Cosmic Rays in the Real Geomagnetic Field
The main part of the geomagnetic field is produced by sources inside the earth: most probably there are electrical currents in the rotated liquid metallic nucleus of the earth supported by convective hydromagnetic flows (see, e.g., Braginsky, 1964a, b). As discussed in Chapter 2 (Sections 2.1–2.7 and 2.12–2.14), in the first approximation, this field can be considered as the field of magnetic dipole displaced near the center of the earth. However, as was shown in the same chapter, (Sections 2.6–2.11), the dipole presentation is not enough for describing CR equator, CR time variations, and planetary distribution of cutoff rigidities.
Outer sources of the geomagnetic field are produced by three systems of electrical currents: ionosphere currents, ring current, and currents on the boundary of the magnetosphere (see Chapter 6 for details). The influence of the magnetic field of ionosphere currents on CR particles' moving is usually considered as negligible. The western directed ring current in the earth's magnetosphere is the most important for the geomagnetic field changing in time as well as for the influence on CR particles moving in the magnetosphere (this influence will be considered in detail in Chapter 7). The ring current is caused by charged particles trapped in the radiation belts: beside the rotation of these particles around the magnetic force lines and moving along the force lines between mirror points in the north and south, they also have a drift in the direction perpendicular to the magnetic field lines and to the gradient of the magnetic field (positive particles drifted in the western direction and negative – in the eastern direction, so the total electrical current will be in the western direction). The distribution of this western ring current depends on the distribution of the charged energetic particles, and their velocities and pitch angles (see for more detail in Dessler and Parker, 1959; Akasofu and Chapman, 1961, and in Chapter 6).
KeywordsSolar Wind Plasma Sheet Cutoff Rigidity Asymptotic Direction Geomagnetic Cutoff Rigidity
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