Principal Magnetic Storms - These data present the principal magnetic storms 
for the month as reported by several observatories through cooperation with 
the International Association of Geomagnetism and Aeronomy.  These are the 
data formerly published in the Journal of Geophysical Research.  They are now, 
however, grouped by the storm rather than by station. The geomagnetic 
latitude of the station is indicated. The beginning time is given to the hour 
and minute in UT.

The type of sudden commencement, if any, together with its magnitude in each 
element D, H or Z is next in the format:  sc = sudden commencement; 
sc* = small initial impulse followed by main impulse (in this case the 
amplitude is that of the main pulse only, neglecting the initial brief pulse); 
dots in these columns represent a storm with gradual commencement; blanks 
indicate no data entries.  Signs of amplitudes of D and Z are taken 
algebraically; D reckoned positive if toward the east and Z reckoned positive 
if vertically downward.  In the next columns the day and the three-hour 
periods on that day when the K index reached its maximum are given followed by 
the K index value.  In the next three columns the maximum ranges in D, H and 
Z during the storm are given.  The ending time is given only to the nearest 
hour.  This is the time of cessation of reasonably marked disturbance 
movements in the trace.  More specifically, it is the time when the K index 
measure has diminished to 2 or less for a reasonable period.  For each date 
the data are listed in north-to-south geomagnetic latitude order.  The 
observatories reporting are listed below the table each month in SGD.  The 
abbreviations used for the observatory names are as follows:

GEOMAGNETIC OBSERVATORIES

Code         Station                  Geomag Latitude

ABG          Alibag                    9.5N
AMS          Martin de Vivies         42.9S
ANN          Annamalainagar            1.5N
API          Apia                     16.0S
BJI          Beijing                  28.5N
CAN          Canberra                 43.9S
CMO          College                  64.6N
CZT          Port Alfred              38.5S
DRV          Dumont d'Urville 
                 (Terre Adelie)       75.6S
ETT          Etaiyapuram              00.6S
FRD          Fredericksburg           49.6N
GNA          Gnangara                 43.2S
GUA          Guam                      4.0N
HER          Hermanus                 33.7S
HON          Honolulu                 21.1N
HYB          Hyderabad                 7.6N
JAI          Jaipur                   17.3N
KRC          Karachi                  16.4N
PAF          Port aux Francais 
                 (Kerguelen)          56.5S
PMG          Port Moresby             18.6S
SHL          Shillong                 14.7N
SIT          Sitka                    60.0N
TRD          Trivandrum                1.1S
UJJ          Ujjain                   13.5N