Halves of points of an odd degree hyperelliptic curve in its jacobian

Let $f(x)$ be a degree $(2g+1)$ monic polynomial with coefficients in an algebraically closed field $K$ with $char(K)\mathrm{\ne }2$ and without repeated roots. Let $\mathfrak{R}\subset K$ be the $(2g+1)$-element set of roots of $f(x)$. Let $\mathcal{C}:y^2=f(x)$ be an odd degree genus $g$ hyperelliptic curve over $K$. Let $J$ be the jacobian of $\mathcal{C}$ and $J[2]\subset J(K)$ the (sub)group of its points of order dividing $2$. We identify $\mathcal{C}$ with the image of its canonical embedding into $J$ (the infinite point of $\mathcal{C}$ goes to the identity element of $J$). Let $P=(a,b)\in $\mathcal{C}$(K)\subset J(K)$and$M_{1/2,P}\subset J(K)$thesetofhalvesof$P$in$J(K)$,whichis$J[2]$-torsor. In a previous work we established an explicit bijection between $M_{1\mathrm{/}2,P}$ and the set of collections of square roots $${\mathfrak{R}}_{1\mathrm{/}2,P}:=\{\mathfrak{r}:\mathfrak{R}\to K\mid \mathfrak{r}(\alpha {)}^2=a-\alpha \mathrm{\forall }\alpha \in \mathfrak{R};\prod _{\alpha \in \mathfrak{R}}\mathfrak{r}(\alpha )=-b\}\mathrm{.}$$ The aim of this paper is to describe the induced action of $J[2]$ on ${\mathfrak{R}}_{1\mathrm{/}2,P}$ (i.e., how signs of square roots $\mathfrak{r}(\alpha )=\sqrt{a-\alpha }$ should change).