Evolution Of Large-scale Magnetic Field Research Articles

Direct electro - gravitational couplings and the behaviour of primordial large-scale magnetic fields

A comprehensive approach is suggested for describing the origin and evolution of large-scale magnetic fields. Vorticity-dependent fluctuations acting on a primordial charged plasma account for field generation, and the properties of gauge-invariant (but conformally non-invariant) couplings of electromagnetic and gravitational fields in a FRW background are applied in order to supply a source-independent, gravity-driven mechanism of conductance induction in the course of the reheating phase of inflationary cosmic scenarios. In consequence, the description of the behaviour of large-scale primordial magnetic fields is complemented so as to cover the whole post-inflationary history of the universe.

Completely bootstrapped tokamak

Numerical simulations of the evolution of large-scale magnetic fields have been developed using a mean-field Ohm’s law. The Ohm’s law is coupled to a Δ′ stabilty analysis and a magnetic island growth equation in order to simulate the behavior of tokamak plasmas that are subject to tearing modes. In one set of calculations, the magnetohydrodynamic (MHD)-stable regime of the tokamak is examined via the construction of an li -qa diagram. The results confirm previous calculations that show that tearing modes introduce a stability boundary into the li -qa space. In another series of simulations, the interaction between tearing modes and the bootstrap current is investigated. The results indicate that a completely bootstrapped tokamak may be possible, even in the absence of any externally applied loop voltage or current drive.

Large-Scale Flow Patterns in the Solar Atmosphere

It is now well established (McIntosh 1979; Makarov and Sivaraman 1983) that the filament and filament channels seen in the H-alpha spectroheliograms (or filtergrams) can be used as reliable tracers for studying the time evolution of large-scale magnetic fields on the Sun. These features represent the neutral lines between the unipolar regions of opposite polarity. Comparison of the synoptic charts compiled from H-alpha pictures with those from full-disc magnetograms for the same period shows very good agreement and hence the former can be used with confidence for time evolution studies of large-scale unipolar regions for those periods when the magnetographs did not even exist. In this paper we shall present one of the results of our study (Makarov and Sivaraman 1983, 1989) on the migration of H-alpha filaments, namely, the existence of the meridional flow on the Sun. We shall extend it further to show the participation of this meridional flow in the solar cycle variation.

Dynamics of Large-Scale Magnetic Field Evolution During Solar Cycle 20

The evolution of large-scale solar magnetic fields has been studied for a complete solar cycle using the atlas of H-alpha synoptic charts for 1964-1974. The results include: a unique magnetic pattern coinciding with major coronal holes; variations in the rate of solar rotation through the solar cycle; discovery of convergence and divergence among long-lived magnetic patterns; periodic discontinuities in the organization of large-scale magnetic fields; and a new cause for coronal transients.