What is the purpose of the .yjp directory ? It appears to contain Idea logs (IntellijIdea13-nnnn.log) and on my current machine seems to start in September 2013 and so far has over 330Mbyte - not a tremendous amount these days but as I was looking around for disc space to delete it did look like a candidate. On linux it's directly under the user's home/username directory.
Is there any value at all in the contents ? I suppose that they may be useful information about a particular session but after the event they seem a complete waste of space. So can you confirm that they can be deleted without any problems ? I would ensure Idea isn't running at the time, of course.