History of Geophysical Research in The Netherlands ... - DWC - KNAW

struments for digitizing the components of the geomagnetic field. by using
proton magnetometers and fluxgate instruments (As. 1973). These modern instruments
are now in operation in the Magnetic Observatory at Witteveen . They
make it possible to calculate and to publish the geomagnetic values almost automatically.
I. 3. DISTURBANCES IN THE EARTH'S MAGNETIC FIELD CAUSED
BY THE SUN
Since the beginning the Netherlands have played an important role internationally
in characterizing the days from a geomagnetic viewpoint . The earth 's
magnetic field is quiet on some days and disturbed on others. The occurrence
of disturbances is related to the phenomenon of sunspots. These disturbances
are much stronger at higher than at lower latitudes; agiobal collection of data
is necessary to study them. M. Snellen. a member of the scientific staff of the
KNMI. was the first to collect. by request of the International Commission of
Terrestrial Magnetism. a commission of the International Union of Geodesy and
Geophysics (IUGG). geomagnetic character figures (0 = undisturbed day. 1 =
Figure 5. The Geomagnetic Observatory of the KNMI at Witteveen • a house without
windows (Photo J . B. van der Kolk. Naarden).
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