Sample records for artificial ionospheric layers

  1. Incidence angle dependence of Langmuir turbulence and artificial ionospheric layers driven by high-power HF-heating

    NASA Astrophysics Data System (ADS)

    Eliasson, B.; Milikh, G.; Shao, X.; Mishin, E. V.; Papadopoulos, K.; Papadopoulos

    2015-04-01

    We have numerically investigated the development of strong Langmuir turbulence (SLT) and associated electron acceleration at different angles of incidence of ordinary (O) mode pump waves. For angles of incidence within the Spitze cone, the turbulence initially develops within the first maximum of the Airy pattern near the plasma resonance altitude. After a few milliseconds, the turbulent layer shifts downwards by about 1 km. For injections outside the Spitze region, the turning point of the pump wave is at lower altitudes. Yet, an Airy-like pattern forms here, and the turbulence development is quite similar to that for injections within the Spitze. SLT leads to the acceleration of 10-20 eV electrons that ionize the neutral gas thereby creating artificial ionospheric layers. Our numerical modeling shows that most efficient electron acceleration and ionization occur at angles between the magnetic and geographic zenith, where SLT dominates over weak turbulence. Possible effects of the focusing of the electromagnetic beam on magnetic field-aligned density irregularities and the finite heating beam width at the magnetic zenith are also discussed. The results have relevance to ionospheric heating experiments using ground-based, high-power radio transmitters to heat the overhead plasma, where recent observations of artificial ionization layers have been made.

  2. Fractal structure of artificial ionospheric turbulence

    Microsoft Academic Search

    V. A. Alimov; F. I. Vybornov; E. N. Myasnikov; A. V. Rakhlin

    2008-01-01

    We show the results of the first experimental studies of the multifractal structure of the developed artificial ionospheric\\u000a turbulence. As a result of the special multifractal analysis of the recorded amplitudes of signals from the orbital satellites,\\u000a which were obtained during the experiments on radio tomography of the irregularities excited in the ionosphere by the powerful\\u000a mid-latitude heating facility “Sura,”

  3. Experimentally investigate ionospheric depletion chemicals in artificially created ionosphere

    SciTech Connect

    Liu Yu; Cao Jinxiang; Wang Jian; Zheng Zhe; Xu Liang; Du Yinchang [CAS Key Laboratory of Basic Plasma Physics, Department of Modern Physics, University of Science and Technology of China, Hefei, Anhui 230026 (China)

    2012-09-15

    A new approach for investigating ionosphere chemical depletion in the laboratory is introduced. Air glow discharge plasma closely resembling the ionosphere in both composition and chemical reactions is used as the artificially created ionosphere. The ionospheric depletion experiment is accomplished by releasing chemicals such as SF{sub 6}, CCl{sub 2}F{sub 2}, and CO{sub 2} into the model discharge. The evolution of the electron density is investigated by varying the plasma pressure and input power. It is found that the negative ion (SF{sub 6}{sup -}, CCl{sub 2}F{sub 2}{sup -}) intermediary species provide larger reduction of the electron density than the positive ion (CO{sub 2}{sup +}) intermediary species. The negative ion intermediary species are also more efficient in producing ionospheric holes because of their fast reaction rates. Airglow enhancement attributed to SF{sub 6} and CO{sub 2} releases agrees well with the published data. Compared to the traditional methods, the new scheme is simpler to use, both in the release of chemicals and in the electron density measurements. It is therefore more efficient for investigating the release of chemicals in the ionosphere.

  4. Meteoric ion layers in planetary ionospheres

    NASA Astrophysics Data System (ADS)

    Withers, P.

    2013-12-01

    Layers of metal ions produced by meteoroid ablation have been known in Earth's ionosphere for decades. Similar layers should, in principle, exist in other planetary ionospheres and putative metal ion layers have been identified in vertical electron density profiles from many planets. Current work primarily focuses on Venus and Mars due to the relative abundance of data there, which enables comparative studies of this phenomenon across all three terrestrial planet atmospheres. Here we review the present state of knowledge concerning meteoric ion layers in planetary ionospheres and highlight key topics in current research.

  5. Observation of artificial ionospheric irregularities on Doppler complex ``Spectr''

    NASA Astrophysics Data System (ADS)

    Petrova, Inna; Latypov, Ruslan; Bochkarev, Vladimir

    At present there is a growing interest to research irregularities at the ionosphere both natural and artificial origin. This research has not only fundamental, but also practical importance for the questions connected with the radio wave propagation. This paper reports the results of our first experiments on registration as radio broadcast signals passed through the disturbed region of the ionosphere ( in this case, we received signals of Moscow exact time station at a frequency of 4996 kHz ) and a powerful radio wave signals used to heat the ionosphere (this method called self-scattering method when the pump wave creates artificial ionospheric irregularities and is scattered on them). Excitation of artificial ionospheric irregularities carried out using heating facility "Sura" , located 100 km eastward of Nizhny Novgorod (coordinates : f = 56,15 N , l = 46.1 E ). Receiving equipment was located in the Kazan (Volga ) Federal University , about 170 km eastward of Sura. Experiment which results are discussed in this paper was carried out from 19 to 22 March 2012. We used the window Fourier transform to analyze the change of radio wave spectrum with time. Quasi-periodic variations with significant amplitude were detected. The periods were equal or multiple to exposure period. The generation of artificial ionospheric disturbances by powerful radio emission of complex “Sura” can be cause of this variation which carries information about the excitation (gain) of internal gravity waves during periodic heating of the ionosphere by powerful HF radio waves.

  6. Nonlinear Interaction of a Powerful Oblique Wave Beam with the Ionosphere Layer F2.

    NASA Astrophysics Data System (ADS)

    Atamaniuk, Barbara; Rothkaehl, Hanna; Anatolevich Molotkov, Ivan; Popov, Alexei

    2013-04-01

    The presentation is devoted to modeling oblique sounding of the ionosphere layer F2 by powerful wave beams. Part of its energy propagates trough the ionospheric layer, the other part goes back along a downward trajectory. However, nonlinearity leads to further stratification of the ionospheric layer. A new feature, in comparison with the linear case, is appearing a narrow waveguide beneath the F2 layer maximum which traps a small part of the beam energy. • We study the relationship between these parts of the wave field in a simplified model of parabolic F2 layer, with nonlinearity caused by thermal plasma expulsion from the high field intensity region. • We model and analyze of the interaction of a powerful obliquely incident wave beam of decameter radio waves with the ionospheric layer F2. Oblique propagation of a powerful HF wave beam in the ionospheric F2 layer leads to additional plasma stratification, in particular to the formation of an artificial waveguide controlled by the beam intensity. We show that formation of the artificial waveguide is a nonlinear effect. The problem of efficient feeding the artificial waveguide depends on the ability to create in the F2 layer high values of the HF electric field compared with the characteristic "plasma fields". Analytical results are supplemented with numerical estimates of the effects. The proposed investigation can be used in Space Weather Services.

  7. Artificial Neural Networks Single Layer Networks Multi Layer Networks Generalization Artificial Neural Networks

    E-print Network

    Kjellström, Hedvig

    Artificial Neural Networks Single Layer Networks Multi Layer Networks Generalization Artificial Neural Networks Artificial Neural Networks Single Layer Networks Multi Layer Networks Generalization 1 Artificial Neural Networks Properties Applications Classical Examples Biological Background 2 Single Layer

  8. Artificial Neural Networks Single Layer Networks Multi Layer Networks Generalization Artificial Neural Networks

    E-print Network

    Kjellström, Hedvig

    Artificial Neural Networks Single Layer Networks Multi Layer Networks Generalization Artificial Neural Networks #12;Artificial Neural Networks Single Layer Networks Multi Layer Networks Generalization 1 Artificial Neural Networks Properties Applications Classical Examples Biological Background 2

  9. Investigation by backscatter radar of artificial irregularities produced in ionospheric plasma heating experiments

    Microsoft Academic Search

    N. V. Bakhmet'eva; V. N. Bubukina; Yu. A. Ignat'ev; G. S. Bochkarev; V. A. Eremenko; V. V. Kol'tsov; I. V. Krasheninnikov; Yu. N. Cherkashin

    1997-01-01

    The artificial ionospheric turbulence occurs in the ionosphere illuminated by high power HF radio waves. There are a lot of irregularities stretched along the geomagnetic field in this region. The investigation of the artificially disturbed ionospheric region is based on the reception of back scattered signals (BSS) which permits the basic parameters of this region to be estimated and its

  10. Morphology of meteoric plasma layers in the ionosphere of Mars

    E-print Network

    Withers, Paul

    Morphology of meteoric plasma layers in the ionosphere of Mars as observed by the Mars Global Radio Science data #12;Meteoric Plasma Layer EUV layer X-ray layer Meteoric layer Layer at 90 km Observations · 71 meteoric plasma layers in 5600 MGS profiles 5217R00A 4353T31A 3176Q39A 0350E42B #12

  11. HAARP-Induced Artificial Ionospheric Ducts

    Microsoft Academic Search

    G. Milikh; D. Papadopoulos; C. Chang; M. Parrot

    2008-01-01

    It is well known that strong electron heating by a powerful HF-facility can lead to electron and ion density perturbations stretching along the geomagnetic field. These density perturbations can serve as ducts for ELF waves, both of natural and artificial origin. This paper presents the experimental evidence of plasma modifications associated with ion outflows due to HF heating. The experiments

  12. Artificial Periodic Inhomogeneities of the Ionosperic Plasma as a Promising Line in the Ionospheric Research

    Microsoft Academic Search

    E. A. Benediktov; V. V. Belikovich; N. V. Bakhmet'eva; A. V. Tolmacheva

    2002-01-01

    This paper is dedicated to a new method of ionospheric studies, developed at the Radiophysical Research Institute (NIRFI) and based on the creation of artificial periodic inhomogeneities (APIs) of the ionospheric plasma. We review the techniques and present the results of determination of the basic parameters of the ionosphere and atmosphere.

  13. Artificial Ionospheric Heating Experiments Conducted by a Magnetosphere-Ionosphere Coupling Model

    NASA Astrophysics Data System (ADS)

    Stevens, R. J.; Otto, A.; Krzykowski, M.; Solie, D.

    2007-12-01

    This presentation discusses computational dynamics and results of artificial heating in the ionosphere. The results are then compared to experiments including a geophysical experiment conducted at the Polar Aeronomy and Radio Science Summer School (PARS) in conjunction with the High Frequency Active Auroral Research Program (HAARP) The computational model includes the following terms: ion inertia, Ohm's law (Hall term, electron pressure term, electron neutral and electron ion collisions), ionization, recombination, electron energy (heat advection, conduction, heating through ionization, ohmic heating, gravity, energy loss to neutrals and ions), as well as parameterized collisions frequencies, and a height resolved neutral atmosphere. Atmospheric conditions for the time of the experiment (plasma density, temperature, etc) are used as initial conditions. The power and frequency of the heater facility are then used to compute the heating of the ionosphere. Data processing for the experiment and model are ongoing.

  14. Radioastronomy through an artificial ionospheric window: Spacelab 2 observations

    NASA Astrophysics Data System (ADS)

    Ellis, G. R. A.; Klekociuk, A.; Woods, A. C.; Reber, G.; Goldstone, G. T.; Burns, G.; Dyson, P.; Essex, E.; Mendillo, M.

    Observations of the galactic background radio emission at a number of frequencies between 2.75 MHz and 0.51 MHz were made in association with the Spacelab 2 plasma depletion experiments to test the concept of making low frequency observations through an artificially created window. Following the Shuttle OMS burn at a time when foF2 was 1.99 MHz, a decrease in the maximum ionospheric electron density of approximately 30% occurred. The first observations of the radio emission at 1.704 MHz at high galactic latitudes with good angular resolution (25 degrees) were made during this event.

  15. Artificial Ducts and Ion Outflows in the Topside Ionosphere at HAARP

    Microsoft Academic Search

    A. Vartanyan; G. M. Milikh; E. V. Mishin; K. Papadopoulos; M. Parrot

    2010-01-01

    New results of the DMSP and DEMETER satellites and HAARP digisonde observations during HF heating at the High-Frequency Active Auroral Program (HAARP) facility are described. The ion outflows related to artificial ducts created by HF-heating at HAARP were measured simultaneously in the topside ionosphere by the DMSP satellites and in the bottom side ionosphere by the HAARP ionosonde. The artificial

  16. Observations of radiation from an electron beam artificially injected into the ionosphere

    Microsoft Academic Search

    D. G. Cartwright; P. J. Kellogg

    1974-01-01

    This paper reports the observations of waves generated by a controlled beam of particles artificially injected into the ionosphere and magnetosphere. The measurements were made during the Electron Echo 1 experiment, in which an electron accelerator was carried to a height of 350 km in the ionosphere from Wallops Island, Virginia, on an Aerobee 350 sounding rocket. It injected into

  17. Artificial field-aligned irregularities in the nightside auroral ionosphere

    NASA Astrophysics Data System (ADS)

    Blagoveshchenskaya, N.; Borisova, T.; Kornienko, V.; Leyser, T.; Rietveld, M.; Thide', B.

    The properties and behaviors of the artificial field-aligned small-scale irregularities (striations) in the nightside high latitudinal F-region in course of the Tromso ionospheric modification experiments are examined. Bistatic scatter measurements of HF diagnostic signals were carried out on the London-Tromso-St.Petersburg and Pori-Tromso-St.Petersburg paths using a Doppler spectral method. Striations act as an artificially produced target for the diagnostic HF radio waves and they are responsible for back-scattered signals. The main attention was paid to the aspect angle dependence of striations. It was found that the spectral features of the scattered signals are strongly dependent on the elevation angles of the HF heater antenna beam. The spectral power, broadening of the Doppler spectra, and median values of Doppler shift were maximal during the field-aligned direction of the HF heater antenna beam, whereas they were minimal during the vertical pointing of the HF beam. Simultaneous measurements from the EISCAT UHF incoherent scatter radar showed also the strongest heating effects in the field-aligned position. Electron temperature increases of up to 3000K (300%) induced by powerful HF pumping waves have been measured. Associated with them are the field-aligned ion outflows. Further observations of striations have been made using a narrower HF heater beam (sometimes termed "superheater"). The comparison between two HF heating experiments in a superheater mode, performed under the same geophysical conditions, also shows the strongest striations in the field-aligned position of the HF heater beam. The possible mechanisms for the directional dependence of striations are discussed.

  18. Electric field disturbance in the Earth-ionosphere layer

    Microsoft Academic Search

    V. M. Sorokin; A. K. Yaschenko

    2000-01-01

    Theoretical studies of the electric field disturbance due to a variation of the atmospheric current, flowing between ionosphere and the Earth, are carried out. This variation is caused by a conductivity variation and the electromotive force generation in the near-ground atmospheric layer. The increase of the atmosphere radioactivity level near the ground results in substantial increase of electric field in

  19. Electric Field Disturbance in the Earth - Ionosphere Layer

    Microsoft Academic Search

    V. M. Sorokin; A. K. Yaschenko

    2000-01-01

    Theoretical studies of the electric field disturbance due to a variation of the atmospheric current, flowing between ionosphere and the Earth, are carried out. This variation is caused by a conductivity variation and the electromotive force generation in the near-ground atmospheric layer. The increase of the atmosphere radioactivity level near the ground results in substantial increase of electric field in

  20. Viscous Forces in Velocity Boundary Layers around Planetary Ionospheres.

    PubMed

    Pérez-De-Tejada

    1999-11-01

    A discussion is presented to examine the role of viscous forces in the transport of solar wind momentum to the ionospheric plasma of weakly magnetized planets (Venus and Mars). Observational data are used to make a comparison of the Reynolds and Maxwell stresses that are operative in the interaction of the solar wind with local plasma (planetary ionospheres). Measurements show the presence of a velocity boundary layer formed around the flanks of the ionosphere where the shocked solar wind has reached super-Alfvénic speeds. It is found that the Reynolds stresses in the solar wind at that region can be larger than the Maxwell stresses and thus are necessary in the local acceleration of the ionospheric plasma. From an order-of-magnitude calculation of the Reynolds stresses, it is possible to derive values of the kinematic viscosity and the Reynolds number that are suitable to the gyrotropic motion of the solar wind particles across the boundary layer. The value of the kinematic viscosity is comparable to those inferred from studies of the transport of solar wind momentum to the earth's magnetosphere and thus suggest a common property of the solar wind around planetary obstacles. Similar conditions could also be applicable to velocity boundary layers formed in other plasma interaction problems in astrophysics. PMID:10511515

  1. Transient layers in the topside ionosphere of Mars A. J. Kopf,1

    E-print Network

    Gurnett, Donald A.

    the pulse travels at the speed of light. The maximum plasma frequency in the ionosphere, fp(max), canTransient layers in the topside ionosphere of Mars A. J. Kopf,1 D. A. Gurnett,1 D. D. Morgan,1 shown that distinct layers can occur in the topside ionosphere of Mars, well above the main photo

  2. Coupling of magnetopause-boundary layer to the polar ionosphere

    NASA Technical Reports Server (NTRS)

    Wei, C. Q.; Lee, L. C.

    1993-01-01

    The plasma dynamics in the low-latitude boundary layer and its coupling to the polar ionosphere under boundary conditions at the magnetopause are investigated. In the presence of a driven plasma flow along the magnetopause, the Kelvin-Helmholtz instability can develop, leading to the formation and growth of plasma vortices in the boundary layer. The finite ionospheric conductivity leads to the decay of these vortices. The competing effect of the formation and decay of vortices leads to the formation of strong vortices only in a limited region. Several enhanced field-aligned power density regions associated with the boundary layer vortices and the upward field-aligned current (FAC) filaments can be found along the postnoon auroral oval. These enhanced field-aligned power density regions may account for the observed auroral bright spots.

  3. An analysis of pump-induced artificial ionospheric ion upwelling at EISCAT

    NASA Astrophysics Data System (ADS)

    Kosch, M. J.; Ogawa, Y.; Rietveld, M. T.; Nozawa, S.; Fujii, R.

    2010-12-01

    Ion outflow from the high-latitude ionosphere is a well-known phenomenon and an important source of plasma for the magnetosphere. It is also well known that pumping the ionosphere with high-power high-frequency radio waves causes electron heating. On a few occasions, this has been accompanied by artificially induced ion upwelling. We analyze such a controlled experiment at EISCAT up to 600 km altitude. The pump-enhanced electron temperatures reached up to ˜4000 K above 350 km, and ion upwelling reached up to ˜300 m/s above 500 km altitude. The pump-induced electron pressure gradient can explain the ion velocity below 450 km. Between 450 and 600 km the electron pressure gradient correlates equally with ion acceleration and ion velocity, which represents the transition altitude to free ion acceleration. The electron gas pressure gradient can explain ion upwelling, at least up to 600 km altitude. In addition, such active experiments open the possibility to estimating the F layer ion-neutral collision frequency and neutral density with altitude from ground-based observations.

  4. Generation of Artificial Acoustic-Gravity Waves and Traveling Ionospheric Disturbances in HF Heating Experiments

    NASA Astrophysics Data System (ADS)

    Pradipta, R.; Lee, M. C.; Cohen, J. A.; Watkins, B. J.

    2015-02-01

    We report the results of our ionospheric HF heating experiments to generate artificial acoustic-gravity waves (AGW) and traveling ionospheric disturbances (TID), which were conducted at the High-frequency Active Auroral Research Program facility in Gakona, Alaska. Based on the data from UHF radar, GPS total electron content, and ionosonde measurements, we found that artificial AGW/TID can be generated in ionospheric modification experiments by sinusoidally modulating the power envelope of the transmitted O-mode HF heater waves. In this case, the modulation frequency needs to be set below the characteristic Brunt-Vaisala frequency at the relevant altitudes. We avoided potential contamination from naturally-occurring AGW/TID of auroral origin by conducting the experiments during geomagnetically quiet time period. We determine that these artificial AGW/TID propagate away from the edge of the heated region with a horizontal speed of approximately 160 m/s.

  5. Attenuation of high-frequency radio waves in the low ionosphere at high latitudes when the ionosphere is artificially perturbed by powerful radio emission

    Microsoft Academic Search

    S. I. Martynenko; V. A. Misyura; V. G. Simov; L. F. Chernogor; A. S. Shemet

    1983-01-01

    We have discovered a significant (up to 60% and more) attenuation of the intensity of high frequency probe signals received from the low nighttime ionosphere at high altitudes. The reason for the attenuation is that the ionosphere is being influenced by powerful shortwave radio emission. The Polar Geophysical Institute (PGI) was set up so that powerful shortwave radiation could artificially

  6. Characterization of the lower layer in the dayside Venus ionosphere

    NASA Astrophysics Data System (ADS)

    Girazian, Zachary; Withers, Paul; Paetzold, Martin; Tellmann, Silvia; Peter, Kerstin

    2014-11-01

    The dayside Venus ionosphere consists of two layers: the V2 layer at 141 km, produced by solar extreme ultraviolet (EUV) photons, and the V1 layer at 127 km, produced by solar soft X-rays. The influence of solar zenith angle (SZA) and solar irradiance has been well characterized for the V2 layer, but not the V1 layer, where previous efforts were limited by data scarcity and incomplete SZA coverage. Here we use over 200 radio occultation profiles from Venus Express to characterize how the V1 peak altitude, peak density, and morphology respond to changes in SZA and solar activity. The V1 and V2 peak altitudes do not vary with SZA, and both peak electron densities vary with SZA in a Chapman-like manner. These results imply that the thermal structures of the atmosphere and ionosphere between 141 km and 127 km vary little with SZA. Also, the V1 peak density increases more with solar activity than the V2 peak density and the V1 morphology can change much more than the V2 morphology. These results are due to the soft X-ray flux increasing relative to the EUV flux as solar activity increases.

  7. A sporadic layer in the Venus lower ionosphere of meteoric origin M. Patzold,1

    E-print Network

    Mendillo, Michael

    A sporadic layer in the Venus lower ionosphere of meteoric origin M. Pa¨tzold,1 S. Tellmann,1 B. Ha meteor layer electron densities increase with decreasing solar zenith angle. Layer shapes are symmetric in the Venus lower ionosphere of meteoric origin, Geophys. Res. Lett., 36, L05203, doi:10.1029/ 2008GL035875. 1

  8. A Chapman-Layers Ionospheric Model for Mars

    NASA Astrophysics Data System (ADS)

    Pi, Xiaoqing; Edwards, Charles D.; Hajj, George A.; Hajj, George A.; Ao, Chi; Romans, Larry J.; Callas, John L.; Mannucci, Anthony J.; Asmar, Sami W.; Kahan, Daniel S.

    2008-08-01

    A numerical model (CLIMM) is developed that adopts functions of two Chapman layers to compute Mars ionospheric electron densities at given local solar zenith angle and height. Electron density profiles derived from Mars Global Survey (MGS)-to-Earth radio occultation measurements collected during 1998 through 2005 are used to fit the model. The present model does not include variations with solar extreme ultraviolet (EUV) radiation cycles and seasons, and may have increased errors at lower latitudes. A more sophisticated model taking into account these variations is being developed and will be available in the future.

  9. Coupling of magnetopause-boundary layer to the polar ionosphere

    SciTech Connect

    Wei, C.Q.; Lee, L.C. (Univ. of Alaska, Fairbanks (United States))

    1993-04-01

    The authors develop a model which seeks to explain ultraviolet auroral images from the Viking satellite which show periodic bright regions which resemble [open quotes]beads[close quotes] or [open quotes]pearls[close quotes] aligned along the postnoon auroral oval. ULF geomagnetic pulsations observed in the cusp region are also addressed by this model. The model addresses plasma dynamics in the low-latitude boundary layer and interactions with the polar ionosphere by means of field-aligned current. The Kelvin-Helmholtz instability can develop in the presence of driven plasma flow, which can lead to the formation and growth of plasma vortices in the boundary layer. The finite conductivity of the earth ionosphere causes these vortices to decay. However regions of enhanced field-aligned power density in the postnoon auroral oval can be associated with field-aligned current filaments and boundary layer vortices. These structures may explain the observed bright spots. The authors also discuss the frequency spectrum and the polarization state of the pulsations.

  10. Patch antennas with new artificial magnetic layers

    E-print Network

    M. Ermutlu; C. R. Simovski; M. Karkainen; P. Ikonen; A. A. Sochava; S. A. Tretyakov

    2005-04-11

    A new type of high-impedance surfaces (HIS) has been introduced by C.R. Simovski et al. recently. In this paper, we propose to use such layers as artificial magnetic materials in the design of patch antennas. The new HIS is simulated and patch antennas partially filled by these composite layers are measured in order to test how much the antenna dimensions can be reduced. In order to experimentally investigate the frequency behavior of the material, different sizes of the patches are designed and tested with the same material layer. Also the height of the patch is changed in order to find the best possible position for minimizing the antenna size. This composite layer of an artificial magnetic material has made the antenna smaller while keeping the bandwidth characteristics of the antenna about the same. About 40% of size reduction has been achieved.

  11. Determination of internal scale of artificial ionospheric turbulence in direction of geomagnetic field

    Microsoft Academic Search

    F. I. Vybornov; L. M. Erukhimov; N. V. Murav'eva; E. N. Myasnikov

    1994-01-01

    A 150-MHz satellite beacon is used to determine the internal scale in the direction of the geomagnetic field I0? for the spectrum of artificial ionospheric turbulence created by the Yastreb heating facility located near Nizhny Novgorod in continuous operation at a frequency of 5.75 MHz (ordinary polarization) with effective power P·G?100·150 kW. It is found that I0? ? 3-4 km

  12. Determination of internal scale of artificial ionospheric turbulence in direction of geomagnetic field

    Microsoft Academic Search

    F. I. Vybornov; L. M. Erukhimov; N. V. Murav'eva; E. N. Myasnikov

    1994-01-01

    A 150-MHz satellite beacon is used to determine the internal scale in the direction of the geomagnetic field I0|| for the spectrum of artificial ionospheric turbulence created by the Yastreb heating facility located near Nizhny Novgorod in continuous operation at a frequency of 5.75 MHz (ordinary polarization) with effective power P·G~=100·150 kW. It is found that I0|| ~= 3-4 km

  13. Comparison of dayside current layers in Venus' ionosphere and earth's equatorial electrojet

    NASA Technical Reports Server (NTRS)

    Cole, Keith D.

    1993-01-01

    The major physical aspects of the equatorial electrojet of Earth and the dayside ionospheric current layers of Venus are compared, viz., the electric current intensity and total current, roles of electric field, pressure and gravity, diffusion time scales, and the Bernouille effect. The largest potential differences, of the order of 10 volts, horizontally across the dayside ionosphere of Venus, have important implications for possible dynamo action in the Venus ionosphere and the application of an electric field from the lower atmosphere or from the solar wind. An upper limit to the horizontal scale of vertical magnetic fields in the Venus ionosphere is estimated thereby for the first time. New upper limits on the velocity in, and thickness of, a possible S layer at Venus are presented. If an S layer exists, it is only for extreme conditions of the solar wind. A mechanism for formation of magnetic ropes in the Venus ionosphere is also proposed.

  14. Comparison of dayside current layers in Venus' ionosphere and earth's equatorial electrojet

    NASA Astrophysics Data System (ADS)

    Cole, K. D.

    1993-03-01

    The major physical aspects of the equatorial electrojet of Earth and the dayside ionospheric current layers of Venus are compared, viz., the electric current intensity and total current, roles of electric field, pressure and gravity, diffusion time scales, and the Bernouille effect. The largest potential differences, of the order of 10 volts, horizontally across the dayside ionosphere of Venus, have important implications for possible dynamo action in the Venus ionosphere and the application of an electric field from the lower atmosphere or from the solar wind. An upper limit to the horizontal scale of vertical magnetic fields in the Venus ionosphere is estimated thereby for the first time. New upper limits on the velocity in, and thickness of, a possible S layer at Venus are presented. If an S layer exists, it is only for extreme conditions of the solar wind. A mechanism for formation of magnetic ropes in the Venus ionosphere is also proposed.

  15. Simulation of Self-consistent Radio Wave Artificial Ionospheric Turbulence Pumping and Damping

    NASA Astrophysics Data System (ADS)

    Kochetov, Andrey

    The numerical simulations of the action of self-consistent incident powerful electromagnetic wave absorption arising in the regions of artificial plasma turbulence excitation at formation, saturation and relaxation stages of turbulent structures (Kochetov, A.V., Mironov, V.A., Te-rina, G.I., Bubukina V. N, Physica D, Nonlinear phenomena, 2001, 152-153, 723) to reflection index dynamics are carried out. The nonlinear Schrüdinger equation in inhomogeneous plasma layer with incident electromagnetic wave pumping and backscattered radiation damping (Ko-chetov, et al, Adv. Space Res., 2002, 29, 1369 and 2006, 38, 2490) is extended with the imagi-nary part of plasma dielectric constant (volume damping), which is should be taken into account in strong electromagnetic field plasma regions and results the energy transformation from elec-tromagnetic waves to plasma ones at resonance interaction (D.V. Shapiro, V.I. Shevchenko, in Handbook of Plasma Physics 2, eds. A.A Galeev, R.N. Sudan. Elsevier, Amsterdam, 1984). The volume damping reproduces the basic energy transformation peculiarities: hard excitation, nonlinearity, hysteresis (A.V. Kochetov, E. Mjoelhus, Proc. of IV Intern. Workshop "SMP", Ed. A.G. Litvak, Vol.2, N. Novgorod, 2000, 491). Computer modeling demonstrates that the amplitude and period of reflection index oscillations at the formation stage slowly depend on damping parameters of turbulent plasma regions. The transformation from complicated: quasi-periodic and chaotic dynamics, to quasi-stationary regimes is shown at the saturation stage. Transient processes time becomes longer if the incident wave amplitude and nonlinear plasma response increase, but damping decreases. It is obtained that the calculated reflection and absorption index dynamics at the beginning of the saturation stage agrees qualitatively to the experimental results for ionosphere plasma modification study (Thide B., E.N. Sergeev, S.M. Grach, et. al., Phys. Rev. Lett., 2005, 95, 255002). The work was supported in part by RFBR grant 09-02-01150-a.

  16. Magnetic zenith effect and some features of the multifractal structure of the small-scale artificial ionospheric turbulence

    Microsoft Academic Search

    V. A. Alimov; F. I. Vybornov; E. N. Myasnikov; A. V. Rakhlin; V. L. Frolov

    2009-01-01

    We present the results of the experiment on studying the multifractal structure (with inhomogeneity sizes from tens to hundreds\\u000a of meters across the Earth’s magnetic field) of the artificial ionospheric turbulence when the midlatitude ionosphere is affected\\u000a by high-power HF radio waves. The experimental studies were performed on the basis of the “Sura” heating facility with the\\u000a help of radio

  17. On Diffusion in the F Layer of the Ionosphere

    Microsoft Academic Search

    Ye. Ye. Tsedilina

    1973-01-01

    Translated from Geomagn. Aeron.; 13: No. 2, 233-241(1973). Ionization ; balance equations taking into account the diffusion were obtained and analyzed ; for a nonisothermal ionosphere containing two types of positive ions. The ; spreading of weak inhomogeneities along the magnetic field in such an ionosphere ; is discussed. It is shown that the distribution of electron and ion ;

  18. Thermal response of the F region ionosphere in artificial modification experiments by HF radio waves

    NASA Technical Reports Server (NTRS)

    Mantas, G. P.; Lahoz, C. H.; Carlson, H. C., Jr.

    1981-01-01

    The thermal response of the nighttime F region ionosphere to local heating by HF radio waves has been observed with the incoherent scatter radar at Arecibo, Puerto Rico. The observations consist of high-resolution space and time variation of the electron temperature as a high-power HF transmitter is switched on and off with a period 240 s. As soon as the HF transmitter is turned on, the electron temperature begins to rise rapidly in a narrow altitude region near 300 km, below the F2 layer peak. The electron temperature perturbation subsequently spreads over a broader altitude region. The observations are compared with the anticipated thermal response of the ionosphere based on numerical solutions of the coupled time-dependent heat conduction equations for the electron and composite ion gases and are found to be in good agreement over the entire altitude region covered by the observations.

  19. Sporadic E ionization layers observed with radar imaging and ionospheric modification

    NASA Astrophysics Data System (ADS)

    Hysell, D. L.; Munk, J.; McCarrick, M.

    2014-10-01

    Sporadic E ionization layers have been observed in the daytime subauroral ionospheric E layer by a 30 MHz radar in Alaska. The radar detects coherent backscatter from meter-scale field-aligned plasma density irregularities. The irregularities were generated by ionospheric modification—by the emission of strong HF electromagnetic waves directly beneath the layers—making the layers visible to the radar. Aperture-synthesis methods are used to generate imagery of the layers from the radar data. The layers are patchy, with patches organized along fronts spaced by tens of kilometers and propagating slowly toward the southwest. Similar, naturally occurring layers are commonly observed at middle latitudes at night in the absence of ionospheric modification. That the patchy layers can be found at high magnetic latitudes during the day argues that they are most likely produced through the interaction of the ionospheric layer with neutral atmospheric waves and instabilities. Attenuation of the radar echoes when the HF emission frequency exceeded the third harmonic of the electron gyrofrequency was observed and is discussed.

  20. The variations of ionosphere critical frequency of E layer over Chumphon during solar cycle 24

    NASA Astrophysics Data System (ADS)

    Kenpankho, Prasert; Tsugawa, Takuya; Supnithi, Pornchai; Wongcharoen, Poramintra

    The values of the critical frequency of the ionospheric E layer, foE, obtained at Chumphon ionospheric observatory station (geographic 99.37 E, 10.72 N, 3 dip), Thailand, during the year 2007-2012, have been used to investigate the variations of foE over the geomagnetic equatorial region during the solar cycle 24. The investigation, including variations with local time, day, seasons and solar cycle, is in agreement with the observations. A comparison between the observation data and International Reference Ionosphere (IRI) 2012 model has also been made. The IRI 2012 model underestimates foE especially during the period of 7-11 am and after 6 pm for each day and all seasons. Combining with previous investigations, we suggest that underestimation of ionospheric foE by IRI 2012 model is very helpful for the correction of IRI model in an equatorial Asia region.

  1. Last studies of artificial airglow emission of ionospheric plasma at the "Sura" facility

    NASA Astrophysics Data System (ADS)

    Nasyrov, Igor; Grach, Savely; Albert, Nasyrov; Rustam, Gumerov; Vladimir, Klimenko

    Experimental results of September 2007 on artificial airglow emission at 557.7 nm [green line, the radiation of atomic oxygen level O(1 S), the excitation threshold 4.17 eV, radiation lifetime 0.7 s)] and 630 nm [red line, the radiation of atomic oxygen level O(1 D), the excitation threshold 1.96.17 eV, radiation lifetime ˜ 100 s)] during HF pumping of the ionosphere with specially designed HF pulsing sequence are reported. Ionospheric radio pumping was performed at the "Sura" radio facility situated near Nizhny Novgorod, Russia. The airglow measurements were handled by the CCD camera S1C/079FP(FU) and the newly developed mobile photometric instrument (MFI) of Kazan university (Nasyrov et al., 2007). During several "Sura" runs enhancements of the 557.7 nm airglow intensity caused by 25 ms-long pulses of pump wave were with an interpulse period 3 s were observed after the pump wave switch from continuous pumping to low duty cycle pulse radiation. The enhancements achieve the maximum (˜ +5% above the background) at ˜ 0, 6 s after the pump pulse. Then a signal intensity decreases and achieves a minimum (˜ -7% below the background) at 1.6-1.7 s after the pump pulse. In ˜ 2-2.3 s ater the pulse the airglow intensity recovers to the background level. The work is supported by RFBR (Grant No 06-02-17334). Nasyrov, I.A., Gumerov, R.I., Nasyrov, A.M., Grach, S.M.: Mobile photometric instrument for studies of ionospheric airglow emission caused by anthropogenous disturbances. VII International Suzdal URSI Symposium (ISS-07), Abstracts, p.36, 2007.

  2. A modeling study of intermediate layers in the midlatitude ionosphere. Ph.D. Thesis

    SciTech Connect

    Osterman, G.B.

    1994-01-01

    A computational model of the ionosphere is used to investigate the formation of regions of enhanced ionization that appear in the nighttime ionosphere between 100 and 200 km. The basic mechanism that produces intermediate layers is known to be convergent plasma transport due to meridional neutral wind shear. However, this process alone was not thought to be capable of producing the layers without larger than normal nighttime ionization levels in this altitude region. This dissertation is the end result of an attempt to understand more completely the relative contributions of the processes that contribute to intermediate layer formation. The first phase of this research involved a parameter study of various meridional neutral wind characteristics. The results showed that layers formed as a result of both an enhancement in ion density near the peak as well as a depletion of plasma in the region surrounding the peak. Also examined, were the timescales for layer formation and the effects on layers of changes in the properties of the meridional neutral wind system. The addition of a vertical phase velocity to the neutral wind allowed for simulation of the observed motion of the layer down through the ionosphere. The next phase of the research involved examining the effects on the properties of intermediate layers of zonal neutral winds and metallic ions. Interaction between a zonal wind and the meridional wind can affect the position and size of the layers that form. It can also account for the appearance of multiple layers. The model was modified to include metallic ions, in particular Fe(+). This addition provided a chance to investigate how the properties of a layer might vary depending on its composition. Finally, a short study was carried out examining how the winds that create intermediate layers as well as the plasma enhancements themselves affect certain parameters important to the electrodynamics of the ionosphere.

  3. Characterization of propagation and communication properties of the natural and artificially disturbed ionosphere. Final report, September 1990-December 1994

    SciTech Connect

    Reinisch, B.W.; Sales, G.S.; Brent, R.; Ostergaard, J.; Huang, Y.

    1995-05-01

    This basic research project, conducted during the period starting 12 September 1990 and ending 12 December 1994, studied the effects of natural and artificial ionospheric disturbances on HF and VHF propagation and communication. This project was reasonably divided into two parts where each stood by itself; VHF meteor scatter investigation and HF ionospheric modification studies. In addition to these two studies, a third study was later added to the project to include a Joint Electromagnetic Warfare Center (JEWC) electromagnetic wave propagation and signal loss study. Each of these studies are addressed independently within this final report.

  4. The sheath/ionosphere boundary layer at Venus

    NASA Technical Reports Server (NTRS)

    Szego, K.; Shapiro, V. D.; Ride, S. K.; Nagy, A. F.; Shevchenko, V. I.

    1995-01-01

    At Venus the interaction of the shocked solar wind and cold planetary ions takes place in the dayside mantle. The shocked solar wind is a warm, drifting Maxwellian plasma whereas the planetary plasma is cold; the plasma in the mantle is strongly magnetized. The coexistence of these two populations is unstable, and it leads to wave excitations that organize the energy and momentum exchange between the shocked solar wind and the plasma of planetary origin. The source of the free energy is the solar wind. The intensive wave activity seen in the 100 Hz channel of the wave instrument onboard the Pioneer-Venus Orbiter in the dayside mantle region of Venus can be identified as almost electrostatic VLF waves excited by the kinetic branch of the modified two-stream lower hybrid instability. The waves interact with the particles, and the planetary plasma is heated and accelerated outside the ionosphere, close to its upper boundary. This way solar wind scavenges the ionosphere, and planetary ions leave the planetary magnetosphere. A portion of the wave energy is capable of penetrating directly into the ionosphere and heating it.

  5. Reflections on layers of the ionosphere, reflections on ionised meteorite trails,

    E-print Network

    Boyer, Edmond

    Reflections on layers of the ionosphere, reflections on ionised meteorite trails, echoes on airplanes, EME, reflections on auroral ionised clouds ... Various modes of radio propagation have been. 1.0 Theoretical point of view 1.1 Is a flash of lightning able to reflect radio waves? Any ionised

  6. Effects of the Earth's Ionosphere on HF Radio Astronomy from Artificial Satellites

    Microsoft Academic Search

    M. D. Grossi; K. M. Strom; S. E. Strom

    1961-01-01

    A theoretical analysis of the effects of the ionosphere on HF observations from satellite-borne radio telescopes is presented. The primary effect investigated is the focusing effect of the ionosphere on incoming cosmic noise. This effect was computed according to the Hamiltonian equations for a ray path in a general magnetoionic medium, assuming the ionosphere to be a nonhomogenous, nonisotropic, magnetoionic

  7. Electron density modification in ionospheric E layer by inserting fine dust particles

    NASA Astrophysics Data System (ADS)

    Misra, Shikha; Mishra, S. K.

    2015-02-01

    In this paper, we have developed the kinetics of E-region ionospheric plasma comprising of fine dust grains and shown that the electron density in E-layer can purposely be reduced/enhanced up to desired level by inserting fine dust particles of appropriate physical/material properties; this may certainly be promising for preferred rf-signal processing through these layers. The analytical formulation is based on average charge theory and includes the number and energy balance of the plasma constituents along with charge balance over dust particles. The effect of varying number density, work function, and photo-efficiency of dust particles on ionospheric plasma density at different altitude in E-layer has been critically examined and presented graphically.

  8. Effects of artificially modified ionospheres on HF propagation: Negative Ion Cation Release Experiment 2 and CRRES Coqui experiments

    SciTech Connect

    Fitzgerald, T.J.; Argo, P.E.; Carlos, R.C. [Los Alamos National Laboratory, Los Alamos, New Mexico (United States)] [Los Alamos National Laboratory, Los Alamos, New Mexico (United States)

    1997-03-01

    We report the results of measurements obtained in conjunction with a series of high-altitude chemical release experiments of effects of artificially modified ionospheres upon high-frequency, ionospherically reflected radio paths. Computer simulations indicate that under optimum conditions, ionospheric modifications induced by chemical releases could perturb or even disrupt a communication channel; our experiments corroborate this but also indicate that it is very difficult to actualize such disruptions. Our experiments have shown that an ionospheric depletion, in which the electron density hole forms a huge radio frequency lens, generates new modes which, however, do not significantly affect a communications system. Under optimum path geometry a signal strength decrease of 10 dB or more is possible for several tens of minutes. Enhancements, such as those produced by barium releases, act as reflecting mirrors that can create a large shadow zone on the ground and block off significant amounts of energy. We measured signal strength decreases of up to 20 dB.{copyright} 1997 American Geophysical Union

  9. Observations of ionospheric F layer quadruple stratification near equatorial region

    NASA Astrophysics Data System (ADS)

    Tardelli, A.; Fagundes, P. R.

    2015-01-01

    paper presents and discusses the occurrence of F layer quadruple stratification (StF-1, StF-2, StF-3, and StF-4) during southern hemisphere winter season (June, July, and August 2002) and high solar activity condition, which was observed at Palmas (10.3°S, 48.3°W; dip latitude 5.5°S—near equatorial region), Brazilian sector. This is the first time that the formation of F layer quadruple stratification (StF-1, StF-2, StF-3, and StF-4) has been reported in the South American sector. The StF-4 has a short lifetime compared with triple stratification/F3 layer, and it is antecedent and followed by triple/F3 layer stratification.

  10. Effects of an atmospheric gravity wave on the midlatitude ionospheric F layer

    SciTech Connect

    Millward, G.H.; Moffett, R.J.; Quegan, S. [Univ. of Sheffield (United Kingdom); Fuller-Rowell, T.J. [Univ. of Colorado, Boulder, CO (United States)]|[Nationa Oceanic and Atmospheric Administration, Space Environment Lab., Boulder, CO (United States)

    1993-11-01

    A modeling study of the atmospheric response to a single short burst of enhanced ion convection at high latitudes, undertaken using the Sheffield/University College London/Space Environment Laboratory coupled ionosphere/thermosphere model, has revealed a large-scale atmospheric gravity wave (AGW) moving equatorward from a source in the dawn sector auroral zone. The wave propagates to midlatitude, perturbing the ionosphere and creating a traveling ionospheric disturbance. Analysis of the interaction between the thermosphere and ionosphere during the passage of the AGW at midlatitudes is undertaken and reveals a complex height-dependent response. At lower altitudes the field-aligned velocity of the ions follows closely the field-aligned wind. Above the F peak, diffusion processes become important and the field-aligned ion velocity shows fluctuations which exceded those in the wind. Changes in N{sub m}F{sub 2} and h{sub m} F{sub 2}, during the interaction, are due to redistribution of plasma alone with changes in production and loss insignificant. As the F layer is lifted by the positive surge in the gravity wave, N{sub m}F{sub 2} decreases, due to a divergence in the ion flux, itself caused by the combination of a divergent neutral wind and an increase in the effects of diffusion with altitude. The slab thickness also increases. Subsequently, the opposite happens as h{sub m}F{sub 2} falls below its equilibrium value. 14 refs., 9 figs., 1 tab.

  11. Unifying Undergraduate Artificial Intelligence Robotics: Layers Of Abstraction Over Two Channels

    E-print Network

    Crabbe, Frederick

    Unifying Undergraduate Artificial Intelligence Robotics: Layers Of Abstraction Over Two Channels Annapolis, Maryland 21402 Abstract From a Computer Science and Artificial Intelligence perspec- tive based on these ideas. Introduction Modern Artificial Intelligence Robotics education treats the field

  12. Effect of double layers on magnetosphere-ionosphere coupling

    NASA Technical Reports Server (NTRS)

    Lysak, Robert L.; Hudson, Mary K.

    1987-01-01

    The Earth's auroral zone contains dynamic processes occurring on scales from the length of an auroral zone field line which characterizes Alfven wave propagation to the scale of microscopic processes which occur over a few Debye lengths. These processes interact in a time-dependent fashion since the current carried by the Alfven waves can excite microscopic turbulence which can in turn provide dissipation of the Alfven wave energy. This review will first describe the dynamic aspects of auroral current structures with emphasis on consequences for models of microscopic turbulence. A number of models of microscopic turbulence will be introduced into a large-scale model of Alfven wave propagation to determine the effect of various models on the overall structure of auroral currents. In particular, the effects of a double layer electric field which scales with the plasma temperature and Debye length is compared with the effect of anomalous resistivity due to electrostatic ion cyclotron turbulence in which the electric field scales with the magnetic field strength. It is found that the double layer model is less diffusive than in the resistive model leading to the possibility of narrow, intense current structures.

  13. F layer postsunset height rise due to electric field prereversal enhancement: 1. Traveling planetary wave ionospheric disturbance effects

    Microsoft Academic Search

    P. R. Fagundes; J. A. Bittencourt; J. R. Abalde; Y. Sahai; M. J. A. Bolzan; V. G. Pillat; W. L. C. Lima

    2009-01-01

    An ionospheric sounding station is operational at Palmas (10.2°S, 48.2°W, dip latitude 5.5°S), Brazil, since 2002. Observations of F layer virtual height day-to-day variations during evening hours (1800 LT to 2000 LT) show a strong variability, even during geomagnetically quiet periods. From the ionospheric multifrequency virtual height variations (at 3, 4, 5, 6, 7, and 8 MHz), observed from July

  14. Artificial magnetism and magnetoelectric coupling from dielectric layers

    E-print Network

    Liu, Yan; Gralak, Boris

    2013-01-01

    We investigate a high-order homogenization (HOH) algorithm for periodic multilayered stacks. The mathematical tool of choice is a transfer matrix method. Expressions for effective permeability, permittivity and magnetoelectric coupling are explored by frequency power expansions. On the physical side, this high-order homogenization uncovers a magnetoelectric coupling effect (odd order approximation) and artificial magnetism (even order approximation) in moderate contrast photonic crystals. Comparing the effective parameters' expressions of a stack with three layers against that of a stack with two layers, we note that the magnetoelectric coupling effect vanishes while the artificial magnetism can still be achieved in a center symmetric periodic structure. Furthermore, we numerically check the effective parameters through the dispersion law and transmission curves of a stack with two dielectric layers against that of an effective bianisotropic medium: they present a good agreement in the low frequency (acoustic...

  15. The Formation and Vertical Movement of Dense Ionized Layers in the Ionosphere Due to Neutral Wind Shears

    Microsoft Academic Search

    W. I. Axford

    1963-01-01

    This paper analyzes Dungey's wind-shear mechamsm for the formation of sporadic E layers and the extension of this mechanism, proposed by the author, which causes vertical transport of ionospheric ionization. Approximate equations are derived to describe quasi-steady ionized layers in which forces due to wind shear in the neutral atmosphere are balanced by the effects of pressure gradients and recombination.

  16. Resonant scattering of energetic electrons in the plasmasphere by monotonic whistler-mode waves artificially generated by ionospheric modification

    NASA Astrophysics Data System (ADS)

    Chang, S. S.; Ni, B. B.; Bortnik, J.; Zhou, C.; Zhao, Z. Y.; Li, J. X.; Gu, X. D.

    2014-05-01

    Modulated high-frequency (HF) heating of the ionosphere provides a feasible means of artificially generating extremely low-frequency (ELF)/very low-frequency (VLF) whistler waves, which can leak into the inner magnetosphere and contribute to resonant interactions with high-energy electrons in the plasmasphere. By ray tracing the magnetospheric propagation of ELF/VLF emissions artificially generated at low-invariant latitudes, we evaluate the relativistic electron resonant energies along the ray paths and show that propagating artificial ELF/VLF waves can resonate with electrons from ~ 100 keV to ~ 10 MeV. We further implement test particle simulations to investigate the effects of resonant scattering of energetic electrons due to triggered monotonic/single-frequency ELF/VLF waves. The results indicate that within the period of a resonance timescale, changes in electron pitch angle and kinetic energy are stochastic, and the overall effect is cumulative, that is, the changes averaged over all test electrons increase monotonically with time. The localized rates of wave-induced pitch-angle scattering and momentum diffusion in the plasmasphere are analyzed in detail for artificially generated ELF/VLF whistlers with an observable in situ amplitude of ~ 10 pT. While the local momentum diffusion of relativistic electrons is small, with a rate of < 10-7 s-1, the local pitch-angle scattering can be intense near the loss cone with a rate of ~ 10-4 s-1. Our investigation further supports the feasibility of artificial triggering of ELF/VLF whistler waves for removal of high-energy electrons at lower L shells within the plasmasphere. Moreover, our test particle simulation results show quantitatively good agreement with quasi-linear diffusion coefficients, confirming the applicability of both methods to evaluate the resonant diffusion effect of artificial generated ELF/VLF whistlers.

  17. A comparative sporadic-E layer study between two mid-latitude ionospheric stations

    NASA Astrophysics Data System (ADS)

    Pietrella, M.; Pezzopane, M.; Bianchi, C.

    2014-07-01

    Hourly systematic measurements of the highest frequency reflected by the sporadic-E layer (foEs) recorded from January 1976 to June 2009 at the ionospheric stations of Rome (Italy, 41.8°N, 12.5°E) and Gibilmanna (Italy, 37.9°N, 14.0°E) were considered to carry out a comparative study between the sporadic E layer (Es) over Rome and Gibilmanna. Different statistical analysis were performed taking into account foEs observations near the periods of minimum and maximum solar activity. The results reveal that: (1) independently from the solar activity, Es develops concurrently over extended regions in space, instead of being a spatially limited layer which is transported horizontally by neutral winds over a larger area; especially during summer months, when an Es layer is present at Rome, there is a high probability that an Es layer is also present over Gibilmanna, and vice versa; (2) Es layer lifetimes of 1-5 h were found; in particular, Es layers with lifetimes of 5 h both over Gibilmanna and Rome are observed with highest percentages of occurrence in summer ranging between 80% and 90%, independently from the solar activity; (3) latitudinal effects on Es layer occurrence emerge mostly for low solar activity during winter, equinoctial, and summer months, when Es layers are detected more frequently over Gibilmanna rather than Rome; (4) when the presence of an Es layer over Rome and Gibilmanna is not simultaneous, Es layer appearance both over Rome and Gibilmanna confirms to be a locally confined event, because drifting phenomena from Rome to Gibilmanna or vice versa have not been emphasized.

  18. Characteristics of layers, waves and turbulence in the atmosphere and ionosphere as estimated by GPS space radio-holography

    NASA Astrophysics Data System (ADS)

    Pavelyev, Alexander; Gubenko, Vladimir; Matyugov, Stanislav; Pavelyev, Alexey

    The spatial, seasonal and geographical distrubutions of the intensity of layers, turbulence and internal waves at different altitudes in the atmosphere and ionosphere of the Earth are presented. The results have been obtained on the base of locality principle using a new phase acceleration-intensity method for analysis of the GPS radio occultation signals. This methodology has been applied to mesearements of the inclination and altitude of ionospheric layers. Obtained information has been used for estimation of the front orientation, internal frequency and phase speed of the internal waves in the ionosphere and neutral atmosphere. A new index of the ionospheric activity as measured from the phase of radio waves passed through the ionosphere is introduced and its high correlation with S4 scintillation index is established. This correlation indicates the significant influence of ionospheric layers on variations of characteristics of radio waves in transionospheric communication links. Specially for the troposphere the geographical distribution of the weak total absorption (about of 1-2 db) of the radio waves at GPS frequencies in the Earth atmosphere corresponding to influence of the oxygen and water vapor in the troposphere is measured with accuracy better than 0.1 db. Obtained results expanded the applicable domain of the GPS space radio-holography for global investigation of the natural processes in the atmosphere and ionosphere as function of solar activity and space weather effects. The new phase acceleration-intensity method is also a basic tool which can be applied for data analysis of future planetary radio occultation missions

  19. Properties of ionospheric gyroechoes in the presence of a sporadic E-layer

    NASA Astrophysics Data System (ADS)

    Jalonen, L.; Nygren, T.; Turunen, T.

    1981-10-01

    Generation and properties of ionospheric gyroechoes in the presence of a thin sporadic E-layer are investigated theoretically. Full wave analysis is used to calculate the transmission coefficients of model Es-layers. The intensification of the echo and the decrease in its virtual height at the onset of the Es-layer are explained in terms of mode coupling, the phenomena of which are shown to be more complicated than expected by Ellis (1960). A mechanism is also found of producing gyroechoes when an otherwise totally blanketing flat type Es-layer is present. When the maximum plasma frequency is so high that the whistler mode can propagate within the Es-layer at frequencies relevant to the gyroecho, the layer may be transparent for the extraordinary mode. Penetration of the ordinary wave becomes impossible, and the 0X0-reflection and ordinary F-trace can no longer be registered. Thus, the gyrotrace may be caused by the XXX-reflection only, and the resulting polarization on the ground is extraordinary.

  20. Measurements and modelling of intermediate, descending, and sporadic layers in the lower ionosphere: Results and implications for global-scale ionospheric-thermospheric studies

    SciTech Connect

    Wilkinson, P.J.; Szuszczewicz, E.P.; Roble, R.G.

    1992-01-24

    The authors demonstrate that conventional ionosondes can provide long-term observations on intermediate, descending, and transitional layers in the 100-200 km altitude region of the ionosphere. Using 15 consecutive days of observations at Townsville, Australia, during the SUNDIAL campaign of September 1989, they tracked the birth of the layers at altitudes above 150 km and their systematic downward motion to the 110 km region at rates between 4 and 5 km/hr. The observations are compared with NCAR TIGCM simulations, and the results show: (1) that the layering process is identifiable with meridional wind-shear-node convergence of ions; (2) that zonal wind controls of the layers are insignificant under the prevailing conditions; and (3) that electric fields play an important role in the effectiveness of the ion-convergence and downward transport processes at altitudes above 125 km. The measurement and modeling comparisons are the first of a kind, providing insight into the relative roles of winds and electric fields, and opening possibilities for determining the global characteristics of the layers and their cause-effect roles in the dynamics of the lower ionospheric-thermospheric domain.

  1. Ionospheric disturbances in D-layer recorded by VLF receiver at Tashkent IHY station

    NASA Astrophysics Data System (ADS)

    Ahmedov, Bobomurat

    Tashkent International Heliophysical Year (IHY) station is a member of Atmospheric Weather Electromagnetic System for Observation, Modeling and Education (AWESOME) network being operated globally to study the ionosphere and the magnetosphere with the help of electromagnetic waves in Very Low Frequency (VLF) band. Regular monitoring of the D- and F-layers of ionosphere over Central Asia territory is being performed on the permanent basis starting year 2008. Solar flare events are permanently observed and the analysis showed that there is simultaneous correlation between the times of change of amplitude of the waves and the Solar flares. Features of the lightning discharge generated by radio atmospherics are studied and its effectiveness in D-region ionosphere diagnostics is explained. We have studied VLF amplitude anomalies related to the earthquakes (EQs) occurred in the recent years with magnitude more than 5 on the path way from the VLF transmitters to the Tashkent station assuming that propagation of VLF ground-based transmitters signals can be perturbed by EQ preparation can be detectable from the ground-based measurements in the VLF bands. For analyzing narrowband data we have used the Nighttime Fluctuation (NF) method paying attention to the data obtained during the local nighttime (20:00 LT-04:00 LT). The mean nighttime amplitude (or trend) and nighttime fluctuation are found to increase significantly before the EQ occurred on the path way from the transmitters to the receiver. The obtained results have revealed an agreement with VLF amplitude anomalies observed in Tashkent VLF station during the strong EQs occurred on the path way from the transmitters to the receiver. Some results are presented to show the probing potentiality of VLF waves to predict short term EQs with high magnitude.

  2. An empirical model of the occurrence of an additional layer in the ionosphere from the occultation technique: Preliminary results

    NASA Astrophysics Data System (ADS)

    Zhao, Biqiang; Zhu, J.; Xiong, B.; Yue, X.; Zhang, M.; Wang, M.; Wan, W.

    2014-12-01

    About 8 year electron density profile (EDP) data from the COSMIC/FORMOSAT-3 satellites radio occultation technique were used to investigate the additional stratification of the F2 (the so-called F3 layer) layer over the equatorial and low-latitude ionosphere on a global scale for both the bottomside and topside ionosphere. The F3 layer was recognized through the altitude differential profile featured by two maxima existing from the selected EDP profile. There were ~37,000 (bottomside) and 25,000 (topside) cases of F3 layer selected out of ~1.27 million occultation events at equatorial and low-latitude areas during the period of April 2006 to August 2014. The statistical results for the bottomside ionosphere resemble that reported in Zhao et al. (2011a), while in the topside the highest occurrence of F3 layer shows a 3-4 h delay depending on the altitude range of the stratification. The magnetic latitude distribution shows different dependence with a tendency to form a single crest toward high altitude. Also, the seasonal variation is weaker in the topside ionosphere compared to the bottomside one, especially in the high altitude. Then we build up an empirical model of the F3 layer occurrence using the bottomside statistics based on empirical orthogonal function (EOF) decomposition as it gets the inherent characters inside the data set and converges quickly. The model well grasps the main features of the F3 occurrence, e.g., the F3 occurrence's sensitivity on the magnetic latitude. Further, in order to accommodate the ground observation a corrected factor was introduced. As F3 layer is an important phenomenon in the low-latitude ionosphere, we have made an attempt to describe its feature with a consecutive function although future work needs to be done for an overall expression of this structure.

  3. The effects of solar cycle and latitude dependence on the formation of ionospheric C layer

    NASA Astrophysics Data System (ADS)

    Requiakuntz, Vera Lucia

    1987-09-01

    The C-layer effect is observed on long distance very low frequency (VLF) signal propagation at sunrise, when the solar illumination line (terminator) makes a small angle (alpha is less than 20 deg) with the propagation path. The effect may be described as an additional phase advance, just after the sunrise normal phase advance, recovering in about 90 minutes. Analysis of different propagation paths shows that the magnitude of the observed effect presents a latitudinal and solar cycle dependence. Data obtained for geomagnetic latitudes ranging 14 deg N to 50 deg S have shown that the C-layer effect seems to be more pronounced at higher latitudes. Finally analysis of data at different phases of the solar cycle suggest that for the period of maximum activity the magnitude of the observed C-layer effect is reduced. These effects may be understood bearing in mind that cosmic radiation is mainly responsible for the ionization of regions below the ionospheric D-layer. It is more intense at higher latitudes and also presents a variation with the solar cycle, being minimum when maximum solar activity occurs. In the analysis, different phenomena which could influence the C-layer effect were taken into account, such as SIDs at sunrise, Forbush decrease, stratwarm and magnetic storms.

  4. Comparison of a Multi-Layered Artificial Immune System with a Kohonen Network

    E-print Network

    Timmis, Jon

    Comparison of a Multi-Layered Artificial Immune System with a Kohonen Network T. Knight and J Networks on some clustering tasks. I. INTRODUCTION Many artificial immune systems (AIS) have been devel is organised as follows. Section II presents a novel multi-layered artificial immune system inspired

  5. Ion outflows and artificial ducts in the topside ionosphere at HAARP

    Microsoft Academic Search

    G. M. Milikh; E. Mishin; I. Galkin; A. Vartanyan; C. Roth; B. W. Reinisch

    2010-01-01

    New results of the DMSP satellite and HAARP digisonde observations during HF heating at the High-Frequency Active Auroral Program (HAARP) facility are described. For the first time, the DMSP satellites detected significant ion outflows associated with 10–30% density enhancements in the topside ionosphere above the heated region near the magnetic zenith. In addition, coincident high-cadence skymaps from the HAARP digisonde

  6. Characterization of Artificial Guidestars Generated in the Mesospheric Sodium Layer

    NASA Technical Reports Server (NTRS)

    Jelonek, M. P.; Fugate, R. Q.; Lange, W. J.; Slavin, A. C.; Ruane, R. E.; Cleis, R. A.

    1992-01-01

    Using a 10 W average power sum-frequency laser, we have generated resonant fluorescence beacons in the mesospheric sodium layer and are currently evaluating them for use as an artificial guidestar for atmospheric compensation using adaptive optics. Two flashlamp pumped Nd:YAG lasers operating at 1.064 and 1.319 microns are mixed in a lithium triborate crystal to produce 589 nm light at 840 Hz. The laser emits 47.5 microsec mode-locked pulse trains at 11-14 mJ per pulse and is tuned to the sodium resonance transition with intracavity etalons.

  7. The effects of 450 kg surface explosions at the E layer of the ionosphere. Los Alamos Source Region Project

    SciTech Connect

    Fitzgerald, T.J.; Carlos, R.C.

    1992-10-22

    A network of hf ionospheric sounders consisting of two transmitter and two receiver stations was deployed to detect the effects of acoustic waves generated by surface ground motion following an underground nuclear test (UGT) at the Nevada Test Site. The frequency of the transmissions were chosen so that the hf radio waves were totally reflected in the E layer of the ionosphere at an altitude of approximately 100 km. The transmissions were highly stable cw tones at two frequencies separated by 100 kHz so that two altitudes separated by approximately .5 km could be sensed. The network sampled four geographic locations in the ionosphere ranging from almost directly overhead of the UGT out to a horizontal range of 60 km. The ionospheric sounders detected disturbances on all the paths beginning at approximately 325 s after the UGT which persisted for up to 100 s. These disturbances will be described in detail in a later paper. Shortly after the UGT an extended series of ionospheric disturbances were detected which we ascribe to the arrival of acoustic shock waves at the E layer caused by the surface detonation of ordinance with effective yields of 450 kg of high explosive during an unrelated exercise conducted by the U. S. Air Force at a nearby bombing range. The conjunction of these disturbances produced a direct comparison of the effects of UGT`s and surface explosions in the ionosphere. In this paper we describe the effects produced by the surface explosions and interpret the disturbance in terms of diffraction induced by electron density changes accompanying the passage of the acoustic waves from the explosions through the reflection altitudes.

  8. E layer dominated ionosphere observed by EISCAT/ESR radars during solar minimum

    NASA Astrophysics Data System (ADS)

    Cai, Hongtao; Li, Fei; Shen, Ge; Zhan, Weijia; Zhou, Kangjun; Willian McCrea, Ian; Ma, Shuying

    2014-10-01

    According to the study by Mayer and Jakowski (2009), periods of E layer dominated ionosphere (ELDI) are defined as being characterized by vertical electron density profiles having a maximum density at E layer altitudes. In this paper, characteristics of ELDI intervals have been investigated, focusing on their temporal variations, using field-aligned measurements from the EISCAT and ESR radars during the interval 2009-2011. ELDI events were identified using simple but reasonable criteria, in which a minimal duration was required to exclude possible "fake" events induced by random errors in measurements. It was found that ELDIs were observed more often in winter and earlier spring than other seasons, especially in the auroral zone. The occurrence of ELDI intervals peaks around geomagnetic midnight at auroral latitudes, while it reaches a maximum around geomagnetic local noon at the latitude of the ESR. Our results imply that ELDI intervals appear to be a sporadic rather than a regular phenomenon, in disagreement with previous results inferred from radio occultation measurements. The discrepancy between the typical durations of ELDI events observed by the two radars is remarkable, being 30 min on average at Tromsø but about a half of this at Svalbard. During intervals of ELDI, the mean thicknesses of the E layer are quite close at the two sites, as are the values of HmE and the ratio of NmE / NmF2. Case studies confirm that either extra E layer ionization or F layer density depletion alone could lead to the presence of ELDIs. Based on a careful check on ELDI intervals of various types, however, we suggest that both of them play a critical role in ELDI formation.

  9. The Impact of Flares on August 21 and 25 on the Earth's Magnetic Field and the Ionosphere F2 Layer

    NASA Astrophysics Data System (ADS)

    Suhartini, Sri

    1999-04-01

    Impact of two flare events on August 21 (M9.0/2B) and 25 (X1.0/3B) 1998, studied for knowing their influence on geomagnetic field, ionospheric F layer and MUF (Maximum Usable Frequency) of the HF (High Frequency) communication. The data used on this paper are geomagnetic H components of Biak (1.1 deg. S, 136.05 deg. E), critical frequency of ionospheric F2 layer (foF2) over Sumedang (6.5 deg. S, 107.47 deg. E) and MUF for HF communication between Manado (1.45 deg. N, 124.75 deg. E) and Sumedang from 21 to 27 August 1998. The flare on August 21 caused active magnetic storm 23 hours after the event, caused by shock waves which accompany the flare. This magnetic storm followed by the decrease of foF2 and MUF Manado-Sumedang of about 25% and 20%, respectively. The flare on August 25 caused the decrease of foF2 of about 25 % only 3 hours after. The reason of this disturbance is the increase of the absorption in ionospheric F region. Magnetic storm commenced on August 26 (active to minor storm), followed by the ionospheric disturbance showed as 10% and 20% reduction of foF2 and MUF respectively. Major storm on August 27 caused by shock waves which accompany the flare, but the effect cannot be explained due to lack of data since the observation stopped on 09.45.

  10. A New Grid based Ionosphere Algorithm for GAGAN using Data Fusion Technique (ISRO GIVE Model-Multi Layer Data Fusion)

    NASA Astrophysics Data System (ADS)

    Srinivasan, Nirmala; Ganeshan, A. S.; Mishra, Saumyaketu

    2012-07-01

    A New Grid based Ionosphere Algorithm for GAGAN using Data Fusion Technique (ISRO GIVE Model-Multi Layer Data Fusion) Saumyaketu Mishra, Nirmala S, A S Ganeshan ISRO Satellite Centre, Bangalore and Timothy Schempp, Gregory Um, Hans Habereder Raytheon Company Development of a region-specific ionosphere model is the key element in providing precision approach services for civil aviation with GAGAN (GPS Aided GEO Augmented Navigation). GAGAN is an Indian SBAS (Space Based Augmentation System) comprising of three segments; space segment (GEO and GPS), ground segment (15 Indian reference stations (INRES), 2 master control centers and 3 ground uplink stations) and user segment. The GAGAN system is intended to provide air navigation services for APV 1/1.5 precision approach over the Indian land mass and RNP 0.1 navigation service over Indian Flight Information Region (FIR), conforming to the standards of GNSS ICAO-SARPS. Ionosphere being largest source of error is of prime concern for a SBAS. India is a low latitude country, posing challenges for grid based ionosphere algorithm development; large spatial and temporal gradients, Equatorial anomaly, Depletions (bubbles), Scintillations etc. To meet the required GAGAN performance, it is necessary to develop and implement a best suitable ionosphere model, applicable for the Indian region as thin shell models like planar does not meet the requirement. ISRO GIVE Model - Multi Layer Data Fusion (IGM-MLDF) employs an innovative approach for computing the ionosphere corrections and confidences at pre-defined grid points at 350 Km shell height. Ionosphere variations over the Geo-magnetic equatorial regions shows peak electron density shell height variations from 200 km to 500 km, so single thin shell assumption at 350 km is not valid over Indian region. Hence IGM-MLDF employs innovative scheme of modeling at two shell heights. Through empirical analysis the shell heights of 250 km and 450 km are chosen. The ionosphere measurement source for these two shells is obtained through a novel idea of utilizing both the Indian reference equipments (INREEs) residing at each of INRESs. Kriging algorithm is applied to compute the grid vertical delay error and error estimates at the IGP in the designated shell heights. A new approach of data fusion is applied at the vertical IGPs to fuse delays and confidences at 350 km shell height. Ionosphere storm detection algorithm utilizes goodness of fit test to protect the user from irregular behavior of ionosphere. Moreover, IGM-MLDF models the associated uncertainties of reference station failures and edge of storm effects through the under sample threat models to protect a GAGAN user from ionosphere abnormalities getting not monitored by the ground system. The algorithm also takes a conservative yet mathematically correct path of including measurement covariance bound at fusion step due to utilization of similar ionosphere measurements from 2 INREEs. To protect user against depletion threat, based on exhaustive empirical analysis algorithm uses the floor value of 6 for error estimate bound. Based on the data collected over the region, performance analysis of new algorithm is presented in this paper. IGM-MLDF is achieving APV-1/1.5 performance over 75 percentage of Indian land mass for GAGAN users. And this algorithm achieves it without requiring any changes in the user message structure, resulting in ease of GAGAN message usage by all the users, including the legacy users.

