1. The problem statement, all variables and given/known data A cosmic-ray proton in interstellar space has an energy of 21.5 MeV and executes a circular orbit having a radius equal to that of Earth's orbit around the Sun (1.50 X 10^11 m). What is the magnetic field in that region of space? 2. Relevant equations B=(Mo)(I)/ (2pie)(r) Mo= 4pie X 10^-7 3. The attempt at a solution My unknown is I which is the current. I am unsure how to use the energy given to find the current.