Speaker
Mr
Jiro Shimoda
(Department of Physics and Mathematics, Aoyama-Gakuin University, Sagamihara, Kanagawa 252-5258, Japan)
Description
Using three-dimensional (3D) magnetohydrodynamics (MHD) simulations, we show that the efficiency of cosmic-ray (CR) production at supernova remnants (SNRs) is over-predicted if it could be estimated based on proper motion measurements of H$\alpha$ filaments in combination with shock-jump conditions.
The CR production efficiency at the SNR has been widely discussed, which seems to be ubiquitously so high that back reaction of CRs onto background shock structure is significant. One way to estimate the CR production efficiency is given by a combination of measurements of proper motion of shock front and temperature of shocked gas (e.g., Helder et al. 2009; Morlino et al. 2013, 2014). The downstream temperature has been predicted from measurements of the expansion speed of the SNR using Rankine-Hugoniot relation for plane parallel shock. If actual downstream temperature can be identically measured, then the CR production efficiency is given by downstream thermal missing energy with assuming all of energy loss due to CR acceleration.
Recent multi-dimensional MHD simulations of shock propagation through inhomogeneous diffuse interstellar medium (ISM) with Kolmogorov-like density power spectrum have shown that the shock front is rippled due to the fluctuating inertia of the preshock ISM (Giacalone & Jokipii 2007 for 2D case and Inoue et al. 2013 for 3D case). The kinetic energy of the shock wave is transferred into that of downstream turbulence as well as thermal energy which is related to the shock velocity component normal to the shock surface.
In order to study influence of upstream inhomogeneities, we perform 3D MHD simulation of a shock wave propagating into inhomogeneous medium, and we simulate H$\alpha$ filaments whose proper motion is synthetically measured. Our synthetic observation shows that the CR production efficiency as estimated from a lower downstream plasma temperature, is overestimated by 10-40 % in spite of no CR acceleration, because rippled shock does not immediately dissipate all upstream kinetic energy. Furthermore, our simple analytical argument gives upper and lower bounds of apparent CR production efficiency, which is roughly consistent with our numerical results.
| Registration number following "ICRC2015-I/" | 324 |
|---|---|
| Collaboration | -- not specified -- |
Primary author
Mr
Jiro Shimoda
(Department of Physics and Mathematics, Aoyama-Gakuin University, Sagamihara, Kanagawa 252-5258, Japan)
Co-authors
Prof.
Aya Bamba
(Department of Physics and Mathematics, Aoyama-Gakuin University, Sagamihara, Kanagawa 252-5258, Japan;)
Prof.
Ryo Yamazaki
(Department of Physics and Mathematics, Aoyama-Gakuin University, Sagamihara, Kanagawa 252-5258, Japan)
Dr
Tsuyoshi Inoue
(National Astronomical Observatory of Japan, Mitaka, Tokyo 181-8588, Japan)
Prof.
Vink
(Astronomical Institute Anton Pannekoek/Gravitation and AstroParticle Physics Amsterdam (GRAPPA), University of Amsterdam, Science Park 904, 1098XH Amsterdam, The Netherlands)
Dr
Yutaka Ohira
(Department of Physics and Mathematics, Aoyama-Gakuin University, Sagamihara, Kanagawa 252-5258, Japan)
