It became clear in June that SEB activity following RS started previous month was a new SEB Revival. At first, it was suspected that it was minor mid-SEB outbreak, because SEB had just started fading. But it was considerably developing not only white clouds within SEB but also dark spots chain along SEBs. In this region, the characteristic as SEB Revival became apparent as a whole, since fading of SEB was making steady progress at all longitudes except for this region.

The activity of SEB Revival consists of three branches, that is, north branch, south branch, and central branch. The central branch which is an activity within SEB is very similar to mid-SEB outbreak. In this activity, a disturbed region inclined from preceding north to following south direction was prograding toward RS from source region close to STrD-2 (II:181.2 deg., Jun. 13, T. Akutsu). It seemed that white clouds still keep emerging from the initial source, and the region was filled up with delicate white spots and bluish materials, though large white ovals and dark columns which were typical in normal SEB Revival were not seen. The p. end of central branch reached RS around Jun. 13, and following half of RS bay revived late June. After that, it was arrested by RS, and no sign of expanding beyond RS was seen.

The southern branch retrograding along SEBs was very conspicuous. Dark material went beyond STrD-2 in late May and formed the initial retrograding dark spot (Leading Spot). After that, dark spots emerged one after another, and were rapidly retrograding on SEBs jetstream at +3.7 deg./day (9h58m14s in rotation period). Along with them, faded SEBs revived as dark thick component following the source region. Though in many cases, dark spots of southern branch fade RS when they reach it, STrD-1 was formed in STrZ on the way to RS in this apparition (II:321.7 deg., Jun. 29, Miyazaki). Because STrD is a structure that block SEBs jetstream and reconnect with STBn jetstream, it is expected that, when dark spots of southern branch reach STrD-1, they will make U-turn along its p. end and begin to prograde on STBn. This phenomenon is known as 'Circulating Current', which was confirmed by BAA observers in 1930s. Though there were several cases to suggest Circulating Current afterward, complete U-turn motion of dark spot has not been observed, even by Voyager. As of the end of June, the Leading Spot was going to reach STrD-1 soon. If U-turn motion of dark spot is actually observed, it will be the first observation for 70 years.

[Flash report] According to observations by Miyazaki in Okinawa, Leading Spot of southern branch reached STrD-1 in early July, and it was re-circulated onto STBn then started to prograde, as expected. Details will be described in next report.

Though northern branch was indistinct at first because SEBn was originally dark, possible p. end of the branch appeared in mid-June as conspicuous SEBn dark section, which prograded at -4 deg./day, darkening a sector between RS and p. end of it. It was at about II:340 deg. in late June, being passed by EZs large oval (SED-2).

SEB fading was still in progress at longitudes except for SEB Revival. SEBs almost disappeared between STrD-1 and RS, leaving several small dark spots preceding RS and following STrD-1. Though SEBZ was dusky yellowish when SEB Revival began, it had changed to white broad zone from the source region of Revival to RS.

RS was remarkable reddish oval with distinct outline and darker core as previous month. No change was observed, though central branch of SEB Revival reached and following half of RS bay was restored. It may fade rapidly after mid-August, when dark spots of southern branch were expected to reach RS. However, if dark spots make U-turns at STrD-1, it will remain conspicuous. It was at II:121.0 deg. (Jun. 27, Oyamada), somewhat retrograded from previous month. BA was prominent as reddish ring at II:310.7 deg. (Jun. 11, Yoneyama). It was followed by about 45 deg. long STB dark segment which shortened a little by fading its f. end. Activity of NTB ceased, and it was generally stable reddish and dark belt, without disturbed markings. But it was indistinct at tens of degrees in longitude preceding I:180 deg. It may indicate that NTB has started to fade again. The region north of NEBn was dusky with warm tint in general. It seems to be aftermath of NTBs outbreak.

(2) Saturn

Saturn was in the southwest sky after sunset, and was gradually decreasing altitude towards solar conjunction in August. This month, we have received observations listed below.

Yunoki reported some white spots this month too, though conditions for observation became much poorer, since it was the last stage of the apparition. Among these, white spot on Jun. 6 was comparatively clear at around III:200 deg. On the other hand, those on Jun. 9 and 10 showed much crumbling aspect, different from former examples. Therefore, it may be false markings that were noises emphasized under poor condition.

(July 11, K. Horikawa)

(Translated on December 3)

[Fig.1] Development of SEB Revival

The initial source of the Revival was indicated by bold short lines around center. Leftward and rightward arrows showes leading edge of northern branch and southern branch, respectively. Created from images by Isao Miyazaki, Christopher Go, Hideto Fukui, Toshihiko Ikemura, and Tiazano Olivetti.

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