Interpretation of Ionospheric Measurements made during Solar Eclipses

Abstract

Hunaerts and Nicolet¹ have pointed out that the interpretation of E-layer measurements made during solar eclipses is very sensitive to the value of the effective recombination coefficient (α = 10⁻⁸ cm.³ s.⁻¹) in the range α = 1–3. For the eclipse of February 25, 1952, at points in the belt of totality, a value of α near the lower end of this range implies, in general, that the west limb of the Sun must have been much brighter than the east limb, and also that there can have been no source of ionizing radiation outside the visible disk. Conversely, a higher value of α requires the existence, in the corona, of sources which remained unobscured during totality, and only a small difference between the brightness of the west and east limbs. At Khartoum, for example, the intensity of the coronal component (I _e) and the difference between the intensities of the sources near the west and east limbs (I _w − I _e), both expressed as a percentage of the total radiation, are given by I _c = 12 − 18/α and I _w − I _e = 2 + 39/α. The arbitrary assumption that there was no coronal radiation thus leads to the result: α = 1.5.