observations of eruptive events with two radioheliographs, ssrt and norh

Observations of Observations of Eruptive Events with Eruptive Events with

Two Radioheliographs, Two Radioheliographs, SSRT and NoRHSSRT 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

OutlineOutline 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 2001/01/14 2000/09/04: The Whole Picture of Eruption Dual-Filament CME Initiation Model Self-Similar Expansion of CME

Siberian Solar Radio Telescope, Siberian Solar Radio Telescope, SSRTSSRT

Cross-shaped equidistant interferometer 128 + 128 antennas, diameter of 2.5 m, stepped by 4.9 m in E–W & N–S directions (baselines of 622.3 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, Nobeyama Radioheliograph, NoRHNoRH

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 Advantages of Observations with Two RadioheliographsTwo 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: 2/32

2

T

Lne

Observations RevealObservations Reveal

Three Stages of Filament EruptionThree Stages of Filament Eruption

1st stage. Filament ascends very slowly with a constant velocity and does not show helical structure.

2nd stage. Eruptive acceleration. Filament takes helical structure. Flare ribbons not yet present.

3rd stage. Filament moves with high speed, but small acceleration. Flare ribbons appear.

11stst Stage: Pre-Eruptive Activation of a Stage: Pre-Eruptive Activation of a Prominence on 19Prominence on 199797/09//09/2727

SOHOSOHO/EIT /EIT && HH

19199797/09//09/2727: NoRH Observations : NoRH Observations @ 17 GHz@ 17 GHz

The whole daytime. The eruption occurred beyond observations at NoRH and SSRT.

19199797/09//09/2727: SSRT Observations : SSRT Observations @ 5.7 GHz@ 5.7 GHzPosition angle

Left: not corrected Right: corrected

19199797/09//09/2727: Comparison of : Comparison of NoRH & SSRT ImagesNoRH & 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 19Results on 199797/09//09/2727 Pre-eruptive ascension speed ~4 km/s consists with known

measurements

Difference of TB 5.7 and TB 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 & Overlapping Fields of View SSRT & LASCO/C2: Eruption of 2001/01/LASCO/C2: Eruption of 2001/01/1414

SSRT observes the prominence up to 2R

SSRT & LASCO : core prominence

EIT

MDI

Yohkoh/SXT

NoRH

NoRH

2001/01/2001/01/1414: Observations at : Observations at 5.7 & 17 GHz5.7 & 17 GHz

TQS 5.7 = 16,000 K; TQS 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/Results on 2001/01/1414

On-Disk Event of 2000/09/04On-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, andSubsequent inertial motion and posteruptive flare

2000/09/04: SSRT Observations2000/09/04: SSRT Observations Filament eruption Microwave flare emission is thermal

2000/09/04: SSRT & NoRH2000/09/04: SSRT & NoRH

2000/09/04: SOHO/EIT 195 2000/09/04: SOHO/EIT 195 ÅÅHelical structure of

the filament

CME’s Frontal Structure

(Leading Edge)

Dual-Filament CME Initiation ModelDual-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 ModelDual-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 1st and 2nd 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 ModelDual-Filament CME Initiation Model

Self-Similar Expansion of CMESelf-Similar Expansion of CME

1: frontal structure

(leading edge)

2: core (prominence)

Self-similarity with = 2.45

Uralov & Grechnev, 2004, IAUS 223

r

Rvv 01

Self-Similar Expansion of CMESelf-Similar Expansion of CME

Vp 500 km/s

Vfs 1260 km/s

Rp0 85 Mm

Rfs0 210 Mm

ap0 1.5 km/s2

afs0 3.8 km/s2

= 2.45Uralov & Grechnev, 2004, IAUS 223

Results on 2000/09/04Results 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

filamentEruptive filament remains coolCME spends almost ½ of its start energy to

overcome gravityCME initiation scenario is proposed

AcknowledgmentsAcknowledgments

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 03-02-16591)

– Ministry of Education & Science (grant NSh-477.2003.2)