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1

Observational analysis of VLF emissions through the mechanism of lightning  

Science.gov (United States)

Lightning, being an end product of the cloud electrification occurs above, below and inside the thunderclouds as well as in other environmental conditions. So far several experimental techniques have been used for the study of the electromagnetic waves associated with lightning. The present paper deals with the observational analysis of the very low frequency emissions (lightning being one of the generators of VLF) through the lightning mechanism. The observational analysis would comprise of the graphical representation of the gain with respect to relative time base. This plot would be based on the recorded sferics obtained at the receiving stations. This work being a part of the World Wide Lightning Location (WWLL) programme refers to the "TOGA" network followed by various stations in which the observations are being taken. Bhopal (23°12'N, 77.4°E, Dip 18.5°N) due to its supportive geographical location has been chosen as one of the prime locations with the probability of frequent lightning.

Gwal, A. K.; Mishra, O. P.; Bhattacharya, S.; Shrivastava, A.

2

Substorm-associated VLF emissions with frequency drift observed in the premidnight sector  

Energy Technology Data Exchange (ETDEWEB)

Characteristics of premidnight substorm-associated VLF emissions are examined on the basis of the data obtained by the authors VLF/ELF campaign during November 1978 to February 1979 by means of the direction-finding measurements at two stations, Brorfelde in Denmark (L {approximately} 3) and Chambon-la-Foret in France (L {approximately} 2) as well as ISIS satellite measurements. Two remarkable events have been analyzed, and the following main properties have emerged: (1) the emissions observed are of hiss type and are excited mainly within the plasmapause, (2) the emission activity is preceded by development of two subsequent substorms, and (3) the emission frequency increases sharply at the first stage of the events and is followed by its subsequent gradual decrease. These properties of the temporal evolution of the wave spectrum are interpreted in terms of a quasi-linear electron cyclotron instability model for wave excitation. The initial frequency increase is believed to be due to a combined effect of L shell drift of energetic elecrons injected during the first substorm and decrease of a large-scale convection electric field during the development of the events. The subsequent frequency decrease may be related to the additional injection of energetic electrons due to the development of the second substorm.

Hayakawa, M.; Tanaka, Y.; Okada, T. (Nagoya Univ., Toyokawa (Japan)); Tixier, M. (Univ. de Poitiers, Saint Julien L' ars (France)); Sazhin, S.S.

1988-06-01

3

Magnetospheric VLF emissions observed by ISIS satellites during four geomagnetic storms in July and September, 1982  

Energy Technology Data Exchange (ETDEWEB)

Wide-band VLF hisses similar to the auroral hiss, choruses and a hook were observed at mid-geomagnetic latitudes during the daytime of four geomagnetic storms in July and September, 1982 by ISIS satellites. These high-latitude-type VLF emissions observed at mid-latitudes seem to be caused by precipitated particles from the magnetosphere for the geomagnetic storms. During the main phase of geomagnetic storm of July 14, 1982, auroral-type hisses occurred at frequencies above 4 kHz at invariant latitudes above 43/sup 0/ which were lower than the observed latitude, 47/sup 0/ of whistler echo trains. This implies that the auroral-type hiss observed at mid-latitudes is generated by the Cherenkov radiations from precipitated electrons above a few keV resulting from an interaction between the equatorial ring-current particles and cold plasma in the plasmasphere. The appearance of choruses at mid-latitudes during geomagnetic storm of September 22 seems to represent inward movements of the outer-radiation-zone electrons due to enhancements of magnetospheric westward electric field during the geomagnetic storm. The bandwidth and lower cutoff frequency of the ELF hiss observed by ISIS satellites decrease with decreasing geomagnetic latitude. This seems to depend on the ionic compositions of the topside ionosphere and the conditions of the outer plasmasphere, where the ELF hiss is generated, during geomagnetic storms.

Ondoh, T.; Nakamura, Y.; Watanabe, S.

1985-12-01

4

Early VLF perturbations observed in association with elves  

Directory of Open Access Journals (Sweden)

Full Text Available VLF remote sensing is used to detect lower-ionospheric electron density changes associated with a certain type of transient luminous events known as elves. Both ground- and satellite-based observations of elves are analysed in relation to VLF data acquired at various receiver sites in Europe, the United States and Antarctica. Ground-based observations were performed during the EuroSprite2003 campaign, when five elves were captured by low-light cameras located in the Pyrenees. Analysis of VLF recordings from Crete shows early VLF perturbations accompanying all of the elves. A large dataset consisting of elves captured by the ISUAL (Imager of Sprites and Upper Atmospheric Lightning) payload on Taiwan's FORMOSAT-2 satellite over Europe and North America has also been analysed. Early/fast VLF perturbations were found to accompany some of the elves observed over Europe. However, no VLF perturbations were detected in relation to the elves observed by ISUAL over North America. The present analysis – based on the largest database of optical elve observations used for VLF studies so far – constitutes evidence of processes initiated by the lightning EMP (electromagnetic pulse) causing electron density changes in the lower ionosphere in line with theoretical predictions. It also proves that sub-ionospheric electron density changes associated with elves can intrude to lower heights and thus perturb VLF transmissions. The possibility of VLF detection, however, depends on several factors, e.g., the distance of the elve from the receiver and the transmitter–receiver great circle path (GCP), the altitude of the ionised region and the characteristics of the VLF transmitter, as well as the EMP energy, which occasionally may be sufficient to cause optical emissions but not ionisation.

Á. Mika; C. Haldoupis; T. Neubert; H. T. Su; R. R. Hsu; R. J. Steiner; R. A. Marshall

2006-01-01

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Perturbations of ionosphere-magnetosphere coupling by powerful VLF emissions from ground-based transmitters  

Energy Technology Data Exchange (ETDEWEB)

The characteristics of the plasma-wave disturbances stimulated in the near-Earth plasma by powerful VLF radiation from ground-based transmitters are investigated. Radio communication VLF transmitters of about 1 MW in power are shown to produce artificial plasma-wave channels (density ducts) in the near-Earth space that originate in the lower ionosphere above the disturbing emission source and extend through the entire ionosphere and magnetosphere of the Earth along the magnetic field lines. Measurements with the onboard equipment of the DEMETER satellite have revealed that under the action of emission from the NWC transmitter, which is one of the most powerful VLF radio transmitters, the generation of quasi-electrostatic (plasma) waves is observed on most of the satellite trajectory along the disturbed magnetic flux tube. This may probably be indicative of stimulated emission of a magnetospheric maser.

Belov, A. S., E-mail: alexis-belov@yandex.ru; Markov, G. A.; Ryabov, A. O. [Lobachevsky Nizhni Novgorod State University (Russian Federation); Parrot, M. [Environment Physics and Chemistry Laboratory (France)

2012-12-15

6

Perturbations of ionosphere-magnetosphere coupling by powerful VLF emissions from ground-based transmitters  

International Nuclear Information System (INIS)

The characteristics of the plasma-wave disturbances stimulated in the near-Earth plasma by powerful VLF radiation from ground-based transmitters are investigated. Radio communication VLF transmitters of about 1 MW in power are shown to produce artificial plasma-wave channels (density ducts) in the near-Earth space that originate in the lower ionosphere above the disturbing emission source and extend through the entire ionosphere and magnetosphere of the Earth along the magnetic field lines. Measurements with the onboard equipment of the DEMETER satellite have revealed that under the action of emission from the NWC transmitter, which is one of the most powerful VLF radio transmitters, the generation of quasi-electrostatic (plasma) waves is observed on most of the satellite trajectory along the disturbed magnetic flux tube. This may probably be indicative of stimulated emission of a magnetospheric maser.

2012-01-01

7

Perturbations of ionosphere-magnetosphere coupling by powerful VLF emissions from ground-based transmitters  

Science.gov (United States)

The characteristics of the plasma-wave disturbances stimulated in the near-Earth plasma by powerful VLF radiation from ground-based transmitters are investigated. Radio communication VLF transmitters of about 1 MW in power are shown to produce artificial plasma-wave channels (density ducts) in the near-Earth space that originate in the lower ionosphere above the disturbing emission source and extend through the entire ionosphere and magnetosphere of the Earth along the magnetic field lines. Measurements with the onboard equipment of the DEMETER satellite have revealed that under the action of emission from the NWC transmitter, which is one of the most powerful VLF radio transmitters, the generation of quasi-electrostatic (plasma) waves is observed on most of the satellite trajectory along the disturbed magnetic flux tube. This may probably be indicative of stimulated emission of a magnetospheric maser.

Belov, A. S.; Markov, G. A.; Ryabov, A. O.; Parrot, M.

2012-12-01

8

On the frequency modulation of VLF emissions  

Directory of Open Access Journals (Sweden)

Full Text Available The VLF-wave frequency modulation efficiency as a function of magnetosphere plasma parameters under the weak pitch-angle diffusion regime is studied. The study is based on the VLF growth-rate modulation both in the magnetosphere equatorial plane and after integrating along the magnetic field line. It is shown that for the typical quiet magnetosphere plasma parameters the relative shift of the maximum intensity frequency ??m/?m is approximately equal to relative disturbance of the magnetic field in the magnetosphere equatorial plane, but may exceed it when both electron temperature anisotropy and the parameter ???are small; here ? is the total-to-warm electron content ratio and ?? is the electron parallel beta. It is also shown that relative shift of the maximum intensity frequency ??m/?m after integrating along the field line is not less than 50% from its value at the equatorial plane, which allows the use of the equatorial-plasma-parameter data to estimate the VLF frequency modulation on the ground. The upper cut-off frequency modulation is considered as well. The calculated theoretical sonagrams show that this frequency modulation may be related to the non-dispersive and to the "inverted-V'' structures of QP hiss.

M. Goncharova; W. Lyatsky

0000-01-01

9

Prediction Capabilities of VLF/LF Emission as the Main Precursor of Earthquake  

CERN Document Server

Recent satellite and ground-based observations proved that in earthquake preparation period in the seismogenic area we have VLF/LF and ULF electromagnetic emissions. According to the opinion of the authors of the present paper this phenomenon is more universal and reliable than other earthquake indicators. Hypothetically, in case of availability of adequate methodological grounds, in the nearest future, earth VLF/LF electromagnetic emission might be declared as the main precursor of earthquake. In particular, permanent monitoring of frequency spectrum of earth electromagnetic emission generated in the earthquake preparation period might turn out very useful with the view of prediction of large (M 5) inland earthquakes. The present paper offers a scheme of the methodology according to which the reality of the above given hypothesis can be checked up. To prove the prediction capabilities of earth electromagnetic emission we have used avalanche-like unstable model of fault formation and an analogous model of ele...

Kachakhidze, Manana

2013-01-01

10

A parametric study of the numerical simulations of triggered VLF emissions  

Directory of Open Access Journals (Sweden)

Full Text Available This work is concerned with the numerical modelling of VLF emissions triggered in the equatorial region of the Earth's magnetosphere, using a well established 1-D Vlasov Hybrid Simulation (VHS) code. Although this code reproduces observed ground based emissions well there is some uncertainty regarding the magnitude of simulation parameters such as saturation wave amplitude, cold plasma density, linear growth rate and simulation bandwidth. Concentrating on emissions triggered by pulses of VLF radio waves from the transmitter at Siple Station, Antarctica (L=4.2), these parameters, as well as triggering pulse length and amplitude, are systematically varied. This parametric study leads to an understanding of the physics of the triggering process and also of how the properties of these emissions, particularly their frequency time profile, depend upon these parameters. The main results are that weak power input tends to generate fallers, intermediate power input gives stable risers and strong growth rates give fallers, hooks or oscillating tones. The main factor determining the frequency sweep rate - of either sign - turns out to be the cold plasma density, lower densities giving larger sweep rates.

D. Nunn; M. Rycroft; V. Trakhtengerts

2005-01-01

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VLF observations of ionospheric disturbances in association with TLEs from the EuroSprite-2007 campaign  

DEFF Research Database (Denmark)

Two Very Low Frequency (VLF) AWESOME remote sensing systems located at Algiers, Algeria (36.45°N, 3.28°E) and Sebha, Libya (27.02°N, 14.26°E) monitor VLF signal perturbations for evidence of ionospheric disturbances. During the EuroSprite-2007 campaign a number of Transient Luminous Events (TLEs) were captured over the Mediterranean Sea by cameras at Pic du Midi (42.94°N, 0.14°E) and at Centre de Recherches Atmospheriques (CRA) in southwestern France (43.13°N, 0.37°E). The cameras observations are compared to collected VLF AWESOME data. We consider early VLF perturbations observed on 12-13, 17-18 October and 17-18 December, 2007. The data from the two VLF receivers confirm the association between TLEs and early VLF signal perturbations with the perturbations amplitudes dependent on the observation configuration i.e. whether the TLE is near the receiver, near the transmitter, or far from both and the scattering process. The results also reveal that the early VLF perturbations can occur in the absence of a TLE.

NaitAmor, S.; AlAbdoadaim, M. A.

2010-01-01

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On the nonlinear triggering of VLF emissions by power line harmonic radiation  

Directory of Open Access Journals (Sweden)

Full Text Available VLF ground data from Porojarvi in N. Finland has been presented. Spectrograms reveal frequent occurrence of power line harmonic radiation (PLHR), originating from the Finnish power system and from heavy industrial plant. The radiation is seen to penetrate the magnetosphere since numerous occurrences of PLHR triggered emissions are seen. Risers predominate but fallers and hooks are also observed. A well-established 1D Vlasov simulation code has been used to simulate these emissions, using plausible magnetospheric data for a range of L values from L = 4 to L = 5.5. The code is able to reproduce risers fallers and hooks in close agreement with observations. The results shed considerable insight into the generation structure of both risers and fallers.Key words. Electromagnetics (numerical methods) · Ionosphere (wave-particle interactions) · Magnetospheric physics (plasma waves and instabilities)

D. Nunn; J. Manninen; T. Turunen; V. Trakhtengerts; N. Erokhin

0000-01-01

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Subionospheric VLF signatures and their association with sprites observed during EuroSprite 2003  

DEFF Research Database (Denmark)

In this study, VLF observations during EuroSprite-2003 are analyzed in connection with many sprites observed above thunderstorms in central France. The sprites were detected with a sensitive camera from the Observatoire du Pic du Midi in the Pyrenees overlooking storms monitored by the French national lightning detection network. The VLF observations were made in Crete, Greece with a narrowband receiver, and in Nancay, France with a broadband receiver. The storms were in the vicinity of a VLF transmitter (HWV) at Le Blanc, France, whose signal was received on Crete, arriving over a great circle path that cut through the storms to the southeast. The Nancay broadband receiver was located near HWV to the northeast of the transmitter. This setup provided a unique observational set for investigation. The receiver in Crete observed early VLF perturbations in nearly one-to-one association with the sprites, which endorses the findings of earlier work based on EuroSprite-2003 observations from a single storm. While part of the sprite-related VLF perturbations were of the early/fast type, many classified as "early/slow" having onset durations up to similar to 2s and thus suggesting a new mechanism at work which may cause a slow build up of ionization after a sprite. The only elve in the data set was found to associate also with an early/fast VLF perturbation. Moreover, the analysis showed basically no early VLF events to occur in relation to the numerous +/- CG discharges that did not lead to sprites. Bandpass filtering of the broadband VLF signal revealed that only about 5% of the sprites were escorted by early VLF perturbations, possibly due to backscatter. Finally, by using all 131 sprites captured during EuroSprite-2003, the time lags of the sprites to the preceding +/- CG discharges were computed and analyzed. The time-lag distribution had a well defined tail suggesting that at least one third of the sprites observed were lagging the +/- CG discharges by more than 30 up to 300 ms. In addition these "long-delayed" sprites were not accompanied by any radio-sferics during the sprite observation period, in sharp contrast to the short-delayed sprites which were escorted nearly always by enhanced, burst-like, sferic activity. These observations endorse the notion of long delayed sprites reported in past studies, but also show that their occurrence is much more frequent than it was thought before.

Mika, A.; Haldoupis, C.

2005-01-01

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In connection with identification of VLF emissions before L'Aquila earthquake  

Directory of Open Access Journals (Sweden)

Full Text Available The present paper deals with an attempt to check the theoretical model of self-generated seismo-electromagnetic oscillations of LAI system on the basis of retrospective data. Application of the offered simple model enables one to explain qualitatively the mechanism of VLF electromagnetic emission initiated in the process of an earthquake preparation. Besides, the model enables us to associate telluric character geoelectric and geomagnetic perturbations incited by rock polarization and self-generated electromagnetic oscillations of lithosphere-atmosphere system. L'Aquila earthquake taken as an example to isolate reliably the Earth VLF emission from the magnetospheric electromagnetic emission of the same frequency range, MHD criterion is offered together with geomagnetic activity indexes. On the basis of the considered three earthquakes, according to the opinion of authors the model of self-generated seismo-electromagnetic oscillations of the LAI system will enable us to approach the problem of resolution of earthquake prediction with certain accuracy.

M. K. Kachakhidze; Z. A. Kereselidze; N. K. Kachakhidze; G. T. Ramishvili; V. J. Kukhianidze

2012-01-01

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VLF/ELF wave activity in the vicinity of the polar cusp: Cluster observations  

Directory of Open Access Journals (Sweden)

Full Text Available Observations by the Cluster spacecraft of VLF/ELF wave activity show distinct signatures for different regions in the vicinity of high altitude polar cusps, which are identified by using magnetic field and plasma data along spacecraft trajectories. These waves include: (1) Broad band magnetic noise observed in the polar cusp at frequencies from several Hz to ~100 Hz, below the local electron cyclotron frequency, fce. Similar magnetic noise is also observed in the high latitude magnetosheath and the magnetopause boundary layer. (2) Strong broad band electrostatic emissions observed in the cusp, in the magnetosheath, and in the high latitude magnetopause boundary layer, at frequencies extending from several Hz to tens of kHz, with maximum intensities below ~100 Hz. (3) Narrow-band electromagnetic whistler waves at frequencies ~0.2–0.6 fce, frequently observed in the closed boundary layer (CBL) adjacent to the polar cusp. These waves are for the first time observed in this region to be accompanied by counter-streaming electron beams of ~100 eV, which suggests that the waves are excited by these electrons through wave-particle interaction. (4) Narrow-band electrostatic waves observed slightly above the local fce in the CBL. (5) Lion roars, observed in the high latitude magnetosheath, often in magnetic troughs of mirror mode oscillations. The above wave signatures can serve as indicators of the regions in the vicinity of the magnetospheric cusp.

N. Lin; E. S. Lee; J. McFadden; G. Parks; M. Wilber; M. Maksimovic; N. Cornilleau-Wehrlin; A. Fazakarley; E. Lucek; H. Rème; O. Santolik; Q.-G. Zong

2006-01-01

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Cluster observations of ELF/VLF signals generated by modulated heating of the lower ionosphere with the HAARP HF transmitter  

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Full Text Available It is now well known that amplitude modulated HF transmissions into the ionosphere can be used to generate ELF/VLF signals using the so-called "electrojet antenna". Although most observations of the generated ELF/VLF signals have been made on the ground, several low and high-altitude satellite observations have also been reported (James et al., 1990). One of the important unknowns in the physics of ELF/VLF wave generation by ionospheric heating is the volume of the magnetosphere illuminated by the ELF/VLF waves. In an attempt to investigate this question further, ground-satellite conjunction experiments have recently been conducted using the four Cluster satellites and the HF heater of the High-Frequency Active Auroral Research Program (HAARP) facility in Gakona, Alaska. Being located on largely closed field lines at L?4.9, HAARP is currently also being used for ground-to-ground type of ELF/VLF wave-injection experiments, and will be increasingly used for this purpose as it is now being upgraded for higher power operation. In this paper, we describe the HAARP installation and present recent results of the HAARP-Cluster experiments. We give an overview of the detected ELF/VLF signals at Cluster, and a possible explanation of the spectral signature detected, as well as the determination of the location of the point of injection of the HAARP ELF/VLF signals into the magnetosphere using ray tracing.

M. Platino; U. S. Inan; T. F. Bell; J. Pickett; E. J. Kennedy; J. G. Trotignon; J. L. Rauch; P. Canu

2004-01-01

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VLF emission triggering by a highly anisotropic energetic electron plasma  

Directory of Open Access Journals (Sweden)

Full Text Available One of the objectives of the Cluster mission is to study sources of various electromagnetic waves using the four satellites. This paper describes the methods we have applied to data recorded from the STAFF spectrum analyser. This instrument provides the cross spectral matrix of three magnetic and two electric field components. This spectral matrix is analysed to determine, for each satellite, the direction of the wave normal relative to the Earth’s magnetic field as a function of frequency and of time. Due to the Cluster orbit, chorus emissions are often observed close to perigee, and the data analysis determines the direction of these waves. Three events observed during different levels of magnetic activity are reported. It is shown that the component of the Poynting vector parallel to the magnetic field changes its sense when the satellites cross the magnetic equator, which indicates that the chorus waves propagate away from the equator. Detailed analysis indicates that the source is located in close vicinity of the plane of the geomagnetic equator. Key words. Magnetospheric physics (plasma waves and instabilities; storms and substorms); Space plasma physics (waves and instabilities)

D. Nunn; A. Demekhov; V. Trakhtengerts; M. J. Rycroft

0000-01-01

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Initial results of VLF Campaign observation with High-resolution Aurora Imaging Network (VLF-Chain) over Canada  

Science.gov (United States)

Whistler-mode waves in the VLF/ELF frequency range interact with high-energy (~10 keV) electrons to cause diffuse and pulsating auroras, and with MeV electrons in the radiation belts. However, simultaneous high-time resolution measurements of aurora and these waves have previously not been done sufficiently. We made a campaign observation of such high-time resolution measurements at Athabasca (54.72N, 246.69E, MLAT=61.3) and Fort Vermillion (58.38N, 243.99E, MLAT=64.5) using two loop antennas and several auroral cameras for February 16-26, 2012. The loop antennas at both stations measure east-west and north-south magnetic field variations with a sampling rate of 100 kHz. The panchromatic all-sky cameras at both stations measure auroras with a sampling rate of 30 Hz. The sampling timings of both instruments are corrected by GPS receivers. In addition we installed an oblique looking narrow-FoV EMCCD camera at Athabasca with a sampling rate of 100 Hz, to measure height variation of pulsating aurora. At Athabasca, routine measurements by an induction magnetometer, a proton photometer, an all-sky airglow imager, LF standard wave receiver, were also carried out. We also tried to compare these observations with satellite measurements by REIMEI, THEMIS, NOAA, and DMSP. In this presentation we will show initial results obtained from this comprehensive campaign of aurora and radio wave measurements at subauroral latitudes.

Shiokawa, Kazuo

2012-07-01

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In connection with identification of VLF emissions before L'Aquila earthquake  

CERN Multimedia

The present paper deals with an attempt to check up the theoretical model of self-generated seismo-electromagnetic oscillations of LAI system on the basis of retrospective data. Application of the offered simple model enables one to explain qualitatively the mechanism of VLF electromagnetic emission initiated in the process of an earthquake preparation. It is worth to pay attention to the fact that frequency changes from MHz to kHz in electromagnetic emission spectrum comes to a good agreement with avalanche-like unstable model of fault formation. L'Aquila earthquake taken as an example to isolate reliably the Earth VLF emission from the magnetospheric electromagnetic emission of the same frequency range, MHD criterion is offered together with geomagnetic activity indexes. On the basis of the considered three earthquakes, according to the opinion of authors the model of self-generated seismo-electromagnetic oscillations of the LAI system will enable us to approach the problem of resolution of earthquake predi...

Kachakhidze, M; Kachakhidze, N

2012-01-01

20

The role of upstream ULF waves in the generation of quasi-periodic ELF-VLF emissions  

Directory of Open Access Journals (Sweden)

Full Text Available Recent work suggests that the quasi-periodic (QP) modulation ~10–50 s of naturally occurring ELF-VLF radio emissions (~0.5–5 kHz) is produced by the compressional action of Pc3 magnetic pulsations on the source of the emissions. Whilst it is generally accepted that these magnetic pulsations have an exogenic source, it is not clear what the mechanism of their generation is. A study of QP emissions observed during 1988 at Halley, Antarctica, in conjunction with IMP-8 satellite solar wind data, shows that the occurrence and modulation frequency of the emissions are strongly dependent upon the direction and strength of the IMF, respectively. The observed relationships are very similar to those previously reported for Pc3 pulsations associated with upstream ion-cyclotron resonance, involving proton beams reflected at the bowshock. In comparing the observed QP modulation frequencies with upstream wave theory, agreement was found by considering wave excitation exclusively associated with a proton beam reflected from a position on the bowshock at which the shock normal is parallel to the ambient IMF direction. Other geometries were found to be either impropitious or uncertain. The work indicates the useful diagnostic role QP emissions could play in the study of compressional ULF waves in the upstream solar wind and in monitoring the IMF conditions responsible for their generation.

K. Morrison; M. P. Freeman

0000-01-01

 
 
 
 
21

Correlation between observed VLF phase deviation and solar X-ray flux during solar flares  

International Nuclear Information System (INIS)

Correlation between the observed phase deviation of GBR 16 kHz VLF signals and the solar X-ray flux in the bands 0.5-4 and 1-8 A during solar flare events has been studied. It is found that the unnormalized phase deviations show a better correlation with the observed X-ray flux than the correlation with the normalized phase deviations. The threshold X-ray flux to produce a detectable sudden phase anomaly (SPA) has been estimated. (author)

1983-01-01

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A study of quasi-periodic ELF-VLF emissions at three Antarctic stations: evidence for off-equatorial generation?  

Directory of Open Access Journals (Sweden)

Full Text Available The spatial extent and temporal behaviour of quasi-periodic (QP) intensity modulations of 0.5-2 kHz ELF-VLF signals were investigated in a comparative study of data collected at the Antarctic stations of South Pole (L=14), Halley (L=4), and Siple (L=4). Frequently, the waveforms of ELF-VLF signals simultaneously received at each site were identical. Although of similar frequency structure, the waveforms of the accompanying Pc3 magnetic pulsations did not show a one-to-one association. Whereas both are dayside phenomena, QP emissions occur over a smaller range of local times, and have a maximum of occurrence later in the day closer to local noon. QP emissions are identified with the periodic modulation of the electron pitch-angle distribution by the propagation of ULF compressional fast-mode waves through a region. However, contrary to previous ideas, rising-tone emissions do not represent the frequency-time signatures of such waves. In addition to generation close to the equatorial plane, we propose an additional high-latitude source of QP emissions. These emissions are associated with regions of minimum B produced by the dayside compression of the magnetosphere close to the magnetopause. Model magnetic field calculations of these minimum-B regions as a function of magnetic local time and invariant latitude are presented.

K. Morrison; M. J. Engebretson; J. R. Beck; J. E. Johnson; R. L. Arnoldy; L. J. Cahill ,Jr; D. L. Carpenter; M. Gallani

0000-01-01

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Assessing global lightning activity with ELF/VLF observations, Schumann resonances and ionospheric potential  

International Nuclear Information System (INIS)

Complete text of publication follows. Global lightning activity is estimated from globally spaced ELF/VLF receivers and used to investigate the dynamics of the global atmospheric electric circuit. ELF/VLF radiation generated by lightning is known to propagate long distances in the Earth ionosphere waveguide, but propagation effects resulting from diurnal ionospheric variations often dominate received amplitudes at a fixed station. Day/night propagation effects thus make meaningful comparison and summation of activity across multiple stations difficult. Exact inversion of the propagation channel is possible only with knowledge of the location of each lightning impulse, a feat unattainable even with current detection networks. In a novel approach, propagation effects are accounted for using established monthly averages of lightning location provided by the Lightning Image Sensor (LIS) and applying known frequency specific attenuation parameters for daytime/nighttime ELF/VLF propagation. The method allows for quantification of daily lightning activity on a global scale using a small number of receiver sites. Obtained curves of daily lightning activity are compared to measurements of atmospheric electric field at mid and polar latitudes and also to lightning activity estimates based on Schumann resonances. For Schumann resonances we utilize a method of field decomposition that separates propagating and standing modes. It is found that in most examined cases daily global lightning activity and the atmospheric electric field are poorly correlated.

2009-01-01

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ELF/VLF Wave-injection Experiments with HAARP  

Science.gov (United States)

The potential use of modulated HF heating of the lower ionosphere as a means to generate ELF/VLF waves has long been recognized. Located conveniently at L ? 4.9, thus lying on closed sub-auroral field lines most of the time, the High-Frequency Active Auroral Research Program (HAARP) heater in Gakona, Alaska is well positioned for the conduct of ELF/VLF wave-injection experiments for magnetospheric wave-particle interaction studies. Early results (2004) have alreay demonstrated that whistler-mode wave amplification can be initiated by ELF/VLf signals injected from HAARP, leading to multiple-hop propagation of signals between hemispheres and triggering of discrete emissions. With the upcomign completion of the upgrade of HAARP to full power (3.6 MW radiated), a new set of experiments have become possible, and the first opportunity for the conduct of such experiments is now before us. During February 23-March 6th, Stanford University personnel will be deploying two large Buoys equipped with ELF/VLF erceivers in the geomagneticaly conjugate region of HAARP, and will also conduct continuous ELF/VLF observations on the research ship which will deploy them. The experiments are aimed at generating specially designed ELF/VLF modulation formats, for initiation of wave growth, emission triggering and excitation of one-hop and two-hop whistler-mode waves. ELF/VLf observations will be conducted on teh ship and buoys near the conjugate region, but also on several distributed sites in Alaska as well as on teh DEMETER spacecraft. In this paper, we will discuss these experiments and present initial results from them. This papers constitutes a brief summary of the extensive work contributed by many other not-listed authors, at Stanford University, at AFRL, ONR, and at LPCE/CNRS in Orleans. The presenter listed as the single author is simply the team leader, listed solely for purposes of brevity.

Inan, U. S.

2007-05-01

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Conjugacy of daytime ELF-VLF emission activities in the auroral zones  

International Nuclear Information System (INIS)

[en] Statistical characteristics of emission occurrence are examined, using 1 year of digital data of 750-Hz, 2-kHz, and 4-kHz intensity records. These waves were measured simultaneously at a conjugate pair of stations, namely Syowa Station in Antarctica and Husafell in Iceland. The following notable diurnal and seasonal variation and Kp dependence was found for the daytime emissions (04-14 MLT): (1) The 750-Hz emissions were mostly observed during the daytime around noon in both conjugate regions. The emission occurrence reached a maximum 1-3 hours earlier at Syowa than at Husafell during the equinox season. The seasonal variation of 750-Hz emission occurrence showed a maximum during local summer and a minimum during local winter at both stations. The ratio of the emission enhancement in summer to that at the equinox is higher at Husafell than at Syowa. The emissions mostly occurred during moderately disturbed conditions of Kp ? 2-4 at both stations. (2) The 2-kHz emission occurrence reached a maximum around 13 MLT at Syowa and around 11 MLT at Husafell. Peaks of the emission occurrence during summer shifted to the afternoonside at Syowa and to the morningside at Husafell. The occurrences at Syowa reached a maximum during local summer and a minimum during winter. (3) The occurrence of 4-kHz emissions was much more frequent at Husafell than at Syowa. The emissions at Husafell occurred mostly in the morning (?08 MLT) and in local winter, and the occurrences became more frequent with increasing magnetic activity. On the bases of these statistical characteristics, the authors discuss the effects of sunlight and geomagnetic activity which cause an asymmetry of wave propagation from the magnetosphere to the ionosphere in the two hemispheres

1990-06-01

26

Conjugacy of daytime ELF-VLF emission activities in the auroral zones  

Energy Technology Data Exchange (ETDEWEB)

Statistical characteristics of emission occurrence are examined, using 1 year of digital data of 750-Hz, 2-kHz, and 4-kHz intensity records. These waves were measured simultaneously at a conjugate pair of stations, namely Syowa Station in Antarctica and Husafell in Iceland. The following notable diurnal and seasonal variation and Kp dependence was found for the daytime emissions (04-14 MLT): (1) The 750-Hz emissions were mostly observed during the daytime around noon in both conjugate regions. The emission occurrence reached a maximum 1-3 hours earlier at Syowa than at Husafell during the equinox season. The seasonal variation of 750-Hz emission occurrence showed a maximum during local summer and a minimum during local winter at both stations. The ratio of the emission enhancement in summer to that at the equinox is higher at Husafell than at Syowa. The emissions mostly occurred during moderately disturbed conditions of Kp {approximately} 2-4 at both stations. (2) The 2-kHz emission occurrence reached a maximum around 13 MLT at Syowa and around 11 MLT at Husafell. Peaks of the emission occurrence during summer shifted to the afternoonside at Syowa and to the morningside at Husafell. The occurrences at Syowa reached a maximum during local summer and a minimum during winter. (3) The occurrence of 4-kHz emissions was much more frequent at Husafell than at Syowa. The emissions at Husafell occurred mostly in the morning ({approximately}08 MLT) and in local winter, and the occurrences became more frequent with increasing magnetic activity. On the bases of these statistical characteristics, the authors discuss the effects of sunlight and geomagnetic activity which cause an asymmetry of wave propagation from the magnetosphere to the ionosphere in the two hemispheres.

Sato, Natsuo (National Institute of Polar Research, Tokyo (Japan)); Suzuki, Hiroyuki; Maezawa, Kiyoshi (Yamagata Univ. (Japan)); Saemundsson, T. (Univ. of Iceland, Reykjavik (Iceland))

1990-06-01

27

Decrease of VLF transmitter signal and Chorus-whistler waves before l'Aquila earthquake occurrence  

Directory of Open Access Journals (Sweden)

Full Text Available We investigate the VLF emissions observed by the Instrument Champ Electrique (ICE) experiment onboard the DEMETER micro-satellite. We analyze intensity level variation 10 days before and after the occurrence of l'Aquila earthquake (EQ). We found a clear decrease of the VLF received signal related to ionospheric whistler mode (mainly Chorus emission) and to signal transmitted by the DFY VLF station in Germany, few days (more than one week) before the earthquake. The VLF power spectral density decreases of more than two orders of magnitude until the EQ, and it recovers to normal levels just after the EQ occurrence. The geomagnetic activity is principally weak four days before EQ and increases again one day before l'Aquila seismic event. Our results are discussed in the frame of short- and long-terms earthquakes prediction focusing on the crucial role of the magnetic field of the Earth.

M. Y. Boudjada; K. Schwingenschuh; R. Döller; A. Rohznoi; M. Parrot; P. F. Biagi; P. H. M. Galopeau; M. Solovieva; O. Molchanov; H. K. Biernat; G. Stangl; H. Lammer; I. Moldovan; W. Voller; M. Ampferer

2010-01-01

28

Survey of ELF-VLF plasma waves in outer radiation belt observed by Cluster STAFF-SA experiment  

Directory of Open Access Journals (Sweden)

Full Text Available Various types of plasma waves have profound effects on acceleration and scattering of radiation belt particles. For the purposes of radiation belt modeling it is necessary to know statistical distributions of plasma wave parameters. This paper analyzes four years of plasma wave observations in the Earth's outer radiation belt obtained by the STAFF-SA experiment on board Cluster spacecraft. Statistical distributions of spectral density of different plasma waves observed in ELF-VLF range (chorus, plasmaspheric hiss, magnetosonic waves) are presented as a function of magnetospheric coordinates and geomagnetic activity indices. Comparison with other spacecraft studies supports some earlier conclusions about the distribution of chorus and hiss waves and helps to remove the long-term controversy regarding the distribution of equatorial magnetosonic waves. This study represents a step towards the development of multi-spacecraft database of plasma wave activity in radiation belts.

D. Pokhotelov; F. Lefeuvre; R. B. Horne; N. Cornilleau-Wehrlin

2008-01-01

29

Subionospheric VLF perturbations observed at low latitude associated with earthquake from Indonesia region  

Science.gov (United States)

Subionospheric propagation from a Very Low Frequency (VLF) transmitter (VTX, 18.2 kHz) received at a low latitude station Suva, Fiji over a Transmitter–Receiver Great Circle Path (TRGCP) length of 11,400 km has been utilized to identify any possible ionospheric perturbations associated with the earthquakes that occurred in the Indonesia region during the period December 2006–October 2010. Out of five earthquakes that occurred with their epicenter in the fifth Fresnel zone, only an earthquake on 18 December 2006, in the North Sumatra region, has shown convincing evidence of lower ionospheric perturbations on the VTX transmission. The magnitude of this earthquake was 5.8 measured on the Richter scale and occurred at a depth of 53 km with its epicenter located 45 km off the TRGCP. The VLF amplitude data for this earthquake was analyzed using (1) terminator time (TT), (2) average nighttime and daytime amplitude variation, and (3) nighttime fluctuation (NF) methods. The results show that the sunrise TTs deviated considerably in the period 14–22 December 2006 measuring up to ~20 min on the day of the earthquake. The results also show that the average nighttime as well as the average daytime signal amplitudes decreased by about 5 dB and 3 dB, respectively, during the period of the earthquake. The NF method revealed a decline in the trend at least 2 days before the earthquake though not exceeding the 2? criteria and enhancements in the NF exceeding 2? mark, however, the normalized values of the trend, NF and dispersion did not reveal an increase above the 2? marks as reported by previous researchers. This could be due to the very long path length and the prevalence of lightning activity along the TRGCP in the Asia-Oceania Region.

Kumar, Abhikesh; Kumar, Sushil; Hayakawa, Masashi; Menk, Frederik

2013-09-01

30

ELF/VLF emissions generated in the ionosphere by heating facilities - a new tool for ionospheric and magnetospheric research  

International Nuclear Information System (INIS)

A brief summary of ELF/VLF generation experiments using the SURA heating facility is presented. The possibilities of applications of the measured ionospherically generated low frequency signal parameters for diagnosing the physical phenomena in the ionosphere and the magnetosphere are discussed.

1994-01-01

31

Longitudinal drift of substorm electrons as the reason of impulsive precipitation events and VLF emissions  

Directory of Open Access Journals (Sweden)

Full Text Available Using the data from satellite CRRES and three geostationary LANL spacecraft, the propagation of an electron cloud from midnight to the evening sector is investigated. An electron cloud was injected during a weak isolated substorm that developed on a quiet geomagnetic background. It is found that within the local time sector from 03:00 until at least 08:00 MLT, the propagation of electrons at perpendicular pitch-angles is well described by a simple model of drift in the dipole magnetic field. The flux levels in the field-aligned electrons increase simultaneously with the flux at perpendicular pitch angles, which is attributed to the pitch angle diffusion by the whistler mode. This pitch-angle diffusion leads to precipitation of electrons from a drifting cloud and an increase in the ionospheric electron density, simultaneously observed above Tromsø, Norway, by the EISCAT UHF radar in the morning sector (04:40–05:25 MLT). The precipitation develops as quasi-periodic pulses with a period of about 100 s. We discuss the models of pulsating precipitation due to the whistler cyclotron instability and show that our observations can be explained by such a model.

A. A. Lubchich; A. G. Yahnin; E. E. Titova; A. G. Demekhov; V. Yu. Trakhtengerts; J. Manninen; T. Turunen

2006-01-01

32

ELF/VLF signatures of sprite-producing lightning discharges observed during the 2005 EuroSprite campaign  

Science.gov (United States)

During the summer of 2005, transient luminous events were optically imaged from the French Pyrénées as part of the EuroSprite campaign. Simultaneously, extremely low frequency (ELF: 3-3000 Hz) and broadband very low frequency (VLF: 3-30 kHz) data were recorded continuously at two separate receivers in Israel, located about 3300 km from the area of the parent lightning discharges responsible for the generation of sprites. Additionally, narrowband VLF data were collected in Crete, at about 2300 km away from the region of sprites. The motivation for the present study was to identify the signature of the sprite-producing lightning discharges in the ELF and VLF electromagnetic frequency bands, to qualify and compare their parameters, and to study the influence of the thunderstorm-activated region on its overlaying ionosphere. For the 15 sprites analyzed, their causative positive cloud-to-ground (+CG) discharges had peak current intensities between +8 and +130 kA whereas their charge moment changes (CMC) ranged from 500 to 3500 C km. Furthermore, the peak current reported by the Météorage lightning network are well correlated with the amplitudes of the VLF bursts, while showing poor correlation with the CMCs which were estimated using ELF methods. Additionally, more than one +CG was associated with six of the sprites, implying that lightning discharges that produce sprites can sometimes have multiple ground connections separated in time and space. Finally, for a significant number of events (33%) an ELF transient was not associated with sprite occurrence, suggesting that long continuing current of tens of ms may not always be a necessary condition for sprite production, a finding which influences the estimation of the global sprite rate based on Schumann resonance (SR) measurements.

Greenberg, E.; Price, C.; Yair, Y.; Haldoupis, C.; Chanrion, O.; Neubert, T.

2009-08-01

33

ELF/VLF signatures of sprite-producing lightning discharges observed during the 2005 EuroSprite campaign  

International Nuclear Information System (INIS)

Complete text of publication follows. During the summer of 2005, transient luminous events were optically imaged from the French Pyrenees as part of the EuroSprite campaign. Simultaneously, ELF (Extremely Low Frequency: 3-3000Hz) and broadband VLF (Very Low Frequency: 3-30 kHz) data were recorded continuously at two separate receivers in Israel, located about 3300 km from the area of the parent lightning discharges responsible for the generation of sprites. Additionally, narrowband VLF data were collected in Crete, at about 2300 km away from the region of sprites. The motivation for the present study was to identify the signature of the sprite-producing lightning discharges in the ELF and VLF electromagnetic frequency bands, to qualify and compare their parameters, and to study the influence of the thunderstorm activated region on its overlaying ionosphere. For the 15 sprites analyzed, their causative positive cloud-to-ground (+CG) discharges had peak current intensities between +8 and +130 kA whereas their charge moment changes (CMC) ranged from 500 to 3500 C ? km. Furthermore, the peak current reported by the Meteorage lightning network are well correlated with the amplitudes of the VLF bursts, while showing poor correlation with the CMCs which were estimated using ELF methods. Additionally, more than one +CG was associated with 6 of the sprites, implying that lightning discharges that produce sprites can sometimes have multiple ground connections separated in time and space. Finally, for a significant number of events (33%) an ELF transient was not associated with sprite occurrence, suggesting that long continuing current of tens of msec may not always be a necessary condition for sprite production, a finding which influences the estimation of the global sprite rate based on Schumann Resonance (SR) measurements.

2009-01-01

34

ELF/VLF signatures of sprite-producing lightning discharges observed during the 2005 EuroSprite campaign  

DEFF Research Database (Denmark)

During the summer of 2005, transient luminous events were optically imaged from the French Pyrénées as part of the EuroSprite campaign. Simultaneously, extremely low frequency (ELF: 3–3000 Hz) and broadband very low frequency (VLF: 3–30 kHz) data were recorded continuously at two separate receivers in Israel, located about 3300 km from the area of the parent lightning discharges responsible for the generation of sprites. Additionally, narrowband VLF data were collected in Crete, at about 2300 km away from the region of sprites. The motivation for the present study was to identify the signature of the sprite-producing lightning discharges in the ELF and VLF electromagnetic frequency bands, to qualify and compare their parameters, and to study the influence of the thunderstorm-activated region on its overlaying ionosphere. For the 15 sprites analyzed, their causative positive cloud-to-ground (+CG) discharges had peak current intensities between +8 and +130 kA whereas their charge moment changes (CMC) ranged from 500 to 3500 C km. Furthermore, the peak current reported by the Météorage lightning network are well correlated with the amplitudes of the VLF bursts, while showing poor correlation with the CMCs which were estimated using ELF methods. Additionally, more than one +CG was associated with six of the sprites, implying that lightning discharges that produce sprites can sometimes have multiple ground connections separated in time and space. Finally, for a significant number of events (33%) an ELF transient was not associated with sprite occurrence, suggesting that long continuing current of tens of ms may not always be a necessary condition for sprite production, a finding which influences the estimation of the global sprite rate based on Schumann resonance (SR) measurements.

Greenberg, E.; Price, C.

2009-01-01

35

Modeling solar flare induced lower ionosphere changes using VLF/LF transmitter amplitude and phase observations at a midlatitude site  

Directory of Open Access Journals (Sweden)

Full Text Available Remote sensing of the ionosphere bottom using long wave radio signal propagation is a still going strong and inexpensive method for continuous monitoring purposes. We present a propagation model describing the time development of solar flare effects. Based on monitored amplitude and phase data from VLF/LF transmitters gained at a mid-latitude site during the currently increasing solar cycle no. 24 a parameterized electron density profile is calculated as a function of time and fed into propagation calculations using the LWPC (Long Wave Propagation Capability). The model allows to include lower ionosphere recombination and attachment coefficients, as well as to identify the relevant forcing X-ray wavelength band, and is intended to be a small step forward to a better understanding of the solar–lower ionosphere interaction mechanisms within a consistent framework.

E. D. Schmitter

2013-01-01

36

Ground observation of electromagnetic emissions related to clusters of earthquakes  

Science.gov (United States)

ULF-VLF data obtained from three ground based experiments working at Agra station (geograph. Lat. 27.20N, Long. 780E) in India namely measurement of ultra low frequency (ULF) magnetic field emissions using a 3-component search coil magnetometer, vertical component of very low frequency (VLF) electric field emissions with a borehole antenna, and phase and amplitude of fixed frequency VLF transmitter signals using AbsPAL receiver are analysed in search of possible precursors of two major seismic activities that occurred in Sumatra (Indonesia) during post-tsunami period between January and April, 2005. These two major seismic events occurred as clusters of earthquakes during 27-29 January and 28-30 March, 2005. The results show that barring borehole all the experiments showed precursors due to these clusters of earthquakes. Such precursors were not seen in the case of isolated large magnitude earthquakes. Further, the precursory duration was influenced by the magnetic storm which occurred about a week before the clusters. The mechanism of ULF propagation to long distances between Sumatra and Agra, and perturbations in the ionosphere before the clusters are discussed.

Singh, Vikram; Singh, Birbal

2010-05-01

37

VLF Loop Array Antenna.  

Science.gov (United States)

The report describes a directional loop array antenna for very low frequency (VLF) reception. The array comprises four closely spaced loop antennas forming a unidirectional reception pattern with a main beam of less than 43 deg between half power points. ...

E. W. Seeley

1978-01-01

38

X ray microbursts and VLF chorus  

Energy Technology Data Exchange (ETDEWEB)

On January 4, 1978, at 1140 UT, a SuperArcas sounding rocket was launched from Siple Station, Antarctica (L = 4.2, 76/sup 0/S, 84/sup 0/W), during a geomagnetically disturbed period (Kp = 6--) with intense X ray and VLF chorus activity. The parachuted payload observed an intense microburst precipitation event of 10-minute duration. These data have been correlated with measurements of VLF chorus by receivers on the ground at both Siple and its magnetic conjugate point, Roberval, Quebec. Detailed one-to-one correspondence between the microbursts and the chorus was not a consistent feature of the data. Time series analysis of the data did indicate a significant correlation between the Siple X ray precipitation and the Roberval VLF waves with an arrival time delay of 0.1 +- 0.3 seconds.

Roeder, J.L.; Benbrook, J.R.; Bering E.A. III; Sheldon, W.R.

1982-11-01

39

X ray microbursts and VLF chorus  

International Nuclear Information System (INIS)

On January 4, 1978, at 1140 UT, a SuperArcas sounding rocket was launched from Siple Station, Antarctica (L = 4.2, 760S, 840W), during a geomagnetically disturbed period (Kp = 6--) with intense X ray and VLF chorus activity. The parachuted payload observed an intense microburst precipitation event of 10-minute duration. These data have been correlated with measurements of VLF chorus by receivers on the ground at both Siple and its magnetic conjugate point, Roberval, Quebec. Detailed one-to-one correspondence between the microbursts and the chorus was not a consistent feature of the data. Time series analysis of the data did indicate a significant correlation between the Siple X ray precipitation and the Roberval VLF waves with an arrival time delay of 0.1 +- 0.3 seconds.

1982-01-01

40

Simultaneous observations of VLF ground transmitter signals on the DE 1 and COSMOS 1809 satellites: Detection of a magnetospheric caustic and a duct  

Energy Technology Data Exchange (ETDEWEB)

Khabarovsk transmitter signals (15.0 kHz, 48{degrees}N, 135{degrees}E) were observed on the high-latitude ({approximately}15000 km) Dynamic Explorer 1 (DE 1) and the low-altitude ({approximately}960) km COSMOS 1809 satellites during a 9-day period in August 1989. On 7 out of 9 days the linear wave receiver (LWR) on the DE 1 satellite detected signals from the Khabarovsk transmitter. On two days, August 23 and 27, 1989, observations of the Khabarovsk transmitter signals were simultaneously carried out at high altitude on the DE 1 satellite and at low altitude on the COSMOS 1809 satellite. Analysis of data from these 2 days has led to several new results on the propagation of whistler mode signals in the Earth`s magnetosphere. New evidence was found of previously reported propagation phenomena, such as (1) confinement of transmitter signals in the conjugate hemisphere at ionospheric heights ({approximately} 1000 km), (2) observation of direct multipath propagation on both DE 1 and COSMOS 1809, (3) detection of ionospheric irregularities of {le} 100 km scale size with a few percent enhancement in electron density, believed to be responsible for the observed multipath propagation. The authors report the first detection of an exterior caustic surface near L {approximately} 3.5 for VLF ground transmitter signals injected into the magnetosphere; the location of the caustic surface depended on the signal frequency, and the electric and magnetic fields decreased by several hundred decibels per L shell in the dark (shadow) side of the caustic. The authors also report the first direct detection of a magnetospheric duct as L = 2.94 which was believed to be responsible for the ducted propagation of Khabarovsk signals observed on the COSMOS 1809 satellite; the measured duct parameters were {Delta}L{approximately} 0.06 and {Delta}N{sub e}{approximately}10 -13%. 54 refs., 8 figs. 3 tabs.

Sonwalkar, V.S.; Inan, U.S.; Bell, T.F. [Stanford Univ., CA (United States)] [and others

1994-09-01

 
 
 
 
41

Statistical study of ELF/VLF emissions recorded by a low-altitude satellite during seismic events  

Energy Technology Data Exchange (ETDEWEB)

The author reports a study of correlations between 325 earthquakes registering M{sub s}>5, and frequency filtered data observed by the low altitude satellite AUREOL 3 within a 24 hour window around the event. Data is sorted by time difference, difference in longitude, and difference in invariant latitude, between the satellite location and the epicenter. It is found that for the averaged data, the strongest signals are observed when the longitudinal differences are less than 10{degrees}, independent of latitude. The collected data was not continuous in nature, and therefore limits the nature of the statistical study which can be done.

Parrot, M. [Centre National de la Recherche Scientifique, Orleans (France)

1994-12-01

42

VLF saucers with attenuation bands  

International Nuclear Information System (INIS)

From a study of 43 VLF saucers exhibiting attenuation bands related to the proton gyrofrequency and observed on the ISIS satellites over Kerguelen in local winter (June-August, 1977), it is deduced that the generation/interaction region is generally located very near the satellite at distances often smaller than 50 km, either below or above it. It is also found that saucers with attenuation bands are observed in the 2000-0500 local time sector, between 60 deg and 70 deg geomagnetic latitude, in an auroral region closely correlated to the plasmapause. It is inferred from observations that the equatorward edges of the saucers region and of the plasma sheet are closely related.

1985-01-01

43

Higher harmonic tweek sferics observed at low latitude: estimation of VLF reflection heights and tweek propagation distance  

Directory of Open Access Journals (Sweden)

Full Text Available Lightning generated signals recorded at a low-latitude station, Suva (18.2° S, 178.3° E) Fiji, in the South Pacific region, during September 2003–July 2004, are used to study the propagation features and the reflection heights of tweek atmospherics in the waveguide formed by the Earth's surface and the lower ionosphere. Tweeks are observed only during the local night and the maximum harmonic (n) recorded is six. The occurrence of tweeks with higher n progressively decreases as n increases. The dispersed part of tweeks decreases as n increases. The attenuation factor has been calculated for tweeks with n=1–3. The ionospheric reflection heights obtained assuming the transverse magnetic mode of propagation for tweek signals vary from 83–92 km. A higher harmonic of the same tweek is reflected from about 2.0 km higher than the lower harmonic. For 90% of tweeks, propagation distances are estimated to be between 1000–5000 km. Tweeks with lower n propagate longer distances than the tweeks with higher n.

S. Kumar; A. Kishore; V. Ramachandran

2008-01-01

44

VLF wave intensity in the plasmasphere due to tropospheric lightning  

Science.gov (United States)

climatology of VLF (very low frequency) wave intensity from lightning in the plasmasphere is constructed. Starting from Optical Transient Detector/Lightning Imaging Sensor (OTD/LIS) lightning data representing 1995-2005, a climatology of strikes is assembled with 1° × 1° latitude-longitude spatial resolution, averaged into 2 h bins for each month of the year. Assuming a linear relationship between optical flash rate and VLF power flux, and that the VLF amplitude drops off as one over distance, a proxy for VLF power is developed. A typical lightning spectrum is applied and the values are scaled by appropriate transionospheric absorptions for each time and place. These values are mapped along geomagnetic field lines in order to compare them to E-field spectral densities measured by the DEMETER satellite between 2005 and 2009. An overview of the DEMETER survey mode data is presented which leads to the best scaling of the lightning VLF climatology in LEO (low earth orbit). The resulting data set represents a monthly, 2-hour, solar minimum climatology of VLF wave intensity from lightning in LEO. Finally, the E-field spectral densities are converted to Poynting flux, mapped to the plasmasphere, and converted to B-field spectral densities. Good overall agreement is found with previous observations and estimates. This new climatology is expected to have a significant impact on calculations of pitch-angle diffusion for relativistic electrons in the inner radiation belt.

Colman, J. J.; Starks, M. J.

2013-07-01

45

Microwave ISM Emission Observed by WMAP  

CERN Multimedia

We investigate the nature of the diffuse Galactic emission in the Wilkinson Microwave Anisotropy Probe (WMAP) temperature anisotropy data. Substantial dust-correlated emission is observed at all WMAP frequencies, far exceeding the expected thermal dust emission in the lowest frequency channels (23, 33, 41 GHz). The WMAP team (Bennett et al.) interpret this emission as dust-correlated synchrotron radiation, attributing the correlation to the natural association of relativistic electrons produced by SNae with massive star formation in dusty clouds, and deriving an upper limit of 5% on the contribution of Draine & Lazarian spinning dust at K-band (23 GHz). We pursue an alternative interpretation that much, perhaps most, of the dust-correlated emission at these frequencies is indeed spinning dust, and explore the spectral dependence on environment by considering a few specific objects as well as the full sky average. Models similar to Draine & Lazarian spinning dust provide a good fit to the full-sky data...

Finkbeiner, D P

2003-01-01

46

X-ray microbursts and VLF chorus  

Science.gov (United States)

On January 4, 1978, at 1140 UT, a Super Arcas sounding rocket was launched from Siple Station, Antarctica (L = 4.2, 76 S, 84 W) during a geomagnetically disturbed period (K sub p = 6-) with intense X-ray and VLF chorus activity. The parachuted payload observed an intense microburst precipitation event of 10 minute duration. These data have been correlated with measurements of Very Low Frequency chorus by receivers on the ground at both Siple and its magnetic conjugate point, Roberval, Quebec. Detailed one-to-one correspondence between the microbursts and the chorus was not a consistent feature of the data. Time series analysis of the data did indicate a significant correlation between the Siple X-ray precipitation and the Roberval VLF waves with an arrival time delay of 0.1 + or - 0.

Roeder, J. L.; Benbrook, J. R.; Bering, E. A.; Sheldon, W. R.; Stansberry, E. G.

1985-09-01

47

X ray microbursts and VLF chorus  

Science.gov (United States)

On January 4, 1978, at 1140 UT, a SuperArcas sounding rocket was launched from Siple Station, Antarctica (L = 4.2, 76 deg S, 84 deg W), during a geomagnetically disturbed period (Kp = 6-) with intense X-ray and VLF chorus activity. The parachuted payload observed an intense microburst precipitation event of 10-minute duration. These data have been correlated with measurements of FLF chorus by receivers on the ground at both Siple and its magnetic conjugate point, Roberval, Quebec. Detailed one-to-one correspondence between the microbursts and the chorus was not a consistent feature of the data. Time series analysis fo the data did indicate a significant correlation between the Siple X-ray precipitation and the Roberval VLF waves with an arrival time delay of 0.1 + or 0.3.

Roeder, J. L.; Benbrook, J. R.; Bering, E. A., III; Sheldon, W. R.

1985-11-01

48

Stimulated growth of coherent VLF waves in the magnetosphere  

International Nuclear Information System (INIS)

The amplitude behavior of several hundred VLF whistler mode pulse signals and of their associated artificially stimulated emissions (ASE's) was analyzed with digital signal processing techniques. A survey of the results indicates that the pulse signals characteristically show exponential growth with time that is highly repeatable over short periods. However, the growth rate varies widely from time to time, covering a range of 25 to 250 dB/s. During the exponential growth phase of the pulse there is no observable change in frequency. Emissions may begin when growth stops or when the input pulse terminates, whichever occurs first. Low growth rates and falling emissions characterize the beginning and ending of extended periods of emission activity. Rising emissions are prominent at the height of activity. ASE's triggered by station NAA (14.7 kHz, 1 MW radiated) begin when the transmitted Morse dash terminates (dash length, 150 ms). Some ASE's triggered by pulses from Siple Station, Antarctica (1.6 to 7 kHz,

1977-02-01

49

Anomalies observed in VLF and LF radio signals on the occasion of the western Turkey earthquake (Mw=5.7) at May 19, 2011  

Science.gov (United States)

Since 2009 a network of VLF (20-60 kHz) and LF (150-300 kHz) radio receivers is operating in Europe in order to study the disturbances produced by the earthquakes on the propagation of these signals. In 2011 the network was formed by nine receivers, of which three are located in Italy and one is in Austria, Greece, Portugal, Romania, Russia and Turkey. On May 19, 2001 an earthquake (Mw=5.7) occurred in western Turkey, that is inside the "sensitive" area of the network. The radio data collected during April-May 2011 were studied using the Wavelet spectra, the Principal Component Analysis and the Standard Deviation trends as different methods of analysis. Evident anomalies were revealed both in the signals broadcasted by the TRT transmitter (180 kHz) located near Ankara and in a VLF signal coming from a transmitter located in western Europe and collected by the receiver TUR of the network located in eastern Turkey. Evident precursor phases were pointed out. Some differences in the efficiency of the three analysis methods were revealed.

