Author name code: brynildsen
ADS astronomy entries on 2022-09-14
author:"Brynildsen, Nils"
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Title: Dual Flows with Supersonic Velocities in the Sunspot Transition
Region
Authors: Brynildsen, N.; Maltby, P.; Kjeldseth-Moe, O.; Wilhelm, K.
Bibcode: 2004ApJ...612.1193B
Altcode:
Observations of sunspot transition region lines that deviate
significantly from a Gaussian shape are presented. Attention is given
to ``dual flows,'' a line profile phenomenon in which two distinct
velocities are observed within the same spatial resolution element. In
5 out of 12 sunspots we observe dual flows. Several emission line
profiles are well represented by two Gaussian line components, one
with a subsonic and one with a supersonic line-of-sight velocity.
Title: Oscillations in the Umbral Atmosphere
Authors: Brynildsen, N.; Maltby, P.; Foley, C. R.; Fredvik, T.;
Kjeldseth-Moe, O.
Bibcode: 2004SoPh..221..237B
Altcode:
The results of simultaneous observations of oscillations in the
chromosphere, transition region, and corona above nine sunspots are
presented. The data are obtained through coordinated observing with the
Solar and Heliospheric Observatory — SOHO and the Transition Region
And Coronal Explorer — TRACE. Oscillations are detected above each
umbra. The power spectra show one dominant frequency corresponding to
a period close to 3 min. We show that the oscillations in the sunspot
transition region can be modeled by upwardly propagating acoustic
waves. In the corona the oscillations are limited to small regions that
often coincide with the endpoints of sunspot coronal loops. Spectral
observations show that oscillations in the corona contribute to the
observed oscillations in the TRACE 171 Å channel observations. We
show that a recent suggestion regarding a connection between sunspot
plumes and 3-min oscillations conflicts with the observations.
Title: Oscillations Above the Umbra of Sunspots
Authors: Brynildsen, N.; Maltby, P.; Fredvik, T.; Kjeldseth-Moe, O.
Bibcode: 2004ESASP.547...45B
Altcode: 2004soho...13...45B
Oscillations above thirteen sunspots are investigated with the Coronal
Diagnostic Spectrometer (CDS) and the Transition Region And Coronal
Explorer (TRACE). The CDS observations give knowledge about the
oscillations in the chromosphere, transition region, and corona and
information regarding the contributions of different emission lines to
the TRACE 171 Å and 195 Å channel intensities. A period close to 3
min is observed above the umbra of each sunspot. The observations give
support to the idea that the 3 min oscillations are caused by upwardly
propagating acoustic waves. This is evident from the asymmetry of
the oscillation amplitudes in the red and blue wings of the emission
lines, where the oscillations are decidedly more pronounced in the
blue than in the red line wing. Additional support for the acoustic
wave hypothesis emerges from the agreement between the observed and
predicted relations in phase and magnitude between the oscillations in
intensity and line-ofsight velocity. The frequency of the oscillations
is above the acoustic cutoff frequency in the umbral atmosphere and
the observed phase differences between lines emitting at different
temperatures point to an upwardly propagating disturbance.
Title: Search for a chromospheric resonator above sunspots
Authors: Brynildsen, N.; Maltby, P.; Brekke, P.; Redvik, T.;
Kjeldseth-Moe, O.
Bibcode: 2003AdSpR..32.1097B
Altcode:
We have recently observed thirteen sunspots, both with CDS on SOHO
and TRACE. For each sunspot we investigate the oscillations in the
chromosphere, transition region and corona. Above the umbra the
power spectra show one dominant peak corresponding to a period of 3
minutes. The intensity oscillation amplitude increases with increasing
temperature, reaches a maximum for lines emitting close to 1-2 ×
10 5 K, and decreases for higher temperatures. Part of
the wave energy penetrates into the corona, channeled into small
areas that appear to coincide with the endpoints of sunspot coronal
loops. The observations support the hypothesis that the oscillations
are caused by upwardly propagating acoustic waves and show no signs
of the resonances, equally spaced ≈1 mHz in frequency, predicted by
the chromospheric resonator theories.
Title: Sunspot Oscillations and Acoustic Wave Propagation
Authors: Brekke, P.; Brynildsen, N.; Maltby, P.; Fredvik, T.;
Kjeldseth-Moe, O.
Bibcode: 2003SPD....34.0401B
Altcode: 2003BAAS...35..810B
Observations with the Coronal Diagnostic Spectrometer of 3 min
oscillations in sunspot umbrae support the hypothesis that they are
caused by upwardly propagating acoustic waves. This is evident from
the asymmetry of oscillation amplitudes in the red and blue wings of
spectral lines, where the oscillations are decidedly more pronounced
in the blue than in the red line wing. Additional evidence include the
fact that the relation between oscillations in intensity and velocity
agree with that predicted for an acoustic wave with regard to phase
as well as magnitude. Finally, the observed phase difference between
lines formed at different temperatures points to an upward propagating
disturbance, and the value of dominant frequency of the oscillations,
close to 6 mHz, is above the acoustic cutoff frequency in the sunspot
atmosphere. SOHO is a mission of international cooperation between ESA
and NASA. This study was supported by the Research Council of Norway.
Title: Oscillations in the wings of sunspot transition region lines
Authors: Brynildsen, N.; Maltby, P.; Kjeldseth-Moe, O.; Wilhelm, K.
Bibcode: 2003A&A...398L..15B
Altcode:
We explore a new approach to the investigation of optically thin
emission lines by comparing the intensity variations in opposite
wings of the spectral lines and apply the method to investigate the
oscillations above sunspots. The observations show that it is easier to
detect the 3 min oscillations above sunspots in the short wavelength
(``blue'') wing than in the long wavelength (``red'') wing of the
lines. The observed oscillations are compatible with the spectral line
signatures of upwardly propagating acoustic waves.
Title: Sunspot oscillations in the chromosphere, transition region,
and corona
Authors: Brynildsen, N.; Maltby, P.; Fredvik, T.; Kjeldseth-Moe, O.
Bibcode: 2002ESASP.506..513B
Altcode: 2002ESPM...10..513B; 2002svco.conf..513B
The results of simultaneous observations with CDS on SOHO and TRACE
for thirteen sunspots in 2001 and 2002 are combined with previous
results for six sunspots observed with CDS and SUMER on SOHO. Intensity
oscillations are detected above each umbra and spectral observations
of chromospheric and transition region lines allow us to measure
oscillations in the line-of-sight velocity in several sunspots. The
power spectra show one dominant peak close to 6 mHz, corresponding
to a period of 3 minutes. The oscillation amplitude increases with
increasing temperature, reaches a maximum for lines emitting close
to 1-2×105K, and decreases for higher temperatures. Part
of the wave energy penetrates into the corona, channeled into small
areas that appear to coincide with the endpoints of sunspot coronal
lops. The observations support the hypothesis that the oscillations
are caused by upwardly propagating acoustic waves. The observations
are not compatible with the concept of a chromospheric resonator.
Title: On the nature of the 3 minute oscillations above sunspots
Authors: Hansteen, V. H.; Wikstøl, Ø.; Brynildsen, N.; Maltby, P.;
Fredvik, T.; Kjeldseth-Moe, O.
Bibcode: 2002ESASP.505..183H
Altcode: 2002IAUCo.188..183H; 2002solm.conf..183H
Oscillations in the sunspot transition region and corona are observed
simultaneously with the Coronal Diagnostic Spectrometer - CDS on SOHO
and the Transition Region And Coronal Explorer - TRACE. Observations
of thirteen sunspots in 2001 and 2002 show that the amplitude in
the relative integrated line intensity increases with increasing
temperature, reaches a maximum for emission lines formed close to
1-2×105K, and decreases at higher temperatures. Part of the
wave energy penetrates into the corona, channeled into small areas that
appear to coincide with the endpoints of sunspot coronal loops. The
observed power spectra show one dominating peak close to 6 mHz. To
explore the nature of the waves we calculate upwardly propagating
acoustic waves confined to a magnetic flux tube and compare the results
with the observations.
