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Author name code: maltby
ADS astronomy entries on 2022-09-14
author:"Maltby, Per"
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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.
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.
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Title: Oscillations in the Umbral Atmosphere
Authors: Brynildsen, N.; Maltby, P.; Foley, C. R.; Fredvik, T.;
Kjeldseth-Moe, O.
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.
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Title: Oscillations Above the Umbra of Sunspots
Authors: Brynildsen, N.; Maltby, P.; Fredvik, T.; Kjeldseth-Moe, O.
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.
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Title: Search for a chromospheric resonator above sunspots
Authors: Brynildsen, N.; Maltby, P.; Brekke, P.; Redvik, T.;
Kjeldseth-Moe, O.
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 <SUP>5</SUP> 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.
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Title: Sunspot Oscillations and Acoustic Wave Propagation
Authors: Brekke, P.; Brynildsen, N.; Maltby, P.; Fredvik, T.;
Kjeldseth-Moe, O.
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.
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Title: Oscillations in the wings of sunspot transition region lines
Authors: Brynildsen, N.; Maltby, P.; Kjeldseth-Moe, O.; Wilhelm, K.
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.
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Title: Sunspot oscillations in the chromosphere, transition region,
and corona
Authors: Brynildsen, N.; Maltby, P.; Fredvik, T.; Kjeldseth-Moe, O.
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 1-2×10<SUP>5</SUP>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
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.
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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.
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
1-2×10<SUP>5</SUP>K, 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.
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Title: Oscillations Above Sunspots
Authors: Brynildsen, N.; Maltby, P.; Fredvik, T.; Kjeldseth-Moe, O.
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×
10<SUP>5</SUP> 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.
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Title: 3 minute oscillations above sunspots
Authors: Brynildsen, N.; Maltby, P.; Fredvik, T.; Kjeldseth-Moe, O.
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.
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Title: The 6 mHz Oscillations above Sunspots
Authors: Brekke, P.; Brynildsen, N.; Maltby, P.; Fredvik, T.;
Kjeldseth-Moe, O.
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.
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Title: Redshift in sunspot plumes
Authors: Brynildsen, N.; Maltby, P.; Kjeldseth-Moe, O.
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.
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Title: Search for a chromospheric resonator above sunspots
Authors: Brynildsen, N.; Maltby, P.; Brekke, P.; Fredvik, T.;
Kjeldseth-Moe, O.
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.
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Title: Plumes and oscillations in the sunspot transition region
Authors: Maltby, P.; Brynildsen, N.; Kjeldseth-Moe, O.; Wilhelm, K.
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.
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Title: Dual Flows and Oscillations in the Sunspot Transition Region
Authors: Brynildsen, N.; Maltby, P.; Kjeldseth-Moe, O.; Wilhelm, K.
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.
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Title: Velocities in Sunspot Plumes
Authors: Maltby, P.; Kjeldseth-Moe, O.; Brynildsen, N.
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<SUP>-1</SUP>
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.
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Title: Sunspot Plumes and Flow Channels
Authors: Brynildsen, N.; Maltby, P.; Fredvik, T.; Kjeldseth-Moe, O.;
Wilhelm, K.
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 <SUP>”</SUP> from the sunspot. Most sunspots show
downflows that exceed 25 km s<SUP>−1</SUP> 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.
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Title: On Sunspot Plumes and Dynamics above Sunspot Regions (CD-ROM
Directory: contribs/brynild)
Authors: Brynildsen, N.; Maltby, P.; Kjeldseth-Moe, O.
2001ASPC..223..595B Altcode: 2001csss...11..595B
No abstract at ADS
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Title: Sunspots: Wilson Effect
Authors: Maltby, P.
2000eaa..bookE2056M Altcode:
The Wilson effect refers to the depressed appearance of SUNSPOTS when
positioned close to the solar limb. The impression is that sunspots are
cavities in the SOLAR PHOTOSPHERE. The reason is that the radiation
we observe is coming from deeper layers in the sunspot than in the
surrounding photosphere. The detection of this depression by Alexander
Wilson dates back to 1769. The phenomenon is exp...
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Title: Observations of sunspot transition region oscillations
Authors: Brynildsen, N.; Maltby, P.; Leifsen, T.; Kjeldseth-Moe, O.;
Wilhelm, K.
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.
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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.
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 ×10<SUP>5</SUP> K than
at 1.5 - 1.7 ×10<SUP>5</SUP> 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
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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.
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
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Title: On the sunspot transition region
Authors: Maltby, P.; Brynildsen, N.; Fredvik, T.; Kjeldseth-Moe, O.;
Wilhelm, K.
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<SUP>−1</SUP>. The
velocity increases with increasing temperature, reaches a maximum
close to log T=5.5 and then decreases abruptly.
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Title: EUV Line Emission and Dynamics in Sunspot Regions
Authors: Brynildsen, N.; Maltby, P.; Kjeldseth-Moe, O.
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.
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Title: Sunspot Transition Region Oscillations
Authors: Brynildsen, N.; Kjeldseth-Moe, O.; Maltby, P.; Wilhelm, K.
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.
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Title: EUV Observations of Sunspot Regions with CDS on SOHO
Authors: Brynildsen, N.; Brekke, P.; Haugan, S. V. H.; Kjeldseth-Moe,
O.; Maltby, P.
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<SUP>-1</SUP> 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.
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Title: Transition Region Oscillations in a Sunspot Region
Authors: Brynildsen, N.; Fredvik, T.; Kjeldseth-Moe, O.; Maltby, P.
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.
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Title: Nonlinear Sunspot Transition Region Oscillations in NOAA 8378
Authors: Brynildsen, N.; Kjeldseth-Moe, O.; Maltby, P.; Wilhelm, K.
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.
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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.
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: Professor Øystein Elgarøy (1929 - 8 September 1998).
Authors: Maltby, P.
1999ATi....33...12M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Sunspot Transition Region Oscillations in NOAA 8156
Authors: Brynildsen, N.; Leifsen, T.; Kjeldseth-Moe, O.; Maltby, P.;
Wilhelm, K.
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: Coronal Radiation and Helium λ584 Emission in Active Regions
Authors: Fredvik, T.; Maltby, P.
1999SoPh..184..113F Altcode:
Based on EUV observations of eleven sunspot regions obtained with
the Coronal Diagnostic Spectrometer, CDS, on SOHO we have studied the
spatial distribution, temporal variation and wavelength shift of the
He i λ584 line. We find a relatively high spatial correlation between
the coronal line Fe xvi λ360 and the He i λ584 line. This points to
coronal back-radiation as an important contributor to the formation
of the He i line in active regions. However, contribution to the
line formation from another source is suggested by the following two
findings: First, the red-shifted line profiles of both He i λ584 and
the transition region lines tend to be more intense than blue-shifted
profiles. Second, the He i λ584 emission changes significantly faster
than the coronal line emission.
---------------------------------------------------------
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.
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: <P />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.
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<SUP>”</SUP>×120<SUP>”</SUP>. 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<SUP>-1</SUP> 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.
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.
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.
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.
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.
1998ASPC..155..171B Altcode: 1998sasp.conf..171B
No abstract at ADS
---------------------------------------------------------
Title: Closing summary
Authors: Maltby, P.
1998AdSpR..21..351M Altcode:
Emphasis is given to the search for an ingenious space mission proposal
that aims to solve an important scientific problem of general interest.
---------------------------------------------------------
Title: European Plans for the Solar/Heliospheric Stereo Mission
Authors: Bothmer, V.; Bougeret, J. -L.; Cargill, P.; Davila, J.;
Delaboudiniere, J. -P.; Harrison, R.; Koutchmy, S.; Liewer, P.;
Maltby, P.; Rust, D.; Schwenn, R.
