Relation between trees of fragmenting granules and supergranulation evolution

Abstract

Context. The determination of the underlying mechanisms of the magnetic elements diffusion over the solar surface is still a challenge. Understanding the formation and evolution of the solar network (NE) is a challenge, because it provides a magnetic flux over the solar surface comparable to the flux of active regions at solar maximum. Aims. We investigate the structure and evolution of interior cells of solar supergranulation. From Hinode observations, we explore the motions on solar surface at high spatial and temporal resolution. We derive the main organization of the flows inside supergranules and their effect on the magnetic elements. Methods. To probe the superganule interior cell, we used the trees of fragmenting granules (TFG) evolution and their relations to horizontal flows. Results. Evolution of TFG and their mutual interactions result in cumulative effects able to build horizontal coherent flows with longer lifetime than granulation (1 to 2 h) over a scale up to 12 . These flows clearly act on the diffusion of the intranetwork (IN) magnetic elements and also on the location and shape of the network. Conclusions. From our analysis during 24 h, TFG appear as one of the major elements of the supergranules which diffuse and advect the magnetic field on the Sun's surface. The strongest supergranules contribute the most to magnetic flux diffusion in the solar photosphere.

Evolution and wave-like properties of the average solar supergranule

“…This ring of higher cork density stands out more clearly than for the observed magnetic field. The observed network field is stronger on the west side of the average supergranule than on the east side, as we detected in our previous study (Langfellner et al 2015a) and as was later also found by Roudier et al (2016). This observation is successfully reproduced by the cork simulation (run #5).…”

“…The occurrence of the 6-hour time lag both in the magnetic field observations and the cork simulation is indicative of the passive nature of the magnetic field in supergranules and confirms the findings of Simon & Weiss (1989), Orozco Suárez et al (2012 and Roudier et al (2016). In our measurements and simulations, there is no sign of magnetic fields shaping the supergranular flows as proposed by Crouch et al (2007) or network field arising from random walks (Thibault et al 2012).…”

Unexpectedly strong effect of supergranulation on the detectability of Earth twins orbiting Sun-like stars with radial velocities

“…At any given time, there are far fewer supergranules than granules, therefore the resulting RV jitter associated with supergranules remains large. The supergranulation scale appears to Send offprint requests to: N. Meunier be strongly related to the large-scale dynamics of granules (e.g., Rieutord et al 2000;Roudier et al 2016). Furthermore, both granulation and supergranulation are expected to exhibit some power at low frequency, as suggested by the shape of the power spectrum proposed by Harvey (1984).…”

Helioseismic Imaging of Supergranulation Throughout the Sun’s Near-Surface Shear Layer

“…The flows in the photosphere can be observed either directly from Dopplergrams (e.g., Hathaway et al 2000), which provide estimates of the line-of-sight velocity component, or by the tracking of features, magnetic or otherwise, as they move across the surface (November & Simon 1988;Roudier et al 1999Roudier et al , 2012DeRosa & Toomre 2004;Meunier et al 2007b). The horizontal size of a supergranule can range between 20 and 60 Mm, with a typical size around 35 Mm (Hathaway et al 2000(Hathaway et al , 2002Del Moro et al 2004;DeRosa & Toomre 2004;Hirzberger et al 2008;Rieutord et al 2008).…”