Total Electron Content of the Ionosphere over Singapore during a Magnetic Disturbance

Abstract

OBSERVATIONS made at middle latitudes have frequently shown that during a magnetic storm the number density (N_m) of the electrons at the peak of the F₂-layer is much less than usual. In speculating on the cause of this decrease, it is important to know whether or not the total number of electrons (n_t) in a unit column right through the ionosphere changes in the same way as N_m. It has already been shown by Yeh and Swenson¹ that the decrease in N_m at middle latitudes is, in fact, accompanied by a decrease in n_t. On the evidence of results obtained given by these authors, the mean value of n_t during storms was about half its normal value, but on one occasion it fell to one-fifth of the quiet-day value. It is well known that during a magnetic storm the changes in N_m near the geomagnetic equator may differ from those which are typical at middle latitudes, and it is important to know whether, at low latitudes, the changes in n_t are also different.