Author name code: dewijn ADS astronomy entries on 2022-09-14 author:"De Wijn, Alfred G." ------------------------------------------------------------------------ Title: Multi-height Measurements Of The Solar Vector Magnetic Field: A White Paper Submitted To The Decadal Survey For Solar And Space Physics (Heliophysics) 2024-2033 Authors: Bertello, L.; Arge, N.; De Wijn, A. G.; Gosain, S.; Henney, C.; Leka, K. D.; Linker, J.; Liu, Y.; Luhmann, J.; Macniece, P. J.; Petrie, G.; Pevtsov, A.; Pevtsov, A. A. Bibcode: 2022arXiv220904453B Altcode: This white paper advocates the importance of multi-height measurements of the vector magnetic field in the solar atmosphere. As briefly described in this document, these measurements are critical for addressing some of the most fundamental questions in solar and heliospheric physics today, including: (1) What is the origin of the magnetic field observed in the solar atmosphere? (2) What is the coupling between magnetic fields and flows throughout the solar atmosphere? Accurate measurements of the photospheric and chromospheric three-dimensional magnetic fields are required for a precise determination of the emergence and evolution of active regions. Newly emerging magnetic flux in pre-existing magnetic regions causes an increase in the topological complexity of the magnetic field, which leads to flares and coronal mass ejections. Measurements of the vector magnetic field constitute also the primary product for space weather operations, research, and modeling of the solar atmosphere and heliosphere. The proposed next generation Ground-based solar Observing Network Group (ngGONG), a coordinated system of multi-platform instruments, will address these questions and provide large datasets for statistical investigations of solar feature behavior and evolution and continuity in monitoring for space-weather focused endeavors both research and operational. It will also enable sun-as-a-star investigations, crucial as we look toward understanding other planet-hosting stars. Title: Ground-based instrumentation and observational techniques Authors: Rimmele, Thomas; Kuhn, Jeff; Woeger, Friedrich; Tritschler, . Alexandra; Lin, Haosheng; Casini, Roberto; Schad, Thomas; Jaeggli, Sarah; de Wijn, Alfred; Fehlmann, Andre; Anan, Tetsu; Schmidt, Dirk Bibcode: 2022cosp...44.2507R Altcode: We'll review the current state-of-the-art for ground-based instrumentation and techniques to achieve high-resolution observations. We'll use the 4m Daniel K. Inouye Solar Telescope (DKIST), the European Solar Telescope (EST) and other ground-based instrumentation as examples to demonstrate instrument designs and observing techniques. Using adaptive optics and post-facto image processing techniques, the recently completed DKIST provides unprecedented resolution and high polarimetric sensitivity that enables astronomers to unravel many of the mysteries the Sun presents, including the origin of solar magnetism, the mechanisms of coronal heating and drivers of flares and coronal mass ejections. Versatile ground-based instruments provide highly sensitive measurements of solar magnetic fields, that in the case of DKIST, also include measurements of the illusive magnetic field of the faint solar corona. Ground-based instruments produce large and diverse data sets that require complex calibration and data processing to provide science-ready to a broad community. We'll briefly touch on ongoing and future instrumentation developments, including multi-conjugate adaptive optics. Title: The Visible Spectro-Polarimeter of the Daniel K. Inouye Solar Telescope Authors: de Wijn, A. G.; Casini, R.; Carlile, A.; Lecinski, A. R.; Sewell, S.; Zmarzly, P.; Eigenbrot, A. D.; Beck, C.; Wöger, F.; Knölker, M. Bibcode: 2022SoPh..297...22D Altcode: 2022arXiv220300117D The Daniel K. Inouye Solar Telescope (DKIST) Visible Spectro-Polarimeter (ViSP) is a traditional slit-scanning spectrograph with the ability to observe solar regions up to a 120 ×78 arcsec2 area. The design implements dual-beam polarimetry, a polychromatic polarization modulator, a high-dispersion echelle grating, and three spectral channels that can be automatically positioned. A defining feature of the instrument is its capability to tune anywhere within the 380 - 900 nm range of the solar spectrum, allowing for a virtually infinite number of combinations of three wavelengths to be observed simultaneously. This enables the ViSP user to pursue well-established spectro-polarimetric studies of the magnetic structure and plasma dynamics of the solar atmosphere, as well as completely novel investigations of the solar spectrum. Within the suite of first-generation instruments at the DKIST, ViSP is the only wavelength-versatile spectro-polarimeter available to the scientific community. It was specifically designed as a discovery instrument to explore new spectroscopic and polarimetric diagnostics and test improved models of polarized line formation through high spatial-, spectral-, and temporal-resolution observations of the Sun's polarized spectrum. In this instrument article, we describe the science requirements and design drivers of ViSP and present preliminary science data collected during the commissioning of the instrument. Title: The Next Generation GONG (ngGONG) Project: Ground-based Synoptic Studies of the Sun Authors: Pillet, Valentin; Gilbert, Holly; Pevtsov, Alexei; de Wijn, Alfred Bibcode: 2021AGUFMSH45E2406P Altcode: Ground-based synoptic solar observations provide crucial contextual data used to model the large-scale state of the heliosphere. Existing ground-based synoptic programs are aging rapidly and are used in ways that differ from their original objectives. Most prominently, GONG was designed for helioseismology but is most demanded today as a provider of the magnetic boundary conditions for solar wind models. A wealth of theoretical knowledge about the connectivity between the Sun and the planets has emerged in recent years. NSO and HAO (and other international partners) are collaborating in defining a next-generation GONG (ngGONG) network that incorporates this knowledge. This contribution describes current and future contextual synoptic observations needed to fully exploit our new understanding of the underlying microphysics that leads to magnetic linkages between the Earth