Biagi, P. F.; Righetti, F.; Maggipinto, T.; Schiavulli, L.; Ligonzo, T.; Ermini, A.; Moldovan, I. A.; Moldovan, A. S.; Silva, H. G.; Bezzeghoud, M.; Contadakis, M. E.; Arabelos, D. N.; Xenos, T. D.; Buyuksarac, A.

2012-09-01

50

Magion 5 observations of chorus-like emissions and their propagation features as inferred from ray-tracing simulation  

Directory of Open Access Journals (Sweden)

Full Text Available After reviewing briefly the present state of knowledge about chorus-like emissions, we present an overview of Magion 5 satellite observations of these emissions in the inner magnetosphere of the Earth. From the extensive VLF data recorded on board the Magion 5 satellite, we show examples of different types of discrete elements, representing rising and falling tones, and discuss their spectral properties, such as the bandwidth and the characteristic frequency as compared to the equatorial electron gyrofrequency. We analyse the possibility of satellite observation of discrete elements, assuming nonducted wave propagation from the source. As for the characteristic dimension of the generation region, we apply the figures obtained from the recently published correlation analysis of chorus emission recorded by four satellites in the Cluster experiment. We conclude that different frequencies in the chorus element should be emitted in a certain span of wave normal angles, so that the whole element could be observed far from the generation region.Key words. Magnetospheric physics (plasmasphere; plasma waves and instabilities) – Space plasma physics (wave-particle interactions) – Ionosphere (wave propagation)

J. Chum; F. Ji?í?ek; J. Šmilauer; D. Shklyar

0000-01-01

51

The Graz seismo-electromagnetic VLF facility  

Directory of Open Access Journals (Sweden)

Full Text Available In this paper we describe the Graz seismo-electromagnetic very low frequency (VLF) facility, as part of the European VLF receiver network, together with the scientific objectives and results from two years operation. After a brief technical summary of the present system – with heritage from a predecessor facility – i.e. hardware, software, operational modes and environmental influences, we discuss results from statistical data and scientific events related to terrestrial VLF propagation over Europe.

K. Schwingenschuh; G. Prattes; B. P. Besser; K. Mo?nik; M. Stachel; Ö. Aydogar; I. Jernej; M. Y. Boudjada; G. Stangl; A. Rozhnoi; M. Solovieva; P. F. Biagi; M. Hayakawa; H. U. Eichelberger

2011-01-01

52

Constraining CO emission estimates using atmospheric observations  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We apply a four-dimensional variational (4D-Var) data assimilation system to optimize carbon monoxide (CO) emissions and to reduce the uncertainty of emission estimates from individual sources using the chemistry transport model TM5. In the first study only a limited amount of surface network obs...

Hooghiemstra, P.B.

53

Observation of the helium 10830 A airglow emission in midlatitude  

Energy Technology Data Exchange (ETDEWEB)

The helium 10830 A airglow in twilight was observed by a tilting filter photometer. Over three years observation reveals the seasonal variation and the solar zenith angle dependence of the helium emission. The enhancement of the emission was observed in winter. The solar zenith angle dependence was also investigated. The observation results show that the conjugate photoelectrons and the diurnal variation of the exsospheric temperature affect the helium emission.

Suzuki, Katsuhisa (Tokyo Univ. (Japan))

1983-01-01

54

Observation of the helium 10830 A airglow emission in midlatitude  

International Nuclear Information System (INIS)

The helium 10830 A airglow in twilight was observed by a tilting filter photometer. Over three years observation reveals the seasonal variation and the solar zenith angle dependence of the helium emission. The enhancement of the emission was observed in winter. The solar zenith angle dependence was also investigated. The observation results show that the conjugate photoelectrons and the diurnal variation of the exsospheric temperature affect the helium emission. (author).

1983-01-01

55

ULF/ELF emissions observed in Japan, possibly associated with the Chi-Chi earthquake in Taiwan  

Directory of Open Access Journals (Sweden)

Full Text Available ULF/ELF emission observation has been performed at Nakatsugawa observatory (geographic coordinates; 35.4° N, 137.5° E, Gifu prefecture) since January 1999. The equipment consists of three-orthogonal magnetic sensors (induction coils), amplifiers, A/D converters and the data logger with a computer. The frequency range of observation is from 0.001 Hz to 50 Hz. The serious changes in ELF magnetic field intensity were detected on 20 September 1999, in such a way that the ELF noise level is found to increase by more than 5 dB from the normal level for about 1.5 h during 21:30–23:00 Japanese Standard Time on 20 September and also the upper limit extends up to 50 Hz. A careful comparison with the nearby lightning as detected by VLF, enables us to confirm that this abnormal ELF noise level increase is not due to the nearby lightning. The phase difference of these ELF emissions (BX , BY) was measured, and indicates that these ELF emissions are linearly polarized, suggesting that they have propagated in the subionospheric waveguide over long distances. This polarization result enables us to perform goniometric direction finding and the result shows that the main direction of these ULF/ELF emissions is toward Taiwan. Hence, it is likely that such ULF/ELF emissions are associated with the Chi-Chi earth-quake in Taiwan at 02:27 Japanese Standard Time on 21 September 1999 (M = 7.6; depth 11 km).

K. Ohta; K. Umeda; N. Watanabe; M. Hayakawa

2001-01-01

56

More evidence for a one-to-one correlation between Sprites and Early VLF perturbations  

DEFF Research Database (Denmark)

Past studies have shown a correlation between sprites and early VLF perturbations, but the reported correlation varies widely from ?50% to 100%. The present study resolves these large discrepancies by analyzing several case studies of sprite and narrowband VLF observations, in which multiple transmitter?receiver VLF pairs with great circle paths (GCPs) passing near a sprite?producing thunderstorm were available. In this setup, the multiple paths act in a complementary way that makes the detection of early VLF perturbations much more probable compared to a single VLF path that can miss several of them, a fact that was overlooked in past studies. The evidence shows that visible sprite occurrences are accompanied by early VLF perturbations in a one?to?one correspondence. This implies that the sprite generation mechanism may cause also sub?ionospheric conductivity disturbances that produce early VLF events. However, the one?to?one visible sprite to early VLF event correspondence, if viewed conversely, appears notto be always reciprocal. This is because the number of early events detected in some case studies was considerably larger than the number of visible sprites. Since the great majority of the early events not accompanied by visible sprites appeared to be caused by positive cloud to ground (+CG) lightning discharges, it is possible that sprites or sprite halos were concurrently present in these events as well but were missed by the sprite?watch camera detection system. In order for this option to be resolved we need more studies using highly sensitive optical systems capable of detecting weaker sprites, sprite halos and elves.

Haldoupis, C.; Amvrosiadi, N.

2010-01-01

57

High Resolution Observations of Emission Line Stars  

Science.gov (United States)

We present the high resolution spectra of early-type emission line stars and peculiar binaries obtained with the new SARG spectrograph of the Italian Galileo Telescope and with other telescopes as well. Problems arising in the spectral analysis are discussed and scientific results are presented.

Viotti, Roberto F.; Claudi, Riccardo; Rossi, Corinne; Iijima, Takashi

58

Experimental evidence of the simultaneous occurrence of VLF chorus on the ground in the global azimuthal scale – from pre-midnight to the late morning  

Directory of Open Access Journals (Sweden)

Full Text Available Night-time VLF (very low frequency) chorus bursts lasting about one hour have been recorded at Finnish temporal station Kannuslehto (CGM: 64.2°; 107.9°, L = 5.3) during two VLF campaigns (on 25 February–4 March 2008 and 27 March–17 April 2011). The chorus bursts were associated with substorm development. They were accompanied by riometer absorption enhancements, which occurred simultaneously within as large longitude areas as from pre-midnight (Sodankylä, ~22:00 MLT) to the late morning (Tixie, ~03:00 MLT and Gakona, ~08:00 MLT) longitudes. It was found that the pre-midnight chorus observed on the ground occurred simultaneously with VLF chorus emissions recorded in the late morning on the low-altitude DEMETER satellite crossing the similar geomagnetic latitudes on the opposite local time sector. For the first time some evidence of simultaneous chorus burst generation in the global longitudinal scale was found (from pre-midnight to the late morning) by using direct comparison with satellite data as well as using non-direct indicator–azimuthally extended riometer absorption enhancements.

J. Manninen; N. G. Kleimenova; O. V. Kozyreva; M. Parrot; T. Raita; T. Turunen

2012-01-01

59

Mg+ and other metallic emissions observed in the thermosphere  

International Nuclear Information System (INIS)

[en] Limb observations of UV dayglow emissions from 80 to 300 km tangent heights were made in December, 1992, using the GLO instrument, which flew on STS-53 as a Hitchhiker-G experiment. STS-53 was at 330 km altitude and had an orbit inclination of 57 degree. The orbit placed the shuttle near the terminator for the entire mission, resulting in a unique set of observations. The GLO instrument consisted of 12 imagers and 9 spectrographs on an Az/El gimbal system. The data was obtained over 6 days of the mission. Emissions from Mg+ and Ca+ were observed, as were emissions from the neutral metallic species Mg and Na. The ultimate source of the metals is ablation of meteors; however, the spatial distribution of the emissions is controlled by upper mesospheric and thermospheric winds and, in the case of the ions, by the electromagnetic fields of the ionosphere. The observed Mg+ emission was the brightest of the metal emissions, and was observed near the poles and around the geomagnetic equator near sunset. The polar emissions were short-lived and intense, indicative of auroral activity. The equatorial emissions were more continuous, with several luminous patches propagating poleward over the period of several orbits. The instrumentation will be described, as will spatial and temporal variations of the metal emissions with emphasis on the metal ions. These observations will be compared to previous observations of thermospheric metallic species

1994-01-01

60

Binding of the baculovirus very late expression factor 1 (VLF-1) to different DNA structures  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract Background Baculovirus genomes encode a gene called very late expression factor 1 (VLF-1) that is a member of the integrase (Int) family of proteins. In this report we describe the binding properties of purified Autographa californica multiple capsid nucleopolyhedrovirus (AcMNPV) VLF-1 to a number of different DNA structures including homologous regions. In addition, its enzymatic activity was examined. Results VLF-1 was expressed in a recombinant baculovirus as a fusion with both HA and HIS6 tags and its binding activity to different DNA structures was tested. No binding was evident to single and double strand structures, very low binding was observed to Y-forks, more binding was observed to three-way junctions, whereas cruciform structures showed high levels of binding. VLF-1 binding was affected by divalent cations; optimal binding to three-way junctions and cruciforms was 2 and 0 mM MgCl2, respectively. Homologous region (hr) sequences was also examined including oligomers designed to expose the hr palindrome as a hairpin, linear double strand, or H-shaped structure. Efficient binding was observed to the hairpin and H-shaped structure. No topoisomerase or endonuclease activity was detected. Sedimentation analysis indicated that *VLF-1 is present as a monomer. Conclusions An HA- and HIS-tagged version of AcMNPV VLF-1 showed structure-dependent binding to DNA substrates with the highest binding affinity to cruciform DNA. These results are consistent with the involvement of VLF-1 in the processing of branched DNA molecules at the late stages of viral genome replication. We were unable to detect enzymatic activity associated with these complexes.

Mikhailov Victor S; Rohrmann George F

2002-01-01

 
 
 
 
61

OBSERVATION OF CORRELATED OPTICAL AND GAMMA EMISSIONS FROM GRB 081126  

International Nuclear Information System (INIS)

We present an analysis of time-resolved optical emissions observed from the gamma-ray burst GRB 081126 during the prompt phase. The analysis employed time-resolved photometry using optical data obtained by the TAROT telescope, using BAT data from the Swift spacecraft, and time-resolved spectroscopy at high energies from the GBM instrument onboard the Fermi spacecraft. The optical emission of GRB 081126 is found to be compatible with the second gamma emission pulse shifted by a positive time lag of 8.4 ± 3.9 s. This is the first well-resolved observation of a time lag between optical and gamma emissions during a gamma-ray burst. Our observations could potentially provide new constraints on the fireball model for gamma-ray burst early emissions. Furthermore, observations of time lags between optical and gamma ray photons provides an exciting opportunity to constrain quantum gravity theories.

2009-05-20

62

Statistical X ray auroral emissions - PIXIE observations  

Science.gov (United States)

The Polar Ionospheric X ray Imaging Experiment (PIXIE) on board the NASA/GGS POLAR spacecraft has been making observations of X rays emitted simultaneously over the entire auroral zone since March, 1996. PIXIE remotely senses the bremsstrahlung produced by the loss of multi-keV electrons from the magnetosphere into the ionosphere. In this study we examine twenty-six months (April 1996 - July 1998) of X ray observations of the northern auroral region from the PIXIE instrument. X ray flux is obtained from the PIXIE observations, which allows us to produce for the first time synoptic auroral maps representing the precipitation of energetic electrons, as a function of geomagnetic activity.

Petrinec, S. M.; Chenette, D. L.; Mobilia, J.; Rinaldi, M. A.; Imhof, W. L.

63

The Zodiacal Emission Observations with the AKARI Infrared Camera  

Science.gov (United States)

From the pointed and scanning observations of the AKARI at the mid-infrared wavelengths, we retrieved the fine-, small-, and global-scale properties of the zodiacal emission and the interplanetary dust cloud.

Pyo, J.; Ueno, M.; Kwon, S. M.; Hong, S. S.; Ishihara, D.; Ishiguro, M.; Usui, F.; Matsumoto, T.; Jeong, W.-S.; Ootsubo, T.; Matsuura, S.; Mukai, T.

2012-05-01

64

Observations and modelling of pulsed radio emission from CU Virginis  

CERN Multimedia

We present 13 cm and 20 cm radio observations of the magnetic chemically peculiar star CU Virginis taken with the Australia Telescope Compact Array. We detect two circularly polarised radio pulses every rotation period which confirm previous detections. In the first pulse, the lower frequency emission arrives before the higher frequency emission and the ordering reverses in the second pulse. In order to explain the frequency dependence of the time between the two pulses, we construct a geometric model of the magnetosphere of CU Virginis, and consider various emission angles relative to the magnetic field lines. A simple electron cyclotron maser emission model, in which the emission is perpendicular to the magnetic field lines, is not consistent with our data. A model in which the emission is refracted through cold plasma in the magnetosphere is shown to have the correct pulse arrival time frequency dependence.

Lo, K K; Hobbs, G; Murphy, T; Gaensler, B M; Melrose, D; Ravi, V; Manchester, R M; Keith, M J

2012-01-01

65

Comparative statistical and spectral studies of seismic and non-seismic sub-ionospheric VLF anomalies  

Science.gov (United States)

We present a comparative study of seismic and non-seismic sub-ionospheric VLF anomalies. Our method is based on parameter variations of the sub-ionospheric VLF waveguide formed by the surface and the lower ionosphere. The used radio links working in the frequency range between 10 and 50 kHz, the receivers are part of the European and Russian networks. Various authors investigated the lithopsheric-atmospheric-ionospheric coupling and predicted the lowering of the ionosphere over earthquake preparation zones [1]. The received nighttime signal of a sub-ionospheric waveguide depends strongly on the height of the ionospheric E-layer, typically 80 to 85 km. This height is characterized by a typical gradient of the electron density near the atmospheric-ionospheric boundary [2]. In the last years it has been turned out that one of the major issues of sub-ionospheric seismo-electromagnetic VLF studies are the non-seismic influences on the links, which have to be carefully characterized. Among others this could be traveling ionospheric disturbances, geomagnetic storms as well as electron precipitation. Our emphasis is on the analysis of daily, monthly and annual variations of the VLF amplitude. To improve the statistics we investigate the behavior and typical variations of the VLF amplitude and phase over a period of more than 2 years. One important parameter considered is the rate how often the fluctuations are falling below a significant level derived from a mean value. The temporal variations and the amplitudes of these depressions are studied for several years for sub-ionospheric VLF radio links with the receivers in Graz and Kamchatka. In order to study the difference between seismic and non-seismic turbulences in the lower ionosphere a power spectrum analysis of the received signal is performed too. We are especially interested in variations T>6 min which are typical for atmospheric gravity waves causing the lithospheric-atmospheric-ionospheric coupling [3]. All measured and derived VLF parameters are compared with VLF observations several weeks before an earthquake (e.g. L'Aquila, Italy, April 6, 2009) and with co- and post-seismic phenomena. It is shown that this comparative study will improve the one parameter seismo-electromagnetic VLF methods. References: [1] A. Molchanov, M. Hayakawa: Seismo-Electromagnetics and related Phenomena: History and latest results, Terrapub, 2008. [2] S. Pulinets, K. Boyarchuk: Ionospheric Precursors of Earthquakes, Springer, 2004 [3] A. Rozhnoi et al.: Observation evidences of atmospheric Gravity Waves induced by seismic activity from analysis of subionospheric LF signal spectra, National Hazards and Earth System Sciences, 7, 625-628, 2007.

Wolbang, Daniel; Biernat, Helfried; Schwingenschuh, Konrad; Eichelberger, Hans; Prattes, Gustav; Besser, Bruno; Boudjada, Mohammed Y.; Rozhnoi, Alexander; Solovieva, Maria; Biagi, Pier Francesco; Friedrich, Martin

2013-04-01

66

Links between mesopause temperatures and ground-based VLF narrowband radio signals  

Science.gov (United States)

Upper Mesosphere-Lower Thermosphere (UMLT) region of the atmosphere is known to vary on many temporal and spatial scales. However, this region of the atmosphere is very difficult to measure and monitor continuously. In this paper, we demonstrate an intriguing connection between mesopause temperatures and the intensity of very low frequencies (VLF) narrowband (NB) signals reflected off the lower ionosphere. The temperature data used are from the SABER instrument onboard the TIMED satellite, while the VLF data are obtained from various ground-based receiving systems. The results of the analysis show a high anticorrelation between temperature and VLF amplitude. It is shown that the variability of the UMLT temperatures and VLF amplitudes can be explained by global seasonal solar irradiance changes (~72% of the variability), while the remaining variability has its origins from other sources (~28%). High-resolution mesopause temperature estimates might be achieved in the future by combining VLF NB observations and calculated solar irradiance variability (as a function of hour, day, and location, i.e., latitude).

Silber, Israel; Price, Colin; Rodger, Craig J.; Haldoupis, Christos

2013-05-01

67

SCIAMACHY formaldehyde observations: constraint for isoprene emissions over Europe?  

Directory of Open Access Journals (Sweden)

Full Text Available Formaldehyde (HCHO) is an important intermediate compound in the degradation of volatile organic compounds (VOCs) in the troposphere. Sources of HCHO are largely dominated by its secondary production from VOC oxidation, methane and isoprene being the main precursors in unpolluted areas. As a result of the moderate lifetime of HCHO, its spatial distribution is determined by reactive hydrocarbon emissions. We focus here on Europe, never studied before, and investigate the influence of the different emissions on HCHO tropospheric columns with the CHIMERE chemical transport model in order to interpret the comparisons between SCIAMACHY and simulated HCHO columns. Observed columns present a bias less than 20% on average. The differences are discussed according to the errors on the model and the observations and the remaining discrepancies are attributed to a misrepresentation of biogenic emissions. This study requires the characterisation of: (1) the model errors and performances concerning formaldehyde. The errors on the HCHO columns, mainly related to chemistry and mixed emission types, are evaluated to 2×1015 molecule/cm2 and the model performances evaluated using surface measurements are satisfactory (~13%); (2) the observation errors that define the needs in spatial and temporal averaging for meaningful comparisons. Perspectives of using SCIAMACHY observations as constraint for biogenic isoprene emissions with an adapted averaging are approached: this new constraint should help to reduce their uncertainties more than 50% in region of intense emissions.

G. Dufour; F. Wittrock; M. Camredon; M. Beekmann; A. Richter; J. Burrows

2008-01-01

68

Observations of Anomalous Microwave Emission from HII regions  

CERN Multimedia

In this brief review, I give a summary of the observations of Anomalous Microwave Emission (AME) from HII regions. AME has been detected in, or in the vicinity of, HII regions. Given the difficulties in measuring accurate SEDs over a wide range of frequencies and in complex environments, many of these detections require more data to confirm them as emitting significant AME. The contribution from optically thick free-free emission from UCHII regions may be also be significant in some cases. The AME emissivity, defined as the ratio of the AME brightness to the 100 micron brightness, is comparable to the value observed in high-latitude diffuse cirrus in some regions, but is significantly lower in others. However, this value is dependent on the dust temperature. More data, both at high frequencies (>5 GHz) and high resolution (~1 arcmin or better) is required to disentangle the emission processes in such complex regions.

Dickinson, Clive

2013-01-01

69

Egret observations of the extragalactic gamma-ray emission  

DEFF Research Database (Denmark)

The all-sky survey in high-energy gamma rays (E > 30 MeV) carried out by EGRET aboard the Compton Gamma Ray Observatory provides a unique opportunity to examine in detail the diffuse gamma-ray emission. The observed diffuse emission has a Galactic component arising from cosmic-ray interactions with the local interstellar gas and radiation, as well as an almost uniformly distributed component that is generally believed to originate outside the Galaxy. Through a careful study and removal of the Galactic diffuse emission, the flux, spectrum, and uniformity of the extragalactic emission are deduced. The analysis indicates that the extragalactic emission is well described by a power-law photon spectrum with an index of -(2.10 +/- 0.03) in the 30 MeV to 100 GeV energy range. No large-scale spatial anisotropy or changes in the energy spectrum are observed in the deduced extragalactic emission. The most likely explanation for the origin of this extragalactic high-energy gamma-ray emission is that it arises primarily from unresolved gamma-ray-emitting blazars.

Sreekumar, P.; Bertsch, D.L.

1998-01-01

70

Galactic water vapor emission: further observations of variability.  

UK PubMed Central (United Kingdom)

Recent observations of the 1.35-centimeter line emission of water vapor from galactic sources show short-term variability in the spectra of several sources. Two additional sources, Cygnus 1 and NGC 6334N, have been observed, and the spectra of W49 and VY Canis Majoris were measured over a wider range of radial velocity.

Knowles SH; Mayer CH; Sullivan WT 3rd; Cheung AC

1969-10-01

71

SCIAMACHY formaldehyde observations: constraint for isoprene emission estimates over Europe?  

Directory of Open Access Journals (Sweden)

Full Text Available Formaldehyde (HCHO) is an important intermediate compound in the degradation of volatile organic compounds (VOCs) in the troposphere. Sources of HCHO are largely dominated by its secondary production from VOC oxidation, methane and isoprene being the main precursors in unpolluted areas. As a result of the moderate lifetime of HCHO, its spatial distribution is determined by reactive hydrocarbon emissions. We focus here on Europe and investigate the influence of the different emissions on HCHO tropospheric columns with the CHIMERE chemical transport model in order to interpret the comparisons between SCIAMACHY and simulated HCHO columns. Europe was never specifically studied before for these purposes using satellite observations. The bias between measurements and model is less than 20% on average. The differences are discussed according to the errors on the model and the observations and remaining discrepancies are attributed to a misrepresentation of biogenic emissions. This study requires the characterisation of: (1) the model errors and performances concerning formaldehyde. The errors on the HCHO columns, mainly related to chemistry and mixed emission types, are evaluated to 2×1015 molecule/cm2 and the model performances evaluated using surface measurements are satisfactory (~13%); (2) the observation errors that define the needs in spatial and temporal averaging for meaningful comparisons. Using SCIAMACHY observations as constraint for biogenic isoprene emissions in an inverse modelling scheme reduces their uncertainties by about a factor of two in region of intense emissions. The retrieved correction factors for the isoprene emissions range from a factor of 0.15 (North Africa) to a factor of 2 (Poland, the United Kingdom) depending on the regions.

G. Dufour; F. Wittrock; M. Camredon; M. Beekmann; A. Richter; B. Aumont; J. P. Burrows

2009-01-01

72

Equatorial Emissions in the Inner Magnetosphere From THEMIS Observations  

Science.gov (United States)

The observational data of THEMIS are adopted to identify possible equatorial emissions in the inner magnetosphere near the equatorial plane. By analyzing wave data from SCM (Search Coil Magnetometer) in the local afternoon sector for the year of 2008, two possible events are found. These events are both with emissions of frequencies at about 70Hz and 110Hz between fcH+ and flhr around 5RE. The analyzed wave vectors shows to be near perpendicular to the ambient geomagnetic fields. The ion velocities are with ring distributions at around 2000km/sec and the associated pitch-angle distribution are peaked in 90° at the event time, as measured by SST (Solid State Telescope). While for wave data at similar location with no specific emission events in the aforementioned frequency range, the corresponding ion velocities exhibit no clear ring distributions. The above results suggest that these events can be equatorial emissions.

Wang, K.; Chen, R.; Tam, S. W.; Jan, Y.

2011-12-01

73

Optimizing ELF/VLF generation via HF heating utilizing beam motion  

Science.gov (United States)

ELF/VLF (300 Hz - 30 kHz) waves are difficult to generate with conventional antennae due to their extraordinary long wavelengths, and the good conductance of the Earth at these frequencies. Recently, ELF and VLF waves have been generated using HF (3-10 MHz) heating of the lower ionosphere, in the presence of natural currents such as the auroral electrojet, which modulates the ionospheric conductivity and therefore turns the lower ionosphere into a large radiating element. The recently upgraded HAARP facility, near Gakona Alaska, utilizes 3.6 MW of HF power, along with an unprecedented ability to steer the HF heating beam over a large area extremely rapidly. Since the completion of the upgrade in 2007, the first successful implementation of techniques such as geometric modulation [Cohen et al. 2008, Borisov et al. 1998], and beam painting [Papadopoulos et al. 1989] have occurred. These results have shown as much as 7-11 dB improvement in the signal strengths, as well as the first ability to direct ELF/VLF signals via an unprecedented ELF/VLF phased array. Here, we use a combination of experimental and theoretical investigations to discuss the optimization of ELF/VLF generation via HF heating, including the effect of HF and ELF frequency on the amplitude and the directional pattern for various generation techniques. The experimental observations occur over an array of receivers across Alaska. The theoretical formulation utilizes a 3D model of the HF heating and subsequent electron cooling processes, leading to spatial structure of modulated ionospheric conductivities, the results of which are input into a model of ELF/VLF propagation in the Earth-ionosphere waveguide.

Cohen, M. B.; Inan, U. S.; Lehtinen, N. G.; Golkowski, M. A.

2008-12-01

74

Thermal emission from isolated neutron stars: theoretical and observational aspects  

CERN Multimedia

The possibility for direct investigation of thermal emission from isolated neutron stars was opened about 25 years ago with the launch of the first X-ray observatory, Einstein. A significant contribution to this study was provided by ROSAT in 1990's. The outstanding capabilities of the currently operating observatories, Chandra and XMM-Newton, have greatly increased the potential to observe and analyze thermal radiation from the neutron star surfaces. Confronting observational data with theoretical models of thermal emission, presumably formed in neutron star atmospheres, allows one to infer the surface temperatures, magnetic fields, chemical composition, and neutron star masses and radii. This information, supplemented with model equations of state and neutron star cooling models, provides an opportunity to understand the fundamental properties of the superdense matter in the neutron star interiors. I review the current status and most important results obtained from modeling neutron star thermal emission an...

Zavlin, V E

2007-01-01

75

Synoptic observations of Jupiter's radio emissions: average statistical properties observed by voyager  

Energy Technology Data Exchange (ETDEWEB)

Observations of Jupiter's low-frequency radio emission collected over one-month intervals before and after each Voyager encounter have been analyzed to provide a synoptic view of the average statistical properties of the emissions. Compilations of occurrence probability, average power flux density, and average sense of circular polarization are presented as a function of central meridian longitude, phase of Io, and frequency. The results are compared with ground-based observations. The necessary geometrical conditions and preferred polarization sense for Io-related decametric emission observed by Voyager from above both the dayside and nightside hemispheres are found to be essentially the same as those observed in earth-based studies. On the other hand, there is a clear local time dependence in the Io-dependent decametric emission. The emission is prevalent at longitudes >200/sup 0/ when observed from over the dayside hemisphere but is dominant at longitudes >200/sup 0/ when observed from over the postmidnight sector. Decametric emission, which comprises the dynamic spectral lesser arcs near 10 MHz, displays a distinct, bimodal polarization pattern that is predominantly in the left-hand sense at longitudes below 150/sup 0/ and in the right-hand sense at longitudes above 150/sup 0/. The central meridian longitude distributions of occurrence probability and average flux density at hectometric wavelengths appear to depend significantly on both the observer's latitude and local time. Io appears to have an influence on average flux density of the emission down to below 2 MHz. The average power flux density sectrum of Jupiter's emission has a broad peak near 9 MHz. Intergration of the average spectrum over all frequencies and all longitudes gives a total radiated power for an equivalent isotropic source of 4 x 10/sup 11/ W.

Alexander, J.K.; Carr, T.D.; Thieman, J.R.; Schauble, J.J.; Riddle, A.C.

1981-09-30

76

Synoptic observations of Jupiter's radio emissions: average statistical properties observed by voyager  

International Nuclear Information System (INIS)

Observations of Jupiter's low-frequency radio emission collected over one-month intervals before and after each Voyager encounter have been analyzed to provide a synoptic view of the average statistical properties of the emissions. Compilations of occurrence probability, average power flux density, and average sense of circular polarization are presented as a function of central meridian longitude, phase of Io, and frequency. The results are compared with ground-based observations. The necessary geometrical conditions and preferred polarization sense for Io-related decametric emission observed by Voyager from above both the dayside and nightside hemispheres are found to be essentially the same as those observed in earth-based studies. On the other hand, there is a clear local time dependence in the Io-dependent decametric emission. The emission is prevalent at longitudes >2000 when observed from over the dayside hemisphere but is dominant at longitudes >2000 when observed from over the postmidnight sector. Decametric emission, which comprises the dynamic spectral lesser arcs near 10 MHz, displays a distinct, bimodal polarization pattern that is predominantly in the left-hand sense at longitudes below 1500 and in the right-hand sense at longitudes above 1500. The central meridian longitude distributions of occurrence probability and average flux density at hectometric wavelengths appear to depend significantly on both the observer's latitude and local time. Io appears to have an influence on average flux density of the emission down to below 2 MHz. The average power flux density sectrum of Jupiter's emission has a broad peak near 9 MHz. Intergration of the average spectrum over all frequencies and all longitudes gives a total radiated power for an equivalent isotropic source of 4 x 1011 W

1981-09-30

77

Ray-based modeling of lightning-induced ionospheric effects on short range VLF skywave signals  

Science.gov (United States)

At locations close (~100-km) to a VLF transmitter, observation of the sky wave signal from the transmitter becomes possible by aligning a proximate magnetic loop antenna to null the ground signal. Previous observations using such an arrangement [e.g., Rodriguez et al. 1992], and [Pasko et al., 2002] show a very high degree of temporal variability in received signal amplitude. Observation of VLF signatures of Early/Fast and Lightning-induced Electron Precipitation (LEP) events under these constraints show an unusual number of remarkably large events, more than ten times larger than a typical long-distance path, and often exhibit non-exponential recovery, or no recovery at all. Because of the large spatial extent of LEP events compared to the sky wave path distances, at least portions of the disturbed region must necessarily be nearly overhead the receiver and/or transmitter and we can employ simple ray tracing techniques to determine the evolution of the scattered field from the ionospheric disturbance over time, taking into account path-length difference, absorption, ground, and ionospheric reflection coefficients and multiple hops. We present several examples of characteristic VLF perturbations observed on short paths, and interpret these in terms of a simple ray-path-based model of the VLF scattering from the lower ionosphere.

Cotts, B. R.; Inan, U. S.

2005-12-01

78

Solar Flare Impulsive Phase Emission Observed with SDO/EVE  

CERN Multimedia

Differential emission measures (DEMs) during the impulsive phase of solar flares were constructed using observations from the EUV Variability Experiment (EVE) and the Markov-Chain Monte Carlo method. Emission lines from ions formed over the temperature range log T = 5.8 - 7.2 allow the evolution of the DEM to be studied over a wide temperature range at 10s cadence. The technique was applied to several M- and X-class flares, where impulsive phase EUV emission is observable in the disk-integrated EVE spectra from emission lines formed up to 3 - 4 MK, and we use spatially-unresolved EVE observations to infer the thermal structure of the emitting region. For the nine events studied the DEMs exhibited a two component distribution during the impulsive phase, a low temperature component with peak temperature of 1 - 2 MK, and a broad high temperature one from 7 - 30 MK. A bimodal high temperature component is also found for several events, with peaks at 8 and 25 MK during the impulsive phase. The origin of the emissi...

Kennedy, Michael B; Mathioudakis, Mihalis; Keenan, Francis P

2013-01-01

79

Fermi-LAT observations of GRBs with weak LAT emission  

CERN Document Server

We present the analysis results of three Gamma-Ray Bursts (GRBs) detected by the Gamma-ray Burst Monitor (GBM) and the Large Area Telescope (LAT) onboard Fermi: the two long GRB 080825C and GRB 090217, and the first short burst with GeV photons GRB 081024B. The emission from GRB 081024B observed by the LAT above 100 MeV is delayed with respect to the GBM trigger, and significantly extends after the low-energy episode. Some hints for spectral hardening was observed in this burst as well as in GRB 080825C, possibly related to a separate and harder component showing up at late times. Conversely, GRB 090217 does not exhibit any noticeable feature. Together with the other bright LAT detected bursts (e.g. GRB 080916C and GRB 090510), these observations help to classify the GRB properties and give new insight on the acceleration mechanisms responsible for their emission at the highest energies.

Ohno, Masanori

2010-01-01

80

Biogenic nonmethane hydrocarbon emissions estimated from tethered balloon observations  

Science.gov (United States)

A new technique for estimating surface fluxes of trace gases, the mixed-layer gradient technique, is used to calculate isoprene and terpene emissions from forests. The technique is applied to tethered balloon measurements made over the Amazon forest and a pine-oak forest in Alabama at altitudes up to 300 m. The observations were made during the dry season Amazon Boundary Layer Experiment (ABLE 2A) and the Rural Oxidants in the Southern Environment 1990 experiment (ROSE I). Results from large eddy simulations of scalar transport in the clear convective boundary layer are used to infer fluxes from the balloon profiles. Profiles from the Amazon give a mean daytime emission of 3630±1400 ?g isoprene m-2 h-1, where the uncertainty represents the standard deviation of the mean of eight flux estimates. Twenty profiles from Alabama give emissions of 4470±3300 ?g isoprene m-2 h-1, 1740±1060 ?g alpha-pinene m-2 h-1, and 790±560 ?g beta-pinene m-2 h-1, respectively. These results are in agreement with emissions derived from chemical budgets. The emissions may be overestimated because of uncertainty about how to incorporate the effects of the canopy on the mixed-layer gradients. The large variability in these emission estimates is probably due to the relatively short sampling times of the balloon profiles, though spatially heterogeneous emissions may also play a role. Fluxes derived using this technique are representative of an upwind footprint of several kilometers and are independent of hydrocarbon oxidation rate and mean advection.

Davis, K. J.; Lenschow, D. H.; Zimmerman, P. R.

1994-12-01

 
 
 
 
81

GOSAT specific observation targeting urban CO2 emissions  

Science.gov (United States)

One important step to estimate total carbon dioxide (CO2) emissions from a mega-sized city is to monitor concentrations at sufficiently numerous observation sites and thereby cover all regions of the city. The greenhouse gas observing satellite (GOSAT) has functioned normally since its launch on 23 January 2009. Although its main purpose is the measurement of greenhouse gases globally to reduce the estimation error of source/sink strength in a sub-continental size region, it can measure gas concentrations at multiple targets on a regional scale during one orbital over-flight. The science team of the project has initiated and conducted special observations to demonstrate the usefulness of intensive observations for quantifying urban CO2 emissions. The main sensor of the satellite, the “thermal and near infrared sensor for carbon observation Fourier transform spectrometer (TANSO-FTS)”, has been operated in a “specific operation mode” to measure carbon dioxide, methane, and tropospheric ozone at 4 × 4 (totally 16) mesh points over the Kanto Plain, the center of which is Tokyo. This specific observation covers about 100 km × 100 km of the plain. To validate the satellite observations and to measure the vertical structure of the atmospheric condition, in situ and remote sensing measurements were conducted. Collocating the satellite over-path, a group from Nagoya University released CO2 sondes from three sites. Furthermore, a group from Kyoto University measured the vertical profile of CO2 concentration using a fiber etalon spectrometer. One satellite observation footprint is very close to Narita International Airport, where CO2 data are most frequently obtained by the CONTRAIL project. These observational data will be analyzed using CO2 transport models. The AIST meso-scale model (AIST-MM), whose highest spatial resolution is 1 km, is used to evaluate CO2 emissions from the urban area. Boundary conditions in a large area outside the regional target are provided by the NICAM based transport model (NICAM-TM).

Imasu, R.; Inoue, G.; Kondo, H.; Niwa, Y.; Matsueda, H.; Machida, T.; Matsumi, Y.; Kawasaki, M.; Nakayama, T.; Hayashi, Y.; Inagoya, A.; Saitoh, N.; Yokota, T.

2010-12-01

82

X-ray Emissions From the Earth's Ionosphere - PIXIE Observations  

Science.gov (United States)

In this study we examine observations of global X-ray bremsstrahlung from the Earth's polar regions as observed by the POLAR Ionospheric X-ray Imaging Experiment (PIXIE) instrument on board the NASA/GGS POLAR spacecraft. The emitted X rays are observed as a consequence of geomagnetic storm and substorm activity, as high energy (> 2 keV) magnetospheric electrons precipitate into the upper ionosphere. We discuss the physical mechanisms which at least qualitatively describe the observations, including the effects that electron precipitation have on polar region ionospheric conductivity, as a function of local time and season. Qualitative and quantitative comparisons with other sets of observations of upper atmospheric emissions are also described. Other observations of X rays from PIXIE are also briefly described, including solar X rays scattered from the Earth's dayside ionosphere, and cosmic X-ray sources.

Petrinec, S. M.; Mobilia, J.; Imhof, W. L.; Chenette, D. L.

2001-05-01

83

Observation of microwave emission from extensive air showers with CROME  

Directory of Open Access Journals (Sweden)

Full Text Available We report on the measurement of microwave radio signals from air showers with the CROME (Cosmic Ray Observation via Microwave Emission) experiment. CROME is located in the center of the KASCADE-Grande air shower array. The radio signals of the CROME antennas are stored for each high-energy trigger from the KASCADE-Grande array and matched o?ine with the KASCADE-Grande data. After almost one year of data taking microwave signals have been observed for more than ten air showers.

Šmída R.; Baur S.; Bertaina M.; Blümer J.; Chiavassa A.; Engel R.; Haungs A.; Huege T.; Kampert K.-H.; Klages H.; Kleifges M.; Krömer O.; Ludwig M.; Mathys S.; Neunteufel P.; Pekala J.; Rautenberg J.; Riegel M.; Roth M.; Salamida F.; Schieler H.; Stasielak J.; Unger M.; Weber M.; Werner F.; Wilczy?ski H.; Wochele J.

2013-01-01

84

Investigation of TEC and VLF space measurements associated to L'Aquila (Italy) earthquakes  

Directory of Open Access Journals (Sweden)

Full Text Available In this study, we report on Total Electron Content (TEC) and Very Low Frequency (VLF) space measurements derived from Global Positioning System (GPS) and DEMETER satellites, respectively. These measurements are associated with the earthquake (EQ) of a magnitude of 6.3, which occurred on 6 April 2009, in L'Aquila (Italy). Anomaly features are derived from the analysis of TEC and VLF observations recorded two weeks before and after the seismic event occurrence. A TEC map with an interpolated regional pixel resolution of 1° × 1° × 15 min in latitude, longitude and time was generated, allowing for the checking of a possible presence of disturbances over the L'Aquila region. This analysis is combined with the study of the time profile associated to the VLF flux density variations recorded by the Instrument Champ Electrique (ICE) experiment on-board DEMETER satellite. We discuss, on the one hand, the combination efficiency of the electronic density and the VLF electromagnetic measurements and, on the other hand, the difficulty to distinguish between global effects and regional ones related to the earthquake.

G. Stangl; M. Y. Boudjada; P. F. Biagi; S. Krauss; A. Maier; K. Schwingenschuh; E. Al-Haddad; M. Parrot; W. Voller

2011-01-01

85

Study of Ionospheric Perturbations in D-Layer Using Awesome VLF Receiver Data at Tashkent Station  

Science.gov (United States)

One VLF receiver and two SuperSID receivers were provided to Uzbekistan IHY cite by Stanford University and are operating in Tashkent, under the International Heliophysical Year (IHY). The results obtained at Tashkent IHY station are applied to earthquake electromagnetic precursors, lightning, and solar flares and to ionospheric disturbances originating from gamma ray flares of Soft Gamma-Ray Repeaters connected with evolution of strongly magnetized neutron stars believed as magnetars. Regular monitoring of the D-layer of ionosphere over Central Asia territory has been performed on the permanent basis. Few Solar flare events are observed during February in 2010-2011 years and the analysis showed that there is simultaneous correlation between the times of change of amplitude of the waves and the Solar flares. Features of the lightning discharge generated by radio atmospherics are studied and its effectiveness in D-region ionosphere diagnostics is explained. Assuming that earthquakes (EQs) can be preceded by the electromagnetic signals in the VLF bands detectable from ground-based measurements we have studied VLF amplitude anomalies related to the earthquakes occurred in 2009-2010 years with magnitude more than 5 on the path way from the VLF transmitters to the Tashkent station. For analysing narrowband data we have used the Nighttime Fluctuation (NF) method paying attention to the data obtained during the local nighttime (18:00 LT-06:00 LT). The amplitude data are analysed only for the reason that perturbations are identified more clearly in the amplitude data than in phase data. The mean nighttime amplitude (or trend) and normalized trend are found to increase significantly before the EQ with the same tendency as the NF and normalized NF. The obtained results have revealed a fine agreement with VLF amplitude anomalies observed in Tashkent VLF station during the strong earthquakes occurred on the path way from the transmitters to the receiver. Some of the initial results obtained from the preliminary analysis are presented to show the probing potentiality of VLF waves in ionosphere studies.

Ahmedov, Bobomurat

2012-07-01

86

Iron Emission Lines on the Galactic Ridge Observed with Suzaku  

CERN Multimedia

In order to elucidate origin of the Galactic Ridge X-ray Emission, we analyzed Suzaku data taken at various regions along the Galactic plane and studied their Fe-K emission line features. Suzaku resolved the Fe line complex into three narrow lines at ~6.4 keV,~6.7 keV and ~6.97 keV, which are K-lines from neutral (or low-ionized), He-like, and H-like iron ions, respectively. The 6.7 keV line is clearly seen in all the observed regions and its longitudinal distribution is consistent with that determined from previous observations. The 6.4 keV emission line was also found in various Galactic plane regions (b~0). Differences in flux ratios of the 6.4 keV/6.7 keV and 6.97 keV/6.7 keV lines between the Galactic plane and the Galactic center regions are studied and its implication is discussed.

Yamauchi, Shigeo; Tanaka, Yasuo; Koyama, Katsuji; Matsumoto, Hironori; Yamasaki, Noriko Y; Takahashi, Hiromitsu; Ezoe, Yuichiro

2008-01-01

87

The low ionosphere electron density changes during events of the extreme solar activity as deduced from VLF measurements  

International Nuclear Information System (INIS)

Complete text of publication follows. It is well known that solar X-ray flares increase the electron density at the lower ionosphere edge and that it can be detected from changes in the VLF propagation through Earth-ionosphere waveguide. The influence of the CME and SEP events, usually accompanying the extreme X-ray flares, on the electron density at the ionosphere-atmosphere boundary, can be also studied using the VLF data and appropriate choice of the processes introduced into continuity equation. Several examples of electron density disturbances, induced by X class flares: X1.3 at 1054 UT on July 2005, X17 class flare at 1740 UT on September 7, 2005, X9 at 1018 UT on December 5 2006 and accompanying events, are analyzed. The lack of the proportionality between VLF amplitude/phase (determined by electron density) and X-ray irradiance in the case of huge flares, indicates that processes else than photoionization-dissociative recombination take place. The continuity equation, including the three-body recombination is solved. The time variation of the electron density height profile N(z,t) during disturbed conditions is evaluated and compared with calculations, obtained from the Wait's N(z,t) model developed for the simulation of VLF propagation. The accordance in the order of magnitude was found. Also, the effects of the series of events in period from January 15 - 22, 2005, were analyzed. The VLF recordings reveal the absence of regular diurnal pattern in amplitude and phase, suggesting that the high level of electron density persists through night hours. It can be explained by impact of energetic particles, colliding with atmospheric neutrals. The X-ray emission released in 'bremsstrahlung' process cause the ionization of atmospheric constituents. The VLF signals on two traces, NAA/24 kHz (Maine, USA - Belgrade) and GQD/22.1 kHz (Skelton, UK - Belgrade), were recorded by AbsPal system and used in this study.

2009-01-01

88

VLF radio propagation conditions. Computational analysis techniques  

International Nuclear Information System (INIS)

[en] Complete text of publication follows. Very low frequency (VLF) radio waves propagate within the Earth-ionosphere waveguide with very little attenuation. Modifications of the waveguide geometry effect the propagation conditions, and hence, the attenuation. Changes in the ionosphere, such as the presence of the D-region during the day, or the precipitation of energetic particles, are the main causes of this modification. Using narrowband receivers monitoring VLF transmitters, the amplitude and phase of these signals are recorded. Multivariate data analysis techniques, namely Principal Component Analysis (PCA) and Singular Spectrum Analysis (SSA), are applied to the data in order to determine parameters, such as seasonal and diurnal changes, affecting the variation of these signals. Transient effects may then be easier to detect.

2009-01-01

89

CBR anisotropy and galactic emission observations from Antarctica. [LMC; SMC  

Energy Technology Data Exchange (ETDEWEB)

In this paper we report the results of an experiment on the CBR anisotropy at 2 mm and 2.5 degrees angular resolution carried out during the Antarctic summer of 1987-88. We find evidence of statistical fluctuations at a level of T/T=2x10{sup {minus}4}, most of which can be ascribed to both atmospheric residual noise and/or patch galactic emission. In addition, we observed the Magellanic Clouds and obtained an excess of mm-wave radiation in dicating the presence of a cold dust component coexisting with the IRAS wa rm dust. (AIP)

Andreani, P.; Dall' Oglio, G.; Bari, M.D. (University of Rome, Physics Dept. P.leA. Moro 2,00185 Rome (Italy)); Martinis, L. (ENEA T.I.B., Frascati (Italy)); Piccirillo, L. (University of Rome, Physics Dept. P.LeA. Moro 2,00185 Rome (Italy) Istituto Superiore P.T., V.le Europe 190,00144 Rome (Italy)); Pizzo, L.; Santillo, C. (Unviersity of Rome, Physcis Dept, P.LeA. Moro 2,00185 Rome (Italy))

1990-01-15

90

Cassini Composite Infrared Spectrometer (CIRS) Observations of Phoebe's Thermal Emission  

Science.gov (United States)

The Cassini Composite Infrared Spectrometer (CIRS) has three focal planes that together cover the thermal spectrum from 10 to 1420 cm-1 (1 mm to 7 ? m). Focal plane 1 (FP1) covers 10 to 600 cm-1 with a circular field of view of 3.9 milliradians diameter. Focal plane 3 (FP3) covers 600 to 1100 cm-1, and focal plane 4 (FP4) covers 1100 - 1420 cm-1, both with a linear array of 10 pixels, each 0.3 milliradians square. Spectral resolution is selectable from 0.5 to 15.5 cm-1 (apodized). During the Cassini flyby of Phoebe on June 11 th 2004, CIRS obtained numerous observations of thermal emission from its surface with all three detectors, though FP4 only detected emission from the very warmest regions. FP3 achieved a spatial resolution as small as 12 km for full-disk observations, and 600 m for local observations near closest approach. Spectral resolving power for most observations was about 50. The signal to noise ratio (S/N) of the FP3 observations allows measurement of brightness temperatures as low as ˜ 75 K but is not sufficient to detect any deviations from blackbody behavior in the Phoebe data. There is strong topographic control of temperature, particularly around the prominent large crater seen in Cassini visible-wavelength images, where temperatures were observed over nearly half a Phoebe rotation. Low-latitude temperatures on Phoebe vary between 82 K before dawn to 112 K near the subsolar point. The diurnal variation can be matched with a thermal inertia near 3 x 104 erg cm-2 s-1/2 K-1, about half the thermal inertia derived from diurnal temperature variations on the Galilean satellites but similar to that of Rhea, Dione, and Tethys. This low thermal inertia implies that the upper centimeter of Phoebe's surface is covered in very porous material. FP1 had lower spatial resolution than FP3 (near 9 km at closest approach), but higher S/N, allowing extraction of spectral information. At 50 cm-1 (200 ? m) brightness temperatures varied from 68K in predawn locations, to 101K near the subsolar point. However, strong spectral gradients were apparent in all spectra, with brightness temperatures at 400 cm-1 (25 ? m) in the above instances varying from 76K to 111K. No strong emissivity variations are present. Consequently, these spectral characteristics are due to a combination of unresolved thermal inertia and slope (shadowing) variations. These effects will be discussed.

Spencer, J. R.; Pearl, J. C.; Segura, M.

2004-12-01

91

Tectonomagnetic and VLF electromagnetic signals in Central Italy  

Directory of Open Access Journals (Sweden)

Full Text Available Tectonomagnetic field observations from absolute magnetic field level measurements were undertaken in Central Italy in an area extending between latitude 41°N and 43°N and between longitude 13°E and 15°E. Moreover,natural electromagnetic signals from a system of two VLF search coil wide-band antennas were collected at the geomagnetic observatory of L Aquila (42º23'N, 13º19'E). The analysis of these data allowed the investigation of the electromagnetic properties of the study area at different time and spatial lengthscales. Tectonomagnetic field observations were obtained comparing data simultaneously recorded at three magnetometer stations using L'Aquila Observatory as a reference for differentiation. We report on the time evolution of magnetic and electromagnetic indicators related to local and regional seismic activity.

A. Meloni; D. Di Mauro; S. Lepidi; G. Mele; P. Palangio

2004-01-01

92

Radiofrequency emissions observed during macroscopic hypervelocity impact experiments  

Energy Technology Data Exchange (ETDEWEB)

Observations of banded radiofrequency emission generated during and after macroscopic hypervelocity impacts of small projectiles on hard rocks are reported. Tests were conducted in air at atmospheric pressure and in vacuo at residual pressure varying between 6 and 0.1 torr. The receiver system consisted of several coils oriented so as to allow the simultaneous detection of various components of any transient magnetic field. The values of the recorded output frequencies varied from test to test but were generally of the same order of magnitude irrespective of ambient pressure or target material. These values are too low to have been generated in the impact-produced plasma by an oscillating dipole type of mechanism, and they cannot be due to conversion of electron plasma waves into electromagnetic waves, for reasons that are discussed. The frequencies are comparable to those observed in association with some strong earthquakes. 13 references.

Bianchi, R.; Capaccioni, F.; Cerroni, P.

1984-04-26

93

RXTE Observations of the SGR 1806-20 Steady Emission  

CERN Multimedia

We discuss observations of the quiescent emission from the soft gamma repeater SGR 1806-20 by the Rossi X-ray Timing Explorer. We find that the 2-20 keV RXTE data is consistent with a constant spectral shape during both active bursting periods and periods of relative quiescence, and is best described by a nonthermal (power law) spectral shape. Using archival ASCA data we find that the quiescent spectrum of SGR 1806-20 is well fit over the energy range 1-30 keV by a power law of photon index 2.31 +/- 0.04, with thermal bremsstrahlung and Raymond-Smith models producing much worse fits to the data.

Marsden, D C; Kouveliotou, C; Dieters, S W; Van Paradijs, J

1998-01-01

94

Observations of Microwave Continuum Emission from Air Shower Plasmas  

CERN Multimedia

We investigate a possible new technique for microwave measurements of ultra-high energy cosmic ray (UHECR) extensive air showers which relies on detection of expected continuum radiation in the microwave range, caused by free-electron collisions with neutrals in the tenuous plasma left after the passage of the shower. We performed an initial experiment at the AWA (Argonne Wakefield Accelerator) laboratory in 2003 and measured broadband microwave emission from air ionized via high energy electrons and photons. A follow-up experiment at SLAC (Stanford Linear Accelerator Center) in summer of 2004 confirmed the major features of the previous AWA observations with better precision and made additional measurements relevant to the calorimetric capabilities of the method. Prompted by these results we built a prototype detector using satellite television technology, and have made measurements indicating possible detection of cosmic ray extensive air showers. The method, if confirmed by experiments now in progress, cou...

Gorham, P W; Varner, G S; Beatty, J J; Connolly, A; Chen, P; Conde, M E; Gai, W; Hast, C; Hebert, C L; Miki, C; Konecny, R; Kowalski, J; Ng, J; Power, J G; Reil, K; Saltzberg, D; Stokes, B T; Walz, D

2007-01-01

95

The Stanford University ELF/VLF radiometer project Measurement of the global distribution of ELF/VLF electromagnetic noise  

Science.gov (United States)

The Stanford University ELF/VLF radiometer considered in this paper is a new dual-channel computer-controlled system which provides quantitative measurements of electromagnetic activity in the frequency range from 10 Hz to 32 kHz. Both analog and digital recording are used. Attention is given to the frequency designation, technical details regarding the radiometer, previous ELF/VLF noise measurements, and applications of the noise data. It is pointed out that the Stanford ELF/VLF noise survey will provide new information about the global distribution and temporal variation of ELF/VLF noise. An immediate practical application of the noise measurements is related to communication in the ELF/VLF band. Another possibility, still speculative at this stage, is concerned with earthquake prediction.

Fraser-Smith, A. C.; Helliwell, R. A.

96

EMISSION PATTERNS OF SOLAR TYPE III RADIO BURSTS: STEREOSCOPIC OBSERVATIONS  

Energy Technology Data Exchange (ETDEWEB)

Simultaneous observations of solar type III radio bursts obtained by the STEREO A, B, and WIND spacecraft at low frequencies from different vantage points in the ecliptic plane are used to determine their directivity. The heliolongitudes of the sources of these bursts, estimated at different frequencies by assuming that they are located on the Parker spiral magnetic field lines emerging from the associated active regions into the spherically symmetric solar atmosphere, and the heliolongitudes of the spacecraft are used to estimate the viewing angle, which is the angle between the direction of the magnetic field at the source and the line connecting the source to the spacecraft. The normalized peak intensities at each spacecraft R{sub j} = I{sub j} /{Sigma}I{sub j} (the subscript j corresponds to the spacecraft STEREO A, B, and WIND), which are defined as the directivity factors are determined using the time profiles of the type III bursts. It is shown that the distribution of the viewing angles divides the type III bursts into: (1) bursts emitting into a very narrow cone centered around the tangent to the magnetic field with angular width of {approx}2 Degree-Sign and (2) bursts emitting into a wider cone with angular width spanning from {approx} - 100 Degree-Sign to {approx}100 Degree-Sign . The plots of the directivity factors versus the viewing angles of the sources from all three spacecraft indicate that the type III emissions are very intense along the tangent to the spiral magnetic field lines at the source, and steadily fall as the viewing angles increase to higher values. The comparison of these emission patterns with the computed distributions of the ray trajectories indicate that the intense bursts visible in a narrow range of angles around the magnetic field directions probably are emitted in the fundamental mode, whereas the relatively weaker bursts visible to a wide range of angles are probably emitted in the harmonic mode.

Thejappa, G.; Bergamo, M. [Astronomy Department, University of Maryland, College Park, MD 20742 (United States); MacDowall, R. J., E-mail: thejappa.golla@nasa.gov, E-mail: mbergamo@umd.edu, E-mail: Robert.MacDowall@nasa.gov [NASA/Goddard Space Flight Center, Greenbelt, MD 20771 (United States)

2012-02-01

97

EMISSION PATTERNS OF SOLAR TYPE III RADIO BURSTS: STEREOSCOPIC OBSERVATIONS  

International Nuclear Information System (INIS)

Simultaneous observations of solar type III radio bursts obtained by the STEREO A, B, and WIND spacecraft at low frequencies from different vantage points in the ecliptic plane are used to determine their directivity. The heliolongitudes of the sources of these bursts, estimated at different frequencies by assuming that they are located on the Parker spiral magnetic field lines emerging from the associated active regions into the spherically symmetric solar atmosphere, and the heliolongitudes of the spacecraft are used to estimate the viewing angle, which is the angle between the direction of the magnetic field at the source and the line connecting the source to the spacecraft. The normalized peak intensities at each spacecraft Rj = Ij /?Ij (the subscript j corresponds to the spacecraft STEREO A, B, and WIND), which are defined as the directivity factors are determined using the time profiles of the type III bursts. It is shown that the distribution of the viewing angles divides the type III bursts into: (1) bursts emitting into a very narrow cone centered around the tangent to the magnetic field with angular width of ?2° and (2) bursts emitting into a wider cone with angular width spanning from ? – 100° to ?100°. The plots of the directivity factors versus the viewing angles of the sources from all three spacecraft indicate that the type III emissions are very intense along the tangent to the spiral magnetic field lines at the source, and steadily fall as the viewing angles increase to higher values. The comparison of these emission patterns with the computed distributions of the ray trajectories indicate that the intense bursts visible in a narrow range of angles around the magnetic field directions probably are emitted in the fundamental mode, whereas the relatively weaker bursts visible to a wide range of angles are probably emitted in the harmonic mode.

2012-02-01

98

Rocket investigations of electron precipitation and VLF waves in the Antarctic upper atmosphere  

Science.gov (United States)

The results of two Antarctic rocket campaigns, primarily initiated to investigate electron precipitation stimulated by signals from the Siple-Station ground-based VLF transmitter, are presented. While the primary objective of the campaigns was not achieved, the Siple VLF transmitter facilitated a study of the wave environment in the ionosphere. Standing wave patterns in the ionosphere were observed for the first time by detectors flown aboard the Nike-Tomahawk rockets; the same detectors monitored a continuous signal from the transmitter through the neutral atmosphere and into the ionosphere, providing unique data for comparison with theoretical studies of wave propagation. The measurements of penetrating electron precipitation were interpreted in terms of a model of energetic electron precipitation from the trapped radiational belts.

Sheldon, W. R.; Benbrook, J. R.; Bering, E. A.

1988-08-01

99

Rocket investigations of electron precipitation and VLF waves in the Antarctic upper atmosphere  

International Nuclear Information System (INIS)

The results of two Antarctic rocket campaigns, primarily initiated to investigate electron precipitation stimulated by signals from the Siple-Station ground-based VLF transmitter, are presented. While the primary objective of the campaigns was not achieved, the Siple VLF transmitter facilitated a study of the wave environment in the ionosphere. Standing wave patterns in the ionosphere were observed for the first time by detectors flown aboard the Nike-Tomahawk rockets; the same detectors monitored a continuous signal from the transmitter through the neutral atmosphere and into the ionosphere, providing unique data for comparison with theoretical studies of wave propagation. The measurements of penetrating electron precipitation were interpreted in terms of a model of energetic electron precipitation from the trapped radiational belts. 52 references.

