Several envelope soliton fine structures have been observed in solar radio metric-wave emission.present a model of longitudinal modulational instability to explain these fine structures.It is found that this instabili...Several envelope soliton fine structures have been observed in solar radio metric-wave emission.present a model of longitudinal modulational instability to explain these fine structures.It is found that this instability can only occur in the condition of sound velocity being larger than Alfvin velocity in corona.Therefore,the envelope soliton fine structures should display in the coronal region with high temperature and low magnetic 6eld,which corresponds to the solar radio emission in the region of meter and decameter wavelength.展开更多
We present 19 cases of zebra pattern structure (ZPS) and fiber bursts (FB) in radio bursts in frequency range around 3 GHz, and one such case in the range 5.2-7.6 GHz, using the new microwave spectrometer of NAOC betw...We present 19 cases of zebra pattern structure (ZPS) and fiber bursts (FB) in radio bursts in frequency range around 3 GHz, and one such case in the range 5.2-7.6 GHz, using the new microwave spectrometer of NAOC between 2.6-3.8 and 5.2-7.6 GHz (China, Huairou station) with high resolution (10 MHz and 8 ms). The FB and ZPS have about the same spectral parameters: the frequency bandwidth of emission stripes △f-20MHz, the frequency separation between the emission and the neighboring low frequency absorption -△fea-30MHz and the frequency separation between emission stripes (when a periodic structure persists) △fs -60-70 MHz. Therefore we consider both these fine structures to be whistler manifestations, i.e., interactions of plasma electrostatic waves with whistler waves (generated by the same fast particles with loss-cone anisotropy) l + w → t. The duration of the fiber bursts of about 2 s corresponds to whistler waves propagating undamped at about 2s, which requires a whistler increment < 0.5 s-1. In the frequency range 3-7 GHz the relation between the ratios of plasma to cyclotron frequencies and whistler to cyclotron frequencies is almost independent of the decrement of whistler electron damping. This finding is used to obtain the magnetic field strength in the region of generation. For a reasonable value of electron temperature (2-20 MK), we find B = 125-190 G when the electron density is (8-18) × 1010 cm-3 and B = 520 - 610 G when the electron density is (35-60) × 1010 cm-3. In two remarkable events, 1998-04-15 and 2000-10-29, the right-hand polarization is strong for all the fine structures and corresponds to ordinary wave.展开更多
基金Supported by the National Natural Science Foundation of China under Grant No.19803050.
文摘Several envelope soliton fine structures have been observed in solar radio metric-wave emission.present a model of longitudinal modulational instability to explain these fine structures.It is found that this instability can only occur in the condition of sound velocity being larger than Alfvin velocity in corona.Therefore,the envelope soliton fine structures should display in the coronal region with high temperature and low magnetic 6eld,which corresponds to the solar radio emission in the region of meter and decameter wavelength.
基金This work was supported by the Chinese Academy of Sciences, the NSFC (19833050,199730()8) the Ministry of Science and Tech
文摘We present 19 cases of zebra pattern structure (ZPS) and fiber bursts (FB) in radio bursts in frequency range around 3 GHz, and one such case in the range 5.2-7.6 GHz, using the new microwave spectrometer of NAOC between 2.6-3.8 and 5.2-7.6 GHz (China, Huairou station) with high resolution (10 MHz and 8 ms). The FB and ZPS have about the same spectral parameters: the frequency bandwidth of emission stripes △f-20MHz, the frequency separation between the emission and the neighboring low frequency absorption -△fea-30MHz and the frequency separation between emission stripes (when a periodic structure persists) △fs -60-70 MHz. Therefore we consider both these fine structures to be whistler manifestations, i.e., interactions of plasma electrostatic waves with whistler waves (generated by the same fast particles with loss-cone anisotropy) l + w → t. The duration of the fiber bursts of about 2 s corresponds to whistler waves propagating undamped at about 2s, which requires a whistler increment < 0.5 s-1. In the frequency range 3-7 GHz the relation between the ratios of plasma to cyclotron frequencies and whistler to cyclotron frequencies is almost independent of the decrement of whistler electron damping. This finding is used to obtain the magnetic field strength in the region of generation. For a reasonable value of electron temperature (2-20 MK), we find B = 125-190 G when the electron density is (8-18) × 1010 cm-3 and B = 520 - 610 G when the electron density is (35-60) × 1010 cm-3. In two remarkable events, 1998-04-15 and 2000-10-29, the right-hand polarization is strong for all the fine structures and corresponds to ordinary wave.
