Ionospheric Plasma Irregularities Research Articles

ROTI-based statistical regression models for GNSS precise point positioning errors associated with ionospheric plasma irregularities

ROTI-based statistical regression models for GNSS precise point positioning errors associated with ionospheric plasma irregularities

Modeling Equatorial to Mid‐Latitudinal Global Night Time Ionospheric Plasma Irregularities Using Machine Learning

AbstractThis study focuses on modeling the characteristics of nighttime topside Ionospheric Plasma Irregularities (PI) on a global scale. We utilize Random Forest (RF) and a one‐dimensional Convolutional Neural Network (1D‐CNN) model, incorporating data from the Swarm A, B, and C satellites, space weather data from the OMNIWeb data center, as well as zonal and meridional wind model data. Our objective is to simulate monthly global PI characteristics using a multilayer 1D‐CNN model trained on 12 space weather and ionospheric parameters. In addition, we investigate the most influential input parameters for predicting global nighttime PI characteristics. Our findings indicate that non‐equinox months exhibit the highest equatorial PI magnitude over the American‐African longitudinal sector, contrary to the expected higher Rayleigh‐Taylor instability growth rate during equinox months. Winter months display the most intense and widespread vertically and horizontally distributed equatorial PI patterns. We also observe double peaks across geomagnetic latitudes and longitudinally varying wavelike irregularity structures, particularly in May, August, and predominantly in September. Furthermore, north‐south hemispherical asymmetry in PI observed across different seasons. Through the RF parameter importance analysis method, we determine that temporal, geographical, and magnetic disturbance‐related factors play a crucial role in predicting global PI variabilities. These findings emphasize the significance of these variables in controlling the strongest PI characteristics observed in the Atlantic sector, which has garnered considerable attention in PI research. The employed 1D‐CNN model demonstrates exceptional predictive capabilities, exhibiting a strong correlation of 0.98 for global PI characteristics across all months and satellites.

Spectral Characteristics of Phase Fluctuations at High Latitude

AbstractIt has long been established that ionospheric electron density irregularities cause random rapid amplitude and phase fluctuations in trans‐ionospheric radio signals. Various types of ground‐based measurements, including radar and Global Navigation Satellite System (GNSS) receivers, have been utilized to gain insights into the plasma mechanisms that could lead to the development of these ionospheric irregularities. The spectral characteristics of radio wave signals emitted by GNSSs and detected by the Canadian High Arctic Ionospheric Network Global Positioning System (GPS) receivers are analyzed to try and identify the spectral signatures of the ionospheric plasma irregularities. In the polar region, we have confirmed that phase fluctuations in the GPS signal are not always accompanied by amplitude fluctuations. For the first time, a systematic comparison is conducted on the spectral properties of phase‐fluctuation events in the absence and presence of amplitude scintillations, respectively. More specifically, a spectral characterization is performed on 41 events recorded by three receivers positioned within the auroral oval. When fluctuations above the background level are solely observed in the signal's phase, the spectrum of phase variations exhibits a consistent steepness. Conversely, the presence of amplitude scintillation is accompanied by an increase in power at higher frequencies, resulting in shallower spectra. This analysis provides yet another physical element suggesting that the rapid fluctuations observed in the signal's amplitude may be caused by Fresnel‐scale irregularities arising from a gradient‐drift‐like instability while the phase variations seem to be consistent with a refractive mechanism caused by large‐scale ionospheric structures.

Towards mitigating the effect of plasma bubbles on GPS positioning accuracy through wavelet transformation over Southeast Asian region

