Oscillations and waves in a sunspot |
| |
| Authors: | R G Giovanelli |
| |
| Institution: | (1) CSIRO Division of Physics, National Standards Laboratory, 2008 Sydney, Australia |
| |
| Abstract: | Observations have been made in H of the vertical velocity distribution in a sunspot. Over the umbra the pattern consists of structures of scale-size 2–3 . The velocity distribution undergoes oscillations with a period of about 165 s and typical amplitude ±3 km s–1, but the pattern breaks down after one or two cycles because the period of oscillation varies typically by ±20 s from place to place. Transverse waves develop in the outer 0.1 of the umbral radius and propagate outwards with a velocity of about 20 km s–1, becoming gradually invisible by or before the outer penumbral boundary; the amplitude is about ±1 km s–1 at the umbra-penumbra border.The penumbral waves are believed to be basically of the Alfvén type, with   3 × 10–8 g cm–3. The umbral oscillations presumably represent gravity waves. In both cases the fluxes are inadequate by two orders of magnitude to account for the sunspot energy deficit. |
| |
| Keywords: | |
| 本文献已被 SpringerLink 等数据库收录！ |
|
