gaizauskas

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Author name code: gaizauskas
ADS astronomy entries on 2022-09-14
author:"Gaizauskas, V."

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Title: Where Do Solar Filaments Form?
Authors: Mackay, Duncan H.; Gaizauskas, Victor; Yeates, Anthony R.
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.

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Title: The Grand Schism in Canadian Astronomy III: Exploring the
Origins of the Conflict
Authors: Gaizauskas, Victor
2012JRASC.106..230G Altcode:
No abstract at ADS

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Title: The Grand Schism in Canadian Astronomy II: Exploring the
Origins of the Conflict
Authors: Gaizauskas, Victor
2012JRASC.106..190G Altcode:
No abstract at ADS

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Title: The Grand Schism in Canadian Astronomy I: The Rise and Fall
of Mount Kobau
Authors: Gaizauskas, Victor
2011JRASC.105...95G Altcode:
No abstract at ADS

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Title: Jack Lambourne Locke (1921-2010)
Authors: Gaizauskas, Victor
2010JRASC.104..253G Altcode:
No abstract at ADS

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Title: Early Years at the David Dunlap Observatory
Authors: Gaizauskas, Victor
2008JRASC.102..222G Altcode:
No abstract at ADS

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Title: Development of Flux Imbalances in Solar Activity Nests and
the Evolution of Filament Channels
Authors: Gaizauskas, V.
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 (&lt;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.

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Title: Where Do Solar Filaments Form?: Consequences for Theoretical
Models
Authors: Mackay, Duncan H.; Gaizauskas, Victor; Yeates, Anthony R.
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.

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Title: Helicity as a Component of Filament Formation
Authors: Mackay, D. H.; Gaizauskas, V.
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.

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Title: Formation of a Switchback During the Rising Phase of Solar
Cycle 21
Authors: Gaizauskas, V.
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.

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Title: Obituary: Arthur Edwin Covington, 1913-2001
Authors: Gaizauskas, Victor
2002BAAS...34.1357G Altcode:
No abstract at ADS

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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.
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, &amp; 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.

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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.
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.

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Title: Solar Activity Complexes
Authors: Gaizauskas, V.
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...

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Title: Solar Filament Channels
Authors: Gaizauskas, V.
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...

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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.
2000IAUTA..24...73F Altcode:
No abstract at ADS

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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.
1999ESASP.448..507M Altcode: 1999mfsp.conf..507M; 1999ESPM....9..507M
No abstract at ADS

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Title: Role of Helicity in the Formation of Intermediate Filaments
Authors: Mackay, D. H.; Priest, E. R.; Gaizauskas, V.; van
Ballegooijen, A. A.
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.

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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.
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.

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Title: Are All Prominences Either Sinistral or Dextral?
Authors: Zirker, J. B.; Leroy, J. -L.; Gaizauskas, V.
1998ASPC..150..439Z Altcode: 1998IAUCo.167..439Z; 1998npsp.conf..439Z
No abstract at ADS

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Title: Force-Free Models of a Filament Channel in Which a Filament
Forms
Authors: Mackay, D. H.; Gaizauskas, V.; Priest, E. R.
1998ASPC..150..286M Altcode: 1998npsp.conf..286M; 1998IAUCo.167..286M
No abstract at ADS

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Title: Filament Channels: Essential Ingredients for Filament Formation
(Review)
Authors: Gaizauskas, V.
1998ASPC..150..257G Altcode: 1998npsp.conf..257G; 1998IAUCo.167..257G
No abstract at ADS

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Title: Filament Channels: Contrasting Their Structure in H-alpha
and H epsilon I 1083 NM
Authors: Harvey, K. L.; Gaizauskas, V.
1998ASPC..150..269H Altcode: 1998IAUCo.167..269H; 1998npsp.conf..269H
No abstract at ADS

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Title: The Sinistral-Dextral Regularity: An Independent Test
Authors: Zirker, J. B.; Leroy, J. -L.; Gaizauskas, V.
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.

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Title: Global Magnetic Patterns of Chirality
Authors: Zirker, J. B.; Martin, S. F.; Harvey, K.; Gaizauskas, V.
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.

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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.
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.

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Title: Why and Where do Filaments Form in Active Regions?
Authors: Gaizauskas, V.; Zwaan, C.
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.

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Title: Formation of a Solar Filament Channel
Authors: Gaizauskas, V.; Zirker, J. B.; Sweetland, C.; Kovacs, A.
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.

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Title: Fulguraciones en una configuración tipo δ
Authors: Luoni, M. L.; Mandrini, C. H.; Rovira, M. G.; Démoulin,
P.; Gaizauskas, V.
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.

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Title: Creation of prominences and filaments.
Authors: Gaizauskas, V.
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.

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Title: Magnetic Reconnection as a Driver of Chromospheric Surges
Authors: Gaizauskas, V.
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.

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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.
1996mpsa.conf..491G Altcode: 1996IAUCo.153..491G
No abstract at ADS

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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.
1995SPD....26.1319G Altcode: 1995BAAS...27R.991G
No abstract at ADS

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Title: Bright Rims Adjacent to a Quiescent Hα Filament
Authors: Gaizauskas, V.; de Luca, E.; Golub, L.; Jones, H. P.
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).

