Author name code: rabin ADS astronomy entries on 2022-09-14 author:"Rabin, Douglas M." ------------------------------------------------------------------------ Title: First Imaging Spectroscopy of 92-115 Angstrom Solar Soft X-rays by EUNIS: Implications for Solar Coronal Heating Authors: Brosius, Jeffrey; Daw, Adrian; Rabin, Douglas; Landi, Enrico; Schmit, Donald Bibcode: 2021AGUFMSH12B..04B Altcode: The Extreme Ultraviolet Normal Incidence Spectrograph (EUNIS) sounding rocket waslaunched from White Sands Missile Range, NM, on May 18, 2021. The instrumentcomprised a pair of coaligned imaging spectrographs, one of which observed solarline emission in first order at wavelengths between 525 and 639 A, and the secondof which observed line emission in third order at wavelengths between 92 and 115 Aand in first order between 277 and 345 A. Images of AR 12824, quiet-sun area, andoff-limb area were obtained by rastering the slits over the selected targets. Thisis the first time that solar imaging spectroscopy has been performed in the 92-115A soft X-ray range. This waveband was selected to (1) observe Fe XVIII 93.932 and103.948 A and Fe XIX 108.355 A line emission in a quiescent active region, and (2)explore a relatively unobserved portion of the solar electromagnetic spectrum. Theinstrument performed well during its 6-minute observing run. We report preliminaryresults on observations of Fe XVIII and Fe XIX in the quiescent active region, anddiscuss implications for the nanoflare model of solar coronal heating. EUNIS wassupported by NASA Heliophysics Low Cost Access to Space award 13-HTIDS13_2-0074. Title: Distributed Space Telescopes Enabled by Constellation of Small Satellites Authors: Kamalabadi, Farzad; Lightsey, E.; Rabin, Douglas; Daw, Adrian; D'Amico, Simone; Koenig, Adam; Chamberlin, Philip; Woods, Thomas; Gupta, Subhanshu; Ekici, Eylem; Sample, John; Park, Hyeongjun; Alexeenko, Alina; Hwang, John; Denis, Kevin; Klimchuk, James Bibcode: 2021AGUFM.A33C..03K Altcode: New pathways to high-resolution sensing and imaging for a multitude of high-priority scientific investigations are being realized by small multi-spacecraft systems. Such pathfinder mission concepts circumvent the limitations of conventional remote sensing/imaging systems by utilizing multiple baselines, synthesized apertures, diffractive optics, combined with computational imaging via interferometry, tomography, or super-resolution. Regardless of the specific scientific questions targeted, such small satellite constellation pathfinders require technological breakthroughs in precision formation flying and associated advances in guidance, navigation, and control; proximity operations and associated autonomy and robust orbit design with passive safety; innovations in sensor miniaturization; inter-satellite communication; and sophisticated computational sensing and reconstruction algorithms. We describe recent advances in such enabling technologies in the context of a scalable ultra-high-resolution spectral imaging mission for investigating the solar corona currently under development by a multi-university consortium in collaboration with NASA and under sponsorship by NSF. Title: Solar Coronagraphs Authors: Rabin, Douglas Bibcode: 2021hai3.book..339R Altcode: No abstract at ADS Title: Photon sieves and the future of EUV imaging spectroscopy Authors: Daw, Adrian N.; Rabin, Douglas M.; Schmit, Donald James; Denis, Kevin Bibcode: 2019AAS...23412605D Altcode: Large-aperture photon sieves fabricated at NASA-GSFC can provide diffraction-limited imaging at EUV and X-ray wavelengths, that is, spatial scales down to milli-arcseconds, and are also being used to provide monochromatic, collimated beams for the calibration of solar EUV instruments such as the Extreme Ultraviolet Normal Incidence Spectrograph (EUNIS). EUNIS is a two-channel imaging spectrograph with unprecedented dynamic range and broad spectral coverage (9-11 nm and 52-64 nm), scheduled for a sounding rocket flight in September 2019. This will be the first time the 9-11 nm wavelength range of the Sun has ever been observed by an imaging spectrograph, despite the importance of these short EUV/soft X-ray wavelengths to observing the hottest (>5MK) plasma in the non-flaring atmosphere, which is critical to understanding the energization of the solar corona. Recent results will be presented, and capabilities for future solar EUV missions will be discussed. Title: Ultrahigh-Resolution Imaging of the Solar Corona using a Distributed Diffractive Telescope Authors: Rabin, Douglas M.; Daw, Adrian N.; Denis, Kevin; Kamalabadi, Farzad; Klimchuk, James A. Bibcode: 2019AAS...23410704R Altcode: Several observational and theoretical considerations suggest that energy is often released in the solar corona on small spatial scales of order 100 km. It has been a longstanding goal of solar physics to subject this hypothesis to direct observational test. However, extreme ultraviolet (EUV) and soft x-ray (SXR) telescopes rarely approach diffraction-limited performance because conventional reflective optics of adequate size typically cannot be manufactured to the requisite figure accuracy. Diffractive optics can overcome the angular-resolution limitations of EUV/SXR mirrors. We describe a mission approach that employs diffractive optics and small satellites flying in formation to form a distributed solar telescope operating at EUV wavelengths. Title: Ultrahigh-Resolution Solar Imaging with Diffractive Optics Authors: Rabin, Douglas; Davila, Joseph M.; Daw, Adrian Nigel; Denis, Kevin; Shah, Neerav; Mason, Emily; Novo-Gradac, Anne-Marie; Widmyer, Thomas Bibcode: 2018tess.conf40443R Altcode: Extreme ultraviolet (EUV) and soft X-ray (SXR) telescopes rarely achieve diffraction-limited performance because conventional reflective optics of the required size typically cannot be manufactured to the requisite figure accuracy. Diffractive optics can overcome the angular-resolution limitations of EUV/SXR mirrors but present other design and performance challenges. A diffractive telescope is well-suited for probing for the first time the expected energy dissipation scales of the solar corona (<100 km). We have previously described the fabrication of photon sieves and Fresnel zone plates as large as 80-mm clear aperture, as well as laboratory measurements and vibration testing. Here we report on the design of more efficient phase zone plates, the path to larger apertures, and our approach to a virtual telescope based on formation-flying smallsats. Title: Building a Futuristic Telescope on the Moon - A Fun Project for Research, Science Teaching, and Outreach Authors: Chen, Peter C.; Rabin, Douglas M.; Haas, J. Patrick; Mirel, Paul Bibcode: 2018AAS...23136107C Altcode: We present the design and demonstrate the operation of a model lunar observatory. While this is a research project, it is also intended to stimulate student interest in space science, astronomy, physics, chemistry, and engineering. First, we discuss the science objectives of a lunar observatory. The Moon is a great location for astronomy. Why? What science can best be done from there? What are exoplanets? We would like to see what planets around other stars look like. Why is it so difficult? What are optical interferometers and why do we need them? Next, we discuss the physics, chemistry, and engineering principles involved. The lunar environment is totally different from Earth. It features high vacuum, low gravity, very slow rotation rate, cryogenic temperatures, and dust. How can an observatory be designed that not only survives, but can take advantage of the environment? We present a “cool” solution (the model uses liquid nitrogen) that combines the following elements: high temperature superconductors, telescope mirrors made of “moondust”, novel telescope support system, an observatory structure made of simulated lunar soil, 3D printing, and methods for dust mitigation. Information will be provided on how similar systems can be built and what further refinements (e.g. voice control, precision stepper drives, autonomous operation, and telerobotics) can be added. Title: Mission Concepts for High-Resolution Solar Imaging with a Photon Sieve Authors: Rabin, Douglas M.; Davila, Joseph; Daw, Adrian N.; Denis, Kevin L.; Novo-Gradac, Anne-Marie; Shah, Neerav; Widmyer, Thomas R. Bibcode: 2017SPD....4811006R Altcode: The best EUV coronal imagers are unable to probe the expected energy dissipation scales of the solar corona (<100 km) because conventional optics cannot be figured to near diffraction-limited accuracy at these wavelengths. Davila (2011) has proposed that a photon sieve, a diffractive imaging element similar to a Fresnel zone plate, provides a technically feasible path to the required angular resolution. We have produced photon sieves as large as 80 mm clear aperture. We discuss laboratory measurements of these devices and the path to larger apertures. The focal length of a sieve with high EUV resolution is at least 10 m. Options for solar imaging with such a sieve include a sounding rocket, a single spacecraft with a deployed boom, and two spacecraft flying in precise formation. Title: Electron temperature maps of the low solar corona: ISCORE results from the total solar eclipse of 1 August 2008 in China Authors: Reginald, Nelson L.; Davila, Joseph M.; St. Cyr, Orville C.; Rabin, Douglas M. Bibcode: 2017JGRA..122.5856R Altcode: We conducted an experiment in conjunction with the total solar eclipse of 1 August 2008 in China to determine the thermal electron temperature in the low solar corona close to the solar limb. The instrument, Imaging Spectrograph of Coronal Electrons (ISCORE), consisted of an 8 inch f/10 Schmidt Cassegrain telescope with a thermoelectrically cooled CCD camera at the focal plane. Results are electron temperatures of 1 MK at 1.08 R and 1.13 R from the Sun center in the polar and equatorial regions, respectively. This experiment confirms the results of an earlier experiment conducted in conjunction with the total eclipse of 29 March 2006 in Libya, and results are that at a given coronal height the electron temperature in the polar region is larger than at the equatorial region. In this paper we show the importance of using the correct photospheric spectrum pertinent to the solar activity phase at the time of the experiment, which is a required parameter for modeling the underlying theoretical concept for temperature interpretation of the measured intensity ratios using color filters. Title: Detecting the Beacons of Life with Exo-Life Beacon Space Telescope (ELBST) Authors: Airapetian, V. S.; Danchi, W. C.; Chen, P. C.; Rabin, D. M.; Carpenter, K. G.; Mlynczak, M. G. Bibcode: 2017LPICo1989.8214A Altcode: We propose a new observational strategy, the “Exo-Life Beacon Space Telescope,” for detecting the signatures of “beacons” of life defined as high signal and low spectral resolution thermal emission from molecules associated with life signatures. Title: Diffraction Analysis of Solar Coronagraphs Authors: Rabin, Douglas M.; gong, qian Bibcode: 2016SPD....4730601R Altcode: The design of a solar coronagraph is predicated on controlling diffracted and scattered light using principles dating back to Bernard Lyot in the 1930’s. The existence of many successful ground- and space-based coronagraphs testifies to our ability to apply these principles in specific cases, but it is difficult to explore a significant range of design parameters because the calculations are tricky and time-consuming. Indeed, scattered light is so design-specific that ad hoc analysis is unavoidable once guidelines from experience are used to create a first-guess system of baffles and low-scatter surfaces. Here we describe a combination of analytic and computational approaches that has the potential to explore coronagraph design space somewhat more systematically with respect to diffracted light. Title: Milli-Arcsecond (MAS) Imaging of the Solar Corona Authors: Davila, Joseph M.; Oktem, Figen S.; Kamalabadi, Farzad; O'Neill, John; Novo-Gradac, Anne-Marie; Daw, Adrian N.; Rabin, Douglas M. Bibcode: 2016SPD....47.0310D Altcode: Dissipation in the solar corona is believed to occur in extremely thin current sheets of order 1-100 km. Emission from these hot but thin current sheets should be visible in coronal EUV emission lines. However, this spatial scale is far below the resolution of existing imaging instruments, so these dissipation sites have never been observed individually. Conventional optics cannot be manufactured with sufficient surface figure accuracy to obtain the required spatial resolution in the extreme-ultraviolet where these hot plasmas radiate. A photon sieve, a diffractive imaging element similar to a Fresnel zone plate, can be manufactured to provide a few milli-arcsec (MAS) resolution, with much more readily achievable tolerances than with conventional imaging technology. Prototype photon sieve elements have been fabricated and tested in the laboratory. A full-scale ultra-high resolution instrument will require formation flying and computational image deconvolution. Significant progress has been made in overcoming these challenges, and some recent results in these areas are discussed. A simple design for a sounding rocket concept demonstration payload is presented that obtains 80 MAS (0.080 arcsec) imaging with a 100 mm diameter photon sieve to image Fe XIV 334 and Fe XVI 335. These images will show the structure of the corona at a resolution never before obtained, and they will also allow a study of the temperature structure in the dissipation region. Title: Evidence for Nanoflare Heating of the Solar Corona from the EUNIS Sounding Rocket Authors: Brosius, J. W.; Daw, A. N.; Rabin, D. M. Bibcode: 2015AGUFMSH31D..01B Altcode: We present spatially resolved EUV spectroscopic measurements ofpervasive, faint Fe XIX 592.2 A line emission in AR 11726,observed during the 2013 April 23 flight of the Extreme UltravioletNormal Incidence Spectrograph (EUNIS-13) sounding rocket instrument. With cooled detectors, high sensitivity, and high spectralresolution, EUNIS-13 resolves the lines of Fe XIX at 592.2 A (formedat temperature T around 8.9 MK) and Fe XII at 592.6 A (T around 1.6MK). The Fe XIX line emission, observed over an area in excess of4920 square arcsec (2.58x10^9 square km, more than 60% of the activeregion), provides strong evidence for the nanoflare heating model ofthe solar corona. No GOES events occurred in the region less than 2hours before the rocket flight, but a microflare was observed northand east of the region with RHESSI and EUNIS during the flight. Theabsence of significant upward velocities anywhere in the region,particularly the microflare, indicates that the pervasive Fe XIXemission is not propelled outward from the microflare site, but ismost likely attributed to localized heating (due to reconnection,wave dissipation, or some other mechanism) consistent with thenanoflare heating model of the solar corona. We measure average FeXIX/Fe XII intensity ratios of 0.070 outside the AR core, 0.22 inarea of bright coronal emission (the area in which the Fe XIIintensity exceeds half its maximum observed value), and 0.55 in theregion's hot core. Using the CHIANTI atomic physics database andassuming ionization equilibrium, we estimate corresponding Fe XIX/FeXII emission measure ratios of about 0.076, 0.23 and 0.59. Theemission measure ratios must be viewed with caution in light oflingering uncertainties in the Fe XII contribution functions.EUNIS-13 was supported by the NASA Heliophysics Division through itsLow Cost Access to Space program. Title: A Geomagnetic Precursor Technique for Predicting the Solar Activity Cycle Authors: Sobel, E. I.; Rabin, D. M. Bibcode: 2015AGUFMSH23A2427S Altcode: The Western hemisphere has been recording sunspot numbers since Galileo discovered sunspots in the early 17th century, and the roughly 11-year solar cycle has been recognized since the 19th century. However, predicting the strength of any particular cycle remains a relatively imprecise task. This project's aim was to update and improve a forecasting technique based on geomagnetic precursors of future solar activity The model is a refinement of R. J. Thompson's 1993 paper that relates the number of geomagnetically disturbed days, as defined by the aa and Ap indices, to the sum of the sunspot number in the current and the previous cycle, Rn + Rn-1.[1] The method exploits the fact that two cycles coexist for some period on the Sun near solar minimum and therefore that the number of sunspots and disturbed days during the declining phase of one cycle gives an indication of the following cycle's strength. We wrote and updated IDL software procedures to define disturbed days with varying threshold values and graphed Rn + Rn-1 against them. The aa threshold was derived from the Ap threshold. After comparing the graphs for Ap values from 20 to 50, an Ap threshold of 30 and the corresponding aa threshold of 44 were chosen as yielding the best correlation. Confidence regions were computed to provide a quantitative uncertainty on future predictions. The 80% confidence region gives a range of ±40 in sunspot number.

