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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS2021

Dynamics of the Terrestrial Radiation Belts: a Review of Recent Results During the VarSITI (Variability of the Sun and Its Terrestrial Impact) Era, 2014–2018

The Earth’s magnetosphere is region that is carved out by the solar wind as it flows past and interacts with the terrestrial magnetic field. The inner magnetosphere is the region that contains the plasmasphere, ring current, and the radiation belts all co-located within about 6.6 Re, nominally taken to be bounding this region. This region is highly dynamic and is home to a variety of plasma waves and particle populations ranging in energy from a few eV to relativistic and ultra-relativistic electrons and ions. The interplanetary magnetic field (IMF) embedded in the solar wind via the process of magnetic reconnection at the sub-solar point sets up plasma convection and creates the magnetotail. Magnetic reconnection also occurs in the tail and is responsible for explosive phenomena known as substorms. Substorms inject low-energy particles into the inner magnetosphere and help generate and sustain plasma waves. Transients in the solar wind such as coronal mass ejections (CMEs), co-rotating interaction regions (CIRs), and interplanetary shocks compress the magnetosphere resulting in geomagnetic storms, energization, and loss of energetic electrons in the outer radiation belt and enhance the ring current, thereby driving the geomagnetic dynamics. The Specification and Prediction of the Coupled Inner-Magnetospheric Environment (SPeCIMEN) is one of the four elements of VarSITI (Variability of the Sun and Its Terrestrial Impact) program which seeks to quantitatively predict and specify the inner magnetospheric environment based on Sun/solar wind driving inputs. During the past 4 years, the SPeCIMEN project has brought together scientists and researchers from across the world and facilitated their efforts to achieve the project goal. This review provides an overview of some of the significant scientific advances in understanding the dynamical processes and their interconnectedness during the VarSITI era. Major space missions, with instrument suites providing in situ measurements, ground-based programs, progress in theory, and modeling are briefly discussed. Open outstanding questions and future directions of inner magnetospheric research are explored.

Shrikanth Kanekal↗
NASA NTRS2021

Simultaneous UV Images and High-Latitude Particle and Field Measurements During an Auroral Dawn Storm at Jupiter

We present multi-instrument Juno observations on day-of-year 86, 2017 that link particles and fields in Jupiter's polar magnetosphere to transient UV emissions in Jupiter's northern auroral region known as dawn storms. Juno ranged from 42°N to 51°N in magnetic latitude and 5.8–7.8 Jovian radii (1 RJ = 71,492 km) during this period. These dawn storm emissions consisted of two separate, elongated structures which extended into the nightside, rotated with the planet, had enhanced brightness (up to at least 1.4 megaRayleigh) and high color ratios. The color ratio is a proxy for the atmospheric penetration depth and therefore the energy of the electrons that produce the UV emissions. Juno observed electrons and ions on magnetic field lines mapping to these emissions. The electrons were primarily field-aligned, bidirectional, and, at times, exhibited sudden intensity decreases below ∼10 keV coincident with intensity enhancements up to energies of ∼1,000 keV, consistent with the high color ratio observations. The more energetic electron distributions had characteristic energies of ∼160–280 keV and downward energy fluxes (∼70–135 mW m−2) that were a significant fraction needed to produce the UV emissions for this event. Magnetic field perturbations up to ∼0.7% of the local magnetic field showing evidence of upward and downward field-aligned currents, whistler mode waves, and broadband kilometric radio emissions were also observed along Juno's trajectory during this time frame. These high-latitude observations show similarities to those in the equatorial magnetosphere associated with dynamics processes such as interchange events, plasma injections, and/or tail reconnection.

R. W. Ebert↗
NASA NTRS1977

Analytic studies of local-severe-storm observables by satellites

Attention is concentrated on the exceptionally violet whirlwind, often characterized by a fairly vertical axis of rotation. For a cylindrical polar coordinate system with axis coincident with the axis of rotation, the secondary flow involves the radial and axial velocity components. The thesis advanced is, first, that a violent whirlwind is characterized by swirl speeds relative to the axis of rotation on the order of 90 m/s, with 100 m/s being close to an upper bound. This estimate is based on interpretation of funnel-cloud shape (which also suggests properties of the radial profile of swirl, as well as the maximum magnitude); an error assessment of the funnel-cloud interpretation procedure is developed. Second, computation of ground-level pressure deficits achievable from typical tornado-spawning ambients by idealized thermohydrostatic processes suggests that a two-cell structure is required to sustain such large speeds.

