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 rains
This 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.