Millisecond Spikes Research Articles

Low-temperature fabrication of spiking soma circuits using nanocrystalline-silicon TFTs.

Spiking neuron circuits consisting of ambipolar nanocrystalline-silicon (nc-Si) thin-film transistors (TFTs) have been fabricated using low temperature processing conditions (maximum of 250 °C) that allow the use of flexible substrates. These circuits display behaviors commonly observed in biological neurons such as millisecond spike duration, nonlinear frequency-current relationship, and spike frequency adaptation. The maximum drive capacity of a simple soma circuit was estimated to be approximately 9200 synapses. The effect of bias stress-induced threshold voltage degradation of component nc-Si TFTs on the spike frequency of soma circuits is explored. The measured power consumption of the circuit when spiking at 100 Hz was approximately 12 nW. Finally, the power consumption of the soma circuits at different spiking conditions and its implications on a large-scale system are discussed. The fabricated circuits can be employed as part of a compact multilayer learning network.

高压下LaBr3电子结构与光学性质的第一性原理

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 profiles 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 interpretation of microwave millisecond spikes: the main obstacles are too high values of the magnetic field strength in the source (omega_(Pe) ≤ omega_(Be)). 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.

Concerning spikes in emission and absorption in the microwave range

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 profiles 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 interpretation of microwave millisecond spikes: the main obstacles are too high values of the magnetic field strength in the source (ωPe ≤ ωBe). 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.

Intrinsic firing properties in the avian auditory brain stem allow both integration and encoding of temporally modulated noisy inputs in vitro

The intrinsic properties of tonically firing neurons in the cochlear nucleus contribute to representing average sound intensity by favoring synaptic integration across auditory nerve inputs, reducing phase locking to fine temporal acoustic structure and enhancing envelope locking. To determine whether tonically firing neurons of the avian cochlear nucleus angularis (NA) resemble ideal integrators, we investigated their firing responses to noisy current injections during whole cell patch-clamp recordings in brain slices. One subclass of neurons (36% of tonically firing neurons, mainly subtype tonic III) showed no significant changes in firing rate with noise fluctuations, acting like pure integrators. In contrast, many tonically firing neurons (>60%, mainly subtype tonic I or II) showed a robust sensitivity to noisy current fluctuations, increasing their firing rates with increased fluctuation amplitudes. For noise-sensitive tonic neurons, the firing rate vs. average current curves with noise had larger maximal firing rates, lower gains, and wider dynamic ranges compared with FI curves for current steps without noise. All NA neurons showed fluctuation-driven patterning of spikes with a high degree of temporal reliability and millisecond spike time precision. Single-spiking neurons in NA also responded to noisy currents with higher firing rates and reliable spike trains, although less precisely than nucleus magnocellularis neurons. Thus some NA neurons function as integrators by encoding average input levels over wide dynamic ranges regardless of current fluctuations, others detect the degree of coherence in the inputs, and most encode the temporal patterns contained in their inputs with a high degree of precision.

Peculiar microwave quasi-periodic pulsations with zigzag pattern in a CME-related Flare on 2005-01-15

AbstractA microwave quasi-periodic pulsation with zigzag pattern (Z-QPP) in a solar flare on 2005-01-15 is observed by the Chinese Solar Broadband Spectrometer in Huairou (SBRS/Huairou) at 1.10-1.34 GHz. The zigzag pulsation occurred just in the early rising phase of the flare with weakly right-handed circular polarization. Its period is only several decades millisecond. Particularly, before and after the pulsation, there are many spectral fine structures, such as zebra patterns, fibers, and millisecond spikes. The microwave Z-QPP can provide some kinematic information of the source region in the early rising phase of the flare, and the source width changes from ~1000 km to 3300 km, even if we have no imaging observations. The abundant spectral fine structures possibly reflect the dynamic features of non-thermal particles.

