FORWARD MODELING IN THE FREQUENCY-SPACE DOMAIN*

Forward modeling of zero-offset data is performed in the frequency-space domain using a one-way extrapolation equation. The use of the frequency domain offers several advantages over conventional time domain methods. The greatest advantage of the frequency domain is that all time derivatives are evaluated exactly by a simple multiplication. Synthetic zero-offset sections are computed with a high degree of accuracy for arbitrary velocity and reflectivity structures. Examples are shown for realistic complicated models and compared with results from physical modeling.     

Remarks on the magnetic support of quiescent prominences

The development of magnetic field structures which can lead to prominence configurations of the Kuperus-Raadu type is discussed. Starting from streamer type configurations and preserving the total current in the system we find that simple two-dimensional static configurations lead to prominences which in general lie systematically much lower than the heights found from observations. We therefore conclude that either more complex field configurations are needed to explain the recent observations by Leroy et al. (1983) or the initial configurations must be very special.     

The future of solar physics

The future of solar physics is founded on the existing fundamental unsolved problems in stellar physics. Thus, for instance, the physics of stellar interiors has been called into serious question by the very low-measured neutrino flux. The ⁷¹Ga neutrino detection experiment is the next step in unravelling this mystery. If that experiment should find the expected neutrino flux from the basic p-p reaction in the Sun, then astrophysics is in a difficult situation, because the most likely explanation for the low neutrino flux found in the ³⁷Cl experiment would be an error in our calculation of the opacity or an error in our understanding of the elemental abundances in stellar interiors, with serious implications for present ideas on stellar structure and the age of the galaxy.The new methods of helioseismology, for probing the interior of the Sun, have already found the primordial rapid rotation of the central core. The forthcoming world-wide helioseismology observing network will permit fuller exploitation of the method, promising to provide the first direct sounding of the interior of a star, hitherto known to us only through theoretical inference and the discrepant neutrino emission.The activity of all stars involves much the same phenomena as make up the activity of the Sun. The effects are too complex, and too foreign to the familiar dynamics in the terrestrial laboratory, to be deciphered by theoretical effort alone. It has become clear through the observational and theoretical work of the past decade or two that much of the essential dynamics of the activity of the atmosphere takes place on scales of the order of 10² km. Thus, an essential step in developing the physics of stellar activity will be the Solar Optical Telescope (presently planned by NASA to be launched early in the next decade) to permit a microscopic examination of the surface of the Sun to study the source of the action. The activity and X-ray emission of other stars depend on much the same effects, so that the study is essential to determining the significance of the X-ray emission from other stars.This work was supported in part by the National Aeronautics and Space Administration under grant NGL-14-001-001.