A5058736637- Ionosphere and magnetosphere dynamics
- Solar and Space Plasma Dynamics
- Geomagnetism and Paleomagnetism Studies
- Earthquake Detection and Analysis
- GNSS positioning and interference
- Geophysics and Gravity Measurements
- Astro and Planetary Science
- Atmospheric Ozone and Climate
- Magnetic confinement fusion research
- Spacecraft Design and Technology
- Planetary Science and Exploration
- Plasma Diagnostics and Applications
- Laser-induced spectroscopy and plasma
- Radiation Detection and Scintillator Technologies
- earthquake and tectonic studies
- Lightning and Electromagnetic Phenomena
- Meteorological Phenomena and Simulations
- Space exploration and regulation
- Astronomical Observations and Instrumentation
- Methane Hydrates and Related Phenomena
- Atmospheric and Environmental Gas Dynamics
- Space Satellite Systems and Control
- Seismic Waves and Analysis
- Tropical and Extratropical Cyclones Research
- Inertial Sensor and Navigation
The University of Texas at Dallas
2015-2024
University of Dallas
1993-2021
High Altitude Observatory
2021
NSF National Center for Atmospheric Research
2021
Utah State University
2016
National Central University
1999
Rice University
1997
University of Oslo
1997
Queen Mary University of London
1996
Boston College
1994
Mathematical expressions have been constructed that allow the large‐scale global convection characteristics of high‐latitude ionosphere to be reproduced. The model contains no discontinuities in ion velocity and as such should useful F region chemical models. number variables features dayside throat Harang discontinuity modeled. applicability magnetospheric physics is limited by exclusion large‐magnitude small‐scale flow associated with discrete arcs inability produce separate cells at same...
Large subauroral convection velocities are striking features of the vector ion drift measurements made with RPA's and meters on Atmosphere Explorer satellites. The large AE‐C data base has been utilized to investigate character morphology this phenomenon. These latitudinally narrow found be confined predominantly local time sector between 18:00 hrs 02:00 hrs. They occur either singly or as multiple events, one which nearly always straddles equatorward edge auroral zone. Their occurrence...
The ionosphere is a highly dynamic medium that exhibits weather disturbances at all latitudes, longitudes, and altitudes, these can have detrimental effects on both military civilian systems. In an effort to mitigate the adverse effects, we are developing physics‐based data assimilation model of neutral atmosphere called Global Assimilation Ionospheric Measurements (GAIM). GAIM will use ionosphere‐plasmasphere Kalman filter as basis for assimilating diverse set real‐time (or near real‐time)...
The Atmosphere Explorer C data base of northern hemisphere ionospheric convection signatures at high latitudes is examined during times when the interplanetary magnetic field orientation relatively stable. It found that (IMF) has its expected garden hose orientation, center a region where ion flow rotates from sunward to antisunward displaced local noon toward dawn irrespective sign B y . Poleward this rotation region, called cleft, directed or dusk depending on whether positive negative,...
The theta aurora is a remarkable configuration of auroral and polar cap luminosities for which generally sun‐aligned transpolar arc extends contiguously from the dayside to nightside sectors oval. Four individual occurrences over earth's northern hemisphere are examined in detail with global imaging instrumentation on board high‐altitude, polar‐orbiting spacecraft DE 1. Simultaneous measurements fields plasmas this high‐altitude its low‐altitude, companion, 2, order establish an overview...
Multisatellite data are used to examine the temporal relationship between Subauroral Ion Drifts (SAID) and phases of an auroral substorm. Utilizing images luminosities taken by Dynamics Explorer 1 (DE 1) spacecraft observations particle injection at geosynchronous orbit, we identify time expansive phase onset estimate which recovery begins. Noting times SAID observed simultaneously DE 2 spacecraft, find that typically occur well after substorm (more than 30 min), during phase. Substantial...
Subauroral ion drifts (SAID) are latitudinally narrow regions of rapid westward drift located in the evening sector and centered on equatorward edge diffuse aurora. Observations SAID as identified by meters Atmosphere Explorer C Dynamics B spacecraft utilized to determine their effect F region composition, relationship mid‐latitude trough, temporal evolution. At altitudes near peak a deep ionization trough is formed large where O + concentration considerably depleted NO enhanced, while at...
Plasma, magnetic‐field and dc electric‐field observations from Dynamics Explorers 1 2 are used to investigate the morphology of solar‐wind ion injection, Birkeland currents, plasma convection in morning sector for both positive negative interplanetary magnetic field (IMF) B y components. The results study construct a ‐dependent global model southward IMF. A significant element is coexistence three types cells (“merging cells,” “viscous “lobe cells”). This can account nearly stationary (in...
