Sample records for order ionospheric effects

  1. Ionospheric modelling using GPS to calibrate the MWA. 1: Comparison of first order ionospheric effects between GPS models and MWA observations

    E-print Network

    Arora, B S; Ord, S M; Tingay, S J; Hurley-Walker, N; Bell, M; Bernardi, G; Bhat, R; Briggs, F; Callingham, J R; Deshpande, A A; Dwarakanath, K S; Ewall-Wice, A; Feng, L; For, B -Q; Hancock, P; Hazelton, B J; Hindson, L; Jacobs, D; Johnston-Hollitt, M; Kapi?ska, A D; Kudryavtseva, N; Lenc, E; McKinley, B; Mitchell, D; Oberoi, D; Offringa, A R; Pindor, B; Procopio, P; Riding, J; Staveley-Smith, L; Wayth, R B; Wu, C; Zheng, Q; Bowman, J D; Cappallo, R J; Corey, B E; Emrich, D; Goeke, R; Greenhill, L J; Kaplan, D L; Kasper, J C; Kratzenberg, E; Lonsdale, C J; Lynch, M J; McWhirter, S R; Morales, M F; Morgan, E; Prabu, T; Rogers, A E E; Roshi, A; Shankar, N Udaya; Srivani, K S; Subrahmanyan, R; Waterson, M; Webster, R L; Whitney, A R; Williams, A; Williams, C L

    2015-01-01

    We compare first order (refractive) ionospheric effects seen by the Murchison Widefield Array (MWA) with the ionosphere as inferred from Global Positioning System (GPS) data. The first order ionosphere manifests itself as a bulk position shift of the observed sources across an MWA field of view. These effects can be computed from global ionosphere maps provided by GPS analysis centres, namely the Center for Orbit Determination in Europe (CODE), using data from globally distributed GPS receivers. However, for the more accurate local ionosphere estimates required for precision radio astronomy applications, data from local GPS networks needs to be incorporated into ionospheric modelling. For GPS observations, the ionospheric parameters are biased by GPS receiver instrument delays, among other effects, also known as receiver Differential Code Biases (DCBs). The receiver DCBs need to be estimated for any non-CODE GPS station used for ionosphere modelling, a requirement for establishing dense GPS networks in arbitr...

  2. A Review of Higher Order Ionospheric Refraction Effects on Dual Frequency GPS

    Microsoft Academic Search

    Elizabeth J. Petrie; Manuel Hernández-Pajares; Paolo Spalla; Philip Moore; Matt A. King

    2011-01-01

    Higher order ionospheric effects are increasingly relevant as precision requirements on GPS data and products increase. The\\u000a refractive index of the ionosphere is affected by its electron content and the magnetic field of the Earth, so the carrier\\u000a phase of the GPS L1 and L2 signals is advanced and the modulated code delayed. Due to system design the polarisation is

  3. Effects of the 2nd order ionospheric terms on VLBI measurements

    NASA Astrophysics Data System (ADS)

    Hawarey, Mosab; Hobiger, Thomas; Schuh, Harald

    2005-06-01

    Current VLBI software packages take into account ionospheric terms of 1st order only. This research investigates the effects of considering additionally the 2nd order terms on geodetic VLBI measurements. The mathematical algorithm follows the framework that has been presented for GPS in the literature. However, the approximation of the Earth's magnetic field and the assumption of a 400-km high ionospheric shell are avoided here by using the IGRF and PIM models to calculate the geomagnetic field vectors and electron densities at 100 representative points along the paths of incoming rays. The 2nd order effects are at the level of 10-12 seconds, which we introduced to the VLBI input files to determine the geodetic impact. Results of the VLBI software OCCAM reveal a maximum difference between baseline lengths with and without 2nd order ionospheric terms equivalent to 0.5 mm. Thus, the effect might become visible in VLBI within a few years.

  4. Solar cosmic ray effects in the lower ionosphere

    NASA Technical Reports Server (NTRS)

    Shirochkov, A. V.

    1989-01-01

    The polar cap absorption (PCA) events are the most remarkable geophysical phenomena in the high latitude ionosphere. Their effects are extended on the whole polar region in both hemispheres. The PCA events are caused by the intense fluxes of the solar cosmic rays (SCR) which are generated by the solar proton flares. Entering into the Earth's magnetosphere and ionosphere the SCR fluxes create excessive anomal ionization at the ionospheric heights of 50 to 100 km which exceeds usual undisturbed level of ionization in several orders of magnitude. The PCA events can be considered as catastrophic in relation to the polar ionosphere because all radio systems using ionospheric radio channels ceased to operate during these events. On the other hand the abnormally high level of ionization in the ionospheric D region during the PCA events create excellent opportunities to conduct fruitful aeronomical research for the lower ionosphere. Obvious scientific and practical importance of the PCA events leads to publishing of special PCA catalogues. The ionospheric effects caused by the SCR fluxes were profoundly described in the classical paper (Bailey, 1964). Nevertheless several aspects of this problem were not studied properly. An attempt is made to clarify these questions.

  5. Ionospheric effects of the Chelyabinsk meteoroid

    NASA Astrophysics Data System (ADS)

    Chernogor, L. F.

    2015-05-01

    Observation results are presented for the lower and upper ionosphere disturbances accompanying the passage and explosion of the Chelyabinsk space body. The effects near the meteoroid's path are investigated from the total electron content variations detected by GPS radio receivers. The ionosphere observations at distances of ˜2000-300 km are based on the ionosonde data and the phase and amplitude measurements for a radio signal at 66.67 kHz on the route from Moscow to Kharkiv. Manifestations are found both of acoustic and gravity waves following the passage and explosion of the space body. Their connection with the passage of the Chelyabinsk meteoroid is discussed.

  6. Filtering ionosphere parameters to detect trends linked to anthropogenic effects

    NASA Astrophysics Data System (ADS)

    Elias, Ana G.

    2014-12-01

    The great concern about the global warming observed in the troposphere has generated a large interest in the study of long-term trends in the ionosphere since the early 1990s, which has now become a significant topic in global change investigations. Some research works link ionosphere trends to anthropogenic sources such as the increase in greenhouse gas concentration, and others to natural causes such as solar and geomagnetic activity long-term changes, and secular variations in the Earth's main magnetic field. In all the cases, in order to analyze ionospheric trends, solar activity effect must be filtered out first since around 90% of ionosphere parameter variance is due to solar variations. The filtering process can generate `spurious' trends in the filtered data series which may lead to erroneous conclusions. foF2 data series which include solar cycle 23 are analyzed in the present work in order to detect the effect of different filtering procedures on the determination of long-term trends. In particular, solar cycle 23 seems to have had an extreme ultraviolet (EUV) emission greater than that deduced from traditional solar EUV proxies during the maximum epoch and lower during the minimum epoch. When solar activity is filtered assessing the residuals of a linear regression between foF2 and Rz, or between foF2 and F10.7, this fact may bias trend values especially because it is at the end of the time series. The length of the period considered for trend assessment, the saturation and hysteresis effect of some ionosphere parameters, and the solar EUV proxy used are also considered in this study in order to quantify a possible spurious trend that may result as a by-product of a filtering process. Since trends expected as a consequence of anthropogenic effects are relatively small, these spurious effects may surely mask, or enhance, trends expected from anthropogenic origins.

  7. Modeling the effect of the ionosphere on electromagnetic sounding

    Microsoft Academic Search

    V. I. Dmitriev

    2009-01-01

    We derive the asymptotic behavior of the electromagnetic field on the surface of a layered Earth allowing for the effect of\\u000a the ionosphere. The analysis of the fields enables us to estimate the distance over which the ionosphere has a substantial\\u000a effect. We show that the ratio of the tangential field components is independent of the effect of the ionosphere.

  8. Ionospheric effects to antenna impedance

    NASA Technical Reports Server (NTRS)

    Bethke, K. H.

    1986-01-01

    The reciprocity between high power satellite antennas and the surrounding plasma are examined. The relevant plasma states for antenna impedance calculations are presented and plasma models, and hydrodynamic and kinetic theory, are discussed. A theory from which a variation in antenna impedance with regard to the radiated power can be calculated for a frequency range well above the plasma resonance frequency is give. The theory can include photo and secondary emission effects in antenna impedance calculations.

  9. Measurements of ionospheric effects on wideband signals at VHF

    SciTech Connect

    Fitzgerald, T.J.

    1998-08-17

    Radars operating at very high frequency (VHF) have enhanced foliage and ground penetration compared to radars operated at higher frequencies. For example, VHF systems operated from airplanes have been used as synthetic aperture radars (SAR); a satellite-borne VHF SAR would have considerable utility. In order to operate with high resolution it would have to use both a large relative bandwidth and a large aperture. A satellite-borne radar would likely have to operate at altitudes above the maximum density of the ionosphere; the presence of the ionosphere in the propagation path of the radar will cause a deterioration of the performance because of dispersion over the bandwidth. The author presents measurements of the effects of the ionosphere on radar signals propagated from a source on the surface of the Earth and received by instruments on the FORTE satellite at altitudes of 800 km. The author employs signals with a 90 MHz bandwidth centered at 240 MHz with a continuous digital recording period of 0.6 s.

  10. Ionospheric effects upon a satellite navigation system at Mars

    Microsoft Academic Search

    Michael Mendillo; Xiaoqing Pi; Steven Smith; Carlos Martinis; Jody Wilson; David Hinson

    2004-01-01

    Trans-ionospheric radio propagation effects resulting in ranging errors are examined for a potential orbital network of communications and navigational satellites at Mars. Using recent results from the radio science experiment on board the Mars Global Surveyor (MGS) spacecraft and a photochemical model of Mars' ionosphere, we study the total electron content (TEC) at Mars to investigate how its latitude, local

  11. Plasma jet effects on the ionospheric plasma

    NASA Technical Reports Server (NTRS)

    Moore, T. E.; Arnoldy, R. L.; Cahill, L. J.; Kintner, P. M.

    1983-01-01

    Heavy ion beams were injected into the ionospheric plasma (experiments ARCS 1 and ARCS 2). In ARCS 1, operation of a 25eV argon ion source, mounted on a plasma diagnostic payload, produced an accelerated electron population; broadband electric field turbulence; large, spin synchronized electric field perturbations; and depletions of thermal ions. In ARCS 2, the ion source was deployed upward along the local magnetic field direction away from the diagnostic payload, and observed effects are contained within several meters of the ion source. However, enhanced wave levels near the LHR frequency are observed at distances up to 1 km, as are the injected ions themselves. A measurement of the dominant wavelength of the enhanced waves is consistent with an inference based upon the accelerated electron population seen in ARCS 1. This electron population is not evident during ARCS 2.

  12. Mitigation of ionospheric scintillation effects in kinematic LEO precise orbit determination

    NASA Astrophysics Data System (ADS)

    Zehentner, Norbert; Mayer-Gürr, Torsten

    2015-04-01

    Kinematic orbit determination for Low Earth Orbiting satellites is one of the core elements in gravity field recovery from GNSS tracked satellites. The accuracy of the kinematic orbit positions directly determines the achievable accuracy in terms of gravity field results. We apply a precise point positioning approach based on raw GNSS observations, without using any linear combinations. This method requires to take every effect directly into account, as non of the effects is eliminated by forming differences or linear combinations. For example, the ionospheric influence is taken into account by estimating the slant TEC, including higher order terms and corrections for ionospheric bending. Our approach preserves the original high measurement accuracy of the phase observations. The remaining factors reducing the achieved accuracy are not or incorrectly modeled systematic effects. The GOCE mission revealed one of these systematic effects: ionospheric scintillations. These are small and short term irregularities in the Earth's ionosphere which cause errors in GNSS observations. GOCE gravity field results showed a huge systematic effect along the geomagnetic equator. GOCE was flying in a sun-synchronous dusk-dawn orbit, which means that the satellite orbit is nearly stationary with respect to the Earth's ionosphere. As it is hardly possible to realistically model ionospheric irregularities they can not be corrected from the raw observations. We introduce an observation weighting method based on the rate of TEC index to reduce the influence of observations affected by ionospheric scintillations. This weighting scheme in combination with variance component estimation greatly reduces the influence of ionospheric scintillation on the kinematic orbit and in turn also on the gravity field result. We will show that by using the introduced weighting scheme the error in GOCE kinematic orbits is almost removed, without removing observations.

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

    NASA Astrophysics Data System (ADS)

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

    2012-04-01

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

  14. Effects of UGTs on the ionosphere

    NASA Astrophysics Data System (ADS)

    Argo, P. E.; Fitzgerald, T. J.

    The processes that propagate local effects of underground nuclear tests from the ground into the upper atmosphere, and produce a detectable signal in the ionosphere are described. Initially, the blast wave from a underground test (UGT) radially expands, until it reaches the surface of the earth. The wave is both reflected and transmitted at this sharp discontinuity in propagation media. Tne reflected wave combines with the incident wave to form an 'Airy surface,' at which very strong ripping forces tear the earth apart. This broken region is called the 'spat zone,' and is launched into ballistic motion. The resultant ground motion launches an acoustical wave into the atmosphere. This acoustic wave, with overpressures of a few tenths of one percent, propagates upwards at the speed of sound. Assuming purely linear propagation, the path of the acoustic energy can be tracked using raytracing models. Most of the wave energy, which is radiated nearly vertically, tends to propagate into the upper atmosphere, while wave energy radiated at angles greater than about 30 degrees to the vertical will be reflected back to earth and is probably what is seen by most infrasonde measurements.

  15. Ionospheric Effects of Underground Nuclear Explosions

    NASA Astrophysics Data System (ADS)

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

    2010-12-01

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

  16. A greenhouse effect in the ionosphere?

    Microsoft Academic Search

    H. Rishbeth

    1990-01-01

    Following a suggestion by Roble and Dickenson that increases in the mixing ratios of mesospheric carbon dioxide and methane will cool the thermosphere by about 50 K, this paper examines the consequences for the ionosphre. It is concluded that physical and chemical factors that may affect the ionosphere have not been considered in this analysis and therefore further global monitoring

  17. Estimating and Removing Ionospheric Effects From GESS Interferometric SAR Imagery

    NASA Astrophysics Data System (ADS)

    Freedman, A. P.; Madsen, S. N.

    2002-05-01

    Many users of differential interferometry report image artifacts that cannot be attributed to surface deformation or terrain mismodeling. These artifacts are often ascribed to propagation delays due to the atmosphere or ionosphere. When atmospheric (primarily wet troposphere) delays can be ruled out, the ionosphere is usually blamed for the artifacts. There is rarely sufficient knowledge of the ionosphere at the spatial and temporal scales to prove or refute this assumption, however. In present-day, focused-based processing, large-scale ionospheric effects are typically removed in the baseline correction process before image formation. The large-scale mapping envisioned for the Global Earthquake Satellite System (GESS) precludes the use of baseline correction for removing anything other than physical orbit errors. Thus any effects induced by the ionosphere will be present in full measure. The ionosphere is a dispersive medium and produces several frequency-dependent effects on a radar signal, affecting both the resulting single-channel Synthetic Aperture Radar (SAR) imagery and two-channel interferometric imagery in a number of distinct ways. The signal propagation or group delay slows down the radar pulse relative to free space, while the phase delay advances the phase relative to that of free space. The Faraday rotation alters the polarization of the return signal. One may take advantage of the frequency dependence of the group and phase delays to evaluate the magnitude of the ionospheric total electron count (TEC). Global and large-scale ionospheric fluctuations are associated with solar UV excitation, and are modulated diurnally and seasonally. These can cause propagation delays at L-band of typically 10 to 20 meters, but up to a hundred meters and more in rare instances. Intermediate-scale disturbances (tens to hundreds of kilometers in extent) include traveling ionospheric disturbances (TIDs) and gravity waves induced by a variety of phenomena. These can alter the propagation delay by up to 5-10%. Small-scale disturbances (ionospheric "blobs" less than ~10 km in size) may result in scintillation or SAR defocusing but tend to be small in magnitude. Total day-to-day variability can exceed a few meters of delay, or up to 25% of the total delay. We examine two dual-frequency scenarios. In the first, we assume that GESS transmits a chirp waveform at two L-band ( ~1250 MHz) frequencies, each 10 MHz wide, separated by 70 MHz. In the second, we envision an additional C-band antenna transmitting a 10 MHz-wide chirp centered at 5350 MHz. We apply to interferometric SAR concepts similar to those developed for removing ionospheric effects from GPS signals using the GPS dual frequency range and phase observables. Although there are big differences between GPS and SAR, much work appears applicable. These dual-frequency approaches appear to be capable of removing the ionosphere at the level that GESS requires, at least for intermediate- and larger-scale ionospheric features (10 km and up).

  18. Bounding Higher Order Ionosphere Errors for the Dual Frequency GPS User

    E-print Network

    Stanford University

    range and all non-dispersive errors such as troposphere, satellite clock bias, and receiver clock biasBounding Higher Order Ionosphere Errors for the Dual Frequency GPS User Seebany Datta-Barua, Todd Walter, Juan Blanch, Per Enge, Stanford University ABSTRACT The advent of a second civil GPS frequency

  19. Electromagnetic effects in the ionosphere and magnetosphere under seismoacoustic disturbances

    Microsoft Academic Search

    M. B. Gokhberg

    1986-01-01

    Aureole-3 observations of seismoacoustic effects on the magnetosphere carried out in the framework of the MASSA program are reported. It is shown that electromagnetic processes in the ionosphere and magnetosphere can be effectively studied using a large-scale acoustic wave from industrial explosions with a force of hundreds of tons of TNT. In a force tube conjugate with the epicenter, there

  20. Effects of ionospheric conductance in high-latitude phenomena

    NASA Astrophysics Data System (ADS)

    Benkevitch, Leonid

    In this thesis, the relationship between several high-latitude phenomena and the ionospheric conductance in both hemispheres is studied theoretically and experimentally. Theoretically, the high-latitude electrodynamics is studied by considering currents in the magnetosphere-ionosphere system resulting from the ionospheric sheet current redistribution between the conjugate ionospheres. It is shown that strong flow between the conjugate ionospheres, the interhemispheric currents (IHC), can be set up if the conductance distribution is asymmetric in the conjugate ionospheric regions. Such conditions are typical for solstices owing to the differences in the solar illumination. Analytical and numerical modeling shows that IHCs can appear in the regions of strong conductance gradient, more specifically around the solar terminator line, and that the intensity of the IHCs can be comparable to the intensity of the well known Region 1/Region 2 currents. The effect of IHC excitation on observable magnetic perturbations on the ground is investigated. It is shown that in the vicinity of the solar terminator line, the pattern of magnetic perturbation can be such that an apparent equivalent current vortex can be detected. In addition, strong conductance gradients are shown to affect significantly the quality of the ionospheric plasma flow estimates from the ground-based magnetometer data. Experimentally, the effect of the nightside ionospheric conductance on occurrence of substorms, global storm sudden commencement and radar auroras is investigated. To characterize substorm occurrence, new parameters, the derivatives of the classical AE and AO indices, are introduced. It is shown that the seasonal and diurnal variations of these parameters are controlled by the total nightside ionospheric conductance in the conjugate regions. The substorm onsets preferentially occur at low levels of the total conductance, which is consistent with the idea of the substorm triggering through the magnetosphere-ionosphere feedback instability. It is hypothesized that the total conductance affects the global storm onsets as well. To check this idea, the 33-year sudden storm commencement (SSC) data are considered. The semiannual, annual, semidiurnal, and diurnal variations in the SSC occurrence rate are found to be significant and these components exhibit a strong relationship with the total conductance of the high-latitude ionospheres. Finally, the SuperDARN midnight echo occurrence is shown to correlate, for some radars, with the total conductance minima and presumably with electric field maxima, which is consistent with general expectation that the F-region irregularities occur preferentially during times of enhanced electric fields. The gradients of the high-latitude conductance can also lead to significant errors in the plasma convection estimates from the ground-based magnetometers, and to investigate this effect a statistical assessment of the difference between the true plasma convection (SuperDARN) and the magnetometer-inferred equivalent convection direction is performed. The largest differences are found for the transition region between the dark and sunlit ionospheres and in the midnight sector where strong conductance gradients are expected due to particle precipitation. Consideration of regular conductance gradients due to solar illumination improves the agreement between the radar and magnetometer data. Finally, an attempt is made to demonstrate the effects of conductance upon the properties of traveling convection vortices (TCVs). Joint SuperDARN and magnetometer data reveal that there is resemblance between the magnetometer and radar inferred TCV images on a scale of thousands of kilometers. However, on a smaller scale of hundreds of kilometers, significant differences are observed.

  1. Effect of Moon phases in riometer absorption and in the ionospheric and geomagnetic parameters

    Microsoft Academic Search

    S. N. Samsonov; V. F. Smirnov; D. G. Baishev; A. A. Toropov; N. G. Skryabin

    2007-01-01

    Variations in the frequency of occurrence of riometer absorption, minimum frequency of reflection of the ionospheric F layer, minimum height, and height of maximum electron density of the ionospheric F layer near the solar minimum have been studied. Application of the superposed epoch technique has detected the Moon phase\\u000a effect on these ionospheric parameters. This effect was: three events per

  2. Effect of Moon phases in riometer absorption and in the ionospheric and geomagnetic parameters

    Microsoft Academic Search

    S. N. Samsonov; V. F. Smirnov; D. G. Baishev; A. A. Toropov; N. G. Skryabin

    2007-01-01

    Variations in the frequency of occurrence of riometer absorption, minimum frequency of reflection of the ionospheric F layer, minimum height, and height of maximum electron density of the ionospheric F layer near the solar minimum have been studied. Application of the superposed epoch technique has detected the Moon phase effect on these ionospheric parameters. This effect was: three events per

  3. The Effects of the Ionosphere and C/A Frequency on GPS Signal Shape

    E-print Network

    Stanford University

    The Effects of the Ionosphere and C/A Frequency on GPS Signal Shape: Considerations for GNSS-2 Jock at MIT (1992). This investigation is based on the standard model of the ionosphere, which assumes was developed to analytically determine the shape of the GPS signal after passing through the ionosphere

  4. Ionospheric Effects Observed by Radio Tomography during Severe Geomagnetic Storms

    NASA Astrophysics Data System (ADS)

    Andreeva, Elena S.; Kunitsyn, Vyacheslav E.; Tereshchenko, Evgeniy D.; Nazarenko, Marina O.; Nesterov, Ivan A.; Tumanova, Yuila S.

    2014-05-01

    The geomagnetic storms are an important element of space weather. As known, the distributions of all ionospheric parameters are determined by the interplay of many complex diverse processes of solar-terrestrial coupling. The intervals of geomagnetic storms are marked by dramatic changes in the dynamics of the ionosphere, whose parameters experience significant disturbances. The ionospheric signatures of geomagnetic perturbations are highly diverse in both spatiotemporal scales, ranging from a few seconds to few days and from a few meters to dozen thousand kilometers, and intensity. The methods of GNSS-based radio tomography (RT) are suitable for diagnosing the spatiotemporal structure of ionospheric disturbances caused by different space-weather factors. GNSS comprise the first-generation satellite navigation systems such as low-orbiting (LO) Russian Tsikada and American Transit satellites and second-generation satellite systems such as high-orbiting GPS and GLONASS constellations. The LORT methods reconstruct two-dimensional (2D) structure of the ionospheric electron density distribution in the vertical (altitude-latitude) plane within a spatial sector spanning a few thousand km and a time interval of 10-15 min. The horizontal and vertical resolution of LORT is typically 15-25 km and 25-30 km, respectively. The HORT methods use radio transmissions from HO satellites recorded at the receiving ground network of the International Geodetic Service (IGS), which currently comprises about 2000 receivers. The HORT methods are capable of reconstructing the four-dimensional (4D) (three spatial coordinates and time) structure of the ionosphere. Generally, HORT has a spatial resolution of 100 km at best and a time step of 60-20 min. In the regions covered by dense receiving networks (e.g., in Europe, Alaska, USA), the resolution can be improved to 30-50 and the time step reduced to 30-10 min. The resolution of 10-30 km in space and up to 2 min in time is only achievable in Japan and California, where the receiving networks are very dense. We present the results of HORT and LORT imaging of the ionosphere during the periods of geomagnetic storms of 2003-2013 in different regions of the world -- in the European part of Russia and North America. Different factors acting during the storm time make the ionosphere complexly structured. Radio tomography reveals multi-extremal distributions of the ionospheric plasma with the spots of enhanced ionization, wall-like steep gradients of electron concentration; a complex structure of the ionization trough with the polar wall shifted equatorwards is observed. Many reconstructions show various wavelike structures, travelling ionospheric disturbances, wave effects caused by corpuscular emissions, etc. We demonstrate the comparisons of radio tomography with the ionosonde measurements. In contrast to the ionosondes, which use short radio waves, the RT methods are suitable for diagnosing the ionosphere even during the periods of strong geomagnetic storms, since absorption can typically be neglected in the RT problems due to the high frequencies used. The work was supported by the Russian Foundation for Basic Research (grants 14-05-00855 and 13-05-01122). We are grateful to the North-West Research Associates (NWRA) for providing the experimental relative TEC data from the RT system in Alaska.

  5. Effects of high-latitude drivers on Ionosphere/Thermosphere parameters

    NASA Astrophysics Data System (ADS)

    Shim, J.; Kuznetsova, M. M.; Rastaetter, L.; Berrios, D.; Codrescu, M.; Emery, B. A.; Fedrizzi, M.; Foerster, M.; Foster, B. T.; Fuller-Rowell, T. J.; Mannucci, A.; Negrea, C.; Pi, X.; Prokhorov, B. E.; Ridley, A. J.; Coster, A. J.; Goncharenko, L.; Lomidze, L.; Scherliess, L.

    2012-12-01

    In order to study effects of high-latitude drivers, we compared Ionosphere/Thermosphere (IT) model performance for predicting IT parameters, which were obtained using different models for the high-latitude ionospheric electric potential including Weimer 2005, AMIE (assimilative mapping of ionospheric electrodynamics) and global magnetosphere models (e.g. Space Weather Modeling Framework). For this study, the physical parameters selected are Total Electron Content (TEC) obtained by GPS ground stations, and NmF2 and hmF2 from COSMIC LEO satellites in the selected 5 degree eight longitude sectors. In addition, Ne, Te, Ti, and Tn at about 300 km height from ISRs are considered. We compared the modeled values with the observations for the 2006 AGU storm period and quantified the performance of the models using skill scores. Furthermore, the skill scores are obtained for three latitude regions (low, middle and high latitudes) in order to investigate latitudinal dependence of the models' performance. This study is supported by the Community Coordinated Modeling Center (CCMC) at the Goddard Space Flight Center. The CCMC converted ionosphere drivers from a variety of sources and developed an interpolation tool that can be employed by any modelers for easy driver swapping. Model outputs and observational data used for the study will be permanently posted at the CCMC website (http://ccmc.gsfc.nasa.gov) as a resource for the space science communities to use.

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

    E-print Network

    Withers, Paul

    5E-7 4E-6 Density (kg m-3) Mars Earth Venus Planet 0.01 0.03 0.1 Pressure (Pa) 1405 ­ 1587 ­ 971E10Observations of the effects of meteors on the ionospheres of Venus, Earth and Mars Paul Withers1, A Planetology: Venus-Earth-Mars, ESLAB 2009 ESTEC, The Netherlands #12;Observations of the effects of meteors

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

    NASA Astrophysics Data System (ADS)

    Maruyama, Takashi; Jin, Hidekatsu

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

  8. The Effect of Ionospheric Models on Electromagnetic Pulse Locations

    SciTech Connect

    Fenimore, Edward E. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Triplett, Laurie A. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2014-07-01

    Locations of electromagnetic pulses (EMPs) determined by time-of-arrival (TOA) often have outliers with significantly larger errors than expected. In the past, these errors were thought to arise from high order terms in the Appleton-Hartree equation. We simulated 1000 events randomly spread around the Earth into a constellation of 22 GPS satellites. We used four different ionospheres: “simple” where the time delay goes as the inverse of the frequency-squared, “full Appleton-Hartree”, the “BobRD integrals” and a full raytracing code. The simple and full Appleton-Hartree ionospheres do not show outliers whereas the BobRD and raytracing do. This strongly suggests that the cause of the outliers is not additional terms in the Appleton-Hartree equation, but rather is due to the additional path length due to refraction. A method to fix the outliers is suggested based on fitting a time to the delays calculated at the 5 GPS frequencies with BobRD and simple ionospheres. The difference in time is used as a correction to the TOAs.

  9. Ionospheric Disturbance Effects on IPS signals from MEXART

    NASA Astrophysics Data System (ADS)

    Rodriguez-Martinez, M.; Perez-Enriquez, R.; Carrillo-Vargas, A.; Lopez-Montes, R.; Araujo-Pradere, E. A.; Casillas-Perez, G.; Lopez Cruz-Abeyro, J.

    2011-12-01

    We present a study related to the impact by ionospheric disturbances in the radio-signal of sources observed with MEXican Array Radio Telescope (MEXART) from April 20th to May 31th of 2010. Along this time interval, we observed the behavior of radio-signal for the sources: 3C048, 3C144, 3C274, Cas A, Cen A, and 3C405, in a daily basis. We found that there were days in which some of these sources showed slight fluctuations, even when there was no major solar event. We analyzed the time series of each source using a Wavelet tool that allowed us to highlight those periods which can exist in the signal related with these fluctuations. In addition, to characterize and identify ionospheric effects, we have calculated the Total Electron Content (TEC) from Global Positioning System (GPS) data and have taken into account the Dst index for the same period with the purpose of discard effect from geomagnetic storms. We found that the TEC can be used as a potential tool to discriminate between interplanetary scintillation and ionospheric fluctuations in MEXART data.

  10. Effect of anomalous transport coefficients on the thermal structure of the storm time auroral ionosphere

    NASA Technical Reports Server (NTRS)

    Fontheim, E. G.; Ong, R. S. B.; Roble, R. G.; Mayr, H. G.; Hoegy, W. H.; Ionson, J. A.; Baron, M. J.; Wickwar, V. B.; Vondrak, R. R.

    1978-01-01

    By analyzing an observed storm time auroral electron temperature profile it is shown that anomalous transport effects strongly influence the thermal structure of the disturbed auroral ionosphere. Such anomalous transport effects are a consequence of plasma turbulence, the existence of which has been established by a large number of observations in the auroral ionosphere. The electron and composite ion energy equations are solved with anomalous electron thermal conductivity and parallel electrical resistivity coefficients. The solutions are parameterized with respect to a phenomenological altitude-dependent anomaly coefficient A and are compared with an observed storm time electron temperature profile above Chatanika. The calculated temperature profile for the classical case (A = 1) disagrees considerably with the measured profile over most of the altitude range up to 450 km. It is shown that an anomaly coefficient with a sharp peak of the order of 10,000 centered around the F2 peak is consistent with observations.

