Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Solar Activity”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 775 records · Page 43
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Solar photocatalytic activities of porous Nb-doped TiO{sub 2} microspheres by coupling with tungsten oxide

Highlights: • Nb-TiO{sub 2}/WO{sub 3} was prepared by USP method combined impregnation method. • Nb-doping extend the spectral absorption of TiO{sub 2} into visible spectrum. • Nb-TiO{sub 2}/WO{sub 3} has a similar optical band gap as Nb-TiO{sub 2}. • PL spectra indicate WO{sub 3} can accept the photoexcited electrons from Nb-TiO{sub 2}. • Nb-TiO{sub 2}/WO{sub 3} shows higher activity than TiO{sub 2} and Nb-TiO{sub 2} under solar light. - Abstract: Nb doped TiO{sub 2} microspheres modified with WO{sub 3} (Nb-TiO{sub 2}/WO{sub 3}) was prepared by ultrasonic spray pyrolysis method combined with impregnation method. The microspheres were characterized with SEM, TEM, XRD, BET, photoluminescence and UV–vis absorption spectra. The Nb-doping was observed to extend the spectral absorption of TiO{sub 2} into visible spectrum, and the absorption onset was red-shifted for about 88 nm compared to pristine TiO{sub 2} microspheres. Nb-TiO{sub 2}/WO{sub 3} microspheres do not display a red-shifted absorption edge compared with Nb doped TiO{sub 2} microspheres. Under solar irradiation, Nb-TiO{sub 2}/WO{sub 3} microspheres showed higher photocatalytic activity for methylene blue degradation compared with that of pure TiO{sub 2} microspheres and Nb doped TiO{sub 2} microspheres, which could be ascribed to the extended light absorption range and the suppression of electron-hole pair recombination.

36 MATERIALS SCIENCE↗
NASA NTRS1997

Solar energetic particle events and coronal mass ejections: New insights from SOHO

The scientific payload of SOHO, launched in December 1995, enables comprehensive studies of the sun from its interior, to the outer corona and solar wind. In its halo orbit around the Lagrangian point of the sun-earth system, the comprehensive suprathermal and energetic particle analyzer (COSTEP) measures in situ energetic partiles in the energy range 44 keV/particle to greater than 53 MeV/n. Although solar activity was at minimum, COSTEP detected from mid December 1995 until the end of July 1997, 30 solar energetic particle (SEP) events, including both gradual and implusive type SEPs. These minimum phase SEP events are unique in the sense that their associated solar source phenomena can be investigated in detail without interference by other simultaneous solar events as is usually the case at times around solar activity maximum. Simultaneous observations of the solar corona are provided by the large angle spectroscopic coronagraph (LASCO) and the extreme ultraviolet imaging telescope (EIT). From the correlated SOHO observations, a one to one correspondence of SEP events with coronal mass ejections (CMEs) was found. Most of the SEP events were associated with west-limb CMEs, some with halo CMEs that later passed the SOHO spacecraft and with Moreton-like disturbances in the lower solar atmosphere as observed by the EIT. Many SEP events were detected at sector boundaries of the interplanetary magnetic field (IMF) suggesting a magnetic connection to coronal streamers at the sun as supported by LASCO observations of mass ejections at the base of helmet streamers. Energetic particle and LASCO white-light observations yield evidence that CMEs often lead to large-scale disturbances of the sun's corona, probably affecting at times areas all around the sun.

Bothmer, V.↗
NASA NTRS1984

User's guide for the Nimbus 7 ERB Solar Analysis Tape (ESAT)

Five years of Nimbus 7 ERB solar data is available in compact form on a single ERB solar analysis tape (ESAT). The period covered is November 16, 1978 through October 31, 1983. The Nimbus 7 satellite performs just under 14 orbits a day and the ERB solar telescope observe the Sun once per orbit as the satellite passes + or - near the south pole. The data were carefully calibrated and screened. Mean orbital and daily values are given for the total solar irradiance plus selected spectral intervals. In addition, selected solar activity indicators are on the tape. The ERB experiment, the solar data calibration and screening procedures, the solar activity indicators, and the tape format are described briefly.

Hickey, J. R.↗
NASA NTRS1994

Automated maneuver planning using a fuzzy logic algorithm

Spacecraft orbital control requires intensive interaction between the analyst and the system used to model the spacecraft trajectory. For orbits with right mission constraints and a large number of maneuvers, this interaction is difficult or expensive to accomplish in a timely manner. Some automation of maneuver planning can reduce these difficulties for maneuver-intensive missions. One approach to this automation is to use fuzzy logic in the control mechanism. Such a prototype system currently under development is discussed. The Tropical Rainfall Measurement Mission (TRMM) is one of several missions that could benefit from automated maneuver planning. TRMM is scheduled for launch in August 1997. The spacecraft is to be maintained in a 350-km circular orbit throughout the 3-year lifetime of the mission, with very small variations in this orbit allowed. Since solar maximum will occur as early as 1999, the solar activity during the TRMM mission will be increasing. The increasing solar activity will result in orbital maneuvers being performed as often as every other day. The results of automated maneuver planning for the TRMM mission will be presented to demonstrate the prototype of the fuzzy logic tool.

