An official website of the United States government
Abstract We report a new ionosphere phenomenon: Equatorial ionization anomaly (EIA) discontinuity (EIAD), based on OI 135.6 nm radiance observations from the Global Observations of Limb and Disk (GOLD), ground‐based total electron content maps and in‐situ ion density data from Constellation Observing System for Meteorology, Ionosphere, and Climate‐2. The EIAD occurs when the OI radiance of the EIA crest has a local minimum, at a fixed UT, with the radiance in the local longitude region being weaker than that on the east and west sides. In the GOLD field‐of‐view, EIAD follows the seasonal variations of EIA. EIAD appears more often over the Atlantic Ocean and Africa than over South America. It occurs more in the southern crest during the December solstice, and more in the northern crest during both equinoxes. EIAD can occur under both quiet and disturbed times.
more »
« less
Early Morning Equatorial Ionization Anomaly From GOLD Observations
Abstract During geomagnetically quiet and solar minimum conditions, spatial variations of the early morning thermosphere‐ionosphere (TI) system are expected to be mainly governed by wave dynamics. To study the postmidnight dynamical coupling, we investigated the early morning equatorial ionization anomaly (EIA) using Global‐scale Observations of the Limb and Disk (GOLD) measurements of OI‐135.6 nm nightglow emission and global navigation satellite system (GNSS)‐based total electron content (TEC) maps. The EIA structures in the OI‐135.6 nm emission over the American landmass resemble, spatially and temporally, those observed in the GNSS‐TEC maps. The early morning EIA (EM‐EIA) crests are well separated in latitude and mostly located over the middle of South America during October–November. In February–April the crests are less separated in latitude and predominantly located over the west coast sector of South America. Whole Atmosphere Community Climate Model with thermosphere and ionosphere eXtension (WACCMX) simulations with constant solar minimum and quiet‐geomagnetic conditions show that EM‐EIA can occur globally and shows properties similar to longitudinal Wave 4 pattern. Thus, we propose that EM‐EIA is driven by dynamical changes associated with the lower atmospheric waves.
more »
« less
- Award ID(s):
- 1659304
- PAR ID:
- 10375428
- Publisher / Repository:
- DOI PREFIX: 10.1029
- Date Published:
- Journal Name:
- Journal of Geophysical Research: Space Physics
- Volume:
- 125
- Issue:
- 7
- ISSN:
- 2169-9380
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Abstract Medium‐scale Traveling Ionospheric Disturbances (MSTIDs) are prominent and ubiquitous features of the mid‐latitude ionosphere, and are observed in Super Dual Auroral Radar Network (SuperDARN) and high‐resolution Global Navigational Satellite Service (GNSS) Total Electron Content (TEC) data. The mechanisms driving these MSTIDs are an open area of research, especially during geomagnetic storms. Previous studies have demonstrated that nightside MSTIDs are associated with an electrodynamic instability mechanism like Perkins, especially during geomagnetically quiet conditions. However, dayside MSTIDs are often associated with atmospheric gravity waves. Very few studies have analyzed the mechanisms driving MSTIDs during strong geomagnetic storms at mid‐latitudes. In this study, we present mid‐latitude MSTIDs observed in de‐trended GNSS TEC data and SuperDARN radars over the North American sector, during a geomagnetic storm (peakKpreaching 9) on 7–8 September 2017. In SuperDARN, MSTIDs were observed in ionospheric backscatter with Line of Sight (LOS) velocities exceeding 800 m/s. Additionally, radar LOS velocities oscillated with amplitudes reaching ±500 m/s as the MSTIDs passed through the fields‐of‐view. In detrended TEC, these MSTIDs produced perturbations reaching ∼50 percent of background TEC magnitude. The MSTIDs were observed to propagate in the westward/south‐westward direction with a time period of ∼15 min. Projecting de‐trended GNSS TEC data along SuperDARN beams showed that enhancements in TEC were correlated with enhancements in SuperDARN SNR and positive LOS velocities. Finally, SuperDARN LOS velocities systematically switched polarities between the crests and the troughs of the MSTIDs, indicating the presence of polarization electric fields and an electrodynamic instability process during these MSTIDs.more » « less
-
