流体力学セミナー流体力学セミナー

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流体力学セミナー ２００９

＃数理解析研究所の建物耐震改修工事のため，場所が京大理学部の
　建物になっています．ご注意ください．

日時： 11月30日（月） 15:00 から 16:30

場所： 京大 理学部６号館 ２０３号室

講師： Abraham C.-L. Chian
(National Institute for Space Research (INPE), Brazil
& RIMS, Kyoto University)

題目: Nonlinear dynamics of fluids and plasmas: On-off intermittent
turbulence

概要：The amplitude and phase dynamics of coherent structures in
intermittent turbulence in fluids and plasmas is studied using
direct simulations of Navier-Stokes equations and
magnetohydrodynamics equations, as well as in-situ observations of
atmospheric and interplanetary turbulence. Nonlinear surrogate
techniques are applied to quantify the degree of phase
synchronization in simulated and observed data of fluid and plasma
turbulence. We adopt the complex Morlet wavelet to characterize
the amplitude dynamics by computing the Local Intermittency
Measure, and to characterize the phase dynamics by computing a
phase coherence index. Our techniques are able to detect and
measure coherent structures in magnetic field turbulence in
unshocked and shocked solar wind, as well as in atmospheric
turbulence above and within the Amazon forest canopy.
Intermittent mean-field dynamo is investigated using numerical
modeling of magnetohydrodynamic turbulence driven by helical
forcing. The importance of phase synchronization and on-off
intermittent turbulence in the variability of stellar magnetic
field and its impact on the dynamics of climate and space weather
of a planet and exoplanet is discussed.

Chian ACL, Miranda RA. Cluster and ACE observations of phase
synchronization in intermittent magnetic field turbulence: a
comparative study of shocked and unshocked solar wind. Ann.
Geophys. 27, 1789, 2009.

Chian ACL, Han M, Miranda RA, Shu, C, Valdivia, JA. The planetary
-exoplanetary environment: a nonlinear perspective. Adv. Space
Res., in press, 2010.

Chian ACL, Miranda RA, Koga D, Bolzan MJA, Ramos FM, Rempel EL.
Analysis of phase coherence in fully developed atmospheric
turbulence: Amazon forest canopy. Nonlinear Proc. Geophys. 15, 567,
2008.

Koga D, Chian ACL, Miranda RM, Rempel EL. Intermittent nature of
solar wind turbulence near the Earth’s bow shock: Phase coherence
and non-Gaussianity. Phys. Rev. E 75, 046401, 2007.

Koga, D, Chian ACL, Hada T, Rempel EL. Experimental evidence of
phase coherence of magnetohydrodynamic turbulence in the solar
wind: GEOTAIL satellite data. Phil. Trans. Royal Soc. London-
Math. Phys. Sciences 366, 447, 2008.

Rempel EL, Proctor MR, Chian ACL. Intermittent nonlinear dynamo in
compressible magnetohydrodynamics. Monthly Not. Royal Astron. Soc.,
in press, 2009.

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世話人：山田 道夫(京大数理研)， 藤 定義(京大)，松本 剛(京大理)
アドバイザー：船越 満明（京大情報学）、水島 二郎(同志社大工)、
余田 成男（京大理）
連絡先：山田道夫 yamada＠kurims.kyoto-u.ac.jp
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