Intercomparisons of proxies for past solar variability
Records of several direct and indirect proxies for solar variability of different length and quality are discussed and compared: irradiance, aa-index, aurorae, radius, sunspot numbers and 14C and 10Be concentrations. All records of corresponding length except the sunspot record show modulation associated with the 22 year Hale cycle and its harmonics, but all these records show the 11 year Schwabe cycle and its harmonics as well as the minima in solar activity in the 17th and 19th centuries [Maunder (1645–1715), Dalton (1800–1820)]. There are clear differences in amplitudes and phases which indicates that these time records are not related in a simple linear fashion to the evolution of the Sun’s magnetic field and its consequences at the surface of the Sun and throughout the Heliosphere. Although the quality and time resolution of most direct proxies is generally high, their length is limited and never exceeds 400 years. The indirect proxies 10Be and 14C on the other hand provide information with a generally much smaller signal to noise ratio, but offer the possibility to extend the record of solar variability much further back in time.
KeywordsSolar Wind Solar Activity Tree Ring Sunspot Number Solar Irradiance
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