  11. Unifying Undergraduate Artificial Intelligence Robotics: Layers Of Abstraction Over Two Channels

    E-print Network

    Crabbe, Frederick

    Unifying Undergraduate Artificial Intelligence Robotics: Layers Of Abstraction Over Two Channels Annapolis, Maryland 21402 Abstract From a Computer Science and Artificial Intelligence perspec- tive to undergraduates. The paper presents an alternative synthesis of the various sub-fields of Artificial Intelligence

  12. Modeling of Sporadic Layers Meteoritic in Origin in the Mars' Ionosphere

    NASA Astrophysics Data System (ADS)

    Molina-Cuberos, G. J.; Peter, K.; Witasse, O. G.; Nuñez, M. J.; Paetzold, M.

    2011-12-01

    Recent measurements of the Martian ionosphere has revealed the existence of low altitude layers at altitudes ranging from 70 and 90 km, well below the main photoionospheric peak. These peaks were detected by radio science experiments both Mars Global Surveyor (in 71 of 56000 profiles, [1]) and Mars Express (in 75 of 465 profiles, [2]). The presence of these layers was not limited to specific times of the day, longitude or latitude. Previous theoretical models [3,4] predicted the existence of a constant low altitude layer, with a maximum density of the same order of magnitude compared with the recent observations. Long-live metallic ions coming from meteoroid particles can increase the concentration of electrons. However, the models are not able to explain the huge variability of the observations. Similar layers have been observed in the Earth's atmosphere, especially during strong meteor shower and it is well known that they contain metallic ions coming from the ablation of extraterrestrial dust. Here we present a model of the vertical density profile of metallic species (magnesium and iron) between 60 and 120 km altitude. The model includes ablation of meteoroids, metal diffusion in the atmosphere, photoionization of neutrals by ultraviolet photons, and the chemistry of ions and neutrals including charge exchange between neutrals and ions. We have found that the presence of Mg and Fe reduces the concentration of the most abundant atmospheric ions and also increase the concentration of electrons below 90 km of altitude. Model results are compared with some selected electron density profiles observed by Mars Express in order to understand the existence of this sporadic layer. We obtain that in some conditions a low altitude layer can be formed which compared relatively well with the observations, even under steady state scenarios. However dynamic models or high meteoroid fluxes, i.e. meteor showers, are required to explain fully the observations. [1] Withers et al. (2008), J. Geophys. Res. 113, A12314. [2] Patzold et al. (2005), Science 310, 837-838. [3] Pesnell et al. (2000), J. Geophys. Res.105, 1695. [4] Molina-Cuberos et al. (2003), Planet. and Space Sci. 51, 239

  13. Anomalous auroral electron distributions due to an artificial ion beam in the ionosphere

    NASA Technical Reports Server (NTRS)

    Moore, T. E.; Arnoldy, R. L.; Kaufmann, R. L.; Cahill, L. J., Jr.; Kintner, P. M.; Walker, D. N.

    1982-01-01

    Results are reported for the perturbation of the auroral ionosphere by the operation of an ion gun which injected about 100 mA of 25-eV Ar(+) ions at upgoing pitch angles over a discrete auroral arc. The major effects observed were the excitation of intense broadband electric field fluctuations at zero-10 kHz, and the appearance of streaming and isotropic heating in different parts of superthermal electron velocity space. A scenario is explored in which electron runaway or streaming is expected between the trapping speed and the critical velocity for cyclotron interactions with the waves, where the streaming electrons carry the current that would be carried by thermals or energetic electrons in the absence of the waves. A current of about 1.0 microA/sq m is carried by the streaming electrons. The gun-associated electrons were anomalous in the sense that their anisotropy was the opposite of that observed in the natural aurora.

  14. Nonlinear propagation of Rossby-Khantadze electromagnetic planetary waves in the ionospheric E-layer

    SciTech Connect

    Futatani, S. [LMFA-CNRS, École Centrale de Lyon, Université de Lyon, Ecully (France)] [LMFA-CNRS, École Centrale de Lyon, Université de Lyon, Ecully (France); Horton, W. [Applied Research Laboratory, The University of Texas at Austin, Austin, Texas 78758 (United States)] [Applied Research Laboratory, The University of Texas at Austin, Austin, Texas 78758 (United States); Kaladze, T. D. [I. Vekua Institute of Applied Mathematics, Tbilisi State University, 2 University St., 0186 Tbilisi, Georgia (United States) [I. Vekua Institute of Applied Mathematics, Tbilisi State University, 2 University St., 0186 Tbilisi, Georgia (United States); Physics Department, Government College University, Lahore 54000 (Pakistan)

    2013-10-15

    Nonlinear vortex propagation of electromagnetic coupled Rossby and Khantadze planetary waves in the weakly ionized ionospheric E-layer is investigated with numerical simulations. Large scale, finite amplitude vortex structures are launched as initial conditions at low, mid, and high latitudes. For each k-vector the linear dispersion relation has two eigenmodes corresponding to the slow magnetized Rossby wave and the fast magnetic Khantadze wave. Both waves propagate westward with local speeds of the order of 10–20 m/s for the slow wave and of the order of 500–1000 km/s for the fast wave. We show that for finite amplitudes there are dipole solitary structures emitted from the initial conditions. These structures are neutrally stable, nonlinear states that avoid radiating waves by propagating faster than the corresponding linear wave speeds. The condition for these coherent structures to occur is that their amplitudes are such that the nonlinear convection around the core of the disturbance is faster than the linear wave speed for the corresponding dominant Fourier components of the initial disturbance. The presence of the solitary vortex states is indicative of an initial strong disturbance such as that from a solar storm or a tectonic plate movement. We show that for generic, large amplitude initial disturbances both slow and fast vortex structures propagate out of the initial structure.

  15. Relationship between vertical ExB drift and F2-layer characteristics in the equatorial ionosphere at solar minimum conditions

    NASA Astrophysics Data System (ADS)

    Oyekola, Oyedemi S.

    2012-07-01

    Equatorial and low-latitude electrodynamics plays a dominant role in determining the structure and dynamics of the equatorial and low-latitude ionospheric F-region. Thus, they constitute essential input parameters for quantitative global and regional modeling studies. In this work, hourly median value of ionosonde measurements namely, peak height F2-layer (hmF2), F2-layer critical frequency (foF2) and propagation factor M(3000)F2 made at near equatorial dip latitude, Ouagadougou, Burkina Faso (12oN, 1.5oW; dip: 1.5oN) and relevant F2-layer parameters such as thickness parameter (Bo), electron temperature (Te), ion temperature (Ti), total electron content (TEC) and electron density (Ne, at the fixed altitude of 300 km) provided by the International Reference Ionosphere (IRI) model for the longitude of Ouagadougou are contrasted with the IRI vertical drift model to explore in detail the monthly climatological behavior of equatorial ionosphere and the effects of equatorial vertical plasma drift velocities on the diurnal structure of F2-layer parameters. The analysis period covers four months representative of solstitial and equinoctial seasonal periods during solar minimum year of 1987 for geomagnetically quiet-day. We show that month-by-month morphological patterns between vertical E×B drifts and F2-layer parameters range from worst to reasonably good and are largely seasonally dependent. A cross-correlation analysis conducted between equatorial drift and F2-layer characteristics yield statistically significant correlations for equatorial vertical drift and IRI-Bo, IRI-Te and IRI-TEC, whereas little or no acceptable correlation is obtained with observational evidence. Assessment of the association between measured foF2, hmF2 and M(3000)F2 illustrates consistent much more smaller correlation coefficients with no systematic linkage. In general, our research indicates strong departure from simple electrodynamically controlled behavior.

  16. 25 Years of Ionospheric Modification with the Space Shuttle

    NASA Astrophysics Data System (ADS)

    Bernhardt, P. A.

    2011-12-01

    The ionosphere is a low temperature (0.1 eV) plasma layer that surrounds the Earth and affects a wide range of radio systems that involve communications, navigation, and radar. The unmodified ionosphere is in an equilibrium state defined by the balance of production, transport and loss of plasma. The modified ionosphere responds to neutral gas injections with (1) the generation and propagation of plasma waves and (2) the production of plasma irregularities. A single 10 second burn of the on-orbit engines on the Space Shuttle injects 1 GJoule of energy into the upper atmosphere. Injection of hypersonic exhaust vapors from rocket engines pushes the ionosphere out of its equilibrium to yield 20 eV ion beams, launch both neutral and plasma waves, and trigger several instability processes. A wide range of optical emissions, plasma density fluctuations, enhanced temperatures, and changes in composition may be detected during these experiments. Multiple sensors such as instrumented satellites, ground radars, and ground optical instruments are used to determine the extent and lifetime for ionospheric modification. This presentation will focus on experimental data and theoretical discussions of the Space Shuttle Orbital Maneuver Subsystem (OMS) Engines used to modify the upper atmosphere from 1985 to the present. Artificial disturbances in the ionosphere produced by OMS burns have two applications. First, the artificial modification of the ionosphere can provide some control on the radio propagation environment. Second, the man-made disturbances are being produced as proxies to natural disturbances.

  17. 27/10/2010 12:42AGU: Modification of midlatitude ionospheric parameters in the F2 layer by persistent highspeed solar wind streams Page 1 of 1http://europa.agu.org/?view=article&uri=/journals/sw/sw0904/2008SW000443/2008SW000443.xml&t=

    E-print Network

    Ulich, Thomas

    27/10/2010 12:42AGU: Modification of midlatitude ionospheric parameters in the F2 layer://europa.agu.org/?view=article&uri=/journals/sw/sw0904/2008SW000443/2008SW000443.xml&t= Keywords F layer HSS ionosphere Index Terms Space Weather: Corotating streams Ionosphere: Ionosphere/magnetosphere interactions Abstract Modification of midlatitude

  18. Unfolding Spectral Patterns Induced by Artificial Weakly Relativistic Beam in the Ionosphere

    NASA Astrophysics Data System (ADS)

    Kiraga, Arek

    Very diverse set of HF spectra was induced by artificial electron beam injections from the APEX satellite. The spectra were registered in unplanned absence of Xe+ plasma jet, aimed to protect spacecraft against overcharging. Acceleration voltage of 10kV, current modulation frequency ranging from d.c. to 250kHz, low divergence of 4deg, slow variations of pitch angle and maximum instantaneous intensity of 0.15A characterize electron beam. In these time intervals a radiospectrometer operated in a survey mode providing one spectrum every 2s or 8s. The single spectrum was measured in 1s with an equally spaced mesh of 200 frequencies starting from 100kHz with a step of 50kHz. The receiver with a bandwidth of 15 kHz was connected to a tubular dipole antenna having half length of 7.5m. Total number of 400 spectra is not impressive but they are characterized by reproducibility of spectral patterns. From reproducibility or slow evolution of the spectra, it may be inferred that distinct interactions prevail for some ranges of ambient electron gyro (fc) and plasma (fn) frequencies, injection pitch angles and beam intensities. It appears that discrete emission can be identified at least on ambient plasma frequency or ambient upper hybrid frequency (fu). One class of arguments supporting such identifications is provided by interrelation between spectral signatures of local plasma density in passive mode and beam induced spectra. Another class of arguments is provided by interrelations between spectral structures induced by electron beam. For large angles of e-beam injection, electromagnetic character of gyroharmonics radiation from weakly relativistic beam and emissions at harmonics of upper hybrid frequency were reported. In this presentation we extend investigation to pitch angle dependence of electron beam induced spectra. Few examples of spectra induced by very weak beam and by strong beam draw attention to relevance of its intensity. We estimate relevance of propagation for spectral bandwidth with ray tracing of inferred emission modes. The diversity and reproducibility of spectral patterns support viability of simulation of astrophysical plasma in controlled electron beam-space plasma experiments. Narrow single mode emission induced in weak beam regime can be used for monitoring of ambient plasma density.

  19. Signature of 3-4 day planetary waves in the equatorial ionospheric F layer height and medium frequency radar winds over Tirunelveli (8.7oN)

    NASA Astrophysics Data System (ADS)

    Sundararaman, Sathishkumar

    Signature of 3-4 day planetary waves in the equatorial ionospheric F layer height and medium frequency radar winds over Tirunelveli (8.7oN) S. Sathishkumar1, R. Dhanya1, K. Emperumal1, D. Tiwari2, S. Gurubaran1 and A. Bhattacharyya2 1. Equatorial Geophysical Research Laboratory, Indian Institute of Geomagnetism, Tirunelveli, India 2. Indian Institute of Geomagnetism, Navi Mumbai, India Email: sathishmaths@gmail.com Abstract The equatorial atmosphere-ionosphere system has been studied theoretically and observationally in the past. In the equatorial atmosphere, oscillations with periods of 3-4 days are often observed in the medium frequency (MF) radar over Tirunelveli (8.7oN, 77.8oE, 1.34oN geomag. lat.). Earlier observations show the clear evidence that these waves can propagate from the stratosphere to ionosphere. A digital ionosonde has been providing useful information on several ionospheric parameters from the same site. Simultaneous observations of mesospheric winds using medium frequency radar and F-layer height (h'F) from ionosonde reveal that the 3-4 day wave was evident in both the component during the 01 June 2007 and 31 July 2007. The 3-4 day wave could have an important role in the day to day variability of the equatorial ionosphere evening uplift. Results from an extensive analysis that is being carried out in the direction of 3-4 day wave present in the ionosphere will be presented.

  20. On the possibility of producing artificial ionization and polar aurora in the ionosphere by radio-waves emitted from the ground

    NASA Astrophysics Data System (ADS)

    Cutolo, Mario; Argenziano, Angela

    1989-04-01

    In 1938 Prof. V. A. Bailey demonstrated by calculations that some resonance may occur between electrons and a wave as the frequency of this wave varies around the local gyrofrequency, fh. A radio-wave having a frequency equal to the gyrofrequency is called a, gyro-wave. The resonance increases the collision frequency in the low ionosphere by an appreciable amount (I). There are two principal consequencies of the resonance: If a second wave unmodulated passes through the ionosphere region where the gyro-wave acts, an interaction is found between these two waves. This phenomenon is called gyrointeraction and was demonstrated experimentally. If the radiowave is a gyro-wave, with a carrier frequency varying around the local gyrofrequency and is powerful it could produce in the ionosphere an artificial aurora or airglow. The powerful gyro-wave would reduce strongly the electric voltage of the region illuminated by the gyro-wave as to generate an electrical discharge. Moreover with a suitable system of 800 aerial and with a power of 500 kW or of 1,000,000 kW it would be possible to generate an artificial aurora between 60 and 88 km in the ionosphere. Starting form the experiments of H. A. Wilson and D. M. Myers with high-frequency discharges on the lines developed by J. S Towsend and his associates, Bailey developed his theory. These experiments, made by Wilson and Myers, showed that the electric discharges can occur in the air when in the uniform column z/p the ratio of the electric force z to the gas pressure p is approximately 16. It is possible therefore to conclude that two of the necessary conditions for producing electrons and light, are satisfied when E/p 16. An investigation was made in 1959 of the possible increases of both the collision frequencies and the electron density N caused by a powerful extraordinary circular gyrowave in the nocturnal lower-E-region and in the daytime D-region. The principal process then freshly introduced was the attachment of the electrons to molecules in some collisions. According to this new thory the power density requirement for the excitations of an artificial airglow by means of gyrowaves were reconsidered.

  1. Crystallographic structure and superconductive properties of Nb-Ti films with an artificially layered structure

    SciTech Connect

    Sato, N. (SONY Corporation, Research Center, 7-35 Kitashinagawa-6, Shinagawa-ku, Tokyo 141, Japan (JP))

    1990-06-15

    Artificially layered niobium-titanium (Nb-Ti) films with various thickness ratios (3/1--1/3) and periodicities (2--100 A) are made in an argon or in a mixed argon/nitrogen atmosphere by a dc magnetron sputtering method. Films with small periodicities (less than 30 A) have an artificial superlattice structure (ASL) with crystallographic coherence between constituent layers, where Nb and Ti grow epitaxially on the closest planes. The crystallographic structures of films are bcc with the (110) plane parallel to the film for films with the same or a thicker Nb layer than a Ti layer, and hcp with the (001) plane parallel to the film for films with a thinner Nb layer than a Ti layer. Films with large periodicities have an artificial superstructure (ASS) with only periodic stacking of constituent layers. Films deposited in the Ar/N atmosphere also have the artificially layered structures of ASL or ASS. The artificially layered structure is thermally stable at temperatures up to 500 {degree}C. The superconducting properties of the films depend strongly on the periodicity and thickness ratio of Nb and Ti layers. The dependence of the transition temperature on the periodicity and thickness ratio is qualitatively explained by a proximity effect with a three-region model. Films with periodicities less than 20 A, composed of the same or a thicker Nb layer than a Ti layer, show high transition temperatures (above 9.3 K). The highest {ital T}{sub {ital c}} of about 13.6 K is obtained in the film composed of monatomic layers of constituents deposited in an Ar atmosphere including 30 vol % N.

  2. Observations and model calculations of an additional layer in the topside ionosphere above Fortaleza, Brazil

    E-print Network

    Boyer, Edmond

    at around Æ16 latitude and causes a plasma trough to form at the equator, the equatorial anomaly anomaly in the ionosphere over Jicamarca under equinoctial conditions for moderate solar activity that change the amount of upward ¯ux, such as the E Â B drift, neutral wind, season and solar activity

  3. VLF/LF pulse reflections from layers below the ionospheric D-region

    NASA Astrophysics Data System (ADS)

    Rasmussen, J. E.; Kossey, P. A.; Turtle, J. P.

    1982-02-01

    Long wave ionospheric reflectivity data are described from experiments using a VLF/LF pulse ionosounding system. The sounding technique utilized pulses so short, that even at distances of a few hundred kilometers from the transmitter, ground wave and ionospherically reflected sky wave pulses were received separated in time. Pulse reflection data are shown that strongly suggest the simultaneous presence of at least two discrete reflections from different heights in the daytime ionosphere. The upper reflections are identified with the classical D-region, caused primarily by Lyman alpha radiation, while the low-altitude reflections, which occur from shortly before sunrise to shortly after sunset, are believed to be due to ionization caused by cosmic rays and photodetachment. The variability of the low altitude daytime ionosphere is described from VLF/LF pulse reflection data obtained during different seasons, at mid- and low-geomagnetic latitudes, and over different phases of the solar cycle. The effects of the low altitude ionization on the propagation of long radio waves are estimated.

  4. The Surface Layer during Artificial Carious Lesion Formation

    Microsoft Academic Search

    H. M. Theuns; J. W. E. van Dijk; F. C. M. Driessens; A. Groeneveld

    1984-01-01

    This paper gives a detailed description of the development of the surface layer during demineralization of human enamel. Optical inspection of microradiograms of lesions in different stages of development can give the impression that the surface layer increases in thickness with time. Using a more objective method of inspection together with an explicit description, the development of the surface layer

  5. Fundamental character of the field structure in formation of atmospheric and ionospheric layers: unified field of waves

    NASA Astrophysics Data System (ADS)

    Rusinov, Yu. I.

    2004-02-01

    The suggested direction of research is based on the original methodology where plasma, gas, planetary and star systems are considered as a trial (experimental) material. This material is reactive to the changes of the environment according to the law of conservation of symmetry. It was discovered through the algorithm of symmetry conservation that the layered structure of the atmospher and the iososphere is generated by the thin structure of deformation of closed (stable, fixed) waves of density of space-mass continuum, which carry the Earth. In space the continuation of this thin structure is demonstrated by the phenomenon of LDE, inside the planet - by the spheres of compression and underpressure. Cases of closing of corresponding star deformations are seen in novas and supernovas, cases of closing of planet deformations are seen in asteroid belts. The Earth has a deformation, known as layer F2 in ionosphere, on the verge of closing a new wave.

  6. The Influence of the Composition of Demineralizing Buffers on the Surface Layers of Artificial Carious Lesions

    Microsoft Academic Search

    H. M. Theuns; J. W. E. van Dijk; F. C. M. Driessens; A. Groeneveld

    1984-01-01

    This paper deals with the influence of (1) the pH, (2) the degree of saturation with respect to hydroxylapatite (OHA) and (3) the fluoride concentration of demineralizing buffer solutions on the development of surface layers of artificial carious lesions. The pH did not affect the surface layer during demineralization. With increasing saturation with respect to OHA, the mineral content of

  7. Dried earth layers of artificial forestland in the Loess Plateau of Shaanxi Province

    Microsoft Academic Search

    Jingbo Zhao; Juan Du; Baoqun Chen

    2007-01-01

    By determining the earth moisture content of artificial forestland between 0 and 6 m deep in the Loess Plateau of Shaanxi\\u000a province, the vertical change of moisture content, distribution and formation causes of a dried earth layer are researched.\\u000a The results show that the average moisture content is 9.3%–9.5% between 2 and 4 m under artificial forest of over 10

  8. The Production of Free Electrons in the Ionospheric D Layer by Solar and Galactic Cosmic Rays and the Resultant Absorption of Radio Waves

    Microsoft Academic Search

    William Webber

    1962-01-01

    The behavior of the D layer under bombardment by solar and galactic cosmic rays of energy greater than a few Mev is discussed. In particular, the variation with incident particle flux of the ionospheric parameters that determine the equilibrium electron density is deduced by means of the measurements of mid-day and mid-night absorption of cosmic radio noise corre- sponding to

  9. Rossby-Khantadze electromagnetic planetary waves driven by sheared zonal winds in the E-layer ionosphere

    NASA Astrophysics Data System (ADS)

    Futatani, S.; Horton, W.; Kahlon, L. Z.; Kaladze, T. D.

    2015-01-01

    Nonlinear simulations of electromagnetic Rossby and Khantadze planetary waves in the presence of a shearless and sheared zonal flows in the weakly ionized ionospheric E-layer are carried out. The simulations show that the nonlinear action of the vortex structures keeps the solitary character in the presence of shearless zonal winds as well as the ideal solutions of solitary vortex in the absence of zonal winds. In the presence of sheared zonal winds, the zonal flows result in breaking into separate multiple smaller pieces. A passively convected scalar field is shown to clarify the transport associated with the vortices. The work shows that the zonal shear flows provide an energy source into the vortex structure according to the shear rate of the zonal winds.

  10. Coordinated optical and radar observations of ionospheric pumping for a frequency pass through the second electron gyroharmonic at HAARP

    Microsoft Academic Search

    M. J. Kosch; T. Pedersen; E. Mishin; S. Oyama; J. Hughes; A. Senior; B. Watkins; B. Bristow

    2007-01-01

    On 4 February 2005, the High-frequency Active Auroral Research Program (HAARP) facility was operated in O and X mode while pointing into the magnetic zenith to produce artificial optical emissions in the ionospheric F layer. The pump frequency was set to 2.85 MHz to ensure passing through the second electron gyroharmonic of the decaying ionosphere. Optical recordings at 557.7 and

  11. Ionospheric model-observation comparisons: E layer at Arecibo Incorporation of SDO-EVE solar irradiances

    NASA Astrophysics Data System (ADS)

    Sojka, Jan J.; Jensen, Joseph B.; David, Michael; Schunk, Robert W.; Woods, Tom; Eparvier, Frank; Sulzer, Michael P.; Gonzalez, Sixto A.; Eccles, J. Vincent

    2014-05-01

    This study evaluates how the new irradiance observations from the NASA Solar Dynamics Observatory (SDO) Extreme Ultraviolet Variability Experiment (EVE) can, with its high spectral resolution and 10 s cadence, improve the modeling of the E region. To demonstrate this a campaign combining EVE observations with that of the NSF Arecibo incoherent scatter radar (ISR) was conducted. The ISR provides E region electron density observations with high-altitude resolution, 300 m, and absolute densities using the plasma line technique. Two independent ionospheric models were used, the Utah State University Time-Dependent Ionospheric Model (TDIM) and Space Environment Corporation's Data-Driven D Region (DDDR) model. Each used the same EVE irradiance spectrum binned at 1 nm resolution from 0.1 to 106 nm. At the E region peak the modeled TDIM density is 20% lower and that of the DDDR is 6% higher than observed. These differences could correspond to a 36% lower (TDIM) and 12% higher (DDDR) production rate if the differences were entirely attributed to the solar irradiance source. The detailed profile shapes that included the E region altitude and that of the valley region were only qualitatively similar to observations. Differences on the order of a neutral-scale height were present. Neither model captured a distinct dawn to dusk tilt in the E region peak altitude. A model sensitivity study demonstrated how future improved spectral resolution of the 0.1 to 7 nm irradiance could account for some of these model shortcomings although other relevant processes are also poorly modeled.

  12. Artificial excitation of ELF waves with frequency of Schumann resonance

    NASA Astrophysics Data System (ADS)

    Streltsov, A. V.; Guido, T.; Tulegenov, B.; Labenski, J.; Chang, C.-L.

    2014-11-01

    We report results from the experiment aimed at the artificial excitation of extremely low-frequency (ELF) electromagnetic waves with frequencies corresponding to the frequency of Schumann resonance. Electromagnetic waves with these frequencies can form a standing pattern inside the spherical cavity formed by the surface of the Earth and the ionosphere. In the experiment the ELF waves were excited by heating the ionosphere with X-mode HF electromagnetic waves generated at the High Frequency Active Auroral Research Program (HAARP) facility in Alaska. The experiment demonstrates that heating of the ionosphere can excite relatively large-amplitude electromagnetic waves with frequencies in the range 7.8-8.0 Hz when the ionosphere has a strong F layer, the frequency of the HF radiation is in the range 3.20-4.57 MHz, and the electric field greater than 5 mV/m is present in the ionosphere.

  13. Evaluation of a technique to generate artificially thickened boundary layers in supersonic and hypersonic flows

    NASA Technical Reports Server (NTRS)

    Porro, A. R.; Hingst, W. R.; Davis, D. O.; Blair, A. B., Jr.

    1991-01-01

    The feasibility of using a contoured honeycomb model to generate a thick boundary layer in high-speed, compressible flow was investigated. The contour of the honeycomb was tailored to selectively remove momentum in a minimum of streamwise distance to create an artificially thickened turbulent boundary layer. Three wind tunnel experiments were conducted to verify the concept. Results indicate that this technique is a viable concept, especially for high-speed inlet testing applications. In addition, the compactness of the honeycomb boundary layer simulator allows relatively easy integration into existing wind tunnel model hardware.

  14. Surface characterization of artificial corrosion layers on copper alloy reference materials

    NASA Astrophysics Data System (ADS)

    Constantinides, I.; Adriaens, A.; Adams, F.

    2002-04-01

    This paper describes the surface characterization of artificial patina layers on five different copper alloys. The chemical composition of the examined bronzes covers the major families of archaeological copper alloys from antiquity until the Roman period. The patina layers of the five samples were formed under identical conditions by electrochemical means. Light microscopy, scanning electron microscopy with energy dispersive X-ray micro analysis (SEM-EDX) and Fourier transform infrared spectroscopy (FTIR) were used to describe the main properties of the patina layers. The results were interpreted and classified according to an existing corrosion model for copper alloys.

  15. Statistical study of relationship between medium-scale traveling ionospheric disturbance and sporadic E layer activities in summer night over Japan

    Microsoft Academic Search

    Y. Otsuka; T. Tani; T. Tsugawa; T. Ogawa; A. Saito

    2008-01-01

    We investigate the relationship between medium-scale traveling ionospheric disturbance (MSTID) and sporadic E (Es) layer activities in summer nights by analyzing total electron content (TEC) data obtained from a global positioning system (GPS) network in Japan and ionosonde data obtained at Kokubunji, Japan during May–August in 2001–2005. MSTID activity is defined as ?I\\/I¯, where ?I is standard deviation of the

  16. Excitation of guided ELF-VLF waves through modification of the F{sub 2} ionospheric layer by high-power radio waves

    SciTech Connect

    Markov, G. A.; Belov, A. S.; Komrakov, G. P. [Lobachevsky State University (Russian Federation); Parrot, M. [Environmental Physics and Chemistry Laboratory (France)

    2012-03-15

    The possibility of controlled excitation of ELF-VLF electromagnetic waves through modification of the F{sub 2} ionospheric layer by high-power high-frequency emission is demonstrated in a natural experiment by using the Sura midlatitude heating facility. The excited low-frequency waves can be used to explore the near-Earth space and stimulate the excitation of a magnetospheric maser.

  17. GPS Vertical Total Electron Content (TEC) Dual Frequency Technique and TEC Map at Ionosphere Layer Using Malaysian Data

    Microsoft Academic Search

    Norsuzila Ya' acob; Mardina Abdullah; Mahamod Ismail

    2009-01-01

    The parameter of ionosphere that produces most of the effects on radio signals is total electron content (TEC). Ionospheric TEC variation with time can be viewed as a stationary random process under quiet conditions. This paper investigate the TEC covering the period from 8 November 2005 using Malaysia data for KTPK station. During this period with Kp, Dst, and Ap

  18. Radio-frequency radiation energy transfer in an ionospheric layer with random small-scale inhomogeneities

    SciTech Connect

    Zabotin, N.A.

    1994-06-01

    The equation of radiation energy balance in a randomly inhomogeneous plane-stratified plasma layer was derived based on the phenomenological approach. The use of the small-angle scattering approximation in the invariate ray coordinates allows it to be transformed into a drift-type equation. The latter describes the deformation of the spatial distribution of the radio-frequency radiation energy due to multiple scattering by anisotropic inhomogeneities. Two effects are investigated numerically: shift of the radio wave arrival angles under a slightly oblique propagation, and variation of the intensity of the radio-frequency radiation reflected from a plasma layer.

  19. Oxidation characteristics of artificially layered Fe\\/Al and Fe\\/Mg thin films

    Microsoft Academic Search

    S. Veena Kumari; V. K. Vaidyan; K. G. Sathyanarayana

    1992-01-01

    Investigations were carried out on the oxidation characteristics of artificially layered Fe\\/Al and Fe\\/Mg thin films using X-ray diffraction and Raman spectroscopy at 303, 473, 673 and 773 K in the laboratory atmosphere. X-ray diffractograms and Raman spectra reveal diffusion phenomena occurring in Fe\\/Al thin films. Individual oxides and a spinel-phase MgFe2O4, were the oxidation products in Fe\\/Mg multilayers while

  20. TRANSIENT LAYERS IN THE TOPSIDE IONOSPHERE OF MARS Andrew James Kopf

    E-print Network

    Gurnett, Donald A.

    . The best fit linear function in the last panel shows an upward trend in altitude with increasing solar TABLE OF CONTENTS LIST OF FIGURES CHAPTER 1. MARS EXPRESS AND MARSIS 2. SOUNDING THEORY AND MODELING 3. TOPSIDE LAYERS 4. INTERPRETATION REFERENCES iii 1 4 7 14 17 #12;iii LIST OF FIGURES Figure 1. The top

  1. Artificial dispersion via high-order homogenization: magnetoelectric coupling and magnetism from dielectric layers

    PubMed Central

    Liu, Yan; Guenneau, Sébastien; Gralak, Boris

    2013-01-01

    We investigate a high-order homogenization (HOH) algorithm for periodic multi-layered stacks. The mathematical tool of choice is a transfer matrix method. Expressions for effective permeability, permittivity and magnetoelectric coupling are explored by frequency power expansions. On the physical side, this HOH uncovers a magnetoelectric coupling effect (odd-order approximation) and artificial magnetism (even-order approximation) in moderate contrast photonic crystals. Comparing the effective parameters' expressions of a stack with three layers against that of a stack with two layers, we note that the magnetoelectric coupling effect vanishes while the artificial magnetism can still be achieved in a centre-symmetric periodic structure. Furthermore, we numerically check the effective parameters through the dispersion law and transmission property of a stack with two dielectric layers against that of an effective bianisotropic medium: they are in good agreement throughout the low-frequency (acoustic) band until the first stop band, where the analyticity of the logarithm function of the transfer matrix () breaks down. PMID:24101891

  2. Natural hazards monitoring and forecast using the GNSS and other technologies of the ionosphere monitoring

    NASA Astrophysics Data System (ADS)

    Pulinets, S. A.; Davidenko, D.

    2013-12-01

    It is well established now that Atmosphere-Ionosphere Coupling is provided through the local changes of the Global Electric Circuit parameters. Main agent - is column conductivity, modulated mainly at the altitudes of the Global Boundary Layer. We demonstrate the ionospheric effects for different types of natural hazards including volcano eruptions, dusty storms from Western Africa, ionospheric effects from tropical hurricanes, multiple earthquakes. We consider the important role of air ionization from natural (natural ground radioactivity and galactic cosmic rays) and artificial sources (nuclear weapon tests in atmosphere and underground, nuclear power stations and other nuclear enterprises emergencies). We rise also important question that such effects of the ionosphere variability are not taken into account by any ionospheric model and their correct recognition is important not only from the point of view the disasters monitoring but for navigation itself because the magnitude of the ionospheric effects sometimes exceeds the effects from strong magnetic storms and other severe space weather conditions. Some effects like ionospheric effects from tropical hurricanes have more complex physical nature including the formation of streams of neutral atmosphere over the hurricane eye and formation of the strong positive plasma concentration anomaly at the altitude near 1000 km. Some plasma anomalies registered over the tropical depressions before hurricane formation give hope on predictive capabilities of plasma observations over the tropical depressions.

  3. Feasibility of generating an artificial burst in a turbulent boundary layer, phase 2

    NASA Technical Reports Server (NTRS)

    Gad-El-hak, Mohamed

    1989-01-01

    Various drag accounts for about half of the total drag on commercial aircraft at subsonic cruise conditions. Two avenues are available to achieve drag reduction: either laminar flow control or turbulence manipulation. The present research deals with the latter approach. The primary objective of Phase 2 research was to investigate experimentally the feasibility of substantially reducing the skin-friction drag in a turbulent boundary layer. The method combines the beneficial effects of suction and a longitudinally ribbed surface. At a sufficiently large spanwise separation, the streamwise grooves act as a nucleation site causing a focusing of low-speed streaks over the peaks. Suction is then applied intermittently through longitudinal slots located at selected locations along those peaks to obliterate the low-speed regions and to prevent bursting. Phase 2 research was divided into two tasks. In the first, selective suction from a single streamwise slot was used to eliminate either a single burst-like event or a periodic train of artificially generated bursts in laminar and turbulent boundary layers that develop on a flat plate towed in a water channel. The results indicate that equivalent values of the suction coefficient as low as 0.0006 were sufficient to eliminate the artificially generated bursts in a laminar boundary layer.

  4. Artificial disturbances of the ionosphere over the Millstone Hill Incoherent Scatter Radar from dedicated burns of the space shuttle orbital maneuver subsystem engines

    Microsoft Academic Search

    Paul A. Bernhardt; Philip J. Erickson; Frank D. Lind; John C. Foster; Bodo W. Reinisch

    2005-01-01

    Two ionospheric modification experiments were carried out over the incoherent scatter radar (ISR) located at Millstone Hill, Massachusetts. These experiments are part of the Shuttle Ionospheric Modification with Pulsed Localized Exhaust (SIMPLEX) program at the Naval Research Laboratory. The experiments use 10-s burns of the dual orbital maneuver subsystem (OMS) engines to produce the injection of high-speed molecules in the

  5. Zipper and layer-by-layer assemblies of artificial photosystems analyzed by combining optical and piezoelectric surface techniques.

    PubMed

    Porus, Mariya; Maroni, Plinio; Bhosale, Rajesh; Sakai, Naomi; Matile, Stefan; Borkovec, Michal

    2011-06-01

    Quartz crystal microbalance (QCM) and surface plasmon resonance (SPR) were used to study zipper and layer-by-layer multilayer assemblies of artificial photosystems based on naphthalenediimides (NDIs) attached to an oligophenylethynyl (OPE-NDI) or p-oligophenyl (POP-NDI) backbone in dry and wet state. For the most interesting OPE-NDI zipper, one obtains for the dry film a monolayer thickness of 1.85 nm and a density of 1.58 g/cm(3), while the wet film has a larger monolayer thickness of 3.6 nm with a water content of 36%. The dry thickness of a monolayer in OPE-NDI zippers corresponds to about one-half of the length of the OPE scaffold in agreement with the proposed structure of the zipper. The low water content of the OPE-NDI films confirms their compact structure. The dry monolayer thickness of the POP-NDI films of 1.45 nm is smaller than that for the OPE-NDI films, which is probably related to a tilt of the POP scaffolds within the adsorbed layer. The POP-NDI films swell in water much more substantially, suggesting a much more open structure. These features are in excellent agreement with the better photophysical performance of the OPE-NDI assemblies when compared to the POP-NDI films. PMID:21526834

  6. A study on ionospheric TEC forecast using genetic algorithm and neural network

    NASA Astrophysics Data System (ADS)

    Huang, Zhi; Yuan, Hong

    Back propagation artificial neural network (ANN) augmented by genetic algorithm (GA) is introduced to forecast ionospheric TEC with the dual-frequency GPS measurements from the low and high solar activity years in this paper due to ionosphere space characterizing by the highly nonlinear and time-varying with random variations. First, with different number of neurons in the hidden layer, different transfer function and training function, the training performance of network model is analyzed and then optimized network structure is determined. The ionospheric TEC values one hour in advance are forecasted and further the prediction performance of the developed network model is evaluated at the given criterions. The results show that predicted TEC using BP neural network improved by genetic algorithm has good agreement with observed data. In addition, the prediction errors are smaller in middle and high latitudes than in low latitudes, smaller in low solar activity than in high solar activity. Compared with BP Network with three layers structure, Prediction precision of network model optimized by genetic algorithm is further improved. The resolution quality indicate that the proposed algorithm can offer a powerful and reliable alternative to the design of ionospheric TEC forecast technologies, and provide advice for the regional ionospheric TEC maps. Key words: Neural network, Genetic algorithm, Ionospheric TEC, Forecast,

  7. Formation of artificially-layered thin-film compounds using pulsed-laser deposition

    SciTech Connect

    Norton, D.P.; Chakoumakos, B.C.; Lowndes, D.H.; Budai, J.D.

    1995-04-01

    Superlattice structures, consisting of SrCuO{sub 2}, (Sr,Ca)CuO{sub 2}, and BaCuO{sub 2} layers in the tetragonal, ``infinite layer`` crystal structure, have been grown by pulsed-laser deposition (PLD). Superlattice chemical modulation is observed for structures with component layers as thin as a single unit cell ({approximately}3.4 {angstrom}), indicating that unit-cell control of (Sr,Ca)CuO{sub 2} growth is possible using conventional pulsed-laser deposition over a wide oxygen pressure regime. X-ray diffraction intensity oscillations, due to the finite thickness of the film, indicate that these films are extremely flat with a thickness variation of only {approximately}20 {angstrom} over a length scale of several thousand angstroms. Using the constraint of epitaxy to grow metastable cuprates in the infinite layer structure, novel high-temperature superconducting structural families have been formed. In particular, epitaxially-stabilized SrCuO{sub 2}/BaCuO{sub 2} superlattices, grown by sequentially depositing on lattice-matched (100) SrTiO{sub 3} from BaCuO{sub 2} and SrCuO{sub 2} ablation targets in a PLD system, show metallic conductivity and superconductivity at {Tc}(onset) {approximately}70 K. These results show that pulsed-laser deposition and epitaxial stabilization have been used to effectively ``engineer`` artificially-layered thin-film materials.

  8. Formation and properties of novel artificially-layered cuprate superconductors using pulsed-laser deposition

    SciTech Connect

    Norton, D.P.; Chakoumakos, B.C.; Budai, J.D.

    1996-03-01

    Pulsed-laser deposition and epitaxial stabilization have been effectively used to engineer artificially-layered thin-film materials. Novel cuprate compounds have been synthesized using the constraint of epitaxy to stabilize (Ca,Sr)CuO{sub 2}/(Ba,Ca,Sr)CuO{sub 2} superconducting superlattices in the infinite layer structure. Superlattice chemical modulation can be observed from the x-ray diffraction patterns for structures with SrCuO{sub 2} and (Ca, Sr)CuO{sub 2} layers as thin as a single unit cell ({approximately}3. 4 {angstrom}). X-ray diffraction intensity oscillations, due to the finite thickness of the film, indicate that (Ca,Sr)CuO{sub 2} films grown by pulsed-laser deposition are extremely flat with a thickness variation of only {approximately}20 {angstrom} over a length scale of several thousand angstroms. This enables the unit-cell control of (Ca, Sr)CuO{sub 2} film growth in an oxygen pressure regime in which in situ surface analysis using electron diffraction is not possible. With the incorporation of BaCuO{sub 2} layers, superlattice structures have been synthesized which superconduct at temperatures as high as 70 K. Dc transport measurements indicate that (Ca, Sr)CuO{sub 2}/BaCuO{sub 2} superlattices are two dimensional superconductors with the superconducting transition primarily associated with the BaCuO{sub 2} layers. Superconductivity is observed only for structures with BaCuO{sub 2} layers at least two unit cells thick with {Tc} decreasing as the (Ca,Sr)CuO{sub 2} layer thickness increases. Normalized resistance in the superconducting region collapse to the Ginzburg-Landau Coulomb gas universal resistance curve consistent with the two-dimensional vortex fluctuation model.

  9. Verification of ionospheric sensors

    NASA Astrophysics Data System (ADS)

    Coker, Clayton; Kronschnabl, Glenn; Coco, David S.; Bust, Gary S.; Gaussiran, Thomas L., II

    2001-01-01

    Ionospheric products from sensors and models were compared to investigate strengths and limitations of each. Total electron content data from computerized ionospheric tomography (CIT) and TOPEX sensors in the Caribbean region in 1997 were compared to estimates produced by models Parameterized Ionospheric Model (PIM) and Raytrace/ICED-Bent-Gallagher (RIBG) and global maps from GPS. A 5 total electron content unit (TECU) bias was observed in TOPEX. CIT and TOPEX confirmed the location and structure of the equatorial anomaly. A GPS map confirmed the location of the anomaly but did not reproduce structure less than 1000 km in latitude and 1500 km in longitude and underestimated TEC by at least 11 TECU or 25%. PIM positioned the anomaly 13° equatorward of its observed location and greatly underestimated (˜50%) the rise in content over 5°-25°N range. RIBG overestimated the latitudinal extent of the anomaly and underestimated TEC at the peak by 40%. Additional comparisons were made using CIT and ionosonde sensors at midlatitude during the summer of 1998. Fourteen days of TEC, hmF2, NmF2, and half-thickness comparisons showed reasonable agreement between CIT and ionosonde for TEC and NmF2. The hmF2 and half-thickness comparisons were contaminated by noise, which accounted for a significant portion of the ionospheric variation. Daytime cases where CIT overestimated maximum density were attributed to underestimating layer thickness. Finally, TOPEX and multiple GPS sensors were compared to verify regional ionospheric conditions associated with occurrence of nighttime ionospheric depletions in the Caribbean during Combined Ionospheric Campaigns in June of 1998. From 0300 to 0800 UT on June 26, GPS and TOPEX showed elevated nighttime content over the entire Caribbean region. Vertical TEC approached 25 TECU in some places with interspersed depletions, which in some cases evacuated nearly the entire ionospheric content.

  10. Empirical model of ionospheric storm effects on the F2 layer peak height associated with changes of peak electron density

    NASA Astrophysics Data System (ADS)

    Gulyaeva, T. L.

    2012-02-01

    An empirical model of storm-time behavior of the ionospheric peak height hmF2 associated with changes of peak electron density NmF2 is inferred from the topside true-height profiles provided by ISIS 1, ISIS 2, IK-19, and Cosmos-1809 satellites for the period of 1969-1987. The topside-derived quiet-time models of the ionospheric peak height hqF2 and peak electron density NqF2 are used as a frame of reference. To harmonize the model with storm and substorm effects induced by large-scale traveling ionospheric disturbances (LSTIDs), constraints are applied to the topside data, excluding their changes deviating above LSTID extreme limits. The degree of disturbance is estimated by the ionospheric weather W index; then, the least squares fitting is applied to the median of log(hm/hq) versus log(Nm/Nq). Anticorrelation between instant changes of hmF2 and NmF2 has a particular seasonal-magnetic latitude structure varying with solar activity that is used for the buildup of the analytical model. The model allows the deduction of the instantaneous hmF2 associated with the assessment or forecast of the respective NmF2. The model is validated with the data of five ground-based ionosondes during severe space weather storms at times of high solar activity (2000) and low solar activity (2006), and results agree reasonably well with the peak parameters derived from an ionogram. The model is incorporated into the coupled International Reference Ionosphere-Plasmasphere (IRI-Plas) code, used in the assimilative mode as the three-dimensional (3-D) interpolator of the GPS-derived total electron content, TECgps.

  11. Tunable ferroelectricity in artificial tri-layer superlattices comprised of non-ferroic components

    NASA Astrophysics Data System (ADS)

    Rogdakis, K.; Seo, J. W.; Viskadourakis, Z.; Wang, Y.; Ah Qune, L. F. N.; Choi, E.; Burton, J. D.; Tsymbal, E. Y.; Lee, J.; Panagopoulos, C.

    2012-09-01

    Heterostructured material systems devoid of ferroic components are presumed not to display ordering associated with ferroelectricity. In heterostructures composed of transition metal oxides, however, the disruption introduced by an interface can affect the balance of the competing interactions among electronic spins, charges and orbitals. This has led to the emergence of properties absent in the original building blocks of a heterostructure, including metallicity, magnetism and superconductivity. Here we report the discovery of ferroelectricity in artificial tri-layer superlattices consisting solely of non-ferroelectric NdMnO3/SrMnO3/LaMnO3 layers. Ferroelectricity was observed below 40 K exhibiting strong tunability by superlattice periodicity. Furthermore, magnetoelectric coupling resulted in 150% magnetic modulation of the polarization. Density functional calculations indicate that broken space inversion symmetry and mixed valency, because of cationic asymmetry and interfacial polar discontinuity, respectively, give rise to the observed behaviour. Our results demonstrate the engineering of asymmetric layered structures with emergent ferroelectric and magnetic field tunable functions distinct from that of normal devices, for which the components are typically ferroelectrics.

  12. An observational study of the influence of solar zenith angle on properties of the M1 layer of the Mars ionosphere

    NASA Astrophysics Data System (ADS)

    Fallows, K.; Withers, P.; Matta, M.

    2015-02-01

    The variations in peak properties of the M1 layer (the lower photochemical plasma layer) with solar zenith angle (SZA) are important relationships for understanding the physical processes which control this region of the Mars ionosphere. The behavior of the M1 layer has been poorly characterized to date. Here we introduce an automated and repeatable method for determining properties of the M1 and M2 layers simultaneously in 5600 Mars Global Surveyor radio occultation profiles of dayside electron density. The results support previous findings for M1 and M2 subsolar peak densities and the dependence of peak densities on solar zenith angle. The ratio of M1 peak density to M2 peak density remains constant at 0.4 for 70° layer, L2 = 5.2 km, indicating that the two layers become increasingly separated at high solar zenith angles. The vertical width of the M1 layer, H1, decreases from 7 km to 5 km as solar zenith angle increases from 70° to 90°, whereas the vertical width of the M2 layer, H2, increases from 10 km to 14 km. The prediction of ideal Chapman theory that both the widths Hi and the lengthscales Li equal the neutral scale height is not supported by observations. These findings provide meaningful observational constraints for numerical models, which are known to have trouble reproducing observations and observed trends associated with the M1 layer.

  13. Manipulation of an artificial large scale horse-shoe vortex by a thin plate placed in a turbulent boundary layer

    NASA Astrophysics Data System (ADS)

    Makita, H.; Sassa, K.; Abe, M.; Itabashi, A.

    1987-06-01

    A horseshoe vortex was artificially induced in a fully-developed turbulent boundary layer by injecting a pair of small swirling jets from a flat plate beneath. The artificial vortex grew toward the outer layer and came to have a structure almost the same as the natural coherent bulge as it flowed downstream. A thin manipulator plate was installed parallel to the flat plate and the artificial horseshoe vortex was broken. Velocity-vector plots and the shear-stress contour maps were obtained by the conditional sampling method. When the horseshoe vortex was manipulated, its coherent structure decayed rapidly, and the intensity of the induced shear stress concentrated between its two legs was reduced effectively. These results suggest the possibility of drag reduction by the large-eddy breakup method.

  14. Ionospheric modifications in high frequency heating experiments

    NASA Astrophysics Data System (ADS)

    Kuo, Spencer P.

    2015-01-01

    Featured observations in high-frequency (HF) heating experiments conducted at Arecibo, EISCAT, and high frequency active auroral research program are discussed. These phenomena appearing in the F region of the ionosphere include high-frequency heater enhanced plasma lines, airglow enhancement, energetic electron flux, artificial ionization layers, artificial spread-F, ionization enhancement, artificial cusp, wideband absorption, short-scale (meters) density irregularities, and stimulated electromagnetic emissions, which were observed when the O-mode HF heater waves with frequencies below foF2 were applied. The implication and associated physical mechanism of each observation are discussed and explained. It is shown that these phenomena caused by the HF heating are all ascribed directly or indirectly to the excitation of parametric instabilities which instigate anomalous heating. Formulation and analysis of parametric instabilities are presented. The results show that oscillating two stream instability and parametric decay instability can be excited by the O-mode HF heater waves, transmitted from all three heating facilities, in the regions near the HF reflection height and near the upper hybrid resonance layer. The excited Langmuir waves, upper hybrid waves, ion acoustic waves, lower hybrid waves, and field-aligned density irregularities set off subsequent wave-wave and wave-electron interactions, giving rise to the observed phenomena.

  15. Modeling of plasma chemical processes in the artificial ionized layer in the upper atmosphere by the nanosecond corona discharge

    Microsoft Academic Search

    A. L. Vikharev; A. M. Gorbachev; O. A. Ivanov; A. L. Kolisko; A. G. Litvak

    1993-01-01

    The plasma chemical processes in the corona discharge formed in air by a series of high voltage pulses of nanosecond duration are investigated experimentally. The experimental conditions (reduced electric field, duration and repetition frequency of the pulses, gas pressure in the chamber) modeled the regime of creation of the artificial ionized layer (AIL) in the upper atmosphere by a nanosecond

  16. Generation of zonal flow and magnetic field by coupled internal-gravity and alfvén waves in the ionospheric E-layer

    NASA Astrophysics Data System (ADS)

    Kaladze, Tamaz; Kahlon, Laila

    Nonlinear dynamics of coupled internal-gravity (IG) and alfven electromagnetic planetary waves in the weakly ionized ionospheric E-layer is investigated. Under such coupling new type of alfven waves is revealed. It is shown that such short wavelength turbulence of IG and alfvén waves is unstable with respect to the excitation of low-frequency and large-scale perturbations of the zonal flow and magnetic field. A set of coupled equations describing the nonlinear interaction of coupled IG and alfven waves with zonal flows is derived. The nonlinear mechanism of the instability is driven by the advection of vorticity and is based on the parametric excitation of convective cells by finite-amplitude coupled IG and alfven waves leading to the inverse energy cascade toward the longer wavelength. The growth rates of the corresponding instability and the conditions for driving them are determined. The possibility of generation of the intense mean magnetic field is shown.

  17. Echo III: The study of electric and magnetic fields with conjugate echoes from artificial electron beams injected into the auroral zone ionosphere

    Microsoft Academic Search

    R. A. Hendrickson; J. R. Winckler; R. L. Arnoldy

    1976-01-01

    The third in a series of rocket flights carrying large electron guns for electron beam-plasma analysis and magnetosphere probing has been carried out from the Poker Flat rocket range near Fairbanks, Alaska at L=6. Echoes from the injected electrons mirroring at the southern hemisphere conjugate point were observed on the rocket by particle detectors and in the nearby ionosphere by

  18. Ionosphere research

    NASA Technical Reports Server (NTRS)

    1976-01-01

    A report is presented on on-going research projects in ionospheric studies. The topics discussed are planetary atmospheres, E and F region, D region, mass spectrometer measurements, direct measurements and atmospheric reactions.

  19. Artificial disturbances of the ionosphere over the Millstone Hill Incoherent Scatter Radar from dedicated burns of the space shuttle orbital maneuver subsystem engines

    NASA Astrophysics Data System (ADS)

    Bernhardt, Paul A.; Erickson, Philip J.; Lind, Frank D.; Foster, John C.; Reinisch, Bodo W.

    2005-05-01

    Two ionospheric modification experiments were carried out over the incoherent scatter radar (ISR) located at Millstone Hill, Massachusetts. These experiments are part of the Shuttle Ionospheric Modification with Pulsed Localized Exhaust (SIMPLEX) program at the Naval Research Laboratory. The experiments use 10-s burns of the dual orbital maneuver subsystem (OMS) engines to produce the injection of high-speed molecules in the ionosphere near 380 km altitude. Charge exchange between the high-speed exhaust molecules and the ambient oxygen ions yields molecular ion beams that disturb the natural state of the ionosphere. Radar scatter provides measurements of the ion velocity distributions and plasma turbulence that result from the ion beam interactions. Ground-based observations with the University of Massachusetts Digisonde record the ionospheric density depressions resulting from recombination of the molecular ions with electrons. Prompt signatures of nonequilibrium ion distributions in the OMS engine plume are seen in the data taken during the SIMPLEX III and IV experiments for the space shuttle flights STS-108 and STS-110, respectively. The SIMPLEX III observations are much weaker than those during SIMPLEX IV. These differences are primarily attributed to the changes in the viewing directions for the radar beam. During SIMPLEX IV, the radar is looking more downstream from the exhaust injection and the stimulation of plasma turbulence is seen with the ISR for over 30 s at distances up to 200 km from the burn altitude along the radar beam. Strong backscatter in the radar spectra is attributed to ion acoustic waves driven by the pickup ion beams. Both experiments provide large-scale cavities detected by the Digisonde for up to 20 min after the engine burn. These cavities are the result of ion-electron recombination of the pickup ions.

  20. Artificial optical emissions at HAARP for pump frequencies near the third and second electron gyro-harmonic

    Microsoft Academic Search

    T. Pedersen; J. Hughes; R. Marshall; E. Gerken; A. Senior; D. Sentman; M. McCarrick

    2005-01-01

    High-power high-frequency radio waves beamed into the ionosphere cause plasma turbulence, which can accelerate electrons. These electrons collide with the F-layer neutral oxygen causing artificial optical emissions identical to natural aurora. Pumping at electron gyro-harmonic frequencies has special significance as many phenomena change their character. In particular, artificial optical emissions become strongly reduced for the third and higher gyro-harmonics. The

  1. Photoluminescence quenching and charge transfer in artificial heterostacks of monolayer transition metal dichalcogenides and few-layer black phosphorus.

    PubMed

    Yuan, Jiangtan; Najmaei, Sina; Zhang, Zhuhua; Zhang, Jing; Lei, Sidong; M Ajayan, Pulickel; Yakobson, Boris I; Lou, Jun

    2015-01-27

    Transition metal dichalcogenides monolayers and black phosphorus thin crystals are emerging two-dimensional materials that demonstrated extraordinary optoelectronic properties. Exotic properties and physics may arise when atomic layers of different materials are stacked together to form van der Waals solids. Understanding the important interlayer couplings in such heterostructures could provide avenues for control and creation of characteristics in these artificial stacks. Here we systematically investigate the optical and optoelectronic properties of artificial stacks of molybdenum disulfide, tungsten disulfide, and black phosphorus atomic layers. An anomalous photoluminescence quenching was observed in tungsten disulfide-molybdenum disulfide stacks. This was attributed to a direct to indirect band gap transition of tungsten disulfide in such stacks while molybdenum disulfide maintains its monolayer properties by first-principles calculations. On the other hand, due to the strong build-in electric fields in tungsten disulfide-black phosphorus or molybdenum disulfide-black phosphorus stacks, the excitons can be efficiently splitted despite both the component layers having a direct band gap in these stacks. We further examine optoelectronic properties of tungsten disulfide-molybdenum disulfide artificial stacks and demonstrate their great potentials in future optoelectronic applications. PMID:25569715

  2. AM Radio Ionosphere Station: Teacher's Guide

    NSDL National Science Digital Library

    In this activity students will monitor the ionosphere by using an amplitude modulated (AM) radio to track solar storms and other changes in ionosphere reflectivity. They will discover that above the earth's surface a layer of charged particles called the ionosphere is capable of reflecting radio waves and that the reflectivity properties of the ionosphere can be changed dramatically by solar activity. In order to detect and study some of these changes, students will use the radio to listen for changes in background noise and the appearance of distant stations, learning that a simple everyday device can let them detect invisible changes in their environment caused by solar activity.

  3. "Twisted Beam" SEE Observations of Ionospheric Heating from HAARP

    NASA Astrophysics Data System (ADS)

    Briczinski, S. J.; Bernhardt, P. A.; Siefring, C. L.; Han, S.-M.; Pedersen, T. R.; Scales, W. A.

    2015-02-01

    Nonlinear interactions of high power HF radio waves in the ionosphere provide aeronomers with a unique space-based laboratory capability. The High-Frequency Active Auroral Research Program (HAARP) in Gakona, Alaska is the world's largest heating facility, yielding effective radiated powers in the gigawatt range. New results are present from HAARP experiments using a "twisted beam" excitation mode. Analysis of twisted beam heating shows that the SEE results obtained are identical to more traditional patterns. One difference in the twisted beam mode is the heating region produced is in the shape of a ring as opposed to the more traditional "solid spot" region from a pencil beam. The ring heating pattern may be more conducive to the creation of stable artificial airglow layers because of the horizontal structure of the ring. The results of these runs include artificial layer creation and evolution as pertaining to the twisted beam pattern. The SEE measurements aid the interpretation of the twisted beam interactions in the ionosphere.

  4. Ionization distribution in the F2 layer during the March 16-20 and December 5-10, 1988 SUNDIAL campaign intervals, and its comparison with an empirical high latitude model ionosphere

    Microsoft Academic Search

    A. S. Besprozvannaia; P. V. Kishcha; E. V. Nepomniashchaia; S. A. Pulinets; T. I. Shchuka

    1993-01-01

    Results of coordinated vertical ionization measurements in the F2 layer made during the SUNDIAL March 16-20 and December 5-10, 1988 campaign periods are compared with the values of maximal electron concentrations estimated using an empirical high-latitude model ionosphere described by Besprozvannaia (1986). It is shown that, for both the daytime and the nighttime hours, the average error of the model

  5. 3D Tomography of Ionospheric Perturbations Produced by Earthquakes Using Global Positioning System

    Microsoft Academic Search

    F. Crespon; R. Garcia; P. Lognonné; M. Murakami

    2004-01-01

    The recent development of Global Positioning System led to establish dense regional networks of bistatic GPS receivers providing today a powerful ionospheric observing system. Now the ionosphere can be imaged by tomographic methods using GPS data. Therefore the ionospheric perturbations can be characterized by monitoring Total Electronic Content (TEC). These disturbances have multiple sources located adove and below ionospheric layers.

  6. Comparison of Observations of Sporadic-E Layers in the Nighttime and Daytime Mid-Latitude Ionosphere

    NASA Technical Reports Server (NTRS)

    Pfaff, R.; Freudenreich, H.; Rowland, D.; Klenzing, J.; Clemmons, J.; Larsen, M.; Kudeki, E.; Franke, S.; Urbina, J.; Bullett, T.

    2012-01-01

    A comparison of numerous rocket experiments to investigate mid-latitude sporadic-E layers is presented. Electric field and plasma density data gathered on sounding rockets launched in the presence of sporadic-E layers and QP radar echoes reveal a complex electrodynamics including both DC parameters and plasma waves detected over a large range of scales. We show both DC and wave electric fields and discuss their relationship to intense sporadic-E layers in both nighttime and daytime conditions. Where available, neutral wind observations provide the complete electrodynamic picture revealing an essential source of free energy that both sets up the layers and drives them unstable. Electric field data from the nighttime experiments reveal the presence of km-scale waves as well as well-defined packets of broadband (10's of meters to meters) irregularities. What is surprising is that in both the nighttime and daytime experiments, neither the large scale nor short scale waves appear to be distinctly organized by the sporadic-E density layer itself. The observations are discussed in the context of current theories regarding sporadic-E layer generation and quasi-periodic echoes.

  7. Tsunamis warning from space :Ionosphere seismology

    SciTech Connect

    Larmat, Carene [Los Alamos National Laboratory

    2012-09-04

    Ionosphere is the layer of the atmosphere from about 85 to 600km containing electrons and electrically charged atoms that are produced by solar radiation. Perturbations - layering affected by day and night, X-rays and high-energy protons from the solar flares, geomagnetic storms, lightning, drivers-from-below. Strategic for radio-wave transmission. This project discusses the inversion of ionosphere signals, tsunami wave amplitude and coupling parameters, which improves tsunami warning systems.

  8. Online, automatic, ionospheric maps: IRI-PLAS-MAP

    NASA Astrophysics Data System (ADS)

    Arikan, F.; Sezen, U.; Gulyaeva, T. L.; Cilibas, O.

    2015-04-01

    Global and regional behavior of the ionosphere is an important component of space weather. The peak height and critical frequency of ionospheric layer for the maximum ionization, namely, hmF2 and foF2, and the total number of electrons on a ray path, Total Electron Content (TEC), are the most investigated and monitored values of ionosphere in capturing and observing ionospheric variability. Typically ionospheric models such as International Reference Ionosphere (IRI) can provide electron density profile, critical parameters of ionospheric layers and Ionospheric electron content for a given location, date and time. Yet, IRI model is limited by only foF2 STORM option in reflecting the dynamics of ionospheric/plasmaspheric/geomagnetic storms. Global Ionospheric Maps (GIM) are provided by IGS analysis centers for global TEC distribution estimated from ground-based GPS stations that can capture the actual dynamics of ionosphere and plasmasphere, but this service is not available for other ionospheric observables. In this study, a unique and original space weather service is introduced as IRI-PLAS-MAP from http://www.ionolab.org.

  9. Solar Wind/Magnetosphere/Ionosphere Coupling and the Temporal and Spatial Evolution of Boundary Layers using Cluster, Polar and other ISTP Satellites

    NASA Technical Reports Server (NTRS)

    Maynard, Nelson C.

    2004-01-01

    Our analysis concerns macro and meso-scale aspects of coupling between the IMF and the magnetosphere-ionosphere system, as opposed to the microphysics of determining how electron gyrotropy is broken and merging actually occurs. We correlate observed behaviors at Cluster and at Polar with temporal variations in other regions, such as in the ionosphere as measured by SuperDARN. Addressing problems with simultaneous observations from diverse locations properly constrains our interpretations.

  10. Role of ionospheric conductance in magnetosphere-ionosphere coupling

    NASA Astrophysics Data System (ADS)

    Bhattacharya, Tapas

    Magnetosphere-ionosphere (MI) coupling has been studied for a long time. However, not much work has been done on a systematic understanding of the relation between ionospheric Pedersen conductance, its effect on the evolution and modification of field-aligned currents (FACs), and the influence of conductance and FACs on the formation of parallel electric fields which cause particle precipitation. Though the roles of ionospheric conductance gradients for FACs and parallel electric field evolution are directly related, they are poorly understood. This dissertation advances the understanding of these areas and all results of this study are based on numerical simulations that employ a three-dimensional - two-fluid (ions and neutrals) simulation code. The first part of this dissertation presents a systematic study of the magnetospheric and ionospheric influences on the evolution and modification of FACs with focus on the role of ionospheric Pedersen conductance and its gradients. FACs are typically generated in the magnetosphere and are carried into the ionosphere by Alfven waves. During their reflection from the ionosphere these FACs are modified depending on the magnitude and distribution of ionospheric conductance. For conductance gradients along the polarization of the wave, strong Pedersen currents can be generated which in turn enhance the FAC as well. The second part of this dissertation addresses the properties and evolution of parallel electric fields in an attempt to better understand the formation of discrete auroral arcs in response to the evolution of FACs for predetermined ionospheric conductance patterns. Frequently, auroral acceleration is believed to occur through U or V shaped potentials. Therefore, this part examines the properties of localized parallel electric fields in a uniform magnetic field. It is demonstrated that localized parallel electric fields generate magnetic flux in the absence of source of free energy. It is also shown that parallel electric fields generated in a FAC in the presence of a (anomalous) resistivity represent a load and can provide physical explanation for the auroral acceleration geometry. The results demonstrate that such electric fields can be significantly enhanced by Alfven wave reflection where both magnitude and gradients of the ionospheric conductance are important. The strongly enhanced parallel electric field is associated with magnetic reconnection and modifies the FAC system such that thin current layers (with curls and folds) are observed to be embedded in the large scale current system.

  11. Optical and ionospheric phenomena at EISCAT under continuous X-mode HF pumping

    NASA Astrophysics Data System (ADS)

    Blagoveshchenskaya, N. F.; Borisova, T. D.; Kosch, M.; Sergienko, T.; Brändström, U.; Yeoman, T. K.; Häggström, I.

    2014-12-01

    We present experimental results from multiinstrument observations in the high-latitude ionospheric F2 layer at the EISCAT (European Incoherent Scatter Scientific Association) heating facility. The results come from a set of experiments, when an X-polarized HF pump wave at high heater frequencies (fH > 6.0 MHz) was injected into the F region of the ionosphere toward the magnetic zenith. Experiments were carried out under quiet magnetic conditions with an effective radiated power of 458-548 MW. HF pumping was produced at different heater frequencies, away from electron gyroharmonic frequencies, and different durations of heater pulses. We show the first experimental evidence of the excitation of artificial optical emissions at red (630 nm) and green (557.7 nm) lines in the high-latitude ionospheric F2 layer induced by an X-polarized HF pump wave. Intensities at red and green lines varied in the range 110-950 R and 50-350 R, respectively, with a ratio of green to red line of 0.35-0.5. The results of optical observations are compared with behaviors of the HF-enhanced ion and plasma lines from EISCAT UHF incoherent scatter radar data and small-scale field-aligned artificial irregularities from Cooperative UK Twin Located Auroral Sounding System observations. It was found that the X-mode radio-induced optical emissions coexisted with HF-enhanced ion and plasma lines and strong artificial field-aligned irregularities throughout the whole heater pulse. It is indicative that parametric decay or oscillating two-stream instabilities were not quenched by fully established small-scale field-aligned artificial irregularities excited by an X-mode HF pump wave.

  12. REVIEWS OF TOPICAL PROBLEMS: Nonlinear effects in the ionosphere

    NASA Astrophysics Data System (ADS)

    Gurevich, A. V.

    2007-11-01

    The review is based in a report presented by the author at the RAS Physical Sciences Division's session in honor of Vitaly L Ginzburg's 90th birthday. It examines the current status of theoretical and experimental research on nonlinear phenomena arising when a powerful radio wave propagates in the ionosphere. The focus is on the modification of the ionosphere under the resonance excitation of natural plasma oscillations by radio waves. The upper-hybrid resonance gives rise to strong upper- and lower-hybrid plasma waves; excites strongly elongated ionospheric irregularities, and induces artificial ionospheric radio emission. Nonlinear processes are found to undergo complete transformation near double resonances, when the upper-hybrid frequency is close to a multiple of the electron gyromagnetic frequency. In the neighborhood of the Langmuir resonance, intense plasma waves and ion-sound waves are excited, electrons are effectively accelerated, and an artificial glow of the ionosphere appears.

  13. Physics of planetary atmospheres and ionospheres

    NASA Technical Reports Server (NTRS)

    Bauer, S. J.

    1981-01-01

    The traditional atmospheric regions, the distinction between homosphere and heterosphere, and changing atmospheric composition are discussed. The validity of the barometric law based on a Maxwell-Boltzmann distribution, for the major part of a planetary atmosphere and its breakdown in the exosphere due to escape of atmospheric particles is considered. The formation and maintenance of photochemical and diffusion-controlled ionospheric layers are treated. Their applicability to planetary ionospheres is dealt with. The spatial extent of magnetic and nonmagnetic planet ionospheres is investigated. Thermal and nonthermal processes responsible for the mass loss of planetary atmospheres are surveyed.

  14. HAARP-Induced Ionospheric Ducts

    SciTech Connect

    Milikh, Gennady; Vartanyan, Aram [University of Maryland, College Park, MD, 20742 (United States)

    2011-01-04

    It is well known that strong electron heating by a powerful HF-facility can lead to the formation of electron and ion density perturbations that stretch along the magnetic field line. Those density perturbations can serve as ducts for ELF waves, both of natural and artificial origin. This paper presents observations of the plasma density perturbations caused by the HF-heating of the ionosphere by the HAARP facility. The low orbit satellite DEMETER was used as a diagnostic tool to measure the electron and ion temperature and density along the satellite orbit overflying close to the magnetic zenith of the HF-heater. Those observations will be then checked against the theoretical model of duct formation due to HF-heating of the ionosphere. The model is based on the modified SAMI2 code, and is validated by comparison with well documented experiments.

  15. Characterizing redox conditions and monitoring attenuation of selected pharmaceuticals during artificial recharge through a reactive layer.

