaizauskas, V.; Priest, E. R. Bibcode: 1998ASPC..150..286M Altcode: 1998npsp.conf..286M; 1998IAUCo.167..286M No abstract at ADS Title: Filament Channels: Essential Ingredients for Filament Formation (Review) Authors: Gaizauskas, V. Bibcode: 1998ASPC..150..257G Altcode: 1998npsp.conf..257G; 1998IAUCo.167..257G No abstract at ADS Title: Filament Channels: Contrasting Their Structure in H-alpha and H epsilon I 1083 NM Authors: Harvey, K. L.; Gaizauskas, V. Bibcode: 1998ASPC..150..269H Altcode: 1998IAUCo.167..269H; 1998npsp.conf..269H No abstract at ADS Title: The Sinistral-Dextral Regularity: An Independent Test Authors: Zirker, J. B.; Leroy, J. -L.; Gaizauskas, V. Bibcode: 1997SoPh..176..279Z Altcode: Leroy, Bommier, and Sahal-Bréchot (1984) determined the vector magnetic field in a large sample of quiescent prominences. The direction of the axial component is in general subject to a 180 deg uncertainty. We have selected those prominences in the sample whose field direction is unambiguous. For 95 such prominences, only 3 do not obey the hemispheric preferences of sinistral or dextral filaments, discovered by Martin, Tracadas, and Billamoria (1994). No explanation for the exceptional cases was found. Title: Global Magnetic Patterns of Chirality Authors: Zirker, J. B.; Martin, S. F.; Harvey, K.; Gaizauskas, V. Bibcode: 1997SoPh..175...27Z Altcode: During the past five years at least six manifestations of a global organization of solar magnetic fields have been recognized. The magnetic chirality (handedness) of the following features shows a hemispheric preference: filament channels, quiescent filaments, sunspot whorls, superpenumbral fibrils, coronal arcades, and interplanetary clouds associated with CMEs. Although the patterns are clear in the data, their interpretation and their possible connection to the dynamo is open to question. This paper reviews the observations of the patterns, corrects some misinterpretations, and offers a scenario for the origin of the most marked pattern, the chirality of filaments. We suggest the pattern arises from the reconnection of coronal loops, under the influence of supergranulation and differential rotation. Unlike alternative scenarios, ours relies only on observable surface motions and fields. Title: Force-free and Potential Models of a Filament Channel in Which a Filament Forms Authors: Mackay, D. H.; Gaizauskas, V.; Rickard, G. J.; Priest, E. R. Bibcode: 1997ApJ...486..534M Altcode: Few examples of the creation of a filament channel or filament have ever been documented. In a recent paper, Gaizauskas and coworkers observed the early stages of creation of such a channel and then the formation of a filament in it. The filament channel was born when a new activity complex emerged near an old, decaying bipolar active region. The filament itself then formed after convergence of flux in the channel.

In this paper, force-free models are constructed for two phases of the channel's development. For the early days, the models show that the formation of the filament channel seen in Hα is due to the emerging activity complex. The field lines that give the best comparison to the fibril observations are low-lying and have a strong horizontal component. Later, when the activity complex has matured and a filament has formed between it and the adjacent decaying bipolar region, the models give a good representation of the path of the filament in the channel. It is found that the presence of flat or dipped field lines and of converging flux are necessary but not sufficient conditions for filament formation. Furthermore, the magnetic field lines of the filament itself form a narrow, vertical, sheetlike flux-tube corridor that is flat and low-lying. It connects one particular magnetic source to a sink and is bounded by separatrix surfaces that separate the filament from the old remnant region and most of the newly emerged flux. Title: Why and Where do Filaments Form in Active Regions? Authors: Gaizauskas, V.; Zwaan, C. Bibcode: 1997SPD....28.0249G Altcode: 1997BAAS...29..902G New prominence models based on recent observations depend upon magnetic reconnection between small-scale magnetic elements converging at a polarity inversion (PI). How then to explain active-region filaments where magnetic flux diverges over much of the lifetime of the region? A partial answer is that still-growing active regions containing filaments are not simple bipolar entities. They are instead multipolar activity complexes (`sunspot nests') wherein magnetic flux can be compressed along a meandering PI wherever new bipolar units emerge near old ones. A complete answer requires particulars about the distribution and motions of magnetic fields internal and external to the sunspot nests. We therefore surveyed over 150 active regions photographed on a large spatial scale at ORSO during 5 successive solar rotations in 1979, an epoch of rapid emergence and decay. Of the total number of regions: - 5% are simple decaying bipolar plages with filaments on the PI; - 5% are ambiguous cases with sometimes a filament and field transition arches (FTA) sharing adjacent parts of a PI in a bipolar plage; -70% have boundary filaments exterior to the concentrations of magnetic flux around sunspots; - 61% are single bipoles of which 84% have no internal filament on their PI; - 52% are activity complexes (on at least one day, otherwise they are single bipoles) of which 60% have one or more filaments inside the complex. We find that filaments inside sunspot nests mark off bipolar entities from one another, thus fulfilling the role of boundary filaments on the inside of the nests. We conclude that the boundary filament is the quintessential active- region filament. Examination of specific cases leads to the further conclusion that force-free fields together with cancelling flux play a critical role in forming boundary filaments. Title: Formation of a Solar Filament Channel Authors: Gaizauskas, V.; Zirker, J. B.; Sweetland, C.; Kovacs, A. Bibcode: 1997ApJ...479..448G Altcode: We present observations of the early stages of formation of a filament channel when a compact activity complex emerged in a previously quiet, near-equatorial area. In a few hours, and while flux was rising rapidly in one bipolar component in the complex, H alpha fine structure overlying a polarity inversion zone organized into a conspicuous pattern of parallel fibrils enclosing the trailing end of the new activity complex. Yet it took another 4 days for a stable filament to form inside that pattern. It did so at a place where migrating positive polarity flux from the new activity complex contacted the negative polarity flux in a plage of an adjacent decaying bipolar active region. In contrast, no filament formed along an existing channel inside the adjacent decaying region; the opposite-polarity fluxes on the borders of the existing channel showed no signs of convergence. We attribute the fibril-aligning forces in the new channel to the horizontal component of an extended nonpotential magnetic field caused by currents in the multipolar activity complex. The channel is, in this view, an elementary part of the magnetic topology of an activity complex. We propose that the later formation of the filament in the new channel requires an additional and separate process. A plausible candidate for this second step is the development of a current sheet at the site of converging magnetic flux. Title: Fulguraciones en una configuración tipo δ Authors: Luoni, M. L.; Mandrini, C. H.; Rovira, M. G.; Démoulin, P.; Gaizauskas, V. Bibcode: 1997BAAA...41...62L Altcode: Through the determination of the magnetic field topology, we focus this study on the flaring activity occurring in a nest of five bipoles. These bipoles belonged to a ``great complex of activity" (Mc Math 15314). We are interested in the largest and best observed flare on May 28, 1978, a class 1B/X1, occurring in a δ spot. The usual spreading action during the growth of the bipoles lead to the formation of a δ-configuration: the preceding and following spots of the two inner regions overlapped into a single penumbra. In this case, the spots approached continuously during five days. We first compute the coronal magnetic field using subphotospheric sources to model the longitudinal magnetograms and derive the location of separatrices, for May 27 and 28. Quasi-separatrix