The Origin of Magnetic Fields in Galaxies TeX Export

@article{deSouza:2009na, abstract = {Microgauss magnetic fields are observed in all galaxies at low and high redshifts. The origin of these intense magnetic fields is a challenging question in astrophysics. We showed that the natural plasma fluctuations in the primordial universe, produces random dipole magnetic fields of comoving size \$\sim 1\$ pc and intensity \$\sim 0.1 \mu G\$ at a redshift \emph{z} \$\sim\$ 10. The theory predicts an average magnetic field \$\sim 0.003 \~{} nG\$ over a 2 kpc region at \emph{z} \$\sim 10\$. We assume this seed field and examine its amplification by a turbulent dynamo in a protogalaxy. Whereas the standard \$\alpha-\Omega\$ dynamo for a typical disk galaxy creates only a 2 e-fold amplification of the field in \$\sim 10^{9}\$ years, the turbulent dynamo has a much shorter amplification time. Starting with the average seed magnetic field of \$B\sim 0.003 nG\$ over \$\sim 2\$ kpc at \emph{z} = 10, we find that in \$10^{9}\$ years, \$B\$ is amplified to \$\sim 1 nG\$. This corresponds to a \$\sim 6\$ e-fold amplification of the field. In the process of collapsing to form galaxies at \$\emph{z}\sim10\$, the plasma density rises by a factor of \$\sim 200\$ and the magnetic fields, by a factor of \$\sim 34\$. Thus, \$0.03 \mu G\$ fields over 0.34 kpc regions in galaxies are predicted. If the dipole magnetic fields predicted by the Fluctuation-Dissipation-Theorem are not completely random, microgauss fields over regions \$\gtrsim 0.34\$ kpc are easily obtained. The model is thus a strong candidate for resolving the problem of the origin of magnetic fields in \$\lesssim 10^{9}\$ years in high redshift galaxies.}, archivePrefix = {arXiv}, author = {Rafael da Silva de Souza and Opher, Reuven}, citeulike-article-id = {6031537}, citeulike-linkout-0 = {http://arxiv.org/abs/0910.5248}, citeulike-linkout-1 = {http://arxiv.org/pdf/0910.5248}, day = {27}, eprint = {0910.5248}, keywords = {astrophysics, dynamo, magnetic-fields}, month = {Oct}, posted-at = {2009-10-30 08:51:34}, priority = {2}, title = {The Origin of Magnetic Fields in Galaxies}, url = {http://arxiv.org/abs/0910.5248}, year = {2009} }

TY - JOUR ID - deSouza:2009na L3 - citeulike-article-id:6031537 N2 - Microgauss magnetic fields are observed in all galaxies at low and high redshifts. The origin of these intense magnetic fields is a challenging question in astrophysics. We showed that the natural plasma fluctuations in the primordial universe, produces random dipole magnetic fields of comoving size $\sim 1$ pc and intensity $\sim 0.1 \mu G$ at a redshift \emph{z} $\sim$ 10. The theory predicts an average magnetic field $\sim 0.003 ~ nG$ over a 2 kpc region at \emph{z} $\sim 10$. We assume this seed field and examine its amplification by a turbulent dynamo in a protogalaxy. Whereas the standard $\alpha-\Omega$ dynamo for a typical disk galaxy creates only a 2 e-fold amplification of the field in $\sim 10^{9}$ years, the turbulent dynamo has a much shorter amplification time. Starting with the average seed magnetic field of $B\sim 0.003 nG$ over $\sim 2$ kpc at \emph{z} = 10, we find that in $10^{9}$ years, $B$ is amplified to $\sim 1 nG$. This corresponds to a $\sim 6$ e-fold amplification of the field. In the process of collapsing to form galaxies at $\emph{z}\sim10$, the plasma density rises by a factor of $\sim 200$ and the magnetic fields, by a factor of $\sim 34$. Thus, $0.03 \mu G$ fields over 0.34 kpc regions in galaxies are predicted. If the dipole magnetic fields predicted by the Fluctuation-Dissipation-Theorem are not completely random, microgauss fields over regions $\gtrsim 0.34$ kpc are easily obtained. The model is thus a strong candidate for resolving the problem of the origin of magnetic fields in $\lesssim 10^{9}$ years in high redshift galaxies. TI - The Origin of Magnetic Fields in Galaxies KW - astrophysics KW - dynamo KW - magnetic-fields AU - Rafael da Silva de Souza AU - Opher, Reuven PY - 2009/Oct/27/ UR - http://arxiv.org/abs/0910.5248 ER -