9:15 AM - 9:30 AM
[PEM16-02] Dependence on the background magnetic field of ion Weibel instability
Keywords:Collisionless shocks, Weibel instability, Cosmic ray
Weibel instability is an electromagnetic instability caused by plasma beams or temperature anisotropy. It is a good candidate for electron heating at collisionless shock transition layers. In astrophysics, Weibel instability usually refers to the instability caused by counterstreaming beams in the absence of a background magnetic field. However, it has been found that the instability caused by high Alfven Mach number ring distribution around the background magnetic field can also be regarded as Weibel instability [1]. It corresponds to an extreme case of electromagnetic ion cyclotron (EMIC) instability. This implies that the beam instability in unmagnetized plasmas and ring instability in magnetized plasmas are connected seamlessly.
We discuss the ion beam instability in the case of a moderate background magnetic field in the sense that the timescale of the instability is shorter than the ion gyro period but longer than the electron gyro period. It is to be noted that a typical young supernova remnant parameter lies in this category. We performed 2D particle-in-cell simulation in various parameters.
We found that the magnetized electrons in the moderate background magnetic field case can amplify the magnetic field further compared to the unmagnetized case, and the amplified magnetic field can cause turbulent structure after magnetic reconnection and Kelvin Helmholtz like instability. Electron heating is also the most efficient in the moderately magnetized case.
[1] T. Nishigai and T. Amano, "Mach number dependence of ion-scale kinetic instability at collisionless perpendicular shock: Condition for Weibel-dominated shock", Physics of Plasmas 28, 072903 (2021)
We discuss the ion beam instability in the case of a moderate background magnetic field in the sense that the timescale of the instability is shorter than the ion gyro period but longer than the electron gyro period. It is to be noted that a typical young supernova remnant parameter lies in this category. We performed 2D particle-in-cell simulation in various parameters.
We found that the magnetized electrons in the moderate background magnetic field case can amplify the magnetic field further compared to the unmagnetized case, and the amplified magnetic field can cause turbulent structure after magnetic reconnection and Kelvin Helmholtz like instability. Electron heating is also the most efficient in the moderately magnetized case.
[1] T. Nishigai and T. Amano, "Mach number dependence of ion-scale kinetic instability at collisionless perpendicular shock: Condition for Weibel-dominated shock", Physics of Plasmas 28, 072903 (2021)