Answer
The electric field is directed upward.
Work Step by Step
We can find the magnitude of the electric field:
$q~E = Mg$
$E = \frac{Mg}{q}$
$E = \frac{(6.64\times 10^{-27}~kg)(9.8~m/s^2)}{(2)(1.6\times 10^{-19}~C)}$
$E = 2.03\times 10^{-7}~N/C$
To balance the gravitational force, the electrostatic force on the particle must be directed upward. Since the alpha particle has a positive charge, the electric field must be directed upward.
