Height Distribution Of Electron Density Research Articles

Ionosphere F2 layer stratification caused by shear excited atmospheric vortical perturbation

We found that the height distribution of electron density of the mid-latitude ionosphere F2 region during nighttime being under the influence of a vortical perturbation excited in the horizontal shear flow (horizontal wind with horizontal linear shear) is characterized with a multiple structure. The analytical description for the ionosphere F2 region electron density height distribution was obtained by solving the ambipolar diffusion equation taking into account the presence of atmospheric shear waves (vortical perturbations excited in the horizontal shear flow). The peak heights and corresponding multi-layer electron densities in the F2 region depend on the values of the meridional wind zonal shear and the shear wave vertical wavenumber. The atmospheric shear wave is transformed into short-period atmospheric gravity wave (AGW) which is reflected in the oscillations of the F2 layer peak height ( hmF2) and peak density ( NmF2).

Errors of ionospheric parameter diagnostics by vertical sounding method

The problem of RMS error determination in ionospheric parameters measured by the method of vertical HF soundings is considered here. This problem is solved for the case of topside ionospheric soundings when the height distribution of electron density is monotonic. An analytical expression is obtained which relates the variance of deduced parameters to the correlation function of errors in measured characteristics of sounding signals. The computing simulation provides for errors in real height determination, in reconstruction of vertical velocities of plasma motion, and in effective electron collision frequencies for the measurements of virtual heights, Doppler frequency shift, and radio wave absorption, respectively. Their dependencies on signal polarization, working frequency range, and geomagnetic latitude of observation point are determined. The obtained results are useful for planning plasma diagnostics experiments using HF sounding technique.

Ionosphere F-region as an indicator of the evolution of atmospheric gravity waves in horizontal shear flow

The behavior of the electron density of the night ionosphere F2-layer influenced by the atmospheric gravity waves (AGW) evolving in the meridional wind with zonal shear is investigated. The height distribution of electron density in the ionosphere F2-region is obtained by presence of shear flow. The evolution of shear waves excited by the shear flow in the night time F2-layer is demonstrated.

Ionosphere F2-region under the influence of the evolutional atmospheric gravity waves in horizontal shear flow

The ambipolar diffusion equation for the height distribution of electron density in the ionospheric F2-layer is solved in the presence of neutral horizontal shear flow. By using this nonstationary solution the reaction of the F2-region electron density on the evolution of atmospheric acoustic–gravity waves (AGW) is investigated. The evolution of the AGW and the corresponding behaviour of the height distribution of the F2-region electron density are described by the characteristic time, t a, of transient development of shear waves in the horizontal shear flow. For long times t > t a, the gravity wave frequency tends to the isothermal Brunt–Väisälä frequency, which appears in the F2-layer as wavelike behaviour of h m F2 and N m F2 with periods close to 16–20 min, when the scale height of the neutral gas is H = 60 km. The shear wave, which is due to the presence of horizontal shear flow, gives sufficient changes of the height profile of electron density for times of t ⩽ t a.

D-region IRI profiles in relation to radio observations

The D-region IRI profiles are compared with the direct rocket measurements as well as with ground-based radio observations by a variety of techniques. The characteristics of D-region IRI profiles and the dependence of electron density on solar zenith angle, sunspot number, latitude and season are discussed. The sensitivity of certain reflection coefficients on the height distribution of electron density below 70 km is illustrated with a typical example. For D-region modelling, the results show the importance of simultaneous measurement of reflection and conversion coefficients together with polarization phase over a wide frequency range.

