Author name code: kjeldseth-moe
ADS astronomy entries on 2022-09-14
author:"Kjeldseth-Moe, Olav" OR author:"Kjeldseth Moe, Olav"
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Title: Implications for how planets form and evolve
Authors: Dawson, Rebekah; Becker; Dong; Lee; Moe; Mulders; Wang
Bibcode: 2019psce.confE..35D
Altcode:
No abstract at ADS
Title: Hiwind Balloon Fabry-Perot Interferometer Measurements Show
the Importance of the Solar Wind Influence on Thermospheric Density
and Wind Models at Quiet Times
Authors: Wu, Q.; Moe, O. K.
Bibcode: 2014AGUFMSH21C4133W
Altcode:
Recent measurements by the HIWIND balloon have revealed persistent
dayside equatorward winds in the earth's thermosphere at high latitudes
during geomagnetically quiet times. Although thermospheric density
models have included the effects of magnetic storms, they have not
included a dependence on solar wind conditions affecting the energy
and configuration of charged particles in the earth's magnetosphere
at geomagnetically quiet times. Consequently, most thermospheric
models could not predict the direction of the high-latitude winds
at geomagnetically quiet times, nor could they predict the depth of
the thermospheric density minimum at the last solar minimum in the
year 2009. We discuss the importance of having a solar wind index
appropriate to the needs of thermospheric density models.
Title: Are there variations in Earth's global mean temperature
related to the solar activity?
Authors: Kjeldseth-Moe, Olav; Wedemeyer-Böhm, Sven
Bibcode: 2010IAUS..264..320K
Altcode:
We have analyzed the record of Earth's global temperature variations
between 1850 and 2007 looking for signals of periodic variations and
compared our results with solar activity variations in the same time
period. Significant periods are found at 9.4, 10.6 and 20.9 years. These
periodic variations may be caused by solar activity. However, and
amazingly enough, we also find at least 17 other significant periodic
variations in addition to expected variations with periods of 1 year
and of half a year. The result is considered in terms of solar related
forcing mechanisms. These may be variable solar heating associated
with the small changes in solar irradiance over the solar cycle,
or direct effects of interactions between variable magnetic fields
carried by the solar wind and particles and fields in interplanetary
space or in the Earth's ionosphere.
Title: The many periods in the variation of the Earth's global
temperature
Authors: Kjeldseth-Moe, Olav
Bibcode: 2010cosp...38.1723K
Altcode: 2010cosp.meet.1723K
At least 20 distinct harmonic variations are present in the Earth's
global temperature record between years 1850 and 2008 (Kjeldseth-Moe
and Wedemeyer-Bühm, 2009). Here we report on the significance of the
determined periods, and look for further and less prominent variations
that may also be real. We furthermore investigate long time series of
measured local (i.e. non-global) temperatures for periodic variations
and compare the results to the global temperatures. The variable energy
input required in maintaining the global temperature variations is
estimated and compared with variable thermal and non-thermal forcing
resulting from solar activity.
Title: Obituary: Per E. Maltby, 1933-2006
Authors: Kjeldseth-Moe, Olav
Bibcode: 2007BAAS...39.1072K
Altcode:
Professor Per Maltby, prominent Norwegian Solar Physicist at the
Institute of Theoretical Astrophysics, University of Oslo, Norway,
died on 24 May 2006. Lung cancer was diagnosed in February, but he
was expected to improve. Until the end of March he came to his office
every day, got recent papers off the web, and followed his field
closely as he had always done. Per Maltby was born in Oslo,
Norway, on 3 November 1933. He started his studies at the University
of Oslo in 1952 and took his candidate degree in 1957. Between 1955
and 1958 he was a research assistant at the Institute of Theoretical
Astrophysics in Oslo. In 1960 Maltby became an assistant professor
(amanuensis) at the University of Bergen and from January 1963 he held a
corresponding position at the University of Oslo. He became an associate
professor in 1967, and from 1983 until he retired in 2003 he was a full
Professor at the Institute of Theoretical Astrophysics, University of
Oslo. Per Maltby is survived by his wife Elisabet (née Ruud),
whom he married in 1956. They had two children. The daughter, Bente,
is a medical doctor and gynecologist serving as a section head at the
district hospital in Kristiansand in southern Norway. Their son, Lars,
holds a doctoral degree in engineering, specializing in the properties
of powders. He is currently managing director in the Norwegian division
of the French multinational company Saint Gobain. As a father Per Maltby
expressed pride in his children and was pleased with their progress
in life. He also enjoyed his five grandchildren. As a scientist,
Per Maltby was versatile and productive. In the early 1960s he visited
the California Institute of Technology where he did pioneering studies
of the distribution and time variation of the radio emission from
active galaxies, using the Owens Valley Radio Observatory. His work
with Alan Moffet contributed to revealing the secrets of these remote
objects. Their results drew attention and were indeed mentioned in
the pages of Time magazine. However, Maltby's lifelong interest
was in our Sun, and most of his more than 200 published articles
and presentations are within the field of solar physics. Throughout
his career, and into his years as an emeritus professor, he obtained
significant results, results to which colleagues all over the world
will continue to refer. In 1964 Maltby took his doctoral degree
(Doctor Philosopiae) on a study of the Evershed effect. He elegantly
demonstrated that the flow was predominantly radial with only minor
vertical and azimuthal components and that flow speeds increased all
the way to the edge of the penumbra where the flow seemed to abruptly
disappear. This disagreed with conventional knowledge at the time. His
results are, however, confirmed in all later investigations. Per
Maltby highly valued his work with colleague Gunnar Eriksen. They
studied the effect of progressive sonic and Alfvén waves on the
profiles of spectral lines. The results demonstrated the characteristic
spectral signatures of such waves and laid the foundation for a proper
use of line profiles as a diagnostic tool for waves in solar and stellar
atmospheres. Sunspots continued to be a main interest. For twenty
years Per Maltby and his students measured the relative intensity of
sunspots at a number of wavelengths from blue and into the infrared. The
infrared measurements represented entirely new knowledge, giving access
to the deepest layers in the sunspot photospheres. This refined series
of spectral sunspot measurements stretched over two eleven-year activity
cycles and resulted in his models of the umbra and penumbra of spots,
models that have served as standard reference models until this day. Already before the start of the SOHO era in solar physics, Per Maltby
had shifted his attention to the conditions in the transition region
and coronal layers above sunspots. Together with his collaborators he
studied rapid down flows, often at supersonic speeds, from the corona
into sunspot umbrae. He rediscovered sunspot plumes, the dense, cold
pillars of gas rising above sunspot umbrae and penumbrae into the
corona, and mapped their properties. In his last works Maltby
unambiguously showed that the transition region over sunspot umbrae
were filled with upward propagating sound waves that penetrate into
the corona under certain conditions. This result deserves special
attention since many have believed that such penetrations must take
place, but nobody was earlier able to demonstrate it observationally
in a convincing manner. Per Maltby was always looking forward and
always aware of new possibilities. He was an influential member on the
Norwegian government committee that recommended Norwegian membership
in the European Space Agency (ESA), and was the force behind securing
sufficient domestic government funds to allow Norwegian scientists
to participate in SOHO and Cluster. He took part in SOHO from the
earliest planning stages and later played a prominent role in the
Norwegian SOHO project. Through his activities, Norwegian space
research came to life, introducing new and rich possibilities for
research in astronomy and geophysics in Norway. Maltby played
important roles in many national and international advisory groups
and committees. For a number of years he was a member of several
of ESA's advisory groups. He served as leader of the Institute of
Theoretical Astrophysics in Oslo in 1976-1977, and in 1976-1981 he was
a member, and later the chairman, of the project selection committee
for natural sciences for the Norwegian Foundation of Science and the
Humanities. Finally, Maltby was instrumental in securing a Norwegian
role in the Japanese solar space observatory Hinode, which will be a
rich source for Norwegian solar physics in the years to come. Per
Maltby had a remarkably wide scientific orientation. His papers most
frequently describe observations and their interpretation. He had an
enormous respect for what is "real," the solid and measurable. But he
combined this with deep theoretical insights that he demonstrated
in his interpretations and theoretical papers. Per taught
his students a rational, scientific way of thinking and encouraged
their curiosity. He was open and always dedicated to develop the best
scientific cooperation. And he was generous, which was always important
to his young collaborators. He might appear quiet and reserved, but
showed his warm heart and appreciation when you got close to him. His
death is a sad loss for his colleagues and for our discipline.
Title: E nergetic, Dynamics And Fine-Scale Structure Of The Sun's
Magnetized Atmosphere, Observational Strategies For The Solar Orbiter
Authors: Kjeldseth-Moe, O.
Bibcode: 2007ESASP.641E..16K
Altcode:
We look at so me known fine stru cture features, or processes on
the Sun th at goes on at a small scale, notably explosive even ts and
blinkers. From th eir proper ties we dr aw up a list of ob- servational
strateg ies for the So lar Orbiter, based on how we could extend our
knowledge of these f eatures. W e then show examples from other f
eatures and processes on a small scale in cluding specu lations on
th e possibility that th e upper solar atmosph ere consist of hy-
per fine reso lution elemen ts much smaller than the pr esen t limit
of r esolu tion at ultrav iolet or X-ray wavelengths, i.e. 725 km on
the Sun. The applicab ility of the So lar Orbiter instru- ments and
observation strateg ies for deter min- ing th e properties of the v
arious structures will be discussed. Finally we shall co mmen t on the
importance of the out of eclip tic observ ation in the extended mission
phase for studying the fast solar w ind in the polar coronal holes.
Title: Thermospheric Density Model Including High-Latitude Energy
Sources
Authors: Moe, O. K.; Moe, M. M.
Bibcode: 2006AGUFMSA13A0260M
Altcode:
As was predicted long ago by Sydney Chapman, there is a major
contribution to thermospheric energy from the magnetosphere at all
times. The contribution of this magnetospheric energy source produces
a neutral density bulge at high latitudes even during geomagnetically
quiet times. We present an analytical, semi- empirical model of
the global neutral density at such quiet times. The total density
is expressed as the sum of two terms: The first term describes the
combined effects of the solar ultra-violet heating and various other
contributions like the semi-annual variation; the second term gives
the contribution to the density associated with particle precipitation
and joule heating coming from magnetospheric sources during times
of low geomagnetic activity. The region of density enhancement
at high latitudes is associated with the locations of the dayside
cusps. Therefore the model produces a density distribution which
depends on universal time as well as on altitude, latitude, local time,
and the usual solar UV energy source. The numerical values of the
parameters in the empirical model were originally determined 30 years
ago from density data collected by the Bell-MESA accelerometer on the
LOGACS satellite and the pressure gauge on the SPADES satellite. As
an example of the model output, we show a Mercator projection of
the global density distribution at 400 km altitude at 12 hours GMT
in late May at a time of moderate solar activity and low geomagnetic
activity. The parameters in the model can now be substantially improved
by using recent advances like the latest description of the semi-annual
variation and by incorporating the precise density measurements made
by the accelerometers on board the CHAMP and GRACE satellites. In the
original model, density values at times of high geomagnetic activity
were included in the second density term. The parameters in that term
can also be improved as accurate storm-time densities become available.
Title: Dual Flows with Supersonic Velocities in the Sunspot Transition
Region
Authors: Brynildsen, N.; Maltby, P.; Kjeldseth-Moe, O.; Wilhelm, K.
Bibcode: 2004ApJ...612.1193B
Altcode:
Observations of sunspot transition region lines that deviate
significantly from a Gaussian shape are presented. Attention is given
to ``dual flows,'' a line profile phenomenon in which two distinct
velocities are observed within the same spatial resolution element. In
5 out of 12 sunspots we observe dual flows. Several emission line
profiles are well represented by two Gaussian line components, one
with a subsonic and one with a supersonic line-of-sight velocity.
Title: Oscillations in the Umbral Atmosphere
Authors: Brynildsen, N.; Maltby, P.; Foley, C. R.; Fredvik, T.;
Kjeldseth-Moe, O.
Bibcode: 2004SoPh..221..237B
Altcode:
The results of simultaneous observations of oscillations in the
chromosphere, transition region, and corona above nine sunspots are
presented. The data are obtained through coordinated observing with the
Solar and Heliospheric Observatory — SOHO and the Transition Region
And Coronal Explorer — TRACE. Oscillations are detected above each
umbra. The power spectra show one dominant frequency corresponding to
a period close to 3 min. We show that the oscillations in the sunspot
transition region can be modeled by upwardly propagating acoustic
waves. In the corona the oscillations are limited to small regions that
often coincide with the endpoints of sunspot coronal loops. Spectral
observations show that oscillations in the corona contribute to the
observed oscillations in the TRACE 171 Å channel observations. We
show that a recent suggestion regarding a connection between sunspot
plumes and 3-min oscillations conflicts with the observations.
Title: Oscillations Above the Umbra of Sunspots
Authors: Brynildsen, N.; Maltby, P.; Fredvik, T.; Kjeldseth-Moe, O.
Bibcode: 2004ESASP.547...45B
Altcode: 2004soho...13...45B
Oscillations above thirteen sunspots are investigated with the Coronal
Diagnostic Spectrometer (CDS) and the Transition Region And Coronal
Explorer (TRACE). The CDS observations give knowledge about the
oscillations in the chromosphere, transition region, and corona and
information regarding the contributions of different emission lines to
the TRACE 171 Å and 195 Å channel intensities. A period close to 3
min is observed above the umbra of each sunspot. The observations give
support to the idea that the 3 min oscillations are caused by upwardly
propagating acoustic waves. This is evident from the asymmetry of
the oscillation amplitudes in the red and blue wings of the emission
lines, where the oscillations are decidedly more pronounced in the
blue than in the red line wing. Additional support for the acoustic
wave hypothesis emerges from the agreement between the observed and
predicted relations in phase and magnitude between the oscillations in
intensity and line-ofsight velocity. The frequency of the oscillations
is above the acoustic cutoff frequency in the umbral atmosphere and
the observed phase differences between lines emitting at different
temperatures point to an upwardly propagating disturbance.
Title: Multi Wavelength Observations of Solar Active Region Loops
Authors: Fredvik, T.; Kjeldseth-Moe, O.
Bibcode: 2004cosp...35.2832F
Altcode: 2004cosp.meet.2832F
Simultaneous observations with the UV/EUV spectrometers CDS and
SUMER on SOHO, and the UV/EUV imaging telescope, TRACE, have been
used to investigate rapid intensity variations in solar active
region loops. In lines formed at temperatures 10,000 - 250,000 K,
the loop structures seem to be dominated by quasiperiodic intensity
enhancements moving rapidly along the loops down to the surface
of the sun. We will demonstrate that it is difficult to understand
the nature of these changes without combining high cadence imaging
and spectroscopic observations. From the high cadence observations
the enhancements appear to be the result of plasma condensation: hot
coronal plasma at the top of loops may be cooled to transition region
or even chromospheric temperatures and slides down the loop legs at
speeds up to 100 km/s. At coronal temperatures, ~ 1 MK, the observed
loops are less variable and moving intensity enhancements are seen
less frequently than in the transition region.
Title: Thermospheric Composition from Scale Height Analysis
Authors: Moe, O. K.; Moe, M. M.
Bibcode: 2003AGUFMSA12B1087M
Altcode:
Efforts to validate spectroscopic methods of monitoring the thermosphere
and ionosphere have led to renewed interest in thermospheric composition
and models. In the past, different methods of measuring composition
have produced conflicting results. In the present work, we use scale
heights to constrain the composition measurements through the mean
molecular mass and temperature. Scale height analysis has the advantage
that it compresses the measurements, thus facilitating comparison and
evaluation. To determine a physically reasonable composition profile,
we start with a consideration of eddy diffusion near the intersection
of the thermosphere with the mesosphere, and use scale height analysis
at the higher altitudes. Neutral density measurements using improved
drag coefficients constrain the sum of the constituents. The resulting
composition at altitudes between 90 and 350 km at a time of average
solar and geomagnetic activity will be compared with several data sets,
and with some old and new thermospheric models.
Title: Search for a chromospheric resonator above sunspots
Authors: Brynildsen, N.; Maltby, P.; Brekke, P.; Redvik, T.;
Kjeldseth-Moe, O.
