2016-17, Report no.9: Interactions of ovals in high northern latitudes, 2017 March-April
There is currently much interest in the behaviour of features in the high northern latitudes, as these are shown in spectacular detail in the JunoCam images; close pairs of white ovals in the N4 and N5 domains were noticed in the Juno PJ-5 images and in images by Chris Go and others. Are they merging? Here I report on 3 such pairs, from the best amateur images and the JUPOS charts. In summary:
1) A trio of ovals in the N4 domain (51-55ºN), named a,b,c: a overtook b then possibly merged with c, reversing its drift on March 17; but then b converged on a in turn, and they were nearly in contact on April 21, so they may now be merging, or changing places again. [Addendum: Further v-hi-res images (shown in a new figure, below) showed that ovals a and b merged on April 30—May 1, and there was just a single oval thereafter.]
2) A pair of ovals in the N4 domain: one (d) caught up the other (e) and they apparently merged on April 8-10, at 54ºN.
3) A pair of ovals in the N5 domain (~62ºN): they probably merged on April 11.
Given the chaotic nature of these domain, such events may well be common, but this is an exceptional opportunity to study them in detail.
The full text is here as a PDF: Report-on-N4-N5-WOs-merging(2017april).pdf
and the figures are here in a ZIP file: Report-on-N4-N5-WOs-merging_2017april.zip
Set of maps: