Hα oscillations in sunspot umbrae

✍ Scribed by Gary L. Phillis

• Publisher: Springer
• Year: 1975
• Tongue: English
• Weight: 689 KB
• Volume: 41
• Category: Article
• ISSN: 0038-0938
• DOI: 10.1007/bf00152957

✦ Synopsis

Direct measurement of intensity and photographic subtractions of simultaneous Doppler filtergrams at Hc~zk0.3 ,~ in a time-lapse sequence of McMath 11482 has shown velocity oscillations in sunspot umbrae. These oscillations exhibit the following characteristics: (a) A characteristic oscillation frequency for each umbra, with the periods ranging from 145:k10s to 180zkl0s. (b) A duration of at least 8 cycles. (c) A Doppler shift of 10 km s z. (d) An oscillating element size of 3" or less. (e) A visibility to a radius vector of about 0.9.