Periods of the Magnetospheric Oscillations and the Plasma Density

Abstract

Using the model magnetosphere of the Mead's type, periods of self oscillation of the magntosphere are calculated for the cases of weak or strong dependence of its amplitude on longitude. It is shown that the transverse wave can exist when the periods of these two modes are equal. This condition is satisfied at latitudes near the auroral zone. The oscillations with a longitudinal dependence in form of Gauss-function are also considered, and the values of Ne/T2 are calculated. The plasma density Ne in the magnetosphere is estimated using the period T of observed geomagnetic pulsations ; the result is in agreement with the data of other methods.The idea that the geomagnetic pulsations are due to hydromagnetic oscillations of the magnetosphere gave the possibility that their periods are connected with the plasma density distribution of magnetosphere. In several works (Obayashi 1958, 01' 1963, Gul'elmi 1967 this possibility was utilized, the period of pulsations being taken equal to the echoing period of Alfven wave along the geomagnetic field line. Radoski (1966), Radoski and Carouillano (1966) pointed out that the WKB-approximation is applicable only in the (1968) found the period of self-oscillations, making the numerical integration of equation concordant with the boundary conditions. Dungey (1963) has formulated the equation of magnetospheric oscillationsIn the coordinatite system (q1, q2, q3) with unit-vectors shown in Fig 1, it can be written as (2)and it is assumed that E1=0 in consequence of