Bibcode: 2003AdSpR..32.1097B
Altcode:
We have recently observed thirteen sunspots, both with CDS on SOHO
and TRACE. For each sunspot we investigate the oscillations in the
chromosphere, transition region and corona. Above the umbra the
power spectra show one dominant peak corresponding to a period of 3
minutes. The intensity oscillation amplitude increases with increasing
temperature, reaches a maximum for lines emitting close to 1-2 ×
10 5 K, and decreases for higher temperatures. Part of
the wave energy penetrates into the corona, channeled into small
areas that appear to coincide with the endpoints of sunspot coronal
loops. The observations support the hypothesis that the oscillations
are caused by upwardly propagating acoustic waves and show no signs
of the resonances, equally spaced ≈1 mHz in frequency, predicted by
the chromospheric resonator theories.
Title: Sunspot Oscillations and Acoustic Wave Propagation
Authors: Brekke, P.; Brynildsen, N.; Maltby, P.; Fredvik, T.;
Kjeldseth-Moe, O.
Bibcode: 2003SPD....34.0401B
Altcode: 2003BAAS...35..810B
Observations with the Coronal Diagnostic Spectrometer of 3 min
oscillations in sunspot umbrae support the hypothesis that they are
caused by upwardly propagating acoustic waves. This is evident from
the asymmetry of oscillation amplitudes in the red and blue wings of
spectral lines, where the oscillations are decidedly more pronounced
in the blue than in the red line wing. Additional evidence include the
fact that the relation between oscillations in intensity and velocity
agree with that predicted for an acoustic wave with regard to phase
as well as magnitude. Finally, the observed phase difference between
lines formed at different temperatures points to an upward propagating
disturbance, and the value of dominant frequency of the oscillations,
close to 6 mHz, is above the acoustic cutoff frequency in the sunspot
atmosphere. SOHO is a mission of international cooperation between ESA
and NASA. This study was supported by the Research Council of Norway.
Title: Oscillations in the wings of sunspot transition region lines
Authors: Brynildsen, N.; Maltby, P.; Kjeldseth-Moe, O.; Wilhelm, K.
Bibcode: 2003A&A...398L..15B
Altcode:
We explore a new approach to the investigation of optically thin
emission lines by comparing the intensity variations in opposite
wings of the spectral lines and apply the method to investigate the
oscillations above sunspots. The observations show that it is easier to
detect the 3 min oscillations above sunspots in the short wavelength
(``blue'') wing than in the long wavelength (``red'') wing of the
lines. The observed oscillations are compatible with the spectral line
signatures of upwardly propagating acoustic waves.
Title: The solar transition region
Authors: Kjeldseth-Moe, O.
Bibcode: 2003dysu.book..196K
Altcode:
What is the solar transition region like? The view of a static,
thin transition region has long been left behind. Modern concepts
are emerging, but a new model is not generally agreed upon. The
observational facts and theoretical considerations, however,
consistently point towards a strongly dynamic solar plasma. A
comprehensive account of all this is presented here.
Title: Sunspot oscillations in the chromosphere, transition region,
and corona
Authors: Brynildsen, N.; Maltby, P.; Fredvik, T.; Kjeldseth-Moe, O.
Bibcode: 2002ESASP.506..513B
Altcode: 2002ESPM...10..513B; 2002svco.conf..513B
The results of simultaneous observations with CDS on SOHO and TRACE
for thirteen sunspots in 2001 and 2002 are combined with previous
results for six sunspots observed with CDS and SUMER on SOHO. Intensity
oscillations are detected above each umbra and spectral observations
of chromospheric and transition region lines allow us to measure
oscillations in the line-of-sight velocity in several sunspots. The
power spectra show one dominant peak close to 6 mHz, corresponding
to a period of 3 minutes. The oscillation amplitude increases with
increasing temperature, reaches a maximum for lines emitting close
to 1-2×105K, and decreases for higher temperatures. Part
of the wave energy penetrates into the corona, channeled into small
areas that appear to coincide with the endpoints of sunspot coronal
lops. The observations support the hypothesis that the oscillations
are caused by upwardly propagating acoustic waves. The observations
are not compatible with the concept of a chromospheric resonator.
Title: On the nature of the 3 minute oscillations above sunspots
Authors: Hansteen, V. H.; Wikstøl, Ø.; Brynildsen, N.; Maltby, P.;
Fredvik, T.; Kjeldseth-Moe, O.
Bibcode: 2002ESASP.505..183H
Altcode: 2002IAUCo.188..183H; 2002solm.conf..183H
Oscillations in the sunspot transition region and corona are observed
simultaneously with the Coronal Diagnostic Spectrometer - CDS on SOHO
and the Transition Region And Coronal Explorer - TRACE. Observations
of thirteen sunspots in 2001 and 2002 show that the amplitude in
the relative integrated line intensity increases with increasing
temperature, reaches a maximum for emission lines formed close to
1-2×105K, and decreases at higher temperatures. Part of the
wave energy penetrates into the corona, channeled into small areas that
appear to coincide with the endpoints of sunspot coronal loops. The
observed power spectra show one dominating peak close to 6 mHz. To
explore the nature of the waves we calculate upwardly propagating
acoustic waves confined to a magnetic flux tube and compare the results
with the observations.
Title: Oscillations Above Sunspots
Authors: Brynildsen, N.; Maltby, P.; Fredvik, T.; Kjeldseth-Moe, O.
Bibcode: 2002SoPh..207..259B
Altcode:
The 3-min oscillations in the sunspot atmosphere are discussed, based
on joint observing with the Transition Region and Coronal Explorer -
TRACE and the Solar and Heliospheric Observatory - SOHO. We find that
the oscillation amplitude above the umbra increases with increasing
temperature, reaches a maximum for emission lines formed close to 1-2×
105 K, and decreases for higher temperatures. Oscillations
observed with a high signal-to-noise ratio show deviations from pure
linear oscillations. The results do not support the sunspot filter
theory, based on the idea of a chromospheric resonator. Whereas the
filter theory predicts several resonant peaks in the power spectra,
equally spaced ∼ 1 mHz in frequency, the observed power spectra show
one dominating peak, close to 6 mHz. Spectral observations show that the
transition region lines contribute less than 13 percent to the TRACE 171
Å channel intensity above the umbra. The 3-min oscillations fill the
sunspot umbra in the transition region. In the corona the oscillations
are concentrated to smaller regions that appear to coincide with the
endpoints of sunspot coronal loops, suggesting that wave propagation
along the magnetic field makes it possible for the oscillations to
reach the corona.
Title: 3 minute oscillations above sunspots
Authors: Brynildsen, N.; Maltby, P.; Fredvik, T.; Kjeldseth-Moe, O.
Bibcode: 2002ESASP.508..283B
Altcode: 2002soho...11..283B
The aim of this investigation is a better understanding of the 3 minute
oscillations above sunspots. We present the first results from a joint
observing programme with SOHO and TRACE. Attention is given to the wave
amplitude as a function of the temperature and to the penetration of
part of the wave energy into the corona. The results appear to disagree
with the sunspot filter theory.
Title: The 6 mHz Oscillations above Sunspots
Authors: Brekke, P.; Brynildsen, N.; Maltby, P.; Fredvik, T.;
Kjeldseth-Moe, O.
Bibcode: 2002AAS...200.8806B
Altcode: 2002BAAS...34..790B
Sunspot oscillations in the transition region and corona are observed
simultaneously with CDS on SOHO and TRACE. Results obtained from
investigations of ten sunspots in 2001 and 2002 are presented. We
find that the oscillation amplitude above the umbra increases with
increasing temperature, reaches a maximum for lines emitted close to 200
000 K, and decreases for higher temperatures. Part of the wave energy
penetrates into the corona, channeled into small areas that appear
to coincide with the endpoints of sunspot coronal loops. The observed
power spectra show one dominating peak, near 6 mHz, and not several,
equally spaced resonances as predicted by theories based on the idea
of a chromospheric resonator. We conclude that the observations are
compatible with upwardly propagating acoustic waves.
Title: Redshift in sunspot plumes
Authors: Brynildsen, N.; Maltby, P.; Kjeldseth-Moe, O.
Bibcode: 2002AdSpR..30..529B
Altcode:
The non-uniform spatial distributions of emission and wavelength
shift in ten EUV lines formed in the chromosphere, transition region
and corona above 50 sunspots are investigated, based on observations
with the Coronal Diagnostic Spectrometer on the Solar and Heliospheric
Observatory. The sunspot plumes are the most prominent features in the
transition region line emissions. We find that almost all sunspots
show a plume when one magnetic polarity dominates the region out
to a distance of 50″ from the sunspot. Both the enhanced emission
and the redshift in sunspot plumes increase with the line formation
temperature, T, reach a maximum close to log T = 5.5 and cease to
exist close to log T = 6.0. The mass flow in the corona is too small
to explain the observed redshift in the transition region. We present
a working hypothesis where gas at transition region temperatures moves
in flow channels from the surroundings into the sunspot.
Title: Variability and dynamic state of active region loops
Authors: Fredvik, T.; Kjeldseth-Moe, O.; Haugan, S. V. H.; Brekke,
P.; Gurman, J. B.; Wilhelm, K.
Bibcode: 2002AdSpR..30..635F
Altcode:
A set of 218 consecutive CDS rasters taken at the solar limb on October
26-28 1999 has been used to investigate the variability and plasma
dynamics of active region loops. Each raster contains simultaneous
images in 6 different lines, covering the full temperature range of
CDS, 10 000 K (He I) to 2.7 MK (Fe XVI). Activity is seen to go on
without breaks at temperatures below 1 MK for the full 39 hours of the
series. Transition region loops or extended sections of loops, 50-200
Mm long, appear and disappear in intervals as short as 11 minutes,
the observing cadence. In the corona the emission is less variable,
but significant changes are seen. Measured Doppler shifts correspond
to typical plasma velocities of 20 km s -1 to 100 km
s -1, at temperatures 10 000 K to 450 000 K, and siphon
flows may occur in some of the loops. High velocities are frequently
seen where the emitted intensities are weak, often on the outer edges
of loops as defined in that particular spectral line. At coronal
temperatures, 1 MK and higher, systematic loop velocities occur only
occasionally. Simultaneous observations with EIT and SUMER were made
during part of the raster series and are compared with the CDS result.
Title: An Upper Temperature Limit For Strong Dynamic Activity In
The Solar Transition Region and Corona
Authors: Fredvik, T.; Kjeldseth-Moe, O.
Bibcode: 2002EGSGA..27.5258F
Altcode:
The transition region plasmas in loop structures above active regions
display evi- dence of high velocities, 20-100 km/s, and rapid time
variations, < 10 min, see e.g. Kjeldseth-Moe and Brekke (1998,
in Solar Phys., vol. 182, 73) or Fredvik and Kjeldseth-Moe (2002, in
Adv. Space Res., forthcoming). We have compared mate- rial velocities
in the plasma over a wide temperature range using spectral data from
the Solar Ultraviolet Measurements of Emitted Radiation, SUMER, to give
the best possible angular resolution. Simultaneous observations in the
lines N V 1238 A, O V 629 A and Mg X 624 A, emitted at 1.8 × 105 K,
2.4 × 105 K, and 1.1 MK, re- spectively, demonstrate convincingly
the lack of any observable dynamic behavior at coronal temperatures,
in the form of Doppler shifts (v < 10 km/s) as well as strong
intensity variations. The results are compared to calculations of
line shifts caused by sound waves in the plasma. The observations are
relevant for the selection of future instrumentation to study physical
conditions in the upper solar atmosphere. Future ob- servations giving
an improved temperature mapping between 5 × 105 K and 1 MK is planned
for April 2002.
Title: Search for a chromospheric resonator above sunspots
Authors: Brynildsen, N.; Maltby, P.; Brekke, P.; Fredvik, T.;
Kjeldseth-Moe, O.
Bibcode: 2002cosp...34E.178B
Altcode: 2002cosp.meetE.178B
We have recently observed eleven sunspots, both with CDS on SOHO
and TRACE as part of our on-going investigations of the sunspot
atmosphere. For each sunspot we investigate the oscillations in
the chromosphere, transition region and corona. The observed power
spectra show one dominating peak corresponding to a period of 3
minutes. The oscillation amplitude above the umbra increases with
increasing temperature, reaches a maximum for lines emitting close to
200 000 K, and decreases for higher temperatures. Part of the wave
energy penetrates into the corona, channeled into small areas that
appear to coincide with the endpoints of sunspot coronal loops. The
observations support the hypothesis that the oscillations are caused
by upwardly propagating acoustic waves and show no signs of equally
spaced resonances as predicted by theories based on the idea of a
chromospheric resonator.
Title: Plumes and oscillations in the sunspot transition region
Authors: Maltby, P.; Brynildsen, N.; Kjeldseth-Moe, O.; Wilhelm, K.
Bibcode: 2001A&A...373L...1M
Altcode:
The suggestion that sunspot transition region oscillations are a typical
feature of the sunspot plumes is examined. The present observations show
3 min oscillations in the umbra that end at the umbral rim. We find
that sunspot plumes located above the umbra show these oscillations,
in contrast to plumes above the penumbra. These two findings suggest
that the oscillations may be a property of the umbral transition region.
Title: Dual Flows and Oscillations in the Sunspot Transition Region
Authors: Brynildsen, N.; Maltby, P.; Kjeldseth-Moe, O.; Wilhelm, K.
Bibcode: 2001ApJ...552L..77B
Altcode:
New knowledge about sunspot transition region lines that deviate
significantly from a Gaussian shape are presented. Attention is given
to ``multiple flows,'' a line profile phenomenon in which two or more
distinct velocities are observed within the same spatial resolution
element. We observe line profiles that are well represented by two
Gaussian line components in the N V λ1242 and O V λ629 lines and
introduce the notation ``dual flow.'' We have detected transition region
oscillations in one of the line components in the dual-flow events.
Title: Velocities in Sunspot Plumes
Authors: Maltby, P.; Kjeldseth-Moe, O.; Brynildsen, N.
Bibcode: 2001IAUS..203..300M
Altcode:
We investigate the line-of-sight velocities in 50 sunspot regions,
based on observations of ten or six EUV emission lines with the
Coronal Diagnostic Spectrometer - CDS on the Solar and Heliospheric
Observatory - SOHO. The position of the sunspots on the solar disk
ranges from disk centre to locations close to the solar limb. Attention
is given to the sunspot plumes, the most prominent features in the
transition region intensity maps. More than half of the sunspots
show downflows in the sunspot plumes that exceed 25 km s-1
at temperatures close to 300 000 K. The observations show that this
downflow cannot be maintained by inflow from the corona. The downflow
in the sunspot plumes appears to be maintained by gas at transition
region temperatures, streaming in flow channels from locations well
outside the sunspot. Although individual flow channels show significant
changes during approximately 10 minutes, part of the velocity pattern
remains unaltered for approximately one day. The velocity fields in
the transition region and the chromosphere are compared and the siphon
flow mechanism is confronted with the observations.
Title: Sunspot Plumes and Flow Channels
Authors: Brynildsen, N.; Maltby, P.; Fredvik, T.; Kjeldseth-Moe, O.;
Wilhelm, K.
Bibcode: 2001SoPh..198...89B
Altcode:
It is well known that sunspots are dark. This statement is not correct
in the sunspot atmosphere between the chromosphere and the corona,
where sunspots often are brighter than their surroundings. The brightest
feature in the sunspot transition region is called a sunspot plume. Not
all sunspots contain a plume. We find that 20 out of 21 sunspots show
a plume when one magnetic polarity dominates the sunspot region out
to a distance of 50 '' from the sunspot. Most sunspots show
downflows that exceed 25 km s−1 in the sunspot plumes at
temperatures close to 250 000 K. This downflow is not maintained by
inflow from the corona, but by gas at transition region temperatures,
streaming in flow channels from locations well outside the sunspot. We
suggest that this inflow is a necessary requirement for the sunspot
plume to occur and present a working hypothesis for the origin of
sunspot plumes. This paper is the first thorough spectral analysis of
sunspot plumes. It is based on simultaneous observations of ten or six
EUV emission lines in 42 sunspot regions with the Coronal Diagnostic
Spectrometer - CDS on the Solar and Heliospheric Observatory - SOHO. The
line profiles are studied in detail with another SOHO instrument,
the Solar Ultraviolet Measurements of Emitted Radiation - SUMER.
