SPACE AND COSMIC RAY PHYSICS SEMINAR

University of Maryland
Atlantic Building, Room 2400
4:30 PM Monday, May 6, 2013
Coffee, Tea & Snacks 4:15-4:30 PM

Dr. Peter Biermann
Max Planck Institute for Radioastronomy, Bonn, Germany
GALACTIC WIND HAZE

We present a comprehensive interpretation of the Galactic wind haze at radio and gamma-ray wavelengths: We propose that the solution is an unsteady Galactic wind, driven by cosmic rays and massive star activity. With this ansatz we discuss i) the Planck and WMAP haze, ii) the Fermi haze and the Fermi bubble, iii) the cosmic ray electron and positron data, iv) the 511 keV emission line, v) the 130 GeV feature, vi) the magnetic fields in the wind, vii) the radial profile, viii) the energetics, and ix) the non-stationarity and spectrum of magnetic irregularities in the wind. The three key elements in the proposed solution are:
a) a much thinner cosmic ray disk in the central part of our Galaxy, where at the transition point between diffusive and convective transport the transport time scale is shorter than the loss time scale for high energy electrons;
b) the polar-cap component of cosmic ray particles accelerated by shocks racing through the magnetic wind of very massive stars, which gives an E−2 spectrum at source, a E−7/3 in the diffusion limit, and a E−3 spectrum in the loss limit; and
c) reacceleration by weak shocks running through the Galactic wind, which then give a magnetic irregularity spectrum of k −2. This ansatz also explains the overall halo radio spectrum determined by Planck for the outer Galaxy, of about ν −1. A further consequence derives from the fact, that the bend in the CR electron/positron spectrum near TeV is at the same energy throughout the inner Galaxy, in the halo and also near our location in the Galaxy. This is possible if the electrons/positrons are all secondary from Helium nuclei collisions with matter. Then the cosmic ray knee of normal cosmic rays turns into a corresponding bend in the secondary cosmic ray electron/positron spectrum. This proposal then at once explains the spectrum, the cutoff spectrum, and the constancy of the energy of the bend everywhere in the Galaxy. This solution requires that the cosmic ray knee energy itself is the same for all massive stars contributing, a property which suggests that the knee energy is derived from a universal magnetic field property of massive rotating stars late in the lifetime (see Biermann 1993). This in turn supports the mechanism proposed by Bisnovatyi-Kogan (1970) to explode massive star supernovae, the magnetorotational mechanism (see Moiseenko et al. 2005). This mechanism would allow to explode very massive stars as Supernovae, Jet-Supernovae or Gamma Ray Bursts, all with the same mechanism, while the observed appearance just depends on the thickness of the outer mass shell of the star at the time of explosion, and the aspect angle towards the observer.


Sponsored by: Department of Physics and the Institute for Physical Science and Technology, University of Maryland. For information call Catha Stewart at (301) 405-4811 or go to the UMD Space Physics group seminar web site.

There is free parking after 4:00 PM in lot B (the big parking garage across the street from the ATL building). There are a limited number of spaces in lot Q next to the new ATL wing with free parking after 4PM even when there is a basketball game on campus.