Ionospheric irregularities remain as a challenging concern among space scientists and engineers as it can pose severe threats to satellite-based services by introducing amplitude and phase scintillations in the transionospheric radio signals. The scintillations may cause degradation of the positioning, navigation, and timing (PNT) services or even complete system failure under extreme conditions. The present work focuses on understanding the ionospheric irregularities during the space weather event on May 12, 2021, witnessing the first strong geomagnetic storm in the 25th solar cycle. This particular event commenced around 13.00 UT, apparently altering the regular development of equatorial plasma bubbles around the local post-sunset terminator. We selected three global positioning system (GPS) stations, one at the near-magnetic equator (CUSV) and two at far low-latitude locations with a longitudinal separation (THKK and HWKS) over the Southeast Asian longitudes to investigate the characteristics of ionospheric plasma irregularities on the storm day. The results showed that the amplitude of ROTI was highest at the low-latitude CUSV, followed by the THKK and HKWS stations. The increased ROTI at CUSV is due to its latitudinal location close to the geomagnetic equator in the equatorial ionization anomaly (EIA) region which often witnesses more fluctuations than the inter-mediate latitudes. The strong TEC fluctuation occurrences were comparatively minimal at HWKS station on the storm day (May 12, 2021), whereas both intermediate and relatively higher TEC fluctuation occurrences were found at THKK and CUSV stations, respectively. Moreover, the occurrence rate of moderate irregularities was the highest at CUSV, followed by THKK and HKWS, while that of weak irregularities was maximum at HKWS, followed by THKK and CUSV. This happens because the systematic longitudinal time delay observed at the onset of ionospheric scintillations corresponds to the rise of PBs velocity at the magnetic equator that strongly depended upon the F-region dynamo electric fields in the east–west direction. Furthermore, the three-dimensional (3-D) positioning errors were estimated at a 30-sec interval to understand the impact of storm-induced irregularity on the positioning solution. An excellent agreement is realized between the ROTI pattern and positioning errors at all stations, irrespective of latitudinal extent from the magnetic equator. In order to model the amplitude of the scintillation index against the SNR measurements, the linear, quadratic, and cubic regression curve fittings are utilized that indicate the cubic polynomial manifesting the best fitted SNR measurements with the weak as well as moderate scintillation index. The continuous wavelet transformation (CWT) method was implemented to mitigate the ionospheric scintillation effects on positioning accuracy. The CWT estimation reveals the hidden information in positioning error due to the scintillation index, which makes it easy to understand the ionospheric scintillation effects on positioning. The attempt in this work is aligned with the efforts towards reliable PNT operations over equatorial and low latitudes.

Dependence of Ionospheric Responses on Solar Wind Dynamic Pressure During Geomagnetic Storms Using Global Long‐Term GNSS‐TEC Data

AbstractTo elucidate the effect of solar wind dynamic pressure on the activities of ionospheric plasma irregularities in both high‐latitude and equatorial regions, we analyzed the long‐term global navigation satellite system (GNSS) total electron content (TEC) data from 2000 to 2018 and performed a superposed epoch analysis of the GNSS rate of the TEC index (ROTI), solar wind, interplanetary magnetic field (IMF), and geomagnetic index. We found that during the main phase of geomagnetic storms, the activities of ionospheric plasma irregularities were considerably enhanced in both high‐latitude and equatorial regions under high‐pressure conditions, and the equatorward edge of the auroral oval moved to lower latitudes. The poleward edge of the enhanced low‐latitude ROTI region (occurrence region of the plasma bubbles) in the evening sector extended to higher latitudes under high‐pressure conditions. During the recovery phase of geomagnetic storms, the plasma bubble occurrence in the dusk sector was suppressed under high‐pressure conditions. Our results suggest that the high‐latitude convection electric field and the penetration and disturbance dynamo electric fields at low latitudes become stronger during geomagnetic storms when the solar wind dynamic pressure is enhanced. This is because the conversion from solar wind energy to electromagnetic energy in the magnetosphere is enhanced by the formation of a high plasma pressure area in the high‐latitude cusp and mantle region. Therefore, not only the southward IMF but also solar wind dynamic pressure are important factors for varying global ionospheric responses during geomagnetic storms.

Incoherent Scattering of a Bessel Vortex Electromagnetic Beam From a Nonmagnetized Plasma

Starting from the description of plane wave angular spectrum superposition of a Bessel vortex beam, with the aid of Thomson scattering theory of a Bessel vortex electromagnetic beam (BVEB) by a low-velocity election, the incoherent scattering power spectra of a BVEB by a non-magnetized plasma is investigated in this paper. The incoherent scattering power spectrum for a BVEB incidence is defined for the backscattered case, and the expression of the scattered power spectral density function is derived. The proposed method is verified in the physical sense by comparing the profiles of distribution parameter of scattered power and the magnitude of average Poynting vector of the incident beam. The effects of the beam parameters (topological charge and half-cone angle) on the scattered power spectral density function are analyzed for the plasmas with Maxwellian velocity distribution. Furtherly, the expression of the scattered power spectral density function is extended to the case of macroscopic moving plasmas. Taking plasma vortices as an example, the results indicate that the direction of the frequency shift of the scattered power spectral density function due to the rotational Doppler effect of the vortex beam is related to angular velocity of the plasma vortex. Additionally, as the topological charge increases, the magnitude of the frequency shifts also increases. Our proposed method provides a theoretical basis for exploring the feasibility of using vortex beams with single or multi orbital angular momentum (OAM) modes in the identifying and inverting parameters of plasma irregularities in ionospheric plasma or laboratory plasma environments.

