ABSTRACT We present an analysis of the expected ultraviolet auroral emission strengths from extra... more ABSTRACT We present an analysis of the expected ultraviolet auroral emission strengths from extrasolar giant planets and the feasibility of detecting such exoplanetary aurora. Searching for and studying the ultraviolet auroral emission generated by extrasolar giant planets has unique advantages not offered by other methods. First, UV auroral emission is a means of detecting a planet directly as opposed to the indirect methods employed to date, such as radial velocity and pulsar timing. Second, the detection of an auroral signature would provide evidence of the presence of a planetary magnetic field. No other detection method can provide such evidence. Third, UV auroral emission could play a role in characterizing the near space environment around these planets, providing information about basic atmospheric composition and the deposition energies of the impacting particles. Fourth, ultraviolet wavelengths provide observational advantages compared to the optical. For instance, more favorable contrast ratios can be achieved and the UV diffraction limit allows planets to be detected at smaller angular separations to their host stars. Using Jupiter as a template and taking into account some basic properties involved in auroral production, possible emission fluxes were estimated for a given set of planetary system parameters. Potential candidate planets for UV observations are identified and the possibility of detecting UV auroral emissions with current and future technology is explored. This research has been supported by NSF IGERT Grant No. DGE-9870713 through the Astrobiology Program at the University of Washington, Seattle.
Comets are the oldest and least modified bodies orbiting the sun, and investigations into their c... more Comets are the oldest and least modified bodies orbiting the sun, and investigations into their composition are a key to understanding the development of the early solar system. Studying the daughters of photochemical reactions occurring within a comet's coma provides information concerning the composition and other important properties, such as density and temperature. These can eventually be inverted to give
The properties of the radiation belts can vary dramatically under the influence of magnetic storm... more The properties of the radiation belts can vary dramatically under the influence of magnetic storms and storm-time substorms. The task of understanding and predicting radiation belt properties is made difficult because their properties determined by global processes as well as small-scale wave-particle interactions. A full solution to the problem will require major innovations in technique and computer hardware. The proposed
GPUs are intrinsically highly parallelized systems that provide more than an order of magnitude c... more GPUs are intrinsically highly parallelized systems that provide more than an order of magnitude computing speed over a CPU based systems, for less cost than a high end-workstation. Recent advancements in GPU technologies allow for full IEEE float specifications with performance up to several hundred GFLOPs per GPU, and new software architectures have recently become available to ease the transition
Controlled-source seismologists seek to detonate charges in lakes or rivers because source coupli... more Controlled-source seismologists seek to detonate charges in lakes or rivers because source coupling is an order of magnitude larger in water than in drill holes. Previous studies have documented the biological impact of dynamite explosions on small fish populations; however, little attention has been paid to the potential chemical changes associated with the dispersal of a dynamite charge in a
1] Using single-particle tracking with time-dependent global magnetic and electric fields from mu... more 1] Using single-particle tracking with time-dependent global magnetic and electric fields from multifluid simulations, we model the 10 March 1998 storm and investigate storm time acceleration, injection, and trapping mechanisms associated with the formation of the ring current. We examine the contribution from various ionospheric source regions to the storm time ring current and the effect interplanetary magnetic field B z has on producing an asymmetric and symmetric ring current; we provide the first maps for the relative importance of ionospheric outflow (H + and O + ) regions as a function of all magnetic local times (MLTs) and latitudes between 60°and 80°. During the early part of the storm, high-latitude outflow regions between 00 and 06 MLT are the most efficient sectors at contributing particle density to the ring current, whereas during the main phase of the storm, there is more even contribution from all MLTs. The sectors that contribute the majority of the energy are consistently the high-latitude regions between 03 and 09 MLT. An increase in the contribution of O + to the current density is observed from the predawn high-latitude region during each of two decreases in Dst examined for the 10 March 1998 storm, supporting the central role oxygen plays in storm development. Asymmetries are observed between H + and O + contributions. The dominant ionospheric species contributing to the ring current energy density is shown to vary during the course of the storm with a significant increase in ionospheric O + contribution to the ring current associated with large decreases in Dst. Citation: Cash, M. D., R. M. Winglee, and E. M. Harnett (2010), Storm time production of ring current ions: Variations in particle energization and injection with ionospheric source region,