Title: Oscillations Above Sunspots
Authors: Brynildsen, N.; Maltby, P.; Fredvik, T.; Kjeldseth-Moe, O.
Bibcode: 2002SoPh..207..259B
Altcode:
The 3-min oscillations in the sunspot atmosphere are discussed, based
on joint observing with the Transition Region and Coronal Explorer -
TRACE and the Solar and Heliospheric Observatory - SOHO. We find that
the oscillation amplitude above the umbra increases with increasing
temperature, reaches a maximum for emission lines formed close to 1-2×
105 K, and decreases for higher temperatures. Oscillations
observed with a high signal-to-noise ratio show deviations from pure
linear oscillations. The results do not support the sunspot filter
theory, based on the idea of a chromospheric resonator. Whereas the
filter theory predicts several resonant peaks in the power spectra,
equally spaced ∼ 1 mHz in frequency, the observed power spectra show
one dominating peak, close to 6 mHz. Spectral observations show that the
transition region lines contribute less than 13 percent to the TRACE 171
Å channel intensity above the umbra. The 3-min oscillations fill the
sunspot umbra in the transition region. In the corona the oscillations
are concentrated to smaller regions that appear to coincide with the
endpoints of sunspot coronal loops, suggesting that wave propagation
along the magnetic field makes it possible for the oscillations to
reach the corona.
Title: 3 minute oscillations above sunspots
Authors: Brynildsen, N.; Maltby, P.; Fredvik, T.; Kjeldseth-Moe, O.
Bibcode: 2002ESASP.508..283B
Altcode: 2002soho...11..283B
The aim of this investigation is a better understanding of the 3 minute
oscillations above sunspots. We present the first results from a joint
observing programme with SOHO and TRACE. Attention is given to the wave
amplitude as a function of the temperature and to the penetration of
part of the wave energy into the corona. The results appear to disagree
with the sunspot filter theory.
Title: The 6 mHz Oscillations above Sunspots
Authors: Brekke, P.; Brynildsen, N.; Maltby, P.; Fredvik, T.;
Kjeldseth-Moe, O.
Bibcode: 2002AAS...200.8806B
Altcode: 2002BAAS...34..790B
Sunspot oscillations in the transition region and corona are observed
simultaneously with CDS on SOHO and TRACE. Results obtained from
investigations of ten sunspots in 2001 and 2002 are presented. We
find that the oscillation amplitude above the umbra increases with
increasing temperature, reaches a maximum for lines emitted close to 200
000 K, and decreases for higher temperatures. Part of the wave energy
penetrates into the corona, channeled into small areas that appear
to coincide with the endpoints of sunspot coronal loops. The observed
power spectra show one dominating peak, near 6 mHz, and not several,
equally spaced resonances as predicted by theories based on the idea
of a chromospheric resonator. We conclude that the observations are
compatible with upwardly propagating acoustic waves.
Title: Redshift in sunspot plumes
Authors: Brynildsen, N.; Maltby, P.; Kjeldseth-Moe, O.
Bibcode: 2002AdSpR..30..529B
Altcode:
The non-uniform spatial distributions of emission and wavelength
shift in ten EUV lines formed in the chromosphere, transition region
and corona above 50 sunspots are investigated, based on observations
with the Coronal Diagnostic Spectrometer on the Solar and Heliospheric
Observatory. The sunspot plumes are the most prominent features in the
transition region line emissions. We find that almost all sunspots
show a plume when one magnetic polarity dominates the region out
to a distance of 50″ from the sunspot. Both the enhanced emission
and the redshift in sunspot plumes increase with the line formation
temperature, T, reach a maximum close to log T = 5.5 and cease to
exist close to log T = 6.0. The mass flow in the corona is too small
to explain the observed redshift in the transition region. We present
a working hypothesis where gas at transition region temperatures moves
in flow channels from the surroundings into the sunspot.
Title: Search for a chromospheric resonator above sunspots
Authors: Brynildsen, N.; Maltby, P.; Brekke, P.; Fredvik, T.;
Kjeldseth-Moe, O.
Bibcode: 2002cosp...34E.178B
Altcode: 2002cosp.meetE.178B
We have recently observed eleven sunspots, both with CDS on SOHO
and TRACE as part of our on-going investigations of the sunspot
atmosphere. For each sunspot we investigate the oscillations in
the chromosphere, transition region and corona. The observed power
spectra show one dominating peak corresponding to a period of 3
minutes. The oscillation amplitude above the umbra increases with
increasing temperature, reaches a maximum for lines emitting close to
200 000 K, and decreases for higher temperatures. Part of the wave
energy penetrates into the corona, channeled into small areas that
appear to coincide with the endpoints of sunspot coronal loops. The
observations support the hypothesis that the oscillations are caused
by upwardly propagating acoustic waves and show no signs of equally
spaced resonances as predicted by theories based on the idea of a
chromospheric resonator.
Title: Plumes and oscillations in the sunspot transition region
Authors: Maltby, P.; Brynildsen, N.; Kjeldseth-Moe, O.; Wilhelm, K.
Bibcode: 2001A&A...373L...1M
Altcode:
The suggestion that sunspot transition region oscillations are a typical
feature of the sunspot plumes is examined. The present observations show
3 min oscillations in the umbra that end at the umbral rim. We find
that sunspot plumes located above the umbra show these oscillations,
in contrast to plumes above the penumbra. These two findings suggest
that the oscillations may be a property of the umbral transition region.
Title: Dual Flows and Oscillations in the Sunspot Transition Region
Authors: Brynildsen, N.; Maltby, P.; Kjeldseth-Moe, O.; Wilhelm, K.
Bibcode: 2001ApJ...552L..77B
Altcode:
New knowledge about sunspot transition region lines that deviate
significantly from a Gaussian shape are presented. Attention is given
to ``multiple flows,'' a line profile phenomenon in which two or more
distinct velocities are observed within the same spatial resolution
element. We observe line profiles that are well represented by two
Gaussian line components in the N V λ1242 and O V λ629 lines and
introduce the notation ``dual flow.'' We have detected transition region
oscillations in one of the line components in the dual-flow events.
Title: Velocities in Sunspot Plumes
Authors: Maltby, P.; Kjeldseth-Moe, O.; Brynildsen, N.
Bibcode: 2001IAUS..203..300M
Altcode:
We investigate the line-of-sight velocities in 50 sunspot regions,
based on observations of ten or six EUV emission lines with the
Coronal Diagnostic Spectrometer - CDS on the Solar and Heliospheric
Observatory - SOHO. The position of the sunspots on the solar disk
ranges from disk centre to locations close to the solar limb. Attention
is given to the sunspot plumes, the most prominent features in the
transition region intensity maps. More than half of the sunspots
show downflows in the sunspot plumes that exceed 25 km s-1
at temperatures close to 300 000 K. The observations show that this
downflow cannot be maintained by inflow from the corona. The downflow
in the sunspot plumes appears to be maintained by gas at transition
region temperatures, streaming in flow channels from locations well
outside the sunspot. Although individual flow channels show significant
changes during approximately 10 minutes, part of the velocity pattern
remains unaltered for approximately one day. The velocity fields in
the transition region and the chromosphere are compared and the siphon
flow mechanism is confronted with the observations.