1988-01-01

100

Rocket investigations of electron precipitation and VLF waves in the Antarctic upper atmosphere  

Energy Technology Data Exchange (ETDEWEB)

The results of two Antarctic rocket campaigns, primarily initiated to investigate electron precipitation stimulated by signals from the Siple-Station ground-based VLF transmitter, are presented. While the primary objective of the campaigns was not achieved, the Siple VLF transmitter facilitated a study of the wave environment in the ionosphere. Standing wave patterns in the ionosphere were observed for the first time by detectors flown aboard the Nike-Tomahawk rockets; the same detectors monitored a continuous signal from the transmitter through the neutral atmosphere and into the ionosphere, providing unique data for comparison with theoretical studies of wave propagation. The measurements of penetrating electron precipitation were interpreted in terms of a model of energetic electron precipitation from the trapped radiational belts. 52 references.

Sheldon, W.R.; Benbrook, J.R.; Bering, E.A.

1988-08-01

 
 
 
 
101

Impact of SPS heating on VLF, LF, and MF telecommunications systems ascertained by experimental means  

Energy Technology Data Exchange (ETDEWEB)

The results of experiments undertaken to assess the potential impact of the operation of the Satellite Power System on the D and E regions of the ionosphere, and on telecommunication systems that are dependent upon the structure of the lower ionosphere are summarized. Using the high-power high-frequency transmitter facility located at Platteville, Colorado, power densities comparable to the Satellite Power System can be delivered to the heights of 70 to 100 km above the surface of the earth. Observations of the performance of telecommunication systems that operate in the VLF, LF, and MF portions of the spectrum have been investigated during times when the ionosphere was modified with SPS comparable power density and when it was not. The results obtained indicte that the SPS, as currently configured with a peak power density of 23 mW/cm/sup 2/, will not adversely impact upon the performance of VLF, LF, and MF telecommunication systems.

Rush, C.M.; Violette, E.J.; Espeland, R.H.; Carroll, J.C.; Allen, K.C.

1980-07-01

102

Excitation of guided ELF-VLF waves through modification of the F2 ionospheric layer by high-power radio waves  

International Nuclear Information System (INIS)

The possibility of controlled excitation of ELF-VLF electromagnetic waves through modification of the F2 ionospheric layer by high-power high-frequency emission is demonstrated in a natural experiment by using the Sura midlatitude heating facility. The excited low-frequency waves can be used to explore the near-Earth space and stimulate the excitation of a magnetospheric maser.

2012-01-01

103

Optical emission line monitor with background observation and cancellation  

Energy Technology Data Exchange (ETDEWEB)

A fiber optics based optical emission line monitoring system is provided in which selected spectral emission lines, such as the sodium D-line emission in coal combustion, may be detected in the presence of interferring background or blackbody radiation with emissions much greater in intensity than that of the emission line being detected. A bifurcated fiber optic light guide is adapted at the end of one branch to view the combustion light which is guided to a first bandpass filter, adapted to the common trunk end of the fiber. A portion of the light is reflected back through the common trunk portion of the fiber to a second bandpass filter adapted to the end of the other branch of the fiber. The first filter bandpass is centered at a wavelength corresponding to the emission line to be detected with a bandwidth of about three nanometers (nm). The second filter is centered at the same wavelength but having a width of about 10 nm. First and second light detectors are located to view the light passing through the first and second filters respectively. Thus, the second detector is blind to the light corresponding to the emission line of interest detected by the first detector and the difference between the two detector outputs is uniquely indicative of the intensity of only the combustion flame emission of interest. This instrument can reduce the effects of interferring blackbody radiation by greater than 20 dB.

Goff, David R. (Star City, WV); Notestein, John E. (Morgantown, WV)

1986-01-01

104

Microwave observations of spinning dust emission in NGC6946  

CERN Multimedia

We report new cm-wave measurements at five frequencies between 15 and 18GHz of the continuum emission from the reportedly anomalous "region 4" of the nearby galaxy NGC6946. We find that the emission in this frequency range is significantly in excess of that measured at 8.5GHz, but has a spectrum from 15-18GHz consistent with optically thin free-free emission from a compact HII region. In combination with previously published data we fit four emission models containing different continuum components using the Bayesian spectrum analysis package radiospec. These fits show that, in combination with data at other frequencies, a model with a spinning dust component is slightly preferred to those that possess better-established emission mechanisms.

Scaife, Anna M M; Green, David A; Beck, Rainer; Davies, Matthew L; Franzen, Thomas M O; Grainge, Keith J B; Hobson, Michael P; Hurley-Walker, Natasha; Lasenby, Anthony N; Olamaie, Malak; Pooley, Guy G; Rodriguez-Gonzalvez, Carmen; Saunders, Richard D E; Scott, Paul F; Shimwell, Timothy W; Titterington, David J; Waldram, Elizabeth M; Zwart, Jonathan T L

2010-01-01

105

Observations on the clinical value of emission tomography. [Brain  

Energy Technology Data Exchange (ETDEWEB)

Data comparing emission computed tomography (ECT), transmission computed tomography (TCT), and radionuclide scintigraphy suggest that in many patients more accurate diagnostic information may be available from emission tomography. ECT was performed during a 4-mo period on 200 of 235 patients referred for brain scans. The data suggest that ECT has a 10% greater sensitivity than scintigraphy, and better specificity. The accuracy of ECT was comparable to that of TCT performed in this group of patients. Selected cases demonstrate areas in which ECT improved lesion detection.

Hill, T.C.; Lovett, R.D.; McNeil, B.J.

1980-07-01

106

Observation method of the Barkhausen jumps by sound emission  

International Nuclear Information System (INIS)

[en] The recording of acoustic emission, accompanying remagnetization of ferromagnetics and conditioned by the Barkhausen jumps, has been described. The use of acoustic method in combination with traditional electromagnetic method of the Barkhausen effect recording when studying the remagnetization processes permits to separate the remagnetization process at the expense of 180 deg - and 90 deg - domain shifts. Experiments on nickel and structural steel 34KhN3M have shown a linear connection between mean qUadratic values of acoustic emission signals and magnetostriction value. Using the method suggested it is possible to record the presence of magnetostriction > or approximately 0.35x10-6

1984-01-01

107

Type II Radio Emission and Solar Particle Observations  

CERN Document Server

The 28 October 2003 flare gave us the unique opportunity to compare the acceleration time of high-energy protons with the escaping time of those particles which have been measured onboard spacecraft and by neutron monitors network as GLE event. High-energy emission time scale and shock wave height and velocity time dependencies were also studied.

Kuznetsov, S N; Yushkov, B; Yu, B; Myagkova, I N; Kudela, K; Belov, A V; Caroubalos, C; Hilaris, A; Mavromichalaki, H; Moussas, X; Preka-Papadema, P; 10.1142/S0217751X05029873

2010-01-01

108

Mg{sup +} and other metallic emissions observed in the thermosphere  

Energy Technology Data Exchange (ETDEWEB)

Limb observations of UV dayglow emissions from 80 to 300 km tangent heights were made in December, 1992, using the GLO instrument, which flew on STS-53 as a Hitchhiker-G experiment. STS-53 was at 330 km altitude and had an orbit inclination of 57{degree}. The orbit placed the shuttle near the terminator for the entire mission, resulting in a unique set of observations. The GLO instrument consisted of 12 imagers and 9 spectrographs on an Az/El gimbal system. The data was obtained over 6 days of the mission. Emissions from Mg{sup +} and Ca{sup +} were observed, as were emissions from the neutral metallic species Mg and Na. The ultimate source of the metals is ablation of meteors; however, the spatial distribution of the emissions is controlled by upper mesospheric and thermospheric winds and, in the case of the ions, by the electromagnetic fields of the ionosphere. The observed Mg{sup +} emission was the brightest of the metal emissions, and was observed near the poles and around the geomagnetic equator near sunset. The polar emissions were short-lived and intense, indicative of auroral activity. The equatorial emissions were more continuous, with several luminous patches propagating poleward over the period of several orbits. The instrumentation will be described, as will spatial and temporal variations of the metal emissions with emphasis on the metal ions. These observations will be compared to previous observations of thermospheric metallic species.

Gardner, J.A. [PhotoMetrics, Inc., Woburn, MA (United States); Viereck, R.A.; Murad, E.; Lai, S.T.; Knecht, D.J.; Pike, C.P. [USAF Phillips Lab., Hanscom AFB, MA (United States). Spacecraft Interactions Branch; Broadfoot, A.L.; Anderson, E.R. [Univ. of Arizona, Tucson, AZ (United States). Lunar and Planetary Observatory; McNeil, W.J. [Radex, Inc., Bedford, MA (United States)

1994-12-31

109

Satellite observations indicate substantial spatiotemporal variability in biomass burning NOx emission factors for South America  

Directory of Open Access Journals (Sweden)

Full Text Available Biomass burning is an important contributor to global total emissions of NOx (NO + NO2). Generally bottom-up fire emissions models calculate NOx emissions by multiplying fuel consumption estimates with static biome specific emission factors, defined in units of grams of NO per kilogram of dry matter consumed. Emission factors are a significant source of uncertainty in bottom-up fire emissions modeling because relatively few observations are available to characterize the large spatial and temporal variability of burning conditions. In this paper we use NO2 tropospheric column observations from the Ozone Monitoring Instrument (OMI) from the year 2005 over South America to calculate monthly NOx emission factors for four fire types: deforestation, savanna/grassland, woodland, and agricultural waste burning. In general, the spatial trends in NOx emission factors calculated in this work are consistent with emission factors derived from in situ measurements from the region, but are more variable than published biome specific global average emission factors widely used in bottom up fire emissions inventories such as the Global Fire Emissions Database (GFED) v3. Satellite based NOx emission factors also indicate substantial temporal variability in burning conditions. Overall, we found that deforestation fires have the lowest NOx emission factors, on average 30 % lower than the emission factors used in GFED v3. Agricultural fire NOx emission factors were the highest, on average a factor of 2 higher than GFED v3 values. For savanna, woodland, and deforestation fires early dry season NOx emission factors were a factor of ~1.5–2.0 higher than late dry season emission factors. A minimum in the NOx emission factor seasonal cycle for deforestation fires occurred in August, the time period of severe drought in South America in 2005. Our results support the hypothesis that prolonged dry spells may lead to an increase in the contribution of smoldering combustion from large diameter fuels to total fire emissions, which would lower the overall modified combustion efficiency (MCE) and NOx emission factor, and offset the higher combustion efficiency of dryer fine fuels. We evaluated the OMI derived NOx emission factors with SCIAMACHY NO2 tropospheric column observations and found improved model performance in regions dominated by fire emissions.

P. Castellanos; K. F. Boersma; G. R. van der Werf

2013-01-01

110

Optical emission line monitor with background observation and cancellation  

Energy Technology Data Exchange (ETDEWEB)

An optical emission line monitoring system is described for remotely detecting a selected emission line from a light source in the presence of interferring background radiation, comprising: a bifurcated fiber optic cable having first and second branches and a common trunk and adapted at the end of the first branch to optically couple light from the light source to the cable; a first bandpass optical filter having a bandpass centered about and corresponding in width to the selected emission line and disposed to intercept light passing from the end of the common trunk end of the cable and reflect light outside of the bandpass of the first filter back into the common trunk end of the cable; and second bandpass optical filter having a bandpass centered about a wavelength identical to the first filter and a bandwidth substantially wider than the bandwidth of the first filter, the second filter disposed at the end of the second branch of the cable to view a portion of the light reflected back into the common trunk of the cable.

Goff, D.R.; Notestein, J.E.

1986-10-07

111

Observations that can unravel the coherent radio emission mechanism in pulsars  

CERN Document Server

Searching for the physical mechanism that can excite the coherent radio emission in pulsars is still an enigmatic problem. A wealth of high quality observations exist, which over the years have been instrumental in putting stringent constraints to pulsar emission models. In this article we will discuss the observational results that strongly suggests that pulsar radio emission is excited by coherent curvature radiation. We will also mention issues that remain to be resolved.

Mitra, Dipanjan

2013-01-01

112

A dynamic bandwidth and phase linearity measurement technique for 4-channel MSK VLF antenna systems  

Science.gov (United States)

This paper presents a method for performing dynamic measurements of antenna bandwidth and phase linearity parameters for VLF transmitter systems. These measurements were undertaken in support of both National and NATO VLF MSK upgrade programs and relate to VLF transmitting antenna characteristics required in order to comply with STANAG 5030.

Harrington, M. D.

1993-05-01

113

Observation of increases in emission from modern vehicles over time in Hong Kong using remote sensing  

International Nuclear Information System (INIS)

In this study on-road gaseous emissions of vehicles are investigated using remote sensing measurements collected over three different periods. The results show that a high percentage of gaseous pollutants were emitted from a small percentage of vehicles. Liquified Petroleum Gas (LPG) vehicles generally have higher gaseous emissions compared to other vehicles, particularly among higher-emitting vehicles. Vehicles with high vehicle specific power (VSP) tend to have lower CO and HC emissions while petrol and LPG vehicles tend to have higher NO emissions when engine load is high. It can be observed that gaseous emission factors of petrol and LPG vehicles increase greatly within 2 years of being introduced to the vehicle fleet, suggesting that engine and catalyst performance deteriorate rapidly. It can be observed that LPG vehicles have higher levels of gaseous emissions than petrol vehicles, suggesting that proper maintenance of LPG vehicles is essential in reducing gaseous emissions from vehicles. - Highlights: ? Emissions collected in 3 different periods to examine changes in emission over time. ? LPG vehicles generally emit more gaseous pollutants compared to other vehicles. ? Large increase in emissions from modern petrol/LPG vehicles after 2 years' operation. ? CO and NO emissions of modern diesel vehicles are similar to those of older vehicles. - Remote sensing measurements show large increases in gaseous emissions from vehicles in Hong Kong after 2 years of operation, indicating that engine and catalyst performance deteriorate rapidly.

2012-01-01

114

A method for determining intracloud lightning and ionospheric heights from VLF/LF electric field records  

Science.gov (United States)

The Los Alamos Sferic Array (LASA) recorded VLF/LF electric-field-change signals from over ten million lightning discharges during the period from 1998 to 2001. Using the differential-times-of-arrival of lightning sferics recorded by three or more stations, the latitudes and longitudes of the source discharges were determined. Under conditions of favorable geometry and ionospheric propagation, sensors obtained ionospherically reflected skywave signals from the lightning discharges in addition to the standard groundwave sferics. In approximately 1% of all waveforms, automated processing identified two 1-hop skywave reflection paths with delays indicative of an intracloud (height greater than 5 km) lightning source origin. For these events it was possible to determine both the height of the source above ground and the virtual reflection height of the ionosphere. Ionosphere heights agreed well with published values of 60 to 95 km with an expected diurnal variation. Source height determinations for 100,000+ intracloud lightning events ranged from 7 to 20 km AGL with negative-polarity events occurring above ˜15 km and positive-polarity events occurring below ˜15 km. The negative-polarity events are at a suprisingly high altitude and may be associated with discharges between the upper charge layer of a storm and a screening layer of charge above the storm. Approximately 100 of the intracloud events with LASA height determinations were also recorded by VHF receivers on the FORTE satellite. Independent FORTE source height estimates based on delays between direct and ground-reflected radio emissions showed excellent correlation with the VLF/LF estimates, but with a +1 km bias for the VLF/LF height determinations.

Smith, D. A.; Heavner, M. J.; Jacobson, A. R.; Shao, X. M.; Massey, R. S.; Sheldon, R. J.; Wiens, K. C.

2004-02-01

115

Observations of twilight helium 10830 A emission with an tilting filter photometer  

International Nuclear Information System (INIS)

A tilting filter photometer was used to observe the helium 10830 A emission in twilight. The observed intensities of the helium emission show the seasonal variation. The enhancement occurs in winter. It agrees with the previous observation of Christensen et al. It was observed also that the solar zenith angle dependencies of the intensity variations differ in the evening and morning twilights. It can be explained by the asymmetry of the exospheric temperature in evening and morning qualitatively. (author).

1979-11-14

116

Laser excitation of clusters: observables from electron emission  

International Nuclear Information System (INIS)

We give a brief review of the theoretical description of photo-electron spectra (PES) and photo-angular distributions (PAD) and discuss a few selected, typical results. The description is based on time-dependent density-functional theory at the level of the local-density approximation augmented by a self-interaction correction which is crucial for a quantitative assessment of emission processes. Coordinate-space grids are used together with absorbing boundary conditions. We discuss the basic features and trends of PES and PAD for two typical test cases, the clusters Na8 and C60.

2012-11-26

117

Observations at 843 MHz of quiescent emission from the flare star AT Mic  

International Nuclear Information System (INIS)

The Molonglo Observatory Synthesis Telescope was used in 1983 and on four occasions in 1985 to map the 843-MHz continuum emission from a field including the flare star AT Mic. Quiescent emission, apparently from the star, was detected. The flux density varied from one observation to another, in the range 3 to 8 mJy at 843 MHz. These observations are thought to be the first reported of quiescent emission from a flare star at such a low frequency. The emission mechanism is not known. (author).

1986-01-01

118

Observations at 843 MHz of quiescent emission from the flare star AT Mic  

Energy Technology Data Exchange (ETDEWEB)

The Molonglo Observatory Synthesis Telescope was used in 1983 and on four occasions in 1985 to map the 843-MHz continuum emission from a field including the flare star AT Mic. Quiescent emission, apparently from the star, was detected. The flux density varied from one observation to another, in the range 3 to 8 mJy at 843 MHz. These observations are thought to be the first reported of quiescent emission from a flare star at such a low frequency. The emission mechanism is not known.

Vaughan, A.E.; Large, M.I.

1986-11-15

119

Regional nitrogen oxides emission trends in East Asia observed from space  

Directory of Open Access Journals (Sweden)

Full Text Available Due to changing economic activity, emissions of air pollutants in East Asia change rapidly in space and time. Monthly emission estimates of nitrogen oxides derived from satellite observations provide valuable insight in the evolution of anthropogenic activity on a regional scale. We present the first results of a new emission estimation algorithm, specifically designed to use daily satellite observations of column concentrations for fast updates of emissions of short-lived atmospheric constituents on a~mesoscopic scale (~ 0.25° × 0.25°). The algorithm is used to construct a monthly NOx emission time series for 2007–2011 from tropospheric NO2 observations of GOME-2 for East Chinese provinces and surrounding countries. The new emission estimates correspond well with the bottom-up inventory of EDGAR v4.2, but are smaller than the inventories of INTEX-B and MEIC. They reveal a strong positive trend during 2007–2011 for almost all Chinese provinces, related to the country's economic development. We find a 41% increment of NOx emissions in East China during this period, which shows the need to update emission inventories in this region on a regular basis. Negative emission trends are found in Japan and South Korea, which can be attributed to a combined effect of local environmental policy and global economic crises. Analysis of seasonal variation distinguishes between regions with dominant anthropogenic or biogenic emissions. For regions with a mixed anthropogenic and biogenic signature, the opposite seasonality can be used for an estimation of the separate emission contributions. Finally, the non-local concentration/emission relationships calculated by the algorithm are used to quantify the direct effect of regional NOx emissions on tropospheric NO2 concentrations outside the region. For regions such as North Korea and Beijing province, a substantial part of the tropospheric NO2 originates from emissions elsewhere.

B. Mijling; R. J. van der A; Q. Zhang

2013-01-01

120

Sawtooth-like X-ray emission observed in EBIT  

International Nuclear Information System (INIS)

The evolution of a mixture of highly charged Ar and Ba ions was measured in an electron beam ion trap (EBIT) by recording the characteristic X-ray emission from trapped ions. A special feature in the spectra are sawtooth-like intensity variations caused by a periodic collapse of the ion inventory in the trap. The effect requires favorable conditions to become present and is very sensitive to the trapping conditions. Analysis of the measurements is based on a time-dependent calculation of the trapping process. Simulations show that sawtooth activity results from the feedback between the low-Z Ar and high-Z Ba ions (Hopf bifurcation). Sawtooth spectra open up a spectroscopic method to test theoretical EBIT models and probe the dynamics in ion traps and sources.

2003-01-01

 
 
 
 
121

First observation of proton emission from 117La  

International Nuclear Information System (INIS)

We report the first measurement, at the XTU Tandem+LINAC accelerator of the Laboratori Nazionali di Legnaro, of the decay of the very neutron deficient nucleus 117La using a 310 MeV 58Ni beam on a 64Zn target; the 117La nucleus was populated via the (p, 4n) evaporation channel. The Recoil Mass Spectrometer (RMS) was used to select M/q=117/30 recoils that were implanted in a (40x40) mm2 Double Sided Silicon Strip Detector (DSSD) detector. The analysis has revealed that 117La decays to 116Ba via proton emission with Ep=(783±6)keV and T1/2=(20±5) ms. From this result deformation parameters of ?2=0.3 and ?4=0.1 have been deduced for the 117La ground state which was assigned to J?=3/2+.

2000-05-25

122

First Observation of Proton Emission from 117La  

International Nuclear Information System (INIS)

We report the first measurement, at the XTU Tandem + LINAC accelerator of the Laboratori Nazionali di Legnaro, of the decay of the very neutron deficient nucleus 117La using a 310 MeV 58Ni beam on a 64Zn target; the 117La nucleus was populated via the (p,4n) evaporation channel. The Recoil Mass Spectrometer (RMS) was used to select M/q = 117/30 recoils that were implanted in a (40x40) mm2 Double Sided Silicon Strip Detector (DSSD) detector. The analysis has revealed that 117La decays to 116Ba via proton emission with Ep = (783±6)keV and T1/2 = (20±5) ms. From this result deformation parameters of ?2 = 0.3 and ?4 = 0.1 have been deduced for the 117La ground state which was assigned to J? 3/2+.

2000-01-01

123

VLF emergency warning system for underground mines  

Energy Technology Data Exchange (ETDEWEB)

An underground mine fire can seriously threaten the lives of all personnel in the mine. This fact makes fire emergency planning a high priority in the mining industry. The optimum warning alarm must be fast and able to reach all miners, regardless of their location or work activity. Current means of fire warning are varied, and include such methods as stench, telephones, and word-of-mouth (messengers). Unfortunately, none of these methods are entirely satisfactory. A novel fire warning alarm which enables instantaneous warning of all underground personnel, the Canary Mine Messenger System, has been developed by VLF Magnetic Systems Inc. in conjunction with Noranda Technology Centre and the U.S. Department of the Interior - Bureau of Mines. The warning is sent by an electromagnetic signal which penetrates through mine rock to receivers housed in the battery packs which also power each miner`s cap lamp. A loud buzzer in the integrated battery/receiver unit and the flashing of the cap lamp alerts miners to incoming messages. Testing of prototype equipment has demonstrated that the transmitted signal is capable of penetrating through over a mile of mine rock and activating the receiver. This report describes the theoretical basis for through-the-rock ultra-low frequency electromagnetic transmission, and the design of recently available transmitter and receivers.

Vanderlaag, J.H.; McDougall, J.S. [VLF Magnetic Systems Inc., Woodbridge, Ontario (Canada)

1995-12-31

124

Can a Long Nanoflare Storm Explain the Observed Emission Measure Distributions in Active Region Cores?  

CERN Multimedia

All theories that attempt to explain the heating of the high temperature plasma observed in the solar corona are based on short bursts of energy. The intensities and velocities measured in the cores of quiescent active regions, however, can be steady over many hours of observation. One heating scenario that has been proposed to reconcile such observations with impulsive heating models is the "long nanoflare storm," where short duration heating events occur infrequently on many sub-resolutions strands; the emission of the strands is then averaged together to explain the observed steady structures. In this Letter, we examine the emission measure distribution predicted for such a long nanoflare storm by modeling an arcade of strands in an active region core. Comparisons of the computed emission measure distributions with recent observations indicate that that the long nanoflare storm scenario implies greater than 5 times more 1 MK emission than is actually observed for all plausible combinations of loop lengths,...

Mulu-Moore, Fana M; Warren, Harry P

2012-01-01

125

On the numerical modelling of VLF chorus dynamical spectra  

Directory of Open Access Journals (Sweden)

Full Text Available This paper presents a study of the use of a one-dimensional Vlasov Hybrid Simulation (VHS) computer code to simulate the dynamical spectra (i.e. frequency versus time spectrograms) of ELF/VLF chorus signals (from ~a fraction to ~10 kHz). Recently excellent measurements of chorus have been made in the source region close to the geomagnetic equator aboard the four spacecraft Cluster mission. Using Cluster data for wave amplitude, which is up to 300 pT, local gyrofrequency, cold plasma density, and L-shell, observed chorus signals are reproduced with remarkable fidelity and, in particular, sweep rates in the range 1–10 kHz result as observed. Further, we find that the sweep rate is a falling function of increasing cold plasma density, again in accord with observations. Finally, we have satisfactorily simulated the rather rare falling frequency elements of chorus which are sometimes observed aboard Cluster in the generation region. For both rising and falling chorus we have presented detailed structural analyses of the generation regions. The main contributor to the frequency sweep rate is primarily the establishment of wave number/frequency gradients across the generation region by the out of phase component of the resonant particle current. The secondary contributor is the shortening of the wavelength of resonant particle current relative to that of the wave field. In view of the close agreement between observation and simulation, we conclude that nonlinear electron cyclotron resonance is indeed the mechanism underlying the generation of chorus signals just outside the plasmasphere.

D. Nunn; O. Santolik; M. Rycroft; V. Trakhtengerts

2009-01-01

126

Generation mechanism of plasmaspheric ELF/VLF hiss: A statistical study from GEOS 1 data  

Energy Technology Data Exchange (ETDEWEB)

The authors report the results of a study of ELF/VLF hiss in the plasmasphere, where they looked at a set of data from the GEOS 1 satellite to do a statistical study of such events. They correlated the appearance and intensity of such whistler wave activity with electron fluxes. They observed correlations between the wave events and electron fluxes, and found in general that electron fluxes were larger than previous work had assumed. In addition the results were consistent with the origin of the hiss coming from equatorial regions, and gaining amplitude on one pass through this region.

Cornilleau-Wehrlin, N.; Solomon, J. [Centre National d`Etudes des Telecommunications, Issy-les-Moulineaux (France); Korth, A.; Kremser, G. [Max-Planck-Institut fuer Aeronomie, Katlenburg-Lindau (Germany)

1993-12-01

127

First Observation of Proton Emission from {sup 117}La  

Energy Technology Data Exchange (ETDEWEB)

We report the first measurement, at the XTU Tandem + LINAC accelerator of the Laboratori Nazionali di Legnaro, of the decay of the very neutron deficient nucleus {sup 117}La using a 310 MeV {sup 58}Ni beam on a {sup 64}Zn target; the {sup 117}La nucleus was populated via the (p,4n) evaporation channel. The Recoil Mass Spectrometer (RMS) was used to select M/q = 117/30 recoils that were implanted in a (40x40) mm{sup 2} Double Sided Silicon Strip Detector (DSSD) detector. The analysis has revealed that {sup 117}La decays to {sup 116}Ba via proton emission with E{sub p} = (783{+-}6)keV and T{sub 1/2} = (20{+-}5) ms. From this result deformation parameters of {beta}{sub 2} = 0.3 and {beta}{sub 4} = 0.1 have been deduced for the {sup 117}La ground state which was assigned to J{sup {pi}} = 3/2{sup +}.

Soramel, F.; Guglielmetti, A.; Stroe, L.; Muller, L.; Bonetti, R.; Malerba, F.; Poli, G.L.; Boiano, C.; Andrighetto, A.; Li, Z.C.; Scarlassara, F.; Signorini, C.; Dal Bello, A.; Isocrate, R.; Liu, Z.H.; Ruan, M.; Ivascu, M.; Bednarczyk, P.; Broude, C.

2000-12-31

128

ENA Emission from Low Altitude: A Survey of Medium Energy Neutral Atom (MENA) Observations from IMAGE  

Science.gov (United States)

The precipitation of ring current ions into the upper atmosphere can provide a regionally important source of energy and ionization. The interaction of these ions with the upper atmosphere produces a non-isotropic Energetic Neutral Atom (ENA) emission that can be observed remotely by ENA imaging instrumentation on a suitably located spacecraft. We have recently developed a numerical algorithm for recognizing the signature of ENA emissions from low altitude in the IMAGE/MENA summary spectrograms. We use this algorithm to gather statistics on the observation of these emissions. We will present an overview of MENA observations of ENA emissions from low altitude throughout the IMAGE mission life, focusing on the spatial distributions of these emitted ENAs around Earth and the dependence of the emission on geomagnetic activity, especially the phase of the geomagnetic storm. Finally, we are working to extend our recognition algorithm to the TWINS data set and will provide a progress report on that activity.

Mackler, D.; Jahn, J.; McComas, D.; Pollock, C.; Schaefer, D.; Valek, P.

2008-12-01

129

Observation of optical emission from beam-foil excited Li-  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We have verified by a method of charge assignment by Doppler effect that the line observed at 348.9 nm in a lithium beam excited by a carbon foil is due to Li- negative ion, in agreement with a calculation of Bunge [5].

Denis, A.; Desesquelles, J.

130

Observations of CO J = 3 ? 2 emission from molecular clouds  

International Nuclear Information System (INIS)

Extensive observations in the J = 3 ? 2 transition of carbon monoxide at 345 GHz (870 ?m) have been obtained using an indium anti-monide heterodyne spectral-line receiver with the United Kingdom 3.8-m Infrared Telescope (UKIRT) at Mauna Kea. Mapping observations of up to 1/2 deg2 areas are reported towards the sources NGC 1333, 2023, 2024 and 2068. These maps, obtained with a 55-arcsec beam, reveal a number of new molecular hotspots as well as confirming the previous detection of molecular cool-spots. High-quality spectra have been obtained towards the self-absorbed sources NGC 1333 IRS-1, NGC 2071, Mon R2, AFGL 961 and DR 21. These spectra are similar to those observed in lower CO transitions, but there is a tendency for the redshifted wing to be enhanced in the J = 3 ? 2 transition. Spectral observations are also reported for L 1551/HH-29. Analysis of the variation of gas kinetic temperature around several of the mapped sources shows close agreement with the expected grain kinetic temperature, assuming these sources to be irradiated by single central stars of a spectral class similar to that estimated from other methods. The present data support the previous model (from CO J = 1 ? 0 data) for NGC 2071 and show it to be a rotating cloud. (author)

1981-01-01

131

Study of electromagnetic emissions associated with seismic activity in Kamchatka region  

Directory of Open Access Journals (Sweden)

Full Text Available A review of data processing of electromagnetic emission observation collected at the Complex Geophysical Observatory Karimshino (Kamchatka peninsula) during the first 5 months (July–November, 2000) of its operation is given. The main goal of this study addresses the detection of the phenomena associated with Kamchatka seismic activity. The following observations have been conducted at CGO: variations of ULF/ELF magnetic field, geoelectric potentials (telluric currents), and VLF signals from navigation radio transmitters. The methods of data processing of these observations are discussed. The examples of the first experimental results are presented.

V. Gladychev; L. Baransky; A. Schekotov; E. Fedorov; O. Pokhotelov; S. Andreevsky; A. Rozhnoi; Y. Khabazin; G. Belyaev; A. Gorbatikov; E. Gordeev; V. Chebrov; V. Sinitsin; A. Lutikov; S. Yunga; G. Kosarev; V. Surkov; O. Molchanov; M. Hayakawa; S. Uyeda; T. Nagao; K. Hattori; Y. Noda

2001-01-01

132

Parity violating observables in radiative neutrino pair emission from metastable atoms  

CERN Multimedia

We report on a possibility of measuring parity violating effects in radiative neutrino pair emission from metastable atoms; asymmetric angular distribution of emitted photons from oriented atoms and emergent circular polarization. Their observation, along with the continuous photon energy spectrum which has 6 thresholds, may be interpreted as events being a combined weak and QED process, emission of $\\gamma \

Yoshimura, M; Sasao, N; Yamaguchi, T

2009-01-01

133

Observations and predictions of EUV emission from classical novae  

Energy Technology Data Exchange (ETDEWEB)

Theoretical modeling of novae in outburst predicts that they should be active emitters of radiation both in the EUV and soft X-ray wavelengths twice during the outburst. The first time is very early in the outburst when only an all sky survey can detect them. This period lasts only a few hours. They again become bright EUV and soft X-ray emitters late in the outburst when the remnant object becomes very hot and is still luminous. The predictions imply both that a nova can remain very hot for months to years and that the peak temperature at this time strongly depends upon the mass of the white dwarf. It is important to observe novae at these late times because a measurement of both the flux and temperature can provide information about the mass of the white dwarf, the tun-off time scale, and the energy budget of the outburst. We review the existing observations of novae in late stages of their outburst and present some newly obtained data for GQ Mus 1983. We then provide results of new hydrodynamic simulations of novae in outburst and compare the predictions to the observations. 43 refs., 6 figs.

Starrfield, S.; Truran, J.W.; Sparks, W.M.; Krautter, J.

1989-01-01

134

Top-down estimate of China's black carbon emissions using surface observations: Sensitivity to observation representativeness and transport model error  

Science.gov (United States)

This study examines the sensitivity of "top-down" quantification of Chinese black carbon (BC) emissions to the temporal resolution of surface observations and to the transport model error associated with the grid resolution and wet deposition. At two rural sites (Miyun in North China Plain and Chongming in Yangtze River Delta), the model-inferred emission bias based on hourly BC observations can differ by up to 41% from that based on monthly mean observations. This difference relates to the intrinsic inability of the grid-based model in simulating high pollution plumes, which often exert a larger influence on the arithmetic mean of observations at monthly time steps. Adopting the variation of BC to carbon monoxide correlation slope with precipitation as a suitable measure to evaluate the model's wet deposition, we found that wet removal of BC in the model was too weak, due in part to the model's underestimation of large precipitation events. After filtering out the observations during high pollution plumes and large precipitation events for which the transport model error should not be translated into the emission error, the inferred emission bias changed from -11% (without filtering) to -2% (with filtering) at the Miyun site, and from -22% to +1% at the Chongming site. Using surface BC observations from three more rural sites (located in Northeast, Central, and Central South China, respectively) as constraints, our top-down estimate of total BC emissions over China was 1.80 ± 0.65 Tg/yr in 2006, 0.5% lower than the bottom-up inventory of Zhang et al. (2009) but with smaller uncertainty.

Wang, Xuan; Wang, Yuxuan; Hao, Jiming; Kondo, Yutaka; Irwin, Martin; Munger, J. William; Zhao, Yongjing

2013-06-01

135

VLF/LF (very low frequency/low frequency) reflection properties of the low-latitude ionosphere. Interim technical report  

Energy Technology Data Exchange (ETDEWEB)

Low-latitude observations of VLF/LF pulse reflections from the lower ionosphere obtained at nine locations to the east and west of a transmitter in southeastern Brazil are described. The data provide a variety of information on the reflection properties of the ionosphere below about 90-km altitude. Aspects of the data are presented in quasi-dimensional formats useful for identifying ionosphere structure and variability, and detailed analyses of portions of the data provided, which characterize the effective heights of the reflection coefficients of the ionosphere at noon and midnight, over a frequency range from 15 to 65 kHz. Electron-density models of the ionosphere, derived from VLF/LF reflection data are also discussed.

Klemetti, W.I.; Kossey, P.A.; Rasmussen, J.E.; Sueli Da Silveira Macedo Moura, M.

1988-02-04

136

The observation of chemiluminescent NiO* emissions in the laboratory and in the night airglow  

Directory of Open Access Journals (Sweden)

Full Text Available The recent finding of an orange spectral feature in OSIRIS/Odin spectra of the night airglow near 87 km has raised interest in the origin of the emission. The feature was positively identified as the chemiluminescent FeO* emission where the iron is of meteoric origin. Since the meteorite source of atomic metals in the mesosphere contains both iron and nickel, with Ni being typically 6 % of Fe, it is expected that faint emissions involving Ni should also be present in the night airglow. The present study summarizes the laboratory observations of chemiluminescent NiO* emissions and includes a search for the NiO* signature in the night airglow. A very faint previously unidentified "continuum" extending longwave of 440 nm has been detected in the night airglow spectra obtained with two space-borne limb viewing instruments. Through a comparison with laboratory spectra this continuum is identified as arising from the NiO* emission. The altitude profile of the new airglow emission has also been measured. The similarity of the altitude profiles of the FeO* and NiO* emissions also suggests the emission is NiO as both can originate from reaction of the metal atoms with mesospheric ozone. The observed NiO* to FeO* ratio exhibits considerable variability; possible causes of this observed variation are briefly discussed.

W. F. J. Evans; R. L. Gattinger; A. L. Broadfoot; E. J. Llewellyn

2011-01-01

137

Estimating Aerosol Emissions by Assimilating Remote Sensing Observations into a Global Transport Model  

Directory of Open Access Journals (Sweden)

Full Text Available We present a fixed-lag ensemble Kalman smoother for estimating emissions for a global aerosol transport model from remote sensing observations. We assimilate AERONET AOT and AE as well as MODIS Terra AOT over ocean to estimate the emissions for dust, sea salt and carbon aerosol and the precursor gas SO2. For January 2009, globally dust emission decreases by 26% (to 3,244 Tg/yr), sea salt emission increases by 190% (to 9073 Tg/yr), while carbon emission increases by 45% (to 136 Tg/yr), compared with the standard emissions. Remaining errors in global emissions are estimated at 62% (dust), 18% (sea salt) and 78% (carbons), with the large errors over land mostly due to the sparseness of AERONET observations. The new emissions are verified by comparing a forecast run against independent MODIS Aqua AOT, which shows significant improvement over both ocean and land. This paper confirms the usefulness of remote sensing observations for improving global aerosol modelling.

Nick Schutgens; Makiko Nakata; Teruyuki Nakajima

2012-01-01

138

Observations of the solar radio emission with the Callisto spectrometer  

Science.gov (United States)

In the framework of the program for setting the Callisto spectrometer network into operation, the spectral measurements were carried out at the sites of spectrometer locations in India and Russia in winter 2006. The results achieved at Badary, the site where the Siberian Solar Radio Telescope (SSRT) is located, are presented. The measurements were performed using a broadband log-periodic antenna connected to the Callisto spectrometer developed at the Institute of Astronomy (Zurich). The results of these measurements should explain whether spectral studies at frequencies below 1 GHz can be performed using such antennas or new antennas should be developed. The presented results are compared with the similar results obtained in Switzerland in the frequency intervals of interest for radio astronomy. Concerning electromagnetic noise, Badary is a better site for observing the Sun in the 50-800 MHz frequency range as compared to observatories in Switzerland.

Monstein, Kh. A.; Lesovoy, S. V.; Maslov, A. I.

2009-12-01

139

Electric fields, electron precipitation, and VLF radiation during a simultaneous magnetospheric substorm and atmospheric thunderstorm  

Energy Technology Data Exchange (ETDEWEB)

A balloon payload instrumented with a double-probe electric field detector and an X ray scintillation counter was launched from Roberval, Quebec, Canada (L=4.1) at 0828 UT (0328 LT) on July 9, 1975. A magnetospheric substorm was observed locally between 0815 and 1100 UT, which produced a maximum ..delta..B of approx.500 nT at approx.0930 UT. A single-cell atmospheric thunderstorm developed northeast of Roberval beginning around 0925 UT which was most intense from approx.1000 to 1035 UT. Detailed study of the electrical properties of the thunderstorm, the X ray precipitation data, and VLF spheric data leads to three conclusions. First, the electrical coupling from the thunderstorm to the magnetosphere increases with frequency from dc to the VLF; for the observed storm the amplitude at the ionosphere of thunderstorm produced electric fields was not significant at frequencies below 0.1 Hz. Second, the atmospheric conductivity above the thunderstorm was observed to be about one-half the fair weather value prior to 1000 UT; decreased to about one-quarter the fair weather value at about 1000 UT; and remained depressed after the end of the thunderstorm. This result was contrary to that expected on the basis of previous work and is one which merits considerably more investigation. Third, the data show a high probability that half-hop whistlers initiated by sferics from the thunderstorm triggered energetic electron precipitation from the magnetosphere.

Bering, E.A.; Rosenberg, T.J.; Benbrook, J.R.; Detrick, D.; Matthews, D.L.; Rycroft, M.J.; Saunders, M.A.; Sheldon, W.R.

1980-01-01

140

Electric fields, electron precipitation, and VLF radiation during a simultaneous magnetospheric substorm and atmospheric thunderstorm  

International Nuclear Information System (INIS)

A balloon payload instrumented with a double-probe electric field detector and an X ray scintillation counter was launched from Roberval, Quebec, Canada (L=4.1) at 0828 UT (0328 LT) on July 9, 1975. A magnetospheric substorm was observed locally between 0815 and 1100 UT, which produced a maximum ?B of approx.500 nT at approx.0930 UT. A single-cell atmospheric thunderstorm developed northeast of Roberval beginning around 0925 UT which was most intense from approx.1000 to 1035 UT. Detailed study of the electrical properties of the thunderstorm, the X ray precipitation data, and VLF spheric data leads to three conclusions. First, the electrical coupling from the thunderstorm to the magnetosphere increases with frequency from dc to the VLF; for the observed storm the amplitude at the ionosphere of thunderstorm produced electric fields was not significant at frequencies below 0.1 Hz. Second, the atmospheric conductivity above the thunderstorm was observed to be about one-half the fair weather value prior to 1000 UT; decreased to about one-quarter the fair weather value at about 1000 UT; and remained depressed after the end of the thunderstorm. This result was contrary to that expected on the basis of previous work and is one which merits considerably more investigation. Third, the data show a high probability that half-hop whistlers initiated by sferics from the thunderstorm triggered energetic electron precipitation from the magnetosphere.

1980-01-01

 
 
 
 
141

Mid-IR Observations of Uranus’ H2 Quadrupole Emission Near Equinox  

Science.gov (United States)

The dominant process causing the high thermospheric temperatures observed for the major planets remains an unsolved problem. Uranus is of particular interest for identifying this source of heating because of its extreme obliquity and weak internal heat source, which permit large seasonal extremes driven by radiative and dynamical processes. Sources of thermospheric heating may be investigated indirectly through the energy balance of the offsetting line emission, which radiates the generated heat to space. The cooling rate can be characterized by observing the line emission vs. position over the planet. The primary coolant in Uranus’ thermosphere is emission in the rotational H2 quadrupole lines. We report observations of Uranus’ rotational H2 quadrupole line emission obtained near the 2007 equinox using TEXES at Gemini in late October, 2007. Good data were obtained for the H2 S(1) line, which was scanned longitudinally across Uranus’ disk to make an emission map showing all latitudes. This map shows bimodal emission along Uranus’ central meridian with the brightest peak in the northern (end of winter) hemisphere. Intermittent clouds interfered with the observation of the relatively faint S(2) line, which precluded scanning, thus leaving the observations vulnerable to pointing uncertainties. We combine these data with non-equinox observations of Uranus obtained with TEXES at the IRTF to estimate the positional variation of Uranus’ thermospheric cooling rate, ultimately to help constrain the unknown dominant source of heating.

Trafton, Laurence M.; Orton, G. S.; Greathouse, T. K.; Lacy, J. H.; Encrenaz, T.

2012-10-01

142

Simultaneous NIR/sub-mm observation of flare emission from SgrA*  

CERN Document Server

We report on a successful, simultaneous observation and modeling of the sub-millimeter to near-infrared flare emission of the Sgr A* counterpart associated with the super-massive black hole at the Galactic center. Our modeling is based on simultaneous observations that have been carried out on 03 June, 2008 using the NACO adaptive optics (AO) instrument at the ESO VLT and the LABOCA bolometer at the APEX telescope. Inspection and modeling of the light curves show that the sub-mm follows the NIR emission with a delay of 1.5+/-0.5 hours. We explain the flare emission delay by an adiabatic expansion of the source components.

Eckart, A; García-Marín, M; Witzel, G; Weiss, A; Baganoff, F K; Morris, M R; Bertram, T; Dovciak, M; Duschl, W J; Karas, V; König, S; Krichbaum, T P; Krips, M; Kunneriath, D; Lu, R S; Markoff, S; Mauerhan, J; Meyer, L; Moultaka, J; Muzic, K; Najarro, F; Pott, J U; Schuster, K F; Sjouwerman, L O; Straubmeier, C; Thum, C; Vogel, S N; Wiesemeyer, H; Zamaninasab, M; Zensus, J A

2008-01-01

143

Spitzer observations of the thermal emission from WASP-43b  

CERN Multimedia

WASP-43b (Hellier et al.; Gillon et al.) is one of the closest-orbiting hot Jupiters, with a semimajor axis a = 0.01526 +/- 0.00018 AU and a period of only 0.81 days. However, it orbits one of the coolest stars with a hot Jupiter (K7V, Tstar = 4520 +/- 120 K), giving the planet a modest equilibrium temperature of Teq = 1440 +/- 40 K, assuming zero Bond albedo and uniform planetary energy redistribution. This has resulted in strong signal-to-noise-ratio (S/N) observations and deep eclipses in both Warm Spitzer channels (3.6 and 4.5 microns). The eclipse depths and brightness temperatures from our jointly fit model are 0.346 +/- 0.013% and 1684 +/- 24 K at 3.6 microns and 0.382 +/- 0.015% and 1485 +/- 24 K at 4.5 microns. The eclipse timings improved the estimate of the orbital period, P, by a factor of three (P = 0.81347459 +/- 2.1x10-7 days) compared to Gillon et al. and put an upper limit on the eccentricity (e = 0.007+0.013-0.004). We use our Spitzer eclipse depths with two previously reported ground-based ...

Blecic, Jasmina; Madhusudhan, Nikku; Stevenson, Kevin B; Hardy, Ryan A; Cubillos, Patricio E; Hardin, Matthew; Nymeyer, Sarah; Anderson, David R; Hellier, Coel; Smith, Alexis M S; Cameron, Andrew Collier

2013-01-01

144

X-Ray Microbursts and VLF (Very Low Frequency) Chorus.  

Science.gov (United States)

On January 4, 1978, at 1140 UT, a Super Arcas sounding rocket was launched from Siple Station, Antarctica (L = 4.2, 76 S, 84 W) during a geomagnetically disturbed period (K sub p = 6-) with intense X-ray and VLF chorus activity. The parachuted payload obs...

J. L. Roeder J. R. Benbrook E. A. Bering W. R. Sheldon E. G. Stansberry

1985-01-01

145

Models of ionospheric VLF absorption of powerful ground based transmitters  

Science.gov (United States)

Ground based Very Low Frequency (VLF, 3-30 kHz) radio transmitters play a role in precipitation of energetic Van Allen electrons. Initial analyses of the contribution of VLF transmitters to radiation belt losses were based on early models of trans-ionospheric propagation known as the Helliwell absorption curves, but some recent studies have found that the model overestimates (by 20-100 dB) the VLF energy reaching the magnetosphere. It was subsequently suggested that conversion of wave energy into electrostatic modes may be responsible for the error. We utilize a newly available extensive record of VLF transmitter energy reaching the magnetosphere, taken from the DEMETER satellite, and perform a direct comparison with a sophisticated full wave model of trans-ionospheric propagation. Although the model does not include the effect of ionospheric irregularities, it correctly predicts the average total power injected into the magnetosphere within several dB. The results, particularly at nighttime, appear to be robust against the variability of the ionospheric electron density. We conclude that the global effect of irregularity scattering on whistler mode conversion to quasi-electrostatic may be no larger than 6 dB.

Cohen, M. B.; Lehtinen, N. G.; Inan, U. S.

2012-12-01

146

Submillimeter Array Observations of CS J=14--13 Emission from the Evolved Star IRC+10216  

CERN Document Server

We present imaging observations of the evolved star IRC+10216 in the CS J=14--13 line at 685.4 GHz and associated submillimeter continuum at about 2'' resolution made with the partially constructed Submillimeter Array. The CS J=14--13 line emission from the stellar envelope is well resolved both spatially and spectrally. The strong central concentration of the line emission provides direct evidence that CS is a parent molecule that forms close to the stellar photosphere, in accord with previous images of the lower excitation CS J=2--1 line and inferences from unresolved observations of vibrationally excited transitions. The continuum emission is dominated by a compact, unresolved component, consistent with the photospheric emission, that accounts for about 20% of the broadband 450 micron flux. These are the first interferometer imaging observations made in the semi-transparent 450 micron atmospheric window.

Young, K H; Wilner, D J; Gurwell, M A

2004-01-01

147

Excitation of guided ELF-VLF waves through modification of the F{sub 2} ionospheric layer by high-power radio waves  

Energy Technology Data Exchange (ETDEWEB)

The possibility of controlled excitation of ELF-VLF electromagnetic waves through modification of the F{sub 2} ionospheric layer by high-power high-frequency emission is demonstrated in a natural experiment by using the Sura midlatitude heating facility. The excited low-frequency waves can be used to explore the near-Earth space and stimulate the excitation of a magnetospheric maser.

Markov, G. A.; Belov, A. S.; Komrakov, G. P. [Lobachevsky State University (Russian Federation); Parrot, M. [Environmental Physics and Chemistry Laboratory (France)

2012-03-15

148

VSA Observations of the Anomalous Microwave Emission in the Perseus Region  

CERN Multimedia

The dust feature G159.6--18.5 in the Perseus region has previously been observed with the COSMOSOMAS experiment \\citep{Watson:05} on angular scales of $\\approx$ 1$^{\\circ}$, and was found to exhibit anomalous microwave emission. We present new observations of this dust feature, performed with the Very Small Array (VSA) at 33 GHz, to help increase the understanding of the nature of this anomalous emission. On the angular scales observed with the VSA ($\\approx$ 10 -- 40$^{\\prime}$), G159.6--18.5 consists of five distinct components, each of which have been individually analysed. All five of these components are found to exhibit an excess of emission at 33 GHz, and are found to be highly correlated with far-infrared emission. We provide evidence that each of these compact components have anomalous emission that is consistent with electric dipole emission from very small, rapidly rotating dust grains. These components contribute $\\approx$ 10 % to the flux density of the diffuse extended emission detected by COSMO...

Tibbs, Christopher T; Dickinson, Clive; Davies, Rodney D; Davis, Richard J; del Burgo, Carlos; Franzen, Thomas M O; Génova-Santos, Ricardo; Grainge, Keith; Hobson, Michael P; Padilla-Torres, Carmen P; Rebolo, Rafael; Rubiño-Martín, Jóse Alberto; Saunders, Richard D E; Scaife, Anna M M; Scott, Paul F

2009-01-01

149

Geomagnetic indices for prediction of ionospheric irregularities producing VLF scintillations  

International Nuclear Information System (INIS)

Complete text of publication follows. Great diversity of the ionospheric phenomena leads to a variety of irregularity types with spatial size from many thousands of kilometers to few centimeters and lifetimes from days to fractions of second. Since the ionosphere strongly influences the propagation of radio waves, signal distortions caused by these irregularities affect short-wave transmissions on Earth, transionospheric satellite communications and navigation. In this work the solar wind and the equatorial ionosphere parameters, Kp, Dst, AU, AL indices characterized contribution of different magnetospheric and ionospheric currents to the H-component of geomagnetic field are examined to test the space weather effect on the generation of ionospheric irregularities producing VLF scintillations. According to the results of the current statistical studies, one can predict scintillations from Aarons' criteria using the Dst index, which mainly depicts the magnetospheric ring current field. To amplify Aarons' criteria or to propose new criteria for predicting scintillation characteristics is the question. In the present phase of the experimental investigations of electron density irregularities in the ionosphere new ways are opened up because observations in the interaction between the solar wind - magnetosphere ionosphere during magnetic storms have progressed greatly. We have examined scintillation relation to magnetospheric and ionospheric currents and show that the factor, which presents during magnetic storms to fully inhibit scintillation, is the positive Bz-component of the IMF. During the positive Bz IMF F layer cannot raise altitude where scintillations are formed. The auroral indices and Kp do better for the prediction of the ionospheric scintillations at the equator. The interplanetary magnetic field data and models can be used to explain the relationship between the equatorial ionospheric parameters, h'F, foF2, and the equatorial geomagnetic variations with the polar ionosphere currents and the solar wind. Taking into account the time delay between the solar wind and the ionosphere phenomena, the relationship between the solar wind, geomagnetic indices and the ionosphere parameters can be used for predicting of scintillations.

2009-01-01

150

Relative changes in CO emissions over megacities based on observations from space  

Science.gov (United States)

Urban areas are large sources of several air pollutants, with carbon monoxide (CO) among the largest. Yet measurement from space of their CO emissions remains elusive due to its long lifetime. Here we introduce a new method of estimating relative changes in CO emissions over megacities. A new multichannel Measurements of Pollution in the Troposphere (MOPITT) CO data product, offering improved sensitivity to the boundary layer, is used to estimate this relative change over eight megacities: Moscow, Paris, Mexico, Tehran, Baghdad, Los Angeles, Sao Paulo, and Delhi. By combining MOPITT observations with wind information from a meteorological reanalysis, changes in the CO upwind-downwind difference are used as a proxy for changes in emissions. Most locations show a clear reduction in CO emission between 2000-2003 and 2004-2008, reaching -43% over Tehran and -47% over Baghdad. There is a contrasted agreement between these results and the MACCity and Emission Database for Global Atmospheric Research v4.2 inventories.

Pommier, Matthieu; McLinden, Chris A.; Deeter, Merritt

2013-07-01

151

Methane emissions estimated from atmospheric observations of methane and its carbon isotopes: MOZART - 2 modeling study  

Science.gov (United States)

Methane is an important contributor to global warming with atmospheric concentrations nearly three times higher than the pre-industrial levels. Successful verifications of emission reductions from countries around the world depend on accurate modeling of atmospheric methane. Global model simulations of tropospheric methane, using the Model for Ozone and Related Chemical Tracers (MOZART-2), are presented. The magnitude of methane sources in the model is determined based on the a priori estimates of the source strengths, and the observed spatial distribution of atmospheric methane and its carbon isotopes. The results call for increased global emissions relative to the bottom-up source estimates. The significant increase in emissions in the Southern Hemisphere is required to match the observations. The proposed new set of methane emissions for MOZART-2 is consistent with the long-term global measurements of CH4 and 13C/12C.

Biberic, A.; Khalil, A.; Butenhoff, C.

2008-12-01

152

Observations of the microwave emission of Venus from 1.3 to 3.6 cm  

International Nuclear Information System (INIS)

An account is given of the methodology as well as the results of coordinated Venus emission observations conducted at four wavelengths between 1.35 and 3.6 cm; the results are compared with other observations and with calculated mission spectra, with a view to suggestions that the microwave spectrum of Venus could be sensitive to the subcloud abundance of such constituents as SO2 and gaseous H2SO4. The observed emission spectrum is consistent with an average subcloud abundance of gaseous H2SO4 in equatorial and midlatitude regions of about 5 ppm. An upper limit is established for the subcloud SO2 abundance. 19 refs.

1990-01-01

153

Observations of the microwave emission of Venus from 1. 3 to 3. 6 cm  

Energy Technology Data Exchange (ETDEWEB)

An account is given of the methodology as well as the results of coordinated Venus emission observations conducted at four wavelengths between 1.35 and 3.6 cm; the results are compared with other observations and with calculated mission spectra, with a view to suggestions that the microwave spectrum of Venus could be sensitive to the subcloud abundance of such constituents as SO2 and gaseous H2SO4. The observed emission spectrum is consistent with an average subcloud abundance of gaseous H2SO4 in equatorial and midlatitude regions of about 5 ppm. An upper limit is established for the subcloud SO2 abundance. 19 refs.

Steffes, P.G.; Jenkins, J.M.; Klein, M.J. (Georgia Institute of Technology, Atlanta (USA) JPL, Pasadena, CA (USA))

1990-03-01

154

Coordinated NIR/mm observations of flare emission from Sagittarius A*  

CERN Document Server

We report on a successful, simultaneous observation and modelling of the millimeter (mm) to near-infrared (NIR) flare emission of the Sgr A* counterpart associated with the supermassive black hole at the Galactic centre (GC). We present a mm/sub-mm light curve of Sgr A* with one of the highest quality continuous time coverages and study and model the physical processes giving rise to the variable emission of Sgr A*.

Kunneriath, D; Eckart, A; Zamaninasab, M; übel, R Gie\\ss; Schödel, R; Baganoff, F K; Morris, M R; Dov?iak, M; Duschl, W J; García-Marín, M; Karas, V; König, S; Krichbaum, T P; Krips, M; Lu, R -S; Mauerhan, J; Moultaka, J; Muži?, K; Sabha, N; Najarro, F; Pott, J -U; Schuster, K F; Sjouwerman, L O; Straubmeier, C; Thum, C; Vogel, S N; Teuben, P; Weiss, A; Wiesemeyer, H; Zensus, J A; 10.1051/0004-6361/200913613

2010-01-01

155

Tropospheric methanol observations from space: retrieval evaluation and constraints on the seasonality of biogenic emissions  

Directory of Open Access Journals (Sweden)

Full Text Available Methanol retrievals from nadir-viewing space-based sensors offer powerful new information for quantifying methanol emissions on a global scale. Here we apply an ensemble of aircraft observations over North America to evaluate new methanol measurements from the Tropospheric Emission Spectrometer (TES) on the Aura satellite, and combine the TES data with observations from the Infrared Atmospheric Sounding Interferometer (IASI) on the MetOp-A satellite to investigate the seasonality of methanol emissions from northern midlatitude ecosystems. Using the GEOS-Chem chemical transport model as an intercomparison platform, we find that the TES retrieval performs well when the degrees of freedom for signal (DOFS) are above 0.5, in which case the model:TES regressions are generally consistent with the model:aircraft comparisons. Including retrievals with DOFS below 0.5 degrades the comparisons, as these are excessively influenced by the a priori. The comparisons suggest DOFS >0.5 as a minimum threshold for interpreting retrievals of trace gases with a weak tropospheric signal. We analyze one full year of satellite observations and find that GEOS-Chem, driven with MEGANv2.1 biogenic emissions, underestimates observed methanol concentrations throughout the midlatitudes in springtime, with the timing of the seasonal peak in model emissions 1–2 months too late. We attribute this discrepancy to an underestimate of emissions from new leaves in MEGAN, and apply the satellite data to better quantify the seasonal change in methanol emissions for midlatitude ecosystems. The derived parameters (relative emission factors of 11.0, 0.26, 0.12 and 3.0 for new, growing, mature, and old leaves, respectively, plus a leaf area index activity factor of 0.5 for expanding canopies with leaf area index <1.2) provide a more realistic simulation of seasonal methanol concentrations in midlatitudes on the basis of both the IASI and TES measurements.

