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Pervasive Field Model

Evidence For A Weak Galactic Center Magnetic Field : T. N. LaRosa (Kennesaw St. Univ.) Crystal Brogan (U. of Hawaii) S.N. Shore (U. of Pisa) T. J. W. Lazio, N. Kassim, M. Nord, (NRL). Pervasive Field Model.

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Pervasive Field Model

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  1. Evidence For A Weak Galactic Center Magnetic Field: T. N. LaRosa (Kennesaw St. Univ.)Crystal Brogan (U. of Hawaii) S.N. Shore (U. of Pisa) T. J. W. Lazio, N. Kassim, M. Nord, (NRL)

  2. Pervasive Field Model • NTF magnetic fields of order 1 mG. Magnetic pressure exceeds the thermal pressure, therefore unless confined the filaments would expand on a timescale short compared to their synchrotron lifetime • NTFs are the illuminated flux tubes of a space-filling, globally organized field. A local interaction (magnetic reconnection) is responsible for the electron acceleration • Large magnetic field energy required – 5 x 1054 ergs, equipartition with local ISM turbulence

  3. Minimum Energy Analysis 327/74 MHz spectral index  =0.7 Luminosity  2.5 x 1036 ergs/s Minimum energy  1 4/7 x 1052 ergs Magnetic field  6 (/f)-2/7G Particle energy density 1.3 f-2/7 eV/cm3 ( is the proton to electron energy ratio, f is the filling factor)

  4. Energy Requirements • 1 SNe every 3 x 105 years • The higher star formation rate in the GC (Figer et al 2004) gives an expected SN rate in the inner 50 pc of 1 SNe every 105 years • Consistent with the energy requirements to account for the soft X-ray emission (Muno et al 2004)

  5. Discussion: • A strong 1 mG field with a solar value for the cosmic ray energy density (1.8 eV/cm3) would generate a 327 MHz emissivity of 41 KJy/beam - orders of magnitude more emission than the observed, 229 Jy/beam • Radiative lifetime of an electron emitting at 74 MHz in a 1 mG is 105 years. Requires that the source by resupplied at an implausibly high rate

  6. Conclusions • The derived particle energy density is consistent with the EGRET data • Evidence from H3+, Li and B, and cloud heating all suggest a GC cosmic ray energy comparable with the solar values • A strong 1 mG space filling global magnetic field is not consistent with the radio emission

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