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Full-Text Articles in Physics

Radar Studies Of Height-Dependent Equatorial F Region Vertical And Zonal Plasma Drifts, S. A. Shidler, F. S. Rodrigues, Bela G. Fejer, M. A. Milla Feb 2019

Radar Studies Of Height-Dependent Equatorial F Region Vertical And Zonal Plasma Drifts, S. A. Shidler, F. S. Rodrigues, Bela G. Fejer, M. A. Milla

All Physics Faculty Publications

We present the results of an analysis of long-term measurements of ionospheric F region E × B plasma drifts in the American/Peruvian sector. The analysis used observations made between 1986 and 2017 by the incoherent scatter radar of the Jicamarca Radio Observatory. Unlike previous studies, we analyzed both vertical and zonal components of the plasma drifts to derive the geomagnetically quiet time climatological variation of the drifts as a function of height and local time. We determine the average behavior of the height profiles of the drifts for different seasons and distinct solar flux conditions. Our results show good agreement ...


Polar Topside Ionosphere During Geomagnetic Storms: Comparison Of Isis-Ii With Tdim, Jan J. Sojka, Donald Rice, Vince Eccles, Michael David, Robert W. Schunk, Robert Frederick Benson, H. G. James Jun 2018

Polar Topside Ionosphere During Geomagnetic Storms: Comparison Of Isis-Ii With Tdim, Jan J. Sojka, Donald Rice, Vince Eccles, Michael David, Robert W. Schunk, Robert Frederick Benson, H. G. James

All Physics Faculty Publications

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 ...


Large-Scale Gravity Wave Perturbations In The Mesopause Region Above Northern Hemisphere Midlatitudes During Autumnal Equinox: A Joint Study By The Usu Na Lidar And Whole Atmosphere Community Climate Model, Xuguang Cai, Titus Yuan, Han-Li Liu Feb 2017

Large-Scale Gravity Wave Perturbations In The Mesopause Region Above Northern Hemisphere Midlatitudes During Autumnal Equinox: A Joint Study By The Usu Na Lidar And Whole Atmosphere Community Climate Model, Xuguang Cai, Titus Yuan, Han-Li Liu

All Physics Faculty Publications

To investigate gravity wave (GW) perturbations in the midlatitude mesopause region during boreal equinox, 433h of continuous Na lidar full diurnal cycle temperature measurements in September between 2011 and 2015 are utilized to derive the monthly profiles of GW-induced temperature variance, T2, and the potential energy density (PED). Operating at Utah State University (42°N, 112°W), these lidar measurements reveal severe GW dissipation near 90km, where both parameters drop to their minima (∼ 20K2 and ∼50m2s−2, respectively). The study also shows that GWs with periods of 3–5h dominate the midlatitude mesopause region during the ...


Magnetic Meridional Winds In The Thermosphere Obtained From Global Assimilation Of Ionospheric Measurements (Gaim) Model, Levan Lomidze, Ludger Scherliess, Robert W. Schunk Sep 2015

Magnetic Meridional Winds In The Thermosphere Obtained From Global Assimilation Of Ionospheric Measurements (Gaim) Model, Levan Lomidze, Ludger Scherliess, Robert W. Schunk

All Physics Faculty Publications

Thermospheric neutral winds play an important part in the dynamics of ionospheric plasma and represent one of the key inputs for ionospheric physics-based models. Yet wind measurements are scarce and generally lack global coverage and continuity. To help mitigate this shortcoming, a data assimilation model was used to estimate neutral winds in the low- and middle-latitude thermosphere. Seasonal global maps of NmF2 andhmF2 were generated from Constellation Observing System for Meteorology, Ionosphere, and Climate radio occultation measurements for geomagnetically quiet and low solar flux conditions. The maps were assimilated into the Utah State University Global Assimilation of ...