K. C. Wells; D. B. Millet; L. Hu; K. E. Cady-Pereira; Y. Xiao; M. W. Shephard; C. L. Clerbaux; L. Clarisse; P.-F. Coheur; E. C. Apel; J. de Gouw; C. Warneke; H. B. Singh; A. H. Goldstein; B. C. Sive

2012-01-01

156

Tropospheric methanol observations from space: retrieval evaluation and constraints on the seasonality of biogenic emissions  

Directory of Open Access Journals (Sweden)

Full Text Available Methanol retrievals from nadir-viewing space-based sensors offer powerful new information for quantifying methanol emissions on a global scale. Here we apply an ensemble of aircraft observations over North America to evaluate new methanol measurements from the Tropospheric Emission Spectrometer (TES) on the Aura satellite, and combine the TES data with observations from the Infrared Atmospheric Sounding Interferometer (IASI) on the MetOp-A satellite to investigate the seasonality of methanol emissions from northern midlatitude ecosystems. Using the GEOS-Chem chemical transport model as an intercomparison platform, we find that the TES retrieval performs well when the degrees of freedom for signal (DOFS) are above 0.5, in which case the model : TES regressions are generally consistent with the model : aircraft comparisons. Including retrievals with DOFS below 0.5 degrades the comparisons, as these are excessively influenced by the a priori. The comparisons suggest DOFS > 0.5 as a minimum threshold for interpreting retrievals of trace gases with a weak tropospheric signal. We analyze one full year of satellite observations and find that GEOS-Chem, driven with MEGANv2.1 biogenic emissions, underestimates observed methanol concentrations throughout the midlatitudes in springtime, with the timing of the seasonal peak in model emissions 1–2 months too late. We attribute this discrepancy to an underestimate of emissions from new leaves in MEGAN, and apply the satellite data to better quantify the seasonal change in methanol emissions for midlatitude ecosystems. The derived parameters (relative emission factors of 11.0, 1.0, 0.05 and 8.6 for new, growing, mature, and old leaves, respectively, plus a leaf area index activity factor of 0.75 for expanding canopies with leaf area index < 2.0) provide a more realistic simulation of seasonal methanol concentrations in midlatitudes on the basis of IASI, TES, and ground-based measurements.

K. C. Wells; D. B. Millet; L. Hu; K. E. Cady-Pereira; Y. Xiao; M. W. Shephard; C. L. Clerbaux; L. Clarisse; P.-F. Coheur; E. C. Apel; J. de Gouw; C. Warneke; H. B. Singh; A. H. Goldstein; B. C. Sive

2012-01-01

157

Observations of the 10 micrometer natural laser emission from the mesospheres of Mars and Venus  

International Nuclear Information System (INIS)

[en] Observations of the total flux and center to limb dependence of the nonthermal emission occurring in the cores of the 9.4 and 10.4 micrometers CO2 bands on Mars are compared to a theoretical model based on this mechanism. The model successfully reproduces the observed center to limb dependence of this emission, to within the limits imposed by the spatial resolution of the observations of Mars and Venus. The observed flux from Mars agrees closely with the prediction of the model the flux observed from Venus is 74% of the flux predicted by the model. This emission is used to obtain the kinetic temperatures of the Martian and Venusian mesospheres. For Mars near 70 km altitude, a rotational temperature analysis using five lines gives T 135 + or - 20 K. The frequency width of the emission is also analyzed to derive a temperature of 126 + or - 6 K. In the case of the Venusian mesosphere near 109 km, the frequency width of the emission gives T 204 + or - 10 K

1983-01-01

158

High Spatial Resolution Observations of Thermal Emission from Enceladus' Active South Pole  

Science.gov (United States)

Cassini's four close flybys of Enceladus in 2008 are providing unprecedented views of the active "tiger stripe" fractures in the moon's south polar region. The Composite Infrared Spectrometer (CIRS) instrument is obtaining spectral maps of the endogenic thermal emission from the tiger stripes at wavelengths from 7 to 1000 microns. Here we concentrate on observations of the short-wavelength radiation made with CIRS's high spatial resolution focal planes "FP3" (9 -- 16 microns) and "FP4" (7 -- 9 microns). FP3 and FP4 observations during the March 12 2008 flyby mapped most of the active region at a spatial resolution of 4 -- 10 km, revealing large variations in emission along and between the tiger stripes. FP4 data revealed temperatures in excess of 180 K along the brightest parts of the tiger stripe fracture named Damascus Sulcus. The August 11th flyby provided some scattered observations with spatial resolution as high as 400 meters, a very high signal-to-noise spectrum of 7 -- 9 micron emission from Damascus Sulcus with 1.5 x 3.0 km resolution, and high-resolution mapping of emission along parts of Baghdad Sulcus. Lower spatial resolution observations helped to complete the mapping of the entire active south polar region, and provided constraints on the time variability of the emission on month-to-year timescales. Additional high- resolution observations are planned during the two upcoming flybys on October 9 and October 31 2008.

Spencer, J. R.; Pearl, J. C.; Howett, C. J.; Segura, M. E.; Cassini Team

2008-12-01

159

FERMI LARGE AREA TELESCOPE OBSERVATIONS OF TWO GAMMA-RAY EMISSION COMPONENTS FROM THE QUIESCENT SUN  

International Nuclear Information System (INIS)

We report the detection of high-energy ?-rays from the quiescent Sun with the Large Area Telescope on board the Fermi Gamma-Ray Space Telescope (Fermi) during the first 18 months of the mission. These observations correspond to the recent period of low solar activity when the emission induced by cosmic rays (CRs) is brightest. For the first time, the high statistical significance of the observations allows clear separation of the two components: the point-like emission from the solar disk due to CR cascades in the solar atmosphere and extended emission from the inverse Compton (IC) scattering of CR electrons on solar photons in the heliosphere. The observed integral flux (?100 MeV) from the solar disk is (4.6 ± 0.2[statistical error]+1.0-0.8[systematic error]) x 10-7 cm-2 s-1, which is ?7 times higher than predicted by the 'nominal' model of Seckel et al. In contrast, the observed integral flux (?100 MeV) of the extended emission from a region of 20 deg. radius centered on the Sun, but excluding the disk itself, (6.8 ± 0.7[stat.]+0.5-0.4[syst.]) x 10-7 cm-2 s-1, along with the observed spectrum and the angular profile, is in good agreement with the theoretical predictions for the IC emission.

2011-06-20

160

Modeling of the Very Low Frequency (VLF) radio wave signal profile due to solar flares using the GEANT4 Monte Carlo simulation coupled with ionospheric chemistry  

Directory of Open Access Journals (Sweden)

Full Text Available X-ray photons emitted during solar flares cause ionization in the lower ionosphere (~ 60 to 100 km) in excess of what is expected from a quiet sun. Very Low Frequency (VLF) radio wave signals reflected from the D region are affected by this excess ionization. In this paper, we reproduce the deviation in VLF signal strength during solar flares by numerical modeling. We use GEANT4 Monte Carlo simulation code to compute the rate of ionization due to a M-class and a X-class flare. The output of the simulation is then used in a simplified ionospheric chemistry model to calculate the time variation of electron density at different altitudes in the lower ionosphere. The resulting electron density variation profile is then self-consistently used in the LWPC code to obtain the time variation of the VLF signal change. We did the modeling of the VLF signal along the NWC (Australia) to IERC/ICSP (India) propagation path and compared the results with observations. The agreement is found to be very satisfactory.

S. Palit; T. Basak; S. K. Mondal; S. Pal; S. K. Chakrabarti

2013-01-01

 
 
 
 
161

The south America VLF NETwork (SAVNET): Development, installation status, first results  

Scientific Electronic Library Online (English)

Full Text Available Abstract in spanish Se presenta la red South America VLF Networks (SAVNET) que es una nueva instalación de observación en frecuencias muy bajas. SAVNET se instaló recientemente en diversas localidades en América LAtina (Brasil, Perú y Argentina) Consiste en una red de siete receptores cuyo principal objetivo científico es monitorear la actividad solar en escalas temporales cortas (minutos/horas) y extensas (años). Otros objetivos incluyen una mejor comprensión de la estructura espaci (more) al de la anomalía Magnética del Atlántico sur, el estudio de fenómenos atmosféricos y la búsqueda sistemática de efectos sismico-electromágneticos genuinos. Abstract in english The South America VLF Network, a new observing facility at Very Low Frequencies is presented. It has been recently installed at different locations in Latin America (in Brazil, Peru and Argentina). It consists of a network of seven Very Low Frequency tracking receivers with the main scientific objective of monitoring the solar activity on short (minutes to hours) and long (years) time scales. Other objectives include a better understanding of the spatial structure of the (more) South Atlantic Magnetic Anomaly, the study of atmospheric phenomena and the search for genuine seismic-electromagnetic effects.

Raulin, J. P.; Correia de Matos David, P.; Hadano, R.; Saraiva, A. C. V.; Correia, E.; Kaufmann, P.

2009-09-01

162

Earth observations for estimating greenhouse gas emissions from deforestation in developing countries  

International Nuclear Information System (INIS)

In response to the United Nations Framework Convention on Climate Change (UNFCCC) process investigating the technical issues surrounding the ability to reduce greenhouse gas (GHG) emissions from deforestation in developing countries, this paper reviews technical capabilities for monitoring deforestation and estimating emissions. Implementation of policies to reduce emissions from deforestation require effective deforestation monitoring systems that are reproducible, provide consistent results, meet standards for mapping accuracy, and can be implemented at the national level. Remotely sensed data supported by ground observations are key to effective monitoring. Capacity in developing countries for deforestation monitoring is well-advanced in a few countries and is a feasible goal in most others. Data sources exist to determine base periods in the 1990s as historical reference points. Forest degradation (e.g. from high impact logging and fragmentation) also contribute to greenhouse gas emissions but it is more technically challenging to measure than deforestation. Data on carbon stocks, which are needed to estimate emissions, cannot currently be observed directly over large areas with remote sensing. Guidelines for carbon accounting from deforestation exist and are available in approved Intergovernmental Panel on Climate Change (IPCC) reports and can be applied at national scales in the absence of forest inventory or other data. Key constraints for implementing programs to monitor greenhouse gas emissions from deforestation are international commitment of resources to increase capacity, coordination of observations to ensure pan-tropical coverage, access to free or low-cost data, and standard and consensual protocols for data interpretation and analysis.

2007-01-01

163

Observations, theory and implications of thermal emission from gamma-ray bursts  

CERN Document Server

Recent analyses show evidence for a thermal emission component that accompanies the non-thermal emission during the prompt phase of GRBs. First, we show the evidence for the existence of this component; Second, we show that this component is naturally explained by considering emission from the photosphere, taking into account high latitude emission from optically thick relativistically expanding plasma. We show that the thermal flux is expected to decay at late times as F_BB ~ t^{-2}, and the observed temperature as T ~ t^{-\\alpha}, with \\alpha ~ 1/2 - 2/3. These theoretical predictions are in very good agreement with the observations. Finally, we discuss three implications of this interpretation: (a) The relation between thermal emission and high energy, non-thermal spectra observed by Fermi. (b) We show how thermal emission can be used to directly measure the Lorentz factor of the flow and the initial radius of the jet. (c) We show how the lack of detection of the thermal component can be used to constrain ...

Pe'er, Asaf

2010-01-01

164

Auroral NO+ 4.3 ?m emission observed from the Midcourse Space Experiment: Multiplatform observations of 9 February 1997  

Science.gov (United States)

The Spatial Infrared Imaging Telescope III (SPIRIT III) radiometer on the Midcourse Space Experiment satellite (MSX), observed enhanced 4.3 ?m emission from a very well characterized aurora over the Barents Sea on 9 February 1997, in conjunction with observations by the POLAR and FAST satellites, the Loparskaya ground site, and ultraviolet and visible spectrometers aboard MSX. Measurements of the auroral location, form, spatial extent and dosing conditions were applied to specify the component of auroral 4.3 ?m radiance due to the slowly produced and optically thick CO2?3 (001-000) transition. An analysis based on the Auroral Atmospheric Radiance Code (AARC) indicates: (1) the emission originates near and beyond the tangent point; (2) the optically thick CO2?3 radiation is largely self absorbed by the intervening atmosphere; and (3) the auroral enhancement is predominantly due to NO+ ?v = 1 vibrational state transitions. In addition, the analysis indicates that the previously reported laboratory result for the NO+ v ? 1 vibrational yield from the reaction, N+ + O2, is insufficient to account for the observed 4.3 ?m emission. In order to explain the current results, we propose that there is additional production from the reaction, N2+ + O, forming NO+ in vibrational levels 0, 1, and 2 with relative populations of approximately 0.25, 0.5, and 0.25, respectively. The combined production processes yield an energetic electron induced efficiency of 0.56 ± 0.18 photons per auroral ion pair for NO+ ?v = 1 emission at altitudes equal to or greater than 112 km.

O'Neil, R. R.; Winick, J. R.; Picard, R. H.; Kendra, M.

2007-06-01

165

AMI OBSERVATIONS OF THE ANOMALOUS MICROWAVE EMISSION IN THE PERSEUS MOLECULAR CLOUD  

Energy Technology Data Exchange (ETDEWEB)

We present observations of the known anomalous microwave emission region, G159.6-18.5, in the Perseus molecular cloud at 16 GHz performed with the Arcminute Microkelvin Imager Small Array. These are the highest angular resolution observations of G159.6-18.5 at microwave wavelengths. By combining these microwave data with infrared observations between 5.8 and 160 {mu}m from the Spitzer Space Telescope, we investigate the existence of a microwave-infrared correlation on angular scales of {approx}2'. We find that the overall correlation appears to increase toward shorter infrared wavelengths, which is consistent with the microwave emission being produced by electric dipole radiation from small, spinning dust grains. We also find that the microwave-infrared correlation peaks at 24 {mu}m (6.7{sigma}), suggesting that the microwave emission is originating from a population of stochastically heated small interstellar dust grains rather than polycyclic aromatic hydrocarbons.

Tibbs, C. T. [Spitzer Science Center, California Institute of Technology, Pasadena, CA 91125 (United States); Scaife, A. M. M. [School of Physics and Astronomy, University of Southampton, Highfield, Southampton SO17 1BJ (United Kingdom); Dickinson, C.; Davies, R. D.; Davis, R. J.; Watson, R. A. [Jodrell Bank Centre for Astrophysics, School of Physics and Astronomy, The University of Manchester, Manchester M13 9PL (United Kingdom); Paladini, R. [NASA Herschel Science Center, California Institute of Technology, Pasadena, CA 91125 (United States); Grainge, K. J. B., E-mail: ctibbs@ipac.caltech.edu [Astrophysics Group, Cavendish Laboratory, J J Thomson Avenue, Cambridge CB3 0HE (United Kingdom)

2013-05-10

166

AMI Observations of the Anomalous Microwave Emission in the Perseus Molecular Cloud  

CERN Multimedia

We present observations of the known anomalous microwave emission region, G159.6-18.5, in the Perseus molecular cloud at 16 GHz performed with the Arcminute Microkelvin Imager Small Array. These are the highest angular resolution observations of G159.6-18.5 at microwave wavelengths. By combining these microwave data with infrared observations between 5.8 and 160 \\mu m from the Spitzer Space Telescope, we investigate the existence of a microwave - infrared correlation on angular scales of ~2 arcmin. We find that the overall correlation appears to increase towards shorter infrared wavelengths, which is consistent with the microwave emission being produced by electric dipole radiation from small, spinning dust grains. We also find that the microwave - infrared correlation peaks at 24 \\mu m (6.7\\sigma), suggesting that the microwave emission is originating from a population of stochastically heated small interstellar dust grains rather than polycyclic aromatic hydrocarbons.

Tibbs, C T; Dickinson, C; Paladini, R; Davies, R D; Davis, R J; Grainge, K J B; Watson, R A

2013-01-01

167

AMI Observations of the Anomalous Microwave Emission in the Perseus Molecular Cloud  

Science.gov (United States)

We present observations of the known anomalous microwave emission region, G159.6-18.5, in the Perseus molecular cloud at 16 GHz performed with the Arcminute Microkelvin Imager Small Array. These are the highest angular resolution observations of G159.6-18.5 at microwave wavelengths. By combining these microwave data with infrared observations between 5.8 and 160 ?m from the Spitzer Space Telescope, we investigate the existence of a microwave-infrared correlation on angular scales of ~2'. We find that the overall correlation appears to increase toward shorter infrared wavelengths, which is consistent with the microwave emission being produced by electric dipole radiation from small, spinning dust grains. We also find that the microwave-infrared correlation peaks at 24 ?m (6.7?), suggesting that the microwave emission is originating from a population of stochastically heated small interstellar dust grains rather than polycyclic aromatic hydrocarbons.

Tibbs, C. T.; Scaife, A. M. M.; Dickinson, C.; Paladini, R.; Davies, R. D.; Davis, R. J.; Grainge, K. J. B.; Watson, R. A.

2013-05-01

168

Observations of Far-Ultraviolet Diffuse Emission from the Small Magellanic Cloud  

CERN Document Server

We report the first observations of far-ultraviolet (FUV: 1000 -- 1150 \\AA) diffuse radiation from the Small Magellanic Cloud (SMC) using observations from the {\\em Far Ultraviolet Spectroscopic Explorer (FUSE)}. The strength of FUV diffuse surface brightness in the SMC ranges from the detection limit of 2000 photons cm$^{-2}$ s$^{-1}$ sr$^{-1}$ \\AA$^{-1}$ to a maximum of $3 \\times 10^{5}$ photons cm$^{-2}$ s$^{-1}$ sr$^{-1}$ \\AA$^{-1}$ at 1004 \\AA. The contribution of diffuse emission to the total radiation field was found to be 34% at 1004 \\AA to 44% at 1117 \\AA with a maximum observed uncertainty of 30%. There is a striking difference between the FUV diffuse fraction from the SMC and the Large Magellanic Cloud (LMC) with the SMC fraction being higher probable because the higher dust albedo. The FUV diffuse emission correlates with H$\\alpha$ emission in the H {\\small II} regions of the SMC.

Pradhan, Ananta C; Pathak, Amit

2011-01-01

169

PULSED VERY HIGH ENERGY ?-RAY EMISSION CONSTRAINTS FOR PSR B1951+32 FROM STACEE OBSERVATIONS  

International Nuclear Information System (INIS)

The Solar Tower Atmospheric Cherenkov Effect Experiment (STACEE) is a ground-based telescope that uses the wave-front-sampling technique to detect very high energy (VHE) gamma rays. STACEE's sensitivity in the energy range near 100 GeV permits useful observations of pulsars with the potential to discriminate between various proposed mechanisms for pulsed gamma-ray emission. Based on the 11.3 hr of data taken during the 2005 and 2006 observing seasons, we derive an upper limit on the pulsed gamma-ray emission from PSR B1951+32 of -11 photons cm-2 s-1 above an energy threshold of 117 GeV.

170

Observations of the 12.3 micron Mg I emission line during a major solar flare  

International Nuclear Information System (INIS)

[en] The extremely Zeeman-sensitive 12.32 micron Mg I solar emission line was observed during a 3B/X5.7 solar flare on October 24, 1989. When compared to postflare values, Mg I emission-line intensity in the penumbral flare ribbon was 20 percent greater at the peak of the flare in soft X-rays, and the 12 micron continuum intensity was 7 percent greater. The flare also excited the emission line in the umbra where it is normally absent. The umbral flare emission exhibits a Zeeman splitting 200 G less than the adjacent penumbra, suggesting that it is excited at higher altitude. The absolute penumbral magnetic field strength did not change by more than 100 G between the flare peak and postflare period. However, a change in the inclination of the field lines, probably related to the formation and development of the flare loop system, was seen. 21 refs

1990-01-01

171

Validation of a methane emission model using eddy covariance observations and footprint modeling.  

Science.gov (United States)

Several methane emission models were developed recently to quantify methane emissions. However, calibration of these models is currently performed using chamber flux methane measurements, which have a number of limitations, such as small footprint area and low temporal resolution. Furthermore, chamber measurements are unsuitable to register ebullition events, which can have a significant influence on observed fluxes. Eddy covariance measurements on the other hand provide high frequency (5 to 20 Hz) data and cover larger areas, while being a non-intrusive way to measure fluxes and account for ebullition. In this study, we present a validation of methane emission model using eddy covariance data, collected in summer periods at the Indigirka lowland site in Eastern Siberia. A flux footprint model was used together with a high resolution vegetation map of the area to retrieve vegetation distribution inside the footprint. Subsequently, this data with eddy covariance data is used to calibrate a methane emission model.

Budishchev, A.; Mi, Y.; Gallagher, A.; van Huissteden, J.; Schaepman-Strub, G.; Dolman, A. J.; Maximov, T. C.

2012-04-01

172

Oscillating current observed in field emission from a single zinc oxide nanostructure and the physical mechanism  

Science.gov (United States)

A phenomenon of field emission instability is reported. Field emission current oscillation was observed when a single zinc oxide (ZnO) one dimensional nanostructure operated at high current density. As a result, the radius curvature of the nanoemitter apex was sharpened to less than 15 nm. This indicates the oscillation was associated with melting of the emitter material. We found that the oscillation may be ascribed to (i) the behavior of charging and (ii) the shape changing of a metallic liquid ball that exists at the tip apex under high electric field. The net force of electric force and surface tension modifies the radius of the apex periodically, which results in the oscillation of field emission current. This finding may enhance the understanding of the physical process of field emission from ZnO nanostructures.

Xiao, Z. M.; She, J. C.; Li, Z. B.; Yang, Y. H.; Yang, G. W.; Deng, S. Z.; Chen, Jun; Xu, N. S.

2009-07-01

173

Detection of karst structures using airborne EM and VLF  

International Nuclear Information System (INIS)

Through the combined use of multi-frequency helicopter electromagnetic and VLF data, it is possible to detect and delineate a wide variety of karst structures and possibly to assess their interconnectedness. Multi-frequency EM Can detect karst features if some element of the structure is conductive. This conductive aspect may derive from thick, moist soils in the depression commonly associated with a doline, from conductive fluids in the cavity, or from conductive sediments in the cavity if these occupy a significant portion of it. Multiple loop configurations may also increase the likelihood of detecting karst features. Preliminary evidence indicates total field VLF measurements may be able to detect interconnected karst pathways, so long as the pathways are water or sediment filled. Neither technique can effectively detect dry, resistive air-filled cavities

1994-01-01

174

Detection of karst structures using airborne EM and VLF  

Energy Technology Data Exchange (ETDEWEB)

Through the combined use of multi-frequency helicopter electromagnetic and VLF data, it is possible to detect and delineate a wide variety of karst structures and possibly to assess their interconnectedness. Multi-frequency EM Can detect karst features if some element of the structure is conductive. This conductive aspect may derive from thick, moist soils in the depression commonly associated with a doline, from conductive fluids in the cavity, or from conductive sediments in the cavity if these occupy a significant portion of it. Multiple loop configurations may also increase the likelihood of detecting karst features. Preliminary evidence indicates total field VLF measurements may be able to detect interconnected karst pathways, so long as the pathways are water or sediment filled. Neither technique can effectively detect dry, resistive air-filled cavities.

Beard, L.P. Nyquist, J.E. [Oak Ridge National Lab., TN (United States); Carpenter, P.J. [Northern Illinois Univ., De Kalb, IL (United States)

1994-12-31

175

Tropospheric methanol observations from space: constraints on the seasonality of biogenic emissions  

Science.gov (United States)

Methanol is the most abundant non-methane organic compound in the atmosphere, and is an important precursor of atmospheric pollutants such as CO and formaldehyde. The recent development of methanol retrievals from nadir-viewing satellite-based platforms offers powerful new information for quantifying methanol emissions on a global scale. This study uses methanol observations from the Tropospheric Emission Spectrometer (TES) on the Aura satellite and the Infrared Atmospheric Sounding Interferometer (IASI) on the MetOp-A satellite, in conjunction with aircraft data, to investigate methanol emissions from major plant functional types in the GEOS-Chem global chemical transport model (driven with MEGAN biogenic emissions). We first evaluate the TES methanol retrievals by comparing to simulation results and flight observations from several North American field campaigns. Results show that the retrieval performs well when the degrees of freedom for signal are above 0.5. We analyze one full year of TES and IASI observations and find a persistent model underestimate in springtime, and make recommendations for an improved seasonal distribution of biogenic methanol emissions over temperate regions of the globe.

Wells, K. C.; Millet, D. B.; Cady-Pereira, K. E.; Shephard, M. W.; Xiao, Y.; Razavi, A.; Clerbaux, C.

2011-12-01

176

Modelling of X-ray emission supernova remnants observed by the European satellite XMM-Newton  

International Nuclear Information System (INIS)

This thesis deals with the X-ray emission of supernova remnants (SNRs) observed by the European satellite XMM-Newton. In SNRs, the matter heated to millions of degrees shines brightly in X-rays. This emission depends on the hydrodynamical evolution of the SNR, on the chemical composition of the ejected matter and on the ambient medium. Moreover, the blast-wave is considered to be the prime site of the production and the acceleration of cosmic-rays in our Galaxy. XMM-Newton is one of the first to allow the investigation of these different aspects thanks to its spatially-resolved spectroscopy and its very good sensitivity. l first studied Kepler's SNR (SN 1604) whose X-ray emission is dominated by the ejecta. Its observation has allowed to obtain information on the nucleosynthesis products, on their spatial distribution and on the temperature structure in the shocked ejecta. This gives strong constraints on the physics of the explosion and on the progenitor's type. l have shown also that the X-ray emission at the shock is likely to be non-thermal. Then, l studied the SNR G347.3-0.5 whose X-ray emission is entirely due to the synchrotron radiation of relativistic (TeV) electrons accelerated at the shock. From five pointing, l made a full mapping of the X-ray emission characteristics (brightness, absorption and spectral index) at small scale. Combined to radio observations, these results have indicated a clear interaction between the SNR and molecular clouds located at 1 kpc and not at 6 kpc as previously estimated. Lastly, in the framework of a self-similar hydrodynamical model coupled with non-linear particle acceleration, l have obtained the synchrotron emission profile in SNRs, including the adiabatic and radiative losses of the accelerated electrons. (author)

2004-01-01

177

PANCHROMATIC OBSERVATIONS OF THE TEXTBOOK GRB 110205A: CONSTRAINING PHYSICAL MECHANISMS OF PROMPT EMISSION AND AFTERGLOW  

Energy Technology Data Exchange (ETDEWEB)

We present a comprehensive analysis of a bright, long-duration (T{sub 90} {approx} 257 s) GRB 110205A at redshift z = 2.22. The optical prompt emission was detected by Swift/UVOT, ROTSE-IIIb, and BOOTES telescopes when the gamma-ray burst (GRB) was still radiating in the {gamma}-ray band, with optical light curve showing correlation with {gamma}-ray data. Nearly 200 s of observations were obtained simultaneously from optical, X-ray, to {gamma}-ray (1 eV to 5 MeV), which makes it one of the exceptional cases to study the broadband spectral energy distribution during the prompt emission phase. In particular, we clearly identify, for the first time, an interesting two-break energy spectrum, roughly consistent with the standard synchrotron emission model in the fast cooling regime. Shortly after prompt emission ({approx}1100 s), a bright (R = 14.0) optical emission hump with very steep rise ({alpha} {approx} 5.5) was observed, which we interpret as the reverse shock (RS) emission. It is the first time that the rising phase of an RS component has been closely observed. The full optical and X-ray afterglow light curves can be interpreted within the standard reverse shock (RS) + forward shock (FS) model. In general, the high-quality prompt and afterglow data allow us to apply the standard fireball model to extract valuable information, including the radiation mechanism (synchrotron), radius of prompt emission (R{sub GRB} {approx} 3 Multiplication-Sign 10{sup 13} cm), initial Lorentz factor of the outflow ({Gamma}{sub 0} {approx} 250), the composition of the ejecta (mildly magnetized), the collimation angle, and the total energy budget.

Zheng, W. [Department of Physics, University of Michigan, 450 Church Street, Ann Arbor, MI 48109 (United States); Shen, R. F. [Department of Astronomy and Astrophysics, University of Toronto, Toronto, Ontario M5S 3H4 (Canada); Sakamoto, T. [Center for Research and Exploration in Space Science and Technology (CRESST), NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Beardmore, A. P. [Department of Physics and Astronomy, University of Leicester, Leicester LE1 7RH (United Kingdom); De Pasquale, M. [Mullard Space Science Laboratory, University College London, Holmbury Road, Holmbury St. Mary, Dorking RH5 6NT (United Kingdom); Wu, X. F.; Zhang, B. [Department of Physics and Astronomy, University of Nevada Las Vegas, Las Vegas, NV 89154 (United States); Gorosabel, J. [Instituto de Astrofisica de Andalucia (IAA-CSIC), 18008 Granada (Spain); Urata, Y. [Institute of Astronomy, National Central University, Chung-Li 32054, Taiwan (China); Sugita, S. [EcoTopia Science Institute, Nagoya University, Furo-cho, chikusa, Nagoya 464-8603 (Japan); Pozanenko, A. [Space Research Institute (IKI), 84/32 Profsoyuznaya St., Moscow 117997 (Russian Federation); Nissinen, M. [Taurus Hill Observatory, Haerkaemaeentie 88, 79480 Kangaslampi (Finland); Sahu, D. K. [CREST, Indian Institute of Astrophysics, Koramangala, Bangalore 560034 (India); Im, M. [Center for the Exploration of the Origin of the Universe, Department of Physics and Astronomy, FPRD, Seoul National University, Shillim-dong, San 56-1, Kwanak-gu, Seoul (Korea, Republic of); Ukwatta, T. N. [Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824 (United States); Andreev, M. [Terskol Branch of Institute of Astronomy of RAS, Kabardino-Balkaria Republic 361605 (Russian Federation); Klunko, E., E-mail: zwk@umich.edu, E-mail: rfshen@astro.utoronto.ca, E-mail: zhang@physics.unlv.edu [Institute of Solar-Terrestrial Physics, Lermontov St., 126a, Irkutsk 664033 (Russian Federation); and others

2012-06-01

178

PANCHROMATIC OBSERVATIONS OF THE TEXTBOOK GRB 110205A: CONSTRAINING PHYSICAL MECHANISMS OF PROMPT EMISSION AND AFTERGLOW  

International Nuclear Information System (INIS)

[en] We present a comprehensive analysis of a bright, long-duration (T90 ? 257 s) GRB 110205A at redshift z = 2.22. The optical prompt emission was detected by Swift/UVOT, ROTSE-IIIb, and BOOTES telescopes when the gamma-ray burst (GRB) was still radiating in the ?-ray band, with optical light curve showing correlation with ?-ray data. Nearly 200 s of observations were obtained simultaneously from optical, X-ray, to ?-ray (1 eV to 5 MeV), which makes it one of the exceptional cases to study the broadband spectral energy distribution during the prompt emission phase. In particular, we clearly identify, for the first time, an interesting two-break energy spectrum, roughly consistent with the standard synchrotron emission model in the fast cooling regime. Shortly after prompt emission (?1100 s), a bright (R = 14.0) optical emission hump with very steep rise (? ? 5.5) was observed, which we interpret as the reverse shock (RS) emission. It is the first time that the rising phase of an RS component has been closely observed. The full optical and X-ray afterglow light curves can be interpreted within the standard reverse shock (RS) + forward shock (FS) model. In general, the high-quality prompt and afterglow data allow us to apply the standard fireball model to extract valuable information, including the radiation mechanism (synchrotron), radius of prompt emission (RGRB ? 3 × 1013 cm), initial Lorentz factor of the outflow (?0 ? 250), the composition of the ejecta (mildly magnetized), the collimation angle, and the total energy budget.

2012-06-01

179

Quantifying global terrestrial methanol emissions using observations from the TES satellite sensor  

Science.gov (United States)

We employ new global space-based measurements of atmospheric methanol from the Tropospheric Emission Spectrometer (TES) with the adjoint of the GEOS-Chem chemical transport model to quantify terrestrial emissions of methanol to the atmosphere. Biogenic methanol emissions in the model are based on MEGANv2.1 emission algorithms, using MODIS leaf area and GEOS-5 assimilated meteorological fields. We first carry out a pseudo observation test to validate the overall approach, and find that the TES sampling density is sufficient to accurately quantify regional- to continental-scale methanol emissions using this method. A global inversion of two years of TES data yields an optimized annual global surface flux of 117 Tg yr-1 (including biogenic, pyrogenic, and anthropogenic sources), an increase of 56% from the a priori global flux of 75 Tg yr-1. Global terrestrial methanol emissions are thus approximately 25% those of isoprene (~540 Tg yr-1), and are comparable to the combined emissions of all anthropogenic volatile organic compounds (~100-200 Tg yr-1). Our a posteriori terrestrial methanol source leads to a strong improvement of the simulation relative to an ensemble of airborne observations, and corroborates two other recent top-down estimates (114-120 Tg yr-1) derived using in-situ and space-based measurements. The TES data imply a relatively modest revision of model emissions over most of the tropics, but a significant upward revision in midlatitudes, particularly over Europe and North America. We interpret the inversion results in terms of specific source types using the methanol:CO correlations measured by TES, and find that biogenic emissions are overestimated relative to biomass burning and anthropogenic emissions in central Africa and southeastern China, while they are underestimated in regions such as Brazil and the US. Based on our optimized emissions, methanol accounts for >25% of the photochemical source of CO and HCHO over many parts of the northern extratropics during springtime, and contributes ~6% of the global secondary source of those compounds annually.

Wells, K. C.; Millet, D. B.; Cady-Pereira, K. E.; Shephard, M. W.; Henze, D. K.; Bousserez, N.; Apel, E. C.; de Gouw, J.; Warneke, C.; Singh, H. B.

2013-08-01

180

Quantifying global terrestrial methanol emissions using observations from the TES satellite sensor  

Directory of Open Access Journals (Sweden)

Full Text Available We employ new global space-based measurements of atmospheric methanol from the Tropospheric Emission Spectrometer (TES) with the adjoint of the GEOS-Chem chemical transport model to quantify terrestrial emissions of methanol to the atmosphere. Biogenic methanol emissions in the model are based on MEGANv2.1 emission algorithms, using MODIS leaf area and GEOS-5 assimilated meteorological fields. We first carry out a pseudo observation test to validate the overall approach, and find that the TES sampling density is sufficient to accurately quantify regional- to continental-scale methanol emissions using this method. A global inversion of two years of TES data yields an optimized annual global surface flux of 117 Tg yr?1 (including biogenic, pyrogenic, and anthropogenic sources), an increase of 56% from the a priori global flux of 75 Tg yr?1. Global terrestrial methanol emissions are thus approximately 25% those of isoprene (~540 Tg yr?1), and are comparable to the combined emissions of all anthropogenic volatile organic compounds (~100–200 Tg yr?1). Our a posteriori terrestrial methanol source leads to a strong improvement of the simulation relative to an ensemble of airborne observations, and corroborates two other recent top-down estimates (114–120 Tg yr?1) derived using in-situ and space-based measurements. The TES data imply a relatively modest revision of model emissions over most of the tropics, but a significant upward revision in midlatitudes, particularly over Europe and North America. We interpret the inversion results in terms of specific source types using the methanol:CO correlations measured by TES, and find that biogenic emissions are overestimated relative to biomass burning and anthropogenic emissions in central Africa and southeastern China, while they are underestimated in regions such as Brazil and the US. Based on our optimized emissions, methanol accounts for >25% of the photochemical source of CO and HCHO over many parts of the northern extratropics during springtime, and contributes ~6% of the global secondary source of those compounds annually.

K. C. Wells; D. B. Millet; K. E. Cady-Pereira; M. W. Shephard; D. K. Henze; N. Bousserez; E. C. Apel; J. de Gouw; C. Warneke; H. B. Singh

2013-01-01

 
 
 
 
181

Fine structure observed in the thermal emission process for defects in semiconductors  

Energy Technology Data Exchange (ETDEWEB)

High-resolution Laplace-transform DLTS technique has been used to study the influence of small disturbances on the carrier emission process for transition metal- and thermal donors-related defects in silicon. For the iron-boron pair in the p-type silicon, two different configurations of the defect have been observed: stable and metastable. For both of them the influence of the magnetic field on the hole emission is demonstrated and a possible microscopic structure of the metastable defect configuration is discussed. Due to the resolution of the method it was also possible to demonstrate a complex character of the electron emission for two charge states of thermal donors in the n-type silicon and observe the influence of the magnetic field on the process.

Dobaczewski, L.; Surma, M. [Polish Academy of Sciences, Warsaw (Poland)

1996-12-01

182

Observations of a seasonal cycle in NOx emissions from fires in African woody savannas  

Science.gov (United States)

Nitrogen oxide (NOx) emissions from wildfires account for ~15% of the global total, inducing large fluctuations in the chemical production and loss rates of O3 and CH4 and thereby affecting Earth's radiative balance. NOx emissions from fires depend on fuel nitrogen (N) content, the relative contributions of flaming and smoldering combustion, and total biomass burned. Current understanding of the variability in these factors across biomes is limited by sparse observations. Here we use satellite-based measurements to study emission coefficients (ECs), a value proportional to NOx emitted per unit of biomass burned, from fires in African savannas. We show that ECs for NOx exhibit a pronounced seasonal cycle in woody savannas, with early-season ECs 20-40% above and late-season ECs 30-40% below the mean, while no cycle exists in nonwoody savannas. We discuss several possible mechanisms of the observed cycle including seasonal differences in fuel N content and modified combustion efficiency.

Mebust, Anna K.; Cohen, Ronald C.

2013-04-01

183

Megamaser galaxy Markarian 273. I. VLA observations of the hydroxyl emission  

Energy Technology Data Exchange (ETDEWEB)

The hydroxyl megamaser emission in Mrk 273 was observed with the VLA in its high-resolution A array. The radio continuum source is extended at 18 cm; observations published by Ulvestad and Wilson (1984) reveal a double at 6 cm where the stronger component is resolved into a triple at 2 cm. The OH emission is certainly associated only with the stronger component of the 6-cm double and possibly only with the stongest component of the 2-cm triple. Unfortunately, the three velocity-resolved components of the OH line are not spatially resolved, and no information on the molecular disk rotation properties of this galaxy can be determined. This is very different from the VLA results of the megamaser prototype in IC 4553, where the emission is associated with all the continuum components and actually mimics the spatial structure of the radio continuum. Relevant properties of the known megamasers are listed and compared. 22 references.

Schmelz, J.T.; Baan, W.A.; Haschick, A.D.

1987-10-01

184

Observation of phase transitions in hydrogenated Yttrium films via normalized infrared emissivity  

International Nuclear Information System (INIS)

The direct observation of a sequence of phase transitions during hydrogenation of Y thin films has been realized through the use of in situ isothermal infrared emissivity measurements. The formation of different phases, ?-Y(H), YH2 and YH3, has been identified based on the observation of changes in the slope of the normalized IR emissivity vs. time curve during hydrogen loading. The presence of ?-Y(H), YH2 and YH3 was confirmed by ex situ X-ray diffraction, transmission electron microscopy, and prompt gamma activation analysis. Transmission electron microscopy further demonstrated epitaxial orientation relationships between the Al2O3 substrate, Ti buffer layer, the as-deposited Y film, as well as its hydrides. These results clearly demonstrate the power of IR emissivity imaging to monitor, in real time, the formation of hydride phases of both metallic and insulating character near the surface of a thin-film sample.

2010-02-04

185

An unusual VLF signature structure recorded by the DEMETER satellite  

Science.gov (United States)

A type of electromagnetic phenomenon has been found in the electric VLF data measured by the low Earth orbit DEMETER satellite, which was nonidentified earlier as a different class of electromagnetic VLF events. The phenomenon, termed as “swallow-tailed whistler” (STW) after its shape, seems to be similar to a whistler, but following the main trace, an additional trace appears with monotonously increasing frequency. The secondary trace, lasting less than 80 ms within the recorded 20 kHz bandwidth joins at a given Starting Furcation Frequency. In a 7 month long time interval three series of strong STWs were found in a geographically confined search zone. Further, 10 weak STW periods have been identified by a thorough review of a 2 month long recording. Several STWs were found by the investigation of randomly selected DEMETER burst VLF recording acquired globally. On the basis of comparisons with previous studies, we can exclude that this phenomenon is generated by plasma processes in the vicinity of the satellite though the formation mechanism of this (ionospheric) signal is so far unclear. It is possible that this event type appeared in earlier records too, however, without identification.

Ferencz, Csaba; Lichtenberger, János; Hamar, Dániel; Ferencz, Orsolya E.; Steinbach, Péter; Székely, Balázs; Parrot, Michel; Lefeuvre, François; Berthelier, Jean-Jacques; Clilverd, Mark

2010-02-01

186

Simultaneous observation of fundamental and second harmonic radio emission from the terrestrial foreshock  

Science.gov (United States)

Unambiguous measurements of simultaneous fundamental and second harmonic electromagnetic emission from the earth's electron foreshock made with the sounder experiment aboard ISEE-1 and the radio experiment on ISEE-3 are presented. The resulting spectra are shown and discussed. The observations further strengthen the analogy between type II solar radio bursts and the processes occurring in the foreshock.

Burgess, D.; Harvey, C. C.; Steinberg, J.-L.; Lacombe, C.

1987-12-01

187

Emission inventory evaluation using observations of regional atmospheric background stations of China.  

UK PubMed Central (United Kingdom)

Any accurate simulation of regional air quality by numerical models entails accurate and up-to-date emissions data for that region. The INTEX-B2006 (I06), one of the newest emission inventories recently popularly used in China and East Asia, has been assessed using the Community Multiscale Air Quality model and observations from regional atmospheric background stations of China. Comparisons of the model results with the observations for the species SO2, NO2, O3 and CO from the three regional atmospheric background stations of Shangdianzi, Longfengshan and Linan show that the model can basically capture the temporal characteristics of observations such as the monthly, seasonal and diurnal variance trends. Compared to the other three species, the simulated CO values were grossly underestimated by about two-third or one-half of the observed values, related to the uncertainty in CO emissions. Compared to the other two stations, Shangdianzi had poorer simulations, especially for SO2 and CO, which partly resulted from the site location close to local emission sources from the Beijing area; and the regional inventory used was not capable of capturing the influencing factors of strong regional sources on stations. Generally, the fact that summer gave poor simulation, especially for SO2 and O3, might partly relate to poor simulations of meteorological fields such as temperature and wind.

An X; Sun Z; Lin W; Jin M; Li N

2013-03-01

188

Effects of LatticeQCD EoS and Continuous Emission on Some Observables  

International Nuclear Information System (INIS)

[en] Effects of lattice-QCD-inspired equations of state and continuous emission on some observables are discussed, by solving a 3D hydrodynamics. The particle multiplicity as well ? 2 are found to increase in the mid-rapidity. We also discuss the effects of the initial-condition fluctuations

2006-04-11

189

Hard X-ray Emission from the Arches Cluster Region Observed with NuSTAR  

Science.gov (United States)

The Arches cluster is a young, densely packed massive star cluster in our Galaxy, showing high level of star formation activity. The X-ray emission from the cluster is a mix of thermal and nonthermal radiation. The thermal emission is thought to arise from collisions between the strong winds of massive stars. The nonthermal diffuse emission prominent in the iron K_alpha line emission at 6.4 keV, detected in the broad area around the cluster, may be produced by the interaction of low-energy cosmic-ray electrons and ions with neutral ambient gas. The diffuse 6.4 keV fluorescent line emission may be also the result of the irradiation of cold matter by hard X-rays photons. Previously, the lack of spectral measurements above 10 keV did not allow for a definitive conclusion about the ionizing mechanism. Thanks to the recently launched NuSTAR mission, we performed the first imaging and spectral measurements of the Arches cluster at energies above 10 keV. Preliminary analysis of the NuSTAR data shows that hard X-ray emission is extended in the broad region around the cluster where the 6.4 keV iron line is observed. The details of the analysis and possible interpretation will be discussed in this presentation.

Krivonos, Roman; Tomsick, J.; Boggs, S. E.; Hailey, C. J.; Harrison, F.; NuSTAR Team

2013-04-01

190

The observation of chemiluminescent NiO* emissions in the laboratory and in the night airglow  

Directory of Open Access Journals (Sweden)

Full Text Available The recent finding of an orange spectral feature in OSIRIS/Odin spectra of the night airglow near 85 km has raised interest in the origin of the emission. The feature was positively identified as the chemiluminescent FeO* emission where the iron is of meteoric origin. Since the meteorite source of atomic metals in the mesosphere contains both iron and nickel, with Ni being typically 6% of Fe, it is expected that faint emissions involving Ni should also be present in the night airglow. The present study summarizes the laboratory observations of chemiluminescent NiO* emissions and includes a search for the NiO* signature in the night airglow. A faint previously unidentified "continuum" extending longwave of 440 nm has been identified in night airglow spectra obtained with two space-borne limb viewing instruments and through a comparison with laboratory spectra this continuum is identified as arising from the NiO* emission. The FeO* and NiO* emissions both originate from a reaction of the metal atoms with mesospheric ozone and so support the presence of NiO* in the night airglow.

W. F. J. Evans; R. L. Gattinger; A. L. Broadfoot; E. J. Llewellyn

2011-01-01

191

FUSE Observations of the Cygnus Loop OVI Emission from a Nonradiative Shock  

CERN Document Server

We present Far Ultraviolet Spectroscopic Explorer (FUSE) observations of a Balmer filament in the northeast region of the Cygnus Loop supernova remnant. The data consist of one spectrum obtained through the 30"x30" (LWRS) aperture and three spectra at adjacent positions obtained through the 4"x20" (MDRS) aperture. The nonradiative shocks in the region giving rise to these faint optical filaments produce strong OVI 1032,1038 emission, which is detected in all the spectra. The OVI emission is resolved by FUSE into a strong component centered at 0 km/s, and weaker components centered at +/- 140 km/s. The MDRS spectra allow us to study the variation of OVI emission in the post-shock structure. We find that the zero velocity emission is associated directly with the Balmer filament shock, while the high velocity emission comes from a more uniformly distributed component elsewhere along the line of sight. We also find that the shocks producing the emission at +/- 140 km/s have velocities between 180 km/s and 220 km/...

Sankrit, R; Sankrit, Ravi; Blair, William P.

2001-01-01

192

X-Ray Emission from Supernova Remnants Observed in the ASCA Galactic Plane Survey  

CERN Multimedia

X-ray images and spectra of 5 cataloged supernova remnants (SNRs), G12.0-0.1, G346.6-0.2, G348.5+0.1, G348.7+0.3, and G355.6-0.0, observed in the ASCA galactic plane survey are presented. The sizes of X-ray emission from G12.0-0.1, G348.5+0.1, G348.7+0.3, and G355.6-0.0 are comparable to their radio structures, while that of G346.6-0.2 is smaller than the radio structure. The X-ray spectra of all of the SNRs were heavily absorbed by interstellar matter with N_H>10^{22} cm^{-2}. The spectrum of G355.6-0.0 exhibited emission lines, indicating that the X-ray emission has a thin thermal plasma origin, and was well represented by two-temperature thin thermal emission model. On the other hand, no clear emission line features were found in the spectra of the others and the spectra could be represented by either a thin thermal emission model or a power-law model.

Yamauchi, Shigeo; Koyama, Katsuji; Bamba, Aya

2008-01-01

193

Space-based observations of fire NOx emission coefficients: a global biome-scale comparison  

Directory of Open Access Journals (Sweden)

Full Text Available Biomass burning represents both a significant and highly variable source of NOx to the atmosphere. This variability stems from both the episodic nature of fires, and from fire conditions such as the modified combustion efficiency of the fire, the nitrogen content of the fuel and possibly other factors that have not been identified or evaluated by comparison with observations. Satellite instruments offer an opportunity to observe emissions from wildfires, providing a large suite of measurements which allow us to study mean behavior and variability on the regional scale in a statistically rigorous manner. Here we use space-based measurements of fire radiative power from the Moderate Resolution Imaging Spectroradiometer in combination with NO2 tropospheric column densities from the Ozone Monitoring Instrument to measure mean emission coefficients (ECs in g NO MJ?1) from fires for global biomes, and across a wide range of smaller-scale ecoregions, defined as spatially-distinct clusters of fires with similar fuel type. Mean ECs for all biomes fall between 0.250–0.362 g NO MJ?1, a range that is smaller than found in previous studies of biome-scale emission factors. The majority of ecoregion ECs fall within or near this range, implying that under most conditions, mean fire emissions per unit energy are similar between different regions regardless of fuel type or spatial variability. In contrast to these similarities, we find that about 24% of individual ecoregion ECs deviate significantly (p x emissions.

A. K. Mebust; R. C. Cohen

2013-01-01

194

The observation of photon cascade emission in Pr3+-doped compounds under X-ray excitation  

Science.gov (United States)

The problem of obtaining two visible photons from a single incident vacuum ultraviolet photon is considered and conditions of cascade emission observation in various Pr3+-activated compounds are reviewed. Hosts with weak crystal field, low phonon energies, large band gap, large cation-anion distance, and large coordination number for the substitution site are desirable. Emission spectra and decay curves under X-ray excitation of some Pr3+-doped materials: LaAlO3, LaMgAl11O19, SrAl12O19 and SrAlF5 have been measured. Photon cascade emission has been observed in SrAl12O19:Pr3+ and SrAlF5:Pr3+. The influence of the Pr3+ concentration on the emission has been studied in SrAl12O19:Pr3+. Intrinsic (excitonic) luminescence, which has an adverse effect on the cascade emission, is usually suppressed in compounds containing 0.5 or more percent of Pr3+.

Rodnyi, P. A.; Mikhrin, S. B.; Dorenbos, P.; van der Kolk, E.; van Eijk, C. W. E.; Vink, A. P.; Avanesov, A. G.

2002-04-01

195

Observations of secondary emission chamber degradation from very high intensity proton beams at the AGS  

Energy Technology Data Exchange (ETDEWEB)

Degradation of Secondary Emission Chamber (SEC) efficiencies has been seen in the past. As a result, instruments in use today are built to minimize any such effects. With beam intensities as high as 6 x 10{sup 13} protons per pulse incident on these devices the authors are again observing significant degradation in SEC efficiencies. In this report the authors will present observations of these effects and methods they have developed to cope with them.

Brown, K.A.; Chiang, I.H.; Pendzick, A.; Tallerico, T.

1997-08-01

196

Interferometric Observations of RS Ophiuchi and the Origin of the Near-IR Emission  

CERN Document Server

We report observations of the recurrent nova RS Oph using long-baseline near-IR interferometry. We are able to resolve emission from the nova for several weeks after the February 2006 outburst. The near-IR source initially expands to a size of approximately 5 milli-arcseconds. However, beginning around day 10 the IR source appears to begin to shrink, reaching approximately 2 milli-arcseconds by day 100. We combine our measured angular diameters with previously available interferometric and photometric data to derive an emission measure for the source, and hence are able to determine the mass-loss rate of the nova in the days following the outburst.

Lane, B F; Barry, R K; Traub, W A; Retter, A; Muterspaugh, M W; Thompson, R R; Eisner, J A; Serabyn, E; Mennesson, B

2006-01-01

197

Experimental observation of neutron emission insaturation of titanium chips with gaseous deuterium  

International Nuclear Information System (INIS)

An experiment on investigation of low-temperature nuclear dd-fusion in saturation of titanium chips (86%+6%Al+6%V+2%Sn) with gaseous deuterium was carried out. Emission of neutrons (produced in dd-fusion reactions) in the form of separate sporadic bursts was observed. The neutron emission density in the burst was found to be ln=(3.0±0.9)x104s-1. The neutron burst duration was estimated to be ??300?s. The measurements were carried out while the target was naturally heated from the liquid nitrogen temperature (78 K) to room temperature (300)K. 7 refs.; 4 figs

1991-01-01

198

The near infrared emission band observed in electron irradiated Xe and Xe in other rare gases  

International Nuclear Information System (INIS)

The near-infrared emission spectra were studied for xenon diluted with krypton, argon, and neon, respectively, in order to estimate the origin of an emission band at 1260 nm which was previously observed at several hundred Torr(1 Torr = 133.2 Pa) of pure Xe irradiated with pulses of high-energy electrons. A continuous band around 1260 nm was observed only in Xe-Ar mixtures. This band appeared at Xe pressures above 20 Torr(diluted in 600 Torr of Ar) while it was detected above 190 Torr in pure Xe. In Xe-Ar mixtures, three emission lines due to Xe 5d(3/2)1 were also observed at 1700, 2020, and 2650 nm. On the basis of the reported kinetic data for the reactions of rare gas mixtures, the present results led to the conclusion that the band at 1260 nm was due to emission from highly excited excimer states, of which the dissociation limits were higher Rydberg states above the energy level of the Xe2+ ion. (author).

1985-01-01

199

ULTRAVIOLET AND EXTREME-ULTRAVIOLET EMISSIONS AT THE FLARE FOOTPOINTS OBSERVED BY ATMOSPHERE IMAGING ASSEMBLY  

Energy Technology Data Exchange (ETDEWEB)

A solar flare is composed of impulsive energy release events by magnetic reconnection, which forms and heats flare loops. Recent studies have revealed a two-phase evolution pattern of UV 1600 A emission at the feet of these loops: a rapid pulse lasting for a few seconds to a few minutes, followed by a gradual decay on timescales of a few tens of minutes. Multiple band EUV observations by the Atmosphere Imaging Assembly further reveal very similar signatures. These two phases represent different but related signatures of an impulsive energy release in the corona. The rapid pulse is an immediate response of the lower atmosphere to an intense thermal conduction flux resulting from the sudden heating of the corona to high temperatures (we rule out energetic particles due to a lack of significant hard X-ray emission). The gradual phase is associated with the cooling of hot plasma that has been evaporated into the corona. The observed footpoint emission is again powered by thermal conduction (and enthalpy), but now during a period when approximate steady-state conditions are established in the loop. UV and EUV light curves of individual pixels may therefore be separated into contributions from two distinct physical mechanisms to shed light on the nature of energy transport in a flare. We demonstrate this technique using coordinated, spatially resolved observations of UV and EUV emissions from the footpoints of a C3.2 thermal flare.

Qiu Jiong; Longcope, Dana W.; Liu Wenjuan [Department of Physics, Montana State University, Bozeman, MT 59717-3840 (United States); Sturrock, Zoe [Department of Applied Mathematics, University of St. Andrews (United Kingdom); Klimchuk, James A. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)

2013-09-01

200

UV and EUV Emissions at the Flare Foot-points Observed by AIA  

Science.gov (United States)

A solar flare is composed of impulsive energy release events by magnetic reconnection, which forms and heats flare loops. Recent studies have revealed a two-phase evolution pattern of UV 1600A emission at the feet of these loops: a rapid pulse lasting for a few seconds to a few minutes, followed by a gradual decay on timescales of a few tens of minutes. Multiple band EUV observations by AIA further reveal very similar signatures. These two phases represent different but related signatures of an impulsive energy release in the corona. The rapid pulse is an immediate response of the lower atmosphere to an intense thermal conduction flux resulting from the sudden heating of the corona to high temperatures (we rule out energetic particles due to a lack of significant hard X-ray emission). The gradual phase is associated with the cooling of hot plasma that has been evaporated into the corona. The observed footpoint emission is again powered by thermal conduction (and enthalpy), but now during a period when approximate steady state conditions are established in the loop. UV and EUV light curves of individual pixels may therefore be separated into contributions from two distinct physical mechanisms to shed light on the nature of energy transport in a flare. We demonstrate this technique using coordinated, spatially resolved observations of UV and EUV emission from the footpoints of a C3.2 thermal flare.

Qiu, Jiong; Sturrock, Z.; Longcope, D.; Klimchuk, J. A.; Liu, W.

2013-07-01

 
 
 
 
201

Satellite observations of a seasonal cycle in NOx emission factors from fires in African woody savannas  

Science.gov (United States)

Nitrogen oxide (NOx) emissions from wildfires account for ~15% of the global total, inducing large fluctuations in the chemical production and loss rates of O3 and CH4 and thereby affecting Earth's radiative balance. NOx emissions from fires depend on fuel N content, combustion stage, and total biomass burned; sparse observations limit current understanding of the variability in these factors across biomes. Here we use NO2 column measurements from the Ozone Monitoring Instrument (OMI) and fire radiative power retrieved from the Moderate Resolution Imaging Spectroradiometer (MODIS) to study emission coefficients (ECs), a value proportional to emission factors i.e. NOx emitted per unit of biomass burned, from fires in African savannas and woody savannas. In woody savannas, NOx ECs decrease steadily across the fire season, rather than remaining constant as is currently assumed; in constrast, no seasonal pattern is observed in (non-woody) savannas. We speculate that the observed cycle is due to reallocation of nutrients, including N, to plant roots after the growing season.

Mebust, Anna; Cohen, Ron

2013-04-01

202

Conjugate observations of quasi-periodic emissions by Cluster and DEMETER spacecraft  

Science.gov (United States)

AbstractQuasi-periodic (QP) emissions are electromagnetic emissions at frequencies of about 0.5-4 kHz that are characterized by a periodic time modulation of the wave intensity. Typical periods of this modulation are on the order of minutes. We present a case study of a large-scale long-lasting QP event observed simultaneously on board the DEMETER (Detection of Electro-Magnetic Emissions Transmitted from Earthquake Regions) and the Cluster spacecraft. The measurements by the Wide-Band Data instrument on board the Cluster spacecraft enabled us to obtain high-resolution frequency-time spectrograms of the event close to the equatorial region over a large range of radial distances, while the measurements by the STAFF-SA instrument allowed us to perform a detailed wave analysis. Conjugate observations by the DEMETER spacecraft have been used to estimate the spatial and temporal extent of the emissions. The analyzed QP event lasted as long as 5 h and it spanned over the L-shells from about 1.5 to 5.5. Simultaneous observations of the same event by DEMETER and Cluster show that the same QP modulation of the wave intensity is observed at the same time at very different locations in the inner magnetosphere. ULF magnetic field fluctuations with a period roughly comparable to, but somewhat larger than the period of the QP modulation were detected by the fluxgate magnetometers instrument on board the Cluster spacecraft near the equatorial region, suggesting these are likely to be related to the QP generation. Results of a detailed wave analysis show that the QP emissions detected by Cluster propagate unducted, with oblique wave normal angles at higher geomagnetic latitudes.

N?Mec, F.; SantolíK, O.; Parrot, M.; Pickett, J. S.; Hayosh, M.; Cornilleau-Wehrlin, N.

