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

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

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