Science.gov

Sample records for artificial ionospheric layers

  1. 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

  2. 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.

  3. 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.

  4. 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.

  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. Production of artificial ionospheric layers by frequency sweeping near the 2nd gyroharmonic

    NASA Astrophysics Data System (ADS)

    Pedersen, T.; McCarrick, M.; Reinisch, B.; Watkins, B.; Hamel, R.; Paznukhov, V.

    2011-01-01

    Artificial ionospheric plasmas descending from the background F-region have been observed on multiple occasions at the High Frequency Active Auroral Research Program (HAARP) facility since it reached full 3.6 MW power. Proximity of the transmitter frequency to the 2nd harmonic of the electron gyrofrequency (2fce) has been noted as a requirement for their occurrence, and their disappearance after only a few minutes has been attributed to the increasing frequency mismatch at lower altitudes. We report new experiments employing frequency sweeps to match 2fce in the artificial plasmas as they descend. In addition to revealing the dependence on the 2fce resonance, this technique reliably produces descending plasmas in multiple transmitter beam positions and appears to increase their stability and lifetime. High-speed ionosonde measurements are used to monitor the altitude and density of the artificial plasmas during both the formation and decay stages.

  9. 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.

  10. 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.

  11. Ionospheric effects of magnetic storm observed by means of oblique sounding of artificial ionospheric turbulence

    NASA Astrophysics Data System (ADS)

    Uryadov, V. P.; Vertogradov, G. G.; Vertogradov, V. G.; Ponyatov, A. A.

    Results of experimental studies of the influence of the artificial ionospheric turbulence (AIT) on HF propagation are presented. Ionospheric modification and the creation of a scatterer was produced by powerful radio emission of the SURA heating facility (Nizhny Novgorod region). For diagnostics of the AIT were used the Russian chirp sounders network and HF Doppler radar. The reception of scattered signals was carried out in the Rostov-Don on the oblique V-type antenna oriented to the SURA heating facility. It is investigated ionospheric effects of magnetic storm during August 17-22, 2003 accompanied a period of the experiment. It is shown that ionospheric effects of the magnetic storm observed by means of Doppler frequency shift (DFS) measurements signals scattered from artificial small-scale field-aligned irregularities correlate well with the behavior of the southward component Bz of the interplanetary magnetic field and with variations in the geomagnetic field near the Earth surface. It has been found that at heights of the mid-latitude ionospheric F region under undisturbed conditions the electric field and the drift velocity of irregularities correspond to the typical values about 1 mV m-1 and 20 m s-1, respectively. During magnetic storm these values increase up to values of about 8.6 mV m-1 and 186 m s-1, which better correspond to the values typical for the high-latitude ionosphere. It is found that in the magnetically-disturbed period sporadically appearing trains with quasi-periodical modulation of DFS for the scattered signal with a period of 40-60 s and amplitude reaching 2 Hz were observed. The relation of the quasi-periodical oscillations of the DFS for the scattered signal to the presence of magnetohydrodynamics waves excited during a magnetic storm is considered. It is concluded that use HF Doppler radar for AIT sounding is of interest for diagnostics of wave processes in the ionosphere and magnetosphere. The conditions of formation of the HF signal field in the upper ionosphere have been studied using the diagnostics of the ionospheric channel by means of radio wave aspect scattering from artificial small-scale field-aligned irregularities. It has been shown that at long-distance paths the Es-layer may play the key role in formation in the upper ionosphere of the radio wave field at frequencies exceeding maximum usable frequency (MUF) of the standard hop propagation via the ionosphere F region. Modeling of oblique sounding ionogram on long-distance path in presence of the "lateral" signal received due to artificial field-aligned scattering is carried out.

  12. Modeling 3-D artificial ionospheric ducts

    NASA Astrophysics Data System (ADS)

    Zawdie, K. A.; Huba, J. D.; Wu, T.-W.

    2013-11-01

    The injection of powerful HF waves into the ionosphere leads to strong electron heating followed by a pressure perturbation, which can drive electrons along the field line to the conjugate side, creating what is known as an artificial duct. The electron temperature along the duct is above the ambient temperature; the electron density is depleted on the heating side and increased on the conjugate side. Duct formation due to HF heating has previously been studied using a modified version of SAMI2 (Sami2 is Another Model of the Ionosphere). We use a similarly modified version of SAMI3 to examine the effects of zonal E B drifts on interhemispheric ducts created by heating over Arecibo. We found that the longitudinal E B drifts, particularly those caused by the zonal neutral winds, significantly suppress the effects of HF heating on the conjugate side, reducing the temperature and density increases by about 90% and 75%, respectively.

  13. Physics studies in Artificial Ionospheric Mirror (AIM) related phenomena

    NASA Astrophysics Data System (ADS)

    Short, R.; Ali, A.; Lallement, P.; Koert, P.; Papadopoulos, D.; Shanny, R.; Wallace, T.; Stewart, C.; Drobot, A.; Tsang, K.

    1990-02-01

    A study was made into the fundamental physics of electromagnetic induced ionization in the lower ionosphere (60 to 80 km), using a ground based radiation source. The technique of remotely controlled ionization can be used to create a layered region of ionization and to then use the Artificial Ionospheric Mirror (AIM) to reflect HF/VHF signals for over the horizon communications and radar applications. The objective was to identify the basic physics issues controlling RF breakdown phenomena and to develop an understanding of those issues sufficient for performing quantitative prediction of AIM characteristics and the impact of those characteristics on the reflecting wave. Results of the study indicate that AIM is a viable concept and has the potential of providing important benefits over more traditional communication/radar technology.

  14. 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.

  15. 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.

  16. Investigations of the ionospheric using radio signals from artificial satellites

    NASA Technical Reports Server (NTRS)

    Titheridge, J. E.

    1973-01-01

    The occurrence and characteristics of ionospheric irregularities in medium latitudes and in polar regions were measured using radio signals from artificial satellites. Ionospheric changes during quiet and disturbed conditions were also measured. Electron density, elevation angle, and amplitude and frequency of these high frequency signals were determined as well as the direction of their arrival.

  17. Studies of the Lower Ionosphere using Artificial Periodic Irregularities

    NASA Astrophysics Data System (ADS)

    Bakhmetieva, Nataliya V.; Egerev, Mikhael N.; Tolmacheva, Ariadna V.; Vyakhirev, Valeriy D.

    Artificial periodic irregularities (API) created in the ionosphere plasma are used for the iono-sphere diagnostics. We present a new applications of API technique for experimental studies of the electron density in the lower ionosphere, atmospheric waves and sporadic E-layers. The applications are based on the new so-called two-frequency method of the API creation. The main results of the ionosphere studies carried out in 2006-2009 by the API technique using SURA heating facility are presented. API are formed in the field of a powerful standing radio wave produced by interference of the incident wave and reflected one by the ionosphere (V.V. Belikovich, E.A. Benediktov, N.V. Bakhmet'eva, A.V. Tolmacheva, Ionospheric Research by Means of Artificial Periodic Irregularities-Katlenburg-Lindau, Germany. 2002. Copernicus GmbH. ISBN 3-936586-03-9). The spatial period of the irregular structure is equal to the standing wavelength ? or the one-half the powerful wavelength ?/2. Ionosphere diagnostics is carried out in the API relaxation (or decay) stage by their sounding of probing radio pulses. The two frequency method bases upon the API creation and the scattering of the probe waves from API at two different frequencies i.e., having different spatial periods of the quasi periodic struc-ture. In the E -region of the ionosphere API are formed as a result of the diffusion redistribution of the ionosphere plasma in the field of the powerful wave. Relaxation of the periodic structure is specified by the ambipolar diffusion process. The API relaxation time is ? = (K 2 Da )-1 where K = 2?/? and Da is the ambipolar diffusion rate. It means that API having different spatial scales destroys with different time scales ? . The API spatial scale depends on the refractive in-dex n that is determined by the electron density N. It is shown the ratio of API relaxation times ? at two frequencies f1 and f2 , measured at the same heights, is connected with the frequencies ratio and the refractive index ratio as ? = ?1 /?2 = (f2 /f1 ) (n2 /n2 ). The measurement of the 2 2 2 1 ?(h) dependence makes it possible to determine electron density profile N(h). The profile is used for determination of the neutral temperature and density, the turbulent velocity and also the sporadic E -layer parameters. Plasma vertical velocity V was determined by measuring the phase of the probe radio waves scattered from API after switching off the power heating facility, i.e., at the API relaxation stage. The velocity and N(h) data have been used for estimation the total density metallic ions and the effective recombination rate at the sporadic E -layer height. The measured vertical velocity shift was about 10-4 c-1 - 3.5 10-3 c-1 . The shift can be caused by acoustic gravity waves and is sufficient for collecting of metal ions in sporadic E -layer. The waves with periods of 10-180 min have been found by the spectral analysis applied to the scat-tered signals characteristics. The temporal variations of the electron density 10-30% in the Es-layer were observed in some occasions. It is possible they connected with patch structure of the sporadic E -layer. One of the API application is a determination of the masses of the predominant metallic ions at the sporadic E -layer height. It is based on the experimental ob-servation that height dependence of the API relaxation time ? (h) has a local maximum at the sporadic E -layer location. The long-lived metallic ions cause the growth of the API relaxation time ? . We have obtained that the observed by API technique sporadic E -layers at the height of 95-110 km contained Ca+ and F e+ ions predominantly and the total density of the metallic percentage wise the electron density reached 60-90% sometimes. Acknowledgments. The work has been supported by RFBR grants No. 08-02-97036 and 09-05-00450.

  18. Artificial ionospheric disturbances caused by powerful radio waves

    NASA Astrophysics Data System (ADS)

    Lee, M. C.; Kuo, S. P.

    1984-11-01

    Artificial ionospheric disturbances evidenced as fluctuations in plasma density and geomagnetic field can be caused by powerful radio waves with a broad frequency band ranging from a few KHz to several GHz. The filamentation instability of radio waves with a broad frequency band ranging from a few KHz to several GHz can produce both large-scale plasma density fluctuations and large-scale geomagnetic field fluctuations simultaneously. The excitation of this instability is examined in the VLF wave injection experiments, the envisioned MF ionospheric heating experiments, the HF ionospheric heating experiments and the conceptualized Solar Power Satellite project. Significant geomagnetic field fluctuations with magnitudes even comparable to those observed in magnetospheric (sub)systems can be excited in all of the cases investigated. Particle precipitation and airglow enhancement are expected to be the concomitant ionospheric effects associated with the wave-induced geomagnetic field fluctuations.

  19. The HERO project: Rocket experiments in the artificially heated ionosphere

    NASA Astrophysics Data System (ADS)

    Rose, G.

    1980-06-01

    Heating experiments will be carried out near Tromsoe, Norway: very powerful radio-waves transmitted upwards into the ionosphere give rise to artificially induced modifications of the natural ionospheric plasma. Many of these modification effects can be followed and interpreted by ground based diagnostic installations such as the EISCAT incoherent scatter facility. Some, however, require in situ methods. Therefore heating rocket (HERO) measurements will complement the ground based observations, gathering data on the modified F region plasma. The planned four payloads are described briefly.

  20. Automatic ionospheric layers detection: Algorithms analysis

    NASA Astrophysics Data System (ADS)

    Molina, María G.; Zuccheretti, Enrico; Cabrera, Miguel A.; Bianchi, Cesidio; Sciacca, Umberto; Baskaradas, James

    2016-03-01

    Vertical sounding is a widely used technique to obtain ionosphere measurements, such as an estimation of virtual height versus frequency scanning. It is performed by high frequency radar for geophysical applications called "ionospheric sounder" (or "ionosonde"). Radar detection depends mainly on targets characteristics. While several targets behavior and correspondent echo detection algorithms have been studied, a survey to address a suitable algorithm for ionospheric sounder has to be carried out. This paper is focused on automatic echo detection algorithms implemented in particular for an ionospheric sounder, target specific characteristics were studied as well. Adaptive threshold detection algorithms are proposed, compared to the current implemented algorithm, and tested using actual data obtained from the Advanced Ionospheric Sounder (AIS-INGV) at Rome Ionospheric Observatory. Different cases of study have been selected according typical ionospheric and detection conditions.

  1. Model for artificial ionospheric duct formation due to HF heating

    NASA Astrophysics Data System (ADS)

    Milikh, G. M.; Demekhov, A. G.; Papadopoulos, K.; Vartanyan, A.; Huba, J. D.; Joyce, G.

    2010-04-01

    Strong electron heating by the injection of highly powerful HF waves can lead to the formation of ionospheric plasma density perturbations that stretch along the magnetic field lines. Those density perturbations can serve as ducts for guiding natural and artificial ELF/VLF waves. This paper presents a 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 two well documented experiments. One experiment, conducted at the SURA heating facility, used the low orbit satellite DEMETER as a diagnostic tool to measure the electron and ion temperature and density along the overflying satellite orbit close to the magnetic zenith of the HF-heater. The second experiment, conducted at the EISCAT HF facility and diagnosed by the EISCAT Incoherent Scatter Radar, measured the vertical profiles of the electron and ion temperature between 150-600 km. The model agrees well with the observations, and provides a new understanding of the processes during ionospheric modification.

  2. 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.

  3. 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

  4. 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.

  5. Electromagnetic fluctuations generated in the boundary layer of laboratory-created ionospheric depletions

    NASA Astrophysics Data System (ADS)

    Liu, Yu; Lei, Jiuhou; Cao, Jinxiang; Xu, Liang

    2016-01-01

    Ionospheric depletions, produced by release of attachment chemicals into the ionosphere, were widely investigated and taken as a potential technique for the artificial modification of space weather. In this work, we reported the experimental evidence of spontaneously generated electromagnetic fluctuations in the boundary layer of laboratory-created ionospheric depletions. These depletions were produced by releasing attachment chemicals into the ambient plasmas. Electron density gradients and sheared flows arose in the boundary layer between the ambient and the negative ions plasmas. These generated electromagnetic fluctuations with fundamental frequency f0 = 70 kHz lie in the lower hybrid frequency range, and the mode propagates with angles smaller than 90° (0.3π-0.4π) relative to the magnetic field. Our results revealed that these observed structures were most likely due to electromagnetic components of the electron-ion hybrid instability. This research demonstrates that electromagnetic fluctuations also can be excited during active release experiments, which should be considered as an essential ingredient in the boundary layer processes of ionospheric depletions.

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

    PubMed

    Ptzold, M; Tellmann, S; Husler, 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

  7. 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

  8. 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}.

  9. 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.

  10. 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.

  11. Three-dimensional, high resolution, computerized ionospheric tomographic imaging and computational modeling of an artificial ionospheric cavity

    NASA Astrophysics Data System (ADS)

    Selcher, Craig A.

    Tomographic techniques use line integral measurements to reconstruct local values of the measured parameter. These techniques have been applied to the ionosphere by using radio transmissions to measure the integral of electron density between a satellite and a chain of ground-based receiving stations. The resultant reconstructions form a two-dimensional map of the electron density in the plane of the satellite/receiver chain. Insufficient quantity of receivers and not having a complete range of accessible look angles with the available receivers are responsible for the non-uniqueness in the reconstructions. The limited look angle problem can be alleviated by making use of alternative data sources such as incoherent scatter radars ( ISR) that provide information on the vertical structure of the electron density. The non-optimal receiver placement problem can be alleviated through the use of sophisticated reconstruction algorithms. The computerized ionospheric tomography (CIT) technique has recently been used to image the artificially modified ionosphere above the Arecibo Observatory (AO) HF heating facility. A total of nine radio beacon receivers forming a three by three matrix were deployed across the entire island of Puerto Rico. The arrangement maximizes the likelihood that several of the receiver-to-satellite lines of sight would intersect the heated region of the ionosphere. Several satellite passes associated with such an intersection occurred, and the resultant tomographic inversions indicate the existence of an electron density cavity approximately 45 kilometers in latitudinal extent. The reduction of electron density in this cavity was typically on the order of 20%. The experimental observations were supported by theoretical work using the open-source SAMI2 ionospheric model. Methods were developed to model both the ohmic heating of the electrons and the suprathermal heating caused by nonlinear effects. Modeled ohmic heating values of 941 K/s match the observed heated temperature profiles. Modeled suprathermal electrons effects on the vibrational temperature of N2 indicate a vibrational/translation temperature differential of 308K.

  12. 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.

  13. Photometric instrument for studies of ionospheric artificial airglow emission caused by antropogenous disturbances

    NASA Astrophysics Data System (ADS)

    Nasyrov, Igor; Gumerov, Rustam; Nasyrov, Albert; Nikonenkov, Andrey

    One of informative methods of ionospheric processes data acquisition is based on registration of artificial airglow emission. In fact, artificial modifications of the ionosphere by powerful decameter radiowaves cause airglow emission on waves lengths 1270, 630, 557.7, 427.8 nm. In these experiments airglow emission were found at long expositions only as the registration systems of low sensitivity were used. It has allowed investigating the stages when developing of thermal parametric instabilities mechanism contribute mainly into the electron acceleration. The increase of artificial airglow emission at 557.7 nm was caused by impulses with 5 ms duration that corresponds to times of development of pondermotive parametric instability of ionosphere. That effect was found for the first time at the Kazan State University in collabora-tion with NIRFI (N. Novgorod) [Gumerov R.I., Kapkov V.B. et al. //Radiophysics and Quant. Electronics. 1999. Vol 42. P. 463.]. A new mobile photometric instrument equipped with a high-sensitive photometer and CCD-camera, system of GPS time-synchronization, system of "SURA"-channel review by HF-receiver, and systems of experimental data automatic registration by computer was engineered in the Kazan University. One makes possible the investigation of physical processes at the ionosphere disturbed by powerful radioemission, injections of chemically active substances and plasmas beams. The authors gratefully acknowledge Russian Foundation for Basic Research (Grant No 08-02-01188) for the financial support.

  14. Airborne studies of equatorial F layer ionospheric irregularities

    SciTech Connect

    Weber, E.J.; Buchau, J.; Moore, J.G.

    1980-09-01

    Radio wave and optical experiments were conducted onboard a U.S. Air Force research aircraft in March 1977 and March 1978 at low magnetic latitudes to investigate the effects of F region electron density amplitude. Scintillation measurements were used to monitor the development and motion of F region 6300-A O I airglow depletions, spread F, and scintillation producing irregularities that are all associated with low-density bubbles in the postsunset equatorial ionosphere. The 6300-A airglow depletions are the bottomside signature of low plasma density within the bubbles. Examples of multiple airglow depletions and their relation to variations in the F layer virtual height (h'F) and to the occurrence of amplitude scintillations on 250-MHz satellite signals are described. Estimates of the average bottomside electron density, from simultaneous ionosonde measurements and 6300-A airglow intensities, show electron density decreases of approx.66% within the bubbles. These decreases are approximately the same for bubbles observed at the magnetic equator and near Ascension Island (18 /sup 0/S magnetic latitude). The measurements at Ascension Island show that airglow depletions extend away from the magnetic equator into the southern 6300-A intertropical arc. Variations in the maximum poleward extent of airglow depletions and of associated ionospheric irregularities that give rise to amplitude scintillations were observed. These latitudinal variations are interpreted, using field line mapping considerations, as variations in the maximum altitude of plasma bubbles over the magnetic equator. A north-south flight confirms that the overall pattern of airglow depletions and associated ionospheric irregularities extends continuously across the magnetic equator to +-15/sup 0/ magnetic latitude.

  15. 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.

  16. 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.

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

    NASA Astrophysics Data System (ADS)

    Cole, K. D.

    1993-03-01

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

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

    NASA Technical Reports Server (NTRS)

    Cartwright, D. G.; Kellogg, P. J.

    1974-01-01

    This paper reports the observations of waves generated by a controlled beam of particles artificially injected into the ionosphere and magnetosphere. The measurements were made during the Electron Echo 1 experiment, in which an electron accelerator was carried to a height of 350 km in the ionosphere from Wallops Island, Virginia, on an Aerobee 350 sounding rocket. It injected into the earth's magnetic field over 3000 16-ms pulses of electrons with 40-keV energy and a current of 70 mA at pitch angles between 70 and 110 deg. The ejected fiber glass nose cone carried antennas and receivers to measure the electric field of waves generated by the beam. Associated with the electron beam was radiation detected at frequencies near the electron plasma frequency of the background ionosphere, near twice the electron cyclotron frequency in the whistler mode, and near zero frequency. Associated with the operation of an argon plasma generator used to keep the accelerator neutralized were continuous emissions detected at frequencies near the lower-hybrid resonance (LHR).

  19. Biomimetic layer-by-layer assembly of artificial nacre.

    PubMed

    Finnemore, Alexander; Cunha, Pedro; Shean, Tamaryn; Vignolini, Silvia; Guldin, Stefan; Oyen, Michelle; Steiner, Ullrich

    2012-01-01

    Nacre is a technologically remarkable organic-inorganic composite biomaterial. It consists of an ordered multilayer structure of crystalline calcium carbonate platelets separated by porous organic layers. This microstructure exhibits both optical iridescence and mechanical toughness, which transcend those of its constituent components. Replication of nacre is essential for understanding this complex biomineral, and paves the way for tough coatings fabricated from cheap abundant materials. Fabricating a calcitic nacre imitation with biologically similar optical and mechanical properties will likely require following all steps taken in biogenic nacre synthesis. Here we present a route to artificial nacre that mimics the natural layer-by-layer approach to fabricate a hierarchical crystalline multilayer material. Its structure-function relationship was confirmed by nacre-like mechanical properties and striking optical iridescence. Our biomimetic route uses the interplay of polymer-mediated mineral growth, combined with layer-by-layer deposition of porous organic films. This is the first successful attempt to replicate nacre, using CaCO(3). PMID:22828626

  20. 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.

  1. 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.

  2. 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 423'15.22''E and the latitude of 5159'9.63''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.

  3. 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.

  4. 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.

  5. 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.

  6. The sheath/ionosphere boundary layer at Venus

    NASA Technical Reports Server (NTRS)

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

    1995-01-01

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

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

    SciTech Connect

    Osterman, G.B.

    1994-01-01

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

  8. 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 probeswith their in situ observing capabilitiespassed 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.

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

    SciTech Connect

    Misra, Shikha; Mishra, S. K.

    2015-02-15

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

  10. Artificially stacked atomic layers: toward new van der Waals solids.

    PubMed

    Gao, Guanhui; Gao, Wei; Cannuccia, E; Taha-Tijerina, Jaime; Balicas, Luis; Mathkar, Akshay; Narayanan, T N; Liu, Zhen; Gupta, Bipin K; Peng, Juan; Yin, Yansheng; Rubio, Angel; Ajayan, Pulickel M

    2012-07-11

    Strong in-plane bonding and weak van der Waals interplanar interactions characterize a large number of layered materials, as epitomized by graphite. The advent of graphene (G), individual layers from graphite, and atomic layers isolated from a few other van der Waals bonded layered compounds has enabled the ability to pick, place, and stack atomic layers of arbitrary compositions and build unique layered materials, which would be otherwise impossible to synthesize via other known techniques. Here we demonstrate this concept for solids consisting of randomly stacked layers of graphene and hexagonal boron nitride (h-BN). Dispersions of exfoliated h-BN layers and graphene have been prepared by liquid phase exfoliation methods and mixed, in various concentrations, to create artificially stacked h-BN/G solids. These van der Waals stacked hybrid solid materials show interesting electrical, mechanical, and optical properties distinctly different from their starting parent layers. From extensive first principle calculations we identify (i) a novel approach to control the dipole at the h-BN/G interface by properly sandwiching or sliding layers of h-BN and graphene, and (ii) a way to inject carriers in graphene upon UV excitations of the Frenkell-like excitons of the h-BN layer(s). Our combined approach could be used to create artificial materials, made predominantly from inter planar van der Waals stacking of robust bond saturated atomic layers of different solids with vastly different properties. PMID:22731861

  11. A snapshot of the polar ionosphere. [satellite observation of F layer and topside

    NASA Technical Reports Server (NTRS)

    Whitteker, J. H.; Brace, L. H.; Maier, E. J.; Burrows, J. R.; Dodson, W. H.; Winningham, J. D.

    1976-01-01

    This paper presents a picture of the north polar F layer and topside ionosphere obtained primarily from three satellites (Alouette 2, ISIS 1, ISIS 2) that passed over the region within a time interval of about 50 min on a magnetically quiet day. The horizontal distribution of electron densities at the peak of the F layer is found to be similar to synoptic results from the IGY. Energetic-particle and ionospheric-plasma data are also presented, and the F-layer data are discussed in terms of these measurements as well as in terms of electric-field and neutral N2 density measurements made by other satellites on other occasions. The major feature observed is a tongue of F-region ionization extending from the dayside across the polar cap, which is accounted for by antisunward drift due to magnetospheric convection. In the F layer and topside ionosphere, the main effect of auroral precipitation appears to be heating and expansion of the topside. A region of low F-layer density appears on the morning side of the polar cap, which may be due to convection and possibly also to enhanced N2 densities.

  12. 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.

  13. Formation of an F3 layer in the equatorial ionosphere: A result from strong IMF changes

    NASA Astrophysics Data System (ADS)

    Paznukhov, V. V.; Reinisch, B. W.; Song, P.; Huang, X.; Bullett, T. W.; Veliz, O.

    2007-07-01

    We analyzed ionospheric observations made with digisondes in Jicamarca, Ramey, Wallops Island, Ascension Island, and Kwajalein Island during the major magnetic storm of November 9 10, 2004, which was associated with rapid interplanetary magnetic field (IMF) Bz changes. The strongest ionospheric responses to the southward IMF Bz turning were observed at the dip equator at Jicamarca where during the magnetic disturbance a dramatic F2 peak density depletion occurred at around 15:00 local time, accompanied by a fast upward motion of the plasma. In this process, an additional ionospheric layer, the F3 layer, formed with peak densities NmF3 exceeding NmF2. This observation may be considered evidence of an equatorial plasma fountain enhancement caused by the magnetic field disturbance. Responses were observed in a large range of latitudes and local times. The best indicator of the responses appears to be the peak height of the F layer, since competing processes determine the peak densities. The observed responses at low latitude locations in the morning and dusk sectors pose challenges to the simple penetrating electric field model because the upward motion is inconsistent with the E×B drift associated with a dawn dusk electric field. Clear responses in the Jicamarca local time sector occurred at latitudes as high as 28°, at Ramey, Puerto Rico. This latitude range appears to be beyond the range of the flux tube corresponding to the 900 km F3 layer peak height at Jicamarca, indicating a more extended uplifting of flux tubes.

  14. Gyroharmonic Features of Generation of Artificial Irregularities Hf-Induced in the Ionospheric F_2 Region

    NASA Astrophysics Data System (ADS)

    Frolov, Vladimir; Akchurin, Adel; Bolotin, Ilya; Zykov, Evgeniy; Vertogradov, Gennadiy

    In the report, basing on experimental data obtained at the SURA heating facility [1-4], we consider gyroharmonic features of generation of artificial irregularities HF-induced in the ionospheric F _{2} region. In [5] it was revealed that, when the pump wave frequency (f _{PW}) is slightly above the 4th electron gyro harmonic frequency (4f_{ce}) in the ionosphere disturbed volume, spectra of signals field-aligned scattered from irregularities with l_⊥ ≃ 10 - 20 m had widths up to DeltaF ≃ 10 Hz in comparison with DeltaF ≃ 0.5 Hz, when the f _{PW} was below 4f_{ce}. Obtained in our experiments data have shown that the scattering from decameter irregularities consists of two components (narrow- and wideband) distinguished by their spectral characteristics, relaxation times, and dependence on f _{PW}. The narrowband component is related to scattered signals when f _{PW} is outside the gyro harmonic frequency range. The wideband component is observed at deltaf = f_{PW} - 4f_{ce} ≃ 0 - 150 kHz and shows well-pronounced gyro features; it has the maximum width (up to 10 Hz) at deltaf_{m} ≃ 20 - 60 kHz, where the BUM component in SEE spectra has the greatest intensity. A typical growth time for the wideband component is of the same order of magnitude as the growth time of decameter irregularities (0.3 - 0.5 s); its typical decay time is of about 0.4 - 0.9 s, which is much shorter of the decay time for decameter irregularities. It is significant that at the decay stage the fast narrowing of the wideband component spectra is observed. In [4] it was observed short-term decreases in TEC of about 0.03 - 0.05 TECU when a sounding wave crossed the magnetic zenith region in the ionosphere disturbed volume. According to [6] such TEC variations can be produced by generation of super small-scale striations with l_⊥ ≃ 10 - 20 sm. Basing on obtained experimental data it may be concluded that not only the generation of small-scale irregularities with l_⊥ < 50 m, but the generation of medium- and larger-scale irregularities with scale-lengths from 100 m to a few km has also gyro properties. It means that the generation of high-frequency plasma waves exerts some influence on development of these irregularities, most likely through the generation of small-scale striations. The work was supported by RFBR grants (## 12-05-00312, 13-02-12074, 13-02-12241) and by the scientific program “Geophysics”. References: 1. V.L. Frolov, et al. // Radiophys. Quant. Electron., Engl. Transl., 2000. V. 43(6), p. 446. 2. Kagan, L.M., et al. // J. Radiophysics and Radio Astronomy, 11(3), 221-242, 2006. 3. Frolov V.L., et al. // Radiophys. Quant. Electron., Engl. Transl., 2008. Vol. 51(5), p. 367. 4. Frolov V.L., et al. // Radiophys. Quant. Electron., Engl. Transl., 2012. Vol.55(6), p. 357. 5. Ponomarenko et al. // J. Geophys. Res., 1999. Vol. 104, No. A5, p. 10,081. 6. Gurevich and Zybin. // Phys. Lett. A. 2006. Vol. 358, p.159.

  15. 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.

  16. In-situ observations of intermediate layers in the night time ionosphere

    NASA Astrophysics Data System (ADS)

    Gregory, J.; Swenson, C. M.; Humphries, S.; Fish, C.; Carlson, C.; Barjatya, A.

    2005-12-01

    Night time ionospheric electron density profiles have been obtained using impedance and Langmuir probe techniques showing the presence of intermediate layers. Four sounding rockets were launched in July of 2003 at Wallops Island, VA and two more were launched in August of 2004 from Kwajalein atoll, Marshall Islands. Although these rocket campaigns were conducted at different latitudes they both indicated a patchy spatial structure. All six flights used essentially the same plasma impedance probe but the later campaign included a sweeping Langmuir probe. More emphasis is given to the data from the later campaign, "Scattering Layer in the Bottomside Equatorial F-region Ionosphere" investigation, which was a part of the NASA EQUIS II campaign. Electron density from this data set is analyzed using Balmain's theory for a short antenna in a cold magnetoplasma and compared with data from the sweeping Langmuir probe.

  17. Excitation of artificial airglow by high power radio waves from the SURA ionospheric heating facility

    SciTech Connect

    Bernhardt, P.A.; Scales, W.A. ); Grach, S.M.; Keroshtin, A.N.; Kotik, D.S.; Polyakov, S.V. )

    1991-08-01

    The SURA facility for generation of high power radio waves, located near the village of Vasil'sursk USSR, operates between 4.5 and 9.0 MHz and has a maximum effective radiated power (ERP) of 300 MW. Nonlinear interactions between the HF radio waves and F-layer plasma occur near the electromagnetic wave reflection point. Energetic electrons are accelerated out of the interaction regions by the electrostatic waves. Ambient oxygen atoms collisionally excited by these suprathermal electrons yield enhanced airglow. Low-light-level, optical measurements were made at SURA during September 1990. Images of enhanced red-line (630 nm) emissions were recorded during radio wave transmissions at 4.786, 5.455, and 5.828 MHz. The antenna radiation pattern, ionospheric irregularities, and the magnetic field orientation affected the shape of the observed airglow structures. The airglow clouds drifted across the night sky, disappeared, and reformed at the zenith of the antenna array. This has been interpreted in terms of radio beam refraction in drifting plasma irregularities and bifurcation when the beam is split between two density cavities. Subject to clear skies, the authors experience indicates that the low-light-level-imaging technique is a reliable method to study large scale irregularities and electron acceleration with high-power HF transmitting facilities.

  18. [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

  19. Double crests of peak height in the equatorial ionospheric F2 layer observed by COSMIC

    NASA Astrophysics Data System (ADS)

    Luan, Xiaoli; Lei, Jiuhou; Dou, Xiankang; Dang, Tong

    2016-01-01

    For the first time, we report daytime double crests of peak height (hmF2) in the F2 layer based on the Constellation Observing System for Meteorology Ionosphere and Climate (COSMIC) observations during 2007-2014. Evident double crests of hmF2 occurred at around ±10° geomagnetic latitude with a trough over the magnetic equator at low solar activity and at March equinox. This phenomenon is referred to as an equatorial height anomaly (EHA) of the ionospheric F2 layer. The double crests became less obvious at September equinox and disappeared at solstices. At solstices only one crest was observed in the summer hemisphere, which is probably associated with transequatorial neutral winds. In addition, the double EHA crests generally take place during 10:00-14:00 local times. Our results indicate that the EHA favors the conditions of strong vertical plasma drifts and weak transequatorial neutral winds during low solar activity. The EHA feature is reproduced by the Thermosphere Ionosphere Electrodynamics Global Circulation Model at March equinox and low solar activity.

  20. 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.

  1. Layered Structures and Internal Waves in the Ionosphere and Atmosphere as Seen from GPS Occultation Data

    NASA Astrophysics Data System (ADS)

    Pavelyev, Alexander; Pavelyev, Alexander; Gubenko, Vladimir; Wickert, Jens; Liou, Yuei An

    High-precision signals emitted by GPS satellites create favourable conditions both for monitoring of the atmosphere and ionosphere and for investigation of the radio wave propagation effects. Comparative theoretical and experimental analysis of the phase and amplitude variations of the GPS radio-holograms discovered a relationship which relates the refraction attenuation, the phase path excess acceleration and Doppler frequency via a classical dynamics equationtype. The advantages of the introduced relationship consist in: (1) a possibility to separate the layered structure and turbulence contributions to RO signal; (2) a possibility to estimate the absorption in the atmosphere by dividing the refraction attenuations found from amplitude and phase data; (3) a possibility to locate the tangent point in the atmosphere with accuracy in the distance from the standard position of of about 100 km. The suggested method has a general importance because it may be applied for analysis in the trans-ionospheric satellite-to-Earth links. We showed also that the amplitude variations of GPS occultation signals are very sensitive sensors to the internal waves in the atmosphere. The sensitivity of the amplitude method is inversely proportional to the square of the vertical period of the internal wave, indicating high sensitivity of the amplitude data to the wave structures with small vertical periods in the 0.8-4 km interval. Combined analysis of the amplitude and phase of radio occultation signal allows one to determine with high level of reliability the main characteristics of the atmospheric and ionospheric layeres including the vertical distribution of the refractivity, electron density and their gradients. A possibility exists to measure important parameters of the internal waves: the intrinsic phase speed, the horizontal wind perturbations and, under some assumptions, the intrinsic frequency as functions of height in the atmosphere. A new technique has been applied to measurements provided during CHAllenging Minisatellite Payload (CHAMP) and the Formosa Satellite-3 and Constellation Observing System for Meteorology, Ionosphere, and Climate (FORMOSAT-3/COSMIC) radio occultation (RO) missions.

  2. 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.

  3. 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.

  4. 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.

  5. (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.

  6. Kinetic Simulation of Local Transition Layers Associated With the Magnetosphere-Ionosphere Interface

    NASA Astrophysics Data System (ADS)

    Newman, D. L.; Goldman, M. V.; Ergun, R. E.; Andersson, L.

