Average Peak Energy Research Articles

Characteristics of Auroral Electron Precipitation at Geomagnetic Latitude 67° Over Tromsø

AbstractWe use the EISCAT incoherent scatter radar data measured in years 2001–2021 to study statistical characteristics of 1–100 keV electron precipitation at 66.7° MLAT over Tromsø. Peak energies, auroral powers and number fluxes of precipitating electrons are derived from electron density altitude profiles measured along the geomagnetic field line during periods of no photoionization. The method allows us to include energetic 30–100 keV electrons, which are poorly covered in earlier satellite‐based studies. Locations of the radar within the auroral oval are determined using a model with the 1‐hr Hpo geomagnetic index as input. The average peak energy of precipitating electrons increases almost monotonically from evening (18 MLT) to morning hours (09 MLT). The 30–50 keV electrons dominate the energetic electron precipitation before 06 MLT, after which the 50–100 keV precipitation becomes dominant. Large auroral powers (>60 mWm−2) are observed in the 18–02 MLT sector in the main auroral oval. We obtain occurrence rate of electron precipitation in Tromsø by calculating the fraction of data points with auroral power larger than 2 mWm−2. The occurrence rate peaks during the declining phases of solar cycles (sc), in 2002–2004 for sc23 and in 2015–2017 for sc24, caused by variations in geomagnetic activity. In addition, the occurrence rate has maxima during March and September, minimum in December to January, and it increases monotonically from evening to morning hours, reaching maximum at 05–06 MLT.

Performance improvement of a 200TW/1Hz Ti:sapphire laser for laser wakefield electron accelerator

For investigations on laser wakefield electron acceleration, there is a strong demand for driving laser exhibiting high stability and good spatial-temporal quality. Here we present an upgraded 200TW/1Hz Ti:sapphire laser with following key characteristics. The fluctuation of pulse energy and beam pointing for consecutive 5400 pulses in 90 min are as low as 0.55% and 1.5μrad respectively. The compressed pulse duration is 23.7 fs, which is about 1.1 times of the Fourier-transform limit. The focal spot obtained by an f/30 off-axis parabolic mirror is 54 μm × 52 μm at 1/e2, which is very close to the diffraction limit. Moreover, in the laser wakefield electron acceleration experiments driven by this upgraded 200TW/1Hz laser, quasi-mono-energetic electron beams are reproduced in consecutive shots. For successive 300 shots, the average peak energy of produced electron beams is 667 MeV, and the peak energy fluctuation is only 3.4%. The progresses on both driving laser and laser wakefield electron acceleration make the realization of compact X-ray free electron laser possible.

Mozaffarian, F. and Sanborn, A. F.: Descriptions of the calling and courtship songs of Tibicen esfandiarii Dlabola, 1970 (Auchenorrhyncha: Cicadidae)

The calling song of Tibicen esfandiarii Dlabola, 1970 is described for the first time. The calling song consists of a continuous train of syllables (3–9 ms) and short intersyllable intervals (0.4 to 1.9 ms). The song begins at a lower intensity, increasing intensity through a series of steps to the ultimate portion of the call that is produced for an extended period at this loudest intensity. The song terminates after a short pause (2 ms) that is followed by about 0.5 s of singing. The total syllable repetition frequency is 193.1±60.24 Hz (n = 48 measurements from six individuals) and the frequency of the average peak energy of calling song is 4875±59.45 Hz (n = 6 individuals) and courtship songs (n = 15 parts of call from one individual) is 4875±0 Hz. The courtship song consists of alternative phrases usually starting after a short pause (average of 70.8±4.85 ms) and syllable frequency reducing from the average of 157.0±7.1 Hz to 128.4±1.67 Hz. The duration, frequency of syllables and the average RMS amplitude in different portions of the song and in different specimens are measured and the behavior of the specimen during song production is described. We show significant differences in the frequency and temporal components of T. esfandiarii from its congeneric species, Tibicen plebejus (Scopoli, 1763), with which is shares part of its range in Iran.

