Effect of the azimuthal component of the IMF on the frequency of occurrence of magnetic disturbances

An analysis of experimental data indicates that there are three types of effects of the azimuthal component of the IMF on the frequency of occurrence of magnetic disturbances with characteristic seasonal variations. These are: (1) an effect due to the Russel-McPherron mechanism, manifested in all types of disturbances during equinox periods; (2) the /By/ modulus effect, most noticeable in the frequency of occurrence of convective disturbances, with a peak in summer; and (3) the effect of the negative component By less than 0, evidently operating during the whole year.