Evolution and Signatures of Helical Magnetic Fields Tina Kahniashvili McWilliams Center for Cosmology Carnegie Mellon University & Abastumani Astrophysical Observatory Ilia State University NORDITA June 24 2015
Based On Kahniashvili, Maravin, Lavrelashvili, Kosowsky PRD 2014 Kahniashvili, Tevzadze, Brandenburg, Neronov, PRD 2013 Tevzadze, Kisslinger, Brandenburg, Kahniashvili, ApJ 2013 Ongoing Collaboration (papers in preparation) Axel Brandenburg, Ruth Durrer, Victoria Merten, Alexander Tevzadze, Tanmay Vachaspati, Winston Yin
Earth MF Cosmic Magnetic Fields Interstellar MF Galaxy MF Sun MF
How do we observe cosmic magnetic fields? Electromagnetic waves & Effects induced by magnetic fields
Magnetic Helicity Solar activity: Sunspots Solar flares Coronal mass ejection Solar wind Magnetic helicity reflects mirror symmetry (parity) breaking DIFFICULT TO DETECT cosmic rays: Kahniashvili & Vachaspati 2006 gamma-rays: Tashiro and Vachaspati 2011
Gamma Rays vs Magnetic Helicity Tashiro and Vachaspati 2015 Tashiro, Chen, Francesc, Vachaspati 2014 Chen, Chowdhury, Francesc, Tashiro, Vachaspati 2014
Primordial Magnetic Field Hypothesis F. Hoyle in Proc. La structure et l evolution de l Universe (1958) Inflation Phase transitions Supersymmetry String Cosmology Topological defects Springel Millenium simulations
Inflation Magnetogenesis (Turner & Widrow 1988, Ratra 1992) The correlation length larger than horizon Scale invariant spectrum Well agree with the lower bounds Diffuculties Backreaction Symmetries violation Phase Transitions (Harrisonl 1970, Vachaspati 1991) Bubble collisions first order phase transitions QCDPT EWPT Causal fields Limitation of the correlation length Smoothed and effective fields approaches
Cosmological vs. Astrophysical Magnetogenesis MHD Simulations by Donnert et al. 2008 Ejection Primordial Z=4 Z=4 Z=0 Z=0
Cosmological Magnetic Fields (Obvious Limits) BBN limits: 10% of additional relativistic component 0.1 1 microgauss (comoving value) Grasso and Rubistein 2000 Yamazaki and Kusakabe 2012 Kawasaki and Kusakabe 2012 Faraday Rotation Measure At z~2-3 microgauss Bernet et al. 2009 Kronberg et al. 2008
Magnetized CMB Perturbations Faraday rotation does not depend on magnetic helicity Density perturbations - scalar mode Fast and slow magnetosound waves Adams et al. 1996 Jedamzik, Katalinic, Olinto, 1996 Vorticity perturbations - vector mode Alfven waves Subramanian and Baroow, 1998 Durrer, Kahniashvili, and Yates, 1998 Gravitational waves - tensor Mode Deryagin et al. 1986 Durrer, Ferreira, Kahniashvili 2000
Modeling Helical Magnetic Field Kahniashvili, Kosowsky, Lavrelashvili, Maravin, 2014
Magnetic Helicity Effects on CMB Parity-even fluctuations Temperature - Temperature Temperature - E polarization E-polarization E-polarization B-polarization B-polarization Parity-odd fluctuations Temperature B-polarization E-polarization B-polarization Pogosian, Vachaspati, and Winitski 2000, Caprini, Durrer, and Kahniashvili, 2003, Kahniashvili and Ratra 2005, Kunze 2012, Kahniashvili, et al. 2014, Balardini, Finelli, and Paoletti, 2014
Magnetic Helicity vs. WMAP 9 years data Kahniashvili, Kosowsky, Lavrelashvili, Maravin, 2014
Magnetic Helicity Effects
Magnetic Helicity Limits Kahniashvili, Kosowsky, Lavrelashvili, Maravin, 2014
Phenomenology If the magnetic field has been generated through a causal process in the early universe it s correlation length could not exceed the Hubble horizon at the moment of the generation
MHD Modeling Coupling of the magnetic field with primordial plasma Injection of the magnetic energy at a given scale (phase transition bubble) Brandenburg, Kahniashvili, Tevzadze 2014
Modeling Magnetic Field smoothed vs. effective magnetic field one-scale (delta function) magnetic field Kahniashvili, Tevzadze, Brandenburg, Neronov 2013
Phase Transitions Generated Magnetic Field Phenomenology Non-helical field Helical field Helicity conservation law
Kahniashvili, Tevzadze, Brandenburg, Neronov 2013
Kahniashvili, Tevzadze, Brandenburg, Neronov 2013
Magnetic field from QCD Phase Transitions Tevzadze, Kisslinger, Brandenburg, Kahniashvili 2012 Our analysis show that in the most optimistic scenario the magnetic correlation length in the comoving frame can reach 10 kpc with the amplitude of the effective magnetic field being 0.007 ng. We demonstrate that the considered model of magneto-genesis can provide the seed magnetic field for galaxies and clusters.
Magnetic Helicity Growth Tevzadze, Kisslinger, Brandenburg, Kahniashvili 2012 The correlation length should satisfy: Fractional magnetic helicity grows until it reaches its maximal value
Helical Magnetic Fields Decay Brandenburg, Kahniashvili, Tevzadze 2015 Causal fields correlation length limitation n B =2 or n B =0 Inverse Cascade
Helical Magnetic Fields Decay Vachaspati 2001
Helical Magnetic Field Brandenburg, Kahniashvili, Tevzadze 2015
Inflationary Magnetic Helicity Magnetic field correlation length might be as large as the Hubble horizon today or even larger (infinity) Can we see the imprints of an a-causal field? Kahniashvili, Brandenburg, Durrer, Tevzadze, Yin, 2015
Inflation Generated Helical Magnetic Field Kahniashvili, Brandenburgh, Durrer, Tevzadze, Yin 2015 The absence of inverse cascade for Inflation generated magnetic fields
Helical Magnetic Fields Scaling Laws Brandenburg, Kahniashvili, Tevzadze 2015
Conclusion The lower bound of the extragalactic magnetic field favors a primordial magnetogenesis approach (in particular, helical magnetic fields) The primordial magnetic field might be a plausible explanation for the galaxy magnetic field Cosmological magnetic field order of 0.1 nanogauss can be detectable by the nearest future CMB polarization and LSS measurements On the other hand, if the field is significantly smaller it would satisfy the LOWER limit bound but would not been observable through cosmological observations