Copyright © National Academy of Sciences. All rights reserved.
Solar and Space Physics: A Science for a Technological Society
REPORT OF THE PANEL ON SOLAR AND HELIOSPHERIC PHYSICS
297
10.4.7 Goals for Ground-Based Facilities
10.4.7.1 Science Goals for the Advanced Technology Solar Telescope
The Advanced Technology Solar Telescope (ATST) is a ground-based, 4-m-aperture solar telescope
whose first observations are expected in 2016. By far the largest optical solar telescope in the world, ATST
will provide revolutionary observational resolution as small as 30 km. Comparing observations on this scale
with equally resolved numerical models will transform physical understanding of many solar features from
informed speculation to hard science. ATST will furnish enough intensity to feed a large array of sensitive
and powerful instruments. As a general-purpose community facility, ATST will address a wide variety of
ever-changing science goals over its decades-long lifetime. 10
Within the photosphere, nearly all the Sun’s magnetic flux is in the form of small, dynamic elements.
Constantly energized by convection, this magnetic sea directs upward flows of mass and energy to create
the chromosphere, corona, and solar wind. Studying that fundamental process is a major initial ATST science goal. The key observations will include dynamic magnetic and velocity field measurements of small
magnetic features at several heights in the solar atmosphere. Small magnetic features may contribute to
the total solar irradiance. ATST observations will be used to define the spectral emission characteristics
of a sample of those features as an important contribution to understanding TSI variations. Revolutionary
observations will be made of larger magnetic features, such as sunspots and active regions, and of transient
drivers of space weather, such as flares and erupting prominences.
ATST will also provide high-resolution observations in the infrared portion of the solar spectrum
where molecular signatures appear. That capability will be used to study indications of extraordinarily
cool molecular clouds in the upper photosphere. In addition, ATST can be operated as a coronagraph.
The primary goal of early coronal observations will be to characterize the magnetic and changing velocity
fields of coronal features above both active and quiet regions on time and spatial scales that have heretofore been beyond reach. The relative importance of heating of the corona by dissipation of wave motions
excited from below will be a specific research target.
10.4.7.2 Science Goals for Ground-Based Solar Research
Important science results of the past decade were accomplished at ground-based facilities. 11 A
summary of the principal U.S. ground-based observatories and their observational emphasis is given in
Table 10.3. Compared with space missions, these facilities can be far larger, more flexible and exploratory,
and longer-lived. Accordingly, emphasis is on achieving high spatial resolution (as with the NST and the
ATST), making unique measurements of physical processes at long wavelengths (as with E-OVSA and
FASR), and collecting sufficient light flux to make high-time-resolution, high-precision measurements of
10 S.L. Keil et al., Science and Operation of the Advanced Technology Solar Telescope, white paper submitted to the Decadal
Strategy for Solar and Space Physics (Heliophysics), Paper 130; S.L.Keil et al., Generation, Evolution, and Destruction of Solar Magnetic Fields, white paper submitted to the Decadal Strategy for Solar and Space Physics (Heliophysics), Paper 131; T. Ayers and D.
Longcope, Ground-based Solar Physics in the Era of Space Astronomy, white paper submitted to the Decadal Strategy for Solar and
Space Physics (Heliophysics), Paper 3.
11 T. Ayres and D. Longcope, Ground-based Solar Physics in the Era of Space Astronomy, white paper submitted to the Decadal
Strategy for Solar and Space Physics (Heliophysics), Paper 3; A.A. Pevtsov, Cur rent and Future State of Ground-based Solar Physics
in the U.S., white paper submitted to the Decadal Strategy for Solar and Space Physics (Heliophysics), Paper 218; K.P. Reardon et al.,
Approaches to Optimize Scientific Productivity of Ground-Based Solar Telescopes, white paper submitted to the Decadal Strategy for
Solar and Space Physics (Heliophysics), Paper 224; S. McIntosh et al., The Solar Chromosphere: The Inner Frontier of the Heliospheric
System, white paper submitted to the Decadal Strategy for Solar and Space Physics (Heliophysics), Paper 193.
