japanese university circles/clubs 日本の大学サークル

Japanese schools from junior high to uni tend to have after school activities called bukatsu 部活 - clubs.
In Universities, they can be called circles - サークル or clubs.  The difference between these two are circles tend to have more freedom in them. When you go into Uni you may not have the same schedules as everyone, so within the circle you may choose the fitting time amongst your selves. With clubs, Teachers tend to be associated within the group, so it may be more strict in the timing and attendance.
furthermore clubs tend to have more members e.g football club - サッカー部
unlike circles such as film research group　映画研究会
However, in my opinion, there isn't too much difference in them. I see it as a two different way of calling a group name.
Around the time when Uni gets going, the circles and clubs look for new members especially the first years to join the clubs because, one to keep it going and two to increase popularity and three of course, to make more friends and have more fun. They tend to go around the campus to find a place that most student will be found and yell out if anyone would like to join the circles.

日本のサークルと部活の違いは、サークルにはもっと自由感があるとみられます。時間が成り立たないとき、授業の時間が他の人と違う時、どうしてもちゃんとした時間にはいけない時にサークルが一番なのです。自分たちで時間の予定を決められるとの事です。部活には担任の教師がつく事が多いため、時間と予定には厳しいのです。
サッカー部とか野球部は人数は多い、そして週に５／６／７日間はやっている。
サークルは週に１回２回のところもあるし、ある週に５回とか他の週は２回とか適当なところもあります。しかも人数が少ないところも多い。
春になるとサークルは新入生を求め、人からめだつところ、大人数の学生がいるところに行き入部者を求めます。