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Topic: Solar radius

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In this photograph, the solar poles are distinguished by a relative absence of supergranulation network, and a much darker tone than the central portions of the disk.
This image of the solar corona was acquired on 23 December 1996 by the LASCO instrument on the SOHO spacecraft.
This sequence of images of the the Sun in ultraviolet light was taken by the Solar and Heliospheric Observatory (SOHO) spacecraft on February 11, 1996 from its unique vantage point at the "L1" gravity neutral point 1 million miles sunward from the Earth.
www.solarviews.com /eng/sun.htm   (1246 words)

  Solar wind - Wikipedia, the free encyclopedia
In the solar system, the composition of the solar wind is identical to the Sun's corona: 73% ionized hydrogen and 25% ionized helium with the remainder as trace impurities.
Outside the plane of the ecliptic the solar wind is steady and rapid, at speeds between 600-800 km/s; this is called the fast solar wind and it is known to emanate from solar coronal holes.
The solar wind blows a "bubble" in the interstellar medium (the rarefied hydrogen and helium gas that permeates the galaxy).
en.wikipedia.org /wiki/Solar_wind   (1688 words)

 [No title]
The solar corona material is massive in size (they can occupy up to a quarter of the solar limb), and frequently accompanied by the remnants of an eruptive prominence, and less often by a strong solar flare.
Beyond that critical radius, the solar wind particles move in a straight line with constant velocity to a good approximation, but because the Sun is rotating and with it the footprints of the magnetic field lines, the magnetic field takes up a spiral structure known as an Archimedean spiral.
The earlier spots in the solar cycle appear at higher latitudes and the later spots in the solar cycle emerge nearer to the equator.
solar-center.stanford.edu /gloss.html   (2724 words)

 [26.02] Variability of the Solar Radius   (Site not responding. Last check: 2007-11-07)
Although the variability of this solar output is definitely established, the detailed dependence of the rate of energy output on the level of solar magnetic activity has not yet been measured with enough continuity and precision to establish the correlation throughout the full solar cycle.
However, studies of the solar radius variation have reported contradictory results in the form of both correlations and anticorrelations between the solar radius and, for example, the cycle of sunspot numbers.
Two definitions of the solar radius are used: the longest reduced record beginning in 1975 is derived from the fit of a circle to the isophote having an intensity equal to 40%\ of the central intensity and more recently we have developed a definition based on intensity fits within 16 sectors around the solar circumference.
www.aas.org /publications/baas/v35n3/spd2003/183.htm   (342 words)

 [No title]   (Site not responding. Last check: 2007-11-07)
The solar limb is potentially a sharp spatial reference with which we can hope to detect the effect of solar oscillations (both p-mode and g-mode); the gravitational quadrupole moment (or the solar oblateness); and changes in the solar radius (e.g.
Global solar changes on decadal to interglacial time scales with small amplitudes and their effect on climate will only be understood if we combine our knowledge of the physics of the terrestrial climate system (as a detector) with astrophysical models which might account for such small, but important variations.
Solar variations at this level are caused by physical changes in both the photosphere and in the interior, these data can provide a unique view of solar cycle changes that occur in the deep within the Sun.
www-rcf.usc.edu /~arjones/APT/sec-poster.html   (2815 words)

 On-Line Glossary of Solar-Terrestrial Terms
Of the white-light CORONA (that is, the corona seen by the eye at a total solar (ECLIPSE), that portion which is caused by sunlight scattered or reflected by solid particles (dust) in inter- planetary space.
Solar flares that occur repetitively in the same ACTIVE REGION, with essentially the same position and with a common pattern of development.
Of the white-light CORONA (that is, the corona seen by the eye at a total solar eclipse), that portion which is caused by sunlight scattered by electrons in the hot outer atmosphere of the sun.
www.sec.noaa.gov /info/glossary.html   (3279 words)

