Author name code: maltby ADS astronomy entries on 2022-09-14 author:"Maltby, Per" ------------------------------------------------------------------------ Title: Dual Flows with Supersonic Velocities in the Sunspot Transition Region Authors: Brynildsen, N.; Maltby, P.; Kjeldseth-Moe, O.; Wilhelm, K. Bibcode: 2004ApJ...612.1193B Altcode: Observations of sunspot transition region lines that deviate significantly from a Gaussian shape are presented. Attention is given to ``dual flows,'' a line profile phenomenon in which two distinct velocities are observed within the same spatial resolution element. In 5 out of 12 sunspots we observe dual flows. Several emission line profiles are well represented by two Gaussian line components, one with a subsonic and one with a supersonic line-of-sight velocity. Title: Oscillations in the Umbral Atmosphere Authors: Brynildsen, N.; Maltby, P.; Foley, C. R.; Fredvik, T.; Kjeldseth-Moe, O. Bibcode: 2004SoPh..221..237B Altcode: The results of simultaneous observations of oscillations in the chromosphere, transition region, and corona above nine sunspots are presented. The data are obtained through coordinated observing with the Solar and Heliospheric Observatory — SOHO and the Transition Region And Coronal Explorer — TRACE. Oscillations are detected above each umbra. The power spectra show one dominant frequency corresponding to a period close to 3 min. We show that the oscillations in the sunspot transition region can be modeled by upwardly propagating acoustic waves. In the corona the oscillations are limited to small regions that often coincide with the endpoints of sunspot coronal loops. Spectral observations show that oscillations in the corona contribute to the observed oscillations in the TRACE 171 Å channel observations. We show that a recent suggestion regarding a connection between sunspot plumes and 3-min oscillations conflicts with the observations. Title: Oscillations Above the Umbra of Sunspots Authors: Brynildsen, N.; Maltby, P.; Fredvik, T.; Kjeldseth-Moe, O. Bibcode: 2004ESASP.547...45B Altcode: 2004soho...13...45B Oscillations above thirteen sunspots are investigated with the Coronal Diagnostic Spectrometer (CDS) and the Transition Region And Coronal Explorer (TRACE). The CDS observations give knowledge about the oscillations in the chromosphere, transition region, and corona and information regarding the contributions of different emission lines to the TRACE 171 Å and 195 Å channel intensities. A period close to 3 min is observed above the umbra of each sunspot. The observations give support to the idea that the 3 min oscillations are caused by upwardly propagating acoustic waves. This is evident from the asymmetry of the oscillation amplitudes in the red and blue wings of the emission lines, where the oscillations are decidedly more pronounced in the blue than in the red line wing. Additional support for the acoustic wave hypothesis emerges from the agreement between the observed and predicted relations in phase and magnitude between the oscillations in intensity and line-ofsight velocity. The frequency of the oscillations is above the acoustic cutoff frequency in the umbral atmosphere and the observed phase differences between lines emitting at different temperatures point to an upwardly propagating disturbance. Title: Search for a chromospheric resonator above sunspots Authors: Brynildsen, N.; Maltby, P.; Brekke, P.; Redvik, T.; Kjeldseth-Moe, O. Bibcode: 2003AdSpR..32.1097B Altcode: We have recently observed thirteen sunspots, both with CDS on SOHO and TRACE. For each sunspot we investigate the oscillations in the chromosphere, transition region and corona. Above the umbra the power spectra show one dominant peak corresponding to a period of 3 minutes. The intensity oscillation amplitude increases with increasing temperature, reaches a maximum for lines emitting close to 1-2 × 10 5 K, and decreases for higher temperatures. Part of the wave energy penetrates into the corona, channeled into small areas that appear to coincide with the endpoints of sunspot coronal loops. The observations support the hypothesis that the oscillations are caused by upwardly propagating acoustic waves and show no signs of the resonances, equally spaced ≈1 mHz in frequency, predicted by the chromospheric resonator theories. Title: Sunspot Oscillations and Acoustic Wave Propagation Authors: Brekke, P.; Brynildsen, N.; Maltby, P.; Fredvik, T.; Kjeldseth-Moe, O. Bibcode: 2003SPD....34.0401B Altcode: 2003BAAS...35..810B Observations with the Coronal Diagnostic Spectrometer of 3 min oscillations in sunspot umbrae support the hypothesis that they are caused by upwardly propagating acoustic waves. This is evident from the asymmetry of oscillation amplitudes in the red and blue wings of spectral lines, where the oscillations are decidedly more pronounced in the blue than in the red line wing. Additional evidence include the fact that the relation between oscillations in intensity and velocity agree with that predicted for an acoustic wave with regard to phase as well as magnitude. Finally, the observed phase difference between lines formed at different temperatures points to an upward propagating disturbance, and the value of dominant frequency of the oscillations, close to 6 mHz, is above the acoustic cutoff frequency in the sunspot atmosphere. SOHO is a mission of international cooperation between ESA and NASA. This study was supported by the Research Council of Norway. Title: Oscillations in the wings of sunspot transition region lines Authors: Brynildsen, N.; Maltby, P.; Kjeldseth-Moe, O.; Wilhelm, K. Bibcode: 2003A&A...398L..15B Altcode: We explore a new approach to the investigation of optically thin emission lines by comparing the intensity variations in opposite wings of the spectral lines and apply the method to investigate the oscillations above sunspots. The observations show that it is easier to detect the 3 min oscillations above sunspots in the short wavelength (``blue'') wing than in the long wavelength (``red'') wing of the lines. The observed oscillations are compatible with the spectral line signatures of upwardly propagating acoustic waves. Title: Sunspot oscillations in the chromosphere, transition region, and corona Authors: Brynildsen, N.; Maltby, P.; Fredvik, T.; Kjeldseth-Moe, O. Bibcode: 2002ESASP.506..513B Altcode: 2002ESPM...10..513B; 2002svco.conf..513B The results of simultaneous observations with CDS on SOHO and TRACE for thirteen sunspots in 2001 and 2002 are combined with previous results for six sunspots observed with CDS and SUMER on SOHO. Intensity oscillations are detected above each umbra and spectral observations of chromospheric and transition region lines allow us to measure oscillations in the line-of-sight velocity in several sunspots. The power spectra show one dominant peak close to 6 mHz, corresponding to a period of 3 minutes. The oscillation amplitude increases with increasing temperature, reaches a maximum for lines emitting close to 1-2×105K, and decreases for higher temperatures. Part of the wave energy penetrates into the corona, channeled into small areas that appear to coincide with the endpoints of sunspot coronal lops. The observations support the hypothesis that the oscillations are caused by upwardly propagating acoustic waves. The observations are not compatible with the concept of a chromospheric resonator. Title: On the nature of the 3 minute oscillations above sunspots Authors: Hansteen, V. H.; Wikstøl, Ø.; Brynildsen, N.; Maltby, P.; Fredvik, T.; Kjeldseth-Moe, O. Bibcode: 2002ESASP.505..183H Altcode: 2002IAUCo.188..183H; 2002solm.conf..183H Oscillations in the sunspot transition region and corona are observed simultaneously with the Coronal Diagnostic Spectrometer - CDS on SOHO and the Transition Region And Coronal Explorer - TRACE. Observations of thirteen sunspots in 2001 and 2002 show that the amplitude in the relative integrated line intensity increases with increasing temperature, reaches a maximum for emission lines formed close to 1-2×105K, and decreases at higher temperatures. Part of the wave energy penetrates into the corona, channeled into small areas that appear to coincide with the endpoints of sunspot coronal loops. The observed power spectra show one dominating peak close to 6 mHz. To explore the nature of the waves we calculate upwardly propagating acoustic waves confined to a magnetic flux tube and compare the results with the observations. Title: Oscillations Above Sunspots Authors: Brynildsen, N.; Maltby, P.; Fredvik, T.; Kjeldseth-Moe, O. Bibcode: 2002SoPh..207..259B Altcode: The 3-min oscillations in the sunspot atmosphere are discussed, based on joint observing with the Transition Region and Coronal Explorer - TRACE and the Solar and Heliospheric Observatory - SOHO. We find that the oscillation amplitude above the umbra increases with increasing temperature, reaches a maximum for emission lines formed close to 1-2× 105 K, and decreases for higher temperatures. Oscillations observed with a high signal-to-noise ratio show deviations from pure linear oscillations. The results do not support the sunspot filter theory, based on the idea of a chromospheric resonator. Whereas the filter theory predicts several resonant peaks in the power spectra, equally spaced ∼ 1 mHz in frequency, the observed power spectra show one dominating peak, close to 6 mHz. Spectral observations show that the transition region lines contribute less than 13 percent to the TRACE 171 Å channel intensity above the umbra. The 3-min oscillations fill the sunspot umbra in the transition region. In the corona the oscillations are concentrated to smaller regions that appear to coincide with the endpoints of sunspot coronal loops, suggesting that