The F2 Region as an Indicating Mechanism for Solar Activity

Article metrics


THE fact that F2 region critical frequencies and solar activity correlate in a general way is well known. Moreover, I have shown1 that the effect of changes in ionization which occur throughout the year can be eliminated in such a way as to bring out a clear-cut correspondence between these critical frequencies and smoothed average sunspot numbers. In an effort to find a more sensitive index for correlation purposes, a study has been made using both whole disk and central zone character figures for calcium and hydrogen flocculi as well as relative sunspot numbers. It has been found that the central zone indexes are better than those for the whole disk. When the monthly averages of the character figures for calcium flocculi are used, it is found that no smoothing is necessary, provided the effect of changes that occur throughout the year is eliminated.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.


  1. 1

    "On the Ionization of the F2 Region." Proc. Inst. Radio. Eng., 25, (Nov. 1937).

Download references

Author information

Rights and permissions

Reprints and Permissions

About this article

Cite this article

GOODALL, W. The F2 Region as an Indicating Mechanism for Solar Activity. Nature 143, 977–978 (1939) doi:10.1038/143977a0

Download citation

Further reading


By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.