Overview of the Research Unit for Astro-fusion Plasma Physics（AFP）

The purpose and activities of the IRCC-AFP research unit

More than 99% of the materials that we know of in the universe are in the plasma state. Therefore plasma physics offers basic principles for understanding various phenomena occurring in the universe. Plasma physics also provides the fundamental research engine in developing the fusion reactor, which is expected to be the ultimate energy source for human beings.

The National Institute for Fusion Science (NIFS) and the National Astronomical Observatory of Japan (NAOJ) are two representative institutes in the National Institutes of Natural Sciences (NINS) for plasma physics research. These institutes have been conducting international research collaborations based on their worldwide research networks. For the purpose of strengthening such international collaboration activities with the emphasis on promoting the interdisciplinary scope of research, a new research unit of IRCC-AFP (International Research Collaboration Center, Astro-fusion Plasma Physics research unit) was established.

A new direction of the research activity of the Integrated Plasma Physics, which merges fusion plasma physics and astronomical plasma physics, is becoming more active recently in the United States and in Europe as well. The Max-Planck Society established the Max-Planck Center for the plasma physics together with Princeton University in the United States. This Max-Planck Center is an official (virtual) institute in society and has the role of international research collaborations. IRCC-AFP is promoting new research activities of the Integral Plasma Physics in collaboration with the Max-Planck Center for plasma physics as an international network involving three regions in the world.

An important elements of the research activities of IRCC-AFP are the IRCC-AFP fellows who are young scientists employed in the IRCC for the exclusive role of international research collaboration in plasma physics. This fellow is selected by the open job call under the collaboration of IRCC-AFP with Princeton University and the Max-Planck institutes. The main work place of this fellow is either in Princeton University or the Max-Planck institutes where he/she will be devoted to the role of promoting the collaboration research between Japan and the United States or Europe. Another part of IRCC-AFP research activities is establishing the international research collaboration network for plasma physics including domestic collaboration networks together with researchers in Japanese Universities who are active in international collaboration.

Research activity

(1) International research collaboration with Max Planck Institute for Plasma Physics

International Specially Appointed Research Employee (Ph.D.): Fabien Widmer

Supervisor 1: Associate Professor Mami Machida (National Astronomical Observatory of Japan)

Supervisor 2: Dr. Emanuele Poli (Max Planck Institute for Plasma Physics)

Main research location: Max Planck Institute for Plasma Physics (Garching, Germany)

It is known that strong interactions exist in astrophysical plasmas and fusion plasmas among turbulence, magnetic reconnection phenomena and dynamics of magnetic island formation. It is because the non-linear interactions and exchanges of energy take place between the microscopic turbulent processes and the large-scale structural formation of the magnetic islands. We will use the 5D gyrokinetic framework, a reduced kinetic model, which is the most advanced theory of micro-turbulence in magnetic fusion plasmas, for studying important physics problems in these phenomena such as 1) the analysis of the dynamic processes triggering the magnetic reconnection phenomena, 2) the interactions between the turbulent processes and magnetic island formation.More details [PDF file / 36KB]

(2) International research collaboration with the Department of Astrophysical Sciences, Princeton University

International Specially Appointed Research Employee (Ph.D.): Arno Vanthieghem

Supervisor 1: Prof. Yasushi Todo (National Institute for Fusion Science)

Supervisor 2: Prof. Anatoly Spitkovsky (Department of Astrophysical Sciences, Princeton University)

Main research location: Department of Astrophysical Sciences, Princeton University

Powerful astrophysical objects such as gamma-ray bursts, blazars, and supernovae provide ideal environments for efficient particle acceleration and energy channeling between different plasma species. Bursts of high-energy particles and heating result from an efficient conversion of kinetic or Poynting flux in thermal and nonthermal distributions through collective plasma processes. Astrophysical shock waves are one of the most outstanding and extensively studied representatives of such complex many-body phenomena. They cover a large variety of physical conditions in magnetization, velocity, and composition, and are intrinsically nonlinear across very disparate scales. The study of these systems is a key challenge to unveiling the physics underlying observed multimessenger spectra. This nonlinear problem is tackled using large-scale Particle-In-Cell (PIC) simulations in combination with linear and nonlinear analytical models.Further explanation [PDF file/50KB]

(3 International research collaboration with the Department of Astrophysical Sciences, Princeton University

Joint Appointment for the Associate Research Scholar of the Department of Astrophysical Sciences, Princeton University : Dr. Samuel Totorica

Collaborator (PI) 1: Prof. Mami Machida (National Institutes of Natural Sciences)

Collaborator (PI) 2: Prof. Amitava Bhattacharjee (Department of Astrophysical Sciences, Princeton University) Research locations：National Institutes of Natural Sciences and Department of Astrophysical Sciences, Princeton University

Astrophysical jets with well-collimated supersonic plasma flows can be observed in various layers of the universe, such as protostars, X-ray binaries (compact objects), and active galactic nuclei (AGN). One of the most important aspects of jet activity is the energy release of the black hole gravitational energy, which reaches over 108 times the Schwarzschild radius. The jet is considered to be the origin of accelerated cosmic ray particles in the energy range of 1015 to 1017 eV for X-ray binaries and 1018 eV or more for AGNs. Supersonic jets form various shocks in the jet beam, and these shocks become the sites of particle acceleration. Since the jet is a magnetized plasma, magnetic reconnection is expected to occur. We will use fully kinetic particle-in-cell (PIC) simulations to study particle acceleration and radiation associated with these systems and develop reduced models to improve magnetohydrodynamic simulations of global jet evolution.More details [PDF file / 59KB]

(4) International cooperation Section Japan, the United States and Germany