Three methods are described to obtain ionospheric electron densities from transionospheric, rocket‐beacon total electron content (TEC) data. First, when the line‐of‐sight from a ground receiver to the rocket beacon is tangent to the flight trajectory, the electron concentration can be obtained by differentiating the TEC with respect to the distance to the rocket. A similar method may be used to obtain the electron‐density profile if the layer is horizontally stratified. Second, TEC data obtained during chemical release experiments may be interpreted with the aid of physical models of the disturbed ionosphere to yield spatial maps of the modified regions. Third, computerized tomography (CT) can be used to analyze TEC data obtained along a chain of ground‐based receivers aligned along the plane of the rocket trajectory. CT analysis of TEC data is used to reconstruct a two‐dimensional image of a simulated equatorial plume. TEC data is computed for a linear chain of nine receivers with adjacent spacings of either 100 or 200 km. The simulation data are analyzed to provide an F region reconstruction on a grid with 15×15 km pixels. Ionospheric rocket tomography may also be applied to rocket‐assisted measurements of amplitude and phase scintillations and airglow intensities.
The second space-plasma negative-ion experiment (SPINEX-2), a chemical-release active experiment to investigate negative-ion effects in the ionospheric F region, is described by Mendillo et al. This paper describes the electron-content measurements in somewhat more detail than would be appropriate therc. The circumstances of the experiment, particularly the use of a vehicle with a very high spin rate, presented some unusual challenges during interpretation of the electron-content data. These are described. The resulting profiles show clearly that the chemical release caused a very significant "hole" in the ionosphere. Under certain fairly realistic assumptions, the actual number of free electrons removed from the region of the peak of the ionospheric F layer is estimated to be about 4 x IO". The same assumptions lead to a simple radial distribution of the depleted region about the rocket trajectory in the neighborhood of the release.<
The statistical characteristics of ionosphcric irrcgularitics arc often dcscribcd by specifying onc or two of thc statistical parametcrs of thc scintillations that the irregularities producc in satcllitc radio signals. Thc most commonly used paramctcr for this purposc is thc spectral indcx (slope of thc powcr spcctral density function on a log-log plot). While it is becoming increasingly clcar that thc characterization of cithcr phasc or arnplitudc scintillations by a singlc pararnctcr may obscure significant characteristics of thc scintillations, this simple approach has provcn to bc ~rscful for the prediction of thc bchaviour of transionosphcric propagation paths such as thosc used in wrious space application systcms. This papcr cxplorcs the use, in addition to thc usual phase and amplitudc obscrvations, of measurcmcnts of anglc-of-arrival, in ordcr to charactcrizc thc scintillations. Sincc cach of these obscrvations rcprcscnt a diffcrcnt kind of obscrvational "filtering", the combination of one statistical paralnctcr from each typc of rncasurcmcnt should providc a morc adcquatc characterization of thc scintillations. I t is found that thc usc of thc widths of thc autocorrclation functions for this purposc is prcfcrrcd ovcr thc usc of spcctral indices.On dicrit souvcnt Ics caractdristiqucs statistiqucs dcs irrdgularitds ionosphdriqucs cn spdcifiant un ou deux dcs paramttres statistiqucs dcs scintillations quc Ics irrdgularitds produiscnt dans Ics signaux radio, dcs satcllitcs. LC parametre lc plus comrnun6rncnt utilisd h cctte fin cst I'indice spectral (la pentc dc la fonction dcnsitd spectralc dc puissance en Cchcllc log-log). Bien qu'il dcviennc de plus cn plus dvidcnt que la caractkrisation dcs scintillations dc phase ou d'amplitude par un scul paramttrc pcut obscurcir lcs calacteristiqucs significatives dcs scintillations. ccttc approchc simple s'cst averde utile pour la prediction du comportcnicnt dcs parcours de propagation trans-ionosphdricluc comme ccux qu'on utilisc dans divers systemes d'applications spatialcs. Dans cet article, on explore I'utilisation. en plus dcs obscrvations usucllcs de phase ct d'amplitude, de mcsurcs dc I'anglc d'arrivdc pour caracteriscr lcs scintillations. Etant donne quc chacune de ccs obscrvations rcprescnte une diffCrcntc sortc de "filtrage" obscrvationnel, on dcvrait obtenir, en prenant un paranittre statistiquc vcnant dc chaque type de mcsure, Lrne combinaison donnnnt une caractkrisation plus adequate dcs scintillations. On trouve qu'il cst prefCrablc d'utiliscr h cette fin lcs largeurs dcs fonctions d'autocorrdlation, plutBt que les indices spcctraux.[Traduit par le journal]Can.
The ionospheric electron content was measured at La Ronge, Sask. for a variety of auroral conditions during the Pulsating Aurora Campaign in February of 1980. The two-frequency differential phase technique was used with the NNSS satellite beacons. Comparisons of optical data and the radio results indicate that for quite strong pulsations the electron content is modulated by less than 2%. Even this small change is somewhat larger than the purely temporal variations to be expected on the basis of currently accepted relaxation times in the ionosphere. If the observed fluctuations are interpreted as representing both temporal and spatial variations, good agreement is obtained with model calculations. For irregularity sizes and strengths to which the experiment is sensitive, structure was present in diffuse or patchy aurora but absent from at least some well defined forms. This suggests that the technique can be used to explore the mechanism of formation of the irregularities.
The "Waterhole" experiment is described elsewhere by Whalen et al. This paper describes the somewhat surprising results obtained from the differential phase measurements made during the experiment. While there is evidence that the electron concentration in the immediate neighborhood of the explosion dropped as expected, the more dramatic outcome was the sudden cessation of particle precipitation. The radio measurements show that the electron concentration in the E-region below the "hole" began to decay at the time of the explosion with a rate which is consistent with recombination. It continued to decay over the time that it could be observed, about 2.5 min. It must be concluded that the particle precipitation along magnetic field lines through the hole was cut off for at least that length of time.
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