MICROWAVE QUASI-PERIODIC PULSATION WITH MILLISECOND BURSTS IN A SOLAR FLARE ON 2011 AUGUST 9

An peculiar microwave quasi-periodic pulsation (QPP) accompanying with a hard X-ray (HXR) QPP of about 20 s duration occurred just before the maximum of an X6.9 solar flare on 2011 August 9. The most interesting is that the microwave QPP is consisting of millisecond timescale superfine structures. Each microwave QPP pulse is made up of clusters of millisecond spike bursts or narrow band type III bursts. There are three different frequency drift rates: global frequency drift rate of microwave QPP pulse group, frequency drift rate of microwave QPP pulse, and frequency drift rate of individual millisecond spikes or type III bursts. The physical analysis indicates that the energetic electrons accelerating from a large-scale highly dynamic magnetic reconnecting current sheet above the flaring loop propagate downwards, impact on the flaring plasma loop, and produce HXR bursts. The tearing-mode (TM) oscillations in the current sheet modulate HXR emission and generate HXR QPP; the energetic electrons propagating downwards produce Langmuir turbulence and plasma waves, result in plasma emission. The modulation of TM oscillation on the plasma emission in the current-carrying plasma loop may generate microwave QPP. The TM instability produces magnetic islands in the loop. Each X-point will be a small reconnection site and accelerate the ambient electrons. These accelerated electrons impact on the ambient plasma and trigger the millisecond spike clusters or the group of type III bursts. Possibly each millisecond spike burst or type III burst is one of the elementary burst (EB). Large numbers of such EB clusters form an intense flaring microwave burst.

Microwave burst with fine spectral structures in a solar flare on 2011 August 9

On August 9, 2011, there was an X6.9 flare event occurred near the west limb of solar disk. From the observation obtained by the spectrometer of the Chinese Solar Broadband Radio Spectrometer in Huairou (SBRS/Huairou) around the flare, we find that this powerful flare has only a short-duration microwave burst of about only 5 minutes, and during the short-duration microwave burst, there are several kinds of fine structures on the spectrogram. These fine structures include very short-period pulsations, millisecond spike bursts, and type III bursts. The most interesting is that almost all of the pulses of very short-period pulsation (VSP) are structured by clusters of millisecond timescales of spike bursts or type III bursts. And there exists three different kinds of frequency drift rates in the VSP: the frequency drift rates with absolute value of about 55 - 130 MHz s^{-1} in the pulse groups, the frequency drift rates with absolute value of about 2.91 - 16.9 GHz s^{-1} on each individual pulse, and the frequency drift rates with absolute value of about 15 - 25 GHz s$^{-1}$) at each individual spike burst or type III burst.

Temperature Measurement in Rapid Thermal Processing with Focus on the Application to Flash Lamp Annealing

The present review intends to help its reader find a suitable method for temperature measurement in Millisecond Spike Annealing (MSA). For this purpose it is going to highlight current and former industrial and research approaches for both RTP (Rapid Thermal Processing) and MSA to measure the “true wafer temperature.” The theoretical background of each measurement technique is considered along with its capability to be applied in MSA tools as well as its suitability for industry in terms of time and temperature resolution.

Recent results of zebra patterns in solar radio bursts

This review covers the most recent experimental results and theoretical research on zebra patterns (ZPs) in solar radio bursts. The basic attention is given to events with new peculiar elements of zebra patterns received over the last few years. All new properties are considered in light of both what was known earlier and new theoretical models. Large-scale ZPs consisting of small-scale fiber bursts could be explained by simultaneous inclusion of two mechanisms when whistler waves “highlight" the levels of double plasma resonance (DPR). A unique fine structure was observed in the event on 2006 December 13: spikes in absorption formed dark ZP stripes against the absorptive type III-like bursts. The spikes in absorption can appear in accordance with well known mechanisms of absorptive bursts. The additional injection of fast particles filled the loss-cone (breaking the loss-cone distribution), and the generation of the continuum was quenched at these moments. The maximum absorptive effect occurs at the DPR levels. The parameters of millisecond spikes are determined by small dimensions of the particle beams and local scale heights in the radio source. Thus, the DPR model helps to understand several aspects of unusual elements of ZPs. However, the simultaneous existence of several tens of the DPR levels in the corona is impossible for any realistic profile of the plasma density and magnetic field. Three new theories of ZPs are examined. The formation of eigenmodes of transparency and opacity during the propagation of radio waves through regular coronal inhomogeneities is the most natural and promising mechanism. Two other models (nonlinear periodic space – charge waves and scattering of fast protons on ion-sound harmonics) could happen in large radio bursts.

