Measurement and analysis of earth's magnetic field based on low-magnetic field standards
The Cheongyang (CYG) observatory has been built to measure earth's magnetic field and to study prediction of earthquake and space weather. The equipments of the CYG observatory are a 3-axis fluxgate magnetometer, an overhauser effect proton magnetometer, a declination/inclination magnetometer and a data logger. A Cs-4He atomic magnetic resonance magnetometer was used to correct the measured data obtained by the proton magnetometer. All the measurement equipments were calibrated using magnetic field standard system maintained at KRISS. The Measurement results show a variation of the baselines less than 5 nT within one year, which is the most critical requirement criteria for joining the INTERMAGNET (International Real-time Magnetic Observatory Network).
Maintenance of magnetic flux density standards on the basis of proton gyromagnetic ratio at KRISS
The proton gyromagnetic ratio (/spl gamma/'/sub p/) plays a fundamental role in achieving high accuracy in magnetic measurements. We have improved our magnetic flux density standards using the /spl gamma/'/sub p/-value and related techniques developed at Korea Research Institute of Standards and Science (KRISS). The standards are used for the calibration of magnetometers and support the test of sensors and materials in the range from 20 /spl mu/T to 2.5 T with (4 to 80) /spl mu/T/T uncertainties (k=2).
The Invariance of the Vacuum is the Invariance of the World
The following theorem is demonstrated: If the vacuum is invariant under the group generated by the space integral of the time component of a local vector current, then the Hamiltonian is invariant also. A similar theorem holds for the group generated by the space integral of a space component of a local axial-vector current.