Dergarabedian, P.↗
NASA NTRS1973

Interpretation of the Jupiter Red Spot, 1

With the aid of 8900 micron CH4 filter photographs it is shown that the Red Spot is normally the highest cloud feature in the Jovian atmosphere, located squarely on the South Tropical Zone at 22 deg. S. The Red Spot is a rising column, obviously having its own energy source; it spreads outward at the top level, in anticyclonic rotation. It is concluded that the large and persistent Jovian cloud masses, of which the Red Spot is the largest, are major organized storm arrays embedded in a near stagnant atmosphere, each probably possessing numerous short-lived rising hot columns driven by released latent heat; and covered by a horizontally-expanding gigantic cirrus cloud system, in anti-cyclonic rotation. The meteorological theory of Organized Cumulus Convection is applied to the Red Spot and the White Ovals. Evidence exists that the array of hot towers under the Red Spot is eccentric. The 90-day and the occassional 5-8 year fluctuations in the motion of the Red Spot may be due to processes analogous to those found in the Earth's Tropical Convergence. The 90-day oscillation has been observed for 8 years.

Kuiper, G. P.↗
DOE OSTI2025

3D Radio Frequency Mapping and Polarization Observations Show Lightning Flashes Were Ignited by Cosmic‐Ray Showers

Previous 2D radio frequency interferometric observations showed that lightning is commonly started with a positive fast discharge (+FD) before a normal negative leader continues from the origin of the +FD to the ensuing lightning flash. However, the inception and development of the +FD cannot be convincingly explained by existing discharge theories. With our new 3D broadband interferometric mapping and polarization system, we observed that the +FD was sometimes followed by an even faster and more extensive negative discharge (−FD) that propagated backward and overshoot the origin by a few hundred meters, as reported by an earlier 2D study. Surprisingly, the signal polarization, which measures the orientation of the discharge current, systematically slanted from the discharge propagation direction and rotated between the two opposite discharges, showing the +FD and −FD were driven by other storm-independent factors in addition to the storm electric field, or otherwise all would align in the same direction. Assuming a cosmic-ray shower (CRS) piercing through the cloud immediately before the +FD/−FD discharge, we found that their path is consistent with a pre-ionized path by the CRS, and the polarizations for the two opposite discharges are consistent with the respective deflected trajectories of high-energy positrons and electrons in the geomagnetic and an electric field. We further analyzed the more commonly observed +FD and showed that it is consistent with the CRS interpretation, suggesting these flashes in thunderstorms were ignited by cosmic-ray showers.

58 GEOSCIENCES↗
NASA NTRS1981

Evolution of downdrafts and rotation in an Illinois thunderstorm

Multiple-Doppler radar observations of a non-severe Illinois thunderstorm with nearly rectilinear vertical wind shear and storm motion related to the wind at a height of 2.5 km are discussed. The cell examined had a radar top of 10 km, and reflectivities of 60 dB(Z). Attention is given the evolution of updraft, downdrafts, and vorticity in this cell, where typical magnitudes were 12 m/sec, 8 m/sec and 0.005/sec, respectively. The main downdrafts were found to be the upshear downdraft during the growth period of the cell, and the left bank downdraft during the mature and downdraft periods. The location of upshear downdraft at mid to upper levels resembles the Lennon and Doswell (1979) conceptual model, as well as three-dimensional cloud model results of severe storms.

Heymsfield, G. M.↗
NASA NTRS1992

Observables for anticipating tornadogenesis in mesocyclones

We seek to identify an observable for anticipating tornadogenesis in mesocyclones, because such tornadoes are characterized by particularly long life, long and wide path, and high wind speed. We associate tornadogenesis with the transition from a one-cell vortex to a two-cell vortex. In such a transition, 'insertion' of a virtually nonrotating, slowly recirculating core displaces that high-swirl-speed air which is rapidly ascending along a moist-adiabatic locus of thermodynamic states, to an annulus at small but finite distance from the axis of rotation. Such a transition, on a vastly larger lateral scale, is known to characterize intensification of a tropical storm to a typhoon. We examine analytically a quasisteady axisymmetric model of a four-part vortex structure consisting of a bulk potential vortex, near-ground inflow layer, 'eyewall', and 'eye'. We inquire whether such a four-part intense vortex, formed in convectively unstably stratified air, is self-sustaining. In particular, we inquire whether the vertical profile of the angular momentum at the periphery is a discriminant for identifying self-sustaining vortices.