    PubMed

    Valhondo, Cristina; Carrera, Jesús; Ayora, Carlos; Tubau, Isabel; Martinez-Landa, Lurdes; Nödler, Karsten; Licha, Tobias

    2015-04-15

    A permeable reactive layer was installed at the floor of an infiltration basin. The reactive layer comprised 1) vegetable compost to provide a sorption surface for neutral organic compounds and to release easily degradable organic matter, thus generating a sequence of redox states, and 2) minor amounts of clay and iron oxide to increase sorption of cationic and anionic species, respectively. Field application of this design was successful in generating denitrification, and manganese-, and iron-reducing conditions beneath the basin. This, together with the increase in types of sorption sites, may explain the improved removal of three of the four selected pharmaceuticals compared with their behavior prior to installation of the layer. After installation of the reactive layer, atenolol concentrations were below the detection limits in the vadose zone. Moreover, concentrations of gemfibrozil and cetirizine were reduced to 20% and 40% of their initial concentrations, respectively, after 200h of residence time. In contrast, prior to installation of the reactive layer, the concentrations of these three pharmaceuticals in both the vadose zone and the aquifer were more than 60% of the initial concentration. Carbamazepine exhibited recalcitrant behavior both prior to and after the reactive barrier installation. PMID:25625636

  16. Production of Double-Layered Metal Nanocups for Artificial Nanospace of Biomolecular Reaction

    Microsoft Academic Search

    Hyonchol Kim; Masahito Hayashi; Hideyuki Terazono; Hiroyuki Takei; Kenji Yasuda

    2011-01-01

    Nanocups (NCs), sub-micrometer semispherical bowls consisting of two different nanometer-thick metals on inner and outer layers, have been fabricated to mimic a localized nano-scale biochemical reaction environment for reactive biomolecules. Homogeneous polystyrene beads were used as a cast of the NCs, placed on a Si substrate, dried, and processed by oxygen plasma etching until the desired diameters and gaps among

  17. Experimental and theoretical study of artificial plasma layers produced by two intersecting beams in a chamber

    NASA Technical Reports Server (NTRS)

    Kuo, S. P.; Zhang, Y. S.

    1989-01-01

    The work done on the Bragg scattering of electromagnetic waves by microwave produced plasma layers is reported. Also summarized is the work accomplished on the propagation of high power microwave pulses in an air breakdown environment. Ongoing work on the theoretical model and numerical results of pulse propagation in air is also presented as are the results of studying the decay of plasma density and temperature.

  18. Artificial Alteration of Biotite into a 14 ? Layer Silicate with Hydroxy-Aluminium Interlayers

    Microsoft Academic Search

    K. Nagasawa; G. BROWN; A. C. D. NEWMAN

    1974-01-01

    Biotite was altered by boiling in 0.2 M AIC13 solution, and the products were examined by X-ray powder and single-crystal diffraction, chemical analysis and thermogravimetry. The altered material is a 14 A clay mineral with hydroxy-Al interlayers. It has a stacking sequence characteristic ?9 of vermiculite and its silicate layers are similar in chemical composition to trioctahedral vermiculite. The results

  19. Ionospheric characteristics: a review

    SciTech Connect

    Rich, F.J.

    1983-01-01

    The ionosphere is important to spacecraft charging because the thermal ions and electrons provide a significant current to a spacecraft surface. Low, mid, and high altitude ionospheric characteristics are discussed.

  20. Ultra-thin film superconductors of artificially synthesized Au/Ge layers

    NASA Astrophysics Data System (ADS)

    Seguchi, Yasuhiro; Tsuboi, Takefumi; Suzuki, Takao

    1990-08-01

    We have investigated the resistive transition of Au/Ge layered films. The ultra-thin bilayer of Au(10?)/Ge(13?) exhibits superconductivi ty below a temperature of 0.6 K. It has been found thatthe critical temperature T C is enhanced above T C0 by the application of low magnetic field parallel to the film surface. We have observed dimensional crossover in the temperature dependence of parallel critical field for the multilayers with Ge film ~25 ? thick. Those with Ge film thicker than ~30 ? show two-dimensional behavior and also the T C enhancement as observed in the bilayer.

  1. LIFDAR: A Diagnostic Tool for the Ionosphere

    NASA Astrophysics Data System (ADS)

    Kia, O. E.; Rodgers, C. T.; Batholomew, J. L.

    2011-12-01

    ITT Corporation proposes a novel system to measure and monitor the ion species within the Earth's ionosphere called Laser Induced Fluorescence Detection and Ranging (LIFDAR). Unlike current ionosphere measurements that detect electrons and magnetic field, LIFDAR remotely measures the major contributing ion species to the electron plasma. The LIFDAR dataset has the added capability to demonstrate stratification and classification of the layers of the ionosphere to ultimately give a true tomographic view. We propose a proof of concept study using existing atmospheric LIDAR sensors combined with a mountaintop observatory for a single ion species that is prevalent in all layers of the atmosphere. We envision the LIFDAR concept will enable verification, validation, and exploration of the physics of the magneto-hydrodynamic models used in ionosphere forecasting community. The LIFDAR dataset will provide the necessary ion and electron density data for the system wide data gap. To begin a proof of concept, we present the science justification of the LIFDAR system based on the model photon budget. This analysis is based on the fluorescence of ionized oxygen within the ionosphere versus altitude. We use existing model abundance data of the ionosphere during normal and perturbed states. We propagate the photon uncertainties from the laser source through the atmosphere to the plasma and back to the collecting optics and detector. We calculate the expected photon budget to determine signal to noise estimates based on the targeted altitude and detection efficiency. Finally, we use these results to derive a LIFDAR observation strategy compatible with operational parameters.

  2. Physical mechanisms associated with long-range propagation of the signals from ionospheric heating experiments

    NASA Astrophysics Data System (ADS)

    Zabotin, Nikolay A.; Zavorotny, Valery U.; Rietveld, Michael T.

    2014-10-01

    Long-range propagation of heater-produced signals has been studied in experiments with the European Incoherent Scatter Scientific Association ionospheric heating facility and with several globally distributed receiving sites by Zalizovski et al. [2009]. Two distinctive components were present in the signals' spectra, and these can be attributed to two modes of propagation of the signals. One of the components is narrowband and stable; it obviously can be associated with the multihop ionospheric propagation of HF waves radiated by the side lobes of the heater's antenna array. Prominent features of the second component are its wider spectral band (up to few tens of hertz) and strong variations in the average Doppler frequency shift and in the power, which in many cases were synchronous at the different receiving sites. These effects are most likely produced by the ionospheric scattering and dynamics within the heater's main beam. The tricky part is to explain how a portion of the HF energy contained in the relatively narrow main beam of the heater is redirected toward the remote receiving locations. We suggest a robust mechanism explaining the long-range propagation of the wideband component of the heater-generated signal based on the theory of scattering from rough surfaces. This mechanism preserves all the observed properties of the remote signals. We show that mountain relief in the vicinity of the heater plays the role of the rough surface causing almost isotropic scattering of the heater's main beam after it is reflected by the ionosphere. Multiple scattering by natural and artificial field-aligned irregularities in the ionospheric layer may be related to the ground-scattered remote signals through its role in spatial redistribution of the heater's radiation.

  3. Interaction of an Artificially Thickened Boundary Layer with a Vertically Mounted Pitching Airfoil

    NASA Astrophysics Data System (ADS)

    Hohman, Tristen; Smits, Alexander; Martinelli, Luigi

    2011-11-01

    Wind energy represents a large portion of the growing market in alternative energy technologies and the current landscape has been dominated by the more prevalent horizontal axis wind turbine. However, there are several advantages to the vertical axis wind turbine (VAWT) or Darrieus type design and yet there is much to be understood about how the atmospheric boundary layer (ABL) affects their performance. In this study the ABL was simulated in a wind tunnel through the use of elliptical shaped vortex generators, a castellated wall, and floor roughness elements as described in the method of Counihan (1967) and then verified its validity by hot wire measurement of the mean velocity profile as well as the turbulence intensity. The motion of an blade element around a vertical axis is approximated through the use of a pitching airfoil. The wake of the airfoil is investigated through hot wire anemometry in both uniform flow and in the simulated boundary layer both at Re = 1.37x10^5 based on the chord of the airfoil.

  4. Ionospheric effect of partial solar eclipse of 31 July 1981

    NASA Astrophysics Data System (ADS)

    Datsko, Y. P.; Kasymova, A. G.; Maksimenko, O. I.

    1984-05-01

    Vertical sounding of the ionosphere before, during, and some time after the eclipse was at 1- and 5-minute intervals. Scintillations of radio signals from artificial satellites were registered at frequencies of 150 MHz (3-channel spaced reception), 40 MHz and 180 MHz (single-channel reception). Slant sounding was along the path Moscow-Kiev in the frequency range from 3.5 to 27.5 MHz. A very strong magnetic storm was registered at the Kiev Magnetic Observatory before the eclipse; this storm which lasted 150 hours was preceded by considerable helioactivity. The solar flares and magnetic storm caused an ionospheric storm with very great delta f(0)F2 deviations. During the eclipse, the usual effect was not registered due to strong helio-geomagnetic activity. The E-region anomalies were observed: a local ionization cloud was formed with a very narrow range of electron concentration, decreasing from the low-frequency end. The F1 layer was formed an hour earlier. The effective recombination coefficient obtained during the period of the eclipse agrees with data from rocket experiments.

  5. Electron cyclotron harmonic resonances in high-frequency heating of the ionosphere

    SciTech Connect

    Kuo, Spencer P. [Polytechnic Institute of New York University, 6 MetroTech Center, Brooklyn, New York 11201 (United States)] [Polytechnic Institute of New York University, 6 MetroTech Center, Brooklyn, New York 11201 (United States)

    2013-09-15

    Electron acceleration by upper hybrid waves under cyclotron harmonic resonance interaction is studied. Theory is formulated; the analytical solutions in the second and fourth harmonic cyclotron resonance cases are obtained, and in the third harmonic case, a first order differential equation governing the evolution of the electron energy is derived. The theory is applied for explaining the generation of artificial ionization layers observed in high-frequency (HF) ionospheric heating experiments. The upper hybrid waves are assumed to be excited parametrically by the O-mode HF heating wave. As the decay mode is the lower hybrid wave, the excited upper hybrid waves have wavelengths ranging from 0.25 to 0.5 m, which are short enough to effectively incorporate the finite Larmour radius effect for the harmonic cyclotron resonance interactions as well as have a frequency bandwidth of about 20 kHz, which provides an altitude region of about 10 km for continuous harmonic cyclotron resonance interaction between electrons and descending waves in the slightly inhomogeneous geomagnetic field. The numerical results on electron acceleration show that electron fluxes with energies larger than 14 eV are generated in the three harmonic cases. These energetic electrons cause impact ionizations, which are descending to form artificial ionization layers at the bottom of the ionospheric F region.

  6. Artificial vision by multi-layered neural networks: neocognitron and its advances.

    PubMed

    Fukushima, Kunihiko

    2013-01-01

    The neocognitron is a neural network model proposed by Fukushima (1980). Its architecture was suggested by neurophysiological findings on the visual systems of mammals. It is a hierarchical multi-layered network. It acquires the ability to robustly recognize visual patterns through learning. Although the neocognitron has a long history, modifications of the network to improve its performance are still going on. For example, a recent neocognitron uses a new learning rule, named add-if-silent, which makes the learning process much simpler and more stable. Nevertheless, a high recognition rate can be kept with a smaller scale of the network. Referring to the history of the neocognitron, this paper discusses recent advances in the neocognitron. We also show that various new functions can be realized by, for example, introducing top-down connections to the neocognitron: mechanism of selective attention, recognition and completion of partly occluded patterns, restoring occluded contours, and so on. PMID:23098752

  7. Ionosphere. [of Jupiter

    NASA Technical Reports Server (NTRS)

    Strobel, D. F.; Atreya, S. K.

    1983-01-01

    The original interest in an ionosphere on Jupiter was generated by the discovery of strong radio-frequency emissions at approximately 20 MHz which were thought to be plasma frequencies associated with Jupiter's ionosphere. The ionosphere of Jupiter provides a means to couple the magnetosphere to the atmosphere by virtue of its high conductivity and collisional interaction with the neutral atmosphere. The Pioneer and Voyager have provided direct measurements of profiles of electron concentration at selected locations on Jupiter. Attention is given to basic principles regarding the characteristics of the Jovian ionosphere, the ionization sources, aspects of ion recombination, ion chemistry, observations of Jupiter's ionosphere, the structure of Jupiter's upper atmosphere, and questions of ionospheric modeling. On the basis of the Pioneer and Voyager observations it appears that Jupiter's ionosphere and thermosphere undergo significant solar cycle changes.

  8. Sputnik 1 and the First Satellite Ionospheric Experiment

    NASA Astrophysics Data System (ADS)

    Sinelnikov, Vyacheslav; Kuznetsov, Vladimir; Alpert, Svetlana

    The world's first scientific space experiment was carried out in 1957 during the flight of the first Artificial Earth Satellite (AES) - Sputnik 1. It was an ionospheric experiment performed at IZMIRAN under the direction of Prof. Ya.L.Alpert (1911-2010). The sunrise and sunset variations in the AES radio signal were recorded in order to determine the distribution of electron density in the topside ionosphere (above the maximum). The experiment demonstrated the capabilities of the satellite radio beacon method, which is now very important and widely used for studying the ionosphere. Our report submitted to the COSPAR General Assembly in Russia describes the history and results of that experiment, as well as some other contributions by Ya.L.Alpert to ionospheric research. Yakov L.Alpert was one of the most famous and influential radiophysicists of his time, the author of many fundamental studies and of a number of classic books on the theory of propagation of electromagnetic waves, interaction of artificial bodies with ionospheric plasmas, ionospheric radio scattering, and the use of satellite radio beacon methods for studying the ionosphere.

  9. A short-term ionospheric forecasting empirical regional model (IFERM) to predict the critical frequency of the F2 layer during moderate, disturbed, and very disturbed geomagnetic conditions over the European area

    NASA Astrophysics Data System (ADS)

    Pietrella, M.

    2012-02-01

    A short-term ionospheric forecasting empirical regional model (IFERM) has been developed to predict the state of the critical frequency of the F2 layer (foF2) under different geomagnetic conditions. IFERM is based on 13 short term ionospheric forecasting empirical local models (IFELM) developed to predict foF2 at 13 ionospheric observatories scattered around the European area. The forecasting procedures were developed by taking into account, hourly measurements of foF2, hourly quiet-time reference values of foF2 (foF2QT), and the hourly time-weighted accumulation series derived from the geomagnetic planetary index ap, (ap(?)), for each observatory. Under the assumption that the ionospheric disturbance index ln(foF2/foF2QT) is correlated to the integrated geomagnetic disturbance index ap(?), a set of statistically significant regression coefficients were established for each observatory, over 12 months, over 24 h, and under 3 different ranges of geomagnetic activity. This data was then used as input to compute short-term ionospheric forecasting of foF2 at the 13 local stations under consideration. The empirical storm-time ionospheric correction model (STORM) was used to predict foF2 in two different ways: scaling both the hourly median prediction provided by IRI (STORM_foF2MED,IRI model), and the foF2QT values (STORM_foF2QT model) from each local station. The comparison between the performance of STORM_foF2MED,IRI, STORM_foF2QT, IFELM, and the foF2QT values, was made on the basis of root mean square deviation (r.m.s.) for a large number of periods characterized by moderate, disturbed, and very disturbed geomagnetic activity. The results showed that the 13 IFELM perform much better than STORM_foF2,sub>MED,IRI and STORM_foF2QT especially in the eastern part of the European area during the summer months (May, June, July, and August) and equinoctial months (March, April, September, and October) under disturbed and very disturbed geomagnetic conditions, respectively. The performance of IFELM is also very good in the western and central part of the Europe during the summer months under disturbed geomagnetic conditions. STORM_foF2MED,IRI performs particularly well in central Europe during the equinoctial months under moderate geomagnetic conditions and during the summer months under very disturbed geomagnetic conditions. The forecasting maps generated by IFERM on the basis of the results provided by the 13 IFELM, show very large areas located at middle-high and high latitudes where the foF2 predictions quite faithfully match the foF2 measurements, and consequently IFERM can be used for generating short-term forecasting maps of foF2 (up to 3 h ahead) over the European area.

  10. Atmospheric Lithosphere-Ionosphere Charge Exchange (ALICE) for coupling between earthquake regions, clouds and the ionosphere

    NASA Astrophysics Data System (ADS)

    Harrison, Giles; Aplin, Karen; Rycroft, Michael

    2014-05-01

    Atmospheric Lithosphere-Ionosphere Charge Exchange (ALICE) has been proposed as a mechanism to link seismic activity and ionospheric changes detected overhead, which has been observed in data obtained by the DEMETER spacecraft. The ALICE mechanism can explain changes in the natural extremely low frequency (ELF) radio noise observed by DEMETER nocturnally before major earthquakes. ALICE operates through the vertical fair weather current density of global atmospheric electricity, through the modification of surface layer ionisation rates and the associated current flow to the ionosphere. These ideas are extended here to include possible effects on layer clouds through which the current density passes. Specifically, we estimate possible layer cloud changes for changes in surface layer ionisation known in some earthquakes.

  11. Solving the non-linear model of the electron density of the ionosphere

    NASA Astrophysics Data System (ADS)

    Liang, W.; Schmidt, M.; Dettmering, D.; Hugentobler, U.; Limberger, M.

    2012-04-01

    Precise and high precision ionosphere models are important for modern satellite navigation and positioning systems. In most cases, the ionosphere models are based on pure mathematical approaches, e.g. by applying spherical harmonic expansions for the vertical total electron content. In order to achieve a deeper understanding of the complex phenomena within the ionosphere, physical conditions have to be considered and introduced. The physics-motivated Chapman function is very efficient for describing the vertical structure of the electron density. Introducing the Chapman function and a plasmasphere layer, the vertical distribution of the electron density can be described by five parameters altogether, namely (1) the F2 peak electron density (NmF2), (2) the peak height (hmF2), (3) the topside scale height (HF2), (4) the plasmasphere basic density (NP) and (5) the scale height (HP). In our approach, each of these parameters is decomposed into an initial part, derived from a given ionosphere model or other initial assumptions, and an unknown correction term. Exploiting the localizing property of B-spline base functions, the latter is modeled as a series expansion in terms of tensor products of three one-dimensional endpoint-interpolating B-splines depending on latitude, longitude and time, respectively. Considering the necessary linearization of the exponential terms of the Chapman and the plasmaspheric layer, the unknown model coefficients are solved by an appropriate parameter estimation procedure using an iterative algorithm. In this contribution we focus on the numerical solution of the linearized model. This includes a closer view on the iterative method, the regularization scheme and the convergence analysis. Due to complexity of the problem, the topside scale height HF2 is expanded in a first step to test the adjustment approach. Data gaps are artificially created to investigate inhomogeneous data availability. In this case proper prior information and regularization are needed to ensure the convergence of the system.

  12. Radio Waves and the Ionosphere

    NSDL National Science Digital Library

    Susan Higley

    In this activity students will discover that when amplitude modulated (AM) radio waves travel from transmitter to a receiver far away, they have to bounce off the underside of the ionosphere and that the waves lose some of their energy each time they are reflected. Students will learn that although this is normally a small amount, it can be several times larger during a solar storm. They also learn that radio signals passing through this layer and bouncing off the ionosphere higher up, have some or all of their intensity absorbed. During this activity students will calculate the percent of change, determine the final percentage of radio wave strength at the receiving station, and will learn that solar flares can cause disruptions in radio waves.

  13. Ionospheric phenomena before strong earthquakes

    Microsoft Academic Search

    A. S. Silina; E. V. Liperovskaya; V. A. Liperovsky; C.-V. Meister

    2001-01-01

    A statistical analysis of several ionospheric parameters before earthquakes with magnitude M > 5.5 located less than 500 km from an ionospheric vertical sounding station is performed. Ionospheric effects preceding \\

  14. High-latitude E and F region ionospheric predictions

    NASA Technical Reports Server (NTRS)

    Hunsucker, R. D.; Allen, R.; Argo, P. E.; Babcock, R.; Bakshi, P.; Lund, D.; Matsushita, S.; Smith, G.; Shirochkov, A. V.; Wortham, G.

    1979-01-01

    The physical processes and morphology of the high latitude E and F layers are discussed. The existence and adequacy of models, and features to be included are examined, as well as reliability of ionospheric predictions.

  15. Ionospheric Prediction and Forecasting Services in Mediterranean Area

    NASA Astrophysics Data System (ADS)

    Pezzopane, Michael; Zolesi, Bruno; Haralambous, Haris; Oikonomou, Christina; Cander, Ljiljana R.

    2014-05-01

    This paper will present the basic approach on ionospheric prediction and forecasting used to provide services in Mediterranean area. Both services based on two ionospheric stations (Geomagnetic Indices Forecasting and Ionospheric Nowcasting Tools - GIFINT project) and one ionospheric station (Cyprus Ionospheric Forecasting Service - CIFS project) rely on background ionosphere described by the Simplified Ionospheric Regional Model (SIRM). In case of GIFINT the update of SIRM model is performed by the critical frequency of the F2 layer (foF2) and the propagation factor (M(3000)F2) values coming from the Rome and Gibilmanna ionospheric stations, while in case of CIFS the update of SIRM model is performed by the foF2 and M(3000)F2 values coming from the Nicosia ionospheric station. Some examples of nowcasting and long term maps for foF2 and M(3000)F2 will be shown. Discussion will be focused on the role of real time updating of the SIRM model.

  16. Field aligned plasma coupling between the ionosphere and plasmasphere

    NASA Astrophysics Data System (ADS)

    Maruyama, N.; Richards, P. G.; Fang, T.; Mayer, L.; Fuller-Rowell, T. J.; Richmond, A. D.; Maute, A. I.

    2012-12-01

    The overarching objective of this study is to improve consistent understanding of the altitude coupling and interaction between ionosphere and plasmasphere during storms. From the plasmaspheric viewpoint, during the main phase of a storm, morphology of the plasmasphere, such as characterized by plasmaspheric boundary layers, plumes and erosions, is mainly determined by an increase in the global scale magnetospheric convection, whereas during the recovery phase of the storm, mass loading from the ionosphere tends to dominate the plasmaspheric density variation. On the other hand, from the ionospheric viewpoint, plasma redistribution is generated by the prompt penetration electric field, resulting in the so-called positive storms observed in GPS-TEC. At the same time, the disturbances in the neutral winds and compositions change the ionosphere as well. Although individual viewpoints have been renewed thanks to the recent progress in the observation capabilities, however, we do not have a good overall picture about how the plasma should be flowing between the ionosphere and plasmasphere during storms to explain multiple near simultaneous observations in a consistent manner. The Ionosphere-Plasmasphere-Electrodynamics (IPE) model is used to address the altitude coupling issues between the ionosphere and plasmasphere. The model consists of a physics based model of an ionosphere and plasmasphere using the IGRF geomagnetic field configuration. In this presentation, we will show the response of the plasma field aligned distribution between the ionosphere and plasmasphere during storms, as well as the corresponding TEC variations.

  17. Effects of the active auroral ionosphere on magnetosphere - ionosphere coupling

    Microsoft Academic Search

    Dimitri Pokhotelov

    2003-01-01

    The thesis is devoted to the effects of electromagnetic coupling between the Earth's magnetosphere and the active auroral ionosphere. The research has been focused, in particular, on the concept of ionospheric feedback instability. The feedback instability arises when localized perturbations in ionospheric conductivity become polarized in the presence of background electric field. Under favorable conditions of low ionospheric conductivity and

  18. International reference ionosphere 1990

    NASA Technical Reports Server (NTRS)

    Bilitza, Dieter; Rawer, K.; Bossy, L.; Kutiev, I.; Oyama, K.-I.; Leitinger, R.; Kazimirovsky, E.

    1990-01-01

    The International Reference Ionosphere 1990 (IRI-90) is described. IRI described monthly averages of the electron density, electron temperature, ion temperature, and ion composition in the altitude range from 50 to 1000 km for magnetically quiet conditions in the non-auroral ionosphere. The most important improvements and new developments are summarized.

  19. Wenchuan Earthquake Ionospheric Precursors: Modeling and Experiment

    NASA Astrophysics Data System (ADS)

    Klimenko, Maxim; Klimenko, Vladimir; Zhao, Biqiang; Pulinets, Sergej; Zakharenkova, Irina; Bryukhanov, Valerij

    Early it was shown, that for strong middle-latitude earthquakes the effects in Total Electron Content (TEC) and in critical frequency of F2-layer (foF2) look like local changes in electron concentration which maxima are located in immediate proximity from epicenter area. Pre-cursory effects of strong near-equatorial earthquakes might be in the form of deepening and widening of electron concentration minimum over the magnetic equator and displacement of equatorial ionization anomaly crests. The problems of physical explanation of possible forma-tion mechanisms of the seismo-ionospheric effects are under discussion now. In Namgaladze et al., 2009 it has been come out with the assumption, that the most probable formation mech-anism of TEC disturbed areas, observable prior strong earthquakes, is the vertical transport of the F2-region ionospheric plasma under the zonal electric field action. The geomagnetic conjugacy of the earthquake ionospheric precursors and effects in equatorial anomaly which development is controlled by zonal electric field are strong arguments in favor of this hypoth-esis. Besides, the analysis of model calculation results with use of the Global Self-consistent Model of the Thermosphere, Ionosphere, Protonosphere (GSM TIP) in Namgaladze et al., 2009 testifies in favor of this hypothesis. There is a question how such electric fields can arise in the ionosphere prior to earthquakes? Now it is not answer to this question. Therefore, for understanding of formation mechanisms of earthquake ionospheric precursors it is necessary to understand the physics of lithosphere-atmosphere-ionosphere coupling prior to earthquake. Many researchers tried to solve this problem. However, until now there is not common opinion concerning to the lithosphere-atmosphere-ionosphere coupling prior to earthquake. Some ba-sic hypotheses for the explanation of this mechanism have been offered: the Internal Gravity Waves (IGWs) of seismogenic origin with the period 1-3 hours, the IGWs with the period from several minutes up to tens minutes, the seismogenic electric field with amplitude from units up to tens mV/m, the abnormal electromagnetic fields and emissions. However, the appearance of local large-scale seismo-ionospheric anomalies in TEC and foF2 it is possible to explain only by two of the mentioned mechanisms: an atmospheric electric field and/or small-scale IGWs. In this study, we present the numerical calculation results for reproduction of observed changes in the ionosphere prior to strong Wenchuan earthquake. This earthquake has been fixed on 12 May 2008. The geomagnetic activity indices for the period on 1-13 May were low. The calcu-lations of Wenchuan earthquake ionospheric precursors were carried out with use of the GSM TIP model. In calculations, the small-scale IGWs and/or the penetration of vertical electric field are considered as the formation mechanisms of earthquake ionospheric precursors. It was carried out the comparison of calculation results with experimental data of TEC and foF2 at various stations, located in China and nearby areas. The obtained results confirm the proposed mechanisms of seismo-ionospheric effect formation by small-scale IGWs and the penetration of the seismogenic vertical electric field from the atmosphere into the ionosphere. References Namgaladze A.A., Klimenko M.V., Klimenko V.V. and Zakharenkova I.E. Physical Mechanism and Mathematical Simulation of Ionosphere Earthquake Precursors Observed in Total Electron Content. Geomagnetism and Aeronomy, 2009, Vol. 49, 252-262.

  20. Ionospheric Effects of Underground Nuclear Explosions

    NASA Astrophysics Data System (ADS)

    Park, J.; von Frese, R. R.; G-Brzezinska, D. A.; Morton, Y.

    2010-12-01

    Telemetry from the Russian INTERCOSMOS 24 satellite recorded ELF and VLF electromagnetic disturbances in the outer ionosphere from an underground nuclear explosion that was detonated at Novaya Zemlya Island on 24 October 1994. The IC24 satellite observations were obtained at about 900 km altitude within a few degrees of ground zero. The disturbances were interpreted for magnetohydrodynamic excitation of the ionosphere’s E layer by the acoustic wave. Electrons are accelerated along the magnetic force lines to amplify longitudinal currents and magnetic disturbances that may be measured by magnetometers at ground-based observatories and on-board satellites. The underground nuclear test near P’unggye, North Korea on 25 May 2009 provides a further significant opportunity for studying the utility of ionospheric disturbances for characterizing ground zero. Of the seismic, infrasound, hydroacoustic, and radionuclide detection elements of the International Monitoring System (IMS) established by the Comprehensive Nuclear Test Ban Treaty Organization (CTBTO), only the first two elements detected this event. However, the event also appears to have been recorded as a direct traveling ionospheric disturbance (TID) in the slant total electron content (TEC) observations derived from a network of the Global Navigation Satellite System (GNSS) measurements. The TID was observed to distances of at least 600 km from the explosion site propagating with a speed of about 281m/s. Thus, the global distributions and temporal variations of the TEC, may provide important information to help detect and characterize clandestine underground nuclear explosions.

  1. Anomalies in the Ionosphere around the Southern faults of Haiti near the 2010 Earthquake

    NASA Astrophysics Data System (ADS)

    Cornely, P.; Daniell, R. E.

    2013-12-01

    In the last few decades, research on earthquake prediction has resulted in the recognition that there may exist many earthquake precursors in the lithosphere, atmosphere and ionosphere. The ionosphere is naturally perturbed by solar and geomagnetic disturbances and it is difficult to extract the variations connected with earthquakes particularly for the equatorial and high latitude ionosphere. Several researchers have contending theories on the mechanisms associated with pre-earthquake signals. The basic premise is that a thin layer of particles created before earthquakes due to ions originating from the earth's crust travel to the earth's surface and begin radiating from the earth's surface due to strong electric fields Namgaladze et al., [2009]. The ions can then travel from above earth's surface to the ionosphere where they can create ionospheric disturbances. When solar and geomagnetic disturbances can be ruled out, the effects of pre-seismic activities in the ionosphere can be assessed using fluctuations in the ionospheric electron density in the vicinity of fault lines. The Parameterized Ionospheric Model (PIM) is a fast global ionospheric model which produces electron density profiles (EDPs) between 90 and 25000 km altitude, which corresponds to critical altitudes of the ionosphere Daniell et al., [1995]. Since PIM only simulates a statistical mean ionosphere, sudden variations in ionospheric electron density will not be represented in the models, which make PIM ideal for background electron density predictions. The background predictions can then removed from the actual electron density data which could provide means for identifying pre-seismic electron density perturbations.

  2. Artificial Photosynthesis

    Microsoft Academic Search

    Gion Calzaferri

    2010-01-01

    One-dimensional channel materials, such as zeolites and mesoporous silicas, are very attractive hosts for the preparation\\u000a and investigation of hierarchically organized structures, presenting a successive ordering from the molecular up to macroscopic\\u000a scale. The focus of this article is on artificial photonic antenna systems and on photocatalytically active layers that have\\u000a been built by incorporating organic dyes, complexes, metal cations

  3. Solar zenith angle does not affect Mars ionosphere's electron temperature

    NASA Astrophysics Data System (ADS)

    Wendel, JoAnna

    2014-08-01

    Exploration of Mars, whether by spacecraft or by humans in the far-flung future, requires a deep understanding of Mars's ionosphere—the upper layer of atmosphere where molecules are ionized by the Sun's energy. For example, scientists on Earth trying to communicate with current and future Mars rovers are and will continue to be hindered by free electrons in the ionosphere that can absorb and reflect radio waves. Scientists therefore wonder, What are the various physical properties that can influence the behavior of Mars's ionosphere?

  4. Investigations on structural and multiferroic properties of artificially engineered lead zirconate titanate-cobalt iron oxide layered nanostructures

    NASA Astrophysics Data System (ADS)

    Ortega Achury, Nora Patricia

    Mutiferroics are a novel class of next generation multifunctional materials, which display simultaneous magnetic, electric, and ferroelastic ordering, have drawn increasing interest due to their multi-functionality for a variety of device applications. Since, very rare single phase materials exist in nature this kind of properties, an intensive research activity is being pursued towards the development of new engineered materials with strong magneto-electric (ME) coupling. In the present investigation, we have fabricated polycrystalline and highly oriented PbZr0.53,Ti0.47O3--CoFe 2O4 (PZT/CFO) artificially multilayers (MLs) engineered nanostructures thin films which were grown on Pt/TiO2/SiO2/Si and La 0.5Sr0.5CoO3 (LSCO) coated (001) MgO substrates respectively, using the pulsed laser deposition technique. The effect of various PZT/CFO sandwich configurations having 3, 5, and 9 layers, while maintaining similar total PZT and CFO thickness, has been systematically investigated. The first part of this thesis is devoted to the analysis of structural and microstructure properties of the PZT/CFO MLs. X-ray diffraction (XRD) and micro Raman analysis revealed that PZT and CFO were in the perovskite and spinel phases respectively in the all layered nanostructure, without any intermediate phase. The TEM and STEM line scan of the ML thin films showed that the layered structure was maintained with little inter-diffusion near the interfaces at nano-metric scale without any impurity phase, however better interface was observed in highly oriented films. Second part of this dissertation was dedicated to study of the dielectric, impedance, modulus, and conductivity spectroscopies. These measurements were carried out over a wide range of temperatures (100 K to 600 K) and frequencies (100 Hz to 1 MHz) to investigate the grain and grain boundary effects on electrical properties of MLs. The temperature dependent dielectric and loss tangent illustrated step-like behavior and relaxation peaks near the step-up characteristic respectively. The Cole-Cole plots indicate that the most of the dielectric response came from the bulk (grains) MLs below 300 K, whereas grain boundaries and electrode-MLs effects prominent at elevated temperature. The dielectric loss relaxation peaks shifted to higher frequency side with increase in temperature, finally above 300 K, it went out experimental frequency window. Our Cole-Cole fitting of dielectric loss spectra indicated marked deviation from the ideal Debye type of relaxation which is more prominent at elevated temperature. Master modulus spectra support the observation from impedance spectra, it also indicate that the difference between C g and Cgb are higher compared to polycrystalline MLs indicating less effects of grain boundary in highly oriented MLs. We have explained these electrical properties of MLs by Maxwell-Wagner type contributions arising from the interfacial charge at the interface of the MLs structure. Three different types of frequency dependent conduction process were observed at elevated temperature (>300 K), which well fitted with the double power law, sigma(o) = sigma(0) + A 1on1 + A 2on2, it indicates conduction at: Low frequency (<1 kHz) may be due to long range ordering (frequency independent), mid frequency (<10 kHz) may be due to short range hopping, and high frequency (<1 MHz) due to the localized relaxation hopping mechanism. The last part of the thesis is devoted to the study of the multiferroic and magnetoelectric properties of the ML thin films. Both polycrystalline and highly oriented films showed well saturated ferroelectric and ferromagnetic hysteresis loops at room temperature. Temperature dependence of ferroelectric properties showed that polarization slowly decreases from 300 K to 200 K, with complete collapse of polarization at ˜ 100 K, but there was complete recovery of the polarization during heating, which was repeatable over many different experiments. At the same time, in the same temperature interval the remanent magnetization of the MLs showed slo

  5. Structure and evolution of internal gravity waves and traveling ionospheric disturbances in regions with sharp gradients of the ionospheric parameters

    NASA Astrophysics Data System (ADS)

    Belashova, Elena S.; Belashov, Vasily Y.; Vladimirov, Sergey V.

    2007-07-01

    The dynamics of the solitary nonlinear internal gravity waves (IGW), as well as traveling ionospheric disturbances (TID) of the electron density excited by IGW at the heights of the ionosphere's F region, for conditions close to those of the F layer assuming that the source of initial perturbation has the pulse character are studied. In particular, the cases when the solitary IGW and TID propagate in the regions with sharp gradients of the ionospheric parameters, such as electron density, temperature, scale heights for the ions and neutral particles, etc., are considered.

  6. Investigation of the D and E regions of the ionosphere

    NASA Technical Reports Server (NTRS)

    Kelly, R. N.; Engelman, A.; Tobey, A. F.

    1973-01-01

    Details of an experimental program that investigates the ionosphere using sounding rockets are presented. The investigation is part of a continuing program to gather data on the D and E regions of the ionosphere during periods of recurring natural phenomena that influence these regions. To achieve these ends, four vehicles were launched during the eclipse of the sun on March 7, 1970. Other vehicles totalling 10 in all were launched to investigate transient phenomena such as the sporadic E layer.

  7. Dynamics of IGW and traveling ionospheric disturbances in regions with sharp gradients of the ionospheric parameters

    NASA Astrophysics Data System (ADS)

    Belashov, Vasily; Belashova, Elena

    We study the dynamics of the solitary nonlinear internal gravity waves (IGW), as well as traveling ionospheric disturbances (TID) of the electron density excited by them at the heights of the ionosphere's F-region, for conditions close to those of the F-layer assuming that the source of initial perturbation has the pulse character. We consider the cases when the solitary IGW and TID propagate in the regions with sharp gradients of the ionospheric parameters such as electron density, temperature, scale heights for the ions and neutral particles etc. Taking into account the weak nonlinearity at heights of the ionosphere F-region, from the hydrodynamic equations for the neutral gas we obtain the equation which is the generalization of the KP equation for the velocity of the neutral component and describes the nonlinear IGW solitons and nonlinear wave packets with the structure determined by both the coefficients (they are the functions of the ionospheric parameters which are the functions of space coordinates and time) and the form of the sort of perturbation and accordingly the type of source as well. To study the excitation by the IGW solitons of the middle- and large-scale TID for the conditions close to those in the F-layer, we include also the continuity equation for electron density (with due account of magnetic inclination and the processes of ambipolar diffusion, ionization and recombination) into the full set of the equations. We solve the obtained set of the equations analytically and numerically taking into account the dependence of the coefficient functions on coordinates and time, including the most interesting cases when the sharp gradients of them take place. As particular cases we consider the frontal regions of the solar terminator and solar eclipse. The results obtained describe the dynamical structure, evolution and transformation of the IGW and TID at heights of the ionosphere F-layer including its strongly heterogeneous regions.

  8. Tsunami Ionospheric warning and Ionospheric seismology

    NASA Astrophysics Data System (ADS)

    Lognonne, Philippe; Rolland, Lucie; Rakoto, Virgile; Coisson, Pierdavide; Occhipinti, Giovanni; Larmat, Carene; Walwer, Damien; Astafyeva, Elvira; Hebert, Helene; Okal, Emile; Makela, Jonathan

    2014-05-01

    The last decade demonstrated that seismic waves and tsunamis are coupled to the ionosphere. Observations of Total Electron Content (TEC) and airglow perturbations of unique quality and amplitude were made during the Tohoku, 2011 giant Japan quake, and observations of much lower tsunamis down to a few cm in sea uplift are now routinely done, including for the Kuril 2006, Samoa 2009, Chili 2010, Haida Gwai 2012 tsunamis. This new branch of seismology is now mature enough to tackle the new challenge associated to the inversion of these data, with either the goal to provide from these data maps or profile of the earth surface vertical displacement (and therefore crucial information for tsunami warning system) or inversion, with ground and ionospheric data set, of the various parameters (atmospheric sound speed, viscosity, collision frequencies) controlling the coupling between the surface, lower atmosphere and the ionosphere. We first present the state of the art in the modeling of the tsunami-atmospheric coupling, including in terms of slight perturbation in the tsunami phase and group velocity and dependance of the coupling strength with local time, ocean depth and season. We then show the confrontation of modelled signals with observations. For tsunami, this is made with the different type of measurement having proven ionospheric tsunami detection over the last 5 years (ground and space GPS, Airglow), while we focus on GPS and GOCE observation for seismic waves. These observation systems allowed to track the propagation of the signal from the ground (with GPS and seismometers) to the neutral atmosphere (with infrasound sensors and GOCE drag measurement) to the ionosphere (with GPS TEC and airglow among other ionospheric sounding techniques). Modelling with different techniques (normal modes, spectral element methods, finite differences) are used and shown. While the fits of the waveform are generally very good, we analyse the differences and draw direction of future studies and improvements, enabling the integration of lateral variations of the solid earth, bathymetry or atmosphere, finite model sources, non-linearity of the waves and better attenuation and coupling processes. All these effects are revealed by phase or amplitude discrepancies in selected observations. We then present goals and first results of source inversions, with a focus on estimations of the sea level uplift location and amplitude, either by using GPS networks close from the epicentre or, for tsunamis, GPS of the Hawaii Islands.

  9. Evaluation of the STORM-Time Ionospheric Empirical Model for the Bastille Day event

    Microsoft Academic Search

    E. A. Araujo-Pradere; T. J. Fuller-Rowell

    2001-01-01

    Recent theoretical model simulations of the ionospheric response to geomagnetic storms have provided the understanding for the development of an empirical storm-time ionospheric model (STORM). The empirical model is driven by the previous time-history of a p, and is designed to scale the quiet-time F-layer critical frequency (f o F 2) to account for storm-time changes in the ionosphere. The

  10. Estimation of optical turbulence in the atmospheric surface layer from routine meteorological observations: an artificial neural network approach

    NASA Astrophysics Data System (ADS)

    Wang, Yao; Basu, Sukanta

    2014-10-01

    The focus of this paper is on the estimation of optical turbulence (commonly characterized by C2n ) near the land-surface using routinely measured meteorological variables (e.g., temperature, wind speed). We demonstrate that an artificial neural network-based approach has the potential to be effectively utilized for this purpose. We use an extensive scintillometer-based C2n dataset from a recent field experiment in Texas, USA to evaluate the accuracy of the proposed approach.

  11. The thermophysical and microstructural effects of an artificial ice layer in natural snow under kinetic growth metamorphism

    Microsoft Academic Search

    Ethan M. Greene

    2007-01-01

    The macrostructure of a seasonal snow cover evolves with each new weather event. With wind and precipitation, layers of snow coat the old snow surface and the microstructure within these layers develops as a function of the environmental conditions. The thermal, mechanical and optical properties of snow are highly dependent on its microstructure. Many researchers have investigated metamorphism in homogenous

  12. Regional ionospheric TEC modelling; working towards mapping Africa's ionosphere

    Microsoft Academic Search

    John Bosco Habarulema; Lee-Anne McKinnell; Ben Opperman

    2011-01-01

    Currently the available data over the African continent does not allow for the construction of a truly representative ionospheric map for the purposes of long term predictions. In addition, the forecasting of the ionospheric variability over long term is a complicated task. This is because the ionospheric medium is continuously changing, it exhibits behavior that is not easily predictable and

  13. First observation of the anomalous electric field in the topside ionosphere by ionospheric modification over EISCAT

    NASA Astrophysics Data System (ADS)

    Kosch, M. J.; Vickers, H.; Ogawa, Y.; Senior, A.; Blagoveshchenskaya, N.

    2014-11-01

    We have developed an active ground-based technique to estimate the steady state field-aligned anomalous electric field (E*) in the topside ionosphere, up to ~600 km, using the European Incoherent Scatter (EISCAT) ionospheric modification facility and UHF incoherent scatter radar. When pumping the ionosphere with high-power high-frequency radio waves, the F region electron temperature is significantly raised, increasing the plasma pressure gradient in the topside ionosphere, resulting in ion upflow along the magnetic field line. We estimate E* using a modified ion momentum equation and the Mass Spectrometer Incoherent Scatter model. From an experiment on 23 October 2013, E* points downward with an average amplitude of ~1.6 ?V/m, becoming weaker at higher altitudes. The mechanism for anomalous resistivity is thought to be low-frequency ion acoustic waves generated by the pump-induced flux of suprathermal electrons. These high-energy electrons are produced near the pump wave reflection altitude by plasma resonance and also result in observed artificially induced optical emissions.

  14. Robust detection of ionospheric irregularities

    NASA Technical Reports Server (NTRS)

    Walter, T.; Hansen, A.; Blanch, J.; Enge, P.; Mannucci, T.; Pi, X.; Sparks, L.; Iijima, B.; El-Arini, B.; Lejeune, R.; Hagen, M.; Altshuler, E.; Fries, R.; Chu, A.

    2000-01-01

    The approach outlined in this paper conservatively bounds the ionospheric errors even for the worst observed ionospheric conditions to date, using data sets taken from the operational receivers in the WAAS reference station network.

  15. The thermophysical and microstructural effects of an artificial ice layer in natural snow under kinetic growth metamorphism

    NASA Astrophysics Data System (ADS)

    Greene, Ethan M.

    The macrostructure of a seasonal snow cover evolves with each new weather event. With wind and precipitation, layers of snow coat the old snow surface and the microstructure within these layers develops as a function of the environmental conditions. The thermal, mechanical and optical properties of snow are highly dependent on its microstructure. Many researchers have investigated metamorphism in homogenous snow, but little is known of snow metamorphism at the interface of two layers. In this study I observe the thermal and microstructural evolution of layered and non-layered samples of natural snow in kinetic growth metamorphism. The layered samples contain a 4 mm thick ice layer, which creates a large gradient in thermal conductivity and porosity. I collected samples of natural snow with a density range of 150-290 kg m-3 from the mountains of northern Colorado. In a cold laboratory, I subjected paired, treatment (layered) and control (non-layered), samples to a vertical temperature gradient of 60-110 K m-1 for a period of 5 days. During the experiment I measured the heat flux at the boundaries and the temperature profile within the sample. At the end of each experiment I cast the snow samples and performed serial sectioning and three-dimensional reconstruction of the snow microstructure. I also used the thermophysical data and microstructural data to simulate the evolution of the microstructure and the thermal state at the end of the experiment. The temperature profiles show snow in a steady-state thermal environment. There is no consistent signal from the ice layer in the temperature data. The microstructure within the snow samples undergoes a dramatic change during the experiments. In the control samples vertical chains of faceted and hollow particles develop and are responsible for transporting most of the thermal energy in the sample. Faceted structures grow off the bottom of the ice layer, while the upper surface erodes and becomes smooth and round. The presence of the ice layer affects thermal, mechanical and optical properties of the snow, these effects occur within several particles of the interface and would be difficult to detect with standard field techniques.

  16. Swarm SCARF Dedicated Ionospheric Field Inversion chain

    NASA Astrophysics Data System (ADS)

    Chulliat, Arnaud; Vigneron, Pierre; Thébault, Erwan; Sirol, Olivier; Hulot, Gauthier

    2013-11-01

    The geomagnetic daily variation at mid-to-low latitudes, referred to as the geomagnetic Sq field, is generated by electrical currents within the conducting layers of the ionosphere on the dayside of the Earth. It is enhanced in a narrow equatorial band, due to the equatorial electrojet. The upcoming ESA Swarm satellite mission, to be launched end of 2013, will consist of three satellites in low-Earth orbit, providing a dense spatial and temporal coverage of the ionospheric Sq field. A Satellite Constellation Application and Research Facility (SCARF) has been set up by a consortium of research institutions, aiming at producing various level-2 data products during the Swarm mission. The Dedicated Ionospheric Field Inversion (DIFI) chain is a SCARF algorithm calculating global, spherical harmonic models of the Sq field at quiet times. It describes seasonal and solar cycle variations, separates primary and induced magnetic fields based upon advanced 3D-models of the mantle electrical conductivity, and relies on core, lithospheric and magnetospheric field models derived from other SCARF algorithms for removing non-ionospheric fields from the data. The DIFI chain was thoroughly tested on synthetic data during the SCARF preparation phase; it is now ready to be used for deriving models from real Swarm data.

  17. Magnetosphere-ionosphere waves

    NASA Astrophysics Data System (ADS)

    Russell, A. J. B.; Wright, A. N.

    2012-01-01

    Self-consistent electrodynamic coupling of the ionosphere and magnetosphere produces waves with clearly defined properties, described here for the first time. Large scale (ideal) disturbances to the equilibrium, for which electron inertia is unimportant, move in the direction of the electric field at a characteristic speed. This may be as fast as several hundred meters per second or approximately half the E × B drift speed. In contrast, narrow scale (strongly inertial) waves are nearly stationary and oscillate at a specific frequency. Estimates of this frequency suggest periods from several tenths of a second to several minutes may be typical. Both the advection speed and frequency of oscillation are derived for a simple model and depend on a combination of ionospheric and magnetospheric parameters. Advection of large scale waves is nonlinear: troughs in E-region number density move faster than crests and this causes waves to break on their trailing edge. Wavebreaking is a very efficient mechanism for producing narrow (inertial) scale waves in the coupled system, readily accessing scales of a few hundred meters in just a few minutes. All magnetosphere-ionosphere waves are damped by recombination in the E-region, suggesting that they are to be best observed at night and in regions of low ionospheric plasma density. Links with observations, previous numerical studies and ionospheric feedback instability are discussed, and we propose key features of experiments that would test the new theory.

  18. Natural electromagnetic ULF noise due to fluctuations of ionospheric currents

    NASA Astrophysics Data System (ADS)

    Surkov, V. V.; Hayakawa, M.

    2008-11-01

    An origin of natural electromagnetic noise observed on the ground surface in the frequency range 10-4-10-2 Hz was examined. Following a recent paper by Surkov and Hayakawa (2007), a flicker noise or 1/f noise, provided by random currents, is treated as a possible source of the ULF electromagnetic noise. In contrast to the cited paper, MHD wave incident on the ionosphere and neutral gas flow in the altitude range of conducting E layer of the ionosphere are considered to be a candidate mechanism for random current fluctuations, which in turn produce random electromagnetic fluctuations in the atmosphere. The main emphasis is on the flicker noise provided by the wind-driven ionospheric currents, which is assumed to be steady, uniform, and isotropic random fields inside the ionosphere. A correlation radius of random ionospheric fields is supposed to be controlled by neutral gas transfer and by acoustic/gravity wave propagation inside the E layer. A correlation matrix and power spectra of the random electromagnetic fields on the ground surface were calculated. The predicted spectral index of the power spectrum of the ULF magnetic noise was found to be 3, which is consistent with ground-based observations. The experimental data were demonstrated to be sandwiched between two theoretical lines, which correspond to daytime and nighttime ionospheric parameters.

  19. Generation of Acoustic-Gravity Waves in Ionospheric HF Heating Experiments: Simulating Large-Scale Natural Heat Sources

    NASA Astrophysics Data System (ADS)

    Pradipta, Rezy

    In this thesis, we investigate the potential role played by large-scale anomalous heat sources (e.g. prolonged heat wave events) in generating acoustic-gravity waves (AGWs) that might trigger widespread plasma turbulence in the ionospheric layer. The main hypothesis is that, the thermal gradients associated with the heat wave fronts could act as a source of powerful AGW capable of triggering ionospheric plasma turbulence over extensive areas. In our investigations, first we are going to examine a case study of the summer 2006 North American heat wave event. Our examination of GPS-derived total electron content (TEC) data over the North American sector reveals a quite noticeable increase in the level of daily plasma density fluctuations during the summer 2006 heat wave period. Comparison with the summer 2005 and summer 2007 data further confirms that the observed increase of traveling ionospheric disturbances (TIDs) during the summer 2006 heat wave period was not simply a regular seasonal phenomenon. Furthermore, a series of field experiments had been carried out at the High-frequency Active Auroral Research Program (HAARP) facility in order to physically simulate the process of AGW/TID generation by large-scale thermal gradients in the ionosphere. In these ionospheric HF heating experiments, we create some time-varying artificial thermal gradients at an altitude of 200--300 km above the Earth's surface using vertically-transmitted amplitude-modulated 0-mode HF heater waves. For our experiments, a number of radio diagnostic instruments had been utilized to detect the characteristic signatures of heater-generated AGW/TID. So far, we have been able to obtain several affirmative indications that some artificial AGW/TID are indeed being radiated out from the heated plasma volume during the HAARP-AGW experiments. Based on the experimental evidence, we may conclude that it is certainly quite plausible for large-scale thermal gradients associated with severe heat wave events to generate some AGW which might induce widespread plasma turbulence far in space. (Copies available exclusively from MIT Libraries, libraries.mit.edu/docs - docs mit.edu)

  20. Intercepted signals for ionospheric science

    NASA Astrophysics Data System (ADS)

    Lind, F. D.; Erickson, P. J.; Coster, A. J.; Foster, J. C.; Marchese, J. R.; Berkowitz, Z.; Sahr, J. D.

    2013-05-01

    The ISIS array (Intercepted Signals for Ionospheric Science) is a distributed, coherent software radio array designed for the study of geospace phenomena by observing the scatter of ambient radio frequency (RF) signals. ISIS data acquisition and analysis is performed using the MIDAS-M platform (Millstone Data Acquisition System - Mobile). Observations of RF signals can be performed between HF and L-band using the Array nodes and appropriate antennas. The deployment of the Array focuses on observations of the plasmasphere boundary layer. We discuss the concept of the coherent software radio array, describe the ISIS hardware, and give examples of data from the system for selected applications. In particular, we include the first observations of E region irregularities using the Array. We also present single-site passive radar observations of both meteor trails and E region irregularities using adaptive filtering techniques.

  1. Relationship of solar wind parameters to continuous, dayside, high latitude traveling ionospheric convection vortices

    Microsoft Academic Search

    Mark A. McHenry; C. Robert Clauer; Eigil Friis-Christensen

    1990-01-01

    In a companion paper the authors have shown that many continuous, dayside, high latitude magnetic pulsations are caused by steady, traveling ionospheric convection vortices (McHenry et al. this issue). A variety of evidence indicates that these vortices are the ionospheric signatures of the Kelvin-Helmholtz instability at the inner edge of the magnetospheric boundary layer. In this paper the authors present

  2. Ionospheric manifestations of acoustic-gravity waves under quiet and disturbed conditions

    NASA Astrophysics Data System (ADS)

    Barabash, Vladimir; Chernogor, Leonid; Panasenko, Sergii; Domnin, Igor

    2014-05-01

    We present the observation results of wave disturbances in the ionosphere, which are known to be manifestations of atmospheric acoustic-gravity waves (AGWs). The observations have been conducted under quiet and naturally or artificially disturbed conditions by ionosonde and incoherent scatter radar located near Kharkiv, Ukraine. Wave disturbance parameters under quiet conditions were obtained and analysed during geophysical periods including vernal and autumn equinoxes as well as summer and winter solstices. The prevailing oscillation in ionospheric F2- layer had the period of 140 - 200 min and relative amplitude of 0.1 - 0.2. The duration of this oscillation changed from 5 - 7 to 24 hours, depending on a season. The amplitude of fluctuations with other periods was noticeably smaller. The time intervals at which the intensity of incoherent scatter signals varied quasi-periodically in the altitude range from 150 to 300 km were detected. The parameters of these variations were estimated using statistical analysis and bandpass filtering. The periods of wave processes were shown to be of 30 - 120 min, there durations did not exceed of 2 - 6 periods and relative amplitudes usually ranged from 0.03 to 0.15. The phase of oscillations was detected to propagate downwards. The vertical phase velocity of travelling ionospheric disturbances (TIDs) was estimated to be in the range from 50 to 200 m/s and increased with altitude. The observations of the partial solar eclipse on January, 4, 2011 near Kharkiv were used to study the ionospheric parameters in naturally disturbed conditions. The F2-layer critical frequency dropped by a factor of 2.1. The time delay of these variations with respect to the main magnitude of the solar disk obscuration was equal to about 16 minutes. The virtual height of signal reflection near the maximum of the F2-layer ionization increased by 70 km, and the height of the model parabolic layer increased by 10 km. Some decrease in electron density and growth of quasi-periodic variations with periods of about 30 and 60 min were detected at all observable heights during this solar eclipse. The diagnostics of wave processes has been performed during ionospheric modification experiments with EISCAT heater. This heater is at a distance of about 2400 km from Kharkiv incoherent scatter radar. We have detected the TIDs over Kharkiv with periods of 40 - 80 min. The duration of these disturbances has not exceeded 120 - 180 min. The relative amplitudes of the TIDs in electron density ranged from 0.05 to 0.15 and those in electron and ion temperatures were about 0.02 - 0.05. The possible mechanisms for the generation of AGWs and TIDs by high power HF radio waves are sharp thermal gradients at the edge of the heated region and modulation of the ionospheric current systems by periodic high power radio transmission.

  3. Characterizing Extreme Ionospheric Storms

    NASA Astrophysics Data System (ADS)

    Sparks, L.; Komjathy, A.; Altshuler, E.

    2011-12-01

    Ionospheric storms consist of disturbances of the upper atmosphere that generate regions of enhanced electron density typically lasting several hours. Depending upon the storm magnitude, gradients in electron density can sometimes become large and highly localized. The existence of such localized, dense irregularities is a major source of positioning error for users of the Global Positioning System (GPS). Consequently, satellite-based augmentation systems have been implemented to improve the accuracy and to ensure the integrity of user position estimates derived from GPS measurements. Large-scale irregularities generally do not pose a serious threat to estimate integrity as they can be readily detected by such systems. Of greater concern, however, are highly localized irregularities that interfere with the propagation of a signal detected by a user measurement but are poorly sampled by the receivers in the system network. The most challenging conditions have been found to arise following disturbances of large magnitude that occur only rarely over the course of a solar cycle. These extremely disturbed conditions exhibit behavior distinct from moderately disturbed conditions and, hence, have been designated "extreme storms". In this paper we examine and compare the behavior of the extreme ionospheric storms of solar cycle 23 (or, more precisely, extreme storms occurring between January 1, 2000, and December 31, 2008), as represented in maps of vertical total electron content. To identify these storms, we present a robust means of quantifying the regional magnitude of an ionospheric storm. Ionospheric storms are observed frequently to occur in conjunction with magnetic storms, i.e., periods of geophysical activity as measured by magnetometers. While various geomagnetic indices, such as the disturbance storm time (Dst) and the planetary Kp index, have long been used to rank the magnitudes of distinct magnetic storms, no comparable, generally recognized index exists for measuring ionospheric storm magnitudes. Since the level of ionospheric disturbance (as represented, for example, by enhancements or depletions in total electron content) does not always scale directly with the level of geophysical disturbance in a coincident magnetic storm, however, an independent, purely ionospheric storm index is preferable for ranking ionospheric storms by their magnitudes. Our storm magnitude metric is calculated from the standard ?2 goodness-of-fit parameter values associated with estimates of vertical total electron content (derived from observations collected by networks of GPS receivers) on a grid at regularly spaced intervals of geodetic latitude and longitude. It takes into account both the instantaneous magnitude of the storm and its temporal duration.

  4. In-Situ Transmission Electron Microscopy Probing of Native Oxide and Artificial Layers on Silicon Nanoparticles for Lithium Ion Batteries

    SciTech Connect

    He, Yang; Piper, Daniela M.; Gu, Meng; Travis, Jonathan J.; George, Steven M.; Lee, Se-Hee; Genc, Arda; Pullan, Lee; Liu, Jun; Mao, Scott X.; Zhang, Jiguang; Ban, Chunmei; Wang, Chong M.

    2014-10-27

    Surface modification of silicon nanoparticle via molecular layer deposition (MLD) has been recently proved to be an effective way for dramatically enhancing the cyclic performance in lithium ion batteries. However, the fundamental mechanism as how this thin layer of coating function is not known, which is even complicated by the inevitable presence of native oxide of several nanometers on the silicon nanoparticle. Using in-situ TEM, we probed in detail the structural and chemical evolution of both uncoated and coated silicon particles upon cyclic lithiation/delithation. We discovered that upon initial lithiation, the native oxide layer converts to crystalline Li2O islands, which essentially increases the impedance on the particle, resulting in ineffective lithiation/delithiation, and therefore low coulombic efficiency. In contrast, the alucone MLD coated particles show extremely fast, thorough and highly reversible lithiation behaviors, which are clarified to be associated with the mechanical flexibility and fast Li+/e- conductivity of the alucone coating. Surprisingly, the alucone MLD coating process chemically changes the silicon surface, essentially removing the native oxide layer and therefore mitigates side reaction and detrimental effects of the native oxide. This study provides a vivid picture of how the MLD coating works to enhance the coulombic efficiency and preserve capacity and clarifies the role of the native oxide on silicon nanoparticles during cyclic lithiation and delithiation. More broadly, this work also demonstrated that the effect of the subtle chemical modification of the surface during the coating process may be of equal importance as the coating layer itself.

  5. Features of artificial ULF/VLF signals induced by SURA facility under increased solar activity conditions

    NASA Astrophysics Data System (ADS)

    Kotik, Dmitry; Ryabov, Alexander; Pershin, Alexsander; Ermakova, Elena

    It was conducted a comprehensive study of artificial ionospheric signal generation in the ULF/VLF bands at SURA facility during the past four years. We investigated the influence of geomagnetic activity on the characteristics of artificial low-frequency signals in recent years under the background of increasing solar activity. No correlation with variations of Earth's magnetic field was observed for weak geomagnetic disturbances (Kp < 3). It was observed decreasing in the amplitude of signals at frequencies of 3 and 6 Hz, while the VLF signals at frequencies of 2 and 2.6 kHz increased for growth phase of the geomagnetic field perturbations during a small magnetic storms October 7, 2011 (Ki = 4 according to Moscow station). A similar pattern was traced in 2013 during storms March 21 (Kp = 5), May 24-25 (Kp = 5 +) and August 16 (Kp = 5 +). There are two possible reasons for the observed dependence - increasing the absorption of HF and VLF waves in the lower ionosphere, and / or reduction of the critical frequency of the F-layer, usually accompanied by a magnetic storm. The last factor is perhaps the most likely. This dependence was traced more convincingly on May 24-25, when during a storm time SURE had operated from evening until 6:00 MST in the morning. Signal amplitude explicitly followed the F- layer critical frequency variation. Some of the measurements in June 2012 were conducted during a magnetic storm on June 16-18, (Kp = 6). It was also found a decrease in the amplitude of the signal at the rise of the magnetic disturbance. In addition, during the daytime session 18.06.2012 during the recovery phase, it was detected modulation of artificial signals at frequencies 11 and 17 Hz with a period of 30 seconds. Note that the period of 30s is the main period of oscillation of the geomagnetic field line passing through the SURA facility, and more, the periods for torsional and the toroidal oscillation modes of this field line surprising coincidence for SURA geomagnetic latitude. Also the peculiarities were displayed in the polarization of artificial VLF signals during magnetic storms. Typically, the artificial emission is elliptically polarized at all frequencies of VLF signals with a predominance of the left- polarization. During a storm time, it was detected a change in the polarization of artificial VLF emissions. The right polarization becomes predominant. This fact can be associated with changes in ionospheric plasma parameters under a magnetic storm conditions. This work was supported by RFBR grants 13-02-0072 and 13-02-12074.

  6. Ionosphere Waves Service - A demonstration

    NASA Astrophysics Data System (ADS)

    Crespon, François

    2013-04-01

    In the frame of the FP7 POPDAT project the Ionosphere Waves Service was developed by ionosphere experts to answer several questions: How make the old ionosphere missions more valuable? How provide scientific community with a new insight on wave processes that take place in the ionosphere? The answer is a unique data mining service accessing a collection of topical catalogues that characterize a huge number of Atmospheric Gravity Waves, Travelling Ionosphere Disturbances and Whistlers events. The Ionosphere Waves Service regroups databases of specific events extracted by experts from a ten of ionosphere missions which end users can access by applying specific searches and by using statistical analysis modules for their domain of interest. The scientific applications covered by the IWS are relative to earthquake precursors, ionosphere climatology, geomagnetic storms, troposphere-ionosphere energy transfer, and trans-ionosphere link perturbations. In this presentation we propose to detail the service design, the hardware and software architecture, and the service functions. The service interface and capabilities will be the focus of a demonstration in order to help potential end-users for their first access to the Ionosphere Waves Service portal. This work is made with the support of FP7 grant # 263240.

  7. Artificial Particle Beams in Space Plasma Studies. Vol. 79

    Microsoft Academic Search

    Grandal

    1982-01-01

    This book examines the various methods for artificial modification of the upper atmosphere in order to study, under controlled conditions, the various beam-plasma interactions in space, such as those taking place in the auroral ionosphere. Topics considered include accelerator experiments in space (e.g., the use of artificial electrons beams as probes of the distant magnetosphere, charged particle measurements, wave excitation

  8. Solitons and ionospheric heating

    NASA Technical Reports Server (NTRS)

    Weatherall, J. C.; Goldman, M. V.; Sheerin, J. P.; Nicholson, D. R.; Payne, G. L.; Hansen, P. J.

    1982-01-01

    It is noted that for parameters characterizing the Platteville ionospheric heating facility, the Langmuir wave evolution at the exact reflection point of the heater wave involves an oscillating two-stream instability followed by a collisionally damped three-dimensional soliton collapse. The result gives an alternative explanation for certain experimental observations.

  9. The permeability of SPION over an artificial three-layer membrane is enhanced by external magnetic field

    PubMed Central

    Mondalek, Fadee G; Zhang, Yuan Yuan; Kropp, Bradley; Kopke, Richard D; Ge, Xianxi; Jackson, Ronald L; Dormer, Kenneth J

    2006-01-01

    Background Sensorineural hearing loss, a subset of all clinical hearing loss, may be correctable through the use of gene therapy. We are testing a delivery system of therapeutics through a 3 cell-layer round window membrane model (RWM model) that may provide an entry of drugs or genes to the inner ear. We designed an in vitro RWM model similar to the RWM (will be referred to throughout the paper as RWM model) to determine the feasibility of using superparamagnetic iron oxide (Fe3O4) nanoparticles (SPION) for targeted delivery of therapeutics to the inner ear. The RWM model is a 3 cell-layer model with epithelial cells cultured on both sides of a small intestinal submucosal (SIS) matrix and fibroblasts seeded in between. Dextran encapsulated nanoparticle clusters 130 nm in diameter were pulled through the RWM model using permanent magnets with flux density 0.410 Tesla at the pole face. The SIS membranes were harvested at day 7 and then fixed in 4% paraformaldehyde. Transmission electron microscopy and fluorescence spectrophotometry were used to verify transepithelial transport of the SPION across the cell-culture model. Histological sections were examined for evidence of SPION toxicity, as well to generate a timeline of the position of the SPION at different times. SPION also were added to cells in culture to assess in vitro toxicity. Results Transepithelial electrical resistance measurements confirmed epithelial confluence, as SPION crossed a membrane consisting of three co-cultured layers of cells, under the influence of a magnetic field. Micrographs showed SPION distributed throughout the membrane model, in between cell layers, and sometimes on the surface of cells. TEM verified that the SPION were pulled through the membrane into the culture well below. Fluorescence spectrophotometry quantified the number of SPION that went through the SIS membrane. SPION showed no toxicity to cells in culture. Conclusion A three-cell layer model of the human round window membrane has been constructed. SPION have been magnetically transported through this model, allowing quantitative evaluation of prospective targeted drug or gene delivery through the RWM. Putative in vivo carrier superparamagnetic nanoparticles may be evaluated using this model. PMID:16603066

  10. Ionospheric threats to the integrity of airborne GPS users

    NASA Astrophysics Data System (ADS)

    Datta-Barua, Seebany

    The Global Positioning System (GPS) has both revolutionized and entwined the worlds of aviation and atmospheric science. As the largest and most unpredictable source of GPS positioning error, the ionospheric layer of the atmosphere, if left unchecked, can endanger the safety, or "integrity," of the single frequency airborne user. An augmentation system is a differential-GPS-based navigation system that provides integrity through independent ionospheric monitoring by reference stations. However, the monitor stations are not in general colocated with the user's GPS receiver. The augmentation system must protect users from possible ionosphere density variations occurring between its measurements and the user's. This study analyzes observations from ionospherically active periods to identify what types of ionospheric disturbances may cause threats to user safety if left unmitigated. This work identifies when such disturbances may occur using a geomagnetic measure of activity and then considers two disturbances as case studies. The first case study indicates the need for a non-trivial threat model for the Federal Aviation Administration's Local Area Augmentation System (LAAS) that was not known prior to the work. The second case study uses ground- and space-based data to model an ionospheric disturbance of interest to the Federal Aviation Administration's Wide Area Augmentation System (WAAS). This work is a step in the justification for, and possible future refinement of, one of the WAAS integrity algorithms. For both WAAS and LAAS, integrity threats are basically caused by events that may be occurring but are unobservable. Prior to the data available in this solar cycle, events of such magnitude were not known to be possible. This work serves as evidence that the ionospheric threat models developed for WARS and LAAS are warranted and that they are sufficiently conservative to maintain user integrity even under extreme ionospheric behavior.

  11. Chemistry in the Thermosphere and Ionosphere.

    ERIC Educational Resources Information Center

    Roble, Raymond G.

    1986-01-01

    An informative review which summarizes information about chemical reactions in the thermosphere and ionosphere. Topics include thermal structure, ultraviolet radiation, ionospheric photochemistry, thermospheric photochemistry, chemical heating, thermospheric circulation, auroral processes and ionospheric interactions. Provides suggested followup…

  12. Radio Sounding of the Martian and Venusian Ionospheres

    NASA Astrophysics Data System (ADS)

    Paetzold, M.; Haeusler, B.; Bird, M. K.; Peter, K.; Tellmann, S.; Tyler, G. L.; Withers, P.

