  In this article we study the seasonal effect on the diurnal variation of the
geomagnetic field registered in the Huancayo Observatory, located in the
Magnetic Equator, which is driven by "ionospheric currents" and its counterpart
induced by "telluric currents". Huancayo Observatory has the highest amplitude
in the diurnal variation, because of being in the Magnetic Equator and under
the "Equatorial Electrojet". We present the pattern of seasonal variation in
diurnal variation of components X, Y and Z, the same as confirmed by previous
works since 1940. The effect of solar activity cycle of about 11 years in the
diurnal variation is also confirmed; it is observed that amplitudes are greater
in the maximum of solar activity.
