Research on the Solar Corona and Ionosphere based on the Total Solar Eclipse on 11 Aug.1999

为1999年8月11日日全食派出了三个观测队。来自国家天文台（NAOJ）和京都大学的团队在土耳其的Elasig进行了实验。NAOJ对北方日冕进行了光谱观测，获得了8条精细光谱。他们发现低日冕的电子温度约为2MK，与过去的测量结果相比明显偏高。京都大学的研究小组使用15厘米折射镜、4种滤光片和400万像素的CCD相机，在3种温度下拍摄了高分辨率的日冕图像。九州大学的研究小组在欧洲和非洲南部的5个观测站观测了地磁场，研究了日全食期间地磁场的非对称边界条件对地磁场的影响。他们发现地磁场只在月球阴影穿过的北方半球发生变化，而在南半球没有变化。这表明在电离层中存在一个封闭的电流系统，这种效应不会传播到另一个半球。这一发现揭示了一种新的机制，这种机制抑制了沿沿着地磁场的全球电流。2000年，在东京举行了一次会议，会上介绍了每个实验的结果，并广泛讨论了观测日全食的未来计划。

Three observation teams were dispatched for the total solar eclipse on 11 August 1999. Teams from the National Astronomical Observatory (NAOJ) and Kyoto University made experiments at Elasig in Turkey. NAOJ performed a spectroscopic observation of the corona on northern pole and obtained 8 fine spectra. They found that the electron temperature of the lower corona was about 2MK, which is significantly high compared with past measurements.Team of the Kyoto University took high resolution coronal images at three temperatures using a 15-cm refractor, 4 types of filters, and CCD camera with 4M pixels. They plan to study the coronal structures in wide temperature range (10^4K=5x10^6K) combining with the data from space observatories.Team of the Kyusyu University observed geomagnetic fields at 5 stations among Europe and southern Africa to investigate the effect of the asymmetric boundary condition for geomagnetic fields during the total solar eclipse. They found a variation of geomagnetic field only in northern hemisphere in which the shadow of the moon passed through, but no variation in southern hemisphere. This implies that there was a closed electric current system in the ionosphere and the effect did not propagate to another hemisphere, This discovery highlighted a new mechanism which inhibits a global current along geomagnetic fields. In 2000, a conference was held in Tokyo in which results from each experiments were presented and future plan of observing total eclipses were discussed extensively.