Ivan A. Galkin

Ionospheric sounding in support of over‐the‐horizon radar

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 Internet. The availability of real-time 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.

First results from the Radio Plasma Imager on IMAGE

The Radio Plasma Imager (RPI) is a 3 kHz to 3 MHz radio sounder, incorporating modern digital processing techniques and long electronically-tuned antennas, that is flown to large radial distances into the high-latitude magnetosphere on the Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) satellite. Clear echoes, similar to those observed by ionospheric topside sounders, are routinely observed from the polar-cap ionosphere by RPI even when IMAGE is located at geocentric distances up to approximately 5 Earth radii. Using an inversion technique, these echoes have been used to determine electron-density distributions from the polar-cap ionosphere to the location of the IMAGE satellite. Typical echoes from the plasmapause boundary, observed from outside the plasmasphere, are of a diffuse nature indicating persistently irregular structure. Echoes attributed to the cusp and the magnetopause have also been identified, those from the cusp have been identified more often and with greater confidence.

Exploring Digisonde Ionogram Data with SAO-X and DIDBase

A comprehensive suite of software tools for ionogram data analysis and archiving has been developed at UMLCAR to support the exploration of raw and processed data from the worldwide network of digisondes in a low-latency, user-friendly environment. Paired with the remotely accessible Digital Ionogram Data Base (DIDBase), the SAO Explorer software serves as an example of how an academic institution conscientiously manages its resident data archive while local experts continue to work on design of new and improved data products, all in the name of free public access to the full roster of acquired ionospheric sounding data.

International Reference Ionosphere 2016: From ionospheric climate to real‐time weather predictions

The paper presents the latest version of the International Reference Ionosphere model (IRI-2016) describing the most important changes and improvements that were included with this version and discussing their impact on the IRI predictions of ionospheric parameters. IRI-2016 includes two new model options for the F2 peak height hmF2 and a better representation of topside ion densities at very low and high solar activities. In addition, a number of smaller changes were made concerning the use of solar indices and the speedup of the computer program. We also review the latest developments toward a Real-Time IRI. The goal is to progress from predicting climatology to describing the real-time weather conditions in the ionosphere.

The ARTIST 5

Version 5 of the Automatic Real-Time Ionogram Scaler with True height (ARTIST), an intelligent system developed at UMLCAR for extraction of ionospheric specification data from Digisonde ionograms, entered its operational phase in May 2007. Version 5 implements the classic ARTIST techniques re-vamped for modern computers and programming environments, as well as new approaches developed to strengthen the ARTIST performance. This paper describes progress in the ionogram autoscaling research at UMLCAR that has culminated into release of the ARTIST 5 software.

Feedback Neural Networks For Artist Ionogram Processing

Modern pattern recognition techniques are applied to achieve high quality automatic processing of Digisonde ionograms. An artificial neural network (ANN) was found to be a promising technique for ionospheric echo tracing. A modified rotor model was tested to construct the Hopfield ANN with the mean field theory updating scheme. Tests of the models against various ionospheric data showed that the modified rotor model gives good results where conventional tracing techniques have difficulties. Use of the ANN made it possible to implement a robust scheme of trace interpretation that considers local trace inclination angles available after ANN completes tracing. The interpretation scheme features a new algorithm for ƒ0F1 identification that estimates an α angle for the trace segments in the vicinity of the critical frequency ƒ0F1. First results from off-line tests suggest the potential of implementing new operational autoscaling software in the worldwide Digisonde network.

Advancing Digisonde Technology: the DPS-4D

A new ionosonde, the Digisonde model DPS-4D, replaces the aging DPS-4. Faster computer hardware and operating systems together with digital transmitters/receivers provide unprecedented measurement flexibility, data precision, and signal processing gain. The novel features in this latest Digisonde are discussed and explained.

The SAOXML 5: New Format for Ionogram-Derived Data

A new format for the unified data exchange between ionosonde data producers and users of ionogram-derived characteristics is introduced, dubbed SAOXML 5 to reflect its heritage in the previous Standard Archiving Output (SAO) format version 4 and a general-purpose computer language XML commonly used for data exchange. The SAOXML 5 specification shall serve as the reference for development of input and output interfaces for the software projects that read and write ionogram-derived data. The paper discusses motivation for introducing new format and outlines basic principles of its design and use.

Precise Radar Range Measurements with Digisondes

A digisonde phase-difference technique measures precise radar ranges of echoes reflected from the ionosphere. The technique, which analyzes the phase differences between signals at slightly different frequencies, allows measuring the reflection range, i.e., the virtual height h′(f) for vertical sounding, with accuracies of better than one kilometer. First results of measurements carried out at Millstone Hill demonstrate the robustness and reliability of the developed technique, and show the potential of the method for routine application.

Internet access to ionosondes

Abstract Connecting ionosondes to the Internet gives easy access to real-time information on ionospheric conditions. Some of the ionosonde sites provide just the ionogram displays, others give in addition the scaled ionospheric characteristics directly usable for frequency management and HF channel assessment. Some sounders also store days or months of station data, which makes it possible remotely to evaluate the time history of geophysical events. The Internet link is also a convenient means for remote system maintenance and control. The paper addresses various aspects of the Internet ionosonde scenario, including data base support, WWW publishing, user interface, security, and data format. A list of Internet accessible ionosonde stations is provided with a brief description.