    2002-12-01

    Recent FAST observations1 have revealed strong localized unipolar parallel electric fields (i.e., potential ramps) together with the electric-field signature of upward moving electron holes in the auroral downward current region. These potential jumps separate a colder, denser plasma on the ionospheric side from a hotter, rarer plasma on the magnetospheric side. Thus, the magnetosphere-ionosphere interface may be composed, in part, of a sequence of such transition layers. We have shown via 1-D current-driven Vlasov simulations2 that the observed potential ramps are consistent with transition layers in the form of laminar double layers. The electron-hole turbulence and electron heating on the magnetospheric side are the result of saturation of a two-stream instability driven by electrons accelerated through the potential jump. These simulations, together with more recent 2-D Vlasov simulations with strongly magnetized electrons and ions, suggest that the transition layer can be turbulent as well as laminar and still support significant changes in potential, temperature, and density across the layer. We will present results from the most recent 2-D simulations contrasting the laminar and turbulent regimes. We will also discuss mechanisms, such as the inclusion of realistic ion magnetization and variation in the angle between B and the normal to the layer, that can influence the stability of laminar double layers. Research supported by NSF, NASA, and DOE. 1 R. E. Ergun, et al., Phys. Rev. Lett., 87, 045003 (2001); L. Andersson et al., Phys. Plasmas, 9, 3600 (2002). 2 D. L. Newman, M. V. Goldman, R. E. Ergun, and A. Mangeney, Phys. Rev. Lett., 87, 255001 (2001).

  7. Effectiveness Criteria for Methods of Identifying Ionospheric Earthquake Precursors by Parameters of a Sporadic E Layer and Regular F2 Layer

    NASA Astrophysics Data System (ADS)

    Korsunova, Lidiya P.; Hegai, Valery V.

    2015-06-01

    The results of the study of ionospheric variations in the summer months of 1998-2002 at an ionospheric station of vertical sounding "Petropavlovsk-Kamchatsky" are presented. Anomalous variations of virtual sporadic-E height (h'Es), Es blanketing frequency (fbEs), and the critical frequency of the ionospheric F2 layer (foF2) (which can be attributed to the possible earthquake precursors) are selected. The high efficiency of the selection of ionospheric earthquake precursors based on the several parameters of Es and F2 layers is shown. The empirical dependence, which reflects the connection between the lead-time of the earthquake moment, the distance to the epicenter from the observation point, and the magnitude of the earthquake are obtained. This empirical dependence is consistent with the results of the detection of earthquake precursors by measuring the physical parameters of the Earth's crust in the same region.

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

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

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

  9. 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-Alfvn, coupled Rossby-Khantadze and coupled Rossby-Alfvn-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.

  10. Ionospheric F2 layer responses to total solar eclipses at low and mid-latitude

    NASA Astrophysics Data System (ADS)

    Adekoya, B. J.; Chukwuma, V. U.

    2016-02-01

    In this article, we presented ionospheric F2 responses to total solar eclipses on the basis of the data obtained from five (5) equatorial/low-latitude and twenty-seven (27) mid-latitude ionosonde stations, which are within the obscuration percentage of 50-100% of the path of the total solar eclipses progression. Statistically, the diurnal changes in the F2 layer peak height hmF2 and electron density NmF2, as well as the latitudinal and hemispheric dependence and the contribution of both magnetic and solar activities during the eclipse window were investigated. The estimation of the solar ionizing radiation that remains unmasked during the eclipse window was as well carried out. Plasma diffusion processes dominate the F2 region plasma, and determine the height at which the F2 peak formed at mid-latitude. The electron density decreased during the eclipse window, closely following the variation in the local solar radiation at the mid-latitude. However, at equatorial/low-latitude, the plasma distribution during total solar eclipse depends on combine effect of solar radiation and the background nighttime ionospheric irregularities mechanism. The uncertainty level of the estimated solar ionizing radiation was <±0.3 at mid-latitude and greater±0.3 at equatorial/low-latitude. Their correlation ranges from (0.42-0.99). The ionospheric F2 layer eclipse effect is latitudinal and hemispheric dependent. The effect is largest at mid-latitude and relatively small at equatorial/low-latitudes. It is more pronounced at the equator, and decreases toward the equatorial ionospheric anomaly (EIA) region. The better correlation of 0.5840 and 0.6435 between geographic latitude and E(t) and electron density justifies the latitudinal relationship. The increase in percentage deviation of electron density increases with latitude and delay time (∆T) in the northern hemisphere of the mid-latitude. Conversely, in the southern hemisphere the percentage deviation decreases with an increase in ∆T and the latitude. The influence of the combined effect of solar activity and magnetic disturbances cannot the overlooked during total solar eclipse. At the eclipse shadow, the deviation increases with decreasing magnetic disturbances and solar activity. During magnetic quiet conditions the variation in maximum NmF2/hmF2 on the eclipse day are more decrease/increase than the control day and overturned during the magnetic disturbed condition.

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

    NASA Astrophysics Data System (ADS)

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

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

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

    NASA Technical Reports Server (NTRS)

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

    1992-01-01

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

  13. 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.

  14. The mechanism of whistlers absorption in the F-layer of the earth`s ionosphere

    SciTech Connect

    Bilikmen, S.; Oke, G.; Jilmaz, A.

    1995-12-31

    The Earth`s ionospheric F-layer represents an inhomogeneous flat plasma layer with the characteristic size of inhomogeneity {approx_equal} 10km, whereas the size of the layer in which {omega}{sub Le}{sup 2} > {Omega}{sub e}{sup 2} is of the order of a {approx_equal}100-150km. In this region B{sub o} {approx_equal} 0,5Gauss, 3 * 10{sup 6}cm{sup -3} {ge} n{sub e} {ge} 3 * 10{sup 5} cm{sup -3} and therefore the whistlers with frequency range {Omega}{sub e} > {omega} {approx_equal} 10{sup 7} - 10{sup 5}s{sup -1} > {omega}{sub Li}, {Omega}{sub i} can propagate. For the long wavelength whistlers with {Lambda} > 10km the F-layer may be considered as a plasma layer with sharp density profile, whereas in the short wavelength limit when {Lambda} < 10km for their description the geometrical optics approximation is valid. The Earth`s magnetic field {rvec B}{sub o} is supposed to be directed along the oz axis and the direction parallel to the Earth`s surface is along the oy axis.

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

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

    E-layer dominated ionosphere (ELDI) is referred to vertical profiles having peak density at E-layer altitudes (Mayer and Jakowski, 2009). In this paper, characteristics of ELDI were investigated with the help of field-aligned measurements of EISCAT/ESR radars during 2009-2011. ELDI events were identified with simple but reasonable criterions, in which a minimal duration was required to exclude possible 'fake' events induced by random errors in measurements. It was found that ELDI were observed more often in winter than other seasons. In winter, occurrence of ELDI peaks around mid-night at auroral latitude, while it reaches its maximum around geomagnetic local noon at ESR latitude. Our results imply that ELDI looks like a sporadic rather than a regular phenomenon, being contrary to previous results inferred from radio occultation measurements. Discrepancy in duration of ELDI events observed by the two radars is remarkable, being 30 minutes at Troms on average and about a half of it at Svalbard. During the presence of ELDI, average thickness of E-layer exhibits undetectable variations at the two sites, as well as HmE and the ratio of NmE/NmF. Case studies reveal that either extra E-layer ionization possible induced by auroral precipitation or density depletion in F-layer caused by plasma convection alone could lead to the presence of ELDI. We suggest that both them play an important role in ELDI formation.

  16. Auroral ionospheric signatures of the plasma sheet boundary layer in the evening sector

    NASA Technical Reports Server (NTRS)

    Burke, W. J.; Machuzak, J. S.; Maynard, N. C.; Basinska, E. M.; Erickson, G. M.; Hoffman, R. A.; Slavin, J. A.; Hanson, W. B.

    1994-01-01

    We report on particles and fields observed during Defense Meteorological Satellite Program (DMSP) F9 and DE 2 crossings of the polar cap/auroral oval boundary in the evening magnetic local time (MLT) sector. Season-dependent, latitudinally narrow regions of rapid, eastward plasma flows were encountered by DMSP near the poleward boundary of auroral electron precipitation. Ten DE 2 orbits exhibiting electric field spikes that drive these plasma flows were chosen for detailed analysis. The boundary region is characterized by pairs of oppositely-directed, field-aligned current sheets. The more poleward of the two current sheets is directed into the ionosphere. Within this downward current sheet, precipitating electrons either had average energies of a few hundred eV or were below polar rain flux levels. Near the transition to upward currents, DE 2 generally detected intense fluxes of accelerated electrons and weak fluxes of ions, both with average energies between 5 and 12 keV. In two instances, precipitating ions with energies greater than 5 keV spanned both current sheets. Comparisons with satellite measurements at higher altitudes suggest that the particles and fields originated in the magnetotail inside the distant reconnection region and propagated to Earth through the plasma sheet boundary layer. Auroral electrons are accelerated by parallel electric fields produced by the different pitch angle distributions of protons and electrons in this layer interacting with the near-Earth magnetic mirror. Electric field spikes driving rapid plasma flows along the poleward boundaries of intense, keV electron precipitation represent ionospheric responses to the field-aligned currents and conductivity gradients. The generation of field-aligned currents in the boundary layer may be understood qualitatively as resulting from the different rates of earthward drift for electrons and protons in the magnetotail's current sheet.

  17. Modelling of the equatorial ionospheric E-layer based on cos ? index

    NASA Astrophysics Data System (ADS)

    Kazeem, A. K.; Adeniyi, J. O.; Adediji, A. T.

    2014-06-01

    Daytime hourly values of the critical frequency of the ionospheric E-layer, f oE, obtained at Ouagadougou Ionospheric Observatory (12.4N, 1.5W) in Burkina Faso, West Africa, an equatorial station, during the solar cycle 22 (1985-1995) have been used to develop a model based on solar zenith angle through cos ? index factor using the relation f oE = a (cos ?)n, The average value of the diurnal cos ? index, n, at Ouagadougou was found to be 0.30 for both low and high solar activity. The model was tested with f oE data from Korhogo (9.3N, 5.4W) in Cote-d'Ivoire, another equatorial station, and there is good agreement between the model and observations. The validity of the f oE model was also compared with predicted values by IRI-2012 model and good agreement has been observed. The percentage difference, when f oE observed compared with IRI-2012 model, was found to be within f 10% for both equinoxes and solstices for the two levels of solar activity.

  18. 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.

  19. 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.

  20. Sounding of HF heating-induced artificial ionospheric disturbances by navigational satellite radio transmissions

    NASA Astrophysics Data System (ADS)

    Kunitsyn, V. E.; Andreeva, E. S.; Frolov, V. L.; Komrakov, G. P.; Nazarenko, M. O.; Padokhin, A. M.

    2012-01-01

    During experiments carried out in 2009-2011 the midlatitude ionosphere was modified by powerful HF pulses from the Sura heating facility located near Nizhny Novgorod (Russia) and operated by the Radio Physical Research Institute. GPS/GLONASS and Parus/Tsikada satellite radio transmissions responding to the heating-induced disturbances in electron density were analyzed. The variations in the total electron content (TEC), which are proportional to the reduced phase of navigational signals, were studied for various schemes of radiation of the heating wave. The variations in TEC (their amplitudes and temporal behavior) caused by HF heating are identified in several examples. The TEC spectra contain frequency components corresponding to the modulation periods of the heating wave. For the first time, the spatial structure of the wave disturbances generated in the ionosphere by high-power radio waves radiated by the Sura heating facility with a square wave modulation of the effective radiated power at a frequency lower than or of the order of the Brunt-Vaisala frequency of the neutral atmosphere is imaged using the method of low-orbital radio tomography and GPS/GLONASS data.

  1. 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.

  2. Evidence for lightning-associated enhancement of the ionospheric sporadic E layer dependent on lightning stroke energy

    NASA Astrophysics Data System (ADS)

    Yu, Bingkun; Xue, Xianghui; Lu, Gaopeng; Ma, Ming; Dou, Xiankang; Qie, Xiushu; Ning, Baiqi; Hu, Lianhuan; Wu, Jianfei; Chi, Yutian

    2015-10-01

    In this study we analyze the lightning data obtained by the World-Wide Lightning Location Network (WWLLN) and hourly ionospheric data observed by ionosondes located at Sanya and Beijing, to examine the changes in ionospheric electron density in response to the underlying thunderstorms and to investigate the possible connection between lightning discharges and the enhancement of the ionospheric sporadic E(Es) layer. We identify a statistically significant enhancement and a decrease in altitude of the Es layer at Sanya station, in agreement with the results found at Chilton, UK. However, the lightning-associated modification of the Es layer investigated using the same approach is not evident at Beijing station. Furthermore, we compare the responses to weak and strong lightning strokes using WWLLN-determined energies at Sanya in 2012. The lightning-associated enhancement of the Es layer is predominantly attributed to powerful strokes with high stroke energy. A statistically significant intensification of the Es layer with higher-energy strokes at Sanya, along with the statistical dependence of lightning-associated enhancement of the Es layer on stroke energy, leads us to conclude that the magnitude of the enhancement is likely associated with lightning stroke energy.

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

    SciTech Connect

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

    1992-10-22

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

  4. Excitation of artificial airglow by high power radio waves from the 'SURA' ionospheric heating facility

    NASA Astrophysics Data System (ADS)

    Bernhardt, P. A.; Scales, Wayne A.; Grach, S. M.; Keroshtin, A. N.; Kotik, D. S.

    1991-08-01

    The present study considers low-light-level optical measurements made in September 1990 at a Soviet facility for generation of high power radio waves. Images of enhanced red-line (630-nm) emissions were recorded during radio wave transmissions. The antenna radiation pattern, ionospheric irregularities, and the magnetic field orientation affected the shape of the observed airglow structures. The airglow clouds drifted across the night sky, disappeared, and reformed at the zenith of the antenna array. This was interpreted in terms of radio beam refraction in drifting plasma irregularities and bifurcation when the beam is split between two density cavities. It is concluded that given clear skies, the low-light-level imaging technique is a reliable method for studying large-scale irregularities and electron acceleration with high-power HF transmitting facilities.

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

    NASA Astrophysics Data System (ADS)

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

    2014-10-01

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

  6. 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 sites 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).

  7. Results of Experimental and Theoretical Studies of the Atmospheric Turbulence, Internal Gravity Waves and Sporadic-E Layers by Resonant Scattering of Radio Waves on Artificial Periodic Irregularities

    NASA Astrophysics Data System (ADS)

    Bakhmetieva, Nataliya V.; Grigoriev; Tolmacheva, Ariadna V.

    Artificial periodic irregularities (API) formed by the powerful standing radio waves in the ionospheric plasma give the good chance for the lower ionosphere comprehensive studies. In this paper we present some applications of the API technique for experimental studies of sporadic E-layers (E _{s}), internal gravity waves and turbulent events in the lower ionosphere. API are formed in the field of the standing radio wave produced by interference of the incident wave and reflected one from the ionosphere (in more details about the API technique one can see in the book Belikovich et al., Ionospheric Research by Means of Artificial Periodic Irregularities - Katlenburg-Lindau, Germany. 2002. Copernicus GmbH. ISBN 3-936586-03-9). The spatial period of the irregular structure is equal to the standing wavelength Lambda or one-half the powerful wavelength lambda/2. API diagnostics are carried out at the API relaxation or decay stage by their sounding of probing radio pulses. Based on the measurement of an amplitude and a phase of the API scattered signal their relaxation time and regular vertical plasma velocity are measured. In the E-region of the ionosphere API are formed as a result of the diffusion redistribution of the non-uniformly heated plasma. The relaxation of the periodic structure is specified by the ambipolar diffusion process. The diffusion time is tau=(K (2) D _{a}) (-1) where K=2pi/Lambda and D _{a} is the ambipolar diffusion rate. The atmospheric turbulence causes reduction of the API relaxation time in comparison the diffusion time. Determination of the turbulent velocity is based on this fact. The vertical plasma velocity is determined by measuring the phase of the scattered signal. Atmospheric waves having the periods from 5-10 minutes to 5-6 hours give the contribution to temporal variations of the velocity. Parameters and effects of atmospheric waves and the turbulence on the API relaxation process are presented. Determination of the masses of the predominant metallic ions at the E _{s}-layer height is one of the API applications (Bakhmetieva N.V. and Belikovich V.V. Radiophys. Quantum Electron., 2008, Vol. 51, No 11, pp. 956-969). It is based on the observed fact of the local maximum of the API relaxation time at the sporadic E-layer location. The long-lived metallic ions cause the growth of the API relaxation time tau? at the E _{s}-layer height. It is shown by API technique the sporadic E-layers contain Mg (+) , Ca (+) and Fe (+) ions predominantly at heights of 95-110 km. The new applications are based on the so-called two-frequency method of the API creation and their diagnostics. The method allows one to define the neutral atmosphere and the ionosphere parameters with high accuracy. The main results of the lower ionosphere studies carried out in 2006-2012 by the API technique using the SURA heating facility (56,1 N; 46,15 E) are presented and discussed. We aslo discuss the studies of the HF pumping effects on the formation and parameters of the sporadic E-layers and the modification of the semitransparent E _{s}-layer by the powerful radio wave and diagnostics by the API technique. The work was supported by Russian Foundation for Basic Research under project No 13-02-97067, 13-02-12074 and 13-05-00511.

  8. Relationship of dayside main layer ionosphere height to local solar time on Mars and implications for solar wind interaction influence

    NASA Astrophysics Data System (ADS)

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

    2015-08-01

    To understand the influence of solar wind on the daytime main layer ionosphere of Mars, we investigated the local solar time (LST) variations of three characteristic heights of the ionosphere, namely, the heights of the 1 MHz and 1.5 MHz reflection points (i.e., 1.24 1010 m-3 and 2.79 1010 m-3 isodensity contours, respectively) and the density peak. We used a total of 19,996 Mars Advanced Radar for Subsurface and Ionosphere Sounding observations distributed on the northern hemisphere, with solar zenith angle ?80, acquired from June 2005 to October 2013. We exploited the kernel partial least squares regression method to extract the nonlinear relationships of the heights to LST and a few other variables. The average height of the 1 MHz reflection point decreased from ~218 km at 10:00 A.M. to ~206 km at 16:00 P.M. local time; the height of the 1.5 MHz reflection point decreased simultaneously from ~190 km to ~181 km. These decreasing trends are in contrast to the LST variation of the density peak height, which increased from ~128 km to ~137 km over the same LST interval. Based on these findings and previous results, we suggest that the solar wind may penetrate the Martian ionosphere down to altitudes of about 50 km above the main density peak and may, in conjunction with the asymmetric draping of the interplanetary magnetic field, compress the upper part of the main ionosphere layer on the P.M. side ~10 km more than on the A.M. side.

  9. A new model for formation of artificial ducts due to ionospheric HF-heating

    NASA Astrophysics Data System (ADS)

    Milikh, G. M.; Demekhov, A.; Vartanyan, A.; Mishin, E. V.; Huba, J.

    2012-05-01

    We present the results of numerical simulations of artificial ducts during high-power HF heating performed by a novel model accounting for the effect of self-action. This effect interferes with the HF-plasma matching in the heated region and hence with electron heating. The model satisfactorily explains recent experimental observations. It helps for choosing the heating parameters optimal for duct formation, such as proper duration of the heating pulse and its frequency. It also suggests that distortion of the ducts caused by the self-action effect can be avoided by down-chirping the heating frequency. The down-chirping rates needed to suppress such distortions are evaluated.

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

    SciTech Connect

    Futatani, S.; Horton, W.; Kaladze, T. D.; Physics Department, Government College University, Lahore 54000

    2013-10-15

    Nonlinear vortex propagation of electromagnetic coupled Rossby and Khantadze planetary waves in the weakly ionized ionospheric E-layer is investigated with numerical simulations. Large scale, finite amplitude vortex structures are launched as initial conditions at low, mid, and high latitudes. For each k-vector the linear dispersion relation has two eigenmodes corresponding to the slow magnetized Rossby wave and the fast magnetic Khantadze wave. Both waves propagate westward with local speeds of the order of 1020 m/s for the slow wave and of the order of 5001000 km/s for the fast wave. We show that for finite amplitudes there are dipole solitary structures emitted from the initial conditions. These structures are neutrally stable, nonlinear states that avoid radiating waves by propagating faster than the corresponding linear wave speeds. The condition for these coherent structures to occur is that their amplitudes are such that the nonlinear convection around the core of the disturbance is faster than the linear wave speed for the corresponding dominant Fourier components of the initial disturbance. The presence of the solitary vortex states is indicative of an initial strong disturbance such as that from a solar storm or a tectonic plate movement. We show that for generic, large amplitude initial disturbances both slow and fast vortex structures propagate out of the initial structure.

  11. Seasonal variation of the ionospheric F2-layer intensity at midlatitudes during the solar cycle 23

    NASA Astrophysics Data System (ADS)

    Lee, W.; Kil, H.; Wu, Q.; Chung, J.; Cho, S.; Park, J.

    2009-12-01

    We investigate the seasonal variation of the ionospheric F2-layer intensity at midlatitudes during the solar cycle 23. The occurrence of larger daytime electron density in winter than in summer is called as seasonal anomaly or winter anomaly. The seasonal anomaly occurs mainly at midlatitudes and is more pronounced in the northern hemisphere than in the southern hemisphere. We investigate the variation of the seasonal anomaly with solar cycle and local time by analyzing the radio occultation measurements from FORMOSAT-3/COSMIC satellites during the solar minimum period (2007-2008) and from the CHAMP satellite during the solar maximum period (2001-2002). The vertical electron density profiles obtained from COSMIC and CHAMP will be compared with those observed by the Incoherent Scatter Radar at Millstone Hill. The hemispheric difference in the seasonal anomaly will also be investigated by using the ionosonde measurements of the F-peak electron density at Osan in Korea and Darwin in Australia. We discuss the combined effects of the neutral composition and the global annual asymmetry on the creation of the seasonal anomaly.

  12. Annual and semiannual variations in the ionospheric F2-layer: II. Physical discussion

    NASA Astrophysics Data System (ADS)

    Rishbeth, H.; Mller-Wodarg, I. C. F.; Zou, L.; Fuller-Rowell, T. J.; Millward, G. H.; Moffett, R. J.; Idenden, D. W.; Aylward, A. D.

    2000-08-01

    The companion paper by Zou et al. shows that the annual and semiannual variations in the peak F2-layer electron density (NmF2) at midlatitudes can be reproduced by a coupled thermosphere-ionosphere computational model (CTIP), without recourse to external influences such as the solar wind, or waves and tides originating in the lower atmosphere. The present work discusses the physics in greater detail. It shows that noon NmF2 is closely related to the ambient atomic/molecular concentration ratio, and suggests that the variations of NmF2 with geographic and magnetic longitude are largely due to the geometry of the auroral ovals. It also concludes that electric fields play no important part in the dynamics of the midlatitude thermosphere. Our modelling leads to the following picture of the global three-dimensional thermospheric circulation which, as envisaged by Duncan, is the key to explaining the F2-layer variations. At solstice, the almost continuous solar input at high summer latitudes drives a prevailing summer-to-winter wind, with upwelling at low latitudes and throughout most of the summer hemisphere, and a zone of downwelling in the winter hemisphere, just equatorward of the auroral oval. These motions affect thermospheric composition more than do the alternating day/night (up-and-down) motions at equinox. As a result, the thermosphere as a whole is more molecular at solstice than at equinox. Taken in conjunction with the well-known relation of F2-layer electron density to the atomic/molecular ratio in the neutral air, this explains the F2-layer semiannual effect in NmF2 that prevails at low and middle latitudes. At higher midlatitudes, the seasonal behaviour depends on the geographic latitude of the winter downwelling zone, though the effect of the composition changes is modified by the large solar zenith angle at midwinter. The zenith angle effect is especially important in longitudes far from the magnetic poles. Here, the downwelling occurs at high geographic latitudes, where the zenith angle effect becomes overwhelming and causes a midwinter depression of electron density, despite the enhanced atomic/molecular ratio. This leads to a semiannual variation of NmF2. A different situation exists in winter at longitudes near the magnetic poles, where the downwelling occurs at relatively low geographic latitudes so that solar radiation is strong enough to produce large values of NmF2. This circulation-driven mechanism provides a reasonably complete explanation of the observed pattern of F2 layer annual and semiannual quiet-day variations.

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

    NASA Astrophysics Data System (ADS)

    Oyekola, Oyedemi S.

    2012-07-01

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

  14. 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.

  15. Selective reduction of layers at low temperature in artificial superlattice thin films

    PubMed Central

    Matsumoto, Kazuya; Haruta, Mitsutaka; Kawai, Masanori; Sakaiguchi, Aya; Ichikawa, Noriya; Kurata, Hiroki; Shimakawa, Yuichi

    2011-01-01

    Reduction and oxidation in transition-metal oxides are keys to develop technologies related to energy and the environment. Here we report the selective topochemical reduction observed when artificial superlattices with transition-metal oxides are treated at a temperature below 300 C with CaH2. [CaFeO2]m/[SrTiO3]n infinite-layer/perovskite artificial superlattice thin films were obtained by low-temperature reduction of [CaFeO2.5]m/[SrTiO3]n brownmillerite/perovskite artificial superlattice thin films. By the reduction only the CaFeO2.5 layers in the artificial superlattices were reduced to the CaFeO2 infinite layers whereas the SrTiO3 layers were unchanged. The observed low-temperature reduction behaviors strongly suggest that the oxygen ion diffusion in the artificial superlattices is confined within the two-dimensional brownmillerite layers. The reduced artificial superlattice could be reoxidized, and thus, the selective reduction and oxidation of the constituent layers in the perovskite-structure framework occur reversibly. PMID:22355546

  16. Selective reduction of layers at low temperature in artificial superlattice thin films.

    PubMed

    Matsumoto, Kazuya; Haruta, Mitsutaka; Kawai, Masanori; Sakaiguchi, Aya; Ichikawa, Noriya; Kurata, Hiroki; Shimakawa, Yuichi

    2011-01-01

    Reduction and oxidation in transition-metal oxides are keys to develop technologies related to energy and the environment. Here we report the selective topochemical reduction observed when artificial superlattices with transition-metal oxides are treated at a temperature below 300 °C with CaH(2). [CaFeO(2)](m)/[SrTiO(3)](n) infinite-layer/perovskite artificial superlattice thin films were obtained by low-temperature reduction of [CaFeO(2.5)](m)/[SrTiO(3)](n) brownmillerite/perovskite artificial superlattice thin films. By the reduction only the CaFeO(2.5) layers in the artificial superlattices were reduced to the CaFeO(2) infinite layers whereas the SrTiO(3) layers were unchanged. The observed low-temperature reduction behaviors strongly suggest that the oxygen ion diffusion in the artificial superlattices is confined within the two-dimensional brownmillerite layers. The reduced artificial superlattice could be reoxidized, and thus, the selective reduction and oxidation of the constituent layers in the perovskite-structure framework occur reversibly. PMID:22355546

  17. 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.

  18. 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.

  19. Anomalous Enhancement of Ionospheric F2 layer critical frequency and Total Electron Content over Low Latitudes before three recent major Earthquakes of China

    NASA Astrophysics Data System (ADS)

    Sharma, Kavita

    This paper reports unusual variations in the ionospheric Total electron Content (TEC) and the critical frequency of the F2 layer (foF2) few days before the main shock of three major earthquakes (magnitude greater than 6 on Rector Scale). Epicenters of these earthquakes are distributed in China. Ionospheric data, recorded by a network of ionosonde and GPS receivers at Delhi (28.6N, 77.2E) Bhopal (23.29N, 77.46E) and Trivandrum (8.4N, 76.6E) are analyzed for finding the seismo-ionospheric signatures of these major earthquakes recently occurred in China. The results clearly indicate large enhancements in foF2 and TEC on geomagnetic quiet days, observed mainly at a low latitude station Delhi, which is nearest to the earthquake epi-centers. This anomalous behavior of foF2 and TEC appeared 1 to 4 days before the main shock and especially during 1100 -1700 LT. However the ionospheric foF2 and TEC variability at equatorial station, Trivandrum and equatorial anomaly station, Bhopal did not show any significant changes, thereby indicating the localized nature of such unusual ionospheric vari-ations. The observed results suggest that the unusual enhancements of ionospheric foF2 and TEC over Delhi few days before the main shock of each earthquake are most possibly due to seismo-ionospheric link.

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

    SciTech Connect

    Sato, N. )

    1990-06-15

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

  1. 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.

  2. Low-frequency waves and ion heating associated with double layers in the downward current region of the auroral ionosphere

    NASA Astrophysics Data System (ADS)

    Sen, Naresh

    2009-06-01

    Recent observations by satellites in the auroral ionosphere have established the presence of strong narrowly localized electric fields parallel to the ambient magnetic field. Physically these fields are formed by two layers of opposite charges in close proximity existing self-consistently in the plasma; this is known as a double layer (DL). The DL field accelerates plasma particles to form beams which excite wave modes and saturate to form electron phase-space holes (EHs). Intense perpendicular heating of ions is concurrently observed, leading to speculations regarding the heating mechanism(s). In this thesis, we address this issue via numerical simulations and analysis. We have performed electrostatic kinetic simulations using the Vlasov-Poisson system of equations for conditions prevalent in the downward current region (DCR) of the auroral ionosphere. The simulations display low-frequency waves, EHs and ion heating, consistent with observations. We determine the relative importance of two proposed mechanisms for ion heating: stochastic heating due to EHs and due to wave-particle interactions at identifiable wave modes. Stochastic heating of ions via EH-ion scattering is estimated to account for approximately 10-15% of the observed increase in ion temperature in regions of intense wave activity. Spectral analysis shows that the energy exchange between waves and ions is concentrated at frequencies and wave numbers associated with nearly perpendicular magnetized ion wave modes and not EHs. We conclude that, in the vicinity of DLs in the DCR of the auroral ionosphere where both intense waves and EHs are present, wave-particle interactions are the principal mechanism of ion heating, with stochastic heating by electron phase-space holes playing a minor role.

  3. Perspective ground-based method for diagnostics of the lower ionosphere and the neutral atmosphere

    NASA Astrophysics Data System (ADS)

    Bakhmetieva, N. V.; Grigoriev, G. I.; Tolmacheva, A. V.

    We present a new perspective ground-based method for diagnostics of the ionosphere and atmosphere parameters. The method uses one of the numerous physical phenomena observed in the ionosphere illuminated by high-power radio waves. It is a generation of the artificial periodic irregularities (APIs) in the ionospheric plasma. The APIs were found while studying the effects of ionospheric high-power HF modification. It was established that the APIs are formed by a standing wave that occurs due to interference between the upwardly radiated radio wave and its reflection off the ionosphere. The API studies are based upon observation of the Bragg backscatter of the pulsed probe radio wave from the artificial periodic structure. Bragg backscatter occurs if the spatial period of the irregularities is equal to half a wavelength of the probe signal. The API techniques makes it possible to obtain the following information: the profiles of electron density from the lower D-region up to the maximum of the F-layer; the irregular structure of the ionosphere including split of the regular E-layer, the sporadic layers; the vertical velocities in the D- and E-regions of the ionosphere; the turbulent velocities, turbulent diffusion coefficients and the turbopause altitude; the neutral temperatures and densities at the E-region altitudes; the parameters of the internal gravity waves and their spectral characteristics; the relative concentration of negative oxygen ions in the D-region. Some new results obtained by the API technique are discussed .

  4. Regional spherical modeling of 2-D functions: The case of the critical frequency of the F2 ionospheric layer

    NASA Astrophysics Data System (ADS)

    De Santis, A.; De Franceschi, G.; Kerridge, D. J.

    1994-06-01

    In this paper it is shown that Adjusted Spherical Harmonic Analysis (ASHA), previously used for modeling the three-dimensional (3-D) geomagnetic field in a restricted area can be adapted to model general bidimensional (2-D) spherical functions, f(γ, θ). As an example of application the case of the critical frequency of the F2 ionospheric layer, f0F2 is described. By assuming that, at a fixed epoch, the monthly median value of f0F2 is a function only of the geographic longitude γ and colatitude θ, that is f0F2 = f( γ, θ), ASHA has been applied to modeling and mapping this ionospheric parameter over Europe. Here, the FORTRAN-77 computer programs and subprograms are presented enabling the practical and easy use of the ASHA technique to obtain, as a final output, either a grid (2 × 2 degrees) of the computed monthly medians of f0F2 in the European area and the calculated value of the parameter at one point, in the region of interest, as a function of time. The same codes can be adapted easily to be used for modeling any bidimensional function defined over a spherical portion of the Earth.

  5. Artificial small-scale field-aligned irregularities in the high latitude F region of the ionosphere induced by an X-mode HF heater wave

    NASA Astrophysics Data System (ADS)

    Blagoveshchenskaya, N. F.; Borisova, T. D.; Yeoman, T. K.; Rietveld, M. T.; Ivanova, I. M.; Baddeley, L. J.

    2011-04-01

    The effects on the high-latitude F region of the ionosphere by X-mode powerful HF radio waves injected towards the magnetic zenith (MZ) are analysed. The experiments were conducted using the EISCAT/Heating facility and UHF radar at Troms, Norway, the CUTLASS (SuperDARN) radar and the EISCAT ionosonde (dynasonde). The results show that the X-mode HF pump wave, radiated into the magnetic zenith from the HF heater, can generate very strong small-scale artificial field aligned irregularities (AFAIs) in the F-region of the high-latitude ionosphere. These irregularities, with spatial scales across the geomagnetic field of the order of 8-15 m, are generated when the heater frequency is above the ordinary-mode critical frequency but comparable with the extraordinary-mode critical frequency. The generation of the X-mode AFAIs was accompanied by electron temperature (Te) enhancements up to 50% above the background level and an increase in the electron density (Ne) by up to 30%.

  6. Drift Velocity of Small-Scale Artificial Ionospheric Irregularities According to a Multifrequency HF Doppler Radar. II. Observation and Modeling Results

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

    We present the results of observations of the Doppler frequency shift for the radar radio signals of broadcast and exact-time RWM stations, which are scattered by small-scale artificial ionospheric irregularities. By the method described in our previous paper [1] and using the multifrequency HF Doppler radar, estimates were made for a three-dimensional vector of the drift velocity of irregularities. It is shown that the drift velocity of irregularities can vary considerably both in magnitude and direction for short periods of time. The velocity lies in a wide range of values, 20-270 m/s, but sometimes it exceeds 500-700 m/s. The most probable drift velocity ranges from 40 to 70 m/s.

  7. Remote sensing of natural and artificial variations in the Earth-ionosphere cavity via very low frequency

    NASA Astrophysics Data System (ADS)

    Eichelberger, H. U.; Leitgeb, E.; Prattes, G.; Schwingenschuh, K.; Biagi, P. F.; Maggipinto, T.; Rozhnoi, A.; Solovieva, M.; Besser, B. P.; Stachel, M.; Jernej, I.; Aydogar, O.

    2012-01-01

    In this article we present results from very low frequency (VLF) observations of transient and intermittent phenomena in the Earth-ionosphere waveguide. The scientific objectives are remote localisation and characterisation of short time disturbances. The VLF amplitude and phase variations aid to physically investigate the atmospheric media from the Earth's surface up to the lower ionosphere (~ 70-90 km, D- and E-region) which is part of propagation channels for satellite communications and navigational applications. We consider two common types of anomalies in the waveguide, these events are associated with (i) solar flares and (ii) geomagnetic storms. We conclude that with a continuous operating VLF receiver network a service for lower atmospheric channel monitoring / characterisation can be established.

  8. 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.

  9. 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.

  10. Artificial large-scale-motion perturbation of a turbulent boundary layer

    NASA Astrophysics Data System (ADS)

    Jacobi, I.; McKeon, B. J.

    2011-11-01

    A zero-pressure-gradient flat-plate boundary layer is perturbed dynamically with a spatially-impulsive strip of two-dimensional roughness elements (which alternate with a flush-surface condition periodically in time). The perturbation knocks the boundary layer out of equilibrium and artificially introduces a very-large-scale, periodic structure into the flow. Large-scale- motions in the turbulent boundary layer have recently been understood as a significant source of both turbulent kinetic energy and Reynolds stress, and in addition, have been shown to take part in an apparent amplitude modulation of smaller scales in the flow. The properties of this artificially generated large-scale-motion are studied with particular emphasis on the phase relationship between it and smaller scale structures. The behavior of the artificially-introduced large-scale-motion is also compared with the natural large-scales of the unperturbed turbulent boundary layer, and the interaction between the artificial and natural large-scales is explored. This study is supported by the Air Force Office of Scientific Research under grant #FA9550-08-1-0049 (program manager John Schmisseur).