wave propagation along the magnetic field makes it possible for the oscillations to reach the corona. Title: 3 minute oscillations above sunspots Authors: Brynildsen, N.; Maltby, P.; Fredvik, T.; Kjeldseth-Moe, O. Bibcode: 2002ESASP.508..283B Altcode: 2002soho...11..283B The aim of this investigation is a better understanding of the 3 minute oscillations above sunspots. We present the first results from a joint observing programme with SOHO and TRACE. Attention is given to the wave amplitude as a function of the temperature and to the penetration of part of the wave energy into the corona. The results appear to disagree with the sunspot filter theory. Title: The 6 mHz Oscillations above Sunspots Authors: Brekke, P.; Brynildsen, N.; Maltby, P.; Fredvik, T.; Kjeldseth-Moe, O. Bibcode: 2002AAS...200.8806B Altcode: 2002BAAS...34..790B Sunspot oscillations in the transition region and corona are observed simultaneously with CDS on SOHO and TRACE. Results obtained from investigations of ten sunspots in 2001 and 2002 are presented. We find that the oscillation amplitude above the umbra increases with increasing temperature, reaches a maximum for lines emitted close to 200 000 K, and decreases for higher temperatures. Part of the wave energy penetrates into the corona, channeled into small areas that appear to coincide with the endpoints of sunspot coronal loops. The observed power spectra show one dominating peak, near 6 mHz, and not several, equally spaced resonances as predicted by theories based on the idea of a chromospheric resonator. We conclude that the observations are compatible with upwardly propagating acoustic waves. Title: Redshift in sunspot plumes Authors: Brynildsen, N.; Maltby, P.; Kjeldseth-Moe, O. Bibcode: 2002AdSpR..30..529B Altcode: The non-uniform spatial distributions of emission and wavelength shift in ten EUV lines formed in the chromosphere, transition region and corona above 50 sunspots are investigated, based on observations with the Coronal Diagnostic Spectrometer on the Solar and Heliospheric Observatory. The sunspot plumes are the most prominent features in the transition region line emissions. We find that almost all sunspots show a plume when one magnetic polarity dominates the region out to a distance of 50″ from the sunspot. Both the enhanced emission and the redshift in sunspot plumes increase with the line formation temperature, T, reach a maximum close to log T = 5.5 and cease to exist close to log T = 6.0. The mass flow in the corona is too small to explain the observed redshift in the transition region. We present a working hypothesis where gas at transition region temperatures moves in flow channels from the surroundings into the sunspot. Title: Search for a chromospheric resonator above sunspots Authors: Brynildsen, N.; Maltby, P.; Brekke, P.; Fredvik, T.; Kjeldseth-Moe, O. Bibcode: 2002cosp...34E.178B Altcode: 2002cosp.meetE.178B We have recently observed eleven sunspots, both with CDS on SOHO and TRACE as part of our on-going investigations of the sunspot atmosphere. For each sunspot we investigate the oscillations in the chromosphere, transition region and corona. The observed power spectra show one dominating peak corresponding to a period of 3 minutes. The oscillation amplitude above the umbra increases with increasing temperature, reaches a maximum for lines emitting close to 200 000 K, and decreases for higher temperatures. Part of the wave energy penetrates into the corona, channeled into small areas that appear to coincide with the endpoints of sunspot coronal loops. The observations support the hypothesis that the oscillations are caused by upwardly propagating acoustic waves and show no signs of equally spaced resonances as predicted by theories based on the idea of a chromospheric resonator. Title: Plumes and oscillations in the sunspot transition region Authors: Maltby, P.; Brynildsen, N.; Kjeldseth-Moe, O.; Wilhelm, K. Bibcode: 2001A&A...373L...1M Altcode: The suggestion that sunspot transition region oscillations are a typical feature of the sunspot plumes is examined. The present observations show 3 min oscillations in the umbra that end at the umbral rim. We find that sunspot plumes located above the umbra show these oscillations, in contrast to plumes above the penumbra. These two findings suggest that the oscillations may be a property of the umbral transition region. Title: Dual Flows and Oscillations in the Sunspot Transition Region Authors: Brynildsen, N.; Maltby, P.; Kjeldseth-Moe, O.; Wilhelm, K. Bibcode: 2001ApJ...552L..77B Altcode: New knowledge about sunspot transition region lines that deviate significantly from a Gaussian shape are presented. Attention is given to ``multiple flows,'' a line profile phenomenon in which two or more distinct velocities are observed within the same spatial resolution element. We observe line profiles that are well represented by two Gaussian line components in the N V λ1242 and O V λ629 lines and introduce the notation ``dual flow.'' We have detected transition region oscillations in one of the line components in the dual-flow events. Title: Velocities in Sunspot Plumes Authors: Maltby, P.; Kjeldseth-Moe, O.; Brynildsen, N. Bibcode: 2001IAUS..203..300M Altcode: We investigate the line-of-sight velocities in 50 sunspot regions, based on observations of ten or six EUV emission lines with the Coronal Diagnostic Spectrometer - CDS on the Solar and Heliospheric Observatory - SOHO. The position of the sunspots on the solar disk ranges from disk centre to locations close to the solar limb. Attention is given to the sunspot plumes, the most prominent features in the transition region intensity maps. More than half of the sunspots show downflows in the sunspot plumes that exceed 25 km s-1 at temperatures close to 300 000 K. The observations show that this downflow cannot be maintained by inflow from the corona. The downflow in the sunspot plumes appears to be maintained by gas at transition region temperatures, streaming in flow channels from locations well outside the sunspot. Although individual flow channels show significant changes during approximately 10 minutes, part of the velocity pattern remains unaltered for approximately one day. The velocity fields in the transition region and the chromosphere are compared and the siphon flow mechanism is confronted with the observations. Title: Sunspot Plumes and Flow Channels Authors: Brynildsen, N.; Maltby, P.; Fredvik, T.; Kjeldseth-Moe, O.; Wilhelm, K. Bibcode: 2001SoPh..198...89B Altcode: It is well known that sunspots are dark. This statement is not correct in the sunspot atmosphere between the chromosphere and the corona, where sunspots often are brighter than their surroundings. The brightest feature in the sunspot transition region is called a sunspot plume. Not all sunspots contain a plume. We find that 20 out of 21 sunspots show a plume when one magnetic polarity dominates the sunspot region out to a distance of 50 '' from the sunspot. Most sunspots show downflows that exceed 25 km s−1 in the sunspot plumes at temperatures close to 250 000 K. This downflow is not maintained by inflow from the corona, but by gas at transition region temperatures, streaming in flow channels from locations well outside the sunspot. We suggest that this inflow is a necessary requirement for the sunspot plume to occur and present a working hypothesis for the origin of sunspot plumes. This paper is the first thorough spectral analysis of sunspot plumes. It is based on simultaneous observations of ten or six EUV emission lines in 42 sunspot regions with the Coronal Diagnostic Spectrometer - CDS on the Solar and Heliospheric Observatory - SOHO. The line profiles are studied in detail with another SOHO instrument, the Solar Ultraviolet Measurements of Emitted Radiation - SUMER. Title: On Sunspot Plumes and Dynamics above Sunspot Regions (CD-ROM Directory: contribs/brynild) Authors: Brynildsen, N.; Maltby, P.; Kjeldseth-Moe, O. Bibcode: 2001ASPC..223..595B Altcode: 2001csss...11..595B No abstract at ADS Title: Sunspots: Wilson Effect Authors: Maltby, P. Bibcode: 2000eaa..bookE2056M Altcode: The Wilson effect refers to the depressed appearance of SUNSPOTS when positioned close to the solar limb. The impression is that sunspots are cavities in the SOLAR PHOTOSPHERE. The reason is that the radiation we observe is coming from deeper layers in the sunspot than in the surrounding photosphere. The detection of this depression by Alexander Wilson dates back to 1769. The phenomenon is exp... 