Astronomy and Astrophysics in the New Millennium Panel Reports (2001) / Chapter Skim
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5 Report of the Panel on Solar Astronomy
5 Report of the Panel on Solar Astronomy
Pages 221-274
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act Report of the Panel on Solar Astronomy
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processes allowed for tailoring solarlike scenarios on the computer. All these advances have led to the formulation of a new strategy a systems approach for solar physics in the next decade: iAstronomy and Astrophysics Survey Committee, National Research Council.
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The Dunn solar telescope with the Advanced Stokes Polarimeter and its adaptive optics (AO) program, the McMath-Pierce telescope with its infrared program, and the Fouriertransform spectrograph should be operated until the Advanced Solar Telescope (AST)
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This would give nearly continuous coverage in full-disk solar vector magnetic field monitoring and would form the backbone of an assessment of the solar magnetic flux budget over the solar cycle. Cost: $4.8 million.
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WHY DO 50LAR PHY51C5 RESEARCH? The complexities of the Sun its internal structure, rotation, and convection and the resulting cyclic and random generation of its magnetic fields and the magnetoactive, hot, explosive, extended solar atmosphere and solar wind are fascinating and challenging (see Figure 5.11.
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Earth's climate, the state and extent of the upper atmosphere and magnetosphere, and space weather inside and outside the magnetosphere are determined and driven by the Sun's luminosity, by its W and x-ray spectrum, by the solar wind, and by explosive events on the Sun. Solar irradiance variations appear to be correlated with the level of the Sun's magnetic activity.
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To evaluate the magnitude of such effects, astronomers need to understand the Sun's production of magnetic field, the mechanisms underlying the acceleration of the solar wind, and their variation over solar cycles and longer times. Similar considerations apply to the Sun's output of W and x rays over its history with this output being controlled by the solar magnetic cycle.
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Numerical simulations are beginning to address the question of how deep in the convection zone these irradiance variations first arise. The total change in solar irradiance over a solar cycle, however, remains unexplained.
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· The diffuse x-ray irradiance of the corona shows a pronounced variation with the solar cycle. This variation exceeds the variation expected from the number and size of active regions.
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solar research is being systematized, (3) diverse datasets are being integrated into a framework, (4)
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Measurements of vector magnetic fields at the surface have allowed detailed study of the physical interaction between the magnetic field and the thermally radiating plasma (see Figure 5.21. MHD models have captured the process of convective collapse, by which magnetic flux tubes form.
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This effort has to be closely coupled to theoretical modeling that uses existing models and develops new ones. Since the domains of the Sun are physically linked by the solar magnetic field, an understanding of the Sun and its variability will require that all domains be considered together in a consistent 3 - truss __ ~~-tirtYidd <~F~Fard)
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The National Oceanic and Atmospheric Administration's (NOAA) Space Environment Center, the nation's provider of space weather services, uses a variety of means to predict solar activity on timescales as short as a day to as long as the solar cycle.
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From the presentations of these with AO 20 15 10 5 o 235 without AO 15 10 0 2 4 6 8 10 12 0 2 4 6 8 10 FIGURE 5.3 Snapshots of observations of solar granulation at the Dunn solar telescope without and with adaptive optics. Courtesy of T
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EXI 5TI N G PRO G RAM 5 GROUND-BASED OBSERVATIONAL EFFORTS NATIONAL SONAR OBSERVATORY (NSO) · Evans Facility 40-cm coronagraph at Sacramento Peak; · Dunn solar telescope 0.76-m vacuum telescope at Sacramento Peak with a prototype AO and the High-Altitude Observatory (HAO)
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The 1 50-ft tower telescope, operated by the University of California at Los Angeles, investigates long-term changes of solar magnetic activity and large-scale flow systems; · Wilcox Solar Observatory operated by Stanford University. The observatory began daily observations of the Sun's global magnetic field in May 1975; and · Owens Valley Radio Observatory (OVRO)
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MISSIONS IN FRIGHT Yokhoh Yohkoh is a Japanese mission in cooperation with the United States and United Kingdom to observe high-energy radiation in the solar atmosphere. Launched in the autumn of 1991, Yohkoh has provided continuous coverage of solar coronal activity throughout nearly a complete solar cycle.
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from the equatorto the poles, which extends to a depth of at least 26,000 km. The return flow at the bottom ofthe convection zone is from a simple model and has not been observed yet.
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240 ASTRONOMY AND ASTROPHYSICS IN THE NEW MILLENNIUM: PANEL REPORTS FIGURE 5.5 Sample picture of coronal loops from TRACE observed in Fe IX/X at 1 71 A Courtesy of NASA and the Stanford-Lockheed Institute for Space Research.
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Located at the Li, SOHO has enough fuel to fully cover a solar cycle. The SOHO mission has three principal goals to gain an understanding of the mechanisms responsible for the heating of the Sun's outer atmosphere; to determine where the solar wind originates and how it is accelerated; and to measure the properties of the solar interior and flows into it.
