[Reply to “On magnetospheric research”] On the number of ringlets in the Saturnian rings



G. L. Tyler claims (Eos, January 29, 1985, p. 41) that there are 22 ringlets in the Saturnian ring and criticizes me be-cause I have given numbers which are or-ders of magnitude larger. The controversy is largely semantic.

It is theoretically expected that the rings should have a “fine structure” [Alfvén, 1984; Alfvén and Cech, 1984] from which we can derive important processes at the formation of the rings and, in a wider context, gain essential information about the evolutionary history of the solar system. A recent study demonstrates that a detailed analysis of the C ring, as well as of the A and B rings, makes it possible to reconstruct certain events which probably occurred 4–5 billion years ago with an accuracy of 1% [Alfvén et al., 1985]. In some regions, e.g., the Holberg minimum, this fine structure is superimposed on a continuous background so that the opacity does not go down to zero; in others, e.g., the Cassini division, it does. Still, similar cosmogonically relevant information can be extracted from both regions. For example, in both regions there is a double peak, which can very well be called a double ringlet.