Altitudinal Variability Of Quiet-Time Plasma Drifts In The Equatorial Ionosphere, Debrup Hui May 2015

Altitudinal Variability Of Quiet-Time Plasma Drifts In The Equatorial Ionosphere, Debrup Hui

All Graduate Theses and Dissertations

The plasma drifts or electric fields and their structures in the ionosphere affect the accuracy of the present-day space-based systems. For the first time, we have used ionospheric plasma drift data from Jicamarca radar measurements to study the climatology of altitudinal variations of vertical and zonal plasma drifts in low latitudes during daytime. We used data from 1998 to 2014 to derive these climatological values in bimonthly bins from 150 km to 600 km. For the vertical plasma drifts, we observed the drifts increasing with altitudes in the morning and slowly changing to drifts decreasing with altitude in the afternoon ...


Ensemble Modeling With Data Assimilation Models: A New Strategy For Space Weather Specifications, Forecasts, And Science, Robert W. Schunk, Ludger Scherliess, V. Eccles, L. C. Gardner, Jan J. Sojka, L. Zhu, X. Pi, A. J. Mannucci, B. D. Wilson, A. Komjathy, C, Wang, G. Rosen Mar 2014

Ensemble Modeling With Data Assimilation Models: A New Strategy For Space Weather Specifications, Forecasts, And Science, Robert W. Schunk, Ludger Scherliess, V. Eccles, L. C. Gardner, Jan J. Sojka, L. Zhu, X. Pi, A. J. Mannucci, B. D. Wilson, A. Komjathy, C, Wang, G. Rosen

All Physics Faculty Publications

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 pro- cesses that lead to space weather disturbances and to both mitigate and forecast near-Earth space weather.


Resolving Ionospheric E-Region Modeling Challenges: The Solar Photon Flux Dependence, Joseph B. Jensen, Jan J. Sojka, Michael David, Kent Tobiska, Robert W. Schunk, Tom Woods, Frank Eparvier Apr 2013

Resolving Ionospheric E-Region Modeling Challenges: The Solar Photon Flux Dependence, Joseph B. Jensen, Jan J. Sojka, Michael David, Kent Tobiska, Robert W. Schunk, Tom Woods, Frank Eparvier

Browse All Undergraduate research

The EVE instrument of the NASA Solar Dynamics Observatory (SDO) provides for the first time EUV and XUV measurements of the solar irradiance that adequately define the major source of ionization of the atmosphere. In our study we modeled the E-region of the ionosphere and analyzed how it is affected by the solar irradiance data obtained by EVE and contrast this with the S2000 Solar Irradiance model, used previously. The ionosphere has two major layers, the E-layer at 100 km, and the F-layer at 300 km. The difference in solar irradiances are small except at some wavelength bands, it is ...


Resolving Ionospheric E-Region Modeling Challenges: The Solar Photon Flux Dependence, Joseph B. Jensen, Jan J. Sojka, Michael David, Kent Tobiska, Robert W. Schunk, Tom Woods, Frank Eparvier Apr 2013

Resolving Ionospheric E-Region Modeling Challenges: The Solar Photon Flux Dependence, Joseph B. Jensen, Jan J. Sojka, Michael David, Kent Tobiska, Robert W. Schunk, Tom Woods, Frank Eparvier

Student Showcase

No abstract provided.


Using Sdo-Eve Satellite Data To Model For The First Time How Large Solar Flares Influence The Earths Ionosphere, Joseph B. Jensen, Jan J. Sojka, Michael David, Bob Schunk, Tom Woods, Frank Eparvier Jan 2013

Using Sdo-Eve Satellite Data To Model For The First Time How Large Solar Flares Influence The Earths Ionosphere, Joseph B. Jensen, Jan J. Sojka, Michael David, Bob Schunk, Tom Woods, Frank Eparvier

Research on the Hill (Salt Lake City)

The ionosphere is important in our everyday communicaBons. Many satellites, like GPS satellites, have to send signals through the ionosphere, and many emergency radio communicators depend on the ionosphere to extend the range of their communicaBons. We also have many satellites and even the InternaBonal space staBon located in this region of the atmosphere. It becomes important for the astronauts in the ISS and for the health of the satellites to know what is going on in the ionosphere and how it can affect their systems.

