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Astrophysics and Space Science Proceedings Phần 7

GRH quan sát ngày 11 tháng 8 năm 2006 tại 77 MHz. Các giá trị đỉnh cao là 02:06 108 K. vòng tròn Tb mở tại trung tâm đại diện cho chi của quyển sáng mặt trời, hình elip gần góc dưới bên phải GRH "chùm" tại 77 MHz. | 320 R. Ramesh et al. Fig-2 Same as Fig. 1 but at 109 MHz. The hump between 6.1 and 6.3 UT to the left of the Stokes I deflection is a sidelobe artifact Fig. 3 GRH observations of 11 August 2006 at 77 MHz. The peak value is Tb 2.6 X 108 K. The open circle at the center represents the limb of the solar photosphere the ellipse near the bottom-right corner the GRH beam at 77 MHz x 105 Sun - 109 MHz - 2006 08 11 6.1 6.2 6.3 6.4 6.5 6.6 6.7 6.8 6.9 7 7.1 Universal Time hrs Solar radii the radioheliograms was about 4.10 day. This corresponds to r 1.1 Ro in the solar atmosphere for the emission region Ramesh et al. 2000 . A comparison of the radioheliograms from 11 and 18 August 2006 with the ones observed on 10 and 19 August 2006 indicates that the discrete source of intense emission was present only during the interval 11-18 August 2006. We calculated the spectral index of the Stokes I emission observed with the polarimeter its average value was 0.84 indicating that the observed emission is nonthermal in nature. As radio noise storms are the only long-duration days events in the solar atmosphere that belong to this category McLean and Labrum 1985 and references therein we argue that the circularly polarized emission observed with the new Gauribidanur radio polarimeter must be due to noise storm emission. The estimated average degree of circular polarization was V I 0.53 at 77MHz and 0.64 at 109MHz which supports this claim Kai 1962 . Low-Frequency Radio Observations of Coronal Magnetic Fields Fig. 4 Same as Fig. 3 but for 18 August 2006. The peak value is Tb 3.1 X 108 K. The isolated contour beyond the east limb is due to local interference 321 Fig. 5 SoHO-MDI magnetogram obtained on 11 August 2006. The bright region located close to the east limb is AR 10904. Other than AR 10903 located to the west of AR 10904 there are no dominant magnetic regions on the solar disk 3 Results and Discussion In general any transient or long-duration phenomenon observed in the solar .