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TOPIC: The Sun
Blobrana


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RE: The Sun
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Blobrana


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Title: On the seismic age of the Sun
Authors: G. Houdek, D.O. Gough

We use low-degree acoustic modes obtained by the BiSON to estimate the main-sequence age t_\odot of the Sun. The calibration is accomplished by linearising the deviations from a standard solar model the seismic frequencies of which are close to those of the Sun. Formally, we obtain the preliminary value t_\odot=4.68 ±0.02 Gy, coupled with an initial heavy-element abundance Z=0.0169 ±0.0005. The quoted standard errors, which are not independent, are upper bounds implied under the assumption that the standard errors in the observed frequencies are independent.

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Blobrana


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Last week in Boulder, Colorado, scientists converged on the "Living With A Star" workshop to share the latest research in solar physics. At one point, nearly 200 participants sat slack-jawed as they watched a new movie recorded by Japan's Hinode spacecraft showing a sunspot emerging from the depths of the sun. The newborn spot resembled nothing less than a swimming planet-sized trilobite.



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Blobrana


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New measurements provide the strongest evidence yet for wriggling magnetic waves that may explain why the solar corona is a good 200 times hotter than the surface of the sun: regular pulsations in the speed of charged, high-energy gas or plasma streaming from the sun combined with matching magnetic fields.
The findings point to magnetic field ripples known as Alfvén waves whipping plasma back and forth, releasing heat, according to a report published online by Science. Although the waves seem to be too tiny to transfer the energy needed to fully heat the corona, researchers say improved measurements may reveal that the waves are larger than they appear.

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Title: Vector spectropolarimetry of dark-cored penumbral filaments with Hinode
Authors: L.R. Bellot Rubio, S. Tsuneta, K. Ichimoto, Y. Katsukawa, B.W. Lites, S. Nagata, T. Shimizu, R.A. Shine, Y. Suematsu, T.D. Tarbell, A.M. Title, J.C. del Toro Iniesta

We present spectropolarimetric measurements of dark-cored penumbral filaments taken with Hinode at a resolution of 0.3". Our observations demonstrate that dark-cored filaments are more prominent in polarised light than in continuum intensity. Far from disk centre, the Stokes profiles emerging from these structures are very asymmetric and show evidence for magnetic fields of different inclinations along the line of sight, together with strong Evershed flows of at least 6-7 km/s. In sunspots closer to disk centre, dark-cored penumbral filaments exhibit regular Stokes profiles with little asymmetries due to the vanishing line-of-sight component of the horizontal Evershed flow. An inversion of the observed spectra indicates that the magnetic field is weaker and more inclined in the dark cores as compared with the surrounding bright structures. This is compatible with the idea that dark-cored filaments are the manifestation of flux tubes carrying hot Evershed flows.

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Blobrana


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The Sun Loses its Spots
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While sidewalks crackle in the summer heat, NASA scientists are keeping a close eye on the sun. It is almost spotless, a sign that the Sun may have reached solar minimum. Scientists are now watching for the first spot of the new solar cycle to appear.
The 11 year long solar cycle is marked by two extremes, solar minimum and solar maximum. Solar minimum is the period of least solar activity in the solar cycle of the sun. During this time sunspot and solar flare activity diminishes, and often does not occur for days at a time.
When spots begin to appear on the sun once again, scientists know that the sun is heading into a new season of extreme solar activity. At the cycles peak, solar maximum, the sun is continually peppered with spots, solar flares erupt, and the sun hurls billion-ton clouds of electrified gas into space.
Solar maximum is often compared to the hurricane season here on Earth. Violent solar events, like flares and coronal mass ejections, are the hurricanes of space weather. These solar storms are capable of wreaking havoc with satellites, power grids, and radio communication, including the Global Positioning System.
NOAAs Space Environment centre, Boulder CO, forecasts that the next solar cycle should begin in March 2008 and should peak in late 2011 or mid 2012.

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Blobrana


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RE: The Sun
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Geomagnetic Field:
Solar X-rays: 		Status
Status
watch tv

Meteor count

-5 hours -4 hours -3 hours -2 hours -1 hour

 

 Real-time data for today


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Blobrana


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The chromosphere
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Sound waves escaping the sun's interior create fountains of hot gas that shape and power a thin region of the sun's atmosphere which appears as a ruby red "ring of fire" around the moon during a total solar eclipse, according to research funded by the National Science Foundation (NSF) and NASA.
The results are presented today at the American Astronomical Society's Solar Physics Division meeting in Hawaii.
This region, called the chromosphere because of its colour, is largely responsible for the deep ultraviolet radiation that bathes the Earth, producing the atmosphere's ozone layer.
It also has the strongest solar connection to climate variability.

"The sun's interior vibrates with the peal of millions of bells, but the bells are all on the inside of the building.  We've been able to show how the sound can escape the building and travel a long way using the magnetic field as a guide" - Scott McIntosh of the Southwest Research Institute in Boulder, Colorado, lead member of the research team.

The new result also helps explain a mystery that's existed since the middle of the last century -- why the sun's chromosphere (and the corona above) is much hotter than the visible surface of the star.

 "It's getting warmer as you move away from the fire instead of cooler, certainly not what you would expect" - Scott McIntosh.

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Title: The Magnetic Field of the Solar Corona from Pulsar Observations
Authors: S. M. Ord, S. Johnston, J. Sarkissian
(version v2)

We present a novel experiment with the capacity to independently measure both the electron density and the magnetic field of the solar corona. We achieve this through measurement of the excess Faraday rotation due to propagation of the polarised emission from a number of pulsars through the magnetic field of the solar corona. This method yields independent measures of the integrated electron density, via dispersion of the pulsed signal and the magnetic field, via the amount of Faraday rotation. In principle this allows the determination of the integrated magnetic field through the solar corona along many lines of sight without any assumptions regarding the electron density distribution. We present a detection of an increase in the rotation measure of the pulsar J1801-2304 of approximately 160
ad at an elongation of 0.95^\circ from the centre of the solar disk. This corresponds to a lower limit of the magnetic field strength along this line of sight of > 393\mu\mathrm{G}. The lack of precision in the integrated electron density measurement restricts this result to a limit, but application of coronal plasma models can further constrain this to approximately 20mG, along a path passing 2.5 solar radii from the solar limb. Which is consistent with predictions obtained using extensions to the Source Surface models published by Wilcox Solar Observatory

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Blobrana


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Heliosphere
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Our solar system is hurtling through space while angled nearly perpendicular to the plane of the Milky Way, new computer models suggest.

"It's almost like we're sailing through the galaxy sideways" -  astrophysicist  Merav Opher, study team leader, George Mason University in Virginia.

The findings, detailed in the May 11 issue of the journal Science, suggest the magnetic field in the galactic environment surrounding our solar system is pitched at a sharp angle and not oriented parallel to the plane of the Milky Way as previously thought.

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This image shows the locations of Voyagers 1 and 2. Voyager 1 is travelling a lot and has crossed into the heliosheath, the region where interstellar gas and solar wind start to mix.

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