Report no.5: NEB activity

Jupiter in 2023/24, Report no.5: Increasing activity of the NEB

(Mid-NEB plume and NTropZ anticyclonic dark spots)

by Shinji Mizumoto (ALPO-Japan)


[Note by John Rogers:] 

As noted in our Reports nos.1 & 4, the NEB has continued to grow more active during 2023-24, particularly since a vigorous rift system appeared, beginning with the brilliant mid-NEB plume on 2023 Oct.8 [Report no.1].  The rift system has become extensive, and dark NEB material has been spreading north towards the NTropZ at many longitudes.

Shinji Mizumoto has tracked this rift system and dark spots produced from it, and the present report is his account of it.  The edited text is copied below, and the report in PPT-PDF form is attached here:

2023-24_NEB plume & NTrZ ADS_v8-final

This, and an extensive set of maps of the NEB, are also published on the ALPO-Japan web site:

The JPEG figure below shows JunoCam images of a particularly interesting sector of the NEB at PJ55, PJ56, and PJ57, taken from our reports on those three perijoves.  It includes the long-lived WS-Z; ADS#1 (fading from dark grey to pale reddish); the original white plume (Oct.15 only); a very long faded barge; and a new dark barge.  Magenta arrows indicate the approximate course of the retrograding NEBn jet.


ALPO-Japan summary report:  2023-24 / Mid-NEB Plume & NTrZ ADSs

by Shinji Mizumoto 

Guidance (Definitions)

⚫ Plume: White cloud eruption phenomenon.

⚫ Rift/Rift Activity: Ruptures created by white clouds being stretched east-west and north-south by wind velocity gradients in the relevant latitude region, and such activity.

⚫ (NTrZ) ADS: Anticyclonic Dark Spot

⚫ NEB Expansion/NEB Revival/NEB Outbreak: In the past, they occurred at 3-5 year intervals.


Plume Eruption

October 8, 2023: Mid-NEB plume erupted on p-side of WS-Z (obs. by I. Miyazaki).

L3=250 deg, L2=219 deg.

The plume was a progressive and intermittent eruption of white clouds.

White clouds emerging from the plume were stretched in east-west and north-south directions by wind velocity gradients, forming a rift.

This phenomenon continued for nearly six months until the end of the apparition.

Mean DL3 = -1.62 deg/day.


ADS#1 Formation

October 12, 2023: White clouds supplied by the plume reached the NTrZ through rift activity, forming the ring-shaped NTrZ ADS#1 (obs. by K. Suzuki, F. Reali).   L3=246 deg, L2=214 deg.

Late October 2023: ADS#1 weakened.

Early November 2023: The ADS became surrounded by a white cloud, fed by the plume.

Late January 2024: The dark spot gradually faded and had disappeared, apparently changing to only white spot.

Similar phenomena were also observed with ADS#3.


ADS#5 Formation

January 22, 2024: ADS#5 was formed (obs. by A. Wesley). L3=70 deg, L2=11 deg.

Initially, it showed a rapid change in latitude, reaching nearly +20 deg, but about one month after its formation, it settled at around +18 to +19 deg (See slide 12).

Among the five ADSs formed, it was the largest and its existence was confirmed over a period of 82 days until the end of the apparition.


The progressing plume intermittently erupted.

White clouds supplied by the plume formed the ADS five times due to rift activity.

[They were numbered #1,2,3,5,6.  #4 was not an ADS and was not thought to have a direct relationship with plume-rift activity.]

For drift rates, see slide 11.  For latitudes, see slide 12.

ADS#1 and ADS#5 initially moved very rapidly (DL3 = -0.80, -1.11 deg/day) and reached a latitude of very nearly +20 deg.

But later they settled at around +18 to +19 deg, as did the other ADSs.


Relationship between Plume, Rift & NEB Expansion

Following the plume’s passage, the region between the NEB and NTrZ became notably active and unstable, as indicated by pronounced unevenness along the northern edge of the NEB.

The northern edge of the NEB extended and thickened northward.

As the plume progressed, the expansion of the NEB extended in the direction of decreasing longitude.




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