the solar wind deflects charged particles.

Propagation Models
------------------

Interstellar propagation can be implemented via the well known stationary, cylindrically symmetric, two-zone diffusion model identical to the setup used for [$\overline{\text{D}}~$]{}in Ibarra & Wild [@ibarra2013] with the exception of obvious replacements including the [$^3\overline{\text{He}}~$]{}cross-sections, charge, and atomic mass. We assume a diffusion zone of radius 20 kpc and variable height $L$ with a thin, Galactic disk of half-height $h=100$ pc containing the interstellar medium. The model is parametrized by an additional three components: an energy dependent diffusion constant $K(T)=K_0 ~ \beta ~\mathcal{R}^\delta$ with spectral index $\delta$, $\beta=v/c$ and rigidity $\mathcal{R}\equiv p(\text{GeV})/Z$ where Z is proton number, and $V_c$, which characterizes Galactic wind convection. It is then possible to write the propagation in terms of the following transport equation: $$\begin{aligned}
\begin{aligned}
\label{eq:transport}
\begin{split}
0=\frac{\partial n}{\partial t}=\nabla \cdot (K(T,\vec{r})~\nabla n) -\nabla\cdot (V_c ~\text{sign}(z)~\vec{k}~n) \\ -
2~h~\delta(z)~\Gamma_{\text{int}}~n + Q_{\overline{\text{He}}}(T,\vec{r}).
\end{split}
\end{aligned}\end{aligned}$$

Here $n(T,\vec{r})$ is the antihelium number density and $\Gamma_{\mathrm{int}}$ is the interaction rate for antihelium within the ISM, described thoroughly in § \[subsec:cross-sections\].

The four parameters $L, K_0, \delta,$ and $V_c$ are then varied over the space consistent with the measured ratio of boron to carbon, with values producing the MIN/MED/MAX flux 