@article{86c297ffdfba404ca6e25e21bbcdec0f,
title = "Vortical Amplification of the Magnetic Field at an Inward Shock of Supernova Remnant Cassiopeia A",
abstract = "We present an interpretation of the time variability of the x-ray flux recently reported from a multiepoch campaign of 15 years of observations of the supernova remnant Cassiopeia A by Chandra. We show for the first time quantitatively that the [4.2-6] keV nonthermal flux increase up to 50% traces the growth of the magnetic field due to a vortical amplification mechanism at a reflection inward shock colliding with inner overdensities. The fast synchrotron cooling as compared with shock-acceleration time scale qualitatively supports the flux decrease.",
author = "F. Fraschetti and S. Katsuda and T. Sato and Jokipii, {J. R.} and J. Giacalone",
note = "Funding Information: We thank the referees for useful feedback. F.F. acknowledges very helpful discussions with J. Raymond. The work of F.F. was supported in part by NASA under Grant No.NNX15AJ71G. F.F. also acknowledges support from Smithsonian Institution Scholarly Studies Grant No.40488100HH00181. This work was partially supported by the Japan Society for the Promotion of Science KAKENHI Grant No.16K17673 and No.17H02864 (S.K.) and partially by Leading Initiative for Excellent Young Researchers, MEXT, Japan. T.S. is supported by the Special Postdoctoral Researchers Program in RIKEN. Publisher Copyright: {\textcopyright} 2018 American Physical Society.",
year = "2018",
month = jun,
day = "21",
doi = "10.1103/PhysRevLett.120.251101",
language = "English (US)",
volume = "120",
journal = "Physical review letters",
issn = "0031-9007",
publisher = "American Physical Society",
number = "25",
}