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Solar wind interactions with the Earth’s magnetosphere cause geomagnetic storms and thereby induce ionospheric storms. This study investigates the spatio-temporal evolution of the ionospheric Total Electron Content (TEC) during a moderate but long duration storm driven by solar wind high-speed streams (HSSs) and associated co-rotating interaction region (CIR) during 14-21 March 2016. The storm starts with a strong storm sudden commencement (SSC) with a peak close to 19 UT on 14 March 2016. The GNSS/TEC maps are obtained from the Madrigal database. The associated field-aligned currents (FACs) from AMPERE, ionospheric convection maps from SuperDARN, and the O/N2 ratio from TIMED/GUVI are also studied for understanding the physics behind the different features observed in TEC during the storm.The study predominantly focuses on the changes of TEC at high and middle latitudes. The storm induced changes in the TEC were extracted by removing the quiet time background (mean of five quietest days of the month) from the TEC maps. During the initial phase, TEC enhancements and depletions are found mainly at high latitudes within the auroral oval and close to the cusp, plausibly associated with auroral precipitation and variations in the upward and downward field-aligned currents (FACs). After the onset of the main phase, the TEC is enhanced at mid-latitudes and auroral ovals with a maximum of ~10 TECU. Meanwhile, a significant decrease in TEC is observed in the polar cap region. During the main phase, we observe the evolution of a storm-enhanced-density (SED) plume and a transient enhancement of TEC in the polar cap. Later during the storm, a strong TEC depletion at high and middle latitudes is found on the dayside and in the evening sector. The depletion of O/N2 ratio, triggered by Joule heating and atmospheric upwelling, could be a plausible reason for the TEC depletion. The possible physical mechanisms associated with the observed TEC variations will be discussed.

Assessing space weather modeling capability is a key element in improving existing models and developing new ones. In order to track improvement of the models and investigate impacts of forcing, from the lower atmosphere below and from the magnetosphere above, on the performance of ionosphere-thermosphere models, we expand our previous assessment for 2013 March storm event [Shim et al., 2018]. In this study, we evaluate new simulations from upgraded models (Coupled Thermosphere Ionosphere Plasmasphere Electrodynamics (CTIPe) model version 4.1 and Global Ionosphere Thermosphere Model (GITM) version 21.11) and from NCAR Whole Atmosphere Community Climate Model with thermosphere and ionosphere extension (WACCM-X) version 2.2 including 8 simulations in the previous study. A simulation of NCAR Thermosphere-Ionosphere-Electrodynamics General Circulation Model version 2 (TIE-GCM 2) is also included for comparison with WACCM-X. TEC and foF2 changes from quiet-time background are considered to evaluate the model performance on the storm impacts. For evaluation, we employ 4 skill scores: Correlation coefficient (CC), root-mean square error (RMSE), ratio of the modeled to observed maximum percentage changes (Yield), and timing error(TE). It is found that the models tend to underestimate the storm-time enhancements of foF2 (F2-layer critical frequency) and TEC (Total Electron Content) and to predict foF2 and/or TEC better in the North America but worse in the Southern Hemisphere. The ensemble simulation for TEC is comparable to results from a data assimilation model (Utah State University-Global Assimilation of Ionospheric Measurement (USU-GAIM)) with differences in skill score less than 3% and 6% for CC and RMSE, respectively.

The Earth’s magnetosphere is the outermost layer of the geospace system deflecting energetic charged particles from the Sun and solar wind. The solar wind has major impacts on the Earth’s magnetosphere, but it is unclear whether the same holds for solar flares—a sudden eruption of electromagnetic radiation on the Sun. Here we use a recently developed whole geospace model combined with observational data from the 6 September 2017 X9.3 solar flare event to reveal solar flare effects on magnetospheric dynamics and on the electrodynamic coupling between the magnetosphere and its adjacent ionosphere, the ionized part of Earth’s upper atmosphere. We observe a rapid and large increase in flare-induced photoionization of the polar ionospheric E-region at altitudes between 90 km and 150 km. This reduces the efficiency of mechanical energy conversion in the dayside solar wind–magnetosphere interaction, resulting in less Joule heating of the Earth’s upper atmosphere, a reconfiguration of magnetosphere convection, as well as changes in dayside and nightside auroral precipitation. This work thus demonstrates that solar flare effects extend throughout the geospace via electrodynamic coupling, and are not limited—as previously believed—to the atmospheric region where radiation energy is absorbed1. The solar wind affects the magnetosphere, but whether this holds true for solar flares was unclear. By combining geospace modelling with observations, solar flares are shown to influence the dynamics of the magnetosphere and its ionosphere coupling.

