North Bethesda, MD, United States
North Bethesda, MD, United States

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Kuo C.L.,National Central University | Kuo C.L.,National Cheng Kung University | Huba J.D.,U.S. Navy | Joyce G.,Icarus Research Inc. | And 2 more authors.
Journal of Geophysical Research: Space Physics | Year: 2011

Recent ionospheric observations indicate that the total electron content (TEC) may anomalously decrease or increase up to 5-20% before the occurrence of big earthquakes. The ionospheric density variations can be caused by earth surface charges/currents produced from electric currents associated with the stressed rock. We formulate a coupling model for the stressed rock-Earth surface charges-atmosphere-ionosphere system. The stressed-rock acts as the dynamo to provide the currents for the coupling system. The electric fields and currents in the atmosphere and the lower boundary of ionosphere are obtained by solving the current continuity equation, ∇ · J = 0, where J is the current density. A three-dimensional ionosphere simulation code is then used to study the ionospheric dynamics based on the obtained electric fields and currents. The simulation results show that a current density Jrock = 0.2-10 μA/m2 in an earthquake fault zone is required to cause daytime TEC variations of 2-25%. The simulation results also show that a current density Jrock = 0.01-1 μA/m2 can lead to nighttime TEC variations of 1-30% as well as the formation of a nighttime plasma bubble (equatorial spread F) extending over the whole magnetic flux tube containing the earthquake epicenter. We suggest that observations of daytime and nighttime TEC variations and a nighttime plasma bubble within the affected region can be used as precursors for earthquake prediction. Copyright © 2011 by the American Geophysical Union.


Krall J.,U.S. Navy | Huba J.D.,U.S. Navy | Joyce G.,Icarus Research Inc. | Yokoyama T.,Cornell University
Annales Geophysicae | Year: 2010

Forces governing the three-dimensional structure of equatorial spread-F (ESF) plumes are examined using the NRL SAMI3/ESF three-dimensional simulation code. As is the case with the equatorial ionization anomaly (IA), density crests within the plume occur where gravitational and diffusive forces are in balance. Large E × B drifts within the ESF plume place these crests on field lines with apex heights higher than those of the background IA crests. Large poleward field-aligned ion velocities within the plume result in large ion-neutral diffusive forces that support these ionization crests at altitudes higher than background IA crest altitudes. We show examples in which density enhancements associated with ESF, also called 'plasma blobs,' can occur within an ESF plume on density-crest field lines, at or above the density crests. Simulated ESF density enhancements reproduce all key features of those that have been observed in situ.


Sprangle P.,U.S. Navy | Penano J.,U.S. Navy | Hafizi B.,Icarus Research Inc. | Gordon D.,U.S. Navy | And 2 more authors.
Applied Physics Letters | Year: 2011

We propose and analyze a remote atmospheric lasing configuration which utilizes a combination of an ultrashort pulse laser to form a plasma filament (seed electrons) by tunneling ionization and a heater pulse which thermalizes the seed electrons. Electrons collisionally excite nitrogen molecules and induce lasing in the ultraviolet. The lasing gain is sufficiently high to reach saturation within the length of the plasma filament. A remotely generated ultraviolet source may have applications for standoff detection of biological and chemical agents. © 2011 American Institute of Physics.


Huba J.D.,U.S. Navy | Joyce G.,Icarus Research Inc. | Krall J.,U.S. Navy | Siefring C.L.,U.S. Navy | Bernhardt P.A.,U.S. Navy
Geophysical Research Letters | Year: 2010

Large-scale, dawn density depletions in the equatorial ionosphere have been observed by instruments on the STPSat1 and CHAMP satellites. The Naval Research Laboratory (NRL) ionosphere model SAMI3 (Sami3 is Also a Model of the Ionosphere) is used to study this new phenomenon using a self-consistent electric field. Two empirical Horizontal Wind Models (HWM) are used in the simulation study: HWM93 and HWM07. Dawn density depletions are found using HWM07 but not with HWM93. The cause of the depletions is a post-midnight enhancement of the eastward electric field that generates an upward plasma drift. This drift lifts low density plasma to high altitudes (i.e., ∼600 km). We compare our model results to remote sensing data and to in situ satellite data. Copyright © 2010 by the American Geophysical Union.


Huba J.D.,U.S. Navy | Joyce G.,Icarus Research Inc.
Geophysical Research Letters | Year: 2010

The NRL three-dimensional ionospheric simulation code SAMI3 is used to model the onset and evolution of equatorial spread F (ESF). SAMI3 is a comprehensive ionosphere model that has been modified to self-consistently solve for the global neutral wind driven dynamo electric field as well as the gravity driven electric field associated with plasma bubbles. The latter is achieved with a high resolution longitudinal grid in the pre- to post-sunset sector (i.e., 1630 MLT-2230 MLT). Initial results from the new simulation model are presented. It is shown that ESF can be triggered by pre-sunset ionospheric density perturbations, and that an existing ESF bubble can trigger a new bubble. © 2010 by the American Geophysical Union.


