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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 199 records · Page 11
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NASA NTRS1999

A Solar Dynamic Power Option for Space Solar Power

A study was performed to determine the potential performance and related technology requirements of Solar Dynamic power systems for a Space Solar Power satellite. Space Solar Power is a concept where solar energy is collected in orbit and beamed to Earth receiving stations to supplement terrestrial electric power service. Solar Dynamic systems offer the benefits of high solar-to-electric efficiency, long life with minimal performance degradation, and high power scalability. System analyses indicate that with moderate component development, SD systems can exhibit excellent mass and deployed area characteristics. Using the analyses as a guide, a technology roadmap was -enerated which identifies the component advances necessary to make SD power generation a competitive option for the SSP mission.

Mason, Lee S.↗
NASA NTRS1995

Solar Particle Induced Upsets in the TDRS-1 Attitude Control System RAM During the October 1989 Solar Particle Events

The three large solar particle events, beginning on October 19, 1989 and lasting approximately six days, were characterized by high fluences of solar protons and heavy ions at 1 AU. During these events, an abnormally large number of upsets (243) were observed in the random access memory of the attitude control system (ACS) control processing electronics (CPE) on-board the geosynchronous TDRS-1 (Telemetry and Data Relay Satellite). The RAM unit affected was composed of eight Fairchild 93L422 memory chips. The Galileo spacecraft, launched on October 18, 1989 (one day prior to the solar particle events) observed the fluxes of heavy ions experienced by TDRS-1. Two solid-state detector telescopes on-board Galileo, designed to measure heavy ion species and energy, were turned on during time periods within each of the three separate events. The heavy ion data have been modeled and the time history of the events reconstructed to estimate heavy ion fluences. These fluences were converted to effective LET spectra after transport through the estimated shielding distribution around the TDRS-1 ACS system. The number of single event upsets (SEU) expected was calculated by integrating the measured cross section for the Fairchild 93L422 memory chip with average effective LET spectrum. The expected number of heavy ion induced SEU's calculated was 176. GOES-7 proton data, observed during the solar particle events, were used to estimate the number of proton-induced SEU's by integrating the proton fluence spectrum incident on the memory chips, with the two-parameter Bendel cross section for proton SEU'S. The proton fluence spectrum at the device level was gotten by transporting the protons through the estimated shielding distribution. The number of calculated proton-induced SEU's was 72, yielding a total of 248 predicted SEU'S, very dose to the 243 observed SEU'S. These calculations uniquely demonstrate the roles that solar heavy ions and protons played in the production of SEU's during the October 1989 solar particle events.

Croley, D. R.↗
NASA NTRS2000

MACS, An Instrument and a Methodology for Simultaneous and Global Measurements of the Coronal Electron Temperature and the Solar Wind Velocity on the Solar Corona

In Cram's theory for the formation of the K-coronal spectrum he observed the existence of temperature sensitive anti-nodes, which were separated by temperature insensitive nodes, at certain wave-lengths in the K-coronal spectrum. Cram also showed these properties were remarkably independent of altitude above the solar limb. In this thesis Cram's theory has been extended to incorporate the role of the solar wind in the formation of the K-corona, and we have identified both temperature and wind sensitive intensity ratios. The instrument, MACS, for Multi Aperture Coronal Spectrometer, a fiber optic based spectrograph, was designed for global and simultaneous measurements of the thermal electron temperature and the solar wind velocity in the solar corona. The first ever experiment of this nature was conducted in conjunction with the total solar eclipse of 11 August 1999 in Elazig, Turkey. Here twenty fiber optic tips were positioned in the focal plane of the telescope to observe simultaneously at many different latitudes and two different radial distances in the solar corona. The other ends were vertically stacked and placed at the primary focus of the spectrograph. By isolating the K-coronal spectrum from each fiber the temperature and the wind sensitive intensity ratios were calculated.

