  This paper investigates the use of $\ell^1$ regularization for solving
hyperbolic conservation laws based on high order discontinuous Galerkin (DG)
approximations. We first use the polynomial annihilation method to construct a
high order edge sensor which enables us to flag troubled elements. The DG
approximation is enhanced in these troubled regions by activating $\ell^1$
regularization to promote sparsity in the corresponding jump function of the
numerical solution. The resulting $\ell^1$ optimization problem is efficiently
implemented using the alternating direction method of multipliers. By enacting
$\ell^1$ regularization only in troubled cells, our method remains accurate and
efficient, as no additional regularization or expensive iterative procedures
are needed in smooth regions. We present results for the inviscid Burgers'
equation as well as a nonlinear system of conservation laws using a nodal
collocation-type DG method as a solver.
