主持人：刘四明 教授

时间：2022年10月15日（周六）19：00

ZOOM 会议号: 85494133228

题目：Magnetic field and electron density turbulence spectra in the local interstellar medium in-situ measured by Voyager spacecraft

主讲人： Professor Lou-Chuang Lee （李羅權）

Institute of Earth Sciences, Academia Sinica, Taipei, Taiwan

    Professor Lou-Chuang Lee received Ph.D. degree from the California Institute of Technology in 1975. He performed research and teaching at the NASA/Goddard Space Flight Center, University of Maryland, University of Alaska, National Cheng Kung University, National Central University and Academia Sinica. He served as Director of National Space Program Office, the first President of the National Applied Research Laboratories, the President of National Central University and the Minister of National Science Council.

Prof. Lee has published more than 300 scientific papers as well as three academic monographs. During his career, Prof. Lee developed several new theories to explain observed space phenomena. His major research achievements include: (a)Proposed in 1976 that the interstellar medium has a Kolmogorov turbulence spectrum based on scintillation data, (b) the electron cyclotron maser theory for the generation of auroral kilometric radiation, (c) the multiple X-line reconnection(MXR) model for magnetic flux transfer events, (d) the formation mechanism of solar prominences, (e) a new mechanism for solar coronal heating, and (f) the discovery of "gigantic jets" in the Earth’s upper atmosphere.

Prof. Lee has received many awards, including the Fullbright Scholar Award, the Presidential Science Prize (The highest honor in science in Taiwan), Subramanyan Chandrasekhar Prize of Plasma Physics. Prof. Lee is an Academician of Academia Sinica(AS), elected member of The World Academy of Sciences (TWAS), and elected foreign member of the US National Academy of Engineering (NAE).

Abstract：We present the turbulence spectra of magnetic and electron density fluctuations in-situ measured by Voyager 1 in the local interstellar medium from 2012 to 2019. The magnetic spectrum shows a Kolmogorov power law with a one-dimensional power law index -5/3 at k10^-8.8m^-1 , where k is a wavenumber and m is the unit meter. On the other hand, the electron density spectrum also shows a Kolmogorov power law with a one-dimensional power law index -5/3 in the inertial range. Based on the observational data, the relations between the outer scale of the turbulent system and the powers of electron density and magnetic fluctuations are obtained. We then calculate the spectra locally for six individual time periods, within which the electron density and magnetic fluctuations are simultaneously observed. It is found that the power of perpendicular magnetic fluctuations is usually higher than that of parallel magnetic fluctuations, indicating the dominance of Alfvén waves in turbulence spectrum. Part of the observed turbulence spectra reveal that the normalized parallel magnetic power exhibits a much higher intensity than the normalized electron density power in the local interstellar medium of low to moderate plasma beta (0.1-0.8). Such dominance in the parallel magnetic power cannot be explained by the linear magnetohydrodynamic modes alone and may be associated with the arc/spherically polarized Alfvén mode. The first satellite observation of arc/spherically polarized Alfvén wave in the interstellar medium will be presented.