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Full-Text Articles in Physical Sciences and Mathematics
Distributions Of Beryllium 7 And Lead 2109, And Soluble Aerosol-Associated Ionic Species Over The Western Pacific: Pem West B, February-March 1994, Jack E. Dibb, R. Talbot, Barry Lefer, Eric Scheuer, G L. Gregory, E V. Browell, J D. Bradshaw, S T. Sandholm, H B. Singh
Distributions Of Beryllium 7 And Lead 2109, And Soluble Aerosol-Associated Ionic Species Over The Western Pacific: Pem West B, February-March 1994, Jack E. Dibb, R. Talbot, Barry Lefer, Eric Scheuer, G L. Gregory, E V. Browell, J D. Bradshaw, S T. Sandholm, H B. Singh
Earth Sciences
Aerosol sampling for the determination of the concentrations of soluble ionic species and the natural radionuclides 7Be and 210Pb was conducted from the NASA DC-8 over the western Pacific as part of GTE/PEM-West B during February-March 1994. Concentrations of most soluble ionic species in the free troposphere were higher in samples collected on flights originating from Hong Kong and Japan than those collected further east over the open ocean. In both regions the measured concentrations were higher than those found during PEM-West A (fall 1991). Activities of 210Pb, a tracer of air masses influenced by sources on …
Chemical Characteristics Of Continental Outflow From Asia To The Troposphere Over The Western Pacific Ocean During February-March 1994: Results From Pem-West B, R. Talbot, Jack E. Dibb, Barry Lefer, J D. Bradshaw, S T. Sandholm, D R. Blake, N J. Blake, G W. Sachse, J E. Collins Jr, B J. Heikes, J T. Merrill, G L. Gregory, B E. Anderson, H B. Singh, D C. Thornton, A R. Bandy, R F. Pueschel
Chemical Characteristics Of Continental Outflow From Asia To The Troposphere Over The Western Pacific Ocean During February-March 1994: Results From Pem-West B, R. Talbot, Jack E. Dibb, Barry Lefer, J D. Bradshaw, S T. Sandholm, D R. Blake, N J. Blake, G W. Sachse, J E. Collins Jr, B J. Heikes, J T. Merrill, G L. Gregory, B E. Anderson, H B. Singh, D C. Thornton, A R. Bandy, R F. Pueschel
Earth Sciences
We present here the chemical composition of outflow from the Asian continent to the atmosphere over the western Pacific basin during the Pacific Exploratory Mission-West (PEM-West B) in February–March 1994. Comprehensive measurements of important tropospheric trace gases and aerosol particulate matter were performed from the NASA DC-8 airborne laboratory. Backward 5 day isentropic trajectories were used to partition the outflow from two major source regions: continental north (>20°N) and continental south (<20°N). Air parcels that had not passed over continental areas for the previous 5 days were classified as originating from an aged marine source. The trajectories and the chemistry together indicated that there was extensive rapid outflow of air parcels at altitudes below 5 km, while aged marine air was rarely encountered and only at <20°N latitude. The outflow at low altitudes had enhancements in common industrial solvent vapors such as C2Cl4, CH3CCl3, and C6H6, intermixed with the combustion emission products C2H2, C …
Comparisons Of Trace Constituents From Ground Stations And The Dc-8 Aircraft During Pem-West B, Richard Arimoto, R A. Duce, J M. Prospero, D L. Savoie, R. Talbot, Jack E. Dibb, B J. Heikes, B J. Ray, N F. Lewis, U Tomza
Comparisons Of Trace Constituents From Ground Stations And The Dc-8 Aircraft During Pem-West B, Richard Arimoto, R A. Duce, J M. Prospero, D L. Savoie, R. Talbot, Jack E. Dibb, B J. Heikes, B J. Ray, N F. Lewis, U Tomza
Earth Sciences
Chemical data from ground stations in Asia and the North Pacific are compared with data from the DC-8 aircraft collected during the Pacific Exploratory Measurements in the Western Pacific Ocean (PEM-West B) mission. Ground station sampling took place on Hong Kong, Taiwan, Okinawa, and Cheju; and at three Pacific islands, Shemya, Midway, and Oahu. Aircraft samples were collected during 19 flights, most over the western North Pacific. Aluminum was used as an indicator of mineral aerosol, and even though the aircraft did sample Asian dust, strong dust storms were not encountered. The frequency distribution for non-sea-salt sulfate (nss SO4 …
