Geomagnetic field excursions occurred often during the last million years

摘要: Scientists studying western North Atlantic Ocean deep-sea sediments have discovered that the Earth's magnetic field underwent 14 local excursions since last global magnetic-field polarity reversal 780,000 years ago. These coincide with similar identified elsewhere on planet—leading to conclusion are in nature, occur a significant portion of time, and an integral part geomagnetic secular variation between reversals. Excursions defined [Verosub Banerjee, 1977] as anomalous directions whose equivalent virtual poles (VGPs) more than 45° away from Geographic Pole, while VGPs within Pole considered be typical variation. (VGPs calculated which locate magneticfield by assuming caused simple dipole or bar magnet situated at center Earth.)