Division of Theoretical Astronomy, National Astronomical Observatory of Japan

Research Highlights

Stochastic electron acceleration during spontaneous turbulent reconnection in a strong shock wave

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Explosive phenomena such as supernova remnant shocks and solar flares have demonstrated evidence for the production of relativistic particles. Interest has therefore been renewed in collisionless shock waves and magnetic reconnection as a means to achieve such energies. Although ions can be energized during such phenomena, the relativistic energy of the electrons remains a puzzle for theory. We present supercomputer simulations showing that efficient electron energization can occur during turbulent magnetic reconnection arising from a strong collisionless shock. Upstream electrons undergo first-order Fermi acceleration by colliding with reconnection jets and magnetic islands, giving rise to a nonthermal relativistic population downstream. These results shed new light on magnetic reconnection as an agent of energy dissipation and particle acceleration in strong shock waves.
(2015/02/27)
“Stochastic electron acceleration during spontaneous turbulent reconnection in a strong shock wave” by Y. Matsumoto, T. Amano, T. N. Kato, M. Hoshino, 2015, Science, Vol. 347 no. 6225 pp. 974-978
Tsunehiko Kato [personal website]

Web Release

The world’s most extensive simulation of the Milky Way galaxy

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An international research team including Jeroen Bédorf, Simon Portegies Zwart (Leiden University, the Netherlands), Michiko Fujii (NAOJ, Japan) and others developed a new application “Bonsai” for numerical simulations of galaxies. Using this, they performed the world’s most extensive simulation of the Milky Way galaxy using 18600 GPUs. Around 240 billion particles are used in this simulation, and it provides detailed enough data for direct comparison to the observed stars in the Milky Way. In addition, the simulation achieved a computational speed of 24.77 Pflops (Peta Floating-point Operations Per Second), which is currently the world record. Because of these results, the research team is one of five finalists nominated for this year’s Gordon Bell Prize.

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(2014/12/16)
“24.77 Pflops on a Gravitational Tree-Code to Simulate the Milky Way Galaxy with 18600 GPUs” by Jeroen Bédorf, Evghenii Gaburov, Michiko S. Fujii, Keigo Nitadori, Tomoaki Ishiyama, Simon Portegies Zwart, 2014, MACM/IEEE conference on Supercomputing (SC14), New Orleans, Louisiana, USA, Nov. 2014
Michiko Fujii [personal website]

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