  11. Features of additional stratification in ionospheric F2 layer observed for half a solar cycle over Indian low latitudes

    NASA Astrophysics Data System (ADS)

    Rama Rao, P. V. S.; Niranjan, K.; Prasad, D. S. V. V. D.; Brahmanandam, P. S.; Gopikrishna, S.

    2005-04-01

    The features of the additional stratification in the ionospheric F2 layer often referred to as the F3 layer observed over an Indian low-latitude station Waltair (17.7°N, 83.3°E, magnetic latitude (Mag. Lat.) 8.2°N) during the period 1997-2003 are presented along with the data from two other Indian stations. The observations grossly confirm those reported earlier in the occurrence and seasonal variability of the F3 layer. From an analysis of half a solar cycle ionosonde data (1997-2003), it is observed that the layer appeared more frequently during the summer solstice months of low solar activity period and persisted for longer durations during this season compared with equinox and winter solstice. The best stratification is seen between 10-12 hours IST. The occurrence of the F3 layer does not seem to depend on magnetic activity but the percentage of occurrence decreased with increasing solar activity. The solar activity dependence over Waltair confirms the model predictions of Balan et al. (1998) that the layer becomes less distinct and less frequent as solar activity increases. The ionosonde data for the same period (1997-2003) from an equatorial station, Trivandrum (8.4°N, 76.9°E, Mag. Lat. 0.47°N) and another low-latitude station, SHAR (14°N, 80°E, Mag. Lat. 6.8°N) are also analyzed with a view to examine the effect of the equatorial plasma dynamics on the occurrence of such events.

  12. Artificial retardation of barotropic waves in layered ocean models

    SciTech Connect

    Jensen, T.G.

    1996-06-01

    The effect of reducing the barotropic gravity wave speed in a layered ocean model in order to gain computational speed is explored. In theory the error in the propagation of baroclinic gravity waves typically is less than 3% for a reduction of the external gravity speed by one order of magnitude. This is confirmed in a numerical experiment. For baroclinic Rossby waves, the phase speed error is even less. The barotropic response is limited to the reduced radius of deformation. The method, which we will refer to as gravity wave retardation, is therefore applicable only for oceanic flows where the barotropic mode is of minor importance. It is demonstrated that the method gives very good results for the baroclinic flow of an equatorial jet, spinup of a midlatitude ocean and flow over a midoceanic ridge. The method can be considered as an alternative to multilayer reduced gravity models, and has the advantage that bottom topography can be included. 24 refs., 15 figs.

  13. Anomalous enhancement of ionospheric F2 layer critical frequency and total electron content over low latitudes before three recent major earthquakes in China

    NASA Astrophysics Data System (ADS)

    Sharma, Kavita; Dabas, R. S.; Sarkar, S. K.; Das, R. M.; Ravindran, Sudha; Gwal, A. K.

    2010-11-01

    This paper reports unusual variations in the ionospheric total electron content (TEC) and the critical frequency of the F2 layer (foF2) a few days before the main shock of three major earthquakes (M > 6). Epicenters of these earthquakes are distributed in China. Ionospheric data, recorded by an Indian network of ionosonde and GPS receivers at Delhi (28.6N, 77.2E), Bhopal (23.29N, 77.46E), and Trivandrum (8.4N, 76.6E) are analyzed to find seismoionospheric signatures of three recent major earthquakes in China. The results clearly indicate large enhancements in foF2 and TEC on geomagnetic quiet days, observed mainly at a low-latitude station in Delhi, which is nearest to the earthquake epicenters. The anomalous behavior of foF2 and TEC appeared 1-4 days before the main shock and especially during 1100-1700 LT. However, the ionospheric foF2 and TEC variability at the equatorial station Trivandrum and equatorial anomaly station Bhopal did not show any significant changes, thereby indicating the localized nature of such unusual ionospheric variations. The observed results suggest that the unusual enhancements of ionospheric foF2 and TEC over Delhi a few days before the main shock of each earthquake are most likely due to a seismoionospheric link.

  14. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

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

  16. 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.

  17. 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.

  18. 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.

  19. Optical spectroscopy of interlayer coupling in artificially stacked MoS2 layers

    NASA Astrophysics Data System (ADS)

    Plechinger, G.; Mooshammer, F.; Castellanos-Gomez, A.; Steele, G. A.; Schller, C.; Korn, T.

    2015-09-01

    We perform an optical spectroscopy study to investigate the properties of different artificial MoS2 bi- and trilayer stacks created from individual monolayers by a deterministic transfer process. These twisted bi- and trilayers differ from the common 2H stacking in mineral MoS2 in the relative stacking angle of adjacent layers and the interlayer distance. The combination of Raman spectroscopy, second-harmonic-generation microscopy and photoluminescence measurements allows us to determine the degree of interlayer coupling in our samples. We find that even for electronically decoupled artificial structures, which show the same valley polarization degree as the constituent MoS2 monolayers at low temperatures, there is a resonant energy transfer between individual layers which acts as an effective luminescence quenching mechanism.

  20. 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.

  1. Ionospheric chemical releases

    NASA Technical Reports Server (NTRS)

    Bernhardt, Paul A.; Scales, W. A.

    1990-01-01

    Ionospheric plasma density irregularities can be produced by chemical releases into the upper atmosphere. F-region plasma modification occurs by: (1) chemically enhancing the electron number density; (2) chemically reducing the electron population; or (3) physically convecting the plasma from one region to another. The three processes (production, loss, and transport) determine the effectiveness of ionospheric chemical releases in subtle and surprising ways. Initially, a chemical release produces a localized change in plasma density. Subsequent processes, however, can lead to enhanced transport in chemically modified regions. Ionospheric modifications by chemical releases excites artificial enhancements in airglow intensities by exothermic chemical reactions between the newly created plasma species. Numerical models were developed to describe the creation and evolution of large scale density irregularities and airglow clouds generated by artificial means. Experimental data compares favorably with theses models. It was found that chemical releases produce transient, large amplitude perturbations in electron density which can evolve into fine scale irregularities via nonlinear transport properties.

  2. 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.

  3. 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.

  4. Ion Acceleration in Vlasov Simulations of Double Layers, Electron Holes, and Associated Waves in Earth's Auroral Ionosphere

    NASA Astrophysics Data System (ADS)

    Sen, N.; Newman, D. L.; Goldman, M. V.; Andersson, L.; Ergun, R. E.

    2007-12-01

    The localized unipolar electric field of strong double layers (DLs), such as those observed1 by FAST in the downward current region of the auroral ionosphere, can produce significant acceleration of anti-earthward electrons and earthward ions. However, DLs can also contribute to the energization of ion perpendicular to the geomagnetic field through several different processes: If the DL itself develops structure perpendicular to \\mathbf{B}0, strong local ion heating can result. On the high-potential (high-altitude) side of the DL, electron holes (nonlinear structures with bipolar electric fields resulting from the saturation of a DL-driven electron two-stream instability) can also contribute to the acceleration of ions \\perp to \\mathbf{B}0. Finally, oblique wave modes with E\\perp\\gg Eallel (e.g., lower-hybrid and ion-Bernstein waves) can contribute to perpendicular ion heating both above and below the DL. Two-dimensional Vlasov simulations are employed to study the interactions of DLs, holes, and oblique waves, together with their contributions to perpendicular ion heating rates. Fully kinetic algorithms for unmagnetized ions as well as reduced2 algorithms for magnetized ions, are used in this study. *Research supported by NASA, NSF, and DOE 1 R.~E.~Ergun, et al., Phys.~Rev.~Lett., 87, 045003 (2001). 2 D.~L.~Newman, et al., Phys.~Plasmas, 14, 055907 (2007).

  5. Impact of vibrational excitation on ionospheric parameters and artificial airglow during HF heating in the F region

    NASA Astrophysics Data System (ADS)

    Vlasov, Michael N.; Kelley, Michael C.; Gerken, Elizabeth

    2004-09-01

    Vibrational excitation by the impact of electrons on molecular nitrogen in the energy range of 1.8-3.2 eV is well known. Electrons heated by high-power HF radio waves can effectively lose energy due to this vibrational excitation, which, in turn, creates a sharp energy barrier. Electrons must overcome this barrier in order to reach higher energies. A model for this vibrational barrier has been developed, and deviations of the electron energy distribution from a Maxwellian distribution have been estimated under different conditions. The depletion of electrons with energy higher than 2 eV decreases the excitation rate of the optical emissions (for example, 630.0 nm airglow) observed during HF heating. We show that the vibrational barrier can explain why the 630 nm airglow reported by [2001] was only slightly enhanced during HF heating, in spite of the measured electron temperature being higher than 3000 K. In some cases, vibrationally excited molecules can accumulate in the ionosphere due to slow deactivation. These species increase the recombination coefficient, which, in turn, may result in the decrease of electron density. This effect can also contribute to the saturation of the optical emission strength as a function of heater power, as reported by [2003].

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

    PubMed Central

    Liu, Yan; Guenneau, Sbastien; Gralak, Boris

    2013-01-01

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

  7. 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

  8. 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.

  9. Estimating Deliverability in Multi-Layered Gas Reservoirs Using Artificial Intelligence

    NASA Astrophysics Data System (ADS)

    Al-Arfaj, Malik Khalid

    In this research, an artificial intelligence (AI) model has been created to estimate the production rate of each layer in a multi-layered gas reservoir using static properties such as those obtained from well logging, in addition to dynamic properties such as pressure. This approach will be helpful in several reservoir engineering applications, such as understanding layers' depletion, or targeting specific layers for workover. It could also be used for PLT analysis where the measured PLT values are compared to the expected values and a variance analysis could be performed. Data were collected from more than 100 wells in a certain reservoir spanning over four fields. They were combined in related input variables and fed to the AI model for learning purposes. To compare different AI methods, the data were fed to 5 methods, namely ANFIS, MLP, RBF, SVM, and GRNN, and results were optimized for each method. Between the tested AI methods, SVM and GRNN performed best as shown by a low mean absolute percentage error and a very high correlation coefficient. This research shows promising use for AI methods in estimating production rate from each layer in a multi-layered gas reservoir.

  10. 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.

  11. Artificially layered PbTiO3/BaTiO3 superlattices

    NASA Astrophysics Data System (ADS)

    Ziegler, Benedikt; Callori, Sara; Sinsheimer, John; Dawber, Matthew

    2010-03-01

    Artificially layered superlattices of ferroelectric oxides provide an appealing route for the tailoring of materials to particular applications [1] by taking advantage of electrostatics, strain and more exotic interactions between different materials at interfaces [2]. First principles calculations [3] suggest that the piezoelectric properties can be enhanced at certain ratios of layer thicknesses in the PbTiO3/BaTiO3 superlattice system. We have fabricated high quality artificially layered PbTiO3/BaTiO3 superlattices on SrTiO3 substrates (with SrRuO3 electrodes) using an off-axis RF magnetron sputtering technique, allowing us to perform a range of experiments, including x-diffraction, electrical measurements and atomic force microscopy. We will discuss our experimental results and their relationship with the theoretical expectations for this system and highlight the potential of using a superlattice approach to create enhanced materials for piezoelectric applications. References [1] M. Dawber, N. Stucki, C. Lichtensteiger, S. Gariglio, P. Ghosez and J.-M. Triscone, Advanced Materials, 19, 4153 (2007). [2] E. Bousquet, M. Dawber, N. Stucki, C. Lichtensteiger, P. Hermet, S.Gariglio, J.-M. Triscone, and P. Ghosez, Nature, 452, 732 (2008). [3] V. R. Cooper and K. M. Rabe, Phys. Rev. B 79, 180101 (R) (2009)

  12. First experience on spatial discrimination of large-scale natural elf interference on the example of two-point measurements of the magnetic field of an artificial ionospheric source

    NASA Astrophysics Data System (ADS)

    Polyakov, S. V.; Reznikov, B. I.; Shlyugaev, Yu. V.; Kopytenko, E. A.

    2006-12-01

    We present the results of an experiment on the generation of extremely low-frequency (ELF) electromagnetic fields at frequencies near the first Schumann resonance upon the ionosphere modification by modulated powerful radio emission. The reception was performed at two sites spaced by 14 km in the distance from “SURA” facility. It was found that the natural noise at different reception sites is highly correlated, which allows one to achieve the noise suppression by about an order of magnitude by subtracting the measurement results. We demonstrate the opportunities of spatial discrimination of the interference upon the two-site reception of the “small-scale” field of an artificial ionospheric source. The directions of future studies and possible applications are discussed.

  13. Development of a low cost high precision three-layer 3D artificial compound eye.

    PubMed

    Zhang, Hao; Li, Lei; McCray, David L; Scheiding, Sebastian; Naples, Neil J; Gebhardt, Andreas; Risse, Stefan; Eberhardt, Ramona; Tnnermann, Andreas; Yi, Allen Y

    2013-09-23

    Artificial compound eyes are typically designed on planar substrates due to the limits of current imaging devices and available manufacturing processes. In this study, a high precision, low cost, three-layer 3D artificial compound eye consisting of a 3D microlens array, a freeform lens array, and a field lens array was constructed to mimic an apposition compound eye on a curved substrate. The freeform microlens array was manufactured on a curved substrate to alter incident light beams and steer their respective images onto a flat image plane. The optical design was performed using ZEMAX. The optical simulation shows that the artificial compound eye can form multiple images with aberrations below 11 ?m; adequate for many imaging applications. Both the freeform lens array and the field lens array were manufactured using microinjection molding process to reduce cost. Aluminum mold inserts were diamond machined by the slow tool servo method. The performance of the compound eye was tested using a home-built optical setup. The images captured demonstrate that the proposed structures can successfully steer images from a curved surface onto a planar photoreceptor. Experimental results show that the compound eye in this research has a field of view of 87. In addition, images formed by multiple channels were found to be evenly distributed on the flat photoreceptor. Additionally, overlapping views of the adjacent channels allow higher resolution images to be re-constructed from multiple 3D images taken simultaneously. PMID:24104115

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

    SciTech Connect

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

    1995-04-01

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

  15. Harnessing competition in artificially layered ferroelectric superlattices to engineer enhanced piezoelectrics

    NASA Astrophysics Data System (ADS)

    Dawber, Matthew; Ziegler, Benedikt; Callori, Sara; Sinsheimer, John; Cooper, Valentino; Yusufaly, Tahir; Rabe, Karin M.; Chandra, Premala

    2011-03-01

    First principles calculations by Cooper and Rabe (V. R. Cooper and K.M. Rabe, Phys. Rev. B 79, 180101 (R) (2009)), predicted that in PbTi O3 / BaTi O3 superlattices an enhancement of the d 33 piezoelectric coefficient could be achieved at a particular ratio of the thickness of the constituent layers. We have fabricated high quality artificially layered PbTi O3 / BaTi O3 superlattices on SrTi O3 substrates (with SrRu O3 bottom electrodes) using an off-axis RF magnetron sputtering technique, allowing us to perform x-ray diffraction, electrical measurements and atomic force microscopy on this system. The experimental results confirm the prediction from first principles calculations, and we apply a Landau theory model as a useful bridge between the first principles predictions and experimental results at elevated temperature. In this work we have demonstrated that by finely balancing competing material properties in artificial heterostructures, desirable properties that exceed those of the parent compounds can be achieved.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  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. 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

  2. Density distribution of solar wind protons and "loaded" ions in the shock layer ahead of a cometary ionosphere.

    NASA Astrophysics Data System (ADS)

    Baranov, V. B.; Lebedev, M. G.

    2014-10-01

    We propose a simple method that allows the density fields of solar wind protons and heavy ions of cometary origin ("loaded" ions) in the solar wind-cometary ionosphere interaction region to be separated from the general density field calculated within the framework of a single-fluid model. The method is based on the assumption that the velocities of both components are identical. We analyze the density fields in the solar wind obtained in this way before and after the passage of the bow shock ahead of the cometary ionosphere and make a comparison with the distributions measured with various instruments onboard the Giotto spacecraft when it flew past Comet Halley and calculated on the basis of more complex multi-fluid models.

  3. Effects of artificial sea film slick upon the atmospheric boundary layer structure

    NASA Astrophysics Data System (ADS)

    Repina, Irina; Artamonov, Arseniy; Malinovsky, Vladimir; Chechin, Dmitriy

    2010-05-01

    Organic surface-active compounds accumulate at the ocean-atmosphere boundary, influencing several air-sea interaction processes. In coastal areas with high biological activity this accumulation frequently becomes visible as mirrorlike patches ("slicks") on the sea surface. The artificial surface films of oleyl alcohol and vegetable oil were produced in the Black Sea coastal zone (one site was located near Gelendjik and another was near Crimea coast) to investigate its influence on energy and gas exchange between atmosphere and sea surface under different meteorological conditions. The atmospheric turbulence measurements during the passage of an artificial sea slick are compared with similar measurements without a sea slick. The effects of the slick are modifications of roughness length z0, and a possible increase in mean wind speed. In the mean, during the passage of the slick, the roughness length decreased while the mean wind speed appeared to increase. For the spectral comparison we compared the wind field over the sea during the time the film slick was in the vicinity of the measurement site with the wind field observed after the slick had passed. The cross-spectral density was computed between horizontal velocity and vertical velocity (Reynolds stress) and between atmospheric temperature and vertical velocity (heat flux). The introduction of the sea film slick, with its damping and suppression of capillary waves, appears to completely destroy the atmospheric turbulence generation. When a slick is present, the U-W phase angle and Reynolds stress spectrum for the atmosphere appear to be completely unaffected by undulating sea surface directly below the sensors. Spectral and wavelet analysis of the atmospheric surface layer characteristics showed a significant correlation between the processes on the sea surface and the atmospheric boundary layer. An intensification of change processes in the vicinity of the windward slick boundary are detected. It may be connected with the formation of internal boundary layer over the slick. Gas exchange, in this case desorption of CO2 was determined before and after formation of the artificial surface film. In the one experiment performed inhibition of exchange was significant when the film was present. These results demonstrate the importance of observing small-scale atmospheric processes near the sea surface. It is strongly recommended that this technique be exploited to its fullest to enhance our understanding of the small-scale processes at the air-sea boundary. The experiments have confirmed the influence of surface-active compounds, including oil pollution, which have been significantly changed the state of the sea surface, the processes in the atmospheric turbulent layer.The results also have important implications on ocean remote sensing applications. The work was supported by RFBR (grant 08-05-00099, grant 08-05-00890).

  4. 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.

  5. `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.

  6. 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.

  7. Ionospheric foF2 morphology and response of F2 layer height over Jicamarca during different solar epochs and comparison with IRI-2012 model

    NASA Astrophysics Data System (ADS)

    Adebesin, B. O.; Adekoya, B. J.; Ikubanni, S. O.; Adebiyi, S. J.; Adebesin, O. A.; Joshua, B. W.; Olonade, K. O.

    2014-06-01

    Diurnal, seasonal and annual foF2 variability and the response of the F2-layer height over Jicamarca (11.9 S, 76.8 W, 1 N dip) during periods of low (LSA), moderate (MSA) and high (HSA) solar activities was investigated. The relative standard deviation ( V R ) was used for the analysis. The F2-layer critical frequency pre-noon peak increases by a factor of 2 more than the post-noon peak as the solar activity increases. The variability coefficient ( V R ) is lowest during the day (7-16%) for the three solar epochs; increases during nighttime (20-26%, 14-26%, and 10-20%, respectively for the LSA, MSA and HSA years); and attained highest magnitude during sunrise (21-27%, 24-27%, and 19-30%, respectively in similar order). Two major peaks were observed in V R - the pre-sunrise peak, which is higher, and the post-sunset peak. Generally, the variability increases as the solar activity decreases. Annually, V R peaks within 23-24%, 19-24% and 15-24% for the LSA, MSA, and HSA periods, respectively. The ionospheric F2-layer height rises to the higher level with increasing solar activity. The foF2 comparison results revealed that Jicamarca is well represented on the IRI-2012 model, with an improvement on the URSI option. The importance of vertical plasma drift and photochemistry in the F2-layer was emphasized.

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

    NASA Astrophysics Data System (ADS)

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

    2005-05-01

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

  9. Comparison of electron concentrations in the ionospheric E-layer maximum in spring conditions obtained by calculations and Moscow ionosonde measurements

    NASA Astrophysics Data System (ADS)

    Pavlov, A. V.; Pavlova, N. M.

    2015-03-01

    The electron concentrations in the ionospheric E-layer maximum NmE, as measured by the Moscow ionosonde, are compared with the results of theoretical calculations of NmE for geomagnetically quiet conditions at low solar activity on April 1, 1986, and April 6, 1996, moderate solar activity on April 9, 1978, and April 6, 1998, and high solar activity on April 20, 1980, and April 15, 1991. On the basis of this comparison, a correction of the model flux of solar X-ray radiation is proposed. The discovered variability of the correction factors manifests the influence of solar X-ray radiation flux variations on NmE variability. The dependence of the influence of the neutral constituents ionization by photoelectrons on NmE on the solar activity level is studied.

  10. Ionospheric modifications in high frequency heating experiments

    NASA Astrophysics Data System (ADS)

    Kuo, Spencer P.

    2015-01-01

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

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. Ionospheric modeling

    NASA Astrophysics Data System (ADS)

    Dandekar, B. S.

    1982-01-01

    The purpose of this report is to familiarize a user of ionospheric models with the options presently available for ionospheric prediction and specification. Two types of ionospheric models are available: the numerical-phenomenological and theoretical models. From the numerical type, the ITS-78, IONCAP, and Bent models have been discussed. In the theoretical models the main concern is the number of parameters included in the model. Nine ionoshperic models available have been summarized. The differences and limitations of these models are compared and tabulated. This information will help a user make a judicious selection of an ionospheric model to satisfy his specific needs. The sources for obtaining the programs for these models have been listed for ready reference.

  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. 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.

  18. Propagation in the ionosphere, B

    NASA Astrophysics Data System (ADS)

    Cannon, Paul S.

    1994-09-01

    Sophisticated computer programs or equipment, high frequency systems, satellite to ground systems and meteor burst systems are discussed with respect to ionospheric propagation models. Short term ionospheric forecasts (electron density) and geomagnetic activity level forecasts are reviewed. The goal is to design automatic decision aids which allow skilled personnel to adapt to systems operation and interpret the output from computer programs or experimental techniques. In the future, an artificial intelligence system might replace human operators in selecting and using the models and experimental techniques to best advantage.

  19. 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.

  20. Accuracy of theoretical calculations of the main parameters of the F2-layer of the daytime ionosphere

    NASA Astrophysics Data System (ADS)

    Pavlov, A. V.; Sitnov, Iu. S.

    1985-10-01

    Pavlov's (1984) method is used to determine the relative errors (due to errors in measuring the input parameters of the model) in theoretical calculations of the main parameters of the daytime F2-layer under quiet conditions. The parameters calculated are the height of the F2-layer maximum and the electron density.

  1. 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.

  2. The detection of the ionospheric irregularities by GNSS signal and the incoherent scatter radio measurements

    NASA Astrophysics Data System (ADS)

    Cherniak, Iurii; Shagimuratov, Irk; Krankowski, Andrzej; Sieradsky, Rafal; Zakharenkova, Irina; Rietveld, Michael; Kapcia, Jacek

    2013-04-01

    The high-latitude ionosphere has a very complicated structure and high dynamics. The ionospheric irregularities can produce scintillations of radio waves that occur predominantly in the ionosphere F-layer. The strong fluctuations can influence on the performance of the different space communication and navigation radio systems. The fluctuations of GPS/GLONASS signals are caused by the ionospheric irregularities with spatial dimensions more than 10 km. These structures can be detected by high potential incoherent scatter radars. It was proposed and carried out at the beginning of June 2012 experiment for a detailed study of the nature of the ionospheric irregularities, influencing on GPS/GLONASS signals parameters, by incoherent scatter and trans-ionospheric radio measurements simultaneously. The EISCAT facilities position provides the unique opportunity to study the ionospheric irregularities' parameters associated with TEC fluctuations and GPS/GLONASS signals scintillations. The EISCAT heating facility provides unique possibility to generate the artificial ionospheric irregularities and to estimate the impact factor of these irregularities on GPS/GLONASS signals transionospheric propagation. In order to detect the ionosphere irregularities it is used the IS radar measurements (electron density and plasma temperatures profiles) and simultaneously registered on EISCAT site amplitude and phase fluctuations in GPS/GLONASS signals by use of the Javad multi-constellation GPS/GLONASS receiver with high samples rate (100 Hz) and special scintillation GPS receiver PolaRxS PRO that dedicated to ionospheric monitoring and space weather applications and provides TEC and S4 scintillation index measurements. The low frequency fluctuations can be directly measured due to the electron density changes along the radio ray path between a GPS/GLONASS satellite and a ground-based receiver on EISCAT site. The raw data (under scintillating conditions) obtained by use of the high samples rate GPS/GLONASS receiver are processed in order to derive the scintillation parameters. The practical aspect of this investigation is a detailed study of nature and impact level of the ionospheric irregularities that can influence on the GPS/GLONASS performance especially at high latitudes and during geomagnetically disturbed period and to obtain new knowledge that may improve the reliability of the global navigation systems in Arctic and Antarctic regions. The authors are grateful to the EISCAT Scientific Association for observing time on the EISCAT facilities within the framework of Peer-reviewed Program.

  3. Diffraction properties of a defocusing ionospheric lens

    SciTech Connect

    Alimov, V.A.

    1995-12-01

    The problem of short-wave signal diffraction by a defocusing lens induced by powerful short-wave radiation in the ionosphere has been solved. It is shown that the received signal is subject both to a noticeable attenuation and a significant increase in the local caustic areas at the terrestrial surface. The result of calculations are compared with the experimental data. The basic characteristics of an artificial ionospheric lens are presented.

  4. "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.

  5. The ionospheric focused heating experiment

    SciTech Connect

    Bernhardt, P.A.; Siefring, C.L.; Rodriguez, P.

    1995-09-01

    The Ionospheric Focused Heating rocket was launched on May 30, 1992. The sounding rocket carried an instrument and chemical payload along a trajectory that crossed the intersection of the beams from the 430-MHz incoherent scatter radar and the 5.1-MHz high-power radio wave facility near Arecibo. The release of 30 kg of CF{sub 3}Br into the F region at 285 km altitude produced an ionospheric hole that acted like a convergent lens to focus the HF transmission. The power density inside the radio beam was raised by 12 dB immediately after the release. A wide range of new processes were recorded by in situ and ground-based instruments. Measurements by instruments flying through the modified ionosphere show small-scale microcavities (< 1 m) and downshifted electron plasma (Langmuir) waves inside the artificial cavity, electron density spikes at the edge of the cavity, and Langmuir waves coincident with ion gyroradius (4 m) cavities near the radio wave reflection altitude. The Arecibo incoherent scatter radar showed 20 dB or greater enhancements in ion acoustic and Langmuir wave turbulence after the 5.1-MHz radio beam was focused by the artificial lens. Enhancements in airglow from chemical reactions and, possibly, electron acceleration were recorded with optical instruments. The Ionospheric Focused Heating experiment verified some of the preflight predictions and demonstrated the value of active experiments that combine high-power radio waves with chemical releases. 30 refs., 14 figs., 1 tab.

  6. The Ionospheric Focused Heating experiment

    NASA Astrophysics Data System (ADS)

    Bernhardt, P. A.; Siefring, C. L.; Rodriguez, P.; Haas, D. G.; Baumback, M. M.; Romero, H. A.; Solin, D. A.; Djuth, F. T.; Duncan, L. M.; Hunton, D. E.; Pollock, C. J.; Sulzer, M. P.; Tepley, C. A.; Wagner, L. S.; Goldstein, J. A.

    1995-09-01

    The Ionospheric Focused Heating rocket was launched on May 30, 1992. The sounding rocket carried an instrument and chemical payload along a trajectory that crossed the intersection of the beams from the 430-MHz incoherent scatter radar and the 5.1-MHz high-power radio wave facility near Arecibo. The release of 30 kg of CF3Br into the F region at 285 km altitude produced an ionospheric hole that acted like a convergent lens to focus the HF transmissions. The power density inside the radio beam was raised by 12 dB immediately after the release. A wide range of new processes were recorded by in situ and ground-based instruments. Measurements by instruments flying through the modified ionosphere show small-scale microcavities (<1 m) and downshifted electron plasma (Langmuir) waves inside the artificial cavity, electron density spikes at the edge of the cavity, and Langmuir waves coincident with ion gyroradius (4 m) cavities near the radio wave reflection altitude. The Arecibo incoherent scatter radar showed 20 dB or greater enhancements in ion acoustic and Langmuir wave turbulence after the 5.1-MHz radio beam was focused by the artificial lens. Enhancements in airglow from chemical reactions and, possibly, electron acceleration were recorded with optical instruments. The Ionospheric Focused Heating experiment verified some of the preflight predictions and demonstrated the value of active experiments that combine high-power radio waves with chemical releases.

  7. 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.

  8. 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 Frsterling equations. A model based on the Frsterling 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.

  9. "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.

  10. Ionosphere/thermosphere heating determined from dynamic magnetosphere-ionosphere/thermosphere coupling

    NASA Astrophysics Data System (ADS)

    Tu, Jiannan; Song, Paul; Vasyliūnas, Vytenis M.

    2011-09-01

    Ionosphere/thermosphere heating driven by magnetospheric convection is investigated through a three-fluid inductive (including Faraday's law) approach to describing magnetosphere-ionosphere/thermosphere coupling, for a 1-D stratified ionosphere/thermosphere in this initial study. It is shown that the response of the ionosphere/thermosphere and thus the heating is dynamic and height-dependent. The heating is essentially frictional in nature rather than Joule heating as commonly assumed. The heating rate reaches a quasi-steady state after about 25 Alfvén travel times. During the dynamic period, the heating can be enhanced and displays peaks at multiple times due to wave reflections. The dynamic heating rate can be more than twice greater than the quasi-steady state value. The heating is strongest in the E-layer but the heating rate per unit mass is concentrated around the F-layer peak height. This implies a potential mechanism of driving O+ upflow from O+ rich F-layer. It is shown that the ionosphere/thermosphere heating caused by the magnetosphere-ionosphere coupling can be simply evaluated through the relative velocity between the plasma and neutrals without invoking field-aligned currents, ionospheric conductance, and electric field. The present study provides understanding of the dynamic magnetosphere-ionosphere/thermosphere coupling from the ionospheric/thermospheric view in addition to magnetospheric perspectives.

  11. Artificial Synaptic Devices Based on Natural Chicken Albumen Coupled Electric-Double-Layer Transistors.

    PubMed

    Wu, Guodong; Feng, Ping; Wan, Xiang; Zhu, Liqiang; Shi, Yi; Wan, Qing

    2016-01-01

    Recent progress in using biomaterials to fabricate functional electronics has got growing attention for the new generation of environmentally friendly and biocompatible electronic devices. As a kind of biological material with rich source, proteins are essential natural component of all organisms. At the same time, artificial synaptic devices are of great significance for neuromorphic systems because they can emulate the signal process and memory behaviors of biological synapses. In this report, natural chicken albumen with high proton conductivity was used as the coupling electrolyte film for organic/inorganic hybrid synaptic devices fabrication. Some important synaptic functions including paired-pulse facilitation, dynamic filtering, short-term to long-term memory transition and spatial summation and shunting inhibition were successfully mimicked. Our results are very interesting for biological friendly artificial neuron networks and neuromorphic systems. PMID:27008981

  12. Artificial Synaptic Devices Based on Natural Chicken Albumen Coupled Electric-Double-Layer Transistors

    PubMed Central

    Wu, Guodong; Feng, Ping; Wan, Xiang; Zhu, Liqiang; Shi, Yi; Wan, Qing

    2016-01-01

    Recent progress in using biomaterials to fabricate functional electronics has got growing attention for the new generation of environmentally friendly and biocompatible electronic devices. As a kind of biological material with rich source, proteins are essential natural component of all organisms. At the same time, artificial synaptic devices are of great significance for neuromorphic systems because they can emulate the signal process and memory behaviors of biological synapses. In this report, natural chicken albumen with high proton conductivity was used as the coupling electrolyte film for organic/inorganic hybrid synaptic devices fabrication. Some important synaptic functions including paired-pulse facilitation, dynamic filtering, short-term to long-term memory transition and spatial summation and shunting inhibition were successfully mimicked. Our results are very interesting for biological friendly artificial neuron networks and neuromorphic systems. PMID:27008981

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

    NASA Technical Reports Server (NTRS)

    Maynard, Nelson C.

    2004-01-01

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

  14. 25th anniversary article: Artificial carbonate nanocrystals and layered structural nanocomposites inspired by nacre: synthesis, fabrication and applications.

    PubMed

    Yao, Hong-Bin; Ge, Jin; Mao, Li-Bo; Yan, You-Xian; Yu, Shu-Hong

    2014-01-01

    Rigid biological systems are increasingly becoming a source of inspiration for the fabrication of next generation advanced functional materials due to their diverse hierarchical structures and remarkable engineering properties. Among these rigid biomaterials, nacre, as the main constituent of the armor system of seashells, exhibiting a well-defined 'brick-and-mortar' architecture, excellent mechanical properties, and interesting iridescence, has become one of the most attractive models for novel artificial materials design. In this review, recent advances in nacre-inspired artificial carbonate nanocrystals and layered structural nanocomposites are presented. To clearly illustrate the inspiration of nacre, the basic principles relating to plate-like aragonite single-crystal growth and the contribution of hierarchical structure to outstanding properties in nacre are discussed. The inspiration of nacre for the synthesis of carbonate nanocrystals and the fabrication of layered structural nanocomposites is also discussed. Furthermore, the broad applications of these nacre inspired materials are emphasized. Finally, a brief summary of present nacre-inspired materials and challenges for the next generation of nacre-inspired materials is given. PMID:24338814

  15. 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.

  16. Role of ionospheric conductance in magnetosphere-ionosphere coupling

    NASA Astrophysics Data System (ADS)

    Bhattacharya, Tapas

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

  17. An Artificial Solid Electrolyte Interphase Layer for Stable Lithium Metal Anodes.

    PubMed

    Li, Nian-Wu; Yin, Ya-Xia; Yang, Chun-Peng; Guo, Yu-Guo

    2016-03-01

    A Li3 PO4 solid electrolyte interphase (SEI) layer is demonstrated to be stable in the organic electrolyte, even during the Li deposition/dissolution process. Thus, the Li-conducting Li3 PO4 SEI layer with a high Young's modulus can effectively reduce side reactions between Li metal and the electrolyte and can restrain Li dendrite growth in lithium-metal batteries during cycling. PMID:26698171

  18. Determination of ionospheric electron-density profiles from satellite uv (ultraviolet) emission measurements

    SciTech Connect

    Decker, D.T.; Daniell, R.E.; Jasperse, J.R.; Strickland, D.J.

    1986-01-01

    This paper addresses the problem of using satellite ultraviolet measurements to deduce the ionospheric electron density profile (EDP). The ionospheric processes that produce the ultraviolet emissions differ from region to region, so it is necessary to consider separate approaches for the various ionospheric subregions. The authors discuss approaches suitable for (1) the midlatitude daytime ionosphere, (2) the midlatitude nighttime ionosphere, and (3) the undisturbed auroral E layer.

  19. 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.

  20. 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 earths 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.

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

    PubMed

    Valhondo, Cristina; Carrera, Jess; Ayora, Carlos; Tubau, Isabel; Martinez-Landa, Lurdes; Ndler, 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

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  3. Prediction of mining subsidence under thin bedrocks and thick unconsolidated layers based on field measurement and artificial neural networks

    NASA Astrophysics Data System (ADS)

    Yang, Weifeng; Xia, Xiaohong

    2013-03-01

    The deformation characteristics of subsidence and movement induced by mining under thin bedrocks and thick unconsolidated layers are researched using field measurement and the prediction method of artificial neural networks (ANN). Firstly, the occurrence characteristics of thin bedrock and thick unconsolidated layers were analyzed in a research coal field. Based on the measured data, the characteristics of ground movement show that the surface subsidence deformation of mining under thin bedrock is more intensive than that of mining under normal thickness bedrock. Such is evident through the settlement time concentrating, the maximum surface subsidence being greater than the thickness of coal seam, the distribution of ground movement and deformation being concentrated, the range extension being wide, the active period being intensive and concentrated, the surface damage being very serious, and the crack development being significant. A quantitative prediction method is made on mining subsidence under thin bedrocks and thick unconsolidated layers by means of ANN. The improved neural network was used for modeling and predicting the mining subsidence. The ANN output can reflect the change trend of ground movement and deformation. The forecasting results are in good agreement with the real observation results.

