1st Stage Joint Research Projects (2005-2009)
Project 3: Effect of Solar Activity on Global Environment
The Sun affects the Earth’s environment in various ways. In this project we investigate processes by which solar activity could have influenced the Earth’s environment in the past and at present. In order to understand long-term variations in solar activity over several solar cycles or longer, we study past solar-activity variations by measuring radioactive isotopes. To understand mechanisms by which the Sun can influence the Earth, we measure present-day variations in the atmosphere by using infrared and millimeter-length radio waves and conduct laboratory experiments by using a laser system.
- Kimiaki Masuda (Division 3)
- Akira Mizuno, Yutaka Matsumi, Tomoo Nagahama, Kenshi Takahashi
High-sensitivity atmospheric observation system using millimeter-length radio waves. Monitoring measurements are carried out in Tsukuba, Rikubetsu (Hokkaido), and Chile (South America). Fourier components related to the 11-year solar cycle will be extracted from the measured longer-term changes in atmospheric constituents.
Seasonal and annual variations in mesospheric ozone content. Data shown at left were obtained above the city of Tsukuba with National Institute for Environmental Studies (NIES) at 110.836 GHz. Seasonal variation is clearly seen at altitudes of 76 km (upper panels) and 60 km (middle panels). The gradual increase in ozone content since 1997 correlates well with solar activity.
Tree rings in Japanese cedar from Yaku Island. Measurements of radiocarbon 14C concentration in tree rings (e.g., of this 700-year-old Yaku cedar) provide information about past variations in solar activity. Such variations over the past two millennia will be measured and compared with variations of Earth’s climate.
Analysis of chemical reactions by using UV lasers. Laboratory experiments with the laser apparatus shown above provide information about elementary processes involved in photochemical reactions and thus help to clarify the effects of solar UV radiation on atmospheric constituents. The results will be useful for modeling and simulation of atmospheric processes.
Variation of the sunspot number over the past 400 years. The sunspot number is a good index for solar activity. It reveals an 11-year periodicity and also shows variations on longer (~100-year) time scale. Solar activity was especially low during the second half of the 17th century (an interval known as the Maunder minimum), which corresponded to an interval of unusually cold climate (the Little Ice Age).