Large-Scale Distributions Of Tropospheric Nitric, Formic, And Acetic Acids Over The Western Pacific Basin During Wintertime, R. Talbot, Jack E. Dibb, Barry Lefer, Eric Scheuer, J D. Bradshaw, S T. Sandholm, S Smyth, D R. Blake, N J. Blake, G W. Sachse, J E. Collins Jr, G L. Gregory
Large-Scale Distributions Of Tropospheric Nitric, Formic, And Acetic Acids Over The Western Pacific Basin During Wintertime, R. Talbot, Jack E. Dibb, Barry Lefer, Eric Scheuer, J D. Bradshaw, S T. Sandholm, S Smyth, D R. Blake, N J. Blake, G W. Sachse, J E. Collins Jr, G L. Gregory
Earth Sciences
We report here measurements of the acidic gases nitric (HNO3), formic (HCOOH), and acetic (CH3COOH) over the western Pacific basin during the February-March 1994 Pacific Exploratory Mission-West (PEM-West B). These data were obtained aboard the NASA DC-8 research aircraft as it flew missions in the altitude range of 0.3–12.5 km over equatorial regions near Guam and then further westward encompassing the entire Pacific Rim arc. Aged marine air over the equatorial Pacific generally exhibited mixing ratios of acidic gases <100 parts per trillion by volume (pptv). Near the Asian continent, discrete plumes encountered below 6 km altitude contained up to 8 parts per billion by volume (ppbv) HNO3 and 10 ppbv HCOOH and CH3COOH. Overall there was a general correlation between mixing …
Transport Of Sulfur Dioxide From The Asian Pacific Rim To The North Pacific Troposphere, D C. Thornton, A R. Bandy, Byrin W. Blomquist, R. Talbot, Jack E. Dibb
Transport Of Sulfur Dioxide From The Asian Pacific Rim To The North Pacific Troposphere, D C. Thornton, A R. Bandy, Byrin W. Blomquist, R. Talbot, Jack E. Dibb
Earth Sciences
The NASA Pacific Exploratory Mission over the Western Pacific Ocean (PEM-West B) field experiment provided an opportunity to study sulfur dioxide (SO2) in the troposphere over the western Pacific Ocean from the tropics to 60°N during February–March 1993. The large suite of chemical and physical measurements yielded a complex matrix in which to understand the distribution of sulfur dioxide over the western Pacific region. In contrast to the late summer period of Pacific Exploratory Mission-West A (PEM-West A) (1991) over this same area, SO2showed little increase with altitude, and concentrations were much lower in the free …
Global Energetic Neutral Atom (Ena) Measurements And Their Association With The Dst Index, A. M. Jorgensen, Harlan E. Spence, M. G. Henderson, G. D. Reeves, M. Sugiura, T. Kamei
Global Energetic Neutral Atom (Ena) Measurements And Their Association With The Dst Index, A. M. Jorgensen, Harlan E. Spence, M. G. Henderson, G. D. Reeves, M. Sugiura, T. Kamei
Physics & Astronomy
We present a new global magnetospheric index that measures the intensity of the Earth's ring current through energetic neutral atoms (ENAs). We have named it the Global Energetic Neutral Index (GENI), and it is derived from ENA measurements obtained by the Imaging Proton Spectrometer (IPS), part of the Comprehensive Energetic Particle and Pitch Angle Distribution (CEPPAD) experiment on the POLAR satellite. GENI provides a simple orbit-independent global sum of ENAs measured with IPS. Actual ENA measurements for the same magnetospheric state look different when seen from different points in the POLAR orbit. In addition, the instrument is sensitive …
Assessment Of The Record Of The 1982 El Chichón Eruption As Preserved In Greenland Snow, Gregory A. Zielinski, Jack E. Dibb, Qinzhao Yang, Paul A. Mayewski, Sallie I. Whitlow, Mark S. Twickler, Mark S. Germani
