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Sample records for artificial ionospheric layers

  1. Artificial Ionospheric Layers during Pump Frequency Stepping Near the 4th Gyroharmonic at HAARP

    NASA Astrophysics Data System (ADS)

    Sergeev, E.; Grach, S.; Shindin, A.; Mishin, E.; Bernhardt, P.; Briczinski, S.; Isham, B.; Broughton, M.; LaBelle, J.; Watkins, B.

    2013-02-01

    We report on artificial descending plasma layers created in the ionosphere F region by high-power high-frequency (HF) radio waves from High-frequency Active Auroral Research Program at frequencies f0 near the fourth electron gyroharmonic 4fce. The data come from concurrent measurements of the secondary escaping radiation from the HF-pumped ionosphere, also known as stimulated electromagnetic emission, reflected probing signals at f0, and plasma line radar echoes. The artificial layers appeared only for injections along the magnetic field and f0>4fce at the nominal HF interaction altitude in the background ionosphere. Their average downward speed ˜0.5km/s holds until the terminal altitude where the local fourth gyroharmonic matches f0. The total descent increases with the nominal offset f0-4fce.

  2. Artificial ionospheric layers during pump frequency stepping near the 4th gyroharmonic at HAARP.

    PubMed

    Sergeev, E; Grach, S; Shindin, A; Mishin, E; Bernhardt, P; Briczinski, S; Isham, B; Broughton, M; LaBelle, J; Watkins, B

    2013-02-01

    We report on artificial descending plasma layers created in the ionosphere F region by high-power high-frequency (HF) radio waves from High-frequency Active Auroral Research Program at frequencies f(0) near the fourth electron gyroharmonic 4f(ce). The data come from concurrent measurements of the secondary escaping radiation from the HF-pumped ionosphere, also known as stimulated electromagnetic emission, reflected probing signals at f(0), and plasma line radar echoes. The artificial layers appeared only for injections along the magnetic field and f(0)>4f(ce) at the nominal HF interaction altitude in the background ionosphere. Their average downward speed ~0.5 km/s holds until the terminal altitude where the local fourth gyroharmonic matches f(0). The total descent increases with the nominal offset f(0)-4f(ce). PMID:23432261

  3. Numerical modeling of artificial ionospheric layers driven by high-power HF-heating

    NASA Astrophysics Data System (ADS)

    Eliasson, Bengt; Shao, Xi; Milikh, G.; Mishin, E. V.; Papadopoulos, K.

    2012-10-01

    We present a multi-scale dynamic model for the creation and propagation of artificial plasma layers in the ionosphere observed during high-power high frequency (HF) heating experiments at HAARP. Ordinary mode electromagnetic waves excite parametric instabilities and strong Langmuir turbulence near the reflection point. The coupling between high frequency electromagnetic and Langmuir waves and low-frequency ion acoustic waves is numerically simulated using a generalized Zakharov equation. The acceleration of plasma electrons is described by a Fokker-Planck model with an effective diffusion coefficient constructed using the simulated Langmuir wave spectrum. The propagation of the accelerated electrons through the non-uniform ionosphere is simulated by a kinetic model accounting for elastic and inelastic collisions with neutrals. The resulting ionization of neutral gas increases the plasma density below the acceleration region, so that the pump wave is reflected at a lower altitude. This leads to a new turbulent layer at the lower altitude, resulting in a descending artificial ionized layer that moves from near 230 km to about 150 km. The modeling results reproduce artificial ionospheric layers produced for similar sets of parameters during the high-power HF experiments at HAARP.

  4. Numerical modeling of artificial ionospheric layers driven by high-power HF-heating

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

    We present a multi-scale dynamic model for the creation and propagation of artificial plasma layers in the ionosphere observed during high-power high frequency heating experiments at HAARP. Ordinary mode electromagnetic waves excite parametric instabilities and strong Langmuir turbulence near the reflection point. The coupling between high frequency electromagnetic and Langmuir waves and low-frequency ion acoustic waves is numerically simulated using a generalized Zakharov equation. The acceleration of plasma electrons is described by a Fokker-Planck model with an effective diffusion coefficient constructed using the simulated Langmuir wave spectrum. The propagation of the accelerated electrons through the non-uniform ionosphere is simulated by a kinetic model accounting for elastic and inelastic collisions with neutrals. The resulting ionization of neutral gas increases the plasma density below the acceleration region, so that the pump wave is reflected at a lower altitude. This leads to a new turbulent layer at the lower altitude, resulting in a descending artificial ionized layer, that moves from near 230 km to about 150 km. At the terminal altitude, ionization, recombination, and ambipolar diffusion reach equilibrium, so the descent stops. The modeling results reproduce artificial ionospheric layers produced for similar sets of parameters during the high-power HF experiments at HAARP.

  5. Numerical modeling of artificial ionospheric layers driven by high-power HF heating

    NASA Astrophysics Data System (ADS)

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

    2012-10-01

    We present a multi-scale dynamic model for the creation and propagation of artificial plasma layers in the ionosphere observed during high-power high-frequency (HF) heating experiments at HAARP. Ordinary (O) mode electromagnetic (EM) waves excite parametric instabilities and strong Langmuir turbulence (SLT) near the reflection point. The coupling between high-frequency electromagnetic and Langmuir waves and low-frequency ion acoustic waves is numerically simulated using a generalized Zakharov equation. The acceleration of plasma electrons is described by a Fokker-Planck model with an effective diffusion coefficient constructed using the simulated Langmuir wave spectrum. The propagation of the accelerated electrons through the non-uniform ionosphere is simulated by a kinetic model accounting for elastic and inelastic collisions with neutrals. The resulting ionization of neutral gas increases the plasma density below the acceleration region, so that the pump wave is reflected at a lower altitude. This leads to a new turbulent layer at the lower altitude, resulting in a descending artificial ionized layer (DAIL), that moves from near 230 km to about 150 km. At the terminal altitude, ionization, recombination, and ambipolar diffusion reach equilibrium, so the descent stops. The modeling results reproduce artificial ionospheric layers produced for similar sets of parameters during the high-power HF experiments at HAARP.

  6. Geometric Aspects of Artificial Ionospheric Layers Driven by High-Power HF-Heating

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

    We have generalized earlier developed multi-scale dynamic model for the creation and propagation of artificial plasma layers in the ionosphere [Eliasson et al, 2012] by including two dimensional effects in the horizontal direction. Such layers were observed during high-power high frequency HF heating experiments at HAARP [Pedersen et al., 2010]. We have numerically investigated the importance of different angles of incidence of ordinary mode waves on the Langmuir turbulence and the resulting electron acceleration that leads to the formation of artificial ionospheric layers. It was shown that the most efficient electron acceleration and subsequent ionization is obtained at angles between magnetic zenith and the vertical, where strong Langmuir turbulence dominates over weak turbulence. A role played by the heating wave propagation near caustics was also investigated. Eliasson, B. et al. (2012), J. Geophys. Res. 117, A10321, doi:10.1029/2012JA018105. Pedersen, T., et al. (2010), Geophys. Res. Lett., 37, L02106, doi:10.1029/2009GL041895.

  7. Artificial ionosphere layers for pumping-wave frequencies near the fourth electron gyroharmonic in experiments at the HAARP facility

    NASA Astrophysics Data System (ADS)

    Grach, S. M.; Sergeev, E. N.; Shindin, A. V.; Mishin, E. V.; Watkins, B.

    2014-02-01

    In this paper we consider the action (in the magnetic-zenith direction) of powerful high frequency (HF) radiation of ordinary polarization on the ionosphere F region. We deal with frequencies f 0 > 4 f ce ( f ce is the electron cyclotron frequency) of 1.7 GW equivalent radiated power. This action results in the appearance in the ionosphere of an artificial ionization layer. The layer descends with respect to the basic (unperturbed) layer at a rate of ˜500 m s-1 down to the altitude, where f 0 ? 4 f ce .

  8. 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.

    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.

  9. Artificial ionospheric mirrors for radar applications

    NASA Astrophysics Data System (ADS)

    Short, Robert D.; Wallace, Tom; Stewart, Clayton V.; Lallement, Pierre; Koert, Peter

    1990-10-01

    Recognition of performance limitations associated with traditional skywave over-the-horizon (OTH) HF radars has led a number of investigators to propose the creation of an Artificial Ionospheric Mirror (AIM) in the upper atmosphere, in order to reflect ground-based radar signals for OTH surveillance. The AIM is produced by beaming sufficient electromagnetic power to the lower ionosphere (around 70 km) to enhance the in situ ionization level to 10(exp 7) to 10(exp 8) electrons/cu cm, thereby providing an ionized layer capable of reflecting radar frequencies of 5 to 90 MHz. A baseline AIM system concept and an associated performance evaluation are presented, based upon the relevant ionization and propagation physics and in the context of air surveillance for the cruise missile threat. Results of the subject indicate that a system using this concept would both complement and enhance the performance of the existing skywave OTH radars.

  10. Meteoric layers in planetary ionospheres

    E-print Network

    Withers, Paul

    ;Sporadic E layer at Earth Sporadic E = Dense layers of plasma at E-region altitudes that aren't related) #12;Making narrow layers on Earth Mechanism for producing narrow layers of metal ion plasma by windMeteoric layers in planetary ionospheres Paul Withers Boston University Abstract SA11B-1919 withers

  11. Experimentally investigate ionospheric depletion chemicals in artificially created ionosphere

    SciTech Connect

    Liu Yu; Cao Jinxiang; Wang Jian; Zheng Zhe; Xu Liang; Du Yinchang

    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.

  12. Artificially created holes in the ionosphere

    NASA Technical Reports Server (NTRS)

    Mendillo, M.; Forbes, J. M.

    1978-01-01

    The artificial creation of ionospheric holes by the release of highly reactive molecules into the F region is investigated. Through ion-atom interchange or charge transfer reactions, H2 or H2O reacts with O(+) to form OH(+) or H2O(+), respectively, which subsequently dissociatively recombines with electrons at a very rapid rate. The diffusion of H2 is also modified by chemical loss to the ambient atomic oxygen atmosphere. The limited spatial and temporal extent of the hole-making process allows several approximations to be made which permit three-dimensional analytic solutions of the continuity equations for the released particles, the O(+) and e(-) densities, and the intermediary molecular ions. A versatile formalism is developed whereby the hole-making capability of virtually any spatial-temporal configuration of released particles can be determined by convolving a set of destruction operators which can be viewed as Green's functions for the problem. As a specific application of the techniques developed, the modification of a winter nighttime ionosphere is described by simulating the release of 1000 kg of water vapor near a height of 300 km.

  13. HF Radio Wave Production of Artificial Ionospheres

    NASA Astrophysics Data System (ADS)

    Carlson, Herbert

    In 1993 it was predicted that artificial ionospheres would be produced by high power HF radio waves, once HF transmitters approached a GWatt ERP. When that threshold was very recently achieved, such production was indeed detected and published at two high latitude high power HF facilities. Here we review: the first-principles logic behind that prediction, which aspects of such production are critically dependent on magnetic latitude, and which aspects of such production depend only on physical parameters independent of latitude. These distinctions follow directly from decomposition of the problem of ionization production into its components of: radio-wave propagation, wave-particle interactions, electron transport, and quantitative elastic/inelastic cross-sections. We outline this analysis to show that, within the context of early observations, the production of ionization is inevitable, and only a question of competing instability thresholds, and scale of ionization production. This illustrates complimentary aeronomy and plasma physics to advance understanding of both.

  14. 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.

  15. 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

  16. Formation of artificial plasma disturbances in the lower ionosphere

    NASA Astrophysics Data System (ADS)

    Bakhmet'eva, N. V.; Frolov, V. L.; Vyakhirev, V. D.; Kalinina, E. E.; Bolotin, I. A.; Akchurin, A. D.; Zykov, E. Yu.

    2012-06-01

    We present the results of experiments on sounding the disturbed ionospheric region produced by the high-power RF radiation of the "Sura" heating facility, which were performed simultaneously at two observation points. One point is located on the territory of the heating facility the other, and the other, at the observatory of Kazan State University (the "Observatory" point) in 170 km to the East from the facility. The experiments were aimed at studying the mechanism of formation of artificial disturbances in the lower ionosphere in the case of reflection of a high-power wave in the F region and determining the parameters of the signals of backscattering from artificial electron density irregularities which are formed as a result of ionospheric perturbations. The ionosphere was modified by a high-power RF O-mode wave, which was emitted by the transmitters of the "Sura" facility, in sessions several seconds or minutes long. The disturbed region was sounded using the vertical-sounding technique at the "Vasil'sursk" laboratory by the partial-reflection facility at a frequency of 2.95 MHz, and by the modified ionospheric station "Tsiklon" at ten frequencies ranged from 2 to 6.5 MHz at the "Observatory" point. At the same time, vertical-sounding ionograms were recorded in the usual regime. At the reception points, simultaneous changes in the amplitudes of the vertical-sounding signals and the aspect backscattering signals were recorded. These records correlate with the periods of operation of the heating facility. The characteristics and dynamics of the signals are discussed.

  17. Electrostatic and Electromagnetic Fluctuation in the Boundary Layer of Laboratory-Created Ionospheric Depletion

    NASA Astrophysics Data System (ADS)

    Liu, Y.; Cao, J.; Xu, L.; Zhang, X.

    2014-12-01

    Ionospheric depletions have been frequently artificially-created in the past decades from releasing attachment chemicals[Mendillo and Forbes, 1978]. In the early phase of the ionospheric depletion, a boundary layer of width of electric scale length emerged and separated the ionosphere into two regions, the ambient plasmas and the negative ion plasmas. In the localized boundary layer, there exists sharp electron gradients and strong sheared flows, which have a pronounced effect on the nonlinear evolution of many plasma systems. Therefore, it reflects essential research significance to study the boundary layer processes in an ionospheric depletion. However, until now, few experiments have specially designed and conducted to characterize and study those boundary layer processes[ Liu et al., 2014]. In the work, We studied the evolution of boundary layer in laboratory-created ionospheric depletions. These experiments were performed in plasma conditions with key dimensionless parameters scaled to those of the ionosphere. These electrons depletions were produced by releasing attachment chemicals into pre-existing plasmas. These plasmas were separated into two regions by a boundary layer of width of electric scale length. In the modeling ionospheric hole, localized boundary layer, those fluctuations of the electron density , floating potential, and magnetic field were investigated varying with the plasma pressure and the partial pressure of released chemicals. These fluctuations were recorded by Langmuir probes and magnetic probes. We analyzed the fluctuation using digital spectral analysis techniques, and electrostatic and electromagnetic fluctuations in the lower hybrid range were observed. These modes may be electron-ion hybrid(EIH) and whistler mode, respectively. The possibility will be discussed in more detail during the presentation. Reference Liu, Y., J. Cao, L. Xu, X. Zhang, P. Wang, J. Wang, Y. Du, and Z. Zheng (2014a), Coherent structure generated in the boundary layer of a laboratory-created ionospheric depletion, Geophysical Research Letters, 41(5), 1413-1419, doi:10.1002/2014GL059211. Mendillo, M., and J. Forbes (1978), Artificially created holes in the ionosphere, Journalof Geophysical Research, 83 (A1), 151-163.

  18. Lightning-induced intensification of the ionospheric sporadic E layer.

    PubMed

    Davis, C J; Johnson, C G

    2005-06-01

    A connection between thunderstorms and the ionosphere has been hypothesized since the mid-1920s. Several mechanisms have been proposed to explain this connection, and evidence from modelling as well as various types of measurements demonstrate that lightning can interact with the lower ionosphere. It has been proposed, on the basis of a few observed events, that the ionospheric 'sporadic E' layer--transient, localized patches of relatively high electron density in the mid-ionosphere E layer, which significantly affect radio-wave propagation--can be modulated by thunderstorms, but a more formal statistical analysis is still needed. Here we identify a statistically significant intensification and descent in altitude of the mid-latitude sporadic E layer directly above thunderstorms. Because no ionospheric response to low-pressure systems without lightning is detected, we conclude that this localized intensification of the sporadic E layer can be attributed to lightning. We suggest that the co-location of lightning and ionospheric enhancement can be explained by either vertically propagating gravity waves that transfer energy from the site of lightning into the ionosphere, or vertical electrical discharge, or by a combination of these two mechanisms. PMID:15944700

  19. System concept and analysis of an Artificial Ionospheric Mirror (AIM) radar

    NASA Astrophysics Data System (ADS)

    Short, Robert D.; Stewart, Clayton V.; Wallace, Tom; Lallement, Pierre; Koert, Peter

    1990-08-01

    Recognition of performance limitations associated with traditional skywave over-the-horizon (OTH) high frequency (HF) radars has led a number of investigators to propose the creation of an Artificial Ionospheric Mirror (AIM) in the upper atmosphere, in order to reflect ground-based radar signals for OTH surveillance. The AIM is produced by beaming sufficient electromagnetic power to the lower ionosphere (around 70 km) to enhance the in situ ionization level to 10(exp 7) to 10(exp 8) electrons/cu cm, thereby providing an ionized layer capable of reflecting radar frequencies of 30 to 90 MHz. This paper presents a baseline AIM system concept and an associated performance evaluation, based upon the relevant ionization and propagation physics and in the context of air surveillance for the cruise missile threat. Results of the subject study indicate that a system using this concept would both complement and enhance the performance of the existing skywave OTH radars.

  20. Model of Optical Emissions and Artificial Ionization Produced by Ionospheric HF-Heating

    NASA Astrophysics Data System (ADS)

    Milikh, G. M.; Elliason, B.; Shao, X.; Sharma, S.; Chang, C.; Mishin, E. V.; Papadopoulos, K.

    2011-12-01

    Using the upgraded HAARP transmitter capabilities Pedersen et al., [2010] demonstrated for the first time the formation and control of artificial ionospheric layers by resonant F-region heating. The paper presents a model of the underlying physics based on preheating the electrons at the upper hybrid resonance followed by acceleration at the plasma resonant layer by the ensuing Langmuir turbulence. A number of component models are integrated in a novel numerical scheme to address the issue. A multi-grid approach based on propagation and the generalized Zakharov equations is used to study the formation of the Langmuir turbulence at the F-region peak. Super-thermal formation of electron tails is modeled by using a test particle approach as well as the solution of the diffusion equation in velocity space. A transport model including elastic and inelastic processes is used to study ionization and optical emissions. The model addresses several issues related to Artificial Plasma Layers, including thresholds for artificial ionization structure and the speed of the descending ionization front. The model results are compared with available observations. The work was supported by DARPA via a subcontract with BAE Systems, and by the ONR MURI Grant. Pedersen T., et al. Geophys. Res. Lett., 36, doi:10.1029/2009GL040047, 2009.

  1. A sporadic third layer in the ionosphere of Mars.

    PubMed

    Pätzold, M; Tellmann, S; Häusler, B; Hinson, D; Schaa, R; Tyler, G L

    2005-11-01

    The daytime martian ionosphere has been observed as a two-layer structure with electron densities that peak at altitudes between about 110 and 130 kilometers. The Mars Express Orbiter Radio Science Experiment on the European Mars Express spacecraft observed, in 10 out of 120 electron density profiles, a third ionospheric layer at altitude ranges of 65 to 110 kilometers, where electron densities, on average, peaked at 0.8 x 10(10) per cubic meter. Such a layer has been predicted to be permanent and continuous. Its origin has been attributed to ablation of meteors and charge exchange of magnesium and iron. Our observations imply that this layer is present sporadically and locally. PMID:16272118

  2. 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

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

    E-print Network

    Gurnett, Donald A.

    Transient 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 levels of the ionosphere. Citation: Kopf, A. J., D. A. Gurnett, D. D. Morgan, and D. L. Kirchner (2008

  4. Quasi-periodic variations in the Doppler shift of HF signals scattered by artificial ionospheric turbulence

    SciTech Connect

    Belenov, A.F.; Ponomarenko, P.V.; Sinitsyn, V.G.; Yampol`skii, Yu.M.

    1994-06-01

    The results of an experimental study of quasi-periodic variations of the Doppler shift (DS) of decimeter-wave signals scattered by artificial ionospheric turbulence are presented. It is suggested that ionospheric MHD waves of natural origin are a possible cause of such variations. The amplitude of the magnetic component of such waves that leads to observable values of DS variations is estimated to be 1{gamma}.

  5. Long-term Changes in Ionospheric F-layer Characteristics

    NASA Astrophysics Data System (ADS)

    Stamper, R.; Davis, C. J.; Blake, R. M.; Rishbeth, H.

    2006-12-01

    A study of ionospheric sounding data from Slough and Chilton, UK from 1935 to 2005, and from Stanley in the Falkland Islands between 1945 and 2005, revealed long-term and apparently systematic changes in the characteristics of the F1 and F2 layers. Specifically, the visibility of the critical frequency of the ionospheric F1 layer has changed with time, with the trends anti-correlated between the two hemispheres. The relative strengths of the semi-annual and annual variations in the critical frequency of the F2 layer also exhibit strong trends with similar hemispheric anti-correlation. Both effects are attributed to changes in composition driven by the variability in geomagnetic activity which controls the average latitudinal extent of the auroral ovals. The extent of the auroral ovals modulates the latitudinal extent of convection cells transporting molecular-rich air into the upper thermosphere. The anti-correlation between stations is harder to explain and may be due to the relative sensitivity of the ionosphere to changes in the position of the geomagnetic pole at each of the stations.

  6. 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.

    2015-10-01

    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.

  7. E-layer ionospheric disturbances following the Coalinga earthquake

    SciTech Connect

    Fitzgerald, T.J.; Wolcott, J.H.

    1985-11-01

    A bistatic HF Doppler network in California recorded ionospheric disturbances after the Coalinga, California, earthquake of May 2, 1983. The ionospheric disturbances appear to be associated with acoustic waves launched vertically into the atmosphere from the ground motion caused by radially propagating surface seismic (Rayleigh) waves. The ionospheric disturbances were detected by variations in the frequency of the received transmissions (Doppler shifts); such disturbances have been observed in association with a number of previous earthquakes. The Doppler shifts were caused by phase path changes induced by the motion of the neutral atmosphere at the reflection height of the radio wave (200 km). We have also detected changes in the spectrum of the received transmissions following the Coalinga earthquake at the time of the passage of the acoustic waves through the E-layer. We interpret these spectral changes as an indication of specular reflection of the radio waves from index of refraction gradients induced by the acoustic waves, which have undergone significant nonlinear steepening during their propagation to 100 km. Since the acoustic waves were propagating upwards, the relections had negative Doppler shifts.

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

    SciTech Connect

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

    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.

  9. Ionospheric F3 layer: Implications for the IRI model

    NASA Astrophysics Data System (ADS)

    Batista, I. S.; Abdu, M. A.; da Silva, A. M.; Souza, J. R.

    Recent studies have revealed the existence of an additional layer in the topside equatorial ionosphere, which was named the F3 layer. Statistical studies using Fortaleza ionograms show that the F3 layer is present on 75% of the days during December solstices (local summer) of low solar activity period, becoming a very common feature on that location. During those events, the F peak density becomes smaller than its usual value and the peak height can be much higher than the usual hmax value. Vertical profiles obtained from ionograms, using true height inversion methods, show the existence of a very broad F layer peak, with a very slow height gradient. In this work we compare the observed F layer critical frequency and peak height with their IRI predictions (calculated using the URSI and CCIR coefficients). It was found that the IRI model overestimates the observed frequency by up to 3 MHz and underestimates the peak height by up to 100 km, when the F3 layer phenomena is present. The vertical distribution of the F region electron density calculated by IRI also differs significantly from the observations during periods of F3 layer occurrence. It is suggested that this phenomenon could account for some of the discrepancies between IRI predictions and observations, at least for daytime low-latitude locations.

  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. 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.

  12. HF Propagation Effects Caused by an Artificial Plasma Cloud in the Ionosphere

    NASA Astrophysics Data System (ADS)

    Joshi, D. R.; Groves, K. M.; McNeil, W. J.; Caton, R. G.; Parris, R. T.; Pedersen, T. R.; Cannon, P. S.; Angling, M. J.; Jackson-Booth, N. K.

    2014-12-01

    In a campaign carried out by the NASA sounding rocket team, the Air Force Research Laboratory (AFRL) launched two sounding rockets in the Kwajalein Atoll, Marshall Islands, in May 2013 known as the Metal Oxide Space Cloud (MOSC) experiment to study the interactions of artificial ionization and the background plasma and measure the effects on high frequency (HF) radio wave propagation. The rockets released samarium metal vapor in the lower F-region of the ionosphere that ionized forming a plasma cloud that persisted for tens of minutes to hours in the post-sunset period. Data from the experiments has been analyzed to understand the impacts of the artificial ionization on HF radio wave propagation. Swept frequency HF links transiting the artificial ionization region were employed to produce oblique ionograms that clearly showed the effects of the samarium cloud. Ray tracing has been used to successfully model the effects of the ionized cloud. Comparisons between observations and modeled results will be presented, including model output using the International Reference Ionosphere (IRI), the Parameterized Ionospheric Model (PIM) and PIM constrained by electron density profiles measured with the ALTAIR radar at Kwajalein. Observations and modeling confirm that the cloud acted as a divergent lens refracting energy away from direct propagation paths and scattering energy at large angles relative to the initial propagation direction. The results confirm that even small amounts of ionized material injected in the upper atmosphere can result in significant changes to the natural propagation environment.

  13. Meteoric ion layers in the ionospheres of venus and mars: Early observations and consideration of the role of meteor showers

    E-print Network

    Withers, Paul

    have minimal observed effect on meteoric layers in Earth's ionosphere. In order to aid progress towardsMeteoric ion layers in the ionospheres of venus and mars: Early observations and consideration June 2013 Available online 26 June 2013 Abstract Layers of metal ions produced by meteoroid ablation

  14. 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.

  15. Ionospheric correction for spaceborne single-frequency GPS based on single layer model

    NASA Astrophysics Data System (ADS)

    Yang, Xia; Li, Jiancheng; Zhang, Shoujian

    2014-06-01

    A modified ionospheric correction method and the corresponding approximate algorithm for spaceborne single-frequency Global Positioning System (GPS) users are proposed in this study. Single Layer Model (SLM) mapping function for spaceborne GPS was analyzed. SLM mapping functions at different altitudes were calculated. Ionospheric Pierce Point (IPP) trajectories of the dlft station (An IGS station located at the longitude of 4°23'15.22''E and the latitude of 51°59'9.63''N, in the TU Delft University, The Netherlands.) and the GRACE satellite were computed with the corresponding single layer height of 350 and 500 km, respectively. The Klobuchar model was used to compute ionospheric delays for the dlft station, and modified Klobuchar model, together with scale factors, was used to compute the fractional ionospheric corrections above the GRACE altitudes. Calculation results were validated using dual-frequency observations. The study shows that the single layer height needs to be changed from 350 to 500 km according to the altitude of GRACE. Approximate forms of Earth angle and slant factor developed for modified Klobuchar model are applicable to GRACE, with accuracy adequate to preserve the essential elements required to compute ionospheric delays. Results show that the Klobuchar model is effective for ground GPS, and the modified Klobuchar model corrects more than 80% on average of the ionospheric delays for spaceborne single-frequency GPS.

  16. Artificial ducts caused by HF heating of the ionosphere by HAARP

    NASA Astrophysics Data System (ADS)

    Vartanyan, A.; Milikh, G. M.; Mishin, E.; Parrot, M.; Galkin, I.; Reinisch, B.; Huba, J.; Joyce, G.; Papadopoulos, K.

    2012-10-01

    We report on satellite observations of plasma density enhancements (ducts) in the topside ionosphere during four HAARP/BRIOCHE campaigns during 2009-2010. Artificial ducts, caused by high-power HF radio wave injections from the HAARP transmitter toward the magnetic zenith, are detected by the DEMETER and DMSP satellites on a regular basis when there is a perceptible ionospheric F2 peak density. Overall, the plasma density enhancements detected between 0930 and 1230 LT varied from 3-13%, while those during ˜1730-2215 LT were typically 15-40%. We also used a modified SAMI2 model to study the artificial ducts' mechanism driven by HF electron heating in the bottomside F2 region. The heating builds up the plasma pressure, thus pushing plasma along the magnetic field. The simulation results performed for the input parameters similar to the conditions of the heating experiments are in fair agreement with the pertinent observations. The ducts seem to be produced most efficiently for heating frequencies quite close to the critical frequency foF2.

  17. 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 October 2008; accepted 29 October 2008; published 12 March 2009. [1] The Venus Express Radio Science (VeRa) experiment aboard Venus Express has detected, by means of radio occultation, distinct, low-lying layers

  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. The Mars Ionosphere: More than a Chapman Layer

    E-print Network

    Withers, Paul

    is same everywhere · 740 K at surface, slow winds, no storms, no rain · H2SO4 clouds at 50 km, where.uk/spat/research/space_magnetometer_laboratory/spacemissionpages/venusexpresshomepage/science · Ionosphere formed by EUV photoionization of CO2, but CO2 + + O -> O2 + + CO · O2 + is dominant at Chapman

  20. Why the Viking descent probes found only one ionospheric layer at Mars

    NASA Astrophysics Data System (ADS)

    Mayyasi, Majd; Mendillo, Michael

    2015-09-01

    Radio wave transmissions from satellites revealed that Mars had two relatively distinct layers of ionization: a maximum electron density near 130 km, and a secondary layer near 110 km. When the Viking descent probes—with their in situ observing capabilities—passed through the ionosphere, the peak electron density was found, with no indication of a secondary layer below. Here we use an ionospheric model to show that profiles of electron density versus height have shapes that favor the detection of two layers at local times near dawn and dusk (where many thousands of radio occultation observations have been made), but that the two layers essentially merge into one during midday hours (when Viking measurements were made). The profile shapes are attributed to ionizing geometry of solar photons and to chemical processes that affect the profile shapes in a way that favors secondary peak formation near sunrise and sunset.

  1. Application of Artificial Bee Colony algorithm in TEC seismo-ionospheric anomalies detection

    NASA Astrophysics Data System (ADS)

    Akhoondzadeh, M.

    2015-09-01

    In this study, the efficiency of Artificial Bee Colony (ABC) algorithm is investigated to detect the TEC (Total Electron Content) seismo-ionospheric anomalies around the time of some strong earthquakes including Chile (27 February 2010; 01 April 2014), Varzeghan (11 August 2012), Saravan (16 April 2013) and Papua New Guinea (29 March 2015). In comparison with other anomaly detection algorithms, ABC has a number of advantages which can be numerated as (1) detection of discord patterns in a large non linear data during a short time, (2) simplicity, (3) having less control parameters and (4) efficiently for solving multimodal and multidimensional optimization problems. Also the results of this study acknowledge the TEC time-series as a robust earthquake precursor.

  2. Remote sensing of ELF/VLF radiation induced in experiments on artificial modification of the ionosphere

    NASA Astrophysics Data System (ADS)

    Gavrilov, B. G.; Zetser, Yu. I.; Ryakhovskii, I. A.; Poklad, Yu. V.; Ermak, V. M.

    2015-07-01

    In 2012, remote measurements of electromagnetic signals in the ELF/VLF band were taken at different points in Russia during experiments on artificial ionospheric modification with the powerful HF wave at the EISCAT heating facility (Tromsø, Norway). The use of the new, highly sensitive magnetometric equipment allowed signals with an amplitude of a few femtoteslas to be recorded at a distance of up to 2000 km from the source. Analysis of the measurement results discovered substantial differences in the amplitude-phase characteristics of the signals, which were caused by a change in helio-geophysical conditions in the region of heating and along the signal passage route, and features of signal propagation, which are related to their mode of guided propagation, the directivity of the source, and angles of reception.

  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. Variability of an additional layer in the equatorial ionosphere over Fortaleza

    NASA Astrophysics Data System (ADS)

    Balan, N.; Batista, I. S.; Abdu, M. A.; Bailey, G. J.; Watanabe, S.; MacDougall, J.; Sobral, J. H. A.

    2000-05-01

    The day-to-day variations (or the weather) of an additional layer, called the F3 layer, that has been predicted to exist at altitudes above the F2 peak in the equatorial ionosphere are studied through ionosonde observations and theoretical modeling. The ionograms recorded in 1995 at the equatorial station Fortaleza (4°S, 38°W dip angle 9°S) in Brazil show the occurrence of the F3 layer during daytime from 0800 to 1630 LT, with the duration of occurrence ranging from 15 min to 6 hours. Although the layer occurs most frequently (75% of the days) in local summer as previously predicted, there are consecutive and individual magnetically quiet and disturbed days when the layer does not occur. There are also days when the layer reoccurs. The model results, obtained using the Sheffield University plasmasphere-ionosphere model, show that the day-to-day variations of the F3 layer arise from the corresponding variations of the vertical plasma velocity. The layer occurs when the time-cumulative vertical velocity displaces the daytime F2 peak to high altitudes, to form the F3 layer, while the normal F2 layer develops at low altitudes. Sudden displacements result in more distinct F3 layers than gradual displacements. Model results also show that the plasma temperature within the F3 layer decreases as the plasma density increases, and, like the plasma density, the plasma temperature also undergoes large day-to-day variations.

  5. E Layer ionospheric disturbances following the Coalinga earthquake

    SciTech Connect

    Fitzgerald, T.J.; Wolcott, J.H.

    1988-01-01

    In a previous report, Doppler shifts in HF radio transmissions through the ionospheric F region following the Coalinga, California earthquake of May 1983 were described. We report here on disturbances which appeared between 400 and 500 s after the earthquake as peaks or broad bands of enhanced power in the spectra of the HF transmissions and not as Doppler shifts. While the time delay (600--800 s) before the occurrence of the Dopppler shifts corresponds to the acoustic travel time to the F region. We believe that the occurrence of the spectral changes represents the presence of temporary E-region propagation modes induced by the passage of the acoustic waves responsible for the Doppler shifts observed at high altitudes. Because the enhanced spectral power occurs at negative frequency relative to that of the F-region propagation modes, the disturbances could be the result of reflections from electron density gradients induced by upwardly propagating acoustic waves. copyright American Geophysical Union 1988

  6. Online Chapmann Layer Calculator for Simulating the Ionosphere with Undergraduate and Graduate Students

    NASA Astrophysics Data System (ADS)

    Gross, N. A.; Withers, P.; Sojka, J. J.

    2014-12-01

    The Chapman Layer Model is a "textbook" model of the ionosphere (for example, "Theory of Planetary Atmospheres" by Chamberlain and Hunten, Academic Press (1978)). The model use fundamental assumptions about the neutral atmosphere, the flux of ionizing radiation, and the recombination rate to calculation the ionization rate, and ion/electron density for a single species atmosphere. We have developed a "Chapman Layer Calculator" application that is deployed on the web using Java. It allows the user to see how various parameters control ion density, peak height, and profile of the ionospheric layer. Users can adjust parameters relevant to thermosphere scale height (temperature, gravitational acceleration, molecular weight, neutral atmosphere density) and to Extreme Ultraviolet solar flux (reference EUV, distance from the Sun, and solar Zenith Angle) and then see how the layer changes. This allows the user to simulate the ionosphere on other planets, by adjusting to the appropriate parameters. This simulation has been used as an exploratory activity for the NASA/LWS - Heliophysics Summer School 2014 and has an accompanying activity guide.

  7. Comparing different assimilation techniques for the ionospheric F2 layer reconstruction

    NASA Astrophysics Data System (ADS)

    Gerzen, Tatjana; Minkwitz, David; Schlueter, Stefan

    2015-08-01

    From the applications perspective the electron density is the major determining parameter of the ionosphere due to its strong impact on the radio signal propagation. As the most ionized ionospheric region, the F2 layer has the most pronounced effect on transionospheric radio wave propagation. The maximum electron density of the F2 layer, NmF2, and its height, hmF2, are of particular interest for radio communication applications as well as for characterizing the ionosphere. Since these ionospheric key parameters decisively shape the vertical electron density profiles, the precise calculation of them is of crucial importance for an accurate 3-D electron density reconstruction. The vertical sounding by ionosondes provides the most reliable source of F2 peak measurements. Within this paper, we compare the following data assimilation methods incorporating ionosonde measurements into a background model: Optimal Interpolation (OI), OI with time forecast (OI FC), the Successive Correction Method (SCM), and a modified SCM (MSCM) working with a daytime-dependent measurement error variance. These approaches are validated with the measurements of nine ionosonde stations for two periods covering quiet and disturbed ionospheric conditions. In particular, for the quiet period, we show that MSCM outperforms the other assimilation methods and allows an accuracy gain up to 75% for NmF2 and 37% for hmF2 compared to the background model. For the disturbed period, OI FC reveals the most promising results with improvements up to 79% for NmF2 and 50% for hmF2 compared to the background and up to 42% for NmF2 and 16% for hmF2 compared to OI.

  8. Rocket/Radar Investigation of Lower Ionospheric Electrodynamics Associated with Intense Midlatitude Sporadic-E Layers

    NASA Technical Reports Server (NTRS)

    Heelis, R. A.

    1998-01-01

    Sporadic layers, which appear in the region from 100 km to 120 km are thought to be formed by convergent Pedersen drifts induced by altitude gradients in the zonal neutral wind. In this altitude region NO+ and 02+ are the major ions produced by photoionization and charge exchange of atmospheric and ionospheric species. The relative composition of atmospheric ions and meteoric ions in sporadic layers is important in determining their persistence, the time scales for formation, and the electrical conductivity of the layers. This rocket investigation will include a diagnosis of the neutral wind field and the electric field distribution. Coupled with ion composition measurements we will be able to expose the relevant formation mechanisms and the electrodynamic consequences of their existence. A rocket trajectory has been chosen to provide substantial horizontal sampling of the layer properties and knowledge of the horizontal gradients in composition and density are essential to determine the polarization electric fields that may be associated with ionospheric layers. The University of Texas at Dallas (UTD) is responsible for designing, building, and operating the ion mass spectrometers included on these rockets. The following provides a summary of the UTD accomplishments in the second year of the project as well as a description of the plans for the third year's activities. The UTD mass spectrometer acronym has been coined as PRIMS for Puerto Rico Ion Mass Spectrometer.

  9. Identification and localization of layers in the ionosphere using the eikonal and amplitude of radio occultation signals

    NASA Astrophysics Data System (ADS)

    Pavelyev, A. G.; Liou, Y. A.; Zhang, K.; Wang, C. S.; Wickert, J.; Schmidt, T.; Gubenko, V. N.; Pavelyev, A. A.; Kuleshov, Y.

    2012-01-01

    By using the CHAllenge Minisatellite Payload (CHAMP) radio occultation (RO) data, a description of different types of the ionospheric impacts on the RO signals at the altitudes 30-90 km of the RO ray perigee is given and compared with the results of measurements obtained earlier in the satellite-to-Earth communication link at frequency 1.5415 GHz. An analytical model is introduced for describing propagation of radio waves in a stratified medium consisting of sectors with spherically symmetric refractivity distribution. This model gives analytical expressions for the phase, bending angle, and refractive attenuation of radio waves and is applied to the analysis of radio wave propagation phenomena along an extended path including the atmosphere and two parts of the ionosphere. The model explains significant amplitude and phase variations at altitudes 30-90 km of the RO ray perigee and attributes them to inclined ionospheric layers. Based on this analytical model, an innovative technique is introduced to locate layers in the atmosphere and ionosphere. A necessary and sufficient criterion is obtained for a layer to be located at the RO ray perigee. This criterion gives both qualitative and quantitative estimation of the displacement of an ionospheric and/or atmospheric layer from the RO ray perigee. This is important, in particular, for determining the location of wind shears and directions of the internal wave propagation in the lower ionosphere, and, possibly, in the atmosphere.

  10. 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.

  11. Anomalous Behavior of D-Layer Preparation Time of the Ionosphere Due to Earthquakes as observed from Malda (India)

    SciTech Connect

    Chatterjee, Achintya K.; Nandy, Nilmadhab; Bari, Md. Washimul; Choudhury, Asit K.

    2010-10-20

    The anomalous behavior of D-layer preparation time of the ionosphere are observed only before, during and after the earthquakes, which took place in the neighbouring region by monitoring the Very Low Frequency (VLF) signal using Gyrator II loop antenna. The anomalies were also observed in the sunrise terminator times during seismically active days. These anomalous behavior may be due to the Lithosphere-Ionosphere coupling. These anomalies may be a precursor of earthquake.

  12. Characterization of the lower layer in the dayside Venus ionosphere and comparisons with Mars

    NASA Astrophysics Data System (ADS)

    Girazian, Zachary; Withers, Paul; Häusler, Bernd; Pätzold, Martin; Tellmann, Silvia; Peter, Kerstin

    2015-11-01

    The influence of solar zenith angle (SZA) and solar irradiance has been well characterized for the V2 layer in the Venus ionosphere, but not the V1 layer, where previous efforts were limited by data scarcity and incomplete SZA coverage. Here we use more than 200 radio occultation profiles from Venus Express with good SZA coverage 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 vary little with SZA, and both peak electron densities vary with SZA in an approximately Chapman-like manner. These results imply that the thermal structures of the atmosphere and ionosphere between ?125 km and ?140 km vary little with SZA. As solar activity increases, the ratio of the V1 to V2 peak density increases, and the V1 morphology changes 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. We compare the behavior of the V1 layer to the analogous M1 layer at Mars, and find that their peak altitudes respond differently to changes in SZA and solar activity. The V1 peak density also increases more with solar activity than the M1 peak density. These distinct behaviors arise from differences in their underlying neutral atmospheres.

  13. Artificial thickening of transonic boundary layers

    NASA Technical Reports Server (NTRS)

    Otten, L. J.; Van Kuren, J. T.

    1976-01-01

    A wind-tunnel experiment was performed to examine the effect of turbulence enhancers on the growth of a flat-plate turbulent boundary layer. The free-stream Mach number was varied from 0.6 to 0.9 with unit Reynolds numbers of 6.56 million/m and 13.12 million/m. Several configurations of high-drag objects were mounted near the leading edge of a long flat plate to introduce momentum losses. Measurements of both mean and time-variable flow parameters were made at downstream locations to quantify the influence of the turbulence enhancers. A configuration consisting of two rows of alternately spaced, vertical, 0.317-cm-diameter cylinders of 16 and 12 diameters length produced 1/9to 1/7-power velocity profiles. Unsteady total-temperature and static-pressure profiles were found to be similar to natural turbulent boundary-layer profiles. The techniques presented can be useful whenever thick turbulent boundary layers are required, but the natural growth of the layer is limited by the test facility.

  14. Physical mechanism and statistics of occurrence of an additional layer in the equatorial ionosphere

    NASA Astrophysics Data System (ADS)

    Balan, N.; Batista, I. S.; Abdu, M. A.; MacDougall, J.; Bailey, G. J.

    1998-12-01

    A physical mechanism and the location and latitudinal extent of an additional layer, called the F3 layer, that exists in the equatorial ionosphere are presented. A statistical analysis of the occurrence of the layer recorded at the equatorial station Fortaleza (4°S, 38°W dip 9°S) in Brazil is also presented. The F3 layer forms during the morning-noon period in that equatorial region where the combined effect of the upward E×B drift and neutral wind provides a vertically upward plasma drift velocity at altitudes near and above the F2 peak. This velocity causes the F2 peak to drift upward and form the F3 layer while the normal F2 layer develops at lower altitudes through the usual photochemical and dynamical effects of the equatorial region. The peak electron density of the F3 layer can exceed that of the F2 layer. The F3 layer is predicted to be distinct on the summer side of the geomagnetic equator during periods of low solar activity and to become less distinct as the solar activity increases. Ionograms recorded at Fortaleza in 1995 show the existence of an F3 layer on 49% of the days, with the occurrence being most frequent (75%) and distinct in summer, as expected. During summer the layer occurs earlier and lasts longer compared to the other seasons; on the average, the layer occurs at around 0930 LT and lasts for about 3 hours. The altitude of the layer is also high in summer, with the mean peak virtual height being about 570 km. However, the critical frequency of the layer (foF3) exceeds that of the F2 layer (foF2) by the largest amounts in winter and equinox; foF3 exceeds foF2 by a yearly average of about 1.3 MHz.

  15. Forcing of the thermosphere-ionosphere through gravity wave dissipation in the bottom F-Layer

    NASA Astrophysics Data System (ADS)

    Negrea, Catalin; Zabotin, Nikolay; Bullett, Terry; Rietveld, Mike

    2015-04-01

    The importance of gravity waves for thermospheric and ionospheric dynamics has been amply demonstrated by both observational and modelling studies. This is true for both the initial perturbations and the changes to background conditions due to wave attenuation. In detecting and analyzing atmospheric GWs, Travelling Ionospheric Disturbances act as a tracer. We use Dynasonde derived ionospheric measurements to determine the amplitude, phase, frequency, wavelength and direction of propagation for gravity waves at Wallops Island, San Juan and Tromso. The objective of this study is to determine the magnitude and variability of the body forces exerted on the background system by waves as they are attenuated and dump their momenta. For atmospheric dynamics it is very important to know both the spatial and temporal variability of this momentum source. The continuous operation of Dynasonde instruments allows for temporal variations to be monitored within the altitude interval covered by the bottom F-Layer. The method we use is illustrated using a sample dataset from Wallops Island. The forcing due to gravity waves is then inferred for several time intervals in 2013 and 2014. Our approach allows for the impact of each wave mode to be determined, and also the cumulative effect of the gravity wave spectra at any given time and altitude. Characteristics common to each location are determined, such as the predominant direction of propagation and the seasonal variations in the wave spectra and the total body force.

  16. [Characteristics of soil moisture in artificial impermeable layers].

    PubMed

    Suo, Gai-Di; Xie, Yong-Sheng; Tian, Fei; Chuai, Jun-Feng; Jing, Min-Xiao

    2014-09-01

    For the problem of low water and fertilizer use efficiency caused by nitrate nitrogen lea- ching into deep soil layer and soil desiccation in dryland apple orchard, characteristics of soil moisture were investigated by means of hand tamping in order to find a new approach in improving the water and fertilizer use efficiency in the apple orchard. Two artificial impermeable layers of red clay and dark loessial soil were built in soil, with a thickness of 3 or 5 cm. Results showed that artificial impermeable layers with the two different thicknesses were effective in reducing or blocking water infiltration into soil and had higher seepage controlling efficiency. Seepage controlling efficiency for the red clay impermeable layer was better than that for the dark loessial soil impermeable layer. Among all the treatments, the red clay impermeable layer of 5 cm thickness had the highest bulk density, the lowest initial infiltration rate (0.033 mm · min(-1)) and stable infiltration rate (0.018 mm · min(-1)) among all treatments. After dry-wet alternation in summer and freezing-thawing cycle in winter, its physiochemical properties changed little. Increase in years did not affect stable infiltration rate of soil water. The red clay impermeable layer of 5 cm thickness could effectively increase soil moisture content in upper soil layer which was conducive to raise the water and nutrient use efficiency. The approach could be applied to the apple production of dryland orchard. PMID:25757307

  17. Features of the F3 layer in the low-latitude ionosphere at sunset

    NASA Astrophysics Data System (ADS)

    Zhao, Biqiang; Wan, Weixing; Reinisch, Bodo; Yue, Xinan; Le, Huijun; Liu, Jing; Xiong, Bo

    2011-01-01

    The F3 layer is a common feature within ±10° of the magnetic equatorial ionosphere in the daytime. According to Balan et al. (1998) the F3 layer occurs mainly during the morning-noon period due to the combined effect of the upward E × B drift and the neutral wind that provides upward plasma drifts at and above the F2 layer. The F3 layer occurrence rate is higher in summer and decreases with increasing solar activity. In this study, the characteristic of the sunset F3 layer is first investigated using a solar cycle of ionosonde data (1995-2010) from the magnetic equatorial station at Jicamarca, and compared with the features derived from the four subtropical stations at Sao Luis, Fortaleza, Kwajalein, and Vanimo. Evidence shows that the local time distribution of the occurrence of the F3 layer can extend to the postsunset time (1800-2100 local time). The sunset F3 layer has a strong seasonal dependence occurring mainly during the summertime. Unlike the daytime F3 layer, the occurrence of the sunset F3 layer clearly increases and the virtual height of the bottom side of the F3 layer statistically increases from 620 to 1000 km with increasing solar activity. In addition, the occurrence of the sunset F3 layer at the other stations is much less than that at Jicamarca. These features of the dependence on the season, solar activity, and latitude are clearly related to the geomagnetic control of the evening prereversal enhancement of the equatorial zonal electric field and geomagnetic configuration.

  18. Generation of zonal flow and magnetic field in the ionospheric E-layer

    NASA Astrophysics Data System (ADS)

    Kahlon, L. Z.; Kaladze, T. D.

    2015-10-01

    > We review the generation of zonal flow and magnetic field by coupled electromagnetic ultra-low-frequency waves in the Earth's ionospheric E-layer. It is shown that, under typical ionospheric E-layer conditions, different planetary low-frequency waves can couple with each other. Propagation of coupled internal-gravity-Alfvén, coupled Rossby-Khantadze and coupled Rossby-Alfvén-Khantadze waves is revealed and studied. A set of appropriate equations describing the nonlinear interaction of such waves with sheared zonal flow is derived. The conclusion on the instability of short-wavelength turbulence of such coupled waves with respect to the excitation of low-frequency and large-scale perturbation of the sheared zonal flow and sheared magnetic field is deduced. The nonlinear mechanism of the instability is based on the parametric triple interaction of finite-amplitude coupled waves leading to the inverse energy cascade towards longer wavelength. The possibility of generation of an intense mean magnetic field is shown. Obtained growth rates are discussed for each case of the considered coupled waves.

  19. Characterizing the V1 layer in the Venus ionosphere using VeRa observations from Venus Express

    NASA Astrophysics Data System (ADS)

    Girazian, Z.; Withers, P.; Fallows, K.; Tarrh, A.; Paetzold, M.; Tellmann, S.; Haesler, B.

    2013-12-01

    The Venus Radio Science Experiment (VeRa) on the Venus Express spacecraft sounds the Venus atmosphere during Earth occultations to obtain vertical profiles of electron density in the ionosphere. The resultant profiles reveal the vertical structure of the Venus ionosphere from the topside down to below the lower layers (< 115 km). On the dayside, the dominant plasma layer is the V2 layer at ~142 km, which is produced primarily by photoionization of CO2. Embedded on the bottomside of the V2 layer is the less prominent, and much less studied, V1 layer at ~127 km. The V1 layer is also produced by photoionization of CO2, but secondary ionization due to energetic photoelectrons is much more important. Here we investigate properties of the V1 layer using VeRa profiles from 2006 to 2012 during which the Sun went from the deep solar minimum of Solar Cycle 23 to the rising solar activity levels of Solar Cycle 24. We investigate how the peak electron density and peak altitude of the V1 layer depend on solar zenith angle. We also characterize the shapes of the V1 layer and show how they are related to the solar activity level. Solar spectra from the Solar EUV Experiment (SEE) on the Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) spacecraft are used to characterize the shapes of the V1 layer with solar activity.

  20. 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.

  1. (Workshop on artificially ionized layers in the atmosphere)

    SciTech Connect

    Tunnell, T.W.

    1989-10-30

    I presented our report which described our technique of inferring electron temperature in a microwave induced plasma. The primary purpose of my trip to Kiev was to present a paper entitled Analysis of Nitrogen Light Emission from Artificially Ionized Layers (AIL) Breakdown'' at the AIL workshop. The AIL concept is to produce an ionized layer in the atmosphere from which radio frequency waves can be reflected. The workshop provided for the transfer of unclassified technology between the US and the USSR, who are reportedly years, if not decades, ahead of the US in this area of research.

