Specifically when it comes to forbidden relationships during niddah and/or the following "clean" days, what constitutes an act of sexual intercourse punishable with Karet?
Presumably, a violation of the Harchakot would not constitute Halachic sexual intercourse, but where is the line between Harchakot and explicitly prohibited intercourse?
My understanding is that, with regard to other forbidden relationships, the Halachically enforceable definition of sexual intercourse extends to other forms of touching that fall under Derech Chiba, but again, regarding Niddah, would seemingly be a violation of the Harchakot rather than a punishable act of sex.