Title: Sunspot Plumes and Flow Channels
Authors: Brynildsen, N.; Maltby, P.; Fredvik, T.; Kjeldseth-Moe, O.;
Wilhelm, K.
Bibcode: 2001SoPh..198...89B
Altcode:
It is well known that sunspots are dark. This statement is not correct
in the sunspot atmosphere between the chromosphere and the corona,
where sunspots often are brighter than their surroundings. The brightest
feature in the sunspot transition region is called a sunspot plume. Not
all sunspots contain a plume. We find that 20 out of 21 sunspots show
a plume when one magnetic polarity dominates the sunspot region out
to a distance of 50 '' from the sunspot. Most sunspots show
downflows that exceed 25 km s−1 in the sunspot plumes at
temperatures close to 250 000 K. This downflow is not maintained by
inflow from the corona, but by gas at transition region temperatures,
streaming in flow channels from locations well outside the sunspot. We
suggest that this inflow is a necessary requirement for the sunspot
plume to occur and present a working hypothesis for the origin of
sunspot plumes. This paper is the first thorough spectral analysis of
sunspot plumes. It is based on simultaneous observations of ten or six
EUV emission lines in 42 sunspot regions with the Coronal Diagnostic
Spectrometer - CDS on the Solar and Heliospheric Observatory - SOHO. The
line profiles are studied in detail with another SOHO instrument,
the Solar Ultraviolet Measurements of Emitted Radiation - SUMER.
Title: On Sunspot Plumes and Dynamics above Sunspot Regions (CD-ROM
Directory: contribs/brynild)
Authors: Brynildsen, N.; Maltby, P.; Kjeldseth-Moe, O.
Bibcode: 2001ASPC..223..595B
Altcode: 2001csss...11..595B
No abstract at ADS
Title: Observations of sunspot transition region oscillations
Authors: Brynildsen, N.; Maltby, P.; Leifsen, T.; Kjeldseth-Moe, O.;
Wilhelm, K.
Bibcode: 2000SoPh..191..129B
Altcode:
Oscillations with a period of 3 minutes are observed in the transition
region of six sunspots with the Solar and Heliospheric Observatory
- SOHO joint observing programme for velocity fields in sunspot
regions. Observations of the transition region lines O v λ629
and N v λλ1238, 1242 with the SUMER instrument show significant
differences in the amplitude of the 3-minute oscillations from one
sunspot to another, both in intensity and line-of-sight velocity. In
four sunspots the central part of the umbra is observed. Two of these
sunspots show coincidence between the maxima in peak line intensity
and velocity directed towards the observer, as is expected for an
upward-propagating acoustic wave. The two other sunspots show large
oscillation amplitudes and a difference of 25° between maxima in
intensity and blue shift. The possible effect of partial wave reflection
on the observed phase relation is discussed. For one sunspot only a part
of the umbra, close to the penumbra, was observed and the observations
show a difference of 50° between maxima in intensity and blueshift. For
the smallest sunspot the observations are found to be contaminated by
contributions from an area without oscillations. Observed oscillations
in line width are small, but probably significant in two sunspots. The
observations of NOAA 8378 allow us to compare simultaneous recordings
of the oscillations in the chromospheric Si ii λ1260 line with the
oscillations in the transition region lines. We question the suggestion
by Fludra (1999) that the sunspot transition region oscillations are
a typical feature of the sunspot plumes.
Title: Dynamics in Restructuring Active Regions Observed During
Soho/Yohkoh/Gbo Campaigns
Authors: Schmieder, B.; Deng, Y.; Mandrini, C. H.; Rudawy, P.; Nitta,
N.; Mason, H.; Fletcher, L.; Martens, P.; Brynildsen, N.
Bibcode: 2000AdSpR..25.1879S
Altcode:
JOP17 and JOP 33 are SOHO Joint Observing Programs in collaboration
with Yohkoh/SXT and ground based observatories (GBO's), dedicated to
observe dynamical events through the atmosphere. During runs of these
programs we observed in restructuring active regions (ARs), surges,
subflares, bright knots, but not large flares and jets. From these
observations we have been able to derive some of the responses of the
coronal and chromospheric plasma to the evolution of the photospheric
magnetic field. Emerging flux in an AR led to the formation of Arch
Filament Systems in the chromosphere, hot loops and knots in the
transition region, and X-ray loops. Frequent surges have been observed
in relation to parasitic or mixed polarities, but coronal jets have not
yet been found. We discuss the possible mechanisms acting during the
restructuring of the active regions (reconnection or ``sea-serpent''
geometries)
Title: Signatures of Magnetic Reconnection and Observed EUV Emission
Line Profiles in An Active Region
Authors: Brekke, P.; Brynildsen, N.; Kjeldseth-Moe, O.; Maltby, P.;
Wilhelm, K.
Bibcode: 2000AdSpR..26..457B
Altcode:
We report on observations with SUMER on SOHO of high-velocity events,
also called explosive events. The high spatial and spectral resolutions
of SUMER allow simultaneous observations of EUV emission lines formed
at different temperatures within the transition region. Complex
line profiles with three separate line components appear to be
a characteristic feature of many high-velocity events based on a
survey of Si IV λ1393 observations. The present study is based on
551 spectra of the active region NOAA 7995 obtained on 17 November
1996. We find that the complex line profiles of explosive events may be
represented by a composite line profile consisting of three Gaussian
line components. Both positive and negative line-of-sight velocities
are found to be significantly larger at 6.3 ×105 K than
at 1.5 - 1.7 ×105 K. We briefly confront the observations
with signatures predicted from magnetic reconnections, disturbances
originating in the corona and flows in an extremely structured
transition region
Title: Structure and Dynamics in the Atmosphere Above Sunspot Regions
Authors: Brynildsen, N.; Brekke, P.; Haugan, S. V. H.; Kjeldseth-Moe,
O.; Maltby, P.; Wikstøl, Ø.
Bibcode: 2000AdSpR..25.1743B
Altcode:
Based on simultaneous observations of 10 EUV emission lines with the
Coronal Diagnostic Spectrometer - CDS on the Solar and Heliospheric
Observatory - SOHO we study the spatial distributions of both line
emission and line-of-sight velocity in the atmosphere above 17
sunspots. We find that both the enhanced EUV line emissions and the
velocities are distributed non-uniformly over the sunspot regions. Areas
with enhanced line emission tend to be red shifted, but they seldom
coincide exactly with areas with enhanced velocity. Bright sunspot
plumes with motion directed away from the observer are observed in
most of the sunspot regions
Title: On the sunspot transition region
Authors: Maltby, P.; Brynildsen, N.; Fredvik, T.; Kjeldseth-Moe, O.;
Wilhelm, K.
Bibcode: 1999SoPh..190..437M
Altcode:
The EUV line emission and relative line-of-sight velocity in the
transition region between the chromosphere and corona of 36 sunspot
regions are investigated, based on observations with the Coronal
Diagnostic Spectrometer - CDS and the Solar Ultraviolet Measurements of
Emitted Radiation - SUMER on the Solar and Heliospheric Observatory -
SOHO. The most prominent features in the transition-region intensity
maps are the sunspot plumes. In the temperature range between log T=5.2
and log T=5.6 we find that 29 of the 36 sunspots contain one or two
sunspot plumes. The relative line-of-sight velocity in sunspot plumes
is high and directed into the Sun in the transition region, for 19 of
the sunspots the maximum velocity exceeds 25 km s−1. The
velocity increases with increasing temperature, reaches a maximum
close to log T=5.5 and then decreases abruptly.
Title: EUV Line Emission and Dynamics in Sunspot Regions
Authors: Brynildsen, N.; Maltby, P.; Kjeldseth-Moe, O.
