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The Sun

13

Observational possibilities of RATAN-600 and some problems of solar activity
V. Bogod, V. Garaimov, N. Komar, L. Opeikina
Special astrophysical observatory, Karachaevo-Cherkessia, Russia

Introduction
RATAN-600 Special Astrophysics Observatory, Zelenchuk, Russia is one of a few regular working instrument in the world which give the daily spectral information on solar radio emission in the centimeter and decimeter wavelengths. Solar observations are performed now with antenna system including South sector and Periscope Korol'kov & Parijskij, 1979. Now this regime has an additional possibility for multi-scanning and tracking of the Sun. Because this new regime is used wewould like to consider the several tendencies in study of solar activity.

New technical possibilities of RATAN-600
The antenna system South sector and Periscope" together with the multi-channel panoramic spectral analyzer in wide frequency range from 0.9 GHz to 17 GHz are using now for the monitoring of solar activity. The additional tracking of the Sun during during 2 hours near meridian time using all circular railway track opens new possibilities in the study of the Sun with RATAN-600 and allows us to research some actual problems of solar physics. In principle, two new aspects appear in the analysis of solar emission: temporal oscillation of the spectrum, polarization and structure of the sources; spatial separation of the sources. New possibilities are as follows: monitoring of the Sun 1 - 3 observations in the range 1.7 cm - 32 cm with intensity and circular polarization measurements with frequency resolution 5; study of temporal parameters of AR structure, spectra on the scales minutes and tens of minutes during four hours; study of weak spike sources with high temporal resolution in decimeter wavelengths in tracking regime; study a polarization emission of di erent solar sources with high accuracy up to 0.3; spatial separation AR in North and South hemispheres; mapping of the Sun on the base of azimuth observations. Now, there is a nice chance to use 2D-maps of Nobeyama radioheliograph in order to determinate the radio sources location on the disk together with wide range spectral data of RATAN-600.

Solar astrophysical problems
1. Radiomagnetography. Spectral observations allow to separate the contribution of chromosphere and corona in the polarized emission. Methods of radio tomography based on spectral data are under development Bogod & Grebinskij, 1997; Grebinskij et al., 1999.


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The Sun

Combination of 2D-maps of Nobeyama and RATAN spectral data will allow to create 3D-magnetic structure of AR. Hereby, the Metsahovi data are very essential.
2. Oscil lation and helioseismology of AR. Nobeyama data allow begin to study the oscillation of cyclotron thermal sources above sunspots with the period of 3-5 minutes at radio wavelengths. Combination of spectral RATAN-600 data and long time azimuth observations maybe very promising for this task. 3. Bursts and CME. The long-term observations allowus to carry out the regular study of ares and compare the are data with weak pre- are spectral phenomena. The last are studied with RATAN-600 traditionally Akhmedov et al., 1986; Borovik et al., 1989. 4. Emergence of new magnetic ux. The emergence of magnetic ux have being studied in solar physics in connection with problems of corona heating, CME and ares. Here we demonstrate of these phenomena on the example of spectral-polarization observations. The comparison of multi-channel polarization solar scans for May 12 and 13, 1997 is presented in Fig.1. In the West part of the disk there is the active region AR NOAA 8038. One can see from Fig.1 for May 12 that the polarization emission has simple bipolar structure in wide wavelength range with R-hand polarization for leading spot and L-hand polarization for the following part of the group. But for May 13, the spectral polarization structure is quiet complicate at all wavelengths with several inversions of polarization. Detailed consideration indicates the appearance of new opposite polarity magnetic ux on the level of chromosphere-corona transition region short centimeter range and perturbation of coronal plasma decimeter range driven by bursts and or CME.

The short wavelength part of the spectrum from 1.83 cm to 3.21 cm is used preferably for the analysis of sunspot magnetic eld structure. The polarized emission spectrum of sunspot associated source informs us about the magnitude, sign and structure of magnetic eld. According to cyclotron emission mechanism, in the case, when the third gyrofrequency harmonic reach the coronal temperature levels Akhmedov et al., 1986, the maximal value of longitudinal magnetic eld can be estimated as: B G = 3570= cm . RATAN-600 observations in May 12 see Fig.1 give the evidence of very weak polarization signal in the AR NOAA 8038 only at the shortest wavelength 2.67 cm. It permits us to estimate the magnetic eld value about 1330 G. Here the R-hand polarization associates with North polarity of magnetic eld and it corresponds to the x-mode emission at third harmonic of gyrofrequency. The northern polarity dominates in the middle part of the spectrum from 2.67 cm to 10.17 cm for both day of observations see Fig.1. On the next day the new polarized signal with L-hand polarization is appeared at the short wavelengths 2.11 cm and 2.24 cm. The estimation of the southern polarity magnetic eld gives 1700 G. The di erence in both magnitudes and uxes for magnetic elds with opposite polarities in AR NOAA 8038 led to appearance of the new type of polarization inversion at short wavelengths, which was detected in spectral polarization observations during May 13. Such phenomenon di ers from well-known inversion in the quasi-transverse QT eld regions and current sheets Bogod et al., 1995. In our case this e ect is the sum of old southern polarity eld and new north polarity. This sum is equal to zero at wavelength 2.32 cm for May 13. The ascent of new ux occurred between May 12 and 13 observations.


