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