  4. Nonlinear scattering of acoustic waves by natural and artificially generated subsurface bubble layers in sea.

    PubMed

    Ostrovsky, Lev A; Sutin, Alexander M; Soustova, Irina A; Matveyev, Alexander L; Potapov, Andrey I; Kluzek, Zigmund

    2003-02-01

    The paper describes nonlinear effects due to a biharmonic acoustic signal scattering from air bubbles in the sea. The results of field experiments in a shallow sea are presented. Two waves radiated at frequencies 30 and 31-37 kHz generated backscattered signals at sum and difference frequencies in a bubble layer. A motorboat propeller was used to generate bubbles with different concentrations at different times, up to the return to the natural subsurface layer. Theoretical consideration is given for these effects. The experimental data are in a reasonably good agreement with theoretical predictions. PMID:12597169

  5. Nonlinear scattering of acoustic waves by natural and artificially generated subsurface bubble layers in sea

    NASA Astrophysics Data System (ADS)

    Ostrovsky, Lev A.; Sutin, Alexander M.; Soustova, Irina A.; Matveyev, Alexander L.; Potapov, Andrey I.; Kluzek, Zigmund

    2003-02-01

    The paper describes nonlinear effects due to a biharmonic acoustic signal scattering from air bubbles in the sea. The results of field experiments in a shallow sea are presented. Two waves radiated at frequencies 30 and 31-37 kHz generated backscattered signals at sum and difference frequencies in a bubble layer. A motorboat propeller was used to generate bubbles with different concentrations at different times, up to the return to the natural subsurface layer. Theoretical consideration is given for these effects. The experimental data are in a reasonably good agreement with theoretical predictions.

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

    PubMed

    Pittaway, P; Martnez-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

  7. Artificially MoO3 graded ITO anodes for acidic buffer layer free organic photovoltaics

    NASA Astrophysics Data System (ADS)

    Lee, Hye-Min; Kim, Seok-Soon; Kim, Han-Ki

    2016-02-01

    We report characteristics of MoO3 graded ITO anodes prepared by a RF/DC graded sputtering for acidic poly(3,4-ethylene dioxylene thiophene):poly(styrene sulfonic acid) (PEDOT:PSS)-free organic solar cells (OSCs). Graded sputtering of the MoO3 buffer layer on top of the ITO layer produced MoO3 graded ITO anodes with a sheet resistance of 12.67 Ω/square, a resistivity of 2.54 × 10-4 Ω cm, and an optical transmittance of 86.78%, all of which were comparable to a conventional ITO anode. In addition, the MoO3 graded ITO electrode showed a greater work function of 4.92 eV than that (4.6 eV) of an ITO anode, which is beneficial for hole extraction from an organic active layer. Due to the high work function of MoO3 graded ITO electrodes, the acidic PEDOT:PSS-free OSCs fabricated on the MoO3 graded ITO electrode exhibited a power conversion efficiency 3.60% greater than that of a PEDOT:PSS-free OSC on the conventional ITO anode. The successful operation of PEDOT:PSS-free OSCs indicates simpler fabrication steps for cost-effective OSCs and elimination of interfacial reactions caused by the acidic PEDOT:PSS layer for reliable OSCs.

  8. Hygroscopic behavior and liquid-layer composition of aerosol particles generated from natural and artificial seawater

    NASA Astrophysics Data System (ADS)

    Wise, Matthew E.; Freney, Evelyn J.; Tyree, Corey A.; Allen, Jonathan O.; Martin, Scot T.; Russell, Lynn M.; Buseck, Peter R.

    2009-02-01

    Sea-salt aerosol (SSA) particles affect the Earth's radiative balance and moderate heterogeneous chemistry in the marine boundary layer. Using conventional and environmental transmission electron microscopes (ETEM), we investigated the hygroscopic growth and liquid-layer compositions of particles generated from three types of aqueous salt solutions: sodium chloride, laboratory-synthesized seawater (S-SSA particles), and natural seawater (N-SSA particles). Three levels of morphological change were observed with the ETEM as the laboratory-generated particles were exposed to increasing relative humidity (RH). The first level, onset of observable morphological changes, occurred on average at 70, 48, and 35% RH for the NaCl, S-SSA, and N-SSA particles, respectively. The second level, rounding, occurred at 74, 66, and 57% RH for NaCl, S-SSA, and N-SSA particles, respectively. The third level, complete deliquescence, occurred at 75% RH for all particles. Collected ambient SSA particles were also examined. With the exception of deliquescence, they did not exhibit the same hygroscopic characteristics as the NaCl particles. The ambient particles, however, behaved most similarly to the synthesized and natural SSA particles, although the onset of morphological change was slightly higher for the S-SSA particles. We used energy-dispersive X-ray spectrometry to study the composition of the liquid layer formed on the S-SSA and N-SSA particles. The layer was enriched in Mg, S, and O relative to the solid particle core. An important implication of these results is that MgSO4-enriched solutions on the surface of SSA particles may be the solvents of many heterogeneous reactions.

  9. 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.

  10. 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.

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

    NASA Astrophysics Data System (ADS)

    Hohman, Tristen; Smits, Alexander; Martinelli, Luigi

    2011-11-01

    Wind energy represents a large portion of the growing market in alternative energy technologies and the current landscape has been dominated by the more prevalent horizontal axis wind turbine. However, there are several advantages to the vertical axis wind turbine (VAWT) or Darrieus type design and yet there is much to be understood about how the atmospheric boundary layer (ABL) affects their performance. In this study the ABL was simulated in a wind tunnel through the use of elliptical shaped vortex generators, a castellated wall, and floor roughness elements as described in the method of Counihan (1967) and then verified its validity by hot wire measurement of the mean velocity profile as well as the turbulence intensity. The motion of an blade element around a vertical axis is approximated through the use of a pitching airfoil. The wake of the airfoil is investigated through hot wire anemometry in both uniform flow and in the simulated boundary layer both at Re = 1 . 37 ×105 based on the chord of the airfoil. Sponsored by Hopewell Wind Power (Hong Kong) Limited.

  12. 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.

  13. Investigation of Tsunami-Ionospheric Coupling Efficiency

    NASA Astrophysics Data System (ADS)

    Fisher, D. J.; Grawe, M.; Makela, J. J.; Coisson, P.; Rolland, L.; Rakoto, V.; Lognonne, P. H.

    2014-12-01

    Recent studies have shown that coupling exists between ocean tsunamis and the upper atmosphere, opening up the possibility of tsunami monitoring through observing the ionosphere. Several measurement techniques have demonstrated the effects of this coupling in the ionosphere. Here, we present data from two techniques that allow for deducing properties of a tsunami from the ionosphere (e.g., wavelength, orientation, and velocity), namely total electron content (TEC) measurements from dual-frequency GPS receivers and ionospheric imaging through monitoring the airglow layers surrounding the earth. However, a quantitative relationship between the wave amplitudes observed in the ionosphere and the height of the tsunami remains elusive. Ionospheric signatures from two tsunamis in the Pacific Ocean, caused by the 2011 Tohoku and 2012 Haida Gwaii earthquakes, have been observed in airglow imaging systems and a network of dual-frequency GPS receivers located in Hawaii. These two events provide excellent test cases for the study of tsunami-ionospheric coupling efficiency, most notably the effects of the relative orientation between the tsunami-induced gravity waves and the Earth's magnetic field. We present a quantitative comparison of the TEC and airglow intensity variation from these events, including results from tsunami normal mode summation modeling.

  14. 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 γ-alumina and inner-most dense layer of α-alumina. The α-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

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

    NASA Astrophysics Data System (ADS)

    Pietrella, M.

    2012-02-01

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

  16. Large scale plasma irregularities and airglow enhancements from ionospheric heating

    NASA Astrophysics Data System (ADS)

    Bernhardt, Paul A.; Rowland, Harvey; Duncan, Lewis M.; Tepley, Craig A.

    1990-10-01

    Ionospheric modification with high power radio waves may generate plasma irregularities and airglow clouds. Large scale irregularities are produced in a convecting F-layer by a mechanism called the plasma relaxation oscillator. When a continuous beam of powerful electromagnetic waves heats the ionosphere, a cavity is produced by thermal pressure gradients. The cavity drifts under the influence of ambient electric fields causing the vertically-incident, radio beam to be refracted from the zenith. At some point, the cavity can no longer 'capture' the beam and it returns to the zenith to form another cavity. This relaxation process repeats to yield irregularities on the scale of the heater beam diameter. Airglow enhancements are produced by energetic electrons accelerated out of the heated region. Large amplitude electrostatic waves may be excited by linear mode coupling, by parametric decay instabilities, and by strong plasma turbulence. This occurs near the point where the plasma frequency of the ionosphere matches wave frequency. The electrostatic waves accelerate ambient electrons to high enough energy to collisionally excite ambient oxygen atoms. Clouds of enhanced red-line (630.0 nm) and green-line (557.7 nm) emissions were recorded with low-light-level imaging systems located at Arecibo, Puerto Rico. Comparison of the imager data with data from the Arecibo incoherent scatter radar shows that artificial airglow clouds are physically tied to the density cavities and to regions of enhanced electrostatic waves by the earth's magnetic field lines. At currently available power levels (around 80 MW effective radiated power), HF modification yields 10-30 percent fluctuations in density and 10-100 Rayleigh enhancements in airglow intensity.

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

    NASA Astrophysics Data System (ADS)

    Kuo, Spencer P.

    2013-09-01

    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.

  18. 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.

  19. Ionospheric holes - A review of theory and recent experiments

    NASA Technical Reports Server (NTRS)

    Mendillo, Michael

    1988-01-01

    Artificially induced ionospheric holes result from in situ injections of highly reactive molecules, which greatly enhance the chemical recombination rates between the ions and electrons found in the upper atmosphere. During the past decade, experiment-of-opportunity observations, theory and computer simulations have succeeded in establishing plasma-depletion experiments as a useful tool for probing the normal and disturbed behavior of the ionosphere. Ionospheric-hole experiments now focus on applications of the technique to laboratory-in-space investigations of various space plasma processes.

  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. Wave-like perturbations in the ionospheric F2-layer observed after the M s8.1 Samoa earthquake of September 29, 2009

    NASA Astrophysics Data System (ADS)

    Hegai, V. V.; Legen'ka, A. D.; Kim, V. P.; Georgieva, K.

    2011-06-01

    A study of the critical frequency foF2 variations after the large earthquake (M s = 8.1) which occurred on 29 September, 2009 in the region of Samoa Islands in the Pacific Ocean is carried out using data of the ionospheric station of Kwajalein. The epicenter of the earthquake was located at about 184 km southwest from Apia (the capital of West Samoa). It was found that wave-like perturbations of foF2 were observed for 3 h above the station (located approximately 3560 km northwest from the epicenter). The amplitude of the disturbance was as large as 20% of the average magnetic quiet day foF2 values. A comparison of the observed perturbations of foF2 with the ones detected at Stanford ionospheric station after the Alaska earthquake of 28 March 1964 (M s = 8.4) showed a close similarity of the wave-like perturbations of foF2 in both cases.

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

    NASA Astrophysics Data System (ADS)

    Harrison, Giles; Aplin, Karen; Rycroft, Michael

    2014-05-01

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

  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. Spatial and temporal evolution of 630.0 nm airglow enhancement during ionospheric heating experiments

    NASA Astrophysics Data System (ADS)

    Bernhardt, P. A.; Duncan, L. M.; Tepley, C. A.; Behnke, R. A.; Sheerin, J. P.

    Images of 630.00 nm enhancements have been recorded during the January, 1986 ionospheric heating campaign at Arecibo. The artificial airglow clouds convected eastward, vanished, and then reappeared at the zenith of the HF heater. Occasionally, the airglow patches are bifurcated. The structure and motion of the airglow clouds is an indication of the dynamic behavior of the modified ionosphere.

  7. 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.

  8. 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.

  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. Geometry of the 'exponential' middle ionosphere

    SciTech Connect

    Guliaeva, T.L.

    1984-01-01

    The required numbers of exponential sections fitting an electron density profile between the E- and F-layer peak heights of the ionosphere are considered. The range of the scale height variation and the angles of slope of the F region sub-peak profile are obtained under the different solar-geophysical conditions. 15 references.

  11. The ionosphere and upper atmosphere of Venus

    NASA Technical Reports Server (NTRS)

    Kumar, S.

    1975-01-01

    A summary is presented of current understanding of the upper atmosphere and ionosphere of Venus and its interaction with the solar wind, based on data from the Mariner 5 and Mariner 10 fly-bys and on far UV spectra obtained in rocket experiments. The major constituent of the upper atmosphere is CO2. Minor constituents include H, He, O, C, and CO and probably N2, Cl, and S. Although the thermal escape rate is only about 10,000/sq cm/sec, the H content in the exosphere appears to be highly variable. A prominent peak in the ionosphere profile near 140 km, appearing both on the day and nightside, is identified as an F(1) layer. An E layer and possibly an F(2) layer are present at 125 and 170 km, respectively. The dayside ionosphere may be explained in terms of the absorption of solar radiation by CO2, O, and He. The transport of ions from day to nightside may be important in the formation of the nightside ionosphere; an additional source may be needed to explain the nightside E layer. There is observational evidence that the solar wind interacts directly with the Venusian atmosphere, resulting in the formation of a bow shock. This may in part be explained by a balance at the ionopause between the solar wind ram pressure and the planetary plasma pressure.

  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. 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.

  14. 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.

  15. Ionospheric variability over Grocka during low solar activity conditions

    NASA Astrophysics Data System (ADS)

    Mitic, Maja; Cander, Ljiljana R.

    2008-12-01

    The variability of the critical frequency of F2 layer, foF2, over ionospheric station Grocka (44.48N, 20.31E) has been studied during the declining phase of solar cycle 23 from 2004 to 2006. The variability index was introduced to identify the daily and seasonal patterns characterizing the local mid-latitude ionosphere during quiet and disturbed geomagnetic conditions. In addition, the behaviour of the vertical total electron content values, vTEC, obtained from global positioning system (GPS) measurements in the surrounding area under these conditions is reported. The analysis shows a number of interesting features representative of the ionospheric variability relevant for ionospheric modelling as well as ionospheric propagation applications based on a single station approach.

  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. 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.

  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. Ionospheric Effects of Underground Nuclear Explosions

    NASA Astrophysics Data System (ADS)

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

    2010-12-01

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

  20. HICO and RAIDS Experiment Payload - Remote Atmospheric and Ionospheric Detection System (RAIDS)

    NASA Technical Reports Server (NTRS)

    Budzien, Scott

    2009-01-01

    The HICO and RAIDS Experiment Payload - Remote Atmospheric and Ionospheric Detection System (HREP-RAIDS) experiment will provide atmospheric scientists with a complete description of the major constituents of the thermosphere (layer of the Earth's atmosphere) and ionosphere (uppermost layer of the Earth's atmosphere), global electron density profiles at altitudes between 100 - 350 kilometers.

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

    NASA Astrophysics Data System (ADS)

    Cornely, P.; Daniell, R. E.

    2013-12-01

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

  2. Ionospheric irregularity physics modelling

    SciTech Connect

    Ossakow, S.L.; Keskinen, M.J.; Zalesak, S.T.

    1982-01-01

    Theoretical and numerical simulation techniques have been employed to study ionospheric F region plasma cloud striation phenomena, equatorial spread F phenomena, and high latitude diffuse auroral F region irregularity phenomena. Each of these phenomena can cause scintillation effects. The results and ideas from these studies are state-of-the-art, agree well with experimental observations, and have induced experimentalists to look for theoretically predicted results. One conclusion that can be drawn from these studies is that ionospheric irregularity phenomena can be modelled from a first principles physics point of view. Theoretical and numerical simulation results from the aforementioned ionospheric irregularity areas will be presented.

  3. Propagation of electromagnetic waves in a structured ionosphere

    SciTech Connect

    Murphy, T.

    1996-06-01

    The ionosphere is a birefringent medium which strongly affects the transmission of very high frequency (vhf) radio signals. These effects must be understood in detail if one wishes to look at the propagation of wide bandwidth coherent signals through the ionosphere. We develop a general perturbative solution of Maxwell`s equations for vhf signals propagating in the ionosphere, subject only to mild restrictions on the ionospheric structure. This solution can be extended to give the propagating field to any desired degree of precision. The case of a laminar ionosphere with harmonic waves is developed in greater detail, and we show how to calculate the ray path in this case. This solution is used to elucidate the effects of refraction on the phase of the signal, and we calculate the spatial- and frequency-coherence functions. The electric field for a laminar ionosphere without waves is analyzed to clarify the physical origins of the terms modifying the signal phase. We then calculate the solution in this case for the Appleton-Hartree model of the ionospheric dielectric function and express the result as a series in inverse powers of frequency. We conclude by calculating the ray path for a model ionosphere using the Appleton-Hartree dielectric function and a parabolic layer for the electron density.

  4. 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.

  5. Ionospheric plasma cloud dynamics

    NASA Technical Reports Server (NTRS)

    1976-01-01

    Measurements of the thermospheric neutral wind and ionospheric drift made at Eglin AFB, Florida and Kwajalein Atoll are discussed. The neutral wind measurements at Eglin had little variation over a period of four years for moderate magnetic activity (Kp 4); the ionospheric drifts are small. Evidence is presented that indicates that increased magnetic activity has a significant effect on the neutral wind magnitude and direction at this midlatitude station. The neutral wind at dusk near the equator is generally small although in one case out of seven it was significantly larger. It is described how observations of large barium releases can be used to infer the degree of electrodynamic coupling of ion clouds to the background ionosphere. Evidence is presented that indicates that large barium releases are coupled to the conjugate ionosphere at midlatitudes.

  6. Modeling the martian ionosphere

    NASA Astrophysics Data System (ADS)

    Matta, Majd Mayyasi

    The accessibility of the Martian atmosphere to spacecraft provides an opportunity to study an ionosphere that differs from our own. Yet, despite the half century of measurements made at Mars, the current state of the neutral atmosphere and its embedded plasma (ionosphere) remains largely uncharacterized. In situ measurements of the neutral and ionized constituents versus height exist only from the two Viking Landers from the 1970s. Subsequent satellite and remote sensing data offer sparse global coverage of the ionosphere. Thermal characteristics of the plasma environment are not well understood. Patchy crustal magnetic fields interact with the Martian plasma in a way that has not been fully studied. Hence, investigating the coupled compositional, thermal and crustal-field-affected properties of the ionosphere can provide insight into comparative systems at Earth and other planets, as well as to atypical processes such as the solar wind interaction with topside ionospheric plasma and associated pathways to escape. Ionospheric models are fundamental tools that advance our understanding of complex plasma systems. A pre-existing one-dimensional model of the Martian ionosphere has been upgraded to include more comprehensive chemistry and transport physics. This new BU Mars Ionosphere Model has been used to study the composition, thermal structure and dynamics of the Martian ionosphere. Specifically: the sensitivity of the abundance of ions to neutral atmospheric composition has been quantified, diurnal patterns of ion and electron temperatures have been derived self-consistently using supra-thermal electron heating rates, and the behavior of ionospheric plasma in crustal field regions was simulated by constructing a two-dimensional ionospheric model. Results from these studies were compared with measurements and show that (1) ion composition at Mars is highly sensitive to the abundance of neutral molecular and atomic hydrogen, (2) lighter ions heat up more efficiently than heavier ones and provide additional heating sources for cooler plasma, and (3) crustal field morphology affects plasma dynamics and structure at Mars in a way that is consistent with observations. Finally, model predictions of ion composition and plasma temperatures are provided for observations to be made by several instruments on board the upcoming 2013 MAVEN orbiter.

  7. 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.

  8. Ionospheric disturbances at the equatorial anomaly crest region during the March 1989 magnetic storms

    SciTech Connect

    Yinn-Nien Huang; Kang, Cheng )

    1991-08-01

    On March 6, 1989, the largest sunspot group since 1982 came into view as it moved out of the eastern limb of the Sun. It was highly active during March8-18, and a great many transient ionospheric and geomagnetic variations were triggered by this sunspot group. The intensive ionospheric observations at Lunping Observatory and Chungli Ionosphere Station during this period recorded 30 solar flares manifested as shortwave fade-outs, sudden frequency deviations, and solar flare effects and three storm sudden commencement (SSC)-tupe geomagnetic storms, among which the March 13 SSC-type geomagnetic storm triggered an unusually severe ionospheric disturbance. The ionospheric total electron content, the critical frequency of the F{sub 2} layer, f{sub o}F{sub 2}, and the virtual heights at given frequencies all show wavelike up-and-down oscillations of the ionosphere. This oscillatory ionospheric motion is explained as due to the compression and expansion of the plasmasphere.

  9. 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.

  10. Asymmetry of the Venus nightside ionosphere: Magnus force effects

    NASA Astrophysics Data System (ADS)

    Prez-de-Tejada, H.

    2008-11-01

    A study of the dawn-dusk asymmetry of the Venus nightside ionosphere is conducted by examining the configuration of the ionospheric trans-terminator flow around Venus and also the dawn-ward displacement of the region where most of the ionospheric holes and the electron density plateau profiles are observed (dawn meaning the west in the retrograde rotation of Venus and that corresponds to the trailing side in its orbital motion). The study describes the position of the holes and the density plateau profiles which occur at neighboring locations in a region that is scanned as the trajectory of the Pioneer Venus Orbiter (PVO) sweeps through the nightside hemisphere with increasing orbit number. The holes are interpreted as crossings through plasma channels that extend downstream from the magnetic polar regions of the Venus ionosphere and the plateau profiles represent cases in which the electron density maintains nearly constant values in the upper ionosphere along the PVO trajectory. From a collection of PVO passes in which these profiles were observed it is found that they appear at neighboring positions of the ionospheric holes in a local solar time (LST) map including cases where only a density plateau profile or an ionospheric hole was detected. It is argued that the ionospheric holes and the density plateau profiles have a common origin at the magnetic polar regions where plasma channels are formed and that the density plateau profiles represent crossings through a friction layer that is adjacent to the plasma channels. It is further suggested that the dawn-dusk asymmetry in the position of both features in the nightside ionosphere results from a fluid dynamic force (Magnus force) that is produced by the combined effects of the trans-terminator flow and the rotational motion of the ionosphere that have been inferred from the PVO measurements.

  11. 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.

  12. Proactive control of the metal-ceramic interface behavior of thermal barrier coatings using an artificial alpha-Al2O 3 layer

    NASA Astrophysics Data System (ADS)

    Su, Yi-Feng

    The reliability and life of thermal barrier coatings (TBCs) used in the hottest sections of advanced aircraft engines and power generation systems are largely dictated by: (1) the ability of a metallic bond coating to form an adherent thermally grown oxide (TGO) at the metal-ceramic interface and (2) the rate at which the TGO grows upon oxidation. It is postulated that a thin alpha-Al2O3 layer, if it could be directly deposited on a Ni-based alloy, will guide the alloy surface to form a TGO that is more tenacious and slower growing than what is attainable with state-of-the-art bond coatings. A chemical vapor deposition (CVD) process was used to directly deposit an alpha-Al2O3 layer on the surface of a single crystal Ni-bases superalloy. The layer was 150 nm thick, and consisted of small columnar grains (100 to 200 nm) with alpha-Al2O 3 as the major phase with a minute amount of theta-Al2O 3. Within 0.5 h of oxidation at 1150C, the resulting TGO formed on the alloy surface underwent significant lateral grain growth. Consequently, within this time scale, the columnar nature of the TGO became well established. After 50 h, a network of ridges was clearly observed on the TGO surface instead of equiaxed grains typically observed on uncoated alloy surface. Comparison of the TGO morphologies observed with and without the CVD-Al2O 3 layer suggested that the transient oxidation of the alloy surface was considerably reduced. The alloy coated with the CVD-Al2O 3 layer also produced a much more adherent and slow growing TGO in comparison to that formed on the uncoated alloy surface. The CVD-Al2O 3 layer also improved its spallation resistance. Without the CVD-Al 2O3 layer, more than 50% of the TGO spalled off the alloy surface after 500 h in oxidation with significant wrinkling of the TGO that remained on the alloy surface. In contrast, the TGO remained intact with the CVD-Al2O3 layer after the 500 h exposure. Furthermore, the CVD layer significantly reduced the degree of internal oxidation of Ta-rich areas which were present in the alloy as casting defects. The present study demonstrated that this artificial alpha-Al2O3 coating concept could be used as a novel means of favorably altering TGO growth and morphological characteristics, consequently increasing the oxidation resistance of Ni-based superalloys, and improving the reliability and life of next generation TBCs.

  13. 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.

  14. Using DORIS measurements for ionosphere modeling

    NASA Astrophysics Data System (ADS)

    Dettmering, Denise; Schmidt, Michael; Limberger, Marco

    2013-04-01

    Nowadays, most of the ionosphere models used in geodesy are based on terrestrial GNSS measurements and describe the Vertical Total Electron Content (VTEC) depending on longitude, latitude, and time. Since modeling the height distribution of the electrons is difficult due to the measurement geometry, the VTEC maps are based on the the assumption of a single-layer ionosphere. Moreover, the accuracy of the VTEC maps is different for different regions of the Earth, because the GNSS stations are unevenly distributed over the globe and some regions (especially the ocean areas) are not very well covered by observations. To overcome the unsatisfying measurement geometry of the terrestrial GNSS measurements and to take advantage of the different sensitivities of other space-geodetic observation techniques, we work on the development of multi-dimensional models of the ionosphere from the combination of modern space-geodetic satellite techniques. Our approach consists of a given background model and an unknown correction part expanded in terms of B-spline functions. Different space-geodetic measurements are used to estimate the unknown model coefficients. In order to take into account the different accuracy levels of the observations, a Variance Component Estimation (VCE) is applied. We already have proven the usefulness of radio occultation data from space-borne GPS receivers and of two-frequency altimetry data. Currently, we test the capability of DORIS observations to derive ionospheric parameters such as VTEC. Although DORIS was primarily designed for precise orbit computation of satellites, it can be used as a tool to study the Earth's ionosphere. The DORIS ground beacons are almost globally distributed and the system is on board of various Low Earth Orbiters (LEO) with different orbit heights, such as Jason-2, Cryosat-2, and HY-2. The last generation of DORIS receivers directly provides phase measurements on two frequencies. In this contribution, we test the DORIS capability for ionosphere VTEC modeling in combination with other space-geodetic observations. For this purpose, we derive DORIS VTEC values in a pre-processing step and integrate them in our ionosphere model. From the analysis of VCE we get information on the quality of DORIS for ionospheric modeling and on the consistency with other observation techniques.

  15. On spatial scales of seismo-ionospheric effects

    NASA Astrophysics Data System (ADS)

    Liperovskaya, Elena V.; Meister, Claudia-Veronika; Hoffmann, Dieter H. H.; Silina, Alexandra S.

    2014-05-01

    In the present work disturbances of the ionisation intensity in the E- and F-layers of the ionosphere a few days before earthquakes are investigated using data observed by ionospheric sounding stations in Japan, on Kamchatka, and of Middle Asia. Earthquakes with magnitudes M > 5 and depths H < 80 km are considered. The seismo-ionospheric effects are distinguished from seasonal, geomagnetic, 11-years, and 27-days Solar variations of the ionosphere. Days with high Solar and geomagnetic disturbances are excluded from the analysis. To reveal the statistical seismo-ionospheric effects, the superimposed epoches method is applied. It is shown that an earthquake precursor may be observed for seismic shocks with magnitudes M > 5, when the ionospheric station is situated at a distance from the seismic event not larger than the Dobrovolsky radius R = exp(M) km. It seems that the seismo-ionospheric effects are caused by the Earth crust near the station, and not by processes in the epicenter of the upcoming earthquake.

  16. Compliant layer bearings in artificial joints. Part 1: the effects of different manufacturing techniques on the interface strength between an elastomeric layer and a rigid substrate.

    PubMed

    Burgess, I C; Jones, E; Scholes, S C; Unsworth, A

    2008-08-01

    The premise that elastomeric materials could be used as one or more of the articulating components in both hip and knee prostheses was postulated first by Unsworth and co-workers. It was thought that such materials might have the capacity to mimic natural joint behaviour more closely than the more rigid bearing surfaces commonly in use. A more natural joint function in artificial joints should promote better tribology, with full fluid-film lubrication being the goal. Early tests showed that this objective could potentially be achieved with a judicious choice of materials and carefully controlled manufacturing techniques. This paper (Part 1 of a two-part series) describes and explains the techniques used to verify the material selection as well as to determine the most appropriate manufacturing procedure to obtain a strong and robust interface between the support and bearing material of the prosthesis. Two polycarbonate urethane (PU) materials with different hardness values (Corethane 80A and Corethane 75D) gave sufficient interfacial strength when moulded under optimum conditions. Corethane 80A was used as the soft bearing material while Corethane 75D provided the rigid backing component. Peel tests revealed strong interface bonds, varying with processing conditions between 350 and 862 N. Fourier transform infrared spectroscopy and micro-thermal analysis showed that a fusion bond over 30 microm thick formed at the interface. The results of the range of tests and analyses, which have been used in this study, have provided sufficient evidence to validate the process used to manufacture these components. PMID:18935802

  17. Ionospheric topside sounding.

    PubMed

    Calvert, W

    1966-10-14

    Over the past few years, the satellite topside sounders have significantly contributed to the understanding of the upper ionosphere. A great quantity of radio echo data has been accumulated, from which the ionospheric electrondensity distribution can be determined. The topside measurements of electron density essentially agree with similar measurements from the ground, except for an occasional 10-percent discrepancy near the peak of the ionosphere. While horizontal non-uniformity is a likely cause, this discrepancy has not yet been adequately explained. The electron-density scale heights measured at a constant altitude indicate both a higher temperature and a heavier mean ion mass at high latitudes. At low latitudes the topside measurements have shown the detailed latitudinal structure of the equatorial anomaly, demonstrating control by the geomagnetic field. A variety of electron-density irregularities have been studied. Most are greatly elongated along the magnetic field, and produce echoes either by lateral scattering, if they are thin, or by longitudinal ducting, if they are thick. Some of the thick irregularities are continuous between the hemispheres and support conjugate echo propagation. The topside sounders have revealed the complex structure of the ionosphere near the auroral zone and at higher latitudes. At night an east-west trough of greatly reduced electron density occurs equatorward of the auroral zone. At the auroral zone itself the electron density is high and quite variable, both in space and time. The electron density at the polar cap within the auroral zone is often uniform and smooth. Ionospheric irregularities are common in the area of the trough and the auroral zone. Among other satellites, the topside sounders have been used in various plasma studies involving the excitation and propagation of waves. These studies suggest that the ionosphere is an appropriate region for future plasma physics investigations, especially with rocket and satellite payloads designed specifically for that purpose. PMID:17810299

  18. 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.

  19. Structure of the Dayside Martian Upper Ionosphere from MEX MARSIS Topside Soundings

    NASA Astrophysics Data System (ADS)

    Morgan, D. D.; Gurnett, D. A.; Modolo, R.; Nielsen, E.; Nemec, F.; Duru, F.

    2011-12-01

    The MARSIS Active Ionospheric Sounder on board the Mars Express spacecraft takes radar soundings of the Martian topside ionosphere. The ionospheric trace typically has a hook or cusp shape near the maximum plasma frequency in the ionosphere, indicating that the sounding wave is traveling through a region where its frequency is just below the ionospheric maximum. This kind of structure can also occur at frequencies well below the maximum, where it is sometimes reduced to a discountinuous change in the slope of the ionospheric trace. Cusp-like features at sounding frequencies below the ionospheric maximum have been interpreted as indicative of ionospheric layers above the main layer, variously attributed to waves, instabilities, or the transition from a photochemical- to a transport-dominated ionosphere; previous work on the generation of this phenomenon has been inconclusive. In this study, we continue this work by studying the correlation of the frequency of the slope discontinuity to the maximum ionospheric plasma frequency. We use standard inversion techniques to study the altitude of the discontinuity as a function of the solar zenith angle. Finally, for a few long-lived cases, we follow the evolution of the cusp-like or discontinuous feature. These results will tell us whether this layer is caused by processes in photochemical equilibrium, whether the altitude and density of the high-altitude structure are correlated with properties of the ionosphere at lower altitudes, and how these structures evolve in density and altitude, thus giving us definitive information about the morphology and dynamics of the Martian upper ionosphere.

  20. The Geomagnetic Control Concept of The Ionospheric Long- Term Trends

    NASA Astrophysics Data System (ADS)

    Mikhailov, A. V.

    The geomagnetic control concept has been developed to explain long-term trends of the electron concentration in the F2 and E ionospheric regions. Periods with negative and positive foF2, hmF2 and foE trends correspond to the periods of increasing or decreasing geomagnetic activity with the turning points around the end of 1950s, 1960s, and 1980s where trends change their signs. Strong latitudinal and diurnal variations revealed for the foF2 and hmF2 trends can be explained by neutral composition, temperature and thermospheric wind changes. Particle precipitation is important in the auroral zone. The newly proposed concept proceeds from a natural origin of the F2-layer trends rather than an artificial one related to the greenhouse effect. Using the proposed method a very long-term foF2 and foE trends related with general increase of geomagnetic activity in the 20th century has been revealed for the first time. The firstly revealed relationship of the foE trends with geomagnetic activity is due to nitric oxide variations at the E-region heights. This "natural" relationship of the foE trends with geomagnetic activity breaks down around 1970 on many stations presumably due to chemical polution of the upper atmosphere. The increasing rate of rocket and satellite launchings in the late 1960s is considered as a reason.

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

    NASA Astrophysics Data System (ADS)

    Pradipta, Rezy

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

  2. Spatial and temporal evolution of 630. 0 nm airglow enhancement during ionospheric heating experiments

    SciTech Connect

    Bernhardt, P.A.; Duncan, L.M.; Tepley, C.A.; Behnke, R.A.; Sheerin, J.P.

    1986-01-01

    Images of 630.00 nm enhancements have been recorded during the January, 1986 ionospheric heating campaign at Arecibo. The artificial airglow clouds convected eastward, vanished, and then reappeared at the zenith of the HF heater. Occasionally, the airglow patches are bifurcated. The structure and motion of the airglow clouds is an indication of the dynamic behavior of the modified ionosphere. 5 refs., 8 figs.

  3. Large-scale plasma irregularities and airglow enhancements from ionospheric heating

    SciTech Connect

    Bernhart, P.A.; Rowland, H.

    1990-10-01

    Ionospheric modification with high power radio waves may generate plasma irregularities and airglow clouds. Large scale irregularities are produced in a convecting F-layer by a mechanism called the plasma-relaxation-oscillator. When a continuous beam of powerful electromagnetic waves heats the ionosphere, a cavity is produced by thermal pressure gradients. The cavity drifts under the influence of ambient electric fields causing the vertically-incident, radio beam to be refracted from the zenith. At some point, the cavity can no longer capture the beam and it returns to the zenith to form another cavity. This relaxation process repeats to yield irregularities on the scale of the heater beam diameter. Airglow enhancements are produced by energetic electrons accelerated out of the heated region. Large amplitude electrostatic waves may be excited by linear mode coupling, by parametric decay instabilities, and by strong plasma turbulence. This occurs near the point where the plasma frequency of the ionosphere matches wave frequency. The electrostatic waves accelerate ambient electrons to high enough energy to collisionally excite ambient oxygen atoms. Clouds of enhanced red-line (630.0 nm) and green-line (557.7 nm) emissions have been recorded with low-light-level imaging systems located at Arecibo, Puerto Rico. Comparison of the Imager data with data from the Arecibo incoherent scatter radar shows that artificial airglow clouds are physically tied to the density cavities and to regions of enhanced electrostatic waves by the earth's magnetic field lines. At currently available power levels (around 80 MW effective radiated power), HF modification yields 10-30% fluctuations in density and 10-100 Rayleigh enhancements in airglow intensity.

