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Science Highlight February 2010: First view at the genuine Lyman-alpha profile
/ en / topics / topic_201002 /

First view at the genuine Lyman-α profile

The hydrogen Lyman-α line outshines all other emission lines. It is the prime vehicle for radiative energy transport in the solar atmosphere. Blinded by its brightness, the <SUMER instrument did not dare to look at it. Now, after 12 years of its operation, the SUMER team found a trick to observe it with 'twinkling eyes'. Such high-resolution observations - not hampered by geocoronal absorption - have never been completed before and produced a surprising new result.

Different from most other emission lines, which are symmetric and have a Gaussian shape, Lyman lines are self-reversed because of <opacity effects. As an unexpected result, we found that the strongly self-reversed spectral line profile of Lyman-α is asymmetric so that the peak on the blue side of the central reversal is stronger, oppositely to all the other self-reversed lines of the Lyman series. This has been used to study:

  • the Lyman profile and the downflows
  • (click on image for details)

Our results show that the magnetically structured atmosphere plays a dominating role in the line profile formation and indicates the presence of a persistent downflow at the footpoints of closed loops. We claim that this is the manifestation of a fundamental mass transport process, which Foukal way back in 1978 introduced as 'coronal convection'.

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