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: On the sunspot transition region Authors: Maltby, P.; Brynildsen, N.; Fredvik, T.; Kjeldseth-Moe, O.; Wilhelm, K. Bibcode: 1999SoPh..190..437M Altcode: The EUV line emission and relative line-of-sight velocity in the transition region between the chromosphere and corona of 36 sunspot regions are investigated, based on observations with the Coronal Diagnostic Spectrometer - CDS and the Solar Ultraviolet Measurements of Emitted Radiation - SUMER on the Solar and Heliospheric Observatory - SOHO. The most prominent features in the transition-region intensity maps are the sunspot plumes. In the temperature range between log T=5.2 and log T=5.6 we find that 29 of the 36 sunspots contain one or two sunspot plumes. The relative line-of-sight velocity in sunspot plumes is high and directed into the Sun in the transition region, for 19 of the sunspots the maximum velocity exceeds 25 km s−1. The velocity increases with increasing temperature, reaches a maximum close to log T=5.5 and then decreases abruptly. Title: EUV Line Emission and Dynamics in Sunspot Regions Authors: Brynildsen, N.; Maltby, P.; Kjeldseth-Moe, O. Bibcode: 1999ESASP.446..201B Altcode: 1999soho....8..201B The spatial distributions of EUV line emission and relative line-of-sight velocity in the atmosphere above 22 sunspot regions are investigated. The study is based on simultaneous observations of ten EUV emission lines with the Coronal Diagnostic Spectrometer -- CDS on SOHO. Since the EUV emission lines are formed at different temperatures, we study the sunspot atmosphere from the chromosphere to the corona. We observe both a rapid variation with a characteristic time of a few to several minutes and a slow variation with a time constant of several hours to approximately one day. The sunspot plume concept is reinvented to describe the most prominent emission feature in the intensity maps in the temperature range log T approx 5.2 - 5.6. The relative line-of-sight velocity in sunspot plumes is high and directed into the Sun in the transition region. The flow is maintained by plasmas at transition region temperatures, moving from regions located at greater heights outside the sunspot and towards the sunspot. Only a few features show the signatures of a siphon flow. Comparisons of intensity and velocity maps suggest that gas at transition region temperatures occur in loops different from loops with coronal temperatures. However, we cannot exclude the presence of transition region temperatures close to the footpoints of flux tubes emitting at coronal temperatures. Title: Sunspot Transition Region Oscillations Authors: Brynildsen, N.; Kjeldseth-Moe, O.; Maltby, P.; Wilhelm, K. Bibcode: 1999ESASP.446..207B Altcode: 1999soho....8..207B Based on the SOHO joint observing programme for velocity fields in sunspots, we have detected 3 min transition region umbral oscillations in six sunspots. Simultaneous recordings of O V lambda 629, NV lambdas 1238, 1242 and Si I lambda 1260 with the SUMER instrument allow us to compare the transition region oscillations with the 3 min chromospheric oscillations above the sunspot. We investigate the amplitudes and phase relations of the oscillations in peak line intensity, line-of-sight velocity and line width. The spatial distributions of power in the 3 min oscillations, both in intensity and line-of-sight velocity, are presented. The observations show that the maxima in peak line intensity are nearly, but not exactly in phase with the maxima in velocity directed towards the observer. The suggestion that the waves are upward propagating acoustic waves is confronted with observations. Title: EUV Observations of Sunspot Regions with CDS on SOHO Authors: Brynildsen, N.; Brekke, P.; Haugan, S. V. H.; Kjeldseth-Moe, O.; Maltby, P. Bibcode: 1999ASPC..184..266B Altcode: The spatial distributions of line emission and line-of-sight velocity in seventeen different sunspot regions are studied, based on observations with the Coronal Diagnostic Spectrometer - CDS on SOHO. Ten EUV emission lines, formed in the chromosphere, transition region, and corona are observed. Enhanced EUV line emissions in the transition region are distributed non-uniformly over the active regions and are located both inside and outside sunspots. Most sunspot regions show strongly enhanced transition region line emission above the spot, i.e. sunspot plumes are reinvented. From wavelength shifts we derive the line-of-sight velocity, relative to the average velocity in the rastered area, 120" x 120". In sunspot plumes we find that the motion is directed away from the observer and increases with increasing line formation temperature, T, reaches a maximum up to 40 km s-1 close to log T ≅ 5.5, then decreases abruptly. The spatial extent of both emission features and flow regions increase with increasing temperature within the transition region. The observations show a marked difference between the transition region and the low corona, both regarding the spatial distributions of line emission and line-of-sight velocity. Title: Transition Region Oscillations in a Sunspot Region Authors: Brynildsen, N.; Fredvik, T.; Kjeldseth-Moe, O.; Maltby, P. Bibcode: 1999ASPC..184..146B Altcode: Umbral oscillations in the sunspot transition region have been detected and described from SOHO observations, mainly taken with SUMER of NOAA 8156 on 18 February 1998 between 16:00 UT and 21:07 UT. SUMER recorded simultaneously in the transition regions lines O V λ629, N V λ1238 and N V λ1242, combined with long exposures for wavelength calibration. Transition region oscillations with periods close to 3 min were observed both in intensity and in line-of-sight velocity; the maximum intensity is nearly in phase with maximum velocity directed towards the observer. The wave characteristics appear to be compatible with the results of Gurman et al. (1982) from UVSP on SMM, who interpreted them as upward propagating acoustic waves. Title: Nonlinear Sunspot Transition Region Oscillations in NOAA 8378 Authors: Brynildsen, N.; Kjeldseth-Moe, O.; Maltby, P.; Wilhelm, K. Bibcode: 1999ApJ...517L.159B Altcode: Observations obtained with the Solar and Heliospheric Observatory joint observing program for velocity fields in sunspot regions are used to study the 3 minute transition region oscillations above four sunspots. Here we report mainly on the results obtained for NOAA 8378, based on simultaneous recordings of the transition region lines O V λ629 and N V λλ1238, 1242 and the chromospheric Si II λ1260 line with the Solar Ultraviolet Measurements of Emitted Radiation instrument. The 3 minute transition region oscillations in NOAA 8378 occur mainly above the umbra and show (1) larger peak line intensity amplitudes than reported before, (2) clear signs of nonlinearities, (3) significant oscillations in line width, (4) maxima in peak line intensity and maxima in velocity directed toward the observer that are nearly, but not exactly in phase, and (5) a clear connection to the oscillations in the sunspot chromosphere. The suggestion that the waves are upward-propagating acoustic waves is confronted with the observations by a simple test. Title: SOHO Observations of the Structure and Dynamics of Sunspot Region Atmospheres Authors: Brynildsen, N.; Maltby, P.; Brekke, P.; Haugan, S. V. H.; Kjeldseth-Moe, O. Bibcode: 1999SoPh..186..141B Altcode: We present results from a study of the spatial distributions of line emission and relative line-of-sight velocity in the atmosphere above 17 sunspot regions, from the chromosphere, through the transition region and into the corona, based on simultaneous observations of ten EUV emission lines with the Coronal Diagnostic Spectrometer - CDS on SOHO. We find that the spatial distributions are nonuniform over the sunspot region and introduce the notation 'sunspot loop' to describe an enhanced transition region emission feature that looks like a magnetic loop, extending from inside the sunspot to the surrounding regions. We find little evidence for the siphon flow. Attention is given to the time variations since we observe both a rapid variation with a characteristic time of a few to several minutes and a slow variation with a time constant of several hours to ≈ 1 day. The most prominent features in the transition region intensity maps are the sunspot plumes. We introduce an updated criterion for the presence of plumes and find that 15 out of 17 sunspots contain a plume in the temperature range logT≈5.2-5.6. The relative line-of-sight velocity in sunspot plumes is high and directed into the Sun in the transition region. Almost all the sunspot regions contain one or a few prominent, strongly redshifted velocity channels, several of the channels extend from the sunspot plume to considerable distances from the sunspot. The flow appears to be maintained by plasmas at transition region temperatures, moving from regions located at a greater height outside the sunspots and towards the sunspot. The spatial correlation is high to moderate between emission lines formed in the transition region lines, but low between the transition region lines and the coronal lines. From detailed comparisons of intensity and velocity maps we find transition region emission features without any sign of coronal emission in the vicinity. A possible explanation is that the emission originates in magnetic flux tubes that are too cold to emit coronal emission. The comparisons suggest that gas at transition region temperature occur in loops different from loops with coronal temperature. However, we cannot exclude the presence of transition region temperatures close to the footpoints of flux tubes emitting at coronal temperatures. Regions with enhanced transition region line emission tend to be redshifted, but the correlation between line emission and relative line-of-sight velocity is weak. We extend our conditional probability studies and confirm that there is a tendency for line profiles with large intensities and red shifts (blue shifts) above the average to constitute an increasing (decreasing) fraction of the profiles as the wavelength shift increases. Title: Professor Øystein Elgarøy (1929 - 8 September 1998). Authors: Maltby, P. Bibcode: 1999ATi....33...12M Altcode: No abstract at ADS Title: Sunspot Transition Region Oscillations in NOAA 8156 Authors: Brynildsen, N.; Leifsen, T.; Kjeldseth-Moe, O.; Maltby, P.; Wilhelm, K. 