Determination of the vertical electron-density pro®le in ionospheric tomography: experimental results

The reconstruction of the vertical electrondensity pro®le is a fundamental problem in ionospheric tomography. Lack of near-horizontal ray paths limits the information available on the vertical pro®le, so that the resultant image of electron density is biased in a horizontal sense. The vertical pro®le is of great importance as it a€ects the authenticity of the entire tomographic image. A new method is described whereby the vertical pro®le is selected using relative total-electroncontent measurements. The new reconstruction process has been developed from modelling studies. A range of background ionospheres, representing many possible peak heights, scale heights and electron densities are formed from a Chapman pro®le on the bottomside with a range of topside pro®les. The iterative reconstruction process is performed on all of these background ionospheres and a numerical selection criterion employed to select the ®nal image. The resulting tomographic images show excellent agreement in electron density when compared with independent veri®cation provided by the EISCAT radar.