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
506 2013-03-11 16:00  E6, 1501  Physics Colloquium : 2013 Spring
505 2013-09-09 16:00  E6, 1501  Physics Colloquium : 2013 Fall
504 2014-03-10 16:00  E6, 1501  Physics Colloquium : 2014 Spring file
503 2014-05-28 17:00  KI Building, Matrix Hall  부품소재산업이 미래다
502 2014-12-22 14:00  E6, Rm1319  Dynamics of molecular motors: Power stroke vs Brownian ratchet file
501 2015-03-04 12:00  1323호, E6-2  Bioimaging and Biosensing Using Near-Infrared Fluorescence file
500 2015-03-09 16:00  E6, 1501  Physics Colloquium : 2015 Spring file
499 2015-03-13 14:00  Connect Room, KI Bldg.  The 15th Innovative Workshop on Soft/Bio Materials file
498 2015-06-03 12:00  Room 101, E11  The First Wednesday Multidisciplinary Forum file
497 2015-07-15 14:00  E6-2,1323  Electronic and optical properties of titanate-based oxide superlattices
496 2015-07-16 16:00  E6-2, 1318  Next-generation ultrafast laser technology for nonlinear optics and strong-field physics
495 2015-07-16 16:00  E6-2, 1501  KAIST Physics Distinguished Lecture
494 2015-07-23 13:30  E4, B401  Enhanced ZnO based UV photonics and related applications file
493 2015-08-03 10:30  E6-2, #1323 (Seminar Room)  Axion Search
492 2015-08-04 11:00  B501, Room Red, KI bldg. 5nd fl.  Propagation of ultrasound through two- and three-dimensional strongly scattering media
491 2015-09-07 15:00  E6-2. 1st fl. #1318  Advanced Optical Materials and Devices at NRL
490 2015-09-07 16:00  E6, 1501  Physics Colloquium : 2015 Fall file
489 2015-09-14 14:00  E6-2. 2nd fl. #2501  Ultrafast X-ray Studies on Dynamics Matter in Extreme Conditions
488 2015-09-15 16:00  E6, 1501  Physics Colloquium : 2014 Fall file
487 2015-10-14 18:00  KAIST Munji Campus Supex Hall  인터스텔라 영화 속의 물리 file