Measurements of the atmospheric radiation environment from CREAM and comparisons with models for quiet time and solar particle events

Flight data on neutron fluxes and dose rates obtained over a wide range of latitudes and altitudes are compared with several models of atmospheric radiation for both quiet-time and solar particle events. For quiet-time, general agreement between the models and measurements is within about 25%. Geomagnetic disturbances can increase atmospheric cosmic ray fluxes by up to 10% due to suppression of cut-off rigidities. Solar particle events are more difficult to model but for this solar maximum reasonable agreement has been obtained with a measurement during the event of 15 April 2001. On 20 January 2005 the second largest ground level event in recorded history could have raised atmospheric fluxes at flight altitudes by several hundredfold at high southern latitudes.