Motions in solar magnetic tubes

✍ Scribed by R. G. Giovanelli; G. M. Nikolsky; J. W. Harvey

• Publisher: Springer
• Year: 1978
• Tongue: English
• Weight: 809 KB
• Volume: 59
• Category: Article
• ISSN: 0038-0938
• DOI: 10.1007/bf00154931

✦ Synopsis

The method of has been used with a variety of spectral lines to study oscillating longitudinal gas velocities inside solar magnetic elements. Oscillations have been found inside all elements observed, the amplitudes increasing with height from typically +0.27kms -I in Fe 15166 ~ (a line of low origin) to + 0.75 km s-1 in Ha. Simultaneous observations in pairs of lines show that a given disturbance occurs later with height, so that disturbances propagate outwards. The period is typically 5 rain in all lines originating near or below Mg bx, but is about 3 min in Ha.

Simultaneous observations of the gas velocities within the magnetic element and in the immediatelysurrounding non-magnetic region often show closely similar behaviour; the amplitudes are almost the same, and the mean phase difference is effectively zero, but there is a large individual variability of the order of + 0.5 rain. These results imply that either there is a strong local interaction between outside and inside magnetic tubes, or the disturbances are excited by a common mechanism.

The velocities observed inside and immediately outside magnetic elements have the same pattern and amplitudes as those far away from magnetic elements. In particular, the disturbance velocities never exceed about 0.1 of the velocity of sound, suggesting the absence of large-amplitude shock waves anywhere in the magnetic or non-magnetic solar atmosphere between the levels of formation of Fe 1 5166 ~ and Ha.