A rare large Type Ⅳμ burst, appeared above active region NOAA/USAF 5278 was observed at Yunnan Observatory with Phoenix Ⅱ Microwave Spectrometer at three frequencies (4 00, 2 84 and 1 42 GHz) on December 16, 1988. ...A rare large Type Ⅳμ burst, appeared above active region NOAA/USAF 5278 was observed at Yunnan Observatory with Phoenix Ⅱ Microwave Spectrometer at three frequencies (4 00, 2 84 and 1 42 GHz) on December 16, 1988. The burst consisted of 5 main peaks with a quasiperiod of 12 5 min, on which many complex millisecond spike emissions were superimposed. Within the first main peak there were 8 secondary peaks with a quasi period of 98s (at 4 00 GHz), 72s (2 84 GHz) and 60s (1 42 GHz). A semi quantitative explanation is given for the variation of the quasi period with frequency in terms of MHD modulated oscillations in the magnetic flux tube.展开更多
Neurons at rest can exhibit diverse firing activities patterns in response to various external deterministic and random stimuli, especially additional currents. In this paper, neuronal firing patterns from bursting to...Neurons at rest can exhibit diverse firing activities patterns in response to various external deterministic and random stimuli, especially additional currents. In this paper, neuronal firing patterns from bursting to spiking, induced by additional direct and stochastic currents, are explored in rest states corresponding to two values of the parameter VK in the Chay neuron system. Three cases are considered by numerical simulation and fast/slow dynamic analysis, in which only the direct current or the stochastic current exists, or the direct and stochastic currents coexist. Meanwhile, several important bursting patterns in neuronal experiments, such as the period-1 ＂circle/homoclinic＂ bursting and the integer multiple ＂fold/homoclinic＂ bursting with onc spike per burst, as well as the transition from integer multiple bursting to period-1 ＂circle/homoclinic＂ bursting and that from stochastic ＂Hopf/homoclinic＂ bursting to ＂Hopf/homoclinic＂ bursting, are investigated in detail.展开更多
In this study, we explore the interesting phenomenon of firing spikes and complex dynamics of Morris-Lecar model. We consider a set of parameters such that the model exhibits a wide range of phenomenons. We investigat...In this study, we explore the interesting phenomenon of firing spikes and complex dynamics of Morris-Lecar model. We consider a set of parameters such that the model exhibits a wide range of phenomenons. We investigate the influences of injected current and temperature on the spiking dynamics of Morris-Lecar model. Moreover, we study bifurcations, and computational properties of this neuron model. Also, we define a bound (Max and Min voltage) for membrane potential and a certain voltage value or threshold for firing the spikes. Studying the two co-dimension bifurcations demonstrates much more complicated behaviors for this single neuron model. We also describe the phenomenon of neural bursting, and investigate the dynamics of Morris-Lecar model as a square-wave burster, elliptic burster and parabolic burster.展开更多
In some events, weak fast solar bursts （near the level of the quiet Sun） were observed in the background of numerous spikes in emission and absorption. In such a case, the background contains the noise signals of th...In some events, weak fast solar bursts （near the level of the quiet Sun） were observed in the background of numerous spikes in emission and absorption. In such a case, the background contains the noise signals of the receiver. In events on 2005 September 16 and 2002 April 14, the solar origin of fast bursts was confirmed by simultaneous recording of the bursts at several remote observatories. The noisy background pixels in emission and absorption can be excluded by subtracting a higher level of continuum when constructing the spectra. The wavelet spectrum, noisy pro- files in different polarization channels and a spectrum with continuum level greater than zero demonstrates the noisy character of pixels with the lowest levels of emission and absorption. Thus, in each case, in order to judge the solar origin of all spikes, it is necessary to determine the level of continuum against the background of which the solar bursts are observed. Several models of microwave spikes are discussed. The electron cyclotron maser emission mechanism runs into serious problems with the in- terpretation of microwave millisecond spikes： the main obstacles are too high values of the magnetic field strength in the source （Pe 〈 uB）. The probable mechanism is the interaction of plasma Langmuir waves with ion-sound waves （l ＋ s → t） in a source related to shock fronts in the reconnection region.展开更多
文摘A rare large Type Ⅳμ burst, appeared above active region NOAA/USAF 5278 was observed at Yunnan Observatory with Phoenix Ⅱ Microwave Spectrometer at three frequencies (4 00, 2 84 and 1 42 GHz) on December 16, 1988. The burst consisted of 5 main peaks with a quasiperiod of 12 5 min, on which many complex millisecond spike emissions were superimposed. Within the first main peak there were 8 secondary peaks with a quasi period of 98s (at 4 00 GHz), 72s (2 84 GHz) and 60s (1 42 GHz). A semi quantitative explanation is given for the variation of the quasi period with frequency in terms of MHD modulated oscillations in the magnetic flux tube.
