Electron concentration variations in the topside ionosphere between 60°N and 60°S geomagnetic latitude associated with geomagnetic disturbances

Abstract

Variations of electron concentration in the topside ionosphere associated with geomagnetic disturbances were analyzed between 60°N and 60°S geomagnetic latitude over the American continents, using Alouette 1 satellite data. Twenty individual storm‐time variation profiles of electron concentration were derived. In low and equatorial latitudes two types of profiles, D and N, were observed. The D‐type profile, which is composed of both enhancement and reduction parts, occurs in the daytime in the majority of cases, whereas the N type, characterized by enhancement, seems to occur mainly at night. In the midlatitudes no definite daytime and nighttime profiles were found, though an enhancement was observed most often at 25° ∼ 35° geomagnetic latitudes, and a reduction was observed at 45° ∼ 55°. Relationships between latitudinal and height extents, magnitudes of the storm‐time variation of the electron concentration, Kp index, and season were not clear in this analysis. A qualitative explanation was attempted for these results, based on electron drift due to electromagnetic forces and ambipolar diffusion. This explanation seems to be applicable at least at low and equatorial latitudes.

Theoretical models of ionospheric storms

“…Latitude variations of electron content under magnetically quiet and disturbed conditions are compared and shown in Figure 16. Similar changes of electron density in the topside ionosphere have been observed by King et al (1967b) and Sato (1968). Similar changes of electron density in the topside ionosphere have been observed by King et al (1967b) and Sato (1968).…”

“…Ratios of values of foF2 on disturbed days to quiet days are illustrated in Figure 11 against latitudes at midday, and at midnight, in each season (Rajaram and Rastogi, 1969). Sato (1968) has investigated disturbance variations of electron density in the topside ionosphere up to 1000 km. Recent results obtained by Lakshmi and Reddy (1970) show an asymmetry in electron density changes during disturbances (After Rajaram and Rastogi, 1969.…”

A review of the theories concerning the equatorial F2 region ionosphere

“…Recent studies of the topside ionosphere under storm conditions (King et. al., 1967;Dunford, 1967;Sato, 1968) …”

“…Others, (Dunford, 1967) find the opposite trend for disturbed conditions. Sato (1968) has categorized storms as D type or N typo depending on whether enhancement or depletion is observed, and finds that most D type effects occur or begin during daylight hours.…”

Ionospheric specification with analytical profilers: Evidences of non-Chapman electron density distribution in the upper ionosphere

“…It should be noted, however, that at all topside TEC values there are profiles with an a-Chapman shape. This is to be expected, since the data was taken at all possible local times and seasons and at different magnetic longitudes and latitudes; it is well known that the storm time behaviour at different times and location can be very different (Ondoh, 1967;Sato, 1968;Warren, 1969;Fuller-Rowell et al, 1994;Kutiev and Muhtarov, 2001), and it should be noted that a TEC value that is considered depleted at certain times and locations might be a normal, quiet time value at others (Kutiev et al, 2005;2006b). The same issues exist with regard to the topside slab thickness (defined as the topside TEC divided by the peak electron density), which are displayed in Fig.…”