Speaker
Igor Rogachevskii
(Ben-Gurion University, Beer Sheva, Israel)
Description
We discuss an analytic theory for a new scaling for the alpha effect in turbulence
with large Reynolds numbers and slow rotation. Using this theory and direct numerical
simulations of slowly rotating stratified turbulence, we show that the alpha effect
responsible for the generation of astrophysical magnetic fields is proportional to
the logarithmic gradient of kinetic energy density rather than that of momentum, as was
previously thought. Thus, the contribution of density stratification is less
important than that of turbulent velocity. The alpha effect and other turbulent
transport coefficients are determined by means of the test-field method. In addition
to forced turbulence, we also investigate supernova-driven turbulence and stellar
convection. In some cases (intermediate rotation rate for forced turbulence,
convection with intermediate temperature stratification, and supernova-driven
turbulence) we find that the contribution of density stratification might be even
less important than suggested by the analytic theory.
Primary authors
Axel Brandenburg
(NORDITA, KTH Royal Institute of Technology and Stockholm University)
Igor Rogachevskii
(Ben-Gurion University, Beer Sheva, Israel)
Maarit J. Mantere
(University of Helsinki)
Nathan J. Kleeorin
(Ben-Gurion University, Beer Sheva, Israel)
Oliver Gressel
(NORDITA, KTH Royal Institute of Technology and Stockholm University)
Petri J. Kaepylae
(University of Helsinki)