Bibcode: 1999ESASP.446..201B
Altcode: 1999soho....8..201B
The spatial distributions of EUV line emission and relative
line-of-sight velocity in the atmosphere above 22 sunspot regions are
investigated. The study is based on simultaneous observations of ten
EUV emission lines with the Coronal Diagnostic Spectrometer -- CDS on
SOHO. Since the EUV emission lines are formed at different temperatures,
we study the sunspot atmosphere from the chromosphere to the corona. We
observe both a rapid variation with a characteristic time of a few to
several minutes and a slow variation with a time constant of several
hours to approximately one day. The sunspot plume concept is reinvented
to describe the most prominent emission feature in the intensity maps in
the temperature range log T approx 5.2 - 5.6. The relative line-of-sight
velocity in sunspot plumes is high and directed into the Sun in the
transition region. The flow is maintained by plasmas at transition
region temperatures, moving from regions located at greater heights
outside the sunspot and towards the sunspot. Only a few features show
the signatures of a siphon flow. Comparisons of intensity and velocity
maps suggest that gas at transition region temperatures occur in loops
different from loops with coronal temperatures. However, we cannot
exclude the presence of transition region temperatures close to the
footpoints of flux tubes emitting at coronal temperatures.
Title: Sunspot Transition Region Oscillations
Authors: Brynildsen, N.; Kjeldseth-Moe, O.; Maltby, P.; Wilhelm, K.
Bibcode: 1999ESASP.446..207B
Altcode: 1999soho....8..207B
Based on the SOHO joint observing programme for velocity fields in
sunspots, we have detected 3 min transition region umbral oscillations
in six sunspots. Simultaneous recordings of O V lambda 629, NV lambdas
1238, 1242 and Si I lambda 1260 with the SUMER instrument allow us to
compare the transition region oscillations with the 3 min chromospheric
oscillations above the sunspot. We investigate the amplitudes and phase
relations of the oscillations in peak line intensity, line-of-sight
velocity and line width. The spatial distributions of power in the
3 min oscillations, both in intensity and line-of-sight velocity,
are presented. The observations show that the maxima in peak line
intensity are nearly, but not exactly in phase with the maxima in
velocity directed towards the observer. The suggestion that the waves
are upward propagating acoustic waves is confronted with observations.
Title: EUV Observations of Sunspot Regions with CDS on SOHO
Authors: Brynildsen, N.; Brekke, P.; Haugan, S. V. H.; Kjeldseth-Moe,
O.; Maltby, P.
Bibcode: 1999ASPC..184..266B
Altcode:
The spatial distributions of line emission and line-of-sight velocity in
seventeen different sunspot regions are studied, based on observations
with the Coronal Diagnostic Spectrometer - CDS on SOHO. Ten EUV emission
lines, formed in the chromosphere, transition region, and corona are
observed. Enhanced EUV line emissions in the transition region are
distributed non-uniformly over the active regions and are located both
inside and outside sunspots. Most sunspot regions show strongly enhanced
transition region line emission above the spot, i.e. sunspot plumes
are reinvented. From wavelength shifts we derive the line-of-sight
velocity, relative to the average velocity in the rastered area, 120"
x 120". In sunspot plumes we find that the motion is directed away from
the observer and increases with increasing line formation temperature,
T, reaches a maximum up to 40 km s-1 close to log T ≅ 5.5,
then decreases abruptly. The spatial extent of both emission features
and flow regions increase with increasing temperature within the
transition region. The observations show a marked difference between
the transition region and the low corona, both regarding the spatial
distributions of line emission and line-of-sight velocity.
Title: Transition Region Oscillations in a Sunspot Region
Authors: Brynildsen, N.; Fredvik, T.; Kjeldseth-Moe, O.; Maltby, P.
Bibcode: 1999ASPC..184..146B
Altcode:
Umbral oscillations in the sunspot transition region have been detected
and described from SOHO observations, mainly taken with SUMER of
NOAA 8156 on 18 February 1998 between 16:00 UT and 21:07 UT. SUMER
recorded simultaneously in the transition regions lines O V λ629, N
V λ1238 and N V λ1242, combined with long exposures for wavelength
calibration. Transition region oscillations with periods close to 3
min were observed both in intensity and in line-of-sight velocity;
the maximum intensity is nearly in phase with maximum velocity
directed towards the observer. The wave characteristics appear to be
compatible with the results of Gurman et al. (1982) from UVSP on SMM,
who interpreted them as upward propagating acoustic waves.
Title: Nonlinear Sunspot Transition Region Oscillations in NOAA 8378
Authors: Brynildsen, N.; Kjeldseth-Moe, O.; Maltby, P.; Wilhelm, K.
Bibcode: 1999ApJ...517L.159B
Altcode:
Observations obtained with the Solar and Heliospheric Observatory
joint observing program for velocity fields in sunspot regions are
used to study the 3 minute transition region oscillations above four
sunspots. Here we report mainly on the results obtained for NOAA 8378,
based on simultaneous recordings of the transition region lines O
V λ629 and N V λλ1238, 1242 and the chromospheric Si II λ1260
line with the Solar Ultraviolet Measurements of Emitted Radiation
instrument. The 3 minute transition region oscillations in NOAA 8378
occur mainly above the umbra and show (1) larger peak line intensity
amplitudes than reported before, (2) clear signs of nonlinearities,
(3) significant oscillations in line width, (4) maxima in peak line
intensity and maxima in velocity directed toward the observer that
are nearly, but not exactly in phase, and (5) a clear connection to
the oscillations in the sunspot chromosphere. The suggestion that the
waves are upward-propagating acoustic waves is confronted with the
observations by a simple test.
Title: SOHO Observations of the Structure and Dynamics of Sunspot
Region Atmospheres
Authors: Brynildsen, N.; Maltby, P.; Brekke, P.; Haugan, S. V. H.;
Kjeldseth-Moe, O.
Bibcode: 1999SoPh..186..141B
Altcode:
We present results from a study of the spatial distributions of line
emission and relative line-of-sight velocity in the atmosphere above
17 sunspot regions, from the chromosphere, through the transition
region and into the corona, based on simultaneous observations of ten
EUV emission lines with the Coronal Diagnostic Spectrometer - CDS on
SOHO. We find that the spatial distributions are nonuniform over the
sunspot region and introduce the notation 'sunspot loop' to describe an
enhanced transition region emission feature that looks like a magnetic
loop, extending from inside the sunspot to the surrounding regions. We
find little evidence for the siphon flow. Attention is given to the time
variations since we observe both a rapid variation with a characteristic
time of a few to several minutes and a slow variation with a time
constant of several hours to ≈ 1 day. The most prominent features
in the transition region intensity maps are the sunspot plumes. We
introduce an updated criterion for the presence of plumes and find
that 15 out of 17 sunspots contain a plume in the temperature range
logT≈5.2-5.6. The relative line-of-sight velocity in sunspot plumes
is high and directed into the Sun in the transition region. Almost
all the sunspot regions contain one or a few prominent, strongly
redshifted velocity channels, several of the channels extend from the
sunspot plume to considerable distances from the sunspot. The flow
appears to be maintained by plasmas at transition region temperatures,
moving from regions located at a greater height outside the sunspots
and towards the sunspot. The spatial correlation is high to moderate
between emission lines formed in the transition region lines, but
low between the transition region lines and the coronal lines. From
detailed comparisons of intensity and velocity maps we find transition
region emission features without any sign of coronal emission in the
vicinity. A possible explanation is that the emission originates in
magnetic flux tubes that are too cold to emit coronal emission. The
comparisons suggest that gas at transition region temperature occur in
loops different from loops with coronal temperature. However, we cannot
exclude the presence of transition region temperatures close to the
footpoints of flux tubes emitting at coronal temperatures. Regions with
enhanced transition region line emission tend to be redshifted, but the
correlation between line emission and relative line-of-sight velocity
is weak. We extend our conditional probability studies and confirm
that there is a tendency for line profiles with large intensities and
red shifts (blue shifts) above the average to constitute an increasing
(decreasing) fraction of the profiles as the wavelength shift increases.