Conway, D.↗
DOE OSTI2016

HOT PLASMA FROM SOLAR ACTIVE-REGION CORES: CONSTRAINTS FROM THE HINODE X-RAY TELESCOPE

Mechanisms invoked to heat the solar corona to millions of degrees kelvin involve either magnetic waves or magnetic reconnections. Turbulence in the convection zone produces MHD waves, which travel upward and dissipate. Photospheric motions continuously build up magnetic energy, which is released through magnetic reconnection. In this paper, we concentrate on hot non-flaring plasma with temperatures of 5 MK < T < 10 MK because it is one of the few observables for which wave and reconnection models make different predictions. Wave models predict no (or little) hot plasma, whereas reconnection models predict it, although in amounts that are challenging to detect with current instrumentation. We used data from the X-ray Telescope (XRT) and the Atmospheric Imaging Assembly (AIA). We requested a special XRT observing sequence, which cycled through the thickest XRT filter several times per hour so we could average these images and improve the signal-to-noise. We did differential emission measure (DEM) analysis using the time-averaged thick-filter data as well as all available channels from both the XRT and AIA for regions observed on 2014 December 11. Whereas our earlier work was only able to determine that plasma with a temperature greater than 5 MK was present , we are now able to find a well-constrained DEM distribution. We have therefore added a strong observational constraint that must be explained by any viable coronal heating model. Comparing state-of-the-art wave and reconnection model predictions, we can conclude that reconnection is heating the hot plasma in these active regions.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1985

North-south asymmetry in activity on the Sun and cosmic ray density gradients

The marked N-S asymmetry in solar activity (with predominant activity in the Sun's Northern Hemisphere) during the 1960's could certainly account for a S-pointing cosmic ray gradient. It is also clear from the data that the response to this change in solar activity asymmetry, and the related change in the perpendicular cosmic ray density gradient, is different for cosmic ray telescopes in the Earth's Northern and Southern Hemispheres. Northern Hemisphere detectors see a S-pointing gradient in the 60's and a N-pointing gradient after 1971, while Southern Hemisphere telescopes see a S-pointing gradient both before and after the reversal.

Swinson, D. B.↗
DOE OSTI2016

THERMODYNAMIC SPECTRUM OF SOLAR FLARES BASED ON SDO/EVE OBSERVATIONS: TECHNIQUES AND FIRST RESULTS

The Solar Dynamics Observatory (SDO)/EUV Variability Experiment (EVE) provides rich information on the thermodynamic processes of solar activities, particularly on solar flares. Here, we develop a method to construct thermodynamic spectrum (TDS) charts based on the EVE spectral lines. This tool could potentially be useful for extreme ultraviolet (EUV) astronomy to learn about the eruptive activities on distant astronomical objects. Through several cases, we illustrate what we can learn from the TDS charts. Furthermore, we apply the TDS method to 74 flares equal to or greater than the M5.0 class, and reach the following statistical results. First, EUV peaks are always behind the soft X-ray (SXR) peaks and stronger flares tend to have faster cooling rates. There is a power-law correlation between the peak delay times and the cooling rates, suggesting a coherent cooling process of flares from SXR to EUV emissions. Second, there are two distinct temperature drift patterns, called Type I and Type II. For Type I flares, the enhanced emission drifts from high to low temperature like a quadrilateral, whereas for Type II flares the drift pattern looks like a triangle. Statistical analysis suggests that Type II flares are more impulsive than Type I flares. Third, for late-phase flares, the peak intensity ratio of the late phase to the main phase is roughly correlated with the flare class, and the flares with a strong late phase are all confined. We believe that the re-deposition of the energy carried by a flux rope, which unsuccessfully erupts out, into thermal emissions is responsible for the strong late phase found in a confined flare. Furthermore, we show the signatures of the flare thermodynamic process in the chromosphere and transition region in the TDS charts. These results provide new clues to advance our understanding of the thermodynamic processes of solar flares and associated solar eruptions, e.g., coronal mass ejections.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS2016

Thermodynamic Spectrum of Solar Flares Based on SDO/EVE Observations: Techniques and First Results

