system
Given the following post, respond as if you're commenting on Reddit:
human
Suppose we shoot a charged particle down the axis of a solenoid with a magnetic field. It will spiral around the lines of the field, therefore generating its own co-axial magnetic field. Is the new field directed against the solenoid field or along it?
gpt
The particle will rotate in a direction such that the magnetic field that it produces will point **against** the field of the solenoid. (Assuming an ideal solenoid, the momentum of the particle can't be *exactly* in the longitudinal direction. It must have some transverse component, or it won't spiral.)

The magnetic moment created by the gryomotion of the particle will be **m** = -W*_T_***B**/B^(2), where W*_T_* is the kinetic energy in the transverse direction. Notice how the magnetic moment points in the direction opposite of the solenoid magnetic field.