[show abstract][hide abstract] ABSTRACT: We have built a small proportional tube air shower array on the surface above the Soudan 2 proton decay detector in Soudan, Minnesota, USA. This array, in coincidence with the underground detector, allows simultaneous surface and underground observations of high energy cosmic ray showers. These observations, still in their initial stages, may eventually be able to provide information about the composition of cosmic ray primaries in the ``knee`` region of the energy spectrum. 4 refs.
[show abstract][hide abstract] ABSTRACT: A 37 mÂ² surface array which has been operating in coincidence with the Soudan 1 underground experiment is described. A comparison is made between measured and expected underground-surface coincident events. The surface array is used to tag'' the energy of the cosmic ray primary. Distributions of event rates and multiple muon rates as a function of energy are shown. Expected rates and plans for an enhanced array and for coincidences with Soudan 2 are also discussed. 1 ref., 6 figs.