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SUMMARY:MHD turbulence in space and astrophysical plasmas
DTSTART;VALUE=DATE-TIME:20260409T060000Z
DTEND;VALUE=DATE-TIME:20260409T070000Z
DTSTAMP;VALUE=DATE-TIME:20260428T220500Z
UID:indico-event-4895@indico-tdli.sjtu.edu.cn
DESCRIPTION:Speakers: Ka Ho Yuen\n\nHost: Longqing YiJoin Tencent Meeting
 ：https://meeting.tencent.com/dm/9MrqQ2sgyTsxMeeting ID: 844303116 (no p
 assword）Abstract:Magnetized turbulence in space plasmas is often interpr
 eted through the Goldreich–Sridhar critical-balance paradigm\, yet solar
 -wind observations and modern simulations consistently show major departur
 es: the expected −5/3 velocity scaling and the predicted scale-dependent
  anisotropy are frequently absent\, and a dominant quasi-two-dimensional (
 2D) component can contain most of the fluctuation energy. I will present a
  unified spatio-temporal MHD turbulence framework built from fully time-re
 solved\, ultra-high-resolution simulations that treats the cascade simulta
 neously in wavevector and frequency space and predicts a measurable four-d
 imensional distribution P(k\,ω). The central result (Yuen et al. 2025\, A
 pJ\, 986\, 221) is that MHD turbulence naturally generates an overwhelming
  population of low-frequency\, 2D-like fluctuations that exhibit strong no
 nlinear frequency broadening\, couple efficiently to compressible perturba
 tions\, and dominate the long-timescale dynamics. This “low-frequency re
 servoir” changes how we interpret spectral slopes and anisotropy in spac
 ecraft data and provides a concrete route to connect turbulent structure t
 o transport: because these modes persist and interact strongly\, they can 
 regulate energetic-particle scattering and cross-field diffusion across sp
 ace and astrophysical environments. I will close by noting how controlled 
 turbulence experiments\, including laser-driven platforms with high-qualit
 y field diagnostics\, could test key signatures of the theory—particular
 ly the partition of energy into near-2D\, near-zero-frequency fluctuations
  and the scale-dependent frequency broadening—without relying on device-
 specific details.Biography:Ka Ho is an Assistant Professor at Nanjing Univ
 ersity\, specializing in computational astrophysics\, turbulence\, and sta
 r formation. Formerly an Oppenheimer Distinguished Postdoctoral Fellow at 
 Los Alamos National Laboratory\, he holds a Ph.D. from UW-Madison and has 
 published over 30 papers in leading journals like Nature and ApJ. He curre
 ntly leads major computational initiatives (INCITE\, NERSC) and serves as 
 a grant reviewer for top-tier agencies\, including NASA and the DOE.\n\nht
 tps://indico-tdli.sjtu.edu.cn/event/4895/
LOCATION:Tsung-Dao Lee Institute/S4F-SW - Open Area (Tsung-Dao Lee Institu
 te)
URL:https://indico-tdli.sjtu.edu.cn/event/4895/
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