visual
visual

세미나

  • HOME
  • >
  • 소식
  • >
  • 세미나
날짜 2016-06-01 16:00 
연사  
장소 #1323(E6-2 1st fl.) 

Laboratory experiments relevant to mesospheric clouds, Saturn’s rings & astrophysical jets

 

Jun 1 (Wed) 4 PM, #1323(E6-2 1st fl.)
Kil-Byoung Chai, Caltech

 

An rf discharge with liquid nitrogen cooled electrodes and injected water vapor has been used to study nucleation, growth, and dynamics of water-ice grains spontaneously formed in a plasma environment. Examples of water-ice dusty plasmas include polar mesospheric clouds, Saturn’s diffusive rings, and protoplanetary disks. We found that fast grain growth to nonspherical shape with up to 5:1 elongation occurs when the water molecule mean free path exceeds the ice grain screening length. Ice grains grow largest in light gas plasmas, up to 500 µm long in hydrogen plasma. Elongated ice grains align along the plasma ambipolar electric field. Microscope images reveal that the ice grains have fractal nature with 1.7 typical fractal dimension. After the growth process ends, poloidal vortex motion of ice grains is observed and is shown to result from the non-conservative ion drag force.

The Caltech jet experiment produces low beta, high Lundquist number, high density (~1022 m-3) MHD-driven plasma jets and so is similar to astrophysical jets and solar corona loops. We have recently studied various phenomena associated with magnetic reconnection induced by a kink-driven Rayleigh-Taylor instability using comprehensive diagnostics. The results of this study include the following: A spatially localized EUV burst is imaged at the presumed position of fast magnetic reconnection in a plasma jet; the existence of this localized EUV burst indicates strong localized electron heating. Circularly polarized high frequency whistler waves are simultaneously observed indicating that Hall dynamics likely governs the reconnection. Spectroscopic measurement shows simultaneous fast ion heating. We propose that the electron heating is consistent with Ohmic dissipation while the ion heating is consistent with ion trajectories becoming stochastic.

 

번호 날짜 연사 제목
공지 2025-02-24 16:00    2025년 봄학기 콜로키움 안내
공지 2025-02-27 16:00    2025년 봄 물리학과 특별세미나 (광학/응집물리 분야)
514 2016-10-27 16:00    Terahertz Metal Optics
513 2016-11-01 14:30    Search for dark sector particles in the B-factory experiments
512 2016-11-04 13:30    Exotic phenomena at oxide LaAlO3/SrTiO3 hetero-interface and their applications
511 2016-11-04 15:00    Quantum information experiments using few electron spins in semiconductors
510 2016-11-1 10:30    Time scale dependent dynamics in InAs/InP quantum dot gain media
509 2016-11-10 16:00    Low Dimensional Active Plasmonics and Electron Optics in Graphene
508 2016-11-11 13:30    Bandgap Engineering of Black Phosphorus
507 2016-11-11 16:00    Dirac fermions in condensed matters
506 2016-11-16 16:00    Realizing Haldane Model in Fe-based Honeycomb Ferromagnetic Insulators
505 2016-11-18 10:30    Non-equilibrium many-body spin dynamics in diamond
504 2016-11-24 16:00    Harmonic oscillator physics with single atoms in a state-selective optical potential
503 2016-11-29 16:00    Symmetry Protected Kondo Metals and Their Phase Transitions
502 2016-12-09 13:30    Entanglement area law in strongly-correlated systems
501 2016-12-09 16:00    Shift Charge and Spin Photocurrents in Dirac Surface States of Topological Insulator
500 2016-12-12 13:30    “Possible symmetry in the phase diagrams of electron- & hole-doped cuprate high-Tc superconductors”
499 2016-12-8 16:00    Dynamical Resonance between Two Optical Cavities via Optomechanical Oscillator
498 2017-01-09 16:00    Topological Defects and Phase Transitions" file
497 2017-02-01 14:00    Quantum electron optics using flying electrons
496 2017-03-02 16:00    “Progress in the comparison of ARPES to DMFT for d and f strongly correlated electron systems”
495 2017-03-06 16:00    Spring 2017: Physics Colloquium file