Concerning mechanisms for the zebra pattern formation in the solar radio emission

The nature of the zebra patterns in continuous type-IV solar radio bursts is discussed. The most comprehensively developed models of such patterns involve mechanisms based on the double plasma resonance and plasma wave-whistler interaction. Over the last five years, there have appeared a dozen papers concerning the refinement of the mechanism based on the double plasma resonance, because, in its initial formulation, this mechanism failed to describe many features of the zebra pattern. It is shown that the improved model of this mechanism with a power-law distribution function of hot electrons within the loss cone is inapplicable to the coronal plasma. In recent papers, the formation of the zebra pattern in the course of electromagnetic wave propagation through the solar corona was considered. In the present paper, all these models are estimated comparatively. An analysis of recent theories shows that any types of zebra patterns can form in the course of radio wave propagation in the corona, provided that there are plasma inhomogeneities of different scales on the wave path. The superfine structure of zebra stripes in the form of millisecond spikes with a strict period of ∼30 ms can be attributed to the generation of continuous radio emission in the radio source itself, assuming that plasma inhomogeneities are formed by a finite-amplitude wave with the same period.

Microwave Millisecond Spike Emission in the Solar Flare of 1991 May 16

Properties, including the time duration, polarization, quasi-periodical oscillations and so on, of the microwave spike emissions observed at 2.5 GHz and 2.6 GHz during the solar flare of 1991 May 16 are analyzed statistically. The left-handed and right-handed circular polarizations of the spike emissions at 2.5, 2.6 and 3.1 GHz are reported in detail. At these 3 frequencies, most of the spikes are superposed on both the rising (and maximum) and the descending phase of the burst. It is noteworthy that spikes also appeared superposed on the small bursts that appeared after the main burst. The spike emission lasted 17 minutes. Polarization reversals on different timescales appearing in the spike emissions at 2.5 and 2.6 GHZ are described. Our statistical analysis indicates that the polarization reversals at 2.5 and 2.6 GHz differ in characters on average, the polarization reversal at 2.5 GHz is earlier than that of 2.6 GHz by about 1.5 minutes, and polarization reversal of the spike emission is more frequent at 2.5 GHZ.

Superfine Temporal Structure of the Microwave Burst on 21 April 2002: What Can We Learn about the Emission Mechanism?

Zebra pattern is observed as a number of almost parallel bright and dark stripes in the dynamic spectrum of solar radio emission. Recent observations show that zebra patterns in the microwave range often have superfine temporal structure, when the zebra stripes consist of individual short pulses similar to millisecond spikes. In this article, the burst on 21 April 2002 is investigated. The burst with a distinct superfine structure was detected at the Huairou Station (China) in 2.6 – 3.8 GHz frequency range. It is found that the emission pulses are quasi-periodic, the pulse period is about 25 – 40 ms and decreases with an increase of the emission frequency. The degree of circular polarization of zebra pattern increases with an increase of the emission frequency, it varies from moderate (about 20%) to relatively high (>60%) values. The temporal delay between the signals with left- and right-handed polarization is not found. The conclusion is made that the emission is generated by plasma mechanism at the fundamental plasma frequency in a relatively weak magnetic field. The observed polarization of the emission is formed during its propagation due to depolarization effects. A model is proposed in which the superfine temporal structure is formed due to modulation of the emission mechanism by downward propagating MHD oscillations; this model allows us to explain the observed variation of the pulse period with the emission frequency.

Coronal scattering of radio emission under strong regular refraction

Abstract The influence of strong regular refraction (that leads to regular caustics and multipathing) in the solar corona on the structure of radio emission scattered by coronal turbulence is investigated. Distant cosmic sources and Sun's own radio sources are considered. It is shown that observations of the energy spectrum of spacecraft radio signals and of the mean profile of a pulsar pulse in the Sun's caustic shadow zone can be used for coronal turbulence diagnostics. It is also shown that strong regular refraction plays an important role in formation of solar millisecond spike bursts and of type IIId solar decameter radio bursts with echo components.

