Drift Type Research Articles

Effects of nonuniform radial electric fields on plasma low-frequency stability

The stability of a low-β magnetized plasma column, in the presence of radial nonuniform electric fields, has been numerically investigated in a weakly collisional regime. The analysis has been done for electrostatic low-frequency perturbations of the drift type. Numerical results for the frequency and the growth of the waves are presented as a function of the electric-field amplitude and the dimensionless parameter $$\varepsilon ^* = \omega ^* v_{ei} /k_\parallel ^2 v_e^2 (\omega ^* $$ being the drift frequency,v ei the electron-ion collision frequency,v e the electron thermal speed andk ll the wave number component parallel to magnetic lines). It is shown that in the presence of a nonuniform electric field more than one mode can be unstable.

Magnetic drift instability in a collisionless plasma

In this paper the stability of plasma in a toroidal system is investigated, for drift type oscillations which have phase velocities in the range vTc » ω/k|| » vTi. Making the assumption that the shear is not too small, our main attention is turned to finding out whether or not curvature of the lines of force causes any new instabilities to appear not already present in the slab-model approximation to the magnetic field. It is well known that, in this approximation, there is just one large-scale instability, namely the temperature drift instability. It is shown here that, when the temperature gradient differs from zero, particle drift due to the magnetic field gradient allows large-scale oscillations to be excited with a localization region having a width which exceeds that characteristic of the electrons:

Magnetic drift instability in a collisionless plasma

In this paper the stability of plasma in a toroidal system is investigated, for drift type oscillations which have phase velocities in the range vTc » ω/k|| » vTi. Making the assumption that the shear is not too small, our main attention is turned to finding out whether or not curvature of the lines of force causes any new instabilities to appear not already present in the slab-model approximation to the magnetic field. It is well known that, in this approximation, there is just one large-scale instability, namely the temperature drift instability. It is shown here that, when the temperature gradient differs from zero, particle drift due to the magnetic field gradient allows large-scale oscillations to be excited with a localization region having a width which exceeds that characteristic of the electrons:

Observation of a Solar Type Radio Burst from a Flare Star

During observations of the star UV Ceti in Oct. 1963, radioemission was recorded on two frequencies that appears to have a different relationship with the visible flare. A pronounced time lag between the maximum of the optical flare and the maxima of the radioflares, and the time difference between the radio maxima on the two frequencies was compared with frequency drift type solar radio bursts A comparison of the major features of the UV Ceti flare with the mean values for the drift type solar bursts is tabulated. Available evidence both in regard to temporal relationships and spectra suggests that the flare on UV Ceti is analogous to the large solar noise storms or Type I bursts, whereas the other represents a much rarer type of event analogous to frequency drift solar bursts. (P.C.H)

Velocities of Shock Fronts in Solar Corona Generating Type II Radio Bursts at Metre Wavelengths

At the time of intense solar flares, various types of enhanced radio emission from the Sun have been observed. Using such techniques as the swept frequency technique first developed by Wild and his associates, these enhanced emissions have been classified into five types. Of particular interest to radio astronomy at metre wavelengths is the slow drift type II bursts. A comprehensive study of these bursts has been made by Roberts (1959). It is now supposed that at the start of a flare an explosion occurs in the lower regions of the solar atmosphere ejecting a column of gas which travels radially outward from the region of the flare. This column of gas is bounded by a shock front which moves forward relative to this gas. This shock front is assumed to excite plasma oscillations in the solar corona giving rise to type II radiation. Velocities of these shock fronts have been determined by various workers.