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Planetary effects on magnetic activity Atkinson, Gerald


Statistical evidence indicates that the positions of the moon, Mercury, and Venus affect magnetic activity frequency observed at the earth, and the position of the earth affects the frequency of blue clearings on Mars. This study shows that these effects may be explained as a result of the action of shock and bow waves formed by these bodies in the supersonically streaming interplanetary plasma. The attenuation of large kinetic energy variations in the streaming plasma behind such bodies is shown to be equal to the square of the ratio of the Mach number upstream to the Mach number downstream. For typical solar induced activity, this implies an attenuation coefficient of approximately 1/2 - 1/3. It is also shown that an activity increase is expected in the bow wave. The observational data fits a model with bow waves of Mach numbers 2.5 and 15 corresponding to the two bow waves predicted by the theory. The moon's effect varies from that of the planets in a manner that can be explained by its closeness to the magnetosphere.

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