Electron density fluctuations from Swarm as a proxy for ground-based scintillation data: A statistical perspective

The Swarm satellite mission has been used for numerous studies of the ionosphere. Here we use a global product, based on electron density measurements from Swarm that characterises ionospheric variability. The IPIR (Ionospheric Plasma IRregularities product) provides characteristics of plasma irregularities in terms of their amplitudes, gradients and spatial scales and assigns them to geomagnetic regions. Ionospheric irregularities and fluctuations are often the cause of errors in position, navigation, and timing (PNT) based on the Global Navigation Satellite Systems (GNSS), in which signals pass through the ionosphere. The IPIR dataset also provides an indication, in the form of a numerical value index (IPIR index), of the severity of irregularities affecting the integrity of trans-ionospheric radio signals and hence, the accuracy of GNSS positioning. We analysed datasets from Swarm A and ground-based scintillation receivers. Time intervals (when Swarm A passes over the field of view of the ground-based GPS receiver) are compared to ground-based scintillation data, collecting an azimuthal selection of the GNSS data relevant to the Swarm satellite overpass. We provide validations of the IPIR product against the ground-based measurements from 23 ground-based receivers, focusing on GPS TEC and scintillation data in low-latitude, auroral and polar regions, and in different longitudinal sectors. We have determined the median, mean, maximum and standard deviation of the parameter values for both datasets and each conjunction point. We found a weak correlation of the intensity of both phase and amplitude scintillation with the IPIR index.

Relationship between geomagnetic storms and occurrence of ionospheric irregularities in the west sector of Africa during the peak of the 24th solar cycle

The study of ionospheric irregularities is important since many technological systems might be influenced by the ionosphere. In this work, we use data from the Global Navigation Satellite Systems (GNSS) receiver installed in Abuja, Nigeria, GPS Scintillation Network Decision Aid (SCINDA) TEC data from the Air Force Research Laboratory (AFRL) data archive, and the geomagnetic data from the World Data Center (WDC) in Kyoto, Japan, to investigate the relationship between geomagnetic storm and ionospheric irregularity occurrences using the rate of change of total electron content (TEC) index (ROTI), with a validation using the S4 indices, during the peak of the 24th solar cycle. The occurrences of irregularities were investigated on day-to-day and seasonal bases. The nighttime ionospheric irregularities, which are attributed to ionospheric plasma irregularities in the equatorial ionospheric F-region, were found to be prevalent. To investigate the relationship between the strength of ionospheric irregularities (ROTI) and the geomagnetic storm (Dst), the periodogram power spectral density (PSD) and regression analysis were used. The results showed that there was no correlation, cc = 0.073, between the Dst and ROTI, implying that the strengths of ionospheric irregularities occurring during geomagnetic storms are not strictly decided by the magnitudes of the storms; this was also confirmed using the S4 index. The impact of geomagnetic storms caused enhanced development or inhibition of ionospheric irregularities. We observed that the bulk of the storms occurring during the period of this study is not associated with ionospheric irregularities. Finally, the investigation showed that the correlation between the ROTI and Dst observed during the coronal mass ejection (CME)-driven geomagnetic storms was higher than that during the corotating interaction region (CIR)-driven geomagnetic storms, during the peak of the 24th solar cycle. The results of this work confirm the findings by other researchers.

Interferometric Study of Ionospheric Plasma Irregularities in Regions of Phase Scintillations and HF Backscatter.

We investigate the nature of small‐scale irregularities observed in the cusp by the Twin Rockets to Investigate Cusp Electrodynamics‐2 (TRICE‐2) in regions of enhanced phase scintillations and high‐frequency coherent radar backscatter. We take advantage of the fact that the irregularities were detected by spatially separated probes, and present an interferometric analysis of both the observed electron density and electric field fluctuations. We provide evidence that fluctuations spanning a few decameters to about a meter have low phase velocity in the plasma reference frame and are nondispersive, confirming that decameter‐scale irregularities follow the E × B velocity. Furthermore, we show that these “spatial” structures are intermittent and prominent outside of regions with strongest precipitation. The observations are then discussed in the context of possible mechanisms for irregularity creation.

