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Full-Text Articles in Physical Sciences and Mathematics
Recent Laboratory Tests Of A Hard X-Ray Solar Flare Polarimeter, Mark L. Mcconnell, John R. Macri, M Mcclish, Jack Ryalls
Recent Laboratory Tests Of A Hard X-Ray Solar Flare Polarimeter, Mark L. Mcconnell, John R. Macri, M Mcclish, Jack Ryalls
Space Science Center
We report on the development of a Compton scatter polarimeter for measuring the linear polarization of hard X-rays (50 - 300 keV) from solar flares. Such measurements would be useful for studying the directivity (or beaming) of the electrons that are accelerated in solar flares. We initially used a simple prototype polarimeter to successfully demonstrate the reliability of our Monte Carlo simulation code and to demonstrate our ability to generate a polarized photon source in the lab. We have recently fabricated a science model based on a modular design concept that places a self-contained polarimeter module on the front-end of …
Coded-Aperture X-Ray/Gamma-Ray Telescope For Arc-Minute Localization Of Gamma-Ray Bursts, M L. Cherry, P P. Altice, D L. Band, J Buckley, T G. Guzik, P L. Hink, S C. Kappadath, John R. Macri, J L. Matteson, Mark L. Mcconnell, Terence J. O'Neill, James M. Ryan, K R. Slavis, J G. Stacy, Allen Zych
Coded-Aperture X-Ray/Gamma-Ray Telescope For Arc-Minute Localization Of Gamma-Ray Bursts, M L. Cherry, P P. Altice, D L. Band, J Buckley, T G. Guzik, P L. Hink, S C. Kappadath, John R. Macri, J L. Matteson, Mark L. Mcconnell, Terence J. O'Neill, James M. Ryan, K R. Slavis, J G. Stacy, Allen Zych
Space Science Center
MARGIE will be a large-area, wide field-of-view, hard x- ray/gamma-ray imaging telescope capable of providing accurate positions for faint gamma-ray bursts in near-real- time and of performing a sensitive survey of both steady and transient cosmic sources. The instrument is designed to image faint bursts at the low-intensity end of the log N - log S distribution. MARGIE was recently selected by NASA for a mission-concept study for an Ultra Long Duration Balloon flight. We describe a program to develop an instrument based on the new detector technology of either cadmium zinc telluride room-temperature semiconductors or pixelated cesium iodide scintillators …
Fiberglast: A Scintillating Fiber Approach To The Glast Mission, Geoffrey N. Pendleton, W Robert Binns, Martin W. Israel, P L. Hink, M L. Cherry, W Paciesas, R M. Kippen, Robert S. Mallozzi, Thomas A. Parnell, Gerald J. Fishman, O T. Tumer, Mark J. Christl, Robert B. Wilson, J Buckley, Georgia A. Richardson, Surasak Phengchamnan, Keith R. Rielage, Gerald Karr, Donald B. Wallace, James M. Ryan, Mark L. Mcconnell, John R. Macri
Fiberglast: A Scintillating Fiber Approach To The Glast Mission, Geoffrey N. Pendleton, W Robert Binns, Martin W. Israel, P L. Hink, M L. Cherry, W Paciesas, R M. Kippen, Robert S. Mallozzi, Thomas A. Parnell, Gerald J. Fishman, O T. Tumer, Mark J. Christl, Robert B. Wilson, J Buckley, Georgia A. Richardson, Surasak Phengchamnan, Keith R. Rielage, Gerald Karr, Donald B. Wallace, James M. Ryan, Mark L. Mcconnell, John R. Macri
Space Science Center
FiberGLAST is a scintillating fiber gamma-ray detector designed for the GLAST mission. The system described below provides superior effective area and field of view for modest cost and risk. An overview of the FiberGLAST instrument is presented, as well as a more detailed description of the principle elements of the primary detector volume. The triggering and readout electronics are described, and Monte Carlo Simulations of the instrument performance are presented.
