Signs of deep mixing in starspot variability

¹ Space Research Institute (IWF), Austrian Academy of Sciences, Schmiedlstrasse 6, 8042 Graz, Austria
e-mail: oleksiy.arkhypov@oeaw.ac.at
² Skobeltsyn Institute of Nuclear Physics, Moscow State University, 119992 Moscow, Russia
³ Institute for Astronomy (IfA), University of Vienna, Türkenschanzstrasse 17, 1180 Vienna, Austria
e-mail: manuel.guedel@univie.ac.at
⁴ Karl-Franzens-Universität Graz (KFUG), 8010 Vienna, Austria

Received: 10 November 2014
Accepted: 14 January 2015

Abstract

The current knowledge on plasma mixing in stellar interiors is based on theoretical modeling, which calibrates the empirical relations between the mixing and observable stellar parameters. Hence, a model-independent method of studying the mixing process is a desirable, but yet unfounded approach. Here, using a new spectral-correlation method, verified for the Sun, we show that deep mixing is manifested in stellar photometric light curves. We measure the timescales of the stochastic change in the spectral power of rotational variability of hundreds of main-sequence stars from the Kepler mission archive. The discovered proportionality of these timescales to the turnover time of the standard mixing length theory, their consistency with Kolmogorov’s theory of turbulence, and the relation with stellar activity provide a new approach to the probing of stellar interiors. This opens a broad perspective for experimental studies of deep mixing and magnetic dynamos in stars.