The lower regions are important because the E-­‐region will extend the distance that ...


Cedar Electrodynamics Thermosphere Ionosphere (Eti) Challenge For Systematic Assessment Of Ionosphere/Thermosphere Models: Electron Density, Neutral Density, Nmf2, And Hmf2 Using Space Based Observations, J. S. Shim, M. Kuznetsova, L. Rastätter, D. Bilitza, L. Butala, M. Emery, B. Foster, T. J. Fuller-Rowell, J. Huba, A. J. Mannucci, X. Pi, A. Ridley, Ludger Scherliess, Jan J. Sojka, P. Stephens, D. C. Thompson, D. Weimer, Lie Zhu, E. Sutton Oct 2012

Cedar Electrodynamics Thermosphere Ionosphere (Eti) Challenge For Systematic Assessment Of Ionosphere/Thermosphere Models: Electron Density, Neutral Density, Nmf2, And Hmf2 Using Space Based Observations, J. S. Shim, M. Kuznetsova, L. Rastätter, D. Bilitza, L. Butala, M. Emery, B. Foster, T. J. Fuller-Rowell, J. Huba, A. J. Mannucci, X. Pi, A. Ridley, Ludger Scherliess, Jan J. Sojka, P. Stephens, D. C. Thompson, D. Weimer, Lie Zhu, E. Sutton

All Physics Faculty Publications

In an effort to quantitatively assess the current capabilities of Ionosphere/Thermosphere (IT) models, an IT model validation study using metrics was performed. This study is a main part of the CEDAR Electrodynamics Thermosphere Ionosphere (ETI) Challenge, which was initiated at the CEDAR workshop in 2009 to better comprehend strengths and weaknesses of models in predicting the IT system, and to trace improvements in ionospheric/thermospheric specification and forecast. For the challenge, two strong geomagnetic storms, four moderate storms, and three quiet time intervals were selected. For the selected events, we obtained four scores (i.e., RMS error, prediction efficiency ...


Observations Of The Vertical Ion Drift In The Equatorial Ionosphere During The Solar Minimum Period Of 2009, R. A. Stoneback, R. A. Heelis, A. G. Burrell, W. R. Coley, Bela G. Fejer, E. Pacheco Dec 2011

Observations Of The Vertical Ion Drift In The Equatorial Ionosphere During The Solar Minimum Period Of 2009, R. A. Stoneback, R. A. Heelis, A. G. Burrell, W. R. Coley, Bela G. Fejer, E. Pacheco

Bela G. Fejer

[1] The extended solar minimum conditions in 2008 and 2009 presented an opportunity to investigate the ionosphere at lower solar activity levels than previously observed. The Coupled Ion Neutral Dynamics Investigation (CINDI) Ion Velocity Meter (IVM) instrument onboard the Communication/Navigation Outage Forecasting System is used to construct the median meridional (vertical) ion drifts, ion densities, and O+ concentrations during periods of low geomagnetic activity for four characteristic seasons each year spanning late 2008 to 2010. The presence of a large semidiurnal component in the ion drift variation at the equator produced significant differences from typical ionospheric conditions. Instead of ...


Duskside F-Region Dynamo Currents: Itsrelationship With Prereversal Enhancement Of Vertical Plasma Drift, P. Park, H. Luhr, Bela G. Fejer, K. W. Mim Jan 2010

Duskside F-Region Dynamo Currents: Itsrelationship With Prereversal Enhancement Of Vertical Plasma Drift, P. Park, H. Luhr, Bela G. Fejer, K. W. Mim

Bela G. Fejer

From magnetic field observations by CHAMP we estimate F-region dynamo current densities near the sunset terminator during solar maximum years from 2001 to 2002. The dynamo currents are compared with the pre-reversal enhancement (PRE) of vertical plasma drift as observed by ROCSAT-1. The seasonal-longitudinal variation of PRE can be largely related to the F-region dynamo current density, with the correlation coefficient reaching 0.74. The correlation can be further improved if we consider a zonal gradient of the E-region Pedersen conductivity, which also depends on season and longitude. It is widely accepted that the Fregion dynamo drives PRE near sunset ...


