Director: K. Horikawa, Secretary: Y. Iga
Jupiter was at stationary on Jul. 7, and turned to prograding motion. This month, we have received observations listed below. Bad weather of rainy season prevented us from observation. Especcially, no domestic observation was reported from Jul. 17 to 24, due to nationwide bad weather. Morita's image was forwarded by Mars section.
| Observer | Location | Telescope | Images/Drawings | |
|---|---|---|---|---|
| Adachi, Makoto | (Otsu, Japan) | 31cm Refl. | 1 | drawing |
| Akutsu, Tomio | (Philippines) | 28cm SCT | 5 | images |
| Einaga, Hideo | (Hyogo, Japan) | 25cm Refl. | 49 | images, 4 maps |
| Fukui, Hideto | (Shizuoka, Japan) | 25cm Refl. | 8 | images |
| Hatanaka, Akitoshi | (Mie, Japan) | 40cm Refl. | 4 | images |
| Hayashi, Toshio | (Kyoto, Japan) | 35cm SCT | 2 | images |
| Horikawa, Kuniaki | (Yokohama, Japan) | 16cm Refl. | 4 | drawings |
| Ikemura, Toshihiko | (Nagoya, Japan) | 31cm Refl. | 4 | images |
| Kazemoto, Akira | (Kyoto, Japan) | 31cm Refl. | 10 | images |
| Kumamori, Teruaki | (Osaka, Japan) | 60cm Refl. | 7 | images |
| Mishina, Toshiroh | (Yokohama, Japan) | 20cm Refl. | 20 | images |
| Miyazaki, Isao | (Okinawa, Japan) | 40cm Refl. | 4 | images |
| Morita, Yukio | (Hiroshima, Japan) | 25cm Refl. | 1 | image |
| Nakai, Kenji | (Hiroshima, Japan) | 25cm MCT | 1 | image |
| Narita, Hiroshi | (Kawasaki, Japan) | 20cm Refr. | 6 | drawings |
| Pellier, Christophe | (France) | 21cm MCT | 84 | images |
| Takimoto, Ikuo | (Kagawa, Japan) | 31cm Refl. | 44 | images |
| Tomita, Yasuaki | (Gunma, Japan) | 25cm Refl. | 4 | images |
| Vandebergh, Ralf | (Netherlands) | 25cm Refl. | 9 | images |
| Yoneyama, Seiichi | (Yokohama, Japan) | 20cm Refl. | 2 | images |
| Yunoki, Kenkichi | (Osaka, Japan) | 20cm Refl. | 25 | images |
At first, follow-up about collision of anticyclonic spots on NEBn is described. NEBn portholes WSZ and WSY encountered in late June was observed in July as single oval which was a little larger than before. Because, on Jul. 1 just after the encounter, tiny white spot was seen in following-south of the oval (Miyazaki's image), it seemed that two spots passed each other without merger. But tiny spot disappeared soon, and outstanding single oval was observed after then. Therefore, WSZ and WSY probably merged. Mishina stated from his own drift chart which plotted both ends of area coupled two spots that both spots must have merged, since length of the area had been contracting before encounter taken place in late June, but it was constant after then. He also pointed out that merged spot was prorading with the same rate as WSZ. Although, in the first half of July, it was suspected that two spots were orbiting each other from irregular shape of merged spot, it was not confirmed. In contrast to the view of simple merger, Rogers of BAA stated an interesting remark that WSZ and WSY might passed each other without merger (WSZ destroyed WSY) or WSY might merged with WSZ partially, inferring from a dwarf spot observed on Jul. 1.
In the southern hemisphere, an encounter of RS and BA was underway. After BA reached the f. end of RS late June, it passed through the south of RS in mid-July and was at p. end of RS at the end of July. In the meantime, BA itself remained unchanged concerning its oval shape and inner reddish ring structure, but faded STBn darkened preceding BA and many STBn jetstream spots were again visible.
On the other hand, development of dark streak in STrZ was observed preceding RS. Short streak about 20 deg. long was already seen for a few month extending from dark arch of RS to white spot Q at about II:80 deg. After Jun. 9, it extended beyond spot Q to grow into prominent dark streak about 70 deg. longat the end of June, when its p. end reached II:30 deg. However, when STBn revived preceding RS in July described above, dark streak rapidly faded away as if STBn had replaced it. Since faded sector of the streak roughly corresponded to darkened STBn, the streak faded away from RS toward p. direction. In Takimoto's image on Jul. 29, dark streak remained as inclined component between II:340 deg. and 30 deg., followed by darkened STBn. In July, dark arch of RS became faint after a long time, and orangish RS was distinct with dark core on its center. It was at II:113.5 deg. (Jul. 13, Einaga).
EZ was darkening through this apparition, and was characterized by conspicuous festoons and dark broad EB EZs was also yellowish with irregular dark filaments. Early July, a rift was formed on SEBn at around I:350 deg. The rift developed conspicuously and was connected to SEBZ when it passed north of RS mid-July, showing an aspect in which white cloud of SEBZ flowed into EZs through the rift. This reminds us of EZs white oval accompanie by SEBn rift observed in 1970s, but no oval was observed in EZs this time. Rogers of BAA pointed out that the rift was followed by long-lived dusky feature (South Equatorial Disturbance) and its formation was a part of the activity of SED. The rift was at about I:20 deg. late July, and was rapidly retrograding at about +1.5 deg./day. On the other hand, two dark masses were also seen in EZs at I:280-300 deg., but these were stationary.
(August 10, K. Horikawa)
(Translated on Nobember 27)