Open AccessModulation of Geomagnetic Lunar Daily Variation in H at Alibag with Lunar Distance
Author(s) -
Arora B. R.,
Rao D. R. K.
Publication year - 1975
Publication title -
geophysical journal of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.302
H-Index - 168
eISSN - 1365-246X
pISSN - 0016-8009
DOI - 10.1111/j.1365-246x.1975.tb00652.x
Subject(s) - earth's magnetic field , variation (astronomy) , geodesy , geology , atmospheric sciences , atmosphere (unit) , amplitude , physics , solar cycle , geophysics , astrophysics , meteorology , magnetic field , solar wind , optics , quantum mechanics
Summary The dependence of geomagnetic lunar daily variation ( L ) on lunar distance in different seasons and for varied epochs of solar activity is investigated using the long series of horizontal intensity observations at Alibag. The close agreement of the observed ratio of L when the moon is at perigee to that when it is at apogee during different seasons and for the total period to that expected from gravitational tide theory clearly indicates that the direct effect of the moon on the upper atmosphere is primarily gravitational and also suggests that the amplitudes ratio N 2 : M 2 in all seasons departs insignificantly from that expected from tidal theory. A systematic increase of the ratio of L at lunar perigee to apogee with change in phase of solar cycle implies that N 2 : M 2 has a measure of dependence on solar activity. Ionospheric and oceanic parts of L are poorly determined and no definite cause for their behaviour could be given.