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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 991 records · Page 55
All sourcesNASA NTRSDOE OSTI
NASA NTRS1983

The composition, propagation and acceleration of energetic solar particles - A review of United States research 1979-1982

The present review has the objective to cover major developments in American research related to solar energetic particles, both observational and theoretical, taking into account the period from late 1978 to late 1982. It is pointed out that particular progress has been made in the area of solar energetic particle composition with respect to elemental, isotopic, and the distribution of charge states. This progress is primarily the result of improved instrumentation available at a time of higher solar activity. An important aspect of solar particle studies is to understand the propagation of particles from the vicinity of the sun through interplanetary space to wherever the observing instruments are located. Almost all mathematical models for the transport of solar cosmic rays are derived in some sense from the same general Boltzmann or Vlasov equations. Attention is also given to advances related to an understanding of coronal propagation, and acceleration and injection processes.

Mcguire, R. E.↗
NASA NTRS1988

Shuttle high resolution accelerometer package experiment results - Atmospheric density measurements between 60-160 km

Indirect or inferred values of atmospheric density encountered by the Shuttle Orbiter during reentry have been calculated from acceleration measurements made by the High Resolution Accelerometer Package (HiRAP) and the Orbiter Inertial Measurement Unit (IMU) liner accelerometers. The atmospheric density data developed from this study represent a significant gain with respect to the body of data collected to date by various techniques in the altitude range of 60 to 160 km. The data are unique in that they cover a very wide horizontal range during each flight and provide insight into the actual density variations encountered along the reentry flight path. The data, which were collected over about 3 years, are also characterized by variations in solar activity, geomagnetic index, and local solar time. Comparison of the flight-derived densities with various atmospheric models have been made, and analyses have attempted to characterize the data and to show correlation with selected physical variables.

Blanchard, R. C.↗
NASA NTRS2001

Correlation of Upper-Atmospheric 7-Be with Solar Energetic Particle Events

A surprisingly large concentration of radioactive 7-Be was observed in the upper atmosphere at altitudes above 320 km on the LDEF satellite that was recovered in January 1990. We report on follow-up experiments on Russian spacecraft at altitudes of 167 to 370 km during the period of 1996 to 1999, specifically designed to measure 7-Be concentrations in low earth orbit. Our data show a significant correlation between the 7-Be concentration and the solar energetic proton fluence at Earth, but not with the overall solar activity. During periods of low solar proton fluence, the concentration is correlated with the galactic cosmic ray fluence. This indicates that spallation of atmospheric N by both solar energetic particles and cosmic rays is the primary source of 7-Be in the ionosphere.

Phillips, G. W.↗
NASA NTRS2004

NASA's Integrated Development of Solar Sail Propulsion Project

Solar sails have been studied for a variety of missions and have the potential to provide cost effective, propellantless propulsion that enables longer on-station operation, increased scientific payload mass fraction, and access to previously inaccessible orbits (e. g., non-Keplerian, high solar latitudes, etc.). Research being conducted by the In-Space Propulsion (ISP) Technologies Projects is at the forefront of NASA's efforts to mature propulsion technologies that will enable or enhance a variety of space science missions. Solar sail propulsion systems will be required to meet the challenge of monitoring and predicting space weather by the Office of Space Science's (OSS) Living with a Star (LWS) program. Near-to-mid-term mission needs include monitoring of solar activity and observations at high solar latitudes. Work currently funded by the ISP s Solar Sail Propulsion (SSP) project is based on the quantitative demonstration of scalability of present solar sail subsystem designs and concepts to future mission requirements through ground testing of hardware, computational modeling and analytical simulations. This paper will give an overview of the Solar Sail Propulsion project's major development tasks of fabricating and testing two different subscale (400 square meter sail) solar sail system architectures. It will then be shown how either of these subscale prototypes can evolve into a flight validation system and briefly discuss the mission parameter. The paper will conclude with a discussion on how a flight validation will exercise the quantitative tools needed to demonstrate the scale to the size needed for the Solar Polar Imager and L1-Diamond SEC roadmap missions.

Garbe, Gregory↗
NASA NTRS2007

RADECS Short Course Session I: The Space Radiation Environment

The presented slides and accompanying paper focus on radiation in the space environment. Since space exploration has begun it has become evident that the space environment is a highly aggressive medium. Beyond the natural protection provided by the Earth's atmosphere, various types of radiation can be encountered. Their characteristics (energy and nature), origins and distributions in space are extremely variable. This environment degrades electronic systems and on-board equipment in particular and creates radiobiological hazards during manned space flights. Based on several years of space exploration, a detailed analysis of the problems on satellites shows that the part due to the space environment is not negligible. It appears that the malfunctions are due to problems linked to the space environment, electronic problems, design problems, quality problems, other issues, and unexplained reasons. The space environment is largely responsible for about 20% of the anomalies occurring on satellites and a better knowledge of that environment could only increase the average lifetime of space vehicles. This naturally leads to a detailed study of the space environment and of the effects that it induces on space vehicles and astronauts. Sources of radiation in the space environment are discussed here and include the solar activity cycle, galactic cosmic rays, solar particle events, and Earth radiation belts. Future challenges for space radiation environment models are briefly addressed.