    2011-12-01

    The Mars Express Radio Science Experiment MaRS and the radio science experiment Vera on Venus Express sound the ionospheres of Mars and Venus, respectively, at two frequencies in the microwave band and cover altitudes from the base of the ionosphere at 80 km (100 km at Venus) to the ionopause at altitudes between 300 km and 600 km. In general, both ionospheres consists of a lower layer M1 (V1 at Venus) at about 110 km (115 km), and the main layer M2 (V2) at about 135 km (145 km) altitude, both formed mainly by solar radiation at X-ray and EUV, respectively. The specific derivation and interpretation of the vertical electron density profiles at two radio frequencies from radio sounding is demonstrated in detail. Cases of quiet and disturbed ionospheric electron density profiles and cases of potential misinterpretations are presented. The behavior of the peak densities and peak altitudes of both ionospheres as a function of solar zenith angle and phase of the solar cycle as seen with Mars Express and Venus Express will be compared with past observations, models and conclusions.

  13. Calculation of ray paths in the ionosphere using an analytic raytracing technique

    NASA Astrophysics Data System (ADS)

    Yukon, Stanford P.

    1986-07-01

    A method for tracing rays in the ionosphere using analytic solutions to approximate path varying ionospheric potentials is outlined in this report. Using the ionospheric parameters generated by IONCAP and approximating the E-F2 and ground-E layer potential wells by a scaled Morse potential and a linear potential respectively, known solutions to these potentials are promoted to final ray paths by using methods developed for solving the time dependent Schroedinger equation. The computer code necessary to fit the potentials, connect the solutions at the E layer peak, and trace arbitrarily launched rays is described.

  14. Magnetosphere-ionosphere coupling

    Microsoft Academic Search

    C. K. Goertz; R. W. Boswell

    1979-01-01

    A simple two-dimensional model of the magnetosphere-ionosphere system is discussed in which a localized electromotive force applied across a magnetic field line at t=0 is shown to propagate along the magnetic field with the Alfven velocity. The perpendicular electric field is assumed to reverse direction across the field line. Since the perpendicular electric field is limited in space, the propagation

  15. GPS and ionospheric scintillations

    NASA Astrophysics Data System (ADS)

    Kintner, P. M.; Ledvina, B. M.; de Paula, E. R.

    2007-09-01

    Ionospheric scintillations are one of the earliest known effects of space weather. Caused by ionization density irregularities, scintillating signals change phase unexpectedly and vary rapidly in amplitude. GPS signals are vulnerable to ionospheric irregularities and scintillate with amplitude variations exceeding 20 dB. GPS is a weak signal system and scintillations can interrupt or degrade GPS receiver operation. For individual signals, interruption is caused by fading of the in-phase and quadrature signals, making the determination of phase by a tracking loop impossible. Degradation occurs when phase scintillations introduce ranging errors or when loss of tracking and failure to acquire signals increases the dilution of precision. GPS scintillations occur most often near the magnetic equator during solar maximum, but they can occur anywhere on Earth during any phase of the solar cycle. In this article we review the subject of GPS and ionospheric scintillations for scientists interested in space weather and engineers interested in the impact of scintillations on GPS receiver design and use.

  16. Ionospheric imaging in Africa

    NASA Astrophysics Data System (ADS)

    Chartier, Alex T.; Kinrade, Joe; Mitchell, Cathryn N.; Rose, Julian A. R.; Jackson, David R.; Cilliers, Pierre; Habarulema, John-Bosco; Katamzi, Zama; Mckinnell, Lee-Anne; Matamba, Tshimangadzo; Opperman, Ben; Ssessanga, Nicholas; Giday, Nigussie Mezgebe; Tyalimpi, Vumile; Franceschi, Giorgiana De; Romano, Vincenzo; Scotto, Carlo; Notarpietro, Riccardo; Dovis, Fabio; Avenant, Eugene; Wonnacott, Richard; Oyeyemi, Elijah; Mahrous, Ayman; Tsidu, Gizaw Mengistu; Lekamisy, Harvey; Olwendo, Joseph Ouko; Sibanda, Patrick; Gogie, Tsegaye Kassa; Rabiu, Babatunde; Jong, Kees De; Adewale, Adekola

    2014-01-01

    ionospheric specification is necessary for improving human activities such as radar detection, navigation, and Earth observation. This is of particular importance in Africa, where strong plasma density gradients exist due to the equatorial ionization anomaly. In this paper the accuracy of three-dimensional ionospheric images is assessed over a 2 week test period (2-16 December 2012). These images are produced using differential Global Positioning System (GPS) slant total electron content observations and a time-dependent tomography algorithm. The test period is selected to coincide with a period of increased GPS data availability from the African Geodetic Reference Frame (AFREF) project. A simulation approach that includes the addition of realistic errors is employed in order to provide a ground truth. Results show that the inclusion of observations from the AFREF archive significantly reduces ionospheric specification errors across the African sector, especially in regions that are poorly served by the permanent network of GPS receivers. The permanent network could be improved by adding extra sites and by reducing the number of service outages that affect the existing sites.

  17. Observations of the effects of meteors on the ionospheres of

    E-print Network

    Withers, Paul

    Observations of the effects of meteors on the ionospheres of Venus, Earth and Mars Paul Withers1, A Planetology: Venus-Earth-Mars, ESLAB 2009 ESTEC, The Netherlands #12;Observations of the effects of meteors that affect metal ion layers ­ Meteor showers ­ Sporadic meteoroids ­ Magnetic fields and winds · Status

  18. Comparison of Ionospheric Observations and Dynamical Predictions of Meteor

    E-print Network

    Withers, Paul

    Comparison of Ionospheric Observations and Dynamical Predictions of Meteor Showers at Mars Paul intervals when there are many of these profiles and call them meteor showers We study cometary orbits to identify the parent bodies responsible for the meteor showers #12;Meteoric Layers (MEX) Profile with EUV

  19. Simulation of ion outflows in the ionosphere

    NASA Astrophysics Data System (ADS)

    Sydorenko, D.; Rankin, R.

    2012-12-01

    Ion outflows are observed in the polar region in response to particle precipitation and magnetospheric wave activity. In order to study the ion outflow, we modified the previously developed two-dimensional model of realistic active ionosphere [Sydorenko, 2012] by including ion motion along the geomagnetic field. The new model considers a layer of near-Earth plasma of thickness of a few thousand kilometers. The plasma consists of multiple ion species. Collisions between particles are accounted for everywhere, even at high altitudes where they are negligible. Therefore, unlike in the previous model, the electron and ion dynamics is continuous. Chemical reactions between different ion and neutral species are included. Simulations demonstrate formation of field-aligned ion flows when an intense Alfven wave or electron precipitation perturbs the ionosphere. The significance of the results is discussed in the context of Canadian Space Agency e-POP spacecraft mission. Sydorenko D. and R. Rankin, "Simulation of ionospheric disturbances created by Alfven waves", submitted to Journal of Geophysical Research, 2012.

  20. Venus Ionosphere and Solar Wind Interaction

    NASA Astrophysics Data System (ADS)

    Russell, C. T.; Luhmann, Janet G.; Ma, Yingjuan; Zhang, Tielong; Villarreal, M.

    Venus Express, which was inserted into orbit in mid-2006, has added significantly to the knowledge gained from Pioneer Venus from 1978 to 1992. This observational database interpreted in terms of modern multi-fluid codes and hybrid simulations has deepened our understanding of Earth’s very different twin sister planet. Furthermore, the very different orbits of VEX and PVO has allowed the more complete mapping of the volume of space around the planet. Now the bow shock has been probed over its full surface, the ionosphere mapped everywhere, and the tail studied from the ionosphere to 12 Venus radii. Some unexpected discoveries have been made. The exospheric hydrogen at Venus, unlike that at Mars, does not produce ion-cyclotron waves, perhaps because the stronger gravity of Venus produces a smaller geocorona. The solar wind interaction drapes the magnetic field around the planet, and a strong layer of magnetic field builds up at low altitudes. While the layer does not appear to penetrate into the dayside atmosphere (perhaps diffusing only slowly through the low atmosphere), it does appear to dip into the atmosphere at night. Surprisingly, over the poles, this layer is most strongly seen when the IMF BY component has a positive Y-component in Venus-Solar-Orbital coordinates. Multi-fluid simulations show that this result is consistent with the pressure of significant ion densities of ions with quite different mass which causes magnetic polarity control of the ion flow over the terminators. Reconnection is found in the tail close to the planet, and the structure of the outer tail found by PVO is confirmed to exist in the inner tail by VEX. When combined, the VEX and PVO Data provide a very comprehensive picture of the physics of the solar wind interaction with the ionosphere of Venus.

  1. Artificial Construction of the Layered Ruddlesden–Popper Manganite La2Sr2Mn3O10 by Reflection High Energy Electron Diffraction Monitored Pulsed Laser Deposition

    PubMed Central

    2012-01-01

    Pulsed laser deposition has been used to artificially construct the n = 3 Ruddlesden–Popper structure La2Sr2Mn3O10 in epitaxial thin film form by sequentially layering La1–xSrxMnO3 and SrO unit cells aided by in situ reflection high energy electron diffraction monitoring. The interval deposition technique was used to promote two-dimensional SrO growth. X-ray diffraction and cross-sectional transmission electron microscopy indicated that the trilayer structure had been formed. A site ordering was found to differ from that expected thermodynamically, with the smaller Sr2+ predominantly on the R site due to kinetic trapping of the deposited cation sequence. A dependence of the out-of-plane lattice parameter on growth pressure was interpreted as changing the oxygen content of the films. Magnetic and transport measurements on fully oxygenated films indicated a frustrated magnetic ground state characterized as a spin glass-like magnetic phase with the glass temperature Tg ? 34 K. The magnetic frustration has a clear in-plane (ab) magnetic anisotropy, which is maintained up to temperatures of 150 K. Density functional theory calculations suggest competing antiferromagnetic and ferromagnetic long-range orders, which are proposed as the origin of the low-temperature glassy state. PMID:22463768

  2. Qualitative and quantitative high performance thin layer chromatography analysis of Calendula officinalis using high resolution plate imaging and artificial neural network data modelling.

    PubMed

    Agatonovic-Kustrin, S; Loescher, Christine M

    2013-10-10

    Calendula officinalis, commonly known Marigold, has been traditionally used for its anti-inflammatory effects. The aim of this study was to investigate the capacity of an artificial neural network (ANN) to analyse thin layer chromatography (TLC) chromatograms as fingerprint patterns for quantitative estimation of chlorogenic acid, caffeic acid and rutin in Calendula plant extracts. By applying samples with different weight ratios of marker compounds to the system, a database of chromatograms was constructed. A hundred and one signal intensities in each of the HPTLC chromatograms were correlated to the amounts of applied chlorogenic acid, caffeic acid, and rutin using an ANN. The developed ANN correlation was used to quantify the amounts of 3 marker compounds in calendula plant extracts. The minimum quantifiable level (MQL) of 610, 190 and 940 ng and the limit of detection (LD) of 183, 57 and 282 ng were established for chlorogenic, caffeic acid and rutin, respectively. A novel method for quality control of herbal products, based on HPTLC separation, high resolution digital plate imaging and ANN data analysis has been developed. The proposed method can be adopted for routine evaluation of the phytochemical variability in calendula extracts. PMID:24070490

  3. Ionospheric Response to the Acoustic Gravity Wave Singularity

    NASA Astrophysics Data System (ADS)

    Savina, Olga N.; Bespalov, Peter A.

    2015-02-01

    An original model of atmospheric wave propagation from ground sources to the ionosphere in the atmosphere with a realistic high-altitude temperature profile is analyzed. Shaping of a narrow domain with elevated pressure in the resonance region where the horizontal phase wave velocity is equal to the sound velocity is examined theoretically within the framework of linearized Eq.s. Numerical simulations for the model profiles of atmospheric temperature and viscosity confirm analytical result for the special feature of wave fields. The formation of the narrow domain with plasma irregularities in the D and low E ionospheric layers caused by the acoustic gravity wave singularity is discussed

  4. Oblique sounding of the ionosphere by powerful wave beams

    NASA Astrophysics Data System (ADS)

    Molotkov, I. A.; Atamaniuk, B.

    2011-04-01

    The article is devoted to modeling the impact on the ionosphere powerful obliquely incident wave beam. The basis of this analysis will be orbital variational principle for the intense wave beams-generalization of Fermat's principle to the case of a nonlinear medium (Molotkov and Vakulenko, 1988a,b; Molotkov, 2003, 2005). Under the influence of a powerful wave beam appears manageable the additional stratification of the ionospheric layer F2. Explicit expressions show how the properties of the test beam, with a shifted frequency, released in the same direction as the beam depend on the intensity of a powerful beam and the frequency shift.

  5. Ionospheric response to the acoustic gravity wave singularity

    NASA Astrophysics Data System (ADS)

    Savina, Olga N.; Bespalov, Peter A.

    2014-11-01

    An original model of atmospheric wave propagation from ground sources to the ionosphere in the atmosphere with a realistic high-altitude temperature profile is analyzed. Shaping of a narrow domain with elevated pressure in the resonance region where the horizontal phase wave velocity is equal to the sound velocity is examined theoretically within the framework of linearized Eq.s. Numerical simulations for the model profiles of atmospheric temperature and viscosity confirm analytical result for the special feature of wave fields. The formation of the narrow domain with plasma irregularities in the D and low E ionospheric layers caused by the acoustic gravity wave singularity is discussed.

  6. Ionospheric modification using relativistic electron beams

    NASA Technical Reports Server (NTRS)

    Banks, Peter M.; Fraser-Smith, Anthony C.; Gilchrist, B. E.

    1990-01-01

    The recent development of comparatively small electron linear accelerators (linacs) now makes possible a new class of ionospheric modification experiments using beams of relativistic electrons. These experiments can potentially provide much new information about the interactions of natural relativistic electrons with other particles in the upper atmosphere, and it may also make possible new forms of ionization structures extending down from the lower ionosphere into the largely un-ionized upper atmosphere. The consequences of firing a pulsed 1 A, 5 Mev electron beam downwards into the upper atmosphere are investigated. If a small pitch angle with respect to the ambient geomagnetic field is selected, the beam produces a narrow column of substantial ionization extending down from the source altitude to altitudes of approximately 40 to 45 km. This column is immediately polarized by the natural middle atmosphere fair weather electric field and an increasingly large potential difference is established between the column and the surrounding atmosphere. In the regions between 40 to 60 km, this potential can amount to many tens of kilovolts and the associated electric field can be greater than the field required for breakdown and discharge. Under these conditions, it may be possible to initiate lightning discharges along the initial ionization channel. Filamentation may also occur at the lower end to drive further currents in the partially ionized gases of the stratosphere. Such discharges would derive their energy from the earth-ionosphere electrical system and would be sustained until plasma depletion and/or electric field reduction brought the discharge under control. It is likely that this artificially-triggered lightning would produce measurable low-frequency radiation.

  7. Tohoku earthquake shook the ionosphere

    Microsoft Academic Search

    Ernie Balcerak

    2011-01-01

    The giant 11 March 2011 magnitude 9 Tohoku earthquake not only shook the Earth and caused devastating tsunamis but also rattled the ionosphere, according to a new study. The surface seismic waves and tsunamis triggered waves in the atmosphere. These atmospheric waves propagated upward into the ionosphere, creating ripples in ionized gas nearly 350 kilometers above the Earth. Liu et

  8. Ionospheres of the terrestrial planets

    Microsoft Academic Search

    R. W. Schunk; A. F. Nagy

    1980-01-01

    The theory and observations relating to the ionospheres of the terrestrial planets Venus, the earth and Mars are reviewed. Emphasis is placed on comparing the basic differences and similarities between the planetary ionospheres. The review covers the plasma and electric-magnetic field environments that surround the planets, the theory leading to the creation and transport of ionization in the ionspheres, the

  9. Layers

    NASA Astrophysics Data System (ADS)

    Hong, K. J.; Jeong, T. S.; Youn, C. J.

    2014-09-01

    The temperature-dependent photoresponse characteristics of MnAl2S4 layers have been investigated, for the first time, by use of photocurrent (PC) spectroscopy. Three peaks were observed at all temperatures. The electronic origin of these peaks was associated with band-to-band transitions from the valence-band states ?4( z), ?5( x), and ?5( y) to the conduction-band state ?1( s). On the basis of the relationship between PC-peak energy and temperature, the optical band gap could be well expressed by the expression E g( T) = E g(0) - 2.80 × 10-4 T 2/(287 + T), where E g(0) was estimated to be 3.7920 eV, 3.7955 eV, and 3.8354 eV for the valence-band states ?4( z), ?5( x), and ?5( y), respectively. Results from PC spectroscopy revealed the crystal-field and spin-orbit splitting were 3.5 meV and 39.9 meV. The gradual decrease of PC intensity with decreasing temperature can be explained on the basis of trapping centers associated with native defects in the MnAl2S4 layers. Plots of log J ph, the PC current density, against 1/ T, revealed a dominant trap level in the high-temperature region. By comparing PC and the Hall effect results, we confirmed that this trap level is a shallow donor 18.9 meV below the conduction band.

  10. Hardware and software complex monitoring the Earth ionosphere

    NASA Astrophysics Data System (ADS)

    Smirnov, Vladimir; Smirnova, Elena; Skobelkin, Vladimir; Tynyankin, Sergey

    The complex structure of the propagation medium, as well as continuous change in time ionospheric plasma parameters affect the propagation of radio waves. Therefore, objectives of the study processes in the ionosphere associated with both the practical tasks of ensuring stable operation of radiocommunication systems and with no less important scientific - research tasks of monitoring near-Earth space. A promising approach to the control of the ionosphere based on the method of radio occultation and to identify the main ionospheric parameters ( total electron content of the critical frequency and height of the ionospheric layer F2) on the results of the reception and signal processing of satellite navigation systems GLONASS and GPS. To solve this problem the theory for solving the inverse problem of radio sounding of the ionosphere on the track satellite-the Earth developed. It based on the use of functional connections parameters probing signals and their propagation medium and the mathematical apparatus of solutions of Fredholm integral equations of the 1st kind, belonging to the class of inverse ill-posed problems of atmospheric refraction. On its basis the continuous monitoring technology designed for the reconstruction of the spatiotemporal structure of the ionosphere and solving operational control and the total electron content of the ionosphere by radio translucence method with using radio navigation satellite system GPS/GLONASS. Based on developed technology of continuous monitoring an automated hardware and software complex intended for determining the parameters of altitude distribution of the electron density of the ionosphere of the Earth designed. It uses the information of the navigation satellite system GPS/GLONASS and works in real time. Automated hardware-software system designed based on dual-frequency receiver firm NovAtel, operating signals navigation satellite systems GPS/GLONASS. The complex allows determine the parameters of the Earth's ionosphere by radio translucence method on track satellite - the Earth simultaneously 10-20 azimuthal directions over the territory, an area of about 3 million square km’s.

  11. GIM-TEC adaptive ionospheric weather assessment and forecast system

    NASA Astrophysics Data System (ADS)

    Gulyaeva, T. L.; Arikan, F.; Hernandez-Pajares, M.; Stanislawska, I.

    2013-09-01

    The Ionospheric Weather Assessment and Forecast (IWAF) system is a computer software package designed to assess and predict the world-wide representation of 3-D electron density profiles from the Global Ionospheric Maps of Total Electron Content (GIM-TEC). The unique system products include daily-hourly numerical global maps of the F2 layer critical frequency (foF2) and the peak height (hmF2) generated with the International Reference Ionosphere extended to the plasmasphere, IRI-Plas, upgraded by importing the daily-hourly GIM-TEC as a new model driving parameter. Since GIM-TEC maps are provided with 1- or 2-days latency, the global maps forecast for 1 day and 2 days ahead are derived using an harmonic analysis applied to the temporal changes of TEC, foF2 and hmF2 at 5112 grid points of a map encapsulated in IONEX format (-87.5°:2.5°:87.5°N in latitude, -180°:5°:180°E in longitude). The system provides online the ionospheric disturbance warnings in the global W-index map establishing categories of the ionospheric weather from the quiet state (W=±1) to intense storm (W=±4) according to the thresholds set for instant TEC perturbations regarding quiet reference median for the preceding 7 days. The accuracy of IWAF system predictions of TEC, foF2 and hmF2 maps is superior to the standard persistence model with prediction equal to the most recent ‘true’ map. The paper presents outcomes of the new service expressed by the global ionospheric foF2, hmF2 and W-index maps demonstrating the process of origin and propagation of positive and negative ionosphere disturbances in space and time and their forecast under different scenarios.

  12. Sources of uncertainty in ionospheric modeling: The neutral wind

    NASA Astrophysics Data System (ADS)

    David, Michael; Sojka, Jan J.; Schunk, Robert W.

    2014-08-01

    The neutral wind is a critical input parameter for physics-based ionospheric models, affecting both the height of the F layer and the total electron content. Unfortunately, the currently available models of the thermospheric wind do not seem to represent it very accurately, and this places a serious limitation on the effectiveness of ionospheric modeling and forecasting. We make use of several decades' worth of midlatitude ionosonde observations of the F region peak, in order to compare the effectiveness of several neutral wind models when used as drivers for an ionospheric model. We check the simulation results against the ground truth of the ionosonde observations using the technique of forecast skill scores. We find that with the ionospheric model in use here (the Utah State University Time Dependent Ionospheric Model (TDIM)), a very simple neutral wind pattern outperforms the more complex models. Increases in skill scores as high as 50% are obtained, relative to the reference case of zero wind; also, in some cases, there are similarly large decreases in skill scores. We view this as a sensitivity study, rather than an effort to identify the best wind model in an absolute sense, because any ionospheric model is an assemblage of algorithms, boundary conditions, and drivers that are themselves imperfect. We identify reasons for the large variability in skill scores with respect to season, longitude, and solar cycle level. We close with a brief discussion of other parameters in ionospheric modeling that are similarly uncertain, e.g., a downward electron flux and the Burnside factor.

  13. Active experiments in the ionosphere and variations of geophysical and meteorological parameters

    NASA Astrophysics Data System (ADS)

    Sivokon, Vladimir; Cherneva, Nina; Shevtsov, Boris

    Energy distribution in ionospheric-magnetospheric relations, as one of the possible external climatological factors, may be traced on the basis of the analysis of natural geophysical phenomena such as ionosphere artificial radio radiation and magnetic storms. Development of magnetic disturbances is, to some extent, associated with current variations in electrojet. In its turn, some technologies are known which may affect electrojet and its characteristics. The method, developed by the authors, is based on a complex comparison of different geophysical fields and allows us to determine the degree of active experiment effect on energy change in ionospheric-magnetospheric relations and to evaluate on this basis the degree of active experiment effect on climate in the ionosphere. Within the framework of RAS Presidium Program Project “Determination of climate-forming characteristic changes on the basis of monitoring of geophysical field variations”, investigations have been carried out, which showed the possibility of ionosphere modification effect on the energy of magnetospheric-ionospheric relations. Evaluation of possible climate changes considering ionospheric-magnetospheric relations has not been previously discussed.

  14. Real-Time Ionospheric Characterization and Modeling

    Microsoft Academic Search

    Suman Ganguly; Andrew Brown

    Complete descriptions of spatial and temporal distributions of the ionosphere are obtained using a real-time ionospheric characterization (RTIC) system developed at CRS (and described by Ganguly and Brown, 2001). The system accepts data from various sources, regions, and times, then assimilates these data within the framework of physical ionospheric models, providing a 4-D description of the ionosphere anywhere in the

  15. Solitons and ionospheric modification

    NASA Technical Reports Server (NTRS)

    Sheerin, J. P.; Nicholson, D. R.; Payne, G. L.; Hansen, P. J.; Weatherall, J. C.; Goldman, M. V.

    1982-01-01

    The possibility of Langmuir soliton formation and collapse during ionospheric modification is investigated. Parameters characterizing former facilities, existing facilities, and planned facilities are considered, using a combination of analytical and numerical techniques. At a spatial location corresponding to the exact classical reflection point of the modifier wave, the Langmuir wave evolution is found to be dominated by modulational instability followed by soliton formation and three-dimensional collapse. The earth's magnetic field is found to affect the shape of the collapsing soliton. These results provide an alternative explanation for some recent observations.

  16. Are ionospheric storms the same during different solar cycles?

    NASA Astrophysics Data System (ADS)

    Mendillo, Michael; Narvaez, Clara; Marusiak, Angela G.

    2013-10-01

    ionosphere's response to geomagnetic storms has been studied since the earliest days of terrestrial space physics. In terms of temporal coverage, the largest data sets used extensively have been from the global network of ionosondes. Many previous investigations examined the behavior of the F layer's maximum electron density (Nmax)—often contrasting the difference seen between storms that occur during solar maximum years versus those during solar minimum years. We report on the first attempt to study systematically the patterns of ionospheric disturbance seen during different solar cycles. We select two midlatitude sites with long-term consistency in data: Wallops Island (Virginia) and Hobart (Tasmania)—stations with comparable geographic and geomagnetic coordinates—but in different hemispheres and widely separated longitude sectors. We compare average ionospheric storm patterns using over 200 moderate to severe geomagnetic storms within each of solar cycle #20 (October 1964 to June 1976) and cycle #23 (May 1996 to December 2008). We compute average patterns of ?Nmax(%), measured with respect to monthly mean conditions, following storm and local time. The overall results show remarkable consistency in characteristic patterns of an ionospheric storm: a short positive phase that occurs during the daytime hours on the first day of a storm, with a prolonged negative phase on subsequent days. Statistical differences occur in the overall magnitudes and longevities of these patterns, consistently showing that cycle #23 had less severe ionospheric storms. An analysis of geomagnetic indices shows that degrees of disturbance were, in fact, lower during solar cycle #23 than cycle #20.

  17. Ionospheric mid-latitude response to solar wind discontinuities

    NASA Astrophysics Data System (ADS)

    Munteanu, Costel; Mosna, Zbysek; Kouba, Daniel; Echim, Marius

    2013-04-01

    We have compiled a database of 356 discontinuities detected by both the Advanced Composition Explorer ACE) and Cluster satellites in the solar wind between 2001-2012 and analyzed their ionospheric response. Each discontinuity of the data base is defined by a change of at least 5 nT in less than 5 min in one or more components of the interplanetary magnetic field (IMF). The discontinuities are observed in January-April every year, when Cluster enters the solar wind. The ionospheric effects of solar wind discontinuities are investigated by checking the variations of critical frequencies foF2, the heights of the F layer and the ionospheric plasma dynamics recorded using ground measurement with a time resolution of 15 minutes from mid-latitude digisondes located in Czech Republic. The time delay between solar wind input and the ionospheric response is analyzed using the characteristics and the shape of the ionograms. The geoeffectiveness of the solar wind discontinuities is expressed as correlation between key plasma parameters (e,g, the solar wind velocity, magnetic jump across the discontinuity) and the ionospheric variations. Solar cycle effects are also discussed.

  18. Theory and Observations of Plasma Waves Excited Space Shuttle OMS Burns in the Ionosphere

    Microsoft Academic Search

    P. A. Bernhardt; R. F. Pfaff; P. W. Schuck; D. E. Hunton; M. R. Hairston

    2010-01-01

    Measurements of artificial plasma turbulence were obtained during two Shuttle Exhaust Ionospheric Turbulence Experiments (SEITE) conducted during the flights of the Space Shuttle (STS-127 and STS-129). Based on computer modeling at the NRL PPD and Laboratory for Computational Physics & Fluid Dynamics (LCP), two dedicated burns of the Space Shuttle Orbital Maneuver Subsystem (OMS) engines were scheduled to produce 200

  19. Seasonal and Solar Cycle Variation of the Martian Ionosphere from Nine Years of MARSIS Active Sounding

    NASA Astrophysics Data System (ADS)

    Morgan, David D.; Withers, Paul; Gurnett, Donald; Nemec, Frantisek

    This past June, we celebrated nine years of continuous operation by MARSIS, the radar sounder on the Mars Express spacecraft, in orbit around Mars since Christmas of 2003. The copious data from this instrument in its Active Ionospheric Sounding mode has been used in numerous scientific endeavors to generate empirical models of the Martian ionosphere. The full ionospheric profiles gleaned from analysis of these data are ideal for this kind of effort. Out of more than 170,000 traces collected, we have selected only about 10%, deemed to be of the best quality, and that can be fit to a Chapman layer function. We now have nine years, or 4-3/4 Mars years, worth of ionospheric traces. In addition to sampling nearly five years of seasonal variation, these nine years of data also represent 80% of a normal solar cycle. Therefore, in this work we shall analyze ionospheric traces with the objective of determining variation of atmospheric and ionospheric parameters such as the neutral atmospheric scale height, ionospheric peak altitude, and ionospheric peak density as they vary with the solar cycle and the change in season.

  20. Cubesat-Based Dtv Receiver Constellation for Ionospheric Tomography

    NASA Astrophysics Data System (ADS)

    Bahcivan, H.; Leveque, K.; Doe, R. A.

    2013-12-01

    The Radio Aurora Explorer mission, funded by NSF's Space Weather and Atmospheric Research program, has demonstrated the utility of CubeSat-based radio receiver payloads for ionospheric research. RAX has primarily been an investigation of microphysics of meter-scale ionospheric structures; however, the data products are also suitable for research on ionospheric effects on radio propagation. To date, the spacecraft has acquired (1) ground-based UHF radar signals that are backscattered from meter-scale ionospheric irregularities, which have been used to measure the dispersion properties of meter-scale plasma waves and (2) ground-based signals, directly on the transmitter-spacecraft path, which have been used to measure radio propagation disturbances (scintillations). Herein we describe the application of a CubeSat constellation of UHF receivers to expand the latter research topic for global-scale ionospheric tomography. The enabling factor for this expansion is the worldwide availability of ground-based digital television (DTV) broadcast signals whose characteristics are optimal for scintillation analysis. A significant part of the populated world have transitioned, or soon to be transitioned, to DTV. The DTV signal has a standard format that contains a highly phase-stable pilot carrier that can be readily adapted for propagation diagnostics. A multi-frequency software-defined radar receiver, similar to the RAX payload, can measure these signals at a large number of pilot carrier frequencies to make radio ray and diffraction tomographic measurements of the ionosphere and the irregularities contained in it. A constellation of CubeSats, launched simultaneously, or in sequence over years, similar to DMSPs, can listen to the DTV stations, providing a vast and dense probing of the ionosphere. Each spacecraft can establish links to a preprogrammed list of DTV stations and cycle through them using time-division frequency multiplexing (TDFM) method. An on board program can sort the frequencies and de-trend the phase variations due to spacecraft motion. For a single channel and a spacecraft-DTV transmitter path scan, TEC can be determined from the incremental phase variations for each channel. Determination of the absolute TEC requires knowledge of the absolute phase, i.e., including the number of 2? cycles. The absolute TEC can be determined in the case of multi-channel transmissions from a single tower (most towers house multiple television stations). A CubeSat constellation using DTV transmissions as signals of opportunity is a composite instrument for frontier ionospheric research. It is a novel application of CubeSats to understand the ionospheric response to solar, magnetospheric and upper atmospheric forcing. Combined tomographic measurements of ionospheric density can be used to study the global-scale ionospheric circulation and small-scale ionospheric structures that cause scintillation of trans-ionospheric signals. The data can support a wide range of studies, including Sub-auroral Polarization Streams (SAPS), low latitude plasma instabilities and the generation of equatorial spread F bubbles, and the role of atmospheric waves and layers and sudden stratospheric warming (SSW) events in traveling ionospheric disturbances (TID).

  1. The ionosphere of Triton

    NASA Technical Reports Server (NTRS)

    Majeed, T.; Mcconnell, J. C.; Strobel, D. F.; Summers, M. E.

    1990-01-01

    A model of the atmospheric temperature structure and composition inferred from the Voyager (UVS) solar occultations was used together with a one-dimensional chemical diffusive model to interpret the Voyager Radio Science Spectrometer (RSS) ingress measurements of Triton's electron density. Although N2(+) is the major ion created, N(+) produced by dissociative ionization is the dominant ion. Reaction of thermospheric H2, produced by Lyman-alpha dissociation of CH4 in the lower atmosphere, is the major loss for N(+) ions and maintains these ions in PCSS below 600 km. Solar EUV ionization cannot generate electron densities at the magnitude measured by the RSS experiment and an additional ionization source about 3 x 10 to the 8th ions/sq cm per sec is required. The ionosphere may undergo a transition from PCSS to diffusive control if the N(+) ion production rates were greater than the H2 flux derived from CH4. In this case, the upward flowing H2 is totally converted to H by reaction with N(+) and the remaining N(+) ions recombine radiatively to create an ionosphere under diffusive control above the peak.

  2. Ionospherically reflected proton whistlers

    NASA Astrophysics Data System (ADS)

    Vavilov, D. I.; Shklyar, D. R.

    2014-12-01

    We present experimental observations and detailed investigation of the variety of proton whistlers that includes transequatorial and ionospherically reflected proton whistlers. The latter have previously been indicated from numerical modeling of spectrograms. The study is based on six-component ELF wave data from the Detection of Electro-Magnetic Emissions Transmitted from Earthquake Regions (DEMETER) satellite which permits to obtain not only spectrograms displaying the power spectral density but also such wave properties as the polarization, wave normal angle, wave refractive index, and normalized parallel component of the Poynting vector. The explanation of various types of proton whistlers is based on the properties of ion cyclotron wave propagation in a multicomponent magnetoplasma, with special consideration of the effect of ion hybrid resonance reflection. Analysis of experimental data is supplemented by numerical modeling of spectrograms that reproduces the main features of experimental ones. As a self-contained result, we provide conclusive experimental evidences that the region illuminated by a lightning stroke in the Earth-ionosphere waveguide may spread over a distance of 4000 km in both hemispheres.

  3. Artificial modification meeting reminder

    NASA Astrophysics Data System (ADS)

    Gordon, W. E.

    A symposium on artificial modification of the ionosphere by high-powered radio waves (V. V. Migulin, Honorary Chairman) will be held September 19-23, 1988, at the Scandic Hotel, Tromso, Norway. The symposium, sponsored by Union Radio Scientifique Internationale Commissions (URSI) G and H, is in the URSI series which started at Suzdal in 1983. Information on the scientific program is available from V.V. Migulin, U.S.S.R. Academy of Sciences, 103907, Moscow Center, Marx Avl8, U.S.S.R.; Peter Stubbe, Max- Planck-Institut fuer Aeronomy, D-3411 Katlenburg- Lindau 3, Federal Republic of Germany; or W.E. Gordon, Rice University, Space Physics and Astronomy Dept., Houston, TX 77251. For local arrangements information, contact Asgeir Brekke, Institute Matematisk Realfag, Aurora Observatory, Box 953, N-9001, Tromso, Norway.

  4. Artificial Limbs

    MedlinePLUS

    ... you are missing an arm or leg, an artificial limb can sometimes replace it. The device, which is ... activities such as walking, eating, or dressing. Some artificial limbs let you function nearly as well as before.

  5. Lightning induced brightening in the airglow layer

    Microsoft Academic Search

    W. L. Boeck; O. H. Vaughan Jr.; R. Blakeslee; B. Vonnegut; M. Brook

    1992-01-01

    This report describes a transient luminosity observed at the altitude of the airglow layer (about 95 km) in coincidence with a lightning flash in a tropical oceanic thunderstorm directly beneath it. This event provides new evidence of direct coupling between lightning and ionospheric events. This luminous event in the ionosphere was the only one of its kind observed during an

  6. Evaluation of the STORM-Time Ionospheric Empirical Model for the Bastille Day event

    Microsoft Academic Search

    E. A. Araujo-Pradere; T. J. Fuller-Rowell

    2001-01-01

    Recent theoretical model simulations of the ionospheric response to geomagnetic storms have provided the understanding for\\u000a the development of an empirical storm-time ionospheric model (STORM). The empirical model is driven by the previous time-history\\u000a of a\\u000a p, and is designed to scale the quiet-time F-layer critical frequency (f\\u000a o\\u000a F\\u000a 2) to account for storm-time changes in the ionosphere. The

  7. Phenomena associated with complex (dusty) plasmas in the ionosphere during high-speed meteor showers

    SciTech Connect

    Kopnin, S. I. [Institute for Dynamics of Geospheres, RAS, Moscow 119334 (Russian Federation); Popel, S. I. [Institute for Dynamics of Geospheres, RAS, Moscow 119334 (Russian Federation); Space Research Institute, RAS, Moscow 117997 (Russian Federation); Yu, M. Y. [Department of Physics, Institute for Fusion Theory and Simulation, Zhejiang University, Hangzhou 310027, China and Institute for Theoretical Physics I, Ruhr University, D-44780 Bochum (Germany)

    2009-06-15

    Formation of dusty plasmas in the Earth's ionosphere at 80-120 km altitudes during high-speed meteor showers and its detectable manifestations are discussed. Emphasis is given to ground-based observations such as detection of low-frequency (<50 Hz) ionospheric radio noise, ground-based observations of infrasonic waves, and amplification of the intensity of green radiation at 557.7 nm from a layer at the 110-120 km altitude in the lower ionosphere. The physical processes responsible for these manifestations are considered.

  8. Estimation of the Doppler frequency and direction of arrival of the ionospherically propagated HF signals

    NASA Astrophysics Data System (ADS)

    Su, Hongtao; Liu, Hongwei; Shui, Penglang; Bao, Zheng

    2009-08-01

    High-frequency (HF) signals reflected from different points within each ionospheric layer may have slightly different Doppler frequencies and angles of arrival. The superposition of these signals leads to time varying and nonplanar wavefronts. Investigation of temporal and spatial characteristics of the ionospherically propagated HF signals plays an important role in designing the signal processing algorithms for the HF over-the-horizon radar (OTHR). A cost-efficient superresolution algorithm for simultaneously estimating the Doppler frequencies and angles of arrival of the ionospherically propagated HF signals is proposed in this paper. The effectiveness of the proposed algorithm is verified by the experimental data from a trial HF OTHR. Furthermore, the superposition model with the HF signal reflected by a smooth ionospheric layer consisting of a number of submode signals is also confirmed by the experimental data processing results.

  9. Terahertz resonant artificial interface layers

    Microsoft Academic Search

    D. Dietze; J. Darmo; M. Martl; K. Unterrainer

    2010-01-01

    Planar metamaterials, so-called metasurfaces, can efficiently be described by a modified transfer matrix formalism, that takes into account anisotropic, conductive interfaces. This method is applied for evaluation of the transmission of THz pulses through different metasurface geometries.

  10. Artificial Intelligence.

    ERIC Educational Resources Information Center

    Information Technology Quarterly, 1985

    1985-01-01

    This issue of "Information Technology Quarterly" is devoted to the theme of "Artificial Intelligence." It contains two major articles: (1) Artificial Intelligence and Law" (D. Peter O'Neill and George D. Wood); (2) "Artificial Intelligence: A Long and Winding Road" (John J. Simon, Jr.). In addition, it contains two sidebars: (1) "Calculating and…

  11. Analysis of appearance of moving ionospheric disturbances of the “sickle” type at middle latitudes

    Microsoft Academic Search

    F. I. Vybornov; E. E. Mityakova; A. V. Rakhlin; N. D. Krupenya

    1997-01-01

    We present the results of analysis of the data of vertical ionospheric sounding at the Zimenki test site (Nizhny Novgorod).\\u000a The January and July ionograms are used to plot the dependences of the number of “sickle” type disturbances on the time of\\u000a the day for the period from 1996 to 1992. A comparison with the scattering in an ionospheric F-layer

  12. Ionospheric effects of the solar eclipse of September 23, 1987, around the equatorial anomaly crest region

    Microsoft Academic Search

    Kang Cheng; Yinn-Nien Huang; Sen-Wen Chen

    1992-01-01

    The ionospheric responses to the solar eclipse of September 23, 1987, in the equatorial anomaly crest region have been investigated by using ionospheric vertical sounding, VLF propagation delay time, and differential Doppler shift data observed at Chungli, (24.91 deg N, 121.24 deg E). It has been found that temporal variations of the F1 layer and D region are mainly controlled

  13. Ionospheric transients observed at mid-latitudes prior to earthquake activity in Central Italy

    Microsoft Academic Search

    P. Nenovski; Ch. Spassov; M. Pezzopane; U. Villante; M. Vellante; M. Serafimova

    2010-01-01

    Ionograms from Rome (41.8N, 12.5E) and Sofia (42.4N, 23.2E) ionospheric stations during earthquake (EQ) activity with magnitude (M) between 5 and 6 in Central Italy are analyzed. It is found that several ionospheric disturbances occur in the intermediate E-F region before the EQ shock. In fact, besides sporadic E (Es) layer development (of type h) of short duration (transients), fmin

  14. Plasma Interactions in Titan's Ionosphere

    E-print Network

    Richard, Matthew

    2013-05-31

    calculations of the thermal electron population (electrons with energies less than 2 eV), and chemical reactions in the ionosphere. The results of these models will be compared to data collected by instruments aboard Cassini. Modeled ion production rates...

  15. Ionospheric scintillation studies

    NASA Technical Reports Server (NTRS)

    Rino, C. L.; Freemouw, E. J.

    1973-01-01

    The diffracted field of a monochromatic plane wave was characterized by two complex correlation functions. For a Gaussian complex field, these quantities suffice to completely define the statistics of the field. Thus, one can in principle calculate the statistics of any measurable quantity in terms of the model parameters. The best data fits were achieved for intensity statistics derived under the Gaussian statistics hypothesis. The signal structure that achieved the best fit was nearly invariant with scintillation level and irregularity source (ionosphere or solar wind). It was characterized by the fact that more than 80% of the scattered signal power is in phase quadrature with the undeviated or coherent signal component. Thus, the Gaussian-statistics hypothesis is both convenient and accurate for channel modeling work.

  16. Dayside ionospheric conductivities at Mars

    Microsoft Academic Search

    Hermann Opgenoorth; Ranvir Dhillon; Lisa Rosenqvist; Mark Lester; Niklas Edberg; Steve Milan; Paul Withers; David Brain

    2010-01-01

    We present estimates of the day-side ionospheric conductivities at Mars based on magnetic field measurements by Mars Global Surveyor (MGS) at altitudes down to ?100km during aerobraking orbits early in the mission. At Mars, the so-called ionospheric dynamo region, where plasma\\/neutral collisions permit electric currents perpendicular to the magnetic field, lies between 100 and 250km altitude. We find that the

  17. Relationship between strong range SF and ionospheric scintillation in low latitude ionosphere

    NASA Astrophysics Data System (ADS)

    Shi, Jiankui; Wang, Guojun; Wang, Zheng; Wang, Xiao; Zherebtsov, Geliy; Romanova, Erina; Ratovsky, Konst

    2013-04-01

    The data from the Digisondes and the ionospheric scintillation monitors located at the low latitude station Hainan (109.1°E, 19.5°N geogr., dip lat. 9°N) and Vanimo (141.3°E, 2.7°N geogr., dip lat. 11°S) are analyzed to study the ionospheric spread F (SF) and its correlation with the scintillation. According to the Digisonde observation in the low latitude ionosphere, we divide the SF as four types: range SF (R-SF), strong range SF (S-SF), frequency SF (F-SF), and mixed SF (M-SF). The S-SF is characterized by extended range spread on F layer echo traces that significantly extend beyond the local foF2 value. For the Hainan station, the results show that the maximum and minimum of the occurrence of S-SF appeared in nearly the same months as those of the GPS L-band scintillations. The variation of the S-SF occurrence was also similar to that of the scintillation. From 2003 to 2007, both the S-SF and the scintillation occurrences decreased from the high solar activity year to the low solar activity year. The correlation coefficient between the occurrences of the S-SF and the GPS L-band scintillation was as high as 0.93 suggesting associated mechanisms producing S-SF and scintillation. For the Vanimo station, the data analysis showed that the occurrence variation of the S-SF was also similar to that of the scintillation. The correlation coefficient between the two phenomena was as high as 0.88, which supports the view of the associated mechanisms to produce S-SF and scintillation. Electron density depletions extending from the bottomside to the topside ionosphere are the most likely cause explaining the high correlation.

  18. The worldwide ionospheric data base

    NASA Technical Reports Server (NTRS)

    Bilitza, Dieter

    1989-01-01

    The worldwide ionospheric data base is scattered over the entire globe. Different data sets are held at different institutions in the U.S., U.S.S.R., Australia, Europe, and Asia. The World Data Centers on the different continents archive and distribute part of the huge data base; the scope and cross section of the individual data holdings depend on the regional and special interest of the center. An attempt is made to pull together all the strings that point toward different ionospheric data holdings. Requesters are provided with the information about what is available and where to get it. An attempt is also made to evaluate the reliability and compatibility of the different data sets based on the consensus in the ionospheric research community. The status and accuracy of the standard ionospheric models are also discussed because they may facilitate first order assessment of ionospheric effects. This is a first step toward an ionospheric data directory within the framework of NSSDC's master directory.

  19. Comparative statistical and spectral studies of seismic and non-seismic sub-ionospheric VLF anomalies

    NASA Astrophysics Data System (ADS)

    Wolbang, Daniel; Biernat, Helfried; Schwingenschuh, Konrad; Eichelberger, Hans; Prattes, Gustav; Besser, Bruno; Boudjada, Mohammed Y.; Rozhnoi, Alexander; Solovieva, Maria; Biagi, Pier Francesco; Friedrich, Martin

    2013-04-01

    We present a comparative study of seismic and non-seismic sub-ionospheric VLF anomalies. Our method is based on parameter variations of the sub-ionospheric VLF waveguide formed by the surface and the lower ionosphere. The used radio links working in the frequency range between 10 and 50 kHz, the receivers are part of the European and Russian networks. Various authors investigated the lithopsheric-atmospheric-ionospheric coupling and predicted the lowering of the ionosphere over earthquake preparation zones [1]. The received nighttime signal of a sub-ionospheric waveguide depends strongly on the height of the ionospheric E-layer, typically 80 to 85 km. This height is characterized by a typical gradient of the electron density near the atmospheric-ionospheric boundary [2]. In the last years it has been turned out that one of the major issues of sub-ionospheric seismo-electromagnetic VLF studies are the non-seismic influences on the links, which have to be carefully characterized. Among others this could be traveling ionospheric disturbances, geomagnetic storms as well as electron precipitation. Our emphasis is on the analysis of daily, monthly and annual variations of the VLF amplitude. To improve the statistics we investigate the behavior and typical variations of the VLF amplitude and phase over a period of more than 2 years. One important parameter considered is the rate how often the fluctuations are falling below a significant level derived from a mean value. The temporal variations and the amplitudes of these depressions are studied for several years for sub-ionospheric VLF radio links with the receivers in Graz and Kamchatka. In order to study the difference between seismic and non-seismic turbulences in the lower ionosphere a power spectrum analysis of the received signal is performed too. We are especially interested in variations T>6 min which are typical for atmospheric gravity waves causing the lithospheric-atmospheric-ionospheric coupling [3]. All measured and derived VLF parameters are compared with VLF observations several weeks before an earthquake (e.g. L'Aquila, Italy, April 6, 2009) and with co- and post-seismic phenomena. It is shown that this comparative study will improve the one parameter seismo-electromagnetic VLF methods. References: [1] A. Molchanov, M. Hayakawa: Seismo-Electromagnetics and related Phenomena: History and latest results, Terrapub, 2008. [2] S. Pulinets, K. Boyarchuk: Ionospheric Precursors of Earthquakes, Springer, 2004 [3] A. Rozhnoi et al.: Observation evidences of atmospheric Gravity Waves induced by seismic activity from analysis of subionospheric LF signal spectra, National Hazards and Earth System Sciences, 7, 625-628, 2007.

  20. Nighttime ionosphere thermosphere coupling observed during an intense geomagnetic storm

    NASA Astrophysics Data System (ADS)

    Fagundes, P. R.; Muella, M. T. A. H.; Bittencourt, J. A.; Sahai, Y.; Lima, W. L. C.; Guarnieri, F. L.; Becker-Guedes, F.; Pillat, V. G.; Ferreira, A. S.; Lima, N. S.

    The electrodynamics of the ionosphere in the tropical region presents various scientific aspects, which remain subject of intensive investigations and debates by the scientific community. During the year 2002, in a joint project between the Universidade do Vale do Paraíba (UNIVAP) and Universidade Luterana do Brasil (ULBRA), a chain of three Canadian Advanced Digital Ionosondes (CADIs) was established nearly along the geomagnetic meridian direction, for tropical ionospheric studies, such as, changes and response due to geomagnetic disturbances and thermosphere ionosphere coupling and the generation and dynamics of ionospheric irregularities, in the Brazilian sector. The locations of the three ionosondes stations are São José dos Campos (23.2°S, 45.9°W, dip latitude 17.6°S under the southern crest of equatorial ionospheric anomaly), Palmas (10.2°S, 48.2°W, dip latitude 5.5°S near the magnetic equator) and Manaus (2.9°S, 60.0°W, dip latitude 6.4°N between the geographic and geomagnetic dip equators). It should be pointed out that Palmas and Manaus are located on the opposite sides of the magnetic equator but both are south of the geographic equator. The three CADIs work in time-synchronized mode and obtain ionograms every 5 min. This configuration of the ionospheric sounding stations allowed us to study the F-region dynamics during geomagnetically disturbed period in the meridional direction. Just after the installation and testing of the three CADIs, on September 05, 2002 a coronal mass ejection (CME) left the Sun and about 2 days after the CME left the Sun, it reached the Earth’s magnetosphere and complex and multi step events took place during the period September 07 09. In the study we note that the equatorial stations located north (Manaus, dip latitude 6.4°N) and south (Palmas, dip latitude 5.5°S) of the dip equator presented significant F-layer height asymmetries during the storm main phase. In addition, the low-latitude station SJC (dip latitude 17.6°S) presented decrease in the F-layer densities (negative phase), whereas Palmas presented increase in the F-layer densities (positive phase) during the main phase. This was followed by positive phase at both the stations. During the first night of the recovery phase a strong formation and evolution of large-scale ionospheric irregularities (equatorial spread-F (ESF)) was observed, but on the second night of the recovery phase, there was strong and almost simultaneous sporadic E (Es) formation at all three stations. During the presence of Es, spread-F formation is not observed, indicating the suppression of spread-F, possibly by sporadic E.

  1. A simulation study with a new residual ionospheric error model for GPS radio occultation climatologies

    NASA Astrophysics Data System (ADS)

    Danzer, J.; Healy, S. B.; Culverwell, I. D.

    2015-01-01

    In this study, a new model was explored, which corrects for higher order ionospheric residuals in global positioning system (GPS) radio occultation (RO) data. Recently, the theoretical basis of this new "residual ionospheric error model" has been outlined (Healy and Culverwell, 2015). The method was tested in simulations with a one-dimensional model ionosphere. The proposed new model for computing the residual ionospheric error is the product of two factors, one of which expresses its variation from profile-to-profile and from time-to-time in terms of measurable quantities (the L1 and L2 bending angles), the other of which describes the weak variation with altitude. A simple integral expression for the residual error (Vorob'ev and Krasil'nikova, 1994) has been shown to be in excellent numerical agreement with the exact value, for a simple Chapman layer ionosphere. In this case, the "altitudinal" element of the residual error varies (decreases) by no more than about 25% between ~10 and ~100 km for physically reasonable Chapman layer parameters. For other simple model ionospheres the integral can be evaluated exactly, and results are in reasonable agreement with those of an equivalent Chapman layer. In this follow-up study the overall objective was to explore the validity of the new residual ionospheric error model for more detailed simulations, based on modelling through a complex three-dimensional ionosphere. The simulation study was set up, simulating day and night GPS RO profiles for the period of a solar cycle with and without an ionosphere. The residual ionospheric error was studied, the new error model was tested, and temporal and spatial variations of the model were investigated. The model performed well in the simulation study, capturing the temporal variability of the ionospheric residual. Although, it was not possible, due to high noise of the simulated bending angle profiles at mid to high latitudes, to perform a thorough latitudinal investigation of the performance of the model, first positive and encouraging results were found at low latitudes. Furthermore, first application tests of the model on the data showed a reduction on temperature level of the ionospheric residual at 40 km from about -2.2 to -0.2 K.

  2. The synthesis of travelling ionospheric disturbance (TID) signatures in HF radar observations using ray tracing

    E-print Network

    Paris-Sud XI, Université de

    The synthesis of travelling ionospheric disturbance (TID) signatures in HF radar observations using-time-intensity plots when travelling ionospheric disturbances (TIDs) are present. These signatures, in particular- iments. Key words. Ionosphere (auroral ionosphere; ionosphere ±atmosphere interactions; ionospheric

  3. Diagnostics of the ionospheric turbulence by wide band radio signals

    NASA Astrophysics Data System (ADS)

    Sergeev, Evgeny; Shindin, Alexey; Grach, Savely

    Results of the investigations of the time-space structure of the HF-pumped ionospheric volume above the SURA heating facility are presented. The method of investigations is based on mea-surements of the amplitude and phase of pulsed (pulse duration < 200µs and interpulse period 20-200 ms), wide band (˜ 300 kHz) and powerful (Effective Radiated Power ˜ 20-150 MW) radio signals radiated by three SURA transmitter and used for multifrequency sounding of the ionospheric plasma in frequency band up to ˜ 1 MHz. For simultaneous modification of the ionosphere and its diagnostics, technical capabilities of SURA transmitter-receiver system, specially elaborated time-frequency modes of transmitter operation, space diversity three point reception, wide band signal recording, digital filtering, spectral and correlation analysis of the short radio pulses reflected from ionosphere were used. As a result of numerically solved in-verse problem of vertical sounding of the HF-perturbed ionosphere, dynamic behavior of the electron plasma density variations was obtained in the regions close to plasma resonance and upper hybrid resonance of the pump wave. In our experiments the pumping usually leaded to plasma expulsion from the resonance regions. A magnitude of artificial plasma density pertur-bations achieved 0.8% from the background density for pump power about P 60 MW ERP. The methods of a similarity and full correlation analysis were used for pulse signal amplitude processing, which were obtained by diversity three point reception with the receiving aerial separation of 84 m. As a result, novel data on fine structure of the space field of the vertical and horizontal velocities of plasma in the perturbed ionosphere volume with high time (up to 20 ms) and frequency (˜ 1 kHz) resolution are obtained. This frequency resolution can be translated into altitude resolution (˜ 50-100 m) in the ionosphere. The work was supported by RFBR grants 10-02-00642, 09-02-01150 and Federal Special-purpose Program "Scientific and pedagogical personnel of innovative Russia".

  4. Global Imaging Monitor of the Ionosphere (GIMI): a far-ultraviolet imaging experiment on ARGOS

    NASA Astrophysics Data System (ADS)

    Carruthers, George R.; Seeley, Timothy D.

    1996-11-01

    The Global Imaging Monitor of the Ionosphere (GIMI) is one of several remote-sensing instruments under development for flight on the Air Force Space Test Program's P91-1 Advanced Research and Global Observation Satellite, planned for launch in 1997. The primary objective of GIMI is to map and monitor the ionospheric O+ and electron density on a global basis, by means of wide-field imaging of ionospheric far-ultraviolet emissions. it will also be used to detect and characterize local perturbations of the ionosphere due to natural and artificial events. Atomic nitrogen in the upper atmosphere will be measured by nitric oxide nightglow emissions resulting from its combination with atomic oxygen. Observations of stellar occultations by Earth's atmosphere will be used to measure the neutral density distributions of N2 and O2. Other objectives are to map and monitor the ultraviolet background in near-Earth space due to ionospheric and airglow emissions and extraterrestrial sources, and to obtain all-sky surveys of celestial point and diffuse sources. GIMI consists of two wide-field imaging cameras sensitive in three far- and extreme-UV spectral ranges (75 - 110 nm, 131 - 160 nm, and 131 - 200 nm), selected for their utility in day and night ionospheric and neutral atmospheric remote sensing. The GIMI sensors are based on electron-bombarded CCD arrays, with opaque alkali halide photocathodes and Schmidt or all-reflective optical systems.

  5. Spacelab-2 plasma depletion experiments for ionospheric and radio astronomical studies.

    PubMed

    Mendillo, M; Baumgardner, J; Allen, D P; Foster, J; Holt, J; Ellis, G R; Klekociuk, A; Reber, G

    1987-11-27

    The Spacelab-2 Plasma Depletion Experiments were a series of studies to examine shuttle-induced perturbations in the ionosphere and their application to ground-based radio astronomy. The space shuttle Challenger fired its orbital maneuvering subsystem engines on 30 July and 5 August 1985, releasing large amounts of exhaust molecules (water, hydrogen, and carbon dioxide) that caused the electrons and ions in Earth's upper atmosphere to chemically recombine, thereby creating so-called "ionospheric holes." Two burns conducted over New England produced ionospheric peak depletions ranging from 25 to 50 percent, affected the ionosphere over a 200-kilometer altitude range, and covered 1 degrees to 2 degrees of latitude. Optical emissions associated with the hole spanned an area of several hundred thousand square kilometers. A third burn was conducted over a low-frequency radio observatory in Hobart, Australia, to create an "artificial window" for ground-based observations at frequencies normally below the natural ionospheric cutoff (penetration) frequency. The Hobart experiment succeeded in making high-resolution observations at 1.7 megahertz through the induced ionospheric hole. PMID:17744364

  6. Spacelab-2 plasma depletion experiments for ionospheric and radio astronomical studies

    NASA Astrophysics Data System (ADS)

    Mendillo, M.; Baumgardner, J.; Allen, D. P.; Foster, J.; Holt, J.

    1987-11-01

    The Spacelab-2 Plasma Depletion Experiments were a series of studies to examine Shuttle-induced perturbations in the ionosphere and their application to ground-based radio astronomy. The Space Shuttle Challenger fired its orbital maneuvering subsystem engines, releasing large amounts of exhaust molecules that caused the electrons and ions in earth's upper atmosphere to chemically recombine, thereby creating so-called 'ionospheric holes'. Two burns conducted over New England produced ionospheric peak depletions ranging from 25 to 50 percent, affected the ionosphere over a 200-kilometer altitude range, and covered 1 to 2 deg of latitude. Optical emissions associated with the hole spanned an area of several hundred thousand square kilometers. A third burn was conducted over a low-frequency radio observatory in Hobart, Australia, to create an 'artificial window' for ground-based observations at frequencies normally below the natural ionospheric cutoff (penetration) frequency. The Hobart experiment succeeded in making high-resolution observations at 1.7 megahertz through the induced ionospheric hole.

  7. Ionospheric parameter analysis techniques and anomaly identification in periods of ionospheric perturbations

    NASA Astrophysics Data System (ADS)

    Mandrikova, Oksana; Polozov, Yury; Fetisova Glushkova, Nadejda; Shevtsov, Boris

    In the present paper we suggest intellectual techniques intended for the analysis of ionospheric parameters. These techniques are directed at studying dynamic processes in the "magnetosphere-ionosphere" system during perturbations. Using the combination of the wavelet transform and neural networks, the authors have developed a technique of approximating the time variation of ionospheric parameters. This technique allows us to make data predictions and detect anomalies in the ionosphere. Multiscale component approximations of the critical frequency of the ionosphere layer F2 were constructed. These approximations can be presented in the following form: begin{center} c_{l,k+m} (t) = varphi_m(3) Bigl (sum_i omega(3_{mi}) varphi_i(2) Bigl (sum_j omega(2_{ij}) varphi_j(1) Bigl (sum_k omega(1_{jk}) c_{l,k} (t) Bigr ) Bigr ) Bigr ) , where c_{l,k} = bigl < f , Psi_{l,k} bigr > ; Psi_{l,k} (t) = 2(l/2) Psi (2(l) t - k) is the wavelet basis; omega(1_{jk}) are the weighting coefficients of the neuron j of the network input layer; omega(2_{ij}) are the weighting coefficients of the neuron i of the network hidden layer; omega(3_{mi}) are the weighting coefficients of the neuron m of the network output layer; varphi(1_j) (z) = varphi(2_i) (z) = (1)/(1+exp(-z))) ; varphi(3_m) (z) = x*z+y . The coefficients c_{l,k} can be found as a result of transforming the original function f into the space with the scale l . In order to obtain the approximations of the time variation of data, neural networks can be united in groups. In the paper we have suggested a multicomponent time variation model of ionospheric parameters, which makes it possible to perform the analysis of the ionospheric dynamic mode, receive predictions about parameter variations, and detect anomalies in periods of perturbations. The multicomponent model also allows us to fill missing values in critical frequency data taking into account diurnal and seasonal variations. Identification of the model is based on combining the wavelet transform with autoregressive integrated moving average methods. The general expression of the multicomponent model is f_0 (t) = sum_{mu = /line{1,M}} sum_{k = /line{1,N_1(mu}}) s_{l,k}(mu) (t) b_{l,k}(mu) (t) , where s_{l,k}(mu) (t) = sum_{q=1}(p_l(mu)) gamma_{l,q}(mu) w(mu_{l,k-q}) (t) - sum_{n=1}(h_l(mu)) theta_{l,n}(mu) alpha(mu_{l,k-n}) (t) is the estimated value of the mu -th component, p_l(mu) is the autoregressive model order of the mu -th component, gamma_{l,q}(mu) are the autoregressive parameters of the mu -th component, w_{l,k}(mu) (t) = nabla(nu(mu)) beta_{l,k}(mu) (t) , nu(mu) is the difference order of the mu -th component, beta_{l,k}(mu) are the decomposition coefficients of the mu -th component, h_l(mu) , theta_{l,k}(mu) are the model orders and moving average parameters of the mu -th component model, alpha(mu_{l,k}) are the residual errors of the mu -th component model, M is the number of characteristic components, N_l(mu) is the length of the mu -th component, b_{l,k}(mu) is the wavelet basis of the mu -th component, l is the scale. Using these techniques we have obtained the approximation of the ionospheric critical frequency time variation for regions located in Kamchatka and Magadan. The analysis of the quiet variation of the parameters was performed, the 5-hour prediction was made, and anomalies occurring in periods of increased solar activity and prior to strong earthquakes in Kamchatka were discovered in the ionosphere. The developed methods are useful for studying the properties of ionospheric perturbations, obtaining information about various parameters of ionospheric plasma irregularities and the dynamic mode of these parameters.

  8. Fine structure of artificial auroral rays

    SciTech Connect

    Mishin, E.V.; Ivchenko, V.N.; Milinevskii, G.P.

    1981-01-01

    Luminosity height profiles measured in the ray of artificial and natural auroras by highly sensitive television equipment with a super-orthicon are presented. It is noted that the photographic registration of the video monitor display image was made at a rate of 5 frames/sec and an exposition time of 0.17 sec. The artificial auroras were generated by electron beams with an energy of 7.2 keV injected into the ionosphere from a rocket. Seven photos are obtained showing a double-peak luminosity distribution.

  9. Plasma sheet boundary layer

    Microsoft Academic Search

    T. E. Eastman; L. A. Frank; W.K. Peterson; W. Lennartsson

    1984-01-01

    The plasma sheet boundary layer is a temporally variable transition region located between the magnetotail lobes and the central plasma sheet. We have made a survey of these regions by using particle spectra and three-dimensional velocity-space distributions sampled by the ISEE 1 LEPEDEA. Ion composition measurements obtained by the Lockhead ion mass spectrometers indicate that ionospheric ions play a crucial

  10. The calculation of ionospheric ray paths

    E-print Network

    Koehler, Buford Ray

    1967-01-01

    path calculation by calculating ray paths from a cosmic radio source to a satellite in orbit above the level of the ionosphere. Radiation of this type may be totally reflected by the ionosphere thus making reception on the earth impossible... ray paths with constant frequency and variable angle of propagation and range, parabolic ionosphere of electrons assumed, earth's magnetic field neglected 2- 1 The vertical and lateral deviations of a radio wave propagated in a plane ionosphere...

  11. Earthquake-Ionosphere Coupling Processes

    NASA Astrophysics Data System (ADS)

    Kamogawa, Masashi

    After a giant earthquake (EQ), acoustic and gravity waves are excited by the displacement of land and sea surface, propagate through atmosphere, and then reach thermosphere, which causes ionospheric disturbances. This phenomenon was detected first by ionosonde and by HF Doppler sounderin the 1964 M9.2 Great Alaskan EQ. Developing Global Positioning System (GPS), seismogenic ionospheric disturbance detected by total electron content (TEC) measurement has been reported. A value of TEC is estimated by the phase difference between two different carrier frequencies through the propagation in the dispersive ionospheric plasma. The variation of TEC is mostly similar to that of F-region plasma. Acoustic-gravity waves triggered by an earthquake [Heki and Ping, EPSL, 2005; Liu et al., JGR, 2010] and a tsunami [Artu et al., GJI, 2005; Liu et al., JGR, 2006; Rolland, GRL, 2010] disturb the ionosphere and travel in the ionosphere. Besides the traveling ionospheric disturbances, ionospheric disturbances excited by Rayleigh waves [Ducic et al, GRL, 2003; Liu et al., GRL, 2006] as well as post-seismic 4-minute monoperiodic atmospheric resonances [Choosakul et al., JGR, 2009] have been observed after the large earthquakes. Since GPS Earth Observation Network System (GEONET) with more than 1200 GPS receiving points in Japan is a dense GPS network, seismogenic ionospheric disturbance is spatially observed. In particular, the seismogenic ionospheric disturbance caused by the M9.0 off the Pacific coast of Tohoku EQ (henceforth the Tohoku EQ) on 11 March 2011 was clearly observed. Approximately 9 minutes after the mainshock, acoustic waves which propagated radially emitted from the tsunami source area were observed through the TEC measurement (e. g., Liu et al. [JGR, 2011]). Moreover, there was a depression of TEC lasting for several tens of minutes after a huge earthquake, which was a large-scale phenomenon extending to a radius of a few hundred kilometers. This TEC depression may be an ionospheric phenomenon attributed to tsunami, termed tsunamigenic ionospheric hole (TIH) [Kakinami and Kamogwa et al., GRL, 2012]. After the TEC depression accompanying a monoperiodic variation with approximately 4-minute period as an acoustic resonance between the ionosphere and the solid earth, the TIH gradually recovered. In addition, geomagnetic pulsations with the periods of 150, 180 and 210 seconds were observed on the ground in Japan approximately 5 minutes after the mainshock. Since the variation with the period of 180 seconds was simultaneously detected at the magnetic conjugate of points of Japan, namely Australia, field aligned currents along the magnetic field line were excited. The field aligned currents might be excited due to E and F region dynamo current caused by acoustic waves originating from the tsunami. This result implies that a large earthquake generates seismogenic field aligned currents. Furthermore, monoperiodical geomagnetic oscillation pointing to the epicenter of which velocity corresponds to Rayleigh waves occurs. This may occur due to seismogenic arc-current in E region. Removing such magnetic oscillations from the observed data, clear tsunami dynamo effect was found. This result implies that a large EQ generates seismogenic field aligned currents, seismogenic arc-current and tsunami dynamo current which disturb geomagnetic field. Thus, we found the complex coupling process between a large EQ and an ionosphere from the results of Tohoku EQ.

  12. Ionospheric characteristics in response to gradients of magnetic eta index

    NASA Astrophysics Data System (ADS)

    Dziak-Jankowska, Beata; Stanislawska, Iwona; Tomasik, Lukasz; Ernst, Tomasz

    We present the analysis of correlation of typical ionospheric characteristics with the changes of the magnetic eta index. The eta index is defined as the square root of a ratio of the energy of the external part of the vertical component to that of the horizontal components. The values of eta typical ranged between 0 and 0.1 sometimes exceeds 1 or even higher values which means that the changes of the vertical component of magnetic field is larger than the changes of the horizontal magnetic field components. In most cases when eta index indicate some magnetic disturbances other magnetic indices (i.e. Kp, Dst) inform about quiet conditions. During increasing phase of eta index value ionospheric characteristics present large deviations from their monthly median. Our analysis for 2004 present deviations of foE up to +/- 0.9 MHz and both deviations negative and positive appear during enormous increase of eta index. Another ionospheric characteristic, the virtual height of F2 layer (h’F2) decreases in some cases up to 90 km from monthly median value. Here the analysis of correlation between ionospheric characteristics and the eta index will be presented taking into account time interval covering the whole solar cycle for European region.

  13. Interplanetary Radio Transmission Through Serial Ionospheric and Material Barriers

    SciTech Connect

    Fields, David [ORNL; Kennedy, Robert G [ORNL; Roy, Kenneth I [ORNL; Vacaliuc, Bogdan [ORNL

    2013-01-01

    A usual first principle in planning radio astronomy observations from the earth is that monitoring must be carried out well above the ionospheric plasma cutoff frequency (~5 MHz). Before space probes existed, radio astronomy was almost entirely done above 6 MHz, and this value is considered a practical lower limit by most radio astronomers. Furthermore, daytime ionization (especially D-layer formation) places additional constraints on wave propagation, and waves of frequency below 10-20 MHz suffer significant attenuation. More careful calculations of wave propagation through the earth s ionosphere suggest that for certain conditions (primarily the presence of a magnetic field) there may be a transmission window well below this assumed limit. Indeed, for receiving extraterrestrial radiation below the ionospheric plasma cutoff frequency, a choice of VLF frequency appears optimal to minimize loss. The calculation, experimental validation, and conclusions are presented here. This work demonstrates the possibility of VLF transmission through the ionosphere and various subsequent material barriers. Implications include development of a new robust communications channel, communications with submerged or subterranean receivers / instruments on or offworld, and a new approach to SETI.

