visual
visual

세미나

  • HOME
  • >
  • 소식
  • >
  • 세미나
날짜 2016-06-01 16:00 
일시 Jun 1 (Wed) 4 PM 
장소 #1323(E6-2 1st fl.) 
연사 Kil-Byoung Chai, Caltech 

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 장소 제목
103 2018-10-04 16:00  #1323, E6-2  Engineering light absorption in an ultrathin semiconductor metafilm file
102 2018-05-31 16:00  #1323, E6-2  Dynamic control of optical properties with gated-graphene metamaterials file
101 2019-12-05 16:00  #1323, E6-2  Subwavelenth Photonic Devices: From Single Photon Sources to Solar Cell file
100 2019-10-15 16:00  #1323, E6-2  Moiré superlattices and graphene quasicrystal file
99 2018-10-16 10:00  #1323, E6-2  Capturing protein cluster dynamics and gene expression output in live cells file
98 2019-11-05 16:00  #1323, E6-2  Study on nanomaterials by the development of ultrahigh resolution laser-photoelectron microscopy (PEEM) file
97 2018-11-01 16:00  #1323, E6-2  Direct holography from a single snapshot file
96 2018-11-21 15:00  #1323, E6-2  Engineering topological quantum physics at the atomic scale file
95 2018-05-09 16:00  #1323, E6-2  Recent advances in thermoelectric bulk composites file
94 2018-10-11 16:00  #1323, E6-2  Dirac electrons in a graphene quasicrystal file
93 2018-10-15 16:00  #1323, E6-2  Universal properties of macroscopic current-carrying systems file
92 2019-12-18 16:00  #1323, E6-2  Road to Higher Tc Superconductivity file
91 2019-09-18 16:00  #1323, E6-2  Exploring Synthetic Quantum Matter in Superconducting Circuits file
90 2019-10-25 15:00  #1323, E6-2  Physics Seminar file
89 2019-11-28 16:00  #1323, E6-2  Generation of coherent EUV emissions using ultrashort laser pulses file
88 2018-06-22 16:00  #1323, E6-2  Tuning functional properties of BiFeO3 films using strain and growth chemistry file
87 2018-06-22 16:00  #1323, E6-2  Tuning functional properties of BiFeO3 films using strain and growth chemistry file
86 2019-11-14 16:00  #1323, E6-2  Semi-classical model of polariton propagation file
85 2019-10-17 16:00  #1323, E6-2  Top down manipulation of Waves : From Metamaterials, Correlated Disorder, Quantum Analogy, to Digital Processing file
84 2018-10-18 16:00  #1323, E6-2  Applications of nonlinear optics for condensed matter researches file