 The Astrophysics Spectator: Table: Characteristic of the Sun
, the mean radius, the solar constant, and the value of the astronomical unit, are used to derive other quantities in the table.
The obliquity to the ecliptic is the tilt of the Sun's rotation axis relative to the ecliptic.
Despite its name, the solar constant is not constant; the flux averaged over a year can vary by 0.04% over the course of the 11-year solar cycle, and at solar maximum, sun spots can cause 0.25% changes in the solar flux over the one-month rotation period of the Sun.
www.astrophysicsspectator.com /background/table/solar/Sun.html   (531 words)

 NGDC/STP - On-Line Glossary of Solar-Terrestrial Terms
A daytime layer of the earth's IONOSPHERE approximately 50 to 90 km in altitude.
Of the white-light CORONA (that is, the corona seen by the eye at a total solar eclipse), that portion which is caused by sunlight scattered by electrons in the hot outer atmosphere of the sun.
This flare is the basis for the forecast of geomagstorm, cosmic storm and/or protons in the earth's vicinity.
www.ngdc.noaa.gov /stp/GLOSSARY/glossary.html   (2480 words)

The transient phenomena occurring in the solar atmosphere can be grouped together under the term solar activity: sunspots and faculae occur in the photosphere; flares and plages belong to the chromosphere; and prominences and coronal structures develop in the corona.
Recent observations have indicated that the magnetic solar cycle is a coherent phenomenon throughout the solar surface.
A solar flare is actually the result of an intensely hot electromagnetic explosion in the corona and produces vast quantities of x-rays which brighten the chromospheric gases.
www.columbia.edu /~ah297/un-esa/sun/sun-chapter1.html   (2929 words)

 Geofísica Internacional   (Site not responding. Last check: 2007-11-07)
The total solar irradiance for the Maunder minimum (1645-1715) is obtained using the solar rotation rate calculated from the observations of sunspots recorded at the Observatoire de Paris from 1660-1719.
The reduction of the solar rotation rate was the cause of the reduced solar activity in the period known as the Maunder minimum.
The apparent solar radius change is difficult to interpret in terms of other physical parameters, and results obtained using it are probably best taken as qualitative rather than quantitative.
www.unam.mx /serv_hem/revistas/fisica/1996/02/mendoza.html   (3815 words)

 Solar Sails for Polar Observation
Solar sails are comprised of a large reflective surface, support structure and payload.
The equation of motion for a solar sail orbiting the earth's center is shown in Equation 3 [2].
In this equation, r is the vector from the earth to the sail, n is the unit normal to the solar sail m is the earth gravitational constant and l is the unit vector along the sun-line.
ccar.colorado.edu /asen5050/projects/projects_2000/silver   (1895 words)

 Encyclopedia: List of solar system objects by radius   (Site not responding. Last check: 2007-11-07)
In the case of the Sun, Jupiter, and Saturn, the volumetric mean radius is used.
For mostly spherical objects (oblate) such as planets and large planetoids, the equatorial radius is used.
The ordering is not the same as the order of a list of solar system objects by mass because some objects are denser than others.
www.nationmaster.com /encyclopedia/List-of-solar-system-objects-by-radius   (304 words)

 Sun Article, Sun Information   (Site not responding. Last check: 2007-11-07)
tons of TNT per second) which escapes from the surface of the Sun in the form of electromagnetic radiation and neutrinos (and to a smaller extent as the kinetic and thermal energy of solar wind plasma and as the energy in the Sun's magnetic field).
For some time it was thought that the number of neutrinos produced by thenuclear reactions in the Sun was only one third of the number predicted by theory, a result that was termed the solar neutrino problem.
To obtain an uninterrupted view of the Sun, the EuropeanSpace Agency and NASA cooperatively launched the Solar and Heliospheric Observatory (SOHO) on December 2, 1995.
www.anoca.org /solar/surface/sun.html   (711 words)

 Introduction   (Site not responding. Last check: 2007-11-07)
One final quantity remains to be measured in order to calculate the solar radius and distance: the linear velocity of the surface of the sun.
The ratio of linear velocity to angular velocity (calculated from the sunspots) yields the solar radius.
The ratio of radius to angular radius (measured in the previous section) yields the solar distance.
www.bea.st /text/jrlab1/node10.html   (124 words)

