This proposal targets the instrument and technology development (ITD) element of the h-tides program. Magnetic fields form a foundation for all solar active phenomena from tiny g-band bright points to…

This is a federal grant award from the National Aeronautics and Space Administration (NASA) to the Association of Universities for Research in Astronomy, Inc. (AURA), a non-profit organization that manages and operates major astronomical observatories and facilities. The award, valued at $558,040.86, is under the Instrument and Technology Development (ITD) element of the H-TIDES program, which focuses on the development of advanced magnetograph instruments for solar observation missions. The goal is to explore a novel, compact magnetograph concept that can measure broad-band polarization without complex optical systems, potentially enabling the inclusion of such critical instruments on future space weather-oriented missions despite size and weight constraints. The award does not have a set-aside designation. AURA plans to investigate the proposed magnetograph concept through modeling, laboratory testing, and the development of a prototype instrument to be tested at ground-based telescopes, with the potential for future flight opportunities on the International Space Station or other missions.

This proposal targets the instrument and technology development (ITD) element of the h-tides program. Magnetic fields form a foundation for all solar active phenomena from tiny g-band bright points to sunspots and coronal mass ejections (cmes). They serve as a reservoir of energy for flares, play a critical role in triggering mechanisms for cmes, and provide the means of transporting energy from the photosphere to corona. Thus, arguably, the magnetograph should be considered as a critical instrument for every heliophysics mission that studies the solar atmosphere or the effects of solar activity on heliosphere. While the importance of magnetograph instrument is widely recognized by the community, in practice, their inclusion as a spacecraft payload is often limited due to weight and size restrictions. The magnetograph concepts which are currently in use require sampling a magneto-sensitive spectral line at different positions across solar disk. Spectrograph-based magnetographs are superior in terms of spectral sampling, but require scanning of solar image to build up its magnetic map. Narrow-band filter-based magnetographs take simultaneous snapshots of extended area of solar surface, but require taking multiple observations with different wavelength offset between separate frames. Both approaches may require relatively large number of optical and electro-mechanical elements for spectral tuning and/or spatial scanning. These addition elements tend to increase the overall weight and size of instrument, and the added complexity might affect the reliability of system. Goals and objectives: as the main goal of this project, we will explore a novel alternative to the standard filter based magnetograph, which we call the simplest magnetograph. The proposed instrument concept is based on measuring a broad-band polarization over the whole line profile, which could be done without moving optical elements and complicated optical schemes. If successful, this concept will lead to creation of extremely simple and compact line-of-sight (LOS) or full vector magnetograph suitable for space missions. Such instrument could be especially attractive for space weather-oriented missions. The methodology: the concept of the proposed magnetograph is based on a well-known fact that zeeman split spectrum lines in a lineof- sight (LOS) field are asymmetric, with one of the v stokes profile lobes stronger than the other in a way that switches with polarity. In transverse field, there is a net linear polarization averaged across the line profile because the central part of the spectrum line is saturated relative to the wings so the wing polarization dominates in q and u polarization profiles. Thus, measuring net polarization over the entire spectral line profile (without scanning in spectral or spatial directions) allows to determine both polarity and the field strength (magnetic flux) for each pixel of image. Preliminary tests with stokes-v spectra taken with gong instrument support the feasibility of this approach. Proposed contribution: the NSO team will investigate the concept of this simplest magnetograph both via modeling and laboratory measurements. We will also build a prototype instrument. The performance of this magnetograph will be tested at the groundbased telescopes operated by the NSO. In addition, the prototype instrument can be proposed for flight on the international space station and perhaps also on mission of opportunities such as the UK/EU lagrange L5 mission.