Earth's lower atmosphere contains negative and positive ions that are produced by radioactive elements In the soil and cosmic rays from space. In a certain region, the atmospheric electric field strength is 137 W/'m and the field is directed vertically down. This field causes singly charged positive ions, at a density of 519 cm . to drift downward and singly charged negative ions, at a density of 685 cm', to drift upward (see the figure). The measured conductivity of the air in that region is 2.57 * 10:14 (0-m)"], Calculate (a) the magnitude of the current density and (b] the ion drift speed, assumed to be the same for positive and negative ions. (al Number Units (b) Number i Units eTextbook and Media Hint