Data taken between February 8-12, 1999 at NASA, Goddard Space Flight Center with the Mark 2 magnetometer by Dr. Sten Odenwald.
Solar conditions during this time: 2-8-99 Quiet...no auroral oval 2-9-99 Quiet 2-10-99 Quiet..weak oval present 2-11-99 Quiet..Weak oval over US, Substorm in progress over Iceland 2-12-99 Quiet Note, the Quiet/Disturbed/Active index used at the Space Weather site is rather crude. In several instances a 'Quiet' condition was posted even though the 'Current View' image of the Earth from space by the POLAR satellite clearly showed the ring-shaped oval of auroral activity in progress over Alaska and Canada. In the next data runs I will indicate both the posted condition, and the strength of the 'auroral oval' on a scale B=Bright, W=weak and A=absent. All times are in local Eastern Standard Time. Data: 2-8-99 9:00 10.5s 9:25 10.0s 10:10 9.5s 10:35 8.0s 11:35 8.0s 12:35 6.5s 13:10 -3.0s 13:30 -2.0s 14:00 4.5s 14:30 4.5s 15:20 5.0s 15:50 5.0s 16:20 4.0s 17:00 5.0s 2-9-99 9:55 6.0s 10:25 6.0o +/- 1 centimeter amplitude of oscillation 11:05 4.0s 11:30 4.0s 13:35 4.0s 14:10 4.0s 14:55 5.0s 15:05 5.5s 15:20 4.5s 15:50 5.0s 16:40 5.0s 17:00 4.5s 2-10-99 9:55 3.0s 10:30 2.5s 12:55 1.5s 13:30 0.0s 15:35 0.0s 16:35 -3.0s 17:05 -2.0s Day 41, POLAR UV imager shows 21:45UT strong oval, substorm over Iceland. 2-11-99 9:00 0.0s 9:35 0.0s shifted to 8.0 cm for next measurement 9:50 7.5s 11:10 6.0s 13:30 11.0o +/- 2 cm amplitude oscillation. Day 42 weak oval over US, strong sub-storm over Siberia 18:29 UT 14:00 5.0s 14:25 5.0s 14:55 5.0s 15:45 5.0s 15:55 4.5s Latest POLAR image shows sub-storm over Canada 20:54 UT 17:00 5.0s 2-12-99 16:55 15.0s Local storm front passes through. Cloudy with heavy rainsThis completes the third consecutive week of observations. We feel certain that the activity seen on 2-10-99 was caused by the geomagnetic sub-storm which was strong over Iceland and Siberia. We note that, in distinction to lightning storms which cause almost constant oscillations in the magnetometer, geomagnetic storms cause a gradual change in the pointing direction with no detectable oscillations at each moment of measurement! The progress of the 2-10-99 substorm can be seen in the following two images taken on Day 41 at 21:45 UT and on Day 42 at 20:54 UT.
We found the two 'real-time' magnetometer stations at Kiruna, Sweden system and Flinders very helpful in corroborating the effects of the 2-10-99 storm. Also, the Effective Sun Spot Number value of 70 during this day was a good cross check, but not very helpful. In the future, this number will be more important in long-term studies of detected activity.