Observations of Eruptive Events with Two Radioheliographs, SSRT and NoRH
description
Transcript of 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)