Distributions of Magnetic Field Variations, Differences and Residuals
Abstract
The search for submarines by means of Magnetic Anomaly Detection (MAD) is effected by a low-flying aircraft with a magnetometer installed onboard, or, for better sensitivity, mounted on an external boom. The magnetic field produced by a submarine appears as a local quasistatic distortion ("anomaly") of the geomagnetic field. The technique requires a remote reference magnetometer at a fixed place in order to compensate for the omni-present temporal variations of the geomagnetic field. This place may be many kilometres away from the position of the aircraft, in which case the technique requires a high spatial uniformity of the ambient magnetic field variations. While application of the MAD technique may be possible in many areas, there are some areas where this method must fail. These are either areas with poorly mapped magnetostatic anomalies of small spatial scale, or areas with high levels of non-uniform, man-made magnetic noise. The latter typically include coastal zones with industrial and service centers in the vicinity. We find among them the southern Ligurian coastal zone which is magnetically highly disturbed by a busy electrified railway line. Electric train supply currents leak several kilometres out into the sea and produce non-uniform magnetic field distortions (anomalies) of large amplitude.
Document Details
- Document Type
- Technical Report
- Publication Date
- Mar 01, 2006
- Accession Number
- AD1113041
Entities
People
- J. Lam
- J. Watermann