layers are a generalization of separatrices for any magnetic field configuration, these are thin volumes where the connectivity of field lines changes drastically. We calculate them using a model of the field obtained by extrapolation of the observations based on the fast Fourier transform method. With both approaches, we show that the plage brightenings, on the 27, and the flare kernels, on the 28, are located at the intersection of separatrices with the photosphere. This confirms the importance of the magnetic field topology for solar flares. Taking into account Hα observations and the magnetic field modelling, we conclude that energy is released in the solar corona, between the preceding and following spots, in the region of the separator. Bright and dark post-flare loops follow the location of separatrices and quasi-separatrix layers. This is consistent with magnetic reconnection models. Our results confirm the importance of the field topology for the comprehension of the active phenomena and allow us to characterize the energy release mechanism that is at their origin. Title: Creation of prominences and filaments. Authors: Gaizauskas, V. Bibcode: 1997ASIC..494..141G Altcode: 1997topr.conf..141G Because chromospheric filaments are invariably associated with polarity inversions in the photospheric magnetic field, they have long been used to trace the evolution of global patterns of magnetic flux. Individual quiescent filaments may last a single solar rotation or less, but it is commonly believed that the channels in which they form are much longer-lived. Attempts to trace the inverse process - the origin of a filament channel and a filament during the evolution of specific patches of flux - are of more recent origin. New observations are now forcing a revision in the ideas about filament formation. After reviewing some of the new key facts, a recent case study is reported in which a filament channel and filament are seen to form on the edge of a growing activity complex. The evidence points to the formation of this channel as a surface phenomenon driven by emerging magnetic flux. The filament forms when its channel is constructed between the expanding new region and a preexisting plage. Title: Magnetic Reconnection as a Driver of Chromospheric Surges Authors: Gaizauskas, V. Bibcode: 1996SoPh..169..357G Altcode: The basal structure of a surge precisely on the limb has been photographed with 1″-resolution in the core and wings of Hα. The dynamics observed in the fine structures are consistent in general with reconnection theory, but they also display flows more complicated than those predicted by 2D-reconnection models. The magnetic topology of the surrounding long-lived plage indicates that flux cancellation rather than its emergence is the key factor in promoting recurrent surges at this site. Title: Observations of a Quiescent Prominence Straddling the Solar Limb during the Total Eclipse of 11 July 1991 Authors: Gaizauskas, V.; Deluca, E.; Golub, L.; Jones, H. P.; November, L. Bibcode: 1996mpsa.conf..491G Altcode: 1996IAUCo.153..491G No abstract at ADS Title: Magnetic Field Topology at the Location of an X1/1B Solar Flare Authors: Gaizauskas, V.; Démoulin, P.; Mandrini, C. H.; Rovira, M. G.; Harvey, K. L. Bibcode: 1995SPD....26.1319G Altcode: 1995BAAS...27R.991G No abstract at ADS Title: Bright Rims Adjacent to a Quiescent Hα Filament Authors: Gaizauskas, V.; de Luca, E.; Golub, L.; Jones, H. P. Bibcode: 1994AAS...18512304G Altcode: 1994BAAS...26.1522G Recent models of filament-formation invoke reconnection between small-scale magnetic elements adjacent to the polarity inversion line separating large areas of unipolar magnetic fields. In an attempt to confirm this process, we examine joint observations of a quiescent filament straddling the SW limb of the Sun during the total solar eclipse of 1991 July 11. We test a hypothesis that a signature of the reconnection process might be carried by the prominent bright rims beside or enclosed between curved feet, or 'barbs', which connect the body of the Hα filament to structures near the base of the atmosphere. We spatially register digitized Hα (ORSO) images of the filament with coronal (NIXT) images and with photospheric magnetograms (NSO/KP) to a precision of +/- 2". Our findings relate to five rims, elongated bright patches in Hα with a maximum length of 20". We find a better spatial association of the rims with bipolar magnetic elements (4/5) than with small patches of weakly enhanced soft X-rays (2/4). We point out that projection effects at these extreme limb positions could alter these associations. We conclude from these limited 'snapshot' observations that we are not yet able to decide whether or not bright rims on quiescent prominences are locations of magnetic reconnection on a small scale. Because reconnection is highly dynamic, compelling evidence for or against this process will have to await prolonged observations at multiple wavelengths in X-rays of a single filament at high spatial and temporal resolution, such as those envisaged for the Transition Region and Coronal Explorer (TRACE). Title: The twisting of filament that resulted in a solar flare Authors: Lin, Yuan-zhang; Gaizauskas, V. Bibcode: 1994ChA&A..18..455L Altcode: Based mainly on filtergrams ofH α line center and various offbands and supplemented with measurements of the CIV 1548 line, we analyzed the evolution of a filament during a period of 15 minutes prior to the eruption of the flare of 1980 June 25 in the active region AR 2522. The filament underwent three spasmodic twistings of increasing size which finally led to its disruption and the flare eruption. We simulated the twisting motion of the filament by a force-free magnetic rope, estimated the variation of the force-free factor and the increase in the axial electric current, discussed the stability of the filament and attempted to give a theoretical explanation of the collapse of the filament and the eruption of the flare. Title: Preflare State Authors: Rust, David M.; Sakurai, Takashi; Gaizauskas, Victor; Hofmann, Axel; Martin, Sara F.; Priest, Eric R.; Wang, Jing-Xiu Bibcode: 1994SoPh..153....1R Altcode: Discussion on the preflare state held at the Ottawa Flares 22 Workshop focused on the interpretation of solar magnetograms and of Hα filament activity. Magnetograms from several observatories provided evidence of significant build up of electric currents in flaring regions. Images of X-ray emitting structures provided a clear example of magnetic relaxation in the course of a flare. Emerging and cancelling magnetic fields appear to be important for triggering flares and for the formation of filaments, which are associated with eruptive flares. Filaments may become unstable by the build up of electric current helicity. Examples of heliform eruptive filaments were presented at the Workshop. Theoretical models linking filaments and flares are briefly reviewed. Title: Recent observations and theories of solar flares. Proceedings. 2. Flares22 Workshop on Recent Observations and Theories of Solar Flares, Ottawa (Canada), 22 - 28 May 1993. Authors: Gaizauskas, V.; Machado, M. E. Bibcode: 1994SoPh..153....1G Altcode: Reports of the five teams are given. Title: Recent observations and theories of solar flares; Second Flares 22 Workshop, Ottawa, Canada, May 22-28, 1993 Authors: Gaizauskas, Victor; Machado, Marcus E. Bibcode: 1994SoPh..153.....G Altcode: 1994SoPh..153....1G A conference on recent observations and theories of solar flares produced papers in the areas of particle acceleration, energy storage, energy release, energy transport, and material ejection. The results from new ground-based and space-based facilities were also prominent in these papers. For individual titles, see A95-70250 through A95-70279. Title: Interactions between Nested Sunspots. I. The Formation and Breakup of a Delta-Type Sunspot Authors: Gaizauskas, V.; Harvey, K. L.; Proulx, M. Bibcode: 1994ApJ...422..883G Altcode: We investigate a nest of sunspots in which three ordinary bipolar pairs of sunspots are aligned collinearly. The usual spreading action of the growing regions brings two spots of leading polarity together (p-p collision) and forces the leading and trailing spots of the two interior regions to overlap into a single penumbra (p-f collision), thus forming a delta-spot. We examine digitally