Instantaneous amplitude of low-latitude ionospheric irregularities probed by ROCSAT-1, DEMETER, and FORMOSAT-7/COSMIC-2

The occurrence probability of plasma irregularities has long been used to quantify that of ionospheric scintillations. We use the Hilbert-Huang transform to examine the occurrence probability and the instantaneous total amplitude of plasma irregularities in the low-latitude nighttime ionosphere observed by the low-inclination satellites, ROCSAT-1 during 1999–2004 and FORMOSAT-7/COSMIC-2 (F7C2) in 2020, as well as a high-inclination satellite, DEMETER, during 2006–2010. Generally, the longitudinal distribution of the occurrence probability is similar to that of the total amplitude, except that the probability of ion density irregularity observed by F7C2 and DEMETER yields nonphysical anomalous enhancements over the South American sector during May–August of 2007–2010 and 2020, respectively. S4 scintillations observed by F7C2 show that the anomalous enhancement results from the low ambient density in calculating the occurrence probability during the low solar activity year of 2020. We suggest the instantaneous total amplitude as a better indicator for describing ionospheric plasma irregularities.

Ionospheric Plasma IRregularities - IPIR - Data Product Based on Data From the Swarm Satellites.

Ionospheric plasma irregularities can be successfully studied with the Swarm satellites. Parameters derived from the in‐situ plasma measurements and from the topside ionosphere total electron content provide a comprehensive dataset for characterizing plasma structuring along the orbits of the Swarm satellites. The Ionospheric Plasma IRregularities (IPIR) data product summarizes these parameters and allows for systematic studies of ionospheric irregularities. IPIR has already been used in investigations of structuring and variability of ionospheric plasma. This report provides a detailed description of algorithms behind the IPIR data product and demonstrates its use for ionospheric studies.

Development of the Storm‐Induced Ionospheric Irregularities at Equatorial and Middle Latitudes During the 25–26 August 2018 Geomagnetic Storm

AbstractCan geomagnetic storms during low solar activity trigger formation of extreme equatorial plasma bubbles (EPBs) that affect low and midlatitudes? We analyzed the ionospheric response to the 25–26 August 2018 geomagnetic storm and revealed formation of intense ionospheric plasma irregularities over broad latitudinal ranges from equatorial toward middle latitudes in the American and Pacific sectors. Storm‐induced penetration electric fields created favorable conditions for strong fountain effect uplifted the equatorial ionosphere, enhancement of the equatorial ionization anomaly (EIA), and postsunset EPBs generation. We found two patterns of equatorial ionospheric irregularities expansion toward low and middle latitudes: (a) storm‐induced EPBs developed over a large latitudinal extent between widely spread EIA crests, (b) narrow channel of the ionospheric irregularities stretched away from the EPB location toward the auroral zone in the northwestward direction. The EPBs latitudinal extent largely exceeded climatological‐based expectations for solar minimum conditions; EPBs reached atypically high latitudes (20°–25° magnetic latitude [MLAT]) in the Pacific Ocean sector. The poleward‐streaming plasma density depletions were registered along the western coast of North America. The ionospheric irregularities transported in the northwestward direction toward midlatitudes reaching as high as 40°–45° MLAT. The passage of these ionospheric irregularities coincided with the spread‐F conditions recorded at a midlatitude ionosonde (42° MLAT)—rather atypical phenomenon for midlatitudes. It is suggested that enhanced westward drifts associated with prompt penetration and Sub Auroral Polarization Stream electric fields can support the northwestward plasma transportation.

Signatures of Equatorial Plasma Bubbles and Ionospheric Scintillations from Magnetometer and GNSS Observations in the Indian Longitudes during the Space Weather Events of Early September 2017

