PhD thesis (2000 - 2003):

Multi-dimensional Radiation Hydrodynamic Simulations of the Non-Magnetic Solar Atmosphere

Fig.1 : The solar chromosphere.
Dissipation of acoustic waves is likely to be an efficient heating mechanism for the lower and middle chromosphere of the quiet Sun. The basic idea is that the motions at the top of the solar convection zone generate acoustic waves which propagate upwards and dissipate in the lower and middle chromosphere, transporting energy into the higher layers. But still the question remains if this amount of energy is sufficient to explain the temperatures derived from observations without invoking magnetic fields.
With a new version of the CO5BOLD radiation hydrodynamics code (developed by B.Freytag and M.Steffen) we are able to compute 2-D and 3-D models extending all the way from the upper convection zone to the middle chromosphere.
Fig.2 : 2-D sim., temperature & velocity field in a vertical x-z-slice 2-D models:
2-D models are not only used for testing the code and numerical parameters but also give a first idea of what is going on in the solar photosphere and chromosphere. Fig.2 shows the temperature in a vertical 2-D slice (xz) in a single time step from a 2-D simulation. You can clearly see hot wave fronts which progate from the top of the convection zone into the chromosphere.

Fig.3 : 3-D sim., temperature in a horizontal x-y-slice at z=1000 
3-D models:
First 3-D simulations reveal a complex, inhomogenous and highly dynamical structure of the lower and middle chromosphere which evolves on rather short timescales. On small spatial dimensions very cool regions are present next to a "network" of hotter matter. This can be seen in the horizontal 2-D slice at a height of z=1000 km, showing the temperature (Fig.3).
The structures are caused by interaction of propagating wave fronts.

(Dimensions: horizontal: 5500 km, vertical: 3300 km, resolution: horizontal: 40 km, vertical: 12 km)
Fig.4 : 3-D temperature cube Dissertation

  • Abstract/Download thesis

  • Images, movies, more information

  • Images

  • Movies

  • Presentations, talks, conference contributions

  • IDL Analysis Software: CAT

  • In close cooperation with

  • Dr. Bernd Freytag (see also for CO5BOLD User Manual)

  • Dr. Matthias Steffen

  • Dr. Hans-Günter Ludwig

  • Prof.Dr. Hartmut Holweger

  • Fig.5 : Granulation (dt=30s)


    Fig.6 : Chromospheric structure at z = 1000 km (dt=10s)

    Chromospheric structure at z = 1000 km


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