Electrostatic Structures in Space Plasmas: Stability of Two-dimensional Magnetic Bernstein-Greene-Kruskal Modes

Electrostatic structures have been observed in many regions of space plasmas, including the solar wind, the magnetosphere, the auroral acceleration region, and in association with shocks, turbulence, and magnetic reconnection. Due to potentially large amplitude of electric fields within these structures, their effects on particle heating, scattering, or acceleration can be important. One possible theoretical description of some of these structures is the concept of Bernstein-Greene-Kruskal (BGK) modes, which are exact nonlinear solutions of the Vlasov-Poisson system of equations in collisionless kinetic theory. BGK modes have been studied extensively for many decades, predominately in one dimension (1D), although there have been observations showing that some of these structures have clear 3D features. While there have been approximate solutions of higher dimensional BGK modes, an exact 3D BGK mode solution in a finite magnetic field has not been found yet. Recently we have constructed exact solutions of 2D BGK modes in a magnetized plasma with finite magnetic field strength in order to gain insights of the ultimate 3D theory [Ng, Bhattacharjee, and Skiff, Phys. Plasmas 13, 055903 (2006)]. Based on the analytic form of these solutions, as well as Particle-in-Cell (PIC) simulations, we will present numerical studies of their stability for different levels of background magnetic field strength.Comment: Submitted to AIP Journal Proceedings for "Tenth Annual International Astrophysics Conference

Karakterisasi Kutu Kebul (Bemisia Tabaci) Sebagai Vektor Virus Gemini Dengan Teknik Pcr-rapd

Characterization of whitefly (Bemisia tabaci) as geminivirus vector based on RAPD-PCR. The variation of whitefly was performed by the appearance of population having diferent DNA sequence. PCR-RAPD and dendogram was expected to be used to investigate the variation of whitefly in Sumatera. Morphological observation on the whitefly colleted from field area showed that the geminivirus-transmitting vector was Bemisia tabaci with varied population. Based on PCR-RAPD and dendogram analysis in Sumatera, it was known that Bemicia tabaci had a high variation both intra and inter field area