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Bursts with sufficient count-rate can be imaged in as short as 10 ms, although the best imaging will be obtained in 2 s, set by the spacecraft rotation rate. HESSI will locate the energy release site of flares, trace the propagation of particles from the release site, locate and determine the role of secondary particle acceleration, determine the composition of accelerated ions, and examine the role of long-term storage and acceleration of ions in flares.
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Solar Probe The Solar Probe, evaluated in A Science Strategy for Space Physics,4 will fly from pole to pole through the solar atmosphere, as close as 3 solar radii above the surface at perihelion, and will perform the first close-up exploration of the Sun. Scheduled for launch in February 2007, Solar Probe will travel along a polar trajectory to the Sun, where it will arrive in 2010.
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The payload will consist of miniaturized imaging and in situ instruments. Together they will provide the first threedimensional view of the corona, high-resolution spatial and temporal observations of the magnetic fields, helioseismic measurements of the solar polar regions, and local sampling of plasmas and fields at all latitudes.
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. , origin OT solar wind Surface and atmosphere structure and dynamics FIGURE 5.7 Schematic overview of a global approach to understanding the Sun and the coverage of the various physical regimes by existing and future observational facilities.
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The AST will replace NSO facilities at Sacramento Peak and Kitt Peak. Solar physics has advanced to a point where existing solar telescopes are no longer sufficient to conduct critical observational tests of models for the underlying physical mechanisms.
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The observed spectra appear to be explained only by dynamic models of the solar atmosphere. Numerical simulations indicate that the temperature structures occur on spatial scales that cannot be resolved with current solar telescopes.
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Structure of Sunspots Strong photospheric magnetic fields are concentrated in flux rope units in which local fields are strong enough to control the local environment but whose collective behavior is controlled by the photospheric convection patterns. In sunspots the total magnetic field is large enough to dominate the hydrodynamic behavior of the solar atmosphere.
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. The middle panel corresponds to a layer near the upper boundary; the bottom panel corresponds to a deeper layer.
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precisely measure the vector magnetic field and test models of wave generation in magnetic flux tubes by the surrounding granulation and (2) use the Hanle effect to test models of extremely weak magnetic fields in the photosphere, chromosphere, and prominences.
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PANEL ON SOLAR ASTRONOMY TABLE 5.1 AST Investment Strategy (thousand dollars) Year CostIncrement I 2 4 5 6 7 8 9 Total Adaptive optics 1,500 1,500 1,500 500 5,000 Site tests 550 150 150 150 1,000 Conceptual 500 1,100 1,500 design 3,100 IR technology 100 300 300 300 1,000 Focal-plane instrument packages AST construction Total 2,650 3,050 3,650 200 500 1,000 3,000 3,000 2,000 2,000 11,700 14,000 13,000 12,000 3,000 42,000 1,450 15,000 16,000 15,000 5,000 2,000 63,800 granular intensities, even in the red.
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Since the AST should involve a wide spectrum of the solar community and since it will require international partners, an AST board consisting of representatives of the national FIGURE 5.9 Roaclmap forthe development ofthe Aclvancecl Solar Telescope. Courtesy of S
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transient energetic phenomena: energy release, plasma heating and electron acceleration, electron transport, and formation and destabilization of large-scale structures, (2) the nature and evolution of coronal magnetic fields: precise measurement of coronal magnetic fields, temporal evolution of coronal magnetic fields, the role of coronal currents, and the storage and release of magnetic energy, and (3)
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to 0.5"(30GHz) Full Sun requisite spatial and spectral resolution, image quality, and temporal resolution to address the following topics: release; · Spatial, temporal, and spectral characteristics of the site of energy · Measurement of magnetic field strength at coronal heights in flares and active regions; · Determination of the electron energy distribution; · Detection of CMEs, both off the limb and on the solar disk; · Elucidation of causes of coronal heating (nanoflares or destabilization of coronal currents)
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Precision spectropolarimetry with a SOLIS network affords the possibility of monitoring the evolution of solar surface vector magnetic fields as toroidal flux rope systems, created by dynamo action at the base of the solar convection zone, rise through the solar surface. The full history of the birth, evolution, and decay of solar magnetic flux during the disk passage of active regions (10 to 14 days)
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. This array would have significant impact on space weather research.
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SOHO/EIT and TRACE observations have demonstrated a requirement for high temporal and spatial resolution over the full disk to understand the interconnected dynamic structures of the transition region and the low corona and to conduct coronal helioseismology. EW spectroscopic imaging with 1-arcsec resolution will determine the atmospheric magnetic connectivity of active regions.
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SDO carries the Atmospheric Imaging Assembly, an array of telescopes that image the Sun in the temperature range 4000 to 9,000,000 K; an advanced Doppler and vector magnetogram instrument package (Helioseismic and Magnetogram Imager, or HMI) that images subsurface structures, detects spots on the opposite side of the Sun, and produces vector magnetograms; and a pair of coronagraphs (the Coronal Imaging Assembly, or CIA)
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Then the surface magnetic fields and flow systems can be tracked using polarized spectral images. TRACE has shown that it is necessary to take data with a cadence of less than 10 s to follow the small- and large-scale 259
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Line-of-sight magnetogram 10.5 x 10.5 1.2 KIT Intensity 40 x 40 5 Intensity 40 x 40 5 Intensity 40 x 40 5 Intensity 40 x 40 5 LASCO C1 Intensity 1.1-3solarradii 11 C2 Intensity 1.5-6 solar radii 25 C3 Intensity 3.7-30 solar radii 110 NOTE: MDI is Michelson Doppler Imager, KIT is Extreme Imaging Telescope, LASCO is Large-Angle and Spectrometric Coronagraph Experiment, and C1, C2, and C3 are detectors on LASCO. reconnections of magnetic fields in the corona.
