Particle acceleration & magnetic field amplification in ...€¦ · Hadrons Tycho. 11/6/12 MODE meeting Montpellier 5-7 November 2012 7 ... in spatial/energy scales. •Two approaches:

Particle acceleration & magneticfield amplification in supernova

remnants

A.Marcowith (L.U.P.M.)

11/6/12 MODE meeting Montpellier 5-7November 2012

2

Outlines

• Observations: Links between particle accelerationand magnetic field amplification: isolated youngsupernova remnants.

• Theory: From modeling to first principles.• Some other special cases.• Conclusions.


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I/ Observations


4

X-ray FilamentsCasA Tycho

SN1006 Kepler

RCW86

Blue: synchrotron non-thermal X-rays @ keV(Vink’08)

Filament size %Rsh


5

X-ray filaments

• Filament size => shockmagnetic field– Lower limit– (mostly) downstream MF.– Multi TeV electrons

ΔRX=Max (ΔRdiff, ΔRadv)

Parizot+06


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SNR at Gamma-rays

Uchiyama+11, Morlino & Caprioli’12

s=2.2 may be up to VHE

ECR consistent with 10% ofESN for next=0.3 cm-3

Fermi data more consistent withhadronic model = multi-TeVHadrons

Tycho


7

II/ Modeling


8

The (30 years) theoreticalproblem

Fluid thermal plasma +

background magnetic field +

radiation + microinstabilities

Shock structure: Temperature, MF

Obliquity, radiation precursor

+ Energetic particlesDiffusive shock

Acceleration (DSA)

Krymsky’77, Bell’78,Blandford & Ostriker’78

Zeldovichbook


9

Principles of DSA

Bturb

BISM

! " #

$ % &

2

= Ma

2 ush

c

! "

$ %

PCR

'ush

2

! " #

$ % &

= 500( )2(1/50)(1/5) = 1000

precursor

r=4 strong shock


10








Acceleration (DSA)

Drury & Völk’ 81

CR precursor and mediation


11

Non-linear DSA

CR Escape flux

= More compression


12








Acceleration (DSA)+ MF amplification

CR precursor and Mediation

MF “precursor”: pre-heating

Bykov+12Caprioli+09


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MFA feed-back

• MFA: reduce plasma compressibility andcompression ratio– Increase Va hence reduce U1=> U1-Va– Energy imparted into turbulence and heating

Caprioli+09

Va (B0): no MFATrans: Ua in the kineticCR Eq.Trans+Ampl: Ua in thekinetic CR Eq.+growthrate


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Modeling: an updated view

• Young (isolated SNRs): Magnetic field amplification +energetic particles– [Ekin:ECR:Em]=[1:0.1:(>)0.01]– CRs:

• Modify the shock structure, increase compression (pressure,escape energy flux)

• Non-liear effects: soft (s=2.5) => hard (s=1.5) spectrum

– MFA:• Pump energy to CRs, increases Va• Reduce non-linear effects s=2.3-2.4• Help in confinement => higher CR energies (see next)


15

New diagnostic? X-ray stripes

Eriksen+11


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X-ray stripes: coherent turbulentpatterns

Bykov+11


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III/ Theory


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Status

• No model able to describe 9 orders of magnitudein spatial/energy scales.

• Two approaches:– Simulations and analytical work from approximate

models (see previous slides)– Analytical & numerical work from first principles or

at different level of approximation.


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Magnetic field amplification atshocks

• Analytical approach (limited to linear analysis)– Source of free energy: Shock kinetic energy

Shock kinetic energy ρvsh2

Cosmic RaysρCR,JCRF(p,x,θ)

Magnetic instabilities

• Streaming instabilities (non-resonant, resonant) (CR current) (Bell’78’04,Pelletier+06, Amato &Blasi’09)

• Firehose/Mirror instabilities (anisotropy in CR pressure) (Bykov+11)• Acoustic instability (spatial CR pressure gradient) (Drury & Falle’86) or related

(Beresnyak+09)• Instabilities independent of CRs (Giacalone & Jokipii’07)


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Streaming instability

Bell’04

resonant Non resonant


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Streaming Instability

JCR

F(x,p)

