Abstract:
It is known that equatorial sporadic E disappears at night when dynamo field is east to west. During some DP/sub2 type magnetic sub-storms, which cause a depression of the geomagnetic horizontal field at the equator, the q type of sporadic E is found to- disappear at the equatorial stations Huancayo and Kodaikanal. This suggests that one of the mechanisms causing the temporary disappearance of E/subs – q during daytime in equatorial ionograms is the replacement of the east to west dynamo electric field by a west to east electric field due to the imposition of an electric field opposing the normal daytime S/subq field.
