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Results for “IONOSPHERIC IRREGULARITY”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

Formation and detection of high latitude ionospheric irregularities

Measurements of Total Electron Content (TEC) and airglow variations show that large scale plasma patches appearing in the high-latitude ionsophere have irregular structures evidenced by the satellite phase and amplitude scintillations. Whistler waves, intense quasi-DC electric field, and atmospheric gravity waves can become potential sources of various plamsa instabilities. The role of thermal effects in generating ionospheric irregularities by these sources is discussed. Meter-scale irregularities in the ionospheric E and F regions can be excited parametrically with lower hybrid waves by intense whistler waves. Ohmic dissipation of Pedersen current in the electron gas is able to create ionospheric F region irregularities in plasma blobs or plasma patches (i.e., high ambient plasma density environment) with broad scale lengths ranging from tens of meters to a few kilometers. Through the neutral-charged particle collisions, gravity waves can excite large-scale (less than tens of kilometers) ionospheric irregularities simultaneously with forced ion acoustic modes in the E region. The large-scale ionospheric density fluctuations produced in the E region can extend subsequently alogn the earth's magnetic field to the F region and the topside ionospheric regions. These mechanisms characterized by various thermal effects can contribute additively with other processes to the formation of ionospheric irregularities in the high latitude region.

Lee, M. C.↗
NASA NTRS2024

Variability and Distribution of Nighttime Equatorial to Mid Latitude Ionospheric Irregularities and Vertical Plasma Drift Observed by FORMOSAT-5 Advanced Ionospheric Probe In-Situ Measurements from 2017 – 2020

Irregularities in ionospheric plasma distribution can result in severe scintillation and disruption to the radio frequencies utilized for satellite communications and navigation. In the low and mid latitudes, these irregularities can include Equatorial Plasma Bubbles (EPBs) and Travelling Ionospheric Disturbances (TIDs). EPBs are irregularities manifesting in low latitude nighttime ionosphere plasma density that can extend along magnetic field lines with zonal scales on the order of 100 km or less, while TIDs are propagating wave disturbances. High frequency in-situ measurements of ionospheric plasma aboard spacecraft in Low Earth Orbit (LEO) are a direct measurement of irregularities in plasma density and are therefore valuable for resolving EPB and TID occurrences, variability, and relation to other ionospheric parameters that are believed to play a driving role in the formation of such irregularities. In this study, we utilize observations taken over a three-year period between 2017 and 2020 by the Advanced Ionospheric Probe (AIP) carried aboard the FORMOSAT-5 satellite to examine the spatial, seasonal, and interannual variability of equatorial to mid latitude ionospheric irregularities and vertical ion drift during this time. AIP provides in-situ measurements of ion density and vertical ion drift in the equatorial to mid latitude ionosphere at approximately 720 km altitude with local times between 22:00 – 23:00 local time. Our global scale results resolve distinct and inter-annually recurrent seasonal patterns in the distribution of nighttime ionospheric irregularities and vertical plasma drift during this time. Elevated occurrences of ion density irregularities are resolved along the Equatorial Ionization Anomaly (EIA) latitudes, while notable occurrences with variability consistent with EPBs also observed along the low and equatorial magnetic latitudes. Zonal variability of equatorial irregularities consistent with the signatures of nonmigrating atmospheric tides are observed. It is also notable that the occurrences and geographic distribution of ion density irregularities showed a considerable level of interannual variability, especially at mid latitudes over the South Atlantic and Southern African sectors, which showed much higher levels of irregularities in 2017–––2018, compared to 2019 and 2020. In comparison, the spatial and interannual variation of the co-located vertical ion drifts were much more consistent during the years examined, indicating that the driver for the observed interannual variability in ion density irregularities cannot be attributed to the vertical ion drift at the same time and location of the observations. This highlights the need for in-situ instruments distributed across multiple satellites in different local time zones.

ionosphere↗
NASA NTRS2021

Applying Machine Learning to Predict Alaskan Ionospheric Irregularities

In this work several machine-learning (ML) techniques for predicting ionospheric irregularities in the northern auroral zone were tested. The techniques include Ridge Regression, Long Short-Term Memory Neural Network (LSTM), Classification Neural Network (CNN), Autoencoder Classification Neural Network (ACNN), and LSTM Autoencoder Classification Neural Network (LACNN). These techniques were tested with the rate of total electron content (TEC) index (ROTI) data collected during 2008 and 2009 from a geodetic station in Fairbanks, Alaska (64.98°N, 147.50°W), which is in the auroral zone. Using ROTI data with the ML techniques, experiments were conducted to reach two goals: (1) examine what space weather measurements present good correlation with ROTI so that they may be helpful in ML-based prediction of ionospheric irregularities in the polar region; (2) predict ROTI hours and days ahead by training the neural network models with historical ROTI data alone. The Ridge Regression experiments indicate that a combination of measurements of local geomagnetic horizontal components, geomagnetic SYM-H index, 3-hour Kp and ap indices, and F10.7 solar flux index appears to be more correlated to the single-site ROTI measurements than other parameters. The neural network (NN) experiments show that although the LACNN model allows for predictions of non-irregularity and irregularity conditions defined by ROTI levels up to 3 hours in advance, with an overall accuracy ≥ 92%, a number of irregularity events can still be missed. Hence, further development is needed to reduce the number of missed events. In this paper, the models, data processing, model performance, prediction results, and potential applications are presented.