Assessment Of The Record Of The 1982 El Chichón Eruption As Preserved In Greenland Snow, Gregory A. Zielinski, Jack E. Dibb, Qinzhao Yang, Paul A. Mayewski, Sallie I. Whitlow, Mark S. Twickler, Mark S. Germani
Earth Sciences
Variability in the SO4 2- and Cl- time series for the 1980s from 12 shallow snow pits across the Greenland ice sheet is used to evaluate the record of the 1982 El Chichón eruption and the potential for recording a moderate northern equatorial eruption in a single Greenland ice core. Composition of volcanic glass found in spring 1983 snow in one of the pits in the Summit region matches that from El Chichón glass, thereby verifying the deposition of material from the eruption. High Na+ and Cl- concentrations in this same layer probably represent deposition of the reaction products of …
Temporal And Spatial Variability Of Snow Accumulation In Central Greenland, H Kuhns, C Davidson, Jack E. Dibb, C Stearns, M H. Bergin, J L. Jaffrezo
Temporal And Spatial Variability Of Snow Accumulation In Central Greenland, H Kuhns, C Davidson, Jack E. Dibb, C Stearns, M H. Bergin, J L. Jaffrezo
Earth Sciences
Snow accumulation records from central Greenland are explored to improve the understanding of the accumulation signal in Greenland ice core records. Results from a “forest” of 100 bamboo poles and automated accumulation monitors in the vicinity of Summit as well as shallow cores collected in the Summit and Crete areas are presented. Based on these accumulation data, a regression has been calculated to quantify the signal-to-noise variance ratio of ice core accumulation signals on a variety of temporal (1 week to 2 years) and spatial (20 m to 200 km) scales. Results are consistent with data obtained from year-round automated …
Layout For Visualizing Large Software Structures In 3d, Colin Ware, Glenn Franck, Monica Parkhi, Tim Dudley
Layout For Visualizing Large Software Structures In 3d, Colin Ware, Glenn Franck, Monica Parkhi, Tim Dudley
Center for Coastal and Ocean Mapping
There is increasing evidence that 3D visualization of complex structures has advantages over 2D visualization. While nested directed graphs are an important method of representing information in 2D or 3D, they must be effectively organized in order to be understood. Most work on graph layout has assumed that fully automatic layout is desirable. Through our work with graphs representing large software structures, we have found that, due to the importance of the semantic content, it is necessary to combine automatic layout with manual layout. This paper describes a system called GraphVisualizer3D, which was designed to help people understand large nested …
Air-Snow Exchange Investigations At Summit, Greenland: An Overview, Jack E. Dibb, J L. Jaffrezo
Air-Snow Exchange Investigations At Summit, Greenland: An Overview, Jack E. Dibb, J L. Jaffrezo
Earth Sciences
The Greenland Ice Sheet Project 2 (GISP2) and Greenland Ice Core Project (GRIP) deep drilling programs at Summit, Greenland included support (both logistical and scientific) of extensive investigation of atmospheric transport and air-snow exchange processes of gases and particles relevant to the interpretation of the ice-core records. Much of the sampling for the air-snow exchange investigations was conducted at a unique solar-powered camp 30 km southwest of the GISP2 drill camp (even further from the GRIP camp) and was characterized by a high degree of international collaboration and cooperation. The wide range of expertise and analytical capabilities of the 20-plus …
Prototype For Sontrac: A Scintillating Plastic Fiber Detector For Solar Neutron Spectroscopy, James M. Ryan, Janis Baltgalvis, D Holslin, John R. Macri, Mark L. Mcconnell, Cornelia B. Wunderer, Aaron R. Polichar
Prototype For Sontrac: A Scintillating Plastic Fiber Detector For Solar Neutron Spectroscopy, James M. Ryan, Janis Baltgalvis, D Holslin, John R. Macri, Mark L. Mcconnell, Cornelia B. Wunderer, Aaron R. Polichar
