Ionospheric reconstruction using Faraday rotation data: A new technique

Abstract

Abstract. Measurements of total electron content of the ionosphere by recording group delay or differential phase of transionospheric satellite signals have been used for reconstruction of ionospheric profiles. Integrated electron content measurements contain little information of ionospheric height distribution and require precise observations. These measurements are difficult for VHF and higher frequencies and require reasonably sophisticated instruments. Faraday rotation measurements, on the other hand, require relatively simple instruments and were widely used throughout the world. Faraday rotation of HF, VHF, and lower UHF band signals contains an additional term, e.g., a known function of the magnetic field. The functional form depends on the ray path and orientation of the magnetic field and in general is a complex quantity. Since the magnetic field distribution in the Earth's ionosphere is known with very high precision, this information can be used to obtain improved reconstruction of the ionospheric profiles. The magnetic field components have a strong dependence with the height, and this provides additional information regarding the ionospheric height retrieval. We have performed simulations using these techniques, and we present results using both simulated data as well as Faraday rotation data measured from several stations. We compare the sensitivities and reconstruction of ionospheric profiles using group delay and Faraday rotation techniques and demonstrate the improvements with the use of Faraday rotation data. The most difficult (in terms of radio propagation) regions, i.e., those near the equatorial regions, are simulated, and data from several stations, i.e., those near Calcutta, India, as well as those from several stations in Africa, are used. For the first time, we present the results of the reconstruction of the ionosphere using both simulated and observed Faraday rotation data. Large amounts of Faraday rotation data have been acquired during the 1960s and 1970s. These data contain a history of the ionosphere. The present technique would allow retrieval of ionospheric profiles over extended regions and could allow inferences to be drawn regarding the long-term changes in the ionosphere. The technique can also be incorporated in future satellite beacons, and the combination of group delay and Faraday rotation techniques will allow us to obtain superior reconstructions. IntroductionTotal electron content (TEC) has been measured since the earliest days of artificial satellites. Propagation of radio waves in the ionospheric plasma leads to advancement in carrier phase and produces group delay for modulation. Both of these quantities are related directly to the integrated column densities and have been used to measure the integrated elec-

Developments in Nanosecond Pulse Detection Methods and Technology

“…This hardware can also be used to implement real time de-dispersion algorithms and we have developed a technique for obtaining measurements of the ionospheric TEC which are both instantaneous and line-of-sight to the lunar observations. The ionospheric TEC can be deduced from Faraday Rotation measurements of a polarised source combined with geomagnetic field models, which are more stable than ionospheric models [4]. The Faraday Rotation induced in a radio wave is related to the ionospheric electron content via Equation 2…”

Novel improvements to magnetospheric tomography using MHD

“…In the last decade, tomographic reconstruction techniques were introduced within space physics for imaging the ionosphere [ Na and Lee , 1994; Brown and Ganguly , 2001; Ganguly et al , 2001; Kamalabadi et al , 2002]. Because of the possibility of a more favorable geometry with measurements surrounding the region of interest, and the ability of Faraday rotation tomography (FRT) to simultaneously measure both electron density and the magnetic field vector, the use of tomography for imaging the magnetosphere has gained recent theoretical interest.…”