Pi, Xiaoqing↗
NASA NTRS2013

Observations of Global and Regional Ionospheric Irregularities and Scintillation Using GNSS Tracking Networks

The rate of TEC index (ROTI) is a measurement that characterizes ionospheric irregularities. It can be obtained from standard GNSS dual-frequency phase data collected using a geodetic type of GNSS receiver. By processing GPS data from ground-based networks of International GNSS Service and Continuously Operating Reference Station (CORS), ROTI maps have been produced to observe global and regional scintillation activities. A major mid-latitude scintillation event in the contiguous United States is reported here that was captured in ROTI maps produced using CORS GPS data collected during a space weather storm. The analyses conducted in this work and previously by another group indicate that ROTI is a good occurrence indicator of both amplitude and phase scintillations of GPS L-band signals, even though the magnitudes of ROTI, S4, and sigma(sub phi) can be different. For example, our analysis indicates that prominent ROTI and the L1 phase scintillation (sigma(sub phi)) are well correlated temporally in the polar region while L1 amplitude scintillation rarely occurs. The differences are partially attributed to physics processes in different latitude regions, such as high-speed plasma convection in the polar region that can suppress the amplitude scintillation. An analysis of the impact of ionospheric scintillation on precise positioning, which requires use of dual-frequency phase data, is also conducted. The results indicate that significant (more than an order of magnitude) positioning errors can occur under phase scintillation conditions.

ionospheric measurements↗
NASA NTRS1966

The height of large ionospheric irregularities.

Signal amplitude of Transit IVA satellite recorded at two stations, using time difference between observing similar fluctuations in fading period to determine height of ionospheric irregularities

TIME DELAY↗
NASA NTRS1974

Geophysical properties of the ionospheric irregularities responsible for radio scintillation

The properties of F-region ionospheric irregularities are described based on in-situ measurements of the actual waveforms of ion concentration. The spectral properties of the irregularities are discussed. In high, middle and low latitudes most of the irregularities observed fall into a single 'noiselike' category having power spectra which can be approximated by f to the negative n-th power and S to the n-th power, where S is the irregularity scale size and n is approximately 2. Thus the spectral components have a maximum gradient which is almost independent of their size. Other categories of irregularities are also observed occasionally.

Mcclure, J. P.↗
NASA NTRS1974

The use of global ionospheric irregularity models for satellite communications

Scintillation data obtained in the VHF region were used by Fremouw to develop a global scintillation model. An attempt has been made in the present study to improve this model in several respects. One of these is to modify the high latitude term in the model to better represent data obtained in the northern high latitude regions. Another improvement is the extention of the frequency region of validity to the L band and microwave regions. This attempt is based on certain theoretical considerations regarding the effects of distribution in irregularity sizes. Recent satellite in situ measurements indicate that the ionospheric irregularity description is functionally different from that assumed in the past. These satellite measurements are used in connection with the theoretical development to improve the model.

Pope, J. H.↗
NASA NTRS1992

Experimental studies of ionospheric irregularities and related plasma processes

Utah State University (USU) continued its program of measuring and interpreting electron density and its variations in a variety of ionospheric conditions with the Experimental Studies of Ionospheric Irregularities and Related Plasma Processes program. The program represented a nearly ten year effort to provide key measurements of electron density and its fluctuations using sounding rockets. The program also involved the joint interpretation of the results in terms of ionospheric processes. A complete campaign summary and a brief description of the major rocket campaigns are also included.

Baker, Kay D.↗
NASA NTRS1975

Effect of small ionospheric irregularities on radio wave absorption

The ionospheric absorption of a radio wave caused by small-scale irregularities with a gaussian autocorrelation function is calculated for various values of the linear scale height, the radio frequency, the scale size of the irregularities, and the mean-square fractional electron density fluctuations. The absorption is due to scattering of the radio wave into plasma oscillations by the irregularities. It is concluded that the absorption due to such irregularities with a mean-square fractional electron density deviation greater than about 0.000001 exceeds the normal collisional height-integrated absorption. Absorption of this type could play a significant part in heating experiments or in an ionosphere containing naturally occurring irregularities.

Chen, H. C.↗