Space Science Center
We report the scientific motivation for and performance measurements of a prototype detector system for SONTRAC, a solar neutron tracking experiment designed to study high- energy solar flare processes. The full SONTRAC instrument will measure the energy and direction of 20 to 200 MeV neutrons by imaging the ionization tracks of the recoil protons in a densely packed bundle of scintillating plastic fibers. The prototype detector consists of a 12.7 mm square bundle of 250 micrometer scintillating plastic fibers, 10 cm long. A photomultiplier detects scintillation light from one end of the fiber bundle and provides a detection trigger to …
A Prototype For Sontrac, A Scintillating Plastic Fiber Tracking Detector For Neutron Imaging And Spectroscopy, James M. Ryan, John R. Macri, Mark L. Mcconnell, C B. Wunderer, D Holslin, Aaron R. Polichar, Janis Baltgalvis
A Prototype For Sontrac, A Scintillating Plastic Fiber Tracking Detector For Neutron Imaging And Spectroscopy, James M. Ryan, John R. Macri, Mark L. Mcconnell, C B. Wunderer, D Holslin, Aaron R. Polichar, Janis Baltgalvis
Space Science Center
We report on tests of a prototype detector system designed to perform imaging and spectroscopy on 20 to 250 MeV neutrons. Although developed for the study of high-energy solar flare processes, the detection techniques employed for SONTRAC, the SOlar Neutron TRACking experiment, can be applied to measurements in a variety of disciplines including atmospheric physics, radiation therapy and nuclear materials monitoring. The SONTRAC instrument measures the energy and direction ofneutrons by detecting double neutron-proton scatters and recording images of the ionization tracks of the recoil protons in a densely packed bundle of scintillating plastic fibers stacked in orthogonal layers. By …
Sontrac-A Low Background, Large Area Solar Neutron Spectrometer, C B. Wunderer, D Holslin, John R. Macri, Mark L. Mcconnell, James M. Ryan
Sontrac-A Low Background, Large Area Solar Neutron Spectrometer, C B. Wunderer, D Holslin, John R. Macri, Mark L. Mcconnell, James M. Ryan
Space Science Center
SONTRAC will measure 20-250 MeV neutrons from solar flares using scintillator fibers viewed by CCD cameras to track neutron-proton scatters. SONTRAC can also be used to track gamma rays above 20 MeV. Veto shields are used to reject all charged particles. Gamma-ray and neutron events have very different track densities, allowing discrimination between the two. Double neutron-proton scatters allow unambiguous determination of the incident neutron energy and direction. Therefore, SONTRAC is capable of rejecting almost all background except neutrons from the solar direction. SONTRAC would have detected the June 15, 1991 flare with 42σ for 20-100 MeV neutrons, having an …
Activation In The Comptel Double-Scattering Gamma-Ray Telescope, D Morris, Mark L. Mcconnell, James M. Ryan, R Diehl, U Oberlack, V Schonfelder, M Varendorff, G Weidenspointer, H Deboer, K Bennett
Activation In The Comptel Double-Scattering Gamma-Ray Telescope, D Morris, Mark L. Mcconnell, James M. Ryan, R Diehl, U Oberlack, V Schonfelder, M Varendorff, G Weidenspointer, H Deboer, K Bennett
Space Science Center
Abstract-The COMPTEL gamma-ray telescope has been operating in low Earth orbit for six years, since the launch of the Compton Gamma-Ray Observatory in April 1991. Comparisons of data for different orbits and epochs show evidence of activation on time scales from minutes (27Mg, q,2=9.5 min) to years C2Na, q&.58 yr). The activation is correlated with both the orbital altitude and solar cosmic-ray modulation. Because it requires coincident measurements in two different detectors, COMPTEL is most susceptible to instrumental background events in which two or more photons are produced simultaneously.
