Author name code: svestka
ADS astronomy entries on 2022-09-14
author:"Svestka, Zdenek"
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Title: Sixty Years in Solar Physics
Authors: Švestka, Zdeněk
Bibcode: 2010SoPh..267..235S
Altcode: 2010SoPh..tmp..235S; 2010SoPh..tmp..211S
I recount my career in solar physics beginning at Ondřejov Observatory
in 1948 and ending with my ∼30 year stay at the Laboratory of Space
Research in Utrecht.
Title: The Misnomer of ``Post-Flare Loops''
Authors: Švestka, Zdeněk
Bibcode: 2007SoPh..246..393S
Altcode:
Attention is drawn to the fact that the term "post-flare loops" is
incorrect and should be avoided, because the loops are parts of the
flare itself. Two other names for these loop systems are suggested.
Title: Editorial Appreciation
Authors: Engvold, Oddbjørn; Harvey, Jack; Leibacher, John; Sakurai,
Takashi; Švestka, Zdeněk; van Driel-Gesztelyi, Lidia; Solar Physics
editors
Bibcode: 2006SoPh..233....1E
Altcode:
No abstract at ADS
Title: Preface
Authors: Rottman, G.; Woods, T.; George, V.; Harvey, J.; Švestka,
Z.; Engvold, O.
Bibcode: 2005SoPh..230....1R
Altcode:
No abstract at ADS
Title: Evidence Linking Slow Solar Wind Streams to Long-Decay
X-Ray Events
Authors: Švestka, Zdeněk; Fárník, František
Bibcode: 2005SoPh..229..305S
Altcode:
Outflow of slow solar wind from solar active regions has been reported
in recent years by many different authors. Therefore, in this paper
we have studied synoptic maps of the solar wind density (SWD) based
on interplanetary scintillation (IPS) data for available parts of all
the years 1991-1994 and 1997-2001 to verify correlations of maxima in
SWD with sources in active regions. We have found convincing evidence
that eruptive flares in active regions, and thus X-ray long-decay
events (LDEs) in general, can produce short-lived enhancements of
the SWD. However, we were not able to get statistically convincing
evidence that active regions can be permanent sources of slow solar
wind, and propose three possible reasons for this negative result.
Title: Editorial
Authors: Engvold, Oddbjorn; Harvey, Jack; Švestka, Zdenek
Bibcode: 2005SoPh..229....1E
Altcode:
No abstract at ADS
Title: Hard x-ray Pulsations in the Initial Phase of Flares
Authors: Fárník, F.; Karlický, M.; Švestka, Z.
Bibcode: 2003SoPh..218..183F
Altcode:
When analyzing light curves of hard X-ray bursts recorded by the Hard
X-Ray Spectrometer on board the MTI satellite, we have found three
events (all associated with major solar flares, two of them in the same
active region) which show pulsations in the very initial phase of the
burst. Periods of the pulsations range from 25 to 48 s. We compare them
with other observations of pulsations of radio waves and in X-rays
and conclude that pulsations of this kind have not been observed
before. We mention several possible causes and prefer interactions
between current-carrying loops as the most likely interpretation of
the observed variations.
Title: Solar activity
Authors: Švestka, Z.
Bibcode: 2003dysu.book..237S
Altcode:
What is the active Sun which is a very important factor in our
life? Observations from SOHO and TRACE reveal the highly turbulent
nature of Sun's surface and its atmospheric layers: all the time and
everywhere we see brightness variations, loop formations and decays,
plasma flows and ejections of gas. However, this is not what we call
solar activity. The real processes called solar activity appear only
in limited parts of the solar surface, and their occurrence varies
quasi-periodically with time, creating 11-year cycles of solar activity
whose main characteristics are described in this chapter. Particular
attention is paid to coronal mass ejections, as the most important
phenomenon affecting the Earth.
Title: Preface
Authors: Lin, R.; Dennis, B.; Benz, A.; Harvey, J.; Engvold, O.;
švestka, Z.
Bibcode: 2002SoPh..210....1L
Altcode:
No abstract at ADS
Title: X-ray Jets in Interconnecting Loops
Authors: Fárník, František; Švestka, Zdeněk.
Bibcode: 2002SoPh..206..143F
Altcode:
We present examples of X-ray jets, observed by the Soft X-ray Telescope
on board Yohkoh, which followed trajectories of transequatorial
interconnecting loops (TILs). All these TILs were preexisting, seen
some time before, but were mostly invisible at the time of the onset
of the jet which often made them bright along their total length. With
few exceptions, these TIL-associated jets have properties very similar
to other jets ejected inside active regions or along open field lines
(footpoints in X-ray bright points, recurrence, strong collimation,
average speed close to 350 km s−1), but may reach larger
lengths, in our examples up to 450 000 km. Exceptions are one jet that
moved slower and one that had no brightened area at its supposed source
region at the time of its origin (an X-ray bright point appeared there
only 3 hours later). It appears that quite a high number of X-ray jets
may be of this TIL-associated kind.
Title: Flare Changes Associated with Peaks of Hard X-Ray Bursts
Authors: Farnik, F.; Svestka, Z.; Karlicky, M.
Bibcode: 2002cosp...34E1403F
Altcode: 2002cosp.meetE1403F
Using the high-resolution records made in four energy channels
by the Hard X-Ray Spectrometer (HXRS) on board the MTI spacecraft
(launched on 12 March 2000) we try to refine the study made by Dwivedi
et al. 18 years ago (Dwivedi, B.N., Hudson, H.S., Kane, S.R., and
Svestka, Z.: 1984, Solar Phys. 90, 331) who looked for changes in the
flare development associated with changes in the hard X-ray flux. In
addition to H-alpha and SOHO data we can, at least for some flares,
also use high-resolution TRACE images which make it possible to see
fine changes which could not be detected before. We try to find, in
particular, which parts of flares produce hard X ray peaks of various
hardness in the HXRS records and we also- compare them with peaks in
microwave records. Intense peaks often correspond to flaring structures
penetrating into strong magnetic fields (penumbrae and umbrae of
sunspots) which generally confirms Dwivedi et al.'s findings. However,
we can provide more details than they were able to obtain from their
data with worse space and time resolution.
Title: X-Ray Jets in Interconnecting Loops
Authors: Fárník, F.; Švestka, Z.
Bibcode: 2002mwoc.conf...81F
Altcode:
We present several examples of X-ray jets, observed by the SXT onboard
Yohkoh, which followed trajectories of transequatorial interconnecting
loops (TILs). All these TILs were preexisting, seen some time before,
but mostly invisible at the time of the onset of the jet which often
made them bright along their total length. With few exceptions, these
TIL-associated jets have properties very similar to other jets ejected
inside active regions or along open field lines (footpoints in X-ray
bright points, recurrence, strong collimation, average speed between
340 and 380 km s-1, but may reach very large lengths, in excess of
450 000 km. Exceptions are one jet that moved slower and one that
had no brightened area at its source region at the time of its origin
(an X-ray bright point appeared there only 3 hours later). It appears
that less than 20% of X-ray jets are of this kind.
Title: Locations of Footpoints of Transequatorial Interconnecting
Loops
Authors: Fárník, František; Karlický, Marian; Švestka, Zdeněk.
Bibcode: 2001SoPh..202...81F
Altcode:
We discuss footpoints of loops seen by Yohkoh in soft X-rays
that connect active regions across the equator (transequatorial
interconnecting loops - TILs). While most TILs are rooted in moderately
strong fields at peripheries of active regions, there are also cases
when these loops are anchored in very weak or very strong fields,
ranging from < 30 G to several hundred gauss. Some have their
footpoints near sunspot penumbrae, creating `X-ray fountains' in a
combination with active region loops. But TILs are never rooted in
sunspots. The most likely explanation is that magnetic field lines
leave spots almost vertically so that TILs rooted in them extend high
into the corona and density in them is below the limit of visibility
in X-rays. The fact that in force-free modeling some TILs are rooted
in sunspots is most probably due to the difference between field-line
connections in `vacuum' and in the highly conductive plasma on the
Sun. Some TILs end before they reach active regions which sometimes
may indicate the real situation, but mostly this `gap' is probably due
to a temperature decrease near the loop footpoints which makes them
invisible in X-rays. In that case the fact that these cool lowest parts
of TILs are never found in TRACE or SOHO EIT images indicates that
plasma density in TILs must be very low. Still, the total absence of
any counterparts of X-ray TILs in TRACE and EIT images is puzzling and,
therefore, other possible interpretations of the `gap' origin are also
briefly mentioned.
Title: Varieties of Coronal Mass Ejections and Their Relation
to Flares
Authors: Švestka, Zdeněk.
Bibcode: 2001SSRv...95..135S
Altcode:
Most coronal mass ejections (CMEs) start as coronal storms which are
caused by an opening of channels of closed field lines along the zero
line of the longitudinal magnetic field. This can happen along any
zero line on the Sun where the configuration is destabilized. If
the opening includes a zero line inside an active region, one
observes a chromospheric flare. If this does not happen, no flare
is associated with the CME in the chromosphere, but the process,
as well as the response in the corona (a Long Decay Event in X-rays)
remains the same. The only difference between flare-associated and
non-flare-associated CMEs is the strength of the magnetic field in
the region of the field line opening. This can explain essentially
all differences which have been observed between these two kinds
of CMEs. However, there are obviously also other sources of CMEs,
different from coronal storms: sprays (giving rise to narrow, pointed
ejections), erupting interconnecting loops (often destabilized by
flares), and growing coronal holes. This paper tries to summarize
and interpret observations which support this general picture, and
demonstrates that both CMEs and flares must be properly discussed in
any study of solar-terrestrial relations.
Title: Solar Flares: Main Phase
Authors: Švestka, Z.
Bibcode: 2000eaa..bookE2290S
Altcode:
After the impulsive phase of a flare is over (see SOLAR FLARES:
IMPULSIVE PHASE), we talk about the main phase or gradual phase. Most
FLARES (often called compact or confined flares) are short lived
and they simply cool during the main phase, decaying within minutes
or tens of minutes. However, there is also another kind of flares
(eruptive flares) which continue to release energy during their ma...
Title: Helioseismic Diagnostics of Solar Convection and Activity
Authors: Svestka, Zdenek; Harvey, John W.
Bibcode: 2000hdsc.conf.....S
Altcode:
This book focuses on the recent advances in our understanding of
solar convection and activity, and on new methods and results of
helioseismic diagnostics of the internal structures and dynamics
of solar convection and active regions. The methods of local
helioseismology (time-distance tomography, ring-diagram analysis,
acoustic imaging, and holography) intensively developed in the past
few years have provided promising results on the deep structure
of large-scale convection and flows, emerging active regions, and
sunspots. The book includes reviews and contributed papers presented at
the SOHO-9 Workshop held on July 12-15, 1999, at Stanford University,
California, U.S.A. It provides a comprehensive overview of the
current status of the field and presents new ideas and approaches
to helioseismic diagnostics and theoretical modeling of the physical
processes inside the Sun. The book is recommended for graduate students
and specialists in solar physics, astrophysics, and geophysics. Link:
http://www.wkap.nl/book.htm/0-7923-6520-8
Title: Helioseismic diagnostics of solar convection and activity. Part
1, 2. Proceedings. SOHO-9 Workshop, Stanford, CA (USA), 12 - 15
Jul 1999.
Authors: Švestka, Z.; Harvey, J. W.; Kosovichev, A. G.; Duvall,
T. L., Jr.
Bibcode: 2000SoPh..192....1S
Altcode:
The following topics were dealt with: theories of solar convection,
rotation and activity, helioseismic tomography, acoustic imaging and
holography, ring-diagram analysis, magnetic fields and oscillations,
solar cycle variations of the internal structure and rotation, solar
convective structures and oscillations.
Title: Solar activity: An overview
Authors: Švestka, Zdenek
Bibcode: 1999CSci...77.1503S
Altcode:
No abstract at ADS
Title: G. Burkhardt, U. Esser, H. Hefele, I. Heinrich, W. Hofmann,
V. R. Matas, L. D. Schmadel, R. Wielen, and G. Zech (eds.), Astronomy
and Astrophysics Abstracts, Volumes 69A and 69B
Authors: Švestka, Z.
Bibcode: 1999SoPh..188..217S
Altcode:
No abstract at ADS
Title: Quiet solar wind signatures above active regions observed
in X-rays
Authors: Hick, P.; Svestka, Z.; Jackson, B. V.; Farnik, F.; Hudson, H.
Bibcode: 1999AIPC..471..231H
Altcode: 1999sowi.conf..231H
X-ray images from the Yohkoh satellite, obtained following occurrences
of limb flares sometimes show coronal fan-like structures extending
above a growing post-flare loop system. We show one such event
observed in AR 7270 on the east limb of the Sun on 28/29 August
1992. We suggest that these rays are `ministreamers,' formed as a
result of the re-structuring of the corona following the occurrence
of a flare-associated CME. Synoptic maps of the solar wind density,
constructed from a tomographic analysis of interplanetary scintillation
(IPS) measurements, show enhanced scintillation matching the position
of AR 7270 if we assume a radial outflow at a reasonable slow solar
wind speed of 400 km s-1. From this agreement we argue that outflow
of mass occurs from the active region into interplanetary space.
Title: Long transequatorial interconnecting loops of the new solar
cycle
Authors: Fárník, F.; Karlický, M.; Švestka, Z.
Bibcode: 1999SoPh..187...33F
Altcode:
We study two long transequatorial loops connecting high-latitude
regions of the new solar cycle. These loops (with lengths of 47 and
61 heliographic degrees) provide evidence that the upper length limit
of 37° found by Chase et al. (1976) from Skylab data was determined
simply by the typical distances between northern and southern active
regions during the period of Skylab observations. We find strong
support for the idea that these long interconnecting loops originate
through reconnection of field lines extending from the two active
regions towards and beyond the equator, and confirm the earlier
finding by Canfield, Pevtsov, and McClymont (1996) that only field
lines from active regions with the same chirality reconnect. As we
are not aware of any longitudinal (E-W) loops of comparable lengths,
we suggest that it is mainly the solar differential rotation which
drives the reconnection of latitudinal (N-S) field lines.
Title: The Gradual Phase of Flares
Authors: Svestka, Z. F.; Poletto, G.; Fontenla, J.; Hick, P.; Kopp,
R. A.; Sylwester, B.; Sylwester, J.
Bibcode: 1999mfs..conf..409S
Altcode:
Heating and Cooling in the Gradual Phase Emission Measure-Temperature
Diagrams Flaring Arches Gradual Phase of Eruptive Flares Postflare
Giant Arches Giant Arches: Modeling and Interpretation
Title: Large-Scale Active Coronal Phenomena in Yohkoh SXT Images
IV. Solar Wind Streams from Flaring Active Regions
Authors: Švestka, Zdeněk; Fárník, František; Hudson, Hugh S.;
Hick, Paul
Bibcode: 1998SoPh..182..179S
Altcode:
We demonstrate limb events on the Sun in which growing flare loop
systems are embedded in hot coronal structures looking in soft X-rays
like fans of coronal rays. These structures are formed during the flare
and extend high into the corona. We analyze one of these events, on
28-29 August 1992, which occurred in AR 7270 on the eastern limb, and
interpret these fans of rays either as temporary multiple ministreamers
or plume-like structures formed as a result of restructuring due to
a CME. We suggest that this configuration reflects mass flow from the
active region into interplanetary space. This suggestion is supported
by synoptic maps of solar wind sources constructed from scintillation
measurements which show a source of enhanced solar wind density at
the position of AR 7270, which disappears when 5 days following the
event are removed from the synoptic map data. We also check synoptic
maps for two other active regions in which existence of these fan-like
structures was indicated when the active regions crossed both the east
and west limbs of the Sun, and both these regions appear to be sources
of a density enhancement in the solar wind.
Title: Fan-Like coronal X-ray Structures as Sources of Solar Wind
Authors: Hick, P.; Svestka, Z.; Farnik, F.; Hudson, H. S.; Jackson,
B. V.
Bibcode: 1998AAS...192.1503H
Altcode: 1998BAAS...30..840H
We show coronal soft X-ray images from the Yohkoh satellite, obtained
following occurrences of limb flares. These images show rising
post-flare loops, which are embedded in hot coronal structures looking
like fans of coronal rays. We analyze the event on 28/29 August 1992,
which occurred in AR 7270 on the east limb of the Sun. We suggest that
these rays are multiple 'ministreamers', which apparently are formed as
a result of the restructuring of the corona following the occurrence
of a flare-associated CME. We argue that this configuration allows
outflow of mass from the active region into interplanetary space. This
is supported by synoptic maps of solar wind sources constructed from
scintillation measurements showing a source of enhanced scintillation
at the position of AR 7270.
Title: Post-Flare Structures Rising with Decreasing or Constant Speed
Authors: Svestka, Z.; Farnik, F.
Bibcode: 1998ASSL..229..365S
Altcode: 1998opaf.conf..365S
No abstract at ADS
Title: A Window to the West
Authors: Svestka, Zdenek
Bibcode: 1998fyc..conf...75S
Altcode:
No abstract at ADS
Title: Large-Scale Active Coronal Phenomena in YOHKOH SXT
Images. III. Enhanced Post-Flare Streamer
Authors: Švestka, Zdeněk; Fárník, František; Hick, Paul; Hudson,
Hugh S.; Uchida, Yutaka
Bibcode: 1997SoPh..176..355S
Altcode:
We demonstrate several events where an eruptive flare close to the
limb gave rise to a transient coronal streamer visible in X-rays in
Yohkoh SXT images, and analyze one of these events, on 28-29 October
1992, in detail. A coronal helmet streamer began to appear 2 hours
after the flare, high above rising post-flare loops; the streamer
became progressively narrower, reaching its minimum width 7-12 hours
after the flare, and widened again thereafter, until it eventually
disappeared. Several other events behaved in a similar way. We suggest
that the minimum width indicates the time when the streamer became
fully developed. All the time the temperature in the helmet streamer
structure was decreasing, which can explain the subsequent fictitious
widening of the X-ray streamer. It is suggested that we may see here
two systems of reconnection on widely different altitudes, one giving
rise to the post-flare loops while the other creates (or re-forms)
the coronal helmet streamer. A similar interpretation was suggested in
1990 by Kopp and Polettofor post-flare giant arches observed on board
the SMM; indeed, there are some similarities between these post-flare
helmet streamers and giant arches and, with the low spatial resolution
of SMM instruments, it is possible that some helmet streamers could
have been considered to be a kind of a giant arch.
Title: Solar Physics Announces CD-ROM
Authors: Svestka, Zdenek; Howard, Robert F.; Engvold, Oddbjorn
Bibcode: 1997SoPh..176..443S
Altcode:
No abstract at ADS
Title: Post-Flare Loops Embedded in a Hot Coronal Fan-Like Structure
Authors: Švestka, Z.; Fárnik; Hudson, H. S.; Hick, P.
Bibcode: 1997ESASP.415..139S
Altcode: 1997cpsh.conf..139S
No abstract at ADS
Title: Observations of Faint, Outlying Loop Systems in Large Flares
Authors: Neidig, Donald F.; Švestka, Zdeněk; Cliver, Edward W.;
Airapetian, Vladimir; Henry, Timothy W.
Bibcode: 1997SoPh..170..321N
Altcode:
Faintly visible, darkened regions in Hα lying outside but
adjacentto bright flare emissionwere found to occur in 10 of 31 major
flares investigated. Without exception, the darkenings occur over
`magnetically neutral' areas, and these are usually bordered by ridges
ofoppositely-poled field, where one border is shared in common with a
flare ribbon. Thedarkenings probably result from the formation of faint,
outlying loop systems, similar topost-flare loops seen in absorption,
but which are connected to magnetic features outsidethe flare and
are unresolved or only marginally resolved in patrol images. Simple
modelsfor post-flare loops incorporating the results of statistical
equilibrium calculations readilydemonstrate that darkenings of several
percent (consistent with our photometric measurements) can be produced
by loop structures of cross-sectional diameter ≈ 102 km
(unresolved by patrol instruments) and containing gas at densities 5 ×
1010-5 × 1011 cm-3 andtemperatures
8000-15000 K. Outlying loop systems might be formed by magnetic
fieldreconnection, analogous to the mechanism ascribed to eruptive
two-ribbon flares, butassociated with field structures adjacent to the
flare. Alternatively, these outlying loopsystems may not erupt but
become visible as a result of heating and chromospheric evaporation
at the footpoints shared with the flare ribbon. In either case, the
observations presented here have interesting implications for both
the spatial scale and the topology of thecoronal magnetic fields in
which eruptions occur.
Title: The first results from SOHO.
Authors: Fleck, B.; Švestka, Z.
