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Time-Delayed Response of the Solar Total Irradiance Variation to Long No. 101 Proc. Japan Acad., 72, Ser. B (1996) 197 Time-Delayed Response of the Solar Total Irradiance Variation to Long-Term Solar Magnetic Cycle Amplitude Modulation as Inferred by Sunspot Relative Number and Isotope Data of 10Be in the Greenland Ice Core and Land Air Temperature Variation of the Earth By Hirokazu YOSHIMURA Department of Astronomy, University of Tokyo, Tokyo 113 (Communicated by Yoshio FUJITA, M.J. A., Dec. 12, 1996) Abstract : We found that the time profile of the land air temperature anomalies followed the time profile of the magnetic field variation with remarkable similarity and delay time of about 200 years for both cases of the instrumentally measured temperature data and the data reconstructed from tree ring growth rates of the northern north American continent and the polar Ural mountains of northern Siberia. If this is indeed the case, (i) the present global warming will turn to global cooling in near future. If we assume that the land air temperature anomalies can be a good proxy of the solar total irradiance variation, the present result means that (ii) the present global warming of the Earth is a result of release of heat which has been stored in the solar convection zone in the Maunder Minimum in the 17th century. Key words : Solar total irradiance; solar cycle; dendroclimatology. Introduction. The solar total irradiance is a solar magnetic field on the surface of the Sun, it was relatively new terminology to describe total photon taken for granted that the STI variation is in direct output of the Sun received at the mean orbital distance correlation with the solar magnetic field variation. of the Earth per unit area perpendicular to the line Along this thought, history of the STI in the past was from the Sun to the Earth. It was called solar constant reconstructed from various indices of the magnetic in the past since it is a fundamental parameter for activity of the Sun for use of investigation of the investigating weather and climate system of the Earth possible influence of the solar irradiance variation on as well as for measurement of the luminosity of the the climate of the Earth. Reid1~'2~noticed similarity of Sun. After it was unambiguously found from space by the time profile of the global merged land sea air Nimbus 7 and Solar Maximum Mission that the solar temperature (sea-surface temperature) anomalies with total irradiance changes in time with various time the time profile of the amplitude of the solar magnetic scales, particularly with time scale of the solar cycle, cycle and interpreted that this similarity is an evidence the terminology of solar constant has become to be of the effect of the STI variation on the climate of the thought to be inadequate. The terminology of solar Earth. Friis-Christensen and Lassen3~ pointed out total irradiance or total solar irradiance is now more discrepancy in the similarity claimed by Reidl~'2~ and frequently used. We use the terminology of solar total proposed an empirical interpretation of the discrepan- irradiance (STI) to describe total photon output of the cy in terms of similarity of the time profile of variation Sun in this paper. of the length of the solar cycle with the time profile of Magneto-thermal pulsation of the sun. In the the land air temperature anomalies. On the other beginning of the measurement of the STI from space, hand, the value of the STI observed by Nimbus 7 and it was thought that the variation of the STI is caused Solar Maximum Mission was high in the maximum by dark sunspots and bright faculae on the surface of phase of solar cycle 21 and was low in the minimum the Sun. Since both features result from presence of phase between the solar cycles 21 and 22. The value 198 H. YOSHIMURA [Vol. 72(B), increased when the maximum phase of the next solar number with time delay of the order of 10 years when cycle 22 came. However, as the solar cycle 22 turned variations with time scales which are shorter than 100 toward the minimum phase, the Nimbus 7 measure- days are smoothed out by a new method to compare ment continued to show high value of the STI. This two kinds of time profiles of different lengths.6~ We use was the first indicator that the direct correlation the same method in this paper. The method consists of between the STI and the magnetic field does not hold smoothing the original time series by taking running and that the cause of the STI variation is not on the averages of the two kinds of quantities with various surface of the Sun. In an effort to find the mechanism lengths l's of averaging. Secondly, we calculate the that drives the variation of the STI, we analysed the time-delayed linear-correlation coefficient C1(td)of the data sets of Ca II K index, He I 10830 A index, total two time series of a quantity Q1(ti) and of the other magnetic flux index, and sunspot relative number, as quantity Q2(ti) after displacing the time profile of the well as the data sets of the Nimbus 7 and Solar first quantity toward the past by an amount of delay Maximum Mission STI measurements. The Ca II K time td as a function of length of averaging l and delay and He I 10830 A indices represent bright faculae. The time td. Then we multiply the linear-correlation co- sunspot relative number represents dark features of efficients of different lengths of averaging l from ll to sunspots on the surface. The results showed that (i) all lM to define the multiplied correlation index MCI (td) the data sets of Ca II K index, He I 10830 A index, as a function of time delay td. The purpose of defining total magnetic flux, and sunspot relative number work the multiplied correlation index is to define character- as indicators of time variation of the magnetic field of istics which are common to the correlation coefficients the Sun, (ii) there is no substantial phase lag among between the two quantities for different lengths of the various indices of the magnetic field, (iii) both the averaging and which do not depend on the length of magnetic field indicators and the STI pulsate in time averaging. with period on the order of 200 days, and (iv) there is a Similarity of the time profiles of the solar total distinctive time delay on the order of 50 days between irradiance and the solar magnetic cycle variations. In peaks of the pulsation of the magnetic field and those of order to seek thermal and dynamical meaning of the the STI.4~,5~We call this phenomenon the 200-day similarity of the two kinds of the time profiles, we magneto-thermal pulsation. The pulsation of the made an effort to extend this finding to the distant magnetic field takes place as eruption of cluster of past. For this purpose, we took several steps of magnetic flux tubes each of which makes one active building logic of analyses. First step is to assume that region with two bipolar sunspots which is superposed the Earth is a good recorder of variation of the solar on the 11-year solar cycle. A peak of the STI pulsation, total irradiance, since the Earth, particularly its land which we call a thermal pulse, follows a peak of the area, absorbs sunlight directly and drives weather and magnetic field pulsation, which we call a magnetic climate system of the Earth. The second step is to pulse. A valley of the STI pulsation takes place about adopt the data of the reconstructed air temperature 20 days prior to a magnetic pulse. This means that anomalies of the growth rates of the tree rings over before a surge of a cluster of magnetic flux tubes the world as the data of the air land temperature of the appears on the surface, the surface darkens slightly. past which has much longer length of time interval of This is a definitive evidence that the temporary recording than the instrumentally measured data. The blocking of heat flow, storage of heat, and later release tree-ring data is now widely sampled and the method of heat, are all possible by the presence of the of reconstruction of the land air temperature has been magnetic field within the solar convection zone and tested in many ways due to recognition of importance that the mechanism of the STI irradiance variation is of climate research of the past and the future. The not due to the dark and bright surface features on the reconstruction of the temperature must be done Sun. The cause must lie deep in the solar convection globally for our usage of the temperature anomalies as zone which gives rise to the surface temperature an index of the STI variation. However, due to present variation of the Sun. limitation of data coverage, we use the data sets of the We also found that the STI variation with time northern north American continent by D'Arrigo and scale on the order of 11 years of the solar cycle Jacoby7~ and ' of the eastern slope of the polar Ural observed from space followed the time variation of the mountains in northern Siberia by Graybill and solar magnetic cycle represented by sunspot relative Shiyatov.8~ The eastern slope of the polar Ural No. 10] Solar Total Irradiance Variation 199 mountain area is thought to be sensitive to long-tern trends and variations in temperature over the arctic and possibly the whole northern hemisphere.9) Th€ third step of logic of this paper is that the cosmogenic isotope i0Be is a good proxy of the past solar magnetic activity whose data of duration is longer than that of the sunspot relative number.
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