Results of Rocket and Meteor Research *

1952 ◽  
Vol 33 (1) ◽  
pp. 13-25 ◽  
Author(s):  
Fred L. Whipple
Keyword(s):  
New Mexico ◽  
Solar Radiation ◽  
High Frequency ◽  
Upper Atmosphere ◽  
Sampling Techniques ◽  
The Sun ◽  
X Ray ◽  
The Past ◽  
Atmospheric Data ◽  
Far Ultraviolet

Results are presented of rocket and meteor research in the upper atmosphere during the past three years. Both methods have been valuable in determining the pressures, densities and temperatures in the upper atmosphere and variations with time and place above an altitude of 30 km. The basic atmospheric data are now rather well determined to 130 km over New Mexico. Knowledge of the composition of the atmosphere to 72 km depends solely upon rocket sampling techniques. A great deal of information has been obtained from the rocket measures concerning radiation from the sun in the far ultraviolet to wavelength about 800 Å and in the soft X-ray region below 20 Å. A considerable section of the paper is devoted to the question of micro-meteorites, their existence and effect on the upper atmosphere. In addition, three Appendixes include some more recent information concerning temperatures and composition of the upper atmosphere and concerning high-frequency solar radiation.

Astromaterials Research of Comet Wild 2: Terameters to Nanometers

MRS Bulletin ◽  
2010 ◽  
Vol 35 (2) ◽  
pp. 150-154 ◽  
Author(s):  
Sean Brennan
Keyword(s):  
Solar System ◽  
Elemental Abundance ◽  
The Sun ◽  
Isotopic Abundance ◽  
Solar System Formation ◽  
Sample Return ◽  
X Ray ◽  
The Past ◽  
Cometary Material ◽  
Sample Return Mission

AbstractStardust, a NASA sample return mission, safely landed in the Utah desert in January 2006 after a seven-year mission, bringing with it the first cometary material from a known parent source, Comet 81P/Wild 2. One of the mission goals is to determine the starting material of the solar system. By sampling a comet, which has spent most of the past 4.6 Gyr beyond the orbit of Neptune, we expect to measure material presumed to be unaffected by the ignition of the sun. The Stardust spacecraft swept through the tail of the comet, collecting hundreds of micron-sized particles from that stream into aerogel, a low-density silica foam. An international team of materials scientists have studied the mineralogy, petrology, and elemental and isotopic abundance of these materials. Our group has studied elemental abundance using an x-ray microprobe; the morphology of the particles was examined using an x-ray microscope, which enables nanotomography of the particles while encased in aerogel. The unexpected conclusions are that much of the material from this comet was formed near the sun, after its ignition, and soon thereafter transported to the outer reaches of the solar system. These results have changed the way astrophysicists think about solar system formation.

Gaia or Athena? The Early Faint-Sun Paradox

1997 ◽  
Author(s):  
Douglas V. Hoyt ◽  
Kenneth H. Shatten
Keyword(s):  
Carbon Dioxide ◽  
Solar Radiation ◽  
Surface Temperature ◽  
Stellar Evolution ◽  
The Sun ◽  
Solar Luminosity ◽  
The Past ◽  
The Earth ◽  
Climate Evolution

Stellar evolution theory predicts large, long-term solar large, long-term solar luminosity (L⊙) changes over the lifetime of the sun. The most certain prediction is a general monotonic increase (neglecting short-period variations) in L⊙ of about 30% over the past 4.7 billion years, an increase that will continue. This prediction is well founded theoretically (based on the conversion of hydrogen into heavier elements) and supported observationally by the famous Hertzsprung-Russell diagram showing stellar evolution. If the solar luminosity increases monotonically with time, one might expect to find evidence of increasing surface temperatures in the Earth’s paleoclimatic record. Instead, isotopic indicators show Earth’s mean surface temperature is now significantly lower than it was 3 billion years ago. In 1975, R. K. Ulrich termed this the “faint young sun” paradox. Simultaneous solar luminosity increase and terrestrial temperature decrease imply additional strong influences on climate evolution. To understand climate evolution (and, by inference, the present climate), we must first determine the nature of these “compensatory mechanisms.” The positively increasing line in Figure 12.1 shows the evolution of solar luminosity (in units of present luminosity, L). Since terrestrial surface temperatures have remained nearly constant during the last 2.3 billion years, this requires a very effective compensatory mechanism. Several theories attempt to explain why the Earth’s surface temperature has remained relatively constant even while the solar luminosity has increased by 30%. Also, various scenarios have been advanced to explain why the Earth remained ice-free even during periods when the sun was much dimmer than it is today. Some of these ideas are: • Since it had fewer continents and more oceans, the early Earth was much darker. This same darker surface absorbed enough additional incoming solar radiation to remain ice-free. • In the past, energy transport from the equator to polar regions was easier because the continents had lower elevations. This enhanced heat transport allowed the Earth to remain relatively warm. • The early atmosphere had more carbon dioxide and methane, creating an enhanced greenhouse effect sufficient to trap the incoming solar radiation and keep the Earth warm. The enormous amount of carbon trapped in limestone suggests that Earth’s former atmosphere contained much more carbon dioxide than it does today.

