A non-linear coupling function between sunspot maxima and aa minima modulations has been found as a result of a wavelet analysis of geomagnetic index aa and Wolf sunspot number yearly means since ...1844. It has been demonstrated that the increase of these modulations for the past 158 years has not been steady, instead, it has occurred in less than 30 years starting around 1923. Otherwise sunspot maxima have oscillated about a constant level of 90 and 141, prior to 1923 and after 1949, respectively. The relevance of these findings regarding the forecasting of solar activity is analyzed here. It is found that if sunspot cycle maxima were still oscillating around the 141 constant value, then the Gnevyshev-Ohl rule would be violated for two consecutive even-odd sunspot pairs (22-23 and 24-25) for the first time in 1700 years. Instead, we present evidence that solar activity is in a declining episode that started about 1993. A value for maximum sunspot number in solar cycle 24 (87.5±23.5) is estimated from our results.PUBLICATION ABSTRACT
We summarize the major aspects of the remarkable, fairly long lasting period (
∼
2005
to
∼
2010
) of low solar activity, that we will call
the Transition
. It is the transitional stage between the ...Grand Maximum of the 20th century and a forthcoming (most probably Regular) episode of solar activity. The various kinds of activity in the functioning of the equatorial components of the solar dynamo before and during the Transition are summarized. While the behavior of unipolar magnetic regions and their rest-latitudes already gave very early indications – mid 20th century – of the forthcoming Transition, more such indications became available around 1995 and the main part of it occurred between 2005 and 2010. Some of the inferences are discussed. We submit the hypothesis that the solar tachocline undergoes pulsations and we present some helioseismic evidences. In that scenario we find that its equatorial part has moved downward over a fairly small semi-amplitude (
∼
0.03
solar radii) during the time of the Transition. There are several indications, apart from this ‘pulsation’, that the tachocline may even be pulsating with still smaller amplitudes in more modes. We speculate about the physical mechanism(s).
We analyze the variation of the solar-dynamo magnetic-field components during the last millennium through a study of their proxy data. We introduce a phase diagram with as abscissa and ordinate the ...proxies of the values of the toroidal and poloidal magnetic field components. In this diagram the dynamo system appears to regularly cross a well-defined point, which we call the Transition Point. Such crossings occurred five times during the past millennium. Each of these crossings preceded a Grand Episode, either a Minimum or a Maximum one. In addition to these two types of quasiperiodic behavior, a third type consisting of weaker quasiregular oscillations (R) around the Transition Point’s coordinates is identified. These periods appear to last one or two times the Gleissberg cycle length. Between the various types of episodes there are brief phase transitions. We identify two types of such phase transitions.
Solar variability is controlled by the internal dynamo which is a non-linear system. We develop a physical–statistical method for forecasting solar activity that takes into account the non-linear ...character of the solar dynamo. The method is based on the generally accepted mechanisms of the dynamo and on recently found systematic properties of the long-term solar variability. The amplitude modulation of the Schwabe cycle in dynamo's magnetic field components can be decomposed in an invariant transition level and three types of oscillations around it. The regularities that we observe in the behaviour of these oscillations during the last millennium enable us to forecast solar activity. We find that the system is presently undergoing a transition from the recent Grand Maximum to another regime. This transition started in 2000 and it is expected to end around the maximum of cycle 24, foreseen for 2014, with a maximum sunspot number
R
max=68±17. At that time a period of lower solar activity will start. That period will be one of regular oscillations, as occurred between 1730 and 1923. The first of these oscillations may even turn out to be as strongly negative as around 1810, in which case a short Grand Minimum similar to the Dalton one might develop. This moderate-to-low-activity episode is expected to last for at least one Gleissberg cycle (60–100 years).
This investigation is a follow-up of a paper in which we showed that both major magnetic components of the solar dynamo,
viz. the toroidal and the poloidal ones, are correlated with average ...terrestrial surface temperatures. Here, we quantify, improve and specify that result and search for their causes.
We studied seven recent temperature files. They were smoothed in order to eliminate the Schwabe-type (11 years) variations. While the total temperature gradient over the period of investigation (1610–1970) is 0.087
°C/century; a gradient of 0.077
°C/century is correlated with the equatorial (toroidal) magnetic field component. Half of it is explained by the increase of the Total Solar Irradiance over the period of investigation, while the other half is due to feedback by evaporated water vapour. A yet unexplained gradient of −0.040
°C/century is correlated with the polar (poloidal) magnetic field. The residual temperature increase over that period, not correlated with solar variability, is 0.051
°C/century. It is ascribed to climatologic forcings and internal modes of variation.
