E-Print Archive

There are 4499 abstracts currently viewable.


Advanced Search
Main Page Add New E-Print Submitter
News Help/FAQ About Preferences
Manage Key Phrase
Near-polytropic stellar simulations with a radiative surface View all abstracts by submitter

Axel Brandenburg   Submitted: 2014-12-13 13:52

Studies of solar and stellar convection often employ simple polytropic setups using the diffusion approximation instead of solving the proper radiative transfer equation. This allows one to control separately the polytropic index of the hydrostatic reference solution, the temperature contrast between top and bottom, and the Rayleigh and Peclet numbers. We extend such studies by including radiative transfer in the gray approximation using a Kramers-like opacity with freely adjustable coefficients. We study the properties of such models and compare them with results from the diffusion approximation. We use the Pencil Code, which is a high-order finite difference code where radiation is treated using the method of long characteristics. The source function is given by the Planck function. The opacity is written as kappa=kappa_0 rho^a T^b, where b is varied from -3.5 to +5, and kappa_0 is varied by four orders of magnitude. We consider sets of one dimensional models and perform a comparison with the diffusion approximation. Except for the case where b=5, we find one-dimensional hydrostatic equilibria with a nearly polytropic stratification and a polytropic index close to n=(3-b)/(1+a), covering both convectively stable (n>3/2) and unstable (n<3/2) cases. For b=3 and a=-1, the value of n is undefined a priori and the actual value of n depends then on the depth of the domain. For large values of \kappa_0, the thermal adjustment time becomes long, the Peclet and Rayleigh numbers become large, and the temperature contrast increases and is thus no longer an independent input parameter, unless the Stefan Boltzmann constant is considered adjustable. Proper radiative transfer with Kramers-like opacities provides a useful tool for studying stratified layers with a radiative surface in ways that are more physical than what is possible with polytropic models using the diffusion approximation.

Authors: Barekat, A., & Brandenburg, A.
Projects: None

Publication Status: Astron. Astrophys. 571, A68 (2014)
Last Modified: 2014-12-15 14:00
Go to main E-Print page  Chromospheric Rapid Blueshifted Excursions Observed with IBIS and Their Association with Photospheric Magnetic Field Evolution    Edit Entry  Download Preprint  Submitter's Homepage Delete Entry 

Go to main E-Print pageGo to main E-Print page.
Previous AbstractPrevious Abstract.
Next AbstractNext Abstract.
Download PreprintDownload Preprint.
Submitter's HomepageSubmitters Homepage.
Edit EntryEdit Entry.
View All Abstracts By SubmitterView all abstracts by submitter.
Delete AbstractDelete abstract.

Latest Entries
Small-scale solar jet formation and their associated waves and instabilities
Invited Review: Short-term Variability with the Observations from the Helioseismic and Magnetic Imager (HMI) Onboard the Solar Dynamics Observatory (SDO): Insights into Flare Magnetism
A first look at the submillimeter Sun with ALMA
Data-driven modeling of solar coronal magnetic field evolution and eruptions
Properties and Energetics of Magnetic Reconnection: I. Evolution of Flare Ribbons
A new look at the frequency-dependent damping of slow-mode waves in the solar corona
What determines active region coronal plasma composition?
Characteristics and evolution of sheath and leading edge structures of interplanetary coronal mass ejections in the inner heliosphere based on Helios and Parker Solar Probe observations
Slow magnetoacoustic oscillations in stellar coronal loops
Kink Oscillation of a Flux Rope During a Failed Solar Eruption
A publicly available multi-observatory data set of an enhanced network patch from the Photosphere
Type IV Radio Bursts and Associated Active Regions in the Sunspot Cycle 24
Theory of Fluid Instabilities in Partially Ionized Plasmas: An Overview
Quasiperiodic Energy Release and Jets at the Base of Solar Coronal Plumes
The Coupling of an EUV Coronal Wave and Ion Acceleration in a Fermi-LAT Behind-the-Limb Solar Flare
Reconciling Power Law Slopes in Solar Flare and Nanoflare Size Distributions
A Model of Homologous Confined and Ejective Eruptions Involving Kink Instability and Flux Cancellation
Detection of stellar-like abundance anomalies in the slow solar wind
Magnetosheath jet occurrence rate in relation to CMEs and SIRs
Microwave Perspective on Magnetic Breakout Eruption

Related Pages
MSU Solar Physics.
Max Millennium Science Mail Archive.
Max Millennium Message of the Day Mail Archive.
Max Millennium Flare Catalog

Archive Maintainer
Alisdair Davey

© 2000-2020 Solar Physics Group - Montana State University