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: Coronal Radiation and Helium λ584 Emission in Active Regions Authors: Fredvik, T.; Maltby, P. Bibcode: 1999SoPh..184..113F Altcode: Based on EUV observations of eleven sunspot regions obtained with the Coronal Diagnostic Spectrometer, CDS, on SOHO we have studied the spatial distribution, temporal variation and wavelength shift of the He i λ584 line. We find a relatively high spatial correlation between the coronal line Fe xvi λ360 and the He i λ584 line. This points to coronal back-radiation as an important contributor to the formation of the He i line in active regions. However, contribution to the line formation from another source is suggested by the following two findings: First, the red-shifted line profiles of both He i λ584 and the transition region lines tend to be more intense than blue-shifted profiles. Second, the He i λ584 emission changes significantly faster than the coronal line emission. Title: Flows in Sunspot Plumes Detected with SOHO Authors: Brynildsen, N.; Maltby, P.; Brekke, P.; Fredvik, T.; Haugan, S. V. H.; Kjeldseth-Moe, O.; Wikstol, O. 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: Closing summary Authors: Maltby, P. Bibcode: 1998AdSpR..21..351M Altcode: Emphasis is given to the search for an ingenious space mission proposal that aims to solve an important scientific problem of general interest. Title: European Plans for the Solar/Heliospheric Stereo Mission Authors: Bothmer, V.; Bougeret, J. -L.; Cargill, P.; Davila, J.; Delaboudiniere, J. -P.; Harrison, R.; Koutchmy, S.; Liewer, P.; Maltby, P.; Rust, D.; Schwenn, R. Bibcode: 1998ESASP.417..145B Altcode: 1998cesh.conf..145B No abstract at ADS Title: The Non-Uniformity in the Sunspot Transition Region Authors: Brynildsen, N.; Brekke, P.; Fredvik, T.; Haugan, S. V. H.; Kjeldseth-Moe, O.; Maltby, P.; Harrison, R. A.; Rimmele, T.; Wilhelm, K. Bibcode: 1997ESASP.404..257B Altcode: 1997cswn.conf..257B No abstract at ADS Title: Transition Region Velocities and Line Profiles in the Sunspot Region 7981 Authors: Brynildsen, N.; Brekke, P.; Fredvik, T.; Haugan, S. V. H.; Kjeldseth-Moe, O.; Maltby, P.; Harrison, R. A.; Pike, C. D.; Rimmele, T. Thompson, W. T.; Wilhelm, K. Bibcode: 1997ESASP.404..251B Altcode: 1997cswn.conf..251B No abstract at ADS Title: CDS Observations of the Connection Between Line Intensity and Doppler Shift in the Active Region NOAA 7981 Authors: Fredvik, T.; Brynildsen, N.; Maltby, P.; Kjeldseth-Moe, O.; Brekke, P.; Haugen, S. V. H.; Harrison, R. A. Bibcode: 1997ESASP.404..391F Altcode: 1997cswn.conf..391F No abstract at ADS Title: The Net Redshifts in EUV Emission Lines and the Connection Between Intensity and Doppler Shift Authors: Brynildsen, N.; Fredvik, T.; Maltby, P.; Kjeldseth-Moe, O.; Brekke, P.; Haugan, S. V. H.; Harrison, R. A.; Wilhelm, K. Bibcode: 1997ESASP.404..263B Altcode: 1997cswn.conf..263B No abstract at ADS Title: EUV Line Emission and Time Dependence in the Sunspot Region NOAA 7981 Authors: Brynildsen, N.; Brekke, P.; Fredvik, T.; Haugan, S. V. H.; Kjeldseth-Moe, O.; Maltby, P.; Harrison, R. A.; Pike, C. D.; Rimmele, T.; Thompson, W. T.; Wilhelm, K. Bibcode: 1997ESASP.404..245B Altcode: 1997cswn.conf..245B No abstract at ADS Title: Temporal Variability in the Quiet Sun Transition Region Authors: Wikstoøl, Ø.; Hansteen, V. H.; Brynildsen, N.; Maltby, P.; Kyeldseth-Moe, O.; Harrison, R. A.; Wilhelm, K.; Tarbell, T. D.; Scherrer, P. H. Bibcode: 1997ESASP.404..733W Altcode: 1997cswn.conf..733W No abstract at ADS Title: Flows and Dynamics in the Corona Observed with the Coronal Diagnostic Spectrometer (cds) Authors: Brekke, P.; Kjeldseth-Moe, O.; Brynildsen, N.; Maltby, P.; Haugan, S. V. H.; Harrison, R. A.; Thompson, W. T.; Pike, C. D. Bibcode: 1997SoPh..170..163B Altcode: EUV spectra obtained with the Coronal Diagnostic Spectrometer (CDS) on the Solar and Heliospheric Observatory (SOHO) show significant flows of plasma in active region loops, both at coronal and transition region temperatures. Wavelength shifts in the coronal lines Mgix 368 Å and Mgx 624 Å corresponding to upflows in the plasma reaching velocities of 50 km s-1 have been observed in an active region. Smaller velocities are detected in the coronal lines Fexvi 360 Å and Sixii 520 Å. Flows reaching 100 km s-1 are observed in spectral lines formed at transition region temperatures, i.e., Ov 629 Å and Oiii 599 Å, demonstrating that both the transition region and the corona are clearly dynamic in nature. Some high velocity events show even higher velocities with line profiles corresponding to a velocity dispersion of 300-400 km s-1. Even in the quiet Sun there are velocity fluctuations of 20 km s-1 in transition region lines. Velocities of the magnitude presented in this paper have never previously been observed in coronal lines except in explosive events and flares. Thus, the preliminary results from the CDS spectrometer promise to put constraints on existing models of the flows and energy balance in the solar atmosphere. The present results are compared to previous attempts to observe flows in the corona. Title: Dynamics of Sunspots Authors: Maltby, P. Bibcode: 1997ASPC..118...91M Altcode: 1997fasp.conf...91M Since we are observing the Sun from one vantage point, either in space or from the ground, a complete determination of the velocity field is difficult and critically dependent on the assumptions applied. After a brief review of the characteristics of gas flow in flux tubes the siphon flow hypothesis is presented and confronted with observations. It is found that the inverse Evershed effect in the chromosphere is compatible with a siphon flow, provided new flow channels constantly replace old ones as they lose their mass to the sunspot. The conflicts between the siphon flow hypothesis and the observations of the Evershed effect are discussed and possible solutions presented. New SOHO observations of the sunspot region in the transition region and the corona are presented and the observational basis for the multiple flow concept is discussed. The complexity of the observed flow field in the transition region is underlined and alternative working hypotheses are discussed. Title: Book reviews Authors: Marx, G.; Jaffe, W.; Maltby, P.; Grevesse, N.; Wu, S. T.; Lüst, R.; Kleczek, J.; Chupp, E. L.; Bloemen, Hans; de Jager, Cornelis; van Teeseling, A.; Shea, M. A.; Butcher, H.; van der Kruit, P. C.; Nieuwenhuijzen, H.; Steeghs, Danny; Fälthammar, Carl-Günne; Greenberg, J. M.; Rasool, S. I. Bibcode: 1996SSRv...77..369M Altcode: No abstract at ADS Title: Quiet-Sun Connection between the C IV Resonance Lines and the Photospheric Magnetic Field Authors: Brynildsen, Nils; Kjeldseth-Moe, Olav; Maltby, Per 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: 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: Are the Redshifts Observed in Transition Region Lines Caused by Magnetic Reconnection? Authors: Hansteen, Viggo; Maltby, Per; Malagoli, Andrea Bibcode: 1996ASPC..111..116H Altcode: 1997ASPC..111..116H The detection of differential redshift between transition region and chromospheric line emission, both in spectra of late type stars and in solar spectra has been a puzzle for two decades. The fact that solar observations are inconsistent with a continuous downflow calls for another interpretation. The authors pursue the interpretation that the observed pervasive transition region line shifts are caused by MHD waves propagating along the magnetic field lines from the corona downward towards the chromosphere. Title: The Coronal Diagnostic Spectrometer for the Solar and Heliospheric Observatory Authors: Harrison, R. A.; Sawyer, E. C.; Carter, M. K.; Cruise, A. M.; Cutler, R. M.; Fludra, A.; Hayes, R. W.; Kent, B. J.; Lang, J.; Parker, D. J.; Payne, J.; Pike, C. D.; Peskett, S. C.; Richards, A. G.; Gulhane, J. L.; Norman, K.; Breeveld, A. A.; Breeveld, E. R.; Al Janabi, K. F.; Mccalden, A. J.; Parkinson, J. H.; Self, D. G.; Thomas, P. D.; Poland, A. I.; Thomas, R. J.; Thompson, W. T.; Kjeldseth-Moe, O.; Brekke, P.; Karud, J.; Maltby, P.; Aschenbach, B.; Bräuninger, H.; Kühne, M.; Hollandt, J.; Siegmund, O. H. W.; Huber, M. C. E.; Gabriel, A. H.; Mason, H. E.; Bromage, B. J. I. 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: Frontiers of astrophysics. Proceedings. Authors: Lilje, P. B.; Maltby, P. Bibcode: 1995fap..book.....L Altcode: To honour one of the pioneers of modern astrophysics, Svein Rosseland (1894 - 1985). Title: Frontiers of astrophysics Authors: Lilje, Per B.; Maltby, Per Bibcode: 1995fras.conf.....L Altcode: No abstract at ADS Title: Solar Activity Today Authors: Maltby, P. Bibcode: 1995fras.conf..205M Altcode: No abstract at ADS Title: On the relation between red- and blueshifted UV-emission lines and photospheric magnetic fields Authors: Brynildsen, N.; Kjeldseth-Moe, Olav; Maltby, Per Bibcode: 1994ESASP.373..413B Altcode: 1994soho....3..413B No abstract at ADS Title: Fine structure and the emission filling factor Authors: Kjeldseth-Moe, O.; Brynildsen, N.; Brekke, P.; Maltby, P. 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: Redshifted transition region lines explained Authors: Hansteen, V.; Maltby, P. Bibcode: 1994AdSpR..14d..57H Altcode: 1994AdSpR..14...57H The discovery of differential redshift between transition region and chromospheric line emissions, both in the spectra of late-type stars and in the solar spectra has been a puzzle for more than a decade. The fact that the solar observations appear to be inconsistent with a continuous downflow calls for another interpretation. We propose that this pervasive redshift observed in transition region spectral lines is caused by conduction modified MHD waves propagating along the magnetic field lines from the corona towards the chromosphere. The waves are assumed generated in the corona by nanoflares, i.e.by an episodic heating mechanism. The calculations for acoustic waves show line profiles with many of the same characteristics as the observations. Title: The Thermal Magnetic Structure of Sunspots Authors: Maltby, P. Bibcode: 1994IAUS..154..423M Altcode: No abstract at ADS Title: Fine-scale structure and the Evershed effect Authors: Maltby, P. Bibcode: 1994smf..conf..188M Altcode: No abstract at ADS Title: Sunspot temperatures Authors: Maltby, P. Bibcode: 1994ASIC..433..179M Altcode: No abstract at ADS Title: Multiple Flows and the Fine Structure of the Transition Region around Sunspots Authors: Kjeldseth-Moe, O.; Brynildsen, N.; Brekke, P.; Maltby, P.; Brueckner, G. E. 