Reginald, Nelson L.↗
NASA NTRS2004

The October-November, 2003 Solar Activity and its Relationship to the "approx. 155 day" Solar Periodicity

Periodicities of approx. 155 days in various solar and interplanetary phenomena were first discovered during solar cycle 21 and have been shown to be intermittently present in other solar cycles. In the current solar cycle (23), they have been reported in solar energetic particle events and interplanetary coronal mass ejections. We assess whether the "unexpected" October - November 2003 burst of solar activity during the late declining phase of the cycle may have been a manifestation of such a periodic behavior, and hence might have been to some extent "predictable". If the pattern were to continue, episodes of enhanced activity might be expected around April - May and October, 2004. There was a modest increase activity increase in mid-April, 2004 which may conform to this pattern.

Richardson, I. G.↗
NASA NTRS2005

The October-November, 2003 Solar Activity and its Relationship to the "approximately 155 day" Solar Periodicity

Periodicities of - 155 days in various solar and interplanetary phenomena were first discovered during solar cycle 21 and have been shown t o be intermittently present in other solar cycles. In the current solar cycle (23), they have been reported in solar energetic particle events and interplanetary coronal maSS ejections. We assess whether the "unexpected" October - November 2003 burst of solar activity during the late declining phase of the cycle may have been a manifestation of such a periodic behavior, and hence might have been to =me extent "predictable". If the pattern were to continue, episodes of enhanced activity might be expected around April - May and October, 2004. There was a mod- est increase activity increase in mid-April, 2004 which may conform to this pattern.

Richardson, I. G.↗
NASA NTRS2005

Satellite Measurements of Middle Atmospheric Impacts by Solar Proton Events in Solar Cycle 23

Solar proton events (SPEs) are known to have caused changes in constituents in the Earth's neutral polar middle atmosphere in the most recent solar maximum period (solar cycle 23). The highly energetic protons produced ionizations, excitations, dissociations, and dissociative ionizations of the background constituents in the polar cap regions (greater than 60 degrees geomagnetic latitude), which led to the production of HOx (H, OH, HO2) and NOy (N, NO, NO2, NO3, N2O5, HNO3, HO2NO2, ClONO2, BrONO2). The HOx increases led to short-lived ozone decreases in the polar mesosphere and upper stratosphere due to the short lifetimes of the HOx constituents. Polar middle mesospheric ozone decreases greater than 50% were observed and computed to last for hours to days due to the enhanced HOx. The NOy increases led to long-lived polar stratospheric ozone changes because of the long lifetime of the NOy family in this region. Upper stratospheric ozone decreases of greater than 10% were computed to last for several months past the solar events in the winter polar regions because of the enhanced NOy. Solar cycle 23 was especially replete with SPEs and huge fluxes of high energy protons occurred in July and November 2000, September and November 2001, April 2002, October 2003, and January 2005. Smaller, but still substantial, proton fluxes impacted the Earth during other months in this cycle. Observations by the Upper Atmosphere Research Satellite (UARS) Halogen Occultation Experiment (HALOE) and Solar Backscatter Ultraviolet 2 (SBUV/2) instruments along with GSFC 2D Model predictions will be shown in this talk.

Jackman, C.↗
NASA NTRS2001

Surface Texturing Investigated for a High Solar Absorptance Low Infrared Emittance Solar Collector

The objective of this work was to design, build, and vacuum test a high solar absorptance, low infrared emittance solar collector for heat engine and thermal switching applications. Mini-satellites proposed by the Applied Physics Laboratory for operation in environments that are subject to radiation threat may utilize a heat engine for power and a thermal bus for thermal control. To achieve this goal, a surface having high solar absorptance and low infrared emittance is needed. At the NASA Glenn Research Center, one concept being pursued to achieve this goal is texturing high thermal conductivity graphite epoxy composites using a directed atomic oxygen beam and then coating the textured surface with a reflective metallic coating. Coupons were successfully textured, coated, and evaluated. A variety of texturing conditions were explored, and textures were documented by scanning electron microscopy. Copper, gold, silver, iridium, and aluminum coatings were applied, and the highest solar absorptance to infrared emittance ratio was found to be 1.3. A full-sized solar collector was manufactured with this ratio, and the amount of heat collected was observed using an Inconel calorimeter installed in a bench-top vacuum chamber equipped with a solar simulator. Results to date indicate good heat flow through the system, with 9 W of heat flow measured by the calorimeter.