processed images from the Ottawa River Solar Observatory of two related events inside the delta-spot 5 days after the p-f collision begins: the violent disruption of the f-umbra, and the formation in less than a day of an hydrogen-alpha filament. The evolutionary changes in shape, area, relative motions, and brightness that we measure for each spot in the elongated nest are more compatible with Parker's (1979a) hypothesis of a sunspot as a cluster of flux tubes held together by downdrafts than with the notion of a sunspot as a monolithic plug of magnetic flux. From chromospheric developments over the delta-spot, we show that a shearing motion along a polarity inversion is more effective than convergence for creating a chromospheric filament. We invoke the release of an instability, triggered by a sequence of processes lasting 1 day or more, to explain the disruption of the f-umbra in this delta-spot. We show that the sequence is initiated when the colliding p-f umbrae reach a critical separation around 3200 +/- 200 km. We present a descriptive model in which the reconnected magnetic fields block vertical transport of convective heat flux just beneath the photosphere. We observe the formation of an unusual type of penumbra adjacent to the f-polarity portion of this delta-spot just before its disruption. A tangential penumbral band grows out of disordered matter connected to the f-umbra. We present this as evidence for the extrusion of umbral magnetic flux by thermal plumes rising through a loosely bound umbra. Title: Twisting of a Filament Resulted in a Solar Flare Authors: Lin, Y. Z.; Gaizauskas, V. Bibcode: 1994AcASn..35..219L Altcode: No abstract at ADS Title: CFHT eclipse observation of the very fine-scale solar corona Authors: Koutchmy, S.; Belmahdi, M.; Coulter, R. L.; Demoulin, P.; Gaizauskas, V.; MacQueen, R. M.; Monnet, G.; Mouette, J.; Noens, J. C.; November, L. J. Bibcode: 1994A&A...281..249K Altcode: At the July 11, 1991 solar total eclipse, a modern large optical telescope, Canada-France-Hawaii telescope (CFHT), was used to probe the solar corona. The best possible pictures were obtained with the CFHT, using fast imaging techniques and post-facto image selection and processing. Several cameras were run during totality to acquire sub-arcsec spatial resolution white-light images, with both narrow-band and broad-band filters. The setup and the observing procedure are described. Preliminary results, together with an evaluation of the merits of the experiment, are given, as well as a sample of images. Fine-scale coronal features were observed for the first time in a time series, confirming the importance of plasmoid-like activity in the inner corona. The observation of the smallest coronal feature ever reported is analyzed, giving a typical cross-section of 0.4 +/- 0.1 arcsec. On a larger scale, dark loops around a foreground prominence are resolved for the first time, suggesting that sheet-like voids exist above a filament channel. Title: The Magnetic Chromosphere (invited Review) Authors: Gaizauskas, V. Bibcode: 1994ASIC..433..133G Altcode: No abstract at ADS Title: Report of IAU Commission 10: Solar activity (Activité solaire). Authors: Gaizauskas, V. Bibcode: 1994IAUTA..22...53G Altcode: No abstract at ADS Title: A Historical Perspective on Measurements of Solar Irradiance Authors: Gaizauskas, V. Bibcode: 1994svsp.coll....1G Altcode: 1994IAUCo.143P...1G No abstract at ADS Title: Quasi-periodic Particle Injection into Coronal Loops Authors: Aschwanden, Markus J.; Benz, Arnold O.; Dennis, Brian R.; Gaizauskas, Victor Bibcode: 1993ApJ...416..857A Altcode: We present observations of the flare of 1989 June 22, 1445 UT (in active region NOAA 5555), obtained with the Hard X-Ray Burst Spectrometer (HXRBS) on SMM at energies >52 keV, and with the broad-band radio spectrometer PHOENIX at ETH/Zurich in the frequency range of 100-2800 MHz. The radio emission is dominated by a ≲100% polarized decimetric continuum at 400-1400 MHz, peaking at 750 MHz. The decimetric radio flux is highly correlated with the 50-150 keV hard X-ray flux but is delayed by 3.5-5.4 s with respect to the hard X-rays. The HXR emission shows an excess of ≳10 fast (≳100 ms) spikes (according to Poisson statistics). The radio emission exhibits weak fine structure, consisting of ≍45 quasi-periodic pulses with a mean period of 1.6 s. The frequency-time drift pattern of this fine structure is found to be consistent with segments of inverted-U type bursts, suggesting quasi-periodic injection of electron beams into a loop system. The loop system has an average height of 68,000 km and expands with a velocity of 200 km s-1 due to flare heating. Chromospheric evaporation enhances the electron density near the footpoints. The type III- exciting electrons have a mean velocity of υ/c = 0.30±0.10 (22 keV) and propagate along inverted-U burst trajectories with a mean duration of 2.5 s. For those electrons which reach the mirror point near the opposite footpoint of the loop system, we calculate (from the density and loop length) a low energy cutoff of ≥ 8 keV due to collisional deflection, yielding a propagation velocity of v/c = 0.18 and a propagation delay of 5.1±1.0 s, which agrees well with the observed delay of 5.16 s between the cross-correlated HXR and radio flux. The ≥ 8 keV electrons provide free energy for a loss cone instability near the secondary footpoint, which is observed as decimetric continuum polarized in the same sense of circular polarization as the type III bursts. The constraints from the Hα flare position and the magnetic potential field extrapolation indicate that the loss cone emission is produced in the diverging field region above the umbra of the leading sunspot, which has a photospheric field strength of -1600 G.

This flare allows us to deconvolve quasi-periodic particle injection and subsequently triggered coherent radio emission from trapped particles in flare-associated loops. It demonstrates that quasi-periodic modes of particle acceleration, particle dynamics in mirror loops, and the resulting plasma instabilities can be efficiently diagnosed from correlated hard X-ray and radio signatures. Title: The birth and evolution of solar active regions Authors: Gaizauskas, V. Bibcode: 1993AdSpR..13i...5G Altcode: 1993AdSpR..13....5G The growth of solar active regions is a well-observed surface phenomenon with its origins concealed in the solar interior. We review the salient facts about the emergence of active regions and the consequences of their growth on the solar atmosphere. The most powerful flares, the ones which display a range of phenomena that still pose serious challenges for high-energy astrophysics, are associated with regions of high magnetic complexity. How does that degree of complexity arise when the vast majority of active regions are simple bipolar entities? In order to gain some insight into that problem, we compare the emergence of magnetic flux in ordinary regions with an instance when magnetic complexity is apparent from the very first appearance of a new region - clearly a subsurface prefabrication of complexity - and with others wherein a new region interacts with a pre-existing one to create the complexity in plain view. Title: The Formation and Break-up of a Simple Delta-type Sunspot Authors: Gaizauskas, V.; Harvey, K. L.; Proulx, M. Bibcode: 1993BAAS...25.1220G Altcode: No abstract at ADS Title: Book reviews Authors: van Driel-Gesztelyi, L.; Meynet, G.; Gaizauskas, V.; Cook, J. W.; McKenna-Lawlor, S. M. P.; Garmany, C. D.; Jugaku, Jun; Lamers, Henny J. G. L. M.; Achterberg, A.; De Greve, J. P.; Dommanget, J.; van der Kruit, P. C. Bibcode: 1993SSRv...64..165V Altcode: No abstract at ADS Title: Book Review: Observing the sun / Cambridge U Press, 1991 Authors: Gaizauskas, V. Bibcode: 1993SSRv...64..168G Altcode: 1993SSRv...64..168T No abstract at ADS Title: On Recurrent Solar Activity (Invited) Authors: Gaizauskas, V. Bibcode: 1993ASPC...46..479G Altcode: 1993IAUCo.141..479G; 1993mvfs.conf..479G No abstract at ADS Title: Pre-Flare Conditions in Delta-Type Sunspots Authors: Gaizauskas, V.; Harvey, K.; Proulx, M. Bibcode: 1993stp2.conf..147G Altcode: No abstract at ADS Title: Evidence from a Chromospheric Surge for Coronal Current Sheets Authors: Gaizauskas, V.; Kerton, C. R. Bibcode: 1992AAS...180.3404G Altcode: 1992BAAS...24..783G No abstract at ADS