Title: Sunspot Transition Region Oscillations in NOAA 8156
Authors: Brynildsen, N.; Leifsen, T.; Kjeldseth-Moe, O.; Maltby, P.;
Wilhelm, K.
Bibcode: 1999ApJ...511L.121B
Altcode: 1998astro.ph.12012B
Based on observations obtained with the Solar and Heliospheric
Observatory joint observing program for velocity fields in sunspot
regions, we have detected 3 minute transition region umbral oscillations
in NOAA 8156. Simultaneous recordings of O V λ629 and N V λ1238,
λ1242 with the SUMER instrument give the spatial distribution of power
in the 3 minute oscillations, both in intensity and in line-of-sight
velocity. Comparing loci with the same phase, we find that the entire
umbral transition region oscillates. The observed maxima in peak line
intensity are nearly in phase with the maxima in velocity directed
toward the observer. We discuss the suggestion that the waves are
upward-propagating acoustic waves.
Title: Flows in Sunspot Plumes Detected with SOHO
Authors: Brynildsen, N.; Maltby, P.; Brekke, P.; Fredvik, T.; Haugan,
S. V. H.; Kjeldseth-Moe, O.; Wikstol, O.
Bibcode: 1998ApJ...504L.135B
Altcode: 1998astro.ph..5249B
In the Letter, ``Flows in Sunspot Plumes Detected with the Solar and
Heliospheric Observatory'' by N. Brynildsen, P. Maltby, P. Brekke,
T. Fredvik, S. V. H. Haugan, O. Kjeldseth-Moe, and Ø. Wikstøl (ApJ,
502, L85 [1998]), the following correction should be made: In
the last line on page L86, which reads ``peak line intensity I>=5
are located (1) above the umbra or, '' an ``Ī'' should be inserted so
that the revised line reads ``peak line intensity I>=5Ī are located
(1) above the umbra or.''
Title: Flows in Sunspot Plumes Detected with the Solar and
Heliospheric Observatory
Authors: Brynildsen, N.; Maltby, P.; Brekke, P.; Fredvik, T.; Haugan,
S. V. H.; Kjeldseth-Moe, O.; Wikstøl, Ø.
Bibcode: 1998ApJ...502L..85B
Altcode:
Bright extreme-UV sunspot plumes have been observed in eight out of
11 different sunspot regions with the Coronal Diagnostic Spectrometer
on Solar and Heliospheric Observatory. From wavelength shifts, we
derive the line-of-sight velocity relative to the average velocity
in the rastered area, 120''×120''. In sunspot
plumes, we find that the motion is directed away from the observer
and increases with increasing line formation temperature, reaches a
maximum between 15 and 41 km s-1 close to log logT~5.5,
then decreases abruptly. The flow field in the corona is not well
correlated with the flow in the transition region, and we discuss
briefly the implication of this finding.
Title: SOHO Observations of the Connection Between Line Profile
Parameters in Active and Quiet Regions and the Net Red Shift in EUV
Emission Lines
Authors: Brynildsen, N.; Brekke, P.; Fredvik, T.; Haugan, S. V. H.;
Kjeldseth-Moe, O.; Maltby, P.; Harrison, R. A.; Wilhelm, K.
Bibcode: 1998SoPh..181...23B
Altcode:
We present high spatial and spectral resolution observations of
one active and one quiet-Sun region, obtained with CDS and SUMER on
SOHO. The connections between the line profile parameters are studied
and a systematic wavelength shift towards the red with increasing peak
line intensity (line broadening) is detected. The large scatter in
the data calls for another approach. We apply conditional probability
analysis to a series of EUV emission lines and find significant
correlations between line profile parameters. For a given interval in
wavelength shift we find that: (1) line profiles with large intensities
(line widths) and red shifts above the average constitute an increasing
fraction of the profiles as the relative wavelength shift increases,
(2) line profiles with large intensities (line widths) and blue
shifts compared to the average, on the other hand, constitute a
decreasing fraction of the profiles as the relative wavelength shift
increases. These results extend the findings of an earlier quiet-Sun
study from one to several emission lines and expand the validity to
include the active region. Interestingly, the active region observations
show correlations between peak line intensity and wavelength shift in
the coronal lines.
Title: EUV Spectroscopy of the Sunspot Region NOAA 7981 Using SOHO -
II. Velocities and Line Profiles
Authors: Brynildsen, N.; Brekke, P.; Fredvik, T.; Haugan, S. V. H.;
Kjeldseth-Moe, O.; Maltby, P.; Harrison, R. A.; Pike, C. D.; Rimmele,
T.; Thompson, W. T.; Wilhelm, K.
Bibcode: 1998SoPh..179..279B
Altcode:
We have studied the dynamics in the sunspot transition region between
the chromosphere and the corona and investigated the extension of
the flow field into the corona. Based on EUV spectra of a medium size
sunspot and its surroundings, NOAA 7981, observed with CDS and SUMER
on SOHO, we derive line-of-sight velocities and study the line profiles
for a series of emission lines.
Title: Extreme-Ultraviolet Sunspot Plumes Observed with SOHO
Authors: Maltby, P.; Brynildsen, N.; Brekke, P.; Haugan, S. V. H.;
Kjeldseth-Moe, O.; Wikstøl, Ø.; Rimmele, T.
Bibcode: 1998ApJ...496L.117M
Altcode: 1998astro.ph..1144M
Bright EUV sunspot plumes have been observed in five out of nine sunspot
regions with the Coronal Diagnostic Spectrometer on the Solar and
Heliospheric Observatory. In the other four regions, the brightest line
emissions may appear inside the sunspot but are mainly concentrated in
small regions outside the sunspot areas. These results are in contrast
to those obtained during the Solar Maximum Mission but are compatible
with the Skylab mission results. The present observations show that
sunspot plumes are formed in the upper part of the transition region,
occur in both magnetic unipolar and bipolar regions, and may extend
from the umbra into the penumbra.
Title: EUV Spectroscopy of the Sunspot Region NOAA 7981 Using SOHO -
I. Line Emission and Time Dependence
Authors: Brynildsen, N.; Brekke, P.; Fredvik, T.; Haugan, S. V. H.;
Kjeldseth-Moe, O.; Maltby, P.; Harrison, R. A.; Pike, C. D.; Rimmele,
T.; Thompson, W. T.; Wilhelm, K.
Bibcode: 1998SoPh..179...43B
Altcode:
EUV spectra of a medium-size sunspot and its surroundings, NOAA 7981,
were obtained on 2 August 1996 with the Coronal Diagnostic Spectrometer
(CDS) and the Solar Ultraviolet Measurements of Emitted Radiation
(SUMER) on the Solar and Heliospheric Observatory (SOHO). The spectral
lines formed in the transition region and corona show considerable
structure and large deviations from a uniform spatial distribution over
the active region. Enhanced EUV emissions in transition region lines
are concentrated in small regions outside the umbra of the sunspot
throughout most of the observing sequence. Only during a short,
active period do we find an enhanced line emission that reaches into
the umbra. Preliminary values for the umbral intensity are given.