Jaworske, Donald A.↗
NASA NTRS2005

SOLAR SAIL PROPULSION SENSITIVITY TO MEMBRANE SHAPE AND OPTICAL PROPERTIES USING THE SOLAR VECTORING EVALUATION TOOL (SVET)

Solar sail propulsive performance is dependent on sail membrane optical properties and on sail membrane shape. Assumptions of an ideal sail (flat, perfect reflector) can result in errors which can affect spacecraft control, trajectory analyses, and overall evaluation of solar sail performance. A MATLAB(R) program has been developed to generate sail shape point cloud files for two square-architecture solar sail designs. Simple parabolic profiles are assumed for sail shape under solar pressure loading. These files are then input into the Solar Vectoring Evaluation Tool (SVET) software to determine the propulsive force vector, center of pressure, and moments about the sail body axes as a function of sail shape and optical properties. Also, the impact of the center-line angle, due to non-perfect optical properties, is addressed since this constrains sail force vector cone angle and is often overlooked when assuming ideal-reflector membranes. Preliminary sensitivity analysis using these tools aids in determining the key geometric and optical parameters that drive solar sail propulsive performance.

Ewing, Anthony↗
NASA NTRS2006

Solar Activity and Solar Eruptions

Our Sun is a dynamic, ever-changing star. In general, its atmosphere displays major variation on an 11-year cycle. Throughout the cycle, the atmosphere occasionally exhibits large, sudden outbursts of energy. These "solar eruptions" manifest themselves in the form of solar flares, filament eruptions, coronal mass ejections (CMEs), and energetic particle releases. They are of high interest to scientists both because they represent fundamental processes that occur in various astrophysical context, and because, if directed toward Earth, they can disrupt Earth-based systems and satellites. Research over the last few decades has shown that the source of the eruptions is localized regions of energy-storing magnetic field on the Sun that become destabilized, leading to a release of the stored energy. Solar scientists have (probably) unraveled the basic outline of what happens in these eruptions, but many details are still not understood. In recent years we have been studying what triggers these magnetic eruptions, using ground-based and satellite-based solar observations in combination with predictions from various theoretical models. We will present an overview of solar activity and solar eruptions, give results from some of our own research, and discuss questions that remain to be explored.

Sterling, Alphonse C.↗
NASA NTRS2008

If We Can't Predict Solar Cycle 24, What About Solar Cycle 34?

Predictions of solar activity in Solar Cycle 24 range from 50% larger than SC 23 to the onset of a Grand Minimum. Because low levels of solar activity are associated with global cooling in paleoclimate and isotopic records, anticipating these extremes is required in any longterm extrapolation of climate variability. Climate models often look forward 100 or more years, which would mean 10 solar cycles into the future. Predictions of solar activity are derived from a number of methods, most of which, such as climatology and physics-based models, will be familiar to atmospheric scientists. More than 50 predictions of the maximum amplitude of SC 24 published before solar minimum will be discussed. Descriptions of several methods that result in the extreme predictions and some anticipation of even longer term predictions will be presented.

