Observations of Eruptive Events with Two Radioheliographs, SSRT and NoRH V.V. Grechnev, A.M. Uralov, V.G. Zandanov, N.Y. Baranov, S.V. Lesovoi Kiyosato, October 2004 Institute of Solar-Terrestrial Physics Irkutsk, Russia

Outline Advantages of Observations with Two Radioheliographs Three Stages of Filament Eruption: – Pre-eruptive Activation – Rapid Acceleration – Self-Similar Expansion 1997/09/27: Pre-eruptive Activation of a Prominence Overlapping Fields of View SSRT & LASCO/C2: Eruption of 2001/01/ /09/04: The Whole Picture of Eruption Dual-Filament CME Initiation Model Self-Similar Expansion of CME

Siberian Solar Radio Telescope, SSRT Cross-shaped equidistant interferometer antennas, diameter of 2.5 m, stepped by 4.9 m in E–W & N–S directions (baselines of m) Frequency range 5675–5787 MHz ( = 5.2 cm) 2D imaging: full solar disk – 2 min, active region – 40 s and, simultaneously, Fast 1D mode: 14 ms/scan Angular resolution in 2D mode: 21 , in 1D mode: 15  Sensitivity: 1500 K Directly imaging telescope

Nobeyama Radioheliograph, NoRH T-shaped interferometer, 84 antennas Operating frequencies: 17 & 34 GHz Sensitivity: 400 K Angular resolution: 10  & 5  Temporal resolution: 1 s (0.1 s) Synthesizing telescope

Advantages of Observations with Two Radioheliographs Eruptive filaments/prominences are pronounced at microwaves due to their low kinetic temperature and high density. Thus, they – block brighter emission when observed on the solar disk – produce well detectable own emission when observed against the sky. Unlike long-wave (metric) radio observations, microwaves show initial stages of the eruption. Wide field of view Observational daytimes overlap Frequencies differ three times:

Observations Reveal Three Stages of Filament Eruption 1 st stage. Filament ascends very slowly with a constant velocity and does not show helical structure. 2 nd stage. Eruptive acceleration. Filament takes helical structure. Flare ribbons not yet present. 3 rd stage. Filament moves with high speed, but small acceleration. Flare ribbons appear.

1 st Stage: Pre-Eruptive Activation of a Prominence on 1997/09/27 SOHO/EIT & H 

1997/09/27: NoRH 17 GHz The whole daytime. The eruption occurred beyond observations at NoRH and SSRT.

1997/09/27: SSRT 5.7 GHz Position angle Left: not corrected Right: corrected

1997/09/27: Comparison of NoRH & SSRT Images 17 GHz and Н  images resemble each other 5.7 GHz images are similar to (17 GHz images) 0.36 :  17 < 1 around the prominence visible at 17 GHz

height, km time Results on 1997/09/27 Pre-eruptive ascension speed ~4 km/s consists with known measurements Difference of T B 5.7 and T B 17 implies that the depth of the Corona- to-Prominence Transition Region < some 100 km The prominence is surrounded by low-density material

Overlapping Fields of View SSRT & LASCO/C2: Eruption of 2001/01/14 SSRT observes the prominence up to 2R  SSRT & LASCO  : core  prominence EIT MDI Yohkoh/ SXT NoRH

2001/01/14: Observations at 5.7 & 17 GHz T QS 5.7 = 16,000 K; T QS 17 = 10,000 K Brightness temperatures of the prominence at 5.7 & 17 GHz are close

Microwaves show standard height-time plot CME’s core  eruptive prominence remains cold Pre-eruptive darkening Results on 2001/01/14

On-Disk Event of 2000/09/04 Shows the whole picture of eruption: Slow initial motion, Formation of helical structure and eruptive filament itself, Rapid acceleration, and Subsequent inertial motion and posteruptive flare

2000/09/04: SSRT Observations Filament eruption Microwave flare emission is thermal

2000/09/04: SSRT & NoRH

2000/09/04: SOHO/EIT 195 Å Helical structure of the filament CME’s Frontal Structure (Leading Edge)

Dual-Filament CME Initiation Model Uralov, Lesovoi, Zandanov & Grechnev 2002, Solar Phys., 208, 69

filament consists of  2 segments backbone magnetic field connects the segments filament expansion is prevented by (a) filament barbs (b) overlying coronal arcades. Three driving factors lead to MHD instability 1.Slow reconnection of segments  increase of magnetic moment of backbone field flux  its slow expansion (similar to Tether Cutting model). However, the filament can only rise up to a certain height if preventing factors (a) & (b) are conserved. Dual-Filament CME Initiation Model

2. Lengthening and reconnection of the filament barbs  barbs tear off  form internal helical structure (negative) and eruptive filament itself.  Lifting force (similar to Flux Rope model). Preventing factor ( a) transforms into expansion supporter. 3. If the 1 st and 2 nd lifting forces are sufficient to extend overlying arcades, then reconnection starts below the filament in accordance with the classical scheme: external helical structure (positive) appears and grows, and lifting force increases. Preventing factor ( b) transforms into expansion supporter. Dual-Filament CME Initiation Model

Self-Similar Expansion of CME 1 : frontal structure (leading edge) 2: core (prominence) Self-similarity with  = 2.45 Uralov & Grechnev, 2004, IAUS 223

Self-Similar Expansion of CME V p   500 km/s V fs   1260 km/s R p0  85 Mm R fs0  210 Mm a p0  1.5 km/s 2 a fs0  3.8 km/s 2  = 2.45 Uralov & Grechnev, 2004, IAUS 223

Results on 2000/09/04 Helical structure inside eruptive filament appears when acceleration is maximal CME’s frontal structure: – Maximum acceleration ~km/s -2, – Initial position: ~100 Mm above the pre-eruptive filament Eruptive filament remains cool CME spends almost ½ of its start energy to overcome gravity CME initiation scenario is proposed

Acknowledgments We thank – Nobeyama Solar Group for the opportunity to participate this meeting and the hospitality – NoRH, Yohkoh, SOHO/EIT & LASCO teams for data used – Russian Foundation of Basic Research (grant ) – Ministry of Education & Science (grant NSh )