Title: On Sunspot Plumes and Dynamics above Sunspot Regions (CD-ROM
Directory: contribs/brynild)
Authors: Brynildsen, N.; Maltby, P.; Kjeldseth-Moe, O.
Bibcode: 2001ASPC..223..595B
Altcode: 2001csss...11..595B
No abstract at ADS
Title: Solar Telescopes and Instruments: Space
Authors: Kjeldseth-Moe, O.
Bibcode: 2000eaa..bookE2078K
Altcode:
The first solar space observations...
Title: Observed Variability and Dynamics of Active Region Loops
Authors: Haugan, S. V. H.; Brekke, P.; Fredvik, T.; Kjeldseth-Moe,
O.; Wilhelm, K.; Gurman, J. B.
Bibcode: 2000SPD....31.0205H
Altcode: 2000BAAS...32..811H
A series of 218 rasters taken with the Coronal Diagnostic Spectrometer
(CDS) on SOHO demonstrates the strong time variability and
dynamical state of the plasma in active region loops at transition
region temperatures, i.e. 10 000 K to 500 000 K, first reported
by Kjeldseth-Moe and Brekke (1998). The continuous raster series,
which covered 39 hours, show how transition region loops or sections
of loops, 50-200 Mm in length, appear and disappear in intervals as
short as 10 minutes, the observing cadence. At the same temperatures
plasma velocities of 20 km s-1 to 100 km s-1
are indicated from observed Doppler shifts. Siphon flows may occur in
some of the loops, but in other loops patterns are less obvious. High
velocities are frequently seen where the emitted intensities are weak,
often on the ``outside'' of the loops as defined by the emission in
that particular spectral line. At coronal temperatures the emission
is less time variable, but significant changes are seen. Systematic
loop velocities occur only occasionally in the corona. Simultaneous
observations with EIT and SUMER were made during part of the raster
series and is compared with the CDS result.
Title: Observations of sunspot transition region oscillations
Authors: Brynildsen, N.; Maltby, P.; Leifsen, T.; Kjeldseth-Moe, O.;
Wilhelm, K.
Bibcode: 2000SoPh..191..129B
Altcode:
Oscillations with a period of 3 minutes are observed in the transition
region of six sunspots with the Solar and Heliospheric Observatory
- SOHO joint observing programme for velocity fields in sunspot
regions. Observations of the transition region lines O v λ629
and N v λλ1238, 1242 with the SUMER instrument show significant
differences in the amplitude of the 3-minute oscillations from one
sunspot to another, both in intensity and line-of-sight velocity. In
four sunspots the central part of the umbra is observed. Two of these
sunspots show coincidence between the maxima in peak line intensity
and velocity directed towards the observer, as is expected for an
upward-propagating acoustic wave. The two other sunspots show large
oscillation amplitudes and a difference of 25° between maxima in
intensity and blue shift. The possible effect of partial wave reflection
on the observed phase relation is discussed. For one sunspot only a part
of the umbra, close to the penumbra, was observed and the observations
show a difference of 50° between maxima in intensity and blueshift. For
the smallest sunspot the observations are found to be contaminated by
contributions from an area without oscillations. Observed oscillations
in line width are small, but probably significant in two sunspots. The
observations of NOAA 8378 allow us to compare simultaneous recordings
of the oscillations in the chromospheric Si ii λ1260 line with the
oscillations in the transition region lines. We question the suggestion
by Fludra (1999) that the sunspot transition region oscillations are
a typical feature of the sunspot plumes.
Title: Signatures of Magnetic Reconnection and Observed EUV Emission
Line Profiles in An Active Region
Authors: Brekke, P.; Brynildsen, N.; Kjeldseth-Moe, O.; Maltby, P.;
Wilhelm, K.
Bibcode: 2000AdSpR..26..457B
Altcode:
We report on observations with SUMER on SOHO of high-velocity events,
also called explosive events. The high spatial and spectral resolutions
of SUMER allow simultaneous observations of EUV emission lines formed
at different temperatures within the transition region. Complex
line profiles with three separate line components appear to be
a characteristic feature of many high-velocity events based on a
survey of Si IV λ1393 observations. The present study is based on
551 spectra of the active region NOAA 7995 obtained on 17 November
1996. We find that the complex line profiles of explosive events may be
represented by a composite line profile consisting of three Gaussian
line components. Both positive and negative line-of-sight velocities
are found to be significantly larger at 6.3 ×105 K than
at 1.5 - 1.7 ×105 K. We briefly confront the observations
with signatures predicted from magnetic reconnections, disturbances
originating in the corona and flows in an extremely structured
transition region
Title: Structure and Dynamics in the Atmosphere Above Sunspot Regions
Authors: Brynildsen, N.; Brekke, P.; Haugan, S. V. H.; Kjeldseth-Moe,
O.; Maltby, P.; Wikstøl, Ø.
Bibcode: 2000AdSpR..25.1743B
Altcode:
Based on simultaneous observations of 10 EUV emission lines with the
Coronal Diagnostic Spectrometer - CDS on the Solar and Heliospheric
Observatory - SOHO we study the spatial distributions of both line
emission and line-of-sight velocity in the atmosphere above 17
sunspots. We find that both the enhanced EUV line emissions and the
velocities are distributed non-uniformly over the sunspot regions. Areas
with enhanced line emission tend to be red shifted, but they seldom
coincide exactly with areas with enhanced velocity. Bright sunspot
plumes with motion directed away from the observer are observed in
most of the sunspot regions
Title: The Dynamical and Time Variable Solar Transition Region
Observed with the Coronal Diagnostic Pectrometer (CDS) on Soho
Authors: Kjeldseth-Moe, O.
Bibcode: 2000AdSpR..25.1713K
Altcode:
CDS on SOHO has detected an upper solar atmosphere that is more dynamic
and time variable than previously expected. Exciting and unexpected
is the strongly time variable and dynamic active region loops at
transition region temperatures. Loops in the temperature range of 1-5 ×
105 K, extending 20 000 - 90 000 km above the solar surface,
are seen to appear and disappear in less than one hour. Spectral lines
from the same loops are frequently Doppler shifted corresponding
to plasma velocities of +/-50-100 km s-l in sections of
the loops. The dynamic active region loops may be connected to the
down-flows seen near sunspots, frequently in sunspot plumes. Other new,
time variable and dynamic phenomena are also seen, i.e. the so called
``blinkers'', and rotating transition region features. The blinkers
occur in the quiet Sun network, with similar phenomena also being
seen in active regions. They consist of strong temporal variations
in the EUV line emission at transition region temperatures and last a
few minutes. The rotating features are macro-spicule like structures,
seen both on the limb and on the disk. They show blue- and red-shifted
emission on either side of an axis extending above the foot-points. The
appearance of variable loops and blinkers show that we need to revise
our concepts of the structure of the upper solar atmosphere and the
processes going on in these regions, perhaps in the direction of a
more fine structured atmosphere
Title: On the sunspot transition region
Authors: Maltby, P.; Brynildsen, N.; Fredvik, T.; Kjeldseth-Moe, O.;
Wilhelm, K.
Bibcode: 1999SoPh..190..437M
Altcode:
The EUV line emission and relative line-of-sight velocity in the
transition region between the chromosphere and corona of 36 sunspot
regions are investigated, based on observations with the Coronal
Diagnostic Spectrometer - CDS and the Solar Ultraviolet Measurements of
Emitted Radiation - SUMER on the Solar and Heliospheric Observatory -
SOHO. The most prominent features in the transition-region intensity
maps are the sunspot plumes. In the temperature range between log T=5.2
and log T=5.6 we find that 29 of the 36 sunspots contain one or two
sunspot plumes. The relative line-of-sight velocity in sunspot plumes
is high and directed into the Sun in the transition region, for 19 of
the sunspots the maximum velocity exceeds 25 km s−1. The
velocity increases with increasing temperature, reaches a maximum
close to log T=5.5 and then decreases abruptly.
Title: EUV Line Emission and Dynamics in Sunspot Regions
Authors: Brynildsen, N.; Maltby, P.; Kjeldseth-Moe, O.
Bibcode: 1999ESASP.446..201B
Altcode: 1999soho....8..201B
The spatial distributions of EUV line emission and relative
line-of-sight velocity in the atmosphere above 22 sunspot regions are
investigated. The study is based on simultaneous observations of ten
EUV emission lines with the Coronal Diagnostic Spectrometer -- CDS on
SOHO. Since the EUV emission lines are formed at different temperatures,
we study the sunspot atmosphere from the chromosphere to the corona. We
observe both a rapid variation with a characteristic time of a few to
several minutes and a slow variation with a time constant of several
hours to approximately one day. The sunspot plume concept is reinvented
to describe the most prominent emission feature in the intensity maps in
the temperature range log T approx 5.2 - 5.6. The relative line-of-sight
velocity in sunspot plumes is high and directed into the Sun in the
transition region. The flow is maintained by plasmas at transition
region temperatures, moving from regions located at greater heights
outside the sunspot and towards the sunspot. Only a few features show
the signatures of a siphon flow. Comparisons of intensity and velocity
maps suggest that gas at transition region temperatures occur in loops
different from loops with coronal temperatures. However, we cannot
exclude the presence of transition region temperatures close to the
footpoints of flux tubes emitting at coronal temperatures.
Title: Sunspot Transition Region Oscillations
Authors: Brynildsen, N.; Kjeldseth-Moe, O.; Maltby, P.; Wilhelm, K.
Bibcode: 1999ESASP.446..207B
Altcode: 1999soho....8..207B
Based on the SOHO joint observing programme for velocity fields in
sunspots, we have detected 3 min transition region umbral oscillations
in six sunspots. Simultaneous recordings of O V lambda 629, NV lambdas
1238, 1242 and Si I lambda 1260 with the SUMER instrument allow us to
compare the transition region oscillations with the 3 min chromospheric
oscillations above the sunspot. We investigate the amplitudes and phase
relations of the oscillations in peak line intensity, line-of-sight
velocity and line width. The spatial distributions of power in the
3 min oscillations, both in intensity and line-of-sight velocity,
are presented. The observations show that the maxima in peak line
intensity are nearly, but not exactly in phase with the maxima in
velocity directed towards the observer. The suggestion that the waves
are upward propagating acoustic waves is confronted with observations.
Title: The Time Variable Solar Atmosphere - Dynamical and Variable
Active Region Loops Observed with CDS on SOHO.
Authors: Kjeldseth-Moe, O.; Brekke, P.
Bibcode: 1999ASPC..184..286K
Altcode:
The Coronal Diagnostic Spectrometer, CDS, on SOHO has detected an
upper solar atmosphere that is much more dynamic and time variable than
previously expected. Loops in active regions, particularly in emission
lines formed at temperatures 105 K to 1 MK, traditionally
thought of as the transition region, are seen to change significantly
over an hour. Loops appear or disappear, the emission along their
length change, or they change shape or expand outward, all on time
scales of 10-20 minutes. The structural variability is accompanied by
high Doppler shifts, especially in the 2-5x105 K temperature
range. Velocities corresponding to the shifts typically amount to +/-
50-100 km-1. We find that existing theoretical models for
loops cannot explain the observations. However, models with extreme
fine structure, combined with episodic heating and magneto-acoustic
wave disturbances propagating in the loop legs seem promising. The
rapidly changing conditions that we observe give a new conception of
loop systems that has never before been seriously considered.
Title: EUV Observations of Sunspot Regions with CDS on SOHO
Authors: Brynildsen, N.; Brekke, P.; Haugan, S. V. H.; Kjeldseth-Moe,
O.; Maltby, P.
Bibcode: 1999ASPC..184..266B
Altcode:
The spatial distributions of line emission and line-of-sight velocity in
seventeen different sunspot regions are studied, based on observations
with the Coronal Diagnostic Spectrometer - CDS on SOHO. Ten EUV emission
lines, formed in the chromosphere, transition region, and corona are
observed. Enhanced EUV line emissions in the transition region are
distributed non-uniformly over the active regions and are located both
inside and outside sunspots. Most sunspot regions show strongly enhanced
transition region line emission above the spot, i.e. sunspot plumes
are reinvented. From wavelength shifts we derive the line-of-sight
velocity, relative to the average velocity in the rastered area, 120"
x 120". In sunspot plumes we find that the motion is directed away from
the observer and increases with increasing line formation temperature,
T, reaches a maximum up to 40 km s-1 close to log T ≅ 5.5,
then decreases abruptly. The spatial extent of both emission features
and flow regions increase with increasing temperature within the
transition region. The observations show a marked difference between
the transition region and the low corona, both regarding the spatial
distributions of line emission and line-of-sight velocity.
Title: Transition Region Oscillations in a Sunspot Region
Authors: Brynildsen, N.; Fredvik, T.; Kjeldseth-Moe, O.; Maltby, P.
Bibcode: 1999ASPC..184..146B
Altcode:
Umbral oscillations in the sunspot transition region have been detected
and described from SOHO observations, mainly taken with SUMER of
NOAA 8156 on 18 February 1998 between 16:00 UT and 21:07 UT. SUMER
recorded simultaneously in the transition regions lines O V λ629, N
V λ1238 and N V λ1242, combined with long exposures for wavelength
calibration. Transition region oscillations with periods close to 3
min were observed both in intensity and in line-of-sight velocity;
the maximum intensity is nearly in phase with maximum velocity
directed towards the observer. The wave characteristics appear to be
compatible with the results of Gurman et al. (1982) from UVSP on SMM,
who interpreted them as upward propagating acoustic waves.
Title: Nonlinear Sunspot Transition Region Oscillations in NOAA 8378
Authors: Brynildsen, N.; Kjeldseth-Moe, O.; Maltby, P.; Wilhelm, K.
Bibcode: 1999ApJ...517L.159B
Altcode:
Observations obtained with the Solar and Heliospheric Observatory
joint observing program for velocity fields in sunspot regions are
used to study the 3 minute transition region oscillations above four
sunspots. Here we report mainly on the results obtained for NOAA 8378,
based on simultaneous recordings of the transition region lines O
V λ629 and N V λλ1238, 1242 and the chromospheric Si II λ1260
line with the Solar Ultraviolet Measurements of Emitted Radiation
instrument. The 3 minute transition region oscillations in NOAA 8378
occur mainly above the umbra and show (1) larger peak line intensity
amplitudes than reported before, (2) clear signs of nonlinearities,
(3) significant oscillations in line width, (4) maxima in peak line
intensity and maxima in velocity directed toward the observer that
are nearly, but not exactly in phase, and (5) a clear connection to
the oscillations in the sunspot chromosphere. The suggestion that the
waves are upward-propagating acoustic waves is confronted with the
observations by a simple test.
Title: A Transition Region Eruption Observed with CDS, TRACE and EIT
Authors: Brekke, P.; Kjeldseth-Moe, O.; Fredvik, T.; Haugan, S. V. H.;
Tarbell, T. D.; Gurman, J. B.
Bibcode: 1999AAS...194.5905B
Altcode: 1999BAAS...31..918B
An ejection of plasma on the west limb has been observed with CDS,
TRACE and EIT on 19 May 1998. The start of the eruption coincided
with a weak flare observed with GOES. Erupting material rose to 120
Mm above the solar surface in 17 min, and then fell back to the solar
surface. Vertical velocities of 200 km s(-1) are estimated from a series
of TRACE images in the C(+3) resonance lines at 155 nm and from EIT
images in the 19.5 nm band, while Doppler shifts of the transition
region lines observed with CDS yield maximum horizontal velocities
of 300 km s(-1) at the top of the plasma trajectories. The similar
appearance and time variation of the eruption as seen with all three
instruments indicate the presence of a multi-temperature plasma in
spatial regions less than 1-2 arc seconds, with temperatures ranging
from 10(5) K to 1.5 MK. The material did not have the momentum to break
loose from the Sun and was not associated with any CME observed with
LASCO. However, we may speculate that CMEs are similar to the eruption
observed, with even higher speeds involved.
Title: Time Variation of Active Region Loops Observed with CDS on SOHO
Authors: Fredvik, T.; Kjeldseth-Moe, O.; Brekke, P.; Haugan, S. V. H.
