Chromospheric Science and ChroMag

1. Chromospheric Science and ChroMag Alfred de Wijn, Scott McIntosh, Michael Thompson High Altitude Observatory NCAR

2. ChroMag InstrumentOverview • Provides synoptic full-disk imaging spectro-polarimetry in: • He I 587.6 & 1083.0 nm: chromosphericmagnetograms • Hα 656.3 nm: chromospheric structure and dynamics • Ca II 854.2 nm: chromosphericmagnetograms • Fe I 617.3 nm: photosphericmagnetograms • High cadence: < 1 minute for all lines • Moderate spatial resolution: 2.2 arcsec (1.1 arcsec pixels) • Moderate but sufficient spectral resolution: > 30000 • Field of view: 2.4 Rsun square • High polarimetric sensitivity: SNR > 103

3. ChroMag Instrument Hardware Primary singlet lens 12.5 cm aperture Field lens Focal plane Polarimeter & Lyot filter Pre-filter Camera lens

4. ChroMagLyot Filter Overview Usable range: 587–1085 nm Spectral resolution > 30 000 Fast electro-optical tuning High-efficiency polychromatic polarimetric modulator

5. Chromospheric Science • Chromospheric imaging permitted significant progress in the understanding the interplay of wave-like phenomena with the three dimensional magnetic field of the outer solar atmosphere. [TRACE] • The high resolution chromospheric imaging of Hinode/SOT at the limb revealed a “different” chromosphere. [Hinode] • Chromospheric imaging spectroscopy has enabled the identification of a direct link between chromospheric and coronal energetics in strongly magnetized regions. [SST, DST] • Increasing capabilities of chromospheric imaging spectropolarimetry are allowing the complete physical picture to be linked; studying the “magneto-thermodynamic” interface between the photosphere and outer atmosphere, enabling “Space Climate” and “Space Weather” research. ChroMag enables ground-breaking science opportunities while end-to-end prototyping for the next generation of chromospheric space instruments.

6. Fundamental Science ChroMag is designed to monitor the thermodynamic and magnetic state throughout the Sun’s chromosphere - the physical base of the Solar system. Initially it will be a predominatly research instrument, but our goal is to make observations which eventually improve operational SWx capabilities. Fundamental exploration of the photospheric/chromospheric thermo-magnetic environments is required to understand the observations: - Understanding and Inverting of ChroMag Stokes vector images: - Employ advanced pattern recognition techniques like PCA - Forward/Inverse Studies using MURaM / HANLE+RH line synthesis Connect the inverted chromospheric vector magnetic maps to the 3-dimensional coronal magnetic field models or measurements (made by instruments like CoMP). Quantify the flow of mass and energy through this interface into heliosphere. Understand the coupling of large and small-scale magnetic environments, as observed by similar high-resolution instruments (NSO/IBIS, SST/CRISP, ATST/VFT). We are open to suggestions for the initial science verification of ChroMag.

7. Synoptic Implementation By taking spectropolarimetric images at a cadence of a few minutes through the ChroMaglineset we will provide access to the instantaneous state of the photospheric and chromospheric plasma over the full solar disk. Robust calibration of the instrument will permit synoptic monitoring of small and large scale phenomena that may help constrain models of solar cycle evolution. Observing ubiquitous coronal features and the magnetic structure they are associated with provides unique insight into the mechanics of the solar cycle. There are (almost always) two overlapping activity cycles. A crucial NEW factor for SWx?

8. Transition to “Operation” By taking spectropolarimetric images at a cadence of a few minutes through the ChroMaglineset we will provide access to the instantaneous state of the chromospheric plasma over the full solar disk. Invaluable for SWx. SWx Model Validation: Continuous evolution in vector B, Thermal, and Non-thermal state.

9. Scientific Opportunities • The ChroMag prototype will be deployed to HAO/MLSO in 2014. • A ChroMag-like instrument will be in operation in Slovakia in 2014 (see talk by Peter Gomory) • “GONG ++” - the GONG network of robotichelioseismicobservatories could be upgraded with ChroMag filters. Deliver GONG science and introduce ChroMag’s unique SWxcapability. • Augmenting GONG/ChroMag with an ISS deployment of ChroMag will enable redundancy and seeing-free observations. ChroMag design can be modified to observe Auroral polarization. An ISS solar observatory initiative is ramping up. • The planned JAXA/NASA/ESA “Solar-C” mission will have a tunable filter imaging spectropolarimeter similar to ChroMag. http://gong.nso.edu/

10. Status & Schedule of ChroMag Prototype Initial deployment to NCAR’s Mesa Spar Facility and first light in spring 2013

11. Status & Schedule First results were promising but a thermal problem with the filter was found. Filter thermal problem mitigation: winter 2013/2014 Re-deployment to the Mesa Spar Facility: spring 2014 Initial science: summer 2014 Deployment to NCAR’s Mauna Loa Solar Observatory: fall/winter 2014 Development of diagnostics needed!

12. Initial Science Cases • Use the Fe I 617.3nm line in full Stokes to perform cross-comparison with SDO/HMI. • Use FVISV [CSAC/MERLIN] to Invert. • Perform comparative analysis of Stokes measurements made by NSO/SOLIS with Ca II 854.2nm and He I 1083.0nm. • Compare Hα 656.3nm observations at line core with the GONG contemporaneous images at MLSO GONG site. • Expand for Dopplergrams and Line Width Diagnostics • Feature [AR, CH, etc] recognition in spectral line moments, comparison with NSO measures. • Compose multi-line Dopplergram sequence for helioseismology test for GONG colleagues to analyze.

13. Data Products • ChroMag operates in a synoptic full-disk mode. • Observation programs are flexible and can be tailored to specific science cases. • Low-level products: • Calibrated full-Stokes line scans in Fe I 617.3 nm, Hα 656.3 nm, Ca II 854.2 nm, and He I 587.6 & 1083.0 nm • Higher-level products: • PhotosphericDopplergrams and vector magnetograms • ChromosphericDopplergrams from Hα, 854.2 nm • Prominence & chromospheric vector magnetograms from 1083.0 nm, 854.2 nm? Inversion techniques are not mature.

14. Interpretative tools The Community Spectropolarimetric Analysis Center (CSAC) at HAO is being refocused to handle ChroMag (CoMP) observations and inversions of more complex plasma environments. • We are developing pattern recognition based inversion techniques for the complex non-LTE profiles of the Chromosphere such as Principal Component Analysis (PCA). • These advanced inversion tools will rely upon the combination of spectral (“RH”; Uitenbroek) and polarimetric (“Hanle”; Casini) line synthesis codes. Using this synthesis tool we will perform comparative forward/inverse studies employing state-of-the-art simulations (MuRAM and Bifrost) to determine accuracy of recovery, ambiguity resolution, etc.