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UID:UW-Physics-Event-8004
DTSTART:20221114T180000Z
DTEND:20221114T190000Z
DTSTAMP:20240328T130304Z
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.
\n
\n[1] B.A. Grierson\, et al\, Phys Rev Lett 105\, 20500
4 (2010).
\n
\n[2] B.A. Grierson\, et al\, Phys Plasmas 16\,
055902 (2009).
\n
\n[3] C. Torrence and G.P. Compo\, Bulletin
of the American Meteorological Society\, 61-78 (1998).
\n
\n
[4] B.P. Van Milligen\, et al\, Phys Rev Lett 74\, 395 (1995).
\n
\n[5] T.M. Roberts\, et al\, Phys Plasmas 22\, 055702 (2015).
\n
\n
\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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