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At least 1,441 records · Page 80
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Radiation Belt Response to Fast Reverse Shock at Geosynchronous Orbit

Fast reverse shocks (FRSs) cause the magnetosphere to expand, by contrast to the well-known compressions caused by the impact of fast forward shocks (FFS). Usually, FFSs are more geoeffective than FRSs, and consequently the inner magnetosphere dynamic responses to both shock types can be quite different. In this study, we investigate for the first time the radiation belt response to an FRS impact using multi-satellite observations and numerical simulations. Spacecraft on the dayside observed decreases in magnetic field strength and energetic (~40–475 keV) particle fluxes. Timing analysis shows that the magnetic field signature propagated from the dayside to the nightside magnetosphere. Particles with different energies vary simultaneously at each spacecraft, implying a non-dispersive particle response to the shock. Spacecraft located at lower L-shells did not record any significant signatures. The observations indicate a local time dependence of the response associated with the shock inclination, with the clearest signatures being observed in the dusk–midnight sector. Simulations underestimate the amplitude of the magnetic field variations observed on the nightside. The observed decreases in the electron intensities result from a combination of radial gradient and adiabatic effects. The radial gradients in the spectral index appear to be the dominant contributor to the observed variations of electrons seen on the dayside (near noon and dusk) and on the nightside (near midnight). This work shows that even an FRS can affect the radiation belts significantly and provides an opportunity to understand their dynamic response to a sudden expansion of the magnetosphere.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1985

Investigations of Planetary Ring Phenomena

The structure of Jupiter's rings was studied in an effort to understand the processes that generate the rings. The faint material in the Saturn system was investigated leading to the discovery of a new ring and a way to interpret the wavy features surrounding Encke's division in terms of perturbing moonlets. The interaction of faint rings and magnetospheres helped identify some of the charged particle absorbers seen by Pioneer 11 in the neighborhood of the F ring. Angular momentum drain might account for the slow rotations of intermediate sized asteroids. Much of the Jovian ring structure can be understood in terms of debris loss from satellites, rapid orbital evolution, resonance, and charged dust dynamics.

Burns, J. A.↗
NASA NTRS1986

Multimegawatt nuclear electric propulsion - First order system design and performance evaluation

The development of space nuclear power supplies capable of delivering high levels of power (1 to 10 MWe) for long life (5 to 10 years) is being considered. An important potential application of these systems will be to provide power for advanced electric propulsion devices such as ion thrusters or Magneto-Plasma-Dynamic (MPD) thrusters. High-powered Nuclear Electric Propulsion (NEP) concepts based on both ion and MPD thrusters are reviewed. To allow for mission performance evaluation, power supply, power processing, and thruster subsystems are characterized for both ion and MPD propulsion systems designed for operation in the 1 to 10 MWe power range. Several proposed missions which are significantly enhanced by the performance potential of these devices are investigated. Studied missions include near-earth orbit raising, cis-lunar cargo transportation, and planetary exploration. If developed, these 1 to 10 MWe NEP systems may provide a technological base for the development of even larger propulsion systems with power levels of up to hundreds of megawatts. The potential performance and technologies associated with such ultra-high-powered NEP systems is explored.

Sercel, J. C.↗
NASA NTRS1988

A TEOM (tm) particulate monitor for comet dust, near Earth space, and planetary atmospheres