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Title: The twisting of filament that resulted in a solar flare
Authors: Lin, Yuan-zhang; Gaizauskas, V.
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
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.
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.
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.
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.
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.
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.
1994ASIC..433..133G Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Report of IAU Commission 10: Solar activity (Activité
solaire).
Authors: Gaizauskas, V.
1994IAUTA..22...53G Altcode:
No abstract at ADS

---------------------------------------------------------
Title: A Historical Perspective on Measurements of Solar Irradiance
Authors: Gaizauskas, V.
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
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 &gt;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.
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.
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.
1993SSRv...64..165V Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Book Review: Observing the sun / Cambridge U Press, 1991
Authors: Gaizauskas, V.
1993SSRv...64..168G Altcode: 1993SSRv...64..168T
No abstract at ADS

---------------------------------------------------------
Title: On Recurrent Solar Activity (Invited)
Authors: Gaizauskas, V.
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.
1993stp2.conf..147G Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Evidence from a Chromospheric Surge for Coronal Current Sheets
Authors: Gaizauskas, V.; Kerton, C. R.
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.
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.
1991BAAS...23.1026G Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Needs and constraints for ground-based cooperative programs
on solar flares
Authors: Gaizauskas, V.
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.
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.
1990BAAS...22..890G Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Disintegration of Colliding Sunspots
Authors: Harvey, K. L.; Gaizauskas, V.
1990BAAS...22Q.840H Altcode:
No abstract at ADS

---------------------------------------------------------
Title: OSO-8 Measurements of Velocity Signature of Flare Kernels
Authors: Skumanich, A.; Gaizauskas, V.
1990BAAS...22..891S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: On driving the eruption of a solar filament
Authors: Gaizauskas, V.
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.
1989BAAS...21..835G Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Preflare Activity
Authors: Gaizauskas, V.
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.
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.
1989HvaOB..13..413L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The Origins of the 10.7-CM Solar Flux
Authors: Tapping, K. F.; Gaizauskas, V.
1988JRASC..82..280T Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Digital Processing of Solar Time-Lapse Photographs
Authors: Gaizauskas, V.; Proulx, M.
1988JRASC..82..285G Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Electric currents in solar flare kernels.
Authors: Lin, Yuanzhang; Gaizauskas, V.
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.
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.
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.
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.
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.
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.
1987ArtSa..22...43G Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Electric currents in solar flare kernels.
Authors: Lin, Y. -Z.; Gaizauskas, V.
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.
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.
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
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.
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.
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.
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.
1986lasf.conf..489C Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Morphology of flaring kernels with asymmetrically-broadened
Hα emission.
Authors: Gaizauskas, V.
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.
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.
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.
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.
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.
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.
1985BAAS...17..632G Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Observations of the fine structure of the chromosphere.
Authors: Gaizauskas, V.
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.
1985cdm..proc...63G Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Pre-Flare Activations of Filaments Located Along Inversion
Lines of Magnetic Polarity
Authors: Gaizauskas, V.
1985spit.conf..710G Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Sunspots in Collision
Authors: Gaizauskas, V.; Harvey, K. L.
1984BAAS...16..928G Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Suspended Spicules Associated with the Enhanced Bright Network
in an Active Region
Authors: Gaizauskas, V.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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 (&gt;=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.
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.
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.
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.
1980BAAS...12Q.905G Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Book-Review - Sunspots
Authors: Gaizauskas, V.
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.
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.
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.
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.
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.
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.
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.
1979BAAS...11..410S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Discussion
Authors: Gaizauskas, V.; Glencross, W. M.; Heyvaerts, J.
1979phsp.coll..182G Altcode: 1979IAUCo..44..182G
No abstract at ADS

---------------------------------------------------------
Title: Discussion
Authors: Acton, L. W.; Gaizauskas, V.
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.
1979phsp.coll..301G Altcode: 1979IAUCo..44..301G
No abstract at ADS

---------------------------------------------------------
Title: Braided Structures Observed in Flare-Associated Hα Filaments.
Authors: Gaizauskas, V.
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.
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.
1976JRASC..70..135G Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The Ottawa River Solar Observatory
Authors: Gaizauskas, V.
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.
1975JRASC..69..254G Altcode:
No abstract at ADS

---------------------------------------------------------
Title: High Resolution Observations of Sunspot Hα Fibrils
Authors: Gaizauskas, V.
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.
1974BAAS....6Q.287G Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Site Survey for a Solar Observatory in Canada
Authors: Gaizauskas, V.; Kryworuchko, A.
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.
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.
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.
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.
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.
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.
1970JRASC..64..177G Altcode:
No abstract at ADS

---------------------------------------------------------
Title: A new optical solar observatory. The Ottawa River Solar
Observatory.
Authors: Gaizauskas, V.
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.
1969JRASC..63..309G Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Canadian Scientists Report-XXXIX: Sub-Committees
Authors: Gaizauskas, V.
1969JRASC..63..207G Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Solar Site Selection Based on Time-Lapse Photography of
Granulation
Authors: Gaizauskas, V.
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.
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.
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.
1963JRASC..57...77C Altcode: 1963JRASC..57...73C
No abstract at ADS

---------------------------------------------------------
Title: Light Curves of Solar Flares
Authors: Climenhaga, J. L.; Gaizauskas, V.
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.
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.