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)
445 2016-03-11 13:30    Topological phases of matter in nonequilibrium: Topology of the Wannier-Stark ladder
444 2018-11-01 16:00    Direct holography from a single snapshot file
443 2022-08-18 10:00    Disorder-driven phase transition in the second-order non-Hermitian skin effect
442 2023-04-27 11:00    Inverse Shapiro steps and coherent quantum phase slip in superconducting nanowires
441 2015-07-16 16:00    Next-generation ultrafast laser technology for nonlinear optics and strong-field physics
440 2018-10-26 16:00    Coexisting triple-point and nodal-line topological magnons and thermal Hall effect in pyrochlore iridates file
439 2017-03-24 14:30    Topological Dynamics
438 2015-10-15 10:00    Development of Large-Bore, High Field Magnets at the NHMFL
437 2023-06-22 16:00    [CAPP Seminar] The muon g-2 puzzle file
436 2016-05-19 15:00    The CERN Resonant WISP Search: Development, Results and Lesson-Learned
435 2016-07-08 11:00    Isostatic magnetism
434 2015-11-23 13:30    What's Beyond the Standard Model? Lessons from Run I and what might come in Run II
433 2017-02-01 14:00    Quantum electron optics using flying electrons
432 2019-09-10 15:00    Two-Stage Kondo Effect file
431 2017-11-03 14:30    Quantum Resistor-Capacitor Circuit with Majorana Edge States file
430 2019-07-30 16:00    Dirac fermions and flat bands in correlated kagome metals file
429 2023-07-11 11:00    Ordered phases, non-Fermi liquid, and quantum criticality driven by entanglement between multipoles and conduction electrons
428 2017-04-28 16:00    Carbon nanotubes coupled to superconducting impedance matching circuits
427 2016-09-29 16:00    Exploring the phase diagram of BaBiO3: epic voyage of just another bad trip?
426 2019-06-12 15:00    The relation between free and interacting fermionic SPT phases file