The sources of agitation causing the solar waves that we observe are processes in the larger convective region.
The solar model equations must be solved numerically, and the solutions are usually tables describing solar chemical composition, density, luminosity, mass, pressure and temperature at different depths in the Sun.
At a solar radius of 0.713xR* and upwards to near the solar surface, the temperature is low enough that convection is the dominant mechanism for transporting energy.
soi.stanford.edu /results/heliowhat.html   (1489 words)

 Solar Physics at UCLA: Gallery   (Site not responding. Last check: 2007-11-07)
A fraction of this variability arises from the increased area of cool gas associated with sunspots, which decreases irradiance; but on average the blocking effect of sunspots is more than offset by the increased emission from photospheric faculae and other effects of magnetic activity (although the precise contributions of these opposing effects remain poorly constrained).
Each point is the annual average of the difference between the apparent radius derived from the observations and the ephemeris radius.
The solar wind carries off angular momentum from the Sun and the coupling between the outer and inner parts of the heliosphere might produce effects that are evident in the photosphere and chromosphere.
www.astro.ucla.edu /~solar/gallery.html   (488 words)

 Is the sun shrinking?
He further suggested that the last solar radius maximum occurred in 1911, and that the half-amplitude of variation (half the change in radius between the minimum and maximum of the cycle) is approximately 0.2 second of arc per century or 0.02% of the solar radius.
From different locations, observers had reported on the duration of the totality during the solar eclipses, and from this data Sofia and his colleagues found that the solar radius in 1925 was 0.5 second of arc or 375 kilometres (233 miles) larger than in 1979.
And they also reported that although they had shown the solar radius decreased by 0.5 second of arc between 1925 and 1979, the sun’s size in 1925 was not significantly different from that in 1715.
www.answersingenesis.org /docs/3852.asp   (2240 words)

 Solar Physics Glossary
The layer of the solar atmosphere that is located above the photosphere and beneath the transition region and the corona.
A temporary disturbed area in the solar photosphere that appears dark because it is cooler than the surrounding areas.
In a solar loop structure, it is the distance from the axis of the loop to the center of the "semi-circle" that the loop forms.
hesperia.gsfc.nasa.gov /sftheory/glossary.htm   (1999 words)

 Solar Models   (Site not responding. Last check: 2007-11-07)
The depth of the convective zone is approximately proportional to the contemporary solar radius.
The solar age is measured in units of 10
The figure shows the computed values for the standard solar model of the central temperature (solid line), pressure (dot-dashed line), density (dashed line), and hydrogen mass fraction (dotted line).
www.sns.ias.edu /~jnb/SNviewgraphs/BP2000/bp00.html   (313 words)

 ESA - Space Science - Solar Orbiter
Solar Orbiter is intended to brave the fierce heat and carry its telescopes to just one-fifth of Earth's distance from the Sun, where sunlight will be 25 times more intense than we feel it.
One package consists of detectors for observing particles and events in the immediate vicinity of the spacecraft: the charged particles and magnetic fields of the solar wind, radio, and magnetic waves in the solar wind, energetic charged particles and neutrons flung out by the Sun, and neutral atoms and dust grains drifting in interplanetary space.
Solar power would be used whereby 45 solar radii would be the closest possible orbit due to the heat limits on the solar panels.
www.esa.int /science/solarorbiter   (1052 words)

 Solar Innovations - Greenhouses - Victorian Conservatories - Skylights - Sunroom Additions - Folding Glass Walls - ...
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Solar Innovations’ goal is to help you create a timeless structure that is the perfect blend of design and purpose for your residential or commercial setting.
www.solarinnovations.com   (940 words)

 The Interior of the Sun
Thus, for example, the radius of the Sun is about 109 times that of the Earth, which implies that the volume of the Sun would hold approximately 1.3 million Earths (since the volume goes as the cube of the radius).
It is a region in which the change in temperature with increasing radius is so rapid that the Sun becomes unstable to convection (rapid up and down motion of large packets of gas), much as the Earth's atmosphere becomes convectively unstable on a hot Summer day and produces thunderstorms.
In helioseismology, one attempts to learn about the properties of the Sun by studying the propagation of waves in its body (which, for example, cause small oscillations of the surface that are observable) in a manner similar to geologists learning about the interior of the Earth by studying seismic waves.
csep10.phys.utk.edu /astr162/lect/sun/interior.html   (468 words)

