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At least 181 records · Page 10
All sourcesNASA NTRSDOE OSTI
NASA NTRS2023

Relativistic Electron Beams Accelerated By an Interplanetary Shock

Context: Collisionless shock waves have long been considered to be among the most prolific particle accelerators in the universe. Shocks alter the plasma they propagate through, and often exhibit complex evolution across multiple scales. Interplanetary (IP) traveling shocks have been recorded in situ for over half a century and act as a natural laboratory for experimentally verifying various aspects of large-scale collisionless shocks. A fundamentally interesting problem in both heliophysics and astrophysics is the acceleration of electrons to relativistic energies (> 300 keV) by traveling shocks. Aims: The reason for an incomplete understanding of electron acceleration at IP shocks is due to scale-related challenges and a lack of instrumental capabilities. This Letter presents the first observations of field-aligned beams of relativistic electrons upstream of an IP shock, observed thanks to the instrumental capabilities of Solar Orbiter. This study presents the characteristics of the electron beams close to the source and contributes to the understanding of their acceleration mechanism. Methods: On 25 July 2022, Solar Orbiter encountered an IP shock at 0.98 AU. The shock was associated with an energetic storm particle event, which also featured upstream field-aligned relativistic electron beams observed 14 min prior to the actual shock crossing. The distance of the beam’s origin was investigated using a velocity dispersion analysis (VDA). Peak-intensity energy spectra were analyzed and compared with those obtained from a semi-analytical fast-Fermi acceleration model. Results: By leveraging Solar Orbiter’s high temporal resolution Energetic Particle Detector (EPD), we successfully showcase an IP shock’s ability to accelerate relativistic electron beams. Our proposed acceleration mechanism offers an explanation for the observed electron beam and its characteristics, while we also explore the potential contributions of more complex mechanisms.

acceleration of particles↗
NASA NTRS2016

Nasa Space Flight Instruments: Cost Time Trends

Are NASA’s space flight instruments becoming cheaper or more expensive as time marches forward? After analyzing the costs of hundreds of instruments launched over the last 30 years, the short answer to this question is no… and yes. This paper gives a visual analysis of the cost time trends for various NASA space flight instrument types, such as optical, particles detectors, fields detectors and microwave instruments. In addition to the statistical approaches utilized, such as significance tests, cluster analysis and principle components analysis (PCA), we will also discuss the intangibles which are likely at play, including technological progress, NASA policy and the luck of the draw associated with mission manifests. This analysis was performed as the main driver for the NASA Instrument Cost Model (NICM) recent cost estimating model redesign. Started in 2004, the first version of NICM was based off of instruments launched from 1985-2005, or 20 years’ worth of data. As NICM hit its 10-year anniversary, we wanted to know: should NICM continue to only use the most recent 20 years’ worth of data (1995-2015)? Are instruments becoming cheaper or more expensive as time marches forward? There is evidence in favor of a drop in the median dollar-per-kg value across some instrument types, but little in others. Whereas further research is needed to substantiate, Particles and Optical-Planetary instrument types show moderate to strong evidence of a downward trend in dollar-per-kg. Further research is required to study the nature of this trend (shift, taper, cyclic, etc.). Little evidence for a similar downward trend was detected for Fields or Microwave instruments, or Optical instruments on Earth Orbiting spacecraft. We presented evidence in favor of a drop in the median dollar-per-kg value for Particles and Optical-Planetary instrument types. While similar evidence was weak at best for Fields and Microwave instruments. We can speculate as to the causes for this effect, but we are also equipped to begin to rule out, or at least prioritize, some of the suspected drivers. We observed, for Particles and Optical-Planetary instruments, that perhaps a launch manifest effect was playing part of the role in the observed decrease in dollar-per-kg over the years, noting that the more flagship class missions, which have more money to spend on their instruments, were seen in the earlier years in our data, versus the later years which were dominated by less expensive class missions. However, if this were a dominating driver, would we not have seen the downward trend in the Fields and Microwave instruments as well, which were drawn from that same launch manifest? The fact that we did not observe this helps us rule out the launch manifest effect, and other drivers, such as advances in technology, that seem to be more likely suspects. In that case, however, why would technology advances be helping the Particles and Optical-Planetary instruments only? Why would it not be impacting Optical-Earth Orbiting instruments? Further suspects were looked at as well and ruled out, such as the “Faster, Better, Cheaper”era of NASA development which did not seem to actually impact trends by instrument type on a dollar-perkg scale. VI. Future Work A. Time Series Detailed Statistical Assessment The analysis discussed above sets the foundation for a more rigorous time series analysis of the data. Time series analysis will further explore evidence to-date of time trends for the instrument types which showed the strongest indicators for a decrease in dollar-per-kg: Optical (Planetary) and Particles instruments. More than providing evidence and top-level significance tests, time series analysis would help elucidate what kind of trend that exists in the data, their significance and allow statistically based forecasting (see Figure 10)

Mrozinksi, Joseph↗
NASA NTRS1966

Outer zone protons.

Intensity and spectra of 100 to 1700 kev protons in region above two earth radii measured by charged particle detectors on Explorer XII, XIV AND XV

OUTER RADIATION BELT↗
NASA NTRS1969

Pulse-height analyzer with digital readout

Feedback-controlled pulse-amplitude integrator and amplifier is used as an analog-to-digital converter that converts event-liberated charges, emanating from a nuclear-particle detector, directly to numbers rather than to analog-dependent voltages.

Goldsworthy, W. W.↗
NASA NTRS1972

Design of the particles experiment subsystem of the Apollo lunar subsatellite.

In August 1971 an eighty pound subsatellite was ejected from Apollo 15 into lunar orbit. The subsatellite is expected to remain in lunar orbit for at least one year. The Particles Experiment Subsystem of the subsatellite was designed to implement the Particle Shadows/Boundary Layer Experiment. The objective of the experiment is to obtain data for the study of the formation and the dynamics of the earth's magnetosphere, the interaction of plasmas with the moon, and the physics of solar flares. The design of the particle detector telescopes is considered together with details of collimator design, silicon detectors, the absorber foil, and the power subsystems. The instrument performance in lunar orbit is discussed.

Baum, J. J.↗
NASA NTRS1972

Cosmic ray experiment. Part A: Composition and energy spectra of solar cosmic ray nuclei

The GE experiment consisted of two types of detectors: plastics and glasses located in panel 2 and the lower half of panel 3. In panel 2, the entire exposed detector area of 14.7 by 22.6 cm was composed of 31 sheets of 0.025-cm polycarbonate plastic 9070-112. In panel 3, 39 sheets of 0.02-cm cellulose triacetate with no plasticizer made up the major volume fraction. The lower part of panel 3 contained five types of glass detectors. Particles that entered the array after it was folded were recognized, if they crossed from one sheet to another, by means of a 2-mm relative shift of alternate sheets.

Fleischer, R. L.↗
NASA NTRS1973

Exploring Jupiter, Saturn and their satellites.

By exploring the outer solar system, it is possible to go back in time and sample the conditions and the energetics of primitive solar nebula from which the sun and the planets are believed to have condensed. With the aid of particle detectors and magnetometers on a spacecraft going to the outer planets, it will be possible to study the gradients of the solar plasma, cosmic rays, and the interplanetary magnetic field. A number of questions regarding the outer solar system are examined, giving attention to problems of the origin of excess energy in the case of Jupiter, Jupiter radio emissions, problems of planetary meteorology, the rings of Saturn, and the planetary satellites. Critical in situ measurements are discussed together with exploratory missions, spacecraft characteristics, and aspects of preliminary mission design.

Rasool, S. I.↗