Bibcode: 1999AAS...194.5904F
Altcode: 1999BAAS...31R.918F
The emission from plasma filled loops, 10(4) K < T <1.5 MK,
above active regions are much more time variable than previously
considered. These loops, which define the solar atmosphere above active
regions in this temperature range, appear or disappear, the emission
along their length change, or they change shape or expand outward,
all on time scales of 10-20 minutes. In this paper we report on an
investigation with CDS on SOHO of 20 loop systems observed on the solar
limb between September 1997 and May 1998. We describe the apparent
isothermal appearance of many loops and discuss to what extent loops
radiating in different emission lines, i.e. at different temperatures,
are co-located within their recorded widths. Finally, we demonstrate
the time variability of loop systems at different temperatures, and
show how the rapidly changing conditions require a new conception of
loop systems that has never before been seriously considered.
Title: SOHO Observations of the Structure and Dynamics of Sunspot
Region Atmospheres
Authors: Brynildsen, N.; Maltby, P.; Brekke, P.; Haugan, S. V. H.;
Kjeldseth-Moe, O.
Bibcode: 1999SoPh..186..141B
Altcode:
We present results from a study of the spatial distributions of line
emission and relative line-of-sight velocity in the atmosphere above
17 sunspot regions, from the chromosphere, through the transition
region and into the corona, based on simultaneous observations of ten
EUV emission lines with the Coronal Diagnostic Spectrometer - CDS on
SOHO. We find that the spatial distributions are nonuniform over the
sunspot region and introduce the notation 'sunspot loop' to describe an
enhanced transition region emission feature that looks like a magnetic
loop, extending from inside the sunspot to the surrounding regions. We
find little evidence for the siphon flow. Attention is given to the time
variations since we observe both a rapid variation with a characteristic
time of a few to several minutes and a slow variation with a time
constant of several hours to ≈ 1 day. The most prominent features
in the transition region intensity maps are the sunspot plumes. We
introduce an updated criterion for the presence of plumes and find
that 15 out of 17 sunspots contain a plume in the temperature range
logT≈5.2-5.6. The relative line-of-sight velocity in sunspot plumes
is high and directed into the Sun in the transition region. Almost
all the sunspot regions contain one or a few prominent, strongly
redshifted velocity channels, several of the channels extend from the
sunspot plume to considerable distances from the sunspot. The flow
appears to be maintained by plasmas at transition region temperatures,
moving from regions located at a greater height outside the sunspots
and towards the sunspot. The spatial correlation is high to moderate
between emission lines formed in the transition region lines, but
low between the transition region lines and the coronal lines. From
detailed comparisons of intensity and velocity maps we find transition
region emission features without any sign of coronal emission in the
vicinity. A possible explanation is that the emission originates in
magnetic flux tubes that are too cold to emit coronal emission. The
comparisons suggest that gas at transition region temperature occur in
loops different from loops with coronal temperature. However, we cannot
exclude the presence of transition region temperatures close to the
footpoints of flux tubes emitting at coronal temperatures. Regions with
enhanced transition region line emission tend to be redshifted, but the
correlation between line emission and relative line-of-sight velocity
is weak. We extend our conditional probability studies and confirm
that there is a tendency for line profiles with large intensities and
red shifts (blue shifts) above the average to constitute an increasing
(decreasing) fraction of the profiles as the wavelength shift increases.
Title: Sunspot Transition Region Oscillations in NOAA 8156
Authors: Brynildsen, N.; Leifsen, T.; Kjeldseth-Moe, O.; Maltby, P.;
Wilhelm, K.
Bibcode: 1999ApJ...511L.121B
Altcode: 1998astro.ph.12012B
Based on observations obtained with the Solar and Heliospheric
Observatory joint observing program for velocity fields in sunspot
regions, we have detected 3 minute transition region umbral oscillations
in NOAA 8156. Simultaneous recordings of O V λ629 and N V λ1238,
λ1242 with the SUMER instrument give the spatial distribution of power
in the 3 minute oscillations, both in intensity and in line-of-sight
velocity. Comparing loci with the same phase, we find that the entire
umbral transition region oscillates. The observed maxima in peak line
intensity are nearly in phase with the maxima in velocity directed
toward the observer. We discuss the suggestion that the waves are
upward-propagating acoustic waves.
Title: An eruption in the transition region observed with CDS and
TRACE, on May 19, 1998.
Authors: Brekke, P.; Kjeldseth-Moe, O.; Tarbell, T.
Bibcode: 1999joso.proc..170B
Altcode:
The authors present simultaneous CDS and TRACE observations in the EUV
of an eruption of May 19, 1998. A large ejection of plasma was seen
on the west limb and could be followed in EUV rasters in transition
region lines with CDS and in high cadence images in the C+3
155 nm line from TRACE. The onset of the eruption coincided with a
weak flare observed with GOES. The eruption extended to 120000 km
above the solar surface after 17 min and then fell back to the solar
surface. At the leading edge of the eruption CDS observed Doppler
shifts of 300 km s-1 away from the observer (i.e. parallel
to the solar surface) in the O+4 line at 62.9 nm. High
cadence observations with TRACE indicate that the plasma velocities
perpendicular to the line of sight (i.e. along the solar vertical)
reached similar values, i.e. 200 km s-1. Perhaps this was a
"coronal mass ejection" that did not make it?
Title: Jets and Eruptions in the Transition Region Observed with CDS,
EIT and TRACE
Authors: Brekke, P.; Kjeldseth-Moe, O.; Tarbell, T.; Gurman, J.
Bibcode: 1999ASPC..183..357B
Altcode: 1999hrsp.conf..357B
No abstract at ADS
Title: Time Variability of Active Region Loops Observed with the
Coronal Diagnostic Spectrometer (Cds) on SOHO
Authors: Kjeldseth-Moe, O.; Brekke, P.
Bibcode: 1998SoPh..182...73K
Altcode:
Monochromatic images from the Coronal Diagnostic Spectrometer (CDS)
of loops above active regions show clear evidence of rapid time
variability. The rapidly changing conditions that we observe give a
new conception of loop systems that has never before been seriously
considered. Loop systems, particularly in emission lines formed at
temperatures in the 1-5 × 105 K range, traditionally thought
of as transition region temperatures, are seen to change significantly
over a period of 1 hour. Loops may appear or disappear in certain
emission lines, may show rapid variations in the distribution of the
emission along their lengths, or may change shape or expand outward,
all on time scales of 10-20 min. At other temperatures below 1.5 MK
the variability appears less striking, but is still pronounced. At
high temperatures, i.e., T ≥ 1.5 MK, conditions are normally much
more stable. Examples exist, however, of loop systems showing violent
changes in images at all temperatures up to Fe xvi formed at 2.7
MK. The structural variability is accompanied by high Doppler shifts,
especially in the O v line. Corresponding velocities typically amount to
50-100 km s-1, but values as high as 300 km s-1
have been recorded. Animations with illustrative examples of loop
variability have been prepared and are found on the enclosed CD-ROM. In
addition we briefly discuss other structural and dynamical properties
of active region loops, particularly those with temperatures below 1.5
MK. Theoretical models of loops cannot explain the present observations,
but models that combine extreme fine structure, episodic heating and
magneto-acoustic wave disturbances propagating in the loop legs seem
promissing.
Title: Flows in Sunspot Plumes Detected with SOHO
Authors: Brynildsen, N.; Maltby, P.; Brekke, P.; Fredvik, T.; Haugan,
S. V. H.; Kjeldseth-Moe, O.; Wikstol, O.
Bibcode: 1998ApJ...504L.135B
Altcode: 1998astro.ph..5249B
In the Letter, ``Flows in Sunspot Plumes Detected with the Solar and
Heliospheric Observatory'' by N. Brynildsen, P. Maltby, P. Brekke,
T. Fredvik, S. V. H. Haugan, O. Kjeldseth-Moe, and Ø. Wikstøl (ApJ,
502, L85 [1998]), the following correction should be made: In
the last line on page L86, which reads ``peak line intensity I>=5
are located (1) above the umbra or, '' an ``Ī'' should be inserted so
that the revised line reads ``peak line intensity I>=5Ī are located
(1) above the umbra or.''
Title: Flows in Sunspot Plumes Detected with the Solar and
Heliospheric Observatory
Authors: Brynildsen, N.; Maltby, P.; Brekke, P.; Fredvik, T.; Haugan,
S. V. H.; Kjeldseth-Moe, O.; Wikstøl, Ø.
Bibcode: 1998ApJ...502L..85B
Altcode:
Bright extreme-UV sunspot plumes have been observed in eight out of
11 different sunspot regions with the Coronal Diagnostic Spectrometer
on Solar and Heliospheric Observatory. From wavelength shifts, we
derive the line-of-sight velocity relative to the average velocity
in the rastered area, 120''×120''. In sunspot
plumes, we find that the motion is directed away from the observer
and increases with increasing line formation temperature, reaches a
maximum between 15 and 41 km s-1 close to log logT~5.5,
then decreases abruptly. The flow field in the corona is not well
correlated with the flow in the transition region, and we discuss
briefly the implication of this finding.
Title: SOHO Observations of the Connection Between Line Profile
Parameters in Active and Quiet Regions and the Net Red Shift in EUV
Emission Lines
Authors: Brynildsen, N.; Brekke, P.; Fredvik, T.; Haugan, S. V. H.;
Kjeldseth-Moe, O.; Maltby, P.; Harrison, R. A.; Wilhelm, K.
Bibcode: 1998SoPh..181...23B
Altcode:
We present high spatial and spectral resolution observations of
one active and one quiet-Sun region, obtained with CDS and SUMER on
SOHO. The connections between the line profile parameters are studied
and a systematic wavelength shift towards the red with increasing peak
line intensity (line broadening) is detected. The large scatter in
the data calls for another approach. We apply conditional probability
analysis to a series of EUV emission lines and find significant
correlations between line profile parameters. For a given interval in
wavelength shift we find that: (1) line profiles with large intensities
(line widths) and red shifts above the average constitute an increasing
fraction of the profiles as the relative wavelength shift increases,
(2) line profiles with large intensities (line widths) and blue
shifts compared to the average, on the other hand, constitute a
decreasing fraction of the profiles as the relative wavelength shift
increases. These results extend the findings of an earlier quiet-Sun
study from one to several emission lines and expand the validity to
include the active region. Interestingly, the active region observations
show correlations between peak line intensity and wavelength shift in
the coronal lines.
Title: EUV Spectroscopy of the Sunspot Region NOAA 7981 Using SOHO -
II. Velocities and Line Profiles
Authors: Brynildsen, N.; Brekke, P.; Fredvik, T.; Haugan, S. V. H.;
Kjeldseth-Moe, O.; Maltby, P.; Harrison, R. A.; Pike, C. D.; Rimmele,
T.; Thompson, W. T.; Wilhelm, K.
Bibcode: 1998SoPh..179..279B
Altcode:
We have studied the dynamics in the sunspot transition region between
the chromosphere and the corona and investigated the extension of
the flow field into the corona. Based on EUV spectra of a medium size
sunspot and its surroundings, NOAA 7981, observed with CDS and SUMER
on SOHO, we derive line-of-sight velocities and study the line profiles
for a series of emission lines.
Title: Extreme-Ultraviolet Sunspot Plumes Observed with SOHO
Authors: Maltby, P.; Brynildsen, N.; Brekke, P.; Haugan, S. V. H.;
Kjeldseth-Moe, O.; Wikstøl, Ø.; Rimmele, T.
Bibcode: 1998ApJ...496L.117M
Altcode: 1998astro.ph..1144M
Bright EUV sunspot plumes have been observed in five out of nine sunspot
regions with the Coronal Diagnostic Spectrometer on the Solar and
Heliospheric Observatory. In the other four regions, the brightest line
emissions may appear inside the sunspot but are mainly concentrated in
small regions outside the sunspot areas. These results are in contrast
to those obtained during the Solar Maximum Mission but are compatible
with the Skylab mission results. The present observations show that
sunspot plumes are formed in the upper part of the transition region,
occur in both magnetic unipolar and bipolar regions, and may extend
from the umbra into the penumbra.
Title: EUV Spectroscopy of the Sunspot Region NOAA 7981 Using SOHO -
I. Line Emission and Time Dependence
Authors: Brynildsen, N.; Brekke, P.; Fredvik, T.; Haugan, S. V. H.;
Kjeldseth-Moe, O.; Maltby, P.; Harrison, R. A.; Pike, C. D.; Rimmele,
T.; Thompson, W. T.; Wilhelm, K.
Bibcode: 1998SoPh..179...43B
Altcode:
EUV spectra of a medium-size sunspot and its surroundings, NOAA 7981,
were obtained on 2 August 1996 with the Coronal Diagnostic Spectrometer
(CDS) and the Solar Ultraviolet Measurements of Emitted Radiation
(SUMER) on the Solar and Heliospheric Observatory (SOHO). The spectral
lines formed in the transition region and corona show considerable
structure and large deviations from a uniform spatial distribution over
the active region. Enhanced EUV emissions in transition region lines
are concentrated in small regions outside the umbra of the sunspot
throughout most of the observing sequence. Only during a short,
active period do we find an enhanced line emission that reaches into
the umbra. Preliminary values for the umbral intensity are given.
Title: Three Dimensional EUV Imaging of Sunspot Regions Observed
with SOHO
Authors: Brynildsen, N.; Brekke, P.; Haugan, S. V. H.; Kjeldseth-Moe,
O.; Maltby, P.; Harrison, R. A.; Rimmele, T.; Wilhelm, K.
Bibcode: 1998ASPC..155..171B
Altcode: 1998sasp.conf..171B
No abstract at ADS
Title: Inconstancy of the Transition Region - Variable and Dynamic
Active Region Loops
Authors: Kjeldseth-Moe, O.; Brekke, P.; Haugan, S. V. H.
Bibcode: 1998ESASP.417..153K
Altcode: 1998cesh.conf..153K
No abstract at ADS
Title: High-Velocity Flows in an Active Region Loop System Observed
with the Coronal Diagnostic Spectrometer (Cds) on SOHO
Authors: Brekke, P.; Kjeldseth-Moe, O.; Harrison, R. A.
Bibcode: 1997SoPh..175..511B
Altcode:
EUV spectra of coronal loops above an active region show clear evidence
of strong dynamical activity. We present an example where the Ov
629 Å line, formed at 240 000 K, is shifted from its reference
position corresponding to line-of-sight velocities greater than 50
km s-1 with the shift extending over a large fraction
of a loop. The observations were made with the Coronal Diagnostic
Spectrometer (CDS) on the Solar and Heliospheric Observatory (SOHO),
and are from active region NOAA 7981 on the east solar limb on 27
July 1996. An animation has been prepared showing the variation of the
shift or flow velocity along the loop. This animation is to be found
on the enclosed CD-ROM and gives a clear impression of the dynamical
condition present in the loop. The appearance of the loop system in
different lines formed over a range in temperature as well as the
observed dynamics indicates that loops at different temperatures are
not closely co-located. Finally, the results are discussed and related
to mechanisms that may cause line shifts.
Title: The Non-Uniformity in the Sunspot Transition Region
Authors: Brynildsen, N.; Brekke, P.; Fredvik, T.; Haugan, S. V. H.;
Kjeldseth-Moe, O.; Maltby, P.; Harrison, R. A.; Rimmele, T.;
Wilhelm, K.
Bibcode: 1997ESASP.404..257B
Altcode: 1997cswn.conf..257B
No abstract at ADS
Title: Transition Region Velocities and Line Profiles in the Sunspot
Region 7981
Authors: Brynildsen, N.; Brekke, P.; Fredvik, T.; Haugan, S. V. H.;
Kjeldseth-Moe, O.; Maltby, P.; Harrison, R. A.; Pike, C. D.; Rimmele,
T. Thompson, W. T.; Wilhelm, K.
Bibcode: 1997ESASP.404..251B
Altcode: 1997cswn.conf..251B
No abstract at ADS
Title: CDS Observations of the Connection Between Line Intensity
and Doppler Shift in the Active Region NOAA 7981
Authors: Fredvik, T.; Brynildsen, N.; Maltby, P.; Kjeldseth-Moe, O.;
Brekke, P.; Haugen, S. V. H.; Harrison, R. A.
