Don Ellison, NCSU, Future HE-Observatory, SNR/CR Working Group Magnetic Field Amplification in Astrophysical Shocks 1)There is convincing evidence for large B-fields at outer shocks in supernova remnants: B shock ~  G >> B ISM (e.g., Cowsik & Sarkar 80; Berezhko, Voelk & co-workers; Vink & Laming) a)Broad-band fits: radio/TeV ratio gives limits on B-field b)Sharp X-ray edges: large B  short electron lifetimes  narrow structures 2)Most likely, B-field amplification is an intrinsic part of efficient shock acceleration, i.e. nonlinear diffusive shock acceleration (DSA) 3)Simple basic idea: Cosmic ray streaming instability creates strong turbulence in nonlinear shocks and produces  B/B >> 1. BUT, plasma physics hard (impossible?) when  B/B >> 1. First attempts with simplified approaches: Bell & Lucek 01,04; Amato & Blasi 06; Blasi, Amato & Caprioli 06; Vladimirov, Ellison & Bykov 06; Blandford – Bootstrap model 4)B-fields set maximum CR energy, determine synchrotron emission, and produce losses for relativistic electrons  understanding B-amplification essential for modeling broad-band emission from sources  will determine IC/p-p emission ratio at GeV-TeV energies If physics of particle acceleration in SNRs is typical, unexpectedly large magnetic fields, generated by shocks, may exist in radio jets, shocks in galaxy clusters, GRBs, etc.

Don Ellison, NCSU, Future HE-Observatory, SNR/CR Working Group Initial models (with gross approximations) show that you can start with B ISM  3  G and end up with B  500  G at the shock, but critical unresolved issues remain: ► Large increases in B can occur, but maximum particle energy does not increase in proportion to B. Maximum proton energy set by weak B in far upstream precursor ► Shape of electron and proton spectra near max. energy critical for modeling X-ray synch and GeV-TeV observations. BUT, shape depends on details of amplification ► How does B-amp influence injection of electrons vs. protons? (no clue!) ► At present, PIC simulations are not “large” enough to model B-amp on scales relevant for SNR shocks ► Theories must have observations for constraints and guidance ► TeV observations particularly important because B-amp increases maximum proton energy

Don Ellison, NCSU HESS GLAST TeV Large magnetic fields : Large B  higher energy pion-decay gamma-rays. Observation of turnover essential input for theories. Large B  lower maximum energy for electrons (synch losses) IC emission in GLAST range modified by strong losses in evolving SNR Example with preliminary results for one particular set of input parameters: adapted from Ellison, Patnaude, Slane, Blasi & Gabici et al (Note: B-amp. NOT calculated in these models) TeV Example: GeV-TeV Observations (IC/p-p) ratio Inverse-Compton (IC) and pion-decay emission from SNR with large shocked B-fields B sk ~ 20  G B sk ~ 300  G Only difference in models is assumed B-field GeV IC Broad-band observations to PeV energies essential for understanding B-field amplification