and the Sun. This combination of a better understanding of small-scale processes and the appropriate global context will enable a physics-based approach to Space Weather comparable to Terrestrial Weather forecasting. Title: The National Science Foundation's Daniel K. Inouye Solar Telescope — Status Update Authors: Rimmele, T.; Woeger, F.; Tritschler, A.; Casini, R.; de Wijn, A.; Fehlmann, A.; Harrington, D.; Jaeggli, S.; Anan, T.; Beck, C.; Cauzzi, G.; Schad, T.; Criscuoli, S.; Davey, A.; Lin, H.; Kuhn, J.; Rast, M.; Goode, P.; Knoelker, M.; Rosner, R.; von der Luehe, O.; Mathioudakis, M.; Dkist Team Bibcode: 2021AAS...23810601R Altcode: The National Science Foundation's 4m Daniel K. Inouye Solar Telescope (DKIST) on Haleakala, Maui is now the largest solar telescope in the world. DKIST's superb resolution and polarimetric sensitivity will enable astronomers to unravel many of the mysteries the Sun presents, including the origin of solar magnetism, the mechanisms of coronal heating and drivers of flares and coronal mass ejections. Five instruments, four of which provide highly sensitive measurements of solar magnetic fields, including the illusive magnetic field of the faint solar corona. The DKIST instruments will produce large and complex data sets, which will be distributed through the NSO/DKIST Data Center. DKIST has achieved first engineering solar light in December of 2019. Due to COVID the start of the operations commissioning phase is delayed and is now expected for fall of 2021. We present a status update for the construction effort and progress with the operations commissioning phase. Title: Enhancements to Hinode/SOT-SP Vector Magnetic Field Data Products Authors: DeRosa, M. L.; Leka, K. D.; Barnes, G.; Wagner, E.; Centeno, R.; De Wijn, A.; Bethge, C. Bibcode: 2021AAS...23821305D Altcode: The Solar Optical Telescope Spectro-Polarimeter (SOT-SP), on board the Hinode spacecraft (launched in 2006), is a scanning-slit spectrograph that continues to provide polarization spectra useful for inferring the vector (three-component) magnetic field at the solar photosphere. SOT-SP achieves this goal by obtaining line profiles of two magnetically sensitive lines, namely the Fe I 6302 Angstrom doublet, using a 0.16"×164" slit as it scans a region of interest. Once the data are merged, a Milne-Eddington based spectropolarimetric inversion scheme is used to infer multiple physical parameters in the solar photosphere, including the vector magnetic field, from the calibrated polarization spectra. All of these data are publicly available once the processing has occurred.
As of this year, the Hinode/SOT team is also making available the disambiguated vector magnetic field and the re-projected heliographic components of the field. In making the disambiguated vector field data product, the 180° ambiguity in the plane-of-sky component of the vector magnetic field inherent in the spectropolarimetric inversion process has been resolved. This ambiguity is resolved using the Minimum-Energy algorithm, which is the same algorithm used within the pipeline producing the vector-magnetogram data product for the Helioseismic and Magnetic Imager aboard the Solar Dynamics Observatory. The heliographic field components (Bphi, Btheta, Br) on the same grid as the inverted data are also now provided. This poster provides more details about these data product enhancements, and some examples on how the scientific community may readily obtain these data. Title: Design and Performance Analysis of a Highly Efficient Polychromatic Full Stokes Polarization Modulator for the CRISP Imaging Spectrometer Authors: de Wijn, A. G.; de la Cruz Rodríguez, J.; Scharmer, G. B.; Sliepen, G.; Sütterlin, P. Bibcode: 2021AJ....161...89D Altcode: 2021arXiv210201231D We present the design and performance of a polychromatic polarization modulator for the CRisp Imaging SpectroPolarimeter (CRISP) Fabry-Perot tunable narrow-band imaging spectropolarimer at the Swedish 1 m Solar Telescope (SST). We discuss the design process in depth, compare two possible modulator designs through a tolerance analysis, and investigate thermal sensitivity of the selected design. The trade-offs and procedures described in this paper are generally applicable in the development of broadband polarization modulators. The modulator was built and has been operational since 2015. Its measured performance is close to optimal between 500 and 900 nm, and differences between the design and as-built modulator are largely understood. We show some example data, and briefly review scientific work that used data from SST/CRISP and this modulator. Title: Coronagraphy from the Ground: Current and Future Observations Authors: Burkepile, J.; Tomczyk, S.; Zmarzly, P.; de Wijn, A.; Gibson, S. E.; de Toma, G.; Galloy, M. D. Bibcode: 2020AGUFMSH031..03B Altcode: Ground-based coronagraphs provided the first observations of the ethereal corona outside of a total solar eclipse in 1931. Invented by Bernard Lyot, coronagraphs enabled long time-series images and movies of the emission line corona. Advances in technology have led to more sophisticated coronagraphs capable of observing polarized light from spectral lines and the coronal continuum. These observations, coupled with advances in our understanding of resonance scattering-induced polarization, have greatly facilitated our knowledge of coronal physics and explosive events such as Coronal Mass Ejections (CMEs). While space-based coronagraphs provide spectacular observations of the extended corona, ground-based coronagraphs continue to contribute important, unique and complementary inner coronal observations at a fraction of the cost of a space-based mission. We discuss current ground-based solar coronagraphs, observations and data products and highlight future instruments and network capabilities and benefits. Title: The Daniel K. Inouye Solar Telescope - Observatory Overview Authors: Rimmele, Thomas R.; Warner, Mark; Keil, Stephen L.; Goode, Philip R.; Knölker, Michael; Kuhn, Jeffrey R.; Rosner, Robert R.; McMullin, Joseph P.; Casini, Roberto; Lin, Haosheng; Wöger, Friedrich; von der Lühe, Oskar; Tritschler, Alexandra; Davey, Alisdair; de Wijn, Alfred; Elmore, David F.; Fehlmann, André; Harrington, David M.; Jaeggli, Sarah A.; Rast, Mark P.; Schad, Thomas A.; Schmidt, Wolfgang; Mathioudakis, Mihalis; Mickey, Donald L.; Anan, Tetsu; Beck, Christian; Marshall, Heather K.; Jeffers, Paul F.; Oschmann, Jacobus M.; Beard, Andrew; Berst, David C.; Cowan, Bruce A.; Craig, Simon C.; Cross, Eric; Cummings, Bryan K.; Donnelly, Colleen; de Vanssay, Jean-Benoit; Eigenbrot, Arthur D.; Ferayorni, Andrew; Foster, Christopher; Galapon, Chriselle Ann; Gedrites, Christopher; Gonzales, Kerry; Goodrich, Bret D.; Gregory, Brian S.; Guzman, Stephanie S.; Guzzo, Stephen; Hegwer, Steve; Hubbard, Robert P.; Hubbard, John R.; Johansson, Erik M.; Johnson, Luke C.; Liang, Chen; Liang, Mary; McQuillen, Isaac; Mayer, Christopher; Newman, Karl; Onodera, Brialyn; Phelps, LeEllen; Puentes, Myles M.; Richards, Christopher; Rimmele, Lukas M.; Sekulic, Predrag; Shimko, Stephan R.; Simison, Brett E.; Smith, Brett; Starman, Erik; Sueoka, Stacey R.; Summers, Richard T.; Szabo, Aimee; Szabo, Louis; Wampler, Stephen B.; Williams, Timothy R.; White, Charles Bibcode: 2020SoPh..295..172R Altcode: We present an overview of the National Science Foundation's Daniel K. Inouye Solar Telescope (DKIST), its instruments, and support facilities. The 4 m aperture DKIST provides the highest-resolution observations of the Sun ever achieved. The large aperture of DKIST combined with state-of-the-art instrumentation provide the sensitivity to measure the vector magnetic field in the chromosphere and in the faint corona, i.e. for the first time with DKIST we will be able to measure and study the most important free-energy source in the outer solar atmosphere - the coronal magnetic field. Over its operational lifetime DKIST will advance our knowledge of fundamental astronomical processes, including highly dynamic solar eruptions that are at the source of space-weather events that impact our technological society. Design and construction of DKIST took over two decades. DKIST implements a fast (f/2), off-axis Gregorian optical design. The maximum available field-of-view is 5 arcmin. A complex thermal-control system was implemented in order to remove at prime focus the majority of the 13 kW collected by the primary mirror and to keep optical surfaces and structures at ambient temperature, thus avoiding self-induced local seeing. A high-order adaptive-optics system with 1600 actuators corrects atmospheric seeing enabling diffraction limited imaging and spectroscopy. Five instruments, four of which are polarimeters, provide powerful diagnostic capability over a broad wavelength range covering the visible, near-infrared, and mid-infrared spectrum. New polarization-calibration strategies were developed to achieve the stringent polarization accuracy requirement of 5×10−4. Instruments can be combined and operated simultaneously in order to obtain a maximum of observational information. Observing time on DKIST is allocated through an open, merit-based proposal process. DKIST will be operated primarily in "service mode" and is expected to on average produce 3 PB of raw data per year. A newly developed data center located at the NSO Headquarters in Boulder will initially serve fully calibrated data to the international users community. Higher-level data products, such as physical parameters obtained from inversions of spectro-polarimetric data will be added as resources allow. Title: Venus Transitis the Solar Corona Authors: De Wijn, Alfred; Können, Gunther Bibcode: 2020S&T...140d..11D Altcode: No abstract at ADS Title: Coronal Solar Magnetism Observatory Science Objectives Authors: Gibson, S. E.; Tomczyk, S.; Burkepile, J.; Casini, R.; DeLuca, E.; de Toma, G.; de Wijn, A.; Fan, Y.; Golub, L.; Judge, P. G.; Landi, E.; McIntosh, S. W.; Reeves, K.; Seaton, D. B.; Zhang, J. Bibcode: 2019AGUFMSH11C3395G Altcode: Space-weather forecast capability is held back by our current lack of basic scientific understanding of CME magnetic evolution, and the coronal magnetism that structures and drives the solar wind. Comprehensive observations of the global magnetothermal environment of the solar atmosphere are needed for progress. When fully implemented, the COSMO suite of synoptic ground-based telescopes will provide the community with comprehensive and simultaneous measurements of magnetism, temperature, density and plasma flows and waves from the photosphere through the chromosphere and out into the corona. We will discuss how these observations will uniquely address a set of science objectives that are central to the field of solar and space physics: in particular, to understand the storage and release of magnetic energy, to understand CME dynamics and consequences for shocks, to determine the role of waves in solar atmospheric heating and solar wind acceleration, to understand how the coronal magnetic field relates to the solar dynamo, and to constrain and improve space-weather forecast models. Title: ngGONG: The Next Generation GONG - A New Solar Synoptic Observational Network Authors: Hill, Frank; Hammel, Heidi; Martinez-Pillet, Valentin; de Wijn, A.; Gosain, S.; Burkepile, J.; Henney, C. J.; McAteer, J.; Bain, H. M.; Manchester, W.; Lin, H.; Roth, M.; Ichimoto, K.; Suematsu, Y. Bibcode: 2019BAAS...51g..74H Altcode: 2019astro2020U..74H The white paper describes a next-generation GONG, a ground-based geographically distributed network of instrumentation to continually observe the Sun. This would provide data for solar magnetic field research and space weather forecasting, and would extend the time coverage of helioseismology. Title: Investigating Coronal Magnetism with COSMO: Science on the Critical Path To Understanding The ``Weather'' of Stars and Stellarspheres Authors: McIntosh, Scott; Tomczyk, Steven; Gibson, Sarah E.; Burkepile, Joan; de Wijn, Alfred; Fan, Yuhong; deToma, Giuliana; Casini, Roberto; Landi, Enrico; Zhang, Jie; DeLuca, Edward E.; Reeves, Katharine K.; Golub, Leon; Raymond, John; Seaton, Daniel B.; Lin, Haosheng Bibcode: 2019BAAS...51g.165M Altcode: 2019astro2020U.165M The Coronal Solar Magnetism Observatory (COSMO) is a unique ground-based facility designed to address the shortfall in our capability to measure magnetic fields in the solar corona. Title: Status Update of the COSMO ChroMag Authors: de Wijn, Alfred G. Bibcode: 2019shin.confE.193D Altcode: I present an overview of the COSMO ChroMag instrument, its status, and discuss the inclusion of an