Bibcode: 1997ESASP.404..391F
Altcode: 1997cswn.conf..391F
No abstract at ADS
Title: Flows with High Velocities in an Active Region Loop Observed
with the Coronal Diagnostic Spectrometer
Authors: Kjeldseth-Moe, O.; Brekke, P.; Harrison, R. A.
Bibcode: 1997ESASP.404..457K
Altcode: 1997cswn.conf..457K
No abstract at ADS
Title: The Net Redshifts in EUV Emission Lines and the Connection
Between Intensity and Doppler Shift
Authors: Brynildsen, N.; Fredvik, T.; Maltby, P.; Kjeldseth-Moe, O.;
Brekke, P.; Haugan, S. V. H.; Harrison, R. A.; Wilhelm, K.
Bibcode: 1997ESASP.404..263B
Altcode: 1997cswn.conf..263B
No abstract at ADS
Title: EUV Line Emission and Time Dependence in the Sunspot Region
NOAA 7981
Authors: Brynildsen, N.; Brekke, P.; Fredvik, T.; Haugan, S. V. H.;
Kjeldseth-Moe, O.; Maltby, P.; Harrison, R. A.; Pike, C. D.; Rimmele,
T.; Thompson, W. T.; Wilhelm, K.
Bibcode: 1997ESASP.404..245B
Altcode: 1997cswn.conf..245B
No abstract at ADS
Title: High-Resolution Observations of the Extreme Ultraviolet Sun
Authors: Harrison, R. A.; Fludra, A.; Pike, C. D.; Payne, J.;
Thompson, W. T.; Poland, A. I.; Breeveld, E. R.; Breeveld, A. A.;
Culhane, J. L.; Kjeldseth-Moe, O.; Huber, M. C. E.; Aschenbach, B.
Bibcode: 1997SoPh..170..123H
Altcode:
This paper presents first results of the Coronal Diagnostic Spectrometer
(CDS) recently launched aboard the Solar and Heliospheric Observatory
(SOHO). CDS is a twin spectrometer, operating in the extreme ultraviolet
range 151-785 Å. Thus, it can detect emission lines from trace
elements in the corona and transition region which will be used to
provide diagnostic information on the solar atmosphere. In this paper,
we present early spectra and images, to illustrate the performance of
the instrument and to pave the way for future studies.
Title: Flows and Dynamics in the Corona Observed with the Coronal
Diagnostic Spectrometer (cds)
Authors: Brekke, P.; Kjeldseth-Moe, O.; Brynildsen, N.; Maltby, P.;
Haugan, S. V. H.; Harrison, R. A.; Thompson, W. T.; Pike, C. D.
Bibcode: 1997SoPh..170..163B
Altcode:
EUV spectra obtained with the Coronal Diagnostic Spectrometer (CDS)
on the Solar and Heliospheric Observatory (SOHO) show significant flows
of plasma in active region loops, both at coronal and transition region
temperatures. Wavelength shifts in the coronal lines Mgix 368 Å and
Mgx 624 Å corresponding to upflows in the plasma reaching velocities
of 50 km s-1 have been observed in an active region. Smaller
velocities are detected in the coronal lines Fexvi 360 Å and Sixii
520 Å. Flows reaching 100 km s-1 are observed in spectral
lines formed at transition region temperatures, i.e., Ov 629 Å and
Oiii 599 Å, demonstrating that both the transition region and the
corona are clearly dynamic in nature. Some high velocity events show
even higher velocities with line profiles corresponding to a velocity
dispersion of 300-400 km s-1. Even in the quiet Sun there
are velocity fluctuations of 20 km s-1 in transition region
lines. Velocities of the magnitude presented in this paper have never
previously been observed in coronal lines except in explosive events
and flares. Thus, the preliminary results from the CDS spectrometer
promise to put constraints on existing models of the flows and energy
balance in the solar atmosphere. The present results are compared to
previous attempts to observe flows in the corona.
Title: Solar observations with SOHO.
Authors: Kjeldseth-Moe, O.
Bibcode: 1997smf..conf..115K
Altcode:
SOHO - ESA's and NASA's Solar and Heliospheric Observatory -
has 12 instruments on board. Three of these are classified as
helioseismological, three other instruments study the particles in the
solar wind in situ at the location of SOHO. The author concentrates
on the two spectrometers, CDS and SUMER of the third group of SOHO
instruments, which study the solar corona, and includes some results
from the white light coronagraph LASCO and the UV imager EIT.
Title: Extreme ultraviolet observations of the solar corona: first
results from the coronal diagnostic spectrometer on SOHO
Authors: Harrison, R. A.; Fludra, A.; Sawyer, E. C.; Culhane, J. L.;
Norman, K.; Poland, A. I.; Thompson, W. T.; Kjeldseth-Moe, O.;
Aschenbach, B.; Huber, M. C. E.; Gabriel, A. H.; Mason, H. E.
Bibcode: 1997AdSpR..20.2239H
Altcode:
We present first results from the Coronal Diagnostic Spectrometer (CDS)
aboard the ESA/NASA Solar and Heliospheric Observatory (SOHO). CDS is
a double spectrometer operating in the 151-785 A˚ range. This region
of the solar spectrum is rich in emission lines from trace elements
in the solar atmosphere, which can be used to derive diagnostic
information on coronal and transition region plasma. Early spectra are
presented and well identified lines are listed. In addition, examples
of images in selected wavelength ranges are shown, for a prominence,
a loop system and a bright point, demonstrating well the power of such
extreme ultraviolet observations.
Title: Quiet-Sun Connection between the C IV Resonance Lines and
the Photospheric Magnetic Field
Authors: Brynildsen, Nils; Kjeldseth-Moe, Olav; Maltby, Per
Bibcode: 1996ApJ...462..534B
Altcode:
The quiet-Sun relation between the C iv resonance line parameters and
the photospheric magnetic field is studied with a spatial resolution of
1" x 1". The material is ordered into groups according to the magnitude
of the magnetic flux density, |B|, and conditional probabilities
are calculated. We find that red shifted profiles with either high
intensity, large Doppler shift, or large line broadening occupy an
increasing fraction of the area when |B| increases. These results are
contrasted by blueshifted profiles which indicate a slight decrease
with increasing magnetic flux density. The similarity in the results
obtained with magneto grams taken several hours before and after the
UV data led us to suggest that the tendency for red shifted profiles
to outnumber blueshifted profiles in quiet regions originates in the
super-granular network. Suggestions regarding the origin of the
redshift phenomenon are briefly confronted with the observations. It
appears difficult to explain the observations with models based on
continuous gas flows. However, a model containing Alfvén wave pulses
traveling from the corona toward the transition region promises to be
compatible with the observations.
Title: Ultraviolet Spectroscopy -- First Results From SOHO
Authors: Kjeldseth-Moe, O.
Bibcode: 1996AAS...188.4903K
Altcode: 1996BAAS...28Q.897K
The Solar and Heliospheric Observatory, SOHO, has several instruments
observing in the ultraviolet wavelength range, 15 - 160 nm. These
include the spectrometers, CDS and SUMER, and the UV coronagraph,
UVCS which also has spectroscopic capability. The solar radiation in
this wavelength range is formed at temperatures between 5000 K and 15
MK. They are therefore well suited to study the solar atmosphere, from
the chromosphere to the corona in active regions. All the instruments
have the capability of mapping the structure of the hot corona and
measure intensities, profiles and velocity shifted wavelengths of
individual UV spectral lines. With their great spectral range the
spectrometers may also be used to determine pressure, temperature,
element abundances and other gas parameters. To this is added the
capability of observing virtually uninterrupted the time variations of
the coronal radiation on several time scales. In this talk we describe
some of the first results from the ultraviolet observations of the
sun with SOHO and discuss briefly some of the scientific implications
resulting from the observations.
Title: High Velocity Event Observed with CDS on SOHO
Authors: Kjeldseth-Moe, O.; Brynildsen, N.; Brekke, P.; Harrison, R. A.
Bibcode: 1996AAS...188.3714K
Altcode: 1996BAAS...28..880K
The Coronal Diagnostic Spectrometer, CDS, on SOHO has observed its
first strong High Velocity Event. The event occurred on 22 March
1996 at approximately 13.36 UT and was located in the leg of an
active region loop. The spectral signature is extremely wide emission
lines corresponding to a velocity dispersion of approximately 300-450
km/s. As measured in the 386 A line from Mg IX, the emission also seems
shifted in wavelength with a redshift corresponding to 65 km/s. The
intensity contrast in the line is a factor 2 compared to the surrounding
areas. The spatial extent is small, less than or corresponding to the
angular resolution of CDS of 4". The event occur in all available lines
from He I to Fe XV, i.e. over a temperature range from 10 000 K to
2.2 MK. This is a new result which has not been reported before. The
relation of this type of event to the well studied explosive events
is discussed.
Title: Transition Region Lines and the Photospheric Magnetic Field
Authors: Maltby, P.; Brynildsen, N.; Kjeldseth-Moe, O.
Bibcode: 1996AAS...188.0204M
Altcode: 1996BAAS...28..820M
We have combined quiet Sun observations of the C riptsize IV resonance
lines, obtained by the High Resolution Telescope and Spectrograph --
HRTS during the Spacelab 2 mission with Kitt Peak magnetograms. The
material is ordered into groups according to the magnitude of
the magnetic flux density, |B|, and conditional probabilities are
calculated. We find that redshifted profiles with either high intensity,
large Doppler shift, or large line broadening occupy an increasing
fraction of the area when |B| increases. Blueshifted profiles, on the
other hand, indicate a slight decrease with increasing magnetic flux
density. The similarity in the results obtained with magnetograms taken
several hours before and after the UV data led us to suggest that the
tendency for redshifted profiles to outnumber blueshifted profiles in
quiet regions originates in the supergranular network.
Title: Connection between the C IV resonance lines and the quiet
sun photospheric magnetic field
Authors: Brynildsen, N.; Kjeldseth-Moe, O.; Maltby, P.
Bibcode: 1996ASPC..109..115B
Altcode: 1996csss....9..115B
No abstract at ADS
Title: 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.
Bibcode: 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.
Bibcode: 1995ApJ...455L..81B
Altcode:
The quiet-Sun relations between the C IV line parameters, intensity,
wavelength shift, and line broadening, are studied with high spatial
and spectral resolution. The material is ordered into equal intervals
for one of the line parameters, and conditional probabilities
are calculated. As the Doppler velocity increases, we find that
redshifted profiles with a large intensity or line width constitute
an increasing fraction of the total number of profiles in a given
velocity interval. For blueshifted profiles, on the other hand, the
conditional probabilities for finding a profile with considerable
intensity or line width decrease as the line shift increases. Similar
relations are found when the material is ordered according to intensity
or line-width values.
Title: Observed Redshifts in the Solar Transition Region above Active
and Quiet Regions
Authors: Achour, H.; Brekke, P.; Kjeldseth-Moe, O.; Maltby, P.
Bibcode: 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 105 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. 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 × 105 K and
falls abruptly to zero at 2.3 × 105 K. This observation
is independent of the laboratory wavelengths. Suggestions regarding
the origin of the redshift are confronted with the results.
Title: Coronal Diagnostic Spectrometer: an extreme-ultraviolet
spectrometer for the Solar and Heliospheric Observatory
Authors: Kent, Barry J.; Harrison, Richard A.; Sawyer, Eric C.;
Hayes, R. W.; Richards, Anthony G.; Culhane, John L.; Norman, K.;
Breeveld, A. A.; Thomas, P. D.; Poland, Arthur I.; Thomas, Roger J.;
Thompson, William T.; Aschenbach, Bernd R.; Braeuninger, Heinrich
W.; Kjeldseth-Moe, O.; Kuehne, Mikhael; Hollandt, J.; Paustian, W.;
Bromage, B. J.
Bibcode: 1995SPIE.2517...12K
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 15.0 - 80.0 nm. By observing
the intensities of selected lines and line profiles, it is possible
to derive temperature, density, flow, and abundance information for
the plasmas in the solar atmosphere. Spatial resolution down to
a few arcseconds and temporal resolution of seconds, allows such
studies to be made within the fine-scale structure of the solar
corona. Furthermore, coverage of a large wavelength band provides
the capability for simultaneously observing the properties of plasma
across the wide temperature ranges of the solar atmosphere. The
CDS design makes use of a Wolter-Schwarzschild II telescope which
simultaneously illuminates two spectrometer systems, one operating
in normal incidence the other in grazing incidence. In this paper we
describe the salient features of the design of the CDS instrument and
discuss the performance characteristics of CDS as established through
pre-delivery test and calibration activities.
Title: On the relation between red- and blueshifted UV-emission
lines and photospheric magnetic fields
Authors: Brynildsen, N.; Kjeldseth-Moe, Olav; Maltby, Per
Bibcode: 1994ESASP.373..413B
Altcode: 1994soho....3..413B
No abstract at ADS
Title: Working Group 1: Small scale features
Authors: Kjeldseth-Moe, O.
Bibcode: 1994SSRv...70..123K
Altcode:
A review is given of the activities of the working group on small
scale features at the 2nd SOHO Workshop on Elba, 27 September 1
October 1993. The small scale and filamentary structure of the solar
transition region, and possibly also the corona, was pointed out. The
reported observations furthermore demonstrated that the upper solar
atmosphere is strongly dynamical, containing rapidly flowing gas and
with features changing with time. Theoretical concepts and simulations
of conditions in the transition region and corona were presented and
discussed. Finally some ideas on future observations and modelling
were put forward.
Title: Fine structure and the emission filling factor
Authors: Kjeldseth-Moe, O.; Brynildsen, N.; Brekke, P.; Maltby, P.
Bibcode: 1994SSRv...70...89K
Altcode:
There is observational evidence for an extreme fine structure in
the solar transition region, much smaller than 1″ in size (Dereet
al., 1987, 1988) Corresponding to this extreme fine structure there
appear to be an equally complex dynamical structure. We review the
evidence for such dynamical extreme fine structure as demonstrated
by the frequent appearance of multiple velocities, i.e. distinctly
different velocities in the transition region occurring within the
angular resolution element. Multiple velocities are prominent in active
regions and particularly near sunspots, where velocity components
may be supersonic. However, multiple velocities are frequent also in
quiet regions. The consequences of such fine structure for modeling
the transition region will be outlined. Finally the appropriate CDS and
SUMER observations needed to extend our knowledge of a finely structured
transition region and corona, spatially or in time, are discussed.
Title: The extension of explosive events from the transition region
to the corona
Authors: Kjeldseth-Moe, O.; Cheng, C. C.
Bibcode: 1994SSRv...70...85K
Altcode:
We describe the properties of high velocity events in the corona
and upper transition region and propose that they are the same
phenomenon as the well studied explosive events seen in the lower
transition region around T=105 K. Furthermore, we discuss
how the SOHO spectrometers, CDS and SUMER, may be used to check this
conjecture. Magnetic reconnection has been considered a strong candidate
for the physical mechanism causing explosive events. We present a
phenomenological model showing how some of the observed properties of
explosive events may be explained by reconnection occurring in small
magnetic loops.
Title: New Radiometric Values of the Solar Ultraviolet Continuum
Radiation from 1500 to 1700 Angstrom
Authors: Brekke, P.; Kjeldseth-Moe, O.
Bibcode: 1994ApJ...431L..55B
Altcode:
A high-resolution stigmatic spectrometer, the High Resolution Telescope
and Spectrograph (HRTS), has been calibrated against broad-band
irradiance measurements of the Sun with the Solar Ultraviolet Irradiance
Monitor (SUSIM) and the Solar-Stellar Irradiance Comparison Experiment
(SOLSTICE), resulting in a new value for the radiance of the solar
UV continuum from 1500 to 1700 A. Previous HRTS results were based
on a comparison with the Skylab SO82B calibration rocket, CALROC, and
agreed, within the stated accuracy of +/- 25%, with other independently
calibrated UV radiance measurements over the last 20 years. The new
calibration increases the derived radiance in this wavelength range
by a factor of 1.35-1.5 over previous measurements. The difference
is systematic over the wavelength range and cannot be explained by
contributions to the irradiance from spectral lines or enhanced emission
in active regions. The new radiance values are significant for solar
atmospheric models as well as for related studies of stellar models,
since the radiance at these wavelengths reflects the value of the
minimum temperature at the top of the photosphere.
