Survey of Annual Variations in Geomagnetic Total Intensity Observations
Mitsuharu NISHIMURA, Shin ARITA, Takashi MORIYAMA, Masahiko HASHIMOTO, Masashi SUGAWARA, Norihisa ISHIDA and Hiroshi HASEGAWA
Abstract
In order to identify the causes of annual variations in the total magnetic force observed at the Memambetsu Branch's continuous geomagnetic total intensity station (79F), underground temperatures (at depths of 0.1 m, 0.5 m, and 1 m) near 79F and outdoor temperatures were measured to clarify their relationship with variations in geomagnetic total intensity.
The results of this survey revealed that annual variations have a high correlation with the underground temperature near the ground surface. A magnetic survey in an area of the branch including 79F was also conducted. The results indicated that the magnetic gradient in the east-west direction (10 nT/m) is considerably greater than that in the north-south direction near 79F.
The authors therefore concluded that annual variations at 79F are caused by local variations in the magnetic field around the station as a result of temperature changes.
Received 3 March 2010; received in revised form 8 March 2010; accepted 16 March 2010
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