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  • Coronal radio emission at 2-3 solar radii a new type of narrow-band bursts

     

    Seminar Title  

    Coronal radio emission at 2-3 solar radii a new type of narrow-band bursts

       
    Speaker:   Prof. Y. Voitenko
       

     Affiliation:    

    ( Solar-Terrestrial Center of Excellence, BIRA-IASB, Brussels, Belgium )  

       
    When Friday morning , Aug. 19 , 10:00 a.m
       

    Where:   

    Room 317, Office Block, 2 West Beijing Road (PMO, CAS)
     

                             Welcome to Attend   

     
      ( PMO Academic Committee & Academic Circulating committee)
     

       Abstract:  I will discuss properties and possible emission mechanisms of narrow-band radio bursts discovered recently by world-largest Ukrainian radio telescopes UTR-2 and URAN-2. The burst frequencies 15-30 MHz and frequency drift rates 50-150 kHz/s imply emission sources propagating with near-Alfvén velocities at heliocentric distances 2-3 solar radii. Hence we will call them Alfvén-velocity (AV) bursts. AV bursts are associated with solar flares and coronal mass ejections, and occur simultaneously with or immediately after type III bursts. We propose a new generation mechanism for AV bursts elaborating properties of kinetic Alfvén waves (KAWs). KAWs can be excited by magnetic reconnection in the low corona and propagate upward generating local fluctuations of the plasma density. The KAW density cavities trap and accumulate Langmuir waves excited by electron beams. Enhanced Langmuir waves are progressively released in the course of upward KAW propagation and generate AV radio bursts by the plasma emission mechanism. KAWs with reasonable magnetic amplitudes about 0.03 of the background magnetic field and perpendicular wavelengths about 2-3 ion gyroradii provide a feasible explanation for observed AV bursts. These results can be used for remote diagnostics of the coronal plasma and waves during solar flares and CMEs.  

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