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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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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
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
minimum energy analysis
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)

energy requirements
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)
  • 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
  • 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