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Dynamics of the polar off-limb regions

Dynamics of the polar off-limb regions. D. Banerjee Indian Institute of Astrophysics E.O’Shea & J.G. Doyle ( Armagh Observatory ). Motivation. Coronal Holes (CH)  Source region of the Fast Solar Wind. Spectroscopic observations:. (Doyle, Teriaca, Banerjee, 1999). Observational log:.

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Dynamics of the polar off-limb regions

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  1. Dynamics of the polar off-limb regions D. Banerjee Indian Institute of Astrophysics E.O’Shea & J.G. Doyle (Armagh Observatory)

  2. Motivation Coronal Holes (CH)  Source region of the Fast Solar Wind

  3. Spectroscopic observations:

  4. (Doyle, Teriaca, Banerjee, 1999)

  5. Observational log: • Coronal Diagnostic spectrometer (CDS/SoHO) • Long temporal series sequence for 11 TR and coronal lines formed between 2.5 x 105 to 2.5 x 106 K. • We will present only results from coronal lines Mg x 609,625 Å • Slit width 4 x 240 arc sec • Exposure time 60 sec

  6. Using measurements of Mg x 609 & 624 lines, we seek to find evidence of line width decrease far-off limb –Can they be due to wave dissipation??

  7. Variatiation of Dopler width with radial distance

  8. Coronal hole diagnostics upto 8 solar radii

  9. Concluding remarks: Above 1150 arc sec, the ratio of the two Mg X lines reduces To values that we might expect for a radiatively dominant Excitation mode A Comparison shows that the decrease in line widths happens around the same heights where the dominant excitation changes from collisional to radiative. This should further correspond to sudden drop in electron Density. The reported decrease in line widths in coronal ions at large Altitudes off-limb may not simply related to wave dissipation!!

  10. Let us turn our attention to something else: Namely, dynamic events close to the limb Dynamic activity at the limb Macrospicule?? Location of the limb

  11. Space-time (X-T) plots of the radiant flux for the s26438 dataset We suggest that the decrease in flux is evidence of a localized evacuation of plasma

  12. S26406 dataset, px18 The combination of evidence of evacuated and blue-shifted Plasma indicates presence of dyanamic event...

  13. What is a blinker? Sudden enhancement is flux observed in transition region lines Observed with CDS (Harrison 1997) Preferentially occuring near network boundaries above regions of strong unipolar magnetic field Blinkers may be on-disk signature of spicule?? Explosive events and blinkers are separate phenomenon

  14. Summary: Evacuation event, linked to the reconnection process are Observed as dramatic reduction in intensity flux in OV and Mg X lines. Following the recipe for identifying for blinkers, as outlined By Brkovic et al (2001), we can say blinkers are present off-limb Blinkers are occuring above regions of dynamic activity, That produces evacuation events and quasi-periodic oscillations

  15. Summary Signatures of up-flow of plasma in spicule like event, resulting in brightenings and blue-shifts followed by falling back of this plasma under gravity, resulting in corresponding Red-shift We suggest that the blinkers are signatures of macro-spicules Present at the temperature of the OV line

  16. Blinker

  17. Explosive Event:

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