Plot of Bessel function expression?

Questions
1

Hi, I am trying to make a plot of an expression involving Bessel functions:

J0J1Y0Y1[z_]:=BesselJ[0,z] BesselJ[1,z]+BesselY[0,z] BesselY[1,z];

Plot[N[J0J1Y0Y1[z],500],{z,0,10^15}]

but the result looks doubtful: it is not a smooth curve but a piecewise smooth curve resembling a sawtooth. Do I do anything wrong?

Leslaw

2

Try

Plot[N[J0J1Y0Y1[z],500],{z,0,10^15},WorkingPrecision->50]

The default is WorkingPrecision->MachinePrecision, which is about 16 on my computer (the variable $MachinePrecision).