[1] Thompson, R. J. (1993). A technique for predicting the amplitude of the solar cycle. Solar Physics, 148, 2, 383-388. Title: EUNIS 2013: Unambiguous Evidence for Impulsive Coronal Heating, Data Available Authors: Daw, Adrian; Brosius, Jeffrey; Haas, J. Patrick; Plummer, Thomas; Rabin, Douglas Bibcode: 2015TESS....120401D Altcode: The broad spectral coverage (303-370 Å, 527-635 Å) and unprecedented dynamic range of the Extreme Ultraviolet Normal Incidence Spectrograph (EUNIS) 2013 sounding rocket observations includes emission lines of ionization stages from He I to Fe XX, and thus a wide temperature range of 0.03 to 10 MK. Pervasive, faint Fe XIX 592 Å line emission was observed in active regions. Comparison of observed line intensities with calculations demonstrates that the Fe XIX emission, formed at temperatures around 8 MK, is evidence of the faint hot emission predicted by impulsive heating models of the solar corona (e.g., ‘nano-flares’). The calibration and availability of the EUNIS-2013 dataset is discussed as well. Title: Carbon nanotube optical mirrors Authors: Chen, Peter C.; Rabin, Douglas Bibcode: 2015JATIS...1a4005C Altcode: We report the fabrication of imaging quality optical mirrors with smooth surfaces using carbon nanotubes (CNT) embedded in an epoxy matrix. CNT/epoxy is a multifunctional composite material that has sensing capabilities and can be made to incorporate self-actuation. Moreover, as the precursor is a low density liquid, large and lightweight mirrors can be fabricated by processes such as replication, spincasting, and three-dimensional printing. Therefore, the technology holds promise for the development of a new generation of lightweight, compact "smart" telescope mirrors with figure sensing and active or adaptive figure control. We report on measurements made of optical and mechanical characteristics, active optics experiments, and numerical modeling. We discuss possible paths for future development. Title: New Approaches to Externally Occulted Coronagraphs Authors: Rabin, D. M.; Chamberlin, P. C.; Davila, J. M.; Shah, N. Bibcode: 2014AGUFMSH53B4226R Altcode: The rapidly advancing capabilities of low-cost space platforms prompts us to reconsider concepts for externally occulted solar coronagraphs. Placing the occulter on a separate platform offers superior diffraction control but requires an analysis of alignment and separation tolerances that is different from that applied to conventional architectures. New forms of occulter (e.g., an inflatable sphere or ellipsoid) have potential advantages such as low mass and fabrication cost, simple deployment, and less stringent demands on the relative alignment of the platforms. However, the diffraction behavior of occulters that incorporate curved surfaces (Buffington 2000) is less explored than for edge-type occulters. We illustrate the new possibilities by calculating the performance of some candidate systems using an analytic framework adapted from radio wave propagation (Vogler 1985) and alignment tolerances based on a recent concept for a two-platform guidance, navigation, and control system. Title: Eunis Observation of Pervasive Faint Fe XIX Line Emission from a Solar Active Region: Evidence for Coronal Heating By Nanoflares Authors: Brosius, J. W.; Daw, A. N.; Rabin, D. M. Bibcode: 2014AGUFMSH13C4130B Altcode: We present spatially resolved EUV spectroscopic measurements ofpervasive, faint Fe XIX 592.2 A line emission in an active regionobserved during the 2013 April 23 flight of the Extreme UltravioletNormal Incidence Spectrograph (EUNIS-13) sounding rocket instrument. With cooled detectors, high sensitivity, and high spectralresolution, EUNIS-13 resolves the lines of Fe XIX at 592.2 A (formedat temperature T around 8.9 MK) and Fe XII at 592.6 A (T around 1.6MK). The Fe XIX line emission, observed over an area in excess of4920 square arcsec (2.58x10^9 square km, more than 60% of the activeregion), provides strong evidence for the nanoflare heating model ofthe solar corona. No GOES events occurred in the region less than 2hours before the rocket flight, but a microflare was observed northand east of the region with RHESSI and EUNIS during the flight. Theabsence of significant upward velocities anywhere in the region,particularly the microflare, indicates that the pervasive Fe XIXemission is not propelled outward from the microflare site, but ismost likely attributed to localized heating (due to reconnection,wave dissipation, or some other mechanism) consistent with thenanoflare heating model of the solar corona. We measure average FeXIX/Fe XII intensity ratios of 0.070 outside the AR core, 0.22 inarea of bright coronal emission (the area in which the Fe XIIintensity exceeds half its maximum observed value), and 0.55 in theregion's hot core. Using the CHIANTI atomic physics database andassuming ionization equilibrium, we estimate corresponding Fe XIX/FeXII emission measure ratios of about 0.076, 0.23 and 0.59. Theemission measure ratios must be viewed with caution in light oflingering uncertainties in the Fe XII contribution functions.EUNIS-13 was supported by the NASA Heliophysics Division through itsLow Cost Access to Space program. Title: Smart materials optical mirrors Authors: Chen, Peter C.; Rabin, Douglas M. Bibcode: 2014SPIE.9143E..50C Altcode: We report the fabrication of imaging quality optical mirrors with smooth surfaces using carbon nanotubes embedded in an epoxy matrix. CNT/epoxy is a multifunctional or `smart' composite material that has sensing capabilities and can be made to incorporate self-actuation as well. Moreover, since the precursor is a low density liquid, large and lightweight mirrors can be fabricated by processes such as replication, spincasting, and 3D printing. The technology therefore holds promise for development of a new generation of lightweight, compact `smart' telescope mirrors with figure sensing and active or adaptive figure control. We report on measurements made of optical and mechanical characteristics. We discuss possible paths for future development. Title: Pervasive Faint Fe XIX Emission from a Solar Active Region Observed with EUNIS-13: Evidence for Nanoflare Heating Authors: Brosius, Jeffrey W.; Daw, Adrian N.; Rabin, D. M. Bibcode: 2014ApJ...790..112B Altcode: We present spatially resolved EUV spectroscopic measurements of pervasive, faint Fe XIX 592.2 Å line emission in an active region observed during the 2013 April 23 flight of the Extreme Ultraviolet Normal Incidence Spectrograph (EUNIS-13) sounding rocket instrument. With cooled detectors, high sensitivity, and high spectral resolution, EUNIS-13 resolves the lines of Fe XIX at 592.2 Å (formed at temperature T ≈ 8.9 MK) and Fe XII at 592.6 Å (T ≈ 1.6 MK). The Fe XIX line emission, observed over an area in excess of 4920 arcsec2 (2.58 × 109 km2, more than 60% of the active region), provides strong evidence for the nanoflare heating model of the solar corona. No GOES events occurred in the region less than 2 hr before the rocket flight, but a microflare was observed north and east of the region with RHESSI and EUNIS during the flight. The absence of significant upward velocities anywhere in the region, particularly the microflare, indicates that the pervasive Fe XIX emission is not propelled outward from the microflare site, but is most likely attributed to localized heating (not necessarily due to reconnection) consistent with the nanoflare heating model of the solar corona. Assuming ionization equilibrium we estimate Fe XIX/Fe XII emission measure ratios of ~0.076 just outside the AR core and ~0.59 in the core. Title: Composite telescope technology Authors: Chen, Peter C.; Rabin, Douglas Bibcode: 2014SPIE.9151E..30C Altcode: We report the development of optical mirrors based on polymer matrix composite materials. Advantages of this technology are low cost and versatility. By using appropriate combinations of polymers and various metallic and nonmetallic particles and fibers, the properties of the materials can be tailored to suit a wide variety of applications. We report the fabrication and testing of flat and curved mirrors made with metal powders, multiple mirrors replicated with high degree of uniformity from the same mandrels, cryogenic testing, mirrors made of ferromagnetic materials that can be actively or adaptively controlled by non-contact actuation, optics with very smooth surfaces made by replication, and by spincasting. We discuss development of a new generation of ultra-compact, low power active optics and 3D printing of athermal telescopes. Title: Further Analysis of Active Region Thermal Structure from EUNIS-13 Authors: Rabin, Douglas M.; Landi, Enrico; Daw, Adrian N.; Brosius, Jeffrey W. Bibcode: 2014AAS...22432339R Altcode: The 2013 April 23 flight of the Extreme Ultraviolet Normal Incidence Spectrograph (EUNIS) sounding rocket instrument returned high-quality spectra in two wavelength bands, 30.0-37.0 nm and 52.7-63.5 nm, sampling three active regions (11723, 11724, and 11726). The spectral lines in these bands probe a wide temperature range, 0.03 MK to 8 MK. We have demonstrated that the differential emission measure (DEM) varies significantly between different sub-regions of AR 11726. We extend this analysis to ARs 11723 and 11724 and include a wider selection of spectral lines to delineate better the variations in thermal structure. Title: Evidence for Impulsive Coronal Heating from EUNIS 2013 Authors: Daw, Adrian N.; Brosius, Jeffrey W.; Rabin, Douglas M.; Landi, Enrico; Klimchuk, James A. Bibcode: 2014AAS...22431204D Altcode: Pervasive, faint Fe XIX 592 Å line emission was observed in active regions by the Extreme Ultraviolet Normal Incidence Spectrograph (EUNIS) sounding rocket instrument on 23 April 2013. The broad spectral coverage (303-370 Å, 527-635 Å) and unprecedented dynamic range of the EUNIS observations includes emission lines of ionization stages from He I to Fe XX, and thus a wide temperature range of 0.03 to 10 MK. Comparison of observed line intensities with calculations demonstrates that the Fe XIX emission, formed at temperatures around 8 MK, is evidence of the faint hot emission predicted by impulsive heating models of the solar corona (such as nanoflares). Title: EUNIS 2013 and Beyond: Resolving the AIA 94 and 131 Å Bandpasses Authors: Daw, Adrian N.; Brosius, J. W.; Haas, J. P.; Landi, E.; Plummer, T.; Rabin, D. M.; Wang, T. Bibcode: 2013SPD....44...10D Altcode: The Extreme Ultraviolet Normal Incidence Spectrograph (EUNIS) sounding rocket instrument is a two-channel imaging spectrograph that observes the solar corona and transition region with high spectral resolution and a rapid cadence made possible by unprecedented sensitivity. The 2013 flight on 23 April at 17:30 UT incorporated a new wavelength channel covering the range 525-630 Å, the previously-flown 300-370 Å channel, and the first flight demonstration of cooled active pixel sensor (APS) arrays, resulting in high-signal-to-noise spectral coverage spanning a wide temperature range of 0.025 to 10 MK. Absolute radiometric calibration of the two channels is performed using a hollow cathode discharge lamp and NIST-calibrated AXUV-100G photodiode. For the 2013 flight, EUNIS co-observed dynamic coronal phenomena with DST/IBIS, SoHO/CDS, SDO/AIA and Hinode/EIS and contributes to the absolute radiometric calibrations of these instruments. Plans for future wavelength channels to cover the AIA 94 and 131 Å bandpasses and address the currently unresolved spectral lines (and therefore temperature responses) within them are presented. Title: First Results from the EUNIS 2013 Sounding Rocket Campaign Authors: Daw, Adrian N.; Rabin, D. M.; Brosius, J. W.; Haas, J. P.; Plummer, T.; Cauzzi, G.; Reardon, K. P.; Beck, C. Bibcode: 2013SPD....4410501D Altcode: The Extreme Ultraviolet Normal Incidence Spectrograph (EUNIS) sounding rocket launched 23 April 2013 at 17:30 UT, as part of a campaign including co-ordinated observations with the Dunn Solar Telescope/IBIS, Hinode/EIS, SoHO/CDS, RHESSI and SDO. EUNIS obtained the highest-resolution observations of the solar spectrum from 52-63 nm observed to date, as well as observations with the previously-flown waveband from 30-37 nm. The broad spectral coverage of the EUV observations includes emission lines of ionization stages from He I to Fe XIX, and thus a wide temperature range of 0.025 to 10 MK. Absolute radiometric calibration of EUNIS provides underflight calibration of CDS, EIS and AIA. Spectra were obtained with a 1.3 s cadence as the 660-arcsec long slit was rastered across two different regions. The observations captured a B-class flare in active region NOAA 11726 as well as active regions 11723, 11724, off-limb, quiet sun and a coronal hole. We discuss first results from anaysis of this rich and extensive data set. Title: PICTURE: a sounding rocket experiment for direct imaging of an extrasolar planetary environment Authors: Mendillo, Christopher B.; Hicks, Brian A.; Cook, Timothy A.; Bifano, Thomas G.; Content, David A.; Lane, Benjamin F.; Levine, B. Martin; Rabin, Douglas; Rao, Shanti R.; Samuele, Rocco; Schmidtlin, Edouard; Shao, Michael; Wallace, J. Kent; Chakrabarti, Supriya Bibcode: 2012SPIE.8442E..0EM Altcode: The Planetary Imaging Concept Testbed Using a Rocket Experiment (PICTURE 36.225 UG) was designed to directly image the exozodiacal dust disk of ǫ Eridani (K2V, 3.22 pc) down to an inner radius of 1.5 AU. PICTURE carried four key enabling technologies on board a NASA sounding rocket at 4:25 MDT on October 8th, 2011: a 0.5 m light-weight primary mirror (4.5 kg), a visible nulling coronagraph (VNC) (600-750 nm), a 32x32 element MEMS deformable mirror and a milliarcsecond-class fine pointing system. Unfortunately, due to a telemetry failure, the PICTURE mission did not achieve scientific success. Nonetheless, this flight validated the flight-worthiness of the lightweight primary and the VNC. The fine pointing system, a key requirement for future planet-imaging missions, demonstrated 5.1 mas RMS in-flight pointing stability. We describe the experiment, its subsystems and flight results. We outline the challenges we faced in developing this complex payload and our technical approaches. Title: Underflight Calibration of SOHO/CDS and Hinode/EIS with EUNIS-07 Authors: Wang, Tongjiang; Thomas, Roger J.; Brosius, Jeffrey W.; Young, Peter R.; Rabin, Douglas M.; Davila, Joseph M.; Del Zanna, Giulio Bibcode: 2011ApJS..197...32W Altcode: 2011arXiv1109.6598W Flights of Goddard Space Flight Center's Extreme Ultraviolet Normal Incidence Spectrograph (EUNIS) sounding rocket in 2006 and 2007 provided updated radiometric calibrations for Solar and Heliospheric Observatory/Coronal Diagnostic Spectrometer (SOHO/CDS) and Hinode/Extreme Ultraviolet Imaging Spectrometer (Hinode/EIS). EUNIS carried two independent imaging spectrographs covering wavebands of 300-370 Å in first order and 170-205 Å in second order. After each flight, end-to-end radiometric calibrations of the rocket payload were carried out in the same facility used for pre-launch calibrations of CDS and EIS. During the 2007 flight, EUNIS, SOHO/CDS, and Hinode/EIS observed the same solar locations, allowing the EUNIS calibrations to be directly applied to both CDS and EIS. The measured CDS NIS 1 line intensities calibrated with the standard (version 4) responsivities with the standard long-term corrections are found to be too low by a factor of 1.5 due to the decrease in responsivity. The EIS calibration update is performed in two ways. One uses the direct calibration transfer of the calibrated EUNIS-07 short wavelength (SW) channel. The other uses the insensitive line pairs, in which one member was observed by the EUNIS-07 long wavelength (LW) channel and the other by EIS in either the LW or SW waveband. Measurements from both methods are in good agreement, and confirm (within the measurement uncertainties) the EIS responsivity measured directly before the instrument's launch. The measurements also suggest that the EIS responsivity decreased by a factor of about 1.2 after the first year of operation (although the size of the measurement uncertainties is comparable to this decrease). The shape of the EIS SW response curve obtained by EUNIS-07 is consistent with the one measured in laboratory prior to launch. The absolute value of the quiet-Sun He II 304 Å intensity measured by EUNIS-07 is consistent with the radiance measured by CDS NIS in quiet regions near the disk center and the solar minimum irradiance recently obtained by CDS NIS and the Solar Dynamics Observatory/Extreme Ultraviolet Variability Experiment. Title: Quantitative Evaluation of Continuous Diffractive Baffles for Heliospheric Imagers Authors: Rabin, D. M. Bibcode: 2011AGUFMSH13B1971R Altcode: Wide-angle heliospheric imagers such as those carried on the SMEI and STEREO spacecraft require highly effective baffle systems to exclude diffracted light from the solar disk as well as other sources of stray light. Buffington (2000, Appl. Opt. 39, 2683-2686) has proposed replacing multi-vane baffle systems with a curved surface that can be thought of as the limiting case of closely spaced vanes. Buffington's experimental data showed that the diffractive performance of a continuous baffle is consistent with the limiting form expected from multi-vane diffraction on heuristic grounds, but a detailed prediction was not possible because multi-vane diffraction calculations assume that the diffractive edges act independently, an assumption that breaks down for a continuous surface. I present analytic calculations of diffraction from a curved surface and use them to evaluate the effectiveness of continuous-surface baffles for heliospheric imagers. Title: First Solar Images Using a Photon Sieve Authors: Daw, A. N.; Rabin, D. M.; Dunlap, L.; Vievering, J. Bibcode: 2011AGUFMSH13B1962D Altcode: The first solar images using a photon sieve were obtained in H-alpha at NASA Goddard Space Flight Center. The first sieve used consists of 1500 fresnel zones comprising 15 million holes in a chrome layer on a glass substrate to yield a focal length of 400 mm at a wavelength of 656.3 nm. Results of the observations are discussed, as well as the positive implications for the use of diffractive optics on deployable membranes for extremely high resolution (0.01 arcsec) imaging from space. Title: Electron Temperatures and Flow Speeds of the Low Solar Corona: MACS Results from the Total Solar Eclipse of 29 March 2006 in Libya Authors: Reginald, Nelson L.; Davila, Joseph M.; St. Cyr, O. C.; Rabin, Douglas M.; Guhathakurta, Madhulika; Hassler, Donald M.; Gashut, Hadi Bibcode: 2011SoPh..270..235R Altcode: 2011SoPh..tmp...68R; 2011SoPh..tmp...48R An experiment was conducted in conjunction with the total solar eclipse on 29 March 2006 in Libya to measure both the electron temperature and its flow speed simultaneously at multiple locations in the low solar corona by measuring the visible K-coronal spectrum. Coronal model spectra incorporating the effects of electron temperature and its flow speed were matched with the measured K-coronal spectra to interpret the observations. Results show electron temperatures of (1.10±0.05) MK, (0.70±0.08) MK, and (0.98±0.12) MK, at 1.1 R from Sun center in the solar north, east and west, respectively, and (0.93±0.12) MK, at 1.2 R from Sun center in the solar west. The corresponding outflow speeds obtained from the spectral fit are (103±92) km s−1, (0+10) km s−1, (0+10) km s−1, and (0+10) km s−1. Since the observations were taken only at 1.1 R and 1.2 R from Sun center, these speeds, consistent with zero outflow, are in agreement with expectations and provide additional confirmation that the spectral fitting method is working. The electron temperature at 1.1 R from Sun center is larger at the north (polar region) than the east and west (equatorial region). Title: Coronal Bright Points and Quiet Sun Areas Observed with EUNIS-07 and EIS Authors: Brosius, Jeffrey W.; Wang, T. J.; Rabin, D. M.; Thomas, R. J.; Landi, E. Bibcode: 2011SPD....42.1828B Altcode: 2011BAAS..43S.1828B The Extreme-Ultraviolet Normal-Incidence Spectrograph is a sounding rocket instrument with two independent but co-pointing imaging spectrographs. One spectrograph observes emission lines in a long-wavelength (LW) channel (300-370 A), while a second observes lines in a short-wavelength (SW) channel (170-205 A). The instrument was last flown on 6 November 2007 (EUNIS-07), when there were no active regions on the solar disk. After the flight, the absolute radiometric responses of both channels were derived from laboratory measurements obtained in the same facility used for pre-flight calibrations of SOHO/CDS and Hinode/EIS. Coordinated EUNIS-07 and EIS observations of quiet sun area near disk center reveal that the sensitivity of both EIS wavebands had diminished to 82% of their pre-launch values (Wang et al. 2011). Here we use the combined EUNIS-07 and EIS spectra to investigate quiet sun areas and small bright points observed by both instruments, as well as a larger, brighter bright point that was observed only by EUNIS-07. Title: Evaluation of Diffraction by a Rounded Surface Authors: Rabin, Douglas M. Bibcode: 2011SPD....42.1510R Altcode: 2011BAAS..43S.1510R Wide-angle heliospheric imagers such as those carried on the SMEI and STEREO spacecraft require highly effective baffle systems to exclude diffracted light from the solar disk as well as other sources of stray light. Buffington (2000, Appl. Opt. 39, 2683-2686) has proposed replacing multi-vane baffle systems with a curved surface that can be thought of as the limiting case of closely spaced vanes. Buffington's experimental data showed that the diffractive performance of a continuous baffle is consistent with the limiting form expected from multi-vane diffraction on dimensional grounds, but a detailed prediction was not possible because multi-vane diffraction calculations assume that the diffractive edges act independently, an assumption that breaks down for a continuous surface. I describe analytic calculations of diffraction from a smooth rounded surface based on the approach of Vogler (1985, Radio Sci. 20, 582-590). Title: New Capabilities of the EUNIS Sounding Rocket Instrument Authors: Daw, Adrian N.; Brosius, J.; Criscuolo, E.; Davila, J.; Haas, J. P.; Hilton, G.; Linard, D.; Plummer, T.; Rabin, D.; Thomas, R.; Varney, D.; Wang, T. Bibcode: 2011SPD....42.1502D Altcode: 2011BAAS..43S.1502D The upcoming flight of the Extreme Ultraviolet Normal Incidence Spectrograph (EUNIS) sounding rocket instrument, a two-channel imaging spectrograph that observes the solar corona and transition region with high spectral resolution and a rapid cadence made possible by unprecedented sensitivity, will incorporate a new wavelength channel and cooling of the active pixel sensor (APS) arrays. The new 52.4-63.0 nm channel incorporates a Toroidal Varied Line Space (TVLS) grating coated with B4C/Ir, providing broad spectral coverage and a wide temperature range of 0.025 to 10 MK. The APS arrays for both the 52-63 nm and 30-37 nm channels will be cooled to -20 C to reduce dark current noise. With the resulting read-noise limited performance, over a dozen new diagnostic line pairs become available in the two wavelength channels. To our knowledge, this will be the first flight demonstration of cooled APS arrays. EUNIS will co-observe dynamic coronal phenomena with SDO/AIA and Hinode/EIS and will contribute to the absolute radiometric calibrations of these instruments.