Bibcode: 1997frfs.book.....F
Altcode:
This volume contains papers reporting the first scientific results from
the SOHO mission as well as descriptions of the in-flight performance of
some of the instruments. A CD-ROM with multimedia material is included
as an integral part of this volume. Reprinted from Sol. Phys., Vol. 170,
No. 1 (Jan 1997) (see AAA, Vol. 67) and Vol. 175, No. 2 (Oct 1997)
(see AAA, Vol. 68).
Title: Speeds of Rising Post-Flare Structures
Authors: Švestka, Zdeněk
Bibcode: 1996SoPh..169..403S
Altcode:
There are basically two kinds of post-flare coronal structures: those
rising with decreasing speed, and others which rise with constant speed
for a long period of time. As a rule, those structures with decreasing
speed are post-flare loop systems, while those rising with constant
speed are postflare giant arches. However, there are exceptions. We
demonstrate several cases of post-flare loop systems which rise with
constant speed for many hours, three of them observed by Yohkoh. These
observations imply that the Kopp and Pneuman interpretation of
post-flare loops as sequentially reconnecting open field lines
cannot be generally valid. The most likely interpretation is that all
post-flare loop systems start with the Kopp and Pneuman process, but
in some of them later-formed loops begin to be continuously heated;
thus they cease to cool and begin to expand into the corona. This kind
of post-flare loops might represent an intermediate stage between the
ordinary post-flare loops and post-flare giant arches.
Title: Book reviews
Authors: Howard, R. F.; van den Oord, G. H. J.; Švestka, Z.
Bibcode: 1996SoPh..169..225H
Altcode:
No abstract at ADS
Title: Large-scale active coronal phenomena in Yohkoh SXT images
Authors: Fárník, František; Švestka, Zdeněk; Hudson, Hugh S.;
Uchida, Yutaka
Bibcode: 1996SoPh..168..331F
Altcode: 1996SoPh..168..331U
We discuss Yohkoh SXT observations of stationary giant post-flare
arches which occurred on 3-6 May, 1992 and study in detail the last
arch, associated with the flare at 19:02 UT on 5 May, which extended
above the west limb. The arch was similar to the first giant arch
discovered on board the SMM, on 21-22 May, 1980. We demonstrate that
the long lifetimes of these structures necessarily imply additional
energy input from the underlying active region: otherwise, conduction
would cool these arches in less than one hour and even with the
unlikely assumption of conduction inhibited, pure radiative cooling
would not produce the temperature decrease observed. All arch tops,
although varying in brightness, stayed for several days at a fairly
constant altitude of ∼ 100 000 km, and the arch studied, on 5-6 May,
was just a new brightening of the pre-existing decaying structure. The
brightening was apparently due to inflow of hot plasma from the flare
region. Yohkoh data confirm that these stationary arches are rare
phenomena when compared with the rising arches studied in Paper I and
with Uchida et al.'s expanding active regions.
Title: Flare-like dynamic phenomena
Authors: Rompolt, B.; Švestka, Z.
Bibcode: 1996AdSpR..17d.115R
Altcode: 1996AdSpR..17..115R
Using data from Skylab, SMM, and Yohkoh spacecraft, as well as Hα
observations on the ground, we summarize the present knowledge about
dynamic phenomena on the Sun which usually are not classified as
flares, although they resemble processes observed in flares, often are
associated with flares, and sometimes can be considered for special
kinds of flares. This involves field openings outside active regions
(eruptive flares without chromospheric response), loop eruptions,
with emphasis on brightenings (and possibly eruptions) of loops which
interconnect active regions, sprays, flaring arches (injections of
hot and cool plasma into closed field configurations), Hα and X-ray
surges (injections of hot and cool plasma into `open' fields), X-ray
jets, recently discovered by Yohkoh, as well as Hα jets observed at
Wroclaw and Ottawa. We will try to find relationships between all the
latter phenomena so that one gets a more homogeneous picture of plasma
injections and jets observed on the Sun. There are many active phenomena
on the Sun which usually are not classified as flares, although they
closely resemble processes observed in flares, or are very often,
and quite typically, associated with flares. Some of them are even
caused by the same kind of instability that produces flares.
Title: Large-Scale Active Coronal Phenomena in YOHKOH SXT Images
Authors: Svestka, Z.; Farnik, F.; Hudson, H. S.; Uchida, Y.; Hick, P.
Bibcode: 1996ASPC..111..388S
Altcode: 1997ASPC..111..388S
The authors have checked in Yohkoh SXT images the appearance of giant
post-flare arches which were discovered in hard X-ray images from
the HXIS and FCS instruments onboard the SMM. They have verified the
existence of both the rising and stationary arches. In addition to
these two kinds of giant post-flare arches, known before from SMM
observations, Yohkoh also reveals other large post-flare coronal
structures which might have been considered to be giant arches by the
low-resolution SMM instruments. These include coronal helmet streamers
above rising flare loops or fans of hot structures in which the rising
loops are embedded.
Title: Large-Scale Active Coronal Phenomena in YOHKOH SXT Images
Authors: Svestka, Z.; Farnik, F.; Hudson, H. S.; Uchida, Y.; Hick,
P.; Lemen, J. R.
Bibcode: 1996mpsa.conf..609S
Altcode: 1996IAUCo.153..609S
No abstract at ADS
Title: Coronal phenomena associated with flares.
Authors: Svestka, Z.
Bibcode: 1996joso.proc..135S
Altcode:
The paper reviews various kinds of large-scale coronal phenomena which
are associated with solar flares. Particular attention is paid to Hα
and X-ray observations of "post"-flare loops and to recent Yohkoh
observations of slowly expanding giant arches and extensive "ray"
structures embedding flare loop systems.
Title: Large-Scale Active Coronal Phenomena in YOHKOH SXT Images, I
Authors: Švestka, Zdeněk; Fárník, František; Hudson, Hugh S.;
Uchida, Yutaka; Hick, Paul; Lemen, James R.
Bibcode: 1995SoPh..161..331S
Altcode:
We have found several occurrences of slowly rising giant arches inYohkoh
images. These are similar to the giant post-flare arches previously
discovered by SMM instruments in the 80s. However, we see them now
with 3-5 times better spatial resolution and can recognize well their
loop-like structure. As a rule, these arches followeruptive flares
with gradual soft X-ray bursts, and rise with speeds of 1.1-2.4 km
s−1 which keep constant for >5 to 24 hours, reaching
altitudes up to 250 000 km above the solar limb. These arches differ
from post-flare loop systems by their (much higher) altitudes, (much
longer) lifetimes, and (constant) speed of growth. One event appears
to be a rise of a transequatorial interconnecting loop.
Title: On `The Solar Flare Myth' postulated by Gosling
Authors: Švestka, Zdeněk
Bibcode: 1995SoPh..160...53S
Altcode:
The `Solar Flare Myth' postulated by Gosling (1993) is
a misunderstanding. It is true that most sources of coronal mass
ejections (CMEs) cannot be classified as flares in the common old sense
of that word. However, just for this reason the term `eruptive flare'
has been introduced for all solar active phenomena in which an opening
of field lines is involved and which lead to magnetic-field and mass
ejections resulting in a CME. The process is essentially the same in all
events, irrespective of' whether only adisparition brusque without any
chromospheric brightening or a major two-ribbon flare is involved in it;
the only difference is the different strength of the magnetic field in
which the process was accomplished. The major two-ribbon (cosmic-ray)
flares clearly represent the most energetic events of this kind, and,
therefore, it is very misleading to claim that solar flares in general
are phenomena with very little importance for solar-terrestrial physics.
Title: A comparison of solar activity during the decline of several
solar cycles
Authors: Svestka, Z.
Bibcode: 1995AdSpR..16i..27S
Altcode: 1995AdSpR..16R..27S
This review summarizes the general characteristics of solar activity
during the declining part of solar cycles and compares the behavior
of the Sun during several last cycles. Different characteristics of
solar activity are considered and tentative reasons for their different
behavior in different cycles are suggested. The activity decline is
usually very irregular, characterized by quiet periods interrupted by
temporary bursts of activity. These bursts can be quite impressive:
actually, as a rule, the most outstanding events of solar activity do
not occur at the cycle maximum, but shortly before it, or a few years
later. The duration of quiet periods between activity enhancements
increases as the cycle declines, but even close to the solar minimum
one may still encounter quite interesting flare events. From the
point of view of solar-terrestrial relations, these late events are
particularly favorable, because their effects in interplanetary space
and in planetary magnetospheres can be followed much easier than
during high solar activity: one can uniquely ascribe the observed
consequencies in space to their isolated sources on the Sun.
Title: Book Review: Planetary systems : formation, evolution and
detection / Kluwer, 1994
Authors: Solanki, S. K.; Švestka, Zdeněk; Svestka, Z.
Bibcode: 1995SoPh..159..403S
Altcode: 1995SoPh..159..403B
No abstract at ADS
Title: Flare-Associated Darkenings in H-Alpha: Possible Evidence
for Faint Outlying, Unresolved Loop Systems
Authors: Neidig, D. F.; Cliver, E. W.; Svestka, Z.; Airapetian, V.;
Henry, T. W.
Bibcode: 1995SPD....26.1215N
Altcode: 1995BAAS...27..986N
No abstract at ADS
Title: The Participation of Nuclei in Type-Iii Related Electron
Streams
Authors: Kallenrode, May-Britt; Svestka, Zdenek
Bibcode: 1994SoPh..155..121K
Altcode:
We study 27 increases of the flux of 300-800 keV electrons on board
HELIOS A or B, associated with intense type III radio bursts close
to perihelion passages of the two spacecraft, during the solar
minimum. Electrons can be detected inside cones with an angular
width between 30° and 60°. Though only intense type III bursts
are associated with recognizable electron events in space, such
an association does not exist for all of them; this fact and great
differences in fluxes of the individual events indicate that, apart
from the intensity, also some other charactefistic of the type III
burst acceleration or propagation process determines the resulting
flux of electrons in space; the energy spectrum of the accelerated
electrons is one of the likely candidates. A comparison of the electron
flux in these events with the flux of 1.7-3.7 MeV nucl−1
helium reveals very large variations of the helium/electron flux ratio,
by a factor of at least 15 and possibly much higher. We demonstrate that
these variations are not caused by propagation effects in interplanetary
space. Therefore, they must be due either to propagation effects in the
solar corona or, more likely, to intrinsic variations in the relative
production of electrons and nuclei in the type III burst process. An
extrapolation of the observed fluxes to 1 AU shows that in only 7 of
the 27 electron events studied might a marginal > 1.7 MeV helium
flux be recognized ar the Earth distance.
Title: On the Occurrence of Blue Asymmetry in Chromospheric Flare
Spectra
Authors: Heinzel, Petr; Karlicky, Marian; Kotrc, Pavel; Svestka, Zdenek
Bibcode: 1994SoPh..152..393H
Altcode:
We present observations of optical spectra of a flare in which blue line
asymmetry was seen for more than 4 min close to the flare onset. The
maximum blue asymmetry coincided with the maximum of a hard X-ray
and microwave burst. We discuss possible interpretations of the blue
asymmetry and conclude that the most plausible one is electron-beam
heating with return current. Although this process predicts downflows
in the lower transition region and upper chromosphere, its ultimate
effect on the line profiles can be blue asymmetry: the upper layers
moving away from us absorb the radiation of the red peak thus lowering
its intensity in comparison to the blue one.
Title: Slow-mode oscillations of large-scale coronal loops
Authors: Svestka, Zdenek
Bibcode: 1994SoPh..152..505S
Altcode:
On several occasions, repetitive X-ray brightenings, sometimes
accompanied by mass injections into adjacent loops, appeared
quasi-periodically with mean periods close to 20 minutes. In all cases
when X-ray images were available, the sites of these brightenings were
in active regions which were associated with large-scale coronat loops
of length (2 − 3) × 105 km. Therefore, the primary source
of these long-periodic pulsations might be slow-mode oscillations in
these large-scale loops. Free MHD oscillations, proposed earlier by
Roberts, Edwin, and Benz (1984), may fit the observed data.
Title: Book-Review - Space Science Dictionary
Authors: Kleczek, J.; Ckeczkova, H.; Svestka, Z.
Bibcode: 1994SoPh..151..203K
Altcode:
No abstract at ADS
Title: Book review
Authors: Švestka, Z.
Bibcode: 1994SoPh..151..203S
Altcode:
No abstract at ADS
Title: X-Ray Observations of a Major Eruptive Flare Behind the Limb
Authors: Smith, Kermit L.; Strong, Keith T.; Švestka, Zdeněk;
McCabe, Marie K.
Bibcode: 1994SoPh..149..363S
Altcode:
We analyze X-ray images and spectra of a coronal structure which
extended to altitudes over 130 000 km above an eruptive flare located
20° behind the western solar limb. The images were obtained by the
Flat Crystal Spectrometer (FCS) and the spectra were obtained by the
Bent Crystal Spectrometer (BCS) aboard the SMM spacecraft. Images
in OVIII and MgXI lines cover the period from before the flare onset
(which occurred at 22:31 UT on 16 February, 1986) through 17 UT on 17
February and were used for determination of temperature and emission
measure within the structure. BCS obtained CaXIX spectra of the coronal
event, benefiting from the occultation of the active region behind
the solar limb.
Title: Large-Scale Coronal Structures Associated with Solar Activity
(Invited)
Authors: Svestka, Z.; Farnik, F.
Bibcode: 1994scs..conf..243S
Altcode: 1994IAUCo.144..243S
The authors summarize observations of filament eruptions, post-flare
loops, giant post-flare arches, flaring arches, surges, coronal
responses to chromospheric brightenings, and interconnecting loops,
made by Skylab and SMM, and confront some of them with soft X-ray
observations recently made by Yohkoh. It seems likely that many
structures observed by Yohkoh are the same phenomena that were seen
before, but it may be sometimes difficult to identify them correctly.
Title: Book-Review - Astronomy and Astrophysics Abstracts - Index
- V.51-55
Authors: Burkhardt, B.; Esser, U.; Hefele, H.; Heinrich, I.; Hofmann,
W.; Krahn, D.; Matas, V. R.; Schmadel, L. D.; Wielen, R.; Zech, G.;
Svestka, Z.
Bibcode: 1993SoPh..148..177B
Altcode:
No abstract at ADS
Title: Book review
Authors: Švestka, Z.
Bibcode: 1993SoPh..148..177S
Altcode:
No abstract at ADS
Title: Book-Review - the YOHKOH Solar-A Mission
Authors: Svestka, Z.; Uchida, Y.; Farnik, F.
Bibcode: 1993SSRv...64..367S
Altcode:
No abstract at ADS
Title: An Analysis of SKYLAB X-Ray Pictures of a Giant Coronal Arch
Authors: Simberova, Stanislava; Karlicky, Marian; Svestka, Zdenek
Bibcode: 1993SoPh..146..343S
Altcode:
The limb event of 13/14 August, 1973, imaged by Skylab in soft X-rays,
proved to be a giant arch, quite similar to those observed in 1980-1986
on SMM. High spatial resolution (by a factor of 4-5 better than in SMM
data) made it possible to see the internal structure of the arch. Its
brightest part consisted of loops very similar to, but higher than,
post-flare loops, surrounded by a rich system of weak loop structures
extending up to altitudes of 260 000 km. While the main brightest
structure of the arch was newly formed, the weak very large loops had
existed above the active region before and were only enhanced during
the event.
Title: Responses of large-scale coronal structures to chromospheric
activity
Authors: Farnik, Frantisek; Hick, Paul; Svestka, Zdenek
Bibcode: 1993SoPh..146..313F
Altcode:
We have followed the transit of two active regions across the western
solar limb during June 29 through July 2, 1980, as imaged in 3.5-16
keV X-rays by HXIS aboard the SMM. During frequent brightenings of
large-scale coronal structures, hard X-ray emission in the 11-16 keV
energy band was recorded up to altitudes of 76 000 km. Soft X-rays
could be seen in excess of 250 000 km altitude above the photospheric
active region. Many X-ray brightenings low in the corona in the
active regions were followed by enhancements high in the corona in
the large-scale coronal structures. Although subsequent enhancements
rarely appeared in the same position, similar portions of the corona
brightened intermittently, indicating that the general configuration
of the coronal structures above the active regions did not change much,
in spite of the frequent energy inputs. These inputs were of two kinds:
nonthermal, with very fast response at high coronal altitudes within
seconds or tens of seconds, and thermal, with a delay of several
minutes. The nonthermal response is short-lived, reflecting the time
profile of the primary source; the thermal response is more gradual
and longer lasting than the primary source. In some enhancements of
large-scale coronal structures both these kinds of response occur and
can be clearly recognized. There are also active-region hrightenings
without any response in the high corona and,vice versa, high-corona
brightenings without any obvious primary source; in the latter case,
it is likely that the source was hidden behind the limb.
Title: Book-Review - the YOHKOH Solar-A Mission
Authors: Svestka, Z.; Uchida, Y.; Bromage, B.
Bibcode: 1993Obs...113..165S
Altcode:
No abstract at ADS
Title: Editorial
Authors: de Jager, Cornelis; Howard, Robert F.; švestka, Zdeněk
Bibcode: 1993SoPh..143D...7D
Altcode:
No abstract at ADS
Title: Book-Review - Eruptive Solar Flares
Authors: Svestka, Z.; Jackson, B. V.; Machado, M. E.; Sylwester, J.
Bibcode: 1993SSRv...65..186S
Altcode:
No abstract at ADS
Title: X-Ray Observations of Limb Flare Loops and Post-Flare
Coronal Arch
Authors: Svestka, Zdenek; Smith, Kermit L.; Strong, Keith T.
Bibcode: 1992SoPh..139..405S
Altcode:
We present observations of another post-flare arch following an
eruptive flare, detected in X-ray lines above the western solar limb
on 2 May 1985.
Title: Book-Review - the YOHKOH / Solar-A Mission
Authors: Svestka, Z.; Uchida, Y.
Bibcode: 1992JBAA..102R.109S
Altcode:
No abstract at ADS
Title: Book-Review - the YOHKOH Solar-A Mission
Authors: Svestka, Z.; Uchida, Y.
Bibcode: 1992JBAA..102Q.109S
Altcode:
No abstract at ADS
Title: Book-Review - the YOHKOH Solar-A Mission
Authors: Svestka, Z.; Uchida, Y.
Bibcode: 1992Sci...256R.253S
Altcode:
No abstract at ADS
Title: The Birth of Giant Post-Flare Arches
Authors: Poletto, G.; Svestka, Z.
Bibcode: 1992SoPh..138..189P
Altcode:
Using short accumulation times, we have succeeded in the detection
in HXIS images of the initial growth of the giant post-flare arch
of 6 November, 1980 at 14:44 UT and part of the initial growth of
the giant arch of 7 November, 1980 at 04:30 UT. These observations
are relevant to the problem of the origin of giant arches: the fact
that the arch of 6 November was imaged more than half an hour before
the first flare loops had been recorded in the associated flare,
proves that giant arches cannot: be interpreted as upper products of
the reconnection process that creates the growing systems of flare
loops (as the original interpretation by Švestka et al. (1982a)
suggested). However, also the alternative hypothesis by Poletto and Kopp
(1988) that these structures originate through a reconnection process
in a peripheral, large-scale configuration meets with difficulties:
after the initial rise, the maximum brightness in both arches seems
to descend, until a much slower rise was resumed about two hours later.
Title: Editorial
Authors: de Jager, Cornelis; Švestka, Zdeněk; Howard, Robert F.
Bibcode: 1992SoPh..137D...5D
Altcode:
No abstract at ADS
Title: History and Basic Characteristics of Eruptive Flares
Authors: Svestka, Z.; Cliver, E. W.
Bibcode: 1992LNP...399....1S
Altcode: 1992esf..coll....1S; 1992IAUCo.133....1S
We review the evolution of our knowledge and understanding of the
eruptive (dynamic, two-ribbon) flare phenomenon. Starting with the
first observation of a white-light flare by Carrington and Hodgson in
1859, we cover in succession the highlights: Hale's invention of the
spectroheliograph in 1892 and the spectrohelioscope in 1926 started
flare observations in H. The institution of a world-wide flare patrol
brought significant advances in knowledge of flares in the 1930s and
1940s and new windows were opened to observe flares at short (SID) and
long (radio) wavelengths. In the 1950s and 1960s metric radio bursts
were related to trapped energetic electrons and shocks, and two-ribbon
flares were associated with energetic protons in space. Radio and X-ray
observations gave evidence for two basic types of flare processes:
an impulsive phase followed by a long-duration or gradual phase. It
was found that flares were often preceded by filament activations, and
growing loop prominence systems were recognized as the limb counterpart
of two-ribbon disk flares. The early 1970s brought Skylab observations
of coronal mass ejections (CMEs) and arcades of coronal soft X-ray
loops above two-ribbon flares. In the mid-1970s, the Kopp-Pneuman
reconnection model, based on configurations proposed earlier by
Carmichael, Sturrock, and Hirayama, provided a framework in which the
newly discovered CMEs could be related to the basic characteristics
of two-ribbon flares. The 1980s brought, key new results from SMM
and Hinotori including images of hard X-ray flares and large-scale
coronal structures associated with eruptive flares. In the conclusion,
we summarize the basic characteristics of eruptive flares.