Beam Test Results For The Fiberglast Instrument, Robert S. Mallozzi, R M. Kippen, Geoffrey N. Pendleton, W Paciesas, Georgia A. Richardson, Surasak Phengchamnan, Gerald Karr, Donald B. Wallace, Gerald J. Fishman, Thomas A. Parnell, Robert B. Wilson, Mark J. Christl, W Robert Binns, P L. Hink, Martin W. Israel, Keith R. Rielage, John W. Epstein, Paul F. Dowkontt, J Buckley, James M. Ryan, John R. Macri, Mark L. Mcconnell, O T. Tumer, M L. Cherry, T G. Guzik, J G. Stacy, S C. Kappadath, Muzaffer Atac, Katsushi Arisaka, David B. Cline, Yuriy Pischalnikov
Beam Test Results For The Fiberglast Instrument, Robert S. Mallozzi, R M. Kippen, Geoffrey N. Pendleton, W Paciesas, Georgia A. Richardson, Surasak Phengchamnan, Gerald Karr, Donald B. Wallace, Gerald J. Fishman, Thomas A. Parnell, Robert B. Wilson, Mark J. Christl, W Robert Binns, P L. Hink, Martin W. Israel, Keith R. Rielage, John W. Epstein, Paul F. Dowkontt, J Buckley, James M. Ryan, John R. Macri, Mark L. Mcconnell, O T. Tumer, M L. Cherry, T G. Guzik, J G. Stacy, S C. Kappadath, Muzaffer Atac, Katsushi Arisaka, David B. Cline, Yuriy Pischalnikov
Space Science Center
The FiberGLAST scintillating fiber telescope is a large-area instrument concept for NASA's GLAST program. The detector is designed for high-energy gamma-ray astronomy, and uses plastic scintillating fibers to combine a photon pair tracking telescope and a calorimeter into a single instrument. A small prototype detector has been tested with high energy photons at the Thomas Jefferson National Accelerator Facility. We report on the result of this beam test, including scintillating fiber performance, photon track reconstruction, angular resolution, and detector efficiency.
Recent Progress In The Development Of A Solar Neutron Tracking Device (Sontrac), James M. Ryan, Wenhui Li, John R. Macri, Mark L. Mcconnell, Carlos Castaneda, Juan L. Romero
Recent Progress In The Development Of A Solar Neutron Tracking Device (Sontrac), James M. Ryan, Wenhui Li, John R. Macri, Mark L. Mcconnell, Carlos Castaneda, Juan L. Romero
Space Science Center
We report the results of recent calibration data analysis of a prototype scintillating fiber tracking detector system designed to perform imaging, spectroscopy and particle identification on 20 to 250 MeV neutrons and protons. We present the neutron imaging concept and briefly review the detection principle and the prototype description. The prototype detector system records ionization track data on an event-by-event basis allowing event selection criteria to be used in the off-line analysis. Images of acrylic phantoms from the analysis of recent proton beam calibrations are presented as demonstrations of the particle identification, imaging and energy measurement capabilities. The measured position …
Development And Testing Of A Fiber/Multianode Photomultiplier System For Use On Fiberglast, Keith R. Rielage, Katsushi Arisaka, Muzaffer Atac, W Robert Binns, J Buckley, M L. Cherry, Mark J. Christl, David B. Cline, Paul F. Dowkontt, John W. Epstein, Gerald J. Fishman, T G. Guzik, P L. Hink, Martin H. Israel, S C. Kappadath, Gerald Karr, R M. Kippen, Daniel Leopold, Mark L. Mcconnell, John R. Macri, Robert S. Mallozzi, W Paciesas, Thomas A. Parnell, Geoffrey N. Pendleton, Surasak Phengchamnan, Yuriy Pischalnikov, Georgia A. Richardson, James M. Ryan, J G. Stacy, O T. Tumer, Gerald J. Vissor, Donald B. Wallace, Robert B. Wilson
Development And Testing Of A Fiber/Multianode Photomultiplier System For Use On Fiberglast, Keith R. Rielage, Katsushi Arisaka, Muzaffer Atac, W Robert Binns, J Buckley, M L. Cherry, Mark J. Christl, David B. Cline, Paul F. Dowkontt, John W. Epstein, Gerald J. Fishman, T G. Guzik, P L. Hink, Martin H. Israel, S C. Kappadath, Gerald Karr, R M. Kippen, Daniel Leopold, Mark L. Mcconnell, John R. Macri, Robert S. Mallozzi, W Paciesas, Thomas A. Parnell, Geoffrey N. Pendleton, Surasak Phengchamnan, Yuriy Pischalnikov, Georgia A. Richardson, James M. Ryan, J G. Stacy, O T. Tumer, Gerald J. Vissor, Donald B. Wallace, Robert B. Wilson
Space Science Center
