Report of Ionosphere Investigations at the Huancayo Magnetic Observatory (Peru) during 1933

Equipment for ionosphere investigation was placed in operation at the Huancayo Magnetic Observatory of the Department of Terrestrial Magnetism of the Carnegie Institution of Washington during 1933. The equipment designed for multifrequency operation by manual methods is described. Three layers identified with the E, F
1
, and F
2
layers at Washington, D.C., are found. The F
1
layer appears to be formed by a separation from a general F region during the morning rather than direct ionization of a separate layer. Two reflection components are found near the maximum ionization of the F
1
and F
2
layers, reaching critical values at different frequencies. This difference corresponds very closely to the separation calculated for the effect of magneto-ionic double refraction due to the earth's magnetic field. From these data further information of the actual ionization conditions is obtained. The maximum ionization of the F
1
layer is found to reach 2.5×10
⁵
electrons per cubic centimeter, while the density of heavier ions is not greater than about 10
⁷
per cubic centimeter. The maximum ionization of the F
2
layer reaches 8×10
⁵
to 9×10
⁵
electrons per cubic centimeter and on some occasions exceeds 1.1×10
⁶
electrons per cubic centimeter. A dip in the critical frequency of the F
2
layer usually occurs in the morning in the summer, which may be related to the appearance of the F
1
layer. If this dip in the diurnal critical frequency characteristic is due to absorption rather than ion limitation, the ionization may be higher than indicated during these periods.