Title: Eruptive Solar Flares
Authors: Svestka, Zdenek; Jackson, Bernard V.; Machado, Marcos E.
Bibcode: 1992LNP...399.....S
Altcode: 1992IAUCo.133.....S; 1992esf..coll.....S
This is an exhaustive survey of present-day solar research including
both theory and observations. It deals with eruptive flares, filament
eruption in x-rays and radio waves, energy release and transport, and
terrestrial response to solar flares. Details of the most recent SOLAR-A
project (launched shortly after the conference) are also presented.
Title: A Giant Post-Flare Coronal Arch Observed by SKYLAB
Authors: Svestka, Z.; Simberova, S.
Bibcode: 1992LNP...399..221S
Altcode: 1992esf..coll..221S; 1992IAUCo.133..221S
The limb event of 13 August 1973, observed by Skylab in soft X-rays,
exhibited typical characteristics of the giant post-flare arches
observed by HXIS and FCS on board SMM in the 1980s. We present here
examples of the processed Skylab images which yield 4 times better
angular resolution than the SMM experiments and thus, for the first
time, make it possible to distinguish the real fine structure of a
giant post-flare arch.
Title: A Giant Coronal Arch Observed by Skylab
Authors: Švestka, Zdeněk
Bibcode: 1991SoPh..135..419S
Altcode:
The limb event of 13 August 1973, observed by Skylab in soft X-rays, has
all the typical characteristics of the giant post-flare arches observed
by HXIS and FCS on board SMM in the 1980s. Skylab images provide us
with 4-5 times better angular resolution than the SMM experiments and
thus, for the first time, make it possible to distinguish the real
fine structure of a giant post-flare arch. The image processing of
the 13/14 August 1973 event is now in progress.
Title: Book-Review - Astronomy and Astrophysics Abstracts V.49A/B
Authors: Burghardt, G.; Esser, U.; Hefele, H.; Heinrich, I.; Hofmann,
W.; Krahn, D.; Matas, V. R.; Schmadel, L. D.; Wielen, R.; Zech, G.;
Svestka, Z.
Bibcode: 1991SoPh..134..411B
Altcode:
No abstract at ADS
Title: Book reviews
Authors: Švestka, Z.
Bibcode: 1991SoPh..134..411S
Altcode:
No abstract at ADS
Title: Flaring Arches - Part Three
Authors: Fontenla, Juan M.; Svestka, Zdenek; Farnik, Frantisek; Tang,
Frances Y.
Bibcode: 1991SoPh..134..145F
Altcode:
We show detailed observations in X-rays, UV lines, and Hα of an
extended arch, about 300000 km long, which developed as a consequence
of a compact subflare. This subflare occurred in an `included' magnetic
polarity of relatively low magnetic field strength (compared to that of
the sunspots). The apparition of this big arch was preceded by that of a
smaller arch, about 30000 km long, which masked the polarity inversion
line filament in the early phase of the subflare. The big arch which
developed later, around the time of the main X-ray and UV spike of the
subflare, connected the included polarity and the main leading sunspot
of the region, and became fully developed in a few minutes. The fact
that both arches were simultaneously observed in all spectral domains as
well as their fine structure in Hα can only be explained by considering
the arch as composed of several unresolved portions of material
having widely different temperatures. The Hα observations can be
interpreted as showing the appearance of this cool material as a result
of condensation, but a more appealing interpretation is that there
was almost simultaneous ejection of superhot (107 K), hot
(106 K), mild (105 K), and cool (104
K) material from the subflare site along previously existing magnetic
tubes of much lower density. The termination of the subflare was marked
by a rather hard X-ray and UV spike which appeared to originate in a
different structure than that of the main spike. The material in the
arch gradually cooled and drained down after the end of the subflare.
Title: Book reviews
Authors: Hudson, H. S.; Kleczek, J.; Švestka, Z.
Bibcode: 1991SoPh..133..403H
Altcode:
No abstract at ADS
Title: The YOHKOH (Solar-A) Mission : a series of invited
contributions
Authors: Svestka, Zdenek; Uchida, Yutaka
Bibcode: 1991ysam.book.....S
Altcode: 1991QB526.F6Y64....
No abstract at ADS
Title: Needs and constraints for solar flares space-borne cooperative
programs.
Authors: Svestka, Z.
Bibcode: 1991AdSpR..11e.115S
Altcode: 1991AdSpR..11Q.115S
There are three basic reasons for cooperation in space observations of
flares: (1) observations in different spectral regions, (2) stereoscopic
observations, and (3) in situ data. Using experience from the past
and considering the planned experiments, problems encountered by
flare-related cooperative programs on spacecraft are briefly summarized.
Title: The YOHKOH (SOLAR-A) mission. A series of invited
contributions.
Authors: Švestka, Z.; Uchida, Y.
Bibcode: 1991yohk.book.....S
Altcode:
The SOLAR-A spacecraft was launched by the Institute of Space and
Astronautical Science, Japan (ISAS) in August 1991, and, following
an ISAS tradition, was renamed YOHKOH. This mission is dedicated
principally to the study of solar flares, especially of high-energy
phenomena observed in the X- and gamma-ray ranges. With a coordinated
set of instruments including hard X-ray and soft X-ray imaging
telescopes as well as spectrometers with advanced capabilities, it will
reveal many new aspects of flares and help better understand their
physics, supporting international collaborations with ground-based
observatories as well as theoretical investigations. An overview of
this mission, including the satellite, its scientific instruments,
and its operation, is given.
Title: Evolution of Hot Plasma in Flares
Authors: Svestka, Zdenek F.
Bibcode: 1991LNP...387..165S
Altcode: 1991fpsa.conf..165S
This review discusses, in particular, X-ray manifestations of the
development of hot flare plasma during the cooling phase of flares. In a
preexisting coronal configuration, a small flare source can excite much
larger coronal loops and arches, of which only the footpoints become
visible if their density is low, or their whole structures can be seen
if density is high enough. Flaring arches, through which both cool and,
hot plasma flows from the primary flare source to a secondary footpoint,
are the most spectacular phenomena of this kind. In other cases the
flaring loops did not exist before, but have been newly formed during
the flare process. These are the eruptive flares, in which the preflare
field lines are first disrupted and subsequently reconnect. The main
part of this review is devoted to the development of hot plasma in
this particular kind of flaring structures. It is emphasized that
X-ray observations of growing systems of loops in eruptive flares,
and giant arches following these flares high in the corona, require
large fields of view pointed for several hours at the active region in
which the flare occurred. This makes their observations with SOLAR-A
rather difficult, but one should realize that SOLAR-A represents the
only means for studying these coronal components of the most important
solar flares until, at least, the end of this century.
Title: Real-time simulation of a potential magnetic field in a
post-flare arch
Authors: Poletto, Giannina; Svestka, Zdenek
Bibcode: 1990SoPh..129..363P
Altcode:
We analyze the X-ray observations on 7-8 November of the last revival
of a giant coronal arch first observed in the morning hours of 6
November, 1980. We compare these data with observations of earlier
revivals of this arch, in order to determine whether the successive
brightenings repeat without any apparent modification, or whether they
show a varying behavior as they keep occurring. We also examine the
magnetic structure of the revived arches in order to ascertain whether
the subsequent phenomena involve the same magnetic configuration. The
information about the magnetic structure of the last revival is the
best we have, because the revival started close to the time of the
Kitt Peak magnetogram which has been used for the magnetic modelling
of the whole series of these giant arches.
Title: X-Ray Bright Surges
Authors: Svestka, Zdenek; Farnik, Frantisek; Tang, Frances
Bibcode: 1990SoPh..127..149S
Altcode:
We present evidence of X-ray emission from surges that are bright
in Hα. These surges have many features common to flaring arches of
Martin and Švestka (1988); the basic difference between the two is
that in flaring arches cold and hot plasma are injected into clearly
defined closed magnetic loops, while in the surges the injection
goes into large-scale magnetic field structures of which the second
footpoint is usually unknown. Because of the steep density gradient in
such large-scale structures, the X-ray visibility of bright surges is
limited to a few tens of seconds only. A series of repetitive surges,
some of them bright and emitting X-rays, occurred on 8 July, 1980
from footpoints of two large-scale coronal structures, which might
have been the legs of an enormous arch at least 600 Mm long.
Title: Book-Review - Astronomy and Astrophysics Abstracts
Authors: Esser, U.; Hefele, H.; Heinrich, I.; Hofmann, W.; Krahn,
D.; Matas, V. R.; Schmadel, L. D.; Zech, G.; Svestka, Z.
Bibcode: 1990SoPh..126..411E
Altcode:
No abstract at ADS
Title: Book Review: The sun: an introduction / Springer-Verlag
Authors: Mewe, R.; Švestka, Z.; Mewe, R.
Bibcode: 1990SoPh..126..411M
Altcode: 1990SoPh..126..411S
No abstract at ADS
Title: Book-Review - Astronomy and Astrophysics Abstracts V.44
Authors: Bohme, S.; Svestka, Z.
Bibcode: 1989SoPh..119..420B
Altcode:
No abstract at ADS
Title: Book Review: Solar and stellar physics. / Springer-Verlag, 1987
Authors: Poletto, Giannina; Dimitrov, D. L.; Švestka, Z.; Poletto, G.
Bibcode: 1989SoPh..119..419P
Altcode: 1989SoPh..119..419S
No abstract at ADS
Title: Flaring Arches - Part Two
Authors: Svestka, Zdenek; Farnik, Frantisek; Fontenla, Juan M.;
Martin, Sara F.
Bibcode: 1989SoPh..123..317S
Altcode:
We discuss first the development of the coronal arch-shaped structure of
∼ 57000 km length which was born at or before 08:00 UT on 6 November,
1980 and became the site of 13 quasi-periodic brightenings in hard
X-rays from 10:00 to 14:30 UT. The same structure became the site
of a series of 17 flaring arches between 15:30 and 24:00 UT on that
day. The periodicity of ∼ 19 min, defined well for the quasi-periodic
variations, seems to be partly retained during the occurrence of the
flaring arches.
Title: The Footpoints of Giant Arches
Authors: Martin, Sara F.; Svestka, Zdenek F.; Bhatnagar, Arvind
Bibcode: 1989SoPh..124..339M
Altcode:
We have detected chromospheric footpoints of the giant post-flare
coronal arches discovered by HXIS a few years ago. Hα photographs
obtained at Big Bear and Udaipur Solar Observatories show chromospheric
signatures associated with 5 sequential giant arch events observed
in the interval from 6 to 10 November, 1980. The set of footpoints at
one end of the arches consists of enhancements within a plage at the
northeast periphery of the active region and the set of footpoints at
the other end of the arch consists of brightenings of the chromosphere
south of the active region. Both sets of footpoints show very slow
brightness variations correlated in time with the brightness variations
of the X-ray arches. Current-free modelling of the coronal magnetic
field by Kopp and Poletto (1989), based on a Kitt Peak magnetogram,
confirms the identification of the two sets of footpoints by showing
magnetic field lines connecting them.
Title: Solar Flares - the Gradual Phase
Authors: Svestka, Zdenek
Bibcode: 1989SoPh..121..399S
Altcode: 1989IAUCo.104..399S
One has to distinguish between two kinds of the gradual phase of flares:
(1) a gradual phase during which no energy is released so that we see
only cooling after the impulsive phase (a confined flare), and (2)
a gradual phase during which energy release continues (a dynamic flare).
Title: Book-Review - Astronomy and Astrophysics Abstracts
Authors: Esser, U.; Hefele, H.; Heinrich, I.; Hofmann, W.; Krahn,
D.; Matas, V. R.; Schmadel, L. D.; Zech, G.; Svestka, Z.
Bibcode: 1989SoPh..124..193E
Altcode:
No abstract at ADS
Title: Book-Review - Reports on Astronomy Transactions of the
International Astronomical Union
Authors: Švestka, Zdeněk
Bibcode: 1989SoPh..122..191S
Altcode:
No abstract at ADS
Title: Editorial
Authors: de Jager, Cornelis; Švestka, Zdeněk; Howard, Robert F.
Bibcode: 1989SoPh..121D...9D
Altcode:
No abstract at ADS
Title: Giant solar arches and coronal mass ejections in November 1980
Authors: Svestka, Zdenek F.; Jackson, Bernard V.; Howard, Russell A.;
Sheeley, Neil R., Jr.
Bibcode: 1989SoPh..122..131S
Altcode:
Using data from the SOLWIND coronagraph and photometers aboard
HELIOS-A we examine coronal mass ejections from an active region
which produced a series of giant post-flare coronal arches. HXIS
X-ray observations reveal that in several cases underlying flares
did not disrupt these arch structures, but simply revived them,
enhancing their temperature, density and brightness. Thus we are
curious to know how these quasi-stationary X-ray structures could
survive in the corona in spite of recurrent appearances of powerful
dynamic flares below them. We have found reliable evidence that two
dynamic flares which clearly revived the preexisting giant arch were
not associated with any mass ejection. After two other flares, which
were associated with mass ejections, the arch might have been newly
formed when the ejection was over. In one of these cases, however,
the arch had typical characteristics of a revived structure so that
it is likely that it survived a powerful mass ejection nearby. In a
magnetic configuration of the arch which results from potential-field
modelling (Figure 1(b)) such a survival seems possible.
Title: Book Review: The physics of solar flares. / CUP, 1988
Authors: Svestka, Z.
Bibcode: 1989SoPh..122..192S
Altcode: 1989SoPh..122..192T
No abstract at ADS
Title: Coronal mass ejections and coronal structures.
Authors: Hildner, E.; Bassi, J.; Bougeret, J. L.; Duncan, R. A.;
Gary, D. E.; Gergely, T. E.; Harrison, R. A.; Howard, R. A.; Illing,
R. M. E.; Jackson, B. V.; Kahler, S. W.; Kopp, K.; Low, B. C.; Lantos,
P.; Phillips, K. J. H.; Poletto, G.; Sheeley, N. R., Jr.; Stewart,
R. T.; Svestka, Z.; Waggett, P. W.; Wu, S. T.
Bibcode: 1989epos.conf..493H
Altcode:
The work of this team was concerned with modelling of post-flare arches,
the reconnection theory of flares, the slow variation of coronal
structure, and the coronal and interplanetary detection, evolution,
and consequences of mass ejections.
Title: Book-Review - Astronomy and Astrophysics Abstracts
Authors: Bohme, S.; Svestka, Z.
Bibcode: 1988SoPh..115..409B
Altcode:
No abstract at ADS
Title: Solar and interplanetary observations of the mass ejection
on 7 May, 1979
Authors: Jackson, Bernard V.; Rompolt, Bogdan; Svestka, Zdenek
Bibcode: 1988SoPh..115..327J
Altcode:
We present observations of a mass ejection that was observed by five
different instruments along its way from the solar surface to more
than 100 solar radii. The instruments involved are the ground-based
Hα coronagraph at Wrocław, the white-light SOLWIND coronagraph on
board the P78-1 satellite, zodiacal light photometers of the HELIOS
B spacecraft, in situ plasma detectors and magnetometers on board the
HELIOS B spacecraft, and interplanetary scintillation measurements on
the ground. By using a CAT-scan analysis of the images obtained by the
SOLWIND coronagraph near the Earth and HELIOS B photometers placed at
0.3 AU perpendicular to the Earth-Sun line, we have been able to get a
three-dimensional density reconstruction of the mass ejection and fit
the best velocity curve for its propagation. Although problems exist
in smoothly joining the height-time curves (for instance, we had to
reduce the brightness of the SOLWIND data by more than a factor of two
to make the data sets agree photometrically), both this analysis and
direct measurements by the other experiments clearly indicate higher
speeds at greater distances from the Sun. The plasma acceleration
in this case was obviously not limited only to distances within 3
R0, as is usually the case, but continued beyond the outer
limit of the coronagraph view at ∼ 8 R0.
Title: Book Review: The early universe. / Reidel, 1987
Authors: Kleczek, J.; Švestka, Z.; Kleczek, J.
Bibcode: 1988SoPh..115..409K
Altcode: 1988SoPh..115..409U
No abstract at ADS
Title: Book reviews
Authors: Schindler, K.; Švestka, Zdeněk
Bibcode: 1988SoPh..114..193S
Altcode:
No abstract at ADS
Title: Book Review: The galaxy and the solar system. / U Arizona
Press, 1986.
Authors: Kotov, V. A.; Kostik, R.; Shchukina, N.; Švestka, Zdeněk;
Kotov, V. A.
Bibcode: 1988SoPh..115..203K
Altcode: 1988SoPh..115..203S
No abstract at ADS
Title: Flaring Arches - Part One
Authors: Martin, Sara F.; Svestka, Zdenek F.
Bibcode: 1988SoPh..116...91M
Altcode:
`Flaring arches" is a name assigned to a particular component of
some flares. This component consists of X-ray and Hα emission which
traverses a coronal arch from one to the other of its chromospheric
footpoints. The primary footpoint is at the site of a flare. The
secondary footpoint, tens of thousands of kilometers distant from the
source flare, but in the same active region, brightens in Hα concurrent
with the beginning of the hard X-ray burst at the primary site. From the
inferred travel time of the initial exciting agent we deduce that high
speed electron streams travelling through the arch must be the source
of the initial excitation at the secondary footpoint. Subsequently,
a more slowly moving agent gradually enhances the arch first in
X-rays and subsequently in Hα, starting at the primary footpoint and
propagating along the arch trajectory. The plasma flow in Hα shows
clearly that material is injected into the arch from the site of the
primary footpoint and later on, at least in some events, a part of it
is also falling back.
Title: Book-Review - Solar Radiophysics
Authors: McLean, D. J.; Labrum, N. R.; Svestka, Z.
Bibcode: 1988SoPh..115R.204M
Altcode:
No abstract at ADS
Title: Book-Review - Progress in Solar Physics
Authors: de Jager, C.; Svestka, Z.
Bibcode: 1988ApL&C..26..372D
Altcode: 1988ApL....26..372D
No abstract at ADS
Title: Soft X-ray observations of large-scale coronal structures
Authors: Svestka, Zdenek
Bibcode: 1988AdSpR...8k..81S
Altcode: 1988AdSpR...8...81S
This paper draws attention to large-scale structures in the solar corona
which have been observed only in soft X-rays. Some of them were seen on
Skylab in 1973 with poor time resolution, some other aboard the SMM with
poor spatial resolution. The Soft X-ray Telescope on SOLAR-A can see
them with both kinds of resolution improved by an order of magnitude,
provided that it images large enough field of view. Three kinds of
structures are of particular interest: (a) Loops that interconnect
active regions, even on opposite hemispheres. Observations of their
birth may provide information both on the basic characteristics of solar
activity and on solar atmospheric processes (reconnection). Their
brightenings, losely related to flares, could contribute to our
knowledge of instabilities in the solar corona. (b) Flaring arches
inside active regions. They appear in extensive coronal structures
which may exist for days and intermittently brighten in association
with intense X-ray bursts. (c) Giant arches which appear for many hours
high in the corona after dynamic flares. Their structure, mode of birth,
and their relation to coronal mass ejections, is presently unknown.
Title: Thermal Structures Associated with Post-Flare Coronal Arches
Authors: Hick, Paul; Svestka, Zdenek
Bibcode: 1987SoPh..108..315H
Altcode:
Shortly after the dynamic flare of 14 ∶ 44 UT on 6 November, 1980,
which initiated the second revival in the sequence of post-flare coronal
arches of 6-7 November, a moving thermal disturbance was observed in
the fine field of view of HXIS. From 15 ∶ 40 UT until about 18 UT,
when it left the field of view, the disturbance rose into the corona,
as indicated by a projected velocity of 7.4 km s-1 in the
south-east direction. The feature was located above the reconnection
region of the dynamic flare and was apparently related to the revived
coronal arch. Observations in the coarse field of view after 18 UT
revealed a temperature maximum in the revived arch, rising with a
velocity of 7.0 km s-1 directly in continuation of the
thermal disturbance. The rise velocity of the disturbance was initially
(at least until 17 ∶ 20 UT) very similar to the rise velocities
observed for the post-flare loop tops of the parent flare. This
suggests that the rise of the reconnection point, in the Kopp and
Pneuman (1976) mechanism responsible for the rise of the loop tops,
also dictates the rise of the disturbance. From energy requirements
it follows that in this phase the disturbed region is still a separate
magnetic `island', thermally isolated from the old arch structure and
the post-flare loops. After 18 UT the rise of the post-flare loop tops
slowed down to 2 km s-1, which is significantly slower than
the rise of the brightness and temperature maxima of the revived arch
in the coarse field of view. Thus in this phase the Kopp and Pneuman
mechanism is no longer directly responsible for the rise of the thermal
structure and the rise possibly reflects the merging of the old and
the new arch structures.