A scintillating fiber detector is currently being studied for the NASA Gamma-Ray Large Area Space Telescope (GLAST) mission. This detector utilizes modules composed of a thin converter sheet followed by an x, y plane of scintillating fibers to examine the shower of particles created by high energy gamma-rays interacting in the converter material. The detector is composed of a tracker with 90 such modular planes and a calorimeter with 36 planes. The two major component of this detector are the scintillating fibers and their associated photodetectors. Here we present current status of development and test result of both of these. …
Energy And Position Resolution Of A Cdznte Gamma-Ray Detector With Orthogonal Coplanar Anodes, O Tousignant, L A. Hamel, Pierre C. Dufour, F Joly, John R. Macri, Mark L. Mcconnell, James M. Ryan, V T. Jordanov
Energy And Position Resolution Of A Cdznte Gamma-Ray Detector With Orthogonal Coplanar Anodes, O Tousignant, L A. Hamel, Pierre C. Dufour, F Joly, John R. Macri, Mark L. Mcconnell, James M. Ryan, V T. Jordanov
Space Science Center
We report on the simulation, construction and performance of prototype CZT imaging detectors employing orthogonal coplanar anodes. These detectors employ a novel electrode geometry with non-collecting anode strips in 1D and collecting anode pixels, interconnected in rows, in the orthogonal dimensions. These detectors retain the spectroscopic and detection efficiency advantages of single carried charge sensing devices as well as the principal advantage of conventional strip detectors with orthogonal anode and cathode strips, i.e. an N X N array of imagin pixels are realized with only 2N electronic channels. Charge signals induced on the various electrodes of a prototype detector with …
Reactive Nitrogen Budget During The Nasa Sonex Mission, R. Talbot, Jack E. Dibb, Eric Scheuer, Y Kondo, M Koike, H B. Singh, L Salas, F Fukui, J O. Ballenthin, R F. Meads, T M. Miller, D E. Hunton, A A. Viggiano, D R. Blake, N J. Blake, Elliot Atlas, F Flocke, D J. Jacob, L Jaegle
Reactive Nitrogen Budget During The Nasa Sonex Mission, R. Talbot, Jack E. Dibb, Eric Scheuer, Y Kondo, M Koike, H B. Singh, L Salas, F Fukui, J O. Ballenthin, R F. Meads, T M. Miller, D E. Hunton, A A. Viggiano, D R. Blake, N J. Blake, Elliot Atlas, F Flocke, D J. Jacob, L Jaegle
Earth Sciences
The SASS Ozone and Nitrogen Oxides Experiment (SONEX) over the North Atlantic during October/November 1997 offered an excellent opportunity to examine the budget of reactive nitrogen in the upper troposphere (8–12 km altitude). The median measured total reactive nitrogen (NOy) mixing ratio was 425 parts per trillion by volume (pptv). A data set merged to the HNO3 measurement time resolution was used to calculate NOy (NOy sum) by summing the reactive nitrogen species (a combination of measured plus modeled results) and comparing it to measured NOy (NOy meas.). Comparisons were done for tropospheric …
Mapping A Continental Shelf And Slope In The 1990s: A Tale Of Three Multibeams, James V. Gardner, J.E. Hughes Clarke, Larry A. Mayer, Art Kleiner, Mark Paton
Mapping A Continental Shelf And Slope In The 1990s: A Tale Of Three Multibeams, James V. Gardner, J.E. Hughes Clarke, Larry A. Mayer, Art Kleiner, Mark Paton
Center for Coastal and Ocean Mapping
Increasing societal pressures on the U.S. continental shelves adjacent to dense population centers have brought to light the lack of accurate base maps in these areas. Existing bathymetric maps and random sidescan sonar surveys are either not accurate enough or do not provide the coverage necessary to make policy decisions. Until the mid 1990s, it was not financially prudent nor technically efficient to map the shallow shelves. However, the availability of high-resolution multibeam mapping systems now allow efficient and accurate mapping of the continental margins. In 1996 the U.S. Geological Survey began a large-scale seafloor mapping campaign on the continental …
Data Handling Methods And Target Detection Results For Multibeam And Sidescan Data Collected As Part Of The Search For Swissair Flight 111, John E. Hughes Clarke, Larry A. Mayer, John Shaw, R Parrott, Mike Lamplugh, Jim Bradford
Data Handling Methods And Target Detection Results For Multibeam And Sidescan Data Collected As Part Of The Search For Swissair Flight 111, John E. Hughes Clarke, Larry A. Mayer, John Shaw, R Parrott, Mike Lamplugh, Jim Bradford
Center for Coastal and Ocean Mapping
