What happens when a Storm sorcerer uses Tempestuous Magic to fly 10 feet straight up?

Question

Storm sorcerers have the Tempestuous Magic feature (XGtE, p. 52) at 1st level:

Starting at 1st level, you can use a bonus action on your turn to cause whirling gusts of elemental air to briefly surround you, immediately before or after you cast a spell of 1st level or higher. Doing so allows you to fly up to 10 feet without provoking opportunity attacks.

What happens when you move straight up ten feet?

• Do you stay up there until your next turn and fall or slowly descend?
• Do you immediately fall or descend?
• Can you use your next bonus action to climb another 10 feet by casting another spell?

Answer 1

After your movement, you fall to the ground

The Tempestuous Magic feature doesn't specify that you "hover" or otherwise remain at the position that you moved to, so if you move into the air, you'd immediately fall to the ground once you completed your movement.

If you were to move directly upwards 10 feet, you might be subject to 1d6 falling damage as a consequence of falling 10 feet. If this causes you actual damage (i.e. you are not immune in some way) you fall prone.