How to distinguish the direction of magnetic field around the electrified straight wire

How to distinguish the direction of magnetic field around the electrified straight wire

Judging by the right-hand spiral rule, the thumb direction refers to the current direction, the four fingers point to the magnetic field direction, and there is no fixed N / S pole

What is usually used to determine the direction of the magnetic field around an electrified straight wire?

The result of the formula is the cross product operation of two vectors (IDL * r). In mathematics, the cross product of two vectors (L, R) is a = L * r, the size of a is the area of the parallelogram line composed of LR, the direction is from the minimum angle of fingers to R, and the direction of thumb is the tangent direction of the point B