Scintillation due to ionospheric plasma irregularities remains a challenging task for the space science community as it can severely threaten the dynamic systems relying on space-based navigation services. In the present paper, we probe the ionospheric current and plasma irregularity characteristics from a latitudinal arrangement of magnetometers and Global Navigation Satellite System (GNSS) stations from the equator to the far low latitude location over the Indian longitudes, during the severe space weather events of 6–10 September 2017 that are associated with the strongest and consecutive solar flares in the 24th solar cycle. The night-time influence of partial ring current signatures in ASYH and the daytime influence of the disturbances in the ionospheric E region electric currents (Diono) are highlighted during the event. The total electron content (TEC) from the latitudinal GNSS observables indicate a perturbed equatorial ionization anomaly (EIA) condition on 7 September, due to a sequence of M-class solar flares and associated prompt penetration electric fields (PPEFs), whereas the suppressed EIA on 8 September with an inverted equatorial electrojet (EEJ) suggests the driving disturbance dynamo electric current (Ddyn) corresponding to disturbance dynamo electric fields (DDEFs) penetration in the E region and additional contributions from the plausible storm-time compositional changes (O/N2) in the F-region. The concurrent analysis of the Diono and EEJ strengths help in identifying the pre-reversal effect (PRE) condition to seed the development of equatorial plasma bubbles (EPBs) during the local evening sector on the storm day. The severity of ionospheric irregularities at different latitudes is revealed from the occurrence rate of the rate of change of TEC index (ROTI) variations. Further, the investigations of the hourly maximum absolute error (MAE) and root mean square error (RMSE) of ROTI from the reference quiet days’ levels and the timestamps of ROTI peak magnitudes substantiate the severity, latitudinal time lag in the peak of irregularity, and poleward expansion of EPBs and associated scintillations. The key findings from this study strengthen the understanding of evolution and the drifting characteristics of plasma irregularities over the Indian low latitudes.

Ionospheric Plasma Vertical Drift and Zonal Wind Variations Cause Unusual Evolution of EPBs During a Geomagnetically Quiet Night

AbstractPrevious studies show equatorial plasma bubbles (EPBs) mainly occur after sunset and usually drift from west to east. In this work, two EPBs occurred after midnight and lasted to sunrise, and were observed by multi‐instruments (two all‐sky imagers (ASIs), global positioning system, Swarm satellite, and a digisonde) during a geomagnetically quiet night of December 18–19, 2018. Our observations also show that plasma depletion structure (PDS) also occurred at that night. EPBs occurred in the region of PDS and showed a special evolution process during the night. Those PDS gradually disappeared with time, but strip‐like EPBs remained clearly in airglow images. Near sunrise, new PDS appeared to merge with those EPBs to form large PDS. Meanwhile, EPBs showed different zonal drifts within a very narrow longitudinal zone (∼2°). One EPB remained stationary while the other showed a small eastward drift. These results are different from post‐sunset EPBs in previous studies. During the lifetime of those ionospheric plasma irregularities, upward and downward motion of the peak height and virtual height of the ionospheric F region was observed by a digisonde, which indicates that the evolution of EPBs should be related to the vertical drift of ionospheric plasma. Besides, based Thermosphere‐Ionosphere‐Electrodynamics General Circulation Model (TIE‐GCM) simulations, we suggest the different zonal drifts of those EPBs might related to plasma zonal drifts caused by zonal winds.

Westward Drift of Ionospheric Plasma Irregularities over a Low to Mid-latitude Transition Region in Indian Sector

We report the observation of plasma depletions/plumes in the F region ionosphere over a low to middle latitude transition region in the Indian sector. The observation of these plasma depletions is based on the data obtained in May 2019 through the all-sky airglow CCD imager installed in the campus of University of Kashmir, Srinagar (34.12 °N, 74.83 °E, magnetic latitude 25.91 °N). The depletions on the two consecutive nights of 05 and 06 May 2019 are aligned along the North-South (N-S) direction and drift westward. Several depletion bands along with some enhancement bands are seen in the 630-nm airglow images throughout the two nights. The observed structures show certain characteristics similar to Medium Scale Traveling Ionospheric Disturbances (MSTIDs) but these airglow features are not completely periodic. Further, in the observed depletion bands some East-West asymmetries are observed along with the structured tree-like branches of the airglow depletions. Some depletion bands even bifurcate leading to the inference that the structures are signatures of plasma irregularities rather than the usual MSTIDs observed in low-mid latitude transition region. The westward drift of the depletions especially during geomagnetic quiet times over this region makes this study significant since it offers a possible evidence that shows extension of spread F irregularities from the mid latitude region to the low-mid latitude transition region. In this paper, we point out some possible mechanisms related to the occurrence of plasma depletions at this region and their westward movement during geomagnetic quiet times.  

