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Modulational Stability of Magnetohydrodynamic Turbulence
Modulational Stability of Magnetohydrodynamic Turbulence
상세정보
- 자료유형
- 학위논문 서양
- 최종처리일시
- 20260202103011
- ISBN
- 9798280747746
- DDC
- 530
- 저자명
- Jin, Suying.
- 서명/저자
- Modulational Stability of Magnetohydrodynamic Turbulence
- 발행사항
- [Sl] : Princeton University, 2025
- 발행사항
- Ann Arbor : ProQuest Dissertations & Theses, 2025
- 형태사항
- 139 p
- 주기사항
- Source: Dissertations Abstracts International, Volume: 86-12, Section: B.
- 주기사항
- Advisor: Dodin, Ilya Y.
- 학위논문주기
- Thesis (Ph.D.)--Princeton University, 2025.
- 초록/해제
- 요약Turbulence often self-organizes to generate highly correlated coherent structures. In astrophysical contexts, this phenomenon manifests as the turbulent ("large-scale'') dynamo---the spontaneous generation of curiously coherent magnetic fields from magnetohydrodynamic (MHD) turbulence. This thesis approaches the self-organization problem by treating coherent field formation as a modulational instability (MI) of the underlying turbulence. The main product of this work is mean-field wave kinetics (MFWK)-a Wigner--Moyal-based formalism for describing the coupled evolution of coherent (or "mean'') MHD fields and the second-order correlation functions of the turbulence. This framework allows us to show that structure formation in MHD can be understood in terms of the phase-space dynamics of turbulent "quasiparticles'' self-consistently interacting via mean fields.Besides the MFWK formalism per se, the focus of the thesis is twofold: (i) Application of the MFWK formalism to the turbulent-dynamo problem, in particular, a first-principles calculation of the non-local turbulent electromotive force for generic turbulent backgrounds, and the general dispersion relation of fully coupled modulational modes of MHD (of which the standard "alpha-effect'' dynamo is a special case). This full treatment of the modulational dynamics of MHD suggests a possible new dynamo effect that arises due to flow-current alignment. (ii) An investigation of the validity of the quasilinear approximation (QLA) that underlies MFWK. Through comparisons with direct numerical simulations (DNS), we find that, although quasilinear MFWK yields quantitatively accurate predictions for MHD in some regimes, remarkably, the QLA can be qualitatively inaccurate in adjacent regimes and produces false-positives for instability.To explore the nature of such dramatic variations, we use simple nonlinear backgrounds that allow for a tractable model while retaining the infinite chain of correlations truncated by the QLA as modulational harmonics. We find that while the destabilizing drive for MI is dominated by quasilinear interactions, the modulational spectrum supports propagating spectral waves (PSWs) that ballistically transport energy towards the higher modulational harmonics neglected by the QLA, thereby providing effective dissipation. Modulational stability can therefore be understood as a balancing act between quasilinear drive and effective dissipation provided by PSWs, which persists even in the ideal-MHD limit.
- 일반주제명
- Plasma physics
- 일반주제명
- Astrophysics
- 일반주제명
- Fluid mechanics
- 키워드
- Turbulence
- 기타저자
- Princeton University Astrophysical Sciences-Plasma Physics Program
- 기본자료저록
- Dissertations Abstracts International. 86-12B.
- 전자적 위치 및 접속
- 로그인 후 원문을 볼 수 있습니다.
MARC
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■00520260202103011
■006m o d
■007cr#unu||||||||
■020 ▼a9798280747746
■035 ▼a(MiAaPQ)AAI31842667
■040 ▼aMiAaPQ▼cMiAaPQ
■0820 ▼a530
■1001 ▼aJin, Suying.▼0(orcid)0000-0001-7972-7226
■24510▼aModulational Stability of Magnetohydrodynamic Turbulence
■260 ▼a[Sl]▼bPrinceton University▼c2025
■260 1▼aAnn Arbor▼bProQuest Dissertations & Theses▼c2025
■300 ▼a139 p
■500 ▼aSource: Dissertations Abstracts International, Volume: 86-12, Section: B.
■500 ▼aAdvisor: Dodin, Ilya Y.
■5021 ▼aThesis (Ph.D.)--Princeton University, 2025.
■520 ▼aTurbulence often self-organizes to generate highly correlated coherent structures. In astrophysical contexts, this phenomenon manifests as the turbulent ("large-scale'') dynamo---the spontaneous generation of curiously coherent magnetic fields from magnetohydrodynamic (MHD) turbulence. This thesis approaches the self-organization problem by treating coherent field formation as a modulational instability (MI) of the underlying turbulence. The main product of this work is mean-field wave kinetics (MFWK)-a Wigner--Moyal-based formalism for describing the coupled evolution of coherent (or "mean'') MHD fields and the second-order correlation functions of the turbulence. This framework allows us to show that structure formation in MHD can be understood in terms of the phase-space dynamics of turbulent "quasiparticles'' self-consistently interacting via mean fields.Besides the MFWK formalism per se, the focus of the thesis is twofold: (i) Application of the MFWK formalism to the turbulent-dynamo problem, in particular, a first-principles calculation of the non-local turbulent electromotive force for generic turbulent backgrounds, and the general dispersion relation of fully coupled modulational modes of MHD (of which the standard "alpha-effect'' dynamo is a special case). This full treatment of the modulational dynamics of MHD suggests a possible new dynamo effect that arises due to flow-current alignment. (ii) An investigation of the validity of the quasilinear approximation (QLA) that underlies MFWK. Through comparisons with direct numerical simulations (DNS), we find that, although quasilinear MFWK yields quantitatively accurate predictions for MHD in some regimes, remarkably, the QLA can be qualitatively inaccurate in adjacent regimes and produces false-positives for instability.To explore the nature of such dramatic variations, we use simple nonlinear backgrounds that allow for a tractable model while retaining the infinite chain of correlations truncated by the QLA as modulational harmonics. We find that while the destabilizing drive for MI is dominated by quasilinear interactions, the modulational spectrum supports propagating spectral waves (PSWs) that ballistically transport energy towards the higher modulational harmonics neglected by the QLA, thereby providing effective dissipation. Modulational stability can therefore be understood as a balancing act between quasilinear drive and effective dissipation provided by PSWs, which persists even in the ideal-MHD limit.
■590 ▼aSchool code: 0181.
■650 4▼aPlasma physics
■650 4▼aAstrophysics
■650 4▼aFluid mechanics
■653 ▼aTurbulence
■653 ▼aMagnetohydrodynamic turbulence
■653 ▼aModulational instability
■653 ▼aMean-field wave kinetics
■653 ▼aQuasilinear approximation
■690 ▼a0759
■690 ▼a0596
■690 ▼a0204
■71020▼aPrinceton University▼bAstrophysical Sciences-Plasma Physics Program.
■7730 ▼tDissertations Abstracts International▼g86-12B.
■790 ▼a0181
■791 ▼aPh.D.
■792 ▼a2025
■793 ▼aEnglish
■85640▼uhttp://www.riss.kr/pdu/ddodLink.do?id=T17356654▼nKERIS▼z이 자료의 원문은 한국교육학술정보원에서 제공합니다.
