Sunday, August 13, 2006

Very Cool Solar Images

Well, hot ones, anyway, from the TRACE (Transition Region and Coronal Explorer) instruments. You can actually even build a scale model of the spacecraft directly from these plans!

This one shows the sun at 171 Angstroms

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Coronal Mass Ejections

The Sun's Magnetic Heartbeat (1)The Sun's Magnetic Heartbeat (2)

A composite of the Optical (red/orange) and Magnetic Maps of the sun with each image taken roughly one year apart showing the roughly 11-year cycle from one period of maximum solar activity to the next.

Looking through the Sun's Atmosphere
Looking through the sun's atmosphere:

The Sun's magnetic field connects the different domains in its atmosphere. The bottom panel in this composite shows the visible surface, at about 10,000º F, with dark sunspots where the field is strong and coherent, and faint bright kernels where the field is about half as strong and broken up. Around them the seething motions of the convection form tiny cells (about the size of Texas) called granules.

The second image shows the emission from the chromosphere, some 4,000 miles above the surface. It has a temperature of approximately 18,000º F. The sunspots remain dark, but the smaller magnetic concentrations now emit much more brightly in the light of ionized calcium ions (Ca II K).

The third image shows the Sun in light of neutral hydrogen gas. Because hydrogen is the most abundant element in the Sun, its atoms contribute over a larger range of heights than images taken in the light of other elements at a comparable temperature. It is for that reason that the image reveals segments of the magnetic field with a three-dimensional character, rather than appearing as a thin slice through a fixed level in the atmosphere. Here the fields can be seen to lean away from the strong field in the sunspot in the center.

The top image shows the corona, with emission from gas at a million degrees. The atmosphere is completely transparent at these wavelengths, so we see the field at a range of heights, thus revealing fans and curtains of emission from hot, ionized captured within the magnetic field.

Images: Swedish Solar Observatory on La Palma, Spain (lower three), and with the Transition Region and Coronal Explorer (top).

The dynamic solar outer Atmosphere.The dynamic solar outer Atmosphere.The dynamic solar outer Atmosphere.

The Dynamic Outer Atmosphere of the Sun.

Nothing is static on the Sun, least of all the corona. These three images of a magnetically active region seen at the edge of the Sun, span only two and a half hours, yet look completely different. Each of the loop-like structures, outlining the magnetic field by the glowing of million-degree gas, changes in position, in density, and in temperature, resulting in a beautiful yet extremely complex atmosphere.

Image: Transition Region and Coronal Explorer (in light of ionized iron; Fe IX/X).

The Solar Surface and Below

This high-resolution image reveals the multitude of convective cells, each about the size of Texas, that cover most of the solar surface. In these cells, hot, buoyant gas from the interior rises to the surface where it expands and cools. The cooler, denser gas slides towards the edges and eventually sinks down in the cooler, darker, network of the lanes. The pattern of convection changes wherever there is strong magnetic field. Where the magnetic field is concentrated in fairly strong, but relatively small clusters, we see it reside in the dark lanes, the downdraft regions of the convection. Many of these clusters of magnetic field form bright specks.

Inset: Computer simulations not only manage to recreate the surface appearance of the Sun, they also show us what probably happens below the surface. The sides and the reflection of the bottom of the computed cube show the patterns in the convection down to a few hundred miles below the surface. Gradually, the cellular network that we see at the surface is replaced by narrow, turbulent downdrafts embedded in slow, broad flows where relatively warm gas wells up to the surface.

Image: Swedish Solar Observatory, La Palma, Spain; inset: Ake Nordlund, Nordita (Copenhagen).

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