[1] The new Digisonde-4D, while preserving the basic principles of the Digisonde family, introduces important hardware and software changes that implement the latest capabilities of new digital radio frequency (RF) circuitry and embedded computers. The ''D'' refers to digital transmitters and receivers in which no analog circuitry is used for conversion between the baseband and the RF. In conjunction with the new hardware design, new software solutions offer significantly enhanced measurement flexibility, enhanced signal selectivity, and new types of data, e.g., the complete set of time domain samples of all four antenna signals suitable for independent scientific analysis. With the new method of mitigating in-band RF interference, the ionogram running time can be made as short as a couple of seconds. The h 0 (f) precision ranging technique with an accuracy of better than 1 km can be used on a routine basis. The 4D model runs the new ARTIST-5 ionogram autoscaling software which reports in real time the required data for assimilation in ionospheric models. The paper highlights technical advances of the new Digisonde for research and monitoring applications.
The digital ionospheric sounding system Digisonde 128PS explores ionospheric structure and dynamics by exploiting all observables of the reflected electromagnetic wave: range, amplitude, phase, Doppler, incidence angle, and wave polarization. The Digisonde operates in two complementary modes of observation: the Ionogram Mode with full range and frequency display but limited resolution in Doppler and incidence angle, and the Doppler‐Drift Mode operating with a limited number of frequency‐range bins but full resolution in Doppler and incidence angle. This technique reduces the volume of magnetically recorded output data to a manageable size. Special digital‐analog hybrid techniques are used for the presentation of the multi‐parameter ionograms and the sky maps.
[1] We study the plasma sheath surrounding an antenna that transmits whistler mode waves in the inner magnetosphere in order to investigate the feasibility of conducting controlled experiments on the role of wave-particle interactions in the pitch angle diffusion of relativistic radiation belt electrons. We propose a model for an electrically short antenna-sheath-plasma system with transmission frequencies below the electron characteristic frequencies and much higher than the ion characteristic frequencies. The ion current is neglected. We analytically solve a time-dependent one-dimensional situation by neglecting the effects of the wave's magnetic field. In our model, the antenna is charged to a large negative potential during a steady transmission. Positive charge occurs in the sheath and the sheath is free of electrons and conduction current. The net charge on the antenna and in the sheath is zero. The volume, or the radius in a cylindrical case, of the sheath varies in response to the charge/voltage variation on the antenna. The oscillating radius of the sheath translates to a current in the plasma, which radiates waves into the plasma. A whistler wave transmission experiment conducted by the RPI-IMAGE has shown that the model may describe the most important physical processes occurring in the system. The system response is predominately reactive, showing no evidence for significant sheath current or sheath resistance. The negligibly small sheath conduction electron current can be understood if the antenna is charged to a substantial negative potential, as described by the model. Quantitatively, the model may underestimate the sheath capacitance by about 20%.
Abstract. Precise coordinate registration for HF over-the-horizon (OTH) radar applications requires accurate knowledge of the ionospheric structure. In the mid-1980s Digisonde 256 systems were deployed in the American sector to provide this information from strategically located sites via telephone lines to the user. The mid-1990s saw the development of a new advanced system, the Digisonde portable sounder, or DPS, now being deployed in Australia in support of the Australian OTH radar system. A summary of the new features provided by the DPS is as follows: low radio frequency power (300 W); narrow transmission bandwidth; advanced automatic scaling; and control and data access via the lntemet. The availability of realtime electron density profiles as function of time from a network of stations makes it possible to calculate the three-dimensional electron density distribution in the region of interest using Fourier transform techniques. The resulting density maps are the basis for the OTH radar coordinate registration. The DPS uses Doppler interferometry to determine the development of ionospheric irregularities. Principles of Ionospheric HF Sounding
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.