1998ESASP.417..145B Altcode: 1998cesh.conf..145B
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.
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.
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.
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.
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.
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.
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.
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<SUP>-1</SUP> 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<SUP>-1</SUP> 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<SUP>-1</SUP>. Even in the quiet Sun there
are velocity fluctuations of 20 km s<SUP>-1</SUP> 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: Dynamics of Sunspots
Authors: Maltby, P.
1997ASPC..118...91M Altcode: 1997fasp.conf...91M
Since we are observing the Sun from one vantage point, either in space
or from the ground, a complete determination of the velocity field is
difficult and critically dependent on the assumptions applied. After a
brief review of the characteristics of gas flow in flux tubes the siphon
flow hypothesis is presented and confronted with observations. It is
found that the inverse Evershed effect in the chromosphere is compatible
with a siphon flow, provided new flow channels constantly replace old
ones as they lose their mass to the sunspot. The conflicts between
the siphon flow hypothesis and the observations of the Evershed effect
are discussed and possible solutions presented. New SOHO observations
of the sunspot region in the transition region and the corona are
presented and the observational basis for the multiple flow concept is
discussed. The complexity of the observed flow field in the transition
region is underlined and alternative working hypotheses are discussed.
---------------------------------------------------------
Title: Book reviews
Authors: Marx, G.; Jaffe, W.; Maltby, P.; Grevesse, N.; Wu, S. T.;
Lüst, R.; Kleczek, J.; Chupp, E. L.; Bloemen, Hans; de Jager,
Cornelis; van Teeseling, A.; Shea, M. A.; Butcher, H.; van der Kruit,
P. C.; Nieuwenhuijzen, H.; Steeghs, Danny; Fälthammar, Carl-Günne;
Greenberg, J. M.; Rasool, S. I.
1996SSRv...77..369M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Quiet-Sun Connection between the C IV Resonance Lines and
the Photospheric Magnetic Field
Authors: Brynildsen, Nils; Kjeldseth-Moe, Olav; Maltby, Per
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. <P />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: Transition Region Lines and the Photospheric Magnetic Field
Authors: Maltby, P.; Brynildsen, N.; Kjeldseth-Moe, O.
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.
1996ASPC..109..115B Altcode: 1996csss....9..115B
No abstract at ADS
---------------------------------------------------------
Title: Are the Redshifts Observed in Transition Region Lines Caused
by Magnetic Reconnection?
Authors: Hansteen, Viggo; Maltby, Per; Malagoli, Andrea
1996ASPC..111..116H Altcode: 1997ASPC..111..116H
The detection of differential redshift between transition region and
chromospheric line emission, both in spectra of late type stars and in
solar spectra has been a puzzle for two decades. The fact that solar
observations are inconsistent with a continuous downflow calls for
another interpretation. The authors pursue the interpretation that
the observed pervasive transition region line shifts are caused by
MHD waves propagating along the magnetic field lines from the corona
downward towards the chromosphere.
---------------------------------------------------------
Title: The Coronal Diagnostic Spectrometer for the Solar and
Heliospheric Observatory
Authors: Harrison, R. A.; Sawyer, E. C.; Carter, M. K.; Cruise,
A. M.; Cutler, R. M.; Fludra, A.; Hayes, R. W.; Kent, B. J.; Lang,
J.; Parker, D. J.; Payne, J.; Pike, C. D.; Peskett, S. C.; Richards,
A. G.; Gulhane, J. L.; Norman, K.; Breeveld, A. A.; Breeveld, E. R.; Al
Janabi, K. F.; Mccalden, A. J.; Parkinson, J. H.; Self, D. G.; Thomas,
P. D.; Poland, A. I.; Thomas, R. J.; Thompson, W. T.; Kjeldseth-Moe,
O.; Brekke, P.; Karud, J.; Maltby, P.; Aschenbach, B.; Bräuninger,
H.; Kühne, M.; Hollandt, J.; Siegmund, O. H. W.; Huber, M. C. E.;
Gabriel, A. H.; Mason, H. E.; Bromage, B. J. I.
1995SoPh..162..233H Altcode:
The Coronal Diagnostic Spectrometer is designed to probe the solar
atmosphere through the detection of spectral emission lines in the
extreme ultraviolet wavelength range 150 - 800 å. By observing
the intensities of selected lines and line profiles, we may derive
temperature, density, flow and abundance information for the plasmas
in the solar atmosphere. Spatial and temporal resolutions of down to
a few arcseconds and seconds, respectively, allow such studies to be
made within the fine-scale structure of the solar corona. Futhermore,
coverage of large wavelength bands provides the capability for
simultaneously observing the properties of plasmas across the wide
temperature ranges of the solar atmosphere.
---------------------------------------------------------
Title: Quiet-Sun Connection between Intensity, Doppler Shift, and
Line Broadening in Solar Ultraviolet Emission Lines
Authors: Brynildsen, N.; Kjeldseth-Moe, O.; Maltby, P.
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: Observed Redshifts in the Solar Transition Region above Active
and Quiet Regions
Authors: Achour, H.; Brekke, P.; Kjeldseth-Moe, O.; Maltby, P.
1995ApJ...453..945A Altcode:
Solar UV spectral observations show a redshifted emission at
temperatures between the chromosphere and the corona. We have measured
the magnitude of the redshift as a function of the temperature using
solar spectrograms from the High Resolution Telescope and Spectrograph
HRTS. The velocity derived from the average redshift is found to
increase up to a temperature T ≍ 1.35 x 10<SUP>5</SUP> K in both
quiet and active regions, then decrease with increasing temperature,
with the rate of decrease depending critically on the laboratory
wavelengths adopted for the transition region lines. This result
illustrates the need for improved laboratory measurements. <P />We
find that the differential re shift between an active region and the
surroundings increases smoothly with temperature, reaches a maximum
velocity difference of 7 km s 1 at 1.35 × 10<SUP>5</SUP> K and
falls abruptly to zero at 2.3 × 10<SUP>5</SUP> K. This observation
is independent of the laboratory wavelengths. Suggestions regarding
the origin of the redshift are confronted with the results.
---------------------------------------------------------
Title: Frontiers of astrophysics. Proceedings.
Authors: Lilje, P. B.; Maltby, P.
1995fap..book.....L Altcode:
To honour one of the pioneers of modern astrophysics, Svein Rosseland
(1894 - 1985).
---------------------------------------------------------
Title: Frontiers of astrophysics
Authors: Lilje, Per B.; Maltby, Per
1995fras.conf.....L Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Solar Activity Today
Authors: Maltby, P.
1995fras.conf..205M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: On the relation between red- and blueshifted UV-emission
lines and photospheric magnetic fields
Authors: Brynildsen, N.; Kjeldseth-Moe, Olav; Maltby, Per
1994ESASP.373..413B Altcode: 1994soho....3..413B
No abstract at ADS
---------------------------------------------------------
Title: Fine structure and the emission filling factor
Authors: Kjeldseth-Moe, O.; Brynildsen, N.; Brekke, P.; Maltby, P.
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: Redshifted transition region lines explained
Authors: Hansteen, V.; Maltby, P.
1994AdSpR..14d..57H Altcode: 1994AdSpR..14...57H
The discovery of differential redshift between transition region and
chromospheric line emissions, both in the spectra of late-type stars
and in the solar spectra has been a puzzle for more than a decade. The
fact that the solar observations appear to be inconsistent with a
continuous downflow calls for another interpretation. We propose that
this pervasive redshift observed in transition region spectral lines
is caused by conduction modified MHD waves propagating along the
magnetic field lines from the corona towards the chromosphere. The
waves are assumed generated in the corona by nanoflares, i.e.by an
episodic heating mechanism. The calculations for acoustic waves show
line profiles with many of the same characteristics as the observations.