  2. Study of Ionospheric Perturbations in D-Layer Using Awesome VLF Receiver Data at Tashkent Station

    NASA Astrophysics Data System (ADS)

    Ahmedov, Bobomurat

    2012-07-01

    One VLF receiver and two SuperSID receivers were provided to Uzbekistan IHY cite by Stanford University and are operating in Tashkent, under the International Heliophysical Year (IHY). The results obtained at Tashkent IHY station are applied to earthquake electromagnetic precursors, lightning, and solar flares and to ionospheric disturbances originating from gamma ray flares of Soft Gamma-Ray Repeaters connected with evolution of strongly magnetized neutron stars believed as magnetars. Regular monitoring of the D-layer of ionosphere over Central Asia territory has been performed on the permanent basis. Few Solar flare events are observed during February in 2010-2011 years 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. Assuming that earthquakes (EQs) can be preceded by the electromagnetic signals in the VLF bands detectable from ground-based measurements we have studied VLF amplitude anomalies related to the earthquakes occurred in 2009-2010 years with magnitude more than 5 on the path way from the VLF transmitters to the Tashkent station. For analysing narrowband data we have used the Nighttime Fluctuation (NF) method paying attention to the data obtained during the local nighttime (18:00 LT-06:00 LT). The amplitude data are analysed only for the reason that perturbations are identified more clearly in the amplitude data than in phase data. The mean nighttime amplitude (or trend) and normalized trend are found to increase significantly before the EQ with the same tendency as the NF and normalized NF. The obtained results have revealed a fine agreement with VLF amplitude anomalies observed in Tashkent VLF station during the strong earthquakes occurred on the path way from the transmitters to the receiver. Some of the initial results obtained from the preliminary analysis are presented to show the probing potentiality of VLF waves in ionosphere studies.

  3. Drift Velocity of Small-Scale Artificial Ionospheric Irregularities According to Multifrequency HF Doppler Radar. I. Method of Calculation and Its Hardware Implementation

    NASA Astrophysics Data System (ADS)

    Vertogradov, G. G.; Uryadov, V. P.; Vertogradov, V. G.; Vertogradova, E. G.; Kubatko, S. V.

    2015-10-01

    The method of calculating the total drift velocity vector of small-scale artificial ionospheric irregularities as measured by the effective Doppler frequency shift of aspect-scattered signals from several diagnostic illumination transmitters operated at different frequencies is discussed. The technique of adaptive simulation of decameter radio waves propagating in an inhomogeneous magnetized ionosphere with allowance for the aspect scattering effects due to small-scale field-aligned irregularities is developed. A multifrequency HF Doppler radar for simultaneous measurement of the Doppler spectra of radio signals at a set of frequencies is described.

  4. Peculiar Features of Ionospheric F3-Layer during Prolonged Solar Minimum (2007-2009)

    NASA Astrophysics Data System (ADS)

    Nayak, C.; Yadav, V.; Kakad, B. A.; Sripathi, S.; Emperumal, K.; Pant, T. K.; Bhattacharyya, A.; Jin, S.

    2014-12-01

    Seasonal and local time occurrence of ionospheric F3-layer over Tirunelveli (geo. lon. 77.8° E, geo. lat. 8.7° N, dip 0.7°) during extremely low and prolonged solar activity period (2007-2009) has been presented in this paper. Almost three times increase in the occurence of the F3-layer has been observed 2009 (~ 48%) as compared to that during 2007(~ 16%). The increase of this order just within low solar activity period is unusual. In earlier studies similar increase in F3 occurrence has been reported when solar activity changes from high (F10.7=182) to low (F10.7=72). Another important feature of this study, is the presence of post-noon F3 layers that are observed predominantly during the summer solstice of 2009. Such occurrence of post-noon F3 layers was nearly absent during summer solstice of previous solar minimum (1996) over nearby dip equatorial station Trivandrum. Using the equatorial electrojet (EEJ) as a proxy for eastward electric field, we found that the EEJ strength and the maximum rate of change of EEJ are higher for F3-days as compared to that during non-F3 days. It was also observed that the peak occurrence of pre-noon F3-layer closely coincides with the time of maximum rate of change of EEJ. The present study reveals that the rate of change of eastward electric field (dE/dt) as well plays an important role in the formation of F3-layer.

  5. Peculiar features of ionospheric F3 layer during prolonged solar minimum (2007-2009)

    NASA Astrophysics Data System (ADS)

    Nayak, C. K.; Yadav, V.; Kakad, B.; Sripathi, S.; Emperumal, K.; Pant, T. K.; Bhattacharyya, A.; Jin, Shuanggen

    2014-10-01

    We present the seasonal and local time occurrence of ionospheric F3 layer over Tirunelveli (geographic longitude 77.8°E, geographic latitude 8.7°N, dip 0.7°) during extremely low and prolonged solar activity period (2007-2009). Canadian Advanced Digital Ionosonde observations from this station are used in the present study. We find that the occurrence of F3 layer is nearly 3 times higher during 2009 (˜ 48%) as compared to that during 2007 (˜16%). The increase of this order just within the low solar activity period is unusual. In earlier studies similar increase in F3 occurrence has been reported when solar activity changes from high (F10.7=182) to low (F10.7=72). The other important feature is the presence of postnoon F3 layers which are observed dominantly during summer solstice of 2009. Such occurrence of postnoon F3 layers was nearly absent during summer solstice of the previous solar minimum (1996) over nearby dip equatorial station Trivandrum. We take equatorial electrojet (EEJ) as a proxy for eastward electric field. It is noticed that the EEJ strength and the maximum rate of change of EEJ are higher for F3 days as compared to those on non-F3 days. We find that the peak occurrence of prenoon F3 layer closely coincides with the time of maximum rate of change of EEJ. It is in general accordance with the theory proposed by Balan et al. (1998) that suggests the formation of F3 through vertically upward E × B drift in presence of equatorward neutral wind. The present study reveals that the rate of change of eastward electric field (dE/dt) as well plays an important role in the formation of F3 layer.

  6. 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.

  7. Generation of 'artificial' bursts in a turbulent boundary layer

    NASA Technical Reports Server (NTRS)

    Gad-El-hak, M.; Hussain, A. K. M. F.

    1986-01-01

    In an effort to better understand the physics and structure of coherent events in a turbulent boundary layer, an attempt is made to produce 'artificial' bursts. These are generated in a unique turbulent boundary layer, developed on a flat plate towed in an 18-m water channel, and thus with negligible freestream turbulence. The burst-like events are produced by either withdrawing near-water fluid from two minute holes separated in the spanwise direction, or by pitching a miniature delta wing that is flush-mounted to the wall. Either of these two actions generates a hairpin-like vortex and low-speed streak that resemble naturally occurring structures. The resulting sequence of events that occur at a given location can be controlled at will, thus allowing detailed examination via phase-locked measurements and flow visualization. In this paper, the artificial bursts are compared with natural, random bursts, using flow visualization and hot-film signals. Detailed quantitative data on topographical details and dynamical significance of the bursting structure will be addressed in a forthcoming article.

  8. Interferometric temperature measurements in the F2 ionospheric layer during the June 20, 1990 earthquake in Iran

    NASA Astrophysics Data System (ADS)

    Akmamedov, Kh.

    1993-02-01

    Results are presented of Doppler temperature measurements in the F2 ionospheric layer, carried out near Ashkhabad (Turkmenistan) during an earthquake in Iran on June 20, 1990. Results indicate a significant temperature increase (by about 350 K) in F2 temperature, observed in the northern and the southern directions, at locations which were nearly equidistant from the earthquake focus. An estimate is made of the energy necessary for the measured temperature increase.

  9. Physical Layer Security with Artificial Noise: Secrecy Capacity and Optimal Power Allocation

    E-print Network

    Zhou, Xiangyun "Sean"

    Physical Layer Security with Artificial Noise: Secrecy Capacity and Optimal Power Allocation to simultaneously transmit an information bearing signal to the intended receiver and artificial noise as the objective function to optimize transmit power allocation between the information signal and the artificial

  10. Spaced sensor measurements of artificial airglow emission at 630 nm of ionosphere caused by ``Sura'' facility radiation in November 2013

    NASA Astrophysics Data System (ADS)

    Nasyrov, Igor; Grach, Savely; Gumerov, Rustam; Shindin, Alexey; Kogogin, Denis; Dementiev, Vladislav

    Some first results on simultaneous observation artificial airglow emission at 630 nm during HF pumping of the ionosphere by “Sura” facility from two spatial situated experimental sites are reported. The measurements of artificial airglow are usually conducted in red and green lines of atomic oxygen (the radiation of levels O((1) D) and O((1) S) under their excitation by electronic impact) with wave lengths of 630 and 557.7 nm and excitation energy of 1.96 and 4.17 eV accordingly. An enhancement of airglow intensity in the red line is related at present to the electron heating by powerful radio waves. The idea of the experiment was to estimate the heated volume three-dimensional structure and drift motion one. The experiment was carried out in November 2013 at the “Sura” radio facility, situated near Nizhny Novgorod, Russia (geographical coordinates 56.13(o) N, 46.10(o) E, geomagnetic field declination and inclination are ˜ 10.0(o) east and ˜ 71.5(o) , respectively). Conditions of ionosphere were checked by means of "Cady" ionosonde during “Sura” runs. According to the ionospheric conditions, on the 7(th) of November the “Sura” facility operated at frequency 4.540 MHz. At this frequency the effective radiated power was about 120MW. The HF beam width at the “Sura” facility is ˜ 12(o) . A square wave pump modulation of 5 min on, 5 min off, was used. Measurements were carried out in the period from 14:40 to 17:30 UTC. Optical imaging was performed on two spatial experimental sites: “Vasilsursk” (situated about 500 m from antenna system of “Sura” facility); “Raifa” (situated about 170 km from “Sura” facility at the Magnetic Observatory of Kazan Federal University, geographical coordinates 55.93(o) N, 48.75(o) E). They both were fitted out Peltier-cooled front-illuminated bare CCD cameras with 16-bit slow-scan read-out (S1C3). On “Vasilsursk” site the images were binned down to 256× 256 pixels in addition to cooling, in order to increase sensitivity and to reduce noise. A lens giving a ˜ 20(o) field of view was used. Using the stars, the camera look direction was adjusted to be parallel to the pump beam. On “Raifa” site the CCD camera was equipped with parallactic mount and rapid camera lens ZIKAR-2B. The 3 angular degrees wide rapid camera lens line of sight crossed the central ray of the “Sura” antenna pattern at the altitude of 225 km for those experimental conditions. During further “Vasilsursk” site’s experimental data handling and interpretation the “Cyclone” ionosond ionogramms were used. The “Cyclone” ionosonde is situated at “Orekhovka” site of the Kazan Federal University (about 180 km from the Sura facility to the east direction). The “Cyclone” ionosonde held sounding once a minute. The ionogramms data were recalculated to N_{e}(h) - profile by of IRI-2012 model. The plazma resonance area vertical size (the difference between heights of upper hybrid-Bernstein and Langmuir resonanses observation) was calculated by means of the mentioned profile and the World Magnetic Model (WMM-2010). Beside the plazma resonance area size the reflection altitude of the powerful radio wave was calculated by means of the ray tracing method. Some results of data proceeding and interpretation are presented in the report. This work was supported by the Russian Foundation for Basic Research (grants No. 12-02-00513, 13-02-00957, 14-02-31459).

  11. Ionospheric physics

    SciTech Connect

    Sojka, J.J. )

    1991-01-01

    Advances in all areas of ionospheric research are reviewed for the 1987-1990 time period. Consideration is given to the equatorial ionosphere, the midlatitude ionosphere and plasmasphere, the auroral ionosphere, the polar ionosphere and polar wind, ionospheric electrodynamic inputs, plasma waves and irregularities, active experiments, ionospheric forecasting, and coupling the ionosphere with other regions.

  12. 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.

  13. Numerical simulations 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.

    2015-08-01

    The M1 layer of the Mars ionosphere is one of its most significant features, second only to the M2 layer. Observations have shown how the physical properties of this layer depend on solar zenith angle (SZA) and solar irradiance, but these trends have not yet been explored in detail by numerical simulations. Hence, the full implications of the observational findings for the M1 layer's behavior have not been established. Here we use the Boston University Mars Ionosphere Model to simulate the M1 layer over a period of 6 months. In order to adequately reproduce the SZA dependence of the observed M2 peak density, an ad hoc isothermal electron temperature profile was required. This representation was motivated by detailed energy balance calculations that predict relatively small variations in electron temperature at the M2 peak. We find several model results consistent with observations: the simulated M1 peak density is effectively proportional to Ch(SZA)-0.5, where Ch is the Chapman function; the ratio of M1 to M2 peak electron densities is independent of SZA; the simulated M1 peak altitude decreases with increasing solar irradiance; and the simulated difference in altitude between the M1 and M2 layers increases with SZA at the observed rate. Due to limitations in the assumed neutral atmosphere, the simulated increase in M1 peak altitude with increasing solar zenith angle is significantly greater than observed. In both simulations and observations, limitations in representing the width of the M1 layer prevent meaningful comparisons and connections to the neutral scale height.

  14. 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.

  15. Response of some ionospheric parameters to geomagnetic disturbances at heights below the F2-layer maximum in September and April 2005

    NASA Astrophysics Data System (ADS)

    Kushnarenko, G. P.; Kuznetsova, G. M.; Ratovskii, K. G.; Kolpakova, O. E.

    2012-05-01

    An analysis of ionospheric data obtained during geomagnetic disturbances in April and September 2005 is performed in order to obtain information on the behavior of some ionospheric parameters at heights of the F1 layer. The results of measurements by an Irkutsk digisonde at hourly and 5- and 15-min time intervals were used. It is shown that in September all parameters very actively responded to geomagnetic disturbances in short measurement time intervals. It is also shown that the electron concentration behaves more stable at lower heights of the F1 layer both during strong and moderate disturbances.

  16. Large-scale transport of metallic ions and the occurrence of thin ion layers in the polar ionosphere

    NASA Astrophysics Data System (ADS)

    Bedey, D. F.; Watkins, B. J.

    1997-05-01

    A necessary condition for the formation of thin metallic ion layers in the high-latitude ionosphere, when strong convective electric fields are present, is that these fields have a magnetically westward component. However, observations have shown that proper field direction does not guarantee the occurrence of a layer. A sufficient abundance of metallic ions is also required. We assert that the abundance of metallic ions (and hence occurrence of thin layers) is strongly influenced by large-scale ion transport, which at high latitudes is determined by the spatial and temporal structure of the large-scale convective electric field. A simple model is presented which indicates that on the dayside, ions should be lifted from the nominal background metallic layer below 100 km into the lower F region, where they flow horizontally in a narrow vertical stream (~50km) toward the nightside. Upon entering the nightside this stream of metallic ions precipitates within a limited band of geomagnetic latitudes, leading to spatially selective enhancements of ion abundance within the E region. Given an appropriately directed convective electric field, the rate of occurrence of detectable thin ion layers should be greater at those locations where precipitation has occurred and, conversely, should be less where precipitation has not occurred. We suggest that this process controls the abundance of metallic ions and therefore explains the fact that layers are sometimes absent in observations, despite the presence of westwardly directed electric fields.

  17. Statistical properties of variability of the quiet ionosphere F2-layer maximum parameters over Irkutsk under low solar activity

    NASA Astrophysics Data System (ADS)

    Deminov, M. G.; Deminova, G. F.; Zherebtsov, G. A.; Polekh, N. M.

    2013-03-01

    The statistical analysis of the quiet ionosphere F2-layer maximum parameters variability (deviations of NmF2 and hmF2 from the quiet medians, ?n and ?h) under solar minimum at day (10-16 LT) and night (22-04 LT) hours based on data of Irkutsk station for 2007-2010 is presented. It is found that the experimental distribution (histogram) of ?n can be approximated by a mixture of two normal distributions. The first and second components of the mixture characterize, mainly, relatively weak and strong fluctuations of ?n which are presumably associated with the ionospheric effects of the atmospheric gravity waves and of the planetary waves and tides correspondingly. Deviation of the ?n histogram from a single normal distribution is most considerable at night hours in winter and equinoxes. For these conditions the weak fluctuations of ?n are mainly negative and the strong ones are mainly positive. The ?h histogram is a normal distribution except day hours in winter and equinoxes when a weak deviation of the histogram from the normal distribution occurs.

  18. Networks of Artificial Neurons, Single Layer Perceptrons Neural Computation : Lecture 3

    E-print Network

    Bullinaria, John

    Networks of Artificial Neurons, Single Layer Perceptrons Neural Computation : Lecture 3 © John A. Bullinaria, 2014 1. Networks of McCulloch-Pitts Neurons 2. Single Layer Feed-Forward Neural Networks: The Perceptron 3. Implementing Logic Gates with McCulloch-Pitts Neurons 4. Finding Weights Analytically 5

  19. Built following an artificial life layered architecture, composed mainly of geometry, physics, behavior, and cognition layers.

    E-print Network

    Hamarneh, Ghassan

    by an artificial deformable organism living in the image space. ·Complement current deformable models that uses artificial life modeling concepts to complement the classical bottom-up deformable models Segmentation in Magnetic Resonance Images Using Artificial Organisms G. Hamarneh and C. McIntosh School

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

    SciTech Connect

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

    2015-01-15

    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.

  1. Remote sensing of the ionospheric F layer by use of O I 6300-A and O I 1356-A observations

    NASA Technical Reports Server (NTRS)

    Chandra, S.; Reed, E. I.; Meier, R. R.; Opal, C. B.; Hicks, G. T.

    1975-01-01

    The possibility of using airglow techniques for estimating the electron density and height of the F layer is studied on the basis of a simple relationship between the height of the F2 peak and the column emission rates of the O I 6300 A and O I 1356 A lines. The feasibility of this approach is confirmed by a numerical calculation of F2 peak heights and electron densities from simultaneous measurements of O I 6300 A and O I 1356 A obtained with earth-facing photometers carried by the Ogo 4 satellite. Good agreement is established with the F2 peak heights estimates from top-side and bottom-side ionospheric sounding.

  2. Is there any difference in local time variation in ionospheric F2-layer disturbances between earthquake-induced and Q-disturbance events?

    NASA Astrophysics Data System (ADS)

    Xu, T.; Hu, Y. L.; Wang, F. F.; Chen, Z.; Wu, J.

    2015-06-01

    Ionospheric anomalies before earthquakes have become the subject of one of the most intensive studies in the area of ionospheric variation. The ionosphere has a large class of disturbances under quiet geomagnetic conditions, i.e., quiet time disturbances (Q disturbances). Hence, the characteristics of seismo-ionospheric anomalies obtained by statistical analysis should be compared with those of Q-disturbance events. Using the data of foF2 (F2-layer critical frequency) during the whole interval of 1978-2008 (~3 solar cycles), the local time (LT) variation in Q disturbances is investigated. The results showed that a well-pronounced nighttime peak took place for positive disturbances induced by Q-disturbance events, while positive disturbances related to earthquakes predominately occurred in the daytime, especially in the afternoon LT sector. This remarkable difference in local time variation in foF2 between the earthquake-triggered and Q-disturbance events is of great significance for the identification of ionospheric precursors.

  3. Ionospheric absorption of radio waves on reflection by the E layer and by the shielding Es layer

    NASA Astrophysics Data System (ADS)

    Shirmammedov, M.; Boltaev, D.

    The AI absorption method was used to measure the radio wave absorption values for the normal E and the sporadic Es layers in the vicinity of Ashkhabad. The absorption values obtained for the Es layer are found to be 3-5 dB less than those obtained for the normal E layer, in good agreement with the data obtained in Rostov-on-Don, located at the latitude of Ashkhabad. The decrease in absorption for the Es layer, in comparison with the E layer, is 15-20 percent. Thus, the contribution of the D layer to the absorption of radio waves at 1.8-2.2 MHz is 80-85 percent.

  4. Artificial Excitation of Schumann Resonance with HAARP

    NASA Astrophysics Data System (ADS)

    Streltsov, A. V.; Chang, C. L.

    2014-12-01

    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 (typically, 7.5 - 8.0 Hz frequency range). 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 by 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 of the Schumann resonance, when the ionosphere has a strong F-layer and an electric field greater than 5 mV/m is present in the E-region.

  5. Influence of artificial viscosity on the formation of vortex cascades in the shear layer

    NASA Astrophysics Data System (ADS)

    Fortova, S. V.; Pronina, A. P.

    2015-11-01

    Numerical analysis of development of vortex cascades in a three-dimensional inviscid shear layer depending on the method of determining and the value of artificial viscosity is done. At the developed stage of turbulence the spectral analysis of kinetic energy is carried out and the law -5/3 of Kholmogorov is confirmed. Pulsation and correlation functions of the flow are investigated.

  6. Quantifying changes in weak layer microstructure associated with artificial load changes

    E-print Network

    Marshall, Hans-Peter

    Quantifying changes in weak layer microstructure associated with artificial load changes Eric Lutz Keywords: Snow microstructure Stability Loading event Elastic rebound SnowMicroPen Researchers load and penetrometer-derived microstructural estimates, 2. We utilize the SnowMicroPen (SMP

  7. 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, Robotics often appears as a collection of disjoint, some- times antagonistic sub-fields. The lack robotics, and shows how these traditional sub-fields fit in to the whole. Finally, it presents a curriculum

  8. 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.

  9. 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.; Parrot, M.

    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.

  10. Upper Hybrid Effects in Artificial Ionization

    NASA Astrophysics Data System (ADS)

    Papadopoulos, K.; Eliasson, B. E.

    2014-12-01

    A most fascinating result of recent ionospheric experiments has been the discovery of artificial ionization by Pedersen et al. (GRL, 37, L02106, 2010). The Artificial Ionospheric Layers (AIL) were the result of F-region O-mode HF irradiation using the HAARP ionospheric heater operating at 3.6 MW power. As demonstrated by Eliasson et al. (JGR, 117, A10321, 2012) the physics controlling the observed phenomenon and its threshold can be summarized as: " Collisional ionization due to high energy (~ 20 eV) electron tails generated by the interaction of strong Langmuir turbulence with plasma heated at the upper hybrid resonance and transported at the reflection height". The objective of the current presentation is to explore the role of the upper hybrid heating in the formation of AIL and its implications to future experiments involving HF heaters operating in middle and equatorial latitudes.

  11. 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.

  12. 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.

  13. Magnetic structure of Tb-Fe films with an artificially layered structure

    SciTech Connect

    Yamauchi, K.; Habu, K.; Sato, N.

    1988-11-15

    The magnetic structure of Tb-Fe films with an artificially layered structure has been investigated by measuring the temperature dependence of the magnetization of the films. Ferrimagnetic coupling between Tb and Fe through the interface was explicitly observed up to about 9-A Tb and 10-A Fe layers. Films with thinner Tb and Fe layers than these thicknesses are composed of only ferrimagnetically coupled Tb-Fe regions. Films with thicker layers of Tb and Fe are composed of ferrimagnetically coupled Tb-Fe, ferromagnetic Fe, ferromagnetic Tb, and/or magnetically compensated Tb regions. The Tb-Fe films exhibit various temperature dependencies of the magnetization corresponding to these magnetic structures.

  14. 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.

  15. Topside of the martian ionosphere near the terminator: Variations with season and solar zenith angle and implications for the origin of the transient layers

    NASA Astrophysics Data System (ADS)

    Zhang, Zhenfei; Orosei, Roberto; Huang, Qian; Zhang, Jie

    2015-05-01

    In this paper, the morphological variations of the M2 layer of the martian ionosphere with the martian seasons and solar zenith angle (SZA) at the terminator are investigated. The data used are the MARSIS (Mars Advanced Radar for Subsurface and Ionosphere Sounding) measurements (approximately 5000 ionograms) that were acquired from 2005 to 2012, which have a SZA ? 85° and detect the topside transient layers. A simple, effective data inversion method is developed for the situation in which the upper portion of the height profile is non-monotonic and the observed data are insufficient for adequate reduction. The inverted parameters are subsequently explored using a statistical approach. The results reveal that the main body of the M2 layer (approximately 10 km below the first topside layer) can be well-characterized as a Chapman layer near the terminator (SZA = 85-98°), notwithstanding the high SZA and the presence of the topside layers. The height of the first topside layer tends to be concentrated approximately 60 km (with a standard deviation of ?20 km) above the main density peak. The peak density and height of the first topside layer are positively correlated to the density and height of the main peak, respectively. The density and height of the first topside layer appear to be independent of the SZA, but possess seasonal variations that are similar to those of the main layer. The height of the topside layer is greater (by ?10 km on average) in the southern spring and summer than in the southern autumn and winter, coinciding with the observation that, in the southern spring and summer, the underlying atmosphere is warmer due to dust heating (e.g., Smith, M.D. [2004]. Icarus 167, 148-165). The statistical regularities of the parameters suggest a possibility that the formation of the topside layers are closely related to the processes of photoionization and diffusion that occur on the topside of the M2 layer. We propose that development of beam-plasma instabilities in the transitional region (between the lower Chapman region and the upper transport-dominating region) is possibly a mechanism that is responsible for the occurrences of the topside layers.

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

    PubMed

    Liu, Yan; Guenneau, Sébastien; Gralak, Boris

    2013-10-01

    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 ([Formula: see text]) breaks down. PMID:24101891

  17. Coupled Magnetotail-Ionosphere Asymmetries from Ionospheric Hall Conduction

    NASA Astrophysics Data System (ADS)

    Lotko, W.; Smith, R. H.; Zhang, B.; Ouellette, J.; Brambles, O.; Lyon, J.; Wiltberger, M. J.

    2014-12-01

    Fast convective transport in the plasma sheet is more prevalent in the premidnight (dusk) sector relative to postmidnight. Ionospheric convection exhibits related asymmetries - more flux typically circulates in the dusk cell than in the dawn cell, and the nightside convection pattern is rotated clockwise when viewed over the North Pole. We show, using global simulations of the solar wind-magnetosphere-ionosphere interaction, that the electrodynamic interaction between Earth's magnetosphere and ionosphere produces asymmetries resembling observed distributions in plasmasheet flows and ionospheric convection (Figure, center panel). The primary causal agent in the simulations is a meridional gradient in ionospheric Hall conductance which, through Cowling polarization, regulates the distributions of i) electrical currents flowing within and between the ionosphere and magnetotail and ii) the nightside reconnection rate and resulting dawn-dusk distribution of plasma sheet fast flows. The asymmetry disappears in the simulation when the Hall conductance is taken to be uniform (left panel), and it reverses when the conductance is artificially depleted at auroral latitudes (right panel). The coupling between meridional currents and electric fields in the ionosphere and axial currents and electric fields in the plasmasheet is demonstrated by a simple model for non-ideal coupling of field-aligned currents flowing between the plasma sheet and the region of enhanced ionospheric conductance straddling the nightside convection throat.

  18. Creating a two-layered augmented artificial immune system for application to computer network intrusion detection

    NASA Astrophysics Data System (ADS)

    Judge, Matthew G.; Lamont, Gary B.

    2009-05-01

    Computer network security has become a very serious concern of commercial, industrial, and military organizations due to the increasing number of network threats such as outsider intrusions and insider covert activities. An important security element of course is network intrusion detection which is a difficult real world problem that has been addressed through many different solution attempts. Using an artificial immune system has been shown to be one of the most promising results. By enhancing jREMISA, a multi-objective evolutionary algorithm inspired artificial immune system, with a secondary defense layer; we produce improved accuracy of intrusion classification and a flexibility in responsiveness. This responsiveness can be leveraged to provide a much more powerful and accurate system, through the use of increased processing time and dedicated hardware which has the flexibility of being located out of band.

  19. 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.

  20. Effects of sporadic E-layer characteristics on spread-F generation in the nighttime ionosphere near a northern equatorial anomaly crest during solar minimum

    NASA Astrophysics Data System (ADS)

    Lee, C. C.; Chen, W. S.

    2015-06-01

    This study is to know how the characteristics of sporadic E-layer (Es-layer) affect the generation of spread-F in the nighttime ionosphere near the crest of equatorial ionization anomaly during solar minimum. The data of Es-layer parameters and spread-F are obtained from the Chungli ionograms of 1996. The Es-layer parameters include foEs (critical frequency of Es-layer), fbEs (blanketing frequency of Es-layer), and ?f (?foEs-fbEs). Results show that the nighttime variations of foEs and fbEs medians (?f medians) are different from (similar to) that of the occurrence probabilities of spread-F. Because the total number of Es-layer events is greater than that of spread-F events, the comparison between the medians of Es-layer parameters and the occurrence probabilities of spread-F might have a shortfall. Further, we categorize the Es-layer and spread-F events into each frequency interval of Es-layer parameters. For the occurrence probabilities of spread-F versus foEs, an increasing trend is found in post-midnight of all three seasons. The increasing trend also exists in pre-midnight of the J-months and in post-midnight of all seasons, for the occurrence probabilities of spread-F versus ?f. These demonstrate that the spread-F occurrence increases with increasing foEs and/or ?f. Moreover, the increasing trends indicate that polarization electric fields generated in Es-layer assist to produce spread-F, through the electrodynamical coupling of Es-layer and F-region. Regarding the occurrence probabilities of spread-F versus fbEs, the significant trend only appears in post-midnight of the E-months. This implies that fbEs might not be a major factor for the spread-F formation.

  1. Global median model of the F2-layer peak height based on ionospheric radio-occultation and ground-based Digisonde observations

    NASA Astrophysics Data System (ADS)

    Shubin, V. N.

    2015-09-01

    In this article, we present a global median model of the ionospheric F2-layer peak height (hmF2), which we named Satellite and Digisonde Model of the F2 layer (SDMF2). This model is based on the radio-occultation data of the satellite missions CHAMP (2001-2008), GRACE (2007-2011), COSMIC (2006-2012) as well as the ionospheric sounding data from the 62 Earth-based Digisonde sounders (1987-2012). As the input parameters, the model uses the year, month and time UT as well as the geographic coordinates and F10.7 index averaged over the 3 Sun rotations (F10.7A). The SDMF2 model is based on the spherical functions decomposition with the 12 harmonics for the longitude and the 8 ones for the modified dip latitude (MODIP). For the diurnal variations, we used the 3 Fourier harmonics. We assumed that the dependency of hmF2 on F10.7A index is logarithmic. The model accurately reproduces both the spatial and temporal behavior of the monthly hmF2 median. The root-mean-square (RMS) and the mean relative deviations (MRD) from the original data are MRD ? 3.7%, RMS ? 14.3 km and MRD ? 5.4%, RMS ? 23.4 km for the periods of low and high solar activity, respectively. The large initial dataset allows achieving the higher accuracy than International Reference Ionosphere model (IRI), and this is confirmed by comparing the SDMF2 model with independent data.

  2. 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.

  3. `Earth-ionosphere' mode controlled source electromagnetic method

    NASA Astrophysics Data System (ADS)

    Li, Diquan; Di, Qingyun; Wang, Miaoyue; Nobes, David

    2015-09-01

    In traditional artificial-source electromagnetic exploration, the effects of the ionosphere and displacement current (DC) in the air were neglected, and only the geoelectrical structure of the earth's crust and upper mantle was considered, such as for controlled source audio-frequency magnetotelluric (CSAMT). By employing a transmitter (less than 30 kW) to generate source fields, the CSAMT method overcomes the problems associated with weak natural electromagnetic (EM) fields used in magnetotellurics. However, the transmitter is moved and the source-receiver offset is approximately less than 20 km, because of the limitation of emission energy. We put forward a new idea, that is, a fixed artificial source (greater than 200 kW) is used and the source location selected at a high resistivity region (to ensure a high emission efficiency), so there may be a possibility that as long as the source strength magnitude is strong enough, the artificial EM signal can be easily observed within a distance of several thousand kilometres. Previous studies have provided the evidence to support this idea; they used the `earth-ionosphere' mode in modeling the EM fields with the offset up to a thousand kilometres. Such EM fields still have a signal/noise ratio over 10-20 dB; this means that a new EM method with fixed source is feasible. However, in their calculations, the DC which plays a very important role for large offsets was neglected. This paper pays much attention to derive the formulae of the `earth-ionosphere' mode with a horizontal electric dipole source, and the DC is not neglected. We present some three layers modeling results to illustrate the basic EM field characteristics under the `earth-ionosphere' mode. As the offset increases, the contribution of the conduction current decreases, DC and ionosphere were taken into account, and the EM field attenuation decreases. We also quantitatively compare the predicted and observed data. The comparison of these results with the data reveal the excellent agreement between the experimental and theoretical results. The DC and ionosphere affects the EM fields, however impedances (ratio of E to H) are unaffected, and this means we need to include ionosphere and DC effects to accurately model the EM field amplitudes for optimal setting of measurement parameters, but we do not need to include these complications for the interpretation of the data for the Earth conductivity.

  4. Long-term comparison of the ionospheric F2 layer electron density peak derived from ionosonde data and Formosat-3/COSMIC occultations

    NASA Astrophysics Data System (ADS)

    Limberger, Marco; Hernández-Pajares, Manuel; Aragón-Ángel, Angela; Altadill, David; Dettmering, Denise

    2015-07-01

    Electron density profiles (EDPs) derived from GNSS radio occultation (RO) measurements provide valuable information on the vertical electron density structure of the ionosphere and, among others, allow the extraction of key parameters such as the maximum electron density NmF2 and the corresponding peak height hmF2 of the F2 layer. An efficient electron density retrieval method, developed at the UPC (Barcelona, Spain), has been applied in this work to assess the accuracy of NmF2and hmF2 as determined from Formosat-3/COSMIC (F-3/C) radio occultation measurements for a period of more than half a solar cycle between 2006 and 2014. Ionosonde measurements of the Space Physics Interactive Data Resource (SPIDR) network serve as a reference. Investigations on the global trend as well as comparisons of the F2 layer electron density peaks derived from both occultations and ionosonde measurements are carried out. The studies are performed in the global domain and with the distinction of different latitude sectors around the magnetic equator ±[0°, 20°], ±]20°, 60°] and ±]60°, 90°]) and local times (LT) accounting for different ionospheric conditions at night (02:00 LT ± 2 h), dawn (08:00 LT ± 2 h), and day (14:00 LT ± 2 h). The mean differences of F2 layer electron density peaks observed by F-3/C and ionosondes are found to be insignificant. Relative variations of the peak differences are determined in the range of 22%-30% for NmF2 and 10%-15% for hmF2. The consistency of observations is generally high for the equatorial and mid-latitude sectors at daytime and dawn whereas degradations have been detected in the polar regions and during night. It is shown, that the global averages of NmF2 and hmF2 derived from F-3/C occultations appear as excellent indicators for the solar activity.

  5. An Undergraduate Student Instrumentation Project (USIP) to Develop New Instrument Technology to Study the Auroral Ionosphere and Stratospheric Ozone Layer Using Ultralight Balloon Payloads

    NASA Astrophysics Data System (ADS)

    Gamblin, R.; Marrero, E.; Bering, E. A., III; Leffer, B.; Dunbar, B.; Ahmad, H.; Canales, D.; Bias, C.; Cao, J.; Pina, M.; Ehteshami, A.; Hermosillo, D.; Siddiqui, A.; Guala, D.

    2014-12-01

    This project is currently engaging tweleve undergraduate students in the process of developing new technology and instrumentation for use in balloon borne geospace investigations in the auroral zone. Motivation stems from advances in microelectronics and consumer electronic technology. Given the technological inovations over the past 20 years it now possible to develop new instrumentation to study the auroral ionosphere and stratospheric ozone layer using ultralight balloon payloads for less than 6lbs and $3K per payload. The UH USIP undergraduate team is currently in the process of build ten such payloads for launch using1500 gm latex weather balloons to be deployed in Houston and Fairbanks, AK as well as zero pressure balloons launched from northern Sweden. The latex balloon project will collect vertical profiles of wind speed, wind direction, temperature, electrical conductivity, ozone and odd nitrogen. This instrument payload will also profiles of pressure, electric field, and air-earth electric current. The zero pressure balloons will obtain a suite of geophysical measurements including: DC electric field, electric field and magnetic flux, optical imaging, total electron content of ionosphere via dual-channel GPS, X-ray detection, and infrared/UV spectroscopy. Students will fly payloads with different combinations of these instruments to determine which packages are successful. Data collected by these instruments will be useful in understanding the nature of electrodynamic coupling in the upper atmosphere and how the global earth system is changing. Results and best practices learned from lab tests and initial Houston test flights will be discussed.

  6. Nonlinear Plasma Effects in Natural and Artificial Aurora

    SciTech Connect

    Mishin, E. V.

    2011-01-04

    This report describes common features of natural ('Enhanced') aurora and 'artificial aurora'(AA) created by electron beams injected from sounding rockets. These features cannot be explained solely by col-lisional degradation of energetic electrons, thereby pointing to collisionless plasma effects. The fundamental role in electron beam-ionosphere interactions belongs to Langmuir turbulence. Its development in the (weakly-ionized) ionosphere is significantly affected by electron-neutral collisions, so that the heating and acceleration of plasma electrons proceed more efficiently than in collisionless plasmas. As a result, a narrow layer of enhanced auroral glow/ionization is formed above the standard collisional peak.

  7. HF-induced airglow structure as a proxy for ionospheric irregularity detection

    NASA Astrophysics Data System (ADS)

    Kendall, E. A.

    2013-12-01

    The High Frequency Active Auroral Research Program (HAARP) heating facility allows scientists to test current theories of plasma physics to gain a better understanding of the underlying mechanisms at work in the lower ionosphere. One powerful technique for diagnosing radio frequency interactions in the ionosphere is to use ground-based optical instrumentation. High-frequency (HF), heater-induced artificial airglow observations can be used to diagnose electron energies and distributions in the heated region, illuminate natural and/or artificially induced ionospheric irregularities, determine ExB plasma drifts, and measure quenching rates by neutral species. Artificial airglow is caused by HF-accelerated electrons colliding with various atmospheric constituents, which in turn emit a photon. The most common emissions are 630.0 nm O(1D), 557.7 nm O(1S), and 427.8 nm N2+(1NG). Because more photons will be emitted in regions of higher electron energization, it may be possible to use airglow imaging to map artificial field-aligned irregularities at a particular altitude range in the ionosphere. Since fairly wide field-of-view imagers are typically deployed in airglow campaigns, it is not well-known what meter-scale features exist in the artificial airglow emissions. Rocket data show that heater-induced electron density variations, or irregularities, consist of bundles of ~10-m-wide magnetic field-aligned filaments with a mean depletion depth of 6% [Kelley et al., 1995]. These bundles themselves constitute small-scale structures with widths of 1.5 to 6 km. Telescopic imaging provides high resolution spatial coverage of ionospheric irregularities and goes hand in hand with other observing techniques such as GPS scintillation, radar, and ionosonde. Since airglow observations can presumably image ionospheric irregularities (electron density variations), they can be used to determine the spatial scale variation, the fill factor, and the lifetime characteristics of irregularities. Telescopic imaging of airglow is a technique capable of simultaneously determining the properties of ionospheric irregularities at decameter resolution over a range of several kilometers. The HAARP telescopic imager consists of two cameras, a set of optics for each camera, and a robotic mount that supports and orients the system. The camera and optics systems are identical except for the camera lenses: one has a wide-angle lens (~19 degrees) and the other has a telescopic lens (~3 degrees). The telescopic imager has a resolution of ~20 m in the F layer and ~10 m in the E layer, which allows the observation of decameter- and kilometer-scale features. Analysis of telescopic data from HAARP campaigns over the last five years will be presented.

  8. Ionospheric modifications in high frequency heating experiments

    SciTech Connect

    Kuo, Spencer P.

    2015-01-15

    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.

  9. Tantalum as a buffer layer in diamond-like carbon coated artificial hip joints.

    PubMed

    Kiuru, Mirjami; Alakoski, Esa; Tiainen, Veli-Matti; Lappalainen, Reijo; Anttila, Asko

    2003-07-15

    The acid resistance of tantalum coated and uncoated human hip joint prostheses was studied with commercial CrCoMo acetabular cups. The samples were exposed to 10% HCl solution and the quantities of dissolved Cr, Co, and Mo were measured with proton-induced X-ray emission (PIXE). The absolute quantities were obtained with the use of Cr and Se solution standards. Tantalum coatings (thicknesses 4-6 microm) were prepared in vacuum with magnetron sputtering. Tantalum coating decreased the corrosion rate by a factor of 10(6). As a spinoff from recent wear tests on artificial hip joints it was shown that tantalum has excellent mechanical properties as an intermediate layer of diamond-like carbon (DLC) coatings. When tantalum was tested together with DLC on three metal-on-metal hip joint pairs in a hip simulator, no observable defects occurred during 15 million walking cycles with a periodic 50-300-kg load (Paul curve). PMID:12808604

  10. 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.

  11. Ionospheric research

    NASA Technical Reports Server (NTRS)

    1975-01-01

    Data from research on ionospheric D, E, and F, regions are reported. Wave propagation, mass spectrometer measurements, and atmospheric reactions of HO2 with NO and NO2 and NH2 with NO and O2 are summarized.

  12. Studing Solar Flare Effects on Ionosphere Using AWESOME Receiver

    NASA Astrophysics Data System (ADS)

    Mustafa, Famil; Babayev, Elchin; Alekperov, Ilgar

    2015-08-01

    Ground based observations of Extremely Low Frequency (ELF) / Very Low Frequency (VLF) (300 Hz 30 kHz) waves are considered as an important remote sensing tool for the investigation of the ionosphere and the magnetosphere. VLF waves find their origin in various natural and artificial phenomena; the natural sources include thunderstorms, lightning and associated phenomena. Sub-ionospheric VLF transmissions propagating inside the Earth-ionosphere wave-guide is also being widely used for investigating sudden ionospheric perturbations (SIDs) in lower part of the ionosphere.

  13. "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.

    2015-10-01

    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.

  14. 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.

  15. Geometric Dependence of Electric Field Swelling in Simulation of HF Ionospheric Heating

    NASA Astrophysics Data System (ADS)

    Djordjevic, B. Z.; Shao, X.; Milikh, G. M.; Eliasson, B. E.; Papadopoulos, D.

    2014-12-01

    The interaction between a high frequency (HF) ordinary mode electromagnetic wave and the ionosphere induces electrostatic turbulence near the critical layer which results in the acceleration of electrons and ionization of the neutral gas by energetic electrons. Due to the artificial plasma created by this process, the reflection point of the electromagnetic wave is shifted downwards, leading to descending artificial ionospheric layers (DAILs). This work studies the dependence of DAIL formation on the injection angle of the HF wave and on the related ionospheric conditions. The model is based on a combination of ray-tracing techniques and numerical solutions of the Försterling equations. A model based on the Försterling equations has been developed to calculate the enhancement (swelling) of the electric field near the reflection point. As the swelling exceeds a certain threshold, it excites Langmuir turbulence, which in turn accelerates electrons to high energies, resulting in DAIL formation. Previous full-wave simulations of ionospheric turbulence have been able to capture some of the 2D nature of ionospheric heating but at great computational cost. This works presents an approach to performing rapid calculations of the electric field swelling of the ordinary mode, in order to facilitate a more computationally efficient 2D study of DAIL formation. Results show maximum swelling of the electric field near the magnetic zenith, with an amplitude on the order of several tens of volts per meter for a pump voltage of 1-2 V/m, which is in agreement with previous computational models as well as experiment. Preliminary work to incorporate a model for Langmuir turbulence induced by electric field swelling into the overall algorithm is also presented.

  16. 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

  17. Ionospheric disturbances produced by chemical releases and the resultant effects on short-wave ionospheric propagation

    NASA Astrophysics Data System (ADS)

    Hu, Yaogai; Zhao, Zhengyu; Zhang, Yuannong

    2011-07-01

    As an effective means to actively modify the ionosphere, chemical releases can produce artificial ionospheric holes as a consequence of ionization reduction, which can have a great impact on radio wave propagation. To investigate the morphology control of ionospheric holes by various chemical releases and the resultant effects on radio wave propagation, a quantitative numerical model is developed on the basis of the approximate solutions of the diffusion equation of single-point release in uniform atmosphere. While single-point release produces ellipsoidal ionospheric holes, multipoint release can produce other types of ionospheric holes (such as parabola-like tubular ones), which is strongly dependent on changes in the release species, release altitude, and mass of released neutral gas. Releases of both H2O and SF6 can produce ionospheric holes with a similar spatial extent, but the latter tends to result in clearer boundaries and more pronounced electron density reductions. In addition, either an increase in released amount or releases at higher altitudes can lead to a broader hole. To evaluate the effects of an ionospheric hole on radio wave propagation, three-dimensional ray tracing simulations are performed. The ellipsoidal ionospheric holes can act as a lens focusing and bending radio waves, leading to multiple wave reflections inside the holes. In contrast, in the paraboloid tubular ionospheric holes, the rays can penetrate the disturbed region or reflect back, showing a strong dependence on radio frequency. It is well demonstrated that chemical releases can efficiently give rise to artificial ionospheric disturbances and thus modify ionospheric propagation of radio waves.

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

    NASA Astrophysics Data System (ADS)

    Briczinski, S. J.; Bernhardt, P. A.; Pedersen, T. R.; Rodriguez, S.; SanAntonio, G.

    2012-12-01

    High power HF radio waves exciting the ionosphere provide aeronomers with a unique space-based laboratory capability. The High-Frequency Active Auroral Research Program (HAARP) in Gakona, Alaksa is the world's largest heating facility, providing effective radiated powers in the gigawatt range. Experiments performed at HAARP have allowed researchers to study many non-linear effects of wave-plasma interactions. Stimulated Electromagnetic Emission (SEE) is of interest to the ionospheric community for its diagnostic purposes. Typical SEE experiments at HAARP have focused on characterizing the parametric decay of the electromagnetic pump wave into several different wave modes such as upper and lower hybrid, ion acoustic, ion-Bernstein and electron-Bernstein. These production modes have been extensively studied at HAARP using traditional beam heating patterns and SEE detection. New results are present from HAARP experiments using a "twisted beam" excitation mode. Unlike traditional heating beams used at HAARP or other heating facilities, the twisted beam attempts to impart orbital angular momentum (OAM) into the heating region. Analysis of twisted beam heating shows that the SEE results obtained are nearly identical to the modes without OAM. 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. The ring heating pattern may be more conducive to the creation of artificial airglow layers. 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.

  19. Comparison of peak characteristics of the F2 ionospheric layer obtained from the Cyprus Digisonde and IRI-2012 model during low and high solar activity period

    NASA Astrophysics Data System (ADS)

    Haralambous, Haris; Oikonomou, Christina

    2015-11-01

    We investigate first the climatology expressed by diurnal and seasonal variations of the critical frequency (foF2) and the peak height (hmF2) of the F2-layer derived from digital ionosonde measurements at the low-middle latitude European station in Nicosia, Cyprus (geographical coordinates: 35°N, 33°E, geomagnetic lat. 29.38°N, I = 51.7°). Monthly median hourly values of the F2-layer peak characteristics are obtained using manually scaled data during the 5-year period 2009-2013. The observational results are then compared with the International Reference Ionospheric Model (IRI-2012) predictions using both URSI and CCIR coefficients. It is shown that the semi-annual pattern of daytime foF2 characterized by higher values at equinoxes than either solstices as well as the winter anomaly phenomenon demonstrate strong solar activity dependence. An annual pattern of night-time foF2 is also detected with lower values in winter and higher in summer. The seasonal variation of daytime hmF2 is evident and peaks of hmF2 at pre-sunrise and post-sunset hours are identified during December. The IRI-2012 model is capable to capture the main diurnal and seasonal patterns of foF2 and hmF2. The highest overestimation of daytime foF2 is noted at equinoxes and solstices except from March, October, December of 2011, and June of 2013. Significant foF2 underestimation is observed at evening and after midnight during February and March of 2009. Large positive discrepancies between the modeled and observed hmF2 values are noticed during the deep solar minimum year 2009. Overall, IRI-model estimates are more accurate for hmF2 than foF2 over Cyprus and for the examined period.

  20. Tsunamis warning from space :Ionosphere seismology

    SciTech Connect

    Larmat, Carene

    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.

  1. 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

  2. Radio Tomography and Imaging of Ionospheric Disturbances Caused by Active Experiments

    NASA Astrophysics Data System (ADS)

    Kunitsyn, Viacheslav; Padokhin, Artem; Andreeva, Elena; Tereshchenko, Evgeny; Nesterov, Ivan; Vladimir Frolov, S.

    We present the results of the radiotomographic imaging of the artificial ionospheric disturbances obtained in the experiments on the modification of the midlatitude ionosphere by powerful HF radiowaves carried out during last decade at the Sura heating facility. The experiments were conducted using both O- and X- mode radiowaves at frequencies lower than critical frequency of the ionospheric F2 layer both in daytime and nighttime ionosphere. Various schemes of the radiation of the heating wave were used including square wave modulation of the effective radiated power (ERP) at various frequencies and power stepping. Radio transmissions of the low- (Parus/Tsikada) and high-orbital (GPS/GLONASS) navigational satellites received at the mobile network of receiving sites were used for the remote sensing of the heated area of the ionosphere. We study the variations in TEC caused by HF heating showing that the GNSS TEC spectra often contain frequency components corresponding to the modulation periods of the ERP of the heating wave. The manifestations of the heating-induced variations in TEC are most prominent in the area of magnetic zenith of the pumping wave. In this work we also present the radiotomographic reconstructions of the spatial structure of the disturbed area of the ionosphere corresponding to the directivity pattern of the heater as well as the spatial structure of the wave-like disturbances, which are possibly AGWs, diverging from the heated area of the ionosphere. We also compare the effects obsereved during artificial heating experiments with those obsereved during rocket launches and powerful industiral explosions. The possibility of generation of electromagnetic waves by moving wave-like structures in ionosphere (like AGWs induced by HF-heating observed in our experiments) is also addressed in this work. The authors acknowledge the support of the Russian Foundation for Basic Research (grants ? 13-05-01122, 14-05-31445, 14-05-00855, 14-05-10069), grants of the President of Russian Federation (MK-2670.2014.5) and Lomonosov Moscow State University Program of Development.

  3. Modeling of Plasma Irregularities in Expanding Ionospheric Dust Clouds

    NASA Astrophysics Data System (ADS)

    Fu, H.; Scales, W.; Mahmoudian, A.; Bordikar, M. R.

    2009-12-01

    Natural dust layers occur in the earth’s mesosphere (50km-85km). Plasma irregularities are associated with these natural dust layers that produce radar echoes. Recently, an Ionospheric sounding rocket experiment was performed to investigate the plasma irregularities in upper atmospheric dust layers. The Charged Aerosol Release Experiment (CARE) uses a rocket payload injection of particles in the ionosphere to determine the mechanisms for enhanced radar scatter from plasma irregularities embedded in artificial dusty plasma in space. A 2-D hybrid computational model is described that may be used to study a variety of irregularities in dusty space plasmas which may lead to radar echoes. In this model, the dust and ions are both treated with Particle-In-Cell method while the dust charge varies with time based on the standard dust Orbit Motion Limited charging model. A stochastic model is adopted to remove particle ions due to the dust charging process. Electrons are treated with a fluid model including the parallel dynamics of magnetic fields. Fourier spectral methods with a predictor-corrector time advance are used to solve it. This numerical model will be used to investigate the electrodynamics and several possible plasma irregularity generation mechanisms after the creation of an artificial dust layer. The first is the dust ion-acoustic instability due to the drift of dust relative to the plasma. The instability saturates by trapping some ions. The effects of dust radius and dust drift velocity on plasma irregularities will be analyzed further. Also, a shear- driven instability in expanding dusty clouds is investigated.

  4. Response of the F2 layer of the Equatorial ionosphere to a moderate magnetic storm during a low solar sunspot period

    NASA Astrophysics Data System (ADS)

    Ayokunnu, David Ayokunnu; Adeniyi, Jacob Olusegun

    The equatorial ionosphere has peculiarities which make it different from other ionosphere of other region, in the African sector; the magnetic field is nearly horizontal whereas in the American sector it is nearly vertical. This study is on the comparison of ionospheric parameters at three equatorial stations: namely Ilorin, Nigeria (8.5 oN, 4.5 oE), in the African sector, Fortaleza, Brazil (3 oS, 38 oW) and Jicamarca, Peru (12 oS, 76.8 oW) in the American sector. The data are those of year 2010, a year of low solar activity. The results from the study showed that Ilorin and Jicamarca have almost the same distinct features while Jicamarca shows some disparity.

