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Typical signals Magnetic field variations of interest in this program are those induced by electric currents in the ionosphere. The major signal categories detected by the induction magnetometer are short period magnetic pulsations such as Pc1, Pc2, Pc3, PiB, and PiC in a frequency range above a few tens of milliHertz. Among these, the induction magnetometer most efficiently detects Pc1 waves in the frequency range from 0.1 Hz to 3 Hz. Pc1 signals are the result of ion-cyclotron radiation generated near the equatorial plane of the outer-magnetosphere that make their way to the ionosphere guided by the magnetic lines of force. In addition, signals generated in the atmosphere that are caused by lightning discharges, the Schuman resonances, are also detected and sometimes become strong enough to mask signals from the ionosphere.