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| Paper: |
Origin of Magnetic Fields in the Intracluster Medium |
| Volume: |
498, Numerical Modeling of Space Plasma Flows ASTRONUM-2014 |
| Page: |
53 |
| Authors: |
Cho, J. |
| Abstract: |
In this paper, we discuss constraints on the seed magnetic fields by studying their amplification. In the ICM, the value of the viscosity ν and, hence, the hydrodynamic Reynolds number Re (equiv Lv/ν, where L is the driving scale and v is the r.m.s. velocity) is uncertain. If the viscosity is much smaller than the Spitzer viscosity, turbulence dynamo is so efficient that any primordial or astrophysical seed magnetic fields with very weak strengths can easily magnetize the ICM to the present-day strengths. On the other hand, if the viscosity is comparable to the Spitzer value, Re is likely to be smaller than O(102). In this case, turbulence is not fully developed and turbulence dynamo is so inefficient that very weak seed magnetic fields cannot be the origin of the magnetic fields in the ICM. Numerical simulations show that primordial seed fields should be stronger than O(10–11)G, which is very close to the upper limit of O(10–9)G set by the cosmic microwave background observations. Numerical simulations also show that any astrophysical seed magnetic fields stronger than O(10–9)G can safely magnetize the ICM. Therefore, it is less likely that primordial magnetic fields are the direct origin of present-day magnetic fields in the ICM. |
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