Scientific missions to comets, near earth space, and planetary atmospheres require particulate and mass accumulation instrumentation for both scientific and navigation purposes. The Rupprecht & Patashnick tapered element oscillating microbalance can accurately measure both mass flux and mass distribution of particulates over a wide range of particle sizes and loadings. Individual particles of milligram size down to a few picograms can be resolved and counted, and the accumulation of smaller particles or molecular deposition can be accurately measured using the sensors perfected and toughened under this contract. No other sensor has the dynamic range or sensitivity attained by these picogram direct mass measurement sensors. The purpose of this contract was to develop and implement reliable and repeatable manufacturing methods; build and test prototype sensors; and outline a quality control program. A dust 'thrower' was to be designed and built, and used to verify performance. Characterization and improvement of the optical motion detection system and drive feedback circuitry was to be undertaken, with emphasis on reliability, low noise, and low power consumption. All the goals of the contract were met or exceeded. An automated glass puller was built and used to make repeatable tapered elements. Materials and assembly methods were standardized, and controllers and calibrated fixtures were developed and used in all phases of preparing, coating and assembling the sensors. Quality control and reliability resulted from the use of calibrated manufacturing equipment with measurable working parameters. Thermal and vibration testing of completed prototypes showed low temperature sensitivity and high vibration tolerance. An electrostatic dust thrower was used in vacuum to throw particles from 2 x 10(exp 6) g to 7 x 10(exp -12) g in size. Using long averaging times, particles as small as 0.7 to 4 x 10(exp 11) g were weighted to resolutions in the 5 to 9 x 10(exp -13) g range. The drive circuit and optics systems were developed beyond what was anticipated in the contract, and are now virtually flight prototypes. There is already commercial interest in the developed capability of measuring picogram mass losses and gains. One area is contamination and outgassing research, both measuring picogram losses from samples and collecting products of outgassing.

Source record↗
NASA NTRS1993

Remote sounding of tropospheric minor constituents

The etalon interferometer, or Fabry-Perot interferometer (FPI), with its high throughput and high spectral resolution was widely used in the remote-sensing measurements of the earth's atmospheric composition, winds, and temperatures. The most recent satellite instruments include the Fabry-Perot interferometer flown on the Dynamics Explorer-2 (DE-2) and the High Resolution Doppler Imager (HRDI) to be flown on the Upper Atmosphere Research Satellite (UARS). These instruments measure the Doppler line profiles of the emission and absorption of certain atmospheric species (such as atomic oxygen) in the visible spectral region. The successful space flight of DE-FPI and the test and delivery of UARS-HRDI demonstrated the extremely high spectral resolution and ruggedness of the etalon system for the remote sensing of earth and planetary atmospheres. Recently, an innovative FPI focal plane detection technique called the Circle-to-Line Interferometer Optical (CLIO) system was invented at the Space Physics Research Laboratory (SPRL). The CLIO simplifies the FPI focal plane detection process by converting the circular rings or fringes into a linear pattern similar to that produced by a conventional spectrometer, while retaining the throughput advantage of the etalon interferometer. CLIO makes the use of linear array detectors more practical and efficient with FPI, the combination of FPI and CLIO represents a very promising new technique for the remote sensing of the lower atmospheres of Earth, Mars, Venus, Neptune, and other planets. The Multiorder Etalon Spectrometer (MOES), as a combination of the rugged etalon and the CLIO, compares very favorably to other spaceborne optical instruments in terms of performance versus complexity. The feasibility of an advanced etalon spectrometer for the remote sensing of tropospheric trace species, particularly carbon monoxide (CO), nitrous oxide (N2O), and methane (CH4) was discussed. The etalon atmospheric spectroscopy techniques are described, instrument design and related technical issues are discussed. The primary objective is to establish the concept of atmospheric spectroscopy with the CLIO and etalon system and its applications for the measurements of tropospheric trace species analyze system requirements and performance, determine the feasibility of components and subsystem implementation with available technology, and develop inversion algorithm for retrieval simulation and data analysis.