scholarly journals Measurements of X-ray radiation of the Sun on the heliogeophysical measuring equipment of spacecraft of the Russian Hydrometheorological Service

2019 ◽  
Vol 30 ◽  
pp. 15009
Author(s):  
Anatoly Nusinov ◽  
Vladimir Minligareev ◽  
Andrey Repin ◽  
Igor Shirokov
Keyword(s):  
Solar Radiation ◽  
Measuring Equipment ◽  
Experimental Studies ◽  
Calibration Procedure ◽  
Space Vehicles ◽  
The Sun ◽  
X Ray ◽  
Reference Base ◽  
Geostationary Satellites ◽  
Technological Sample

The characteristics of the equipment for monitoring X-ray solar radiation onboard geostationary satellites. A reference base for X-ray flux meters of the DIR-E was developed and experimental studies of the characteristics on the technological sample of the device were carried out. The calibration procedure of DIR-E for use in measurements on perspective space vehicles was also developed.

scholarly journals The impact of stellar activity on planets

2006 ◽  
Vol 2 (14) ◽  
pp. 295-296
Author(s):  
Ignasi Ribas
Keyword(s):  
Solar Wind ◽  
Solar System ◽  
Stellar Activity ◽  
Particle Emissions ◽  
X Ray ◽  
The Past ◽  
Far Ultraviolet ◽  
The Impact

AbstractThe results of the Sun in Time program indicate that the X ray, far ultraviolet and ultraviolet fluxes of the young Sun were significantly higher than today. Similarly, the solar wind mayhave been much stronger in the past. Such environment of intense energy and particle emissions could have influenced the paleo-atmospheres of Solar System planets and, by extension, the habitability and stability of exoplanets.

Sunburn: Effects and Management

1983 ◽  
Vol 5 (1) ◽  
pp. 13-17
Author(s):  
James Leach
Keyword(s):  
Solar Radiation ◽  
Physical Properties ◽  
Well Being ◽  
Ultraviolet B ◽  
The Sun ◽  
Human Beings ◽  
Ultraviolet A ◽  
The Past ◽  
Cutting Out ◽  
Ancient Times

The salutary benefits of basking in the sun have been sought by human beings since ancient times. Regarded in the past as a deity, the sun still confers its radiant benedictions on its modern devotees who have been persuaded by contemporary fashions that a dark brown tan is a sure sign of well-being, both physical and psychological. At some time, virtually all ardent sun-worshippers discover the unpleasant acute cutaneous reaction commonly called sunburn. PHYSICAL PROPERTIES OF SOLAR RADIATION Constituting a continuous spectrum, the electromagnetic radiation from the sun ranges from the highly energetic short wavelengths to the less energetic longer wavelengths. The wavelengths that impinge on the earth's surface are between 290 and 3,000 nm. On the basis of our visual physiology, they can be arbitrarily divided into visible, ultraviolet, and infrared waves. The portion of solar radiation that elicits the sunburn reaction lies between 290 and 320 nm in the ultraviolet band and is traditionally designated ultraviolet B (UVB). The earth's stratosphere effectively absorbs the potentially more harmful shorter wavelengths. This filtering is accomplished by the thin ozone layer that continually absorbs ultraviolet radiation (UVR) from 200 to 320 nm, completely cutting out all radiation less than 290 nm. The longer ultraviolet wavelengths from 320 to 400 nm, designated ultraviolet A (UVA), are approximately one thousandth as effective as UVB in evoking erythema.

scholarly journals Beryllium-10 production in gaseous protoplanetary disks and implications for the astrophysical setting of refractory inclusions

2019 ◽  
Vol 624 ◽  
pp. A131 ◽  
Author(s):  
Emmanuel Jacquet
Keyword(s):  
Solar System ◽  
Protoplanetary Disks ◽  
Disk Surface ◽  
The Sun ◽  
Early Generation ◽  
X Ray ◽  
The Past ◽  
Show Evidence ◽  
Output Ratio ◽  
Condensation Front

Calcium-aluminum-rich inclusions (CAIs), the oldest known solids of the solar system, show evidence for the past presence of short-lived radionuclide beryllium-10, which was likely produced by spallation during protosolar flares. While such 10Be production has hitherto been modeled at the inner edge of the protoplanetary disk, I calculate here that spallation at the disk surface may reproduce the measured 10Be/9Be ratios at larger heliocentric distances. Beryllium-10 production in the gas prior to CAI formation would dominate that in the solid. Interestingly, provided the Sun’s proton to X-ray output ratio does not decrease strongly, 10Be/9Be at the CAI condensation front would increase with time, explaining the reduced values in a (presumably early) generation of CAIs with nucleosynthetic anomalies. CAIs thus need not have formed very close to the Sun and may have condensed at 0.1–1 AU where sufficiently high temperatures originally prevailed.