In January 2003, as part of the Ethiopia-Afar Geoscientific Lithospheric Experiment (EAGLE) we co... more In January 2003, as part of the Ethiopia-Afar Geoscientific Lithospheric Experiment (EAGLE) we conducted a refraction and wide-angle reflection survey of the Main Ethiopian Rift. 757 RefTek "Texan" seismographs with vertical geophones were deployed in 400 km-long axial and cross-rift lines, with another 231 in a central 3D array 100 km in diameter. An 80-instrument passive array of intermediate and broadband sensors was active during our experiment. We recorded 19 borehole shots loaded in nominal 50-meter boreholes, 2 quarry shots, and 2 lake shots. The shots ranged in size from 50-5750 kg, with the most common shot size being 1 tonne. Prior to loading each shot-hole, we measured distances between shots and the nearest structure, typically un-reinforced mud-and-wood houses, occasionally concrete irrigation ditches and aqueducts. We then used semi-empirical formulae derived by Oriard (Hendron and Oriard, 1972) to calculate expected maximum and minimum bounds on ground velocity at these structures, and selected an appropriate shot size to keep the predicted velocity below the "threshold for cosmetic damage", or 2 inches per second, at the most vulnerable structure. The Oriard formulae are derived from measurements associated with blasting for mining and civil engineering purposes and may not accurately predict the ground velocity from the source depths and explosive type used in the EAGLE and other controlled-source experiments. A detailed, trace-by-trace analysis of maximum ground velocities at our closest seismographs can provide data that will be useful in planning future large-scale seismic experiments. Preliminary results from traces within 20 km of our borehole shots suggest that maximum recorded ground velocities were within or below the maximum-minimum range predicted by Oriard, and hence that larger shot sizes could have been used with acceptable risks. A lake shot fired at the optimum depth (84 m for a 1 tonne shot) produced ground velocities that exceeded the predicted maximum at a few recodrers. However, optimum-depth shots are typically a significant distance offshore (c. 2.3 km for our shot) because of the required depth, so are unlikely to present a hazard to onshore structures. A lake shot fired in a shallower lake at half the optimum depth did not produce ground-velocities that exceed the Oriard maximum. Although we fired shots within 100 m of an unreinforced concrete aqueduct, and within 200 m of poorly engineered native buildings in poor structural condition, no damage was recorded. Our "Texan" seismometers recorded only vertical component velocity, using 4.5 Hz geophones. After removal of the geophone response the peak vertical velocity is typically measured at about 3 Hz and occurs shortly after the first arrival, presumably due to surface waves (ground roll). We are currently extending our analysis to include data from broadband, three-component recorders.
The 2009 AbGradCon was held at the University of Washington in July 2009. It brought together 67 ... more The 2009 AbGradCon was held at the University of Washington in July 2009. It brought together 67 participants from 8 different countries and 34 different universities. AbGradCon also took place in the virtual world of Second Life.
ABSTRACT We present an analysis of the expected ultraviolet auroral emission strengths from extra... more ABSTRACT We present an analysis of the expected ultraviolet auroral emission strengths from extrasolar giant planets and the feasibility of detecting such exoplanetary aurora. Searching for and studying the ultraviolet auroral emission generated by extrasolar giant planets has unique advantages not offered by other methods. First, UV auroral emission is a means of detecting a planet directly as opposed to the indirect methods employed to date, such as radial velocity and pulsar timing. Second, the detection of an auroral signature would provide evidence of the presence of a planetary magnetic field. No other detection method can provide such evidence. Third, UV auroral emission could play a role in characterizing the near space environment around these planets, providing information about basic atmospheric composition and the deposition energies of the impacting particles. Fourth, ultraviolet wavelengths provide observational advantages compared to the optical. For instance, more favorable contrast ratios can be achieved and the UV diffraction limit allows planets to be detected at smaller angular separations to their host stars. Using Jupiter as a template and taking into account some basic properties involved in auroral production, possible emission fluxes were estimated for a given set of planetary system parameters. Potential candidate planets for UV observations are identified and the possibility of detecting UV auroral emissions with current and future technology is explored. This research has been supported by NSF IGERT Grant No. DGE-9870713 through the Astrobiology Program at the University of Washington, Seattle.