EUNIS is supported by NASA through the Low Cost Access to Space Program in Solar and Heliospheric Physics. Title: An Investigation of Solar Coronal Bright Points Based on EUV Spectra Obtained with EUNIS-07 Authors: Schaefer, R.; Brosius, J. W.; Bruhweiler, F.; Rabin, D. M.; Thomas, R.; Wang, T. Bibcode: 2010AGUFMSH31C1805S Altcode: The EUNIS sounding rocket instrument is a two-channel imaging spectrograph that observes the solar corona with a rapid cadence made possible by unprecedented sensitivity. The instrument was successfully flown on 2006 April 12 (EUNIS-06) and 2007 November 6 (EUNIS-07), providing hundreds of spectra in the wavelength ranges 170-205 A and 300-370 A with sustained cadences as fast as 1.3 s. The EUNIS-07 data have provided the first on-orbit radiometric calibration of Hinode's EIS and STEREO's SECCHI/EUVI. Although there were no active regions on the solar disk during this flight, EUNIS-07 repeatedly scanned across several small coronal bright points within a large area of quiet Sun near disk center. We fitted Gaussian profiles to emission lines formed at temperatures ranging from 0.05 MK to 2 MK (with particular attention to He II 304 A, Mg IX 368 A, and Fe XIV 334 A) in the spatially resolved EUV spectra. The resulting line profile fits are used to derive a series of bright point images that we investigate for brightness variations on time scales of one minute, as well as relative Doppler velocities. Evolution of the bright points on time scales of hours are investigated with magnetograms from SOHO's MDI. EUNIS is supported by the NASA Heliophysics Division through its Low Cost Access to Space Program in Solar and Heliospheric Physics, and is scheduled to fly again in 2011. EUNIS data are freely available to the solar physics community. RS acknowledges support under NSF/REU grant ATM-00552671 to CUA. JWB is supported by NASA grant NNX10AK45G. Title: Science Objectives for an X-Ray Microcalorimeter Observing the Sun Authors: Laming, J. Martin; Adams, J.; Alexander, D.; Aschwanden, M; Bailey, C.; Bandler, S.; Bookbinder, J.; Bradshaw, S.; Brickhouse, N.; Chervenak, J.; Christe, S.; Cirtain, J.; Cranmer, S.; Deiker, S.; DeLuca, E.; Del Zanna, G.; Dennis, B.; Doschek, G.; Eckart, M.; Fludra, A.; Finkbeiner, F.; Grigis, P.; Harrison, R.; Ji, L.; Kankelborg, C.; Kashyap, V.; Kelly, D.; Kelley, R.; Kilbourne, C.; Klimchuk, J.; Ko, Y. -K.; Landi, E.; Linton, M.; Longcope, D.; Lukin, V.; Mariska, J.; Martinez-Galarce, D.; Mason, H.; McKenzie, D.; Osten, R.; Peres, G.; Pevtsov, A.; Porter, K. Phillips F. S.; Rabin, D.; Rakowski, C.; Raymond, J.; Reale, F.; Reeves, K.; Sadleir, J.; Savin, D.; Schmelz, J.; Smith, R. K.; Smith, S.; Stern, R.; Sylwester, J.; Tripathi, D.; Ugarte-Urra, I.; Young, P.; Warren, H.; Wood, B. Bibcode: 2010arXiv1011.4052L Altcode: We present the science case for a broadband X-ray imager with high-resolution spectroscopy, including simulations of X-ray spectral diagnostics of both active regions and solar flares. This is part of a trilogy of white papers discussing science, instrument (Bandler et al. 2010), and missions (Bookbinder et al. 2010) to exploit major advances recently made in transition-edge sensor (TES) detector technology that enable resolution better than 2 eV in an array that can handle high count rates. Combined with a modest X-ray mirror, this instrument would combine arcsecondscale imaging with high-resolution spectra over a field of view sufficiently large for the study of active regions and flares, enabling a wide range of studies such as the detection of microheating in active regions, ion-resolved velocity flows, and the presence of non-thermal electrons in hot plasmas. It would also enable more direct comparisons between solar and stellar soft X-ray spectra, a waveband in which (unusually) we currently have much better stellar data than we do of the Sun. Title: Absolute Radiometric Calibration Of EUNIS, And Calibration Updates For Hinode/EIS And SOHO/CDS Authors: Wang, Tongjiang; Thomas, R. J.; Brosius, J. W.; Young, P. R.; Rabin, D. M.; Davila, J. M. Bibcode: 2010AAS...21640704W Altcode: 2010BAAS...41..860W The Extreme-Ultraviolet Normal-Incidence Spectrograph sounding rocket payload was flown in 2006 (EUNIS-06) and 2007 (EUNIS-07), each time carrying two independent imaging spectrographs covering wave bands of 300-370 Angstrom in first order and 170-205 Angstrom in second order. For each flight, the absolute radiometric response of the EUNIS long-wavelength (LW) channel was directly measured in the same facility used for pre-flight calibrations of SOHO/CDS and Hinode/EIS. The wavelength range of the EUNIS LW channel overlaps that of CDS/NIS-1, and so can provide a direct calibration update for it. The EUNIS-06 observation shows that the efficiency of CDS/NIS-1 has decreased by a factor about 1.7 compared to that of the previously implemented calibration. Here we present an update to the absolute calibration for Hinode/EIS derived with a technique that combines a direct comparison of line intensities observed in cospatial EUNIS-07 and EIS spectra, along with density- and temperature-insensitive line intensity ratios. Title: Absolute Radiometric Calibration of the EUNIS-06 170-205 Å Channel and Calibration Update for Coronal Diagnostic Spectrometer/Normal-Incidence Spectrometer Authors: Wang, Tongjiang; Brosius, Jeffrey W.; Thomas, Roger J.; Rabin, Douglas M.; Davila, Joseph M. Bibcode: 2010ApJS..186..222W Altcode: 2009arXiv0912.2328W The Extreme-Ultraviolet Normal-Incidence Spectrograph sounding-rocket payload was flown on 2006 April 12 (EUNIS-06), carrying two independent imaging spectrographs covering wavebands of 300-370 Å in first order and 170-205 Å in second order, respectively. The absolute radiometric response of the EUNIS-06 long-wavelength (LW) channel was directly measured in the same facility used to calibrate Coronal Diagnostic Spectrometer (CDS) prior to the Solar and Heliospheric Observatory (SOHO) launch. Because the absolute calibration of the short-wavelength (SW) channel could not be obtained from the same lab configuration, we here present a technique to derive it using a combination of solar LW spectra and density- and temperature-insensitive line intensity ratios. The first step in this procedure is to use the coordinated, cospatial EUNIS and SOHO/CDS spectra to carry out an intensity calibration update for the CDS NIS-1 waveband, which shows that its efficiency has decreased by a factor about 1.7 compared to that of the previously implemented calibration. Then, theoretical insensitive line ratios obtained from CHIANTI allow us to determine absolute intensities of emission lines within the EUNIS SW bandpass from those of cospatial CDS/NIS-1 spectra after the EUNIS LW calibration correction. A total of 12 ratios derived from intensities of 5 CDS and 12 SW emission lines from Fe X to Fe XIII yield an instrumental response curve for the EUNIS-06 SW channel that matches well to a relative calibration which relied on combining measurements of individual optical components. Taking into account all potential sources of error, we estimate that the EUNIS-06 SW absolute calibration is accurate to ±20%. Title: A Scalable Superconductor Bearing System For Lunar Telescopes And Instruments Authors: Chen, Peter C.; Rabin, D.; Van Steenberg, M. E. Bibcode: 2010AAS...21548102C Altcode: 2010BAAS...42R.570C We report on a new concept for a telescope mount on the Moon based on high temperature superconductors (HTS). Lunar nights are long (15 days), and temperatures range from 100 K to 30 K inside shadowed craters. Telescopes on the Moon therefore require bearing systems that can position and track precisely under cryogenic conditions, over long time periods, preferably with no maintenance, and preferably do not fail with loss of power. HTS bearings, consisting of permanent magnets levitated over bulk superconductors, are well suited to the task. The components do not make physical contact, hence there is no wear. The levitation is passive and stable; no power is required to maintain position. We report on the design and laboratory demonstration of a prototype two-axis pointing system. Unlike previous designs, this new configuration is simple and easy to implement. Most importantly, it can be scaled to accommodate instruments ranging in size from decimeters (laser communication systems) to meters (solar panels, communication dishes, optical telescopes, optical interferometers) to decameters and beyond (VLA-type radio interferometer elements). Title: Electron-Temperature Maps of the Low Solar Corona: ISCORE Results from the Total Solar Eclipse of 29 March 2006 in Libya Authors: Reginald, Nelson L.; St. Cyr, O. C.; Davila, Joseph M.; Rabin, Douglas M.; Guhathakurta, Madhulika; Hassler, Donald M. Bibcode: 2009SoPh..260..347R Altcode: We conducted an experiment in conjunction with the total solar eclipse of 29 March 2006 in Libya that measured the coronal intensity through two filters centered at 3850 Å and 4100 Å with bandwidths of ≈ 40 Å. The purpose of these measurements was to obtain the intensity ratio through these two filters to determine the electron temperature. The instrument, Imaging Spectrograph of Coronal Electrons (ISCORE), consisted of an eight inch, f/10 Schmidt Cassegrain telescope with a thermoelectrically-cooled CCD camera at the focal plane. Results show electron temperatures of 105 K close to the limb to 3×106 K at 1.3R. We describe this novel technique, and we compare our results to other relevant measurements. This technique could be easily implemented on a space-based platform using a coronagraph to produce global maps of the electron temperature of the solar corona. Title: Transition Region Velocity Oscillations Observed by EUNIS-06 Authors: Jess, D. B.; Rabin, D. M.; Thomas, R. J.; Brosius, J. W.; Mathioudakis, M.; Keenan, F. P. Bibcode: 2008ApJ...682.1363J Altcode: 2008arXiv0804.1629J Spectroscopic measurements of NOAA AR 10871, obtained with the Extreme Ultraviolet Normal Incidence Spectrograph (EUNIS) sounding rocket instrument on 2006 April 12, reveal velocity oscillations in the He II 303.8 Å emission line formed at T ≈ 5 × 104 K. The oscillations appear to arise in a bright active region loop arcade about 25'' wide which crosses the EUNIS slit. The period of these transition region oscillations is 26 +/- 4 s, coupled with a velocity amplitude of ±10 km s-1, detected over four complete cycles. Similar oscillations are observed in lines formed at temperatures up to T ≈ 4 × 105 K, but we find no evidence for the coupling of these velocity oscillations with corresponding phenomena in the corona. We interpret the detected oscillations as originating from an almost purely adiabatic plasma, and infer that they are generated by the resonant transmission of MHD waves through the lower active region atmospheres. Through the use of seismological techniques, we establish that the observed velocity oscillations display wave properties most characteristic of fast body global sausage modes. Title: Rapid Cadence EUNIS-06 Observations of a He II Transient Brightening in the Quiet Sun Authors: Brosius, Jeffrey W.; Rabin, Douglas M.; Thomas, Roger J. Bibcode: 2008ApJ...682..630B Altcode: We observed a transient brightening in the quiet Sun at rapid cadence (2.10 s) with the Extreme Ultraviolet Normal Incidence Spectrograph (EUNIS-06) sounding rocket instrument on 2006 April 12. The transient was visible only in He II at 303.78 Å (T ≈ 5 × 104 K), and its maximum temperature T was <4 × 105 K. Taking its linear extent along the EUNIS slit to be the diameter of a circular feature, the transient's solar surface area was 7.8 × 107 km2. EUNIS observed the brightening to begin at 18:12:52 and peak at 18:13:29 UT; coordinated observations with SOHO's EIT confirm that EUNIS observed the onset of the brightening. EUNIS spectra yield maximum and average He II intensity enhancements of 2.09 and 1.46, respectively, relative to the pre-event quiet Sun. He II line profiles from EUNIS reveal that relative upflows were persistent during the transient (with a maximum speed around 20 km s-1) and that the upflow speed and intensity were positively correlated. Variations in the observed He II intensity and relative Doppler velocity were neither abrupt not impulsive, but occurred slowly compared to the EUNIS cadence. The local photospheric longitudinal magnetic field strength measured with SOHO's MDI revealed no significant variability. The transient's measured properties are consistent with its identification as a blinker or an elementary blinker, and its observed behavior suggests a formation mechanism involving gentle chromospheric evaporation. Title: EUNIS-07: First Look Authors: Rabin, D. M.; Thomas, R. J.; Brosius, J. W. Bibcode: 2008AGUSMSP51A..07R Altcode: The Extreme Ultraviolet Normal Incidence Spectrograph (EUNIS) sounding rocket instrument is a two-channel imaging spectrograph that observes the solar corona with high spectral resolution and a rapid cadence made possible by unprecedented sensitivity. EUNIS flew for the first time on 2006 April 12 (EUNIS-06), returning over 140 science exposures at a cadence of 2.1 s; each exposure comprises six 1K x 1K active pixel sensor (APS) images, three for each wavelength channel (170-205 Å and 300-370 Å. Analysis of EUNIS-06 data has so far shed new light on the nature of coronal bright points, cool transients, and coronal loop arcades and has enabled calibration updates for TRACE and SOHO's CDS and EIT. EUNIS flew successfully again on 2007 November 6 (EUNIS-07). Because the APS arrays were operated in video rather than snapshot mode, a faster cadence of 1.3 s was possible (97% duty cycle), resulting in 276 science exposures. We present an overview of the EUNIS-07 spectra and describe the coordinated observing program executed by the Hinode Extreme ultraviolet Imaging Spectrograph (EIS) that will, in conjunction with the absolute radiometric calibration of EUNIS-07, result in the first on-orbit radiometric calibration of EIS. EUNIS data are freely available to the solar physics community. EUNIS is supported by the NASA Heliophysics Division through its Low Cost Access to Space Program in Solar and Heliospheric Physics. Title: EUNIS-06 Rapid Cadence Observations of a He II Transient Brightening in the Quiet Sun Authors: Brosius, J. W.; Rabin, D. M.; Thomas, R. J. Bibcode: 2008AGUSMSP51A..06B Altcode: We observed a transient brightening in the quiet Sun at rapid cadence (2.10 s) with the Extreme Ultraviolet Normal Incidence Spectrograph (EUNIS-06) sounding rocket instrument on 2006 April 12. The transient was visible only in He II at 303.78 Å (T ≍ 5 × 104 K), and its maximum temperature T was < 4 × 105 K. Taking its linear extent along the EUNIS slit to be the diameter of a circular feature, the transient's solar surface area was 7.8 × 107 km2. EUNIS observed the brightening to begin at 18:12:52 and peak at 18:13:29 UT; coordinated observations with SOHO's EIT confirm that EUNIS observed the onset of the brightening. EUNIS spectra yield maximum and average He II intensity enhancements of 2.09 and 1.46, respectively, relative to the pre-event quiet Sun. He II line profiles from EUNIS reveal that relative upflows were persistent during the transient (with a maximum speed around 20 km s-1) and that the upflow speed and intensity were positively correlated. Variations in the observed He II intensity and relative Doppler velocity were neither abrupt not impulsive, but occurred slowly compared to the EUNIS cadence. The local photospheric magnetic flux measured with SOHO's MDI revealed no significant variability. The transient's measured properties are consistent with its identification as a blinker or an elementary blinker, and its observed behavior suggests a formation mechanism involving gentle chromospheric evaporation. The EUNIS program is supported by NASA's Heliophysics Division through its Low Cost Access to Space Program in Solar and Heliospheric Physics. Title: EUNIS Underflight Calibrations of CDS, EIT, TRACE, EIS, and EUVI Authors: Thomas, R.; Wang, T.; Rabin, D. M.; Jess, D. B.; Brosius, J. W. Bibcode: 2008AGUSMSP51B..04T