Equatorial Ionization Anomaly crest magnitude and its implications on the nocturnal equatorial ionospheric plasma irregularity characteristics

In this study, the association of Equatorial Ionization Anomaly (EIA) with various post sunset ionospheric irregularity manifestations are brought out empirically using Global Positioning System derived Total Electron Content (GPS - TEC) data from five stations centered around 77° E longitude as well as ionosonde data at a dip equatorial station Trivandrum (geographic latitude 8.5° N ; geographic longitude 77° E) for the days of vernal equinox season of distinct solar activity conditions. The study reveals that the EIA crest magnitude in the evening hours has a direct control on the base height of post sunset ionospheric F- layer (the primary factor responsible for the generation of ionospheric plasma irregularities) on a day-to-day level. Under the condition of strong (weak) EIA crest, the equatorial spread F irregularities are observed to be manifested earlier (later) and are sustained for a longer (shorter) duration. Further, the GPS signal scintillation intensity (quantified by the parameter S4 index) exhibits a direct association with EIA crest strength. This work emphasizes the need to incorporate various EIA features in the current models for better prediction of post sunset ionospheric plasma irregularities which are known to be hazardous for communication and navigation systems.

Characterization of ionospheric irregularities over Vietnam and adjacent region for the 2008-2018 period

This paper presents the variations of the rate of change of Total Electron Content (TEC) index (ROTI), characterizing the occurrence of ionospheric plasma irregularities over Vietnam and neighboring countries in the Southeast Asian region using the continuous GPS data during the 2008-2018 period. The results showed that the occurrence of strong ROTI in all stations is maximum in equinox months March/April and September/October and depends on solar activity. The ROTI is weak during periods of low solar activity and strong during periods of high solar activity. There is an asymmetry between the two equinoxes. During maximum and declining phases of 2014-2016, occurrence rates in March equinox are larger than in September equinox, but during the descending period of 2010-2011, the occurrence rates in September equinox at almost all stations are larger than in March equinox. The correlation coefficients between the monthly occurrence rate of irregularities and the F10.7 solar index at the stations in the equatorward EIA crest region are higher than at those in the magnetic equatorial and the poleward EIA crest regions. The irregularity occurrence is high in the pre-midnight sector, maximum between 2000 LT to 2200 LT. The maximum irregularity occurrence is located around 4-5° degrees in latitude equator-ward away from the anomaly crests.

Characterizing the accuracy of Global Positioning System for single point positioning at African low-latitude region

ABSTRACT This paper examines the accuracy of the Global Positioning System (GPS) within the African low-latitude sector. We evaluated the vertical and horizontal of the single-point positioning (SPP) accuracy of GPS and critically analysed the effects of the equatorial ionospheric anomaly (EIA) over the region of study. Our results imply that using single-frequency GPS for any application could give a positioning error up to 45.00 m vertically and ~25.00 m horizontally. The study revealed that 54% of GNSS positioning errors during the night-time could be linked to ionospheric plasma irregularities. Also, positioning errors are higher in western Africa than in the eastern region. The influence of geomagnetic activities is not consistent with GPS positioning accuracy. However, positioning errors are lower during geomagnetically disturbed conditions in comparison to quiet conditions. The unique phenomena of the EIA can severely limit GPS services at night-time for positioning in the study area.

Simultaneous detection of medium-scale traveling ionospheric disturbances and ionospheric plasma irregularities over Srinagar, J&K, India

Simultaneous detection of medium-scale traveling ionospheric disturbances and ionospheric plasma irregularities over Srinagar, J&K, India

Multiple Phase Screen Modeling of HF Wave Field Scintillations Caused by the Irregularities in Inhomogeneous Media

AbstractHigh frequency (HF) radio waves propagating through regions of ionospheric plasma irregularities exhibit random fluctuations in both amplitude and phase referred to as scintillations, which heavily influences the detection performance of HF sky‐wave radar and hybrid sky‐surface wave radar systems. In this paper, a numerical multiple phase screen model for HF sky‐wave propagation is developed, which can simulate the HF wave field scintillations caused by the irregularities in inhomogeneous media. In this model, the random phase changes due to irregularities and the diffraction effect due to phase mixing are considered separately and computed sequentially, where the phase change is numerically calculated using a geometric optical phase delay to allow for the consideration of horizontal electron density gradients. Utilizing the proposed model, we first simulate the observations of scintillation from the direct wave of the HF hybrid sky‐surface wave radar. The statistics of simulation and measured data, including power spectrum and scintillation indices on amplitude and phase, are considered to verify the effectiveness of the proposed model. Then, we analyze the effects of traveling ionospheric disturbances (TIDs) on the intensity of scintillation. The simulation indicates that the horizontal electron density gradients due to TIDs cause the fluctuation of the amplitude scintillation index .