Jökull - 01.12.1962, Blaðsíða 63

period and the A number. The longer periods
are associated with lower Ap figures.
The number of days having C events of a
given magnitude and period subrange is given
in Table 4. The same numbers are given in a
more condensed form in Table 5. These data
indicate no correlation between the magnitude
and the period of C oscillations.
TABLE5
Table 4 condensed,
Subranges
(a) + (b) (c) + (d)
Magnitudes I + II 138 150
III + IV 34 28
A comparison of records from Haiwee and
Palomar reveals that the oscillations are almost
identical at both stations. However, there are
occasional srnall deviations.
No numerical data will be given on the cor-
relation of C oscillations with ionospheric data
from the station at Palo Alto, California. The
C events appear to coincide more or less with
the high values of f0F2 (critical frequency of
the F-layer) during the day.
SUMMARY OF MAIN DATA
ON TYPE C OSCILLATIONS
OBSERVED IN CALIFORNIA
(1) Field amplitude: Up to 20 microgauss.
Magnitude scale based on the maximum
record amplitude, that is, on the maxi-
mum amplitude of the north-south com-
ponent of dH/dt.
(2) Period: 10 to 40 sec. Individual C events
may include a wide period band where,
in cases, two periods with a ratio of I : 2
are prominent.
(3) Character: Sinusoidal or quasi-sinusoidal
oscillations with a less regular beating of
a period of few minutes.
(4) Period-magnitude relation: No correlation.
(5) Diurnal pattern: Occur during the day.
Duration 5 to 15 hours.
(Ö) Annual pattern: C activity highest at the
equinoxes. Higher in the summer than in
the winter. Commence at a later hour of
the day in the summer. Period shorter iti
the summer.
(7) Relation of distant recording stations: In
few cases slight transitory differences be-
tween the Palomar and the Plaiwee re-
cords.
(8) Relation to events on slow-run magneio-
grams: Strong positive correlation between
the A figure and the magnitude of C
oscillations. Longer periods associated with
lower A figures.
(9) Relation to solar cycle: C activity increases
with increasing solar activity.
(10) Relation to ionosphere conditions: No de-
finite results but positive correlation of
the C activity with f0F2 probable.
(11) Relation to DP, DI and R. oscillations:
C events on days of high magnetic activity
include large DP oscillations. Association
with R oscillations very rare.
OBSERVATIONAL DATA ON TYPE DP
AND DI OSCILLATIONS
The magnitude of DP and DI oscillations
is given in the same scale as used for C oscil-
lations. The data on the magnitude, period
and timing are given in Fig. 7 to 10. A mode-
rately regular DP event is shown in Fig. 2.
Generally, the DP oscillations consist of i/>
to a few full waves of a fairly sinusoidal
character. In the majority of cases the ampli-
tude decreases with time and the wave train
resembles the typical response of a damped
linear oscillator to a transient excitation. The
integration of the recorded dH/dt reveals that
the oscillation is associated with sudden change
of the strength of the magnetic field.
The correlation of the magnitude of the DP
oscillations with the Ap number is given in
Table 6.
Table 6 does not reveal a clear trend. During
the period Nov. 1, 1954 to December 31, 1955
the DP events appear to occur on days having
slightly higher than average Ap figures. The
trend is different in the period January 1, 1956
to February 28, 1957, and the average Ap for
all days of DP events during the entire re-
cording period is much the same as the figure
for days of no DP events.
The correlation of the period of the DP oscil-
lations to the Ap figure is given in Table 7.
No clear trencl is revealed by the figures in
Table 7.
JÖKULL 61