---------------------------------------------------------
Title: The Thermal Magnetic Structure of Sunspots
Authors: Maltby, P.
1994IAUS..154..423M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Fine-scale structure and the Evershed effect
Authors: Maltby, P.
1994smf..conf..188M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Sunspot temperatures
Authors: Maltby, P.
1994ASIC..433..179M Altcode:
No abstract at ADS
---------------------------------------------------------
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.
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<SUP>−1</SUP>. This
suggests that turbulence is less important than usually considered.
---------------------------------------------------------
Title: Wave phenomena in solar terrestrial plasmas. Proceedings.
Authors: Maltby, P.; Pécseli, H. L.
1993wpst.conf.....M Altcode:
The aim of this Mini-Workshop is to give further insight into physical
processes that are relevant for the scientific output of space
projects with Norwegian participation. It represents a challenge both
in astrophysics and space plasma. New results from CRRES, GEOTAIL,
FREIA, ULYSSES, and YOHKOH were available.
---------------------------------------------------------
Title: Scientific requirements for future solar-physics space missions
Authors: Maltby, P.; Battrick, B.
1993ESASP1157.....M Altcode: 1993srfs.book.....M; 1993QB520.S25......
No abstract at ADS
---------------------------------------------------------
Title: Multiple flows in the solar transition region.
Authors: Brekke, P.; Brynildsen, N.; Kjeldseth-Moe, O.; Maltby, P.;
Brueckner, G. E.
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: On Redshifts in Stellar Ultraviolet Emission Lines
Authors: Hansteen, V.; Maltby, P.
1992ComAp..16..137H Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Continuum Observations and Empirical Models of the Thermal
Structure of Sunspots
Authors: Maltby, P.
1992ASIC..375..103M Altcode: 1992sto..work..103M
Intensity observations of sunspot umbrae and penumbrae in the visible
and infrared are reviewed. The continuum intensity in the darkest
part of the umbra and the average penumbral intensity are known
with relatively high accuracy in large sunspots. With the aim of
understanding conflicting observations of umbral dots it is suggested
that the umbral core is nearly free of umbral dots, and that an umbral
core only occurs in sunspots above a certain size. The present status
of semi-empirical models of the temperature stratification in umbrae and
penumbrae is discussed and the need for extending the model calculations
to more than one dimension is pointed out.
---------------------------------------------------------
Title: Signatures of episodic coronal heating in solar transition
region spectral lines.
Authors: Hansteen, V.; Maltby, P.
1992mrpa.work..127H Altcode:
A brief introduction to the heating mechanisms in the solar atmosphere
and to the observed redshifts in transition region lines is given. The
authors discuss a new interpretation of the observed redshift and
present calculations that support the new explanation.
---------------------------------------------------------
Title: Sunspots: An Observational Overview (Invited)
Authors: Maltby, P.
1992LNP...397..124M Altcode: 1992sils.conf..124M
No abstract at ADS
---------------------------------------------------------
Title: Magnetic reconnection in physics and astrophysics. Proceedings.
Authors: Maltby, P.
1992mrpa.work.....M Altcode:
The workshop focuses on problems of interest to both space physicists
and astrophysicists, as well as researchers working on laboratory
plasmas. Magnetic reconnection in small laboratory experiments and
in fusion devices, processes in the Earth's magnetosphere and in the
solar transition region and the corona are discussed. It is shown how
useful relatively small laboratory experiments can be in generating
and testing out new ideas.
---------------------------------------------------------
Title: Active regions, sunspots and their magnetic fields.
Authors: Semel, Meir; Mouradian, Zadig; Soru-Escaut, Irina; Maltby,
Per; Rees, David; Makita, Mitsugu; Sakurai, Takashi
1991sia..book..844S Altcode:
Surface magnetism is the progenitor of active regions, sunspots, and
all related phenomena. This cause and effect is reversible so that,
using well-established empirical laws, the presence and morphology of
photospheric magnetic fields can be deduced from active-region light
emission structure. In the (simplifying) case of sunspots, MHD and
thermodynamic theory find some success in the interpretation of the
interaction of magnetic fields and solar plasma. Coronal magnetic fields
also appear to be predictable by extrapolation techniques starting
from the photospheric conditions. Alternatively, surface magnetism can
be observed "directly" by means of the spectroscopic Zeeman effect
and Stokes polarimetry. Eventually these empirical, theoretical and
direct-measurement techniques must converge to identical results as
we better understand the physics of active regions.
---------------------------------------------------------
Title: Diagnostics of solar oscillation observations. Proceedings.
Authors: Maltby, P.; Leer, E.
1991dsoo.conf.....M Altcode:
No abstract at ADS
---------------------------------------------------------
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.
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 10<SUP>5</SUP> K, where the
C IV lines are formed, but that the gas flows with essentially unchanged
speed through all temperature layers from 2.5 × 10<SUP>5</SUP> K
to 10<SUP>4</SUP> 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: Coronae and winds in late-type stars. Proceedings.
Authors: Leer, E.; Maltby, P.
1991cwlt.conf.....L Altcode:
No abstract at ADS
---------------------------------------------------------
Title: New Light on Solar Infrared Intensity Oscillations
Authors: Leifsen, T.; Maltby, P.
1990SoPh..125..241L Altcode:
The detection of large-amplitude infrared solar intensity oscillations
in the 5-min region is reported. Using a broad-band multichannel
photometer, the peak-to-peak intensity variation at 2.23 μm is found
to be as high as 2.4% for a circular aperture of 1 arc min and 0.8%
in the full disk observations, i.e., remarkably higher than at the
other four observed wavelength regions.
---------------------------------------------------------
Title: The Effect of MHD-Waves on Transition Region Spectral Lines
Authors: Hansteen, V.; Maltby, P.
1990BAAS...22.1234H Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Imaging Fourier Transform Spectrometer - IFTS and the proposal
Solar Physics Element in Columbus/Space Station - SPECS. Proceedings.
Authors: Maltby, P.
1990ifts.book.....M Altcode:
In November 1985 a new mission proposal Solar Physics Element
in Columbus/Space Station - SPECS was submitted to ESA. ESA has
carried out accommodation and on-board processing studies of the
core instrument IFTS, comprised of the high resolution telescope,
the Imaging Fourier Transform Spectrometer, and high resolution
imagers. The SPECS-team found it appropriate to review the
IFTS concept and arranged this meeting. Contents: 1. Science
objectives and studies of the proposal Solar Physics Element
in Columbus/Space Station - SPECS (P. Maltby). 2. The Imaging
Fourier Transform Spectrometer (A. Thorne). 3. The SIMURIS Imaging
Fourier Spectrometer (B. Foing). 4. Requirements to spectrometers
set by solar UV-observations (O. Kjeldseth-Moe). 5. The coronal
diagnostic spectrometer (B. E. Patchett, K. Phillips). 6. Science
objectives for SUMER experiment on SOHO (P. Lemaire). 7. Signal
processing in instruments based on interferometry (T. Jaeger,
J. K. Hagene). 8. Critical IFTS items (M. C. E. Huber).
---------------------------------------------------------
Title: Physical processes in the solar transition-region and
corona. Proceedings.
Authors: Maltby, P.; Leer, E.
1990ppst.conf.....M Altcode:
No abstract at ADS
---------------------------------------------------------
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.
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: Signatures of magneto-acoustic waves in solar spectral lines.
Authors: Maltby, P.