instrument with similar capabilities in a potential future global network of ground-based observatories from a forecasters and researchers perspective. Title: Synoptic Studies of the Sun as a Key to Understanding Stellar Astrospheres Authors: Martinez Pillet, Valentin; Hill, Frank; Hammel, Heidi B.; de Wijn, Alfred G.; Gosain, Sanjay; Burkepile, Joan; Henney, Carl; McAteer, R. T. James; Bain, Hazel; Manchester, Ward; Lin, Haosheng; Roth, Markus; Ichimoto, Kiyoshi; Suematsu, Yoshinori Bibcode: 2019BAAS...51c.110M Altcode: 2019astro2020T.110M; 2019arXiv190306944M Ground-based solar observations provide key contextual data (i.e., the "big picture") to produce a complete description of the only astrosphere we can study in situ: our Sun's heliosphere. This white paper outlines the current paradigm for ground-based solar synoptic observations, and indicates those areas that will benefit from focused attention. Title: First Results from the Chromosphere and Prominence Magnetometer Authors: de Wijn, A. G. Bibcode: 2019ASPC..526..353D Altcode: The Chromosphere and Prominence Magnetometer (ChroMag) is an instrument with the goal of quantifying the intertwined dynamics and magnetism of the solar chromosphere and prominences through synoptic imaging spectro-polarimetry of the full solar disk. The picture of chromospheric magnetism and dynamics is rapidly developing, and a pressing need exists for breakthrough measurements of the chromospheric vector magnetic field, which can be considered to represent the lower boundary of the heliospheric system. ChroMag will provide measurements that will enable scientists to study and better understand the energetics of the solar atmosphere, how prominences are formed, how energy is stored in the magnetic field structure of the atmosphere, and how it is released during space weather events like flares and coronal mass ejections. A prototype ChroMag instrument is currently deployed in Boulder, CO, USA. We present an overview of the instrument capabilities, a progress update on the ChroMag development, and show initial results. Title: Characterization of Cameras for the COSMO K-coronagraph Authors: de Wijn, A. G. Bibcode: 2019AJ....157....8D Altcode: 2018arXiv181205182D Digital image sensors are ubiquitous in astronomical instrumentation and it is well known that they suffer from issues that must be corrected for data to be scientifically useful. I present discussion on errors resulting from digitization and characterization of nonlinearity and ADC errors of the PhotonFocus MV-D1024E cameras selected for the K-coronagraph of the Coronal Solar Magnetism Observatory. I derive an analytic expression for quantization errors. The MV-D1024E camera has adequate bit depth for which quantization error is not an issue. I show that this is not the case for all cameras, particularly those with deep wells and low read noise. The impact of nonlinearity and ADC errors on science observations of the K-coronagraph is analyzed using a simplified telescope model. Errors caused by the camera ADCs result in systematic errors in the measurement of the polarimetric signal of several times 10-9 B ⊙, which is about an order of magnitude above the desired sensitivity. I demonstrate a method for post-facto data correction using a lookup table and derive parameters from camera characterization measurements that were made with a lab setup. Nonlinearity is traditionally addressed with a global correction. I show through analysis of calibration data that for the MV-D1024E this correction leaves residual systematic errors after dark and gain correction of up to 1% of the signal. I demonstrate that a pixel-wise correction of nonlinearity reduces the errors to below 0.1%. These corrections are necessary for the K-coronagraph data products to meet the science requirements. They have been implemented in the instrument data acquisition system and data reduction pipeline. While no other instruments besides the K-coronagraph or cameras besides the MV-D1024E are discussed here, the results are illustrative for all instruments and cameras. Title: Status of the Daniel K. Inouye Solar Telescope: unraveling the mysteries the Sun. Authors: Rimmele, Thomas R.; Martinez Pillet, Valentin; Goode, Philip R.; Knoelker, Michael; Kuhn, Jeffrey Richard; Rosner, Robert; Casini, Roberto; Lin, Haosheng; von der Luehe, Oskar; Woeger, Friedrich; Tritschler, Alexandra; Fehlmann, Andre; Jaeggli, Sarah A.; Schmidt, Wolfgang; De Wijn, Alfred; Rast, Mark; Harrington, David M.; Sueoka, Stacey R.; Beck, Christian; Schad, Thomas A.; Warner, Mark; McMullin, Joseph P.; Berukoff, Steven J.; Mathioudakis, Mihalis; DKIST Team Bibcode: 2018AAS...23231601R Altcode: The 4m Daniel K. Inouye Solar Telescope (DKIST) currently under construction on Haleakala, Maui will be the world’s largest solar telescope. Designed to meet the needs of critical high resolution and high sensitivity spectral and polarimetric observations of the sun, this facility will perform key observations of our nearest star that matters most to humankind. DKIST’s superb resolution and sensitivity will enable astronomers to address many of the fundamental problems in solar and stellar astrophysics, including the origin of stellar magnetism, the mechanisms of coronal heating and drivers of the solar wind, flares, coronal mass ejections and variability in solar and stellar output. DKIST will also address basic research aspects of Space Weather and help improve predictive capabilities. In combination with synoptic observations and theoretical modeling DKIST will unravel the many remaining mysteries of the Sun.The construction of DKIST is progressing on schedule with 80% of the facility complete. Operations are scheduled to begin early 2020. DKIST will replace the NSO facilities on Kitt Peak and Sac Peak with a national facility with worldwide unique capabilities. The design allows DKIST to operate as a coronagraph. Taking advantage of its large aperture and infrared polarimeters DKIST will be capable to routinely measure the currently illusive coronal magnetic fields. The state-of-the-art adaptive optics system provides diffraction limited imaging and the ability to resolve features approximately 20 km on the Sun. Achieving this resolution is critical for the ability to observe magnetic structures at their