Question

What can you assume has happened if an electron moves to a higher energy level

Answer 1

The extra energy that the electron suddenly has had to
come from somewhere, so I can assume that one of
two things happened:

either 1).  A photon passed by and the electron absorbed it.

      or 2).  Somebody hooked up a battery or a generator in
such a way that the electron was bathed in a field of electrostatic
potential, and suddenly had the get-up-and-go to jump to a higher
energy level, and possibly even to leave its atom completely and
zip over to a neighbor atom.

Answer 2

EXPLANATION :

As per the question, the electron has jumped from ground state to higher energy level.

From Bohr's postulate, we know that electron can only move to higher excited state when the energy equivalent to excitation energy has been given to it. Otherwise, the electron can not move from ground state to the excited state.

Hence, it is obvious that the electron might have excited to higher energy level by providing sufficient energy from outside.

The external source might be light of suitable frequency or  any electric or thermal source.