Statistics of active and idle packets

Hello! I want to know more details about some of the argus/ra fields. In
particular, I am interested in sintpktact and sintpktidl (along with the
similar fields for the destination and jitters). What distinguishes a
packet as active or idle? I have found that the active source jitter
(sjitact) is rarely filled (http/https and ssh traffic).
I am also curious about the distribution fields such as sintdist and
dintdist. Is there a good example of how to use these fields?
I am using Argus v3.0.8.1. Thanks much!
-- Daniel