The time delay of the substorm onset defined by the onset of the earliest Pi2 magnetic pulsations from a southward turning of the north-south component of the interplanetary magnetic field (IMF-Bz) has been investigated for 21 characteristic IMF events. It was found that the time delay had little dependence on the intensity of the IMF southward component in the range of the intensity examined (i. e. from -1.5 to -9nT), or rather it was constant (about 1hr) except for a few cases. This result suggests that the time delay can be interpreted as a response time inherent in the magnetosphere.

View full abstract

The mean virtual pole position for the Cretaceous granites in South Korea is close to the present geographic pole and is consistent with that for Cretaceous, Pliocene and Pleistocene volcanic rocks from the same region. It also accords with pole positions obtained from Chinese, Siberian and European Cretaceous rocks. From the paleomagnetic data for the granites and volcanic rocks of the Cretaceous, it is concluded that the South Korean land mass has not been subjected to sufficient local tectonic movements to generate a change in the direction of primary magnetic vectors of the granites or of the volcanic rocks since the Cretaceous. This means that although some tectonic movement has taken place in South Korea since the Cretaceous, the movement brought about only vertical block displacements with no significant tilting or rotational movements. It also suggests that the virtual geomagnetic pole for the Cretaceous rocks in South Korea provides a valid Cretaceous virtual pole position for the Eurasian land mass.

View full abstract

Linearity of a high-μ metal core solenoid as a magnetic sensor has been checked, comparing its output to that from an air-core loop antenna. Two induction magnetometer systems using these different types of sensors both parallel to the magnetic N-S direction, were run simultaneously in the same manner as for actual field observations. The outputs from these systems during a moderately intense Pc 3 event were compared with each other. No distortion of the magnetic signals due to the high-μ metal core sensor was detected. Theoretical consideration is presented also as to why high-μ metal core solenoids give rise to no signal distortion.

View full abstract