Krall J.,U.S. Navy | Huba J.D.,U.S. Navy | Ossakow S.L.,Berkeley Research Associates | Joyce G.,Icarus Research Inc.
Geophysical Research Letters | Year: 2010

The Naval Research Laboratory (NRL) three-dimensional simulation code SAMI3/ESF is used to study the long time evolution of equatorial spread F (ESF) bubbles. The ESF bubbles are modeled until they stop rising and become-gfossils-h with results analyzed to address previously-untested hypotheses. Specifically, it has been suggested that bubbles stop rising when either the local electron density inside the bubble is equal to that of the nearby background or the fluxtube-integrated electron density inside the bubble is equal to that of the nearby background. It is shown that equatorial bubbles stop rising when the magnetic flux-tube-integrated ion mass density inside the bubble equals that of the surrounding background ionosphere. In the case of a singleion ionosphere this reduces to the condition that the fluxtube-integrated electron densities are in balance, consistent with the hypothesis of Mendillo et al. (2005). Copyright © 2010 by the American Geophysical Union.


Gordon D.F.,U.S. Navy | Hafizi B.,Icarus Research Inc.
Journal of Computational Physics | Year: 2012

A systematic technique for conservatively discretizing the time dependent Schrödinger equation on an arbitrary structured grid is given. Spatial differencing is carried out by finite volumes, and temporal differencing is carried out semi-implicitly. It is shown that the resulting algorithm conserves probability to within a round-off error regardless of the grid geometry. The algorithm is efficient for both serial and parallel computation. The conservative nature of the algorithm, and its phase accuracy, are demonstrated for a bound state, and for a free state in an electromagnetic field. The ionization rate for a hydrogen atom in a strong electromagnetic field is computed, and compared with the rate from tunneling theory. The regime of validity of tunneling theory is clarified. © 2012.


Ganguli G.,U.S. Navy | Rudakov L.,Icarus Research Inc. | Crabtree C.,U.S. Navy | Mithaiwala M.,U.S. Navy
Geophysical Research Letters | Year: 2012

Multi-pass gain in whistler energy is possible in the radiation belts if the wave amplitude is sufficiently large. Large amplitude magnetospherically reflected whistlers can induce nonlinear scattering and form a magnetospheric cavity filled with nearly isotropic spectrum of wave vectors perpendicular to the magnetic field with low obliqueness. This increases the wave-particle resonance time and maintains a large pitch angle scattering rate. Enhanced pitch angle scattering and precipitation of trapped electrons into the radiation belt loss cone provides a proportionate gain in the whistler energy. © 2012. American Geophysical Union. All Rights Reserved.


Mithaiwala M.,U.S. Navy | Rudakov L.,Icarus Research Inc. | Crabtree C.,U.S. Navy | Ganguli G.,U.S. Navy
Physics of Plasmas | Year: 2012

It is shown that the dispersion relation for whistler waves is identical for a high or low beta plasma. Furthermore, in the high-beta solar wind plasma, whistler waves meet the Landau resonance with electrons for velocities less than the thermal speed, and consequently, the electric force is small compared to the mirror force. As whistlers propagate through the inhomogeneous solar wind, the perpendicular wave number increases through refraction, increasing the Landau damping rate. However, the whistlers can survive because the background kinetic Alfven wave (KAW) turbulence creates a plateau by quasilinear (QL) diffusion in the solar wind electron distribution at small velocities. It is found that for whistler energy density of only ∼10 -3 that of the kinetic Alfven waves, the quasilinear diffusion rate due to whistlers is comparable to KAW. Thus, very small amplitude whistler turbulence can have a significant consequence on the evolution of the solar wind electron distribution function. © 2012 American Institute of Physics.


Rudakov L.,Icarus Research Inc. | Mithaiwala M.,U.S. Navy | Ganguli G.,U.S. Navy | Crabtree C.,U.S. Navy
Physics of Plasmas | Year: 2011

Kinetic Alfv́n wave turbulence in solar wind is considered and it is shown that non-Maxwellian electron distribution function has a significant effect on the dynamics of solar wind plasmas. Linear Landau damping leads to the formation of a plateau in the parallel electron distribution function which diminishes the Landau damping rate significantly. Nonlinear scattering of waves by plasma particles is generalized to short wavelengths and it is found that for the solar wind parameters this scattering is the dominant process as compared to three-wave decay and coalescence in the wave vector range 1/ ρ i

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