Altcode: The Extreme-Ultraviolet Normal-Incidence Spectrograph (EUNIS) is a sounding rocket instrument that obtains imaged high-resolution solar spectra. It has now had two successful flights, on 2006 April 12 and 2007 November 16, providing data to support underflight calibrations for a number of orbiting solar experiments on both occasions. A regular part of each campaign is the end-to-end radiometric calibration of the rocket payload carried out at RAL in the UK, using the same facility that provided pre-flight CDS and EIS calibrations. The measurements, traceable to primary radiometric standards, can establish the absolute EUNIS response within a total uncertainty of 10% over its full longwave bandpass of 300--370Å. During each EUNIS flight, coordinated observations are made of overlapping solar locations by all participating space experiments, and identified by subsequent image co-registrations, allowing the EUNIS calibrations to be applied to these other instruments as well. The calibration transfer is straightforward for wavelengths within the EUNIS LW bandpass, and is extended to other wavelengths by means of a series of temperature- and density-insensitive line-ratios, with one line of each pair in the calibrated band and the other in the transfer band. In this way, the EUNIS-06 flight is able to update the radiometric calibrations of CDS NIS1 (and 2nd-order NIS2 near 2x304Å), all four channels of EIT, and the three EUV channels of TRACE. The EUNIS-07 flight will further update those missions, as well as both channels of Hinode/EIS and all four channels of STEREO/SECCHI/EUVI. Future EUNIS flights have been proposed that will continue this underflight calibration service. EUNIS is supported by the NASA Heliophysics Division through its Low Cost Access to Space Program in Solar and Heliospheric Physics. Title: Analysis of a Solar Coronal Bright Point Extreme Ultraviolet Spectrum from the EUNIS Sounding Rocket Instrument Authors: Brosius, Jeffrey W.; Rabin, Douglas M.; Thomas, Roger J.; Landi, Enrico Bibcode: 2008ApJ...677..781B Altcode: We present a well-calibrated EUV spectrum of a solar coronal bright point observed with the Extreme Ultraviolet Normal Incidence Spectrograph (EUNIS) sounding rocket instrument on 2006 April 12. The coronal bright point brightened around 06:30 UT during a period of emerging magnetic flux and remained bright at least until the rocket flight around 18:12 UT, while the magnetic flux merged and canceled. Density-sensitive line intensity ratios yield mutually consistent coronal electron densities (Ne in cm-3) of log Ne ≈ 9.4. The differential emission measure (DEM, in cm-5 K-1) curve derived from the spectrum yields a peak of log DEM ≈ 20.70 at log T ≈ 6.15 and a local minimum of log DEM ≈ 20.15 at log T ≈ 5.35. Photospheric (not coronal) element abundances are required to achieve equality and consistency in the DEM derived from lines of Mg V, Mg VI, Mg VII, and Ca VII (with a low first ionization potential, or FIP) and lines from Ne IV and Ne V (with a high FIP) formed at transition region temperatures. The bright point's photospheric abundance is likely produced by reconnection-driven chromospheric evaporation, a process that is not only central to existing bright point models, but also consistent with measurements of relative Doppler velocities. Title: Analysis of a Bright Point Spectrum From the Extreme Ultraviolet Normal Incidence Spectrograph (EUNIS) Sounding Rocket Instrument Authors: Brosius, J. W.; Rabin, D. M.; Thomas, R. J. Bibcode: 2007AGUFMSH21B..04B Altcode: We present a well-calibrated spectrum of a bright point observed with EUNIS on 2006 April 12. Coordinated observations with SOHO's EIT and MDI were also obtained. The bright point brightened around 06:30 UT during a period of emerging magnetic flux, and remained bright at least until the rocket flight around 18:12 UT while the magnetic flux merged and canceled. Density-sensitive line intensity ratios yield mutually consistent coronal electron densities log Ne ~ 9.5. Based on the method of Landi & Landini (1997), the differential emission measure (DEM) curve derived from the spectrum yields a peak of log DEM ~ 20.70 at log T ~ 6.15, and a local minimum of log DEM ~ 20.15 at log T ~ 5.35. We find that photospheric (not coronal) element abundances are required to achieve equality and consistency in the DEM derived from lines of Mg V, Mg VI, Mg VII, Ca VII (with a low first ionization potential, or FIP) and lines from Ne IV and Ne V (with a high FIP) formed at transition region temperatures. The bright point's photospheric abundance is likely produced by reconnection-driven chromospheric evaporation, a process that is not only central to existing bright point models (e.g., Priest, Parnell, & Martin 1994; Longcope 1998), but also consistent with measurements of relative Doppler velocities (e.g., ± 26 km/s for Fe XIV, ± 35 km/s for Fe XVI) previously presented by Brosius, Rabin, & Thomas (2007). The EUNIS program is supported by NASA's Heliophysics Division through its Low Cost Access to Space Program in Solar and Heliospheric Physics. We thank the entire EUNIS team for the concerted effort that led to a successful first flight. Title: Radiometric Calibration of EUNIS-06 With Theoretical Predicted `Insensitive' Line Ratios Authors: Wang, T.; Brosius, J. W.; Thomas, R. J.; Rabin, D. M. Bibcode: 2007AGUFMSH53A1049W Altcode: The Extreme-Ultraviolet Normal-Incidence Spectrograph (EUNIS) is a sounding-rocket payload that obtains imaged high-resolution spectra of solar active and quiet-Sun regions, providing information about the corona and upper transition region. EUNIS incorporates two independent, co-pointing imaging spectrographs, one covering EUV lines between 300 and 370 Å\ seen in first order (the longwave [LW] channel), and a second covering lines between 170 and 205 Å\ seen in second order (the shortwave [SW] channel). Shortly after the payload's initial successful flight on 2006 April 12, a complete end-to-end radiometric calibration of its LW bandpass was carried out at the Rutherford Appleton Laboratory in England. Here we develop and apply a technique for deriving the absolute radiometric calibration of its SW bandpass from these direct LW results by means of density- and temperature-insensitive line intensity ratios. The first step is to use the EUNIS LW calibration to get absolute intensities for EUV lines recorded from solar positions along its LW slit during the 2006 flight. Then co-registered SOHO/CDS images taken within minutes of the flight are used to transfer these absolute values to solar locations observed by the EUNIS SW slit, spatially offset by about 1 arcmin. Finally, theoretical `insensitive' line ratios obtained from CHIANTI allow us to determine absolute intensities of emission lines within the EUNIS SW bandpass from those observed in its LW channel. A total of 29 ratios composed of 11 LW and 15 SW emission lines from Fe~X - Fe~XIII yield an instrumental response curve that matches very well to a relative calibration which relied on combining measurements of individual optical components. The second EUNIS flight, now scheduled for 2007 October 30, will make coordinated observations and provide similar calibration updates for Hinode/EIS. We will also present some preliminary results from the new observations. EUNIS is supported by the NASA Heliophysics Division through its Low Cost Access to Space Program in Solar and Heliospheric Physics. Title: Advances in Solar Coronagraphy Authors: Rabin, D.; St. Cyr, O. C.; Davila, J. M. Bibcode: 2007lyot.confE..18R Altcode: Could Bernard Lyot have imagined the protean forms in which his most notable invention, the coronagraph, would appear 75 years later? Could he have foreseen that the most widely used solar coronagraphs would be based in space, or that coronagraphs would seek to image planets and disks around other stars? Perhaps so - he was far more than a builder of creative instruments. I will discuss advances in solar coronagraphy since Lyot's time, in both the science that drives the observations and the technology that sustains them. Title: Absolute Radiometric Calibration of EUNIS-06 Authors: Thomas, Roger J.; Rabin, D. M.; Haas, J. P.; Kent, B. J.; Paustian, W.; Jess, D. B. Bibcode: 2007AAS...210.2508T Altcode: 2007BAAS...39..132T The Extreme-Ultraviolet Normal-Incidence Spectrometer (EUNIS) is a sounding-rocket payload that obtains imaged high-resolution spectra of individual solar features, providing information about the Sun's corona and upper transition region. Shortly after its successful initial flight last year, a complete end-to-end calibration was carried out to determine the instrument's absolute radiometric response over its longwave bandpass of 300 - 370 Å. The measurements were done at the Rutherford-Appleton Laboratory (RAL) in England, using the same vacuum facility and EUV radiation source used in the pre-flight calibrations of both SOHO/CDS and Hinode/EIS, as well as in three post-flight calibrations of our SERTS sounding rocket payload, the precursor to EUNIS. The unique radiation source provided by the Physikalisch-Technische Bundesanstalt (PTB) had been absolutely calibrated to a relative uncertainty of 7% (1σ) at 12 wavelengths covering our bandpass directly against the Berlin electron storage ring BESSY, which is itself a primary radiometric source standard. Scans of the EUNIS aperture were made to determine the instrument's absolute spectral sensitivity to ± 25%, considering all sources of error, and demonstrate that EUNIS-06 was the most sensitive solar EUV spectrometer flown to date. The results will be matched against prior calibrations which relied on combining measurements of individual optical components, and on comparisons with theoretically predicted 'insensitive' line ratios. Coordinated observations were made during the EUNIS-06 flight by SOHO/CDS and EIT that will allow re-calibrations of those instruments as well. In addition, future EUNIS flights will provide similar calibration updates for TRACE, Hinode/EIS, and STEREO/SECCHI/EUVI.

EUNIS is supported by the NASA Heliophysics Division through its Low Cost Access to Space Program in Solar and Heliospheric Physics. Title: Forecast of the Amplitude of Solar Cycle 24 Based on the Disturbed Days Precursor Authors: Rabin, Douglas M. Bibcode: 2007AAS...210.9205R Altcode: 2007BAAS...39..209R R. J. Thompson (1993, Solar Physics 148, 383) exhibited a significant linear relationship between the number of geomagnetically disturbed days (those that exceed some threshold value of the Ap or aa index) in a solar cycle and the sum of the peak sunspot number in that cycle and the next cycle. Thus, the number of disturbed days during a full cycle, together with the peak sunspot number in that cycle, is a predictor of the amplitude of the next cycle. The work reported here applies Thompson’s method to the current cycle. Linear relationships as described above are derived both for the pure aa record (1868-2006) and for a composite of aa (1868-1931) and Ap (1932-2006). For the composite record, the relationship between aa and Ap is determined cycle-by-cycle during the period of overlap. The method is tested for sensitivity to the adopted Ap (or equivalent aa) threshold. The highest smoothed monthly sunspot number for Cycle 24 is forecasted to be Rz = 115 ± 30, where the uncertainty is conservatively based on the full spread of the data around the fitted line in the sunspot number direction. In terms of smoothed monthly 10.7-cm radio flux, the forecast is F10.7 = 164 ± 28. Title: EUNIS And SOHO Observations Of A Cool Transient Brightening In The Quiet Sun Authors: Brosius, Jeffrey W.; Rabin, D. M.; Thomas, R. J. Bibcode: 2007AAS...210.2507B Altcode: 2007BAAS...39..132B The Extreme Ultraviolet Normal Incidence Spectrograph (EUNIS) sounding rocket instrument observed a cool transient brightening in the quiet Sun during its first flight on 2006 April 12. The brightening appeared in emission from He II, formed at temperatures around 50,000 K (log T = 4.7), but was not evident in emission from ions formed at greater temperatures, including Mg VI (log T = 5.6), Mg IX (log T = 6.0), and Fe XIV (log T = 6.3). Of these and other lines in the EUNIS spectra, only lines from He II and Mg IX were strong enough in the quiet Sun to measure relative Doppler velocities during this transient; He II revealed continuous upflows around 15 km/s while Mg IX revealed no significant velocities. The average He II intensity enhancement factor observed with EUNIS was 1.34, and its maximum was 1.84. Coordinated observations with SOHO's EIT reveal a source area of 3.3x10^7 km^2, in which the average He II intensity enhancement factor was 1.39 and its maximum was 1.81; the transient did not appear in EIT's hotter wavebands. Variations in the local magnetic field strength measured with SOHO's MDI were marginal. The EUNIS program is supported by NASA through its Low Cost Access to Space Program in Solar and Heliospheric Physics. Title: Doppler Velocities Measured in Coronal Emission Lines from a Bright Point Observed with the EUNIS Sounding Rocket Authors: Brosius, Jeffrey W.; Rabin, Douglas M.; Thomas, Roger J. Bibcode: 2007ApJ...656L..41B Altcode: Spectroscopic measurements of a coronal bright point obtained with the Extreme Ultraviolet Normal Incidence Spectrograph (EUNIS) sounding rocket instrument on 2006 April 12 show both upflows and downflows in all five of the best observed emission lines. Relative velocities on opposite sides of the feature were found to be +/-15 km s-1 in the line of He II 303.8 Å (formed at T~5×104 K), +/-14 km s-1 in Mg IX 368.1 Å (T~9.5×105 K), +/-26 km s-1 in Fe XIV 334.2 Å (T~2.0×106 K), and +/-35 km s-1 in both Fe XVI 335.4 and 360.8 Å (T~2.5×106 K). The latter are the hottest lines for which Doppler velocities have been reported in a bright point. Photospheric longitudinal magnetograms reveal that the photospheric magnetic fields underlying the bright point were canceling during the EUNIS observation. Based on existing bright point models, this suggests that the observed hot flows were associated with magnetic reconnection. Title: Preliminary EUNIS-06 EUV Spectral Catalog Authors: Thomas, Roger J.; Rabin, D. M. Bibcode: 2006SPD....37.0105T Altcode: 2006BAAS...38..216T The recent 2006 April 12 flight of NASA/GSFC's sounding rocket payload, the EUV Normal-Incidence Spectrograph (EUNIS-06), produced 145 spectral images in each of two optical channels with passbands of 170--205 Å and 300--370 Å, respectively. These spectra are spatially resolved along slit lengths of about 660 arcsec covering portions of NOAA Active Region 10871 at S07E28, as well as quiet areas near disk center. We present here examples of spatial variations recorded in some of the stronger lines, along with a preliminary catalog of all spectral lines found by averaging the complete data set.EUNIS is supported by the NASA Heliophysics Division's Solar & Heliospheric Physics Supporting Research and Technology and Low Cost Access to Space Program. Title: First Results from EUNIS-06 Authors: Rabin, Douglas M.; Thomas, R. J.; Davila, J. M. Bibcode: 2006SPD....37.0106R Altcode: 2006BAAS...38..216R The Extreme Ultraviolet Normal-Incidence Spectrograph (EUNIS) sounding rocket experiment successfully completed its first flight on 12 April 2006 from White Sands Missile Range, obtaining 145 science images in each of two wavelength channels. EUNIS is designed to investigate the energetics of the solar corona and hotter transition region through high-resolution imaging spectroscopy with a rapid (2-3 second) cadence. The two independent optical systems of EUNIS simultaneously record spectra over two passbands (170-205 Å and 300-370 Å), each spatially resolved along slit lengths of about 660 arcsec. The longwave channel includes He II 304 Å and strong lines from Fe XI-XVI. The shortwave passband has a sequence of very strong Fe IX-XIII lines. Together, the EUNIS telescopes furnish a wide range of temperature and density diagnostics and enables underflight calibration of instrumental passbands on the SOHO, TRACE, Solar-B, and STEREO missions.

