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
202 2012-04-02 16:00  E6, 1501  A new route to ferroelectricity in magnetic spinels: a case of Co2MnO4
201 2012-02-13 16:00  E6, 1501  Physics Colloquium : 2012 Spring
200 2011-09-03 16:00  E6, 1501  Physics Colloquium : 2011 Fall file
199 2011-05-16 16:00  E6, 1501  Photonics with surface plasmon polaritons
198 2010-02-14 16:00  E6, 1501  Physics Colloquium - 2011 Spring file
197 2010-09-06 16:00  E6, 1501  Physics Colloquium : 2010 Fall file
196 2010-02-08 16:00  E6, 1501  Physics Ciolloquium : 2010 Spring file
195 2009-10-21 16:00  E6, 1501  Interdimensional Universality of Dynamic Interfaces
194 2009-09-07 16:00  E6, 1501  Physics Colloquium : 2009 Fall file
193 2009-02-23 16:00  E6, 1501  Physics Colloquium : 2009 Spring file
192 2024-03-28 11:00  E6, #2501  Geometric characterization of thermoelectric performance of two-dimensional quadratic band-crossing semimetals
191 2022-03-28 16:00  E6, #1501  Ultimate-density atomic semiconductor via flat bands
190 2022-03-21 16:00  E6, #1501  Multi-wavelength Studies on Relativistic Jets from Gamma-ray Bright Active Galactic Nuclei
189 2022-04-25 16:00  E6, #1501  Ultrafast electron beam, a tool to explore the nanoscopic world of materials(우리말강의)
188 2022-03-07 16:00  E6, #1501  Climate Physics and Modelling(우리말강의)
187 2022-03-14 16:00  E6, #1501  Quantitative phase imaging and artificial intelligence: label-free 3D imaging, classification, and inference
186 2022-02-28 16:00  E6, #1501  Spin-based training of optical microscopes
185 2022-05-02 16:00  E6, #1501  What can we learn from the history of science and technology?(우리말강의)
184 2022-04-11 16:00  E6, #1501  Emergence of Statistical Mechanics in Quantum Systems
183 2022-05-23 16:00  E6, #1501  Novel electronic transport in topological van der Waals magnets