Abstract
The time series of total solar irradiance (TSI) satellite observations since
1978 provided by ACRIM and PMOD TSI composites are studied. We find empirical
evidence for planetary-induced forcing and modulation of solar activity. Power
spectra and direct data pattern analysis reveal a clear signature of the
1.09-year Earth-Jupiter conjunction cycle, in particular during solar cycle 23
maximum. This appears to suggest that the Jupiter side of the Sun is slightly
brighter during solar maxima. The effect is observed when the Earth crosses the
Sun-Jupiter conjunction line every 1.09 years. Multiple spectral peaks are
observed in the TSI records that are coherent with known planetary harmonics
such as the spring, orbital and synodic periods among Mercury, Venus, Earth and
Jupiter: the Mercury-Venus spring-tidal cycle (0.20 year); the Mercury orbital
cycle (0.24 year); the Venus-Jupiter spring-tidal cycle (0.32 year); the
Venus-Mercury synodic cycle (0.40 year); the Venus-Jupiter synodic cycle (0.65
year); and the Venus-Earth spring tidal cycle (0.80 year). Strong evidence is
also found for a 0.5-year TSI cycle that could be driven by the Earth's
crossing the solar equatorial plane twice a year and may indicate a latitudinal
solar-luminosity asymmetry. Because both spring and synodic planetary cycles
appear to be present and the amplitudes of their TSI signatures appear enhanced
during sunspot cycle maxima, we conjecture that on annual and sub-annual scales
both gravitational and electro-magnetic planet-sun interactions and internal
non-linear feedbacks may be modulating solar activity. Gravitational tidal
forces should mostly stress spring cycles while electro-magnetic forces could
be linked to the solar wobbling dynamics, and would mostly stress the synodic
cycles.
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