  14. Very Low Frequency Remote Sensing of the Ionosphere and Magnetosphere

    NASA Astrophysics Data System (ADS)

    Cohen, M.

    2013-05-01

    This review talk will explore the technique of Very Low Frequency (VLF, 3-30 kHz) remote sensing of the ionosphere and magnetosphere, in which ground-based transmitter beacons (nominally for submarine communications) are used as a probe wave to study the D-region of the ionosphere (60-90 km), a layer is too low for satellites and too high for balloons. Guided efficiently by the Earth-ionosphere waveguide, VLF waves can be used on a global level, to sensitively quantify any ionospheric disturbance in the D-region. These include the impacts of solar flares, lightning heating (both the EMP and the quasi-static field changes), electron precipitation from lightning, and cosmic gamma-ray bursts. We will review many experimental and modeling efforts that have been made over the past several decades, including recent work on the transionospheric absorption of VLF waves from transmitters and lightning radio emissions. We will also review recent international efforts to build a global network of VLF receivers under the umbrella of the United Nations Basic Space Science Initiative.

  15. The International Reference Ionosphere - Climatological Standard for the Ionosphere

    NASA Technical Reports Server (NTRS)

    Bilitza, Dieter

    2006-01-01

    The International Reference Ionosphere (IRI) a joint project of URSI and COSPAR is the defacto standard for a climatological specification of ionospheric parameters. IRI is based on a wide range of ground and space data and has been steadily improved since its inception in 1969 with the ever-increasing volume of ionospheric data and with better mathematical descriptions of the observed global and temporal variation patterns. The IRI model has been validated with a large amount of data including data from the most recent ionospheric satellites (KOMPSAT, ROCSAT and TIMED) and data from global network of ionosondes. Several IRI teams are working on specific aspects of the IRI modeling effort including an improved representation of the topside ionosphere with a seamless transition to the plasmasphere, a new effort to represent the global variation of F2 peak parameters using the Neural Network (NN) technique, and the inclusion of several additional parameters in IRI, e.g., spread-F probability and ionospheric variability. Annual IRI workshops are the forum for discussions of these efforts and for all science activities related to IRI as well as applications of the IRI model in engineering and education. In this paper I will present a status report about the IRI effort with special emphasis on the presentations and results from the most recent IRI Workshops (Paris, 2004; Tortosa, 2005) and on the most important ongoing IRI activities. I will discuss the latest version of the IRI model, IRI-2006, highlighting the most recent changes and additions. Finally, the talk will review some of the applications of the IRI model with special emphasis on the use for radiowave propagation studies and communication purposes.

  16. Ionospheric calibration from an array signal processing

    E-print Network

    Langendoen, Koen

    of (traveling) disturbances, the dynamics of the ionosphere can be described by turbulent flow. A deterministicIonospheric calibration from an array signal processing perspective Sebastiaan van der Tol S.vanderTol@its.tudelft.nl Delft University of Technology Calibration and Imaging Workshop 2006 ­ p.1/21 #12;Ionospheric

  17. LWA Ionospheric Workshop Christopher Watts1

    E-print Network

    Ellingson, Steven W.

    and their propagation directions, b) traveling ionospheric disturbances (TIDs) and their relationship to acoustic wavesLWA Ionospheric Workshop Christopher Watts1 and Kenneth Dymond2 with: Ronald Caton5 , Clayton Coker The LWA Ionospheric Workshop was held in parallel with the CEDAR workshop at the Eldorado Hotel on Sunday

  18. Direct evidence of double-slope power spectra in the high-latitude ionospheric plasma

    NASA Astrophysics Data System (ADS)

    Spicher, A.; Miloch, W. J.; Moen, J. I.

    2014-03-01

    We report direct observations of the double-slope power spectra for plasma irregularities in the F layer of the polar ionosphere. The investigation of cusp irregularities ICI-2 sounding rocket, which was launched into the polar cusp ionosphere, intersected enhanced plasma density regions with decameter-scale irregularities. Density measurements at unprecedented high resolution with multi-Needle Langmuir Probes allowed for a detailed study of the plasma irregularities down to kinetic scales. Spectral analysis reveals double-slope power spectra for regions of enhanced fluctuations associated mainly with density gradients, with the steepening of the spectra occurring close to the oxygen gyrofrequency. These findings are further supported with the first results from the ICI-3 rocket, which flew through regions with strong precipitation and velocity shears. Previously, double-slope spectra have been observed in the equatorial ionosphere. The present work gives a direct evidence that the double-slope power spectra can be common in the high-latitude ionosphere.

  19. The response of plasma density to breaking inertial gravity wave in the lower regions of ionosphere

    SciTech Connect

    Tang, Wenbo, E-mail: Wenbo.Tang@asu.edu; Mahalov, Alex, E-mail: Alex.Mahalov@asu.edu [School of Mathematical and Statistical Sciences, Arizona State University, Tempe, Arizona 85287 (United States)] [School of Mathematical and Statistical Sciences, Arizona State University, Tempe, Arizona 85287 (United States)

    2014-04-15

    We present a three-dimensional numerical study for the E and lower F region ionosphere coupled with the neutral atmosphere dynamics. This model is developed based on a previous ionospheric model that examines the transport patterns of plasma density given a prescribed neutral atmospheric flow. Inclusion of neutral dynamics in the model allows us to examine the charge-neutral interactions over the full evolution cycle of an inertial gravity wave when the background flow spins up from rest, saturates and eventually breaks. Using Lagrangian analyses, we show the mixing patterns of the ionospheric responses and the formation of ionospheric layers. The corresponding plasma density in this flow develops complex wave structures and small-scale patches during the gravity wave breaking event.

  20. The response of plasma density to breaking inertial gravity wave in the lower regions of ionosphere

    NASA Astrophysics Data System (ADS)

    Tang, Wenbo; Mahalov, Alex

    2014-04-01

    We present a three-dimensional numerical study for the E and lower F region ionosphere coupled with the neutral atmosphere dynamics. This model is developed based on a previous ionospheric model that examines the transport patterns of plasma density given a prescribed neutral atmospheric flow. Inclusion of neutral dynamics in the model allows us to examine the charge-neutral interactions over the full evolution cycle of an inertial gravity wave when the background flow spins up from rest, saturates and eventually breaks. Using Lagrangian analyses, we show the mixing patterns of the ionospheric responses and the formation of ionospheric layers. The corresponding plasma density in this flow develops complex wave structures and small-scale patches during the gravity wave breaking event.

  1. A study of the ionospheric dynamo by using empirical model parameters

    NASA Astrophysics Data System (ADS)

    Shen, Chang-Shou; Li, Qing; Jiao, Wei-Xin; Zi, Min-Yun

    1992-04-01

    The empirical parameters of MSIS-86 and IRI-86 are used to deduce the three-dimensional distribution of ionospheric conductivity and thermospheric wind system. Furthermore, the distribution and variation of the electrostatic potential and layer ionospheric current density at the Northern Hemisphere are calculated by the dynamo theory. The work combines the theoretical research of the ionosphere and thermosphere and the parameters of an empirical model based on vast amount of data. The thermospheric wind system, height-integrated conductivity, electrostatic potential and ionospheric current density are compared with observed data and the results deduced from model calculations. There is good agreement between them. The general significance of the method engaged is discussed.

  2. Experimental investigation of the ionospheric hysteresis effect on the threshold excitation level of the Stimulated Electromagnetic Emission (SEE) during heating at the second electron gyro-harmonic frequency

    NASA Astrophysics Data System (ADS)

    Samimi, A.; Scales, W.; Cruz, M.; Isham, B.; Bernhardt, P. A.

    2012-12-01

    Recent experimental observations of the stimulated electromagnetic emission (SEE) spectrum during heating at the second electron gyro-harmonic show structures ordered by ion gyro-frequency. The proposed generation mechanism considers parametric decay of a pump upper hybrid/electron Bernstein (UH/EB) wave into another UH/EB and a group of neutralized ion Bernstein waves. The presumption of the proposed mechanism is that the pump electromagnetic wave is converted into the UH/EB wave. This conversion process generates field aligned irregularity which exhibits hysteresis effect. The predicted ionospheric hysteresis effect is studied during the PARS 2012 at HAARP. The preliminary results are presented for the first time. Also, experimental study of the effects of 1) the transmitter beam angle and 2) the transmitter frequency offset relative to the second electron gyro-harmonic frequency on the ion gyro-harmonic structures in the SEE spectrum are provided. The aforementioned observations are compared to the predictions of the analytical model. Possible connection of the SEE spectral features and artificially generated ionospheric descending layer is also discussed

  3. Artificial Intelligence

    E-print Network

    Appleton, D. S.

    This paper is a general overview of the field of artificial Intelligence and of some of the application issues within that field. Its first objective is to try and establish a viable definition for what artificial intelligence is, and to make a...

  4. Artificial intelligence

    SciTech Connect

    Ponomaryov, V.M.

    1983-01-01

    This book presents the papers given at a symposium on expert systems and artificial intelligence. Topics considered at the symposium included knowledge representation, industrial expert systems, knowledge bases, computer-aided design, computer-aided manufacturing, mathematical logic, robots, flexible manufacturing systems, decision-making in computer-aided planning, computerized control systems, artificial intelligence applied systems, computerized simulation, and natural language.

  5. Artificial intelligence

    SciTech Connect

    Bonnet, A.

    1986-01-01

    This book is an overview of the field of artificial intelligence. The work emphasizes natural language comprehension and knowledge-based reasoning by computers and analyzes the main difficulties involved in making intelligent programs. Representations of knowledge and reasoning mechanisms are provided and applications of artificial intelligence techniques in the development of expert systems are explored.

  6. Artificial intelligence

    SciTech Connect

    Firschein, O.

    1984-01-01

    This book presents papers on artificial intelligence. Topics considered include knowledge engineering, expert systems, applications of artificial intelligence to scientific reasoning, planning and problem solving, error recovery in robots through failure reason analysis, programming languages, natural language, speech recognition, map-guided interpretation of remotely-sensed imagery, and image understanding architectures.

  7. Artificial Intelligence.

    ERIC Educational Resources Information Center

    Smith, Linda C.; And Others

    1988-01-01

    A series of articles focuses on artificial intelligence research and development to enhance information systems and services. Topics discussed include knowledge base designs, expert system development tools, natural language processing, expert systems for reference services, and the role that artificial intelligence concepts should have in…

  8. Metrology and ionospheric observation standards

    NASA Astrophysics Data System (ADS)

    Panshin, Evgeniy; Minligareev, Vladimir; Pronin, Anton

    Accuracy and ionospheric observation validity are urgent trends nowadays. WMO, URSI and national metrological and standardisation services bring forward requirements and descriptions of the ionospheric observation means. Researches in the sphere of metrological and standardisation observation moved to the next level in the Russian Federation. Fedorov Institute of Applied Geophysics (IAG) is in charge of ionospheric observation in the Russian Federation and the National Technical Committee, TC-101 , which was set up on the base of IAG- of the standardisation in the sphere. TC-101 can be the platform for initiation of the core international committee in the network of ISO The new type of the ionosounde “Parus-A” is engineered, which is up to the national requirements. “Parus-A” calibration and test were conducted by National metrological Institute (NMI) -D.I. Mendeleyev Institute for Metrology (VNIIM), signed CIMP MRA in 1991. VNIIM is a basic NMI in the sphere of Space weather (including ionospheric observations), the founder of which was celebrated chemist and metrologist Dmitriy I. Mendeleyev. Tests and calibration were carried out for the 1st time throughout 50-year-history of ionosonde exploitation in Russia. The following metrological characteristics were tested: -measurement range of radiofrequency time delay 0.5-10 ms; -time measurement inaccuracy of radio- frequency pulse ±12mcs; -frequency range of radio impulse 1-20 MHz ; -measurement inaccuracy of radio impulse carrier frequency± 5KHz. For example, the sound impulse simulator that was built-in in the ionosounde was used for measurement range of radiofrequency time delay testing. The number of standards on different levels is developed. - “Ionospheric observation guidance”; - “The Earth ionosphere. Terms and definitions”.

  9. Study of large-scale irregularities generated in the ionospheric F -region by high-power HF waves

    Microsoft Academic Search

    V. L. Frolov; V. V. Chugurin; G. P. Komrakov; N. A. Mityakov; E. N. Myasnikov; V. O. Rapoport; E. N. Sergeev; V. P. Uryadov; F. I. Vybornov; V. A. Ivanov; V. V. Shumaev; A. M. Nasyrov; I. A. Nasyrov; K. M. Groves

    2000-01-01

    Experimental studies of the features of artificial ionospheric turbulence was performed at the “Sura” heating facility in\\u000a August 1998 using numerous diagnostic tools, such as scintillation, chirp-sounding, backscattering, and stimulated electromagnetic\\u000a emission (SEE) measurements, as well as sounding a HF-disturbed volume (DV) by probing waves. It has been found that generation\\u000a of strong artificial large-scale irregularities (ALSIs), which manifest themselves

  10. A Review of Ionospheric Scintillation Models

    NASA Astrophysics Data System (ADS)

    Priyadarshi, S.

    2015-01-01

    This is a general review of the existing climatological models of ionospheric radio scintillation for high and equatorial latitudes. Trans-ionospheric communication of radio waves from transmitter to user is affected by the ionosphere which is highly variable and dynamic in both time and space. Scintillation is the term given to irregular amplitude and phase fluctuations of the received signals and related to the electron density irregularities in the ionosphere. Key sources of ionospheric irregularities are plasma instabilities; every irregularities model is based on the theory of radio wave propagation in random media. It is important to understand scintillation phenomena and the approach of different theories. Therefore, we have briefly discussed the theories that are used to interpret ionospheric scintillation data. The global morphology of ionospheric scintillation is also discussed briefly. The most important (in our opinion) analytical and physical models of scintillation are reviewed here.

  11. A Review of Ionospheric Scintillation Models

    NASA Astrophysics Data System (ADS)

    Priyadarshi, S.

    2015-03-01

    This is a general review of the existing climatological models of ionospheric radio scintillation for high and equatorial latitudes. Trans-ionospheric communication of radio waves from transmitter to user is affected by the ionosphere which is highly variable and dynamic in both time and space. Scintillation is the term given to irregular amplitude and phase fluctuations of the received signals and related to the electron density irregularities in the ionosphere. Key sources of ionospheric irregularities are plasma instabilities; every irregularities model is based on the theory of radio wave propagation in random media. It is important to understand scintillation phenomena and the approach of different theories. Therefore, we have briefly discussed the theories that are used to interpret ionospheric scintillation data. The global morphology of ionospheric scintillation is also discussed briefly. The most important (in our opinion) analytical and physical models of scintillation are reviewed here.

  12. ULF wave interaction with the ionosphere: radar and magnetometer observations

    NASA Astrophysics Data System (ADS)

    Pilipenko, Viacheslav; Fedorov, Evgeniy; Kozlovsky, Alexander; Belakhovsky, Vladimir; Teramoto, Mariko

    Combined usage of SuperDARN/EISCAT radars and magnetometers, supported by an adequate theory of ULF wave interaction with the multi-layer system magnetosphere - ionosphere - atmosphere - ground, is an effective way to reveal a physical mechanism of ULF disturbances. Many notions derived only from satellite or ground observations may be challenged by additional information from radars (e.g., association of ULF phenomena with magnetospheric domains, ULF wave spatial structure, etc.). To identify the physical nature of global Pc5 pulsations at the recovery phase of strong magnetic storms and to determine relative contributions of different MHD modes into their structure, the method of apparent impedance can be applied. These Pc5 pulsations are considered using the IMAGE magnetometer data and EISCAT radar data from Tromso-Kiruna-Sodankyla system. An approximate analytical relationship derived from the theory of ULF wave transmission through the thin ionosphere has been compared with the measured ratio between the simultaneous ionospheric electric and ground magnetic fields. The impedances of Alfven and compressional modes are to be essentially distinct. From these observations we conclude that the global Pc5 pulsations above the ionosphere are predominantly composed from Alfven waves with a small contribution of fast compressional mode. Combined SuperDARN Hokkaido radar and magnetometer observations of mid-latitude Pi2 pulsations showed that the concept of a pure cavity mode is not sufficient to explain these observations, and that the contribution of an Alfvén waves must be taken in account. ULF waves are not just sounding signals, but an active factor of the near-Earth environment. The comparison of magnetometer data with the ionospheric parameters shows a significant modulation of the electron density, ionospheric height-integrated conductance, and ion temperature by Pc5 pulsations, even in the absence of quasi-periodic electron precipitation. The mechanisms underlying the ULF modulation effects comprise the Joule ion heating by electric field, and feeding/depleting of the ionospheric electrons by field-aligned current. Coordinated radar, magnetometer, and TEC/GPS high-sampling observations will be very promising, especially for small-scale waves not observable on the ground.

  13. Development of a new three-dimensional mathematical ionosphere model at European Space Agency/European Space Operations Centre

    NASA Astrophysics Data System (ADS)

    Feltens, J.

    2007-12-01

    For several years a clear trend from the application of classical so-called "single layer" models to attempts to model the ionosphere in accordance to its real three-dimensional nature can be observed (see, e.g., Scherliess et al., 2003; Hernández-Pajares et al., 1999). European Space Agency (ESA)/European Space Operations Centre (ESOC) commenced in 1998 employing a three-dimensional (3-D) model for ionosphere processing (Feltens, 1998; Feltens et al., 1998). This first version of a 3-D model at ESOC model was based on a simple Chapman profile approach, assuming that the vertical component of the ionosphere could be mathematically expressed in terms of a single ?-layer Chapman profile function. The profile function's parameters, maximum electron density N0 and its height h0, were in turn expressed as surface functions of geomagnetic latitude and local time whose coefficients were estimated. In this way a horizontal variation of N0 and h0 was modeled, and the profile function varied vertically, depending on the actual N0 and h0 values at a certain location. The ionosphere, however, consists of several layers. Additionally, the plasmasphere on top of the ionosphere must be accounted for, and the scale height, needed to compute the profile function z-parameter, is height-dependent. Furthermore, some of the ionosphere layers are so called ?-layers and some parts of the ionosphere show special behavior. All these effects must be accounted for in a proper 3-D mathematical modeling. It is the intent of this paper to give a substantial overview over the 3-D ionosphere models developed at ESOC and their current testing and implementation status.

  14. Seismo-ionospheric transfer function: dependence on time, location and other special features

    NASA Astrophysics Data System (ADS)

    Astafyeva, E.; Rolland, L. M.; Lognonne, P.

    2010-12-01

    Large earthquakes are known to generate ionospheric disturbances, called coseismic ionosphere disturbances (CID). Vertical displacements of the ground induce pressure waves in the neutral atmosphere that propagate upward and grow in amplitude by several orders of magnitude as they reach ionospheric heights, since the atmospheric density decreases exponentially with height. Then, an ionospheric perturbation is formed via the collisions between neutral and charged particles. During favourable atmospheric and ionospheric conditions, a 0.1 mm/s ground displacement induced by the passage of Rayleigh surface waves generated by an earthquake of magnitude M8 at teleseismic distance, ionospheric layers can oscillate with velocities of about 10 m/s at around 150-200 km height. Those velocities are easily measurable by HF-Doppler sounder and significant Total Electron Content (TEC) variations (typically 0.1 TECU = 1x10^15 e-/m^3) can also be detected by GPS (Global Positioning System). However, before the emitted from the ground neutral waves reach the ionosphere they evolve due to a variety of effects provided by the propagation medium, i.e. the atmosphere. Therefore, one of the most interesting and important questions is the so-called transfer function for coseismic ionospheric disturbances that provides information on evolution and transformation of the “initial” neutral waves into the ultimate ionospheric response. This study analyzes the peculiarities of the transfer function for seismic waves in the ionosphere with respect to local time, geographical location, solar activity, etc. The variability of the solid Earth-atmosphere coupling is first investigated by estimating the amount of seismic energy injected in the atmosphere under variable atmospheric conditions. We model the atmospheric perturbation excited by an earthquake by summation of the Earth spheroidal normal modes computed for a 1D model of solid Earth surrounded by a realistic atmosphere. Further, through the atmosphere-ionosphere coupling we model the CID. The study is done under variable ionospheric conditions and based on the example of a series of large earthquakes (M>7.0) occurred in 2002-2010.

  15. A refracting radio telescope. [using ionosphere as lens

    NASA Technical Reports Server (NTRS)

    Bernhardt, P.; Da Rosa, A. V.

    1977-01-01

    Observations of extraterrestrial radio sources at the lower end of the radio frequency spectrum are limited by reflection of waves from the topside ionosphere and by the large size of antenna apertures necessary for the realization of narrow beamwidths. The use of the ionosphere as a lens is considered. The lens is formed by the release of chemicals such as H2 and H2O at the F2-layer peak. These chemicals promote dissociative recombination of O(+) in the ionosphere resulting in a local reduction in plasma density. Gradients in electron density in the vicinity of the gas release tend to focus rays propagating through the depleted region. Preliminary calculations indicate that a lens capable of focusing cosmic radio waves in the 1 to 10 MHz frequency range may be produced by the release of 100 kg of H2 at the peak of the nighttime F layer. The beamwidth of a refracting radio telescope using this lens may be less than 1/5 degree.

  16. Reanalysis of Mars ionospheric electron density profiles from Mariner 9

    NASA Astrophysics Data System (ADS)

    Weiner, S. L.; Withers, P.

    2013-12-01

    The Mariner 9 radio occultation experiment acquired 118 profiles of dayside ionospheric electron density from 1971-2. Relative to the MGS dataset, which contains the only electron density profiles for Mars that are readily available to the public today, the Mariner 9 dataset has some unique characteristics. Profiles extend to 300-400 km, thereby probing the topside ionosphere better than the MGS profiles that typically terminate around 200 km. Profiles were acquired during the waning phase of a tremendous dust storm, when the ionospheric peak was 20-30 km higher than normal. Profiles are distributed globally, whereas MGS profiles are poleward of 60 degrees north latitude, and sample solar zenith angles as low as 47 degrees, whereas MGS was limited to 71 degrees and higher. We have digitized the Mariner 9 electron density profiles from their microfilm archive. Here we report on a broad scientific analysis of these profiles. We examine the dependence of electron densities in the M2 and M1 layers on solar zenith angle and flux, how the dust storm affected both peak altitude and ionopause altitude, and the presence of meteoric layers.

  17. Ionospheric mapping computer contouring techniques

    SciTech Connect

    Samardjiev, T.; Bradley, P.A.; Cander, LJ.R.; Dick, M.I. [Geophysical Inst., Sofia (Bulgaria)

    1993-09-01

    Established methods of generating uniform grids of scalar quantities from irregularly disposed known values are applied to the development of regional maps of ionospheric characteristics for individual instants of time. Figure-of-merit comparisons are presented to show the general superiority of one particular technique. Ways of supplementing measured input values with `screen-point` synthesized data are outlined. 7 refs.

  18. Magnetospheric-ionospheric Poynting flux

    NASA Technical Reports Server (NTRS)

    Thayer, Jeffrey P.

    1994-01-01

    Over the past three years of funding SRI, in collaboration with the University of Texas at Dallas, has been involved in determining the total electromagnetic energy flux into the upper atmosphere from DE-B electric and magnetic field measurements and modeling the electromagnetic energy flux at high latitudes, taking into account the coupled magnetosphere-ionosphere system. This effort has been very successful in establishing the DC Poynting flux as a fundamental quantity in describing the coupling of electromagnetic energy between the magnetosphere and ionosphere. The DE-B satellite electric and magnetic field measurements were carefully scrutinized to provide, for the first time, a large data set of DC, field-aligned, Poynting flux measurement. Investigations describing the field-aligned Poynting flux observations from DE-B orbits under specific geomagnetic conditions and from many orbits were conducted to provide a statistical average of the Poynting flux distribution over the polar cap. The theoretical modeling effort has provided insight into the observations by formulating the connection between Poynting's theorem and the electromagnetic energy conversion processes that occur in the ionosphere. Modeling and evaluation of these processes has helped interpret the satellite observations of the DC Poynting flux and improved our understanding of the coupling between the ionosphere and magnetosphere.

  19. Ionospheric Heating by Hydromagnetic Waves

    Microsoft Academic Search

    A. J. Dessler

    1959-01-01

    The rate of energy dissipation per umt volume is investigated for hydromagnetic waves traveling downward through the ionosphere. A calculation of the heating rate is made, based on assumptions as to the amplitude and Fourier spectrum of the hydromagnetic waves. It is argued in a general way that the peak heating rate due to hydromagnetic waves occurs near 175 kilometers.

  20. Ionospheric trends in mid-latitudes as a possible indicator of the atmospheric greenhouse effect

    Microsoft Academic Search

    J. Bremer

    1992-01-01

    Using long-term ionosonde measurements in mid-latitudes (Juliusruh: 54.6 deg N, 13.4 deg E; 1957-1990), the first experimental hints of a decrease of the peak height of the ionospheric F2-layer were found. In contrast to that, the long-term variations of the peak electron densities in the F2-layer, as well as the E-layer, are small. These results qualitatively agree with the predictions

  1. The ionospheric outflow feedback loop

    NASA Astrophysics Data System (ADS)

    Moore, T. E.; Fok, M.-C.; Garcia-Sage, K.

    2014-08-01

    Following a long period of observation and investigation beginning in the early 1970s, it has been firmly established that Earth's magnetosphere is defined as much by the geogenic plasma within it as by the geomagnetic field. This plasma is not confined to the ionosphere proper, defined as the region within a few density scale heights of the F-region plasma density peak. Rather, it fills the flux tubes on which it is created, and circulates throughout the magnetosphere in a pattern driven by solar wind plasma that becomes magnetically connected to the ionosphere by reconnection through the dayside magnetopause. Under certain solar wind conditions, plasma and field energy is stored in the magnetotail rather than being smoothly recirculated back to the dayside. Its release into the downstream solar wind is produced by magnetotail disconnection of stored plasma and fields both continuously and in the form of discrete plasmoids, with associated generation of energetic Earthward-moving bursty bulk flows and injection fronts. A new generation of global circulation models is showing us that outflowing ionospheric plasmas, especially O+, load the system in a different way than the resistive F-region load of currents dissipating energy in the plasma and atmospheric neutral gas. The extended ionospheric load is reactive to the primary dissipation, forming a time-delayed feedback loop within the system. That sets up or intensifies bursty transient behaviors that would be weaker or absent if the ionosphere did not “strike back” when stimulated. Understanding this response appears to be a necessary, if not sufficient, condition for us to gain accurate predictive capability for space weather. However, full predictive understanding of outflow and incorporation into global simulations requires a clear observational and theoretical identification of the causal mechanisms of the outflows. This remains elusive and requires a dedicated mission effort.

  2. Formation, dynamics and ion composition of sporadic E-layers observed by the API technique

    NASA Astrophysics Data System (ADS)

    Bakhmetieva, N. V.; Belikovich, V. V.; Kagan, L. M.; Ponyatov, A. A.

    We present the results of our studies of sporadic E-layers (Es) in the lower ionosphere by means of the artificial periodic irregularities (API) technique. The experiments were carried out in August 2000 and June 2001 throughout sunset-to-sunrise hours at the SURA facility (56.1N, 44.1E). Both probe and pump waves were of X-mode polarization and were transmitted at 5.6 MHz. API amplitudes were observed with height and time resolutions of 1.4 km and 20 s, respectively. Artificial periodic irregularities were generated in antinodes of the standing electromagnetic wave formed due to interference of HF radio waves transmitted vertically and reflected from the ionosphere (for more details on the API method and its applications see Belikovich et al., Ionospheric Research by Means of Artificial Periodic Irregularities - Katlenburg-Lindau, Germany. 2002. Copernicus GmbH. ISBN 3-936586-03-9. 160 pp.). The API time decay is inversely proportional to the diffusion rate and is directly proportional to the mass of the predominant ion. We have developed a method to determine the sporadic E-layer ion composition (the molecular mass of metallic ions in particular), based on measurements of the ambipolar diffusion rate and the plasma vertical motion velocity. The vertical plasma velocity V was measured by the API technique in the height range 70-120 km. E-layers formed above the E-region maximum and gradually descended with a vertical velocity of about 1 m/s. To determine the total density of positive ions we used vertical velocity data and vertical sounding. Based on measurements made during the sunset hours in June 2001 we evaluated the molecular weight of the predominant metallic ions. We found a clear indication of the presence of Ca+ and Fe+ ions at the Es heights. These ions most probably make up 10-40% of the ion population of the observed sporadic layers with 20-50% density enhancements. The total density of all types of metallic ions was NM˜ 104 cm-3 in the case of the 113-120-km Es and NM˜ 7,3 103 cm-3 for the 95-100-km Es. The total metallic and atmospheric ion densities found are in a good correspondence to those observed with lidars and rocket spectrometers. This work has been supported by RFBR grant 02-05-65281.

  3. Results of ionospheric observations in Alma-Ata on March 16-20 and December 5-10, 1988

    NASA Astrophysics Data System (ADS)

    Burlakova, I. A.; Gordienko, G. I.; Zelenkova, I. A.

    1993-02-01

    Results are presented of an analysis of ionospheric conditions observed at the Alma-Ata station suring the SUNDIAL periods March 16-20 and December 5-10, 1988. Data collected for the March 16-20, 1988 period indicate a quiet period of the ionosphere, with changes of critical frequencies in the F2 layer (f0F2) falling within the 20 percent limit, except of a short-time increase in f0F2 values on March 19. During the December 5-10 period, the lower-latitude ionosphere was disturbed more than in March, with weak negative disturbances followed by positive ones.

  4. Artificial Life

    Microsoft Academic Search

    Chris Langton

    1987-01-01

    Artificial Life is the study of man-made systems that exhibit behaviors characteristic of natural living systems. It complements the traditional biological sciences concerned with the analysis of living organisms by attempting to synthesize life-like behaviors within computers and other artificial media. By extending the empirical foundation upon which biology is based beyond the carbon-chain life that has evolved on earth,

  5. Artificial Ligaments

    Microsoft Academic Search

    Andrew A. Amis

    The history of artificial ligaments includes possibly more than its fair share of controversy and failures. One main task\\u000a of this chapter is to review the history to extract the lessons that will be valuable for the future. Although artificial\\u000a ligaments are presently unpopular, memories of previous disappointments inevitably fade, while at the same time, technology\\u000a continues, opening up novel

  6. DEMETER Observations of Equatorial Plasma Depletions and Related Ionospheric Phenomena

    NASA Astrophysics Data System (ADS)

    Berthelier, J.; Malingre, M.; Pfaff, R.; Jasperse, J.; Parrot, M.

    2008-12-01

    DEMETER, the first micro-satellite of the CNES MYRIAD program, was launched from Baikonour on June 29, 2004 on a nearly circular, quasi helio-synchronous polar orbit at ~ 715 km altitude. The DEMETER mission focuses primarily on the search for a possible coupling between seismic activity and ionospheric disturbances as well as on the effects of natural phenomena such as tropospheric thunderstorms and man-made activities on the ionosphere. The scientific payload provides fairly complete measurements of the ionospheric plasma, energetic particles above ~ 70 keV, and plasma waves, up to 20 kHz for the magnetic and 3.3 MHz for the electric components. Several studies related to space weather and ionospheric physics have been conducted over the past years. Following a brief description of the payload and the satellite modes of operation, this presentation will focus on a set of results that provide a new insight into the physics of instabilities in the night-time equatorial ionosphere. The observations were performed during the major magnetic storm of November 2004. Deep plasma depletions were observed on several night-time passes at low latitudes characterized by the decrease of the plasma density by nearly 3 orders of magnitude relative to the undisturbed plasma, and a significant abundance of molecular ions. These features can be best interpreted as resulting from the rise of the F-layer above the satellite altitude over an extended region of the ionosphere. In one of the passes, DEMETER was operated in the Burst mode and the corresponding high resolution data allowed for the discovery of two unexpected phenomena. The first one is the existence of high intensity monochromatic wave packets at the LH frequency that develop during the decay phase of intense bursts of broadband LH turbulence. The broadband LH turbulence is triggered by whistlers emitted by lightning from atmospheric thunderstorms beneath the satellite. The second unexpected feature is the detection of a population of super-thermal ionospheric ions with a density of about 2-3% of the thermal ion population. The super- thermal ions appeared to be heated to temperatures of a few eV at times when LH turbulence and monochromatic wave packets are observed while the temperature of the core ion population is not affected. High time resolution plasma density measurements show the presence of strong small scale plasma irregularities in the depletions that scatter the high amplitude whistler waves and may lead to the development of strong LH turbulence and of monochromatic wave packets. The ensuing interaction between these waves and the ambient ions may lead to the formation of a super-thermal tail in the ion distribution function. Ion acceleration by LH turbulence and solitary waves is a commonly observed phenomenon along auroral magnetic field lines but, to our knowledge, this is the first time that a similar process has been observed in the equatorial ionosphere. These findings exemplify a novel coupling mechanism between the troposphere and the ionosphere: Under highly disturbed conditions at times of magnetic storms, part of the energy released by lightning and radiated as whistlers can dissipate in the equatorial ionosphere and produce super-thermal ion populations.

  7. Observing rapid quasi-wave ionospheric disturbance using amplitude charts

    NASA Astrophysics Data System (ADS)

    Kurkin, Vladimir; Laryunin, Oleg; Podlesnyi, Alexey

    Data from vertical (quasi-vertical) sounding are traditionally used for determining a number of ionospheric parameters such as critical frequencies of E and F layers, peaks of these layers, and for reconstructing electron density profiles. In this respect, radio sounding is not used to its full capacity. Modern ionosondes provide additional information encoded in ionospheric echoes, including information on reflected-signal amplitude. The time dependence of the amplitude-frequency characteristic of reflected signal has been named "amplitude chart" (A-chart). Ionosondes used by the ISTP SB RAS Geophysical Observatory for constructing A-charts employ the frequency-modulated continuous-wave (FMCW) signal in a range 1.3-15 MHz. One-minute sounding interval allows a more detailed study of dynamic processes in the ionosphere. The ionosonde has a direct digital synthesizer and direct sampling receiver without automatic gain control (AGC). The absence of AGC and the high dynamic range enable determination of the relative field strength at a receiving point and registration of relative long-term variations in reflected-signal amplitude over the entire range of operating frequencies of the ionosonde. We have revealed that the passage of travelling ionospheric disturbances (TID) along with height-frequency distortion modulates amplitude characteristics of signal. The characteristic depth of the modulation reaches 40 dB. The pronounced alternate vertical stripes typical for A-charts are likely to be associated with focusing properties of TID. In order to examine the space-time structure of TID able to induce such a focusing of the radio waves, we performed ray tracing simulations. We used geometrical-optics approximation, took magneto-ionic effects into account and prescribed electron density to be a stratified electron density profile on which an undulating disturbance was superimposed. This work was supported by the RFBR grant ?14-05-00259-?.

  8. Low-latitude ionospheric effects of energetic electrons during a recurrent magnetic storm

    NASA Astrophysics Data System (ADS)

    Suvorova, A. V.; Huang, C.-M.; Matsumoto, H.; Dmitriev, A. V.; Kunitsyn, V. E.; Andreeva, E. S.; Nesterov, I. A.; Tsai, L.-C.

    2014-11-01

    We study a magnetosphere-ionosphere coupling at low latitudes during a moderate (corotating interaction regions/high-speed solar wind streams-driven) geomagnetic storm on 22 July 2009. Recently, it has been shown that during major (coronal mass ejection-driven) storms, quasi-trapped >30 keV electrons largely enhance below the radiation belt in the forbidden zone and produce an additional ionization in the topside ionosphere. In this work, we examine a case of the recurrent storm when the magnetosphere-ionosphere coupling through the quasi-trapped electrons also may take place. Data from NOAA/Polar-orbiting Operational Environmental Satellite and Japanese Greenhouse gases Observing Satellite were used to identify the forbidden electron enhancement (FEE). We find a positive vertical gradient of the electron fluxes that indicates to the radiation belt as a source of FEE. Using global ionospheric maps, radiotomography reconstructions from beacon data and COSMIC/FORMOSAT-3 radio occultation measurements, we have observed an unusually large area in the nighttime ionosphere with increased total electron content (TEC) and prominent elevation of the F layer at low latitudes that coincides with FEEs spatially and temporarily. Ionizing particles are considered as an addition source of ionization along with generally accepted mechanisms for storm time TEC increase (a positive ionospheric storm). We discuss relative contributions of the FEE and disturbance dynamo electric field in the TEC increases during the storm recovery phase.

  9. Extremely Low Ionospheric Peak Altitudes in the Polar-Hole Region

    NASA Technical Reports Server (NTRS)

    Benson, Robert F.; Grebowsky, Joseph M.

    1999-01-01

    Vertical electron-density (N (sub e)) profiles, deduced from newly-available ISIS-II digital ionospheric topside-sounder data, are used to investigate the "polar-hole" region within the winter, nighttime polar cap ionosphere during solar minimum. The hole region is located around 0200 MLT near the poleward side of the auroral oval. Earlier investigations had revealed very low N (sub e) values in this region (down to 200/cu cm near 300 km). In the present study, such low N, values (approx. 100/cu cm) were only found near the ISIS (International Satellite for Ionospheric Study)-II altitude of 1400 km. The peak ionospheric concentration below the spacecraft remained fairly constant (approx. 10 (exp 5)/cu cm across the hole region but the altitude of the peak dropped dramatically. This peak dropped, surprisingly, to the vicinity of 100 km. These observations suggest that the earlier satellite in situ measurements, interpreted as deep holes in the ionospheric F-region concentration, could have been made during conditions of an extreme decrease in the altitude of the ionospheric N (sub e) peak. The observations, in combination with other data, indicate that the absence of an F-layer peak may be a frequent occurrence at high latitudes.

  10. Ionospheric response to the entry and explosion of the South Ural superbolide

    NASA Astrophysics Data System (ADS)

    Ruzhin, Yu. Ya.; Kuznetsov, V. D.; Smirnov, V. M.

    2014-09-01

    The South Ural meteoroid (February 15, 2013; near the city of Chelyabinsk) is undoubtedly the best documented meteoroid in history. Its passage through the atmosphere has been recorded on videos and photographs, visually by observers, with ground-based infrasound microphones and seismographs, and by satellites in orbit. In this work, the results are presented of an analysis of the transionospheric GPS sounding data collected in the vicinity of the South Ural meteoroid site, which show a weak ionospheric effect. The ionospheric disturbances are found to be asymmetric about the explosion epicenter. The received signals are compared, both in shape and amplitude, with the reported ionospheric effects of ground level explosions with radio diagnostics. It is shown that the confident registration of ionospheric effects as acoustic gravity waves (AGWs) by means of vertical sounding and GPS technologies for ground explosions in the range of 0.26-0.6 kt casts doubt on the existing TNT equivalent estimates (up to 500 kt) for the Chelyabinsk event. The absence of effects in the magnetic field and in the ionosphere far zone at distances of 1500-2000 km from the superbolide explosion epicenter also raises a question about the possibility of an overestimated TNT equivalent. An alternative explanation is to consider the superposition of a cylindrical ballistic wave (due to the hypersonic motion of the meteoroid) with spherical shock waves caused by the multiple time points of fragmentation (multiple explosions) of the superbolide as a resulting source of the AGW impact on ionospheric layers.

  11. Development of a new three-dimensional mathematical ionosphere model at European Space Agency\\/European Space Operations Centre

    Microsoft Academic Search

    J. Feltens

    2007-01-01

    For several years a clear trend from the application of classical so-called “single layer” models to attempts to model the ionosphere in accordance to its real three-dimensional nature can be observed (see, e.g., Scherliess et al., 2003; Hernández-Pajares et al., 1999). European Space Agency (ESA)\\/European Space Operations Centre (ESOC) commenced in 1998 employing a three-dimensional (3-D) model for ionosphere processing

  12. Development of a new three-dimensional mathematical ionosphere model at European Space Agency\\/European Space Operations Centre

    Microsoft Academic Search

    J. Feltens

    2007-01-01

    For several years a clear trend from the application of classical so-called ``single layer'' models to attempts to model the ionosphere in accordance to its real three-dimensional nature can be observed (see, e.g., Scherliess et al., 2003; Hernández-Pajares et al., 1999). European Space Agency (ESA)\\/European Space Operations Centre (ESOC) commenced in 1998 employing a three-dimensional (3-D) model for ionosphere processing

  13. Investigation of the seismo-ionospheric effects on the base of GPS/GLONASS measurements

    NASA Astrophysics Data System (ADS)

    Zakharenkova, I.; Cherniak, Iu.; Shagimuratov, I.; Suslova, O.

    2012-04-01

    During last years the monitoring of the ionospheric effects of different origin is carried out mainly with use of Global Navigating Satellite Systems (GPS / GLONASS). By means of measurements of the signals temporal delays it is possible to do the mapping of total electron content (TEC) in a column of unit cross section through the Earth's ionosphere and investigate its temporal evolution depended on the variations of electron concentration (NmF2) in the F2 ionospheric region. In the given report we present results of analysis of spatial-temporal variability of the ionosphere during the earthquake preparation phase for several major earthquakes which took place in Japan. It was revealed that for considered events mainly positive TEC anomalies appeared 1-5 days prior to the earthquake. The enhancement of electron concentration reached the value of 30-70% relative to the quiet geomagnetic conditions. In order to analyze the revealed effects in more details it was additionally involved data of GPS TEC values over GPS stations located at different distances from earthquake epicenters and data of vertical sounding of the ionosphere (NICT database). The hourly values of critical frequency of ionospheric F2 and Es layers were obtained from manually scaled ionograms recorded at Japanese ionospheric sounding stations Wakkanai, Kokubunji and Yamagawa. Acknowledgments. We acknowledge the IGS community for providing GPS permanent data and WDC for Ionosphere, Tokyo, National Institute of Information and Communications Technology (NICT) for providing ionosonde data. This work was supported by Russian Federation President grant MK-2058.2011.5.

  14. Photochemistry of Titan's Atmosphere and Ionosphere

    NASA Astrophysics Data System (ADS)

    Krasnopolsky, Vladimir A.

    2008-09-01

    A global-mean model of coupled neutral and ion chemistry on Titan has been developed. Unlike the previous models, the model involves ambipolar diffusion and escape of ions, hydrodynamic escape of light species, and calculates the H2 density near the surface that was assigned previously. We tried to reduce the numbers of species and reactions in the model and remove all species and reactions that weakly affect the observed species. Hydrocarbon chemistry is extended to C12H10 for neutrals and C10H11+ for ions but does not include PAHs. The model involves 386 reactions of 83 neutrals and 33 ions, effects of magnetospheric electrons and cosmic rays. UV absorption by Titan's haze was calculated using the Huygens observations and a code for aggregate particles. Hydrocarbon, nitrile, and ion chemistries are strongly coupled on Titan, and attempt to calculate them separately (e.g. in models of ionospheric composition) may result in significant error. The model densities of various species are typically in good agreement with the observations except vertical profiles in the stratosphere that are steeper than the CIRS limb data. Influx of O+ 106 cm-2 s-1 from Saturn's magnetosphere is sufficient to support CO at the observed level of 50 ppm without a surface source. The ionosphere includes a peak at 80 km formed by the cosmic rays, a steplike layer at 700-900 km and a peak at 1120 km (SZA = 60º). Nighttime densities of major ions agree with the INMS data. Ion chemistry dominates in the production of bicyclic aromatic hydrocarbons (indene and naphthalene) above 750 km. Precipitation rate of the photochemical products by polymerization and condensation is capable to fill the observed lakes and seas for a geologically short period of 10-100 Myr. The model does not support the low C/N ratio observed by the Huygens ACP in Titan's haze.

  15. NeMars empirical model for the dayside martian ionosphere and its use to validate MARSIS instrument techniques: Possible contribution to the Mars International Reference Ionosphere (MIRI)

    NASA Astrophysics Data System (ADS)

    Sanchez-Cano, Beatriz; Witasse, Olivier; Radicella, Sandro M.; Cartacci, Marco; Orosei, Roberto; Herraiz, Miguel; Rodriguez-Caderot, Gracia

    NeMars is an empirical model of the two main electron density layers of the Martian dayside ionosphere [Sánchez - Cano et al., 2013]. It is mainly based on MARSIS AIS data (Active Ionospheric Sounding from the Mars Advanced Radar and Ionospheric Sounding experiment aboard Mars Express mission) and to a lesser extent on radio-occultation data from the Mars Global Surveyor mission. The model starts from Chapman theory, but allows variation of scale height and altitude of the main layer with solar zenith angle, and assumes the predominance of Chapman-like photochemical processes above 200 km of altitude. The model is able to reproduce with good approximation the main characteristics of both ionospheric regions: electron density and peak altitudes, scale heights, shape of the profiles and Total Electron Content (TEC) of the entire ionosphere. These can be computed in a simple and quick way starting from solar zenith angle, solar flux F10.7 (as a proxy of solar activity), and heliocentric distance. TEC is the integral of the electron density along the vertical direction and constitutes a very useful parameter in characterizing the ionosphere. In particular, in the case of Earth, it is critical for satellite communications and navigation. Independent measurements of the Martian TEC derived from MARSIS subsurface sounding data [Mouginot et al., 2008 and Cartacci et al., 2013] can be used to validate TEC estimates produced by NeMars. However, initial comparisons reveal that TEC estimates based on MARSIS AIS data are not consistent with those obtained from MARSIS subsurface sounding data: this is probably due to the fact that MARSIS in AIS mode is a topside sounder, measuring only the properties of the ionosphere above the maximum plasma frequency, while in subsurface mode it provides an integral information on the TEC for the entire ionosphere. In an attempt to face this problem, the NeMars model outputs are being used to simulate the radio-wave propagation, to study the TEC retrieving techniques constrains and limits. In the context of the ongoing efforts for the creation of a Mars International Reference Ionosphere (MIRI), we propose to contribute to this effort making use of the AIS data and the NeMars model of daytime electron density. References: Cartacci et al 2013. Icarus, 223, 423-437. Mouginot et al. Planet. 2008. Space Sci. 56, 917-926. Sánchez - Cano et al., 2013. Icarus, 225, 236-247.

  16. Preface: International Reference Ionosphere - Progress in Ionospheric Modelling

    NASA Technical Reports Server (NTRS)

    Bilitza Dieter; Reinisch, Bodo

    2010-01-01

    The international reference ionosphere (lRI) is the internationally recommended empirical model for the specification of ionospheric parameters supported by the Committee on Space Research (COSPAR) and the International Union of Radio Science (URSI) and recognized by the International Standardization Organization (ISO). IRI is being continually improved by a team of international experts as new data become available and better models are being developed. This issue chronicles the latest phase of model updates as reported during two IRI-related meetings. The first was a special session during the Scientific Assembly of the Committee of Space Research (COSPAR) in Montreal, Canada in July 2008 and the second was an IRI Task Force Activity at the US Air Force Academy in Colorado Springs in May 2009. This work led to several improvements and additions of the model which will be included in the next version, IRI-201O. The issue is divided into three sections focusing on the improvements made in the topside ionosphere, the F-peak, and the lower ionosphere, respectively. This issue would not have been possible without the reviewing efforts of many individuals. Each paper was reviewed by two referees. We thankfully acknowledge the contribution to this issue made by the following reviewers: Jacob Adeniyi, David Altadill, Eduardo Araujo, Feza Arikan, Dieter Bilitza, Jilijana Cander, Bela Fejer, Tamara Gulyaeva, Manuel Hermindez-Pajares, Ivan Kutiev, John MacDougal, Leo McNamara, Bruno Nava, Olivier Obrou, Elijah Oyeyemi, Vadym Paznukhov, Bodo Reinisch, John Retterer, Phil Richards, Gary Sales, J.H. Sastri, Ludger Scherliess, Iwona Stanislavska, Stamir Stankov, Shin-Yi Su, Manlian Zhang, Y ongliang Zhang, and Irina Zakharenkova. We are grateful to Peggy Ann Shea for her final review and guidance as the editor-in-chief for special issues of Advances in Space Research. We thank the authors for their timely submission and their quick response to the reviewer comments and humbly apologize for any delays in the editing process.

  17. Three-layer microfibrous peripheral nerve guide conduit composed of elastin-laminin mimetic artificial protein and poly(L-lactic acid)

    NASA Astrophysics Data System (ADS)

    Kakinoki, Sachiro; Nakayama, Midori; Moritan, Toshiyuki; Yamaoka, Tetsuji

    2014-07-01

    We developed a microfibrous poly(L-lactic acid) (PLLA) nerve conduit with a three-layered structure to simultaneously enhance nerve regeneration and prevent adhesion of surrounding tissue. The inner layer was composed of PLLA microfiber containing 25% elastin-laminin mimetic protein (AG73-(VPGIG)30) that promotes neurite outgrowth. The thickest middle layer was constructed of pure PLLA microfibers that impart the large mechanical stremgth to the conduit. A 10% poly(ethylene glycol) was added to the outer layer to prevent the adhesion with the surrounding tissue. The AG73-(VPGIG)30 composisting of an elastin-like repetitive sequence (VPGIG)30 and a laminin-derived sequence (RKRLQVQLSIRT: AG73) was biosynthesized using Escherichia coli. The PLLA microfibrous conduits were fabricated using an electrospinning procedure. AG73-(VPGIG)30 was successfully mixed in the PLLA microfibers, and the PLLA/AG73-(VPGIG)30 microfibers were stable under physiological conditions. The PLLA/AG73-(VPGIG)30 microfibers enhanced adhesion and neurite outgrowth of PC12 cells. The electrospun microfibrous conduit with a three-layered structure was implanted for bridging a 2.0-cm gap in the tibial nerve of a rabbit. Two months after implantation, no adhesion of surrounding tissue was observed, and the action potential was slightly improved in the nerve conduit with the PLLA/AG73-(VPGIG)30 inner layer.

  18. Three-layer microfibrous peripheral nerve guide conduit composed of elastin-laminin mimetic artificial protein and poly(L-lactic acid)

    PubMed Central

    Kakinoki, Sachiro; Nakayama, Midori; Moritan, Toshiyuki; Yamaoka, Tetsuji

    2014-01-01

    We developed a microfibrous poly(L-lactic acid) (PLLA) nerve conduit with a three-layered structure to simultaneously enhance nerve regeneration and prevent adhesion of surrounding tissue. The inner layer was composed of PLLA microfiber containing 25% elastin-laminin mimetic protein (AG73-(VPGIG)30) that promotes neurite outgrowth. The thickest middle layer was constructed of pure PLLA microfibers that impart the large mechanical strength to the conduit. A 10% poly(ethylene glycol) was added to the outer layer to prevent the adhesion with the surrounding tissue. The AG73-(VPGIG)30 compositing of an elastin-like repetitive sequence (VPGIG)30 and a laminin-derived sequence (RKRLQVQLSIRT: AG73) was biosynthesized using Escherichia coli. The PLLA microfibrous conduits were fabricated using an electrospinning procedure. AG73-(VPGIG)30 was successfully mixed in the PLLA microfibers, and the PLLA/AG73-(VPGIG)30 microfibers were stable under physiological conditions. The PLLA/AG73-(VPGIG)30 microfibers enhanced adhesion and neurite outgrowth of PC12 cells. The electrospun microfibrous conduit with a three-layered structure was implanted for bridging a 2.0-cm gap in the tibial nerve of a rabbit. Two months after implantation, no adhesion of surrounding tissue was observed, and the action potential was slightly improved in the nerve conduit with the PLLA/AG73-(VPGIG)30 inner layer. PMID:25101261

  19. Interaction of Titan's ionosphere with Saturn's magnetosphere.

    PubMed

    Coates, Andrew J

    2009-02-28

    Titan is the only Moon in the Solar System with a significant permanent atmosphere. Within this nitrogen-methane atmosphere, an ionosphere forms. Titan has no significant magnetic dipole moment, and is usually located inside Saturn's magnetosphere. Atmospheric particles are ionized both by sunlight and by particles from Saturn's magnetosphere, mainly electrons, which reach the top of the atmosphere. So far, the Cassini spacecraft has made over 45 close flybys of Titan, allowing measurements in the ionosphere and the surrounding magnetosphere under different conditions. Here we review how Titan's ionosphere and Saturn's magnetosphere interact, using measurements from Cassini low-energy particle detectors. In particular, we discuss ionization processes and ionospheric photoelectrons, including their effect on ion escape from the ionosphere. We also discuss one of the unexpected discoveries in Titan's ionosphere, the existence of extremely heavy negative ions up to 10000amu at 950km altitude. PMID:19073464

  20. Use of radio occultation to probe the high latitude ionosphere

    NASA Astrophysics Data System (ADS)

    Mannucci, A. J.; Tsurutani, B. T.; Verkhoglyadova, O.; Komjathy, A.; Pi, X.

    2015-02-01

    We have explored the use of COSMIC data to provide valuable scientific information on the ionospheric impacts of energetic particle precipitation during geomagnetic storms. Ionospheric electron density in the E region, and hence ionospheric conductivity, is significantly altered by precipitating particles from the magnetosphere. This has global impacts on the thermosphere-ionosphere because of the important role of conductivity on high latitude Joule heating. Two high-speed stream (HSS) and two coronal mass ejection (CME) storms are examined with the COSMIC data. We find clear correlation between geomagnetic activity and electron density retrievals from COSMIC. At nighttime local times, the number of profiles with maximum electron densities in the E layer (below 200 km altitude) is well correlated with geomagnetic activity. We interpret this to mean that electron density increases due to precipitation are captured by the COSMIC profiles. These "E layer dominant ionosphere" (ELDI) profiles have geomagnetic latitudes that are consistent with climatological models of the auroral location. For the two HSS storms, that occurred in May of 2011 and 2012, a strong hemispheric asymmetry is observed, with nearly all the ELDI profiles found in the southern, less sunlit, hemisphere. Stronger aurora and precipitation have been observed before in winter hemispheres, but the degree of asymmetry deserves further study. For the two CME storms, occurring in July and November of 2012, large increases in the number of ELDI profiles are found starting in the storm's main phase but continuing for several days into the recovery phase. Analysis of the COSMIC profiles was extended to all local times for the July 2012 CME storm by relaxing the ELDI criterion and instead visually inspecting all profiles above 50° magnetic latitude for signatures of precipitation in the E region. For nine days during the July 2012 period, we find a signature of precipitation occurs nearly uniformly in local time, although the magnitude of electron density increase may vary with local time. The latitudinal extent of the precipitation layers is generally consistent with auroral climatology. However, after the storm main phase on 14 July 2012, the precipitation tended to be somewhat more equatorward than predicted by the climatology (by about 5-10° latitude). We conclude that, if analyzed appropriately, high latitude COSMIC profiles have the potential to contribute to our understanding of MI coupling processes and extend and improve existing models of the auroral region.

  1. The ionosphere under extremely prolonged low solar activity

    NASA Astrophysics Data System (ADS)

    Liu, Libo; Chen, Yiding; Le, Huijun; Kurkin, Vladimir I.; Polekh, Nelya M.; Lee, Chien-Chih

    2011-04-01

    A critical question in ionospheric physics is the state of the ionosphere and relevant processes under extreme solar activities. The solar activity during 2007-2009 is extremely prolonged low, which offers us a unique opportunity to explore this issue. In this study, we collected the global ionosonde measurements of the F2 layer critical frequency (foF2), E layer critical frequency (foE), and F layer virtual height (h?F) and the total electron content (TEC) maps produced by the Jet Propulsion Laboratory, which were retrieved from dual-frequency GPS receivers distributed worldwide, to investigate the ionospheric phenomena during solar minimum of cycle 23/24, particularly the difference in the ionosphere between solar minima of cycle 23/24 and the preceding cycles. The analysis indicates that the moving 1 year mean foF2 at most ionosonde stations and the global average TEC went to the lowest during cycle 23/24 minimum. The solar cycle differences in foF2 minima display local time dependence, being more negative during the daytime than at night. Furthermore, the cycle difference in daytime foF2 minima is about -0.5 MHz and even reaches to around -1.2 MHz. In contrast, a complex picture presents in global h?F and foE. Evident reduction exists prevailingly in the moving 1 year mean h?F at most stations, while no huge differences are detected at several stations. A compelling feature is the increase in foE at some stations, which requires independent data for further validation. Quantitative analysis indicates that record low foF2 and low TEC can be explained principally in terms of the decline in solar extreme ultraviolet irradiance recorded by SOHO/SEM, which suggests low solar EUV being the prevailing contributor to the unusual low electron density in the ionosphere during cycle 23/24 minimum. It also verifies that a quadratic fitting still reasonably captures the solar variability of foF2 and global average TEC at such low solar activity levels.

  2. Sources of the traveling ionospheric disturbances observed by the ionospheric TIDDBIT sounder near Wallops Island

    E-print Network

    Vadas, Sharon

    Click Here for Full Article Sources of the traveling ionospheric disturbances observed of these GWs. We then analyze the 59 traveling ionospheric disturbances (TIDs) observed by the TIDDBIT thermospheric body forces. Citation: Vadas, S. L., and G. Crowley (2010), Sources of the traveling ionospheric

  3. Estimating Electron Content Of The Ionosphere

    NASA Technical Reports Server (NTRS)

    Lanyi, G. E.

    1988-01-01

    Method for estimation total electron content of ionosphere. Based on measurements of signals transmitted from global positioning satellites (GPS's). Ionospheric delays obtained by measuring differential arrival times of signals at two different frequencies. Since GPS observations cover certain regions of sky, location of space probe to be calibrated might not overlap GPS field of view. Certain assumptions made about behavior of ionosphere so total electron content estimated in any direction from receiver.

  4. Magnetospheric interaction with Triton's ionosphere

    NASA Technical Reports Server (NTRS)

    Strobel, Darrell F.; Cheng, Andrew F.; Summers, Michael E.; Strickland, Douglas J.

    1990-01-01

    The large electron densities measured by the Voyager radio occultation experiment are attributed to the precipitation of magnetospheric electrons with energy above 10 keV. Because the ionospheric electric Pedersen conductivity of Triton is about 10,000-20,000 mho and the Alfven conductance is about 3.5 mho, direct convective flow of plasma into the essentially infinitely conducting ionosphere is negligible. Magnetospheric electrons are transported to Triton's ionopause by curvature drift as a result of weak magnetic field line draping in a sub-Alfvenic plasma interaction with Triton. At the ionopause energetic electrons have a high probability of elastic and inelastic scattering and precipitate into the upper atmosphere. The average power dissipation is estimated to be about (2 - 3) x 10 to the 8th W.

  5. Saturn's ionosphere - Inferred electron densities

    NASA Astrophysics Data System (ADS)

    Kaiser, M. L.; Desch, M. D.; Connerney, J. E. P.

    1984-04-01

    During the two Voyager encounters with Saturn, radio bursts were detected which appear to have originated from atmospheric lightning storms. Although these bursts generally extended over frequencies from as low as 100 kHz to the upper detection limit of the instrument, 40 MHz, they often exhibited a sharp but variable low frequency cutoff below which bursts were not detected. We interpret the variable low-frequency extent of these bursts to be due to the reflection of the radio waves as they propagate through an ionosphere which varies with local time. We obtain estimates of electron densities at a variety of latitude and local time locations. These compare well with the dawn and dusk densities measured by the Pioneer 11 Voyager Radio Science investigations, and with model predictions for dayside densities. However, we infer a two-order-of-magnitude diurnal variation of electron density, which had not been anticipated by theoretical models of Saturn's ionosphere, and an equally dramatic extinction of ionospheric electron density by Saturn's rings. Previously announced in STAR as N84-17102

  6. CORISS Observations of Ionospheric Scintillation

    NASA Astrophysics Data System (ADS)

    Straus, P. R.; Bishop, R. L.; Caton, R. G.; Groves, K. M.; Carrano, C. S.

    2009-12-01

    Rapid fluctuations in radio occultation (RO) signal to noise ratios and phase can signify the presence of fine scale ionospheric density irregularities along the occultation ray path. While such signatures are clearly identifiable in 1 Hz observations that are typically made at ionospheric tangent altitudes, high-rate (50 Hz) data is required to sample the full range of irregularity scale sizes responsible for L-band scintillation. At times the presence of intermediate-scale ionospheric structures can also be inferred from RO limb TEC and inverted electron density profiles, even when amplitude scintillations are not present. We present results of scintillation analysis of the first year of data from the CORISS instrument on the C/NOFS satellite, together with preliminary comparisons to scintillation data from overflights of the Air Force Research Laboratory’s ground-based SCINDA receivers that illustrate the characteristics of equatorial irregularities. Differences between scintillation indices derived from 1 Hz and 50 Hz observations will be discussed.

  7. Mechanisms of Ionospheric Mass Escape

    NASA Technical Reports Server (NTRS)

    Moore, T. E.; Khazanov, G. V.

    2010-01-01

    The dependence of ionospheric O+ escape flux on electromagnetic energy flux and electron precipitation into the ionosphere is derived for a hypothetical ambipolar pick-up process, powered the relative motion of plasmas and neutral upper atmosphere, and by electron precipitation, at heights where the ions are magnetized but influenced by photo-ionization, collisions with gas atoms, ambipolar and centrifugal acceleration. Ion pick-up by the convection electric field produces "ring-beam" or toroidal velocity distributions, as inferred from direct plasma measurements, from observations of the associated waves, and from the spectra of incoherent radar echoes. Ring-beams are unstable to plasma wave growth, resulting in rapid relaxation via transverse velocity diffusion, into transversely accelerated ion populations. Ion escape is substantially facilitated by the ambipolar potential, but is only weakly affected by centrifugal acceleration. If, as cited simulations suggest, ion ring beams relax into non-thermal velocity distributions with characteristic speed equal to the local ion-neutral flow speed, a generalized "Jeans escape" calculation shows that the escape flux of ionospheric O+ increases with Poynting flux and with precipitating electron density in rough agreement with observations.

  8. Saturn's ionosphere: Inferred electron densities

    NASA Technical Reports Server (NTRS)

    Kaiser, M. L.; Desch, M. D.; Connerney, J. E. P.

    1983-01-01

    During the two Voyager encounters with Saturn, radio bursts were detected which appear to have originated from atmospheric lightning storms. Although these bursts generally extended over frequencies from as low as 100 kHz to the upper detection limit of the instrument, 40 MHz, they often exhibited a sharp but variable low frequency cutoff below which bursts were not detected. We interpret the variable low-frequency extent of these bursts to be due to the reflection of the radio waves as they propagate through an ionosphere which varies with local time. We obtain estimates of electron densities at a variety of latitude and local time locations. These compare well with the dawn and dusk densitis measured by the Pioneer 11 Voyager Radio Science investigations, and with model predictions for dayside densities. However, we infer a two-order-of-magnitude diurnal variation of electron density, which had not been anticipated by theoretical models of Saturn's ionosphere, and an equally dramatic extinction of ionospheric electron density by Saturn's rings.

  9. Mid-latitude ionospheric perturbation associated with the Spacelab-2 plasma depletion experiment at Millstone Hill

    E-print Network

    Paris-Sud XI, Université de

    scatter radar at Millstone Hill captured the ionospheric response to the ®ring of the Space Shuttle In a sequence of planned experiments, the orbital maneuvering subsystem (OMS) engines of the Space Shuttle Challenger OMS thrusters near the peak of the F layer on July 30, 1985. Details of the excitation of airglow

  10. A technique for calculating ionospheric Doppler shifts from standard ionograms suitable for scientific, HF communication, and OTH radar applications

    Microsoft Academic Search

    K. J. W. Lynn

    2009-01-01

    High-resolution Doppler ionograms taken at 5 min intervals were obtained from a KEL IPS 71 ionosonde operating over a full ionosonde sweep range. The ionograms were converted into true height profiles using the program POLAN. POLAN also produced an equivalent parabolic layer model of best fit to the true height profile. A parabolic layer model of the ionosphere is defined

  11. Recent Advances in Studies of Ionospheric Modification Using Rocket Exhaust (Invited)

    NASA Astrophysics Data System (ADS)

    Bernhardt, P. A.

    2009-12-01

    Rocket exhaust interacts with the ionosphere to produce a wide range of disturbances. A ten second burn of the Orbital Maneuver Subsystem (OMS) engines on the Space Shuttle deposits over 1 Giga Joule of energy into the upper atmosphere. The exhaust vapors travel at speeds between 4.7 and 10.7 km/s coupling momentum into the ions by both collisions and charge exchange. Long-lived plasma irregularities are formed by the artificial hypersonic “neutral wind” passing through the ionosphere. Charge exchange between the fast neutrals and the ambient ions yields high-speed ion beams that excite electro-static plasma waves. Ground based radar has been used to detect both field aligned irregularities and electrostatic turbulence driven by the Space Shuttle OMS exhaust. Molecular ions produced by the charge exchange with molecules in the rocket exhaust recombine with a time scale of 10 minutes leaving a residual plasma depression. This ionospheric “hole” fills in by ambipolar diffusion leaving a depleted magnetic flux tube. This large scale reduction in Pedersen conductivity can provide a seed for plasma interchange instabilities. For instance, a rocket firing on the bottom side of the ionosphere near the equator can trigger a Rayleigh-Taylor instability that is naturally seen as equatorial Spread-F. The Naval Research Laboratory has been exploring these phenomena with dedicated burns of the Space Shuttle OMS engines and exhaust releases from rockets. The Shuttle Ionospheric Modification with Pulsed Localized Exhaust (SIMPLEX) series of experiments uses ground radars to probe the ionosphere affected by dedicated burns of the Space Shuttle OMS engines. Radars located at Millstone Hill, Massachusetts; Arecibo, Puerto Rico; Jicamarca, Peru; Kwajalein, Marshall Island; and Alice Springs, Australia have participated in the SIMPLEX program. A companion program called Shuttle Exhaust Ionospheric Turbulence Experiment has or will use satellites to fly through the turbulence ionosphere produced by Space Shuttle Exhaust. This program is employing the Air Force Research Laboratory C/NOFS and the Canadian CASSIOPE/EPoP satellites to make in situ measurements of Space Shuttle exhaust effects. Finally, NRL is conducting the Charged Aerosol Release Experiment which employs a solid rocket motor to modify the ionosphere using supersonic particulate injection and dusty plasma formation. Both the theoretic basis for these experiments and as summary of the experimental results will be presented.

  12. Plasma interactions in Titan's ionosphere

    NASA Astrophysics Data System (ADS)

    Richard, Matthew Scott

    The Cassini mission has collected vast amounts of in situ data within the ionosphere of Saturn's moon Titan and has shown the complexity of the interaction of Saturn's magnetospheric plasma with Titan. Models of the interactions have been created; however, none have been able to completely describe the observed phenomena. Most notably, modeled electron densities are much larger than the electron densities observed by instruments aboard the Cassini spacecraft. This thesis will explore the possible causes of this discrepancy between measured and modeled electron densities using models calculating the production of ions due to solar photons and magnetospheric electrons precipitating down magnetic field lines and into the ionosphere, temperature calculations of the thermal electron population (electrons with energies less than 2 eV), and chemical reactions in the ionosphere. The results of these models will be compared to data collected by instruments aboard Cassini. Modeled ion production rates and thermal electron temperature profiles will be shown to be in good agreement with ion production rates derived from data collected by the Ion -- Neutral Mass Spectrometer (INMS) and electron temperatures measured by the Radio and Plasma Wave Science -- Langmuir Probe above 1000 km. Modeled ion mass spectra will be generated near the ionospheric peak and will be compared with the INMS measured mass spectra to examine the effects of chemical loss processes on the ion densities. From this analysis it will be shown that the overabundance of modeled electrons is not caused by over production of ions and that chemical loss processes, predominantly the electron dissociative recombination coefficient of HCNH+, need to be reexamined. After the model has been proven to reproduce accurate profiles of ion production and temperature, ion production profiles will be generated using solar photons and magnetospheric electron fluxes for four canonical cases detailed in the work of Rymer et al. [2009] and a globally averaged model of the neutral densities based on INMS neutral measurements from more than 30 flybys of Titan. These generic profiles can be combined to predict ionospheric observations made by the Cassini spacecraft for a variety of solar zenith angles and magnetospheric conditions.

  13. Laboratory chamber experiments exploring the potential use of artificially ionized layers of gas as a Bragg reflector for over-the-horizon signals

    Microsoft Academic Search

    S. P. Kuo; Y. S. Zhang; M. C. Lee; Paul Kossey; Robert J. Barker

    1992-01-01

    A set of parallel plasma layers is generated by two intersecting microwave pulses in a chamber containing dry air at a pressure comparable to the upper atmosphere. The dependence of the breakdown conditions on the pressure and pulse length is examined. The results are shown to be consistent with the appearance of tail erosion of microwave pulse caused by air

  14. Artificial Incubation

    Microsoft Academic Search

    C. J. P. Cave; T. Vernon Jones

    1925-01-01

    IN the account of Mr. Llewelyn B. Atkinson's article on ``The Scientific Principles of Artificial Incubation'' (NATURE, February 21, p. 282), the author is quoted as saying that practically every type of incubator has the air too dry. If this is so, the number of eggs hatched should be dependent to some extent on the humidity of the outside air.

  15. Artificial Sweeteners

    NSDL National Science Digital Library

    Science Update

    2004-08-02

    This Science Update, from Science NetLinks, features an interview with Purdue University psychologist Susie Swithers about new research suggesting that artificial sweeteners may promote overeating. Science Updates are audio interviews with scientists and are accompanied by a set of questions as well as links to related Science NetLink lessons and other related resources.

