The internal thermal structure of the Sun consists of ‘granules’ – the localized convective motions distribute and transport the heat (and matter) inside our home star until the energy generated by the nuclear reactions inside the star’s core reaches the surface. Scientists claim they have found the evidence for the giant cellular flows that encompass smaller convective regions and persist for months before they vanish.

According to a paper, which was published at arXiv.org on Jan.2, there are two key forms of solar cellular structures, which are known to astrophysicists as granules and supergranules. These structures are classified by their size: the granules may reach ~1,000 km across, while the supergranules can be as large as 30,000 km in diameter. The existence of larger convectional structures has been proposed several decades ago, and now the authors of the current study David H. Hathaway, Lisa Upton and Owen Colegrove claim that they have observed such giant convection cells by tracking the motions of individual supergranules.

To prove their theory, the authors measured the motions of the supergranules from the images captured by Helioseismic and Magnetic Imager (MHI) on the NASA’s Solar Dynamics Observatory (SDO) and analyzed the paths they make during their voyage throughout the Sun.

Computer simulation of convection zone velocity distributions revealed that there are relations between distinct groups of supergranules. The overall shape of these grouped structures appears slightly elongated due to the heavy influence of Coriolis force caused by the Sun’s rotation. The same structures at lower latitudes are not well known and shorter lived compared to those observed at higher latitudes of the Sun. Despite the lesser manifestation, the low-latitude structures seem to be aligned from north to south; this finding is also supported by the similar structure of the supergranulation pattern observed during earlier studies.

The team admits that conclusions regarding the origin of this discovery are still incomplete, however, they are positive that the statistical correlations between the observed solar matter flows points to the presence of the giant convection cells existing in the Sun. Preliminary evaluation and the earlier predictions suggest these giant convection flows could span 200,000-km-deep solar regions with active lifetimes of approximately from one to three months or even more.

By Alius Noreika, source: www.technology.org