We demonstrate a novel method for observing Large Scale Traveling Ionospheric Disturbances (LSTIDs) using high frequency (HF) amateur radio reporting networks, including the Reverse Beacon Network (RBN), Weak Signal Propagation Reporter Network (WSPRNet), and PSKReporter. LSTIDs are quasi-periodic variations in ionospheric densities with horizontal wavelengths >1,000 km and periods between 30 and 180 min. On Nov 3, 2017, LSTID signatures were observed simultaneously over the continental United States in amateur radio, SuperDARN HF radar, and GNSS Total Electron Content with a period of similar to 2.5 hr, propagation azimuth of similar to 163 degrees, horizontal wavelength of similar to 1680 km, and phase speed of similar to 1,200 km hr(-1). SuperMAG SME index enhancements and Poker Flat Incoherent Scatter Radar measurements suggest the LSTIDs were driven by auroral electrojet intensifications and Joule heating. This novel measurement technique has applications in future scientific studies and for assessing the impact of LSTIDs on HF communications. United States National Science Foundation (NSF) [AGS-2045755, AGS-2002278]; NASA [80NSSC21K0002, 80NSSC21K1772]; NSF [AGS-1952737, AGS-1935110, AGS-1840962, AGS-1853408, AGS-1552269] Published version The authors gratefully acknowledge the support of United States National Science Foundation (NSF) Grants AGS-2045755 and AGS-2002278 and NASA Grants 80NSSC21K0002 and 80NSSC21K1772. We are especially grateful to the amateur radio community who voluntarily produced and provided the HF radio observations used in this presentation, especially the operators of the , , pskreporter.info, and . Blackstone SuperDARN data are made available with support from NSF AGS-1935110. This material is based upon work supported by the Poker Flat Incoherent Scatter Radar which is a major facility funded by the NSF through cooperative agreement AGS-1840962 to SRI International. Algorithms used to calculate the electric field and Joule heating rates were developed under NSF AGS-1853408 and AGS-1552269. GNSS TEC data products and access through the Madrigal distributed data system are provided to the community by the Massachusetts Institute of Technology under support from NSF grant AGS-1952737. Individual contributors of GNSS data are listed in the Open Research section. We gratefully acknowledge the SuperMAG collaborators () who contributed to the SuperMAG database (Gjerloev, 2012) and the SuperMAG SME(r) indices (Newell & Gjerloev, 2011a, 2011b). NAF thanks Rachel Frissell, Bill Liles, Ethan Miller, and Dev Raj Joshi for helpful discussions.

Polar holes were observed in the high-latitude ionosphere during a series of multi-instrument case studies close to the Northern Hemisphere winter solstice in 2014 and 2015. These holes were observed during geomagnetically quiet conditions and under a range of solar activities using the European Incoherent Scatter (EISCAT) Svalbard Radar (ESR) and measurements from Global Navigation Satellite System (GNSS) receivers. Steep electron density gradients have been associated with phase scintillation in previous studies; however, no enhanced scintillation was detected within the electron density gradients at these boundaries. It is suggested that the lack of phase scintillation may be due to low plasma density levels and a lack of intense particle precipitation. It is concluded that both significant electron density gradients and plasma density levels above a certain threshold are required for scintillation to occur.