Analysis Of Total Electron Content (Tec) Variations In The Low- And Middle-Latitude Ionosphere, Ja Soon Shim May 2009

Analysis Of Total Electron Content (Tec) Variations In The Low- And Middle-Latitude Ionosphere, Ja Soon Shim

All Graduate Theses and Dissertations

Detailed study of the spatial correlations of day-to-day ionospheric TEC variations on a global scale was performed for four 30-day-long periods in 2004 (January, March/April, June/July, September/October) using observations from more than 1000 ground-based GPS receivers. In order to obtain the spatial correlations, initially, the day-to-day variability was calculated by first mapping the observed slant TEC values for each 5-minute GPS ground receiver-satellite pair to the vertical and then differencing it with its corresponding value from the previous day. This resulted

in more than 150 million values of day-to-day change in TEC (delta TEC). Next, statistics were ...


Overviewand Summary Of The Spread F Experiment (Spreadfex), D. C. Fritts, M. A. Abdu, B. R. Batista, I. S. Batista, P. P. Batista, R. Buritii, B. R. Clemesha, J. Comberiate, T. Dautermann, E. De Paula, B. J. Fechine, Bela G. Fejer, D. Gobbi, J. Haase, F. Kalamabadi, B. Laughman, P. P. Lima, H. L. Liu, A. Medeiros, D. Pautet, F. Sao Sabbas, J. H.A. Sobral, P. Stamus, H. Takahashi, M. J. Taylor, S. L. Vadas, C. Wrasse Jan 2009

Overviewand Summary Of The Spread F Experiment (Spreadfex), D. C. Fritts, M. A. Abdu, B. R. Batista, I. S. Batista, P. P. Batista, R. Buritii, B. R. Clemesha, J. Comberiate, T. Dautermann, E. De Paula, B. J. Fechine, Bela G. Fejer, D. Gobbi, J. Haase, F. Kalamabadi, B. Laughman, P. P. Lima, H. L. Liu, A. Medeiros, D. Pautet, F. Sao Sabbas, J. H.A. Sobral, P. Stamus, H. Takahashi, M. J. Taylor, S. L. Vadas, C. Wrasse

Bela G. Fejer

We provide here an overview of, and a summary of results arising from, an extensive experimental campaign (the Spread F Experiment, or SpreadFEx) performed from September to November 2005, with primary measurements in Brazil. The motivation was to define the potential role of neutral atmosphere dynamics, specifically gravity wave motions propagating upward from the lower atmosphere, in seeding Rayleigh-Taylor instability (RTI) and plasma bubbles extending to higher altitudes. Campaign measurements focused on the Brazilian sector and included ground-based optical, radar, digisonde, and GPS measurements at a number of fixed and temporary sites. Related data on convection and plasma bubble structures ...


The Adaptability Of Langmuir Probes To The Pico-Satellite Regime, Andrew Jay Auman Dec 2008

The Adaptability Of Langmuir Probes To The Pico-Satellite Regime, Andrew Jay Auman

All Graduate Theses and Dissertations

The purpose of this thesis is to investigate whether it is feasible to use Langmuir probes on pico-satellites flying in low Earth orbit over mid- to low-latitude geographic regions. Following chapters on the expected ionospheric conditions and an overview of Langmuir probe theory, a chapter addressing the difficulties involved with pico-satellite Langmuir probes is presented. Also, the necessary satellite-to-probe surface area requirements in order to achieve confidence in pico-satellite Langmuir probe data, for the orbital regions of interest to this thesis, are stated.


