SOLAR-WIND SPEED AND ITS ACCELERATION INFERRED USING THE INTERPLANETARY SCINTILLATION METHOD IN CARRINGTON ROTATION-1753

Solar wind speeds (SWSs) estimated by interplanetary scintillation (IP S) observations during Carrington rotation 1753 are projected onto the so-called 'source-surface' of 2.5 solar radii along magnetic field li nes in interplanetary space. The following two working hypotheses are examined from different points of view: (1) The SWS is a weighted mean along the line of sight to a radio source; the weight for the SWS dep ends on the distance from the P-point, the closest approach to the Sun on the line of sight. (2) The weighting function has a very sharp pea k at the P-point, so that the SWS shows a real solar wind speed at the P-point. In both the two cases, the SWSs projected onto the source su rface are further projected onto the photosphere along magnetic field lines in the corona. Footpoints of these field lines are inferred as p hotospheric source regions of the solar wind. The intensity of the Her (1083 nm) absorption line (HEI) in the chromosphere corresponding to these photospheric sources is interpolated from observational data. Th e weighted mean of the HEI is calculated in case 1. The HEI correspond ing to the P-point is used in case 2. The SWS is compared with the HEI in both the two cases. It is found that the correlation between the S WS and the HEI is better in case 2 than in case 1. It is further infer red by correlation analysis between the SWS and the HEI that the solar wind is accelerated within similar to 27 solar radii on average. Alth ough the data examined in this paper were limited to just one solar ro tation, these results suggest that the SWS estimated by the IFS techni que corresponds to the solar wind speed near the P-point and the weigh ting function along the line of sight may have a very sharp peak near the P-point.