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Excitation of Langmuir waves by the lower energy cutoff behavior of power-law electrons |
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| Authors: | Jianfei Tang Dejin Wu Guoqing Zhao Ling Chen Chengming Tan |
| Institution: | 1. Xinjiang Astronomical Observatory, CAS, 150 Science 1-Street, Urumqi, Xinjiang, 830011, China 2. Purple Mountain Observatory, CAS, Nanjing, 210008, China 3. Key Laboratory of Solar Activity, National Astronomical Observatories, CAS, Beijing, 100012, China |
| Abstract: | Langmuir waves (LWs), which are believed to play a crucial role in the plasma emission of solar radio bursts, can be excited by streaming instability of energetic electron beams. However, solar hard X-ray observations imply that the energetic flare electrons usually have a power-law energy distribution with a lower energy cutoff. In this paper, we investigate LWs driven by the power-law electrons. The results show that power-law electrons with the steepness cutoff behavior can excite LWs effectively because of the population inversion distribution below the cutoff energy (E c ). The growth rate of LWs increases with the steepness index (δ) and decreases with the power-law index (α). The wave number of the fastest growing LWs (kλ D ), decreases with the characteristic velocity of the power-law electrons ( \(v_{c}=\sqrt{2E_{c}/m_{e}}\) ) and increases with the thermal velocity of ambient electrons (v T ). This can be helpful for us to understand better the physics of LWs and the dynamics of energetic electron beams in space and astrophysical plasmas. |
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