Polar Ring Currents on the sun During a Polar Magnetic Field Reversal

We have studied the variations of the height of polar crown prominences according to daily observations of the Sun at the Kodaikanal Observatory (India) during 1905–1975. Polar ring filaments at latitudes 60°–80° are related to the polar magnetic field reversal. A double decrease of the height of polar ring filaments was found in the course of their migration from 40°to the poles. We estimated the limiting height of the equilibrium of polar ring filaments from the stability condition of a strong electric current. We found that the transition from large-scale to small-scale ring filaments reduces the critical height of the stability for the prominences. A model of an inverse-polarity filament was used.     

Mid-ultraviolet and optical photometry of helium stars

Mid-ultraviolet and optical photometric analysis of helium stars are presented. A linear relation exists between the effective temperature derived from model atmospheres and (1965-V)₀ index. The effective temperatures derived from (1965-V)₀ index are somewhat higher than that of MK spectral type estimates especially for late B-type helium objects.     

Timing and tectonic setting of Grenvillian metamorphism—constraints from a transect along Georgian Bay,Ontario*

Systematic mapping of a transect along the well-exposed shores of Georgian Bay, Ontario, combined with the preliminary results of structural analysis, geochronology and metamorphic petrology, places some constraints on the geological setting of high-grade metamorphism in this part of the Central Gneiss Belt. Correlations within and between map units (gneiss associations) have allowed us to recognize five tectonic units that differ in various aspects of their lithology, metamorphic and plutonic history, and structural style. The lowest unit, which forms the footwall to a regional decollement, locally preserves relic pre-Grenvillian granulite facies assemblages reworked under amphibolite facies conditions during the Grenvillian orogeny. Tectonic units above the decollement apparently lack the early granulite facies metamorphism; out-of-sequence thrusting in the south produced a duplex-like structure. Two distinct stages of Grenvillian metamorphism are apparent. The earlier stage (c. 1160–1120 Ma) produced granulite facies assemblages in the Parry Sound domain and upper amphibolite facies assemblages in the Parry Island thrust sheet. The later stage (c. 1040–1020 Ma) involved widespread, dominantly upper amphibolite facies metamorphism within and beneath the duplex. Deformation and metamorphism recently reported from south and east of the Parry Sound domain at c. 1100–1040 Ma have not yet been documented along the Georgian Bay transect. The data suggest that early convergence was followed by a period of crustal thickening in the orogenic core south-east of the transect area, with further advance to the north-west during and after the waning stages of this deformation.     

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.     

Anisotropy of turbulent transport in a convective layer

An estimate for the anisotropy of the turbulent viscositys is given in a convective layer heated from below and rotating around a vertical axis. In the case of two-dimensional convection, there is a stationary regime withs⊇2 regardless of the rotation. In the case of three-dimensional convection in a slowly rotating layer (with the Taylor number equal to 1600), nonstationary turbulent regimes take place withs⊇1.6 forR=2.5×10⁴ (R is the Rayleigh number) ands⊇1.2 forR=10⁴. The parameters plays an, important role in the theory of differential rotation of the convective solar or stellar envelopes. So far, it has been evaluated empirically or semi-empirically. Some prospects in the development of the theory of differential rotation are discussed here in terms of the moment theory of hydrodynamic fields. The relation between this strict approach and an anisotropic viscosity approximation is considered.