Title: Post-flare coronal arches observed with the SMM/XRP Flat
Crystal Spectrometer
Authors: Hick, Paul; Svestka, Zdenek; Smith, Kermit L.; Strong,
Keith T.
Bibcode: 1987SoPh..114..329H
Altcode:
The phenomenon of post-flare coronal arches, initially discovered with
the Hard X-Ray Imaging Spectrometer (HXIS), was investigated using
observations made with the SMM Flat Crystal Spectrometer (FCS) on 20
through 23 January, 1985. Since these observations were made with
a different type of instrument from HXIS, they provide independent
information on the physical characteristics of the arch phenomenon
and extend our knowledge to lower coronal temperatures.
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: Multi-thermal observations of newly formed loops in a
dynamic flare
Authors: Švestka, Zdeněk F.; Fontenla, Juan M.; Machado, Marcos E.;
Martin, Sara F.; Neidig, Donald F.; Poletto, Giannina
Bibcode: 1987SoPh..108..237S
Altcode:
The dynamic flare of 6 November, 1980 (max ≈ 15:26 UT) developed a
rich system of growing loops which could be followed in Hα for 1.5
hr. Throughout the flare, these loops, near the limb, were seen in
emission against the disk. Theoretical computations of deviations from
LTE populations for a hydrogen atom reveal that this requires electron
densities in the loops close to, or in excess of 1012
cm -3. From measured widths of higher Balmer lines the
density at the tops of the loops was found to be 4 x 1012
cm -3 if no non-thermal motions were present, or 5 ×
1011 cm -3 for a turbulent velocity of ~ 12 km
s -1.
Title: Cooling of a Coronal Flare Loop Through Radiation and
Conduction
Authors: Svestka, Zdenek
Bibcode: 1987SoPh..108..411S
Altcode:
A simple method is proposed for a computation of the cooling of coronal
flare loops by radiation and conduction, for various temperatures,
densities, and lengths of the loops. The relative importance of
conductive and radiative losses is briefly discussed.
Title: Book-Review - Progress in Solar Physics
Authors: de Jager, C.; Svestka, Z.; Jordan, C.
Bibcode: 1987Obs...107..130D
Altcode:
No abstract at ADS
Title: Book-Review - Progress in Solar Physics
Authors: de Jager, C.; Svestka, Z.
Bibcode: 1987Sci...236R1009D
Altcode:
No abstract at ADS
Title: Book Review: Of stars and men: reminiscences of an
astronomer. / Adam Hilger, 1986.
Authors: Svestka, Z.
Bibcode: 1987Ap&SS.133..200S
Altcode: 1987Ap&SS.133..200K
No abstract at ADS
Title: Book reviews
Authors: Dyson, John; Švestka, Zdenêk; Kleczek, Josip
Bibcode: 1987Ap&SS.133..199D
Altcode:
No abstract at ADS
Title: Book reviews
Authors: Hick, Paul; Jackson, B.; Švestka, Zdenek; Křivský, L.
Bibcode: 1987SoPh..108..201H
Altcode:
No abstract at ADS
Title: Book-Review - Astronomy and Astrophysics Abstracts V.42:2
Authors: Bohme, S.; Esser, U.; Hefele, H.; Heinrich, I.; Hofmann,
W.; Krahn, D.; Matas, V. R.; Schmadel, L. D.; Zech, G.; Svestka, Z.
Bibcode: 1987SoPh..114..193B
Altcode:
No abstract at ADS
Title: Relationships among flare images at different wavelengths
Authors: Svestka, Zdenek F.
Bibcode: 1987SoPh..113...67S
Altcode: 1982SoPh..113...67S
The talk reviews briefly historical development of the imaging of the
Sun, and flare imaging in particular, at different wavelengths. The
present state is then critically analyzed, emphasizing and demonstrating
problems related to simultaneity of observed data, differences in time
resolution, limitations of the imaged field of view, unequal spatial
resolution, and alignment of the images. Prospects for the future are
briefly sketched, including imaging in very hard X-rays and γ-rays.
Title: Flaring arches
Authors: Martin, Sara F.; Švestka, Zdenek F.
Bibcode: 1987SoPh..113..303M
Altcode: 1982SoPh..113..303M
No abstract at ADS
Title: Solar and Interplanetary Observations of the Mass Ejection
on 7 May 1979
Authors: Jackson, B. V.; Rompolt, B.; Svestka, Z.
Bibcode: 1987sowi.conf..272J
Altcode:
No abstract at ADS
Title: Book Review: Transactions of the IAU, Vol. XIXB. / Reidel,
1986.
Authors: Svestka, Z.
Bibcode: 1987SoPh..108..202S
Altcode:
No abstract at ADS
Title: Interplanetary Effects of Coronal Mass Ejections
Authors: Hildner, E.; Bassi, J.; Bougeret, J. L.; Duncan, R. A.;
Gary, D. E.; Gergely, T. E.; Harrison, R. A.; Howard, R. A.; Illing,
R. M. E.; Jackson, B. V.; Kahler, S. W.; Kopp, K.; Low, B. C.; Lantos,
P.; Phillips, K. J. H.; Poletto, G.; Sheeley, N. R., Jr.; Steward,
R. T.; Svestka, Z.; Waggett, P. W.; Wu, S. T.
Bibcode: 1986epos.conf.6.52H
Altcode: 1986epos.confF..52H
No abstract at ADS
Title: Initiations of Coronal Mass Ejections
Authors: Hildner, E.; Bassi, J.; Bougeret, J. L.; Duncan, R. A.;
Gary, D. E.; Gergely, T. E.; Harrison, R. A.; Howard, R. A.; Illing,
R. M. E.; Jackson, B. V.; Kahler, S. W.; Kopp, K.; Low, B. C.; Lantos,
P.; Phillips, K. J. H.; Poletto, G.; Sheeley, N. R., Jr.; Steward,
R. T.; Svestka, Z.; Waggett, P. W.; Wu, S. T.
Bibcode: 1986epos.conf.6.27H
Altcode: 1986epos.confF..27H
No abstract at ADS
Title: The Slowly Varying Corona Near Solar Activity Maximum
Authors: Hildner, E.; Bassi, J.; Bougeret, J. L.; Duncan, R. A.;
Gary, D. E.; Gergely, T. E.; Harrison, R. A.; Howard, R. A.; Illing,
R. M. E.; Jackson, B. V.; Kahler, S. W.; Kopp, K.; Low, B. C.; Lantos,
P.; Phillips, K. J. H.; Poletto, G.; Sheeley, N. R., Jr.; Steward,
R. T.; Svestka, Z.; Waggett, P. W.; Wu, S. T.
Bibcode: 1986epos.conf.6.57H
Altcode: 1986epos.confF..57H
No abstract at ADS
Title: Modelling of Coronal Mass Ejections and POST Flare Arches
Authors: Hildner, E.; Bassi, J.; Bougeret, J. L.; Duncan, R. A.;
Gary, D. E.; Gergely, T. E.; Harrison, R. A.; Howard, R. A.; Illing,
R. M. E.; Jackson, B. V.; Kahler, S. W.; Kopp, K.; Low, B. C.; Lantos,
P.; Phillips, K. J. H.; Poletto, G.; Sheeley, N. R., Jr.; Steward,
R. T.; Svestka, Z.; Waggett, P. W.; Wu, S. T.
Bibcode: 1986epos.conf6.366H
Altcode: 1986epos.confF.366H
No abstract at ADS
Title: Book-Review - Progress in Solar Physics
Authors: de Jager, C.; Svestka, Z.
Bibcode: 1986S&T....72R.479D
Altcode:
No abstract at ADS
Title: Flaring Arches in Hα and X-Rays
Authors: Martin, S. F.; Svestka, Z.
Bibcode: 1986BAAS...18Q.898M
Altcode:
No abstract at ADS
Title: X-ray imaging of flare loops and coronal arches
Authors: Svestka, Z.
Bibcode: 1986sfcp.nasa...41S
Altcode:
HXIS (Hard X-ray Imaging Spectrometer) results related to
preflare, flare-decay, and post-flare phases in the solar corona
are summarized. Particularly discussed are miniflares, long-lived
X-ray enhancements along filament channels, flare precursors (some
signifying the flare position, others possibly related to the onset
of mass ejections), growth of post-flare loops, images of sites of
field-line reconnections late in the flare development, giant post-flare
coronal arches with energy contents comparable to coronal transients,
and hot loops interconnecting active regions. The extremely low HXIS
background, in particular, made it possible to discover many new,
previously unknown features in the solar corona. Also emphasized are
some problems that have appeared during the evaluation of HXIS data,
for the benefit of those who plan future hard X-ray imaging experiments.
Title: Coronal interconnection of two active regions observed in
3.5 8.0 keV X-rays
Authors: Farnik, F.; van Beek, H. F.; Svestka, Z.
Bibcode: 1986SoPh..104..321F
Altcode:
Using HXIS data, we have studied the further development of the coronal
arch extending towards the SE above active region No. 17255 in November
1980. The arch, studied originally by Švestka (1984) disappeared
on 10 November (after pronounced revival), but since 9 November HXIS
revealed another arch-like structure towards the SW. We have studied
the development of this new structure which appeared to be most likely
an arch interconnecting AR 17255 with AR 17251, located nearly 30° to
the west. This interconnection revived many times during the following
days with intensity varying with the activity in both active regions. We
have estimated the physical characteristics in this coronal structure
and compared them with observations of interconnecting loops made
at lower energies by Skylab in 1973. The temperature (maximum values
7.5-14 × 106 K) and the density (1.1-5.0 × 109
cm−3) are found to be higher than in the Skylab loops
(a result that could be expected because the HXIS energy range was
harder than that of Skylab) and similar to the values deduced for
the earlier arch system extending to the SE. However, much shorter
decay times of the brightness variations indicate the presence of
conduction in contrast to the SE arch in which conduction was clearly
inhibited. This supports the assumption that the SE and SW coronal
structures were two different phenomena.
Title: Images of Post-Flare Coronal Structures in X-Rays
Authors: Svestka, Z.; Hick, P.
Bibcode: 1986SoPh..104..187S
Altcode:
This is an extended abstract of several papers mentioned in the
references describing extensive coronal structures related to radio
continua and imaged in > 3.5 keV X-rays.
Title: Editorial
Authors: de Jager, Cornelis; Švestka, Zdeněk
Bibcode: 1986SoPh..107..200D
Altcode: 1987SoPh..107..200D
No abstract at ADS
Title: Coronal mass ejection associated with the stationary post-flare
arch of 21 22 May 1980
Authors: McCabe, Marie K.; Švestka, Zdeněk F.; Howard, Russell A.;
Jackson, Bernard V.; Sheeley, Neil R.
Bibcode: 1986SoPh..103..399M
Altcode:
By using a combination of X-ray (HXIS), Hα (Haleakala), white-light
corona (Solwind), and zodiacal light (Helios) images on 21-22 May, 1980
we demonstrate, and try to explain, the co-existence of a coronal mass
ejection with a stationary post-flare coronal arch. The mass ejection
was seen, both by Solwind and Helios, in prolongation of the path of
a powerful spray, whereas the active region filament did not erupt. A
tentative comparison is made with other occurrences of stationary,
or quasi-stationary post-flare coronal arches.
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: White light flares and atmospheric modeling (Working Group
report).
Authors: Machado, M. E.; Avrett, E. H.; Falciani, R.; Fang, C.;
Gesztelyi, L.; Henoux, J. -C.; Hiei, E.; Neidig, D. F.; Rust, D. M.;
Sotirovski, P.; Svestka, Z.; Zirin, H.
Bibcode: 1986lasf.conf..483M
Altcode:
The authors give a short summary of their discussions, and a set
of recommendations which may help in the study of white light flare
emission processes.
Title: Coronal mass ejections and coronal structures.
Authors: Hildner, E.; Bassi, J.; Bougeret, J. L.; Duncan, R. A.;
Gary, D. E.; Gergely, T. E.; Harrison, R. A.; Howard, R. A.; Illing,
R. M. E.; Jackson, B. V.; Kahler, S. W.; Kopp, K.; Low, B. C.; Lantos,
P.; Phillips, K. J. H.; Poletto, G.; Sheeley, N. R., Jr.; Stewart,
R. T.; Svestka, Z.; Waggett, P. W.; Wu, S. T.
Bibcode: 1986NASCP2439....6H
Altcode:
Contents: 1. Introduction. 2. Observations. 3. Initiation of
coronal mass ejections - observations. 4. Modelling of coronal mass
ejections and post-flare arches. 5. Interplanetary effects of coronal
mass ejections. 6. The slowly varying corona near solar activity
maximum. 7. Summary.
Title: X-ray imaging of flare loops and coronal arches.
Authors: Svestka, Z.
Bibcode: 1986NASCP2421...41S
Altcode:
This paper summarizes HXIS results related to preflare, flare-decay,
and post-flare phases in the solar corona. Particularly discussed are
miniflares, long-lived X-ray enhancements along filament channels, flare
precursors (some signifying the flare position, others possibly related
to the onset of mass ejections), growth of post-flare loops, images of
sites of field-line reconnections late in the flare development, giant
post-flare coronal arches with energy contents comparable to coronal
transients, and hot loops interconnecting active regions. The extremely
low HXIS background, in particular, made it possible to discover many
new, previously unknown features in the solar corona. Also emphasized
are some problems that have appeared during the evaluation of HXIS data,
for the benefit of those who plan future hard X-ray imaging experiments.
Title: The physics of solar flares. Proceedings of Symposium 5 of
the COSPARTwenty-sixth Plenary Meeting held in Toulouse, France,
30th June - 11th July 1986.
Authors: de Jager, C.; Svestka, Z.
Bibcode: 1986AdSpR...6f....D
Altcode: 1986AdSpR...6.....D
Observations and theoretical models of solar-flare phenomena
are discussed in reviews and reports presented at the
symposium formally marking the end of the international
Solar-Maximum-Year/Solar-Maximum-Analysis project. Topics examined
include flare buildup, precursors, and onset; the impulsive phase;
the gradual phase; and coronal and interplanetary phenomena.
Title: On the varieties of solar flares.
Authors: Svestka, Zdenek
Bibcode: 1986lasf.conf..332S
Altcode: 1986lasf.symp..332S
An attempt is made to classify flares starting with two axiomatic
assumptions: (1) that a flare is a short-lived release of energy
in consequence of a rearrangement of the magnetic structure, and
(2) the mode of energy release is a reconnection of magnetic field
lines. Somewhat surprisingly, in spite of the enormous diversity
of the flare phenomena, two classes are derived: dynamic flares and
confined flares, where the confined flares may be subdivided in two
subclasses. All the other varieties may be due to differences in
the boundary conditions of the flare process. The paper discusses
the various factors which cause the varieties in flares, and the
association of the two basic types of flares with different kinds of
radiation and with othere active phenomena on the Sun.
Title: Flare build-up study summary
Authors: Gaizauskas, V.; Svestka, Z.
Bibcode: 1986AdSpR...6f...5G
Altcode: 1986AdSpR...6....5G
No abstract at ADS
Title: Progress in solar physics : review papers invited to celebrate
the centennial volume of Solar physics
Authors: de Jager, Cornelis; Svestka, Zdenek
Bibcode: 1986pspr.book.....D
Altcode: 1986QB521.6.P76....
No abstract at ADS
Title: A dynamic flare with anomalously dense flare loops
Authors: Svestka, Z.; Fontenla, J. M.; Machado, M. E.; Martin, S. F.;
Neidig, D. F.; Poletto, G.
Bibcode: 1986AdSpR...6f.253S
Altcode: 1986AdSpR...6..253S
The dynamic flare of 6 November 1980 (max. ~ 15:26 UT) developed a
rich system of growing loops which could be followed in Hα for 1.5
hours. Throughout the flare, these loops, near the limb, were seen in
emission against the disk. Theoretical computations of b-values for
a hydrogen atom reveal that this requires electron densities in the
loops to be close to 1012 cm-3. From measured
widths of higher Balmer lines the density at the loops of the loops
was found to be 4 × 1012 cm-3 if no non-thermal
motions were present. It is now general knowledge that flare loops
are initially observed in X-rays and become visible in Hα only after
cooling. For such a high density a loop would cool through radiation
from 107 K to 104 K within a few minutes so that
the dense Hα loops should have heights very close to the heights of
the X-ray loops. This, however, contradicts the observations obtained by
the HXIS and FCS instruments on board SMM which show the X-ray loops at
much higher altitudes than the loops in Hα. Therefore, the density must
have been significantly smaller when the loops were formed and the flare
loops were apparently both shrinking and becoming denser while cooling.
Title: The stationary post-flare arch of May 21/22, 1980
Authors: Hick, P.; Svestka, Z.
Bibcode: 1985SoPh..102..147H
Altcode:
On May 21/22, 1980 the Hard X-Ray Imaging Spectrometer aboard the
SMM imaged an extensive coronal structure after the occurrence of a
two-ribbon flare on May 21, 20:50 UT. The structure was observed from
22:20 UT on May 21 until its disappearence at 09:00 UT on May 22.
Title: 21 May 1980 flare review
Authors: de Jager, C.; Svestka, Z.
Bibcode: 1985SoPh..100..435D
Altcode:
A review is given of observations and theories relevant to the
solar flare of 21 May, 1980, 20 ∶ 50 UT, the best studied flare
on record. For more than 30 hr before the flare there was filament
activation and plasma heating to above 10 MK. A flare precursor
was present ≥6 min before the flare onset. The flare started with
filament activation (20 ∶ 50 UT), followed by thick-target heating
of two footpoints and subsequent ablation and convective evaporation
involving energies of 1 to 2 × 1031 erg. Coronal explosions
occurred at 20 ∶ 57 UT (possibly associated with a type-II burst)
and at 21 ∶ 04 UT (associated with an Hα spray?). Post-flare loops
were first seen at 20 ∶ 57 UT, and their upward motion is interpreted
as a manifestation of successive field-line reconnections. A type-IV
radio burst which later changed into a type-I noise storm was related
to a giant coronal arch located just below the radio noise storm
region. Some implications and difficulties these observations present
to current flare theories are mentioned.
Title: Hard X-ray images of possible reconnection in the flare of
21 May, 1980
Authors: Svestka, Z.; Poletto, G.
Bibcode: 1985SoPh...97..113S
Altcode:
An analysis of the growth of X-ray loops in the flare of 21 May, 1980,
observed by HXIS on board SMM spacecraft, has been carried out with
high time resolution in six energy channels from 3.5 to 30 keV. This
analysis has revealed that the tops of the loops stay for minutes at a
given altitude before, quite abruptly, other loop tops begin to appear
above them. One of the jumps in altitude, from ∼27 000 to ∼45
000 km if the loops extended radially, which occurred quite late in
the flare development, is studied in detail. The fact that the tops,
of higher loops were first seen in the 22-30 keV energy channel, and
only minutes later at lower energies, suggests a new release of energy
in a very small volume high in the corona. An initial temperature of
at least 50 × 106 K is indicated by the data, inside a
volume which may not exceed a few hundred km in diameter. A magnetic
reconnection of previously distended field lines appears to be a likely
candidate for the observed phenomenon.
Title: Images of a Major Compact Flare in Hard X-rays and H-alpha
Authors: Svestka, Z.; Martin, S. F.
Bibcode: 1985BAAS...17..628S
Altcode:
No abstract at ADS
Title: Book-Review - Astronomy and Astrophysics Abstracts
Authors: Bohme, S.; Svestka, Z.
Bibcode: 1984SoPh...94..427B
Altcode:
No abstract at ADS
Title: Book reviews
Authors: Valníček, B.; Švestka, Zdeněk
Bibcode: 1984SoPh...94..427V
Altcode:
No abstract at ADS
Title: Revivals of a Coronal Arch
Authors: Svestka, Z.
Bibcode: 1984SoPh...94..171S
Altcode:
The giant post-flare arch of 6 November 1980 revived 11 hr and 25 hr
after its formation. Both these revivals were caused by two-ribbon
flares with growing systems of loops. The first two brightenings of
the arch were homologous events with brightness maxima moving upwards
through the corona with rather constant speed; during all three
brightenings the arch showed a velocity pattern with two components:
a slow one (8-12 km−1), related to the moving maxima of
brightness, and a fast one (∼ 35 km s−1), the source
of which is unknown.
Title: Hα and Hard X-Ray Development in Two-Ribbon Flares
Authors: Dwivedi, B. N.; Hudson, H. S.; Kane, S. R.; Svestka, Z.
