by Wei Long
Beijing - June 15, 2000 - The recent series of eruptions on the Sun have affected telecommunication services in China, the official Xinhua News Agency disclosed yesterday (June 12).
Since June 2 solar storms are believed to be responsible for interfering with telecommunications on three occasions. The most serious interference occurred on June 9. With shortwave radio services affected throughout the country for some 17 hours. The solar disturbance also interfered, and even interrupted, a communication satellite and some navigation related systems.
Solar astronomers have predicted that the Sun will reach the peak of its 11-year activity cycle some time this year, and may remain active for another year or two.
When the Sun is active, more sunspots and eruptions occur. Sunspots are cooler, thus darker, areas which have a higher local magnetic field than the rest of the solar atmosphere. Some of the energy generated deep inside the Sun is stored in complex sunspot groups. Energy stored here may be released in violent eruptions called solar flares.
During solar flare eruptions high-energy radiation, such as x-ray, and charged particles are hurled out of the Sun. When these particles and energetic radiation impact Earth, they may cause spectacular displays of aurora.
However, the impact can create geomagnetic storms and deposit excess amount of energy on satellite components and power grids, causing these systems to fail. Solar flares can also disrupt telecommunications, corrode pipelines, upset navigation systems, and pose radiation hazard to orbiting yuhangyuan (astronauts in Chinese).
Solar astronomers classify flares that emit x-ray in four classes according to the energy level of the eruption. In increasing energy release, the classes are labelled B, C, M and X.
The Chinese Radio Transmission Research Institute (CRTRI), which is the No. 22 Electronics Research Institute of the Ministry of Information Industry, is responsible for disseminating information in China on disturbances in the layer of the Earth's atmosphere called the ionosphere.
The ionosphere extends from about 70 km to an altitude under 500 km. Radio transmission, such as from AM and shortwave radio stations, bounces off the ionosphere to reach a distant receiving station. A solar flare drastically reduces the effectiveness of reflected radio signals and solar interference and interaction with the Earth can completely cut off radio transmission for an extended period of time.
According to Suo Yucheng, senior engineer and leader of the Ionospheric Disturbance Forecast Group at the Beijing centre of CRTRI, the institute has ten ionospheric stations throughout China can make observations of the ionosphere every fifteen minutes and issue storm bulletins when necessary.
The ionospheric stations are scattered in different parts of the country, for example, in Lhasa (capital of Xizang Autonomous Region ("Tibet") in the west), Urumqi (capital of Xinjiang Autonomous Region in the northwest), Manzhouli (in Nei Mongol ("Inner Mongolia") Autonomous Region in the north), Changchun (capital of Jilin Province in the northeast), Beijing (in the east), Qingdao (in Shandong Province in the east), Haikou (on Hainan Island, in Guangdong Province, in the Gulf of Tonkin), Guangzhou (capital of Guangdong Province in the south), and Chongqing (in Sichuan Province in the central).
On June 2 at about 3pm local time, the active region on the Sun numbered 9026 (AR 9026) produced a M-class flare. The eruption caused a "sudden ionospheric disturbance (SID)" and disrupted radio transmission in large areas of China for about half an hour. Areas in the south such as Guangzhou, Hong Kong and Haikou were affected by the storm as well.
The next major solar activities occurred between 11:25 p.m. local time on June 6 and during the early morning hours of June 7. Active region 9026 erupted again with two X-class flares and produced large amount of x-ray and charged particles. As China was in the nighttime side of the hemisphere facing away from the x-ray burst, there was no impact in China from the resulting high energy radiation.
However, two days later on June 9, between 5am and 10pm local time, the charged particles slammed into the Earth's atmosphere and caused a severe storm in the ionosphere. Causing wide spread disruption to shortwave radio services.
Areas in northern China were more severely affected than in the south, although the storm impact was felt as far south as Guangzhou, Hong Kong and Haikou.
Suo explained: "Since the density of the ionosphere drops off tremendously [during this ionospheric storm], shortwave radio signals travel through the layer and escape into space."
On June 11 the atmosphere above Manzhouli, Changchun and Beijing experienced the third ionospheric storm in two weeks, although the magnitude and duration of interference to shortwave transmission was much less than the storms on the 9th.
Even though the latest storm had subsided, Suo said that CRTRI and other relevant departments must remain on guard to watch out for more solar storms.
Chinese scientists who study solar-terrestrial relations are combining their effort to gain a better understanding of space weather and its impact.
Two months ago academics from over 20 research units of the Chinese Academy of Sciences gathered to draw up a 15-year "Space Weather Strategic Plan" that would improve China's space weather forecast accuracy and increase monitoring capability.
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