1990ppst.conf..125M Altcode:
The effects of magneto-acoustical waves on spectral line formation are
summarized. In order to simplify the discussion it is assumed that the
effect of gravity may be neglected. Calculated line emission/absorption
coefficients are presented for a sound wave and for an Alfvén wave;
the case with a magneto-sonic wave is also discussed. The effects
of the waves on spectral lines formed in the chromosphere/corona
transition region are explored. Attention is given to the possibility
that sound waves may act differently on lines in different stages of
ionization. The observability of torsional Alfvén waves propagating in
flux tubes is evaluated. It is shown that the signatures of torsional
Alfvén waves on spectral lines are quite similar to those of a rotating
fluid. However, from high quality time sequences one should be able
to discriminate between the two options.
---------------------------------------------------------
Title: Transition Region Massflows Associated with Sunspots
Authors: Kjeldseth-Moe, O.; Brekke, P.; Brynildsen, N.; Maltby, P.;
Brueckner, G. E.; Bartoe, J. -D. F.
1989BAAS...21.1178K Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Gas flow in solar magnetic flux tubes.
Authors: Maltby, P.
1989ftsa.conf....3M Altcode:
In selecting flux tube properties the focus will be on flow
properties. Available information makes it natural to give less
attention to magnetic elements in quiet regions than to the sunspot
region.
---------------------------------------------------------
Title: Mini-Workshop on Flux Tubes in the Solar Atmosphere, held
June 19-21, 1989, in Oslo, Norway
Authors: Leer, E.; Maltby, P.
1989ftsa.conf.....L Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Solar infrared intensity oscillations.
Authors: Leifsen, T.; Maltby, P.
1988ESASP.286..169L Altcode: 1988ssls.rept..169L
The 5-min oscillations are found to be easily observable as intensity
variations in an infrared wavelength band centered at 2.23 μm with
bandwidth (FWHM) 65 nm. The observed peak to peak intensity variation
is 2.4% for a circular aperture of 1 arc min and 0.8% in the full disc
observations, i.e. considerably higher than in the other four observed
channels between 0.67 and 1.65 μm. In addition to the 5-min oscillation
the observed full disc power spectrum shows a strong feature centered
at 4.3 mHz. This frequency coincides with that of the fundamental
p-mode resonance of the chromosphere. Although this identification is
not proven the possibility to study the chromospheric cavity in full
disc observations is interesting.
---------------------------------------------------------
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.
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<SUP>-1</SUP> and are thus supersonic. Upward flows have smaller
velocities, 5 - 20 km s<SUP>-1</SUP>, 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: Interpreting Quasar Redshifts
Authors: Maltby, Per; Pasachoff, Jay M.; Kierein, John
1987PhT....40c.110M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Joint Discussion on Topics of Sessions 5 and 6
Authors: Zwaan, C.; Maltby, P.
1987rfsm.conf..165Z Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Transition Zone Flows in Sunspots
Authors: Kjeldseth-Moe, O.; Brynildsen, N.; Engvold, O.; Maltby, P.;
Bartoe, J. -D. F.; Brueckner, G. E.
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: A New Sunspot Umbral Model and Its Variation with the Solar
Cycle
Authors: Maltby, P.; Avrett, E. H.; Carlsson, M.; Kjeldseth-Moe, O.;
Kurucz, R. L.; Loeser, R.
1986ApJ...306..284M Altcode:
Semiempirical model atmospheres are presented for the darkest parts of
large sunspot umbrae, regions have called umbral cores. The approach is
based on general-purpose computational procedures that are applicable
to different types of stellar atmospheres. It is shown that recent
umbral intensity measurements of the spectral energy distribution may
be accounted for by an umbral core atmospheric model that varies with
time during the solar cycle; the observed center-limb variation can be
accounted for by the properties of the model. Three umbral core models
are presented, corresponding to the early, middle, and late phases of
the solar cycle. These three models also may be regarded as having the
properties of dark, average, and bright umbral cores respectively. The
effects of atomic, opacity, and abundance data uncertainties on
the model calculations are briefly discussed. For comparison, a new
reference model for the average quiet solar photosphere is given.
---------------------------------------------------------
Title: Towards a Multi-Component Semi-Empirical Model for the Solar
Photosphere
Authors: Kjeldseth-Moe, O.; Andreassen, T.; Maltby, P.
1985tphr.conf...98K Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Image processing of HRTS data from Spacelab 2
Authors: Kieldseth Moe, O.; Andreassen, T.; Andreassen, O.; Maltby,
P.; Moen, K.
1985MmSAI..56..561K Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Towards a multi-component semi-empirical model for the solar
photosphere.
Authors: Kjeldseth-Moe, O.; Andreassen, T.; Maltby, P.
1985MPARp.212...98K Altcode:
Models for the solar photosphere should ideally be able to
explain both the spectral intensity variation and the observed
limb-darkening. Comparisons of some recent one-component models with
the best available observed intensities in the visual and infrared show
that the calculated models agree with only one of these observational
criteria. It is suggested that this disagreement may be reduced by
introducing a multi-component atmosphere in an appropriate fashion. This
includes taking into account the transparency of fine structure elements
to radiation in the visual and infrared wavelengths.
---------------------------------------------------------
Title: The energy balance in the solar chromosphere-corona transition
zone.
Authors: Moe, O. K.; Andreassen, T.; Andreassen, O.; Maltby, P.;
Bartoe, J. D. F.; Brueckner, G. E.
1985ESASP.229..145M Altcode: 1985ESASP.229..145K; 1985erbp.symp..145M
The significance of high resolution studies of the solar chromosphere
and transition zone in order to understand the transport of energy and
momentum to the corona is pointed out. The various terms of the energy
equation are discussed in relation to observable quantities such as UV
line intensities and wavelength shifts. Finally an example is given
of an observation of the fine structure of the transition zone in an
active region using the best solar UV instrument presently available,
the "High Resolution Telescope and Spectrograph" - HRTS - constructed
at the US Naval Research Laboratory.
---------------------------------------------------------
Title: Solar cycle variations of sunspot temperatures.
Authors: Maltby, P.; Barth, S. B.; Lilje, P. B.; Vikanes, E. W.
1984ESASP.220..233M Altcode: 1984ESPM....4..233M
Observations obtained during 1983 strengthen the finding that the
umbra/photosphere intensity ratio for large sunspots is a linear
function of the phase in the solar cycle. Data for the period 1968 -
1983 are presented, thus covering most of the solar cycles 20 and 21.
---------------------------------------------------------
Title: Limb Darkening and Solar Cycle Variation of Sunspot Intensities
Authors: Albregtsen, F.; Joras, P. B.; Maltby, P.
1984SoPh...90...17A Altcode:
New observations of the umbral limb-darkening are presented. We find
a real and significant decrease in the umbra/photosphere intensity
ratio towards the limb. This result contrasts the findings of previous
authors and we believe this to be the first time such a decrease is
reported. Our conclusion is based on broad band pinhole photometer
intensity observations of 22 large sunspots covering the spectral region
0.387-2.35 μm. The data are selected from measurements on approximately
600 days during the last 15.5 yr. The application of the limb-darkening
data to the study of the temperature stratification in the umbra is
briefly discussed. The observations confirm the suggestion that the
umbra/photosphere intensity ratio seems to be a linear function of
the phase in the solar cycle.
---------------------------------------------------------
Title: On magnetic effects in solar active regions
Authors: Maltby, P.
1984noas.meet...47M Altcode:
Magnetic field effects in solar active regions are reviewed. The
equations of magnetohydrodynamics are presented and applied to
steady-state conditions. Particular attention is given to the quiet
phase, but the flaring phase is also considered. Waves in the umbral
atmosphere are discussed, and heating by ac and dc currents is
considered. Short accounts of prominence and flare physics are given.