Drayson, S. Roland↗
NASA NTRS1994

Ways to Increase Launch Velocities of 2-Stage Gas Guns

The amount of space debris is rapidly increasing and the debris is distributed over a wide variety of orbits. Satellites, manned space vehicles and space stations will have to pay increasing attention to the dangers of impacts with space debris. Various armoring techniques (i.e., double or triple layer armor) will have to tested extensively to determine the most effective armor per unit weight. Intersecting near-earth orbits can lead to impact velocities up to 15 km/sec. Conventional two-stage light gas guns can launch intact, controlled-shape projectiles with a density of 1.2 gm/cc and length- to-diameter ratios of 0.5-1.0 at velocities up to 8-9 km/sec. Higher velocities (10-11 km/sec) can be obtained' for very light projectiles. The higher launch velocities tend to be very severe on the high pressure coupling and barrel of the gun and lead to short component lifetimes. Clearly, the ability to raise the launch velocity of a gun (for reasonably massive projectile shapes) from 8-9 km/sec to 11-13 km/sec (or higher), without reduction of component lifetimes, would have significant benefits. This would allow much better simulation of the higher velocity debris impacts as well as better simulation of high speed re-entry into planetary atmospheres. Several techniques for increasing the launcher muzzle velocity above 8-9 km/sec have been studied using CFD simulations and appear to offer the potential for significant gains. The first technique is to use multiple compressions, instead of a single compression, in the pump tube of the light gas gun. In a sense, this is a kind of pre-heating of the gas in the pump tube; other types of pre-heating have yielded disappointing results in the past. The dynamics of the multiple compression pump tube is very different, however, from the earlier techniques, where the pump tube was typically heated ohmically before the gun 2 cycle was started. In this paper, we present CFD calculations that show that significant increases in muzzle velocity can be obtained with multiple compressions in the pump tube. With a conventional two-stage gun, an important limitation to obtaining higher velocities is friction and heat transfer to the barrel, which typically has a length- to- diameter ratio of 200-400. These viscous losses greatly reduce the effectiveness of the regions of the barrel far removed from the second stage breech. We have studied computationally the effect of adding an additional breech (or breeches) along the barrel to reduce these viscous losses. Velocity increases from 6.5 to 7.2 km/sec have been obtained using the main breech and one additional breech. In these results, both breeches were operated with hydrogen, heated electrothermally. We have also studied a gun geometry where the main breech is operated in the conventional manner, using piston compression. The additional breech is operated either with electrothermal heating or heating by using a high explosive charge in a novel geometry. The latter option provides very effective compression, heating and acceleration of the hydrogen working gas and is fully reusable. Calculations are presented which show that very substantial increases in muzzle velocity can be obtained this way, without overstressing the projectile or the 'gun. The third technique studied is to add a section of ram accelerator tube after the barrel to further accelerate the projectile. The ram accelerator used here is not the conventional premixed gas ram accelerator, but a new technique using high explosive as the energy source and pure hydrogen as the working gas in a geometry which can be made fully reusable. Preliminary results with this new rain accelerator geometry were presented and showed that stable ram accelerator drive can be established. Herein, detailed calculations axe presented which show that substantial velocity increases can be obtained using this ram accelerator technique in tandem with a conventional light gas gun.

Bogdanoff, David W.↗
NASA NTRS1973

Studies on possible propagation of microbial contamination in planetary clouds

Current U.S. planetary quarantine standards based on international agreements require consideration of the probability of contamination (Pc) of the outer planets, Venus, Jupiter, Saturn, etc. One of the key parameters in estimation of the Pc of these planets is the probability of growth (Pg) of terrestrial microorganisms on or near these planets. For example, Jupiter and Saturn appear to have an atmosphere in which some microbial species could metabolize and propagate. This study includes investigation of the likelihood of metabolism and propagation of microbes suspended in dynamic atmospheres. It is directed toward providing experimental information needed to aid in rational estimation of Pg for these outer plants.

Dimmick, R. L.↗
NASA NTRS1976

A comparison of the Great Red Spot with temporary spots on Jupiter

The International Planetary Patrol collection of Jupiter photographs is used to examine the development of a temporary spot that was visible in the northern equatorial zone for a total of 211 days. The motion and color of this spot are compared with those of the Great Red Spot. It is shown that the temporary spot was bluer than the Great Red Spot and has a longitudinal oscillation of approximately 4 deg with a period of about 45 days, implying that it may have possessed a significant dynamical property in common with other temporary spots and the Great Red Spot. It is concluded that the present spot is more likely to have been associated with a hole in the cloud deck rather than with an elevated surface feature.

