Effect of electric fields on the daytime high-latitudeEandFregions

Abstract

We have obtained solutions of the coupled continuity, momentum, and energy equations for NO+, O2+, and O+ ions for conditions appropriate to the daytime high‐latitude E and F regions. Owing to the rapid increase of the reaction O+ + N2 → NO+ + N with ion energy, high‐latitude electric fields and consequent E⊥ × B drifts deplete O+ in favor of NO+. For electric field strengths less than about 10 mV m−1 the depletion of O+ is small, and the altitude profiles of ion density are similar to those found at mid‐latitudes. However, for moderate electric field strengths (∼50 mV m−1), NO+ is substantially increased in relation to O+ and becomes an important ion throughout the F region. For these conditions the electron density has a tendency to become nearly constant with altitude in the range 160–360 km. For large electric fields (∼200 mV m−1), NO+ completely dominates the ion composition to at least 600 km, decreasing at high altitudes with a diffusive equilibrium scale height. Since the overall F region electron density decreases markedly with increasing electric field strength, it appears that high‐latitude, daytime electron density troughs are directly related to the presence of ionospheric electric fields. In addition, since increases in the N2 density or the N2 vibrational temperature also affect ion composition and electron densities in a manner similar to that of electric fields, the observed daytime troughs may arise from both processes acting simultaneously.

Plasma structure within poleward-moving cusp/cleft auroral transients: EISCAT Svalbard radar observations and an explanation in terms of large local time extent of events

“…Structured electron precipitation, as discussed above, would be the most likely cause of the structure in T e ; however, structure in N e could also arise from other factors. In particular, the concentration of sub-auroral plasma that is convected into the cusp region (Lockwood and Carlson, 1992) may vary and/or the fast ion¯ows that raise the ion temperature may also cause decreases in N e because the loss rates of the plasma are enhanced (Schunk et al, 1975). Rodger et al (1994) suggested these velocity-dependant loss rates may be a signi®cant factor in the cusp/cleft ionosphere.…”

A quantitative study of ionospheric density gradients at midlatitudes

“…Intense convection electric fields appear in the expanded auroral oval [e.g., Yeh et al, 1991] and are responsible for density depletion and ionospheric trough formation due to the effects of enhanced recombination [Schunk et al, 1976]. Collis and Haggstrom [1988] have derived an empirical relationship between the trough location and magnetic Kp index on the basis of observations with the European Incoherent Scatter radars, and Rodger et al [1992] presented an overview of the role of ion drift in the formation of the midlatitude and high-latitude trough.…”

“…The subauroral ionosphere is not subjected to the precipitationinduced localized ionization enhancements which characterize the auroral oval. Instead, E x B plasma motions advect ionospheric plasma with significantly different characteristics through this region [Foster, 1993], and chemical recombination of ions in the presence of large electric fields [Schunk et al, 1976] reduces plasma density, producing the deep nighttime ionization trough. These disturbance effects are superimposed on the regular diumal cycle of solar production and nighttime decay of the F region, which has both a latitude and a solar cycle variation.…”

Variation of variability in tec for quiet and disturbed days at low latitude station bhopal using gps

“…The component of electric field that is responsible for daytime upward ExB drift is eastward during quiet conditions, which decreases during magnetic disturbances at equatorial region results in the reduction of ExB drift and hence increases in positive phase over equatorial region and negative phase over low latitudes [12]. Due to the peculiar magnetic field geometry at low latitude, phenomenon like Joule heating and field-aligned current are not able to produce strong vertical drift as found at high latitudes but their presence, effect the F2 region behaviour via recombination coefficient and this recombination effects depends on the electric field [13]. Thus the increase in the field leads to the depletion of electron concentration that corresponds to the negative phase.…”