Title: The solar UV continuum 1440-1680 Å and its center-to-limb
variation
Authors: Brekke, P.; Kjeldseth-Moe, O.
Bibcode: 1994SoPh..150...19B
Altcode:
The solar UV continuum has been derived from intensity-calibrated
observations with the High-Resolution Telescope and Spectrograph - HRTS
- on its second rocket flight in 1978. A database has been constructed
using the spatially-resolved solar spectrum 1180-1700 å along a slit
extending from near disk center to the solar limb and crossing a sunspot
and two active regions. The angular resolution is approximately 1.8″.
Title: Book Review: The solar transition region / Cambridge U
Press, 1993
Authors: Kjeldseth-Moe, Olav; Kjeldseth-Moe, O.
Bibcode: 1994SoPh..149..421K
Altcode: 1994SoPh..149..421M
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.
Bibcode: 1993SoPh..145..257K
Altcode:
The fine structure in the flow field in the transition region above
and surrounding a sunspot is determined fromCIV 1548 å line profiles,
observed with the High Resolution Telescope and Spectrograph (HRTS)
during the Spacelab 2 mission. The observed line profiles show one, two,
or three distinct velocity components within the resolution element of
1″ × 1″. Supersonic flows occur in small regions where the line
profile has two or three components. The line component that shows
supersonic speed often is weaker than the subsonic line component,
which may explain why some observers have been unable to detect the
supersonic flow component. The broadening of individual line components
shows non-thermal velocities close to 20 km s−1. This
suggests that turbulence is less important than usually considered.
Title: CDS and SUMER observations of fine structure and dynamics of
loops: experience from HRTS.
Authors: Kjeldseth-Moe, Olav
Bibcode: 1992ESASP.348..155K
Altcode: 1992cscl.work..155K
From observations with the High Resolution Telescope and Spectrograph,
HRTS it appears likely that the transition region in the solar
atmosphere is characterized by an extreme fine structure, much smaller
than 1″in size. This paper describes the evidence from HRTS and
other UV spectrometers for such small structures and outlines their
structural and dynamical properties. The appropriate CDS and SUMER
observations needed to extend our kowledge of a finely structured
transition region and corona are discussed.
Title: Multiple flows in the solar transition region.
Authors: Brekke, P.; Brynildsen, N.; Kjeldseth-Moe, O.; Maltby, P.;
Brueckner, G. E.
Bibcode: 1992ESASP.346..211B
Altcode: 1992ssts.rept..211B
The solar transition region between the chromosphere and the corona
shows clear evidence of a fine scale structure that is much smaller
than the best available instrumental resolution in the UV of 1×1
arcsec. Previous studies have suggested filling factors of 0.01
- 0.001, with the solar gas being restricted to thin, extended
fibrills. New evidence of the fine scale structure is found from
its dynamical characteristics, the presence of multiple flows. In
multiple flows the solar gas in small volumes show several distinct
velocities, resulting in line profiles with more than one velocity
component within the spatial resolution element. Multiple velocities
are particularly prominent above sunspots, but by no means restricted
to these regions. Instead they are clearly a general feature in the
solar transition region, occurring in quiet as well as active regions.
Title: Reconnection and energetic high velocity events in the solar
transition region and corona.
Authors: Kjeldseth-Moe, O.; Cheng, Chung-Chieh
Bibcode: 1992mrpa.work..147K
Altcode:
Energetic high velocity events in the corona and throughout the
transition region were observed with the slitless spectrograph SO82A
on Skylab in 1973-74. Magnetic reconnection is a strong candidate for
the physical mechanism causing the energetic high velocity events. The
authors discuss how a reconnection-like mechanism could be related to
the observed features. They outline possible observations with SOHO
designed to check these hypothesis.
Title: An Ultraviolet Spectral Atlas of a Sunspot and an Active
Region 1190--1730 Angstrom
Authors: Brekke, P.; Kjeldseth-Moe, O.; Bartoe, J. -D. F.; Brueckner,
G. E.
Bibcode: 1991ApJS...75.1337B
Altcode:
An ultraviolet spectral atlas of a sunspot with high spectral
and spatial resolution in the wavelength region 1190-1730 A is
presented. The atlas contains spectra of three different areas in the
sunspot and also of an active region and a quiet region. The selected
areas are averaged over several arcsec, ranging from 3.5 arcsec in the
sunspot to 18 arcsec in the quiet region. Brief descriptions of the data
reduction and calibration procedures are given. The absolute intensities
are determined with an accuracy of + or - 30 percent and the wavelength
scale is accurate to better than 0.01 A. The transition region lines
show the most extreme example known of downflowing gas above a sunspot,
a phenomenon which seems to be commonly connected to sunspots.
Title: The Solar UV Continuum 1440 - 1680 Å
Authors: Kjeldseth-Moe, O.; Brekke, P.; Bartoe, J. -D. F.; Brueckner,
G. E.
Bibcode: 1991BAAS...23.1060K
Altcode:
No abstract at ADS
Title: Dynamical Evidence of Fine Structure in the Solar Transition
Region
Authors: Brekke, P.; Kjeldseth-Moe, O.; Bartoe, J. -D. F.; Brueckner,
G. E.
Bibcode: 1991BAAS...23.1060B
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.
Bibcode: 1991AdSpR..11e.251B
Altcode: 1991AdSpR..11..251B
Observations with the High Resolution Telescope and Spectrograph (HRTS)
of the C IV lines at 1550 Å above sunspots reveal the co-existence
of several distinct high velocity gas components within the instrument
resolution element of 1 × 1 arc second. A further investigation of the
HRTS material demonstrates that such multiple gas velocities are not
restricted to the temperature region around 105 K, where the
C IV lines are formed, but that the gas flows with essentially unchanged
speed through all temperature layers from 2.5 × 105 K
to 104 K. Furthermore the phenomenon is not restricted to
sunspots, but occurs also in other solar regions, often most easily
distinguished in active regions. We describe the characteristics of the
velocity fields, analyze the mass fluxes and discuss the requirements
they place on the resolving power of future space instruments.
Title: Energetic high velocity events in the solar transition region
and corona.
Authors: Kjeldseth-Moe, O.; Cheng, Chung-Chieh
Bibcode: 1991cwlt.conf...55K
Altcode:
Energetic high velocity events in the corona and throughout the
transition region were observed with the slitless spectrograph SO82A
on Skylab in 1973 - 74. A further study is made of the properties of
energetic high velocity events in the upper transition region and corona
from the Skylab material. Comparing the observed characteristics the
authors suggest that the high velocity events in the corona are the
same phenomenon as the well studied explosive events mainly observed
in the C IV lines at 1550 Å.
Title: Ultraviolet limb darkening in the eclipsing binary AI
Phoenicis.
Authors: Stagg, C. R.; Milone, E. F.; Clark, T. A.; Kjeldseth Moe, O.
Bibcode: 1990JRASC..84R.423S
Altcode:
No abstract at ADS
Title: An Ultraviolet Spectral Atlas of a Prominence
Authors: Engvold, Oddbjorn; Hansteen, V.; Kjeldseth-Moe, O.; Brueckner,
G. E.
Bibcode: 1990Ap&SS.170..179E
Altcode:
The ultraviolet spectrum of a large prominence has been observed with
the High Resolution Telescope and Spectrograph (HRTS) on SPACELAB 2,
5 August, 1985. The spectrum covers the wavelength range λλ1335 1670
Å and shows numerous emission lines from gas at chromospheric and
transition region temperatures. An Atlas of the prominence spectrum
has been made showing absolute calibrated intensities on an accurate
wavelength scale. The Atlas includes for comparison the corresponding
UV-spectrum from an average quiet solar region.
Title: Multiple downflow velocities above sunspotss
Authors: Brekke, P.; Kjeldseth-Moe, O.; Brueckner, G. E.
Bibcode: 1990Ap&SS.170..135B
Altcode:
Supersonic transition zone downflow appears to be commonly occurring
above sunspots. The downflow has been observed in 29 emission lines
in the ultra-violet spectrum with the High Resolution Telescope and
Spectrograph (HRTS) on two rocket flights and on 5 consecutive days
during the Spacelab-2 mission. Spectra from the second rocket flight,
contain the most extreme example of downflow, showing speeds up to 180
km s-1 and extending over 60 are sec along the slit. The
observations demonstrate the existence of several different distinctive
flow speeds within the 1 arc sec resolution element throughout the
temperature range 7000 240 000 K.
Title: Mass Transport above Sunspots
Authors: Brynildsen, N.; Kjeldseth-Moe, O.; Brueckner, G. E.
Bibcode: 1990Ap&SS.170..149B
Altcode:
Mass transport in the transition zone above a sunspot has been
studied in the Civ line at 1548 Å, formed at 100 000 K. Four spectral
rasters have been used, each covering 60×50 are sec. These have been
observed with the High Resolution Telescope and Spectrograph during
the Spacelab-2 mission in 1985. Flow velocities are derived from
multiple Gaussian components fitted to the observed line intensity
profiles. Density sensitive lines were used to find a relation between
the Civ line intensity and the particle density. This relation is used
in the mass flux calculations. The investigation indicates a clear
net downward mass flux above sunspots.
Title: An Ultraviolet Spectral Atlas of a Sunspot and an Active
Region 1190-1730Å
Authors: Brekke, P.; Kjeldseth-Moe, O.; Bartoe, J. -D. F.; Brueckner,
G. E.
Bibcode: 1990BAAS...22..793B
Altcode:
No abstract at ADS
Title: The Prominence/corona Transition Region Analyzed from SL-2 HRTS
Authors: Engvold, O.; Hansteen, V.; Kjeldseth-Moe, O.; Brueckner, G. E.
Bibcode: 1990LNP...363..250E
Altcode: 1990IAUCo.117..250E; 1990doqp.coll..250E
The ultraviolet spectrum of a large prominence has been observed with
the High Resolution Telescope and Spectrograph (HRTS) on Spacelab 2
August 5, 1985. The spectrum covers the wavelength range 1335-1670Å and
shows numerous emission lines from gas at chromospheric and transition
region temperatures. A spectral atlas of these data is available. The
data reveals a variation with height of the line intensities. The
prominence becomes hotter with height. A value of ~ 0.12 dyn cm-2 for
the gas pressure in the prominence-corona transition region is obtained
from line ratios. The resolved fine structure of the He II 1640.400Å
line indicates that a major part of this emission comes from cold gas. A
broad Fe XI 1467.080Å suggests high velocities in the coronal cavity
region. The Fe XI line in the cavity region is a factor ~ 5 less bright
in the normal corona at the same height. Assuming that the temperature
is the same in the two regions the present obervations suggest that
the pressure in the cavity region is lower by a similar factor.
Title: Modelling of the prominence-corona transition region.
Authors: Engvold, O.; Kjeldseth-Moe, O.
Bibcode: 1990ppst.conf..165E
Altcode:
Empirical modeling of the PC transition region is based on
observed intensities of EUV and UV lines, and emission at radio
wavelengths. Analysis of EUV and UV lines in quiescent prominences
show that the transition region between prominences and corona is
very thin and in general similar to the Chromosphere-Corona (CC)
transition region. This review discusses observations, methods and
some recent results.
Title: Explosive events observed in the solar corona.
Authors: Kjeldseth-Moe, O.; Chieh Cheng, Chung
Bibcode: 1990ppst.conf...37K
Altcode:
Explosive events and high-velocity events in the transition region
around T ≍ 105K and in the corona are described and
compared.
Title: Observed Line Profiles and Mass Fluxes in the Transition
Region above Sunspots
Authors: Maltby, P.; Brekke, P.; Brynildsen, N.; Kjeldseth-Moe, O.;
Bartoe, J. -D. F.; Brueckner, G. E.
Bibcode: 1990PDHO....7..244M
Altcode: 1990dysu.conf..244M; 1990ESPM....6..244M
Spectrograms obtained with the HRTS show strong mass flows through
the transition zone that are particularly prominent above sunspot
regions. Most characteristic for the flow associated with sunspots
are regions with supersonic downflows, but upward flowing gas is
also observed with generally smaller velocities. The flow pattern
changes from one day to the next and even within a time span of
minutes. An apparent lack of balance between up- and downflowing
massfluxes is found. Generally the net massflux appears to be directed
downward. Possible reasons for this result are briefly discussed in
terms of observability and line emission area filling factor.
Title: Transition Region Massflows Associated with Sunspots
Authors: Kjeldseth-Moe, O.; Brekke, P.; Brynildsen, N.; Maltby, P.;
Brueckner, G. E.; Bartoe, J. -D. F.
Bibcode: 1989BAAS...21.1178K
Altcode:
No abstract at ADS
Title: "Explosive Events" at High Temperatures Observed in XUV
from Skylab
Authors: Cheng, C. -C.; Moe, O. K.
Bibcode: 1989BAAS...21..835C
Altcode:
No abstract at ADS
Title: Observational evidence for fine structure in the transition
region and corona.
Authors: Kjeldseth-Moe, O.
Bibcode: 1989ftsa.conf...77K
Altcode:
In this paper the expression fine structure means sub-resolution fine
structure, structures that are much smaller than the best angular
resolution of 1 - 2 arcseconds (or 1000 km) obtained by modern
UV-instruments. The argument for sub-resolution fine structure are
pursued along three observational lines.
Title: CDS: The Coronal Diagnostic Spectrometer
Authors: Patchett, B. E.; Harrison, R. A.; Sawyer, E. C.; Aschenbach,
B.; Culhane, J. L.; Doschek, G. A.; Gabriel, A. H.; Huber, M. C. E.;
Jordan, C.; Kjeldseth-Moe, O.
Bibcode: 1988sohi.rept...39P
Altcode:
The prime objective of the Coronal Diagnostic Spectrometer (CDS) is to
obtain intensity ratios of selected extreme-ultraviolet line pairs, with
spatial and temporal scales appropriate to the fine-scale features of
the solar atmosphere. This will be done simultaneously across a large
portion of the solar atmosphere. From this, density and temperature
information will be derived which coupled with a modest capability for
the detection of flows will be used to study the energy and mass balance
of the atmosphere. Understanding the heating of the solar corona and the
acceleration of the solar wind are the ultimate goals of this research.
Title: Gas Flows in the Transition Region above Sunspots
Authors: Kjeldseth-Moe, O.; Brynildsen, N.; Brekke, P.; Engvold, O.;
Maltby, P.; Bartoe, J. -D. F.; Brueckner, G. E.; Cook, J. W.; Dere,
K. P.; Socker, D. G.
Bibcode: 1988ApJ...334.1066K
Altcode:
Strong downflows and moderate upflows in the transition region over
a sunspot have been observed with the HRTS on Spacelab 2 in 1985. The
flows are persistent in the sense that they are seen in the same spot
for 5 days. The downflows are prominent in regions of limited extent
(4arcsec - 6arcsec), and flow velocities are in the range 40 - 80 km
s-1 and are thus supersonic. Upward flows have smaller
velocities, 5 - 20 km s-1, but may extend over a larger
area. In the downflowing regions there is always an appreciable amount
of gas at rest in the line of sight. Flow speeds derived from the
profiles of different lines formed in the transition region between
30,000 and 230,000K are very similar implying constant downflow in
this temperature range.
Title: Far-ultraviolet and X-ray emission of the long period RS CVn
star sigma Geminorum.
Authors: Engvold, O.; Ayres, T. R.; Elgaroy, O.; Jensen, E.; Joras,
P. B.; Kjeldseth-Moe, O.; Linsky, J. L.; Schnopper, H. W.; Westergaard,
N. J.
Bibcode: 1988A&A...192..234E
Altcode:
The new UV and X-ray observations of σ Gem support the theory that
large active regions associated with starspots are responsible for the
enhanced line emission commonly seen in RS CVn systems. The rotational
modulation of the UV line fluxes increases with temperature of the
line-forming region. The X-ray emission from the stellar corona, on the
other hand, shows only a barely detectable variation with rotational
phase. One may infer that the coronal active regions of the system
are not co-spatial with the activity in the transition region below,
and/or occupy a significantly larger surface area. An equally probable
explanation, however, is that the X-ray emission is emitted from huge,
stellar sized loops.
