Because the gyro radius scales as 1/B, a stronger magnetic field tightens the orbit into a smaller, faster circle with gyrofrequency omega_c = q * B / m. This tightening is exact only for stated charge, mass, speed, and field under the uniform-field assumption. Real plasmas add field gradients, collisions, pitch-angle spread, relativistic corrections, and measurement uncertainty.
At fixed charge, mass, and speed, stronger magnetic field means smaller radius. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.
highlighted = computed this step
The weaker field has the wider orbit
At field 2 tesla, the checked gyro radius is 6 meters.
B=2T⇒r=6m
Doubling the field tightens the orbit
At field 4 tesla with the same charge, speed, and mass, the radius drops to 3 meters.