Lundquist number — when resistivity stops being “simple”

17:40>> Yes, exactly. And what what you want to do is look at the ratio between these two. Okay. This is called a Lundquist number. >> Okay. >> Okay. And at low lungquist number, you're going to get um a place where resistivity dominates. And at high lungquist number, you get that frozen in. You only care about that first term. And these are the different typical Lquist numbers. So for lab plasmas or something inside a tamac, you're looking at 10 the 3 to 10 the 10. But something like the solar corona where you have massive scales, you're looking at like 10 the 12, 10 the 14, right? So you have this massive scale difference that you want your physics to work at. >> And this is always tough.

18:21>> I get the the the point is the map that we're trying to fill in is really large. >> It's really large. You're going from 10 3 to 10 the 13 10 orders of magnitude, right? You're going 10 orders of magnitude and you're trying to say that the same physics works for everything, >> right? And the the point is that obviously that's >> obviously that's not the case. Especially if you watched our hypersonics episode where we talked about how uh supersonic and hypersonic >> uh which is much smaller scales. >> Yeah. >> It doesn't >> it doesn't work because then you got to you got to worry about random stuff. Right. >> Right. And that's what ends up happening here. So before um Nuno came along.

19:04>> Okay.