Bibliography

Towards estimation of atmospheric tidal effects on the ionosphere via data assimilation

The impact of atmospheric tides on the night time ionosphere is now being a subject of the extensive research within the scientific community. The plausible effect has been observed using the multiple space-borne instruments (e.g. COSMIC/FORMOSAT-3 constellation, TIMED GUVI and NASA IMAGE). Along with the observations, several modelling attempts has been undertaken to prove or refute the interrelation between the atmospheric tides and the wave-four longitudinal night time ionosphere structure. The scope of the current article is to assess the data assimilation ionosphere model capabilities in representing the longitudinal effect in the night time ionosphere induced by the DE3 atmospheric tide. Along with this, the core physics-based model capabilities in estimating the same effect are presented and discussed. For the current research, two periods were taken into consideration: the autumn equinox of the years 2006 and 2012. In the current article the data assimilation and physics-based models calculation results are presented and discussed along with the models\textquoteright error estimation and analysis.

Solomentsev, Dmitry; Cherniak, Yakov; Titov, Anton; Khattatov, Boris; Khattatov, Vyacheslav;

Published by: Advances in Space Research      Published on: 11/2015

YEAR: 2015     DOI: 10.1016/j.asr.2015.07.014

Atmosphere tides; data assimilation; Ionosphere longitudinal structure

Global ionospheric response to the 2009 sudden stratospheric warming event using Ionospheric Data Assimilation Four-Dimensional (IDA4D) algorithm

A data assimilation algorithm is used to delineate the time-dependent three-dimensional ionospheric response to the 2009 sudden stratospheric warming (SSW) event. We use the Ionospheric Data Assimilation Four-Dimensional (IDA4D) algorithm to study the global ionospheric response to the 2009 SSW. This is the first study to utilize global ionospheric measurements in a data assimilation framework to unambiguously characterize atmosphere-ionosphere coupling via tidal modifications during the 2009 SSW event. Model results reveal that the dominant mode of ionospheric variability during the 2009 SSW is driven by the enhancements in westward propagating semidiurnal tide with zonal wave number 1. The IDA4D results completely characterize the tidal perturbation during the 2009 SSW for the first time and show the global 3-D structure of the tide in total electron content (TEC) and electron density. The largest ionospheric responses were seen at low latitudes, where ionospheric plasma is extremely sensitive to the zonal electric field and susceptible to modifications by tidal winds in the lower thermosphere. The ionospheric response to the warming was characterized by an increase in TEC in the morning/early afternoon sector and a decrease during the late afternoon/evening period. The effects of coupling between the stratosphere and ionosphere were strongest between 220 km and 380 km. The IDA4D results also show a reversal of asymmetry in the equatorial ionization anomaly crests occurring several days after the peak of the 2009 SSW event. We suggest that this could be a result of the equatorial fountain effect being further modified by the summer-to-winter meridional neutral winds.

Azeem, I.; Crowley, G.; Honniball, C.;

Published by: Journal of Geophysical Research: Space Physics      Published on: 05/2015

YEAR: 2015     DOI: 10.1002/2015JA020993

Atmospheric tides; data assimilation; ionosphere/atmosphere interactions; sudden stratospheric warming

Ground-based GPS observation of SED-associated irregularities over CONUS

\ It has been known that steep total electron content (TEC) gradients observed at the boundary between the storm-enhanced plasma density (SED) and the low TEC region at subauroral and midlatitude regions are associated with ionospheric irregularities that impact communication and navigation systems. However, the relationship between the SED-associated irregularities and TEC gradients is still not well understood, partly because of the difficulties of resolving small-scale TEC gradients from sparsely distributed TEC observations. In this study, we examine the relationship between the SED-associated irregularities and TEC gradients during the intense geomagnetic storms of 31 March 2001 and 30 October 2003. To explore this relationship, TEC maps over the continental United States (CONUS) were constructed from ground-based GPS TEC observations, using Kalman filter update formulae with a recently developed nonstationary wavelet-based covariance model that enables resolution of TEC structures on both large and finer scales. Our results show that intense TEC gradients and ion drifts are thought to be required conditions for the formation of irregularities on the northeast side of the SED. Additionally, our methodology identified the narrow east-west stretch of TEC enhancement within the midlatitude low TEC region on 30 October 2003, and this TEC enhancement is most likely to be caused by auroral precipitation.

Sun, Yang-Yi; Matsuo, Tomoko; Araujo-Pradere, Eduardo; Liu, Jann-Yenq;

Published by: Journal of Geophysical Research: Space Physics      Published on: 05/2013

YEAR: 2013     DOI: 10.1029/2012JA018103

data assimilation; irregularity; nonstationary covariance; SED; TEC gradient

Assimilation of FORMOSAT-3/COSMIC electron density profiles into a coupled thermosphere/ionosphere model using ensemble Kalman filtering

This paper presents our effort to assimilate FORMOSAT-3/COSMIC (F3/C) GPS Occultation Experiment (GOX) observations into the National Center for Atmospheric Research (NCAR) Thermosphere Ionosphere Electrodynamics General Circulation Model (TIE-GCM) by means of ensemble Kalman filtering (EnKF). The F3/C electron density profiles (EDPs) uniformly distributed around the globe which provide an excellent opportunity to monitor the ionospheric electron density structure. The NCAR TIE-GCM simulates the Earth\textquoterights thermosphere and ionosphere by using self-consistent solutions for the coupled nonlinear equations of hydrodynamics, neutral and ion chemistry, and electrodynamics. The F3/C EDP are combined with the TIE-GCM simulations by EnKF algorithms implemented in the NCAR Data Assimilation Research Testbed (DART) open-source community facility to compute the expected value of electron density, which is \textquoteleftthe best\textquoteright estimate of the current ionospheric state. Assimilation analyses obtained with real F3/C electron density profiles are compared with independent ground-based observations as well as the F3/C profiles themselves. The comparison shows the improvement of the primary ionospheric parameters, such as NmF2 and hmF2. Nevertheless, some unrealistic signatures appearing in the results and high rejection rates of observations due to the applied outlier threshold and quality control are found in the assimilation experiments. This paper further discusses the limitations of the model and the impact of ensemble member creation approaches on the assimilation results, and proposes possible methods to avoid these problems for future work.

Lee, I.; Matsuo, T.; Richmond, A.; Liu, J; Wang, W.; Lin, C.; Anderson, J.; Chen, M.;

Published by: Journal of Geophysical Research      Published on: 10/2012

YEAR: 2012     DOI: 10.1029/2012JA017700

data assimilation; ensemble Kalman filter; FORMOSAT-3/COSMIC; Ionosphere