For all radio transmissions above 30 MHz (which are not reflected by the ionosphere) there is a possibility of meteor reflection of the radio signal.[56] Meteors leave a trail of ionised particles and electrons as they pass through the upper atmosphere (a process called ablation) which reflect transmission radio waves which would usually flow into space.[57] These reflected waves are from transmitters which are below the horizon of the received meteor reflection. In Europe this means the brief scattered wave may carry a foreign voice which can interfere with radio receivers. Meteor reflected radio waves last between 0.05 seconds and 1 second, depending on the size of the meteor.[58]