Graphics shows the path of total solar eclipse lasting for over six minutes on July 22 in China, according to the Chinese Academy of Sciences Purple Mountain Observatory. [Xinhua]

Chinese scientists are striving to capture a 40-minute sequence of images of the corona of a solar eclipse along its path across China on Wednesday in a bid to understand the sun's outer atmosphere.

"We have set up 17 observer stations along the central line of the solar eclipse in China to capture the corona images," said Ji Haisheng, an astronomer with the Chinese Academy of Sciences (CAS) on Tuesday.

"If weather permits, we are very likely to get the first-hand materials for the solar corona research.

"The corona is the sun's outermost atmosphere, which is relatively dim, and can only be observed through a coronagraph on a normal day," said Ji, a research fellow with the CAS Purple Mountain Observatory based in Nanjing, eastern Jiangsu Province.

A coronograph is an instrument that is designed to block light from the main solar surface in order to observe the corona.

"However, it can be easily seen during a total solar eclipse, as the brighter parts of the solar atmosphere are shadowed."

The 17 stations were set up in the solar eclipse path from southwestern Yunnan Province to eastern coastal Zhejiang Province, which runs through 2,500 km across China, he said.

He said CAS scientists hoped the corona images could be captured by all 17 video monitors, so that they showed the full path of the solar corona.

"The corona could have a tremendous influence on the Earth, but it remains a puzzle. It has become an interesting research focus for astronomers around the world," Ji said.

Scientists have observed that when a solar wind erupts across the surface of the sun, a result of the coronal mass ejections (CMEs) or eruptions of material from the sun, communication signals on the Earth could be disturbed.

The total solar eclipse on Wednesday has been forecast by the CAS to be the longest observable in China between 1814 and 2309. Viewed from the best observation spots, the total eclipse can last more than six minutes.

"Astronomers from all over the world are heading to China to observe the corona. We will work closely and share each other's statistics and data on solar eclipse observations," said Gan Qunwei, deputy chief of the Purple Mountain Observatory.

Jagdev Singh, of the Bangalore-based Indian Institute of Astrophysics, said he would be studying the corona chromospheric lines and the corona polarization.

The corona is separated from the sun's photosphere by relatively shallow chromosphere. However, scientists have not found the exact mechanism by which the corona is heated. The studies on chrompheric lines and the polarized radiation have helped give clues to the magnetism of the solar atmosphere.

Singh is accompanied by 30 students from the institute, bringing two tons of observation instruments to the observatory in Jiangsu for the solar eclipse.

(Xinhua News Agency July 21, 2009)