The Field of Solar Physics Review and Recommendations for Ground-Based Solar Research (1989) / Chapter Skim
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2. Solar Research Today: A Science Overview
2. Solar Research Today: A Science Overview
Pages 4-15
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From page 4... ...
There is evidence from the study of meteorites that the relative atomic abundances may vary throughout the interior of a star. We know from spectroscopy thatcomposition varies from one star to the next, as do the rotation rates and presumably the primordial magnetic fields.
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From page 5... ...
Indeed current ignorance about the Sun reflects the general lack of progress in understanding stellar activity of all kinds. We cannot fully interpret nuances of the surface emissions of the distant stars until we understand the physics of surface activity through close scrutiny of the Sun.
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From page 7... ...
A particularly important milestone was reached about 2 decades ago, when detailed observational and theoretical considerations revealed that the magnetic field at the surface of the Sun, rather than being smoothly distributed as expected, is effectively discontinuous. The photospheric magnetic field consists of small, individual, intense and widely separated magnetic flux tubes of 1 x 103 to 2 x 103 Gauss.
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From page 8... ...
the Sun. Several spacecraft epochs later, we are beginning to realize that these mass ejection events apparently result from large-scale magnetic field eruptions but why they occur is not clear.
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From page 9... ...
The ability to release energy impulsively and to accelerate particles is a common characteristic of cosmic plasmas at many sites throughout the universe, ranging from magnetospheres to active galaxies. Observations of gamma rays and hard X rays, radiations that' can be unmistakably associated with accelerated particle interactions, as well as the direct detection of accelerated particles, for example the cosmic rays, strongly suggest that at many sites a significant fraction and in some cases even a major fractionof the available energy is converted into high-energy particles.
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From page 10... ...
As a result of the deposition of magnetic energy- most probably by magnetic reconnection bulk plasma heating occurs and electrons and protons are impulsively accelerated. The high-energy emissions or signatures of these particles (e.g., nuclear deexcitation gamma rays from the protons and hard X rays from the electrons)
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From page 11... ...
, in addition to the "normal" moderate level of activity that we are currently experiencing. It is worth noting that, as far as the records go, the centuries of reduced solar activity coincide with the centuries of cold climate in the northern temperate zone, whereas the centuries of enhanced activity coincide with a particularly mild climate.
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From page 12... ...
It is clear from the dilemmas presented by neutrino and helioseismological probing of the solar interior that some new ideas are needed on stellar interiors. The formation of a star may invoke atomic abundances, rotation rates, and magnetic fields in different ways than those currently imagined.
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From page 13... ...
In this connection it is essential to explore further the intense small-scale bursts of energy and the low-frequengy radio microbursts throughout the transition region and corona, as well as the larger microflares and flares. The coronal transients are a product of stressed magnetic fields on both small and large scales, the proportion of small- and large-scale stresses determining the degree of flaring associated with the transient.
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From page 14... ...
These blast waves, together with the strong shock interactions between the fast and slow streams of wind, make the heliosphere an active structure whose properties vary markedly with radial distance from the Sun. We are only beginning to get an idea of the detailed structure of the inner and middle heliosphere as the Voyager and Pioneer spacecraft journey past the outer planets.
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From page 15... ...
What is more, we can be sure that the investigation of the solar surface and the solar interior on so broad a front will pronde surprises, perhaps of a fundamental nature. The present writing, and the list of opportunities and initiatives that follows, is based on contemporary knowledge and cannot anticipate what lies ahead when we probe into the unknown realm of the solar interior and the small-scale phenomena at the solar surface." 1 Ihe reader is referred to the recent comprehensive reviews of contemporary knowledge of the Sun to be found in the three-volume work The Physics of the Sun (~1986)
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