We present a new sub-class of type Ⅲ solar radio burst at the highfrequencies around 6.0 GHz. In addition to a descending and an ascending branch on the dynamicspectrum, it has an inverted morphology different from t...We present a new sub-class of type Ⅲ solar radio burst at the highfrequencies around 6.0 GHz. In addition to a descending and an ascending branch on the dynamicspectrum, it has an inverted morphology different from the simple type U-burst. We call it 'partialN-burst' because it is interpreted as the known N-burst minus its first branch. The partial N-burstpresented here was detected among a reverse slope type Ⅲ (RS-Ⅲ) burst group prior to the type Ⅴsolar radio continuum and was simultaneously recorded by two spectrometers at the NationalAstronomical Observatories, Chinese Academy of Sciences (NAOC, 5.20-7.60 GHz) and at Purple MountainObservatory (PMO, 4.50-7.50 GHz) on 1999 August 25. After the N-burst and M-burst, the partialN-burst is a third piece of evidence for a magnetic mirror effect in solar radio observation, whenthe same electron is reflected at a pinched foot of a flare loop.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
文摘We present a new sub-class of type Ⅲ solar radio burst at the highfrequencies around 6.0 GHz. In addition to a descending and an ascending branch on the dynamicspectrum, it has an inverted morphology different from the simple type U-burst. We call it 'partialN-burst' because it is interpreted as the known N-burst minus its first branch. The partial N-burstpresented here was detected among a reverse slope type Ⅲ (RS-Ⅲ) burst group prior to the type Ⅴsolar radio continuum and was simultaneously recorded by two spectrometers at the NationalAstronomical Observatories, Chinese Academy of Sciences (NAOC, 5.20-7.60 GHz) and at Purple MountainObservatory (PMO, 4.50-7.50 GHz) on 1999 August 25. After the N-burst and M-burst, the partialN-burst is a third piece of evidence for a magnetic mirror effect in solar radio observation, whenthe same electron is reflected at a pinched foot of a flare loop.
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.
