Since alpha particle is positively charge so the current will be in direction in which alpha particle will be projected .
mathematically:
→F=q(→V×→B)
(^−j)=q(→V×^k)
(^−j)=q(^i×^k)
∴^V=^i,eastwardorrightside
Also, by applying flaming left hand rule .
Forefinger will point in upward direction.
And thumb should point in direction in which deflection will takes place ie.south ward so in this case middle finger will point in right direction ie. East
hence alpha particle should be projected in east or right side