Title: Radiation losses in chromospheric and transition region
emission lines from AD Leo (dM4e)
Authors: Sundland, S. R.; Pettersen, B. R.; Hawley, S. L.;
Kjeldseth-Moe, O.; Andersen, B. N.
Bibcode: 1988ASSL..143...61S
Altcode: 1988acse.conf...61S
The authors present line surface fluxes from the red dwarf flare star
AD Leo in its quiescent state. IUE and ground-based instruments cover
the UV and optical (1000 - 9000 Å) domains of the spectrum. The
observed radiation losses from chromospheric and transition region
lines amount to 4.0×106erg cm-2s-1 and
2.7×105erg cm-2s-1, respectively. The
authors estimate the total radiative energy loss in all lines formed
between 25.000K and 250.000K to be of the order of 106 -
107erg cm-2s-1.
Title: Observasjonene av supernova 1987A.
Authors: Kjeldseth-Moe, O.
Bibcode: 1988ATi....21...60K
Altcode:
No abstract at ADS
Title: Supernova 1987A - the "star explosion" of the century.
Authors: Kjeldseth-Moe, O.
Bibcode: 1988FFV....50...38K
Altcode:
No abstract at ADS
Title: Ultraviolet Rocket-Spectra of a Sunspot
Authors: Brekke, P.; Kjeldseth-Moe, O.; Bartoe, J. -D. F.; Brueckner,
G. E.
Bibcode: 1987ESASP.270..341B
Altcode: 1987erbp.symp..341B
Downflows in the transition zone above a sunspot were observed with
a high resolution telescope and spectrograph on a rocket. The rocket
spectra on photographic film were digitized. Noise caused by film grains
was removed by Fourier filtering. The spectral images were corrected
for geometrical distortions and calibrated to give the solar intensity
as a function of wavelength. Maximum speeds of 200 km/sec are reached
in the flows which extend over 60 arc-sec along the slit. Components
with distinct, but lower velocities also appear. The variations with
temperature of the characteristic flow speeds are studied.
Title: Observations and modelling of the prominence/corona transition
region.
Authors: Engvold, O.; Kjeldseth-Moe, O.; Bartoe, J. -D. F.; Brueckner,
G. E.
Bibcode: 1987ESASP.275...21E
Altcode: 1987sspp.symp...21E
The construction of inhomogeneous temperature transition region
models for solar prominences is considered. Models based on UV line
intensities from SO82B on Apollo Telescope Mount (ATM)/Skylab and the
High Resolution Telescope and Spectrograph (HRTS) on Spacelab 2 are
derived. The modeled structures of the transition region are in the
form of thin tubes, similar to the prominence structures seen in the
cool core. An expression for the thickness of the transition region
around prominences is given, and mechanisms for energy transport are
discussed. Uncertainties and possible improvements in the modeling
are pointed out.
Title: Gasflows in the transition region above sunspots.
Authors: Kjeldseth-Moe, O.; Brynildsen, N.; Brekke, P.; Bartoe,
J. -D. F.; Brueckner, G. E.
Bibcode: 1987ESASP.275...27K
Altcode: 1987sspp.symp...27K
Gas flows in the transition region in and above sunspots were observed
with the High Resolution Telescope and Spectrograph on two rocket
flights and during the Spacelab 2 mission. Supersonic downflows of
mass from the corona appear to be generally occurring in sunspots. The
downflows are often concentrated in regions with typical diameters of
4000 km on the Sun, suggesting a flow in a looplike structure. However,
the total flow pattern often has an elongated sheetlike structure
of much larger extent. Flow speeds are typically 80 km/sec and show
small variation with the temperature of the radiating gas. Much higher
flow-speeds (180 km/sec) also occur. Studies of the areas surrounding
the sunspot in the Spacelab material reveal the presence of upflows over
extended regions with flow-speeds of 10 to 30 km/sec. It is not clear
whether the amount of upward flowing gas is sufficient to compensate
for the mass flux in the downflows.
Title: Hot Wind in the Double Degenerate System Am-Canum
Authors: Solheim, J. -E.; Kjeldseth-Moe, O.
Bibcode: 1987Ap&SS.131..785S
Altcode: 1987IAUCo..93..785S
The close binary system Am CVn consists of two helium white dwarf stars
in close orbit. Strong flickering in the optical light curve and the
observed spin-up in the rotation period indicate that mass transfer
takes place (Solheim et al., 1984). The optical spectrum shows broad
helium absorption lines (Robinson and Faulkner, 1975) sometimes partly
filled in by emission (Voikhanskaya, 1982). The optical spectrum
shows no sign of hydrogen, and the line profiles are interpreted
as due to an accretion disk of intermediate angle of inclination
with a temperature of the order of 20.000 K (Robinson and Faulkner,
1975). Another possibility is direct accretion onto a magnetized BD
white dwarf (Voikhanskaya, 1982). In the latter case a magnetic field
B≃106 to 109 gauss is needed. Voikhanskaya
also reports significant changes in the absorption line profiles from
1978 to 1980.
Title: Transition Zone Flows in Sunspots
Authors: Kjeldseth-Moe, O.; Brynildsen, N.; Engvold, O.; Maltby, P.;
Bartoe, J. -D. F.; Brueckner, G. E.
Bibcode: 1987rfsm.conf..317K
Altcode:
Downflow in the transition region over sunspots first detected on HRTS
rocket flights, seems to be a general phenomenon. Although details
in the flow pattern appear to change over a period of minutes, the
phenomenon itself persists for days. While the mechanism producing the
observed redshifts is not understood it seems most likely that they are
produced by actual downflow of gas in thin filamentary structures. This
may be inferred from the co-existence within the same spatial resolution
element of tubes with strong downflows and tubes where the gas is at
rest. Thus the line profiles result from an unresolved fine structure
in a similar fashion that Evershed effect in the photosphere produces
"flag"-like line profiles in visual lines.
Title: The unusual rotational modulation of the UV radiation from
the spotted flare star EV Lac
Authors: Andersen, B. N.; Kjeldseth-Moe, O.; Pettersen, B. R.
Bibcode: 1986ESASP.263...87A
Altcode: 1986NIA86.......87A; 1986niia.conf...87A
The UV line spectrum of the spotted flare star EV Lac in its quiescent
state was observed with IUE. The observed rotational modulation
of chromospheric UV lines is in antiphase with the photospheric
variations in visual light. The visual variation is due to a starspot
region located near the pole of the star. The transition region lines
(80,000 K less than T less than 200,000 K) show no variation. This may
indicate a large extent in altitude of the transition region causing
the emitting regions to be visible throughout the rotation.
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.
Bibcode: 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.
Bibcode: 1985tphr.conf...98K
Altcode:
No abstract at ADS
Title: Excitation mechanisms in the atmospheres of yellow and red
giant and supergiant stars.
Authors: Engvold, O.; Kjeldseth Moe, O.; Jensen, E.; Joras, P.
Bibcode: 1985ESA7..R....151E
Altcode:
No abstract at ADS
Title: Excitation mechanisms in the atmospheres of yellow and red
giant and supergiant stars
Authors: Engvold, O.; Moe, O. K.; Jensen, E.; Joraas, P.
Bibcode: 1985ESASP.229..151E
Altcode: 1985erbp.symp..151E
Far ultraviolet emission line spectra of 16 cool giant and supergiant
stars have been obtained with the IUE satellite of ESA, NASA and
UK. The bright emission lines in the spectra of these stars are
produced primarily through radiative excitation. The formation of
chromospheric lines of O I and S I are discussed. The spectra of
stars with Teff ≥ 4300K contain emission lines formed at
temperatures of 8×104K and 105K which implies
that these stars must have transition regions and hot coronas.
Title: Towards a multi-component semi-empirical model for the solar
photosphere.
Authors: Kjeldseth-Moe, O.; Andreassen, T.; Maltby, P.
Bibcode: 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.
Bibcode: 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: A progress report on the analysis of long exposure SWP high
resolution spectra of cool stars.
Authors: Linsky, J. L.; Ayres, T. R.; Brown, A.; Carpenter, K.;
Jordan, C.; Judge, P.; Gustafsson, B.; Eriksson, K.; Saxner, M.;
Engvold, O.; Jensen, E.; Moe, O. K.; Simon, T.
Bibcode: 1984NASCP2349..445L
Altcode: 1984fiue.rept..445L; 1984IUE84......445L
The IUE is the first experiment with sufficient sensitivity to obtain
high resolution spectra (lambda/delta lambda is approximately 10,000)
of many cool stars in the vitally important 1200 to 2000 A spectral
region. These data provide qualitatively new information with
which to understand the properties of and structures in the outer
atmospheres of these stars. Also, these cool star spectra will be
extremely useful in planning for the Space Telescope High Resolution
Spectrograph, which will be 1000 times more sensitive than IUE but will
be hampered by limited observing time and limited spectral bandwidth
in each exposure. Very long exposure, high disperson SWP spectra of
many stars located throughout the cool half of the HR diagram were
obtained. These 12 to 21 hour exposures were obtained by combining
NASA and Vilspa shifts so as to obtain the longest possible exposures
at times of low background. Included are dwarf stars of spectral type
G0 V to M2 V, G9.5 III to M5 II giants, G2 Ib to M2 Iab supergiants,
a number of RS CVn-type systems, and Barium stars.
Title: Atmospheric Inhomogeneities in Late Type Dwarf Stars
Authors: Moe, O. K.
Bibcode: 1984iue..prop.1997M
Altcode:
No abstract at ADS
Title: Preliminary Results from Studies of High Resolution Line
Spectra in Late-type Giant and Supergiant Stars
Authors: Engvold, O.; Kjeldseth Moe, O.; Jensen, E.; Jordan, C.;
Stencel, R.; Linsky, J.
Bibcode: 1984LNP...193..359E
Altcode: 1984csss....3..359E
No abstract at ADS
Title: Solar Cycle Temperature Variations in Sunspots
Authors: Maltby, P.; Albregtsen, F.; Moe, O. Kjeldseth; Kurucz, R.;
Avrett, E.
Bibcode: 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: Romteleskopet. Eit framtidig hovudinstrument i astronomisk
forsking.
Authors: Kjeldseth Moe, O.
Bibcode: 1984ATi....17..101K
Altcode:
No abstract at ADS
Title: Gammastråle-astronomi - en ny videnskap.
Authors: Kjeldseth Moe, O.
Bibcode: 1984ATi....17...63K
Altcode:
No abstract at ADS
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.
Bibcode: 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: Fe II fluorescence in the atmospheres of late type giants
and supergiant stars.
Authors: Engvold, O.; Jensen, E.; Kjeldseth Moe, O.
Bibcode: 1983ITABO..59...65E
Altcode:
The Fe II triplet lines λλ1785 - 88 Å of UV multiplet 191 are
present in high resolution spectra of α Ori (M2 I ab) and β Gru
(M3 II) observed with IUE. The middle component of the triplet system
is missing in the spectra of giant stars of spectral types K1 -
K5. The line flux of the Fe II triplet increases strongly with the
stellar Teff. The Fe II lines are most probably formed
by fluorescence with the UV radiation field of the stars at λ <
1300 Å.
Title: UV Observations of Inhomogeneous Red Dwarfs Atmospheres
Authors: Moe, O. K.
Bibcode: 1983iue..prop.1608M
Altcode:
No abstract at ADS
Title: Space observations in astronomy.
Authors: Kjeldseth Moe, O.
Bibcode: 1983ITABO..59..103K
Altcode:
No abstract at ADS
Title: Astronomy from Space - Past and Future
Authors: Kjeldseth-Moe, O.
Bibcode: 1983itab.rept....1K
Altcode:
No abstract at ADS
Title: Astronomy from space - past and future.
Authors: Kjeldseth Moe, O.
Bibcode: 1983ITABO..58.....K
Altcode:
No abstract at ADS
Title: Physical conditions in the chromosphere of α Ori.
Authors: Kjeldseth Moe, O.; Engvold, O.; Jensen, E.
Bibcode: 1983ITABO..59...59K
Altcode:
No abstract at ADS
Title: High Resolution Extreme Ultraviolet Structure of the
Chromosphere Corona Transition Region above a Sunspot
Authors: Nicolas, K. R.; Bartoe, J. -D. F.; Brueckner, G. E.;
Kjeldseth-Moe, O.
Bibcode: 1982SoPh...81..253N
Altcode:
Ion emission line intensities between 1170 and 1700 Å allow one
to determine the differential emission measure (DEM) and electron
pressure of the plasma in the solar transition region (TR). These
line intensities together with their Doppler shifts and line widths
are measured simultaneously for the first time above a sunsport from
data obtained with the NRL High Resolution Telescope and Spectrograph
with 0.06 Å spectral and 1″ spatial resolution.
Title: A High Resolution EUV Spectrum of α Ori
Authors: Engvold, O.; Kjeldseth Moe, O.; Jensen, E.; Linsky, J. L.;
Stencel, R. E.
Bibcode: 1982BAAS...14..651E
Altcode:
No abstract at ADS
Title: Gas Flow in the Chromosphere of α Ori
Authors: Kjeldseth Moe, O.; Engvold, O.; Jensen, E.; Linsky, J. L.;
Stencel, R. E.
Bibcode: 1982BAAS...14..651K
Altcode:
No abstract at ADS
Title: Quiet Sun observations of the Al i autoionization lines λ1932
and λ1936
Authors: Cook, J. W.; Kjeldseth Moe, O.
Bibcode: 1982SoPh...76..109C
Altcode:
We present quiet Sun observations obtained during a rocket flight of
the Al I autoionization lines λ1932 and λ1936 at solar pointings
ranging from μ = 0.73 out to the visible limb. Absolute intensities
are estimated to be accurate to approximately ±20%. These lines
progressively weaken with decreasing μ but never go into emission
before finally disappearing with the continuum just beyond the
visible solar limb. The observations are compared with LTE line
profiles computed through the quiet Sun atmosphere of Vernazza et
al. (1976). We discuss several areas of disagreement between the
synthetic and observed profiles.
Title: UV Centre-To-Limb Variations in Solar Type Bright Eclipsing
Binaries
Authors: Moe, O. K.
Bibcode: 1982iue..prop.1350M
Altcode:
No abstract at ADS
Title: Optical Observations of the Primary Minimum of the Solar-Type
Binary AI Phe with the IUE Satellite
Authors: Milone, E. F.; Hrivnak, B. J.; Clark, T. A.; Kjeldseth Moe,
O.; Blades, J. C.; Shelton, I.
Bibcode: 1981IBVS.2060....1M
Altcode:
No abstract at ADS
Title: The chromospheric evershed flow observed in the EUV spectrum
Authors: Nicolas, K. R.; Kjeldseth-Moe, O.
Bibcode: 1981phss.conf..336N
Altcode:
The spectral data analyzed here are from the high-resolution telescope
and spectrograph (HRTS) rocket flight described by Nicolas et al. (1981,
1982). In addition to the Doppler shifts found earlier in the ionized
emission lines emitted from the transition region (TR), systematic
large-scale (extending over 20 arcsec) shifts are found in the sharp
neutral emission lines emitted from chromospheric plasma. The zero
point is defined by averaging the shifts in quiet regions to either
side of the active region. The wavelength scale determined from the
neutral lines is transferred to the ionized lines by the method outlined
in Nicolas et al. The subsequent velocity error for the ionized line
shifts is approximately + or - 3 km/s. For quiet regions, the velocity
correlation coefficient between neutral lines and TR lines formed
above 50,000 K is found to be quite small along most of the slit. It
is believed that this is probably caused by the superposition of both
the flow and oscillation velocities in any given line of sight.
Title: The EUV fine structure of the chromosphere-corona transition
zone above a sunspot.
Authors: Nicolas, K. R.; Kjeldseth Moe, O.; Bartoe, J. -D. F.;
Brueckner, G. E.
Bibcode: 1981BAAS...13..491N
Altcode:
No abstract at ADS
Title: Evidence That HeII 1640 Å Is Not A Transition Region Line
In The Sun
Authors: Schindler, M.; Kjeldseth Moe, O.; Bartoe, J. D. F.; Breuckner,
G. E.; Vanhoosier, M. E.
Bibcode: 1980BAAS...12..916S
Altcode:
No abstract at ADS
Title: EUV observations of quiescent prominences from Skylab.
Authors: Moe, O. K.; Cook, J. W.; Mango, S. A.