The Sun's Influence on Climate

2015 ◽  
Author(s):  
Joanna D. Haigh ◽  
Peter Cargill
Keyword(s):  
Solar Radiation ◽  
Sunspot Cycle ◽  
Climate System ◽  
Upper Atmosphere ◽  
Atmospheric Composition ◽  
The Sun ◽  
Important Relationship ◽  
Earth’S Climate ◽  
And Behavior

The Earth's climate system depends entirely on the Sun for its energy. Solar radiation warms the atmosphere and is fundamental to atmospheric composition, while the distribution of solar heating across the planet produces global wind patterns and contributes to the formation of clouds, storms, and rainfall. This book provides an unparalleled introduction to this vitally important relationship. The book covers the basic properties of the Earth's climate system, the structure and behavior of the Sun, and the absorption of solar radiation in the atmosphere. It explains how solar activity varies and how these variations affect the Earth's environment, from long-term paleoclimate effects to century timescales in the context of human-induced climate change, and from signals of the 11-year sunspot cycle to the impacts of solar emissions on space weather in our planet's upper atmosphere.

scholarly journals Hard Solar X-Ray Bursts

1968 ◽  
Vol 1 ◽  
pp. 541-543
Author(s):  
C. de Jager
Keyword(s):  
Solar Radiation ◽  
Solar Flares ◽  
Spectral Region ◽  
Radiation Flux ◽  
Point Of View ◽  
The Sun ◽  
X Ray ◽  
Quiet Sun ◽  
Observational Techniques

A tentative spectrum of the Sun in the X-ray region is shown in Figure 1 (De Jager, 1967). The quiet Sun emits a measurable spectrum at photon energies below about 3 keV. During the occurrence of solar flares an enhancement of the emitted energy, and a hardening of the spectrum is clearly visible. The soft X-ray bursts apparently show a maximum radiation flux at wavelengths of about 10 Å.In the spectral region above about 10 keV hardly any quiet solar radiation is observable. During the occurrence of solar flares hard X-ray bursts are occasionally observed. From the point of view of observational techniques these bursts may be divided in the so-called deka-keV bursts, covering the range 10-200 keV, and the deci-MeV bursts in the range between 0·2 and 1 MeV. Many deka-keV bursts have been observed during the years 1966-67 by Winckler et al., by means of the OGO-I and OGO-III satellites (see Arnoldy et al., 1967). The existence of deci-MeV bursts has been doubted various times (see e.g. Chubb et al., 1966). Its reality seems now to be proved (see also De Jager, 1967). However, they may be much rarer than the deka-keV bursts, although it is not yet completely sure that the selection is not observational.

The Use of Advanced Analytical Techniques for Characterization of the Chemical, Physical, and Crystallographic Nature of a Surface

1973 ◽  
Vol 31 ◽  
pp. 132-133 ◽  
Author(s):  
R. E. Herfert
Keyword(s):  
Surface Characterization ◽  
Analytical Techniques ◽  
X Ray Diffraction ◽  
Depth Of Penetration ◽  
X Ray ◽  
The Past ◽  
Transmission Electron ◽  
Scanning Electron

Studies of the nature of a surface, either metallic or nonmetallic, in the past, have been limited to the instrumentation available for these measurements. In the past, optical microscopy, replica transmission electron microscopy, electron or X-ray diffraction and optical or X-ray spectroscopy have provided the means of surface characterization. Actually, some of these techniques are not purely surface; the depth of penetration may be a few thousands of an inch. Within the last five years, instrumentation has been made available which now makes it practical for use to study the outer few 100A of layers and characterize it completely from a chemical, physical, and crystallographic standpoint. The scanning electron microscope (SEM) provides a means of viewing the surface of a material in situ to magnifications as high as 250,000X.

RNA polymerase: Preparation and structural analysis of helical polymers

1984 ◽  
Vol 42 ◽  
pp. 152-153
Author(s):  
E. Loren Buhle ◽  
Pamela Rew ◽  
Ueli Aebi
Keyword(s):  
Structural Analysis ◽  
Rna Polymerase ◽  
Molecular Level ◽  
X Ray Diffraction ◽  
Helical Polymers ◽  
X Ray ◽  
E Coli ◽  
The Past ◽  
Ordered Arrays ◽  
Low Ionic Strength

While DNA-dependent RNA polymerase represents one of the key enzymes involved in transcription and ultimately in gene expression in procaryotic and eucaryotic cells, little progress has been made towards elucidation of its 3-D structure at the molecular level over the past few years. This is mainly because to date no 3-D crystals suitable for X-ray diffraction analysis have been obtained with this rather large (MW ~500 kd) multi-subunit (α2ββ'ζ). As an alternative, we have been trying to form ordered arrays of RNA polymerase from E. coli suitable for structural analysis in the electron microscope combined with image processing. Here we report about helical polymers induced from holoenzyme (α2ββ'ζ) at low ionic strength with 5-7 mM MnCl2 (see Fig. 1a). The presence of the ζ-subunit (MW 86 kd) is required to form these polymers, since the core enzyme (α2ββ') does fail to assemble into such structures under these conditions.

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