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60 s 90min 90min o 171 A 23.5min 1 23.5 One 10242 o 195 A 4.7 min 5.6 0.5 o 284A o 304A Three 10242 Broadband Broadband Broadband 25 min in order to study it. Solar researchers expect that coronal helioseismology will teach them as much about the corona as traditional helioseismology has taught about the solar interior.
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HMI Dopplergram 34 x 34 1 Vector magnetogram 34 x 34 1 AIA-EW Intensity 36 x 36 1.1 Intensity 36 x 36 1.1 Intensity 36 x 36 1.1 Intensity 36 x 36 1.1 Intensity 36 x 36 1.1 Intensity 36 x 36 1.1 Intensity 36 x 36 1.1 AIA-W Intensity 36 x 36 1.1 Intensity 36 x 36 1.1 Intensity 36 x 36 1.1 Intensity 36 x 36 1.1 Intensity 36 x 36 1.1 CIA-Inner Intensity, polarization 33.6-72 2.2 CIA-Outer Intensity, polarization 2-18 solar radii 17 NOTE: HMI is the Helioseismic and Magnetogram Imager, AIA is the Atmospheric Imaging Assembly, and CIA is the Coronal Imaging Assembly. intelligence for self-operation and monitoring along these lines.
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A geosynchronous orbit requires a Deltaclass launch vehicle. By using a single ground station at the science data center, operating costs are minimized.
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It is designed to use solar sailing to achieve a near-synchronous orbit at 0.16 to 0.2 AU, that is, an orbital period about equal to the solar rotation period. This would allow continuous observation of particle acceleration from active regions and CME-related solar features from their birth through their rise to a maximum and decay.
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Candidate topics include the solar dynamo and interior dynamics; magnetic flux transport through the convection zone; an observational description of emerging magnetic flux; the history of magnetic flux; the solar magnetic cycle at the solar surface; and the physics of coronal mass ejections, their causes, and heliospheric effects. It is expected that each focus program would take about 1 year, with intensive workshops every 6 months at which progress would be compared and coordinated.
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TECHNOLOGIES FOR THE FUTURE ADAPTIVE O PTICS The AST project will develop a visible adaptive optics (AO) system.
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The AO development is proposed as a collaborative effort of NSO and NJIT/Big Bear Solar Observatory, the Center for Adaptive Optics, and international partners. S O CAR- LITE Solar-B will have 1 50-km resolution, 1 0-G sensitivity to the line-ofsight field component and 100-G sensitivity to the transverse component.
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A continuation of measurements of neutrinos is, however, essential to determine finite mass and possible magnetic moment of the neutrinos. PLASMA PHYSICS Basic plasma physics and magnetohydrodynamic processes, which are thought to be central to solar physics, can be studied in the laboratory.
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university community and the overall balance between the NSF grants program and the two NSF solar physics centers NSO and HAO. It also considered how a major development project like the AST should be optimally organized within the United States as well as with international partners.
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EDUCATION For the broader educational outreach aspects the panel refers the reader to Chapters 4 and 5 of the survey committee report. Solar physics can contribute considerably to the educational effort in astronomy.
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ACRONYMS AND ABBREVIATION 1HT One Hectare Telescope ACOS Advanced Coronal Observing System AIA Atmospheric Imaging Assembly AO adaptive optics ASP Advanced Stokes Polarimeter AST Advanced Solar Telescope AU astronomical unit CCD charge-coupled device CDR concept and design review CEDAR Couplings, Energetics and Dynamics of Atmospheric Region, a part of the NSF solar influences program CIA Coronal Imaging Assembly (on SDO) CME coronal mass ejection KIT Extreme Imaging Telescope (part of SOHO)
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NASA National Aeronautics and Space Administration NCAR National Center for Atmospheric Research NJIT New Jersey Institute of Technology NOAA National Oceanic and Atmospheric Administration NRL Naval Research Laboratory NSF National Science Foundation NSO National Solar Observatory OPACITY A solar physics project conducted by the Institute of Physics, Bristol OSL Orbiting Solar Laboratory (never-built NASA project) OVRO Owens Valley Radio Observatory PASO Particle Acceleration Solar Orbiter PSPT Precision Solar Photometric Telescope RAM Reconnection and Microscale Probe RISE (SunRISE)
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PANEL ON SOLAR ASTRONOMY STEREO Solar-Terrestrial Relations Observatory STP Solar-Terrestrial Probe THEMIS Heliographic Telescope for the Study of Magnetism and Instabilities on the Sun (French/Italian project) TRACE Transition Region and Coronal Explorer W ultraviolet WIRE Wide Field Infrared Explorer 273
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