  16. Ionospheric Perturbation In Association With Seismic Activity, A Statistical Study

    NASA Astrophysics Data System (ADS)

    Hobara, Y.; Parrot, M.

    Ionospheric perturbations in response to major seismic activities are derived either by case study or statistical approach. foF2 (F2 layer o-mode critical frequency) records from ionospheric sounding stations scattered all over the world between 1957 and 1990 are taken into account in this study. Daily plot of foF2 (the deviation of foF2 from its 7day-running median value) for each local hour is used to remove the diurnal and seasonal patterns for each station. Two sharp decreases in foF2 are observed in association with large seismic event like Hachinohe earthquake (M=8.25) a couple of days before and after the main shock. These decreases are seen only at several iono- spheric stations within 1500km from the epicenter and Ap indices during the time of these decreases are small enough not to trigger strong disturbances in the ionosphere. Furthermore, occurrence time is predominantly in the daytime period. As a statistical study, we examine superposed epoch of the foF2 records for more than 1000 seis- mic events occurring during 27 years close to 48 different stations. Preliminary results from mid magnetic latitude range (20 mlat 40) based on the averaging over each station tend to have increase in foF2 around 5 and 15 days before earthquakes within a 160-day time period. They indicate possible link between the seismic ac- tivity and the overlaying ionosphere. However rather large fluctuating characteristics prevent us to reveal a clear relation with earthquakes at low and high latitude stations.

  17. A multi-instrument study of high-latitude ionospheric irregularities and their effects on GPS ionospheric scintillation

    NASA Astrophysics Data System (ADS)

    van der Meeren, Christer; Oksavik, Kjellmar; Moen, Jøran; Romano, Vincenzo

    2013-04-01

    Scintillations are rapid amplitude and phase fluctuations of electromagnetic signals. GNSS-based systems may be disturbed by plasma irregularities and structures such as plasma patches (areas of enhanced electron density) and plasma gradients in the ionosphere. When the GNSS radio signals propagate through such areas, in particular gradients, the signals experience scintillations that at best increases positioning errors and at worst may break the receiver's signal lock, potentially resulting in the GNSS receiver losing track of its position. Due to the importance of many GNSS applications, it is desirable to study the scintillation environment to understand the limitations of the GNSS systems. For this study, GPS receiver scintillation and Total Electron Content (TEC) data from high-latitude locations will be combined with several other data sets, including the EISCAT Svalbard Radar (ESR) and allsky cameras to perform a multi-instrument case study of GPS ionospheric scintillations. The EISCAT data provides a means to determine the altitude and density of the F layer, which can then be used to calibrate allsky projections as well as coordinates of ionospheric piercing points of the GPS signals. The focus will be studying any connection between scintillations and polar cap patches; however, other interesting and related findings will also be presented, herein statistical long-timespan studies of GPS TEC and/or scintillation data.

  18. Ionospheric disturbances on December 10, 1988, observed from the Arkhangelsk station

    NASA Astrophysics Data System (ADS)

    Kozlov, E. F.; Samorokin, N. I.; Ben'kova, N. P.

    1993-02-01

    The paper describes the ionospheric disturbance phenomena on December 10, 1988, recorded at the Arkhangelsk station as part of the SUNDIAL project. On this date, a strong ionospheric substorm was observed which was characterized by a deep trough in the subauroral zone with a polarized jet. A sharp interruption of ionization in the F2 layer in the afternoon hours was observed, as were additional scattered reflections from the trough walls and the corpuscular Es species. Data collected at three stations (Mezen', Arkhangelsk, and Karpogory) made it possible to follow the evolution of the disturbance and its latitudinal distribution.

  19. Delta function excitation of waves in the earth's ionosphere

    NASA Technical Reports Server (NTRS)

    Vidmar, R. J.; Crawford, F. W.; Harker, K. J.

    1983-01-01

    Excitation of the earth's ionosphere by delta function current sheets is considered, and the temporal and spatial evolution of wave packets is analyzed for a two-component collisional F2 layer. Approximations of an inverse Fourier-Laplace transform via saddle point methods provide plots of typical wave packets. These illustrate cold plasma wave theory and may be used as a diagnostic tool since it is possible to relate specific features, e.g., the frequency of a modulation envelope, to plasma parameters such as the electron cyclotron frequency. It is also possible to deduce the propagation path length and orientation of a remote radio beacon.

  20. Ionization sources in Titan's deep ionosphere

    Microsoft Academic Search

    Marina Galand; Roger Yelle; Jun Cui; Jan-Erik Wahlund; Véronique Vuitton; Anne Wellbrock; Andrew Coates

    2010-01-01

    We analyze a multi-instrumental data set from four Titan encounters by the Cassini spacecraft to investigate in detail the formation of the ionosphere. The data set includes observations of thermospheric and ionospheric species and suprathermal electrons. A model describing the solar and electron energy deposition is used as an organizing element of the Cassini data set. We first compare the

  1. Nonlinear effects in the ionospheric Alfvén resonator

    Microsoft Academic Search

    D. Sydorenko; R. Rankin; K. Kabin

    2008-01-01

    A two-dimensional nonlinear multi-fluid MHD model of the ionosperic Alfvén resonator is presented. The resonator is excited by a packet of shear Alfvén waves propagating downward toward the ionosphere from high altitudes. It is shown that the nonlinear (ponderomotive) force of standing oscillations in the ionospheric Alfvén resonator creates plasma flows along the geomagnetic field that modify the plasma density

  2. Solitons versus parametric instabilities during ionospheric heating

    NASA Technical Reports Server (NTRS)

    Nicholson, D. R.; Payne, G. L.; Downie, R. M.; Sheerin, J. P.

    1984-01-01

    Various effects associated with ionospheric heating are investigated by numerically solving the modified Zakharov (1972) equations. It is shown that, for typical ionospheric parameters, the modulational instability is more important than the parametric decay instability in the spatial region of strongest heater electric field. It is concluded that the modulational instability leads to the formation of solitons, as originally predicted by Petviashvili (1976).

  3. The structure of the Venus ionosphere

    Microsoft Academic Search

    L. H. Brace; A. J. Kliore

    1991-01-01

    Our current knowledge of the spatial structure of the Venus ionosphere and its temporal behavior is reviewed, with emphasis on the more recent Pioneer Venus measurements and analysis not covered in earlier reviews. We will stress the ionosphere structure, since other papers in this issue deal with its dynamics, and its magnetic properties. We also discuss some of the limitations

  4. Investigations of the ionosphere by space techniques

    NASA Technical Reports Server (NTRS)

    Bowhill, S. A.

    1974-01-01

    Much of the impetus to ionosphere research since the International Geophysical Year has come from new types of measurement using space vehicles. The key developments are outlined, together with the contributions that they have made to the understanding of the ionosphere.

  5. First measurement of winds in the ionosphere.

    E-print Network

    Danforth, Bryan Nicholas

    and Ionosphere Center (NAIC) is cre- ated to manage the huge radio telescope for the NSF. 1958 William E. Gordon's ionosphere, scientists realize the telescope's impact for radio and radar astronomy, as well. 1964 to get the committee appointed." William E. Gordon Professor Emeritus Rice University (Arecibo telescope

  6. The ionospheres and plasma tails of comets

    Microsoft Academic Search

    D. A. Mendis; W.-H. Ip

    1977-01-01

    The paper reviews the current state of knowledge about cometary plasma (type I) tails and ionospheres. Observational statistics for type I tails are examined along with spectroscopic observations of plasma tails, identified ion species in such tails, and the morphology of cometary plasma tails and ionospheres. Evidence for a strong interaction between comets and the solar wind is evaluated on

  7. Magnetospheric control of the bulk ionospheric plasma

    SciTech Connect

    Sojka, J.J.; Schunk, R.W.

    1987-01-01

    The temperature, composition, and circulation of the high-latitude, ionosphere display a marked variation with altitude, latitude, longitude, universal time, season, solar cycle, and geomagnetic activity. This variation is largely a consequence of the effect that magnetospheric electric fields, particle precipitation, and heat flows have on the ionosphere. At F-region altitudes, the entire ionosphere drifts in response to magnetospheric electric fields, with the horizontal drift generally displaying a two-cell pattern of antisunward flow over the polar cap and return flow at lower latitudes. This ionospheric motion, in combination with downward magnetospheric heat flows and ion production due to energetic-particle precipitation, act to produce interesting ionospheric features such as ion and electron temperature hot spots, plasma blobs, localized ionization troughs, and extended tongue of ionization, and anomalous F-region peak altitudes and densities. The time delay for the ionosphere to respond to changing magnetospheric conditions is a strong function of altitude and can be as long as 3 to 4 hours in the upper F-region. The ionosphere's response to changing magnetospheric conditions are described using a time-dependent high-latitude ionospheric model.

  8. Ionospheric feedback instability and substorm development

    Microsoft Academic Search

    A. V. Streltsov; T. R. Pedersen; E. V. Mishin; A. L. Snyder

    2010-01-01

    We report on ground magnetic and optical observations performed during an ionospheric heating experiment at the High Frequency Active Auroral Research Program (HAARP) facility in Alaska on 29 October 2008. The experiment was aimed at generation of large-amplitude ULF electromagnetic waves by triggering and facilitating development of the ionospheric feedback instability (IFI) in the region adjacent to a bright auroral

  9. Claudia TIERNO ROS: Improvement of multidimensional models of the ionosphere The ionosphere is a portion of the upper atmosphere; it has the characteristic of being easily

    E-print Network

    Schuh, Harald

    . The ionosphere plays an important role in geodesy since the signals travelling through it (correspondingClaudia TIERNO ROS: Improvement of multidimensional models of the ionosphere The ionosphere in ionosphere research. For instance, project VLBIonos aimed at using VLBI observations

  10. GPS Array as a Sensor of Lithosphere, Troposphere and Ionosphere

    NASA Astrophysics Data System (ADS)

    Heki, K.

    2011-12-01

    The Japanese dense array of GPS receivers (GEONET) started operation in 1993, and is currently composed of ~1200 stations. GPS (or GNSS in general) receivers can be compared to a Swiss army knife: it could be used not only for positioning (a knife) but also for various purposes, e.g. remote sensing of tropospheric water vapor or ionospheric electrons (screw driver, tin opener etc). Dense GPS arrays have been found extremely useful for variety of geophysical studies. In this lecture, I briefly review their historical achievements, recent highlights, and future perspectives. In Japan, first generation GPS stations were implemented in 1993 (the Kanto-Tokai region) and 1994 (nationwide) by GSI, Japan. Shortly after the launch, they successfully caught coseismic crustal movement of several major earthquakes, the 1994 October Shikotan (Mw8.3), the 1994 December Sanriku (Mw7.6), and the 1995 January Kobe (Mw7.0) earthquakes. These earthquakes accelerated the densification of the GPS network, achieving 1000 in the number of stations within the following 2-3 years. In addition to coseismic jumps, important discoveries continued in 1990s, e.g. large-scale afterslip of interplate thrust earthquakes and slow slip events (SSE). Later it was shown that tilt- and strainmeter can better observe short-term SSEs, and InSAR can draw more detailed maps of coseismic crustal movements. Now GPS array is recognized as a good tool to measure crustal movement with high temporal resolution and stability and with moderate sensitivity and spatial resolution. GPS data are also useful to study hydrosphere. Seasonal crustal movements in Japan mainly reflect changes in hydrological loads. Multipath signatures in GPS data also provide useful information on the environment around the antenna, e.g. soil moisture, snow depth and vegetation. I will compare the snow depth record over a winter inferred by analyzing GPS multipath signatures, and observed by a conventional apparatus. GPS can also measure precipitable water vapor (PWV) of troposphere. After intense feasibility studies of GPS meteorology in 1990s, PWV information from GEONET has been routinely assimilated in the operational mesoscale model of the Japan Meteorological Agency since 2009. It is found useful in predicting localized heavy rainfalls that often attack Japan in summer. It is fairly easy to measure ionospheric total electron content (TEC) by using phase differences between L1 and L2 carriers from GPS satellites. Applications of GPS for upper atmospheric studies started for ionospheric disturbances of space weather origins. In 2003, clear coseismic ionospheric disturbances of the Tokachi-Oki earthquake were found, and the GPS-TEC technique has been extensively used to study ionospheric disturbances of solid earth origins, e.g. earthquakes and volcanic eruptions. There are also several recent examples of artificial ionospheric disturbances caused by rocket launches and passage of ballistic missiles from North Korea above NE Japan. In the last part of the lecture, I summarize what the GPS array saw before, during and after the 2011 Tohoku-Oki earthquake. The topic covers not only pre-, co- and postseismic crustal movements, but also results of high-rate sampling, and possible detection of precursory changes in ionospheric TEC immediately before the earthquake.

  11. Ion Internal Excitation and Co++ 2 Reactivity: Effect On The Titan, Mars and Venus Ionospheric Chemistry

    NASA Astrophysics Data System (ADS)

    Nicolas, C.; Zabka, J.; Thissen, R.; Dutuit, O.; Alcaraz, C.

    In planetary ionospheres, primary molecular and atomic photoions can be produced with substantial electronic and vibrational internal energy. In some cases, this is known to strongly affect both the rate constants and the branching ratio between the reac- tion products. A previous experimental study (Nicolas et al.) made at the Orsay syn- chrotron radiation facility has shown that many endothermic charge transfer reactions which were not considered in the ionospheric chemistry models of Mars, Venus and Earth have to be included because they are driven by electronic excitation of the parent ions. New measurements on two important reactions for Titan and Mars ionospheres, N+ + CH4 and O+ + CO2, will be presented. Branching ratios between products are very different when the parent atomic ions are prepared in their ground states, N+(3P) and O+(4S), or in their first electronic metastable states N+(1D) and O+(2D or P). 2 As the lifetime of these states are long enough, they survive during the mean time be- tween two collisions in the ionospheric conditions. So, the reactions of these excited states must be included in the ionospheric models. Absolute cross section measurements of the reactivity of stable doubly charged molec- ular ions CO++ and their implications for the Martian ionosphere will also be pre- 2 sented. The molecular dication CO++ production by VUV photoionisation and elec- 2 tron impact in the upper ionosphere of Mars is far from being negligible. However, to determine its concentration, it was necessary to evaluate the major loss channels of these ions. For this purpose, we measured the absolute reaction cross section of the sta- ble dications with CO2, the major neutral species of the Mars ionosphere. CO++ ions 2 were produced either by photoionisation or by electron impact, and a reaction cross section of 45 Å2 with 13CO2 was measured. The reaction leads to charge transfer or to collision induced dissociation. These results were integrated in a model predicting the existence of a CO++ dication layer in the Mars ionosphere. 2 Implications of all these measurements for the ionospheric models are studied in collaboration with O.Witasse (ESA-ESTEC, The Netherlands), J.Lilensten (LPG, France) and P.L.Blelly (CESR, France) who developed a new model for Mars. C. Nicolas, C. Alcaraz, J. Zabka, R. Thissen, and O. Dutuit (submitted to Planet. Space Sci. 2001)

  12. Photochemistry of Titan's Atmosphere and Ionosphere

    NASA Astrophysics Data System (ADS)

    Krasnopolsky, V. A.

    2008-05-01

    A global-mean model of coupled neutral and ion chemistry on Titan has been developed. Unlike the previous models, the model involves ambipolar diffusion and escape of ions, hydrodynamic escape of light species with molecular mass less than 20, and calculates the H2 and CO densities near the surface that were assigned previously. We tried to reduce the numbers of species and reactions in the model and remove all species and reactions that weakly affect balances of the observed atmospheric components. However, all new species observed or derived from the Cassini observations and related reactions are included in the model. Hydrocarbon chemistry is extended to bicyclic aromatic hydrocarbons (up to C12H10 for neutrals and C10H11+ for ions) but does not include PAHs. The model involves 375 reactions of 81 neutrals and 33 ions. Chemistry is driven by the solar UV and EUV photons, magnetospheric electrons, and cosmic rays. Absorption of the solar UV radiation by Titan's haze was calculated using the data on the haze particles from the optical observations at the Huygens probe and a code for the aggregate particles. Hydrocarbon, nitrile, and ion chemistries are strongly coupled on Titan. Therefore the approach in some previous models when at first hydrocarbons, then nitriles, and finally ions were calculated may result in significant error. Similarly, models of ionospheric composition may be in error because they neglect effects of ion reactions on the neutral atmosphere. The model densities of various species are in reasonable agreement with the observations. However, the calculated vertical profiles in the stratosphere are steeper than those retrieved from the CIRS limb observations. The ionosphere includes an E-layer at 700-900 km and F1-layer above 900 km with a peak electron density of 3700 cm-3 at 1120 km (SZA = 60°). A narrow peak at 80 km is due to the cosmic ray ionization. The calculated densities of major ions in the nighttime ionosphere at 1100 km are in good agreement with the observed INMS mass spectrum. Ion chemistry dominates in the production of bicyclic aromatic hydrocarbons (indene and naphthalene) above 750 km. This production peaks at 820 km where [C9H11+] = 450 cm-3. However, the major production of the polymer blocks is in the reaction C6H + C4H2 ? C10H3 which peaks at 440 km. Polymerizations of HC3N and HCN peak at 320 and 220 km, respectively, and the bulk condensation of hydrocarbons occurs below 100 km. Overall, precipitation rate of the photochemical products is equal to 7.5 kg cm-2 Byr-1. Escape rates of methane and hydrogen are 2.2 and 1.5 kg cm-2 Byr-1, respectively. The ion escape is small, and we do not consider nonthermal escape processes in our model. The escape of CH4 and H2 for the age of Titan corresponds to a loss of a methane ocean 0.5 km deep and may be compared to the global-mean depth of the hydrocarbon lakes and seas of ~1 m on Titan. The model does not support the low C/N ratio observed by the Huygens ACP in Titan's haze.

  13. Ionospheric modification by rocket effluents. Final report

    SciTech Connect

    Bernhardt, P.A.; Price, K.M.; da Rosa, A.V.

    1980-06-01

    This report describes experimental and theoretical studies related to ionospheric disturbances produced by rocket exhaust vapors. The purpose of our research was to estimate the ionospheric effects of the rocket launches which will be required to place the Satellite Power System (SPS) in operation. During the past year, we have developed computational tools for numerical simulation of ionospheric changes produced by the injection of rocket exhaust vapors. The theoretical work has dealt with (1) the limitations imposed by condensation phenomena in rocket exhaust; (2) complete modeling of the ionospheric depletion process including neutral gas dynamics, plasma physics, chemistry and thermal processes; and (3) the influence of the modified ionosphere on radio wave propagation. We are also reporting on electron content measurements made during the launch of HEAO-C on Sept. 20, 1979. We conclude by suggesting future experiments and areas for future research.

  14. Long-Term and Transient Variability of the Low Ionosphere from Very Low Frequency Ground-Based Observations

    NASA Astrophysics Data System (ADS)

    Raulin, Jean Pierre

    2012-07-01

    At least three regions are forming the lower part of the ionosphere: the transient C-region at sunrise, the D-region during daytime and the bottom E-region at nighttime. These regions are accessible only through rocket in situ measurements and radio sounding techniques from the ground. Contrary to the upper layers, any prediction is difficult in the low ionosphere because of its important time variability, and its complex chemistry. In this work we will review the time variability of the low ionosphere on different timescales as deduced from Very Low Frequency ground based observations. Long-term variations are essentially due to the solar activity cycle and the solar rotation, and these variations reflect level changes of the ionizing Lyman-alpha radiation. On shorter transient timescales, solar flares and geomagnetic disturbances affect the low ionosphere when large amount of solar X-ray photons and/or particles are injected and deposit their energy at altitudes between 70 and 30 km. Then, the monitoring the low ionosphere regions may be used as an indirect and efficient tool to study space weather conditions. The transient time variability of the low ionosphere can also originate from below, that is due to the neutral atmosphere dynamics, which also includes meteorological phenomena. Then planetary and gravity waves can penetrate the lower ionosphere. To a lower extent, tidal oscillations and acoustic waves may affect the lowermost part of the ionosphere, although experimental researches in these domains are necessary. Finally, lightning induced perturbations of the low ionosphere will be discussed, and, these include sprites, transient gamma-ray flashes (TGF), blue elves and Lightning Precipitation Events (LPE).

  15. Charged particles in Titan's ionosphere

    NASA Astrophysics Data System (ADS)

    Tripathi, Sachchida

    2010-05-01

    Charged particles in Titan's ionosphere Marykutty Michael1, Sachchida Nand Tripathi1,2,3, Pratima Arya1 1Indian Institute of Technology Kanpur 2Oak Ridge Associated Universities 3NASA Goddard Space Flight Center Observations by two instruments onboard the Cassini spacecraft, Ion Neutral Mass Spectrometer (INMS) and CAssini Plasma Spectrometer (CAPS), revealed the existence of heavy hydrocarbon and nitrile species with masses of several thousand atomic mass units at altitudes of 950 - 1400 km in the atmosphere of Titan (Waite et al., 2007; Crary et al., 2009). Though these particles were believed to be molecules, they are most likely aerosols formed by the clumping of smaller molecules (Waite et al., 2009). These particles were estimated to have a density of 10-3 kg m-3 and a size of up to 256 nm. The existence of very heavy ions has also been observed by the CAPS components with a mass by charge ratio of up to 10000 (Coates et al., 2007, 2009; Sittler et al., 2009). The goal of this paper is to find out whether the so called heavy ions (or charged particles) are generated by the charge transfer of ions and electrons to the particles. The charging of these particles has been studied by using the charge balance equations that include positive ions, negative ions, electrons, neutral and charged particles. Information on the most abundant ion clusters are obtained from Vuitton et al., (2009) and Wilson and Atreya, (2004). Mass by charge ratio thus calculated will be compared with those observed by Coates et al. (2007). References: Coates AJ, et al., Discovery of heavy negative ions in Titan's ionosphere, Geophys. Res. Lett., 34:L22103, 2007. Coates AJ, et al., Heavy negative ions in titan's ionosphere: altitude and latitude dependence. Planet. Space Sci., doi:10.1016/j.pss.2009.05.009, 2009. Crary F.J., et al., Heavy ions, temperatures and winds in titan's ionosphere: Combined cassini caps and inms observations. Planet. Space Sci., doi:10.1016/j.pss.2009.09.006, 2009. Sittler,E.C. et al., Heavy ion formation in Titan's ionosphere: Magnetospheric introduction of free oxygen and a source of Titan's aerosols? Planet. Space Sci., doi:10.1016/j.pss.2009.07.017, 2009. Vuitton, V., Negative ion chemistry in Titan's upper atmosphere, Planet. Space Sci., doi:10.1016/j.pss.2009.04.004, 2009. Waite J.H, et al., The process of tholin formation in Titan's upper atmosphere. Science, doi: 10.1126/science.1139727, 316, 870, 2007. Waite JH, et al., High altitude production of Titan's aerosols, In Titan from Cassini-Huygens, edited by RH. Brown, J.P Lebreton, JH Waite, Springer, 2009. Wilson, E.H. and S. Atreya, Current state of modeling the photochemistry of Titan's mutually dependent atmosphere and ionosphere, J. Geophys. Res., 109, E06002, doi:10.1029/2003JE002181, 2004.

  16. Present and Future IGS Ionosphere Working Group Activities

    Microsoft Academic Search

    Andrzej Krankowski

    2008-01-01

    Nowadays the Ionosphere Working Group of the International GNSS Service (IGS) generates two types of ionospheric products: final and rapid, respectively. This IGS Iono WG started the routine generation of ionosphere vertical total electron content (TEC) maps in June 1998. There are currently four IGS Associate Analysis Centres (IAACs) for ionosphere products: CODE (Center for Orbit Determination in Europe, University

  17. Measurement of the amplitude and phase fluctuation spectrum of satellite signals in the case of the action of high-power radio waves on the ionosphere

    Microsoft Academic Search

    F. I. Vybornov; L. M. Erukhimov; G. P. Komrakov; V. I. Kosolapenko; V. A. Kriazhev

    1986-01-01

    Artificial ionospheric irregularities produced by high-power radio-frequency heating were investigated by measuring signals from NNSSA satellites at the coherent frequencies 150 and 400 MHz. Spectral processing of the data indicates the existence of two spectrum types of artificial irregularities excited by high-power short waves: (1) a spectrum with a monotonic power dependence and (2) a spectrum with a peak in

  18. Artificial Rheotaxis

    NASA Astrophysics Data System (ADS)

    Palacci, Jeremie; Sacanna, Stefano; Hanson, Kasey; Vatchinsky, Adrian; Pine, David; Chaikin, Paul

    2013-03-01

    Self propelled colloids realize a controlled realization of an artificial bacterium. However living systems present a range of advanced properties such as the migration in gradients, or taxis, based on complex conformational change of proteins. For example, rheotaxis, the directed movement of an organism resulting from a fluid flow, has been reported notably for fish, e.g. salmon, or spermatozoa. Here, we present experimental observations of artificial rheotaxis, i.e. upstream migration of self propelled particles in the presence of a flow. We will present a simple model to account for this surprising effect. In the absence of biological component, this effect is intriguing and questions the ingredients at stake in the living matter.

  19. Observations of ELF signatures arising from space-vehicle disturbances of the ionosphere

    SciTech Connect

    Dea, J.Y.; Van Bise, W.; Rauscher, E.A.; Boerner, W.

    1991-05-01

    The authors report on observations of Extremely Low Frequency (ELF) signatures during exit or reentry of space vehicles through the ionosphere. The two modes regularly observed gave signals that peaked at 5.6 Hz and 11.2 Hz. The evidence points to the lower ionosphere, i.e., the D- and E-layers, as the generator of these signals. The measurements were performed using ground-based multiturn coil sensors located in Reno and San Diego. The nature of these signals is unclear at present but it is surmised that they are detecting either the evanescent fields of hydromagnetic waves traveling in the ionosphere or the oscillating geomagnetic field associated with these hydromagnetic waves.

  20. Artificial Wetlands

    NSDL National Science Digital Library

    American Association for the Advancement of Science (; )

    2005-04-11

    Golf courses are known as places of recreation. But some of them could someday double as water treatment facilities. Water hazards on golf courses can be used to control environmental hazards. That's according to Purdue University soil microbiologist Ron Turco. He says the artificial wetlands can also control flooding in surrounding communities, by collecting excess water. This Science Update looks at the research, which leads to these findings and offers links to other resources for further inquiry.

  1. Emergent Frame Recognition and Its Use in Artificial Creatures

    Microsoft Academic Search

    Luc Steels

    1991-01-01

    Artificial creatures are autonomous mobile agents that have to react in real-time to sensors and plan and perform actions in the real world. Current effective architectures for artificial creatures are behavior-based and use variants of the subsumption architecture. The paper proposes an extension to these architectures in terms of a layer which intro­ duces cognitive capabilities to artificial creatures. This

  2. Saturn: atmosphere, ionosphere, and magnetosphere.

    PubMed

    Gombosi, Tamas I; Ingersoll, Andrew P

    2010-03-19

    The Cassini spacecraft has been in orbit around Saturn since 30 June 2004, yielding a wealth of data about the Saturn system. This review focuses on the atmosphere and magnetosphere and briefly outlines the state of our knowledge after the Cassini prime mission. The mission has addressed a host of fundamental questions: What processes control the physics, chemistry, and dynamics of the atmosphere? Where does the magnetospheric plasma come from? What are the physical processes coupling the ionosphere and magnetosphere? And, what are the rotation rates of Saturn's atmosphere and magnetosphere? PMID:20299587

  3. Dust Acoustic Solitons in the Dusty Plasma of the Earth's Ionosphere

    SciTech Connect

    Kopnin, S.I.; Kosarev, I.N.; Popel, S.I. [Institute of Geosphere Dynamics, Russian Academy of Sciences, Leninskii pr. 38-1, Moscow, 119334 (Russian Federation); Yu, M.Y. [Institute for Theoretical Physics I, Ruhr University Bochum, D-44780 Bochum (Germany)

    2005-03-15

    Stratified structures that are observed at heights of 80-95 km in the lower part of the Earth's ionosphere are known as noctilucent clouds and polar mesosphere summer echoes. These structures are thought to be associated with the presence of vast amounts of charged dust or aerosols. The layers in the lower ionosphere where there are substantial amounts of dust are called the dusty ionosphere. The dust grains can carry a positive or a negative charge, depending on their constituent materials. As a rule, the grains are ice crystals, which may contain metallic inclusions. A grain with a sufficiently large metallic content can acquire a positive charge. Crystals of pure ice are charged negatively. The distribution of the dust grains over their charges has a profound impact on the ionizational and other properties of dust structures in the dusty ionosphere. In the present paper, a study is made of the effect of the sign of the dust charge on the properties of dust acoustic solitons propagating in the dusty ionosphere. It is shown that, when the dust charge is positive, dust acoustic solitons correspond to a hill in the electron density and a well in the ion density. When the dust is charged negatively, the situation is opposite. These differences in the properties of dust acoustic solitons can be used to diagnose the plasmas of noctilucent clouds and polar mesosphere summer echoes.

  4. Artificial Aurora Generated by HAARP (Invited)

    NASA Astrophysics Data System (ADS)

    Streltsov, A. V.; Kendall, E. A.

    2013-12-01

    We present results from the ionospheric heating experiment conducted on March 12, 2013 at the High Frequency Active Auroral Research Program (HAARP) facility in Alaska. During the experiment HAARP transmitted X-mode 4.57 MHz waves modulated with the frequency 0.9 mHz and pointed in the direction of the magnetic zenith. The beam was focused to ~20 km spot at the altitude 100 km. The heating produces two effects: First, it generates magnetic field-aligned currents producing D and H components of the magnetic field with frequency 0.9 mHz detected by fluxgate magnetometer in Gakona. Second, the heating produced bright luminous structures in the heated region detected with the SRI telescope in 427.8 nm, 557.7 nm, 630.0 nm wavelengths. We emphasize, that for the best of our knowledge, this is the first experiment where the heating of the ionosphere with X-mode produces luminous structures in the ionosphere. We classify this luminosity as an 'artificial aurora', because it correlate with the intensity of the magnetic field-aligned currents, and such correlation is constantly seen in the natural aurora.

  5. North-south components of the annual asymmetry in the ionosphere

    NASA Astrophysics Data System (ADS)

    Gulyaeva, T. L.; Arikan, F.; Hernandez-Pajares, M.; Veselovsky, I. S.

    2014-07-01

    A retrospective study of the asymmetry in the ionosphere during the solstices is made using the different geospace parameters in the North and South magnetic hemispheres. Data of total electron content (TEC) and global electron content (GEC) produced from global ionospheric maps, GIM-TEC for 1999-2013, the ionospheric electron content (IEC) measured by TOPEX-Jason 1 and 2 satellites for 2001-2012, the F2 layer critical frequency and peak height measured on board ISIS 1, ISIS 2, and IK19 satellites during 1969-1982, and the earthquakes M5+ occurrences for 1999-2013 are analyzed. Annual asymmetry is observed with GEC and IEC for the years of observation with asymmetry index, AI, showing January > July excess from 0.02 to 0.25. The coincident pattern of January-to-July asymmetry ratio of TEC and IEC colocated along the magnetic longitude sector of 270° ± 5°E in the Pacific Ocean is obtained varying with local time and magnetic latitude. The sea/land differences in the F2 layer peak electron density, NmF2, and the peak height, hmF2, gathered with topside sounding data exhibit tilted ionosphere along the seashores with denser electron population at greater peak heights over the sea. The topside peak electron density NmF2, TEC, IEC, and the hemisphere part of GEC are dominant in the South hemisphere which resembles the pattern for seismic activity with dominant earthquake occurrence in the South magnetic hemisphere. Though the study is made for the hemispheric and annual asymmetry during solstices in the ionosphere, the conclusions seem valid for other aspects of seismic-ionospheric associations with tectonic plate boundaries representing zones of enhanced risk for space weather.

  6. Mesospheric airglow and ionospheric responses to upward-propagating acoustic and gravity waves above tropospheric sources

    NASA Astrophysics Data System (ADS)

    Snively, J. B.; Zettergren, M. D.

    2013-12-01

    The existence of acoustic waves (periods ~1-5 minutes) and gravity waves (periods >4 minutes) in the ionosphere above active tropospheric convection has been appreciated for more than forty years [e.g., Georges, Rev. Geophys. and Space Phys., 11(3), 1973]. Likewise, gravity waves exhibiting cylindrical symmetry and curvature of phase fronts have been observed via imaging of the mesospheric airglow layers [e.g., Yue et al., JGR, 118(8), 2013], clearly associated with tropospheric convection; gravity wave signatures have also recently been detected above convection in ionospheric total electron content (TEC) measurements [Lay et al., GRL, 40, 2013]. We here investigate the observable features of acoustic waves, and their relationship to upward-propagating gravity waves generated by the same sources, as they arrive in the mesosphere, lower-thermosphere, and ionosphere (MLTI). Numerical simulations using a nonlinear, cylindrically-axisymmetric, compressible atmospheric dynamics model confirm that acoustic waves generated by transient tropospheric sources may produce "concentric ring" signatures in the mesospheric hydroxyl airglow layer that precede the arrival of gravity waves. As amplitudes increase with altitude and decreasing neutral density, the modeled acoustic waves achieve temperature and vertical wind perturbations on the order of ~10s of Kelvin and m/s throughout the E- and F-region. Using a coupled multi-fluid ionospheric model [Zettergren and Semeter, JGR, 117(A6), 2012], extended for low-latitudes using a 2D dipole magnetic field coordinate system, we investigate acoustic wave perturbations to the ionosphere in the meridional direction. Resulting perturbations are predicted to be detectable by ground-based radar and GPS TEC measurements, or via in situ instrumentation. Although transient and short-lived, the acoustic waves' airglow and ionospheric signatures are likely to in some cases be observable, and may provide important insight into the regional forcing of the MLTI system from tropospheric sources below.

  7. Role of the atmospheric gravity waves in lithosphere-ionosphere coupling and in generation of the ionospheric earthquake precursors

    Microsoft Academic Search

    G. Lizunov; M. Hayakawa; K. Hattori; Sh. Mayakawa

    2004-01-01

    Up to the present days there are no well-distinguished physical mechanisms of lithosphere-ionosphere interaction and generation of the ionospheric earthquake precursors. Several hypothetical possibilities have been suggested in the literature: (i) electric currents are generated in the lithosphere during earthquake preparation phase, the electromagnetic emission of these currents influences the ionosphere; (ii) ionosphere responds to the seismogenic variations of air

  8. Feedback instability of the ionospheric resonant cavity

    SciTech Connect

    Lysak, R.L. (Univ. of Minnesota, Minneapolis (USA))

    1991-02-01

    The exponential increase of the Alfven speed in the topside ionosphere leads to the formation of a resonant cavity (Lysak, 1988) which has been termed the ionospheric Alfven resonator by Trakhtengertz and Feldstein (1984). These authors primarily considered the situation where the ionospheric Pedersen conductivity is low, while Lysak (1988) considered the opposite limit of the infinite ionospheric conductivity. These results have been extended to arbitrary ionospheric conductivity by performing a numerical solution of the cavity dispersion relation, which involves Bessel functions of complex argument and order. These results indicate that the damping of excitations of this resonant cavity is strongest when the ionospheric Pedersen and Alfven conductivities are comparable and that growth is possible for incoming wave boundary conditions. The existence of this cavity leads to a modification of the Alfven wave reflection coefficient at the ionosphere. While this reflection coefficient is independent of frequency at low frequencies, it exhibits structure due to the resonant cavity modes at frequencies around 0.1-1 Hz. These cavity modes can also be excited by feedback instabilities (Sato, 1978; Lysak, 1986), leading to growth rates which are enhanced over the case without the cavity. These waves have maximum growth at short wavelengths, particularly when the background Pedersen conductivity is large. The perturbations associated with these instabilities can lead to structuring of auroral currents during substorms, and may help explain the westward traveling surge.

  9. Inductive ionospheric solver for magnetospheric MHD simulations

    NASA Astrophysics Data System (ADS)

    Vanhamäki, H.

    2011-01-01

    We present a new scheme for solving the ionospheric boundary conditions required in magnetospheric MHD simulations. In contrast to the electrostatic ionospheric solvers currently in use, the new solver takes ionospheric induction into account by solving Faraday's law simultaneously with Ohm's law and current continuity. From the viewpoint of an MHD simulation, the new inductive solver is similar to the electrostatic solvers, as the same input data is used (field-aligned current [FAC] and ionospheric conductances) and similar output is produced (ionospheric electric field). The inductive solver is tested using realistic, databased models of an omega-band and westward traveling surge. Although the tests were performed with local models and MHD simulations require a global ionospheric solution, we may nevertheless conclude that the new solution scheme is feasible also in practice. In the test cases the difference between static and electrodynamic solutions is up to ~10 V km-1 in certain locations, or up to 20-40% of the total electric field. This is in agreement with previous estimates. It should also be noted that if FAC is replaced by the ground magnetic field (or ionospheric equivalent current) in the input data set, exactly the same formalism can be used to construct an inductive version of the KRM method originally developed by Kamide et al. (1981).

  10. Artificial layered perovskite oxides A(B0.5B'0.5)O3 as potential solar energy conversion materials

    NASA Astrophysics Data System (ADS)

    Chen, Hungru; Umezawa, Naoto

    2015-02-01

    Perovskite oxides with a d0 electronic configuration are promising photocatalysts and exhibit high electron mobilities. However, their band gaps are too large for efficient solar energy conversion. On the other hand, transition metal cations with partially filled dn electronic configurations give rise to visible light absorption. In this study, by using hybrid density functional theory calculations, it is demonstrated that the virtues of the two categories of materials can be combined in perovskite oxide A(B0.5B'0.5)O3 with a layered B-site ordering along the [001] direction. The electronic structures of the four selected perovskite oxide compounds, La(Ti0.5Ni0.5)O3, La(Ti0.5Zn0.5)O3, Sr(Nb0.5Cr0.5)O3, and Sr(Nb0.5Fe0.5)O3 are calculated and discussed.

  11. Observations of ionospheric convection vortices - Signatures of momentum transfer

    NASA Technical Reports Server (NTRS)

    Mchenry, M. A.; Clauer, C. R.; Friis-Christensen, E.; Kelly, J. D.

    1988-01-01

    Several classes of traveling vortices in the dayside ionospheric flow have been detected and tracked using the Greenland magnetometer chain. One class observed during quiet times consists of a continuous series of vortices moving generally antisunward for several hours at a time. Assuming each vortex to be the convection pattern produced by a small field aligned current moving across the ionosphere, the amount of field aligned current was found by fitting a modeled ground magnetic signature to measurements from the chain of magnetometers. The calculated field aligned current is seen to be steady for each vortex and neighboring vortices have currents of opposite sign. Low altitude DMSP observations indicate the vortices are on field lines which map to the inner edge of the low latitude boundary layer. Because the vortices are conjugate to the boundary layer, repeat in a regular fashion and travel antisunward, it is argued that this class of vortices is caused by surface waves at the magnetopause. No strong correlations between field aligned current strength and solar wind density, velocity, or Bz is found.

  12. Ionospheric effects of the missile destruction on 9 December 2009

    NASA Astrophysics Data System (ADS)

    Kozlovsky, Alexander; Shalimov, Sergey; Lukianova, Renata; Lester, Mark

    2014-05-01

    We report on ionosonde and meteor radar observations made in Sodankylä Geophysical Observatory (SGO, 67°22'N, 26°38'E, Finland) on 9 December 2009, during a test launch of the Russian solid propellant military missile. Due to a technical problem, the missile was self-destroyed around 07 UT at an ionospheric height (near 200 km altitude) over the Kola Peninsula (Russia), at a distance about 500 km to east from the observatory. Products of the explosion were spread into a large area and reached the region of SGO meteor radar observations in about 2 h (around 09 UT). After about 3 h (around 10 UT), a sporadic E layer presumably composed of the remains including long-lived metallic (aluminum and its oxides) ions, was observed near the zenith of the SGO ionosonde. We discuss possible mechanisms accounting for transport of the remains. (1) Since the event occurred during a long-lasting period of extremely low solar and magnetic activity, the ionospheric electric field was unlikely to play a substantial role in the transport of the remains and sporadic E layer formation. (2) The horizontal transport of the remains cannot be explained by the neutral winds based on empirical models. (3) Theoretical estimations suggest that the observed transport could be due to thermospheric turbulence.

  13. Ionospheric effects during severe space weather events seen in ionospheric service data products

    Microsoft Academic Search

    Norbert Jakowski; Michael Danielides; Christoph Mayer; Claudia Borries

    2010-01-01

    Space weather effects are closely related to complex perturbation processes in the magnetosphere-ionosphere-thermosphere systems, initiated by enhanced solar energy input. To understand and model complex space weather processes, different views on the same subject are helpful. One of the ionosphere key parameters is the Total Electron Content (TEC) which provides a first or-der approximation of the ionospheric range error in

  14. Ionospheric calibration for single frequency altimeter measurements

    NASA Technical Reports Server (NTRS)

    Schreiner, William S.; Born, George H.

    1993-01-01

    This report investigates the potential of using Global Positioning System (GPS) data and a model of the ionosphere to supply a measure of the sub-satellite Total Electron Current (TEC) of the required accuracy (10 TECU rms) for the purpose of calibrating single frequency radar altimeter measurements. Since climatological (monthly mean) models are known to be in error by as much as 50 percent, this work focused on the Parameterized Real-Time Ionospheric Specification Model (PRISM) which has the capability to improve model accuracy by ingesting (adjusting to) in situ ionospheric measurements. A set of globally distributed TEC measurements were generated using GPS data and were used as input to improve the accuracy of the PRISM model. The adjusted PRISM TEC values were compared to TOPEX dual frequency TEC measurements (which are considered truth) for a number of TOPEX sub-satellite tracks. The adjusted PRISM values generally compared to the TOPEX measurements within the 10 TECU accuracy requirements when the sub-satellite track passed within 300 to 400 km of the GPS TEC data or when the track passed through a night time ionosphere. However, when the sub-satellite points were greater than 300 to 400 km away from the GPS TEC data or when a local noon ionosphere was sampled, the adjusted PRISM values generally differed by greater than 10 TECU rms with data excursions from the TOPEX TEC measurements of as much as 40 TECU (an 8 cm path delay error at K band). Therefore, it can be concluded from this analysis that an unrealistically large number of GPS stations would be needed to predict sub-satellite TEC at the 10 TECU level in the day time ionosphere using a model such as PRISM. However, a technique currently being studied at the Jet Propulsion Laboratory (JPL) may provide a means of supplying adequate TEC data to meet the 10 TECU ionospheric correction accuracy when using a realistic number of ionospheric stations. This method involves using global GPS TEC data to estimate a global grid of vertical ionospheric TEC as a function of time (i.e. every one half hour) in a sun-fixed longitude frame. Working in a sun-fixed longitude frame, one is not limited by the spatial decorrelation distance of the ionosphere, but instead is limited more by the temporal correlations of the ionosphere in the sun-fixed frame which are a smaller effect. It is the opinion of the authors that using the global sun-fixed TEC grid data, in particular, ingesting it into PRISM, offers the best possibility of meeting the 10 TECU ionospheric correction accuracy requirement, and should be the subject of further study.

  15. Artificial Intelligence

    SciTech Connect

    Shirai, Y.; Tsujii, Jun-ichi

    1985-01-01

    Based on the Japanese 5th Generation Computer Program, this volume provides coverage of the fundamental concepts and various techniques in the different applications of Artificial Intelligence. Also presented are the methods which can be used to put these concepts and techniques into practice. Explanations are presented of all the basic topics in the field, including the representation of problems; searching techniques; the control of problem solving; programming languages for Al, such as LISP, PLANNER, CONNIVER, and PROLOG; the representation and utilization of knowledge; and the approach to human intelligence.

  16. Coupling between tsunamis and ionosphere: ground-based and space-based observation opportunities

    NASA Astrophysics Data System (ADS)

    Coisson, Pierdavide; Makela, Jonathan J.; Occhipinti, Giovanni; Astafyeva, Elvira; alam Kherani, Esfhan; Lognonne, Philippe

    2012-07-01

    Large scale phenomena as tsunamis propagating through the ocean excite gravity waves that can reach ionospheric heights. The coupling between the ground/ocean and the atmosphere up to the ionosphere opens the possibility to observe in the upper atmosphere the effects of the propagation of tsunamis. During all recent major tsunami events ionospheric waves have been observed by ground GPS networks, satellite altimeters and, recently, also by an airglow imager. During the tsunami event of 11 March 2011 an all-sky camera in Hawaii observes the Internal Gravity Waves (IGW) during about one-and-a-half hours before the arrival of the, while it was crossing the Pacific Ocean in that region. Collocated ionospheric measurements were also done with GNSS sounding and Jason satellite. We present results of assessment studies of ground-based and space-based ionospheric remote sensing for tsunami propagation monitoring. We analyze the cases of airglow imager, Over-The-Horizon (OTH) radar, GPS, radio occultation and GNSS reflectometry. We describe modeling results of IGW excited by a realistic tsunami propagation model through the ocean near Hawaii. The model includes the propagation of the gravity wave in the atmosphere, the coupling between neutral and charged particles in the ionosphere and the production of the airglow emission at 630.0 nm. Synthetic all-sky images are calculated by integration of the emission along rays from the camera location to though the airglow layer. Additional ground-based observations could be provided by (OTH) radars, which operate in High Frequency (HF) band and can be used to monitor the bottomside ionosphere. Synthetic radar measurements computed using HF numerical ray-tracing confirm the possibility to detect IGW excited by tsunamis. The large coverage of OTH radar and its sensitivity to low-altitude plasma anomalies provides a wide range of observation. Additionally, we analyze the capabilities of space-based radio occultation and GNSS reflectometry to detect the gravity waves excited by tsunamis while measuring satellite-to-satellite TEC. All these techniques open new opportunities of oceanic monitoring through ionospheric monitoring to support classic techniques for tsunami detetion and confirm that the ionospheric tsunami monitoring has now reached a state-of-the-art compatible with its implementation in a space mission.

  17. Perturbations of ionosphere-magnetosphere coupling by powerful VLF emissions from ground-based transmitters

    SciTech Connect

    Belov, A. S., E-mail: alexis-belov@yandex.ru; Markov, G. A.; Ryabov, A. O. [Lobachevsky Nizhni Novgorod State University (Russian Federation); Parrot, M. [Environment Physics and Chemistry Laboratory (France)

    2012-12-15

    The characteristics of the plasma-wave disturbances stimulated in the near-Earth plasma by powerful VLF radiation from ground-based transmitters are investigated. Radio communication VLF transmitters of about 1 MW in power are shown to produce artificial plasma-wave channels (density ducts) in the near-Earth space that originate in the lower ionosphere above the disturbing emission source and extend through the entire ionosphere and magnetosphere of the Earth along the magnetic field lines. Measurements with the onboard equipment of the DEMETER satellite have revealed that under the action of emission from the NWC transmitter, which is one of the most powerful VLF radio transmitters, the generation of quasi-electrostatic (plasma) waves is observed on most of the satellite trajectory along the disturbed magnetic flux tube. This may probably be indicative of stimulated emission of a magnetospheric maser.

  18. The ionosphere disturbances observation on the Kharkiv incoherent scatter radar

    NASA Astrophysics Data System (ADS)

    Cherniak, Iu.; Lysenko, V.

    2009-04-01

    he ionosphere plasma characteristics are responding on variations of solar and magnetic activity. The research of an ionosphere structure and dynamics is important as for understanding physics of processes and for radiophysical problems solution. The method incoherent scatter (IS) of radio waves allows determining experimentally both regular variations of the basic parameters ionosphere, and their behavior during perturbation. The equipment and measurement technique, developed by authors, are allows obtaining certain data about behavior of an ionosphere during various origin and intensity ionosphere perturbations. The Institute of Ionsphere IS radar located near Kharkiv, Ukraine (geographic coordinates: 49.6oN, 36.3oE, geomagnetic coordinates: 45.7oN, 117.8oE) was used to observe the processes in the ionosphere. The radar is operate with 100-m zenith parabolic antenna at 158 MHz with peak transmitted power of ~2.0 MW. The double-frequency measuring channel mode with compound sounding signal was employed for experiments. That provided ~ 20-km resolution in range ~100-400 km and ~100-km in range ~200-1100 km. Over a period of series of experiment are obtained data about variations of electron density simultaneous in the heights interval 100-1000 km, including three sun eclipses, two superstrong and a few moderate magnetic storms, as well as disturbance, is caused by powerful rockets starts. During strong geomagnetic storm on November 8-12, 2004 was observed night time increasing of electronic temperature up to 3000 ? and ions temperature up to 2000K. Usually at this time temperature of ions is equal to temperature of electrons. During negative ionosphere storm was observed decreasing of electronic density at maximum F2 layer. The height of a F2 layer maximum was increased by 150 km and 70 km at daytime. The interesting phenomenon - high-power backscatter signal coherent backscatter was observed first time during geogeomagnetic storm 29-30 may 2003. A usually observable spectrum of a dispersing medium has two identical on magnitude of a symmetrical extremum appropriate iono-acoustic waves. From distances 900 - 1300 km is registered high-power, unstable signal with a narrow-band spectrum This signal on the correlation, spectral and temporary characteristics are different both from incoherent scatter signal, and from signals reflected from space vehicles. At night time 9.11.2004 and day time 10.11.2004 anomaly signals - coherent backscatter were observed the same way as. It is derived, that the coherent backscatter was observed during a sharp decreasing of Dst index from approximately -40 up to -130 nTl for May 2003 and from approximately -120 up to -240 nTl for 9 November and from -160 up to -290 nTl 10 November 2004. During both event electron density in maximum F2 is increased. Similar characteristics midlatitude coherent backscatters were observed at Millstone Hill , on Irkutsk IS radar. On EISCAT radars was observed so-called naturally enhanced ion-acoustic lines (NEIAL) with similar spectra and amplitude-temporal characteristics. The radar observations ionosphere plasma response on start of heaviest Russian launch vehicle ?Proton-K? was carried out at 25 December 2006. The distance from the rocket launch site and the site of observations is 2500 km. At heights of 250-320 km, a magnitude of the scattered signal sharply raised up to 2 times as compared to the period before start and in reference day on 21.12.2008 (fig. 3). In launch day is clearly seen there are two disturbed areas. The first disturbance was observed 8 min after rocket start. The calculated apparent velocity of disturbance propagation reached the value of 5.2 km/s. This velocity is typical for slow magneto-hydro-dynamic waves in the ionosphere. The second disturbance was observed 60 min after start. The calculated apparent velocity of disturbance propagation was about 700 m/s. The internal gravity waves propagate with similar velocities at the heights of the ionosphere F layer. The moderate geomagnetic storm in April 2006 occurred on the phase of mi

  19. Relationship of solar wind parameters to continuous, dayside, high latitude traveling ionospheric convection vortices

    SciTech Connect

    McHenry, M.A.; Clauer, C.R. (Stanford Univ., CA (USA)); Friis-Christensen, E. (Danish Meteorological Inst., Copenhagen (Denmark))

    1990-09-01

    In a companion paper the authors have shown that many continuous, dayside, high latitude magnetic pulsations are caused by steady, traveling ionospheric convection vortices (McHenry et al. this issue). A variety of evidence indicates that these vortices are the ionospheric signatures of the Kelvin-Helmholtz instability at the inner edge of the magnetospheric boundary layer. In this paper the authors present the results of a statistical study of the occurrence of these vortices and the upstream solar wind parameters observed by the IMP 8 spacecraft. Surveying fifty days of Greenland west coast chain magnetometer data indicates this class of pulsations is most likely to be detected post local noon and when the solar wind speed is low. However, it is possible that observational factors significantly affect the detection of the vortices. the slow solar wind might create large, slow moving traveling vortices of steady strength which are easiest to identify. Little correlation is found between the average IMF and the probability of detecting the vortices. They also find a strong correlation between the frequency of dayside pulsations and the solar wind speed. This suggests that many pulsations are caused by traveling ionospheric current systems that map to the vicinity of the flows in the magnetospheric boundary layer. Periods also exist when the IMF is variable and large pulsations with 5 to 20 min period exist. These pulsations are not caused by traveling ionospheric vortices but are likely to be the result of rapid variations of the large scale field-aligned cusp currents.

  20. A unified framework for investigation of low frequency waves in the collisional ionosphere and collisionless magnetosphere

    NASA Astrophysics Data System (ADS)

    Pandey, B. P.; Vladimirov, S. V.

    2009-04-01

    We utilize a recently developed single fluid theory by Pandey and Wardle [1] that includes electrons, ions, neutrals and their collisions to investigate the waves in the Earth's ionosphere magnetosphere region. These equations capture the interaction between the ionosphere and magnetosphere and describe the transition region in a consistent fashion. It is shown that whereas ambipolar diffusion may affect the wave in the E layer and lower part of the F layer of the Earth, the Hall diffusion will operate throughout the ionosphere and magnetosphere, albeit with a decreasing inertial length scale. Since both Hall and ambipolar diffusion are caused by the collision in the medium, the large scale, low frequency waves in the medium will not be damped in general. In the ambipolar diffusion limit waves of only certain wavelength are undamped by the collision, and, in the Hall limit, the mixture of Alfven and whistler modes propagate undamped. When the electrons and ions are highly magnetized, the relative drift between the plasma and neutral may significantly modify the wave characteristics. It is shown that in the presence of collision, the medium becomes inherently dispersive and the balance between dispersion and nonlinearity leads to derivative nonlinear Schrodinger equation. It is possible that such solitons may help explain the observed structures in the ionosphere—magnetosphere plasmas. [1] B.P. Pandey and M. Wardle, MNRAS, 385, 2269 (2008).

  1. Data verification of a hardware-software complex of sounding an ionosphere and ionosonde DPS-4

    NASA Astrophysics Data System (ADS)

    Smirnov, Vladimir; Ruzhin, Yuri; Smirnova, Elena; Skobelkin, Vladimir; Tynyankin, Sergey

    Appeared in recent years, opportunities to use as a source of signals used to determine the parameters of the ionosphere, the spacecraft global navigation satellite systems GLONASS and GPS are not currently in widespread use practices ionospheric wave frequency and radio centers and dispatch services. Given the urgency of the discussed areas of research, long experiment whose purpose is to conduct a comparative analysis of the results of determining the critical frequency of F2-layer of the ionosphere in two ways - vertical sounding (ionosonde DPS-4) and radio translucence track "satellite-the Earth" with signals using GLONASS satellites and GPS was started in 2013. For a comparative analysis of the results the hardware-software complex ionospheric soundings (HSCIS) was located at territory of the Pushkov Institute of Terrestrial Magnetism, Ionosphere and Radio Wave Propagation of the Russian Academy of Sciences. HSCIS product includes a personal computer with it specialized software, a dual-frequency navigation receiver and small receiving antenna. Used in the product receiver developed by NovAtel allows us to receive the signals of the navigation systems GPS/GLONASS and maintain their processing in real time. Location receiver determined autonomously: antenna position - 55.76o N, 37.94o E, coordinates ionosonde DPS-4 - 55.5o N, 37.3o E. In fact, both devices were in close proximity, which it allows for the identity conditions of observation. Both devices operate in real time. Ionosonde DPS- 4 gave the ionosphere parameters every 15 minutes, HSCIS - every minute. Information from both instruments displayed on the screen monitors, and recorded in the memory used by computers. Along with the numerical parameters on the monitor products HSCIS displayed time course of the critical frequency F2- layer of the ionosphere obtained from observations of the nearest navigation satellite. When limiting elevation observations 15o simultaneous use of navigation satellites can reach 23, their average number is 12-15. Ionosphere parameters were determined for each satellite, located within sight of the receiver, using the radio sounding on the track "navigation satellite - terrestrial receiver". HSCIS has a high degree of automation and provides hour continuous operation mode with archiving thematic and service information. For compare we use the results obtained according to navigation satellite, subionospheric points which were closest to the location of the ionosonde DPS- 4. On average, for the month of June the average daily value of relative root-mean-square error was 7 % during the day - 6.65 %, at night - 6.71 %, in July, 8.77 %, 7.34 % and 9.5 %, respectively.

  2. Generation of ELF and ULF electromagnetic waves by modulated heating of the ionospheric F2 region

    NASA Astrophysics Data System (ADS)

    Eliasson, B.; Chang, C.-L.; Papadopoulos, K.

    2012-10-01

    We present a theoretical and numerical study of the generation of extremely low frequency (ELF) and ultra-low frequency (ULF) waves by the modulation of the electron pressure at the F2-region with an intense high-frequency electromagnetic wave. The study is based on a cold plasma Hall-MHD model, including electron-neutral and ion-neutral collisions, which governs the dynamics of magnetostatic waves and their propagation through the ionospheric layers. Magnetosonic waves generated in the F2 region are propagating isotropically and are channeled in the ionospheric waveguide, while shear Alfvén waves are propagating along the magnetic field. To penetrate the ionosphere from the F2 peak at 300 km to the ground, the magnetostatic waves first propagate as magnetosonic or shear Alfvén waves that encounter a diffusive layer from about 150 km to 120 km where the Pedersen conductivity dominates, and then as helicon (whistler-like) mode waves from about 120 km to 80 km where the ions are collisionally glued to the neutrals and the Hall conductivity dominates. By performing numerical simulations and studying the dispersive properties of the wave modes, we investigate the dynamics and penetration of ELF/ULF waves through the ionospheric layers to the ground and along the geomagnetic field lines to the magnetosphere. Realistic profiles of the ionospheric profiles of conductivity and density are used, together with different configurations of the geomagnetic field, relevant for both the high, mid and equatorial latitudes. Some of the results are compared with recent HAARP experiments.

  3. Plasma layers in the terrestrial, martian and venusian

    E-print Network

    Withers, Paul

    ). #12;#12;Summary for Earth · Lots of data · Properties of layers are spatially and temporally variablePlasma layers in the terrestrial, martian and venusian ionospheres: Their origins and physical sunset Meteoric layers are longer-lived than molecular ions, but they are highly variable From Grebowsky

  4. Magnetic zenith effect in the ionospheric modification by an X-mode HF heater wave

    NASA Astrophysics Data System (ADS)

    Blagoveshchenskaya, N. F.; Borisova, T. D.; Haggstrom, I.; Rietveld, M. T.; Yeoman, T. K.

    2013-12-01

    We report experimental results aimed at an investigation of the magnetic zenith effect in the high latitude ionosphere F region from ionospheric modification by powerful HF heater wave with X-polarization. The ionospheric modification was produced by the HF heating facility at Tromsø (Norway) using the phased array with a narrow beam with of 6 degrees. Effective radiated power was varied between 450 and 1000 MW. The HF pump wave radiated in different directions relative to the magnetic field from 90 degrees (vertical) to 78 degrees (magnetic zenith) at frequencies near or above the ordinary-mode critical frequency. The response of the ionosphere plasma to the HF pump wave impact was checked by the UHF incoherent scatter radar located in the immediate vicinity of the HF heater. UHF radar was probing the plasma parameters, such as electron density and temperature (Ne and Te), HF-induced plasma and ion lines in the altitude range from 90 to 600 km. It was running in a scanning mode when UHF radar look angles were changed from 74 to 90 degrees by 1 or 2 degree step. It was clearly demonstrated that the strongest heater-induced effects took place in the magnetic field-aligned direction when HF pointing was also to the magnetic zenith. It was found that strong Ne enhancement of up to 80 % along magnetic field (artificial density ducts) were excited only under HF pumping towards magnetic zenith. The width of the artificial ducts comes to only 2 degrees. The Ne increases were accompanied by the Te enhancements of up to about 50 %. Less pronounced Te increases were also observed in the directions of 84 and 90 degrees. Strong Ne enhancements can be accompanied by excitation of strong HF-induced plasma and ion lines. Thus experimental results obtained points to the strong magnetic zenith effect due to self-focusing powerful HF radio wave with X-mode polarization.

  5. Pulsating aurora: The importance of the ionosphere

    SciTech Connect

    Stenbaek-Nielsen, H.C.

    1980-05-01

    A number of different, but mainly optical, observations made in pulsating auroras are presented. These observations indicate that active ionospheric processes are likely to play an important role in causing and/or modifying pulsating aurora.

  6. Space weather. Ionospheric control of magnetotail reconnection.

    PubMed

    Lotko, William; Smith, Ryan H; Zhang, Binzheng; Ouellette, Jeremy E; Brambles, Oliver J; Lyon, John G

    2014-07-11

    Observed distributions of high-speed plasma flows at distances of 10 to 30 Earth radii (R(E)) in Earth's magnetotail neutral sheet are highly skewed toward the premidnight sector. The flows are a product of the magnetic reconnection process that converts magnetic energy stored in the magnetotail into plasma kinetic and thermal energy. We show, using global numerical simulations, that the electrodynamic interaction between Earth's magnetosphere and ionosphere produces an asymmetry consistent with observed distributions in nightside reconnection and plasmasheet flows and in accompanying ionospheric convection. The primary causal agent is the meridional gradient in the ionospheric Hall conductance which, through the Cowling effect, regulates the distribution of electrical currents flowing within and between the ionosphere and magnetotail. PMID:25013068

  7. The ionosphere-magnetosphere excitation in the Sura -ISS HF experiments.

    NASA Astrophysics Data System (ADS)

    Ruzhin, Yuri; Kuznetsov, Vladimir; Karabadzhak, G. F.; Plastinin, Yu. A.; Frolov, V. L.; Khmelinin, B. A.; Komrakov, G. P.; Kovalev, V. I.; Parrot, Michel

    We present the results obtained during experiments carried out at the Sura heating facility, when features of artificial ionospheric effects HF-induced in the ionosphere -magnetosphere chain have been studied by means of instruments aboard the International Space Station (ISS) and satellite DEMETER. These are supported by the net of ionosonde and magnetometer ground based measurements from Kaliningrad to Kazan alongside the 55o parallel and the Karpogory IZMIRAN (64o N/44o E) observatory. Series of experiments (last experiments was in 2 series during 9-10.11.2009) have been carried out using the AM O-mode to heat up the electrons of the ionospheric E -F2 regions, when the ISS was close to the Sura facility (or magnetically conjugated region) and/or when the satellite DEMETER and ISS was over (or close to) the heating facility. All series of experiments have been conducted under quiet geo-magnetic conditions in evening and night hours. In these experiments the HF modifications of the ionosphere began 5 -10 min before the satellite or/and ISS was in the closest points of their trajectory to the center of the HF-disturbed ionosphere ground of the geomagnetic plasma tube and continued for 20 min. The normal mode for satellite/ ISS equipments operation, as a rule, was used in our experiments for detecting optical (ISS), electromagnetic and plasma per-turbations (DEMETER). All heating experiments (2007-2009) were carried out when a pump wave frequency was higher than E-and F2-region critical frequencies, second of which during the experiment in 2007 (only) was strongly varied in time showing existence of the intensive plasma irregularities or F2-spread events.

  8. Magnetic Earth Ionosphere Resonant Frequencies

    NASA Technical Reports Server (NTRS)

    Spaniol, Craig

    1994-01-01

    The Community College Division is pleased to report progress of NASA funded research at West Virginia State College. During this reporting period, the project research group has continued with activities to develop instrumentation capability designed to monitor resonant cavity frequencies in the atmospheric region between the Earth's surface and the ionosphere. In addition, the project's principal investigator, Dr. Craig Spaniol, and NASA technical officer, Dr. John Sutton, have written and published technical papers intended to expand the scientific and technical framework needed for project research. This research continues to provide an excellent example of government and education working together to provide significant research in the college environment. This cooperative effort has provided many students with technical project work which compliments their education.

  9. Ionospheric true height profiles from oblique ionograms

    NASA Astrophysics Data System (ADS)

    Reilly, M. H.

    1985-06-01

    An improved direct technique in which HF oblique ionograms are reduced to ionospheric true height profiles is introduced. The benefits of this method result principally from the use of a more accurate Breit-Tuve relation to curved earth and ionosphere geometries. By comparing the results of calculations on known cases, the extent of improvement with this technique relative to the techniques by Gething and Maliphant (1967), George (1970), and Smith (1970), is demonstrated.

  10. TRAVELING IONOSPHERIC DISTURBANCES ASSOCIATED WITH NUCLEAR DETONATIONS

    Microsoft Academic Search

    W. J. Breitling; R. A. Kupferman; G. J. Gassmann

    1967-01-01

    The analysis of ionospheric data taken from 54 ionosonde observatories throughout the orld indicates the presence of several traveling ionospheric disturbances originating from the five high-altitude nuclear tests conducted over Johnston Island in 1962. These disturbances were propagated over large distances and were observed as changes in the F2-1ayer critical frequency. They are interpreted as a series of waves that

  11. Plasma Channels in the Venus Nightside Ionosphere

    NASA Astrophysics Data System (ADS)

    Perez-de-Tejada, H.

    Pioneer Venus Orbiter (PVO) data with information on ionospheric holes in the Venus nightside hemisphere are examined in a study of the plasma channels that extend downstream from the magnetic polar regions. These latter features are produced by the solar wind that erodes the polar upper ionosphere and provide a useful interpretation of the ionospheric holes as regions of depleted plasma density that the PVO traverses in its near polar trajectory through the nightside ionosphere [Pérez-de-Tejada, J. Gephys. Res. 106, 211, 2001]. Data obtained from the PVO Orbiting Electron Temperature Probe (OETP) show that in addition to the ionospheric holes there are orbits in which the electron density remains nearly uniform when it is measured from the high altitude nightside ionopause to very low altitudes along trajectories oriented near the midnight plane. In addition there are some passes in which the nightside ionopause occurs at very low heights (near the trajectory periapsis) and thus imply that no significant electron densities are observed along sections of the trajectory where a strong ionosphere is observed in other orbits. This latter circumstance is remarkable in that it is not necessarily associated with high values of the solar wind dynamic pressure but is present even when the nightside ionopause far from the midnight plane is detected at high altitudes. In such cases it is possible that as the PVO approaches or moves away from periapsis it is located within the plasma channels that extend downstream from the magnetic polar regions and thus skips transit through the nightside upper ionosphere. An important aspect of this view is that it can account for the sharp change of the electron density that is seen within the ionosphere at altitudes that correspond to crossings near the lower boundary of the plasma channels.

  12. Total Artificial Heart

    MedlinePLUS

    ... NHLBI on Twitter. What Is a Total Artificial Heart? A total artificial heart (TAH) is a device ... the chest to an outside power source. Normal Heart and CardioWest Total Artificial Heart Figure A shows ...

  13. Simulations of Atmospheric Neutral Wave Coupling to the Ionosphere

    NASA Astrophysics Data System (ADS)

    Siefring, C. L.; Bernhardt, P. A.

    2005-12-01

    The densities in the E- and F-layer plasmas are much less than the density of background neutral atmosphere. Atmospheric neutral waves are primary sources of plasma density fluctuations and are the sources for triggering plasma instabilities. The neutral atmosphere supports acoustic waves, acoustic gravity waves, and Kelvin Helmholtz waves from wind shears. These waves help determine the structure of the ionosphere by changes in neutral density that affect ion-electron recombination and by neutral velocities that couple to the plasma via ion-neutral collisions. Neutral acoustic disturbances can arise from thunderstorms, chemical factory explosions and intentional high-explosive tests. Based on conservation of energy, acoustic waves grow in amplitude as they propagate upwards to lower atmospheric densities. Shock waves can form in an acoustic pulse that is eventually damped by viscosity. Ionospheric effects from acoustic waves include transient perturbations of E- and F-Regions and triggering of E-Region instabilities. Acoustic-gravity waves affect the ionosphere over large distances. Gravity wave sources include thunderstorms, auroral region disturbances, Space Shuttle launches and possibly solar eclipses. Low frequency acoustic-gravity waves propagate to yield traveling ionospheric disturbances (TID's), triggering of Equatorial bubbles, and possible periodic structuring of the E-Region. Gravity wave triggering of equatorial bubbles is studied numerically by solving the equations for plasma continuity and ion velocity along with Ohms law to provide an equation for the induced electric potential. Slow moving gravity waves provide density depressions on bottom of ionosphere and a gravitational Rayleigh-Taylor instability is initiated. Radar scatter detects field aligned irregularities in the resulting plasma bubble. Neutral Kelvin-Helmholtz waves are produced by strong mesospheric wind shears that are also coincident with the formation of intense E-layers. An atmospheric model for periodic structures with Kelvin-Helmholtz (KH) wavelengths is used to show the development of quasi-periodic structures in the E-layer. For the model, a background atmosphere near 100 km altitude with a scale height of 12.2 km is subjected to a wind shear profile varying by 100 m/s over a distance of 1.7 km. This neutral speed shear drives the KH instability with a growth time of about 100 seconds. The neutral KH wave is a source of plasma turbulence. The E-layer responds to the KH-Wave structure in the neutral atmosphere as an electrodynamic tracer. The plasma flow leads to small scale plasma field aligned irregularities from a gradient drift, plasma interchange instability (GDI) or a Farley-Buneman, two-stream instability (FBI). These irregularities are detected by radar scatter as quasi-periodic structures. All of these plasma phenomena would not occur without the initiation by neutral atmospheric waves.

