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Radio Emission from acceleration sites of the solar flares

PHYS 777 Plasma Physics and Magnetohydrodynamics (MHD) Instructor: Gregory Fleishman. Radio Emission from acceleration sites of the solar flares. Yixuan Li. motivation. There are various acceleration models of solar flares which imply the different radio spectra and light curves.

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Radio Emission from acceleration sites of the solar flares

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  1. PHYS 777 Plasma Physics and Magnetohydrodynamics (MHD) Instructor: Gregory Fleishman Radio Emission from acceleration sites of the solar flares Yixuan Li

  2. motivation • There are various acceleration models of solar flares which imply the different radio spectra and light curves. • We calculate the radio emission in DSR (Diffusive Synchrotron Radiation) and GSR (Gyro-synchrotron Radiation) models to make them observationally distinguishable.

  3. Cartoon of a flare model suggesting a global view of acceleration and evaporation processes. The acceleration site is located in a low-density cusp from where electron beams are accelerated in upward and downward directions.

  4. Diffusive Synchrotron Radiation The electron is trapped by the turbulence on the flare loop-top.

  5. Derived under isotropic random magnetic field and non-relativistic particles.

  6. Some properties of the acceleration site • the size of the site ; • the electron number density ; • the electron temperature ; • the energy density of the magnetic turbulence ; • the power law index δ changing as arctan function from 7 ∼ 3 the break energy Ebr linearly increased from 50 ∼500KeV

  7. The electron distribution remains a Maxwellian distribution when energy is smaller than E0 and a nonthermal electron tail begins to form as power law distribution when energy is larger than E0 ,here E0=4KT.

  8. Radio Power The DSR radiation power in different δ under three different ν. The blue curves indicate larger δ, while the red ones show smaller δ.

  9. Flux observed on the Earth here

  10. The DSR spectra in different temperatures

  11. Gyro-synchrotron Radiation Fig. on left. Formation of contracting magnetic traps in the solar corona during a flare. (a) The magnetic field configuration: the reconnection region (RR) is located above the closed magnetic field loops that rest on the chromospheres (CHR). (b) The schematic view of a magnetic trap.

  12. The number of electrons in a trap Bm : the magnetic field strength at the footpoint.

  13. The initial condition We assume the initial condition as follow: (a) the magnetic field strength B = 30G; (b) the minimum energy Emin = 0.01MeV, the maximum energy Emax = 1MeV; (c) the thermal electron density the non-thermal electron density ; (d) the source size .

  14. The upper panel: the spectra in frequency range 1GHz~100GHz ; The lower panel: the spectra in frequency range 0.1GHz~10GHz Klein’s Computation Code for GSR is used.

  15. The light curves of the emission at some fixed frequencies

  16. Discussion • Synchrotron emission: The emission comes in narrow pulses at the cyclotron frequency, beamed along the direction of motion.  The pulses contain many harmonics.  • Gyro-synchrotron emission: The lines become broader ,so that they blend together into a continuum emission. 

  17. Thank you !

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