Frequency Distributions of Microwave Pulses for the 18 March 2003 Solar Flare

We analyze the pulses in high-frequency drift radio structures observed by the spectrometer at Purple Mountain Observatory (PMO) over the frequency range of 4.5-7.5 GHz during the 18 March 2003 solar flare. A number of individual pulses are determined from the drifting radio structures after the detected gradual component subtraction. The frequency distributions of microwave pulse occurrence as functions of peak flux, duration, bandwidth, and time interval between two adjacent pulses exhibit a power-law behavior, i. e. dN/dx alpha x(-alpha x). From regression fitting in log-log space, we obtain the power-law indexes, alpha(P) = 7.38 +/- 0.40 for the peak flux, alpha(D) = 5.39 +/- 0.86 for the duration, and alpha(B) = 6.35 +/- 0.56 for the bandwidth. We find that the frequency distribution for the time interval displays a broken power law. The break occurs at about 500 ms, and their indexes are alpha(W1) = 1.56 +/- 0.08 and alpha(W2) = 3.19 +/- 0.12, respectively. Our results are consistent with the previous findings of hard X-ray pulses, type III bursts, and decimetric millisecond spikes.

Solar Radio Bursts with Drifting Stripes in Emission and Absorption

This review covers fairly comprehensively experimental and theoretical research on the fine structure of types zebra pattern (ZP) and fiber bursts (FB) in solar type II + IV radio bursts. The basic attention is given to the latest experimental data. A comparative analysis of several recent solar type IV radio outbursts with these fine structure in dynamical radio spectra is carried out using available ground-based and satellite data (Yohkoh, SOHO, TRACE, RHESSI). New data on microwave zebra structures and fiber bursts testifies that they are analogous to similar structures observed at meter wavelengths. The discovery of the superfine structure, in the form of millisecond spikes is the most significant new effect in the cm range. All basic theoretical models of the zebra pattern and fiber bursts are discussed critically. Two main models are studied for their interpretation: (i) interactions between electrostatic plasma waves and whistlers, (ii) radio emission at double plasma resonance (DPR). The relative significance of several possible mechanisms remains uncertain.

Malleability of Spike-Timing-Dependent Plasticity at the CA3-CA1 Synapse

The magnitude and direction of synaptic plasticity can be determined by the precise timing of presynaptic and postsynaptic action potentials on a millisecond timescale. In vivo, however, neural activity has structure on longer timescales. Here we show that plasticity at the CA3-CA1 synapse depends strongly on parameters other than millisecond spike timing. As a result, the notion that a single spike-timing-dependent plasticity (STDP) rule alone can fully describe the mapping between neural activity and synapse strength is invalid. We have begun to explore the influence of additional behaviorally relevant activity parameters on STDP and found conditions under which underlying spike-timing-dependent rules for potentiation and depression can be separated from one another. Potentiation requires postsynaptic burst firing at 5 Hz or higher, a firing pattern that occurs during the theta rhythm. Potentiation is measurable after only tens of presynaptic-before-postsynaptic pairings. Depression requires hundreds of pairings but has less stringent long timescale requirements and broad timing dependence. By varying these parameters, we obtain STDP curves that are long-term potentiation only, bidirectional, or long-term depression only. This expanded description of the CA3-CA1 learning rule reconciles apparent contradictions between spike-timing-dependent plasticity and previous work at CA3-CA1 synapses.