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: Wave phenomena in solar terrestrial plasmas. Proceedings. Authors: Maltby, P.; Pécseli, H. L. Bibcode: 1993wpst.conf.....M Altcode: The aim of this Mini-Workshop is to give further insight into physical processes that are relevant for the scientific output of space projects with Norwegian participation. It represents a challenge both in astrophysics and space plasma. New results from CRRES, GEOTAIL, FREIA, ULYSSES, and YOHKOH were available. Title: Scientific requirements for future solar-physics space missions Authors: Maltby, P.; Battrick, B. Bibcode: 1993ESASP1157.....M Altcode: 1993srfs.book.....M; 1993QB520.S25...... No abstract at ADS Title: Multiple flows in the solar transition region. Authors: Brekke, P.; Brynildsen, N.; Kjeldseth-Moe, O.; Maltby, P.; Brueckner, G. E. 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: On Redshifts in Stellar Ultraviolet Emission Lines Authors: Hansteen, V.; Maltby, P. Bibcode: 1992ComAp..16..137H Altcode: No abstract at ADS Title: Continuum Observations and Empirical Models of the Thermal Structure of Sunspots Authors: Maltby, P. Bibcode: 1992ASIC..375..103M Altcode: 1992sto..work..103M Intensity observations of sunspot umbrae and penumbrae in the visible and infrared are reviewed. The continuum intensity in the darkest part of the umbra and the average penumbral intensity are known with relatively high accuracy in large sunspots. With the aim of understanding conflicting observations of umbral dots it is suggested that the umbral core is nearly free of umbral dots, and that an umbral core only occurs in sunspots above a certain size. The present status of semi-empirical models of the temperature stratification in umbrae and penumbrae is discussed and the need for extending the model calculations to more than one dimension is pointed out. Title: Signatures of episodic coronal heating in solar transition region spectral lines. Authors: Hansteen, V.; Maltby, P. Bibcode: 1992mrpa.work..127H Altcode: A brief introduction to the heating mechanisms in the solar atmosphere and to the observed redshifts in transition region lines is given. The authors discuss a new interpretation of the observed redshift and present calculations that support the new explanation. Title: Sunspots: An Observational Overview (Invited) Authors: Maltby, P. Bibcode: 1992LNP...397..124M Altcode: 1992sils.conf..124M No abstract at ADS Title: Magnetic reconnection in physics and astrophysics. Proceedings. Authors: Maltby, P. Bibcode: 1992mrpa.work.....M Altcode: The workshop focuses on problems of interest to both space physicists and astrophysicists, as well as researchers working on laboratory plasmas. Magnetic reconnection in small laboratory experiments and in fusion devices, processes in the Earth's magnetosphere and in the solar transition region and the corona are discussed. It is shown how useful relatively small laboratory experiments can be in generating and testing out new ideas. Title: Active regions, sunspots and their magnetic fields. Authors: Semel, Meir; Mouradian, Zadig; Soru-Escaut, Irina; Maltby, Per; Rees, David; Makita, Mitsugu; Sakurai, Takashi Bibcode: 1991sia..book..844S Altcode: Surface magnetism is the progenitor of active regions, sunspots, and all related phenomena. This cause and effect is reversible so that, using well-established empirical laws, the presence and morphology of photospheric magnetic fields can be deduced from active-region light emission structure. In the (simplifying) case of sunspots, MHD and thermodynamic theory find some success in the interpretation of the interaction of magnetic fields and solar plasma. Coronal magnetic fields also appear to be predictable by extrapolation techniques starting from the photospheric conditions. Alternatively, surface magnetism can be observed "directly" by means of the spectroscopic Zeeman effect and Stokes polarimetry. Eventually these empirical, theoretical and direct-measurement techniques must converge to identical results as we better understand the physics of active regions. Title: Diagnostics of solar oscillation observations. Proceedings. Authors: Maltby, P.; Leer, E. Bibcode: 1991dsoo.conf.....M Altcode: No abstract at ADS Title: Multiple flow velocities in the transition region Authors: Brekke, P.; Brynildsen, N.; Kjeldseth-Moe, O.; Maltby, P.; Bartoe, J. -D. F.; Brueckner, G. E. 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: Coronae and winds in late-type stars. Proceedings. Authors: Leer, E.; Maltby, P. Bibcode: 1991cwlt.conf.....L Altcode: No abstract at ADS Title: New Light on Solar Infrared Intensity Oscillations Authors: Leifsen, T.; Maltby, P. Bibcode: 1990SoPh..125..241L Altcode: The detection of large-amplitude infrared solar intensity oscillations in the 5-min region is reported. Using a broad-band multichannel photometer, the peak-to-peak intensity variation at 2.23 μm is found to be as high as 2.4% for a circular aperture of 1 arc min and 0.8% in the full disk observations, i.e., remarkably higher than at the other four observed wavelength regions. Title: The Effect of MHD-Waves on Transition Region Spectral Lines Authors: Hansteen, V.; Maltby, P. Bibcode: 1990BAAS...22.1234H Altcode: No abstract at ADS Title: Imaging Fourier Transform Spectrometer - IFTS and the proposal Solar Physics Element in Columbus/Space Station - SPECS. Proceedings. Authors: Maltby, P. Bibcode: 1990ifts.book.....M Altcode: In November 1985 a new mission proposal Solar Physics Element in Columbus/Space Station - SPECS was submitted to ESA. ESA has carried out accommodation and on-board processing studies of the core instrument IFTS, comprised of the high resolution telescope, the Imaging Fourier Transform Spectrometer, and high resolution imagers. The SPECS-team found it appropriate to review the IFTS concept and arranged this meeting. Contents: 1. Science objectives and studies of the proposal Solar Physics Element in Columbus/Space Station - SPECS (P. Maltby). 2. The Imaging Fourier Transform Spectrometer (A. Thorne). 3. The SIMURIS Imaging Fourier Spectrometer (B. Foing). 4. Requirements to spectrometers set by solar UV-observations (O. Kjeldseth-Moe). 5. The coronal diagnostic spectrometer (B. E. Patchett, K. Phillips). 6. Science objectives for SUMER experiment on SOHO (P. Lemaire). 7. Signal processing in instruments based on interferometry (T. Jaeger, J. K. Hagene). 8. Critical IFTS items (M. C. E. Huber). Title: Physical processes in the solar transition-region and corona. Proceedings. Authors: Maltby, P.; Leer, E. Bibcode: 1990ppst.conf.....M Altcode: No abstract at ADS Title: Observed Line Profiles and Mass Fluxes in the Transition Region above Sunspots Authors: Maltby, P.; Brekke, P.; Brynildsen, N.; Kjeldseth-Moe, O.; Bartoe, J. -D. F.; Brueckner, G. E. 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: Signatures of magneto-acoustic waves in solar spectral lines. Authors: Maltby, P. Bibcode: 1990ppst.conf..125M Altcode: The effects of magneto-acoustical waves on spectral line formation are summarized. In order to simplify the discussion it is assumed that the effect of gravity may be neglected. Calculated line emission/absorption coefficients are presented for a sound wave and for an Alfvén wave; the case with a magneto-sonic wave is also discussed. The effects of the waves on spectral lines formed in the chromosphere/corona transition region are explored. Attention is given to the possibility that sound waves may act differently on lines in different stages of ionization. The observability of torsional Alfvén waves propagating in flux tubes is evaluated. It is shown that the signatures of torsional Alfvén waves on spectral lines are quite similar to those of a rotating fluid. However, from high quality time sequences one should be able to discriminate between the two options. Title: Transition Region Massflows Associated with Sunspots Authors: Kjeldseth-Moe, O.; Brekke, P.; Brynildsen, N.; Maltby, P.; Brueckner, G. E.; Bartoe, J. -D. F. Bibcode: 1989BAAS...21.1178K Altcode: No abstract at ADS Title: Gas flow in solar magnetic flux tubes. Authors: Maltby, P. Bibcode: 1989ftsa.conf....3M Altcode: In selecting flux tube properties the focus will be on flow properties. Available information makes it natural to give less attention to magnetic elements in quiet regions than to the sunspot region. Title: Mini-Workshop on Flux Tubes in the Solar Atmosphere, held June 19-21, 1989, in Oslo, Norway Authors: Leer, E.; Maltby, P. Bibcode: 1989ftsa.conf.....L Altcode: No abstract at ADS Title: Solar infrared intensity oscillations. Authors: Leifsen, T.; Maltby, P. Bibcode: 1988ESASP.286..169L Altcode: 1988ssls.rept..169L The 5-min oscillations are found to be easily observable as intensity variations in an infrared wavelength band centered at 2.23 μm with bandwidth (FWHM) 65 nm. The observed peak to peak intensity variation is 2.4% for a circular aperture of 1 arc min and 0.8% in the full disc observations, i.e. considerably higher than in the other four observed channels between 0.67 and 1.65 μm. In addition to the 5-min oscillation the observed full disc power spectrum shows a strong feature centered at 4.3 mHz. This frequency coincides with that of the fundamental p-mode resonance of the chromosphere. Although this identification is not proven the possibility to study the chromospheric cavity in full disc observations is interesting. Title: Gas Flows in the Transition Region above Sunspots Authors: Kjeldseth-Moe, O.; Brynildsen, N.; Brekke, P.; Engvold, O.; Maltby, P.; Bartoe, J. -D. F.; Brueckner, G. E.; Cook, J. W.; Dere, K. P.; Socker, D. G. 