We present an overview of the science images from the first flight with emphasis on transient phenomena. The target was active region NOAA 10871 and adjacent quiet areas. Spectra were recorded with exposure times as short as 0.1 s, demonstrating that EUNIS is the most sensitive solar EUV spectrograph in operation, with over 100 times the throughput of its predecessor, the Solar Extreme ultraviolet Research Telescope and Spectrograph (SERTS).

EUNIS is supported by the NASA Heliophysics Division's Solar & Heliospheric Physics Supporting Research and Technology and Low Cost Access to Space Program. Title: Component Radiometric Calibrations of the EUV Normal-Incidence Spectrograph (EUNIS) Authors: Thomas, R. J.; Rabin, D. M. Bibcode: 2005AAS...20711111T Altcode: 2005BAAS...37.1343T The EUV Normal-Incidence Spectrograph (EUNIS) is a sounding rocket experiment that will investigate the energetics of the solar corona and hotter transition region through high-resolution imaging spectroscopy with a rapid (2 s) cadence. EUNIS features independent optical systems to record spatially co-aligned spectra simultaneously over its two bandpasses of 170--205 and 300--370 Å. All the components in the detection chain have been characterized, including multilayer telescope mirrors, lithographic slits, multilayer diffraction gratings, microchannel-plate intensifiers, and active-pixel sensors. The results demonstrate that EUNIS is the most sensitive solar EUV spectrograph in existence. Its first flight is scheduled for 2005 November. EUNIS is supported by NASA RTOP 432-03-31. Title: First Results From EUNIS 2005 Authors: Rabin, D. M.; Thomas, R. J.; Davila, J. M.; Brosius, J. W.; Swartz, M.; Jordan, S. D. Bibcode: 2005AGUFMSH41B1122R Altcode: The Extreme Ultraviolet Normal-Incidence Spectrograph (EUNIS) is a sounding rocket experiment to investigate the energetics of the solar corona and hotter transition region through high-resolution imaging spectroscopy with a rapid (2 second) cadence. Pre-flight characterization of throughput has demonstrated that EUNIS is the most sensitive solar EUV spectrograph in existence, having over 100 times the throughput of its predecessor, the Solar Extreme ultraviolet Research Telescope and Spectrograph (SERTS). We report initial results from the first flight in November 2005 from White Sands Missile Range. The main scientific goal of the first EUNIS flight is to extend the investigation of transient phenomena, such as nanoflares and blinkers, to shorter timescales than has been possible with previous EUV spectrographs. The two independent optical systems of EUNIS record spatially co-aligned spectra over two passbands (170--205 Å and 300--370 Å) simultaneously with spectral resolution of 60 mÅ or 120 mÅ, respectively. The longwave passband includes He II 304 Å and strong lines from Fe XI--XVI. The shortwave passband has a sequence of very strong Fe IX--XIII lines. Together, the EUNIS telescopes furnish a wide range of temperature and density diagnostics and enable underflight calibration of instrumental passbands on the SOHO, TRACE, Solar-B, and STEREO missions. Title: Measured Pre-Flight Performance of the Extreme Ultraviolet Normal Incidence Spectrograph (EUNIS) Authors: Thomas, R. J.; Rabin, D. M.; Nowak, M. D.; Gum, J. S.; Seely, J. F.; Seshadri, S.; Siegmund, O. H. Bibcode: 2005AGUSMSP43A..06T Altcode: The Extreme Ultraviolet Normal-Incidence Spectrograph (EUNIS) is a sounding rocket experiment that will investigate the energetics of the solar corona and hotter transition region through high-resolution imaging spectroscopy with a rapid (2 s) cadence. EUNIS features independent optical systems to record spatially co-aligned spectra over the two bandpasses 170--205 Å and 300--370 Å simultaneously. All the components in the detection chain have been characterized, including multilayer telescope mirrors, lithographic slits, multilayer diffraction gratings, microchannel plate intensifiers, and active pixel sensors. The results demonstrate that EUNIS is the most sensitive solar EUV spectrograph in existence. Its first flight is scheduled for 2005 August. Title: Coronal Heating, Spicules, and SolarB Authors: Moore, R. L.; Falconer, D. A.; Porter, J. G.; Hathaway, D. H.; Yamauchi, Y.; Rabin, D. M. Bibcode: 2004ASPC..325..283M Altcode: We summarize certain observations of coronal luminosity, network magnetic flux, spicules, and macrospicules. These observations together imply that in quiet regions that are not influenced by active regions the coronal heating comes from magnetic activity in the edges of the network flux, possibly from explosions of sheared core fields around granule-sized inclusions of opposite-polarity flux. This scenario can be tested by SolarB. Title: The Extreme Ultraviolet Normal Incidence Spectrograph (EUNIS) Authors: Rabin, D.; Davila, J.; Thomas, R. J.; Engler, C.; Irish, S.; Keski-Kuha, R.; Novello, J.; Nowak, M.; Payne, L.; Rodriguez, I.; Saha, T.; Scott, R.; Swartz, M.; Trimble, M.; White, L.; Seshadri, S. Bibcode: 2003SPD....34.2007R Altcode: 2003BAAS...35..845R EUNIS is a high-efficiency extreme ultraviolet spectrometer that is expected to fly for the first time in 2004 as a sounding rocket payload. Using two independent optical systems, EUNIS will probe the structure and dynamics of the inner solar corona high spectral resolution in two wavelength regions: 17-21 nm with 3.5 pm resolution and 30-37 nm with 7 pm resolution. The long wavelength channel includes He II 30.4 nm and strong lines from Fe XI-XVI; the short wavelength channel includes strong lines of Fe IX-XIII. Angular resolution of 2 arcsec is maintained along a slit covering a full solar radius.

EUNIS will have 100 times the throughput of the highly successful SERTS payloads that have preceded it. There are only two reflections in each optical channel, from the superpolished, off-axis paraboloidal primary and the toroidal grating. Each optical element is coated with a high-efficiency multilayer coating optimized for its spectral bandpass. The detector in each channel is a microchannel plate image intensifier fiber-coupled to three 1K x 1K active pixel sensors.

EUNIS will obtain spectra with a cadence as short as 1 sec, allowing unprecedented studies of the physical properties of evolving and transient structures. Diagnostics of wave heating and reconnection wil be studied at heights above 2 solar radii, in the wind acceleration region. The broad spectral coverage and high spectral resolution will provide superior temperature and density diagnostics and will enable underflight calibration of several orbital instruments, including SOHO/CDS and EIT, TRACE, Solar-B/EIS, and STEREO/EUVI.

EUNIS is supported by NASA through the Low Cost Access to Space Program in Solar and Heliospheric Physics. Title: SUMI - The Solar Ultraviolet Magnetograph Investigation Authors: Porter, J. G.; West, E. A.; Davis, J. M.; Gary, G. A.; Noble, M. W.; Thomas, R. J.; Rabin, D. M.; Uitenbroek, H. Bibcode: 2003SPD....34.2015P Altcode: 2003BAAS...35..847P Solar physics has been successful in characterizing the full vector magnetic field in the photosphere, where the ratio of gas pressure to magnetic pressure (β ) is greater than 1. However, at higher levels in the atmosphere, where β is much less than 1 and flares and CMEs are believed to be triggered, observations are difficult, severely limiting the understanding of these processes. In response to this situation, we are developing SUMI (the Solar Ultraviolet Magnetograph Investigation) a unique instrument designed to measure the circular and linear polarization of upper chromospheric Mg II lines (280 nm) and circular polarization of transition region C IV lines (155 nm). To date the telescope mirrors have been built, tested and coated with dielectric stacks designed to reflect only the wavelengths of interest. We have also developed a unique UV polarimeter and completed the design of a high-resolution spectrograph that uses dual toroidal varied-line-space (TVLS) gratings. Incorporating measurements of those components developed so far, the revised estimate of the system throughput exceeds our original estimate by more than an order of magnitude. A sounding rocket flight is anticipated in 2006. Our objectives and progress are detailed in this presentation.

This work is supported by NASA SR&T. Title: SHARPI: Solar High Angular Resolution Photometric Imager Authors: Rabin, D.; Davila, J.; Content, D.; Keski-Kuha, R.; Michael, S. Bibcode: 2002AAS...200.5606R Altcode: 2002BAAS...34..735R Observing the lower solar atmosphere with enough linear resolution (< 100 km) to study individual magnetic flux tubes and other features on scales comparable to the photon mean free path remains a challenging and elusive goal. Space-borne instruments based on conventional heavy optics proved to be too expensive, and adaptive optics on the ground made slow progress for many years. Yet, the scientific case for high-resolution imaging and magnetography has only become more compelling over the last ten years. Today, ground-based adaptive optics is a promising approach for small fields of view at visible wavelengths. Space experiments will need to employ lightweight optics and low-cost platforms. The Sunrise balloon experiment is one example. We describe a concept for a sounding rocket experiment that will achieve 0.1-arcsecond imaging using a lightweight, ultraprecise 55-cm mirror in the far ultraviolet (160 nm continuum, Lyman alpha, and possibly C IV 155 nm). The f/1.2 parabolic primary mirror is entering the final stages of production. The mirror is a ULE honeycomb design with front and back face sheets. The front sheet will be figured to 6.3 nm rms with microroughness 1 nm or better. For the initial proof of concept, we describe a no-frills, high-cadence imager aboard a Black Brant sounding rocket. Development of lightweight UV/EUV optics at Goddard Space Flight Center has been supported by the GSFC Internal Research and Development program. Title: Observed properties of the solar cycle dynamo Authors: Rabin, Douglas Bibcode: 2002ocnd.confE..32R Altcode: No abstract at ADS Title: The New Solar Corona Authors: Aschwanden, Markus J.; Poland, Arthur I.; Rabin, Douglas M. Bibcode: 2001ARA&A..39..175A Altcode: We focus on new observational capabilities (Yohkoh, SoHO, TRACE), observations, modeling approaches, and insights into physical processes of the solar corona. The most impressive new results and problems discussed in this article can be appreciated from the movies available on the Annual Reviews website and at http://www.lmsal.com/pub/araa/araa.html. "The Sun is new each day." Heraclites (ca 530-475 BC) "Everything flows." Heraclites (ca 530-475 BC) Title: Overview of the Solar Ultraviolet Magnetograph Investigation Authors: West, Edward A.; Porter, Jason G.; Davis, John M.; Gary, G. Allen; Rabin, Douglas M.; Thomas, Roger J.; Davila, Joseph M. Bibcode: 2000SPIE.4139..350W Altcode: Traditional magnetographs measure the solar magnetic field at the visible 'surface' of the Sun, the photosphere. The Solar Ultraviolet Magnetograph Investigation (SUMI) is a hardware development study for an instrument to measure the solar magnetic field higher in the atmosphere, in the upper chromosphere and in the transition region at the base of the corona. The magnetic pressure at these levels is much stronger than the gas pressure (in contrast to the situation at the photosphere), so the field controls the structure and dynamics of the atmosphere. Rapid changes in the magnetic structure of the atmosphere become possible at this height, with the release of energy. Measurements of the vector magnetic field in this region will significantly improve our understanding of the physical processes heating the Sun's upper atmosphere and driving transient phenomena such as flares and coronal mass ejections. The instrument will incorporate new technologies to achieve the polarization efficiencies required to measure the magnetic splitting of lines in the VUV an UV (CIV at 1550 angstrom and MgII at 2800 angstrom). We describe the scientific goals, the optical components that are being developed for a sounding rocket program, and the SUMI baseline design. Title: Chromosphere: Fibrils Authors: Rabin, D. Bibcode: 2000eaa..bookE2004R Altcode: Fibrils are dark, elongated, curvilinear patterns in the CHROMOSPHERE as seen through a filter that isolates the Hα spectral absorption line of hydrogen. Well-developed fibrils occur in and around SOLAR ACTIVE REGIONS (figure 1) and SOLAR FILAMENT CHANNELS.... Title: The Spatial Distribution of Molecules in Sunspots Authors: Rabin, D. M.; Clark, T. A.; Bergman, M. W. Bibcode: 2000SPD....31.0118R Altcode: 2000BAAS...32..804R We report preliminary results from a program to map the concentration of H2O, OH, and SiO in the atmospheres of sunspots using imaging infrared spectroscopy. The water molecule is confined to the inner core of the umbra, whereas OH can sometimes be detected in the penumbra. Plots of line depth against continuum intensity show an abrupt onset of absorption at a different intensity for each molecule. A larger sample is needed to decide to what extent such features are characteristic. Evershed flow is seen in OH in the penumbra of spots near the limb, with typical outward velocities of 1-2 km s-1. Spatial imaging of molecular concentrations in sunspots should eventually provide new diagnostics for the temperature structure of the umbral atmosphere, as yet poorly determined. This work has been supported by the University of Calgary and by the National Science Foundation through its support of NSO/NOAO. Title: SUMI: The Solar Ultraviolet Magnetograph Authors: Davis, J. M.; Porter, J. G.; Gary, G. A.; West, E. A.; Rabin, D. M.; Thomas, R. J.; Davila, J. M. Bibcode: 2000SPD....31.0299D Altcode: 2000BAAS...32..828D A major focus of solar physics is the measurement of the temporal and spatial variability of solar magnetic fields from the photosphere into the lower corona, together with the study of how their behavior produces the dynamic phenomena in this region such as flares and CMEs. Considerable success has been achieved in the characterization of the full vector field in the photosphere, where β , the ratio of the gas pressure to the magnetic pressure, is gtrsim1. At higher levels in the atmosphere where β <<1, the magnetic field (through the Lorentz force) controls the structure and dynamics of the solar atmosphere, and rapid changes in structure with release of energy become possible. However, observations of the field at these higher levels have proven to be difficult, placing a serious limitation on our understanding of the physical processes occurring there. This poster will discuss the Solar Ultraviolet Magnetograph Investigation (SUMI), a hardware development study for an instrument capable of measuring the polarization in ultraviolet lines of C IV and Mg II formed in the transition region and upper chromosphere. We are currently developing optical technologies necessary to build an instrument that will achieve a major advance in performance over that of earlier attempts (e.g., SMM/UVSP). Initially configured as a sounding rocket payload, such a UV magnetograph would allow us to make exploratory measurements extending the observation of solar magnetic fields into new and dynamic regimes. This work is supported by NASA through the SEC Program in Solar Physics and the program for Technology Development for Explorer Missions and Sofia. Title: Synoptic Solar Physics -- 18th NSO/Sacramento Peak Summer Workshop Authors: Balasubramaniam, K. S.; Harvey, Jack; Rabin, D. Bibcode: 1998ASPC..140.....B Altcode: 1998ssp..conf.....H No abstract at ADS Title: The Solar Magnetic Field in Three Dimensions Authors: Rabin, Douglas Bibcode: 1997SoPh..174..281R Altcode: Historically, our understanding of the solar magnetic field has been shaped by an interplay between theoretical ideas about the subsurface dynamo and precise measurements of magnetic flux at the level of the photosphere. Today we have an unprecedented ability to measure, or to infer from measurements, properties of the magnetic field at every level from the solar interior to interplanetary space, although photospheric observations still lead the way in completeness and precision. I review the state of our capabilities to measure or calculate the magnetic field and suggest that the next major goal should be to follow specific magnetic structures in space and time from before they emerge until they can no longer be detected at any level. Title: Toward Zeeman Magnetometry in the Corona: Line-of-Sight Effects Authors: Rabin, D. Bibcode: 1997SPD....28.0144R Altcode: 1997BAAS...29..887R One of the motivations for a large-aperture ground-based coronagraph is the possibility of measuring magnetic flux in the solar corona using the Zeeman sensitivity (Lande g = 1.5) of emission lines such as Fe XIV 530.3 nm, Fe X 637.4 nm, and Fe XIII 1074.7 nm. However, because the corona is optically thin, it is necessary to consider the effects of superposition along the line-of-sight on the interpretation of a detected Zeeman signal. Simple models are used to explore and illustrate the likely importance of line-of-sight confusion. Title: F. Espenak and J. Anderson, Total Solar Eclipse of 1999 August 11, NASA Reference Publication 1398 Authors: Rabin, Douglas Bibcode: 1997EM&P...76..123R Altcode: No abstract at ADS Title: Microflaring in Sheared Core Magnetic Fields and Episodic Heating in Large Coronal Loops Authors: Porter, J. G.; Falconer, D. A.; Moore, R. L.; Harvey, K. L.; Rabin, D. M.; Shimizu, T. Bibcode: 1996AAS...188.7018P Altcode: 1996BAAS...28..941P We have previously