Direct laser acceleration of electrons in a high-Z gas target and the effect of threshold plasma density on electron beam generation

An experimental study of laser driven electron acceleration in N2 and N2-He mixed gas-jet targets using laser pulses with durations of ∼60–70 fs is presented. Generation of relativistic electron beams with quasi-thermal spectra was observed at a threshold plasma density of ∼1.6 × 1018 cm−3 in the case of pure N2. The threshold density was found to increase with increasing doping concentrations of He. At an optimum fraction of 50% of He in N2, generation of quasi-monoenergetic electron beams was observed at a comparatively higher threshold density of ∼2 × 1018 cm−3, with an average peak energy of ∼168 MeV, average energy spread of ∼21%, and average total beam charge of ∼220 pC. The electron acceleration could be attributed to direct laser acceleration as well as the hybrid mechanism. The observation of an optimum fraction of He in N2 (in turn threshold plasma density) for comparatively better quality electron beam generation can be understood in terms of the plasma density dependent variation in the dephasing rate of electrons with respect to the transverse oscillating laser field. Results are also supported by 2D particle-in-cell simulations performed using the code EPOCH.

Spectral properties of gamma-ray bursts observed by the Suzaku wide-band all-sky monitor

Abstract We have systematically studied the spectral properties of 302 localized gamma-ray bursts (GRBs) observed by the Suzaku wide-band all-sky monitor (WAM) from 2005 August to 2010 December. The energy spectra in the 100–5000 keV range integrated over the entire emission and the 1 s peak were fitted by three models: a single power law, a power law with an exponential cutoff (CPL), and the GRB Band function (GRB). Most of the burst spectra were well fitted by a single power law. The average photon index α was −2.11 and −1.73 for long and short bursts, respectively. For the CPL and GRB models, the low-energy and high-energy photon indices (α and β) for the entire emission spectra were consistent with previous measurements. The averages of the α and β were −0.90 and −2.65 for long-duration GRBs, while the average α was −0.55 and the β was not well constrained for short-duration GRBs. However, the average peak energy Epeak was 645 and 1286 keV for long- and short-duration GRBs respectively, which are higher than previous Fermi/GBM measurements (285 keV and 736 keV). The α and Epeak of the 1 s peak spectra were larger, i.e., the spectra were harder, than the total fluence spectra. Spectral simulations based on Fermi-GBM results suggest that the higher Epeaks measured by the Suzaku WAM could be due to detector selection bias, mainly caused by the limited energy range above 100 keV.

Quasi-monoenergetic electron beams from a few-terawatt laser driven plasma acceleration using a nitrogen gas jet

An experimental investigation on the laser plasma acceleration of electrons has been carried out using 3 TW, 45 fs duration titanium sapphire laser pulse interaction with a nitrogen gas jet at an intensity of 2 × 1018 W cm−2. We have observed the stable generation of a well collimated electron beam with divergence and pointing variation ∼10 mrad from nitrogen gas jet plasma at an optimum plasma density around 3 × 1019 cm−3. The energy spectrum of the electron beam was quasi-monoenergetic with an average peak energy and a charge around 25 MeV and 30 pC respectively. The results will be useful for better understanding and control of ionization injection and the laser wakefield acceleration (LWFA) of electrons in high-Z gases and also towards the development of practical LWFA for various applications including injectors for high energy accelerators.

Pulse-wise Amati correlation in Fermi gamma-ray bursts

We make a detailed pulse-wise study of gamma-ray bursts (GRBs) with known redshift detected by Fermi/Gamma-Ray Burst Monitor. The sample contains 19 GRBs with 43 pulses. We find that the average peak energy is correlated to the radiated energy (the Amati relation) for individual pulses with a correlation coefficient of 0.86, which is slightly better than the correlation for the full GRBs. As the present correlation holds within GRBs, it is strong evidence supporting the reliability of such a correlation. We investigate several aspects of this correlation. (i) We divide our sample into redshift bins and study the evolution of the correlation. Though there is a marginal indication of evolution of the correlation, we can conclude that the present data are consistent with no evolution. (ii) We compare the correlation in the first or single pulses of these GRBs to that of the rest of the pulses, and confirm that the correlation is unaffected by the fact that first/single pulses are generally harder than the rest. Finally, we conclude that the pulse-wise Amati correlation is more robust and it has the potential of refining the correlation so that GRB study could be used as a cosmological tool.

Distribution of the Impurity Resonance Energy in Bi2Sr2CaCu2O8+δ Observed by Scanning Tunneling Spectroscopy

Using scanning tunneling microscopy and spectroscopy (STM/STS) at 4.2 K, we observed Zn impurity resonance states in single crystals of Zn substituted Bi2Sr2Ca(Cu1−xZnx)2O8+δ. Zn impurity resonances were characterized by the peak structure in the local density of states (LDOS). The peaks were appeared near the EF on each of Zn impurity sites. The peak energy showed a wide distribution from −7 to 5 meV. The average peak energy was −1.5 meV and the variance was 1.8 meV. We investigated the correlation between the peak energy at a Zn site and the energy gap value in the region where the Zn site is embedded. Although we observed about hundred Zn sites, no correlation between the local energy gap and the peak energy was observed.

