The magnetic field inside the solenoid is

The magnetic field inside a long solenoid is given by the formula:

$B = \mu_0 n I$

where $n$ is the number of turns per unit length ($n = \dfrac{N}{L}$)$and I$ is the current flowing through the solenoid.

From the formula, it is clear that the magnetic field $B$ is directly proportional to the current $I$ ($B \propto I$).

It is directly proportional to the total number of turns $N$ and inversely proportional to the length $L$.

Thus, the magnetic field is directly proportional to the current.

Answer: directly proportional to current