Abstract Following the 2022 Tonga Volcano eruption, dramatic suppression and deformation of the equatorial ionization anomaly (EIA) crests occurred in the American sector ∼14,000 km away from the epicenter. The EIA crests variations and associated ionosphere‐thermosphere disturbances were investigated using Global Navigation Satellite System total electron content data, Global‐scale Observations of the Limb and Disk ultraviolet images, Ionospheric Connection Explorer wind data, and ionosonde observations. The main results are as follows: (a) Following the eastward passage of expected eruption‐induced atmospheric disturbances, daytime EIA crests, especially the southern one, showed severe suppression of more than 10 TEC Unit and collapsed equatorward over 10° latitudes, forming a single band of enhanced density near the geomagnetic equator around 14–17 UT, (b) Evening EIA crests experienced a drastic deformation around 22 UT, forming a unique X‐pattern in a limited longitudinal area between 20 and 40°W. (c) Thermospheric horizontal winds, especially the zonal winds, showed long‐lasting quasi‐periodic fluctuations between ±200 m/s for 7–8 hr after the passage of volcano‐induced Lamb waves. The EIA suppression and X‐pattern merging was consistent with a westward equatorial zonal dynamo electric field induced by the strong zonal wind oscillation with a westward reversal.more » « less
-
The low-latitude ionosphere has an active behavior causing the total electron content (TEC) to vary spatially and temporally very dynamically. The solar activity and the geomagnetic field have a strong influence over the spatiotemporal distribution of TEC. These facts make it a challenge to attempt modeling the ionization response. Single frequency GNSS users are particularly vulnerable due to these ionospheric variations that cause degradation of positioning performance. Motivated by recent applications of machine learning, temporal series of TEC available in map formats were employed to build an independent TEC estimator model for low-latitude environments. A TEC dataset was applied along with geophysical indices of solar flux and magnetic activity to train a feedforward artificial neural network based on a multilayer perceptron (MLP) approach. The forecast for the next 24 h was made relying on TEC maps over the Brazilian region using data collected on the previous 5 days. The performance of this approach was evaluated and compared with real data. The accuracy of the model was evaluated taking into account seasonality, spatial coverage and dependence on solar flux and geomagnetic activity indices. The results of the analysis show that the developed model has a superior capacity describing the TEC behavior across Brazil, when compared to global ionosphere maps and the NeQuick G model. TEC predictions were applied in single point positioning. The achieved errors were 27% and 33% lower when compared to the results obtained using the NeQuick G and global ionosphere maps, respectively, showing success in estimating TEC with small recent datasets using MLP.more » « less
-
Abstract The space weather event on 10–11 May 2024 was a high‐impact geomagnetic storm, resulting in a SYM‐H index decrease to −518 nT, the lowest level registered in several decades. We investigated the response of the Earth's ionosphere during the main phase of this storm using a comprehensive data set of ionospheric observations (in situ plasma density and/or Total Electron Content (TEC)) from twenty Low‐Earth‐Orbit satellites such as COSMIC‐2, Swarm, GRACE‐FO, Spire, DMSP, and Jason‐3, orbiting at altitudes between 320 and 1,330 km. We found that ionospheric response followed a classical development pattern with the largest positive effects occurred at low and middle latitudes in daytime and evening sectors, associated with significant intensification of the Equatorial Ionization Anomaly (EIA) by the super fountain effect. The greatest effects occurred in the Pacific and American longitudinal sectors, which were in daylight, between 19 and 24 UT on 10 May 2024. This time overlaps with a period of steady southward IMF Bz and favorable conditions for long‐lasting penetration electric fields. The EIA crest‐to‐crest separation expanded to 40–60° in latitude with the largest poleward excursion of the crest to ∼27° magnetic latitude. The extreme EIA expansion with crest separation up to 60° in latitude along with a giant plasma bite‐out near the magnetic equator were observed in the dusk/evening sector over South America. The ground‐based TEC showed an enhancement up to ∼200 TECU, while satellites detected an increase in topside TEC up to ∼100–155 TECU, indicating key contribution of the topside ionosphere into the ground‐based TEC.more » « less
