Magnetic fields control the inconstant Sun. The key to understanding solar variability and its direct impact on the Earth rests with understanding all aspects of these magnetic fields. This is the ?dark energy? problem of solar physics since the magnetic fields lie beyond the resolution limits of current solar telescopes, are obscured by Earth's atmosphere, or hidden by the glare of the solar disk in the outer solar atmosphere. The Sun provides the laboratory where crucial properties of non-linear dynamics in highly ionized magnetic plasma can be observed and understood, and models can be tested and refined. The technology now exists to resolve and measure the Sun?s magnetic fields and how they control the solar atmosphere. All aspects of the Advanced Technology Solar Telescope (ATST) design are optimized to study these fields in our astrophysical backyard. With it, we will understand the life cycle of magnetic fields, how they are born by dynamo mechanisms, evolve by convective and explosive phenomena, and dissipated by resistive and reconnective magnetic events.
The ATST will be a 4-m aperture, off-axis solar telescope with integrated adaptive optics, low-scattered light, infrared, coronagraphic, and polarimetric capabilities. It will resolve the essential, fine-scale magnetic features and their dynamics that dictate the varying release of energy from the Sun?s atmosphere. The ATST design is optimized (throughput, scattered light and instrumental polarization properties) to make vector magnetograms down to its diffraction limit (0.03 arcseconds at 500 nm). Its collecting area, which is a factor of 16 greater than today?s solar telescopes, will provide the sensitivity to measure both weak fields and rapidly evolving stronger fields. It has a factor of 64 greater collecting area than the largest existing coronagraph, and will provide the sensitivity and coronagraphic capability needed to measure the weak, fine-scale coronal magnetic fields. The new technologies, and our increased awareness of what we know we must learn, make ATST the necessary and logical successor to the solar telescopes built in the 1960s and 1970s, and is a natural complement to space missions such the Solar Dynamics Observatory, STEREO, and Solar Orbiter.
The ATST offers tremendous opportunity for the training of students and recruitment of post-docs and faculty in solar physics who will become users of the ATST and the instrument builders and theoreticians of the future. ATST plans to establish a strong synergy with the education and outreach programs at the collaborating institutions, including programs for the K-12 classroom, internships, public outreach through tours, hands-on exhibits, and displays. The ATST program has and will continue to actively involve large segments of the US and international solar physics community, helping to strengthen solar astronomy programs at universities and national centers.
