There's not a fixed number of auroras on Earth at any given time. Auroras are dynamic displays of light caused by charged particles from the sun interacting with Earth's atmosphere. This means:

* They appear in different locations: Auroras are most commonly seen near the Earth's magnetic poles, but their exact location can shift based on solar activity.

* They're constantly changing: Auroras can appear, disappear, and change shape and intensity rapidly.

So, there's no single answer to "how many auroras are on Earth". The best way to think about it is as a constantly changing, natural light show that can be observed in many different locations!