---------------------------------------------------------
Title: Solar Cycle Temperature Variations in Sunspots
Authors: Maltby, P.; Albregtsen, F.; Moe, O. Kjeldseth; Kurucz, R.;
Avrett, E.
1984LNP...193..176M Altcode: 1984csss....3..176M
The observed umbra/photosphere intensity ratio varies from the beginning
to the end of each solar cycle by ∼ 30% at 1.6 μm and by factors >
2 at visible wavelengths. We present the intensity ratios measured in 10
wavelength bands extending from 0.387 to 2.35 μ m for 22 large sunspots
observed during the period 1968-82, thus covering most of solar cycles
20 and 21. These results together with new observations of umbral limb
darkening, and available data on photospheric absolute intensities,
are used to estimate the dependence of the relative umbral intensity,
and the absolute umbral intensity, on wavelength, heliocentric angle,
and phase of the solar cycle. These umbral intensities are used to
determine preliminary sunspot models which show the temperature as a
function of depth in early, mid-, and late phases of the solar cycle. In
the model calculations we use an extensive new compilation of atomic
and molecular line data, allowing us to carry out the analysis by
means of a detailed synthesis of the observed spectral bands.
---------------------------------------------------------
Title: On magnetic effects in solar active regions.
Authors: Maltby, P.
1984POHel...6...47M Altcode:
Magnetic field effects in solar active regions are reviewed. The
equations of magnetohydrodynamics are presented and applied to steady
state conditions. Particular attention is given to the quiet phase, but
the flaring phase is also considered. Waves in the umbral atmosphere
are discussed and heating by AC and DC currents are considered. Short
accounts of prominence and flare physics are given.
---------------------------------------------------------
Title: The chromosphere-corona transition zone above an active region
Authors: Kjeldseth-Moe, O. .; Andreassen, O.; Maltby, P.; Bartoe,
J. -D. F.; Brueckner, G. E.; Nicolas, K. R.
1984AdSpR...4h..63K Altcode: 1984AdSpR...4...63K
Intensities and profiles of ion emission lines between 1170 A and 1700
A from an active region on the Sun are measured from spectra obtained
with the Naval Research Laboratory's High Resolution Telescope and
Spectrograph - HRTS. The measurements provide simultaneous determination
of line intensities, wavelength shifts and Doppler widths at 50 separate
positions in the active region, with spatial resolution of 1 arc second
and spectral resolution 0.07 A. Fine structure variation of intensities
and gas flow velocities in the temperature range 20,000-200,000 K
are determined. The density sensitive line pair I(1486 N IV)/I(1548
C IV) has been used to measure electron pressures. Derived emission
measures imply filling factors of 0.05-0.1 to balance the divergence
of conductive flux width radiative losses above 60,000 K.
---------------------------------------------------------
Title: Has rapid solar core rotation been observed?
Authors: Andersen, B. N.; Maltby, P.
1983Natur.302..808A Altcode:
Internal rotation and gravitational quadropole moment of the Sun are
of interest to solar physics, the study of stellar structure and to
investigations related to the test of gravitational theories. High
precision measurements of fluctuations in the limb darkening function
and in the spectral line shifts have raised the possibility that the
interior of the Sun may be studied more directly than had previously
been possible. Recently, Claverie et al.<SUP>1</SUP> argued that
their detection of a 13.1+/-0.2 day velocity signal give further
experimental evidence that the solar core is rotating more rapidly
than the observable surface. We show here that the phase as well as the
magnitude of the observed signal amplitude may be predicted without any
rapid core rotation by taking into account the presence of sunspots
and their contribution to the spectral line profile as integrated
over the disk of the Sun. Hence, we conclude that the existence of
a 13.1-day apparently periodic velocity signal with amplitude 6.5 m
s<SUP>-1</SUP> during the 88 days observing period cannot be taken as
evidence for a rapidly rotating solar core.
---------------------------------------------------------
Title: Finite amplitude effects of torsional Alfven waves in a
flux tube
Authors: Andreassen, O.; Maltby, P.
1983IAUS..102..401A Altcode:
Consider a cylindrical, homogeneous magnetic flux tube embedded in
a field-free compressible plasma. The authors employ the method of
successive approximations to solve the magnetohydrodynamic equations
analytically for an axisymmetrical (m = 0) torsional Alfvén mode. The m
= 0 mode inside the tube may excite surface-, stationary- or progressive
waves in the field-free plasma. The authors conclude that, in contrast
to the linear theory, the flux tube may lose energy by wave radiation
to the surroundings.
---------------------------------------------------------
Title: On the Need for Space Observations of the Umbra - Photosphere
Intensity Ratio
Authors: Albregtsen, F.; Maltby, P.
1981SoPh...74..147A Altcode:
We draw attention to the possibility of distinguishing between different
sunspot theories by observing: (i) The umbra/photosphere intensity
ratio as a function of spot size and (ii) the morphology and time
evolution of sunspot inhomogeneities such as umbral dots. In arguing
the need for space observations of sunspot intensities we discuss the
corrections for stray light for ground based and space observations.
---------------------------------------------------------
Title: Solar Cycle Variation of Sunspot Intensity
Authors: Albregtsen, F.; Maltby, P.
1981SoPh...71..269A Altcode:
Broad band pinhole photometer intensity observations of 15 large
sunspots covering the spectral region 0.387-2.35 μm are presented. The
data are based on measurements on approximately 500 days during the
period June, 1967 to December, 1979.
---------------------------------------------------------
Title: Constraints on umbral core models as derived from broad-band
intensity observations
Authors: Albregtsen, F.; Maltby, P.
1981phss.conf..127A Altcode:
The umbra/photosphere intensity ratio for sunspots with umbral radii
larger than 5 sec of arc is discussed. The intensity ratio is derived
for a 'typical', large sunspot in the wavelength region 0.387-3.8
microns. The data are used in constructing a new, one-component model
for the umbral core. The umbral intensity differs significantly from one
sunspot to another, particularly in the infrared spectral region. It is
shown that the brightest core observed fits the model of Zwaan (1974),
whereas the darkest core fits the D-model of Kjeldseth Moe and Maltby
(1974).
---------------------------------------------------------
Title: Introduction
Authors: Maltby, P.
1980fsoo.conf..277M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Solflekk-fysikk.
Authors: Maltby, P.
1980kosm.conf...43M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Solar cycle variation of sunspot intensity and X-ray bright
points.
Authors: Maltby, P.; Albregtsen, F.
1979ApJ...234L.147M Altcode:
Evidence is presented for a possible link between the physical
conditions in individual large sunspots and the occurrence of X-ray
bright points. For the period 1970-1978 a close correlation is reported
between the infrared intensity of large sunspots and the number of X-ray
bright points. It is pointed out that the well-known dynamo theory for
sunspots, in its present form, is unable to explain the observations.
---------------------------------------------------------
Title: Energy and Mass Balance in Prominences.
Authors: Maltby, P.
1979phsp.coll..332M Altcode: 1979IAUCo..44..332M; 1979phsp.conf..332M
Some speculations on the energy and mass balance of quiescent
prominences are presented. Consideration is given to such points as:
(1) variations of internal, kinetic, and gravitational energies, (2)
maximum temperature gradients, (3) EUV emission, (4) the role of wave
energy, and (5) the role of mass budget.
---------------------------------------------------------
Title: Discussion
Authors: Maltby, P.; Stellmacher, G.