 NASA - Solar Eclipse Photography   (Site not responding. Last check: 2007-11-07)
Solar eclipses may be easily photographed provided that basic eye safety precautions are followed.
With one solar radius of corona on either side, an eclipse view during totality will cover 9.2 mm.ĂŠAdding a 2x tele-converter will produce a 1000 mm focal length, which doubles the Sun's size to 9.2 mm.
A mylar or glass solar filter must be used on the lens throughout the partial phases for both photography and safe viewing.
sunearth.gsfc.nasa.gov /eclipse/SEhelp/SEphoto.html   (1738 words)

 Solar radius change between 1925 and 1979
By analysing numerous reports, from different locations, on the duration of totality of the solar eclipses on 24 January 1925, and on 26 February 1979, we have found that the solar radius at the earlier date was 0.5 arc s, or 375 km larger than at the later date.
The correction to the standard solar radius found for each eclipse was different when different subsets of the observations were used (for example, edge of path of totality timings compared with central timings), suggesting the existence of systematic inaccuracies in our knowledge of the lunar figure.
However, the differences between the corrections for both eclipses were very similar for all subsets considered, indicating that changes of the solar size may be reliably inferred despite the existence of the lunar figure errors, as long as the proper consideration is made of the distribution of the observations.
www.nature.com /cgi-taf/DynaPage.taf?file=/nature/journal/v304/n5926/abs/304522a0.html   (258 words)

 standard solar models, helioseismology and solar models, and solar neutrinos
Abstract: We show that standard solar models are in good agreement with the helioseismologically determined sound speed and density as a function of solar radius, the depth of the convective zone, and the surface helium abundance, as long as those models do not incorporate the most recent heavy element abundance determinations.
For solar neutrino and for helioseismological applications, we present present-epoch numerical tabulations of characteristics of the standard solar model as a function of solar radius, including the principal physical and composition variables, sound speeds, and neutrino fluxes.
In addition, improvements in the input data for solar interior models are described for nuclear reaction rates, the solar luminosity, the solar age, heavy element abundances, radiative opacities, helium and metal diffusion rates, and neutrino interaction cross sections.
www.sns.ias.edu /~jnb/Papers/Preprints/solarmodels.html   (3129 words)

 Is There Evidence for a Young Earth?
Furthermore, records of solar eclipses infer that this rapid shrinkage has been going on for at least the past 400 years (a).
Their results imply a constant solar radius, within a measurement error of +/- 37 kilometers (km) over the whole 6 years.
If the solar radius were in fact shrinking by 5 feet per hour, that translates into 37 km in about 2.8 years.
www.tim-thompson.com /resp8.html   (838 words)

 Sun's Seismic Radius
The comparison of these frequencies with the corresponding frequencies of the standard solar models suggests that the apparent photospheric solar radius (695.99 Mm) used to calibrate the models should be reduced by approximately 0.3 Mm.
The measurements of the photospheric radius obtained during the past 25 yr from various groups using different instrument types and methods were reviewed by Laclare et al.
In solar models, this profile is set by the calibration radius, which is usually chosen where the local temperature is equal to the Sun's effective temperature and is assumed to be equal to the photospheric radius, 695.99 Mm.
ecf.hq.eso.org /~ralbrech/sepdec97apjl/975381.html   (3034 words)

 Schoolforge News-Journal - The Sun
The Solar atmosphere is permeated with magnetic fields that are generated in or just below the convection zone and emerge through the photosphere as loops.
Solar flares produce the full range of plasma temperatures from 100000K(10 to the fourth) to 100000000K(10 to the 7th).
During a cycle, the magnetic polarity of all the western-most spots in the northern solar hemisphere is the same, and is opposite to the "leader" spots in the southern hemisphere.
opensourceschools.org /article.php?story=20030421050001687   (1743 words)

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