2013-01-01

203

Geomagnetic conjugacy of 30-kHz band auroral hiss emissions observed at L = 6. 1  

Energy Technology Data Exchange (ETDEWEB)

Statistical characteristics of auroral hiss emissions in the 30-kHz band were examined using the data observed simultaneously at the Syowa-Husafell conjugate pair of stations during the period of September-November 1983. The occurrence probabilities of conjugate events observed simultaneously at the two stations were almost the same in September and October and decreased during November. The nonconjugate events observed only at Syowa Station were detected more often in September. The number of nonconjugate events decreased in October and November. These phenomena were mostly observed during 1,700-2,300 MLT around the geographic midnight at Syowa. On the other hand, the number of nonconjugate phenomena detected only at Husafell in iceland incrreased from September to Noverber. The occurrence peaks were around 2,100-0200 MLT, before geographci midnight at Husafell. From these statistical characteristics it is found that auroral hiss emission occurrences strongly depend on not only the magnetic local time but also the geographic local time and seasons, suggesting that auroral hiss emissions observed on the ground are strongly controlled by the sunlit effects in the topside ionosphere.

Sato, Natsuo (National Inst. of Polar Research, Tokyo (Japan)); Kokubun, Susumu (Univ. of Tokyo (Japan)); Saemundsson, T. (Univ. of Iceland, Reykjavik (Iceland))

1987-06-01

204

A theoretical verification of intensity of plasmaspheric ELF hiss emissions: theory versus GEOS-1 observations  

Directory of Open Access Journals (Sweden)

Full Text Available An attempt is made to confirm the generation mechanism of plasmaspheric ELF hiss emissions observed aboard GEOS-1 satellite in the equatorial region both at small and large wave normal angles by calculating their magnetic field intensities in terms of incoherent Cerenkov radiation mechanism and cyclotron resonance instability mechanism, using appropriate and suitable plasma parameters. The ELF intensities calculated by Cerenkov radiation mechanism, being 4 to 5 orders of magnitude lower than the observed intensities, rule out the possibility of their generation by this mechanism. On the other hand, the intensities calculated under electron cyclotron resonance instability mechanism are found to be large enough to account for both the observed intensity and propagation losses and hence to confirm that plasmaspheric ELF hiss emissions observed aboard GEOS-1 satellite both at small and large wave normal angles were originally generated in the equatorial region by this mechanism just near the inner edge of the plasmapause. The difference in the observed intensities of two types of the emissions has been attributed to the propagation effect rather than the generation effect.

R. Prakash; R. P. Singh; R. C. Awasthi; D. P. Singh

0000-01-01

205

Space-based observations of fire NOx emission coefficients: a global biome-scale comparison  

Science.gov (United States)

Biomass burning represents both a significant and highly variable source of NOx to the atmosphere. This variability stems from both the episodic nature of fires, and from fire conditions such as the modified combustion efficiency of the fire, the nitrogen content of the fuel and possibly other factors that have not been identified or evaluated by comparison with observations. Satellite instruments offer an opportunity to observe emissions from wildfires, providing a large suite of measurements which allow us to study mean behavior and variability on the regional scale in a statistically rigorous manner. Here we use space-based measurements of fire radiative power from the Moderate Resolution Imaging Spectroradiometer in combination with NO2 tropospheric column densities from the Ozone Monitoring Instrument to measure mean emission coefficients (ECs in g NO MJ-1) from fires for global biomes, and across a wide range of smaller-scale ecoregions, defined as spatially-distinct clusters of fires with similar fuel type. Mean ECs for all biomes fall between 0.250-0.362 g NO MJ-1, a range that is smaller than found in previous studies of biome-scale emission factors. The majority of ecoregion ECs fall within or near this range, implying that under most conditions, mean fire emissions per unit energy are similar between different regions regardless of fuel type or spatial variability. In contrast to these similarities, we find that about 24% of individual ecoregion ECs deviate significantly (p ECs falls outside this range, implying that there are some regions where fuel type-specific global emission parameterizations fail to capture local fire NOx emissions.

Mebust, A. K.; Cohen, R. C.

2013-08-01

206

Soft x-ray emission from gamma-ray bursts observed with ginga  

International Nuclear Information System (INIS)

[en] The soft X-ray emission of gamma-ray bursts below 10 keV provides information about size, location, and emission mechanism. The Gamma-ray Burst Detector (GBD) on board Ginga, which consists of a proportional counter and a scintillation detector, covers an energy range down to 1.5 keV with 63 cm2 effective area. In several of the observed gamma-ray bursts, the intensity of the soft X-ray emission showed a longer decay time of 50 to 100s after the higher energy gamma-ray emission had ended. Although we cannot rule out other models, such as bremsstrahlung and thermal cyclotron types, due to poor statistics, the soft X-ray spectra are consistent with a blackbody of 1 to 2 keV in the late phase of the gamma-ray bursts. This enables us to estimate the size of the blackbody responsible for the X-ray emission. (author)

1989-01-01

207

Soft x-ray emission from gamma-ray bursts observed with ginga  

Energy Technology Data Exchange (ETDEWEB)

The soft X-ray emission of gamma-ray bursts below 10 keV provides information about size, location, and emission mechanism. The Gamma-ray Burst Detector (GBD) on board Ginga, which consists of a proportional counter and a scintillation detector, covers an energy range down to 1.5 keV with 63 cm{sup 2} effective area. In several of the observed gamma-ray bursts, the intensity of the soft X-ray emission showed a longer decay time of 50 to 100s after the higher energy gamma-ray emission had ended. Although we cannot rule out other models, such as bremsstrahlung and thermal cyclotron types, due to poor statistics, the soft X-ray spectra are consistent with a blackbody of 1 to 2 keV in the late phase of the gamma-ray bursts. This enables us to estimate the size of the blackbody responsible for the X-ray emission. (author).

Yoshida, Atsumasa; Murakami, Toshio; Itoh, Masayuki (Institute of Space and Astronautical Science, Sagamihara, Kanagawa (Japan)) (and others)

1989-08-01

208

A Suzaku Observation of the Low-Ionization Fe-Line Emission from RCW 86  

Science.gov (United States)

The newly operational X-ray satellite Suzaku observed the southwesternquadrant of the supernova remnant (SNR) RCW 86 in February 2006 to study the nature of the 6.4 keV emission line. The new data localize it for the first time; most of the line emission is adjacent and interior to the forward shock and not at the locus of the continuum hard emission. We also report the first detection of a 7.1 keV line that we interpret as the K? emission from low-ionization iron. The Fe-K line features are consistent with a non-equilibrium plasma of Fe-rich ejecta with net > 109 cm-3 s and kTe ˜ 5 keV. This combination of low net and high kTe suggests collisionless electron heating in an SNR shock. The Fe K? line shows evidence for intrinsic broadening, with a width of 47 (34-59) eV (99 spatial distributions of the hard continuum above 3 keV and the Fe-K line emission support a synchrotron origin for the hard continuum.

Ueno, M.; Sato, R.; Kataoka, J.; Harrus, I.; Petre, R.; Suzaku Rcw 86 Team

209

Panchromatic observations of the textbook GRB 110205A: constraining physical mechanisms of prompt emission and afterglow  

CERN Document Server

We present a comprehensive analysis of a bright, long duration (T90 ~ 257 s) GRB 110205A at redshift z= 2.22. The optical prompt emission was detected by Swift/UVOT, ROTSE-IIIb and BOOTES telescopes when the GRB was still radiating in the gamma-ray band. Nearly 200 s of observations were obtained simultaneously from optical, X-ray to gamma-ray, which makes it one of the exceptional cases to study the broadband spectral energy distribution across 6 orders of magnitude in energy during the prompt emission phase. By fitting the time resolved prompt spectra, we clearly identify, for the first time, an interesting two-break energy spectrum, roughly consistent with the standard GRB synchrotron emission model in the fast cooling regime. Although the prompt optical emission is brighter than the extrapolation of the best fit X/gamma-ray spectra, it traces the gamma-ray light curve shape, suggesting a relation to the prompt high energy emission. The synchrotron + SSC scenario is disfavored by the data, but the models i...

Zheng, W; Sakamoto, T; Beardmore, A P; Pasquale, M; Wu, X F; Gorosabel, J; Urata, Y; Sugita, S; Zhang, B; Pozanenko, A; Nissinen, M; Sahu, D K; Im, M; Ukwatta, T N; Andreev, M; Klunko, E; Volnova, A; Akerlof, C W; Anto, P; Barthelmy, S D; Breeveld, A; Carsenty, U; Castillo-Carri'on, S; Castro-Tirado, A J; Chester, M M; Chuang, C J; Cunniffe, R; Postigo, A; Duffard, R; Flewelling, H; Gehrels, N; Guver, T; Guziy, S; Hentunen, V P; Huang, K Y; Jelínek, M; Koch, T S; Kub'anek, P; Kuin, P; McKay, T A; Mottola, S; Oates, S R; O'Brien, P; Page, M J; Pandey, S B; Pulgar, C; Rujopakarn, W; Rykoff, E; Salmi, T; S'anchez-Ramírez, R; Schaefer, B E; Sergeev, A; Sonbas, E; Sota, A; Tello, J C; Yamaoka, K; Yost, S A; Yuan, F

2011-01-01

210

Observations of artificial and natural optical emissions at the HAARP facility  

Directory of Open Access Journals (Sweden)

Full Text Available Extensive optical observations have been carried out at the High Frequency Active Auroral Research Program (HAARP) ionospheric heating facility since it began operations in 1999. A number of modern optical diagnostic instruments are hosted at remote sites as well as the main transmitter facility, which has recently been expanded from the initial 960 kW prototype configuration to its full 3.6 MW design capability. Upgrades to optical diagnostics have allowed a number of interesting new observations to be made at the 960 kW power level since 2004. Systematic beam-swinging experiments generating quantifiable levels of optical emission at various regions in the sky for the first time clearly show that emission intensity is very sensitive to distance from the magnetic zenith, and drops off rapidly at about 15° zenith angle in directions other than magnetic south. High temporal resolution measurements of emissions in the 557.7 nm green line at start-up and in short transmitter pulses demonstrate that localized irregularities are preferentially excited in the initial seconds of heating, with evolution into a more homogenous spot occurring over a period of about 1 min. High-quality emission altitude profiles at both 630.0 and 557.7 nm have recently been isolated from side-looking data, spanning an altitude extent of over 200 km, which has allowed determination of the effective lifetime of O (1D) over an unprecedented altitude range. An innovative automated remote imager network utilizing low-cost mirror optics has been designed and deployed to make such measurements routinely. Observations of natural optical emissions at the site have revealed the common presence of highly structured but faint co-rotating subauroral precipitation that acts to suppress excitation of artificial F region optical emissions in areas of active precipitation. The observed spatial modulation of artificial optical emissions by structured precipitation is consistent with localized absorption of HF waves in the ionospheric D layer enhanced by the energetic particle precipitation.

T. Pedersen; R. Esposito; E. Kendall; D. Sentman; M. Kosch; E. Mishin; R. Marshall

2008-01-01

211

The VLF fingerprint of elves: Step-like and long-recovery early VLF perturbations caused by powerful ±CG lightning EM pulses  

Science.gov (United States)

Subionospheric VLF recordings are investigated in relation with intense cloud-to-ground (CG) lightning data. Lightning impacts the lower ionosphere via heating and ionization changes which produce VLF signal perturbations known as early VLF events. Typically, early events recover in about 100 s, but a small subclass does not recover for many minutes, known as long-recovery early events (LORE). In this study, we identify LORE as a distinct category of early VLF events, whose signature may occur either on its own or alongside the short-lived typical early VLF event. Since LORE onsets coincide with powerful lightning strokes of either polarity (±), we infer that they are due to long-lasting ionization changes in the uppermost D region ionosphere caused by electromagnetic pulses emitted by strong ± CG lightning peak currents of typically > 250 kA, which are also known to generate elves. The LORE perturbations are detected when the discharge is located within ~250 km from the great circle path of a VLF transmitter-receiver link. The probability of occurrence increases with stroke intensity and approaches unity for discharges with peak currents ? ~300 kA. LOREs are nighttime phenomena that occur preferentially, at least in the present regional data set, during winter when strong ± CG discharges are more frequent and intense. The evidence suggests LORE as a distinct signature representing the VLF fingerprint of elves, a fact which, although was predicted by theory, it escaped identification in the long-going VLF research of lightning effects in the lower ionosphere.

Haldoupis, Christos; Cohen, Morris; Arnone, Enrico; Cotts, Benjamin; Dietrich, Stefano

2013-08-01

212

HST/ACS Observations of Europa's Atmospheric UV Emission at Eastern Elongation  

CERN Multimedia

We report results of a Hubble Space Telescope (HST) campaign with the Advanced Camera for Surveys to observe Europa at eastern elongation, i.e. Europa's leading side, on 2008 June 29. With five consecutive HST orbits, we constrain Europa's atmospheric \\ion{O}{1} 1304 \\A and \\ion{O}{1} 1356 \\A emissions using the prism PR130L. The total emissions of both oxygen multiplets range between 132 $\\pm$ 14 and 226 $\\pm$ 14 Rayleigh. An additional systematic error with values on the same order as the statistical errors may be due to uncertainties in modelling the reflected light from Europa's surface. The total emission also shows a clear dependence of Europa's position with respect to Jupiter's magnetospheric plasma sheet. We derive a lower limit for the O$_2$ column density of 6 $\\times$ 10$^{18}$ m$^{-2}$. Previous observations of Europa's atmosphere with STIS in 1999 of Europa's trailing side show an enigmatic surplus of radiation on the anti-Jovian side within the disk of Europa. With emission from a radially symm...

Saur, Joachim; Roth, Lorenz; Nimmo, Francis; Strobel, Darrell F; Retherford, Kurt D; McGrath, Melissa A; Schilling, Nico; Gérard, Jean-Claude; Grodent, Denis

2011-01-01

213

Isoprene emissions in Africa inferred from OMI observations of formaldehyde columns  

Directory of Open Access Journals (Sweden)

Full Text Available We use 2005–2009 satellite observations of formaldehyde (HCHO) columns from OMI to infer biogenic isoprene emissions at monthly 1 × 1° resolution over the African continent. Our work includes new approaches to remove biomass burning influences using OMI absorbing aerosol optical depth data (to account for transport of fire plumes) and anthropogenic influences using AATSR satellite data for persistent small-flame fires (gas flaring). The resulting biogenic HCHO columns (?HCHO) follow closely the distribution of vegetation patterns in Africa. We infer isoprene emission (EISOP) from the local sensitivity S=??HCHO/?EISOP derived with the GEOS-Chem chemical transport model using two alternate isoprene oxidation mechanisms, and verify the validity of this approach using AMMA aircraft observations over West Africa and a longitudinal transect across central Africa. Displacement error (smearing) is diagnosed by anomalously high values of S and the corresponding data are removed. We find significant sensitivity of S to NOx under low-NOx conditions that we fit to a linear function of tropospheric column NO2 from OMI. We estimate a 40% error in our inferred isoprene emissions under high-NOx conditions and 40–90% under low-NOx conditions. Comparison to the state-of-science MEGAN inventory indicates a large overestimate of central African rainforest emissions in that inventory.

E. A. Marais; D. J. Jacob; T. P. Kurosu; K. Chance; J. G. Murphy; C. Reeves; G. Mills; S. Casadio; D. B. Millet; M. P. Barkley; F. Paulot; J. Mao

2012-01-01

214

Isoprene emissions in Africa inferred from OMI observations of formaldehyde columns  

Directory of Open Access Journals (Sweden)

Full Text Available We use 2005–2009 satellite observations of formaldehyde (HCHO) columns from the OMI instrument to infer biogenic isoprene emissions at monthly 1 × 1° resolution over the African continent. Our work includes new approaches to remove biomass burning influences using OMI absorbing aerosol optical depth data (to account for transport of fire plumes) and anthropogenic influences using AATSR satellite data for persistent small-flame fires (gas flaring). The resulting biogenic HCHO columns (?HCHO) from OMI follow closely the distribution of vegetation patterns in Africa. We infer isoprene emission (EISOP) from the local sensitivity S = ??HCHO / ?EISOP derived with the GEOS-Chem chemical transport model using two alternate isoprene oxidation mechanisms, and verify the validity of this approach using AMMA aircraft observations over West Africa and a longitudinal transect across central Africa. Displacement error (smearing) is diagnosed by anomalously high values of S and the corresponding data are removed. We find significant sensitivity of S to NOx under low-NOx conditions that we fit to a linear function of tropospheric column NO2. We estimate a 40% error in our inferred isoprene emissions under high-NOx conditions and 40–90% under low-NOx conditions. Our results suggest that isoprene emission from the central African rainforest is much lower than estimated by the state-of-the-science MEGAN inventory.

E. A. Marais; D. J. Jacob; T. P. Kurosu; K. Chance; J. G. Murphy; C. Reeves; G. Mills; S. Casadio; D. B. Millet; M. P. Barkley; F. Paulot; J. Mao

2012-01-01

215

Atmospheric observations of carbon monoxide and fossil fuel CO2 emissions from East Asia  

DEFF Research Database (Denmark)

Flask samples from two sites in East Asia, Tae-Ahn Peninsula, Korea (TAP), and Shangdianzi, China (SDZ), were measured for trace gases including CO2, CO and fossil fuel CO2(CO(2)ff, derived from Delta(CO2)-C-14 observations). The five-year TAP record shows high CO(2)ff when local air comes from the Korean Peninsula. Most samples, however, reflect air masses from Northeastern China with lower CO(2)ff. Our small set of SDZ samples from winter 2009/2010 have strongly elevated CO(2)ff. Biospheric CO2 contributes substantially to total CO2 variability at both sites, even in winter when non-fossil CO2 sources (including photosynthesis, respiration, biomass burning and biofuel use) contribute 20-30% of the total CO2 enhancement. Carbon monoxide (CO) correlates strongly with CO(2)ff. The SDZ and TAP far-field (China influenced) samples have CO: CO(2)ff ratios (R-CO:CO2ff) of 47 +/- 2 and 44 +/- 3 ppb/ppm respectively, consistent with recent bottom-up inventory estimates and other observational studies. Locally influenced TAP samples fall into two distinct data sets, ascribed to air sourced from South Korea and North Korea. The South Korea samples have low R-CO:CO2ff of 13 +/- 3 ppb/ppm, slightly higher than bottom-up inventories, but consistent with emission ratios for other developed nations. We compare our CO(2)ff observations with modeled CO(2)ff using the FLEXPART Lagrangian particle dispersion model convolved with a bottom-up CO(2)ff emission inventories. The modeled annual mean CO(2)ff mole fractions are consistent with our observations when the model inventory includes the reported 63% increase in Chinese emissions from 2004 to 2010, whereas a model version which holds Chinese emissions flat is unable to replicate the observations.

Turnbull, Jocelyn C.; Tans, Pieter P.

2011-01-01

216

Detection efficiency of the VLF World-Wide Lightning Location Network (WWLLN): initial case study  

Directory of Open Access Journals (Sweden)

Full Text Available An experimental Very Low Frequency (VLF) World-Wide Lightning Location Network (WWLLN) has been developed through collaborations with research institutions across the world, providing global real-time locations of lightning discharges. As of April 2006, the network included 25 stations providing coverage for much of the Earth. In this paper we examine the detection efficiency of the WWLLN by comparing the locations from this network with lightning location data purchased from a commercial lightning location network operating in New Zealand. Our analysis confirms that WWLLN favours high peak current return stroke lightning discharges, and that discharges with larger currents are observed by more stations across the global network. We then construct a first principles detection efficiency model to describe the WWLLN, combining calibration information for each station with theoretical modelling to describe the expected amplitudes of the VLF sferics observed by the network. This detection efficiency model allows the prediction of the global variation in WWLLN lightning detection, and an estimate of the minimum CG return stroke peak current required to trigger the network. There are strong spatial variations across the globe, primarily due to station density and sensitivity. The WWLLN is currently best suited to study the occurrence and impacts of high peak-current lightning. For example, in 2005 about 12% of the global elve-producing lightning will have been located by the network. Since the lightning-EMP which produce elves has a high mean rate (210 per minute) it has the potential to significantly influence the ionosphere on regional scales.

C. J. Rodger; S. Werner; J. B. Brundell; E. H. Lay; N. R. Thomson; R. H. Holzworth; R. L. Dowden

2006-01-01

217

Inverse modelling of European N2O emissions: assimilating observations from different networks  

Directory of Open Access Journals (Sweden)

Full Text Available We describe the setup and first results of an inverse modelling system for atmospheric N2O, based on a four-dimensional variational (4DVAR) technique and the atmospheric transport zoom model TM5. We focus in this study on the European domain, utilizing a comprehensive set of quasi-continuous measurements over Europe, complemented by N2O measurements from the Earth System Research Laboratory of the National Oceanic and Atmospheric Administration (NOAA/ESRL) cooperative global air sampling network. Despite ongoing measurement comparisons among networks parallel measurements at a limited number of stations show that significant offsets exist among the different laboratories. Since the spatial gradients of N2O mixing ratios are of the same order of magnitude as these biases, the direct use of these biased datasets would lead to significant errors in the derived emissions. Therefore, in order to also use measurements with unknown offsets, a new bias correction scheme has been implemented within the TM5-4DVAR inverse modelling system, thus allowing the simultaneous assimilation of observations from different networks. The N2O bias corrections determined in the TM5-4DVAR system agree within 0.1 ppb (dry-air mole fraction) with the bias derived from the measurements at monitoring stations where parallel NOAA discrete air samples are available. The N2O emissions derived for the northwest European countries for 2006 show good agreement with the bottom-up emission inventories reported to the United Nations Framework Convention on Climate Change (UNFCCC). Moreover, the inverse model can significantly narrow the uncertainty range reported in N2O emission inventories, while the lack of measurements does not allow for better emission estimates in southern Europe. Several sensitivity experiments were performed to test the robustness of the results. It is shown that also inversions without detailed a priori spatio-temporal emission distributions are capable to reproduce major regional emission patterns within the footprint of the existing atmospheric network, demonstrating the strong constraints of the atmospheric observations on the derived emissions.

M. Corazza; P. Bergamaschi; A. T. Vermeulen; T. Aalto; L. Haszpra; F. Meinhardt; S. O'Doherty; R. Thompson; J. Moncrieff; E. Popa; M. Steinbacher; A. Jordan; E. Dlugokencky; C. Brühl; M. Krol; F. Dentener

2010-01-01

218

Inverse modelling of European N2O emissions: assimilating observations from different networks  

Directory of Open Access Journals (Sweden)

Full Text Available We describe the setup and first results of an inverse modelling system for atmospheric N2O, based on a four-dimensional variational (4DVAR) technique and the atmospheric transport zoom model TM5. We focus in this study on the European domain, utilizing a comprehensive set of quasi-continuous measurements over Europe, complemented by N2O measurements from the Earth System Research Laboratory of the National Oceanic and Atmospheric Administration (NOAA/ESRL) cooperative global air sampling network. Despite ongoing measurement comparisons among networks parallel measurements at a limited number of stations show that significant offsets exist among the different laboratories. Since the spatial gradients of N2O mixing ratios are of the same order of magnitude as these biases, the direct use of these biased datasets would lead to significant errors in the derived emissions. Therefore, in order to also use measurements with unknown offsets, a new bias correction scheme has been implemented within the TM5-4DVAR inverse modelling system, thus allowing the simultaneous assimilation of observations from different networks. The N2O bias corrections determined in the TM5-4DVAR system agree within ~0.1 ppb (dry-air mole fraction) with the bias derived from the measurements at monitoring stations where parallel NOAA discrete air samples are available. The N2O emissions derived for the northwest European and east European countries for 2006 show good agreement with the bottom-up emission inventories reported to the United Nations Framework Convention on Climate Change (UNFCCC). Moreover, the inverse model can significantly narrow the uncertainty range reported in N2O emission inventories for these countries, while the lack of measurements does not allow to reduce the uncertainties of emission estimates in southern Europe. Several sensitivity experiments were performed to test the robustness of the results. It is shown that also inversions without detailed a priori spatio-temporal emission distributions are capable to reproduce major regional emission patterns within the footprint of the existing atmospheric network, demonstrating the strong constraints of the atmospheric observations on the derived emissions.

M. Corazza; P. Bergamaschi; A. T. Vermeulen; T. Aalto; L. Haszpra; F. Meinhardt; S. O'Doherty; R. Thompson; J. Moncrieff; E. Popa; M. Steinbacher; A. Jordan; E. Dlugokencky; C. Brühl; M. Krol; F. Dentener

2011-01-01

219

Plasma waves observed by sounding rockets  

International Nuclear Information System (INIS)

[en] Observations of plasma wave phenomena have been conducted with several rockets launched at Kagoshima Space Center, Kyushu, Japan, and at Showa Base, Antarctica. This report presents some results of the observations in anticipation of having valuable comments from other plasma physicists, especially from those who are concerned with laboratory plasma. In the K-9M-41 rocket experiment, VLF plasma waves were observed. In this experiment, the electron beam of several tens of uA was emitted from a hot cathode when a positive dc bias changing from 0 to 10V at 1V interval each second was applied to a receiving dipole antenna. The discrete emissions with 'U' shaped frequency spectrum were observed for the dc bias over 3 volts. The U emissions appeared twice per spin period of the rocket. Similar rocket experiment was performed at Showa Base using a loop and dipole antenna and without hot cathode. Emissions were observed with varying conditions. At present, the authors postulate that such emissions may be produced just in the vicinity of a rocket due to a kind of wake effect. (Aoki, K.)

1976-05-29

220

Sensitivity of wetland methane emissions to model assumptions: application and model testing against site observations  

Science.gov (United States)

Methane emissions from natural wetlands and rice paddies constitute a large proportion of atmospheric methane, but the magnitude and year-to-year variation of these methane sources are still unpredictable. Here we describe and evaluate the integration of a methane biogeochemical model (CLM4Me; Riley et al., 2011) into the Community Land Model 4.0 (CLM4CN) in order to better explain spatial and temporal variations in methane emissions. We test new functions for soil pH and redox potential that impact microbial methane production in soils. We also constrain aerenchyma in plants in always-inundated areas in order to better represent wetland vegetation. Satellite inundated fraction is explicitly prescribed in the model, because there are large differences between simulated fractional inundation and satellite observations, and thus we do not use CLM4-simulated hydrology to predict inundated areas. A rice paddy module is also incorporated into the model, where the fraction of land used for rice production is explicitly prescribed. The model is evaluated at the site level with vegetation cover and water table prescribed from measurements. Explicit site level evaluations of simulated methane emissions are quite different than evaluating the grid-cell averaged emissions against available measurements. Using a baseline set of parameter values, our model-estimated average global wetland emissions for the period 1993-2004 were 256 Tg CH4 yr-1 (including the soil sink) and rice paddy emissions in the year 2000 were 42 Tg CH4 yr-1. Tropical wetlands contributed 201 Tg CH4 yr-1, or 78% of the global wetland flux. Northern latitude (>50 N) systems contributed 12 Tg CH4 yr-1. However, sensitivity studies show a large range (150-346 Tg CH4 yr-1) in predicted global methane emissions (excluding emissions from rice paddies). The large range is sensitive to (1) the amount of methane transported through aerenchyma, (2) soil pH (±100 Tg CH4 yr-1), and (3) redox inhibition (±45 Tg CH4 yr-1). Results are sensitive to biases in the CLMCN and to errors in the satellite inundation fraction. In particular, the high latitude methane emission estimate may be biased low due to both underestimates in the high-latitude inundated area captured by satellites and unrealistically low high-latitude productivity and soil carbon predicted by CLM4.

Meng, L.; Hess, P. G. M.; Mahowald, N. M.; Yavitt, J. B.; Riley, W. J.; Subin, Z. M.; Lawrence, D. M.; Swenson, S. C.; Jauhiainen, J.; Fuka, D. R.

2012-07-01

 
 
 
 
221

Sensitivity of wetland methane emissions to model assumptions: application and model testing against site observations  

Directory of Open Access Journals (Sweden)

Full Text Available Methane emissions from natural wetlands and rice paddies constitute a large proportion of atmospheric methane, but the magnitude and year-to-year variation of these methane sources are still unpredictable. Here we describe and evaluate the integration of a methane biogeochemical model (CLM4Me; Riley et al., 2011) into the Community Land Model 4.0 (CLM4CN) in order to better explain spatial and temporal variations in methane emissions. We test new functions for soil pH and redox potential that impact microbial methane production in soils. We also constrain aerenchyma in plants in always-inundated areas in order to better represent wetland vegetation. Satellite inundated fraction is explicitly prescribed in the model, because there are large differences between simulated fractional inundation and satellite observations, and thus we do not use CLM4-simulated hydrology to predict inundated areas. A rice paddy module is also incorporated into the model, where the fraction of land used for rice production is explicitly prescribed. The model is evaluated at the site level with vegetation cover and water table prescribed from measurements. Explicit site level evaluations of simulated methane emissions are quite different than evaluating the grid-cell averaged emissions against available measurements. Using a baseline set of parameter values, our model-estimated average global wetland emissions for the period 1993–2004 were 256 Tg CH4 yr?1 (including the soil sink) and rice paddy emissions in the year 2000 were 42 Tg CH4 yr?1. Tropical wetlands contributed 201 Tg CH4 yr?1, or 78% of the global wetland flux. Northern latitude (>50 N) systems contributed 12 Tg CH4 yr?1. However, sensitivity studies show a large range (150–346 Tg CH4 yr?1) in predicted global methane emissions (excluding emissions from rice paddies). The large range is sensitive to (1) the amount of methane transported through aerenchyma, (2) soil pH (±100 Tg CH4 yr?1), and (3) redox inhibition (±45 Tg CH4 yr?1). Results are sensitive to biases in the CLMCN and to errors in the satellite inundation fraction. In particular, the high latitude methane emission estimate may be biased low due to both underestimates in the high-latitude inundated area captured by satellites and unrealistically low high-latitude productivity and soil carbon predicted by CLM4.

L. Meng; P. G. M. Hess; N. M. Mahowald; J. B. Yavitt; W. J. Riley; Z. M. Subin; D. M. Lawrence; S. C. Swenson; J. Jauhiainen; D. R. Fuka

2012-01-01

222

Observation of vibronic emission spectrum of jet-cooled 3,5-difluorobenzyl radical.  

UK PubMed Central (United Kingdom)

We applied the technique of corona-excited supersonic expansion using a pinhole-type glass nozzle to observe the vibronic emission spectrum of jet-cooled benzyl-type radicals from the corona discharge of precursor 3,5-difluorotoluene seeded in a large amount of inert helium carrier gas. The vibronically well-resolved emission spectrum was recorded with a long-path monochromator in the visible region. After subtracting the vibronic bands originating from isomeric difluorobenzyl radicals from the observed spectrum, we identified for the first time the bands belonging to the 3,5-difluorobenzyl radical, from which the electronic energy and vibrational mode frequencies of the 3,5-difluorobenzyl radical were accurately determined in the ground electronic state by comparison with those of the precursor and with those from an ab initio calculation.

Lee SW; Yoon YW; Lee SK

2010-09-01

223

Observation of vibronic emission spectrum of jet-cooled 3,5-difluorobenzyl radical.  

Science.gov (United States)

We applied the technique of corona-excited supersonic expansion using a pinhole-type glass nozzle to observe the vibronic emission spectrum of jet-cooled benzyl-type radicals from the corona discharge of precursor 3,5-difluorotoluene seeded in a large amount of inert helium carrier gas. The vibronically well-resolved emission spectrum was recorded with a long-path monochromator in the visible region. After subtracting the vibronic bands originating from isomeric difluorobenzyl radicals from the observed spectrum, we identified for the first time the bands belonging to the 3,5-difluorobenzyl radical, from which the electronic energy and vibrational mode frequencies of the 3,5-difluorobenzyl radical were accurately determined in the ground electronic state by comparison with those of the precursor and with those from an ab initio calculation. PMID:20677814

Lee, Seung Woon; Yoon, Young Wook; Lee, Sang Kuk

2010-09-01

224

Observation of Free-Electron-Laser-Induced Collective Spontaneous Emission (Superfluorescence)  

International Nuclear Information System (INIS)

We have observed and characterized 501.6 nm collective spontaneous emission (superfluorescence) following 1s2?1s3p excitation of helium atoms by 53.7 nm free-electron laser radiation. Emitted pulse energies of up to 100 nJ are observed, corresponding to a photon number conversion efficiency of up to 10%. We observe the peak intensity to scale as ?2 and the emitted pulse width and delay to scale as ?-1, where ? is the atom number density. Emitted pulses as short as 1 ps are observed, which corresponds to a rate around 75 000 times faster than the spontaneous 1s3p?1s2s decay rate. To our knowledge, this is the first observation of superfluorescence following pumping in the extreme ultraviolet wavelength region, and extension of the technique to the generation of extreme ultraviolet and x-ray superfluorescence pulses should be straightforward by using suitable atomic systems and pump wavelengths.

2011-11-04

225

Recent increases in trifluoromethane (HFC-23) global emissions and early atmospheric changes observed for other hydrofluorocarbons  

Science.gov (United States)

Trifluoromethane (HFC-23) is an unintended by-product of chlorodifluoromethane (HCFC-22) production and has a 100-yr global warming potential of 14,800. Firn-air and ambient air measurements of HFC-23 from three firn sampling excursions to Antarctica between 2001 and 2009 are used to construct a consistent atmospheric history for this chemical in the Southern Hemisphere. The results show continued increases in the atmospheric abundance of HFC-23 and imply substantial increases in HFC-23 global emissions since 2003. These emission increases are coincident with rapidly increasing HCFC-22 production in developing countries and are observed despite efforts in recent years to limit emissions of HFC-23 through the Kyoto Protocol’s Clean Development Mechanism. These results will be considered along with new observations of additional HFCs from archived air, firn air, and ongoing flask-air measurements. Considered together, atmospheric increases observed for hydrochlorofluorocarbons and hydrofluorocarbons accounted for ~9% of the increase in total direct radiative forcing from anthropogenic gases during 2003-2008, an addition that was slightly larger than attributable to N2O over this same period.

Montzka, S. A.; Miller, B. R.; Battle, M. O.; Aydin, K. M.; Fahey, D. W.; Hall, B. D.; Miller, L.; Verhulst, K. R.; Saltzman, E.; McFarland, M.

2009-12-01

226

XMM-Newton observations of X-ray emission from Jupiter  

CERN Multimedia

We present the results of two XMM-Newton observations of Jupiter carried out in 2003 for 100 and 250 ks (or 3 and 7 planet rotations) respectively. X-ray images from the EPIC CCD cameras show prominent emission from the auroral regions in the 0.2 - 2.0 keV band: the spectra are well modelled by a combination of emission lines, including most prominently those of highly ionised oxygen (OVII and OVIII). In addition, and for the first time, XMM-Newton reveals the presence in both aurorae of a higher energy component (3 - 7 keV) which is well described by an electron bremsstrahlung spectrum. This component is found to be variable in flux and spectral shape during the Nov. 2003 observation, which corresponded to an extended period of intense solar activity. Emission from the equatorial regions of Jupiter's disk is also observed, with a spectrum consistent with that of solar X-rays scattered in the planet's upper atmosphere. Jupiter's X-rays are spectrally resolved with the RGS which clearly separates the prominent...

Branduardi-Raymont, G; Elsner, R F; Gladstone, G R; Ramsay, G; Rodríguez, P; Soria, R; Waite, J H; Cravens, T E

2005-01-01

227

Observation of Collective-Emission-Induced Cooling inside an Optical Cavity  

CERN Multimedia

We report the observation of collective-emission-induced, velocity-dependent light forces. One third of a falling sample containing 3 x 10^6 cesium atoms illuminated by a horizontal standing wave is stopped by cooperatively emitting light into a vertically oriented confocal resonator. We observe decelerations up to 1500 m/s^2 and cooling to temperatures as low as 7 uK, well below the free space Doppler limit. The measured forces substantially exceed those predicted for a single two-level atom.

Chan, H W; Vuletic, V; Chan, Hilton W.; Black, Adam T.; Vuletic, Vladan

2002-01-01

228

Observation of {sup 10}Be Emission in the Cold Ternary Spontaneous Fission of {sup 252}Cf  

Energy Technology Data Exchange (ETDEWEB)

The emission of {sup 10}Be in ternary cold neutronless spontaneous fission of {sup 252}Cf is observed with the Gammasphere consisting of 72 detectors. The {gamma} ray corresponding to the decay of the first 2{sup +} state in {sup 10}Be is observed in coincidence with the {gamma} rays of the fission partners of {sup 96}Sr and {sup 146}Ba . The yield to the first excited state of {sup 10}Be in the {sup 96}Sr- {sup 146}Ba split is the order of 4.0{times}10{sup {minus}4} per 100 fission events. {copyright} {ital 1998} {ital The American Physical Society}

Ramayya, A.V.; Hwang, J.K.; Hamilton, J.H.; Sandulescu, A.; Florescu, A.; Ter-Akopian, G.M.; Daniel, A.V.; Popeko, G.S.; Greiner, W. [Physics Department, Vanderbilt University, Nashville, Tennessee 37235 (United States); Sandulescu, A.; Florescu, A. [Institute for Atomic Physics, Bucharest, P.O. Box MG-6 (Romania); Sandulescu, A.; Greiner, W. [Institute fuer Theoretische Physik der J. W. Goethe Universitaet, D-60054, Frankfurt am Main (Germany); Ter-Akopian, G.M.; Daniel, A.V.; Oganessian, Y.T.; Popeko, G.S. [Joint Institute for Nuclear Research, Dubna 141980 (Russia); Florescu, A.; Ter-Akopian, G.M.; Daniel, A.V.; Greiner, W. [Joint Institute for Heavy Ion Research, Oak Ridge, Tennessee 37830 (United States); Cole, J.D. [Idaho National Engineering Laboratory, Idaho Falls, Idaho 83415-2114 (United States)

1998-08-01

229

The Predicted Signature of Neutrino Emission in Observations of Pulsating Pre-White Dwarf Stars  

CERN Document Server

Pre-white dwarf (PWD) star evolution can be driven by energy losses from neutrino interactions in the core. Unlike solar neutrinos, these are not the by-product of nuclear fusion, but instead result from electron scattering processes in the hot, dense regions of the PWD core. We show that the observed rate of period change in cool PWD pulsators will constrain neutrino emission in their cores, and we identify appropriate targets for future observation. Such a measurement will tell us whether the theories of lepton interactions correctly describe the production rates and therefore neutrino cooling of PWD evolution. This would represent the first test of standard lepton theory in dense plasma.

O'Brien, M S; Kawaler, Steven D.

2000-01-01

230

Chandra Observations of Nuclear X-ray Emission from a Sample of Radio Sources  

CERN Document Server

We present the X-ray properties of a sample of 17 radio sources observed with the Chandra X-ray Observatory as part of a project aimed at studying the X-ray emission from their radio jets. In this paper, we concentrate on the X-ray properties of the unresolved cores. The sample includes 16 quasars (11 core-dominated and 5 lobe-dominated) in the redshift range z=0.30--1.96, and one low-power radio-galaxy at z=0.064. No diffuse X-ray emission is present around the cores of the quasars, except for the nearby low-power galaxy that has diffuse emission on a scale and with a luminosity consistent with other FRIs. No high-amplitude, short-term variability is detected within the relatively short Chandra exposures. However, 1510-089 shows low-amplitude flux changes with a timescale of $\\sim$25 minutes. The X-ray spectra of the quasar cores are generally well described by a single power law model with Galactic absorption. However, in six quasars we find soft X-ray excess emission below 1.6 keV. Interestingly, we detect...

Gambill, J K; Chartas, G; Cheung, C C; Maraschi, L; Tavecchio, F; Urry, C M; Pesce, J E

2003-01-01

231

Soft and hard X-ray excess emission in Abell 3112 observed with Chandra  

CERN Multimedia

Chandra ACIS-S observations of the galaxy cluster A3112 feature the presence of an excess of X-ray emission above the contribution from the diffuse hot gas, which can be equally well modeled with an additional non-thermal power-law model or with a low-temperature thermal model of low metal abundance. We show that the excess emission cannot be due to uncertainties in the background subtraction or in the Galactic HI column density. Calibration uncertainties in the ACIS detector that may affect our results are addressed by comparing the Chandra data to XMM MOS and PN spectra. While differences between the three instruments remain, all detect the excess in similar amounts, providing evidence against an instrumental nature of the excess. Given the presence of non-thermal radio emission near the center of A3112, we argue that the excess X-ray emission is of non-thermal nature and distributed throughout the entire X-ray bandpass, from soft to hard X-rays. The excess can be explained with the presence of a population...

Bonamente, M; Lieu, R

2007-01-01

232

Using Swift observations of prompt and afterglow emission to classify GRBs  

CERN Multimedia

We present an analysis of early BAT and XRT data for 107 gamma--ray bursts (GRBs) observed by the Swift satellite. We use these data to examine the behaviour of the X-ray light curve and propose a classification scheme for GRBs based on this behaviour. As found for previous smaller samples, the earliest X-ray light curve can be well described by an exponential which relaxes into a power law, often with flares superimposed. The later emission is well fit using a similar functional form and we find that these two functions provide a good description of the entire X-ray light curve. For the prompt emission, the transition time between the exponential and the power law gives a well-defined timescale, T_p, for the burst duration. We use T_p, the spectral index of the prompt emission, beta_p, and the prompt power law decay index, alpha_p to define four classes of burst: short, slow, fast and soft. Bursts with slowly declining emission have spectral and temporal properties similar to the short bursts despite having ...

O'Brien, P T

2007-01-01

233

Emission ratios of anthropogenic volatile organic compounds in northern mid-latitude megacities: Observations versus emission inventories in Los Angeles and Paris  

Science.gov (United States)

Ground-based and airborne volatile organic compound (VOC) measurements in Los Angeles, California, and Paris, France, during the Research at the Nexus of Air Quality and Climate Change (CalNex) and Megacities: Emissions, Urban, Regional and Global Atmospheric Pollution and Climate Effects, and Integrated Tools for Assessment and Mitigation (MEGAPOLI) campaigns, respectively, are used to examine the spatial variability of the composition of anthropogenic VOC urban emissions and to evaluate regional emission inventories. Two independent methods that take into account the effect of chemistry were used to determine the emission ratios of anthropogenic VOCs (including anthropogenic isoprene and oxygenated VOCs) over carbon monoxide (CO) and acetylene. Emission ratios from both methods agree within ±20%, showing the reliability of our approach. Emission ratios for alkenes, alkanes, and benzene are fairly similar between Los Angeles and Paris, whereas the emission ratios for C7-C9 aromatics in Paris are higher than in Los Angeles and other French and European Union urban areas by a factor of 2-3. The results suggest that the emissions of gasoline-powered vehicles still dominate the hydrocarbon distribution in northern mid-latitude urban areas, which disagrees with emission inventories. However, regional characteristics like the gasoline composition could affect the composition of hydrocarbon emissions. The observed emission ratios show large discrepancies by a factor of 2-4 (alkanes and oxygenated VOC) with the ones derived from four reference emission databases. A bias in CO emissions was also evident for both megacities. Nevertheless, the difference between measurements and inventory in terms of the overall OH reactivity is, in general, lower than 40%, and the potential to form secondary organic aerosols (SOA) agrees within 30% when considering volatile organic emissions as the main SOA precursors.

Borbon, Agnes; Gilman, J. B.; Kuster, W. C.; Grand, N.; Chevaillier, S.; Colomb, A.; Dolgorouky, C.; Gros, V.; Lopez, M.; Sarda-Esteve, R.; Holloway, J.; Stutz, J.; Petetin, H.; McKeen, S.; Beekmann, M.; Warneke, C.; Parrish, D. D.; Gouw, J. A.

2013-02-01

234

Fermi observations of high-energy gamma-ray emission from GRB 090217A  

CERN Document Server

The Fermi observatory is advancing our knowledge of Gamma-Ray Bursts (GRBs) through pioneering observations at high energies, covering more than 7 decades in energy with the two on-board detectors, the Large Area Telescope (LAT) and the Gamma-ray Burst Monitor (GBM). Here we report on the observation of the long GRB 090217A which triggered the GBM and has been detected by the LAT with a significance greater than 9 sigma. We present the GBM and LAT observations and on-ground analyses, including the time-resolved spectra and the study of the temporal profile from 8 keV up to 1 GeV. All spectra are well reproduced by a Band model. We compare these observations to the first two LAT-detected, long bursts GRB 080825C and GRB 080916C. These bursts were found to have time-dependent spectra and exhibited a delayed onset of the high-energy emission, which are not observed in the case of GRB 090217A. We discuss some theoretical implications for the high-energy emission of GRBs.

Fermi-LAT,

2010-01-01

235

Emissions of mercury in southern Africa derived from long-term observations at Cape Point, South Africa  

Directory of Open Access Journals (Sweden)

Full Text Available Mercury emissions in South Africa have so far been estimated only by a bottom-up approach from activities and emission factors for different processes. In this paper we derive GEM/CO (GEM being gaseous elemental mercury, Hg0), GEM/CO2, GEM/CH4, CO/CO2, CH4/CO2, and CH4/CO emission ratios from plumes observed during long-term monitoring of these species at Cape Point between March 2007 and December 2009. The average observed GEM/CO, GEM/CO2, GEM/CH4, CO/CO2, CH4/CO2, and CH4/CO emission ratios were 2.40 ± 2.65 pg m?3 ppb?1 (n = 47), 62.7 ± 80.2 pg m?3 ppm?1 (n = 44), 3.61 ± 4.66 pg m?3 ppb?1 (n = 46), 35.6 ± 25.4 ppb ppm?1 (n = 52), 20.2 ± 15.5 ppb ppm?1 (n = 48), and 0.876 ± 1.106 ppb ppb?1 (n = 42), respectively. The observed CO/CO2, CH4/CO2, and CH4/CO emission ratios agree within the combined uncertainties of the observations and emissions with the ratios calculated from EDGAR (version 4.2) CO2, CO, and CH4 inventories for South Africa and southern Africa (South Africa, Lesotho, Swaziland, Namibia, Botswana, Zimbabwe, and Mozambique) in 2007 and 2008 (inventories for 2009 are not available yet). Total elemental mercury emission of 13.1, 15.2, and 16.1 t Hg yr?1 are estimated independently using the GEM/CO, GEM/CO2, and GEM/CH4 emission ratios and the annual mean CO, CO2, and CH4 emissions, respectively, of South Africa in 2007 and 2008. The average of these independent estimates of 14.8 t GEM yr?1 is much less than the total emission of 257 t Hg yr?1 shown by older inventories which are now considered to be wrong. Considering the uncertainties of our emission estimate, of the emission inventories, and the fact that emission of GEM represents 50–78 % of all mercury emissions, our estimate is comparable to the currently cited GEM emissions in 2004 and somewhat smaller than emissions in 2006. A further increase of mercury emissions due to increasing electricity consumption will lead to a more pronounced difference. A quantitative assessment of the difference and its significance, however, will require emission inventories for the years of observations (2007–2009) as well as better data on the speciation of the total mercury emissions in South Africa.

E.-G. Brunke; R. Ebinghaus; H. H. Kock; C. Labuschagne; F. Slemr

2012-01-01

236

HST WFC3 Early Release Science: Emission-Line Galaxies from IR Grism Observations  

CERN Document Server

We present grism spectra of emission--line galaxies (ELGs) from 0.6--1.6 microns from the Wide Field Camera 3 (WFC3) on the Hubble Space Telescope (HST). These new infrared grism data augment previous optical Advanced Camera for Surveys G800L (0.6--0.95 micron) grism data in GOODS--South, extending the wavelength covereage well past the G800L red cutoff. The ERS grism field was observed at a depth of 2 orbits per grism, yielding spectra of hundreds of faint objects, a subset of which are presented here. ELGs are studied via the \\Ha, \\OIII, and \\OII\\ emission lines detected in the redshift ranges 0.2$\\cle$z$\\cle$1.6, 1.2$\\cle$z$\\cle$2.4 and 2.0$\\cle$z$\\cle$3.6 respectively in the G102 (0.8--1.1 microns; R$\\sim$210) and G141 (1.1--1.6 microns; R$\\sim$130) grisms. The higher spectral resolution afforded by the WFC3 grisms also reveals emission lines not detectable with the G800L grism (e.g., \\SII\\ and \\SIII\\ lines). From these relatively shallow observations, line luminosities, star--formation rates, and grism s...

Straughn, A N; Kuemmel, M; Walsh, J R; Cohen, S H; Gardner, J P; Windhorst, R A; O'Connell, R W; Pirzkal, N; Meurer, G; McCarthy, P J; Hathi, N P; Malhotra, S; Rhoads, J; Balick, B; Bond, H E; Calzetti, D; Disney, M J; Dopita, M A; Frogel, J A; Hall, D N B; Holtzman, J A; Kimble, R A; Luppino, G; Paresce, F; Saha, A; Silk, J I; Trauger, J T; Walker, A R; Whitmore, B C; Young, E T

2010-01-01

237

OBSERVATION OF EXTENDED VERY HIGH ENERGY EMISSION FROM THE SUPERNOVA REMNANT IC 443 WITH VERITAS  

International Nuclear Information System (INIS)

We present evidence that the very high energy (VHE, E > 100 GeV) gamma-ray emission coincident with the supernova remnant IC 443 is extended. IC 443 contains one of the best studied sites of supernova remnant/molecular cloud interaction and the pulsar wind nebula CXOU J061705.3+222127, both of which are important targets for VHE observations. VERITAS observed IC 443 for 37.9 hr during 2007 and detected emission above 300 GeV with an excess of 247 events, resulting in a significance of 8.3 standard deviations (?) before trials and 7.5? after trials in a point-source search. The emission is centered at 6h16m51s + 22030'11'' (J2000) ±0.003stat ± 0.008sys, with an intrinsic extension of 0.016 ± 0.003stat ± 0.004sys. The VHE spectrum is well fit by a power law (dN/dE = N 0 x (E/TeV)-?) with a photon index of 2.99 ± 0.38stat ± 0.3sys and an integral flux above 300 GeV of (4.63 ± 0.90stat ± 0.93sys) x 10-12 cm-2 s-1. These results are discussed in the context of existing models for gamma-ray production in IC 443.

2009-06-20

238

Observation of Extended VHE Emission from the Supernova Remnant IC 443 with VERITAS  

CERN Multimedia

We present evidence that the very-high-energy (VHE, E > 100 GeV) gamma-ray emission coincident with the supernova remnant IC 443 is extended. IC 443 contains one of the best-studied sites of supernova remnant/molecular cloud interaction and the pulsar wind nebula CXOU J061705.3+222127, both of which are important targets for VHE observations. VERITAS observed IC 443 for 37.9 hours during 2007 and detected emission above 300 GeV with an excess of 247 events, resulting in a significance of 8.3 standard deviations (sigma) before trials and 7.5 sigma after trials in a point-source search. The emission is centered at 06 16 51 +22 30 11 (J2000) +- 0.03_stat +- 0.08_sys degrees, with an intrinsic extension of 0.16 +- 0.03_stat +- 0.04_sys degrees. The VHE spectrum is well fit by a power law (dN/dE = N_0 * (E/TeV)^-Gamma) with a photon index of 2.99 +- 0.38_stat +- 0.3_sys and an integral flux above 300 GeV of (4.63 +- 0.90_stat +- 0.93_sys) * 10^-12 cm^-2 s^-1. These results are discussed in the context of existing ...

Acciari, V A; Arlen, T; Aune, T; Bautista, M; Beilicke, M; Benbow, W; Bradbury, S M; Buckley, J H; Bugaev, V; Butt, Y; Byrum, K; Cannon, A; Celik, O; Cesarini, A; Chow, Y C; Ciupik, L; Cogan, P; Colin, P; Cui, W; Daniel, M K; Dickherber, R; Duke, C; Dwarkadas, V V; Ergin, T; Fegan, S J; Finley, J P; Finnegan, G; Fortin, P; Fortson, L; Furniss, A; Gall, D; Gibbs, K; Gillanders, G H; Godambe, S; Grube, J; Guenette, R; Gyuk, G; Hanna, D; Hays, E; Holder, J; Horan, D; Hui, C M; Humensky, T B; Imran, A; Kaaret, Philip; Karlsson, N; Kertzman, M; Kieda, D; Kildea, J; Konopelko, A; Krawczynski, H; Krennrich, F; Lang, M J; Le Bohec, S; Maier, G; McCann, A; McCutcheon, M; Millis, J; Moriarty, P; Ong, R A; Otte, A N; Pandel, D; Perkins, J S; Pohl, M; Quinn, J; Ragan, K; Reyes, L C; Reynolds, P T; Roache, E; Rose, H J; Schroedter, M; Sembroski, G H; Smith, A W; Steele, D; Swordy, S P; Theiling, M; Toner, J A; Valcarcel, L; Varlotta, A; Vasilev, V V; Vincent, S; Wagner, R G; Wakely, S P; Ward, J E; Weekes, T C; Weinstein, A; Weisgarber, T; Williams, D A; Wissel, S; Wood, M; Zitzer, B

2009-01-01

239

Molecular Hydrogen Emission Lines in Far Ultraviolet Spectroscopic Explorer Observations of Mira B  

CERN Multimedia

We present new Far Ultraviolet Spectroscopic Explorer (FUSE) observations of Mira A's wind-accreting companion star, Mira B. We find that the strongest lines in the FUSE spectrum are H2 lines fluoresced by H I Lyman-alpha. A previously analyzed Hubble Space Telescope (HST) spectrum also shows numerous Lyman-alpha fluoresced H2 lines. The HST lines are all Lyman band lines, while the FUSE H2 lines are mostly Werner band lines, many of them never before identified in an astrophysical spectrum. We combine the FUSE and HST data to refine estimates of the physical properties of the emitting H2 gas. We find that the emission can be reproduced by an H2 layer with a temperature and column density of T=3900 K and log N(H2)=17.1, respectively. Another similarity between the HST and FUSE data, besides the prevalence of H2 emission, is the surprising weakness of the continuum and high temperature emission lines, suggesting that accretion onto Mira B has weakened dramatically. The UV fluxes observed by HST on 1999 August ...

Wood, B E; Wood, Brian E.; Karovska, Margarita

2004-01-01

240

Observation of novel radioactive decay by spontaneous emission of complex nuclei  

International Nuclear Information System (INIS)

[en] Two years of experimental investigation on the subject of spontaneous emission of intermediate-mass fragments is described in this manuscript. A short introduction on this subject and a historical review are presented in chapter 1. In chapter 2, the author describe the experimental methods which led to the observation of 14C emission in polycarbonate etched-track detectors from the isotopes 222Ra, 223Ra, 224Ra and 226Ra at the branching ratios with respect to ?-decay of (3.7 +/- 0.6) x 10-10, (6.1 +/- 1.0) x 10-10, (4.3 +/- 1.2) x 10-10 and (2.9 +/- 1.0) x 10-11 respectively. Branching ratio limits for heavy-ion emission from 221Fr, 221Ra and 225Ac were determined to be at -14, -13 and -13 respectively for the 90% C.L. The emission of 24Ne from 232U at a branching ratio of (2.0 +/- 0.5) x 10-12 has been discovered using polyethylene terephthalate etched-track plastics. A confirmation of 24Ne and/or 25Ne emission from 233U at a branching ratio of (5.3 +/- 2.3) x 10-13 is also reported. In chapter 3, three models of intermediate-mass decay are discussed-the analytic superasymmetric fission model, the model by Shi and Swiatecki, and a model based on a square-well + Coulomb potential

1986-01-01

 
 
 
 
241

First Observation of Beta-Delayed Three-Proton Emission in 45Fe  

Energy Technology Data Exchange (ETDEWEB)

The decay of extremely neutron deficient 45Fe has been studied by means of a new type of a gaseous detector in which a technique of digital imaging was used to record tracks of charged particles. The + decay channels accompanied by proton emission were clearly identified. In addition to -delayed one-proton and -delayed two-proton decays, -delayed three-proton emission was recorded which represents the first direct and unambiguous observation of this decay channel. The branching ratio for the decay of 45Fe and the corresponding partial half-life are found to be 0.30 0.04 and T1/2( ) = 8.7 1.3 ms, respectively.

Miernik, K. [University of Warsaw; Dominik, Wojciech [Warsaw University; Janas, Z. [University of Warsaw; Pfutzner, M. [University of Warsaw; Bingham, C. R. [University of Tennessee, Knoxville (UTK); Czyrkowski, Henryk [Warsaw University; Cwiok, Mikolaj [Warsaw University; Darby, Iain [University of Tennessee, Knoxville (UTK); Djbrowski, R. [University of Warsaw; Ginter, T. N. [Michigan State University, East Lansing; Grzywacz, R. [University of Tennessee, Knoxville (UTK); Karny, M. [University of Warsaw; Korgul, A. [University of Warsaw; Kusmierz, W. [University of Warsaw; Liddick, Sean [University of Tennessee, Knoxville (UTK); Rajabali, Mustafa [University of Tennessee, Knoxville (UTK); Rykaczewski, Krzysztof Piotr [ORNL; Stolz, A. [Michigan State University, East Lansing

2007-01-01

242

Cassini and Wind stereoscopic observations of Jovian nonthermal radio emissions: Measurement of beam widths  

Science.gov (United States)

During two intervals in 1999, simultaneous observations of Jupiter's decametric and hectometric radio emissions were made with the Cassini radio and plasma wave instrument (RPWS) and the radio and plasma wave instrument (WAVES) on the Wind spacecraft in Earth orbit. During January the Jovian longitude difference between the two spacecraft was about 5°, whereas for the August-September Earth flyby of Cassini, the angle ranged from 0° to about 2.5° (the Jovicentric latitudinal difference was <0.3° during both intervals). With these separations the instantaneous widths of the walls of the hollow conical radiation beams of some of the decametric arcs were measured by cross correlating dynamic spectra. The results suggest that the typical width is approximately 1.5°+/-0.5°. The conical beams seem to move at Io's revolution rate for Io-controlled arcs. Additionally, some of the nonarc hectometric wavelength emissions show some properties of both wide and very narrow beam widths.

Kaiser, M. L.; Zarka, P.; Kurth, W. S.; Hospodarsky, G. B.; Gurnett, D. A.

