15 
6 Indices 
The indices presented in this edition (Files wng96.k to wng99.k and Tables 4.x) indicate the local 
disturbances of the geomagnetic field resulting from particle radiation. Their meaning in detail: 
K\ geomagnetic three-hourly index, quasi-logarithmic measure of the maximum disturbance in 
steps of 0 to 9; lower limit for K- 9: 500 nT. 
sum. Sum of the eight three-hourly indices of a day. 
Ak Mean value of the equivalent amplitudes derived from the eight three-hourly indices. The 
mean value of the daily disturbance of the geomagnetic field is 2 Ak nT. 
Ck: daily character figure derived from Ak and scaled from 0.0 to 2.5. 
C: estimated daily character figure; scale: 0, 1,2. 
The indices were derived using the lAGA-recommended FMI-routine (Häkkinen, 1992). 
7 Contents of the CDrom 
The enclosed CDrom contains recorded minute values as well as derived (hourly, daily, monthly) 
mean values and indices for the reporting period. It also provides recalculated epoch values from 
1939.5 on and those of Wilhelmhaven Observatory before then, a complete revised data set of 
hourly means (since 1943) and minute values starting 1981. A revised set of indices (since 1944) is 
also included. 
Using a visualisation software, the one-minute, hourly and daily values located at 
data/19YY/hourYY and minYY, respectively, can be displayed as graphs. 
Files and Directories on the Cdrom: 
readme.txt: 
tree.txt: 
General information 
File structure 
1996, 1997, 1998 and 1999 data (1 nT and 0.T values, respectively): 
yearb/: Directory containing the report and its tables; YY means 96, 97, 98 or 
99, respectively 
yearb/yearb.pdf: This report 
yearb/info.txt: Contains information about instruments and data