Spectral and temporal properties of narrowband dm-spikes and broadband pulses in the August 5, 2003 flare

On August 5, 2003 the Ondřejov radiospectrograph and the Brazilian Solar Spectrograph recorded simultaneously the narrowband dm-spikes superimposed on broadband pulses in the frequency ranges of 0.8–4.5 and 1.75–2.25 GHz, respectively. Using a new method of wavelet filtering broadband sub-second pulses with a frequency width of 0.48 GHz and narrowband millisecond spikes with a frequency width 0.13 GHz were recognized and analysed in detail. Filtered radio spectra showed that the spikes were clustered in stripes at different frequencies. These stripes drifted and their frequency ratios changed during short time intervals. Periods of the narrowband spikes and their stripes were ∼0.4 s and 4, 8–10, and 16 s, respectively. The main period of the broadband pulses was ∼4 s. Values of significant periods of the narrowband spikes coincided with those of the broadband pulses. We found significant peak-to-peak correlations with zero time lags among stripes of the narrowband spikes on different frequencies. The characteristics of the narrowband dm-spikes and broadband pulses indicate that mutually linked emission processes generate both fine structures.

Location and parameters of a microwave millisecond spike event

A typical microwave millisecond spike event on November 2, 1997 was observed by the radio spectrograph of National Astronomical Observatories (NAOs) at 2.6–3.8 GHz with high time and frequency resolution. This event was also recorded by Nobeyama Radio Polarimeters (NoRP) at 1–35 GHz and Radio Heliograph (NoRH) at 17 GHz. The source at 17 GHz is located in one foot-point of a small bright coronal loop of YOHKOH SXT and SOHO EIT images with strong photospheric magnetic field in SOHO MDI magnetograph. It is assumed that the electron cyclotron maser instability and gyro-resonance absorption dominate, respectively, the rising and decay phase of the spike event. For different harmonic number of gyro-frequency or magnetic field strength, a fitting program with free plasma parameters is used to minimize the difference between the observational and theoretical values of the exponential growth and decay rates for a given spike. The plasma parameters at third harmonic number are more comparable to their typical values in solar corona. Hence, it is able to provide a diagnosis for the source parameters (magnetic field, density, and temperature), the properties of radiations (wave vector and propagation angle), and the properties of non-thermal electrons (density, pitch angle, and energy). The results are also comparable with the diagnosis of the gyro-synchrotron radiation model, the frequency drift rates and a dipole magnetic field model, as well as the YOHKOH SXT and SOHO MDI data.

Narrowband dm-spikes in the frequency range above 1 GHz and hard X-ray emission

Narrowband dm-spikes observed in nine intervals during five solar flares in the 1–2 GHz range were analyzed together with the RHESSI and HXRS observations. It was found that the over-frequency integrated radio flux during the spike period is closely related with the hard X-ray bursts (the correlation coefficient was 0.7–0.9) and their time delays after X-rays were 2–14 s, with one exception (March 18, 2003) where the time delay was opposite −15 s. Association of spikes with X-ray spectral characteristics enabled us to divide the spikes into two groups: (a) those observed before the soft X-ray flare maximum and, (b) those observed after this maximum. While for the spikes observed after the flare maximum no systematic spectral characteristics were found, the spikes, observed before the flare maximum were at their beginning associated with relatively hard X-ray spectra and their hardness decreased with time. The RHESSI X-ray sources were compact, only in the March 18, 2003 event an additional X-ray source appeared just at the time of the dm-spikes observation. Fourier transformation of the dynamic spectra of spikes was done to compare their dynamics with the X-ray spectral indices. No correlation between power-law spike and X-ray indices were found. It indicates that the MHD turbulence, if it plays a role, does not represent a strong connection between the spectral characteristics of the dm-spikes and associated X-ray bursts. Furthermore, the results were compared with those obtained by (Aschwanden, M.J., Güdel, M. The coevolution of decimetric millisecond spikes and hard X-ray emission during solar flares. Astrophys. J. 401, 736–753, 1992) for spikes observed on lower radio frequencies. Contrary to their results, no monotonic dependence between time delays and X-ray intensities were found. Finally, the results were discussed using the model of the narrowband dm-spikes and model of electron acceleration in the collapsing magnetic trap.

Multi-spectral characterization of solar gamma ray events radio emission. Study case July 14, 2000.

Solar sporadic radio emission takes place in a wide range of time scales; from milliseconds to days. Researches have been conduced mainly to explain the behavior of radio emission in specific time scales and lately to millisecond spikes research has been devoted a lot of papers.In this work we pay attention to the characteristics of millisecond spikes in relation to the general activity in which they are included, processes with very different time scales.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html