reported that large, outstandingly-bright coronal loops within an active region or stemming from an active region have one end rooted around a magnetic island of included polarity that is itself a site of locally enhanced coronal heating (X-ray bright point) [Porter et al 1996, in Proceedings of the Yohkoh Solar/Stellar IAU Symposium, ed. Y. Uchida, T. Kosugi, H.S. Hudson (Kluwer: Dordrecht), in press]. This suggests that exceptional magnetic structure in and around the magnetic island fosters magnetic activity, such as microflaring, that results in the enhanced coronal heating in both the compact core field around the island and in the body of large loops that extend from this site. We have also reported that enhanced coronal heating in active regions goes hand-in-hand with strong magnetic shear in the core magnetic fields along polarity neutral lines (Falconer et al 1995, BAAS, 27(2), 976). Here, by combining MSFC vector magnetograms with an NSO full-disk magnetogram and Yohkoh SXT coronal images, we examine the incidence of sheared core fields, enhanced coronal heating, and microflaring in two active regions having several good examples of enhanced extended coronal loops. It appears that the localized microflaring activity in sheared core fields is basically similar whether the core field is on the neutral line around an island of included polarity or on the main neutral line of an entire bipolar active region. This suggests that the enhanced coronal heating in an extended loop stemming from near a polarity inversion line requires a special field configuration at its foot to plug it into the activity at the neutral line, rather than a different kind of activity in the core field on the neutral line. We also examine whether the waxing and waning of the coronal brightness of extended loops shows any correlation with the vigor or frequency of microflaring at the feet. This research was supported by the Solar Physics Branch of NASA's Office of Space Science. Title: NIM-2 -- A Near Infrared Imaging Vector Magnetograph Authors: Rabin, D.; Keller, C.; Jaksha, D. Bibcode: 1996AAS...188.6706R Altcode: 1996BAAS...28R.934R NIM-1 is a spectrograph-based Stokes polarimeter for measuring the strength and orientation of magnetic fields in the solar photosphere using two Zeeman-sensitive Fe I lines (g = 3 and g_geff = 1.53) near 1565 nm. NIM-2, now under construction, also uses these spectral lines but is based on a high-resolution Fabry-Perot etalon. NIM-2 will eliminate the image scanning and consequent spatial distortions of NIM-1 and will be compact and light enough to serve as a prototype for balloon or space instruments. The Queensgate etalon will provide a spectral resolving power of 10(5) over a 1-nm free spectral range. The initial detector will be the 256(2) InSb array shared with NIM-1, but NIM-2 is designed to accommodate a 512(2) or 1024(2) ``Aladdin'' InSb array. The data system, also shared with NIM-1, is being upgraded to handle the faster switching speed ( ~ 8 ms) of improved liquid-crystal variable retarders. NOAO is operated for the NSF by the Association of Universities for Research in Astronomy. Near-infrared magnetometry at NSO is supported by the the NASA Space Physics Division through the SR&T program in solar physics. Title: Observations of Solar Carbon Monoxide with an Imaging Infrared Spectrograph. I. Thermal Bifurcation Revisited Authors: Ayres, Thomas R.; Rabin, Douglas Bibcode: 1996ApJ...460.1042A Altcode: We describe long-slit spectroscopy of the solar 4.7 μm carbon monoxide (CO) Δυ = 1 bands at the Main spectrograph of the NSO McMath-Pierce telescope. We utilized stigmatic imaging of the temperature- and velocity-sensitive CO absorptions to map quiet regions near disk center and at the extreme limb. At Sun center the dominant long-lived spatial structures are small-scale hot spots associated with fragments of the supergranulation network seen in cotemporal Ca II filtergrams. Oscillatory thermal and velocity fluctuations of the global p-mode interference pattern are a pervasive feature of the maps, but the rms amplitudes (≍70 K and ≍240 m s-1) are perturbations on a relatively unstructured outer photosphere. We occasionally see small-scale transient cooling episodes longer lived than the p-mode wavepackets that might be overshooting granules or rising magnetic flux ropes. The events are too rare, however, to influence the global properties of the CO fundamental bands.

Seeing-selected frames of the off-limb CO emissions show a typical extension of 0".6 for the strongest lines, with little variation along the limb. The off-limb extensions indicate the presence of cool gas up to 350 km above the "Tmin" of popular reference models of the solar chromosphere.

We carried out two-dimensional model atmosphere simulations to study the effects of thermal inhomogeneities on the disk-center, extreme-limb, and off-limb behavior of the CO lines. The models are spherically symmetric, static, and in LTE. Our data favor a scenario in which the bulk of the low chromosphere below the base of the magnetic "canopy" is in reality a "COmosphere" dominated by gas colder than the minimum temperature in conventional models.

The moderate-scale (≍5"), mild thermal perturbations of the p-mode pattern have little influence on the CO Δυ = 1 spectra. Small-scale (≍1") hot regions embedded in a cool average atmosphere are strongly "shadowed" at the extreme limb. The shadowing is of little consequence, however, because the atmosphere already is dominated by the cool component. The opposite scenario-small-scale cold regions in a warm average produce effective shadowing at the limb for granule-size (≍1"-2") dark points only if the covering fraction is relatively large (f &#8819 0.2). That scenario is ruled out: it predicts high-contrast dark spots at disk center, contrary to our observations. We also argue against the possibility of shadowing by even smaller, subresolution (≍0"3) cold spots with f &#8819 0.1.

We show that multistep reactions, rather than direct radiative associations, dominate the gas-phase chemistry of CO molecules under conditions typical of the outer photosphere. The CO formation and radiative cooling timescales are fast enough that low-temperature plasma conditions can be restored following disruption by a localized heating event such as a Ca II K2v "flash." In cool giant stars, the chemical formation timescales are much longer than in dwarfs like the Sun. Nevertheless, the density dependence is such that the molecular cooling proceeds proportionately more rapidly than the gas dynamics, ensuring an even more important role for autocatalyzed "thermal bifurcation." Title: Magnetic Roots of Enhanced High Coronal Loops Authors: Porter, J. C.; Falconer, D. A.; Moore, R. L.; Harvey, K. L.; Rabin, D. M.; Shimizu, T. Bibcode: 1996mpsa.conf..429P Altcode: 1996IAUCo.153..429P No abstract at ADS Title: Line-of-sight magnetic flux imbalances caused by electric currents Authors: Gary, G. Allen; Rabin, Douglas Bibcode: 1995SoPh..157..185G Altcode: 1995SoPh..157..185A Several physical and observational effects may contribute to the significant imbalances of magnetic flux that are often observed in active regions. We consider an effect not previously treated: the influence of electric currents in the photosphere. Electric currents can cause a line-of-sight flux imbalance because of the directionality of the magnetic field they produce. Currents associated with magnetic flux tubes produce larger imbalances than do smoothly-varying distributions of flux and current. We estimate the magnitude of this effect for current densities, total currents, and magnetic geometry consistent with observations. The expected imbalances lie approximately in the range 0-15%, depending on the character of the current-carrying fields and the angle from which they are viewed. Observationally, current-induced flux imbalances could be indicated by a statistical dependence of the imbalance on angular distance from disk center. A general study of magnetic flux balance in active regions is needed to determine the relative importance of other - probably larger -effects such as dilute flux (too weak to measure or rendered invisible by radiative transfer effects), merging with weak background fields, and long-range connections between active regions. Title: Photospheric Origins of Enhanced High Coronal Loops Authors: Porter, J. G.; Falconer, D. A.; Moore, R. L.; Harvey, K. L.; Rabin, D. M. Bibcode: 1995SPD....26..704P Altcode: 1995BAAS...27..966P No abstract at ADS Title: Eclipse Measurements of the Distribution of CO Emission Above the Solar Limb Authors: Clark, T. A.; Lindsey, C.; Rabin, D. M.; Livingston, W. C. Bibcode: 1995itsa.conf..133C Altcode: No abstract at ADS Title: The Next Generation of Near-Infrared Solar Magnetographs (Abstract only) Authors: Rabin, D. Bibcode: 1995itsa.conf...87R Altcode: No abstract at ADS Title: Scaling of Solar Magnetic Fields Authors: Ruzmaikin, A.; Cadavid, C.; Lawrence, J.; Rabin, D.; Lin, H. -S. Bibcode: 1995itsa.conf..375R Altcode: No abstract at ADS Title: Stokes Polarimetry with the Near Infrared Magnetograph --- Telescope Polarization Effects Authors: Rabin, D. Bibcode: 1994AAS...18512302R Altcode: 1994BAAS...26.1522R NIM produces spatial images of magnetic field properties in the low photosphere from polarized spectra of the g = 3 line Fe I 6388.64 cm^{-1} (1.5648 \micron). Designed initially for circular polarimetry, NIM can now acquire full Stokes information. I discuss the approximate polarization transfer (Mueller) matrix for NIM as used at the McMath-Pierce Telescope and compare it with the transfer matrix at visible wavelengths. Although telescope polarization effects are generally smaller in the infrared, in one respect the infrared requires careful treatment. In the visible, the net linear polarization due to the Zeeman effect is often small enough compared to circular polarization that linear-to-circular instrumental crosstalk is unimportant. In the infrared, the Zeeman components are usually so strongly split that the linearly polarized Stokes components (Q and U) are comparable in magnitude to the circular component (V). This work has been supported by the NASA SR&T program in solar physics. Title: Eclipse Observations of the Extreme Solar Limb Profile of HI Pfund beta Emission. Authors: Clark, T. A.; Lindsey, C. A.; Rabin, D. M.; Livingston, W. C. Bibcode: 1994AAS...185.4412C Altcode: 1994BAAS...26.1378C A region of the infrared solar spectrum (2147.7 - 2150.1 cm(-1) ) around the HI Pfund beta line (2148.79 cm(-1) ) was monitored through 3 eclipse "contacts" with the Amber InSb array on the Main spectrograph on the McMath-Pierce telescope during the 10 May 1994 partial solar eclipse over Kitt Peak National Observatory to produce limb profiles of intensity and line width to an angular resolution of 0.15 arc second. This line is broad (FWHM = 0.9 cm(-1) and shallow (5.7%) in absorption at disk center but shows a narrow emission core above the continuum envelope at 2 arc seconds inside the limb which remains visible out to 4.5 arc seconds beyond the continuum limb. The Pfund beta peak intensity appears to follow the continuum profile at the limb but then intensifies again to reach a peak at about 1000 km above the limb in a manner similar to that of the HeI D3 line. The line width becomes narrower with height above the limb, reaching a FWHM of 0.22 cm(-1) at several arc seconds above the limb. These profiles will be discussed in relation to those of other HI lines above the solar limb. This work was supported by NSERC of Canada and by NSO, Tucson. Title: Imaging spectroscopy of the solar CO lines at 4.67 microns Authors: Uitenbroek, Han; Noyes, R. W.; Rabin, Douglas Bibcode: 1994ApJ...432L..67U Altcode: We analyze spatially and temporally resolved spectra of the fundamental vibration-rotation transitions of carbon monoxide (CO) in the solar spectrum at 4.67 micrometers. Our observations imply that, in the quiet Sun, spatial variations in CO intensity are largely dynamical in nature, reinforcing the suggestion that dynamical effects play a key role in the formation of the dark CO cores. Time sequences of resolved spectra exhibit mainly 3 minute power in line-core intensity but mainly a 5 minute period in Doppler shift. The weak 7-6 R68 line shows normal Evershed flow in the penumbra of a sunspot; we find evidence for the onset of inverse Evershed flow in the strong 3-2 R14 line. Spectra at the limb indicate that 3-2 R14 emission extends approximately 360 km beyond the continuum limb. Title: A Magnetic Field Strength vs. Temperature Relation in Sunspots Authors: Kopp, G.; Rabin, D. Bibcode: 1994IAUS..154..477K Altcode: No abstract at ADS Title: Near Infrared Imaging Magnetometry Authors: Rabin, D. Bibcode: 1994IAUS..154..449R Altcode: No abstract at ADS Title: Infrared solar physics: proceedings of the 154th Symposium of the International Astronomical Union, held in Tucson, Arizona, U.S.A., March 2-6, 1992. Authors: Rabin, D. M.; Jefferies, John T.; Lindsey, C. Bibcode: 1994IAUS..154.....R Altcode: No abstract at ADS Title: Recent array-detector Observations of the solar CO Fundamental vibration--rotation Transitions at 4.67 microns Authors: Uitenbroek, H.; Noyes, R. W.; Rabin, D. Bibcode: 1993AAS...183.5902U Altcode: 1993BAAS...25.1386U We present recent observations of lines of the fundamental vibration--rotation transitions of carbon monoxide (CO) in the solar atmosphere obtained with the 256(2) infrared array detector at the McMath telescope on Kitt Peak. Standard, plane parallel, solar models have these lines form in LTE around the temperature minimum region; they should be indicative of electron temperatures there. However, matching observed line profiles in a standard solar model requires temperatures as low as 3700 K which are not confirmed by any other spectral diagnostic. We investigate whether this discrepancy can be solved by invoking spatial inhomogeneities or temporal variations or a combination of both. To this end we obtained series of spectra-spectroheliograms at different positions on the disk as well as time series of slit-spectra at a single position. The former type of observations allow us to study spatial inhomogeneities in stronger and weaker lines and the IR continuum at 4.6 microns and to distinguish between variations due to the 5-minute oscillations and the more steady patterns due to magnetic fields by comparing heliograms taken several minutes apart. We also obtained spectra with the slit crossing the limb giving us a more rigid registration of the intensity variations above the limb as compared to previous single-detector measurements. Early analysis shows that high and low excitation lines behave differently at the limb which may bear information on the temperature structure of the atmosphere just above the minimum. Title: A Magnetograph Comparison Workshop Authors: Jones, H.; Bogart, R.; Canfield, R.; Chapman, G.; Henney, C.; Kopp, G.; Lites, B.; Mickey, D.; Montgomery, R.; Pillet, V.; Rabin, D.; Ulrich, R.; Walton, S. Bibcode: 1993BAAS...25.1216J Altcode: No abstract at ADS Title: Intercomparison of Seven Magnetographs Authors: Walton, S. R.; Bogart, R. S.; Chapman, G. A.; Henney, C.; Jones, H.; Kopp, G.; Lites, B.; Mickey, D.; Montgomery, R.; Pillet, V.; Rabin, D. Bibcode: 1993BAAS...25.1205W Altcode: No abstract at ADS Title: Measurement of p-Mode Energy Propagation in the Quiet Solar Photosphere Authors: Fontenla, J. M.; Rabin, D.; Hathaway, D. H.; Moore, R. L. Bibcode: 1993ApJ...405..787F Altcode: We have measured and analyzed the p-mode oscillations in the profile of the Mg I 4571 A line in a quiet region near disk center. The oscillations are found to be mostly standing waves, in agreement with previous work. However, a small propagating component is measured, and we determine the direction, magnitude, and vertical variation of the energy propagation. The work integral indicates an upward energy flow of about 2 x 10 exp 7 ergs/sq cm/s at a height of 50 km above the base of the photosphere for waves with frequencies of 2-16 mHz. This energy flow decreases exponentially with height and drops below 10 exp 5 ergs/sq cm/s in the uppermost photosphere. The energy flow leaving the upper photosphere is at least an order of magnitude too small to constitute a significant source of heating for the chromosphere. However, the p-mode damping in the lower photosphere approaches levels large enough to account for the measured p-mode line widths. The relative amplitudes and phases of the thermodynamic quantities indicate that the p-mode are neither adiabatic nor isothermal in the photosphere. Title: Siphon Flow Across the Magnetic Neutral-Line of an Active Region Authors: Solanki, S. K.; Ruedi, I.; Rabin, D. Bibcode: 1993ASPC...46..534S Altcode: 1993IAUCo.141..534S; 1993mvfs.conf..534S No abstract at ADS Title: NIM --- A Near Infrared Magnetograph Authors: Rabin, D.; Jaksha, D.; Kopp, G.; Mahaffey, C. Bibcode: 1992AAS...181.8101R Altcode: 1992BAAS...24.1251R \newcommand{\micron}{microns} \newcommand{\kayser}{cm(-1) } \newcommand{\NIM}{NIM} We describe a new instrument for mapping magnetic field strength in the active solar photosphere. \NIM\ is a Stokes spectropolarimeter that exploits the high Zeeman sensitivity of the line Fe I 6388.64 \kayser\ (15648.5 Angstroms, e\:(7D_1) -- 3d(6) 4s 5p\:(7D^) o_1, Lande g = 3.00, chi_e = 5.36 eV) to measure vec {B}. For |B| ga 850 G, the magnitude of the field is derived, without adjustable parameters, from the complete splitting of the Zeeman components. The relative strengths of the Stokes components indicate the direction of the field. The absolute strength of