On NTB, emergence of spots moving with North Temperate Current-C was observed after long quiet period of recent years. This activity is an outbreak on NTBs jetstream, which is the fastest on the planet, and the belt is disturbed by rapidly prograding spots. Though continuous activity of North Temperate Current-C had been observed in the 1990s, outbreak accompanied by white spot which moves more rapidly has been the first time in 17 years since 1990. The first observation of the outbreak was made by Carvalho on Mar. 27, when two bright spots were seen on faded NTB. In Pujic's image on Mar. 29, dark spot newly appeared following the spot, as well as tiny white spot at somewhat north. Of the two white spots, preceding one (LS1) was at I:37.7 deg. (Mar. 29, Pujic), and the other (LS2) was at I:97.5 deg. (Mar. 30, Olivetti). Initial drift rate of LS1 was -4.1 deg./day (9h47m45s in rotation period), which is a value typical as Leading spot of the outbreak. NTB had faded away more than 4 years since late 2002. It is expected that outbreak will revive NTB within several months by forming a chain of dark spots following Leading spot, and moving with rotation period of 9h48-49m which is a little slower than Leading spot. Though System II is generally applied to markings of higher latitude than Equatorial region, observer should use System I for markings on NTBs, since these move very rapidly.

Both South Tropical Disturbance (STrD-1 and STrD-2) were marked by dark columns at p. end. STrD-1 was at II:342.9 deg. (Mar. 30, Olivetti), and STrD-2 was at 206.9 deg. (Mar. 20, Kumamori). Main part of STrD-1 was observed as a plateau on SEBs, and expanded to a little less than 30 deg. There is little change in relative position of BA and STrD-1, because of near prograding speed. STrD-2 was about 15 deg. in width, shorter than STrD-1, and had a triangular shape as a whole. STBn was dark preceding both STrDs, suggesting existence of Circulating Current from SEBs to STBn. But it could not be confirmed, as no dark markings were observed on SEBs this apparition. On the other hand, though no distinct feature was seen at f. end of STrD, Pujic's images on Mar. 16 showed faint festoon-like markings from STB to SEBs at f. end of STrD-2, implying weak Circulating Current. This month, STrD-2 showed a definite prograding motion at -0.4 deg./day, while STrD-1 decelerated to -0.2 deg./day. It seems that drift rates are not uniform.

Remarkably darkened EZs was dusky at all longitude, and filled with bluish filaments and delicate features. Disturbed region as the main part of darkening was between I:200 and 300 deg., and white cloud in SEBZ flowed out into EZs from two rifts at preceding part of the region, where large ovals were formed (I:220.3 deg. and I:249.7 deg., both Mar. 18, Go). Following the large ovals, EZs was brownish and merged with SEB like a belt.

RS was strongly reddish definite oval with dark outline and core at II:116.7 deg. (Mar. 20, Fukui). Its surrounding zone was remarkably white. BA was doughnut-like oval at II:345.6 deg. (Mar. 30, Olivetti). It was very reddish as well as RS, but peripheral white region became narrower than before. Activity of white clouds in SEB following RS was not seen at all. The whole SEB may fade in the near future, since the belt became featureless without dark spots and irregular shadings, though there were a lot of reddish barges within SEBs. In northern hemisphere, NEBn edge began to retreat, and portholes in NEBn including WSZ at II:78.5 deg. (Mar. 12, Go) were being exposed to NTrZ.

(2) Saturn

Saturn was retrograding in Leo, being in good period for observation. This month, we have received observations listed below. Go and Olivetti joined us from this month as well as Jupiter.

Two white spots were observed in SEB this month, too. On Mar. 1, Yunoki and Ikemura found a small white spot in SEBZ at about III:170 deg. Yunoki succeeded in detecting the spot on the next day, Mar. 2, and he pointed out that similar spot was seen in his image on Feb. 21. But these may not be identical, because it seems that the spot has prograding motion when images on Mar. 1 and 2 are compared. The other was observed on Mar. 28 by Yunoki and Vandebergh as a white spot lying a little south of mid-SEB at III:345 deg. Olivetti's image on Mar. 30 also showed a small white spot in SEBZ at III:330 deg. If these are identical spot, it is prograding at fast drift rate of about -7.5 deg./day.

As the tilt of the ring is decreasing, light NTrZ came to appear from the north of ring A. According to Go's high resolution image, northern hemisphere contained faint two belts, NTB and probable NNTB, and narrow light NNTZ was seen at north of them.

(April 12, K. Horikawa)

(Translated on August 24)

[Fig.1] Leading spots of NTBs jetstream outbreak and South Tropical Disturbance

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