Premium
Geomagnetic lunar and solar daily variations during the last 100 years
Author(s) -
Yamazaki Y.,
Kosch M. J.
Publication year - 2014
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
eISSN - 2169-9402
pISSN - 2169-9380
DOI - 10.1002/2014ja020203
Subject(s) - earth's magnetic field , astrobiology , geology , atmospheric sciences , environmental science , geophysics , meteorology , physics , magnetic field , quantum mechanics
This paper describes long‐term changes in the geomagnetic lunar ( L ) and solar ( S ) daily variations. We analyze the eastward component of the geomagnetic field observed at eight midlatitude stations during 1903–2012. The amplitude and phase for the semidiurnal component of the L and S variations are examined. Both L and S amplitudes correlate with the solar activity index F 10.7 , revealing a prominent 11 year solar cycle. In both cases, the correlation is slightly better withF 10 . 7than F 10.7 . The sensitivity of the L variation to solar activity is comparable with that of the S variation. The solar cycle effect is also found in the phase of the S variation but not apparent in the phase of the L variation. The ratio in the amplitude of the L to S variation shows a long‐term decrease (approximately 10% per century), which may be due to a reduction in lunar tidal waves from the lower atmosphere to the upper atmosphere in association with climate change.