The authors conclude that the double peaks of one cycle are due to surges of opposite polarity in the polar surface magnetic field observed in the previous cycle. One possible explanation was suggested by Karak et al. It was noted that the two peak phenomena seem to appear in both hemispheres ( Norton & Gallagher 2010 Temmer et al. The period between the two peaks is known as the Gnevyshev gap. Investigating the cycle variation in more detail, it was found that the SSN for many maxima displays a double peak known as the Gnevyshev peak ( Gnevyshev 1977, 1963 Karak et al. The connection between the solar cycle and a variation in the Sun’s magnetic activity was only recognised at the beginning of the 20th century by the American astronomer Hale (see Hathaway 2010, for a review paper). Based on Wolf’s numbering, cycle number one falls into the period 1755–1766. A few years later, Wolf compiled Schwabe’s observations of sunspots with other observations dating back to Galileo’s first recordings. In 1843, the German astronomer Schwabe discovered the 11-year solar cycle. Open Access funding provided by Max Planck Society.
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Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License ( ), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The strongest asymmetries in the unsigned magnetic flux are between the two SSN peaks. The coupling between the hemispheres increases with height. On average, cycle 24 had a higher number of sunspots in the northern hemisphere (NH) but stronger flux in the southern hemisphere (SH) which could more effectively reach the higher layers of the atmosphere. We find a correlation value of 0.8 between the derived magnetic energy from our model and the flare energy index derived from observations. The magnetic flux variation during solar cycle 24 shows a different evolution in the corona than in the photosphere. The major contribution to the total unsigned flux is provided by the flux coming from the magnetic field structures other than sunspots (MSOS) within latitudes of −30° and +30°. From our results, we find that during solar cycle 24, the maximum of the Sun’s dynamics is different than the sunspot number (SSN) maximum peak. To model the magnetic field over cycle 24 we apply the nonlinear force-free field (NLFFF) optimization method to the entire set of the synoptic vector magnetic maps derived from observations made using the Heliospheric and Magnetic Imager (HMI) on board Solar Dynamic Observatory (SDO). We want to investigate whether or not we can obtain better estimates of the magnetic field at Earth using the nonlinear force-free field extrapolation method.
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The aim of this paper is to analyze the temporal variation of the magnetic field and free magnetic energy in the solar corona for solar cycle 24 and the behavior of the magnetic field in the two hemispheres. Until now, there has been no study of the evolution of the coronal magnetic flux in the corona or of the evolution of solar cycle magnetic free energy.Īims. For decades, the cycle variation of the magnetic field in the photosphere has been investigated. The photospheric magnetic field vector is continuously derived from measurements, while reconstruction of the three-dimensional (3D) coronal magnetic field requires modelling with photospheric measurements as a boundary condition. Max-Planck-Institut für Sonnensystemforschung, Justus-von-Liebig-Weg 3, 37077 Göttingen, GermanyĮ-mail: of Astrophysics and Geophysics, University of Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, GermanyĬontext. Astronomical objects: linking to databases.Including author names using non-Roman alphabets.Suggested resources for more tips on language editing in the sciences
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