Title: Three Dimensional EUV Imaging of Sunspot Regions Observed
with SOHO
Authors: Brynildsen, N.; Brekke, P.; Haugan, S. V. H.; Kjeldseth-Moe,
O.; Maltby, P.; Harrison, R. A.; Rimmele, T.; Wilhelm, K.
Bibcode: 1998ASPC..155..171B
Altcode: 1998sasp.conf..171B
No abstract at ADS
Title: The Non-Uniformity in the Sunspot Transition Region
Authors: Brynildsen, N.; Brekke, P.; Fredvik, T.; Haugan, S. V. H.;
Kjeldseth-Moe, O.; Maltby, P.; Harrison, R. A.; Rimmele, T.;
Wilhelm, K.
Bibcode: 1997ESASP.404..257B
Altcode: 1997cswn.conf..257B
No abstract at ADS
Title: Transition Region Velocities and Line Profiles in the Sunspot
Region 7981
Authors: Brynildsen, N.; Brekke, P.; Fredvik, T.; Haugan, S. V. H.;
Kjeldseth-Moe, O.; Maltby, P.; Harrison, R. A.; Pike, C. D.; Rimmele,
T. Thompson, W. T.; Wilhelm, K.
Bibcode: 1997ESASP.404..251B
Altcode: 1997cswn.conf..251B
No abstract at ADS
Title: CDS Observations of the Connection Between Line Intensity
and Doppler Shift in the Active Region NOAA 7981
Authors: Fredvik, T.; Brynildsen, N.; Maltby, P.; Kjeldseth-Moe, O.;
Brekke, P.; Haugen, S. V. H.; Harrison, R. A.
Bibcode: 1997ESASP.404..391F
Altcode: 1997cswn.conf..391F
No abstract at ADS
Title: The Net Redshifts in EUV Emission Lines and the Connection
Between Intensity and Doppler Shift
Authors: Brynildsen, N.; Fredvik, T.; Maltby, P.; Kjeldseth-Moe, O.;
Brekke, P.; Haugan, S. V. H.; Harrison, R. A.; Wilhelm, K.
Bibcode: 1997ESASP.404..263B
Altcode: 1997cswn.conf..263B
No abstract at ADS
Title: EUV Line Emission and Time Dependence in the Sunspot Region
NOAA 7981
Authors: Brynildsen, N.; Brekke, P.; Fredvik, T.; Haugan, S. V. H.;
Kjeldseth-Moe, O.; Maltby, P.; Harrison, R. A.; Pike, C. D.; Rimmele,
T.; Thompson, W. T.; Wilhelm, K.
Bibcode: 1997ESASP.404..245B
Altcode: 1997cswn.conf..245B
No abstract at ADS
Title: Temporal Variability in the Quiet Sun Transition Region
Authors: Wikstoøl, Ø.; Hansteen, V. H.; Brynildsen, N.; Maltby,
P.; Kyeldseth-Moe, O.; Harrison, R. A.; Wilhelm, K.; Tarbell, T. D.;
Scherrer, P. H.
Bibcode: 1997ESASP.404..733W
Altcode: 1997cswn.conf..733W
No abstract at ADS
Title: Flows and Dynamics in the Corona Observed with the Coronal
Diagnostic Spectrometer (cds)
Authors: Brekke, P.; Kjeldseth-Moe, O.; Brynildsen, N.; Maltby, P.;
Haugan, S. V. H.; Harrison, R. A.; Thompson, W. T.; Pike, C. D.
Bibcode: 1997SoPh..170..163B
Altcode:
EUV spectra obtained with the Coronal Diagnostic Spectrometer (CDS)
on the Solar and Heliospheric Observatory (SOHO) show significant flows
of plasma in active region loops, both at coronal and transition region
temperatures. Wavelength shifts in the coronal lines Mgix 368 Å and
Mgx 624 Å corresponding to upflows in the plasma reaching velocities
of 50 km s-1 have been observed in an active region. Smaller
velocities are detected in the coronal lines Fexvi 360 Å and Sixii
520 Å. Flows reaching 100 km s-1 are observed in spectral
lines formed at transition region temperatures, i.e., Ov 629 Å and
Oiii 599 Å, demonstrating that both the transition region and the
corona are clearly dynamic in nature. Some high velocity events show
even higher velocities with line profiles corresponding to a velocity
dispersion of 300-400 km s-1. Even in the quiet Sun there
are velocity fluctuations of 20 km s-1 in transition region
lines. Velocities of the magnitude presented in this paper have never
previously been observed in coronal lines except in explosive events
and flares. Thus, the preliminary results from the CDS spectrometer
promise to put constraints on existing models of the flows and energy
balance in the solar atmosphere. The present results are compared to
previous attempts to observe flows in the corona.
Title: Quiet-Sun Connection between the C IV Resonance Lines and
the Photospheric Magnetic Field
Authors: Brynildsen, Nils; Kjeldseth-Moe, Olav; Maltby, Per
Bibcode: 1996ApJ...462..534B
Altcode:
The quiet-Sun relation between the C iv resonance line parameters and
the photospheric magnetic field is studied with a spatial resolution of
1" x 1". The material is ordered into groups according to the magnitude
of the magnetic flux density, |B|, and conditional probabilities
are calculated. We find that red shifted profiles with either high
intensity, large Doppler shift, or large line broadening occupy an
increasing fraction of the area when |B| increases. These results are
contrasted by blueshifted profiles which indicate a slight decrease
with increasing magnetic flux density. The similarity in the results
obtained with magneto grams taken several hours before and after the
UV data led us to suggest that the tendency for red shifted profiles
to outnumber blueshifted profiles in quiet regions originates in the
super-granular network. Suggestions regarding the origin of the
redshift phenomenon are briefly confronted with the observations. It
appears difficult to explain the observations with models based on
continuous gas flows. However, a model containing Alfvén wave pulses
traveling from the corona toward the transition region promises to be
compatible with the observations.
Title: High Velocity Event Observed with CDS on SOHO
Authors: Kjeldseth-Moe, O.; Brynildsen, N.; Brekke, P.; Harrison, R. A.
Bibcode: 1996AAS...188.3714K
Altcode: 1996BAAS...28..880K
The Coronal Diagnostic Spectrometer, CDS, on SOHO has observed its
first strong High Velocity Event. The event occurred on 22 March
1996 at approximately 13.36 UT and was located in the leg of an
active region loop. The spectral signature is extremely wide emission
lines corresponding to a velocity dispersion of approximately 300-450
km/s. As measured in the 386 A line from Mg IX, the emission also seems
shifted in wavelength with a redshift corresponding to 65 km/s. The
intensity contrast in the line is a factor 2 compared to the surrounding
areas. The spatial extent is small, less than or corresponding to the
angular resolution of CDS of 4". The event occur in all available lines
from He I to Fe XV, i.e. over a temperature range from 10 000 K to
2.2 MK. This is a new result which has not been reported before. The
relation of this type of event to the well studied explosive events
is discussed.
Title: Transition Region Lines and the Photospheric Magnetic Field
Authors: Maltby, P.; Brynildsen, N.; Kjeldseth-Moe, O.
Bibcode: 1996AAS...188.0204M
Altcode: 1996BAAS...28..820M
We have combined quiet Sun observations of the C riptsize IV resonance
lines, obtained by the High Resolution Telescope and Spectrograph --
HRTS during the Spacelab 2 mission with Kitt Peak magnetograms. The
material is ordered into groups according to the magnitude of
the magnetic flux density, |B|, and conditional probabilities are
calculated. We find that redshifted profiles with either high intensity,
large Doppler shift, or large line broadening occupy an increasing
fraction of the area when |B| increases. Blueshifted profiles, on the
other hand, indicate a slight decrease with increasing magnetic flux
density. The similarity in the results obtained with magnetograms taken
several hours before and after the UV data led us to suggest that the
tendency for redshifted profiles to outnumber blueshifted profiles in
quiet regions originates in the supergranular network.