Title: The X12 limb flare and spray of 01 June 1991 Authors: Gaizauskas, V.; Kerton, C. R. Bibcode: 1992LNP...399..347G Altcode: 1992LNP...399..347K; 1992esf..coll..347G; 1992IAUCo.133..347G No abstract at ADS Title: Chromospheric Response Across an Active Region to Impulsive Energy Release During a Two-Ribbon Subflare Authors: Gaizauskas, V.; Proulx, M. Bibcode: 1991BAAS...23.1026G Altcode: No abstract at ADS Title: Needs and constraints for ground-based cooperative programs on solar flares Authors: Gaizauskas, V. Bibcode: 1991AdSpR..11e.105G Altcode: 1991AdSpR..11..105G Future needs of coordinated ground-based observations of solar flares are examined in terms of current barriers to our knowledge of the flare process and of advances in technology. Title: Book Review: The Restless Sun / Smithsonian Institution Press, 1989 Authors: Gaizauskas, V. Bibcode: 1990JRASC..84..367G Altcode: 1990JRASC..84..367W No abstract at ADS Title: Development of Kernels in a Two-Ribbon Subflare Authors: Gaizauskas, V.; Proulx, M.; Skumanich, A. P. Bibcode: 1990BAAS...22..890G Altcode: No abstract at ADS Title: Disintegration of Colliding Sunspots Authors: Harvey, K. L.; Gaizauskas, V. Bibcode: 1990BAAS...22Q.840H Altcode: No abstract at ADS Title: OSO-8 Measurements of Velocity Signature of Flare Kernels Authors: Skumanich, A.; Gaizauskas, V. Bibcode: 1990BAAS...22..891S Altcode: No abstract at ADS Title: On driving the eruption of a solar filament Authors: Gaizauskas, V. Bibcode: 1990GMS....58..331G Altcode: The evolution of an active-region filament has been followed over its lifetime of 5 days. Its activation on one of those days was observed in detail by a spacecraft and ground-based telescopes. Impulsive axial flows along the filament, its untwisting and rapid expulsion all precede the eruption of a two-ribbon flare directly beneath its rest position. Local magnetic changes are ruled out by the observations as the origin of this dynamism. The evolution of the magnetic flux cells adjacent to either side of the disrupted filament shows prominent, steady changes remote from the filament for days. The filament disruption and subsequent flare can be reasonably explained by a gradual increase beyond a critical threshold of field-aligned currents generated by the expansion, shifting, and contraction of bipolar regions at the separator between adjacent flux cells. Title: Two-Dimensional Spectrophotometry of a Flare Using Hα Filtergrams Authors: Gaizauskas, V.; Proulx, M. Bibcode: 1989BAAS...21..835G Altcode: No abstract at ADS Title: Preflare Activity Authors: Gaizauskas, V. Bibcode: 1989SoPh..121..135G Altcode: 1989IAUCo.104..135G Magnetic reconnection at current sheets or in current-bearing arches in the solar atmosphere is generally accepted as the mechanism responsible for the sudden energy release in solar flares. Attempts have so far been unsuccessful to isolate from the observations some unique preconditions which would be necessary and sufficient to ensure rapid conversion of energy by this process. Here we survey recent multi-wavelength observations which illustrate the variety of preflare activity. Multiple structures are now believed to participate in the energy release. Dynamic global coupling of the magnetic fields between a flaring site and the rest of an activity complex is seen from the data to be an important aspect of preflare activity. Title: The 10.7-cm microwave observations of AR 5395 and related terrestrial effects Authors: Gaizauskas, V.; Hughes, T. J.; Tapping, K. F. Bibcode: 1989dots.work..242G Altcode: The 10.7 cm flux patrols in Canada recorded 4 Great Bursts (peaks greater than 500 sfu) during the disk passage of AR 5395 in March 1989. The Great Bursts of 16 and 17 March were simple events of great amplitude and with half-life durations of only several minutes. Earlier Great Bursts, originating on 6 March towards the NE limb and on 10 March closer to the central meridian, belong to an entirely different category of event. Each started with a very strong impulsive event lasting just minutes. After an initial recovery, however, the emission climbed back to level as greater or greater than the initial impulsive burst. The events of 6 and 10 March stayed above the Great Burst threshold for at least 100 minutes. The second component of long duration in these cases is associated with Type 4 continuum emission and thus very likely with CMEs. Major geomagnetic disturbances did not occur as a result of the massive complex event of 6 March or the two simple but strong events of 16 and 17 March. But some 55 hours after the peak in the long-enduring burst of 10 March, a storm began which qualifies as the fourth strongest geomagnetic storm in Canada since 1932. The vertical component of the earth's field measured during the storm by a fluxgate magnetometer at a station in Manitoba is presented. Within a minute of the sudden commencement of this storm, a series of breakdowns began in the transmission system of Hydro-Quebec which resulted in a total loss of power, on a bitterly cold winter's day, for at least 10 hours. The loss of power provoked an enormous outcry from the public resulting in the power utilities being more receptive to the need to monitor solar as well as geomagnetic activity. Title: Spasmodic Twisting of an Active-Region Filament Prior to Flare Authors: Lin, Y.; Gaizauskas, V. Bibcode: 1989HvaOB..13..413L Altcode: No abstract at ADS Title: Preflare activity. Authors: Priest, E. R.; Gaizauskas, V.; Hagyard, M. J.; Schmahl, E. J.; Webb, D. F.; Cargill, P.; Forbes, T. G.; Hood, A. W.; Steinolfson, R. S.; Chapman, G. A.; Deloach, A. C.; Gary, G. A.; Jones, H. P.; Karpen, J. T.; Martres, M. -J.; Porter, J. G.; Schmieder, B.; Smith, J. B., Jr.; Toomre, J.; Woodgate, B.; Waggett, P.; Bentley, R.; Hurford, G.; Schadee, A.; Schrijver, J.; Harrison, R.; Martens, P. Bibcode: 1989epos.conf....1P Altcode: Contents: 1. Introduction. 2. Magnetohydrodynamic instability. 3. Preflare magnetic and velocity fields. 4. Coronal manifestations of preflare activity. Title: The Origins of the 10.7-CM Solar Flux Authors: Tapping, K. F.; Gaizauskas, V. Bibcode: 1988JRASC..82..280T Altcode: No abstract at ADS Title: Digital Processing of Solar Time-Lapse Photographs Authors: Gaizauskas, V.; Proulx, M. Bibcode: 1988JRASC..82..285G Altcode: No abstract at ADS Title: Electric currents in solar flare kernels. Authors: Lin, Yuanzhang; Gaizauskas, V. Bibcode: 1988SSSMP..31..576L Altcode: Using the high-resolution Hα off-band filtergrams for a flare of importance 1B/M1 occurring in the active region AR2372 on April 6, 1980 and the really simultaneous vector magnetograms, the development of flare kernels during flash phase and the relations between these kernels with the features in the magnetograms and in the maps of longitudinal electric current are investigated. Title: Compact Sites of Microwave Emission at 2.8 Centimeter Wavelength inside Solar Active Regions Authors: Gaizauskas, V.; Tapping, K. F. Bibcode: 1988ApJ...325..912G Altcode: The authors have located the positions of 59 hot, compact sources of 2.8 cm emission in 28 active regions with respect to photospheric and chromospheric structures. The same regions were photographed at high spatial resolution on the same days through a wavelength-scanning Hα filter. Almost 90% of these compact sources are associated with either a plage or a polarity reversal (or both together); they are found in just part of a plage (or polarity reversal) which may be one of several in the same active region. The authors propose that the observed properties of these compact sources can be explained in terms of emission from current-driven instabilities which are excited by evolutionary stresses acting on active regions. Title: Highlights of the Flare Build-Up Study Authors: Gaizauskas, V.; Svestka, Z. Bibcode: 1987SoPh..114..389G Altcode: Years of preparation within the framework of the Flare Build-up Study culminated with intensive observations of solar flares during the Solar Maximum Year (1979-1981). Scientists operating several spacecraft and roughly 70 ground-based observatories participated in an internationally coordinated effort to observe flares with higher spatial, spectral, and temporal resolution over a wider range of wavelengths than heretofore. The FBS stimulated important advances in theories of magnetic reconnection and the growth