Mid-SEB outbreak emerged last month was developing as expected. According to Einaga's image on Jan. 23, there were four elongate light areas separated by conspicuous bluish columns following II:280 deg. It was interesting aspect just like a train looking from the side (Einaga's image). These light areas formed oblique light band, in which leading spot had the lowest latitude and following one became higher, similar to previous instances. Later, these light areas were broken up into smaller white spots, and according to images on Jan. 28 by Yunoki and Ikemura, those was transformed into light band filled with numerous tiny spots. Leading edge of mid-SEB outbreak moved with about -2.0 deg./day, which is typical value of this activity. On the other hand, initial source of mid-SEB outbreak also shifted forward about 10 deg. in a month from beginning of activity, and it was located about II:340 deg. at the end of January. Following mid-SEB outbreak, SEBs edge was seen wavy and disturbed, which suggested that activity of mid-SEB outbreak affected SEBs jetstream.

Large scale activity of white clouds in SEB was also seen following RS, extending to about II:200 deg. Following RS, an active region of white clouds generally exists in the longitude range of 30-60 deg., called post-GRS disturbance, which is considered as another phenomenon from mid-SEB outbreak, though both show similar outbreak of white spots inside SEB. Since whole length of light region described above exceeded 80 deg. in longitude, which was too long for post-GRS disturbance in taking the previous instances into consideration, it was suspected that it was another mid-SEB outbreak taken place during solar conjunction. But it would be difficult to confirm whether it is true or not, because three months have already passed since solar conjunction, and conditions are very poor. It might have been possible to distinguish both activities, if it had been detected in early stage of outbreak. By the way, elongated light portion about 20 deg. long was also seen in SEB about II:250 deg., but it is seemed to be static.

RS was almost stationary at II:107.6 deg. (Jan. 14, Horikawa's CMT). Though it was seen as reddish oval at the beginning of the month, images taken late January showed that dark bluish arch emerged along its south edge. It is seemed that this was affected by wavy SEBs edge following mid-SEB outbreak, and it implies that there is an activity corresponding to south branch in SEB Disturbance (SEB Revival) apart from main part of mid-SEB outbreak. BA was elongate oval at II:201.1 deg. (Jan. 8, Einaga). Since its interior was dusky and low contrast, it was difficult to see under poor condition. STB remnant which was observed as bluish filamentary feature following RS, prograded to about II:25 deg. this apparition, and another isolated dark spot was seen around II:340 deg. Along NEBn edge, there were four prominent white spots (portholes), one of which at II:301.5 deg. (Jan. 8, Einaga) was long-lived spot survived since 1997, called 'Z'.

(2) Saturn

Saturn was at opposition on Jan. 27 close to M44. Though seeing was very poor, it was somewhat better than the case of Jupiter, because celestial declination of Saturn was much higher. This month, we have received observations listed below. Images by Parker and Tyler were forwarded by Minami, the Director of Mars Section.

Although Saturn's surface had been very quiet with few spots this apparition, remarkable spot appeared late January. It was detected on Jan. 24, when Yunoki, Parker, and Pellier obtained images of the spot. According to Parker's image, it was white spot at about III:170 deg. breaking north component of double STB, and was smaller than width of Cassini's division. Since the spot had high contrast though small, it was easily seen even under somewhat poor condition. Therefore, a lot of images was obtained by many observers by the end of January. Yunoki's images on Jan. 28 using filters showed the spot in blue, red, and infrared images, and blue was highest contrast. The spot will be able to track for the time being. It is expected that a sufficient number of longitude measurement will be made for rotation period of the spot.

The opposition effect of Saturn's ring which attracted attention last apparition, was again observed this apparition. Yunoki and Yoneyama examined luminosity of ring and body using images on Jan. 28 and before, and indicated that ring B was evidently brighter than EZ in images on Jan. 28, though both were almost the same luminosity or EZ was a little lighter until mid January.

(February 13, K. Horikawa)

(Translated on June 2)

[Fig.1] Development of mid-SEB outbreak

[Fig.2] White spot on Saturn

Return to OAA Top