We used these results to study present terrestrial surface warming. By subtracting the above-mentioned components from the observed temperatures we found a residual excess of 0.31° in 1999, this being the triangularly weighted residual over the period 1990–2008.
We show that solar forcing of the ground temperature associated with significant feedback is a regularly occurring feature, by describing some well observed events during the Holocene.
By applying the wavelet formalism to sudden storm commencements and
aa geomagnetic indices and solar total irradiation, as a proxy data for solar sources of climate-forcing, we have searched the ...signatures of those variables on the Northern Hemisphere surface temperature. We have found that cyclical behaviour in surface temperature is not clearly related to none of these variables, so we have suggested that besides them surface temperature might be related to Earth’s rotation rate variations. Also it has been suggested that in the long-term Earth’s rotation rate variations might be excited by geomagnetic storm time variations which, in turn, depends on solar activity.
The study of these phenomena and its relationships is addressed in the present paper. With this purpose we perform an analysis of the evolution during the last 350
years of the signals that conform the 11-year sunspot cycle maxima envelope for different time scales. The result is applied to analyze the relationship between long-term variations in sunspot number and excess of length of day; and to unearth the signature in surface temperature of this last from that of sudden storm commencement and
aa geomagnetic indices and total solar irradiation.
As solar dynamo experiments transient processes in all the time scales from seconds to centuries, Fourier analysis and its requirement for the process to be stationary is likely to produce spurious periodicities. We resort instead to wavelet formalism. By this representation we found that sunspot maxima envelope for the last 350
years may be described by means of the superposition of two cycles – a decadal and a semi-secular one – and a secular trend. And that the changing amplitude and phase of the cycles are well reconstructed using the superposition of two wavelets with nearby periods. The strong temporal changes in amplitude of the cycles facilitate to detect its phase in a given time series. It is found that a strong semi-secular cycle in the sunspot maxima envelope that started during the 1705 chaotic transition having its maximum amplitude at the Dalton minimum, was mapped 94
years later in Earth’s rotation rate and simultaneously in surface temperature. Also, there was a decrease (increase) of 0.022
°C for each millisecond of decrease (increase) in the Earth’s rotation period for the semi-secular cycle as well as the secular trend.
Episodes of relative global warming de Jager, C.; Duhau, S.
Journal of atmospheric and solar-terrestrial physics,
02/2009, Letnik:
71, Številka:
2
Journal Article
Recenzirano
Solar activity is regulated by the solar dynamo. The dynamo is a non-linear interplay between the equatorial and polar magnetic field components. So far, in Sun–climate studies, only the equatorial ...component has been considered as a possible driver of tropospheric temperature variations. We show that, next to this, there is a significant contribution of the polar component. Based on direct observations of proxy data for the two main solar magnetic fields components since 1844, we derive an empirical relation between tropospheric temperature variation and those of the solar equatorial and polar activities. When applying that relation to the period 1610–1995, we find some quasi-regular episodes of residual temperature increases and decreases, with semi-amplitudes up to ∼0.3
°C. The present period of global warming is one of them.
There are some indications that the coupling function between the polar and the toroidal solar magnetic field strengths are time dependent. Therefore, as proxy data of these strengths, the ...relationship between long‐term modulation of solar and geomagnetic activity is analyzed here by means of a wavelet multi‐resolution analysis of yearly means of sunspot number and geomagnetic index aa since 1844. It is found that aa index and relative sunspot number long‐term modulations oscillate around constant levels that have increased to be 1.9 and 1.6, respectively of its values prior 1923. The oscillations of the aa and Rz long‐term modulation appear to be well represented by the superposition of a decadal cycle and the Gleissberg cycle. The amplitude ratio and the phase shift between the Rz and aa decadal cycles changed sharply at year 1923, and the Gleissberg cycle was interrupted to be restarted at year 1949. The synchronicity of these changes with temporal changes in several solar and solar‐terrestrial variables indicates that the non‐linear nature of the solar dynamo has lead to a major change of its background state after 1923.
•There are some evidences that sunspot cycle and solar inertial force variability are related.•It is known that differential rotation drives sunspot cycle.•Solar inertial force is too weak to drive ...differential rotation.•A mechanism able to amplify solar inertial force to its required strength is still missing.
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