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1. INTRODUCTION

Modelling numerically any astrophysical phenomena in general has proven challenging, even taking into consideration some considerable simplifications. However with the improvements in computing from the late nineties onwards reasonable 3-dimensional approximations of galactic features have been developed.

The aim of this section of the chapter is to briefly review progress and to summarise some key findings to date. To impose some finite limit on the scope of the review we restrict our attention to three dimensional models, which include realistic parameters on galactic scales. Please attribute any omissions as a reflection of the ignorance of this author and not on the value of the work.

We present a roughly chronological review of models and their methods, objectives and results. This approach evolves out of the earlier 2D study by Rosen et al. (1993) which investigated the hydrodynamical turbulent structure of the ISM using stellar heating and star formation.

Tomisaka (1998) attempted to model multiple supernovae (SNe) in 3D using a super-bubble approximation of in a stratified ISM with magnetic field. We summarise in Table 1 some key features of the models, which followed subsequently.

Table 1.Recent comprehensive 3D numerical models of the ISM

Korpi (a) Avillez (b) Hanasz (f) Balsara (c) Slyz (d) Piontek (d) Joung (b) Gressel (e)

Domain, kpc 0.5 × 0.5 × 2 1 × 1 × 5-20 0.5 × 1 × 1.2 0.23 1.283 0.23 1 × 1 × 10 0.5 × 0.5 × 4
Res, pc 8 1.25-10 10-100 0.78-1.56 10-20 0.78-1.56 1.95 2-8
Heating SN II+SN I SN II+SN I CR SN SN - SN II+SN I SN II+SN I
Temp, K 102-108 2 × 102-106 2 × 102-106 102-108 102-108 101.5-m104 2 × 102-107 1-107
Phases warm(W)+hot(H) cold(C)+W+H C+W+H W+H C+W+H C+W C+W+H C+W+H
MHD non-ideal hydro & ideal non-ideal ideal hydro ideal hydro non-ideal
Diffusion hyper eta nu chi - eta - - chi - eta nu chi
Gravity stellar+halo stellar+halo stellar+halo - self gravity linear z stellar+halo yes
Rotation differential - rigid & differential - - differential - differential
Cosmic rays - - yes - - - - -
Star forming - - - - yes - - -
Duration 100 Myr 400 Myr 4.8 Gyr - 350 Myr 2 Gyr 80 Myr 1 Gyr

A summary of three dimensional simulated models of galaxy features by: Korpi et al. (1999)(a), de Avillez and Breitschwerdt (2007)(b) from 2000, Hanasz et al. (2009)(c) from 2004, Balsara et al. (2004)(d), Slyz et al. (2005)(e), Piontek and Ostriker (2007)(f) from 2005, Gressel et al. (2008)(f).

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