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: Interpreting Quasar Redshifts Authors: Maltby, Per; Pasachoff, Jay M.; Kierein, John Bibcode: 1987PhT....40c.110M Altcode: No abstract at ADS Title: Joint Discussion on Topics of Sessions 5 and 6 Authors: Zwaan, C.; Maltby, P. Bibcode: 1987rfsm.conf..165Z Altcode: No abstract at ADS Title: Transition Zone Flows in Sunspots Authors: Kjeldseth-Moe, O.; Brynildsen, N.; Engvold, O.; Maltby, P.; Bartoe, J. -D. F.; Brueckner, G. E. 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: 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: Image processing of HRTS data from Spacelab 2 Authors: Kieldseth Moe, O.; Andreassen, T.; Andreassen, O.; Maltby, P.; Moen, K. Bibcode: 1985MmSAI..56..561K Altcode: No abstract at ADS Title: Towards a multi-component semi-empirical model for the solar photosphere. Authors: Kjeldseth-Moe, O.; Andreassen, T.; Maltby, P. 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: Solar cycle variations of sunspot temperatures. Authors: Maltby, P.; Barth, S. B.; Lilje, P. B.; Vikanes, E. W. Bibcode: 1984ESASP.220..233M Altcode: 1984ESPM....4..233M Observations obtained during 1983 strengthen the finding that the umbra/photosphere intensity ratio for large sunspots is a linear function of the phase in the solar cycle. Data for the period 1968 - 1983 are presented, thus covering most of the solar cycles 20 and 21. Title: Limb Darkening and Solar Cycle Variation of Sunspot Intensities Authors: Albregtsen, F.; Joras, P. B.; Maltby, P. Bibcode: 1984SoPh...90...17A Altcode: New observations of the umbral limb-darkening are presented. We find a real and significant decrease in the umbra/photosphere intensity ratio towards the limb. This result contrasts the findings of previous authors and we believe this to be the first time such a decrease is reported. Our conclusion is based on broad band pinhole photometer intensity observations of 22 large sunspots covering the spectral region 0.387-2.35 μm. The data are selected from measurements on approximately 600 days during the last 15.5 yr. The application of the limb-darkening data to the study of the temperature stratification in the umbra is briefly discussed. The observations confirm the suggestion that the umbra/photosphere intensity ratio seems to be a linear function of the phase in the solar cycle. Title: On magnetic effects in solar active regions Authors: Maltby, P. Bibcode: 1984noas.meet...47M Altcode: Magnetic field effects in solar active regions are reviewed. The equations of magnetohydrodynamics are presented and applied to steady-state conditions. Particular attention is given to the quiet phase, but the flaring phase is also considered. Waves in the umbral atmosphere are discussed, and heating by ac and dc currents is considered. Short accounts of prominence and flare physics are given. Title: Solar Cycle Temperature Variations in Sunspots Authors: Maltby, P.; Albregtsen, F.; Moe, O. Kjeldseth; Kurucz, R.; Avrett, E. 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: On magnetic effects in solar active regions. Authors: Maltby, P. Bibcode: 1984POHel...6...47M Altcode: Magnetic field effects in solar active regions are reviewed. The equations of magnetohydrodynamics are presented and applied to steady state conditions. Particular attention is given to the quiet phase, but the flaring phase is also considered. Waves in the umbral atmosphere are discussed and heating by AC and DC currents are considered. Short accounts of prominence and flare physics are given. Title: The chromosphere-corona transition zone above an active region Authors: Kjeldseth-Moe, O. .; Andreassen, O.; Maltby, P.; Bartoe, J. -D. F.; Brueckner, G. E.; Nicolas, K. R. 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: Has rapid solar core rotation been observed? Authors: Andersen, B. N.; Maltby, P. Bibcode: 1983Natur.302..808A Altcode: Internal rotation and gravitational quadropole moment of the Sun are of interest to solar physics, the study of stellar structure and to investigations related to the test of gravitational theories. High precision measurements of fluctuations in the limb darkening function and in the spectral line shifts have raised the possibility that the interior of the Sun may be studied more directly than had previously been possible. Recently, Claverie et al.1 argued that their detection of a 13.1+/-0.2 day velocity signal give further experimental evidence that the solar core is rotating more rapidly than the observable surface. We show here that the phase as well as the magnitude of the observed signal amplitude may be predicted without any rapid core rotation by taking into account the presence of sunspots and their contribution to the spectral line profile as integrated over the disk of the Sun. Hence, we conclude that the existence of a 13.1-day apparently periodic velocity signal with amplitude 6.5 m s-1 during the 88 days observing period cannot be taken as evidence for a rapidly rotating solar core. Title: Finite amplitude effects of torsional Alfven waves in a flux tube Authors: Andreassen, O.; Maltby, P. Bibcode: 1983IAUS..102..401A Altcode: Consider a cylindrical, homogeneous magnetic flux tube embedded in a field-free compressible plasma. The authors employ the method of successive approximations to solve the magnetohydrodynamic equations analytically for an axisymmetrical (m = 0) torsional Alfvén mode. The m = 0 mode inside the tube may excite surface-, stationary- or progressive waves in the field-free plasma. The authors conclude that, in contrast to the linear theory, the flux tube may lose energy by wave radiation to the surroundings. Title: On the Need for Space Observations of the Umbra - Photosphere Intensity Ratio Authors: Albregtsen, F.; Maltby, P. Bibcode: 1981SoPh...74..147A Altcode: We draw attention to the possibility of distinguishing between different sunspot theories by observing: (i) The umbra/photosphere intensity ratio as a function of spot size and (ii) the morphology and time evolution of sunspot inhomogeneities such as umbral dots. In arguing the need for space observations of sunspot intensities we discuss the corrections for stray light for ground based and space observations. Title: Solar Cycle Variation of Sunspot Intensity Authors: Albregtsen, F.; Maltby, P. Bibcode: 1981SoPh...71..269A Altcode: Broad band pinhole photometer intensity observations of 15 large sunspots covering the spectral region 0.387-2.35 μm are presented. The data are based on measurements on approximately 500 days during the period June, 1967 to December, 1979. Title: Constraints on umbral core models as derived from broad-band intensity observations Authors: Albregtsen, F.; Maltby, P. Bibcode: 1981phss.conf..127A Altcode: The umbra/photosphere intensity ratio for sunspots with umbral radii larger than 5 sec of arc is discussed. The intensity ratio is derived for a 'typical', large sunspot in the wavelength region 0.387-3.8 microns. The data are used in constructing a new, one-component model for the umbral core. The umbral intensity differs significantly from one sunspot to another, particularly in the infrared spectral region. It is shown that the brightest core observed fits the model of Zwaan (1974), whereas the darkest core fits the D-model of Kjeldseth Moe and Maltby (1974). Title: Introduction Authors: Maltby, P. Bibcode: 1980fsoo.conf..277M Altcode: No abstract at ADS Title: Solflekk-fysikk. Authors: Maltby, P. Bibcode: 1980kosm.conf...43M Altcode: No abstract at ADS Title: Solar cycle variation of sunspot intensity and X-ray bright points. Authors: Maltby, P.; Albregtsen, F. Bibcode: 1979ApJ...234L.147M Altcode: Evidence is presented for a possible link between the physical conditions in individual large sunspots and the occurrence of X-ray bright points. For the period 1970-1978 a close correlation is reported between the infrared intensity of large sunspots and the number of X-ray bright points. It is pointed out that the well-known dynamo theory for sunspots, in its present form, is unable to explain the observations. Title: Energy and Mass Balance in Prominences. Authors: Maltby, P. Bibcode: 1979phsp.coll..332M Altcode: 1979IAUCo..44..332M; 1979phsp.conf..332M Some speculations on the energy and mass balance of quiescent prominences are presented. Consideration is given to such points as: (1) variations of internal, kinetic, and gravitational energies, (2) maximum temperature gradients, (3) EUV emission, (4) the role of wave energy, and (5) the role of mass budget. Title: Discussion Authors: Maltby, P.; Stellmacher, G. Bibcode: 1979phsp.coll...35M Altcode: 1979IAUCo..44...35M No abstract at ADS Title: Discussion Authors: Brueckner, J.; Hirayama, T.; Maltby, P.; Schmahl, E. J.; Zirin, H. Bibcode: 1979phsp.coll..121B Altcode: 1979IAUCo..44..121B No abstract at ADS Title: Discussion Authors: Hirayama, T.; Maltby, P.; Malville, J.; Martin, S. F.; Rust, D. M.; Spicer, D. S. Bibcode: 1979phsp.coll..267H Altcode: 1979IAUCo..44..267H No abstract at ADS Title: Discussion Authors: Anzer, U.; Maltby, P.; Spicer, D. S. Bibcode: 1979phsp.coll..348A Altcode: 1979IAUCo..44..348A No abstract at ADS Title: Physics of solar prominences Authors: Jensen, E.; Maltby, P.; Orrall, F. Q. Bibcode: 1979phsp.coll.....J Altcode: 1979IAUCo..44.....J These papers deal with recent theoretical and observational studies of the physics of solar prominences. Specific topics include reviews of prominence spectra and their interpretation, polarimetric observations and magnetic-field determination in prominences, observations of the prominence-corona interface, theories on the formation and