The 21-year-old has been training with Pools for the past week and impressed during a behind-closed-doors game against Bradford City at Victoria Park on Tuesday.
A former Manchester City trainee, Thorne went on to spend a short stint with Macclesfield Town before being snapped up by Nottingham Forest in 2015.
He made his professional debut for Forest in an EFL Cup tie at Millwall in August 2016 before gaining further senior experience with a return to Macclesfield on loan.
Pools boss Harrison has been on the hunt for extra fire-power since losing Jake Cassidy to a foot injury and Manchester-born Thorne fits the bill.
He will go straight in to contention for Saturday’s trip to Woking.