  5. HAARP-Induced Ionospheric Ducts

    SciTech Connect

    Milikh, Gennady; Vartanyan, Aram

    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.

  6. Electromagnetic emissions detected in the topside ionosphere related to the human activity

    NASA Astrophysics Data System (ADS)

    Rothkaehl, H.; Parrot, M.

    2005-05-01

    The Earth ionosphere undergoes various man-made influences. The electromagnetic emissions in the topside ionosphere have been investigated ever since first satellites were located on the orbits. Despite the fact that the analysis of properties of Earth electromagnetic environment has had a long history, the topics related to the electromagnetic pollutions are still not sufficiently reported. The development of new telecommunication technologies and the increased level of electromagnetic noises from VLF to microwave frequency range in the Earth environment should focus our investigations on that problem. The RF measurements can be used to diagnose the different electron plasma waves, the local electron densities as well as the maximum F2 layer electron densities. The HF diagnostics performed on the low orbiting satellite detected the enhancement of radiation, particularly over the Euro-Asia region. Thus over the Euro-Asia area enhancements of background radiation were detected in the whole frequency band, which is connected with natural plasma radiation, and for frequencies greater than the plasma frequency at maximum F2 layer, triggered by artificial ground-based origin noises. Electromagnetic waves permanently pumped to the ionosphere by the system of broadcasting stations can disturb the nearest space environment. The observed broadband emissions are a superposition of natural plasma emissions and man-made noises. The aim of this paper is to discuss the morphological properties and origins of the observed HF and VLF wave activity generated by human activity, detected at the low orbiting satellite CORONAS- I and AUREOL-3.

  7. 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 200 h 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

  8. Contrasting suspended covers reveal the impact of an artificial monolayer on heat transfer processes at the interfacial boundary layer.

    PubMed

    Pittaway, P; Martínez-Alvarez, V; Hancock, N

    2015-01-01

    The highly variable performance of artificial monolayers in reducing evaporation from water storages has been attributed to wind speed and wave turbulence. Other factors operating at the interfacial boundary layer have seldom been considered. In this paper, two physical shade covers differing in porosity and reflectivity were suspended over 10 m diameter water tanks to attenuate wind and wave turbulence. The monolayer octadecanol was applied to one of the covered tanks, and micrometeorological conditions above and below the covers were monitored to characterise diurnal variation in the energy balance. A high downward (air-to-water) convective heat flux developed under the black cover during the day, whereas diurnal variation in the heat flux under the more reflective, wind-permeable white cover was much less. Hourly air and water temperature profiles under the covers over 3 days when forced convection was minimal (low wind speed) were selected for analysis. Monolayer application reduced temperature gain in surface water under a downward convective heat flux, and conversely reduced temperature loss under an upward convective heat flux. This 'dual property' may explain why repeat application of an artificial monolayer to retard evaporative loss (reducing latent heat loss) does not inevitably increase water temperature. PMID:26524454

  9. Planetary atmospheres and ionospheres...

    E-print Network

    Withers, Paul

    Planetary atmospheres and ionospheres... How does a solar energetic particle event disrupt the ionosphere of Mars? Paul Withers withers@bu.edu BU Astronomy Symposium Boston, MA 2011.10.14 #12;What's going on? Katy Fallows ­ How does the lower ionosphere of Mars work? Zach Girazian ­ How does the main

  10. Ionospheric Correction Using Tomography

    E-print Network

    Stanford University

    Ionospheric Correction Using Tomography Andrew J. Hansen Todd Walter Per Enge Stanford University to the ight crew within six seconds. The ionosphere is the foremost impedi- ment to satisfying for estimat- ing the ionosphere in real-time. Previous research has established a connection between

  11. IONOSPHERIC THREATS TO THE INTEGRITY OF AIRBORNE GPS USERS A DISSERTATION

    E-print Network

    Stanford University

    IONOSPHERIC THREATS TO THE INTEGRITY OF AIRBORNE GPS USERS A DISSERTATION SUBMITTED, the ionospheric layer of the atmosphere, if left unchecked, can endanger the safety, or "integrity," of the single integrity through independent ionospheric monitoring by reference stations. However, the monitor stations

  12. The Vertical Structure of the Martian Ionosphere Martin Paetzold, Silvia Tellmann

    E-print Network

    Withers, Paul

    The Vertical Structure of the Martian Ionosphere Martin Paetzold, Silvia Tellmann University of Cologne The vertical structure of the Martian ionosphere consists of two main layers. Maximum electron-rays and associated electron impact ionization1. Interpreting the vertical shape of the Martian ionosphere is a key

  13. Response of the background ionosphere and the TIDs to atmospheric tides in the bottom F-Layer as determined from Dynasonde measurements

    NASA Astrophysics Data System (ADS)

    Negrea, Catalin; Zabotin, Nikolay; Bullett, Terry; Fuller-Rowell, Tim; Codrescu, Mihail

    2015-04-01

    The study of atmospheric tides is a particularly challenging proposition in the thermosphere-ionosphere. In addition to purely thermal tides propagating from the lower atmosphere, the spectrum of tidal waves is complicated by in-situ generation through EUV absorption and non-linear interactions with gravity and planetary waves. A largely unexplored aspect is the extent to which tidal amplitudes and phases exhibit variations about the steady state values on time scales shorter than the so called "setup time" of 10-15 days. Such a goal is currently beyond the capabilities of existing satellite missions. We address the issue by means of ground based Dynasonde measurements covering the bottom-side ionosphere. The inversion procedure produces vertical profiles of electron density and ionospheric tilts at a cadence of 2 minutes and with a vertical resolution typically below 1 km. Because of the normal day-night variability of the ionosphere, the sampling at any given altitude is non-uniform, with data gaps of up to 12 hours. An implementation of the Lomb-Scargle method is used to determine both the magnitude and phase of the diurnal, semidiurnal and terdiurnal harmonics. The raw measurements of electron density and the X (East-West) tilt, together with the derived zonal plasma density gradient are analyzed. Measurements are used from Wallops Island, Virginia and San Juan, Puerto Rico for 2013 and 2014. The dominant seasonal variability is captured using month-long subsets of the data. Day-to-day variations in tidal parameters are obtained by using a subset size of only several days. Finally, the contribution of non-linear interactions between tides and acoustic gravity waves is investigated by measuring the correlation between tidal to AGW spectral amplitudes. To our knowledge, this is the only method that allows for continuous observation of tidal induced perturbations over a broad range of thermospheric heights.

  14. 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.

  15. Dynamics of the artificially created vacancies in the monomolecular C60 layers

    NASA Astrophysics Data System (ADS)

    Olyanich, D. A.; Utas, T. V.; Zotov, A. V.; Saranin, A. A.

    2015-07-01

    Dynamics of single and double vacancies within the monomolecular C60 layer on the In-modified Au/Si(111) ?{ 3} ×?{ 3} surface have been studied by means of variable temperature scanning tunneling microscopy (STM). The vacancies were deliberately created in the layer using STM tip impact in the regimes below decomposition threshold. Single vacancy motion has been found to be a thermally activated process characterized by the activation energy of 1.5 ± 0.3 eV. This is an effective activation energy which agrees with the net value consisted of the term responsible for vacancy migration within the free-standing C60 layer, 0.88 eV and that for individual C60 migration on (Au, In)/Si(111) surface, 0.4 eV. Mobility of C60 vacancies has been found to be affected by In adatoms. It can be slowed down by more than an order of magnitude by deposition of only 0.2 monolayer of additional In. The double vacancies have been found to be more mobile than single vacancies in which its effect is provided by a specific rotational mechanism of their motion.

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

    SciTech Connect

    Kuo, Spencer P.

    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.

  17. 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.

  18. 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

    by persistent highspeed solar wind streams Page 1 of 1http ionospheric parameters in the F2 layer by persistent high speed solar wind streams M. H. Denton Department, Finland E. Turunen Sodankylä Geophysical Observatory, Sodankylä, Finland Highspeed solar wind streams

  19. Sputtered-silica defect layer in artificial opals: tunability of highly transmitted and reflected optical modes

    E-print Network

    Hong, Phan Ngoc; Coolen, Laurent; Maître, Agnès; Schwob, Catherine

    2013-01-01

    We propose an original and efficient method to engineer a defect between two well-ordered silica opals by sputtering silica on the top of the first one. As the amount of sputtered silica can be well controlled, it is also the case for the thickness of the layer and consequently for the spectral position of the defect mode. The optical response of these sandwich structures is studied in terms of specular reflection and transmission spectroscopy. Tunable highly transmitted and reflected optical modes are evidenced. The very good agreement between the experimental results and the simulations, run without fitting parameters, demonstrates the almost perfect order of the synthesized structures.

  20. Active experiments in the ionosphere and geomagnetic field variations

    NASA Astrophysics Data System (ADS)

    Sivokon, V. P.; Cherneva, N. V.; Khomutov, S. Y.; Serovetnikov, A. S.

    2014-11-01

    Variations of ionospheric-magnetospheric relation energy, as one of the possible outer climatology factors, may be traced on the basis of analysis of natural geophysical phenomena such as ionosphere artificial radio radiation and magnetic storms. Experiments on active impact on the ionosphere have been carried out for quite a long time in Russia as well. The most modern heating stand is located in Alaska; it has been used within the HAARP Program. The possibility of this stand to affect geophysical fields, in particular, the geomagnetic field is of interest.

  1. Yakov Alpert: Sputnik-1 and the first satellite ionospheric experiment

    NASA Astrophysics Data System (ADS)

    Kuznetsov, V. D.; Sinelnikov, V. M.; Alpert, S. N.

    2015-06-01

    The world 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 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. The paper describes the history and results of that experiment as well as the contribution of Ya.L. Alpert to ionospheric research. Ya.L. Alpert was one of the most famous and influential radiophysicists, the author of many fundamental studies and a number of classic books on the theory of propagation of electromagnetic waves, interaction of artificial bodies with ionospheric plasma, ionospheric radio scattering, and the use of satellite radio beacon methods for studying the ionosphere. We give in the paper some extracts from Ya.L. Alpert's research notes. They include the history of the publication of the results from recordings of the Sputnik-1 transmitter signals, and described the method of data analysis. The first scientific publication based on Sputnik-1 data is given in the abbreviated summary. At the end of the paper there is an outline of Ya.L. Alpert's scientific biography.

  2. 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.

  3. The effect of rocket launches on the ionosphere

    NASA Technical Reports Server (NTRS)

    Mendillo, M.

    1981-01-01

    A summary is provided of the known theoretical and observational aspects of 'inadvertent' rocket-exhaust effects upon the ionosphere. The atmospheric regions susceptible to rocket exhaust effects are examined. The major perturbations occur in those regions where the sun's radiation causes partial ionization to occur. These regions include the D, E, F1, and F2 regions of the ionosphere. It is found that the dominant cause of atmospheric perturbations due to rocket exhaust rests in the variety of chemical reactions that can occur between the exhaust material (usually molecular species, e.g., H2O, H2, CO2) and the neutral and ionized components of the atmosphere. The observational evidence for artificially-induced ionospheric modifications is discussed and a description is presented of physical processes responsible for ionospheric holes. Attention is given to scientific and technological interest in artificially-created ionospheric holes, and to the large-scale, artificially-induced depletion of the earth's ionosphere which could be monitored in connection with the launch of NASA's third High Energy Astrophysical Observatory.

  4. 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

  5. ULF Generation by Modulated Ionospheric Heating

    NASA Astrophysics Data System (ADS)

    Chang, C.; Labenski, J.; Wallace, T.; Papadopoulos, K.

    2013-12-01

    Modulated ionospheric heating experiments designed to generate ULF waves using the HAARP heater have been conducted since 2007. Artificial ULF waves in the Pc1 frequency range were observed from space and by ground induction magnetometers located in the vicinity of the heater as well as at long distances. Two distinct generation mechanisms of artificial ULF waves were identified. The first was electroject modulation under geomagnetically disturbed conditions. The second was pressure modulation in the E and F regions of the ionosphere under quiet conditions. Ground detections of ULF waves near the heater included both Shear Alfven waves and Magnetosonic waves generated by electrojet and/or pressure modulations. Distant ULF detections involved Magnetosonic wave propagation in the Alfvenic duct with pressure modulation as the most likely source. Summary of our observations and theoretical interpretations will be presented at the meeting. We would like to acknowledge the support provided by the staff at the HAARP facility during our ULF experiments.

  6. 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.

  7. Ionospheric disturbance overview

    NASA Technical Reports Server (NTRS)

    Rush, C. M.

    1980-01-01

    A program of research and exploratory development was undertaken to assess the potential impact of Satellite Power System operation on the ionosphere. The program relies on the utilization of ground-based ionospheric heating facilities in order to simulate the ionospheric heating that will come from the Satellite Power System. Thus far, the experimental program directed toward assessing telecommunications impacts has received the most attention, and little impact was observed on VLF, LF, and MF operations.

  8. Novel artificial hip joint: A layer of alumina on Ti-6Al-4V alloy formed by micro-arc oxidation.

    PubMed

    Khanna, Rohit; Kokubo, Tadashi; Matsushita, Tomiharu; Nomura, Yuuji; Nose, Norihiro; Oomori, Yoshiyuki; Yoshida, Takuya; Wakita, Koichi; Takadama, Hiroaki

    2015-10-01

    In many hip replacement surgeries, monolithic alumina is used as a femoral head due to its high wear resistance. However, it is liable to fracture under load bearing operations in artificial joints. We propose a promising way to overcome this limitation by forming a dense alumina layer onto a relatively tough substrate such as Ti-6Al-4V alloy to obtain high wear resistance on a material that can sustain relatively high toughness. For this purpose, Al metal powders were deposited onto Ti-6Al-4V alloy by cold spraying in N2 atmosphere. Interfacial adhesion between Al and the Ti alloy was improved by the formation of a reaction layer of Al3Ti between them by heating at 640 °C for 1h in air. Subsequently, micro-arc oxidation treatment was performed to oxidize Al. The oxidized layer was composed of an outer porous layer of ?-alumina and inner-most dense layer of ?-alumina. The ?-alumina layer was almost fully densified and exhibited high Vickers hardness almost equal to that of alumina ceramics used as the femoral head. Thus, the newly developed dense alumina/Ti alloy can be potentially used to produce the reliable bearing surfaces of artificial hip joint. PMID:26117770

  9. TRIO (Triplet Ionospheric Observatory) Mission

    NASA Astrophysics Data System (ADS)

    Lee, D.; Seon, J.; Jin, H.; Kim, K.; Lee, J.; Jang, M.; Pak, S.; Kim, K.; Lin, R. P.; Parks, G. K.; Halekas, J. S.; Larson, D. E.; Eastwood, J. P.; Roelof, E. C.; Horbury, T. S.

    2009-12-01

    Triplets of identical cubesats will be built to carry out the following scientific objectives: i) multi-observations of ionospheric ENA (Energetic Neutral Atom) imaging, ii) ionospheric signature of suprathermal electrons and ions associated with auroral acceleration as well as electron microbursts, and iii) complementary measurements of magnetic fields for particle data. Each satellite, a cubesat for ion, neutral, electron, and magnetic fields (CINEMA), is equipped with a suprathermal electron, ion, neutral (STEIN) instrument and a 3-axis magnetometer of magnetoresistive sensors. TRIO is developed by three institutes: i) two CINEMA by Kyung Hee University (KHU) under the WCU program, ii) one CINEMA by UC Berkeley under the NSF support, and iii) three magnetometers by Imperial College, respectively. Multi-spacecraft observations in the STEIN instruments will provide i) stereo ENA imaging with a wide angle in local times, which are sensitive to the evolution of ring current phase space distributions, ii) suprathermal electron measurements with narrow spacings, which reveal the differential signature of accelerated electrons driven by Alfven waves and/or double layer formation in the ionosphere between the acceleration region and the aurora, and iii) suprathermal ion precipitation when the storm-time ring current appears. In addition, multi-spacecraft magnetic field measurements in low earth orbits will allow the tracking of the phase fronts of ULF waves, FTEs, and quasi-periodic reconnection events between ground-based magnetometer data and upstream satellite data.

  10. Novel Stimulated Electromagnetic Emission Observations with Artificial Airglow Using RF Excitation with HAARP

    NASA Astrophysics Data System (ADS)

    Briczinski, S. J., Jr.; Bernhardt, P. A.; Siefring, C. L.; Michell, R.; Hampton, D. L.; Watkins, B. J.; Bristow, W. A.

    2014-12-01

    High power HF radio waves interacting with the ionosphere provide aeronomers with a unique space-based laboratory capability. The High-Frequency Active Auroral Research Program (HAARP) in Gakona, Alaksa is the world's largest heating facility, producing effective radiated powers in the gigawatt range. Experiments performed at HAARP have allowed researchers to study many non-linear effects of wave-plasma interactions. Stimulated Electromagnetic Emissions (SEE) are of interest to the ionospheric community for its diagnostic purposes. Typical SEE experiments at HAARP have focused on characterizing the parametric decay of the electromagnetic pump wave into several different wave modes such as upper and lower hybrid, ion acoustic, ion-Bernstein and electron-Bernstein. Recent HAARP experiments have used both conventional and novel techniques to excite ionospheric disturbances at gyroharmonic frequencies. Stable layers of artificial ionization have been generated using a "twisted beam" pattern with the heating array. Compared to pencil beam techniques, these layers are long-lived and produce their own unique SEE patterns. The "downshifted mass" or DSM has shown to be a strong indicator of artificial ionization generation. Additionally, several other previously uncharacterized SEE features have been observed. These emissions are under study to be linked with other heating phenomena such as enhanced optical emissions, ion and plasma line generation, HF radar backscatter and enhanced electron acceleration.

  11. An Initial Investigation of Ionospheric Gradients for Detection of Ionospheric Disturbances over Turkey

    NASA Astrophysics Data System (ADS)

    Koroglu, Meltem; Arikan, Feza; Koroglu, Ozan

    2015-04-01

    Ionosphere is an ionized layer of earth's atmosphere which affect the propagation of radio signals due to highly varying electron density structure. Total Electron Content (TEC) and Slant Total Electron Content (STEC) are convenient measures of total electron density along a ray path. STEC model is given by the line integral of the electron density between the receiver and GPS satellite. TEC and STEC can be estimated by observing the difference between the two GPS signal time delays that have different frequencies L1 (1575 MHz) and L2 (1227 MHz). During extreme ionospheric storms ionospheric gradients becomes larger than those of quiet days since time delays of the radio signals becomes anomalous. Ionosphere gradients can be modeled as a linear semi-infinite wave front with constant propagation speed. One way of computing the ionospheric gradients is to compare the STEC values estimated between two neighbouring GPS stations. In this so-called station-pair method, ionospheric gradients are defined by dividing the difference of the time delays of two receivers, that see the same satellite at the same time period. In this study, ionospheric gradients over Turkey are computed using the Turkish National Permanent GPS Network (TNPGN-Active) between May 2009 and September 2012. The GPS receivers are paired in east-west and north-south directions with distances less than 150 km. GPS-STEC for each station are calculated using IONOLAB-TEC and IONOLAB-BIAS softwares (www.ionolab.org). Ionospheric delays are calculated for each paired station for both L1 and L2 frequencies and for each satellite in view with 30 s time resolution. During the investigation period, different types of geomagnetic storms, Travelling Ionospheric Disturbances (TID), Sudden Ionospheric Disturbances (SID) and various earthquakes with magnitudes between 3 to 7.4 have occured. Significant variations in the structure of station-pair gradients have been observed depending on location of station-pairs, the path of the satellites, strength of the geomagnetic storms and type, depth and magnitude of the earthquakes. For a typical geomagnetic storm the gradients can get as high as 30 mm/km. For the earthquakes, both the magnitude and the structure of the ionospheric delay gradients exhibit strong variability. This study forms a basis for a comprehensive understanding of ionospheric variability for midlatitude GBAS and SBAS systems. This study is supported by a joint grant of TUBITAK 112E568 and RFBR 13-02-91370-CT_a.

  12. 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.

  13. 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.

  14. The vertical structure of the ionosphere of Mars P. Withers, K. Fallows, Z. Girazian, A. Lollo and M. Matta

    E-print Network

    Withers, Paul

    The vertical structure of the ionosphere of Mars P. Withers, K. Fallows, Z. Girazian, A. Lollo The vertical structure of the ionosphere of Mars con- sists of two main photochemical layers. Maximum electron-rays and associated electron impact ionization. Many vertical profiles of ionospheric elec- tron density have been

  15. Incredibly distant ionospheric responses to earthquake

    NASA Astrophysics Data System (ADS)

    Yusupov, Kamil; Akchurin, Adel

    2015-04-01

    Attempts to observe ionospheric responses to the earthquake has been going on for decades. In recent years, the greatest progress in the study of this question have GPS-measurements with simultaneous HF-measurements. The use of a dense network of GPS-receivers and getting with it sufficiently detailed two-dimensional maps of the total electron content (TEC) greatly clarified the nature of the ionospheric response to strong earthquakes. For ionospheric responses observation, that are remote more than 1000 km from the strong earthquakes epicentres, it is necessary to applying more sensitive methods than GPS. The most experience in the observation of the ionospheric responses to earthquakes accumulated with Doppler sounding. Using these measurements, ionospheric disturbances characteristic features (signature) have been allocated, which associated with the passage of Rayleigh waves on the surface. Particular, this Rayleigh wave signatures allocation is implemented in the Nostradamus coherent backscatter radar. The authors of this method suggest using radar techniques like a sensitive "ionospheric seismometer." The most productive allocation and studying of the vertical structure ionospheric responses could be ionosonde observations. However, their typical 15 minute sounding rate is quite sufficient for observing the regular ionosphere, but it is not enough for studying the ionospheric responses to earthquakes, because ionospheric responses is often seen only in one ionogram and it is absent in adjacent. The decisive factor in establishing the striking ionospheric response to the earthquake was the Tohoku earthquake in 2011, when there was three ionosondes distant at 870-2000 km from the epicentre. These ionosondes simultaneously showed distortion of the F1-layer traces as its multiple stratification (multiple-cusp signature - MCS), which generated by Rayleigh wave. Note that there was another fourth Japanese ionosonde. It is located a little further near boundaries area of medium-scale wave (387 km), which ionograms showed F-spread rather than MCS. Obviously, this is due to the vertical structure of the disturbance in the near zone. Another interesting feature associated with the vertical structure is a 1-2 minute advance of the appearance MCS in ionograms in relation to the advent of large-scale TEC disturbance. Naturally, such appearance time comparison can only be in such distances, when there are large-scale TEC disturbances (<1000-1200 km). Only MCS and Doppler shifts are observing at large distances. Look-back analysis of Japanese ionograms showed only eight cases of ionogram MCS observation from 43 strongest earthquakes (magnitude> 8) during the period from 1957-2011. This indirectly explains why it had to wait 50 years to recognize the MCS as a response to the earthquake. Previously performed statistical analyses showed that the MCS appear mainly from 9 to 15 LT and the epicentre distances range is the 800-6000 km. The MCS signatures at distances removing from earthquake epicentre more than 6000 km seen in ionosondes in Kazan, Kaliningrad and Sodankyla. These MCS in Kazan (as well in Kaliningrad, in Sodankyla) observed during the daytime from 9 to 15 LT. At this time, the height electron concentration gradient is significantly reducing in the F1-layer. This leads to the fact that a small disturbance of this gradient distorts some area of electron density profile and it reduces the value of the local gradient to zero (or even negative) values. Observations in our ionosonde first showed that the ionospheric response to the strong earthquakes (magnitude more than 8) could be observing at distances more than 15,000 km. In the daytime such responses appearance distort the form of the electron density profile of the F-layer, which is appearing in the ionograms as a multiple trace stratification of F1-layer.

  16. Rocket studies of the lower ionosphere

    NASA Technical Reports Server (NTRS)

    Bowhill, Sidney A.

    1990-01-01

    The earth's ionosphere in the altitude range of 50 to 200 km was investigated by rocket-borne sensors, supplemented by ground-based measurement. The rocket payloads included mass spectrometers, energetic particle detectors, Langmuir probes and radio propagation experiments. Where possible, rocket flights were included in studies of specific phenomena, and the availability of data from other experiments greatly increased the significance of the results. The principal ionospheric phenomena studied were: winter anomaly in radiowave absorption, ozone and molecular oxygen densities, mid-latitude sporadic-E layers, energetic particle precipitation at middle and low latitudes, ionospheric instabilities and turbulence, and solar eclipse effects in the D and E regions. This document lists personnel who worked on the project, and provides a bibliography of resultant publications.

  17. Exploring the ionosphere of Mars

    E-print Network

    Withers, Paul

    Exploring the ionosphere of Mars Paul Withers Boston University (withers@bu.edu) UK NAM St. Andrews and ionosphere of Mars NASA #12;www.nineplanets.org Mars in context Let's focus here 0.5 x R-Earth Carbon dioxide ionosphere Withers (2010) The ionosphere of Mars #12;How does the system work? Chemistry, dynamics

  18. Propagation of whistler mode waves through the ionosphere

    NASA Astrophysics Data System (ADS)

    Streltsov, A. V.; Woodroffe, J. R.; Huba, J. D.

    2012-08-01

    We present results from numerical studies of whistler mode wave propagation in the Earth's ionosphere when artificially created plasma ducts are present. Using realistic density profiles from the SAMI2 ionospheric code, we solve the two-dimensional electron magnetohydrodynamics equations to study the trans-ionospheric propagation of artificially generated whistler waves at HAARP latitudes (L = 4.9). Both ducted and non-ducted propagation is considered, but only ducted whistlers are able to propagate without a significant reduction in wave amplitude. The conditions necessary for the trapping of waves in both high- and low-density ducts are discussed with particular attention paid to the practical accessibility of these parameter regimes.

  19. Phenomena in the High-Latitude Ionospheric F Region Induced by a HF Heater Wave at Frequencies Near the Fourth Electron Gyroharmonic

    NASA Astrophysics Data System (ADS)

    Borisova, T. D.; Blagoveshchenskaya, N. F.; Kalishin, A. S.; Kosch, M.; Senior, A.; Rietveld, M. T.; Yeoman, T. K.; Hagstrom, I.

    2014-06-01

    We present the results of multi-instrument studies of the phenomena in the high-latitude ionospheric F region stimulated by high-power HF O-mode radio waves injected towards the magnetic zenith when the ratio of the heater frequency to the cutoff frequency of the F2 layer is near the fourth electron gyroharmonic. Based on the stimulated electromagnetic emission (SEE), spectral observations in the kilohertz and hertz frequency bands of detunings relative to the heater wave frequency, the behaviors of different parameters of the ionospheric plasma and small-scale artificial field-aligned irregularities are compared and analyzed. The coexistence of the thermal (resonance) parametric instability (TPI) and parametric decay (striction) instability (PDI) was found in the vicinity of the fourth gyroresonance harmonic.

  20. Modeling Ionospheric Electrodynamics (Invited)

    NASA Astrophysics Data System (ADS)

    Huba, J. D.

    2009-12-01

    We present modeling results of ionospheric electrodynamics using the 3D NRL ionosphere model SAMI3. Recently, SAMI3 has been upgraded to solve the potential equation that determines the electrostatic potential from the ionospheric conductances (Pedersen and Hall) and drivers: neutral wind, gravity, and parallel current systems. We present results showing the impact of different neutral wind models (e.g., HWM93, HWM07, TIMEGCM) on the dynamics of the low- to mid-latitude ionosphere, as well as the Region 1 and 2 current systems. We point out issues and concerns with obtaining an accurate specification of the global electric field within the context of existing models.(with J. Krall, G. Joyce, S. Slinker, and G. Crowley). Research supported by NASA and ONR

  1. Global Ionosphere Radio Observatory

    NASA Astrophysics Data System (ADS)

    Galkin, I. A.; Reinisch, B. W.; Huang, X. A.

    2014-12-01

    The Global Ionosphere Radio Observatory (GIRO) comprises a network of ground-based high-frequency vertical sounding sensors, ionosondes, with instrument installations in 27 countries and a central Lowell GIRO Data Center (LGDC) for data acquisition and assimilation, including 46 real-time data streams as of August 2014. The LGDC implemented a suite of technologies for post-processing, modeling, analysis, and dissemination of the acquired and derived data products, including: (1) IRI-based Real-time Assimilative Model, "IRTAM", that builds and publishes every 15-minutes an updated "global weather" map of the peak density and height in the ionosphere, as well as a map of deviations from the classic IRI climate; (2) Global Assimilative Model of Bottomside Ionosphere Timelines (GAMBIT) Database and Explorer holding 15 years worth of IRTAM computed maps at 15 minute cadence;. (3) 17+ million ionograms and matching ionogram-derived records of URSI-standard ionospheric characteristics and vertical profiles of electron density; (4) 10+ million records of the Doppler Skymaps showing spatial distributions over the GIRO locations and plasma drifts; (5) Data and software for Traveling Ionospheric Disturbance (TID) diagnostics; and (6) HR2006 ray tracing software mated to the "realistic" IRTAM ionosphere. In cooperation with the URSI Ionosonde Network Advisory Group (INAG), the LGDC promotes cooperative agreements with the ionosonde observatories of the world to accept and process real-time data of HF radio monitoring of the ionosphere, and to promote a variety of investigations that benefit from the global-scale, prompt, detailed, and accurate descriptions of the ionospheric variability.

  2. Dayside Ionospheric Superfountain

    NASA Technical Reports Server (NTRS)

    Tsurutani, Bruce T.; Verkhoglyadova, Olga P.; Mannucci, Anthony J.

    2010-01-01

    The Dayside Ionospheric Super-fountain modified SAMI2 code predicts the uplift, given storm-time electric fields, of the dayside near-equatorial ionosphere to heights of over 800 kilometers during magnetic storm intervals. This software is a simple 2D code developed over many years at the Naval Research Laboratory, and has importance relating to accuracy of GPS positioning, and for satellite drag.

  3. Electron Acceleration by High Power Radio Waves in the Ionosphere

    NASA Astrophysics Data System (ADS)

    Bernhardt, Paul

    2012-10-01

    At the highest ERP of the High Altitude Auroral Research Program (HAARP) facility in Alaska, high frequency (HF) electromagnetic (EM) waves in the ionosphere produce artificial aurora and electron-ion plasma layers. Using HAARP, electrons are accelerated by high power electrostatic (ES) waves to energies >100 times the thermal temperature of the ambient plasma. These ES waves are driven by decay of the pump EM wave tuned to plasma resonances. The most efficient acceleration process occurs near the harmonics of the electron cyclotron frequency in earth's magnetic field. Mode conversion plays a role in transforming the ES waves into EM signals that are recorded with ground receivers. These diagnostic waves, called stimulated EM emissions (SEE), show unique resonant signatures of the strongest electron acceleration. This SEE also provides clues about the ES waves responsible for electron acceleration. The electron gas is accelerated by high frequency modes including Langmuir (electron plasma), upper hybrid, and electron Bernstein waves. All of these waves have been identified in the scattered EM spectra as downshifted sidebands of the EM pump frequency. Parametric decay is responsible low frequency companion modes such as ion acoustic, lower hybrid, and ion Bernstein waves. The temporal evolution of the scattered EM spectrum indicates development of field aligned irregularities that aid the mode conversion process. The onset of certain spectral features is strongly correlated with glow plasma discharge structures that are both visible with the unaided eye and detectable using radio backscatter techniques at HF and UHF frequencies. The primary goals are to understand natural plasma layers, to study basic plasma physics in a unique ``laboratory with walls,'' and to create artificial plasma structures that can aid radio communications.

  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. Plasma irregularities associated with artificially created dusty plasmas during active space experiments

    NASA Astrophysics Data System (ADS)

    Scales, Wayne; Fu, Haiyang; Bordikar, Maitrayee

    It is well known that natural dust layers in the earth's mesosphere produce radar echoes. For example, one class of these radar echoes are referred to a Polar Mesopheric Summer Echoes PMSE and they are a well investigated phenomena and are a direct consequence of the sub-visible charged dust that exists at altitudes above visible noctilucent cloud NLC regions. The charging of electrons in the background plasma onto an irregular dust background results in electron irregularities that scatter the radar signals. Recent and upcoming active space ex-periments artificially create dust layers in the earth's ionosphere in a controlled manner to investigate the creation, evolution, dynamics, and charging of dust layers in the near earth space environment. A critically important process to be investigated during these experiments is the generation of plasma irregularities. Currently plasma irregularity generation in artificially created dust clouds in the space environment is a much less well understood and investigated issue even though it may have important consequences for the understanding of irregularities associated with natural dust layers. This presentation will address some of the physical pro-cesses expected to be important to generation of plasma irregularities during the early time phase after creation of an artificial dust cloud in the earth's ionosphere during an active release of dust in space. First, parameter regimes and their relevance to plasma irregularity generation during recent and upcoming space experiments will be discussed. Several possible physical mechanisms for generation of plasma irregularities will then be discussed. These include in-homogeneities in the boundary layer of the cloud as well as streaming of the dust particles relative to the background plasma. Next, computational plasma models will be described that may be used for investigating early time evolution after expansion of an artificial dust cloud in the ionosphere. These models will then be used to investigate the electrodynamics and possible plasma irregularity generation mechanisms after creation of an artificial dust cloud. Finally, some predictions will be made on the most important relevant processes for upcoming space experiments that may lead to radar signatures.

  6. Role of the Spore Coat Layers in Bacillus subtilis Spore Resistance to Hydrogen Peroxide, Artificial UV-C, UV-B, and Solar UV Radiation

    PubMed Central

    Riesenman, Paul J.; Nicholson, Wayne L.

    2000-01-01

    Spores of Bacillus subtilis possess a thick protein coat that consists of an electron-dense outer coat layer and a lamellalike inner coat layer. The spore coat has been shown to confer resistance to lysozyme and other sporicidal substances. In this study, spore coat-defective mutants of B. subtilis (containing the gerE36 and/or cotE::cat mutation) were used to study the relative contributions of spore coat layers to spore resistance to hydrogen peroxide (H2O2) and various artificial and solar UV treatments. Spores of strains carrying mutations in gerE and/or cotE were very sensitive to lysozyme and to 5% H2O2, as were chemically decoated spores of the wild-type parental strain. Spores of all coat-defective strains were as resistant to 254-nm UV-C radiation as wild-type spores were. Spores possessing the gerE36 mutation were significantly more sensitive to artificial UV-B and solar UV radiation than wild-type spores were. In contrast, spores of strains possessing the cotE::cat mutation were significantly more resistant to all of the UV treatments used than wild-type spores were. Spores of strains carrying both the gerE36 and cotE::cat mutations behaved like gerE36 mutant spores. Our results indicate that the spore coat, particularly the inner coat layer, plays a role in spore resistance to environmentally relevant UV wavelengths. PMID:10653726

  7. Imaging the Ionosphere Submitted by

    E-print Network

    Kassie, Endawoke Yizengaw

    Imaging the Ionosphere Submitted by Endawoke Yizengaw B.Sc. (Applied Physics), Addis Ababa.1. Project Overview 1 1.2. Discovery of the Ionosphere 3 1.3. How is the Ionosphere Formed? 6 1.3.1. Definition of the Ionospheric Regions (Structures) 7 1.3.1.1. D region 8 1.3.1.2. E region 8 1.3.1.3. F

  8. The Structure of the Mars Ionosphere M. Ptzold (1), S. Tellmann (1), K. Peter (1), M. Mendillo (2), P. Withers (2), B. Husler (3), D.P. Hinson (4),

    E-print Network

    Withers, Paul

    The Structure of the Mars Ionosphere M. Pätzold (1), S. Tellmann (1), K. Peter (1), M. Mendillo (2.paetzold@uni-koeln.de) Abstract The Mars Express Radio Science Experiment MaRS sounds the ionosphere of Mars at microwavelengths and 800 km. The Mars ionosphere consists of a lower secondary layer M1 at about 110 km, and the main layer

  9. 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.

  10. 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.

  11. 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.

  12. 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.

    2014-11-25

    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.

  13. Wet model of Saturn's ionosphere: water from the rings

    SciTech Connect

    Connerney, J.E.P.; Waite, J.H.

    1984-06-01

    Current theoretical models of Saturn's ionosphere are difficult to reconcile with the ionospheric electron density profiles obtained from the Pioneer and Voyager radio occultation observations and the large diurnal variation of maximum ionospheric electron density deduced from studies of Saturn lightning discharges. A model of Saturn's ionosphere is proposed in which water plays a major role as a minor constituent present by virtue of downward diffusion from an external source. This model of the Saturn ionosphere is a classical F2 type layer resulting from the photodissociative production of H(+) from H2 and rapid chemical loss due to a series of charge exchange reactions with water. A planet-wide influx of about 4x10 to the 7th power molecules/sec/sq cm of water from the rings is consistent with the observed ionospheric electron densities and estimates of influx due to micrometeoride bombardment of the rings. An enhanced influx of water occurs at latitudes (-38 deg, +44 deg) magnetically connected to the inner edge of Saturn's B ring which results from an electromagnetic erosion process contributing substantially to the (local) upper atmosphere water content. Present day influx at these latitudes is possibly as large as 2x10 to the 9th power molecules/sec/sq cm.

  14. 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…

  15. Planetary waves in rotating ionosphere

    SciTech Connect

    Khantadze, A. G.; Jandieri, V. G.; Jandieri, G. V.

    2008-06-15

    The problem of propagation of ultralong planetary waves in the Earth's upper atmosphere is considered. A new exact solution to the MHD equations for the ionosphere is obtained in spherical coordinates with allowance for the geomagnetic field and Earth's rotation. A general dispersion relation is derived for planetary waves in the ionospheric E and F regions, and the characteristic features of their propagation in a weakly ionized ionospheric plasma are discussed.

  16. 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.

  17. Meteoric Ions in Planetary Ionospheres

    NASA Technical Reports Server (NTRS)

    Pesnell, W. D.; Grebowsky, Joseph M.; Vondrak, Richard R. (Technical Monitor)

    2001-01-01

    Solar system debris, in the form of meteoroids, impacts every planet. The flux, relative composition and speed of the debris at each planet depends on the planet's size and location in the solar system. Ablation in the atmosphere evaporates the meteoric material and leaves behind metal atoms. During the ablation process metallic ions are formed by impact ionization. For small inner solar system planets, including Earth, this source of ionization is typically small compared to either photoionization or charge exchange with ambient molecular ions. For Earth, the atmosphere above the main deposition region absorbs the spectral lines capable of ionizing the major metallic atoms (Fe and Mg) so that charge exchange with ambient ions is the dominant source. Within the carbon dioxide atmosphere of Mars (and possibly Venus), photoionization is important in determining the ion density. For a heavy planet like Jupiter, far from the sun, impact ionization of ablated neutral atoms by impacts with molecules becomes a prominent source of ionization due to the gravitational acceleration to high incident speeds. We will describe the processes and location and extent of metal ion layers for Mars, Earth and Jupiter, concentrating on flagging the uncertainties in the models at the present time. This is an important problem, because low altitude ionosphere layers for the planets, particularly at night, probably consist predominantly of metallic ions. Comparisons with Earth will be used to illustrate the differing processes in the three planetary atmospheres.

  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. Solar cycle modulation of Titan's ionosphere

    NASA Astrophysics Data System (ADS)

    Edberg, N. J. T.; Andrews, D. J.; Shebanits, O.; Ågren, K.; Wahlund, J.-E.; Opgenoorth, H. J.; Cravens, T. E.; Girazian, Z.

    2013-08-01

    During the six Cassini Titan flybys T83-T88 (May 2012 to November 2012) the electron density in the ionospheric peak region, as measured by the radio and plasma wave science instrument/Langmuir probe, has increased significantly, by 15-30%, compared to previous average. These measurements suggest that a long?term change has occurred in the ionosphere of Titan, likely caused by the rise to the new solar maximum with increased EUV fluxes. We compare measurements from TA, TB, and T5, from the declining phase of solar cycle 23 to the recent T83-T88 measurements during cycle 24, since the solar irradiances from those two intervals are comparable. The peak electron densities normalized to a common solar zenith angle Nnorm from those two groups of flybys are comparable but increased compared to the solar minimum flybys (T16-T71). The integrated solar irradiance over the wavelengths 1-80nm, i.e., the solar energy flux, Fe, correlates well with the observed ionospheric peak density values. Chapman layer theory predicts that Nnorm?Fek, with k=0.5. We find observationally that the exponent k=0.54±0.18. Hence, the observations are in good agreement with theory despite the fact that many assumptions in Chapman theory are violated. This is also in good agreement with a similar study by Girazian and Withers (2013) on the ionosphere of Mars. We use this power law to estimate the peak electron density at the subsolar point of Titan during solar maximum conditions and find it to be about 6500cm-3, i.e., 85-160% more than has been measured during the entire Cassini mission.

  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. Mass spectrometry in ionospheric research.

    PubMed

    Ferguson, Eldon E

    2007-01-01

    Mass spectrometry played a key role in the development of the understanding of the earth's ionosphere. Of primary importance was its use for in situ atmospheric measurements of the ion and neutral composition of the atmosphere. Mass spectrometry has also played an essential role in the laboratory measurement of critical ionospheric molecular processes. Examples of both are given. PMID:17099890

  2. Midlatitude Ionospheric Dynamics and Disturbances

    NASA Astrophysics Data System (ADS)

    Kintner, Paul M., Jr.; Coster, Anthea J.; Fuller-Rowell, Tim; Mannucci, Anthony J.; Mendillo, Michael; Heelis, Roderick

    Filling the need for a 20-year lag in substantial consideration of the midlatitude ionosphere, this volume focuses on work that takes advantage of GPS and UV imaging from satellites over the past decade, two methods that have profoundly transformed our understanding of this stratum of the atmosphere. Its interdisciplinary content brings together researchers of the solar wind, magnetosphere, ionosphere, thermosphere, polar and equatorial ionospheres, and space weather. Modeling and assimilative imaging of the ionosphere and thermosphere show for the first time the complex and global impact of midlatitude ionospheric storms. The editors invited the leading experts in the following areas to contribute the chapters herein: • Characterization of Midlatitude Storms • Electric Field Coupling From the Heliosphere and Inner Magnetosphere • Thermospheric Control of the Midlatitude IonosphereIonospheric Irregularities • Experimental Methods and New Techniques These themes were chosen to create a path for understanding the midlatitude ionosphere. They continue to be largely valid and represent a coherent division of the subject matter. They will be critical for understanding space weather during the upcoming solar maximum. This book was inspired by the Chapman Conference of the same name held January 2007.

  3. 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.

  4. 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.

  5. 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.

  6. Ionospheric Estimation and Integrity Threat Detection

    E-print Network

    Stanford University

    Ionospheric Estimation and Integrity Threat Detection Andrew J. Hansen Todd Walter Y.C. Chao Per is focused on ionospheric estimation using tomographic inversion and integrity monitoring of WAAS ionospheric currently focuses on the study of GPS dual-frequency measure- ment calibration, WAAS ionospheric modeling

  7. 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.

  8. QSAR analysis for nano-sized layered manganese-calcium oxide in water oxidation: An application of chemometric methods in artificial photosynthesis.

    PubMed

    Shahbazy, Mohammad; Kompany-Zareh, Mohsen; Najafpour, Mohammad Mahdi

    2015-11-01

    Water oxidation is among the most important reactions in artificial photosynthesis, and nano-sized layered manganese-calcium oxides are efficient catalysts toward this reaction. Herein, a quantitative structure-activity relationship (QSAR) model was constructed to predict the catalytic activities of twenty manganese-calcium oxides toward water oxidation using multiple linear regression (MLR) and genetic algorithm (GA) for multivariate calibration and feature selection, respectively. Although there are eight controlled parameters during synthesizing of the desired catalysts including ripening time, temperature, manganese content, calcium content, potassium content, the ratio of calcium:manganese, the average manganese oxidation state and the surface of catalyst, by using GA only three of them (potassium content, the ratio of calcium:manganese and the average manganese oxidation state) were selected as the most effective parameters on catalytic activities of these compounds. The model's accuracy criteria such as R(2)test and Q(2)test in order to predict catalytic rate for external test set experiments; were equal to 0.941 and 0.906, respectively. Therefore, model reveals acceptable capability to anticipate the catalytic activity. PMID:25591399

  9. 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

  10. Regional model-based computerized ionospheric tomography using GPS measurements: IONOLAB-CIT

    NASA Astrophysics Data System (ADS)

    Tuna, Hakan; Arikan, Orhan; Arikan, Feza

    2015-10-01

    Three-dimensional imaging of the electron density distribution in the ionosphere is a crucial task for investigating the ionospheric effects. Dual-frequency Global Positioning System (GPS) satellite signals can be used to estimate the slant total electron content (STEC) along the propagation path between a GPS satellite and ground-based receiver station. However, the estimated GPS-STEC is very sparse and highly nonuniformly distributed for obtaining reliable 3-D electron density distributions derived from the measurements alone. Standard tomographic reconstruction techniques are not accurate or reliable enough to represent the full complexity of variable ionosphere. On the other hand, model-based electron density distributions are produced according to the general trends of ionosphere, and these distributions do not agree with measurements, especially for geomagnetically active hours. In this study, a regional 3-D electron density distribution reconstruction method, namely, IONOLAB-CIT, is proposed to assimilate GPS-STEC into physical ionospheric models. The proposed method is based on an iterative optimization framework that tracks the deviations from the ionospheric model in terms of F2 layer critical frequency and maximum ionization height resulting from the comparison of International Reference Ionosphere extended to Plasmasphere (IRI-Plas) model-generated STEC and GPS-STEC. The suggested tomography algorithm is applied successfully for the reconstruction of electron density profiles over Turkey, during quiet and disturbed hours of ionosphere using Turkish National Permanent GPS Network.

  11. Solar cycle modulation of Titan's ionosphere

    NASA Astrophysics Data System (ADS)

    Edberg, N. J.; Andrews, D. J.; Shebanits, O.; Agren, K.; Wahlund, J.; Opgenoorth, H. J.; Cravens, T.

    2013-12-01

    During the six Cassini Titan flybys T83-T88 (May 2012 - Nov 2012) the electron density in the ionospheric peak region measured by the RPWS/LP instrument, has increased significantly, by 15-30%, compared to previous average. These measurements suggest that a long-term change has occurred in the ionosphere of Titan, likely caused by the rise to the new solar maximum with increased EUV fluxes. We compare measurements from TA, TB and T5, from the declining phase of solar cycle 23 to the recent T83-T88 measurements, since the solar irradiances from those two groups were comparable. We show that the peak electron densities, normalised to a common solar zenith angle, N_norm from those two groups of flybys are also comparable, but increased compared to the solar minimum flybys (T16-T71). The integrated solar irradiance over the wavelengths 1-80 nm, i.e. the solar energy flux F_e correlates well with the observed ionospheric peak density values. Chapman layer theory predicts that N_norm ? F_e^k, with k=0.5. We find observationally that the exponent k = 0.54 × 0.18. Hence, the observations are in good agreement with theory despite the fact that many assumptions in Chapman theory are violated. This is also in good agreement with a similar study by Girazian and Withers (2013) on the ionosphere of Mars. We use this power-law to estimate the peak electron density at the sub-solar point of Titan during solar maximum conditions, and find it to be about 6500 cm-3, i.e., 85-160 % more than has been measured during the entire Cassini mission. (Top) TIMED/SEE measured solar EUV flux extrapolated to Saturn. Cassini Titan flybys span a large fraction of the solar cycle. (Bottom) RPWS/LP measurements of electron densities in Titan's ionosphere over the entire mission. During solar max, the densities are increased.

  12. 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).

  13. 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.

  14. Thermosphere-ionosphere coupling - An experiment in interactive modeling

    NASA Technical Reports Server (NTRS)

    Forbes, Jeffrey M.; Roble, Raymond G.

    1990-01-01

    Using the NCAR thermosphere general circulation model, a series of controlled experiments is performed to investigate the interactive coupling between ionospheric plasma densities and thermospheric neutral winds. The interaction is accomplished by parameterizing the F layer peak height, h(m)F2, in an empirical ionospheric model in terms of the meridional wind, v(south), and by forcing the h(m)F2 and the v(south) parameters to remain mutually coupled in a dynamical calculation. It was found that mutual coupling between forcing and meridional wind is weak during the daytime when the F layer exhibits a broad vertical structure. At night, when the F2 layer is more localized, the neutral dynamical structure is dependent on whether forcing is significantly above or below the altitude (about 275-300 km) at which ion drag effectively competes with viscosity in the neutral momentum balance.

  15. Onion artificial muscles

    NASA Astrophysics Data System (ADS)

    Chen, Chien-Chun; Shih, Wen-Pin; Chang, Pei-Zen; Lai, Hsi-Mei; Chang, Shing-Yun; Huang, Pin-Chun; Jeng, Huai-An

    2015-05-01

    Artificial muscles are soft actuators with the capability of either bending or contraction/elongation subjected to external stimulation. However, there are currently no artificial muscles that can accomplish these actions simultaneously. We found that the single layered, latticed microstructure of onion epidermal cells after acid treatment became elastic and could simultaneously stretch and bend when an electric field was applied. By modulating the magnitude of the voltage, the artificial muscle made of onion epidermal cells would deflect in opposing directions while either contracting or elongating. At voltages of 0-50 V, the artificial muscle elongated and had a maximum deflection of -30 ?m; at voltages of 50-1000 V, the artificial muscle contracted and deflected 1.0 mm. The maximum force response is 20 ?N at 1000 V.

  16. The Ionosphere and Ocean Altimetry

    NASA Technical Reports Server (NTRS)

    Lindqwister, Ulf J.

    1999-01-01

    The accuracy of satellite-based single-frequency radar ocean altimeters benefits from calibration of the total electron content (TEC) of the ionosphere below the satellite. Data from the global network of Global Positioning System (GPS) receivers provides timely, continuous, and globally well-distributed measurements of ionospheric electron content. We have created a daily automated process called Daily Global Ionospheric Map (Daily-GIM) whose primary purpose is to use global GPS data to provide ionospheric calibration data for the Geosat Follow-On (GFO) ocean altimeter. This process also produces an hourly time-series of global maps of the electron content of the ionosphere. This system is designed to deliver "quick-look" ionospheric calibrations within 24 hours with 90+% reliability and with a root-mean-square accuracy of 2 cm at 13.6 GHz. In addition we produce a second product within 72 hours which takes advantage of additional GPS data which were not available in time for the first process. The diagram shows an example of a comparison between TEC data from the Topographic Experiment (TOPEX) ocean altimeter and Daily-GIM. TEC are displayed in TEC units, TECU, where 5 TECU is 1 cm at 13.6 GHz. Data from a single TOPEX track is shown. Also shown is the Bent climatological model TEC for the track. Although the GFO satellite is not yet in its operational mode, we have been running Daily-GIM reliably (much better than 90%) with better than 2-cm accuracy (based on comparisons against TOPEX) for several months. When timely ephemeris files for the European Remote Sensing Satellite 2 (ERS-2) are available, daily ERS-2 altimeter ionospheric calibration files are produced. When GFO ephemeris files are made available to us, we produce GFO ionosphere calibration files. Users of these GFO ionosphere calibration files find they are a great improvement over the alternative International Reference Ionosphere 1995 (IRI-95) climatological model. In addition, the TOPEX orbit determination team at JPL has been using the global ionospheric maps to calibrate the single frequency GPS data from the TOPEX receiver, and report highly significant improvements in the ephemeris. The global ionospheric maps are delivered daily to the International GPS Service (IGS), making them available to the scientific community. Additional information is contained in the original.