Comets are the oldest and least modified bodies orbiting the sun, and investigations into their c... more Comets are the oldest and least modified bodies orbiting the sun, and investigations into their composition are a key to understanding the development of the early solar system. Studying the daughters of photochemical reactions occurring within a comet's coma provides information concerning the composition and other important properties, such as density and temperature. These can eventually be inverted to give
The properties of the radiation belts can vary dramatically under the influence of magnetic storm... more The properties of the radiation belts can vary dramatically under the influence of magnetic storms and storm-time substorms. The task of understanding and predicting radiation belt properties is made difficult because their properties determined by global processes as well as small-scale wave-particle interactions. A full solution to the problem will require major innovations in technique and computer hardware. The proposed
GPUs are intrinsically highly parallelized systems that provide more than an order of magnitude c... more GPUs are intrinsically highly parallelized systems that provide more than an order of magnitude computing speed over a CPU based systems, for less cost than a high end-workstation. Recent advancements in GPU technologies allow for full IEEE float specifications with performance up to several hundred GFLOPs per GPU, and new software architectures have recently become available to ease the transition
Controlled-source seismologists seek to detonate charges in lakes or rivers because source coupli... more Controlled-source seismologists seek to detonate charges in lakes or rivers because source coupling is an order of magnitude larger in water than in drill holes. Previous studies have documented the biological impact of dynamite explosions on small fish populations; however, little attention has been paid to the potential chemical changes associated with the dispersal of a dynamite charge in a
1] Using single-particle tracking with time-dependent global magnetic and electric fields from mu... more 1] Using single-particle tracking with time-dependent global magnetic and electric fields from multifluid simulations, we model the 10 March 1998 storm and investigate storm time acceleration, injection, and trapping mechanisms associated with the formation of the ring current. We examine the contribution from various ionospheric source regions to the storm time ring current and the effect interplanetary magnetic field B z has on producing an asymmetric and symmetric ring current; we provide the first maps for the relative importance of ionospheric outflow (H + and O + ) regions as a function of all magnetic local times (MLTs) and latitudes between 60°and 80°. During the early part of the storm, high-latitude outflow regions between 00 and 06 MLT are the most efficient sectors at contributing particle density to the ring current, whereas during the main phase of the storm, there is more even contribution from all MLTs. The sectors that contribute the majority of the energy are consistently the high-latitude regions between 03 and 09 MLT. An increase in the contribution of O + to the current density is observed from the predawn high-latitude region during each of two decreases in Dst examined for the 10 March 1998 storm, supporting the central role oxygen plays in storm development. Asymmetries are observed between H + and O + contributions. The dominant ionospheric species contributing to the ring current energy density is shown to vary during the course of the storm with a significant increase in ionospheric O + contribution to the ring current associated with large decreases in Dst. Citation: Cash, M. D., R. M. Winglee, and E. M. Harnett (2010), Storm time production of ring current ions: Variations in particle energization and injection with ionospheric source region,
In January 2003, as part of the Ethiopia-Afar Geoscientific Lithospheric Experiment (EAGLE) we co... more In January 2003, as part of the Ethiopia-Afar Geoscientific Lithospheric Experiment (EAGLE) we conducted a refraction and wide-angle reflection survey of the Main Ethiopian Rift. 757 RefTek "Texan" seismographs with vertical geophones were deployed in 400 km-long axial and cross-rift lines, with another 231 in a central 3D array 100 km in diameter. An 80-instrument passive array of intermediate and broadband sensors was active during our experiment. We recorded 19 borehole shots loaded in nominal 50-meter boreholes, 2 quarry shots, and 2 lake shots. The shots ranged in size from 50-5750 kg, with the most common shot size being 1 tonne. Prior to loading each shot-hole, we measured distances between shots and the nearest structure, typically un-reinforced mud-and-wood houses, occasionally concrete irrigation ditches and aqueducts. We then used semi-empirical formulae derived by Oriard (Hendron and Oriard, 1972) to calculate expected maximum and minimum bounds on ground velocity at these structures, and selected an appropriate shot size to keep the predicted velocity below the "threshold for cosmetic damage", or 2 inches per second, at the most vulnerable structure. The Oriard formulae are derived from measurements associated with blasting for mining and civil engineering purposes and may not accurately predict the ground velocity from the source depths and explosive type used in the EAGLE and other controlled-source experiments. A detailed, trace-by-trace analysis of maximum ground velocities at our closest seismographs can provide data that will be useful in planning future large-scale seismic experiments. Preliminary results from traces within 20 km of our borehole shots suggest that maximum recorded ground velocities were within or below the maximum-minimum range predicted by Oriard, and hence that larger shot sizes could have been used with acceptable risks. A lake shot fired at the optimum depth (84 m for a 1 tonne shot) produced ground velocities that exceeded the predicted maximum at a few recodrers. However, optimum-depth shots are typically a significant distance offshore (c. 2.3 km for our shot) because of the required depth, so are unlikely to present a hazard to onshore structures. A lake shot fired in a shallower lake at half the optimum depth did not produce ground-velocities that exceed the Oriard maximum. Although we fired shots within 100 m of an unreinforced concrete aqueduct, and within 200 m of poorly engineered native buildings in poor structural condition, no damage was recorded. Our "Texan" seismometers recorded only vertical component velocity, using 4.5 Hz geophones. After removal of the geophone response the peak vertical velocity is typically measured at about 3 Hz and occurs shortly after the first arrival, presumably due to surface waves (ground roll). We are currently extending our analysis to include data from broadband, three-component recorders.
The 2009 AbGradCon was held at the University of Washington in July 2009. It brought together 67 ... more The 2009 AbGradCon was held at the University of Washington in July 2009. It brought together 67 participants from 8 different countries and 34 different universities. AbGradCon also took place in the virtual world of Second Life.
Uploads
Papers by M. Cash