1. Cosmological Seed Fields versus Seed Fields Generated in Protogalaxies Dmitry Sokoloff Moscow State University Moscow, Russia in collaboration with D.Moss and V.Semikoz Galactic Magnetism –Perspectives of Observation and Modeling May 16 - 20, 2011 Pushchino, Moscow region, Russia

2. BrBr BTBT Ω Differential rotation BTBT BrBr α Helicity GALACTIC DYNAMO Basic mechanism The excitation mechanism requires a seed magnetic field. Two options: 1.Magnetic field is created in after recombination 2.A cosmological seed field How to decide which option is better?

3. A standard approach: formulate scenarios for both cases, isolate specific features and try to confront them with observations A scenario for magnetic fields created after recombination: talks of Moss, Arshakian, …

4. Seeds in protogalaxies + conventional mean-field dynamo

5. Spatial configurations

6. Cosmological seeds (a standard viewpoint)  Homogeneous magnetic field.  Do not destroy isotropy provided is weak enough (< 10 11 G is more then sufficient).  Still can be strong enough to be a seed

7. Homogeneous relic field+ dynamo: it works unexpectedly bad (simulations of D.Moss)

8. Rotation expels homogeneous field on the remote part of the galaxy (simulations of D.Moss)

9. A cosmological magnetic field is useful to explain the baryon asymmetry Semikoz, Sokoloff, Valle, PRD 2009

10. We can not distinguish between  Small-scale cosmological seed + dynamo  A battery mechanism + small scale dynamo + mean-field dynamo  A large-scale seed + small-scale dynamo + Mean-field dynamo

11. What says cosmology?  1. Everything is known (this statement persists)  Nothing about homogeneous magnetic field  This idea looked strange 10 years ago  It looks attractive today  My interpretation: the topic is completely obscure

12. A possibility to go further  Neronov and D.Semikoz:  Magnetic fields between galactic clusters  (10 -15 G)  Faraday rotation?  Small-scale or large-scale fields?