Initial Polar Mfe Observation Of Substorm Signatures In The Polar Magnetosphere, H. Kawano, G. Le, C. T. Russell, G. Rostoker, T. Mukai, Harlan E. Spence
Initial Polar Mfe Observation Of Substorm Signatures In The Polar Magnetosphere, H. Kawano, G. Le, C. T. Russell, G. Rostoker, T. Mukai, Harlan E. Spence
Physics & Astronomy
This paper studies substorm influences in the polar magnetosphere using data from the POLAR magnetic field experiment (MFE). The POLAR spacecraft remains in the high altitude polar magnetosphere for extended periods around apogee. There it can stay at nearly constant altitude through all phases of a substorm, which was not possible on previous missions. We report such an event on March 28, 1996. Ground magnetometers monitored substorm activity, while the POLAR spacecraft, directly over the pole at (−0.8, −0.6, 8.5) RE in GSM coordinates, observed a corresponding perturbation in the total magnetic field strength. The total magnetic field first …
First Polar And 1995-034 Observations Of The Midaltitude Cusp During A Persistent Northward Imf Condition, M. Grande, J. Fennell, S. Livi, B. Kellett, C. Perry, P. Anderson, J. Roeder, Harlan E. Spence, T. Fritz, B. Wilken
First Polar And 1995-034 Observations Of The Midaltitude Cusp During A Persistent Northward Imf Condition, M. Grande, J. Fennell, S. Livi, B. Kellett, C. Perry, P. Anderson, J. Roeder, Harlan E. Spence, T. Fritz, B. Wilken
Physics & Astronomy
We present the first observations by Polar and 1995-034 of the mid-altitude cusp. On May 29, 1996, the Polar and 1995-034 spacecraft crossed into an extended cusp region. The region was characterized by intense fluxes of solar wind like ions in the energy range 1–10 keV that had angular distributions that showed evidence of flows and trapping. The ion composition data are combined with energetic proton observations from Polar and plasma observations from 1995-034 and DMSP satellites to examine the spatial and temporal extent and plasma characteristics of the cusp during a persistent northward IMF condition. The composition data is …
A New, Temporarily Confined Population In The Polar Cap During The August 27, 1996 Geomagnetic Field Distortion Period, Jiasheng Chen, Theodore A. Fritz, Robert B. Sheldon, Harlan E. Spence, Walther N. Spjeldvik, Joseph F. Fennell, Stefano Livi
A New, Temporarily Confined Population In The Polar Cap During The August 27, 1996 Geomagnetic Field Distortion Period, Jiasheng Chen, Theodore A. Fritz, Robert B. Sheldon, Harlan E. Spence, Walther N. Spjeldvik, Joseph F. Fennell, Stefano Livi
Physics & Astronomy
On August 27, 1996, a two-hour energetic heavy ion event (∼1 MeV) was detected at 8:25 UT at apogee (∼9 Re and an invariant latitude of ∼80°), by the Charge and Mass Magnetospheric Ion Composition Experiment onboard POLAR. The event, with a maximum spin averaged peak flux of ∼150 particles/(cm²-sr-s-MeV), showed three local peaks corresponding to three localized regions; the ion pitch angle distributions in the three regions were different from an isotropic distribution and different from each other. No comparable flux was observed by the WIND spacecraft. The appearance of lower energy He++ and O > +2 during the event …
First Energetic Neutral Atom Images From Polar, M. G. Henderson, G. D. Reeves, Harlan E. Spence, R. B. Sheldon, A. M. Jorgensen, J. B. Blake, J. F. Fennell
First Energetic Neutral Atom Images From Polar, M. G. Henderson, G. D. Reeves, Harlan E. Spence, R. B. Sheldon, A. M. Jorgensen, J. B. Blake, J. F. Fennell
Physics & Astronomy
Energetic neutral atoms are created when energetic magnetospheric ions undergo charge exchange with cold neutral atoms in the Earth's tenuous extended atmosphere (the geocorona). Since they are unaffected by the Earth's magnetic field, these energetic neutrals travel away in straight line trajectories from the points of charge exchange. The remote detection of these particles provides a powerful means through which the global distribution and properties of the geocorona and ring current can be inferred. Due to its 2 × 9 RE polar orbit, the Polar spacecraft provides an excellent platform from which to observe ENAs because it spends much of …