of plasma instabilities under preflare circumstances. A series of international FBS workshops facilitated data exchanges and collaborative studies for interpreting and synthesizing the wealth of new information about flares. The FBS ended officially at the Symposium on Synopsis of the Solar Maximum Analysis held 2-5 July, 1986 at the COSPAR meeting in Toulouse, France. Here we summarize highlights of its progress towards an understanding of the storage and release of preflare energy. Title: Coincidence between H-alpha flare kernels and peaks of observed longitudinal electric current densities Authors: Lin, Yuanzhang; Gaizauskas, V. Bibcode: 1987SoPh..109...81L Altcode: Large-scale filtergrams of a hitherto neglected class 1B flare are compared with previously published vector magnetograms and maps of photospheric longitudinal electric current density (Hagyard et al., 1985). The vector magnetic fields were mapped simultaneously with the eruption of this flare. A coincidence, to within the + or - 2 arcsec registration accuracy of the data, is found between the flare kernels and the locations of maximum shear and of peak values in the longitudinal electric current density. The kernels brighten in a way which implies that the preflare heating and the main release of flare energy are spatially coincident within the limits of resolution (about 2 arcsec). A pronounced magnetic shear exists in the vertical direction at the location of the strongest flare kernels. Evidence is provided that the electric currents could be maintained by the energy stored in the sheared transverse magnetic field and that the amount of energy released is proportional to the amount stored. These circumstances are consistent with theories in which flares are triggered by plasma instabilities due to surplus electric currents. Title: Compact Sources of Microwave Emission at 2.8 cm Wavelength Inside Solar Active Regions Authors: Gaizauskas, V.; Tapping, K. F. Bibcode: 1987BAAS...19..942G Altcode: No abstract at ADS Title: Coincidence between Hα flare kernels and peaks of observed longitudinal electric current densities Authors: Yuanzhang, Lin; Gaizauskas, V. Bibcode: 1987SoPh..109...81Y Altcode: We compare large-scale filtergrams of a hitherto neglected class 1B flare with previously published vector magnetograms and maps of photospheric longitudinal electric current density (Hagyard et al., 1985). The vector magnetic fields were mapped simultaneously with the eruption of this flare. We find a coincidence, to within the ±2″ registration accuracy of the data, between the flare kernels and the locations of maximum shear and of peak values in the longitudinal electric current density. The kernels brighten in a way which implies that the preflare heating and the main release of flare energy are spatially coincident within the limits of resolution (≈2″). A pronounced magnetic shear exists in the vertical direction at the location of the strongest flare kernels. We provide evidence that the electric currents could be maintained by the energy stored in the sheared transverse magnetic field and that the amount of energy released is proportional to the amount stored. These circumstances are consistent with theories in which flares are triggered by plasma instabilities due to surplus electric currents. Title: Active Solar Longitudes Authors: Gaizauskas, V. Bibcode: 1987ArtSa..22...43G Altcode: No abstract at ADS Title: Electric currents in solar flare kernels. Authors: Lin, Y. -Z.; Gaizauskas, V. Bibcode: 1987PBeiO..10...59L Altcode: No abstract at ADS Title: Preflare magnetic and velocity fields Authors: Hagyard, M. J.; Gaizauskas, V.; Chapman, G. A.; Deloach, A. C.; Gary, G. A.; Jones, H. P.; Karpen, J. T.; Martres, M. -J.; Porter, J. G.; Schmeider, B. Bibcode: 1986epos.conf.1.16H Altcode: 1986epos.confA..16H A characterization is given of the preflare magnetic field, using theoretical models of force free fields together with observed field structure to determine the general morphology. Direct observational evidence for sheared magnetic fields is presented. The role of this magnetic shear in the flare process is considered within the context of a MHD model that describes the buildup of magnetic energy, and the concept of a critical value of shear is explored. The related subject of electric currents in the preflare state is discussed next, with emphasis on new insights provided by direct calculations of the vertical electric current density from vector magnetograph data and on the role of these currents in producing preflare brightenings. Results from investigations concerning velocity fields in flaring active regions, describing observations and analyses of preflare ejecta, sheared velocities, and vortical motions near flaring sites are given. This is followed by a critical review of prevalent concepts concerning the association of flux emergence with flares Title: The Preflare State Authors: Priest, E. R.; Gaizauskas, V.; Hagyard, M. H.; Schmahl, E. J.; Webb, D. F. Bibcode: 1986epos.conf..1.1P Altcode: 1986epos.confA...1P No abstract at ADS Title: The association of chromospheric and coronal phenomena with the evolution of the quiet sun magnetic fields. Authors: Harvey, Karen L.; Tang, Frances; Gaizauskas, Victor Bibcode: 1986NASCP2442..359H Altcode: 1986copp.nasa..359H Using daily full-disk magnetograms and He I 10830 spectroheliograms to study the count and surface distribution of ephemeral regions over the solar cycle, Harvey (1985) concluded that the small dark structures seen in 10830, thought to correspond to X-ray bright points, were more often associated with magnetic bipoles that appeared to result from an encounter of already existing opposite polarity magentic flux than with emerging small magnetic bipoles (ephemeral regions). Such encounters would be more likely to occur in areas of mixed polarity. The fractional area of the sun covered by mixed polarity fields varies anti-correlated with the solar cycle leading to a possible explanation for the 180 degrees out of phase solar cycle variation of X-ray bright points. To establish the validity of this suggestion, a detailed study of time-sequence magnetic field, He I wavelength 10830, Ha, C IV, and Si II observations of selected areas of the quiet sun was initiated about 2 years ago. The preliminary results of this study are reported. Title: Flare Build-Up Study Workshop - National Solar Observatory Sacramento-Peak New Mexico 1985AUG26-29 Authors: Gaizauskas, V. Bibcode: 1986SoPh..105...67G Altcode: This final Workshop of the Flare Build-up Study (FBS) aimed for an up-to-date synthesis of the preflare state based on new knowledge gained during and since the Solar Maximum Year (SMY). More joint discussions were held than was customary at previous FBS Workshops among the study groups. Consensus was possible on some broad issues, but for the thornier aspects of preflare activity the Workshop had to settle for tentative conclusions and to redefine goals for improved future studies. Some of the highlights are summarized below for each study group. Title: Ephemeral active regions and coronal bright points: A solar maximum Mission 2 guest investigator study Authors: Harvey, K. L.; Tang, F. Y. C.; Gaizauskas, V.; Poland, A. I. Bibcode: 1986gsfc.rept.....H Altcode: A dominate association of coronal bright points (as seen in He wavelength 10830) was confirmed with the approach and subsequent disappearance of opposite polarity magnetic network. While coronal bright points do occur with ephemeral regions, this association is a factor of 2 to 4 less than with sites of disappearing magnetic flux. The intensity variations seen in He I wavelength 10830 are intermittent and often rapid, varying over the 3 minute time resolution of the data; their bright point counterparts in the C IV wavelength 1548 and 20 cm wavelength show similar, though not always coincident time variations. Ejecta are associated with about 1/3 of the dark points and are evident in the C IV and H alpha data. These results support the idea that the anti-correlation of X-ray bright points with the solar cycle can be explained by the correlation of these coronal emission structures with sites of cancelling flux, indicating that, in some cases, the process of magnetic flux removal results in the release of energy. That the intensity variations are rapid and variable suggests that this process works intermittently. Title: Preflare activity. Authors: Priest, E. R.; Gaizauskas, V.; Hagyard, M. J.; Schmahl, E. J.; Webb, D. F.; Cargill, P.; Forbes, T. G.; Hood, A. W.; Steinolfson, R. S.; Chapman, G. A.; Deloach, A. C.; Gary, G. A.; Jones, H. P.; Karpen, J. T.; Martres, M. -J.; Porter, J. G.; Schmieder, B.; Smith, J. B., Jr.; Toomre, J.; Woodgate, B.; Waggett, P.; Bentley, R.; Hurford, G.; Schadee, A.; Schrijver, J.; Harrison, R.; Martens, P. Bibcode: 1986NASCP2439....1P Altcode: Contents: 1. Introduction: the preflare state - a review of previous results. 