Observations of quiet solar features with the

SSRT and NoRH

V.V. Grechnev & SSRT team

Institute of Solar-Terrestrial Physics,

Irkutsk, Russia

Relatively

Observations of quiet solar features with the

SSRT and NoRH

V.V. Grechnev & SSRT team

Institute of Solar-Terrestrial Physics,

Irkutsk, Russia

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Outline

Advantages of Observations with Two Radioheliographs

Filaments & Prominences Coronal Holes Coronal Bright Points Coronal Arcades Magnetic Field Measurements Importance of Observations with

two Radioheliographs

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

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Siberian Solar Radio Telescope, SSRT 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

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Advantages of Observations with Two Radioheliographs

Two-frequency observations:~10 times different optical thickness

Overlapping in time Different imaging principles Despite of relatively poor spatial

resolution…

2/32

2

T

Lne

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SSRT & NoRH Images Compared with Other Observations

October 6, 1997

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Filaments & Prominences

F F F

F F F

October 6, 1997

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October 6, 1997

CBP CBP CBP

CBP CBP CBP

Coronal Bright Points

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1996/06/03

5.7 GHz, 02:09

17 GHz, 02:08

SXR, 02:08

Coronal Bright Points

Coronal Bright Points at 1.5-17 GHz are due to optically thin bremsstrahlung.

Some Coronal Bright Points visible in other emissions are not pronounced in NoRH maps due to CLEAN routine.

Everywhere Not all counterparts No counterparts

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Coronal Holes Coronal holes are inhomogeneous. T5.7 correlate with T17 in

coronal bright points & diffuse brightenings, filaments.

T5.7 anticorrelate with T17 in radial features that are darkest at 5.7 GHz, but not pronounced in 195 Å or H images.

Favorable heating mechanism in those features is dissipation of Alfvén waves.

Criterion: Dark feature at both 5.7 & 17 GHz filament (channel).

See poster by Maksimov et al.

1998/04/20-26

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Coronal Arcades, also Posteruptive Ne ~1010 cm-3, Te ~6 MK (soft X-rays &

microwaves).

Long-living giant hot structures in the corona at 100 Mm: B > 20 G or >1?

Dark lanes likely due to falling remnants of a filament can contribute to mass supply & equilibrium conditions.

See poster by Grechnev et al.2001/10/22

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2000/11/23

Coronal Arcades, also Posteruptive Large-scale coronal magnetic configurations

are revealed, in accord with magnetograms and extrapolated magnetic fields.

Due to nonthermal contributions, magnetic fields can be well overestimated.

See poster by Grechnev et al.

2001/10/22

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Magnetic Field Estimates High-sensitivity NoRH data (20 K) Microwave spectrum – combined

with RATAN-600 Non-radial observations See also talk by Ryabov

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Projection effect: quiet AR 487, sunspot-associated source @ 5.7 GHz

Color :B

Contours: I5.7

Color: V5.7

Contours: I5.7

Color: extrapolated Br

Contours: I5.7

Oct. 27

- -7 +0

Oct. 31 Nov. 4

Method of extrapolated Br magnetograms allows

• avoiding projection effects in B magnetograms• identification of the type of microwave source in NoRH maps

Results:• Neutral Line associated Sources (NLS) are widespread at 17 GHz • NLS birth or displacement precedes powerful flares & CMEs.

See poster by Uralov & Rudenko

Day: 28 October 28 Oct., 2 hr. later 29 October 30 October

Before flares: X 17.2 М 3.5, X 10 М 1.5Caused by: NLS birth NLS displacement

NLS birth

M i d d l e r e s o l u t i o n Low resolution

Color: 17 GHz I, Contours: extrapolated Br

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Radio Source Type Identification

NLS at 17 GHz are indistinguishable from sunspot-associated gyroresonance sources in the degree of polarization, which can vary for sources of both type from small values to 100 %

Extrapolated Br magnetograms allow their identification

See poster by Uralov & Rudenko

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Importance of Observations with two Radioheliographs

Observations at several radio frequencies only assure Identification of emission mechanisms Correct estimates of magnetic fields in the corona

Free-free diagnostics: measuring magnetic fields New research areas:

Detection of flare-productive sites Coronal magnetography (Ryabov) Non-local diagnostics (coronal holes…)

etc…

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Conclusion• Putting additional constraints on physical conditions

based on the observed quantities, microwave imaging data crucially enhance the reliability of results and consistency of interpretations. This is why microwave imaging data is a necessary constituent of observational data sets on solar phenomena.

• The results presented here have been possible due to the usage of microwave imaging data obtained with the solar dedicated radioheliographs NoRH and SSRT operating without interruption for over a decade.

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Acknowledgments

We thank Pulkovo and Nobeyama Solar Groups and,

especially, Prof. H. Nakajima and Prof. G. Gelfreikh for fruitful discussions and assistance

Nobeyama Solar Group for the opportunity to participate this meeting and the hospitality