The crash of SwissAir Flight 111, off Nova Scotia in September 1998, triggered one of the largest seabed search surveys in Canadian history. The primary search tools used were sidescan sonars (both conventional and focussed types) and multibeam sonars. The processed search data needed to be distributed on a daily basis to other elements of the fleet for precise location of divers and other optical seabed search instruments (including laser linescan and ROV video). As a result of the glacial history of the region, many natural targets, similar in gross nature to aircraft debris were present. These included widespread linear …
A Scintillating Plastic Fiber Tracking Detector For Neutron And Proton Imaging And Spectroscopy, James M. Ryan, John R. Macri, Mark L. Mcconnell, Richard A. Messner, Wenhui Li, Hansford H. Cutlip, Quihua Zheng, Carlos Castaneda, Juan L. Romero
A Scintillating Plastic Fiber Tracking Detector For Neutron And Proton Imaging And Spectroscopy, James M. Ryan, John R. Macri, Mark L. Mcconnell, Richard A. Messner, Wenhui Li, Hansford H. Cutlip, Quihua Zheng, Carlos Castaneda, Juan L. Romero
Space Science Center
We report the results of recent calibration data analysis of a prototype scintillating fiber tracking detector system designed to perform imaging, spectroscopy and particle identification on 20 to 250 MeV neutrons and protons. We present the neutron imaging concept and briefly review the detection principle and the prototype description. The prototype detector system records ionization track data on an event-by-event basis allowing event selection criteria to be used in the off-line analysis. Images of acrylic phantoms from the analysis of recent proton beam calibrations (14 to 65 MeV range) are presented as demonstrations of the particle identification, imaging and energy …
Maximum Temperature Trends In The Himalaya And Its Vicinity: An Analysis Based On Temperature Records From Nepal For The Period 1971–94, Arun B. Shrestha, Cameron P. Wake, Paul A. Mayewski, Jack E. Dibb
Maximum Temperature Trends In The Himalaya And Its Vicinity: An Analysis Based On Temperature Records From Nepal For The Period 1971–94, Arun B. Shrestha, Cameron P. Wake, Paul A. Mayewski, Jack E. Dibb
Earth Sciences
Analyses of maximum temperature data from 49 stations in Nepal for the period 1971–94 reveal warming trends after 1977 ranging from 0.068 to 0.128C yr21 in most of the Middle Mountain and Himalayan regions, while the Siwalik and Terai (southern plains) regions show warming trends less than 0.038C yr21. The subset of records (14 stations) extending back to the early 1960s suggests that the recent warming trends were preceded by similar widespread cooling trends. Distributions of seasonal and annual temperature trends show high rates of warming in the high-elevation regions of the country (Middle Mountains and Himalaya), while low warming …
Development Of A Hard X-Ray Polarimeter For Astrophysics, Mark L. Mcconnell, John R. Macri, M Mcclish, James M. Ryan, D J. Forrest, W T. Vestrand
Development Of A Hard X-Ray Polarimeter For Astrophysics, Mark L. Mcconnell, John R. Macri, M Mcclish, James M. Ryan, D J. Forrest, W T. Vestrand
Space Science Center
We have been developing a Compton scatter polarimeter for measuring the linear polarization of hard X-rays (100-300 keV) from astrophysical sources. A laboratory prototype polarimeter has been used to successfully demonstrate the reliability of our Monte Carlo simulation code and to demonstrate our ability to generate a polarized photon source in the lab. Our design concept places a self-containedpolarimeter module on the front-end of a a 5-inch position sensitive PMT (PSPMT). We are currently working on the fabrication of a science model based on this PSPMT concept. Although the emphasis of our development effort is towards measuring hard X-rays from …
Chemical Characteristics Of Air From Differing Source Regions During The Pacific Exploratory Mission-Tropics A (Pem-Tropics A), Ashley S. Board, H Fuelberg, G L. Gregory, B J. Heikes, Martin G. Schultz, D R. Blake, Jack E. Dibb, S T. Sandholm, R. Talbot
Chemical Characteristics Of Air From Differing Source Regions During The Pacific Exploratory Mission-Tropics A (Pem-Tropics A), Ashley S. Board, H Fuelberg, G L. Gregory, B J. Heikes, Martin G. Schultz, D R. Blake, Jack E. Dibb, S T. Sandholm, R. Talbot
