Basic research for space climate

点击翻译按钮获取中文摘要

Hakamada of Chubu University traced magnetic field lines, with the Radial-Field model for the coronal magnetic field devised by himself, between the source surface of 2.5 solar radii and the photosphere in the corona and drew high resolution maps from which we can identify both the three-dimensional structure and the magnitude of the field. He drew 201 maps for 201 Carrington rotations during almost two solar activity cycles and compiled them into a motion picture from which we can found the reversal of magnetic polarity around the maximum phase and the steady dipole like structure of the field around the minimum phase. We obtain the radial components of the coronal magnetic field (Br_sou) and the photospheric magnetic field (Br_pho) at both the ends of the same field line by the trace of field lines. Hakamada constructed synoptic maps for Br_sou and ones for Br_pho on the source surface for thirteen Carrington rotations. Kojima of Nagoya University drew the synoptic maps of the solar wind velocity (V) on the source surface estimated by the tomography technique with the observations of interplanetary scintillation during the same thirteen rotations as the magnetic data. We divided these data into two groups and found good relations of the equation of plane among V, Br_sou and Br_pho as follows ; (1)the group for -1.5<log_<10>|Br_sou|<0.0, and -1.0<log_<10>|Br_pho|<1.5, V=960.5+328.6log_<10>|Br_sou|-72.0log_<10>|Br_pho|, and (2)the group for the outside range of the group 1, V=495.4+21.3log_<10>|Br_sou|-18.5log_<10>|Br_pho|. This result suggests that the solar wind consists of two kinds of wind ; that is, (1)the wind that is accelerated from 400 km/s to 900 km/s by the mechanism related to the magnitude of the coronal field, and (2)the background wind that is independent of the magnetic fields and has the speed of about 436 km/s on the average.