Astronomy and Astrophysics – Astrophysics
Scientific paper
May 2001
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2001a%26a...370..533s&link_type=abstract
Astronomy and Astrophysics, v.370, p.533-540 (2001)
Astronomy and Astrophysics
Astrophysics
1
Magnetic Fields, Turbulence, Stars: Magnetic Fields, Sun: Magnetic Fields
Scientific paper
We qualitatively analyze the equations of the magnetohydrodynamics for various quadratic fluctuations of the magnetic field and the vector potential. For the stationary inhomogeneous state, we have established the exact integral relations between the magnetic field fluctuations b(r,t) and the mean magnetic field B0(r,t). We estimate alpha ~ (eta +beta )B00* (nabla x B0)/B02, where eta and beta are the Johmic (molecular) and turbulent diffusivities, respectively. The alpha - coefficient describes the enhancement of the mean magnetic field. We found that the exact Seehafer formula B0* < ux b> = -eta < b * (nabla x b)> is also valid for the locally stationary and homogeneous evolution of magnetic fluctuations (u is the Euler turbulent velocity). It is shown that the usual alpha -coefficient, more correctly the term alpha B0* (nabla x B0), presents with opposite signs in equations for B02 and < b2>, i.e. the rate of increase of the total magnetic energy does not depend directly on this coefficient. We show that at the moment t_b of the maximum of magnetic fluctuations, < b2> ~ B_02. The same also holds for the locally homogeneous and stationary regime if the spectrum of the turbulence has a slow decrease in the inertial region of wave numbers. The detailed analysis of two-dimensional turbulence has shown that the Zeldovich estimate < b2> ~ beta /eta B_02 is valid only at the maximum of the vector potential fluctuations. This estimate is corrected such that at t_b it also gives < b2> ~ B_02. We also give the approximate expression for the alpha -coefficient which takes into account the back reaction of the mean magnetic field onto the turbulence itself.
No associations
LandOfFree
The estimations of magnetic field fluctuations in turbulent atmospheres does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with The estimations of magnetic field fluctuations in turbulent atmospheres, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and The estimations of magnetic field fluctuations in turbulent atmospheres will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1266273