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

Shake Table Tests to Measure the Dynamic Performance of Geotextile-reinforced Embankment

Using geosynthetics in highway embankments can reduce theimpact of hazardous earthquakes by transmitting less excitationto improve the seismic performance. This study uses a 1-greduced scale (1/50) approach and subjects the model embankmentto an earthquake time history as well as several levelsof uniform cyclic loading. The main focus of comparison isbetween an unreinforced embankment and a one, reinforcedwith two levels of geosynthetics material. Results reveal thatgeotextile reinforced highway embankment models performmuch better under the applied motions. Larger amplitudes causemore severe deformations as a result of the increased dynamicloads. It is also revealed that the effectiveness of the geosyntheticsis dominated by the seismic frequency. Deamplificationis observed within the geotextile reinforced embankment but thedegree of deamplification is highly depended on the predominantfrequency of the dynamic load

PENGGUNAAN TEKNOLOGI INFORMASI DALAM MANAJEMEN DATA DI DESA BAGAN ASAHAN

Kehadiran teknologi informasi ini tentulah disambut dengan sangat baik sebagai pusat berkembangnya IPTEK dan penghasil SDM yang berkualitas. Penguasaan IPTEK bidang teknologi informasi perlu mendapat perhatian khususnya bidang pemerintahan tingkat desa. Penggunaan teknologi informasi dapat memberikan efektifitas terhadap aktifitas di desa dalam meningkatkan layanan. Desa Bagan Asahan adalah salah satu desa yang terletak di kabupaten Asahan. Desa ini merupakan desa yang termasuk lokasinya cukup jauh dengan ibukota Kabupaten Asahan sekitar lebih kurang 40 Km atau sekitar 1 jam setengah perjalanan menuju desanya. Infrastruktur untuk teknologi informasi seperti jaringan data Telkomsel cukup bagus. Sehingga pemanfaatan teknologi informasi untuk pengelolaan data desa bisa lebih maksimal. Aparatur desa sebagai pelaksana administrasi di desa harus memiliki pengetahuan tentang teknologi informasi serta mampu menerapkan teknologi informasi dalam memberikan pelayanan terbaik bagi masyarakat. Dasar tujuan tersebut maka dilakukan kegiatan pengabdian masyarakat di Desa Bagan Asahan Kec. Tanjung Balai Kab. Asahan dengan memberikan materi tentang penggunaan teknologi informasi dalam pengelolaan data desa. Kata Kunci : Teknologi Informasi, Data Desa, Cloud Storage, Google Driv