A gamma-ray telescope intercepts a pulse of gamma radiation from a magnetar, a type of star with a spectacularly large magnetic field. The pulse lasts 0.21 second and delivers 7.0 × 10-6 Joule of energy perpendicularly to the 51 m2 surface area of the telescope's detector. The magnetar is thought to be 4.10 × 1020 meter (about 43000 light-years) from earth, and to have a radius of 8.1 × 103 meter. Obtain the magnitude of the rms magnetic field of the gamma-ray pulse at the surface of the magnetar, Assuming that the pulse radiates uniformly outward in all directions. (Assume a year is 365.25 days.)