ULF geomagnetic power nearL=4, 4. Relationship to the FredericksburgKindex

The total power and slope of 2-hour nonoverlapping H component geomagnetic power spectra obtained during a 12-day period in January 1972 are statistically related at corresponding times to the K indices determined at the longitude of the stations and the global Dst indices. Although the power level increases and the spectral slope steepens with more positive K and more negative Dst values, there is no one-to-one relationship between the spectral parameters (power and best-fit slope) and the geomagnetic indices. Thus it is not readily possible to accurately predict the latitudinal distribution of geomagnetic power from a given value of the K index. It is proposed that the introduction of geophysical indices based upon geomagnetic power levels should eventually provide more physical insight into geomagnetic disturbance phenomena.