Fri, Jun 27, 2003 - Page 2 News List

Taiwanese research makes waves

NATURE WATCH A letter to a scientific magazine details the first conclusive data on a direct optical path between thunderclouds and the ionosphere above them

By Chiu Yu-tzu  /  STAFF REPORTER

Lee Lou-chuang, director of the National Space Program Office under the National Science Council, gives a briefing on the Taiwanese research results on gigantic jets at a press conference in Taipei yesterday.

PHOTO: SEAN CHAO, TAIPEI TIMES

Research by Taiwanese scientists on gigantic jets of lighting linking thunderclouds and the ionosphere was published yesterday in this week's edition of Nature magazine.

According to Lee Lou-chuang (李羅權), director of the council's National Space Program Office, the letter to Nature detailed the first conclusive observation data in the world indicating that a direct optical path was established from the thunderclouds about 15km above the Earth's surface to the ionosphere at the height of about 90km.

Lee, one of co-authors of the letter, stressed that the conventional picture of the global electric circuit needs to be modified to include the contributions of these gigantic jets and possibly sprites.

On July 22 last year, a team led by two physicists at National Cheng Kung University, Su Han-tzong (蘇漢宗) and Hsu Ruey-rong (許瑞榮), took high-resolution images of a rare "giant blue jet," which feeds energy from thunderstorms up into the ionosphere.

Researchers stationed on the southern tip of Taiwan and the university campus observed five giant blue jets, which extended from a thundercloud above the South China Sea near Luzon Island, The Philippines, to the electrically conducting ionosphere.

"A fully-developed gigantic jet optically spanned the thundercloud top at 15 km and the ionosphere at 90 km elevation," Lee said.

The upper bodies of the gigantic jets, which lasted for just 800 milliseconds, was similar to sprites, but their lower bodies resembled blue jets, Lee said.

Lee said that there was no evidence suggesting that the event was triggered by cloud-to-ground lightning. However, Lee said, extremely-low-frequency (ELF) radio waves associated with four of the five gigantic jets were detected by Japanese scientists working at stations in Antarctica and Japan.

In the last 10 years, scientists have discovered that the atmosphere above thunderclouds is not as tranquil as many people imagined.

Anecdotes told by pilots about transient luminous event have been captured by high-tech equipment since 1994. Those events have been classified into three categories: lighting-induced red sprites, upwardly discharging blue jets and gigantic jets.

The discovery of a "giant blue jet" by Victor Pasko of Pennsylvania State University in September 2001 was reported in a Nature cover story in April last year.

In 2001, a National Cheng Kung University team's images of red sprites were chosen as cover photo of Vol. 29 of Geophysical Research Letters,which was published in April last year.

"The potential of Taiwanese scientists deserved to be greatly encouraged," National Science Council Vice Chairman Hsieh Ching-chih (謝清志) said yesterday at a press conference in Taipei.

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