基金Project supported by the National Natural Science Foundation of China （Grant Nos 10432010 and 10526002）.Acknowledgement The bifurcation diagrams in this paper are obtained by means of the package C0NTENT.
文摘Neurons at rest can exhibit diverse firing activities patterns in response to various external deterministic and random stimuli, especially additional currents. In this paper, neuronal firing patterns from bursting to spiking, induced by additional direct and stochastic currents, are explored in rest states corresponding to two values of the parameter VK in the Chay neuron system. Three cases are considered by numerical simulation and fast/slow dynamic analysis, in which only the direct current or the stochastic current exists, or the direct and stochastic currents coexist. Meanwhile, several important bursting patterns in neuronal experiments, such as the period-1 ＂circle/homoclinic＂ bursting and the integer multiple ＂fold/homoclinic＂ bursting with onc spike per burst, as well as the transition from integer multiple bursting to period-1 ＂circle/homoclinic＂ bursting and that from stochastic ＂Hopf/homoclinic＂ bursting to ＂Hopf/homoclinic＂ bursting, are investigated in detail.
文摘In this study, we explore the interesting phenomenon of firing spikes and complex dynamics of Morris-Lecar model. We consider a set of parameters such that the model exhibits a wide range of phenomenons. We investigate the influences of injected current and temperature on the spiking dynamics of Morris-Lecar model. Moreover, we study bifurcations, and computational properties of this neuron model. Also, we define a bound (Max and Min voltage) for membrane potential and a certain voltage value or threshold for firing the spikes. Studying the two co-dimension bifurcations demonstrates much more complicated behaviors for this single neuron model. We also describe the phenomenon of neural bursting, and investigate the dynamics of Morris-Lecar model as a square-wave burster, elliptic burster and parabolic burster.
基金supported by the Ministry of Education and Science of theRussian Federationsupported by the Chinese Academy of Sciences Visiting Professorship for Senior International Scientists (Grant Nos. 2011T1J20 and 2010T2J24)+2 种基金supported by the Russian Foundation of Basic Research (RFBR,GrantNos. 11-02-00757,11-02-91151,10-02-00153,12-02-91161-GFEN and FP7-PEOPLE-2011-IRSES)The National Basic Research Program of the Ministry of Science and Technology of China(Grant No. 2006CB806301)CAS-NSFC Key Project (Grant No. 10778605) support the Chinese
文摘In some events, weak fast solar bursts （near the level of the quiet Sun） were observed in the background of numerous spikes in emission and absorption. In such a case, the background contains the noise signals of the receiver. In events on 2005 September 16 and 2002 April 14, the solar origin of fast bursts was confirmed by simultaneous recording of the bursts at several remote observatories. The noisy background pixels in emission and absorption can be excluded by subtracting a higher level of continuum when constructing the spectra. The wavelet spectrum, noisy pro- files in different polarization channels and a spectrum with continuum level greater than zero demonstrates the noisy character of pixels with the lowest levels of emission and absorption. Thus, in each case, in order to judge the solar origin of all spikes, it is necessary to determine the level of continuum against the background of which the solar bursts are observed. Several models of microwave spikes are discussed. The electron cyclotron maser emission mechanism runs into serious problems with the in- terpretation of microwave millisecond spikes： the main obstacles are too high values of the magnetic field strength in the source （Pe 〈 uB）. The probable mechanism is the interaction of plasma Langmuir waves with ion-sound waves （l ＋ s → t） in a source related to shock fronts in the reconnection region.
