STUDY OF PECULIAR SOLAR WIND STRUCTURE AT CYCLE 24 SOLAR MINIMUM

我们改进了名古屋大学日地环境实验室的行星际闪烁测量系统，并利用该系统获得的数据研究了在第24周太阳极小期观测到的特殊太阳风结构的长期演变。结果发现，第24周太阳风结构随太阳活动上升的演变与过去的太阳风结构有很大的不同。我们还发现，在第24周，太阳风密度在全球范围内都有所下降，这表明日球层正在显著地收缩，这对于探索外日球层和研究空间气候具有重要意义。

We improved the interplanetary scintillation measurement system of the Solar-Terrestrial Environment Laboratory of Nagoya University, and investigated long-term evolution of the peculiar solar wind structure observed at Cycle 24 solar minimum using data obtained from the system. As result, we found that the solar wind structure evolves with rising solar activity in Cycle 24 rather differently from that in the past cycle. We also found that the solar wind density globally drops in Cycle 24.Our result suggests that the heliosphere is significantly shrinking, and this is of great importance from viewpoint of exploration of the outer heliosphere and study of the space climate.