  4. MAGNUS FORCE EFFECTS IN THE ROTATING IONOSPHERES OF VENUS AND MARS

    NASA Astrophysics Data System (ADS)

    Perez de Tejada, H. A.; Lundin, R.

    2009-12-01

    Measurements conducted with the ORPA instrument of the Pioneer Venus Orbiter in the Venus ionosphere and with the ASPERA-3 instrument of the Mars Express spacecraft in the Mars ionosphere have been examined to identify effects related to the Magnus force that is produced by the combined presence of the directed motion of each planet's eroded upper ionospheric plasma and the rotating lower altitude region of their ionosphere. The overall response of the ionosphere to that force is a dawn-dusk asymmetry in the distribution of the upper nightside ionosphere as well as in the plasma wake that extends downstream from it. At Venus the high altitude ionospheric trans-terminator flow is displaced towards the dawn side consistent with the fast retrograde rotation of that planet's atmosphere. At Mars the velocity vectors derived from the ASPERA-3 measurements in that planet's ionosphere are examined to determine if there is a dawnward deflection in the distribution of the eroded ionospheric plasma consistent with the prograde rotational motion of the planet and its atmosphere. Calculations are carried out to estimate the angular deflection of the upper layers of the ionospheric plasma that is eroded by the solar wind in each planet.

  5. 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.

  6. Meteorological effects of ionospheric disturbances from vertical radio sounding data

    NASA Astrophysics Data System (ADS)

    Chernigovskaya, M. A.; Shpynev, B. G.; Ratovsky, K. G.

    2015-12-01

    We studied ionospheric disturbances caused by the wave-like processes in the middle atmosphere. The ionospheric data were obtained from continuous measurements with the DPS-4 vertical sounding ionosondes in Irkutsk and Norilsk over 2008-2010. The ionospheric disturbances were considered as deviations of the F2 layer peak density variations from the daily average values. We also used ECMWF ERA-Interim reanalysis data for the middle atmosphere dynamics analysis, and the Aura MLS data on the atmospheric temperature at the stratosphere and upper mesosphere heights obtained within the above period. The analysis allowed us to reveal periods of middle-scale wave motions in the stratosphere and lower mesosphere during winter seasons in the Northern Hemisphere. The wave motions observed in the study were associated with the jet streams at the stratosphere/lower mesosphere heights localized mainly between 50 and 80°N. The middle-scale waves in the stratosphere were compared with ionospheric disturbances over two ionosonde stations in Irkutsk and Norilsk. A noticeable increase in the wave activity was found at the F2 layer heights during the periods of stratospheric wave activity. For both stations, the maximal variability in the ionosphere F2 layer parameters was observed in winter with the minimal variability observed in summer. The summer-winter difference was more pronounced in the case of the high-latitude ionosonde in Norilsk.

  7. Ionospheric irregularities due to powerful HF radio transmissions

    NASA Astrophysics Data System (ADS)

    Fejer, J. A.

    1989-04-01

    It was known for some time that sufficiently powerful HF radio transmissions produce a great variety of ionospheric irregularities. Ionospheric modification facilities with effective radiated powers of the order of 100 MW directed toward the ionosphere were used for the study of such irregularities since 1970. Such man-made irregularities were employed to establish experimental scatter communications links. Very powerful short wave broadcast transmitters must also produce man-made irregularities which affect the ionospheric propagation of short waves. All aspects of the physical phenomena which play a role in the production of ionospheric irregularities by powerful HF transmissions, are discussed. These include thermal self-focusing of radio waves, formation of short-scale field-aligned irregularities by a thermal parametric instability in which the scattering of the HF pump wave by the irregularities into Langmuir waves plays an important role, and those parametric instabilities in which the ponderomotive force dominates over thermal forces. The latter two parametric instabilities can lead to the acceleration of electrons to energies of tens of electron volts. Such accelerated electrons can produce artificial airglow and also additional ionization which under certain conditions could be significant. In their strongly nonlinear stage parametric instabilities can lead to the formation of localized electron density depletions (cavitons) maintained by the ponderomotive force of Langmuir waves trapped in them.

  8. Electromagnetically Driven Plasma-Field Dynamics in Modified Ionosphere

    NASA Astrophysics Data System (ADS)

    Kochetov, Andrey; Terina, Galina

    Under sounding of an artificial ionospheric turbulence by short probing radio pulses of ordinary polarization the two types of scattered signals were observed: a "caviton" signal (CS) and a "plasma" signal (PS), which appeared with the heating transmitter switching on and disap-peared after its switching off (G.I. Terina J. Atm. Terr. Phys, 57, 1995, 273, Izv. VUZov, Radiofizika, 39, 1998, 203). The scattered signal of PS type was revealed also after the heating switching off. It was called an "aftereffect plasma signal" (AEPS) (G.I. Terina Izv .VUZov, Radiofizika, 43, 2000, 958). This signal had large time and spatial delays and appeared mostly when corresponding PS had envelope fluctuations. The aftereffect phenomenon was expressed at time on CS by amplitude increasing at once after the heating transmitter turning off. The theoretical model of this phenomenon is proposed in and some peculiarities of the aftereffect phenomena of the scattered signals in modified ionospheric plasma are considered and discussed. For theoretical interpretation of the characteristics of CS and AEPS the numerical solution of nonlinear Shrüdinger equation (NSE) with driven extension were carried out in inhomogeneous plasma layer with linear electron density profile (A.V. Kochetov, V.A. Mironov, G.I. Terina, Adv. Space Reseacrh, 29, 2002, 1369) and for the one with prescribed density depletion (and A.V. Kochetov, G.I. Terina, Adv. Space Reseacrh, 38, 2006, 2490). The simulation results obtained for linear inhomogeneous plasma layer and for plasma one with density depletion al-low us to interpret the aftereffect of CS and PS qualitatively. The field amplitude increase at relaxation stage displayed at calculations allows us to interpret of CS aftereffect. The large time delays of AEPS can be explained as a result of powerful radio waves trapping in the forming at the plasma resonance regions density depletions (E. Mjøhus, J. Geophys. Res. 103, 1998, 14711; B. Eliasson and L. Stenflo, J. Geophys. Res., 113, 2008, A02305). It should be noted that PS and CS are analogous to different components of the stimulated electromagnetic emis-sion (SEE): "broad continuum" (BC) and narrow continuum" (NC) accordingly (see, e.g. (B. Isham, C. La Hoz, M.T. Rietveld, T. Hagfors, T.B. Leyser, Phys. Rev. Lett., 83, 1999, 2576)). AEPS is corresponded to Diagnostic SEE at the relaxation stage. The work was supported in part by RFBR grant 09-02-01150-a.

  9. 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.

  10. Remote sensing of ionosphere by using ultraviolet and visible emissions

    SciTech Connect

    Meng, C.I.; Huffman, R.E.; Skrivanek, R.A.; Strickland, D.J.; Daniell, R.E.

    1986-01-01

    The ability to remotely sense ionospheric conditions for improved operation of communications and radar systems has been a long term goal of some DOD programs. This capability now appears to be possible through improvements in computer models of the ionosphere and in UV remote-sensing methods. The approach is to use passive ultraviolet optical measurements and in-situ ion-density measurements as inputs to a comprehensive ionospheric model, which will calculate the electron-density measurements as inputs to a comprehensive ionospheric model which will calculate the electron-density profile. A novel feature of this approach is the use of naturally occurring airglow and auroral ultraviolet radiation. This method can be used for the mid-latitude day ionosphere (90 to 800 km) and the night auroral E layer. Eventually, extensions of the technique will cover the night mid-latitude as well. The remote-sensing measurement can also be used to locate regions of ionospheric irregularity, and hence probable phase scintillation, in both equatorial and polar-cap regions and to locate the real-time position of the auroral-oval particle precipitation.

  11. Wet model of Saturn's ionosphere: Water from the rings

    NASA Technical Reports Server (NTRS)

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

    1984-01-01

    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.

  12. 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

  13. Ionospheric effects on GPS positioning

    NASA Astrophysics Data System (ADS)

    Gwal, A. K.; Gwal, A.; Wahi, R.; Dubey, S.

    Ionospheric scintillation is rapid variation in the amplitude and phase of radio signals caused by irregularities in the ionosphere. Ionosphere contains large amplitude variations over spatial scales from few cms to 100's of kms. VHF- UHF communications as well as automated navigation and precision positioning via GPS are affected by scintillations. Ionospheric effects are the major constraints for GPS precise positioning over long base lines. The ionosphere affects the GPS receiver by degrading the signal performance, in some cases causing loss of carrier lock and by degrading the accuracy of differential corrections. Scintillations do not have major effect on mid latitude regions, but low latitude scintillations are the greatest cause of GPS position errors. In this present work we study the effect of ionospheric scintillations on GPS signal at low latitude station , Chiang Rai , Thailand.

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

    PubMed Central

    2012-01-01

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

  15. 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

  16. The Maunder Minimum Ionosphere

    NASA Astrophysics Data System (ADS)

    Smithtro, C. G.; Sojka, J. J.

    2004-12-01

    The Maunder Minimum epoch, from 1645 to 1715 A.D. was characterized by a near absence of sunspots. Studies of cosmogenic isotopes and Sun-like stars suggest that solar chromospheric and coronal emissions during this period were significantly lower than contemporary solar minima. To study the effect of such a reduction on the Earth's upper atmosphere, we employ a 1-D global average ionosphere and thermosphere model that accounts for the photon flux between 3 and 360 nm. Within the ionosphere, an unexpected transition occurs as the irradiance falls below normal solar minimum levels. The concentration of O+ ions decreases rapidly relative to the other ions, such that NO+ becomes the dominant F-region ion. The state of the underlying thermosphere, particularly the neutral gas temperature, is largely responsible for this behavior.

  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. 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 μm; at voltages of 50-1000 V, the artificial muscle contracted and deflected 1.0 mm. The maximum force response is 20 μN at 1000 V.

  19. Study of Ionospheric Storms Using Global Assimilative Ionospheric Models

    NASA Astrophysics Data System (ADS)

    Pi, X.; Butala, M.; Mannucci, A. J.; Wilson, B. D.; Komjathy, A.; Wang, C.; Rosen, G.; Schunk, R. W.; Scherliess, L.; Eccles, V.; Gardner, L. C.; Sojka, J. J.; Zhu, L.

    2014-12-01

    Under the development of the Multimodel Ensemble Prediction System (MEPS) for ionosphere-thermosphere-electrodynamics, several global assimilative ionospheric models (GAIMs) have been applied to studies of ionospheric storms during space weather disturbances. The GAIMs are physics-based four-dimensional models and capable of assimilating a variety of ground-based and spaceborne observations on global scales. In this presentation, we will discuss various data assimilation techniques and data sources used in GAIMs to capture ionospheric perturbations. The results of GAIM studies of ionospheric disturbances during the April 2011 and March 2013 geomagnetic storms, respectively, will be presented. The two storms were driven by space weather perturbations caused by high speed stream (HSS) and coronal mass ejection (CME) events, respectively. With distinguished solar wind characteristics these two types of Sun-Earth connection events caused different variations in the magnetosphere-ionosphere-thermosphere system. In the assimilative ionospheric modeling, GPS data from hundreds of globally-distributed ground stations and six COSMIC satellites are assimilated into GAIMs. Both storm-time and quiet-time ionosphere have been reproduced to reveal disturbance patterns and to help investigate the differences in the M-I-T coupling processes driven by the two types of storms.

  20. 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.

  1. 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.

  2. 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

  3. Ionospheric modification using relativistic electrons beams

    SciTech Connect

    Banks, P.M.; Fraser-Smith, A.C.; Gilchrist, B.E.

    1990-10-01

    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 unionized upper atmosphere. In this paper we investigate the consequences of firing a pulsed 1 A, 5 Mev electron beam downwards into the upper atmosphere. 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 - 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.

  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. Vertical characteristics of midlatitude E and F region ionospheric drifts during disturbed conditions..

    NASA Astrophysics Data System (ADS)

    Boska, Josef; Kouba, Daniel; Koucka Knizova, Petra; Potuznikova, Katerina

    2015-04-01

    Modern HF digisonde DPS-4 D (Digisonde Portable Sounder), which is in operation at the Pruhonice observatory of the Institute of Atmospheric Physics, Prague (IAP) from 2004, enables us to carry out standard ionospheric sounding and ionospheric drifts measurements. Using standard mode of automatic drift (autodrift mode) measurements the velocity of the F region drifts is usually determined in the vicinity of the peak of the electron density profile (N(h) profile). Since 2005 we are also measuring ionospheric drifts at the heights of the ionospheric E region. This new experimental arrangement makes possible to study vertical changes and profiles of the ionospheric drift velocity in two different ionospheric regions. From E region within the altitudinal interval of 90-150 km to F region in altitudes from 150 km up to height of the maximum electron density profile N(h). This paper present the results of the analysis of the plasma drifts velocity in two different ionospheric regions observed under quiet geomagnetic and ionospheric conditions and especially during ionospheric spread F conditions. These spread F conditions are often observed in the ionosphere as effect of travelling ionopheric disturbances TIDs. The presence of this TIDS can be detected from the F layer isoelectrondensity contours. The spread F conditions are often present also under moderate-to-intense ionospheric and geomagnetic storm conditions. Our results shows, that behavior of Es layer drifts can be different than drifts in E-layer. During winter geomagnetic storm -more dramatic increasing of all drift velocities components was observed (50 - 100 m/s vertical drift component). Different behaviour ionospheric drifts at the heights intervals 90 - 110 km and 110 - 130 km was observed during winter storm. Significant height changes of the drift velocity height profile in the interval of heights 90 - 130 km during winter event was observed. Our results shows that behavior of Es layer drifts can be different than drifts in E-layer. All components of the ionospheric F region drift velocity, measured during medium and strong geomagnetic events are strongly disturbed by storm conditions. Observed drift velocity components reached during strong storm values ~100- 150 m/s during summer and ~500 m/s during winter storms.

  6. New observations of HF-induced optical emissions from the ionospheric E region

    NASA Astrophysics Data System (ADS)

    Pedersen, T.; Mishin, E.; Esposito, R.

    2009-06-01

    A new independent instance of highly localized artificial 557.7 nm optical emissions induced by high-power HF waves incident upon a precipitation-produced E layer at High Frequency Active Auroral Research Program (HAARP) confirms the original discovery of this phenomenon and adds a number of new observational facts. The features are excited by O mode transmissions but not X mode transmissions and disappear entirely during deliberate off periods. The specific transmitter pulsing period does not appear to be a critical factor, ruling out ULF resonances as a possible mechanism. The observed locations of the enhanced emissions are consistent with a small number of long-lived inhomogeneities traveling steadily across the field of view over several minutes. These persistent regions are preferentially excited even at a small fraction of peak power well away from the beam center and can reappear along the same trajectory after gaps of more than 1 min. The absence of any detectable enhancements in directly coincident 630.0 nm data or side-looking 557.7 and 630.0 nm images focused on the F region portion of the field line conclusively locates these artificial emissions in the ionospheric E region. We suggest possible hypotheses that might explain the new observations and the earlier results.

  7. Ionospheric effects on GPS positioning

    NASA Astrophysics Data System (ADS)

    Dubey, Smita; Wahi, Rashmi; Gwal, A. K.

    2006-01-01

    Ionospheric scintillation results from a single frequency global positioning system (GPS) receiver have been presented in this paper. Ionospheric scintillation is rapid variation in the amplitude and phase of radio signals caused by irregularities in the ionosphere. Ionosphere contains large amplitude variations over spatial scales from few cm to 100s of km. It is observed that VHF UHF communications as well as automated navigation and precision positioning via GPS are affected by scintillations. Scintillations do not have major effects on mid latitude regions, but low latitude scintillations are the greatest cause of GPS position errors. In the present work, we study the effect of ionospheric scintillations on GPS signal at low latitude station, Chiang Rai, Thailand. The data were analyzed from January 2001 to December 2001. Results show that scintillation has a significant problem at this latitude and position error increases during active scintillation condition, which causes loss of lock on several satellites.

  8. Tohoku earthquake shook the ionosphere

    NASA Astrophysics Data System (ADS)

    Balcerak, Ernie

    2011-08-01

    The giant 11 March 2011 magnitude 9 Tohoku earthquake not only shook the Earth and caused devastating tsunamis but also rattled the ionosphere, according to a new study. The surface seismic waves and tsunamis triggered waves in the atmosphere. These atmospheric waves propagated upward into the ionosphere, creating ripples in ionized gas nearly 350 kilometers above the Earth. Liu et al. measured these disturbances, called seismotraveling ionospheric disturbances (STID), using GPS receivers in Japan. The first disturbance appeared as a disk-shaped increase in electron density in the ionosphere about 7 minutes after the earthquake. Sequences of concentric waves of increased electron density then traveled from the STID center. Similar ionospheric disturbances have been observed following other earthquakes, but these were the largest ever seen, the authors report. (Journal of Geophysical Research-Space Physics, doi:10.1029/2011JA016761, 2011)

  9. Generation of cyclotron harmonic waves in the ionospheric modification experiments

    SciTech Connect

    Janabi, A.H.A.; Kumar, A.; Sharma, R.P.; Tripathi, Y.K. . Centre for Energy Studies)

    1994-02-01

    In the present paper, the parametric decay instability of the pump X-mode into electron Bernstein wave (EBW) near second harmonics of electron cyclotron frequency and IBW at different harmonics ([omega] < n[omega][sub ci];n = 2, 3, 4) is examined. Expressions are derived for homogeneous threshold, growth rate and convective threshold for this instability. Applications and relevances of the present investigation to ionospheric modification experiment in the F-layer of the ionosphere as well as during intense electron cyclotron resonance heating in the upcoming MTX tokamak have been given.

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

    NASA Astrophysics Data System (ADS)

    Wendel, JoAnna

    2014-08-01

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

  11. Artificial Intelligence.

    ERIC Educational Resources Information Center

    Waltz, David L.

    1982-01-01

    Describes kinds of results achieved by computer programs in artificial intelligence. Topics discussed include heuristic searches, artificial intelligence/psychology, planning program, backward chaining, learning (focusing on Winograd's blocks to explore learning strategies), concept learning, constraint propagation, language understanding…

  12. 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 ...

  13. 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

  14. 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…

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

    NASA Astrophysics Data System (ADS)

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

    2014-08-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-09-01

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

  17. Ionosphere Electrodynamics and its Influence on the Main Ionospheric Trough and Equatorial Ionization Anomaly

    NASA Astrophysics Data System (ADS)

    Klimenko, M. V.; Klimenko, V. V.; Bryukhanov, V. V.

    2007-12-01

    In the given work the numerical simulation results of global distributions of the zonal current in the Earth's ionosphere and the critical frequency of the F2-layer of the ionosphere are presented. The calculations are executed with use of the Global Self-consistent Model of the Thermosphere, Ionosphere and Protonosphere (GSM TIP) developed in West Department of IZMIRAN and added by the new block of calculation of the electric field of the dynamo and magnetospheric origin. The calculations are executed for quiet geomagnetic conditions during various seasons and levels of Solar activity without taking into account the electric field, and also with taking into account only dynamo-field or superposition of a dynamo-field and magnetospheric convection field with and without taking into account the shielding by field aligned currents of the second zone. It is shown, that the Main Ionospheric Trough is formed without taking into account the electric field as a result of joint action of processes of ionization, recombination and diffusion. The account of the dynamo-field alters this trough, and magnetospheric convection completes formation of the trough. Equatorial Ionization Anomaly is not formed in the absence of the electric field. The main part in formation of Equatorial Ionization Anomaly plays a dynamo-field. Zonal component of dynamo-field together with diffusion of thermal plasma along geomagnetic field lines under action of the pressure gradients in the Earth's gravity field cause a fountain effect at geomagnetic equator. Equatorial Electrojet is formed by the dynamo-field. Magnetospheric convection at presence of shielding weakly influences on behavior of Equatorial Electrojet. Without the shielding of magnetospheric convection electric field by Alfven layer electric field the magnetospheric convection influence on Equatorial Electrojet becomes stronger. It occurs during magnetospheric disturbances when the shielding is broken due to fast changes of the field aligned currents of the first zone. The Auroral Electrojet is formed mainly by magnetospheric convection electric field and depends on conditions of shielding and conductivity of a high-latitude ionosphere which depends on photoionization and ionization by fluxes of precipitating particles. There are presented the seasonal, Solar-cyclic and UT-variations of Equatorial and Auroral Electrojets, Main Ionospheric Trough and Equatorial Ionization Anomaly.

  18. The polar-ionosphere phenomena induced by high-power radio waves from the spear heating facility

    NASA Astrophysics Data System (ADS)

    Blagoveshchenskaya, N. F.; Borisova, T. D.; Kornienko, V. A.; Janzhura, A. S.; Kalishin, A. S.; Robinson, T. R.; Yeoman, T. K.; Wright, D. M.; Baddeley, L. J.

    2008-11-01

    We present the results of experimental studies of specific features in the behavior of small-scale artificial field-aligned irregularities (AFAIs) and the DM component in the spectra of stimulated electromagnetic emission (SEE). Analysis of experimental data shows that AFAIs in the polar ionosphere are generated under different background geophysical conditions (season, local time, the presence of sporadic layers in the E region, etc.). It is shown that AFAIs can be excited not only in the F region, but also in thick sporadic E s layers of the polar ionosphere. The AFAIs were observed in some cycles of heating when the HF heater frequency exceeded the critical frequency by 0.3-0.5 MHz. Propagation paths of diagnostic HF radio waves scattered by AFAIs were modelled for geophysical conditions prevailing during the SPEAR heating experiments. Two components, namely, a narrow-banded one with a Doppler-spectrum width of up to 2 Hz and a broadband one observed in a band of up to 20 Hz, were found in the sporadic E s layer during the AFAI excitation. Analysis of the SEE spectra shows that the behavior of the DM component in time is irregular, which is possibly due to strong variations in the critical frequency of the F 2 layer from 3.5 to 4.6 MHz. An interesting feature observed in the SPEAR heating experiments is that the generation of the DM component was similar to the excitation of AFAIs when the heater frequency was up to 0.5 MHz higher than the critical frequency.

  19. The Jovian ionospheric E region

    NASA Astrophysics Data System (ADS)

    Kim, Y. H.; Fox, J. L.

    1991-02-01

    A model of the Jovian ionosphere was constructed, that includes direct photoionization of hydrocarbon molecules. A high-resolution solar spectrum was synthesized from Hinteregger's solar maximum spectrum (F79050N), and high-resolution cross sections for photoabsorption by H2 bands in the range 842 to 1116 A were constructed. Two strong solar lines and about 30 percent of the continuum flux between 912 and 1116 A penetrate below the methane homopause despite strong absorption by CH4 and H2. It is found that hydrocarbons (mainly C2H2 are ionized at a maximum rate of 55/cu cm per sec at 320 km above the ammonia cloud tops. The hydrocarbon ions produced are quickly converted to more complex hydrocarbon ions through reactions with CH4, C2H2, C2H6, and C2H4. It is found that a hydrocarbon ion layer is formed near 320 km that is about 50 km wide with a peak density in excess of 10,000/cu cm.

  20. Approaches to studying the multiscale ionospheric structure using nanosatellites

    NASA Astrophysics Data System (ADS)

    Chernyshov, A. A.; Chugunin, D. V.; Mogilevsky, M. M.; Moiseenko, I. L.; Ilyasov, A. A.; Vovchenko, V. V.; Pulinets, S. A.; Klimenko, M. V.; Zakharenkova, I. E.; Kostrov, A. V.; Gushchin, M. E.; Korobkov, S. V.

    2016-01-01

    Permanent variation in parameters affecting the key characteristics of the auroral ionosphere hinders the creation of a sufficiently accurate model for practical application within classical approaches describing quasi-stationary phenomena. The fractal approach for describing the properties of plasma in the auroral region has the following advantages: the results are versatile and the emergence of self-similar structures is nature-independent. Due to the self-similarity and fractality of ionospheric structures, it will suffice to have a few measurements within a characteristic scale; therefore, it is necessary to obtain a series of simultaneous measurements at intervals of tens of meters to tens of kilometers to describe the spatial and temporal distribution of inhomogeneities in the ionospheric plasma. Small and relatively low-cost satellites (the socalled cubesats) are supposed to be used to check whether the fractal approach can be applied to study the inhomogeneous structure of the ionosphere, including with artificial heating. The satellites should be located at different distances from each other to span the scales ranging from the inertial length of electrons to the inertial length of O+ ions. For each satellite, it is supposed to measure the variations in plasma density and electric and magnetic fields.

  1. Ionospherically reflected proton whistlers

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  2. Ionospheric and magnetospheric plasmapauses'

    NASA Technical Reports Server (NTRS)

    Grebowsky, J. M.; Hoffman, J. H.; Maynard, N. C.

    1977-01-01

    During August 1972, Explorer 45 orbiting near the equatorial plane with an apogee of about 5.2 R sub e traversed magnetic field lines in close proximity to those simultaneously traversed by the topside ionospheric satellite ISIS 2 near dusk in the L range 2-5.4. The locations of the Explorer 45 plasmapause crossings during this month were compared to the latitudinal decreases of the H(+) density observed on ISIS 2 near the same magnetic field lines. The equatorially determined plasmapause field lines typically passed through or poleward of the minimum of the ionospheric light ion trough, with coincident satellite passes occurring for which the L separation between the plasmapause and trough field lines was between 1 and 2. Vertical flows of the H(+) ions in the light ion trough as detected by the magnetic ion mass spectrometer on ISIS were directed upward with velocities between 1 and 2 kilometers/sec near dusk on these passes. These velocities decreased to lower values on the low latitude side of the H(+) trough but did not show any noticeable change across the field lines corresponding to the magnetospheric plasmapause.

  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. Precision correction of radioastronomical polarization measurements for ionospheric faraday rotation

    SciTech Connect

    Minter, A.; Spangler, S.

    1992-01-01

    A widely used model for ionospheric faraday rotation is the model contained within the AIPS package. This model is based on a phenomenological model by Y.T. Chiu and reduces the electron density profile of the ionosphere into a slab of constant height, thickness and density near the observing site. The height of the slab is taken to be the height of the F2 layer. The rotation measure due to the ionosphere is then calculated using a simple dipole for the Earth's magnetic field. The accuracy of the Chiu model is claimed to be 20 percent but it is also noted that the model performs poorly during the daytime around solar maximum. Hence, a model that reproduces the electron density profile and is capable of performing well at solar maximum is desirable. The International Reference Ionosphere (IRI) meets these criteria. Comparison of these two models against measured values of the total electron content (TEC) have been carried out at high and low solar activity with sunspot number being the only geophysical parameter entered into the models. At low solar activity the models essentially have the same distribution around the real TEC values with an error of about 35 percent of the observed TEC value. At high solar activity, however, the IRI model is much better than the AIPS model, with an error of about 20 percent compared to an error of about 30 percent for AIPS. The error can be reduced further, to about 15 percent, in the IRI model by specifying the peak plasma frequency of the F2 layer. These errors in the value of the TEC are expected to be approximately the same as those in the rotation measure due to the ionosphere. In calculating the rotation measure in the ionosphere, there can be differences as great as 2 to 3 radians/m[sup 2] between the two models.

  5. Studies of the high latitude ionospheric convection

    NASA Astrophysics Data System (ADS)

    Drake, Kelly Ann

    The electrostatic potential distribution in the high latitude ionosphere is representative of the response of the ionosphere magnetosphere system to drivers in the solar wind and conditions in the interplanetary medium. The cross polar cap potential drop, used as a single parameter to describe the global distribution of electrostatic potential, often serves as an input driver for various magnetospheric and space weather models. For a given solar wind condition the cross polar cap potential drop derived from satellite measurements of the electric field, or ion drift in the ionosphere, are observed to have a significant variation, often on the order of thirty percent or greater. Such a large variability could influence the uncertainty of results from models that utilize this electrostatic potential drop as an input, so a further understanding of the sources and organization of these uncertainties will improve the specification itself and the confidence limits of the observations. Sources of this variability are investigated using two years (2000-2001) of ionospheric plasma flow data provided by the DMSP F13 and F15 satellites to calculate the cross polar cap potential drop, along with solar wind data from the ACE satellite in order to explore the behavior of this potential in response to a wide range of interplanetary magnetic field (IMF) conditions during southward IMF (BZ ? 0). A variety of IMF conditions are examined to show how the stability of the IMF and the solar wind speed over both short and long time periods affects variations in the cross polar cap potential drop. The most interesting discovery is that, even during steady state IMF conditions, the largest amount of variability is caused by the displacement of the satellite track with respect to the extrema in potential at the center of the two convection cells in the high-latitude region, especially when the displacement is caused by substorm activity. Included is a study of the average properties of the electrostatic potential drop and its relationship to particle precipitation boundaries across the ionospheric projection of the low latitude boundary layer and the interplanetary electric field.

  6. 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.

  7. 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 2π 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).

  8. A post-Pioneer Venus reassessment of the Martian dayside ionosphere as observed by radio occultation methods

    NASA Technical Reports Server (NTRS)

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

    1990-01-01

    Global characteristics of the dayside ionosphere of Mars were investigated by reanalyzing the electron-density dayside altitude profiles obtained by Mariners 4, 6, 7, and 9 and the Viking 1 and 2. The properties of both the electron density peaks and the topside profiles with the behavior expected for a Chapman layer in the Mars ionosphere were compared with those observed at Venus with the Pioneer Venus. The results yield an improved picture of the solar zenith angle dependences of both the peaks and the scale heights of the ionosphere of Mars, and their comparison with Venus at solar minimum. It is shown that, under similar conditions where the incident solar wind dynamic pressure exceeds the peak ionospheric thermal pressure, the Martian dayside ionosphere peaks at higher altitudes in the flanks and has a greater scale height. Thus, Martian and Venusian ionospheres would present different obstacles to solar wind.

  9. 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.

  10. Space weather and the Earth ionosphere from auroral zone to equator

    NASA Astrophysics Data System (ADS)

    Biktash, L.

    2007-08-01

    Space weather conditions, geomagnetic variations, virtual ionospheric height and the critical frequency foF2 data during the geomagnetic storms are studied to demonstrate relationships between these phenomena. We examine the solar wind conditions and the auroral equatorial ionosphere response to illustrate what kind of solar wind parameters during the geomagnetic storms leads to short-term variations of the critical frequency foF2 and virtual height at the Earth ionosphere from the auroral zone to the equator. Model simulations as disturbed ionospheric wind dynamo do not allow explaining a significant part of the experimental data. Additional investigations of the ionospheric characteristics are required to clear up the origin of the short-term equatorial ionospheric variations. The critical frequency foF2 and virtual heights observed by the ionosondes are good indicators of the true layer heights and electron concentration and may provide information about the equatorial ionosphere dynamics. Intensive magnetospheric and ionospheric currents during geomagnetic storms disturb the quiet ionosphere and cause the observed short-term variations of the ionospheric characteristics. The ionosheric wind dynamo is considered as an important and the main mechanism in generation of ionospheric electric currents and fields. The disturbed ionospheric wind dynamo can be the generator of the equatorial ionospheric electric currents during geomagnetic storms in the aftermath of strong auroral heating. The magnetospheric electric field directly penetrating into the low-latitude ionosphere can be another source of electric field. During disturbed space weather conditions magnetospheric electric fields disturb the auroral ionosphere forming auroral electrojets and by the high-latitude electric field and termospheric disturbances can penetrate to the equatorial ionosphere. That is the reason the equatorial ionospheric electric field variations like geomagnetic variations are complex and result of superposition of different disturbing agents. Numerous studies present the experimental and theoretical relations between the solar wind, auroral ionosphere and geomagnetic variations. However, the equatorial ionosphere has been assumed to be free from the influence of the auroral electric fields. We study 5-min ionospheric variations using the first Western Pacific Ionosphere Campaign (1998 - 1999) observations, 5-min interplanetary magnetic field (IMF) and 5-min auroral electrojets data during a geomagnetic storm. The ionospheric 5-min variations at the equatorial stations which allow calculating in detail time delays of the auroral and equatorial ionospheric phenomena are scantily known. These data demonstrate that the auroral and the equatorial ionospheric phenomena are developed practically simultaneously. We suppose that these ionospheric phenomena are due space weather conditions and interaction between electric fields of the auroral and the equatorial ionosphere during geomagnetic storms. It is shown that the low-latitude ionosphere dynamics during these storms was defined by the southward direction of the Bz-component of the interplanetary magnetic field. A southward IMF produces the Region 1 and Region 2 the field-aligned currents (FAC) and polar electrojet current systems. We assume that the short-term ionospheric variations during geomagnetic storms can be explained mainly by the electric field of the FAC. The electric fields of the field-aligned currents can penetrate throughout the mid-latitude ionosphere to the equator and may serve as a coupling agent between the auroral and the equatorial ionosphere. We show that the equatorial ionosphere is a very sensitive indicator of the solar wind conditions and geomagnetic storms. Nowadays geomagnetic storms can be presented as a measure of energy transfer from the solar wind to the magnetosphere. Its magnitude is inevitably a function of the solar wind properties, the state of the magnetosphere, and the physical processes involved in the solar wind-magnetosphere interaction. Ionosphere effects of the solar wind is much complex. It is very difficult to separate the agents forming ionospheric disturbances during geomagnetic storms. It is considered that the storm wind driven electric fields are responsible for the larger amplitudes and longer lifetimes of the drift perturbations following sudden decreases in convection compared to those associated with sudden convection enhancements. In addition to these reasons we suppose that day-time and night-time equatorial ionosphere have to respond to westward and eastward auroral electrojets and the field-aligned currents by the different way while large-scale internal gravity waves and changes in neutral composition and in neutral wind system have to show the same effect in sign and there are problems to explain positive ionospheric storms. Furthermore, from the presented geomagnetic storms which AU and AL indices have very different amplitudes (nighttime auroral electrojets are much stronger daytime ones AL/AU5) and yet it is impossible from models to take account theses effects from termospheric models. It should be noted that amplitudes of AU and AL very variable during different storms, so there are different the IMF Bz and By patterns of auroral electrojets and related the field-aligned currents. Numerical modeling of auroral electrojets during geomagnetic disturbances effects of FAC as well as the polar cap potential drop difference in the auroral electrojet distribution and precipitation of high-energy auroral particles are considered. We suppose to explain of substorm effects in foF2 it is not enough to involve local processes but it is necessary to consider existential distribution of all parameters of near-Earth plasma. In our cases the IMF Bz and Joule heating can show the same effect to decrease of foF2 variations but quick foF2 depression and its correlation the negative the IMF Bz duration seems to show the field-aligned current effect on the equatorial ionosphere. The examples demonstrated in our study show that the strong auroral electrojets were formed by coupling of the solar wind with the magnetosphere when the Bz turned southward and the solar wind velocity increased. At the same time the equatorial night-time ionosphere parameters showed the short-term variations in the virtual ionospheric height and foF2. For example, the ionospheric heights and the critical frequency foF2 at low latitudes were very different in periods when the Bz-component turns to north (the quiet day conditions) and when Bz-component turns on south (the main phase of magnetic storms). Distinction between the quiet and disturbed periods in the heights reached values up to 150 km and more. It is also evident from these examples that the solar wind controls not only the auroral ionosphere but the eqtatorial ionosphere too. Time delay around 40 min between the Bz IMF and the equatorial ionospheric variations during the geomagnetic storms allows us to make this assumption. The latitudinal and the longitudinal extent the auroral electrojets and its movements are well determined by the IMF Bz. These conditions and a good conductivity of the night ionosphere allow the auroral electric fields move closer to the equator. In consequence, the auroral electric fields penetrate to the equator and an additional night-time current system can form at the equatorial ionosphere and change the true layer heights and electron concentration. This current system may be linked to the Region II field-aligned currents (FAC) during the westward auroral electrojet formation at the night ionosphere. It is well known that the field-aligned currents are closely connected with the auroral electrojets and the DP systems. These currents location and intensity are defined by the solar wind conditions. If the electric fields from FAC of Region II can penetrate through the midlatitudes to the low-latitude ionosphere and create the eastward equatorial electric field there then this electric field can decrease the nighttime equatorial electrojet current and increase the ionospheric plasma vertical drift velocity. In this case, the plasma moves upward away from the F layer, the F2 maximum is observed at the greater heights and one can see the foF depression caused by the upward movement of electrons. Unfortunately, we do not have high latitude ionospheric data with 5-15 min resolution for our data, resolution auroral indices too rough for calculation of time-delay. Furthermore, the auroral and equatorial ionospheric variations have differences associated with geomagnetic field of the Earth that produce addition troubles for comparison. It should be noted also that during geomagnetic storms the low latitude stations can provide more precision measurements than auroral stations. It is well known that auroral zones are the major regions of the ionospheric instability, especially during geomagnetic storms and substorms. The equatorial ionosphere has often been neglected and only the auroral ionosphere had been taken into account when considering the solar wind, magnetosphere and ionosphere coupling. Therefore the coupling between high and low latitude ionosphere is the least understood aspect of this problem. In recent years one can observe a revived interest on the equatorial ionosphere because as polar the polar ionosphere it produces serious problems in communication and navigation systems during of geomagnetic disturbances and storms. Because of its high conductivity, the equatorial ionosphere in the region confined between of 20 degrees magnetic dip latitudes is very sensitive to variations of electric field due to several effects including magnetospheric convection, ionospheric dynamo disturbance, and various kinds of wave disturbances. So, from the practical point of view, the relationships between the solar wind and the ionospheric parameters can be used for prediction of different ionospheric phenomena. For example, the changes of the ionosphere height may serve as a good measure for predictions of the spread F or intense ionospheric scintillations. It should be noted that more detail investigations of the high and low latitude quantitative relationships with high-precision data are required to include in features of the ionosheric models during geomagnetic storms.