Xapsos, Michael↗
NASA NTRS1960

Preliminary Results from the Space Probe Pioneer V

The space probe Pioneer V was launched March 11, 1960, into an orbit around the sun and inside the orbit of earth. The scientific apparatus included instruments identical with the University of Chicago apparatus used on Explorer VI [Fan, Meyer, and Simpson, 1960b], namely, energetic particle detectors which measure fluxes of protons with energies greater than 75 Mev, electrons with energies greater than 15 Mev, and the bremsstrahlung from electrons and y rays of lower energy. Simultaneously with the measurements in Pioneer V a series of four neutron monitor piles were recording the changes in cosmic radiation intensity at the earth. We report here on some preliminary results obtained from the Chicago experiments during the time within which Pioneer V traveled to a distance of approximately 8 x 10 km from earth. Beginning on March 20, solar activity rapidly increased with many solar flares, radio noise bursts, etc., over a period of 10 days. Most of our results relate to this period. The preliminary data are given in Figures 1 and 2.

Fan, C. Y.↗
NASA NTRSDate not supplied

TPSAS-NF1676L-17909-DND

Infrared radiative cooling of the thermosphere by carbon dioxide and nitric oxide has been observed continuously since January 2002 by the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument on the NASA Thermosphere-Ionosphere-Mesosphere Energetics and Dynamics (TIMED) satellite. SABER has documented dramatic variability in the radiative cooling on timescales ranging from days to longer than the nominal 11-year solar cycle. SABER radiance measurements from emission by CO2 (at 15 um) and NO (at 5.3 um) are used to calculate global daily emitted thermosphere power. This unique dataset shows the direct effects of solar variability on the temperature (via CO2 emission) and composition (from NO emission) for nearly twelve years. The deep solar minimum between solar cycles 23 and 24 is evident in the low values of global mean radiative cooling that occur in the 2008-2009 period. Since then radiative cooling has been observed to increase in response to the transition into solar cycle 24. To more clearly identify extrema in the time series of radiative cooling, NO and CO2 cooling rates are deseasonalized to remove effects of the spacecraft yaw cycle. The deseasonalized data show a clear peak of radiative cooling in NO and CO2 occurring in December 2011. This peak in cooling corresponds to similar peaks in the ultraviolet flux emitted from the Sun measured by the SORCE and SEE instruments. These results show that a maximum in solar activity has clearly occurred. This may be a local maximum in time, depending on the future activity of the Sun in solar cycle 24. Reprocessing of version 2.0 of the SABER dataset is nearly complete and results from this new release will be presented. The SABER thermosphere power dataset will be continuously updated as new data are acquired to monitor the occurrence of solar maximum from the perspective of atmospheric cooling.

L A Hunt↗
DOE OSTI2017

SIMULATION STUDY OF HEMISPHERIC PHASE-ASYMMETRY IN THE SOLAR CYCLE

Observations of the Sun suggest that solar activities systematically create north–south hemispheric asymmetries. For instance, the hemisphere in which sunspot activity is more active tends to switch after the early half of each solar cycle. Svalgaard and Kamide recently pointed out that the time gaps of polar field reversal between the northern and southern hemispheres are simply consequences of the asymmetry of sunspot activity. However, the mechanism underlying the asymmetric feature in solar cycle activity is not yet well understood. In this paper, in order to explain the cause of the asymmetry from the theoretical point of view, we investigate the relationship between the dipole- and quadrupole-type components of the magnetic field in the solar cycle using the mean-field theory based on the flux transport dynamo model. As a result, we found that there are two different attractors of the solar cycle, in which either the north or the south polar field is first reversed, and that the flux transport dynamo model explains well the phase-asymmetry of sunspot activity and the polar field reversal without any ad hoc source of asymmetry.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2017

A Numerical Study of Forbush Decreases with a 3D Cosmic-Ray Modulation Model Based on an SDE Approach