Pesnell. William Dean↗
NASA NTRS2011

New Observations of Solar Plasma Variability from the Solar Dynamics Observatory (SDO)

The launch of the Solar Dynamics Observatory (SDO) in February 2010 now allows for continuous observations of the Sun on all times scales from seconds to years. The variations in the solar plasma on these time scales cause significant deviations in the Earth and space environments on similar time scales, such as affecting the densities and composition of particular atoms, molecules, and ions in the atmospheres of Earth and other planets. Presented and discussed will be examples of initial results from SDO that show how different temperature plasmas (from 50,OOOK to 20MK+), corresponding to different solar features in the solar atmosphere, evolve and change during solar eruptive events. The presentation will emphasize how the Solar Dynamics Observatory (SDO), the first satellite in NASA's Living with a Star program, has already improved upon current observations and how it will continue provide further insights into the variable Sun and its Heliospheric influence.

Chamberlin, Phillip C.↗
NASA NTRS2017

Electron Temperature Maps of the Low Solar Corona: ISCORE Results from the Total Solar Eclipse of 1 August 2008 in China

We conducted an experiment in conjunction with the total solar eclipse of 1 August 2008 in China to determine the thermal electron temperature in the low solar corona close to the solar limb. The instrument, Imaging Spectrograph of Coronal Electrons (ISCORE), consisted of an 8 inch f/10 Schmidt Cassegrain telescope with a thermoelectrically cooled CCD camera at the focal plane. Results are electron temperatures of 1 MK at 1.08 R(solar system) and 1.13 R(solar system) from the Sun center in the polar and equatorial regions, respectively. This experiment confirms the results of an earlier experiment conducted in conjunction with the total eclipse of 29 March 2006 in Libya, and results are that at a given coronal height the electron temperature in the polar region is larger than at the equatorial region. In this paper we show the importance of using the correct photospheric spectrum pertinent to the solar activity phase at the time of the experiment, which is a required parameter for modeling the underlying theoretical concept for temperature interpretation of the measured intensity ratios using color filters.

Reginald, Nelson L.↗
NASA NTRS2019

Global Evolution of Solar Magnetic Fields and Prediction of Solar Activity Cycles

Prediction of solar activity cycles is challenging because the physical processes inside the Sun involve a broad range of multiscale dynamics that no model can reproduce, and the available observations are highly limited and cover mostly surface layers. Helioseismology makes it possible to probe solar dynamics in the convective zone, but variations in the differential rotation and meridional circulation are currently available for only two solar activity cycles. It has been demonstrated that sunspot observations, which cover over 400 years, can be used to calibrate the Parker-Kleeorin-Ruzmaikin model and that the Ensemble Kalman Filter (EnKF) method can be used to link the model magnetic fields to sunspot observations to make reliable predictions of a following cycle. However, for more accurate predictions, it is necessary to use actual observations of the solar magnetic fields, which are available for only four solar cycles. This raises the question of how limitations in observational data and model uncertainties affect predictive capabilities and implies the need for the development of new forecast methodologies and validation criteria. In this presentation, I will discuss the influence of the limited number of available observations on the accuracy of EnKF estimates of solar cycle parameters.

Kitiashvili, Irina N.↗
NASA NTRS2021

The First Widespread Solar Energetic Particle Event Observed By Solar Orbiter on 2020 November 29