Browne, G. C.↗
NASA NTRS1992

Results of a zonally truncated three-dimensional model of the Venus middle atmosphere

Although the equatorial rotational speed of the solid surface of Venus is only 4 m s(exp-1), the atmospheric rotational speed reaches a maximum of approximately 100 m s(exp-1) near the equatorial cloud top level (65 to 70 km). This phenomenon, known as superrotation, is the central dynamical problem of the Venus atmosphere. We report here the results of numerical simulations aimed at clarifying the mechanism for maintaining the equatorial cloud top rotation. Maintenance of an equatorial rotational speed maximum above the surface requires waves or eddies that systematically transport angular momentum against its zonal mean gradient. The zonally symmetric Hadley circulation is driven thermally and acts to reduce the rotational speed at the equatorial cloud top level; thus wave or eddy transport must counter this tendency as well as friction. Planetary waves arising from horizontal shear instability of the zonal flow (barotropic instability) could maintain the equatorial rotation by transporting angular momentum horizontally from midlatitudes toward the equator. Alternatively, vertically propagating waves could provide the required momentum source. The relative motion between the rotating atmosphere and the pattern of solar heating, which as a maximum where solar radiation is absorbed near the cloud tops, drives diurnal and semidiurnal thermal tides that propagate vertically away from the cloud top level. The effect of this wave propagation is to transport momentum toward the cloud top level at low latitudes and accelerate the mean zonal flow there. We employ a semispectral primitive equation model with a zonal mean flow and zonal wavenumbers 1 and 2. These waves correspond to the diurnal and semidiurnal tides, but they can also be excited by barotropic or baroclinic instability. Waves of higher wavenumbers and interactions between the waves are neglected. Symmetry about the equator is assumed, so the model applies to one hemisphere and covers the altitude range 30 to 110 km. Horizontal resolution is 1.5 deg latitude, and vertical resolution is 1.5 km. Solar and thermal infrared heating, based on Venus observations and calculations drive the model flow. Dissipation is accomplished mainly by Rayleigh friction, chosen to produce strong dissipation above 85 km in order to absorb upward propagating waves and limit extreme flow velocities there, yet to give very weak Rayleigh friction below 70 km; results in the cloud layer do not appear to be sensitive to the Rayleigh friction. The model also has weak vertical diffusion, and very weak horizontal diffusion, which has a smoothing effect on the flow only at the two grid points nearest the pole.

Newman, M.↗
NASA NTRS2010

The Impact History Of The Moon

The bombardment history of the Earth-Moon system has been debated since the first recognition that the circular features on the Moon may be impact craters. Because the lunar impact record is the only planetary impact record to be calibrated with absolute ages, it underpins our understanding of geologic ages on every other terrestrial planet. One of the more remarkable results to come out of lunar sample analyses is the hypothesis that a large number of impact events occurred on the Moon during a narrow window in time approximately 3.8 to 4.1 billion years ago (the lunar cataclysm ). Subsequent work on the lunar and martian meteorite suites; remote sensing of the Moon, Mars, asteroids, and icy satellites; improved dynamical modeling; and investigation of terrestrial zircons extend the cataclysm hypothesis to the Earth, other terrestrial planets, and possibly the entire solar system. Renewed US and international interest in exploring the Moon offers new potential to constrain the Earth-Moon bombardment history. This paper will review the lunar bombardment record, timing and mechanisms for cataclysmic bombardment, and questions that may be answered in a new age of exploration.

Cohen, B. A.↗
NASA NTRS2013

Spiral Arms in the Asymmetrically Illuminated Disk of MWC 758 and Constraints on Giant Planets

