Ionospheric Measurements at Central China College, Wuchang, China, October 1937 to June 1938

A brief description is given of a manually operated ionospheric equipment with which a single operator can take necessary readings of virtual heights and critical frequencies. Data for noon‐hour runs from October 1937 to January 1938 and from April to June 1938, and half‐hour evening‐runs in March and April, 1938, are arranged in two tables. Sample and average diurnal‐variation curves for virtual heights and critical frequencies are plotted. It is found that the critical frequencies at Wuchang are higher than those at Washington for both the E‐ and F2‐layers during the same months. The E‐layer critical frequency, as is the case elsewhere, reaches a maximum near the local noon, whereas for the F2‐layer the critical frequency reaches a high value about 14h and maintains nearly the same value till about 17h, 120° east meridian time. When plotted month by month, the E‐layer critical frequency increases with the approach of summer, while the F2‐layer critical frequency tends toward a minimum in July with two probable maxima in October and April. This would make the Wuchang seasonal characteristics approximate those of Watheroo rather than of Washington, but it must be emphasized that data are insufficient to make this point definite. Very often the E‐layer virtual height undergoes a dip when a higher layer begins to appear and continues to keep its normal height long after the upper layer has appeared. In a few cases, the E‐layer echoes persist even after the F‐ or F2‐layer has been penetrated. Magnetic splitting is quite evident, especially for the readings during daylight. The observed mean value of 620 kc, as the difference between the ‐component and the x‐component of the F2‐layer penetrating frequency, checks very well with the theoretical value of 614 kc. A case is reported of a chain of closely packed echoes (scattered reflections) following the first echo from the F‐layer on April 2 between 22h 30m and midnight, 120° east meridian time (or 14h 30m to 16h GMT). It is interpreted to be a multiple‐reflection phenomenon, when the two F‐layers are approaching each other to form one layer in an unsteady fashion.