Vch

precursor

MIS

Non resonant

Resonant


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MF amplification• Non-resonant instability:

– Fastest especially at high shockvelocity (Pelletier, Lemoine, AM’06)

– Expected MF amplitude at the shockfront (B ∝ Vsh3/2)

– But:• only small scales : Issue for

confinement of high-energyparticles (but see Bykov+11)

Bturb

BISM

! " #

$ % &

2

= Ma

2 ush

c

! "

$ %

PCR

'ush

2

! " #

$ % &

= 500( )2(1/50)(1/5) = 1000

Vink’09


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Different numerical approaches

Particle‐In‐Cell (PIC): all species kinetic: Small scales l ~ rthi :instabilities that mediate the 

shock formation ‐ injection problem. (Riquelme & Spitkovsky’09’10)

“Hybrid” (electron as fluid, ions as kinetic): Dominant instability for particle acceleration ‐ 

back reaction over the CR current (Gargaté & Spitkovsky’12)

Kinetic‐magneto‐hydrodynamic (MHD) (electron+ion fluid, energetic particles as kinetic): Large scales l~rCR ‐ long term 

evolution of the dominant Instability ‐ CR transport and escape. (Reville+08, AM & Casse’10, Reville & Bell’12)

Microscopic M

esoscopic Macroscopic

Numerical simulations => non-linear stages


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Numerical highlightsPIC Riquelme & Spitkovsky’09 Di‐Hybrid Gargaté & Spitkovsky’12

Non-resonant instability saturation non-linear effect due to feed-back over CR current

Non-thermal acceleration bythe Fermi process for differentAlfvén Mach numbers (// shock)

Solid blue: 3D simulations transverse MFDotted: longitudinal MF


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Numerical highlightsPIC Riquelme & Spitkovsky’09 Di‐Hybrid Gargaté & Spitkovsky’12

Non-resonant instability saturation non-linear effect due to feed-backover CR current rL~Lturb

Non-thermal acceleration bythe Fermi process for differentAlfvén Mach numbers (// shock)

Solid blue: 3D simulations transverse MFDotted: longitudinal MF


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IV/ Other special cases

1. Very young SNRs2. SNR in interaction with molecular clouds3. Multiple shocks in various contexts (massive star

clusters, molecular clouds)


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Very young SNR: SN 1993J case

• Acceleration & instability amplification timescales decrease:– Fast shocks (NB relativistic shocks issues with precursor size)– Higher CR densities

• Points towards very young (year) SNR propagating into dense stellar windslike SN 1993J (Type IIb).

• Radio observations– MF strengths ~ a few Gauss (Fransson+06) >> equipartition wind fields

(mG)• CR (e/p) acceleration model coupled with MF dynamics (Tatischeff’09,

Renaud+in prep) + MFA:

! max"1

=50#

PeV

$0.03u73ncm

years

NR inst. Young SNR NR inst. 93J

!max

"1=

1000#PeV

$0.03u93J

3n93J

seconds


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SNR / cloudinteraction

• MF Amplification due to turbulentmedium (shock rippling) that isshocked (Giacalone & Jokipii’07)– B grows due to velocity shear

along mean B– B => few hundred microG

• Network secondary shocks– M < 2 (M=√5 in the dense cloud

limit)– Behind the blast wave =>

propagate in an ionized medium.– Can re-accelerate CRs

Ino

ue+0

9+1

0

2D MHD simulations (perpstrong shock)


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V/ Conclusions

• Observations:– Evidences particle acceleration and magnetic field amplification are

connected.– Highest energies are found in relation with MFA.

• Modeling:– Fluid-CR-MF have to be considered as a whole.– MFA contributes to reduce compression and produce softer CR spectra.– Turbulence diagnostics: polarization.– HE gamma-rays from very young objects/SNR-cloud interaction.

• Theory:– Simulations at multi-scales with different adapted strategies.– PIC/Hybrid: MF effectively amplified and DSA regime recovered.

Documents

Particle acceleration & magnetic field amplification in ...€¦ · Hadrons Tycho. 11/6/12 MODE meeting Montpellier 5-7 November 2012 7 ... in spatial/energy scales. •Two approaches: