Cyclical and Secular Variations of Solar Activity

Presented here is a review of present knowledge of the long-term behavior of solar activity on a multi-millennial timescale, as reconstructed using the indirect proxy method. The concept of solar activity is discussed along with an overview of the special indices used to quantify different aspects of variable solar activity, with special emphasis upon sunspot number. Over long timescales, quantitative information about past solar activity can only be obtained using a method based upon indirect proxies, such as the cosmogenic isotopes 14 C and 10 Be in natural stratified archives (e.g., tree rings or ice cores). We give an historical overview of the development of the proxy-based method for past solar-activity reconstruction over millennia, as well as a description of the modern state. Special attention is paid to the verification and cross-calibration of reconstructions. It is argued that this method of cosmogenic isotopes makes a solid basis for studies of solar variability in the past on a long timescale (centuries to millennia) during the Holocene. A separate section is devoted to reconstructions of strong solar energetic-particle (SEP) events in the past, that suggest that the present-day average SEP flux is broadly consistent with estimates on longer timescales, and that the occurrence of extra-strong events is unlikely. Finally, the main features of the long-term evolution of solar magnetic activity, including the

show abstract

Section: Centennial Gleissberg Cyclementioning

confidence: 99%

A history of solar activity over millennia

Usoskin

2017

Living Rev Sol Phys

391

241

View full text Add to dashboard Cite

show abstract

“…However, the Gleissberg cycle is not a cycle in the strict periodic sense but rather a modulation of the cycle envelope with a varying timescale of 60 -120 years (e.g., Gleissberg, 1971;Kuklin, 1976;Ogurtsov et al, 2002). This secular cycle has also been reported, using a spectral analysis of radiocarbon data as a proxy for solar activity (see Section 3), to exist on long timescales (Feynman and Gabriel, 1990;Peristykh and Damon, 2003), but the question of its phase locking and persistency/intermittency still remains open.…”

Section: Quasi-periodicitiesmentioning

confidence: 99%

A History of Solar Activity over Millennia

Usoskin

2008

Living Rev. Sol. Phys.

195

200

View full text Add to dashboard Cite

Presented here is a review of present knowledge of the long-term behavior of solar activity on a multi-millennial timescale, as reconstructed using the indirect proxy method.The concept of solar activity is discussed along with an overview of the special indices used to quantify different aspects of variable solar activity, with special emphasis upon sunspot number.Over long timescales, quantitative information about past solar activity can only be obtained using a method based upon indirect proxy, such as the cosmogenic isotopes 14 C and 10 Be in natural stratified archives (e.g., tree rings or ice cores). We give an historical overview of the development of the proxy-based method for past solar-activity reconstruction over millennia, as well as a description of the modern state. Special attention is paid to the verification and cross-calibration of reconstructions. It is argued that this method of cosmogenic isotopes makes a solid basis for studies of solar variability in the past on a long timescale (centuries to millennia) during the Holocene.A separate section is devoted to reconstructions of strong solar-energetic-particle (SEP) events in the past, that suggest that the present-day average SEP flux is broadly consistent with estimates on longer timescales, and that the occurrence of extra-strong events is unlikely.Finally, the main features of the long-term evolution of solar magnetic activity, including the statistics of grand minima and maxima occurrence, are summarized and their possible implications, especially for solar/stellar dynamo theory, are discussed.

show abstract

“…Similarly, some internal mechanism in the Sun might also amplify the effect of solar-planetary interaction. The idea that planetary motions may influence the solar activity has a very long history (Kuklin 1976) and seems to have been initiated by the astronomer Rudolf Wolf in the late 1850s (Charbonneau 2002). While energy considerations clearly show that the planets cannot be the direct cause of the solar activity, since this would lead to observable variations in the orbital parameters (Zaqarashvili 1997), it still remains an open question whether the planets can perturb the operation of the solar dynamo.…”

Section: Introductionmentioning

confidence: 99%

Is there a planetary influence on solar activity?

Abreu

Beer

Ferriz-Mas

et al. 2012

A&A

147

189

View full text Add to dashboard Cite

Context. Understanding the Sun's magnetic activity is important because of its impact on the Earth's environment. Direct observations of the sunspots since 1610 reveal an irregular activity cycle with an average period of about 11 years, which is modulated on longer timescales. Proxies of solar activity such as 14 C and 10 Be show consistently longer cycles with well-defined periodicities and varying amplitudes. Current models of solar activity assume that the origin and modulation of solar activity lie within the Sun itself; however, correlations between direct solar activity indices and planetary configurations have been reported on many occasions. Since no successful physical mechanism was suggested to explain these correlations, the possible link between planetary motion and solar activity has been largely ignored. Aims. While energy considerations clearly show that the planets cannot be the direct cause of the solar activity, it remains an open question whether the planets can perturb the operation of the solar dynamo. Here we use a 9400 year solar activity reconstruction derived from cosmogenic radionuclides to test this hypothesis. Methods. We developed a simple physical model for describing the time-dependent torque exerted by the planets on a non-spherical tachocline and compared the corresponding power spectrum with that of the reconstructed solar activity record. Results. We find an excellent agreement between the long-term cycles in proxies of solar activity and the periodicities in the planetary torque and also that some periodicities remain phase-locked over 9400 years. Conclusions. Based on these observations we put forward the idea that the long-term solar magnetic activity is modulated by planetary effects. If correct, our hypothesis has important implications for solar physics and the solar-terrestrial connection.

show abstract

Cyclical and Secular Variations of Solar Activity

Cited by 18 publications

References 48 publications

A history of solar activity over millennia

A history of solar activity over millennia

A History of Solar Activity over Millennia

Is there a planetary influence on solar activity?

Contact Info

Product

Resources

About