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
317
and its complementary role with respect to other important instruments being developed to address the Sun
and heliosphere. The Astro2010 decadal survey characterized FASR as a “compelling” midscale project
and recognized it, with ATST, as a core facility in the U.S. ground-based solar portfolio. 36 An independent
analysis of cost and technical readiness (CATE analysis) described FASR as “doable today.” FASR thus has
broad constituencies in solar and space physics and in astronomy and astrophysics.
The major advance offered by FASR over previous solar radio instrumentation is its unique combination of ultra-wide-frequency coverage, high spectral resolution, and high image quality. FASR measures the
polarized brightness temperature spectrum over a broad frequency range (50 MHz to 21 GHz, or 1.4-600
cm) along every line of sight to the Sun as a function of time. Radiation in this radio wavelength range
probes the solar atmosphere from the middle chromosphere to well into the corona. In essence, FASR
images the entire solar atmosphere in three dimensions once every second from the chromosphere through
the corona while retaining the capability to image a restricted frequency range with time resolution as small
as 20 ms. In so doing, FASR enables fundamentally new, unique observables, including:
• Quantitative measurements of coronal magnetic fields, both on the disk and above the limb, under
quiet conditions and during flares;
• Measurements of tracers of energy release and the spatiotemporal evolution of the electron distribution function during flares;
• Imaging CMEs and the associated coronal dimming, “EIT waves,” 37 and coronal shocks; and
• Imaging of thermal emission from the solar atmosphere from chromospheric to coronal heights,
including the quiet Sun, coronal holes, active regions, and prominences.
FASR’s panoramic view allows the solar atmosphere and physical phenomena therein to be studied
as a coupled system. Its powerful and unique capabilities allow it to address such high-priority science
questions as these:
• The nature and evolution of coronal magnetic fields
—What is the quantitative distribution of coronal magnetic fields?
—How do coronal magnetic fields evolve in time and space?
—How is magnetic energy stored?
• The physics of flares
—What is the physics of magnetic energy release?
—How and where are electrons accelerated?
—What are the relevant particle transport processes?
• The drivers of space weather
—How are CMEs initiated and accelerated?
—What is the origin of coronal shocks?
—How are solar energetic particles in the heliosphere accelerated?
• The physics of the quiet sun
—How are the solar chromosphere and corona heated?
—What is the origin of the solar wind?
—What is the structure of prominences and filaments?
36 NRC, New Worlds, New Horizons, 2010, p. 191.
37 So named because they were first discovered by the Extreme-ultraviolet Imaging Telescope (EIT) on the SOHO spacecraft.
Solar and Space Physics: A Science for a Technological Society
REPORT OF THE PANEL ON SOLAR AND HELIOSPHERIC PHYSICS
317
and its complementary role with respect to other important instruments being developed to address the Sun
and heliosphere. The Astro2010 decadal survey characterized FASR as a “compelling” midscale project
and recognized it, with ATST, as a core facility in the U.S. ground-based solar portfolio. 36 An independent
analysis of cost and technical readiness (CATE analysis) described FASR as “doable today.” FASR thus has
broad constituencies in solar and space physics and in astronomy and astrophysics.
The major advance offered by FASR over previous solar radio instrumentation is its unique combination of ultra-wide-frequency coverage, high spectral resolution, and high image quality. FASR measures the
polarized brightness temperature spectrum over a broad frequency range (50 MHz to 21 GHz, or 1.4-600
cm) along every line of sight to the Sun as a function of time. Radiation in this radio wavelength range
probes the solar atmosphere from the middle chromosphere to well into the corona. In essence, FASR
images the entire solar atmosphere in three dimensions once every second from the chromosphere through
the corona while retaining the capability to image a restricted frequency range with time resolution as small
as 20 ms. In so doing, FASR enables fundamentally new, unique observables, including:
• Quantitative measurements of coronal magnetic fields, both on the disk and above the limb, under
quiet conditions and during flares;
• Measurements of tracers of energy release and the spatiotemporal evolution of the electron distribution function during flares;
• Imaging CMEs and the associated coronal dimming, “EIT waves,” 37 and coronal shocks; and
• Imaging of thermal emission from the solar atmosphere from chromospheric to coronal heights,
including the quiet Sun, coronal holes, active regions, and prominences.
FASR’s panoramic view allows the solar atmosphere and physical phenomena therein to be studied
as a coupled system. Its powerful and unique capabilities allow it to address such high-priority science
questions as these:
• The nature and evolution of coronal magnetic fields
—What is the quantitative distribution of coronal magnetic fields?
—How do coronal magnetic fields evolve in time and space?
—How is magnetic energy stored?
• The physics of flares
—What is the physics of magnetic energy release?
—How and where are electrons accelerated?
—What are the relevant particle transport processes?
• The drivers of space weather
—How are CMEs initiated and accelerated?
—What is the origin of coronal shocks?
—How are solar energetic particles in the heliosphere accelerated?
• The physics of the quiet sun
—How are the solar chromosphere and corona heated?
—What is the origin of the solar wind?
—What is the structure of prominences and filaments?
36 NRC, New Worlds, New Horizons, 2010, p. 191.
37 So named because they were first discovered by the Extreme-ultraviolet Imaging Telescope (EIT) on the SOHO spacecraft.