The Sun

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RATAN-600 data, May 12-13, 1997
SUN: 1997/05/12
Ta,V 710

SUN: 1997/05/13
Ta,V 790

30.46 cm 29.56 cm

30.46 cm
29.56 cm

498

28.71 cm 16.13 cm

L
562

28.71 cm 17.96 cm 17.05 cm
335

285

15.38 cm 14.63 cm

16.13 cm 15.38 cm 14.63 cm

72

13.22 cm 11.49 cm

108

13.95 cm 13.22 cm 11.49 cm

R
-2"
473"

-140

-953"

-477"

948"

-951"

-477"

-2"

472"

947"

SUN: 1997/05/12
Ta,V 3600

SUN: 1997/05/13
Ta,V
2900

11.49 cm 10.60 cm

11.49 cm 10.60 cm 10.17 cm 9.74 cm 8.96 cm

2575

10.17 cm 9.74 cm

L

2075

1550

8.96 cm 8.17 cm 7.59 cm

1250

8.17 cm 7.59 cm 7.03 cm

525

7.03 cm 4.93 cm

425

6.52 cm 4.93 cm

R
-2"
473"

-953"

-477"

948"

-951"

-477"

-2"

472"

947"

SUN: 1997/05/12
Ta,V
1100

SUN: 1997/05/13
Ta,V
1200

4.93 cm 4.62 cm

L
825

4.93 cm 4.62 cm 4.32 cm 4.08 cm

775

4.32 cm 4.08 cm

450

3.83 cm 3.21 cm

450

3.83 cm 3.21 cm 3.06 cm

125

3.06 cm 2.90 cm

75

R
-2"
473"

2.90 cm

-953"

-477"

948"

-951"

-477"

2"

472"

947"

SUN: 1997/05/12
Ta,V 550

SUN: 1997/05/13
Ta,V
340

2.90 cm 2.74 cm 2.67 cm 2.32 cm

2.90 cm 2.74 cm

L
230

380

2.67 cm 2.32 cm

210

2.24 cm 2.11 cm 1.92 cm

120

2.24 cm 2.11 cm 1.92 cm

40

1.83 cm

R
-2"
473"

10

1.83 cm

-953"

-477"

948"

-951"

-477"

-2"

472"

947"

E

W

E

W

Figure 1: One-dimensional polarization scans with Panoramic Analyzer of Spectrum at RATAN-600 for May 12 left and May 13 right. Entire wavelength range is presented in 4 sub-ranges with di erent scales. One can see stable bipolar behavior of AR NOAA 8038 on May 12 and perturbated character on May 13. In the short part on May 13 the lowest picture at wavelengths 2.24 cm and 2.11 cm new magnetic ux opposite polarity is recorded Analysis of the long wavelength part of the spectrum demonstrates the complicated inversion polarization structure for May 13 events. Except the short inversion mention above


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The Sun

there is the inversion in the range from 10 cm to 15 cm. Such inversion also di ers from inversion in QT-region, which has the very strong exponential dependence of the inversion on frequency. One can propose that in this case the inversion may be the result of plasma emergence from the AR.
SUN: 1997/05/06
Ta,V
1300

SUN: 1997/05/10
Ta,V
2000

8.17 cm

8.17 cm 7.59 cm

L
875

7.59 cm 7.03 cm

1350

7.03 cm
700

450

6.52 cm
25

4.93 cm
50

4.93 cm

R
-600 1425" -1428" -715" -2"

4.62 cm

-400 -1430" -716" -2" 712"

711"

1424"

SUN: 1997/05/07
Ta,V
1000

SUN: 1997/05/11
Ta,V
1900

8.17 cm 7.59 cm 7.03 cm

8.17 cm

L
1300

675

7.59 cm

7.03 cm
700

350

4.93 cm
25

4.93 cm
100

4.62 cm

R
-300 -1432" -717" -2" 713" 1428" -500 -1430"

