1. Laboratory of Lightning Physics and Protection Engineering, State Key Laboratory of Severe Weather, Chinese Academy of Meteorological Sciences, Beijing 100081, China
2. Meteorological Disaster Prevention Technology Center of Shanxi Province, Taiyuan 030002, China
3. Institute of Atmospheric Sciences, Fudan University, Shanghai 200438, China
4. Meteorological Disaster Prevention Technology Center of Xinjiang, Urmuqi 830001, China
Abstract：Spectra of altitude triggered lightning channel in the range of 400～660 nm had been obtained by Slit-less spectrograph. The spectra of mini-return stroke and upward positive leader channel were analyzed. The difference of the spectra between metal and air of the lightning channel was discussed. It is shown that duration of the spectra of metal channel was about 140 ms, while the air portion channel was only 0.167 ms. The reasons why the metal channel has high brightness and long duration were given through analyzing the excitation energy and ionization energy of Fe, N, O elements. When the current intensity is same, there are more excited particles in the metal than in the air channel which leads to trigger lightning channel to generate more radiation, brighter channel and stronger spectral intensities. And what is more, the duration of the recombination processes of metal channel was also longer in the subsequent phase of dissipating the plasma channel. Through comparing the spectra structure and temperature of mini-return stroke and lower and upper air portion of positive leader channel to the natural lightning in Guangdong, it depicted that the spectra of mini-return stroke channels were mainly composed of transitions between low excited states of NⅡ ions, and had NⅡ 444.7 nm, NⅡ 517.9 nm, NⅡ 616.8 nm which were the characteristic lines of the general intensity natural lightning in Guangdong area. The spectra with high excitation energy in the lower air portion channel of upper positive leader began to disappear. The spectral with low excitation energy such as Hα，Hβ，and OⅠ 615.8 nm appeared, and had spectral structure of the late stage of lightning return stroke. The temperature of the mini-return stroke and lower air portion upward positive leader channel were 21 000 and 20 000 K, lower than natural lightning temperature.
Key words：Altitude triggered lightning; Metal channel; Air channel; Lightning spectra
