Satellite‐beacon Ionospheric‐scintillation Global Model of the upper Atmosphere (SIGMA) II: Inverse modeling with high‐latitude observations to deduce irregularity physics

Abstract

Ionospheric scintillation is caused by irregularities in the ionospheric electron density. The characterization of ionospheric irregularities is important to further our understanding of the underlying physics. Our goal is to characterize the intermediate (0.1–10 km) to medium (10–100 km) scale high‐latitude irregularities which are likely to produce these scintillations. In this paper, we characterize irregularities observed by Global Navigation Satellite System (GNSS) during a geomagnetically active period on 9 March 2012. For this purpose, along with the measurements, we are using the recently developed model: “Satellite‐beacon Ionospheric‐scintillation Global Model of the upper Atmosphere” (SIGMA). The model is particularly applicable at high latitudes as it accounts for the complicated geometry of the magnetic field lines in these regions and is presented in an earlier paper. We use an inverse modeling technique to derive irregularity parameters by comparing the high rate (50 Hz) GNSS observations to the modeled outputs. In this investigation, we consider experimental observations from both the northern and southern high latitudes. The results include predominance of phase scintillations compared to amplitude scintillations that imply the presence of larger‐scale irregularities of sizes above the Fresnel scale at GPS frequencies, and the spectral index ranges from 2.4 to 4.2 and the RMS number density ranges from 3e11 to 2.3e12 el/m3. The best fits we obtained from our inverse method that considers only weak scattering mostly agree with the observations. Finally, we suggest some improvements in order to facilitate the possibility of accomplishing a unique solution to such inverse problems.

Automated Ionospheric Scattering Layer Hypothesis Generation for Detected and Classified Auroral Global Positioning System Scintillation Events

“…Ongoing work includes investigating a number of the events identified here and applying alternate methods of estimating the scattering layer to refine the estimated site of irregularities (Datta‐Barua et al, ). This can be done through the process of examining collocated all‐sky images from Poker Flat Research Range, or through the use of the high‐rate SAGA power and phase data (Su et al, ) and through inverse modeling (Deshpande et al, ).…”

Satellite‐Beacon Ionospheric‐Scintillation Global Model of the Upper Atmosphere (SIGMA) III: Scintillation Simulation Using A Physics‐Based Plasma Model

“…This section briefly describes the models used in the present study, GEMINI and SIGMA. A more detailed description of each code and their corresponding capability can be found in Deshpande et al (, ) and Zettergren and Snively () and Zettergren et al (). We also describe how we couple the two models together to achieve the new capability of directly simulating of GNSS scintillation from an initial mesoscale ionospheric state.…”

“…The Satellite‐beacon Ionospheric‐scintillation Global Model of the upper Atmosphere (SIGMA) is full three‐dimensional (3‐D) EM wave propagation model that simulates the effects of propagating the radio signal (VHF‐UHF and L band frequencies) through plasma density irregularities at anywhere on the globe. Prior articles in this series (Deshpande et al, , ) present the SIGMA model, including a sensitivity study, and present an inverse method that uses SIGMA to investigate the physics of ionospheric irregularities for specific observations of scintillation.…”

“…Deshpande et al (; henceforth referred to as SIGMA 2 paper) present six cases of scintillation observations from both hemispheres, over the polar cap to auroral latitudes during a moderate geomagnetic storm on 9 March 2012 (minimum Dst index of −145 nT). SIGMA is used along with an inverse method to predict the input parameters that best model the observations.…”

The Ionospheric Scintillation Effects on the BeiDou Signal Receiver

“…They simulated the full 3-D propagation of an obliquely incident satellite signal by using the MPS technique and a split-step method. The outputs from their model included the peak to peak (P2P) variations in the power and phase received on the ground, scintillation indices S 4 and ${\sigma }_{\varnothing }$ [16,17]. Considering that the MPS technique works well in moderate and intense scintillation cases, this paper utilizes it to model the ionospheric scintillation for the BeiDou system.…”