2000-07-01

243

Sensitivity of wetland methane emissions to model assumptions: application and model testing against site observations  

Directory of Open Access Journals (Sweden)

Full Text Available Methane emissions from natural wetlands and rice paddies constitute a large proportion of atmospheric methane, but the magnitude and year-to-year variation of these methane sources is still unpredictable. Here we describe and evaluate the integration of a methane biogeochemical model (CLM4Me; Riley et al., 2011) into the Community Land Model 4.0 (CLM4CN) in order to better explain spatial and temporal variations in methane emissions. We test new functions for soil pH and redox potential that impact microbial methane production in soils. We also constrain aerenchyma in plants in always-inundated areas in order to better represent wetland vegetation. Satellite inundated fraction is explicitly prescribed in the model because there are large differences between simulated fractional inundation and satellite observations. A rice paddy module is also incorporated into the model, where the fraction of land used for rice production is explicitly prescribed. The model is evaluated at the site level with vegetation cover and water table prescribed from measurements. Explicit site level evaluations of simulated methane emissions are quite different than evaluating the grid cell averaged emissions against available measurements. Using a baseline set of parameter values, our model-estimated average global wetland emissions for the period 1993–2004 were 256 Tg CH4 yr?1, and rice paddy emissions in the year 2000 were 42 Tg CH4 yr?1. Tropical wetlands contributed 201 Tg CH4 yr?1, or 78 % of the global wetland flux. Northern latitude (>50 N) systems contributed 12 Tg CH4 yr?1. We expect this latter number may be an underestimate due to the low high-latitude inundated area captured by satellites and unrealistically low high-latitude productivity and soil carbon predicted by CLM4. Sensitivity analysis showed a large range (150–346 Tg CH4 yr?1) in predicted global methane emissions. The large range was sensitive to: (1) the amount of methane transported through aerenchyma, (2) soil pH (± 100 Tg CH4 yr?1), and (3) redox inhibition (± 45 Tg CH4 yr?1).

L. Meng; P. G. M. Hess; N. M. Mahowald; J. B. Yavitt; W. J. Riley; Z. M. Subin; D. M. Lawrence; S. C. Swenson; J. Jauhiainen; D. R. Fuka

2011-01-01

244

Directivity of high-energy emission from solar flares: solar-maximum mission observations  

Energy Technology Data Exchange (ETDEWEB)

The data base consisting of flares detected by the gamma-ray spectrometer (GRS) on board the Solar Maximum Mission (SMM) satellite is used to study the directivity of high-energy radiation. A number of observations strongly indicate that the high-energy emission from flares is anisotropic. They are the following: the fraction of events detected at energies > 300 keV near the limb is higher than is expected for isotropically emitting flares; there is a statistically significant center-to-limb variation in the 300-keV to 1-MeV spectra of flares detected by the SMM GRS; the 25-200 keV hard x-ray spectra measured during the impulsive phase by the SMM GRS show a center-to-limb variation; and nearly all of the events detected at > 10 MeV are located near the limb. Then these observations are best explained by models in which nonthermal electrons radiate in a thick-target emission region lower in the atmosphere. To produce the observed center-to-limb variations, one needs an electron distribution that has an intensity which increases with angle from the outward normal. Candidate distributions are downwardly directed Gaussian beams and pancake distributions that peak in directions parallel to the photosphere. During the impulsive phase of the flare this nonthermal component seems to be visible down to energies less than 40 keV. These results imply that the procedure normally used to deduce the properties of flare-accelerated electrons from hard x-ray and gamma-ray observations an substantially underestimate the spectral hardness and number of high-energy electrons. Another consequence is that, on the average, disk flares should appear to be richer in nuclear emission than limb flares.

Vestrand, W.T.; Forrest, D.J.; Chupp, E.L.; Rieger, E.; Share, G.H.

1987-11-15

245

Global SF6 emission estimates inferred from atmospheric observations - a test case for Kyoto reporting  

Science.gov (United States)

Sulphur hexafluoride (SF6) is one of the strongest greenhouse gases per molecule in the atmosphere. SF6 emissions are also one of the six greenhouse gases targeted for reduction under the Kyoto Protocol. Here we present a long-term data set of globally distributed high-precision atmospheric SF6 observations which show an increase in mixing ratios from near zero in the 1970s to a global mean value of 6.3 ppt by the end of 2007. Because of its long atmospheric lifetime of around 3000 years, the accumulation of SF6 in the atmosphere is a direct measure of its global emissions: Analysis of our long-term data records implies a decrease of global SF6 sources after 1995, most likely due to emission reductions in industrialised countries. However, after 1998 the global SF6 source increases again, which is probably due to enhanced emissions from transition economies such as in China and India. Moreover, observed north-south concentration differences in SF6 suggest that emissions calculated from statistical (bottom-up) information and reported by Annex II parties to the United Nations Framework Convention on Climate Change (UNFCCC) may be too low by up to 50%. This clearly shows the importance and need for atmospheric (top-down) validation of Kyoto reporting which is only feasible with a dense world-wide observational network for greenhouse and other trace gases. Other members of the Global SF6 Trends Team: R. Heinz (1), D. Osusko (1), E. Cuevas (2), A. Engel (3), J. Ilmberger (1), R.L. Langenfelds (4), B. Neininger (5), C.v. Rohden (1), L.P. Steele (4), A. Varlagin (6), R. Weller (7), D.E. Worthy (8), S.A. Zimov (9) (1) Institut für Umweltphysik, University of Heidelberg, 69120 Heidelberg, Germany, (2) Centro de Investigación Atmosférica de Izaña, Instituto Nacional de Meteorología (INM), 38071 Santa Cruz de Tenerife, Spain, (3) Institut für Atmosphäre und Umwelt, J.W. Goethe Universität Frankfurt, 60438 Frankfurt/Main, Germany, (4) Centre for Australian Weather and Climate Research / CSIRO Marine and Atmospheric Research (CMAR), Aspendale, Victoria 3195, Australia, (5) MetAir AG, 6313 Menzingen, Switzerland, (6) Svertsov Institute for Evolutionary and Ecological Problems (IPEE), 117071 Moscow, Russia, (7) Alfred Wegener Institute for Polar and Marine Research, 27568 Bremerhaven, Germany, (8) Environment Canada, Climate Research Division / CCMR, Toronto, ON M3H 5T4, Canada, (9) Cherskii, Republic of Sakha (Yakutia), Russia

Levin, I.; Naegler, T.

2009-04-01

246

Emission Height and Temperature Distribution of White-Light Emission Observed by Hinode/SOT from the 2012 January 27 X-class Solar Flare  

CERN Document Server

White-light emissions were observed from an X1.7 class solar flare on 27 January 2012, using three continuum bands (red, green, and blue) of the Solar Optical Telescope (SOT) onboard the Hinode satellite. This event occurred near the solar limb, and so differences in locations of the various emissions are consistent with differences in heights above the photosphere of the various emission sources. Under this interpretation, our observations are consistent with the white-light emissions occurring at the lowest levels of where the Ca II H emission occurs. Moreover, the centers of the source regions of the red, green, and blue wavelengths of the white-light emissions are significantly displaced from each other, suggesting that those respective emissions are emanating from progressively lower heights in the solar atmosphere. The temperature distribution was also calculated from the white-light data, and we found the lower-layer emission to have a higher temperature. This indicates that high-energy particles penet...

Watanabe, Kyoko; Masuda, Satoshi; Ichimoto, Kiyoshi; Ohno, Masanori

2013-01-01

247

BROAD RELATIVISTIC IRON EMISSION LINE OBSERVED IN SAX J1808.4-3658  

International Nuclear Information System (INIS)

During the 2008 September-October outburst of the accreting millisecond pulsar SAX J1808.4-3658, the source was observed by both Suzaku and XMM-Newton approximately 1 day apart. Spectral analysis reveals a broad relativistic Fe K? emission line which is present in both data sets, as has recently been reported for other neutron star low-mass X-ray binaries. The properties of the Fe K line observed during each observation are very similar. From modeling the Fe line, we determine the inner accretion disk radius to be 13.2 ± 2.5 GM c-2. The inner disk radius measured from the Fe K line suggests that the accretion disk is not very receded in the hard state. If the inner disk (as measured by the Fe line) is truncated at the magnetospheric radius this implies a magnetic field strength of ?3 x 108 G at the magnetic poles, consistent with other independent estimates.

2009-03-20

248

Determining The Galactic Halo's Emission Measure from UV and X-ray Observations  

CERN Document Server

We analyze a pair of Suzaku shadowing observations in order to determine the X-ray spectrum of the Galaxy's gaseous halo. We simultaneously fit the spectra with models having halo, local, and extragalactic components. The intrinsic intensities of the halo OVII triplet and OVIII Lyman alpha emission lines are 9.98^{+1.10}_{-1.99} LU (line unit; photons cm^-2 s^-1 Sr^-1) and 2.66^{+0.37}_{-0.30} LU, respectively. Meanwhile, FUSE OVI observations for the same directions and SPEAR CIV observations for a nearby direction indicate the existence of hot halo gas at temperatures of ~10^{5.0} K to ~10^{6.0} K. This collection of data implies that the hot gas in the Galactic halo is not isothermal, but its temperature spans a relatively wide range from ~10^{5.0} K to ~10^{7.0} K. We therefore construct a differential emission measure (DEM) model for the halo's hot gas, consisting of two components. In each, dEM/dlog T is assumed to follow a power-law function of the temperature and the gas is assumed to be in collisiona...

Lei, Shijun; Henley, David B

2009-01-01

249

Milagro Observations of TeV Emission from Galactic Sources in the Fermi Bright Source List  

CERN Document Server

We present the result of a search of Milagro sky map for spatial correlations with sources from a subset of the recent Fermi Bright Source List (BSL). The BSL consists of the 205 most significant sources detected above 100 MeV by the Fermi Large Area Telescope. We select sources based on their categorization in the BSL, taking all confirmed or possible Galactic sources in the field of view of Milagro. Of the 34 Fermi sources selected, 14 are observed by Milagro at a significance of 3 standard deviations or more. We conduct this search with a new analysis which employs newly-optimized gamma-hadron separation and utilizes the full 8-year Milagro dataset. Milagro is sensitive to gamma rays above 1 TeV and these results extend the observation of these sources far above the Fermi energy band. With the new analysis and additional data, TeV emission is definitively observed associated with the Fermi pulsar J2229.0+6114, in the the Boomerang Pulsar Wind Nebula (PWN). Furthermore, an extended region of TeV emission is...

Abdo, A A; Aune, T; Berley, D; Chen, C; Christopher, G E; DeYoung, T; Dingus, B L; Ellsworth, R W; González, M M; Goodman, J A; Hays, E; Hoffman, C M; Huentemeyer, P H; Kolterman, B E; Linnemann, J T; McEnery, J E; Morgan, T; Mincer, A I; Némethy, P; Pretz, J; Ryan, J M; Parkinson, P M Saz; Shoup, A; Sinnis, G; Smith, A J; Vasileiou, V; Walker, G P; Williams, D A; Yodh, G B

2009-01-01

250

Efficiency of cold pool outflows in dust emission: central Saharan observations from Fennec  

Science.gov (United States)

The Fennec project has, for the first time, provided high quality high resolution instrument observations of the remote central Saharan atmosphere. Fennec Supersite 1 at Bordj-Badji Mokhtar (BBM) in south-west Algeria is located very close to the boreal summer global dust maximum and is an ideal location from which to investigate dust production mechanisms. A detailed analysis of observations taken during the 2011 intensive observation period (IOP) allows the dust to be partitioned by emission mechanism. Cold pool outflows are the most important mechanism, responsible for up to 65% of the dust during the IOP, followed by low level jets (LLJs) and dry convective plumes. This ranking is maintained whether the partitioning is done using lidar backscatter, nephelometer scattering or uplift potential. It is also consistent with aerosol optical thickness (AOT) measurements: the dustiest cold pool AOTs are always 3.0 or over, the dustiest LLJ AOTs are between 1.0 and 2.0 and the dustiest dry convective plume has an AOT of 1.25. The reason cold pool outflows raise more dust than the other two mechanisms is examined further. For locally emitting dust events, there is a positive correlation between lidar backscatter and wind speed at BBM as expected, but it is not particularly strong (r=0.4688, pBBM suggest that these emission schemes may have missing processes.

Allen, Christopher; Washington, Richard; Engelstaedter, Sebastian

2013-04-01

251

SHARC-II 350 micron Observations of Thermal Emission from Warm Dust in z>=5 Quasars  

CERN Document Server

We present observations of four z>= SDSS quasars at 350 micron with the SHARC-II bolometer camera on the Caltech Submillimeter Observatory. These are among the deepest observations that have been made by SHARC-II at 350 micron, and three quasars are detected at >=3 sigma significance, greatly increasing the sample of 350 micron (corresponds to rest frame wavelengths of =5), detected high-redshift quasars. The derived rest frame far-infrared (FIR) emission in the three detected sources is about five to ten times stronger than that expected from the average SED of the local quasars given the same 1450A luminosity. Combining the previous submillimeter and millimeter observations at longer wavelengths, the temperatures of the FIR-emitting warm dust from the three quasar detections are estimated to be in the range of 39 to 52 K. Additionally, the FIR-to-radio SEDs of the three 350 micron detections are consistent with the emission from typical star forming galaxies. The FIR luminosities are ~10^{13} L_solar and th...

Wang, Ran; Carilli, Chris L; Benford, Dominic J; Dowell, C Darren; Bertoldi, Frank; Walter, Fabian; Menten, Karl M; Omont, Alain; Cox, Pierre; Strauss, Michael A; Fan, Xiaohui; Jiang, Linhua

2007-01-01

252

Observation of field-induced electron emission in porous polycrystalline silicon nano-structured diode  

International Nuclear Information System (INIS)

[en] Field-induced electron emission properties of porous poly-silicon nano-structured (PNS) diodes were investigated as a function of anodizing conditions, including morphological analysis, various kinds of top electrode thickness and the measuring substrate temperature. Also, the vacuum packaging process was performed by the normal glass frit method. The PNS layer was formed on heavily-dope n-type Si substrate. Non-doped poly-silicon layer was grown by low-pressure chemical vapor deposition (LPCVD) to a thickness of 2mm. Subsequently, the poly-silicon layer was anodized in a mixed solution HF (50 wt%): ethanol(99.8 wt%) = 1:1 as a function of anodizing condition. After anodizing, the PNS layer was thermally oxidized for 1 hr at 900 .deg. C. Subsequently, the top electrode was deposited as a function of Au thickness using E-beam evaporator and, in order to establish ohmic contact, thermally evaporated Al was deposited on the back side of a Si substrate. The prepared PNS diode was packaged using the normal vacuum sealing method. After the vacuum sealing process, the PNS diode was mounted on the PC measurement table. When a positive bias was applied to the top electrode, the electron emission was observed, which was caused by field-induced electron emission through the top metal

2003-01-01

253

Multiwavelength Observations of Radio-quiet Quasars with Weak Emission Lines  

CERN Document Server

We present radio and X-ray observations, as well as optical light curves, for a subset of 26 BL Lac candidates from the Sloan Digital Sky Survey (SDSS) lacking strong radio emission and with z<2.2. Half of these 26 objects are shown to be stars, galaxies, or absorbed quasars. We conclude that the other 13 objects are Active Galactic Nuclei (AGN) with abnormally weak emission features; ten of those 13 are definitively radio-quiet, and, for those with available optical light curves, their level of optical flux variability is consistent with radio-quiet quasars. We cannot exclude the possibility that some of these 13 AGN lie on the extremely radio-faint tail of the BL Lac distribution, but our study generally supports the notion that all BL Lac objects are radio-loud. These radio-quiet AGN appear to have intrinsically weak or absent broad emission line regions, and, based on their X-ray properties, we argue that some are low-redshift analogs to weak line quasars (WLQs). SDSS BL Lac searches are so far the onl...

Plotkin, Richard M; Brandt, W N; Diamond-Stanic, Aleksandar M; Fan, Xiaohui; MacLeod, Chelsea L; Schneider, Donald P; Shemmer, Ohad

2010-01-01

254

Persistent emission and bursts from Aquila X-1 observed by Einstein  

International Nuclear Information System (INIS)

A two-component model is applied to an X-ray outburst from Aql X-1 recorded by the Einstein Observatory in March-April 1979. The model treats such outbursts as a combination of a soft, multicolor component (accretion disk) and a hard-blackbody component (boundary layer emission). Evaluation of the light curves indicates that the bursts were caused by an increase in the accretion rate. The calculations also suggest that the system observed is inclined at a 33 deg angle. 37 references.

1987-01-01

255

Temporal feature of X-ray laser plasma observed from 3?0/2, 2?0 harmonic emission  

International Nuclear Information System (INIS)

Temporal feature of X-ray laser plasma density was observed from 3?0/2, 2?0 harmonic emission in the experiments. The temporal feature of 3?0/2 harmonic emission of the germanium film is much different from that of the slab germanium target. The production of x-ray laser is closely related to 3?0/2 harmonic emission in the slab germanium targets.

1995-01-01

256

A study of the behavior of the terminator time shifts using multiple VLF propagation paths during the Pakistan earthquake (M = 7.2) of 18 January 2011  

Science.gov (United States)

On 18 January 2011, at 20:23 UTC, an earthquake of magnitude 7.2 occurred in southwestern Pakistan (latitude 28°44' N, longitude 63°56' E) at a depth of 68 km. We present the results of the analysis of very low frequency (VLF) radio signals, received at three stations located in India. We analyze the VLF signals around this earthquake day and look for possible precursory effects of this earthquake. For our analysis, we use four different VLF propagation paths. These propagation paths are DHO-IERC (Sitapur), VTX-Pune, VTX-ICSP (Indian Centre for Space Physics, Kolkata) and NWC-IERC. We observed significant shifts of the "sunrise terminator time" (SRT) for DHO-IERC and VTX-Pune paths. For DHO-IERC path, the SRT of the VLF signals shifted towards nighttime three days before the earthquake day, and in the case of VTX-Pune path it shifted towards nighttime just one day before the earthquake day. For VTX-Kolkata path, the shift of SRT is four days before the earthquake day, but here the shift is not so strong, somewhere between 2? and 3? lines. For the other two paths, namely, DHO-IERC and VTX-Pune, the terminator time shifts crossed the 3? line. We found no significant shifts of SRT for NWC-IERC propagation path. Higher deviation in the VTX-Pune path as compared to VTX-ICSP path could be due to the proximity of the former to the epicenter. Similarly, DHO-IERC path is over the epicenter while NWC-IERC path is totally away from the epicenter. This could be the reason why the effect in DHO-IERC path is stronger than that in NWC-IERC path.

Ray, S.; Chakrabarti, S. K.

2013-06-01

257

A study of the behavior of the terminator time shifts using multiple VLF propagation paths during the Pakistan earthquake (M = 7.2) of 18 January 2011  

Directory of Open Access Journals (Sweden)

Full Text Available On 18 January 2011, at 20:23 UTC, an earthquake of magnitude 7.2 occurred in southwestern Pakistan (latitude 28°44' N, longitude 63°56' E) at a depth of 68 km. We present the results of the analysis of very low frequency (VLF) radio signals, received at three stations located in India. We analyze the VLF signals around this earthquake day and look for possible precursory effects of this earthquake. For our analysis, we use four different VLF propagation paths. These propagation paths are DHO–IERC (Sitapur), VTX–Pune, VTX–ICSP (Indian Centre for Space Physics, Kolkata) and NWC–IERC. We observed significant shifts of the "sunrise terminator time" (SRT) for DHO–IERC and VTX–Pune paths. For DHO–IERC path, the SRT of the VLF signals shifted towards nighttime three days before the earthquake day, and in the case of VTX–Pune path it shifted towards nighttime just one day before the earthquake day. For VTX–Kolkata path, the shift of SRT is four days before the earthquake day, but here the shift is not so strong, somewhere between 2? and 3? lines. For the other two paths, namely, DHO–IERC and VTX–Pune, the terminator time shifts crossed the 3? line. We found no significant shifts of SRT for NWC–IERC propagation path. Higher deviation in the VTX–Pune path as compared to VTX–ICSP path could be due to the proximity of the former to the epicenter. Similarly, DHO–IERC path is over the epicenter while NWC–IERC path is totally away from the epicenter. This could be the reason why the effect in DHO–IERC path is stronger than that in NWC–IERC path.

S. Ray; S. K. Chakrabarti

2013-01-01

258

Observation capability of Superconducting Submillimeter-Wave Limb-Emission Sounder (SMILES) from International Space Station  

Science.gov (United States)

A new generation of sub-millimeter-wave receivers employing sensitive SIS (Superconductor-Insulator-Superconductor) detector technology will provide new opportunities for precise pas-sive remote sensing observation of minor constituents in atmosphere. Superconducting Submillimeter-Wave Limb-Emission Sounder (SMILES) had been launched in September 11, 2009 and installed to the Japanese Experiment Module (JEM) on the International Space Station (ISS). SMILES is a collaboration project of National Institute of Information and Communications Technology (NICT) and Japan Aerospace Exploration Agency (JAXA). Mission objectives of SMILES are: 1. Space demonstration of super-sensitive SIS mixer and 4-K mechanical cooler technology 2. Super-sensitive global observation of atmospheric minor constituents with sub-millimeter-wave limb emission sounder JEM/SMILES will allow to observe the atmospheric species such as O3, H35Cl, H37Cl, ClO, HO2, BrO, HOCl, HOBr, HNO3, CH3CN, Ozone isotope species, H2O, and Ice Cloud with the precisions in a few to several tens percents. The altitude region of observation is from the upper troposphere to the mesopouse. We performed the early comparison/validation of ozone with 4 satellites measurements, AURA/MLS, Odin/SMR, ACE, and Odin/OSIRIS, and ozonesonde. SMILES ozone was in good agreement with these data. For example, difference between SMILES and MLS was less than 2 percent be-tween 20-50km. These results are consistent with the observation capabilities of JEM/SMILES with error analysis. This super technology may allow us to open new issues in atmospheric science.

Kasai, Yasuko; Tanaka, Takahiro; Dupuy, Eric; Kita, Kazuyuki; Baron, Philippe; Ochiai, Satoshi; Nishibori, Toshiyuki; Kikuchi, Kenichi; Mendrok, Jana; Murtagh, Donal P.; Urban, Joachim; Smiles Mission Team

259

New insights on dust emission mechanisms in the central Sahara: observations from Fennec  

Science.gov (United States)

The central Sahara is the dustiest region of the world in boreal summer. The Fennec project instrumented this remote region and the data that has come back has furnished some intriguing insights into the mechanisms of dust emission. Here, observations are presented for the June 2011 intensive observation period (IOP) from the supersite at Bordj-Badji Mokhtar (BBM), in south-west Algeria. Cold pool outflows produced 11 of the top 15 dustiest events at BBM. Their duration over BBM varied from 3-19h. Several of these outflows travelled long distances to reach the site (~600km). The average propagation speed of two of the dustiest, 11.6m/s and 16.2m/s, is much higher than the average speed of density currents in the Atlas foothills, estimated at 3-11.1m/s in published work by other authors. Such long-travelled currents also appear to have brought unexpectedly large dust particles to BBM: the three dust events during the IOP with the lowest Angstrom Exponent (?0) are all convective outflows spawned by mesoscale convective complexes over western Niger. It is therefore possible that i) the sedimentology over the western Niger region provides much larger particles for emission than over the BBM region ii) the density currents over western Niger have much stronger gust fronts than those spawned near BBM, allowing much larger particles to be uplifted. A third possibility, which may have been the case on the night 16-17 June, is that dust was uplifted over Niger, transported in an elevated intrusion above a stable nocturnal surface layer, and then mixed down to the ground after the surface temperature inversion was eroded. 2m temperatures at BBM were between 1 and 2 standard deviations below the June mean on the morning of 17 June, making it possible that the 'cold pool' could in fact have been warmer than the surface and propagated as an elevated intrusion. Dry convective plume emission and low level jet (LLJ) induced emission and was also observed. Dry convective plume emission started with very large and rapid increases in wind speed after a period of very low wind (an increase of 21m/s in 20 minutes on one occasion), lasted 0.5-2h with a 1hPa pressure well during the strongest plumes, and often exhibited a superadiabatic temperature gradient at low levels. LLJ emission appears to conform to the classic 'jet breakdown' theory and observations from other parts of the Sahara. The degeneration of the surface temperature inversion and the propagation of wind speeds towards the surface after sunrise were frequently clear in the lidar wind profiles and radiosonde measurements.

Allen, Christopher; Washington, Richard

2013-04-01

260

Study of the NWC electrons belt observed on DEMETER Satellite  

CERN Document Server

We analyzed the data from 2007 to 2008, which is observed by IDP onboard DEMETER satellite, during ten months of NWC working and seven months of NWC shutdown. The characteristic of the space instantaneous electron belts, which come from the influence of the VLF transmitted by NWC, is studied comprehensively. The main distribution region of the NWC electron belts and the flux change are given. We also studied the distribution characteristic of the average energy spectrum in different magnetic shell at the height of DEMETER orbit and the difference of the average energy spectrum of the electrons in the drift loss-cone between day and night. As a result, the powerful power of NWC transmitter and the 19.8 kHz narrow bandwidth VLF emission not only created a momentary electrons enhancement region, which strides 180 degree in them longitude direction and from 1.6 to 1.9 in L value, with the rise of the electrons flux reaching to 3 orders of magnitude mostly, but also induced the enhancement or loss of electrons in ...

Li, Xinqiao; Wang, Ping; Wang, Huanyu; Lu, Hong; Zhang, Xuemin; Huang, Jianping; Shi, Feng; Yu, Xiaoxia; Xu, Yanbing; Meng, Xiangcheng; Wang, Hui; Zhao, Xiaoyun; Parrot, M

2010-01-01

 
 
 
 
261

Observations of wave-driven fluctuations of OH nightglow emission from Sondre Stromfjord, Greenland  

Energy Technology Data Exchange (ETDEWEB)

OH nightglow emission from the (6,2) band were observed during February 12-14, 1986, at Sondre Stromfjord, Greenland. The data were analyzed using time series analysis techniques to determine {eta} = ({Delta}I/{anti I})/({Delta}T/{anti T}), where {Delta}I and {Delta}T represent correlated fluctuations from the mean OH intensity ({anti I}) and temperature ({anti T}) in various frequency bands. For correlated fluctuations due to measurement error, {vert bar}{eta}{vert bar} < 1, while for correlated fluctuationscaused by atmospheric gravity waves (AGWs) that pass through the OH emission layer the measured {vert bar}{eta}{vert bar} should be generally greater than 1.5. While some of the observed OH intensity-temperature fluctuations were correlated and had an {vert bar}{eta}{vert bar} < 1, two correlated intensity-temperature waves with periods of 4 and 2 hours were seen with an {vert bar}{eta}{vert bar} > 1.5. The 4-hour (2-hour) period wave has an {vert bar}{eta}{vert bar} equal to 3.1 {plus minus} 1.1 (1.6 {plus minus} 0.5) and a phase angle, between the intensity and temperature components, of 5{degree} {plus minus} 23{degree} (40{degree} {plus minus} 20{degree}). These results are consistent with a recent theoretical model for the passage of AGWs through an OH emission layer. Agreement is closest for the 4-hour (2-hour) period wave when the layer is peaked at 87 km (83 km) and the O scale height is {minus}2.0 ({minus}4.0km).

Hecht, J.H.; Walterscheid, R.L.; Sivjee, G.G.; Christensen, A.B.; Pranke, J.B. (Aerospace Corp., Los Angeles, CA (United States))

1987-06-01

262

High-J CO emission in the Cepheus E protostellar outflow observed with SOFIA/GREAT  

CERN Document Server

We present and analyze two spectrally resolved high-J CO lines towards the molecular outflow Cep E, driven by an intermediate-mass class 0 protostar. Using the GREAT receiver on board SOFIA, we observed the CO (12--11) and (13--12) transitions (E_u ~ 430 and 500 K, respectively) towards one position in the blue lobe of this outflow, that had been known to display high-velocity molecular emission. We detect the outflow emission in both transitions, up to extremely high velocities (~ 100 km/s with respect to the systemic velocity). We divide the line profiles into three velocity ranges that each have interesting spectral features: standard, intermediate, and extremely high-velocity. One distinct bullet is detected in each of the last two. A large velocity gradient analysis for these three velocity ranges provides constraints on the kinetic temperature and volume density of the emitting gas, >~ 100 K and > ~ 10^4 cm^-3, respectively. These results are in agreement with previous ISO observations and are comparabl...

Gómez-Ruiz, A I; Leurini, S; Codella, C; Güsten, R; Wyrowski, F; Requena-Torres, M A; Risacher, C; Wampfler, S F

2012-01-01

263

X-ray and EUV observations of the boundary layer emission of nonmagnetic cataclysmic variables  

Energy Technology Data Exchange (ETDEWEB)

EUVE, ROSAT, and ASCA observations of the boundary layer emission of nonmagnetic cataclysmic variables (CVs) are reviewed. EUVE spectra reveal that the effective temperature of the soft component of high-M nonmagnetic CVs is kT {approx}10-20 eV and that its luminosity is {approx} 0.1-0.5 times the accretion disk luminosity. Although the EUV spectra are very complex and belie simple interpretation, the physical conditions of the boundary layer gas are constrained by emission lines of highly ionized Ne, Mg, Si, and Fe. ROSAT and ASCA spectra of the hard component of nonmagnetic CVs are satisfactorily but only phenomenologically described by multi-temperature thermal plasmas, and the constraints imposed on the physical conditions of this gas are limited by the relatively weak and blended fines. It is argued that significant progress in our understanding of the X-ray spectra of nonmagnetic CVs will come with future observations with XMM, AXAF, and Astro-E.

Mauche, C.W.

1996-03-09

264

X-ray emission from classical and recurrent-novae observed with ROSAT  

CERN Multimedia

We have analysed 350 pointed and serendipitous observations of 108 different classical and recurrent novae in outburst and in quiescence, contained in the ROSAT archive. One aim was to search for super-soft X-ray sources and we found only 3 of them among post-novae. Thus, the super-soft X-ray phase of novae is relatively short lived (up to 10 years) and is observed only for up to 20% of novae. Most classical and recurrent novae instead emit hard X-rays (in the ROSAT band) in the first months after the outburst, with peak X-ray luminosity of a few times 10(33) erg/s. The emission, which we attribute to shocks in the nova ejecta, lasts at least 2 years and even much longer under special circumstances (like preexisting circumstellar material, or a prolonged wind phase). We also investigate X-ray emission due to accretion in quiescent novae. Only 11 out of 81 Galactic classical and recurrent novae were detected. The average X-ray uminosity is not higher than for dwarf novae, and some novae are variable in X-rays ...

Orio, M; Ögelman, H B

2001-01-01

265

On the Possibility of Observing H2 Emission from Primordial Molecular Cloud Kernels  

CERN Document Server

We study the prospects for observing H$_2$ emission during the assembly of primordial molecular cloud kernels. The primordial molecular cloud cores, which resemble those at the present epoch, can emerge around $1+z=20$ according to recent numerical simulations. The kernels form inside the cores, and the first stars will appear inside the kernels. A kernel typically contracts to form one of the first generation stars with an accretion rate that is as large as $\\sim 0.01 M_\\odot$ year$^{-1}$. This occurs due to the primordial abundances that result in a kernel temperature of order 1000K, and the collapsing kernel emits H$_2$ line radiation at a rate $\\sim 10^{35}$ erg sec$^{-1}$. Principally $J=5-3$ (v=0) rotational emission of H$_2$ is expected. At redshift $1+z=20$, the expected flux is $\\sim 0.01~\\mu$Jy for a single kernel. While an individual object is not observable by any facilities available in the near future, the expected assembly of primordial star clusters on sub-galactic scales can result in fluxes ...

Kamaya, H; Kamaya, Hideyuki; Silk, Joseph

2002-01-01

266

X-ray Emission from the Type Ic Supernova 1994I Observed with Chandra  

CERN Multimedia

We present two high-resolution Chandra X-ray observations of supernova (SN) 1994I which show, for the first time, that the interaction of the blast wave from a Type Ic SN with its surrounding circumstellar material (CSM) can give rise to soft X-ray emission. Given a 0.3-2 keV band X-ray luminosity of L_x ~ 1 x 10^{37} ergs/s between six and seven years after the outburst of SN 1994I, and assuming the X-ray emission arises from the shock-heated CSM, we derive a pre-SN mass-loss rate of \\dot{M} ~ 1 x 10^{-5} M_sun/yr (v_w/10 km/s). Combining the results with earlier ROSAT observations, we construct the X-ray lightcurve of SN 1994I. A best-fit X-ray rate of decline of L_x \\propto t^{-s} with index s~1 and a CSM density profile of rho_csm \\propto r^{-1.9\\pm0.1} are inferred, consistent with what is expected for a constant mass-loss rate and constant wind velocity profile for the SN progenitor (rho_csm \\propto r^{-2}).

Immler, S; Terashima, Y; Immler, Stefan; Wilson, Andrew S.; Terashima, Yuichi

2002-01-01

267

Fermi Observations of High-Energy Gamma-Ray Emission from GRB 080916C  

International Nuclear Information System (INIS)

[en] Gamma-ray bursts (GRBs) are highly energetic explosions signaling the death of massive stars in distant galaxies. The Gamma-ray Burst Monitor and Large Area Telescope onboard the Fermi Observatory together record GRBs over a broad energy range spanning about 7 decades of gamma-ray energy. In September 2008, Fermi observed the exceptionally luminous GRB 080916C, with the largest apparent energy release yet measured. The high-energy gamma rays are observed to start later and persist longer than the lower energy photons. A simple spectral form fits the entire GRB spectrum, providing strong constraints on emission models. The known distance of the burst enables placing lower limits on the bulk Lorentz factor of the outflow and on the quantum gravity mass. (authors)

2009-01-01

268

Fermi Observations of high-energy gamma-ray emissions from GRB 080916C  

CERN Document Server

Gamma-ray bursts (GRBs) are highly energetic explosions signaling the death of massive stars in distant galaxies. The Gamma-ray Burst Monitor and Large Area Telescope onboard the Fermi Observatory together record GRBs over a broad energy range spanning about 7 decades of gammaray energy. In September 2008, Fermi observed the exceptionally luminous GRB 080916C, with the largest apparent energy release yet measured. The high-energy gamma rays are observed to start later and persist longer than the lower energy photons. A simple spectral form fits the entire GRB spectrum, providing strong constraints on emission models. The known distance of the burst enables placing lower limits on the bulk Lorentz factor of the outflow and on the quantum gravity mass.

Abdo, A A; Arimoto, M; Asano, K; Atwood, W B; Axelsson, M; Baldini, L; Ballet, J; Band, D L; Barbiellini, Guido; Baring, Matthew G; Bastieri, Denis; Battelino, M; Baughman, B M; Bechtol, K; Bellardi, F; Bellazzini, R; Berenji, B; Bhat, P N; Bissaldi, E; Blandford, R D; Bloom, Elliott D; Bogaert, G; Bogart, J R; Bonamente, E; Bonnell, J; Borgland, A W; Bouvier, A; Bregeon, J; Brez, A; Briggs, M S; Brigida, M; Bruel, P; Burnett, Thompson H; Burrows, David N; Busetto, Giovanni; Caliandro, G A; Cameron, R A; Caraveo, P A; Casandjian, J M; Ceccanti, M; Cecchi, C; Celotti, Annalisa; Charles, E; Chekhtman, A; Cheung, C.C.Teddy; Chiang, J; Ciprini, S; Claus, R; Cohen-Tanugi, Johann; Cominsky, Lynn R; Connaughton, V; Conrad, J; Costamante, L; Cutini, S; DeKlotz, M; Dermer, C D; De Angelis, Alessandro; de Palma, F; Digel, S W; Dingus, B L; do Couto e Silva, Eduardo; Drell, P S; Dubois, R; Dumora, D; Edmonds, Y; Evans, P A; Fabiani, D; Farnier, C; Favuzzi, C; Finke, Justin D; Fishman, G; Focke, W B; Frailis, M; Fukazawa, Y; Funk, S; Fusco, P; Gargano, F; Gasparrini, D; Gehrels, N; Germani, S; Giebels, B; Giglietto, N; Giommi, P; Giordano, F; Glanzman, Thomas Lynn; Godfrey, Gary L; Goldstein, A; Granot, J; Greiner, J; Grenier, I A; Grondin, M H; Grove, J.Eric; Guillemot, L; Guiriec, S; Haller, G; Hanabata, Y; Harding, Alice K; Hayashida, M; Hays, Elizabeth A; Hernando Morata, J A; Hoover, A; Hughes, R E; Johannesson, G; Johnson, A S; Johnson, R P; Johnson, T J; Johnson, W N; Kamae, Tsuneyoshi; Katagiri, H; Kataoka, J; Kavelaars, A; Kawai, N; Kelly, H; Kennea, J; Kerr, M; Kippen, R M; Knodlseder, J; Kocevski, D; Kocian, M L; Komin, N; Kouveliotou, C; Kuehn, Frederick Gabriel Ivar; Kuss, Michael; Lande, J; Landriu, D; Larsson, S; Latronico, L; Lavalley, C; Lee, B; Lee, S H; Lemoine-Goumard, M; Lichti, G G; Longo, F; Loparco, F; Lott, B; Lovellette, M N; Lubrano, Pasquale; Madejski, G M; Makeev, A; Marangelli, B; Mazziotta, M N; McBreen, Sheila; McEnery, J E; McGlynn, S; Meegan, C; Miszaros, P; Meurer, C; Michelson, P F; Minuti, M; Mirizzi, N; Mitthumsiri, W; Mizuno, T; Moiseev, A A; Monte, C; Monzani, M E; Moretti, E; Morselli, A; Moskalenko, Igor Vladimirovich; Murgia, Simona; Nakamori, T; Nelson, D; Nolan, P L; Norris, J P; Nuss, E; Ohno, M; Ohsugi, Takashi; Okumura, Akira; Omodei, N; Orlando, E; Ormes, J F; Ozaki, M; Paciesas, W S; Paneque, D; Panetta, J H; Parent, D; Pelassa, V; Pepe, M; Perri, M; Pesce-Rollins, M; Petrosian, Vahe; Pinchera, M; Piron, F; Porter, Troy A; Preece, R; Rainr, S; Ramirez-Ruiz, E; Rando, R; Rapposelli, E; Razzano, M; Razzaque, Soebur; Rea, N; Reimer, A; Reimer, O; Reposeur, Thierry; Reyes, Luis C; Ritz, S; Rochester, L S; Rodriguez, A Y; Roth, M; Ryde, F; Sadrozinski, H F W; Sanchez, D; Sander, A; Parkinson, P.M.Saz; Scargle, J D; Schalk, T L; Segal, K N; Sgro, C; Shimokawabe, T; Siskind, E J; Smith, D A; Smith, P D; Spandre, G; Spinelli, P; Stamatikos, M; Starck, Jean-Luc; Stecker, Floyd William; Steinle, H; Stephens, T E; Strickman, M S; Suson, Daniel J; Tagliaferri, G.; Tajima, Hiroyasu; Takahashi, H; Takahashi, T; Tanaka, T; Tenze, A; Thayer, J B; Thayer, J G; Thompson, D J; Tibaldo, L; Torres, Diego F; Tosti, G; Tramacere, A; Turri, M; Tuvi, S; Usher, T L; van der Horst, A J; Vigiani, L; Vilchez, N; Vitale, V; von Kienlin, A; Waite, A P; Williams, D A; Wilson-Hodge, C; Winer, B L; Wood, K S; Wu, X F; Yamazaki, R; Ylinen, T; Ziegler, M; 10.1126/science.1169101

2009-01-01

269

Fermi observations of high-energy gamma-ray emission from GRB 080916C.  

Science.gov (United States)

Gamma-ray bursts (GRBs) are highly energetic explosions signaling the death of massive stars in distant galaxies. The Gamma-ray Burst Monitor and Large Area Telescope onboard the Fermi Observatory together record GRBs over a broad energy range spanning about 7 decades of gammaray energy. In September 2008, Fermi observed the exceptionally luminous GRB 080916C, with the largest apparent energy release yet measured. The high-energy gamma rays are observed to start later and persist longer than the lower energy photons. A simple spectral form fits the entire GRB spectrum, providing strong constraints on emission models. The known distance of the burst enables placing lower limits on the bulk Lorentz factor of the outflow and on the quantum gravity mass. PMID:19228997

Abdo, A A; Ackermann, M; Arimoto, M; Asano, K; Atwood, W B; Axelsson, M; Baldini, L; Ballet, J; Band, D L; Barbiellini, G; Baring, M G; Bastieri, D; Battelino, M; Baughman, B M; Bechtol, K; Bellardi, F; Bellazzini, R; Berenji, B; Bhat, P N; Bissaldi, E; Blandford, R D; Bloom, E D; Bogaert, G; Bogart, J R; Bonamente, E; Bonnell, J; Borgland, A W; Bouvier, A; Bregeon, J; Brez, A; Briggs, M S; Brigida, M; Bruel, P; Burnett, T H; Burrows, D; Busetto, G; Caliandro, G A; Cameron, R A; Caraveo, P A; Casandjian, J M; Ceccanti, M; Cecchi, C; Celotti, A; Charles, E; Chekhtman, A; Cheung, C C; Chiang, J; Ciprini, S; Claus, R; Cohen-Tanugi, J; Cominsky, L R; Connaughton, V; Conrad, J; Costamante, L; Cutini, S; Deklotz, M; Dermer, C D; de Angelis, A; de Palma, F; Digel, S W; Dingus, B L; do Couto E Silva, E; Drell, P S; Dubois, R; Dumora, D; Edmonds, Y; Evans, P A; Fabiani, D; Farnier, C; Favuzzi, C; Finke, J; Fishman, G; Focke, W B; Frailis, M; Fukazawa, Y; Funk, S; Fusco, P; Gargano, F; Gasparrini, D; Gehrels, N; Germani, S; Giebels, B; Giglietto, N; Giommi, P; Giordano, F; Glanzman, T; Godfrey, G; Goldstein, A; Granot, J; Greiner, J; Grenier, I A; Grondin, M-H; Grove, J E; Guillemot, L; Guiriec, S; Haller, G; Hanabata, Y; Harding, A K; Hayashida, M; Hays, E; Hernando Morat, J A; Hoover, A; Hughes, R E; Jóhannesson, G; Johnson, A S; Johnson, R P; Johnson, T J; Johnson, W N; Kamae, T; Katagiri, H; Kataoka, J; Kavelaars, A; Kawai, N; Kelly, H; Kennea, J; Kerr, M; Kippen, R M; Knödlseder, J; Kocevski, D; Kocian, M L; Komin, N; Kouveliotou, C; Kuehn, F; Kuss, M; Lande, J; Landriu, D; Larsson, S; Latronico, L; Lavalley, C; Lee, B; Lee, S-H; Lemoine-Goumard, M; Lichti, G G; Longo, F; Loparco, F; Lott, B; Lovellette, M N; Lubrano, P; Madejski, G M; Makeev, A; Marangelli, B; Mazziotta, M N; McBreen, S; McEnery, J E; McGlynn, S; Meegan, C; Mészáros, P; Meurer, C; Michelson, P F; Minuti, M; Mirizzi, N; Mitthumsiri, W; Mizuno, T; Moiseev, A A; Monte, C; Monzani, M E; Moretti, E; Morselli, A; Moskalenko, I V; Murgia, S; Nakamori, T; Nelson, D; Nolan, P L; Norris, J P; Nuss, E; Ohno, M; Ohsugi, T; Okumura, A; Omodei, N; Orlando, E; Ormes, J F; Ozaki, M; Paciesas, W S; Paneque, D; Panetta, J H; Parent, D; Pelassa, V; Pepe, M; Perri, M; Pesce-Rollins, M; Petrosian, V; Pinchera, M; Piron, F; Porter, T A; Preece, R; Rainò, S; Ramirez-Ruiz, E; Rando, R; Rapposelli, E; Razzano, M; Razzaque, S; Rea, N; Reimer, A; Reimer, O; Reposeur, T; Reyes, L C; Ritz, S; Rochester, L S; Rodriguez, A Y; Roth, M; Ryde, F; Sadrozinski, H F-W; Sanchez, D; Sander, A; Saz Parkinson, P M; Scargle, J D; Schalk, T L; Segal, K N; Sgrò, C; Shimokawabe, T; Siskind, E J; Smith, D A; Smith, P D; Spandre, G; Spinelli, P; Stamatikos, M; Starck, J-L; Stecker, F W; Steinle, H; Stephens, T E; Strickman, M S; Suson, D J; Tagliaferri, G; Tajima, H; Takahashi, H; Takahashi, T; Tanaka, T; Tenze, A; Thayer, J B; Thayer, J G; Thompson, D J; Tibaldo, L; Torres, D F; Tosti, G; Tramacere, A; Turri, M; Tuvi, S; Usher, T L; van der Horst, A J; Vigiani, L; Vilchez, N; Vitale, V; von Kienlin, A; Waite, A P; Williams, D A; Wilson-Hodge, C; Winer, B L; Wood, K S; Wu, X F; Yamazaki, R; Ylinen, T; Ziegler, M

2009-02-19

270

First Observation of Planet-Induced X-ray Emission: The System HD 179949  

CERN Document Server

We present the first observation of planet-induced stellar X-ray activity, identified for the HD 179949 system, using Chandra / ACIS-S. The HD 179949 system consists of a close-in giant planet orbiting an F9V star. Previous ground-based observations already showed enhancements in Ca II K in phase with the planetary orbit. We find an ~30% increase in the X-ray flux over quiescent levels coincident with the phase of the Ca II enhancements. There is also a trend for the emission to be hotter at increased fluxes, confirmed by modeling, showing the enhancement at ~1 keV compared to ~0.4 keV for the background star.

Saar, S H; Kashyap, V L; Hall, J C

2007-01-01

271

Comparison of observed and theoretical Fe L emission from CIE plasmas  

Energy Technology Data Exchange (ETDEWEB)

We analyze data from the Lawrence Livermore National Lab (LLNL) Electron Beam Ion Trap (EBIT) that simulates a CIE plasma by sweeping the electron beam to approximate a Maxwellian velocity distribution. These results are compared to spectra of confirmed astronomical CIE plasmas (e.g. outer regions of x-ray clusters) observed by XMM/RGS. We utilize the Photon Clean Method (PCM) to quantify these spectra (EBIT and XMM/RGS) in the form of ratios of Fe L lines in the emission complex near 1 keV. The variances of line fluxes are measured with bootstrap methods (Efron 1979). Both of these observations are further compared with theoretical predictions of Fe L line fluxes from APED and similar atomic databases.

Carpenter, M; Beiersdorfer, P; Brown, G V; Chen, H C; Gu, M F; Jernigan, J G

2007-11-08

272

Fermi observations of high-energy gamma-ray emission from GRB 080916C.  

UK PubMed Central (United Kingdom)

Gamma-ray bursts (GRBs) are highly energetic explosions signaling the death of massive stars in distant galaxies. The Gamma-ray Burst Monitor and Large Area Telescope onboard the Fermi Observatory together record GRBs over a broad energy range spanning about 7 decades of gammaray energy. In September 2008, Fermi observed the exceptionally luminous GRB 080916C, with the largest apparent energy release yet measured. The high-energy gamma rays are observed to start later and persist longer than the lower energy photons. A simple spectral form fits the entire GRB spectrum, providing strong constraints on emission models. The known distance of the burst enables placing lower limits on the bulk Lorentz factor of the outflow and on the quantum gravity mass.

Abdo AA; Ackermann M; Arimoto M; Asano K; Atwood WB; Axelsson M; Baldini L; Ballet J; Band DL; Barbiellini G; Baring MG; Bastieri D; Battelino M; Baughman BM; Bechtol K; Bellardi F; Bellazzini R; Berenji B; Bhat PN; Bissaldi E; Blandford RD; Bloom ED; Bogaert G; Bogart JR; Bonamente E; Bonnell J; Borgland AW; Bouvier A; Bregeon J; Brez A; Briggs MS; Brigida M; Bruel P; Burnett TH; Burrows D; Busetto G; Caliandro GA; Cameron RA; Caraveo PA; Casandjian JM; Ceccanti M; Cecchi C; Celotti A; Charles E; Chekhtman A; Cheung CC; Chiang J; Ciprini S; Claus R; Cohen-Tanugi J; Cominsky LR; Connaughton V; Conrad J; Costamante L; Cutini S; Deklotz M; Dermer CD; de Angelis A; de Palma F; Digel SW; Dingus BL; do Couto E Silva E; Drell PS; Dubois R; Dumora D; Edmonds Y; Evans PA; Fabiani D; Farnier C; Favuzzi C; Finke J; Fishman G; Focke WB; Frailis M; Fukazawa Y; Funk S; Fusco P; Gargano F; Gasparrini D; Gehrels N; Germani S; Giebels B; Giglietto N; Giommi P; Giordano F; Glanzman T; Godfrey G; Goldstein A; Granot J; Greiner J; Grenier IA; Grondin MH; Grove JE; Guillemot L; Guiriec S; Haller G; Hanabata Y; Harding AK; Hayashida M; Hays E; Hernando Morat JA; Hoover A; Hughes RE; Jóhannesson G; Johnson AS; Johnson RP; Johnson TJ; Johnson WN; Kamae T; Katagiri H; Kataoka J; Kavelaars A; Kawai N; Kelly H; Kennea J; Kerr M; Kippen RM; Knödlseder J; Kocevski D; Kocian ML; Komin N; Kouveliotou C; Kuehn F; Kuss M; Lande J; Landriu D; Larsson S; Latronico L; Lavalley C; Lee B; Lee SH; Lemoine-Goumard M; Lichti GG; Longo F; Loparco F; Lott B; Lovellette MN; Lubrano P; Madejski GM; Makeev A; Marangelli B; Mazziotta MN; McBreen S; McEnery JE; McGlynn S; Meegan C; Mészáros P; Meurer C; Michelson PF; Minuti M; Mirizzi N; Mitthumsiri W; Mizuno T; Moiseev AA; Monte C; Monzani ME; Moretti E; Morselli A; Moskalenko IV; Murgia S; Nakamori T; Nelson D; Nolan PL; Norris JP; Nuss E; Ohno M; Ohsugi T; Okumura A; Omodei N; Orlando E; Ormes JF; Ozaki M; Paciesas WS; Paneque D; Panetta JH; Parent D; Pelassa V; Pepe M; Perri M; Pesce-Rollins M; Petrosian V; Pinchera M; Piron F; Porter TA; Preece R; Rainò S; Ramirez-Ruiz E; Rando R; Rapposelli E; Razzano M; Razzaque S; Rea N; Reimer A; Reimer O; Reposeur T; Reyes LC; Ritz S; Rochester LS; Rodriguez AY; Roth M; Ryde F; Sadrozinski HF; Sanchez D; Sander A; Saz Parkinson PM; Scargle JD; Schalk TL; Segal KN; Sgrò C; Shimokawabe T; Siskind EJ; Smith DA; Smith PD; Spandre G; Spinelli P; Stamatikos M; Starck JL; Stecker FW; Steinle H; Stephens TE; Strickman MS; Suson DJ; Tagliaferri G; Tajima H; Takahashi H; Takahashi T; Tanaka T; Tenze A; Thayer JB; Thayer JG; Thompson DJ; Tibaldo L; Torres DF; Tosti G; Tramacere A; Turri M; Tuvi S; Usher TL; van der Horst AJ; Vigiani L; Vilchez N; Vitale V; von Kienlin A; Waite AP; Williams DA; Wilson-Hodge C; Winer BL; Wood KS; Wu XF; Yamazaki R; Ylinen T; Ziegler M

2009-03-01

273

Comparison of observed and theoretical Fe L emission from CIE plasmas  

International Nuclear Information System (INIS)

We analyze data from the Lawrence Livermore National Lab (LLNL) Electron Beam Ion Trap (EBIT) that simulates a CIE plasma by sweeping the electron beam to approximate a Maxwellian velocity distribution. These results are compared to spectra of confirmed astronomical CIE plasmas (e.g. outer regions of x-ray clusters) observed by XMM/RGS. We utilize the Photon Clean Method (PCM) to quantify these spectra (EBIT and XMM/RGS) in the form of ratios of Fe L lines in the emission complex near 1 keV. The variances of line fluxes are measured with bootstrap methods (Efron 1979). Both of these observations are further compared with theoretical predictions of Fe L line fluxes from APED and similar atomic databases.

2007-01-01

274

Solar flares detected by the new narrowband VLF receiver at SANAE IV  

Directory of Open Access Journals (Sweden)

Full Text Available A narrowband receiver was installed at the SANAE IV base in Antarctica to monitor specific very low frequency (VLF) radio signals from transmitters around the world. VLF waves propagating through the Earth–Ionosphere Waveguide are excellent probes of the varying properties of the lower region of the ionosphere. This paper describes the set-up of the narrowband system and demonstrates its capabilities with data from a set of solar flares on 08 February and 12 February 2010.

Hanna Dahlgren; Torbjörn Sundberg; Andrew B. Collier; Etienne Koen; Stephen Meyer

2011-01-01

275

Modal Sequencing and Dynamic Emission Properties of an 8-hour GMRT Observation of Pulsar B1822-09  

CERN Document Server

The research presented here examines an 8-hour observation of pulsar B1822-09,taken by the Giant Metrewave Radio Telescope. B1822-09 has been known to exhibit two stable emission modes, the B-mode, where the precursor (PC) `turns-on', and the Q-mode, which is defined by interpulse (IP) emission. The results of our analysis, of this extremely long observation, have shown that B1822-09 exhibits at least three other emission behaviors that have not been seen before in other similar pulsars or in other observations of B1822-09. These three behaviors can be described as: Q-mode emission with PC emission, B-mode emission with IP emission, and instances where both the PC and IP are `on' when transitioning from one mode to the other. The pulse structure has been found to be more complex than previously thought. The MP has an inner cone/core triple (T) configuration together with a central sightline traverse. The IP is a 15/degr-wide region, that along with the MP originate from an open dipolar field. The PC emission ...

Latham, Crystal; Rankin, Joanna

2012-01-01

276

Vector tomographic reconstruction for the coronal magnetic field from Fe XIII 10747 A emission line observations  

Science.gov (United States)

Magnetic fields in the solar corona are the dominant fields that determine the static and dy-namic properties of this outermost region of the solar atmosphere. It is within this tenuous region that the magnetic force dominates the gas pressure. Direct measurement of the coronal magnetic field is one of the most challenging problems in observational solar astronomy. To date, one of the promising measurement methods that have been successfully demonstrated is the spectropolarimetric measurement of the Fe XIII 10747 A forbidden emission line (Lin, Penn Tomczyk 2000; Lin, Kuhn Coulter 2004; Tomczyk et al. 2007) formed due to Hanle and Zeeman effects. However, because coronal measurements are integrated over line-of-site (LOS), it is impossible to derive the configuration of the coronal magnetic field from a single obser-vation (from a single viewing direction). In this paper, we study the sensitivity of the vector tomographic inversion to possible pre-CME coronal magnetic field configurations and number of available observations. We show that the vector tomography techniques based on Hanle and/or Zeeman effect observations has the potential to resolve the 3D coronal non-potential magnetic field structure.

Kramar, Maxim; Lin, Haosheng; Inhester, Bernd; Davila, Joseph

277

VHE gamma-ray emission from the FSRQs observed by the MAGIC telescopes  

CERN Document Server

Among more than fifty blazars detected in very high energy (VHE, E>100GeV) gamma-rays, only three belong to the subclass of Flat Spectrum Radio Quasars (FSRQs): PKS 1510-089, PKS 1222+216 and 3C 279. The detection of FSRQs in the VHE range is challenging, mainly because of their steep soft spectra in the GeV-TeV regime. MAGIC has observed and detected all FSRQs known to be VHE emitters up to now and found that they exhibit very different behavior. The 2010 discovery of PKS 1222+216 (z = 0.432) with the fast variability observed, challenges simple one-zone emission models and more complicated scenarios have been proposed. 3C 279 is the most distant VHE gamma-ray emitting AGN (z = 0.536), which was discovered by MAGIC in 2006 and detected again in 2007. In 2011 MAGIC observed 3C 279 two times: first during a monitoring campaign and later observations were triggered by a flare detected with Fermi-LAT. We present the MAGIC results and the multiwavelength behavior during this flaring epoch. Finally, we report the ...

Lindfors, E; de Almeida, U Barres; Mazin, D; Paneque, D; Saito, K; Gonzalez, J Becerra; Berger, K; De Caneva, G; Schultz, C; Sitarek, J; Stamerra, A; Tavecchio, F; Buson, S; D'Ammando, F; Hayashida, M; Tornikoski, M; Hovatta, T

2013-01-01

278

Localization of grasp representations in humans by positron emission tomography. 2. Observation compared with imagination.  

Science.gov (United States)

Positron emission tomography imaging of cerebral blood flow was used to localize brain areas involved in the representation of hand grasping movements. Seven normal subjects were scanned under three conditions. In the first, they observed precision grasping of common objects performed by the examiner. In the second, they imagined themselves grasping the objects without actually moving the hand. These two tasks were compared with a control task of object viewing. Grasp observation activated the left rostral superior temporal sulcus, left inferior frontal cortex (area 45), left rostral inferior parietal cortex (area 40), the rostral part of left supplementary motor area (SMA-proper), and the right dorsal premotor cortex. Imagined grasping activated the left inferior frontal (area 44) and middle frontal cortex, left caudal inferior parietal cortex (area 40), a more extensive response in left rostral SMA-proper, and left dorsal premotor cortex. The two conditions activated different areas of the right posterior cerebellar cortex. We propose that the areas active during grasping observation may form a circuit for recognition of hand-object interactions, whereas the areas active during imagined grasping may be a putative human homologue of a circuit for hand grasping movements recently defined in nonhuman primates. The location of responses in SMA-proper confirms the rostrocaudal segregation of this area for imagined and real movement. A similar segregation is also present in the cerebellum, with imagined and observed grasping movements activating different parts of the posterior lobe and real movements activating the anterior lobe. PMID:8951412

Grafton, S T; Arbib, M A; Fadiga, L; Rizzolatti, G

1996-11-01

279

Localization of grasp representations in humans by positron emission tomography. 2. Observation compared with imagination.  

UK PubMed Central (United Kingdom)

Positron emission tomography imaging of cerebral blood flow was used to localize brain areas involved in the representation of hand grasping movements. Seven normal subjects were scanned under three conditions. In the first, they observed precision grasping of common objects performed by the examiner. In the second, they imagined themselves grasping the objects without actually moving the hand. These two tasks were compared with a control task of object viewing. Grasp observation activated the left rostral superior temporal sulcus, left inferior frontal cortex (area 45), left rostral inferior parietal cortex (area 40), the rostral part of left supplementary motor area (SMA-proper), and the right dorsal premotor cortex. Imagined grasping activated the left inferior frontal (area 44) and middle frontal cortex, left caudal inferior parietal cortex (area 40), a more extensive response in left rostral SMA-proper, and left dorsal premotor cortex. The two conditions activated different areas of the right posterior cerebellar cortex. We propose that the areas active during grasping observation may form a circuit for recognition of hand-object interactions, whereas the areas active during imagined grasping may be a putative human homologue of a circuit for hand grasping movements recently defined in nonhuman primates. The location of responses in SMA-proper confirms the rostrocaudal segregation of this area for imagined and real movement. A similar segregation is also present in the cerebellum, with imagined and observed grasping movements activating different parts of the posterior lobe and real movements activating the anterior lobe.