Relation Between The Occurrence Rate Of Esf And The Verticalplasma Drift Velocity At Sunset Derived Form Global Observations, C. Stolle, H. Luhr, Bela G. Fejer Jan 2008

Relation Between The Occurrence Rate Of Esf And The Verticalplasma Drift Velocity At Sunset Derived Form Global Observations, C. Stolle, H. Luhr, Bela G. Fejer

Bela G. Fejer

In this study, we investigate two global climatological data sets; the occurrence rate of Equatorial Spread- F (ESF), associated with equatorial plasma irregularities, at 400 km altitude obtained from CHAMP observations, and the evening equatorial vertical plasma drift, vz, from ROCSAT-1 measurements. First, as retrieved for a solar flux level of F10.7=150, the longitudinal variation of the two independently derived quantities correlates between 84% and 93% in the seasons December solstice, equinox and June solstice. The highest correlation is found for the solstice seasons when vz is integrated over local time around the prereversal enhancement (PRE) and displaced ...


Gravity Wave And Tidalinfluences On Equatorial Spread F Based On Observations During The Spread F Experiment(Spreadfex), D. C. Fritts, S. L. Vadas, D. M. Riggin, M. A. Abdu, I. S. Batista, H. Takahashi, A. Medeiros, F. Kalamabadi, H. L. Liu, Bela G. Fejer, M. J. Taylor, F. Vargas Jan 2008

Gravity Wave And Tidalinfluences On Equatorial Spread F Based On Observations During The Spread F Experiment(Spreadfex), D. C. Fritts, S. L. Vadas, D. M. Riggin, M. A. Abdu, I. S. Batista, H. Takahashi, A. Medeiros, F. Kalamabadi, H. L. Liu, Bela G. Fejer, M. J. Taylor, F. Vargas

Bela G. Fejer

The Spread F Experiment, or SpreadFEx, was performed from September to November 2005 to define the potential role of neutral atmosphere dynamics, primarily gravity waves propagating upward from the lower atmosphere, in seeding equatorial spread F (ESF) and plasma bubbles extending to higher altitudes. A description of the SpreadFEx campaign motivations, goals, instrumentation, and structure, and an overview of the results presented in this special issue, are provided by Fritts et al. (2008a). The various analyses of neutral atmosphere and ionosphere dynamics and structure described in this special issue provide enticing evidence of gravity waves arising from deep convection in ...


Equatorial Ionospheric Electric Fields During The November 2004 Magnetic Storm, Bela G. Fejer, J. W. Jensen, T. Kikuchi, M. A. Abdu, J. L. Chau Oct 2007

Equatorial Ionospheric Electric Fields During The November 2004 Magnetic Storm, Bela G. Fejer, J. W. Jensen, T. Kikuchi, M. A. Abdu, J. L. Chau

Bela G. Fejer

[1] We use radar measurements from the Jicamarca Radio Observatory, magnetometer observations from the Pacific sector and ionosonde data from Brazil to study equatorial ionospheric electric fields during the November 2004 geomagnetic storm. Our data show very large eastward and westward daytime electrojet current perturbations with lifetimes of about an hour (indicative of undershielding and overshielding prompt penetration electric fields) in the Pacific equatorial region during the November 7 main phase of the storm, when the southward IMF, the solar wind and reconnection electric fields, and the polar cap potential drops had very large and nearly steady values. This result ...


Evolution Of Equatorial Ionospheric Bubbles During A Large Auroral Electrojet Increase In The Recovery Phase Of A Magnetic Storm, M. J. Keskinen, S. L. Ossakow, Bela G. Fejer, J. Emmert Feb 2006

Evolution Of Equatorial Ionospheric Bubbles During A Large Auroral Electrojet Increase In The Recovery Phase Of A Magnetic Storm, M. J. Keskinen, S. L. Ossakow, Bela G. Fejer, J. Emmert

Bela G. Fejer

[1] We present a model and observations of the evolution of equatorial ionospheric bubbles during a large auroral electrojet (AE) index increase in the recovery phase of a geomagnetic storm. Using a three-dimensional time-dependent numerical simulation model, we find, for the 19–21 October 1998 storm, that the equatorial bubble evolution is different during storm time as compared to quiet time conditions. We have found that the storm time vertical drift in conjunction with reduced off-equatorial E region shorting is the primary mechanism that distinguishes the large AE increase recovery phase storm time evolution from the quiet time case. Comparison ...