stability of quiescent prominences, prominence classifications, observations of active prominences, observations and interpretations of coronal manifestations of eruptive prominences, and models of prominence structure and dynamics. Other contributions discuss simultaneous observations of Ca II and hydrogen Balmer lines in quiescent prominences, recent results in quiescent-prominence spectroscopy, the solar helium abundance obtained from optical spectra of quiescent prominences, and Stokes polarimetry of quiescent prominences in the He I D3 line. Magnetic-field determination based on the Hanle effect is also examined, along with the orientation of prominence microstructure relative to magnetic-field direction, radio observations of quiescent-prominence filaments at centimeter and millimeter wavelengths, EUV observations of filaments, and a magnetic-field reconnection model of quiescent prominences. Title: Discussion Authors: Acton, L. W.; Brueckner, J.; Heyvaerts, J.; Maltby, P.; Spicer, D. S. Bibcode: 1979phsp.coll..314A Altcode: 1979IAUCo..44..314A No abstract at ADS Title: Introduction Authors: Jensen, E.; Maltby, P.; Orrall, F. Q. Bibcode: 1979phsp.coll....1J Altcode: 1979IAUCo..44....1J No abstract at ADS Title: Physics of solar prominences. Proceedings of the International Astronomical Union Colloquium No._44, Oslo, August 14_-_18,_1978. Authors: Jensen, E.; Maltby, P.; Orrall, F. Q. Bibcode: 1979pspp.book.....J Altcode: No abstract at ADS Title: Discussion Authors: Acton, L. W.; Kundu, M. R.; Maltby, P.; Malville, J.; Orrall, F. Q.; Sheeley, N.; Spicer, D. S. Bibcode: 1979phsp.coll..225A Altcode: 1979IAUCo..44..225A No abstract at ADS Title: New light on sunspot darkness and the solar cycle Authors: Albregtsen, F.; Maltby, P. Bibcode: 1978Natur.274...41A Altcode: NUMEROUS attempts have been made to find the physical mechanism responsible for the sunspot cycle. Present theoretical discussions of the basic mechanism of solar activity are usually based on a dynamo theory with a reversing magnetic field1, but objections and alternative interpretations1,2 have recently been advanced. Our understanding of the sunspot cycle seems to be in a stage where new observational insight may be valuable. We report here a variation in the infrared umbra intensity of large sunspots with the phase in the solar cycle. Title: The Evershed flow in the transition region chromosphere-photosphere. Authors: Bones, J.; Maltby, P. Bibcode: 1978SoPh...57...65B Altcode: The Mgb1 line profile is studied as a function of spatial position in the sunspot region. Comparing the wavelengths of the core and the wing, in and just outside the penumbra, a reversal in the shift is detected. The displacements of the core and the wing are interpreted as horizontal motions directed into the spot in the chromosphere and as a flow directed out of the spot in deeper layers. Title: Solflekkforskningen, før og nå. Authors: Albregtsen, F.; Maltby, P. Bibcode: 1978ATi....11..157A Altcode: No abstract at ADS Title: On the difference in darkness between sunspots. Authors: Maltby, P. Bibcode: 1977SoPh...55..335M Altcode: The effects of the magnetic field as well as the velocity field on sunspot equilibrium are discussed. The gas pressure difference, ΔP, between a spot and the environments in the same horizontal layer is primarily determined by the magnetic field. Using recent model atmospheres we find that ΔP shows a maximum value, ΔPmax, at a depth of 650 ± 150 km below the photosphere. The value of ΔPmax suggests that the curvature of the field lines is important for the equilibrium. Title: Compton Effect and Solar Spectral Lines Authors: Maltby, P. Bibcode: 1977Ap&SS..47L..21M Altcode: No abstract at ADS Title: Hα contrast profiles of filament features Authors: Maltby, P. Bibcode: 1976SoPh...46..149M Altcode: The wavelength dependence of filament features is studied, using high-resolution filtergrams taken at seven wavelengths in Hα. The observed contrast profiles are compared with profiles calculated on the basis of Beckers' (1964) `cloud' model. The deviation between observed and calculated profiles is used to suggest a progression among the observed profiles that depends on the height of the filament feature. Title: Mode of propagation of penumbral waves Authors: Maltby, P. Bibcode: 1975Natur.257..468M Altcode: THE solar atmosphere provides an interesting possibility for the study of low frequency waves both in magnetic and nonmagnetic regions, and the most spectacular result (see ref. 1) has been the discovery of waves propagating outwards over sun-spot penumbrae with periods of 180-240 s, horizontal wavelengths of 2,350-3,800 km, and horizontal phase velocities of 12-25 km s-1. The theoretical interpretation of these waves has aroused considerable interest and, in particular, a number of authors have attempted to identify the precise mode of wave propagation involved. The modes proposed include Alfvén waves1, acoustic waves2, Lamb waves3, and magnetogravity waves of the `plus' type vertically trapped at photospheric levels4. In the face of so many possibilities, further progress will probably depend on a more adequate observational knowledge of the actual propagation characteristics of the penumbral waves. Of special importance would be a determination of the direction of the particle velocity with respect to the wave propagation vector. Title: The Chromospheric Evershed Flow Authors: Maltby, P. Bibcode: 1975SoPh...43...91M Altcode: High-resolution filtergrams of a sunspot region observed at seven wavelengths in Hα with a resolution of 1/8 Å have been used to investigate the three-dimensional structure of the chromospheric Evershed flow and its time variation. Title: The Temperature of Penumbral Filaments Authors: Kjeldseth Moe, O.; Maltby, P. 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: Umbral Intensities of large Sunspots Authors: Ekmann, G.; Maltby, P. Bibcode: 1974SoPh...35..317E Altcode: Observations of the intensities of sunspot umbrae at the Oslo Solar Observatory during 5 yr are described. From the observational material we have selected measurements where the corrections for scattered light are small. The results for 5 large sunspots observed in 6 (alternatively 7) wavelength regions are presented. The observations show that possible intensity differences between individual sunspots are difficult to detect in the visible part of the spectrum. Real differences between individual sunspots are detected in the infrared region. Title: The Intensity of the Penumbra of Sunspots Authors: Eriksen, G.; Maltby, P. Bibcode: 1973sari.conf...87E Altcode: No abstract at ADS Title: Observations of the Intensity of the Penumbra of Sunspots Authors: Maltby, P. Bibcode: 1972SoPh...26...76M Altcode: Observations of the penumbral intensity of sunspots in 13 wavelength regions are presented. In 4 wavelength regions 54 sunspots are measured. In the other wavelength regions the number of sunspots considered ranges from 3-19. Title: Sunspot Intensity Observations during the 9 May 1970 Mercury Transit Authors: Maltby, P.; Staveland, L. Bibcode: 1971SoPh...18..443M Altcode: The intensity of a sunspot was measured in eight wavelength regions during the Mercury transit of 9 May 1970. The observations have been corrected for scattered light in the Earth's atmosphere as well as in the instrument using two different methods plus a combination of these. One method consists of using Mercury as a calibration spot. In the second method the corrections for scattered light are determined from solar limb observations. Title: The effect of scattered light on solar intensity observations as derived from 9 May, 1970 Mercury transit Authors: Maltby, P. Bibcode: 1971SoPh...18....3M Altcode: The method for correcting observed sunspot intensities for scattered light has been tested using the transit of Mercury. It is found that the correction method of Zwaan (1965), Staveland (1970) has an uncertainty (rms value) of 0.05 times the photospheric intensity. During good observing conditions the uncertainty is 0.02 (rms value) with the scanning speed used in this study. A simpler and quicker correction method is suggested. Title: Joint Organization for Solar Observations. Annual report 1970. Authors: de Jager, C.; Kiepenheuer, K. O.; Michard, R.; Maltby, P.; Rösch, J.; Brandt, P. N. Bibcode: 1971joso.book.....D Altcode: No abstract at ADS Title: Paschen-Back Effect of the Lithium Resonance Doublet in Sunspots Authors: Maltby, P. Bibcode: 1971IAUS...43..141M 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: Self-Reversal of the Lithium Resonance Doublet in Sunspots Authors: Maltby, P.; Engvold, O. Bibcode: 1970SoPh...14..129M Altcode: No abstract at ADS Title: On the Continuum Intensity of the Umbra of Large Sunspots Authors: Maltby, P. Bibcode: 1970SoPh...13..312M Altcode: Spectral observations of large sunspots during the period June 1968 - Dec. 1969 in five wavelength regions between λ 4795 and λ 6775 are discussed. Selecting the best observations of two very large sunspots, we find slightly lower umbral intensities than derived by earlier observers. It is suggested that the small difference may be explained by the fact that earlier observers have used an average value, whereas we believe that the minimum value gives a more correct estimate of the umbral intensity. Title: The velocity field in sunspots. Authors: Maltby, P. Bibcode: 1970SciSn.105..259M 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: The Intensity of the Penumbra of Large Sunspots Authors: Maltby, P.; Mykland, N. Bibcode: 1969SoPh....8...23M Altcode: Simultaneous photoelectric observations of sunspot penumbrae at 5790, 6690, 8760 and 16700Å are presented. No change in penumbral intensity from spot to spot