Nitric oxide density determination from rocket experiments at the geomagnetic equator

Two instrumented rockets, for the study of the D-region, were flown from Thumba, India (8.5°N 76.9°E) on 19 March 1970. The payload included propagation experiment, Lyman-alpha experiment and positive ion mass spectrometer. The data obtained from these experiments have been used to derive the nitric oxide density profiles. The technique of deriving the nitric oxide distribution is based on the use of the continuity equation for NO + ion and utilizing the experimentally measured data of the height distribution of electron density, positive ion composition and Lyman-alpha intensity. The derived values of nitric oxide for χ = 53° are higher by a factor of 2 compared to the values obtained by Meira (1971), in the altitude range of 67–77 km, above this it decreases and becomes as low as by a factor of 2 at 84 km while the profile derived for χ = 28° shows values substantially lower, by a factor ranging from 2 to 4. Above 80 km, both the profiles are in very good agreement.

On the solution of the integral equation relating height distribution of electron density to radio-wave absorption

The integral equation relating radio-wave absorption, A( ω), to electron density profile in the quasilongitudinal case has been solved for the absorption coefficient according to classical magneto-ionic theory as well as according to Sen and Wyller (1960). Explicit formulas are given for the electron density distribution as a polynomial in In ν—which is very close to a linear function of height over a limited height interval—for the case when ( ω ± ω( L ) × A( ω ± ω L ) has been determined as a polynomial in In ( ω ± ω L ) from the absorption measurements. A numerical example is finally discussed.

The behaviour of the D-region at mid-latitudes during a sudden ionospheric disturbance

The ‘full-wave’ integration technique is used to deduce, from observations of the propagation of l.f. and v.l.f. radio waves, the changes which take place in the height distribution of electron density during a ‘sudden ionospheric disturbance’ Two S.I.D.s have been studied, the first is an ‘average’ S.I.D. which gives rise to most of the observed characteristics of the propagation of the radio waves and the second is an S.I.D. which occurred on 7 October 1948, during which continuous measurements were made at Cambridge of the strength and phase of downeoming waves at 16 and 70 kc/s at steep incidence. During the latter S.I.D. the electron density increased at all heights from 65 to 80 km by factors of 1·2, 2·4, 5·8 and 4·0 at heights of 65, 70, 75 and 80 km respectively.

Atmospheric conductivities over Fort Churchill

Two models were considered for the height distribution of electron density. Model A corresponds to that of “normal” ionosphere at winter-night-time while Model B corresponds to that of “aurora-excited” ionosphere. Assuming the atmosphere to be that of the “ARDC Model Atmosphere, 1959”, the atmospheric conductivities k 0 to k 3, over Fort Churchill at winter-night-time were calculated for each model. Model A— K 0 (Longitudinal conductivity) increases upwards over the range considered. The peak values of k 1 (Pedersen conductivity), k 2 (Hall conductivity) and k 3 (Cowling conductivity) are 1·64 × 10 −16, 2·89 × 10 −16, 6·13 × 10 −16 e.m.u. cm respectively. The peak values of k 1, k 2 and k 3 occur at the heights of 119, 106 and 96 km respectively. The total integrated conductivities, K 1, K 2, K 3 are 10·96 × 10 −10, 8·86 × 10 −10, 10·16 × 10 −9 e.m.u. cm respectively. The values of K 1, K 2, K 3 over Fort Churchill at winter-night-time are approximately 1 15; of the corresponding values over White Sands at summer-day-time in the sunspot maximum year. Model B— K 0 increases abruptly in the region of auroral heights. The peak values of k 1, K 2, k 3 for Model B are 8·32 × 10 −14, 2·70 × 10 −13 and 2·86 × 10 −12 e.m.u. cm respectively. The peak values of k 1, K 2 and k 3 occur at 115, 105, and 102 km respectively. The total integrated conductivities, K 1, K 2, K 3 are respectively 21·38 × 10 −8, 40·59 × 10 −8 and 22·49 × 10 −7 e.m.u. cm for Model B. The effective layers for k 1, k 2 and k 3 for Model B are confined to the region of auroral heights. In particular, the effective layers of k 3 are very thin and located in the region of 100–110 km. The height-integrated conductivities of “aurora excited” ionosphere are approximately 200 times greater than those of quiet ionosphere.