Context. On 2020 November 29, the first widespread solar energetic particle (SEP) event of solar cycle 25 was observed at four widely separated locations in the inner (. 1AU) heliosphere. Relativistic electrons as well as protons with energies > 50MeV were observed by Solar Orbiter (SolO), Parker Solar Probe (PSP), the Solar Terrestrial Relations Observatory (STEREO)-A and multiple near-Earth spacecraft. The SEP event was associated with an M4.4 class X-ray flare and accompanied by a coronal mass ejection (CME) and an extreme ultraviolet (EUV) wave as well as a type II radio burst and multiple type III radio bursts. Aims. We present multi-spacecraft particle observations and place them in context with source observations from remote sensing instruments and discuss how such observations may further our understanding of particle acceleration and transport in this widespread event. Methods. Velocity dispersion analysis (VDA) and time shift analysis (TSA) were used to infer the particle release times at the Sun. Solar wind plasma and magnetic field measurements were examined to identify structures that influence the properties of the energetic particles such as their intensity. Pitch angle distributions and first-order anisotropies were analyzed in order to characterize the particle propagation in the interplanetary medium. Results. We find that during the 2020 November 29 SEP event, particles spread over more than 230° in longitude close to 1AU. The particle onset delays observed at the different spacecraft are larger as the flare–footpoint angle increases and are consistent with those from previous STEREO observations. Comparing the timing when the EUV wave intersects the estimated magnetic footpoints of each spacecraft with particle release times from TSA and VDA, we conclude that a simple scenario where the particle release is only determined by the EUV wave propagation is unlikely for this event. Observations of anisotropic particle distributions at SolO, Wind, and STEREO-A do not rule out that particles are injected over a wide longitudinal range close to the Sun. However, the low values of the first-order anisotropy observed by near-Earth spacecraft suggest that diffusive propagation processes are likely involved.

A Kollhoff↗
NASA NTRS2022

Quantifying Energy Release in Solar Flares and Solar Eruptive Events

Solar flares and the often associated solar eruptive events serve as an outstanding laboratory to study the magnetic reconnection and the associated energy release and conversion processes under plasma conditions difficult to reproduce in the laboratory, and with considerable spatiotemporal details not possible elsewhere in the universe. In the past decade, thanks to advances in multiwavelength imaging spectroscopy, as well as developments in theories and numerical modeling, significant progress has been made in improving our understanding of solar flare/eruption energy release. In particular, broadband imaging spectroscopy at microwave wavelengths offered by the Expanded Owens Valley Solar Array (EOVSA) has enabled the revolutionary capability of measuring the time-evolving coronal magnetic fields at or near the flare reconnection region. However, owing to EOVSA’s limited dynamic range, imaging fidelity, and angular resolution, such measurements can only be done in a region around the brightest source(s) where the signal-to-noise is sufficiently large. In this white paper, after a brief introduction to the outstanding questions and challenges pertinent to magnetic energy release in solar flares and eruptions, we will demonstrate how a next-generation radio facility with many (∼100–200) antenna elements can bring the next revolution by enabling high dynamic range, high fidelity broadband imaging spectropolarimetry along with a sub-second time resolution and arcsecond level angular resolution. We recommend to prioritize the implementation of such a ground-based instrument within this decade. We also call for facilitating multi-wavelength, multi-messenger observations and advanced numerical modeling in order to achieve a comprehensive understanding of the “system science” of solar flares and eruptions.

Bin Chen↗
NASA NTRS2023

Prediction and Verification of Parker Solar Probe Solar Wind Sources at 13.3 Rs

Drawing connections between heliospheric spacecraft and solar wind sources is a vital step in understanding the evolution of the solar corona into the solar wind and contextualizing in situ timeseries. Furthermore, making advanced predictions of this linkage for ongoing heliospheric missions, such as Parker Solar Probe (Parker), is necessary for achieving useful coordinated remote observations and maximizing scientific return. The general procedure for estimating such connectivity is straightforward (i.e., magnetic field line tracing in a coronal model) but validating the resulting estimates is difficult due to the lack of an independent ground truth and limited model constraints. In its most recent orbits, Parker has reached perihelia of 13.3R⊙ and moreover travels extremely fast prograde relative to the solar surface, covering over 120° longitude in 3 days. Here we present footpoint predictions and subsequent validation efforts for Parker Encounter 10, the first of the 13.3R⊙ orbits, which occurred in November 2021. We show that the longitudinal dependence of in situ plasma data from these novel orbits provides a powerful method of footpoint validation. With reference to other encounters, we also illustrate that the conditions under which source mapping is most accurate for near-ecliptic spacecraft (such as Parker) occur when solar activity is low, but also require that the heliospheric current sheet is strongly warped by mid-latitude or equatorial coronal holes. Lastly, we comment on the large-scale coronal structure implied by the Encounter 10 mapping, highlighting an empirical equatorial cut of the Alfvèn surface consisting of localized protrusions above unipolar magnetic separatrices.

