Multi-Frequency Radio Observations of the Partial Solar Eclipse at Yunnan Observatory on September 23, 1987

The main results of multi-frequency radio observations of the Sept. 23, 1987 eclipse carried out at Yunnan Observatory are summarized. We have found: 1. Radius of the radio sun in solar minimum year amounts to 1,060,1.068 and 1.083 r_⊙ at 8.2 em, 10.6cm and 21.1cm respectively. 2. A radio source above the filament N-2 was observed during the eclipse. The cubic angle extent at Tri-frequency were 0.4~1.0×10^-8 Sr, 1.2~2.0×10^-8 Sr and 4.2×10^-8 Sr respectively. Their mean brighiness temperatures were about 1.0~1.2×10⁶ K at 8.2cm, 1.7~2.4×10⁶ K at 10.6cm and 3.4×10⁶ K at 21.1cm. 3. A radio source above the prominence E~1 was also observed. The cubic angle extent at Tri-frequency were 0.4×10^-8 Sr, 0.3×10^-8 Sr, 3.0×10^-8 Sr respectively. However, worth noting that it is hot source. The mean brightness temperatures were about 3.0×10⁶ K at 8.2 cm, 5.3×10⁶ K at 10.6cm and 8.0×10⁶ K at 21.1cm. 4.The radio sources above three plages were observed. The cubic angle extent at Tri-frequency were 0.8~1.3×10^-8 Sr, 0.8~1.8×10^-8 Sr and 1.6~6.0×10^-8 Sr respectively. The mean brightness temperatures were about 0.7~0.8×10⁶ K at 8.2cm, 1.0~1.1×106 K at 10.6cm and 1.0~2.8×106 K at21.1 cm. The emission measure of the halo N²L is calculated to be 8.0×10²⁸. 6.7×10²⁸ and 3.7×10²⁸ clectron²/cm⁵ respectively. 5. A coronal condensation was observed between 100°~115° of the northwestern limb of solar disk. The cubic angle extent at Tri-frequency were 0.3~0.7×10^-8 Sr, 0.6×10^-8 Sr and 1.3×10^-8 Sr respectively. Their mean brightness temperatures were 0.8~1.6×10⁶ K at 8.2cm, 5.4×106K at 10.6cm and 7.4×10⁹ K at 21.1cm. Heights of the sources increase with wavelength from 2.10×104 km at 8.2cm to 4.72×104 km at 21.1 cm. 6. The radio sources above two sunspots were all observed. The cubic angle extent at Tre-frequency were 1.1~2.3×10^-8 Sr, 0.3~1.2×10^-8 Sr and 1.3~1.6×10^-8 Sr respectively. Their mean brightness temperatures were 1.0×10⁶ K al: 8.2 cm, 1.4~3.7×10⁶ K at 10.6cm and 3.7~6.0×10⁶K at 21.1cm. 7. The cubic angle extent at the radio sun of Tri-frequency were 7.7×10^-5 Sr at 8.2cm, 7.8×10^-5 Sr at 10.6 cm and 7.9×10^-5 Sr at 21.1 cm. Their mean brightness temperatures were about 2.6×10⁴ K, 3.8×10⁴ K and 1.2×10⁵ K respectively. 8. The quiet sun emissions of Tri-frequency are obtained from these observations. Their mean brightness temperatures were 2.3×10⁴ K at 8.2cm, 3.2×10⁴ K at 10.6cm, and 1.0×10⁵ K at 21.1cm.