  11. Effects of the equatorial ionosphere on L-band Earth-space transmissions

    NASA Technical Reports Server (NTRS)

    Smith, Ernest K.; Flock, Warren L.

    1993-01-01

    Ionosphere scintillation can effect satellite telecommunication up to Ku-band. Nighttime scintillation can be attributed to large-scale inhomogeneity in the F-region of the ionosphere predominantly between heights of 200 and 600 km. Daytime scintillation has been attributed to sporadic E. It can be thought of as occurring in three belts: equatorial, high-latitude, and mid-latitude, in order of severity. Equatorial scintillation occurs between magnetic latitudes +/- 25 degrees, peaking near +/- 10 degrees. It commonly starts abruptly near 2000 local time and dies out shortly after midnight. There is a strong solar cycle dependence and a seasonal preference for the equinoxes, particularly the vernal one. Equatorial scintillation occurs more frequently on magnetically quiet than on magnetically disturbed days in most longitudes. At the peak of the sunspot cycle scintillation depths as great as 20 dB were observed at L-band.

  12. Effects of solar flares on the ionosphere of Mars.

    PubMed

    Mendillo, Michael; Withers, Paul; Hinson, David; Rishbeth, Henry; Reinisch, Bodo

    2006-02-24

    All planetary atmospheres respond to the enhanced x-rays and ultraviolet (UV) light emitted from the Sun during a flare. Yet only on Earth are observations so continuous that the consequences of these essentially unpredictable events can be measured reliably. Here, we report observations of solar flares, causing up to 200% enhancements to the ionosphere of Mars, as recorded by the Mars Global Surveyor in April 2001. Modeling the altitude dependence of these effects requires that relative enhancements in the soft x-ray fluxes far exceed those in the UV. PMID:16497929

  13. Ionospheric Effects of X-Ray Solar Bursts in the Brazilian Sector

    NASA Astrophysics Data System (ADS)

    Becker-Guedes, F.; Takahashi, H.; Costa, J. E.; Otsuka, Y.

    2011-12-01

    When the solar X-ray flux in the interplanetary medium reaches values above a certain threshold, some undesired effects affecting radio communications are expected. Basically, the magnitudes of these effects depend on the X-ray peak brightness and duration, which drive the intensity of the ionosphere response when the associated electromagnetic wave hit the sunlit side of the Earth atmosphere. An important aspect defining the severity of damages to HF radio communications and LF navigation signals in a certain area is the local time when each event takes place. In order to create more accurate warnings referred to possible radio signal loss or degradation in the Brazilian sector, we analyze TEC maps obtained by a GPS network, formed by dual-frequency receivers spread all over the country, to observe ionospheric local changes during several X-ray events in the 0.1-0.8 nm range measured by GOES satellite. Considering the duration, peak brightness, and local time of the events, the final purpose of this study is to understand and predict the degree of changes suffered by the ionosphere during these X-ray bursts. We intend using these results to create a radio blackout warning product to be offered by the Brazilian space weather program named EMBRACE (Estudo e Monitoramento BRAsileiro do Clima Espacial): Brazilian Monitoring and Study of Space Weather.

  14. Effects of ionospheric oxygen on magnetospheric structure and dynamics

    NASA Astrophysics Data System (ADS)

    Garcia-Sage, Katherine

    During geomagnetically active times, ionospheric O + can contribute a significant fraction of the magnetospheric mass and energy densities. The global response of Earth's magnetosphere to the presence of ionospheric oxygen is still largely unknown and impossible to examine fully with in situ, single point satellite measurements. Global magnetohydrodynamic (MHD) models provide a picture of this large-scale response to ionospheric outflow. The goal of this dissertation is to examine the behavior and effects of outflowing oxygen in a multi-fluid MHD model by determining (1) how O+ outflow from different regions of the ionosphere contributes to plasma sheet populations and (2) the effect of these oxygen populations on convection and global magnetospheric structure. I implement two empirical outflow models at the inner boundary of the recently-developed Multi-Fluid Lyon-Fedder-Mobarry MHD code and examine the response of the model to various outflow conditions. A model based on data from the Akebono spacecraft (Ebihara et al., 2006) provides a low-energy polar and auroral region outflow, whereas a model based on data from the FAST spacecraft (Strangeway et al., 2005) provides higher-energy outflow confined to the auroral regions. Using the Akebono model outflow, I show that both centrifugal acceleration and pressure gradients accelerate thermal O+ along the magnetic field into the plasma sheet and downtail into the solar wind. I examine O+ and H + plasma sheet populations for different outflow and solar wind conditions. To account for observed densities, nightside outflows must be augmented by polar wind, cusp outflows, or both. O+ outflow in general, and nightside outflow in particular, loads the plasma sheet with O +, inflating the plasma sheet, increasing the width of the tail and distance to the tail x-line, and reducing cross polar cap potential (CPCP). These effects are shown to relate to the width of the magnetosheath, indicating that the reduction in CPCP may be due to changes in the bow shock and magnetosheath that divert the solar wind around the magnetosphere. Finally, I show that during a realistic substorm simulation, the timing and strength of substorms are changed by a global O+ outflow.

  15. Hemispheric Effects in Ionospheric Plasma Convection and Irregularity Occurrence

    NASA Astrophysics Data System (ADS)

    Ruohoniemi, J. M.; Baker, J. B. H.; Bristow, W. A.; Shepherd, S. G.; Kunduri, B.; Cousins, E. D. P.

    2014-12-01

    Extensive statistical studies have demonstrated the extent of asymmetries between the hemispheres in terms of the global pattern of plasma convection in the high-latitude ionosphere. However, relatively little is known about the asymmetries that arise on meso and smaller spatial scales or in the course of reconfiguration of the global convection following changes in IMF or substorm onsets. Moreover the correspondence between the hemispheres in space weather effects such as the occurrence of ionospheric plasma irregularities is almost unexplored. Some of the challenges in conducting such studies are traceable to more limited observational capabilities in the southern hemisphere. New capabilities have recently been achieved with the expansion of the SuperDARN radar network such that simultaneous and quasi-conjugate coverage is sometimes possible from midlatitudes to the polar cap. We review findings on the asymmetric aspects of high-latitude convection and press further to consider evidence of correspondence and asymmetry in convection when varying in time and across the equatorward auroral and midlatitude regions where conjugacy should obtain more reliably. We also discuss evidence of correlation between the hemispheres in terms of the occurrence of small-scale irregularities as a space weather phenomenon of practical importance.

  16. Ionospheric Analysis with Langmuir Probes: Sheath and Edge Effects

    NASA Astrophysics Data System (ADS)

    Albarran, R. M.; Klenzing, J.; Cooke, D. L.; Roddy, P. A.

    2014-12-01

    The Langmuir probe has been an essential instrument in the space sciences since the 1920s, providing data throughout the heliosphere. In this investigation of Langmuir probes, simulations were performed via the Spacecraft Plasma Interaction System (SPIS) to determine the influence of plasma sheath effects on the Planar Langmuir Probe (PLP) of the Communication/Navigation Outage Forecast Satellite (C/NOFS) subject an International Reference Ionosphere (IRI) model plasma environment. Electron temperatures extracted by a fitting routine employed onto SPIS results and PLP data assist in qualifying the accuracy of PLP measurements. Ultimately, the question is asked- what is the extent that sheath and edge effects have on data returned by Langmuir probes?

  17. Effects on the Ionosphere Due to Phenomena Occurring Below it

    NASA Astrophysics Data System (ADS)

    Kazimirovsky, E.; Herraiz, M.; De La Morena, B. A.

    2003-03-01

    The terrestrial thermosphere and ionosphere form the most variable part of the Earth's atmosphere. Because our society depends on technological systems that can be affected by thermospheric and ionospheric phenomena, understanding, monitoring and ultimately forecasting the changes of the thermosphere-ionosphere system are of crucial importance to communications, navigation and the exploration of near-Earth space. The reason for the extreme variability of the thermosphere-ionosphere system is its rapid response to external forcing from various sources, i.e., the solar ionizing flux, energetic charged particles and electric fields imposed via the interaction between the solar wind, magnetosphere and ionosphere, as well as coupling from below (``meteorological influences'') by the upward propagating, broad spectrum, internal atmospheric waves (planetary waves, tides, gravity waves) generated in the stratosphere and troposphere. Thunderstorms, typhoons, hurricanes, tornadoes and even seismological events may also have observable consequences in the ionosphere. The release of trace gases due to human activity have the potential to cause changes in the lower and the upper atmosphere. A brief overview is presented concerning the discoveries and experimental results that have confirmed that the ionosphere is subject to meteorological control (especially for geomagnetic quiet conditions and for middle latitudes). D-region aeronomy, the winter anomaly of radiowave absorption, wave-like travelling ionospheric disturbances, the non-zonality and regional peculiarities of lower thermospheric winds, sporadic-E occurrence and structure, spread-F events, the variability of ionospheric electron density profiles and Total Electron Content, the variability of foF2, etc., should all be considered in connection with tropospheric and stratospheric processes. ``Ionospheric weather'', as a part of space weather, (i.e., hour-to-hour and day-to-day variability of the ionospheric parameters) awaits explanation and prediction within the framework of the climatological, seasonal, and solar-cycle variations.

  18. Nightside ionosphere of Mars: Modeling the effects of crustal magnetic fields and electron pitch angle distributions on electron impact

    E-print Network

    California at Berkeley, University of

    Nightside ionosphere of Mars: Modeling the effects of crustal magnetic fields and electron pitch 2009; accepted 3 August 2009; published 20 November 2009. [1] The night side ionosphere of Mars nearly as strong as the photoionization-produced dayside ionosphere in others. The factors controlling

  19. Effects of ionospheric O+ on the magnetopause boundary wave activity

    NASA Astrophysics Data System (ADS)

    Merkin, V. G.

    2011-01-01

    In this paper we use a multi-fluid magnetohydrodynamic (MHD) model to explore effects of ionospheric O+ ions on the development of the Kelvin-Helmholtz (KH) instability at the flanks of the earth's magnetopause. The model used is the multi-fluid version of the Lyon-Fedder-Mobarry (LFM) global magnetospheric MHD simulation code. We set up a controlled numerical experiment whereby the solar wind speed is slowly increased resulting in building up the velocity shear across the magnetopause. As this happens, the KH waves at the magnetopause flanks increase their intensity. Along with the solar wind velocity ramp-up, we introduce O+ fluid in the plasma sheet and watch its influence on the development of the KH instability. We find that the simulation with the O+ ions present at the magnetopause shows a significantly weaker KH wave activity on both edges of the low-latitude boundary layer than the simulation without oxygen but identical otherwise.

  20. Investigations into the properties, conditions and effects of the ionosphere

    NASA Astrophysics Data System (ADS)

    Bussey, R. M.; Fremouw, E. J.; Reinisch, B. W.; Szuszczewicz, E. P.

    1988-01-01

    The investigations address ionospheric composition, structure, specification, scintillation and chemistry as well as remote sensing of the ionosphere through ultraviolet sensors. Specific work is carried out in the following six categories: laboratory measurements; field measurements; aircraft measurements; rocket, balloon, shuttle, and satellite measurements; analytical and theoretical investigations; and scientific and engineering analysis.

  1. Ionospheric physics

    SciTech Connect

    Sojka, J.J. (USAF, Geophysics Laboratory, Hanscom AFB, MA (United States))

    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.

  2. The Search for Ionospheric Effects at 150 MHz with PAPER

    NASA Astrophysics Data System (ADS)

    Gugliucci, Nicole E.; Bradley, R.; PAPER Collaboration

    2012-01-01

    PAPER (the Precision Array to Probe the Epoch of Reionization) is a telescope designed to detect the redshifted hydrogen signal from the early universe. The hydrogen is at a redshift of approximately 6-14, bringing the spin-flip transition of neutral hydrogen from 1.4 GHz to a regime between 100 and 230 GHz. PAPER has a test site with 32 antennas in the Radio Quiet Zone of Green Bank, West Virginia, and a 64-antenna array at the Square Kilometer Array candidate site in the Karoo, South Africa. Astronomical observations at such low frequencies are made more challenging by the refractive properties of the ionosphere. We present the angular shifts in bright source positions (Cyg A, Cas A, Vir A, and Tau A) as probes of the variations in the total electron content (TEC) along the lines of sight between the sources and the 32-element array in Green Bank. With an integration time of 10 seconds, we can probe for the small fluctuations, using the visibilities, that may be the most difficult to calibrate in upcoming experiments and observations. More sensitive probes of longer timescales are also done by imaging the sky with both the 32 and 64-element arrays. Here again, the bright source position stability is used as an indicator of the TEC stability. The wideband nature of the PAPER instrument enables it to probe the effects of a varying TEC over a nearly 100 MHz bandwidth. We compare these measurements to more traditional methods of probing the ionosphere, such as GPS satellites, and we discuss the implications that these measurements will have on experiments aimed at detecting the epoch of reionization.

  3. An investigation of ionospheric irregularity effects on SIR-B image processing and information extraction

    NASA Technical Reports Server (NTRS)

    Szuszczewicz, E. P.; Abdu, M. A.; Sobral, J. H. A.; Jost, J.; Reddy, B. M.; Rino, C.; Robinson, T.; Rodrigues, P.; Singh, M.; Woodman, R.

    1984-01-01

    Ionospheric irregularities and associated effects on space-time synthetic aperture radar (SAR) image processing and information extraction, including sensor calibration, target statistics determination, resolution, distortion, and overall image integrity were investigated.

  4. Effects of Atmospheric Variability on Ionospheric Manifestations of Earthquakes and Tsunamis

    NASA Astrophysics Data System (ADS)

    Godin, O. A.; Zabotin, N. A.; Zabotina, L.

    2014-12-01

    There is a large and increasing number of ground-based and satellite-borne instruments, which reliably reveal ionospheric manifestations of natural hazards such as large earthquakes, strong tsunamis, and powerful tornadoes. As the focus shifts from detecting the ionospheric features associated with the natural hazards to characterizing the hazards for the purposes of improving early warning systems and contributing to disaster recovery, it becomes imperative to relate quantitatively characteristics of the observed ionospheric disturbances and the underlying natural hazard. The relation between perturbations at the ground level and their ionospheric manifestations is strongly affected by parameters of the intervening atmosphere. In this paper, we employ the ray theory to model propagation of acoustic gravity waves in three-dimensionally inhomogeneous atmosphere. Huygens' wavefront-tracing and Hamiltonian ray-tracing algorithms are used to simulate wave propagation from an earthquake hypocenter through the earth's crust and ocean to the upper atmosphere as well as the generation of atmospheric waves by seismic surface waves and tsunamis. We quantify the influence of temperature stratification and winds, including their seasonal variability, and air viscosity and thermal conductivity on the geometry and amplitude of ionospheric disturbances. Modeling results are verified by comparing observations of the velocity fluctuations at altitudes of 150-160 km by a coastal Dynasonde HF radar system with theoretical predictions of ionospheric manifestations of background infragravity waves in the ocean. Dynasonde radar systems are shown to be a promising means for monitoring acoustic-gravity wave activity and observing ionospheric perturbations due to earthquakes and tsunamis. The effects will be discussed of background ionospheric disturbances and uncertainty in atmospheric parameters on the feasibility and accuracy of retrieval of open-ocean tsunami heights from observations of the ionosphere.

  5. Solar Flare Effects on the Thermosphere and Ionosphere

    NASA Astrophysics Data System (ADS)

    Solomon, S.; Qian, L.; Rodgers, E.; Bailey, S.

    The Solar Extreme-ultraviolet Experiment SEE on the TIMED satellite and by the X-ray Photometer System XPS on the SORCE satellite provide the first comprehensive irradiance measurements of the complete solar spectrum during large solar flares However the soft X-ray portion of these observations are performed using silicon photodiodes coated with metallic filters to provide photometric measurements with multiple band passes which leads to complexities in obtaining spectral information A new analysis technique developed specifically for flare conditions is used to infer flare spectra in this region These are combined with spectrographic measurements in the extreme ultraviolet and far ultraviolet and applied to the NCAR Thermosphere-Ionosphere-Electrodynamics General Circulation Model TIE-GCM The electron content neutral density and airglow response to large flares during the declining phase of solar cycle 23 are calculated using this model and compared to several measurement sets obtaining good agreement This supports both the validity of the solar X-ray analysis and the modeling methodology showing that although flare-driven effects in the upper atmosphere are significant they are shorter and of much smaller magnitude than geomagnetic disturbances

  6. Neutral wind control of the Jovian magnetosphere-ionosphere current system

    Microsoft Academic Search

    Chihiro Tao; Hitoshi Fujiwara; Yasumasa Kasaba

    2009-01-01

    In order to clarify the role of neutral dynamics in the Jovian magnetosphere-ionosphere-thermosphere coupling system, we have developed a new numerical model that includes the effect of neutral dynamics on the coupling current. The model calculates axisymmetric thermospheric dynamics and ion composition by considering fundamental physical and chemical processes. The ionospheric Pedersen current is obtained from the thermospheric and ionospheric

  7. Ionosphere Activity Effects on Anthropogenic VLF Wave measured by DEMETER and Application to Earth Electromagnetic Survey

    NASA Astrophysics Data System (ADS)

    Leye, P. O.; Tarits, P.

    2012-04-01

    Very Low Frequency (VLF) signal from the world-wide powerful VLF stations network, for navigation and military communication is commonly used for ground level electromagnetic survey in geophysics because part of the recorded signal is of internal origin, from induction in the Earth. This VLF signal has been observed also at satellite altitude during the DEMETER mission. The VLF electromagnetic field is recorded on the 15 - 20 kHz frequency band by the ICE et IMSC sensors on-board the spacecraft and provide simultaneously the electric and magnetic component of the electromagnetic signal. The waves transmitted by the ground-based VLF antennas propagate in free space and may pass through the ionosphere, depending on ionosphere properties or orientation of the wave vector relative to the Earth magnetic field. They can only cross the ionosphere and reach the satellite in the case of low ionosphere activities. The ionization varies according to time of day or season and it has been shown that man made VLF waves can precipitate radiation belt energetic electrons into the ionosphere. We study the effect of the interaction between VLF wave transmitted from ground and the ionosphere to analyze the contribution of ionosphere to the signal measured by DEMETER. We calculate the electromagnetic field of the VLF antennas placed on the surface of the Earth and transmitted through the ionosphere up to the satellite as a function of earth electrical resistivity. To compare with the data, we define the ratio between the electric and magnetic field that we call wave impedance. The comparison between the theoretical and observed impedance allows to deduce the average resistivity of the earth for shallow depth from the satellite data.

  8. Investigations into the properties, conditions, and effects of the ionosphere

    NASA Astrophysics Data System (ADS)

    Biello, G. D.; Fremouw, E. J.; Reinisch, B. W.; Szuszczewicz, E. P.

    1989-01-01

    The investigations address ionospheric composition, structure, specification, scintillation and chemistry as well as remote sensing of the ionosphere through ultraviolet sensors. Specific work is carried out under individual task requirement notices (TRNs) written for conduct and/or support of investigations in the following six categories; laboratory measurements; field measurements; aircraft measurements; rocket, balloon, shuttle, and satellite measurements; analytical and theoretical investigations; and scientific and engineering analysis. A summary of the work performed during the period 16 December 1987 through 31 December 1988 is provided.

  9. Solar flare and IMF sector structure effects in the lower ionosphere

    SciTech Connect

    Lastovicka, J.

    1984-05-01

    About 1% of all sudden ionospheric disturbances (SIDs) observed at the Panska Ves Observatory (Czechoslovakia), were found to be not of solar-XUV origin. Among them, the very rare SWF events (observed at L 2.4) of corpuscular origin are the most interesting. The IMF sector structure effects in the midlatitude lower ionosphere are minor in comparison with effects of solar flares, geomagnetic storms, etc. There are two basic types of effects. The first type is a disturbance, best developed in geomagnetic activity, and observed in the night-time ionosphere. It can be interpreted as a response to sector structure related changes of geomagnetic (magnetospheric) activity. The other type is best developed in the tropospheric vorticity area index and is also observed in the day-time ionosphere in winter. This effect is quietening in the ionosphere as well as troposphere. While the occurrence of the former type is persistent in time, the latter is severely diminished in some periods. All the stratosphere, the 10-mb level temperature and height above Berlin-Tempelhof do not display any observable IMF section structure effect.

  10. Solar flare and IMF sector structure effects in the lower ionosphere

    NASA Astrophysics Data System (ADS)

    Lastovicka, J.

    1984-05-01

    About 1% of all sudden ionospheric disturbances (SIDs) observed at the Panska Ves Observatory (Czechoslovakia), were found to be not of solar-XUV origin. Among them, the very rare SWF events (observed at L = 2.4) of corpuscular origin are the most interesting. The IMF sector structure effects in the midlatitude lower ionosphere are minor in comparison with effects of solar flares, geomagnetic storms, etc. There are two basic types of effects. The first type is a disturbance, best developed in geomagnetic activity, and observed in the night-time ionosphere. It can be interpreted as a response to sector structure related changes of geomagnetic (= magnetospheric) activity. The other type is best developed in the tropospheric vorticity area index and is also observed in the day-time ionosphere in winter. This effect is quietening in the ionosphere as well as troposphere. While the occurrence of the former type is persistent in time, the latter is severely diminished in some periods. All the stratosphere, the 10-mb level temperature and height above Berlin-Tempelhof do not display any observable IMF section structure effect.

  11. Solar Flare and IMF Sector Structure Effects in the Lower Ionosphere

    NASA Technical Reports Server (NTRS)

    Lastovicka, J.

    1984-01-01

    About 1% of all sudden ionospheric disturbances (SIDs) observed at the Panska Ves Observatory (Czechoslovakia), were found to be not of solar-XUV origin. Among them, the very rare SWF events (observed at L = 2.4) of corpuscular origin are the most interesting. The IMF sector structure effects in the midlatitude lower ionosphere are minor in comparison with effects of solar flares, geomagnetic storms, etc. There are two basic types of effects. The first type is a disturbance, best developed in geomagnetic activity, and observed in the night-time ionosphere. It can be interpreted as a response to sector structure related changes of geomagnetic (= magnetospheric) activity. The other type is best developed in the tropospheric vorticity area index and is also observed in the day-time ionosphere in winter. This effect is quietening in the ionosphere as well as troposphere. While the occurrence of the former type is persistent in time, the latter is severely diminished in some periods. All the stratosphere, the 10-mb level temperature and height above Berlin-Tempelhof do not display any observable IMF section structure effect.

  12. The nighttime winter anomaly (NWA) effect in the american sector as a consequence of interhemispheric ionospheric coupling

    Microsoft Academic Search

    M. Foerster; N. Jakowski

    1988-01-01

    The nighttime winter anomaly (NWA) effect was observed during solar minimum conditions at the American sector by means of ionospheric electron content and vertical sounding measurements in Havana (Cuba). An effective interhemispheric transport of plasma is suggested to explain enhanced northern nighttime ionization during winter solstice. To elucidate this effect, an adequate physicalnumerical model of the coupled system ionosphere-plasmasphere is

  13. Ionization effects due to solar flare on terrestrial ionosphere

    NASA Technical Reports Server (NTRS)

    Wu, S. T.; Tan, A.

    1976-01-01

    Sudden frequency deviation ionospheric disturbances related to the flares of May 18 and 19, 1973 were observed from the NASA/MSFC high frequency Doppler sounder array system in Huntsville, Alabama. The results are compared with those observed at Table Mountain near Boulder, Colorado and at the University of Hawaii.

  14. Ionospheric Effects on GPS Range Finding Using 3D Ray-Tracing and Nelder-Mead Optimisation Algorithm

    Microsoft Academic Search

    SITI SARAH NIK ZULKIFLI; MARDINA ABDULLAH; AZAMI ZAHARIM; MAHAMOD ISMAIL

    2009-01-01

    The Earth's ionosphere plays a crucial role in Global Positioning System (GPS) accuracy because this layer represents the largest source of positioning error for the users of the GPS after the turn-off of Selective Availability (SA). This paper studies the ionospheric effect on transionospheric signal propagation for the Earth-satellite path using 3D Jones Ray-Tracing utilizing Nelder-Mead optimisation algorithm. The ionospheric

  15. Ionospheric Effects Prior to the Napa Earthquake of August 24, 2014

    NASA Astrophysics Data System (ADS)

    Kelley, M. C.; Swartz, W. E.; Komjathy, A.; Mannucci, A. J.; Shume, E. B.; Heki, K.; Fraser-Smith, A. C.; McCready, M. A.

    2014-12-01

    Recently, evidence that the ionosphere reacts in a reliable, reproducible manner before major earthquakes has been increasing. Fraser-Smith (1990) reported ULF magnetic field fluctuations prior to the Loma Prieta quake. Although not an ionospheric measurement, such magnetic fields before a quake are part of our explanation for the ionospheric effect. Heki (2011) and Heki and Enomoto (2013) reported in great detail the devastating March 11, 2011 Tohoku-Oki earthquake in which numerous GPS satellite/ground-station pairs showed apparent changes, both increases and decreases, starting 40 minutes before the event. We say "apparent" since our theory is that electric fields associated with stresses before an earthquake map through the ionosphere at the speed of light and raise or lower the main ionosphere. Both effects have been detected. Heki's results for four quakes exceeding M = 7 are shown in Figure 4 of Heki (2011). Based on the inserted curve of Heki's Figure 4 relating the size of the ionospheric effect to the quake's magnitude, we were not optimistic about detecting an effect for the 6.0 Napa quake. However, it occurred at night, when the well-known shielding effect of the ionospheric D and lower E regions for EM fields becomes very small. When this special session with a later abstract deadline was announced, JPL researchers were asked to examine GPS data from California stations. Based on their data, the plot shown (left panel) combined with a similar plot for the Tohoku-Oki earthquake (right panel, based on Heki's data) was produced. Both panels show fluctuations of STEC (Slant Total Electron Content) before the quake times (indicated by asterisks showing the positions of ionospheric penetration points (IPP) at the respective quake times). Although alternative explanations for the TEC fluctuations cannot be ruled out entirely, these results suggest that a patent-pending system able to predict an earthquake some 30 minutes before an event by using satellites and ground stations to measure disturbances in the earth's ionosphere would be of great value. Such a system would be a major boon for vulnerable sites such as nuclear power plants and natural gas lines in populated areas as well as an early warning to evacuate vulnerable buildings, much like today's early warning system for tornados.

  16. Effects of the 20 March 2015 total solar eclipse on the ionosphere-thermosphere system

    NASA Astrophysics Data System (ADS)

    Grandin, Maxime; Marchaudon, Aurelie; Aikio, Anita; Blelly, Pierre-Louis; Kozlovsky, Alexander; Pitout, Frederic; Ulich, Thomas; Lester, Mark; Miller, Ethan; Yeoman, Tim

    2015-04-01

    A total solar eclipse is a spectacular natural phenomenon whose consequences over the underlying ionosphere and thermosphere remain complex and not fully explained. On 20 March 2015, a total solar eclipse lasting almost 2 hours passed over the Atlantic Ocean, then over Svalbard. These specific regions are extremely interesting as they are covered by several ground-based instruments: SuperDARN radars, EISCAT Svalbard radar (ESR), magnetometers, and imaging instruments. We take advantage of this excellent instrumental configuration coupled with results from detailed ionosphere models to study the dynamic consequences of this eclipse on the underlying ionosphere and thermosphere. In particular, we run specific scanning modes on the SuperDARN radars in order to identify a possible generation of Atmospheric Gravity Waves (AGW) caused by the eclipse. We present the observations of the different instruments and compare them with initial simulations made with the TRANSCAR ionosphere model. As this eclipse is first located on closed field lines, we also investigate the possible exchange of energy and particle fluxes with the opposite sunlit hemisphere by running the interhemispheric version of our ionosphere model.

  17. 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.

  18. Ionospheric effects during first 2 hours after the Chelyabinsk meteorite impact

    E-print Network

    Berngardt, O I; Zherebtsov, G A; Kusonski, O A; Grigorieva, S A

    2013-01-01

    This paper presents the analysis of ionospheric effects in the region close to the Chelyabinsk meteorite explosion at 03:20UT 2013 February 15 from the Institute of Solar-Terrestrial Physics of Siberian Branch of Russian Academy of Sciences (ISTP SB RAS) EKB radar data, and from the Institute of Geophysics of Ural Branch of Russian Academy of Sciences (IG UB RAS) PARUS ionosonde data. Both instruments are located within the IG UB RAS Arti Observatory approximately 200 km northward from the estimated explosion site. According to the data obtained, the ionospheric disturbance caused by the meteorite flyby, explosion, and impact had high dynamics and amplitude. However, it obviously did not lead to a variation in the ionosphere mean parameters in the region above the disturbance center during the first 2 hours. Essential effects, however, were observed at more than 100-200 km from the explosion site and farther up to 1500 km.

  19. IMF polarity effects on the equatorial ionospheric F-region

    Microsoft Academic Search

    J. H. Sastri

    1985-01-01

    An exploratory study is made of the influence, during the equinoxes, of the interplanetary magnetic field (IMF) sector structure on the ionospheric F-region using ionosonde data from several equatorial stations for a 3-yr period around the 19th sunspot cycle maximum. It is found that, compared with days having positive IMF polarity, the post-sunset increase of h'F near the dip equator

  20. The effect of moving cold fronts over Central Europe to the variability of the ionosphere

    NASA Astrophysics Data System (ADS)

    Potuznikova, Katerina; Koucka Knizova, Petra; Boska, Josef; Sindelarova, Tereza; Mosna, Zbysek

    2015-04-01

    Cold fronts represent well known source of atmospheric waves, (especially short and medium scale AGW - acoustic gravity waves), that are able to propagate up to the ionospheric heights. In our study we focus on the effects of the transitions of cold front over the region of Central Europe on the variations of the ionosphere. We concentrate on periods of low solar and geomagnetic activity. Neutral atmosphere data are compared with the wave-like oscillations in the E and F layer. Our tropospheric data comprise synoptic maps on of 500 hPa and 850 hPa geopotential heights. Within ionospheric data we search for variability that is linked to the tropospheric disturbances. The ionospheric parameters (electron concentration and corresponding height) we analyse by the wavelet transform method. The Modern HF digisonde DPS-4 D (Digisonde Portable Sounder), which is in operation at the Pruhonice observatory (49.59 N; 14.33 E) of the Institute of Atmospheric Physics, Prague (IAP) since 2004, represents an excellent source of the ionospheric data for Central Europe. Pruhonice digisonde usually operates in standard mode - one ionogram and electron density profie N(h) each 15 minutes. Besides that, data from several european stations of the digisonde world network (data from Juliusruhe, Chilton, Brusel, Roma and Tortosa digisonde stations) are included in the study.

  1. Effects of Gravity Waves on the Thermosphere/Ionosphere system simulated by an atmosphere-ionosphere coupled Model

    NASA Astrophysics Data System (ADS)

    Miyoshi, Y.; Jin, H.; Fujiwara, H.; Shinagawa, H.

    2013-12-01

    Behaviors of gravity waves in the thermosphere ionosphere are studied by using a whole atmosphere-ionosphere coupled model (GAIA), in which a whole atmosphere general circulation model (GCM), an ionosphere model and an electrodynamics model are integrated. The whole atmosphere GCM contains the region from the ground surface to the upper thermosphere, so that we can simulate excitation of gravity waves in the lower atmosphere and their upward propagation to the thermosphere. We have recently developed an atmosphere-ionosphere coupled model with high horizontal resolution (about 1 degree longitude by 1degree latitude). In this study, we would like to present a preliminary result obtained by the GAIA simulation. Using this coupled model, we investigate the upward propagation of gravity waves from the lower atmosphere to the thermosphere and its impact on ionospheric variability. In particular, we focus our attention on the relation between the convective activity in the troposphere and the thermosphere/ionosphere variability. Our simulation result indicates that gravity waves with a larger horizontal phase velocity (larger vertical wavelength) can penetrate into the thermosphere and affect the general circulation of the upper atmosphere. The longitudinal distribution of the gravity wave activity in low latitudes of the thermosphere is closely related to the cumulus convective activity in the tropics. The impact of the thermospheric gravity wave on the ionosphere is also discussed.

  2. Ionospheric Asymmetry Evaluation using Tomography to Assess the Effectiveness of Radio Occultation Data Inversion

    NASA Astrophysics Data System (ADS)

    Shaikh, M. M.; Notarpietro, R.; Yin, P.; Nava, B.

    2013-12-01

    The Multi-Instrument Data Analysis System (MIDAS) algorithm is based on the oceanographic imaging techniques first applied to do the imaging of 2D slices of the ionosphere. The first version of MIDAS (version 1.0) was able to deal with any line-integral data such as GPS-ground or GPS-LEO differential-phase data or inverted ionograms. The current version extends tomography into four dimensional (lat, long, height and time) spatial-temporal mapping that combines all observations simultaneously in a single inversion with the minimum of a priori assumptions about the form of the ionospheric electron-concentration distribution. This work is an attempt to investigate the Radio Occultation (RO) data assimilation into MIDAS by assessing the ionospheric asymmetry and its impact on RO data inversion, when the Onion-peeling algorithm is used. Ionospheric RO data from COSMIC mission, specifically data collected during 24 September 2011 storm over mid-latitudes, has been used for the data assimilation. Using output electron density data from Midas (with/without RO assimilation) and ideal RO geometries, we tried to assess ionospheric asymmetry. It has been observed that the level of asymmetry was significantly increased when the storm was active. This was due to the increased ionization, which in turn produced large gradients along occulted ray path in the ionosphere. The presence of larger gradients was better observed when Midas was used with RO assimilated data. A very good correlation has been found between the evaluated asymmetry and errors related to the inversion products, when the inversion is performed considering standard techniques based on the assumption of spherical symmetry of the ionosphere. Errors are evaluated considering the peak electron density (NmF2) estimate and the Vertical TEC (VTEC) evaluation. This work highlights the importance of having a tool which should be able to state the effectiveness of Radio Occultation data inversion considering standard algorithms, like Onion-peeling, which are based on ionospheric spherical symmetry assumption. The outcome of this work will lead to find a better inversion algorithm which will deal with the ionospheric asymmetry in more realistic way. This is foreseen as a task for future research. This work has been done under the framework of TRANSMIT project (ITN Marie Curie Actions - GA No. 264476).

  3. Plausible effect of atmospheric tides on the equatorial ionosphere observed by the FORMOSAT-3/COSMIC: Three-dimensional electron

    E-print Network

    California at Berkeley, University of

    Plausible effect of atmospheric tides on the equatorial ionosphere observed by the FORMOSAT-3 of atmospheric tides on the longitudinal structure of the equatorial ionosphere is observed by the FORMOSAT-3 the magnetic field lines from E-region where longitudinal variations in atmospheric tides affect

  4. Techniques and Tools for Estimating Ionospheric Effects in Interferometric and Polarimetric SAR Data

    NASA Technical Reports Server (NTRS)

    Rosen, P.; Lavalle, M.; Pi, X.; Buckley, S.; Szeliga, W.; Zebker, H.; Gurrola, E.

    2011-01-01

    The InSAR Scientific Computing Environment (ISCE) is a flexible, extensible software tool designed for the end-to-end processing and analysis of synthetic aperture radar data. ISCE inherits the core of the ROI_PAC interferometric tool, but contains improvements at all levels of the radar processing chain, including a modular and extensible architecture, new focusing approach, better geocoding of the data, handling of multi-polarization data, radiometric calibration, and estimation and correction of ionospheric effects. In this paper we describe the characteristics of ISCE with emphasis on the ionospheric modules. To detect ionospheric anomalies, ISCE implements the Faraday rotation method using quadpolarimetric images, and the split-spectrum technique using interferometric single-, dual- and quad-polarimetric images. The ability to generate co-registered time series of quad-polarimetric images makes ISCE also an ideal tool to be used for polarimetric-interferometric radar applications.

  5. Ionospheric effects of the Mt. Kirishima volcanic eruption as seen from subionospheric VLF observations

    NASA Astrophysics Data System (ADS)

    Rozhnoi, A.; Hayakawa, M.; Solovieva, M.; Hobara, Y.; Fedun, V.

    2014-01-01

    Data from the Pacific network of VLF receivers have been used to study the response of the lower ionosphere to the January 2011 Mt. Kirishima (South Japan) volcanic eruption. A major explosive eruption occurred on January 27, which was preceded by several small eruptions. Perturbations of nighttime subionospheric VLF signals have been detected on the day of the first small eruption on January 18 (UT) with the maximum observed about 1.5 h after the eruption. The nighttime signal remained disturbed during the subsequent pre-eruptive and eruptive activity of Mt. Kirishima. The daytime perturbations were not observed. The frequency of the maximum spectral amplitude was found to be in the range of periods of 6-30 min, which corresponds to the periods of internal gravity waves. These results suggest that the observed VLF ionospheric effects can possibly be produced by the penetration of gravity waves caused by the volcanic activity into the ionosphere.

  6. Three-dimensional multifluid simulations of ionospheric loss at Mars from nominal solar wind conditions to magnetic cloud events

    Microsoft Academic Search

    E. M. Harnett; R. M. Winglee

    2006-01-01

    Three-dimensional multifluid simulations of the solar wind interaction with a magnetized Mars are used to determine both the effect of the crustal magnetic field on ionospheric loss rate and the ionospheric loss rate as a function of solar wind conditions. Ionospheric losses on the order of 1025 O2+ ions per second are found for quiet solar wind conditions. This is

  7. Possible effects of ionospheric beating for the formation of Pc1 pearl structures based on 6-year ground observations in Canada, Russia and Japan

    NASA Astrophysics Data System (ADS)

    Jun, C. W.; Shiokawa, K.; Connors, M. G.; Schofield, I.; Poddelsky, I.; Shevtsov, B.

    2014-12-01

    We investigate pearl structures (amplitude modulation) of Pc1 pulsations simultaneously observed at Athabasca (ATH, 54.7N, 246.7E, L=4.3) in Canada, Magadan (MGD, 60.1N, 150.7E, L=2.6) in Russia, and Moshiri (MOS, 44.4N, 142.3E, L=1.5) in Japan. From a 6-year period of ground observations, from 2008 to 2013, we selected 150 events at longitudinally separated stations (ATH and MGD, group 1), 782 at latitudinally separated stations (MGD and MOS, group 2), all with high coherence of Pc1 waveforms (r > 0.5). As a result, we found that the peak occurrence rates of simultaneous Pc1 events were at 12-18 UT in group1, when ATH was in the morning sector and MGD in the midnight sector. In group 2, the peak was at 18-21 UT, with MGD and MOS in the morning sector. Using cross-correlation analysis, we confirmed the similarity of Pc1 pearl structures at different stations during Pc1 event timing. 82 % of Pc1 events in group 1 were less than 40 % of similarity of Pc1 pearl structures. In addition, 18 % of Pc1 events in group 1, which are over than 40 % of similarity of Pc1 pearl structures, were concentrated at 10-18 UT. According to polarization angle distribution in group 1, 57 % of Pc1 events occurred between ATH and MGD. Most of those events had high similarity of Pc1 amplitude envelopes. We investigated the relationship between the similarity of Pc1 pearl structures and geomagnetic activities (AE and SYM-H indices). The AE index seemed suddenly to start decreasing before the Pc1 onset and increasing after 80 min. The variation of SYM-H index was increasing 2 hours before Pc1 onset. From our statistical analysis, we suggest that the beating process in the ionosphere could be the dominant generation mechanism of Pc1 pearl structures in the ionosphere. It seems that the ionospheric duct in dawn sector of the ionosphere is well-defined during Pc1 pulsation propagating from ionospheric sources to stations. In order to understand the beating process in the ionosphere more clearly, we are going to take into account the possible effects such as distributed ionospheric source, attenuation effect in the ionosphere, dispersive propagation in the ionosphere and Pc1 source amplitude. Using the same procedure, we will also investigate Pc1 pearl structures simultaneously observed at latitudinally separated ground stations (MGD and MOS).

  8. Effects of solar wind dynamic pressure on the ionospheric fluence during the 31 August 2005 storm

    E-print Network

    Effects of solar wind dynamic pressure on the ionospheric O+ fluence during the 31 August 2005 solar wind data is contrasted against a case where the solar wind dynamic pressure (Pdyn with the solar wind dynamic pressure. Additionally, changes in Pdyn affect the downward Poynting flux only

  9. Space weather effects on the Mars ionosphere due to solar flares and meteors

    E-print Network

    Withers, Paul

    Space weather effects on the Mars ionosphere due to solar flares and meteors P. Withers (1), M) Using data from the Radio Science Experiment onboard the Mars Global Surveyor (MGS) satellite, we have observed two aspects of space weather at Mars. Following solar flares of both moderate to strong magnitude

  10. The Effects of Solar Flares on the Ionospheres of Earth and Mars

    E-print Network

    Withers, Paul

    The Effects of Solar Flares on the Ionospheres of Earth and Mars Paul Withers Boston University.10.31 (withers@bu.edu) #12;Solar Flares http://www.assabfn.co.za/pictures/solar_boydenflare_historical_articles photons, and lots of them, but they don't create any ions · Variable (eg 27 day solar rotation) flux

  11. The High Latitude Ionosphere and its Effects on Radio Propagation, R. D. Hunsucker and J. K. Hargreaves, Cambridge University Press, xix + 617pp, 2003

    E-print Network

    The High Latitude Ionosphere and its Effects on Radio Propagation, R. D. Hunsucker and J. K emphasis on the high latitude ionosphere, the book contains much more. Indeed, it is a veritable compendium of ionosphere lore, data, and experimental and theoretical developments over the decades. Studies of the Earth

  12. The lower ionosphere effects caused by the tsunami-driven internal gravity waves

    NASA Astrophysics Data System (ADS)

    Rozhnoi, Alexander; Solovieva, Maria; Shalimov, Sergei; Levin, Boris; Shevchenko, Georgy; Hayakawa, Masashi

    2014-05-01

    Measurements from the VLF/LF station in Petropavlovsk-Kamchatsky (Russia) were used to observe the response of the lower ionosphere to the tsunami triggered by the 2010 Chili earthquake. This earthquake produced the trans-ocean tsunami, which severely affected the coastal communities of Chile and presented a serious threat for all Pacific Ocean coasts including the far eastern coast of Russia. Disturbances in the phase and amplitude of the VLF signal propagating from the transmitter in Hawaiian Islands were observed during the tsunami wave passage recorded by the Deep-ocean Assessments and Reporting of Tsunamis (DART) bottom pressure stations. The tsunami propagation time from the source to Hawaii Islands was about 14 h and to the coast of Russia about 21 h. The new point discussed here is that we observed a second tsunami and its ionospheric effects which have been missed in the previous observations in the upper ionosphere. Nevertheless, the presence of the second tsunami is confirmed by both the VLF and DART's measurements. The tsunamigenic effects in the ionosphere were compared to the in-situ sea-level DART measurements near Hawaii Islands and not far from Kamchatka. The frequency of the maximum spectral amplitude both for the VLF and DART data was found to be in the range of periods of 8-60 min which corresponds to the period of the internal gravity waves generated by tsunami.

  13. Disturbance Effects Seen in the Midlatitude Ionosphere with SuperDARN

    NASA Astrophysics Data System (ADS)

    Ruohoniemi, J. M.; Baker, J. B. H.; Bristow, W. A.; Shepherd, S. G.; Miller, E. S.

    2014-12-01

    With the construction of the first midlatitude SuperDARN radar at NASA Wallops Flight Facility in 2005 it quickly became apparent that much activity can be observed in the midlatitude ionosphere even outside of large storm intervals. Over the last five years a chain of SuperDARN radars has been deployed at midlatitudes under the NSF Mid-Sized Infrastructure program that extends across the western hemisphere as far as east Asia. The new radars are providing unprecedented large-scale views of disturbance effects such as the storm-time expansion of auroral flows, subauroral polarization streams (SAPS), and travelling ionospheric disturbances (TIDs). When combined with large-scale mapping of GPS/TEC it is possible to observe directly the generation of plasma structures such as storm-enhanced density features (SEDs), tongues of ionization (TOIs), and polar cap patches, and to understand their dependence on the dynamic convection pattern reaching to the mid-latitude region. One unexpected result is the observation of backscatter from irregularities distributed throughout the quiet-time nightside subauroral ionosphere. This phenomenon gives us views of electric fields that are conjugate to the inner magnetosphere and also reveals the occurrence of large transients in the quiet-time subauroral electric fields. In this talk we summarize over the effects identified to date and discuss the insights gained in understanding the disturbed midlatitude ionosphere.

  14. Interplanetary magnetic field effects on high latitude ionospheric convection

    NASA Technical Reports Server (NTRS)

    Heelis, R. A.

    1985-01-01

    Relations between the electric field and the electric current in the ionosphere can be established on the basis of a system of mathematical and physical equations provided by the equations of current continuity and Ohm's law. For this reason, much of the synthesis of electric field and plasma velocity data in the F-region is made with the aid of similar data sets derived from field-aligned current and horizontal current measurements. During the past decade, the development of a self-consistent picture of the distribution and behavior of these measurements has proceeded almost in parallel. The present paper is concerned with the picture as it applies to the electric field and plasma drift velocity and its dependence on the interplanetary magnetic field. Attention is given to the southward interplanetary magnetic field and the northward interplanetary magnetic field.

  15. IMF polarity effects on the equatorial ionospheric F-region

    SciTech Connect

    Sastri, J.H.

    1985-01-01

    An exploratory study is made of the influence, during the equinoxes, of the interplanetary magnetic field (IMF) sector structure on the ionospheric F-region using ionosonde data from several equatorial stations for a 3-yr period around the 19th sunspot cycle maximum. It is found that, compared with days having positive IMF polarity, the post-sunset increase of h'F near the dip equator and the depth of the equatorial ionization anomaly (EIA) are reduced during the vernal equinox and enhanced during the autumnal equinox on days with negative IMF polarity. Similar trends are also noted in the data for the 20th sunspot cycle maximum, but with reduced amplitude. The systematic changes in the F-region characteristics suggest a modification of the equatorial zonal electric fields in association with the IMF polarity-related changes in the semi-annual variation of geomagnetic activity. 24 references.

  16. Cyclotron resonance effects on stochastic acceleration of light ionospheric ions

    NASA Technical Reports Server (NTRS)

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

    1982-01-01

    The production of energetic ions with conical pitch angle distributions along the auroral field lines is a subject of considerable current interest. There are several theoretical treatments showing the acceleration (heating) of the ions by ion cyclotron waves. The quasi-linear theory predicts no acceleration when the ions are nonresonant. In the present investigation, it is demonstrated that the cyclotron resonances are not crucial for the transverse acceleration of ions by ion cyclotron waves. It is found that transverse energization of ionospheric ions, such as He(+), He(++), O(++), and O(+), is possible by an Electrostatic Hydrogen Cyclotron (EHC) wave even in the absence of cyclotron resonance. The mechanism of acceleration is the nonresonant stochastic heating. However, when there are resonant ions both the total energy gain and the number of accelerated ions increase with increasing parallel wave number.

  17. Quasi-static electric fields phenomena in the ionosphere associated with pre- and post earthquake effects

    NASA Astrophysics Data System (ADS)

    Gousheva, M.; Danov, D.; Hristov, P.; Matova, M.

    2008-02-01

    To prove a direct relationship between the quasi-static electric field disturbances and seismic activity is a difficult, but actual task of the modern ionosphere physics. This paper presents new results on the processing and analysis of the quasi-static electric field in the upper ionosphere (h=800-900 km) observed from the satellite INTERCOSMOS-BULGARIA-1300 over earthquakes' source regions (seismic data of World Data Center, Denver, Colorado, USA). Present research focuses on three main areas (i) development of methodology of satellite and seismic data selecting, (ii) data processing and observations of the quasi-static electric field (iii) study and accumulation of statistics of possible connection between anomalous vertical electric fields penetrating from the earthquake zone into the ionosphere, and seismic activity. The most appropriate data (for satellite orbits above sources of forthcoming or just happened seismic events) have been selected from more than 250 investigated cases.The increase of about 5-10-15 mV/m in the vertical component of the quasi-static electric field observed by INTERCOSMOS-BULGARIA-1300 during seismic activity over Southern Ocean, Greenland Sea, South-Weat Pacific Ocean, Indian Ocean, Central America, South-East Pacific Ocean, Malay Archipelago regions are presented. These anomalies, as phenomena accompanying the seismogenic process, can be considered eventually as possible pre-, co- (coeval to) and post-earthquake effects in the ionosphere.

  18. Ionospheric and magnetospheric effects of solar flares monitored by ground-based riometer and magnetometers

    NASA Astrophysics Data System (ADS)

    Ronan Coelho Stekel, Tardelli; Schuch, Nelson Jorge; Echer, Ezequiel; Guarnieri, Fernando; Makita, Kazuo; Espindola Antunes, Cassio; Moro, Juliano; Machado Paulo, Claudio

    The solar flare incidence follows a behavior similar to the solar cycle activity, which results in periodic disturbances on the Earth's ionosphere and magnetosphere. The correlation of this phenomenon can provide important information about the magnetosphere, the Sun/Earth interaction, as well as events occurring in the ionosphere which can, for instance, generate disturbances in telecommunications, small satellites or even in the space weather. Riometer and magnetometers data analysis can provide useful way for measuring and understanding the effects of solar flare radiation in the ionosphere and magnetosphere. The Solar Flare effect (SFE) is associated with the sudden change of ionospheric currents caused by the extra ionization produced by soft X-ray (0.1 to 9.0 nm) and EUV (9.0 to 100.0 nm) radiation from the solar flare. The objective of this work is to present the correlation of the ionospheric and magnetospheric (H, D, Z) sudden disturbances due to high-intensity solar flares (M and X class), that can emit up to 1032 ergs of energy. For this purpose, analysis were performed for the riometer and magnetometers dedicated to study the Solar-Earth interactions at the Southern Space Observatory (SSO/CRS/INPE -MCT), (29.4° S, 53.8° W, 480m a.s.l), São Martinho da a Serra, RS, Brazil. To identify and investigate the sudden radiation increase caused by the solar flare, the X-ray data (0.1 to 0.8 nm) from GOES Satellites and the EUV data (26.0 to 34.0 nm and 0.1 to 50.0 nm) from the Solar EUV Monitor (SEM) on the SOHO spacecraft are correlated. With the analysis of these ground-based instruments and spacecrafts data, the correlation of the solar activity and the magnetospheric and ionospheric disturbances were performed, as for the Sudden Ionospheric Disturbance (SID) and Magnetic Crochet about 60% D-component variation during a large solar flare was observed.

  19. Effects of Fast Co-rotating Beams\\/HILDCAAs on the Brazilian ionosphere

    Microsoft Academic Search

    D. C. S. Arruda; J. H. A. Sobral; V. M. Castilho

    2006-01-01

    The effects of Fast Co-rotating Beams HILDCAAs High Intensity Long-Duration Continuous AE Activity events on the Brazilian ionosphere low and equatorial latitudes are investigated here The HILDCAAs events are associated with Fast Co-rotating Beams following a selection criteria empirically defined by AE index which are commonly embedded with alfvenic fluctuations originated in coronal holes of the Sun The Fast Co-rotating

  20. Ionospheric irregularities and effects on GNSS navigation systems in the polar cap

    NASA Astrophysics Data System (ADS)

    Oksavik, Kjellmar; van der Meeren, Christer; Moen, Joran I.; Lester, Mark

    2013-04-01

    In this presentation we describe efforts that are currently ongoing at Svalbard to study ionospheric irregularities and their effects on GNSS navigation systems in the polar cap. We present initial measurements from a series of new multi-constellation TEC and scintillation receivers that we are installing around Svalbard. These data will be compared with multi-instrument observations from EISCAT, SuperDARN, ground-based optics, and sounding rockets.

  1. Effect of solar flares flux on the propagation and modal composition of VLF signal in the lower ionosphere

    NASA Astrophysics Data System (ADS)

    Bouderba, Yasmina; Nait Amor, Samir; Tribeche, Mouloud

    2015-04-01

    The VLF radio waves propagating in the Earth-Ionosphere waveguide are sensitive to the ionospheric disturbances due to X rays solar flux. In order to understand the VLF signal response to the solar flares, the LWPC code is used to simulate the signal perturbation parameters (amplitude and phase) at fixed solar zenith angle. In this work, we used the NRK-Algiers signal data and the study was done for different flares classes. The results show that the perturbed parameters increase with the increasing solar flares flux. This increases is due to the growth of the electron density resulting from the changes of the Wait's parameters. However, the behavior of the perturbation parameters as function of distance shows different forms of signal perturbations. It was also observed that the null points move towards the transmitter location when the flare flux increases which is related to the modal composition of the propagating signal. Effectively, for a given mode, the plot of the attenuation coefficient as function of the flare flux shows a decreases when the flux increases which is more significant for high modes. Thus, the solar flares effect is to amplify the VLF signal by reducing the attenuation coefficient.

  2. Effects of the Ionosphere on Passive Microwave Remote Sensing of Ocean Salinity from Space

    NASA Technical Reports Server (NTRS)

    LeVine, D. M.; Abaham, Saji; Hildebrand, Peter H. (Technical Monitor)

    2001-01-01

    Among the remote sensing applications currently being considered from space is the measurement of sea surface salinity. The salinity of the open ocean is important for understanding ocean circulation and for modeling energy exchange with the atmosphere. Passive microwave remote sensors operating near 1.4 GHz (L-band) could provide data needed to fill the gap in current coverage and to complement in situ arrays being planned to provide subsurface profiles in the future. However, the dynamic range of the salinity signal in the open ocean is relatively small and propagation effects along the path from surface to sensor must be taken into account. In particular, Faraday rotation and even attenuation/emission in the ionosphere can be important sources of error. The purpose or this work is to estimate the magnitude of these effects in the context of a future remote sensing system in space to measure salinity in L-band. Data will be presented as a function of time location and solar activity using IRI-95 to model the ionosphere. The ionosphere presents two potential sources of error for the measurement of salinity: Rotation of the polarization vector (Faraday rotation) and attenuation/emission. Estimates of the effect of these two phenomena on passive remote sensing over the oceans at L-band (1.4 GHz) are presented.

  3. 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.

  4. GPS and ionospheric scintillations

    Microsoft Academic Search

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

    2007-01-01

    Ionospheric scintillations are one of the earliest known effects of space weather. Caused by ionization density irregularities, scintillating signals change phase unexpectedly and vary rapidly in amplitude. GPS signals are vulnerable to ionospheric irregularities and scintillate with amplitude variations exceeding 20 dB. GPS is a weak signal system and scintillations can interrupt or degrade GPS receiver operation. For individual signals,

  5. Dispersive ionospheric Alfvén resonator

    Microsoft Academic Search

    Oleg A. Pokhotelov; D. Pokhotelov; A. Streltsov; V. Khruschev; M. Parrot

    2000-01-01

    A new model of the ionospheric Alfvén resonator (IAR) including the effect of wave frequency dispersion is presented. It is shown that the shear Alfvén waves in the IAR are coupled to the compressional mode through the boundary conditions at the ionosphere. This coupling results in the appearance of the Hall dispersion and subsequent shift of the IAR frequency spectrum.

  6. On conformity of the EEJ based ionospheric model to the fountain effect and resulting improvements

    NASA Astrophysics Data System (ADS)

    Acharya, Rajat; Roy, Bijoy; Sivaraman, M. R.; Dasgupta, Ashish

    2011-05-01

    The total electron content (TEC) of the equatorial ionosphere is controlled by photochemical processes as well as the transport of the ionospheric plasma near the magnetic equator. The transport phenomenon is initiated by the vertical drift driven by the eastward electric field, which also drives the Equatorial Electrojet. The empirical relation between the Equatorial Electrojet and the anomaly component of the equatorial TEC has already been established. Taking this relation as a reference, a simplified physical model of the anomaly component of equatorial TEC is obtained as a function of Equatorial Electrojet. Influence of other factors like the solar incidence angle and the solar flux are also considered here and the extent of their influence are also investigated. This has been done using TEC data obtained from dual frequency GPS receivers during the low solar activity period of 2005. The derived model is based on the physics of the underlying fountain effect and matches with the observed empirical relation to a fair extent. Obtained results are found to corroborate with previous findings and these physical model values are found to have improved correlation with the observed data than the reference empirical relation. This establishes the conformity between the EEJ based ionospheric model and the physical phenomenon of the fountain effect.

  7. Effect of ray and speed perturbations on Ionospheric Tomography by Over-the-horizon radar: A new method

    NASA Astrophysics Data System (ADS)

    Roy, C.; Occhipinti, G.; Boschi, L.; Molinié, J. P.

    2014-12-01

    Most recent methods in ionospheric tomography are based on the inversion of the Total Electron Content (TEC) measured by ground-based GPS receivers. As a consequence of the high frequency of the GPS signal and the absence of horizontal ray paths, the electron density structure is mainly reconstructed in the F2 region (300 km), where the ionosphere reaches the maximum of ionization, and is not sensitive to the lower ionospheric structure. We propose here a new tomographic method of the lower ionosphere, based on the full inversion of over-the-horizon (OTH) radar data. Previous studies using OTH radar for ionospheric tomography inverted only the leading edge echo curve of backscatter ionograms. The major advantage of our methodology is taking into account, numerically and jointly, the effect that the electron density perturbations induce not only in the speed of electromagnetic waves, but also on the ray-path geometry. This last point is extremely critical for OTH radar inversions as the emitted signal propagates through the ionosphere between a fixed starting-point (the radar) and an unknown end-point on the Earth surface where the signal is backscattered. We detail our ionospheric tomography method with the aid of benchmark tests. Having proved the necessity to take into account both effects simultaneously, we apply our method to real data. This is the first time that the effect of the ray-path deflection has been quantified and that the ionospheric plasma density has been estimated over the entirety of Europe with an OTH radar.

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

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

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

  9. Effects of artificially injected electron beams on the characteristics of ground VLF transmitter signals in the ionosphere

    NASA Astrophysics Data System (ADS)

    Oraevsky, V.; Chmyrev, V.; Shibaev, I.; Dokoukin, V.; Sobolev, Ya.; Shklyar, D.; Lundin, B.; Sadovnikov, A.; Tischenko, A.; Triska, P.

    1994-03-01

    Spectral broadening of signals from a ground-based VLF transmitter was observed onboard the Magion-3 sub-satellite during electron beam injection from the Intercosmos-25 (APEX) satellite. Broadening of the order of 300-500 Hz was apparently correlated with the 2 s-periodic sequence of the electron gun pulses which were modulated in amplitude with frequencies 30.5 less than f(sub m) less than 31,250 Hz. No effects were found for those electron gun pulses with f(sub m) = 62.5, 125 and 250 kHz. The observations were made in the middle latitude ionosphere at altitudes between 1175 and 1580 km; the distance between satellite and sub-satellite was about 250 km. The electron gun current and the energy of electrons were 100 mA and 10 keV, respectively, and the duration of the elementary pulse of current was 2 microseconds. The data are interpreted in terms of the scattering of whistler mode waves into quasi-electrostatic waves by periodic small-scale plasma inhomogeneities or ELF plasma turbulence created by the pulse-modulated electron beam in the ionosphere.

  10. The ionospheric storms' dynamics at new solar activity cycle biginning

    NASA Astrophysics Data System (ADS)

    Cherniak, Iu.; Krankowski, A.; Shagimuratov, I.; Sieradzki, R.; Zakharenkova, I.; Korenkova, N.; Leschenko, V.

    2012-04-01

    At the beginning of the new 24th Solar Cycle several geomagnetic storms took place. In this study we analyzed the geomagnetic disturbances occurred on May 2010 and March, August- October 2011, which caused the most considerable ionospheric response. The ionospheric behavior during these selected events were analyzed by using the multi-instrumental diagnostic facilities data. The data about peak electron density (foF2) variations was obtained by local "Parus" ionosonde in Kaliningard observatory and provided with European, Japanese and Australian ionosonde networks. The shape of the electron density profiles was derived from FORMOSAT-3 / COSMIC GPS Radio Occultation measurements. The global ionospheric maps of TEC (GIMs TEC), provided by International GNSS Service, were used in order to estimate global storm effects on the ionosphere. For detailed analysis of the height ionospheric structure changes we combined ionosonde-derived data with GPS TEC variations and the electron density profiles retrieved from Radio Occultation measurements. The geomagnetic storms with similar magnitude lead to the different ionospheric response (positive and negative) over European, Japan and Australian regions. The considered ionospheric storms were mainly negative over European region with average duration of about 36 hours, but in May 2010 and September 2011 the significant positive ionospheric disturbances took place. The temporal and quantitative characteristics of the ionosphere modification during selected geomagnetic storms were revealed. It was carried out the comparison of observations with IRI-2007 model, that has the storm-time option. The best agreement between model and observations results was corresponded to the Northern Hemisphere midlatitude stations for negative ionospheric storms. Also it was estimated the effect of storm-time ionospheric variability on GNSS performance. We acknowledge the European Digital Upper Atmosphere Server (DIAS), Australian IPS Radio and Space service and the National Institute of Information and Communications Technology (NICT) in Japan for providing ionosonde data. We are also grateful to International GNSS Service (IGS) for GIMs IONEX Data.

  11. A laboratory experiment to examine the effect of auroral beams on spacecraft charging in the ionosphere

    SciTech Connect

    Siddiqui, M. U. [Department of Engineering Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States); Gayetsky, L. E.; Mella, M. R.; Lynch, K. A. [Department of Physics and Astronomy, Dartmouth College, Hanover, New Hampshire 03755 (United States); Lessard, M. R. [Space Science Center, University of New Hampshire, Durham, New Hampshire 03824 (United States)

    2011-09-15

    A 2.54 cm diameter conducting electrically isolated Copper sphere is suspended in a low density (10{sup 4} cm{sup -3}), low temperature (T{sub e} = 0.5 eV) Argon plasma, which mimics a spacecraft in an ionospheric plasma. An electron beam with current density of approximately 10{sup -10} A/cm{sup 2} and beam spot of 10.2 cm diameter, which mimics an auroral electron beam, is fired at the sphere while varying the beam energy from 100 eV to 2 keV. The plasma potential in the sheath around the sphere is measured using an emissive probe as the electron beam energy is varied. To observe the effects of the electron beam, the experimental sheath potential profiles are compared to a model of the plasma potential around a spherically symmetric charge distribution in the absence of electron beams. Comparison between the experimental data and the model shows that the sphere is less negative than the model predicts by up to half a volt for beam energies that produce high secondary electron emission from the surface of the sphere. It is shown that this secondary emission can account for changes in potential of spacecraft in the ionosphere as they pass through auroral beams and thus helps to improve interpretations of ionospheric thermal ion distributions.

  12. 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.

  13. Ionospheric effects in uncalibrated phase delay estimation and ambiguity-fixed PPP based on raw observable model

    NASA Astrophysics Data System (ADS)

    Gu, Shengfeng; Shi, Chuang; Lou, Yidong; Liu, Jingnan

    2015-05-01

    Zero-difference (ZD) ambiguity resolution (AR) reveals the potential to further improve the performance of precise point positioning (PPP). Traditionally, PPP AR is achieved by Melbourne-Wübbena and ionosphere-free combinations in which the ionosphere effect are removed. To exploit the ionosphere characteristics, PPP AR with L1 and L2 raw observable has also been developed recently. In this study, we apply this new approach in uncalibrated phase delay (UPD) generation and ZD AR and compare it with the traditional model. The raw observable processing strategy treats each ionosphere delay as an unknown parameter. In this manner, both a priori ionosphere correction model and its spatio-temporal correlation can be employed as constraints to improve the ambiguity resolution. However, theoretical analysis indicates that for the wide-lane (WL) UPD retrieved from L1/L2 ambiguities to benefit from this raw observable approach, high precision ionosphere correction of better than 0.7 total electron content unit (TECU) is essential. This conclusion is then confirmed with over 1 year data collected at about 360 stations. Firstly, both global and regional ionosphere model were generated and evaluated, the results of which demonstrated that, for large-scale ionosphere modeling, only an accuracy of 3.9 TECU can be achieved on average for the vertical delays, and this accuracy can be improved to about 0.64 TECU when dense network is involved. Based on these ionosphere products, WL/narrow-lane (NL) UPDs are then extracted with the raw observable model. The NL ambiguity reveals a better stability and consistency compared to traditional approach. Nonetheless, the WL ambiguity can be hardly improved even constrained with the high spatio-temporal resolution ionospheric corrections. By applying both these approaches in PPP-RTK, it is interesting to find that the traditional model is more efficient in AR as evidenced by the shorter time to first fix, while the three-dimensional positioning accuracy of the RAW model outperforms the combination model by about . This reveals that, with the current ionosphere models, there is actually no optimal strategy for the dual-frequency ZD ambiguity resolution, and the combination approach and raw approach each has merits and demerits.

  14. Regionally based alarm index to mitigate ionospheric scintillation effects for GNSS receivers

    NASA Astrophysics Data System (ADS)

    Tiwari, R.; Strangeways, H. J.

    2015-01-01

    An approach to mitigate the effect of ionospheric scintillation on GNSS (Global Navigation Satellite System) users in the European region using TEC (total electron content) at 1 Hz rate is presented. The TEC in the study is derived using raw GPS (Global Positioning System) observations obtained from the EUREF networks. The study also presents derivation of a geographic mesh-map warning of the expected standard deviation of phase jitter in receiver carrier tracking loops, information which would help to mitigate scintillation effects in GPS software receivers.

  15. Prompt and delayed effects of solar disturbances in magnetosphere-ionosphere system on March 4-7, 2012

    NASA Astrophysics Data System (ADS)

    Romanova, Elena; Kurkin, Vladimir; Zolotukhina, Nina; Polekh, Nelya

    We analyze prompt and delayed effects of five X-class solar flares observed on March 4-7, 2012 at Siberian and Far Eastern ionospheric stations. The flares were associated with intensification of solar cosmic rays and Earth-directed coronal mass ejections. The prompt effects were caused by EUV, X-rays and relativistic particles. They were observed as increase in the daytime lowest frequency reflected from the ionosphere from 1.5-2 MHz to 4-8 MHz and the disappearance of reflections (complete blackout) from the high-latitude ionosphere. Delayed effects were caused by heliospheric inhomogeneity created by four interacting coronal mass ejections. The inhomogeneity enveloped the Earth’s magnetosphere during 80 hours and triggered two (moderate and strong) magnetic storms accompanied by ionospheric storms. Because of the strong variability of the solar wind and the interplanetary magnetic field in the inhomogeneity, the magnetospheric and ionospheric storms had specific features discussed in our report. The work was supported by the Russian Foundation for Basic Research (grant 13-05-91159 and 13-05-00733) and RF President Grant of Public Support for RF Leading Scientific Schools (NSh-2942.2014.5).

  16. Propagation of Alfvén surface waves along the ionospheric plasma slab with the effect of gravity

    NASA Astrophysics Data System (ADS)

    Rathinavelu, G. D.; Sivaraman, M.

    2012-02-01

    Ionospheric regions connecting the neutral gas atmosphere have been considered to be an incompressible plasma slab surrounded by incompressible plasma on one side and neutral gas on the other side. The effect of gravity on Alfvén surface waves in the slab geometry is studied. As a special case, the propagation of ASW along the plasma-neutral gas interface is also discussed. The existence of two modes of surface waves has been identified and their characteristic behaviour affected by the gravity has been discussed.

  17. The Determination of Ionospheric Electron Content from Satellite Doppler Measurements 1. Method of Analysis

    Microsoft Academic Search

    W. J. Ross

    1960-01-01

    A procedure for determining the ionospheric electron content up to the height of an active satellite from Doppler data is developed. The equations derived from first-order theory are discussed and corrected separately for earth curvature, large refraction, off-zenith orbit, vertical satellite motion, horizontal ionospheric variations, and the effects of the earth's magnetic field. The methods were developed initially for use

  18. Perturbation effect of the Coulomb drag on the orbital elements of the earth satellite moving in the ionosphere

    NASA Astrophysics Data System (ADS)

    Li, Lin-Sen

    2011-04-01

    The perturbation effects of the Coulomb drag on the orbital elements of the earth satellite moving in the ionosphere are studied. The theoretical results show that the Coulomb drag results in both the secular and periodic variation in the semi-major axis and eccentricity. However, the argument of the perigee exhibits no secular variation, but only periodic variation. The inclination and the ascending node remain no variation. As an example, the secular effects of the Coulomb drag on the semi-major axis and the eccentricity of an ionosphere satellite Alouette (S-27) are calculated in the ionosphere with the mean height 1000 km. It can be shown that the semi-major axis contracts and the eccentricity decreases for the case of the Coulomb drag under the interaction of the ions with the electric field of an earth satellite.

  19. A modern trans-ionospheric propagation sensing system

    NASA Astrophysics Data System (ADS)

    Bishop, G. J.; Klobuchar, J. A.; Ronn, A. E.; Bedard, M. G.

    1989-09-01

    One of the most important potential problems with modern military systems which utilize spacecraft is the effect of the ionosphere on the radio signals which pass to and from the spacecraft. Such systems include active communications and navigation satellites as well as both ground-based and potential space-based ranging systems. The major effects the ionosphere can have on such systems are the additional time delay the electrons in the earth's ionosphere add to the free space path delay, the short term rate of change of this additional delay, amplitude scintillation or fading effects the signal encounters due to irregularities in the ionosphere, and Faraday rotation of linearly polarized radio waves transmitted through the ionosphere. While some of these effects were studied adequate models of these effects on military systems still do not exist. A modern trans-ionospheric sensing system, called TISS, is being procured which will consist of a number of stations located throughout the world, making real time measurements of the time delay of the ionosphere, and its rate of change, as well as amplitude scintillation, along several different viewing directions from each station. These trans-ionospheric measurements will be used to allow models, which currently provide only monthly propagation parameters. The real-time specifications of these parameters can then be used as decision aids in both the tactical and the strategic military environments. The TISS will include first order artificial intelligence design to aid in gathering the most appropriate sets of available real-time trans-ionospheric propagation data, and will communicate these data sets to the Air Weather Service Forecasting Center where they will be tailored to specific military customers.

  20. Effects of atomic nitrogen on the nocturnal ionosphere

    NASA Technical Reports Server (NTRS)

    Torr, M. R.; Torr, D. G.; Walker, J. C. G.; Hays, P. B.; Hanson, W. B.; Hoffman, J. H.; Kayser, D. C.

    1975-01-01

    Recently, atomic nitrogen densities of 50-500 million/cu cm were inferred in the daytime thermosphere from studies of the NI(2D-4S) 5200 A emission and from the photochemistry of various ion species using data measured by the Atmosphere Explorer-C satellite. In this paper we use the photochemistry of NO(+) and O2(+) at night to determine nocturnal N(4S) densities in the thermosphere. We present evidence for a missing source of NO(+) and a missing sink for O2(+) at night and show that this can be adequately supplied by the reaction O2(+) + N yields NO(+) + O if the N density at 200 km is about 7 million/cu cm. The atomic nitrogen has an important effect on studies of the 6300 A airglow. The omission of N in calculations of O(1D) using ground-based data results in an overestimate of the rate coefficient for quenching of O(1D) by N2.

  1. Satellite-based augmentation systems: A novel and cost-effective tool for ionospheric and space weather studies

    NASA Astrophysics Data System (ADS)

    Sunda, Surendra; Sridharan, R.; Vyas, B. M.; Khekale, P. V.; Parikh, K. S.; Ganeshan, A. S.; Sudhir, C. R.; Satish, S. V.; Bagiya, Mala S.

    2015-01-01

    Satellite-Based Augmentation Systems (SBASes) are designed to provide additional accuracy and robustness to existing satellite-based radio navigation systems for all phases of a flight. However, similar to navigation systems such as GPS which has proven its worth for the investigation of the ionosphere, the SBASes do have certain advantages. In the present paper, we propose and demonstrate SBAS applicability to ionospheric and space weather research in a novel and cost-effective way. The recent commissioning of the Indian SBAS, named GPS Aided Geo Augmented Navigation (GAGAN), covering the equatorial and low-latitude regions centered around the Indian longitudes provides the motivation for this approach. Two case studies involving different ionospheric behavior over low-latitude regions vindicate the potential of SBAS over extended areas.

  2. Ionospheric Effects of Sudden Stratospheric Warming During Solar Maximum and Minimum Periods: What Do We See from Puerto Rico?

    NASA Astrophysics Data System (ADS)

    Hernandez-Espiet, A.; Goncharenko, L. P.; Spraggs, M. E.; Coster, A. J.; Galkin, I. A.; Aponte, N.

    2014-12-01

    Some of the main factors that contribute to changes in multiple ionospheric parameters are solar flux, geomagnetic activity, seasonal behavior, and coupling with lower atmosphere, which is particularly strong during sudden stratospheric warming events (SSW). Studying the way that these factors induce changes in the ionosphere is important, since these changes can have a negative effect on different types of communication systems. Multiple case studies have demonstrated large variations in ionospheric electron density in association with SSW in the low-latitude ionosphere, in particular near the crests of the equatorial ionization anomaly. However, the latitudinal extend of these variations was not addressed. In this study, we utilize data obtained in Puerto Rico by three instruments - Ramey digisonde, Arecibo Incoherent Scatter Radar (ISR) and GPS receivers to analyze four winter-time periods: two years with major SSW events (2005-2006, 2012-2013) and two years with minor SSW events (2006-2007, 2013-2014). In addition, selected cases represent two winters with low solar activity and two winters with moderate to high solar activity. The study focuses on the location of Arecibo, Puerto Rico (18.34°N, 66.75°W), ~15° to the north of the northern crest of the equatorial ionization anomaly. We report good agreement in ionospheric parameters between all three instruments. To investigate possible association with SSW events, we remove influences of seasonal behavior, solar flux, and geomagnetic activity by building empirical model and subtracting expected variations from the observational data. The analysis of residuals between the data and the model shows that ionospheric disturbances were observed in Puerto Rico for both minor and major SSW events in the ISR, digisonde and GPS Total Electron Content (TEC) data. We report 20-60% variations in NmF2 and TEC due to SSW effects. Large variations are also observed in electron density, electron temperature and plasma velocity during both daytime and nighttime.

  3. Interplanetary magnetic field By and auroral conductance effects on high-latitude ionospheric convection patterns

    NASA Astrophysics Data System (ADS)

    Tanaka, T.

    2001-11-01

    The dependence of the ionospheric electric potential (convection) on the interplanetary magnetic field (IMF) and the ionospheric conductivity is investigated to understand the generation of convection patterns in the framework of the solar wind-magnetosphere-ionosphere (S-M-I) coupling scheme and the merging concept. A numerical magnetohydrodynamic (MHD) simulation is adopted for the study of the present problem. To achieve a high resolution in the ionosphere, the MHD calculation employs the finite volume (FV) total-variation diminishing (TVD) scheme with an unstructured grid system. The two-cell convection patterns reproduced from simulation are shown for several cases under the southward IMF condition during the growth-phase interval. In the investigation of these results, special attention is paid to the analysis of mirror symmetry in the convection patterns with respect to the IMF By. On the dayside in the Northern Hemisphere, IMF By- (By+) generates flow deflection on newly opened field lines toward the dusk (dawn) without a severe violation of the mirror symmetry. While the mirror symmetry of the convection pattern is maintained even on the nightside when the ionospheric conductivity is uniform, it is not maintained on the nightside when the ionospheric conductivity is nonuniform. A realistic ionospheric conductivity modifies the convection pattern in the Northern (Southern) Hemisphere so as to emphasize distinctive features seen for IMF By+ (By-) under a uniform conductivity, and the reproduced convection patterns coincide with the observation quite well including fine signatures on the nightside, both for IMF By- and By+. Because of the nonuniform conductivity, cell centers of convection are shifted to the earlier magnetic local times, and the antisunward flow in the northern polar cap is nearly aligned with noon-midnight meridian for IMF By-, while the flow in the northern polar cap has a significant inclination from prenoon to premidnight for IMF By+. These convection patterns can be understood by considering the effect due to the Hall current closure of the region-1 field-aligned current. The analysis for the dependence of nightside convection on IMF By and ionospheric conductivity shows that the Harang discontinuity is attributed partially to the structure of magnetospheric driver but mainly to the effect of nonuniform auroral conductivity. As a consequence, it is more adequate to say that convection patterns are more or less caused by the synthesized effect of more than one process rather than a single elementary process. Reproduced convection patterns in this paper show a particular coincidence with satellite observations summarized by adopting the pattern-recognition-based approach.

  4. 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.

  5. Effects of the low-latitude ionospheric boundary condition on the global magnetosphere

    Microsoft Academic Search

    V. G. Merkin; J. G. Lyon

    2010-01-01

    In common treatment of magnetosphere-ionosphere coupling at high latitudes, the ionosphere is represented by a thin conducting spherical shell, which closes field-aligned currents generated in the magnetosphere. In this approach, the current continuity yields a Poisson equation for the electrostatic potential associated with the ionospheric convection pattern. Solution of the Poisson equation then provides a means of self-consistently describing magnetospheric

  6. Investigating magnetospheric interaction effects on Titan's ionosphere with the Cassini orbiter Ion Neutral Mass Spectrometer, Langmuir Probe

    E-print Network

    California at Berkeley, University of

    conditions of 3D models including the plasma interaction and features such as neutral winds. PublishedInvestigating magnetospheric interaction effects on Titan's ionosphere with the Cassini orbiter Ion Keywords: Titan Titan, atmosphere Saturn, satellites a b s t r a c t In the $6 years since the Cassini

  7. Analysis on 29 March 2006 eclipse effect on the ionosphere over Ilorin, Nigeria

    NASA Astrophysics Data System (ADS)

    Adeniyi, J. O.; Oladipo, O. A.; Radicella, S. M.; Adimula, I. A.; Olawepo, A. O.

    2009-11-01

    Ionospheric measurements obtained during the 29 March 2006 eclipse period over Ilorin, Nigeria (longitude 4.57°E, latitude 8.53°N, dip 4.1°S), an equatorial station, are used for this study. The data are used in the determination of photoionisation rates (q) and loss coefficients at various heights. It was found that the transition height between the regions where the linear (?) and quadratic (?) loss coefficients hold is around 200 km. Some form of validations of the parameters q and ? were carried out. A comparison of the results of production rates, vertical velocities and loss coefficients obtained for the F region from our study with those obtained at high solar activity for a previous eclipse at a station close to Ilorin indicates solar activity effects.

  8. Ionospheric refraction effects on orbit determination using the orbit determination error analysis system

    Microsoft Academic Search

    C. P. Yee; D. A. Kelbel; T. Lee; J. B. Dunham; G. D. Mistretta

    1990-01-01

    The influence of ionospheric refraction on orbit determination was studied through the use of the Orbit Determination Error Analysis System (ODEAS). The results of a study of the orbital state estimate errors due to the ionospheric refraction corrections, particularly for measurements involving spacecraft-to-spacecraft tracking links, are presented. In current operational practice at the Goddard Space Flight Center (GSFC) Flight Dynamics

  9. FAST observations of downward current regions: Effect of ionospheric constraints on parallel

    E-print Network

    California at Berkeley, University of

    but partially couple to the low-altitude ionosphere (composite). Using FAST data from above 3000 km altitude, we of electron velocity moments and ion energies, and power spectral density scaling laws of wave turbulence because of lower ionospheric constraints. These results support a picture of an evolutionary process from

  10. Ionospheric and magnetospheric effects of solar flares monitored by ground-based riometer and magnetometers

    Microsoft Academic Search

    Tardelli Ronan Coelho Stekel; Nelson Jorge Schuch; Ezequiel Echer; Fernando Guarnieri; Kazuo Makita; Cassio Espindola Antunes; Juliano Moro; Claudio Machado Paulo

    2010-01-01

    The solar flare incidence follows a behavior similar to the solar cycle activity, which results in periodic disturbances on the Earth's ionosphere and magnetosphere. The correlation of this phenomenon can provide important information about the magnetosphere, the Sun\\/Earth interaction, as well as events occurring in the ionosphere which can, for instance, generate disturbances in telecommunications, small satellites or even in

  11. Ionospheric Effects on GPS Signals in Real Time Kinematic (RTK) Applications

    Microsoft Academic Search

    Adeniyi Iyiade

    2006-01-01

    The need for satellite navigation technology, with its capability to provide real time positioning using Global Navigation Satellite System (GNSS) has increased tremendously over the years. However, the positioning accuracy tends to degrade as the baseline increases. The degradation comes from different sources of errors, amongst which is the ionospheric error in the signal propagation. During geomagnetic storm, ionospheric scintillations

  12. On the estimate and assessment of the ionospheric effects affecting low frequency radio astronomy measurements

    Microsoft Academic Search

    Biagio Forte; Marcio Aquino

    2011-01-01

    The development of the LOw Frequency telescopes ARray (LOFAR) has posed a serious issue on the calibration of those measurements in the presence of the Earth’s ionosphere. The purpose of measuring at radio frequencies as low as VHF exposes LOFAR to a number of ionospheric phenomena, capable of deteriorating the accuracy of the measurements and subsequently of the sky imaging.

  13. Whole Atmosphere-Ionosphere Coupled Model (GAIA) for Space Weather Research

    NASA Astrophysics Data System (ADS)

    Shinagawa, H.; Jin, H.; Miyoshi, Y.; Fujiwara, H.; Tanaka, T.; Fujita, S.; Terada, K.; Murata, K. T.

    2011-12-01

    Space near the Earth, called geospace, is a highly complex system, consisting of the solar wind, the magnetosphere, the ionosphere, and the neutral atmosphere. Those regions have different physical characteristics with different temporal and spatial scales. In particular, the magnetosphere, the ionosphere, and the neutral atmosphere are strongly coupled with each other, and interaction between the regions is nonlinear and extremely complicated. Even within each region, there are strong interactions between physical processes with different temporal and spatial scales. Furthermore, the geospace environment significantly varies as electromagnetic energy and particles from the sun vary. In order to quantitatively understand such a complicated system, it is necessary to model the entire region by including all fundamental processes self-consistently. Various types of global numerical models of geospace have been constructed and used to study space weather disturbances in many institutions in the world. At the National Institute of Information and Communications Technology (NICT) of Japan, a real-time solar wind model, magnetosphere model, and ionosphere-thermosphere model have been developed and used for daily space weather forecast. In addition to the effect of geospace disturbance on the upper atmosphere, recent observations of the ionosphere and the thermosphere have revealed that atmospheric waves generated in the lower atmosphere significantly influence the upper atmosphere, the ionosphere, and possibly the magnetosphere. In order to quantitatively study the effects of the lower atmosphere on the ionosphere, we have developed an atmosphere-ionosphere coupled model, which includes the whole neutral atmosphere and the ionosphere. The model is called GAIA (Ground-to-topside model of Atmosphere and Ionosphere for Aeronomy). Using GAIA, relationship between the ionosphere and the atmosphere is being studied. We plan to incorporate magnetospheric inputs to the polar ionosphere by using a magnetospheric model. We will report the status and future plan of the space environment study using GAIA.

  14. Ionosphere Weighted GPS Cycle Ambiguity Resolution1

    E-print Network

    Calgary, University of

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

  15. 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.

  16. 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.

  17. Atmosphere-Ionosphere Electrodynamic Coupling

    Microsoft Academic Search

    V. M. Sorokin; V. M. Chmyrev

    2010-01-01

    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

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

    NASA Astrophysics Data System (ADS)

    Gulyaeva, T. L.

    2012-02-01

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

  19. Order effects in dynamic semantics.

    PubMed

    Graben, Peter Beim

    2014-01-01

    In their target article, Wang and Busemeyer (2013) discuss question order effects in terms of incompatible projectors on a Hilbert space. In a similar vein, Blutner recently presented an orthoalgebraic query language essentially relying on dynamic update semantics. Here, I shall comment on some interesting analogies between the different variants of dynamic semantics and generalized quantum theory to illustrate other kinds of order effects in human cognition, such as belief revision, the resolution of anaphors, and default reasoning that result from the crucial non-commutativity of mental operations upon the belief state of a cognitive agent. PMID:24259268

  20. High Resolution Reconstruction of the Ionosphere for SAR Applications

    NASA Astrophysics Data System (ADS)

    Minkwitz, David; Gerzen, Tatjana; Hoque, Mainul

    2014-05-01

    Caused by ionosphere's strong impact on radio signal propagation, high resolution and highly accurate reconstructions of the ionosphere's electron density distribution are demanded for a large number of applications, e.g. to contribute to the mitigation of ionospheric effects on Synthetic Aperture Radar (SAR) measurements. As a new generation of remote sensing satellites the TanDEM-L radar mission is planned to improve the understanding and modelling ability of global environmental processes and ecosystem change. TanDEM-L will operate in L-band with a wavelength of approximately 24 cm enabling a stronger penetration capability compared to X-band (3 cm) or C-band (5 cm). But accompanied by the lower frequency of the TanDEM-L signals the influence of the ionosphere will increase. In particular small scale irregularities of the ionosphere might lead to electron density variations within the synthetic aperture length of the TanDEM-L satellite and in turn might result into blurring and azimuth pixel shifts. Hence the quality of the radar image worsens if the ionospheric effects are not mitigated. The Helmholtz Alliance project "Remote Sensing and Earth System Dynamics" (EDA) aims in the preparation of the HGF centres and the science community for the utilisation and integration of the TanDEM-L products into the study of the Earth's system. One significant point thereby is to cope with the mentioned ionospheric effects. Therefore different strategies towards achieving this objective are pursued: the mitigation of the ionospheric effects based on the radar data itself, the mitigation based on external information like global Total Electron Content (TEC) maps or reconstructions of the ionosphere and the combination of external information and radar data. In this presentation we describe the geostatistical approach chosen to analyse the behaviour of the ionosphere and to provide a high resolution 3D electron density reconstruction. As first step the horizontal structure of the ionosphere is studied in space and time on the base of ground-based TEC measurements in the European region. In order to determine the correlation of measurements at different locations or points of time the TEC measurements are subtracted by a base model to define a stationary random field. We outline the application of the NeQuick model and the final IGS TEC maps as background and show first results regarding the distribution and the stationarity of the resulting residuals. Moreover, the occurred problems and questions are discussed and finally an outlook towards the next modelling steps is presented.

  1. 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

  2. Wave generation and transformation in the ionosphere possibly caused by seismic effects

    NASA Astrophysics Data System (ADS)

    Meister, Claudia-Veronika; Hoffmann, Dieter H. H.

    2015-04-01

    The dielectric model of waves in the Earth's ionosphere presented at the EGU General Assembly 2014 is further developed and applied to electromagnetic phenomena in seismoactive regions. The dielectric model consists of the magnetohydrodynamic system of equations describing the partially-ionized stratified convecting ionosphere and of the system of Maxwell equations. While in 2014, a new wave model was presented which takes the atmospheric stratification better into account in the Maxwell equations, now improved mathematical solutions for the dispersion relation of the excited waves are obtained. Especially, the influence of neutral gas winds is considered. Applications are performed for Alfvén and magnetohydrodynamic waves, as well as for the transformation of seismic infrasound waves into electromagnetic ionospheric ones. Expressions for ionospheric heating at different altitudes are derived and numerically analysed.

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

    Microsoft Academic Search

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

    1992-01-01

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

  4. 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.

  5. The effect of the ionosphere on remote sensing of sea surface salinity from space: absorption and emission at L band

    Microsoft Academic Search

    David M. Le Vine; Saji Abraham

    2002-01-01

    The purpose of this work is to examine the effects of Faraday rotation and attenuation\\/emission in the ionosphere in the context of a future remote sensing system in space to measure salinity. Sea surface salinity is important for understanding ocean circulation and for modeling energy exchange with the atmosphere. A passive microwave sensor in space operating near 1.4 GHz (L-band)

  6. Plasma and electromagnetic effects in the ionosphere related to the dynamics of charged aerosols in the lower atmosphere

    Microsoft Academic Search

    V. M. Sorokin

    2007-01-01

    The paper presents a physical model of the electrodynamic effect on the ionosphere of natural and artificial processes that\\u000a occur in the near-Earth atmospheric layer and are accompanied by the transfer of charged aerosols in the atmosphere. These\\u000a processes include the preparation of earthquakes and typhoons, dust storms, and nuclear accidents. The model is based experimentally\\u000a on satellite and ground-based

  7. About the nature of the Night-time Winter Anomaly effect (NWA) in the F-region of the ionosphere

    Microsoft Academic Search

    N. Jakowski; M. Förster

    1995-01-01

    The Night-time Winter Anomaly (NWA) effect is shown to be a regular phenomenon at the mid-latitude ionosphere in the American and Asian longitude sectors under low solar activity conditions. Total electron content, vertical sounding data as well as topside sounder measurements onboard Alouette indicate a significant higher night-time ionization level in winter than in summer under certain conditions which are

  8. Effective electron recombination coefficient in ionospheric D-region during the relaxation regime after solar flare from February 18, 2011

    E-print Network

    Nina, A; Sulic, D; Sreckovic, V; Zigman, V; 10.1016/j.nimb.2011.10.026

    2012-01-01

    In this paper, we present a model for determination of a weakly time dependent effective recombination coefficient for the perturbed terrestrial ionospheric D-region plasma. We study consequences of a class M1.0 X-ray solar flare, recorded by GOES-15 satellite on February 18, 2011 between 14:00 UT and 14:15 UT, by analyzing the amplitude and phase real time variations of very low frequency (VLF) radio waves emitted by transmitter DHO (located in Germany) at frequency 23.4 kHz and recorded by the AWESOME receiver in Belgrade (Serbia). Our analysis is limited to ionospheric perturbations localized at altitudes around 70 km where the dominant electron gain and electron loss processes are the photo-ionization and recombination respectively.

  9. Ensemble Ionospheric Total Electron Content Forecasting during Storms

    NASA Astrophysics Data System (ADS)

    Chartier, A.; Mitchell, C. N.; Lu, G.; Anderson, J. L.; Collins, N.; Hoar, T. J.; Bust, G. S.; Matsuo, T.

    2014-12-01

    Earth's ionosphere presents a threat to human activities such as satellite positioning and timing, radio communications and surveillance. Nowcasts and forecasts of the ionosphere could help mitigate these damaging effects. Recent advances in the field of ionospheric imaging, as well as new storm-time ionospheric forecasting results are presented here. The approach combines globally distributed GPS Total Electron Content (TEC) measurements with an ensemble of coupled thermosphere-ionosphere models in order to produce short-term forecasts during a storm. One-hour forecast accuracy is much better than a climatological model run. Using this ensemble approach, it is possible to infer the neutral O/N2 ratio from TEC measurements so that subsequent TEC forecasts are improved. A review of ionospheric physics and data assimilation will also be given. The term data assimilation refers to a group of techniques designed to estimate atmospheric or oceanic states. In practice, data assimilation techniques seek to improve modeled estimates of the atmospheric state by incorporating observations. The relationship between data assimilation and forecasting is explored with reference to the physics of the thermosphere-ionosphere system. The work presented here uses the Data Assimilation Research Testbed (DART), which is an ensemble Kalman filter data assimilation framework. This is combined with a version of the Thermosphere Ionosphere Electrodynamics General Circulation Model (TIEGCM) that has been modified to accept more detailed solar and geomagnetic driver specifications. Future directions of work include the inference of Solar and geomagnetic drivers from the data assimilation process as well as coupling with lower-atmospheric models.

  10. Radio Tomography of Ionospheric Structures (probably) due to Underground-Surface-Atmosphere-Ionosphere Coupling

    NASA Astrophysics Data System (ADS)

    Kunitsyn, V.; Nesterov, I.; Andreeva, E.; Rekenthaler, D. A.

    2012-12-01

    Ionospheric radio-tomography (RT) utilizes radio signals transmitted from the global navigational satellite systems (GNSS), including low-orbiting (LO) navigational systems such as Transit, Tsikada, etc., and high-orbiting (HO) navigational systems such as GPS, GLONASS, Galileo, Beidou, etc. The signals that are transmitted from the LO navigational satellites and recorded by ground receiving chains can be inverted for almost instantaneous (5-8 min) 2D snapshots of electron density. The data from the networks of ground receivers that record the signals of the HO satellites are suitable for implementing high-orbital RT (HORT), i.e. reconstructing the 4D distributions of the ionospheric electron density (one 3D image every 20-30 min). In the regions densely covered by the GNSS receivers, it is currently possible to get a time step of 2-4 min. The LORT and HORT approaches have a common methodical basis: in both these techniques, the integrals of electron density along the ray between the satellite and the receiver are measured, and then the tomographic procedures are applied to reconstruct the distributions of electron density. We present several examples of the experiments on the ionospheric RT, which are related to the Underground-Surface-Atmosphere-Ionosphere (USAI) coupling. In particular, we demonstrate examples of RT images of the ionosphere after industrial explosions, rocket launches, and modification of the ionosphere by high-power radio waves. We also show RT cross sections reflecting ionospheric disturbances caused by the earthquakes (EQ) and tsunami waves. In these cases, there is an evident cause-and-effect relationship. The perturbations are transferred between the geospheres predominantly by acoustic gravity waves (AGW), whose amplitudes increase with increasing height. As far as EQ are concerned, the cause of the USAI coupling mechanism is not obvious. It is clear, however, that the regular RT studies can promote the solution of this challenging problem. The single-point measurements (by ionosondes or by isolated receivers) are not amenable to unambiguous interpretation; based on these data, it is impossible to distinguish the contribution of USAI coupling from the ionospheric effects induced by the "ordinary" impacts (the Sun, the solar wind, geomagnetic perturbations, galactic cosmic rays, etc.). In order to localize sources of the ionospheric disturbances, the geophysicist needs information on the spatial structure and dynamics of the ionospheric perturbations. This information (2D-4D RT images) is optimally provided by RT methods. We present examples of the ionospheric disturbances caused by EQs as well as the ionospheric precursors of these EQs in the form of specific ionospheric irregularities: AGW- and soliton-like wave disturbances, which we identified using RT methods. Based on the results of the RT studies in the Alaska and Taiwan regions, we have detected several dozen AGW-related precursors of EQs. These data allow us to attempt to locate the source of these perturbations. We discuss the possibilities and prospects of further research aimed at identifying and analyzing precursors of EQs and establishing the mechanisms of USAI coupling. We are grateful to Northwest Research Associates, Inc., and Dr. L.-C.Tsai for providing raw RT data for Alaska and Taiwan.

  11. Space weather effects on the low latitude D-region ionosphere during solar minimum

    NASA Astrophysics Data System (ADS)

    Kumar, Abhikesh; Kumar, Sushil

    2014-12-01

    The effects of the solar flares and the geomagnetic storms (disturbance storm time ( Dst) < -50 nT) during December 2006 to 2008, a period during the unprecedented solar minimum of solar cycles 23 and 24, have been examined on sub-ionospheric very low frequency (VLF) signals from NWC (19.8 kHz), NPM (21.4 kHz), VTX (18.2 kHz), and NLK (24.8 kHz) transmitters monitored at Suva (18.2° S, 178.4° E), Fiji. Apart from the higher class solar flares (C to X), a solar flare of class B8.5 also produced enhancements both on the amplitude and phase. The amplitude enhancements in NLK, NPM, and NWC signals as a function of peak solar flare X-ray flux in decibel (dB; relative to 1 ?W/m2) shows that the relationship curve is steeper and quite linear between the flare power levels of 0 to 15 dB; below 0 dB, the curve gets less steep and flattens towards -5 dB flare power level, while it also gets less steep above 15 dB and almost flattens above 20 dB. In general, the level of amplitude enhancement for NLK signal is higher than that for NPM and NWC signals for all solar flares. The enhancement in the amplitude and phase of VLF signals by solar flares is due to the increase in the D-region electron density by the solar flare-produced extra ionization. The modeling of VLF perturbations produced by B8.5 and C1.5 classes of solar flares on 29 January 2007 using LWPC (Long Wave Propagation Capability) V2.1 codes show that reflection height ( H') was reduced by 0.6 and 1.2 km and the exponential sharpness factor ( ?) was raised by 0.010 and 0.005 km-1, respectively. Out of seven storms with Dst < -50 nT, only the intense storm of 14 to 16 December 2006 with a minimum Dst of -145 nT has shown a clear reduction in the signal strength of NWC and NPM sub-ionospheric signals due to storm-induced reduction in the D-region electron density.

  12. A case study of Ionospheric storm effects during long-lasting southward IMF Bz driven geomagnetic storm

    NASA Astrophysics Data System (ADS)

    Liu, J., Sr.

    2014-12-01

    Multiple instrumental observations including GPS TEC, foF2 and hmF2 from ionosondes, vertical ion drift measurements from C/NOFS, magnetometer data and far-ultraviolet airglow measured by TIMED/GUVI are used to investigate the profound ionospheric disturbances at mid- and low-latitudes during the 14-17 July 2012 geomagnetic storm event, which was featured by prolonged southward interplanetary geomagnetic field component for about 30 hours below -10 nT. In the East Asian/Australian sector, latitudinal profile of TEC variations in the main phase were characterized by three bands of increments and separated by weak depressions in the Equatorial Ionospheric Anomaly (EIA) crest regions, which were caused by the combined effects of disturbance dynamo electric fields (DDEF) and equatorward neutral winds. In the recovery phase, strong inhibition of EIA occurred and the summer crest of EIA disappeared on 16 July due to the combined effects of intrusion of neutral composition disturbance zone as shown by the TIME/GUVI O/N2 measurements and long-lasting daytime westward DDEF inferred from the equatorial electric electrojet (EEJ) observations. The transit time of DDEF over the dip equator from westward to eastward is around 2200 LT. In the American longitude, the salient ionospheric disturbances in the summer hemisphere were characterized by daytime periodical intrusion of negative phase for three consecutive days in the recovery phase, preceded by storm enhanced density (SED) plume in the initial phase. In addition, multiple short-lived prompt penetration electric ?elds (PPEF) appeared during stable southward IMF Bz in the recovery phase and were responsible for enhanced the EIA and equatorial ionospheric uplift around sunset.

  13. The long-duration positive storm effects in the equatorial ionosphere over Jicamarca

    NASA Astrophysics Data System (ADS)

    Kuai, Jiawei; Liu, Libo; Liu, Jing; Zhao, Biqiang; Chen, Yiding; Le, Huijun; Wan, Weixing

    2015-02-01

    The long-duration positive storm (LPS) in the equatorial regions is relatively poorly understood. In this report, we conducted a statistical analysis of the LPS effects in the equatorial ionosphere over Jicamarca (12.0°S, 283.2°E) in 1998-2010. There are 250 geomagnetic storms (minimum Dst < -50 nT) in 1998-2010, but the ionosonde observations at Jicamarca are available only for 204 storms. A total of 46 LPSs are identified in terms of the criterion that the storm time relative deviation of peak density of F2 layer (NmF2) exceeds 25% for more than 6 h. A salient feature is that the occurrence of LPSs tends to decay approximately exponentially on the following days after the main phase of geomagnetic storms. The ratios of the number of equatorial LPSs to that of geomagnetic storms have no obvious dependence on season and solar activity. During the daytime LPSs, the disturbed zonal electric field is mostly westward, as indicated from the geomagnetic field changes in the equatorial American region. For the nighttime LPSs, the significant uplifting of F2 layer caused by an eastward electric field is the most important feature. Therefore, the disturbed electric field should play an essential role in forming the equatorial LPSs.

  14. Effects of ionospheric O{sup +} on the magnetopause boundary wave activity

    SciTech Connect

    Merkin, V. G. [Center for Space Physics, Boston University, MA (United States)

    2011-01-04

    In this paper we use a multi-fluid magnetohydrodynamic (MHD) model to explore effects of ionospheric O{sup +} ions on the development of the Kelvin-Helmholtz (KH) instability at the flanks of the earth's magnetopause. The model used is the multi-fluid version of the Lyon-Fedder-Mobarry (LFM) global magnetospheric MHD simulation code. We set up a controlled numerical experiment whereby the solar wind speed is slowly increased resulting in building up the velocity shear across the magnetopause. As this happens, the KH waves at the magnetopause flanks increase their intensity. Along with the solar wind velocity ramp-up, we introduce O{sup +} fluid in the plasma sheet and watch its influence on the development of the KH instability. We find that the simulation with the O{sup +} ions present at the magnetopause shows a significantly weaker KH wave activity on both edges of the low-latitude boundary layer than the simulation without oxygen but identical otherwise.

  15. Digisonde Observation of April and August 2010 Magnetic Storm Effects on the Ionosphere over Ilorin, Nigeria

    NASA Astrophysics Data System (ADS)

    Adeniyi, J.; Reinisch, B. W.; Krause, L. H.; Oladipo, O. A.; Adimula, I. A.; Olawepo, A. O.; McHarg, M. G.; Veliz, O.

    2010-12-01

    In March 2010 a digisonde was installed at the University of Ilorin, Nigeria (Geog-Latitude 8.47 °N, Geog Longitude 4.68 °E, Dip 4.1 °S), a typical equatorial station. This is quite timely since it coincides with the period when the solar cycle is just emerging from the period of a very deep minimum and solar activity is rising. Two magnetic storms that recently occurred are those of April 5 -6 (maximum Ap index 50, minimum DST -83 nT) and that of August 3-6, 2010 (maximum Ap index 43, minimum DST -70 nT). The effects of these two storms on the ionosphere over Ilorin are discussed. Increase in NmF2, typical for equatorial regions during the main phase of magnetic storms, occurred for both storms. Changes in the thickness of the F2 layer (IRI parameter B0), the N(h) electron density profiles, and in the F region plasma drift are discussed and compared with those observed by the Jicamarca digisonde in Peru.

  16. Three-dimensional Martian ionosphere model: II. Effect of transport processes due to pressure gradients

    NASA Astrophysics Data System (ADS)

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

    2014-07-01

    To study the transport of the ionospheric plasma on Mars, we have included a 3-D multifluid dynamical core in a Martian general circulation model. Vertical transport modifies the ion density above ~160 km on the dayside, especially the ions produced at high altitudes like O+, N+, and C+. Near the exobase, the dayside to nightside flow velocity reaches few hundreds of m/s, due to a large horizontal pressure gradient. Comparison with Mars Express/Analyzer of Space Plasmas and Energetic Atoms-3 measurements between 290 and 500 km suggests that this flow could account for at least 20% of the flow produced by the solar wind. This flow is not sufficient to populate substantially the nightside ionosphere at high altitudes, in agreement with recent observations, because of a strong nightside downward flow produced by vertical pressure gradient. The O2+ and NO+ ion densities on the nightside at low altitudes (~130 km) are modified by this downward flow, compared to simulated densities without ion dynamics, while other ions are lost by chemical reactions. Variability at different time scales (diurnal, seasonal, and solar cycles) are studied. We simulate diurnal and seasonal variations of the ionospheric composition due to the variability of the neutral atmosphere and solar flux at the top of the atmosphere. The ionospheric dynamics are not strongly affected by seasons and solar cycles, and the retroaction of the ionosphere on the neutral atmosphere temperature and velocity is negligible compared to other physical processes below the exobase.

  17. Hf propagation through actively modified ionospheres

    SciTech Connect

    Argo, P.E.; Fitzgerald, T.J.; Wolcott, J.H.; Simons, D.J. (Los Alamos National Lab., NM (USA)); Warshaw, S.; Carlson, R. (Lawrence Livermore National Lab., CA (USA))

    1990-01-01

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

  18. Effects of Gravity Waves on the thermosphere during Stratospheric Sudden Warming simulated by an atmosphere-ionosphere coupled Model.

    NASA Astrophysics Data System (ADS)

    Miyoshi, Y.; Fujiwara, H.; Jin, H.; Shinagawa, H.

    2014-12-01

    It has been recognized that gravity waves play an important role on the momentum and energy balance in the thermosphere. Using a whole atmosphere-ionosphere coupled model (GAIA), effects of upward propagating gravity waves on the general circulation in the thermosphere are studied. The GAIA contains the region from the ground surface to the upper thermosphere, so that we can simulate excitation of gravity waves in the lower atmosphere, their upward propagation to the thermosphere, and their impact on the general circulation in the thermosphere. We have recently developed an atmosphere-ionosphere coupled model with high horizontal resolution (about 1 degree longitude by 1degree latitude). In this study, we focus our attention on behaviors of gravity waves in the mesosphere and thermosphere during stratospheric sudden warming event (SSW). The changes of the zonal mean zonal wind in the stratosphere during SSW alter propagation condition of gravity waves from the lower atmosphere to the upper atmosphere. This means that SSW affects behaviors of thermospheric gravity waves. Our simulation result indicates that gravity wave drag in the thermosphere of the winter hemisphere is strongly influenced by SSW. This change of the gravity wave drag also modifies the mean meridional circulation and atmospheric composition in the thermosphere. The impact of the thermospheric gravity wave on the ionosphere during SSW is also discussed.

  19. The Effects of Neutral Inertia on Ionospheric Currents in the High-Latitude Thermosphere Following a Geomagnetic Storm

    NASA Technical Reports Server (NTRS)

    Deng, W.; Killeen, T. L.; Burns, A. G.; Roble, R. G.; Slavin, J. A.; Wharton, L. E.

    1993-01-01

    Results of an experimental and theoretical investigation into the effects of the time dependent neutral wind flywheel on high-latitude ionospheric electrodynamics are presented. The results extend our previous work which used the National Center for Atmospheric Research Thermosphere/Ionosphere General Circulation Model (NCAR TIGCM) to theoretically simulate flywheel effects in the aftermath of a geomagnetic storm. The previous results indicated that the neutral circulation, set up by ion-neutral momentum coupling in the main phase of a geomagnetic storm, is maintained for several hours after the main phase has ended and may dominate height-integrated Hall currents and field-aligned currents for up to 4-5 hours. We extend the work of Deng et al. to include comparisons between the calculated time-dependent ionospheric Hall current system in the storm-time recovery period and that measured by instruments on board the Dynamics Explorer 2 (DE 2) satellite. Also, comparisons are made between calculated field-aligned currents and those derived from DE 2 magnetometer measurements. These calculations also allow us to calculate the power transfer rate (sometimes called the Poynting flux) between the magnetosphere and ionosphere. The following conclusions have been drawn: (1) Neutral winds can contribute significantly to the horizontal ionospheric current system in the period immediately following the main phase of a geomagnetic storm, especially over the magnetic polar cap and in regions of ion drift shear. (2) Neutral winds drive Hall currents that flow in the opposite direction to those driven by ion drifts. (3) The overall morphology of the calculated field-aligned current system agrees with previously published observations for the interplanetary magnetic field (IMF) B(sub Z) southward conditions, although the region I and region 2 currents are smeared by the TI(ICM model grid resolution. (4) Neutral winds can make significant contributions to the field-aligned current system when B(sub Z) northward conditions prevail following the main phase of a storm, but can account for only a fraction of the observed currents. (5) DE 2 measurements provide a demonstration of "local" (satellite-altitude) flywheel effects. (6) On the assumption that the magnetosphere acts as an insulator, we calculate neutral-wind-induced polarization electric fields of approx. 20-30 kV in the period immediately following the geomagnetic storm.

  20. Tsunami Ionospheric warning and Ionospheric seismology

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

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

  1. Ionospheric irregularities

    Microsoft Academic Search

    B.G. Fejer; M. C. Kelley

    1980-01-01

    Extensive experimental and theoretical research has been performed in the last decade to study ionospheric irregularities. These studies have shown that plasma instabilities play a major role in the generation of the irregularities. In this work we describe in detail the recent experimental studies of the E and F region irregularities and also the extensive work on plasma instability theories

  2. Ionospheric range-rate effects in satellite-to-satellite tracking

    NASA Technical Reports Server (NTRS)

    Lipofsky, J. R.; Bent, R. B.; Llewellyn, S. K.; Schmid, P. E.

    1977-01-01

    Investigation of ionospheric range and range-rate corrections in satellite-to-satellite tracking were investigated. Major problems were cited and the magnitude of errors that have to be considered for communications between satellites and related experiments was defined. The results point to the need of using a sophisticated modeling approach incorporating daily solar data, and where possible actual ionospheric measurements as update information, as a simple median model cannot possibly account for the complex interaction of the many variables. The findings provide a basis from which the residual errors can be estimated after ionospheric modeling is incorporated in the reduction. Simulations were performed for satellites at various heights: Apollo, Geos, and Nimbus tracked by ATS-6; and in two different geometric configurations: coplanar and perpendicular orbits.

  3. Effect of Precipitating Electrons on Ring Current Energy Content, Ionospheric Conductance, and Thermospheric Properties

    NASA Astrophysics Data System (ADS)

    Chen, M.; Lemon, C. L.; Walterscheid, R. L.; Yoo, B.; Hecht, J. H.; Shprits, Y.; Orlova, K.; Schulz, M.; Evans, J. S.

    2014-12-01

    We investigate how scattering of electrons by waves in the plasma sheet and plasmasphere affects precipitating energy flux distributions during magnetic storms, how the precipitating electrons modify the ionospheric Hall and Pederson conductivity and electric potential, how these processes feedback on magnetospheric particle transport and redistribute the ring current, and how the ionization and energy deposition of precipitating electrons affects thermospheric winds and temperature. Our main approach is to couple simulation models: (1) the magnetically and electrically self-consistent Rice Convection Model - Equilibrium (RCM-E) of the inner magnetosphere, (2) the B3c transport model for electron-proton-hydrogen atom aurora in the ionosphere, and (3) the Thermosphere-Ionsphere-Electrodynamics General Circulation Model (TIEGCM) of the ionosphere and thermosphere. Realistic descriptions of electron pitch-angle diffusion by whistler chorus in the plasma sheet/magnetotail and hiss in the plasmasphere are included in the RCM-E. We use parameterized rates of electron pitch-angle scattering with whistler chorus of Orlova and Shprits [JGR, 2014] that depend on equatorial radial distance, magnetic activity (Kp), and magnetic local time. To study how the precipitating electron energy flux distributions affect ionospheric conductivity and ionospheric electric potential patterns, we have performed a one-way coupling of the RCM-E and ionospheric B3c model. The simulated precipitating electron flux distributions are used to specify the energy flux and particle heating due to precipitating auroral electrons for TIEGCM simulations of the neutral atmosphere. We simulate a storm event and compare simulated quantities with in situ observations.

  4. UHF Radar observations at HAARP with HF pump frequencies near electron gyro-harmonics and associated ionospheric effects

    NASA Astrophysics Data System (ADS)

    Watkins, Brenton; Fallen, Christopher; Secan, James

    Results for HF modification experiments at the HAARP facility in Alaska are presented for experiments with the HF pump frequency near third and fourth electron gyro-harmonics. A UHF diagnostic radar with range resolution of 600 m was used to determine time-dependent altitudes of scattering from plasma turbulence during heating experiments. Experiments were conducted with multiple HF frequencies stepped by 20 kHz above and below the gyro-harmonic values. During times of HF heating the HAARP facility has sufficient power to enhance large-scale ionospheric densities in the lower ionosphere (about 150-200 km altitude) and also in the topside ionosphere (above about 350 km). In the lower ionosphere, time-dependent decreases of the altitude of radar scatter result from electron density enhancements. The effects are substantially different even for relatively small frequency steps of 20 kHz. In all cases the time-varying altitude decrease of radar scatter stops about 5-10 km below the gyro-harmonic altitude that is frequency dependent; we infer that electron density enhancements stop at this altitude where the radar signals stop decreasing with altitude. Experiments with corresponding total electron content (TEC) data show that for HF interaction altitudes above about 170 km there is substantial topside electron density increases due to upward electron thermal conduction. For lower altitudes of HF interaction the majority of the thermal energy is transferred to the neutral gas and no significant topside density increases are observed. By selecting an appropriate HF frequency a little greater than the gyro-harmonic value we have demonstrated that the ionospheric response to HF heating is a self-oscillating mode where the HF interaction altitude moves up and down with a period of several minutes. If the interaction region is above about 170 km this also produces a continuously enhanced topside electron density and upward plasma flux. Experiments using an FM scan with the HF frequency increasing near the gyro-harmonic value were conducted. The FM scan rate was sufficiently slow that the electron density was approximately in an equilibrium state. For these experiments the altitude of the HF interaction follows a near straight line downward parallel to the altitude-dependent gyro-harmonic level.

  5. Quiet time solar illumination effects on the fluxes and characteristic energies of ionospheric outflow

    Microsoft Academic Search

    W. K. Peterson; H. L. Collin; O. W. Lennartsson; A. W. Yau

    2006-01-01

    We report on the characteristic energy, intensity, and flow rate of escaping ionospheric ions as a function of solar illumination. The data presented here were acquired with the Toroidal Ion Mass-Angle Spectrograph (TIMAS) instrument on the Polar satellite at altitudes of 6000 to 9000 km, during solar minimum. To obtain uniform coverage under various solar illumination conditions, data were restricted

  6. Equinoctial asymmetry of ionospheric vertical plasma drifts and its effect on F-region plasma density

    Microsoft Academic Search

    Zhipeng Ren; Weixing Wan; Libo Liu; Yiding Chen; Huijun Le

    2011-01-01

    The equinoctial asymmetry of the ionospheric vertical E × B plasma drift velocity (V$\\\\perp$) in the equatorial F region is investigated based on observations from ROCSAT-1 during 1999 to 2004. It is found that the observed asymmetry exhibits obvious local time dependence with three noticeable features. First, in the Eastern Hemisphere during the interval between 0900 and 1300 LT, V$\\\\perp$

  7. Solar Wind Effect on Joule Heating in the High-Latitude Ionosphere

    NASA Astrophysics Data System (ADS)

    Cai, L.; Aikio, A. T.; Nygren, T. J.

    2014-12-01

    The interplanetary magnetic field (IMF) carried by solar wind affects strongly several key parameters in the high-latitude ionosphere. In this study, the solar wind effect on those parameters especially on Joule heating is conducted statistically based on the simultaneous measurements by the EISCAT radars in Tromsø (TRO, 66.6° cgmLat, mainly within the auroral oval on the nightside), and on Svalbard (ESR, 75.4º cgmLat, mostly within the polar cap). The most important findings are as follows: (i) At TRO, the decrease in Joule heating in the afternoon-evening sector due to neutral winds reported by Aikio et al. [2012] requires southward IMF conditions and a sufficiently high solar wind electric field. The increase in the morning sector takes place for all IMF directions within a region where the upper-E neutral wind has a large equatorward component and the F-region plasma flow is directed eastward. (ii) At ESR, an afternoon hot spot of joule heating centred typically at 14-15 MLT is observed during all IMF conditions. Enhanced Pedersen conductances within the hot spot region are observed only for the IMF Bz+/By- conditions, and the corresponding convection electric field values within the hot spot are smaller than during the other IMF conditions. Hence, the hot spot represents a region of persistent magnetopsheric electromagnetic energy input. (iii) For the southward IMF conditions, the MLT-integrated Joule heating rate without neutral winds for By- is twice the value for By+ at TRO. This can plausibly be explained by the higher average solar wind electric field values for By-.

  8. Equatorial ionosphere

    NASA Astrophysics Data System (ADS)

    Rastogi, R. G.

    1990-12-01

    The development of research in E and F regions of the ionosphere in India since about 1950 is briefly described. The various geomagnetic factors controlling the F region at low latitudes during quiet, disturbed days, on different ages of the moon are described. The equatorial electrojet current, its association with general Sq currents, geomagnetic disturbance and solar disturbance are shown due to changes of the electric fields at the equator. The phenomenon of spread-F at low latitudes is shown to be associated with the regeneration of equatorial plasma fountain during the post sunset hours similar to the daytime plasma fountain associated with equatorial ionization anomaly. The narrow belt of ionosphere, the magnetic equator, is shown to be very sensitive to electric field of local origin or even to electric field generated at the magnetopause due to the interaction of the solar wind on the earth's magnetosphere.

  9. Magnetic Field Measurement on the C/NOFS Satellite: Geomagnetic Storm Effects in the Low Latitude Ionosphere

    NASA Technical Reports Server (NTRS)

    Le, Guan; Pfaff, Rob; Kepko, Larry; Rowland, Doug; Bromund, Ken; Freudenreich, Henry; Martin, Steve; Liebrecht, C.; Maus, S.

    2010-01-01

    The Vector Electric Field Investigation (VEFI) suite onboard the Communications/Navigation Outage Forecasting System (C/NOFS) spacecraft includes a sensitive fluxgate magnetometer to measure DC and ULF magnetic fields in the low latitude ionosphere. The instrument includes a DC vector measurement at 1 sample/sec with a range of +/- 45,000 nT whose primary objective is to provide direct measurements of both V x B and E x B that are more accurate than those obtained using a simple magnetic field model. These data can also be used for scientific research to provide information of large-scale ionospheric and magnetospheric current systems, which, when analyzed in conjunction with the C/NOFS DC electric field measurements, promise to advance our understanding of the electrodynamics of the low latitude ionosphere. In this study, we use the magnetic field data to study the temporal and local time variations of the ring currents during geomagnetic storms. We first compare the in situ measurements with the POMME (the POtsdam Magnetic Model of the Earth) model in order to provide an in-flight "calibration" of the data as well as compute magnetic field residuals essential for revealing large scale external current systems. We then compare the magnetic field residuals observed both during quiet times and during geomagnetic storms at the same geographic locations to deduce the magnetic field signatures of the ring current. As will be shown, the low inclination of the C/NOFS satellite provides a unique opportunity to study the evolution of the ring current as a function of local time, which is particularly insightful during periods of magnetic storms. This paper will present the initial results of this study.

  10. Atmosphere–Ionosphere Electrodynamic Coupling

    Microsoft Academic Search

    V. M. Sorokin; V. M. Chmyrev

    \\u000a Numerous phenomena that occur in the mesosphere, ionosphere, and the magnetosphere of the Earth are caused by the sources\\u000a located in the lower atmosphere and on the ground. We describe the effects produced by lightning activity and by ground-based\\u000a transmitters operated in high frequency (HF) and very low frequency (VLF) ranges. Among these phenomena are the ionosphere\\u000a heating and the

  11. Counterbalancing for Serial Order Carryover Effects in Experimental Condition Orders

    ERIC Educational Resources Information Center

    Brooks, Joseph L.

    2012-01-01

    Reactions of neural, psychological, and social systems are rarely, if ever, independent of previous inputs and states. The potential for serial order carryover effects from one condition to the next in a sequence of experimental trials makes counterbalancing of condition order an essential part of experimental design. Here, a method is proposed…

  12. Analysis of Ionosphere Gradient Using Japan GEONET Data

    Microsoft Academic Search

    Hiroyuki Konno; Sam Pullen; Ming Luo; Per Enge

    Large spatial gradients in ionosphere delay are a potentially threatening error source for the Local Area Augmentation System (LAAS). Therefore a better understanding of the ionosphere behavior during strong magnetic storms is crucial for LAAS so that it can more accurately evaluate its integrity and availability during these events. In order to obtain spatially-dense information on severe ionosphere delays, we

  13. Exploring the Cigala/calibra Network Data Base for Ionosphere Monitoring Over Brazil

    NASA Astrophysics Data System (ADS)

    Vani, B. C.; Galera Monico, J. F.; Shimabukuro, M. H.; Pereira, V. A.; Aquino, M. H.

    2013-12-01

    The ionosphere in Brazil is strongly influenced by the equatorial anomaly, therefore GNSS based applications are widely affected by ionospheric disturbances. A network for continuous monitoring of the ionosphere has been deployed over its territory since February/2011, as part of the CIGALA and CALIBRA projects. Through CIGALA (Concept for Ionospheric Scintillation Mitigation for Professional GNSS in Latin America), which was funded by European Commission (EC) in the framework of the FP7-GALILEO-2009-GSA (European GNSS Agency), the first stations were deployed at Presidente Prudente, São Paulo state, in February 2011. CIGALA was finalized in February 2012 with eight stations distributed over the Brazilian territory. Through CALIBRA (Countering GNSS high Accuracy applications Limitations due to Ionospheric disturbances in BRAzil), which is also funded by the European Commission now in the framework of the FP7-GALILEO-2011-GSA, new stations are being deployed. Some of the stations are being specifically placed according to geomagnetic considerations aiming to support the development of a local scintillation and TEC model. CALIBRA started in November 2012 and will have two years of duration, focusing on the development of improved and new algorithms that can be applied to high accuracy GNSS techniques in order to tackle the effects of ionospheric disturbances. PolarRxS-PRO receivers, manufactured by Septentrio, have been deployed at all stations This multi-GNSS receiver can collect data at rates of up to 100 Hz, providing ionospheric TEC, scintillation parameters like S4 and Sigma-Phi, and other signal metrics like locktime for all satellites and frequencies tracked. All collected data (raw and ionosphere monitoring records) is stored at a central facility located at the Faculdade de Ciências e Tecnologia da Universidade Estadual Paulista (FCT/UNESP) in Presidente Prudente. To deal with the large amount of data, an analysis infrastructure has also been established in the form of a web based software named ISMR Query Tool, which provides a capability to identify specific behaviors of ionospheric activity through data visualization and data mining. Its web availability and user-specified features allow the users to interact with the data through a simple internet connection, enabling to obtain insight about the ionosphere according with their own previous knowledge. Information about the network, the projects and the tool can be found at the FCT/UNESP Ionosphere web portal available at http://is-cigala-calibra.fct.unesp.br/. This contribution will provide an overview of results extracted using the monitoring and analysis infrastructure, explaining the possibilities offered by the ISMR Query Tool to support analysis of the ionosphere as well as the development of models and mitigation techniques to counter the effects of ionospheric disturbances on GNSS.

  14. Electron gyroharmonic effects in ionization and electron acceleration during high-frequency pumping in the ionosphere.

    PubMed

    Gustavsson, B; Leyser, T B; Kosch, M; Rietveld, M T; Steen, A; Brändström, B U E; Aso, T

    2006-11-10

    Optical emissions and incoherent scatter radar data obtained during high-frequency electromagnetic pumping of the ionospheric plasma from the ground give data on electron energization in an energy range from 2 to 100 eV. Optical emissions at 4278 A from N2+ that require electrons with energies above the 18 eV ionization energy give the first images ever of pump-induced ionization of the thermosphere. The intensity at 4278 A is asymmetric around the ionospheric electron gyroharmonic, being stronger above the gyroresonance. This contrasts with emissions at 6300 A from O(1D) and of electron temperature enhancements, which have minima at the gyroharmonic but have no apparent asymmetry. This direct evidence of pump-induced ionization contradicts previous indirect evidence, which indicated that ionization is most efficiently produced when the pump frequency was below the gyroharmonic. PMID:17155639

  15. Comparison of ionospheric peak parameters derived from different modeling approaches

    NASA Astrophysics Data System (ADS)

    Mahdi Alizadeh, M.; Schuh, Harald

    2014-05-01

    Due to the fact that Ionosphere is a dispersive medium, microwave signals travelling through this medium are affected proportional to their frequencies. This effect allows gaining information about the parameters of the ionosphere in terms of Total Electron Content (TEC) or the electron density. There are different approaches for modeling these parameters. Some models are based on physical properties such as the Global Assimilative Ionospheric Model (GAIM). Some are empirical models, e.g. the International Reference Ionosphere (IRI), the NeQuick model, or the Neustrelitz TEC Model (NTCM). Finally some models are based on purely mathematical/statistical approaches. In the mathematical models, the corresponding model parameters are calculated using measurements from different space geodetic techniques or the ionosonde data. This study investigates different approaches for computing the electron density along the ray path. First the mathematical approach developed at Technical University of Berlin (TUB) for global 3D reconstruction of the ionospheric F2-peak parameters is presented. In this approach, the F2-peak parameters, i.e. the maximum electron density and its corresponding height are represented as a function of geographic or geomagnetic longitude, latitude, and height with two sets of spherical harmonic expansions of degree and order 15, which correspond to a spatial resolution of 5° in longitude and 2.5° in latitude. To assess this modeling approach, the estimated F2-peak parameters are compared with the peak parameters derived from several other modeling approaches.

  16. Neutral composition effects on ionospheric storms at middle and low latitudes

    Microsoft Academic Search

    K. Liou; P. T. Newell; B. J. Anderson; L. Zanetti; C.-I. Meng

    2005-01-01

    The two-dimensional structure of thermospheric neutral composition, specifically, the atomic oxygen to molecular nitrogen column density ratio, [O\\/N2], is studied during the 17–24 April 2002 geomagnetic storms to understand the cause of ionospheric storms in regions equatorward of the auroral oval on an instantaneous large scale. The [O\\/N2] ratio is derived from the dayglow emission ratio of O I 1356

  17. Exploring the Effects of Ionospheric Outflow on the Inner Magnetosphere using RAM-SCB

    Microsoft Academic Search

    Daniel Welling; Vania Jordanova; Sorin Zaharia; Gabor Toth

    2010-01-01

    The Ring current Atmosphere interactions Model with Self-Consistently calculated 3D Mag-netic field (RAM-SCB) has been used to successfully study inner magnetosphere dynamics during different solar wind and magnetosphere conditions. Historically, this numerical model has relied on empirical formulations to provide magnetic field boundary conditions, ionospheric electric potential, and to specify heavy ion composition at the outer boundary. Either empirical models

  18. General overview of the solar activity effects on the lower ionosphere

    NASA Technical Reports Server (NTRS)

    Danilov, A. D.

    1989-01-01

    Solar activity influences the ionospheric D region. That influence manifests itself both in the form of various solar induced disturbances and in the form of the D region dependence on solar activity parameters (UV-flux, interplanetary magnetic field, solar wind etc.) in quiet conditions. Relationship between solar activity and meteorological control of the D region behavior is considered in detail and examples of strong variations of aeronomical parameters due to solar or meteorological events are given.

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

    Microsoft Academic Search

    J. Bremer

    1992-01-01

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

  20. Results from the SEEP active space plasma experiment - Effects on the ionosphere

    Microsoft Academic Search

    W. L. Imhof; E. E. Gaines; H. D. Voss; J. B. Reagan; D. W. Datlowe; J. Mobilia; R. A. Helliwell; J. Katsufrakis; R. G. Joiner

    1985-01-01

    An active satellite-ground coordinated space plasma experiment was conducted from May to December, 1982, in which electrons were precipitated from the radiation belts into the ionosphere by the controlled injection of VLF signals from ground-based transmitters. The results confirm the hypothesis that electrons can be precipitated from the radiation belts by ground-based VLF transmitters, and they provide information relating to

  1. Ionospheric bending correction for GNSS radio occultation signals

    NASA Astrophysics Data System (ADS)

    Hoque, M. M.; Jakowski, N.

    2011-12-01

    Ionospheric propagation effects on Global Navigation Satellite Systems (GNSS) signals are the most pronounced during radio occultation due to long ionospheric travel paths of the received signal on low Earth orbiting satellites. Inhomogeneous plasma distribution and anisotropy cause higher-order nonlinear refraction effects on GNSS signals which cannot be fully removed through a linear combination of dual-frequency observables. In this paper, higher-order ionospheric effects due to straight line of sight (LOS) propagation assumption such as the excess path length of the signal in addition to the LOS path and the total electron content difference between the curved path and the LOS path have been investigated for selected GPS-CHAMP occultation events. Based on simulation studies we have derived correction formulas for computing raypath bending effects as functions of signal frequency, tangential height of the raypath, ionospheric parameters such as the maximum ionization and total electron content. If these parameters are known, the proposed correction method is able to correct on an average about 65-80% bending errors of GNSS occultation signals.

  2. Ionospheric effects of solar flares and their associated particle ejections in March 2012

    NASA Astrophysics Data System (ADS)

    Zolotukhina, N.; Polekh, N.; Kurkin, V.; Romanova, E.

    2015-06-01

    Flares of March 4-9, 2012 were accompanied by an intensification of solar electromagnetic and corpuscular radiations and five coronal mass ejections. Bursts of X-rays and increased solar cosmic ray fluxes caused an increase in ionospheric absorption manifesting itself in data from vertical sounding stations as enhancements of the lowest frequency of reflections up to 4-6 MHz at the daytime and as the disappearance of reflections in the ionograms of high latitude stations. Interplanetary coronal mass ejections (ICME) generated March 7-8 moderate and March 8-11 intense magnetic storms accompanied by ionospheric disturbances. At the peaks of both magnetic storms there were abrupt afternoon-evening decreases in the ionospheric F2-layer critical frequency (foF2). During the March 7-8 storm, the foF2 decrease concurred with the reversal of the interplanetary magnetic field azimuthal component (IMF By) which initiated restructuring of magnetospheric convection; during the March 8-11 storm, with the abrupt weakening of the interplanetary magnetic field southward component (IMF Bz) which triggered a substorm.

  3. Magnetosphere-ionosphere mapping at Jupiter: Quantifying the effects of using different internal field models

    NASA Astrophysics Data System (ADS)

    Vogt, Marissa F.; Bunce, Emma J.; Kivelson, Margaret G.; Khurana, Krishan K.; Walker, Raymond J.; Radioti, Aikaterini; Bonfond, Bertrand; Grodent, Denis

    2015-04-01

    The lack of global field models accurate beyond the inner magnetosphere (<30 RJ) makes it difficult to relate Jupiter's polar auroral features to magnetospheric source regions. We recently developed a model that maps Jupiter's equatorial magnetosphere to the ionosphere using a flux equivalence calculation that requires equal flux at the equatorial and ionospheric ends of flux tubes. This approach is more accurate than tracing field lines in a global field model but only if it is based on an accurate model of Jupiter's internal field. At present there are three widely used internal field models—Voyager Io Pioneer 4 (VIP4), the Grodent Anomaly Model (GAM), and VIP Anomaly Longitude (VIPAL). The purpose of this study is to quantify how the choice of an internal field model affects the mapping of various auroral features using the flux equivalence calculation. We find that different internal field models can shift the ionospheric mapping of points in the equatorial plane by several degrees and shift the magnetospheric mapping to the equator by ~30 RJ radially and by less than 1 h in local time. These shifts are consistent with differences in how well each model maps the Ganymede footprint, underscoring the need for more accurate Jovian internal field models. We discuss differences in the mapping of specific auroral features and the size and location of the open/closed field line boundary. Understanding these differences is important for the continued analysis of Hubble Space Telescope images and in planning for Juno's arrival at Jupiter in 2016.

  4. Vibrationally excited nitrogen in stable auroral red arcs and its effect on ionospheric recombination

    NASA Technical Reports Server (NTRS)

    Newton, G. P.; Walker, J. C. G.; Meijer, P. H. E.

    1974-01-01

    The time-dependent continuity equations, including diffusion, were solved for the first six energy levels of molecular nitrogen for conditions in the thermosphere corresponding to stable auroral red (SAR) arcs. The results show that molecular nitrogen is excited vibrationally to the degree that the rate constant for the ionospheric loss process, O(+) + N2 yields NO(+) + N, is increased by as much as a factor of 7.6 at F2 region altitudes. It was found that deviations from the energetically equivalent Boltzmann distribution were large, causing the rate constant to be as much as 1.6 times the rate constant calculated for the Boltzmann distribution. These results indicate that SAR arc intensities as small as 58 R can produce noticeable increases in the ionosphere ion-atom interchange reaction rate and hence in the rate of loss of ionospheric electrons. It is suggested that the observed decrease of electron density in the F2 region in SAR arcs can probably be explained by enhanced reaction rates for ion-atom interchange between O(+) and N2 caused by vibrational excitation of molecular nitrogen by electron impact.

  5. Ordered delinquency: the "effects" of birth order on delinquency.

    PubMed

    Cundiff, Patrick R

    2013-08-01

    Juvenile delinquency has long been associated with birth order in popular culture. While images of the middle child acting out for attention or the rebellious youngest child readily spring to mind, little research has attempted to explain why. Drawing from Adlerian birth order theory and Sulloway's born-to-rebel hypothesis, I examine the relationship between birth order and a variety of delinquent outcomes during adolescence. Following some recent research on birth order and intelligence, I use new methods that allow for the examination of between-individual and within-family differences to better address the potential spurious relationship. My findings suggest that contrary to popular belief, the relationship between birth order and delinquency is spurious. Specifically, I find that birth order effects on delinquency are spurious and largely products of the analytic methods used in previous tests of the relationship. The implications of this finding are discussed. PMID:23719623

  6. Ordered Delinquency: The “Effects” of Birth Order On Delinquency

    PubMed Central

    Cundiff, Patrick R.

    2014-01-01

    Juvenile delinquency has long been associated with birth order in popular culture. While images of the middle child acting out for attention or the rebellious youngest child readily spring to mind, little research has attempted to explain why. Drawing from Adlerian birth order theory and Sulloway's born to rebel hypothesis I examine the relationship between birth order and a variety of delinquent outcomes during adolescence. Following some recent research on birth order and intelligence, I use new methods that allow for the examination of both between-individual and within-family differences to better address the potential spurious relationship. My findings suggest that contrary to popular belief the relationship between birth order and delinquency is spurious. Specifically, I find that birth order effects on delinquency are spurious and largely products of the analytic methods used in previous tests of the relationship. The implications of this finding are discussed. PMID:23719623

  7. Birth Order: Reconciling Conflicting Effects.

    ERIC Educational Resources Information Center

    Zajonc, Robert B.; Mullally, Patricia R.

    1997-01-01

    Introduces the confluence model as a theory specifying the process by which the intellectual environment modifies intellectual development. Using this model, explores the contradiction between prediction of secular trends in test scores by trends in aggregate birth order and the lack of prediction of individual test scores by birth order using…

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

    E-print Network

    Mendillo, Michael

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

  9. Relationship between phase path and effective path for oblique ionospheric propagation

    Microsoft Academic Search

    P. J. D. Gething

    1965-01-01

    The effects of earth curvature were neglected by Appleton in deriving the well-known relationship between phase path P and effective path P' for oblique propagation of a signal of frequency . It is shown that this equation is still rigorously satisfied when earth curvature is taken into account. An expression for phase path, correct to first order curvature terms, is

  10. Ionospheric effects of earthquakes in Japan in March 2011 obtained from observations of lightning electromagnetic radio signals

    NASA Astrophysics Data System (ADS)

    Mullayarov, V. A.; Argunov, V. V.; Abzaletdinova, L. M.; Kozlov, V. I.

    2012-10-01

    Manifestations of disturbances in the lower ionosphere caused by a complex series of earthquakes (the strong earthquakes with M = 7.3 and M = 9 - known as M9 Tohoku EQ - and the subsequent aftershocks) that occurred near the Japanese island of Honshu have been considered with the use of monitoring measurements of the amplitude of lightning electromagnetic signals (atmospherics) received at Yakutsk. Some data of one-point lightning location systems have been compared with the data of the WWLLN network. The analysis of hourly values variation of the atmospheric amplitude passing over the earthquake epicenters shows that during the initial period (the strong earthquakes on 9 March and 11 March) a typical pattern of variations was observed. It was manifested in the increased amplitude after both earthquakes. There were also possible precursors in the form of the increase in amplitude 12-14 days before the events. Though the focuses of these earthquakes were very close to each other, the registration of both precursors may indicate that both of the lithospheric processes developed to a certain extent independently. During all the days of the atmospheric amplitude enhancement the quasi-periodic variation trains were recorded. Together with the delay of earthquake effects relative to the time of the events, they may testify in favor of transferring the energy of lithospheric processes into the lower ionosphere by means of atmospheric gravity waves.

  11. Disturbances of the ionosphere of blast and acoustic waves generated at ionospheric heights by rockets

    NASA Astrophysics Data System (ADS)

    Drobzheva, Y.; Krasnov, V.

    2003-04-01

    We present a model, which describes the propagation of acoustic pulses through the atmosphere produced by flight of rockets, and effects of these pulses on the ionosphere above a rocket. The model takes into account nonlinear effects, inhomogeneities of the atmosphere, absorption, expansion of a wave acoustic front, etc. We show, that experimentally observed ionospheric disturbances with duration about hundreds seconds cannot be explained by effect of acoustic pulses on the ionosphere. We calculated parameters of a blast wave generated by rocket at the ionospheric heights. It was shown that the blast wave is intense and it can generate great disturbance of electron density. The disturbance of electron density can exceed the ambient electron density 2.6 as much. We supposed that the observed ionospheric disturbances might be generated by propagation of delayed magnetoacoustic wave generated during the propagation of a blast wave through the ionosphere.

  12. Global effects on Ionospheric Weather over the Indian subcontinent at Sunrise and Sunset

    SciTech Connect

    Basak, Tamal; Pal, S. [S. N. Bose National Centre for Basic Sciences, JD Block, Salt-Lake, Kolkata-700098 (India); Chakrabarti, S. K. [S. N. Bose National Centre for Basic Sciences, JD Block, Salt-Lake, Kolkata-700098 (India); Indian Centre for Space Physics, 43 Chalantika, Garia Station Road, Kolkata-700084 (India)

    2010-10-20

    Study of Very Low Frequency (VLF) electromagnetic wave is very important for knowing the behavior of the Ionospheric layers due to Sunrise-Sunset, Earthquakes, Solar flares, Solar eclipses and other terrestrial and extra terrestrial radiations. We study the properties of the variation of the VLF signal strength theoretically all over Indian sub-continent. As an example, we concentrate on the VLF signal transmitted by Indian Naval Transmitter VTX at Vijayanarayanam (Latitude 08 deg. 23', Longitude 77 deg. 45') near the southern tip of Indian subcontinent. As has been noticed, several receiving stations placed during the VLF campaign in all over India, the VLF signal strength varies significantly with place and time. To understand the diurnal and seasonal variation of the received signal, a complete knowledge of physics of intensity distribution of the VLF signal is essential. The spatial variation of VLF signal plays an important role in selecting future VLF stations. In the wave-hop theoretical model presented here, horizontally stratified ionospheric layers have been considered. The VLF wave emitted by the transmitter has both the ground wave and the sky wave components. The ground wave attenuates during propagation. The sky wave component experiences reflections by the ionosphere on its way to the receiver and its attenuation depends on the degree of ionization. Intensity variation occurs at a given receiver location for interference among singly and multiply reflected waves. This has been simulated considering some simplified and justifiable assumptions. This spatial variation wave-hop theoretical model developed here has been compared with LWPC code generated results.

  13. The effect of the magnetosphere processes on the ionosphere during the magnetic storm of December 1, 1977 based on the Cosmos900 data

    Microsoft Academic Search

    E. N. Sosnovets; V. V. Afonin; G. L. Gdalevich; A. V. Dronov; V. D. Ozerov; M. I. Panasyuk; L. V. Tverskaya; V. I. Tulupov; O. V. Korosheva; J. Smilauer

    1979-01-01

    The effect of the magnetospheric disturbances on the high latitude ionospheric plasma during the magnetic storm of December 1, 1977 was investigated using data from measurements onboard Cosmos 900 satellite. (The circular orbit is at the height of about 500 km, its inclination is 83 deg, the orbit period is 94.4.) The regions of energetic electron precipitation are correlated with

  14. Momentum coupling in ionospheric critical ionization velocity experiments

    Microsoft Academic Search

    N. Brenning; O. Bolin

    1993-01-01

    The critical ionization velocity (CIV) effect is a process that can rapidly ionize a neutral gas which moves through a magnetized plasma. In ionospheric injection experiments, the neutral gas component is released at high velocity with respect to the ionosphere from a rocket or a satellite. Efficient momentum coupling between the injected cloud and the ambient ionosphere is achieved by

  15. Local Ionosphere Model Estimation From Dual-Frequency GNSS Observables

    E-print Network

    Psiaki, Mark L.

    Local Ionosphere Model Estimation From Dual-Frequency GNSS Observables by Ryan Mitch and Mark for the removal of ionospheric effects from single-frequency non-GPS radio navigation data through the use of data ionosphere model to estimate the total electron con- tent (TEC) along any line of sight that differs from

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

    E-print Network

    Stanford University

    Using WAAS Ionospheric Data to Estimate LAAS Short Baseline Gradients Seebany Datta-Barua, Todd due to ionospheric effects must be bounded such that integrity is maintained with minimal loss during severe ionospheric storms. We seek an answer to the question of how much spatial variation

  17. Solitons versus parametric instabilities during ionospheric heating

    NASA Technical Reports Server (NTRS)

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

    1984-01-01

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

  18. Effects of Meteorological Variability on the Thermosphere-Ionosphere System during the Moderate Geomagnetic Disturbed January 2013 Period As Simulated By Time-GCM

    NASA Astrophysics Data System (ADS)

    Maute, A. I.; Hagan, M. E.; Richmond, A. D.; Liu, H.; Yudin, V. A.

    2014-12-01

    The ionosphere-thermosphere system is affected by solar and magnetospheric processes and by meteorological variability. Ionospheric observations of total electron content during the current solar cycle have shown that variability associated with meteorological forcing is important during solar minimum, and can have significant ionospheric effects during solar medium to maximum conditions. Numerical models can be used to study the comparative importance of geomagnetic and meterological forcing.This study focuses on the January 2013 Stratospheric Sudden Warming (SSW) period, which is associated with a very disturbed middle atmosphere as well as with moderately disturbed solar geomagntic conditions. We employ the NCAR Thermosphere-Ionosphere-Mesosphere-Electrodynamics General Circulation Model (TIME-GCM) with a nudging scheme using Whole-Atmosphere-Community-Climate-Model-Extended (WACCM-X)/Goddard Earth Observing System Model, Version 5 (GEOS5) results to simulate the effects of the meteorological and solar wind forcing on the upper atmosphere. The model results are evaluated by comparing with observations e.g., TEC, NmF2, ion drifts. We study the effect of the SSW on the wave spectrum, and the associated changes in the low latitude vertical drifts. These changes are compared to the impact of the moderate geomagnetic forcing on the TI-system during the January 2013 time period by conducting numerical experiments. We will present select highlights from our study and elude to the comparative importance of the forcing from above and below as simulated by the TIME-GCM.

  19. The Ptolemaic Approach to Ionospheric Electrodynamics

    NASA Astrophysics Data System (ADS)

    Vasyliunas, V. M.

    2010-12-01

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

  20. Effects of lightning and sprites on the ionospheric potential, and threshold effects on sprite initiation, obtained using an analog model of the global atmospheric electric circuit

    NASA Astrophysics Data System (ADS)

    Rycroft, M. J.; Odzimek, A.

    2010-06-01

    A quantitative model of the global atmospheric electric circuit has been constructed using the PSpice electrical engineering software package. Currents (˜1 kA) above thunderstorms and electrified rain/shower clouds raise the potential of the ionosphere (presumed to be an equipotential surface at 80 km altitude) to ˜250 kV with respect to the Earth's surface. The circuit is completed by currents flowing down through the fair-weather atmosphere in the land/sea surface and up to the cloud systems. Using a model for the atmospheric conductivity profile, the effects of both negative and positive cloud-to-ground (CG) lightning discharges on the ionospheric potential have been estimated. A large positive CG discharge creates an electric field that exceeds the breakdown field from the ionosphere down to ˜74 km, thereby forming a halo, a column sprite, and some milliseconds later, from ˜67 km down to ˜55 km at ˜60 ms after the discharge, a "carrot" sprite. Estimates are made of the return stroke current and the thundercloud charge moment change of a +CG discharge required to exceed the threshold breakdown field, or the threshold field for creating and sustaining negative or positive streamers. The values for breakdown at 80 km altitude are 35 kA and 350 C.km, (Coulomb.kilometers), respectively, and those at 70 km altitude are 45 kA and 360 C.km, respectively. The different temporal and spatial developments of the mesospheric electric field distinguishing between column and carrot sprites agree with the latest deductions from recent observations. The current flowing in the highly conducting sprite reduces the ionospheric potential by ˜1 V.

  1. The effects of lightning and sprites on the ionospheric potential, and threshold effects on sprite initiation, obtained using a PSpice model

    NASA Astrophysics Data System (ADS)

    Rycroft, Michael J.; Odzimek, Anna

    2010-05-01

    A quantitative model of the global atmospheric electric circuit has been constructed using the PSpice electrical engineering software package. Currents (~ 1 kA) above thunderstorms and electrified rain/shower clouds raise the potential of the ionosphere, which is presumed to be an equipotential surface at 80 km altitude, to ~ 250 kV with respect to the Earth's surface. The circuit is completed by currents flowing down through the fair weather atmosphere, in the land/sea surface and up to the cloud systems. Using a model for the atmospheric conductivity profile (Rycroft et al., JASTP, 2007), the effects of both negative and positive cloud-to-ground (CG) lightning discharges ion the ionospheric potential have been estimated. A large positive CG discharge creates an electric field which exceeds the breakdown field from the ionosphere down to ~ 74 km, so forming a halo and a column sprite, and, some ms later, from ~ 67 km down to ~ 55 km at ~ 60 ms after the discharge, thereby forming a "carrot" sprite. Estimates are made of the return stroke current and the thundercloud charge moment change (CMC) for a +CG discharge required to exceed the threshold breakdown field, or the threshold field for creating and sustaining negative or positive streamers. The values for breakdown at 80 km altitude are 35 kA and 350 C.km, respectively, and 45 kA and 360 C.km at 70 km altitude. The different temporal and spatial developments of the mesospheric electric field distinguishing between column and carrot sprites agree with the latest deductions from from recent observations. A current flowing in the highly conducting sprite reduces the ionospheric potential by ~ 1 V.

  2. Effects of lightning and sprites on the ionospheric potential, and threshold effects on sprite initiation, obtained using an analog model of the global atmospheric electric circuit

    NASA Astrophysics Data System (ADS)

    Rycroft, M. J.; Odzimek, A.

    2010-06-01

    A quantitative model of the global atmospheric electric circuit has been constructed using the PSpice electrical engineering software package. Currents (˜1 kA) above thunderstorms and electrified rain/shower clouds raise the potential of the ionosphere (presumed to be an equipotential surface at 80 km altitude) to ˜250 kV with respect to the Earth's surface. The circuit is completed by currents flowing down through the fair-weather atmosphere in the land/sea surface and up to the cloud systems. Using a model for the atmospheric conductivity profile, the effects of both negative and positive cloud-to-ground (CG) lightning discharges on the ionospheric potential have been estimated. A large positive CG discharge creates an electric field that exceeds the breakdown field from the ionosphere down to ˜74 km, thereby forming a halo, a column sprite, and some milliseconds later, from ˜67 km down to ˜55 km at ˜60 ms after the discharge, a “carrot” sprite. Estimates are made of the return stroke current and the thundercloud charge moment change of a +CG discharge required to exceed the threshold breakdown field, or the threshold field for creating and sustaining negative or positive streamers. The values for breakdown at 80 km altitude are 35 kA and 350 C.km, (Coulomb.kilometers), respectively, and those at 70 km altitude are 45 kA and 360 C.km, respectively. The different temporal and spatial developments of the mesospheric electric field distinguishing between column and carrot sprites agree with the latest deductions from recent observations. The current flowing in the highly conducting sprite reduces the ionospheric potential by ˜1 V.

  3. Effects of ionospheric oxygen on the magnetopause boundary waves using a high-resolution multi-fluid MHD model

    NASA Astrophysics Data System (ADS)

    Lyon, J.; Merkin, V. G.

    2011-12-01

    Recent advances in numerical modeling of ionospheric oxygen in the magnetosphere have revealed a number of global effects. The presence of the heavy ion component was shown to influence substorm dynamics, plasma sheet pressure and composition, the rate and location of the night side reconnection. One of the effects that has long been argued to take place is the influence of oxygen plasma component on the development of magnetopause boundary waves due to Kelvin-Helmholtz (KH) instability. The argument is that the heavier ions increase the Alfven speed inside the magnetosphere thereby lowering the instability threshold. This argument is based on the linear stability analysis derived for a tangential discontinuity between two incompressible plasmas streaming past each other. However, our previously reported results using the multi-fluid Lyon-Fedder-Mobarry (MFLFM) model (Merkin, 2011) suggested that the presence of oxygen ions actually can stabilize the growth of KH waves in the simulation. In the present work we build upon these earlier results by developing a high-resolution version of the MFLFM model. With this new development we are able to better resolve the Low-Latitude Boundary Layer (LLBL) which appears to play an important role in the development of KH waves, not described by the aforementioned linear analysis. We study the dependence of KH waves on the density and temperature of oxygen ions in the magnetosphere, their effects on the properties of the LLBL, including its width and the degree to which it is populated by oxygen. To explore the wave activity in a more quantitative fashion, we analyze the spectral characteristics of the KH waves, including the spatial distribution and temporal evolution of the wave power. The ultimate question that we seek to answer is whether the ionospheric oxygen stabilizes or makes more intense the magnetopause boundary wave activity and under what conditions this occurs.

  4. Ionospheric delay estimation strategies for airborne gravity surveys

    NASA Astrophysics Data System (ADS)

    Herring, T.; Centinello, F. J., III; Martins, J. L.

    2011-12-01

    Noise in GPS determined aircraft trajectories is a major source of error in airborne gravity surveys. Frequency dependent noise, such as the ionospheric delay and signal multipath, can have a large impact when aircraft to base station separations are more than a few kilometers. For large separations (more than ten kilometers) between base stations and aircraft, GPS phase data is processed with the linear combination of measurements at the L1 (1.5 GHz) and L2 (1.24 GHz) frequencies that eliminates the first order effects of the ionosphere. However due the closeness of the GPS frequencies, the random noise and often the noise from multipath is 2 to 3 times larger than in the individual L1 and L2 phase measurements. In this talk, we explore methods for processing kinematic GPS trajectories using L1 and L2 phase data separately with an ionospheric delay model used that is based on coarse resolution global ionospheric delay models combined with high time resolution estimates from the kinematic GPS phase data passed through a smoothing Kalman filter. We test this approach with a comparison of repeat pass airborne gravity surveys where the base station for the survey was 200 km from the flight path. Initial results are encouraging with root-mean-square (RMS) differences between filtered gravity anomalies along the repeated flights decreasing from 0.9 mgal to 0.6 mgal when the L1/L2 calibrated solution is compared to the standard ionospheric free analysis. Further improvements are expected as ambiguity resolution is improved in the calibrated solutions and the filters used both for the ionospheric delays and gravity anomalies are optimized.

  5. Predictions and observations of HF radio propagation in the northerly ionosphere: The effect of the solar flares and a weak CME in early January 2014.

    NASA Astrophysics Data System (ADS)

    Hallam, Jonathan; Stocker, Alan J.; Warrington, Mike; Siddle, Dave; Zaalov, Nikolay; Honary, Farideh; Rogers, Neil; Boteler, David; Danskin, Donald

    2014-05-01

    We have previously reported on a significant new multi-national project to provide improved predictions and forecasts of HF radio propagation for commercial aircraft operating on trans-polar routes. In these regions, there are limited or no VHF air-traffic control facilities and geostationary satellites are below the horizon. Therefore HF radio remains important in maintaining communications with the aircraft at all times. Space weather disturbances can have a range of effects on the ionosphere and hence HF radio propagation - particularly in the polar cap. While severe space weather effects can lead to a total loss of communications (i.e. radio blackout), less intense events can still cause significant disruption. In this paper we will present the effect of a series of M and X class solar flares and a relatively weak CME on HF radio performance from 6 to 13 January 2014. This is an interesting interval from the point of view of HF radio propagation because while the solar effects on the ionosphere are significant, except for an interval of approximately 12 hours duration, they are not so intense as to produce a complete radio blackout on all paths. Observations of the signal-to-noise ratio, direction of arrival, and time of flight of HF radio signals on six paths (one entirely within the polar cap, three trans-auroral, and two sub-auroral) will be presented together with riometer measurements of the ionospheric absorption. Global maps of D-region absorption (D-region absorption prediction, DRAP) inferred from satellite measurements of the solar wind parameters will be compared with the HF and riometer observations. In addition, a ray-tracing model using a realistic background ionosphere and including localised features found in the ionospheric polar cap (e.g. polar patches and arcs) will be used to model the expected and observed HF radio propagation characteristics.

  6. 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.

  7. Thermal imbalance and shock wave effects on low latitude ionosphere : asymmetric case of a total solar eclipse

    NASA Astrophysics Data System (ADS)

    Vila, P. M.; Fleury, R.; Le Roux, Y.; Kone, E.

    2003-04-01

    The total solar eclipse of June 21 2001 crossed Africa under favourablr conditions for observing distant effects on the ionosphere, especially IN equatorial and subtropical F layer magnetic tubes:1^o)magnetically quiet Solar and magnetospheric activity; 2^o) totality at the noon phase in the GMT meridians of observation; 3^o) totality path nearly parallel to the magnetic equator at about the 10^o south geographic. Two West African digital ionosondes recorded h'f profiles at 5 minute intervals at Korhogo (Ivory Coast, geogr lat. 9.5^oNorth, magn. lat. -2.5^o, where the eclipse occultation was 40%) and Dakar (Senegal, geogr. Latitude 15^oNorth, magn. latitude + 4.8^o, just outside the penumbra). The h'f ionograms have been inverted to trace fp(h,t) variations over both sites from 07 to 17 UT. these plots are completed by the TEC variations observed along the 8 GPS satelltite tracks over the Atlantic and African areas.The results approximate (3D, time)variations as follows : (I). At the mesoscale range from 5^o South to 25^o North latitudes, intense asymmetric cooling of the southern tropic zone around the local noon enhanced the normal southward cross-equator neutral wind; hence a strong southward plasma flow from the less eclipsed northern half of the intertropical ionospheric domain (from Dakar onwards to the 25^o North) to the southern half. The attenuated ionization depletion in the strongly eclipsed Southern crest area from 0^oto 10^o South. Also the GPS meridian segments of TEC records show counter-coupling between i) adiabatic cooling (Raghava Rao's Equatorial Temperature Anomaly), and ii) conjugate photoelectron heat deposition on the equatorial side of the southern F2 density crest. We thereby infer that in West Africa such unstable dynamics often distort crest evolution at post-noon hours, except around the magnetic equinoxes of May 21 and August 20. (II) Two gravity wave modes were identified after eclipse maximum phase on the F2 Korhogo ionogram peak frequency, as well as on GPS TEC values. Analogic analysis of these modes show that local atmospheric shock waves were generated by the rapid eclipse totality cooling from sources at troposphere, mesosphere and lower thermosphere levels. For the general case of low latitudes Africa, we infer that similar oscillations from atmospheric storms can disturb the equatorial ionosphere during daytime (e.g. electrojet shears, layer strata) and nighttime (the irregular ESF seed component).

  8. A Model of Callisto's Ionosphere

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  9. Speed-dependent collision effects on radar back-scattering from the ionosphere. [incoherent scatter radar

    NASA Technical Reports Server (NTRS)

    Behl, Y. K.; Theimer, O. H.

    1982-01-01

    The question whether the differences between fluctuation spectra for linearly speed-dependent and speed-independent collision frequencies could account for disagreements between rocket and incoherent scatter estimate was addressed. The basic theory used for computing the fluctuation spectrum is outlined. The speed-dependence of the charge-neutral collision frequency is discussed, with special emphasis on its derivation from the mobility measurements. Various developments of the computer code used for the computation of the fluctuation spectrum are described. The range of values of input parameters typical to the collision-dominated ionosphere are briefly described. The computational results are presented, and the significance and limitation of these results and the future scope of the research are discussed.

  10. Time and Order Effects on Causal Learning

    ERIC Educational Resources Information Center

    Alvarado, Angelica; Jara, Elvia; Vila, Javier; Rosas, Juan M.

    2006-01-01

    Five experiments were conducted to explore trial order and retention interval effects upon causal predictive judgments. Experiment 1 found that participants show a strong effect of trial order when a stimulus was sequentially paired with two different outcomes compared to a condition where both outcomes were presented intermixed. Experiment 2…

  11. Ionospheric Correction Using Tomography

    E-print Network

    Stanford University

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

  12. Photochemistry of planetary ionospheres

    NASA Technical Reports Server (NTRS)

    Nagy, Andrew F.

    1987-01-01

    The dominant photochemical reactions taking place in the ionospheres of Venus, Saturn, and Comet P/Halley are presented. It is shown that the differences in the ionospheres of these celestial bodies result from the different chemistry, energetics, and dynamics of the respective atmospheres. The role of photochemistry in the formation of the individual ionospheres is discussed.

  13. Ionospheric modification by rocket effluents. Final report

    SciTech Connect

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

    1980-06-01

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

  14. Roughness in lattice ordered effect algebras.

    PubMed

    Xin, Xiao Long; Hua, Xiu Juan; Zhu, Xi

    2014-01-01

    Many authors have studied roughness on various algebraic systems. In this paper, we consider a lattice ordered effect algebra and discuss its roughness in this context. Moreover, we introduce the notions of the interior and the closure of a subset and give some of their properties in effect algebras. Finally, we use a Riesz ideal induced congruence and define a function e(a, b) in a lattice ordered effect algebra E and build a relationship between it and congruence classes. Then we study some properties about approximation of lattice ordered effect algebras. PMID:25170523

  15. Overview of midlatitude ionospheric storms

    NASA Astrophysics Data System (ADS)

    Kintner, Paul; Coster, Anthea; Fuller-Rowell, Tim; Mannucci, Anthony J.

    Solar flares and coronal mass ejections erupting from the roiling Sun can smash into the Earth's magnetosphere causing geomagnetic storms that penetrate deep into the atmosphere, which can short out satellites, upset radio communications, disrupt navigation, and even damage terrestrial electrical power grids. Though effects on other regions of the atmosphere have been analyzed, the mechanism by which geomagnetic storms influence the ionosphere's middle latitudes remains poorly understood.This brief report provides an overview of current knowledge in midlatitude ionospheric dynamics and disturbances, from the historic record to recent discoveries presented at a January AGU Chapman Conference.

  16. 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.

  17. Ionospheric correction based on ingestion of global ionospheric maps into the NeQuick 2 model.

    PubMed

    Yu, Xiao; She, Chengli; Zhen, Weimin; Bruno, Nava; Liu, Dun; Yue, Xinan; Ou, Ming; Xu, Jisheng

    2015-01-01

    The global ionospheric maps (GIMs), generated by Jet Propulsion Laboratory (JPL) and Center for Orbit Determination in Europe (CODE) during a period over 13 years, have been adopted as the primary source of data to provide global ionospheric correction for possible single frequency positioning applications. The investigation aims to assess the performance of new NeQuick model, NeQuick 2, in predicting global total electron content (TEC) through ingesting the GIMs data from the previous day(s). The results show good performance of the GIMs-driven-NeQuick model with average 86% of vertical TEC error less than 10 TECU, when the global daily effective ionization indices (Az) versus modified dip latitude (MODIP) are constructed as a second order polynomial. The performance of GIMs-driven-NeQuick model presents variability with solar activity and behaves better during low solar activity years. The accuracy of TEC prediction can be improved further through performing a four-coefficient function expression of Az versus MODIP. As more measurements from earlier days are involved in the Az optimization procedure, the accuracy may decrease. The results also reveal that more efforts are needed to improve the NeQuick 2 model capabilities to represent the ionosphere in the equatorial and high-latitude regions. PMID:25815369

  18. Low/Mid-latitude Ionospheric irregularities and scintillation climatology

    NASA Astrophysics Data System (ADS)

    Abdallah, Amr; Groves, K. M.; Mahrous, Ayman; Hussein, Fayrouz

    Ionospheric scintillation occur when radio signals propagate through an irregular ionosphere (e.g., plasma bubbles). Since plasma bubbles are regions of depleted ion and electron densities, a plasma bubble located on the satellite-to-ground signal path will cause radio signals to fluctuate in phase and amplitude. Ionospheric scintillation data were analyzed in the magnetic latitudinal field-of-view 29° N -13.4° N, observed by a stand-alone SCINDA (Scintillation Network Decision Aid) - GPS receiver at Helwan, Egypt (29.86° N, 31.32° E). A minimum 20° elevation cut off angle has been set in order to minimize the multipath effect. During the enhancing phase of the current solar cycle 24 (years 2010, 2011, 2012 and 2013), the behaviour of the scintillation occurrence were characterized. The seasonal, annual and solar cycle variation of scintillation occurrence is investigated together with the Total Electron Content (TEC), to put in evidence the relation between the electron density gradients and the ionospheric irregularities causing scintillation. This study considers a first step to develop a scintillation climatology over Northern Africa.

  19. Birth order effect on childhood food allergy.

    PubMed

    Kusunoki, Takashi; Mukaida, Kumiko; Morimoto, Takeshi; Sakuma, Mio; Yasumi, Takahiro; Nishikomori, Ryuta; Heike, Toshio

    2012-05-01

    Higher birth order is associated with a smaller risk of allergy (birth order effect). The purpose of this study was to compare the significance of the birth order effect on the prevalence of specific allergic diseases [bronchial asthma (BA), atopic dermatitis (AD), allergic rhinitis (AR), allergic conjunctivitis (AC), and food allergy (FA)] among schoolchildren. A questionnaire survey dealing with the prevalence of allergic diseases was administered to the parents of 14,669 schoolchildren aged 7-15?yr. Based on the data, the prevalence of each allergic disease was compared according to birth order (1st, 2nd, and 3rd or later). Multiple regression analysis was performed to test the significance of the differences. There was no significant difference in the prevalence of BA or AD according to birth order. The prevalence of AR, AC, and FA decreased significantly as birth order increased. The prevalence of FA among those with 1st, 2nd, and 3rd or later birth order was 4.0%, 3.4%, and 2.6%, respectively (p?=?0.01). With respect to symptoms in infancy, the prevalence of wheeze increased significantly and that of FA and eczema in infancy decreased significantly as birth order increased. The present data show a significant birth order effect on FA. The effect was also observed for the prevalence of FA and eczema in infancy. These data support the concept of early, non-allergen-specific programming of IgE-mediated immunity. PMID:22300402

  20. The Impact of Ionospheric Disturbances on High Accuracy Positioning in Brazil

    NASA Astrophysics Data System (ADS)

    Yang, L.; Park, J.; Susnik, A.; Aquino, M. H.; Dodson, A.

    2013-12-01

    High positioning accuracy is a key requirement to a number of applications with a high economic impact, such as precision agriculture, surveying, geodesy, land management, off-shore operations. Global Navigation Satellite Systems (GNSS) carrier phase measurement based techniques, such as Real Time Kinematic (RTK), Network-RTK (NRTK) and Precise Point Positioning (PPP), have played an important role in providing centimetre-level positioning accuracy, and become the core of the above applications. However these techniques are especially sensitive to ionospheric perturbations, in particular scintillation. Brazil sits in one of the most affected regions of the Earth and can be regarded as a test-bed for scenarios of the severe ionospheric condition. Over the Brazilian territory, the ionosphere behaves in a considerably unpredictable way and scintillation activity is very prominent, occurring especially after sunset hours. NRTK services may not be able to provide satisfactory accuracy, or even continuous positioning during strong scintillation periods. CALIBRA (Countering GNSS high Accuracy applications Limitations due to Ionospheric disturbances in BRAzil) started in late 2012 and is a project funded by the GSA (European GNSS Agency) and the European Commission under the Framework Program 7 to deliver improvements on carrier phase based high accuracy algorithms and their implementation in GNSS receivers, aiming to counter the adverse ionospheric effects over Brazil. As the first stage of this project, the ionospheric disturbances, which affect the applications of RTK, NRTK or PPP, are characterized. Typical problems include degraded positioning accuracy, difficulties in ambiguity fixing, NRTK network interpolation errors, long PPP convergence time etc. It will identify how GNSS observables and existing algorithms are degraded by ionosphere related phenomena, evaluating the impact on positioning techniques in terms of accuracy, integrity and availability. Through the use of ionospheric estimators such as the TEC (Total Electron Content) fluctuations, I95 index and scintillation parameters (such as S4 and ??), observed positioning degradation has been correlated with ionospheric disturbances in order to characterise the impact. The ultimate objective is to quantify how residual errors remaining in both the double differenced and undifferenced GNSS observables are driven by ionospheric related phenomena. Two different scale GNSS networks have been used in this study. One is a large scale sparse network (Brazilian wide), which is a specialized ionospheric monitoring network, built by the CIGALA project (http://cigala.galileoic.org/); the other is a regional (state of São Paulo) network, which can provide case study data and also ground truth. The outcome of the above characterization study will be discussed in this paper. It will enable and facilitate the development of the mitigation algorithms, which include the screening of contaminated observations, observation de-weighting, enhanced network interpolation and ambiguity fixing strategy.

  1. Periodic and quiescent solar activity effects in the low ionosphere, using SAVNET data

    NASA Astrophysics Data System (ADS)

    Bertoni, F. C. P.; Raulin, J.-P.; Gavilan, H. R.; Kaufmann, P.; Raymundo, T. E.

    2010-10-01

    Important results have been acquired using the measurements of VLF amplitude and phase signals from the South America VLF Network (SAVNET) stations. This network is an international project coordinated by CRAAM, Brazil in cooperation with Peru and Argentina. It started operating in April 2006, and now counts on eight stations (Atibaia, Palmas, Santa Maria and Estaça~o Antártica Comandante Ferraz in Brazil; Piura, Punta-Lobos and Ica, in Peru; CASLEO, in Argentina). Researches, through the last decades, have demonstrated the versatility of the VLF technique for many scientific and technological purposes. In this work, we summarize some recent results using SAVNET data base. We have obtained daily maximum diurnal amplitude time series that exhibited behavior patterns in different time scales: 1) 1ong term variations indicating the solar activity level control of the low ionosphere; 2) characteristic periods of alternated slow and fast variations, the former being related to solar illumination conditions, and the latter that have been associated with the winter anomaly at high latitudes; 3) 27-days period related to the solar rotation and consequently associated to the solar Lyman-? radiation flux variations, reinforcing earlier theories about the importance of this spectral line for the D-region formation. Finally, we conclude presenting preliminary results of simulation using LWPC, which showed very good agreement at times of observed modal amplitude minima for a given VLF propagation path.

  2. Searching for Appropriate Data and Parameters for Effective Representation of Ionospheric Dynamics; Modelling and Observational Results over the African Sector

    NASA Astrophysics Data System (ADS)

    Habarulema, J. B.; Katamzi, Z. T.; McKinnell, L. A.; Tshimangadzo, M.

    2014-12-01

    We report on the ongoing efforts of modelling and characterising the ionospheric dynamics over the African sector. We have investigated the usage of a combination of data sources (GPS, ionosonde, radio occultation) along with other geophysical parameters such as magnetic and solar activities to generate realistic ionospheric behaviour for both scientific understanding and application purposes. However a number of outstanding questions remain such as capturing all storm phases, and accurate validation of some data sources. This is in addition to complicated electrodynamics over the African sector coupled with significant data-gaps that hinder the development of truly representative modelling approaches. Our ultimate aim is to develop a model that can be used for accurately representing the ionospheric behaviour and can be utilised as a space weather product for application purposes. In this presentation, the current modelling options under investigation for ionospheric modelling and mapping over the African sector will be discussed.

  3. Is Jupiter's ionosphere a significant plasma source for its magnetosphere?

    NASA Astrophysics Data System (ADS)

    Nagy, A. F.; Barakat, A. R.; Schunk, R. W.

    1986-01-01

    A semikinetic model was used to study the steady state, collisionless, polar wind outflow from the Jovian polar caps. H+ escape fluxes and energies were calculated for a range of conditions, including several values of the ambient electron temperature, different hot electron populations, and both with and without the effects of the centrifugal force. The calculations indicate that if hot electron populations exist over the Jovian polar caps, as they do on earth, polar wind escape fluxes of the order of 108cm-2s-1 are possible. When integrated over the polar cap area, escape fluxes of this order of magnitude imply an ionospheric source strength of 2×1028ions/s, which is comparable to the present estimate of the total magnetospheric plasma source population. Therefore, the ionosphere may play an important role in populating the Jovian magnetosphere, specifically the "hidden", low energy, light ion component of the population.

  4. Is Jupiter's ionosphere a significant plasma source for its magnetosphere?

    NASA Technical Reports Server (NTRS)

    Nagy, A. F.; Barakat, A. R.; Schunk, R. W.

    1986-01-01

    A semikinetic model was used to study the steady state, collisionless, polar wind outflow from the Jovian polar caps. H(+)-escape fluxes and energies were calculated for a range of conditions, including several values of the ambient electron temperature, different hot electron populations, and both with and without the effects of the centrifugal force. The calculations indicate that if hot electron populations exist over the Jovian polar caps, as they do on earth, polar wind escape fluxes of the order of 10 to the 8th per sq cm s are possible. When integrated over the polar cap area, escape fluxes of this order of magnitude imply an ionospheric source strength of 2 x 10 to the 28th ions/s, which is comparable to the present estimate of the total magnetospheric plasma source population. Therefore, the ionosphere may play an important role in populating the Jovian magnetosphere, specifically the hidden, low energy, light ion component of the population.

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

    Microsoft Academic Search

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

    2009-01-01

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

  6. 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.

  7. 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 (Dsteffect 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.

  8. 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.

  9. Arrival of a tongue of ionization in the nightside polar ionosphere and effects on GPS scintillation

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

    In this case study we present findings of Global Positioning System (GPS) scintillation in relation to the arriving front of a tongue of ionization in the nightside polar cap over Svalbard. We find almost no amplitude and some phase scintillation in relation to the leading density gradient, which is interpreted as "false" refractive scintillation due to suboptimal data detrending, as opposed to diffractive scintillation from decametre-to-kilometre-scale irregularities. During active geomagnetic conditions, high-density plasma may convect into and across the polar cap. The plasma may be segmented into F region polar cap patches upon entry in the cusp/cleft region, or it may form a continuous tongue of ionization when no such segmentation occurs. Large-scale ionospheric plasma structures such as polar cap patches may contain decametre- to kilometre-scale irregularities, particularly at the edges. Irregularities of these scale sizes cause problems for global navigation satellite system (GNSS) signals, causing amplitude and phase variations known as scintillations. A drawback of most high-latitude GNSS scintillation studies is the use of a 0.1 Hz detrending filter cutoff frequency, which in the literature has been shown to cause "false" phase scintillation. In the literature, much of the high-latitude scintillation research is statistically oriented and concerns polar cap patches. Scintillation directly in relation to ionization tongues is far less studied. We present findings of GPS scintillation in relation to the arriving front of a tongue of ionization on 31 October 2011 in the nightside polar cap over Svalbard, using GPS scintillation and total electron content (TEC) monitors, the EISCAT Svalbard Radar (ESR), and an optical all-sky airglow imager. To our knowledge, this is the first study presenting such detailed multi-instrument data of scintillation in the Svalbard region as well as taking into account the problems of a 0.1 Hz detrending cutoff filter.

  10. Three-dimensional current systems and ionospheric effects associated with small dipolarization fronts

    NASA Astrophysics Data System (ADS)

    Palin, L.; Jacquey, C.; Opgenoorth, H.; Connors, M.; Sergeev, V.; Sauvaud, J.-A.; Nakamura, R.; Reeves, G. D.; Singer, H. J.; Angelopoulos, V.; Turc, L.

    2015-05-01

    We present a case study of eight successive plasma sheet (PS) activations (usually referred to as bursty bulk flows or dipolarization fronts), associated with small individual BZGSM increases on 31 March 2009 (0200-0900 UT), observed by the Time History of Events and Macroscale Interactions During Substorms mission. This series of events happens during very quiet solar wind conditions, over a period of 7 h preceding a substorm onset at 1230 UT. The amplitude of the dipolarizations increases with time. The low-amplitude dipolarization fronts are associated with few (1 or 2) rapid flux transport events (RFT, Eh>2 mV/m), whereas the large-amplitude ones encompass many more RFT events. All PS activations are associated with small and localized substorm current wedge (SCW)-like current system signatures, which seems to be the consequence of RFT arrival in the near tail. The associated ground magnetic perturbations affect a larger part of the contracted auroral oval when, in the magnetotail, more RFT are embedded in PS activations (>5). Dipolarization fronts with very low amplitude, a type usually not included in statistical studies, are of particular interest because we found even those to be associated with clear small SCW-like current system and particle injections at geosynchronous orbit. This exceptional data set highlights the role of flow bursts in the magnetotail and leads to the conclusion that we may be observing the smallest form of a substorm or rather its smallest element. This study also highlights the gradual evolution of the ionospheric current disturbance as the plasma sheet is observed to heat up.

  11. Disturbances of the ionosphere of blast and acoustic waves generated at ionospheric heights by rockets

    NASA Astrophysics Data System (ADS)

    Drobzheva, Ya. V.; Krasnov, V. M.; Sokolova, O. I.

    2003-11-01

    In this paper we present a model, which describes the propagation of acoustic impulses produced by flight of rockets through a model terrestrial atmosphere, and effect of these impulses onto the ionosphere above a rocket. We show, that experimentally observed ionospheric disturbances with duration about 300s cannot be explained by effect of acoustic impulses onto the ionosphere. We have calculated parameters of a blast wave produced by launch vehicle on the ionospheric heights. It was shown that the blast wave is intense and this wave can generate great disturbance of electron density. The disturbance of electron density can exceed the ambient electron density in 2.6 times. We supposed that the observed ionospheric disturbances might be produced by propagation of delayed magnetoacoustic wave, which, in turn, was produced by the blast wave.

  12. Effects of a Parallel Electric Field and the Geomagnetic Field in the Topside Ionosphere on Auroral and Photoelectron Energy Distributions

    NASA Technical Reports Server (NTRS)

    Min, Q.-L.; Lummerzheim, D.; Rees, M. H.; Stamnes, K.

    1993-01-01

    The consequences of electric field acceleration and an inhomogencous magnetic field on auroral electron energy distributions in the topside ionosphere are investigated. The one- dimensional, steady state electron transport equation includes elastic and inelastic collisions, an inhomogencous magnetic field, and a field-aligned electric field. The case of a self-consistent polarization electric field is considered first. The self-consistent field is derived by solving the continuity equation for all ions of importance, including diffusion of 0(+) and H(+), and the electron and ion energy equations to derive the electron and ion temperatures. The system of coupled electron transport, continuity, and energy equations is solved numerically. Recognizing observations of parallel electric fields of larger magnitude than the baseline case of the polarization field, the effect of two model fields on the electron distribution function in investigated. In one case the field is increased from the polarization field magnitude at 300 km to a maximum at the upper boundary of 800 km, and in another case a uniform field is added to the polarization field. Substantial perturbations of the low energy portion of the electron flux are produced: an upward directed electric field accelerates the downward directed flux of low-energy secondary electrons and decelerates the upward directed component. Above about 400 km the inhomogencous magnetic field produces anisotropies in the angular distribution of the electron flux. The effects of the perturbed energy distributions on auroral spectral emission features are noted.

  13. Effects of a parallel electric field and the geomagnetic field in the topside ionosphere on auroral and photoelectron energy distributions

    NASA Technical Reports Server (NTRS)

    Min, Q.-L.; Lummerzheim, D.; Rees, M. H.; Stamnes, K.

    1993-01-01

    The consequences of electric field acceleration and an inhomogeneous magnetic field on auroral electron energy distributions in the topside ionosphere are investigated. The one-dimensional, steady state electron transport equation includes elastic and inelastic collisions, an inhomogeneous magnetic field, and a field-aligned electric field. The case of a self-consistent polarization electric field is considered first. The self-consistent field is derived by solving the continuity equation for all ions of importance, including diffusion of O(+) and H(+), and the electron and ion energy equations to derive the electron and ion temperatures. The system of coupled electron transport, continuity, and energy equations is solved numerically. Recognizing observations of parallel electric fields of larger magnitude than the baseline case of the polarization field, the effect of two model fields on the electron distribution function is investigated. In one case the field is increased from the polarization field magnitude at 300 km to a maximum at the upper boundary of 800 km, and in another case a uniform field is added to the polarization field. Substantial perturbations of the low energy portion of the electron flux are produced: an upward directed electric field accelerates the downward directed flux of low-energy secondary electrons and decelerates the upward directed component. Above about 400 km the inhomogeneous magnetic field produces anisotropies in the angular distribution of the electron flux. The effects of the perturbed energy distributions on auroral spectral emission features are noted.

  14. A New Ionosphere Tomography Algorithm with Two-Grids Virtual Observations Constraints and 3D Velocity Profile

    NASA Astrophysics Data System (ADS)

    Kong, Jian; Yao, Yibin; Shum, Che-Kwan

    2014-05-01

    Due to the sparsity of world's GNSS stations and limitations of projection angles, GNSS-based ionosphere tomography is a typical ill-posed problem. There are two main ways to solve this problem. Firstly the joint inversion method combining multi-source data is one of the effective ways. Secondly using a priori or reference ionosphere models, e.g., IRI or GIM models, as the constraints to improve the state of normal equation is another effective approach. The traditional way for adding constraints with virtual observations can only solve the problem of sparse stations but the virtual observations still lack horizontal grid constraints therefore unable to fundamentally improve the near-singularity characteristic of the normal equation. In this paper, we impose a priori constraints by increasing the virtual observations in n-dimensional space, which can greatly reduce the condition number of the normal equation. Then after the inversion region is gridded, we can form a stable structure among the grids with loose constraints. We then further consider that the ionosphere indeed changes within certain temporal scale, e.g., two hours. In order to establish a more sophisticated and realistic ionosphere model and obtain the real time ionosphere electron density velocity (IEDV) information, we introduce the grid electron density velocity parameters, which can be estimated with electron density parameters simultaneously. The velocity parameters not only can enhance the temporal resolution of the ionosphere model thereby reflecting more elaborate structure (short-term disturbances) under ionosphere disturbances status, but also provide a new way for the real-time detection and prediction of ionosphere 3D changes. We applied the new algorithm to the GNSS data collected in Europe for tomography inversion for ionosphere electron density and velocity at 2-hour resolutions, which are consistent throughout the whole day variation. We then validate the resulting tomography model using independent GNSS station data, and results using the conventional algorithm (Multiplicative Algebraic Reconstruction Techniques), as well as ionosphere ionosonde data in the study area. Key words Ionosphere Tomography, Grid Constraints, Virtual observations, 3D Ionosphere Velocity Image

  15. Presentation Order Effects in Product Taste Tests.

    ERIC Educational Resources Information Center

    Dean, Michael L.

    1980-01-01

    Presentation order in paired-comparison testing was varied to measure the impact of primacy v recency effects on consumer product evaluation. First position preference bias characterized the findings, lending support to the attention decrement hypothesis or a suggested palate desensitization effect on subsequent taste trial behavior. (Author)

  16. Production of Ionospheric Perturbations by Cloud-to-Ground Lightning and the Recovery of the Lower Ionosphere

    NASA Astrophysics Data System (ADS)

    Liu, Ningyu; Dwyer, Joseph; Rassoul, Hamid

    2013-04-01

    The fact that lightning/thunderstorm activities can directly modify the lower ionosphere has long been established by observations of the perturbations of very low frequency (VLF) signals propagating in the earth-ionosphere waveguide. These perturbations are known as early VLF events [Inan et al., 2010, JGR, 115, A00E36, 2010]. More recently discovered transient luminous events caused by the lightning/thunderstorm activities only last ~1-100 ms, but studies of the early VLF events show that the lightning ionospheric effects can persist much longer, >10s min [Cotts and Inan, GRL, 34, L14809, 2007; Haldoupis et al., JGR, 39, L16801, 2012; Salut et al., JGR, 117, A08311, 2012]. It has been suggested that the long recovery is caused by long-lasting conductivity perturbations in the lower ionosphere, which can be created by sprites/sprite halos which in turn are triggered by cloud-to-ground (CG) lightning [Moore et al., JGR, 108, 1363, 2003; Haldoupis et al., 2012]. We recently developed a two-dimensional fluid model with simplified ionospheric chemistry for studying the quasi-electrostatic effects of lightning in the lower ionosphere [Liu, JGR, 117, A03308, 2012]. The model chemistry captures major ion species and reactions in the lower ionosphere. Additional important features of the model include self-consistent background ion density profiles and full description of electron and ion transport. In this talk, we present the simulation results on the dynamics of sprite halos caused by negative CG lightning. The modeling results indicate that electron density around 60 km altitude can be enhanced in a region as wide as 80 km. The enhancement reaches its full extent in ~1 s and recovers in 1-10 s, which are on the same orders as the durations of slow onset and post-onset peaks of some VLF events, respectively. In addition, long-lasting electron and ion density perturbations can occur around 80 km altitude due to negative halos as well as positive halos, which can explain long-recovery VLF events and step-change VLF events.

  17. Geomagnetic storm effects on the thermosphere and the ionosphere revealed by in situ measurements from OGO 6

    NASA Technical Reports Server (NTRS)

    Marubashi, K.; Reber, C. A.; Taylor, H. A., Jr.

    1976-01-01

    The temporal response of the densities of upper-atmospheric ion and neutral constituents to a particular geomagnetic storm is studied using simultaneous ion and neutral-composition data obtained by the OGO 6 satellite during consecutive orbits at altitudes greater than 400 km. The investigated constituents include H(+), O(+), N2, O, He, and H. Derivation of the H density is reviewed, and the main effects of the storm are discussed, particularly temporal and global variations in the densities. It is found that: (1) the H and He densities began to decrease near the time of sudden commencement, with the decrease amounting to more than 40% of the quiet-time densities during the maximum stage at high latitudes; (2) the O and N2 densities exhibited an overall increase which began later than the change in H and He densities; (3) the H(+) density decreased differently in two distinct regions separated near the low-latitude boundary of the light-ion trough; and (4) the O(+) density showed an increase during earlier stages of the storm and decreased only in the Northern Hemisphere during the recovery phase. Certain physical and chemical processes are suggested which play principal roles in the ionospheric response to the storm

  18. Low Latitude Ionosphere Measurements by the Global-scale Observations of the Limb and Disk (GOLD) Mission

    NASA Astrophysics Data System (ADS)

    Eastes, R. W.; Anderson, D. N.; McClintock, W. E.; Aksnes, A.; Andersson, L.; Burns, A. G.; Budzien, S. A.; Codrescu, M. V.; Daniell, R. E.; Dymond, K. F.; England, S. L.; Eparvier, F. J.; Harvey, J. E.; Immel, T. J.; Krywonos, A.; Lankton, M. R.; Lumpe, J. D.; Richmond, A. D.; Rusch, D. W.; Siegmund, O. H.; Solomon, S. C.; Strickland, D. J.; Woods, T. N.

    2008-12-01

    The GOLD Mission of Opportunity will provide answers to key elements of an overarching question for Heliophysics science: what is the global-scale response of the thermosphere and ionosphere to forcing in the integrated Sun-Earth system? GOLD will perform remote-sensing measurements of the Earth's thermosphere and ionosphere, using an ultraviolet imager on board a commercial, geosynchronous satellite. The resulting measurements of the electron densities in the nighttime ionosphere as well as the neutral composition and temperature in the thermosphere, when combined with current modeling capabilities, will advance our understanding of Thermosphere-Ionosphere (T-I) forcing. GOLD will provide the first global- scale "snapshot" of temperature that can be compared with the coincident "snapshot" of composition changes to understand how these two major parameters simultaneously react to the various forcing mechanisms. GOLD will continue observing the same longitudes from the daytime into the night allowing the relationship between presunset conditions in the T-I system and the longitudinal dependence of variations in the ionosphere to be separated. One question that GOLD will address is: do vertical ion drifts, as manifested in the structure of the equatorial anomaly, affect the occurrence of ionospheric irregularities? Solar and geomagnetic forcing produces variations in the structure of the equatorial ionosphere at night (equatorial anomaly) and the occurrence of irregularities within the ionosphere. These ionospheric density variations, with scale sizes ranging from hundreds to tens of km, have profound effects on systems using radio frequencies. Irregularities at low latitudes are produced in the post-sunset ionosphere by the Rayleigh-Taylor (R-T) instability. The growth of these R-T instabilities into large-scale plasma bubbles has an optical signature and is the greatest source of ionospheric irregularities at low latitudes. Simulations of GOLD observations indicate that bubbles on the order of 25 km will be observable. At low latitudes, our understanding is currently based on relatively limited geographic coverage, and even that understanding is not well connected to the global-scale variations/changes. In particular, the longitude dependence of the pre-reversal enhancement in upward E×B drift velocity, which initiates the R-T instability mechanism, is poorly known. The relationships between these vertical E×B drifts, as manifested in the structure of the equatorial anomaly, and the occurrence of ionospheric irregularities will be established using observations from GOLD.

  19. Frequency characteristics of the action of powerful radio-frequency radiation on the ionospheric F layer

    SciTech Connect

    Erukhimov, L.M.; Ivanov, V.A.; Mityakov, N.A.; Uryadov, V.P.; Frolov, V.A.; Shumaev, V.V.