S. T. Badman↗
NASA NTRS2023

Revisiting Empirical Solar Energetic Particle Scaling Relations. I. Solar Flares

Aims. The possible influence of solar superflares on the near-Earth space radiation environment are assessed through the investigation of scaling laws between the peak proton flux and fluence of solar energetic particle (SEP) events with the solar flare soft X-ray peak photon flux. Methods. We compiled a catalog of 65 well-connected (W20-90) SEP events during the last three solar cycles covering a period of ∼34 yr (1984–2020) that were associated with flares of class ≥C6.0, and investigated the statistical relations between the recorded peak proton fluxes (I p ) and the fluences (F p ) at a set of integral energies from E > 10, > 30, and > 60 to > 100 MeV versus the associated solar flare peak soft X-ray flux in the 1–8 Å band (F SXR ). Based on the inferred relations, we calculated the integrated energy dependence of the peak proton flux (I p ) and fluence (F p ) of the SEP events, assuming that they follow an inverse power law with respect to energy. Finally, we made use of simple physical assumptions, combining our derived scaling laws, and estimated the upper limits for I p and F p focusing on the flare associated with the strongest ground level enhancement (GLE) directly observed to date (GLE 05 on 23 February 1956), and that inferred for the cosmogenic radionuclide-based SEP event of AD774/775. Results. A scaling law relating I p and F p to the solar soft X-ray peak intensity (F SXR ) as ∝ F 5/6 SXR for a flare with a F SXR = X600 (in the revised scale) is consistent with values of FP inferred for the cosmogenic nuclide event of AD774/775.

Athanasios Papaioannou↗
NASA NTRS2012

Deep Solar Activity Minimum 2007-2009: Solar Wind Properties and Major Effects on the Terrestrial Magnetosphere

We discuss the temporal variations and frequency distributions of solar wind and interplanetary magnetic field parameters during the solar minimum of 2007 - 2009 from measurements returned by the IMPACT and PLASTIC instruments on STEREO-A.We find that the density and total field strength were significantly weaker than in the previous minimum. The Alfven Mach number was higher than typical. This reflects the weakness of magnetohydrodynamic (MHD) forces, and has a direct effect on the solar wind-magnetosphere interactions.We then discuss two major aspects that this weak solar activity had on the magnetosphere, using data from Wind and ground-based observations: i) the dayside contribution to the cross-polar cap potential (CPCP), and ii) the shapes of the magnetopause and bow shock. For i) we find a low interplanetary electric field of 1.3+/-0.9 mV/m and a CPCP of 37.3+/-20.2 kV. The auroral activity is closely correlated to the prevalent stream-stream interactions. We suggest that the Alfven wave trains in the fast streams and Kelvin-Helmholtz instability were the predominant agents mediating the transfer of solar wind momentum and energy to the magnetosphere during this three-year period. For ii) we determine 328 magnetopause and 271 bow shock crossings made by Geotail, Cluster 1, and the THEMIS B and C spacecraft during a three-month interval when the daily averages of the magnetic and kinetic energy densities attained their lowest value during the three years under survey.We use the same numerical approach as in Fairfield's empirical model and compare our findings with three magnetopause models. The stand-off distance of the subsolar magnetopause and bow shock were 11.8 R(sub E) and 14.35 R(sub E), respectively. When comparing with Fairfield's classic result, we find that the subsolar magnetosheath is thinner by approx. 1 R(sub E). This is mainly due to the low dynamic pressure which results in a sunward shift of the magnetopause. The magnetopause is more flared than in Fairfield's model. By contrast the bow shock is less flared, and the latter is the result of weaker MHD forces.

solar minimum↗