Cdznte Strip Detectors As Sub-Millimeter Resolution Imaging Gamma Radiation Spectrometers, K Larson, V Boykin, M L. Cherry, J F. Courville, F P. Doty, A Drake, T G. Guzik, L A. Hamel, John R. Macri, M Mayer, Mark L. Mcconnell, James M. Ryan, O Tousignant
Cdznte Strip Detectors As Sub-Millimeter Resolution Imaging Gamma Radiation Spectrometers, K Larson, V Boykin, M L. Cherry, J F. Courville, F P. Doty, A Drake, T G. Guzik, L A. Hamel, John R. Macri, M Mayer, Mark L. Mcconnell, James M. Ryan, O Tousignant
Space Science Center
We report γ-ray detection performance measurements and computer simulations of a sub-millimeter pitch CdZnTe strip detector. The detector is a prototype for γ-ray measurements in the range of 20-600 keV. The prototype is a 1.5 mm thick, 64×64 orthogonal stripe CdZnTe detector of 0.375 mm pitch in both dimensions, with approximately one square inch of sensitive area. Using discrete laboratory electronics to process signals from an 8×8 stripe region of the prototype we measured good spectroscopic uniformity and sub-pitch (~0.2 mm) spatial resolution in both x and y dimensions. We present below measurements of the spatial uniformity, relative timing and …
A 200-Year 210pb Record From Greenland, Jack E. Dibb, Henrick B. Clausen
A 200-Year 210pb Record From Greenland, Jack E. Dibb, Henrick B. Clausen
Earth Sciences
A continuous profile of 210Pb activity extending back to 1766 has been developed for a firn/ice core collected at Site D in central Greenland in 1984. Unexpectedly high activities of 210Pb were found at the base of this core (0.032 pCi kg−1 in samples more than 200 years old), calling into question the common assumption that supported 210Pb can be neglected when constructing chronologies in glacial snow and ice. It is problematic to assert that all of the 210Pb measured at depth should be attributed to the supported fraction, given previous estimates of dust loading …
Core-Log-Seismic Integration As A Framework For Determining The Basin-Wide Significance Of Regional Reflectors In The Eastern Equatorial Pacific, Stephen F. Bloomer, Larry A. Mayer
Core-Log-Seismic Integration As A Framework For Determining The Basin-Wide Significance Of Regional Reflectors In The Eastern Equatorial Pacific, Stephen F. Bloomer, Larry A. Mayer
Affiliate Scholarship
ODP Leg 138 in the eastern equatorial Pacific (EEP) provided a unique opportunity to understand the paleoceanographic significance of seismic reflectors in this climatically sensitive region. Carefully offset multiple cores were spliced into a complete stratigraphic section for the upper 250 m at each site and accurate, astronomically tuned time scales were generated from these composites. Well log data provided a means to correct composite depths to true depths as well as density and velocity data for the generation of synthetic seismograms. These synthetic seismograms were used to determine the paleoceanographic significance of regionally traceable reflectors by linking variations in …
Progress In The Study Of Cdznte Strip Detectors, O Tousignant, L A. Hamel, J F. Courville, P Paki, John R. Macri, K Larson, M Mayer, Mark L. Mcconnell, James M. Ryan
Progress In The Study Of Cdznte Strip Detectors, O Tousignant, L A. Hamel, J F. Courville, P Paki, John R. Macri, K Larson, M Mayer, Mark L. Mcconnell, James M. Ryan
Space Science Center
We report new performance measurements and computer simulations of a sub-millimeter pitch CdZnTe strip detector under study as a prototype imaging spectrometer for astronomical x-ray and gamma-ray observations. The prototype is 1.5 mm thick with 375 micron strip pitch in both the x and y dimensions. Previously reported work included demonstrations of half-pitch spatial resolution (approximately 190 microns) and good energy resolution and spectral uniformity. Strip detector efficiency measurements have also been presented. A model that includes the photon interaction, carrier transport and the electronics was developed that qualitatively reproduced the measurements. The new studies include measurements of the CdZnTe …
Galactic Black Hole Binaries: High-Energy Radiation, J E. Grove, J E. Grindlay, B A. Harmon, X M. Hua, D Kazanas, Mark L. Mcconnell
