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A large-scale darkening observed in EUV and radio emissions

A large-scale darkening observed in EUV and radio emissions. V. Grechnev, A. Uralov, I. Kuzmenko, I. Chertok et al. SOHO/EIT 304 Å. Before, during, and after. 2004 July 13. SOHO/EIT 195 Å & LASCO/C2. SOHO telescopes show an eruptive event:. 00:16:50. 00:48:08. 00:07:52. 00:19:42.

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A large-scale darkening observed in EUV and radio emissions

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  1. A large-scale darkening observed in EUV and radio emissions V. Grechnev, A. Uralov, I. Kuzmenko, I. Chertok et al.

  2. SOHO/EIT 304 Å Before, during, and after 2004 July 13

  3. SOHO/EIT 195 Å & LASCO/C2 • SOHO telescopes show an eruptive event:

  4. 00:16:50 00:48:08 00:07:52 00:19:42 00:13:37 00:21:36 TRACE 171 Å

  5. Big Bear H images Flare and eruptive filament

  6. Mauna Loa H images Original image Fixed-base difference

  7. 2004 July 13 event: • GOES M6.7 in AR 10646 (N15W49) • Very impulsive microwave burst • Flux 1200 sfu @ 17 GHz • Duration ~10 min • H flare not reported by patrol stations • but Big Bear images show it • Filament eruption and CME

  8. 304 Å Probable causes of large darkening in HeII 304 Å • Dimming due to density depletion? – Usually well observed in 195 Å • Occultation by absorbing material: • resonant absorption in cooler HeII (<50000 K)? • non-resonant absorption in H (<10000 K)?

  9. Evolution of 195 Å dimming

  10. 304 Å 195 Å Summary on 195 Å dimming • Density-depletion 195 Å dimming lives much longer • Configuration quite different •  Not a density-depletion dimming Min{Images} Images[0] Min{Images}/ Images[0]

  11. NoRH shows • Ejected material: • First bright on the disk • Then bright above the limb, and dark on the disk • Dark moving feature is not large • Ejecta is inhomogeneous

  12. EIT 304 Å observation Multi-frequency radio fluxes • NoRP & Ussuriysk 2.8 GHz • Solid: observed • Dotted: thermal emission of flare subtracted • Normalized to the quiet sun’s level • Absorption  • TFil < TQS 3.75 = 23,000 K

  13. AreaEIT304=0.067 , GHz Frequency dependence of radio absorption • Symbols: observed • Solid: calculated considering the ejecta and corona above it  Ejected mass  (6–9)·1015 g with depth = (20–200) Mm

  14. Epilogue-I • The phenomenon was due to occultation of the quiet sun rather than an active region • This unique event was revealed from EIT 304 Å data and independently from Ussuriysk 10.7 cm records • It was possible to detect it from total flux radio records thanks to shortness of the main burst

  15. Epilogue-II • Murphy’s Low works perfectly: • No SSRT 5.7 GHz data • No high-cadence CORONAS-F/SPIRIT 304 Å data …Which would be important… • Nevertheless, non-imaging multi-frequency total flux records allowed us to study the event

  16. We acknowledge • Shibasaki San and NSRO for the opportunity to work here under perfect conditions • Staff members of the NSRO for the hospitality

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