Title: Connection between the C IV resonance lines and the quiet
sun photospheric magnetic field
Authors: Brynildsen, N.; Kjeldseth-Moe, O.; Maltby, P.
Bibcode: 1996ASPC..109..115B
Altcode: 1996csss....9..115B
No abstract at ADS
Title: Quiet-Sun Connection between Intensity, Doppler Shift, and
Line Broadening in Solar Ultraviolet Emission Lines
Authors: Brynildsen, N.; Kjeldseth-Moe, O.; Maltby, P.
Bibcode: 1995ApJ...455L..81B
Altcode:
The quiet-Sun relations between the C IV line parameters, intensity,
wavelength shift, and line broadening, are studied with high spatial
and spectral resolution. The material is ordered into equal intervals
for one of the line parameters, and conditional probabilities
are calculated. As the Doppler velocity increases, we find that
redshifted profiles with a large intensity or line width constitute
an increasing fraction of the total number of profiles in a given
velocity interval. For blueshifted profiles, on the other hand, the
conditional probabilities for finding a profile with considerable
intensity or line width decrease as the line shift increases. Similar
relations are found when the material is ordered according to intensity
or line-width values.
Title: On the relation between red- and blueshifted UV-emission
lines and photospheric magnetic fields
Authors: Brynildsen, N.; Kjeldseth-Moe, Olav; Maltby, Per
Bibcode: 1994ESASP.373..413B
Altcode: 1994soho....3..413B
No abstract at ADS
Title: CDS quicklook display software
Authors: Brekke, P.; Haugan, S. V. H.; Brynildsen, Nils
Bibcode: 1994ESASP.373..437B
Altcode: 1994soho....3..437B
No abstract at ADS
Title: Fine structure and the emission filling factor
Authors: Kjeldseth-Moe, O.; Brynildsen, N.; Brekke, P.; Maltby, P.
Bibcode: 1994SSRv...70...89K
Altcode:
There is observational evidence for an extreme fine structure in
the solar transition region, much smaller than 1″ in size (Dereet
al., 1987, 1988) Corresponding to this extreme fine structure there
appear to be an equally complex dynamical structure. We review the
evidence for such dynamical extreme fine structure as demonstrated
by the frequent appearance of multiple velocities, i.e. distinctly
different velocities in the transition region occurring within the
angular resolution element. Multiple velocities are prominent in active
regions and particularly near sunspots, where velocity components
may be supersonic. However, multiple velocities are frequent also in
quiet regions. The consequences of such fine structure for modeling
the transition region will be outlined. Finally the appropriate CDS and
SUMER observations needed to extend our knowledge of a finely structured
transition region and corona, spatially or in time, are discussed.
Title: Multiple Flows and the Fine Structure of the Transition Region
around Sunspots
Authors: Kjeldseth-Moe, O.; Brynildsen, N.; Brekke, P.; Maltby, P.;
Brueckner, G. E.
Bibcode: 1993SoPh..145..257K
Altcode:
The fine structure in the flow field in the transition region above
and surrounding a sunspot is determined fromCIV 1548 å line profiles,
observed with the High Resolution Telescope and Spectrograph (HRTS)
during the Spacelab 2 mission. The observed line profiles show one, two,
or three distinct velocity components within the resolution element of
1″ × 1″. Supersonic flows occur in small regions where the line
profile has two or three components. The line component that shows
supersonic speed often is weaker than the subsonic line component,
which may explain why some observers have been unable to detect the
supersonic flow component. The broadening of individual line components
shows non-thermal velocities close to 20 km s−1. This
suggests that turbulence is less important than usually considered.
Title: Multiple flows in the solar transition region.
Authors: Brekke, P.; Brynildsen, N.; Kjeldseth-Moe, O.; Maltby, P.;
Brueckner, G. E.
Bibcode: 1992ESASP.346..211B
Altcode: 1992ssts.rept..211B
The solar transition region between the chromosphere and the corona
shows clear evidence of a fine scale structure that is much smaller
than the best available instrumental resolution in the UV of 1×1
arcsec. Previous studies have suggested filling factors of 0.01
- 0.001, with the solar gas being restricted to thin, extended
fibrills. New evidence of the fine scale structure is found from
its dynamical characteristics, the presence of multiple flows. In
multiple flows the solar gas in small volumes show several distinct
velocities, resulting in line profiles with more than one velocity
component within the spatial resolution element. Multiple velocities
are particularly prominent above sunspots, but by no means restricted
to these regions. Instead they are clearly a general feature in the
solar transition region, occurring in quiet as well as active regions.
Title: Evidence for fine structure in the solar transition region.
Authors: Brynildsen, N.
Bibcode: 1992mrpa.work..141B
Altcode:
The term fine structure in this paper means sub-resolution
structures. The arguments for a sub-resolution fine structure in
the solar transition region come from the following considerations:
1. Is it possible for the low transition region to radiate away
the energy conducted into it? 2. The observed vertical extent of
emission features at the solar limb is much larger than predicted from
models. 3. Transition region spectral lines show multiple velocities
along the line-of-sight within the spatial resolution element.
Title: Dynamics in the solar transition region.
Authors: Brekke, P.; Brynildsen, N.
Bibcode: 1991cwlt.conf...71B
Altcode:
The authors present an analysis of the dynamical evidence for extreme
fine structure in the transition region using the Si IV line at
1402 Å. Gas velocities, line widths and intensities are measured
from the line profiles by fitting the profiles to a set of Gaussian
components using a least squares method. Both quiet and active regions
are studied. The relation of the observed supersonic flow velocities
to possible shocks in the flow is briefly discussed.
Title: Multiple flow velocities in the transition region
Authors: Brekke, P.; Brynildsen, N.; Kjeldseth-Moe, O.; Maltby, P.;
Bartoe, J. -D. F.; Brueckner, G. E.
Bibcode: 1991AdSpR..11e.251B
Altcode: 1991AdSpR..11..251B
Observations with the High Resolution Telescope and Spectrograph (HRTS)
of the C IV lines at 1550 Å above sunspots reveal the co-existence
of several distinct high velocity gas components within the instrument
resolution element of 1 × 1 arc second. A further investigation of the
HRTS material demonstrates that such multiple gas velocities are not
restricted to the temperature region around 105 K, where the
C IV lines are formed, but that the gas flows with essentially unchanged
speed through all temperature layers from 2.5 × 105 K
to 104 K. Furthermore the phenomenon is not restricted to
sunspots, but occurs also in other solar regions, often most easily
distinguished in active regions. We describe the characteristics of the
velocity fields, analyze the mass fluxes and discuss the requirements
they place on the resolving power of future space instruments.
Title: Mass Transport above Sunspots
Authors: Brynildsen, N.; Kjeldseth-Moe, O.; Brueckner, G. E.
Bibcode: 1990Ap&SS.170..149B
Altcode:
Mass transport in the transition zone above a sunspot has been
studied in the Civ line at 1548 Å, formed at 100 000 K. Four spectral
rasters have been used, each covering 60×50 are sec. These have been
observed with the High Resolution Telescope and Spectrograph during
the Spacelab-2 mission in 1985. Flow velocities are derived from
multiple Gaussian components fitted to the observed line intensity
profiles. Density sensitive lines were used to find a relation between
the Civ line intensity and the particle density. This relation is used
in the mass flux calculations. The investigation indicates a clear
net downward mass flux above sunspots.