During magnetic storms the ionospheric total electron content (TEC) at low‐ and midlatitudes often shows great enhancements, which may be associated with mechanisms producing midlatitude storm‐enhanced density (SED). The TEC enhancements result from different drivers such as electric fields, neutral winds, composition effects. To study importance of in enhancement, we perform numerical simulations for 29–30 October 2003 superstorm period American longitude sector (∼ −70°W) using Sheffield...
We analyzed measurements of ion number density made by the retarding potential analyzer aboard Atmosphere Explorer‐E (AE‐E) satellite, which was in an approximately circular orbit at altitude near 300 km 1977 and later 400 km. Large‐scale (>60 km) high‐altitude regions show large depletions bubble‐like structures are confined to narrow local time, longitude, magnetic latitude ranges, while those low‐altitude relatively small broadly distributed space. For this reason we considered below...
Ion drift meter observations from the Atmosphere Explorer E satellite during period of January 1977 to December 1979 are used study dependence equatorial (dip latitudes ≤ 7.5°) F region vertical plasma drifts (east‐west electric fields) on solar activity, season, and longitude. The satellite‐observed ion show large day‐to‐day seasonal variations. Solar cycle effects most pronounced near dusk sector with a increase prereversal velocity enhancement minimum maximum. diurnal, seasonal,...
Measurements of total ion concentration and drift velocity from Atmosphere Explorer C have been used to examine the convective flow plasma in vicinity mid‐latitude F region ionization trough. It is found that low‐latitude portion premidnight trough a slow eastward while poleward characterized by generally westward flow. The reversal typically occurs on edge where N i observed vary smoothly. We propose flux tubes within corotated into evening local time sector dusk before stagnating flowing...
Recent observations indicate that low‐altitude (below 1500 km) ion energization and thermal upwelling are colocated in the convective flow reversal region. In this region velocity V ⊥ is generally small but spatial gradients can be large. As a result, Joule heating small. The observed high level of (few electron volts or more) cannot explained by classical alone requires additional sources such as plasma waves. At these lower altitudes, free energy not obvious hence nature remains ill...
DE‐1 hot plasma observations in the mid‐altitude polar cusp have shown evidence of a significant velocity filtering phenomenon which is consistent with latitudinally narrow region injection located at geocentric distance about 8 R E (in dipole approximation). Plasma convection from into cap results ‘V’‐shaped log vs. α o relation distances near 4 . This effect allows measurement much smaller flow velocities (∼10 km/s) than heretofore been possible measurements. The flows thus determined are...
We study a set of south (summer) polar passes from the Dynamics Explorer 2 data base that provide measurements ion and neutral velocities along track spacecraft for various geomagnetic conditions. The are obtained drift meter retarding potential analyzer instruments; Fabry‐Perot interferometer wind temperature spectrometer instruments. These enable direct determination in situ ion‐neutral difference velocity. Simultaneous atmospheric composition using atmosphere electron temperatures...
Typically the solar radio emission at 10.7 cm is used to scale critical euv radiation that absorbed by Earth's neutral atmosphere. In latter half of 2008 this from Sun was lowest levels seen in last 50 years and persistence these low has never been recorded before. Here we show uniquely produce similarly unique behavior ionosphere upper Most remarkably, altitude extent significantly smaller than our present reference models would predict for activity. The transition height resides near 450...
[1] The extended solar minimum conditions in 2008 and 2009 presented an opportunity to investigate the ionosphere at lower activity levels than previously observed. The Coupled Ion Neutral Dynamics Investigation (CINDI) Velocity Meter (IVM) instrument onboard Communication/Navigation Outage Forecasting System is used construct median meridional (vertical) ion drifts, densities, O+ concentrations during periods of low geomagnetic for four characteristic seasons each year spanning late 2010....
Abstract The equatorial zonal electric field responses to prompt penetration of eastward convection fields (PPEF) were compared at closely spaced longitudinal intervals dusk premidnight sectors during the intense geomagnetic storm 17 March 2015. At sector (Indian longitudes), a rapid uplift F layer >550 km and development plasma bubbles (EPBs) observed. These EPBs found extend up 27.13°N 25.98°S magnetic dip latitudes indicating their altitude ~1670 apex. In contrast, few degrees east in...
Abstract We discuss, in a limited way, some of the challenges to advancing our understanding and description coupled plasma neutral gas that make up ionosphere thermosphere (I‐T). The I‐T is strongly influenced by wave motions atmosphere from lower magnetosphere, which supplies energetic particle precipitation field‐aligned currents at high latitudes. resulting dynamics are associated with generated solar heating upward propagating waves, particles electromagnetic energy magnetosphere...
We respond to several criticisms of the view that there is a physical linkage between solar activity and dynamics troposphere lower stratosphere, we provide further evidence in support mechanism for such involving atmospheric electricity cloud microphysics. The main are (1) decadal time scale variations stratified data result from aliasing introduced by sampling process not responses input; (2) observed correlations due chance coincidence or an periodicity uniquely related variability; (3)...