We present the first near-IR scattered light detection of the transitional disk associated with the Herbig Ae star MWC 758 using data obtained as part of the Strategic Exploration of Exoplanets and Disks with Subaru, and 1.1 micrometer Hubble Space Telescope/NICMOS data. While submillimeter studies suggested there is a dust-depleted cavity with r = 0".35, we find scattered light as close as 0".1 (20-28 AU) from the star, with no visible cavity at H, K', or Ks . We find two small-scaled spiral structures that asymmetrically shadow the outer disk. We model one of the spirals using spiral density wave theory, and derive a disk aspect ratio of h approximately 0.18, indicating a dynamically warm disk. If the spiral pattern is excited by a perturber, we estimate its mass to be 5(exp +3)(sub -4) M(sub J), in the range where planet filtration models predict accretion continuing onto the star. Using a combination of non-redundant aperture masking data at L' and angular differential imaging with Locally Optimized Combination of Images at K' and Ks , we exclude stellar or massive brown dwarf companions within 300 mas of the Herbig Ae star, and all but planetary mass companions exterior to 0".5. We reach 5 sigma contrasts limiting companions to planetary masses, 3-4 M(sub J) at 1".0 and 2 M(sub J) at 1".55, using the COND models. Collectively, these data strengthen the case for MWC 758 already being a young planetary system.

Grady, C. A.↗
NASA NTRSDate not supplied

Simulating the Martian Middle and Upper Atmosphere with the NASA Ames Mars GCM.

The NASA Ames Mars Global Climate Model (MGCM) continues to be utilized to examine the dynamical coupling between the lower atmosphere and middle/upper atmosphere. This coupling impacts the transport of water, dust, and chemistry which augments the thermal structure and circulation. The interactions and coupling within the atmosphere are important for understanding the present-day and past atmosphere and climate. MGCM simulations are compared with observations from recent Mars missions to provide model constraints, and in turn, the simulations can then provide context to the observations. This cycle is important to move us forward in our understanding of planetary atmospheres. We will present on one of the fundamental atmospheric features, the thermal structure, and how the physics in the MGCM can elucidate the observed diurnal and seasonal behavior. Additionally, we will focus on the distribution of chemical species which influences the thermal structure and provides additional information on the coupling between the lower and middle/upper atmosphere. Lastly, we will provide a summary of the model capabilities, as the MGCM continues to be improved upon to properly simulate Mars’ atmosphere from the ground to ~250 km.

Amanda Susanne Brecht↗
DOE OSTI2020

Recreating Giants Impacts in the Laboratory: Shock Compression of MgSiO 3 Bridgmanite to 14 Mbar

Understanding giant impacts requires accurate description of how extreme pressures and temperatures affect the physical properties of the constituent materials. Here, we report shock experiments on two polymorphs of MgSiO 3 : enstatite and bridgmanite (perovskite) crystals.We obtain pressure-density shock equation of state to 14 Mbar and more than 9 g/cm 3 , a 40% increase in density from previous data on MgSiO 3 . Density-functional-theory molecular dynamics (DFT-MD) simulations provide predictions for the shock Hugoniot curves for bridgmanite and enstatite and suggest that the Grüneisen parameter decreases with increasing density. The good agreement between the simulations and the experimental data, including for the shock temperature along the enstatite Hugoniot reveals that DFT-MD simulations reproduce well the behavior of dense fluid MgSiO 3 .We also reveal a high optical reflectance indicative of a metal-like electrical conductivity which supports the hypothesis that magma oceans may contribute to planetary magnetic field generation.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2023

TRACER-Coastal Urban Boundary-Layer Interactions with Convection (TRACER-CUBIC) Field Campaign Report

