Solar Adaptive Optics

Abstract

Adaptive optics (AO) has become an indispensable tool at ground-based solar telescopes. AO enables the ground-based observer to overcome the adverse effects of atmospheric seeing and obtain diffraction limited observations. Over the last decade adaptive optics systems have been deployed at major ground-based solar telescopes and revitalized ground-based solar astronomy. The relatively small aperture of solar telescopes and the bright source make solar AO possible for visible wavelengths where the majority of solar observations are still performed. Solar AO systems enable diffraction limited observations of the Sun for a significant fraction of the available observing time at ground-based solar telescopes, which often have a larger aperture than equivalent space based observatories, such as HINODE. New ground breaking scientific results have been achieved with solar adaptive optics and this trend continues. New large aperture telescopes are currently being deployed or are under construction. With the aid of solar AO these telescopes will obtain observations of the highly structured and dynamic solar atmosphere with unprecedented resolution. This paper reviews solar adaptive optics techniques and summarizes the recent progress in the field of solar adaptive optics. An outlook to future solar AO developments, including a discussion of Multi-Conjugate AO (MCAO) and Ground-Layer AO (GLAO) will be given.Electronic Supplementary MaterialSupplementary material is available for this article at 10.12942/lrsp-2011-2.

Clearwidens the field for observations of the Sun with multi-conjugate adaptive optics

“…The high-altitude DMs were conjugated to about 3 and 8 km beyond the telescope on the line of sight, such that they almost continuously cover the first 11 km (see Rigaut et al 2000). The wavefront sensor field of view was subdivided into 3 × 3 guideregions in which digital image correlation was performed to estimate wavefront slopes in the Shack-Hartmann subapertures; this is the standard method used for solar Shack-Hartmann sensors (Rimmele & Marino 2011). We used this configuration in a ten-day long observational run at the end of July 2016 when we saw the most impressive boost to the solar image by MCAO so far.…”

“…While CAO systems can provide diffraction-limited images of the Sun within the isoplanatic angle, the image quality may roll off quickly, depending on the instantaneous distribution of the atmospheric turbulence in altitude. The isoplanatic angle is typically of order 5 to 15 for observations in the visible light regime at good telescope sites (e.g., Rimmele & Marino 2011). While adaptive optics has revitalized ground-based solar observations, many problems in solar…”

“…While success of GLAO is closely related to the instantaneous turbulence distribution in height (e.g., Tokovinin 2004), it is an interesting complementary mode of AO, which can lead to a more efficient use of a telescope if both the observational program and the AO mode are chosen wisely. GLAO might also be attractive for small synoptic solar telescopes, such as SOLIS or SPRING, because of its potential to provide neardiffraction-limited imaging of the full solar disk for this class of telescopes depending on the seeing characteristics of their sites (Rimmele & Marino 2011). Dedicated solar GLAO experiments without MCAO were performed first at the 76-cm Dunn Solar Telescope (Rimmele et al 2010) in the visible light regime and recently at the McMath-Pierce Solar Telescope and the Dunn Solar Telescope (Ren et al 2015) in the near-infrared H band (1.5−1.8 µm), but a side-by-side comparison of CAO and GLAO observations demonstrating the merit of GLAO for solar observations was lacking.…”

High-resolution, high-sensitivity, ground-based solar spectropolarimetry with a new fast imaging polarimeter

“…M = 1, of the 20 and 11.1 Hz cases (images c and d respectively), while not being above the noise level for the 100 Hz image (b). Moreover, the artifact tends to have larger amplitudes towards the borders of the FOV because the AO corrections of the wavefront are worse further away from the system's locking point, which is located approximately at the center of the image, owing to seeing anisoplanatism (Rimmele & Marino 2011).…”

Ultra‐High‐Resolution Observations of MHD Waves in Photospheric Magnetic Structures

“…2 Solar Physics and Space Plasma Research Centre (SP 2 RC), The University of Sheffield, Hicks Building, Hounsfield Road, Sheffield, S3 7RH, UK. as it is today, and as a result, key modern techniques such as adaptive optics [AO; e.g., Rimmele & Marino, 2011], multi-object multi-frame blind deconvolution [MOMFBD;van Noort et al, 2005] and speckle reconstruction [Wöger et al, 2008] were unavailable to help combat the fine-scale image degradation caused by the Earth's atmosphere. Therefore, initial research was dedicated to probing large-scale solar structures, including sunspots and super-granules.…”