Why is the aurora only visible at high latitudes?

Where/ when would be a good place and time to see the aurora?|||Because it involves the electrons from the sun entering the atmosphere through the indentation in the magnetic field at the poles and interacting with the dry air which is non-conductive. To get further south, the electron flux has to be higher (sun spots), or the magnetic field weaker or the weather colder to dry out the air. Usually the last one is the greatest variable as to how far south they can be seen in US