  17. Seasonal changes in the amplitude and phase of diurnal and semidiurnal variations in parameters of the midlatitude F2 layer under minimum solar activity conditions according to the data of an ionospheric station in Irkutsk (52.5°N, 104.0°E)

    NASA Astrophysics Data System (ADS)

    Zolotukhina, N. A.; Pirog, O. M.; Polekh, N. M.

    2011-12-01

    We performed a statistical and spectral analysis of variations in two main parameters of the ionospheric F2 layer: critical frequency ( f 0F2) and peak height ( h m F2), recorded at an ionospheric station in Irkutsk (52.5°N, 104.0°E) in the period from December 1, 2006, to January 31, 2008, under low solar activity conditions. It was found that the f 0F2 and h m F2 variations contained quasi-harmonic oscillations with periods T n = 24/ n h ( n = 1-7). We studied the seasonal changes in the mean and median values of monthly f 0F2 and h m F2 time series, their spectra, as well as the amplitudes and phases of the diurnal ( n = 1) and semidiurnal ( n = 2) variations. It is shown that the amplitude of the diurnal f 0F2 variations was maximal in October-March 2007 and minimal in May-August 2007. The diurnal f 0F2 variations were maximal at noon in the winter months and at 1600 LT in the summer months. The semidiurnal f 0F2 variations had two maxima: a primary maximum in December and January and a secondary maximum in May-July. The maxima of semidiurnal f 0F2 variations were shifted from 0000 and 1200 LT in winter to 0900 and 2100 LT in summer.

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

    SciTech Connect

    Kopnin, S. I.; Popel, S. I.; Yu, M. Y.

    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.

  19. Stability of a cometary ionosphere/ionopause determined by ion-neutral friction

    SciTech Connect

    Ershkovich, A.I.; Mckenzie, J.F.; Axford, W.I.; Tel Aviv Univ.; Natal Univ., Durban; Max-Planck-Institut fuer Astronomie, Heidelberg )

    1989-09-01

    The linear MHD stability of the magnetic field structure discovered in the ionosphere of Comet Halley during the Giotto mission encounter is analyzed in terms of the hydromagnetic counterpart of the bounce frequency for a stratified atmosphere. The structure resulting from the balance between the Lorentz body force and the ion-neutral friction, as suggested by Cravens (1986) and by Ip and Axford (1982) turns out to be unstable. If, however, effects of the mass-loading (due to photoionization) and dissociative recombination are taken into account, the ionosphere becomes stabilized except for the Halley ionopause and adjacent ionosphere layer (of thickness 100 km) which remain unstable. 16 refs.

  20. The ionosphere and the Latin America VLF Network Mexico (LAVNet-Mex) station

    NASA Astrophysics Data System (ADS)

    Borgazzi, A.; Lara, A.; Paz, G.; Raulin, J. P.

    2014-08-01

    In order to detect and study the ionospheric response to solar flares (transient high energy solar radiation), we have constructed a radio receiver station at Mexico City, which is part of the “Latin American Very low frequency Network” (LAVNet-Mex). This station extends to the northern hemisphere the so called “South American VLF Network”. LAVNet is able to detect small changes in the amplitude and phase of VLF electromagnetic waves (generated by strong transmitters located all around the world) which are affected by changes of the lowest layer of the ionosphere, where these waves are “reflected”. In this way, LAVNet is an excellent tool to study the dynamics of the lower ionospheric layers. In this work we present a technical description and show the capabilities of the new LAVNet-Mex station. Moreover, as an example of its performance, we present the analysis of the ionospheric effects of two solar flares detected on October 16, 2010 and June 7, 2011.

  1. Determination of Ionospheric Total Electron Content Derived from Gnss Measurements

    NASA Astrophysics Data System (ADS)

    Inyurt, S.; Mekik, C.; Yildirim, O.

    2014-12-01

    Global Navigation Satellite System (GNSS) has been used in numerous fields especially related to satellite- based radio navigation system for a long time. Ionosphere, one of the upper atmosphere layers ranges from 60 km to 1500 km, is a dispersive medium and it includes a number of free electrons and ions. The ionization is mainly subject to the sun and its activity. Ionospheric activity depends also on seasonal, diurnal variations and geographical location. Total Electron Content (TEC), which is also called Slant Total Electron Content (STEC), is a parameter that changes according to ionospheric conditions and has highly variable structure. Furthermore, Vertical TEC (VTEC) can be explained as TEC value in the direction of zenith. Thanks to VTEC, TEC values can be modelled. TEC is measured in units of TECU and 1TECU= 1016 electrons/m2. Ionospheric modelling has a great importance for improving the accuracies of positioning and understanding the ionosphere. Thus, various models have been developed to detect TEC value in the last years. Single Layer Model (SLM) which provides determining TEC value and GPS positioning in the ionosphere accurately is one of the most commonly used models. SLM assumes that all free electrons are concentrated in a shell of infinitesimal thickness. In this paper SLM model was used to derive TEC values by means of Bernese 5.0 program developed by the University of Bern, Sweden. In this study, we have used regional ionosphere model to derive TEC value. First of all, GPS data have been collected from 10 stations in Turkey and 13 IGS stations for 7 days from 06.03.2010 to 12.03.2010. Then, Regional Ionosphere Model (RIM) is created with the reference of the GPS data. At the end of the process, the result files are stored as IONEX format. TEC results for those days are obtained with two hours interval. TEC variation related to the research area ranges from nearly 6 TECU to approximately 20 TECU. The obtained results show that TEC values start increasing until mid-days and reach peak value at 12:00 UT. After 12:00 UT it begins decreasing gradually towards night because of recombination of the ions. As a result, SLM is an effective model for mapping TEC values and determination of TEC variation can be used to identify many studies such as precursor of earthquakes, volcanic eruptions and launching site determination etc.

  2. Physical Model of Earthquake Ionospheric Precursors (Invited)

    NASA Astrophysics Data System (ADS)

    Namgaladze, A. A.

    2010-12-01

    The GPS derived ionospheric TEC (Total Electron Content) disturbances before earthquakes were discovered in the last years using global and regional TEC maps, TEC measurements over individual stations as well as measurements along individual GPS satellite passes. For strong mid-latitudinal earthquakes the seismo-ionospheric anomalies look like local TEC enhancements or decreases located in the vicinity of the forthcoming earthquake epicenter. Such structures are generated in the ionosphere for several days prior to the main shock. The amplitude of plasma modification reaches the value of 30-90% relative to the non-disturbed level. The zone of the anomaly maximum manifestation extends larger than 1500 km in latitude and 3500-4000 km in longitude. In case of strong low-latitudinal earthquakes there are effects related with the modification of the equatorial F2-region anomaly: deepening or filling of the ionospheric electron density trough over the magnetic equator. The possible physical mechanism which can cause such anomalies has been proposed. We consider that the most probable reason of the NmF2 and TEC disturbances observed before the earthquakes is the vertical drift of the F2-region ionospheric plasma under the influence of the zonal electric field of seismogenic origin related with the vertical transportation of the injected aerosols and radioactive particles. In the middle latitudes the upward electromagnetic drift, created by the eastward electric field, leads to the increase of the NmF2 and TEC due to the plasma transportation to the regions with lower concentration of the neutral molecules and, consequently, with lower loss rate of dominating ions O+ in the ion-molecular reactions. The electric field of the opposite direction (westward) creates the opposite - negative - effect in NmF2 and TEC. In the low latitude regions (near the geomagnetic equator) the increase of the eastward electric field leads to the deepening of the equatorial anomaly minimum (“trough” over the magnetic equator in the latitudinal distribution of electron concentration) due to the intensification of the fountain-effect. To check this hypothesis, the model calculations have been carried out with the use of the UAM (Upper Atmosphere Model) - the global numerical model of the Earth’s upper atmosphere. The electric potential distribution at the near-epicenter region boundary required for the electric field maintenance has been proposed. The upper atmosphere state, presumably foregone a strong earthquake, has been modeled by means of switching-on of additional sources of the electric field in the UAM electric potential equation which was solved numerically jointly with all other UAM equations (continuity, momentum and heat balance) for neutral and ionized gases. The efficiency of the proposed mechanism has been investigated by means of model calculations of the ionosphere response to the action of zonal electric field produced by seismogenic sources located at the middle and low latitudes. The results of the corresponding numerical model calculations of the electric field and its effects in the ionospheric F2-layer and plasmasphere have been presented. They have revealed a fine agreement with TEC anomalies observed before strong earthquakes at the middle and low latitudes both in spatial scales and in amplitude characteristics.

  3. Methods for Creation and Detection of Ultra-Strong Artificial Ionization in the Upper Atmosphere (Invited)

    NASA Astrophysics Data System (ADS)

    Bernhardt, P. A.; Siefring, C. L.; Briczinski, S. J.; Kendall, E. A.; Watkins, B. J.; Bristow, W. A.; Michell, R.

    2013-12-01

    The High Frequency Active Auroral Research Program (HAARP) transmitter in Alaska has been used to produce localized regions of artificial ionization at altitudes between 150 and 250 km. High power radio waves tuned near harmonics of the electron gyro frequency were discovered by Todd Pederson of the Air Force Research Laboratory to produce ionosonde traces that looked like artificial ionization layers below the natural F-region. The initial regions of artificial ionization (AI) were not stable but had moved down in altitude over a period of 15 minutes. Recently, artificial ionization has been produced by the 2nd, 3rd, 4th and 6th harmonics transmissions by the HAARP. In march 2013, the artificial ionization clouds were sustained for more the 5 hours using HAARP tuned to the 4 fce at the full power of 3.6 Mega-Watts with a twisted-beam antenna pattern. Frequency selection with narrow-band sweeps and antenna pattern shaping has been employed for optimal generation of AI. Recent research at HAARP has produced the longest lived and denser artificial ionization clouds using HF transmissions at the harmonics of the electron cyclotron frequency and ring-shaped radio beams tailored to prevent the descent of the clouds. Detection of artificial ionization employs (1) ionosonde echoes, (2) coherent backscatter from the Kodiak SuperDARN radar, (3) enhanced ion and plasma line echoes from the HAARP MUIR radar at 400 MHz, (4) high resolution optical image from ground sites, and (5) unique stimulated electromagnetic emissions, and (6) strong UHF and L-Band scintillation induced into trans-ionospheric signals from satellite radio beacons. Future HAARP experiments will determine the uses of long-sustained AI for enhanced HF communications.

  4. Very Low Frequency (VLF) studies of Ionospheric/Magnetospheric Electromagnetic phenomena in Indian Low Latitude Region using AWESOME Receivers

    NASA Astrophysics Data System (ADS)

    Singh, R.; Veenadhari, B.; Alex, S.

    2006-11-01

    Ground based observations of whistler mode ELF/VLF (300 Hz 30 kHz) waves are considered as an important remote sensing tool for the investigation of upper atmosphere and magnetosphere. These VLF waves find their origin in various natural and artificial phenomena, the natural sources include thunderstorms, lightning and associated phenomena. Despite of the fact that conjugate region of India having less lightning activity as it lies in Indian Ocean and also the height of the magnetic field lines connecting the conjugate regions lies in the ionosphere/atmosphere, lot of interesting VLF activity through the magnetosphere is observed in Indian low latitude region. Sub-ionospheric VLF transmissions propagating inside the Earth-ionosphere wave-guide is also being widely used for investigating sudden ionospheric perturbations in lower part of the ionosphere. For this purpose we propose to monitor VLF signals continuously at several locations in Indian sector with the help of AWESOME VLF receivers from Stanford University. AWESOME receivers are capable of collecting both broadband (used for the study of natural signals) and narrowband (sub-ionospheric VLF signals corresponding to VLF transmitters) data. The obtained data will enable us to understand the generation and propagation mechanism of radio atmospherics from lightning flashes, magnetospheric whistlers, VLF emissions and other naturally occurring phenomena. Narrowband sub- ionospheric VLF signals and ground based geomagnetic data in Indian low latitude region will help us to study sudden ionospheric disturbances associated with transient phenomena like solar flares, geomagnetic storms, cosmic gamma-ray flares, etc.

  5. 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.

  6. Low latitude ionosphere response to severe geomagnetic storms

    NASA Astrophysics Data System (ADS)

    Batista, I. S.; Abdu, M. A.; Bertoni, F.; Souza, J. R.

    During the occurrence of a geomagnetic storm a series of disturbances can affect the ionosphere at all latitudes and longitudes. Over the low latitudes, the ionospheric F layer height can be affected mainly by magnetospheric electric fields that penetrate to the low latitudes and by disturbance dynamo electric fields. Disturbed meridional winds have minor effect over low latitudes and disturbed zonal winds are important only near sunset. The ionospheric heights are directly affected by the disturbed electric fields through the effect of the ExB drift. The density distribution and the equatorial ionization anomaly are also affected in the process due to occurrence of a disturbed vertical drift. Changes in the atmospheric composition due to disturbance winds are also responsible for part of the electron density changes during magnetic storms. The solar events that occurred in the end of October 2003 gave rise to very strong geomagnetic disturbances that peaked twice with Dst values reaching less that -300 nT between 00:00 UT on the 29th and 04:00 UT on the 30th, and between 22:00 UT on the 30th and 01:00 UT on the 31st. Several disturbances were observed in the ionospheric stations over the Brazilian region, but the most severe of them occurred on the evening (around 21 UT) of October 30th. A very strong vertical drift shifted the ionosphere over the equatorial station São Luís to heights above 800 km. The effect was observed also at the low- and sub-tropical stations Fortaleza and Cachoeira Paulista, but it was less intense over those latitudes, due to the higher efficiency of the ExB drift at the magnetic equator. The ionospheric effects of these very strong geomagnetic storms over the Brazilian region are investigated in this work, and the results are compared to previous results of other very intense storms.

  7. 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.

  8. 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.

  9. 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.

    2015-08-01

    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), while the other 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 modeling 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 in temperature level of the ionospheric residual at 40 km from about -2.2 to -0.2 K.

  10. 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.

  11. Ionospheric Research Issues for SBAS A White Paper SBAS Ionospheric Working Group

    E-print Network

    Boneh, Dan

    Ionospheric Research Issues for SBAS ­ A White Paper SBAS Ionospheric Working Group February 2003 OUTLINE Executive Summary 1. Introduction 2. Ionospheric Regions 2.1. Mid-latitude Regions 2.2. Equatorial and Scintillation Effects 4. Summary of Ionospheric Effects by Region and Phenomena 5. Mitigation Techniques Against

  12. Beating HF waves to generate VLF waves in the ionosphere

    NASA Astrophysics Data System (ADS)

    Kuo, Spencer; Snyder, Arnold; Kossey, Paul; Chang, Chia-Lie; Labenski, John

    2012-03-01

    Beat-wave generation of very low frequency (VLF) waves by two HF heaters in the ionosphere is formulated theoretically and demonstrated experimentally. The heater-induced differential thermal pressure force and ponderomotive force, which dominate separately in the D and F regions of the ionosphere, drive an electron current for the VLF emission. A comparison, applying appropriate ionospheric parameters shows that the ponderomotive force dominates in beat-wave generation of VLF waves. Three experiments, one in the nighttime in the absence of D and E layers and two in the daytime in the presence of D and E layers, were performed. X mode HF heaters of slightly different frequencies were transmitted at CW full power. VLF waves at 10 frequencies ranging from 3.5 to 21.5 kHz were generated. The frequency dependencies of the daytime and nighttime radiation intensities are quite similar, but the nighttime radiation is much stronger than the daytime one at the same radiation frequency. The intensity ratio is as large as 9 dB at 11.5 kHz. An experiment directly comparing VLF waves generated by the beat-wave approach and by the amplitude modulation (AM) approach was also conducted. The results rule out the likely contribution of the AM mechanism acting on the electrojet and indicate that beat-wave in the VLF range prefers to be generated in the F region of the ionosphere through the ponderomotive nonlinearity, consistent with the theory. In the nighttime experiment, the ionosphere was underdense to the HF heaters, suggesting a likely setting for effective beat-wave generation of VLF waves by the HF heaters.

  13. Ionospheric effects of rocket exhaust products: Skylab and HEAO-C

    SciTech Connect

    Zinn, J.; Sutherland, C.D.; Duncan, L.M.; Stone, S.N.

    1981-01-01

    This paper is about ionospheric F-layer depletions produced by chemical reactions with exhaust gases from large rockets. It describes a 2-dimensional computer model of the ionosphere, and it compares model results with experimental data on the structure and variability of the natural ionosphere, as well as data on ionospheric holes produced by the launches of Skylab (May, 1973) and HEAO-C (September, 1979). It also describes measurements made in conjunction with the HEAO-C launch. The computer model includes an approximate representation of thermospheric tidal winds and E fields in addition to vertical motions associated with diurnal changes in temperature. The computed ionospheric structure is sensitive to all the above. For a small number of cases, results are compared of computations of the normal diurnal variations of ionospheric structure with incoherent scatter and total electron content data. Computations of ionospheric depletions from the Skylab and HEAO-C launches are in satisfactory agreement with the observations. The winds appear to be essential for interpretation of the Skylab results.

  14. Artificial Limbs

    MedlinePLUS

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

  15. Whistler propagation in ionospheric density ducts: Simulations and DEMETER observations

    NASA Astrophysics Data System (ADS)

    Woodroffe, J. R.; Streltsov, A. V.; Vartanyan, A.; Milikh, G. M.

    2013-11-01

    On 16 October 2009, the Detection of Electromagnetic Emissions Transmitted from Earthquake Regions (DEMETER) satellite observed VLF whistler wave activity coincident with an ionospheric heating experiment conducted at HAARP. At the same time, density measurements by DEMETER indicate the presence of multiple field-aligned enhancements. Using an electron MHD model, we show that the distribution of VLF power observed by DEMETER is consistent with the propagation of whistlers from the heating region inside the observed density enhancements. We also discuss other interesting features of this event, including coupling of the lower hybrid and whistler modes, whistler trapping in artificial density ducts, and the interference of whistlers waves from two adjacent ducts.

  16. Artificial plasma cusp generated by upper hybrid instabilities in HF heating experiments at HAARP

    NASA Astrophysics Data System (ADS)

    Kuo, Spencer; Snyder, Arnold

    2013-05-01

    High Frequency Active Auroral Research Program digisonde was operated in a fast mode to record ionospheric modifications by the HF heating wave. With the O mode heater of 3.2 MHz turned on for 2 min, significant virtual height spread was observed in the heater off ionograms, acquired beginning the moment the heater turned off. Moreover, there is a noticeable bump in the virtual height spread of the ionogram trace that appears next to the plasma frequency (~ 2.88 MHz) of the upper hybrid resonance layer of the HF heating wave. The enhanced spread and the bump disappear in the subsequent heater off ionograms recorded 1 min later. The height distribution of the ionosphere in the spread situation indicates that both electron density and temperature increases exceed 10% over a large altitude region (> 30 km) from below to above the upper hybrid resonance layer. This "mini cusp" (bump) is similar to the cusp occurring in daytime ionograms at the F1-F2 layer transition, indicating that there is a small ledge in the density profile reminiscent of F1-F2 layer transitions. Two parametric processes exciting upper hybrid waves as the sidebands by the HF heating waves are studied. Field-aligned purely growing mode and lower hybrid wave are the respective decay modes. The excited upper hybrid and lower hybrid waves introduce the anomalous electron heating which results in the ionization enhancement and localized density ledge. The large-scale density irregularities formed in the heat flow, together with the density irregularities formed through the parametric instability, give rise to the enhanced virtual height spread. The results of upper hybrid instability analysis are also applied to explain the descending feature in the development of the artificial ionization layers observed in electron cyclotron harmonic resonance heating experiments.

  17. Whistler wave-induced ionospheric plasma turbulence: Source mechanisms and remote sensing

    NASA Astrophysics Data System (ADS)

    Pradipta, R.; Rooker, L. A.; Whitehurst, L. N.; Lee, M. C.; Ross, L. M.; Sulzer, M. P.; Gonzalez, S.; Tepley, C.; Aponte, N.; See, B. Z.; Hu, K. P.

    2013-10-01

    We report a series of experiments conducted at Arecibo Observatory in the past, aimed at the investigation of 40.75 kHz whistler wave interactions with ionospheric plasmas and the inner radiation belts at L=1.35. The whistler waves are launched from a Naval transmitter (code-named NAU) operating in Aguadilla, Puerto Rico at the frequency and power of 40.75 kHz and 100 kW, respectively. Arecibo radar, CADI, and optical instruments were used to monitor the background ionospheric conditions and detect the induced ionospheric plasma effects. Four-wave interaction processes produced by whistler waves in the ionosphere can excite lower hybrid waves, which can accelerate ionospheric electrons. Furthermore, whistler waves propagating into the magnetosphere can trigger precipitation of energetic electrons from the radiation belts. Radar and optical measurements can distinguish wave-wave and wave-particle interaction processes occurring at different altitudes. Electron acceleration by different mechanisms can be verified from the radar measurements of plasma lines. To facilitate the coupling of NAU-launched 40.75 kHz whistler waves into the ionosphere, we can rely on naturally occurring spread F irregularities to serve as ionospheric ducts. We can also use HF wave-created ducts/artificial waveguides, as demonstrated in our earlier Arecibo experiments and recent Gakona experiments at HAARP. The newly constructed Arecibo HF heater will be employed in our future experiments, which can extend the study of whistler wave interactions with the ionosphere and the magnetosphere/radiation belts as well as the whistler wave conjugate propagation between Arecibo and Puerto Madryn, Argentina.

  18. 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.

  19. Ionospheric slab thickness and its seasonal variations observed by GPS

    NASA Astrophysics Data System (ADS)

    Jin, Shuanggen; Cho, Jung-Ho; Park, Jung-Uk

    2007-11-01

    The ionospheric slab thickness, the ratio of the total electron content (TEC) to the F2-layer peak electron density (NmF2), is closely related to the shape of the ionospheric electron density profile Ne (h) and the TEC. Therefore, the ionospheric slab thickness is a significant parameter representative of the ionosphere. In this paper, the continuous GPS observations in South Korea are firstly used to study the equivalent slab thickness (EST) and its seasonal variability. The averaged diurnal medians of December January February (DJF), March April May (MAM), June July August (JJA) and September October November (SON) in 2003 have been considered to represent the winter, spring, summer and autumn seasons, respectively. The results show that the systematic diurnal changes of TEC, NmF2 and EST significantly appeared in each season and the higher values of TEC and NmF2 are observed during the equinoxes (semiannual anomaly) as well as in the mid-daytime of each season. The EST is significantly smaller in winter than in summer, but with a consistent variation pattern. During 14 16 LT in daytime, the larger EST values are observed in spring and autumn, while the smaller ones are in summer and winter. The peaks of EST diurnal variation are around 10 18 LT which are probably caused by the action of the thermospheric wind and the plasmapheric flow into the F2-region.

  20. Interplanetary Radio Transmission Through Serial Ionospheric and Material Barriers

    SciTech Connect

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

    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.

  1. 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.

  2. 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…

  3. 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.

  4. Automated Ionospheric Front Velocity Estimation Algorithm for

    E-print Network

    Stanford University

    Automated Ionospheric Front Velocity Estimation Algorithm for Ground-Based Augmentation Systems, and Sigrid Close Stanford University ABSTRACT Ionospheric anomalies, which may occur during severe ionospheric storms, could pose integrity threats to Ground-based Augmentation System (GBAS) users [1], [2], [3

  5. Introduction to the Ionosphere Alan Aylward

    E-print Network

    Introduction to the Ionosphere Alan Aylward Atmospheric Physics Laboratory,UCL #12;Beginnings.... · The ionosphere is that part of the atmosphere where radio propagation is affected (even that is a fairly sounder: · The ionospheric sounder or ionosonde became the main tool of research into this for 20 years

  6. LWA Ionospheric Workshop Christopher Watts1

    E-print Network

    Ellingson, Steven W.

    LWA 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 June 28, 2009. The purpose of the workshop was to bring together the ionospheric and astronomy

  7. Radar Soundings of the Ionosphere of Mars

    E-print Network

    Gurnett, Donald A.

    Radar Soundings of the Ionosphere of Mars D. A. Gurnett,1 * D. L. Kirchner,1 R. L. Huff,1 D. D4 We report the first radar soundings of the ionosphere of Mars with the MARSIS (Mars Advanced Radar for Subsurface and Ionosphere Sounding) instrument on board the orbiting Mars Express spacecraft. Several types

  8. Ionosphere Weighted GPS Cycle Ambiguity Resolution1

    E-print Network

    Calgary, University of

    1 Ionosphere Weighted GPS Cycle Ambiguity Resolution1 George Chia Liu, Gérard Lachapelle Department approach to mitigate the high ionospheric effect has been either to reduce the inter-station separation or to form ionosphere-free observables. Neither is satisfactory: the first restricts the operating range

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

    SciTech Connect

    Tang, Wenbo Mahalov, Alex

    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.

  10. The High-Latitude Ionosphere and Its Effects on Radio Propagation

    NASA Astrophysics Data System (ADS)

    Moses, Ronald W., Jr.

    2004-05-01

    The ionosphere is indeed the place where Earth and space come together. Correspondingly, the ionosphere is subject to the details and complexities of both Earth and space. If one is to develop a logical understanding of even a limited portion of the ionosphere, that knowledge will be constructed on a foundation of many facts of nature. Awareness of those facts will in turn be supported by a vast historical array of scientific effort to ascertain the fundamentals of Earth and space that combine to form the ionosphere as we know it. Fortunately for us, R. D. Hunsucker and J. K. Hargreaves have written a book that goes from the Earth up and comes from the Sun down to arrive at a remarkably detailed physical description of the ionosphere and its impact on human activities, especially radio-frequency (RF) communications. The High-Latitude Ionosphere and its Effects on Radio Propagation is a bit of a misnomer, because the book covers many more topics than its title suggests. The authors set the stage by developing a detailed picture of the density, temperature, chemical, neutral, and charge states of the atmosphere-ionosphere system. Basic models of the ionization and recombination processes are presented with supporting mathematics and graphical examples. Concepts such as the Chapman production function are introduced and applied, whereby ionizing solar radiation produces electron-ion pairs. One can then grasp how the so-called D, E, and F layers of the ionosphere are related to the ionization of specific molecular species. Along the way, the authors are careful to introduce the extensive nomenclature of ionospheric descriptors. There is a comfortable relationship of prose, mathematics, and graphical material. Reading this book is a pleasure for the scientifically curious mind.

  11. Ionospheric informatics and empirical modelling; Proceedings of Workshop XII of the 27th COSPAR Plenary Meeting, Espoo, Finland, July 18-29, 1988

    NASA Astrophysics Data System (ADS)

    Rawer, K.; Bradley, P. A.

    The present conference discusses topics in the fields of plasma densities, plasma mapping, plasma temperatures, ion composition and drift, and applications of the IRI spacecraft. Attention is given to an expression for the electron density profile below the F2 peak, aeronomical calculations of valley size in the ionosphere, a novel method for standardizing Langmuir-probe data, the mapping of the critical frequency of the F2 layer, and the ionospheric mapping significance of longitude features in topside sounder data. Also discussed are atmospheric gravity waves and ionospheric modeling, solar activity variations of ionospheric plasma temperatures, variations of He ion density from theoretical considerations, digital ionogram data, and oblique propagation studies.

  12. 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.

  13. Intensity of nightside MARSIS AIS surface reflections and implications for low-altitude ionospheric densities

    NASA Astrophysics Data System (ADS)

    N?mec, F.; Morgan, D. D.; Diéval, C.; Gurnett, D. A.

    2015-04-01

    Spacecraft radar sounding signals at frequencies higher than the ionospheric peak plasma frequency are not reflected by the ionosphere. Instead, they make it to the ground where they are reflected by the planetary surface. We analyze the intensity of the surface reflections measured by the Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) ionospheric radar sounder on board the Mars Express spacecraft. Apart from the surface reflectivity and the spacecraft altitude, the detected intensity of surface reflections is controlled primarily by the signal attenuation during the ionospheric propagation. We focus on the nightside region, where the ionospheric densities in the main layer are too low to cause a significant attenuation and allow sampling of the surface reflections at frequencies down to 3 MHz. The attenuation occurs mainly at altitudes below 100 km, where the electron-neutral collision frequency is a maximum. The intensity of surface reflections can thus serve as a proxy for electron densities at low altitudes not accessible by the direct ionospheric radar sounding. We analyze the intensity of surface reflections as a function of relevant controlling parameters. The intensity of surface reflections is lower at higher solar zenith angles on the nightside and during the periods of larger solar activity. Moreover, it exhibits a seasonal variation that is related to the dust storm occurrence. The intensity of surface reflections is lower in areas of closed magnetic field lines, suggesting that nightside electron densities behave rather differently at low altitudes than at higher altitudes. This is confirmed by comparison with simultaneous observations of the main ionospheric layer.

  14. 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

  15. Theory for modeling the equatorial evening ionosphere and the origin of the shear in the horizontal plasma flow

    SciTech Connect

    Haerendel, G.; Eccles, J.V.; Cakir, S. )

    1992-02-01

    Companion papers in this series present (1) the role of equatorial E region postsunset ionosphere, (2) the origin of horizontal plasma shear flow in the postsunset equatorial ionosphere (this paper), (3) the Colored Bubbles experiments results, and (4) computer simulations of artificial initiation of plasma density depletions (bubbles) in the equatorial ionosphere. Within this paper, equations describing the time evolution of the equatorial ionosphere are developed using flux tube integrated and flux tube weighted quantities which model the chemistry, dynamics, and electrodynamics of the equatorial ionosphere. The resulting two-dimensional set of equations can be used to investigate equatorial ionosphere. The resulting two-dimensional set of equations can be used to investigate equatorial electric fields neglecting small-scale phenomena ({lambda} < 1 km). An immediate result derived from the integrated current equations is an equation describing the physics of the shear in the horizontal flow of the equatorial plasma during the evening hours. The profile of the horizontal flow has three important contributing terms relating to the neutral wind dynamo, Hall conduction, and the equatorial electrojet current divergence. Using a one-dimensional model of the velocity shear equation and the integrated ionosphere transport equations, a time history of the development of the shear feature during postsunset hours is presented. The one-dimensional model results are compared to the velocity shear measurements from the Colored Bubbles experiments.

  16. Radar soundings of the ionosphere of Mars.

    PubMed

    Gurnett, D A; Kirchner, D L; Huff, R L; Morgan, D D; Persoon, A M; Averkamp, T F; Duru, F; Nielsen, E; Safaeinili, A; Plaut, J J; Picardi, G

    2005-12-23

    We report the first radar soundings of the ionosphere of Mars with the MARSIS (Mars Advanced Radar for Subsurface and Ionosphere Sounding) instrument on board the orbiting Mars Express spacecraft. Several types of ionospheric echoes are observed, ranging from vertical echoes caused by specular reflection from the horizontally stratified ionosphere to a wide variety of oblique and diffuse echoes. The oblique echoes are believed to arise mainly from ionospheric structures associated with the complex crustal magnetic fields of Mars. Echoes at the electron plasma frequency and the cyclotron period also provide measurements of the local electron density and magnetic field strength. PMID:16319123

  17. IMF-By effect on the mid-latitude ionosphere

    NASA Astrophysics Data System (ADS)

    Maruyama, Takashi; Jin, Hidekatsu

    The primary factor that controls ionospheric total electron content (TEC) variations is solar UV/EUV radiations through the ionization of the thermospheric neutral particles and through the modification of the thermosphere. Changes in temperature and composition of the neutral atmosphere and the atmospheric circulation greatly affect the ionospheric electron density. Because such a relationship between the solar spectral irradiance and the ionospheric TEC is highly complex, we applied an artificial neural network (ANN) technique that has a great capability of function approximation of complex systems to model solar irradiance effects on TEC. Three solar proxies, F_{10.7}, SOHO_SEM_{26-34} EUV emission index, and MgII_c-w-r were chosen as input parameters to the ANN-TEC model. Another channel of energy flow from the sun to the earth’s ionosphere is the solar wind. The am index and several solar wind magnetosphere coupling functions were chosen as additional inputs to the ANN to model the effects of magnetic disturbances. Somewhat minor but interesting effects on TEC variations emerged when the major effects of solar irradiance and magnetic disturbances were removed. We analyzed the time series of the residual error in TEC prediction by using a wavelet transformation, which revealed a periodic increase in error approximately every 27 days in the summer. Possible origins of the error are (1) insufficient modeling of the solar activity effect, (2) lunar tidal forcing, (3) coupling with planetary waves in the lower atmosphere, and (4) solar wind effects. Examinations refused the first three possibilities. We investigated solar wind parameters that are not concerned in geomagnetic disturbances. The 27-day periodic error during the summer disappeared when the IMF-By component and the solar wind velocity were included in the input space of the ANN. Possible explanation of the IMF-By effect is discussed in terms of changes in the thermospheric general circulation pattern.

  18. A Campaign to Study Equatorial Ionospheric Phenomena over Guam

    NASA Astrophysics Data System (ADS)

    Habash Krause, L.; Balthazor, R.; Dearborn, M.; Enloe, L.; Lawrence, T.; McHarg, M.; Petrash, D.; Reinisch, B. W.; Stuart, T.

    2007-05-01

    With the development of a series of ground-based and space-based experiments, the United States Air Force Academy (USAFA) is in the process of planning a campaign to investigate the relationship between equatorial ionospheric plasma dynamics and a variety of space weather effects, including: 1) ionospheric plasma turbulence in the F region, and 2) scintillation of radio signals at low latitudes. A Digisonde Portable Sounder DPS-4 will operate from the island of Guam (with a magnetic latitude of 5.6° N) and will provide measurements of ionospheric total electron content (TEC), vertical drifts of the bulk ionospheric plasma, and electron density profiles. Additionally, a dual-frequency GPS TEC/scintillation monitor will be located along the Guam magnetic meridian at a magnetic latitude of approximately 15° N. In campaign mode, we will combine these ground-based observations with those collected from space during USAFA's FalconSAT-3 and FalconSAT-5 low-earth orbit satellite missions, the first of which is scheduled to be active over a period of several months beginning in the 2007 calendar year. The satellite experiments are designed to characterize in situ irregularities in plasma density, and include measurements of bulk ion density and temperature, minority-to- majority ion mixing ratios, small scale (10 cm to 1 m) plasma turbulence, and ion distribution spectra in energy with sufficient resolution for observations of non-thermalized distributions that may be associated with velocity- space instabilities. Specific targets of investigation include: a) a comparison of plasma turbulence observed on- orbit with spread F on ionograms as measured with the Digisonde, b) a correlation between the vertical lifting of the ionospheric layer over Guam and the onset of radio scintillation activity along the Guam meridian at 15° N magnetic latitude, and c) a correlation between on-orbit turbulence and ionospheric scintillation at 15° N magnetic latitude. These relationships may provide further clues into understanding the trigger mechanisms responsible for instigating disturbances in the ionospheric plasma, thus resulting in a turbulent radio propagation medium that may cause outages of radio based communication and navigation systems.

  19. Moment expansion for ionospheric range error

    NASA Technical Reports Server (NTRS)

    Mallinckrodt, A.; Reich, R.; Parker, H.; Berbert, J.

    1972-01-01

    On a plane earth, the ionospheric or tropospheric range error depends only on the total refractivity content or zeroth moment of the refracting layer and the elevation angle. On a spherical earth, however, the dependence is more complex; so for more accurate results it has been necessary to resort to complex ray-tracing calculations. A simple, high-accuracy alternative to the ray-tracing calculation is presented. By appropriate expansion of the angular dependence in the ray-tracing integral in a power series in height, an expression is obtained for the range error in terms of a simple function of elevation angle, E, at the expansion height and of the mth moment of the refractivity, N, distribution about the expansion height. The rapidity of convergence is heavily dependent on the choice of expansion height. For expansion heights in the neighborhood of the centroid of the layer (300-490 km), the expansion to N = 2 (three terms) gives results accurate to about 0.4% at E = 10 deg. As an analytic tool, the expansion affords some insight on the influence of layer shape on range errors in special problems.

  20. 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.

  1. Ionospheric precursors of earthquakes and Global Electric Circuit

    NASA Astrophysics Data System (ADS)

    Pulinets, Sergey; Davidenko, Dmitry

    2014-03-01

    The electromagnetic coupling between the seismically activated area and the ionosphere is considered within the framework of the Global Electric Circuit (GEC) conception. First we consider the anomalous variations in the ionosphere associated with the earthquake preparation process, their temporal and spatial characteristics using the results from recent publications. Then the GEC conception is presented shortly with main accent put on ionization processes which play key role in the complex chain of physical and chemical interactions changing the electric properties of the planetary boundary layer of atmosphere. We treat this part of troposphere as an open complex system with dissipation where so called “blow up” processes are developed leading to sharp and fast changes of atmospheric parameters including the electric properties of the boundary layer. The new concept named Spatial Scintillation Index is introduced in the last part of the paper. In general, this paper may be considered as a short review of the recent achievements in understanding of the seismo-ionospheric coupling.

  2. Effect of Ionospheric Scintillations on GNSS A White Paper

    E-print Network

    Boneh, Dan

    1 Effect of Ionospheric Scintillations on GNSS ­ A White Paper SBAS Ionospheric Working Group................................................................................... 19 #12;2 1 Introduction The ionosphere is a highly variable and complex physical system-region of the ionosphere, contains the greatest concentration of free electrons. At times, the F-region of the ionosphere

  3. Ionospheric redistribution during geomagnetic storms

    PubMed Central

    Immel, T J; Mannucci, A J

    2013-01-01

    [1]The abundance of plasma in the daytime ionosphere is often seen to grow greatly during geomagnetic storms. Recent reports suggest that the magnitude of the plasma density enhancement depends on the UT of storm onset. This possibility is investigated over a 7year period using global maps of ionospheric total electron content (TEC) produced at the Jet Propulsion Laboratory. The analysis confirms that the American sector exhibits, on average, larger storm time enhancement in ionospheric plasma content, up to 50% in the afternoon middle-latitude region and 30% in the vicinity of the high-latitude auroral cusp, with largest effect in the Southern Hemisphere. We investigate whether this effect is related to the magnitude of the causative magnetic storms. Using the same advanced Dst index employed to sort the TEC maps into quiet and active (Dstionospheric storm response on the measured strength of the terrestrial ring current, possibly connected through UT-dependent modulation of ion outflow. PMID:26167429

  4. 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.

  5. Modification of conductivity due to acceleration of the ionospheric medium

    NASA Astrophysics Data System (ADS)

    Denisenko, V. V.; Biernat, H. K.; Mezentsev, A. V.; Shaidurov, V. A.; Zamay, S. S.

    2008-07-01

    A quantitative division of the ionosphere into dynamo and motor regions is performed on the base of empirical models of space distributions of ionospheric parameters. Pedersen and Hall conductivities are modified to represent an impact of acceleration of the medium because of Ampére's force. It is shown that the currents in the F2 layer are greatly reduced for processes of a few hours duration. This reduction is in particular important for the night-side low-latitude ionosphere. The International Reference Ionosphere model is used to analyze the effect quantitatively. This model gives a second high conducting layer in the night-side low-latitude ionosphere that reduces the electric field and equatorial electrojets, but intensifies night-side currents during the short-term events. These currents occupy regions which are much wider than those of equatorial electrojets. It is demonstrated that the parameter ?d=?P+?H?H/?P that involves the integral Pedersen and Hall conductances ?P, ?H ought to be used instead of the local Cowling conductivity ?C in calculations of the electric current density in the equatorial ionosphere. We may note that Gurevich et al. (1976) derived a parameter similar to ?d for more general conditions as those which we discuss in this paper; a more detailed description of this point is given in Sect. 6. Both, ?d and ?C, appear when a magnetic field line is near a nonconducting domain which means zero current through the boundary of this domain. The main difference between ?d and ?C is that ?d definition includes the possibility for the electric current to flow along a magnetic field line in order to close all currents which go to this line from neighboring ones. The local Cowling conductivity ?C corresponds to the current closure at each point of a magnetic field line. It is adequate only for a magnetic field line with constant local conductivity at the whole line when field-aligned currents do not exist because of symmetry, but ?C=?d in this case. So, there is no reason to use the local Cowling conductivity while the Cowling conductance ?C=?P+?H2/?P is a useful and well defined parameter.

  6. Early MAVEN Deep Dip campaign reveals thermosphere and ionosphere variability

    NASA Astrophysics Data System (ADS)

    Bougher, S.; Jakosky, B.; Halekas, J.; Grebowsky, J.; Luhmann, J.; Mahaffy, P.; Connerney, J.; Eparvier, F.; Ergun, R.; Larson, D.; McFadden, J.; Mitchell, D.; Schneider, N.; Zurek, R.; Mazelle, C.; Andersson, L.; Andrews, D.; Baird, D.; Baker, D. N.; Bell, J. M.; Benna, M.; Brain, D.; Chaffin, M.; Chamberlin, P.; Chaufray, J.-Y.; Clarke, J.; Collinson, G.; Combi, M.; Crary, F.; Cravens, T.; Crismani, M.; Curry, S.; Curtis, D.; Deighan, J.; Delory, G.; Dewey, R.; DiBraccio, G.; Dong, C.; Dong, Y.; Dunn, P.; Elrod, M.; England, S.; Eriksson, A.; Espley, J.; Evans, S.; Fang, X.; Fillingim, M.; Fortier, K.; Fowler, C. M.; Fox, J.; Gröller, H.; Guzewich, S.; Hara, T.; Harada, Y.; Holsclaw, G.; Jain, S. K.; Jolitz, R.; Leblanc, F.; Lee, C. O.; Lee, Y.; Lefevre, F.; Lillis, R.; Livi, R.; Lo, D.; Ma, Y.; Mayyasi, M.; McClintock, W.; McEnulty, T.; Modolo, R.; Montmessin, F.; Morooka, M.; Nagy, A.; Olsen, K.; Peterson, W.; Rahmati, A.; Ruhunusiri, S.; Russell, C. T.; Sakai, S.; Sauvaud, J.-A.; Seki, K.; Steckiewicz, M.; Stevens, M.; Stewart, A. I. F.; Stiepen, A.; Stone, S.; Tenishev, V.; Thiemann, E.; Tolson, R.; Toublanc, D.; Vogt, M.; Weber, T.; Withers, P.; Woods, T.; Yelle, R.

    2015-11-01

    The Mars Atmosphere and Volatile Evolution (MAVEN) mission, during the second of its Deep Dip campaigns, made comprehensive measurements of martian thermosphere and ionosphere composition, structure, and variability at altitudes down to ~130 kilometers in the subsolar region. This altitude range contains the diffusively separated upper atmosphere just above the well-mixed atmosphere, the layer of peak extreme ultraviolet heating and primary reservoir for atmospheric escape. In situ measurements of the upper atmosphere reveal previously unmeasured populations of neutral and charged particles, the homopause altitude at approximately 130 kilometers, and an unexpected level of variability both on an orbit-to-orbit basis and within individual orbits. These observations help constrain volatile escape processes controlled by thermosphere and ionosphere structure and variability.

  7. Early MAVEN Deep Dip campaign reveals thermosphere and ionosphere variability.

    PubMed

    Bougher, S; Jakosky, B; Halekas, J; Grebowsky, J; Luhmann, J; Mahaffy, P; Connerney, J; Eparvier, F; Ergun, R; Larson, D; McFadden, J; Mitchell, D; Schneider, N; Zurek, R; Mazelle, C; Andersson, L; Andrews, D; Baird, D; Baker, D N; Bell, J M; Benna, M; Brain, D; Chaffin, M; Chamberlin, P; Chaufray, J-Y; Clarke, J; Collinson, G; Combi, M; Crary, F; Cravens, T; Crismani, M; Curry, S; Curtis, D; Deighan, J; Delory, G; Dewey, R; DiBraccio, G; Dong, C; Dong, Y; Dunn, P; Elrod, M; England, S; Eriksson, A; Espley, J; Evans, S; Fang, X; Fillingim, M; Fortier, K; Fowler, C M; Fox, J; Gröller, H; Guzewich, S; Hara, T; Harada, Y; Holsclaw, G; Jain, S K; Jolitz, R; Leblanc, F; Lee, C O; Lee, Y; Lefevre, F; Lillis, R; Livi, R; Lo, D; Ma, Y; Mayyasi, M; McClintock, W; McEnulty, T; Modolo, R; Montmessin, F; Morooka, M; Nagy, A; Olsen, K; Peterson, W; Rahmati, A; Ruhunusiri, S; Russell, C T; Sakai, S; Sauvaud, J-A; Seki, K; Steckiewicz, M; Stevens, M; Stewart, A I F; Stiepen, A; Stone, S; Tenishev, V; Thiemann, E; Tolson, R; Toublanc, D; Vogt, M; Weber, T; Withers, P; Woods, T; Yelle, R

    2015-11-01

    The Mars Atmosphere and Volatile Evolution (MAVEN) mission, during the second of its Deep Dip campaigns, made comprehensive measurements of martian thermosphere and ionosphere composition, structure, and variability at altitudes down to ~130 kilometers in the subsolar region. This altitude range contains the diffusively separated upper atmosphere just above the well-mixed atmosphere, the layer of peak extreme ultraviolet heating and primary reservoir for atmospheric escape. In situ measurements of the upper atmosphere reveal previously unmeasured populations of neutral and charged particles, the homopause altitude at approximately 130 kilometers, and an unexpected level of variability both on an orbit-to-orbit basis and within individual orbits. These observations help constrain volatile escape processes controlled by thermosphere and ionosphere structure and variability. PMID:26542579

  8. 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-?.

  9. The ultra-fast Kelvin waves in the equatorial ionosphere: observations and modeling

    NASA Astrophysics Data System (ADS)

    Onohara, A. N.; Batista, I. S.; Takahashi, H.

    2013-02-01

    The main purpose of this study is to investigate the vertical coupling between the mesosphere and lower thermosphere (MLT) region and the ionosphere through ultra-fast Kelvin (UFK) waves in the equatorial atmosphere. The effect of UFK waves on the ionospheric parameters was estimated using an ionospheric model which calculates electrostatic potential in the E-region and solves coupled electrodynamics of the equatorial ionosphere in the E- and F-regions. The UFK wave was observed in the South American equatorial region during February-March 2005. The MLT wind data obtained by meteor radar at São João do Cariri (7.5° S, 37.5° W) and ionospheric F-layer bottom height (h'F) observed by ionosonde at Fortaleza (3.9° S; 38.4° W) were used in order to calculate the wave characteristics and amplitude of oscillation. The simulation results showed that the combined electrodynamical effect of tides and UFK waves in the MLT region could explain the oscillations observed in the ionospheric parameters.

  10. 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.

  11. 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.

  12. Nonlinear unstable auroral-arc driven thermospheric winds in an ionosphere-magnetosphere coupled model

    NASA Technical Reports Server (NTRS)

    Keskinen, M. J.; Satyanarayana, P.

    1993-01-01

    The nonlinear evolution of thermospheric winds in an ionosphere-magnetosphere coupled model has been studied for the first time for a dynamic unstable auroral-arc environment. We treat the problem using a multi-layer, quasi-three-dimensional model which averages in altitude the thermospheric dynamics over each layer. For the upper thermosphere, we find that (1) the thermosphere can respond to the ionospheric Kelvin-Helmholtz (KH) instability on temporal scales on the order of an hour, depending on ambient conditions, and on spatial scales of tens to hundreds of kilometers, (2) strong thermospheric meridional and zonal vortical flows with embedded nonlinear jet-like structures can be generated by the ionospheric/magnetospheric KH instability and (3) neutral thermospheric winds, vortices, and associated power spectra develop in a distinctly different manner in the presence of magnetospheric coupling effects. Comparison with recent observations is made.

  13. The morphology of the topside ionosphere of Mars under different solar

    E-print Network

    Withers, Paul

    The morphology of the topside ionosphere of Mars under different solar wind conditions: Results of the ionosphere Ionosphere #12;Observational study of solar wind, magnetosphere, and ionosphere coupling using ­ WIND extrapolation, ASPERA · Magnetospheric data ­ ASPERA · Ionospheric data ­ Radio occultations

  14. Manifestation of seismo-ionospheric effect outside of eartquakes preparation zone

    NASA Astrophysics Data System (ADS)

    Ruzhin, Yuri

    We have researched the large-scale abnormal disturbances of the low-latitude ionosphere, which are taking place under quiet geomagnetic conditions, on a background of data on seismic activity with the view of revealing of features of spatial-time variations of a low-latitude ionosphere during the periods of the raised seismic activity. The daily variations of foF2 values(deviations of measured foF2 from monthly medians) at the ionospheric stations were analyzed. The data on seismic events of the moderate power (M=4-5)in low-latitude area were used for the purpose of specification of spatial and time scales of ionospheric effect manifestations of earthquakes. Reaction of a low-latitude ionosphere, in some cases strongly pronounced, on processes of earthquake preparation is confirmed, including in the removed centers of earthquakes (on the distances considerably exceeding radius of a zone of earthquake preparation). The ionosphere reaction manifests in development of the expressed disturbances of F2-layer critical frequencies in night, pre-sunrise and evening hours under quiet geomagnetic conditions. The remarkable example of occurrence of abnormal disturbances in a low-latitude ionosphere due to removed centers of earthquakes are the disturbances of F2-layer critical frequencies during the catastrophic Chilean (on May 21, 1960, 1002UT, the main shock magnitude M=8.5) and the Alaska (on March 28, 1964, 0336UT, M=8.3) earthquakes. The maximal distances, on which abnormal disturbances were noted, are 3700 km for the Chilean and 9100 km for the Alaska earthquakes. Displacement of the disturbances in a direction from epicenter areas to the geomagnetic equator was noted: from the south - during the Chilean earthquake and from the north - during the Alaska one. Positive disturbances were marked for three days up to the first shock during the Chilean earthquake, during the Alaska one - for a day; development of negative disturbances were occurred on time in immediate proximity by the moments of the first shocks at local time of the stations. The analysis of variations of F2-layer critical frequencies in low-latitude area (results on the South-American region) has confirmed the conclusion about that groups of earthquakes of the moderate power, rather localized in time and space in low-latitude area, can cause abnormal disturbances of F2-layer critical frequencies in this area of ionosphere which may be similar on amplitude with ionospheric effects of strong earthquakes (variations of foF2 more than 50

  15. Mesospheric, Thermospheric, and Ionospheric Responses to Acoustic and Gravity Waves Generated by Transient Forcing

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

    Strong acoustic waves with periods ~1-4 minutes have been confirmed to perturb the ionosphere following their generation by earthquakes [e.g., Garcia et al., GRL, 40(5), 2013] and volcanic eruption events [e.g., Heki, GRL, 33, L14303, 2006]. Clear acoustic and gravity wave signatures have also been reported in ionospheric data above strong tropospheric convection [Nishioka, GRL, 40(21), 2013], and prior modeling results suggest that convectively-generated acoustic waves with ~3-4 minute periods are readily detectable above their sources in TEC [Zettergren and Snively, GRL, 40(20), 2013]. These observations have provided quantitative insight into the coupling of processes occurring near Earth's surface with the upper atmosphere and ionosphere over short time-scales. Here, we investigate acoustic waves and short-period gravity waves generated by sources near ground level, and the observable responses of the mesosphere, lower-thermosphere, and ionosphere (MLTI) systems. Numerical simulations are performed using a nonlinear, compressible, atmospheric dynamics model, in cylindrically-axisymmetric coordinates, to investigate wave generation, upward propagation, steepening, and dissipation. Acoustic waves may produce observable signatures in the mesospheric hydroxyl airglow layer [e.g., Snively, GRL, 40(17), 2013], and can strongly perturb the lower-thermosphere and E- and F-region ionosphere, prior to the arrival of simultaneously-generated gravity waves. Using a coupled multi-fluid ionospheric model [Zettergren and Semeter, JGR, 117(A6), 2012], extended for mid and low latitudes using a 2D dipole magnetic field coordinate system [Zettergren and Snively, GRL, 40(20), 2013], we investigate its response to realistic acoustic wave perturbations. In particular, we demonstrate that the MLT and ionospheric responses are significantly and nonlinearly determined by the acoustic wave source geometry, spectrum, and amplitude, in addition to the local ambient state of the ionosphere.

