For what it's worth, by using a quick-n-dirty sparker circuit simulation from circuitJS, at different simulation time step times I get the following peak discharge currents:
Time step size (ns) | Peak current (A) |
---|---|
3.3 | 1383 |
10.0 | 636 |
100.0 | 76 |
This is done through Options > Other Options > Time Step Size (s)
Although real-life conditions will be far from those of this idealized simulation, I think this shows in practice that sampling potentially very short signals like spark discharges with a high-bandwidth oscilloscope is important.