Simultaneous multi‐instrument observations of the redistribution of cold (, National Aeronautics and Space Administration (NASA) (Contract NAS5-01072)

A plasma density hole was created in the ionosphere by a rocket launch from Cape Canaveral, Florida near local sunset on 30 August 2020, which is called rocket exhaust depletion (RED). The hole persisted for several hours into the night and was observed in total electron content (TEC) maps, the Global-scale Observations of the Limb and Disk (GOLD) imager, and multiple low-earth-orbit satellites. The RED created a nightglow pit in the GOLD 135.6 nm image. Swarm satellites found that the RED exhibited insignificant changes in electron/ion temperature and field-aligned currents. On the other hand, magnetic field strength was enhanced inside the RED by a few tenths of a nanotesla. Assimilation data products of the Constellation Observing System for Meteorology, Ionosphere, and Climate 2 (COSMIC-2) mission reveal that ionospheric slab thickness increased at the center of the RED, which is supported by combined analyses of the GOLD and TEC data. The RED did not host conspicuous substructures that are stronger and longer-lasting than the ambient plasma did.

We present results of the NASA Living With a Star Institute 2019: “Space Weather Impacts TEC and scintillations at MidLatitudes.” We analyzed available ground-based observations of GPS scintillation events in the context of geophysical drivers associated with ionospheric space weather. We leverage geodetic receivers with a 1-Hz temporal resolution to drive proxy scintillation indices. We discuss observability limits of the 1-Hz receivers and their utility as a space weather diagnostic. The GPS receivers cover the American longitude sector, spanning from Panama to Canada in latitudes. We surveyed 8 years of available data between 2012 and 2020 and found 9 events during which a portion of the receiver network observed amplitude scintillations at magnetic mid-latitudes. All events occurred during geomagnetic storms. The storm’s Dst ranged between -204 nT and -51 nT, with a median of -131 nT, and median Kp 7-. We discuss some individual events in more detail.

Low-latitude plasma blobs have been studied since their first being reported in 1986. However, investigations on temporal evolution of a blob or on continental scale (2,000 km) ionospheric contexts around it are relatively rare. Overcoming these limitations can help elucidate the blob generation mechanisms. On 21 January 2021, the Ionospheric Connection Explorer satellite encountered a typical low-latitude blob near the northeastern coast of South America. The event was collocated with a local enhancement in 135.6 nm nightglow at the poleward edge of an equatorial plasma bubble (EPB), as observed by the Global-scale Observations of the Limb and Disk (GOLD) imager. Total electron content maps from the Global Navigation Satellite System confirm the GOLD observations. Unlike typical medium-scale traveling ionospheric disturbances (MSTIDs), the blob had neither well-organized wavefronts nor moved in the southwest direction. Neither was the blob a monotonically decaying equatorial ionization anomaly crest past sunset. Rather, the blob varied following latitudinal expansion/contraction of EPBs at similar magnetic longitudes. The observational results support that mechanisms other than MSTIDs, such as EPBs, can also contribute to blob generation.

We report on an extreme ionospheric plasma density enhancement and Global Positioning System (GPS) scintillation at dawn, observed within the expanding equatorial ionization anomaly (EIA). The tota...

The role a geospace plume in influencing the efficiency of magnetopause reconnection is an open question with two contrasting theories being debated. A local‐control theory suggests that a plume decreases both local and global reconnection rates, whereas a global‐control theory argues that the global reconnection rate is controlled by the solar wind rather than local physics. Observationally, limited numbers of point measurements from spacecraft cannot reveal whether a local change affects the global reconnection. A distributed observatory is hence needed to assess the validity of the two theories. We use THEMIS and Los Alamos National Laboratory spacecraft to identify the occurrence of a geospace plume and its contact with the magnetopause. Global evolution and morphology of the plume is traced using GPS measurements. SuperDARN is then used to monitor the distribution and the strength of dayside reconnection. Two storm‐time geospace plume events are examined and show that as the plume contacts the magnetopause, the efficiency of reconnection decreases at the contact longitude. The amount of local decrease is 81% and 68% for the two events, and both values are consistent with the mass loading effect of the plume if the plume's atomic mass is ∼4 amu. Reconnection in the surrounding is enhanced, and when the solar wind driving is stable, little variation is seen in the cross polar cap potential. This study illuminates a pathway to resolve the role of cold dense plasma on solar wind‐magnetosphere coupling, and the observations suggest that plumes redistribute magnetopause reconnection activity without changing the global strength substantially., Key Points We strategically coordinate measurements made by THEMIS and Los Alamos National Laboratory spacecraft, GPS network, and SuperDARN to investigate geospace plumesPlumes decrease the local reconnection rate at the plume longitude and increase the reconnection rate in regions adjacent to the plumeWhen the solar wind is stable, the global reconnection remains unchanged in presence of plumes, supporting a global‐control theory