Bibcode: 1984SoPh...90..331D
Altcode:
Morphological features of two-ribbon flares have been studied, using
simultaneous ISEE-3 hard X-ray records and high-resolution Big Bear
Hα movies for more than 20 events. Long-lasting and complex hard
X-ray bursts are almost invariably found associated with flares of the
two-ribbon type. We find at least three events, namely March 31, 1979,
April 10, 1980, and July 1, 1980, where the occurrence of individual
spikes in hard X-ray radiation coincides with suddenly enhanced Hα
emission covering the sunspot penumbra. There definitely exist important
(≥ 1B) two-ribbon Hα flares without significant hard X-ray emission.
Title: Imaging of reconnection processes in hard X-rays
Authors: Švestka, Zdenek; Poletto, Giannina
Bibcode: 1984AdSpR...4g.287S
Altcode: 1984AdSpR...4Q.287S
The Hard X-ray Spectrometer aboard the SMM detected several events of
energy release late in the development of two-ribbon flares. One such
event, at 21:12 UT on 21 May, 1980 (~ 20 min after the flare onset and
15 min after the peak of the impulsive phase) is studied in detail. The
site of new brightening first became visible in hard X-rays (> 22
keV) and only afterwards showed up at lower energies. It was clearly
located high in the corona so that one can identify it with energy
release at the tops of newly formed post-flare loops. Thus, if the
Kopp and Pneuman model of the loop formation is adopted, we may have
imaged here a reconnection process in the solar corona. An attempt is
made to estimate physical parameters at the reconnection site.
Title: Post-flare thermal waves in the solar corona
Authors: Svestka, Z.
Bibcode: 1984AdSpR...4g.179S
Altcode: 1984AdSpR...4..179S
While imaging giant post-flare arches in the solar corona, the Hard
X-Ray Spectrometer aboard the SMM detected thermal disturbances
propagating through the corona after two-ribbon flares. The speed
of propagation is close to, or below, 10 km s-1, and no
obvious time-variation of the speed is indicated in the HXIS data. For
subsequent two-ribbon flares in the same active region, these thermal
disturbances (waves) exhibit highly homologous properties; thus the
waves appear to propagate through preexisting arches formed after
earlier flares. Temperatures of > 20 × 106 K have been
detected in these moving phenomena. We suggest that we see here in
X-rays upper products of the consecutive reconnections which create
the post-flare loops below. Temperature maps in fine field of view
of HXIS offer now a new possibility to detect postflare arches in the
corona built during two-ribbon flares.
Title: Large post-flare arch-like structures in the solar corona
Authors: Svestka, Z.
Bibcode: 1984MmSAI..55..725S
Altcode:
Hard (3.5-10-keV) X-ray observations of large archlike structures in the
solar corona, obtained with the SMM HXIS after two-ribbon flares on May
22 and November 6, 1980 (Svestka et al., 1982), are presented in maps
and graphs along with Culgoora radioheliograph, Bonn radio-telescope,
Nancay radio-interferometer, and GOES-2 X-ray data and analyzed using a
theoretical model of postflare loop formation by sequential reconnection
of distended field lines (Kopp and Pneuman, 1976). Stationary or
slowly expanding arches of temperature 2 x 10 to the 7th K or more,
with thermal disturbances propagating upward at about 10 km/s, are
observed in association with type I radio noise storms for periods of
10 h or more. The quasi-periodic X-ray and radio flux variations seen
above and below the arches in the later stages are attributed to the
transition from a system of interconnected loops along the neutral
line to groups of isolated plasmoids with repetitive instabilities.
Title: Enhanced X-Ray Emission above 3.5-KEV in Active Regions in
the Absence of Flares
Authors: Schadee, A.; de Jager, C.; Svestka, Z.
Bibcode: 1983SoPh...89..287S
Altcode:
We demonstrate that even in the absence of flares there are very
often volumes of hot plasma in the corona above active regions with
temperatures in excess of 10 million degrees. Characteristics of
this hot plasma and its time variations seem to be different in
active regions of different phase of development. These hot plasma
regions are sources of very weak, but clearly recognizable, X-ray
emission above 3.5 keV. Long-lived X-ray brightenings, 104
times weaker than a flare, but lasting up to 10 hr occur predominantly
along the H∥ = 0 line, apparently low in the corona. After
major flares, long-lived X-ray emission is also radiated from tops of
arches extending high into the corona. Some other long-lived sources,
far from the H∥ = 0 line, may be associated with newly
emerging flux. Short-lived X-ray sources, with fluxes ranging from
subflare levels to 10−3 times the flare flux, last for
2 to more than 30 min and are probably microflares. They seem to be
most frequent in growing young active regions and appear often in
areas with newly emerging flux.
Title: Radio, X-ray, and optical observations of the flare of June
13, 1980, at 6h22m UT
Authors: Kattenberg, A.; Allaart, M.; de Jager, C.; Schadee, A.;
Schrijver, J.; Shibasaki, K.; Švestka, Z.; van Tend, W.
Bibcode: 1983SoPh...88..315K
Altcode:
A subflare of importance Sf was observed on June 13, 1980 simultaneously
by instruments aboard the Solar Maximum Mission (SMM) and various
ground based observatories. We describe and compare different kinds
of observations, with emphasis on the Hard X-Ray Imaging Spectrometer
(HXIS) images and spectra, and on the one-dimensional microwave images
with high time and spatial resolution, obtained with the Westerbork
Synthesis Radio Telescope (WSRT). The fast electrons causing the X-ray
and microwave impulsive bursts had a common acceleration source, but the
burst were produced at the opposite footpoints of the loops involved,
with microwaves emitted near to a sunspot penumbra. The flare (of a
`compact' type) was probably triggered by an emerging flux, and two
possible interpretations of this process are briefly discussed.
Title: Transient brightenings of interconnecting
loops. III. Interpretation.
Authors: Spicer, D. S.; Svestka, Z.
Bibcode: 1983SoPh...87..271S
Altcode:
We present two alternative interpretations of the sudden X-ray
brightenings observed in loops that interconnect active regions. A
fast tearing mode may be excited in those newly formed interconnecting
loops within which sufficient magnetic free energy is stored to drive
the mode. Alternatively anomalous Joule heating driven by an inductive
electric field parallel to the magnetic field varying on a time scale
of order of a minute may cause the brightenings. We argue that it is
plausible that the fast tearing mode may be the cause of brightenings
in the young newly formed interconnecting loops, whereas the anomalous
Joule heating might occur in old loop connections when an external
disturbance propagates through them.
Title: POST Flare Coronal Arches
Authors: Svestka, Z.
Bibcode: 1983SSRv...35..259S
Altcode:
The Hard X-ray Imaging Spectrometer aboard the SMM detected gigantic
arches in the corona which are formed or, if preexisting, become
excited after major two-ribbon flares. They are seen in 3.5 8 keV
X-rays and extend along the H ∥ = 0 line to altitudes
between 105 and 2 × 105 km. These arches are
stationary and form the base of a stationary type I radio noise storm
initiated by the flare. They are visible in X-rays for ten hours or
more and may be revived, in temperature, density, and brightness, if
another two-ribbon flare appears below them. We suggest that they are
built-up through reconnection process during the flare from the upper
reconnected loops in the Kopp and Pneuman model. These loops become
interconnected along the H ∥ = 0 line in consequence
of great shear of the reconnecting loops. Obviously, the coronal
transient associated with such flares must be either accomplished prior
to the formation of the arch, or it must be formed through a process
different from the Anzer-Kopp-Pneuman mechanism. Striking brightness
variations occur quasi-periodically in the corona below and above
the arch a few hours after the flare. These variations are seen at
about the same time in soft X-rays, hard X-rays, and on centimeter
microwaves in the low corona, as well as at metric waves in the type
I noise-storm region. In spite of their flare-like intensity, however,
the variations have little response in the transition layer (O v line)
and no response at all in the chromosphere (Hα). We suggest that
these semi-periodic brightenings are due to repetitive acceleration
processes in plasmoids that encircle the arch perpendicular to the H
∥ = 0 line from the low corona through the noise storm
region, being completely detached from the lower atmospheric layers.
Title: Pre-Flare and Post-Flare X-Ray Variations in Active Regions
Authors: Svestka, Z.; Schadee, A.
Bibcode: 1983SoPh...86..267S
Altcode:
Extremely low background noise of the HXIS experiment aboard the SMM
made it possible to detect > 3.5 keV X-ray emissions from non-flaring
active regions which are 103-104 times weaker than
the X-ray flux from flares. Short-lived X-ray bursts and long-lived
X-ray enhancements of various intensities seem to characterize active
regions in different phases of their development. After major two-ribbon
flares, giant X-ray arches are seen in the corona, slowly decaying for
many hours after the flare end. Associated with these arches appear
to be quasi-periodic flare-like variations of purely coronal nature.
Title: Purely Coronal Flare-Like Variations
Authors: Svestka, Z.; Schrijver, J.; Somov, B.; Dennis, B. R.;
Woodgate, B. E.; Fuerst, E.; Hirth, W.; Klein, L.; Raoult, A.
Bibcode: 1983SoPh...85..313S
Altcode:
A detailed study of the quasi-periodical post-flare variations on
November 6, 1980 in X-rays, UV lines, microwaves, and metric waves
confirms that these variations were predominantly thermal phenomena
and occurred solely in the corona. Only the short-lived impulsive
components that preceded all or most of the individual variations
were of non-thermal character and penetrated down to the transition
layer. The chromosphere (in Hα) did not participate in any part of
these events, in contrast to a flare that appeared at the same place a
few hours later. However, the X-ray emission of these variations was
so strong that the transition layer and the chromosphere definitely
should have been enhanced through heat conduction along the magnetic
field lines. The expected heat flux at the top of the chromosphere
coming from some of these coronal brightenings was 60-80% of the flux
expected in the flare at 17:26 which gave rise to a 2B flare in Hα
(Figure 8). Therefore, we suggest that the variations were produced in
a coronal plasmoid with closed field lines completely detached from the
lower atmospheric layers (Figure 9b). We also give reasons why such a
detached plasmoid can be expected to be formded in the very late phase
(some 4-5 hr after the onset) of a major two-ribbon flare.
Title: The Queen's Flare - its Structure and Development - Precursors
Pre-Flare Brightenings and Aftermaths
Authors: de Jager, Cornelis; Machado, Marcos E.; Schadee, Aert;
Strong, Keith T.; Švestka, Zdeněk; Woodgate, Bruce E.; van Tend, W.
Bibcode: 1983SoPh...84..205D
Altcode:
We continue previous research on the limb flare of 30 April, 1980, 20:20
UT, observed in X-rays by several instruments aboard the Solar Maximum
Mission (SMM). It is shown quantitatively that the flare originated in
an emerging magnetically confined kernel (diameter ∼ 20″) which
existed for about ten to fifteen minutes, and from which energetic
electrons streamed, in at least two injections, into a previously
existing complicated magnetic loop system thus forming a less bright but
extended and long-lived tongue. The tongue had a length of ∼ 35 000 km
and lasted ∼ 90 min in X-rays (∼ 10 keV); at lower energies (∼ 0.7
keV) it was larger (∼ 80 000 km) and lasted longer. The total number
of energetic electrons (≈ 1037) initially present in the
kernel is of the same order as the number present in the tongue after
the kernel's decline. This gives evidence that the energetic electrons
in the tongue originated mainly in the kernel. The electron number
densities in the kernel and tongue at maximum brightness were ∼ 4.5
× 1011 and ∼ 1 × 1011 cm#X2212;3,
respectively. During the first eight minutes of its existence the tongue
was hotter than the kernel, but it cooled off gradually. Its decline in
intensity and temperature was exponential; energy was lost by radiation
and by conduction through the footpoints of the loop system. These
footpoints have a cross-section of only ∼ 3 × 106
km2. This small value, as well as photographs in a CIV UV
emission line, suggests a highly filamentary structure of the system;
this is further supported by the finding that the tongue had a `filling
factor' of ∼ 10#X2212;2. Several faint X-ray brightenings
(≲ 0.005 of the flare's maximum intensity) were observed at various
locations along the solar limb for several hours before and after the
flare. At ∼ 30 min before the flare's onset a faint (≲ 0.02) flare
precursor occurred, coinciding in place and shape with the flare. First
the kernel precursor was brightest but the tongue precursor increased
continuously in brightness and was the brightest part of the precursor
some 10-15 min after the first visibility of the kernel precursor,
until the start of the main flare. This suggests (weak) continuous
electron acceleration in the tongue during a period of at least 30
min. The main flare was caused by strong emergence of magnetic field
followed by two consecutive field line reconnections and accelerations
in a small loop system, causing footpoint heating. Subsequently plasma
streamed (convectively) into a pre-existing system of larger loops,
forming the tongue.
Title: 3.5 keV X-ray Emission in Absence of Flares
Authors: Schadee, A.; de Jager, C.; Svestka, Z.
Bibcode: 1983BAAS...15R.704S
Altcode:
No abstract at ADS
Title: Revival of a Coronal Arch
Authors: Svestka, Z.
Bibcode: 1983BAAS...15..714S
Altcode:
No abstract at ADS
Title: Particle acceleration in two-ribbon flares.
Authors: Švestka, Z.
Bibcode: 1983POEM...14...69S
Altcode:
The author points out the basic differences between compact and
two-ribbon flares, and discusses observations indicating particle
acceleration during a long-enduring reconnection process in the
two-ribbon flares.
Title: Particle acceleration in two-ribbon flares
Authors: Svestka, Z.
Bibcode: 1983ebro.conf...69S
Altcode:
Particle acceleration during a long reconnection process in two-ribbon
flares is discussed. The evolution in the understanding of solar
flares is summarized, pointing out the contributions of the Skylab
mission and other satellite observation missions. A model of a
two-ribbon flare is described. Particle acceleration is associated
with magnetic reconnection when new loops are formed. Particles are
trapped in the loops and produce the hard X-ray, H alpha and white light
emission. According to the model, particle acceleration in two-ribbon
flares may last for hours, and in filament disruptions, in particular
along the boundaries of growing coronal holes, non negligible particle
fluxes in space may be produced.
Title: Unusual coronal activity following the flare of 6 November 1980
Authors: Švestka, Z.; Dennis, B. R.; Pick, M.; Raoult, A.; Rapley,
C. G.; Stewart, R. T.; Woodgate, B. E.
Bibcode: 1982SoPh...80..143S
Altcode:
For almost 30 hr after the major (gamma-ray) two-ribbon flare on 6
November 1980, 03:30 UT, the Hard X-Ray Imaging Spectrometer (HXIS)
aboard the SMM satellite imaged in > 3.5 keV X-rays a gigantic
arch extending above the active region over the limb. Like a similar
configuration on 22 May 1980, this arch formed the lowest part of a
stationary post-flare radio noise storm recorded at metric wavelengths
at Nançay and Culgoora. 6.5 hr after the flare a coronal region below
the arch started quasi-periodic pulsations in X-ray brightness, observed
by several SMM instruments. These brightness variations had no response
in the chromosphere (Hα), very little in the transition layer (O v),
but they clearly correlated with similar variations in brightness at
169 MHz. There were 13 pulses of this kind, with apparent periodicity
of about 20 min, until another flare occurred in the active region at
∼ 15:00 UT. All the brightenings appeared within a localized area of
about 30000 km2 in the northern part of the active region,
but they definitely did not occur all at the same place.
Title: Study of the Post-Flare Loops on 1973JUL29 - Part Four -
Revision of T and NE Values and Comparison with the Flare of 1980MAY21
Authors: Švestka, Z.; Dodson-Prince, H. W.; Martin, S. F.; Mohler,
O. C.; Moore, R. L.; Nolte, J. T.; Petrasso, R. D.
Bibcode: 1982SoPh...78..271S
Altcode:
We present revised values of temperature and density for the flare
loops of 29 July 1973 and compare the revised parameters with those
obtained aboard the SMM for the two-ribbon flare of 21 May 1980. The 21
May flare occurred in a developed sunspot group; the 29 July event was a
spotless two-ribbon flare. We find that the loops in the spotless flare
extended higher (by a factor of 1.4-2.2), were less dense (by a factor
of 5 or more in the first hour of development), were generally hotter,
and the whole loop system decayed much slower than in the spotted flare
(i.e. staying at higher temperature for a longer time). We also align
the hot X-ray loops of the 29 July flare with the bright Hα ribbons
and show that the Hα emission is brightest at the places where the
spatial density of the hot elementary loops is enhanced.
Title: Observations of a POST Flare Radio Burst in X-Rays
Authors: Svestka, Z.; Hoyng, P.; van Tend, W.; Boelee, A.; de Jager,
C.; Stewart, R. T.; Acton, L. W.; Bruner, E. C.; Gabriel, A. H.;
Rapley, C. G.; de Jager, C.; LaFleur, H.; Nelson, G.; Simnett, G. M.;
van Beek, H. F.; Wagner, W. J.
Bibcode: 1982SoPh...75..305S
Altcode:
More than six hours after the two-ribbon flare of 21 May 1980, the
hard X-ray spectrometer aboard the SMM imaged an extensive arch above
the flare region which proved to be the lowest part of a stationary
post-flare noise storm recorded at the same time at Culgoora. The X-ray
arch extended over 3 or more arc minutes to a projected distance of
95 000 km, and its real altitude was most probably between 110 000
and 180 000 km. The mean electron density in the cloud was close to
109 cm−3 and its temperature stayed for many
hours at a fairly constant value of about 6.5 × 106 K. The
bent crystal spectrometer aboard the SMM confirms that the arch emission
was basically thermal. Variations in brightness and energy spectrum at
one of the supposed footpoints of the arch seem to correlate in time
with radio brightness suggesting that suprathermal particles from
the radio noise regions dumped in variable quantities into the low
corona and transition layer; these particles may have contributed to
the population of the arch, after being trapped and thermalized. The
arch extended along the H∥ = 0 line thus apparently
hindering any upward movement of the upper loops reconnected in the
flare process. There is evidence from Culgoora that this obstacle may
have been present above the flare since 15-30 min after its onset.
Title: Solar Maximum Year; Proceedings of the Symposium, Ottawa,
Canada, May 16-June 2, 1982
Authors: Svestka, Z.; Rust, D. M.; Dryer, M.
Bibcode: 1982AdSpR...2k....S
Altcode: 1982AdSpR...2.....S
Results of research conducted during the Solar Maximum Year from
August 1979 to through February 1981 are presented, focusing on flare
build-up, energy release in flares, and travelling interplanetary
phenomena. Topics examined include the relation of solar flares to the
evolution and proper motions of magnetic fields, pre-flare heating of
filaments, mass motions in a quiescent filament, multiple wavelength
observations of flaring active regions, energy transfer in solar flares,
direct evidence for chromosphere evaporation in a well-observed compact
flare, physics of the impulsive phase of solar flares, and the analysis
of ultra-fast fine structures of microwave bursts. Also considered
are the effects of electron-cyclotron masers during flares, high
energy particle acceleration in flares, particle charge interchange
during acceleration in flare regions, diamagnetic aspects of the
coronal transient phenomenon, particle acceleration by coronal and
interplanetary shock waves, and the propagation of energetic particles
in the solar wind. For individual items see A83-35202 to A83-35235
Title: Transient Brightenings of Interconnecting Loops - Part Two -
Dynamics of the Brightened Loops
Authors: Svestka, Z.; Howard, R.
Bibcode: 1981SoPh...71..349S
Altcode:
We discuss three different kinds of dynamic events related to
interconnecting loops observed in soft X-rays aboard Skylab: (1)
A newly born transequatorial loop that was either emerging from
subphotospheric layers or gradually filled in with hot plasma. (2)
Large-scale twists of interconnecting loops which never relax, and
often only form, after the loop brightenings. (3) Three events where
the loop that later interconnected two active regions had been visible
long before one of the interconnecting regions was born. Several impacts
this observation might have upon our understanding of the process of
flux emergence are suggested.
Title: Origin and Location of the Hard X-Ray Emission in a Two-Ribbon
Flare
Authors: Hoyng, P.; Duijveman, A.; Machado, M. E.; Rust, D. M.;
Svestka, Z.; Boelee, A.; de Jager, C.; Frost, K. T.; Lafleur, H.;
Simnett, G. M.; van Beek, H. F.; Woodgate, B. E.
Bibcode: 1981ApJ...246L.155H
Altcode:
No abstract at ADS
Title: On the outburst of flare activity of 26 November, 1973
Authors: Howard, R.; Svestka, Z.
Bibcode: 1981SoPh...71...49H
Altcode:
We draw attention of flare build-up observers to a strong 30 hour-long
outburst of homologous flare activity and unusual growth and brightening
of coronal loops, seen on Skylab. We suggest that these events might
have been closely associated with newly emerging magnetic flux, in
spite of the fact that the flux effects in Hα and EUV were first seen
only late after the activity had started, and the flux emerged at the
opposite end of the coronal loops from where the flares occurred.
Title: Coronal Variations Imaged in 3.5 - 30 keV X-Rays
Authors: Svestka, Z.
