Jupiter’s high northern latitudes: patterns and dynamics of the N3 to N6 domains

–John Rogers , Gianluigi Adamoli, Michel Jacquesson, Marco Vedovato, & Hans-Jörg Mettig

(JUPOS team and British Astronomical Association)                         (2017 Sep.27)

Summary 

Here we present an overview of three domains in high northern latitudes of Jupiter, named N3, N4 and N5, covering latitudes 43 to 64ºN, with limited information in N6 up to 68ºN.  We review their organisation and dynamics as shown by previous spacecraft, and then compare this with analysis of ground-based images in the JUPOS project.  This analysis from the JUPOS database covers the years 2010-2016, with more limited data back to 1999.  Analysis of the drift rates and latitudes of visible spots gives speed-vs-latitude relations for these spots (Zonal Drift Profiles, ZDP), which are close to the Zonal Wind Profile (ZWP) derived from spacecraft imagery and, for most of each domain, to the Zonal Slow Current (ZSC) derived from historical ground-based spot tracking.  (The ZSC is the mean speed of the major spots in the domain, numbered accordingly; e.g. for the N3 domain, N3TC, originally N.N.N. Temperate Current.)

The N3, N4 and N5 domains all have the standard structure, the equatorward part being cyclonic and containing folded filamentary regions (FFRs), and the poleward part being anticyclonic and containing anticyclonic white ovals (AWOs) and smaller ovals. However, the two parts are not well separated in these domains, so there is some intermingling of cyclonic and anticyclonic structures, with chaotic interactions between them.  It is likely that these large FFRs move with the ZSC, as well as the smaller spots that we track.  We find no evidence for higher-order structures or phenomena in these domains.  However, they do have individual characteristics. 

The N3 domain is particularly narrow, with no retrograde jet. At times it has had numerous small AWOs, but recently spots are rather sparse though distinct, all moving with the N3TC. 

The N4 domain is particularly broad and is almost filled with structures, esp. FFRs which are the broadest in any of these domains (and are the location of the most frequent lightning flashes on the planet).  It has long-lived AWOs but they can be found at any latitude within the domain, shifting unpredictably, so their drift rates are very variable.  Sometimes they pass each other without substantial interaction; sometimes they merge. All the FFRs probably move with the N4TC, as do the low-latitude ovals.  There may be no retrograde jet except within individual FFR circulations.

The N5 domain contains some FFRs and ovals.  It commonly contains 1 or 2 large AWOs, larger than any others in these domains, which are probably long-lived but cannot be tracked long-term because of their extreme and variable speeds.  The organisation is similar to the N4 domain, with most features moving with a previously undefined retrograding ‘N5TC’, and high-latitude AWOs moving much faster.

The N6 domain approximately coincides with a visibly bland zone.  We have tracked a very few features in this domain, all of them rapidly-prograding white ovals under the influence of the N6 or N7 jets.  The northernmost was at 67.3ºN and drifted at -91 deg/mth, close to the N7 jet.

We have detected occasional small dark spots on the N3 jet, and one ephemeral one on the N4 jet.  Otherwise, we do not detect the peak speeds of the N4, N5, N6 and N7 jets.

The drift rates of AWOs in the N4 and N5 domains, as in the N2, S3 and S4 domains, are very variable and show sudden unpredictable alternations between slow and fast rates.  Circumstantial evidence suggests that some of these speed changes are caused by interactions with FFRs: specifically, that high-latitude AWOs naturally drift fast, but can be blocked by encounters with FFRs moving with the ZSC. 

THE FULL ARTICLE IS HERE:   Report_N3-N4-N5-domains_text_final.pdf

THE FIGURES (MINATURE COPIES) ARE HERE:   Report_N3-N4-N5_Minifigs.pdf

THE FULL-SIZE FIGURES AND APPENDICES ARE HERE:   Report-N3-N4-N5_Figs&Appxs.zip