Magnetic Fields from Phase Transitions Magnetic Fields from Phase Transitions Tina Kahniashvili...
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Transcript of Magnetic Fields from Phase Transitions Magnetic Fields from Phase Transitions Tina Kahniashvili...
Magnetic Fields from Phase TransitionsMagnetic Fields from Phase Transitions
Tina KahniashviliTina Kahniashvili
McWilliams Center for CosmologyMcWilliams Center for CosmologyCarnegie Mellon UniversityCarnegie Mellon University
&&Abastumani Astrophysical ObservatoryAbastumani Astrophysical Observatory
Ilia State UniversityIlia State University
Tbilisi 2015Tbilisi 2015
Axel Brandenburg, NORDITA, SwedenAxel Brandenburg, NORDITA, SwedenAndrii Neronov, Geneva University, SwitzerlandAndrii Neronov, Geneva University, SwitzerlandBharat Ratra, Kansas State University, USABharat Ratra, Kansas State University, USAAlexander Tevzadze, Tbilisi State University, GeorgiaAlexander Tevzadze, Tbilisi State University, GeorgiaTanmay Vachaspati, Arizona State University, USATanmay Vachaspati, Arizona State University, USA
CollaborationCollaboration
Cosmic Magnetic Fields
Sun MF
Galaxy MF
Earth MF
Interstellar MF
Magnetic HelicityMagnetic Helicity
Magnetic helicity reflects mirror symmetry (parity) breaking
Solar activity: SunspotsSolar flaresCoronal mass ejectionSolar wind
Ultra High Energy Gamma Rays Tests
Gamma Ray map
Blazars
The ultra high energy photons The ultra high energy photons (gamma rays above 0.1 TeV) (gamma rays above 0.1 TeV) interact with the diffuse interact with the diffuse extragalactic background light extragalactic background light
If the magnetic field along the If the magnetic field along the path of the cascade production path of the cascade production is strong enough to bend the pair is strong enough to bend the pair trajectories then the cascade trajectories then the cascade emission appears as an extended emission appears as an extended halo around the initial point halo around the initial point sourcesource
Neronov and Semikoz 2009
ee
Gamma Rays vs Magnetic FieldsGamma Rays vs Magnetic Fields
Tashiro, Chen, Francesc, Vachaspati 2014
Neronov and Vovk 2010
Cosmic Magnetic Fields Some History
E. Fermi “On the origin of the cosmic radiation”,PRD, 75, 1169 (1949)
Known - Unknown
What we know: • The amplitude of the The amplitude of the
magnetic fieldmagnetic field• The spectral shape of The spectral shape of
the magnetic fieldthe magnetic field• The correlation length The correlation length
scalescale
What we do not What we do not know:know:• When and how
magnetic fields were generated
• What were initial conditions
Two Options:
Cosmological and Astrophysical Scenarious
Are the observed magnetic fieldsof a primordial origin
Might serve as seeds Might serve as seeds for the observed fields for the observed fields in galaxies and clustersin galaxies and clusters
Might be responsible for Might be responsible for large scale correlated large scale correlated magnetic fields in the magnetic fields in the voids voids
Might explain some Might explain some cosmological cosmological observations observations
Why Cosmological Magnetic Fields are attractive?
Cosmological vs. Astrophysical Magnetogenesis
MHD Simulations by Donnert et al. 2008
Z=4
Z=0
Z=4
Z=0
Ejection Primordial
Primordial Magnetic Field Hypothesis
F. Hoyle in Proc. F. Hoyle in Proc. ““La structure et La structure et ll ’’evolution de levolution de l’’UniverseUniverse”” (1958) (1958)
InflationInflation Phase transitionsPhase transitions SupersymmetrySupersymmetry String CosmologyString Cosmology Topological defectsTopological defects Phase TransitionsPhase Transitions
• Bubble collisions – first Bubble collisions – first order phase transitionsorder phase transitions
QCDPTQCDPT EWPTEWPT
• Causal fields Causal fields • Limitation of the Limitation of the
correlation lengthcorrelation length Smoothed and effective Smoothed and effective
fields approachesfields approaches
Cosmological Magnetic Fields
BBN limits: 10% of BBN limits: 10% of additional additional relativistic relativistic component component • 0.1 – 1 microGauss 0.1 – 1 microGauss
(comoving value)(comoving value)
Faraday Rotation Faraday Rotation Measure Measure • At z~2-3 At z~2-3
microGauss microGauss • Initial picoGauss?Initial picoGauss?
Phenomenology
If the magnetic field has been generated If the magnetic field has been generated through a causal process in the early through a causal process in the early Universe itUniverse it’’s correlation length could not s correlation length could not exceed the Hubble horizon at the moment exceed the Hubble horizon at the moment of the generation of the generation
Non-helical fieldNon-helical field
Helical fieldHelical field• Helicity conservation law Helicity conservation law
"»M E3=2Ma2
Phase Transitions Generated Magnetic Field Phenomenology
Kahniashvili, Tevzadze, Brandenburg, Neronov 2012
a2
MHD Simulations
Brandenburg, Kahniashvili, Tevzadze, 2014
Modeling Magnetic FieldModeling Magnetic Field
MHD Modeling
Coupling of the magnetic Coupling of the magnetic field with primordial field with primordial plasmaplasma
Injection of the magnetic Injection of the magnetic energy at a given scale energy at a given scale (phase transition bubble)(phase transition bubble)
Kahniashvili, Brandenburg, Ratra, Tevzadze 2010
We recover k4 spectrum at large scales for both – helical and non-helical PMF
Initial Conditions for the decay stage were prepared through forced case
The velocity field at large scales is described by white noise
Magnetic Field Spectrum
Kahniashvili, Tevzadze, Brandenburg, Neronov 2012
ResultsKahniashvili, Tevzadze, Brandenburg, Neronov 2012
Magnetic field from QCD Phase Transitions
Tevzadze, Kisslinger, Brandenburg, Kahniashvili 2012
Magnetic Helicity GrowthTevzadze, Kisslinger, Brandenburg, Kahniashvili 2012
The correlation length should The correlation length should satisfy: satisfy:
Magnetic helicity grows until Magnetic helicity grows until it reaches its maximal valueit reaches its maximal value
High Resolution MHD Simulations
2304230433 meshpoints on meshpoints on 9216 processors9216 processors
Runs A and B with Runs A and B with magnetic Prandtl magnetic Prandtl numbers = 1 and 10numbers = 1 and 10
Intermediate region:Intermediate region:Iroshnikov-KraichnanIroshnikov-Kraichnan
Goldreich-SridharGoldreich-Sridhar
Weak-turbulenceWeak-turbulence Non-helical Non-helical magnetic fieldsmagnetic fields
Brandenburg, Kahniashvili, Tevzadze 2015
Energies CascadesEnergies Cascades
Non-helical Non-helical magnetic fieldsmagnetic fields• Forward cascadeForward cascade
Helical magnetic Helical magnetic fields fields • Inverse cascadeInverse cascade
We have shown the inverse We have shown the inverse transfer for non-helical fieldstransfer for non-helical fields
Inverse Inverse TransferTransfer
Brandenburg, Kahniashvili, Tevzadze 2014
Brandenburg, Kahniashvili, Tevzadze 2014
Brandenburg, Kahniashvili, Tevzadze 2014
Brandenburg, Kahniashvili, Tevzadze 2014
Brandenburg, Kahniashvili, Tevzadze 2014
Nonhelical Magnetic Fields DecayNonhelical Magnetic Fields Decay
Brandenburg, Kahniashvili, Tevzadze 2015
Helical Magnetic Fields DecayHelical Magnetic Fields Decay
Helical Magnetic Fields DecayHelical Magnetic Fields Decay
Brandenburg, Kahniashvili, Tevzadze 2015
Causal fields – correlation length limitationCausal fields – correlation length limitationnnBB=2 or n=2 or nBB=0=0
Inverse CascadeInverse Cascade
Inflation Generated Helical Magnetic FieldInflation Generated Helical Magnetic Field
Kahniashvili, Durrer, Brandenburgh, Tevzadze 2015
The absence of inverse cascade for Inflation generated magnetic fields
Helical Magnetic FieldsHelical Magnetic FieldsScaling LawsScaling Laws
Brandenburg, Kahniashvili, Tevzadze 2015
Helical Magnetic FieldHelical Magnetic Field
Brandenburg, Kahniashvili, Tevzadze 2015
Classes of TurbulenceClasses of TurbulenceBrandenburg & Kahniashvili, 2015
ConclusionConclusion
The lower bound of the extragalactic magnetic field The lower bound of the extragalactic magnetic field favors a primordial (phase transitions) favors a primordial (phase transitions) magnetogenesis approach (in particular, helical magnetogenesis approach (in particular, helical magnetic fields)magnetic fields)
The primordial magnetic field might be a plausible The primordial magnetic field might be a plausible explanation for the galaxy magnetic fieldexplanation for the galaxy magnetic field