Effect of ion cyclotron motion on the structure of wakes: A Vlasov simulation

Abstract

The global structure of wake fields behind an unmagnetized object in the solar wind is studied by means of a 2.5-dimensional full electromagnetic Vlasov simulation. The interaction of a plasma flow with an unmagnetized object is quite different from that with a magnetized object such as the Earth. Due to the absence of the global magnetic field, the unmagnetized object absorbs plasma particles which reach the surface, generating a plasma cavity called a wake on the anti-solar side of the object. The interaction between the solar wind with an out-ofplane interplanetary magnetic field and an unmagnetized object of ion-gyro scale is examined to study the effect of the ion cyclotron motion on the structure of wake fields. It is shown that the wake boundary layer is broadened when the inner product of the electric force and the density gradient of the wake boundary layer is negative. On the other hand, a steep wake boundary layer is formed with a negative inner product. The result suggests that the structures of wake fields become asymmetric due to the in-plane E cross B drift motion of ions.

A Scalable Full-Electromagnetic Vlasov Solver for Cross-Scale Coupling in Space Plasma

“…As results, we obtained the best computational speed of 8.19 TFlops (performance efficiency of 10.9%) with 8192 cores on the HA8000, 2.95 TFlops (14.6%) with 2304 cores on the R815, 3.17 TFlops (15.5%) with 2048 cores on the HX600, 4.10 TFlops (13.3%) with 3072 cores on the FX1, and 255 GFlops (10.6%) with 128 cores on the SR16000/L2. Note that we have applied the present parallel 2P2V and 2P3V Vlasov-Maxwell solvers to the K-H instability [3], magnetic reconnection [6], and the interaction between solar/stellar winds and dielectric bodies [7], [8]. Currently, 256-1024 cores are used for the parallel computations.…”

“…Fig. 4(c) shows the magnetosphere of a small dielectric body obtained by the 2P3V Vlasov simulation [7], [8]. The solarwind plasma is injected from the left boundary.…”

“…It is still difficult to treat the 3P3V (three dimensions for position and three dimensions for velocity) phase space even with the recent supercomputers. With the help of recent development of new Vlasov solvers, however, there are several successful attempts for studies of the K-H instability [3], magnetic reconnection [4]- [6], and the interaction between solar/stellar winds and unmagnetized dielectric bodies [7], [8] via 2P2V and 2P3V fullelectromagnetic Vlasov codes. It should be noted, however, that numerical schemes for the Vlasov method are still developing and that the Vlasov method is computationally much more expensive than the PIC method.…”

Performance Tuning of Vlasov Code for Space Plasma on the K Computer

“…The present parallel Vlasov code is a one of a few examples of successful hyperdimensional Vlasov simulations which has been applied to studies of practical problems of plasma physics, such as the magnetic reconnection [10,11], the Kelvin-Helmholtz instability [12,13], and the global interaction between the solar wind and a small astronomical body with a spatial scale of ion gyro radius [14,15,16]. Our parallel Vlasov code is designed with a high-accuracy and memory-saving scheme, especially for recent supercomputer systems with a small shared memory, and a memory size of 1GB per core is enough for stable and high-performance computation.…”

A high-resolution global Vlasov simulation of a small dielectric body with a weak intrinsic magnetic field on the K computer

“…The Vlasov simulation can use a grid spacing longer than the Debye length as long as the E × B drift motion of thermal plasma is resolved appropriately (Umeda et al 2009(Umeda et al , 2010. Thus, the Vlasov simulation can handle solar system bodies with the spatial scale of several tens of the gyro radius of thermal electrons (r e ) (Umeda et al 2011;Umeda 2012a;Umeda and Ito 2014). One critical drawback of the Vlasov simulation is that huge computational resources are required.…”