Hi, I've seen a video of the US navy test firing a rail gun and in the video there is a plasma plume that follows the projectile. I am unsure of what exactly is causing the plasma plume... specifically: Is it the electrical energy passing through the rails that ignites the air and causes the plasma? Is it leftover magnetic charge on the projectile that ignites the air as it moves and causes the plasma plume? I'm guessing it is not merely due to the velocity of the projectile but is mach 7 enough to cause just the friction of the projectile against the atmosphere to cause a plasma plume? And also, for how long would one expect there to be a plasma plume following the projectile?