[P-EM16] Space Plasma Physics: Theory and Simulation

[PEM16-P04] Comuputer simulation on the structure of double layer in the auroral
acceleration region

*Ryouta Ikeba^1,2, Takayuki Umeda^1,2, Yoshizumi Miyoshi^1,2 (1.Nagoya University, 2.Institute for Space-Earth Environmental Research)

Keywords:the auroral acceleration region

The existence of electric fields in the auroral region was predicted by Alfven (1957). Rocket observations of aurora in 1960's showed the precipitation of high energy electrons, possible due to electric fields in the acceleration region (McIlwain 1960). Evans (1974) reproduced the result of rocket observation by a model calculation, which demonstrated the existence of the auroral acceleration region. Electric fields due to the electric double layers in the auroral acceleration region were first observed by spacecrafts in 1970's (Mozer et al. 1977). The FAST observation showed detailed multi-dimensional structures of the auroral double layer (Ergun et al. 2001). The previous one-dimensional Vlasov-Poisson simulation of a current-carrying plasma showed that a double layer was generated by a strong density depression (Newman et al. 2001). However, multi-dimensional kinetic simulations have not been performed yet due to both computational resources and computational techniques. In the present study, we first perform a two-dimensional particleincell simulation of a current-carrying plasma with a density depression. It is demonstrated that a double layer is driven generated in the two-dimensional system with a weak ambient magnetic field. An electrostatic wave is excited inside the double layer at the frequency around the ion plasma frequency and at the phase velocity around the ion acoustic speed, which propagates in the direction oblique to the ambient magneto field.