intrinsic, fundamental scales. Five instruments will be available at the start of operations, four of which will provide highly sensitive measurements of solar magnetic fields throughout the solar atmosphere - from the photosphere to the corona. The data from these instruments will be distributed to the world wide community via the NSO/DKIST data center located in Boulder. We present examples of science objectives and provide an overview of the facility and project status, including the ongoing efforts of the community to develop the critical science plan for the first 2-3 years of operations. Title: First Detection of Sign-reversed Linear Polarization from the Forbidden [O I] 630.03 nm Line Authors: de Wijn, A. G.; Socas-Navarro, H.; Vitas, N. Bibcode: 2017ApJ...836...29D Altcode: 2017arXiv170108793D We report on the detection of linear polarization of the forbidden [O I] 630.03 nm spectral line. The observations were carried out in the broader context of the determination of the solar oxygen abundance, an important problem in astrophysics that still remains unresolved. We obtained spectro-polarimetric data of the forbidden [O I] line at 630.03 nm as well as other neighboring permitted lines with the Solar Optical Telescope of the Hinode satellite. A novel averaging technique was used, yielding very high signal-to-noise ratios in excess of 105. We confirm that the linear polarization is sign-reversed compared to permitted lines as a result of the line being dominated by a magnetic dipole transition. Our observations open a new window for solar oxygen abundance studies, offering an alternative method to disentangle the Ni I blend from the [O I] line at 630.03 nm that has the advantage of simple LTE formation physics. Title: What’s New at the Mauna Loa Solar Observatory Authors: Burkepile, Joan; de Toma, Giuliana; Galloy, Michael; Kolinski, Don; Berkey, Ben; Stueben, Allen; Tomczyk, Steven; De Wijn, Alfred; Casini, Roberto; Card, Greg; Larson, Brandon; Stanger, Andrew; Oakley, Phil; Gallagher, Dennis; Waters, Lisa; Rose, Greg; Sewell, Scott Bibcode: 2016SPD....47.0801B Altcode: The Mauna Loa Solar Observatory (MLSO) is located at 3440 meters on the island of Hawaii. The site provides the dark, clear skies required for observing the solar corona. The National Center for Atmosphere Research (NCAR) High Altitude Observatory (HAO) operates two coronagraphs at the site: the Coronal Multi-Channel Polarimeter (CoMP) and the COSMO K-Coronagraph (K-Cor). CoMP is designed to study coronal magnetic fields by observing full Stokes polarimetry of two forbidden emission lines of FeXIII at 1074.7 and 1079.8 nm. CoMP also observes active and erupting prominences over the solar limb in neutral Helium emission at 1083.nm. The K-Cor is designed to study the onset and early evolution of coronal mass ejections (CMEs). It is the only white light coronagraph to routinely view the low corona down to 1.05 solar radii in order to capture the formation of CMEs. Information is provided on new Helium data products of active and erupting prominences observed by the CoMP instrument as well as results from the K-Cor observations of CMEs. Information on current and upcoming upgrades to the MLSO facility, instrument hardware, and calibrations are reported along with an accounting of new data products, tools and services from the MLSO website. Title: A Progress Update for the COronal Solar Magnetism Observatory for Coronal and Chromospheric Polarimetry Authors: de Wijn, A. G.; Tomczyk, S.; Burkepile, J. Bibcode: 2014ASPC..489..323D Altcode: We present a progress update for the COronal Solar Magnetism Observatory (COSMO), consisting of a suite of three instruments: a large-aperture coronagraph for coronal magnetometry, a full-disk imaging spectro-polarimeter for magnetometry and plasma diagnostics of the chromosphere and prominences, and a white-light coronagraph to observe the K-corona. COSMO will provide unique observations of the global coronal magnetic fields and its environment to enhance the value of data collected by other observatories on the ground and in space. We provide an overview of COSMO, and discuss each instrument in some detail. Title: On the instrument profile of slit spectrographs Authors: Casini, R.; de Wijn, A. G. Bibcode: 2014JOSAA..31.2002C Altcode: 2014arXiv1409.0137C We derive an analytic expression for the instrument profile of a slit spectrograph, also known as the line spread function. While this problem is not new, our treatment relies on the operatorial approach to the description of diffractive optical systems, which provides a general framework for the analysis of the performance of slit spectrographs under different illumination conditions. Based on our results, we propose an approximation to the spectral resolution of slit spectrographs, taking into account diffraction effects and sampling by the detector, which improves upon the often adopted approximation based on the root-sumsquare of the individual contributions from the slit, the grating, and the detector pixel. Title: The Chromosphere and Prominence Magnetometer Authors: de Wijn, Alfred G.; McIntosh, Scott W.; Tomczyk, Steven Bibcode: 2014shin.confE..76D Altcode: The Chromosphere and Prominence Magnetometer (ChroMag) is a synoptic instrument with the goal of quantifying the intertwined dynamics and magnetism of the solar chromosphere and in prominences through imaging spectro-polarimetry of the full solar disk in a synoptic fashion. The picture of chromospheric magnetism and dynamics is rapidly developing, and a pressing need exists for breakthrough observations of chromospheric vector magnetic field measurements at the true lower boundary of the heliospheric system. ChroMag will provide measurements that will enable scientists to study and better understand the energetics of the solar atmosphere, how prominences are formed, how energy is stored in the magnetic field structure of the atmosphere and how it is released during space weather events like flares and coronal mass ejections. An essential part of the ChroMag program is a commitment to develop and provide community access to the `inversion' tools necessary to interpret the measurements and derive the magneto-hydrodynamic parameters of the plasma. Measurements of an instrument like ChroMag provide critical physical context