Peculiar interactions between granules and network bright points in the solar photosphere
Abstract
The magnetic elements which form the photospheric network, outside active regions, are visible as tiny bright features, smaller than 0.5", called network bright points (NBPs). 15 to 20% of them elongate during their life, when they are squeezed between two expanding granules, or simply pushed by an expanding or a moving granule. Some statistical properties are reported. The most interesting property is that their size and brightness increases simultaneously indicating a strong increase of radiative flux as they grow. They can become as large as 1000 km x 400 km and as bright as 1.25 the brightness of the average photosphere. As theoretical models predict that magnetic flux tubes of size larger than 300 km should be darker than the mean photosphere, our observations suggest that during the elongation, some mechanical energy should contribute in the heating of the tubes. This additional energy may heat some features in the upper photosphere like chromospheric spicules and transition zone jets or microflares, whose production rates and lifetimes are about the same as those of elongation of NBPS. Elongated NBPs are shaked by the turbulent granules, similarly to the normal NBPs and thus should contribute to the heating of the solar corona too.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- July 1994
- Bibcode:
- 1994A&A...287..982R
- Keywords:
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- SUN: GRANULATION;
- SUN: MAGNETIC FIELDS