1979phsp.coll...35M Altcode: 1979IAUCo..44...35M
No abstract at ADS
---------------------------------------------------------
Title: Discussion
Authors: Brueckner, J.; Hirayama, T.; Maltby, P.; Schmahl, E. J.;
Zirin, H.
1979phsp.coll..121B Altcode: 1979IAUCo..44..121B
No abstract at ADS
---------------------------------------------------------
Title: Discussion
Authors: Hirayama, T.; Maltby, P.; Malville, J.; Martin, S. F.; Rust,
D. M.; Spicer, D. S.
1979phsp.coll..267H Altcode: 1979IAUCo..44..267H
No abstract at ADS
---------------------------------------------------------
Title: Discussion
Authors: Anzer, U.; Maltby, P.; Spicer, D. S.
1979phsp.coll..348A Altcode: 1979IAUCo..44..348A
No abstract at ADS
---------------------------------------------------------
Title: Physics of solar prominences
Authors: Jensen, E.; Maltby, P.; Orrall, F. Q.
1979phsp.coll.....J Altcode: 1979IAUCo..44.....J
These papers deal with recent theoretical and observational studies of
the physics of solar prominences. Specific topics include reviews of
prominence spectra and their interpretation, polarimetric observations
and magnetic-field determination in prominences, observations of
the prominence-corona interface, theories on the formation and
stability of quiescent prominences, prominence classifications,
observations of active prominences, observations and interpretations
of coronal manifestations of eruptive prominences, and models of
prominence structure and dynamics. Other contributions discuss
simultaneous observations of Ca II and hydrogen Balmer lines in
quiescent prominences, recent results in quiescent-prominence
spectroscopy, the solar helium abundance obtained from optical
spectra of quiescent prominences, and Stokes polarimetry of quiescent
prominences in the He I D3 line. Magnetic-field determination based
on the Hanle effect is also examined, along with the orientation
of prominence microstructure relative to magnetic-field direction,
radio observations of quiescent-prominence filaments at centimeter
and millimeter wavelengths, EUV observations of filaments, and a
magnetic-field reconnection model of quiescent prominences.
---------------------------------------------------------
Title: Discussion
Authors: Acton, L. W.; Brueckner, J.; Heyvaerts, J.; Maltby, P.;
Spicer, D. S.
1979phsp.coll..314A Altcode: 1979IAUCo..44..314A
No abstract at ADS
---------------------------------------------------------
Title: Introduction
Authors: Jensen, E.; Maltby, P.; Orrall, F. Q.
1979phsp.coll....1J Altcode: 1979IAUCo..44....1J
No abstract at ADS
---------------------------------------------------------
Title: Physics of solar prominences. Proceedings of the International
Astronomical Union Colloquium No._44, Oslo, August 14_-_18,_1978.
Authors: Jensen, E.; Maltby, P.; Orrall, F. Q.
1979pspp.book.....J Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Discussion
Authors: Acton, L. W.; Kundu, M. R.; Maltby, P.; Malville, J.; Orrall,
F. Q.; Sheeley, N.; Spicer, D. S.
1979phsp.coll..225A Altcode: 1979IAUCo..44..225A
No abstract at ADS
---------------------------------------------------------
Title: New light on sunspot darkness and the solar cycle
Authors: Albregtsen, F.; Maltby, P.
1978Natur.274...41A Altcode:
NUMEROUS attempts have been made to find the physical mechanism
responsible for the sunspot cycle. Present theoretical discussions of
the basic mechanism of solar activity are usually based on a dynamo
theory with a reversing magnetic field<SUP>1</SUP>, but objections
and alternative interpretations<SUP>1,2</SUP> have recently been
advanced. Our understanding of the sunspot cycle seems to be in a
stage where new observational insight may be valuable. We report here
a variation in the infrared umbra intensity of large sunspots with
the phase in the solar cycle.
---------------------------------------------------------
Title: The Evershed flow in the transition region
chromosphere-photosphere.
Authors: Bones, J.; Maltby, P.
1978SoPh...57...65B Altcode:
The Mgb<SUB>1</SUB> line profile is studied as a function of spatial
position in the sunspot region. Comparing the wavelengths of the core
and the wing, in and just outside the penumbra, a reversal in the shift
is detected. The displacements of the core and the wing are interpreted
as horizontal motions directed into the spot in the chromosphere and
as a flow directed out of the spot in deeper layers.
---------------------------------------------------------
Title: Solflekkforskningen, før og nå.
Authors: Albregtsen, F.; Maltby, P.
1978ATi....11..157A Altcode:
No abstract at ADS
---------------------------------------------------------
Title: On the difference in darkness between sunspots.
Authors: Maltby, P.
1977SoPh...55..335M Altcode:
The effects of the magnetic field as well as the velocity field on
sunspot equilibrium are discussed. The gas pressure difference, ΔP,
between a spot and the environments in the same horizontal layer
is primarily determined by the magnetic field. Using recent model
atmospheres we find that ΔP shows a maximum value, ΔP<SUB>max</SUB>,
at a depth of 650 ± 150 km below the photosphere. The value of
ΔP<SUB>max</SUB> suggests that the curvature of the field lines is
important for the equilibrium.
---------------------------------------------------------
Title: Compton Effect and Solar Spectral Lines
Authors: Maltby, P.
1977Ap&SS..47L..21M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Hα contrast profiles of filament features
Authors: Maltby, P.
1976SoPh...46..149M Altcode:
The wavelength dependence of filament features is studied, using
high-resolution filtergrams taken at seven wavelengths in Hα. The
observed contrast profiles are compared with profiles calculated on the
basis of Beckers' (1964) `cloud' model. The deviation between observed
and calculated profiles is used to suggest a progression among the
observed profiles that depends on the height of the filament feature.
---------------------------------------------------------
Title: Mode of propagation of penumbral waves
Authors: Maltby, P.
1975Natur.257..468M Altcode:
THE solar atmosphere provides an interesting possibility for the study
of low frequency waves both in magnetic and nonmagnetic regions, and the
most spectacular result (see ref. 1) has been the discovery of waves
propagating outwards over sun-spot penumbrae with periods of 180-240
s, horizontal wavelengths of 2,350-3,800 km, and horizontal phase
velocities of 12-25 km s<SUP>-1</SUP>. The theoretical interpretation
of these waves has aroused considerable interest and, in particular,
a number of authors have attempted to identify the precise mode
of wave propagation involved. The modes proposed include Alfvén
waves<SUP>1</SUP>, acoustic waves<SUP>2</SUP>, Lamb waves<SUP>3</SUP>,
and magnetogravity waves of the `plus' type vertically trapped at
photospheric levels<SUP>4</SUP>. In the face of so many possibilities,
further progress will probably depend on a more adequate observational
knowledge of the actual propagation characteristics of the penumbral
waves. Of special importance would be a determination of the direction
of the particle velocity with respect to the wave propagation vector.
---------------------------------------------------------
Title: The Chromospheric Evershed Flow
Authors: Maltby, P.
1975SoPh...43...91M Altcode:
High-resolution filtergrams of a sunspot region observed at seven
wavelengths in Hα with a resolution of 1/8 Å have been used to
investigate the three-dimensional structure of the chromospheric
Evershed flow and its time variation.
---------------------------------------------------------
Title: The Temperature of Penumbral Filaments
Authors: Kjeldseth Moe, O.; Maltby, P.
1974SoPh...36..101K Altcode: 1974SoPh...36..101M
The intensity of individual penumbral filaments has recently been
measured at the Pic-du-Midi Observatory as well as from observations
obtained during the third flight of the Soviet Stratospheric Solar
Station. We have used the results of these measurements to calculate the
corresponding average penumbral intensity as function of wavelength. The
calculated average intensity is compared with the average intensity
observed at the Oslo Solar Observatory. The Pic-du-Midi observations
are supported by this comparison. The run of temperature versus optical
depth is given for bright and dark penumbral filaments.
