/pdf/a-review-of-holocene-solar-linked-climatic-variation-on-4n7wosaevj.pdf

A review of Holocene solar-linked climatic variation on centennial to millennial timescales: Physical processes, interpretative frameworks and a new multiple cross-wavelet transform algorithm

Solar activity is evident both in the equatorial activity centres and in the polar magnetic field variations. The total solar irradiance variation is due to the former component. During the extraordinarily long minimum of activity between sunspot cycles 23 and 24, the variations related to the equatorial field components reached their minimum values in the first half of 2008, while those related to the polar field variations had their extreme values rather at the end of 2009 and the first half of 2010. The explanation of this delay is another challenge for dynamo theories. The role of the open solar flux has so far been grossly underestimated in discussions of Sun-climate relations. The gradual increase in the average terrestrial ground temperature since 1610 is related both to the equatorial and polar field variations. The main component (0.077 K/century) is due to the variation of the total solar irradiance. The second component (0.040 K/century) waits for an explanation. The smoothed residual increase, presumably antropogenic, obtained after subtraction of the known components from the total increase was 0.31 K in 1999.

/pdf/solar-forcing-of-climate-eorx1kys01.pdf

Solar Forcing of Climate

Reconstruction and prediction of the total solar irradiance: From the Medieval Warm Period to the 21st century

The causes of solar variations and their impact on climatic environments have been andstill are the subject of large debate. The possible influence of planetary perturbations on thesolar cycles have also been recently the subject of multiples controverses. The goal of thepresent thesis is to provide some insight on this problem by a new computation of the planetaryperturbations on the Sun, at short, middle and and long time scales.At first, we describe our current understanding of the physical causes of the solar activityand their major observable manifestations, such as the sun spots records. We provide somehistorical background for the numerous records of solar activity proxies. We also review thedifferent approaches to explain the solar planetary relationships through an analysis of thepublished literature.The main purpose of the present work is to study the possible influence of the planetarygravitational perturbations on the solar cycles. In a first part, we analyse the short, middle andlong term solar activity behavior by using the quasiperiodic approximations provided by thefrequency map analysis method to determine the main periodicities of the solar cycles. Thisallows us to provide some reconstruction of the long timescale changes of solar activity variation.The reconstructed activity series are compared with the observed solar activity data and thelong term natural archives such as radioisotopes proxies. The reconstructed series still preservethe well recorded historical grand minima and maxima events and provide us some extendeddata for the study of the long timescale evolution of solar cycles.There has already been some attempts to explain the direct or partial influences of anexternal (e.g., the planets ) or an internal (e.g., its dynamo) effects on the solar changes. In thepresent work, we investigate the planetary tidal influence on solar cycle variations. We havedeveloped a realistic dynamical model for describing the tidal effect exerted by the perturbationof the planets of the Solar system on the deformation of the non-spherical Sun’s surface whichmay partially modulate its activity variations. The model is limited to the dynamical effects ofthe planets on the Sun and do not take account any physical interior process of the Sun. TheSun is considered as an homogeneous three axial non spherical body.The variations of the potential coefficients induced by the effects of body tides are com-puted, using the last INPOP planetary ephemerides and the long term solutions La2004. Thesemi-analytical expressions of the deformation coefficients of potential are derived. Thus, theestimations of the planetary tides effects of each planets and their combinations are comparedto the solar activity records and their reconstructed series. Hence, the correlations between thevariations of the deformation of Sun’s surface and its activity records are discussed.

Search for planetary influences on solar activity

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.

M.C. Leal-Silva

Papers

Solar forcing on the ice winter severity index in the western Baltic region