  16. Shear Alfven Wave Injection in the Magnetosphere by Ionospheric Modifications in the Absence of Electrojet Currents

    NASA Astrophysics Data System (ADS)

    Papadopoulos, K.; Eliasson, B.; Shao, X.; Labenski, J.; Chang, C.

    2011-12-01

    A new concept of generating ionospheric currents in the ULF/ELF range with modulated HF heating using ground-based transmitters even in the absence of electrojet currents is presented. The new concept relies on using HF heating of the F-region to modulate the electron temperature and has been given the name Ionospheric Current Drive (ICD). In ICD, the pressure gradient associated with anomalous or collisional F-region electron heating drives a local diamagnetic current that acts as an antenna to inject mainly Magneto-Sonic (MS) waves in the ionospheric plasma. The electric field associated with the MS wave drives Hall currents when it reaches the E region of the ionosphere. The Hall currents act as a secondary antenna that inject waves in the Earth-Ionosphere Waveguide (EIW) below and shear Alfven waves or EMIC waves upwards towards the conjugate regions. The paper presents: (i) Theoretical results using a cold Hall MHD model to study ICD and the generation of ULF/ELF waves by the modulation of the electron pressure at the F2-region with an intense HF electromagnetic wave. The model solves equations governing the dynamics of the shear Alfven and magnetosonic modes, of the damped modes in the diffusive Pedersen layer, and of the weakly damped helicon wave mode in the Hall-dominated E-region. The model incorporates realistic profile of the ionospheric conductivities and magnetic field configuration. We use the model to simulate propagation and dynamics of the low-frequency waves and their injection into the magnetosphere from the HAARP and Arecibo ionospheric heaters. (ii) Proof of principle experiments using the HAARP ionospheric heater in conjunction with measurements by the DEMETER satellite This work is supported by ONR MURI grant and DARPA BRIOCHE Program

  17. Artificial Intelligence.

    ERIC Educational Resources Information Center

    Thornburg, David D.

    1986-01-01

    Overview of the artificial intelligence (AI) field provides a definition; discusses past research and areas of future research; describes the design, functions, and capabilities of expert systems and the "Turing Test" for machine intelligence; and lists additional sources for information on artificial intelligence. Languages of AI are also briefly…

  18. 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.

  19. 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.

  20. 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.

  1. 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

  2. The Dependence of the Strength and Thickness of Field-Aligned Currents on Solar Wind and Ionospheric Parameters

    SciTech Connect

    Johnson, Jay R.; Wing, Simon

    2014-08-01

    Sheared plasma flows at the low-latitude boundary layer correlate well with early afternoon auroral arcs and #12;eld-aligned currents [Sonnerup, 1980; Lundin and Evans, 1985]. We present a simple analytic model that relates solar wind and ionospheric parameters to the strength and thickness of field-aligned currents in a region of sheared velocity, such as the low latitude boundary layer. We compare the predictions of the model with DMSP observations and #12;nd remarkably good scaling of the currents with solar wind and ionospheric parameters. The sheared boundary layer thickness is inferred to be around 3000km consistent with observational studies. The analytic model provides a simple way to organize data and to infer boundary layer structures from ionospheric data.

  3. Properties of Regions of ELF Radiation Induced by HF Ionospheric Heating

    NASA Astrophysics Data System (ADS)

    Piddyachiy, D.; Bell, T. F.; Inan, U. S.; Foust, F.; Lehtinen, N. G.; Parrot, M.

    2011-12-01

    ELF wave (30 - 3000 Hz) generation and propagation is an important topic of research affecting many areas of space physics. For example, ELF waves generated by lightning discharges can effectively interact with particles in the Earth's radiation belts. Also, ELF waves can penetrate effectively under water to allow wireless communication with submersible crafts. However, it is difficult to generate ELF waves artificially because of their long wavelengths. In this work, the High Frequency Active Auroral Research Program (HAARP) transmitter array (3.6 MW, 2.75 - 10 MHz) is used to generate ELF waves in a controlled manner through periodic heating of the ionospheric D-layer and subsequent modulation of the conductivity of the auroral electrojet. The low-earth-orbit DEMETER satellite is used to study ELF power distribution as a function of the distance from the source. The spatial power distribution depends on many factors. Some of them can be controlled: the ELF and HF frequencies, direction, and modulation techniques. Other parameters are natural and cannot be directly affected: strength of the electrojet current, plasma density, and so on. Initial studies were conducted on a case by case basis, but now they are complemented by a statistical study of multiple experiments over four years. Three regions of ELF radiation are seen in case studies and in an averaged pattern. The most important feature is a column of radiation into space about the size of the heated region (~50 km) and average field strength of 100-150 uV/m. Total ELF power in the column is estimated to be about 1 W. It is found that the column is displaced by 50 - 100 km to the South from the field line of the source. A full-wave model predicts a column of about the same size, but displaced to the North from the field line by 50 km. In addition, the model enables the identification of different physical mechanisms of wave propagation to the three regions of radiation. In brief, in region 1 (the column) and region 2 (up to 300 km from the source in the horizontal distance) waves reach the satellite directly; while in region 3 waves at first are propagating in the Earth-ionosphere waveguide and then leak to the satellite through the ionosphere. The sizes of regions in observations and modeling are comparable. Raytracing is used to interpret the difference between the position of the column in the observations and full-wave modeling. Full-wave modeling assumes vertically stratified ionospheric density, while ray tracing can be used with more realistic models of plasma density including horizontal gradients. It is shown that a horizontal gradient indeed can explain the bending of the column in observations. Employing simple model with linear horizontal gradient of Log(Ne), it was deduced that density should change by an order magnitude over about 5 degrees in latitude in order for ray trajectories to match observations.

  4. Ionospheric disturbances initiated by impact of the Chelyabinsk meteoroid

    NASA Astrophysics Data System (ADS)

    Kuzmicheva, M.; Losseva, T. V.; Lyakhov, A.

    2013-12-01

    It has been demonstrated, that impact of the Chelyabinsk meteoroid on the 15th of February, 2013 caused oscillations of critical plasma frequency of the F2 layer of ionosphere (foF2), but there were no detectable variations of the Earth's magnetic field. Also on tomograms of ionosphere, obtained by GPS stations located along 40 th meridian, wave-like disturbances of electron density at heights 200-700 km have been observed. As followed from ionosondes' measurements foF2 oscillations have been detected tens minutes after a main burst in Irkutsk, Norilsk, Yakutsk and then in Moscow and Europe. This time sequence of beginning of the oscillations could be explained by hypothesis that a source lied on the trajectory of the meteoroid far from Chelyabinsk. Post-impact ballistic plume outgoing to the rarefied layers of the atmosphere and then falling back on the dense layers provides the disturbance transmission in a time of tens minutes at a distance of 1500-2000 km. By numerical modeling a possibility for the plume to be formed has been shown. Also modeling of oscillations in F2-layer initiated by the falling plume has been fulfilled. Calculated amplitudes of density variations are in a good agreement with observable ones. Geomagnetic disturbances generated by the impact have been estimated. They appeared to be too small to be detected by nearby stations.

  5. Response of ions of ionospheric origin to storm time substorms: Coordinated observations over the ionosphere

    E-print Network

    Carlson, Charles W.

    Response of ions of ionospheric origin to storm time substorms: Coordinated observations over the ionosphere and in the plasma sheet M. Nose´,1 S. Taguchi,2 S. P. Christon,3 M. R. Collier,4 T. E. Moore,4 C 2009; published 12 May 2009. [1] We investigate variations of ion flux over the ionosphere

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

    SciTech Connect

    Grandal, B.

    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 in electron beam experiments, plasma waves and electrical discharges, plasma diagnostics by electron guns, plasma heating effects in the ionosphere, the EXCEDE SPECTRAL artificial auroral experiment), natural beam-plasma interactions in space (observations of nonlinear processes in the ionosphere; interaction between natural particle beams and space plasmas), accelerator experiments in the laboratory (e.g., simulation of the injection of particle beams in the ionosphere, electron energy distribution produced by beam-plasma discharge, plasma waves stimulated by electron beams, beam-plasma interactions in a space simulation chamber, the Plasma Diagnostic Package, electromagnetic radiation), theoretical aspects of the beamplasma interactions (e.g., the electron beam as a source of electrostatic waves, plasma waves generated by electron beams), the neutralization of a charged body in space, and future plans.

  7. Large-Scale Ionospheric Effects Related to Electron-Gyro Harmonics: What We Have Learned from HAARP.

    NASA Astrophysics Data System (ADS)

    Watkins, B. J.; Fallen, C. T.; Secan, J. A.

    2014-12-01

    The HAARP ionospheric modification facility has unique capabilities that enable a wide range of HF frequencies with transmit powers ranging from very low to very high values. We will review a range of experiment results that illustrate large-scale ionospheric effects when the HF frequencies used are close to electron gyro-harmoncs and we focus mainly on the 3rd and 4th harmonics. The data are primarily from the UHF diagnosticc radar and total electron content (TEC) observations through the heated topside ionosphere. Radar data for HF frequencies just above and just below gyro harmoncs show significant differences in radar scatter cross-section that suggest differing plasma processes, and this effect is HF power dependent with some effects only observable with full HF power. For the production of artificial ionization in the E-region when the HF frequency is near gyro-harmoncs the results differ significantly for relatively small (50 kHz) variations in the HF frequency. We show how slow FM scans in conjunction with gyro-harmonic effects are effective in producing artificial ionization in the lower ionosphere.In the topside ionosphere enhanced density and upward fluxes have been observed and these may act as effective ducts for the propagation of VLF waves upward into the magneosphere. Experimental techniques have been developed that may be used to continuously maintain these effects in the topside ionossphere.

  8. The Ionosphere and the Latin America Very Low Frequency Network Mexico (LAVNet-Mex)

    NASA Astrophysics Data System (ADS)

    Borgazzi, A.; Lara, A.; Santiago, A.

    2013-05-01

    The radiation emitted by the most energetic transient events in the solar system, solar flares, covers a wide range of wavelengths, from radio waves to gamma rays. When the transient excess of high energy radiation produced by solar flares reach the Earth environment, the upper layers of the Earth atmosphere are affected and highly disturbed. The dynamics (particularly the conductivity) of the ionosphere, is altered during solar explosive events. In order to detect and study the ionospheric response to the transient solar radiative input, we have constructed a VLF receiver station: the `Latin American Very low frequency Network at Mexico' (LAVNet-Mex), which extends to the northern hemisphere the South American VLF Network. LAVNet-Mex detects electromagnetic waves generated by strong transmitters located around the world. These waves travel inside the Earth-Ionosphere waveguide, along the Great Circle Path formed between the emitter and the observer. By observing changes in the phase and amplitude of these waves, it is possible to study the dynamics of the lower layer of the ionosphere during solar eruptive events. In this work we present preliminary results of the analysis of the effects of solar flares (class M and X) occurred in 2012 and that were observed by LAVNet-Mex. We explore the relationship between VLF signals coming from different paths during these solar burst to infer the degree of correlation that can exist between different sectors of the ionosphere.

  9. 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.

  10. Sudden ionospheric disturbances in solar cycle 24

    NASA Astrophysics Data System (ADS)

    Bothmer, Volker; Bernert, Barbara

    2014-05-01

    Sudden ionospheric disturbances in solar cycle 24 Within the framework of the UN International Space Weather Initiative, and building upon the achievements of the International Heliophysical Year, the German project SIMONE (Sun Ionosphere MOnitoring NEtwork) operates several SID monitors provided by the University of Stanford. Here we present an overview of sudden ionospheric disturbances recorded since 2006 at the high school Gymnasium Walsrode until to date. The continous measurements allow a detailed comparison of locally measured SIDs with the general trend of solar activity during the current solar maximum. We further show that the measurements reveal specific information on the variable response of the dayside ionosphere to solar flares.

  11. Exploration of artificial multiferroic thin-film heterostructures using composition spreads

    E-print Network

    Rubloff, Gary W.

    Exploration of artificial multiferroic thin-film heterostructures using composition spreads K layers of varying thicknesses modulated at nanometer level in order to explore artificial magnetoelectric­5 made the first artificial magnetoelectric material by combining a ferroelec- tric piezoelectric

  12. Sources for Traveling Ionospheric Disturbances

    NASA Astrophysics Data System (ADS)

    MacDougall, J. W.; Jayachandran, P. T.

    2009-12-01

    A number of different sources have been suggested for the gravity waves that cause Traveling Ionospheric Disturbances (TIDs). Our studies of TIDs indicate that at least two sources are important: The terminators, and auroral electrojets. The terminators cause TIDs in both daytime and nighttime. At midlatitudes the electrojets are a major source only during nighttime. Details about the midlatitude behaviour of TIDs will be presented.

  13. Ionospheric very low frequency transmitter

    NASA Astrophysics Data System (ADS)

    Kuo, Spencer P.

    2015-02-01

    The theme of this paper is to establish a reliable ionospheric very low frequency (VLF) transmitter, which is also broad band. Two approaches are studied that generate VLF waves in the ionosphere. The first, classic approach employs a ground-based HF heater to directly modulate the high latitude ionospheric, or auroral electrojet. In the classic approach, the intensity-modulated HF heater induces an alternating current in the electrojet, which serves as a virtual antenna to transmit VLF waves. The spatial and temporal variations of the electrojet impact the reliability of the classic approach. The second, beat-wave approach also employs a ground-based HF heater; however, in this approach, the heater operates in a continuous wave mode at two HF frequencies separated by the desired VLF frequency. Theories for both approaches are formulated, calculations performed with numerical model simulations, and the calculations are compared to experimental results. Theory for the classic approach shows that an HF heater wave, intensity-modulated at VLF, modulates the electron temperature dependent electrical conductivity of the ionospheric electrojet, which, in turn, induces an ac electrojet current. Thus, the electrojet becomes a virtual VLF antenna. The numerical results show that the radiation intensity of the modulated electrojet decreases with an increase in VLF radiation frequency. Theory for the beat wave approach shows that the VLF radiation intensity depends upon the HF heater intensity rather than the electrojet strength, and yet this approach can also modulate the electrojet when present. HF heater experiments were conducted for both the intensity modulated and beat wave approaches. VLF radiations were generated and the experimental results confirm the numerical simulations. Theory and experimental results both show that in the absence of the electrojet, VLF radiation from the F-region is generated via the beat wave approach. Additionally, the beat wave approach generates VLF radiations over a larger frequency band than by the modulated electrojet.

  14. Lithosphere - Atmosphere - Ionosphere Circuit Model

    NASA Astrophysics Data System (ADS)

    Kereselidze, Z.; Kachakhidze, N.; Kachakhidze, M.

    2012-04-01

    There are offered possibilities of original LAI circuit model. The problem concerns of existence of self-generated electromagnetic oscillations in the segment of LAI system, which are results of tectonic stress developing in the focus area of expected earthquake. By this model the main (lowest) frequency of these electromagnetic oscillations frequency spectrum is expressed analytically by following formula: ? = ? c l where ?(?) is the coefficient depended on the frequency and geological characteristics of the medium and approximate to one, c-is the speed of light, and l- the length of the fault in the focus of the expected earthquake. On the base of relevant diagnosis of experimental data, the model gives us possibility to discuss the problem about location, time of occurrence and intensity of an expected earthquake with certain accuracy. In addition to it, considered model does not block the fall-unstable model of earthquake preparing and electromagnetic phenomena accompanied earthquake preparing process. On the contrary, the imagination of physical picture may be simplified in the separate stage of earthquakes preparing. Namely, it is possible to reliably separate series of foreshocks and aftershocks. By this point of view, the certain optimism about using of EM emission as earthquake precursor of full value may be expressed. The base of such optimism is developing of various phenomena connected to VLF emission many times fixed in the surroundings of epicentral area and cosmic space (changing of intensity of electro-telluric current, perturbations of geomagnetic field in forms of irregular pulsations or regular short-period pulsations, perturbations of atmospheric electric field, perturbations of ionosphere critical frequency and TEC, variations of height of lower ionosphere, parameters of ionospheric medium: changing of specific dielectric conductivity and spectrum of MGD waves in it, atmospheric-ionospheric discharging and etc.).

  15. Heat budget of ionospheric electrons

    NASA Technical Reports Server (NTRS)

    Prasad, S. S.; Schneck, L. J.

    1976-01-01

    Heat input calculations were detached from solar extreme UV data and monatomic oxygen densities were derived from simultaneously measured data sets (ion composition 146-191 km) in a study of the heat budget of ionosphere electrons. Earlier inferences that cooling predominates over heating are supported. A search for additional heat sources or a revision of the cooling rates is recommended, by way of balancing the heat budget. Importance is attached to electron cooling by fine structure excitation of monatomic oxygen.

  16. Ionosphere TEC disturbances before strong earthquakes: observations, physics, modeling (Invited)

    NASA Astrophysics Data System (ADS)

    Namgaladze, A. A.

    2013-12-01

    The phenomenon of the pre-earthquake ionospheric disturbances is discussed. A number of typical TEC (Total Electron Content) relative disturbances is presented for several recent strong earthquakes occurred in different ionospheric conditions. Stable typical TEC deviations from quiet background state are observed few days before the strong seismic events in the vicinity of the earthquake epicenter and treated as ionospheric earthquake precursors. They don't move away from the source in contrast to the disturbances related with geomagnetic activity. Sunlit ionosphere approach leads to reduction of the disturbances up to their full disappearance, and effects regenerate at night. The TEC disturbances often observed in the magnetically conjugated areas as well. At low latitudes they accompany with equatorial anomaly modifications. The hypothesis about the electromagnetic channel of the pre-earthquake ionospheric disturbances' creation is discussed. The lithosphere and ionosphere are coupled by the vertical external electric currents as a result of ionization of the near-Earth air layer and vertical transport of the charged particles through the atmosphere over the fault. The external electric current densities exceeding the regular fair-weather electric currents by several orders are required to produce stable long-living seismogenic electric fields such as observed by onboard measurements of the 'Intercosmos-Bulgaria 1300' satellite over the seismic active zones. The numerical calculation results using the Upper Atmosphere Model demonstrate the ability of the external electric currents with the densities of 10-8-10-9 A/m2 to produce such electric fields. The sumulations reproduce the basic features of typical pre-earthquake TEC relative disturbances. It is shown that the plasma ExB drift under the action of the seismogenic electric field leads to the changes of the F2 region electron number density and TEC. The upward drift velocity component enhances NmF2 and TEC and the downward component decreases it, while horizontal components redistribute plasma in the horizontal plane around the source. The UAM calculations also show that the external electric currents of the seismic origin generate the small disturbances of the neutral atmosphere with the characteristics of the internal gravity waves but they don't influence noticeably on the relative pre-earthquake TEC disturbances.

  17. Artificial urushi.

    PubMed

    Kobayashi, S; Uyama, H; Ikeda, R

    2001-11-19

    A new concept for the design and laccase-catalyzed preparation of "artificial urushi" from new urushiol analogues is described. The curing proceeded under mild reaction conditions to produce the very hard cross-linked film (artificial urushi) with a high gloss surface. A new cross-linkable polyphenol was synthesized by oxidative polymerization of cardanol, a phenol derivative from cashew-nut-shell liquid, by enzyme-related catalysts. The polyphenol was readily cured to produce the film (also artificial urushi) showing excellent dynamic viscoelasticity. PMID:11763444

  18. 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.

  19. 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.

  20. Statistical analysis of the ionospheric response during geomagnetic storm conditions over South Africa using ionosonde and GPS data

    NASA Astrophysics Data System (ADS)

    Matamba, Tshimangadzo Merline; Habarulema, John Bosco; McKinnell, Lee-Anne

    2015-09-01

    This paper presents a statistical analysis of ionospheric response over ionosonde stations Grahamstown (33.3°S, 26.5°E, geographic) and Madimbo (22.4°S, 30.9°E, geographic), South Africa, during geomagnetic storm conditions which occurred during the period 1996-2011. Such a climatological study is important in establishing local ionospheric behavior trend which later forms a basis for accurate modeling and forecasting electron density and critical frequency of the F2 layer (foF2) useful for high-frequency communication. The analysis was done using foF2 and total electron content (TEC), and to identify the geomagnetically disturbed conditions, the Dst index with a storm criterion of Dst ? nT was used. Results show a strong solar cycle dependence with negative ionospheric storm effects following the solar cycle and positive ionospheric storm effects occurring most frequently during solar minimum. Seasonally, negative and positive ionospheric storm effects occurred most in summer (63.24%) and in winter (53.62%), respectively. An important finding is that only negative ionospheric storms were observed during great geomagnetic storm activity (Dst ? nT). For periods when both foF2 and TEC data (from colocated ionosonde and GPS receiver stations) were available, a similar response in terms of variational trend was observed. Hence, GPS data can be used to effectively identify the ionospheric response in the absence of ionosonde data.

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

    PubMed

    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

  2. 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.

  3. High-midlatitude ionosphere response to major stratospheric warming

    NASA Astrophysics Data System (ADS)

    Shpynev, Boris G.; Kurkin, Vladimir I.; Ratovsky, Konstantin G.; Chernigovskaya, Marina A.; Belinskaya, Anastasiya Yu; Grigorieva, Svetlana A.; Stepanov, Alexander E.; Bychkov, Vasily V.; Pancheva, Dora; Mukhtarov, Plamen

    2015-12-01

    This study investigates the impact of dynamical processes in the neutral atmosphere on the high-midlatitude ionosphere during two sudden stratospheric warming (SSW) events. For this purpose, the reanalysis meteorological data of the National Centers for Environmental Prediction /National Center for Atmospheric Research (NCEP/NCAR) and UK Met Office (UKMO) were used in addition to that from the high-midlatitude chain of Russian ionosonde stations. The results show that the ionospheric response to the SSW events at high-midlatitudes depends on the position of the ionosonde stations relative to the stratospheric circulation pattern. Two well-pronounced effects were detected in this study. The first effect, observed in January 2009, was a negative effect in critical frequency (foF2) and a positive effect in F2 layer maximum (hmF2) above the border of a stratospheric cyclone and an anticyclone with northward flow direction. During a 6-day period, the ionosphere exhibited a sharply inhomogeneous longitudinal structure when ionosondes, displaced at a longitude of approximately 20°, showed differences of approximately 1 MHz in foF2 and more than 50 km in hmF2. The second feature, which was clearly observed in January 2013, implied a positive effect in foF2 up to approximately 2.5 MHz and a negative effect in hmF2 at approximately 10 km above the center of the stratospheric cyclone. We conclude that these effects were caused by upward transport of molecular gas to the lower thermosphere for the first case and a pulldown forcing of molecular species above the low-pressure zone inside the cyclone for the second case. Changes in the O+/N2 ratio in the lower thermosphere altered the O+ recombination rate and the corresponding variations of ionosphere parameters.

  4. Computer model of chemistry and dynamics of the mesosphere, thermosphere, and ionosphere

    SciTech Connect

    Sutherland, C.D.; Zinn, J.

    1983-01-01

    This report describes a computer model of the mesosphere, thermosphere, and ionosphere and compares computed results with experimental data on the diurnal variations of that system under normal ambient and magnetically disturbed conditions. The model includes the effects of time-varying thermospheric winds and E fields, electron, ion and neutral temperatures, solar and geomagnetic activity, eddy diffusion, and molecular diffusion. The computer model is designed to be two-dimensional for application to problems of F-layer depletions due to rocket exhaust products. This report describes one-dimensional results and comparisons with data on the natural ionosphere at the time of the Skylab I launch in May 1973.

  5. Experimental investigation of ULF/VLF radio wave generation and propagation in the upper atmosphere and ionosphere during EISCAT heating experiment in 2012

    NASA Astrophysics Data System (ADS)

    Ryakhovskiy, Iliya; Gavrilov, Boris; Zetzer, Julius; Rietveld, Michael; Poklad, Yuriy; Blagoveshchenskaya, Nataly

    Powerful high frequency radio waves transmitted from high-power HF heating facilities modify the ionospheric plasma. The X-mode HF pump wave generates strong small-scale artificial field aligned irregularities in the F region of the ionosphere when the heater frequency is near or above the critical frequency of F2 layer [Blagoveshchenskaya et al]. One of the tasks of the Russian EISCAT heating campaign in February 2012 was an investigation of the generation and propagation of ULF/VLF signals generated as the result of HF radiation modulation. Despite the numerous attempts of long-range detection of such signals, there are a few successful results. The most reliable and important results were obtained by [Barr et al.] more than 20 years ago. They measured the VLF radio waves in Lindau, Germany at the distance of about 2000 km from EISCAT Heater. We present the results of the ULF/VLF registrations at the same distance during heating campaign of February 2012. The measurements were conducted at Mikhnevo Geohysical Observatory located in 80 km to the south of Moscow and at the distance of about 1900 km from Tromsø. For measurements were used a sensitive receivers with crossed air-coil loop antennas in the frequency range from 800 Hz to 30 kHz in the femtotesla amplitude range. We recorded the radial and azimuthal magnetic component of the signals and from their ratio obtained the mode polarization. The radiated heater frequency was modulated by 517, 1017, 2017, 3017, 4017 and 6017 Hz. It was shown the signals with frequency less than 2 kHz propagate in the QTEM mode, and signals at the frequency from 2 to 4 kHz are in the QTE mode. Observed magnetic field strengths and waveguide polarizations are found to be in line with the predictions of simple waveguide models. Qualitative coincidence of the signals polarization character and its dependence on the frequency specifies adequacy of numerical models and reliability of the data received in campaign 2012. Blagoveshchenskaya N. F., M. T. Rietveld et al. Artificial field-aligned irregularities in the high-latitude F region of the ionosphere induced by an X-mode HF heater wave. // Geophys. Res. Lett. - 2011. V. 38, doi: 10.1029/2011GL046724. Barr, R., P. Stubbe, and H. Kopka, 1991, Long-range detection of VLF radiation produced by heating the auroral electrojet. Radio Science, Volume 26, Number 4, Pages 871-879, July-August 1991

  6. 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.

  7. Long-term changes in thermospheric composition inferred from a spectral analysis of ionospheric F-region data

    NASA Astrophysics Data System (ADS)

    Scott, C. J.; Stamper, R.; Rishbeth, H.

    2014-02-01

    A study of ionospheric data recorded at Slough/Chilton, UK, from 1935 to 2012, has revealed long-term changes in the relative strength of the annual and semi-annual variability in the ionospheric F2 layer critical frequencies. Comparing these results with data from the southern hemisphere station at Stanley in the Falkland Islands between 1945 and 2012 reveals a trend that appears to be anti-correlated with that at Chilton. The behaviour of foF2 is a function of thermospheric composition and so we argue that the observed long-term changes are driven by composition change. The ionospheric trends share some of their larger features with the trend in the variability of the aa geomagnetic index. Changes to the semi-annual/annual ratio in the Slough/Chilton and Stanley data may therefore be attributable to the variability in geomagnetic activity which controls the average latitudinal extent of the auroral ovals and subsequent thermospheric circulation patterns. Changes in ionospheric composition or thermospheric wind patterns are known to influence the height of the F2 layer at a given location. Long-term changes to the height of the F2 layer have been used to infer an ionospheric response to greenhouse warming. We suggest that our observations may influence such measurements and since the results appear to be dependent on geomagnetic longitude, this could explain why the long-term drifts observed in F2 layer height differ between locations.

  8. 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).

  9. Microwave heating of the lower ionosphere

    NASA Technical Reports Server (NTRS)

    Meltz, G.; Nighan, W. L.

    1980-01-01

    Changes in the properties of the lower ionosphere due to ohmic heating of the plasma by the solar power satellite (SPS) microwave power beam are considered. The development of a predictive model of the underdense interaction of an electromagnetic beam and the lower ionosphere is described. The extent to which the Platteville and Arecibo experiments simulate SPS conditions is considered.

  10. Topside Ionospheric Sounder for CubeSats

    NASA Astrophysics Data System (ADS)

    Swenson, C.; Pratt, J.; Fish, C. S.; Winkler, C.; Pilinski, M.; Azeem, I.; Crowley, G.; Jeppesen, M.; Martineau, R.

    2014-12-01

    This presentation will outline the design of a Topside Ionospheric Sounder (TIS) for CubeSats. In the same way that an ionosonde measures the ionospheric profile from the ground, a Topside Sounder measures the ionospheric profile from a location above the F-region peak. The TIS will address the need for increased space situational awareness and environmental monitoring by estimating electron density profiles in the topside of the ionosphere. The TIS will measure topside electron density profiles for plasma frequencies ranging from 0.89 MHz to 28.4 MHz below the satellite altitude. The precision of the measurement will be 5% or 10,000 p/cm^3. The TIS average power consumption will be below 10 W and a mass of less than 10 kg, so it is appropriate for a 6U Cubesat (or multiple of that size). The sounder will operate via a transmitted frequency sweep across the desired plasma frequencies which, upon reception, can be differenced to determine range and density information of the topside ionosphere. The velocity of the spacecraft necessitates careful balancing of range resolution and frequency knowledge requirements as well as novel processing techniques to correctly associate the return signal with the correct plasma frequency. TIS is being designed to provide a low cost, low mass spacecraft that can provide accurate topside profiles of the ionospheric electron density in order to further understanding of ionospheric structure and dynamic processes in the ionosphere.

  11. 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.

  12. New model of Saturn's ionosphere with an influx of water from the rings

    NASA Technical Reports Server (NTRS)

    Connerney, J. E. P.; Waite, J. H.

    1984-01-01

    A radically different model of Saturn's ionosphere is proposed in which water plays a major role as a minor constituent present by downward diffusion from an external source. The model ionosphere is a classical F2 type layer resulting from the photodissociative production of H(+) from H2 and rapid chemical loss by a series of charge exchange reactions with water. A planet-wide influx of about 4 x 10 to the 7th molecules/sq cm/s of water from the rings is consistent with the observed ionospheric electron densities. An enhanced influx of water occurs at latitudes (-38, +44 deg) connected magnetically at the inner edge of Saturn's B ring, where an electromagnetic erosion process takes place. The present-day influx at these latitudes may be as large as 2 x 10 to the 9th molecules/sq cm/s.

  13. 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.

  14. Ionospheric storms on Mars: Impact of the corotating interaction region

    E-print Network

    Gurnett, Donald A.

    Ionospheric storms on Mars: Impact of the corotating interaction region E. Dubinin,1 M. Fraenz,1 J) on Mars cause strong perturbations in the martian induced magnetosphere and ionosphere. The magnetic plasma from the ionosphere. The topside martian ionosphere becomes very fragmented consisting

  15. Ionospheric Research Issues for SBAS Summary of A White Paper

    E-print Network

    Boneh, Dan

    Ionospheric Research Issues for SBAS ­ Summary of A White Paper SBAS Ionospheric Working Group September 2002 Introduction: SBAS precision approach services require correction for ionospheric range delay. The ionosphere over mid-latitude regions (e.g., CONUS and most of Europe) normally has small spatial range delay

  16. Assessment of Nominal Ionosphere Spatial Decorrelation for LAAS

    E-print Network

    Stanford University

    Assessment of Nominal Ionosphere Spatial Decorrelation for LAAS Jiyun Lee, Sam Pullen, Seebany deviation of ionosphere spatial decorrelation because the range errors introduced by the ionosphere vary between LGF receivers and LAAS users. Thus, it is necessary to estimate typical ionosphere gradients

  17. Measurement Noise versus Process Noise in Ionosphere Estimation for WAAS

    E-print Network

    Stanford University

    Measurement Noise versus Process Noise in Ionosphere Estimation for WAAS Juan Blanch, Todd Walter Augmentation System (WAAS) is the Grid Ionospheric Vertical Error (GIVE). The GIVE bounds the estimation error of the ionospheric delay at each Ionospheric Grid Point (IGP). The GIVE is generated such that a user interpolating

  18. MAGNETICALLY CONTROLLED STRUCTURES IN THE IONOSPHERE OF MARS

    E-print Network

    Gurnett, Donald A.

    MAGNETICALLY CONTROLLED STRUCTURES IN THE IONOSPHERE OF MARS by Firdevs Duru A thesis submitted ABSTRACT The ionospheric sounding data obtained by the MARSIS (Mars Advanced Radar for Subsurface and Ionospheric Sounding) instrument on the Mars Express spacecraft shows that the dayside ionosphere has

  19. The ionosphere of Mars and its importance for climate

    E-print Network

    Withers, Paul

    The ionosphere of Mars and its importance for climate evolution A community white paper · The science of the ionosphere of Mars will not end with MAVEN · Present some ideas for future ionospheric instruments and missions (with realism) #12;Structure of white paper · Introduction ­ Ionospheres in general

  20. An Ionosphere Estimation Algorithm for WAAS Based on Kriging

    E-print Network

    Stanford University

    An Ionosphere Estimation Algorithm for WAAS Based on Kriging Juan Blanch, Stanford University for single frequency users is the ionosphere. For this reason, ionospheric behavior drives the performance of the Wide Area Augmentation System (WAAS). At any given time, the only information we have of the ionosphere

  1. Data Assimilation Using the Global Ionosphere-Thermosphere Model

    E-print Network

    Bernstein, Dennis S.

    Data Assimilation Using the Global Ionosphere-Thermosphere Model I.S. Kim1 , J. Chandrasekar1 , A dynamics. The Global Ionosphere-Thermo- sphere Model (GITM) is used to simulate the ionospheric and thermo on a section of the ionosphere. 1 Data Assimilation for Space Weather Prediction The Sun drives our atmosphere

  2. Ionospheric erosion by Alfven waves C. C. Chaston,1

    E-print Network

    Bonnell, John W.

    Ionospheric erosion by Alfve´n waves C. C. Chaston,1 V. Genot,2 J. W. Bonnell,1 C. W. Carlson,1 J oval showing the erosion of ionospheric plasmas from the topside ionosphere by the action of Alfve), Ionospheric erosion by Alfve´n waves, J. Geophys. Res., 111, A03206, doi:10.1029/2005JA011367. 1. Introduction

  3. Magnetospheric disturbances associated with the 13 December 2006 solar flare and their ionospheric effects over North-East Asia

    NASA Astrophysics Data System (ADS)

    Zolotukhina, N.; Polekh, N.; Kurkin, V.; Pirog, O.; Samsonov, S.; Moiseyev, A.

    2012-03-01

    We present an observational study of magnetospheric and ionospheric disturbances during the December 2006 intense magnetic storm associated with the 4?/?3.4 class solar flare. To perform the study we utilize the ground data from North-East Asian ionospheric and magnetic observatories (60-72°N, 88-152°E) and in situ measurements from LANL, GOES, Geotail and ACE satellites. The comparative analysis of ionospheric, magnetospheric and heliospheric disturbances shows that the interaction of the magnetosphere with heavily compressed solar wind and interplanetary magnetic field caused the initial phase of the magnetic storm. It was accompanied by the intense sporadic E and F2 layers and the total black-out in the nocturnal subauroral ionosphere. During the storm main phase, LANL-97A, LANL 1994_084, LANL 1989-046 and GOES_11 satellites registered a compression of the dayside magnetosphere up to their orbits. In the morning-noon sector the compression was accompanied by an absence of reflections from ionosphere over subauroral ionospheric station Zhigansk (66.8°N, 123.3°E), and a drastic decrease in the F2 layer critical frequency (foF2) up to 54% of the quite one over subauroral Yakutsk station (62°N, 129.7°E). At the end of the main phase, these stations registered a sharp foF2 increase in the afternoon sector. At Yakutsk the peak foF2 was 1.9 time higher than the undisturbed one. The mentioned ionospheric disturbances occurred simultaneously with changes in the temperature, density and temperature anisotropy of particles at geosynchronous orbit, registered by the LANL-97A satellite nearby the meridian of ionospheric and magnetic measurements. The whole complex of disturbances may be caused by radial displacement of the main magnetospheric domains (magnetopause, cusp/cleft, plasma sheet) with respect to the observation points, caused by changes in the solar wind dynamic pressure, the field of magnetospheric convection, and rotation of the Earth.

  4. A MLP neural network as an investigator of TEC time series to detect seismo-ionospheric anomalies

    NASA Astrophysics Data System (ADS)

    Akhoondzadeh, M.

    2013-06-01

    Anomaly detection is extremely important for earthquake parameters estimation. In this paper, an application of Artificial Neural Networks (ANNs) in the earthquake precursor's domain has been developed. This study is concerned with investigating the Total Electron Content (TEC) time series by using a Multi-Layer Perceptron (MLP) neural network to detect seismo-ionospheric anomalous variations induced by the powerful Tohoku earthquake of March 11, 2011.The duration of TEC time series dataset is 120 days at time resolution of 2 h. The results show that the MLP presents anomalies better than referenced and conventional methods such as Auto-Regressive Integrated Moving Average (ARIMA) technique. In this study, also the detected TEC anomalies using the proposed method, are compared to the previous results (Akhoondzadeh, 2012) dealing with the observed TEC anomalies by applying the mean, median, wavelet and Kalman filter methods. The MLP detected anomalies are similar to those detected using the previous methods applied on the same case study. The results indicate that a MLP feed-forward neural network can be a suitable non-parametric method to detect changes of a non linear time series such as variations of earthquake precursors.

  5. 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

  6. Aerosol growth in Titan's ionosphere.

    PubMed

    Lavvas, Panayotis; Yelle, Roger V; Koskinen, Tommi; Bazin, Axel; Vuitton, Véronique; Vigren, Erik; Galand, Marina; Wellbrock, Anne; Coates, Andrew J; Wahlund, Jan-Erik; Crary, Frank J; Snowden, Darci

    2013-02-19

    Photochemically produced aerosols are common among the atmospheres of our solar system and beyond. Observations and models have shown that photochemical aerosols have direct consequences on atmospheric properties as well as important astrobiological ramifications, but the mechanisms involved in their formation remain unclear. Here we show that the formation of aerosols in Titan's upper atmosphere is directly related to ion processes, and we provide a complete interpretation of observed mass spectra by the Cassini instruments from small to large masses. Because all planetary atmospheres possess ionospheres, we anticipate that the mechanisms identified here will be efficient in other environments as well, modulated by the chemical complexity of each atmosphere. PMID:23382231

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

    SciTech Connect

    Kopnin, S.I.; Kosarev, I.N.; Popel, S.I.; Yu, M.Y.

    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.

  8. Traveling ionospheric disturbances in the Weddell Sea Anomaly associated with geomagnetic activity

    NASA Astrophysics Data System (ADS)

    Milan, S. E.; Grocott, A.; Larquier, S.; Lester, M.; Yeoman, T. K.; Freeman, M. P.; Chisham, G.

    2013-10-01

    present observations from the Falkland Islands Super Dual Auroral Radar Network radar of the propagation of HF radio waves via the Weddell Sea Ionospheric Anomaly (WSA), a region of enhanced austral summer nighttime ionospheric electron densities covering the southern Pacific and South Americas region. This anomaly is thought to be produced by uplift of the ionosphere by prevailing equatorward thermospheric winds. Of particular interest are perturbations of the WSA-supported propagation, which suggest that during periods of geomagnetic disturbance, the ionospheric layer can be lowered by several tens of kilometers and subsequently recover over a period of 1 to 2 h. Perturbations can appear singly or as a train of two to three events. We discuss possible causes of the perturbations and conclude that they are associated with equatorward propagating large-scale atmospheric waves produced by magnetospheric energy deposition in the auroral or subauroral ionosphere. Changes in high/middle latitude electrodynamics during geomagnetic storms may also account for the perturbations, but further modeling is required to fully understand their cause.

  9. Analysis of the backscatter spectrum in an ionospheric modification experiment

    NASA Technical Reports Server (NTRS)

    Kim, H.

    1973-01-01

    Predictions of the backscatter spectrum are compared, including effects of ionospheric inhomogeneity with experimental observations of incoherent backscatter from an artificially heated region. Calculations show that the strongest backscatter echo received is not, in fact, from the reflection level, but from a region some distance below (about 0.5 km for an experiment carried out at Arecibo), where the pump wave from a HF transmitter approximately 100 kW) is below the threshold for parametric amplification. By taking the standing wave pattern of the pump into account, asymmetry is explained of the up-shifted and down-shifted plasma lines in the backscatter spectrum, and the several peaks typically observed in the region of the spectrum near the HF transmitter frequency.

  10. 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.

  11. Effect of enhanced x-ray flux on the ionosphere over Cyprus during solar flares

    NASA Astrophysics Data System (ADS)

    Mostafa, Md. Golam; Haralambous, Haris

    2015-06-01

    In this work we study the effect of solar flares on the ionosphere over Cyprus. Solar flares are impulsive solar activity events usually coupled with Coronal Mass Ejection (CME). The arrival and the subsequent impact of solar flares on geospace, following an eruption on the Sun's surface is almost immediate (around 9 min) whereas the impact of CMEs is rather delayed (2-3 days) as the former is based on X-ray radiation whereas the latter phenomenon is related with particles and magnetic fields travelling at lower speeds via the Solar Wind. The penetration of X-rays down to the Dregion following such an event enhances the electron density. This increase can be monitored by ionosondes, which measure the electron density up to the maximum electron density NmF2. The significance of this increase lies on the increase of signal absorption causing limited window of operating frequencies for HF communications. In this study the effect of enhanced X-ray flux on the ionosphere over Cyprus during solar flares has been investigated. To establish the correlation and extent of impact on different layers, data of X-ray intensity from Geostationary Operational Environmental Satellite (GOES) and ionospheric characteristics (D & F layer) over Nicosia station (35° N, 33° E) were examined for all solar flares during the period 2011-2014. The analysis revealed a positive and good correlation between frequency of minimum reflection, fmin and X-ray intensity for D layer demonstrating that X-rays play a dominant role in the ionization of lower ionosphere. Hence, X-ray flux can be used as a good proxy for studying the solar flare effects on lower ionosphere. The correlation coefficient between maximum electron density of F layer, NmF2 and X-ray intensity was found to be poor.

  12. Longitudinal variations in the F region ionosphere and the topside ionosphere-plasmasphere: Observations and model simulations

    E-print Network

    Larson, Kristine

    Longitudinal variations in the F region ionosphere and the topside ionosphere October 2011; published 7 December 2011. [1] Constellation Observing System for Meteorology Ionosphere the local time and seasonal variation of longitude structures in both the F region ionosphere as well

  13. Artificial Intelligence 

    E-print Network

    Appleton, D. S.

    1985-01-01

    Xisting technology. The Fifth Generation Computer Project was sol d on the Idea that after new technology, Is developed, new requirements will appear. WIthin the general "science" we call artifIcIal Intelligence, there Is stili confusion between the technolog... to discuss computl ng Issues. Magaz I nes, newspapers, specl al conferences, and al most every other Imagl nabl e ferum fer discussion of AI has addressed the Issue of what artifIcial Intelligence Is and whether It can be ach I eved. In the 1930s, Dr...

  14. Connecting Stratospheric and Ionospheric Anomalies

    NASA Astrophysics Data System (ADS)

    Spraggs, M. E.; Goncharenko, L. P.; Zhang, S.; Coster, A. J.; Benkevitch, L. V.

    2014-12-01

    This study investigates any relationship between lunar phases and ionospheric anomalies that appear at low latitudes concurrently with sudden stratospheric warmings (SSWs). The study utilizes World-wide GPS Receiver Network Total Electron Content (TEC) data spanning 13 years (2001-2014) and focuses on the changes in the equatorial ionization anomaly the Western hemisphere. TEC is highly variable due to the influences of solar flux, geomagnetic activity, and seasonal variation and these influences are removed by the use of model. This empirical TEC model is a combination of linear dependencies of solar flux (F10.7) and geomagnetic activity (Ap3) with a third degree polynomial dependency for day-of-year (DOY). With such dependencies removed, the remaining TEC variation could be resolved and attributed to an appropriate mechanism. Lunar phase and apside was investigated in particular, especially the new and full moon phases during perigees when tidal forcing would be most powerful. Lunar tidal forcing on planetary waves is also examined as being physically responsible for setting up conditions that may give rise to SSWs and ionospheric anomalies. Preliminary results suggest that such anomalies may be enhanced in intensity during the full or new moon and even more so during perigee by different amounts depending on whether the SSW is a major (40-60%) or minor (20-45%) event.

  15. Ionospheric modification research at HIPAS

    SciTech Connect

    Brandt, R.G.

    1990-10-01

    The HIPAS ionospheric heating facility radiates a total power of 1.2 MW with an ERP of 84 MW. it presently operates at an HF frequency of 2.85 MHz but is tunable to about 5 MHz. Electrojet modulation experiments have been conducted at frequencies from 5 Hz to 5 kHz. The magnetic field amplitudes, measured close to the heater, can be 1 pT or larger under very strong electrojet conditions. Even under much weaker conditions when the amplitudes are highly variable, the phase of the ELF signal is relatively stable. The efficiency of converting HF to ELF is presently too low for a practical communication system. Beam painting has been proposed as a method for improving the conversion efficiency in D region heating by causing a much larger area of the ionosphere to radiate coherently; this concept will be tested using microsecond beam steering. Use of shorter heating pulses (lower duty cycle) already seems promising. Even larger gains are expected for E region heating as compared to region heating.

  16. Ion Escape from the Ionosphere of Titan

    NASA Technical Reports Server (NTRS)

    Hartle, R.; Sittler, E.; Lipatov, A.

    2008-01-01

    Ions have been observed to flow away from Titan along its induced magnetic tail by the Plasma Science Instrument (PLS) on Voyager 1 and the Cassini Plasma Spectrometer (CAPS) on Cassini. In both cases, the ions have been inferred to be of ionospheric origin. Recent plasma measurements made at another unmagnetized body, Venus, have also observed similar flow in its magnetic tail. Much earlier, the possibility of such flow was inferred when ionospheric measurements made from the Pioneer Venus Orbiter (PVO) were used to derive upward flow and acceleration of H(+), D(+) and O(+) within the nightside ionosphere of Venus. The measurements revealed that the polarization electric field in the ionosphere produced the principal upward force on these light ions. The resulting vertical flow of H(+) and D(+) was found to be the dominant escape mechanism of hydrogen and deuterium, corresponding to loss rates consistent with large oceans in early Venus. Other electrodynamic forces were unimportant because the plasma beta in the nightside ionosphere of Venus is much greater than one. Although the plasma beta is also greater than one on Titan, ion acceleration is expected to be more complex, especially because the subsolar point and the subflow points can be 180 degrees apart. Following what we learned at Venus, upward acceleration of light ions by the polarization electric field opposing gravity in the ionosphere of Titan will be described. Additional electrodynamic forces resulting from the interaction of Saturn's magnetosphere with Titan's ionosphere will be examined using a recent hybrid model.

  17. Coupling of Earth's Atmosphere and Ionosphere

    NASA Astrophysics Data System (ADS)

    Singh, A. K.

    2012-12-01

    The coupling between the Earth's atmosphere and ionosphere is very complex and many aspects are not well understood till date. Recent measurements show that coupling influences both the electron density and electrical conductivity. The ionosphere reacts to various natural hazards related phenomena such as lightening discharges, thunderstorms, high-power explosion, earthquakes, volcano eruptions, and typhoons through a chain of interconnected processes in the lithosphere-atmosphere-ionosphere interaction system. The precipitation of magnetospheric electrons affects higher latitudes while the radioactive elements emitted during the earthquakes affect electron density and conductivity in the lower atmosphere. Thunderstorms and lightning discharges play a major role in transferring energy from the atmosphere to the ionosphere and in establishing electrical coupling between atmosphere and ionosphere through the global electric circuit (GEC). Electrical processes occurring in the atmosphere couple the atmosphere and ionosphere, because both DC and AC effects operate at the speed of light. The electrostatic and electromagnetic field changes in global electric circuit arise from thunderstorm, lightning discharges, and optical emissions in the mesosphere. In the present paper, our present understanding of how various processes play pivotal role in energy transfer from the lower atmosphere to the ionosphere would be briefly reviewed.

  18. Artificial Ionization and UHF Radar Response Associated with HF Frequencies near Electron Gyro-Harmonics (Invited)

    NASA Astrophysics Data System (ADS)

    Watkins, B. J.; Fallen, C. T.; Secan, J. A.

    2013-12-01

    We present new results from O-mode ionospheric heating experiments at the HAARP facility in Alaska to demonstrate that the magnitude of artificial ionization production is critically dependent on the choice of HF frequency near gyro-harmonics. For O-mode heating in the lower F-region ionosphere, typically about 200 km altitude, artificial ionization enhancements are observed in the lower ionosphere (about 150 - 220 km) and also in the topside ionosphere above about 500 km. Lower ionosphere density enhancements are inferred from HF-enhanced ion and plasma-line signals observed with UHF radar. Upper ionospheric density enhancements have been observed with TEC (total electron content) experiments by monitoring satellite radio beacons where signal paths traverse the HF-modified ionosphere. Both density enhancements and corresponding upward plasma fluxes have also been observed in the upper ionosphere via in-situ satellite observations. The data presented focus mainly on observations near the third and fourth gyro-harmonics. The specific values of the height-dependent gyro-harmonics have been computed from a magnetic model of the field line through the HF heated volume. Experiments with several closely spaced HF frequencies around the gyro-harmonic frequency region show that the magnitude of the lower-ionosphere artificial ionization production maximizes for HF frequencies about 1.0 - 1.5 MHz above the gyro-harmonic frequency. The response is progressively larger as the HF frequency is increased in the frequency region near the gyro-harmonics. For HF frequencies that are initially greater than the gyro-harmonic value the UHF radar scattering cross-section is relatively small, and non-existent or very weak signals are observed; as the signal returns drop in altitude due to density enhancements the HF interaction region passes through lower altitudes where the HF frequency is less than the gyro-harmonic value, for these conditions the radar scattering cross-section is significantly increased and strong signals persist while the high-power HF is present . Simultaneous observations of topside TEC measurements and lower-ionosphere UHF radar observations suggest there is an optimum altitude region to heat the lower F-region in order to produce topside ionosphere density enhancements. The observations are dependent on HF power levels and we show several examples where heating results are only observed for the high-power levels attainable with the HAARP facility.

  19. Artificial Intelligence.

    ERIC Educational Resources Information Center

    Wash, Darrel Patrick

    1989-01-01

    Making a machine seem intelligent is not easy. As a consequence, demand has been rising for computer professionals skilled in artificial intelligence and is likely to continue to go up. These workers develop expert systems and solve the mysteries of machine vision, natural language processing, and neural networks. (Editor)

  20. 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.

  1. Effect of small-scale ionospheric variability on GNSS radio occultation data quality

    NASA Astrophysics Data System (ADS)

    Verkhoglyadova, O. P.; Mannucci, A. J.; Ao, C. O.; Iijima, B. A.; Kursinski, E. R.

    2015-09-01

    Global Navigation Satellite Systems (GNSS) radio occultation (RO) measurements are sensitive to thin ionization layers and small-scale ionosphere structures. To evaluate error bounds and possible biases in atmospheric retrievals, we characterized ionospheric irregularities encountered in the affected profiles by analyzing the L1 signal-to-noise ratio (SNR) variability at E layer altitudes (from 90 km to 130 km). New metrics to analyze statistical effects of small-scale ionospheric irregularities on refractivity retrievals are proposed. We analyzed refractivity (N) retrievals with Constellation Observing System for Meteorology, Ionosphere and Climate (COSMIC) ROs in 2011. Using refractivity from European Centre for Medium-Range Weather Forecasts (ECMWF) analysis (NECMWF) as the reference data set, we studied statistical properties of the fractional refractivity bias (?N) defined by the difference (NECMWF - N)/NECMWF and averaged in the altitude range from 20 to 25 km for each individual profile. We found that (1) persistently larger variability of the L1 SNR as measured by the interquartile range (IQR) existed when the occultation tangent point was in the 90 km to 110 km altitude range than at higher E layer altitudes; (2) the upper limits on the fractional refractivity bias for COSMIC ROs are 0.06% (for daytime local time), 0.1% (for nighttime local time), and ~0.01% (for all local times); (3) distributions of ?N are non-Gaussian (leptokurtic); (4) latitudinal distributions of small and large ?N for different levels of ionospheric variability show large tails (NECMWF > N) occurring around the Himalaya and the Andes regions, which are possibly due to biases in ECMWF analysis. We conclude that the refractivity bias due to small-scale irregularities is small below 25 km altitude and can be neglected.

