A Science Strategy for Space Physics (1995) / Chapter Skim
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A Science Strategy for Space Physics: Chapter 1
A Science Strategy for Space Physics: Chapter 1
Pages 34-46
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From page 34... ...
CHAPTER 5 PART III APPENDIX Researchers have not directly observed solar irradiance variations on longer time scales. However, space physicists do know that the Sun has shown greater swings of activity in the past than it has recently.
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From page 35... ...
Over the last two decades, two new types of solar observations-neutrino-flux measurements and helioseismology-have changed this picture profoundly and challenged "standard" models of the Sun's interior and its magnetic dynamo. These challenges must be taken into account when space physicists study solar variability because all forms of solar activity are thought to derive ultimately from the interaction of magnetic fields with differential rotation and turbulent convection in the solar interior and atmosphere.
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From page 36... ...
If strong fields near the base of the Sun's convection zone are the source of surface phenomena such as sunspots and plage regions, then understanding the mechanisms that connect the deep and surface fields is necessary. Helioseismology measurements carried out through a solar cycle would permit the study of subsurface magnetic fields through their effect on the propagation velocities of different oscillation modes.
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From page 37... ...
Study of the largest individual flux tubes requires observations that achieve a consistent resolution of 150 km for hours at a time, over angular fields many arc seconds on a side-conditions unachievable from the ground, but possible with future space missions. However, both indirect observations and magnetohydrodynamic models show that the physical properties of flux tubes (including their contribution to the solar irradiance)
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From page 38... ...
In summary, the goals of the study of solar structure and variability are to understand the basic processes governing the nuclear and rotational evolution of the Sun and, by inference, other main-sequence stars, to understand the physics of neutrino production and propagation, to understand the solar cycle and concomitant variations of the solar radiative output, and to understand solar activity well enough to produce useful forecasts of solar flares, coronal mass ejections, solar energetic particle events, and other forms of impulsive activity. Specific research questions that should be addressed to achieve those goals are as follows: What are the mechanisms responsible for variations in the spectral and total irradiance of the Sun and solar-type stars?
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From page 39... ...
CURRENT PROGRAM The current program seeks to improve our knowledge of the solar interior and solar variability principally through monitoring of the solar irradiance and measurements of solar oscillations. Solar variability is monitored through several experiments on the Upper Atmosphere Research Satellite (UARS)
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From page 40... ...
Consequently, continuation of all the experiments will produce an important narrowing of the experimental uncertainty and permit fewer interpretations of the combined results. The current program in helioseismology comprises a variety of small scale experiments with different ranges of spatial resolution, sensitivity, temporal continuity, and duration of operation.
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From page 41... ...
The SOHO instruments will provide high spatial resolution and the most complete determination to date of solar interior structure, especially of convection in the solar envelope, together with stable and sensitive measurements of solar velocities. SOHO also offers the best chance of detecting the elusive low frequency gravity modes.
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From page 42... ...
For example, frequency-agile radio imaging has provided new information about the magnetic configuration of active regions before and after flares. There has been an explosive growth in infrared observations, enabled by the development of infrared array detectors, with applications ranging from the deepest photosphere to the corona.
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From page 43... ...
Other frontiers in research on flares and active regions lie in the exploration of poorly known regions of the flare electromagnetic spectrum, such as the infrared and submillimeter domains; in multifrequency radio imaging; in continuous observations of vector magnetic fields and velocity fields in active regions through their entire life cycle; and in acquiring a three-dimensional view of coronal structures and mass ejections. file:///C|/SSB_old_web/strach1.html (10 of 13)
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From page 44... ...
The Solar Astronomy Panel of the NRC's Astronomy and Astrophysics Survey Committee7 emphasized the need for a major effort to develop observational capabilities in the infrared. For solar physics, infrared wavelengths allow unique diagnostic capabilities for the measurement of magnetic field strength and temperature.
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From page 45... ...
It is possible that new insights into two of the more important issues in solar physics-the solar dynamo and magnetic reconnection in solar flares-may emerge from a combination of new laboratory experiments and theoretical research. The potential for the application of laboratory plasma physics to space physics problems has been summarized in reports by the NRC's Plasma Science Committee8 and Panel on Opportunities in Plasma Science and Technology.9 NOTES 1.
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From page 46... ...
A Science Strategy for Space Physics: Chapter 1 Science: From Fundamental Research to Technology Applications, National Academy Press, Washington, D.C., 1995. Last update 2/17/00 at 4:32 pm Site managed by Anne Simmons, Space Studies Board The National Academies Current Projects Publications Directories Search Site Map Feedback file:///C|/SSB_old_web/strach1.html (13 of 13)
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