Galactic Black Hole Binaries: High-Energy Radiation, J E. Grove, J E. Grindlay, B A. Harmon, X M. Hua, D Kazanas, Mark L. Mcconnell
Space Science Center
Observations of galactic black hole candidates made by the instruments aboard the Compton GRO in the hard X-ray and γ-ray bands have significantly enhanced our knowledge of the phenomenology of the emission from these objects. Understanding these observations presents a formidable challenge to theoretical models of the accretion flow onto the compact object and of the physical mechanisms that generate high-energy radiation. Here we summarize the current state of observations and theoretical interpretation of the emission from black holecandidates above 20 keV. The all-sky monitoring capability of BATSE allows, for the first time, nearly continuous studies of the high-energy emission …
5 Years Of Crab Pulsar Observations With Comptel, R Much, K Bennett, C Winkler, R Diehl, G G. Lichti, V Schonfelder, H Steinle, A W. Strong, M Varendorff, W Hermsen, L Kuiper, R Van Der Meulen, A Connors, Mark L. Mcconnell, James M. Ryan, R Buccheri
5 Years Of Crab Pulsar Observations With Comptel, R Much, K Bennett, C Winkler, R Diehl, G G. Lichti, V Schonfelder, H Steinle, A W. Strong, M Varendorff, W Hermsen, L Kuiper, R Van Der Meulen, A Connors, Mark L. Mcconnell, James M. Ryan, R Buccheri
Space Science Center
Using the COMPTEL data of the first 5 years of the CGRO mission we have derived the average pulsed spectrum of the Crab Pulsar, as well as phase-resolved spectra of the pulsed emission of the Crab Pulsar. The spectra in the COMPTEL energy range (0.75 to 30 MeV) are compared to those in the neighboring energy bands. The pulsed flux has been examined for its stability. Pulsed lightcurves have been derived for different energy intervals. Preliminary results of this analysis are presented.
Evidence For Γ-Ray Flares In 3c 279 And Pks 1622-297 At ∼10 Mev, W Collmar, V Schonfelder, H Bloemen, J J. Blom, W Hermsen, Mark L. Mcconnell, J G. Stacy, K Bennett, O R. Williams
Evidence For Γ-Ray Flares In 3c 279 And Pks 1622-297 At ∼10 Mev, W Collmar, V Schonfelder, H Bloemen, J J. Blom, W Hermsen, Mark L. Mcconnell, J G. Stacy, K Bennett, O R. Williams
Space Science Center
The EGRET experiment aboard the Compton Gamma-Ray Observatory (CGRO) has observed at energies above 100 MeV strong gamma-ray flares with short-term time variability from thegamma-ray blazars 3C 279 [1] and PKS 1622-297 [2]. During these flaring periods both blazarshave been detected by the COMPTEL experiment aboard CGRO at photon energies of ∼10 MeV, revealing simultaneous γ-ray activity down to these energies. For both cases the derived fluxes exceed those measured in previous observations, and 3C 279 shows an indication for time variability within the observational period. Both sources show evidence for ‘hard’ MeV spectra. In general the behaviour of both …
Improved Comptel 10–30 Mev Event Selections For Point Sources From Inflight Data, W Collmar, U Wessolowski, V Schonfelder, G Weidenspointer, S C. Kappadath, Mark L. Mcconnell, K Bennett
Improved Comptel 10–30 Mev Event Selections For Point Sources From Inflight Data, W Collmar, U Wessolowski, V Schonfelder, G Weidenspointer, S C. Kappadath, Mark L. Mcconnell, K Bennett
Space Science Center
After several years in orbit the COMPTEL experiment aboard the COMPTON Gamma-RayObservatory has collected a substantial amount of data from the MeV sky. We have used the inflight event data collected from the Crab, which is the brightest point source at MeV energies, to optimize our event selections for point sources. For the COMPTEL 10–30 MeV range we have derived a set of improved parameter selections, which leads to a reduction of background events and—at the same time—increases the number of source events, resulting in an obvious improvement in the signal-to-background ratio for point sources. Due to a revised cut …
The Prompt Cosmic-Ray-Induced Background In The Orbiting Compton Telescope Comptel, James M. Ryan, S C. Kappadath, Mark L. Mcconnell, D Morris, V Schonfelder, M Varendorff, G Weidenspointer, W Hermsen, K Bennett
