Abstract
The Sun’s long-term magnetic variability is the primary driver of space climate. This variability is manifested not only in the longobserved and dramatic change of magnetic fields on the solar surface, but also in the changing solar radiative output across all wavelengths. The Sun’s magnetic variability also modulates the particulate and magnetic fluxes in the heliosphere, which determine the interplanetary conditions and impose significant electromagnetic forces and effects upon planetary atmospheres. All these effects due to the changing solar magnetic fields are also relevant for planetary climates, including the climate of the Earth. The ultimate cause of solar variability, at time scales much shorter than stellar evolutionary time scales, i.e., at decadal to centennial and, maybe, even millennial or longer scales, has its origin in the solar dynamo mechanism. Therefore, in order to better understand the origin of space climate, one must analyze different proxies of solar magnetic variability and develop models of the solar dynamo mechanism that correctly produce the observed properties of the magnetic fields. This Preface summarizes the most important findings of the papers of this Special Issue, most of which were presented in the Space Climate-4 Symposium organized in 2011 in Goa, India.
Highlights
By comparing the distribution of sunspots and sunspot groups of different morphology, they find that the number of small spots without penumbra and of groups without large spots dropped by a factor of more than 2 in cycle 23, causing the observed lower values of the ISN relative to other, more global indices of solar activity like the UV proxies
The extensive suite of parameters and detailed analysis make this an important paper in studying the structure of interplanetary coronal mass ejection (ICME) observed at 1 AU, which will have future application to space weather studies. In this Special issue, Richardson and Cane contributed with two papers. These papers report the analysis of the properties of solar wind and interplanetary magnetic field at 1 AU, and their effect in the near-Earth environment causing geomagnetic activity and storminess
The authors calculate the contribution of the three flow types to the aa index of geomagnetic activity and the intensity of the interplanetary magnetic field (IMF), finding that both the recent minimum and cycle 20 follow the same pattern as other, more active cycles, in that the IMF intensity closely tracks the mean fields found in high-speed streams and slow solar wind
Summary
By comparing the distribution of sunspots and sunspot groups of different morphology, they find that the number of small spots without penumbra and of groups without large spots dropped by a factor of more than 2 in cycle 23, causing the observed lower values of the ISN relative to other, more global indices of solar activity like the UV proxies. These papers report the analysis of the properties of solar wind and interplanetary magnetic field at 1 AU, and their effect in the near-Earth environment causing geomagnetic activity and storminess.
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