Utah State University Global Assimilation Of Ionospheric Measurements Gauss-Markov Kalman Filter Model Of The Ionosphere: Model Description And Validation, L. Scherliess, Robert W. Schunk, Jan Josef Sojka, Donald C. Thompson, Lie Zhu Jan 2006

Utah State University Global Assimilation Of Ionospheric Measurements Gauss-Markov Kalman Filter Model Of The Ionosphere: Model Description And Validation, L. Scherliess, Robert W. Schunk, Jan Josef Sojka, Donald C. Thompson, Lie Zhu

All Physics Faculty Publications

The Utah State University Gauss-Markov Kalman Filter (GMKF) was developed as part of the Global Assimilation of Ionospheric Measurements (GAIM) program. The GMKF uses a physics-based model of the ionosphere and a Gauss-Markov Kalman filter as a basis for assimilating a diverse set of real-time (or near real-time) observations. The physics-based model is the Ionospheric Forecast Model (IFM), which accounts for five ion species and covers the E region, F region, and the topside from 90 to 1400 km altitude. Within the GMKF, the IFM derived ionospheric densities constitute a background density field on which perturbations are superimposed based on ...


Assimilative Modeling Of The Equatorial Ionosphere For Scintillation Forecasting: Modeling With Vertical Drifts, J. M. Retterer, D. T. Decker, W. S. Borer, R. E. Daniell, Bela G. Fejer Nov 2005

Assimilative Modeling Of The Equatorial Ionosphere For Scintillation Forecasting: Modeling With Vertical Drifts, J. M. Retterer, D. T. Decker, W. S. Borer, R. E. Daniell, Bela G. Fejer

Bela G. Fejer

[1] Knowledge of the vertical plasma drift velocity observed by the Jicamarca incoherent radar in seven events is assimilated into a theoretical model for the ambient F region plasma density. Comparisons of the calculated plasma density model and the observed plasma density show that, apart from the signature effects of equatorial plasma bubbles, the ambient model captures much of the detail of the plasma density profiles. Rayleigh-Taylor growth rates calculated with the ambient model show a good correlation with the occurrence of spread F.


A New Global Average Model Of The Coupled Thermosphere And Ionosphere, C. G. Smithtro, Jan Josef Sojka Jan 2005

A New Global Average Model Of The Coupled Thermosphere And Ionosphere, C. G. Smithtro, Jan Josef Sojka

All Physics Faculty Publications

A model representing the global average ionosphere and thermosphere (GAIT) is developed as a tool to explore the response of the coupled system to changes in the input solar irradiance between 3 and 360 nm. The GAIT model self-consistently solves the coupled continuity, momentum, and energy equations for the three major neutral species, N2, O2, and O, as well as minor neutral constituents important to the global energy budget. In the ionosphere the model includes five different ion species and two excited states of O+. The GAIT model also includes an approximate treatment of photoelectrons, in order to ...


Behavior Of The Ionosphere And Thermosphere Subject To Extreme Solar Cycle Conditions, C. G. Smithtro, Jan Josef Sojka Jan 2005

Behavior Of The Ionosphere And Thermosphere Subject To Extreme Solar Cycle Conditions, C. G. Smithtro, Jan Josef Sojka

All Physics Faculty Publications

A 1-D global average ionosphere and thermosphere (GAIT) model is used to examine the climatological behavior of the upper atmosphere, subject to both extremely low and high solar flux. These extremes are justified, in part, by the Maunder Minimum and Grand Maximum epochs described by J. A. Eddy, as well as other studies involving cosmogenic isotopes and Sun-like stars. As the irradiance falls below normal solar minimum levels, the concentration of O+ decreases rapidly relative to the molecular ions, such that the ratio ƒoF2oF1 approaches unity. When subject to exceptionally high solar fluxes ...


