Vince Eccles

Lunar atmospheric tidal effects in the plasma drifts observed by the Low‐Latitude Ionospheric Sensor Network

[1] Data from the Low‐Latitude Ionospheric Sensor Network are used to examine ionospheric electrodynamics during quiet, low solar conditions from September to November 2009. The ground‐based magnetometers and the Jicamarca Vertical Incidence Pulsed Ionospheric Radar ionosonde in the Peruvian Sector are used to identify the neutral winds and plasma drifts that control the large‐scale plasma structure of the ionosphere. It is observed that the solar‐ and lunar‐driven semidiurnal tides have a significant influence on the background electrodynamics during this period of extreme solar minimum. The lunar tidal influence of the ionosphere electrodynamics is a large component of the variation of the vertical drift during the geophysically quiet study period. A significant portion, though not all, of the variation through the lunar month can be attributed to the lunar semidiurnal tide.

Ensemble Modeling with Data Assimilation Models: A New Strategy for Space Weather Specifications, Forecasts, and Science

The Earth’s Ionosphere-Thermosphere-Electrodynamics (I-T-E) system varies markedly on a range of spatial and temporal scales and these variations have adverse effects on human operations and systems, including high-frequency communications, over-the-horizon radars, and survey and navigation systems that use Global Positioning System (GPS) satellites. Consequently, there is a need to elucidate the underlying physical processes that lead to space weather disturbances and to both mitigate and forecast near-Earth space weather.

Estimation of cold plasma outflow during geomagnetic storms

Low-energy ions of ionospheric origin constitute a significant contributor to the magnetospheric plasma population. Measuring cold ions is difficult though. Observations have to be done at sufficiently high altitudes and typically in regions of space where spacecraft attain a positive charge due to solar illumination. Cold ions are therefore shielded from the satellite particle detectors. Furthermore, spacecraft can only cover key regions of ion outflow during segments of their orbit, so additional complications arise if continuous longtime observations, such as during a geomagnetic storm, are needed. In this paper we suggest a new approach, based on a combination of synoptic observations and a novel technique to estimate the flux and total outflow during the various phases of geomagnetic storms. Our results indicate large variations in both outflow rates and transport throughout the storm. Prior to the storm main phase, outflow rates are moderate, and the cold ions are mainly emanating from moderately sized polar cap regions. Throughout the main phase of the storm, outflow rates increase and the polar cap source regions expand. Furthermore, faster transport, resulting from enhanced convection, leads to a much larger supply of cold ions to the near-Earth region during geomagnetic storms.

Space weather forecasting with a Multimodel Ensemble Prediction System (MEPS)

The goal of the MEPS program is to improve space weather specification and forecasting with ensemble modeling. Space weather can have detrimental effects on a variety of civilian and military systems and operations, and many of the applications pertain to the ionosphere and upper atmosphere. Space weather can affect over-the-horizon (OTH) radars, HF communications, surveying and navigation systems, surveillance, spacecraft charging, power grids, pipelines, and the FAAs Wide-Area Augmentation System (WAAS). Because of its importance, numerous space weather forecasting approaches are being pursued, including those involving empirical, physics-based, and data assimilation models. Clearly, if there are sufficient data, the data assimilation modeling approach is expected to be the most reliable, but different data assimilation models can produce different results. Therefore, like the meteorology community, we created a Multimodel Ensemble Prediction System (MEPS) for the Ionosphere-Thermosphere-Electrodynamics (I-T-E) system that is based on different data assimilation models [Schunk et al., 2014a, b]. The MEPS ensemble is composed of seven physics-based data assimilation models for the ionosphere, ionosphere-plasmasphere, thermosphere, high-latitude ionosphere-electrodynamics, and mid-low latitude ionosphere-electrodynamics. Hence, multiple data assimilation models can be used to describe each region. A selected storm event that was reconstructed with four different data assimilation models covering the middle and low latitude ionosphere is presented and discussed. In addition, the effect of different data types on the reconstructions is shown.

Terminator field‐aligned currents: A new finding from the Ionospheric Dynamics and Electrodynamics Data Assimilation Model

A new field-aligned current system in the high-latitude ionosphere has been discovered. The finding was based on the reconstructions from the Ionospheric Dynamics and Electrodynamics Data Assimilation Model with the ingestion of ground-based magnetometer measurements. The new current system develops and evolves along the ionospheric terminator, and it is thus termed as the terminator field-aligned currents. This is the first field-aligned current system in the high-latitude ionosphere that is not directly driven by the magnetospheric dynamics and has an ionospheric origin. The study of it will help us to explore the active role of the ionosphere in the magnetosphere-ionosphere coupling and improve the physical understanding of the electrodynamics and plasma dynamics of many small-scale structures in the polar ionosphere.

Polar Topside Ionosphere During Geomagnetic Storms: Comparison of ISIS‐II With TDIM

Space weather deposits energy into the high polar latitudes, primarily via Joule heating that is associated with the Poynting flux electromagnetic energy flow between the magnetosphere and ionosphere. One way to observe this energy flow is to look at the ionospheric electron density profile (EDP), especially that of the topside. The altitude location of the ionospheric peak provides additional information on the net field-aligned vertical transport at high latitudes. To date, there have been few studies in which physics-based ionospheric model storm simulations have been compared with topside EDPs. A rich database of high-latitude topside ionograms obtained from polar orbiting satellites of the International Satellites for Ionospheric Studies (ISIS) program exists but has not been utilized in comparisons with physics-based models. Of specific importance is that the Alouette/ISIS topside EDPs spanned the timeframe from 1962 to 1983, a period that experienced very large geomagnetic storms. We use a physics-based ionospheric model, the Utah State University Time Dependent Ionospheric Model (TDIM), to simulate ionospheric EDPs for quiet and storm high-latitude passes of ISIS-II for two geomagnetic storms. This initial study finds that under quiet conditions there is good agreement between model and observations. During disturbed conditions, however, a large difference is seen between model and observations. The model limitation is probably associated with the inability of its topside boundary to replicate strong outflow conditions. As a result, modeling of the ionospheric outflows needs to be extended well into the magnetosphere, thereby moving the upper boundary much higher and requiring the use of polar wind models.