---------------------------------------------------------
Title: Models for Different Sunspot Umbrae
Authors: Kjeldseth Moe, O.; Maltby, P.
1974SoPh...36..109K Altcode: 1974SoPh...36..109M
The recently detected intensity difference between individual, large
sunspots in the infrared spectral region is considered. We show that
the intensity difference may be explained by a temperature difference
of 140-160K in the upper atmosphere keeping the temperature nearly
unchanged below an optical depth approximately equal to unity. The
change in temperature in the upper layers alters the observability of
the deeper layers and the corresponding intensity.
---------------------------------------------------------
Title: Umbral Intensities of large Sunspots
Authors: Ekmann, G.; Maltby, P.
1974SoPh...35..317E Altcode:
Observations of the intensities of sunspot umbrae at the Oslo Solar
Observatory during 5 yr are described. From the observational material
we have selected measurements where the corrections for scattered light
are small. The results for 5 large sunspots observed in 6 (alternatively
7) wavelength regions are presented. The observations show that possible
intensity differences between individual sunspots are difficult to
detect in the visible part of the spectrum. Real differences between
individual sunspots are detected in the infrared region.
---------------------------------------------------------
Title: The Intensity of the Penumbra of Sunspots
Authors: Eriksen, G.; Maltby, P.
1973sari.conf...87E Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Observations of the Intensity of the Penumbra of Sunspots
Authors: Maltby, P.
1972SoPh...26...76M Altcode:
Observations of the penumbral intensity of sunspots in 13 wavelength
regions are presented. In 4 wavelength regions 54 sunspots are
measured. In the other wavelength regions the number of sunspots
considered ranges from 3-19.
---------------------------------------------------------
Title: Sunspot Intensity Observations during the 9 May 1970 Mercury
Transit
Authors: Maltby, P.; Staveland, L.
1971SoPh...18..443M Altcode:
The intensity of a sunspot was measured in eight wavelength regions
during the Mercury transit of 9 May 1970. The observations have been
corrected for scattered light in the Earth's atmosphere as well as
in the instrument using two different methods plus a combination of
these. One method consists of using Mercury as a calibration spot. In
the second method the corrections for scattered light are determined
from solar limb observations.
---------------------------------------------------------
Title: The effect of scattered light on solar intensity observations
as derived from 9 May, 1970 Mercury transit
Authors: Maltby, P.
1971SoPh...18....3M Altcode:
The method for correcting observed sunspot intensities for scattered
light has been tested using the transit of Mercury. It is found that the
correction method of Zwaan (1965), Staveland (1970) has an uncertainty
(rms value) of 0.05 times the photospheric intensity. During good
observing conditions the uncertainty is 0.02 (rms value) with the
scanning speed used in this study. A simpler and quicker correction
method is suggested.
---------------------------------------------------------
Title: Joint Organization for Solar Observations. Annual report 1970.
Authors: de Jager, C.; Kiepenheuer, K. O.; Michard, R.; Maltby, P.;
Rösch, J.; Brandt, P. N.
1971joso.book.....D Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Paschen-Back Effect of the Lithium Resonance Doublet in
Sunspots
Authors: Maltby, P.
1971IAUS...43..141M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The Solar Lithium Abundance
Authors: Engold, O.; Kjeldseth Moe, O.; Maltby, P.
1970A&A.....9...79E Altcode:
The abundance of lithium is determined from selected sunspot spectra. We
have analyzed the best sunspot spectra obtained during 10 months of
observation. Taking into account the scattered light of the instrument
and the atmosphere as well as the effect of the instrumental profile
we find a larger depth of the Li 6707.8 line than derived by earlier
observers. The Li resonance doublets are found to be blended with lines
of TiO in the sunspot spectrum. We have calculated the resulting line
profile of the maguetic active resonance doublets together with the
molecular lines using the theory of Kjeldseth Moe (1968) for maguetic
active lines. Comparison of observed and calculated line profiles
gave log N (Li) = 0.80 + 0.25 on the scale of log N (H) = 12.00. The
Lie/Li7 isotope ratio is found to be less than 0.20.
---------------------------------------------------------
Title: Self-Reversal of the Lithium Resonance Doublet in Sunspots
Authors: Maltby, P.; Engvold, O.
1970SoPh...14..129M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: On the Continuum Intensity of the Umbra of Large Sunspots
Authors: Maltby, P.
1970SoPh...13..312M Altcode:
Spectral observations of large sunspots during the period June 1968 -
Dec. 1969 in five wavelength regions between λ 4795 and λ 6775 are
discussed. Selecting the best observations of two very large sunspots,
we find slightly lower umbral intensities than derived by earlier
observers. It is suggested that the small difference may be explained
by the fact that earlier observers have used an average value, whereas
we believe that the minimum value gives a more correct estimate of
the umbral intensity.
---------------------------------------------------------
Title: The velocity field in sunspots.
Authors: Maltby, P.
1970SciSn.105..259M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: A Model for the Penumbra of Sunspots
Authors: Kjeldseth Moe, O.; Maltby, P.
1969SoPh....8..275K Altcode: 1969SoPh....8..275M
A penumbra model in hydrostatic equilibrium is presented. The model
accounts for the continuum observations as well as the observations
of Fraunhofer lines in the penumbra. The uncertainty in the model in
deeper layers is discussed. It is shown that the penumbra is probably
not in strict radiative equilibrium.
---------------------------------------------------------
Title: The Intensity of the Penumbra of Large Sunspots
Authors: Maltby, P.; Mykland, N.
1969SoPh....8...23M Altcode:
Simultaneous photoelectric observations of sunspot penumbrae at 5790,
6690, 8760 and 16700Å are presented. No change in penumbral intensity
from spot to spot is found in a sample of 11 large sunspots.
---------------------------------------------------------
Title: A Model for the Penumbra of Sunspots
Authors: Maltby, P.; Kjeldseth Moe, O.
1969BAAS....1..285M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Effect of Progressive Alfv&eacuten Waves on the Profiles
of Solar Spectral Lines
Authors: Maltby, P.
1968SoPh....5....3M Altcode:
Progressive Alfvén waves set the atoms in oscillatory motion. The
radiation will be absorbed (emitted) at a Doppler-shifted wavelength;
the Doppler shift is determined by the velocity given to the atoms
by the wave. The effect of the waves on the line profile, integrated
over one period, is given for a few simple cases. A brief discussion
of the possible application to sunspots is presented.
---------------------------------------------------------
Title: The Effect of Magneto-Sonic Waves on a Zeeman Triplet with
Application to Sunspots
Authors: Maltby, P.
1968SoPh....4...96M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: A spectroscopic study of the Hα profile of moustaches
Authors: Engvold, O.; Maltby, P.
1968mmsf.conf..109E Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Effect of Saturation on Zeeman Triplets
Authors: Kjeldseth Moe, O.; Maltby, P.
1968ApL.....1..189K Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The Evershed Effect as a Wave Phenomenon
Authors: Maltby, P.; Eriksen, G.
1967SoPh....2..249M Altcode:
It is suggested that longitudinal compression waves are propagating
parallel to the solar surface from the umbra towards the photosphere. It
is shown that the line-absorption coefficient is asymmetrical, when
integrated over a wavelength of the compression wave. The effect
of the waves on the line profile is discussed, and it is shown that
asymmetrical line profiles of the type observed in sunspot penumbrae
will be produced.