Bibcode: 1981BAAS...13..909S
Altcode:
No abstract at ADS
Title: Giant X-Ray Arches Associated with Post-Flare Radio Noise
Storms
Authors: Svestka, Z.; Pick, M.; Rapley, C. G.; Stewart, R. T.;
Woodgate, B.
Bibcode: 1981BAAS...13..555S
Altcode:
No abstract at ADS
Title: X-Ray Observations of Two Different Systems of "Post Flare"
Loops
Authors: Svestka, Z.; Dodson-Prince, H. W.; Mohler, O. C.; Martin,
S. F.; Moore, R. L.; Nolte, J. T.; Petrasso, R. D.
Bibcode: 1981BAAS...13R.542S
Altcode:
No abstract at ADS
Title: The limb flare of 1980 April 30 as seen by the hard X-ray
imaging spectrometer
Authors: van Beek, H. F.; de Jager, C.; Schadee, A.; Svestka, Z.;
Boelee, A.; Duijveman, A.; Galama, M.; Hoekstra, R.; Hoyng, P.; Fryer,
R.; Simnett, G. M.; Imhof, J. P.; LaFleur, H.; Maseland, H. V. A. M.;
Mels, W. M.; Schrijver, J.; van der Laan, J. J. M.; van Rens, P.; van
Tend, W.; Werkhoven, F.; Willmore, A. P.; Wilson, J. W. G.; Machado,
M. E.; Zandee, W.
Bibcode: 1981ApJ...244L.157V
Altcode:
X-ray imaging of the limb event of 1980 April 30 shows that the flaring
involved two distinct components: a pointlike component, which was the
source of the initial hard X-ray burst and an extensive tongue reaching
some 30,000 km above the limb. The tongue had a higher temperature
than the other parts of the structure and seemed to be enhanced by
energetic electrons that derived their energy from the initial source.
Title: Introduction
Authors: De Jager, Cornelis; Švestka, Zdeněk
Bibcode: 1981SoPh...72D...7D
Altcode:
No abstract at ADS
Title: Book-Review - Astronomy and Astrophysics Abstracts V.25
& 26
Authors: Bohme, S.; Esser, U.; Fricke, W.; Svestka, Z.
Bibcode: 1981SoPh...69..419B
Altcode:
No abstract at ADS
Title: Book review
Authors: Švestka, Z.
Bibcode: 1981SoPh...69..419S
Altcode:
No abstract at ADS
Title: Structural development of the X-ray limb flare of 30 April 1980
Authors: de Jager, C.; Hoyng, P.; Lafleur, H.; Schadee, A.; Svestka,
Z.; van Beek, H. F.; van Tend, W.; Fryer, R.; Simnett, G. M.
Bibcode: 1981AdSpR...1m.251D
Altcode: 1981AdSpR...1..251D
We describe the development of the limb flare of 30 April 1980, 20:20
UT, as observed by the Hard X-ray Imaging Spectrometer (HXIS) aboard
the Solar Maximum Mission (SMM). It consisted of a short-lived bright
nucleus (FWHM < 10,000 km), just inside the Sun's limb; a longer
lasting tongue, extending to a height of ~ 30,000 km, and a more
complicated feature, approximately situated at the Sun's limb. The
tongue was a pre-existing magnetic structure that started emitting
X-rays only a few seconds after the bright nucleus, and which had a
slightly higher temperature than the nucleus; its X-ray emission may
be caused by electrons escaped from the nucleus.
Title: Solar maximum mission experiment: Early results of the hard
X-ray imaging experiment
Authors: Boelee, A.; de Jager, C.; Duijveman, A.; Galama, M.; Hoekstra,
R.; Hoyng, P.; Imhof, J. P.; Lafleur, H.; Maseland, H. V. A. M.; Mels,
W. A.; Schadee, A.; Schrijver, J.; Svestka, Z.; van Beek, H. F.;
van Rens, P.; van der Laan, J. J. M.; van Tend, W.; Werkhoven, F.;
Wiersma, G.; Zandee, W.; Simnett, G. M.; Charlton, C. P.; Fryer, R.;
Willmore, A. P.; Wilson, J. W. G.; Machado, M. E.
Bibcode: 1981AdSpR...1m.255B
Altcode: 1981AdSpR...1R.255B
We have selected four widely different flares from the early
period of operations of the Hard X-Ray Imaging Spectrometer (HXIS)
on SMM to illustrate the characteristic imaging properties of this
experiment. For the small flare of April 4, 1980, we demonstrate the
instrument's capability for locating a compact source. In the weak,
but extensive, flare of April 6 we show how well the instrument can
display spatial structure, and also the low level of the instrument
background. In the 1B flare of April 7 we are able to locate positions
of the X-ray emission in the soft and hard channels, and estimate
the positional variations of the emission patches. Finally, in the IN
flare of April 10, which produced the strongest hard X-ray burst we
have seen so far, we repeat some of the studies made for the April 7
event, and also demonstrate the capability of the HXIS instrument to
study the development, with high time resolution, of individual 8''
× 8'' elements of the flare.
Title: Flare observations
Authors: Svestka, Z.
Bibcode: 1981sfmh.book...47S
Altcode:
The solar flare represents a sudden release of energy in the atmospheric
layers of the sun. In tens of seconds or a few minutes the temperature
rises throughout the solar atmosphere, reaching its peak, often
well above 10 million K, in the solar corona. Flare observations
in the H-alpha light are considered along with chromospheric flare
spectra, thermal flares in soft X-rays, impulsive hard X-ray and
microwave bursts, energy transfer through the transition layer,
metric radio bursts, flare ejecta, and the production and effects of
high-energy particles in flares. Attention is given to the general
characteristics of flares, flare emissions, flare classification,
two-ribbon and compact flares, flare theory, flares in relation to
magnetic fields, flare occurrence, flares in relation to velocity
fields, flare-associated changes in the magnetic field, the EUV
spectrum, the EUV flare morphology and density, and flare waves.
Title: Structural development of the X-ray limb flare of 30 April
1980.
Authors: de Jager, C.; Fryer, R.; Hoyng, P.; Lafleur, H.; Schadee,
A.; Simnett, G. M.; Svestka, Z.; van Beek, H. F.; van Tend, W.
Bibcode: 1981hea..conf..251D
Altcode:
No abstract at ADS
Title: Solar Maximum Mission experiment: early results of the hard
X-ray imaging experiment.
Authors: Simnett, G. M.; Boelee, A.; Charlton, C. P.; de Jager, C.;
Duijveman, A.; Fryer, R.; Galama, M.; Hoekstra, R.; Hoyng, P.; Imhof,
J. P.; Lafleur, H.; Machado, M. E.; Maseland, H. V. A. M.; Mels,
W. A.; Schadee, A.; Schrijver, J.; Svestka, Z.; van Beek, H. F.;
van Rens, P.; van der Laan, J. J. M.; van Tend, W.; Werkhoven, F.;
Wiersma, G.; Willmore, A. P.; Wilson, J. W. G.; Zandee, W.
Bibcode: 1981hea..conf..255S
Altcode:
No abstract at ADS
Title: Hα and Hard X-Ray Development in Two-Ribbon Flares
Authors: Dwivedi, B. N.; Hudson, H. S.; Kane, S. R.; Svestka, Z.
Bibcode: 1980BAAS...12..905D
Altcode:
No abstract at ADS
Title: A Study of the Impulsive Flares and Homologous Flares From
AR2372 From April 6-13, Using Hard X-Ray Images
Authors: Simnett, G. M.; Machado, M.; Harrison, R. A.; Hoyng, P.;
Lafleur, H.; Svestka, Z.; Vanbeek, H. F.
Bibcode: 1980BAAS...12S.899S
Altcode:
No abstract at ADS
Title: The Solar Maximum Year and Related Space Experiments
Authors: Svestka, Z.; de Jager, C.
Bibcode: 1980SSRv...26..317S
Altcode:
The Solar Maximum Year is a world-wide cooperative project to gain
more insight in certain aspects of solar flares. It consists of three
sub-programs: The Flare Build-up Study (FBS), the Study of Energy
Release from Flares (SERF), and the Study of Travelling Interplanetary
Phenomena (STIP). These programs are described. We also describe space
observations to be performed during SMY, particularly the Solar Maximum
Mission Satellite.
Title: Activated Solar Filaments and Flares
Authors: Svestka, Z.
Bibcode: 1980RSPTA.297..575S
Altcode: 1980RSLPT.297..575S
Activations and disruptions of dark Hα filaments are very common
phenomena on the Sun. They precede the most powerful two-ribbon
solar flares, but they also appear far from any active region
without any chromospheric flaring. Therefore, until very recently,
filament disruptions were considered as interesting, but physically
insignificant, flare precursors. Only Skylab observations have shown
that the filament disruptions actually represent one of the basic
and most important mechanisms of solar activity. These observations
have revealed (1) that many coronal transients originate in eruptive
filaments without chromospheric flares, (2) that Bruzek's slow-mode
waves originate in disrupted filaments and not in flares themselves,
and (3) that many coronal X-ray enhancements outside active regions
are also tops of newly formed loops, similar to the post-flare loops
observed after filament disruptions in active regions. An interpretation
of these data stems from Kopp & Pneuman's theory of post-flare
loops: the process that disrupts a filament opens the magnetic field
and causes a greatly enhanced mass-flow along the field lines. The
open field lines subsequently reconnect, starting from the bottom
of the corona and proceeding upwards. This process can last for many
hours. Hot loops are first seen in X-rays, later in extreme ultraviolet
(e.u.v.) lines, and, after an appropriate cooling time, in Hα as the
loop prominence systems. The visibility of loops depends on plasma
density. Several observed properties of solar flares indicate that
the primary acceleration occurs as the field lines reconnect. Thus
the process of particle acceleration in two-ribbon flares can last
for hours. Because reconnection is accomplished after essentially all
filament disruptions, 'disparitions brusques' outside active regions
should also accelerate particles.
Title: The Dynamics of Brightened Interconnecting Loops
Authors: Howard, R.; Svestka, Z.
Bibcode: 1980BAAS...12..519H
Altcode:
No abstract at ADS
Title: Particle acceleration in the process of eruptive opening and
reconnection of magnetic fields
Authors: Svestka, Z.; Martin, S. F.; Kopp, R. A.
Bibcode: 1980IAUS...91..217S
Altcode:
No abstract at ADS
Title: The thermal X-ray flare plasma
Authors: Moore, R.; McKenzie, D. L.; Svestka, Z.; Widing, K. G.; Dere,
K. P.; Antiochos, S. K.; Dodson-Prince, H. W.; Hiei, E.; Krall, K. R.;
Krieger, A. S.
Bibcode: 1980sfsl.work..341M
Altcode: 1980sofl.symp..341M
Following a review of current observational and theoretical knowledge
of the approximately 10 to the 7th K plasma emitting the thermal soft
X-ray bursts accompanying every H alpha solar flare, the fundamental
physical problem of the plasma, namely the formation and evolution of
the observed X-ray arches, is examined. Extensive Skylab observations
of the thermal X-ray plasmas in two large flares, a large subflare and
several compact subflares are analyzed to determine plasma physical
properties, deduce the dominant physical processes governing the plasma
and compare large and small flare characteristics. Results indicate
the density of the thermal X-ray plasma to be higher than previously
thought (from 10 to the 10th to 10 to the 12th/cu cm for large to
small flares), cooling to occur radiatively as much as conductively,
heating to continue into the decay phase of large flares, and the
mass of the thermal X-ray plasma to be supplied primarily through
chromospheric evaporation. Implications of the results for the basic
flare mechanism are indicated.
Title: Gibt es Cluster von Hellen Punkten?
Authors: Kittelberger, G.; Elwert, G.; Svestka, Z.
Bibcode: 1980MitAG..50...96K
Altcode:
No abstract at ADS
Title: The needs for prediction and real-time monitoring for the
flare build-up study
Authors: Svestka, Z.
Bibcode: 1979stp.....2..322S
Altcode:
Similarities between plasma instabilities occurring in
the magnetospheric tail and in active regions on the Sun are
discussed. Intense observations of the flare build-up processes on the
Sun planned for May and June 1980 as a part of the Solar Maximum Year
are described.
Title: Slowly moving disturbances in the X-ray corona.
Authors: Rust, D. M.; Svestka, Z.
Bibcode: 1979SoPh...63..279R
Altcode:
Sequences of soft X-ray pictures, taken aboard Skylab between May
and November, 1973, have made it possible to detect slowly moving
disturbances originating in disrupted filaments and causing subsequent
brightenings of distant coronal structures. With speeds decreasing
from ∼400 km s-1 shortly after the filament disruption to
∼10 km s-1 four or five hours later, these disturbances
appear to be identical with slow waves earlier inferred by Bruzek,
Öhman, and Yajima from chromospheric observations.
Title: Transient brightenings of interconnecting loops. Morphology
of the sudden brightenings.
Authors: Svestka, Z.; Howard, R.
Bibcode: 1979SoPh...63..297S
Altcode:
We study sudden brightenings of coronal loops that interconnect
active regions. Such brightenings often occur within one or two
days after the birth of a new interconnecting loop, as well as
in some old interconnections. The brightenings of young loops are
obviously associated with the emergence of new magnetic flux near their
footpoints, whereas some enhancements of old loops may be triggered by
slowly moving disturbances propagating from other centers of activity. A
few loop brightenings are associated with flares, but the loop does
not brighten in consequence of energy supply from the flare. Both the
flare and the loop brightening are independent consequences of one
common agent, presumably newly emerging flux.
Title: The birthplaces of active regions and X-ray bright points.
Authors: Howard, R.; Fritzova-Svestkova, L.; Svestka, Z.
Bibcode: 1979SoPh...63..105H
Altcode:
A comparison of soft X-ray pictures of the Sun (S-054 experiment of
Skylab) with K-line spectroheliograms (Mount Wilson) shows that the
X-ray bright points tend to emerge randomly throughout the Ca network
pattern. However, all those bright points that developed into active
regions emerged at the boundaries of network cells. This suggests that
the magnetic flux of active regions comes from greater depths in the
convection zone than the shallow flux that gives rise to the random
emergence of bright points.
Title: Study of the post-flare loops on 29 July 1973. II. Physical
parameters in the X-ray loops.
Authors: Petrasso, R. D.; Nolte, J. T.; Gerassimenko, M.; Krieger,
A. S.; Krogstad, R.; Seguin, F. H.; Svestka, Z.
Bibcode: 1979SoPh...62..133P
Altcode:
We use the filter ratio method of analysis to determine spatially
resolved values of plasma parameters in the X-ray emitting post-flare
loop system which developed on 29 and 30 July 1973. We find that
the loops were hotter and had higher plasma pressure at their tops
than near their footpoints. The loop tops were at nearly the same
temperature at different places 3 hr after the flare maximum and were
also at nearly this same temperature 3 and 8 hr later. Variations in
brightness transverse to the loops were due to variations in emission
measure. We show by consideration of radiative losses alone that energy
must have been added to the hottest part of the flare, at the tops of
the loops, late into the decay phase of the flare.
Title: Study of the post-flare loops on 29 July 1973. I. Dynamics
of the x-ray loops.
Authors: Nolte, J. T.; Gerassimenko, M.; Krieger, A. S.; Petrasso,
R. D.; Svestka, Z.
Bibcode: 1979SoPh...62..123N
Altcode:
We derive an empirical model of the X-ray emitting post-flare loops
observed during the decay phase of the 29 July 1973 flare. We find that
the loops are elliptical, with the brightest emitting region at the
tops. We determine the height, velocity of growth, and ratio of height
to width of the loops at times from 3 to 12 hr after the flare onset.
Title: Prominences and Solar Activity.
Authors: Svestka, Z.
Bibcode: 1979phsp.coll..357S
Altcode: 1979phsp.conf..357S; 1979phsp.coll..356S; 1979IAUCo..44..357S
Various aspects of solar prominences are discussed. These include
(1) filament activation, (2) postflare loops, (3) surges and sprays,
(4) coronal transients, (5) disk vs limb observations, (6) solar
cycle variations of prominence occurrence, and (7) active prominences
patrol service.
Title: Slowly-Moving Disturbances in the X-Ray Corona.
Authors: Rust, D. M.; Svestka, Z.
Bibcode: 1979phsp.coll..276R
Altcode: 1979IAUCo..44..276R; 1979phsp.conf..276R
A synoptic movie made from nearly 1000 pictures of the solar X-ray
corona taken by the S-054 X-ray telescope on Skylab has led to
the discovery of disturbances with propagation velocities under
100 km/sec and extending over distances of the order of one solar
radius. The disturbances are revealed as brightened coronal structures
at progressively greater distances from a central point, usually an
active region with an activated or disappearing filament. In a number of
cases these coronal brightenings were accompanied by quiescent filament
disappearances. The inferred coronal velocities and the rates of damping
were found to be in excellent agreement with the velocity curves deduced
by Bruzek (1952), in his slow wave hypothesis, and possibly confirmed
by Oehman and Oehman (1953) and Yajima (1971) to explain the activation
of filaments at great distances from flares. The fact that many of
the events showed little or no flaring associated with the filament
disappearance at onset leads to the conclusion that the source of the
slow disturbances is linked to the initial filament eruption itself,
possibly in restructuring of the magnetic fields or in the coronal
heating that typically accompanies active region filament eruptions.
Title: E. N. Parker first recipient of the George Ellery Hale Prize.
Authors: De Jager, Cornelis; Švestka, Zdeněk
Bibcode: 1978SoPh...60....3D
Altcode: 1978SoPh...60....3.
No abstract at ADS
Title: Low-energy protons: Gradients in interplanetary space and
distribution in the solar corona
Authors: Stevens, G. A.; Vanrooijen, J. J.; Svestka, Z.; De Jager, C.
Bibcode: 1978clus.nasa..234S
Altcode:
First and second order anisotropy measurements are proposed as a tool
for studying the coronal source function and interplanetary propagation
of low energy protons. Optimum orbit and attitude requirements are
suggested for a three telescope system. Some limitations with regard
to the lower energy limit for a feasible set-up are discussed.
Title: Book review
Authors: švestka, Z.
Bibcode: 1978SoPh...57..483S
Altcode: 1978SoPh...57..483.
No abstract at ADS
Title: X-Ray Analysis of the 29 July 1973 Flare.
Authors: Nolte, J.; Geras-Simenko, M.; Krieger, A.; Krogstad, R.;
Petrasso, R.; Seguin, F.; Svestka, Z.
Bibcode: 1978BAAS...10Q.457N
Altcode:
No abstract at ADS
Title: Erratum: "Development of a complex of activity in the solar
corona" [Sol. Phys., Vol. 54, p. 65 - 105 (1977)].
Authors: Howard, R.; Svestka, Z.
Bibcode: 1978SoPh...56..471H
Altcode:
No abstract at ADS
Title: Editorial
Authors: De Jager, Cornelis; Švestka, Zdeněk
Bibcode: 1978SoPh...56....3D
Altcode: 1978SoPh...56....3.
No abstract at ADS
Title: Do changes in coronal emission structure imply magnetic
reconnection?
Authors: Nolte, J. T.; Gerassimenko, M.; Krieger, A. S.; Petrasso,
R. D.; Svestka, Z.; Wentzel, D. G.
Bibcode: 1977SoPh...55..401N
Altcode:
We examine three major possible interpretations of observed
reconfigurations of coronal X-ray and XUV emitting structures on a scale
comparable to the size of the structures themselves. One possibility
is that little change in the large-scale magnetic field configuration
is associated with the change in emission. The other two possibilities
are processes by which the magnetic field structure can change.
Title: Open magnetic fields in active regions.
Authors: Svestka, Z.; Solodyna, C. V.; Howard, R.; Levine, R. H.
Bibcode: 1977SoPh...55..359S
Altcode:
Soft X-ray observations confirm that some of the dark gaps seen between
interconnecting loops and inner cores of active regions may be loci of
open fields, as it has been predicted by global potential extrapolation
of photospheric magnetic fields. It seems that the field lines may
open only in a later state of the active region development.
Title: Development of a complex of activity in the solar corona.
Authors: Howard, R.; Svestka, Z.
Bibcode: 1977SoPh...54...65H
Altcode:
Skylab observations of the Sun in soft X-rays gave us the first
possibility to study the development of a complex of activity in the
solar corona during its whole lifetime of seven solar rotations. The
basic components of the activity complex were permanently interconnected
(including across the equator) through sets of magnetic field lines,
which suggests similar connections also below the photosphere. However,
the visibility of individual loops in these connections was greatly
variable and typically shorter than one day. Each brightening of
a coronal loop in X-rays seems to be related to a variation in the
photospheric magnetic field near its footpoint. Only loops (rarely
visible) connecting active regions with remnants of old fields can be
seen in about the same shape for many days. The interconnecting X-ray
loops do not connect sunspots.
Title: Introductory Talk (Proceedings of the Meeting `How Can Flares
be Understood?', held during the 16th General Assembly of the IAU
in Grenoble, France, on 27 August, 1976.)