Grafton ST; Arbib MA; Fadiga L; Rizzolatti G

1996-11-01

280

The impact of PMSE and NLC particles on VLF propagation  

Directory of Open Access Journals (Sweden)

Full Text Available PMSE or Polar Mesosphere Summer Echoes are a well-known phenomenon in the summer northern polar regions, in which anomalous VHF/UHF radar echoes are returned from heights ~85km. Noctilucent clouds and electron density biteouts are two phenomena that sometimes occur together with PMSE. Electron density biteouts are electron density depletion layers of up to 90%, which may be several kms thick. Using the NOSC Modefndr code based on Wait's modal theory for subionospheric propagation, we calculate the shifts in received VLF amplitude and phase that occur as a result of electron density biteouts. The code assumes a homogeneous background ionosphere and a homogeneous biteout layer along the Great Circle Path (GCP) corridor, for transmitter receiver path lengths in the range of 500–6000km. For profiles during the 10h about midnight and under quiet geomagnetic conditions, where the electron density at 85km would normally be less than 500el/cc, it was found that received signal perturbations were significant, of the order of 1–4dB and 5–40° of phase. Perturbation amplitudes increase roughly as the square root of frequency. At short range perturbations are rather erratic, but more consistent at large ranges, readily interpretable in terms of the shifts in excitation factor, attenuation factor and v/c ratios for Wait's modes. Under these conditions such shifts should be detectable by a well constituted experiment involving multiple paths and multiple frequencies in the north polar region in summer. It is anticipated that VLF propagation could be a valuable diagnostic for biteout/PMSE when electron density at 85km is under 500el/cc, under which circumstances PMSE are not directly detectable by VHF/UHF radars. Key words. Electromagnetism (wave propagation) – Ionosphere (polar ionosphere) – Radioscience (ionospheric propagation)

D. Nunn; M. A. Clilverd; C. J. Rodger; N. R. Thomson

2004-01-01

 
 
 
 
281

Infrared Spectroscopy of NGC 4151 Infrared Space Observatory Observations and Narrow Emission Line Region Line Profiles  

CERN Document Server

We present ISO-SWS and ISOPHOT-S spectroscopy of the Seyfert galaxy NGC 4151. We detect a total of 17 fine structure emission lines emitted by a wide range of low- and high-excitation ions, two rotational lines of molecular hydrogen, and the Br beta HI line. We find that the mid-IR fine structure line profiles display blue asymmetries which are very similar to those observed in the optical lines produced in the narrow line region. Because the mid-infrared lines are much less sensitive to extinction than are the optical lines this similarity places strong constraints on scenarios which have been invoked to explain the optical line asymmetries. For example, we are able to rule out the simplest radial-motion-plus-dust scenarios for the production of the line asymmetries. Our preferred model is that of a central, geometrically thin but optically thick, obscuring screen of sub-arcsecond extension, enclosing a total hydrogen gas mass of >~5E6 Msun. This mass may be molecular. The weakness of `PAH' emission features...

Sturm, E; Lutz, D; Sternberg, A; Netzer, H; Genzel, R

1999-01-01

282

Observations of wave-driven fluctuations of OH nightglow emission from Sondre Stromfjord, Greenland  

International Nuclear Information System (INIS)

OH nightglow emission from the (6,2) band were observed during February 12-14, 1986, at Sondre Stromfjord, Greenland. The data were analyzed using time series analysis techniques to determine ? = (?I/anti I)/(?T/anti T), where ?I and ?T represent correlated fluctuations from the mean OH intensity (anti I) and temperature (anti T) in various frequency bands. For correlated fluctuations due to measurement error, |?| 1.5. The 4-hour (2-hour) period wave has an |?| equal to 3.1 ± 1.1 (1.6 ± 0.5) and a phase angle, between the intensity and temperature components, of 5 degree ± 23 degree (40 degree ± 20 degree). These results are consistent with a recent theoretical model for the passage of AGWs through an OH emission layer. Agreement is closest for the 4-hour (2-hour) period wave when the layer is peaked at 87 km (83 km) and the O scale height is -2.0 (-4.0km).

1987-01-01

283

SOFIA observations of CO(12-11) emission along the L1157 bipolar outflow  

CERN Multimedia

Carbon monoxide is an excellent tracer of the physical conditions of gas in molecular outflows from young stars. To understand the outflow mechanism we need to investigate the origin of the molecular emission and the structure and interaction of the outflowing molecular gas. Deriving the physical parameters of the gas will help us to trace and understand the various gas components in the flow. We observed CO(12-11) line emission at various positions along the L1157 bipolar outflow with GREAT aboard SOFIA. Comparing these new data with CO(2-1), we find basically constant line ratios along the outflow and even at the position of the source. These line ratios lead us to estimates of 10^5 to 10^6 cm^-3 for the gas density and 60 to 100 K for the gas temperature of the outflowing gas. The constrained density and temperature values indicate that we are mostly tracing a low-velocity gas component everywhere along the outflow, which is intermediate between the already known cold gas component, which gets entrained in...

Eislöffel, Jochen; Güsten, Rolf; Wiesemeyer, Helmut; Gusdorf, Antoine

2012-01-01

284

Observations of Vortex Emissions from Superfluid 4He Turbulence at High Temperatures  

Science.gov (United States)

An immersed object with high velocity oscillations causes quantum turbulence in superfluid 4He, even at very low temperatures. The continuously generated turbulence may emit vortex rings from a turbulent region. In the present work, we report vortex emissions from quantum turbulence in superfluid 4He at high temperatures, by using three vibrating wires as a turbulence generator and vortex detectors. Two detector wires were mounted beside a generator wire: one in parallel and the other in perpendicular to the oscillation direction of the generator. The detection times of vortex rings represent an exponential distribution with a delay time t 0 and a mean detection period t 1. The delay time includes the generation time of a fully developed turbulence and the time-of-flight of a vortex ring. At high temperatures, vortices are dissipated by relative motion between a normal fluid component and the vortices, resulting that only large vortex rings are reachable to the detectors. Using this method, we detected vortex rings with a diameter of 100 ?m, comparable to a peak-to-peak vibration amplitude of 104 ?m of the generator. The large vortices observed here are emitted anisotropically from the generator. The emissions parallel to the vibrating direction are much less than those perpendicular to the direction.

Oda, S.; Wakasa, Y.; Kubo, H.; Obara, K.; Yano, H.; Ishikawa, O.; Hata, T.

2013-10-01

285

CONTINUUM OBSERVATIONS AT 350 MICRONS OF HIGH-REDSHIFT MOLECULAR EMISSION LINE GALAXIES  

International Nuclear Information System (INIS)

We report observations of 15 high-redshift (z = 1 - 5) galaxies at 350 ?m using the Caltech Submillimeter Observatory and Submillimeter High Angular Resolution Camera II array detector. Emission was detected from eight galaxies, for which far-infrared luminosities, star formation rates (SFRs), total dust masses, and minimum source size estimates are derived. These galaxies have SFRs and star formation efficiencies comparable to other high-redshift molecular emission line galaxies. The results are used to test the idea that star formation in these galaxies occurs in a large number of basic units, the units being similar to star-forming clumps in the Milky Way. The luminosity of these extreme galaxies can be reproduced in a simple model with (0.9-30)x106 dense clumps, each with a luminosity of 5 x 105 Lsun, the mean value for such clumps in the Milky Way. Radiative transfer models of such clumps can provide reasonable matches to the overall spectral energy distributions (SEDs) of the galaxies. They indicate that the individual clumps are quite opaque in the far-infrared. Luminosity-to-mass ratios vary over two orders of magnitude, correlating strongly with the dust temperature derived from simple fits to the SED. The gas masses derived from the dust modeling are in remarkable agreement with those from CO luminosities, suggesting that the assumptions going into both calculations are reasonable.

2009-12-20

286

Modelling observations of hot gas emission from embedded low-mass protostars  

CERN Document Server

Aims. Young stars interact vigorously with their surroundings, as evident from the highly rotationally excited CO (up to Eup=4000 K) and H2O emission (up to 600 K) detected by the Herschel Space Observatory in embedded low-mass protostars. Our aim is to construct a model that reproduces the observations quantitatively, to investigate the origin of the emission, and to use the lines as probes of the various heating mechanisms. Methods. The model consists of a spherical envelope with a bipolar outflow cavity. Three heating mechanisms are considered: passive heating by the protostellar luminosity, UV irradiation of the outflow cavity walls, and C-type shocks along the cavity walls. Line fluxes are calculated for CO and H2O and compared to Herschel data and complementary ground-based data for the protostars NGC1333 IRAS2A, HH 46 and DK Cha. The three sources are selected to span a range of evolutionary phases and physical characteristics. Results. The passively heated gas in the envelope accounts for 3-10% of the...

Visser, R; Bruderer, S; van Dishoeck, E F; Herczeg, G J; Brinch, C; Doty, S D; Harsono, D; Wolfire, M G

2011-01-01

287

Directivity of high-energy emission from solar flares - Solar Maximum Mission observations  

Energy Technology Data Exchange (ETDEWEB)

The data base consisting of flares detected by the gamma-ray spectrometer (GRS) on board the Solar Maximum Mission (SMM) satellite is used to study the directivity of high-energy radiation. A number of observations are presented that, strongly indicate that the high-energy emission from flares is anisotropic. They are the following: (1) the fraction of events detected at energies above 300 keV near the limb is higher than is expected for isotropically emitting flares; (2) there is a statistically significant center-to-limb variation in the 300 keV to 1 MeV spectra of flares detected by the SMM GRS; (3) the 25-200 keV hard X-ray spectra measured during the impulsive phase by the SMM GRS show a center-to-limb variation; and (4) nearly all of the events detected at above 10 MeV are located near the limb. 38 references.

Vestrand, W.T.; Forrest, D.J.; Chupp, E.L.; Rieger, E.; Share, G.H.

1987-11-01

288

Observation of resonance enhanced neutron standing waves using charged particle emission after neutron capture  

International Nuclear Information System (INIS)

[en] The effect of resonance enhancement of neutron standing waves in a structure glass/Cu (1000 Angstrom)/Ti (2000 Angstrom)/6LiF (200 Angstrom) is investigated. For particular neutron wavelengths there is observed a decrease in the intensity of the reflected neutrons and the corresponding increase in the emission of alpha-particles and tritons induced by neutron capture in 6Li nuclei. It is the evidence of an increase in the neutron density of the 6LiF layer for such wavelengths and is connected with the interference of the incident neutron wave and the neutron wave reflected from the Cu layer. The experimental and calculated data point to the existence of a resonance enhanced neutron wave field in the Ti and 6LiF layers

1998-01-01

289

Observations of a Greenstein effect in the O I 1302A emission of Comet Halley  

Energy Technology Data Exchange (ETDEWEB)

Far-ultraviolet spectra of Comet Halley (1986 III) were obtained on February 26, 1986, 17 days after perihelion, and on March 13, 1986, 13 hr before the Giotto encounter, using an imaging spectrograph aboard a sounding rocket. A sunward-antisunward asymmetry observed in the brightness distribution of the O I 1302A emission is a result of the differential Swings effect first discussed by Greenstein (1958) for Fraunhofer structure in the solar continuum. The mean velocity of the O atoms in the coma at cometocentric radii greater than 10,000 km was 2.2 + or - 0.8 km/s based on model calculations which incorporate the Greenstein effect. This velocity is consistent with H/sub 2/O as the principal source of oxygen. 27 references.

Dymond, K.F.; Feldman, P.D.; Woods, T.N.

1989-03-01

290

Observations of a Greenstein effect in the O I 1302A emission of Comet Halley  

International Nuclear Information System (INIS)

Far-ultraviolet spectra of Comet Halley (1986 III) were obtained on February 26, 1986, 17 days after perihelion, and on March 13, 1986, 13 hr before the Giotto encounter, using an imaging spectrograph aboard a sounding rocket. A sunward-antisunward asymmetry observed in the brightness distribution of the O I 1302A emission is a result of the differential Swings effect first discussed by Greenstein (1958) for Fraunhofer structure in the solar continuum. The mean velocity of the O atoms in the coma at cometocentric radii greater than 10,000 km was 2.2 + or - 0.8 km/s based on model calculations which incorporate the Greenstein effect. This velocity is consistent with H2O as the principal source of oxygen. 27 references.

1989-01-01

291

Estimation of NOx emissions from Delhi using Car MAX-DOAS observations and comparison with OMI satellite data  

Directory of Open Access Journals (Sweden)

Full Text Available We present the first Multi-Axis-(MAX-) DOAS observations in India performed during April 2010 and January 2011 in Delhi and nearby regions. The MAX-DOAS instrument was mounted on a car roof, which allowed us to perform measurements along individual driving routes. From car MAX-DOAS observations along closed circles around Delhi, together with information on wind speed and direction, the NOx emissions from the greater Delhi area were determined: our estimate of 4.4 × 1025 molecules s?1 is found to be slightly lower than the corresponding emission estimates using the EDGAR emission inventory and substantially smaller compared to a recent study by Gurjar et al. (2004). We also determined NOx emissions from Delhi using OMI satellite observations on the same days. These emissions are slightly smaller than those from the car MAX-DOAS measurements. Finally the car MAX-DOAS observations were also used for the validation of simultaneous OMI satellite measurements of the tropospheric NO2 VCD and found a good agreement of the spatial patterns. Concerning the absolute values, OMI data are, on average, higher than the car MAX-DOAS observations close to strong emission sources, and vice versa over less polluted regions. Our results indicate that OMI NO2 VCDs are biased low over strongly polluted regions, probably caused by inadequate a-priori profiles used in the OMI satellite retrieval.

R. Shaiganfar; S. Beirle; M. Sharma; A. Chauhan; R. P. Singh; T. Wagner

2011-01-01

292

Chandra Observation of NGC4449. Analysis of the X-ray Emission from a Dwarf Starburst Galaxy  

CERN Multimedia

We present CHANDRA X-ray data of the nearby Magellanic Irregular dwarf starburst galaxy NGC4449. Contributions to the X-ray emission come from discrete point sources and extended diffuse emission. The extended emission has a complex morphology with an extent of 2.4x1.6kpc down to a flux density of 1.3E-13 erg/s/cm2/arcmin2. The best spectral fit to this emission is obtained with an absorbed, two temperature model giving temperatures for the two gas components of 0.28keV and 0.86keV, a total mass content of ~10^7 Msun compared with a galactic mass of several 10^{10} Msun and a total thermal energy content of ~2.5E55erg, with an average energy injection rate for the galaxy of a few 1E41 erg/s. Comparison of the morphology of the diffuse X-ray emission with that of the observed Halpha emission shows similarities in the two emissions. An expanding super-bubble is suggested by the presence of diffuse X-ray emission within what appears to be a cavity in the Halpha emission. The kinematics of this bubble suggest an ...

Summers, L K; Strickland, D K; Heckman, T M; Summers, Lesley K.; Stevens, Ian R.; Strickland, David K.; Heckman, Timothy M.

2003-01-01

293

Observations and modeling of forward and reflected chorus waves captured by THEMIS  

Directory of Open Access Journals (Sweden)

Full Text Available Discrete ELF/VLF chorus emissions are the most intense electromagnetic plasma waves observed in the radiation belts of the Earth's magnetosphere. Chorus emissions, whistler-mode wave packets propagating roughly along magnetic field lines from a well-localized source in the vicinity of the magnetic equator to polar regions, can be reflected at low altitudes. After reflection, wave packets can return to the equatorial plane region. Understanding of whistler wave propagation and reflection is critical to a correct description of wave-particle interaction in the radiation belts. We focus on properties of reflected chorus emissions observed by the THEMIS (Time History of Events and Macroscale Interactions During Substorms) spacecraft Search Coil Magnetometer (SCM) and Electric Field Instrument (EFI) at ELF/VLF frequencies up to 4 kHz at L?8. We determine the direction of the Poynting flux and wave vector distribution for forward and reflected chorus waves. Although both types of chorus waves were detected near the magnetic equator and have similar, discrete structure and rising tones, reflected waves are attenuated by a factor of 10–30 and have 10% higher frequency than concurrently-observed forward waves. Modeling of wave propagation and reflection using geometrical optics ray-tracing allowed us to determine the chorus source region location and explain observed propagation characteristics. We find that reflected wave attenuation at a certain spatial region is caused by divergence of the ray paths of these non-ducted emissions, and that the frequency shift is caused by generation of the reflected waves at lower L-shells where the local equatorial gyrofrequency is larger.

O. Agapitov; V. Krasnoselskikh; Yu. Zaliznyak; V. Angelopoulos; O. Le Contel; G. Rolland

2011-01-01

294

Observations and modeling of forward and reflected chorus waves captured by THEMIS  

Science.gov (United States)

Discrete ELF/VLF chorus emissions are the most intense electromagnetic plasma waves observed in the radiation belts of the Earth's magnetosphere. Chorus emissions, whistler-mode wave packets propagating roughly along magnetic field lines from a well-localized source in the vicinity of the magnetic equator to polar regions, can be reflected at low altitudes. After reflection, wave packets can return to the equatorial plane region. Understanding of whistler wave propagation and reflection is critical to a correct description of wave-particle interaction in the radiation belts. We focus on properties of reflected chorus emissions observed by the THEMIS (Time History of Events and Macroscale Interactions During Substorms) spacecraft Search Coil Magnetometer (SCM) and Electric Field Instrument (EFI) at ELF/VLF frequencies up to 4 kHz at L?8. We determine the direction of the Poynting flux and wave vector distribution for forward and reflected chorus waves. Although both types of chorus waves were detected near the magnetic equator and have similar, discrete structure and rising tones, reflected waves are attenuated by a factor of 10-30 and have 10% higher frequency than concurrently-observed forward waves. Modeling of wave propagation and reflection using geometrical optics ray-tracing allowed us to determine the chorus source region location and explain observed propagation characteristics. We find that reflected wave attenuation at a certain spatial region is caused by divergence of the ray paths of these non-ducted emissions, and that the frequency shift is caused by generation of the reflected waves at lower L-shells where the local equatorial gyrofrequency is larger.

Agapitov, O.; Krasnoselskikh, V.; Zaliznyak, Yu.; Angelopoulos, V.; Le Contel, O.; Rolland, G.

2011-03-01

295

Emissions of mercury in Southern Africa derived from long-term observations at Cape Point, South Africa  

Directory of Open Access Journals (Sweden)

Full Text Available Mercury emissions in South Africa have so far been estimated only by a bottom-up approach from activities and emission factors for different processes. In this paper we derive GEM/CO (GEM being gaseous elemental mercury, Hg0), GEM/CO2, GEM/CH4, CO/CO2, CH4/CO2, and CH4/CO emission ratios from plumes observed during long-term monitoring of these species at Cape Point between March 2007 and December 2009. The average observed GEM/CO, GEM/CO2, GEM/CH4, CO/CO2, CH4/CO2, and CH4/CO emission ratios were 2.40 ± 2.65 pg m?3 ppb?1 (n = 47), 62.7 ± 80.2 pg m?3 ppb?1 (n = 44), 3.61 ± 4.66 pg m?3 ppb?1 (n = 46), 35.6 ± 25.4 ppb ppm?1 (n = 52), 20.2 ± 15.5 ppb ppm?1 (n=48), and 0.876 ± 1.106 ppb ppm?1 (n=42), respectively. The observed CO/CO2, CH4/CO2, and CH4/CO emission ratios agree within the combined uncertainties of the observations and emissions with the ratios calculated from EDGAR (version 4.2) CO2, CO, and CH4 inventories for South Africa and Southern Africa (South Africa, Lesotho, Swaziland, Namibia, Botswana, Zimbabwe, and Mozambique) in 2007 and 2008 (inventories for 2009 are not available yet). Total elemental mercury emission of 13.1, 15.2, and 16.1 t Hg yr?1 are estimated independently using the GEM/CO, GEM/CO2, and GEM/CH4 emission ratios and the annual mean CO, CO2, and CH4 emissions, respectively, of South Africa in 2007 and 2008. The average of these independent estimates of 14.8 ± 1.5 t GEM yr?1 is much less than the total emission of 257 t Hg yr?1 from older inventories. Considering that emission of GEM represents only 50–78% of all mercury emissions, our estimates come close to the total mercury emission estimates ranging between 40–50 t Hg yr?1 from more recent inventories.

E.-G. Brunke; R. Ebinghaus; H. H. Kock; C. Labuschagne; F. Slemr

2012-01-01

296

Constraints on ship NOx emissions in Europe using GEOS-Chem and OMI satellite NO2 observations  

Directory of Open Access Journals (Sweden)

Full Text Available We present a top-down ship NOx emission inventory for the Baltic Sea, North Sea, Bay of Biscay and Mediterranean Sea, based on satellite observed tropospheric NO2 columns of the Ozone Monitoring Instrument (OMI) for 2005–2006. We improved the representation of ship emissions in the GEOS-Chem chemistry transport model, and compared simulated NO2 columns to consistent satellite observations. Relative differences between simulated and observed NO2 columns have been used to constrain ship emissions in four European seas (Baltic Sea, North Sea, Bay of Biscay and Mediterranean Sea). The constrained ship tracks account for 39% of total top-down European ship NOx emissions, which amounts to 0.96 Tg N for 2005, and 1.0 Tg N for 2006 (11–15% lower than the bottom-up EMEP ship emission inventory). Our results indicate that EMEP emissions in the Mediterranean Sea are too high (by 60%) and misplaced by up to 150 km, which can have important consequences for local air quality simulations. In the North Sea, our top-down emissions amount to 0.05 Tg N for 2005 (35% lower than EMEP). Increased top-down emissions were found for the Baltic Sea and Bay of Biscay, with emission totals of 0.05 Tg N (131% higher than EMEP) and 0.08 Tg N for 2005 (128% higher than EMEP), respectively. Our study explicitly accounts for the (non-linear) sensitivity of satellite retrievals to changes in the a priori NO2 profiles. Although the effect of this sensitivity might be minor for small emission increments, our findings stress the need for consistent information in satellite retrieval and model, as satellite observations are never fully independent of model information (i.e. assumptions on vertical NO2 profiles). Our study provides for the first time a space-based top-down ship NOx emission inventory, and can serve as a framework for future studies to constrain ship emissions using satellite NO2 observations in other seas.

G. C. M. Vinken; K. F. Boersma; A. van Donkelaar; L. Zhang

2013-01-01

297

A statistical study of ELF-VLF plasma waves at the magnetopause  

International Nuclear Information System (INIS)

A statistical study of the broadband ELF-VLF plasma waves at the magnetopause has been performed using ISEE 1 plasma wave data. It is found that enhanced wave intensities are detected at 85% of all magnetopause crossings. Although wave amplitudes are highly variable from event to event and even within an event (particularly during high-intensity events), the wave spectra averaged over many passes are remarkably similar at dawn, noon, and dusk local hours. Thus to first order, the average wave intensity and spectral shape are independent of local time. The average wave intensity is independent of latitude, magnetosheath field strength, and magnetopause position. The only parameter found to be correlated with wave intensity is the magnitude of the Z component of the magnetosheath magnetic field. The broadband wave intensities increase with increasing negative Bz. These observational results put strong constraints on any proposed generation mechanism for the broadband magnetopause boundary layer waves. Reasonable mechanisms should be able to explain the lack of local time, latitude, and interplanetary parameter dependences. The dependence of IMF Bz and possible correlation with magnetic reconnection should be a principal feature in the model. These observations support the conjecture that cross-field diffusion of magnetosheath plasma by wave particle interaction with these waves is the steady state source of the low-latitude boundary layer, and that pitch angle scattering and the consequential particle precipitation into the ionosphere is the mechanism for the dayside aurora.

1989-01-01

298

A statistical study of ELF-VLF plasma waves at the magnetopause  

Energy Technology Data Exchange (ETDEWEB)

A statistical study of the broadband ELF-VLF plasma waves at the magnetopause has been performed using ISEE 1 plasma wave data. It is found that enhanced wave intensities are detected at 85% of all magnetopause crossings. Although wave amplitudes are highly variable from event to event and even within an event (particularly during high-intensity events), the wave spectra averaged over many passes are remarkably similar at dawn, noon, and dusk local hours. Thus to first order, the average wave intensity and spectral shape are independent of local time. The average wave intensity is independent of latitude, magnetosheath field strength, and magnetopause position. The only parameter found to be correlated with wave intensity is the magnitude of the Z component of the magnetosheath magnetic field. The broadband wave intensities increase with increasing negative B{sub z}. These observational results put strong constraints on any proposed generation mechanism for the broadband magnetopause boundary layer waves. Reasonable mechanisms should be able to explain the lack of local time, latitude, and interplanetary parameter dependences. The dependence of IMF B{sub z} and possible correlation with magnetic reconnection should be a principal feature in the model. These observations support the conjecture that cross-field diffusion of magnetosheath plasma by wave particle interaction with these waves is the steady state source of the low-latitude boundary layer, and that pitch angle scattering and the consequential particle precipitation into the ionosphere is the mechanism for the dayside aurora.

Tsurutani, B.T.; Brinca, A.L.; Smith, E.J.; Okida, R.T. (Jet Propulsion Lab., Pasadena, CA (USA)); Anderson, R.R. (Univ. of Iowa, Iowa City (USA)); Eastman, T.E. (Univ. of Maryland, College Park (USA))

1989-02-01

299

A possible excitation mechanism for observed superthermal ion cyclotron emission from tokamak plasmas  

International Nuclear Information System (INIS)

Intense superthermal ion cyclotron emission (ICE) has been observed from tokamak plasmas. The power spectrum displays narrow peaks at multiple harmonics of the background ion cyclotron frequency [Cottrell and Dendy, Phys. Rev. Lett. 60, 33 (1988)] in Ohmic deuterium plasmas, and the radiation appears to be driven by the fusion ion population in the edge plasma. Theoretical investigation of this phenomenon may be rewarding, in terms of the information about the behavior of energetic ions in tokamaks that can be extracted from ICE observations. The interpretation presented here is based on the resonant excitation of fast Alfven waves with ion Bernstein waves supported by an energetic ion species (?), in the presence of a more numerous thermal ion species (i). Because the ion cyclotron frequencies may be commensurate (l??=s?i for some low integers l,s), and observations indicate that ? is comparable in magnitude to ?i, the standard theory [Belikov and Kolesnichenko, Sov. Phys. Tech. Phys. 20, 1146 (1976)] which assumes ? much-gt ?i is not immediately applicable, and is accordingly extended here to the low-frequency regime. The results show that excitation of the fast Alfven wave at proton cyclotron harmonics can occur for fusion proton concentrations n?/ni as low as 10-7, and that multiple cyclotron harmonics can be simultaneously unstable. Furthermore, while fusion protons born at 3.0 MeV are above the energy threshold required to drive the instability, the other primary fusion products in deuterium---1.0 MeV tritons and 0.82 MeV helium-3 nuclei---fall below it, consistent with the observation that radiation at cyclotron harmonics of the latter is not detected.

1992-01-01

300

The Electron Spectrum in 3C279 and the Observed Emission Spectrum  

CERN Multimedia

The emission mechanisms of the blazar 3C 279 are studied by solving the kinetic equations of electrons and photons in a relativistically moving blob. The gamma-ray spectral energy distribution (SED) is fitted by inverse Compton scattering of external photons. The bulk Lorentz factor of the emitting blob is found to be 25, and the magnetic field is found to be 0.3 G. GeV gamma-rays are well explained by inefficiently cooled electrons because of the Klein-Nishina effects. The electron spectrum is not a broken power law with a steeper spectrum above a break energy, which is often used to fit the observed SED. The kinetic energy density of the nonthermal electrons dominates the magnetic energy density; this result is qualitatively the same as that for TeV blazars such as Mrk 421 and Mrk 501. The gamma-ray luminosity of 3C 279 is often observed to increase rapidly. We show that one of the better sampled gamma-ray flares can be explain by the internal shock model.

Kusunose, M; Kato, T; Kusunose, Masaaki; Takahara, Fumio; Kato, Tomohiro

2003-01-01

 
 
 
 
301

Chandra Observations of SN 2004et and the X-ray Emission of Type IIp Supernovae  

CERN Multimedia

We report the X-ray detection of the Type II-plateau supernova SN 2004et in the spiral galaxy NGC 6946, using the Chandra X-Ray Observatory. The position of the X-ray source was found to agree with the optical position within ~0.4 arcsec. Chandra also surveyed the region before the 2004 event, finding no X-ray emission at the location of the progenitor. For the post-explosion observations, a total of 202, 151, and 158 photons were detected in three pointings, each ~29 ks in length, on 2004 October 22, November 6, and December 3, respectively. The spectrum of the first observation is best fit by a thermal model with a temperature of kT=1.3 keV and a line-of-sight absorption of N_H=1.0 x 10^{22} cm^{-2}. The inferred unabsorbed luminosity (0.4-8 keV) is ~4x10^{38} erg/s, adopting a distance of 5.5 Mpc. A comparison between hard and soft counts on the first and third epochs indicates a softening over this time, although there is an insufficient number of photons to constrain the variation of temperature and abso...

Rho, J; Chugai, N N; Chevalier, R A

2007-01-01

302

On the reconstructing the coronal magnetic field from Fe XIII 10747 A emission line observations  

Science.gov (United States)

Magnetic fields in the solar corona are the dominant fields that determine the static and dynamic properties of this outermost region of the solar atmosphere. It is within this tenuous region that the magnetic force dominates the gas pressure. Direct measurement of the coronal magnetic field is one of the most challenging problems in observational solar astronomy. To date, one of the promising measurement methods that have been successfully demonstrated is the spectropolarimetric measurement of the Fe XIII 10747 A forbidden emission line (CEL) (Lin, Penn, Tomczyk 2000; Lin, Kuhn, Coulter 2004; Tomczyk et al. 2007) formed due to Hanle and Zeeman effects. However, because coronal measurements are integrated over line-of-site (LOS), it is impossible to derive the configuration of the coronal magnetic field from a single observation (from a single viewing direction). Recent development in vector tomography techniques based on IR forbidden CEL polarization measurements from several viewing direction (Kramar, Inhester, Solanki 2006; Kramar, Inhester 2007) has the potential to resolve the 3D coronal magnetic field structure. In this paper, we will present a study of the effects of instrumental characteristics on the results of vector tomographic inversion using simulated data. We also investigate the sensitivity of the vector tomographic inversion to different coronal magnetic field configuration.

Kramar, M.; Lin, H.; Inhester, B.

2009-12-01

303

First observation of 54Zn and its decay by two-proton emission  

CERN Multimedia

The nucleus 54Zn has been observed for the first time in an experiment at the SISSI/LISE3 facility of GANIL in the quasi-fragmentation of a 58Ni beam at 74.5 MeV/nucleon in a natNi target. The fragments were analysed by means of the ALPHA-LISE3 separator and implanted in a silicon-strip detector where correlations in space and time between implantation and subsequent decay events allowed us to generate almost background free decay spectra for about 25 different nuclei at the same time. Eight 54Zn implantation events were observed. From the correlated decay events, the half-life of 54Zn is determined to be 3.2 +1.8/-0.8 ms. Seven of the eight implantations are followed by two-proton emission with a decay energy of 1.48(2) MeV. The decay energy and the partial half-life are compared to model predictions and allow for a test of these two-proton decay models.

Blank, B; Canchel, G; Dossat, C; Fleury, A; Giovinazzo, J; Matea, I; Adimi, N; De Oliveira, F; Stefan, I; Georgiev, G; Grévy, S; Thomas, J C; Borcea, C; Cortina-Gil, D; Caamano, M; Stanoiu, M; Aksouh, F; Brown, B A; Barker, F C; Richter, W A

2005-01-01

304

SOFIA observations of far-infrared hydroxyl emission toward classical ultracompact HII/OH maser regions  

CERN Multimedia

The hydroxyl radical (OH) is found in various environments within the interstellar medium (ISM) of the Milky Way and external galaxies, mostly either in diffuse interstellar clouds or in the warm, dense environments of newly formed low-mass and high-mass stars, i.e, in the dense shells of compact and ultracompact HII regions (UCHIIRs). Until today, most studies of interstellar OH involved the molecule's radio wavelength hyperfine structure (hfs) transitions. These lines are generally not in LTE and either masing or over-cooling complicates their interpretation. In the past, observations of transitions between different rotational levels of OH, which are at far-infrared wavelengths, have suffered from limited spectral and angular resolution. Since these lines have critical densities many orders of magnitude higher than the radio wavelength ground state hfs lines and are emitted from levels with more than 100 K above the ground state, when observed in emission, they probe very dense and warm material. We probe ...

Csengeri, T; Wyrowski, F; Requena-Torres, M A; Güsten, R; Wiesemeyer, H; Hübers, H -W; Hartogh, P; Jacobs, K

2012-01-01

305

Fermi Observations of GRB 090902B: A Distinct Spectral Component in the Prompt and Delayed Emission  

CERN Document Server

We report on the observation of the bright, long gamma-ray burst, GRB 090902B, by the Gamma-ray Burst Monitor (GBM) and Large Area Telescope (LAT) instruments on-board the Fermi observatory. This was one of the brightest GRBs to have been observed by the LAT, which detected several hundred photons during the prompt phase. With a redshift of z = 1.822, this burst is among the most luminous detected by Fermi. Time-resolved spectral analysis reveals a significant power-law component in the LAT data that is distinct from the usual Band model emission that is seen in the sub-MeV energy range. This power-law component appears to extrapolate from the GeV range to the lowest energies and is more intense than the Band component both below $\\sim$ 50 keV and above 100 MeV. The Band component undergoes substantial spectral evolution over the entire course of the burst, while the photon index of the power-law component remains constant for most of the prompt phase, then hardens significantly towards the end. After the pro...

2009-01-01

306

NEW MASER EMISSION FROM NONMETASTABLE AMMONIA IN NGC 7538. II. GREEN BANK TELESCOPE OBSERVATIONS INCLUDING WATER MASERS  

Energy Technology Data Exchange (ETDEWEB)

We present new maser emission from {sup 14}NH{sub 3} (9,6) in NGC 7538. Our observations include the known spectral features near v{sub LSR} = -60 km s{sup -1} and -57 km s{sup -1} and several more features extending to -46 km s{sup -1}. In three epochs of observation spanning two months we do not detect any variability in the ammonia masers, in contrast to the >10-fold variability observed in other {sup 14}NH{sub 3} (9,6) masers in the Galaxy over comparable timescales. We also present observations of water masers in all three epochs for which emission is observed over the velocity range -105 km s{sup -1} < v{sub LSR} < -4 km s{sup -1}, including the highest velocity water emission yet observed from NGC 7538. Of the remarkable number of maser species in IRS 1, H{sub 2}O and, now, {sup 14}NH{sub 3} are the only masers known to exhibit emission outside of the velocity range -62 km s{sup -1} < v{sub LSR} < -51 km s{sup -1}. However, we find no significant intensity or velocity correlations between the water emission and ammonia emission. We also present a non-detection in the most sensitive search to date toward any source for emission from the CC{sup 32}S and CC{sup 34}S molecules, indicating an age greater than Almost-Equal-To 10{sup 4} yr for IRS 1-3. We discuss these findings in the context of embedded stellar cores and recent models of the region.

Hoffman, Ian M. [St. Paul' s School, Concord, NH 03301 (United States); Seojin Kim, Stella, E-mail: ihoffman@sps.edu [Current address: Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139 (United States)

2011-12-15

307

HUBBLE SPACE TELESCOPE WFC3 EARLY RELEASE SCIENCE: EMISSION-LINE GALAXIES FROM INFRARED GRISM OBSERVATIONS  

International Nuclear Information System (INIS)

We present grism spectra of emission-line galaxies (ELGs) from 0.6 to 1.6 ?m from the Wide Field Camera 3 (WFC3) on the Hubble Space Telescope. These new infrared grism data augment previous optical Advanced Camera for Surveys G800L 0.6-0.95 ?m grism data in GOODS-South from the PEARS program, extending the wavelength coverage well past the G800L red cutoff. The Early Release Science (ERS) grism field was observed at a depth of two orbits per grism, yielding spectra of hundreds of faint objects, a subset of which is presented here. ELGs are studied via the H?, [O III], and [O II] emission lines detected in the redshift ranges 0.2 ?B(F098M) ? 25 mag. Seventeen GOODS-South galaxies that previously only had photometric redshifts now have new grism-spectroscopic redshifts, in some cases with large corrections to the photometric redshifts (?z ? 0.3-0.5). Additionally, one galaxy had no previously measured redshift but now has a secure grism-spectroscopic redshift, for a total of 18 new GOODS-South spectroscopic redshifts. The faintest source in our sample has a magnitude mAB(F098M)= 26.9 mag. The ERS grism data also reflect the expected trend of lower specific star formation rates for the highest mass galaxies in the sample as a function of redshift, consistent with downsizing and discovered previously from large surveys. These results demonstrate the remarkable efficiency and capability of the WFC3 NIR grisms for measuring galaxy properties to faint magnitudes and redshifts to z ?> 2.

2011-01-01

308

Observation of CH4 and other Non-CO2 Green House Gas Emissions from California  

Energy Technology Data Exchange (ETDEWEB)

In 2006, California passed the landmark assembly bill AB-32 to reduce California's emissions of greenhouse gases (GHGs) that contribute to global climate change. AB-32 commits California to reduce total GHG emissions to 1990 levels by 2020, a reduction of 25 percent from current levels. To verify that GHG emission reductions are actually taking place, it will be necessary to measure emissions. We describe atmospheric inverse model estimates of GHG emissions obtained from the California Greenhouse Gas Emissions Measurement (CALGEM) project. In collaboration with NOAA, we are measuring the dominant long-lived GHGs at two tall-towers in central California. Here, we present estimates of CH{sub 4} emissions obtained by statistical comparison of measured and predicted atmospheric mixing ratios. The predicted mixing ratios are calculated using spatially resolved a priori CH{sub 4} emissions and surface footprints, that provide a proportional relationship between the surface emissions and the mixing ratio signal at tower locations. The footprints are computed using the Weather Research and Forecast (WRF) coupled to the Stochastic Time-Inverted Lagrangian Transport (STILT) model. Integral to the inverse estimates, we perform a quantitative analysis of errors in atmospheric transport and other factors to provide quantitative uncertainties in estimated emissions. Regressions of modeled and measured mixing ratios suggest that total CH{sub 4} emissions are within 25% of the inventory estimates. A Bayesian source sector analysis obtains posterior scaling factors for CH{sub 4} emissions, indicating that emissions from several of the sources (e.g., landfills, natural gas use, petroleum production, crops, and wetlands) are roughly consistent with inventory estimates, but livestock emissions are significantly higher than the inventory. A Bayesian 'region' analysis is used to identify spatial variations in CH{sub 4} emissions from 13 sub-regions within California. Although, only regions near the tower are significantly constrained by the tower measurements, CH{sub 4} emissions from the south Central Valley appear to be underestimated in a manner consistent with the under-prediction of livestock emissions. Finally, we describe a pseudo-experiment using predicted CH{sub 4} signals to explore the uncertainty reductions that might be obtained if additional measurements were made by a future network of tall-tower stations spread over California. These results show that it should be possible to provide high-accuracy estimates of surface CH{sub 4} emissions for multiple regions as a means to verify future emissions reductions.

Fischer, Marc L.; Zhao, Chuanfeng; Riley, William J.; Andrews, Arlyn C.

2009-01-09

309

ROSAT observations of the soft X-ray background and of the cluster soft excess emission in the Hercules supercluster  

CERN Document Server

Recent observations with the XMM-Newton satellite confirmed the existence of the soft excess phenomenon in galaxy clusters, earlier discovered in several EUVE, ROSAT and BeppoSAX observations. Among the clusters for which XMM has reported detection of soft excess emission are MKW03s and A2052, two clusters in the Hercules concentration. The Hercules supercluster lies along the southern extension of the North Polar Spur, a region of bright soft X-ray emission clearly visible in ROSAT All-Sky Survey images. We analyze 11 pointed ROSAT PSPC observations toward 3 clusters in the Hercule concentration, MKW03s, A2052 and A2063, and 8 neighboring fields in order to investigate the soft X-ray emission in that region of the sky. We find that the soft X-ray emission varies by a factor of few on scales of few degrees, rendering the background subtraction a complex task. If the Noth Polar Spur emission is of local origin, we find that only A2052 and A2063 have evidence of cluster soft excess emission, and that the OVII e...

Bonamente, M; Kaastra, J; Bonamente, Max; Lieu, Richard; Kaastra, Jelle

2005-01-01

310

X-ray Emission from the Wolf-Rayet Bubble NGC 6888. I. Chandra ACIS-S Observations  

CERN Document Server

We analyze Chandra observations of the Wolf-Rayet (WR) bubble NGC 6888. This WR bubble presents similar spectral and morphological X-ray characteristics to those of S 308, the only other WR bubble also showing X-ray emission. The observed spectrum is soft, peaking at the N VII line emission at 0.5 keV with additional line emission at 0.7 - 0.9 keV and a weak tail of harder emission up to ~1.5 keV. This spectrum can be described by a two-temperature optically thin plasma emission model (T_{1}~1.4x10^{6} K, T_{2}~7.4x10^{6} K). We confirm the results of previous X-ray observations that no noticeable temperature variations are detected in the nebula. The X-ray-emitting plasma is distributed in three apparent morphological components: two caps along the tips of the major axis and an extra contribution toward the northwest blowout not reported in previous analysis of the X-ray emission toward this WR nebula. Using the plasma model fits of the Chandra ACIS spectra for the physical properties of the hot gas and the ...

Toalá, J A; Gruendl, R A; Chu, Y -H

2013-01-01

311

Eddy covariance observations of methane and nitrous oxide emissions. Towards more accurate estimates from ecosystems  

International Nuclear Information System (INIS)

About 30% of the increased greenhouse gas (GHG) emissions of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) are related to land use changes and agricultural activities. In order to select effective measures, knowledge is required about GHG emissions from these ecosystems and how these emissions are influenced by management and meteorological conditions. Accurate emission values are therefore needed for all three GHGs to compile the full GHG balance. However, the current annual estimates of CH4 and N2O emissions from ecosystems have significant uncertainties, even larger than 50%. The present study showed that an advanced technique, micrometeorological eddy covariance flux technique, could obtain more accurate estimates with uncertainties even smaller than 10%. The current regional and global trace gas flux estimates of CH4 and N2O are possibly seriously underestimated due to incorrect measurement procedures. Accurate measurements of both gases are really important since they could even contribute for more than two-third to the total GHG emission. For example: the total GHG emission of a dairy farm site was estimated at 16.103 kg ha-1 yr-1 in CO2-equivalents from which 25% and 45% was contributed by CH4 and N2O, respectively. About 60% of the CH4 emission was emitted by ditches and their bordering edges. These emissions are not yet included in the national inventory reports. We recommend including these emissions in coming reports.

2010-01-01

312

On the effectiveness of the vlf-em method For ground water prospecting in the Basement terrains, Sinai, Egypt ??? ?????? ????? ??????? ??????????????? ??? ?????? ??????? ???? ??????? ?? ?????? ??????? ?? ???? ??????? ? ????? ? ???  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The VLF-EM method is proved to be an effective, fast and inexpensive tool for ground water prospecting in the basement terrains of Southern Sinai. The resistive shallow alluvial deposits increase the penetration depth of the received VLF waves to as deep as 40 meters which is very reasonable to dete...

Shendi, El-Arabi Hendi [??????? ???? ????

313

NUV/Blue spectral observations of sprites in the 320-460 nm region: ${\\mathrm N_2}$ (2PG) Emissions  

CERN Document Server

A near-ultraviolet (NUV) spectrograph (320-460 nm) was flown on the EXL98 aircraft sprite observation campaign during July 1998. In this wavelength range video rate (60 fields/sec) spectrographic observations found the NUV/blue emissions to be predominantly N2 (2PG). The negligible level of N2+ (1NG) present in the spectrum is confirmed by observations of a co-aligned, narrowly filtered 427.8 nm imager and is in agreement with previous ground-based filtered photometer observations. The synthetic spectral fit to the observations indicates a characteristic energy of ~1.8 eV, in agreement with our other NUV observations.

Heavner, M J; Siefring, C; Sentman, D D; Moudry, D R; Wescott, E M; Bucsela, E J

2010-01-01

314

Observational cosmology with the PLANCK satellite: modelling of the polarized Galactic emissions  

International Nuclear Information System (INIS)

This thesis is dedicated to the Cosmic Microwave Background (CMB) anisotropies measurement and to the characterisation of the foreground Galactic emissions. This work is in the framework of the Planck satellite data analysis preparation. First, this thesis give a description of the Big Bang model and of the CMB physics. Then, we present the Archeops, WMAP and PLANCK experiments and their data analysis. Part two is devoted to the description of the diffuse Galactic synchrotron, free-free and thermal dust emissions and to the study of those emissions in the Galactic plane. Using comparison between our simulations and the WMAP, Archeops and IRIS data we are able to provide partial maps of the spatial variations of the dust grain temperature and of the spectral index of the synchrotron and thermal dust emissions. Third part is dedicated to the study of the two main polarized Galactic emissions: synchrotron and thermal dust emissions. We evaluate effective models based on template maps. We also build physical model based on physics for these emissions that is to say shape of the Galactic magnetic field and matter density in our Galaxy. Using maps and Galactic profiles, we compare our simulations of these emissions to the Archeops and WMAP data. Thanks to that we are able to provide for the first time a coherent model of the synchrotron and thermal dust emissions. Then we propose a method to improved the constraints on our model using the PLANCK data. Finally the last part focuses on the angular power spectra of the polarized Galactic emissions. We estimate the contamination due to these foreground emissions on the CMB signal. In addition we propose a method to minimize the contamination of the CMB PLANCK data by the thermal dust emission using masks. (author)

2010-01-01

315

Variations of the spectral index of dust emissivity from Hi-GAL observations of the Galactic plane  

CERN Document Server

Variations in the dust emissivity are critical for gas mass determinations derived from far-infrared observations, but also for separating dust foreground emission from the Cosmic Microwave Background (CMB). Hi-GAL observations allow us for the first time to study the dust emissivity variations in the inner regions of the Galactic plane at resolution below 1 degree. We present maps of the emissivity spectral index derived from the combined Herschel PACS 160 \\mu m, SPIRE 250 \\mu m, 350 \\mu m, and 500 \\mu m data, and the IRIS 100 \\mu m data, and we analyze the spatial variations of the spectral index as a function of dust temperature and wavelength in the two Science Demonstration Phase Hi-GAL fields, centered at l=30{\\deg} and l=59{\\deg}. Applying two different methods, we determine both dust temperature and emissivity spectral index between 100 and 500 \\mu m, at an angular resolution of 4'. Combining both fields, the results show variations of the emissivity spectral index in the range 1.8-2.6 for temperature...

Paradis, D; Noriega-Crespo, A; Paladini, R; Piacentini, F; Bernard, J P; de Bernardis, P; Calzoletti, L; Faustini, F; Martin, P; Masi, S; Montier, L; Natoli, P; Ristorcelli, I; Thompson, M A; Traficante, A; Molinari, S

2010-01-01

316

Evolution of magnetotelluric, total magnetic field, and VLF field parameters in Central Italy: relations to local seismic activity  

Directory of Open Access Journals (Sweden)

Full Text Available Magnetotelluric data were collected at Collemeluccio (41.72°N, 14.37°E) in Central Italy from summer 1991 to spring 1998. Analyzed by means of tensor decomposition on the geoelectric potential and robust estimation on the geomagnetic field, this set of data allowed the investigation of the electric properties at different time-periods. The variation of some indicators, related to the phenomenon of electromagnetic induction, is presented here in its time evolution and compared to local and regional seismic activity. Tectonomagnetic field observations from absolute magnetic field level in Central Italy were also made on data simultaneously recorded at four magnetometer stations, using L'Aquila Geomagnetic Observatory as a reference for differentiation. Recent results gathered from a system of two VLF search coil wide-band antennas, installed in the L'Aquila Observatory, are also discussed in relation to local seismic activity.

A. Meloni; D. Di Mauro; G. Mele; P. Palangio; T. Ernst; R. Teisseyre

2001-01-01

317

Comparative analysis of airglow emissions in terrestrial planets, observed with VIRTIS-M instruments on board Rosetta and Venus Express  

Science.gov (United States)

Airglow emissions are optimal processes to investigate the chemistry and dynamics in planetary atmospheres. In this study, we focus on the O2 and OH airglow emissions in Venus, Earth, and Mars atmospheres, which are controlled by chemical reactions common to the three planets. By studying these phenomena on Venus, Earth, and Mars using similar instruments, we are able to derive information about their photochemistry and the physical conditions of the atmospheres, but also to constrain the dynamics responsible for transport of atomic oxygen, ozone and other minor species. After a review of the nightglow emissions observed in the Venus atmosphere, we analyze the O2 and OH airglow emissions in the Earth's atmosphere observed during the 3 swing-bys of our planet by the Rosetta spacecraft. We also report the detection of the O2 nightglow emission in the Mars atmosphere, observed in February 2007 during the Rosetta fly-by of the planet. The airglow characteristics are in agreement with the measurements obtained from sensors on board Mars Express.

Migliorini, A.; Piccioni, G.; Capaccioni, F.; Filacchione, G.; Tosi, F.; Gérard, J.-C.

2013-09-01

318

Surface observations for monitoring urban fossil fuel CO2 emissions: Minimum site location requirements for the Los Angeles megacity  

Science.gov (United States)

The contemporary global carbon cycle is dominated by perturbations from anthropogenic CO2 emissions. One approach to identify, quantify, and monitor anthropogenic emissions is to focus on intensely emitting urban areas. In this study, we compare the ability of different CO2 observing systems to constrain anthropogenic flux estimates in the Los Angeles megacity. We consider different observing system configurations based on existing observations and realistic near-term extensions of the current ad hoc network. We use a high-resolution regional model (Stochastic Time-Inverted Lagrangian Transport-Weather Research and Forecasting) to simulate different observations and observational network designs within and downwind of the Los Angeles (LA) basin. A Bayesian inverse method is employed to quantify the relative ability of each network to improve constraints on flux estimates. Ground-based column CO2 observations provide useful complementary information to surface observations due to lower sensitivity to localized dynamics, but column CO2 observations from a single site do not appear to provide sensitivity to emissions from the entire LA megacity. Surface observations from remote, downwind sites contain weak, sporadic urban signals and are complicated by other source/sink impacts, limiting their usefulness for quantifying urban fluxes in LA. We find a network of eight optimally located in-city surface observation sites provides the minimum sampling required for accurate monitoring of CO2 emissions in LA, and present a recommended baseline network design. We estimate that this network can distinguish fluxes on 8 week time scales and 10 km spatial scales to within ~12 g C m-2 d-1 (~10% of average peak fossil CO2 flux in the LA domain).

Kort, Eric A.; Angevine, Wayne M.; Duren, Riley; Miller, Charles E.

2013-02-01

319

Fermi large area telescope observations of the cosmic-ray induced ?-ray emission of the Earth's atmosphere  

International Nuclear Information System (INIS)

[en] We report on measurements of the cosmic-ray induced ?-ray emission of Earth's atmosphere by the Large Area Telescope on board the Fermi Gamma-ray Space Telescope. The Large Area Telescope has observed the Earth during its commissioning phase and with a dedicated Earth limb following observation in September 2008. These measurements yielded ?6.4x106 photons with energies >100 MeV and ?250 hours total live time for the highest quality data selection. This allows the study of the spatial and spectral distributions of these photons with unprecedented detail. The spectrum of the emission--often referred to as Earth albedo gamma-ray emission--has a power-law shape up to 500 GeV with spectral index ?=2.79±0.06.

2009-12-15

320

Assessing and evaluating urban VOC emissions in mid-latitude megacities from intensive observations in Paris and Los Angeles  

Science.gov (United States)

Volatile Organic Compounds (VOC) affect urban air quality and regional climate change by contributing to ozone formation and the build-up of Secondary Organic Aerosols (SOA). Quantification of VOC emissions is a first critical step to predict VOC environmental impacts and to design effective abatement strategies. Indeed, the quality of ozone and SOA forecasts strongly depends on an accurate knowledge of the primary VOC emissions. However, commonly used bottom-up approaches are highly uncertain due to source multiplicity (combustion processes, storage and distribution of fossil fuels, solvent use, etc.) because of numerous controlling factors (driving conditions, fuel type, temperature, radiation, etc.), and their great variability in time and space. Field observations of VOC and other trace gases can provide valuable top-down constraints to evaluate VOC emission inventories at urban scales. In addition, the implementation of emission reduction measures raises the question of the increasing importance of VOC sources other than traffic. Here, we will evaluate VOC emissions of two mid-latitude megacities in the Northern Hemisphere: the Greater Paris area (Europe) and Los Angeles (USA). In 2009 and 2010, three intensive field campaigns took place in Paris and Los Angeles in the framework of the MEGAPOLI (EU FP7) and CalNex-2010 projects, respectively. Very detailed measurements of aerosol composition and properties, and their gaseous VOC precursors were carried out at ground-based sites (urban center and suburban) and on various mobile platforms. This contribution uses a comprehensive suite of VOC measurements collected by GC-MS/FID techniques at ground-based sites in both cities by a source-receptor methodology. First, emission ratios were estimated from the observations (uncertainty of ± 20%) and compared regarding regional characteristics and European vs. Californian control policies. Then, determined emission ratios were used to assess the accuracy of up-to-date emission inventories. While emission ratios agree within the uncertainties for many VOCs, remarkable differences are observed for aromatic VOCs (C7-C9) depending on the season. Moreover, the evaluation of emission inventories shows large discrepancies for VOCs for which traffic is not the dominant source. Commonalities and/or differences are also discussed in term of implication for urban atmospheric chemistry (ozone and SOA formation potential) in both megacities.

Borbon, A.; Gilman, J. B.; Kuster, W. C.; McKeen, S. A.; Holloway, J. S.; Gros, V.; Gaimoz, C.; Beekmann, M.; De Gouw, J. A.

2011-12-01

 
 
 
 
321

Investigation of VLF and HF waves showing seismo-ionospheric anomalies induced by the 29 September 2009 Samoa earthquake (Mw=8.1)  

Directory of Open Access Journals (Sweden)

Full Text Available In Samoa Islands, a powerful earthquake took place at 17:48:10.99 UTC (06:48:10.99 LT) on 29 September 2009 with a magnitude Mw=8.1. Using ICE (Instrument Champ Electrique) and IMSC (Instrument Magnetic Search Coil) experiments onboard the DEMETER (Detection of Electromagnetic Emissions Transmitted from Earthquake Regions) satellite we have surveyed possible variations in electromagnetic signals transmitted by the ground-based VLF transmitter NPM in Hawaii and in HF plasma waves close to the Samoa earthquake during the seismic activity. The indices Dst and Kp were used to distinguish pre-earthquake anomalies from the other anomalies related to the geomagnetic activities. In a previous study we have shown that anomalies in IAP (plasma analyzer) and ISL (Langmuir probe) experiments onboard the DEMETER and also TEC (Total Electron Content) data appear 1 to 5 days before the Samoa earthquake. In this paper we show that the anomalies in the VLF transmitter signal and in the HF range appear with the same time scale. The lack of significant geomagnetic activities indicates that these anomalous behaviors could be regarded as seismo-ionospheric precursors. It is also shown that comparative analysis is more effective in seismo-ionospheric studies.

M. Akhoondzadeh; M. Parrot; M. R. Saradjian

2010-01-01

322

Inverse modeling of Texas NOx emissions using space-based and ground-based NO2 observations  

Science.gov (United States)

Inverse modeling of nitrogen oxide (NOx) emissions using satellite-based NO2 observations has become more prevalent in recent years, but has rarely been applied to regulatory modeling at regional scales. In this study, OMI satellite observations of NO2 column densities are used to conduct inverse modeling of NOx emission inventories for two Texas State Implementation Plan (SIP) modeling episodes. Addition of lightning, aircraft, and soil NOx emissions to the regulatory inventory narrowed but did not close the gap between modeled and satellite observed NO2 over rural regions. Satellite-based top-down emission inventories are created with the regional Comprehensive Air Quality Model with extensions (CAMx) using two techniques: the direct scaling method and discrete Kalman filter (DKF) with Decoupled Direct Method (DDM) sensitivity analysis. The simulations with satellite-inverted inventories are compared to the modeling results using the a priori inventory as well as an inventory created by a ground-level NO2 based DKF inversion. The DKF inversions yield conflicting results: the satellite-based inversion scales up the a priori NOx emissions in most regions by factors of 1.02 to 1.84, leading to 3-55% increase in modeled NO2 column densities and 1-7 ppb increase in ground 8 h ozone concentrations, while the ground-based inversion indicates the a priori NOx emissions should be scaled by factors of 0.34 to 0.57 in each region. However, none of the inversions improve the model performance in simulating aircraft-observed NO2 or ground-level ozone (O3) concentrations.

Tang, W.; Cohan, D.; Lamsal, L. N.; Xiao, X.; Zhou, W.

2013-07-01

323

Observation and analysis of self-amplified spontaneous emission at the APS low-energy undulator test line  

International Nuclear Information System (INIS)

Exponential growth of self-amplified spontaneous emission at 530 nm was first experimentally observed at the Advanced Photon Source low-energy undulator test line in December 1999. Since then, further detailed measurements and analysis of the results have been made. Here, we present the measurements and compare these with calculations based on measured electron beam properties and theoretical expectations.

2001-12-21

324

Sensitivity of Inverse Estimation of 2004 Elemental Carbon Emissions Inventory in the United States to the Choice of Observational Networks  

Science.gov (United States)

Choice of observational networks used for inverse re-estimation of elemental (or black) carbon (EC) emissions in the United States impacts results. We convert the Thermal Optical Transmittance (TOT) EC measurements to the Thermal Optical Reflectance (TOR) equivalent to make full...

325

Observation and analysis of self-amplified spontaneous emission at the APS low-energy undulator test line  

CERN Document Server

Exponential growth of self-amplified spontaneous emission at 530 nm was first experimentally observed at the Advanced Photon Source low-energy undulator test line in December 1999. Since then, further detailed measurements and analysis of the results have been made. Here, we present the measurements and compare these with calculations based on measured electron beam properties and theoretical expectations.

