Jökull - 01.12.1962, Blaðsíða 73

However, some characteristics of the events are
strikingly different. This is mainly due to the
very disturbed conditions in the auroral zone,
but Reykjavik is located witliin the most active
part of this zone.
The Reykjavik records are generally very
disturbed, and the level of disturbance does
not exhibit a clear diurnal variation as general-
ly observed in California. Relatively irregular
C oscillations and very irregular DI trains may
occur at any time of the day.
In general tlie amplitude of C and DI oscil-
lations is one order of magnitude larger in
Reykjavik than in California. On disturbed
days amplitudes up to several hundred micro-
gauss may be observed.
It is interesting to note that Uppsala, Swe-
den, stands in a similar relation to Reykjavik
as the California stations. The Uppsala records
are much less disturbed than the Reykjavik
records. It is significant that afthough the dist-
ance between Uppsala and Reykjavik is only
about 2,000 km there is practically no detailed
correfation between the records. The finer
structures of the magnetic fielcl in Reykjavik
appear to be dominatecl by local sources.
Type A oscillations occur relatively fre-
quently in Reykjavik. As in California their
frequency increases with decreasing solar ac-
tivity. They have been observed in Reykjavik
nearly daily during the winter 1963. However,
their cliurnal pattern in Reykjavik differs signi-
ficantly from Caliíornia. In Reykjavik type A
oscillations are mainly observed between 1000
and 1600 local time. On the other hand, their
amplitudes and period are not signiíicantly dif-
f'erent frorn the recordings in California.
REFERENCES
Benioff, H.: Observations of Geomagnetic FIuc-
tuations in the Periocl Range 0.3 to 120
Seconds. Journal Geoph. Research, 65, No.
5, 1413-1422, 1960.
Campbell, W. H. and Matsushita, S.: Auroral-
Zone Geomagnetic Micropulsations with
Periods of 5 to 30 Seconds. Journal Geoph.
Research, 67, No. 2, 555—573, 1962.
Kato, Y. and Watanabe, T.: A Survey of Ob-
servational Knowledge of the Geomagnetic
Pulsations. Science Reporls Tohoku Uni-
versity, Series V, 1—29, 1957.
Troitskaya, V. A.: Pulsations of the Earth’s
Electromagnetic Field with Periods of 1 to
15 Seconds. Journal Geoph. Research, 66,
No. 1, 5-18, 1961.
Westphal, K. O. and Jacobs, J. A.: Oscillations
of the Earth’s outer Atmosphere and Micro-
pulsations. Geophys. Journal, 6, No. 3, 360
-376, 1962.
DIAGRAMS
OCT66E*. HovEwett DtcE^Oefi.
Fig. 3. Observational data on type C oscilla-
tions observed in California in 1954. The time
of occurence is given as Pacific Standard Time
in the upper part of the figure. The period range
is given in the middle part, and the magnitude
in the lower part. The reference station is in-
dicatecl above the period section. Figures 3 to
12 are all built up in the same way.
JÖKULL 71