A new approach for identifying ionospheric backscatter in midlatitude SuperDARN HF radar observations

Abstract

[1] The Super Dual Auroral Radar Network (SuperDARN) is a network of HF radars that are traditionally used for monitoring phenomena in the Earth's ionosphere at high latitudes. The radar backscatter is due primarily to reflections from plasma irregularities in the ionosphere, known as ionospheric scatter, and to signal reflected from the ground, known as ground scatter. In recent years, SuperDARN has expanded to midlatitudes to provide improved coverage of the auroral region during times of enhanced geomagnetic activity. In addition to high-speed auroral flows, the radars commonly see a variety of low-velocity plasma drift associated with the quiet time midlatitude ionosphere. The traditional method of distinguishing between scatter types in SuperDARN data was developed for high latitudes and depends solely on the Doppler velocity and Doppler spectral width of each data point. This method has proven inadequate for identifying quiet time midlatitude ionospheric scatter. In this paper, we present a new technique for the classification of SuperDARN data, which operates on a distributed range time basis and involves procedures similar to "depth first search." Using the new method for classification of ground and ionospheric scatter, we show a dramatic improvement in the determination of ionospheric scatter within extended (>1 h) events. Compared to the traditional method, the number of ionospheric measurements resolved increases by more than 50%. The new classification algorithm identifies discrete events of ionospheric scatter and can be applied to statistical analysis of event occurrence and characteristics.

First results of the high-resolution multibeam ULF wave experiment at the Ekaterinburg SuperDARN radar: Ionospheric signatures of coupled poloidal Alfvén and drift-compressional modes

“…2 the value of the groundscatter (GS) flag, calculated with standard SuperDARN procedure FitACF (I-L), is shown. The use of the standard procedure for detection of GS at midlatitude radars is sometimes associated with erroneous definition of ionospheric scattering (IS), as GS (Ribeiro et al, 2011). As is seen from Fig.…”

“…It takes into account the values of velocity and spectral broadening of the signal, as well as some additional parameters (Milan et al, 1997;Ribeiro et al, 2011). Fig.…”

A survey of plasma irregularities as seen by the midlatitude Blackstone SuperDARN radar

“… Ribeiro et al [2011]developed a method that is able to identify periods of low velocity, low spectral width ionospheric scatter by finding clusters of connected backscatter points and analyzing their velocity characteristics as a whole to classify them as “events” (long‐lived periods of ionospheric scatter) or “non‐events” (other types of backscatter). To demonstrate its application, we present an example of midlatitude Doppler velocity data obtained on a single beam of the Blackstone radar on a typical day Figure 3b.…”

HF radar observations of ionospheric backscatter during geomagnetically quiet periods

“…Examples of cases when other methods are preferred include backscatter from midlatitude irregularities generated by the temperaturegradient instability (TGI) (Greenwald et al, 2006) and mixed scatter (Ponomarenko et al, 2008). In the most recent study on the issue, Ribeiro et al (2011) have employed the data from the midlatitude SuperDARN radar at Blackstone, Virginia to develop a new method for identifying TGI-generated scatter detected with midlatitude HF radars (defined in that study as being located at magnetic latitudes lower than 60 • ). Due to its magnetic latitude of ∼54.7 • S, the TIG radar is a nominally midlatitude radar.…”