Torsor über Kurve/Stark semistabil/Affinitätskriterium/Fakt/en

Let $C$ denote a smooth projective curve over an algebraically closed field $K$ and let $𝒮$ be a strongly semistable vector bundle over $C$ together with a cohomology class  $c\in H^1(C,𝒮)$. 

Then the torsor $T(c)$ is an affine scheme if and only if  ${\mathrm{deg}}_{}^{}\left(𝒮\right)<0$  and  $c\ne 0$  ($F^e(c)\ne 0$ for all $e$ in positive characteristic).