  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. 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.

  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. 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

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

    SciTech Connect

    Belov, A. S. Markov, G. A.; Ryabov, A. O.; Parrot, M.

    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.

  7. Space physics of the ionosphere of Mars

    E-print Network

    Withers, Paul

    Morgan et al. (2008) ­ Radar sounder observations #12;The solar cycle matters Hantsch and Bauer (1990 is the ionosphere like in strongly-magnetized regions? Gurnett et al. (2008) (both figs) Oblique echoes seen over

  8. 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.

  9. The upper atmosphere and ionosphere of Mars

    NASA Technical Reports Server (NTRS)

    Brace, Larry H.

    1992-01-01

    The topics discussed include the following: the dynamic atmosphere of Mars; possible similarities with Earth and Venus; the atmosphere and ionosphere of Mars; solar wind interactions; future approved missions; and possible future mission.

  10. Propagation studies using a theoretical ionosphere model

    NASA Technical Reports Server (NTRS)

    Lee, M.

    1973-01-01

    The mid-latitude ionospheric and neutral atmospheric models are coupled with an advanced three dimensional ray tracing program to see what success would be obtained in predicting the wave propagation conditions and to study to what extent the use of theoretical ionospheric models is practical. The Penn State MK 1 ionospheric model, the Mitra-Rowe D region model, and the Groves' neutral atmospheric model are used throughout this work to represent the real electron densities and collision frequencies. The Faraday rotation and differential Doppler velocities from satellites, the propagation modes for long distance high frequency propagation, the group delays for each mode, the ionospheric absorption, and the spatial loss are all predicted.

  11. 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

  12. Magnetic Fluctuations in the Martian Ionosphere

    NASA Technical Reports Server (NTRS)

    Espley, Jared

    2010-01-01

    The Martian ionosphere is influenced by both the solar wind and the regional magnetic fields present in the Martian crust. Both influences ought to cause time variable changes in the magnetic fields present in the ionosphere. I report observations of these magnetic field fluctuations in the Martian ionosphere. I use data from the Mars Global Surveyor magnetometer instrument. By using data from the aerobraking low altitude passes (approx. 200 km) I find that there are numerous fluctuations both near and far from the strong crustal sources. Using data from the 400 km altitude mapping phase (which is near the topside of the primary ionosphere), I look at the comparative strength of the fluctuations relative to the solar wind and temporal variations. I discuss which wave modes and instabilities could be contributing to these fluctuations. I also discuss the implications of these fluctuations for understanding energy transfer in the Martian system and the effects on atmospheric escape.

  13. Artificial Rheotaxis

    NASA Astrophysics Data System (ADS)

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

    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.

  14. Artificial Rheotaxis

    NASA Astrophysics Data System (ADS)

    Palacci, Jeremie; Sacanna, Stefano; Abramian, Anais; Hanson, Kasey; Pine, David; Chaikin, Paul; CSMR, NYU Team

    2013-11-01

    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.

  15. 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.

  16. Artificial Wormhole

    E-print Network

    A. A. Kirillov; E. P. Savelova

    2012-04-18

    It is shown that recently reported result by the OPERA Collaboration (arXive:1109.4897) of an early arrival time of muon neutrinos with respect to the speed of light in vacuum does not violate standard physical laws. We show that vacuum polarization effects in intensive external fields may form a wormhole-like object. The simplest theory of such an effect is presented and basic principles of formation of an artificial wormhole are also considered.

  17. Ionospheric effects on a large radio telescope.

    NASA Astrophysics Data System (ADS)

    Zhang, Xizhen; Han, Wenjun; Zheng, Yijia

    1996-12-01

    Based on the calibrator-observations of the Miyun Synthesis Radio Telescope and Westerbork Synthesis Radio Telescope statistical results of phase errors induced in the output of radio telescope due to ionosphere are presented. One conclusion is that the occurrence probability of phase-errors larger than 5 degrees/km is about 40% at 232 MHz. Influences of large and small scale irregularities of ionosphere on radio observations of large telescope at meter and decimeter bands are also discussed.

  18. A Model of Callisto's Ionosphere

    NASA Astrophysics Data System (ADS)

    Hartkorn, O. A.; Saur, J.; Bloecker, A.; Strobel, D. F.; Simon, S.

    2014-12-01

    We develop a model of the ionosphere of Jupiter's moon Callisto, where we assume a stationary balance between sources and sinks of electrons and electron energy. Hence, effects of electron transport and electron energy transport are neglected. At Callisto, the production of electrons and electron energy is basically driven by photoionization, which is implemented using the EUVAC model for solar activity. Dissociative recombination is the main electron loss process, whereas electron energy loss is further driven by dissociation, electron impact ionization as well as vibrational and rotational excitations of neutral atmospheric particles. All these effects are incorporated within our model by considering the associated cross sections. The neutral atmosphere is assumed to be stationary and consists of molecular oxygen with a column density of 3 to 4 x 1020 m-2 (e.g. Kliore et al. (2002), Liang et al. (2005)). Our results can be compared to radio occultation observations of four Galileo spacecraft flybys reported by Kliore et al. (2002), which shows that this simple model can explain the general pattern of the observational data. Indeed, our results indicate that the detection of enhanced electron densities is very sensitive to the exact position of the tangential point of the radio occultation method. Our model shows that photoionization produces a strong asymmetry of the electron density distribution between day and night-side of the moon. Further, model results for the electron energy allow for an estimation of the day glow of Callisto's atmosphere. This can be compared to HST observations (Strobel et al. (2002)) in order to evaluate the density of the neutral oxygen atmosphere. Future studies imply the modeling of the modification of the ionospheric structure through interaction with upstreaming jovian magnetospheric plasma.

  19. 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.

  20. 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.

  1. Radiotomographic imaging and GNSS remote sensing of the midlatitude ionosphere modified by powerful HF radiowaves.

    NASA Astrophysics Data System (ADS)

    Kunitsyn, V.; Andreeva, E. S.; Padokhin, A. M.; Vorontsov, A.; Frolov, V. L.; Komrakov, G.; Bernhardt, P. A.; Siefring, C. L.

    2014-12-01

    We present the results of the radiotomographic imaging and GNSS remote sensing of the artificial ionospheric disturbances obtained in the recent experiments on the modification of the midlatitude ionosphere by powerful HF radiowaves carried out at the Sura heating facility. The experiments were conducted using both O- and X- mode radiowaves, in daytime and nighttime conditions with various schemes of the radiation of the heating wave. Radio transmissions from the low- (Parus, e-POP on CASSIOPE) and high-orbital (GPS/GLONASS) navigational satellites received at the mobile network of receiving sites were used for the remote sensing of the heated area of the ionosphere. We study the variations in TEC caused by HF heating showing that the GNSS TEC spectra often contain frequency components corresponding to the modulation periods of the ERP of the heating wave. The manifestations of the heating-induced variations in TEC are most prominent in the area of magnetic zenith of the pumping wave. In this work we also present the radiotomographic reconstructions (including first time e-POP-SURA reconstructions) of the spatial structure of the disturbed area of the ionosphere corresponding to the directivity pattern of the heater as well as the spatial structure of the wave- like disturbances, which are possibly heating-induced AGWs, diverging from the heated area of the ionosphere. The spatial period of observed disturbances is 200-250 km and they are easily traced up to a distance of 700-800 km from the heated region, which is in good agreement with the modeling results.

  2. Long term changes in the ionosphere over Indian low latitudes: Impact of greenhouse gases

    NASA Astrophysics Data System (ADS)

    Sharma, Som; Chandra, H.; Beig, G.

    2015-06-01

    Increased concentration of greenhouse gases due to anthropogenic activities warm the troposphere and have a cooling effect in the middle and upper atmosphere. Ionospheric densities and heights are affected due to cooling. Carbon dioxide is one of the most dominant gases for the cause of long term ionospheric trends along with other radiatively active greenhouse gases. Regular ionospheric soundings are made over Ahmedabad (23.1°N, 72.7°E), since 1953. Long term changes in the ionosphere as a consequence of the cooling of the mesosphere and thermosphere due to the increased concentration of greenhouse gases have been studied. Ionospheric observations over Ahmedabad, a low latitude station in the anomaly crest region, for the years 1955-2003 are examined to study the long term changes in the critical frequencies of the various ionospheric layers and the height of the maximum ionization as characterized by hPF2. A decrease in foF2 (1.9 MHz for midday, 1.4 MHz for midnight) and hPF2 (18 km for midday, 17 km for midnight) during about five decades are noted. An increase is noted in foF1 (0.4 MHz). The foF2 data are also examined over an equatorial station Kodaikanal (10.2°N, 77.5°E), situated near the magnetic equator for the years 1960-1995 and a decrease of 0.5 MHz for midday and 0.7 MHz for midnight are noted in ~35 years.

  3. Ionospheric precursors observed at low latitudes around the time of koyna earthquake

    NASA Astrophysics Data System (ADS)

    Sharma, Kavita; Das, Rupesh M.; Dabas, R. S.; Pillai, K. G. M.; Garg, S. C.; Mishra, A. K.

    2008-10-01

    On December 11, 1967 at 05:21 LT, an immense earthquake of magnitude 6.7 struck Koyna, the Indian province of Maharashtra. Its epicenter was located at geographic latitude 17.37°N and longitude 73.75°E with depth of about 3 km. Ground based measurements show variation in the critical frequency of ionospheric F2 layer (foF2) before and after the shock. In the present study the behavior of F2-region of ionosphere has been examined over the equatorial and low latitudinal region ionosphere during the month of December 1967 around the time of Koyna earthquake. For this purpose, the ionospheric data collected with the help of ground-based ionosondes installed at Hyderabad (located close to the earthquake epicenter) Ahmedabad, Trichirapulli, Kodaikanal and Trivendrum have been utilized. The upper and lower bound of Interquartile range (IRQ) are constructed to monitor the variations in foF2 other than day-to-day and diurnal pattern for finding the seismo-ionospheric precursors. Some anomalous electron density variations are observed between post midnight hours to local pre-noon hours at each station. These anomalies are strongly time dependent and appeared a couple of days before the main shock. The period considered in this study comes under the quiet geomagnetic conditions. Hence, the observed anomalies (which are more than the usual day-to-day variability) over all stations are likely to be associated with this imminent earthquake. The possible mechanism to explain these anomalies is the effect of seismogenic electric field generated just above the surface of earth within the earthquake preparation zone well before the earthquake due to emission of radioactive particles and then propagated upward, which perturbs the F-region ionosphere.

  4. Ionospheric convection driven by NBZ currents

    NASA Technical Reports Server (NTRS)

    Rasmussen, C. E.; Schunk, R. W.

    1987-01-01

    Computer simulations of Birkeland currents and electric fields in the polar ionosphere during periods of northward IMF were conducted. When the IMF z component is northward, an additional current system, called the NBZ current system, is present in the polar cap. These simulations show the effect of the addition of NBZ currents on ionospheric convection, particularly in the polar cap. When the total current in the NBZ system is roughly 25 to 50 percent of the net region 1 and 2 currents, convection in the central portion of the polar cap reverses direction and turns sunward. This creates a pattern of four-cell convection with two small cells located in the polar cap, rotating in an opposite direction from the larger cells. When the Birkeland currents are fixed (constant current source), the electric field is reduced in regions of relatively high conductivity, which affects the pattern of ionospheric convection. Day-night asymmetries in conductivity change convection in such a way that the two polar-cap cells are located within the large dusk cell. When ionospheric convection is fixed (constant voltage source), Birkeland currents are increased in regions of relatively high conductivity. Ionospheric currents, which flow horizontally to close the Birkeland currents, are changed appreciably by the NBZ current system. The principal effect is an increase in ionospheric current in the polar cap.

  5. Solar Cycle Variations in the Polar Ionosphere

    NASA Astrophysics Data System (ADS)

    Burrell, A. G.; Yeoman, T. K.; Milan, S. E.; Lester, M.

    2014-12-01

    The polar ionosphere is a dynamic region that readily responds to changes in solar irradiance, solar wind, the magnetosphere, and the neutral atmosphere. The most recent solar minimum brought to light gaps in the current understanding of the relationship between ionospheric structure and solar irradiance. The Super Dual Auroral Radar Network (SuperDARN) offers an invaluable dataset for studying long-term ionospheric variability, as it has been continuously providing extensive coverage of the northern and southern polar ionosphere since 1995 (the solar minimum preceding the 23rd solar cycle). An under-utilized portion of the SuperDARN dataset is the ground-backscatter: the backscatter that returns from a reflection point on the ground along an open (or irregularity-free) propagation path. The ground-backscatter provides a measure the ionospheric density at the peak of the radar signal's path. These measurements are used to the examine the changes in the bottomside, polar ionosphere over the 23rd and 24th solar cycles.

  6. HF-enhanced 4278-Å airglow: evidence of accelerated ionosphere electrons?

    NASA Astrophysics Data System (ADS)

    Fallen, C. T.; Watkins, B. J.

    2013-12-01

    We report calculations from a one-dimensional physics-based self-consistent ionosphere model (SCIM) demonstrating that HF-heating of F-region electrons can produce 4278-Å airglow enhancements comparable in magnitude to those reported during ionosphere HF modification experiments at the High-frequency Active Auroral Research Program (HAARP) observatory in Alaska. These artificial 'blue-line' emissions, also observed at the EISCAT ionosphere heating facility in Norway, have been attributed to arise solely from additional production of N2+ ions through impact ionization of N2 molecules by HF-accelerated electrons. Each N2+ ion produced by impact ionization or photoionization has a probability of being created in the N2+(1N) excited state, resulting in a blue-line emission from the allowed transition to its ground state. The ionization potential of N2 exceeds 18 eV, so enhanced impact ionization of N2 implies that significant electron acceleration processes occur in the HF-modified ionosphere. Further, because of the fast N2+ emission time, measurements of 4278-Å intensity during ionosphere HF modification experiments at HAARP have also been used to estimate artificial ionization rates. To the best of our knowledge, all observations of HF-enhanced blue-line emissions have been made during twilight conditions when resonant scattering of sunlight by N2+ ions is a significant source of 4278-Å airglow. Our model calculations show that F-region electron heating by powerful O-mode HF waves transmitted from HAARP is sufficient to increase N2+ ion densities above the shadow height through temperature-enhanced ambipolar diffusion and temperature-suppressed ion recombination. Resonant scattering from the modified sunlit region can cause a 10-20 R increase in 4278-Å airglow intensity, comparable in magnitude to artificial emissions measured during ionosphere HF-modification experiments. This thermally-induced artificial 4278-Å aurora occurs independently of any artificial aurora maintained by HF-accelerated (non-thermal) electrons. The numerical results presented here do not necessarily rule out the presence of HF-accelerated electrons with energies exceeding 18 eV. However, vertical or field-aligned airglow intensity measurements made during twilight conditions do not provide definitive evidence of energetic HF-accelerated electrons. Consequently, artificial blue-line airglow measurements should not be used to estimate N2+ ionization rates without also accounting for temperature-dependent chemistry and diffusion. Future experiments that make simultaneous measurements of N2+ ion airglow emissions from both the first negative bands and the Meinel bands can potentially resolve the relative contributions of accelerated electron and resonant scattering mechanisms. Airglow emission rates from these bands are expected to be in strict proportion when the emissions result from electron impact ionization of N2 molecules. Side-view altitude-resolved 4278-Å airglow measurements may also indicate the presence of energetic HF-accelerated electrons if the blue-line emissions are determined to occur below the shadow height.

  7. 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.

  8. A simulation study on the impact of altitudinal dependent vertical plasma drift on the equatorial ionosphere in the evening

    NASA Astrophysics Data System (ADS)

    Qian, Cheng; Lei, Jiuhou; Wang, Wenbin

    2015-04-01

    We carry out a simulation study on the impact of altitudinal dependent plasma drift on the equatorial ionosphere in the evening, under geomagnetically quiet conditions. Our study used the vertical plasma drift velocity data measured by an incoherent scatter radar at Jicamarca (11.95°S, 76.87°W). The data covered the local sunset period on 15 and 16 November 2004. The plasma drift had significant altitudinal variations in the vertical component, which is perpendicular to the magnetic field. We employed SAMI2 (SAMI2 is another model of the ionosphere) to evaluate the effect of the altitude-dependent ion drift on the equatorial ionosphere. Three types of plasma drift velocity inputs were used in our simulations. The first input is calculated from an empirical model, the second is a height-averaged drift obtained from the observed drift velocity, and the third one corresponds to the observed altitudinal dependent drift data. A strong equatorial ionization anomaly occurred in the results of all numerical experiments. Additional layers (F3 layers) in electron densities over the equatorial F region and "arch" latitudinal structures extending to lower middle latitudes were seen in the simulations driven by the observed altitudinal dependent drift. We further show that neutral winds do not have a significant effect on the simulated F3 layers. The results of our numerical experiments suggest that the simulated additional ionospheric layers and arch structures are associated with the altitudinal gradients in the vertical plasma drift velocity.

  9. 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. Belov, A. S.; Frolov, V. L.; Rapoport, V. O.; Parrot, M.

    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.

  10. Real-time imaging of density ducts between the plasmasphere and ionosphere

    E-print Network

    Loi, Shyeh Tjing; Cairns, Iver H; Menk, Frederick W; Waters, Colin L; Erickson, Philip J; Trott, Cathryn M; Hurley-Walker, Natasha; Morgan, John; Lenc, Emil; Offringa, Andre R; Bell, Martin E; Ekers, Ronald D; Gaensler, B M; Lonsdale, Colin J; Feng, Lu; Hancock, Paul J; Kaplan, David L; Bernardi, G; Bowman, J D; Briggs, F; Cappallo, R J; Deshpande, A A; Greenhill, L J; Hazelton, B J; Johnston-Hollitt, M; McWhirter, S R; Mitchell, D A; Morales, M F; Morgan, E; Oberoi, D; Ord, S M; Prabu, T; Shankar, N Udaya; Srivani, K S; Subrahmanyan, R; Tingay, S J; Wayth, R B; Webster, R L; Williams, A; Williams, C L

    2015-01-01

    Ionization of the Earth's atmosphere by sunlight forms a complex, multi-layered plasma environment within the Earth's magnetosphere, the innermost layers being the ionosphere and plasmasphere. The plasmasphere is believed to be embedded with cylindrical density structures (ducts) aligned along the Earth's magnetic field, but direct evidence for these remains scarce. Here we report the first direct wide-angle observation of an extensive array of field-aligned ducts bridging the upper ionosphere and inner plasmasphere, using a novel ground-based imaging technique. We establish their heights and motions by feature-tracking and parallax analysis. The structures are strikingly organized, appearing as regularly-spaced, alternating tubes of overdensities and underdensities strongly aligned with the Earth's magnetic field. These findings represent the first direct visual evidence for the existence of such structures.

  11. Response of the auroral lower ionosphere to solar flares in March 2012 according to ELF observations

    NASA Astrophysics Data System (ADS)

    Lebed', O. M.; Fedorenko, Yu. V.; Larchenko, A. V.; Pil'gaev, S. V.

    2015-11-01

    The response of the lower ionosphere to the solar flares that occurred in March 2012 is considered. Measurements of the propagation velocity and wave impedance of ELF electromagnetic pulses (atmospherics) performed at Lovozero and Barentsburg high-latitude observatories were used to estimate this response. It was shown that the daily average propagation velocity of atmospherics decreased by 20-30 thousand km/s under disturbed heliogeophysical conditions as compared to the velocity measured under quiet conditions. This is related to a decrease in the effective waveguide height that results from the change in the ionospheric conductivity profile during a solar flare. It was detected that pronounced bursts of wave impedance, the maximums of which exceed the impedance average value by a factor of more than 2, are observed during strong heliogeophysical disturbances. This fact cannot be explained in the scope of a spherically layered model; consequently, such deviations indicate an increase in the D-layer conductivity inhomogeneities.

  12. Signatures of Sudden Stratospheric Warming on the Equatorial Ionosphere-Thermosphere System

    NASA Astrophysics Data System (ADS)

    Sumod, S. G.; Pant, T. K.; Jose, Lijo; Hossain, M. M.; Kumar, K. K.

    2012-04-01

    The effect of Sudden Stratospheric Warming (SSW) event of January 2008 on the Equatorial Ionosphere-Thermosphere System (EITS) over Trivandrum (8.5°N, 77°E, 0.5°N diplat.), a geomagnetic dip equatorial station in India has been investigated. It has been observed that the entire EITS exhibits significant variability during the SSW period. EITS parameters like Equatorial Electrojet (EEJ), F2 layer critical frequency (foF2), F1 layer base height (h'F), Total Electron Content (TEC) and 630 nm thermospheric dayglow showed clear cut signatures of the SSW induced effects. It is suggested that dynamical perturbations associated with the SSW and subsequent modifications in the tidal components through wave-tidal interactions are responsible for such changes in the equatorial electrodynamics. The present study comprehensively brings out the quiet time equatorial ionosphere/thermosphere variability, during both night and daytimes, vis-à-vis the SSW event of January 2008.

  13. An observational study of the nightside ionospheres of Mars and Venus with radio occultation methods

    SciTech Connect

    Zhang, M.H.G. ); Luhmann, J.G. ); Kliore, A.J. )

    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.

  14. Artificial halos

    NASA Astrophysics Data System (ADS)

    Selmke, Markus

    2015-09-01

    Judged by their frequency and beauty, ice halos easily rival rainbows as a prominent atmospheric optics phenomenon. This article presents experimental halo demonstrations of varying complexity. Using a single commercially available hexagonal glass prism, a variety of artificial halos can be simulated. The experiments include laser beam path analysis, a modified classic spinning prism experiment, and a novel Monte-Carlo machine for three-dimensional rotations. Each of these experiments emulates different conditions of certain halo displays, and in combination, they allow a thorough understanding of these striking phenomena.

  15. Planetary waves in the equatorial mesosphere and ionosphere

    NASA Astrophysics Data System (ADS)

    Takahashi, H.; Wrasse, C. M.; Pancheva, D.; Abdu, M. A.; Batista, I. S.; Lima, L. M.; Batista, P. P.; Clemesha, B. R.; Shiokawa, K.

    Meteor radar wind observations from two sites in the equatorial region one at Cariri 7 4oS 36 5oW and the other at Ascension Island 7 9oS 14 4oW with a distance of 2400 km in longitude revealed that there are common period oscillations with 3-4-day 6-8-day and 16-days in the zonal winds and 2-day period in the meridional wind suggesting that these are longitudinally propagating planetary waves The day to day variability of the minimum ionospheric virtual height h F measured at Fortaleza 3 9oS 38 4oW also showed similar oscillation period Among these the 6-day wave was prominent during a period from August to November 2004 From the phase difference between the two meteor radar sites it is found that the wave has a horizontal wavelength of about 12 000 km phase velocity of 21 m s propagating eastwards with a vertical wavelength of 60-80 km Although the wave should not penetrate directly to F-region heights it could affect the post-sunset ExB uplifting of the base of the F-layer Possible coupling processes between the upper mesosphere to ionosphere will be presented and discussed

  16. Ionospheric correction of GPS radio occultation data in the troposphere

    NASA Astrophysics Data System (ADS)

    Zeng, Z.; Sokolovskiy, S.; Schreiner, W.; Hunt, D.; Lin, J.; Kuo, Y.-H.

    2015-07-01

    For inversions of the GPS radio occultation (RO) data in the neutral atmosphere, this study investigates an optimal transition height for replacing the standard ionospheric correction by the linear combination of the L1 and L2 bending angles with the correction of the L1 bending angle by the L1-L2 bending angle extrapolated from above. The optimal transition height depends on the RO mission (i.e., the receiver and firmware) and is different between rising and setting occultations and between L2P and L2C GPS signals. This height is within the range approximately 10-20 km. One fixed transition height, which can be used for the processing of currently available GPS RO data, can be set to 20 km. Analysis of the L1CA and the L2C bending angles in the presence of a sharp top of the boundary layer reveals differences that can be explained by shifts in the impact parameter. The ionosphere-induced vertical shifts of the bending angle profiles require further investigation.

  17. Ion distributions in the high-latitude topside ionosphere

    NASA Astrophysics Data System (ADS)

    Allen, B. T.; Bailey, G. J.; Moffett, R. J.

    1986-04-01

    An earlier model of the high-latitude ionosphere that includes the ions H(+), He(+) and O(+) on an equal footing has been modified. Velocities applied at great altitudes (in this case at 10,000 km) are arranged to give velocities at 1400 km altitude that agree on average with Isis 2 data. Also, light-ion flows in the topside ionosphere respond to changing F-layer conditions. The model has been used to examine ion distributions for different seasons, assuming two-cell convection and sunspot minimum atmospheric parameters. In winter at high latitudes the H(+)/O(+) transition level usually lies above 500 km altitude, apart from the regions of the midlatitude trough and the high-latitude hole; at 500 km altitude, He(+) may be the dominant ion in these trough regions. A deep midlatitude trough present in the F-region may barely be evident in the total ion concentration at altitudes around 800 km. At equinox and in summer the consequences of smaller solar zenith angles and lower neutral atomic hydrogen and neutral helium concentrations are evident.

  18. A Miniature Sweeping Impedance Probe for Ionospheric Plasma Diagnostics

    NASA Astrophysics Data System (ADS)

    Martin-Hidalgo, J.; Swenson, C.

    2013-12-01

    The impedance of a probe immersed in ionospheric plasma at radio frequencies is an important technique for determining absolute electron density. Building on 50 years of history in developing and flying RF probes for plasma diagnostics at Utah State, a new SIP (Sweeping Impedance Probe) design has been completed which will obtain qualitative improvement over previous instruments in terms of accuracy and sweep rate. This instrument will provide a continuous measurement of the plasma impedance magnitude and phase with an expected accuracy of 1% and 1 degree respectively over the 1 to 20 MHz range. This new SIP will be launched in January 2014 onboard the Auroral Spatial Structures Probe (ASSP) NASA sounding rocket mission using a short monopole probe. The rocket apogee of 600 km will allow the characterization of the plasma in the E and F layers at auroral latitudes and the study of short term and spatial variations along the high-altitude profile of the sounding rocket. Although this SIP design has been developed for a sounding rocket, it can be optimized and miniaturized for Cubesat's and included along other ionospheric diagnostic instruments such as double and Langmuir probes. This presentation is focused on the overall design of the instrument, the tests results for the ASSP instrument and conceptual designs for future CubeSat mission similar to the NSF DICE mission.

  19. 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.

  20. Ionospheric Storms in Equatorial Region: Digisonde Observations

    NASA Astrophysics Data System (ADS)

    Paznukhov, V.; Altadill, D.; Blanch, E.

    2011-12-01

    We present a study of the ionospheric storms observed in the low-latitude and equatorial ionosphere at several digisonde stations: Jicamarca (Geomagnetic Coordinates: 2.0 S, 355.3 E), Kwajalein Island (3.8 N, 238.2 E), Ascension Island (2.5 S, 56.8 E), Fortaleza (4.8 N, 33.7 W), and Ramey (28.6 N, 5.2 E). The strongest geomagnetic storms from years 1995-2009 have been analyzed. The main ionospheric characteristics, hmF2 and foF2 were used in the study, making it possible to investigate the changes in the ionosphere peak density and height during the storms. All digisonde data were manually processed to assure the accuracy of the measurements. Solar wind data, geomagnetic field variations, and auroral activity indices have been used to characterize the geomagnetic environment during the events. It was found in our analysis that the major drivers for the ionospheric storms, electric field and neutral wind have approximately equal importance at the low-latitude and equatorial latitudes. This is noticeably different from the behavior of the ionsphere in the middle latitudes, where the neutral wind is usually a dominant factor. It was found that the auroral index, AE is the best precursor of the ionospheric effects observed during the storms in this region. We analyze the difference between time delays of the storm effects observed at the stations located in different local time sectors. The overall statistics of the time delays of the storms as a function of the local time at the stations is also presented. Several very interesting cases of sudden very strong ionospheric uplifting and their possible relation to the equatorial super fountain effect are investigated in greater details.

  1. Ionospheric convection driven by NBZ currents

    SciTech Connect

    Rasmussen, C.E.; Schunk, R.W.

    1987-05-01

    Computer simulations of Birkeland currents and electric fields in the polar ionosphere during periods of northward interplanetary magnetic field (IMF) were conducted. When the IMF z component is northward, an additional current system, called the NBZ current system, is present in the polar cap. These simulations show the effect of the addition of NBZ currents on ionospheric convection, particularly in the polar cap. When the total current in the NBZ system is roughly 25% to 50% of the net region 1 and 2 currents, convection in the central portion of the polar cap reverses direction and turns sunward. This creates a pattern of four-cell convection with two small cells located in the polar cap, rotating in an opposite direction from the larger cells. The effects of varying ionospheric conductivity were studied by considering both a constant voltage source and a constant current source. Conductivity gradients due to seasonal and local time variations in solar production were considered, as well as gradients due to electron precipitation. When the Birkeland currents are fixed (constant current source), the electric field is reduced in regions of relatively high conductivity, which affects the pattern of ionospheric convection. Day-night asymmetries in conductivity change convection in such a way that the two polar-cap cells are located within the large dusk cell. When ionospheric convection is fixed (constant voltage source), Birkeland currents are increased in regions of relatively high conductivity. Ionospheric currents, which flow horizontally to close the Birkeland currents, are changed appreciably by the NBZ current system. The principal effect is an increase in ionospheric current in the polar cap. Copyright American Geophysical Union 1987.

  2. Role of Ionospheric Plasmas in Earth's Magnetotail

    NASA Technical Reports Server (NTRS)

    Moore, Thomas E.

    2007-01-01

    This tutorial will summarize observations and theories indicating a prominent role of ionospheric plasma in the Earth's magnetotail. At the Global scale, I will argue that it is ionospheric plasma momentum and dynamic pressure that are responsible for the production of plasmoids, through the action of a transient near-Earth neutral or X-line, which serves to release excessive plasma pressure from the magnetotail field. Ionospheric plasma gains the momentum and energy to produce plasmoids and their related effects through its interaction with the solar wind, beginning at the dayside reconnection region and extending across the polar caps through the magnetotail lobes. This distant neutral line can be depicted as a feature much like that found in cometary magnetospheres, where disconnection limits the amount of IMF hung up on the cometary coma. On the other hand, the near-Earth neutral one can be seen as a feature unique to planets with an intrinsic magnetic field and internal source of plasma, the heating of which produces pressures too large to be restrained. Ionospheric plasmas also have other more local roles to play in the magnetotail. The circulation influences the composition of the plasma sheet, and the resultant wave environment, giving rise to reduced wave propagation speeds. Important heavy ion cyclotron resonances, and enhanced finite gyro-radius effects including non-adiabatic particle acceleration. At minimum, the presence of ionospheric plasma must influence the rate of reconnection via its enhanced mass density. Other non-MHD effects of ionospheric plasma presence are likely to be important but need much more investigation to be well understood. The MMS mission is designed to penetrate the subtle diffusion region physics that is involved, and its ability to observe ionospheric plasma involvement in reconnection will contribute significantly toward that goal.

  3. 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.

  4. 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

  5. The global ionosphere thermosphere model

    NASA Astrophysics Data System (ADS)

    Ridley, A. J.; Deng, Y.; Tóth, G.

    2006-05-01

    The recently created global ionosphere thermosphere model (GITM) is presented. GITM uses a three-dimensional spherical grid that can be stretched in both latitude and altitude, while having a fixed resolution in longitude. GITM is nontraditional in that it does not use a pressure-based coordinate system. Instead it uses an altitude-based grid and does not assume a hydrostatic solution. This allows the model to more realistically capture physics in the high-latitude region, where auroral heating is prevalent. The code can be run in a one-dimensional (1-D) or three-dimensional (3-D) mode. In 3-D mode, the modeling region is broken into blocks of equal size for parallelization. In 1-D mode, a single latitude and longitude is modeled by neglecting any horizontal transport or gradients, except in the ionospheric potential. GITM includes a modern advection solver and realistic source terms for the continuity, momentum, and energy equations. Each neutral species has a separate vertical velocity, with coupling of the velocities through a frictional term. The ion momentum equation is solved for assuming steady-state, taking into account the pressure, gravity, neutral winds, and external electric fields. GITM is an extremely flexible code—allowing different models of high-latitude electric fields, auroral particle precipitation, solar EUV inputs, and particle energy deposition to be used. The magnetic field can be represented by an ideal dipole magnetic field or a realistic APEX magnetic field. Many of the source terms can be controlled (switched on and off, or values set) by an easily readable input file. The initial state can be set in three different ways: (1) using an ideal atmosphere, where the user inputs the densities and temperature at the bottom of the atmosphere; (2) using MSIS and IRI; and (3) restarting from a previous run. A 3-D equinox run and a 3-D northern summer solstice run are presented. These simulations are compared with MSIS and IRI to show that the large-scale features are reproduced within the code. We conduct a second equinox simulation with different initial conditions to show that the runs converge after approximately 1.5 days. Additionally, a 1-D simulation is presented to show that GITM works in 1-D and that the dynamics are what is expected for such a model.

  6. Generation of whistler waves by continuous HF heating of the upper ionosphere

    NASA Astrophysics Data System (ADS)

    Vartanyan, A.; Milikh, G. M.; Eliasson, B. E.; Sharma, A.; Chang, C.; Parrot, M.; Papadopoulos, K.

    2013-12-01

    We report observations of VLF waves by the DEMETER satellite overflying the HAARP facility during ionospheric heating experiments. The detected VLF waves were in the range 8-17 kHz and coincided with times of continuous heating. The experiments indicate whistler generation due to conversion of artificial lower hybrid waves to whistlers on small scale field-aligned plasma density striations. The observations are compared with theoretical models, taking into account both linear and nonlinear processes. Implications of the mode conversion technique on VLF generation with subsequent injection into the radiation belts to trigger particle precipitation are discussed.

  7. Effects in the ionosphere and HF radio-wave propagation during an intense substorm

    NASA Astrophysics Data System (ADS)

    Blagoveshchensky, D. V.; Borisova, T. D.; Rogov, D. D.

    2010-08-01

    We present the results of combined radiophysical studies during the period of an intense magnetospheric substorm which occurred from 00:00 to 02:00 UT in April 12, 1999. Measurements of the ionospheric parameters by a chain of European ionosondes for this period were compared with the variations in ionospheric parameters averaged over more than 70 substorms. The latter variations were obtained by data from the ionosondes of Europe, Central Siberia, and North America in 1993-1999. Data from the CUTLASS radar as well as the DMSP and POES satellites were used for the analysis of the April 11-12 substorm. Numerical calculations of HF radio-wave propagation on the St. Petersburg—Longyearbyen (Svalbard) high-latitude path were carried out by the ray tracing technique. Two simultaneous effects have been revealed in the ionosphere. One occurs immediately during the substorm and another is associated with the end of the magnetic storm in April 10, 1999. According to the CUTLASS radar data, the number of backscattering irregularities in the ionospheric F layer notably decreased during the substorm expansion phase. Satellite data showed an increase in the “soft” (hundreds of eV) particle precipitation before and after the substorm. Numerical calculations of HF radio-wave propagation on the St. Petersburg—Longyearbyen path have demonstrated an essential change of propagation mechanisms during the substorm and a tangible change in the wave arrival angles before and after the substorm.

  8. Development of a regional GPS-based ionospheric TEC model for South Africa

    NASA Astrophysics Data System (ADS)

    Opperman, Ben D. L.; Cilliers, Pierre J.; McKinnell, Lee-Anne; Haggard, Ray

    Advances in South African space physics research and related disciplines require better spatial and time resolution ionospheric information than was previously possible with the existing ionosonde network. A GPS-based, variable degree adjusted spherical harmonic (ASHA) model was developed for near real-time regional ionospheric total electron content (TEC) mapping over South Africa. Slant TEC values along oblique GPS signal paths are quantified from a network of GPS receivers and converted to vertical TEC by means of the single layer mapping function. The ASHA model coefficients and GPS differential biases are estimated from vertical TEC at the ionospheric pierce points and used to interpolate TEC at any location within the region of interest. Diurnal TEC variations with one minute time resolution and time-varying 2D regional TEC maps are constructed. In order to validate the ASHA method, simulations with an IRI ionosphere were performed, while the ASHA results from actual data were compared with two independent GPS-based methodologies and measured ionosonde data.

  9. A Comparative Study of the Ionospheric TEC Measurements Using Global Ionospheric Maps of GPS, TOPEX Radar and the Bent Model

    NASA Technical Reports Server (NTRS)

    Ho, C.; Wilson, B.; Mannucci, A.; Lindqwister, U.; Yuan, D.

    1997-01-01

    Global ionospheric mapping (GIM) is a new, emerging technique for determining global ionospheric TEC (total electron content) based on measurements from a worldwide network of Global Positioning System (GPS) receivers.

  10. Ionospheric Specifications for SAR Interferometry (ISSI)

    NASA Technical Reports Server (NTRS)

    Pi, Xiaoqing; Chapman, Bruce D; Freeman, Anthony; Szeliga, Walter; Buckley, Sean M.; Rosen, Paul A.; Lavalle, Marco

    2013-01-01

    The ISSI software package is designed to image the ionosphere from space by calibrating and processing polarimetric synthetic aperture radar (PolSAR) data collected from low Earth orbit satellites. Signals transmitted and received by a PolSAR are subject to the Faraday rotation effect as they traverse the magnetized ionosphere. The ISSI algorithms combine the horizontally and vertically polarized (with respect to the radar system) SAR signals to estimate Faraday rotation and ionospheric total electron content (TEC) with spatial resolutions of sub-kilometers to kilometers, and to derive radar system calibration parameters. The ISSI software package has been designed and developed to integrate the algorithms, process PolSAR data, and image as well as visualize the ionospheric measurements. A number of tests have been conducted using ISSI with PolSAR data collected from various latitude regions using the phase array-type L-band synthetic aperture radar (PALSAR) onboard Japan Aerospace Exploration Agency's Advanced Land Observing Satellite mission, and also with Global Positioning System data. These tests have demonstrated and validated SAR-derived ionospheric images and data correction algorithms.

  11. Characteristics of High Latitude Ionosphere Scintillations

    NASA Astrophysics Data System (ADS)

    Morton, Y.

    2012-12-01

    As we enter a new solar maximum period, global navigation satellite systems (GNSS) receivers, especially the ones operating in high latitude and equatorial regions, are facing an increasing threat from ionosphere scintillations. The increased solar activities, however, also offer a great opportunity to collect scintillation data to characterize scintillation signal parameters and ionosphere irregularities. While there are numerous GPS receivers deployed around the globe to monitor ionosphere scintillations, most of them are commercial receivers whose signal processing mechanisms are not designed to operate under ionosphere scintillation. As a result, they may distort scintillation signal parameters or lose lock of satellite signals under strong scintillations. Since 2008, we have established and continuously improved a unique GNSS receiver array at HAARP, Alaska. The array contains high ends commercial receivers and custom RF front ends which can be automatically triggered to collect high quality GPS and GLONASS satellite signals during controlled heating experiments and natural scintillation events. Custom designed receiver signal tracking algorithms aim to preserve true scintillation signatures are used to process the raw RF samples. Signal strength, carrier phase, and relative TEC measurements generated by the receiver array since its inception have been analyzed to characterize high latitude scintillation phenomena. Daily, seasonal, and solar events dependency of scintillation occurrence, spectral contents of scintillation activities, and plasma drifts derived from these measurements will be presented. These interesting results demonstrate the feasibility and effectiveness of our experimental data collection system in providing insightful details of ionosphere responses to active perturbations and natural disturbances.

  12. 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.

  13. MARS IONOSPHERE STUDIES USING THE MGS RADIO SCIENCE EXPERIMENT

    E-print Network

    Withers, Paul

    MARS IONOSPHERE STUDIES USING THE MGS RADIO SCIENCE EXPERIMENT M. Mendillo and P. Withers Center of the Mars Global Surveyor (MGS) satellite, ionospheric science at Mars depended upon a total of 433 Radio Science (RS) experiment active at Mars since 1997, the MGS ionospheric database now includes

  14. WHISTLER-MODE PROPAGATION IN THE COLLISIONAL IONOSPHERE OF VENUS

    E-print Network

    Strangeway, Robert J.

    WHISTLER-MODE PROPAGATION IN THE COLLISIONAL IONOSPHERE OF VENUS R. J. Strangeway Institute identified as whistler-mode waves have been observed in the nightside ionosphere of Venus by the Pioneer Venus Orbiter. These waves are propagating in a collisional, weakly magnetized ionosphere, and it has

  15. 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

  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. Ionospheric characteristics above Martian crustal magnetic anomalies Paul Withers,1

    E-print Network

    Withers, Paul

    Ionospheric characteristics above Martian crustal magnetic anomalies Paul Withers,1 M. Mendillo,1 H effects upon otherwise global photochemical ionospheric processes. On Mars, unlike most other planets, the magnetic field has a short characteristic lengthscale, so its effects on the ionosphere will vary over

  18. Using WAAS Ionospheric Data to Estimate LAAS Short Baseline Gradients

    E-print Network

    Stanford University

    Using 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 during severe ionospheric storms. We seek an answer to the question of how much spatial variation

  19. Ionosphere Monitoring Methodology for Hybrid Dual-Frequency LAAS

    E-print Network

    Stanford University

    Ionosphere Monitoring Methodology for Hybrid Dual-Frequency LAAS Hiroyuki Konno, Sam Pullen, Jason Rife, and Per Enge Stanford University ABSTRACT Strong ionosphere storms are a potential threat for the Local Area Augmentation System (LAAS). During these storms, very large spatial gradients of ionosphere

  20. Analysis of Ionosphere Gradient Using Japan GEONET Data

    E-print Network

    Stanford University

    Analysis of Ionosphere Gradient Using Japan GEONET Data Hiroyuki Konno, Sam Pullen, Ming Luo, and Per Enge Stanford University ABSTRACT Large spatial gradients in ionosphere delay are a potentially of the ionosphere behavior during strong magnetic storms is crucial for LAAS so that it can more accurately evaluate

  1. Data-Replay Analysis of LAAS Safety during Ionosphere Storms

    E-print Network

    Stanford University

    Data-Replay Analysis of LAAS Safety during Ionosphere Storms Young Shin Park, Godwin Zhang, Sam research has identified the potential for severe ionosphere spatial gradients to affect Local Area was used to maximize LAAS availability in the presence of ionosphere anomalies by broadcasting an inflated

  2. Ionospheric Threats to Space-Based Augmentation System Development

    E-print Network

    Stanford University

    Ionospheric Threats to Space-Based Augmentation System Development S. Datta-Barua, Stanford University ABSTRACT The ionosphere contributes the largest and most unpredictable error to single frequency these ionospheric errors is two-fold. First, the SBAS broadcasts error corrections to its users for improved

  3. Ionospheric Scintillation Effects on Single and Dual Frequency GPS Positioning

    E-print Network

    Stanford University

    Ionospheric Scintillation Effects on Single and Dual Frequency GPS Positioning S. Datta-Barua, P. H studying low latitude ionospheric phenomena at the Boston College Institute for Scientific Research (ISR include studies of ionospheric effects on GPS signals and worldwide systems and in analytical

  4. Application of Spatial Statistics to Ionosphere Estimation for WAAS

    E-print Network

    Stanford University

    Application of Spatial Statistics to Ionosphere Estimation for WAAS Juan Blanch, Todd Walter, Per be required to increase performance substantially is the ionospheric correction algorithm. WAAS incorporates information from reference stations to create a correction map of the ionosphere. More importantly, this map

  5. Ionospheric Estimation using Extended Kriging for a low latitude SBAS

    E-print Network

    Stanford University

    Ionospheric Estimation using Extended Kriging for a low latitude SBAS Juan Blanch, Todd Walter, Per Enge, Stanford University ABSTRACT The ionosphere causes the most difficult error to mitigate, even during quiet days, this approximation does not model correctly the ionosphere in the low latitudes

  6. Ionosphere Threat to LAAS: Updated Model, User Impact, and Mitigations

    E-print Network

    Stanford University

    1 Ionosphere Threat to LAAS: Updated Model, User Impact, and Mitigations Ming Luo, Sam Pullen, Alexandru Ene, Di Qiu, Todd Walter, and Per Enge Stanford University ABSTRACT Several severe ionosphere from the 6 April 2000 ionospheric storm. User vertical error was estimated based on this threat model

  7. Plasma Density and Electro-Magnetic Field Perturbations Hf-Induced in the Outer Ionosphere: Review of Experimental Results

    NASA Astrophysics Data System (ADS)

    Frolov, Vladimir; Rauch, Jean-Louis; Parrot, Michel; Rapoport, Victor; Shorokhova, Elena

    In the report we consider features of plasma density and electro-magnetic field perturbations induced in the Earth’s outer ionosphere by modification of F _{2} region by O-mode powerful HF radio waves radiated by the SURA heating facility. Experiments presented were carried out in 2005 - 2010. Plasma density perturbations were detected at altitudes of about of 700 km by instruments onboard the French DEMETER satellite when it intersected the disturbed magnetic flux tube. The formation of artificial HF-induced plasma density ducts in the outer ionosphere is a central discovery, which was made during the SURA-DEMETER experiments [1,2]. Analysis of experimental data available makes it possible to formulate ducts features and point out the conditions under which the formation of such ducts takes place. 1. Under night conditions ducts are characterized by the increased plasma density in the range from 20% to 80% relatively to its background value. As this takes place, the excess in the plasma ion component is due to O (+) ions dominating at altitudes of about 700 km, whereas the densities of lower mass H (+) and He ({+) } ions typically decrease by a percentage amount that is much more the relative increase in the density of O (+) ions. The duct formation was never observed under daytime conditions. According to [3] the HF-induced ducts were observed by ionosphere pumping in morning and evening hours but in these cases their intensity was no more than a few percentages. 2. The size of the ducts along the satellite orbits is of about 80 - 100 km. It is a reason why such ducts can be observed only if the minimal distance between the satellite and the center of the heated flux tube is less than 50 km. 3. The formation of ducts is observed only if the effective radiated power is more than 40 MW. For the SURA facility, to heat the ionosphere at higher efficiency due to the “magnetic-zenith effect”, the HF beam is often inclined by 12 - 16(°) southward. 4. The pump wave frequency should be no less than 0.5 - 0.7 MHz below the F _{2} layer critical frequency f _{0F2}. In the opposed case the penetration of the radiated power behind the F _{2} ionospheric layer can take place [4]. 5. Strong variations of the electron temperature are observed inside the ducts, at the same time the ion temperature is unchanged. 6. A feature of the ducts is the presence of strong electro-magnetic field fluctuations in a frequency range from a few Hz to tens of kHz [1,5]. 7. It was revealed that the formation of the ducts in the outer ionosphere can stimulate the precipitation of energetic electrons with E ? 100 keV from the Earth’s radiation belts [6]. The work was supported by RFBR grants (## 12-05-00312, 13-02-12074, 13-02-12241) and by the scientific program “Geophysics”. References: 1. Rapoport V.O., V.L. Frolov, G.P. Komrakov, et al. // Radiophysics and Quantum Electronics, 2007. Vol. 50(8), p. 645. 2. Frolov V.L., V.O. Rapoport, G.P. Komrakov, et. al. // JETP Letters, 2008. Vol. 88, No. 12, p. 790. 3. Frolov V.L., I.A. Bolotin, V.O. Rapoport, et. al. // XXIV All-Russian conference “Radio Wave Propagation”. Irkutsk, 2014 (submitted for publication). 4. Frolov V.L., N.A. Mityakov, E.A. Shorokhova, M. Parrot. // Radiophysics and Quantum Electronics, 2013. Vol. 56(6), p. 325. 5. Rapoport V.O., V.L. Frolov, S.V. Polyakov, et al. // J. Geophys. Res., 2010. Vol. 115, A10322, doi:10.1029/2010JA015484. 6. Markov G.A., A.S. Belov, V.L. Frolov, et al. // JETPh, 2010. Vol. 138, No. 6(12), p. 1037.

  8. Ionospheric and plasmaspheric electron contents inferred from radio occultations and global ionospheric maps

    NASA Astrophysics Data System (ADS)

    González-Casado, G.; Juan, J. M.; Sanz, J.; Rovira-Garcia, A.; Aragon-Angel, A.

    2015-07-01

    We introduce a methodology to extract the separate contributions of the ionosphere and the plasmasphere to the vertical total electron content, without relying on a fixed altitude to perform that separation. The method combines two previously developed and tested techniques, namely, the retrieval of electron density profiles from radio occultations using an improved Abel inversion technique and a two-component model for the topside ionosphere plus protonosphere. Taking measurements of the total electron content from global ionospheric maps and radio occultations from the Constellation Observing System for Meteorology, Ionosphere, and Climate/FORMOSAT-3 constellation, the ionospheric and plasmaspheric electron contents are calculated for a sample of observations covering 2007, a period of low solar and geomagnetic activity. The results obtained are shown to be consistent with previous studies for the last solar minimum period and with model calculations, confirming the reversal of the winter anomaly, the hemispheric asymmetry of the semiannual anomaly, and the existence in the plasmasphere of an annual anomaly in the South American sector of longitudes. The analysis of the respective fractional contributions from the ionosphere and the plasmasphere to the total electron content shows quantitatively that during the night the plasmasphere makes the largest contribution, peaking just before sunrise and during winter. On the other hand, the fractional contribution from the ionosphere reaches a maximum value around noon, which is nearly independent of season and geomagnetic latitude.

  9. 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 ...

  10. Workmanship on Artificial Sky 

    E-print Network

    Unknown

    2011-08-17

    , M digitata was found to oviposit on artificial hosts, Parafilm(& domes containing artificial diet. It was determined that females preferred artificial hosts containing the agar-based diet to those containing only agar. Further testing ruled out...

