Terrestrial‐magnetic and ionospheric effects associated with bright chromospheric eruptions

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Abstract
Magnetic changes occurring at a large number of stations simultaneously with bright chromospheric eruptions reveal that the effect is an augmentation of the normal diurnal variation supposedly due to increased atmospheric ionization by ultraviolet light from the eruption. Radio fade‐outs occurring at the same time indicate that this increase of ionization takes place at the base of or below the E‐layer while the upper layers are unaffected. These facts are adduced in support of the Stewart‐Schuster theory which attributes the diurnal variations to dynamo‐currents in the ionosphere, since the lower ionosphere is the region in which these currents are likely to flow. The upper regions of the ionosphere are most favorable for the operation of the drift‐current and diamagnetic theories. Absence of typical features of magnetic disturbance immediately after and for several days after the more intense eruptions is contrary to the effects predicted by the ultra‐violet theory of magnetic storms.Examination of the processes of ionization indicates that the solar eruptions are adequate causes of the effects observed. These eruptions must produce very large increases in ionizing radiation. It is suggested that normal radiation from the Sun in the extreme ultra‐violet is much greater than that calculated on the assumption that the Sun is a black‐body radiator at a temperature between 6000° and 7000° K.Statistical examination of the phenomena suggests that differences in intensity may be adequate explanation for the production of magnetic effects and radio fade‐outs by some eruptions, only fade‐outs by others, and absence of noticeable terrestrial effects in numerous cases. Fade‐outs reported when no eruptions occurred seem attributable to causes of a different nature.

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