the polarized signal depends on the areal filling factor, inclination, continuum contrast, and line strength of the magnetic flux tubes within the angular resolution element. \NIM\ comprises the following subsystems: precision image scanner liquid crystal polarization modulators and control electronics slit spectrograph transfer and minification optics 128 times 128 InSb infrared array camera computer for data acquisition and user interface \NIM\ builds up a two-dimensional array of polarized spectra by scanning the solar image across the spectrograph slit. The spatial and spectral sampling frequencies are 1.0 arcsec or 0.5 arcsec per pixel (depending on which telescope is used) and 0.025 \kayser\ per pixel. At each slit position, 8 polarization pairs for each Stokes parameter (e.g., +/- V) are acquired at 7 Hz, averaged, and recorded in FITS format. A 128 times 128 arcsec(2) map is acquired in about 20 minutes. \NIM\ is available to NSO visiting observers at the McMath-Pierce Telescope on Kitt Peak. Title: Solar infrared presensitization photography Authors: Geary, Joseph M.; Rabin, Douglas Bibcode: 1992OptEn..31.2694G Altcode: Infrared presensitization photography (IRPP) is used to acquire images of the solar disk in the 1 to 2 micrometers regime. This is the first time IRPP has been employed at such short IR wavelengths, used against a thermal (instead of a laser) source, and applied to astronomy. The experiments demonstrate the feasibility of IRPP for solar imaging, but the image quality needs improvement for solar research. Title: A Photometric Study of Faculae and Sunspots Between 1.2-MICRONS and 1.6-MICRONS Authors: Moran, T.; Foukal, P.; Rabin, D. Bibcode: 1992SoPh..142...35M Altcode: We investigate further the interpretation of dark magnetic faculae observed in previous imaging of the solar photosphere at 1.63 μm. We show that their contrast at 1.63 μm increases with magnetic flux beyond a threshold value of Φ ∼ 2 × 1018 Mx and blends smoothly with the contrast vs flux relation measured at this wavelength for larger structures of sunspot size. Not all facular structures that are bright in Ca K are dark at 1.63 μm, apparently because their magnetic flux is not large enough. After correction for blurring, the contrast of the dark faculae observed near the disc center at 1.63 μm is approximately 4%. But our observations at 1.23 μm, which probe slightly higher photospheric levels, do not show these dark faculae. These results indicate that magnetic flux tubes of diameter as small as 500 km significantly inhibit convective heat flow to the photosphere, much as do sunspot flux tubes of much larger diameter. They also suggest that, in even smaller flux tubes, the inhibition becomes rapidly less significant. Finally, we show that the sunspot-size dependence of umbral infrared contrast versus wavelength that we observe can probably be explained in terms of instrumental blurring. Observations with lower scattered light will be required to determine whether a real decrease of contrast with diameter also plays a role. Title: A Relation Between Magnetic Field Strength and Temperature in Sunspots Authors: Kopp, Greg; Rabin, Douglas Bibcode: 1992SoPh..141..253K Altcode: We present Stokes I Zeeman splitting measurements of sunspots using the highly sensitive (g = 3) Fe I line at λ = 1.5649 μm. The splittings are compared with simultaneous intensity measurements in the adjacent continuum. The relation between magnetic field strength and temperature has a characteristic, nonlinear shape in all the spots studied. In the umbra, there is an approximately linear relation between B2 and Tb, consistent with magnetohydrostatic equilibrium in a nearly vertical field. A distinct flattening of the B2 vs Tbrelationship in the inner penumbra may be due to changes in the lateral pressure balance as the magnetic field becomes more horizontal; spatially unresolved intensity inhomogeneities may also influence the observed relation. Title: Pervasive Variability in the Quiet Solar Transition Region Authors: Rabin, Douglas; Dowdy, James F., Jr. Bibcode: 1992ApJ...398..665R Altcode: Extreme UV spectroheliograms from an experimental time series are employed to investigate the nature of the quiet solar transition region with respect to temporal variability. A statistical treatment is developed to analyze the fraction of spatial elements that yield intensity variations significantly higher than the signal noise. The EUV intensity in every spatial resolution varies on a time scale of minutes by about 10-30 percent, and the fractional amplitude of the temporal variations is found to be nearly independent of mean intensity. The paper concludes that the quiet solar transition region is probably generated and modulated by small-scale magnetic activity, since the temporal variability in the transition region is spatially uniform and rather pervasive. Title: Infrared lines as probes of solar magnetic features. IV - Discovery of a siphon flow Authors: Rueedi, I.; Solanki, S. K.; Rabin, D. Bibcode: 1992A&A...261L..21R Altcode: Spectra of two neighboring IR lines, Fe I 15648.5 A and Fe I 15652.9 A, are analyzed. The spectra were obtained with an IR array detector in active region plages with the entrance slit of the spectrograph placed across the polarity-inversion (neutral) line. Near the neutral line the positive polarity field is weaker (about 1200 G) and shows an upflow of up to 2 km/s, while the negative polarity field is stronger (about 1500 G) and exhibits a downflow of up to 1 km/s. This configuration corresponds to the expected signature of a siphon flow along a loop connecting flux tubes across the neutral line. Title: Spatially Extended Measurements of Magnetic Field Strength in Solar Plages Authors: Rabin, Douglas Bibcode: 1992ApJ...391..832R Altcode: The study determines magnetic field strengths along one spatial dimension of a plage region from circularly polarized (Stokes V) spectra of a highly Zeeman-sensitive iron line at 6388.6/cm (1.565 micron). The measured fields are found to lie primarily in the range 1200-1700 G. The mean formal precision for a single determination is +/-65 G. More than 90 percent of the magnetic flux is kilogauss-strength fields. The field strength is coherently organized on spatial scales from 1 arcmin to the limit of angular resolution (2 arcsec). It is inferred from the amplitude of the V signal that the spatial filling factor of the strong-field elements can approach 0.5 within a 2-arcsec resolution element. Magnetic field strength and amplitude are correlated in the sense that locations with stronger mean fields have larger V amplitudes, but the relationship shows more scatter than can be explained by errors in measurement. The individual sigma-components of the V profile are broader than an average quiet-sun line profile would produce by an amount corresponding to 625 G or 4.1 km/s; Zeeman broadening due to a range of magnetic field strength within the resolution element is proposed as the likely explanation. Title: A True-Field Magnetogram in a Solar Plage Region Authors: Rabin, Douglas Bibcode: 1992ApJ...390L.103R Altcode: The Near-Infrared Magnetograph is used to make the first 2D image of true magnetic field strength in the solar photosphere. The magnitude of the magnetic field vector is derived with a typical formal precision of + or - 75 G (2 sigma) from circularly polarized spectra of a highly Zeeman-sensitive iron line at 6388.6/cm. The true-field map demonstrates that the properties of 'kilogauss' flux tubes vary coherently on a variety of spatial scales within the 1-arcmin field of view. The measured fields span the range 1000-1700 G. The amplitude of the polarized signal implies that the spatial filling factor of the flux tubes can approach 0.3 at the seeing-limited resolution of 2 arcsec. Magnetic field strength and magnetic flux are statistically related in the sense that weak-field areas are weak-flux areas, but strong fields are present in both strong-flux and weak-flux areas. This implies a degree of independence in the relationship between the filling factor of flux tubes and their individual properties, such as field strength, pressure, and temperature. Title: Infrared Determinations of Magnetic Profiles in Sunspots Authors: Kopp, G.; Kuhn, J.; Lin, H.; Rabin, D. Bibcode: 1992AAS...180.1202K Altcode: 1992BAAS...24R.747K We present measurements of a sunspot using unpolarized observations of the magnetically-sensitive (Lande g=3) Fe I line at lambda =1.5649 microns (6388.6 cm(-1) ). We compare the magnetic field profile from this fairly symmetric spot with model profiles. Splittings in this infrared line are nearly a factor of 3 greater than in a comparable visible line, since Zeeman splitting as a fraction of linewidth increases linearly with wavelength. The infrared is also less affected by stray light than the visible, because the intensity contrast is reduced, decreasing the effects of stray light, and because instrumental scatter is lower in the infrared. The combination of the magnetic and stray light advantages of the infrared and the recent availability of ``large'' infrared arrays has made possible more sensitive determinations of the magnetic field profile throughout sunspots. From observations of several sunspots, we find that the magnetic field strength, determined in the strong field regime, is not a smooth function of radius from spot center, and that single radial parameter models do not accurately describe the observed spots. Title: Solar infrared presensitization photography Authors: Geary, Joseph M.; Rabin, Douglas Bibcode: 1992SPIE.1638...63G Altcode: Infrared presensitization photography (IRPP) is used to acquire images of the solar disk in the 1 to 2 micrometers regime. This is the first time IRPP has been employed at such short IR wavelengths, used against a thermal (instead of a laser) source, and applied to astronomy. The experiments demonstrate the feasibility of IRPP for solar imaging, but the image quality needs improvement for solar research. Title: Magnetic Field Strength; Continuum Intensity Measurements of Sunspots at 1.56 microns Authors: Kopp, M. G.; Rabin, D. Bibcode: 1992ASPC...26..246K Altcode: 1992csss....7..246K No abstract at ADS Title: Fine-Scale Magnetic Fields in the Solar Photosphere (Invited Review) Authors: Rabin, D. Bibcode: 1992ASPC...26..201R Altcode: 1992csss....7..201R No abstract at ADS Title: Energy Balance in Coronal Funnels Authors: Rabin, Douglas Bibcode: 1991ApJ...383..407R Altcode: The energy balance in magnetic flux tubes is examined semianalytically for the case in which thermal conduction balances radiation or in which enthalpy transport occurs. Different values are considered for areal constriction, shape, length, and maximum temperature. The overall energy budget of the solar corona is not significantly affected by magnetic constriction. A bowl-shaped funnel with a constriction factor of 4 describes the empirical differential-emission measure for log-T values between approximately 5.3 and 6.0. Loop-scaling relationships are derived for the full range of models to illustrate the dependence of the constant of proportionality on the properties of the magnetic constriction. Constriction can reduce the total energy requirement of the funnel by a factor of 5 and not affect the differential emission in flow-dominated models. Title: A True-Field Magnetogram Authors: Rabin, D.; Cole, L.; Jaksha, D.; Iwata, K. Bibcode: 1991BAAS...23.1030R Altcode: No abstract at ADS Title: Zeeman Splitting and Continuum Measurements of Sunspots at 1.56 μm Authors: Kopp, G.; Rabin, D.; Lindsey, C. Bibcode: 1991BAAS...23.1055K Altcode: No abstract at ADS Title: Plage magnetic field strengths from near-infrared spectra. Authors: Rabin, D.; Jaksha, D.; Plymate, C.; Wagner, J.; Iwata, K. Bibcode: 1991sopo.work..361R Altcode: The authors have measured magnetic field strenghts in a small sample of plages from Stokes V spectra of two Zeeman-sensitive iron lines near 6388 cm-1(1.565 μm). The detected fields are strong (≡103gauss), but their strength varies significantly from feature to feature. The individual σ-components are broader than an average quiet-Sun line profile; if this broadening is primarily magnetic, there is typically about a 20% range in field strength within a 2-arcsecond resolution element. These observations represent the first stage of a project to build a near-infrared magnetograph that will produce two-dimensional maps of local magnetic field strength in the low photosphere. Title: The solar activity cycle. Authors: Rabin, Douglas M.; DeVore, C. R.; Sheeley, Neil R., Jr.; Harvey, Karen L.; Hoeksema, J. T. Bibcode: 1991sia..book..781R Altcode: Study of the solar cycle is entering a new era dominated by objective, precise measurements of magnetic, velocity and radiation fields over the surface of the Sun. This review emphasizes observations of photospheric magnetic flux during cycle 21 (1976 - 1986) and how these measurements have been used to model the cyclic variability of the heliospheric magnetic field. Indices of solar activity are discussed in terms of their potential to figure in theoretical or empirical models. Other recent data, such as measurements of large-scale surface flows and information on the Sun's internal rotation from helioseismology, as well as the magnetic flux observations, are considered in the context of Babcock's phenomenological model of the solar cycle: can this model still serve? Is there anything better to replace it? Title: Solar IR presensitization photography Authors: Geary, Joseph M.; Rabin, Douglas; Lindmayer, Joseph Bibcode: 1990SPIE.1235..181G Altcode: The principles involved in the IR presensitization photography (IRPP) are discussed, and the feasibility of using IRPP in solar IR astronomy is investigated. Images of the solar disk were acquired in the 1- to 2-micron regime, demonstrating that IRPP is a feasible technique for solar imaging. However, in order to use IRPP images for solar research, the image quality needs improvement in terms of resolution and photometric accuracy. Title: Infrared Imaging of Faculae at the Deepest Photospheric Layers Authors: Foukal, P.; Little, R.; Graves, J.; Rabin, D.; Lynch, D. Bibcode: 1990ApJ...353..712F Altcode: The NOAO 58 x 62 InSb array and the National Solar Observatory McMath telescope are used to image the deepest photospheric layers of three active regions at the 1.63-micron opacity minimum. The faculae are darker than the photosphere, with a measured contrast of at least 2 percent at positions on the disk with mu = 0.75-1.0. Near the limb, they are brighter than the photosphere, as in the visible. At mu = 0.5-0.75, they are difficult to detect at 1.63 micron. The observation that faculae and their immediate surroundings exhibit a clear deficit of brightness temperature near disk center at 1.63 micron seems to rule out the hillock model put forward to explain their center-to-limb contrast variation. Title: Magnetic Loops in the Chromospheric Network Authors: Moore, R. L.; Rabin, D. M.; Dowdy, J. F., Jr. Bibcode: 1990BAAS...22..815M Altcode: No abstract at ADS Title: Measurement of Dissipation or Pumping of P-Modes in the Solar Photosphere Authors: Fontenla, J. M.; Hathaway, D. H.; Rabin, D.; Moore, R. Bibcode: 1990BAAS...22..856F Altcode: No abstract at ADS Title: Spatially Resolved Measurements of Magnetic Field Strength Outside Sunspots Authors: Rabin, D. M. Bibcode: 1990BAAS...22..840R Altcode: No abstract at ADS Title: Infrared Imaging of Faculae at the Deepest Photospheric Layers Authors: Foukal, P.; Little, R.; Graves, B.; Rabin, D.; Lynch, D. Bibcode: 1989BAAS...21..828F Altcode: No abstract at ADS Title: Ubiquity of magnetic Loops in the Chromospheric Network Authors: Moore, R. L.; Rabin, D. M.; Dowdy, J. F., Jr. Bibcode: 1989BAAS...21..864M Altcode: No abstract at ADS Title: Measuring Sunspot Magnetic Fields with the Infrared Line Fe Iλ15649 Authors: Rabin, D. M.; Graves, J. E. Bibcode: 1989BAAS...21R.854R Altcode: No abstract at ADS Title: Chromospheric explosions. Authors: Doschek, G. A.; Antiochos, S. K.; Antonucci, E.; Cheng, C. -C.; Culhane, J. L.; Fisher, G. H.; Jordan, C.; Leibacher, J. W.; MacNiece, P.; McWhirter, R. W. P.; Moore, R. L.; Rabin, D. M.; Rust, D. M.; Shine, R. A. Bibcode: 1989epos.conf..303D Altcode: The work of this team addressed the question of the response and relationship of the flare chromosphere and transition region to the hot coronal loops that reach temperatures of about 107K and higher. Flare related phenomena such as surges and sprays were also discussed. The team members debate three main topics: 1) whether the blue-shifted components of X-ray spectral lines are signatures of "chromospheric evaporation"; 2) whether the excess line broadening of UV and X-ray lines is accounted for by "convective velocity distribution" in evaporation; and 3) whether most chromospheric heating is driven by electron beams. These debates illustrated the strengths and weaknesses of our current observations and theories. Title: A Three-Dimensional View of the DQ Herculis Nova Shell Authors: Barden, S. C.; Rabin, D. M.; Wade, R. A. Bibcode: 1988BAAS...20R1052B Altcode: 1988BAAS...20Z1052B No abstract at ADS Title: Observed Magnetic Structure and Activity in the Quiet Solar Atmosphere Authors: Moore, R. L.; Dowdy, J. F., Jr.; Rabin, D. M. Bibcode: 1988BAAS...20.1009M Altcode: No abstract at ADS Title: How Quiet is Quiet?