To better understand the complicated web of processes governing convective cloud life cycle and aerosol-convection interactions, the U.S. Department of Energy (DOE)’s Atmospheric Radiation Measurement (ARM) user facility supported deployment of a variety of advanced atmospheric measurement systems to the greater Houston, Texas, area from 1 October 2021 to 30 September 2022 as part of the Tracking Aerosol Convection Interactions Experiment (TRACER). Houston was selected as a study area because isolated convection and a variety of aerosol conditions are common in this region. This one-year ARM Mobile Facility (AMF) deployment featured a four-month intensive operational period (IOP) during summer 2022 (1 June–30 September). The ARM instrumentation was deployed at three sites along an east-west transect from La Porte, Texas to an ancillary site in a less-polluted rural region southwest of downtown Houston (Figure 1). At the La Porte Site, which is located near the Houston ship channel in an area that experiences significant pollution, the first ARM Mobile Facility (AMF1) was deployed. During the IOP, the ARM tethered balloon system (TBS) operated at the ancillary site. The second-generation C-Band Scanning ARM Precipitation Radar (CSAPR) operated near Pearland, Texas, roughly halfway between the Laporte and ancillary sites. As part of the TRACER- Coastal Urban Boundary-Layer Interactions with Convection (CUBIC) project, three boundary-layer profiling systems) were deployed along a north-south transect spanning from the University of Houston Coastal Center to the Aldine site north of downtown Houston (also blue dot in Figure 1) during the TRACER IOP. These systems included the National Oceanic and Atmospheric Administration (NOAA) National Severe Storms Laboratory CLAMPS2 (C2), which was deployed at the UHCC, the University of Wisconsin SPARC, which was deployed at the ARM CSAPR site near Pearland (orange diamond in middle of map in Figure 1), and the University of Oklahoma CLAMPS1 (C1), which was deployed at Aldine. These three systems have been successfully operated in various field campaigns, providing data sets that collectively offer new insights into atmospheric-boundary-layer (ABL) processes, sea-breeze (SB) circulations, and convection initiation (CI). For the TRACER IOP window, these systems ran continuously between 1 June and 26 September, 2022. Due to commitments to NOAA projects, the Doppler lidar at the UHCC site was not available until 24 June 2022. The CLAMPS and SPARC profiling systems are self-contained platforms that have benefited from several years of development and deployment. Instruments and data processing were maintained remotely, which made the 4-month deployment for the TRACER-CUBIC IOP period possible. The same basic instrument configuration comprises each system: a scanning Doppler wind lidar for flow characterization and passive profiler(s) for characterizing planetary-boundary-layer (PBL) thermodynamic properties. Each platform includes a Halo Streamline Doppler wind lidar, an Atmospheric Emitted Radiance Interferometer (AERI), and a surface meteorology station. CLAMPS1 and CLAMPS2 each also include a microwave radiometer (MWR, Figure 1d). The TRACER-CUBIC hypotheses included (i) Interactions of SB and urban circulations and how they affect the PBL structure in the Houston environment, causing spatially (horizontally and vertically) and temporally highly variable flow patterns, (ii) heat, moisture, and aerosol transport and mixing depend on these flow dynamics, and (iii) an improved understanding of the flow patterns and PBL structure are critical for investigating the processes leading to CI. To test these hypotheses, the project aimed at (i) characterizing SB circulations and their impacts on the diurnal evolution of the structure of the ABL, (ii) studying the evolution of Houston’s complex urban boundary layer, and (iii) identifying effects of urban-induced circulations on pre-convective environments. TRACER-CUBIC observations generally provide good coverage during the summer IOP. Initial screening of the data indicates a good number of cases with bay-breeze (BB) and/or SB signatures, local CI, and interesting boundary-layer features such as strong nocturnal low-level jets (LLJs, Table 1). The numbers listed in rows 3-5 in this table will be further updated as part of ongoing in-depth analyses and systematic identification of local circulations and CI events. More detailed information about the data availability and quality for each instrument is provided in the “readme” files that were submitted to the ARM Data Center along with each archived data sets. These “readme” files also provide instrument descriptions, information about the data collection and processing procedures, data formats, and any additional information relevant for further data analysis.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1980

Physical loss of long-period comets

Loss of long-period comets from the solar system through a variety of physical processes is investigated. It is shown that planetary collision, defined as a comet passing within the Roche radius of any planet, has a probability of 1.35 x 10 to the -7th per perihelion passage for a long-period comet on a randomly oriented orbit. Sublimation of all volatiles for a one-kilometer radius hydrate ice nucleus would require on the order of 600 to 27,600 perihelion passages, depending on the surface albedo and assuming a perihelion distance of one astronomical unit. Analysis of observational records indicates that for dynamically 'new' comets in the Oort-Schmidt sense there is about a 10% probability of the comet randomly disrupting on its first perihelion passage. This probability drops to 4% per perihelion passage for older long-period comets, and less than 1% for short-period comets. The consequences of these loss mechanisms when incorporated into Monte-Carlo studies of long-period comet evolution are also discussed.