  14. Ionospheric response to traveling convection twin vortices

    SciTech Connect

    Schunk, R.W.; Zhu, L.; Sojka, J.J. [Utah State Univ., Logan, UT (United States)] [Utah State Univ., Logan, UT (United States)

    1994-08-15

    Traveling convection twin vortices have been observed for several years. At ionospheric altitudes, the twin vortices correspond to spatially localized, transient structures embedded in a large-scale background convection pattern. The convection vortices are typically observed in the morning and evening regions. They are aligned predominantly in the east-west direction and have a horizontal extent of from 500-1000 km. Associated with the twin vortices are enhanced electric fields, particle precipitation, and an upward/downward field-aligned current pair. Once formed, the twin vortex structures propagate in the tailward direction at speeds of several km/s, but they weaken as they propagate and only last for about 10-20 minutes. Because these convection structures might have a significant effect on the localized ionosphere, the USU ionospheric model was used to calculate the response of the ionosphere to {open_quotes}representative{close_quotes} traveling convection twin vortices for a range of background conditions. The ionospheric response includes localized temperature enhancements, ion composition changes, non-Maxwellian ion distributions, and plasma upwelling events. The response is transient and the magnitude of the response depends on the background ionosphere conditions and on the characteristics of the twin vortices. 17 refs., 4 figs.

  15. Radar Ionogram with Oblique Ionospheric Echo

    NASA Technical Reports Server (NTRS)

    2005-01-01

    This plot, called an ionogram, shows data from sounding Mars' ionosphere with the Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS). The horizontal axis is the frequency of the pulse. The left vertical axis is the time delay after transmitting the pulse, with time increasing downward. The right vertical axis is a conversion of time delay to distance, showing the apparent range to the reflection point. The intensity of the received signal at any given frequency and apparent range is indicated by the color, with dark blue being the least intense and green being the most intense.

    The green echo at an apparent range of about 800 kilometers (497 miles) from 2.5 to 5.5 megahertz is the reflected signal from the surface of Mars. The curved bright green feature with an apparent range varying from about 600 to 750 kilometers (373 to 466 miles) at frequencies from about 0.7 to 1.8 megahertz is the echo from the top side of the ionosphere. A second echo of the ionosphere, at an apparent range of about 100 kilometers (62 miles) is labeled 'Oblique ionospheric echo.' Such echoes are believed to come from distorted structures in the ionosphere caused by the magnetic fields in the crust of Mars.

    MARSIS is an instrument on the European Space Agency's Mars Express orbiter. NASA and the Italian Space Agency jointly funded the instrument.

  16. Artificial Hydrogenases

    PubMed Central

    Barton, Bryan E.; Olsen, Matthew T.; Rauchfuss, Thomas B.

    2010-01-01

    Decades of biophysical study on the hydrogenase (H2ase) enzymes have yielded sufficient information to guide the synthesis of analogues of their active sites. Three families of enzymes serve as inspiration for this work: the [FeFe]-, [NiFe]-, and [Fe]-H2ases, all of which feature iron centers bound to both CO and thiolate. Artificial H2ases effect the oxidation of H2 of H2 and the reverse reaction, the reduction of protons. These reactions occur via the intermediacy of metal hydrides. The inclusion of amine bases within the catalysts is an important design feature that is emulated in related bioinspired catalysts. Continuing challenges are the low reactivity of H2 towards biomimetic H2ases. PMID:20356731

  17. Comparison of topside ionospheric profilers for use in modelling and monitoring applications

    NASA Astrophysics Data System (ADS)

    Verhulst, Tobias; Stankov, Stan

    2013-04-01

    Ground-based ionosonde measurements can be used to determine the electron density profile up to the ionospheric density peak, hmF2, only. In order to reconstruct a complete, full-height electron density profile, a model is usually needed for the shape of the topside ionospheric density. Different shapes have been used over the years, most frequently the so-called Chapman- and Epstein-layers. We use topside sounder data to evaluate the quality of the fit obtained by using profiles with different shapes and determine which profile provides the best fit. While the topside sounder database available at the US National Space Science Data Center is quite extensive, it is also very inhomogeneous. Data availability varies widely with local time, day of year, latitude and longitude. Measurements have been obtained over a period spanning more than a full solar cycle but the data coverage is irregular during different levels of solar activity. All these issues cause difficulties in correctly interpreting the results of the data analyses. Also, it must be taken into account that the provided data comes from different satellites, which orbited at different heights. This, too, can cause some biases in the results. These complications are investigated and, if necessary, compensated for. The correlations between the shape of the topside electron density profile and several possible factors that might influence this shape are also investigated. This includes geomagnetic indices (Kp and Dst), solar activity (indicated by F10.7), time of day, day of year and magnetic longitude and latitude. Finally, also the interdependencies of different characteristics of the ionosphere are discussed. For example, if the boundary between the ionosphere and plasmasphere is lower it could be expected that not only the scale height of the topside density changes, but also the shape of the density profile. Results are applied into further improving the RMI ionospheric monitoring service LIEDR (Local Ionospheric Electron Density profile Reconstruction).

  18. Excitation of a magnetospheric maser through modification of the Earth's ionosphere by high-power HF radio emission from a ground-based transmitter

    SciTech Connect

    Markov, G. A., E-mail: markov@rf.unn.ru; Belov, A. S., E-mail: alexis-belov@yandex.ru [Lobachevsky Nizhni Novgorod State University (Russian Federation); Frolov, V. L.; Rapoport, V. O. [Radiophysical Research Institute (Russian Federation); Parrot, M. [Environment Physics and Chemistry Laboratory (France)

    2010-01-15

    A method for controlled excitation of a magnetospheric maser through the production of artificial density ducts by high-power HF radio emission from the Earth's surface has been proposed and implemented in an in-situ experiment. Artificial density ducts allow one to affect the maser resonator system and the excitation and propagation of low-frequency electromagnetic waves in a disturbed magnetic flux tube. The experimental data presented here were obtained at the mid-latitude Sura heating facility. The characteristics of electromagnetic and plasma disturbances at outer-ionosphere altitudes were measured using the onboard equipment of the DEMETER satellite as it passed through the magnetic flux tube rested on the region of intense generation of artificial ionospheric turbulence.

  19. On the artificiality of artificial intelligence

    Microsoft Academic Search

    Hans F. M. Crombag

    1993-01-01

    In this article the question is raised whether artificial intelligence has any psychological relevance, i.e. contributes to our knowledge of how the mind\\/brain works. It is argued that the psychological relevance of artificial intelligence of the symbolic kind is questionable as yet, since there is no indication that the brain structurally resembles or operates like a digital computer. However, artificial

  20. Testing Ionospheric Faraday Rotation Corrections in CASA

    NASA Astrophysics Data System (ADS)

    Kooi, Jason E.; Moellenbrock, George

    2015-04-01

    The Earth’s ionosphere introduces direction- and time-dependent effects over a range of physical and temporal scales and so is a major source for unmodeled phase offsets for low frequency radioastronomical observations. Ionospheric effects are often the limiting factor to making sensitive radioastronomical measurements to probe the solar corona or coronal mass ejections at low frequencies (< 5 GHz). It has become common practice to use global ionospheric models derived from the Global Positioning System (GPS) to provide a means of externally calibrating low frequency data. We have developed a new calibration algorithm in the Common Astronomy Software Applications (CASA) package. CASA, which was developed to meet the data post-processing needs of next generation telescopes such as the Karl G. Jansky Very Large Array (VLA), did not previously have the capability to mitigate ionospheric effects. This algorithm uses GPS-based global ionosphere maps to mitigate the first and second order ionospheric effects (dispersion delay and Faraday rotation, respectively). We investigated several data centers as potential sources for global ionospheric models and chose the International Global Navigation Satellite System Service data product because data from other sources are generally too sparse to use without additional interpolation schemes. This implementation of ionospheric corrections in CASA has been tested on several sets of VLA observations and all of them showed a significant reduction of the dispersion delay. In order to rigorously test CASA’s ability to mitigate ionospheric Faraday rotation, we made VLA full-polarization observations of the standard VLA phase calibrators J0359+5057 and J0423+4150 in August 2014, using L band (1 ? 2 GHz), S band (2 ? 4 GHz), and C band (4 ? 6 GHz) frequencies in the D array configuration. The observations were 4 hours in duration, beginning near local sunrise. In this paper, we give a general description of how these corrections are implemented as well as discussion of the code’s ability to mitigate the ionospheric effects present in these test observations over a range of times and elevation angles. This work was supported at the University of Iowa by grant ATM09-56901.

  1. Interpreting Mars ionospheric anomalies over crustal magnetic field regions using a 2-D ionospheric model

    NASA Astrophysics Data System (ADS)

    Matta, Majd; Mendillo, Michael; Withers, Paul; Morgan, Dave

    2015-01-01

    spatially inhomogeneous, small-scale crustal magnetic fields of Mars influence the escape of planetary atmospheric species and the interaction of the solar wind with the ionosphere. Understanding the plasma response to crustal magnetic field regions can therefore provide insight to ionospheric structure and dynamics. To date, several localized spatial structures in ionospheric properties that have been observed over regions of varying magnetic field at Mars have yet to be explained. In this study, a two-dimensional ionospheric model is used to simulate the effects of field-aligned plasma transport in regions of strong crustal magnetic fields. Resulting spatial and diurnal plasma distributions are analyzed and found to agree with observations from several spacecraft and offer compelling interpretations for many of the anomalous ionospheric behaviors observed at or near regions of strong crustal magnetic fields on Mars.

  2. An observational study of the nightside ionospheres of Mars and Venus with radio occultation methods

    SciTech Connect

    Zhang, M.H.G. (Austrian Academy of Sciences, Graz (Austria)); Luhmann, J.G. (Univ. of California, Los Angeles (United States)); Kliore, A.J. (Jet Propulsion Lab., Pasadena, CA (United States))

    1990-10-01

    An analysis of Mars and Venus nightside electron density profiles obtained with radio occultation methods shows how the nightside ionospheres of both planets vary with solar zenith angle. From previous studies it is known that the dayside peak electron densities at Mars and Venus show a basic similarity in that they both exhibit Chapman layer-like behavior. In contrast, the peak altitudes at mars behave like an ideal Chapman layer on the dayside, whereas the altitude of the peak at Venus is fairly constant up to the terminator. The effect of major dust storms can also be seen in the peak altitudes at Mars. All Venus nightside electron density profiles show a distinct main peak for both solar minimum and maximum, whereas many profiles from the nightside of Mars do not show any peak at all. This suggests that the electron density in the Mars nightside ionosphere is frequently too low to be detected by radio occultation. On the Pioneer Venus orbiter, disappearing ionospheres were observed near solar maximum in the in-situ data when the solar wind dynamic pressure was exceptionally high. This condition occurs because the high solar wind dynamic pressure decreases the altitude of the ionopause near the terminator below {approximately}250 km, thus reducing the normal nightward transport of dayside ionospheric plasma. On the basis of the Venus observations, one might predict that if a positive correlation of nightside peak density with dynamic pressure was found, it could mean that transport from the dayside is the only significant source for the nightside ionosphere of Mars. The lack of a correlation would imply that the precipitation source at Mars is quite variable.

  3. Interactions with planetary ionospheres and atmospheres: A review. [solar wind interactions

    NASA Technical Reports Server (NTRS)

    Saunders, Mark A.; Russell, Christopher T.; Luhmann, Janet G.

    1986-01-01

    The interaction of the solar wind with umnagnetized objects possessing an ionosphere is reviewed. Venus, Mars, Titan, comets (including the artificial comet created by AMPTE) and the unusual interplanetary events interpreted as cometesimals are considered. The role of the interplanetary magnetic field and of mass loading in producing the observed interactions is highlighted. Interpretation to date is based largely on an MHD (fluid) treatment, but results from the first AMPTE barium release and from recordings made at Venus suggest that finite Larmor radius effects introduce asymmetries in the solar wind interaction.

  4. First modulation of high-frequency polar mesospheric summer echoes by radio heating of the ionosphere

    NASA Astrophysics Data System (ADS)

    Senior, A.; Mahmoudian, A.; Pinedo, H.; La Hoz, C.; Rietveld, M. T.; Scales, W. A.; Kosch, M. J.

    2014-08-01

    The first high-frequency (HF, 8 MHz) observations of the modulation of polar mesospheric summer echoes (PMSE) by artificial radio heating of the ionosphere are presented and compared to observations at 224 MHz and model predictions. The experiments were performed at the European Incoherent Scatter facility in northern Norway. It is shown that model results are in qualitative and partial quantitative agreement with the observations, supporting the prediction that with certain ranges of ice particle radii and concentration, PMSE at HF radar wavelengths can be enhanced by heating due to the dominance of dust charging over plasma diffusion.

  5. Ionospheric Variability and Storms on Mars

    NASA Technical Reports Server (NTRS)

    Mendillo, Michael

    2004-01-01

    The goal of this grant was to conduct the first-ever study of ionospheric variability on Mars. To do so, we used data from the Radio Science (RS) experiment onboard the Mars Global Surveyor (MGS) satellite. Dr. David Hinson of the RS team at Stanford University was a most helpful and valuable colleague throughout the studies we conducted. For the initial RS datasets available from the MGS mission, there were no severe storms caused by solar wind activity, so we concentrated on day-to-day effects. This turned out to be a wise approach since understanding "normal variability" had to be done before any claim could be made about "space weather" effects. Our approach was three-fold: (1) select a good dataset for characterization of ionosphere variability at Mars, one for which excellent terrestrial data were also available. This turned out to be the period 9-27 March 1999; (2) once the variability at Mars was described, develop and use a new photochemical model of the martian ionosphere to find the extent to which solar variability on those days caused or contributed to the observed patterns; (3) use the results from the above, together with additional datasets from the MGS/RS experiment, to describe some practical consequences that the martian ionosphere would have upon NASA s proposed navigation and communications systems for Mars. The results of these studies showed that: (a) solar variability is the dominant source of ionospheric variability at Mars (during periods of quiet solar wind), (b) that current models do a good job in portraying such effects at the height of the ionospheric peak electron density, and (c) that ionospheric structure on Mars can affect attempts at precise position-fixing at Mars should relatively high (GPS-like) frequencies not be used in a Mars communications and navigation system.

  6. Novel Modeling of Mars' Ionospheric Electrodynamics

    NASA Astrophysics Data System (ADS)

    Riousset, J. A.; Paty, C. S.; Lillis, R. J.; Fillingim, M. O.; England, S.; Withers, P.

    2011-12-01

    The complex interaction between Mars' unique crustal magnetic fields and upper atmospheric electrons, ions and neutrals leads to the formation of currents in the ionospheric dynamo region (i.e., where electrons are magnetized but ions are collisional). These interactions involve elastic and inelastic collisions between ions, electrons and neutrals in the presence of varying bulk motion, pressures, temperatures and densities. In addition, the inherent inhomogeneities in the crustal field causes open and closed magnetic field regions to be in very close proximity. The resulting 'patchy' ionosphere varies on spatial scales of ? ˜100 km. These conditions make it impossible to derive an analytical solution of these ionospheric currents. Here we present the methodology, validation and preliminary results of a novel model of Mars' ionospheric currents. The model performs three-dimensional, multi-fluid, self-consistent simulations of electrodynamics in the region of Mars' ionosphere (˜75-400 km altitude), where differential motion between ions and electrons occurs. Our work is built upon a multi-fluid plasma dynamic model that tracks three ions species (O2+, CO2+, and O+) and electrons. This method applies equations for conservation of mass, conservation of momentum, charge neutrality, and time-dependent pressure for ion species and electrons while simultaneously solving the generalized Ohm's Law and Maxwell-Ampere equation for the electric and magnetic fields. Incorporated into these equations are the aforementioned collisional interactions between the ions, electrons and neutrals. Our results demonstrate the feasibility of a self-consistent model of Mars' ionospheric electrodynamics, and focus on a thorough and methodic validation of each aspect of the model. Our goal is to build a solid ground for the study of the effects of thermospheric neutral winds, magnetic topologies, and day-night variations on the formation and evolution of ionospheric currents on Mars.

  7. Ionospheric behavior over Europe during the solar eclipse of 3 October 2005

    NASA Astrophysics Data System (ADS)

    Jakowski, N.; Stankov, S. M.; Wilken, V.; Borries, C.; Altadill, D.; Chum, J.; Buresova, D.; Boska, J.; Sauli, P.; Hruska, F.; Cander, Lj R.

    2008-04-01

    An annular eclipse occurred over Europe in the morning hours of 3 October 2005. The well-defined obscuration function of the solar radiation during the eclipse provided a good opportunity to study the ionospheric/thermospheric response to solar radiation changes. Since the peak electron density behavior of the ionospheric F2 layer follows the local balance of plasma production, loss and transport, the ionospheric plasma redistribution processes significantly affect the shape of the electron density profile. These processes are discussed here based on a comparison of vertical incidence sounding (VS) and vertical total electron content (TEC) data above-selected ionosonde stations in Europe. The equivalent slab thickness, derived with a time resolution of 10 min, provides relatively good information on the variation of the electron density profile during the eclipse. The computations reveal an increased width of the ionosphere around the maximum phase. As indicated by the available measurements over Spain, the photo production is significantly reduced during the event leading to a slower increase of the total ionization in comparison with the neighboring days. The supersonic motion of the Moon's cool shadow through the atmosphere may generate atmospheric gravity waves that propagate upward and are detectable as traveling ionospheric disturbances at ionospheric heights. High-frequency (HF) Doppler shift spectrograms were recorded during the eclipse showing a distinct disturbance along the eclipse path. Whereas the ionosonde measurements at the Ebro station/Spain in the vicinity of the eclipse path reveal the origin of the wave activity in the lower thermosphere below about 180 km altitude, the similar observations at Pruhonice/Czech Republic provide arguments to localize the origin of the abnormal waves in the middle atmosphere well below the ionospheric heights. Although ionosonde and HF Doppler measurements show enhanced wave activity, the TEC data analysis does not, which is an indication that the wave amplitudes are too small for detecting them via this interpolation method. The total ionization reduces up to about 30% during the event. A comparison with similar observations from the solar eclipse of 11 August 1999 revealed a quite different ionospheric behavior at different latitudes, a fact that needs further investigation.

  8. The Ionosphere Real-Time Assimilative Model, IRTAM - A Status Report

    NASA Astrophysics Data System (ADS)

    Reinisch, Bodo; Galkin, Ivan; Huang, Xueqin; Vesnin, Artem; Bilitza, Dieter

    2014-05-01

    Ionospheric models are generally unable to correctly predict the effects of space weather events on the ionosphere. Taking advantage of today's real-time availability of measured electron density profiles of the bottomside ionosphere, we have developed a technique "IRTAM" to specify real-time foF2 and hmF2 global maps. The measured data arrive at the Lowell GIRO Data Center (LGDC) from some ~70 ionosonde stations of the Global Ionosphere Radio Observatory (GIRO) [Reinisch and Galkin, 2011], usually at a 15 min cadence, and are ingested in LGDC's databases (http://ulcar.uml.edu/DIDBase/). We use the International Reference Ionosphere (IRI) electron density model [Bilitza et al., 2011] as the background model. It is an empirical monthly median model that critically depends on the correct values of the F2 layer peak height hmF2 and density NmF2 (or critical frequency foF2). The IRI model uses the so-called CCIR (or URSI) coefficients for the specification of the median foF2 and hmF2 maps. IRTAM assimilates the measured GIRO data in IRI by "adjusting" the CCIR coefficients on-the-fly. The updated maps of foF2 and hmF2 for the last 24 hours before now-time are continuously displayed on http://giro.uml.edu/RTAM [Galkin et al., 2012]. The "adjusted" bottomside profiles can be extended to the topside by using the new Vary-Chap topside profile model [Nsumei et al., 2012] which extends the profile from hmF2 to the plasmasphere. References Bilitza D., L.-A. McKinnell, B. Reinisch, and T. Fuller-Rowell (2011), The International Reference Ionosphere (IRI) today and in the future, J. Geodesy, 85:909-920, DOI 10.1007/s00190-010-0427-x Galkin, I. A., B. W. Reinisch, X. Huang, and D. Bilitza (2012), Assimilation of GIRO Data into a Real-Time IRI, Radio Sci., 47, RS0L07, doi:10.1029/2011RS004952. Nsumei, P., B. W. Reinisch, X. Huang, and D. Bilitza (2012), New Vary-Chap profile of the topside ionosphere electron density distribution for use with the IRI Model and the GIRO real time data, Radio Sci., doi:10.1029/2012RS004989. Reinisch, B. W. and I. A. Galkin (2011), Global Ionospheric Radio Observatory (GIRO), Earth, Planets and Space, 63(4), 377-381.

  9. Mid-latitude ionospheric perturbation associated with the Spacelab-2 plasma depletion experiment at Millstone Hill

    NASA Astrophysics Data System (ADS)

    Foster, J. C.; Holt, J. M.; Lanzerotti, L. J.

    2000-01-01

    Elevation scans across geomagnetic mid latitudes by the incoherent scatter radar at Millstone Hill captured the ionospheric response to the firing of the Space Shuttle Challenger OMS thrusters near the peak of the F layer on July 30, 1985. Details of the excitation of airglow and the formation of an ionospheric hole during this event have been reported in an earlier paper by Mendillo et al.. The depletion (factor sim2) near the 320 km Shuttle orbital altitude persisted for sim35 min and then recovered to near normal levels, while at 265 km the density was reduced by a factor of sim6; this significant reduction in the bottomside F-region density persisted for more than 3 hours. Total electron content in the vicinity of the hole was reduced by more than a factor of 2, and an oscillation of the F-region densities with 40-min period ensued and persisted for several hours. Plasma vertical Doppler velocity varied quasi-periodically with a sim80-min period, while magnetic field variations observed on the field line through the Shuttle-burn position exhibited a similar sim80-min periodicity. An interval of magnetic field variations at hydromagnetic frequencies (sim95 s period) accompanied the ionospheric perturbations on this field line. Radar observations revealed a downward phase progression of the 40-min period density enhancements of -1.12° km-1, corresponding to a 320-km vertical wavelength. An auroral-latitude geomagnetic disturbance began near the time of the Spacelab-2 experiment and was associated with the imposition of a strong southward IMF Bz across the magnetosphere. This created an additional complication in the interpretation of the active ionospheric experiment. It cannot be determined uniquely whether the ionospheric oscillations, which followed the Spacelab-2 experiment, were related to the active experiment or were the result of a propagating ionospheric disturbance (TID) launched by the enhanced auroral activity. The most reasonable conclusion is that the ionospheric oscillations were a result of the coincident geomagnetic disturbance. The pronounced depletion of the bottomside ionosphere, however, accentuated the oscillatory behavior during the interval following the Shuttle OMS burn.

  10. Results From YOUTHSAT - Indian experiment in earths thermosphere-ionosphere region.

    NASA Astrophysics Data System (ADS)

    Tarun Kumar, Pant

    It is known that the characterization and modeling of the ionosphere/thermosphere necessitates a comprehensive understanding of the various processes prevailing therein. India’s first, indigenous and dedicated aeronomy satellite 'YOUTHSAT' carrying two Indian payloads - RaBIT (Radio Beacon for Ionospheric Tomography), and LiVHySI (Limb Viewing Hyper Spectral Imager) and one Russian payload SOLRAD, was conceived primarily to address to this aspect and launched on April 20, 2011 in an 818 Km polar orbit from SHAR on ISRO launch vehicle PSLV. The payloads RaBIT and LiVHySI were designed specifically to observe the ionised and neutral components of the upper atmosphere respectively. YOUTHSAT is a small satellite quiet advanced in its class having all the functionalities which are normally associated with a bigger satellite. The rising phase of the 23rd solar cycle was considered to be the best window for various observations from onboard YOUTHSAT. As an Indo Russian endeavour, it was launched with an objective of investigating the terrestrial upper atmosphere vis-a-vis the activity on the sun. RaBIT, an ISRO venture, is a radio beacon emitting coherent radio signal at 150 and 400 MHz frequencies. These are received using a chain of five receivers deployed along the ~76oE meridian at Trivandrum, Bangalore, Hyderabad, Bhopal and Delhi. The receivers estimate the Total Electron Content (TEC) of the ionosphere through the relative phase change of the received radio signals. The TECs thus estimated near simultaneously, are used to generate a tomogram, which gives an Altitude-Latitude distribution of the ionospheric electron density. For YOUTHSAT configuration, the tomogram covers the ionosphere from a few degrees (5-6o) south of Trivandrum to about 3-4o north of Delhi depending upon the satellite elevation. The RaBIT tomography network is by far the longest network existing anywhere in the world, and is unique therefore. Through RaBIT, a unique dataset leading to ionospheric tomograms representing altitude-latitude variation of electron density over the 77oE meridian over the Indian region has been generated around specific times (~10:30 AM/PM). These tomograms have provided, among others: (a) First ever images of the ionospheric nighttime ESF irregularities (b) Quantification of the topside F3 ionospheric layers using Tomography (c) Evidence of wavelike modulations in the overall low and equatorial ionospheric region using tomography (d) Day and night differences in the electron density distribution, (e) Evidence of the presence of the ionospheric top-side layer (f) Modulations in the ionosphere due to space weather activity and (g) Direct evidence of the presence of Travelling Atmospheric Disturbance (TAD). YOUTHSAT recently completed its mission life time of about two years, after having generated a comprehensive set of data on terrestrial upper atmosphere. The YOUTHSAT data are being analysed by various researchers and more results providing a new insight into the upper atmospheric processes are in offing. Some of the important outcomes mentioned above will be discussed in detail.

  11. The Metal Oxide Space Clouds (MOSC) Experiment: High Frequency (HF) Signatures and Interactions with the Ambient Ionosphere

    NASA Astrophysics Data System (ADS)

    Groves, K. M.; Caton, R. G.; Pedersen, T. R.; Parris, R. T.; Su, Y.; Cannon, P. S.; Jackson-booth, N. K.; Angling, M. J.; Retterer, J. M.

    2013-12-01

    With support from the NASA sounding rocket team, AFRL performed two separate 5 kg releases of samarium metal vapor in the lower F-region near Kwajalein Atoll in May 2013. A fraction of the samarium subsequently ionized forming a plasma cloud that persisted for tens of minutes to hours in the post-sunset period. Numerous sensors were used to characterize the clouds including the ALTAIR incoherent scatter radar, multiple GPS and optical instruments, satellite radio beacons, and a dedicated network of high frequency (HF) radio links. The primary objectives of the experiments were to understand the dynamics, evolution and chemistry of Sm atoms in the earth's upper atmosphere. Sm is predicted to both photo-ionize and chemi-ionize through charge exchange with neutral oxygen (O). Ionization rates and loss reactions are not well known. A secondary objective was to understand the interaction of an artificial plasma cloud with the low latitude ionosphere during the pre-reversal enhancement period leading up to the post-sunset development of large-scale Rayleigh-Taylor instability. It was initially hoped that the introduction of the artificial plasma might be sufficient to quench the development of the instability by maintaining high conductivity within the affected flux tubes. Modeling results showed that this result was unlikely due to the relatively small amount of material being released. However, it appeared possible that the presence of SmO+ near the bottomside of the F-region might be capable of reducing the formation of short-scale irregularities within the larger Rayleigh-Taylor 'bubbles'. Indeed, preliminary results indicate that the artificial layers, positioned at 170 and 180 km respectively, did interact with the overlying F region and in at least one case, cause a decrease in the short-scale component of the natural irregularity spectrum. The results suggest that it may be possible to mitigate the formation of low-latitude irregularities responsible for radio wave scintillation with a MOSC-based approach.

  12. Role of the atmospheric gravity waves in lithosphere-ionosphere coupling and in generation of the ionospheric earthquake precursors

    NASA Astrophysics Data System (ADS)

    Lizunov, G.; Hayakawa, M.; Hattori, K.; Mayakawa, Sh.

    Up to the present days there are no well-distinguished physical mechanisms of lithosphere-ionosphere interaction and generation of the ionospheric earthquake precursors. Several hypothetical possibilities have been suggested in the literature: (i) electric currents are generated in the lithosphere during earthquake preparation phase, the electromagnetic emission of these currents influences the ionosphere; (ii) ionosphere responds to the seismogenic variations of air conductivity and related variation of fair-weather electric field; (iii) lithosphere and ionosphere are coupled via middle-scale atmospheric gravity waves (AGW) traveling upwards to the ionospheric heights and producing the effects known as traveling ionospheric disturbances (TID). In spite of great quantity of observations of ionospheric earthquake precursors, there is a lack of appropriate experimental data: such kind of data that will help us to choose between mentioned hypotheses. Our research is devoted to the studying and verification of AGW-mechanism of seismo-ionospheric effects. The original data have been provided by synchronous measurements of atmospheric pressure variations and ionospheric plasma variations carried out in seismically active Chiba area in Japan during the year 2003. Seismogenic AGW with period about 1 hour has been selected from the broad spectra of pressure variations. Correlated ionospheric response has been detected by means of subionospheric VLF/LF propagation. Cross-analysis of barometric and ionospheric parameters has been done in order to recognize the process of AGW-coupling between perturbations at surface and ionospheric levels.

  13. Magnetosphere-Ionosphere Coupling: Understanding the Consequences of Energy and

    E-print Network

    Lotko, William

    Magnetosphere-Ionosphere Coupling: Understanding the Consequences of Energy and Mass Transport #12;ii #12;Thayer School of Engineering Dartmouth College "Magnetosphere-Ionosphere Coupling-Fedder-Mobarry (LFM) global magnetohydrodynamic sim- ulation of the magnetosphere, including electrodynamic coupling

  14. Evaluation and prospects for storm-time corrections in the International Reference Ionosphere

    Microsoft Academic Search

    E. A Araujo-Pradere; T. J Fuller-Rowell; M. V. Codrescu; A. Anghel

    2004-01-01

    IRI2000 [Radio Sci. 36 (2) (2001) 261] now contains a geomagnetic activity dependence based on an empirical storm-time ionospheric correction model STORM [Geof. Int. 39 (1) (2000) 29; Radio Sci. 37 (5) (2002) 1070] The storm correction is driven by the previous time-history of ap, and is designed to scale the quiet-time F-layer critical frequency (foF2) to account for storm-time

  15. Thermospheric wind during a storm-time large-scale traveling ionospheric disturbance

    Microsoft Academic Search

    K. Shiokawa; Y. Otsuka; T. Ogawa; S. Kawamura; M. Yamamoto; S. Fukao; T. Nakamura; T. Tsuda; N. Balan; K. Igarashi; G. Lu; A. Saito; K. Yumoto

    2003-01-01

    A prominent large-scale traveling ionospheric disturbance (LSTID) was observed in Japan during the major magnetic storm (Dst ~ -358 nT) of 31 March 2001. It was detected as enhancements of the 630-nm airglow and foF2, GPS-TEC variations, and a decrease in F-layer virtual height at 1700-1900 UT (0200-0400 LT). It moved equatorward with a speed of ~600 m\\/s. The decrease

  16. A large-scale traveling ionospheric disturbance during the magnetic storm of 15 September 1999

    Microsoft Academic Search

    K. Shiokawa; Y. Otsuka; T. Ogawa; N. Balan; K. Igarashi; A. J. Ridley; D. J. Knipp; A. Saito; K. Yumoto

    2002-01-01

    Using a comprehensive data set and model calculations, we have investigated a prominent large-scale traveling ionospheric disturbance (LSTID) observed in Japan (~37°-16° MLAT) on 15 September 1999, during a recovery phase of sequential storms. The LSTID was detected at 2300-2400 LT (1400-1500 UT) as an enhancement of the 630-nm airglow intensity (50->350 R), a decrease in the F layer virtual

  17. A large-scale traveling ionospheric disturbance during the magnetic storm of 15 September 1999

    Microsoft Academic Search

    K. Shiokawa; Y. Otsuka; T. Ogawa; N. Balan; K. Igarashi; A. J. Ridley; D. J. Knipp; A. Saito; K. Yumoto

    2002-01-01

    Using a comprehensive data set and model calculations, we have investigated a prominent large-scale traveling ionospheric disturbance (LSTID) observed in Japan (?37°–16° MLAT) on 15 September 1999, during a recovery phase of sequential storms. The LSTID was detected at 2300–2400 LT (1400–1500 UT) as an enhancement of the 630-nm airglow intensity (50?350 R), a decrease in the F layer virtual

  18. Ionosphere disturbances observed throughout Southeast Asia of the superstorm of 20–22 November 2003

    Microsoft Academic Search

    B. Zhao; W. Wan; K. Tschu; K. Igarashi; T. Kikuchi; K. Nozaki; S. Watari; G. Li; L. J. Paxton; L. Liu; B. Ning; J.-Y. Liu; S.-Y. Su; Harold P. Bulanon

    2008-01-01

    Ionospheric disturbances in the Southeast Asian region during the super magnetic storm of 20–22 November 2003 were investigated through an ionosonde chain and a GPS network assisted by the space-borne instruments. At early stage of the storm in the postsunset sector, large enhancements in the critical frequency of F2 layer and total electron content were observed at northern crest region

  19. Characteristics of ionospheric irregularities capable of producing quasi-horizontal traces on ionograms

    NASA Astrophysics Data System (ADS)

    Dyson, P. L.; Roberts, D. L.

    1989-04-01

    Simulated ionograms are presented for a parabolic ionospheric layer containing irregularities in the form of small amplitude waves. It is shown that small scale irregularities with vertical wavelengths up to several km and amplitudes up to a few percent can produce echo trace structure which should be evident on high-resolution ionosgrams. Patterns similar to those observed by Bowman et al. (1988) were simulated, suggesting that the irregularities studied in this paper were detected by Bowman et al.

  20. Artificial Intelligence Daniel Polani

    E-print Network

    Polani, Daniel

    Artificial Intelligence Daniel Polani Artificial Intelligence ­ p.1/26 Is it AI? 1. text editor 2 12. Turing test contenders Artificial Intellige The Turing Test: is partner human or not? See: e.g. [Saygin et al., 2000] Artificial Intelligence ­ p.3/26 The Turing Test II

  1. Artificial Intelligence Adversarial Search

    E-print Network

    Srinivasan, Padmini

    Artificial Intelligence Adversarial Search Readings: Chapter 6 of Russell & Norvig. Artificial Rybka. Artificial Intelligence ­ p.2/25 Games vs. Search problems "Unpredictable" opponent: Solution, poker, scrabble nuclear war Artificial Intelligence ­ p.3/25 Tic-Tac-Toe XX XX X X X XX MAX (X) MIN (O

  2. Hydrocarbon ions in the Lower Ionosphere of Saturn

    NASA Astrophysics Data System (ADS)

    Kim, Y.; Fox, J. L.; Black, J. H.; Moses, J. I.

    2011-12-01

    Radio occultation measurements have shown that persistent electron density layers are observed in the lower ionospheres of Saturn. H2 is the major component of the Saturn lower thermosphere, and in the photon range 845 to 1116 A, it absorbs in discrete transitions from the ground state (X) to vibrational levels of excited electronic states. The cross sections for these absorptions vary greatly from the centers to the wings of the H2 absorption lines. We model here the ionization rates of hydrocarbons by photons that penetrate to low altitudes in the wings and gaps in the H2 absorption spectrum in this wavelength range. The calculation requires construction of very high resolution cross sections for H2, and a similarly high resolution solar flux spectrum. We have constructed a photoabsorption spectrum of H2 at a resolution of 0.001 A, using a new set of cross sections for rovibrational lines in H2 Lyman (B - X), Werner (C - X), and the Rydberg B' - X and D - X band systems. We combined the high resolution cross sections with high resolution solar spectra that were constructed from the SOHO/SUMER (Curdt et al., 2001) measured spectrum for the quiet solar disk and a SOLAR2000 spectrum (e.g., Tobiska, 2004) for low solar activity. We compute the photo- and photo-electron-impact processes for H2, H, He, and CH4, and photo processes for 15 of the most important neutral species in the lower ionosphere of Saturn, including C2H2, C2H4, C2H6, CH3, CH3C2H, H2O, CO, C, CH, C2, O, O2, CO2, H2CO, and CH3OH, with updated cross sections for these processes. We find that significant solar fluxes in this wavelength range, especially at the CIII 977.02 and OVI 1031.91 solar lines, penetrate to near the hydrocarbon homopause, resulting in photoionization of hydrocarbons. For the ionospheric chemistry, we compiled from the literature a set of 727 rate coefficients for ion-neutral, neutral-neutral, and dissociative recombination reactions of 47 ion species and 26 neutral species. The reaction set is more-or-less complete for hydrocarbon ions with up to 4 carbon atoms, and those containing one oxygen atom. The model for low solar activity shows a hydrocarbon ion layer in the altitude range of 600 - 900 km above 1 bar level, where the peak densities are 4×103, 7×102, and 1×102 cm-3 at noon dusk and dawn, respectively. The hydrocarbon ion layer is composed mainly of CH5+, C2H3+, C3H5+, C5Hn+, and C6Hn+ at daytime, but at night time CH5+ and C2H3+, as intermediate ions, disappear more quickly than others due to reactions with ambient hydrocarbon neutrals in addition to their own recombination with electrons. The model also shows layers of H3O+ and H3+ above the hydrocarbon ion layer, and H+ ions form the main peak of the ionosphere, as has been shown by many other modelers. We will discuss sensitivities of our models to input solar spectra, background neutral atmosphere models, vibrational temperatures of H2, and recombination coefficient sets for the ions.

  3. Ionospheric calibration for single frequency altimeter measurements

    NASA Technical Reports Server (NTRS)

    Schreiner, William S.; Born, George H.; Markin, Robert E.

    1994-01-01

    This study is a preliminary analysis of the effectiveness (in terms of altimeter calibration accuracy) of various ionosphere models and the Global Positioning System (GPS) to calibrate single frequency altimeter height measurements for ionospheric path delay. In particular, the research focused on ingesting GPS Total Electron Content (TEC) data into the physical Parameterized Real-Time Ionospheric Specification Model (PRISM), which estimates the composition of the ionosphere using independent empirical and physical models and has the capability of adjusting to additional ionospheric measurements. Two types of GPS data were used to adjust the PRISM model: GPS receiver station data mapped from line-of-sight observations to the vertical at the point of interest and a grid map (generated at the Jet Propulsion Laboratory) of GPS derived TEC in a sun-fixed longitude frame. The adjusted PRISM TEC values, as well as predictions by the International Reference Ionosphere (IRI-90), a climatological (monthly mean) model of the ionosphere, were compared to TOPEX dual-frequency TEC measurements (considered as truth) for a number of TOPEX sub-satellite tracks. For a 13.6 GHz altimeter, a Total Electron Content (TEC) of 1 TECU 10(exp 16) electrons/sq m corresponds to approximately 0.218 centimeters of range delay. A maximum expected TEC (at solar maximum or during solar storms) of 10(exp 18) electrons/sq m will create 22 centimeters of range delay. Compared with the TOPEX data, the PRISM predictions were generally accurate within the TECU when the sub-satellite track of interest passed within 300 to 400 km of the GPS TEC data or when the track passed through a night-time ionosphere. If neither was the case, in particular if the track passed through a local noon ionosphere, the PRISM values differed by more than 10 TECU and by as much as 40 TECU. The IRI-90 model, with no current ability to unseat GPS data, predicted TEC to a slightly higher error of 12 TECU. The performance of PRISM is very promising for predicting TEC and will prove useful for calibrating single frequency altimeter height measurements for ionospheric path delay. When adjusted to the GPS line-of-sight data the PRISM URSI empirical model predicted TEC over a day's period to within a global error of 8.60 TECU rms during a nighttime ionosphere and 9.74 TECU rms during the day. When adjusted to the GPS derived TEC grid, the PRISM parametrized model predicted TEC to within an error of 8.47 TECU rms for a nighttime ionosphere and 12.83 TECU rms during the day. However, the grid cannot be considered globally due to the lack of sufficient numbers of GPS stations and large latitude gaps in GPS data. It is the opinion of the authors that using the PRISM model and adjusting to the global sun-fixed TEC grid regenerated with a localized weighted interpolation offers the best possibility of meeting the 10 TECU global rms (or 2 cm at 13.6 GHz) ionosphere range correction accuracy requirement of TOPEX/Poseidon and should be the subject of further study. However, it is clear that the anticipated requirement of 34 TECU global rms for TOPEX/Poseidon Follow-On (corresponding to the TOPEX/Poseidon performance) can not be met with any realizable combination of existing models and data assimilation schemes.

  4. Experimental evidence of electromagnetic pollution of ionosphere

    NASA Astrophysics Data System (ADS)

    Pronenko, Vira; Korepanov, Valery; Dudkin, Denis

    The Earth’s ionosphere responds to external perturbations originated mainly in the Sun, which is the primary driver of the space weather (SW). But solar activity influences on the ionosphere and the Earth's atmosphere (i.e., the energy transfer in the direction of the Sun-magnetosphere-ionosphere-atmosphere-surface of the Earth), though important, is not a unique factor affecting its state - there is also a significant impact of the powerful natural and anthropogenic processes, which occur on the Earth’s surface and propagating in opposite direction along the Earth’s surface-atmosphere-ionosphere-magnetosphere chain. Numerous experimental data confirm that the powerful sources and consumers of electrical energy (radio transmitters, power plants, power lines and industrial objects) cause different ionospheric phenomena, for example, changes of the electromagnetic (EM) field and plasma in the ionosphere, and affect on the state of the Earth atmosphere. Anthropogenic EM effects in the ionosphere are already observed by the scientific satellites and the consequences of their impact on the ionosphere are not currently known. Therefore, it is very important and urgent task to conduct the statistically significant research of the ionospheric parameters variations due to the influence of the powerful man-made factors, primarily owing to substantial increase of the EM energy production. Naturally, the satellite monitoring of the ionosphere and magnetosphere in the frequency range from tens of hertz to tens of MHz with wide ground support offers the best opportunity to observe the EM energy release, both in the global and local scales. Parasitic EM radiation from the power supply lines, when entering the ionosphere-magnetosphere system, might have an impact on the electron population in the radiation belt. Its interaction with trapped particles will change their energy and pitch angles; as a result particle precipitations might occur. Observations of EM emission by multiple low orbiting satellites have confirmed a significant increase in their intensity over the populated areas of Europe and Asia. Recently, there are many experimental evidences of the existence of power line harmonic radiation (PLHR) in the ionosphere. Their spectra consist of succession of 50 (60) Hz harmonics which is accompanied by a set of lines separated by 50 (60) or 100 (120) Hz - the central frequency of which is shifted to high frequency. These lines cover rather wide band - according to the available experimental data, their central frequencies are observed from ~1.5 - 3 kHz up to 15 kHz, and recently the main mains frequencies are also observed. The examples of power line harmonic radiation, which were detected by “Sich-1M”, “Chibis-M” and “Demeter” satellites, have been presented and discussed. The available experimental data, as well as theoretical estimations, allow us with a high degree of certainty to say that the permanent satellite monitoring of the ionospheric and magnetospheric anthropogenic EM perturbations is necessary for: a) objective assessment and prediction of the space weather conditions; b) evaluation of the daily or seasonal changes in the level of energy consumption; c) construction of a map for estimation of near space EM pollution. This study is partially supported by SSAU contract N 4-03/13.

  5. Hemispheric, seasonal and latitudinal dependence of storm-time ionosphere during low solar activity period

    NASA Astrophysics Data System (ADS)

    Adekoya, B. J.; Adebesin, B. O.

    2014-12-01

    Analysis of the seasonal, hemispheric and latitudinal variation of the ionospheric F2 peak during periods of disturbed geomagnetic conditions in 2011, a year of low solar activity, had been studied using hourly data obtained from low- and mid-latitude ionosonde stations. Our results showed an enhancement in F2-layer maximum electron density (NmF2) at daytime over low latitudes. For the mid-latitude stations, NmF2 depletion pre-dominates the daytime and overturned at nighttime. In general, the variation in terms of magnitude is higher in the low-latitude than at mid-latitude. The nighttime decrease in NmF2 is accompanied by a corresponding F2 peak height (hmF2) increase and overturned at daytime. The hmF2 response during the equinoctial months is lower than the solstices. NmF2 shows distinct seasonal, hemispheric and latitudinal dependence in its response. Appearance of a significant ionospheric effect in southern hemisphere is higher than in the northern hemisphere, and is more pronounced in the equinoxes at low latitudes. At mid-latitudes, the ionospheric effect is insignificant at both hemispheres. A negative ionospheric response dominates the whole seasons at the mid-latitude except for March equinox. The reverse is the case for the hmF2 observation. The amplitudes of both the NmF2 and hmF2 increase with increasing latitude and maximize in the southern hemisphere in terms of longitude.

  6. TaiWan Ionospheric Model (TWIM) prediction based on time series autoregressive analysis

    NASA Astrophysics Data System (ADS)

    Tsai, L. C.; Macalalad, Ernest P.; Liu, C. H.

    2014-10-01

    As described in a previous paper, a three-dimensional ionospheric electron density (Ne) model has been constructed from vertical Ne profiles retrieved from the FormoSat3/Constellation Observing System for Meteorology, Ionosphere, and Climate GPS radio occultation measurements and worldwide ionosonde foF2 and foE data and named the TaiWan Ionospheric Model (TWIM). The TWIM exhibits vertically fitted ?-Chapman-type layers with distinct F2, F1, E, and D layers, and surface spherical harmonic approaches for the fitted layer parameters including peak density, peak density height, and scale height. To improve the TWIM into a real-time model, we have developed a time series autoregressive model to forecast short-term TWIM coefficients. The time series of TWIM coefficients are considered as realizations of stationary stochastic processes within a processing window of 30 days. These autocorrelation coefficients are used to derive the autoregressive parameters and then forecast the TWIM coefficients, based on the least squares method and Lagrange multiplier technique. The forecast root-mean-square relative TWIM coefficient errors are generally <30% for 1 day predictions. The forecast TWIM values of foE and foF2 values are also compared and evaluated using worldwide ionosonde data.

  7. Electric fields in the ionosphere

    NASA Technical Reports Server (NTRS)

    Kirchhoff, V. W. J. H.

    1975-01-01

    F-region drift velocities, measured by incoherent-scatter radar were analyzed in terms of diurnal, seasonal, magnetic activity, and solar cycle effects. A comprehensive electric field model was developed that includes the effects of the E and F-region dynamos, magnetospheric sources, and ionospheric conductivities, for both the local and conjugate regions. The E-region dynamo dominates during the day but at night the F-region and convection are more important. This model provides much better agreement with observations of the F-region drifts than previous models. Results indicate that larger magnitudes occur at night, and that daily variation is dominated by the diurnal mode. Seasonal variations in conductivities and thermospheric winds indicate a reversal in direction in the early morning during winter from south to northward. On magnetic perturbed days and the drifts deviate rather strongly from the quiet days average, especially around 13 L.T. for the northward and 18 L.T. for the westward component.

  8. Probabilistic ionospheric models for radiowave propagation problems

    NASA Astrophysics Data System (ADS)

    Bekker, Susanna; Lyakhov, Andrey; Kozlov, Stanislav

    We consider and substantiate the basic principles of the elaboration of the probabilistic ionospheric models which can form the layout for the principally new approach in ionosphere description and simulation. This approach is best suitable for the solution of applied problems in radiowave propagation. In the probabilistic approach the ionosphere is presented as the spatial random field that provides the probability density functions of the required radiophysical parameters (amplitude, signal/noise ratio, radar cross-section etc.). We discuss and compare pure statistical version, when the spatial random fields are generated from the available evidence on the probability density functions of the ionospheric parameters and partially deterministic version, when probability density functions are used for the unknown or highly variable inputs to the deterministic ionospheric model. The critical issues are discussed, namely the set up of spatial and temporal correlation in random field generation and radiowave propagation simulation. A set of certain examples demonstrate the successful usage of probabilistic approach in VLF-LF and HF frequency range.

  9. Solar rotation effects on the Martian ionosphere

    NASA Astrophysics Data System (ADS)

    Venkateswara Rao, N.; Balan, N.; Patra, A. K.

    2014-08-01

    We present a detailed investigation of the solar rotation effects on the Martian high-latitude (~63°N-81°N) ionosphere using the electron density (Ne) data measured by Mars Global Surveyor and solar XUV and EUV fluxes measured by SOHO under high (2000-2001), medium (2003), and low (2005) solar activity conditions. A fast Fourier transform spectral analysis method is used to estimate the amplitude of the rotation period in these parameters. This method clearly reveals the presence of solar rotation effects in the Martian ionospheric Ne at all altitudes (90-220 km), peak electron density (NmM2), and total electron content under the three solar activity conditions. These effects are in phase with the solar UV fluxes (corrected for the Martian orbit). The period of rotation effect (~26 days) is the same at all altitudes, though its amplitude is strongest at the ionospheric M2 peak (~135-140 km, ~3.5-6% of the mean values) and has a secondary enhancement at the M1 peak (~110-115 km). The effect of solar rotation on the M2 peak is larger during medium solar activity (2003) than during high solar activity (2000-2001). The effect, however, is absent in the ionospheric peak height (hmM2). The rotation effects on Mars are also compared with those on the Earth. Unlike at Mars, the Earth's high-latitude ionosphere shows no clear solar rotation effect, though the effect is observed clearly at lower latitudes.

  10. Using WAAS Ionospheric Data to Estimate LAAS Short Baseline Gradients

    E-print Network

    Stanford University

    the ionosphere, e.g. the GPS satellite broadcast, are delayed with respect to the same signal traveling throughUsing WAAS Ionospheric Data to Estimate LAAS Short Baseline Gradients Seebany Datta-Barua, Todd due to ionospheric effects must be bounded such that integrity is maintained with minimal loss

  11. ROUTINE PRODUCTION OF IONOSPHERE TEC MAPS AT ESOC

    Microsoft Academic Search

    J. Feltens; J. M. Dow; T. J. Martín-Mur; I. Romero; C. García Martínez

    The first version of ESOC's Ionosphere Monitoring Facility (IONMON) software is now in operational use since January 1998. Since summer 1998 ESOC contributes with ionosphere products the IGS ionosphere pilot project. An external user interface needed for the support of other ESA missions, like ERS and ENVISAT, with IONMON products is close to com- pletion.

  12. WHISTLER-MODE PROPAGATION IN THE COLLISIONAL IONOSPHERE OF VENUS

    E-print Network

    Strangeway, Robert J.

    that non-linearities do not modify the wave dispersion since the non-linear force causes a longitudinal ionosphere of Venus. Further, we find that while the waves will heat the bottomside ionosphere, little effect in the nightside ionosphere of Venus cannot be electromagnetic waves caused by atmospheric discharges (lightning

  13. Structure of Titan's ionosphere: Model comparisons with Cassini data

    Microsoft Academic Search

    I. P. Robertson; T. E. Cravens; J. H. Waite Jr.; R. V. Yelle; V. Vuitton; A. J. Coates; J. E. Wahlund; K. Ågren; K. Mandt; B. Magee; M. S. Richard; E. Fattig

    2009-01-01

    Solar extreme ultraviolet and X-ray radiation and energetic plasma from Saturn's magnetosphere interact with the upper atmosphere producing an ionosphere at Titan. The highly coupled ionosphere and upper atmosphere system mediates the interaction between Titan and the external environment. New insights into Titan's ionosphere are being facilitated by data from several instruments onboard the Cassini Orbiter, although the Ion and

  14. Latitudinal variations in Saturn's ionosphere: Cassini measurements and model comparisons

    E-print Network

    Mendillo, Michael

    Latitudinal variations in Saturn's ionosphere: Cassini measurements and model comparisons Luke of latitudinal variations in Saturn's ionosphere using Cassini Radio Science Subsystem (RSS) measurements and SaturnThermosphereIonosphereModel (STIM) simulations. On the basis of Cassini RSS observations, the peak

  15. Control of equatorial ionospheric morphology by atmospheric tides

    Microsoft Academic Search

    T. J. Immel; E. Sagawa; S. L. England; S. B. Henderson; M. E. Hagan; S. B. Mende; H. U. Frey; C. M. Swenson; L. J. Paxton

    2006-01-01

    A newly discovered 1000-km scale longitudinal variation in ionospheric densities is an unexpected and heretofore unexplained phenomenon. Here we show that ionospheric densities vary with the strength of non-migrating, diurnal atmospheric tides that are, in turn, driven mainly by weather in the tropics. A strong connection between tropospheric and ionospheric conditions is unexpected, as these upward propagating tides are damped

  16. Magnetosphere-ionosphere waves A. J. B. Russell1

    E-print Network

    Wright, Andrew N.

    Magnetosphere-ionosphere waves A. J. B. Russell1 and A. N. Wright2 Received 22 June 2011; revised-consistent electrodynamic coupling of the ionosphere and magnetosphere produces waves with clearly defined properties on a combination of ionospheric and magnetospheric parameters. Advection of large scale waves is nonlinear: troughs

  17. Challenges of Validating Global Assimilative Models of the Ionosphere

    Microsoft Academic Search

    G. J. Bishop; L. F. McNamara; J. A. Welsh; D. T. Decker; C. R. Baker

    2008-01-01

    This paper addresses the often surprisingly difficult challenges that arise in conceptually simple validations of global models of the ionosphere. AFRL has been tasked with validating the Utah State University GAIM (Global Assimilation of Ionospheric Measurements) model of the ionosphere, which is run in real time by the Air Force Weather Agency. The USU-GAIM model currently assimilates, in addition to

  18. Representation of the Auroral and Polar Ionosphere in the International Reference Ionosphere (IRI)

    NASA Technical Reports Server (NTRS)

    Bilitza, Dieter; Reinisch, Bodo

    2013-01-01

    This issue of Advances in Space Research presents a selection of papers that document the progress in developing and improving the International Reference Ionosphere (IRI), a widely used standard for the parameters that describe the Earths ionosphere. The core set of papers was presented during the 2010 General Assembly of the Committee on Space Research in Bremen, Germany in a session that focused on the representation of the auroral and polar ionosphere in the IRI model. In addition, papers were solicited and submitted from the scientific community in a general call for appropriate papers.

  19. Observations and simulations of quasiperiodic ionospheric oscillations and large-scale traveling ionospheric disturbances during the December 2006 geomagnetic storm

    Microsoft Academic Search

    Jiuhou Lei; Alan G. Burns; Takuya Tsugawa; Wenbin Wang; Stanley C. Solomon; Michael Wiltberger

    2008-01-01

    A numerical simulation was performed to investigate quasiperiodic ionospheric oscillations that were observed with periods of 4-5 h by the ionosonde network (Okinawa, Yamagawa, Kokubunji, and Wakkanai) in Japan during the 15 December 2006 magnetic storm. This simulation used the Coupled Magnetosphere Ionosphere Thermosphere (CMIT) 2.0 model. The CMIT model reproduced the main characteristics of the observed ionospheric oscillations, although

  20. Feedback instability of the ionospheric resonant cavity

    NASA Technical Reports Server (NTRS)

    Lysak, Robert L.

    1991-01-01

    A model is developed that provides a theoretical basis for previous numerical results showing a feedback instability with frequencies characteristic of Alfven travel times within the region of the large increase of Alfven speed above the ionosphere. These results have been extended to arbitrary ionospheric conductivity by developing a numerical solution of the cavity dispersion relation that involves Bessel functions of complex order and argument. It is concluded that the large contrast between the magnetospheric and ionospheric Alfven speed leads to the formation of resonant cavity modes with frequencies ranging from 0.1 to 1 Hz. The presence of the cavity leads to a modification of the reflection characteristics of Alfven waves with frequencies that compare to the cavity's normal modes.

  1. Ionospheric correction of space radar data

    NASA Astrophysics Data System (ADS)

    Hapgood, Mike

    2010-06-01

    Radar is a critical tool for maintaining knowledge of the many objects in low Earth orbit and thus for maintaining confidence that societies around the world are secure against a variety of space-based threats. It is therefore important to raise awareness that LEO objects are embedded in the envelope of relatively dense plasma that co-rotates with the Earth (ionosphere-plasmasphere system) and thus accurate tracking must correct for the group delay and refraction caused by that system. This paper seeks to promote that awareness by reviewing those effects and high-lighting key issues: the need to customise correction to the altitude of the tracked object and prevailing space weather conditions, that ionospheric correction may be particularly important as an object approaches reentry. The paper outlines research approaches that should lead to better techniques for ionospheric correction and shows how these might be pursued in the context of the EURIPOS initiative.

  2. Beacon satellite receiver for ionospheric tomography

    NASA Astrophysics Data System (ADS)

    Vierinen, J.; Norberg, J.; Lehtinen, M. S.; Amm, O.; Roininen, L.; Väänänen, A.; Erickson, P. J.; McKay-Bukowski, D.

    2014-12-01

    We introduce a new coherent dual-channel beacon satellite receiver intended for ionospheric tomography. The measurement equation includes neutral atmosphere and ionosphere propagation effects, relative errors in satellite and receiver clocks, and residual Doppler shifts caused by errors in the satellite ephemeris. We also investigate the distribution of errors for phase curve measurements and the use of phase curve measurements for limited angle tomography using the framework of statistical linear inverse problems. We describe the design of our beacon satellite receiver software and present one possible hardware configuration. Finally, we present results obtained using a network of four newly developed receivers and compare the results with those of an existing ionospheric tomography network at Sodankylä Geophysical Observatory.

  3. Ionospheric effects of the missile destruction on December 9, 2009

    NASA Astrophysics Data System (ADS)

    Kozlovsky, Alexander; Shalimov, Sergey; Lukianova, Renata

    2014-05-01

    We report on ionosonde and meteor radar observations made in Sodankyla Geophysical Observatory (SGO, 67N, 27E, Finland) on December 9, 2009 during a test launch of the Russian solid propellant military missile. Because of the technical problem the missile was self-destroyed around 07 UT at ionospheric height (170-260 km) over the Kola Peninsula (Russia), at a distance about 500 km to east from the observatory. Products of the explosion, including long-lived ionized aluminum oxides, were spread into the large area and reached the region of SGO meteor radar observations in about 2 hours (around 09 UT). After about 3 hours (around 10 UT) a sporadic E layer presumably composed of the remains was observed close to the zenith of the SGO ionosonde. We present the data and discuss possible mechanisms accounting for both vertical and horizontal transport of the remains. Theoretical estimations suggest that the observed transport could be likely due to thermospheric turbulence.

  4. A Study of the Response of the Mid-Latitude Ionospheric f2 to the Total Solar Eclipses of Solar Cycle 23

    NASA Astrophysics Data System (ADS)

    John, Adekoya; Chukwuma, Victor

    2012-07-01

    A study of the response of the mid-latitude ionospheric F2 to the total eclipses of solar cycle 23 is presented using 5 minute resolution ionospheric foF2 data obtained from 14 mid-latitude ionosonde stations located in the path of totality of eclipse. The changes in foF2 is analyzed using D(foF2), the normalize deviation of critical frequency F2 from the quite days reference. The results show that the F2 layer behaviors during solar eclipses are accompanied with various amplitudes of decreases and a small increase in the electron density. The D(foF2) variation of all the ionosphere of the path of totality as recorded by the ionosonde stations in this path are characterized by simultaneous decrease in electron density at elapsed time of totality. Our analysis also revealed that sudden Sun radiation removal by the moon reduces the electron production processes in the ionospheric F2 layer. The impact of total solar eclipse is clearly evidenced simultaneously with the time of maximum occultation as decrease in the electron density in all ionospheric stations. The results further suggest that the maximum effects were observed not at the time of totality of eclipse but occurring shortly before and after the elapsed time (i.e. about 4min to few hours). It is noteworthy that largest response of electron density in ionospheric F2 region does not coincide with the duration of the totality. Also an increase in maximum obscuration of eclipse causes reduction in electron density production processes. This result obtained was reasonably in good agreement with the previous study of ionospheric response to total solar eclipse using different measurement and methods. Keywords: Solar eclipse, ionosphere, ionosonde, F2 region critical frequency, mid-latitude station, electron density).

  5. Ionospheric tomography using the FORTE satellite

    SciTech Connect

    Murphy, T.C.

    1993-08-01

    The possibility of obtaining ionospheric profile data via tomographic techniques has elicited considerable interest in recent years. The input data for the method is a set of total electron content measurements along intersecting lines of sight which form a grid. This can conveniently be provided by a fast-moving satellite with a VHF beacon which will generate the multiple paths needed for effective tomography. Los Alamos and Sandia National Laboratories will launch and operate the FORTE satellite for the US Department of Energy, with launch scheduled in 1995. FORTE will provide such a beacon. Additionally, wideband VHF receivers aboard the satellite will allow corraborative measurements of ionospheric profile parameters in some cases.

  6. The secondary radiation of the Earth's ionosphere

    NASA Astrophysics Data System (ADS)

    Szcz??niak, M.; Szcz??niak, R.; Durajski, A. P.; Jarosik, M. W.

    2011-01-01

    The modernization of the KLAUDIA radiotelescope, used for the detection of the Earth ionosphere's secondary radiation at 40 kHz±{200} Hz waves, is presented in the paper. In particular, the scope of the Very Low Frequency receiver's modernization and the construction of the high frequency grounding module is briefly discussed. The most typical features of the radio radiation of the Earth's ionosphere at 40 kHz frequency waves are presented and discussed in detail in the second part of the paper.

  7. Characteristics of ionospheric storms in East Asia

    NASA Astrophysics Data System (ADS)

    Wang, Xiao; Wang, Guojun; Shi, Jiankui

    ???The ionosphere experiences intense response during the geomagnetic storm and it varies with latitude and longitude. The DPS-4 digisonde measurements and GPS-TEC data of ionospheric stations located at different latitudes in the longitudinal sector of 90-130E during 2002 to 2012 were analyzed to investigate the ionospheric effects in the different latitude of East Asia during geomagnetic storm. About 70 geomagnetic storms are selected according to the Dst index and observed data and they are in different seasons and different solar activity levels. A few quiet days’ averages of data before geomagnetic storm were used as the undisturbed level. Results show that for the middle and high latitude, the short-lived positive disturbance associated with the initial phase of the every storm was observed in each season and then the disturbances were negative till the termination of storm. At the low latitude, storm-time disturbances of foF2 have obvious diurnal, seasonal and solar cycle characteristics. Generally, geomagnetic activity will cause foF2 to increase at daytime and decrease at nighttime except for the summer in low solar activity period. The intensity of response of foF2 is stronger at nighttime than that at daytime. The negative ionospheric storm effect is the strongest in summer and the positive ionospheric storm effect is the strongest in winter. In high solar activity period, the diurnal variation of the response of foF2 is very pronounced in each season, and the strong ionospheric response can last several days. In low solar activity period, ionospheric response has very pronounced diurnal variation in winter only. It’s notable that geomagnetic activities occurred at local time nighttime can cause stronger and longer responses of foF2 at the low latitude. All in all, the obvious negative phase ionospheric storms often occurred at the low latitude. Moreover a notable phenomenon was observed for the low latitude, there are the intensive oscillations of foF2 occurring during the main storm phase of enhanced storm in Hainan, and it occurred in the morning generally. For the TEC data, strong disturbances can be observed simultaneously from high latitude to low latitude during the main phase of some storms. Generally strong/weak storms can cause the negative/positive phase storms of TEC in the low latitude and which are obvious in the daytime for the summer and winter and in the period from noon to midnight for the equinox. The differences of the responses of foF2 and TEC are also investigated.

  8. Role of acoustic-gravity waves in generating equatorial ionospheric irregularities

    SciTech Connect

    Argo, P.E.

    1980-01-01

    Irregularities in the equatorial ionospheric plasma (F-layer) have been observed and studied for many years. Even so, the creation mechanisms have successfully remained a source of controversy for equally many years. This is mainly due to the difficulty in observing the irregularities, because in situ measurements give a spatial trace at a near single time, while radio observations have tended to give a series of height profiles with changing time. One mechanism is the spatial resonance amplification of traveling ionospheric disturbance (TIDs) generated by acoustic gravity waves. As the wave profile in the plasma steepens, the stored energy begins to release through the Rayleigh-Taylor instability, which then creates a spectrum of smaller scale irregularities. In this dissertation the interaction of the acoustic gravity wave and the ionospheric plasma are examined, and it is found that the above mechanism is indeed feasible. In Chapter 3, the interaction between a neutral wave and the plasma is quantified, and the condiions for growth of resonant plasma waves is established. These conditions are met during the post-sunset period near the geomagnetic equator, which is exactly when and where the irregularities are encountered. For irregularity generation the Rayleigh-Taylor mechanism requires a steep positive gradient of density - a fact that previously has seemed to be impossible on the topside of the F-layer. However, in this thesis it is shown that acoustic gravity waves can generate positive slopes even on the topsideF-layer. Consequently, acoustic gravity waves constitute a single mechanism that can be used to explain both bottomside and topside irregularities. Experimental evidence for the creation of equatorial ionospheric irregularities by acoustic gravity waves has been sparse, although wavelike structures appear to permeate the irregularity profiles.

  9. CIGALA: an FP7 innovative activity to tackle the threat of Ionospheric Scintillation to GNSS operations in Latin America

    NASA Astrophysics Data System (ADS)

    Francisco Galera Monico, João.; Bougard, Bruno; Sleewaegen, Jean-Marie; Willems, Tom; Saüt, Carine; Aquino, Marcio; de Franceschi, Giorgiana; Ferreira da Silva, Elcia; Forte, Biagio; Wernik, Andrzej W.

    2010-05-01

    Drifting ionospheric electron density irregularities may lead to the scintillation of transionospheric radio waves, as in the case of signals broadcast from artificial satellites. Scintillations can not only degrade signal quality but also cause receiver loss of lock on GNSS satellites, therefore posing a major threat to GNSS based applications demanding high levels of accuracy, availability and integrity, including EGNOS-based applications notably in low latitude areas. The problem is particularly acute in Latin America and will be further amplified with the next solar maximum, predicted for 2013. The CIGALA (Concept for Ionospheric Scintillation Mitigation for Professional GNSS in Latin America) project, led by Septentrio NV and co-funded by the European GNSS Supervisory Authority (GSA) through the European 7th Framework Program, will tackle this problem. The aim of the CIGALA project is to develop ionospheric scintillation mitigation countermeasures to be implemented in Septentrio's professional multi-frequency multi-constellation GNSS receivers and tested in Latin America. The project will leverage research and development activities coordinated between European and Brazilian experts and will involve a wide scale ionospheric measurement and test campaigns that will be conducted in Brazil with the support of several local academic and industrial partners. Details on the objectives, current status, and workflow of the project will be presented and discussed.

  10. Inter-hemispheric imaging of the ionosphere with the upgraded IRI-Plas model during the space weather storms

    NASA Astrophysics Data System (ADS)

    Gulyaeva, T. L.; Arikan, F.; Stanislawska, I.

    2011-08-01

    International Reference Ionosphere extended to the plasmasphere (IRI-Plas) is upgraded analytically for assimilative mode of operation using GPS-derived Total Electron Content (TEC) for reconstruction of instantaneous ionospheric critical frequency and topside scale height at magnetic conjugate hemisphere. The performance of IRI-Plas code is examined with TECgps retrieved from Global Ionospheric Maps compared with the F 2-layer critical frequency at eight ionosonde locations in East Asia region on both hemispheres during the space weather storms at solar maximum (2000) and solar minimum (2006). Missing ionosonde data are completed by cloning of critical frequency. Decomposition of TECgps in electron density profile with IRI-Plas code reveals the opposite relative changes of critical frequency and the topside scale height depending on solar activity. The ionospheric weather W index is computed for the desired locations in conjugate hemispheres and consistent results are obtained indicating the departure of instantaneous values of ionospheric parameters from their respective median varying from quiet state to intense storm.

  11. Nanostructured artificial nacre

    NASA Astrophysics Data System (ADS)

    Tang, Zhiyong; Kotov, Nicholas A.; Magonov, Sergei; Ozturk, Birol

    2003-06-01

    Finding a synthetic pathway to artificial analogs of nacre and bones represents a fundamental milestone in the development of composite materials. The ordered brick-and-mortar arrangement of organic and inorganic layers is believed to be the most essential strength- and toughness-determining structural feature of nacre. It has also been found that the ionic crosslinking of tightly folded macromolecules is equally important. Here, we demonstrate that both structural features can be reproduced by sequential deposition of polyelectrolytes and clays. This simple process results in a nanoscale version of nacre with alternating organic and inorganic layers. The macromolecular folding effect reveals itself in the unique saw-tooth pattern of differential stretching curves attributed to the gradual breakage of ionic crosslinks in polyelectrolyte chains. The tensile strength of the prepared multilayers approached that of nacre, whereas their ultimate Young modulus was similar to that of lamellar bones. Structural and functional resemblance makes clay- polyelectrolyte multilayers a close replica of natural biocomposites. Their nanoscale nature enables elucidation of molecular processes occurring under stress.

  12. Application of locality principle to radio occultation studies of the Earth's atmosphere and ionosphere

    NASA Astrophysics Data System (ADS)

    Pavelyev, A. G.; Liou, Y. A.; Matyugov, S. S.; Pavelyev, A. A.; Gubenko, V. N.; Zhang, K.; Kuleshov, Y.