Arnold, N D; Banks, G; Bechtold, R; Beczek, K; Benson, C; Berg, S; Berg, W; Biedron, S G; Biggs, J A; Boerste, K; Borland, M; Bosek, M; Brzowski, W R; Budz, J; Carwardine, J A; Castro, P; Chae, Y C; Christensen, S; Clark, C; Conde, M; Crosbie, E A; Decker, G A; Dejus, Roger J; Deleon, H; Den Hartog, P K; Deriy, B N; Dohan, D; Dombrowski, P; Donkers, D; Doose, C L; Dortwegt, R J; Edwards, G A; Eidelman, Y; Erdmann, M J; Error, J J; Ferry, R; Flood, R; Forrestal, J; Freund, H; Friedsam, H; Gagliano, J; Gai, W; Galayda, J N; Gerig, R; Gilmore, R L; Gluskin, E; Goeppner, G A; Goetzen, J; Gold, C; Grelick, A E; Hahne, M W; Hanuska, S; Harkay, K C; Harris, G; Hillman, A L; Hogrefe, R; Hoyt, J; Huang, Z; Jagger, J M; Jansma, W G; Jaski, M; Jones, S J; Keane, R T; Kelly, A L; Keyser, C; Kim, K J; Kim, S H; Kirshenbaum, M; Klick, J H; Knoerzer, K; Knott, M; Koldenhoven, R J; Labuda, S; Laird, R; Lang, J; Lenkszus, F R; Lessner, E S; Lewellen, J W; Li, Y; Lill, R M; Lumpkin, Alex H; Makarov, O A; Markovich, G M; McDowell, M; McDowell, W P; McNamara, P E; Meier, T; Meyer, D; Michalek, W; Milton, S V; Moe, H; Moog, E; Morrison, L; Nassiri, A; Noonan, J R; Otto, R; Pace, J; Pasky, S J; Penicka, J M; Pietryla, A F; Pile, G; Pitts, C; Power, J; Powers, T; Putnam, C C; Puttkammer, A J; Reigle, D; Reigle, L; Ronzhin, D; Rotela, E R; Russell, E F; Sajaev, Vadim; Sarkar, S; Scapino, J C; Schröder, K; Seglem, R A; Sereno, N S; Sharma, S K; Sidarous, J F; Singh, O; Smith, T L; Soliday, R; Sprau, G A; Stein, S J; Stejskal, B; Svirtun, V; Teng, L C; Theres, E; Thompson, K; Tieman, B J; Torres, J A; Trakhtenberg, E; Travish, G; Trento, G F; Vacca, J; Vasserman, I B; Vinokurov, N A; Walters, D R; Wang, J; Wang, X J; Warren, J; Wesling, S; Weyer, D L; Wiemerslage, G; Wilhelmi, K; Wright, R; Wyncott, D; Xu, S; Yang, B X; Yoder, W; Zabel, R B

2001-01-01

326

Development of a United States - Mexico emissions inventory for the Big Bend Regional Aerosol and Visibility Observational (BRAVO) Study  

Energy Technology Data Exchange (ETDEWEB)

The Big Bend Regional Aerosol and Visibility Observational (BRAVO) Study investigated the sources of haze at Big Bend National Park in southwest Texas. The modeling domain includes most of the continental United States and Mexico. The BRAVO emissions inventory was constructed from the 1999 National Emission Inventory for the United States, modified to include finer-resolution data for Texas and 13 U.S. states in close proximity. The inventory includes emissions for CO, nitrogen oxides, sulfur dioxide, volatile organic compounds (VOCs), ammonia, particulate matter (PM) {lt}10 {mu}m in aerodynamic diameter, and PM {lt}2.5 {mu}m in aerodynamic diameter. The SMOKE modeling system was used to generate gridded emissions fields for use with the Regional Modeling System for Aerosols and Deposition (REMSAD) and the Community Multiscale Air Quality model modified with the Model of Aerosol Dynamics, Reaction, Ionization and Dissolution (CMAQ-MADRID). The compilation of the inventory, supporting model input data, and issues encountered during the development of the inventory are documented. A comparison of the BRAVO emissions inventory for Mexico with other emerging Mexican emission inventories illustrates their uncertainty. 65 refs., 4 figs., 9 tabs.

Hampden Kuhns; Eladio M. Knipping; Jeffrey M. Vukovich, [Desert Research Institute, Reno, NV (US)

2005-05-01

327

Characteristics of fire-generated gas emission observed during a large peatland fire in 2009 at Kalimantan, Indonesia  

Science.gov (United States)

To investigate the characteristics of gas emissions from a tropical peatland fire, ground-level measurement of fire-generated gases was conducted during a large fire event in Kalimantan, Indonesia in 2009. Concentrations of CO and CH4 showed positive linear correlations with that of CO2. The relationship between concentrations of N2O and CO2 were divided into two parts, suggesting the influence of additional N2O generation during sample storage. The CO2-normalized emission ratio was calculated for CO, CH4, and N2O. The molar ratio of these fire-generated gas emissions was summarized as CO2:CO:CH4:N2O = 1.00:0.382:0.0261:0.000156, whereas the emission ratio calculated on the global warming potential (GWP) basis was CO2:CH4:N2O = 1.00:0.237:0.0465. The GWP emission based on this ratio was 87.8–91.2% of a simple evaluation in which all carbon was assumed to be emitted as CO2. This is the first trial to evaluate the emission ratios of major greenhouse gases on the basis of ground-level observation during an actual tropical peatland fire.

Hamada, Yohei; Darung, Untung; Limin, Suwido H.; Hatano, Ryusuke

2013-08-01

328

A Cometary Bow Shock and Mid-Infrared Emission Variations Revealed in Spitzer Observations of HD 34078 and IC 405  

CERN Multimedia

We present new infrared observations of the emission/reflection nebula IC 405 obtained with the Spitzer Space Telescope. Infrared images in the four IRAC bands (3.6, 4.5, 5.8, and 8.0 um) and two MIPS bands (24 and 70 um) are complemented by IRS spectroscopy (5-30 um) of two nebular filaments. The IRAC (8.0 um) and MIPS imaging shows evidence of a bow shock associated with the runaway O9.5V star, HD 34078, created by the interaction between the star and nebular material. The ratio of emission at 24 to 70 um is higher in the immediate vicinity of HD 34078 than in the outer filaments, providing evidence for elevated dust temperatures (T_d > 90 K) in the shock region. The nebular imaging reveals that the morphology is band dependent, with varying contributions from aromatic emission features, H2, and dust emission. Nebular spectroscopy is used to quantify these contributions, showing several aromatic emission bands between 6-14 um, the S(5), S(3), S(2), and S(1) pure rotational emission lines of H2, and atomic f...

France, K; Lupu, R E; France, Kevin; Candliss, Stephan R. Mc; Lupu, Roxana E.

2006-01-01

329

First Observation of Self-Amplified Spontaneous Emission in a Free-Electron Laser at 109 nm Wavelength  

CERN Multimedia

We present the first observation of Self-Amplified Spontaneous Emission (SASE) in a free-electron laser (FEL) in the Vacuum Ultraviolet regime at 109 nm wavelength (11 eV). The observed free-electron laser gain (approx. 3000) and the radiation characteristics, such as dependency on bunch charge, angular distribution, spectral width and intensity fluctuations all corroborate the existing models for SASE FELs.

Andruszków, J; Ayvazyan, V T; Baboi, N I; Bakker, R; Balakin, V; Barni, D; Bazhan, A; Bernard, M; Bosotti, A; Bourdon, J C; Brefeld, W; Brinkmann, R; Bühler, S; Carneiro, J P; Castellano, M G; Castro, P; Catani, L; Chel, S; Cho, Y; Choroba, S; Colby, E R; Decking, W; Den Hartog, P; Desmons, M; Dohlus, M; Edwards, D; Edwards, H T; Faatz, B; Feldhaus, J; Ferrario, M; Fitch, M J; Flöttmann, K; Fouaidy, M; Gamp, A; Garvey, Terence; Geitz, M A; Gluskin, E S; Gretchko, V; Hahn, U; Hartung, W H; Hubert, D; Hüning, M; Ischebek, R; Jablonka, M; Joly, J M; Juillard, M; Junquera, T; Jurkiewicz, P; Kabel, A C; Kahl, J; Kaiser, H; Kamps, T; Katelev, V V; Kirchgessner, J L; Körfer, M; Kravchuk, L V; Kreps, G; Krzywinski, J; Lokajczyk, T; Lange, R; Leblond, B; Leenen, M; Lesrel, J; Liepe, M; Liero, A; Limberg, T; Lorenz, R; Lu, H H; Lu, F H; Magne, C; Maslov, M A; Materlik, G; Matheisen, A; Menzel, J; Michelato, P; Möller, W D; Mosnier, A; Müller, U C; Napoly, O; Novokhatskii, A V; Omeich, M; Padamsee, H; Pagani, C; Peters, F; Petersen, B; Pierini, P; Pflüger, J; Piot, P; Phung Ngoc, B; Plucinski, L; Proch, D; Rehlich, K; Reiche, S; Reschke, D; Reyzl, I; Rosenzweig, J; Rossbach, J; Roth, S; Saldin, E L; Sandner, W; Sanok, Z; Schlarb, H; Schmidt, G; Schmüser, P; Schneider, J R; Schneidmiller, E A; Schreiber, H J; Schreiber, S; Schütt, P; Sekutowicz, J; Serafini, L; Sertore, D; Setzer, S; Simrock, S; Sonntag, B F; Sparr, B; Stephan, F; Sytchev, V V; Tazzari, S; Tazzioli, F; Tigner, Maury; Timm, M; Tonutti, M; Trakhtenberg, E; Treusch, R; Trines, D; Verzilov, V A; Vielitz, T; Vogel, V; Von Walter, G; Wanzenberg, R; Weiland, T; Weise, H; Weisend, J G; Wendt, M; Werner, M; White, M M; Will, I; Wolff, S; Yurkov, M V; Zapfe, K; Zhogolev, P; Zhou, F

2000-01-01

330

New observations of VOC emissions and concentrations in, above, and around the Central Valley of California  

Science.gov (United States)

Large portions of the Central Valley of California are out of compliance with current state and federal air quality standards for ozone and particulate matter, and the relative importance of biogenic and anthropogenic VOC emissions to their photochemical production in this region remains uncertain. In 2009-2011 multiple measurement campaigns were completed investigating the VOC emission inventory and concentration distributions. In 2009 BVOC emissions from more than 20 species of major agricultural crops in California were measured in a greenhouse using branch enclosures by both PTRMS and in-situ GC. Overall, crops were found to emit low amounts of BVOC compared to the natural forests surrounding the valley. Crops mainly emitted methanol and terpenes, with a broad array of other species emitted at lower levels, and all the measured crops showed negligible emissions of isoprene. Navel oranges were the largest crop BVOC emitters measured so a full year of flux measurements were made in an orange grove near Visalia in 2010 by eddy covariance(EC)-PTRMS with two multi-week periods of concentration measurements by hourly in-situ GC, and one month of high mass resolution flux measurements by EC-PTR-TOF-MS. The dominant BVOC emissions from the orange grove were methanol and terpenes, followed by acetone, acetaldehyde, and a low level of emissions for many other species. In 2011 aircraft eddy covariance measurements of BVOC fluxes were made by EC-PTRMS covering a large area of California as part of the California Airborne Bvoc Emission Research in Natural Ecosystem Transects (CABERNET) campaign aimed at improving BVOC emission models on regional scales, mainly profiling BVOC emissions from oak woodlands surrounding the Central Valley. In 2010, hourly in-situ VOC measurements were made via in-situ GC in Bakersfield, CA as part of the CalNex experiment. Additionally, in-situ measurements of fresh motor vehicle exhaust were made in Oakland's Caldecott tunnel. Measurements by in-situ GC included more than 200 anthropogenic and biogenic VOCs with a wide range of volatilities (up to 17 carbon atoms in size) and various functional groups (e.g. aldehydes, ketones, alcohols, halogens, sulfur, & nitrogen). Finally, in 2011 vertical profiles of VOC were made at 5 heights on a communication tower at Walnut Grove (~20 miles south of Sacramento) from 30' to 1550' by PTRMS. Results from all of these studies combined provide a novel overview of the distribution of VOC emissions and concentrations in, around, and above the Central Valley of California.

Goldstein, A. H.; Fares, S.; Gentner, D. R.; Park, J.; Weber, R.; Ormeno, E.; Holzinger, R.; Misztal, P. K.; Karl, T. R.; Guenther, A. B.; Fischer, M. L.; Harley, R. A.; Karlik, J. F.

2011-12-01

331

Integrated Assessment Modeling of Carbon Sequestration and Land Use Emissions Using Detailed Model Results and Observations  

Energy Technology Data Exchange (ETDEWEB)

This report outlines the progress on the development and application of Integrated Assessment Modeling of Carbon Sequestrations and Land Use Emissions supported by the DOE Office of Biological and Environmental Research (OBER), U.S. Department of Energy, Grant No. DOE-DE-FG02-01ER63069. The overall objective of this collaborative project between the University of Illinois at Urbana-Champaign (UIUC), Oak Ridge National Laboratory (ORNL), Lawrence Livermore National Laboratory (LLNL), and Pacific Northwest National Laboratory (PNNL) was to unite the latest advances in carbon cycle research with scientifically based models and policy-related integrated assessment tools that incorporate computationally efficient representations of the latest knowledge concerning science and emission trajectories, and their policy implications. As part of this research we accomplished the following tasks that we originally proposed: (1) In coordination with LLNL and ORNL, we enhanced the Integrated Science Assessment Model's (ISAM) parametric representation of the ocean and terrestrial carbon cycles that better represent spatial and seasonal variations, which are important to study the mechanisms that influence carbon sequestration in the ocean and terrestrial ecosystems; (2) Using the MiniCAM modeling capability, we revised the SRES (IPCC Special Report on Emission Scenarios; IPCC, 2000) land use emission scenarios; and (3) On the application front, the enhanced version of ISAM modeling capability is applied to understand how short- and long-term natural carbon fluxes, carbon sequestration, and human emissions contribute to the net global emissions (concentrations) trajectories required to reach various concentration (emission) targets. Under this grant, 21 research publications were produced. In addition, this grant supported a number of graduate and undergraduate students whose fundamental research was to learn a disciplinary field in climate change (e.g., ecological dynamics and ocean circulations) and then complete research on how this field could be linked to the other factors we need to consider in its dynamics (e.g., land use, ocean and terrestrial carbon sequestration and climate change).

Dr. Atul Jain

2005-04-17

332

Observation of copious emission at the fundamental frequency by a Smith-Purcell free-electron laser with sidewalls  

International Nuclear Information System (INIS)

An experiment at microwave frequencies confirms the recent prediction that a Smith-Purcell [S. J. Smith and E. M. Purcell, Phys. Rev. 92, 1069 (1953)] free-electron laser equipped with sidewalls can emit radiation at the frequency of the surface wave. The power output is considerably greater than for the previously observed emission at the second harmonic, in agreement with three-dimensional simulations. The dependence of frequency on beam energy and emission angle is in good agreement with three-dimensional theory and simulations. Provided that a reduction in scale can be achieved, a path is open to coherent Smith-Purcell radiation at terahertz frequency.

2012-03-26

333

Synthesis of Zn S:Co semiconductor nano particles 2.5 nm and observing wavelength emission 423 nm  

International Nuclear Information System (INIS)

[en] Synthesis of nano crystal semiconductor Zn S:Co are prepared by wet chemical method at room temperature. The effects of increasing cobalt's doped in Zn S are studied, and indicated the size distribution, absorption, excitation, emission, and structure of particles. Band gap and size of nano-particles are calculated by using absorption wavelength, the size values are measured and compared with XRD and Transmission Electron Microscopy results. By using L S- 55, we observed the emissions with excitation of 283 nm for different intensity at 423 nm.

2007-01-01

334

Soft X-ray emissions related to the solar wind charge exchange observed by the X-ray satellite observatories  

International Nuclear Information System (INIS)

We have observed the emission spectra in collisions of bare and hydrogen-like C and O ions with helium atoms and hydrogen molecules as target gases in the soft X-ray region using a window-less Si(Li) detector at collision energies around 100 keV. Because it is found that the 1s-2p emission is dominant in each spectrum, we indicate that the cascade from the upper states give the large population of the 2p state after the consideration using state-selective capture cross sections calculated by the TC-AOCC method.

2012-11-05

335

Observation of strong emission from NeIX and NeX transitions in a laser-driven plasma  

Energy Technology Data Exchange (ETDEWEB)

The authors observe strong emission from the 1s{sup 2}-1snp Rydberg series in He-like neon and from the Lyman-{alpha} transition in H-like neon. These emissions are observed when 1.05 {mu}m light from a 650 femtosecond laser is focused into the dense, localized output of a pulsed, supersonic nozzle. The maximum focal irradiance of the laser was measured at full power in a vacuum to be 2 {times} 10{sup 18} W/cm{sup 2}. Although emissions from lower charge states such as Ne{sup 6+} and Ne{sup 7+} closely follow rates predicted by tunneling theory, emissions from Ne{sup 8+} and Ne{sup 9+} are observed at irradiances two order of magnitude below tunneling theory estimates (e.g. the He-{alpha} line appears at 2 {times} 10{sup 17} W/cm{sup 2}). They discuss the origins of these anomalously high charge states and the implications to recombination-pumped x-rays lasers.

Crane, J.K.; Ditmire, T.; Nguyen, H.; Perry, M.D.

1994-07-01

336

Observations of the Soft $\\gamma$-Ray early Afterglow emission from Two Bright $\\gamma$-ray Bursts  

CERN Multimedia

We present the results of observations of the soft gamma-ray early afterglows with the energy above 100keV from two bright Gamma-ray bursts detected by the PHEBUS instrument of the GRANAT orbital observatory. We show that the light curves of GRB910402 and GRB920723 events present the afterglow emission with fading fluxes. During our observations ~700s for these gamma-ray bursts the afterglow emission was fading as the power law of time with indices equal to -0.70+/-0.04 and -0.60+/-0.05 (at 1sigma confidence level). In both cases just after the end of the GRB event we observed the energy spectrum of the afterglow emissions which was softer than the energy spectrum of the main GRB events. The average photon index of the main GRB event (in 100-800keV range) is equal to \\~1.5. In the beginning of the afterglow emission the energy spectra of both events correspond to the much softer spectra with the photon index of ~2.5. We found that the times of abrupt softening of the burst spectra correspond within statistica...

Tkachenko, A V; Sunyaev, R A; Burenin, R A; Barat, C; Dezalay, J P; Vedrenne, G

2000-01-01

337

Growth in NOx emissions from power plants in China: bottom-up estimates and satellite observations  

Directory of Open Access Journals (Sweden)

Full Text Available Using OMI (Ozone Monitoring Instrument) tropospheric NO2 columns and a nested-grid 3-D global chemical transport model (GEOS-Chem), we investigated the growth in NOx emissions from coal-fired power plants and their contributions to the growth in NO2 columns in 2005–2007 in China. We first developed a unit-based power plant NOx emission inventory for 2005–2007 to support this investigation. The total capacities of coal-fired power generation have increased by 48.8% in 2005–2007, with 92.2% of the total capacity additions coming from generator units with size ?300 MW. The annual NOx emissions from coal-fired power plants were estimated to be 8.11 Tg NO2 for 2005 and 9.58 Tg NO2 for 2007, respectively. The modeled summer average tropospheric NO2 columns were highly correlated (R2 = 0.79–0.82) with OMI measurements over grids dominated by power plant emissions, with only 7–14% low bias, lending support to the high accuracy of the unit-based power plant NOx emission inventory. The ratios of OMI-derived annual and summer average tropospheric NO2 columns between 2007 and 2005 indicated that most of the grids with significant NO2 increases were related to power plant construction activities. OMI had the capability to trace the changes of NOx emissions from individual large power plants in cases where there is less interference from other NOx sources. Scenario runs from GEOS-Chem model suggested that the new power plants contributed 18.5% and 10% to the annual average NO2 columns in 2007 in Inner Mongolia and North China, respectively. The massive new power plant NOx emissions significantly changed the local NO2 profiles, especially in less polluted areas. A sensitivity study found that changes of NO2 shape factors due to including new power plant emissions increased the summer average OMI tropospheric NO2 columns by 3.8–17.2% for six selected locations, indicating that the updated emission information could help to improve the satellite retrievals.

S. W. Wang; Q. Zhang; D. G. Streets; K. B. He; R. V. Martin; L. N. Lamsal; D. Chen; Y. Lei; Z. Lu

2012-01-01

338

Airborne observations of methane emissions from rice cultivation in the Sacramento Valley of California  

Science.gov (United States)

Airborne measurements of methane (CH4) and carbon dioxide (CO2) were taken over the rice growing region of California's Sacramento Valley in the late spring of 2010 and 2011. From these and ancillary measurements, we show that CH4 mixing ratios were higher in the planetary boundary layer above the Sacramento Valley during the rice growing season than they were before it, which we attribute to emissions from rice paddies. We derive daytime emission fluxes of CH4 between 0.6 and 2.0% of the CO2 taken up by photosynthesis on a per carbon, or mole to mole, basis. We also use a mixing model to determine an average CH4/CO2 flux ratio of -0.6% for one day early in the growing season of 2010. We conclude the CH4/CO2 flux ratio estimates from a single rice field in a previous study are representative of rice fields in the Sacramento Valley. If generally true, the California Air Resources Board (CARB) greenhouse gas inventory emission rate of 2.7 × 1010 g CH4/yr is approximately three times lower than the range of probable CH4 emissions (7.8-9.3 × 1010 g CH4/yr) from rice cultivation derived in this study. We attribute this difference to decreased burning of the residual rice crop since 1991, which leads to an increase in CH4 emissions from rice paddies in succeeding years, but which is not accounted for in the CARB inventory.

Peischl, J.; Ryerson, T. B.; Holloway, J. S.; Trainer, M.; Andrews, A. E.; Atlas, E. L.; Blake, D. R.; Daube, B. C.; Dlugokencky, E. J.; Fischer, M. L.; Goldstein, A. H.; Guha, A.; Karl, T.; Kofler, J.; Kosciuch, E.; Misztal, P. K.; Perring, A. E.; Pollack, I. B.; Santoni, G. W.; Schwarz, J. P.; Spackman, J. R.; Wofsy, S. C.; Parrish, D. D.

2012-12-01

339

Assessment of cardiac single-photon emission computed tomography performance using a scanning linear observer.  

UK PubMed Central (United Kingdom)

PURPOSE: Single-photon emission computed tomography (SPECT) is widely used to detect myocardial ischemia and myocardial infarction. It is important to assess and compare different SPECT system designs in order to achieve the highest detectability of cardiac defects. METHODS: Whitaker et al.'s study ["Estimating random signal parameters from noisy images with nuisance parameters: linear and scanning-linear methods," Opt. Express 16(11), 8150-8173 (2008)] on the scanning linear observer (SLO) shows that the SLO can be used to estimate the location and size of signals. One major advantage of the SLO is that it can be used with projection data rather than with reconstruction data. Thus, this observer model assesses the overall hardware performance independent of any reconstruction algorithm. In addition, the computation time of image quality studies is significantly reduced. In this study, three systems based on the design of the GE cadmium zinc telluride-based dedicated cardiac SPECT camera Discovery 530c were assessed. This design, which is officially named the Alcyone Technology: Discovery NM 530c, was commercialized in August, 2009. The three systems, GE27, GE19, and GE13, contain 27, 19, and 13 detectors, respectively. Clinically, a human heart can be virtually segmented into three coronary artery territories: the left-anterior descending artery, left-circumflex artery, and right coronary artery. One of the most important functions of a cardiac SPECT system is to produce images from which a radiologist can accurately predict in which territory the defect exists [http://www.asnc.org/media/PDFs/PPReporting081511.pdf, Guideline from American Society of Nuclear Cardiology]. A good estimation of the extent of the defect from the projection images is also very helpful for determining the seriousness of the myocardial ischemia. In this study, both the location and extent of defects were estimated by the SLO, and the system performance was assessed by localization receiver operating characteristic (LROC) [P. Khurd and G. Gindi, "Decision strategies maximizing the area under the LROC curve," Proc. SPIE 5749, 150-161 (2005)] or estimation receiver operating characteristic (EROC) [E. Clarkson, "Estimation receiver operating characteristic curve and ideal observers for combined detection/estimation tasks," J. Opt. Soc. Am. A 24, B91-B98 (2007)] curves. RESULTS: The area under the LROC/EROC curve (AULC/AUEC) and the true positive fraction (TPF) at a specific false positive fraction (FPF) can be treated as the figures of merit. For radii estimation with a 1 mm tolerance, the AUEC values of the GE27, GE19, and GE13 systems are 0.8545, 0.8488, and 0.8329, and the TPF at FPF = 5% are 77.1%, 76.46%, and 73.55%, respectively. The assessment of all three systems revealed that the GE19 system yields estimated information and cardiac defect detectability very close to those of the GE27 system while using eight fewer detectors. Thus, 30% of the expensive detector units can be removed with confidence. CONCLUSIONS: As the results show, a combination of the SLO and LROC/EROC curves can determine the configuration that yields the most relevant estimation/detection information. Thus, this is a useful method for assessing cardiac SPECT systems.

Lee CJ; Kupinski MA; Volokh L

2013-01-01

340

Assessment of cardiac single-photon emission computed tomography performance using a scanning linear observer  

Energy Technology Data Exchange (ETDEWEB)

Purpose: Single-photon emission computed tomography (SPECT) is widely used to detect myocardial ischemia and myocardial infarction. It is important to assess and compare different SPECT system designs in order to achieve the highest detectability of cardiac defects. Methods: Whitaker et al.'s study ['Estimating random signal parameters from noisy images with nuisance parameters: linear and scanning-linear methods,' Opt. Express 16(11), 8150-8173 (2008)] on the scanning linear observer (SLO) shows that the SLO can be used to estimate the location and size of signals. One major advantage of the SLO is that it can be used with projection data rather than with reconstruction data. Thus, this observer model assesses the overall hardware performance independent of any reconstruction algorithm. In addition, the computation time of image quality studies is significantly reduced. In this study, three systems based on the design of the GE cadmium zinc telluride-based dedicated cardiac SPECT camera Discovery 530c were assessed. This design, which is officially named the Alcyone Technology: Discovery NM 530c, was commercialized in August, 2009. The three systems, GE27, GE19, and GE13, contain 27, 19, and 13 detectors, respectively. Clinically, a human heart can be virtually segmented into three coronary artery territories: the left-anterior descending artery, left-circumflex artery, and right coronary artery. One of the most important functions of a cardiac SPECT system is to produce images from which a radiologist can accurately predict in which territory the defect exists [http://www.asnc.org/media/PDFs/PPReporting081511.pdf, Guideline from American Society of Nuclear Cardiology]. A good estimation of the extent of the defect from the projection images is also very helpful for determining the seriousness of the myocardial ischemia. In this study, both the location and extent of defects were estimated by the SLO, and the system performance was assessed by localization receiver operating characteristic (LROC) [P. Khurd and G. Gindi, 'Decision strategies maximizing the area under the LROC curve,' Proc. SPIE 5749, 150-161 (2005)] or estimation receiver operating characteristic (EROC) [E. Clarkson, 'Estimation receiver operating characteristic curve and ideal observers for combined detection/estimation tasks,' J. Opt. Soc. Am. A 24, B91-B98 (2007)] curves. Results: The area under the LROC/EROC curve (AULC/AUEC) and the true positive fraction (TPF) at a specific false positive fraction (FPF) can be treated as the figures of merit. For radii estimation with a 1 mm tolerance, the AUEC values of the GE27, GE19, and GE13 systems are 0.8545, 0.8488, and 0.8329, and the TPF at FPF = 5% are 77.1%, 76.46%, and 73.55%, respectively. The assessment of all three systems revealed that the GE19 system yields estimated information and cardiac defect detectability very close to those of the GE27 system while using eight fewer detectors. Thus, 30% of the expensive detector units can be removed with confidence. Conclusions: As the results show, a combination of the SLO and LROC/EROC curves can determine the configuration that yields the most relevant estimation/detection information. Thus, this is a useful method for assessing cardiac SPECT systems.

Lee, Chih-Jie; Kupinski, Matthew A.; Volokh, Lana [College of Optical Sciences, University of Arizona, Tucson, Arizona 85721 (United States); GE Healthcare, Haifa 39120 (Israel)

2013-01-15

 
 
 
 
341

SYNCHROTRON SELF-COMPTON EMISSION AS THE ORIGIN OF THE GAMMA-RAY AFTERGLOW OBSERVED IN GRB 980923  

Energy Technology Data Exchange (ETDEWEB)

GRB 980923 was one of the brightest bursts observed by the Burst and Transient Source Experiment. Previous studies have detected two distinct components in addition to the main prompt episode, which is well described by a Band function. The first of these is a tail with a duration of {approx_equal} 400 s, while the second is a high-energy component lasting {approx_equal} 2 s. We summarize the observations and argue for a unified model in which the tail can be understood as the early {gamma}-ray afterglow from forward shock synchrotron emission, while the high-energy component arises from synchrotron self-Compton from the reverse shock. Consistency between the main assumption of thick shell emission and agreement between the observed and computed values for fluxes, break energies, starting times, and spectral indices leads to a requirement that the ejecta must be highly magnetized.

Fraija, N.; Gonzalez, M. M.; Lee, W. H., E-mail: nifraija@astro.unam.mx, E-mail: magda@astro.unam.mx, E-mail: wlee@astro.unam.mx [Instituto de Astronomia, Universidad Nacional Autonoma de Mexico, Apdo. Postal 70-264, Cd. Universitaria, Mexico DF 04510 (Mexico)

2012-05-20

342

SYNCHROTRON SELF-COMPTON EMISSION AS THE ORIGIN OF THE GAMMA-RAY AFTERGLOW OBSERVED IN GRB 980923  

International Nuclear Information System (INIS)

GRB 980923 was one of the brightest bursts observed by the Burst and Transient Source Experiment. Previous studies have detected two distinct components in addition to the main prompt episode, which is well described by a Band function. The first of these is a tail with a duration of ? 400 s, while the second is a high-energy component lasting ? 2 s. We summarize the observations and argue for a unified model in which the tail can be understood as the early ?-ray afterglow from forward shock synchrotron emission, while the high-energy component arises from synchrotron self-Compton from the reverse shock. Consistency between the main assumption of thick shell emission and agreement between the observed and computed values for fluxes, break energies, starting times, and spectral indices leads to a requirement that the ejecta must be highly magnetized.

2012-05-20

343

Geomagnetic conjugacy of 30-kHz band auroral hiss emissions observed at L = 6.1  

International Nuclear Information System (INIS)

[en] Statistical characteristics of auroral hiss emissions in the 30-kHz band were examined using the data observed simultaneously at the Syowa-Husafell conjugate pair of stations during the period of September-November 1983. The occurrence probabilities of conjugate events observed simultaneously at the two stations were almost the same in September and October and decreased during November. The nonconjugate events observed only at Syowa Station were detected more often in September. The number of nonconjugate events decreased in October and November. These phenomena were mostly observed during 1,700-2,300 MLT around the geographic midnight at Syowa. On the other hand, the number of nonconjugate phenomena detected only at Husafell in iceland incrreased from September to Noverber. The occurrence peaks were around 2,100-0200 MLT, before geographci midnight at Husafell. From these statistical characteristics it is found that auroral hiss emission occurrences strongly depend on not only the magnetic local time but also the geographic local time and seasons, suggesting that auroral hiss emissions observed on the ground are strongly controlled by the sunlit effects in the topside ionosphere

1987-06-01

344

Observation of two phases of neutron emission in a low energy plasma focus  

International Nuclear Information System (INIS)

Neutron emissions in a low energy 3.3 kJ (15 kV) plasma focus are studied. The system is operated in deuterium and deuterium-argon admixtures. Enhancement of the neutron yield is obtained with a suitable amount of high Z admixture. Time resolved neutron measurements are made by using four detectors positioned at two different distances at both the end-on and side-on direction. Maxwellian pulse fitting techniques are employed to resolve a two phase neutron emission history. The neutron energy and anisotropy for the two phases are determined. The energy and anisotropy of the two phases are found to be different and that the second phase is of high anisotropy. These results confirm the presence of two phases of neutron emission that are possibly due to at least two different kinds of neutron production mechanisms in the low energy plasma focus. (author)

2005-01-01

345

NON-THERMAL EMISSION FROM GALAXY CLUSTERS AND FUTURE OBSERVATIONS WITH THE FERMI GAMMA-RAY TELESCOPE AND LOFAR  

Directory of Open Access Journals (Sweden)

Full Text Available FERMI (formely GLAST) and LOFAR will shortly provide crucial information on the non-thermal components (relativistic particles and magnetic eld) in galaxy clusters. After discussing relevant observational facts that already put important constraints on the properties and origin of non-thermal components, I will report on the emission spectrum from galaxy clusters as expected in the context of general calculations in which relativistic particles (protons and secondary electrons due to proton-proton collisions) interact with MHD turbulence generated in the cluster volume during cluster-cluster mergers. In this scenario (known as re-acceleration scenario) di use cluster-scale radio emission is produced in massive clusters during merging events, while gamma ray emission, at some level, is expected to be common in clusters. Expectations of interest for LOFAR and FERMI are also brie y discussed.

G. Brunetti

2009-01-01

346

Simultaneous Cassini VIMS and UVIS observations of Saturn's southern aurora: Comparing emissions from H, H2 and H3+ at a high spatial resolution  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Here, for the first time, temporally coincident and spatially overlapping Cassini VIMS and UVIS observations of Saturn's southern aurora are presented. Ultraviolet auroral H and H[SUB]2[/SUB] emissions from UVIS are compared to infrared H[SUB]3[/SUB][SUP]+[/SUP] emission from VIMS. The auroral emiss...

Melin, H.; Stallard, T.; Miller, S.; Gustin, Jacques; Galand, M.; Badman, S. V.; Pryor, W. R.; O'Donoghue, J.; Brown, R. H.

347

HST-COS OBSERVATIONS OF HYDROGEN, HELIUM, CARBON, AND NITROGEN EMISSION FROM THE SN 1987A REVERSE SHOCK  

International Nuclear Information System (INIS)

We present the most sensitive ultraviolet observations of Supernova 1987A to date. Imaging spectroscopy from the Hubble Space Telescope-Cosmic Origins Spectrograph shows many narrow (?v ? 300 km s–1) emission lines from the circumstellar ring, broad (?v ? 10-20 × 103 km s–1) emission lines from the reverse shock, and ultraviolet continuum emission. The high signal-to-noise ratio (>40 per resolution element) broad Ly? emission is excited by soft X-ray and EUV heating of mostly neutral gas in the circumstellar ring and outer supernova debris. The ultraviolet continuum at ? > 1350 Å can be explained by H I two-photon (2s 2 S1/2-1s 2 S1/2) emission from the same region. We confirm our earlier, tentative detection of N V ?1240 emission from the reverse shock and present the first detections of broad He II ?1640, C IV ?1550, and N IV] ?1486 emission lines from the reverse shock. The helium abundance in the high-velocity material is He/H = 0.14 ± 0.06. The N V/H? line ratio requires partial ion-electron equilibration (Te /Tp ? 0.14-0.35). We find that the N/C abundance ratio in the gas crossing the reverse shock is significantly higher than that in the circumstellar ring, a result that may be attributed to chemical stratification in the outer envelope of the supernova progenitor. The N/C abundance may have been stratified prior to the ring expulsion, or this result may indicate continued CNO processing in the progenitor subsequent to the expulsion of the circumstellar ring.

2011-12-20

348

Powerful H2 Emission and Star Formation on the Interacting Galaxy System Arp 143: Observations with Spitzer and Galex  

Science.gov (United States)

We present new mid-infrared (IR; 5-35 ?m) and ultraviolet (1539-2316 Å) observations of the interacting galaxy system Arp 143 (NGC 2444/2445) from the Spitzer Space Telescope and Galaxy Evolution Explorer. In this system, the central nucleus of NGC 2445 is surrounded by knots of massive star formation in a ringlike structure. We find unusually strong emission from warm H2 associated with an expanding shock wave between the nucleus and the western knots. At this ridge, the flux ratio between H2 and polycyclic aromatic hydrocarbon (PAH) emission is nearly ten times higher than in the nucleus. Arp 143 is one of the most extreme cases known in that regard. From our multiwavelength data, we derive a narrow age range of the star forming knots between 2 Myr and 7.5 Myr, suggesting that the ring of knots was formed almost simultaneously in response to the shock wave traced by the H2 emission. However, the knots can be further subdivided into two age groups: those with an age of 2-4 Myr (knots A, C, E, and F), which are associated with 8 ?m emission from PAHs, and those with an age of 7-8 Myr (knots D and G), which show little or no 8 ?m emission shells surrounding them. We attribute this finding to an aging effect of the massive clusters which, after about 6 Myr, no longer excite the PAHs surrounding the knots.

Beirão, P.; Appleton, P. N.; Brandl, B. R.; Seibert, M.; Jarrett, T.; Houck, J. R.

2009-03-01

349

POWERFUL H2 EMISSION AND STAR FORMATION ON THE INTERACTING GALAXY SYSTEM Arp 143: OBSERVATIONS WITH SPITZER AND GALEX  

International Nuclear Information System (INIS)

We present new mid-infrared (IR; 5-35 ?m) and ultraviolet (1539-2316 A) observations of the interacting galaxy system Arp 143 (NGC 2444/2445) from the Spitzer Space Telescope and Galaxy Evolution Explorer. In this system, the central nucleus of NGC 2445 is surrounded by knots of massive star formation in a ringlike structure. We find unusually strong emission from warm H2 associated with an expanding shock wave between the nucleus and the western knots. At this ridge, the flux ratio between H2 and polycyclic aromatic hydrocarbon (PAH) emission is nearly ten times higher than in the nucleus. Arp 143 is one of the most extreme cases known in that regard. From our multiwavelength data, we derive a narrow age range of the star forming knots between 2 Myr and 7.5 Myr, suggesting that the ring of knots was formed almost simultaneously in response to the shock wave traced by the H2 emission. However, the knots can be further subdivided into two age groups: those with an age of 2-4 Myr (knots A, C, E, and F), which are associated with 8 ?m emission from PAHs, and those with an age of 7-8 Myr (knots D and G), which show little or no 8 ?m emission shells surrounding them. We attribute this finding to an aging effect of the massive clusters which, after about 6 Myr, no longer excite the PAHs surrounding the knots.

2009-03-10

350

Characteristics of severe thunderstorms studied with the aid of VLF atmospherics over North-East India  

Science.gov (United States)

Electromagnetic waves from lightning activity, commonly known as atmospherics or sferics serve as an effective tool for studying the lower ionosphere as well as thunderstorm activity. It is also useful for locating lightning strokes regionally and globally. In this paper, we present the analysis of the Integrated Field Intensity of Sferics (IFIS) at six discrete VLF frequencies for 30 lightning-associated overhead thunderstorms in Tripura, within the period from August 2009 to October 2010. An ingeniously developed well calibrated GPS locked software VLF receiver, located at the Department of Physics, Tripura University (23.5°N, 91.25°E), is used for the present study. Two distinct types of variations of IFIS, (i) single peak and (ii) dual peak are found characterizing each thunderstorm and their occurrence show nearly inverse character. The spectral character of IFIS rise rate, fall rate and rate of enhancement for each type is studied searching for suitable frequencies in the VLF range to forecast a thunderstorm. It is concluded that VLF sferics from 3-10 kHz are the most effective in terms nowcasting an incoming thunderstorm well before 3-4 hours of its peak occurrence, when there may not be any visual indication of the thunderstorm.

Guha, A.; Banik, Trisanu; Kumar de, Barin; Roy, Rakesh; Choudhury, Abhijit

2013-08-01

351

Observation of the fine structure for rovibronic spectral lines in visible part of emission spectra of $D_2$  

CERN Document Server

For the first time the fine structure of rovibronic spectral lines in visible part of emission spectra of $D_2$ molecule has been observed. Observed splitting in visible doublets is about 0.2 cm$^{-1}$ in good accordance with previous observations in the infrared part of the spectrum ($a^3\\Sigma_g^+ \\to c^3\\Pi_u$ electronic transition) by means of FTIR and laser spectroscopy. Relative intensities of the fine structure components are in agreement with our calculations of adiabatic line strengths for Hund's case "b" coupling scheme.

Lavrov, B P; Zhukov, A S

2011-01-01

352

Spatially resolved observation of a radio-frequency-powered glow discharge plasma for emission spectrometric analysis.  

UK PubMed Central (United Kingdom)

In glow discharge optical emission spectrometry, two-dimensional emission images for iron atomic lines were measured by using an imaging spectrograph equipped with a CCD detector, when a radio-frequency (r.f.) power source was employed for excitation. Emission images at the Fe I 371.99-nm and the Fe I 375.82-nm lines, having different excitation energies, were analyzed by the two-line method to obtain the spatial distribution of the excitation temperature in the plasma. Their emission intensities had a concentric-circle-like distribution along the radial direction of the plasma to become weaker towards the surrounding portion, which was very similar to a direct-current (d.c.) glow discharge plasma. On the other hand, the spatial distribution in the excitation temperature became relatively uniform over the central portion of the plasma, also being analogous between the r.f. and the d.c. glow discharge plasmas. These results imply that there is a major excitation process that occurs in a glow discharge plasma regardless of the power modes.

Oka R; Wagatsuma K

2013-01-01

353

Panchromatic Observations of the Textbook GRB 110205A: Constraining Physical Mechanisms of Prompt Emission and Afterglow.  

Science.gov (United States)

We present a comprehensive analysis of a bright, long duration (T(sub 90) approx. 257 s) GRB 110205A at redshift z = 2.22. The optical prompt emission was detected by Swift/UVOT, ROTSE-IIIb and BOOTES telescopes when the GRB was still radiating in the gam...

A. Breeveld A. Pozanenko A. Volnova A. P. Beardmore B. Zhang C. W. Akerlof D. K. Sahu E. Klunko E. Sonbas J. Gorosabel M. Andreev M. De Pasquale M. Im M. Nissinen N. Gehrels P. Anto R. F. Shen S. Sugita S. D. Barthelmy T. Sakamoto T. N. Ukwatta U. Carsenty W. Zheng X. F. Wu Y. Urata

2011-01-01

354

Observation of ground-state quantum beats in atomic spontaneous emission  

CERN Document Server

We report ground-state quantum beats in spontaneous emission from a continuously driven atomic ensemble. Beats are visible only in an intensity autocorrelation and evidence spontaneously generated coherence in radiative decay. Our measurement realizes a quantum eraser where a first photon detection prepares a superposition and a second erases the "which-path" information in the intermediate state.

Norris, D G; Barberis-Blostein, P; Carmichael, H J

2010-01-01

355

Observation of near infrared and enhanced visible emissions from electroluminescent devices with organo samarium(III) complex  

International Nuclear Information System (INIS)

Samarium (dibenzoylmethanato)3 bathophenanthroline (Sm(DBM)3 bath) was employed as an emitting and electron transport layer in organic light emitting diodes (OLEDs), and narrow electroluminescent (EL) emissions of a Sm3+ ion were observed in the visible and near infrared (NIR) region, differing from those of the same devices with Eu3+- or Tb3+-complex EL devices with the same structure. The EL emissions of the Sm3+-devices originate from transitions from 4G5/2 to the lower respective levels of Sm3+ ions. A maximum luminance of 490 cd m-2 at 15 V and an EL efficiency of 0.6% at 0.17 mA cm-2 were obtained in the visible region, and the improved efficiency should be attributed to introducing a transitional layer between the N,N'-diphenyl-N,N'-bis(3-methylphenyl)-1,1'-diphenyl-4,4'-diamine (TPD) film and the Sm(DBM)3 bath film and the avoidance of interfacial exciplex emission in devices. Sharp emissions of Sm3+ ions in the NIR region were also observed under a lower threshold value less than 4.5 V

2006-11-07

356

Dust emission and transport mechanisms in the central Sahara: Fennec ground-based observations from Bordj Badji Mokhtar, June 2011  

Science.gov (United States)

A detailed analysis of the first ever high-resolution ground-based dust observations in the remote central Sahara is presented from observations at Bordj Badji Mokhtar (BBM), taken during the Fennec project in June 2011. Detailed case studies are presented for three dust-producing mechanisms (cold pool outflows, low-level jets (LLJs), and dry convective plumes). The results confirm the importance of cold pools in dust emission and transport in the region. Forty-five percent of the dust over BBM is generated by local emission in cold pool outflows. Twenty-seven percent of the dust is advected rather than locally emitted dust; on three occasions, it is advected over 500 km to BBM by cold pool outflows. Dust that has been in long-range transport to the area within such cold pool outflows is found to carry larger particles and be responsible for higher dust loadings than fresh uplift. LLJs are of tertiary importance in the partitioning, responsible for 14% dust over BBM. Dry convective plumes are identifiable in the data but produce much less significant quantities of dust, approximately 2% of the June total. The cube of wind speed has a stronger correlation with dust emission than wind speed. The correlation is strongest (at 95% confidence) for LLJ-induced emission (0.88), followed by locally emitting cold pools (0.78).

Allen, Christopher J. T.; Washington, Richard; Engelstaedter, Sebastian

2013-06-01

357

High Resolution Observations of Dust Continuum Emission at 340 GHz from the Low-mass T Tauri Star FN Tauri  

CERN Multimedia

FN Tau is a rare example of very low-mass T Tauri stars that exhibits a spatially resolved nebulosity in near-infrared scattering light. To directly derive the parameters of a circumstellar disk around FN Tau, observations of dust continuum emission at 340 GHz are carried out with the Submillimeter Array (SMA). A point-like dust continuum emission was detected with a synthesized beam of ~ 0.7" in FWHM. From the analysis of the visibility plot, the radius of the emission is estimated to be <= 0.29", corresponding to 41 AU. This is much smaller than the radius of the nebulosity, 1.85" for its brighter part at 1.6 micron. The 340 GHz continuum emission observed with the SMA and the photometric data at lambda <= 70 micron are explained by a power-law disk model whose outer radius and mass are 41 AU and (0.24 - 5.9) x 10^{-3} M_{sun}, respectively, if the exponent of dust mass opacity (beta) is assumed to be 0-2. The disk model cannot fully reproduce the flux density at 230 GHz obtained with the IRAM 30-mete...

Momose, Munetake; Kudo, Tomoyuki; Tamura, Motohide; Kitamura, Yoshimi

2010-01-01

358

Serendipity observations of far infrared cirrus emission in the Spitzer Infrared Nearby Galaxies Survey: Analysis of far-infrared correlations  

CERN Multimedia

We present an analysis of far-infrared dust emission from diffuse cirrus clouds. This study is based on serendipitous observations at 160 microns at high galactic latitude with the Multiband Imaging Photometer (MIPS) onboard the Spitzer Space Telescope by the Spitzer Infrared Nearby Galaxies Survey (SINGS). These observations are complemented with IRIS data at 100 and 60 microns and constitute one of the most sensitive and unbiased samples of far infrared observations at small scale of diffuse interstellar clouds. Outside regions dominated by the cosmic infrared background fluctuations, we observe a substantial scatter in the 160/100 colors from cirrus emission. We compared the 160/100 color variations to 60/100 colors in the same fields and find a trend of decreasing 60/100 with increasing 160/100. This trend can not be accounted for by current dust models by changing solely the interstellar radiation field. It requires a significant change of dust properties such as grain size distribution or emissivity or ...

Bot, Caroline; Boulanger, Francois; Lagache, Guilaine; Miville-Deschenes, Marc-Antoine; Draine, Bruce; Martin, Peter

2009-01-01

359

High spectral resolution observations of the coronal X-ray emission from the RS CVn binary Sigma Corona Borealis  

International Nuclear Information System (INIS)

[en] Results of the high spectral resolution observation of the RS CVn binary ? Cr B, made with the Focal Plane Crystal Spectrometer (FPCS) on the Einstein Observatory, are reported. A spectral scan in 800-840 eV interval shows clear presence of X-ray emission line at 826 eV identified with 1S0-1P1 transition of Fe XVII while a prominent peak at 1007 eV in the scan band 986-1014 eV is attributed to a blend of lines due to highly ionized iron. Using the observed fluxes of the lines and the Raymond-Smith model, best-fit values of corona temperature and volume emission measures, with associated 90 per cent confidence level uncertainties, are derived. (author)

1985-04-15

360

Balloon observations of fast intensity fluctuations and flare-like enhancements of X-ray emission from Cygnus X-1  

International Nuclear Information System (INIS)

The paper presents the results of the investigation on the short term X-ray emission characteristics of Cyg X-1 in the 20-150 keV range. The observations were made with balloon-borne oriented scintillation telescope and the flights were conducted from Hyderabad, India. The source was tracked over a duration of 1 hr that enabled detailed observations with time resolution of the order of 1 min. Fluctuations in the intensity of Cyg X-1 with time scales of the order of minutes have been detected besides short-term flare-like enhancements. The spectral characteristics of the flare emission features are discussed and their relationship to the phase of the binary is examined. (Auth.)

1975-05-29

 
 
 
 
361

Observation of the spontaneous and stimulated emission from the ISAS compact FEL in the millimeter wave region  

International Nuclear Information System (INIS)

A compact FEL for submillimeter and far-infrared regions is studied in the Institute of Space and Astronautical Science. The FEL can be made compact by using an electrostatic accelerator and a micro wiggler. The FEL has a tabletop size with a total length of 2.5 m. At the preliminary phase, we aim to oscillate the FEL in the short millimeter wave. A photo cathode is used as the source of an electron beam. Characteristics of the electron beam were improved by means of designing the electron gun and the photo cathode. This electron beam was injected into an FEL resonator consisting of a waveguide and distributed Bragg reflectors and a spontaneous emission was observed. When we increased the current of the electron beam that passed through the resonator, a stimulated emission was observed with a frequency of 96 GHz and a peak power of 3.4 mW.

2002-05-01

362

Images Of Gradual Millimeter Emission And Multi--Wavelength Observations Of The 1994 August 17 Solar Flare  

UK PubMed Central (United Kingdom)

We present a comprehensive analysis of the 1994 August 17 flare, thefirst flare imaged at millimeter (86 GHz) wavelengths. The temporal evolution ofthis flare displays a prominent impulsive peak shortly after 0102 UT, observed inhard X--rays and at microwave frequencies, followed by a gradual decay phase. Thegradual phase was also detected at 86 GHz. Soft X--ray images show a compactemitting region (!2000), which is resolved into two sources: a footpoint and a looptop source. Nonthermal emissions at microwave and hard X--ray wavelengths areanalyzed and the accelerated electron spectrum is calculated. This energy spectrumderived from the microwave and hard X--ray observations suggests that these emissionswere created by the same electron population. The millimeter emission duringthe gradual phase is thermal bremsstrahlung originating mostly from the top of theflaring loop. The soft X--rays and the millimeter flux density from the footpointsource are only consisten...

Adriana V. R. Silva; R. P. Lin; Imke De Pater; Stephen M. White; K. Shibasaki; H. Nakajima

363

Radio-emission of pre-main sequence stars of the Rho Ophiuchi cloud: observations and interpretation  

International Nuclear Information System (INIS)

Observations of the radio continuum emission of a young star population have been made at VLA on the whole molecular cloud Rho Ophiuchi, one of the closest site of star formation. A dozen of stellar sources have been detected. Radio emission of some identified objects seems to have a magnetic nature and be produced by gyrosynchrotron mechanism. In particular, one of the sources shows a radio radiation circularly polarized; two other stars have a radiation strongly variable probably due to magnetic eruptions more important than those detected in X radiation. More generally, radio observations select probably a specific population of young stars characterized by magnetic field presence extended on several stellar radii and by absence of dense circumstellar environment. Spatial distribution of these objects suggest, they are younger than most of the pre-main sequence stars

1987-01-01

364

Location accuracy of VLF World-Wide Lightning Location (WWLL) network: Post-algorithm upgrade  

Directory of Open Access Journals (Sweden)

Full Text Available An experimental VLF World-Wide Lightning Location (WWLL) network has been developed through collaborations with research institutions across the globe. The aim of the WWLL is to provide global real-time locations of lightning discharges, with >50% CG flash detection efficiency and mean location accuracy of <10km. While these goals are essentially arbitrary, they do define a point where the WWLL network development can be judged a success, providing a breakpoint for a more stable operational mode. The current network includes 18 stations which cover much of the globe. As part of the initial testing phase of the WWLL the network operated in a simple mode, sending the station trigger times into a central processing point rather than making use of the sferic Time of Group Arrival (TOGA). In this paper the location accuracy of the post-TOGA algorithm WWLL network (after 1 August 2003) is characterised, providing estimates of the globally varying location accuracy for this network configuration which range over 1.9-19km, with the global median being 2.9km, and the global mean 3.4km. The introduction of the TOGA algorithm has significantly improved the location accuracies. The detection efficiency of the WWLL is also considered. In the selected region the WWLL detected ~13% of the total lightning, suggesting a ~26% CG detection efficiency and a ~10% IC detection efficiency. Based on a comparison between all WWLL good lightning locations in February-April 2004, and the activity levels expected from satellite observations we estimate that the WWLL is currently detecting ~2% of the global total lightning, providing good locations for ~5% of global CG activity. The existing WWLL network is capable of providing real-time positions of global thunderstorm locations in its current form.

C. J. Rodger; J. B. Brundell; R. L. Dowden

2005-01-01

365

The Modulation of VLF Wave Growth and Propagation by Global ULF Oscillations  

Science.gov (United States)

Riometer measurements across the auroral zone have shown that electron precipitation down to the D-layer may be modulated at ULF frequencies. Observations [Spanswick et al., Ann. Geophys. 2005] demonstrate that magnetic ULF wave perturbations are a necessary pre-requisite for the precipitation fluctuations. It has long been argued that the ULF modulation of electron precipitation occurs through a complicated wave-wave interaction: long-period ULF waves in the magnetosphere modify the growth-rates of whistler-mode waves, which in turn modulate pitch-angle scattering, leading to fluctuations in the precipitation of electrons from regions close to the equatorial plane [Coroniti & Kennel, JGR, 1970; Haugstad, JATP, 1975]. We investigate aspects of this hypothesis by studying the modification of VLF whistler-mode propagation and growth rates by global ULF oscillations in an idealized dipole magnetosphere. A linear ray-tracing algorithm, with growth-rates obtained from the full warm plasma dispersion relation, is used to study millions of growing ray-paths as waves propagate through the magnetosphere in both an unperturbed magnetic field, and one that is perturbed by the presence of a 2mHz global m=0 ULF wave oscillation. The resulting path-integrated wave gains are used to build a picture of the estimated wave growth as a function of frequency, wavevector angle, and propagation angle at different positions in the magnetosphere relative to the equatorial plane. The predicted change in wave spectra by a ULF wave oscillation is used to estimate the change in particle precipitation. These results are compared to estimates from a more direct model of electron precipitation by ULF waves presented by Degeling et al. (this meeting), as well as to measurements of the D-region modulation from the CGSM riometer network.

Watt, C.; Degeling, A. W.; Rankin, R.; Spanswick, E.; Donovan, E. F.

2010-12-01

366

Verification of NOx emission inventory over South Korea using sectoral activity data and satellite observation of NO2 vertical column densities  

Science.gov (United States)

In this study, the emission inventories of NOx, which is a major air pollutant of South Korea were compared and analyzed. The two bottom-up emission inventories, Clean Air Policy Support System (CAPSS) and Regional Emission inventory in ASia (REAS), which are the latest emission inventories about the air pollutant emissions about South Korea were compared to find out the trend of NOx emission during 1996–2005. Also, these two emission inventories were compared with the top down NOx emissions estimated from satellite observations to validate the amount of NOx emitted from South Korea. The total NOx emission trends, sectoral and regional comparisons were carried out. The trend of the top down estimated NOx emission was similar to CAPSS and REAS. However, the magnitudes of the top down estimated NOx emission were usually closer to those of CAPSS than those of REAS. The NOx emissions from transportation sector of REAS were larger than that of CAPSS, and this corresponded to the difference of total amount of NOx emission between CAPSS and REAS. By comparing the differences of the ratios of the vehicle kilometers traveled (VKT) and emission factors (EFs), it was identified that most of the difference between CAPSS and REAS was due to these factors for diesel vehicles in REAS. Implications of this higher VKT values in REAS were discussed.

Kim, Na Kyung; Kim, Yong Pyo; Morino, Yu; Kurokawa, Jun-ichi; Ohara, Toshimasa

2013-10-01

367

Procedures for reduction of Fe XII 10747 A coronal emission-line polarization observations. Technical note  

International Nuclear Information System (INIS)

The note documents the reducing procedures used to obtain the best estimates of the coronal Stokes parameters from the raw measurements recorded in two spectral channels with the High Altitude Observatory-Sacramento Peak Observatory Coronal Emission-line Polarimeter (KELP). The original reduction programs were modified to survey the KELP data as a whole and to help determine whether corrections are needed for each scan

1987-01-01

368

Location accuracy of long distance VLF lightning locationnetwork  

Directory of Open Access Journals (Sweden)

Full Text Available An experimental VLF WorldWide Lightning Location (WWLL) network is being developed to provide realtime locations of cloud to ground lightning discharges occurring throughout the globe. This network has expanded from a limited number of stations in the Western Pacific to its current state of 11 stations, in most longitude sectors, with additional stations planned in the near future. As part of the initial testing phase of the WWLL the network has operated in a simple mode, sending the station trigger times into a central processing point rather than using the sferic Time of Group Arrival (TOGA). During this initial stage, a significant quantity of lightning location data has been collected, some of which is being applied to research questions. In this paper the operation of the WWLL network is described, and the location accuracy of the pre-TOGA WWLL network is characterised. This is performed by contrasting commercial lightning location data from an Australian network, Kattron, over 2 days in January 2002, with 4 WWLL stations covering the same region. It was found that there were 426 matched lightning events, corresponding to lightning discharges with large lightning return stroke peak currents (mean absolute peak current of ~26kA compared with ~12kA for all Kattron events). By considering the random errors in the difference locations between the matching lightning events, an appropriate Gaussian timing error for the WWLL network of receiving stations is determined, and hence an estimate for the global location errors for the existing 11-station network is found. The "worst-case" global location error for the existing network ranges spatially from 7.5–100km, with the global median being 15km, and the global mean 30km. When the TOGA method is implemented, the station timing errors will decrease, allowing for an increase in the location accuracies. Hence, the location accuracy estimates determined in this paper will be very conservative for the future WWLL network employing the TOGA technique. Key words. Meteorology and atmospheric dynamics (lightning, atmospheric electricity, instruments and techniques)

C. J. Rodger; J. B. Brundell; R. L. Dowden; N. R. Thomson

2004-01-01

369