2. Magnetohydrodynamic instability: magnetic reconnection, nonlinear tearing, nonlinear reconnection experiments, emerging flux and moving satellite sunspots, main phase reconnection in two-ribbon flares, magnetic instability responsible for filament eruption in two-ribbon flares. 3. Preflare magnetic and velocity fields: general morphology of the preflare magnetic field, magnetic field shear, electric currents in the preflare active region, characterization of the preflare velocity field, emerging flux. 4. Coronal manifestations of preflare activity: defining the preflare regime, specific illustrative events, comparison of preflare X-rays and ultraviolet, preflare microwave intensity and polarization changes, non-thermal precursors, precursors of coronal mass ejections, short-lived and long-lived HXIS sources as possible precursors. Title: Observations of chromospheric flare dynamics at the next solar maximum specific recommendations of the Chromospheric Flare Dynamics Group. Authors: Canfield, R. C.; Gaizauskas, V.; Kurokawa, H.; Martin, S. F.; Svestka, Z. Bibcode: 1986lasf.conf..489C Altcode: No abstract at ADS Title: Morphology of flaring kernels with asymmetrically-broadened Hα emission. Authors: Gaizauskas, V. Bibcode: 1986lasf.conf...37G Altcode: 1986lasf.symp...37G The author discusses the morphology of flaring kernels in sharply-resolved filtergrams taken in the wings of Hα for three flares: two occurring in rapid succession in adjacent active regions seen against the disk, and one at the limb. They were all observed with the wavelength-sweeping Hα photoheliograph of the Ottawa River Solar Observatory (ORSO). A cycle of wavelengths was completed every 80 s except for the preflare phase of the limb event when it was 40 s. Title: Magnetic shear produced by colliding sunspots Authors: Gaizauskas, V.; Harvey, K. L. Bibcode: 1986AdSpR...6f..17G Altcode: 1986AdSpR...6Q..17G The leading and trailing sunspots of two adjacent active regions are observed to collide as the evolving regions expand along the same direction. During approximately four days of this collinear motion, fibrils linking the colliding sunspots form a pattern suggestive of a potential magnetic field. No flares can be associated with the collision at this stage. Within a single day, and without an apparent change in the direction of the spots, the pattern of fibrils changes to a non-potential configuration. This onset of shear occurs rapidly in the absence of grazing motions. Thereafter, one spot splits, grazing motions develop, and shear is greatly enhanced along the line of polarity inversion. Sustained subflare activity begins after the onset of shear; stronger flares erupt as shear is enhanced. These circumstances are consistent with concepts based on shear as an essential ingredient of flares and which require critical levels of shear to be exceeded in order to trigger flares. Title: Flare build-up study summary Authors: Gaizauskas, V.; Svestka, Z. Bibcode: 1986AdSpR...6f...5G Altcode: 1986AdSpR...6....5G No abstract at ADS Title: Erratum - a Study of Flare Buildup from Simultaneous Observations in Microwave Hα and Ultraviolet Wavelengths Authors: Kundu, M. R.; Gaizauskas, V.; Woodgate, B. E.; Schmahl, E. J.; Shine, R.; Jones, H. P. Bibcode: 1985ApJS...58..195K Altcode: No abstract at ADS Title: The Association of He I λ10830 'Dark Points' and the Evolution of the Quiet Sun Magnetic Fields Authors: Harvey, K. L.; Tang, F.; Gaizauskas, V. Bibcode: 1985BAAS...17..632H Altcode: No abstract at ADS Title: A study of flare buildup from simultaneous observations in microwave, H-alpha, and UV wavelengths Authors: Kundu, M. R.; Gaizauskas, V.; Woodgate, B. E.; Schmahl, E. J.; Shine, R.; Jones, H. P. Bibcode: 1985ApJS...57..621K Altcode: The results of high-resolution observations of the solar preflare activity of June 25, 1980 are analyzed. The observations were carried out simultaneously in the UV microwave, and H-alpha wavelengths using the VLA, the Ottawa River photoheliograph, and the Solar Max spectrometer and polarimeter instruments. Increases were observed in the intensitiy and polarization of compact sources at a wavelength of 6-cm during the preflare hour. The increases were associated with rising and twisting motions in the magnetic loops near the sight of the subsequent flare. Consistent with this process, analysis of the transverse and Doppler motions observed in the H-alpha filament before disruption showed that the filament was activated internally by the motions of evolving magnetic flux patterns. Ultraviolet data for C IV brightenings and upflows at the first appearance of the H-alpha filament indicated the presence of rising magnetic loops and material rising within the loops. The complete VLA, microwave and H-alpha data sets are given. Title: Sunspots in Collision Authors: Gaizauskas, V.; Harvey, K. L. Bibcode: 1985BAAS...17..632G Altcode: No abstract at ADS Title: Observations of the fine structure of the chromosphere. Authors: Gaizauskas, V. Bibcode: 1985cdm..proc...25G Altcode: The structure of the chromosphere outside of active regions owes its geometry and dynamism to the existence of intense magnetic fields distributed intermittently on a fine scale. Those fields are spatially organized by the supergranule flow into a network of long-lived cells which cover the entire sun. The brightness of the network and the geometry of its chromospheric structure differ between quiet equatorial areas and the active latitudes associated with sunspots. The active network evolves with the sunspot cycle and contributes to the variability of disk-integrated chromospheric emission. In this review, the network provides a basis for discussing fine structure as a chromospheric diagnostic. Its varying contribution to the global emission is discussed, and recent observations of fine structures at cell boundaries as distinct from cell interiors are examined. Title: Suspended spicules above the network on the edge of an active region. Authors: Gaizauskas, V. Bibcode: 1985cdm..proc...63G Altcode: No abstract at ADS Title: Pre-Flare Activations of Filaments Located Along Inversion Lines of Magnetic Polarity Authors: Gaizauskas, V. Bibcode: 1985spit.conf..710G Altcode: No abstract at ADS Title: Sunspots in Collision Authors: Gaizauskas, V.; Harvey, K. L. Bibcode: 1984BAAS...16..928G Altcode: No abstract at ADS Title: Suspended Spicules Associated with the Enhanced Bright Network in an Active Region Authors: Gaizauskas, V. Bibcode: 1984SoPh...93..257G Altcode: The progressive rotation from the limb onto the disk of a long-lived cluster of coaligned Hα spicules was observed at high spatial resolution on the fringe of a large complex of activity. Although individual spicules were steadily changing, the organized cluster appeared consistently suspended above the photospheric limb when viewed in the wings of Hα (|Δλ| ≈ 0.9 Å). The phenomenon is the counterpart near an active region of the dark band discovered in the quiet low chromosphere by Loughhead (1969). But in the present circumstances the effect is perceived as a weakening of emission, i.e. as a gap rather than an obscuration. The initial gap between the off-band spicules and the photospheric limb narrowed and closed in about 4 h. A day later, the cluster of spicules could be identified at the same wavelength with a cluster of elongated dark mottles, similarly coaligned; they were adjacent to, but not in contact with, a foreshortened patch of faculae. Title: Identification of two X-ray miniflares with Hα-subflares Authors: Schadee, A.; Gaizauskas, V. Bibcode: 1984AdSpR...4g.117S Altcode: 1984AdSpR...4..117S Active regions show many short-lived emissions in the 3.5 - 5.5 keV range that are 100 to 1000 times weaker than ``normal'' X-ray flares. The hypothesis that they may well