Weissman, P. R.↗
NASA NTRS1980

Pointing and control for planetary spacecraft - The first twenty years

The evolution of guidance and control systems for United States planetary and unmanned lunar spacecraft over the last 20 years is traced. The characteristics of the guidance and control systems used on spacecraft from the Range lunar impactor to the planned Galileo Jupiter orbiter and entry probe are surveyed, with attention given to the uses of three-axis stabilized, spin-stabilized and dual-spin designs. System performance trends that have evolved to meet the increasing science and mission requirements of the spacecraft are considered in the areas of attitude references, control consumables, dynamics and system modeling, thrust vector control, optical navigation, manuever turns, maneuver velocity control, instrument pointing, and antenna pointing. Hardware trends in optical sensors, inertial sensors, processing electronics, electromechanical devices, and system testing and reliability are also reviewed. The achievements represented by these advances are emphasized, and it is predicted that future developments will be in the areas of increased control system autonomy and performance requirements.

Pace, G. D.↗
NASA NTRS1985

Radiative processes

Solar radiation and the processes that control its deposition in the Earth atmosphere are considered. The published data obtained since 1978 define a reference solar spectral irradiance for use in atmospheric chemical and dynamical studies, while long term satellite measurements are now providing information on variations in the output of the Sun over a range of time scales. As concerns absorption of solar radiation in the atmosphere, new cross section data for molecular oxygen and ozone are now available. Line-by-line calculations used to predict infrared flux divergences, both as regards assumptions made in radiative transfer calculations and in the spectroscopic parameters used as inputs are examined. Also examined are the influence of radiative processes on planetary scale wave activity, photochemical acceleration of radiative damping, and the breakdown of local thermodynamic equilibrium at mesospheric altitudes.

Frederick, J. E.↗
NASA NTRS2003

The Sun to the Earth - and Beyond: A Decadal Research Strategy in Solar and Space Physics

The sun is the source of energy for life on earth and is the strongest modulator of the human physical environment. In fact, the Sun's influence extends throughout the solar system, both through photons, which provide heat, light, and ionization, and through the continuous outflow of a magnetized, supersonic ionized gas known as the solar wind. While the accomplishments of the past decade have answered important questions about the physics of the Sun, the interplanetary medium, and the space environments of Earth and other solar system bodies, they have also highlighted other questions, some of which are long-standing and fundamental. The Sun to the Earth--and Beyond organizes these questions in terms of five challenges that are expected to be the focus of scientific investigations in solar and space physics during the coming decade and beyond. While the accomplishments of the past decades have answered important questions about the physics of the Sun, the interplanetary medium, and the space environments of Earth and other solar system bodies, they have also highlighted other questions, some of which are long-standing and fundamental. This report organizes these questions in terms of five challenges that are expected to be the focus of scientific investigations in solar and space physics during the coming decade and beyond: Challenge 1: Understanding the structure and dynamics of the Sun's interior, the generation of solar magnetic fields, the origin of the solar cycle, the causes of solar activity, and the structure and dynamics of the corona. Challenge 2: Understanding heliospheric structure, the distribution of magnetic fields and matter throughout the solar system, and the interaction of the solar atmosphere with the local interstellar medium. Challenge 3: Understanding the space environments of Earth and other solar system bodies and their dynamical response to external and internal influences. Challenge 4: Understanding the basic physical principles manifest in processes observed in solar and space plasmas. Challenge 5: Developing a near-real-time predictive capability for understanding and quantifying the impact on human activities of dynamical processes at the Sun, in the interplanetary medium, and in Earth's magnetosphere and ionosphere. This report summarizes the state of knowledge about the total heliospheric system, poses key scientific questions for further research, and presents an integrated research strategy, with prioritized initiatives, for the next decade. The recommended strategy embraces both basic research programs and targeted basic research activities that will enhance knowledge and prediction of space weather effects on Earth. The report emphasizes the importance of understanding the Sun, the heliosphere, and planetary magnetospheres and ionospheres as astrophysical objects and as laboratories for the investigation of fundamental plasma physics phenomena.

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