    2015-01-01

    A new formulation of previously introduced principle of locality is presented. The principle can be applied for modernization of the radio occultation (RO) remote sensing of the atmospheres and ionospheres of the Earth and planets. The principle states that significant contributions to variations of the amplitude and phase of the radio waves passing through a layered medium are connected with influence of the vicinities of tangential points where the refractivity gradient is perpendicular to the radio ray trajectory. The RO method assumes spherical symmetry of the investigated medium. In this case if location of a tangent point relative to the spherical symmetry center is known, the derivatives on time of the RO signal phase and Doppler frequency variations can be recalculated into the refractive attenuation. Several important findings are consequences of the locality principle: (i) if position of the center of symmetry is known, the total absorption along the ray path can be determined at a single frequency, (ii) in the case of low absorption the height, displacement from the radio ray perigee, and tilt of the inclined ionospheric (atmospheric) layers can be evaluated, (iii) the contributions of the layered and irregular structures in the RO signal can be separated and parameters of layers and turbulence can be measured at a single frequency using joint analysis of the amplitude and phase variations. Specially for the Earth's troposphere, the altitude distributions of the weak total absorption (about of 1-4 db) of the radio waves at GPS frequencies corresponding to possible influence of the oxygen and water vapor can be measured with accuracy of about 0.1 db at a single frequency. According with the locality principle, a new index of ionospheric activity is introduced. This index is measured from the phase variations of radio waves passing through the ionosphere. Its high correlation with S4 scintillation index is established. This correlation indicates the significant influence of locally spherical symmetric ionospheric layers on variations of the phase and amplitude of the RO signal passing through transionospheric communication links. Obtained results expand the applicable domain of the RO method as a powerful remote sensing technique for geophysical and meteorological research.

  13. Global Imaging Monitor of the Ionosphere (GIMI) - an ultraviolet ionospheric imaging experiment for the ARGOS satellite

    NASA Astrophysics Data System (ADS)

    Carruthers, George R.; Seeley, Timothy D.

    1992-06-01

    The Global Imaging Monitor of the Ionosphere (GIMI) is one of several remote-sensing instruments under development for flight on the Air Force Space Test Program's P91-1 Advanced Research and Global Observation Satellite (ARGOS), planned for launch in late 1995. The primary objective of GIMI is to map and monitor the ionospheric O(+) and electron density on a global basis, by means of wide-field imaging of ionospheric far-ultraviolet emissions. GIMI consists of two wide-field imaging cameras sensitive in two far- and extreme-UV spectral ranges (75-105 nm and 131-160 nm), selected for their utility in day and night ionospheric remote sensing. The GIMI sensors are based on electron-bombarded CCD arrays, with opaque alkali halide photocathodes and Schmidt or all-reflective optical systems.

  14. A review of ionospheric effects on Earth-space propagation

    NASA Technical Reports Server (NTRS)

    Klobuchar, J. A.

    1984-01-01

    A short description is given of each ionospheric total electron content (TEC) effect upon radio waves, along with a representative value of the magnitude of each of these effects under normal ionospheric conditions. A discussion is given of the important characteristics of average ionospheric TEC behavior and the temporal and spatial variability of TEC. Radio waves undergo several effects when they pass through the Earth's ionosphere. One of the most important of these effects is a retardation, or group delay, on the modulation or information carried on the radio wave that is due to its encounter with the free, thermal electrons in the Earth's ionosphere. Other effects the ionosphere has on radio waves include: radio frequency (RF) carrier phase advance; Doppler shift of the RF carrier of the radio wave; Faraday rotation of the plane of polarization of linearly polarized waves; angular refraction or bending of the radio wave path as it travels through the ionosphere; and amplitude and phase scintillations.

  15. ICON: The Ionospheric Connection Explorer - NASA's Next Space Physics and Aeronomy Mission

    NASA Astrophysics Data System (ADS)

    Immel, T. J.; Mende, S. B.; Heelis, R. A.; Englert, C. R.; Edelstein, J.; Forbes, J. M.; England, S.; Maute, A. I.; Makela, J. J.; Kamalabadi, F.; Crowley, G.; Stephan, A. W.; Huba, J. D.; Harlander, J.; Swenson, G. R.; Frey, H. U.; Bust, G. S.; Gerard, J. M.; Hubert, B. A.; Rowland, D. E.; Hysell, D. L.; Saito, A.; Frey, S.; Bester, M.; Valladares, C. E.

    2013-12-01

    Earth's ionosphere is a highly variable layer of plasma surrounding earth that is influenced from below by internal atmospheric waves of various scales and from above by solar and geomagnetic activity. Recent observational findings and modeling studies have raised many questions about the effects and interaction of these drivers in our geospace environment, and how these vary between extremes in solar activity. ICON will address the most compelling science issues that deal with the coupling of the ionosphere to the neutral atmosphere below and space above: 1) The highly variable nature of the electric field in the ionosphere and its potential link to thermospheric wind, 2) the effect of forcing from below: how large-scale atmospheric waves penetrate into the thermosphere and ionosphere, and 3) the effect of forcing from above: how ion-neutral coupling changes during solar and geomagnetically active periods. To address these, ICON will measure all key parameters of the atmosphere and ionosphere simultaneously and continuously with a combination of remote sensing and in-situ measurements. The scientific return from ICON is enhanced by dynamic operational modes of the observatory that provide capabilities well beyond that afforded by a static space platform. Selected for development by NASA, ICON will launch in early 2017 into a low-inclination orbit that is particularly well suited to address the above-noted scientific problems and to make a number of coordinated measurements with other ground- and space-based facilities at low and middle latitudes. The ICON Observatory carries a compliment of 4 instruments on the nadir facing payload integration plate.

  16. Meteor matter interaction with the Earth's atmosphere and the ionospheric E-region structure

    NASA Technical Reports Server (NTRS)

    Alimov, O.

    1987-01-01

    The exploration of the ionospheric E region is a pressing problem, both in the applied and fundamental studies. Results are presented of an investigation: (1) to estimate the meteor ionization contribution to the night time E layer and influx; (2) to study the phenomenon of intensive sporadic layer formation following cessation of meteor stream activity; and (3) to access the role of metallic ions of meteor origin in the diurnal and seasonal variations in the occurrence probabilities of midlatitude E sub s. The contribution was evaluated of meteor matter, Lyman radiation and corpuscular particles to the electron concentration of the night E region. Results are discussed.

  17. Ionospheric effects during severe space weather events seen in ionospheric service data products

    NASA Astrophysics Data System (ADS)

    Jakowski, Norbert; Danielides, Michael; Mayer, Christoph; Borries, Claudia

    Space weather effects are closely related to complex perturbation processes in the magnetosphere-ionosphere-thermosphere systems, initiated by enhanced solar energy input. To understand and model complex space weather processes, different views on the same subject are helpful. One of the ionosphere key parameters is the Total Electron Content (TEC) which provides a first or-der approximation of the ionospheric range error in Global Navigation Satellite System (GNSS) applications. Additionally, horizontal gradients and time rate of change of TEC are important for estimating the perturbation degree of the ionosphere. TEC maps can effectively be gener-ated using ground based GNSS measurements from global receiver networks. Whereas ground based GNSS measurements provide good horizontal resolution, space based radio occultation measurements can complete the view by providing information on the vertical plasma density distribution. The combination of ground based TEC and vertical sounding measurements pro-vide essential information on the shape of the vertical electron density profile by computing the equivalent slab thickness at the ionosonde station site. Since radio beacon measurements at 150/400 MHz are well suited to trace the horizontal structure of Travelling Ionospheric Dis-turbances (TIDs), these data products essentially complete GNSS based TEC mapping results. Radio scintillation data products, characterising small scale irregularities in the ionosphere, are useful to estimate the continuity and availability of transionospheric radio signals. The different data products are addressed while discussing severe space weather events in the ionosphere e.g. events in October/November 2003. The complementary view of different near real time service data products is helpful to better understand the complex dynamics of ionospheric perturbation processes and to forecast the development of parameters customers are interested in.

  18. Model of Jovian F region ionosphere (Saturnian ionosphere in offset dipole approximation)

    NASA Technical Reports Server (NTRS)

    Tan, A.

    1991-01-01

    Researchers investigated the offset effect of Saturn's dipole on its ionosphere. The magnetic field of Saturn is primarily that of a dipole closely aligned to the rotational axis, but displaced northward from the center by a distance approximately equal to 0.05 R sub S, R sub S being the reference radius of Saturn. This offset effect would manifest itself most prominently between the ionospheric profiles in the Northern and Southern Hemispheres of Saturn.

  19. Dynamics of low latitude ionosphere by Digisonde 256 animations in ionospheric research

    Microsoft Academic Search

    V. H. Rios; B. Reinisch; C. Medina; C. Valladares; T. Bullett; Y. Sahai; E. Gomez

    2003-01-01

    A UMLCAR (University of Massachusetts Lowell, Centre for Atmospheric Research) Digital Ionosonde 256 has operated at Tucumán (26.9^o S, 65.4^o W) since 2002, primarily to study the dynamics of the low latitude ionosphere. To gain a better understanding of the ionosphere motions involved and identify dynamical features, animated data displays have been developped using ionspheric drift an ionogram data combined

  20. Tropospheric jet stream as a source of traveling ionospheric disturbances observed by GPS

    NASA Astrophysics Data System (ADS)

    Wautelet, Gilles; Warnant, René

    2014-05-01

    The integrity and the reliability of real-time precise positioning applications with Global Positioning System (GPS) are affected by the ionospheric variability with time and space. As a consequence, scientific community aims at describing, explaining and forecasting the occurrence and the amplitude of ionospheric irregularities observed by GPS. The use of the geometric-free combination of GPS dual frequency signals allows to retrieve the Total Electron Content (TEC) along the satellite-to-receiver path, which is the basic trans-ionospheric observable. Based on L1/L2 GPS phase measurements collected at a given station, the TEC high-frequency variability is isolated. A climatological study performed over 10 years in Western Europe shows that TEC irregularities are mostly observed daytime during quiet geomagnetic background in autumn and winter and correspond to classical Medium-Scale Traveling Ionospheric Disturbances (MSTIDs). The latter are generally understood as the ionospheric signature of Atmospheric Gravity Waves (AGWs), either generated in situ (solar terminator) or in the lower atmosphere and propagating upward. Because of its associated strong wind shears, the tropospheric jetstream, occurring mainly during autumn and winter months, constitutes an ideal candidate for AGW generation. This paper analyzes the spatial correlation between the presence of both MSTIDs and strong jetstream over Western Europe. This correlation is positive when the ionospheric pierce point of the satellite is located above regions of interest where wind shears are very large. In practice, we have selected regions for which wind speed is larger than 50 m/s. In addition, the propagation of AGWs up to the ionospheric layer is taken into account by assuming horizontal and vertical velocities of 200 and 50 m/s respectively. It comes that the region of interest of the correlation study is computed using an isotropic slant propagation of the AGW, which is supposed to be generated at a tropospheric level. Based on 30s GPS data collected over several stations in Belgium and on European Centre for Medium-Range Weather Forecasts (ECMWF) wind velocity maps, the correlation study covers a period ranging from January 2002 to December 2011. Preliminary results based on a limited number of cases show that large amplitude MSTIDs are generally observed during periods of strong wind speeds at an altitude corresponding to a pressure level of 250hPa (about 10 km).

  1. GBAS ionospheric threat model validation: Characterising ionospheric storms in the Australian region

    NASA Astrophysics Data System (ADS)

    Terkildsen, Michael

    Uncorrected ionospheric delay, and its equivalent parameter Total Electron Content (TEC), is the largest source of error for single-frequency GPS applications. In particular, spatial and temporal gradients in TEC provide a non-uniform source of error that is difficult to resolve or correct using simple climatological ionospheric models. Differential or augmented GPS sys-tems suffer increased spatial de-correlation under strong TEC gradients thereby reducing their effective range. The range of anomalous TEC gradients and their effects on GPS augmenta-tion systems, such as GBAS and WAAS, in Conterminus United States (CONUS) has been established. A comparable study of Southern Hemisphere regions, in particular the Australian longitude sector, has not been published. In this study, a validation of the ionospheric threat model within GBAS (Ground-Based Augmentation System) was undertaken in the context of ionospheric storm conditions found in the Australian region. The range of anomalous TEC gradients occurring during ionospheric superstorms over the last solar cycle and their projected impact on a GBAS installation in Australia was quantified. The results are presented in the context of comparable observations from the Northern Hemisphere. Regional characteristics of ionospheric storms in the southern hemisphere, particularly those storm features commonly associated with anomalous TEC gradients, are also presented.

  2. The Artificial Life Roots of Artificial Intelligence

    Microsoft Academic Search

    Luc Steels; R. Brooks

    1994-01-01

    Behavior-oriented Artificial Intelligence (AI) is a scientific discipline that studies how behavior of agents emerges and becomes intelligent and adaptive. Success of the field is defined in terms of success in building physical agents that are capable of maximizing their own self-preservation in interaction with a dynamically changing environment. The paper addresses this Artificial Life route toward AI and reviews

  3. Artificial Immune Systems 209 Artificial Immune Systems

    E-print Network

    Timmis, Jon

    Artificial Immune Systems 209 Chapter XI Artificial Immune Systems: Using the Immune System, Idea Group Publishing. The immune system is highly distributed, highly adaptive, self encounters. From a computational view- point, the immune system has much to offer by way of inspiration

  4. Medium-scale 4-D ionospheric tomography using a dense GPS network

    NASA Astrophysics Data System (ADS)

    van de Kamp, M. M. J. L.

    2013-01-01

    The ionosphere above Scandinavia in December 2006 is successfully imaged by 4-dimensional tomography using the software package MIDAS from the University of Bath. The method concentrates on medium-scale structures: between 100 km and 2000 km in horizontal size. The input consists of TEC measurements from the dense GPS network Geotrim in Finland. In order to ensure sufficient vertical resolution of the result, EISCAT incoherent scatter radar data from Tromsø are used as additional input to provide the vertical profile information. The TEC offset of the measurements is unknown, but the inversion procedure is able to determine this automatically. This auto-calibration is shown to work well. Comparisons with EISCAT radar results and with occultation results show that the inversion using EISCAT data for profile information is much better able to resolve vertical profiles of irregular structures than the inversion using built-in profiles. Still, with either method the intensities of irregular structures of sizes near the resolution (about 100 km horizontal size) can be underestimated. Also, the accuracy of the inversion worsens above areas where no receivers are available. The ionosphere over Scandinavia in December 2006 often showed a dense E-layer in early morning hours, which generally disappeared during midday when a dense F-layer was present. On 14 December, a strong coronal mass ejection occurred, and many intense irregularities appeared in the ionosphere, which extended to high altitudes.

  5. Jupiter's Thermosphere and Ionosphere R. V. Yelle

    E-print Network

    Yelle, Roger V.

    9 Jupiter's Thermosphere and Ionosphere R. V. Yelle University of Arizona S. Miller University College, London 9.1 INTRODUCTION Jupiter's upper atmosphere forms the boundary between the lower of molecular energy levels may depart from their local thermodynamic equilibrium (LTE) values. Jupiter shares

  6. Traveling ionospheric disturbances near London, Canada

    Microsoft Academic Search

    J. W. MacDougall; G. Li; P. T. Jayachandran

    2009-01-01

    Observations of medium scale traveling ionospheric disturbances (TIDs) from near London, Canada (43°N, 81°W geographic) using spaced transmitter technique at 4MHz have been done for 112 years. Most of the best data are for daytime TIDs because of the use of 4MHz. Using this data set we have derived properties of the TIDs such as the speed, direction of propagation

  7. New techniques in ionospheric sounding and studies

    NASA Astrophysics Data System (ADS)

    Reinisch, B. W.

    An overview is given of new techniques in ionospheric sounding and studies. Rapid progress in the integrated circuit market has led to new advanced techniques in the remote probing of the ionosphere with HF radio waves. The classical ionosonde which measured virtual height as a function of frequency has been expanded into a geophysical research tool by measuring all the observables contained in the electromagnetic signals reflected from the ionosphere: amplitude, phase, Doppler, incidence angle, and polarization. A receiving antenna array and high-speed digital processing provide the desired spatial and temporal resolution. The current emphasis is on the on-line and off-line post-processing of the multiparameter ionogram data to extract the geophysically important ionospheric characteristics: the vertical electron density profiles, horizontal gradients (tilts and waves), plasma drift, the mid-latitude F-region trough, and auroral and equatorial spread F. Digital ionosondes deployed in the polar cap and the auroral zone have helped to obtain a better understanding of some of the high latitude features, and measurements of the equatorial spread F show the development and motion of the F-region bubbles. HF coherent radar techniques which measure the velocity of irregularities with scale sizes of one half the radio wavelength have been used mainly in the northern auroral zone.

  8. Photoelectron escape from the ionosphere of Jupiter

    Microsoft Academic Search

    Wesley E. Swartz; Roger W. Reed; Thomas R. McDonough

    1975-01-01

    Photoelectron escape fluxes and ambient electron heating from the Jovian ionosphere are computed as a function of local time and latitude. Several differences for the fluxes expected from a hydrogen at- mosphere, rather than a terrestrial type of atmosphere, are described, including an increase in structure in the energy spectra due to the paucity of ionic states entering the photo-ionization

  9. Ionosphere scintillation effects on navigation systems

    NASA Astrophysics Data System (ADS)

    Béniguel, Yannick; Adam, Jean-Pierre; Bourdillon, Alain; Lassudrie-Duchesne, P.

    2011-03-01

    This article deals with the impact of ionospheric electron density inhomogeneities on the functionality of global navigation satellite systems emphasizing positioning errors. The scintillation characteristics of transmitted signals have been obtained using data gathered in measurement campaigns. The effects on a standard receiver are then presented. Positioning errors due to scintillations were shown to be greater than 10 meters in the worst case.

  10. A greenhouse effect in the ionosphere?

    Microsoft Academic Search

    H. Rishbeth

    1990-01-01

    Following a suggestion by Roble and Dickenson that increases in the mixing ratios of mesospheric carbon dioxide and methane will cool the thermosphere by about 50 K, this paper examines the consequences for the ionosphre. It is concluded that physical and chemical factors that may affect the ionosphere have not been considered in this analysis and therefore further global monitoring

  11. Importance of Ionospheric Gradients for error Correction

    NASA Astrophysics Data System (ADS)

    Ravula, Ramprasad

    Importance of Ionospheric Gradients for error Correction R. Ram Prasad1, P.Nagasekhar2 1Sai Spurthi Institute of Technology-JNTU Hyderabad,2Sai Spurthi Institute of Technology-JNTU Hyderabad Email ID:rams.ravula@gmail.com In India, Indian Space Research Organization (ISRO) has established with an objective to develop space technology and its application to various national tasks. To cater to the needs of civil aviation applications, GPS Aided Geo Augmented Navigation (GAGAN) system is being jointly implemented along with Airports Authority of India (AAI) over the Indian region. The most predominant parameter affecting the navigation accuracy of GAGAN is ionospheric delay which is a function of total number of electrons present in one square meter cylindrical cross sectional area in the line of site direction between the satellite and the user on the earth i.e. Total Electron Content (TEC).The irregular distribution of electron densities i.e. rate of TEC variation, causes Ionospheric gradients such as spatial gradients (Expressed in TECu/km) and temporal gradients (Expressed in TECu /minute). Among the satellite signals arriving to the earth in multiple directions, the signals which suffer from severe ionospheric gradients can be estimated i.e. Rate of TEC Index (ROTI) and Rate of TEC (ROT). These aspects which contribute to errors can be treated for improving GAGAN positional accuracy.

  12. Catalog of ionospheric and atmospheric data

    NASA Technical Reports Server (NTRS)

    Liles, J. N.

    1975-01-01

    Available data from planetary atmospheres and ionospheric physics (aeronomy) are announced. Most of the data sets identified result from individual experiments carried on board various spacecraft. A spacecraft Automated Internal Management File and a Nonsatellite Data File are utilized to maintain information on these data. Photoreduced reports produced by these information files are presented. A variety of user oriented indexes are included.

  13. Empirical modelling of equatorial ionospheric scintillation

    Microsoft Academic Search

    P. K. Pasricha; B. M. Reddy

    1986-01-01

    A computer-based model of ionospheric scintillations has been developed by Fremouw (socalled the WBMOD model) to give a mean scintillation index for a given set of observing conditions. The WBMOD model incorporates some of the scintillation observations made with the DNA wideband satellite. A comparison is made between the scintillation morphology observed at an equatorial station Ooty with the one

  14. Ionospheric scintillations at L & C bands

    Microsoft Academic Search

    Yannick Béniguel; J.-P. Adam; R. Prieto-Cerdeira; B. Arbesser-Rastburg

    2009-01-01

    This paper addresses the problem of ionospheric scintillations at L and C bands. The results of a L band scintillation measurement campaign are presented. The receivers used during this campaign were located in the five regions of the globe allowing to exhibit latitudinal and longitudinal dependence. Comparison with modeling has been done concurrently. The results presented for C band scintillations

  15. Magnetosphere Sawtooth Oscillations Induced by Ionospheric Outflow

    E-print Network

    Magnetosphere Sawtooth Oscillations Induced by Ionospheric Outflow O. J. Brambles,1 * W. Lotko,1 B's magnetosphere is a 2- to 4-hour planetary-scale oscillation powered by the solar wind­magnetosphere can generate sawtooth oscillations. As the outflowing ions fill the inner magnetosphere

  16. Phase perturbation measurements through a heated ionosphere

    NASA Technical Reports Server (NTRS)

    Frey, A.; Gordon, W. E.

    1982-01-01

    High frequency radiowaves incident on an overdense (i.e., HF-frequency penetration frequency) ionosphere produce electron density irregularities. The effect of such ionospheric irregularities on the phase of UHF-radiowaves was determined. For that purpose the phase of radiowaves originating from celestial radio sources was observed with two antennas. The radiosources were chosen such that the line of sight to at least one of the antennas (usually both) passed through the modified volume of the ionosphere. Observations at 430 MHz and at 2380 MHz indicate that natural irregularities have a much stronger effect on the UHF phase fluctuations than the HF-induced irregularities for presently achieved HF-power densities of 20-80 uW/sq m. It is not clear whether some of the effects observed are the result of HF-modification of the ionosphere. Upper limits on the phase perturbations produced by HF-modification are 10 deg at 2380 MHz and 80 deg at 430 MHz.

  17. Global Response to Local Ionospheric Mass Ejection

    NASA Technical Reports Server (NTRS)

    Moore, T. E.; Fok, M.-C.; Delcourt, D. C.; Slinker, S. P.; Fedder, J. A.

    2010-01-01

    We revisit a reported "Ionospheric Mass Ejection" using prior event observations to guide a global simulation of local ionospheric outflows, global magnetospheric circulation, and plasma sheet pressurization, and comparing our results with the observed global response. Our simulation framework is based on test particle motions in the Lyon-Fedder-Mobarry (LFM) global circulation model electromagnetic fields. The inner magnetosphere is simulated with the Comprehensive Ring Current Model (CRCM) of Fok and Wolf, driven by the transpolar potential developed by the LFM magnetosphere, and includes an embedded plasmaspheric simulation. Global circulation is stimulated using the observed solar wind conditions for the period 24-25 Sept 1998. This period begins with the arrival of a Coronal Mass Ejection, initially with northward, but later with southward interplanetary magnetic field. Test particles are launched from the ionosphere with fluxes specified by local empirical relationships of outflow to electrodynamic and particle precipitation imposed by the MIlD simulation. Particles are tracked until they are lost from the system downstream or into the atmosphere, using the full equations of motion. Results are compared with the observed ring current and a simulation of polar and auroral wind outflows driven globally by solar wind dynamic pressure. We find good quantitative agreement with the observed ring current, and reasonable qualitative agreement with earlier simulation results, suggesting that the solar wind driven global simulation generates realistic energy dissipation in the ionosphere and that the Strangeway relations provide a realistic local outflow description.

  18. SOLAR FLARE EFFECTS IN THE IONOSPHERE

    Microsoft Academic Search

    Owen K. Garriott; Aldo V. da Rosa; Michael J. Davis; O. G. Jr. Villard

    1967-01-01

    content of the ionosphere were observed at four or at five stations, simultaneously with the onset of solar flares on May 21 and 23, 1967. The observations are most readily explained by a large, but brief, enhancement of the solar EUV flux on two occasions. An explanation based on X-ray enhancement only does not appear attractive. Time-correlated values of visual

  19. Method for Canceling Ionospheric Doppler Effect

    NASA Technical Reports Server (NTRS)

    Vessot, R. F. C.

    1982-01-01

    Unified transponder system with hydrogen-maser oscillators at both stations can compensate for both motional and ionospheric components of Doppler shift. Appropriate choices of frequency shift in output of mixer m3. System exploits proportionality between dispersive component of frequency shift and reciprocal of frequency to achieve cancellation of dispersive component at output.

  20. Numerical simulations on ion acoustic double layers

    SciTech Connect

    Sato, T.; Okuda, H.

    1980-07-01

    A comprehensive numerical study of ion acoustic double layers has been performed for both periodic as well as for nonperiodic systems by means of one-dimensional particle simulations. For a nonperiodic system, an external battery and a resistance are used to model the magnetospheric convection potential and the ionospheric Pedersen resistance. It is found that the number of double layers and the associated potential buildup across the system increases with the system length.

  1. Artificial Intelligence and Robotics

    E-print Network

    Brady, Michael

    1984-02-01

    Since Robotics is the field concerned with the connection of perception to action, Artificial Intelligence must have a central role in Robotics if the connection is to be intelligent. Artificial Intelligence addresses ...

  2. Trends in Artificial Intelligence.

    ERIC Educational Resources Information Center

    Hayes, Patrick

    1978-01-01

    Discusses the foundations of artificial intelligence as a science and the types of answers that may be given to the question, "What is intelligence?" The paradigms of artificial intelligence and general systems theory are compared. (Author/VT)

  3. Dependence of Characteristics of SURA Induced Artificial ULF/VLF Signals on Geomagnetic Activity

    NASA Astrophysics Data System (ADS)

    Kotik, D. S.; Ryabov, A. V.; Ermakova, E. N.; Pershin, A. V.

    2015-04-01

    A comprehensive study of artificial ionospheric signal generation in the ULF/VLF bands at SURA facility in Russia was conducted during the past 4 years. We investigated the influence of geomagnetic activity on the characteristics of artificial low-frequency signals under the background of increasing solar activity. No correlation of artificial ULF signals with variations of Earth's magnetic field was observed for weak geomagnetic disturbances (Kp ? 3) while the VLF signals increased in the growth phase of the geomagnetic perturbation. In case of strong magnetic storm (Kp ? 5+) a tendency of the amplitude of the ULF/VLF signals decrease with increasing magnetic disturbance was observed. Sometimes, the modulation of artificial ULF signals with a period of 15-30 s was detected in the decay phase of magnetic storms. During storm time, a change in the polarization of artificial VLF emissions was detected. The right polarization becomes predominant. Interpretation of observed peculiarities of artificial VLF signals is given in the context of the physical mechanism of ionospheric current drive by RF pumping.

  4. Torsional carbon nanotube artificial muscles.

    PubMed

    Foroughi, Javad; Spinks, Geoffrey M; Wallace, Gordon G; Oh, Jiyoung; Kozlov, Mikhail E; Fang, Shaoli; Mirfakhrai, Tissaphern; Madden, John D W; Shin, Min Kyoon; Kim, Seon Jeong; Baughman, Ray H

    2011-10-28

    Rotary motors of conventional design can be rather complex and are therefore difficult to miniaturize; previous carbon nanotube artificial muscles provide contraction and bending, but not rotation. We show that an electrolyte-filled twist-spun carbon nanotube yarn, much thinner than a human hair, functions as a torsional artificial muscle in a simple three-electrode electrochemical system, providing a reversible 15,000° rotation and 590 revolutions per minute. A hydrostatic actuation mechanism, as seen in muscular hydrostats in nature, explains the simultaneous occurrence of lengthwise contraction and torsional rotation during the yarn volume increase caused by electrochemical double-layer charge injection. The use of a torsional yarn muscle as a mixer for a fluidic chip is demonstrated. PMID:21998253

  5. Artificial neural networks in predicting current in electric arc furnaces

    NASA Astrophysics Data System (ADS)

    Panoiu, M.; Panoiu, C.; Iordan, A.; Ghiormez, L.

    2014-03-01

    The paper presents a study of the possibility of using artificial neural networks for the prediction of the current and the voltage of Electric Arc Furnaces. Multi-layer perceptron and radial based functions Artificial Neural Networks implemented in Matlab were used. The study is based on measured data items from an Electric Arc Furnace in an industrial plant in Romania.

  6. Comprehensive Ionospheric Polar and Auroral Observations for Solar Minimum of Cycle 23/24

    NASA Astrophysics Data System (ADS)

    Sojka, Jan J.; Nicolls, Michael; van Eyken, Anthony; Heinselman, Craig

    Only the incoherent scatter radar (ISR) is able to simultaneously measure full profiles of elec-tron density, ion temperature, and electron temperatures through the E-and F-layers of the terrestrial ionosphere. Historically ISR's have been operated for periods much less than a month. Hence, their measurements do not constitute a continuous sequence from which quiet, disturbed, and storm periods can reliably be discerned. This is particularly true in the auroral and polar regions. During the International Polar Year (IPY) two ISRs achieved close to 24/7 continuous observations. This presentation describes their data sets and specifically how they can provide the IRI with a fiduciary E-and F-region ionosphere descriptions for solar minimum conditions at auroral and polar cap locations. The ionospheric description being electron den-sity, ion temperature, electron temperature, and even molecular ion composition profiles from as low as 90 km extending several scale heights above the F-layer peak. The auroral location is Poker Flat in Alaska at 65.4° N, 147.5° W where the NSF's new Poker Flat Incoherent Scatter Radar (PFISR) is located. During solar minimum conditions this location is in the auroral region for most of the day and is at mid-latitudes, equatorward of the cusp, for about 4 to 8 hours per day dependent upon geomagnetic activity. In contrast the polar location is Svalbard, at 78° N, 16° E where the EISCAT Svalbard Radar (ESR) is located. For most of the day the ESR is in the Northern Polar Cap often with a noon sector passage through the dayside cusp. Of unique relevance to IRI is that these extended observations have enabled the ionospheric morphology to be demarked between quiet and disturbed. During the IPY year, 1 March 2007 to 29 February 2008, a total of 50 solar wind corotating interaction regions (CIRs) impacted geospace. Each CIR has a one-to-three day geomagnetic disturbance that is observed in the ISR auroral and polar observations. Hence, this data set enables the quiet-background ionosphere to be established as a function of season and local time. This quiet-background ionosphere has the unique attribute that it has self-consistent altitude profiles of the density and the temper-ature. This we believe is a true fiduciary reference for the IRI in a high latitude region, that is otherwise particularly difficult to quantify.

  7. Multi-point Observations of Subauroral Electric Field Signatures in the Ionosphere and Magnetosphere

    NASA Astrophysics Data System (ADS)

    Erickson, P. J.; Foster, J. C.; Wygant, J. R.; Bonnell, J. W.; Tao, J.; Ruohoniemi, J.

    2013-12-01

    The boundary layer between the cold, dense inner plasmasphere and the hot, tenuous outer plasmasphere gives rise to dynamic variations in current systems and electromagnetic signatures as direct manifestations of magnetosphere-ionosphere coupling within the terrestrial geospace system. In particular, sub auroral polarization stream (SAPS) flows occur as electric fields are set up near Region 2 current systems. These electric fields are directed at ionospheric heights in the magnetic meridian, and are associated primarily with radially outward fields in the magnetospheric equatorial plane. Under normal circumstances, we expect from the large parallel conductivity along L=3 to L=5 magnetic field lines that equipotential mapping should be sufficient to allow prediction of the spatial extent and amplitude of these cross-B electric field signatures in the magnetosphere from ionospheric observations, and vice-versa. In this paper, we examine the validity of these assumptions in the sub-auroral region using simultaneous direct multi-point ionospheric and magnetospheric observations of SAPS associated electric field structures. We derive ionospheric electric field features at L=3.5 to 5 using data from both the SuperDARN HF radar network (F region altitude), the Millstone Hill incoherent scatter radar (F region and topside) and DMSP (840 km altitude). These can be directly compared with in-situ electric field observations at high altitude by the Electric Fields and Waves (EFW) instrument onboard Van Allen Probes spacecraft A and B. A number of excellent conjunctions have occurred during 2012 and 2013 as the magnetic footprint of Van Allen Probes passes through the plasmasphere boundary layer and overlaps with the ground based radar and low altitude DMSP fields of view, providing a truly unprecedented multipoint view of SAPS processes. We will present events showing both precise mapping of these electric field features between ionosphere and magnetosphere, and also events with significant discrepancies in both amplitude and position. We will discuss the implications of these latter findings in the larger context of electrodynamic coupling within the subauroral portion of the geospace system.

  8. Isis 1 observations of the high-latitude ionosphere during a geomagnetic storm.

    NASA Technical Reports Server (NTRS)

    Whitteker, J. H.; Hartz, T. R.; Brace, L. H.; Burrows, J. R.; Heikkila, W. J.; Sagalyn, R. C.; Thomas, D. M.

    1972-01-01

    The Isis 1 satellite has made measurements of several ionospheric and related parameters, and the results of the various measurements have been compared in detail for two north transpolar passes during the geomagnetic storm of February 3, 1969. Simultaneous measurements were made of local electron and ion densities and temperatures, electron density between the satellite and the peak of the F layer, radio noise, and particle fluxes over a wide energy range extending down to 10 eV. Several features of the ionosphere (in particular, enhancements of radio noise, scale height, and plasma temperatures) appear to be due to soft-particle (100 eV to 1 keV) precipitation, which is related to magnetospheric structure as delineated by the observation of more energetic particles. The magnetosheath particles precipitating on the dayside of the polar cap are particularly effective.

  9. Grating formation by a high power radio wave in near-equator ionosphere

    SciTech Connect

    Singh, Rohtash; Sharma, A. K.; Tripathi, V. K. [Department of Physics, Indian Institute of Technology Delhi, New Delhi-110016 (India)

    2011-11-15

    The formation of a volume grating in the near-equator regions of ionosphere due to a high power radio wave is investigated. The radio wave, launched from a ground based transmitter, forms a standing wave pattern below the critical layer, heating the electrons in a space periodic manner. The thermal conduction along the magnetic lines of force inhibits the rise in electron temperature, limiting the efficacy of heating to within a latitude of few degrees around the equator. The space periodic electron partial pressure leads to ambipolar diffusion creating a space periodic density ripple with wave vector along the vertical. Such a volume grating is effective to cause strong reflection of radio waves at a frequency one order of magnitude higher than the maximum plasma frequency in the ionosphere. Linearly mode converted plasma wave could scatter even higher frequency radio waves.

  10. Ionospheric effects associated with changes in the levels of geomagnetic and solar activities

    NASA Astrophysics Data System (ADS)

    Karimov, K. A.; Gainutdinova, R. D.

    1993-02-01

    The characteristics of the changes in the dynamics of the lower atmosphere processes over Central Asia, associated with processes taking place in the ionosphere and magnetosphere were investigated using data collected during SUNDIAL observation periods March 16-20 and December 5-10, 1988. Results showed that the wind velocity reversals observed at heights between 80 and 100 km were associated with changing levels of geomagnetic and solar activity. Analyses of data collected in the lower atmosphere and the ionosphere during these periods showed the presence of an anomaly in the dynamics of the electron concentration in the F layer after the October 1988 event, characterized by a disturbance of the 27-30-day variation.

  11. The Evolutionary Emergence Artificial Intelligence

    E-print Network

    Fernandez, Thomas

    The Evolutionary Emergence route to Artificial Intelligence Alastair Channon Degree: MSc with a brief discussion. Keywords: Artificial Intelligence, Emergence, Genetic Algorithms, Artificial Life: Inman Harvey Submitted: 2 September 1996 (Minor revisions October 1996) Abstract The artificial

  12. Ionosphere/thermosphere dynamics as deduced from meridional ionosonde chain at low latitudes

    NASA Astrophysics Data System (ADS)

    Maruyama, Takashi; Uemoto, Junpei; Tsugawa, Takuya; Hidekatsu, Jin; Kubota, Minoru; Saito, Susumu

    Multipoint ionosonde observation was conducted to study ionosphere/thermosphere dynamics in Southeast Asia. For this study, data from three ionosonde stations aligned at 100° E were analyzed. Two of them are near the magnetic conjugate points in Northern Thailand and West Sumatra, Indonesia, and the other is near the magnetic equator in the Malay Peninsula; these are three of five SEALION (Southeast Asia low latitude ionospheric network) ionosonde stations. The F-layer critical frequency (foF2), the propagation factor (M3000F2), and the F-layer virtual height (h'F) were scaled from quarter hourly ionograms at the three stations. The ionospheric height is closely related to the thermospheric dynamics (neutral drags) as well as electromagnetic forces (EXB drifts) and chemical processes (productions and losses). Because h'F strongly depends on the chemical process during daytime, it is better to examine the peak height (hmF2) for the discussion of dynamics. hmF2 was determined from M3000F2 using the modified Shimazaki's formula. The peak height obtained by this method is less accurate near the magnetic equator because the electron density vertical profile around the peak is greatly distorted from the parabolic distribution and the formation of an additional layer (sometimes called the F3 layer). The peak heights at the low-latitude conjugate points were compared for the whole day. The height difference between the two stations is a good indicator of the transequatorial neutral wind as the equatorward wind lifts the ionosphere up, while the poleward wind lowers it. The diurnal variation of the transequatorial wind inferred from the height differences is examined for various seasons. We found that there exists a strong terdiurnal component, which was most significant around the March equinox. Also the results were compared with the HWM model wind. The terdiurnal amplitude inferred in this study was larger than the model wind and the phases of the diurnal variation showed a quite large difference between the model and the measurements depending on the season and time. For nighttime, on the other hand, h'F is a good indicator of the ionospheric height near the magnetic equator and at low latitudes because the chemical process becomes less important. Vertical EXB drifts were evaluated from the height variation at the magnetic equator. By the assist of numerical modeling incorporating with the EXB drift, neutral wind effects during nighttime were examined more quantitatively and accurately. The results of the transequatorial wind effects were generally consistent with that obtained by the hmF2 analysis.

  13. Remote sensing of the earth/sea-ionosphere waveguide using ground based ELF-VLF radio wave observations

    NASA Astrophysics Data System (ADS)

    Kumar, S.; Ramachandran, V.; Kishore, A.

    The results from lightning and man made transmitter generated ELF-VLF signals recorded under the Word Wide Lightning Location (WWLL) Network at low latitude ground wave station, Suva (18.2°S, 178.3°E), Fiji, in the South Pacific region, are used to study the features of the earth/sea-ionosphere waveguide. A ground wave VLF system was established in Aug. 2003 under WWLL, since then ELF and VLF data are recorded in the regular intervals. Matlab codes are used to analyse the data files recorded using lightning software and each of data file is of 11 MB with one minute duration. The analysis of data shows the occurrence of tweeks signals mainly in the night-time. Unusual higher harmonic tweek signals up to fifth harmonic are recorded particularly in the post-midnight period. Tweek signals have been used to determine the height of ionospheric reflecting layer, total propagation distance in the atmospheric waveguide and attenuation rate for tweeks with different modes. The value of ionospheric reflecting height (H) calculated using waveguide mode theory of electromagnetic wave propagation in the spherical cell waveguide having perfectly conducting boundaries is found to vary from 80-95 km in the night-time. The electron density (N) at the ionpspheric reflecting heights is found to vary from 80 to 1.3x10^3 cm-3 which agrees quite well with experimental data. Total distance propagated by the weeks in the atmospheric waveguide before reaching to the receiver is found to be of the order of few thousand km. The propagation time vs frequency characteristics of ELF and VLF signals explain the dispersion of tweeks. The calculated attenuation rate of tweeks shows less attenuation for lower modes as compared to higher modes. The attenuation increases sharply as the frequencies approach the cut-off frequency and conductivity increases, and it also increases when the reflecting layer height falls, for all the modes. The attenuation is less in the night-time than that in the day-time. The waveguide between the sea surface and the lower layer of the ionosphere offers less attenuation than that between the earth surface and the lower layer of the ionosphere, and explains the occurrence of higher mode tweeks at this station. Preliminary results of measurement of amplitude of 19.8 kHz VLF signals from transmitter NWC (21°48'S, 114°9'E) on the North West Cape of Australia, propagated in the earth/sea-ionosphere waveguide, are also presented. From the measured values of diurnal amplitude changes, the daytime ionospheric parameters are estimated.

  14. GNSS station characterisation for ionospheric scintillation applications

    NASA Astrophysics Data System (ADS)

    Romano, Vincenzo; Spogli, Luca; Aquino, Marcio; Dodson, Alan; Hancock, Craig; Forte, Biagio

    2013-10-01

    Ionospheric scintillations are fluctuations in the phase and amplitude of the signals from GNSS (Global Navigation Satellite Systems) occurring when they cross regions of electron density irregularities in the ionosphere. Such disturbances can cause serious degradation of several aspects of GNSS system performance, including integrity, accuracy and availability. The two indices adopted worldwide to characterise ionospheric scintillations are: the amplitude scintillation index, S4, which is the standard deviation of the received power normalised by its mean value, and the phase scintillation index, ??, which is the standard deviation of the de-trended carrier phase. Collaborative work between NGI and INGV supports a permanent network of GISTM (GPS Ionospheric Scintillation and TEC Monitor) receivers that covers a wide range of latitudes in the northern European sector. Data from this network has contributed significantly to several papers during the past few years (see e.g. De Franceschi et al., 2008; Aquino et al., 2009; Spogli et al., 2009, 2010; Alfonsi et al., 2011). In these investigations multipath effects and noise that contaminate the scintillation measurements are largely filtered by applying an elevation angle threshold. A deeper analysis of the data quality and the development of a more complex filtering technique can improve the results obtained so far. The structures in the environment of each receiver in the network which contaminate scintillation measurements should be identified in order to improve the quality of the scintillation and TEC data by removing error sources due to the local environment. The analysis in this paper considers a data set characterised by quiet ionospheric conditions of the mid-latitude station located in Nottingham (UK), followed by a case study of the severe geomagnetic storm, which occurred in late 2003, known generally as the "Halloween Storm".

  15. Intentionality in Artificial Intelligence

    Microsoft Academic Search

    Christopher D. Tennenbaum

    2011-01-01

    This paper addresses the question of whether Artificial Intelligence can have intentionality. This question is part of a larger discussion of whether or not Artificial Intelligence can ever be 'conscious'. Ultimately, I come to the conclusion that while we can see how intentionality can be transferred, it has yet to be shown that intentionality can be created within Artificial Intelligence.

  16. Encyclopedia of Artificial Intelligence

    E-print Network

    Liang, Faming

    Encyclopedia of Artificial Intelligence Juan Ramón Rabuñal Dopico University of A Coruña, Spain of artificial intelligence / Juan Ramon Rabunal Dopico, Julian Dorado de la Calle, and Alejandro Pazos Sierra) -- ISBN 978-1-59904-850-5 (ebook) 1. Artificial intelligence--Encyclopedias. I. Rabunal, Juan Ramon, 1973

  17. Artificiality in Social Sciences

    Microsoft Academic Search

    Jean-Philippe Rennard

    2007-01-01

    This text provides with an introduction to the modern approach of artificiality and simulation in social sciences. It presents the relationship between complexity and artificiality, before introducing the field of artificial societies which greatly benefited from the computer power fast increase, gifting social sciences with formalization and experimentation tools previously owned by \\

  18. Artificial Vision LOGICAL ARCHITECTURE

    E-print Network

    Artificial Vision LOGICAL ARCHITECTURE Dr. Christian Micheloni Department of Computer Science Università Degli Studi di Udine Artificial Vision State of the art (2) Second Systems Generation (1990 PAGE 3 #12;2011 Prof. Micheloni Christian Università Degli Studi di Udine Artificial Vision State

  19. Artificial Vision Image Registration

    E-print Network

    Artificial Vision Image Registration Dr. Christian Micheloni Department of Computer Science. Micheloni Christian Università Degli Studi di Udine Artificial Vision Change Detection: Moving Camera Christian Università Degli Studi di Udine Artificial Vision Image Registration · The image registration

  20. Local ionospheric electron density reconstruction from simultaneous ground-based GNSS and ionosonde measurements

    NASA Astrophysics Data System (ADS)

    Stankov, S. M.; Warnant, R.; Stegen, K.

    2009-04-01

    The purpose of the LIEDR (Local Ionospheric Electron Density Reconstruction) system is to acquire and process data from simultaneous ground-based GNSS TEC and digital ionosonde measurements, and subsequently to deduce the vertical electron density distribution in the local ionosphere. LIEDR is primarily designed to operate in real time for service applications, and, if sufficient data from solar and geomagnetic observations are available, to provide short-term forecast as well. For research applications and further development of the system, a post-processing mode of operation is also envisaged. In essence, the reconstruction procedure consists in the following. The high-precision ionosonde measurements are used for directly obtaining the bottom part of the electron density profile. The ionospheric profiler for the lower side (i.e. below the density peak height, hmF2) is based on the Epstein layer functions using the known values of the critical frequencies, foF2 and foE, and the propagation factor, M3000F2. The corresponding bottom-side part of the total electron content is calculated from this profile and is then subtracted from the GPS TEC value in order to obtain the unknown portion of the TEC in the upper side (i.e. above the hmF2). Ionosonde data, together with the simultaneously-measured TEC and empirically obtained O+/H+ ion transition level values, are all required for the determination of the topside electron density scale height. The topside electron density is considered as a sum of the constituent oxygen and hydrogen ion densities with unknown vertical scale heights. The latter are calculated by solving a system of transcendental equations that arise from the incorporation of a suitable ionospheric profiler (Chapman, Epstein, or Exponential) into formulae describing ionospheric conditions (plasma quasi-neutrality, ion transition level). Once the topside scale heights are determined, the construction of the vertical electron density distribution in the entire altitude range is a straightforward process. As a by-product of the described procedure, the value of the ionospheric slab thickness can be easily computed. To be able to provide forecast, additional information about the current solar and geomagnetic activity is needed. For the purpose, observations available in real time -- at the Royal Institute of Meteorology (RMI), the Royal Observatory of Belgium (ROB), and the US National Oceanic and Atmospheric Administration (NOAA) -- are used. Recently, a new hybrid model for estimating and predicting the local magnetic index K has been developed. This hybrid model has the advantage of using both, ground-based (geomagnetic field components) and space-based (solar wind parameters) measurements, which results in more reliable estimates of the level of geomagnetic activity - current and future. The described reconstruction procedure has been tested on actual measurements at the RMI Dourbes Geophysics Centre (coordinates: 50.1N, 4.6E) where a GPS receiver is collocated with a digital ionosonde (code: DB049, type: Lowell DGS 256). Currently, the nominal time resolution between two consecutive reconstructions is set to 15 minutes with a forecast horizon for each reconstruction of up to 60 minutes. Several applications are envisaged. For example, the ionospheric propagation delays can be estimated and corrected much easier if the electron density profile is available at a nearby location on a real-time basis. Also, both the input data and the reconstruction results can be used for validation purposes in ionospheric models, maps, and services. Recent studies suggest that such ionospheric monitoring systems can help research/services related to aircraft navigation, e.g. for development of the ‘ionospheric threat' methodology.

  1. Storm-time plasma redistribution in the coupled plasmasphere-ionosphere system: Coordinated ground and satellite observations

    NASA Astrophysics Data System (ADS)

    Chi, Peter; Tu, Jiannan; Spasojevic, Maria; Carpenter, Donald; Russell, Christopher

    The plasma distribution in the coupled plasmasphere-ionosphere system can undergo significant changes during magnetic storms, posing a challenging problem to observers and modelers for quantifying all the important physical mechanisms involved. During many magnetic storms, internal depletion occurs within the new plasmaspheric boundary layer, but the responsible physical mechanism for such depletion remains an outstanding problem. As an effort to piece together the jigsaw of this complicated phenomenon, this study examines a collection of critical ground and satellite observations, including the mass density inferred from field line resonance sounding, the charge density deduced from whistler traces, ionosonde data, and the RPI observations from the IMAGE satellite. A case study of the April 2005 storm (min Dst = -85 nT) shows that, within the new plasmaspheric boundary layer, the equatorial mass density dropped by nearly 50% after the first three days of the storm. By contrast, the equatorial charge density decreased by only 25% during the same interval. The stronger degree of heavy ion depletion coincides with a significantly lower ionospheric content at similar L-values. Our observations suggest that the concurrent negative ionospheric storm is a likely cause of the internal depletion of the storm-time plasmasphere, a scenario that can be tested by future numerical simulations of the coupled plasmasphere-ionosphere system.

  2. Theoretical study of lower ionospheric response to solar flares: sluggishness of D-region and peak time delay

    NASA Astrophysics Data System (ADS)

    Palit, Sourav; Basak, Tamal; Pal, Sujay; Chakrabarti, Sandip K.

    2015-03-01

    The rates of ion production and loss processes in the lower ionosphere during solar and other astronomical ionizing events vary with height. This variations influence the time lags of the response in different ionospheric layers. Very Low Frequency (VLF) signals reflected from any of these layers follow this time lag or delay during a transient cosmic events. One of the easiest ways to study this property is to observe the shift in the peak of VLF signal amplitude with respect to the peak of solar flares. We numerically model to find ion densities and resulting VLF signal perturbations during some solar flares. We clearly find from the model that the delay in the peak of the electron densities (with respect to peak of the ionizing event) in the lower ionosphere varies from height to height. The result also depends on the properties of events, such as peak intensity and sharpness. We investigate analytically how the delay of electron density peak should depend on height varying chemical rate parameters as well as the nature of transient events. Our capability is demonstrated using three classes (namely, X, M and C) of solar flares. The work is a step forward in our goal to employ ionosphere as a natural detector for astronomical observations.

  3. Lithosphere-Atmosphere-Ionosphere Coupling (LAIC) Model - An Unified Concept for Earthquake Precursors Validation

    NASA Technical Reports Server (NTRS)

    Pulinets, S.; Ouzounov, D.

    2010-01-01

    The paper presents a conception of complex multidisciplinary approach to the problem of clarification the nature of short-term earthquake precursors observed in atmosphere, atmospheric electricity and in ionosphere and magnetosphere. Our approach is based on the most fundamental principles of tectonics giving understanding that earthquake is an ultimate result of relative movement of tectonic plates and blocks of different sizes. Different kind of gases: methane, helium, hydrogen, and carbon dioxide leaking from the crust can serve as carrier gases for radon including underwater seismically active faults. Radon action on atmospheric gases is similar to the cosmic rays effects in upper layers of atmosphere: it is the air ionization and formation by ions the nucleus of water condensation. Condensation of water vapor is accompanied by the latent heat exhalation is the main cause for observing atmospheric thermal anomalies. Formation of large ion clusters changes the conductivity of boundary layer of atmosphere and parameters of the global electric circuit over the active tectonic faults. Variations of atmospheric electricity are the main source of ionospheric anomalies over seismically active areas. Lithosphere-Atmosphere-Ionosphere Coupling (LAIC) model can explain most of these events as a synergy between different ground surface, atmosphere and ionosphere processes and anomalous variations which are usually named as short-term earthquake precursors. A newly developed approach of Interdisciplinary Space-Terrestrial Framework (ISTF) can provide also a verification of these precursory processes in seismically active regions. The main outcome of this paper is the unified concept for systematic validation of different types of earthquake precursors united by physical basis in one common theory.

  4. Global ionospheric effects of geomagnetic storm on May 2-3, 2010 and their influence on HF radio wave propagation

    NASA Astrophysics Data System (ADS)

    Kotova, Daria; Klimenko, Maxim; Klimenko, Vladimir; Zakharov, Veniamin

    2013-04-01

    In this work we have investigated the global ionospheric response to geomagnetic storm on May 2-3, 2010 using GSM TIP (Global Self-consistent Model of the Thermosphere, Ionosphere and Protonosphere) simulation results. In the GSM TIP storm time model runs, several input parameters such as cross-polar cap potential difference and R2 FAC (Region 2 Field-Aligned Currents) varied as a function of the geomagnetic activity AE-index. Current simulation also uses the empirical model of high-energy particle precipitation by Zhang and Paxton. In this model, the energy and energy flux of precipitating electrons depend on a 3 hour Kp-index. We also have included the 30 min time delay of R2 FAC variations with respect to the variations of cross-polar cap potential difference. In addition, we use the ground-based ionosonde data for comparison our model results with observations. We present an analysis of the physical mechanisms responsible for the ionospheric effects of geomagnetic storms. The obtained simulation results are used by us as a medium for HF radio wave propagation at different latitudes in quiet conditions, and during main and recovery phase of a geomagnetic storm. To solve the problem of the radio wave propagation we used Zakharov's (I. Kant BFU) model based on geometric optics. In this model the solution of the eikonal equation for each of the two normal modes is reduced using the method of characteristics to the integration of the six ray equation system for the coordinates and momentum. All model equations of this system are solved in spherical geomagnetic coordinate system by the Runge-Kutta method. This model was tested for a plane wave in a parabolic layer. In this study, the complex refractive indices of the ordinary and extraordinary waves at ionospheric heights was calculated for the first time using the global first-principal model of the thermosphere-ionosphere system that describes the parameters of an inhomogeneous anisotropic medium during a geomagnetic storm. A comparison of the ordinary and extraordinary modes of HF radio ray paths in quiet and disturbed conditions has been done. We considered in more detail the features of the radio ray paths in the presence of F3 layer in the equatorial ionosphere, the main ionospheric trough and tongue of ionization at high latitudes. It is shown that the results obtained with use of radio propagation and GSM TIP models adequately describe HF radio ray paths in the Earth's ionosphere and can be used in applications. These investigations were carried out at financial support of Russian Foundation for Basic Research (RFBR) - Grant # 12-05-31217 and RAS Program 22.

  5. Longitudinal variation of the equatorial ionosphere: Modeling and experimental results

    NASA Astrophysics Data System (ADS)

    Souza, J. R.; Asevedo, W. D.; dos Santos, P. C. P.; Petry, A.; Bailey, G. J.; Batista, I. S.; Abdu, M. A.

    2013-02-01

    We describe a new version of the Parameterized Regional Ionospheric Model (PARIM) which has been modified to include the longitudinal dependences. This model has been reconstructed using multidimensional Fourier series. To validate PARIM results, the South America maps of critical frequencies for the E (foE) and F (foF2) regions were compared with the values calculated by Sheffield Plasmasphere-Ionosphere Model (SUPIM) and IRI representations. PARIM presents very good results, the general characteristics of both regions, mainly the presence of the equatorial ionization anomaly, were well reproduced for equinoctial conditions of solar minimum and maximum. The values of foF2 and hmF2 recorded over Jicamarca (12°S; 77°W; dip lat. 1°N; mag. declination 0.3°) and sites of the conjugate point equatorial experiment (COPEX) campaign Boa Vista (2.8°N; 60.7°W; dip lat. 11.4°; mag. declination -13.1°), Cachimbo (9.5°S; 54.8°W; dip lat. -1.8°; mag. declination -15.5°), and Campo Grande (20.4°S; 54.6°W; dip lat. -11.1°; mag. declination -14.0°) have been used in this work. foF2 calculated by PARIM show good agreement with the observations, except during morning over Boa Vista and midnight-morning over Campo Grande. Some discrepancies were also found for the F-region peak height (hmF2) near the geomagnetic equator during times of F3 layer occurrences. IRI has underestimated both foF2 and hmF2 over equatorial and low latitude sectors during evening-nighttimes, except for Jicamarca where foF2 values were overestimated.

  6. Combining Radio Occultation Measurements with Other Instruments to Map the Ionospheric Electron

    E-print Network

    tomography. Images showing travelling ionospheric disturbances (TIDs) (Pryse et al. [1995]) have beenCombining Radio Occultation Measurements with Other Instruments to Map the Ionospheric Electron imaging program for the atmosphere and ionosphere. This analysis algorithm can routinely use dual

  7. A study of atmospheric gravity waves and travelling ionospheric disturbances at equatorial latitudes

    E-print Network

    Paris-Sud XI, Université de

    A study of atmospheric gravity waves and travelling ionospheric disturbances at equatorial travelling ionospheric disturbances (TIDs) originating at conjugate magnetic latitudes in the north and south between atmospheric gravity waves (AGWs) and travelling ionospheric disturbances (TIDs) has been

  8. Overlapping ionospheric and surface echoes observed by the Mars Express radar sounder near the Martian terminator

    E-print Network

    Gurnett, Donald A.

    Overlapping ionospheric and surface echoes observed by the Mars Express radar sounder near Express spacecraft occasionally show ionospheric and surface echoes that overlap in frequency ionospheric plasma frequency, respectively. In this paper we show that such overlapping echoes are only

  9. In-situ studies of plasma irregularities in high latitude ionosphere with the ICI-2 sounding rocket within the 4DSpace project

    NASA Astrophysics Data System (ADS)

    Miloch, Wojciech; Moen, Joran; Spicher, Andres

    Ionospheric plasma is often characterized by irregularities, instabilities, and turbulence. Two regions of the ionospheric F-layer are of particular interest: low-latitudes for the equatorial anomaly and electrojet, and high-latitude regions where the most dynamic phenomena occur due to magnetic field lines coupling to the magnetosphere and the solar wind. The spectra of plasma fluctuations in the low-latitude F-layer usually exhibit a power law with a steeper slope at high frequencies [1]. Until recently, there was no clear evidence of the corresponding double slope spectra for plasma fluctuations in the high latitude ionospheric F-layer, and this difference was not well understood. We report the first direct observations of the double slope power spectra for plasma irregularities in the F-layer of the polar ionosphere [2]. The ICI-2 sounding rocket, which intersected enhanced plasma density regions with decameter scale irregularities in the cusp region, measured the electron density with unprecedented high resolution. This allowed for a detailed study of the plasma irregularities down to kinetic scales. Spectral analysis reveals double slope power spectra for regions of enhanced fluctuations associated mainly with density gradients, with the steepening of the spectra occurring close to the oxygen gyro-frequency. The double slope spectra are further supported by the results from the ICI-3 sounding rocket. Double slope spectra were not resolved in previous works presumably due to limited resolution of instruments. The study is a part of the 4DSpace initiative for integrated studies of the ionospheric plasma turbulence with multi-point, multi-scale in-situ studies by sounding rockets and satellites, and numerical and analytical models. A brief overview of the 4DSpace initiative is given. [1] M.C. Kelley, The Earth’s Ionosphere Plasma Physics and Electrodynamics (Elsevier, Amsterdam 2009). [2] A. Spicher, W. J. Miloch, and J. I. Moen, Geophys. Res. Lett. 40, (in press, accepted 13.02.2014).

  10. Day-to-day variability of the E layer Luke Moore,1

    E-print Network

    Mendillo, Michael

    in the E layer, a one-dimensional time-dependent photochemical model of the Earth's upper atmosphere of the E layer, J. Geophys. Res., 111, A06307, doi:10.1029/2005JA011448. 1. Introduction [2] The Earth of the Earth's primary photochemical ionospheric layer in detail is beneficial to the study of other

  11. METEORIC PLASMA LAYERS ON VENUS AND MARS WITHERS PATM 2012 PAGE 1 OF 33

    E-print Network

    Withers, Paul

    METEORIC PLASMA LAYERS ON VENUS AND MARS WITHERS ± PATM 2012 ± PAGE 1 OF 33 Table of Contents Cover meteoroids do to ionospheres 2 2 ± Outline of proposed investigation 4 3 ± Available observations of meteoric layers 4 4 ± Available numerical model of meteoric layers 5 5 ± Task A: Comparison of basic observed

  12. Radio Tomography of Ionospheric Structures (probably) due to Underground-Surface-Atmosphere-Ionosphere Coupling

    NASA Astrophysics Data System (ADS)

    Kunitsyn, V.; Nesterov, I.; Andreeva, E.; Rekenthaler, D. A.

    2012-12-01

    Ionospheric radio-tomography (RT) utilizes radio signals transmitted from the global navigational satellite systems (GNSS), including low-orbiting (LO) navigational systems such as Transit, Tsikada, etc., and high-orbiting (HO) navigational systems such as GPS, GLONASS, Galileo, Beidou, etc. The signals that are transmitted from the LO navigational satellites and recorded by ground receiving chains can be inverted for almost instantaneous (5-8 min) 2D snapshots of electron density. The data from the networks of ground receivers that record the signals of the HO satellites are suitable for implementing high-orbital RT (HORT), i.e. reconstructing the 4D distributions of the ionospheric electron density (one 3D image every 20-30 min). In the regions densely covered by the GNSS receivers, it is currently possible to get a time step of 2-4 min. The LORT and HORT approaches have a common methodical basis: in both these techniques, the integrals of electron density along the ray between the satellite and the receiver are measured, and then the tomographic procedures are applied to reconstruct the distributions of electron density. We present several examples of the experiments on the ionospheric RT, which are related to the Underground-Surface-Atmosphere-Ionosphere (USAI) coupling. In particular, we demonstrate examples of RT images of the ionosphere after industrial explosions, rocket launches, and modification of the ionosphere by high-power radio waves. We also show RT cross sections reflecting ionospheric disturbances caused by the earthquakes (EQ) and tsunami waves. In these cases, there is an evident cause-and-effect relationship. The perturbations are transferred between the geospheres predominantly by acoustic gravity waves (AGW), whose amplitudes increase with increasing height. As far as EQ are concerned, the cause of the USAI coupling mechanism is not obvious. It is clear, however, that the regular RT studies can promote the solution of this challenging problem. The single-point measurements (by ionosondes or by isolated receivers) are not amenable to unambiguous interpretation; based on these data, it is impossible to distinguish the contribution of USAI coupling from the ionospheric effects induced by the "ordinary" impacts (the Sun, the solar wind, geomagnetic perturbations, galactic cosmic rays, etc.). In order to localize sources of the ionospheric disturbances, the geophysicist needs information on the spatial structure and dynamics of the ionospheric perturbations. This information (2D-4D RT images) is optimally provided by RT methods. We present examples of the ionospheric disturbances caused by EQs as well as the ionospheric precursors of these EQs in the form of specific ionospheric irregularities: AGW- and soliton-like wave disturbances, which we identified using RT methods. Based on the results of the RT studies in the Alaska and Taiwan regions, we have detected several dozen AGW-related precursors of EQs. These data allow us to attempt to locate the source of these perturbations. We discuss the possibilities and prospects of further research aimed at identifying and analyzing precursors of EQs and establishing the mechanisms of USAI coupling. We are grateful to Northwest Research Associates, Inc., and Dr. L.-C.Tsai for providing raw RT data for Alaska and Taiwan.

  13. Batch-mode vs Online-mode Supervised Learning Motivations for Artificial Neural Networks

    E-print Network

    Wehenkel, Louis

    Batch-mode vs Online-mode Supervised Learning Motivations for Artificial Neural Networks Linear ANN-mode vs Online-mode Supervised Learning Motivations for Artificial Neural Networks Linear ANN Models for Artificial Neural Networks Linear ANN Models Single neuron models Single layer models Nonlinear ANN Models

  14. Ionospheric anomalies observed over South Korea before Tohoku earthquake

    NASA Astrophysics Data System (ADS)

    Choi, B.; Cho, S.; Roh, K.; Lee, W.

    2011-12-01

    We investigated the ionospheric anomalies before Tohoku earthquake that occurred near the northeast coast of Honshu, Japan on 11 March 2011. Ionospheric anomalies by the total electron content (TEC) derived from a ground-based GPS network in Korean Peninsula were detected during the daytime within a few days before earthquake. It is found that ionospheric TEC anomalies appear on 5, 8 and 11 March. In particular, ionospheric disturbances on 8 March represented a remarkable increase in TEC. GPS TEC associated with Tohoku earthquake had a positive property with an enhancement of about 20 TECU. This positive correlation is revealed in local and global TEC variations simultaneously. To investigate the pre-earthquake ionospheric anomalies, the space weather conditions such as solar activity index (F10.7) and geomagnetic activity indices (the Kp and Dst indices) are taken into account. We have also created two-dimensional TEC maps to show the spatial variations of ionospheric anomalies before earthquake.

  15. From Artificial Evolution to Artificial Life 

    E-print Network

    Taylor, Timothy J

    This work addresses the question: What are the basic design considerations for creating a synthetic model of the evolution of living systems (i.e. an `artificial life' system)? It can also be viewed as an attempt to ...

  16. Ionospheric Delay Compensation Using a Scale Factor Based on an Altitude of a Receiver

    NASA Technical Reports Server (NTRS)

    Zhao, Hui (Inventor); Savoy, John (Inventor)

    2014-01-01

    In one embodiment, a method for ionospheric delay compensation is provided. The method includes determining an ionospheric delay based on a signal having propagated from the navigation satellite to a location below the ionosphere. A scale factor can be applied to the ionospheric delay, wherein the scale factor corresponds to a ratio of an ionospheric delay in the vertical direction based on an altitude of the satellite navigation system receiver. Compensation can be applied based on the ionospheric delay.

  17. Influence of the ionosphere on radio astronomical signals according to GPS sounding and ionospheric modeling

    NASA Astrophysics Data System (ADS)

    Afraimovich, E. L.; Smolkov, G. Ya.; Tatarinov, P. V.; Yasukevich, Yu. V.

    2008-02-01

    VHF signals are widely used for observations of the Sun and pulsars. Nowadays huge VHF radio astronomical arrays (LOFAR, 30-240 MHz; MIRA, 80-300 MHz) are being constructed to record pulsar radiation at maximum possible distance. Registration of VHF solar radio emission is very important along with other methods of monitoring of coronal mass ejections. At the interpretation of the data it is necessary to take into account possible distortions of these signals at the Earth ionosphere. We have developed a method and software for calculation of the ionosphere measure of rotation (RM), and the measure of dispersion (DM). We used the ionosphere model IRI-2001, magnetic field model IGRF-10 and values of ionosphere total electron content as deduced from GPS measurements. The obtained values of the ionosphere DM and RM were recalculated into characteristics of phase delay, Faraday amplitude modulation and polarization changes. In the paper we made calculations for different levels of geomagnetic activity and for different angular position of radio sources as well.

  18. Numerical validations of neural-network-based ionospheric tomography for disturbed ionospheric conditions and sparse data

    NASA Astrophysics Data System (ADS)

    Hirooka, S.; Hattori, K.; Takeda, T.

    2011-10-01

    Three-dimensional ionospheric tomography is effective for investigations of the dynamics of ionospheric phenomena. However, it is an ill-posed problem in the context of sparse data, and accurate electron density reconstruction is difficult. The Residual Minimization Training Neural Network (RMTNN) tomographic approach, a multilayer neural network trained by minimizing an objective function, allows reconstruction of sparse data. In this study, we validate the reconstruction performance of RMTNN using numerical simulations based on both sufficiently sampled and sparse data. First, we use a simple plasma-bubble model representing the disturbed ionosphere and evaluate the reconstruction performance based on 40 GPS receivers in Japan. We subsequently apply our approach to a sparse data set obtained from 24 receivers in Indonesia. The reconstructed images from the disturbed and sparse data are consistent with the model data, except below 200 km altitude. To improve this performance and limit any discrepancies, we used information on the electron density in the lower ionosphere. The results suggest the restricted RMTNN-tomography-assisted approach is very promising for investigations of ionospheric electron density distributions, including studies of irregular structures in different regions. In particular, RMTNN constrained by low-Earth-orbit satellite data is effective in improving the reconstruction accuracy.

  19. Ground observations of magnetospheric boundary layer phenomena

    SciTech Connect

    McHenry, M.A.; Clauer, C.R. (Stanford Univ., CA (USA)); Friis-Christensen, E. (Danish Meteorological Inst., Copenhagen (Denmark)); Newell, P.T. (Johns Hopkins Univ., Laurel, MD (USA)); Kelly, J.D. (SRI International, Menlo Park, CA (USA))

    1990-09-01

    Several classes of traveling vortices in the dayside ionospheric convection have been detected and tracked using the Greenland magnetometer chain (Friis-Christensen et al., 1988, McHenry et al., 1989). One class observed during quiet times consists of a continuous series of vortices moving generally anti-sunward for several hours at a time. The vortices strength is seen to be approximately steady and neighboring vortices rotate in opposite directions. Sondrestrom radar observations show that the vortices are located at the ionospheric convection reversal boundary. Low altitude DMSP observations indicate the vortices are on field lines which map to the inner edge of the low latitude boundary layer. Because the vortices are conjugate to the boundary layer, repeat in a regular fashion and travel antisunward, the authors argue that this class of vortices is caused by the Kelvin-Helmholtz instability of the inner edge of the magnetospheric boundary layer.

  20. Ionospheric disturbances and Coronal Mass Ejection: possible connection

    Microsoft Academic Search

    V. M. Fridman; N. Krupenya; E. Mityakova; A. Rakhlin; O. Sheiner; F. Vybornov

    2000-01-01

    Detailed analysis of appearance and development of Coronal Mass Ejection (CME) and middle latitude ionosphere was carried out. Ionospheric data in the period of 1980 and 1989 has been obtained at Zimenki test station (near Nizhny Novgorod, phi = 56o and lambda = 44o). Diurnal variations of critical frequency f0F2 were analyzed. The appearance of moving ionospheric disturbances and F-spread