Solar and Space Physics: A Science for a Technological Society
REPORT OF THE PANEL ON SOLAR AND HELIOSPHERIC PHYSICS
297
10.4.7 Goals for Ground-Based Facilities
10.4.7.1 Science Goals for the Advanced Technology Solar Telescope
The Advanced Technology Solar Telescope (ATST) is a ground-based, 4-m-aperture solar telescope
whose first observations are expected in 2016. By far the largest optical solar telescope in the world, ATST
will provide revolutionary observational resolution as small as 30 km. Comparing observations on this scale
with equally resolved numerical models will transform physical understanding of many solar features from
informed speculation to hard science. ATST will furnish enough intensity to feed a large array of sensitive
and powerful instruments. As a general-purpose community facility, ATST will address a wide variety of
ever-changing science goals over its decades-long lifetime. 10
Within the photosphere, nearly all the Sun’s magnetic flux is in the form of small, dynamic elements.
Constantly energized by convection, this magnetic sea directs upward flows of mass and energy to create
the chromosphere, corona, and solar wind. Studying that fundamental process is a major initial ATST science goal. The key observations will include dynamic magnetic and velocity field measurements of small
magnetic features at several heights in the solar atmosphere. Small magnetic features may contribute to
the total solar irradiance. ATST observations will be used to define the spectral emission characteristics
of a sample of those features as an important contribution to understanding TSI variations. Revolutionary
observations will be made of larger magnetic features, such as sunspots and active regions, and of transient
drivers of space weather, such as flares and erupting prominences.
ATST will also provide high-resolution observations in the infrared portion of the solar spectrum
where molecular signatures appear. That capability will be used to study indications of extraordinarily
cool molecular clouds in the upper photosphere. In addition, ATST can be operated as a coronagraph.
The primary goal of early coronal observations will be to characterize the magnetic and changing velocity
fields of coronal features above both active and quiet regions on time and spatial scales that have heretofore been beyond reach. The relative importance of heating of the corona by dissipation of wave motions
excited from below will be a specific research target.
10.4.7.2 Science Goals for Ground-Based Solar Research
Important science results of the past decade were accomplished at ground-based facilities. 11 A
summary of the principal U.S. ground-based observatories and their observational emphasis is given in
Table 10.3. Compared with space missions, these facilities can be far larger, more flexible and exploratory,
and longer-lived. Accordingly, emphasis is on achieving high spatial resolution (as with the NST and the
ATST), making unique measurements of physical processes at long wavelengths (as with E-OVSA and
FASR), and collecting sufficient light flux to make high-time-resolution, high-precision measurements of
10 S.L. Keil et al., Science and Operation of the Advanced Technology Solar Telescope, white paper submitted to the Decadal
Strategy for Solar and Space Physics (Heliophysics), Paper 130; S.L.Keil et al., Generation, Evolution, and Destruction of Solar Magnetic Fields, white paper submitted to the Decadal Strategy for Solar and Space Physics (Heliophysics), Paper 131; T. Ayers and D.
Longcope, Ground-based Solar Physics in the Era of Space Astronomy, white paper submitted to the Decadal Strategy for Solar and
Space Physics (Heliophysics), Paper 3.
11 T. Ayres and D. Longcope, Ground-based Solar Physics in the Era of Space Astronomy, white paper submitted to the Decadal
Strategy for Solar and Space Physics (Heliophysics), Paper 3; A.A. Pevtsov, Cur rent and Future State of Ground-based Solar Physics
in the U.S., white paper submitted to the Decadal Strategy for Solar and Space Physics (Heliophysics), Paper 218; K.P. Reardon et al.,
Approaches to Optimize Scientific Productivity of Ground-Based Solar Telescopes, white paper submitted to the Decadal Strategy for
Solar and Space Physics (Heliophysics), Paper 224; S. McIntosh et al., The Solar Chromosphere: The Inner Frontier of the Heliospheric
System, white paper submitted to the Decadal Strategy for Solar and Space Physics (Heliophysics), Paper 193.