极帽加速器中的死区
Dead zone in the polar-cap accelerator of pulsars
摘要：
我们研究了脉冲星极冠上方的等离子体流动，采用等离子体粒子在自洽电场中的随时间变化的模拟。流动行为由无量纲参数α =（j/c rho_GJ）控制，其中j是电流密度，rho_GJ是Goldreich-Julian电荷密度。极冠的0<alpha<1的区域是一个“死区”-在这个区域，粒子加速效率很低，即使是年轻的、快速旋转的恒星也不会产生对。在自转轴附近具有极冠的脉冲星，其射电辐射具有空心锥结构，因为死区占据了极冠的中心部分。我们的结果适用于电荷分离的电子流（j<0）或离子流（j>0）。在后一种情况下，我们考虑的可能性，由不同的离子种类的混合流，并观察两个流的不稳定性的发展。极帽的死区对于零面rho_GJ=0附近的外隙的发展是必不可少的。
英文摘要：
We study plasma flows above pulsar polar caps using time-dependent simulations of plasma particles in the self-consistent electric field. The flow behavior is controlled by the dimensionless parameter alpha=(j/c rho_GJ) where j is the electric current density and rho_GJ is the Goldreich-Julian charge density. The region of the polar cap where 0<alpha<1 is a "dead zone" --- in this zone particle acceleration is inefficient and pair creation is not expected even for young, rapidly rotating pulsars. Pulsars with polar caps near the rotation axis are predicted to have a hollow-cone structure of radio emission, as the dead zone occupies the central part of the polar cap. Our results apply to charge-separated flows of electrons (j<0) or ions (j>0). In the latter case, we consider the possibility of a mixed flow consisting of different ion species, and observe the development of two-stream instability. The dead zone at the polar cap is essential for the development of an outer gap near the null surface rho_GJ=0.
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