Smallest building blocks of the Sun’s magnetic field revealed

Wednesday, November 10, 2010

WASHINGTON - Scientists from the Max Planck Institute for Solar System Research (MPS) in Germany have now for the first time uncovered and characterized the smallest building blocks of the Sun’s magnetic field.

In these tiny regions of only a few hundred kilometers in diameter the strength of the magnetic field exceeds the Earth’s magnetic field strength by a factor of approximately 3,000.

Underneath the bright, hot regions the plasma bubbles to the surface. In the dark, cooler rims it recedes again. Scientists refer to these patterns as granulation.

Since the kinetic energy of these flows of hot plasma can transform into magnetic energy, the currents within the Sun are closely linked to the star’s magnetic properties. One expression of this magnetic nature are the dark sunspots that can even exceed the Earth in size.

However, the Sun’s magnetic field also consists of much smaller structures. Tiny, bright points between the granules are an indicator of these fields. Within the bright points strong magnetic fields squeeze the bubbling plasma outward so that it is possible to look deeper within the Sun’s interior. Due to the higher temperatures there, these bright points appear brighter than their surroundings.

Even though several solar telescopes are able to visualize these bright points, their physical properties such as the magnetic field strength could not be identified until now.

Only the solar observatory Sunrise built and operated by an international team headed by the MPS unites the crucial properties: a high spatial resolution of about 100 kilometers and precise instrumentation for measuring physical parameters such as the magnetic field.

“Sunrise’s instrumentation reached a resolution of 100 kilometers”, explained Dr. Sami K. Solanki, Managing Director of the MPS.

Because of this high resolution, it was possible to characterize the bright points within the photosphere for the first time.

These hot magnetic structures are the building blocks of the solar magnetic field. In the photosphere, their magnetic field lines lie perpendicular to the Sun’s surface-like tubes. Apart from that, the scientists were able to determine the brightness of the bright points for the first time-also in the UV.

“With this information it is possible to estimate the contribution of the bright points to the total radiation variability of the Sun”, said Tino Riethmuller from MPS.

This knowledge is therefore crucial for climate research, since it holds the key to discerning the manmade part of global warming from the Sun’s influences. The variation of the brightness within the photosphere, that Sunrise makes visible like no other mission before, also shows the temperature profile at the Sun’s surface.

The findings have now been published in twelve articles in a special edition of the Astrophysical Journal Letters. (ANI)

Filed under: Science and Technology

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