We have analyzed 209 data of daily sunspot observations made during the period of January 3 to December 31 In 2001 and presented the daily relative sunspot numbers. During the year of 2001, our annual average of relative sunspot numbers is found to be 92.2. This number is obtained from the averaged daily number of 8.4 spot groups, in which there are about 57.5 distinct spots observed. According to the appearance of 370 spot groups, our analysis shows that the mean life time of spot groups is about 4 day and 20.4 hours.

• 심경진(한국천문연구원) | K. J. SIM
• 문용재(한국천문연구원) | Y.-J. MOON
• 이청우(한국천문연구원) | C. W. LEE
• 장비호(한국천문연구원) | B. H. CHANG
• 김연한(한국천문연구원) | Y. H. KIM
• 김정훈(한국천문연구원) | J. H. KIM