  11. The Mars Ionosphere: More than a Chapman Layer

    E-print Network

    Withers, Paul

    is same everywhere · 740 K at surface, slow winds, no storms, no rain · H2SO4 clouds at 50 km, where low for liquid water to be stable, but ongoing gully formation may require liquid water · Saturated

  12. Modeling of Plasma Irregularities Associated with Artificially Created Dusty Plasmas in the Near-Earth Space Environment

    NASA Astrophysics Data System (ADS)

    Fu, Haiyang

    Plasma turbulence associated with the creation of an artificial dust layer in the earth's ionosphere is investigated. The Charged Aerosol Release Experiment (CARE) aims to understand the mechanisms for enhanced radar scatter from plasma irregularities embedded in dusty plasmas in space. Plasma irregularities embedded in a artificial dusty plasma in space may shed light on understanding the mechanism for enhanced radar scatter in Noctilucent Clouds (NLCs) and Polar Mesospheric Summer Echoes (PMSEs) in the earth's mesosphere. Artificially created, charged-particulate layers also have strong impact on radar scatter as well as radio signal propagation in communication and surveillance systems. The sounding rocket experiment was designed to develop theories of radar scatter from artificially created plasma turbulence in charged dust particle environment. Understanding plasma irregularities embedded in a artificial dusty plasma in space will also contribute to addressing possible effects of combustion products in rocket/space shuttle exhaust in the ionosphere. In dusty space plasmas, plasma irregularities and instabilities can be generated during active dust aerosol release experiments. Small scale irregularities (several tens of centimeter to meters) and low frequency waves (in the ion/dust scale time in the order of second) are studied in this work, which can be measured by High Frequency (HF), Very High Frequency (VHF) and Ultra High Frequency (UHF) radars. The existence of dust aerosol particles makes computational modeling of plasma irregularities extremely challenging not only because of multiple spatial and temporal scale issue but also due to complexity of dust aerosol particles. This work will provide theoretical and computational models to study plasma irregularities driven by dust aerosol release for the purpose of designing future experiments with combined ground radar, optical and in-situ measurement. In accordance with linear analysis, feasible hybrid computational models are developed to study nonlinear evolution of plasma instabilities in artificially created dusty space plasmas. First of all, the ion acoustic (IA) instability and dust acoustic (DA) instability in homogenous unmagnetized plasmas are investigated by a computational model using a Boltzmann electron assumption. Such acoustic-type instabilities are attributed to the charged dust and ion streaming along the geomagnetic field. Secondly, in a homogenous magnetized dusty plasma, lower-hybrid (LH) streaming instability will be generated by dust streaming perpendicular to the background geomagnetic field. The magnetic field effect on lower-hybrid streaming instabilities is investigated by including the ratio of electron plasma frequency and electron gyro frequency in this model. The instability in weakly magnetized circumstances agree well with that for the ion acoustic (IA) instability by a Boltzmann model. Finally, in an inhomogeneous unmagnetized/magnetized dust boundary layer, possible instabilities will be addressed, including dust acoustic (DA) wave due to flow along the boundary and lower-hybrid (LH) sheared instability due to flow cross the boundary. With applications to active rocket experiments, plasma irregularity features in a linear/nonlinear saturated stage are characterized and predicted. Important parameters of the dust aerosol clouds that impact the evolution of waves will be also discussed for upcoming dust payload generator design. These computational models, with the advantage of following nonlinear wave-particle interaction, could be used for space dusty plasmas as well as laboratory dusty plasmas. This work received financial support from National Science Foundation.

  13. Artificial rheotaxis

    PubMed Central

    Palacci, Jérémie; Sacanna, Stefano; Abramian, Anaïs; Barral, Jérémie; Hanson, Kasey; Grosberg, Alexander Y.; Pine, David J.; Chaikin, Paul M.

    2015-01-01

    Motility is a basic feature of living microorganisms, and how it works is often determined by environmental cues. Recent efforts have focused on developing artificial systems that can mimic microorganisms, in particular their self-propulsion. We report on the design and characterization of synthetic self-propelled particles that migrate upstream, known as positive rheotaxis. This phenomenon results from a purely physical mechanism involving the interplay between the polarity of the particles and their alignment by a viscous torque. We show quantitative agreement between experimental data and a simple model of an overdamped Brownian pendulum. The model notably predicts the existence of a stagnation point in a diverging flow. We take advantage of this property to demonstrate that our active particles can sense and predictably organize in an imposed flow. Our colloidal system represents an important step toward the realization of biomimetic microsystems with the ability to sense and respond to environmental changes. PMID:26601175

  14. Artificial rheotaxis.

    PubMed

    Palacci, Jérémie; Sacanna, Stefano; Abramian, Anaïs; Barral, Jérémie; Hanson, Kasey; Grosberg, Alexander Y; Pine, David J; Chaikin, Paul M

    2015-05-01

    Motility is a basic feature of living microorganisms, and how it works is often determined by environmental cues. Recent efforts have focused on developing artificial systems that can mimic microorganisms, in particular their self-propulsion. We report on the design and characterization of synthetic self-propelled particles that migrate upstream, known as positive rheotaxis. This phenomenon results from a purely physical mechanism involving the interplay between the polarity of the particles and their alignment by a viscous torque. We show quantitative agreement between experimental data and a simple model of an overdamped Brownian pendulum. The model notably predicts the existence of a stagnation point in a diverging flow. We take advantage of this property to demonstrate that our active particles can sense and predictably organize in an imposed flow. Our colloidal system represents an important step toward the realization of biomimetic microsystems with the ability to sense and respond to environmental changes. PMID:26601175

  15. Artificial Rheotaxis

    E-print Network

    Jeremie Palacci; Stefano Sacanna; Anais Abrahmian; Jeremie Barral; Kasey Hanson; Alexander Y. Grosberg; David J. Pine; Paul M. Chaikin

    2015-05-19

    Motility is a basic feature of living microorganisms, and how it works is often determined by environmental cues. Recent efforts have focused on develop- ing artificial systems that can mimic microorganisms, and in particular their self-propulsion. Here, we report on the design and characterization of syn- thetic self-propelled particles that migrate upstream, known as positive rheo- taxis. This phenomenon results from a purely physical mechanism involving the interplay between the polarity of the particles and their alignment by a viscous torque. We show quantitative agreement between experimental data and a simple model of an overdamped Brownian pendulum. The model no- tably predicts the existence of a stagnation point in a diverging flow. We take advantage of this property to demonstrate that our active particles can sense and predictably organize in an imposed flow. Our colloidal system represents an important step towards the realization of biomimetic micro-systems withthe ability to sense and respond to environmental changes

  16. Experimental and theoretical analysis of the ionospheric impact on the amplitude and phase oscillations of GPS signals in the satellite-to-satellite and satellite-to ground communication links

    NASA Astrophysics Data System (ADS)

    Pavelyev, A. G.; Zhang, K.; Liou, Y.; Wang, C.; Wickert, J.; Schmidt, T.; Pavelyev, A. A.; Kuleshov, Yu.

    2012-04-01

    By using the CHAllenge Minisatellite Payload (CHAMP) radio occultation (RO) data, a description of different types of the ionospheric impacts on the RO signals at the altitudes 30-90 km of the RO ray perigee is given and compared with the results of measurements obtained earlier in the satellite-to-Earth communication link at frequency 1.5415 GHz. An analytical model is introduced for describing propagation of radio waves in a stratified medium consisting of sectors with spherically symmetric refractivity distribution. This model gives analytical expressions for the phase delay, eikonal, bending angle, and refractive attenuation of radio waves given and is applied to the analysis of radio wave propagation phenomena along an extended path including the atmosphere and two parts of the ionosphere. Analytical model can be used for analytical ray tracing. Analytical ray tracing can control different regimes of the GPS signal propagation (multipath, diffraction, waveguide, etc.) and can be performed in general case for the analysis of radio communication and GPS navigation in trans-ionospheric links (satellite-to-satellite, satellite-to-Earth).The model explains significant amplitude and phase variations at altitudes 30-90 km of the RO ray perigee and attributes them to inclined ionospheric layers. Based on this analytical model, an innovative technique is introduced to locate layers in the atmosphere and ionosphere. A necessary and sufficient criterion is obtained for a layer to be located at the radio occultation (RO) ray perigee. The displacement of an ionospheric or atmospheric layer from the RO ray perigee can be assessed both, qualitatively and quantitatively using this criterion. The new criterion opens a new avenue in terms of measuring the altitude and slope of the atmospheric and ionospheric layers. The new criterion provides an improved estimation of the altitude and location of the ionospheric plasma layers compared with the back-propagation radio-holographic method previously used. The work is partly supported by RFBR grant No. 10-02-01015-a.

  17. 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.

  18. 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.

  19. Ionosphere/microwave beam interaction study

    NASA Technical Reports Server (NTRS)

    Gordon, W. E.; Duncan, L. M.

    1978-01-01

    The microwave beam of the Solar Power Satellite (SPS) is predicted to interact with the ionosphere producing thermal runaway up to an altitude of about 100 kilometers at a power density threshold of 12 mW/cm sq (within a factor of two). The operation of the SPS at two frequencies, 2450 and 5800 MHz, is compared. The ionosphere interaction is less at the higher frequency, but the tropospheric problem scattering from heavy rain and hail is worse at the higher frequency. Microwave signals from communication satellites were observed to scintillate, but there is some concern that the uplink pilot signal may be distorted by the SPS heated ionosphere. The microwave scintillations are only observed in the tropics in the early evenings near the equinoxes. Results indicate that large phase errors in the uplink pilot signal can be reduced.

  20. An improved inversion for FORMOSAT-3/COSMIC ionosphere electron density profiles

    NASA Astrophysics Data System (ADS)

    Pedatella, N. M.; Yue, X.; Schreiner, W. S.

    2015-10-01

    An improved method to retrieve electron density profiles from Global Positioning System (GPS) radio occultation (RO) data is presented and applied to Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) observations. The improved inversion uses a monthly grid of COSMIC F region peak densities (NmF2), which are obtained via the standard Abel inversion, to aid the Abel inversion by providing information on the horizontal gradients in the ionosphere. This lessens the impact of ionospheric gradients on the retrieval of GPS RO electron density profiles, reducing the dominant error source in the standard Abel inversion. Results are presented that demonstrate the NmF2 aided retrieval significantly improves the quality of the COSMIC electron density profiles. Improvements are most notable at E region altitudes, where the improved inversion reduces the artificial plasma cave that is generated by the Abel inversion spherical symmetry assumption at low latitudes during the daytime. Occurrence of unphysical negative electron densities at E region altitudes is also reduced. Furthermore, the NmF2 aided inversion has a positive impact at F region altitudes, where it results in a more distinct equatorial ionization anomaly. COSMIC electron density profiles inverted using our new approach are currently available through the University Corporation for Atmospheric Research COSMIC Data Analysis and Archive Center. Owing to the significant improvement in the results, COSMIC data users are encouraged to use electron density profiles based on the improved inversion rather than those inverted by the standard Abel inversion.

  1. Simultaneous Multi-angle Radar Observations of Langmuir Turbulence Excited by RF Ionospheric Interactions at HAARP

    NASA Astrophysics Data System (ADS)

    Sheerin, J. P.; Rayyan, N.; Watanabe, N.; Watkins, B. J.; Bristow, W. A.; Bernhardt, P. A.

    2013-10-01

    The high power HAARP HF transmitter is employed to generate and study strong Langmuir turbulence (SLT) in the interaction region of overdense ionospheric plasma. Diagnostics included the Modular UHF Ionospheric Radar (MUIR) sited at HAARP, the SuperDARN-Kodiak HF radar, and HF receivers to record stimulated electromagnetic emissions (SEE). Dependence of diagnostic signals on HAARP HF parameters, including pulselength, duty-cycle, aspect angle, and frequency were recorded. Short pulse, low duty cycle experiments demonstrate control of artificial field-aligned irregularities (AFAI) and isolation of ponderomotive effects. Among the effects observed and studied are: SLT spectra including cascade, collapse, and co-existence spectra and an outshifted plasma line under certain ionospheric conditions. High time resolution studies of the temporal evolution of the plasma line reveal the appearance of an overshoot effect on ponderomotive timescales. Bursty turbulence is observed in the collapse and cascade lines. For the first time, simultaneous multi-angle radar measurements of plasma line spectra are recorded demonstrating marked dependence on aspect angle with the strongest interaction region observed displaced southward of the HF zenith pointing angle. Numerous measurements of the outshifted plasma line are observed. Experimental results are compared to previous high latitude experiments and predictions from recent modeling efforts.

  2. Multi-angle Spectra Evolution of Langmuir Turbulence Excited by RF Ionospheric Interactions at HAARP

    NASA Astrophysics Data System (ADS)

    Sheerin, J. P.; Rayyan, N.; Watkins, B. J.; Bristow, W. A.; Spaleta, J.; Watanabe, N.; Golkowski, M.; Bernhardt, P. A.

    2013-12-01

    The high power HAARP HF transmitter is employed to generate and study strong Langmuir turbulence (SLT) in the interaction region of overdense ionospheric plasma. Diagnostics included the Modular UHF Ionospheric Radar (MUIR) sited at HAARP, the SuperDARN-Kodiak HF radar, and HF receivers to record stimulated electromagnetic emissions (SEE). Dependence of diagnostic signals on HAARP HF parameters, including pulselength, duty-cycle, aspect angle, and frequency were recorded. Short pulse, low duty cycle experiments demonstrate control of artificial field-aligned irregularities (AFAI) and isolation of ponderomotive effects. Among the effects observed and studied are: SLT spectra including cascade, collapse, and co-existence spectra and an outshifted plasma line under certain ionospheric conditions. High time resolution studies of the temporal evolution of the plasma line reveal the appearance of an overshoot effect on ponderomotive timescales. Bursty turbulence is observed in the collapse and cascade lines. For the first time, simultaneous multi-angle radar measurements of plasma line spectra are recorded demonstrating marked dependence on aspect angle with the strongest interaction region observed displaced southward of the HF zenith pointing angle. Numerous measurements of the outshifted plasma line are observed. Experimental results are compared to previous high latitude experiments and predictions from recent modeling efforts.

  3. Simultaneous Multi-angle Radar Observations of Langmuir Turbulence Excited by RF Ionospheric Interactions at HAARP

    NASA Astrophysics Data System (ADS)

    Sheerin, J. P.; Watanabe, N.; Rayyan, N.; Spry, D.; Adham, N.; Watkins, B. J.; Bristow, W. A.; Spaleta, J.; Bernhardt, P. A.

    2012-12-01

    The high power HAARP HF transmitter is employed to generate and study strong Langmuir turbulence (SLT) in the interaction region of overdense ionospheric plasma. Diagnostics included the Modular UHF Ionospheric Radar (MUIR) sited at HAARP, the SuperDARN-Kodiak HF radar, and HF receivers to record stimulated electromagnetic emissions (SEE). Dependence of diagnostic signals on HAARP HF parameters, including pulselength, duty-cycle, aspect angle, and frequency were recorded. Short pulse, low duty cycle experiments demonstrate control of artificial field-aligned irregularities (AFAI) and isolation of ponderomotive effects. Among the effects observed and studied are: SLT spectra including cascade, collapse, and co-existence spectra and an outshifted plasma line under certain ionospheric conditions. High time resolution studies of the temporal evolution of the plasma line reveal the appearance of an overshoot effect on ponderomotive timescales. Bursty turbulence is observed in the collapse and cascade lines. For the first time, simultaneous multi-angle radar measurements of plasma line spectra are recorded demonstrating marked dependence on aspect angle with the strongest interaction region observed displaced southward of the HF zenith pointing angle. Numerous measurements of the outshifted plasma line are observed. Experimental results are compared to previous high latitude experiments and predictions from recent modeling efforts.

  4. Prediction of the level of ionospheric scintillation at equatorial latitudes in Brazil using a neural network

    NASA Astrophysics Data System (ADS)

    Lima, G. R. T.; Stephany, S.; Paula, E. R.; Batista, I. S.; Abdu, M. A.

    2015-08-01

    Electron density irregularity structures, often associated with ionospheric plasma bubbles, drive amplitude and phase fluctuations in radio signals that, in turn, create a phenomenon known as ionospheric scintillation. The phenomenon occurs frequently around the magnetic equator where plasma instability mechanisms generate postsunset plasma bubbles and density depletions. A previous correlation study suggested that scintillation at the magnetic equator may provide a forecast of subsequent scintillation at the equatorial ionization anomaly southern peak. In this work, it is proposed to predict the level of scintillation over São Luís (2.52°S, 44.3°W; dip latitude: ~2.5°S) near the magnetic equator with lead time of hours but without specifying the moment at which the scintillation starts or ends. A collection of extended databases relating scintillation to ionospheric variables for São Luís is employed to perform the training of an artificial neural network with a new architecture. Two classes are considered, not strong (null/weak/moderate) and strong scintillation. An innovative scheme preprocesses the data taking into account similarities of the values of the variables for the same class. A formerly proposed resampling heuristic is employed to provide a balanced number of tuples of each class in the training set. Tests were performed showing that the proposed neural network is able to predict the level of scintillation over the station on the evening ahead of the data sample considered between 17:30 and 19:00 LT.

  5. Estimating ionospheric property by using simultaneous observations of lightning optical emissions and whistlers from ISS GLIMS mission.

    NASA Astrophysics Data System (ADS)

    Suzuki, Katsunori; Hobara, Yasuhide; Kakinuma, Kanata; Sato, Mitsuteru; Takahashi, Yukihiro; Ushio, Tomoo; Morimoto, Takeshi; Yamazaki, Atsushi; Suzuki, Mutsumi; IR, Linscott; US, Inan

    2015-04-01

    The atmospherics from the lightning penetrating through the ionosphere and are observed as so-called lighting whistlers in the magnetosphere. Since ionosphere is the dispersive medium, group delays of whistler waves with different frequencies contain the information on the electron density along the propagation path. In this paper we estimate the critical frequency of the ionosphere F layer (foF2) by using the time delay between the lightning optical emissions and whistlers, which were simultaneously measured by Global Lightning and SprIte MeasurementS (GLIMS) mission onboard ISS. We found that the calculated Fof2 by using group delay are in good agreement with those estimated from the classical dispersion analysis of lightning whistlers, IRI model and ionosonde for relatively small dispersion events. This method will be useful to cover the area where no ground-based measurements are available such as over the ocean and remote areas.

  6. Small-scale field-aligned currents caused by tropical cyclones as observed by the SWARM satellites above the ionosphere

    NASA Astrophysics Data System (ADS)

    Aoyama, T.; Iyemori, T.; Nakanishi, K.

    2014-12-01

    We present case studies of small-scale magnetic fluctuations above typhoons, hurricanes and cyclones as observed by the swarm constellation. It is reported lately that AGWs(atmospheric gravity waves) generated by meteorological phenomena in the troposphere such as typhoons and tornadoes, large earthquakes and volcanic eruptions propagate to the mesosphere and thermosphere. We observe them in various forms(e.g. airglows, ionospheric disturbances and TEC variations). We are proposing the following model. AGWs caused by atmospheric disturbances in the troposphere propagate to the ionospheric E-layer, drive dynamo action and generate field-aligned currents. The satellites observe magnetic fluctuations above the ionosphere. In this presentation, we focus on cases of tropical cyclone(hurricanes in North America, typhoons in North-West Pacific).

  7. GNSS data filtering optimization for ionospheric observation

    NASA Astrophysics Data System (ADS)

    D'Angelo, G.; Spogli, L.; Cesaroni, C.; Sgrigna, V.; Alfonsi, L.; Aquino, M. H. O.

    2015-12-01

    In the last years, the use of GNSS (Global Navigation Satellite Systems) data has been gradually increasing, for both scientific studies and technological applications. High-rate GNSS data, able to generate and output 50-Hz phase and amplitude samples, are commonly used to study electron density irregularities within the ionosphere. Ionospheric irregularities may cause scintillations, which are rapid and random fluctuations of the phase and the amplitude of the received GNSS signals. For scintillation analysis, usually, GNSS signals observed at an elevation angle lower than an arbitrary threshold (usually 15°, 20° or 30°) are filtered out, to remove the possible error sources due to the local environment where the receiver is deployed. Indeed, the signal scattered by the environment surrounding the receiver could mimic ionospheric scintillation, because buildings, trees, etc. might create diffusion, diffraction and reflection. Although widely adopted, the elevation angle threshold has some downsides, as it may under or overestimate the actual impact of multipath due to local environment. Certainly, an incorrect selection of the field of view spanned by the GNSS antenna may lead to the misidentification of scintillation events at low elevation angles. With the aim to tackle the non-ionospheric effects induced by multipath at ground, in this paper we introduce a filtering technique, termed SOLIDIFY (Standalone OutLiers IDentIfication Filtering analYsis technique), aiming at excluding the multipath sources of non-ionospheric origin to improve the quality of the information obtained by the GNSS signal in a given site. SOLIDIFY is a statistical filtering technique based on the signal quality parameters measured by scintillation receivers. The technique is applied and optimized on the data acquired by a scintillation receiver located at the Istituto Nazionale di Geofisica e Vulcanologia, in Rome. The results of the exercise show that, in the considered case of a noisy site under quiet ionospheric conditions, the SOLIDIFY optimization maximizes the quality, instead of the quantity, of the data.

  8. 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.

  9. A case study of ionospheric storm effects in the Chinese sector during the October 2013 geomagnetic storm

    NASA Astrophysics Data System (ADS)

    Mao, Tian; Sun, Lingfeng; Hu, Lianhuan; Wang, Yungang; Wang, Zhijun

    2015-11-01

    In this study, we investigate the ionospheric storm effects in the Chinese sector during 2 October 2013 geomagnetic storm. The TEC map over China sector (1° × 1°) and eight ionosondes data along the longitude of 110°E are used to show significant positive ionospheric phases (enhancements in TEC and ionospheric peak electron density NmF2) in the high-middle latitude region and the negative effects at the low latitude and equatorial region during the storm. A wave structure with periods about 1-2 h and horizontal speed about 680 m/s, propagating from the high latitudes to the low latitudes is observed in electron densities within the height region from 200 to 400 km, which is caused by the combined effects of neutral wind and the large-scale traveling disturbances (LSTIDs). In the low latitude regions, compared with those in the quiet day, the ionospheric peak heights of the F2 layer (hmF2) in the storm day obviously increase accompanying a notably decrease in TEC and NmF2, which might be as a result of the eastward prompt penetration electric field (PPEF) evidenced by the two magnetometers and the subsequent westward disturbance dynamo electric fields (DDEF). The storm-time TEC enhancement mainly occurs in the topside ionosphere, as revealed from the topside TEC, bottomside TEC and GPS TEC.

  10. Plasma bubbles in the topside ionosphere: solar activity dependence

    NASA Astrophysics Data System (ADS)

    Sidorova, L.

    2009-04-01

    The present study deals with the He+ density depletions, observed during a high solar activity at the topside ionosphere heights. There are the indications that plasma bubbles, produced by Rayleigh-Taylor instability at the bottomside of ionosphere, could rise up to the topside ionosphere and plasmasphere. Maryama and Matuura (1984), using ISS-b spacecraft data (high solar activity - F10.7=200, 1978-80), have seen the plasma bubbles in Ne density over equator at 1100 km heights in 46 cases in 1700 passes (3%). However, there is distinctly another picture in He+ density depletions according to ISS-b spacecraft data for the same period. They occur in the topside ionosphere over low- and middle- latitudinal regions (L=1.3-3) in 11% of the cases (Karpachev, Sidorova, 2002; Sidorova, 2004, 2007). The detailed study of the He+ density depletion characteristics was done. It was noted that the He+ density depletions are mostly seen in the evening-night sector (18-05 LT) from October till May. It was like to the peculiarities of the Equatorial Spread-F (ESF), usually associated with plasma bubble. The monthly mean He+ density depletion statistics, plotted in LT versus month, was compared with the similar plots for ESF statistics, obtained by Abdu and colleagues (2000) from ground-based ionograms over Brazilian regions for the period of the same solar activity. It was revealed good enough correlation (R=0.67). Also depletion values as function of LT were compared with the vertical plasma drift velocity variations, obtained for the same period from AE-E spacecraft and IS radar (Jicamarca) data. Striking similarity in development dynamics was revealed for the different seasons. It was concluded, that the He+ density depletions should be considered as originating from equatorial plasma bubbles. It seems the plasma bubbles, reaching the topside ionosphere altitudes, are mostly seen not in electron density but in He+ density as depletions. According to publications, many cases of the He+ density depletions were revealed on OGO-4, OGO-6, Oreol-1 and DE-2 spacecraft data. The most of these cases occur during high and maximal solar activity periods, when the He+ density layer is very well developed at the topside ionosphere heights (Wilford et al., 2003). Using the model of the plasma bubble formation as suggested by Woodman and La Hoz (1976), it was shown that the topside plasma bubbles, seen in He+ density, are rather typical phenomena for the topside ionosphere for high solar activity epoch. REFERENCE Abdu, M.A., J.H.A. Sobral, I.S. Batista, Equatorial spread F statistics in the american longitudes: some problems relevant to ESF description in the IRI scheme, Adv. Space Res., vol. 25, pp. 113-124, 2000. Karpachev, A.T. and L.N. Sidorova, Occurrence probability of the light ion trough and subtrough in ??+ density on season and local time, Adv. Space Res., vol. 29, pp. 999-1008, 2002. Maryama, T. and N. Matuura, Longitudinal variability of annual changes in activity of equatorial spread F and plasma bubbles, J. Geophys. Res., 89(A12), 10,903-10,912, 1984. Sidorova, L.N., He+ density topside modeling based on ISS-b satellite data, Adv. Space Res., vol. 33, pp. 850-854, 2004. Sidorova, L.N., Plasma bubble phenomenon in the topside ionosphere, Adv. Space Res., Special issue (COSPAR), doi: 10.1016/j.asr.2007.03.067, 2007. Wilford, C.R., R.J. Moffett, J.M. Rees, G.J. Bailey, Comparison of the He+ layer observed over Arecibo during solar maximum and solar minimum with CTIP model results, J. Geophys. Res., vol. 108, A12, pp. 1452, doi:10.1029/2003JA009940, 2003. Woodman, R.F. and C. La Hoz, Radar observations of F-region equatorial irregularities, J. Geophys. Res., vol. 81, pp. 5447-5466, 1976.

  11. Application of the 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.

    2015-07-01

    A new formulation of the 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 other planets. The principle states that significant contributions to variations of the intensity 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 centre is known, the time derivatives 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 centre 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 intensity 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, water vapour, and hydrometeors can be measured with accuracy of about 0.1 db at a single frequency. In accordance 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 the S4 scintillation index is established. This correlation indicates the significant influence of locally spherical symmetric ionospheric layers on variations of the phase and intensity of the RO signal passing through transionospheric communication links. Obtained results expand applicable domain of the RO method as a powerful remote sensing technique for geophysical and meteorological research.

  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. 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.

  14. Studying atmospheric and ionospheric variabilities from long-term spectrometric and radio sounding measurements

    NASA Astrophysics Data System (ADS)

    Medvedeva, Irina; Ratovsky, Konstantin

    2015-06-01

    We investigated the variability in the neutral upper atmosphere and ionosphere parameters over East Siberia. The analysis is based on 2008-2014 data set of mesopause temperature (Tm) obtained from spectrometric measurements of the OH emission (834.0 nm, band (6-2)) at the Institute of Solar-Terrestrial Physics Geophysical Observatory (51.8°N, 103.1°E), and the data of F2 peak electron density (NmF2) from Irkutsk DPS-4 Digisonde (52.3°N, 104.3°E). The seasonal patterns of the NmF2 and Tm variability in different period ranges were analyzed and compared. The period range included day-to-day (periods T > 24 h) and tidal (8 h ? T ? 24 h) variations as well as variations in the internal gravity wave period range (T < 8 h). The comparison revealed both common features and distinctions in the seasonal patterns of the ionospheric and atmospheric variabilities. The main common feature is that the winter variability exceeds the summer one. In both atmospheric and ionospheric day-to-day variability seasonal variations, there are maxima in winter months and an additional maximum around the autumn equinox. The main distinction is that the equinox peaks observed in the seasonal variations of the diurnal atmospheric variability are not seen in the ionospheric seasonal pattern. The physical reasons of the obtained features are discussed. The revealed similarities in the seasonal behaviors may indicate that planetary waves propagating from the lower atmosphere layers have a significant impact on the mesopause temperature regime and ionospheric day-to-day variations.

  15. 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.

  16. Solar illumination control of ionospheric outflow above polar cap arcs

    NASA Astrophysics Data System (ADS)

    Maes, L.; Maggiolo, R.; De Keyser, J.; Dandouras, I.; Fear, R. C.; Fontaine, D.; Haaland, S.

    2015-03-01

    We measure the flux density, composition, and energy of outflowing ions above the polar cap, accelerated by quasi-static electric fields parallel to the magnetic field and associated with polar cap arcs, using Cluster. Mapping the spacecraft position to its ionospheric foot point, we analyze the dependence of these parameters on the solar zenith angle (SZA). We find a clear transition at SZA between ˜94° and ˜107°, with the O+ flux higher above the sunlit ionosphere. This dependence on the illumination of the local ionosphere indicates that significant O+ upflow occurs locally above the polar ionosphere. The same is found for H+, but to a lesser extent. This effect can result in a seasonal variation of the total ion upflow from the polar ionosphere. Furthermore, we show that low-magnitude field-aligned potential drops are preferentially observed above the sunlit ionosphere, suggesting a feedback effect of ionospheric conductivity.

  17. 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.

  18. Lightning induced brightening in the airglow layer

    SciTech Connect

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

    1992-01-24

    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 examination of several thousand images of lightning recorded under suitable viewing conditions with Space Shuttle cameras. Several possible mechanisms and interpretations are discussed briefly.

  19. Monitoring and modeling Hong Kong ionosphere using regional GPS networks

    NASA Astrophysics Data System (ADS)

    Gao, Shan

    The ionosphere is the region from 90 km to 2000 km altitude, where the solar radiation produces partially ionized plasma of different gas components. Knowledge of ionospheric electronic density and its variation is essential for a wide range of applications, such as radio and telecommunications, satellite tracking, earth observation from space, and satellite navigation. This research aims at monitoring detailed low latitude structures of the ionosphere using Hong Kong GPS network. In this study, the distribution characteristics of ionospheric TEC and disturbances are investigated and researched. It is shown that in Hong Kong, there is a two-dimensional peak along local solar time and latitude for the TEC distribution due to the solar radiation and equatorial ionospheric anomaly. The peak values appear around geographic latitude 22° north and the local solar time 2pm. On both sides of the peak, there exist large TEC slopes. Therefore, even with short baselines (i.e. <10 km), ionospheric delays cannot be eliminated by double difference technique. Ionospheric disturbances happen frequently in Hong Kong, with the severe ones mainly concentrating at geographic latitude 22° north and the local solar time 10pm. Both ionospheric TEC values and disturbances reach their seasonal maximum around the equinoxes. With the aids of PPP technique and satellite difference widelane technique, ionospheric modeling equation is reformed with less unknown parameters, which support the stable and precise estimation of ionospheric VTEC along with the constant biases within a short and peace period. On this basis, a new localized ionospheric modeling technique, which models ionospheric VTEC along the satellite track on the assumed ionospheric shell for each satellite with a short piecewise modeling period, is proposed for precise ionospheric TEC modeling, especially in low latitude regions where the ionosphere is active. The numerical results demonstrate that the new model has a several centimeters modeling accuracy about ionospheric vertical delay, which is normally better than the traditional ionospheric model, and is able to support GPS precise positioning (e.g. the single frequency centimeter-level PPP and the millimeter-level DD positioning for 10 km baseline) in Hong Kong. Ionospheric disturbances have strong effects on GPS receiver performances. During periods of ionospheric disturbances, GPS measurement noise level (both pseudorange and carrier phase) increases dramatically, up to several decimeters, and the receivers frequently loss satellite signal lock, which have significant impacts on UPS applications in low latitudes.

  20. MARSIS Radar Echo Ionospheric Correction and The Estimation of Mars Ionosphere's Total Electron Content

    NASA Astrophysics Data System (ADS)

    Safaeinili, A.; Gurnett, D.; Kofman, W.; Picardi, G.; Plaut, J.

    2005-12-01

    On June 19th, 2005, Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) recorded its first radar echoes from the surface of Mars. MARSIS is capable of radiating between 0.1 and 5.5 MHz. The subsurface mode of MARSIS consists of four one-MHz bands with center frequencies at 1.8, 3.0, 4.0, and 5.5 MHz. The primary objectives of the subsurface sounding mode are to detect subsurface structures and search for water reservoirs. The amplitude and phase of MARSIS echoes are distorted by the Mars ionosphere by amounts depending on the number of free electrons and their distribution profile in the ionosphere. The compensation for the ionospheric distortion is one of major steps in MARSIS subsurface mode data processing. In this paper, we present the first results of the de-dispersion processing which yields very detailed information about the total electron content (TEC) between the radar and the Mars surface and to some degree how it is distributed in the ionosphere. For a given orbit, the TEC can be measured at high spatial resolution of approximately 5-10 km. We will also discuss issues related to variability of the TEC in Mars ionosphere and how it impacts MARSIS subsurface echo interpretation. The research described in this paper was carried out by the Jet Propulsion Laboratory, California Institute of Technology under a contract with the National Aeronautical and Space Administration.

  1. Planetary wave type oscillations in the equatorial thermosphere-ionosphere

    NASA Astrophysics Data System (ADS)

    Silva, Diego B.; Makela, Jonathan J.; Buriti, Ricardo; Medeiros, Amauri; Batista, Inez S.; Paulino, Igo; Meriwether, John; Cosme Alexandre Figueiredo, M.

    Planetary wave type oscillations in the thermosphere-ionosphere were observed in zonal and meridional neutral winds and F layer electron density profile. Thermospheric neutral wind estimates are based upon observations made by a bi-static Fabry-Perot interferometers (FPI) experiment using FPIs located at Cajazeiras (6(°) 53’25” S; 38(°) 33’19” W) and São João do Cariri (7(°) 23’27” S; 36(°) 31’58” W) in northeastern Brazil observing the Doppler shift of the OI 630.0 nm emission. The F layer electron density profile was obtained from Digisonde Portable Sounder-4 (DPS-4) located at Eusébio (03(°) 53’24” S, 38(°) 27’02” W), also in the northeastern Brazil region. During October, November and December of 2010, the data illustrate a similar pattern in thermospheric neutral winds and F layer electron density profile. The results presented in this work can help to understand and point out a possible generation mechanism of these oscillations.

  2. Dust storm and electron density in the equatorial D region ionosphere of Mars: Comparison with Earth's ionosphere from rocket measurements in Brazil

    NASA Astrophysics Data System (ADS)

    Haider, S. A.; Batista, I. S.; Abdu, M. A.; Muralikrishna, P.; Shah, Siddhi Y.; Kuroda, T.

    2015-10-01

    We report the first model result for the dust densities and electron densities in the D region ionosphere of Mars for aerosol particles of different sizes during a major dust storm that occurred in Martian Year (MY) 25 at low latitude. These calculations are made at latitude 10°S and solar longitudes (Ls) = 200°, 220°, 250°, and 280° for high, medium, low, and absence of dust storms, respectively. Four corresponding dust layers were found at 50 km, 50 km, 38 km, and 25 km during these events. During high dust storm period, the optical depth and dust density increased by a factor of ~20 from its normal condition. The electron densities estimated for the D region ionosphere of Mars for submicron sized dust particles are largest as compared to that estimated for larger particles. The electron density reduced by ~2 orders of magnitude during high dust storm. The estimated electron density in the clear atmosphere of Mars is compared with measurements of Earth's ionosphere at nearly the same geophysical condition.

  3. 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

  4. Studies of the ionospheric turbulence excited by the fourth gyroharmonic at HAARP

    NASA Astrophysics Data System (ADS)

    Najmi, A.; Milikh, G.; Yampolski, Y. M.; Koloskov, A. V.; Sopin, A. A.; Zalizovski, A.; Bernhardt, P.; Briczinski, S.; Siefring, C.; Chiang, K.; Morton, Y.; Taylor, S.; Mahmoudian, A.; Bristow, W.; Ruohoniemi, M.; Papadopoulos, K.

    2015-08-01

    A study is presented of artificial ionospheric turbulence (AIT) induced by HF heating at High Frequency Active Auroral Research Program (HAARP) using frequencies close to the fourth electron gyroharmonic, in a broad range of radiated powers and using a number of different diagnostics. The diagnostics include GPS scintillations, ground-based stimulated electromagnetic emission (SEE), the HAARP ionosonde, Kodiak radar, and signals received at the Ukrainian Antarctic Station (UAS). The latter allowed analysis of waves scattered by the AIT into the ionospheric waveguide along Earth's terminator, 15.6 mm from the HAARP facility. For the first time, the amplitudes of two prominent SEE features, the downshifted maximum and broad upshifted maximum, were observed to saturate at ~50% of the maximum HAARP effective radiated power. Nonlinear effects in slant total electron content, SEE, and signals received at UAS at different transmitted frequencies and intensities of the pump wave were observed. The correlations between the data from different detectors demonstrate that the scattered waves reach UAS by the waveguide along the Earth's terminator, and that they were injected into the waveguide by scattering off of artificial striations produced by AIT above HAARP, rather than via direct injection from sidelobe radiation.

  5. THE IONOSPHERE OF VENUS WITHERS NSF AAG 2011 PROJECT DESCRIPTION PAGE 1 OF 15

    E-print Network

    Withers, Paul

    THE IONOSPHERE OF VENUS WITHERS ­ NSF AAG 2011 ­ PROJECT DESCRIPTION ­ PAGE 1 OF 15 Note ionospheres "The ionosphere is considered to be that region of an atmosphere where significant numbers of free (e.g. comets), have an ionosphere. Currently, ionospheres have been observed around all but two

  6. Investigation of ionospheric stimulated Brillouin scatter generated at pump frequencies near electron gyroharmonics

    NASA Astrophysics Data System (ADS)

    Mahmoudian, A.; Scales, W. A.; Bernhardt, P. A.; Fu, H.; Briczinski, S. J.; McCarrick, M. J.

    2013-11-01

    Stimulated Electromagnetic Emissions (SEEs), secondary electromagnetic waves excited by high power electromagnetic waves transmitted into the ionosphere, produced by the Magnetized Stimulated Brillouin Scatter (MSBS) process are investigated. Data from four recent research campaigns at the High Frequency Active Auroral Research Program (HAARP) facility is presented in this work. These experiments have provided additional quantitative interpretation of the SEE spectrum produced by MSBS to yield diagnostic measurements of the electron temperature and ion composition in the heated ionosphere. SEE spectral emission lines corresponding to ion acoustic (IA) and electrostatic ion cyclotron (EIC) mode excitation were observed with a shift in frequency up to a few tens of Hz from the pump frequency for heating near the third harmonic of the electron gyrofrequency 3fce. The threshold of each emission line has been measured by changing the pump wave power. The excitation threshold of IA and EIC emission lines originating at the reflection and upper hybrid altitudes is measured for various beam angles relative to the magnetic field. Variation of strength of MSBS emission lines with pump frequency relative to 3fce and 4fce is also studied. A full wave solution has been used to estimate the amplitude of the electric field at the interaction altitude. The estimated instability threshold using the theoretical model is compared with the threshold of MSBS lines in the experiment and possible diagnostic information for the background ionospheric plasma is discussed. Simultaneous formation of artificial field-aligned irregularities (FAIs) and suppression of the MSBS process is investigated. This technique can be used to estimate the growth time of artificial FAIs which may result in determination of plasma waves and physical process involved in the formation of FAIs.

  7. OVERCOMING IONOSPHERIC SCINTILLATION FOR WORLDWIDE GPS AVIATION

    E-print Network

    Stanford University

    OVERCOMING IONOSPHERIC SCINTILLATION FOR WORLDWIDE GPS AVIATION A DISSERTATION SUBMITTED decades, its impact on GPS aviation has not been well understood. As a result, the current GPS aviation to mitigate the impact of scintillation. Although current aviation receivers do not protect against

  8. Solar cycle modulation of Titan's ionosphere

    E-print Network

    Edberg, N. J. T.; Andrews, D. J.; Shebanits, O.; Å gren, K.; Wahlund, J.-E.; Opgenoorth, H. J.; Cravens, Thomas Edward; Girazian, Z.

    2013-08-13

    to previous average. These measurements suggest that a long?term change has occurred in the ionosphere of Titan, likely caused by the rise to the new solar maximum with increased EUV fluxes. We compare measurements from TA, TB, and T5, from the declining phase...

  9. Magnetosphere Sawtooth Oscillations Induced by Ionospheric Outflow

    E-print Network

    Lotko, William

    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

  10. Magnetospheric and Thermospheric Influence on Ionospheric Outflow

    NASA Astrophysics Data System (ADS)

    Garcia-Sage, K.; Moore, T. E.; Mitchell, E. J.; Olson, D. K.

    2013-12-01

    The Fast Auroral SnapshoT (FAST) small explorer has been used extensively to study ionospheric outflow. Past research has used particle and field data to examine the contemporaneous transfer of electromagnetic energy and particle flow downward from the magnetosphere and upward from the ionosphere. Single event studies published by Strangeway et al. [2005] and Brambles et al. [2011, Supporting Online Material] showed that downward electromagnetic energy and particle flow into the ionosphere are correlated with the upward flow of ions out of the ionosphere. It is expected, however, that this correlation will be affected by circumstances that are unique to each specific event, including but not limited to the outflow location (cusp or nightside), preconditioning due to prior geomagnetic activity, and thermospheric neutral densities. Although knowledge of the thermospheric neutral density is usually unavailable, data from the CHAllenging Minisatellite Payload (CHAMP) is able to provide insight into thermospheric populations at altitudes of about 400 km for a few select events. We expand on the previously-mentioned studies by looking at FAST particle and field data for additional events, and we further examine the influence of thermospheric neutral populations, based on CHAMP data.

  11. Ionospheric Alfvén resonator response to remote earthquakes

    NASA Astrophysics Data System (ADS)

    Potapov, Alexander S.; Dovbnya, Boris V.; Tsegmed, Battuulai

    2010-05-01

    The ionospheric Alfvén resonances (IARs) are an interesting wave phenomenon well described in the literature. The IAR formation region is located between two bends of the plasma density profile: in the lower part of the ionospheric F region and at altitudes of about 1000-3000 km. In this region, Alfvén waves are entrapped and form standing waves. The quality factor of the resonator can attain a value of 5-10. We studied local IAR features using data of the Borok Geophysical Observatory (58°N, 38° E) and found that the ionospheric Alfvén resonances observed as geomagnetic pulsations at frequencies of a few hertz respond to remote seismic events. There are different kinds of the seismic wave effect on the IARs mode: sometimes the oscillations arise after an earthquake moment, in other cases they sharply decay, and sometimes they abruptly change their intensity. Among possible mechanisms of the earthquake action on the ionosphere acoustic and electromagnetic waves emerged by a seismic shock are discussed. The work was supported by the RFBR grants 09-05-00048 and 10-05-00661.

  12. 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.

  13. 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.

  14. Broadband Ionospheric Scintillation Measurements from Space

    NASA Astrophysics Data System (ADS)

    Suszcynsky, D. M.; Light, M. E.; Pigue, M. J.

    2014-12-01

    The U.S. Department of Energy's Radio Frequency Propagation (RFProp) experiment consists of a satellite-based radio receiver suite to study various aspects of trans-ionospheric signal propagation and detection in four frequency bands, 2 - 55 MHz, 125 - 175 MHz, 365 - 415 MHz and 825 - 1100 MHz. In this paper, we present an overview of the RFProp on-orbit research and analysis effort with particular focus on an equatorial scintillation experiment called ESCINT. The 3-year ESCINT project is designed to characterize equatorial ionospheric scintillation in the upper HF and lower VHF portions of the radio spectrum (20 - 150 MHz). Both a 40 MHz continuous wave (CW) signal and 30 - 42 MHz swept frequency signal are transmitted to the satellite receiver suite from the Reagan Test Site at Kwajalein Atoll in the Marshall Islands (8.7° N, 167.7° E) in four separate campaigns centered on the 2014 and 2015 equinoxes. Results from the first campaign conducted from April 22 - May 15, 2014 will be presented including (a) coherence bandwidth measurements over a full range of transmission frequencies and scintillation activity levels, (b) spread-Doppler clutter effects arising from preferential ray paths to the satellite due to refraction off of isolated density irregularities, and (c) supporting ray-trace simulations. The broadband nature of the measurements is found to offer unique insight into both the structure of ionospheric irregularities and their impact on HF/VHF trans-ionospheric radio wave propagation.

  15. 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.

  16. 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.

  17. IRI, an International Standard for the Ionosphere

    NASA Astrophysics Data System (ADS)

    Bilitza, D.; Reinisch, B.; Triskova, L.; Friedrich, M.

    2003-04-01

    The International Reference Ionosphere (IRI) is a data-based model of the ionosphere that has been steadily improved and updated by a joint working group of the Committee on Space Research and the International Union of Radio Science. We will report about the most recent IRI workshops and the improvements and additions planned for the next version of the model. In particular new models will be included for the D-region electron density (Friedrich et al., 2002), and for the ion densities (Triskova et al., 2003) the latter based on Atmosphere Explorer C, D, E and Intercosmos 24 data. A correction term will be introduced in the topside electron density model to alleviate problems at high solar activities and high altitudes (Bilitza, 2002). A special IRI task groups is working on an occurrence probability model for spread-F (Abdu et al., 2003) for inclusion in IRI. A quantitative description of ionospheric variability (standard deviation from monthly mean) is the goal of a special IRI task force activity at the International Center for Theoretical Physics (Radicella 2002). We will also report about activities to update IRI with actual measurements and thus obtain a more accurate description of the actual ionosphere. A proposal to make the IRI model the ISO standard for the ionosphere is now pending before the International Standardization Organization (ISO). The IRI homepage is at http://nssdc.gsfc.nasa.gov/space/model/ionos/iri.html and a web-interface for computing and plotting IRI parameters can be found at http://nssdc.gsfc.nasa.gov/space/model/models/iri.html . Abdu, M. A., J. R de Souza, I. S. Batista, and J. H. A. Sobral, Equatorial Spread F statistics and their empirical modeling for the IRI: A regional model for the Brazilian longitude sector, Adv. Space Res., in press, 2003. Triskova, L., V. Truhlik and J. Smilauer, An empirical model of ion composition in the outer ionosphere, Adv. Space Res., in press, 2003 Bilitza, D., A Correction for the IRI Topside Model Based on Alouette/ISIS Data, World Space Congress, Houston, Texas, 2002. Friedrich, M., M. Harrich, R. Steiner, K. M. Torkar, and F.-J. Luebken, The quiet auroral ionosphere and its neutral background, World space congress, Houston, Texas, 2002.

  18. Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) after nine years of operation: A summary

    NASA Astrophysics Data System (ADS)

    Orosei, R.; Jordan, R. L.; Morgan, D. D.; Cartacci, M.; Cicchetti, A.; Duru, F.; Gurnett, D. A.; Heggy, E.; Kirchner, D. L.; Noschese, R.; Kofman, W.; Masdea, A.; Plaut, J. J.; Seu, R.; Watters, T. R.; Picardi, G.

    2015-07-01

    Mars Express, the first European interplanetary mission, carries the Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) to search for ice and water in the Martian subsurface. Developed by an Italian-US team, MARSIS transmits low-frequency, wide-band radio pulses penetrating below the surface and reflected by dielectric discontinuities linked to structural or compositional changes. MARSIS is also a topside ionosphere sounder, transmitting a burst of short, narrow-band pulses at different frequencies that are reflected by plasma with varying densities at different altitudes. The radar operates since July 2005, after the successful deployment of its 40 m antenna, acquiring data at altitudes lower than 1200 km. Subsurface sounding (SS) data are processed on board by stacking together a batch of echoes acquired at the same frequency. On ground, SS data are further processed by correlating the received echo with the transmitted waveform and compensating de-focusing caused by the dispersive ionosphere. Ground processing of active ionospheric sounding (AIS) data consists in the reconstruction of the electron density profile as a function of altitude. MARSIS observed the internal structure of Planum Boreum outlining the Basal Unit, an icy deposit lying beneath the North Polar Layered Deposits thought to have formed in an epoch in which climate was markedly different from the current one. The total volume of ice in polar layered deposits could be estimated, and parts of the Southern residual ice cap were revealed to consist of ? 10 m of CO2 ice. Radar properties of the Vastitas Borealis Formation point to the presence of large quantities of ice buried beneath the surface. Observations of the ionosphere revealed the complex interplay between plasma, crustal magnetic field and solar wind, contributing to space weather studies at Mars. The presence of three-dimensional plasma structures in the ionosphere was revealed for the first time. MARSIS could successfully operate at Phobos, becoming the first instrument of its kind to observe an asteroid-like body. The main goal pursued by MARSIS, the search for liquid water beneath the surface, remains elusive. However, because of the many factors affecting detection and of the difficulties in identifying water in radar echoes, a definitive conclusion on its presence cannot yet be drawn.

  19. Possible influence of ultra-fast Kelvin wave on the equatorial ionosphere evening uplifting

    NASA Astrophysics Data System (ADS)

    Takahashi, H.; Abdu, M. A.; Wrasse, C. M.; Fechine, J.; Batista, I. S.; Pancheva, D.; Lima, L. M.; Batista, P. P.; Clemesha, B. R.; Shiokawa, K.; Gobbi, D.; Mlynczak, M. G.; Russell, J. M.

    2009-04-01

    Equatorial 3.5-day ultra-fast Kelvin wave was observed in the MLT zonal wind measured by meteor radar at Cariri (7.4°S, 36.5°W, geomag. 8°S) and in the stratosphere-mesosphere temperature structures from the TIMED/SABER data. The ionospheric F-layer bottom-side virtual height hT'F and the critical frequency f o F 2 observed at Fortaleza (3.9°S, 38.4°W, geomag. 5°S) also showed similar oscillation structures, indicating an influence of the Kelvin wave in the F region height and modulation of E × B uplifting during the evening period. Consequently the ionospheric spread F onset time was also modulated in the same period, around 4 days.

  20. Chemical composition of Titan’s atmosphere and ionosphere: Observations and the photochemical model

    NASA Astrophysics Data System (ADS)

    Krasnopolsky, Vladimir A.

    2014-07-01

    Basic observational data on hydrocarbons, nitriles, and ions on Titan are compared with predictions of the photochemical model. Uncertainties of the observed abundances and differences between the data from different instruments and observing teams are comparable with the differences between the observations and the model results. Main reactions of production and loss for each species are quantitatively assessed and briefly discussed. Formation of haze by polymerization of hydrocarbons and nitriles and recombination of heavy ions is calculated along with condensation of various species near the tropopause. Overall deposition is a layer of 300 m thick for the age of the Solar System, and nitrogen constitutes 8% of the deposition. The model reproduces the basic observational data and adequately describes basic chemical processes in Titan’s atmosphere and ionosphere. The presented model results and the observational data may be used as a reference to chemical composition of Titan’s atmosphere and ionosphere.

  1. 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.

  2. Investigation of mid-latitude ionospheric currents by combined rocket techniques.

    NASA Technical Reports Server (NTRS)

    Rees, D.; Dorling, E. B.; Wrenn, G. L.; Aggson, T. L.; Burrows, K.; Haerendel, G.; Rieger, E.; Lloyd, K. H.; Wilson, J. W. G.

    1973-01-01

    A comprehensive range of neutral atmospheric and simultaneous ionospheric structure measurements were obtained from a Skylark rocket launched at Woomera during evening twilight on a quiet magnetic day. Above 150 km, good agreement was found between the results obtained from three different methods of electric field measurement despite the low field strength (about 1.5 mV/m). In the immediate vicinity of an intense sporadic E layer, the probe measurements indicated large excursions of the electrostatic field amounting to 6.5 mV/m at 105.3 km and 2.7 mV/m at 104.8 km. The calculated ionospheric current system in the vicinity of the rocket trajectory was of similar magnitude to that indicated by local ground-based magnetometers, but was diametrically opposed in direction.

  3. Grating formation by a high power radio wave in near-equator ionosphere

    SciTech Connect

    Singh, Rohtash; Sharma, A. K.; Tripathi, V. K.

    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.

  4. Real-time imaging of density ducts between the plasmasphere and ionosphere

    NASA Astrophysics Data System (ADS)

    Loi, Shyeh Tjing; Murphy, Tara; Cairns, Iver H.; Menk, Frederick W.; Waters, Colin L.; Erickson, Philip J.; Trott, Cathryn M.; Hurley-Walker, Natasha; Morgan, John; Lenc, Emil; Offringa, André R.; Bell, Martin E.; Ekers, Ronald D.; Gaensler, B. M.; Lonsdale, Colin J.; Feng, Lu; Hancock, Paul J.; Kaplan, David L.; Bernardi, G.; Bowman, J. D.; Briggs, F.; Cappallo, R. J.; Deshpande, A. A.; Greenhill, L. J.; Hazelton, B. J.; Johnston-Hollitt, M.; McWhirter, S. R.; Mitchell, D. A.; Morales, M. F.; Morgan, E.; Oberoi, D.; Ord, S. M.; Prabu, T.; Shankar, N. Udaya; Srivani, K. S.; Subrahmanyan, R.; Tingay, S. J.; Wayth, R. B.; Webster, R. L.; Williams, A.; Williams, C. L.

