On the periodic variations of geomagnetic activity indices Ap and ap

On the periodic variations of geomagnetic activity indices Ap and ap

Yearly averages of geomagnetic activity indices Ap for the years 1967±1984 are compared to the respective averages of m Bs, where v is the solar wind velocity and Bs is the southward interplanetary magnetic ®eld (IMF) component. The correlation of both quantities is known to be rather good. Comparing the averages of Ap with m and Bs separately we ®nd that, during the declining phase of the sola...

Time variations of geomagnetic activity indices Kp and Ap: an update

Kp and Ap indices covering the period 1932 to 1995 are analysed in a fashion similar to that attempted by Bartels for the 1932±1961 epoch to examine the time variations in their characteristics. Modern analysis techniques on the extended data base are used for further insight. The relative frequencies of occurrence of Kp with di€erent magnitudes and the seasonal and solar cycle dependences are ...

Variations of the Ap star HDE 318107 ? , ? ?

The rotation period of the Ap star HDE 318107 has been determined from magnetic and photometric observations obtained between August 1992 and September 1998.

Variations of the Ap star HD 208217 ?

We present a new determination of the rotation period of the Ap star HD 208217 based on photometric and magnetic measurements. The variations of this star are remarkable by the strong anharmonicity of its lightcurves in all colours as well as by the double wave of its mean magnetic field modulus variations.

The geomagnetic field variations and earthquake activity