Global Dayside Ionospheric Uplift And Enhancements Due To Interplanetary Shock Electric Fields, B. R. Tsurutani, A. Mannucci, B. Ijima, A. Saito, K. Yumoto, M. A. Abdu, J. H.A. Sobral, W. D. Gonzalez, F. L. Guarnieri, T. Tsuda, Bela G. Fejer, T. J. Fuller-Rowell, J. U.O. Kozyra, J. C. Foster, A. Coster, V. M. Vasyliumas Jan 2004

Global Dayside Ionospheric Uplift And Enhancements Due To Interplanetary Shock Electric Fields, B. R. Tsurutani, A. Mannucci, B. Ijima, A. Saito, K. Yumoto, M. A. Abdu, J. H.A. Sobral, W. D. Gonzalez, F. L. Guarnieri, T. Tsuda, Bela G. Fejer, T. J. Fuller-Rowell, J. U.O. Kozyra, J. C. Foster, A. Coster, V. M. Vasyliumas

Bela G. Fejer

[1] The interplanetary shock/electric field event of 5–6 November 2001 is analyzed using ACE interplanetary data. The consequential ionospheric effects are studied using GPS receiver data from the CHAMP and SAC-C satellites and altimeter data from the TOPEX/Poseidon satellite. Data from ∼100 ground-based GPS receivers as well as Brazilian Digisonde and Pacific sector magnetometer data are also used. The dawn-to-dusk interplanetary electric field was initially ∼33 mV/m just after the forward shock (IMF BZ = −48 nT) and later reached a peak value of ∼54 mV/m 1 hour and 40 min later (BZ = −78 nT). The ...


Development Of A Physics-Based Reduced State Kalman Filter For The Ionosphere, Ludger Scherliess, Robert W. Schunk, Jan Josef Sojka, Donald C. Thompson Jan 2004

Development Of A Physics-Based Reduced State Kalman Filter For The Ionosphere, Ludger Scherliess, Robert W. Schunk, Jan Josef Sojka, Donald C. Thompson

All Physics Faculty Publications

A physics-based data assimilation model of the ionosphere is under development as the central part of a Department of Defense/Multidisciplinary University Research Initiative (MURI)-funded program called Global Assimilation of Ionospheric Measurements (GAIM). With the significant increase in the number of ionospheric observations that will become available over the next decade, this model will provide a powerful tool toward an improved specification and forecasting of the global ionosphere, with an unprecedented accuracy and reliability. The goal of this effort will be specifications and forecasts on spatial grids that can be global, regional, or local (25 km × 25 km). The ...


Low Latitude Ionospheric Disturbance Electric Field Effects Duringthe Recovery Phase Of The October 19-21, 1998 Magnetic Storm, Bela G. Fejer, J. T. Emmert Dec 2003

Low Latitude Ionospheric Disturbance Electric Field Effects Duringthe Recovery Phase Of The October 19-21, 1998 Magnetic Storm, Bela G. Fejer, J. T. Emmert

Bela G. Fejer

[1] Low-latitude ionospheric electric fields and currents are often strongly disturbed during periods of enhanced geomagnetic activity. These perturbations can last for several hours after geomagnetic quieting. We use incoherent scatter radar measurements from Jicamarca and Arecibo during 19–21 October 1998 to study, for the first time, the low-latitude disturbance electric fields during the recovery phase of a large magnetic storm. On 19 October the Jicamarca data showed initially large and short-lived (time scale of about 10–20 min) upward and westward drift perturbations in the early afternoon sector, due to the penetration of strong magnetospheric electric fields probably ...


