Major Research Results in Astrophysics at Nordita
Mean-field theory & transport coefficients
To describe the large-scale dynamics of magnetic fields and flows, one can solve the averaged equations.
They are similar to the original equations, but there are additional terms involving ill-known turbulent transport coefficients (mean-field coefficients).
In many cases, those can be determined numerically to high precisions.
This has read to many new insights in the last few years; see the page on:
Test-field method: selected and related references.
Mean-field theory & transport coefficients
It is generally accepted that the solar dynamo operates in the shear layer beneath the convection zone.
This idea faces several difficulties that might be avoided in distributed solar dynamos shaped by near-surface shear.
In that scenario, active regions would form due to large-scale (mean-field) instabilities in the near-surface shear layer.
One candidate has been the negative effective magnetic pressure instability (NEMPI).
Until recently, this possibility remained uncertain, because it was based on results from mean-field calculations using turbulent transport coefficients determined analytically or through direct numerical simulations (DNS).
A breakthrough had been achieved through the direct detection of this instability in simulations.
For details; see the page on the:
Detection of negative effective magnetic pressure instability in simulations.
Other research highlights
Some of the research output is being referenced over and over again.
Examples of this are being accumulated on a separate page on:
Research highlights and influential papers.
Reference data & code input
Much of the research involves numerical simulations and those data can be useful to others, either for comparison or as reference.
Particularly important are also the input files to numerical simulations, which makes the reproduction of the results very straightforward.
Examples of data and input files can be found on a separate page on:
Run directories related to some past research projects.
Axel Brandenburg
$Date: 2023/01/22 11:55:50 $, $Author: brandenb $, $Revision: 1.1 $