for the Solar Dynamics Observatory (SDO) and Interface Region Imaging Spectrograph (IRIS) as well as ground-based observatories such as the future Daniel K. Inouye Solar Telescope (DKIST). A prototype is currently deployed in Boulder, CO, USA. We will present an overview of instrument capabilities and a progress update on the ChroMag development. Title: Design and measurement of the Stokes polarimeter for the COSMO K-coronagraph Authors: Hou, Junfeng; de Wijn, Alfred G.; Tomczyk, Steven Bibcode: 2013ApJ...774...85H Altcode: We present the Stokes polarimeter for the new Coronal Solar Magnetism Observatory K-coronagraph. The polarimeter can be used in two modes. In observation mode, it is sensitive to linear polarization only and operates as a "Stokes definition" polarimeter. In the ideal case, such a modulator isolates a particular Stokes parameter in each modulation state. For calibrations, the polarimeter can diagnose the full Stokes vector. We present here the design process of the polarimeter, analyze its tolerances with a Monte Carlo method, develop a way to align the individual elements, and measure and evaluate its performance in both modes. Title: The Chromosphere and Prominence Magnetometer Authors: de Wijn, Alfred; Bethge, Christian; McIntosh, Scott; Tomczyk, Steven; Burkepile, Joan Bibcode: 2013EGUGA..1512765D Altcode: The Chromosphere and Prominence Magnetometer (ChroMag) is a synoptic instrument with the goal of quantifying the intertwined dynamics and magnetism of the solar chromosphere and in prominences through imaging spectro-polarimetry of the full solar disk in a synoptic fashion. The picture of chromospheric magnetism and dynamics is rapidly developing, and a pressing need exists for breakthrough observations of chromospheric vector magnetic field measurements at the true lower boundary of the heliospheric system. ChroMag will provide measurements that will enable scientists to study and better understand the energetics of the solar atmosphere, how prominences are formed, how energy is stored in the magnetic field structure of the atmosphere and how it is released during space weather events like flares and coronal mass ejections. An essential part of the ChroMag program is a commitment to develop and provide community access to the `inversion' tools necessary to interpret the measurements and derive the magneto-hydrodynamic parameters of the plasma. Measurements of an instrument like ChroMag provide critical physical context for the Solar Dynamics Observatory (SDO) and Interface Region Imaging Spectrograph (IRIS) as well as ground-based observatories such as the future Advanced Technology Solar Telescope (ATST). A prototype is currently under construction at the High Altitude Observatory of the National Center for Atmospheric Research in Boulder, CO, USA. The heart of the ChroMag instrument is an electro-optically tunable wide-fielded narrow-band birefringent six-stage Lyot filter with a built-in polarimeter. We will present a progress update on the ChroMag design, and present results from the prototype instrument. Title: Measuring Magnetic Fields in the Solar Atmosphere Authors: de Wijn, A. G. Bibcode: 2013ASPC..470...65D Altcode: 2012arXiv1207.0943D Since the discovery by Hale in the early 1900s that sunspots harbor strong magnetic field, magnetism has become increasingly important in our understanding of processes on the Sun and in the Heliosphere. Many current and planned instruments are capable of diagnosing magnetic field in the solar atmosphere. Photospheric magnetometry is now well-established. However, many challenges remain. For instance, the diagnosis of magnetic field in the chromosphere and corona is difficult, and interpretation of measurements is harder still. As a result only very few measurements have been made so far, yet it is clear that if we are to understand the outer solar atmosphere we must study the magnetic field. I will review the history of solar magnetic field measurements, describe and discuss the three types of magnetometry, and close with an outlook on the future. Title: Measuring Solar Magnetism Authors: de Wijn, Alfred G. Bibcode: 2012Sci...338..476D Altcode: No abstract at ADS Title: Probable Identification of the On-disk Counterpart of Spicules in Hinode Ca II H Observations Authors: de Wijn, A. G. Bibcode: 2012ApJ...757L..17D Altcode: 2012arXiv1208.6329D I present a study of high-resolution time series of Ca II H images and Fe I 630.15 nm spectra taken with the Solar Optical Telescope on the Hinode spacecraft. There is excellent correspondence between the Ca II H and the Fe I line core intensity, except tenuous emission around the network field concentrations in the former that is absent in the latter. Analysis of on-disk observations and a comparison with limb observations suggests that this "network haze" corresponds to spicules, and likely to type-II spicules in particular. They are known to appear in emission in on-disk broadband Ca II H diagnostics and the network haze is strongest in those areas where features similar to type-II spicules are produced in simulations. Title: Stray light and polarimetry considerations for the COSMO K-Coronagraph Authors: de Wijn, Alfred G.; Burkepile, Joan T.; Tomczyk, Steven; Nelson, Peter G.; Huang, Pei; Gallagher, Dennis Bibcode: 2012SPIE.8444E..3ND Altcode: 2012arXiv1207.0978D The COSMO K-Coronagraph is scheduled to replace the aging Mk4 K-Coronameter at the Mauna Loa Solar Observatory of the National Center for Atmospheric Research in 2013. We present briefly the science objectives and derived requirements, and the optical design. We single out two topics for more in-depth discussion: stray light, and performance of the camera and polarimeter. Title: Design of a full-Stokes polarimeter for VLT/X-shooter Authors: Snik, Frans; van Harten, Gerard; Navarro, Ramon; Groot, Paul; Kaper, Lex; de Wijn, Alfred Bibcode: 2012SPIE.8446E..25S Altcode: 2012arXiv1207.2965S X-shooter is one of the most popular instruments at the VLT, offering instantaneous spectroscopy from 300 to 2500 nm. We present the design of a single polarimetric unit at the polarization-free Cassegrain focus that serves all three spectrograph arms of X-shooter. It consists of a calcite Savart plate as a polarizing beam-splitter and a rotatable crystal retarder stack as a "polychromatic modulator". Since even "superachromatic" wave plates have a wavelength range that is too limited for X-shooter, this novel modulator is designed to offer close-to-optimal polarimetric efficiencies for all Stokes parameters at all wavelengths. We analyze the modulator design in terms of its polarimetric performance, its temperature sensitivity, and its polarized fringes. Furthermore, we present the optical design of the polarimetric unit. The X-shooter polarimeter will furnish a myriad of science cases: from measuring stellar magnetic fields (e.g., Ap stars, white dwarfs, massive stars) to determining asymmetric structures around young stars and in supernova explosions. Title: The chromosphere and prominence magnetometer Authors: de Wijn, Alfred G.; Bethge, Christian; Tomczyk, Steven; McIntosh, Scott Bibcode: 2012SPIE.8446E..78D Altcode: 2012arXiv1207.0969D The Chromosphere and Prominence Magnetometer (ChroMag) is conceived with the goal of quantifying the intertwined dynamics and magnetism of the solar chromosphere and in prominences through imaging spectro- polarimetry of the full solar disk. The picture of chromospheric magnetism and dynamics is rapidly developing, and a pressing need exists for breakthrough observations of chromospheric vector magnetic field measurements at the true lower boundary of the heliospheric system. ChroMag will provide measurements that will enable scientists to study and better understand the energetics of the solar atmosphere, how prominences are formed, how energy is stored in the magnetic field structure of the atmosphere and how it is released during space weather events like flares and coronal mass ejections. An integral part of the ChroMag program is a commitment to develop and provide community access to the "inversion" tools necessary for the difficult interpretation of the measurements and derive the magneto-hydrodynamic parameters of the plasma. Measurements of an instrument like ChroMag provide critical physical context for the Solar Dynamics Observatory (SDO) and Interface Region Imaging Spectrograph (IRIS) as well as ground-based observatories such as the future Advanced Technology Solar Telescope (ATST). Title: Analysis of Seeing-induced Polarization Cross-talk and Modulation Scheme Performance Authors: Casini, R.; de Wijn, A. G.; Judge, P. G. Bibcode: 2012ApJ...757...45C Altcode: 2011arXiv1107.0367C We analyze the generation of polarization cross-talk in Stokes polarimeters by atmospheric seeing, and its effects on the noise statistics of spectropolarimetric measurements for both single-beam and dual-beam instruments. We investigate the time evolution of seeing-induced correlations between different states of one modulation cycle and compare the response to these correlations of two popular polarization modulation schemes in a dual-beam system. Extension of the formalism to encompass an arbitrary number of modulation cycles enables us to compare our results with earlier work. Even though we discuss examples pertinent to solar physics, the general treatment of the subject and its fundamental results might be useful to a wider community. Title: Preliminary design of the visible spectro-polarimeter for the Advanced Technology Solar Telescope Authors: de Wijn, Alfred G.; Casini, Roberto; Nelson, Peter G.; Huang, Pei Bibcode: 2012SPIE.8446E..6XD Altcode: 2012arXiv1207.0976D The Visible Spectro-Polarimeter (ViSP) is one of the first light instruments for the Advanced Technology Solar Telescope (ATST). It is an echelle spectrograph designed to measure three different regions of the solar spectrum in three separate focal planes simultaneously between 380 and 900 nm. It will use the polarimetric capabilities of the ATST to measure the full Stokes parameters across the line profiles. By measuring the polarization in magnetically sensitive spectral lines the magnetic field vector as a function of height in the solar atmosphere can be obtained, along with the associated variation of the thermodynamic properties. The ViSP will have a spatial resolution of 0.04 arcsec over a 2 arcmin field of view (at 600 nm). The minimum spectral resolving power for all the focal planes is 180,000. The spectrograph supports up to 4 diffraction gratings and is fully automated to allow for rapid reconfiguration. Title: The Chromospheric Magnetometer ChroMag Authors: Bethge, Christian; de Wijn, A. G.; McIntosh, S. W.; Tomczyk, S.; Casini, R. Bibcode: 2012AAS...22013506B Altcode: We present the Chromosphere Magnetometer (ChroMag), which is part of the Coronal Solar Magnetism Observatory (COSMO) proposed by the High Altitude Observatory (HAO) in collaboration with the University of Hawaii and the University of Michigan. ChroMag will perform routine measurements of chromospheric magnetic fields in a synoptic manner. A prototype is currently being assembled at HAO. The main component of the instrument is a Lyot-type filtergraph polarimeter for both on-disk and off-limb polarization measurements in the spectral lines of H alpha at 656.3 nm, Fe I 617.3 nm, Ca II 854.2 nm, He I 587.6 nm, and He I 1083.0 nm. The Lyot filter is tunable at a fast rate. This allows to determine line-of-sight velocities in addition to the magnetic field measurements. The instrument has a field-of-view of up to 2.5 solar radii and will acquire data at a cadence of less than 1 minute and at a spatial resolution of 2 arcsec. The community will have open access to the data as well as to a set of inversion tools for an easier interpretation of the measurements. We show an overview of the proposed instrument and first results from the protoype. Title: A High-Resolution Study of Ca II H Time Series Authors: de Wijn, A. G. Bibcode: 2012ASPC..456...49D Altcode: I present a study of high-resolution, high-cadence time series of Ca II H images and Fe I 630.15 nm spectra taken with the Solar Optical Telescope on the Hinode spacecraft. There is excellent correspondence between the Ca II H and Fe I line core intensity, except tenuous emission around the network field concentrations in the former that is absent in the latter. Comparison with limb observations shows that this “network haze'' most likely corresponds to type-II spicules. Title: The Chromosphere and Prominence Magnetometer Authors: de Wijn, Alfred; Bethge, Christian; McIntosh, Scott; Tomczyk, Steven; Casini, Roberto