The Solar Dynamics Observatory (SDO)/EUV Variability Experiment (EVE) provides rich information on the thermodynamic processes of solar activities, particularly on solar flares. Here, we develop a method to construct thermodynamic spectrum (TDS) charts based on the EVE spectral lines. This tool could potentially be useful for extreme ultraviolet (EUV) astronomy to learn about the eruptive activities on distant astronomical objects. Through several cases, we illustrate what we can learn from the TDS charts. Furthermore, we apply the TDS method to 74 flares equal to or greater than the M5.0 class, and reach the following statistical results. First, EUV peaks are always behind the soft X-ray (SXR) peaks and stronger flares tend to have faster cooling rates. There is a power-law correlation between the peak delay times and the cooling rates, suggesting a coherent cooling process of flares from SXR to EUV emissions. Second, there are two distinct temperature drift patterns, called Type I and Type II. For Type I flares, the enhanced emission drifts from high to low temperature like a quadrilateral, whereas for Type II flares the drift pattern looks like a triangle. Statistical analysis suggests that Type II flares are more impulsive than Type I flares. Third, for late-phase flares, the peak intensity ratio of the late phase to the main phase is roughly correlated with the flare class, and the flares with a strong late phase are all confined. We believe that the re-deposition of the energy carried by a flux rope, which unsuccessfully erupts out, into thermal emissions is responsible for the strong late phase found in a confined flare. Furthermore, we show the signatures of the flare thermodynamic process in the chromosphere and transition region in the TDS charts. These results provide new clues to advance our understanding of the thermodynamic processes of solar flares and associated solar eruptions, e.g., coronal mass ejections.

Wang, Yuming↗
NASA NTRS1975

La Posta Astrogeophysical Observatory

An overview is presented of the equipment and data acquisition procedures at La Posta Astrogeophysical Observatory, located in the mountains, east of San Diego, Calif. It is a solar observatory, focusing on solar flares and the effect of solar activity on earth. It makes daily radio and optical observations of solar activity. Radio transmission in the earth atmosphere is monitored with VLF and HF equipment. A magnetometer monitors the state of the geomagnetic field.

Bleiweiss, M. P.↗
NASA NTRS2012

Performance of the IRI-2007 and SAMI2 Models during Extreme Solar Minimum

During the recent solar minimum, solar activity reached the lowest levels observed during the space age. This extremely low solar activity has accompanied a number of unexpected observations in the Earth's ionosphere and thermosphere when compared to previous solar minima. Among these is the fact that the ionosphere is significantly contracted beyond expectations based on empirical models. Data from the CINDI instrument on board C/NOFS is used to evaluate the performance of the IRI-2007 and SAMI2 models during the deepest part of the minimum. Additionally, the inputs to SAMI2 are modified in order to estimate the contributions of a contracted thermosphere and reduced EUV on the resultant ionosphere.

Klenzing, J.↗
NASA NTRS1975

Initial results from the S-056 X-ray telescope on Skylab

The S-056 instrument on Skylab-ATM consists of a glancing incidence X-ray telescope with a camera, five X-ray filters, and two small proportional counters to monitor X-rays from the whole sun in the wavelength range from 2 to 18 A. The telescope reflectivity and filter transmissions limit the photographs to the wavelength ranges from 6 to 18 A and from 27 to 37 A. Hence, the instrument is most useful for the study of active regions and solar activity. Active regions usually have bright cores which often appear as linear features straddling the magnetic field neutral line. A large loop appearing on the west limb in connection with prominence activity on Aug. 13, 1973, was analyzed using proportional counter data and photographs. Crude spectral analysis indicates the loop temperature reached 6 million K and the density was enhanced to a few times that obtained from quiet coronal models. Over a hundred solar flares were photographed during the three Skylab missions. Illustrative examples are discussed for solar flares and other transient coronal phenomena.

Mckenzie, D. L.↗
NASA NTRSDate not supplied

Shields-1 Energetic Proton Dose Comparison from Solar Minimum and Active Periods

Shields-1 has been operating in polar low earth orbit since December 2018 as part of the CubeSat Launch Initiative (CSLI) Educational Launch of Nanosatellites (ELaNa)XIX Mission. Shields-1 has 8 Teledyne µdosimeters behind shielding. These shielded µdosimeters have high minimum proton energy thresholds. The Shields-1 electronics enclosure µdosimeter has a minimum proton threshold energy of 151 MeV. The annualized total ionizing dose (TID) in the electronics enclosure was 75.6 +/- 3.2 RAD from July-August 2019, which was a solar minimum period. In contrast, the annualized TID was 61.0 +/- 2.5 RAD in July 2023, a solar active month. The TID change can be attributed to both the reduction in radiation at the South Atlantic Anomaly (SAA) and the decrease in galactic cosmic radiation during increasing solar activity. The measured GCR dose over the poles was reduced during the July 2023 solar active period in comparison with the July 2019 solar minimum period, using the most sensitive µdosimeter channel for the measurement. Shields-1 has demonstrated the capability of measuring the changes in high energy protons in polar low earth orbit during changes in solar activity, which contributes to the understanding of Earth in the heliosphere.