Earth Sciences
Ten-day backward trajectories are used to determine the origins of air parcels arriving at airborne DC-8 chemical measurement sites during NASA's Pacific Exploratory Mission-Tropics A (PEM-T) that was conducted during August-October 1996. Those sites at which the air had a common geographical origin and transport history are grouped together, and statistical measures of chemical characteristics are computed. Temporal changes in potential temperature are used to determine whether trajectories experience a significant convective influence during the 10-day period. Those trajectories that do not experience a significant convective influence are divided into four geographical categories depending on their origins and paths. Air …
Constraints On The Age And Dilution Of Pacific Exploratory Mission-Tropics Biomass Burning Plumes From The Natural Radionuclide Tracer 210pb, Jack E. Dibb, R. Talbot, David Meeker, Eric Scheuer, N J. Blake, D R. Blake, G L. Gregory, G W. Sachse
Constraints On The Age And Dilution Of Pacific Exploratory Mission-Tropics Biomass Burning Plumes From The Natural Radionuclide Tracer 210pb, Jack E. Dibb, R. Talbot, David Meeker, Eric Scheuer, N J. Blake, D R. Blake, G L. Gregory, G W. Sachse
Earth Sciences
During the NASA Global Troposphere Experiment Pacific Exploratory Mission-Tropics (PEM-Tropics) airborne sampling campaign we found unexpectedly high concentrations of aerosol-associated 210Pb throughout the free troposphere over the South Pacific. Because of the remoteness of the study region, we expected specific activities to be generally less than 35 μBq m−3 but found an average in the free troposphere of 107 μBq m−3. This average was elevated by a large number of very active (up to 405 μBq m−3) samples that were associated with biomass burning plumes encountered on nearly every PEM-Tropics flight in the southern …
Ozone And Aerosol Distributions And Air Mass Characteristics Over The South Pacific During The Burning Season, Marta Fenn, Edward V. Browell, Carolyn Butler, William B. Grant, Susan A. Kooi, Marian B. Clayton, G L. Gregory, Reginald E. Newell, Yong Zhu, Jack E. Dibb, H Fuelberg, Bruce E. Anderson, A R. Bandy, D R. Blake, J D. Bradshaw, B J. Heikes, G W. Sachse, S T. Sandholm, H B. Singh, R. Talbot, D C. Thornton
Ozone And Aerosol Distributions And Air Mass Characteristics Over The South Pacific During The Burning Season, Marta Fenn, Edward V. Browell, Carolyn Butler, William B. Grant, Susan A. Kooi, Marian B. Clayton, G L. Gregory, Reginald E. Newell, Yong Zhu, Jack E. Dibb, H Fuelberg, Bruce E. Anderson, A R. Bandy, D R. Blake, J D. Bradshaw, B J. Heikes, G W. Sachse, S T. Sandholm, H B. Singh, R. Talbot, D C. Thornton
Earth Sciences
In situ and laser remote measurements of gases and aerosols were made with airborne instrumentation to establish a baseline chemical signature of the atmosphere above the South Pacific Ocean during the NASA Global Tropospheric Experiment (GTE)/Pacific Exploratory Mission-Tropics A (PEM-Tropics A) conducted in August-October 1996. This paper discusses general characteristics of the air masses encountered during this experiment using an airborne lidar system for measurements of the large-scale variations in ozone (O3) and aerosol distributions across the troposphere, calculated potential vorticity (PV) from the European Centre for Medium-Range Weather Forecasting (ECMWF), and in situ measurements for comprehensive air …
A Study Of Omega Bands And Ps6 Pulsations On The Ground, At Low Altitude And At Geostationary Orbit, A. M. Jorgensen, Harlan E. Spence, T. J. Hughes, D. Mcdiarmid
A Study Of Omega Bands And Ps6 Pulsations On The Ground, At Low Altitude And At Geostationary Orbit, A. M. Jorgensen, Harlan E. Spence, T. J. Hughes, D. Mcdiarmid
Physics & Astronomy
We investigate the electrodynamic coupling between auroral omega bands and the inner magnetosphere. The goal of this study is to determine the features to which omega bands map in the magnetosphere. To establish the auroral-magnetosphere connection, we appeal to the case study analysis of the data rich event of September 26, 1989. At 6 magnetic local time (MLT), two trains of Ps6 pulsations (ground magnetic signatures of omega bands) were observed to drift over the Canadian Auroral Network For the OPEN Program Unified Study (CANOPUS) chain. At the same time periodic ionospheric flow patterns moved through the collocated Bistatic Auroral …