  11. 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.

  12. SPEAR-induced field-aligned irregularities observed from bi-static HF radio scattering in the polar ionosphere

    NASA Astrophysics Data System (ADS)

    Blagoveshchenskaya, N. F.; Borisova, T. D.; Kornienko, V. A.; Kalishin, A. S.; Robinson, T. R.; Yeoman, T. K.; Wright, D. M.; Baddeley, L. J.

    2009-01-01

    Experimental results from SPEAR HF heating experiments in the polar ionosphere are examined. Bi-static scatter measurements of HF diagnostic signals were carried out on the Pori (Finland)-SPEAR-St. Petersburg path at operational frequencies of 11,755 and 15,400 kHz and the London-SPEAR-St. Petersburg path at frequencies of 12,095 and 17,700 kHz, using a Doppler spectral method. The SPEAR HF heating facility generates heater-induced artificial field-aligned small-scale irregularities (AFAIs), which can be detected by HF diagnostic bi-static radio scatter techniques at St. Petersburg at a distance of about 2000 km. In accordance with the Bragg condition, HF bi-static backscatters were sensitive to small-scale irregularities having spatial sizes of the order of 9-13 m across the geomagnetic field line. The properties and behaviour of AFAIs have been considered in the winter and summer seasons under quiet magnetic conditions and under various status of the polar ionosphere (the presence of "thick" and "thin" sporadic Es layers, different structures of the F2 layer). The experimental results obtained have shown that AFAIs can be excited in the F as well as in the E regions of the polar ionosphere. The excitation of a very intense wide-band spectral component with an abrupt increase in the spectral width up to 16-20 Hz has been found in the signals scattered from striations. Along with a wide-band component, a narrow-band spectral component can be also seen in the Doppler sonograms and in the average spectra of the signals scattered from the SPEAR-induced striations. AFAIs were excited even when the HF heater frequency was up to 0.5 MHz larger than the critical frequency. A simulation of the ray geometry for the diagnostic HF radio waves scattered from AFAIs in the polar ionosphere has been made for the geophysical conditions prevailing during experiments carried out in both the winter and summer seasons.

  13. Electron gyroharmonic effects on ionospheric stimulated Brillouin scatter

    NASA Astrophysics Data System (ADS)

    Mahmoudian, A.; Scales, W. A.; Bernhardt, P. A.; Isham, B.; Kendall, E.; Briczinski, S. J.; Fuentes, N. E. B.; Vega-Cancel, O.

    2014-08-01

    Stimulated Brillouin scattering (SBS) and resonant phenomena are well known in the context of laser fusion, fiber optics, and piezoelectric semiconductor plasmas, as well as in various biological applications. Due to recent advances, active space experiments using high-power high-frequency (HF) radio waves may now produce stimulated Brillouin scattering (SBS) in the ionospheric plasma. The sensitivity of the narrowband SBS emission lines to pump frequency stepping across electron gyroharmonics is reported here for the first time. Experimental observations show that SBS emission sidebands are suppressed as the HF pump frequency is stepped across the second and third electron gyroharmonics. A correlation of artificially enhanced airglow and SBS emission lines excited at the upper hybrid altitude is observed and studied for second gyroharmonic heating. The SBS behavior near electron gyroharmonics is shown to have important diagnostic applications for multilayered, multi-ion component plasmas such as the ionosphere.

  14. Summary of ionospheric heating experiments at Tromsoe (Norway)

    NASA Astrophysics Data System (ADS)

    Stubbe, P.; Kopka, H.

    1983-07-01

    Experiments with an ionospheric heating facility which generates a CW power of up to 1.5 MW in the frequency range 2.5 to 8 MHz are summarized. Antenna gain is 24 dBi (relative to isotropic antenna), corresponding to a beam width of 14.5 deg or a maximum effective radiated power of 360 MW. Modulation of the polar electrojet at ELF and VLF; D region modification; generation of artificial micropulsations; VHF backscatter from E region irregularities; and HF backscatter from F region striations are described. Anomalous absorption of HF waves; phase changes of a diagnostic HF wave; large scale field aligned irregularities; plasma and ion line irregularities with EISCAT; and stimulated electromagnetic emission of the ionospheric plasma are treated. Airglow modification; F region cross modulation; and in situ measurements in the modified F region are discussed.

  15. Ionospheric scintillation studies

    NASA Technical Reports Server (NTRS)

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

    1973-01-01

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

  16. 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 Earths 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.

  17. Atmosphere-Ionosphere Electrodynamic Coupling

    NASA Astrophysics Data System (ADS)

    Sorokin, V. M.; Chmyrev, V. M.

    Numerous phenomena that occur in the mesosphere, ionosphere, and the magnetosphere of the Earth are caused by the sources located in the lower atmosphere and on the ground. We describe the effects produced by lightning activity and by ground-based transmitters operated in high frequency (HF) and very low frequency (VLF) ranges. Among these phenomena are the ionosphere heating and the formation of plasma density inhomogeneities, the excitation of gamma ray bursts and atmospheric emissions in different spectral bands, the generation of ULF/ELF/VLF electromagnetic waves and plasma turbulence in the ionosphere, the stimulation of radiation belt electron precipitations and the acceleration of ions in the upper ionosphere. The most interesting results of experimental and theoretical studies of these phenomena are discussed below. The ionosphere is subject to the action of the conductive electric current flowing in the atmosphere-ionosphere circuit. We present a physical model of DC electric field and current formation in this circuit. The key element of this model is an external current, which is formed with the occurrence of convective upward transport of charged aerosols and their gravitational sedimentation in the atmosphere. An increase in the level of atmospheric radioactivity results in the appearance of additional ionization and change of electrical conductivity. Variation of conductivity and external current in the lower atmosphere leads to perturbation of the electric current flowing in the global atmosphere-ionosphere circuit and to the associated DC electric field perturbation both on the Earth's surface and in the ionosphere. Description of these processes and some results of the electric field and current calculations are presented below. The seismic-induced electric field perturbations produce noticeable effects in the ionosphere by generating the electromagnetic field and plasma disturbances. We describe the generation mechanisms of such experimentally observed effects as excitation of plasma density inhomogeneities, field-aligned currents, and ULF/ELF emissions and the modification of electron and ion altitude profiles in the upper ionosphere. The electrodynamic model of the ionosphere modification under the influence of some natural and man-made processes in the atmosphere is also discussed. The model is based on the satellite and ground measurements of electromagnetic field and plasma perturbations and on the data on atmospheric radioactivity and soil gas injection into the atmosphere.

  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. 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.

  1. 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.

  2. 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.

  3. 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.

  4. Ionospheric Storms in the Sub-Auroral Ionosphere: Local Time Effects Driven by Electrodynamics

    NASA Astrophysics Data System (ADS)

    Narvaez, C. L.; Mendillo, M.

    2009-12-01

    The response of the mid-latitude ionosphere to geomagnetic storms depends upon several pre-storm conditions, the dominant ones being season and local time of the storm commencement (SC). The difference between a site’s geographic and geomagnetic latitudes is also of major importance since it governs the blend of processes linked to solar production and magnetospheric input, respectively. Electrodynamics plays a central role in storm morphologies at sub-auroral sites: it contributes to the positive phase near dusk on the first day or a storm, and to the motions of the trough on subsequent nights, and to the Joule heating that drives the negative phase. To explore hemispheric consistency of ionospheric storms, we identify two key locations that are “geophysically-equivalent” sites and offer the optimal ways to assess magnetosphere-ionosphere coupling. At the longitudes of the dipole tilt, we use ionosonde values of the F2-layer maximum electron density (NmF2) to study geophysical equivalency at Wallops Island (VA) and Hobart (Tasmania), using statistical summaries of 206 events during solar cycle #20. We form average patterns of ΔNmF2 (%) versus local time over 7-day storm periods that are constructed in ways that enhance the portrayal of the characteristic features of the positive and negative phases of ionospheric storms. The results show a remarkable consistency between local time patterns of storm-induced perturbations and the processes that cause them in each hemisphere. Subtle differences are found in the role of electrodynamics for two features of the negative phase: convective motions of the trough and the Joule heating that drives the negative phase.

  5. 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.

  6. Small-scale, Intense Electric Fields Measured Above the Ionosphere as a Result of Electrodynamic Magnetosphere-Ionosphere Coupling in ULF range.

    NASA Astrophysics Data System (ADS)

    Streltsov, A. V.; Lotko, W.; Pokhotelov, D.

    2001-12-01

    Results from a numerical investigation of small-scale, intense (>100 mV/m) electric fields, frequently observed by satellites and sounding rockets at relatively low altitude (about 1000 km) above the auroral ionosphere, and their connection with fluxes of precipitating particles are presented. A causal explanation of these fields is given in terms of shear Alfvn waves, generated in the nightside plasmasheet boundary layer or equatorial magnetosphere where various energy sources reside. These waves can produce significant parallel electric fields by interacting with plasma microturbulence in a collisionless resistive layer (auroral auroral acceleration region) that forms at an altitude of about 1 RE. The Alfvn wave-sustained micoturbulence and parallel electric fields heat and accelerate particles along magnetic field lines. Recent investigations of the interaction between Alfvn waves and the microturbulent layer show that this layer effectively reflects the small-scale Alfvn waves, incident from above, preventing them from penetrating to low altitudes. This study shows how small-scale, intense electric fields can be generated below the auroral acceleration region due to the modification of the ionospheric conductivity, when the ionosphere interacts with large-scale Alfvn waves. This non-linear interaction of the magnetospheric Alfvn waves with the ionosphere is investigated as a function of wave parameters (frequency, amplitude, transverse wavelength), as well as parameters of the low-altitude plasma (density, temperature, ionospheric conductivities). Applications of the numerical results to selected auroral observations are discussed.

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

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

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

  8. 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

  9. 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.

  10. Artificial E-region field-aligned plasma irregularities generated at pump frequencies near the second electron gyroharmonic

    NASA Astrophysics Data System (ADS)

    Hysell, D. L.; Nossa, E.

    2009-07-01

    E region ionospheric modification experiments have been performed at HAARP using pump frequencies about 50 kHz above and below the second electron gyroharmonic frequency. Artificial E region field-aligned plasma density irregularities (FAIs) were created and observed using the imaging coherent scatter radar near Homer, Alaska. Echoes from FAIs generated with pump frequencies above and below 2?e did not appear to differ significantly in experiments conducted on summer afternoons in 2008, and the resonance instability seemed to be at work in either case. We argue that upper hybrid wave trapping and resonance instability at pump frequencies below the second electron gyroharmonic frequency are permitted theoretically when the effects of finite parallel wavenumbers are considered. Echoes from a sporadic E layer were observed to be somewhat weaker when the pump frequency was 50 kHz below the second electron gyroharmonic frequency. This may indicate that finite parallel wavenumbers are inconsistent with wave trapping in thin sporadic E ionization layers.

  11. 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.

  12. 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.

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

    PubMed

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

    1987-11-27

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

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

    NASA Astrophysics Data System (ADS)

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

    1987-11-01

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

  15. 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.

  16. Ionospheric Profiling using GPS/MET Data

    NASA Technical Reports Server (NTRS)

    Hajj, George; Romans, Larry

    1996-01-01

    A report on ionospheric profiling using GPS and MET data is presented. A description of the GPS occultation technique, some examples of GPS/MET data products, the data processing system and a preliminary validation of ionospheric profiles is discussed.

  17. 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.

  18. 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.

  19. Two-Dimensional Ionospheric Tomography and Profiling from GPS Occultations

    NASA Astrophysics Data System (ADS)

    Syndergaard, S.

    2001-05-01

    The Satellite-to-Satellite Total Electron Content (SS-TEC) measured with the GPS radio occultation technique provides information of the two-dimensional (2D) structure of the electron density in the occultation plane. The SS-TEC data is inverted in a tomographic framework using a Bayesian approach with a priori information from an ionospheric model. Additional smoothing constraints are also applied between layers and at the bottom of the ionosphere where we know a priori that the electron density must be close to zero. The input of a priori knowledge is necessary in order to constrain the solution in regions far from the ray tangent points and to avoid unrealistic electron densities at low altitudes (below 100 km). The ionosphere in the occultation plane is divided into vertical layers and horizontal slices, corresponding to a resolution of about 1 km in the vertical and 150 km in the horizontal. Preliminary results using GPS/MET data will be presented and discussed. Before the inversion the observations should be corrected for bending and dispersion effects so that the SS-TEC is a measure of the straight-line TEC between the satellites. A simple combination of the L1 and L2 phase data (different from the traditional L1 minus L2 combination) that greatly reduce the bending and dispersion effects is also discussed. Besides giving a high resolution estimate of the 2D electron density structure it is expected that this approach will give a more accurate electron density profile retrieval near the tangent point than the traditional Abel Transform method, which often gives a large bias in the lower part of the ionosphere. Estimation of the 2D structure in the occultation plane could eventually also prove to be useful for a better ionospheric correction in the stratosphere and mesosphere for more accurate refractivity, pressure, and temperature profile retrievals.

  20. Ionosphere Transient Response To Solar Flares: Hf Radio Monitoring Observations

    NASA Astrophysics Data System (ADS)

    Lebreton, J.-P.; Telljohann, U.; Witasse, O.; Sanderson, T. R.

    We use a simple and low cost method to monitor the ionospheric reflection of commer- cial HF radio transmissions. It only requires a standard HF radio receiver with Single Side Band capability, a computer with a sound card, and appropriate audio signal spectral analysis software. We tune the radio receiver such that the carrier frequency of the transmission appears as a ~ 1kHz tone at the output of the radio receiver. The output signal of the radio receiver is processed with appropriate software that allows real time recording of high frequency resolution dynamic spectrograms of the audio spectrum in the 0-5 kHz range. Voice modulation is also present in the audio spectrum and appears as both upper and lower side bands but it is not considered in this study. HF radio signals reach the receiving station after being reflected by ionospheric layers. Any change in the ionospheric layers that affects HF wave reflection is detectable. In this paper, we particularly discuss our observations related to the transient response of the ionosphere to solar flare ionizing radiation. Enhanced ionization due to EUV and soft X-rays may produce a transient perturbation of the ionosphere which lasts typically one to few minutes. The signature of the transient response depends upon local time, solar flare intensity and the rise time of the solar flare ionizing radiation. We discuss both a few typical examples and a preliminary analysis of our 1-year sta- tistical analysis of observed events at 17.640 MHz. The method is easily accessible to amateur scientists. Possible use of the method for spaceweather-related research and outreach and educational activities is discussed.

  1. Vertical structure of medium-scale traveling ionospheric disturbances

    NASA Astrophysics Data System (ADS)

    Ssessanga, Nicholas; Kim, Yong Ha; Kim, Eunsol

    2015-11-01

    We develop an algorithm of computerized ionospheric tomography (CIT) to infer information on the vertical and horizontal structuring of electron density during nighttime medium-scale traveling ionospheric disturbances (MSTIDs). To facilitate digital CIT we have adopted total electron contents (TEC) from a dense Global Positioning System (GPS) receiver network, GEONET, which contains more than 1000 receivers. A multiplicative algebraic reconstruction technique was utilized with a calibrated IRI-2012 model as an initial solution. The reconstructed F2 peak layer varied in altitude with average peak-to-peak amplitude of ~52 km. In addition, the F2 peak layer anticorrelated with TEC variations. This feature supports a theory in which nighttime MSTID is composed of oscillating electric fields due to conductivity variations. Moreover, reconstructed TEC variations over two stations were reasonably close to variations directly derived from the measured TEC data set. Our tomographic analysis may thus help understand three-dimensional structure of MSTIDs in a quantitative way.

  2. Detection of ionospheric perturbatons using dense GPS arrays

    NASA Astrophysics Data System (ADS)

    Calais, E.; Haase, J. S.; Minster, B.

    2003-04-01

    Vertical motions of the Earths surface are known to excite atmospheric infrasonic acoustic and gravity waves that propagate laterally and upward away from the source (e.g. Blanc, 1985; Davies and Archambeau, 1998). These perturbations eventually reach the ionospheric layers, where the coupling between neutral atmosphere and ionized plasma results in fluctuations of the ionospheric electron density. Since the atmospheric density decreases almost exponentially with altitude, energy conservation implies that the pulse amplitude increases upward as it propagates into the atmosphere. For a near-surface source, for instance, the amplification factor can reach 104 at ionospheric heights. Dual-frequency Global Positioning System (GPS) data provide a straightforward means of measuring the ionospheric electron content and are now widely used to monitor variations of the ionospheric electron content at both global and regional scales (e.g. Manucci et al., 1993; Juan et al., 1997; Sylvander et al., 1996). Using dual frequency GPS observations, studies have detected ionospheric disturbances caused by large earthquakes (Calais and Minster, 1995; Afraimovitch et al., 2001), by the shock wave associated with a Space Shuttle ascent (Calais and Minster, 1996), and by a 3-million pound quarry blast in the Black Thunder basin, Wyoming (Calais et al. 1998). The development of permanent networks of densely spaced and continuously recording GPS stations provides the opportunity to investigate ionospheric perturbations and their coupling with the neutral atmosphere with great detail. We show in this paper the possibilities offered by the Southern California Integrated GPS network (SCIGN), a densely spaced GPS array of 250 ground stations centered on the Los Angeles area, to detect ionospheric perturbations. We show how methods derived from seismological array processing techniques can be used to determine basic properties of the perturbation such as its propagation azimuth and velocity. We present several examples of detected disturbances and describe their possible origin. References: Afraimovitch et al., Annales Geophysicae, 19, 395-409, 2001. Blanc, E., Annales Geophysicae, 6, 673-688, 1985. Calais and Minster Geophys. Res. Letters, 22, 1045, 1995. Calais and Minster, Geophys. Res. Letters, 15, 1897-1900, 1996. Calais et al., Geophys. J. Int., 132, 191-202, 1998. Davies and Archambeau, Physics of the Earth and Planetary Interiors, 105, 183199, 1998. Juan et al., Geophys. Res. Letters, 24, 393-396, 1997. Manucci et al., ION GPS-93, Salt Lake City, September 22-24, 1993. Sylvander et al., C.R. Acad. Sci. Paris, 1996.

  3. 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.

  4. 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.

  5. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2001-12-01

    Recent theoretical model simulations of the ionospheric response to geomagnetic storms have provided the understanding for the development of an empirical storm-time ionospheric model (STORM). The empirical model is driven by the previous time-history of a p, and is designed to scale the quiet-time F-layer critical frequency (f o F 2) to account for storm-time changes in the ionosphere. The model provides a useful, yet simple tool for modeling of the perturbed ionosphere. The quality of the model prediction has been evaluated by comparing with the observed ionospheric response during the Bastille Day (July 2000) storm. With a maximum negative D st of -290 nT and an a p of 400, this magnetic perturbation was the strongest of year 2000. For these conditions, the model output was compared with the actual ionospheric response from all available stations, providing a reasonable latitudinal and longitudinal coverage. The comparisons show that the model captures the decreases in electron density particularly well in the northern summer hemisphere. In winter, the observed ionospheric response was more variable, showing a less consistent response, imposing a more severe challenge to the empirical model. The value of the model has been quantified by comparing the root mean square error (RMSE) of the STORM predictions with the monthly mean. The results of this study illustrate that the STORM model reduces the RMSE at the peak of the disturbance from 0.36 to 0.22, a significant improvement over climatology.

  7. 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.

  8. Long-lived artificial ion clouds in the earth's ionosphere

    SciTech Connect

    Milinevsky, G.P. ); Kashirin, A.I. ); Romanovsky, Yu.A. ); Stenbaek-Nielson, H.C. ); Kelley, M.C. )

    1993-06-07

    The authors report on two observations made over the Caribbean during the summer of 1991 of barium ion cloud releases, ten hours after the clouds were released. One release was made in the morning twilight, and one in the evening twilight, and each was observed again in the following twilight period by a low light level TV imager and a TV spectrograph onboard a Russian research vessel. These observations were very surprising at the time, but the authors present arguments as to why in retrospect they may not be so unusual in practise. Such cloud releases may provide very sensitive tests of ionspheric convection models.

  9. Interplanetary radio transmission through serial ionospheric and material barriers

    NASA Astrophysics Data System (ADS)

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

    2013-02-01

    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.

  10. Low- and mid-latitude ionospheric effects of energetic electrons

    NASA Astrophysics Data System (ADS)

    Suvorova, Alla; Matsumoto, Haruhisa; Kunitsyn, Viacheslav; Andreeva, Elena; Nesterov, Ivan; Dmitriev, Alexei; Huang, Chien-Ming

    Recent observations revealed events of energetic and relativistic electron enhancements in the Earths radiation belt (ERB) occurred on timescales of less than a few hours. As it was shown, so-called "rapid rebuilding" events were caused by substorms. We found that similar enhancements were also seen under the ERB in the forbidden zone. Both phenomena of sudden growth of energetic electrons inside and under the ERB relate to substorm dipolarizations, which result in rapid changes in the configuration of the magnetic field and generation of inductive electric fields. In the previous studies we found very intense fluxes of energetic electrons in the forbidden zone which resulted in substantial abundant ionospheric ionization during strong magnetic storms. Here we analyze enhancements of >30-keV quasi-trapped electrons during a moderate recurrent (CIR/HSS-driven) geomagnetic storm on 22 July 2009. We focus on particular issue of the magnetosphere-ionosphere coupling through the quasi-trapped electrons at low-latitudes. We show that unusually large area in the nighttime ionosphere with increased total electron content (TEC) and prominent elevation of the F-layer at low-latitudes coincides spatially and temporarily with enhanced electron fluxes. Ionizing particles are considered now as an addition source of ionization during recurrent magnetic storms along with generally accepted mechanisms for storm-time TEC increases or so-called positive ionospheric storms.

  11. Ionospheric Signatures Associated with the 21 February 2008 Svalbard Earthquake

    NASA Astrophysics Data System (ADS)

    Bjoland, L.; stgaard, N.; Oksavik, K.; Atakan, K.

    2012-04-01

    Previous studies have used different methods to search for a correlation between earthquakes and ionospheric perturbations, including VLF/LF propagation, TEC data, and data from the DEMETER satellite. This study looks for ionospheric disturbances associated with the 21 February 2008 Svalbard earthquake using the EISCAT Svalbard radar(ESR). This earthquake had a moment magnitude of 6.0 and occurred during the International Polar Year(IPY) 2007-2008. As part of the IPY-ICESTAR project the ESR ran continuously during a full year from March 2007 to February 2008, and therefore we have continuous measurements from the time of the earthquake. This is a unique opportunity to study the effects of an earthquake in the ionosphere. From the EISCAT radar, information about electron density, electron temperature, ion temperature and vertical ion velocity, together with the uncertainties of these, for a range of different altitudes, are determined. In this study the main focus has been on a search for signatures in the D-layer electron density. In addition a search for signatures in VLF signals is carried out. Different theories, as enhanced radon emission from the ground and acoustic gravity waves, have been proposed to explain the cause of possible ionospheric signatures associated with earthquakes. The results obtained will be used to test these theories.

  12. 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.

  13. 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.

  14. Passive monitoring of the ionosphere

    NASA Astrophysics Data System (ADS)

    Paul, A. K.

    1985-06-01

    Obtaining ionospheric information in a passive mode by measuring the angle of arrival of signals transmitted by stations of known location over a short or medium length path involving ionospheric reflection is considered. Several tests conducted at the NOAA upper atmospheric research station near Brighton, CO, in 1983 and 1984, are reported. The separation of two superimposed waves and the computation of their characteristics is possible if the amplitude and phase are recorded at four spaced receiving antennas. In the case, since the two receiving antenna pairs are sampled in sequence, and ionospheric changes cause changes in the phase relation of the two waves over periods shorter than the sampling interval of 20 ms, the two-wave separation is not tested. The relevance of these tests to HF direction finding is discussed.

  15. Generic relationships between observational parameters defining ionospheric variability

    NASA Astrophysics Data System (ADS)

    Lynn, Kenneth; Heitmann, Andrew; Gardener-Garden, Robert

    It has long been known that travelling ionospheric disturbances (TIDs) are seen as a tilted descending variation in isolines of constant electron density derived from ionograms. This is the descending phase front of what is actually an ascending TID, as originally noted by Hines. What is less known is that this descent results in a time delay between the motion of the ionosphere at the greatest observed height and the arrival of the disturbance at the base of the layer (typically the F2) which in turn causes a temporary a compression of the layer thickness and a temporary increase in maximum electron density (foF2). The tilt in the descending electron density variation is often used as the identifying mark of a TID. This paper points out that the relationships observed between foF2, descending height and layer thickness is not unique to a TID but is a generic relationship observed whenever ionization is driven up and down magnetic field lines. Examples of this broader relationship are given for the equatorial post sunset rise and fall in electron density and in equatorial and middle latitude variations in ionospheric diurnal patterns which may repeat over a number of days. Such patterns are definitely not caused by TIDs.

  16. Far Ultraviolet Nightside Ionospheric Photometer

    NASA Astrophysics Data System (ADS)

    Fu, L.; Wang, Y.; Peng, J.; Jiang, F.

    2013-12-01

    Far Ultraviolet Nightside Ionopsheric Photometer (FNIP) is an instrument for low earth orbit missions. The paper will introduce a newly-designed FNIP, observing the Earth night airglow nadir at OI 135.6 nm emission produced by ionospheric O++e recombination and receiving the horizontal information on nightside ionosphere with a spatial resolution of about 30 km. This simple, highly robust instrument excludes OI 130.4 nm emission with lower power and achieves a sensitivity of approximately 400 counts/s/Rayleigh at 135.6nm. Some tests of the new design have been conducted and the results will be discussed in the end.

  17. Variations of the mid-latitude ionosphere during strong geomagnetic storms: Observational results

    NASA Astrophysics Data System (ADS)

    Gordiyenko, Galina; Vodyannikov, Victor; Yakovets, Artur

    The ground-based ionosonde data obtained at Alma-Ata station [ϕ = 43.250N, λ = 76.920E, Φ = 33.470N, L = 1.44) are analyzed to study ionospheric responses at fourteen intense (Kp ≥ 8) geomagnetic storms with storm sudden commencement (ssc). The collected data show that ionospheric responses to intensive geomagnetic storms (Dst < -100nT ) are very complex with a great degree of variability; however, negative ionospheric disturbances are a common feature of the responses. The time delay between storm ssc and beginning of the negative ionospheric disturbances shows a tendency to be noticeably larger in winter events than the summer events. Positive ionospheric effects are observed during storm recovery phases or when the Dst almost fully recovered; an enhanced eastward electric field occurred at low and equatorial latitudes after ssc is assumed to be a possible reason for the effects. The occurrence of the unusual for Alma-Ata location night E, F1 layers and auroral type r (retardation) sporadic Es layers is observed during developing or around main phases in Dst index. Employing the International Reference Ionosphere 2001 (IRI-2001), the nighttime E region electron density has been estimated for

  18. The structure of the Venus ionosphere from Venera-15,-16 radio occultation measurements

    NASA Astrophysics Data System (ADS)

    Gavrik, Anatoly; Kopnina, Tatyana; Samoznaev, Lev

    Between 1975 and 1994, regular research of the Venus ionosphere was carried out by Venera-9,-10, Pioneer-Venus, Venera-15,-16 and Magellan spacecrafts. Over 600 altitude distributions of electron densities were derived from occultation data under various conditions. Nowadays, occultations are performed by the Venus-Express spacecraft. The high coherence and stability of radio signals from Venera-15,-16 (1 and 4 GHz), along with the fact that the refraction of the 1 GHz signal in the ionosphere exceeds the refraction of the signals used by other researchers by a factor of 6, allowed one to carry out a more accurate analysis of the radiophysical parameters of the Venus ionosphere. The method used in these investigations is based on the theoretical linear relation between the refraction attenuation and the frequency gradient. It is correct only when the powers and phases of the signals are measured with high-precision in a dual frequency radio sounding. The agreement between the variations in the measured refraction attenuation and the refraction attenuation calculated from frequency data testifies to the influence of the plasma on radio signals in spite of the fact that the refraction effects are comparable with noise. The good correlation of the Venera-15,-16 data indicates the existence of the bottom part of the daytime Venus ionosphere at altitudes of 80-120 km. When the noise level was low, we observed the bottom ionosphere in all 19 occultations at solar zenith angles between 56 and 87 . We also observed the bottom ionosphere in 6 out of 9 occultations near the planet's terminator, but the effect was comparable with noise. In the night ionosphere, none of 25 occultations revealed the bottom plasma layer. Thus, the bottom layer of the daytime Venus ionosphere is permanent. The properties of the bottom ionosphere of Venus depend on the solar zenith angle. Considerable variations in the bottom layer properties of the Venus daytime ionosphere can be associated with some wave processes in the top atmosphere and in the bottom ionosphere.

  19. ASPERA/Phobos measurements of the ion outflow from the Martian ionosphere

    SciTech Connect

    Lundin, R.; Borg, H.; Hultqvist, B. ); Zakharov, A.; Barabasj, S.W.; Dubinin, E.M.; Pissarenko, N. ); Pellinen, R.; Koskinen, H.; Liede, I. )

    1990-05-01

    This report reviews the first results on the ionospheric ion outflow in the Martian magnetosphere by the ion composition experiment ASPERA on Phobos-2. The measurements show that Mars is characterized by a strong loss of plasma from its topside ionosphere. This loss results from both ion pick-up due to mass-loading of the solar wind in the Martian boundary layer and an acceleration mechanism, quite similar to that observed above the Earth's auroral oval, providing intense ionospheric O{sup +} beams of energies up to several keV. A preliminary estimate of the ionospheric outflow from Mars indicates that the planet at present is losing oxygen at a rate of {approx} 3 {times} 10{sup 25} ions/s. This corresponds to an evacuation of its present total atmospheric oxygen content (contained in CO{sub 2} and O{sub 2}) in less than 100 million years.

  20. 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.

  1. 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

  2. The International Reference Ionosphere - a standard for the ionosphere environment

    NASA Astrophysics Data System (ADS)

    Bilitza, Dieter; Tamara, Gulyaeva; Reinisch, Bodo

    The International Reference Ionosphere (IRI) describes monthly averages of electron density, electron temperature, ion temperature, and the percentage of O+, H+, He+, N+, NO+, O2+, and Cluster ions in the altitude range from 50 km to 1500 km. IRI is the result of an international collaboration sponsored by the Committee on Space Research (COSPAR) and the International Union of Radio Science (URSI). The observation-based model represents a synthesis of most of the existing ionospheric data acquired from the ground and in space. IRI is the de facto climatological standard for the ionosphere and is currently undergoing registration as Technical Specification (TS) 16457 of the International Standardization Organization (ISO). It is also the model of choice recommended by the European Cooperation on Space Standardization (ECSS). This talk will report about recent activities within the IRI Working Group with special emphasis on the newest version IRI-2007 and on areas were future improvements are expected. We will highlight the most important results from the 2007 IRI Workshop in Prague, Czech Republic. A special IRI session during this COSPAR Scientific Assembly (C41) has ‘Updating Ionospheric Models with Ground and Space Data' as its topic.

  3. 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.

  4. A Review of Ionospheric Scintillation Models

    NASA Astrophysics Data System (ADS)

    Priyadarshi, S.

    2015-03-01

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

  5. The 630 nm and 557.7 nm Airglow During HF Ionosphere Pumping by the SURA Facility Radiation for Pump Frequencies Near the Fourth Electron Gyroharmonic

    NASA Astrophysics Data System (ADS)

    Shindin, A. V.; Grach, S. M.; Klimenko, V. V.; Nasyrov, I. A.; Sergeev, E. N.; Beletski, A. B.; Taschilin, M. A.; I. Gumerov, R.

    2015-04-01

    We present the results of analysis of the dependence of the ionospheric airglow in the red (630 nm) and green (557.7 nm) lines of atomic oxygen on the pump-wave frequency f 0 near the fourth electron gyroharmonic 4 f ce. The experimental data were obtained in 2012 using the SURA heating facility. Stimulated electromagnetic emission spectra were used to determine the relation between f 0 and 4 f ce. It is found that at f 0 > 4 f ce and ?f = f 0 - 4 f ce ? 15-20 kHz the red-line airglow intensity is about a factor of 1.5 higher for the magnetic zenith pumping (when the pump beam is inclined 12 south of the magnetic field direction) than for the vertical pumping. In the green line for the same offsets ?f, the airglow was recorded with confidence only during magnetic zenith pumping. During vertical pumping, no regular dependence of the red-line airglow intensity on ?f in the range -15 < ?f < 280 kHz was obtained, while the green-line airglow was observed at 15 < ?f < +5 kHz and 230 < ?f < 280 kHz. In the red line during vertical pumping, a change from the artificial airglow generation to the ionospheric background suppression was detected when the F-layer cutoff frequency was decreased. During magnetic zenith pumping, a wide (about 30) background suppression zone was observed around the airglow spot with an about 6 angular width.

  6. 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

  7. Innovative development and application of models for weakly ionized ionospheric plasmas

    NASA Astrophysics Data System (ADS)

    Eccles, J. V.; Hingst, James; Armstrong, Russell

    1993-11-01

    Artificial modifications of the ionosphere through chemical releases and ionospheric heating experiments are examined with models of chemistry and transport to advance understanding of ion chemistry of the upper atmosphere. The specific releases investigated were the SF6 released of the CRRES-at-Kwajalein rocket campaign and the CO2 releases of the Red Air 1 program. Both the SF6 and CO2 releases experienced freezing or clustering of the molecules. This must be accounted for in the composition and airglow observations. In addition, HF heating effects in the E and F region were examined through modeling of energy deposition and resulting chemistry. NO(x) production in a HF ionospheric heater beam is estimated and compared with natural sources of NO(x). Global effects of HF operation are very small but the local effects can be large enough to permit observable modulation to this environment.

  8. Experimental study of an ionospheric disturbance during the cumulative injection of barium vapors

    NASA Astrophysics Data System (ADS)

    Zhulin, I. A.; Milinevskii, G. P.; Loevskii, A. S.; Moisia, R. I.; Romanovskii, Iu. A.; Ruzhin, Iu. Ia.; Skomarovskii, V. S.

    1984-05-01

    The cumulative injection of a barium vapor jet and disturbances arising during the deceleration of a plasma jet in the ionosphere was investigated on June 29, 1978 (21.05 LT) over the Volgograd test area in the course of the Spolokh-2 rocket experiment. Features characterizing the disturbance of the ionosphere during the initial stage of the barium-jet dispersion are examined; particular attention is given to effects associated with shock wave propagation, including collisional ionization. The stimulated precipitation of energetic electrons is disclosed which has the character of artificial pulsations of electron fluxes; it is noted that this stimulated precipitation may be connected with the excitation of MHD waves in the ionosphere during injection of the jet.

