The horizontal component of the geomagnetic field, measured on the ground at two stations near the path of totality, reached the greatest departure from its normal value shortly after maximum eclipse in the nearby E layer. The magnitude of this departure is consistent with the generally accepted hypothesis that the eclipse‐induced current system is located near the 100‐km level. A determination was made of the lag from the time when the E‐layer eclipse occurred at the theoretically optimum location until the time of maximum observed magnetic effect, with corrections for induction delays. Using this time lag, along with the observed decrease in the E‐layer ionization, the effective ion‐recombination coefficient and the percentage of ionizing radiation remaining at totality were determined. The recombination coefficient was found to be 5.5 (±1) × 10−8 cm³ sec−1 and the residual coronal radiation 15 (±3)%.

A simplified model for X‐ray distribution over the sun (based on photographs provided by J. H. Underwood of NASA) was fitted to the changes in electron production rate during the November 12, 1966, eclipse to determine the relative contributions made by diverse solar regions to the formation of the E layer. The production rates were obtained by using Huancayo ionograms and our previously determined E‐layer recombination coefficient (5.5×10−8 cm³ sec−1). It was found that two active regions covering only 6% of the solar disk accounted for 32% of the electron production. Moreover, by combining the results so obtained with Underwood’s analysis of the X‐ray photographs, we were able to determine the relative contributions of soft X rays and of extreme ultraviolet to ion production at the E‐layer peak. At this intermediate epoch of the solar cycle, 68% of the production rate was found to be due to soft X rays and 32% to ultraviolet. Reduced to solar‐minimum conditions, the X‐ray contribution would be 54%, a value about midway between the values predicted by the major theories of E‐layer formation. In addition, comparison of our results with computations made by Widing for coronal sources of X rays enabled us to infer that the temperature in the two active regions was about 3×106 °K.