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Spectral Signature of Emergent Magnetic Flux

Spectral Signature of Emergent Magnetic Flux. Balasubramaniam,K.S., 2001, ApJ, 557, 366. Chae, J. et al., 2000, ApJ, 528, L119. D1 神尾 精 Solar Seminar 2003.05.19. Overview. Spectroheliogram in Ca II K line and vector magnetic field data are studied in detail.

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Spectral Signature of Emergent Magnetic Flux

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  1. Spectral Signature of Emergent Magnetic Flux Balasubramaniam,K.S., 2001, ApJ, 557, 366. Chae, J. et al., 2000, ApJ, 528, L119. D1 神尾 精 Solar Seminar 2003.05.19

  2. Overview • Spectroheliogram in Ca II K line and vector magnetic field data are studied in detail. • Ca II K spectral line anomalies are found at the location of small-scale magnetic flux emerging through the chromosphere. Balasubramaniam,K.S., 2001, ApJ, 557, 366.

  3. Ca II Line Profile 1Å • Typical line profile shows 5 reversals • Enhanced K2 emission and red asymmetry in the impulsive phase of flares (Fang et al.1992) • Observation in active regions suggest magnetic field influences the line profile (Martinez et al. 1990) K2V K2R K3 K1V K1R λ

  4. Transition Region Line • Enhanced emission or broadening of UV lines are correlated with magnetic field (Dere et al. 1989) • Broadening is caused by acceleration of plasma away from the heating site eg microflare (Linsky et al. 1995)

  5. Observation • 1995 Aug 5AR 7896 near disk center • SpectorgraphRBDST at Sacramento Peak/NSO7.3Å band centered on Ca II K linePixel size: 0”.258 x 0.018Å23 min x 5 scans = 115 min • Stokes Vector PolarimeterASP at High Altitude Observatory/NSOFe I 6301.5Å and 6302.5Å

  6. Anomalous Profile • 3 or 5 reversals Normal • Others Anomalous Separation of additional component from the line center is -16～50 km/s. Some profiles do not show recognizable K2 or K3 components. Anomalous

  7. Broadened Profile • 3Å is much wider than the normal width of 1Å. • Size of anomalous or broadened features are1～2". 1" 3Å

  8. Distribution of Anomaly • Anomalous profiles are found at the edge of strong magnetic field regions.

  9. Temporal Variation • Increase of magnetic flux indicates the emergent magnetic flux. • Anomalous profiles are found in these regions 0 +23 +46 +69 min

  10. Spectral Images • Anomalous profiles appear at the emergent flux regions. • Duration of anomalous profile is longer than 2 scans or 46 min.

  11. Discussion • Anomalous profiles are caused by summation of several Doppler shifted profiles whose velocities range from -16 to 50 km/s. • It suggests the existence of localized flow in the emergent flux. • Enhanced emission of K line is most likely a response to heating.

  12. Discussion (cont.) • One possible explanation of heating is the shock caused by supersonic flow of plasma. • Broadening of line profile can be interpreted as microturbulence due to magnetic reconnection, same as transition region explosive events. • Dynamic model of multi component atmosphere is necessary to explain these line profiles.

  13. UV/EUV Brightening • Blinkers(γ)Profiles with enhanced wing, little broadening • Explosive events(α)Broad spectral profiles indicate the presence of high velocity plasmas. Chae, J. et al., 2000, ApJ, 528, L119.

  14. Observation • 1997 Apr 26 16:00-20:30 UT • SOHO/CDS obtained 3 scans of 244” x 240” area.He I, O V, and Mg IX • SOHO/SUMER is fixed so that the slit scans the area of 120” x 43” by solar rotation.Si IV

  15. Short-lived brightening • Blinker consists of many small scale short lived berightening events. • Duration and size of typical unit brightening events are 2-3 min and 3”-5”.

  16. Discussion Explosive events • Explosive events and blinkers are caused by different magnetic reconnection geometries. • Reconnection produces bidirectional flow, which appear as broadened profiles. Blinkers

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