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

    NASA Astrophysics Data System (ADS)

    Němec, 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.

  10. 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 earths 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.

  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. Low Frequency Waves During RF Heating of the Ionosphere

    NASA Astrophysics Data System (ADS)

    Sharma, A. S.; Shao, X.; Eliasson, B. E.; Papadopoulos, D.

    2014-12-01

    Radio frequency heating of the ionosphere produces local plasma heating and the resulting pressure gradient leads to plasma currents. Modulated heating excites waves at the modulation frequency which propagate away from the heating region. The wave generation modulated heating of the F-region ionosphere is modeled using a numerical code with the conducting ground as the lower boundary and the magnetosphere as the top boundary. The diamagnetic current due to the pressure gradient resulting from the localized RF heating oscillates at the modulation frequency and excites hydromagnetic waves, mostly the magnetosonic mode. As these waves propagate away from the heated region in the F-region it encounters regions of different conductivity, driving an oscillating Hall current in the E-region where Hall conductivity is dominant. These currents produce shear Alfven waves propagating along the field lines. Simulations with modulation frequencies in the range 2 - 10 Hz in the high- and mid-latitude ionosphere show their dependence on the ionospheric conductivity, modulation frequency and size of the heated region. In the high-latitudes the wave propagation is simulated using an essentially vertical magnetic field. For the mid-latitudes a dipole magnetic field in polar coordinates is used. With a source at L = 1.6 and altitude of 300 km the EMIC and whistler waves are generated, and field-aligned waves propagate to the conjugate region. In the case of modulation at 10 Hz the EMIC waves encounter the resonance layer, while the whistler waves propagate along the field lines to the conjugate region. These simulations correspond to the ionospheric heating by the Arecibo facility.

  13. Preseismic ionospheric electron enhancements revisited

    NASA Astrophysics Data System (ADS)

    Heki, Kosuke; Enomoto, Yuji

    2013-10-01

    enhancement of ionospheric Total Electron Content (TEC) immediately before the 2011 Tohoku-oki earthquake (Mw9.0) has been reported by Heki (2011). Critical responses to it often come in two stages; they first doubt the enhancement itself and attribute it to an artifact. Second (when they accept the enhancement), they doubt the significance of the enhancement among natural variability of space weather origin. For example, Kamogawa and Kakinami (2013) attributed the enhancement to an artifact falsely detected by the combined effect of the highly variable TEC under active geomagnetic condition and the occurrence of a tsunamigenic ionospheric hole. Here we closely examine the time series of vertical TEC before and after the 2011 Tohoku-oki earthquake. We first demonstrate that the tsunami did not make an ionospheric hole, and next confirm the reality of the enhancement using data of two other sensors, ionosonde and magnetometers. The amplitude of the preseismic TEC enhancement is within the natural variability, and its snapshot resembles to large-scale traveling ionospheric disturbances. However, distinction could be made by examining their propagation properties. Similar TEC anomalies occurred before all the M ? 8.5 earthquakes in this century, suggesting their seismic origin.

  14. Calibrating for Ionospheric Phase Delays

    NASA Technical Reports Server (NTRS)

    Macdoran, P. F.

    1985-01-01

    Technique determines ionospheric phase delay on real-time universally applicable basis in terms of electrons per meter squared by coherently modulating two L-band carrier frequencies received from two Global Positioning System satelites. Two pseudorandom number sequences cross-correlated to derive delay time.

  15. 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.

  16. Ionospheric redistribution during geomagnetic storms

    NASA Astrophysics Data System (ADS)

    Immel, T. J.; Mannucci, A. J.

    2013-12-01

    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 (Dst<-100 nT) sets, we find variation in storm strength that corresponds closely to the TEC variation but follows it by 3-6h. For this and other reasons detailed in this report, we conclude that the UT-dependent peak in storm time TEC is likely not related to the magnitude of external storm time forcing but more likely attributable to phenomena such as the low magnetic field in the South American region. The large Dst variation suggests a possible system-level effect of the observed variation in ionospheric storm response on the measured strength of the terrestrial ring current, possibly connected through UT-dependent modulation of ion outflow.

  17. 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.

  18. 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.

  19. Equatorial ionospheric irregularities produced by the Brazilian ionospheric modification experiment (BIME)

    SciTech Connect

    Klobuchar, J.A.; Abdu, M.A.

    1989-03-01

    On two separate evenings in September 1982, rockets were launched into the bottomside equatorial F2 region off the coast of Natal, Brazil, to inject chemicals, consisting of mainly H2O and CO2, to create a hole in ionization. The chemicals were injected near the height where the density gradient was steepest, and at a time when the F2 region was rising rapidly, to see whether plasma bubble irregularities could be generated from instabilities triggered by the ionization hole. The eastward drifts of these artificial depletions were observed by the time difference in the TEC features observed at various TEC monitoring stations, and from the changing range of oblique ionosonde echoes observed by an ionosonde located 300 km magnetically east of the chemical release point. Their subsequent evolution into plasma bubble irregularities was demonstrated from the observations of spread F echoes, strong-amplitude scintillation, and TEC depletion at distances of from 300 to 500 km eastward of the release points. The fact that similar behavior of the ionosphere was observed during the evenings of both rocket chemical releases, and on no other nights of the campaign, is strong evidence of successful artificial generation of bubble irregularities by chemical injection into the bottomside F2 region.

  20. Equatorial ionospheric irregularities produced by the Brazilian ionospheric modification experiment (BIME)

    SciTech Connect

    Klobuchar, J.A. ); Abdu, M.A. )

    1989-03-01

    On two separate evenings in September 1982, rockets were launched into the bottomside equatorial F{sub 2} region off the coast of Natal, Brazil, to inject chemicals, consisting of mainly H{sub 2}O and CO{sub 2}, to create a hole in ionization. The chemicals were injected near the height where the density gradient was steepest, and at a time when the F{sub 2} region was rising rapidly to see whether plasma bubble irregularities could be generated from instabilities triggered by the ionization hole. On both occasions, hole-induced depletions in total electron content (TEC) of more than 10{sup 16} el/m{sup 2} were observed over horizontal distances of at least 60 km from the chemical injection point. The eastward drifts of these artificial depletions were observed by the time difference in the TEC features observed at various TEC monitoring stations, and from the changing range of oblique ionosonde echoes observed by an ionosonde located 300 km magnetically east of the chemical release point. Their subsequent evolution into plasma bubble irregularities was demonstrated from the observations of spread F echoes, strong amplitude scintillation, and TEC depletion at distances of from 300 to 500 km eastward of the release points. The fact that similar behavior of the ionosphere was observed during the evenings of both rocket chemical releases, and on no other nights of the campaign, is strong evidence of successful artificial generation of bubble irregularities by chemical injection into the bottomside F{sub 2} region.

  1. 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.

  2. Photolysis of methane and the ionosphere of Uranus

    NASA Astrophysics Data System (ADS)

    Atreya, S. K.; Ponthieu, J. J.

    1983-08-01

    Photochemical calculations for Uranus predict an extensive region of condensation of acetylene, ethane and methane in the vicinity of the temperature inversion layer. This could explain why ethane was not detected on Uranus, unlike Neptune which has a much warmer inversion layer. Subsequent snow-out of the condensibles is expected to result in reduced visibility in the troposphere. Ionospheric calculations for the equatorial region to be probed by Voyager, indicate peak electron concentrations on the order of 5103 cm-3, if dynamical effects are important. Upper limit to the electron peak is 3104 cm-3. Exospheric temperatures as high as 200-250K are conceivable.

  3. The energetics of Titan's ionosphere

    NASA Technical Reports Server (NTRS)

    Roboz, A.; Nagy, A. F.

    1994-01-01

    We have developed a comprehensive model to study the dynamics and energetics of the ionosphere of Titan. We solved the one-dimensional, time-dependent, coupled continuity and momentum equations for several ion species, together with single ion and electron energy equations, in order to calculate density, velocity, and temperature profiles. Calculations were carried out for several cases corresponding to different local times and configurations of the Titan-Saturn system. In our model the effects of horizontal magnetic fields were assumed to be negligible, except for their effect on reducing the electron and ion thermal conductivities and inhibiting vertical transport in the subram region. The ionospheric density peak was found to be at an altitude of about 1100 km, in accordance with earlier model calculations. The ionosphere is chemically controlled below an altitude of about 1500 km. Above this level, ion densities differ significantly from their chemical equilibrium values due to strong upward ion velocities. Heat is deposited in a narrow region around the ionospheric peak, resulting in temperature profiles increasing sharply and reaching nearly constant values of 800-1000 deg K for electrons and 300 deg K for ions in the topside, assuming conditions appropriate for the wake region. In the subram region magnetic correction factors make the electron heat conductivities negligible, resulting in electron temperatures increasing strongly with altitude and reaching values in the order of 5000 deg K at our upper boundary located at 2200 km. Ion chemical heating is found to play an important role in shaping the ion energy balance in Titan's ionosphere.

  4. 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.

  5. Phenomena in the ionosphere-magnetosphere system induced by injection of powerful HF radio waves into nightside auroral ionosphere

    NASA Astrophysics Data System (ADS)

    Blagoveshchenskaya, N. F.; Borisova, T. D.; Kornienko, V. A.; Thid, B.; Rietveld, M. T.; Kosch, M. J.; Bsinger, T.

    2005-01-01

    Experimental results from three ionospheric HF pumping experiments in overdense E or F regions are summarized. The experiments were conducted by the use of the EISCAT HF Heating facility located near Troms, Norway, allowing HF pumping the ionosphere in a near geomagnetic field-aligned direction. Distinctive features related to auroral activations in the course of the experiments are identified. Typical features observed in all experiments are the following: generation of scattered components in dynamic HF radio scatter Doppler spectra; strong increase of ion temperatures Ti and local ionospheric electric field E0; modification of the auroral arc and local spiral-like formation. However, some effects were observed only when the HF pump wave was reflected from the F2 layer. Among them are the generation of intense field-aligned ion outflows, and a strong increase in the electron temperature Te with altitude. A possible scenario for the substorm triggering due to HF pumping into an auroral ionosphere is discussed. The authors present their interpretation of the data as follows. It is suggested that two populations of charged particles are at play. One of them is the runaway population of electrons and ions from the ionosphere caused by the effects of the powerful HF radio wave. The other is the population of electrons that precipitate from the magnetosphere. It is shown that the hydrodynamical equilibrium was disrupted due to the effects of the HF pumping. We estimate that the parallel electric field can reach values of the order of 30mV/m during substorm triggering.

  6. Magnetospheric convection and the high-latitude F2 ionosphere

    NASA Technical Reports Server (NTRS)

    Knudsen, W. C.

    1974-01-01

    Behavior of the polar ionospheric F layer as it is convected through the cleft, over the polar cap, and through the nightside F layer trough zone is investigated. Passage through the cleft adds approximately 200,000 ions per cu cm in the vicinity of the F2 peak and redistributes the ionization above approximately 400-km altitude to conform with an increased electron temperature. The redistribution of ionization above 400-km altitude forms the 'averaged' plasma ring seen at 1000-km altitude. The F layer is also raised by approximately 20 km in altitude by the convection electric field. The time required for passage across the polar cap (25 deg) is about the same as that required for the F layer peak concentration to decay by e. The F layer response to passage through the nightside soft electron precipitation zone should be similar to but less than its response to passage through the cleft.

  7. 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.

    2016-02-01

    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 using 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 of 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 shows that in some occultations the errors of standard ionospheric correction substantially increase around the strong inversion layers (such as the top of the boundary layer). This error increase is modeled and explained by the horizontal inhomogeneity of the ionosphere.

  8. Effects of large zonal plasma drifts on the subauroral ionosphere

    NASA Technical Reports Server (NTRS)

    Sellek, R.; Bailey, G. J.; Moffett, R. J.; Heelis, R. A.; Anderson, P. C.

    1991-01-01

    A model of the earth's ionosphere and plasmasphere is used to investigate the effects of an imposed westward plasma drift of maximum velocity 2 km/s. A closed subauroral tube of plasma is considered and the velocity spike persists for 10 min. Ion-neutral frictional heating causes rapid elevation of the F-region O(+) temperature. The F-layer O(+) concentration is decreased due to increased O(+) loss rate and rapid ion flows both upward and downward from the F-region. The upward flux of O(+) through the topside ionosphere can each 5 x 10 exp 9/sq cm/s; when the velocity spike ceases there is a return flow of O(+) that tends to replenish the F-layer. Most of the features revealed by the model for the F-region and topside ionosphere are in accord with observations of subauroral ion drifts. Downward flows that are predicted to be persistently present around the 300 km altitude level appear to agree with observations only occasionally; suggestions are made to resolve this discrepancy.

  9. 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.

  10. Observing system experiments with an ionospheric electrodynamics model

    NASA Astrophysics Data System (ADS)

    Durazo, J.; Kostelich, E.; Mahalov, A.; Tang, W.

    2016-04-01

    We assess the performance of an ensemble Kalman filter for data assimilation and forecasting of ion density in a model of the ionosphere given noisy observations of varying sparsity. The domain of the numerical model is a mid-latitude ionosphere between 80 and 440 km. This domain includes the D–E layers and the peak in the F layer in the ionosphere. The model simulates the time evolution of an ion density field and the coupled electrostatic potential as charge-neutral winds from gravity waves propagate up from the stratosphere. Forecasts are generated for an ensemble of initial conditions, and synthetic observations, which are generated at random locations in the model domain, are assimilated into the ensemble at time intervals corresponding to about a half-period of the gravity wave. The data assimilation scheme, called the local ensemble transform Kalman filter (LETKF), incorporates observations within a fixed radius of each grid point to compute a unique linear combination of the forecast ensembles at each grid point. The collection of updated grid points forms the updated initial conditions (analysis ensemble) for the next forecast. Even when the observation density is spatially sparse, accurate analyses of the ion density still can be obtained, but the results depend on the size of the local region used. The LETKF is robust to large levels of Gaussian noise in the observations. Our results suggest that the LETKF merits consideration as a data assimilation scheme for space weather forecasting.

  11. 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.

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

    NASA Astrophysics Data System (ADS)

    Cherniak, Iu.; Lysenko, V.

    2009-04-01

    he ionosphere plasma characteristics are responding on variations of solar and magnetic activity. The research of an ionosphere structure and dynamics is important as for understanding physics of processes and for radiophysical problems solution. The method incoherent scatter (IS) of radio waves allows determining experimentally both regular variations of the basic parameters ionosphere, and their behavior during perturbation. The equipment and measurement technique, developed by authors, are allows obtaining certain data about behavior of an ionosphere during various origin and intensity ionosphere perturbations. The Institute of Ionsphere IS radar located near Kharkiv, Ukraine (geographic coordinates: 49.6oN, 36.3oE, geomagnetic coordinates: 45.7oN, 117.8oE) was used to observe the processes in the ionosphere. The radar is operate with 100-m zenith parabolic antenna at 158 MHz with peak transmitted power of ~2.0 MW. The double-frequency measuring channel mode with compound sounding signal was employed for experiments. That provided ~ 20-km resolution in range ~100-400 km and ~100-km in range ~200-1100 km. Over a period of series of experiment are obtained data about variations of electron density simultaneous in the heights interval 100-1000 km, including three sun eclipses, two superstrong and a few moderate magnetic storms, as well as disturbance, is caused by powerful rockets starts. During strong geomagnetic storm on November 8-12, 2004 was observed night time increasing of electronic temperature up to 3000 Љ and ions temperature up to 2000K. Usually at this time temperature of ions is equal to temperature of electrons. During negative ionosphere storm was observed decreasing of electronic density at maximum F2 layer. The height of a F2 layer maximum was increased by 150 km and 70 km at daytime. The interesting phenomenon - high-power backscatter signal coherent backscatter was observed first time during geogeomagnetic storm 29-30 may 2003. A usually observable spectrum of a dispersing medium has two identical on magnitude of a symmetrical extremum appropriate iono-acoustic waves. From distances 900 - 1300 km is registered high-power, unstable signal with a narrow-band spectrum This signal on the correlation, spectral and temporary characteristics are different both from incoherent scatter signal, and from signals reflected from space vehicles. At night time 9.11.2004 and day time 10.11.2004 anomaly signals - coherent backscatter were observed the same way as. It is derived, that the coherent backscatter was observed during a sharp decreasing of Dst index from approximately -40 up to -130 nTl for May 2003 and from approximately -120 up to -240 nTl for 9 November and from -160 up to -290 nTl 10 November 2004. During both event electron density in maximum F2 is increased. Similar characteristics midlatitude coherent backscatters were observed at Millstone Hill , on Irkutsk IS radar. On EISCAT radars was observed so-called naturally enhanced ion-acoustic lines (NEIAL) with similar spectra and amplitude-temporal characteristics. The radar observations ionosphere plasma response on start of heaviest Russian launch vehicle ?Proton-K? was carried out at 25 December 2006. The distance from the rocket launch site and the site of observations is 2500 km. At heights of 250-320 km, a magnitude of the scattered signal sharply raised up to 2 times as compared to the period before start and in reference day on 21.12.2008 (fig. 3). In launch day is clearly seen there are two disturbed areas. The first disturbance was observed 8 min after rocket start. The calculated apparent velocity of disturbance propagation reached the value of 5.2 km/s. This velocity is typical for slow magneto-hydro-dynamic waves in the ionosphere. The second disturbance was observed 60 min after start. The calculated apparent velocity of disturbance propagation was about 700 m/s. The internal gravity waves propagate with similar velocities at the heights of the ionosphere F layer. The moderate geomagnetic storm in April 2006 occurred on the phase of minimum of sun activity. It was caused alternated positive and negative ionospheres perturbations that was accompanied of moderate changes of ionosphere plasma parameters. Experimentally obtained on the Kharkiv IS radar altitude-temporary dependences of disturbed ionosphere plasma parameters - electron density Ne, electronic Te and ionic Ti temperatures. During a main phase of storm the positive perturbation was observed (Ne is increased in 1.3 times), April 5, at maximum Dst - negative perturbation (Ne is decreased in 1.6 times), April 6 - positive perturbation (the second positive storm phase - Ne was increased at 1.33 times). During negative ionosphere storm the height of a F2 layer maximum was increased on 30-40 km. Measured ionic temperature in the day time is increased on ~ 150Љ, electronic temperature is increased on ~ 600Љ (fig. 10.). Reference day is 01.0.2006. There is the great interest in research into the comparison of anthropogenic and natural disturbances.

  13. 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

  14. Inverting ionospheric radio occultation measurements using maximum entropy

    NASA Astrophysics Data System (ADS)

    Hysell, D. L.

    2007-08-01

    Practical aspects of the inversion of ionospheric radio occultation data using the Abel transform and its inverse are discussed. The linear inverse transform exhibits poor error propagation characteristics, producing significant artifacts preferentially at low altitudes where they might easily be mistaken for intermediate or sporadic layers in the ionosphere. Tikhonov regularization, which can be viewed as fixed linear filtering, reduces the artifacts at the expense of discarding fine structure in the profiles. Improved results are obtained using maximum entropy and Bayesian statistics. The maximum entropy algorithm can be viewed as a nonlinear adaptive filter which suppresses artifacts while preserving fine structure to the degree the data can support. Other advantages of and avenues for improving the basic maximum entropy algorithm are discussed.

  15. ULF Waves and Transients in the Topside Ionosphere

    NASA Astrophysics Data System (ADS)

    Pilipenko, V. A.; Heilig, B.

    Low earth orbit satellites with precise high-rate sensors onboard have advanced the prospect of examining the different kinds of ultra-low-frequency (ULF) waves in the topside ionosphere. This chapter reviews more recent observations on the behavior of these wave categories. It examines such evidence from these observations that may help settle some of the unsolved problems of ULF wave physics. To model the interaction with the ionosphere of low-frequency waves with periods T > 20 s, the thin layer approximation can be used. Standard magnetotelluric sounding of the crust conductivity profile is used as a determination of ground impedance from the data of synchronous magnetic and telluric electric field observations on the ground, whereas ULF magnetospheric waves are used as sounding electromagnetic signals. The largest spectral density of the atmospheric electrical discharge is concentrated in the VLF band, though comparable spectral power is contained in the lower ELF-ULF bands.

  16. 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.; Grller, 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.

  17. Numerical simulation of the plasma thermal disturbances during ionospheric modification experiments at the SURA heating facility

    NASA Astrophysics Data System (ADS)

    Belov, Alexey; Huba, J. D.

    indent=1cm We present the results of numerical simulation of the near-Earth plasma disturbances produced by resonant heating of the ionospheric F-region by high-power HF radio emission from the SURA facility. The computational model is based on the modified version of the SAMI2 code (release 1.00). The model input parameters are appropriated to the conditions of the SURA-DEMETER experiment. In this work, we study the spatial structure and temporal characteristics of stimulated large-scale disturbances of the electron number density and temperature. It is shown that the stimulated disturbances are observed throughout the ionosphere. Disturbances are recorded both in the region below the pump wave reflection level and in the outer ionosphere (up to 3000 km). At the DEMETER altitude, an increase in the ion number density is stipulated by the oxygen ions O (+) , whereas the number density of lighter H (+) ions decreases. A typical time of the formation of large-scale plasma density disturbances in the outer ionosphere is 2-3 min. After the heater is turned off, the disturbances relaxation time is approximately 30 min. The simulation results are important for planning future promising experiments on the formation of ionospheric artificial density ducts. This work was supported by the Russian Foundation for Basic Research (project No. 12-02-00747-a), and the Government of the Russian Federation (contract No. 14.B25.31.0008).

  18. Doppler investigations of short-period ionospheric variations produced by magnetic disturbances.

    NASA Astrophysics Data System (ADS)

    Kim, V.; Panchenko, V.; Polimatidi, V.; Ruzhin, Yu.

    In the report the results of experimental researches on excitation magnetospheric Alfven resonator by sudden magnetic disturbances and related with this an ionosphere effects are presented. The experiments were conducted with the help of the multifrequency Doppler installation of IZMIRAN since 1998. The research program consist in monitoring ionospheric disturbances related to solar activity. The measurements were conducted by a method of vertical radio sounding simultaneously on 4 frequencies. The set of selected frequencies would provide the signal reflection from Å, F1 and F2 layers of an ionosphere. The data processing consist in dynamic Doppler spectra calculation, which one allows receive the information on time responses of ionospheric disturbances. The effect, which one is discussed in the report, was watched already in the maiden experiments in April, 1998 at the moment of a substorm beginning in the polar ionosphere. It was revealed, that at the moment of a beginning of magnetic disturbance - which arrived from Tiksi Bay region (or substorm ignition area) - the Doppler displacements of sounding signal frequency (at Moscow) exhibit the synchronic variations (the observed period was about one minute duration) on all frequencies. During researches under the program HIRAC/SolarMax, which one was directed on analysis of influencing of solar activity on an ionosphere, it was possible to snap solar flare of April 26, 2001, which one has generated classic effects in an ionosphere -- sharp rise of an electron density and strong absorption of radio waves (black-out effect). The Doppler spectra on all active frequencies have shown in an instance of ignition considerable (more than 1 Hz) displacement of frequency. However most interesting events have begun after 2 day after a flash, when the magnetic disturbance began. At this time on Doppler spectra the quasiperiodic frequency drifts of radio echoes have appeared. Thus the quasiperiodic variations of Doppler displacement of frequency descended synchro on all search frequencies to the period some les 1 minute and were prolonged during more than 10 min. That fact, that such variation descended on all frequencies simultaneously testifies that the factor, disturbing an ionosphere, affects at once all ionosphere layers: from E up to F2 layer. The period of observed quasiperiodic frequency drifts (or ionosphere parameters variation) is the same for both as substorm and as solar flare action and is equal to one minute or bounce time for Alfven oscillation of magnetic field tube above the IZMIRAN region. It means that during magnetic disturbance the local Alfven resonator would be exñitated and in result the quasiperiodic precipitations of energetic particles are expected.

  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. 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-а.

  1. Beat heating of the ionosphere with high-power RF pumps

    SciTech Connect

    Katsouleas, T. )

    1990-12-01

    This report examines the potential for heating a layer of the ionosphere by beating two high-power RF pumps at the local plasma frequency. Simple scaling laws for the heating efficiency and final temperature of the layer as functions of the pump intensities and frequencies are found for both copropagating and counterpropagating pumps. The results are compared to single frequency heating by collisional absorption (inverse bremstrahlung) near the resonance layer. 16 refs.

  2. 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.

  3. 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.

  4. Investigation of ionospheric O+ remote sensing using the 834- airglow

    NASA Astrophysics Data System (ADS)

    Picone, J. M.; Meier, R. R.; Kelley, O. A.; Dymond, K. F.; Thomas, R. J.; Melendez-Alvira, D. J.; McCoy, R. P.

    1997-02-01

    We have studied the feasibility of ionospheric O+ remote sensing through measurements of the 834- airglow. Our approach uses discrete inverse theory (DIT) to retrieve O+ number density profiles from the airglow. Our tests of this method assume observations by a limb-scanning system on an orbiting satellite at an altitude of 850 km. The scans cover the range of 10-26.5 below horizontal, consistent with future multiyear missions. To provide a baseline assessment, we represent the synthetic ground truth (``true'') O+ distribution as a generalized Chapman-type profile with three or more parameters, based on our recent analysis of topside incoherent scattering radar data and standard ionospheric models (International Reference Ionosphere 1990 (IRI-90) and the parameterized ionospheric model (PIM)). The DIT method proves to be robust, converging to an accurate solution for a wide variation in ionospheric profiles. Using a detailed statistical error analysis of synthetic limb intensity data derived from the IRI-90 and PIM models, we work a difficult test case following from recent comments on the concept of 834- remote sensing of ionospheric O+. We find that the DIT method can correctly distinguish between distinctly different F layers that produce nearly identical intensity profiles, consistent with instrument specifications for future missions.

  5. Nighttime ionospheric enhancements induced by the occurrence of an evening solar eclipse

    NASA Astrophysics Data System (ADS)

    Chen, Gang; Qi, Hao; Ning, Baiqi; Zhao, Zhengyu; Yao, Ming; Deng, Zhongxing; Li, Ting; Huang, Shuo; Feng, Wenchao; Wu, Jianhua; Wu, Chen

    2013-10-01

    solar eclipse on 15 January 2010 traversed Asia and completed its travel on the Shandong Peninsula in China at sunset. Two vertical incidence ionosondes at Wuhan and Beijing and the oblique incidence ionosonde network in North China were implemented to record the ionospheric response to the solar eclipse. Following the initial electron density decrease caused by the eclipse, the ionosphere was characterized by a strong premidnight enhancement, and a subsequent ionospheric decay, and a ~10 h later postmidnight enhancement. Neither geomagnetic disturbance occurred during the eclipse day nor did obvious nighttime peak appear for the 10 day mean of the F2-layer critical frequency (foF2). The electron density profilogram of the Beijing ionosonde indicates that the two enhancements were the result of the plasma flux downward from the top ionosphere, possibly due to the steep decrease of the ionospheric electron density and plasma temperature during the solar eclipse. The two-dimensional differential foF2 maps present the regional variations of the nighttime electron density peaks and decay. Both the pre- and postmidnight enhancements initially appeared in a belt almost in parallel with the eclipse track and then drifted southward. The different magnitudes of greatest eclipse in the umbra and outside tend to account for the different occurrence times of the plasma flux. The ionospheric decay following the premidnight enhancement is also considered as a consequence of the eclipse shade.

  6. Extreme Space Weather: Storm Enhanced Density in the Ionosphere and Magnetosphere

    NASA Astrophysics Data System (ADS)

    Foster, J. C.; Coster, A. J.; Erickson, P. J.; Rideout, W.

    2011-12-01

    During geomagnetic storms the equilibrium of production and loss which maintains average ionospheric characteristics is greatly perturbed. High-latitude disturbance electrodynamics penetrates to the equator and dayside ionospheric total electron content (TEC) is greatly enhanced as solar-produced plasma is uplifted into regions of decreased ion-neutral collision-induced recombination. During extreme events dayside mid-latitude TEC can exceed 200 TECu (1 TECu = 1.E16 electrons m-2). At higher altitudes, interactions in the plasmasphere boundary layer involving hot ring current particles and the outer regions of the cold plasmasphere (the high-altitude extent of the mid-latitude ionosphere) lead to the formation of a broad sub-auroral polarization stream (SAPS) flow channel which transports high-TEC plasma poleward and noonward to the ionospheric footprint of the cusp and onto polar cap magnetic field lines. These high-TEC storm enhanced density (SED) plumes mirror the erosion of the outer plasmasphere. This overall process produces large TEC and TEC gradients at ionospheric heights and significantly impacts magnetospheric processes and particle precipitation effects as the heavy ionospheric SED ions are injected into the magnetosphere, altering both the progression of storm development and subsequent inner magnetosphere/ring current characteristics. In this talk we investigate the processes and physical causes of extreme SED plumes originating in the North American longitude sector.

  7. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-09-01

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

  9. 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

  10. 3D Model of the Martian Ionosphere

    NASA Astrophysics Data System (ADS)

    Chaufray, J.-Y.; Gonzalez-Galindo, F.; Forget, F.; Lopez-Valverde, M.; Leblanc, F.; Modolo, R.; Yagi, M.; Hess, S.; Blelly, P.-L.; Witasse, O.

    2012-04-01

    For planets without intrinsic magnetic field like Mars and Venus, the ionosphere is the main obstacle decelerating and deviating the solar wind flow. Therefore, the ionosphere plays an important part in erosion processes associated to Mars-solar wind interaction. Below 180 km, the Martian ionosphere is well described by the photochemical equilibrium. Above 180 km, the transport processes become important. To describe the Martian upper ionosphere, we develop a 3D multi-fluid dynamical core in the LMD Martian general circulation model (GCM) (Forget et al. 1999, Gonzalez-Galindo et al. 2009). This core solves the horizontal and vertical dynamics of the main ionospheric species and their coupling and retroaction on the neutral atmosphere at different seasons. This model will be later coupled to a magnetospheric model in order to describe the Martian ionospheric erosion by the solar wind.

  11. Effect of interplanetary magnetic field on ionosphere over the magnetic equator

    NASA Technical Reports Server (NTRS)

    Rastogi, R. G.; Patel, V. L.

    1975-01-01

    Large and quick changes of the latitude of the interplanetary magnetic field from its southward to northward direction are shown to be associated with the disappearance of the Es-q layer (Knecht, 1959) at the equatorial ionosphere during the daytime or with the reversal of E region horizontal and F region vertical electron drifts during both night and day. This phenomenon is suggested as the imposition of an electric field in the ionosphere in a direction opposite to that of the Sq electric field. The resultant electrostatic field on the equatorial ionosphere would be decreased or even reversed from its normal direction, resulting in the reduction of electron drift velocity. When the normal Sq field is over-compensated by the magnetospheric electric field, the electron drifts are reversed and the irregularities in the E region due to the cross-field instabilities are inhibited, resulting in the sudden disappearance of the Es-q layers.

  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. An extended TRANSCAR model including ionospheric convection: simulation of EISCAT observations using inputs from AMIE

    NASA Astrophysics Data System (ADS)

    Blelly, P.-L.; Lathuillère, C.; Emery, B.; Lilensten, J.; Fontanari, J.; Alcaydé, D.

    2005-02-01

    The TRANSCAR ionospheric model was extended to account for the convection of the magnetic field lines in the auroral and polar ionosphere. A mixed Eulerian-Lagrangian 13-moment approach was used to describe the dynamics of an ionospheric plasma tube. In the present study, one focuses on large scale transports in the polar ionosphere. The model was used to simulate a 35-h period of EISCAT-UHF observations on 16-17 February 1993. The first day was magnetically quiet, and characterized by elevated electron concentrations: the diurnal F2 layer reached as much as 1012m-3, which is unusual for a winter and moderate solar activity (F10.7=130) period. An intense geomagnetic event occurred on the second day, seen in the data as a strong intensification of the ionosphere convection velocities in the early afternoon (with the northward electric field reaching 150mVm-1) and corresponding frictional heating of the ions up to 2500K. The simulation used time-dependent AMIE outputs to infer flux-tube transports in the polar region, and to provide magnetospheric particle and energy inputs to the ionosphere. The overall very good agreement, obtained between the model and the observations, demonstrates the high ability of the extended TRANSCAR model for quantitative modelling of the high-latitude ionosphere; however, some differences are found which are attributed to the precipitation of electrons with very low energy. All these results are finally discussed in the frame of modelling the auroral ionosphere with space weather applications in mind.

  14. 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.

  15. 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

  16. 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

  17. 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 [Snchez - 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. Snchez - Cano et al., 2013. Icarus, 225, 236-247.

  18. Resonance scattering at excited atoms and ions of the upper atmosphere as a possible mechanism for ionosphere investigations

    NASA Astrophysics Data System (ADS)

    Bychkov, Vasily V.; Nepomnyashchiy, Yuri A.; Perezhogin, Andrey S.; Shevtsov, Boris M.

    2015-11-01

    According to the results of lidar observations in 2014, new experimental data are presented. They confirm the possibility of correlation of lidar signals backscattering at the wavelength of 532 nm with the parameters determining plasma content in the nighttime ionospheric F2 layer. The possibility of application of the lidar method in ionosphere investigations is discussed. The physical basis of this method may be the resonance scattering on the exited atoms and ions of the upper atmosphere.

  19. Inverse problem of radiofrequency sounding of ionosphere

    NASA Astrophysics Data System (ADS)

    Velichko, E. N.; Yu. Grishentsev, A.; Korobeynikov, A. G.

    2016-01-01

    An algorithm for the solution of the inverse problem of vertical ionosphere sounding and a mathematical model of noise filtering are presented. An automated system for processing and analysis of spectrograms of vertical ionosphere sounding based on our algorithm is described. It is shown that the algorithm we suggest has a rather high efficiency. This is supported by the data obtained at the ionospheric stations of the so-called “AIS-M” type.

  20. Investigation of traveling ionospheric disturbances

    NASA Technical Reports Server (NTRS)

    Grossi, M.; Estes, R. D.

    1981-01-01

    Maximum entropy power spectra of the ionospheric electron density were constructed to enable PINY to compare them with the power independently obtained by PINY with in situ measurements of ionospheric electron density and neutral species performed with instrumentation carried by the Atmospheric Explorer (AE) satellite. This comparison corroborated evidence on the geophysical reality of the alleged electron density irregularities detected by the ASTP dual frequency Doppler link. Roughly half of the localized wave structures which are confined to dimensions of 1800 km or less (as seen by an orbiting Doppler baseline) were found to be associated with the larger crest of the geomagnetic anomaly in the Southern (winter) Hemisphere in the morning. The observed nighttime structures are also associated with local peaks in the electron density.

  1. Far ultraviolet nighttime ionospheric photometer

    NASA Astrophysics Data System (ADS)

    Fu, Liping; Peng, Ruyi; Shi, Entao; Peng, Jilong; Wang, Tianfang; Jiang, Fang; Jia, Nan; Li, Xiaoyin; Wang, Yongmei

    2015-01-01

    Far Ultraviolet Nighttime Ionopsheric Photometer (FNIP) is a newly-designed instrument for low earth orbit missions, observing the earth night airglow nadir at OI 135.6 nm emission produced by ionospheric O++e recombination and receiving the horizontal information on nighttime ionosphere with a spatial resolution of about 1.6?3.8?. This simple, highly robust instrument excludes OI 130.4 nm emission and Herzberg oxygen bands with lower power and approximately achieves a sensitivity of about 400 counts/s/Rayleigh at 135.6 nm with stray light less than 2 %. Some tests of the instrument have been conducted and the results will be discussed in the end.

  2. 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.

  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. 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.).

  5. 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 (Dst<−100 nT) sets, we find variation in storm strength that corresponds closely to the TEC variation but follows it by 3–6h. For this and other reasons detailed in this report, we conclude that the UT-dependent peak in storm time TEC is likely not related to the magnitude of external storm time forcing but more likely attributable to phenomena such as the low magnetic field in the South American region. The large Dst variation suggests a possible system-level effect of the observed variation in ionospheric storm response on the measured strength of the terrestrial ring current, possibly connected through UT-dependent modulation of ion outflow. PMID:26167429

  6. Ionospheric very low frequency transmitter

    SciTech Connect

    Kuo, Spencer P.