    2015-05-01

    Ionization of the Earth's atmosphere by sunlight forms a complex, multilayered plasma environment within the Earth's magnetosphere, the innermost layers being the ionosphere and plasmasphere. The plasmasphere is believed to be embedded with cylindrical density structures (ducts) aligned along the Earth's magnetic field, but direct evidence for these remains scarce. Here we report the first direct wide-angle observation of an extensive array of field-aligned ducts bridging the upper ionosphere and inner plasmasphere, using a novel ground-based imaging technique. We establish their heights and motions by feature tracking and parallax analysis. The structures are strikingly organized, appearing as regularly spaced, alternating tubes of overdensities and underdensities strongly aligned with the Earth's magnetic field. These findings represent the first direct visual evidence for the existence of such structures.

  5. A General Computer Program for Ionospheric Ray-Tracing

    NASA Technical Reports Server (NTRS)

    Gonzales, Victor H.

    1961-01-01

    The study of the ionosphere using the Faraday rotation effect has been undertaken recently by means of rocket, satellite, and moon echo experiments. Different approximations have been used by different authors, resulting in methods with different degrees of complexity, and it is possible to say that the more accurate a method is, the more difficult its application becomes. However, the use of modern high-speed digital computers offers the possibility of using more complex methods in the solution of this problem, The program described in this report was written for the ILLIAC, the digital computer of the University of Illinois. Only the general features common to most digital computers will be mentioned. This program was prepared having in mind the analysis of the Faraday rotation effect, as recorded from artificial satellites. It is intended to be as general as possible in the conditions imposed on the assumed propagating medium: specifically there are no restrictions on the models of the electron density distribution and the earth's magnetic fields. long as the ray theory Ls valid. The program will trace separately the ordinary and the extraordinary mode, and it will find the virtual phase path length of a ray of each mode between the transmitter (satellite) and a receiver (station). The difference between respective phase path-lengths is related to the Faraday rotation through a constant which depends on the frequency.

  6. 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.

  7. Lithosphere-Atmosphere-Ionosphere Coupling (LAIC) model - An unified concept for earthquake precursors validation

    NASA Astrophysics Data System (ADS)

    Pulinets, S.; Ouzounov, D.

    2011-06-01

    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.

  8. Ionospheric response to the October 2003 geomagnetic superstorm in the South American-Atlantic sector

    NASA Astrophysics Data System (ADS)

    Batista, I. S.; de Souza, J. R.; Abdu, M. A.; Reinisch, B. W.; Bullett, T. W.; Rios, V. H.

    The major geomagnetic storm that started at 0611GMT on 29 th October 2003 in response to the solar event that occurred on the day before has affected the earth ionosphere at a broad range of latitudes and longitudes Drastic and peculiar effects were observed at the equatorial and low latitude ionospheric F region a few hours following the storm onset and also in the following days In this work we analyze ionograms from a chain of Digisonde stations in the South American-Atlantic 280 o - 345 o E longitude sector in order to study the ionospheric response to the intense solar event Less that two hours after the storm onset an unusual early morning enhancement of the equatorial ionization anomaly was observed at the three ionospheric stations located at or close to the equatorial anomaly crest Tucuman TU 26 9 o S 294 6 o E dip -26 24 o Cachoeira Paulista CP 22 5 o S 315 o E dip -32 9 o and Ascension Island AI 7 95 o S 345 6 o E dip -37 8 o The anomaly intensification was more pronounced at TU and CP where the F layer peak electron density increased from 1 1x10 5 el cm -3 to 2 8x10 6 el cm -3 than at AI The most striking fact about this intensification is that it occurred just before sunrise at TU and around sunrise at CP when the conditions for the fountain effect are not set yet Another striking effect of the magnetic storm was the spectacular uplift of the F layer around sunset on 30 th October at the equatorial station S a o Lu i s SL 2 6 o

  9. Evaluation of COMPASS ionospheric model in GNSS positioning

    NASA Astrophysics Data System (ADS)

    Wu, Xiaoli; Hu, Xiaogong; Wang, Gang; Zhong, Huijuan; Tang, Chengpan

    2013-03-01

    As important products of GNSS navigation message, ionospheric delay model parameters are broadcasted for single-frequency users to improve their positioning accuracy. GPS provides daily Klobuchar ionospheric model parameters based on geomagnetic reference frame, while the regional satellite navigation system of China's COMPASS broadcasts an eight-parameter ionospheric model, COMPASS Ionospheric Model(CIM), which was generated by processing data from continuous monitoring stations, with updating the parameters every 2 h. To evaluate its performance, CIM predictions are compared to ionospheric delay measurements, along with GPS positioning accuracy comparisons. Real observed data analysis indicates that CIM provides higher correction precision in middle-latitude regions, but relatively lower correction precision for low-latitude regions where the ionosphere has much higher variability. CIM errors for some users show a common bias for in-coming COMPASS signals from different satellites, and hence ionospheric model errors are somehow translated into the receivers' clock error estimation. In addition, the CIM from the China regional monitoring network are further evaluated for global ionospheric corrections. Results show that in the Northern Hemisphere areas including Asia, Europe and North America, the three-dimensional positioning accuracy using the CIM for ionospheric delay corrections is improved by 7.8%-35.3% when compared to GPS single-frequency positioning ionospheric delay corrections using the Klobuchar model. However, the positioning accuracy in the Southern Hemisphere is degraded due apparently to the lack of monitoring stations there.

  10. 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.

  11. 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.

  12. HF radar observations of ionospheric backscatter during geomagnetically quiet periods

    NASA Astrophysics Data System (ADS)

    Kane, T. A.; Makarevich, R. A.; Devlin, J. C.

    2012-01-01

    The quiet-time coherent backscatter from the F-region observed by the Tasman International Geospace Environment Radar (TIGER) Bruny Island HF radar is analysed statistically in order to determine typical trends and controlling factors in the ionospheric echo occurrence. A comparison of the F-region peak density values from the IRI-2007 model and ionosonde measurements in the vicinity of the radar's footprint shows a very good agreement, particularly at subauroral and auroral latitudes, and model densities within the radar's footprint are used in the following analyses. The occurrence of F-region backscatter is shown to exhibit distinct diurnal, seasonal and solar cycle variations and these are compared with model trends in the F-region peak electron density and Pedersen conductance of the underlying ionosphere. The solar cycle effects in occurrence are demonstrated to be strong and more complex than a simple proportionality on a year-to-year basis. The diurnal and seasonal effects are strongly coupled to each other, with diurnal trends exhibiting a systematic gradual variation from month to month that can be explained when both electron density and conductance trends are considered. During the night, the echo occurrence is suggested to be controlled directly by the density conditions, with a direct proportionality observed between the occurrence and peak electron density. During the day, the echo occurrence appears to be controlled by both conductance and propagation conditions. It is shown that the range of echo occurrence values is smaller for larger conductances and that the electron density determines what value the echo occurrence takes in that range. These results suggest that the irregularity production rates are significantly reduced by the highly conducting E layer during the day while F-region density effects dominate during the night.

  13. 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

  14. 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

  15. 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.

  16. Estimate of higher order ionospheric errors in GNSS positioning

    NASA Astrophysics Data System (ADS)

    Hoque, M. Mainul; Jakowski, N.

    2008-10-01

    Precise navigation and positioning using GPS/GLONASS/Galileo require the ionospheric propagation errors to be accurately determined and corrected for. Current dual-frequency method of ionospheric correction ignores higher order ionospheric errors such as the second and third order ionospheric terms in the refractive index formula and errors due to bending of the signal. The total electron content (TEC) is assumed to be same at two GPS frequencies. All these assumptions lead to erroneous estimations and corrections of the ionospheric errors. In this paper a rigorous treatment of these problems is presented. Different approximation formulas have been proposed to correct errors due to excess path length in addition to the free space path length, TEC difference at two GNSS frequencies, and third-order ionospheric term. The GPS dual-frequency residual range errors can be corrected within millimeter level accuracy using the proposed correction formulas.

  17. 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.

    2015-07-01

    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 9 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 the climatology (by about 5-10° latitude) and equatorward of the auroral boundary data acquired from the SSUSI sensor onboard the F18 DMSP satellite. 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.

  18. 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.

  19. 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.

    2015-10-01

    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.

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

    SciTech Connect

    Kang Cheng; Yinnnien Huang; Senwen 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, which is located near the northern equatorial anomaly crest region. It has been found that temporal variations of the F{sub 1} layer and D region are mainly controlled by local solar radiation. Quantitative analysis of the variations of the F{sub 1} layer critical frequency, F{sub o} F{sub 1}, shows that electrons are removed from the F{sub 1} layer through ionic recombination. However, the temporal variations of f{sub o}F{sub 2} and electron density above 200 km show that the variations o the F{sub 2} layer around the equatorial anomaly region are controlled not by local solar radiation but by solar radiation at the equator. The fountain effect plays an important role even during the solar eclipse. The VLF propagation time delay is controlled by the variations of average path obscuration. Atmospheric gravity waves produced by the moving bow wave front of the solar eclipse are found with a period around 17-23 min and wavelength about 293 km.

  1. Multi-Cone Model for Estimating GPS Ionospheric Delays

    NASA Technical Reports Server (NTRS)

    Sparks, Lawrence; Komjathy, Attila; Mannucci, Anthony

    2009-01-01

    The multi-cone model is a computational model for estimating ionospheric delays of Global Positioning System (GPS) signals. It is a direct descendant of the conical-domain model. A primary motivation for the development of this model is the need to find alternatives for modeling slant delays at low latitudes, where ionospheric behavior poses an acute challenge for GPS signal-delay estimates based upon the thin-shell model of the ionosphere.

  2. Trans-Ionospheric High Frequency Signal Ray Tracing

    NASA Astrophysics Data System (ADS)

    Wright, S.; Gillespie, R. J.

    2012-09-01

    All electromagnetic radiation undergoes refraction as it propagates through the atmosphere. Tropospheric refraction is largely governed by interaction of the radiation with bounded electrons; ionospheric refraction is primarily governed by free electron interactions. The latter phenomenon is important for propagation and refraction of High Frequency (HF) through Extremely High Frequency (EHF) signals. The degree to which HF to EHF signals are bent is dependent upon the integrated refractive effect of the ionosphere: a result of the signal's angle of incidence with the boundaries between adjacent ionospheric regions, the magnitude of change in electron density between two regions, as well as the frequency of the signal. In the case of HF signals, the ionosphere may bend the signal so much that it is directed back down towards the Earth, making over-the-horizon HF radio communication possible. Ionospheric refraction is a major challenge for space-based geolocation applications, where the ionosphere is typically the biggest contributor to geolocation error. Accurate geolocation requires an algorithm that accurately reflects the physical process of a signal transiting the ionosphere, and an accurate specification of the ionosphere at the time of the signal transit. Currently implemented solutions are limited by both the algorithm chosen to perform the ray trace and by the accuracy of the ionospheric data used in the calculations. This paper describes a technique for adapting a ray tracing algorithm to run on a General-Purpose Graphics Processing Unit (GPGPU or GPU), and using a physics-based model specifying the ionosphere at the time of signal transit. This technique allows simultaneous geolocation of significantly more signals than an equivalently priced Central Processing Unit (CPU) based system. Additionally, because this technique makes use of the most widely accepted numeric algorithm for ionospheric ray tracing and a timely physics-based model of the ionosphere instead of the typically used climatologically derived one, we assert that this technique improves geolocation accuracy.

  3. Multi-GNSS assessment of ionospheric threat model parameters for Ground Based Augmentation Systems (GBAS)

    NASA Astrophysics Data System (ADS)

    Onur Karslioglu, Mahmut; Durmaz, Murat; YeganehSahab, Amir

    2015-04-01

    Ground-Based Augmentation Systems (GBAS) makes aircraft precision approach and landing possible by providing differential corrections and integrity information for pseude range measurements obtained from Global Navigation Satellite System (GNSS).These information are transmited to the aviation users by means of very high frequency (VHF) or ultra high frequency (UHF) bands on the basis of GBAS local networks which support avionic receivers approximately within 20 kilometers of the airport. GBAS is strongly affected by anomalous ionospheric gradients during high ionospheric activities which can treaten the safety of the users. Therefore anomalous ionospheric gradients must be determined to understand and mitigate ionosphere threats occurring in different geographical regions. In this work, we assess an ionospheric anomaly threat model by analysing ionospheric gradients around Istanbul Ataturk Airport. For this, real ground-based observations from both GPS and GLONASS during high ionospheric activities since 2009 are pre-processed to extract ionospheric gradients. Afterwards ionospheric delays at each ionospheric piercing point are determined by applying different local ionospheric Total Electron Content (TEC) modeling and filtering techniques on the basis of raw carrier-phase observations. The ionospheric fronts are searched by looking at high ionospheric gradients which result from ionospheric delay differences between ionospheric piercing points. Then, the ionospheric threat parameters in terms of width, slope and velocity of the ionospheric wavefront are estimated from the extracted front occurences and gradients including velocity information of ionospheric piercing points. Finally, the estimated threat model parameters are examined and assessed by comparing the results from different techniques.

  4. Development of Ionospheric Tomography Model Using GPS

    NASA Astrophysics Data System (ADS)

    Choi, Byung-Kyu; Park, Jong-Uk; Lee, Sang-Jeong

    2006-09-01

    We produced the electron density distribution in the ionosphere over South Korea using the data from nine permanent GPS (Global Positioning System) stations which have been operated by KASI (Korea Astronomy and Space Science Institute). The dual-frequency GPS receiver data was used to precisely estimate the electron density in the ionosphere and we obtained the precise electron density profile based on two-dimensional TEC (Total Electron Contents). We applied ART (Algebraic Reconstruction Technique), which is one of the most commonly used algorithms to develop the tomography model. This paper presented the electron density distribution over South Korea with time. We compared with the electron density profiles derived from the GPS tomography reconstruction, Ionosonde measurement data obtained by observations, and the IRI-2001 values. As a result, the electron density profile by GPS reconstruction was in excellent agreement with the electron density profile obtained by Ionosonde measurement data.

  5. Magnetosphere sawtooth oscillations induced by ionospheric outflow.

    PubMed

    Brambles, O J; Lotko, W; Zhang, B; Wiltberger, M; Lyon, J; Strangeway, R J

    2011-06-01

    The sawtooth mode of convection of Earth's magnetosphere is a 2- to 4-hour planetary-scale oscillation powered by the solar wind-magnetosphere-ionosphere (SW-M-I) interaction. Using global simulations of geospace, we have shown that ionospheric O(+) outflows can generate sawtooth oscillations. As the outflowing ions fill the inner magnetosphere, their pressure distends the nightside magnetic field. When the outflow fluence exceeds a threshold, magnetic field tension cannot confine the accumulating fluid; an O(+)-rich plasmoid is ejected, and the field dipolarizes. Below the threshold, the magnetosphere undergoes quasi-steady convection. Repetition and the sawtooth period are controlled by the strength of the SW-M-I interaction, which regulates the outflow fluence. PMID:21636770

  6. Degradation spectra of electrons in the ionosphere

    NASA Astrophysics Data System (ADS)

    Konovalov, V. P.; Son, E. E.

    2015-11-01

    Theory and numerical simulations of degradation spectra of electrons in gases are presented. Theory is based on the power spectra of degradation charged particles as the spectra with fluxes in energy space. Numerical calculations of the electron energy distribution function have been performed for ionospheric gas mixtures constituted of molecules N2, O2 and atom O under influence of high energy electron source with detailed elementary electron collision processes with molecules and atoms being taken into consideration. The energy expenses of electrons into ionization, dissociation and excitation of various levels have been obtained so that to determine the rates of electron collision processes. The dependence of the electron energy expenses into various inelastic electronic processes upon the energy of primary electron source has been revealed. The results are presented for the rates of numerous elementary processes of electron interaction with basic ionospheric components to be suitably determined.

  7. The upper ionospheres of Jupiter and Saturn

    NASA Technical Reports Server (NTRS)

    Majeed, Tariq; Mcconnell, John C.

    1991-01-01

    The electron-density profiles of Jupiter's and Saturn's ionospheres are modeled with a 1D chemical diffusive model incorporating measured parameters of the neutral atmospheric structure. The Voyager RSS ion-density data are modeled by accounting for ion chemistry, the H3(+) recombination-rate coefficient, and H2O chemistry. Electron-density peaks for both ionospheres are 900-1000 km lower in the model than the measured values, and the role of vibrational excitation of H2 is discussed in converting H(+) to H2(+) and H3(+). Vertical ion flow is also considered which can maintain the plasma peaks under the conditions of electrical fields or horizontal neutral winds. An assumed influx of H2O molecules of a specific quantity is theorized to reproduce the measured values on Saturn when combined with a vertical plasma drift.

  8. Connection Between the Magnetosphere and Ionosphere

    NASA Technical Reports Server (NTRS)

    1984-01-01

    Two decades of space research have produced ample evidence that particles and fields originating in the active Sun can gain entry into the terrestrial magnetosphere and deposit their energy in the ionosphere and atmosphere. The final link in this solar-terrestrial chain is generically referred to as magnetosphere-ionosphere coupling (MIC). Because of the far-reaching implications of recent discoveries in MIC and because a coherent assessment of them has yet to be made, the principal task is to critically assess these new observations and the new perspectives that they may engender. The MIC topics of interest are roughly grouped according to the scale lengths of the phenomena being treated. This particular choice of groupings is mainly for convenience, with perhaps some suggestion as to the direction of energy cascade from the largest scales down to the smaller scale.

  9. Hf propagation through actively modified ionospheres

    SciTech Connect

    Argo, P.E.; Fitzgerald, T.J.; Wolcott, J.H.; Simons, D.J. ); Warshaw, S.; Carlson, R. )

    1990-01-01

    We have developed a computer modeling capability to predict the effect of localized electron density perturbations created by chemical releases or high-power radio frequency heating upon oblique, one-hop hf propagation paths. We have included 3-d deterministic descriptions of the depleted or enhanced ionization, including formation, evolution, and drift. We have developed a homing ray trace code to calculate the path of energy propagation through the modified ionosphere in order to predict multipath effects. We also consider the effect of random index of refraction variations using a formalism to calculate the mutual coherence functions for spatial and frequency separations based upon a path integral solution of the parabolic wave equation for a single refracted path through an ionosphere which contains random electron density fluctuations. 5 refs., 8 figs.

  10. Preseismic Lithosphere-Atmosphere-Ionosphere Coupling

    NASA Astrophysics Data System (ADS)

    Kamogawa, Masashi

    Preseismic atmospheric and ionospheric disturbances besides preseismic geo-electric potential anomalies and ultra-low-frequency (ULF) geomagnetic variations observed on the ground have been reported. Both the phenomena have been found since the 1980s and a number of papers have been published. Since most of the reported phenomena transiently appear with accompanying quiescence before the mainshock, this prevents us to intuitively recognize a correlation between the anomaly appearance and the earthquake occurrence. Some of them, however, showed that anomalies monotonically grew into the mainshock, of which a variation supports the concept of seismic nucleation process under the pre-earthquake state. For example, Heki [GRL, 2011] reported that ionospheric electron density monotonically enhanced tens of minutes prior to the subduction mega-earthquake. However, this preseismic enhancement is apparent variation attributed to tsunamigenic ionospheric hole [Kakinami and Kamogawa et al, GRL, 2012], namely wide and long-duration depression of ionospheric electron after tsunami-excited acoustic waves reach the ionosphere. Since the tsunamigenic ionospheric hole could be simulated [Shinagawa et al., GRL, 2013], the reported variations are high-possibly pseudo phenomena [Kamogawa and Kakinami, JGR, 2013]. Thus, there are barely a few reports which show the preseismic monotonic variation supported by the concept of the seismic nucleation process. As far as we discuss the preseismic geoelectromagnetical and atmospheric-ionospheric anomalies, preseismic transient events from a few weeks to a few hours prior to the mainshock are paid attention to for the precursor study. In order to identify precursors from a number of anomalies, one has to show a statistical significance of correlation between the earthquake and the anomalies, to elucidate the physical mechanism, or to conduct both statistical and physical approach. Since many speculation of the physical mechanism have been hardly verified so far, a statistical approach has been unique way to promote the research. After the 2000s, several papers showing robust statistical results have arisen. In this paper, we focus on publications satisfying the following identification criteria: 1) A candidate of precursor, namely anomaly, is quantitatively defied. 2) Two time-series of anomalies and earthquake are constructed within the fixed thresholds such as a minimum magnitude, a region, and a lead-time. 3) To obtain a statistical correlation, a statistical process which includes four relations considering all combination among earthquake - no earthquake versus anomaly and no anomalies is applied, e. g., phi correlation. 4) For correlations under various thresholds the results keep consistency. 5) Large anomalies appear before large earthquakes. One of papers based on the identification criteria, which concerns preseismic geoelectrically anomalies, is introduced as an educative example. VAN method in Greece, i. e., Geo-electric potential difference measurement for precursor study in Greece, has been often discussed in the point of view of success and failure performance for practical prediction [Varotsos et al, Springer, 2011] to show a correlation and then less number of papers shows the statistical correlation with satisfying the identification criteria [Geller (ed.), GRL, 1996], so that the phenomena had been controversial. However, recent related study in Kozu-Island, Japan which satisfied the criteria showed the robust correlation [Orihara and Kamogawa et al., PNAS, 2012]. Therefore, the preseismic geoelectric anomalies are expected to be a precursor. Preseismic lithosphere-atmosphere-ionosphere coupling has been intensively discussed [Kamogawa, Eos, 2006]. According to review based on the identification criteria with considering recent publications, plausible precursors have been found, which are tropospheric anomaly [Fujiwara and Kamogawa, GRL, 2004], daytime electron depletion in F region [Liu et al, JGR, 2006], nighttime decrease of background intensity of VLF electromagnetic waves poss

  11. Ionospheric wave and irregularity measurements using passive radio astronomy techniques

    NASA Technical Reports Server (NTRS)

    Erickson, W. C.; Mahoney, M. J.; Jacobson, A. R.; Knowles, S. H.

    1988-01-01

    The observation of midlatitude structures using passive radio astronomy techniques is discussed, with particular attention being given to the low-frequency radio telescope at the Clark Lake Radio Observatory. The present telescope operates in the 10-125-MHz frequency range. Observations of the ionosphere at separations of a few kilometers to a few hundreds of kilometers by the lines of sight to sources are possible, allowing the determination of the amplitude, wavelength, direction of propagation, and propagation speed of ionospheric waves. Data are considered on large-scale ionospheric gradients and the two-dimensional shapes and sizes of ionospheric irregularities.

  12. On a possible seismomagnetic effect in the topside ionosphere

    NASA Astrophysics Data System (ADS)

    Hegai, V. V.; Kim, V. P.; Liu, J. Y.

    2015-10-01

    In this paper we present the results of the computation of the electric and magnetic fields produced in the ionosphere by the near-earth seismogenic disturbance in the vertical atmospheric electrostatic field under different ionospheric conditions. It is shown that in the nighttime ionosphere during solar minimum and inside large-scale plasma bubbles, the magnitude of the transverse electric field can attain ?0.2 and 1.0 mV/m, respectively. The seismomagnetic effect with the magnitude of ?13 pT is predicted in the topside daytime and nighttime ionosphere at any solar activity.

  13. Study of ionospheric models for satellite orbit determination

    NASA Technical Reports Server (NTRS)

    Bilitza, D.; Rawer, K.; Pallaschke, S.

    1988-01-01

    Means of improving the accuracy of the ionospheric correction of two empirical ionospheric models, the Bent (Schmid et al. 1973) and international reference ionosphere (IRI) models, have been evaluated. An improved IRI topside formula is found to minimize the tendency for the electron density profile to decrease too sharply with increasing altitude, and is shown to produce results which compare well with satellite data and ground-based incoherent scatter measurements. A model for the effective parabolic thickness is proposed for the bottomside. Comparison with results from a Meteosat tracking exercise demonstrates that the present changes improve the overall accuracy of ionospheric delays calculated using the two models.

  14. The properties of ULF/VLF signals generated by the SURA facility without ionospheric currents modulation

    NASA Astrophysics Data System (ADS)

    Kotik, D. S.; Raybov, A. V.; Ermakova, E. N.

    2012-12-01

    During the last three years the comprehensive study of ionospheric generation of the artificial signals in ULF/VLF band was carried out at SURA facility. This research was stimulated by successive HAARP experiments on detection the low frequency signals genreated due the action of the ponderomotive forces. Two experimental campaigns under different ionospheric, geomagnetic and facility operation mode conditions was undertaken every year from 2010 to 2012. Here we are summarizing the main features of the artificial ULF/VLF signals observed in vicinity the SURA site. The signals in the 2-20 Hz band were observed in the small area around the facility with the radius approximately 15 km. It was not signal detection at the 30 km distance. The maximum of the amplitude was detected in the nearest receiving point about 3 km away from the transmitting array. The amplitude increased about 3 times when the beam was inclined on16 degrees to the south so the footprint of the geomagnetic field line comes close to the point of observation. The ULF signals increased slightly when the SURA operating frequency overlaps the critical foF2 frequency. As a rule the daytime signals are smaller then nighttime one. No any correlation was observed with geomagnetic disturbances. The time delay of the ionospheric ULF signals measured by phase method was estimated as 300-400 ms. Polarization of the ULF signals has a pronounced elliptical character. Sometimes it was linear. The part of measurements in June 2012 was coincide with magnetic storm (June 16-18, Kp=6). It was observed broadening of the signal line at frequencies of 11 and 17 Hz up to 0.2 Hz at the recovery stage of the storm at June 18 (see the figure). This fact can be interpreted as the result of the signal interaction with the radiation belt protons appeared over there during the storm time. In 2012 campaigns it was firstly observed at SURA signals on frequencies of several kilohertz at nightime which could not be explained by traditional mechanism of ionospheric current modulation. Also this signals displayed unusual behavior during the magnetic storm deceasing in the amplitude. The work was supported by RFBR grants 11-02-00419, 11-02-97104 and RF Ministry of education and science by state contract 16.518.11.7066.;

  15. How the ionosphere of Mars works

    E-print Network

    Withers, Paul

    How the ionosphere of Mars works Paul Withers Boston University (withers@bu.edu) Department Lecture the top down · Optical depth(z) = n(z) H · Flux = Flux-at-infinity x exp(-optical depth) 9/31Preamble = Flux-at-infinity x exp(-optical depth) · Number of ions produced cm-3 s-1 = F n · Flux x cross

  16. The Ptolemaic Approach to Ionospheric Electrodynamics

    NASA Astrophysics Data System (ADS)

    Vasyliunas, V. M.

    2010-12-01

    The conventional treatment of ionospheric electrodynamics (as expounded in standard textbooks and tutorial publications) consists of a set of equations, plus verbal descriptions of the physical processes supposedly represented by the equations. Key assumptions underlying the equations are: electric field equal to the gradient of a potential, electric current driven by an Ohm's law (with both electric-field and neutral-wind terms), continuity of current then giving a second-order elliptic differential equation for calculating the potential; as a separate assumption, ion and electron bulk flows are determined by ExB drifts plus collision effects. The verbal descriptions are in several respects inconsistent with the equations; furthermore, both the descriptions and the equations are not compatible with the more rigorous physical understanding derived from the complete plasma and Maxwell's equations. The conventional ionospheric equations are applicable under restricted conditions, corresponding to a quasi-steady-state equilibrium limit, and are thus intrinsically incapable of answering questions about causal relations or dynamic developments. Within their limited range of applicability, however, the equations are in most cases adequate to explain the observations, despite the deficient treatment of plasma physics. (A historical precedent that comes to mind is that of astronomical theory at the time of Copernicus and for some decades afterwards, when the Ptolemaic scheme could explain the observations at least as well if not better than the Copernican. Some of the verbal descriptions in conventional ionospheric electrodynamics might be considered Ptolemaic also in the more literal sense of being formulated exclusively in terms of a fixed Earth.) I review the principal differences between the two approaches, point out some questions where the conventional ionospheric theory does not provide unambiguous answers even within its range of validity (e.g., topside and bottomside boundary conditions on electrodynamics), and illustrate with some simple examples of how a neutral-wind dynamo really develops.

  17. Determination of the critical frequency of a quasi-parabolic model of the ionosphere from oblique-incidence/backscatter sounding data

    NASA Astrophysics Data System (ADS)

    Darenskii, V. D.

    A formula is derived which approximates the dependence of the critical frequency of a quasi-parabolic layer on the minimum value of the group path at a given emission frequency, taking terrestrial and ionospheric sphericity into account. It is shown that the approximation error does not exceed 2.2 percent.

  18. 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 ...

  19. Ionosphere Waves Service (IWS) - a problem-oriented tool in ionosphere and Space Weather research produced by POPDAT project

    NASA Astrophysics Data System (ADS)

    Ferencz, Csaba; Lizunov, Georgii; Crespon, François; Price, Ivan; Bankov, Ludmil; Przepiórka, Dorota; Brieß, Klaus; Dudkin, Denis; Girenko, Andrey; Korepanov, Valery; Kuzmych, Andrii; Skorokhod, Tetiana; Marinov, Pencho; Piankova, Olena; Rothkaehl, Hanna; Shtus, Tetyana; Steinbach, Péter; Lichtenberger, János; Sterenharz, Arnold; Vassileva, Any

    2014-05-01

    In the frame of the FP7 POPDAT project the Ionosphere Waves Service (IWS) has been developed and opened for public access by ionosphere experts. IWS is forming a database, derived from archived ionospheric wave records to assist the ionosphere and Space Weather research, and to answer the following questions: How can the data of earlier ionospheric missions be reprocessed with current algorithms to gain more profitable results? How could the scientific community be provided with a new insight on wave processes that take place in the ionosphere? The answer is a specific and unique data mining service accessing a collection of topical catalogs that characterize a huge number of recorded occurrences of Whistler-like Electromagnetic Wave Phenomena, Atmosphere Gravity Waves, and Traveling Ionosphere Disturbances. IWS online service (http://popdat.cbk.waw.pl) offers end users to query optional set of predefined wave phenomena, their detailed characteristics. These were collected by target specific event detection algorithms in selected satellite records during database buildup phase. Result of performed wave processing thus represents useful information on statistical or comparative investigations of wave types, listed in a detailed catalog of ionospheric wave phenomena. The IWS provides wave event characteristics, extracted by specific software systems from data records of the selected satellite missions. The end-user can access targets by making specific searches and use statistical modules within the service in their field of interest. Therefore the IWS opens a new way in ionosphere and Space Weather research. The scientific applications covered by IWS concern beyond Space Weather also other fields like earthquake precursors, ionosphere climatology, geomagnetic storms, troposphere-ionosphere energy transfer, and trans-ionosphere link perturbations.

  20. Solar Flare Impacts on Ionospheric Electrodynamics

    NASA Technical Reports Server (NTRS)

    Qian, Liying; Burns, Alan G.; Solomon, Stanley C.; Chamberlin, Phillip C.

    2012-01-01

    The sudden increase of X-ray and extreme ultra-violet irradiance during flares increases the density of the ionosphere through enhanced photoionization. In this paper, we use model simulations to investigate possible additional contributions from electrodynamics, finding that the vertical E X B drift in the magnetic equatorial region plays a significant role in the ionosphere response to solar flares. During the initial stage of flares, upward E X B drifts weaken in the magnetic equatorial region, causing a weakened equatorial fountain effect, which in turn causes lowering of the peak height of the F2 region and depletion of the peak electron density of the F2 region. In this initial stage, total electron content (TEC) enhancement is predominantly determined by solar zenith angle control of photoionization. As flares decay, upward E X B drifts are enhanced in the magnetic equatorial region, causing increases of the peak height and density of the F2 region. This process lasts for several hours, causing a prolonged F2-region disturbance and TEC enhancement in the magnetic equator region in the aftermath of flares. During this stage, the global morphology of the TEC enhancement becomes predominantly determined by these perturbations to the electrodynamics of the ionosphere.

  1. Understanding Ionospheric Connections to Sun and Earth

    NASA Astrophysics Data System (ADS)

    Immel, Thomas J.; Rowland, Doug; England, Scott; Talaat, Elsayed; Jones, Sarah

    2015-04-01

    Earth's ionosphere is the dense plasma environment that dominates the boundary between our atmosphere and space. In contrast with long-standing understanding of the ionosphere as a phenomenon influenced by changes in solar radiation and solar wind, observations over the past decade have shown us that its large day-to-day variability likely originates with forcing from the lower atmosphere. This realization came with a combination of key observations utilizing pioneering measurement techniques, the emergence of sophisticated whole-atmosphere modeling approaches, and the development and application of innovative analysis techniques. The large and unexpected signatures in the ionosphere drove real ingenuity in the development of modeling and analysis techniques, in part for the lack of needed measurements of key aspects of Earth's space environment. Still, the causal links are incomplete and a significant effort is now being mounted to make these necessary measurements and build a more complete view of the coupled space-atmosphere system. Here we will review these efforts, including the upcoming NASA missions ICON and GOLD, and discuss recent results that offer further promise for future ground-breaking observations and discovery.

  2. Assimilative modeling of low latitude ionosphere

    NASA Technical Reports Server (NTRS)

    Pi, Xiaoqing; Wang, Chunining; Hajj, George A.; Rosen, I. Gary; Wilson, Brian D.; Mannucci, Anthony J.

    2004-01-01

    In this paper we present an observation system simulation experiment for modeling low-latitude ionosphere using a 3-dimensional (3-D) global assimilative ionospheric model (GAIM). The experiment is conducted to test the effectiveness of GAIM with a 4-D variational approach (4DVAR) in estimation of the ExB drift and thermospheric wind in the magnetic meridional planes simultaneously for all longitude or local time sectors. The operational Global Positioning System (GPS) satellites and the ground-based global GPS receiver network of the International GPS Service are used in the experiment as the data assimilation source. 'The optimization of the ionospheric state (electron density) modeling is performed through a nonlinear least-squares minimization process that adjusts the dynamical forces to reduce the difference between the modeled and observed slant total electron content in the entire modeled region. The present experiment for multiple force estimations reinforces our previous assessment made through single driver estimations conducted for the ExB drift only.

  3. GUVI Observations of Thermosphere/Ionosphere Coupling

    NASA Astrophysics Data System (ADS)

    Paxton, L.; Zhang, Y.; Kil, H.; Morrison, D.; Wolven, B.; Meng, C.; Christensen, A.

    The Global Ultraviolet Imager GUVI on the NASA TIMED satellite has established a unique and valuable record of the response of the ionosphere and thermosphere to changes in the solar cycle and the geospace environment The GUVI data are available on the web site http guvi jhuapl edu We are working on developing testing and documenting new products The GUVI instrument provides unique data on the composition and temperature of the dayside thermosphere and the nightside F-region ionosphere In this paper we will present results from our study of special periods including the October and November 2003 superstorms the November 2004 superstorm and compare these to the response during HILDCAA events Because TIMED has been in continuous operation for 4 years and repeats its local solar time coverage from year to year the local time of the ascending node covers 24 hours in 120 days we can compare the behavior as a function of solar cycle and to impulsive events We hope that TIMED will continue to be funded for operation through solar minimum in the hope that we will be able to observe the quiescent state of the thermosphere ionosphere system

  4. Present state of ionospheric time delay prediction

    NASA Astrophysics Data System (ADS)

    Klobuchar, J. A.

    The present capability to predict trans-ionospheric time delay, proportional to the total electron content (TEC), is based largely on the ITS-78 empirical model of f0F2 (May 1969). It is shown that long-term predictions (more than 30 days in advance) suffer from inaccuracy in solar flux prediction, while short-term predictions (day to day) are subject to unknown changes from the mean TEC behavior. The majority of available TEC data is from the Faraday effect, where the contribution to total time delay from heights greater than approximately 2000 km is not measurable. Improvements are suggested for TEC forecasting through the use of an actual TEC measurement in the near time-space of where the prediction is required. Several means are offered for improving data sources: appropriate radio beacon transmitters to provide near real-time measurements, the use of topside sounders for real-time assessment of the ionosphere, use of signals from the NAVSTAR Global Positioning Satellite, with its large geographic coverage, a program of routine, calibrated measurements of solar UV flux. Additional model improvements are also given, including the study of TEC behavior during magnetic storms in a more comprehensive set of longitude zones and a consideration of the effects of the variability of the neutral atmosphere on trans-ionospheric propagation.

  5. Temporal modulation of the four-peaked longitudinal structure of the equatorial ionosphere by the 2 day planetary wave

    NASA Astrophysics Data System (ADS)

    Liu, Guiping; Immel, Thomas J.; England, Scott L.; Kumar, Karanam K.; Ramkumar, Geetha

    2010-12-01

    Observations of electron densities by the Constellation Observing System for Meteorology, Ionosphere, and Climate in August to October 2008 have shown a prominent four-peaked longitudinal structure in the height of the F2 layer (hmF2) in the equatorial ionosphere. The development of this ionospheric structure in daytime is found to be consistent with the forcing by the eastward-propagating nonmigrating diurnal tide with zonal wave number 3 (DE3). It is believed that tidal winds can modify the E region electric fields and subsequently produce variations in the ionosphere through the dynamo effect. This study reveals that the amplitude of the hmF2 four-peaked longitudinal structure is subject to a 2 day periodic modulation on certain intervals in the two-month time period. Simultaneously, wind measurements from the SKiYMET meteor radar at Thumba (8.5°N, 77°E), India indicate corresponding 2 day planetary wave activity in the mesosphere and lower thermosphere (MLT). The 2 day planetary wave has both zonal and meridional wind components, and it is the variability in the zonal component that most closely corresponds to F2 layer changes. The zonal wind observations by the radar also show that the amplitude of the diurnal tide is modulated by the 2 day wave. This study suggests that the identified 2 day variation of the hmF2 four-peaked longitudinal structure in the equatorial ionosphere is caused by the interaction between the DE3 tide and the 2 day planetary wave.

  6. [The artificial lens implant].

    PubMed

    Cârstocea, B; Selaru, D; Filip, M; Sandu, E; Stefan, C; Isp??oiu, C; Banaeu, I

    1993-01-01

    The paper presents a short history of the cataract intervention, starting from the lens luxation in vitreum and going to the implant of artificial lens. From the three classes of artificial lenses, up-to-date options are the posterior chamber artificial lenses. Today, in 80% of the cases, artificial lens implant is done, 80% of the implanted lenses being posterior chamber lenses. The paper also exposes various operatorial techniques, post-operatorial evolution and the results obtained. PMID:8507623

  7. Signatures of 3-6 day planetary waves in the equatorial mesosphere and ionosphere

    NASA Astrophysics Data System (ADS)

    Takahashi, H.; Wrasse, C. M.; Pancheva, D.; Abdu, M. A.; Batista, I. S.; Lima, L. M.; Batista, P. P.; Clemesha, B. R.; Shiokawa, K.

    2006-12-01

    Common periodic oscillations have been observed in meteor radar measurements of the MLT winds at Cariri (7.4° S, 36.5° W) and Ascension Island (7.9° S, 14.4° W) and in the minimum ionospheric virtual height, h'F, measured at Fortaleza (3.9° S, 38.4° W) in 2004, all located in the near equatorial region. Wavelet analysis of these time series reveals that there are 3-4-day, 6-8-day and 12-16-day oscillations in the zonal winds and h'F. The 3-4 day oscillation appeared as a form of a wave packet from 7-17 August 2004. From the wave characteristics analyzed this might be a 3.5-day Ultra Fast Kelvin wave. The 6-day oscillation in the mesosphere was prominent during the period of August to November. In the ionosphere, however, it was apparent only in November. Spectral analysis suggests that this might be a 6.5-day wave previously identified. The 3.5-day and 6.5-day waves in the ionosphere could have important roles in the initiation of equatorial spread F (plasma bubble). These waves might modulate the post-sunset E×B uplifting of the base of the F-layer via the induced lower thermosphere zonal wind and/or the E-region conductivity.

  8. Analysis of rocket beacon transmissions for computerized reconstruction of ionospheric densities

    NASA Technical Reports Server (NTRS)

    Bernhardt, P. A.; Huba, J. D.; Chaturvedi, P. K.; Fulford, J. A.; Forsyth, P. A.; Anderson, D. N.; Zalesak, S. T.

    1993-01-01

    Three methods are described to obtain ionospheric electron densities from transionospheric, rocket-beacon TEC data. First, when the line-of-sight from a ground receiver to the rocket beacon is tangent to the flight trajectory, the electron concentration can be obtained by differentiating the TEC with respect to the distance to the rocket. A similar method may be used to obtain the electron-density profile if the layer is horizontally stratified. Second, TEC data obtained during chemical release experiments may be interpreted with the aid of physical models of the disturbed ionosphere to yield spatial maps of the modified regions. Third, computerized tomography (CT) can be used to analyze TEC data obtained along a chain of ground-based receivers aligned along the plane of the rocket trajectory. CT analysis of TEC data is used to reconstruct a 2D image of a simulated equatorial plume. TEC data is computed for a linear chain of nine receivers with adjacent spacings of either 100 or 200 km. The simulation data are analyzed to provide an F region reconstruction on a grid with 15 x 15 km pixels. Ionospheric rocket tomography may also be applied to rocket-assisted measurements of amplitude and phase scintillations and airglow intensities.

  9. Newly Discovered Parametric Instabilities Excited by High Power Radio Waves in the Ionosphere

    NASA Astrophysics Data System (ADS)

    Bernhardt, Paul

    2010-11-01

    A powerful electromagnetic wave can decay into a large number of low frequency electrostatic waves and a scattered electromagnetic wave by generalized stimulated Brillouin scatter (GSBS). The generalization occurs in the F-layer ionosphere because of the presence of the magnetic field supporting a large number of plasma waves not present in an unmagnetized plasma. Stimulated Brillouin scatter excites the ion acoustic mode. In addition, GSBS can excite slow MHD, Alfven, fast MHD, ion cyclotron, whistler, lower hybrid, ion Bernstein waves. The first detection of this process during ionospheric modification with high power radio waves was demonstrated using the HAARP transmitter in Alaska in 2009. Subsequent experiments have provided additional verification of the GSBS process with quantitative measurements of the scattered electromagnetic waves with low frequency offsets from the pump wave. Relative to ground-based laboratory experiments with laser plasma interactions, the ionospheric HF wave interactions experiments are more completely diagnosed into terms of understanding the basic decay process of the magnetized plasma. Applications of the GSBS observations included remote sensing of the plasma state and launching propagating wave modes.

  10. Ionospheric effects of rocket exhaust products (HEAO-C, Skylab and SPS-HLLV)

    SciTech Connect

    Zinn, J; Sutherland, D; Stone, S N; Duncan, L M; Behnke, R

    1980-10-01

    This paper reviews the current state of our understanding of the problem of ionospheric F-layer depletions produced by chemical effects of the exhaust gases from large rockets, with particular emphasis on the Heavy Lift Launch Vehicles (HLLV) proposed for use in the construction of solar power satellites. The currently planned HLLV flight profile calls for main second-stage propulsion confined to altitudes below 124 km, and a brief orbit-circularization maneuver at apogee. The second-stage engines deposit 9 x 10/sup 31/ H/sub 2/O and H/sub 2/ molecules between 56 and 124 km. Model computations show that they diffuse gradually into the ionospheric F region, where they lead to weak but widespread and persistent depletions of ionization and continuous production of H atoms. The orbit-circularization burn deposits 9 x 10/sup 29/ exhaust molecules at about 480-km altitude. These react rapidly with the F2 region 0/sup +/ ions, leading to a substantial (factor-of-three) reduction in plasma density, which extends over a 1000- by 2000-km region and persists for four to five hours. Also described are experimental airglow and incoherent-scatter radar measurements performed in conjunction with the 1979 launch of satellite HEAO-C, together with prelaunch and post-launch computations of the ionospheric effects. Several improvements in the model have been driven by the experimental observations. The computer model is described in some detail.

  11. Local empirical model of ionospheric plasma density derived from Digisonde measurements at Irkutsk

    NASA Astrophysics Data System (ADS)

    Ratovsky, K. G.; Oinats, A. V.

    2011-04-01

    Ionogram data from routine ionospheric observations in Irkutsk, Russia using a DPS-4 Digisonde sounder were hand-scaled for the 6-year period from December 2002 to December 2008 to derive a local empirical model of the electron density distribution in the bottomside ionosphere that provides a comprehensive description of the diurnal, seasonal, and solar activity variations of the major ionospheric characteristics. The paper describes the technique for building the local empirical model and the results of comparing its diurnal, seasonal, and solar activity specifications with the standard IRI-2007 climatological model for the same period of time, and retrospective observational data from the Millstone Hill incoherent scatter radar (1976-2002) and a collocated Digisonde (1989-1990, 1998-2004). Reasoning for the observed differences between the three datasets is then provided in terms of background physical phenomena. Primary focus of the paper is the behavior of three F 2 layer characteristics: the F 2 peak density ( N m F 2), the peak height ( h m F 2) and the bottomside thickness ( B 0).

  12. Detection of traveling ionospheric disturbances induced by atmospheric gravity waves using the global positioning system

    NASA Technical Reports Server (NTRS)

    Bassiri, Sassan; Hajj, George A.

    1993-01-01

    Natural and man-made events like earthquakes and nuclear explosions launch atmospheric gravity waves (AGW) into the atmosphere. Since the particle density decreases exponentially with height, the gravity waves increase exponentially in amplitude as they propagate toward the upper atmosphere and ionosphere. As atmospheric gravity waves approach the ionospheric heights, the neutral particles carried by gravity waves collide with electrons and ions, setting these particles in motion. This motion of charged particles manifests itself by wave-like fluctuations and disturbances that are known as traveling ionospheric disturbances (TID). The perturbation in the total electron content due to TID's is derived analytically from first principles. Using the tilted dipole magnetic field approximation and a Chapman layer distribution for the electron density, the variations of the total electron content versus the line-of-sight direction are numerically analyzed. The temporal variation associated with the total electron content measurements due to AGW's can be used as a means of detecting characteristics of the gravity waves. As an example, detection of tsunami generated earthquakes from their associated atmospheric gravity waves using the Global Positioning System is simulated.

  13. 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

  14. 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

  15. Spatial-temporal distribution of the ionospheric perturbations prior to Ms?6.0 earthquakes in China main land

    NASA Astrophysics Data System (ADS)

    Liu, Jing; Wan, Weixing; Shen, Xuhui; Zhang, Xuemin

    2015-04-01

    Recently, earthquake precursor in the ionosphere is becoming one of the most challenging issues both in earthquake science and ionospheric science field. Based on the analysis of ionospheric data before strong EQs, some perturbations have been found in D, E, F layers respectively over the epicentral areas, including case and statistics studies. For the earthquake monitoring and prediction, we need to understand the evolutional features both in temporal series and spatial distribution in order to build their relationship with earthquakes. In this study, using GPS TEC data (from Jet Populsion Laboratry), we have statistically analyzed the ionospheric perturbations prior to the Ms?6.0 earthquakes in China main land from November 1st, 1998 to December 31st, 2010. For each earthquake, LB=M-1.5(M-LQ) and UB=M+1.5(UQ-M) were selected as the threshold to abstract the disturbance from 0 to 15 days around the epicenter, and then we summed all the earthquakes results. The obtained results indicated that the GPS TEC had the same variation trend above the epicenter and eastern, southern, western, northern directions 15 days before earthquakes, and decrease occurred in all the 5 directions from 3 days to 5 days. Through different space scale analysis of ±10°, ±20°, ±30°, it was found that the maximum seismo-ionospheric disturbance didn't appear just above the epicenter, but shifted to the magnetic equator, and it was worth to point out that the effected region in ionosphere was about ±15°. Besides this, prior to earthquakes, positive anomalies appeared in the southwestern direction before 14th, 10th days, and there were obviously negative anomalies in the southeastern direction before 5th day. At last, a hypothesis of electrostatic field channel in lithosphere-atmosphere-ionosphere coupling was used to explain the observed phenomena. If there is penetration or secondary electric field in the ionosphere, it will move upward along the magnetic lines, causing E×B motion, and leading to electron movement to equatorward and also to east and west directions under down and up electric field.

  16. ARTIFICIAL INTELLIGENCE Learning to see and act

    E-print Network

    Meeden, Lisa A.

    * by using an artificial neural network -- a function approximator loosely inspired by biological neural approximate the complex Video-game emulator Image convolutions Hidden layers Game controller ac networks -- called a deep Q-network (DQN). The DQN's input (the pixels from four consecutivegamescreens

  17. AMPS data management requirements study. [user manuals (computer programs)/display devices - computerized simulation/experimentation/ionosphere

    NASA Technical Reports Server (NTRS)

    1975-01-01

    A data simulation is presented for instruments and associated control and display functions required to perform controlled active experiments of the atmosphere. A comprehensive user's guide is given for the data requirements and software developed for the following experiments: (1) electromagnetic wave transmission; (2) passive observation of ambient plasmas; (3) ionospheric measurements with a subsatellite; (4) electron accelerator beam measurements; and (5) measurement of acoustic gravity waves in the sodium layer using lasers. A complete description of each experiment is given.

  18. Kilometric irregularities in the E and R regions of the daytime equatorial ionosphere observed by a high resolution HF radar

    SciTech Connect

    Blanc, E.; Mercandalli, B.; Houngninou, E.

    1996-03-15

    The authors describe results from a vertically oriented HF radar operated in the Ivory Coast, which studied irregularities in the E and F regions of the equatorial ionosphere. The authors report on irregularity observations at heights consistent with the equatorial electrojet, and at heights above the electrojet, and into the F1 layer. They observe irregularities into the F region in this work. The radar operated in the frequency range from 1 to 8 MHz.

  19. Venus: ionosphere and atmosphere as measured by dual-frequency radio occultation of mariner v.

    PubMed

    1967-12-29

    Venus has daytime and nighttime ionospheres at the positions probed by radio occulation. The main layers are thin by terrestrial standards, with the nighttime peak concentration of electrons being about two orders of magnitude below that of the daytime peak. Above the nighttime peak were several scale-height regimes extending to a radius of at least 7500, and probably to 9700, kilometers from the center of Venus. Helium and hydrogen at plasma temperatures of 600 degrees to 1100 degrees K seem indicated in the regimes from 6300 to 7500 kilometers, with cooler molecular ions in lower regions. Above the daytime peak a sharp plasmapause was discovered, marking a sudden transition from appreciable ionization concentrations near Venus to the tenuous conditions of the solar wind. This may be indicative of a kind of interaction of the magnetized solar wind with a planetary body that differs from the two different kinds of interaction characterized by Earth and by Moon. For Venus and probably for Mars, the magnetic field of the solar wind may pile up in front of the conducting ionosphere, form an induced magnetosphere that ends at the plasmapause, above which any ionosphere that tends to form is swept away by the shocked solar wind that flows between the stand-off bow-shock and the magnetopause. The neutral atmosphere was also probed and a surface reflection may have been detected, but the data have not yet been studied in detail. Results are consistent with a super-refractive atmosphere, as expected from Soviet measurements near the surface. Thus, two unusual features of Venus can be described in terms of a light trap in the lower atmosphere, and a magnetic trap in the conducting ionosphere. PMID:17749790

  20. HF/VHR radiowave techniques for investigating high-latitude ionospheric disturbances. Final report, Sep 87-Dec 90

    SciTech Connect

    Ostergaard, J.; Weitzen, J.A.; Li, E.; Haines, D.M.; Sales, G.S.

    1991-04-01

    The object of this contract was to develop a unified model for radio wave propagation in the 2-147 MHz band at high latitudes, especially during disturbances. This particularly included the analysis and measurement of the frequency dependence during polar cap absorption events and assessment of the effects of artificially induced perturbations on radio waves within this band. This project concentrated on single hop HF ionospheric propagation in the 2-30 MHz band and VHF meteor scatter in the 45-147 MHz band.