Authors: Švestka, Zdeněk
Bibcode: 1977SoPh...53..221S
Altcode:
No abstract at ADS
Title: Transequatorial loops interconnecting McMath regions 12472
and 12474.
Authors: Svestka, Z.; Krieger, A. S.; Chase, R. C.; Howard, R.
Bibcode: 1977SoPh...52...69S
Altcode:
We discuss the life-story of a transequatorial loop system which
interconnected the newly born active region McMath 12474 with the old
region 12472. The loop system was probably born through reconnection
accomplished 1.5 to 5 days after the birth of 12474 and the loops were
observed in soft X-rays for at least 1.5 days. Transient `sharpenings'
of the interconnection and a striking brightening of the whole loop
system for about 6 hr appear to be caused by magnetic field variations
in the region 12474. A flare might have been related to the brightening,
but only in an indirect way: the same emerging flux could have triggered
the flare and at the same time strengthened the magnetic field at the
foot-points of the loops. Electron temperature in the loop system,
equal to 2.1 × 106 K in its quiet phase, increased to
3.1 × 106 K during the brightening. Electron density in
the loop system was ≤ 1.3 × 109 cm−3 and
it could be estimated to ∼7 × 108 cm−3
prior to the brightening. During the brightening the loops became
twisted. There was no obvious effect whatsoever of the activity in
12474 upon the in erconnected old region. The final decay of the loop
system reflected the decay of magnetic field in the region 12474.
Title: Book reviews
Authors: Švestka, Z.
Bibcode: 1977SoPh...52..229S
Altcode:
No abstract at ADS
Title: Slowly Moving X-Ray Disturbances from Flares.
Authors: Rust, D. M.; Svestka, Z.
Bibcode: 1977BAAS....9..329R
Altcode:
No abstract at ADS
Title: Open Magnetic Fields in Active Regions.
Authors: Svestka, Z.; Solodyna, C. V.; Howard, R.; Levine, R. H.
Bibcode: 1977BAAS....9Q.344S
Altcode:
No abstract at ADS
Title: Solar Flares (Book Review)
Authors: Svestka, Z.
Bibcode: 1977ApL....18..175S
Altcode:
No abstract at ADS
Title: Low-energy particle events associated with sector boundaries.
Authors: Svestka, Z.; Fritzova-Svestkova, L.; Nolte, J. T.;
Dodson-Prince, H. W.; Hedeman, E. R.
Bibcode: 1976SoPh...50..491S
Altcode:
Onsets of some 40 to 45 low-energy proton events during the years
1957-1969 coincided in time with transits of well-defined sector
boundaries across the Earth. These events can be interpreted as
long-lived proton streams filling up some of the magnetic sectors,
indicating an acceleration of protons which is not associated with
typical proton-producing flares. The sharp onsets of these particle
streams, as well as a deficiency of flare-associated particle events
shortly before the boundary transit, indicate that in some cases
magnetic sector boundaries can inhibit transverse propagation of
low-energy particles in the solar corona or in interplanetary space.
Title: On the occurrence of sympathetic flares.
Authors: Fritzova-Svestkova, L.; Chase, R. C.; Svestka, Z.
Bibcode: 1976SoPh...48..275F
Altcode:
We have tried to determine whether statistical evidence on the
occurrence of sympathetic flares, which is negative for whole-disk data,
can be found for particular, physically connected, pairs of active
regions. Recently, Simnett (1974) and Gergely and Erickson (1975)
claimed to have found such evidence, but their results were based on
incorrect computations of the random incidence of flares. If the correct
formula is applied, the supposed evidence disappears. The results
are negative also for pairs of active regions interconnected with
magnetic loops visible in soft X-rays during the Skylab mission. The
only positive result (with statistical confidence of 3.4 σ) is found
for pairs of active regions, which are closer than 30° to each
other, without specifying any kind of physical relationship. For
such pairs of regions the occurrence of short-time (< 20 min)
intervals between flares is increased, but the time interval pattern
does not correspond to any mode of propagation of a triggering agent
in the solar atmosphere. Therefore, if the increase has real physical
significance, it would be indicative of some kind of subphotospheric
synchronization of activity in nearby `sympathetic' active regions.
Title: Optical Observations of Flares
Authors: Svestka, Z.
Bibcode: 1976RSPTA.281..435S
Altcode: 1976RSLPT.281..435S
The lecture describes solar flare effects in the chromosphere and
photosphere, particularly emphasizing problems of the energy transfer,
and the differences between thermal and non-thermal phases of the
flare development. Filamentary and shell models are compared and the
depth of the white-light flare emission is discussed. Optical effects
possibly associated with other, non-optical flare-associated phenomena
are pointed out.
Title: What should be observed on the sun.
Authors: Svestka, Z.
Bibcode: 1976SoPh...47..375S
Altcode:
Three problems are emphasized in particular: the preflare magnetic
field configuration, velocity fields, and the nature of acceleration
processes in flares. It is concluded that what we need most urgently
are high-resolution hard X-ray, soft X-ray, and EUV-pictures, coronal
spectra, and magnetograms with high resolution both in space and
time. A space-shuttle equipped with instrumentation of this kind would
contribute significantly to our knowledge of the flare process.
Title: Low-Energy Particle Events Associated with Sector Boundaries
Authors: Svestka, Z.; Fritzova-Svestkova, L.; Nolte, J. T.;
Dodson-Prince, H. W.; Hedeman, E. R.
Bibcode: 1976BAAS....8R.370S
Altcode:
No abstract at ADS
Title: Flare build-up study
Authors: Svestka, Z.
Bibcode: 1976SoPh...47.....S
Altcode: 1976SoPh...47....1S
The papers deal with problems which might be common to solar flares
and earth's magnetosphere, problems associated with the initial phases
of the flare phenomenon, the acceleration processes that seem to occur
in flares and the magnetosphere, as well as the buildup and storage of
flare energy in magnetic-field structures. Topics include the active
role of magnetic fields in providing flare energy, current-sheet models
of solar flares, the role of plasma turbulence in flare development,
similarities and differences between magnetospheric substorms and
solar flares, observations of magnetic merging in earth's magnetotail
during magnetospheric substorms, evidence for magnetic-energy storage
in coronal active regions, the possible role of transition-zone
instabilities in preflare energy buildup, and flare energy storage and
deposition. Other papers discuss energy release through the interaction
of coronal magnetic fields, photospheric electric currents as a source
of flare energy, magnetic-energy buildup in the solar atmosphere,
magnetic and velocity fields in an active region, flare onset at
meter wavelengths, laboratory experiments on field-line reconnection,
key problems in auroral flare processes, and the solar-physics
Shuttle/Spacelab program. Individual items are announced in this issue.
Title: Preface
Authors: de Jager, Cornelis; Obayashi, Tatsuzo; Švestka, Zdeněk
Bibcode: 1976SoPh...47....9D
Altcode:
No abstract at ADS
Title: Solar Flares
Authors: Svestka, Z.
Bibcode: 1976sofl.book.....S
Altcode: 1976STIN...7634103S
No abstract at ADS
Title: Solar activity (Activité solaire).
Authors: Newkirk, G.; Dunn, R. B.; Mehltretter, P.; MacQueen, R.;
Bonnet, R. M.; White, O. R.; Fokker, A. D.; Zwaan, C.; Bruzek, A.;
Durrant, C.; Grossmann-Doerth, U.; Mehltretter, J. P.; Svestka, Z.;
de Feiter, L. D.; Tandberg-Hanssen, E.; Howard, R.; Stix, M.; Pneuman,
G. W.; Hundhausen, A. J.; Sawyer, C.; Simon, P.
Bibcode: 1976IAUTA..16b..13N
Altcode:
No abstract at ADS
Title: Development of solar active regions.
Authors: Svestka, Z.
Bibcode: 1976pspe.proc..129S
Altcode: 1976pspe.conf..129S
The birth, growth, and decay of solar active regions are described. The
appearance of active regions in different atmospheric layers is
examined, and the coronal extension of active regions is considered. The
use of Skylab soft X-ray and extreme UV observations for studying the
complex loop structure of active regions in the solar corona and the
sensitive reactions of the upper atmospheric layers to newly emerging
flux is explained. It was found that well developed active regions
are much bigger in the corona than in the underlying sunspot groups
and plages, and that many of the active regions are connected with
others through systems of magnetic field lines, occasionally visible in
soft X-rays. These interconnections, which may survive several solar
rotations, indicate bigger complexes on the sun than one individual
active region.
Title: Skylab observations of X-ray loops connecting separate
active regions.
Authors: Chase, R. C.; Krieger, A. S.; Svestka, Z.; Vaiana, G. S.
Bibcode: 1976spre.conf..917C
Altcode: 1976spre.proc..917C
One hundred loops interconnecting 94 separate active solar
regions detectable in soft X-rays were identified during the Skylab
mission. While close active regions are commonly interconnected with
loops, the number of such interconnections decreases steeply for longer
distances; the longest interconnecting loop observed in the Skylab data
connected regions separated by 37 deg. Several arguments are presented
which support the point of view that this is the actual limit of the
size of magnetic interconnections between active regions. No sympathetic
flares could be found in the interconnected regions. These results cast
doubt on the hypothesis that accelerated particles can be guided in
interconnecting loops from one active region to another over distances
of 100 deg or more and eventually produce sympathetic flares in them.
Title: Solar flares
Authors: Svestka, Z.
Bibcode: 1976GAM.....8.....S
Altcode:
The present book covers all important aspects of solar flares,
concentrating mainly on flare morphology. Separate chapters
are devoted to low-temperature flares, high-temperature flares,
flare-associated optical phenomena, particle emission from flares,
and flare models. Flare observations in the H-alpha line are discussed
along with flare spectra, thermal and nonthermal emissions from flares,
flare waves, and loop prominences. Solar proton and electron emission is
examined, particle clouds and interplanetary shock waves are considered,
and characteristics of active regions are reviewed. Flare models are
described with reference to chromospheric flares, flare synthesis,
energy sources, energy release and storage, and particle acceleration.
Title: Several aspects of flare-associated particle events.
Authors: Svestka, Z.
Bibcode: 1976npsa.conf..126S
Altcode:
No abstract at ADS
Title: Book review
Authors: Švestka, Z.
Bibcode: 1975SoPh...45..543S
Altcode: 1975SoPh...45..543.
No abstract at ADS
Title: Transequatorial Loops Interconnecting McMath 12472 and 12474.
Authors: Svestka, Z.; Krieger, A.
Bibcode: 1975BAAS....7Q.444S
Altcode:
No abstract at ADS
Title: On the behaviour of the hydrogen Lyman series in flares
Authors: de Feiter, L. D.; Svestka, Z.
Bibcode: 1975SoPh...41..415D
Altcode:
The Lyman spectrum of hydrogen has been computed for a number of flare
models, characterized by the column density of hydrogen atoms in the
ground state (N1), the electron density (ne)
and the electron temperature (Te). Broadening by the thermal
Doppler effect and by Stark effect has been accounted for. The source
functions for the individual lines of the series have been derived
from non-LTE calculations of the excitation in hydrogen flares. The
aim of the investigation is to evaluate the use of the intensities in
between two successive Lyman lines for a determination of the value
for N1, which is a physical parameter of the flare for
which only indirect determinations are available. Whilst in principle
this method could give reliable results, its practical application
meets with difficulties which hardly can be overcome. Therefore, one
probably has to base the N1 determination on the highest
line resolvable in the spectrum.
Title: Catalog of solar particle events 1955-1969
Authors: Svestka, Z.; Simon, P.
Bibcode: 1975ASSL...49.....S
Altcode: 1975cspe.book.....S
No abstract at ADS
Title: On the Acceleration Process in Solar Flares
Authors: Svestka, Z.
Bibcode: 1975IAUS...68..427S
Altcode:
The paper summarizes the data on the acceleration processes on the
sun. Four different instabilities are distinguished: (1) one with
purely thermal consequences giving rise to the origin of any flare;
(2) a nonthermal process at the flash phase of flares giving rise to
nearby 100 keV electrons and protons, manifested through hard X-ray and
impulsive microwave bursts; (3) an instability giving rise to streams
of electrons, without accelerating protons, manifested by type III
bursts; when (2) and (3) are linked, flare associated electron events in
space are often recorded; and (4) an explosive instability produces a
shock wave which manifests itself as a type II burst. This instability
leads to a second-step acceleration of particles preaccelerated in (2)
and gives origin to more than 10 MeV protons and relativistic electrons.
Title: Catalog of solar particles events, 1955 - 1969.
Authors: Dodson, H. W.; Hedeman, E. R.; Kreplin, R. W.; Martres,
M. -J.; Obridko, V. N.; Shea, M. A.; Smart, D.; Tanaka, H.; Svestka,
Z.; Simon, P.; Fritzová-Svestková, L.; Guitart, A.
Bibcode: 1975cspe.book.....D
Altcode: 1975QB505.C37......
No abstract at ADS
Title: Type II Radio Bursts and Particle Acceleration
Authors: Švestka, Z.; Fritzová-Švestková, L.
Bibcode: 1974SoPh...36..417S
Altcode:
328 particle events recorded during 30 months from January 1, 1966 to
June 30, 1968 (taken from the new Catalog of Solar Particle Events,
1955-1969) are compared with the occurrence of 166 type II radio
bursts during the same period. The results of this comparison give
a convincing evidence that proton acceleration to higher energies in
flares (the `second acceleration step') is closely connected with the
type II burst occurrence. The shock wave appears to originate near the
time when the impulsive burst occurs, and the second acceleration step
follows immediately the first one; in some cases the second step sets
in while the first step is still in progress.
Title: The Hα flare as a secondary product of a coronal instability
Authors: Švestka, Z.
Bibcode: 1973SoPh...31..389S
Altcode:
The assumption that the flare originates in the corona or transition
layer, is confronted with the known properties of chromospheric
flares. It is concluded that the basic mode of the energy transport
into chromosphere is heat conduction. Only in some flares non-thermal
particles contribute to the brightening in lower atmospheric layers:
electrons with energy close to 100 keV produce chromospheric
bright patches, and protons above 20 MeV cause the photospheric
enhancements. The particle-produced brightenings are superposed on
the basic quasi-thermal flare and involve only small areas as compared
with the extensive regions heated through conduction.
Title: A Comment on the Flare Activity in August 1972
Authors: Fritzová-Švestková, L.; Švestka}, Z.
Bibcode: 1973SoPh...29..417F
Altcode:
No abstract at ADS
Title: Observational Aspects of Flares
Authors: Švestka, Z.
Bibcode: 1973str..conf...23S
Altcode:
No abstract at ADS
Title: The Expected Behaviour of the Hydrogen Lyman Lines in Solar
Flares
Authors: Švestka, Z.; de Feiter, L. D.
Bibcode: 1972SSRv...13..824S
Altcode: 1972IAUCo..14..824S
No abstract at ADS
Title: Characteristics of Strong Particle Sources of the Sun
(Invited Paper)
Authors: Svestka, Z.
Bibcode: 1972spen.conf....1S
Altcode:
No abstract at ADS
Title: Editorial
Authors: De Jager, Cornelis; Švestka, Zdeněk
Bibcode: 1972SoPh...25....3D
Altcode: 1972SoPh...25....3.
No abstract at ADS
Title: Book review
Authors: Švestka, Z.
Bibcode: 1972SoPh...24..498S
Altcode: 1972SoPh...24..498.
No abstract at ADS
Title: Spectral Analysis of Highly Inhomogeneous Chromospheric Flares
Authors: Švestka, Z.
Bibcode: 1972SoPh...24..154S
Altcode:
Analysis of a hydrogen flare spectrum is carried out, assuming
that the flare radiation is diluted due to a highly inhomogeneous
space distribution of the flare elements in the chromosphere. It is
shown that one obtains the correct physical parameters in the flare
elements, irrespective of the extent of dilution, if all the elements
are optically thin in the spectral regions considered. However, if
this is not true for all the elements, the parameters deduced are in
error, which increases with the extent of dilution. The worst affected
parameter is the linear thickness of the flaring region which is found
to be too low by a factor which may be as high as 10. Errors also enter
into electron and atom densities which are found to be too high and
into the column density of hydrogen atoms which is underestimated. On
the other hand, the deduced source function, and in consequence of it
the electron temperature as well, remain unaffected, if the analysis
is properly carried out. All the errors may increase strikingly if the
analysis is performed for optically thick regions. Several kinds of
observation are mentioned which indicate that dilution of radiation may
occur in flares. However, reasonable estimates of the flare parameters
are still possible provided that one avoids spectral regions with τ
≳ 1.
Title: Spectra of Solar Flares
Authors: Švestka, Zdeněk
Bibcode: 1972ARA&A..10....1S
Altcode:
No abstract at ADS
Title: Solar discrete particle events.
Authors: Svestka, Z.
Bibcode: 1972sstp.conf...72S
Altcode:
No abstract at ADS
Title: Several Solar Aspects of Flare-Associated Particle Events
Authors: Švestka, Z.
Bibcode: 1972PrAA...30..141S
Altcode:
No abstract at ADS
Title: Neutron and gamma-ray emission from white-light flares.
Authors: de Feiter, L. D.; Svestka, Z.
Bibcode: 1972spre.conf.1547D
Altcode: 1972spre....2.1547D
No abstract at ADS
Title: Solar Discrete Particle Events
Authors: Švestka, Z.
Bibcode: 1972ASSL...29...72S
Altcode: 1972sun..conf...72S
No abstract at ADS
Title: Editorial
Authors: De Jager, Cornelis; Švestka, Zdeněk
Bibcode: 1971SoPh...21....3D
Altcode: 1971SoPh...21....3.
No abstract at ADS
Title: On the Flux of Neutrons from Flares
Authors: Švestka, Z.
Bibcode: 1971SoPh...19..202S
Altcode:
Under the assumption that white-light flares are caused by energetic
particles penetrating into the photosphere (Švestka, 1970a; Najita and
Orrall, 1970) the known number of protons needed for the white-light
emission is used to obtain an estimate of the production of neutrons
occurring at the same time. In the case of the white-light flare of 23
May, 1967, the peak flux of neutrons at the Earth distance had to exceed
3 neutrons/cm2s, thus being detectable in space. This maximum
neutron flux reached the Earth as early as the time of the maximum
phase of the flare in the Hα light. However, reasonable estimates
show that flares associated with a detectable neutron flux should be
fairly rare phenomena, maybe as rare as the white-light flares.
Title: Solar Particle Events
Authors: Svestka, Z.
Bibcode: 1971RSPTA.270..157S
Altcode:
No abstract at ADS
Title: Book Review: Intercorrelated satellite observations related
to solar events. Edited by V. MANNO AND D. E. PAGE. Astrophysics
and Space Science Library Vol. 19. Springer, New York, and Reidel,
Dordrecht, Holland, 1970. xvi + 627 pp. Price $38.20
Authors: Švestka, Z.
Bibcode: 1971Icar...14..489S
Altcode:
No abstract at ADS
Title: Editorial
Authors: de Jager, Cornelis; Švestka, Zdeněk
Bibcode: 1971SoPh...17..287D
Altcode: 1971SoPh...17..287.
No abstract at ADS
Title: Book reviews
Authors: Švestka, Z.; Spiegel, E. A.; van Herk, G.
Bibcode: 1971SSRv...11..867S
Altcode:
No abstract at ADS
Title: Solar radio astronomy from the optical solar researchers
point of view
Authors: Svestka, Z.
Bibcode: 1971cesra...1...15S
Altcode:
No abstract at ADS
Title: The Phase of Particle Acceleration in the Flare Development
Authors: Švestka, Z.
Bibcode: 1970SoPh...13..471S
Altcode:
Evidence is given that the particle acceleration in flares is confined
to the initial phase of the flare development preceding the Hα flare
maximum and lasting for less than 10 min. The impulsive acceleration
process is confined to a relatively small limited volume of about 5
× 1027 cm3 in the region of highest magnetic
gradient in the flare, and its size represents about 0.05 or less of
the total extent of the hot condensation which produces the soft X-ray
and gradual microwave bursts. About one in fifty particles in this
volume is accelerated to energy exceeding 100 keV, the total particle
density being ≈ 1010 cm−3. The accelerated
electrons produce the impulsive hard X-ray burst, but synchrotron losses
greatly reduce the number of relativistic electrons participating in
the bremsstrahlung process. Protons above 20 MeV penetrate to the
lowest chromosphere and upper photosphere and temporarily increase
the temperature in the bombarded region. As the result a flash of
continuous emission appears, which should be most expressive below
1527 Å. The associated white-light emission shows the bottom of the
region where the impulsive acceleration process occurs.
Title: Book Review: Astronomy and Astrophysics Abstracts, Vol. 1:
Literature 1969, Part 1, Springer-Verlag, Berlin, Heidelberg, New York
Authors: Švestka, Z.