be miniflares is supported by the simultaneous occurrence of 2 Hα-subflares at the site of weak X-ray sources. Title: Progress in the study of homologous flares on the sun - Part II Authors: Woodgate, B. E.; Martres, M. -J.; Smith, J. B., Jr.; Strong, K. T.; McCabe, M. K.; Machado, M. E.; Gaizauskas, V.; Stewart, R. T.; Sturrock, P. A. Bibcode: 1984AdSpR...4g..11W Altcode: 1984AdSpR...4...11W Studies of groups of homologous flares in active regions in 1980 have been made using a variety of space and ground based instruments. Detailed properties of three of these groups have been studied, and are combined to form a possible sequence of events. Title: Patterns of the Sun Authors: Gaizauskas, V.; Harvey, K. L.; Harvey, J. W.; Zwaan, C. Bibcode: 1983S&T....66..291G Altcode: No abstract at ADS Title: Optical, microwave and UV imagery of a solar flare. Authors: Gaizauskas, V.; Kundu, M. R.; Schmahl, E. J.; Shine, R. A.; Woodgate, B. E. Bibcode: 1983JRASC..77..261G Altcode: No abstract at ADS Title: Very large array observations of solar active regions. III - Multiple wavelength observations Authors: Lang, K. R.; Willson, R. F.; Gaizauskas, V. Bibcode: 1983ApJ...267..455L Altcode: Very Large Array maps of the active regions AR 2505 and AR 2646 at wavelengths 2 cm, 6 cm, and 20 cm are presented and compared with off-band H-alpha photographs. The 20 cm emission is interpreted in terms of the bremsstrahlung of coronal electrons trapped within magnetic loops; the maximum occurs near the central apex or top of the loop, as would be expected from a hydrostatic coronal loop. The 6 cm emission is interpreted in terms of the gyroresonant emission of thermal electrons spiralling in the legs of magnetic loops. A height of (3.5 + or - 0.5) x 10 to the 9th cm above the solar photosphere is inferred for the 6 cm emission. The 2 cm emission is interpreted in terms of either gyroresonant emission in the low solar corona or bremsstrahlung in the transition region. The 2 cm hot spots may be transitory phenomena related to H-alpha brightenings or flares, or they may mark the legs of warm loops. Title: Book Review - Solar Phenomena in Stars and Stellar Systems (Proceedings of the NATO Advanced Study Institute held at Bonas, France, August 25-September 5, 1980) Authors: Gaizauskas, V. Bibcode: 1983JRASC..77..100G Altcode: 1983JRASC..77..100B; 1983JRASC..77...95. No abstract at ADS Title: On the Flare Effectiveness of Active Regions During the Ascending Phase of Solar Cycle 21 Authors: Gaizauskas, V.; McIntosh, P. S. Bibcode: 1983BAAS...15R.697G Altcode: No abstract at ADS Title: Large-scale patterns formed by solar active regions during the ascending phase of cycle 21 Authors: Gaizauskas, V.; Harvey, K. L.; Harvey, J. W.; Zwaan, C. Bibcode: 1983ApJ...265.1056G Altcode: Synoptic maps of photospheric magnetic fields prepared at the Kitt Peak National Observatory are used in investigating large-scale patterns in the spatial and temporal distribution of solar active regions for 27 solar rotations between 1977 and 1979. The active regions are found to be distributed in 'complexes of activity' (Bumba and Howard, 1965). With the working definition of a complex of activity based on continuity and proximity of the constituent active regions, the phenomenology of complexes is explored. It is found that complexes of activity form within one month and that they are typically maintained for 3 to 6 solar rotations by fresh injections of magnetic flux. During the active lifetime of a complex of activity, the total magnetic flux in the complex remains steady to within a factor of 2. The magnetic polarities are closely balanced, and each complex rotates about the sun at its own special, constant rate. In certain cases, the complexes form two diverging branches. Title: Upflows Immediately Prior to the Impulsive Phase of Solar Flares Authors: Woodgate, B. E.; Shine, R. A.; Schmahl, E. J.; Kundu, M.; Gaizauskas, V. Bibcode: 1982BAAS...14..898W Altcode: No abstract at ADS Title: The relation of solar flares to the evolution and proper motions of magnetic fields Authors: Gaizauskas, V. Bibcode: 1982AdSpR...2k..11G Altcode: 1982AdSpR...2...11G The second Action Interval of the FBS coincided with an extended period of gradual evolution in a large complex of activity which served as the target for a coordinated space-ground study. The complex produced a multitude of subflares, half of which were clustered around just a few sites, each with a distinctive magnetic character. The essential flare-producing conditions at these preferred sites were preserved for many hours, even days, despite disruptions by flares and despite the eroding effects that accompany the disintegration of sunspot groups. Three preferred sites were active for the entire Interval, 22-27 May 1980. A comparison of flaring with non-flaring sites which also contained strong concentrations of flux demonstrates the importance of magnetic complexity, flux emergence, and motions at the photospheric level. The most energetic events by far, a chain of five closely homologous flares, erupted within 13 hours at a site where all these factors were conspicuously combined. The incessant activity preceding and during these flares of the fine chromospheric fibrils that covered and surrounded this particularly energetic site indicates reconfiguration of flux tubes in the chromosphere in a matter of minutes. These rapid (2-5 minutes), small (~10 arc-sec) changes are identified with emerging flux and with pores moving rapidly (>=200 m/s) very close to a magnetic neutral line. Title: Large-Scale Patterns in Solar Activity During the Ascending Phase of Cycle 21 Authors: Gaizauskas, V.; Harvey, K.; Harvey, J.; Zwaan, C. Bibcode: 1981BAAS...13R.906G Altcode: No abstract at ADS Title: Combined radio-optical observations of active solar regions associated with the S-component of solar miocrowave emission. Authors: Gaizauskas, V.; Tapping, K. F. Bibcode: 1980JRASC..74..358G Altcode: No abstract at ADS Title: Long-lived microwave pulsations observed in a complex solar active region Authors: Gaizauskas, V.; Tapping, K. F. Bibcode: 1980ApJ...241..804G Altcode: Microwave pulsations were detected on Sept. 13, 1977 in the intense emission from a compact microwave source associated with the large, slowly rotating, and magnetically complex solar active region, McMath 14943. These pulsations persisted over 5-1/2 hours, with the dominant repetition rate remaining close to 0.4 Hz; they were not associated with flare activity. The core of the microwave emission was located over a plage rather than over the major spot in the region. A mechanism for the pulsating source is proposed in which radial oscillations in an arched magnetic flux tube modulate the gyrosynchrotron emission from high energy electrons trapped in the tube. Title: Changes in Chromospheric Fine Structure as Indicators of the Build-Up Phase of the Large Flares of 21 and 28 May 1980 Authors: Gaizauskas, V. Bibcode: 1980BAAS...12Q.905G Altcode: No abstract at ADS Title: Book-Review - Sunspots Authors: Gaizauskas, V. Bibcode: 1980JRASC..74..247G Altcode: 1980JRASC..74..247B No abstract at ADS Title: Sundial Made from a Microwave Antenna Honours Canada's Pioneer Radio Astronomer Authors: Gaizauskas, V.; Gerylo, S.; Moore, J. D. Bibcode: 1980JRASC..74..174G Altcode: No abstract at ADS Title: The Crimean Solar Maximum Year Workshop, selected reports Authors: Emslie, A. G.; Gaizauskas, V.; Wu, S. T. Bibcode: 1980STIN...8128029E Altcode: Problems associated with the transport of energy and acceleration of charged particles in solar flares are considered. Existing theories are compared with observation with a view to either discriminating between rival theories (such as whether hard X-rays are emitted by thermal or nonthermal bremsstrahlung), constraining existing theories (such as deduction of the number of nonthermal electrons present from spectroscopic diagnostics in the soft X-ray part of the spectrum), or suggesting theories (such as attempting to explain the observed spatial structure of microwave emission relative to alpha). Title: Persistent Quasi-Periodic Microwave Pulsations from a Non-Flaring Compact Source in a Complex Active Region Authors: Gaizauskas, V.; Tapping, K. F. Bibcode: 1980BAAS...12..515G Altcode: No abstract at ADS Title: Location of compact microwave sources with respect to concentrations of