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08/24/12:北京大学Kavli天文与天体物理所闫慧荣教授学术报告

题目: Cosmic Ray Transport and acceleration in Magnetohydrodynamic Turbulence
报告人: 北京大学Kavli天文与天体物理所闫慧荣教授
时间: 2012年8月24日(周五)下午3:00-4:50
地点: 科学实验楼报告厅
内容简介: Recent advances in MHD turbulence call for revisions in the paradigm of
cosmic ray transport. We use the models of magnetohydrodynamic turbulence that were
tested in numerical simulation, in which turbulence is injected at large scale and cascades
to small scales. I shall discuss both the transport and acceleration of CRs, and demonstrate
that compressible fast modes dominate the interactions. Implications for solar flares will be
provided. I shall address the issue of perpendicular to the magnetic field and show that the
concept of cosmic ray subdiffusion is only important for restricted cases when the ambient
turbulence is far from that suggested by numerical simulations and on small scales, it is
actually superdiffusive. Then I'll discuss the feedback of cosmic rays on turbulence
through gyroresonance instability. If time is allowed, I shall also present our recent results
on the acceleration and propagation of cosmic rays in the vicinity of supernova remnants.

报告人简介:
Professor Huirong Yan is a theoretical astrophysicist with interest both in fundamental
astrophysical processes and in relating her work to observations. She graduated on
Astrophysics in 1998 from Peking University, obtained her Master degree on Astronomy
from the University of Wisconsin-Madison (USA) in 2002. There, Professor Yan also got
her PhD on Astronomy in 2005.
Her research experience began during her doctoral in the year of 2000 in the University of
Wisconsin-Madison. Then she was working as independent postdoctoral fellow at
Canadian Institute of Theoretical Astrophysics, University of Arizona, respectively, after a
one year pre-doctoral stay at Stanford University. Starting from 2009, she is a faculty
member at Kavli Institute of Astronomy and Astrophysics in Peking U.
Her research encompasses a wide variety of topics related to the particle acceleration and
interaction with magnetohydrodynamic (MHD) turbulence, as well as plasma instabilities,
high energy astrophysics. Huirong Yan's interests also include technique of studying
astrophysical magnetic field. Her major contribution can be briefly summarized as below:
• advancing the theory of cosmic ray transport and acceleration in tested model of
turbulence. Predicting the super-diffusive transport on small scales, quantifying the
feedback of cosmic rays on turbulence through kinetic instability, application of the results
to supernova remnants and solar flares;
• identifying new diagnostics for astrophysical magnetic field based on alignment of atoms
and ions on their ground states, opening a new window for direct detection of 3D magnetic
field in all diffuse medium from the interplanetary medium to early universe, making
predictions for polarization of multiple atomic species and lines ranging from far infrared
(FIR) to ultraviolet (UV) arising from the ground state alignment.
• proposing new acceleration mechanism for dust grains, demonstrating that turbulence
dominates the dynamics of dust grains, applying the model to the grain size distribution
and extinctions in both galactic and extragalactic environments.