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Sunspot Oscillations from the Chromosphere to the Corona

Sunspot Oscillations from the Chromosphere to the Corona. N. Brynildsen, P. Maltby, T. Fredvik, O. Kjeldseth-Moe Institute for Theoretical Astrophysics, Univ. Oslo. Introduction.

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Sunspot Oscillations from the Chromosphere to the Corona

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  1. Sunspot Oscillations from the Chromosphere to the Corona N. Brynildsen, P. Maltby, T. Fredvik, O. Kjeldseth-Moe Institute for Theoretical Astrophysics, Univ. Oslo

  2. Introduction • Dominant peak in oscillatory power at periods around 3 minutes is seen in the CO2 band at 4.66 micrometer, i.e. cold regions • Oscillations (3 min) continue through the chromosphere and transition region • Penetration of oscillations to the corona from observations with TRACE

  3. Observations • Joint observing between CDS, on SOHO and TRACE • Normal and Grazing Incidence Spectro-meter(s) on CDS, (NIS/GIS) are both used • Using the 171 Å channel on TRACE • CDS/GIS for estimate of contributions in the TRACE 171 Å channel from coronal and transition region lines, respectively,

  4. Oscillations occur above the umbra

  5. Amplitude with temperature

  6. Deviations from linear oscillations

  7. Oscillations observed with NIS

  8. Oscillations observed with GIS

  9. Sunspot chromosphere resonator

  10. Oscillations in the corona • Introduction: Penetration of oscillations to the corona from observations with TRACE, i.e. Fe IX and Fe X, 630 000 K to 1 MK • From GIS observations: Oscillations ”lost” before they reach the temperature level of Ne VIII or Fe IX, i.e. 630 000 K • Is this a contradiction??

  11. Sensitivity response of TRACE 171 Å (or 173 Å) channel

  12. Spectrum in TRACE 171 Channel

  13. TRACE Oscillations

  14. Summary • Oscillations occur in the transition region above the umbra and covers the umbra • Amplitudes largest at 200 000 K, samller at lower and higher temperature values • Deviations from pure linear oscillations are present

  15. Summary (cont) • Power spectra are similar in the chromo-sphere and through the transition region • This disagrees with the sunspot filter theory • Oscillations penetrates to the corona • In the corona they are channeled into smaller areas, coinciding with the endpoints of coronal loops

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