NBYM 2006

A large-scale darkening observed in EUV and radio

emissions

V. Grechnev, A. Uralov, I. Kuzmenko, I. Chertok et

al.

SOHO/EIT 304 ÅBefore, during, and after

2004 July 13

SOHO/EIT 195 Å & LASCO/C2

SOHO telescopes show an eruptive event:

TRACE 171 Å 00:07:5

200:13:37

00:16:50

00:19:42

00:21:36

00:48:08

Big Bear H images

Flare and eruptive filament

Mauna Loa H imagesOriginal 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

304 ÅProbable causes of large darkening in HeII 304 Å

1. Dimming due to density depletion? – Usually well observed in 195 Å

2. 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

Density-depletion 195 Å dimming lives much longer

Configuration quite different Not a density-depletion dimming

Min{Images} Images[0] Min{Images}/ Images[0]

304 Å

195 195 ÅÅ

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 Åobservation

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

Symbols: observed Solid: calculated

considering the ejecta and corona above it

Ejected mass (6–9)·1015 g with depth = (20–200) Mm

, GHz

AreaEIT304=0.067

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

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