Three-Dimensional Nonlinear Evolution Ofequatorial Ionospheric Spread-F Bubbles, M. J. Keskinen, S. L. Ossakow, Bela G. Fejer Aug 2003

Three-Dimensional Nonlinear Evolution Ofequatorial Ionospheric Spread-F Bubbles, M. J. Keskinen, S. L. Ossakow, Bela G. Fejer

Bela G. Fejer

[1] Using numerical simulation techniques, we present the first study of the three-dimensional nonlinear evolution of an equatorial spread-F bubble. The background ionosphere used to initialize the bubble evolution is computed using a time-dependent first-principles equatorial plasma fountain model together with a prereversal enhancement vertical drift model. We find that finite parallel conductivity effects slow down both the linear and nonlinear bubble evolution compared to the two-dimensional evolution. In addition we find that bubble-like structures with extremely sharp density gradients can be generated off the equator at equatorial anomaly latitudes in agreement with recent observations.


Radar Studies Of Mid-Latitude Ionospheric Plasma Drifts, L. Scherliess, Bela G. Fejer, J. Holt, L. Goncharenko, C. Armory-Mazaudier, M. J. Buonsanto Feb 2001

Radar Studies Of Mid-Latitude Ionospheric Plasma Drifts, L. Scherliess, Bela G. Fejer, J. Holt, L. Goncharenko, C. Armory-Mazaudier, M. J. Buonsanto

Bela G. Fejer

We use incoherent scatter radar measurements from Millstone Hill and Saint Santin to study the midlatitude F region electrodynamic plasma drifts during geomagnetically quiet and active periods. We present initially a local time, season, and solar flux dependent analytical model of the quiet time zonal and meridional E × B drifts over these stations. We discuss, for the first time, the Saint Santin drift patterns during solar maximum. We have used these quiet time models to extract the geomagnetic perturbation drifts which were modeled as a function of the time history of the auroral electrojet indices. Our results illustrate the evolution ...


Seasonal And Magnetic Activity Variations Of Ionospheric Electric Fields Above The Southernmid-Latitude Station, Bundoora, Australia, M. L. Parkinson, R. Polglase, Bela G. Fejer, L. Scherliess, P. L. Dyson, S. M. Ujmaia Jan 2001

Seasonal And Magnetic Activity Variations Of Ionospheric Electric Fields Above The Southernmid-Latitude Station, Bundoora, Australia, M. L. Parkinson, R. Polglase, Bela G. Fejer, L. Scherliess, P. L. Dyson, S. M. Ujmaia

Bela G. Fejer

We investigate the seasonal, local solar time, and geomagnetic activity variations of the average Doppler velocity measured by an HF digital ionosonde deployed at Bundoora, Australia. The Doppler velocities were heavily averaged to suppress the short-term effects (<3>hours) of atmospheric gravity waves, and thereby obtain the diurnal variations attributed to the tidally-driven ionospheric dynamo and electric fields generated by magnetic disturbances. The observed seasonal variations in Doppler velocity were probably controlled by variations in the lower thermospheric winds and ionospheric conductivity above Bundoora and in the magnetically conjugate location. The diurnal variations of the meridional (fieldperpendicular) drifts and their perturbations ...


De-2 Observations Of Morningside And Eveningside Plasma Density Depletions In The Equatorial Ionosphere, M. Palmroth, H. Laakso, Bela G. Fejer, R. F. Pfaff Aug 2000

De-2 Observations Of Morningside And Eveningside Plasma Density Depletions In The Equatorial Ionosphere, M. Palmroth, H. Laakso, Bela G. Fejer, R. F. Pfaff

Bela G. Fejer

The occurrence of equatorial density depletions in the nightside F region ionosphere has been investigated by using observations gathered by the polar-orbiting Dynamics Explorer 2 satellite from August 1981 to February 1983. A variety of electric field/plasma drift patterns were observed within these depletions, including updrafting, downdrafting, bifurcating, converging, subsonic, and supersonic flows. The depletions, 116 events in total, are distributed over two groups: group I (eveningside depletions) consists of the events in the 1900–2300 MLT sector, and group II (morningside depletions) are the events in the 2300–0600 MLT sector. A statistical analysis reveals clear differences in ...