Bibcode: 1979SoPh...61..319M
Altcode:
We report measurements of line intensities and line widths for three
quiescent prominences observed with the Naval Research Laboratory slit
spectrograph on ATM/Skylab. The wavelengths of the observed lines
cover the range 1175 Å to 1960 Å. The measured intensities have
been calibrated to within approximately a factor 2 and are average
intensities over a 2 arc sec by 60 arc sec slit. We derive nonthermal
velocities from the measured line widths. The nonthermal velocity
is found to increase with temperature in the prominence transition
zone. Electron densities and pressures are derived from density
sensitive line ratios. Electron pressures for two of the prominences are
found to lie in the range 0.04-0.08 dyn cm−2, while values
for the third and most intense and active of the three prominences
are in the range 0.07-0.22 dyn cm−2.
Title: Emission Measure Analysis of the Solar Transition Region from
20,000 to 200,000 K
Authors: Nicolas, K. R.; Kjeldseth Moe, O.
Bibcode: 1979BAAS...11..420N
Altcode:
No abstract at ADS
Title: Limb darkening 1945 - 3245 Å for the quiet sun from Skylab
data.
Authors: Moe, O. K.; Milone, E. F.
Bibcode: 1978ApJ...226..301M
Altcode: 1978ApJ...226..301K
Limb-darkening measurements of the quiet sun in the spectral range
1945-3245 A have been made using NRL's SO82B instrument on board
Skylab. The spectral intensities have been averaged over 10 A wavelength
bands, and coefficients for linear, quadratic, and logarithmic fits
to the observed center-to-limb variations have been calculated and
tabulated as a function of wavelength. The quadratic fits are found to
represent the observations best, the observed and calculated values
agreeing to better than plus or minus 15% on the average. Attention
is drawn to the value of the results for ultraviolet photometry of
eclipsing binaries.
Title: The EUV continuum emission (1400 1960 Å) in a solar flare
observed from Skylab
Authors: Cheng, C. -C.; Kjeldseth Moe, O.
Bibcode: 1978SoPh...59..361C
Altcode:
The total radiative output in the EUV continuum (1400-1960 Å) from the
5 September 1973 flare has been obtained from the EUV spectra of the
flare observed with the NRL slit spectrograph (SO82B) on Skylab. The
radiative energy in the EUV continuum is of the order of 1029
ergs, which is more than a factor of 2 greater than those radiated in
soft X-rays (8-20 Å) and in Hα for the flare. Thus, the EUV continuum
emission is an important radiative energy loss, and should be included
in the consideration of the energy balance of the flare.
Title: Emission measures and structure of the transition region of
a sunspot from emission lines in the far ultraviolet.
Authors: Cheng, C. -C.; Kjeldseth Moe, O.
Bibcode: 1977SoPh...52..327C
Altcode:
Absolute intensities of emission lines in the wavelength range from
1200 Å to 1817 Å from the large sunspot in McMath region 12510 near
Sun center are presented. The intensities are averaged across the
umbra and penumbra of the sunspot. The observations were made with the
NRL slit spectrograph on Skylab. Emission measures are derived from
the measured intensities. Assuming a balance between the divergence
of the conductive energy flux and the radiative energy losses, a
self-consistent model of the lower transition region in the sunspot
is constructed. The model gives a constant pressure of about 0.19 dyne
cm-2, and a conductive flux which decreases approximately one
order of magnitude between 2 × 105 K and 4 × 104
K. The temperature gradient is relatively constant, increasing slowly
with decreasing temperature.
Title: Emission measures, electron densities, and nonthermal
velocities from optically thin UV lines near a quiet solar limb.
Authors: Kjeldseth Moe, O.; Nicolas, K. R.
Bibcode: 1977ApJ...211..579K
Altcode: 1977ApJ...211..579M
Calibrated intensities and line widths are presented for 45 optically
thin chromospheric and transition-zone UV lines observed in a quiet area
near the solar limb. The observations were made over the wavelength
range from 1175 to 1915 A with the slit spectrograph on the Skylab
Apollo Telescope Mount. Three nonthermal-velocity components are derived
from the transition-zone line widths: a main component of 23 km/s and
two high-velocity components of 45 and 75 km/s, respectively, which
contribute 5% to 10% of the averaged intensity. Absolute intensities are
determined as a function of height, emission measures are obtained as
functions of height as well as temperature, and electron densities are
estimated from density-sensitive line ratios. The densities estimated
from different sets of lines are found not to agree with each other,
but the values obtained from the Si III multiplet between 1297 and
1301 A are considered to be the most reliable. An atmospheric model
with inhomogeneous structures extending high above the solar surface
is suggested.
Title: Absolute solar ultraviolet intensities and their variations
with solar activity. I. The wavelength region 1750 - 2100 Å.
Authors: Brueckner, G. E.; Bartoe, J. -D. F.; Moe, O. K.; Vanhoosier,
M. E.
Bibcode: 1976ApJ...209..935B
Altcode:
Absolute-calibrated high-resolution ultraviolet spectra from 1750
to 2100 A of the quiet Sun and a plage are presented. From these
spectra, the intensity at the center of the disk, the average disk
intensities, and the solar flux at 1 AU are derived. A comparison
with other measurements shows that in this wavelength region most of
the solar intensity measurements fall within an error limit of 120
percent. The variability of the solar flux in the band 1750-2050 A
caused by active regions is estimated. A change of the sunspot number
from 0 to 120 causes an approximate flux variation of 3 percent. The
blackbody radiation temperature of a plage averaged over 2 x 60 arcsec
in this wavelength region is 200 K higher than that of the quiet
Sun. Subject headings: Sun: activity - Sun: plages - Sun: spectra -
ultraviolet: spectra
Title: Center to Limb Variation of the Al I Autoionization Lines at
1934 A.
Authors: Moe, O. K.
Bibcode: 1976BAAS....8..501M
Altcode:
No abstract at ADS
Title: The profile of the solar Lyman β line of hydrogen
Authors: Nicolas, K. R.; Moe, O. K.; Bartoe, J. -D. F.; Tousey, R.
Bibcode: 1976JGR....81.3465N
Altcode:
The solar profile of hydrogen Ly β has been photographed by the Naval
Research Laboratory slit spectrograph on Skylab. The line profile has
a shape that is similar to the profile recorded in 1962 by Tousey et
al. (1964).
Title: Time Dependent Ionization and Radiation of a Gas Moving
through the Solar Transition Zone
Authors: Moe, O. K.
Bibcode: 1976BAAS....8..331M
Altcode:
No abstract at ADS
Title: Spectrophotometry of the Photospheric and Chromospheric
Granulation in the UV Region 1240-1650Å
Authors: Bartoe, J. -D. F.; Brueckner, G. E.; Moe, O. K.; Nicolas,
K. R.; Vanhoosier, M. E.
Bibcode: 1976BAAS....8..312B
Altcode:
No abstract at ADS
Title: The Model Compared with Observations
Authors: Nier, A. O.; Moe, O. K.; Reber, C. A.
Bibcode: 1976NASSP.398...39N
Altcode:
No abstract at ADS
Title: Response of the magnetosphere and atmosphere to the solar wind
Authors: Olson, W. P.; Pfitzer, K. A.; Moe, O. K.
Bibcode: 1975mdss.rept.....O
Altcode:
The general goal of this contract was to obtain a better quantitative
understanding of the interaction of the solar wind with the
magnetosphere and atmosphere. Several scientific goals were formulated
and met. They included the fabrication of quantitative models of
the shape and location of the dayside cusps, the total magnetospheric
magnetic field, and of total neutral atmospheric density. These models,
together with others developed or under developement with other DoD
support, should provide a first set of software capable of being used
to specify environmental behavior, with emphasis being given to those
aspects which influence the performance of hardware systems.
Title: Line profiles and magnetic intensification in magnetic stars.
Authors: Havnes, O.; Moe, O. K.
Bibcode: 1975A&A....42..269H
Altcode:
Summary. Line profiles with Zeeman analyzer and without has been
computed for a 8000 0K magnetic star using the theory of Unno
(t956). Different orientations of the star and its magnetic
field and different values of the magnetic field strengths have
been considered. For a weak Fe 4260 line we find that magnetic
intensification can introduce errors of about 0.25 dex in abundance. The
variable magnetic field as a magnetic Ap star rotates can produce
variations in the apparent equi valent width of a few times ten percent
in a star of homogeneous atmospheric composition. The effect of the
magnetic field on the line profiles is large and we find it unlikely
that reliable values for micro and macroturbulence can be found by
conventional non-magnetic analysis. Key words: magnetic stars magnetic
intensification line profiles in magnetic stars
Title: Measured Variation of the XUV Line Widths and Intensities
Near the Solar Limb
Authors: Moe, O. K.; Nicolas, K. R.
Bibcode: 1975BAAS....7R.460M
Altcode:
No abstract at ADS
Title: Line Profiles of the Fe XXIV Emission at 192 Å and 255 Å
in Solar Flares
Authors: Brueckner, G. E.; Moe, O. K.; van Hoosier, M. E.
Bibcode: 1975BAAS....7..357B
Altcode:
No abstract at ADS
Title: The High-Energy Limb Event of January 17, 1974
Authors: Tousey, R.; Bohlin, J. D.; Moe, O. K.; Purcell, J. D.;
Sheeley, N. R.
Bibcode: 1975BAAS....7..348T
Altcode:
No abstract at ADS
Title: Absolute Solar UV Intensities 1680 Å to 2100 Å
Authors: Kjeldseth Moe, O.; Brueckner, G. E.; Bartoe, J. D. F.;
van Hoosier, M. E.
Bibcode: 1975BAAS....7Q.360K
Altcode:
No abstract at ADS
Title: Absolute solar UV intensities 1680 Å to 2100 Å.
Authors: Moe, O. K.; Brueckner, G. E.; Bartoe, J. -D. F.; van Hoosier,
M. E.
Bibcode: 1975BAAS....7..360M
Altcode:
No abstract at ADS
Title: A Comparison of Spicules in the Hα and He II (304 Å) Lines
Authors: Kjeldseth Moe, O.; Engvold, Olav Oddbjorn; Beckers, Jacques
Maurice
Bibcode: 1975SoPh...40...65K
Altcode: 1975SoPh...40...65M
On 1974 January 29 and 31, simultaneous satellite observations of
spicule-like features in the 304-A L-alpha line of He(+) and ground
observations of H-alpha spicules were obtained. It was then attempted to
find a correlation between features of these two observations. Direct
visual comparison failed to show a significant correspondence between
the spicules in the He II and H-alpha spicules. Then the location and
orientation of spicules in both images were measured and a correlation
criterion was defined. Again no significant correspondence was found. It
is concluded that the spicule-like structures in the He II (304) line
are quite different from the H-alpha spicules. The possibility remains,
though, that spicules are the same structures in both lines but that
some spicules emit more strongly in He II (304) whereas others are
better visible in H-alpha.
Title: A comparison of spicules in the Hα and HeII (304 Å) lines
Authors: Moe, Olav Kjeldseth; Engvold, Oddbjorn; Beckers, Jacques
Maurice
Bibcode: 1975SoPh...40...65M
Altcode:
No abstract at ADS
Title: Absolute Solar Intensities 1750 AÅ - 2100 AÅ and Their
Variations with Solar Activity
Authors: Brueckner, G. E.; Bartoe, J. -D. F.; Moe, O. K.; van Hoosier,
M. E.
Bibcode: 1975scea.conf...71B
Altcode:
No abstract at ADS
Title: The Temperature of Penumbral Filaments
Authors: Kjeldseth Moe, O.; Maltby, P.
Bibcode: 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.
Bibcode: 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: The 1175 Å to 1900 Å Ultraviolet Spectrum of Solar Flares
Authors: Brueckner, G. E.; Bohlin, J. D.; Moe, O. K.; Nicolas, K. R.;
Purcell, J. D.; Scherrer, V. E.; Sheeley, N. R., Jr.; Tousey, R.
Bibcode: 1974BAAS....6..285B
Altcode:
No abstract at ADS
Title: Absolute calibrated solar UV intensities 1700 to 2100 Å.
Authors: Moe, O. K.
Bibcode: 1974JOSA...64.1375M
Altcode:
No abstract at ADS
Title: The Influence of Molecular Blends and Non-Thermal Line
Broadening on the Profile of the Zeeman Triplet λ5250.22 in Sunspots
Authors: Moe, Olav Kjeldseth
Bibcode: 1973SoPh...33..393M
Altcode:
Calculations of the umbral profile of the Zeeman triplet λ5250.22
are presented. We have taken into account the effect of a molecular
blend from TiO at λ5250.24 causing an apparent π-component even for
longitudinal magnetic fields. Also included is the depression of the
spot continuum due to line wings and veiled weak lines in the umbra
spectrum. The effect of different amounts of non-thermal broadening
is investigated.
Title: High angular resolution absolute intensity of the solar
continuum from 1400 Å to 1790 Å.
Authors: Brueckner, G. E.; Moe, O. K.
Bibcode: 1972spre.conf.1595B
Altcode: 1972spre....2.1595B
No abstract at ADS
Title: Absolute intensity of the continuum in the ultraviolet spectrum
of the sun between 1650 - 1800 Å.
Authors: Brueckner, G.; Moe, O.; Pitz, E.
Bibcode: 1971BAAS....3..260B
Altcode:
No abstract at ADS
Title: The Solar Lithium Abundance
Authors: Engold, O.; Kjeldseth Moe, O.; Maltby, P.
Bibcode: 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: Profile and polarization of the Zeeman triplet 5250.22 Å.
Authors: Moe, O. K.; Brueckner, G. E.; Hagyard, M. J.
Bibcode: 1970BAAS....2..331M
Altcode:
No abstract at ADS
Title: Profile and Polarization of the Zeeman Triplet 5250.22 Å
Authors: Kjeldseth Moe, Olav; Brueckner, Guenter E.; Hagyard, Mona J.
Bibcode: 1970BAAS....2..331K
Altcode:
No abstract at ADS
Title: A Model for the Penumbra of Sunspots
Authors: Kjeldseth Moe, O.; Maltby, P.
Bibcode: 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: A Model for the Penumbra of Sunspots
Authors: Maltby, P.; Kjeldseth Moe, O.
Bibcode: 1969BAAS....1..285M
Altcode:
No abstract at ADS
Title: A Generalized Theory for Line Formation in a Homogeneous
Magnetic Field
Authors: Moe, Olav Kjeldseth
Bibcode: 1968SoPh....4..267M
Altcode:
The formation of spectral lines in a homogeneous magnetic field
has been studied. A new method for solving the transfer equations
for polarized light has been found. Using this method, the Stokes
parameters may be derived without any special assumptions regarding
the model atmosphere. With the line formed by pure absorption,
the expressions for the Stokes parameters may easily be adapted to
numerical calculations. In order to illustrate the method, the line
profile for the Zeeman triplet λ 5250 has been calculated using a
photospheric model atmosphere.
Title: On the Magnetic-Field Configuration in Sunspots
Authors: Kjeldseth Moe, O.
Bibcode: 1968IAUS...35..202K
Altcode:
No abstract at ADS
Title: Effect of Saturation on Zeeman Triplets
Authors: Kjeldseth Moe, O.; Maltby, P.
Bibcode: 1968ApL.....1..189K
Altcode:
No abstract at ADS
Title: A Generalized Theory for Line Formation in a Homogeneous
Magnetic Field.
Authors: Moe, Olav Kjeldseth
Bibcode: 1968AJS....73T..72M
Altcode:
The equations of transfer for a Zeeman triplet in a magnetic field have
been developed by Unno (Publ. Astron. Soc. Japan 8,108,1956). Unno gives
three simultaneous differential equations for the Stokes parameters I,
Q and V. We have developed a method for transforming Unno's transfer
equations into a system of linear differential equations analogous to
the transfer equation for the intensity in the field-free case. Using
this method it is possible to calculate the line profile and state of
polarization for a spectral line formed in a homogeneous magnetic field
without using the assumption of a Milne-Eddington model atmosphere.
Title: Instrumental polarization in the solar tower telescope at
Oslo Solar Observatory.
Authors: Moe, Olav Kjeldseth
Bibcode: 1968ipst.book.....M
Altcode: 1968QB461.O8n27....
No abstract at ADS