The Prompt Cosmic-Ray-Induced Background In The Orbiting Compton Telescope Comptel, James M. Ryan, S C. Kappadath, Mark L. Mcconnell, D Morris, V Schonfelder, M Varendorff, G Weidenspointer, W Hermsen, K Bennett
Space Science Center
The authors report the spectrum of background events that the COMPTEL instrument on ComptonGamma Ray Observatory experiences due to the instantaneous effects of cosmic rays. Otherbackgrounds are present in the data of this Compton telescope, but the components that closely follow the instantaneous flux of cosmic rays are the most identifiable. The background varies approximately linearly with the cosmic-ray intensity and exhibits a broad feature from about 1 to 10 MeV suggestive of the nuclear nature of the events. Above 10 MeV there is a marked change in the nature of thebackground that is not understood. It appears that the …
Recurrent Geomagnetic Storms And Relativistic Electron Enhancements In The Outer Magnetosphere: Istp Coordinated Measurements, D. N. Baker, X. Li, N. Turner, J. H. Allen, L. F. Bargatze, J. B. Blake, R. B. Sheldon, Harlan E. Spence, R. D. Belian, G. D. Reeves, S. G. Kanekal, B. Klecker
Recurrent Geomagnetic Storms And Relativistic Electron Enhancements In The Outer Magnetosphere: Istp Coordinated Measurements, D. N. Baker, X. Li, N. Turner, J. H. Allen, L. F. Bargatze, J. B. Blake, R. B. Sheldon, Harlan E. Spence, R. D. Belian, G. D. Reeves, S. G. Kanekal, B. Klecker
Physics & Astronomy
New, coordinated measurements from the International Solar-Terrestrial Physics (ISTP) constellation of spacecraft are presented to show the causes and effects of recurrent geomagnetic activity during recent solar minimum conditions. It is found using WIND and POLAR data that even for modest geomagnetic storms, relativistic electron fluxes are strongly and rapidly enhanced within the outer radiation zone of the Earth's magnetosphere. Solar wind data are utilized to identify the drivers of magnetospheric acceleration processes. Yohkoh solar soft X-ray data are also used to identify the solar coronal holes that produce the high-speed solar wind streams which, in turn, cause the recurrent …
The Total Cosmic Diffuse Gamma-Ray Spectrum From 9 To 30 Mev Measured With Comptel, S C. Kappadath, James M. Ryan, K Bennett, H Bloemen, R Diehl, W Hermsen, Mark L. Mcconnell, V Schonfelder, M Varendorff, G Weidenspointer, C Winkler
The Total Cosmic Diffuse Gamma-Ray Spectrum From 9 To 30 Mev Measured With Comptel, S C. Kappadath, James M. Ryan, K Bennett, H Bloemen, R Diehl, W Hermsen, Mark L. Mcconnell, V Schonfelder, M Varendorff, G Weidenspointer, C Winkler
Space Science Center
A preliminary COMPTEL Cosmic Diffuse Gamma-Ray (CDG) spectrum from 800 keV to 30 MeV was presented earlier at the 3rd Compton Symposium. The COMPTEL results represent the first significant detection of the CDG radiation in the 9 to 30 MeV range. Using high-latitude data from the first 5 years of the mission we have performed a new detailed measurement of the 9 to 30 MeV spectrum with finer energy binning. The new improved results are in good agreement with our previous estimates and are compatible with power-law extrapolations from higher energies. The measured 9–30 MeV spectra from the Virgo and …
The Mev Spectrum Of Cygnus X-1 As Observed With Comptel, Mark L. Mcconnell, K Bennett, H Bloemen, W Collmar, W Hermsen, L Kuiper, R Much, James M. Ryan, V Schonfelder, H Steinle, A W. Strong, R Vandijk
The Mev Spectrum Of Cygnus X-1 As Observed With Comptel, Mark L. Mcconnell, K Bennett, H Bloemen, W Collmar, W Hermsen, L Kuiper, R Much, James M. Ryan, V Schonfelder, H Steinle, A W. Strong, R Vandijk
Space Science Center
The COMPTEL experiment on the Compton Gamma-Ray Observatory (CGRO) has observed the Cygnus region on several occasions since launch. These data represent the most sensitive observations to date of Cygnus X-1 in the 0.75–30 MeV range. The spectrum shows significant evidence for emission extending out to several MeV. These data alone suggest a need to modify the thermal Comptonization models or to incorporate some type of non-thermal emission mechanism. Here we report on the results of an analysis of selected COMPTEL data collected during the first three years of the CGRO mission. These data are then compared with contemporaneous data …