The relation between magnetic field inclination and the apparent motion of penumbral grains
M Sobotka, J Jurčák, JSC Durán… - Astronomy & …, 2024 - aanda.org
M Sobotka, J Jurčák, JSC Durán, M García-Rivas
Astronomy & Astrophysics, 2024•aanda.orgContext. The bright heads of penumbral filaments, penumbral grains (PGs), show apparent
horizontal motions inward, toward the umbra, or outward, away from the umbra. Aims. We
aim to ascertain statistically whether the direction of PGs' apparent motion is related to the
inclination of the surrounding magnetic field. Methods. We used spectropolarimetric
observations of five sunspot penumbrae to compare magnetic inclinations inside PGs with
those in their surroundings. The data were taken by three observatories: the Hinode satellite …
horizontal motions inward, toward the umbra, or outward, away from the umbra. Aims. We
aim to ascertain statistically whether the direction of PGs' apparent motion is related to the
inclination of the surrounding magnetic field. Methods. We used spectropolarimetric
observations of five sunspot penumbrae to compare magnetic inclinations inside PGs with
those in their surroundings. The data were taken by three observatories: the Hinode satellite …
Context
The bright heads of penumbral filaments, penumbral grains (PGs), show apparent horizontal motions inward, toward the umbra, or outward, away from the umbra.
Aims
We aim to ascertain statistically whether the direction of PGs’ apparent motion is related to the inclination of the surrounding magnetic field.
Methods
We used spectropolarimetric observations of five sunspot penumbrae to compare magnetic inclinations inside PGs with those in their surroundings. The data were taken by three observatories: the Hinode satellite, the Swedish Solar Telescope, and the GREGOR solar telescope. The direction of PGs’ motion was determined by feature tracking. The atmospheric conditions in PGs and their surroundings, including magnetic field information, were retrieved by means of height-stratified spectropolarimetric inversions.
Results
Out of a sample of 444 inward-moving PGs and 269 outward-moving ones, we show that 43% of the inward-moving PGs have a magnetic inclination larger by 8° ±4° than the inclination in their surroundings and 51% of the outward-moving PGs have an inclination smaller by 13° ±7° than the surrounding one. The opposite relation of inclinations is observed in only one fifth of the inward- and outward-moving PGs.
Conclusions
Rising hot plasma in PGs surrounded by a less inclined magnetic field may adapt its trajectory to be more vertical, causing an inward apparent motion of PGs. Conversely, it may be dragged by a more horizontal surrounding magnetic field such that an outward apparent motion is observed.
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