Title: Observed Line Profiles and Mass Fluxes in the Transition
Region above Sunspots
Authors: Maltby, P.; Brekke, P.; Brynildsen, N.; Kjeldseth-Moe, O.;
Bartoe, J. -D. F.; Brueckner, G. E.
Bibcode: 1990PDHO....7..244M
Altcode: 1990dysu.conf..244M; 1990ESPM....6..244M
Spectrograms obtained with the HRTS show strong mass flows through
the transition zone that are particularly prominent above sunspot
regions. Most characteristic for the flow associated with sunspots
are regions with supersonic downflows, but upward flowing gas is
also observed with generally smaller velocities. The flow pattern
changes from one day to the next and even within a time span of
minutes. An apparent lack of balance between up- and downflowing
massfluxes is found. Generally the net massflux appears to be directed
downward. Possible reasons for this result are briefly discussed in
terms of observability and line emission area filling factor.
Title: Distribution of Velocities in the Pre-Eruptive Phase of a
Quiescent Prominence
Authors: Engvold, Oddbjørn; Jensen, Eberhart; Zhang, Yi; Brynildsen,
Nils
Bibcode: 1990LNP...363..263E
Altcode: 1990IAUCo.117..263E; 1990doqp.coll..263E
High resolution Ca II K line spectra of a large quiescent prominence
were obtained about one hour before a prominence eruption May 2nd
1974. The observations were made with the main spectrograph of the
vacuum tower of Sacramento Peak Observatory. The observed velocities
in a wide range from -50 to +25 km/s suggest that the very initial
stages of destabilization of the prominence were in fact recorded. The
distribution of line intensities and line widths versus line shift
suggest that one observes 3 threads in the line-of-sight for low
velocities. For larger shifts one is evidently able to observe
individual threads.
Title: Transition Region Massflows Associated with Sunspots
Authors: Kjeldseth-Moe, O.; Brekke, P.; Brynildsen, N.; Maltby, P.;
Brueckner, G. E.; Bartoe, J. -D. F.
Bibcode: 1989BAAS...21.1178K
Altcode:
No abstract at ADS
Title: Distribution of velocities in the Pre-Eruptive Phase of a
Quiscent Prominence
Authors: Engvold, O.; Jensen, E.; Zhang, Yi; Brynildsen, N.
Bibcode: 1989HvaOB..13..205E
Altcode:
No abstract at ADS
Title: Bildebehandling av solspektra fra romfergen.
Authors: Brekke, P.; Brynildsen, N.
Bibcode: 1989ATi....22...49B
Altcode:
No abstract at ADS
Title: Gas Flows in the Transition Region above Sunspots
Authors: Kjeldseth-Moe, O.; Brynildsen, N.; Brekke, P.; Engvold, O.;
Maltby, P.; Bartoe, J. -D. F.; Brueckner, G. E.; Cook, J. W.; Dere,
K. P.; Socker, D. G.
Bibcode: 1988ApJ...334.1066K
Altcode:
Strong downflows and moderate upflows in the transition region over
a sunspot have been observed with the HRTS on Spacelab 2 in 1985. The
flows are persistent in the sense that they are seen in the same spot
for 5 days. The downflows are prominent in regions of limited extent
(4arcsec - 6arcsec), and flow velocities are in the range 40 - 80 km
s-1 and are thus supersonic. Upward flows have smaller
velocities, 5 - 20 km s-1, but may extend over a larger
area. In the downflowing regions there is always an appreciable amount
of gas at rest in the line of sight. Flow speeds derived from the
profiles of different lines formed in the transition region between
30,000 and 230,000K are very similar implying constant downflow in
this temperature range.
Title: Gasflows in the transition region above sunspots.
Authors: Kjeldseth-Moe, O.; Brynildsen, N.; Brekke, P.; Bartoe,
J. -D. F.; Brueckner, G. E.
Bibcode: 1987ESASP.275...27K
Altcode: 1987sspp.symp...27K
Gas flows in the transition region in and above sunspots were observed
with the High Resolution Telescope and Spectrograph on two rocket
flights and during the Spacelab 2 mission. Supersonic downflows of
mass from the corona appear to be generally occurring in sunspots. The
downflows are often concentrated in regions with typical diameters of
4000 km on the Sun, suggesting a flow in a looplike structure. However,
the total flow pattern often has an elongated sheetlike structure
of much larger extent. Flow speeds are typically 80 km/sec and show
small variation with the temperature of the radiating gas. Much higher
flow-speeds (180 km/sec) also occur. Studies of the areas surrounding
the sunspot in the Spacelab material reveal the presence of upflows over
extended regions with flow-speeds of 10 to 30 km/sec. It is not clear
whether the amount of upward flowing gas is sufficient to compensate
for the mass flux in the downflows.
Title: Transition Zone Flows in Sunspots
Authors: Kjeldseth-Moe, O.; Brynildsen, N.; Engvold, O.; Maltby, P.;
Bartoe, J. -D. F.; Brueckner, G. E.
Bibcode: 1987rfsm.conf..317K
Altcode:
Downflow in the transition region over sunspots first detected on HRTS
rocket flights, seems to be a general phenomenon. Although details
in the flow pattern appear to change over a period of minutes, the
phenomenon itself persists for days. While the mechanism producing the
observed redshifts is not understood it seems most likely that they are
produced by actual downflow of gas in thin filamentary structures. This
may be inferred from the co-existence within the same spatial resolution
element of tubes with strong downflows and tubes where the gas is at
rest. Thus the line profiles result from an unresolved fine structure
in a similar fashion that Evershed effect in the photosphere produces
"flag"-like line profiles in visual lines.
Title: Temperatures of quiescent prominences measured from hydrogen
Paschen and Ca II IR lines.
Authors: Engvold, Oddbjorn; Brynildsen, Nils
Bibcode: 1986NASCP2442...97E
Altcode: 1986copp.nasa...97E
During 12 to 17 September 1983 a number of prominences were observed
with the McMatch solar telescope of National Solar Observatories,
using the Fourier transform spectrometer with a InSb detector (Brault
1979). The present study refers to three prominences observed 13
and 14 September. Prominence A: Large quiescent prominence at S28
E90 Prominence B. Stable prominence in weakly enhanced magnetic
region at about NO8 E90 Prominence C: Quiescent prominence at N30
E90. Spectra were obtained at a total of 15 different locations in
the three prominences in the wavelength range lambda, lambda 7740 to
14,000 Angstroms. The observed differences between Texc
and Tkin are hardly significant. Researchers conclude that
the two methods for temperature determination when applied to optically
thin lines give reasonably consistent results, i.e., the population of
the excited levels of hydrogen is collisionally controlled. The well
known increase in T and V towards the edge of equiescent prominences
(Hirayama 1964) is not corroborated by the present data. One explanation
for this could be that prominence A is atypical. The optical thickness
of prominence emission lines tends to increase from center to edges as
demonstrated by the case of He I lambda 10830 angstroms. If line opacity
plays a significant role in earlier center to edge determinations of
T and V, a smaller variation would be expected from measurements in
optically thin lines, such as in the present case.
Title: Variability of spectral lines in full-disk observations of
the sun.
Authors: Barth, S. B.; Brynildsen, N.; Engvold, O.
Bibcode: 1983ITABO..59...27B
Altcode:
Signals of solar activity have been searched for in full-disk line
spectra of the sun. In the chromospheric lines Ca II H and K,
and Hα, one finds that the central flux varies in concert with
solar activity. Hγ shows no clear dependence on activity. Noticeable
variations in the Ca II line flux are seen in the course of an hour. The
photospheric Fe I λ5250 Å line tends to get deeper with increasing
activity.