LAUSR

Abstract Available manually scaled foF2 observations over 50 years on Juliusruh, 33 years on Slough, and 37 years on Rome stations were used to check the association between quiet-time foF2 disturbances (Q-disturbances) and following on isolated magnetic storms. Of course, such cases exist, however Pearson's contingency coefficient, Chi-square and Odds ratio tests applied to check a measure of association gave the absence of relationship even at the 95% confidence level. The lack of association makes it impossible to use F2-layer disturbances as precursors for magnetic storms. The observed cases of apparent relationship between two events should be considered as random and physically unconditioned. The published cases indicating the relationship between two events can be explained in the framework of regular F2-layer variations not related by any means to the following on magnetic storms. Plain language summary The Earth's upper atmosphere, including the ionosphere, is under total solar control – direct or indirect. F2-layer disturbances occurring during magnetically disturbed periods are due to these magnetic disturbances and they are not discussed in the paper. However there are quiet-time F2-layer disturbances (Q-disturbances) occurring under low and very low level of geomagnetic activity. The relationship of such Q-disturbances with following on isolated magnetic storms is analyzed in the paper. All available manually scaled hourly foF2 observations on Juliusruh (50 years), on Rome (37 years), and Slough (33 years) have been analyzed to estimate a measure of association between two binary variables: F2-layer Q-disturbances and isolated magnetic storms. Pearson's contingency coefficient, Chi-square and Odds ratio tests applied to check a measure of association gave the absence of relationship even at the 95% confidence level. This is an expected result as from physical point of view such relationship has no physical explanation. The lack of association makes it impossible to use foF2-layer disturbances as precursors for magnetic storms – the idea being discussed in the literature. The observed cases of apparent relationship between two events should be considered as random and physically unconditioned. The published cases indicating the relationship between two events can be explained in the framework of regular F2-layer variations not related by any means to the following on magnetic storms.