caa a22 4500 445345950 CHVBK 20180317142829.0 cr unu---uuuuu 170323e20110501xx s 000 0 eng 10.1007/s11207-011-9718-5 doi (NATIONALLICENCE)springer-10.1007/s11207-011-9718-5 Comparisons of Supergranule Characteristics During theSolar Minima of Cycles 22/23 and 23/24 [Elektronische Daten] [Peter Williams, W. Pesnell] Supergranulation is a component of solar convection that manifests itself on the photosphere as a cellular network of around 35 Mm across, with a turnover lifetime of 1 - 2days. It is strongly linked to the structure of the magnetic field. The horizontal, divergent flows within supergranule cells carry local field lines to the cell boundaries, while the rotational properties of supergranule upflows may contribute to the restoration of the poloidal field as part of the dynamo mechanism, which controls the solar cycle. The solar minimum at the transition from cycle 23 to 24 was notable for its low level of activity and its extended length. It is of interest to study whether the convective phenomena that influence the solar magnetic field during this time differed in character from periods of previous minima. This study investigates three characteristics (velocity components, sizes and lifetimes) of solar supergranulation. Comparisons of these characteristics are made between the minima of cycles 22/23 and 23/24 using MDI Doppler data from 1996 and 2008, respectively. It is found that whereas the lifetimes are equal during both epochs (around 18 h), the sizes are larger in 1996 (35.9 ± 0.3Mm) than in 2008 (35.0 ± 0.3 Mm), while the dominant horizontal velocity flows are weaker (139 ± 1m s−1 in 1996; 141 ± 1m s−1 in 2008). Although numerical differences are seen, they are not conclusive proof of the most recent minimum being inherently unusual. Springer Science+Business Media B.V., 2011 Convection nationallicence Dopplergrams nationallicence Helioseismology nationallicence Photosphere nationallicence SOHO/MDI nationallicence Solar cycle nationallicence Solar minimum nationallicence Solar dynamo nationallicence Supergranulation nationallicence Williams Peter NASA Postdoctoral Program Fellow, Code 671, NASA Goddard Space Flight Center, Greenbelt, MD, USA aut Pesnell W. Code 671, NASA Goddard Space Flight Center, Greenbelt, MD, USA aut Solar Physics Springer Netherlands 270/1(2011-05-01), 125-136 0038-0938 270:1<125 2011 270 11207 https://doi.org/10.1007/s11207-011-9718-5 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/s11207-011-9718-5 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Williams Peter NASA Postdoctoral Program Fellow, Code 671, NASA Goddard Space Flight Center, Greenbelt, MD, USA aut NATIONALLICENCE 700 1- Pesnell W. Code 671, NASA Goddard Space Flight Center, Greenbelt, MD, USA aut NATIONALLICENCE 773 0- Solar Physics Springer Netherlands 270/1(2011-05-01), 125-136 0038-0938 270:1<125 2011 270 11207 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer