Jökull - 01.12.1962, Page 72

Date Begin End Duration (h-m) Record ampl. (mm) Period (sec) Field ampl. microgauss Reference station Other stations Magni- tude
- 18 20- 45 21- 30 0-45 0.10 (1.0—1.1) 0.025 p H damaged ii
Aug. 3 03-10 03-27 0-17 0.10 1.8 0.031 p H+ ii
— 5 00-25 00-48 0-23 0.30 (1.1-1.2) 0.075 p H+> iii
— - 01-14 02-50 1-36 0.20 1.0 0.049 p H+> n
— - 04-05 04-40 0-35 0.15 (2.0—2.2) 0.049 p H+> ii
— 9 04-00 05-00 1-00 0.10 1.8 0.029 p H + ii
1957 Jan. 8 00-30 03-00 2-30 0.30 (1.5—1.7) 0.084 p H + iii
Mar. 15 16 23-30 04-00 4-30 0.20 0.8 0.051 p H+ 1 + ii
Finally, it should be remarked that the A
oscillations have a similar period range as the
R oscillations which will be discussed below.
OBSERVATIONAL DATA
ON TYPF. R OSCILLATIONS
The observational data obtained on R oscil-
lations are more meagre than the material in
the case of the other types o£ oscillations. There-
fore, only the following results will be given.
The R oscillations are sinusoidal or quasi-
sinusoidal oscillations in the period range 0.5
to 3 sec occurring simultaneously with DP and
DI oscillations and in rare cases also with C
oscillations. The occurrence of R oscillations is
marked on the Fig. 3 to 10 by a + sign at the
period of the R oscillations.
In 1955 and 1956 there is a total of 62 R
events associated with DP and DI oscillations.
If the R oscillations are grouped into two
groups according to whether the period is
smaller or equal to 1.2 sec or larger the follow-
ing average Ap figures are obtained for the
days on which the oscillations occur.
TABLE 18
Average Ap figures for two subranges of the
periods of R oscillations observed in California.
Period < 1.2 sec > 1.2 sec
1955 and 1956
Numer of events 31 31
Average Ap (2y) 20.8 17.3
This is a similar pattern as observed in the
case of the A oscillations.
A study o£ the sudden commencements and
bays found on the Tucson magnetograms and
which are associated with DP and DI oscillations
reveals that there is a correlation between the
magnitude of the Tucson events ancl the occur-
rence of R oscillations. The R oscillations are
definitely associated with Tucson events o£
relatively large magnitude.
OBSERVATIONS IN REYKJAVIK
The magnetic recorder in Reykjavik, Iceland,
was installed in 1958 and has since been in
operation. An examination of the Reykjavik
records reveals that much the same types of
oscillations are observed there as in California.
70 JÖKULL