    2015-02-15

    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.

  7. 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.

  8. The ionosphere under extremely prolonged low solar activity

    NASA Astrophysics Data System (ADS)

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

    2011-04-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-02-01

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

  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. 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.

  12. Challenges in Solar System Ionospheres

    NASA Astrophysics Data System (ADS)

    Mendillo, M.

    2001-12-01

    The solar system contains a robust set of ionospheres among its nine planets, many moons and comets. If one sets aside the transient atmospheres/ionospheres of comets, and those of larger bodies with tenuous surface-boundary-exospheres (e.g., Mercury, Moon, Europa, etc.), plus the under-sampled Pluto, then 10 case studies exist for detailed study and comparison (Venus, Earth, Mars, Jupiter & Io, Saturn & Titan, Uranus, and Neptune & Triton). The ionospheres of these bodies define the full range of natural processes that govern plasma environments in our solar system, and indeed for extra-solar-system planets: (a) photo-chemical mechanisms, (b) energetic (auroral) ionization sources, (c) mesospheric/thermospheric tides, winds and waves, (d) electrodynamics, and (e) solar wind impact and/or shielding by a magnetosphere. This brief review will summarize and compare the dominant production, loss and transport mechanisms thought to occur at each site. Major uncertainties are, surprisingly, not due entirely to remoteness of the bodies being studied.

  13. 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.

  14. Mechanisms of Ionospheric Mass Ejection

    NASA Technical Reports Server (NTRS)

    Moore, Thomas Earle; Khazanov, George V.; Hannah, Mei-Ching; Glocer, Alex

    2010-01-01

    Ionospheric outflows are directly responsive to solar wind disturbances, particularly in the dayside auroral cusp or cleft regions. Inputs of both electromagnetic energy (Poynting flux) and kinetic energy (particle precipitation) are closely correlated with these outflows. We assess the importance of processes thought to drive ionospheric outflows. These begin with the diffuse effects of photoionization and thermal equilibrium of the ionospheric topside, enhancing Jeans' escape, with ambipolar diffusion and acceleration. Auroral outflows begin with dayside reconnexion and resultant field-aligned currents and driven convection. These produce plasmaspheric plumes, collisional heating and wave-particle interactions, centrifugal acceleration, and auroral acceleration by parallel electric fields, including enhanced ambipolar fields from electron heating by precipitation particles. Solar wind energy dissipation is concentrated by the geomagnetic field into auroral regions with an amplification factor of 10-100, enhancing heavy species plasma and gas escape from gravity, and providing more current carrying capacity. Internal plasmas thus enable electromagnetic driving via coupling to the plasma and neutral gas. We assess the importance of each of these processes in terms of local escape flux production as well as global outflow, and suggest methods for their implementation within multi-species global simulation codes. We conclude by assessing outstanding obstacles to this objective.

  15. Topside high latitude ionospheric structures

    NASA Astrophysics Data System (ADS)

    Rothkaehl, Hanna; Przepika, Dorota; Matyjasik, Barbara

    2015-04-01

    The radiations belts region can play a major role in the near Earth environment. Despite the fact that the analysis of properties of Earth electromagnetic environment has had a long history, the topics related to deeply understanding waves particles interaction in radiation belts region and in connecting ionosperic region are still not sufficiently understood. Particularly it seems that description of energy transfer in the ionosphere-magnetosphere coupling processes, can be a major task to solve in near future. By help the wave and plasma diagnostics located on board of past low orbiting satellites operated Demeter satellite and new RELEC mission the description of selected physical processes occurred in auroral region of topside ionosphere are reported. The aim of this presentation is to show the response of ionospheric plasma to the energetic particle fluxes coming from radiation belts region and describe the complex coupling processes of radiation belts region and low altitude near Earth radiation environment. The presented analysis can be very useful for constricting new operation models incorporated in Space Weather program.

  16. Saturn's ionosphere: inferred electron densities

    SciTech Connect

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

    1983-12-01

    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.

  17. A statistical study of short period waves in the ionosphere above Central Europe

    NASA Astrophysics Data System (ADS)

    Sindelarova, Tereza; Chum, Jaroslav; Mosna, Zbysek; Buresova, Dalia; Potuznikova, Katerina; Base, Jiri; Fiser, Jiri

    2015-04-01

    We present a statistical study of waves of periods 0.5-6 min that occurred in the ionosphere above the Czech Republic. The dataset covers one year period from April 2013 to March 2014. Data were obtained from Doppler ionospheric sounding. The sounding is based on measurements of frequency shift between the transmitted wave of a stable known frequency and the wave received after its reflection in the ionosphere. It is a suitable tool for observations of wave activity in the ionosphere, particularly in the period range up to 60 min. The main objective of the study was to find whether there exist a preferred season and time of the day in the occurrence of these waves. We identified altogether 247 events of duration between 1minute and 13 hours. The highest number of events occurred in September 2013 (44 events). Contrary, only 5 events appeared in May 2013. In the diurnal course, the waves tend to occur mainly between sunset and sunrise. The described diurnal variability can be to some measure explained by diurnal changes of electron concentrations in the ionosphere and consequent changes of the reflection height of the Doppler sounding wave. The 3.59 MHz radio wave usually reflects from the ionospheric F layer at night and from the E layer during the daytime. When the sounding wave reflects in the E region, it usually experiences zero or only negligible Doppler shift. Similarly, low number of events in May (and also in July) can be related with seasonal variability of electron concentration in the ionosphere. Sources of oscillations measured by the Doppler sounding system in the studied period range of 0.5-6 min include infrasound, geomagnetic micropulsations or transient changes of electron concentration caused by x-rays arrivals. We will present the interpretation of the statistical study with relation to the stated sources.

  18. Artificial Intelligence.

    PubMed

    Lawrence, David R; Palacios-González, César; Harris, John

    2016-04-01

    It seems natural to think that the same prudential and ethical reasons for mutual respect and tolerance that one has vis-à-vis other human persons would hold toward newly encountered paradigmatic but nonhuman biological persons. One also tends to think that they would have similar reasons for treating we humans as creatures that count morally in our own right. This line of thought transcends biological boundaries-namely, with regard to artificially (super)intelligent persons-but is this a safe assumption? The issue concerns ultimate moral significance: the significance possessed by human persons, persons from other planets, and hypothetical nonorganic persons in the form of artificial intelligence (AI). This article investigates why our possible relations to AI persons could be more complicated than they first might appear, given that they might possess a radically different nature to us, to the point that civilized or peaceful coexistence in a determinate geographical space could be impossible to achieve. PMID:26957450

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. Modelling the Cosmic Ray (CR) Effect in the Polar Ionosphere with Account of Anomalous CR-Component

    NASA Astrophysics Data System (ADS)

    Mateev, L. N.

    1997-01-01

    The lower part of the D-region is created by cosmic rays which form there an independent Cosmic Ray (CR)-layer. The CR-layer is important for the propagation of the long and very long radio waves. For that reason the rates investigation of the ionization rates in the middle atmosphere is significant for the understanding of the electric and other physical and chemical processes there. The CR-layer is a boundary layer between the ionosphere and the neutral gas in the stratosphere. Actually a few models for cosmic ray influence on the middle latitude ionosphere exist. But the effects of the high energy cosmic particles are much more essential in the polar ionosphere, because of the comparatively weak geomagnetic cut-offs. For that reason in the present paper a more adequate model of high latitude ionization of cosmic rays is proposed. The model will include the recently discovered anomalous component of cosmic rays.

  6. Ionospheric Storm Effects above Kharkov during the August 5-6, 2011

    NASA Astrophysics Data System (ADS)

    Chernogor, L.; Domnin, I.; Emelyanov, L.; Kharytonova, S.; Lyashenko, M.

    2012-04-01

    The super strong magnetic storm began at 19:03 UT on August 5, 2011. The geomagnetic activity index Kp during the main storm phase was 8-, Dst = -113 nT. The solar wind radial velocity during the main phase varied within 570 - 620 km s-1. The temperature of solar wind particles increased up to 6.4105 K and their concentration Nsw ? 1.9107 m-3. The value of the interplanetary magnetic field (IMF) Bz component was -(15 - 18) nT, the value of the magnetic induction modulus of the IMF equaled 25 - 27 nT. The aurora activity index was AE ? 1740 nT. The value of Akasofu function was ? ? 37 GJ s-1. For the observations of ionospheric storm effects, the Kharkov incoherent scatter radar was used, which is unique source of information about parameters and processes in ionospheric plasma in mid-latitude Europe. The effects of the magnetic storm on August 5 - 6, 2011 were observed in variations of ionosphere parameters confidently. The storm above Kharkov was accompanied by a negative ionosphere disturbance. The electron density in the F2-layer maximum of ionosphere decreased approximately by a factor up to 2 in comparison with the reference day up to 1011 m-3. Next twenty-four hours on 6 August Nm was approximately more on 30 % than in the reference day of 4th August 2011. The F2-layer maximum height in the main phase of the ionospheric storm increased to 513 km. In quiet conditions of 4th August F2-layer was on a height zm ? 315 km. The electron density on heights 200, 250, 300, 350 and 400 km in the moment of the main phase of the ionospheric storm decreased approximately by 85, 91, 82, 61 and 27% accordingly. The electron temperature in the main phase of the ionospheric storm increased approximately by a factor up to 4 and 2.5 at the heights 200 - 250 km, and in the range of heights 300 - 700 km Te increased approximately by a factor up to 1.5 - 1.8 in comparison with the reference day. The ion temperature in considered period also increased approximately on 700 - 1000 K in the range of heights 200 - 250 km. On heights 300 - 700 km Ti increased approximately by a factor up to 1.5. The storm on August 5 - 6, 2011 had adduced to transform of dynamic and heat conditions in ionosphere.

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

    NASA Astrophysics Data System (ADS)

    Bernhardt, P. A.

    2009-12-01

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

  8. 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.

  9. 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.

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

    NASA Astrophysics Data System (ADS)

    Chen, Hungru; Umezawa, Naoto

    2015-02-01

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

  11. 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.

  12. 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.

  13. Artificial Intelligence

    SciTech Connect

    Shirai, Y.; Tsujii, Jun-ichi

    1985-01-01

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

  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. 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 Troms. 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

  16. 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.

  17. Approaches to ionospheric modelling, simulation and prediction

    NASA Technical Reports Server (NTRS)

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

    1992-01-01

    The ionosphere is a complex, multispecies, anisotropic medium that exhibits a significant variation with time, space, season, solar cycle, and geomagnetic activity. In recent years, a wide range of models have been developed in an effort to describe ionospheric behavior. The modeling efforts include: (1) empirical models based on extensive worldwide data sets; (2) simple analytical models for a restricted number of ionospheric parameters; (3) comprehensive, 3D, time-dependent models that require supercomputers; (4) spherical harmonic models based on fits to output obtained from comprehensive numerical models; and (5) ionospheric models driven by real-time magnetospheric inputs. In an effort to achieve simplicity, some of the models have been restricted to certain altitude or latitude domains, while others have been restricted to certain ionospheric parameters, such as the F-region peak density, the auroral conductivity, and the plasma temperatures. The current status of the modeling efforts is reviewed.

  18. 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.

  19. Modifying the ionosphere with intense radio waves.

    PubMed

    Utlaut, W F; Cohen, R

    1971-10-15

    The ionospheric modification experiments provide an opportunity to better understand the aeronomy of the natural ionosphere and also afford the control of a naturally occurring plasma, which will make possible further progress in plasma physics. The ionospheric modification by powerful radio waves is analogous to studies of laser and microwave heating of laboratory plasmas (20). " Anomalous" reflectivity effects similar to the observed ionospheric attenuation have already been noted in plasmas modulated by microwaves, and anomalous heating may have been observed in plasmas irradiated by lasers. Contacts have now been established between the workers in these diverse areas, which span a wide range of the electromagnetic spectrum. Perhaps ionospheric modification will also be a valuable technique in radio communications. PMID:17778050

  20. Mesospheric Impact on Thermosphere and Ionosphere

    NASA Astrophysics Data System (ADS)

    Wu, Qian; Roble, Raymond; Foster, Benjamin

    To explore the mesospheric effect on the thermosphere and ionosphere, we use the TIMED SABER geopotential height, temperature and TIDI wind data as the lower boundary condition at 97 km to drive the NCAR Thermosphere Ionosphere Electrodynamic General Circulation Model, (TIEGCM). The TIMED data contain both migrating and nonmigrating tides. The model simulation results then can be compared with the observations from COSMIC, and TIMED GUVI observations. There is a great interest in the mesospheric effect on the ther-mosphere and ionosphere, the TIMED data driven TIEGCM is a tool to explore the impact of the mesosphere on the thermosphere and ionosphere. It can be used to analyze more recent satellite thermosphere and ionosphere observations. We will show some preliminary results of the simulation.

  1. Antarctic Peninsula troposphere-stratosphere-ionosphere coupling (APTIC) and conjugate events investigation

    NASA Astrophysics Data System (ADS)

    Milinevsky, G.

    2005-04-01

    Researches of troposphere-stratosphere-ionosphere coupling are based on idea of the strong influence of the long- and short-term solar activity variations on the polar terrestrial climate and the asymmetry in the energy deposition from the magnetosphere into the polar ionospheres. The solar activity variations produce changeable impact on magnetosphere and polar ionosphere in both hemispheres. Results of this impact are (1) differences in the ozone concentrations in the Antarctic and Arctic stratosphere due to different forcing in spring; (2) different planetary wave activity; (3) different gravity wave flux intensity depended on strengths of the weather frontal cyclones activity. The study of upper atmosphere in both hemispheres is necessary to better understand various physical mechanisms responsible for the energy transfer from the Sun into atmosphere and ionosphere as well as reverse flux from troposphere to geospace. A simultaneous consideration of phenomena occurring over both polar regions is very important for understanding of these processes. The solution of the problem of energy exchange between neutral atmosphere and geospace plasma is need in study of industrial EM pollution from Earth surface to geospace. A corresponding work must promote modeling space weather on satellite heights and earthquake prediction using ionosphere parameters changes. A determinative significance of Antarctic Peninsula is caused by following features: (1) Antarctic Peninsula is situated near an extremely cyclonic active region - Drake Passage, (2) only this region in Antarctica is magnetically conjugated to industrial area in Northern hemisphere, and (3) this region contains many Antarctic stations which are good equipped by devices to study weather and climate, ozone layer, ionosphere and magnetic field. Last years weather observations at Vernadsky station show that up to 60 atmospheric frontal cyclones (with pressure variation more 20 millibars) swept over Antarctic Peninsula during year. Therefore this region is the most appropriate to study ionosphere impact of troposphere induced AGW. These features produced the scientific goal of the project APTIC. It is to explore the response of the ionosphere to strong weather systems sweeping the Antarctic Peninsula sector and identify energy transfer mechanisms. Main task of the project consists in research of the energy exchange processes between lower (troposphere) and upper atmosphere and EM impact of weather front (cyclone) on ionosphere over Antarctic Peninsula as well as in conjugate region (east coast of the USA). Multipositional study of the powered atmosphere cyclone fronts on Antarctic Peninsula to ionosphere, magnetosphere and conjugate region using three (and more in future) automatic meteo-mag-receivers (MMR) is a new direction of researches. Main scientific objectives of APTIC project are (1) study of the travelling ionosphere disturbances (TID) within F2-layer hights; (2) study of macroscale atmosphere wavelike processes: tides, planetary waves and their image in ozone layer; (3) study of the impact of troposphere disturbances to ozone layer and ionosphere; (4) search the possible influence of sharp changes and longtime trend in ozone layer to troposphere and climate; (5) study of the spatial-temporal structure of frontal weather systems, their moving velocity and direction; (6) search of the time variations (shift) in the geomagnetic substorm development using long-distance chain (Frei-Palmer-Vernadsky-Rothera); (7) study of the spatial corelation of resonance geomagnetic micropulsation; (8) study of the polarisation structure of geomagnetic micropulsation.

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

    NASA Astrophysics Data System (ADS)

    Heki, K.

    2011-12-01

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

  3. 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.

  4. F-spread In The Ionospheric Seismic Activity Region During The Preparation of Earthquake

    NASA Astrophysics Data System (ADS)

    Alimov, O. A.; Blohin, A. V.; Negmatullaev, S. H.

    On the basis of statistical analysis of data on the F-spread near critical frequence fo F2 of the F2 layer of ionosphere a decrease of plazma turbulence during earthquake preparation was shown, The increase of F-spread of the iono- sphere before 3 days the Gissar 1989 year earthquake ( M=5,5 ) was founded. The possible mechanism of this ionospheric effect have boen studied. Show that the strong F-spread depend on disturbention of the seismical electric field.

  5. Strong scintillation of GNSS signals in the inhomogeneous ionosphere: 1. Theoretical background

    NASA Astrophysics Data System (ADS)

    Zernov, Nikolay N.; Gherm, Vadim E.

    2015-02-01

    The analytical theory of the Global Navigation Satellite Systems (GNSS) signal propagation through the inhomogeneous ionosphere with time-varying embedded localized random inhomogeneities of electron density is constructed in order to describe the regime of strong scintillation of the wave field propagating in the inhomogeneous ionospheric layer. The theory is based on the solutions of the appropriate Markov's parabolic moment equations, extended to the case of the inhomogeneous background medium. The solutions are validated by the comparison with some rigorous (numerical) solutions known for some limiting cases. The developed theory forms the theoretical background for constructing the physically based software simulator of the random transionospheric GNSS signals.

  6. 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.

  7. 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.

  8. Historical overview of HF ionospheric modification research

    SciTech Connect

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

    1990-10-01

    Radio waves have inadvertently modified the Earth's ionosphere since the Luxembourg observations of Tellegen in 1933 and perhaps since Marconi in 1901. The history of ionospheric modification by radio waves is reviewed, beginning with Marconi, describing the Luxembourg effect and its explanations, and its early use to deduce the properties of the lower ionosphere in the 1930s. The measurements became more sophisticated in the 1950s, leading to the call for high-power high-frequency modification experiments in the upper ionosphere. Beginning in 1970, radio facilities became available of sufficient powers to induce changes in the ionospheric plasma detectable by a wide array of diagnostic instruments and techniques. A summary of these effects is presented based upon work up to 1990. These studies were originally motivated as a means of better understanding the natural ionosphere using a weak perturbational approach. However, a rich spectrum of nonlinear wave-plasma interactions was quickly discovered and ionospheric modification research became strongly motivated by issues in basic plasma physics. The ionosphere and near-Earth space are now exploited as an exceptional plasma laboratory-without-walls for the study of fundamental plasma processes requiring large spatial or temporal scales. Here we present a brief overview of these processes and phenomena, illustrated using results obtained from the Arecibo ionospheric modification facilities. The lessons learned and phenomena explored thus far offer many opportunities for controlling the ionospheric environment critical to many civilian and military telecommunications systems, both to disrupt systems normally operational and to create new propagation paths otherwise unavailable.

  9. Ionospheric data assimilation and forecasting during storms

    NASA Astrophysics Data System (ADS)

    Chartier, Alex T.; Matsuo, Tomoko; Anderson, Jeffrey L.; Collins, Nancy; Hoar, Timothy J.; Lu, Gang; Mitchell, Cathryn N.; Coster, Anthea J.; Paxton, Larry J.; Bust, Gary S.

    2016-01-01

    Ionospheric storms can have important effects on radio communications and navigation systems. Storm time ionospheric predictions have the potential to form part of effective mitigation strategies to these problems. Ionospheric storms are caused by strong forcing from the solar wind. Electron density enhancements are driven by penetration electric fields, as well as by thermosphere-ionosphere behavior including Traveling Atmospheric Disturbances and Traveling Ionospheric Disturbances and changes to the neutral composition. This study assesses the effect on 1 h predictions of specifying initial ionospheric and thermospheric conditions using total electron content (TEC) observations under a fixed set of solar and high-latitude drivers. Prediction performance is assessed against TEC observations, incoherent scatter radar, and in situ electron density observations. Corotated TEC data provide a benchmark of forecast accuracy. The primary case study is the storm of 10 September 2005, while the anomalous storm of 21 January 2005 provides a secondary comparison. The study uses an ensemble Kalman filter constructed with the Data Assimilation Research Testbed and the Thermosphere Ionosphere Electrodynamics General Circulation Model. Maps of preprocessed, verticalized GPS TEC are assimilated, while high-latitude specifications from the Assimilative Mapping of Ionospheric Electrodynamics and solar flux observations from the Solar Extreme Ultraviolet Experiment are used to drive the model. The filter adjusts ionospheric and thermospheric parameters, making use of time-evolving covariance estimates. The approach is effective in correcting model biases but does not capture all the behavior of the storms. In particular, a ridge-like enhancement over the continental USA is not predicted, indicating the importance of predicting storm time electric field behavior to the problem of ionospheric forecasting.

  10. Aerosol growth in Titan's ionosphere.

    PubMed

    Lavvas, Panayotis; Yelle, Roger V; Koskinen, Tommi; Bazin, Axel; Vuitton, Vronique; 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

  11. 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

  12. Electrostatic reconnection in the ionosphere

    NASA Astrophysics Data System (ADS)

    Huba, J. D.; Wu, T.-W.; Makela, J. J.

    2015-03-01

    Postsunset equatorial plasma bubble merging is examined using the National Research Laboratory code SAMI3/equatorial spread F. It is found that bubbles merge through an "electrostatic reconnection" process. As multiple bubbles develop, the electrostatic potential associated with one bubble can connect with that of a neighboring bubble: this provides a pathway for the low-density plasma in one bubble to flow into the adjoining bubble and merge with it. Additionally, high-speed plasma channels (approximately greater than hundreds of meters per second) can develop during the merging process. Optical data is presented of equatorial plasma bubble evolution that suggests bubble merging occurs in the nighttime equatorial ionosphere.

  13. On the problem of detection of seismo-ionospheric phenomena by multi-instrumental radiophysical observations

    NASA Astrophysics Data System (ADS)

    Cherniak, Iurii; Zakharenkova, Irina; Shagimuratov, Irk; Suslova, Olga

    2012-07-01

    Analysis of the previous works on lithosphere-ionosphere interactions confirmed the necessity to use simultaneous observations from several independent diagnostics tools in order to raise the reliability of the observed seismo-ionospheric effects. The influence on the ionosphere from below is weaker in comparison with effects of solar or geomagnetic origin. Due to this reason it is very actual the problem of detection of seismo-ionospheric anomalies on the background of strong regular and quasi-regular variation of space weather parameters. For the given research we use integrated processing of the ionospheric data from different sources: total electron content (TEC) data obtained on the basis of regular GPS observations of IGS stations located in Sakhalin and Japan regions, ionospheric E and F2 layers peak parameters, derived from data of Japan ionosonde network and electron density profiles, obtained by FORMOSAT-3/COSMIC radio occultation measurements. As a case-study it was analyzed the Nevelsk earthquake (M 6.2) that took place at the Far East of Russian Federation on August 2, 2007. On July 29, 2007, several days prior to earthquake, the characteristic anomaly was found out as the day-time significant enhancement of TEC at the vicinity of earthquake. This enhancement reached the maximal value of 4-6 TECU in absolute values, that is 40-50% to the background conditions, and it was situated very close to the epicenter position. The noticeable enhancement of F2 peak critical frequency (foF2) was observed over Wakkanai ionosonde. For the evening hours (19-22 LT) it reached the value of 6.8-7.7 MHz whereas monthly median was 5.3-5.7 MHz. This foF2 increase was coincided in time with the appearance of TEC anomaly in TEC maps over the considered region (taken from GIMs IONEX). In order to separate seismo-ionospheric perturbations from geomagnetic disturbances it was done the comparative analysis of the revealed ionospheric effect possibly related with seismic activity and ionosphere changes during geomagnetic storms which took place during July and August of 2007. We acknowledge the University Corporation for Atmospheric Research (UCAR) for providing the COSMIC data, IGS community for GPS permanent data and WDC for Ionosphere, Tokyo, National Institute of Information and Communications Technology (NICT) for ionosonde data. This work was supported by Russian Federation President grant MK-2058.2011.5.

  14. Observations of weak ionosphere disturbances on the Kharkov incoherent scatter radar

    NASA Astrophysics Data System (ADS)

    Cherniak, Iurii; Lysenko, Valery; Cherniak, Iurii

    The ionosphere plasma characteristics are responding on variations of solar and magnetic activity, high-power processes in the Earth atmosphere and lithosphere. The research of an ionosphere structure and dynamics is important as for understanding physics of processes and radiophysical problems solution. The method of incoherent scatter (IS) of radiowaves allows determining experimentally as regular variations of electronic concentration Ne and concomitant ionosphere parameters, and their behaviour during natural and antropogeneous origin disturbances. The equipment and measurement technique, developed by authors, are allows obtaining reliable data about an ionosphere behaviour during various origin and intensity perturbations. Oservations results of main parameters IS signal and ionosphere plasma during weak magnetic storm, solar eclipse, ionosphere disturbances caused by start of the high-power rocket are presented. Experimentally obtained on the Kharkov IS radar altitude-temporary dependences of disturbed ionosphere plasma parameters during weak intensity magnetic storm 04-06 April 2006 (Kp = 5, Dst = -100 nTl) were adduced. During a main storm phase the positive perturbation was observed (Ne is increased in 1.3 times), April 5, at maximum Dst - negative perturbation (Ne is decreased in 1.6 times), April 6 - positive perturbation (the second positive storm phase - Ne was increased at 1.33 times). During negative ionosphere storm the height of a F2 layer maximum was increased on 30-40 km, ionic temperature in the day is increased on 150K, electronic temperature is increased on 600K. For date 29.03.2006, when take place partial Sun eclipse (disk shadow factor 73 During launch heavy class rocket "Proton-K" december 25, 2006 from Baikonur cosmodrome (distance up to a view point of 2500 km) the perturbations in close space were observed. By measurements results of ionosphere plasma cross-section two disturbed areas were registered. First was observed through 8 mines, and second - through 60 mines after start of the rocket. The altitude-temporary diagrams of ionosphere plasma cross-section distribution were adduced.

  15. Artificial layered perovskite oxides A(B{sub 0.5}B′{sub 0.5})O{sub 3} as potential solar energy conversion materials

    SciTech Connect

    Chen, Hungru; Umezawa, Naoto

    2015-02-07

    Perovskite oxides with a d{sup 0} electronic configuration are promising photocatalysts and exhibit high electron mobilities. However, their band gaps are too large for efficient solar energy conversion. On the other hand, transition metal cations with partially filled d{sup n} electronic configurations give rise to visible light absorption. In this study, by using hybrid density functional theory calculations, it is demonstrated that the virtues of the two categories of materials can be combined in perovskite oxide A(B{sub 0.5}B′{sub 0.5})O{sub 3} with a layered B-site ordering along the [001] direction. The electronic structures of the four selected perovskite oxide compounds, La(Ti{sub 0.5}Ni{sub 0.5})O{sub 3}, La(Ti{sub 0.5}Zn{sub 0.5})O{sub 3}, Sr(Nb{sub 0.5}Cr{sub 0.5})O{sub 3}, and Sr(Nb{sub 0.5}Fe{sub 0.5})O{sub 3} are calculated and discussed.

  16. The story of the ionosphere as a global communications medium

    NASA Astrophysics Data System (ADS)

    Hartmann, G. K.

    1987-10-01

    The developing role of the ionosphere in global communications is philosophically examined. The physical characteristics of the ionosphere that enable its use in communications are reviewed. The nature of information theory is discussed and the status of the ionosphere as a helical structure in time within that theory is addressed. Ecological and economic aspects of the communications role of the ionosphere are considered.

  17. Technique for measuring ionospheric irregularities generated by high-power oblique HF heating of the F-region

    SciTech Connect

    Sales, G.S.; Reinisch, B.W.; Ralls, J.A.

    1990-08-01

    A new technique for investigating the changes in the small to medium scale structure of the F-layer of the ionosphere is developed using the existing capabilities of the University of Lowell Center for Atmospheric Research Digisonde 256 vertical ionospheric sounder. When the ionosphere is heated by a high power HF transmitter operating in an oblique radar or communications mode the formation of irregularities has been observed. The development of these irregularities is described in terms of an index of ionospheric roughness which is shown to correlate very well with the natural formation of spread-F. These measurements are relatively simple and can be carried out from a site directly below the heated region.

  18. A case study on ionospheric scintillations at low latitude associated with a plasma blob observed in situ

    NASA Astrophysics Data System (ADS)

    Wang, Z.; Shi, J. K.; Torkar, K.; Wang, G. J.; Wang, X.

    2015-04-01

    In general, ionospheric scintillations at low latitude are considered as signatures of equatorial plasma bubbles (depletions). However, some authors considered that scintillations may also be associated with plasma blobs (enhancements), but there was no in situ measurement hitherto to confirm it. We performed a case study on the concurrent observation of an ionospheric plasma blob with in situ measurements by ROCSAT-1 (i.e. Formosa satellite-1) and of GPS amplitude scintillations in the low-latitude ionosphere on 1 June 2003. The blob measured in situ had a scale size of about 800 km in the F layer, and the ion density inside the blob was severely disturbed. Amplitude scintillation with S4 > 0.3 was observed concurrently in the same longitude range as the blob measured. This case study provides evidence of simultaneously observed GPS amplitude scintillations and a blob in situ, and it confirms that scintillations can be associated with plasma blobs in the low-latitude ionosphere.

  19. 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.

  20. 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.

  1. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2010-06-01

    Ionograms from Rome (41.8N, 12.5E) and Sofia (42.4N, 23.2E) ionospheric stations during earthquake (EQ) activity with magnitude (M) between 5 and 6 in Central Italy are analyzed. It is found that several ionospheric disturbances occur in the intermediate E-F region before the EQ shock. In fact, besides sporadic E (Es) layer development (of type h) of short duration (transients), fmin increase, trace gaps near the critical frequencies, and E region trace disappearance are also observed within one to three hours before the EQ shock. Before the EQ shocks we find that the F2 region parameters are practically undisturbed. The only exception is the so-called fork trace that appears mostly near the critical frequency of the F2 region. Acoustic gravity waves (AGW) are suggested as one of the possible sources of transients observed in the ionosphere before the EQ shock.

  3. The magnetosphere ionosphere system from the perspective of plasma circulation: A tutorial

    NASA Astrophysics Data System (ADS)

    Lotko, W.

    2007-03-01

    This tutorial review examines the role of O+ in the dynamics of magnetosphere ionosphere coupling. The life cycle of an O+ plasma element is considered as it circulates from the mid- to high-latitude ionosphere. Energization and diversion of the convecting plasma element into outflows involves Alfvnic turbulence at the low-altitude base of the cusp and plasmasheet boundary layer and in downward-current pressure cookers. Observational evidence indicating that O+ dominates the plasmasheet and ring current during extreme storm intervals is reviewed. The impacts of an O+-enriched plasma on solar wind magnetosphere ionosphere coupling are considered at both the micro and global scales. A synthesis of results from observation, theory and simulations suggests that the presence of O+ in the magnetosphere is both a disruptive and a moderating agent in maintaining the balance between dayside and nightside magnetic merging.

  4. 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.

  5. Recent discoveries of the thermospheres and ionospheres of Venus and Mars (Invited)

    NASA Astrophysics Data System (ADS)

    Witasse, O. G.

    2013-12-01

    Of all the non-terrestrial ionospheres and thermospheres, those of Venus and Mars have been explored and studied the most, thanks to the Pioneer Venus Orbiter and the Mars Global Surveyor from NASA, and the Venus Express and the Mars Express from ESA. We know that the thermosphere and ionosphere are atmospheric layers strongly influenced by solar wind and solar extreme ultra-violet and soft X-ray flux. This talk will outline the most significant discoveries made recently, which have strong implications on how atmospheres evolve and interact with the Sun. For Venus, there is the sporadic behaviour of the atomic oxygen green line emission, and there is the strong variability of the polar upper atmospheric density. For Mars, there are the responses of the upper atmosphere to solar energetic particle events, the effect of the crustal magnetic field, and the ionospheric vertical structure and boundaries. Finally, this talk will address questions that need to be answered by future missions.

  6. Experimental research on ionospheric disturbance caused by cumulative barium vapor injection

    NASA Astrophysics Data System (ADS)

    Zhulin, I. A.; Milinevskiy, G. P.; Loyevskiy, A. S.; Moysya, R. I.; Romanovskiy, Y. A.; Ruzhin, Y. Y.; Skotarovskiy, V. S.

    1985-05-01

    The Spolokh-2 rocket was used to study a cumulative jet of barium vapor and the disturbances arising during deceleration of the plasma jet in the ionosphere. A capsule with an injector was separated upward along the rocket axis with a relative velocity of 10 m/sec and was stabilized by additional rotation. The barium jet was injected at an altitude of 155 km at the trajectory apogee of an MR-12 rocket. The injector had a higher coefficient of transformation of shot energy into jet kinetic energy. It was possible to register effects associated with shock wave propagation in the ionosphere: the collisionless ionization effect, the phenomenon of raking together of plasma, and others. A stimulated leakage of high energy electrons was discovered; this has the nature of artificial pulsations of electron fluxes. The ionospheric phenomena registered during injection of the jet are satisfactorily explained within the concepts of the snowplow theory. It is shown that the stimulated leakages of high energy electrons can be associated with the excitation of MHD waves in the ionosphere during injection of the jet.

  7. Innovative development and application of models for weakly ionized ionospheric plasmas. Final report, 15 May 1990-30 November 1993

    SciTech Connect

    Eccles, J.V.; Hingst, J.; Armstrong, R.

    1993-11-01

    Artificial modifications of the ionosphere through chemical releases and ionospheric heating experiments are examined with models of chemistry and transport to advance understanding of ion chemistry of the upper atmosphere. The specific releases investigated were the SF6 released of the CRRES-at-Kwajalein rocket campaign and the CO2 releases of the Red Air I program. Both the SF6 and CO2 releases experienced freezing or clustering of the molecules. This must be accounted for in the composition and airglow observations. In addition, HF heating effects in the E and F region were examined through modeling of energy deposition and resulting chemistry. NO sub x production in a HF ionospheric heater beam is estimated and compared with natural sources of NO sub x. Global effects of HF operation are very small but the local effects can be large enough to permit observable modulation to this environment.

  8. 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 (60-72N, 88-152E) 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 (66.8N, 123.3E), and a drastic decrease in the F2 layer critical frequency (foF2) up to 54% of the quite one over subauroral Yakutsk station (62N, 129.7E). 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.

  9. 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

  10. Artificial gravity.

    PubMed

    Scott, William B

    2005-04-25

    NASA's Artificial Gravity program consists of a team of researchers from Wyle Laboratories, NASA Johnson Space Center, and the University of Texas Medical Branch (UTMB). The short-radius centrifuge (SRC), built by Wyle Laboratories, will be integrated with UTMB's conducted bedrest studies, which mimic the detrimental effects of weightlessness (or microgravity). Bedrest subjects will be spun on the SRC at various accelerations and for various time periods, while being monitored medically. Parameters such as bone loss, muscle atrophy, balance control, and oxygen consumption will then be compared in order to research ways of mitigating the impact on astronauts' physiology. Other potential benefits from these studies extend to population groups on Earth, such as bedridden patients. PMID:15852559

  11. Artificial intelligence

    SciTech Connect

    Leepson, M.

    1985-08-16

    A project to develop artificial intelligence (AI) computers that can understand and emulate human speech, perform physical functions, and make reasoned judgments has developed to the point where expert systems with modest powers that suggest reasoning are at work in business and industry. Present-day computers process data, but must be programmed with instructions. AI systems process information more rapidly and can comprehend new types of programming languages that use symbols rather than numbers. The programs compare facts and rules to make deductive, reasoned responses. Sales in AI soft and hardware amount to $150 million a year, and Japan is competing for industry and defense contracts. There is no conclusive proof that computers can do more than make inferences, nor is it known how to instill common sense or spontaneous problem solving.

  12. 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 eff