Carrier, G.↗
NASA NTRS1985

Detection of rotating thunderstorms using satellite imagery

In the case of the Carolina tornadoes, researchers prepared visible and IR GOES imagery covering the period 2000 Z when the storm entered South Carolina from Georgia until it exited North Carolina at 0200 Z into Virginia. The GOES IR imagery clearly demonstrated that this storm was imbedded in a continuously propagating mesolow with a well defined cold dome. The ground damage track paralleled exactly with the cold dome throughout the storm's life across the Carolinas. There were no advanced very high resolution radiometer (AVHRR) data during the period to allow researchers to inspect the cloud top for warm temperature anomalies. The Carolina storm did exhibit rightward deviating outflow which was oriented about 60 degrees to the 300 mb streamlines. The tornadoes of April 27, 1984 were part of a tornado producing cold front which stretched from Oklahoma to Minnesota. As the front moved eastward it touched off numerous tornadoes in eastern Wisconsin. GOES imagery for this data was prepared and it was strikingly clear that all along the North-South oriented squall line, the individual tunderstorms had cirrus plumes which had remarkable right deviation to the upper air flow. Unlike the Carolina long track supercell cell-mesolow system, these storms were isolated individual thunderstorms which touched off at least 16 tornadoes in eastern Wisconsin stretching from the Milwaukee area on the south to Vilas County in the north. The monster tornado of June 8, 1984 which leveled 90 percent of the village of Barneveld, Wisconsin and killed 9 persons is also discussed.

Anderson, C. E.↗
NASA NTRS1962

Ionospheric Studies with the Differential Doppler Technique

This report is essentially a review of the measurements related to the ionosphere utilizing the differential Doppler technique. A brief study of the theory is presented, in which the error incurred in measurements of ionospheric electron content, caused by the assumption of common-path propagation, is shown as a function of the zenith angle of observation for different values of the critical frequency foF2. Some measurements of electron densities, electron content, horizontal gradients, irregularities, and magnetic-storm effects are discussed. Comments are also made about the method of combining the differential Doppler with the Faraday rotation measurements to establish a necessary constant of integration in the measurements made with satellites. It is concluded that the differential Doppler technique, with harmonically related frequencies transmitted to or from rockets or satellites, can provide accurate information about the electron density or electron content of the medium, and that the knowledge of these quantities is valuable in understanding the morphology of the ionospheric processes.

IONOSPHERE↗
NASA NTRS1989

A proposed microburst nowcasting procedure using single-Doppler radar

Thirty-one microburst-producing storms from northweast Colorado were studied using single and multiple Doppler radar for the purpose of identifying radar signatures that indicated the development of a downdraft capable of producing a microburst. Descending reflectivity cores, increasing radial convergence within cloud, rotation, and reflectivity notches, were found to be microburst precursors, appearing typically 2-6 min prior to initial surface outflow. Three conceptual models have been drawn, based on the 31 events, to summarize the radar signatures of importance in low, moderate, and high-reflectivity microburst-producing storms. A forecaster-computer environment is proposed to allow the forecaster to readily view radar reflectivity and Doppler velocity information in both unprocessed and analyzed form. Use of multiimage radar displays and time-height profiles of quantitative radar estimates of reflectivity and radial shear are suggested to provide an environment where rapid progress can be made in developing techniques to nowcast microbursts.

Roberts, Rita D.↗
NASA NTRS1997

Aerodynamics of a Simple Three-Dimensional High-Lift System

Experimental results are presented for a three-element high-lift system with a half-span flap and both a full- and three-quarter span slat. The simplified wing spanned the wind-tunnel test section with no wing sweep or wing tip. Full- and part-span slat configurations were tested to investigate the three-dimensional effects of a finite-span slat in a landing configuration. With a part-span slat, flow visualization and surface pressures revealed two vortices at the flap tip and one at the slat tip. Compared to the full-span slat case, the part-span slat configuration stalled at a lower angle of attack and yielded reduced lift at all angles of attack. At a representative approach attitude (10 deg), wake surveys indicated comparable induced drag for the full- and part-span slat configurations while the profile drag was more than doubled with a part-span slat. The vorticity contribution of the slat-tip vortex was minimal, suggesting that the vortex dissipates through viscous interaction with the main-element boundary layer. The addition of a lower-surface fence at the slat tip yielded two co-rotating vortices and partially alleviated the profile drag increase of the part-span slat.

Storms, Bruce↗
NASA NTRS1983

Possible dust devils - Vortices on Mars

This paper presents the results of a study of local vortices, and dust devils, on Mars as observed by Viking Landers 1 and 2. It is found that these vortices are most common during Martian spring and summer, as occurs on earth. Seven of the vortices involve wind speeds that may raise dust from the Martian surface. There is no indication that these possible dust devils contribute to the planet-wide spread of major dust storms. However, it appears that they may help in maintaining the atmospheric dust content. The data indicate that there is no preference in rotation direction, at least to core diameters of 300 m (corresponding to a region of influence of about 3 km diameter).