Based on the reduced diffusion mechanism for producing Forbush decreases (Fds) in the heliosphere, we constructed a three-dimensional (3D) diffusion barrier, and by incorporating it into a stochastic differential equation (SDE) based time-dependent, cosmic-ray transport model, a 3D numerical model for simulating Fds is built and applied to a period of relatively quiet solar activity. This SDE model generally corroborates previous Fd simulations concerning the effects of the solar magnetic polarity, the tilt angle of the heliospheric current sheet (HCS), and cosmic-ray particle energy. Because the modulation processes in this 3D model are multi-directional, the barrier’s geometrical features affect the intensity profiles of Fds differently. We find that both the latitudinal and longitudinal extent of the barrier have relatively fewer effects on these profiles than its radial extent and the level of decreased diffusion inside the disturbance. We find, with the 3D approach, that the HCS rotational motion causes the relative location from the observation point to the HCS to vary, so that a periodic pattern appears in the cosmic-ray intensity at the observing location. Correspondingly, the magnitude and recovery time of an Fd change, and the recovering intensity profile contains oscillation as well. Investigating the Fd magnitude variation with heliocentric radial distance, we find that the magnitude decreases overall and, additionally, that the Fd magnitude exhibits an oscillating pattern as the radial distance increases, which coincides well with the wavy profile of the HCS under quiet solar modulation conditions.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2017

Inferring the Heliospheric Magnetic Field Back through Maunder Minimum

Recent solar conditions include a prolonged solar minimum (2005–2009) and a solar maximum that has not fully recovered in terms of the Heliospheric Magnetic Field (HMF) strength when compared to the previous maximum values. These anomalies may indicate that we are entering an era of lower solar activity than observed at other times during the space age. We study past solar grand minima, especially the Maunder period (1645–1715) to gain further insight into grand minima. We find the timescale parameters associated with three processes attributed to the magnetic flux balance in the heliosphere using chi-square analysis. We use HMF time series reconstructed based on geomagnetic data and near-Earth spacecraft measurements (OMNI) data to find the fundamental timescales that influence heliospheric field evolution through conversion or opening of magnetic flux from coronal mass ejections (CMEs) into the ambient heliospheric field, removal or loss of the ambient heliospheric field through magnetic reconnection, and interchange reconnection between CME magnetic flux and ambient heliospheric magnetic flux. We also investigate the existence of a floor in the heliospheric magnetic flux, in the absence of CMEs, and show that a floor ⩽1.49nT is sufficient to successfully describe the HMF evolution. The minimum value for the HMF at 1 au in the model-predicted historic record is 3.13 ± 0.35 nT. Our model results favorably reproduce paleocosmic data and near-Earth spacecraft measurements data and show how the HMF may evolve through periods of extremely low activity.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS2011

Cross-Scale Coupling in the Solar Atmosphere

For understanding and eventually predicting solar activity, the fundamental question that Solar-C must answer is: How does energy transfer from the large-scales at which it is injected into the solar atmosphere to the small scales at which it is dissipated? We show that this question of cross-scale coupling is fundamental to all activity, ranging from the smallest nanoflares that are postulated to power coronal heating and solar wind acceleration, to the largest coronal mass ejections and eruptive flares. For the solar atmosphere, the most important process that actually dissipates the energy is believed to be magnetic reconnection. We present results on recent calculations of reconnection in a variety of solar contexts and focus on the coupling between kinetic and MHD scales during reconnection. We discuss the implications of our results for present data and for future observations from Solar-C.

Antiochos, Spiro K.↗
NASA NTRS1964

Aurora

Visual auroras - morphology, correlation with geophysical and solar activity, and energetic particles associated with auroras

GEOPHYSICS↗
NASA NTRS2007

Solar Cycle 24 and the Solar Dynamo

We will discuss the polar field precursor method for solar activity prediction, which predicts cycle 24 will be significantly lower than recent activity cycles, and some new ideas rejuvenating Babcock's shallow surface dynamo. The polar field precursor method is based on Babcock and Leighton's dynamo models wherein the polar field at solar minimum plays a major role in generating the next cycle's toroidal field and sunspots. Thus, by examining the polar fields of the Sun near solar minimum, a forecast for the next cycle's activity is obtained. With the current low value for the Sun's polar fields, this method predicts solar cycle 24 will be one of the lowest in recent times, with smoothed F10.7 radio flux values peaking near 135 plus or minus 35 (2 sigma), in the 2012-2013 timeframe (equivalent to smoothed Rz near 80 plus or minus 35 [2 sigma]). One may have to consider solar activity as far back as the early 20th century to find a cycle of comparable magnitude. We discuss unusual behavior in the Sun's polar fields that support this prediction. Normally, the solar precursor method is consistent with the geomagnetic precursor method, wherein geomagnetic variations are thought to be a good measure of the Sun's polar field strength. Because of the unusual polar field, the Earth does not appear to be currently bathed in the Sun's extended polar field (the interplanetary field), hence negating the primal cause behind the geomagnetic precursor technique. We also discuss how percolation may support Babcock's original shallow solar dynamo. In this process ephemeral regions from the solar magnetic carpet, guided by shallow surface fields, may collect to form pores and sunspots.

Pesnell, W. D.↗