Bibcode: 2012decs.confE..63D Altcode: ChroMag is an imaging polarimeter designed to measure on-disk chromosphere and off-disk prominence magnetic fields using the spectral lines of He I (587.6 and 1083 nm). It is part of the planned CoSMO suite, which includes two more instruments: a large 1.5-m refracting coronagraph for coronal magnetic field measurements, and the K-Coronagraph for measurement of the coronal density. ChroMag will provide insights in the energetics of the solar atmosphere, how prominences are formed, and how energy is stored and released in the magnetic field structure of the atmosphere. An essential part of the ChroMag program is a commitment to develop and provide community access to the "inversion" tools necessary to interpret the measurements and derive the magneto-hydrodynamic parameters of the plasma. A prototype instrument is currently under construction at the High Altitude Observatory. We will present an overview of the ChroMag instrument concept, target science, and prototype status. Title: Synoptic measurements of chromospheric and prominence magnetic fields with the Chromosphere Magnetometer ChroMag Authors: Bethge, C.; de Wijn, A. G.; McIntosh, S. W.; Tomczyk, S.; Casini, R. Bibcode: 2012decs.confE..62B Altcode: The Chromosphere Magnetometer is part of the Coronal Solar Magnetism Observatory (COSMO) proposed by the High Altitude Observatory (HAO) in collaboration with the University of Hawaii and the University of Michigan. Routine measurements of chromospheric and coronal magnetic fields are vital if we want to understand fundamental problems like the energy and mass balance of the corona, the onset and acceleration of the solar wind, the emergence of CMEs, and how these phenomena influence space weather. ChroMag is designed as a Lyot-type filtergraph polarimeter with an FOV of 2.5 solar radii, i.e., it will be capable of both on-disk and off-limb polarimetric measurements. The Lyot filter - currently being built at HAO - is tunable at a fast rate, which allows to determine line-of-sight velocities. This will be done in the spectral lines of H alpha at 656.3 nm, Fe I 617.3 nm, Ca II 854.2 nm, He I 587.6 nm, and He I 1083.0 nm at a high cadence of less than 1 minute, and at a moderate spatial resolution of 2 arcsec. ChroMag data will be freely accessible to the community, along with inversion tools for an easier interpretation of the data. A protoype instrument for ChroMag is currently being assembled at HAO and is expected to perform first measurements at the Boulder Mesa Lab in Summer 2012. We present an overview of the ChroMag instrument and the current status of the protoype. Title: Quiet-Sun imaging asymmetries in Na I D1 compared with other strong Fraunhofer lines Authors: Rutten, R. J.; Leenaarts, J.; Rouppe van der Voort, L. H. M.; de Wijn, A. G.; Carlsson, M.; Hansteen, V. Bibcode: 2011A&A...531A..17R Altcode: 2011arXiv1104.4307R Imaging spectroscopy of the solar atmosphere using the Na I D1 line yields marked asymmetry between the blue and red line wings: sampling a quiet-Sun area in the blue wing displays reversed granulation, whereas sampling in the red wing displays normal granulation. The Mg I b2 line of comparable strength does not show this asymmetry, nor does the stronger Ca II 8542 Å line. We demonstrate the phenomenon with near-simultaneous spectral images in Na I D1, Mg I b2, and Ca II 8542 Å from the Swedish 1-m Solar Telescope. We then explain it with line-formation insights from classical 1D modeling and with a 3D magnetohydrodynamical simulation combined with NLTE spectral line synthesis that permits detailed comparison with the observations in a common format. The cause of the imaging asymmetry is the combination of correlations between intensity and Dopplershift modulation in granular overshoot and the sensitivity to these of the steep profile flanks of the Na I D1 line. The Mg I b2 line has similar core formation but much wider wings due to larger opacity buildup and damping in the photosphere. Both lines obtain marked core asymmetry from photospheric shocks in or near strong magnetic concentrations, less from higher-up internetwork shocks that produce similar asymmetry in the spatially averaged Ca II 8542 Å profile. Title: Wavelength-diverse Polarization Modulators for Stokes Polarimetry Authors: de Wijn, A. G.; Tomczyk, S.; Casini, R.; Nelson, P. G. Bibcode: 2011ASPC..437..413D Altcode: An increasing number of astronomical applications depend on the measurement of polarized light. For example, our knowledge of solar magnetism relies heavily on our ability to measure and interpret polarization signatures introduced by magnetic field. Many new instruments have consequently focused considerable attention on polarimetry. For solar applications, spectro-polarimeters in particular are often designed to observe the solar atmosphere in multiple spectral lines simultaneously, thus requiring that the polarization modulator employed is efficient at all wavelengths of interest. We present designs of polarization modulators that exhibit near-optimal modulation characteristics over broad spectral ranges. Our design process employs a computer code to optimize the efficiency of the modulator at specified wavelengths. We will present several examples of modulator designs based on rotating stacks of Quartz waveplates and ferroelectric liquid crystals (FLCs). An FLC-based modulator of this design was recently deployed for the ProMag instrument at the Evans Solar Facility of NSO/SP. Title: Observations of solar scattering polarization at high spatial resolution Authors: Snik, F.; de Wijn, A. G.; Ichimoto, K.; Fischer, C. E.; Keller, C. U.; Lites, B. W. Bibcode: 2010A&A...519A..18S Altcode: 2010arXiv1005.5042S Context. The weak, turbulent magnetic fields that supposedly permeate most of the solar photosphere are difficult to observe, because the Zeeman effect is virtually blind to them. The Hanle effect, acting on the scattering polarization in suitable lines, can in principle be used as a diagnostic for these fields. However, the prediction that the majority of the weak, turbulent field resides in intergranular lanes also poses significant challenges to scattering polarization observations because high spatial resolution is usually difficult to attain.