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Am Improvement on the Numerical Simulation of CME Event between two Streamers

Am Improvement on the Numerical Simulation of CME Event between two Streamers. YE Zhan-yin, WEI Feng-si, WANG Chi, FENG Xue-shan, and XIANG Chang-qing Chinese Astronomy and Astrophysics 28 (2004), 323-330. Plasma Seminar on 2005.1.12 Daikou Shiota. Introduction. Coronal Mass Ejection (CME ）.

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Am Improvement on the Numerical Simulation of CME Event between two Streamers

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  1. Am Improvement on the Numerical Simulation of CME Event between two Streamers YE Zhan-yin, WEI Feng-si, WANG Chi, FENG Xue-shan, and XIANG Chang-qing Chinese Astronomy and Astrophysics 28 (2004), 323-330 Plasma Seminar on 2005.1.12 Daikou Shiota

  2. Introduction Coronal Mass Ejection (CME） Typical scales Spatial scale：106~7 cm speed：102.3~3.3 cm s-1 mass：1014~16 g energy：~1032 erg SOHO/LASCO C3

  3. Observation of CMEs SMM coronagraph Many CMEs occur near coronal streamers (Hundhausen 1999)

  4. Observation of CMEs Such a scenario is simulated by Wu et. al (1995)

  5. Multi-streamer structure In the corona, there are multi streamers (Li 2000, crooker et al. 1993, and Dahlberg & Karpen 1995) There are cases where a CME occurs in the middle of the two streamers, and its evolution of CME is constrained by two streamers and propagates between the two.

  6. Model of coronal magnetic field • Li Fenglin adopted a quadrupolar potential field for calculationof a coronal field as a steady self-consistent solution. →polarities of the south and north poles are the same • a dipolar, a hexapolar or a decapolar field is assumed, the two polarity become opposite. • In this simulation, suitably combined a hexapolar and a dipolar field • the model of a CME (Wu at al. 1995)

  7. Numerical model and boundary conditions 2-D ideal MHD equations in spherical coordinates 2-D MacCormack II difference-pattern discretization, 200×200 cells

  8. Steady self-consistent corona t=27 h Two streamer density Velocity and magnetic field

  9. Triggering of CME Velocity and magnetic field (Wu at al. 1995) In this model, a flux rope is imposed on the neutral line on the inner boundary. The evolutions depend on the radius of the flux rope.

  10. CME Velocity and magnetic field

  11. Dynamic features of propagation of CME event between coronal mass ejection mistake

  12. Dynamic features of propagation of CME event between coronal mass ejection Entire: αp ~0.5, αL < 0.1 r < 5RS: αg ~0.45, αi < 0.1 5RS < r < 15RS : αg:0.45→0.18, αi: 0.1 →0.32 The structure is characterized by the equilibrium of gravitation, pressure, and fluid inertia.

  13. αp αL

  14. αp αL The front ring-shaped structure is at the position of the front turbulent waves (shock waves) in CME. The rear ring lies near the closed magnetic structure of the CME.

  15. Conclusion • The phenomenon of a CME between two coronal streamers is qualitatively simulated. The background coronal magnetic field is improved. • The results of simulation qualitatively agree with the observation. Although CME can disturb the magnetic structure of the coronal streamer, propagation is confined in the region between the streamers. • It is discovered that infront of the closed magnetic structureof the CME there exist two ring-shaped structure: the front ring corresponds to the shock wave, the rear lies near the closed magnetic structure of the CME leads to the expansion.

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