Division of Theoretical Astronomy, National Astronomical Observatory of Japan

Research Highlights

New classes of electron orbits in magnetic reconnection

Magnetic reconnection, an explosive energy-release process in space plasmas, is mediated by complex particle motion of plasmas. The electron motion is one of the smallest elements in reconnection systems, and has long been studied by using particle-in-cell (PIC) simulations. However, as PIC data have become larger and larger in size, it has become more and more difficult to diagnose particle orbits in simulations.
In this work, we extensively analyzed twenty million electron trajectories during magnetic reconnection by using a 2D PIC simulation, so as not to overlook any interesting trajectories. As a result, we discovered various electron orbits that have never been discussed before. The figure displays typical electron trajectories in magnetic reconnection, in which the new orbits are indicated with bold faces. Surprisingly, it was found that a majority of the electrons follow the new orbits. This raises a serious question to previous discussions on the basis of the conventional electron orbits. Taking the noncrossing populations into account, various theoretical issues need to be revised.
This paper was selected as one of highlight papers, from the 19 journals published by the American Institute of Physics.
S. Zenitani and T. Nagai, Phys. Plasmas 23, 102102 (2016)
Seiji Zenitani (private website)

Avoiding “Traffic Jam” Creates Impossibly Bright “Lighthouse”

A supercomputer recreated a blinking impossibly bright “monster pulsar.” The central energy source of enigmatic pulsating Ultra Luminous X-ray sources (ULX) could be a neutron star according to numerical simulations performed by a research group led by Tomohisa Kawashima at the National Astronomical Observatory of Japan (NAOJ).
see web release from CfCA for more details.

Kawashima, T., Mineshige, S., Ohsuga, K. and Ogawa, T., 2016, PASJ, published online [PASJ] [arXiv]
Kawashima, T. (NAOJ), Mineshige, S. (Kyoto U.), Ohsuga, K. (NAOJ) and Ogawa, T. (Kyoto U.)