4.62 cm

-716"

-2"

712"

1426"

SUN: 1997/05/08
Ta,V
2800

SUN: 1997/05/12
Ta,V
1800

8.17 cm 7.59 cm 7.03 cm

8.17 cm
7.59 cm

L
1225

1900

7.03 cm
650

1000

4.93 cm
100

4.93 cm
75

4.62 cm

4.62 cm

R
-800 -1432" -717" -2" 713" 1428" -500 -1428" -715" -2" 711" 1424"

SUN: 1997/05/09
Ta,V
2000

SUN: 1997/05/13
Ta,V
1300

8.17 cm 7.59 cm 7.03 cm

8.17 cm 7.59 cm

L
875

1350

7.03 cm
450

700

4.93 cm
50

6.52 cm

4.62 cm

25

4.93 cm

R
-600 -1430" -716" -2" 712" 1426" -400 -1430" -716" -2" 712" 1426"

Figure 2: The example of registration of line-like spectral sources in polarized emission during 8 days from May6to May 14 1997. The line-like source at the wavelength 7.03 cm manifestates stability in time and re ects the process of accumulation energy in AR before large are in May 12-13, 1997


The Sun

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5. Cyclotron lines and ne spectral structure. RATAN-600 observations allow to detect ne spectral features in wide frequency range. Existence of line-like structures in the spectra of microwave sources, attributed to the cyclotron emission was predicted a long time ago Zheleznyakov & Zlotnik, 1980; Zheleznyakov, 1970. The distribution of plasma parameters may determined the frequency spectrum and polarization in di erent AR. RATAN-600 observations revealed such line-like structure at the wavelength 8.5 cm Bogod et al., 1998.We also demonstrate here in the Fig.2 another example of such line-like structure at the wavelength 7.03 cm. This line- like source has quiet stable parameters during passage along the disk. It is interesting to note that this AR NOAA 8038 was very active and produced a lot of bursts and CME. Likely, the such type of the sources is connected with processes of accumulation energy before ares. The study of such ne spectral structures is very importantin the contest of corona heating problem. Another types of polarization inversion at decimeter part was studied by Alissandrakis et al. 1998. 6. Polar zone activity. The modern study of solar cyclicity consider this phenomenon likes global process. The observational methodic used in Metsahovy, RATAN-600, Nobeyama and Crimea look very e ective. Spectral method can help a lot in analysis the magnetic eld structure. 7. Magnetic traps, current sheets, particle accelerations outside ares. Here we continue the study of the origin of: i decimeter halo spectrum, polarization, temporal oscillations; ii relation of the polarization inversion with Noise Storms Bogod et al., 1995; iii millisecond spikes in AR.
This research is supp orted by RFBR Grants 99-02-16403.

References
Akhmedov Sh.B., Bogod V.M., Gelfreikh G.B., Hildebrandt J., Kruger A., Contrib. the Astron. Observ. Skalnate Pleso, 1986, v.15, p.339-344 K. Alissandrakis, V. Bogod, V. Garaimov, G. Gelfreikh, V. Zheleznyakov, E. Zlotnik, JOSO Annual Report'97, 1998 Bogod V.M., Vatrushin S.M., Abramov-Maximov V.E., Tsvetkov S.V., Dikij V.N., ASP Conference Series, Vol.46, 1993, 306-309 Bogod V.M., Garaimov V.I., Gelfreikh G.B., Lang K.R., Wilson R.F., Kile J.N., Solar Physics, 160, 133-149, 1995 Bogod V.M., Grebinskij A.S., 1997, Solar Physics, 176, 67 Bogod V., Garaimov V., Zheleznyakov V., Zlotnik E., Nobeyama Radio Observatory, NAOJ, Kiyosato, Japan, 27-30 October, 1998, p.10 Bogod V., Garaimov V., Grebinskij A., Solar Physics, 1998, 182, 139 Borovik V.N., Gelfreikh G.B., Bogod V.M., Korzhavin A.N., Kruger A., Hildebrandt J., Urpo S., Solar Physics, 1989, 124, 157 Grebinskij A., Bogod V., Gelfreikh G., Urpo S., Pohjolainen S., Shibasaki K., Astron. and Astroph., 1998 submitted Korol'kov D.V., Parijskij Yu.N., 1979, Sky and Telescope, 57, 4 Zheleznyakov V.V., Zlotnik E.Ya., 1980, Astron. Zh. 57, 778 Zheleznyakov V.V., 1970. Radio Emission of the Sun and Planets. Pergamon Press, Oxford