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UID:UW-Physics-Event-8004
DTSTART:20221114T180000Z
DTEND:20221114T190000Z
DTSTAMP:20260414T074026Z
LAST-MODIFIED:20221109T113542Z
LOCATION:1610 Engineering Hall
SUMMARY:Characterization of Intermittency and Energy Transfer via Thre
 e-Wave Coupling in a Turbulent Dipole Plasma\, Plasma Physics (Physics
 /ECE/NE 922) Seminar\, Mel Abler\, Space Science Institute
DESCRIPTION:Plasmas confined by a dipole magnetic field exhibit interc
 hange and entropy mode turbulence causing bursty intermittent transpor
 t of particles and energy [1].  On the Collisionless Terrella Experime
 nt (CTX)\, this turbulence is dominated by low-frequency\, long-wavele
 ngth modes with amplitudes and phases that vary chaotically in time [2
 ]. We present a new paradigm for characterizing this turbulence by mea
 suring the time-evolution of the fluctuation power spectrum and the in
 stantaneous bispectrum using the continuous wavelet transform [3\,4] a
 nd computing the statistical properties of turbulent wave kinetics. We
  observe that both the fluctuation power and the energy transfer by th
 ree-wave coupling\, or bispectrum\, between these fluctuations can be 
 intermittent. When antenna are used to actively launch waves into the 
 turbulence\, the intermittency of the driven waves decreases\, while t
 he intermittency of other waves increases. Similarly\, application of 
 active feedback [5] to amplify the turbulence decreases the intermitte
 ncy of the wave energy\, while suppressing feedback increases this int
 ermittency. Measurements based on this new paradigm show that the tran
 sfer of wave energy to larger and smaller scales in a turbulent plasma
  is not steady but occurs in short and intense bursts\, analogous to t
 he better-known short bursts of particle transport in magnetized plasm
 a.<br>
\n <br>
\n[1] B.A. Grierson\, et al\, Phys Rev Lett 105\, 20500
 4 (2010).<br>
\n <br>
\n[2] B.A. Grierson\, et al\, Phys Plasmas 16\, 
 055902 (2009).<br>
\n <br>
\n[3] C. Torrence and G.P. Compo\, Bulletin
  of the American Meteorological Society\, 61-78 (1998).<br>
\n <br>
\n
 [4] B.P. Van Milligen\, et al\, Phys Rev Lett 74\, 395 (1995).<br>
\n 
 <br>
\n[5] T.M. Roberts\, et al\, Phys Plasmas 22\, 055702 (2015).<br>
 
\n <br>
\n <br>
\nBio: Mel Abler is a Postdoctoral Research Associate
  at the Space Science Institute focused on experimental studies of the
  nonlinear behavior of Alfven waves. They recently completed their doc
 toral work characterizing turbulent wave kinetics and energy transfer 
 via three-wave coupling in a dipole-confined plasma at Columbia Univer
 sity. Mel is a passionate advocate for improving inclusion in physics\
 , and currently serves as the Secretary-Treasurer of the APS DPP Pride
  Committee. Outside the lab\, Mel is an avid theater goer\, union orga
 nizer\, and competitive rower.
URL:https://www.physics.wisc.edu/events/?id=8004
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