Bibcode: 1970SoPh...12R.502S
Altcode: 1970SoPh...12R.502Z
No abstract at ADS
Title: Solar Activity.
Authors: Svestka, Z.
Bibcode: 1970IAUTA..14...71S
Altcode:
No abstract at ADS
Title: Solar particle events.
Authors: Svestka, Z.
Bibcode: 1970spre.conf..797S
Altcode:
No abstract at ADS
Title: Book Review: Annals of the IQSY, M. I. T. Press, Vols. 1-5
Authors: Švestka, Z.
Bibcode: 1970SoPh...12Q.502S
Altcode: 1970SoPh...12Q.502Z
No abstract at ADS
Title: Particle Event Forecasting
Authors: Švestka, Z.
Bibcode: 1970ASSL...19...90S
Altcode: 1970iso..conf...90S
No abstract at ADS
Title: The solar proton flares of June and November 1968 and
February 1969.
Authors: Krivský, L.; Svestka, Z.
Bibcode: 1970spre.conf..817K
Altcode:
No abstract at ADS
Title: Editorial
Authors: De Jager, Cornelis; Švestka, Zdeněk
Bibcode: 1969SoPh...10..243D
Altcode: 1969SoPh...10..243.
No abstract at ADS
Title: Proton Flare Project, 1966. Summary of the August/September
Particle Events in the McMath Region 8461. (Invited Review Paper)
Authors: Švestka, Z.; Simon, P.
Bibcode: 1969SoPh...10....3S
Altcode:
The paper summarizes observations of solar and space phenomena related
to the McMath region Number 8461 which passed over the solar disk during
the 1966 Proton Flare Project period, from August 21 to September 4,
and produced two important solar particle events on August 28 and
September 2. The most important results are reviewed and interpretation
of some of them is suggested.
Title: Comment on the Note by Friedman and Hamberger
Authors: Švestka, Z.
Bibcode: 1969SoPh....8..400S
Altcode:
No abstract at ADS
Title: Editorial
Authors: Švestka, Z.; De Jager, C.
Bibcode: 1969SoPh....8....3S
Altcode: 1969SoPh....8....3.
No abstract at ADS
Title: Abstracts of papers from other journals
Authors: Pasachoff, Jay M.; Gussmann, E. A.; Stepanyan, N. N.; de
Feiter, L. D.; Uchida, Yutaka; Švestka, Z.; Vassilyeva, G. J.
Bibcode: 1969SoPh....6..155P
Altcode:
No abstract at ADS
Title: The optical flare
Authors: Švestka, Z.
Bibcode: 1969sfsr.conf...16S
Altcode:
No abstract at ADS
Title: Solar flares and space research
Authors: de Jager, C.; Svestka, Z.
Bibcode: 1969sfsr.conf.....D
Altcode: 1969sfsr.book.....D
No abstract at ADS
Title: Effects associated with the sector boundary crossing on 8
July 1966
Authors: Švestka, Z.
Bibcode: 1969sfsr.conf..319S
Altcode:
No abstract at ADS
Title: General summary on the results of the first Proton Flare
Project period, July 1966.
Authors: Simon, P.; Svestka, Z.
Bibcode: 1969AIQSY...3..469S
Altcode:
No abstract at ADS
Title: Editorial
Authors: De Jager, C.; Švestka, Z.
Bibcode: 1968SoPh....5..259D
Altcode: 1968SoPh....5..259.
No abstract at ADS
Title: Effects associated with the Sector Boundary crossing on July
8, 1966
Authors: Švestka, Zdeněk.
Bibcode: 1968SoPh....4..361S
Altcode:
Thirty hours after the proton flare of July 7, 1966, the earth and
nearby satellites crossed a sector boundary of the interplanetary
magnetic field. This occurred before the flare-associated shockwave
arrived at the earth, so that the space was filled with energetic
particles ejected from the flare. Satellite measurements have shown
that in such a case <20 MeV protons are stored within the range of
the sector boundary and with decreasing energy the particles tend to
accumulate towards and behind the Eastern boundary limit; low-energy
particles, such as <50 keV electrons, are stored exclusively behind
this Eastern limit.
Title: On Long-Term Forecasts of Proton Flares
Authors: Švestka, Zdeněk.
Bibcode: 1968SoPh....4...18S
Altcode:
174 proton flares which were observed during the period from 1956 to
1965, occurred in 81 different active regions. It is shown that these
active regions formed in complexes of activity, which stayed on the
solar surface for many months, and in some cases even for several
years. Since the proton-flare regions develop very rapidly and reach
the proton-flare active stage within a few days, these complexes of
activity represent the areas on the sun, where proton-flare regions
can form at any time. Reference is made to contributions by Bumba and
Howard, who investigated the birth of active regions and detected some
properties of complexes of activity; nevertheless, at the present time,
we do not know any method to predict when a proton-flare region begins
to develop in such a complex of activity.
Title: Introduction and Summary
Authors: Svestka, Z.
Bibcode: 1968IAUS...35..513S
Altcode:
No abstract at ADS
Title: Mass motions in flares indicated by line profiles and
filtergrams Introductory lecture
Authors: Švestka, Z.
Bibcode: 1968mmsf.conf...17S
Altcode:
No abstract at ADS
Title: Loop-Prominence Systems and Proton-Flare Active Regions
Authors: Svestka, Z.
Bibcode: 1968IAUS...35..287S
Altcode:
No abstract at ADS
Title: Editorial
Authors: De Jager, C.; Švestka, Z.
Bibcode: 1968SoPh....3....3D
Altcode: 1968SoPh....3....3.
No abstract at ADS
Title: Electron Density in Flares, II: Results of Measurement
Authors: Fritzová-Švestková, L.; Švestka, Z.
Bibcode: 1967SoPh....2...87F
Altcode:
Measurements of the electron density in 16 flares are summarized and
discussed. For 13 of them the electron density has been determined by
the halfwidth method discussed in Part I of this paper. In the flash
phase of all disk flares of importance 1 + and higher the electron
density exceeds 1013 cm−3 and increases with
the flare importance. In the maximum of large flares the electron
density exceeds 3 × 1013 cm−3 and declines
to 1013 cm−3 and to lower values in about
20 minutes after the flash phase. In limb flares, i.e. higher than
5000 km above the solar limb, the electron density is lower than 5
× 1012 cm−3. This shows a decrease of the
electron density in the flare elements situated in higher parts of the
chromosphere. On the other hand, however, at least in some flares the
electron density remains fairly constant within a wide range of height
in the upper chromosphere and the low corona.
Title: Electron Density in Flares, I: Discussion of the Halfwidth
Method
Authors: Švestka, Z.; Fritzová-Švestková, L.
Bibcode: 1967SoPh....2...75S
Altcode:
The halfwidth method used for the determination of the electron
density in flares is discussed from the point of view of possible
errors which may enter the obtained results. The discussion includes
an analysis of errors of measurement as well as errors of the method
due to: (1) our incomplete knowledge of the electron damping, (2)
the assumption of constant electron temperature, (3) the presence
of residual self-absorption in high Balmer lines, and (4) possibly
present non-thermal motions. It is shown that the factors (2) to (4)
cannot induce any relative error in ne higher than 30 %
of the correct value, and the actual error usually is smaller. A
comparison is made of the halfwidth-method application to active
prominences and limb flares.
Title: Editorial
Authors: de Jager, C.; Švestka, Z.
Bibcode: 1967SoPh....1..303D
Altcode: 1967SoPh....1..303.
No abstract at ADS
Title: Type IV bursts. III. In association with Forbush effects
Authors: Švestka, Z.
Bibcode: 1967BAICz..18...55S
Altcode:
No abstract at ADS
Title: Editorial
Authors: de Jager, C.; Švestka, Z.
Bibcode: 1967SoPh....1....3D
Altcode: 1967SoPh....1....3.
No abstract at ADS
Title: Buchbesprechungen über: Solar Physics. Ed. C. DE JAGER,
and Z. ŠVESTKA. (Ref. R. O. REDMAN)
Authors: de Jager, C.; Švestka, Z.
Bibcode: 1967ZA.....67...95D
Altcode:
No abstract at ADS
Title: Optical Observations of Solar Flares
Authors: Švestka, Zdeněk
Bibcode: 1966SSRv....5..388S
Altcode:
This paper gives a review of the results of optical observations of
solar flares. Observations carried out in the Hα line,
flare spectra, and the methods of analysing the flare spectra are
briefly discussed. Great attention is paid to the continuous emission
of flares in the optical spectral region. In the last section, optical
aspects of proton flares are summarized.
Title: Type IV bursts. II. In association with PCA events
Authors: Fritzová-Švestková, L.; Švestka, Z.
Bibcode: 1966BAICz..17..249F
Altcode:
No abstract at ADS
Title: The H- emission in flares
Authors: Švestka, Z.
Bibcode: 1966BAICz..17..137S
Altcode:
No abstract at ADS
Title: Proton flares before 1956
Authors: Švestka, Z.
Bibcode: 1966BAICz..17..262S
Altcode:
No abstract at ADS
Title: A prediction on proton flare occurrence in 1966-1968
Authors: Švestka, Z.
Bibcode: 1966BAICz..17...95S
Altcode:
No abstract at ADS
Title: Type IV Bursts. I. List of events
Authors: Švestka, Z.; Olmr, J.
Bibcode: 1966BAICz..17....4S
Altcode:
No abstract at ADS
Title: Spectral Analysis of Solar Flares
Authors: Švestka, Zdeněk
Bibcode: 1965AdA&A...3..119S
Altcode:
No abstract at ADS
Title: Spectral anomalies associated with the extraordinary X-ray
emission recorded by the SR-1 satellite on August 7, 1960
Authors: Svestka, Z.
Bibcode: 1964spre.conf..768S
Altcode:
No abstract at ADS
Title: Electron temperature and bn values in flares
Authors: Švestka, Z.
Bibcode: 1964BAICz..15...38S
Altcode:
No abstract at ADS
Title: Broadening of high Balmer lines in flares and prominences
Authors: Švestka, Z.
Bibcode: 1964BAICz..15..162S
Altcode:
No abstract at ADS
Title: Time variation of electron density in a large solar flare
Authors: de Feiter, L. D.; Švestka, Z.
Bibcode: 1964BAICz..15..117D
Altcode:
No abstract at ADS
Title: Qualitative discussion of 244 flare spectra. IV. Splitting
of metal emission lines
Authors: Kopecký, M.; Letfus, V.; Blaha, M.; Švestka, Z.
Bibcode: 1963BAICz..14..146K
Altcode:
No abstract at ADS
Title: On the spectral analysis of flares
Authors: Švestka, Z.
Bibcode: 1963BAICz..14...75S
Altcode:
No abstract at ADS
Title: Spectral analysis of the moustache-like flare of August 7, 1960
Authors: Svestka, Z.
Bibcode: 1963BAICz..14..234S
Altcode:
No abstract at ADS
Title: Astronomicky a astronauticky slovnik.
Authors: Kleczek, Josip; Svestka, Zdenek
Bibcode: 1963aaas.book.....K
Altcode: 1963QB14.K56.......
No abstract at ADS
Title: Evidence of Stark broadening of Balmer lines in flares
Authors: Svestka, Z.
Bibcode: 1962BAICz..13..236S
Altcode:
No abstract at ADS
Title: Qualitative discussion of 244 flare spectra. II. Line asymmetry
and helium lines
Authors: Švestka, Z.; Kopecký, M.; Blaha, M.
Bibcode: 1962BAICz..13...37S
Altcode:
No abstract at ADS
Title: Motions in chromospheric flares
Authors: Švestka, Z.
Bibcode: 1962BAICz..13..190S
Altcode:
No abstract at ADS
Title: Note on planetary nebulae in the Small Magellanic Cloud
Authors: Švestka, Z.
Bibcode: 1962BAICz..13...35S
Altcode:
No abstract at ADS
Title: On a peculiar flare spectrum
Authors: Švestka, Z.
Bibcode: 1962BAICz..13...30S
Altcode:
No abstract at ADS
Title: Qualitative discussion of 244 flare spectra. III. Metal
emission lines
Authors: Blaha, M.; Kopecký, M.; Švestka, Z.
Bibcode: 1962BAICz..13...85B
Altcode:
No abstract at ADS
Title: Qualitative discussion of 244 flare spectra
Authors: Švestka, Z.; Kopecký, M.; Blaha, M.
Bibcode: 1961BAICz..12..229S
Altcode:
No abstract at ADS
Title: Observations of flares at the Ondřejov Observatory in the
year 1959
Authors: Kvičala, F.; Hřebik, F.; Olmr, F.; Švestka, Z.;
Křivský, L.
Bibcode: 1961BAICz..12...47K
Altcode:
No abstract at ADS
Title: Spectrum of the flare of July 20, 1958
Authors: Švestka, Z.
Bibcode: 1961BAICz..12...73S
Altcode:
No abstract at ADS
Title: Measurement of Magnetic Fields in Chromospheric Flares
Authors: Blaha, M.; Kopecký, M.; Švestka, Z.
Bibcode: 1960Natur.187..224B
Altcode:
SPECTRA of two great chromospheric flares taken by the flare
spectrograph at Ondřejov1 show an evident splitting of the
D1 emission line of Na I which is attributed to a magnetic
field existing in that part of the chromosphere where the sodium lines
are formed. This explanation is supported by the following facts :
Title: List of flares observed at Ondrejov observatory during
the I.G.Y.
Authors: Kvicala, J.; Hrebik, F.; Letfus, V.; Olmr, J.; Svestka, Z.;
Krivsky, L.
Bibcode: 1960PAICz..43....1K
Altcode:
No abstract at ADS
Title: Hydrogen spectrum of the flare of July 30, 1959
Authors: Švestka, Z.
Bibcode: 1960BAICz..11..167S
Altcode:
No abstract at ADS
Title: The flare spectrograph at Ondřejov
Authors: Valníček, B.; Letfus, V.; Blaha, M.; Švestka, Z.; Seidl, Z.
Bibcode: 1959BAICz..10..149V
Altcode:
No abstract at ADS
Title: Catalogue of Chromospheric Flares observed at Ondřejov during
the first half of the year 1957
Authors: Letfus, V.; Růžičková, B.; Švestka, Z.
Bibcode: 1959BAICz..10..136L
Altcode:
No abstract at ADS
Title: Damping and Stark broadening of Balmer lines
Authors: Švestka, Z.
Bibcode: 1959BAICz..10...10S
Altcode:
No abstract at ADS
Title: Polarization of Light of the Comets Arend-Roland (1956h)
and Mrkos (1957d)
Authors: Blaha, M.; Hruška, A.; Švestka, Z.; Vanýsek, V.
Bibcode: 1958Natur.182..331B
Altcode:
POLARIZATION of the total light of the Comets 1956h and 1957d
was studied photographically by simultaneous exposures with three
objectives and three `Polaroids'. The planes of polarization of the
three `Polaroids' were at 120°. 2-in. objectives were used at ƒ/9
with Agfa `Astro' panchromatic plates. The characteristic curve was
determined by comparison with an exposed photometric wedge. Errors due
to the instrument were measured by means of light from an artificial
source, polarized to a known degree by reflexion from a glass
surface. The error of the polarization determined is +/- 2.5 per cent.
Title: Catalogue of chromospheric flares observed at Ondřejov during
the years 1952-1956
Authors: Letƒus, V.; RůžiČková, B.; Švestka, Z.
Bibcode: 1958BAICz...9..178L
Altcode:
No abstract at ADS
Title: 536 Mc/s radio events associated with chromospheric flares
during the year 1956
Authors: Budějický, J.; Švestka, Z.
Bibcode: 1958BAICz...9...48B
Altcode:
No abstract at ADS
Title: Fysikalni podminky V chromosferickych erupcich.
Authors: Svestka, Zdenek
Bibcode: 1957PAICz..32.....S
Altcode: 1957QB1.C284A3c32..
No abstract at ADS
Title: Mezihvezdna hmota.
Authors: Svestka, Zdenek; Vanysek, Valdimir
Bibcode: 1956mehm.book.....S
Altcode: 1956QB500.S9.......
No abstract at ADS
Title: Several Notes on the Statistics of Chromosferic Flares
Authors: Švestka, Z.
Bibcode: 1956BAICz...7....9S
Altcode:
No abstract at ADS
Title: The Optical Thickness of Flares and the Broadening of Balmer
Lines in their Spectra
Authors: Švestka, Z.
Bibcode: 1956BAICz...7..130S
Altcode:
No abstract at ADS
Title: The Width of Hα in Solar Flares
Authors: Švestka, Z.; Fritzová, L.
Bibcode: 1956BAICz...7...30S
Altcode:
No abstract at ADS
Title: Secondary Periods of Long-periodic Variables
Authors: Fritzová, L.; Pěkný, Z.; Švestka, Z.
Bibcode: 1954BAICz...5...49F
Altcode:
No abstract at ADS
Title: Hvezdne atmosfery.
Authors: Svestka, Zdenek
Bibcode: 1954hvat.book.....S
Altcode: 1954QB809.S85......
No abstract at ADS
Title: Catalogue des crateres lunaire
Authors: Bouska, J.; Hrebik, F.; Svestka, Z.
Bibcode: 1953PAICz..25..107B
Altcode:
No abstract at ADS
Title: Recurrent and Revived Active Regions on the Sun
Authors: Švestka, Z.
Bibcode: 1953BAICz...4..186S
Altcode:
No abstract at ADS
Title: Slunce a jeho vlivy NA zemi.
Authors: Link, Frantisek; Svestka, Zdenek
Bibcode: 1953sajv.book.....L
Altcode: 1953QB521.L72......
No abstract at ADS
Title: The Hα-Emission from Chromospheric Flares:
Central Intensity and Line-Width
Authors: Švestka, Z.
Bibcode: 1951BAICz...2..165S
Altcode:
No abstract at ADS
Title: The Hα-Emission from Chromospheric Flares: The
Flare of August 5, 1949
Authors: Švestka, Z.
Bibcode: 1951BAICz...2..153S
Altcode:
No abstract at ADS
Title: The Hα-Emission from Chromospheric Flares:
Expanding Source of Radiation
Authors: Švestka, Z.
Bibcode: 1951BAICz...2..150S
Altcode:
No abstract at ADS
Title: The Hα-Emission from Chromospheric Flares: Course
of the Asymmetry
Authors: Švestka, Z.
Bibcode: 1951BAICz...2..120S
Altcode:
No abstract at ADS
Title: The Hα-Emission from Chromospheric Flares:
General Features of the Asymmetry
Authors: Švestka, Z.
Bibcode: 1951BAICz...2..100S
Altcode:
No abstract at ADS
Title: The Hα-Emission from Chromospheric Flares:
Observations
Authors: Švestka, Z.
Bibcode: 1951BAICz...2...81S
Altcode:
No abstract at ADS
Title: On a Possible Development of Planetary Nebulae
Authors: Švestka, Z.
Bibcode: 1950BAICz...2...52S
Altcode:
No abstract at ADS
Title: The Reason of Validity of the Bode's Law
Authors: Švestka, Z.
Bibcode: 1950BAICz...2...45S
Altcode:
No abstract at ADS
Title: A Note on the Brightness of Lunar Eclipses
Authors: Švestka, Z.
Bibcode: 1950BAICz...2...41S
Altcode:
No abstract at ADS
Title: On the Variations of the Enlargement of the Earth's Shadow
during the Lunar Eclipses
Authors: Švestka, Z.
Bibcode: 1950BAICz...2....6S
Altcode:
No abstract at ADS
Title: The Influence of Clouds on the Density of the Central Part
of the Earth's Shadow
Authors: Švestka, Zdeněk.
Bibcode: 1949BAICz...1..131S
Altcode:
No abstract at ADS
Title: On the Variation of the Coma-Diameter of Encke's Comet
Authors: Bouška, Jiří.; Švestka, Zdeněk.
Bibcode: 1949BAICz...1..123B
Altcode:
No abstract at ADS
Title: On the Observed Density of the Earth's Shadow near its Centre
Authors: Švestka, Zdeněk.
Bibcode: 1949BAICz...1..109S
Altcode:
No abstract at ADS
Title: On the Real Number of Solar Flares
Authors: Švestka, Zdeněk.
Bibcode: 1949BAICz...1...95S
Altcode:
No abstract at ADS
Title: Observations of Solar Flares and High-speed Prominences from
July to December 1948
Authors: Švestka, Zdeněk.
Bibcode: 1949BAICz...1...73S
Altcode:
No abstract at ADS
Title: The Illumination by Diffusion in the Centre of the Earth's
Shadow
Authors: Švestka, Zdeněk.
Bibcode: 1948BAICz...1...48S
Altcode:
No abstract at ADS
Title: The Density of the Earth's Shadow near its Centre
Authors: Švestka, Zdeněk.
Bibcode: 1948BAICz...1...29S
Altcode:
No abstract at ADS