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  1. Type IV burst observed on July, 27, 2005 follows a group of Type III bursts (Fig. 6-7). There are sub-bursts with drift rates 10-20 kHz/s against background of these Type III bursts (Fig. 8). Immediately after the group of Type III bursts we see a burst in absorption, which drifts with infinite rate, in broad frequency band from 30 MHz to 10 MHz. It has duration about 2min 30 s at 30MHz and 7min. 30 s at 13MHz. Type IV burst rise and fall last about 1hour and 2 hours correspondingly. Maximum radio flux of Type IV burst equals 40s.f.u. Type IV burst consists of a number of sub-bursts with different drift rates both positive and negative with value in majority 1-2 MHz/s (Fig.8). There are also some sub-bursts in absorption. A succession of sub-bursts in emission and absorption is shown in Fig.9. Sub-bursts in emission have positive drift rates 1.2 MHz/s and 1.6 MHz/s. Their durations are about 15 s. b) Fig. 6. Type IV bursts at July, 27, 2005 Fig.8. The onset of Type IV burst. Fig.9. Sub-bursts in emission and absorption with positive drifts. Fig.7. The time profile of Type IV bursts The first sub-burst changes its rate to negative near frequencies 13-14 MHz. Frequency drift rate of this sub-burst at low frequencies is 0.4 MHz/s. Sub-burst in absorption follows this burst in emission with positive drift rate 3 MHz/s and duration 10 s (Fig.10). A sub-burst in absorption followed the second sub-burst in emission and had drift rate about 10 MHz/s. Its duration is about 40 s at high frequencies and decrease with frequency. One more Type IV burst is shown in Fig. 11, which was observed on July, 28, 2005. This burst has duration about 2 hours. Its front drifts with rate about 10 kHz/s from high to low frequencies. It terminated at frequencies about 12-13 MHz. Fig.10. The time profile of sub-bursts at 25.55 MHz. After 8.30 falling edge of Type IV burst drift to high frequencies. At 9.40 there is a moderate increase of radio emission with duration about half an hour. The frequency profile of Type IV burst is practically constant and equals 200 s.f.u. up to 25 MHz and then quickly decreases to 6 s.f.u. at frequency 12MHz. As in previous cases this Type IV burst has a fine structure in the form of weak sub-bursts. They have in majority forward drift rates equaled 1-2 MHz/s. Their durations are about 5-10 s. There are also some sub-bursts in absorption with negative and positive drift rates and durations about 10-20 s. Fig.11. Type IV burst on July, 28, 2005 C O N C L U S I O N S Type IV bursts observed in decameter range have durations about 2 hours. The bursts front drifts from high to low frequencies with rates 10 kHz/s approximately equaled to that for Type II bursts at decameter wavelengths. All observed decameter Type IV bursts have fine structures in the form of sub-bursts, which remind weak Type III bursts. Their frequency drift rates can be both positive and negative and equal to 1-2MHz/s. Durations of these sub-bursts change in wide range from 10 s to 20 s. Usual phenomenon is bursts in absorption with different rates and durations. Fig.12. Time profile of Type IV burst at 25 MHz. R E F E R E N C E S Boishot, A., 1957, C. R. Acad. Sci., 244, 1326. Chernov, G. P., 2007, Space Sci.Rev. 127, 195. Duncan, R.A., 1981, Solar Phys. 73, 191. Smerd, and Dulk, 1971, In “Solar magnetic fields” (ed. R.Howard) (Proc. IAU Symp. No. 43), 616. Stewart, R.T. Duncan, R.A., Suzuki, S. and Nelson, G.J., 1978, Proc. Astron.Soc.Aust., 3, 247. Stewart, R.T., 1985 in “Solar Radio Physics” (ed. D.J.McLean, and N.R.Labrum), 361. Trottet, G., Kerdraon, A., Benz, A.O., and Treumann, R., 1981, Astron. Astrophys., 93, 129. Fig.13. A fragment of Type IV burst

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