Hydromagnetic Waves in the Magnetosphere and the Ionosphere


Book Description

Here is a fascinating text that integrates topics pertaining to all scales of the MHD-waves, emphasizing the linkages between the ULF-waves below the ionosphere on the ground and magnetospheric MHD-waves. It will be most helpful to graduate and post-graduate students, familiar with advanced calculus, who study the science of MHD-waves in the magnetosphere and ionosphere. The book deals with Ultra-Low-Frequency (ULF)-electromagnetic waves observed on the Earth and in Space.




The Role of Hydromagnetic Waves in the Magnetosphere and the Ionosphere


Book Description

Four research areas were investigated: (1). the propagation and coupling of hydromagnetic waves in the magnetosphere. The coupled hydromagnetic equations in the dipole model of the magnetosphere were solved numerically. A reconstruction of the long period waves in an actual geomagnetic storm was demonstrated (2). non-linear wave-particle interactions in the magnetosphere. Anomalous cross-field diffusion of trapped energetic protons may result in proton precipitation in the equatorial region; (3). the filamentation instability of large amplitude hydromagnetic waves in the solar wind plasma. This work is relevant to observations of Alven waves and magnetosonic waves in space plasmas; (4). parametric excitation of whistler waves in the high latitude ionosphere by a high frequency heater transmitting from the ground. It has been shown that whistler waves and Langmuir waves can be excited by ionospheric heaters. The instability which produces these waves offers a potential mechanism to generate large amplitude long period waves in the ionosphere.










Plasma Waves in the Magnetosphere


Book Description

This book is a study of plasma waves which are observed in the earth's magnetosphere. The emphasis is on a thorough, but concise, treatment of the necessary theory and the use of this theory to understand the manifold varieties of waves which are observed by ground-based instruments and by satellites. We restrict our treatment to waves with wavelengths short compared with the spatial scales of the background plasma in the mag netosphere. By so doing we exclude large scale magnetohydrodynamic phenomena such as ULF pulsations in the Pc2-5 ranges. The field is an active one and we cannot hope to discuss every wave phenomenon ever observed in the magnetosphere! We try instead to give a good treatment of phenomena which are well understood, and which illustrate as many different parts of the theory as possible. It is thus hoped to put the reader in a position to understand the current literature. The treatment is aimed at a beginning graduate student in the field but it is hoped that it will also be of use as a reference to established workers. A knowledge of electromagnetic theory and some elementary plasma physics is assumed. The mathematical background required in cludes a knowledge of vector calculus, linear algebra, and Fourier trans form theory encountered in standard undergraduate physics curricula. A reasonable acquaintance with the theory of functions of a complex vari able including contour integration and the residue theorem is assumed.




Doppler Observations of Associated Ionospheric and Magnetic Fluctuations


Book Description

Observations of ionospheric motions associated with magnetic micropulsations were conducted during a three-year period. Current theoretical models of the interaction indicate that observable Doppler shifts of high-frequency radio waves coherently reflected from the ionosphere should accompany all reasonably large geomagnetic disturbances, and vice versa, but this is not observed. Detailed studies of particular classes of events were therefore undertaken, involving spectral analyses, cross correlations, diurnal and seasonal occurrence statistics, and studies of associations with various types of ionospheric and magnetic records. Certain classes of magnetic pulsation events are found to be directly associated with F-region motions. Of the many possible mechanisms which may be responsible for these associations, two stand out as prime candidates: (1) hydromagnetic waves and (2) neutral-gas waves modulating ionospheric electrojets. At mid-latutudes during quiet-sun years, the direct effects of precipitation of charged particles appear to be of much less importance. (Author).







Spectrum of Hydromagnetic Waves in the Exosphere


Book Description

A disturbance in the exosphere generates waves in three partially separable modes. These modes are described by considering the vorticity about a line of force, the two-dimensional divergence of velocity in the plane perpendicular to the line of force, and the component of velocity along the line of force. The propagation of vorticity is one-dimensional and there is no geometrical attenuation; energy is lost only through the finite conductivity of the medium. The propagation of the longitudinal velocity component is almost one-dimensional but is heavily damped at high frequencies. In a gravitational field, the medium is no longer uniform and at low frequencies the modes are coupled in a complicated way. For parallel magnetic and gravitational fields, the vorticity mode is still separable and gravity leads to anisotropic dispersion in the other modes.-p.i.