Concentrations And Snow-Atmosphere Fluxes Of Reactive Nitrogen At Summit, Greenland, J W. Munger, D J. Jacob, S M. Fan, A S. Colman, Jack E. Dibb
Concentrations And Snow-Atmosphere Fluxes Of Reactive Nitrogen At Summit, Greenland, J W. Munger, D J. Jacob, S M. Fan, A S. Colman, Jack E. Dibb
Earth Sciences
Concentrations and fluxes of NOy (total reactive nitrogen), ozone concentrations and fluxes of sensible heat, water vapor, and momentum were measured from May 1 to July 20, 1995 at Summit, Greenland. Median NOy concentrations declined from 947 ppt in May to 444 ppt by July. NOy fluxes were observed into and out of the snow, but the magnitudes were usually below 1 μmol m−2 h−1 because of the low HNO3 concentration and weak turbulence over the snow surface. Some of the highest observed fluxes may be due to temporary storage by equilibrium sorption of …
Aerosol Chemical Composition And Distribution During The Pacific Exploratory Mission (Pem) Tropics, Jack E. Dibb, R. Talbot, Eric Scheuer, D R. Blake, N J. Blake, G L. Gregory, G W. Sachse, D C. Thornton
Aerosol Chemical Composition And Distribution During The Pacific Exploratory Mission (Pem) Tropics, Jack E. Dibb, R. Talbot, Eric Scheuer, D R. Blake, N J. Blake, G L. Gregory, G W. Sachse, D C. Thornton
Earth Sciences
Distributions of aerosol-associated soluble ions over much of the South Pacific were determined by sampling from the NASA DC-8 as part of the Pacific Exploratory Mission (PEM) Tropics campaign. The mixing ratios of all ionic species were surprisingly low throughout the free troposphere (2-12 km), despite the pervasive influence from biomass burning plumes advecting over the South Pacific from the west during PEM-Tropics. At the same time, the specific activity of 7Be frequently exceeded 1000 fCi m-3 through much of the depth of the troposphere. These distributions indicate that the plumes must have been efficiently scavenged by precipitation (removing the …
Influence Of Biomass Combustion Emissions On The Distribution Of Acidic Trace Gases Over The Southern Pacific Basin During Austral Springtime, R. Talbot, Jack E. Dibb, Eric Scheuer, D R. Blake, N J. Blake, G L. Gregory, G W. Sachse, J D. Bradshaw, S T. Sandholm, H B. Singh
Influence Of Biomass Combustion Emissions On The Distribution Of Acidic Trace Gases Over The Southern Pacific Basin During Austral Springtime, R. Talbot, Jack E. Dibb, Eric Scheuer, D R. Blake, N J. Blake, G L. Gregory, G W. Sachse, J D. Bradshaw, S T. Sandholm, H B. Singh
Earth Sciences
This paper describes the large-scale distributions of HNO3, HCOOH, and CH3COOH over the central and South Pacific basins during the Pacific Exploratory Mission-Tropics (PEM-Tropics) in austral springtime. Because of the remoteness of this region from continental areas, low part per trillion by volume (pptv) mixing ratios of acidic gases were anticipated to be pervasive over the South Pacific basin. However, at altitudes of 2–12 km over the South Pacific, air parcels were encountered frequently with significantly enhanced mixing ratios (up to 1200 pptv) of acidic gases. Most of these air parcels were centered in the 3–7 …
Evidence Of Nox Production Within Or Upon Ice Particles In The Greenland Snowpack, R E. Honrath, Matthew C. Peterson, S Guo, Jack E. Dibb, P B. Shepson, Bradley M. Campbell
Evidence Of Nox Production Within Or Upon Ice Particles In The Greenland Snowpack, R E. Honrath, Matthew C. Peterson, S Guo, Jack E. Dibb, P B. Shepson, Bradley M. Campbell
Earth Sciences
NOx and NOy were determined in the interstitial air of surface snow and in ambient air at Summit, Greenland. NOx levels in interstitial air were 3 to >10 times those in ambient air, and were generally greater than ambient NOy levels. [NOy] in interstitial air varied diurnally in a manner consistent with photochemical generation within the snowpack. These observations imply that photochemical reactions occurring within or upon the ice crystals of surface snow produced NOx from a N-reservoir compound within the snow. Average [NOX]:[HNO3] and [NOx]:[NOy] ratios in ambient air above the snow were elevated relative to other remote sites, …