Ryan, J. A.↗
NASA NTRS2000

Evaluation of Bogus Vortex Techniques with Four-Dimensional Variational Data Assimilation

The effectiveness of techniques for creating "bogus" vortices in numerical simulations of hurricanes is examined by using the Penn State/NCAR nonhydrostatic mesoscale model (MM5) and its adjoint system. A series of four-dimensional variational data assimilation (4-D VAR) experiments is conducted to generate an initial vortex for Hurricane Georges (1998) in the Atlantic Ocean by assimilating bogus sea-level pressure and surface wind information into the mesoscale numerical model. Several different strategies are tested for improving the vortex representation. The initial vortices produced by the 4-D VAR technique are able to reproduce many of the structural features of mature hurricanes. The vortices also result in significant improvements to the hurricane forecasts in terms of both intensity and track. In particular, with assimilation of only bogus sea-level pressure information, the response in the wind field is contained largely within the divergent component, with strong convergence leading to strong upward motion near the center. Although the intensity of the initial vortex seems to be well represented, a dramatic spin down of the storm occurs within the first 6 h of the forecast. With assimilation of bogus surface wind data only, an expected dominance of the rotational component of the wind field is generated, but the minimum pressure is adjusted inadequately compared to the actual hurricane minimum pressure. Only when both the bogus surface pressure and wind information are assimilated together does the model produce a vortex that represents the actual intensity of the hurricane and results in significant improvements to forecasts of both hurricane intensity and track.

Pu, Zhao-Xia↗
NASA NTRS2018

Compact Telescoping Surface Array for Mars Solar Power

This paper describes a lightweight, large-area solar array concept for Mars surface power called the Compact Telescoping Surface Array (CTSA). The design is derived from the Compact Telescoping Array (CTA) proposed in 2015 for high-power spacecraft. The CTSA deploys horizontally from Mars landers, provides 1000 sq.m of solar cell area, and generates about 50-80 kW daytime and 10 kW nighttime power (from energy storage) near the equator with clear skies. The total mass is about 1500 kg, and the stowed volume is about 10 cu.m, equivalent to 200 W/kg and 30 kW/cu.m at 1 astronomical unit (AU) from the sun. These challenging mass and volume goals require compact, lightweight structures to deploy and tension thin solar cell blankets in the Mars 0.38 g gravity field. Other features include single-axis rotation for daily or seasonal sun tracking, dust shedding, and feathering in high winds and sufficient strength for sustained 40 m/s winds in dust storms and brief 100 m/s winds in dust devils (dynamic pressure of 120 Pa). Based on preliminary design and analysis reported in the paper, CTSA appears to be a feasible approach for 1000 sq.m-class Mars solar arrays that autonomously deploy from landers prior to human arrival.

Pappa, Richard↗
DOE OSTI2021

Spontaneous Cyclogenesis without Radiative and Surface-Flux Feedbacks

Tropical cyclones (TCs) are among the most intense and feared storms in the world. What physical processes lead to cyclogenesis remains the most mysterious aspect of TC physics. Here, we study spontaneous TC genesis in rotating radiative–convective equilibrium using cloud-resolving simulations over an f plane with constant sea surface temperature. Previous studies proposed that spontaneous TC genesis requires either radiative or surface-flux feedbacks. To test this hypothesis, we perform mechanism-denial experiments, in which we switch off both feedback processes in numerical simulations. We find that TCs can self-emerge even without radiative and surface-flux feedbacks. Although these feedbacks accelerate the genesis and impact the size of the TCs, TCs in the experiments without them can reach similar intensities as those in the control experiment. We show that TC genesis is associated with an increase in the available potential energy (APE) and that convective heating dominates the APE production. Overall, our result suggests that spontaneous TC genesis may result from a cooperative interaction between convection and circulation and that radiative and surface-flux feedbacks accelerate the process. Furthermore, we find that increasing the planetary rotation favors spontaneous TC genesis.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1983

Electrodynamics of the stratosphere using 5000 cu m superpressure balloons

The Electrodynamics of the Middle Atmosphere research project encompasses the design of a microprocessor-controlled payload and the launch of up to eight small superpressure balloons in the 1982-1984 period. The primary payload instrument will measure the vector electric field from dc to 10 kHz, and the payloads will include instruments measuring local ionization, electrical conductivity, magnetic field, and temperature and pressure fluctuations. In addition, optical lightning will be recorded. The simultaneous measurement of these stratospheric parameters by several balloons, for periods extending over several solar rotations, will allow the study of electrical coupling between atmosphere and magnetosphere, of global current systems, and of global response to solar flares and magnetospheric storms.

Holzworth, R. H.↗
NASA NTRS1991

Carrying Humans To And From Mars

Document presents conceptual design for space vehicle to carry human explorers from Earth to Mars, then back to Earth. Design takes into account promising new technologies making Mars mission possible. Radiation-storm shelters and advanced cryogenic propulsion readily integrated into familiar vehicles. Other technologies demand fundamentally new vehicles. They include modular hardware, robotic assembly and maintenance, rotating artificial gravity, and high-energy aerobraking.

Sherwood, Brent↗