Empirical assessment of strategic behavior in the Italian power exchange

AbstractIn this paper we examine the bidding behavior of Enel in 2004 to estimate the extent to which Enel was bidding opportunistically in temporal and geographic markets in which it was indispensible. Two types of competitive benchmark for bid levels were used. First, bids submitted by Enel in temporal and geographic markets in which it was pivotal were compared with Enel's bids submitted for similar generating units in markets where potential for market power exercise is low. Second, price bids of Enel were compared with bids submitted for comparable plants by other small generators that have no market power. This analysis has shown that over the period from April to August 2004 the bidding behavior of Enel varied across plant types. Both competitive benchmarks suggest that price bids of Enel submitted for Combined Cycle Gas plants were about 40–50% above the competitive level when Enel was pivotal. The excessive bidding was also present for Traditional Oil plants and Repowered Gas plants, although at a lower level, and was not established at all for Traditional Coal plants. We have verified whether this conduct could have had a material impact on market prices. An analysis of impact suggests that Enel's bidding during the peak hours was indeed 40% in excess of competitive levels for its CCGT units, 30% on Repowering units, and 20% on Oil units, such bidding have resulted in 20–30% higher average peak energy prices (PUN) in Italy. Copyright © 2010 John Wiley & Sons, Ltd.

Gamma Decay Heat Distribution in Core: A Known Issue Revisited

Decay heat in fission reactors is almost equally subdivided into two parts, one part due to beta rays and the other due to gamma photons. Beta rays are absorbed practically where they are generated while gamma photons travel some distance in core before being absorbed. The decay power peaking factor is, in fact, affected by this phenomenon of gamma decay heat redistribution. Calculations have been performed by the Monte Carlo MCNP5 computer code on the experimental LOFT reactor and on a larger 1000 MWe PWR using various initial power distributions with variable power peak sharpness (midheight peak width). The results indicate that an average peak energy reduction ratio of 0.82 for gamma (18% peak reduction) can be used with tolerable error up to a midheight width of the produced energy peak (neutron flux shape during operation) of 120 cm. Beyond this value, no peak energy reduction is warranted. This phenomenon of absorbed γ power redistribution in core may be very significant (100 to K reduction in calculated PCT).

Swift observations of GRB 060614: an anomalous burst with a well behaved afterglow

GRB 060614 is a remarkable gamma-ray burst (GRB) observed by Swift with puzzling properties, which challenge current progenitor models. In particular, the lack of any bright supernova (SN) down to very strict limits and the vanishing spectral lags during the whole burst are typical of short GRBs, strikingly at odds with the long (102 s) duration of this event. Here we present detailed spectral and temporal analysis of the Swift observations of GRB 060614. We show that the burst presents standard optical, ultraviolet and X-ray afterglows, detected beginning 4 ks after the trigger. An achromatic break is observed simultaneously in the optical and X-ray bands, at a time consistent with the break in the R-band light curve measured by the VLT. The achromatic behaviour and the consistent postbreak decay slopes make GRB 060614 one of the best examples of a jet break for a Swift burst. The optical and ultraviolet afterglow light curves have also an earlier break at 29.7 ± 4.4 ks, marginally consistent with a corresponding break at 36.6 ± 2.4 ks observed in the X-rays. In the optical, there is strong spectral evolution around this break, suggesting the passage of a break frequency through the optical/ultraviolet band. The very blue spectrum at early times suggests this may be the injection frequency, as also supported by the trend in the light curves: rising at low frequencies, and decaying at higher energies. The early X-ray light curve (from 97 to 480 s) is well interpreted as the X-ray counterpart of the burst extended emission. Spectral analysis of the BAT and XRT data in the ∼80 s overlap time interval show that the peak energy of the burst has decreased to as low as 8 keV at the beginning of the XRT observation. Spectral analysis of following XRT data shows that the peak energy of the burst continues to decrease through the XRT energy band and exits it at about 500 s after the trigger. The average peak energy Ep of the burst is likely below the BAT energy band (<24 keV at the 90% confidence level) but larger than 8 keV. The initial group of peaks observed by BAT (∼5 s) is however distinctly harder than the rest of the prompt emission, with a peak energy of about 300 keV as measured by Konus Wind. Considering the time-averaged spectral properties, GRB 060614 is consistent with the Eiso − E rest , Eγ − E rest ,a ndLp,iso − E rest correlations.