magnetic field in active solar regions Authors: Gaizauskas, V.; Tapping, K. F. Bibcode: 1980IAUS...91...33G Altcode: From September 1977 to July 1979, 28 active regions with compact microwave sources were examined by joint optical and radio observations. In 11 of the 28 observed regions, the compact microwave sources varied in intensity with time-scales from minutes to several hours by as much as 50%, neglecting obviously impulsive events. The brightness temperatures of the sources at 2.8 cm were in the range 30,000 to more than 10 million K; for six sources, the brightness temperatures exceeded 2 million K. The results cannot be explained in terms of thermal emissive processes. Title: The enhanced magnetic network in active solar regions: detection and relationship to chromospheric structures. Authors: Gaizauskas, V. Bibcode: 1979JRASC..73..299G Altcode: No abstract at ADS Title: Detection of a Compact Microwave Source in an Emerging Active Region Authors: Gaizauskas, V.; Tapping, K. F. Bibcode: 1979BAAS...11..420G Altcode: No abstract at ADS Title: A Comparison of the 19 April 1977 Two Ribbon Disk Flare with X-ray Flares Observed at the Limb Authors: Skumanich, A.; Gaizauskas, V.; Ku, W. H. Bibcode: 1979BAAS...11..410S Altcode: No abstract at ADS Title: Discussion Authors: Gaizauskas, V.; Glencross, W. M.; Heyvaerts, J. Bibcode: 1979phsp.coll..182G Altcode: 1979IAUCo..44..182G No abstract at ADS Title: Discussion Authors: Acton, L. W.; Gaizauskas, V. Bibcode: 1979phsp.coll..274A Altcode: 1979IAUCo..44..274A No abstract at ADS Title: Discussion Authors: Gaizauskas, V.; Heyvaerts, J.; Hirayama, T.; Pneuman, G. W.; Spicer, D. S.; Withbroe, G. L.; Zirin, H. Bibcode: 1979phsp.coll..301G Altcode: 1979IAUCo..44..301G No abstract at ADS Title: Braided Structures Observed in Flare-Associated Hα Filaments. Authors: Gaizauskas, V. Bibcode: 1979phsp.coll..272G Altcode: 1979IAUCo..44..272G; 1979phsp.conf..272G The motions of flare-associated filaments and prominences are studied using filtergrams taken in rapid succession on five consecutive days (15-19 April 1977), through a Zeiss filter while the 0.25A passband of the filter is stepped continuously across the H-alpha lines 17 times in the range of + or - 1.4 A. Two active filaments of moderate magnetic complexity, located in regions of strong field gradients and subject to violent agitation by flares, were examined. Records contained at high resolution of two subflares (one within each filament), braided prior to the flare, showed a change in the spacing between successive twists and/or in the apparent pitch angle of the braided structure. The potential of the wavelength-scanning method for deriving the topology of the magnetic field with flare-associated filaments is noted. Title: A search for microwave emission from solar X-ray bright point flares. Authors: Avery, L. W.; Feldman, P. A.; Gaizauskas, V.; Roy, J. -R.; Wolfson, C. J. Bibcode: 1977A&A....56..327A Altcode: An attempt was made to detect 9.4-cm radio emission from flaring X-ray bright points with the 46-m telescope at the Algonquin Radio Observatory. Observations from the X-ray heliometer aboard OSO-8 were combined with optical and magnetic data to substantiate possible events. Reduction of 52 h of radio data has revealed one event which is a candidate for radio emission from a flaring X-ray bright point. Title: Total Solar Eclipses in Canada: 1963-2024 AD Authors: Gaizauskas, V.; Avery, L. W. Bibcode: 1976JRASC..70..135G Altcode: No abstract at ADS Title: The Ottawa River Solar Observatory Authors: Gaizauskas, V. Bibcode: 1976JRASC..70....1G Altcode: An observatory has been built in Canada for high-resolution cinematography of active regions in the solar photosphere and chromosphere. The installation on the shore of the Ottawa River is the successor to solar facilities maintained at the Dominion Observatory from 1905 to 1970. The building, telescope, and automated control system are described with comments on the factors that influenced their design. Title: The height and duration of sunspot fibrils in the Halpha chromosphere. Authors: Gaizauskas, V. Bibcode: 1975JRASC..69..254G Altcode: No abstract at ADS Title: High Resolution Observations of Sunspot Hα Fibrils Authors: Gaizauskas, V. Bibcode: 1975BAAS....7..349G Altcode: No abstract at ADS Title: Comparison of Impulsive Optical and Radio Emission Features of an Energetic Subflare Authors: Gaizauskas, V.; Avery, L. W. Bibcode: 1974BAAS....6Q.287G Altcode: No abstract at ADS Title: Site Survey for a Solar Observatory in Canada Authors: Gaizauskas, V.; Kryworuchko, A. Bibcode: 1973JRASC..67..217G Altcode: No abstract at ADS Title: The Oscillatory Velocity Field Observed in a Unipolar Sunspot Region Authors: Rice, J. B.; Gaizauskas, V. Bibcode: 1973SoPh...32..421R Altcode: The velocity field has been mapped for 42 min in an area 80″ by 85″ containing a unipolar sunspot. Apparent shifts of Fe Iλ5233 were measured photoelectrically using a rectangular scanning aperture 1.6″ × 4.0″. The sunspot did not exert a marked influence on the generally random pattern of oscillations at a period of 300 s. Discrete periods of oscillation both longer and shorter than 300 s were excited within the enhanced magnetic field boundaries of this spot. Umbral oscillations at periods near 180 s were detected in agreement with independent observations of the same spot during the previous solar rotation. Title: A new solar observatory on the Ottawa River. Authors: Gaizauskas, V. Bibcode: 1972JRASC..66...69G Altcode: No abstract at ADS Title: A procedure for observing the solar five minute oscillations in two dimensions. Authors: Rice, J. B.; Gaizauskas, V. Bibcode: 1971JRASC..65..174R Altcode: No abstract at ADS Title: Predictions of Local Circumstances Across Canada of the Total Solar Eclipse of July 10, 1972 Authors: Gaizauskas, V.; Avery, L. W.; Manning, F. D. Bibcode: 1971JRASC..65..107G Altcode: No abstract at ADS Title: Canadian Scientists Report-43: The Meeting of the National Committee for Canada of the IAU at Ottawa, Ontario, October 23, 1970 Authors: Gaizauskas, V. Bibcode: 1971JRASC..65...44G Altcode: No abstract at ADS Title: Canadian Scientists Report- 41: The Meeting of the National Committee for Canada of the IAU at Kingston, March 13-14, 1970 Authors: Gaizauskas, V. Bibcode: 1970JRASC..64..177G Altcode: No abstract at ADS Title: A new optical solar observatory. The Ottawa River Solar Observatory. Authors: Gaizauskas, V. Bibcode: 1970BREEC..20....1G Altcode: No abstract at ADS Title: Canadian Scientists Report-XL The Meeting of the National Committee for Canada of the IAU at London September 4-6, 1969 Authors: Gaizauskas, V. Bibcode: 1969JRASC..63..309G Altcode: No abstract at ADS Title: Canadian Scientists Report-XXXIX: Sub-Committees Authors: Gaizauskas, V. Bibcode: 1969JRASC..63..207G Altcode: No abstract at ADS Title: Solar Site Selection Based on Time-Lapse Photography of Granulation Authors: Gaizauskas, V. Bibcode: 1969BAAS....1..276G Altcode: No abstract at ADS Title: Estimation of solar seeing by means of time lapse photography of solar granulation. Authors: Gaizauskas, V. Bibcode: 1969JRASC..63...95G Altcode: No abstract at ADS Title: R.A.S.C. Papers-Photoelectric Observations of the Solar Corona Taken From an Aircraft During the Eclipse of July 20, 1963 Authors: Locke, J. L.; Gaizauskas, V. Bibcode: 1965JRASC..59...32L Altcode: No abstract at ADS Title: R.A.S.C. Papers- Light Curves of Solar Flares Authors: Climenhaga, J. L.; Gaizauskas, V. Bibcode: 1963JRASC..57...77C Altcode: 1963JRASC..57...73C No abstract at ADS Title: Light Curves of Solar Flares Authors: Climenhaga, J. L.; Gaizauskas, V. Bibcode: 1962PASP...74..399C Altcode: No abstract at ADS Title: Radio and Corpuscular Emission Associated with the Flare Surge on the Western Limb of the Sun on July 20, 1961 Authors: Gaizauskas, V.; Covington, A. E. Bibcode: 1962JGR....67.4119G Altcode: The small cosmic-ray increase of July 20, 1961, was produced by a flare surge occurring on the western limb of the sun at 1552 UT. The evolution of the various features—optical, radio, and geophysical—during a five-hour period are described and related to a series of sketches of the Hα filtergrams made at Ottawa, Canada. The large intensity of the impulsive microwave burst at 10.7 cm and the explosive character of the flare surge give the event special significance.