Space weather can cause serious disturbances of global navigation satellite systems (GNSS) used for positioning and navigation purposes. This paper describes a new method to forecast space weather disturbances on GNSS at high latitudes, in which we describe the formation and propagation of polar cap patches and predict their arrival at the nightside auroral oval. The space weather prediction model builds on the expanding/contracting polar cap (ECPC) paradigm and total electron content (TEC) observations from the Global Positioning System (GPS) network. The input parameter is satellite observations of the interplanetary magnetic field at the first Lagrange point. To validate our prediction model, we perform a case study in which we compare the results from our prediction model to observations from the GPS TEC data from the MIT's Madrigal database, convection data from Super Dual Auroral radar network, and scintillation data from Svalbard. Our results show that the ECPC paradigm describes the polar cap patch motion well and can be used to predict scintillations of GPS signals at high latitudes.

Much theoretical and observational work has been devoted to studying the occurrence of F region polar cap patches in the Northern Hemisphere; considerably less work has been applied to the Southern Hemisphere. In recent years, the Madrigal database of mappings of total electron content (TEC) has improved in Southern Hemisphere coverage, to the point that we can now carry out a study of patch frequency and occurrence. We find that Southern Hemisphere patch occurrence is very similar to that of the Northern Hemisphere with a half‐year offset, plus an offset in universal time of approximately 12 hr. This is further supported by running an ionospheric model for both hemispheres and applying the same patch‐to‐background technique. Further, we present a simple physical mechanism involving a sunlit dayside plasma source concurrent with a dark polar cap, which yields a patch‐to‐background pattern very much like that seen in the TEC mappings for both hemispheres.

The Earth's ionosphere/thermosphere (I/T) system exhibits complicated weather variability that can have adverse effects on human operations and systems, and consequently, there is a need for both accurate and reliable specifications and forecasts for this region. As part of the international effort to evaluate and assess the predictive capabilities of space weather models, four working groups for the I/T system have been created with the goal to devise a concerted model validation effort for the I/T environment. This paper presents an overview of the team efforts and reports on the progress made. As a first step, the working teams have selected to limit the validation efforts to critical I/T parameters that include total electron content, the peak density and height of the ionospheric F region, ionospheric scintillations, and thermospheric neutral densities. As part of this effort, initial lists of participating models and events have been constructed and validation data sets have been identified. In the future appropriate metrics will be selected for the various user and scientific needs.

Source at https://doi.org/10.1109/TGRS.2018.2847026. In ionospheric tomography, the atmospheric electron density is reconstructed from different electron density related measurements, most often from ground-based measurements of satellite signals. Typically, ionospheric tomography suffers from two major complications. First, the information provided by measurements is insufficient and additional information is required to obtain a unique solution. Second, with necessary spatial and temporal resolutions, the problem becomes very high dimensional, and hence, computationally infeasible. With Bayesian framework, the required additional information can be given with prior probability distributions. The approach then provides physically quantifiable probabilistic interpretation for all model variables. Here, Gaussian Markov random fields (GMRFs) are used for constructing the prior electron density distribution. The use of GMRF introduces sparsity to the linear system, making the problem computationally feasible. The method is demonstrated over Fennoscandia with measurements from global navigation satellite system (GNSS) and low Earth orbit (LEO) satellite receiver networks, GNSS occultation receivers, LEO satellite Langmuir probes, and ionosonde and incoherent scatter radar measurements.