-Movies of the Quiet Sun in EUV Emission Lines Authors: Rabin, D. M.; Dowdy, J. F., Jr.; Withbroe, G. L. Bibcode: 1988BAAS...20.1009R Altcode: No abstract at ADS Title: 10.7 cm solar radio flux and the magnetic complexity of active regions. Authors: Wilson, Robert M.; Rabin, Douglas; Moore, Ronald L. Bibcode: 1987SoPh..111..279W Altcode: During sunspot cycles 20 and 21, the maximum in smoothed 10.7-cm solar radio flux occurred about 1.5 yr after the maximum smoothed sunspot number, whereas during cycles 18 and 19 no lag was observed. Thus, although 10.7-cm radio flux and Zürich suspot number are highly correlated, they are not interchangeable, especially near solar maximum. The 10.7-cm flux more closely follows the number of sunspots visible on the solar disk, while the Zürich sunspot number more closely follows the number of sunspot groups. The number of sunspots in an active region is one measure of the complexity of the magnetic structure of the region, and the coincidence in the maxima of radio flux and number of sunspots apparently reflects higher radio emission from active regions of greater magnetic complexity. The presence of a lag between sunspot-number maximum and radio-flux maximum in some cycles but not in others argues that some aspect of the average magnetic complexity near solar maximum must vary from cycle to cycle. A speculative possibility is that the radio-flux lag discriminates between long-period and short-period cycles, being another indicator that the solar cycle switches between long-period and short-period modes. Title: Thermal Conduction in Magnetic Funnels Authors: Rabin, D. M. Bibcode: 1987BAAS...19..940R Altcode: No abstract at ADS Title: The prominence-corona interface and its relationship to the chromosphere-corona transition. Authors: Rabin, Douglas Bibcode: 1986NASCP2442..135R Altcode: 1986copp.nasa..135R The classical model of the chromosphere-corona transition does not account for the observed behavior of the differential emission measure for T approx. less than 100,000 K. Several models have been proposed to resolve this discrepancy in physically different ways. Because the observed differential emission measure at the prominence-corona interface is on average nearly the same as in the chromosphere-corona transition, prominences offer a fresh testing ground for models tailored to the chromosphere-corona transition. The researcher considered three such models and concluded that none extends in a natural way to the environment of prominences. The researcher advanced a simple idea involving thermal conduction both along and across the magnetic field from the corona into cool threads. Title: The Prominence-Corona Interface Authors: Rabin, D. M. Bibcode: 1986BAAS...18..991R Altcode: No abstract at ADS Title: On the Magnetic Structure of the Quiet Transition Region Authors: Dowdy, J. F., Jr.; Rabin, D.; Moore, R. L. Bibcode: 1986SoPh..105...35D Altcode: Existing models of the quiet chromosphere-corona transition region predict a distribution of emission measure over temperature that agrees with observation for T ≳ 105 K. These `network' models assume that all magnetic field lines that emerge from the photosphere extend into and are in thermal contact with the corona. We show that the observed fine-scale structure of the photospheric magnetic network instead suggests a two-component picture in which magnetic funnels that open into the corona emerge from only a fraction of the network. The gas that makes up the hotter transition region is mostly contained within these funnels, as in standard models, but, because the funnels are more constricted in our picture, the heat flowing into the cooler transition region from the corona is reduced by up to an order of magnitude. The remainder of the network is occupied by a population of low-lying loops with lengths ≲ 104 km. We propose that the cooler transition region is mainly located within such loops, which are magnetically insulated from the corona and must, therefore, be heated internally. The fine-scale structure of ultraviolet spectroheliograms is consistent with this proposal, and theoretical models of internally heated loops can explain the behavior of the emission measure below T ≈ 105 K. Title: Bimodality of the solar cycle Authors: Rabin, D.; Wilson, R. M.; Moore, R. L. Bibcode: 1986GeoRL..13..352R Altcode: For sunspot cycles 1-20 (1755-1976), all cycles occurred in strings (two to six cycles in length) during which the period remained longer or shorter than the sample mean period. These strings have coincided with long-term trends of growth or decay in the amplitude of the cycle. In six out of six cases, the period of the cycle has switched from long to short (or the reverse) in coincidence with turning points in the long-term trend. This suggests that the solar dynamo has two modes with different mean periods. In the short-period mode, the amplitude of the cycle grows; in the long-period mode, the amplitude decays. The transition between modes has occurred at irregular intervals. A persistence of the long-period mode would eventually produce a grand minimum such as the Maunder minimum; a persistence of the short-period mode would produce a grand maximum. Unless the present interval between transitions turns out to be shorter than any previously observed interval, the present cycle (cycle 21) is part of a long-period, decaying trend and will be of longer-than-average duration (>133 months). Title: Chromospheric explosions. Authors: Doschek, G. A.; Antiochos, S. K.; Antonucci, E.; Cheng, C. -C.; Culhane, J. L.; Fisher, G. H.; Jordan, C.; Leibacher, J. W.; MacNiece, P.; McWhirter, R. W. P.; Moore, R. L.; Rabin, D. M.; Rust, D. M.; Shine, R. A. Bibcode: 1986NASCP2439....4D Altcode: The work of this team addressed the question of the response and relationship of the flare chromosphere and transition region to the hot coronal loops that reach temperatures of about 107K and higher. Flare related phenomena such as surges and sprays are also discussed. The team members debated three main topics: 1. whether the blue-shifted components of X-ray spectral lines are signatures of "chromospheric evaporation"; 2. whether the excess line broadening of UV and X-ray lines is accounted for by "convective velocity distribution" in evaporation; and 3. whether most chromospheric heating is driven by electron beams. Title: Measurement and interpretation of magnetic shear in solar active regions Authors: Hagyard, M. J.; Rabin, D. M. Bibcode: 1986AdSpR...6f...7H Altcode: 1986AdSpR...6....7H In this paper we summarize and synthesize the results on the role of magnetic shear in the flare process that have been derived from the series of Flare Buildup Study Workshops in the Solar Maximum Analysis program. With emphasis on observations, we discuss the mechanisms that seem to produce the sheared magnetic configurations observed in flaring active regions. The spatial and temporal correlations of this shear with the onset of solar flares are determined from quantitative analyses of measurements of the vector magnetic field. The question of why some areas of sheared magnetic fields are the sites of flares and others are not is investigated observationally. We conclude by synthesizing these findings with current theoretical models of stressed magnetic fields that lead to the eruption of a flare. Title: Evidence for submergencew of magnetic flux in a growing active region Authors: Rabin, D. M.; Moore, R. L.; Hagyard, M. J. Bibcode: 1985svmf.nasa..437R Altcode: In NOAA Active Region 2372 (April 1980), 4 x 10 to the 20th power maxwell of magnetic flux concentrated within a 30" circular area disappeared overnight. Vector magnetograms show that all components of the magnetic field weakened together. If the field had weakened through diffusion or fluid flow, 80% of the original flux would still have been detected by the magnetograph within a suitably enlarged area. In fact there was at least a threefold decrease in detected flux. Evidently, magnetic field was removed from the photosphere. Since the disappearing flux was located in a region of low magnetic shear and low activity, it is unlikely that the field dissipated through reconnection. The most likely possibility is that flux submerged. Observations suggest that even in the growth phase of active regions, submergence is a strong process comparable in magnitude to emergence. Title: Sunspots. Authors: Moore, R.; Rabin, D. Bibcode: 1985ARA&A..23..239M Altcode: It is pointed out that the sun provides a close-up view of many astrophysically important phenomena, nearly all connected with the causes and effects of solar magnetic fields. The present article provides a review of the role of sunspots in a number of new areas of research. Connections with other solar phenomena are examined, taking into account flares, the solar magnetic cycle, global flows, luminosity variation, and global oscillations. A selective review of the structure and dynamic phenomena observed within sunspots is also presented. It is found that sunspots are usually contorted during the growth phase of an active region as magnetic field rapidly emerges and sunspots form, coalesce, and move past or even through each other. Attention is given to structure and flows, oscillations and waves, and plans for future studies. Title: Evidence for submergence of magnetic flux in a growing active region. Authors: Rabin, D. M.; Moore, R. L.; Hagyard, M. J. Bibcode: 1985NASCP2374..437R Altcode: No abstract at ADS Title: Graphic displays of vector magnetograph data. Authors: Rabin, D. M.; West, E. A. Bibcode: 1985NASCP2374..454R Altcode: The authors summarize their experience with graphic displays that have proved useful in dealing with vector magnetograph data in three settings: real-time control, analysis, and final presentation. Among the topics discussed are: flexible, implicit data-scaling; geometrical transformations; methods of comparing fields (e.g., transverse vs. longitudinal; observed vs. computed; one time vs. another); displaying the magnitude and direction of the transverse field; minimizing the display time of serial graphics devices; graphic file structure; and graphic interaction with operators and observers. Title: A case for submergence of magnetic flux in a solar active region Authors: Rabin, D.; Moore, R.; Hagyard, M. J. Bibcode: 1984ApJ...287..404R Altcode: In NOAA Active Region 2372 (April 1980), 4 x 10 to the 20th maxwells of magnetic flux concentrated in an area 30 arcsec across disappeared overnight. Vector magnetograms show that all components of the magnetic field weakened together. If the field had weakened through diffusion or fluid flow, 90 percent of the original flux would still have been detected by the magnetograph within a suitably enlarged area. In fact there was a threefold decrease in detected flux. Evidently, magnetic field was removed from the photosphere. Since the disappearing flux was located in a region of low magnetic shear and low activity in H-alpha and Ly-alpha, it is unlikely that the field dissipated through reconnection. It is argued that the most likely possibility is that flux submerged. The observations suggest that even during the growth phase of active regions, submergence is a strong process comparable in magnitude to emergence. Title: Heating the sun's lower transition region with fine-scale electric currents Authors: Rabin, D.; Moore, R. Bibcode: 1984ApJ...285..359R Altcode: This paper discusses the hypothesis that the lower transition region is locally heated by the dissipation of electric currents. It proposes a model based on ohmic heating by filamentary electric currents that flow along the magnetic field. The current filaments must be of fine scale, with a narrow dimension in the range 1 cm to 1 km, and the ambient magnetic field must be greater than about 10 gauss. An ensemble of filamentary currents that agree in sign across the horizontal scale of a photospheric granule can generate enough heat to match observations without the need for anomalous resistivity. Thermal conduction perpendicular to the axis of a current filament produces a distribution of emission measure over temperature that is in good agreement with observations. Title: Bimodality of the Solar Cycle Authors: Rabin, D. M.; Moore, R. L.; Wilson, R. M. Bibcode: 1984BAAS...16Q.993R Altcode: No abstract at ADS Title: Sunspot Oscillations and the Short-Period Cutoff for Global p-Mode Oscillations Authors: Moore, R.; Rabin, D. Bibcode: 1984BAAS...16..978M Altcode: No abstract at ADS Title: Photospheric Electric Current and Transition Region Brightness Within an Active Region Authors: Deloach, A. C.; Hagyard, M. J.; Rabin, D.; Moore, R. L.; Smith, B. J., Jr.; West, E. A.; Tandberg-Hanssen, E. Bibcode: 1984SoPh...91..235D Altcode: Distributions of vertical electric current density (Jz) calculated from vector measurements of the photospheric magnetic field are compared with ultraviolet spectroheliograms to investigate whether resistive heating is an important source of enhanced emission in the transition region. The photospheric magnetic fields in Active Region 2372 were measured on 6 and 7 April, 1980 with the MSFC vector magnetograph; ultraviolet wavelength spectroheliograms (Lα and Nv 1239 Å) were obtained with the UVSP experiment aboard the Solar Maximum Mission satellite. Spatial registration of the Jz (5 arc sec resolution) and UV (3 arc sec resolution) maps indicates that the maximum current density is cospatial with a minor but persistent UV enhancement, but there is little detected current associated with other nearby bright areas. We conclude that although resistive heating may be important in the transition region, the currents responsible for the heating are largely unresolved in our measurements and have no simple correlation with the residual current measured on 5 arc sec scales. Title: On the Formation of Magnetic Shear: Clues from a Well-Observed Active Region Authors: Moore, R. L.; Rabin, D. M. Bibcode: 1984BAAS...16..528M Altcode: No abstract at ADS Title: A Case for Submergence of Magnetic Flux in a Solar Active Region Authors: Rabin, D. M.; Moore, R. L. Bibcode: 1984BAAS...16..528R Altcode: No abstract at ADS Title: On Heating the Lower Transition Region with Fine-Scale Currents Authors: Rabin, D. M.; Moore, R. L. Bibcode: 1983BAAS...15..700R Altcode: No abstract at ADS Title: Analysis of integrated spectra of red star clusters in the Magellanic Clouds. Authors: Rabin, D. Bibcode: 1982ApJ...261...85R Altcode: The present investigation has the objective to demonstrate that integrated spectra can play an important role in the quantitative analysis of the ages and abundances of star clusters. In particular, it is shown that by comparing the strength of the Balmer lines with the strength of a metallic feature, and guided by a sequence of model star clusters and the empirical sequence of Galactic globular clusters, one may infer age differences between fairly old clusters, for each of which a color-magnitude study to extremely faint magnitudes would be necessary to approach the main sequence. Most Magellanic Cloud clusters are younger than Galactic globulars and lack a developed horizontal branch. Title: Structure of the Lower Transition Zone in an Active Region Authors: Rabin, D. M.; Moore, R. L. Bibcode: 1982BAAS...14..925R Altcode: No abstract at ADS Title: Book-Review - Carbon Stars Authors: Alksne, Z. K.; Klaunieks, Y. Y.; Baumert, J. H.; Rabin, D. Bibcode: 1982JBAA...92Q.153A Altcode: No abstract at ADS Title: Studies of Stellar Populations: Star Clusters in M31, the Galaxy and the Magellanic Clouds. Authors: Rabin, D. M. Bibcode: 1981PhDT.........2R Altcode: 1981PhDT.......114R Medium resolution spectra of the integrated light of star clusters in our own Galaxy and in three nearby systems M31 and the two Magellanic Clouds are described. Since only integrated properties will normally be observable for clusters in more distant galaxies, or for the galaxies themselves, it is important to develop quantitative techniques which relate features of the integrated light to physical characteristics such as age and chemical composition. Here, digital spectra, are analyzed both internally, as multivariate data sets, and externally by comparison with evolutionary models of star clusters and with detailed observations of nearby clusters. Title: Studies of stellar population: star clusters in M31, the galaxy and the Magellanic clouds Authors: Rabin, Douglas Mark Bibcode: 1981PhDT.......129R Altcode: No abstract at ADS Title: Studies of stellar populations: Star clusters in M31. The galaxy and the Magellanic Clouds Authors: Rabin, Douglas Mark Bibcode: 1981ssps.book.....R Altcode: No abstract at ADS Title: Coronal holes, the height of the chromosphere,and the origin of spicules. Authors: Rabin, D.; Moore, R. L. Bibcode: 1980ApJ...241..394R Altcode: Analysis of 650 microphotometric scans across the solar limb reveals that the H(alpha) chromosphere is slightly taller inside coronal holes than in quiet regions outside holes. The change in height occurs as a step at the hole boundaries; this suggests that the increase with latitude in the average height of spicules found by Lippincott and by Athay was the average result of upward steps at the polar hole boundaries rather than a gradual latitude trend. It is estimated that the power consumed by spicules is of the same order as that returning by conduction from the corona, but the bulk of the spicules (which sets the height of the chromosphere) shows almost no response. It is concluded that spicules are not caused by heat conduction from the corona but are driven from below, suggesting that spicules are more closely connected with the heating of the corona than with its cooling. Title: Polar Coronal Holes and the Variation with Latitude of the Height of the Hα Chromosphere. Authors: Rabin, D. M.; Moore, R. L. Bibcode: 1978BAAS...10..430R Altcode: No abstract at ADS