Shields-1 Dosimetry Space Sciences↗
NASA NTRS1994

Coupling between middle atmosphere trend estimates and solar effects in ozone vertical structure

Studies are performed on both the Stratospheric Aerosol and Gas Experiment (SAGE) II (1985-1989) and Solar Backscatter Ultraviolet Spectrometer (SBUV)-Version 6 (1979-1986) global ozone vertical structure satellite data sets to determine the long-term trends in ozone as a function of altitude (pressure) and latitude. SAGE II data are only available during the period of increasing solar activity and show increases in ozone with time in the upper stratosphere which are attributed largely to rising solar activity. Looking at this data set independently, the solar effects and trends are highly coupled and cannot be clearly separated. However, a study of combined SBUV and SAGE II data over the 11-year solar cycle shows a clear response of ozone to 11-year solar variations and allows a decoupling of solar effects, quasibiennial oscillations (QBO), and trends. The detailed pattern of long-term ozone trends become clear using this approach. In the upper stratosphere, ozone depletion increases sharply with latitude. Global trends are fairly symmetric about the equator but are somewhat stronger in the Southern Hemisphere. Near the equator, some layers of ozone are decreasing with time while others appear to be increasing. Near 30 mb, there is evidence of intrusion to mid latitudes of high latitude negative trends. Near 15 mb, trends appear to be very weak. Near the tropopause there appears to be strong ozone depletion on a global scale. Two regions of unexpectedly strong ozone response to 11-year solar variations were detected: the first near 2 mb and the second near 30 mb at low latitudes and near 15 mb at mid latitudes.

Keating, G. M.↗
NASA NTRSDate not supplied

Active Solar-Like Stars and the Production of Prebiotically Relevant Molecules in Young Earth Like Exoplanet

The magnetic activity of young G type stars produces elevated ionizing radiation fluxes for its planetary system. X-ray, Extreme UV, flare radiation and the associated precipitating energetic particles accelerated in coronal mass ejection driven shocks can drive complex chemistry in the exoplanetary atmosphere, and ignite the production of complex molecules (Airapetian et al., 2016; Hayworth et al. 2021). To address the efficiency of the production of prebiotic molecules in young Earth-like environments, we developed and coupled a set of atmospheric models that account for the determination of the flux of precipitating particle, its ionization/dissociation effects in the planetary atmosphere, and the subsequent chemistry that leads to the creation of prebiotic molecules and greenhouse gases. We show that the productions rates are high enough to provide critical input for the origin of prebiotic molecules on the early Earth. Overall, the impact of the space weather on the atmospheric photochemistry should not be neglected when assessing the factors of habitability of the environments of young rocky (exo)planets.

Guillaume Gronoff↗
NASA NTRS1972

Results from the GSFC OSO 7 spectroheliograph

The capabilities of the pointed spectroheliograph on board the OSO 7 are discussed. The range and results of the instrument in recording the evolution of solar active regions and solar flares are considered.

Neupert, W. M.↗
NASA NTRS1972

Lyman-alpha measurements of neutral hydrogen in the outer geocorona and in interplanetary space.

Results of hydrogen Lyman-alpha (1216 A) measurements made on a continuous basis by a two-channel photometer on Ogo 5 from March 1968 to June 1971. The highly elliptical orbit provided measurements of both the outer geocorona and of the 1216-A sky background emission, since geocoronal scattering is minimal at the apogee distance of 150,000 km. Selected data (through 1970) are presented, as well as an interpretation of the three principal discoveries to date - namely, (1) a pronounced antisolar enhancement of the geocoronal scattering beyond 70,000 km, which is regarded as evidence for a hydrogen 'geotail' produced by solar Lyman-alpha radiation pressure; (2) a clear correlation of periodic variations in the sky background emission with solar activity associated with solar rotation; and (3) an annual variation of the 1216-A sky background emission, caused by the earth's orbital motion within the cavity created by the solar wind in the nearby interstellar hydrogen.

Thomas, G. E.↗
NASA NTRS1976

Solar cycle evolution of high-speed solar wind streams

Large amplitude high-speed solar wind streams and streams with maximum speeds in excess of 700 km/sec are far more common in years of declining and minimum solar activity than near solar maximum. Further, the broadest solar wind streams observed directly with space probes during the years 1962-1974 occurred near solar minimum in 1974. Changes in the frequency and nature of solar wind stream structures at the orbit of earth appear to be directly related to the long-term evolution of regions of low density in the solar corona.

Bame, S. J.↗