is found in a sample of 11 large sunspots. Title: A Model for the Penumbra of Sunspots Authors: Maltby, P.; Kjeldseth Moe, O. Bibcode: 1969BAAS....1..285M Altcode: No abstract at ADS Title: Effect of Progressive Alfv&eacuten Waves on the Profiles of Solar Spectral Lines Authors: Maltby, P. Bibcode: 1968SoPh....5....3M Altcode: Progressive Alfvén waves set the atoms in oscillatory motion. The radiation will be absorbed (emitted) at a Doppler-shifted wavelength; the Doppler shift is determined by the velocity given to the atoms by the wave. The effect of the waves on the line profile, integrated over one period, is given for a few simple cases. A brief discussion of the possible application to sunspots is presented. Title: The Effect of Magneto-Sonic Waves on a Zeeman Triplet with Application to Sunspots Authors: Maltby, P. Bibcode: 1968SoPh....4...96M Altcode: No abstract at ADS Title: A spectroscopic study of the Hα profile of moustaches Authors: Engvold, O.; Maltby, P. Bibcode: 1968mmsf.conf..109E 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: The Evershed Effect as a Wave Phenomenon Authors: Maltby, P.; Eriksen, G. Bibcode: 1967SoPh....2..249M Altcode: It is suggested that longitudinal compression waves are propagating parallel to the solar surface from the umbra towards the photosphere. It is shown that the line-absorption coefficient is asymmetrical, when integrated over a wavelength of the compression wave. The effect of the waves on the line profile is discussed, and it is shown that asymmetrical line profiles of the type observed in sunspot penumbrae will be produced. Title: The Effect of Progressive Sound Waves on the Profiles of Stellar Spectral Lines Authors: Eriksen, G.; Maltby, P. Bibcode: 1967ApJ...148..833E Altcode: Progressive sound waves propagating through a region of spectral4ine formation in a stellar atmosphere are considered The sound wave sets the atoms in oscillatory motion While thus performing an ordered motion, the atoms will emit or absorb radiation if properly excited. The radiation will be absorbed (emitted) at a Doppler-shifted wavelength, the Doppler shift being determined by the velocity given to the radiating atoms by the wave The sound wave will also alter the density of atoms capable of absorbing or emitting the line in question. The effect (integrated over one period) of progressive sound waves on the shape of spectral lines is calculated in a few simple cases where the line depth is assumed proportional to the line-absorption coefficient The line profiles are found to be highly asymmetrical when the pressure amplitudes of the wave are relatively large. The degree of asymmetry of the line is found to increase with atomic weight of the atoms producing the line. Title: Comparison of the Degree of Polarization with Other Radio Source Parameters Authors: Maltby, P. Bibcode: 1966ApJ...144..219M Altcode: Observations made at the California Institute of Technology have been used to study the degree of polarization at 10 cm in ninety-six discrete radio sources. No strong connection is found between the degree of polarization at 10 cm and other source parameters. The ratio P(2l)/P(10) between the degrees of polarization at 21 cm and 10 cm has been used as a measure for the depolarization rate. The distribution of P(21)/P(10) according to galactic coordinates indicates that most of the depolarization occurs outside our Galaxy. No strong correlation is evident in a comparison of P(21)/P(10) with other source parameters. Possible explanations of the change in degree of polarization with wavelength are briefly discussed. Title: Observations of Linear Polarization of Fifty-Four Discrete Radio Sources at 10.6 CM Authors: Maltby, P.; Seielstad, G. A. Bibcode: 1966ApJ...144..216M Altcode: The interferometer at the Owens Valley Radio Observatory has been used to study the linear polarization of fifty-four radio sources at a wavelength of 10.6 cm. The measurements were made with two 904oot antennas spaced 100 feet (X 289) in the east-west direction. Title: Erratum: Time Dependence of the Radio Emission from CTA 21 and CTA 102. Authors: Maltby, P.; Moffet, A. T. Bibcode: 1965ApJ...142.1699M Altcode: No abstract at ADS Title: Spectrum of the Intensity Variations in 3C 273B Authors: Maltby, P.; Moffet, A. T. Bibcode: 1965Sci...150...63M Altcode: The intensity variations in radio source 3C 273B have been measured at wavelengths of 31.3, 21.2, and 10.6 centimeters. At 31.3 centimeters the variation is quite small, indicating that the variable component of the source is optically thick at this wavelength. Study of several different model sources shows that the observed dependence of the intensity variations on frequency can best be explained by an increase of the electron density in a source region about 2 parsecs in diameter. This interpretation is consistent with the distance to 3C 273 determined from Hubble's law and the observed red shift. Title: On the Connection Between Liner Polarization and Galactic Latitude of Discrete Radio Sources. Authors: Maltby, P. Bibcode: 1965ApJ...142..621M Altcode: The degree of linear polarization at a wavelength of about 21 cm is considered for 166 presumably extragalactic radio sources A connection between degree of linear polarization and galactic latitude is found; low-latitude sources tend to show a lower degree of polarization than high-latitude sources. It is found that the correlation between degree of polarization and galactic latitude is weaker at a wavelength equal to 10 cm than at 21 cm. This result is derived from a sample of forty-six sources observed at both wavelengths. Possible interpretations of the correlation found at 21 cm are discussed. Title: Time Dependence of the Radio Emission from CTA 21 and CTA 102. Authors: Maltby, P.; Moffet, A. T. Bibcode: 1965ApJ...142..409M Altcode: No abstract at ADS Title: On the velocity field of sunspots Authors: Maltby, P. Bibcode: 1965IAUS...22..281M Altcode: No abstract at ADS Title: Opacity properties of sunspots. Authors: Jensen, Eberhart; Maltby, Per Bibcode: 1965ApNr...10...17J Altcode: No abstract at ADS Title: Brightness Distribution in Discrete Radio Sources. I. a Discussion of 24 Identified Sources Authors: Maltby, P.; Matthews, Thomas A.; Moffet, A. T. Bibcode: 1965qssg.conf..159M Altcode: No abstract at ADS Title: On the velocity field in sunspots Authors: Maltby, Per Bibcode: 1964ApNr....8..205M Altcode: No abstract at ADS Title: The Evershed effect at the outer edge of sunspot penumbras Authors: Brekke, K.; Maltby, P. Bibcode: 1963AnAp...26..383B Altcode: No abstract at ADS Title: Brightness Distribution in Discrete Radio Sources.IV. a Discussion of 24 Identified Sources. Authors: Maltby, P.; Matthews, T. A.; Moffet, A. T. Bibcode: 1963ApJ...137..153M Altcode: Radial distances, linear dimensions, and total luminosities are given for 24 identified extragalactic radio sources, 19 of which have measured radial velocities. Using the synchrotron theory, the total energy and magnetic-field strength required to account for the observed luminosity are estimated for each source. Eight sources are found with energy requirements exceeding 1060 ergs. Typical field strengths are 10- oersted. The linear diameters range from less than 1 to 290 kpc. Illustrations of the radio and optical brightness distributions are given for 11 sources. Title: Brightness Distribution in Discrete Radio Sources. III. The Structure of the Sources. Authors: Maltby, P.; Moffet, Alan T. Bibcode: 1962ApJS....7..141M Altcode: The visibility functions of 195 radio sources are interpreted in terms of the structure of these sources. Of the 195 sources, 174 are known or presumed to be extragalactic. Seventy-five of these extragalactic sources are resolved with the interferometer spacings used, and complex structure is found in all but 13. In the sources showing complex structure, two similar components with nearly equal intensities are found in 15, two or more components of unequal intensities are found in 40, while 7 contain a bright core surrounded by a halo. It is suggested that the majority of all extragalactic sources have complex structure. Data are also given on the brightness distributions in the 21 galactic sources observed. In contrast to the extragalactic sources, emission from the galactic sources is typically confined to a single region. Title: The Radio Source Hercules A Authors: Maltby, P.; Matthews, T. A.; Moffet, A. T. Bibcode: 1962PASP...74..277M Altcode: No abstract at ADS Title: A discussion of 24 identified sources Authors: Maltby, P.; Matthews, T. A.; Moffets, A. T. Bibcode: 1962OOVRO...4.....M Altcode: No abstract at ADS Title: Central Component of the Radio Source Centaurus A Authors: Maltby, P. Bibcode: 1961Natur.191..793M Altcode: THE identification of the radio source Centaurus A with the peculiar galaxy NGC 5128 was first suggested by Bolton, Stanley and Slee1. The radio source consists of an extended component with dimensions of about 2° × 4° and a compact central component. The extended source has recently been shown by Bolton and Clark2 to consist of two components. The compact central component was investigated in 1953 by Mills3. His observations indicated that the radio emission was associated with the wide dust band of NGC 5128. Recent measurements by Twiss, Carter and Little4 have shown that the central source also consists of two components. This result was also obtained by Moffet and Maltby5. In a more recent radio investigation of NGC 5128, reported in this communication, I find that the radio source is not associated with the wide dust band. Title: Distribution of Brightness in Extragalactic Radio Sources Authors: Moffet, A. T.; Maltby, P. Bibcode: 1961Natur.191..453M Altcode: No abstract at ADS