𝔖 Bobbio Scriptorium
✦   LIBER   ✦

The nature of the sunspot phenomenon

✍ Scribed by E. N. Parker

Book ID
104649941
Publisher
Springer
Year
1975
Tongue
English
Weight
563 KB
Volume
40
Category
Article
ISSN
0038-0938

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✦ Synopsis

It is pointed out that the equilibrium configuration of a sunspot magnetic field, confined to the cool umbra by the pressure of the surrounding photospheric gas, is unstable to the familiar hydromagnetic exchange instability. The characteristic time for dissolution of the sunspot is of the order of one hour.

In view of the observed long life of individual sunspots, it is important to understand why the instability does not develop. We review several theoretical possibilities, suggesting, tentatively, that the spot might be stabilized by a suitable redistribution of the cooling in the umbra. In particular, if the cooling extends to greater depth in an elongated portion of the sunspot, the magnetic pressure on the boundary is reduced there, tending to reduce the elongation.

It is important to decide whether there is in fact any truth to this idea, because there are many features of sunspot behavior that are still not understood.

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The nature of the sunspot phenomenon
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✍ E. N. Parker πŸ“‚ Article πŸ“… 1974 πŸ› Springer 🌐 English βš– 781 KB

The properties of Alfv6n waves in a vertical column of field are pointed out as a guide in treating the complicated problem of overstability. There are internal Alfv6n waves of arbitrary form propagating along the magnetic field, without disturbing the fluid outside the column. There are also surfac