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Observations of Moreton waves with Solar-B

The 4 th Solar-B Science Meeting Recent Advances in Solar Physics and Solar-B February 3-5, 2003. Observations of Moreton waves with Solar-B. NARUKAGE Noriyuki Department of Astronomy, Kyoto Univ / Kwasan and Hida Observatories M2. Moreton wave is ….

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Observations of Moreton waves with Solar-B

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  1. The 4thSolar-B Science MeetingRecent Advances in Solar Physics and Solar-BFebruary 3-5, 2003 Observations of Moreton waveswith Solar-B NARUKAGE Noriyuki Department of Astronomy, Kyoto Univ / Kwasan and Hida Observatories M2

  2. Moreton wave is … • flare-associated wave observed to propagate across the solar disk in Ha, especially in the wing of Ha (Moreton, 1960, 1961). • propagate in somewhat restricted angle at the speed of 500 ~ 1500 km/s with arc-like fronts. • identified as the intersections of a coronal MHD fast shock front and the chromosphere (Uchida, 1968, 1970). • At Hida Observatory, more than 10 Moreton waves have been observed. And they were associated with about 10% of X or M-class flares.

  3. Moreton wave 1997/11/04 Eto et al., 2002 solar Flare Monitor Telescope (FMT)Hida Obserbatory, Kyoto Univ. The FMT observes four full disk images, in Ha (linecenter and ＋/－ 0.8 Å) and continuum, and one solar limb image in Ha center.

  4. Uchida model (1968) flare site shock front Moreton wave X-ray wave,coronal counterpart of Moreton wave solar disk

  5. Introduction Observation of flare waves with Solar-B SOT : chromospheric Moreton waves XRT : main topiccoronal X-ray waves EIS :line-of-sight velocity of waves

  6. Observable region of flare waves Flare waves usually become visibleonly at a distance of more than100,000 km fromthe flare site. Some flare wavescan propagateup to distance exceeding 500,000 km. Moreton wave & X-ray wave Observable region of flare waves flare site solar disk

  7. SOT The field of view is too small to observe the propagation of waves. We expect todetect the originof Moreton waves. Solar Optical Telescope Observable region of flare waves flare site 164” x 328”

  8. X-ray wave 1997/11/03 Narukage et al., 2002 Yohkoh / SXT[Soft X-ray] Quarter resolution Half resolution Hida obs / FMT [Ha+0.8Å] Running difference

  9. Advantage of Yohkoh / SXT Using Yohkoh / SXT images, we can estimate the quantities of the X-ray wave.

  10. Is the X-ray wave a MHD fast shock? BEHIND AHEAD Shock front IX2 T2 B2 θ2 v2 IX1 T1 B1 θ1 v1 Using MHD Eq. (1)--(7), the quantitiesahead of the shock (IX1,T1,B1,θ1,v1) determine those behind (IX2,T2,B2,θ2,v2).

  11. Is the X-ray wave a MHD fast shock? In other words, if we know (IX1,T1,B1,θ1,IX2), we can find (v1,T2,B2,θ2,v2). observed parameter IX1Yohkoh / SXT T1= 2.25±0.25 MK(thin Al & AlMg) B1= 1/2 or 1/3 Bp1 (SOHO / MDI) θ1= 90° or 60° (parameter) IX2Yohkoh / SXT BEHIND AHEAD Shock front IX2 T2 B2 θ2 v2 IX1 T1 B1 θ1 v1

  12. Is the X-ray wave a MHD fast shock? Using this method, we can estimate the quantities of the X-ray wave. e.g.The estimated fast shock speed is 400 ~ 760 km/s,which is roughly agreement withthe observed propagation speed of the X-ray wave, 630 km/s. The fast mode Mach number is 1.15 ~ 1.25. These results suggest that the X-ray wave is an MHD fast shock propagating through the corona and hence is the coronal counterpart of the Moreton wave. Narukage et al. 2002, ApJ Letters 572, 109

  13. Solar-B Using this method, we can examinehow X-ray waves are observed with Solar-B / XRT (and EIS).

  14. XRT – field of view The observationsof X-ray waves require the field of view as larger than 512” x 512”. X-Ray Telescope Observable region of flare waves flare site 512” x 512” 1024” x 1024”

  15. XRT – cadence & pixel size X-Ray Telescope • The propagation speeds ofX-ray wave are 500 ~ 1500 km/s. • The thickness of the wave is about 20,000 km. • We can observe forless than 270 ~ 800 sec.The observation needs as high cadence as possible (= 2 sec). • The pixel size should be smaller than 4” x 4”. BEHINDIx2 AHEADIx1

  16. XRT – filter X-Ray Telescope XRT has 9 filters.

  17. XRT – filter selection X-Ray Telescope • To recognize the shockagainst the background,the intensity ratio (=Ix2 / Ix1)should be larger than 3.(e.g. In case of my Yohkoh X-ray wave, Ix2 / Ix1 = 3.27) BEHINDIx2 AHEADIx1 • I select the suitable filters for X-ray waves.

  18. XRT – filter selection I calculate the XRT intensities (Ix1 and Ix2)and their ratios, using my result of Yohkoh X-ray wave. These filters satisfy the condition (Ix2 / Ix1 > 3). Considering the intensity ratio and sensitivity, the best filter is Thin Be.

  19. XRT – exposure time X-Ray Telescope • I examine the enough exposure time ( t )to suppress the effect of photon noise. (Ix2 – Ix1) t > 3s(t) s(t) = (5 Ix1 t) ^ 0.5 : dispersion of Ix1 Ix [DN / sec / pixel]

  20. XRT – exposure time X-Ray Telescope For highest cadence, the exposure time should be shorter than 2 sec.

  21. observational plan for X-ray waves • note : The influence of flare-loop brightness is not considered. • Question : When XRT is operated in flare-mode, are these exposure times safe?

  22. XRT – Discussion X-Ray Telescope • If the X-ray wave frequency is the same as Moreton waves, X-ray waves would occur associated with 10% of X or M-class flares. • If the flare frequency is the same as 11 years before, until 2009 there would be only a few X-ray waves per year. (This is underestimation.) • Good observational plan is very important.

  23. XRT – Conclusion X-Ray Telescope • XRT is the best telescope forX-ray wave (coronal shock wave). • When filter selection for flare-mode is discussed, the detectability of X-ray wave should be considered.

  24. EIS From my analysis, we can estimate the coronal plasma velocity just behind the Moreton wave (fast-mode MHD shock), v1-v2, to be about 100-200 km/s, which would be observed at 50-100 km/s along the line-of-sight with Solar B / EIS. EUV Imaging Spectrometer BEHIND AHEAD

  25. END Thank you very much for your attention.

  26. Simultaneous observation 1997/11/03

  27. Simultaneous observation 1997/11/03 EIT wave : 170 km/s start 04:32 / peak 04:38 AR8100 – S20, W13 GOES-C8.6 Moreton wave : 490±40 km/sX-ray wave : 630±100 km/s

  28. Moreton & X-ray wave 1997/11/03 start 04:32 / peak 04:38 AR8100 – S20, W13 GOES-C8.6

  29. EIT wave 1997/11/03 start 04:32 / peak 04:38 AR8100 – S20, W13 GOES-C8.6

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