C-2 Plasmasphere The domain is torus, of major radius approximatley 3 R (R = radius of earth, = 6380 km) and minor radius 2 R . From Cladis et al.e(19?3), p. 2-15, 28 3 we find that if L = 4, the volume is 3 x 10 cm , which if L = 4.5, the max max 28 3 3 4 —3 volume is 4.5 x 10 cm . The number density of particles is 10 -10 cm , so that on a mean basis we have C-3 Outer Magnetosphere This may be treated as a sphere of radius 6.6 Re, the radius of a geosynchronous ^>rbit. Its volume is 3.1 x ICr cm , so that if there is one particle per cm , the region contains 3 x 10z particles. D.5 ENERGY IN DOMAIN C 2 —2 „At altitudes above 150 km, the geomagnetic field energy B /8tt ~ 10 erg/cm^ is larger than the thermal energy density ankT (a = 1.5 for monatomic and 2.5 for diatomic gases). Thus in the magentosphere whose volume is 3 x lO^^ cn^ the total geomagnetic field energy is 3 x 10^0 joules. Annual energy dissipation due to dynamical processes is much smaller than this. Thus, Burch^ 197L, p* quotes magnetic to substorm power dissipation levels as 10 -10 watts, with a mean duration of perhaps 20 minutes, occurring several times per day on the average. This rate of power dissipation occurring 1/10 of^he time corresponds to an energy dissipation per year of 3 x 10 -3 x 101 joules, which is very much larger than the energy in the exhaust of the COTV argon ion engines. Y.T. Chiu (private communication) points out that this energy estimate applies to the total dynamo, most of which is used in driving the tail current system, so that an estimate of 10% or 3 x 101 - 3 x 101 J/yr is suggested as appropriate for the field energy in the ring current. See also Akasofu (1977), especially pp. 54, 274, 348, 356, 561, and Table D.l for representative values of the total energy flux in "geospace," the near-earth interplanetary medium of which the ionosphere and magnetosphere are important parts.
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