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:

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

Flare and eruptive filament Big Bear H images Flare and eruptive filament

Mauna Loa H images Original image Fixed-base difference

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

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)?

Evolution of 195 Å dimming

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

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

Multi-frequency radio fluxes EIT 304 Å observation 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

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

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

…Which would be important… 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

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