Panchromatic study of GRB 060124: from precursor to afterglow

We present observations of GRB 060124, the first event for which both the prompt and the afterglow emission could be observed simultaneously and in their entirety by the three Swift instruments. Indeed, Swift-BAT triggered on a precursor ~570s before the main burst peak, and this allowed Swift to repoint the narrow field instruments to the burst position ~350s before the main burst occurred. GRB 060124 also triggered Konus-Wind, which observed the prompt emission in a harder gamma-ray band (up to 2MeV). Thanks to these exceptional circumstances, the temporal and spectral properties of the prompt emission can be studied in the optical, X-ray and gamma-ray ranges. While the X-ray emission (0.2-10keV) clearly tracks the gamma-ray burst, the optical component follows a different pattern, likely indicating a different origin, possibly the onset of external shocks. The prompt GRB spectrum shows significant spectral evolution, with both the peak energy and the spectral index varying. As observed in several long GRBs, significant lags are measured between the hard- and low-energy components, showing that this behaviour extends over 3 decades in energy. The GRB peaks are also much broader at soft energies. This is related to the temporal evolution of the spectrum, and can be accounted for by assuming that the electron spectral index softened with time. The burst energy (E_iso~5x10^{53} erg) and average peak energy (E_p~300keV) make GRB 060124 consistent with the Amati relation. The X-ray afterglow is characterized by a decay which presents a break at t_b~10^5s.

The nu F nu Peak Energy Distributions of Gamma-Ray Bursts Observed by BATSE

view Abstract Citations (156) References (25) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The nu F nu Peak Energy Distributions of Gamma-Ray Bursts Observed by BATSE Mallozzi, Robert S. ; Paciesas, William S. ; Pendleton, Geoffrey N. ; Briggs, Michael S. ; Preece, Robert D. ; Meegan, Charles A. ; Fishman, Gerald J. Abstract The majority of gamma-ray bursts exhibit a peak in their νFν photon energy spectra at an energy Ep that is in the range of ∼20-2000 keV available to the Large Area Detectors of the Burst and Transient Source Experiment (BATSE) on the Compton Gamma Ray Observatory. If gamma-ray burst sources are at cosmological distances (d ≳ 1 Gpc), then the spectra of dim bursts should be redshifted to lower energies relative to those of bright bursts. The magnitude of the shift is a function of the cosmological redshifts z of both the dim and bright burst sources and hence yields the range of redshift available to the bursts; this range is further constrained by considering cosmological model fits to the burst number-intensity distribution. We have produced photon energy spectra for ∼400 bursts using data from BATSE to investigate if this expected shift in the νFν peak is observed. We find that he mean peak energies of the burst spectra are correlated with intensity: lower intensity groups of burst spectra exhibit a lower average peak energy, although the distributions of Ep are quite wide. Denoting the redshift of an event with an observed peak photon flux P (photons cm-2 s-1) by zp, we find that the maximum range consistent with the bursts of our sample is (1 + z1)/(1 + z100) = 1.86+0.36-.24. Publication: The Astrophysical Journal Pub Date: December 1995 DOI: 10.1086/176513 Bibcode: 1995ApJ...454..597M Keywords: GAMMA RAYS: BURSTS; COSMOLOGY: OBSERVATIONS full text sources ADS |

The energy selective precipitation of inner zone electrons

The occurrence of L dependent peaks in the energy spectra of quasi‐trapped electrons (&gt;130 keV) precipitating from the inner radiation zone has been previously reported (Imhof et al., 1973) and interpreted in terms of the cyclotron resonance interaction of electrons with waves of a nearly constant frequency over the L range (∼1.4 to ∼1.8) of concern. From satellite data taken in 1971‐1972 the longitude variations in the intensities of these peaks observed at ∼800‐km altitude have been studied in order to establish the spatial extent of the responsible mechanism(s). The data acquired over three different longitude intervals show an increase in the frequency of occurrence of the peaked spectra with increasing longitude east of the South Atlantic anomaly. The distribution in equivalent wave frequencies responsible for formation of the peaks is observed to be nearly the same for the three longitude intervals. These two facts suggest that a similar energy selective precipitation mechanism occurs over a broad range of longitudes. It is difficult to unfold uniquely the dependences of the phenomena upon other geophysical parameters from a data set of limited time duration, but certain trends are indicated. L dependent peaks were more prominent in the hours near dawn and dusk than near midnight. This temporal behavior had little dependence on the Kp value. No significant changes with the local time of observation or with the level of geomagnetic activity were observed in the average peak energy at a given L value. Long‐term variations in the peak energies were observed, consistent with a seasonal dependence in the plasma electron density.