steams of charge particles emitted from the sun during periods of solar activity creates a disturbance in the earth's magnetic field. How does this happen? also, the text in our book discussed the magnetic field of an infinitely long, straight conductor carrying a current. Of course there is no such thing as infinitely long anything. How do you decide whether a particular wire is long enough to be considered infinite? I really dont know how the answer these questions..pls help....lotsa thanks!!