---------------------------------------------------------
Title: The Effect of Progressive Sound Waves on the Profiles of
Stellar Spectral Lines
Authors: Eriksen, G.; Maltby, P.
1967ApJ...148..833E Altcode:
Progressive sound waves propagating through a region of spectral4ine
formation in a stellar atmosphere are considered The sound wave sets the
atoms in oscillatory motion While thus performing an ordered motion, the
atoms will emit or absorb radiation if properly excited. The radiation
will be absorbed (emitted) at a Doppler-shifted wavelength, the Doppler
shift being determined by the velocity given to the radiating atoms by
the wave The sound wave will also alter the density of atoms capable of
absorbing or emitting the line in question. The effect (integrated over
one period) of progressive sound waves on the shape of spectral lines
is calculated in a few simple cases where the line depth is assumed
proportional to the line-absorption coefficient The line profiles
are found to be highly asymmetrical when the pressure amplitudes of
the wave are relatively large. The degree of asymmetry of the line is
found to increase with atomic weight of the atoms producing the line.
---------------------------------------------------------
Title: Comparison of the Degree of Polarization with Other Radio
Source Parameters
Authors: Maltby, P.
1966ApJ...144..219M Altcode:
Observations made at the California Institute of Technology have
been used to study the degree of polarization at 10 cm in ninety-six
discrete radio sources. No strong connection is found between the
degree of polarization at 10 cm and other source parameters. The
ratio P(2l)/P(10) between the degrees of polarization at 21 cm and
10 cm has been used as a measure for the depolarization rate. The
distribution of P(21)/P(10) according to galactic coordinates indicates
that most of the depolarization occurs outside our Galaxy. No strong
correlation is evident in a comparison of P(21)/P(10) with other
source parameters. Possible explanations of the change in degree of
polarization with wavelength are briefly discussed.
---------------------------------------------------------
Title: Observations of Linear Polarization of Fifty-Four Discrete
Radio Sources at 10.6 CM
Authors: Maltby, P.; Seielstad, G. A.
1966ApJ...144..216M Altcode:
The interferometer at the Owens Valley Radio Observatory has been
used to study the linear polarization of fifty-four radio sources at
a wavelength of 10.6 cm. The measurements were made with two 904oot
antennas spaced 100 feet (X 289) in the east-west direction.
---------------------------------------------------------
Title: Erratum: Time Dependence of the Radio Emission from CTA 21
and CTA 102.
Authors: Maltby, P.; Moffet, A. T.
1965ApJ...142.1699M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Spectrum of the Intensity Variations in 3C 273B
Authors: Maltby, P.; Moffet, A. T.
1965Sci...150...63M Altcode:
The intensity variations in radio source 3C 273B have been measured at
wavelengths of 31.3, 21.2, and 10.6 centimeters. At 31.3 centimeters the
variation is quite small, indicating that the variable component of the
source is optically thick at this wavelength. Study of several different
model sources shows that the observed dependence of the intensity
variations on frequency can best be explained by an increase of the
electron density in a source region about 2 parsecs in diameter. This
interpretation is consistent with the distance to 3C 273 determined
from Hubble's law and the observed red shift.
---------------------------------------------------------
Title: On the Connection Between Liner Polarization and Galactic
Latitude of Discrete Radio Sources.
Authors: Maltby, P.
1965ApJ...142..621M Altcode:
The degree of linear polarization at a wavelength of about 21 cm is
considered for 166 presumably extragalactic radio sources A connection
between degree of linear polarization and galactic latitude is found;
low-latitude sources tend to show a lower degree of polarization than
high-latitude sources. It is found that the correlation between degree
of polarization and galactic latitude is weaker at a wavelength equal to
10 cm than at 21 cm. This result is derived from a sample of forty-six
sources observed at both wavelengths. Possible interpretations of the
correlation found at 21 cm are discussed.
---------------------------------------------------------
Title: Time Dependence of the Radio Emission from CTA 21 and CTA 102.
Authors: Maltby, P.; Moffet, A. T.
1965ApJ...142..409M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: On the velocity field of sunspots
Authors: Maltby, P.
1965IAUS...22..281M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Opacity properties of sunspots.
Authors: Jensen, Eberhart; Maltby, Per
1965ApNr...10...17J Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Brightness Distribution in Discrete Radio Sources. I. a
Discussion of 24 Identified Sources
Authors: Maltby, P.; Matthews, Thomas A.; Moffet, A. T.
1965qssg.conf..159M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: On the velocity field in sunspots
Authors: Maltby, Per
1964ApNr....8..205M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The Evershed effect at the outer edge of sunspot penumbras
Authors: Brekke, K.; Maltby, P.
1963AnAp...26..383B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Brightness Distribution in Discrete Radio Sources.IV. a
Discussion of 24 Identified Sources.
Authors: Maltby, P.; Matthews, T. A.; Moffet, A. T.
1963ApJ...137..153M Altcode:
Radial distances, linear dimensions, and total luminosities are given
for 24 identified extragalactic radio sources, 19 of which have measured
radial velocities. Using the synchrotron theory, the total energy
and magnetic-field strength required to account for the observed
luminosity are estimated for each source. Eight sources are found
with energy requirements exceeding 1060 ergs. Typical field strengths
are 10- oersted. The linear diameters range from less than 1 to 290
kpc. Illustrations of the radio and optical brightness distributions
are given for 11 sources.
---------------------------------------------------------
Title: Brightness Distribution in Discrete Radio Sources. III. The
Structure of the Sources.
Authors: Maltby, P.; Moffet, Alan T.
1962ApJS....7..141M Altcode:
The visibility functions of 195 radio sources are interpreted in terms
of the structure of these sources. Of the 195 sources, 174 are known
or presumed to be extragalactic. Seventy-five of these extragalactic
sources are resolved with the interferometer spacings used, and complex
structure is found in all but 13. In the sources showing complex
structure, two similar components with nearly equal intensities are
found in 15, two or more components of unequal intensities are found
in 40, while 7 contain a bright core surrounded by a halo. It is
suggested that the majority of all extragalactic sources have complex
structure. Data are also given on the brightness distributions in
the 21 galactic sources observed. In contrast to the extragalactic
sources, emission from the galactic sources is typically confined to
a single region.
---------------------------------------------------------
Title: The Radio Source Hercules A
Authors: Maltby, P.; Matthews, T. A.; Moffet, A. T.
1962PASP...74..277M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: A discussion of 24 identified sources
Authors: Maltby, P.; Matthews, T. A.; Moffets, A. T.
1962OOVRO...4.....M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Central Component of the Radio Source Centaurus A
Authors: Maltby, P.
1961Natur.191..793M Altcode:
THE identification of the radio source Centaurus A with the
peculiar galaxy NGC 5128 was first suggested by Bolton, Stanley and
Slee<SUP>1</SUP>. The radio source consists of an extended component
with dimensions of about 2° × 4° and a compact central component. The
extended source has recently been shown by Bolton and Clark<SUP>2</SUP>
to consist of two components. The compact central component was
investigated in 1953 by Mills<SUP>3</SUP>. His observations indicated
that the radio emission was associated with the wide dust band of NGC
5128. Recent measurements by Twiss, Carter and Little<SUP>4</SUP> have
shown that the central source also consists of two components. This
result was also obtained by Moffet and Maltby<SUP>5</SUP>. In a more
recent radio investigation of NGC 5128, reported in this communication,
I find that the radio source is not associated with the wide dust band.
---------------------------------------------------------
Title: Distribution of Brightness in Extragalactic Radio Sources
Authors: Moffet, A. T.; Maltby, P.
1961Natur.191..453M Altcode:
No abstract at ADS