    1988-03-01

    The results of an investigation of the effect of artificial ionospheric nonuniformities on the characteristics of LFM signals with vertical and oblique sounding of the ionosphere are presented. A classification of the effects observed on ionograms from vertical and oblique-sounding LFM ionosonde, owing to the effect of artificial nonuniformities of different scale, is given. It was found that powerful beams of radio waves have a characteristic effect on the ionospheric plasma under conditions when moving ionospheric disturbances appear.

  20. Characterisation of the Ionosphere over the Murchison Radio Observatory, Murchison, Western Australia

    NASA Astrophysics Data System (ADS)

    Herne, D. E.

    2009-12-01

    The Murchison Radio Observatory (MRO) is the future home of radio astronomy in Australia. Projects are currently under development at the MRO, including a low-frequency instrument, the Murchison Widefield Array (MWA). The MWA is an aperture synthesis, imaging array that when complete will comprise approximately 8,000 dipole antennas, operating in the frequency range, 80 to 300 MHz. Signals in the frequency range of interest reaching the MWA are subject to distortions caused by the ionosphere. The effects of scintillation and Faraday rotation degrade image quality. Self-calibration techniques compensate for scintillation and in the process, provide accurate relative total electron content (TEC) measures of the ionosphere (milli-TEC). However, to ‘unwind’ Faraday rotation effects, the absolute TEC (aTEC) of the ionosphere must be determined. This step is necessary in order to study processes in space involving magnetism. Over a period of two years, absolute TEC measurements have been made over the MRO using high-precision, dual-frequency GPS systems. Continuous measurements have been performed over the past year and campaign-based measurements prior to that. This paper presents results from those studies, which are providing insights into the nature of the ionosphere over a previously poorly understood, mid-latitude region of the southern hemisphere. This work too, is laying a foundation for the accurate characterisation of the ionosphere over the MRO which is also the possible future site of the Square Kilometre Array (SKA).

  1. Modeling the global positioning system signal propagation through the ionosphere

    NASA Technical Reports Server (NTRS)

    Bassiri, S.; Hajj, G. A.

    1992-01-01

    Based on realistic modeling of the electron density of the ionosphere and using a dipole moment approximation for the Earth's magnetic field, one is able to estimate the effect of the ionosphere on the Global Positioning System (GPS) signal for a ground user. The lowest order effect, which is on the order of 0.1-100 m of group delay, is subtracted out by forming a linear combination of the dual frequencies of the GPS signal. One is left with second- and third-order effects that are estimated typically to be approximately 0-2 cm and approximately 0-2 mm at zenith, respectively, depending on the geographical location, the time of day, the time of year, the solar cycle, and the relative geometry of the magnetic field and the line of sight. Given the total electron content along a line of sight, the authors derive an approximation to the second-order term which is accurate to approximately 90 percent within the magnetic dipole moment model; this approximation can be used to reduce the second-order term to the millimeter level, thus potentially improving precise positioning in space and on the ground. The induced group delay, or phase advance, due to second- and third-order effects is examined for two ground receivers located at equatorial and mid-latitude regions tracking several GPS satellites.

  2. Space weather. Ionospheric control of magnetotail reconnection.

    PubMed

    Lotko, William; Smith, Ryan H; Zhang, Binzheng; Ouellette, Jeremy E; Brambles, Oliver J; Lyon, John G

    2014-07-11

    Observed distributions of high-speed plasma flows at distances of 10 to 30 Earth radii (R(E)) in Earth's magnetotail neutral sheet are highly skewed toward the premidnight sector. The flows are a product of the magnetic reconnection process that converts magnetic energy stored in the magnetotail into plasma kinetic and thermal energy. We show, using global numerical simulations, that the electrodynamic interaction between Earth's magnetosphere and ionosphere produces an asymmetry consistent with observed distributions in nightside reconnection and plasmasheet flows and in accompanying ionospheric convection. The primary causal agent is the meridional gradient in the ionospheric Hall conductance which, through the Cowling effect, regulates the distribution of electrical currents flowing within and between the ionosphere and magnetotail. PMID:25013068

  3. Statistical study of Subauroral Polarization Streams (SAPS): Solar wind, ionospheric control and its effect on the thermosphere

    NASA Astrophysics Data System (ADS)

    Wang, H.; Luhr, H.; Ridley, A. J.; Ma, S.

    2011-12-01

    The effects of cross-polar cap potential (CPCP) and subauroral flux tube-integrated conductivity on the spatial distribution of Subauroral Polarization Streams (SAPS) have been investigated by using DMSP observations. For higher flux tube-integrated conductivity the SAPS tend to occur more poleward than for lower conductivity. The CPCP averaged over 15 min prior to the SAPS correlates best with the SAPS peak velocities. The high-latitude CPCP has a stronger effect on SAPS velocities for low integrated conductivity than for high conductivity. With coordinated CHAMP and DMSP observations we have further investigated the relationship between SAPS, ionospheric Hall current (electrojet), upper thermospheric zonal wind, and mass density at subauroral regions in the dusk and premidnight sectors. For comparison, we have also analyzed the same parameters as a function of magnetic latitude (30°-80° magnetic latitude) during nonSAPS periods. Both neutral and plasma velocities peak at the same latitude regardless of SAPS occurrence. The neutral wind during SAPS events gets enhanced by a factor of 1.5/1.2 for Kp<4 and 1.3/1.9 for Kp?4 in the Northern/Southern Hemisphere, respectively, as compared to nonSAPS time. The velocity difference between plasma drift and neutral wind is also larger during SAPS period than during nonSAPS period, and the difference tends to increase with increasing geomagnetic activity. The peak latitude of the eastward auroral electrojet appears 1.5° poleward of SAPS during SAPS events, confirming the formation of SAPS equatorward of the high conductivity channel. The upper thermosphere is heated during SAPS periods. As a result we observe a 10% enhanced mass density at 400 km altitude with respect to periods without SAPS. In addition a density anomaly peak occurs collocated with the SAPS, displaced from the electrojet peak. We regard this as an indication for efficient thermospheric heating by ion neutral friction.

  4. Relations between proton auroras, intense electric field, and ionospheric electron density depletion

    Microsoft Academic Search

    R. Fujii; Y. Iwata; S. Oyama; S. Nozawa; Y. Ogawa

    2009-01-01

    A case study with simultaneous European Incoherent Scatter and optical auroral observations was conducted in order to determine characteristics of the magnetosphere-ionosphere coupling from the viewpoint of the electrodynamics in the ionosphere. Particularly focused on were the relationships between ionospheric electron density depletion, perpendicular electric fields, and proton auroras. Intense electron density depletion was observed in the E and F

  5. Ionospheric corrections via PIM and real-time data

    NASA Astrophysics Data System (ADS)

    Campbell, R. M.

    1999-11-01

    We describe a method for removing ionospheric effects from single-frequency radio data a posteriori. This method is based on a theoretical climatological model developed by the USAF, which returns n e( r,t) along the line of sight to the source. Together with a model of B?, ionospheric delay and Faraday rotation values ensue. If contemporaneous ionospheric data - GPS TEC observations or ionosonde profiles - exist, they can be incorporated to update the modeled ne.

  6. Characterizing lower ionosphere forcing by a strong lightning stroke using VLF/LF radio wave remote sensing and propagation modeling

    NASA Astrophysics Data System (ADS)

    Schmitter, E. D.

    2013-09-01

    The direct and indirect effects of lightning strokes on the lower ionosphere seen with VLF signal propagation with regard to the generation of Trimpis are well known, e.g. [5]. Additionally to these events with recovery times of the order of seconds disturbance events with long recovery times of the order of minutes to half an hour are observed and related to direct lightning EMP heating of the lower ionosphere [2]. This work discusses remote sensing and modeling of such an event (4th of Nov. 2012, 3:04:27 UT, North Sea) allowing to characterize the disturbance conditions with regard to time development and space extension.

  7. Ionospheric responses to the October 2003 superstorm: Longitude\\/local time effects over equatorial low and middle latitudes

    Microsoft Academic Search

    Mangalathayil A. Abdu; Takashi Maruyama; Inez S. Batista; Susumo Saito; Maho Nakamura

    2007-01-01

    Ionospheric responses to the major magnetic storm disturbances of October 2003 are investigated using database selected in the Brazilian and Japanese-Asian longitude sectors. Data obtained from latitudinally spaced digisondes in the equatorial and low-latitude sites in Brazil and from the Asian and Japanese ionosonde network, the total electron content data from the extensive Japanese GPS receiver chain, and magnetometer data

  8. Observations of Pc5 Alfven wave effects in the quiet time auroral ionosphere: Indications of energetic particle acceleration

    Microsoft Academic Search

    J.-E. Wahlund; H. J. Opgenoorth; A. I. Eriksson; Maths A. L. Persson; I. Haeggstroem

    1991-01-01

    EISCAT observations of periodic variations in the perpendicular electric field, topside ionospheric electron temperature, and weak E region ionization with a period beween 3 to 4 mHz are presented. The six hour long event occurred during quiet auroral conditions with a moderately strong F layer and almost absent E layer. The weak E region pulsations in electron density were well

  9. Ionospheric Effects of Sudden Stratospheric Warming During Moderate-to-High Solar Activity: Case Study of January 2013

    NASA Astrophysics Data System (ADS)

    Goncharenko, L. P.; Chau, J. L.; Condor Patilongo, P. J.; Coster, A. J.; Benkevitch, L. V.

    2013-12-01

    A major and long-lasting sudden stratospheric warming occurred in January 2013 during moderate-to-high solar activity conditions. Analysis of experimental observations of ionospheric parameters during the winter of 2012/13 reveals strong ionospheric disturbances associated with this event. Anomalous variations in vertical ion drift measured at the geomagnetic equator at Jicamarca (12S, 75W) are observed for over 40 days from mid-December 2012 to the end of January 2013. We report strong perturbations in the total electron content (TEC) obtained with global network of GPS receivers. These perturbations maximize in the crests of equatorial ionization anomaly, reach 100% of the background TEC value, exhibit significant longitudinal and hemispheric asymmetry, and last for over 40 days. The magnitude of ionospheric anomalies in both vertical drifts and TEC during the January 2013 SSW is comparable to the anomalies observed during the record-strong SSW of January 2009 that coincided with extreme solar minimum. This observation contrasts with results of numerical simulations that predict a weaker ionospheric response to the tidal forcing during high solar activity due to the higher F-region Pedersen conductivity. The temporal behavior of anomalous variations in both vertical drift and TEC is consistent with the phase change of lunar semidiurnal tide and could result from the superposition of amplified solar and lunar tides.

  10. Effects of solar wind dynamic pressure on the ionospheric O+ fluence during the 31 August 2005 storm

    Microsoft Academic Search

    P. A. Damiano; O. J. Brambles; W. Lotko; B. Zhang; M. Wiltberger; J. Lyon

    2010-01-01

    The Multifluid-Lyon-Fedder-Mobarry (MFLFM) global simulation model incorporating an ionospheric cusp O+ outflow model based on an empirical relation between downward DC Poynting flux and O+ outflow flux regulated by the precipitating electron number flux (Fen) is used to simulate the 31 August 2005 storm. A baseline run incorporating the original solar wind data is contrasted against a case where the

  11. Atmospheric winds between 100 and 700 km and their effects on the ionosphere

    Microsoft Academic Search

    H. Kohl; J. W. King

    1967-01-01

    The global wind system produced at different local times by pressure gradients in the upper atmosphere is calculated using data from Jacchia's model atmosphere. The horizontal wind velocities vary with height, and are of the order of 100 m sec-1 at about 300 km; they depend on ion drag, viscosity and Coriolis forces, but the major importance of ion drag

  12. Model of Jovian F region ionosphere (Saturnian ionosphere in offset dipole approximation)

    NASA Technical Reports Server (NTRS)

    Tan, A.

    1991-01-01

    Researchers investigated the offset effect of Saturn's dipole on its ionosphere. The magnetic field of Saturn is primarily that of a dipole closely aligned to the rotational axis, but displaced northward from the center by a distance approximately equal to 0.05 R sub S, R sub S being the reference radius of Saturn. This offset effect would manifest itself most prominently between the ionospheric profiles in the Northern and Southern Hemispheres of Saturn.

  13. The great magnetic storms of October 29-30, 2003 and their ionospheric effects observed at the equatorial ionization anomaly region

    Microsoft Academic Search

    S. Saroso; J. Y. Liu; C. H. Chen; M. Asnawi

    2006-01-01

    The solar winds ejected from the coronal holes or the coronal mass ejection CME during solar flares form magnetic clouds and high speed streams which may hit magnetosphere and ionosphere of the Earth and induce many complex phenomena including geomagnetic storms The huge injected energy accompanied with the geomagnetic storms will result in thermospheric and ionospheric storms The ionosphere during

  14. Comparative analysis of the effect of ionospheric delay on user position accuracy using single and dual frequency GPS receivers over Indian region

    Microsoft Academic Search

    Ashish K Shukla; Priya Shinghal; M R Sivaraman; K Bandyopadhyay

    The ionosphere acts as a prominent source of range errors for users of Global Positioning System (GPS) satellite signals requiring accurate position determination. Various models and mathematical formulations have been devised to calculate the absolute range error caused due to ionospheric delay. The present study aims at comparing two methods for calculating delay due to ionosphere: (i) using grid based

  15. Statistical analysis of ionosphere parameters and atmospheric pressure correlations

    NASA Astrophysics Data System (ADS)

    Voloskov, Dmitriy; Bochkarev, Vladimir; Maslennikova, Yulia; Zagidullin, Bulat

    Ionosphere parameters such as Total electron content (TEC) and Doppler frequency shift characterize ionosphere influence on signals propagation, and therefore information about these parameters is important for radio communication tasks. Meteorological effects such as atmospheric pressure variations can influence on ionosphere parameters. This work is dedicated to analysis of correlations between meteorological and ionosphere parameters. NCEP/NCAR reanalysis meteorological maps, Jet Propulsion Laboratory (JPL) global TEC maps and data from Doppler phase goniometric complex “Spectr” were analysed. Data for 2009-2011 were investigated. Coherent oscillations with periods of 29-32 and 4 days were detected in atmospheric pressure and Doppler frequency shift variations.

  16. Estimating Ionosphere Conductance on Global Spatial Scales

    NASA Astrophysics Data System (ADS)

    Waters, C. L.; Anderson, B. J.; Green, D. L.; Korth, H.

    2014-12-01

    The ionosphere represents the Earthward boundary of space. For large scale processes, the height integrated conductivities (conductances) of the ionosphere are known to modulate the energy transfer between the magnetosphere and ionosphere. Estimating the Pedersen and Hall conductances on a global scale, particularly in the auroral regions, is fundamental to understanding the dynamics of the high latitude ionosphere and thermosphere. Experimental measurements with sufficient spatial coverage and with time scales of order of minutes or less are required. While the spatial coverage of HF radar and spacecraft measurements has recently improved, it turns out that the most challenging aspects for global estimates of ionosphere conductance are directly related to ground-based magnetometer data. The Iridium satellite constellation consists of more than 70 satellites in circular, polar, 780 km altitude orbits which provides a unique opportunity to obtain in-situ measurements of the global distribution of the Birkeland currents and associated magnetic field perturbations. In this paper, examples and challenges for combining the Iridium satellite, HF radar and ground magnetometer data in order to produce estimates of the Pedersen and Hall conductances on global spatial scales will be presented. We discuss limiting factors in the methodology and some possible alternatives.

  17. Role of Ionospheric Plasmas in Earth's Magnetotail

    NASA Technical Reports Server (NTRS)

    Moore, Thomas E.

    2007-01-01

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

  18. On the convergence of ionospheric constrained precise point positioning (IC-PPP) based on undifferential uncombined raw GNSS observations.

    PubMed

    Zhang, Hongping; Gao, Zhouzheng; Ge, Maorong; Niu, Xiaoji; Huang, Ling; Tu, Rui; Li, Xingxing

    2013-01-01

    Precise Point Positioning (PPP) has become a very hot topic in GNSS research and applications. However, it usually takes about several tens of minutes in order to obtain positions with better than 10 cm accuracy. This prevents PPP from being widely used in real-time kinematic positioning services, therefore, a large effort has been made to tackle the convergence problem. One of the recent approaches is the ionospheric delay constrained precise point positioning (IC-PPP) that uses the spatial and temporal characteristics of ionospheric delays and also delays from an a priori model. In this paper, the impact of the quality of ionospheric models on the convergence of IC-PPP is evaluated using the IGS global ionospheric map (GIM) updated every two hours and a regional satellite-specific correction model. Furthermore, the effect of the receiver differential code bias (DCB) is investigated by comparing the convergence time for IC-PPP with and without estimation of the DCB parameter. From the result of processing a large amount of data, on the one hand, the quality of the a priori ionosphere delays plays a very important role in IC-PPP convergence. Generally, regional dense GNSS networks can provide more precise ionosphere delays than GIM and can consequently reduce the convergence time. On the other hand, ignoring the receiver DCB may considerably extend its convergence, and the larger the DCB, the longer the convergence time. Estimating receiver DCB in IC-PPP is a proper way to overcome this problem. Therefore, current IC-PPP should be enhanced by estimating receiver DCB and employing regional satellite-specific ionospheric correction models in order to speed up its convergence for more practical applications. PMID:24253190

  19. LAAS Ionosphere Spatial Gradient Threat Model and Impact of LGF and Airborne Monitoring

    E-print Network

    Stanford University

    LAAS Ionosphere Spatial Gradient Threat Model and Impact of LGF and Airborne Monitoring Ming Luo The ionosphere spatial gradient and its temporal rate of change in the vicinity of a LAAS-equipped airport requirements. An initial parametric analysis depicts the effects of ionosphere anomalies on the position error

  20. Electric field and ion density anomalies in the mid latitude ionosphere: possible connection with earthquakes?

    Microsoft Academic Search

    M. Gousheva; R. Glavcheva; D. Danov; P. Hristov; P. Angelov; B. Kirov; K. Georgieva

    2006-01-01

    The problem of earthquake prediction has stimulated the search for a correlation between seismic activity and ionospheric anomalies We found observational evidence of possible earthquake effects in the near-equatorial and low latitude ionosphere these ionospheric anomalies have been proposed by Gousheva et al 2005 2006 This paper presents new results from observations of the quasi-static electric field and ion density

  1. Electric field and ion density anomalies in the mid latitude ionosphere: Possible connection with earthquakes?

    Microsoft Academic Search

    M. N. Gousheva; R. P. Glavcheva; D. L. Danov; P. L. Hristov; B. B. Kirov; K. Y. Georgieva

    2008-01-01

    The problem of earthquake prediction has stimulated the search for a correlation between seismic activity and ionospherical anomalies. We found observational evidence of possible earthquake effects in the near-equatorial and low latitude ionosphere; these ionospheric anomalies have been proposed by Gousheva et al. [Gousheva, M., Glavcheva, R., Danov, D., Angelov P., Hristov, P., Influence of earthquakes on the electric field

  2. Ionospheric Total Electron Content Response to the December 26, 2004 North Sumatra Earthquake

    Microsoft Academic Search

    M. Abdullah; A. F. M. Zain; M. H. Jusoh; N. Misran; W. A. Mubarak

    2009-01-01

    Problem statement: Ionospheric precursors of earthquake have been studied by scientists and seismologists. This study aims at examining the relationship between the ionosphere and earthquake precursors. The effects of the anomalous electric field that penetrates the ionosphere on the electron concentration can be measured experimentally. This study reports on the variability of the Total Electron Content (TEC) during the December

  3. 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.

  4. Global Ionosphere Radio Observatory

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  5. 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-?.

  6. Effects of chemical releases by the STS-3 Orbiter on the ionosphere

    NASA Technical Reports Server (NTRS)

    Pickett, J. S.; Murphy, G. B.; Kurth, W. S.; Goertz, C. K.; Shawhan, S. D.

    1983-01-01

    The Plasma Diagnostics Package, flown aboard STS-3 as part of the first Shuttle payload (OSS-1), recorded the effects of various chemical releases from the Orbiter. Changes in the plasma environment was observed during flash evaporator system releases, water dumps and maneuvering thruster operations. During flash evaporator operations, broadband Orbiter-generated electrostatic noise was enhanced and plasma density irregularities were observed to increase by 3 to 30 times with a spectrum which rose steeply and peaked below 6 Hz. In the case of water dumps, background electrostatic noise was enhanced at frequencies below about 3 kHz and suppressed at frequencies above 2 kHz. Thruster activity also stimulated electrostatic noise with a spectrum which peaked at approximately 0.5 kHz. In addition, ions with energies up to 1 keV were seen during some thruster events.

  7. Effects of solar and geomagnetic activities on the sub-ionospheric very low frequency transmitter signals received by the DEMETER micro-satellite

    NASA Astrophysics Data System (ADS)

    Boudjada, Mohammed Yahia; Schwingenschuh, Konrad; Al-Haddad, Emad; Parrot, Michel; Galopeau, Patrick H. M.; Besser, Bruno; Stangl, Guenter; Voller, Wolfgang

    2012-04-01

    In the framework of seismic precursor electromagnetic investigations, we analyzed the very low frequency (VLF) amplitude signals recorded by the Instrument Champ Electrique (ICE) experiment on board the DEMETER micro-satellite. The sun-synchronous orbits of the micro-satellite allowed us to cover an invariant latitude of between -65° and +65° in a time interval of about 40 min. We considered four transmitter signals emitted by stations in Europe (France, FTU, 18.3 kHz; Germany, DFY, 16.58 kHz),Asia (Japan, JP, 17.8 kHz) and Australia (Australia, NWC, 19.8 kHz). We studied the variations of these VLF signals, taking into consideration: the signal-to-noise ratio, sunspots, and the geomagnetic activity. We show that the degree of correlation in periods of high geomagnetic and solar activities is, on average, about 40%. Such effects can be fully neglected in the period of weak activity. We also find that the solar activity can have a more important effect on the VLF transmitter signal than the geomagnetic activity. Our data are combined with models where the coupling between the lithosphere, atmosphere and ionosphere is essential to explain how ionospheric disturbances scatter the VLF transmitter signal.

  8. Ionospheric profiles from dayside UV limb scans

    NASA Astrophysics Data System (ADS)

    Coker, C.; Dymond, K. F.; Bennert, E. E.; Thonnard, S. E.; McDonald, S. E.; Nicholas, A. C.; Budzien, S. A.; McCoy, R. P.

    2004-05-01

    With the launch of the first Special Sensor for Ultraviolet Limb Imaging (SSULI) on the Defense Meteorological Satellite Program (DMSP), ionospheric electron density retrievals from ultraviolet limb scans are receiving much attention as part of the calibration and validation effort. This study evaluates the performance of dayside electron density retrieval algorithms, which use the 91.1-nm emissions observed on the Low Resolution Airglow and Auroral Spectrograph (LORAAS), a similar ultraviolet limb imager. Specifically, the dayside electron density profiles produced by two research algorithms are integrated to produce vertical total electron content (TEC) and compared with radar altimetry observations of TEC from coincident TOPEX satellite passes. These comparisons show the accuracy of the algorithms for reproducing TEC, the location of the Appelton anomaly peaks and their latitudinal extent. Inaccuracies in the comparisons help illuminate deficiencies, which lead to improvements in the algorithms. Additionally, the UV limb data and radar altimetry data are combined in order to reconstruct a high-resolution ionospheric specification. The limb scans provide vertical resolution in the ionosphere and the altimetry data provides horizontal resolution. When combined a 2D reconstruction of the ionosphere is obtained over a large geographic region with high spatial resolution. Comparisons of the electron density generated from this method with the UV-only algorithms also help to demonstrate to utility of the 91.1-nm algorithms for specifying the equatorial ionosphere.

  9. Solar wind effect on Joule heating in the high-latitude ionosphere

    NASA Astrophysics Data System (ADS)

    Cai, L.; Aikio, A. T.; Nygrén, T.

    2014-12-01

    The effect of solar wind on several electrodynamic parameters, measured simultaneously by the European Incoherent Scatter (EISCAT) radars in Tromsø (TRO, 66.6° cgmLat) and on Svalbard (ESR, 75.4° cgmLat), has been evaluated statistically. The main emphasis is on Joule heating rate QJ, which has been estimated by taking into account the neutral wind. In addition, a generally used proxy QE, which is the Pedersen conductance times the electric field squared, has been calculated. The most important findings are as follows. (i) The decrease in Joule heating in the afternoon-evening sector due to winds reported by Aikio et al. (2012) requires southward interplanetary magnetic field (IMF) conditions and a sufficiently high solar wind electric field. The increase in the morning sector takes place for all IMF directions within a region where the upper E neutral wind has a large equatorward component and the F region plasma flow is directed eastward. (ii) At ESR, an afternoon hot spot of Joule heating centered typically at 14-15 magnetic local time (MLT) is observed during all IMF conditions. Enhanced Pedersen conductances within the hot spot region are observed only for the IMF Bz + /By- conditions, and the corresponding convection electric field values within the hot spot are smaller than during the other IMF conditions. Hence, the hot spot represents a region of persistent magnetospheric electromagnetic energy input, and the median value is about 3 mW/m2. (iii) For the southward IMF conditions, the MLT-integrated QE for By- is twice the value for By+ at TRO. This can plausibly be explained by the higher average solar wind electric field values for By-.

  10. The netlander ionosphere and geodesy experiment

    Microsoft Academic Search

    J.-P. Barriot; V. Dehant; W. Folkner; J.-C. Cerisier; A. Ribes; J. Benoist; T. Van Hoolst; P. Defraigne; R. Warnant; R. A. Preston; L. Romans; S. Wu; A. W. Wernik

    2001-01-01

    The NEtlander Ionosphere and Geodesy Experiment (NEIGE) of the Netlander Mission to Mars has two series of scientific objectives: (1) to determine Mars orientation parameters in order to obtain information about the interior of Mars and about the seasonal mass exchange between atmosphere and ice caps; and (2) to determine the total electron content (TEC) and the scintillation of radio

  11. Photolysis of methane and the ionosphere of Uranus

    NASA Technical Reports Server (NTRS)

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

    1983-01-01

    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 5,000 per cu cm, if dynamical effects are important. Upper limit to the electron peak is 30,000 per cu cm. Exospheric temperatures as high as 200-250K are conceivable.

  12. IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING, VOL. 52, NO. 6, JUNE 2014 3421 Joint Correction of Ionosphere Noise and Orbital

    E-print Network

    Fialko, Yuri

    of Ionosphere Noise and Orbital Error in L-Band SAR Interferometry of Interseismic Deformation in Southern studies is largely compromised by ionosphere path delays on the radar signals. The ionosphere effects cause severe ionospheric distortion such as azimuth streaking and long wavelength phase distortion

  13. Ionosphere/microwave beam interaction study. [satellite solar energy conversion

    NASA Technical Reports Server (NTRS)

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

    1977-01-01

    A solar power satellite microwave power density of 20mw sq cm was confirmed as the level where nonlinear interactions may occur in the ionosphere, particularly at 100 km altitude. Radio wave heating at this altitude, produced at the Arecibo Observatory, yielded negative results for radio wave heating of an underdense ionosphere. Overdense heating produced striations in the ionosphere which may cause severe radio frequency interference problems under certain conditions. The effects of thermal self-focusing are shown to be limited severely geographically. The aspect sensitivity of field-aligned striations makes interference-free regions above magnetic latitude about 60 deg. A test program is proposed to simulate the interaction of the SPS beam with the ionosphere, to measure the effects of the interaction on the ionosphere and on communication and navigation systems, and to interpret the results.

  14. 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.

  15. The effects of seasonal and diurnal variations in the Earth's magnetic dipole orientation on solar wind-magnetosphere-ionosphere coupling

    NASA Astrophysics Data System (ADS)

    Cnossen, Ingrid; Wiltberger, Michael; Ouellette, Jeremy E.

    2012-11-01

    The angle ? between the geomagnetic dipole axis and the geocentric solar magnetospheric (GSM) z axis, sometimes called the “dipole tilt,” varies as a function of UT and season. Observations have shown that the cross-polar cap potential tends to maximize near the equinoxes, when on average ? = 0, with smaller values observed near the solstices. This is similar to the well-known semiannual variation in geomagnetic activity. We use numerical model simulations to investigate the role of two possible mechanisms that may be responsible for the influence of ? on the magnetosphere-ionosphere system: variations in the coupling efficiency between the solar wind and the magnetosphere and variations in the ionospheric conductance over the polar caps. Under southward interplanetary magnetic field (IMF) conditions, variations in ionospheric conductance at high magnetic latitudes are responsible for 10-30% of the variations in the cross-polar cap potential associated with ?, but variations in solar wind-magnetosphere coupling are more important and responsible for 70-90%. Variations in viscous processes contribute slightly to this, but variations in the reconnection rate with ? are the dominant cause. The variation in the reconnection rate is primarily the result of a variation in the length of the section of the separator line along which relatively strong reconnection occurs. Changes in solar wind-magnetosphere coupling also affect the field-aligned currents, but these are influenced as well by variations in the conductance associated with variations in ?, more so than the cross-polar cap potential. This may be the case for geomagnetic activity too.

  16. Characteristics of High Latitude Ionosphere Scintillations

    NASA Astrophysics Data System (ADS)

    Morton, Y.

    2012-12-01

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

  17. 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.

  18. Self-organization of internal gravity wave structures in an inhomogeneous ionosphere: 1. Nonlinear model dynamic equations

    NASA Astrophysics Data System (ADS)

    Aburjania, G. D.; Kharshiladze, O. A.; Chargazia, Kh. Z.

    2013-09-01

    A corresponding model system of nonlinear dynamic equations for the lower ionosphere has been constructed in order to study the generation and further nonlinear dynamics of internal gravity wave (IGW) structures in a dissipative ionosphere in the presence of a nonuniform zonal wind (shear flow). The criterion for the development of the IGW shear instability in the ionosphere has been obtained.

  19. International Reference Ionosphere 2010

    NASA Astrophysics Data System (ADS)

    Bilitza, D.; Reinisch, B. W.; McKinnell, L. A.

    2010-12-01

    The International Reference Ionosphere (IRI) is an international project sponsored by the Committee on Space research (COSPAR) and the International Union of Radio Science (URSI) that has as its goal the development and improvement of a data-based model of ionospheric densities, temperatures, and velocities using all available and reliable data sources for these ionospheric parameters. The model is widely recognized as the international standard for the specification of ionospheric parameters and recently was accepted by the International Standardization Organization (ISO) as Technical Specification TS 16457. This presentation will discuss the new version of the model, IRI-2010, which includes several important improvements and additions. The electron and ion densities in the lower ionosphere were significantly improved by using a large volume of ionosonde data as well as photochemical considerations. As an additional parameter IRI-2010 includes the transition height from molecular to cluster ions. At the F2 peak Neural Network based models for the peak density and the propagation factor M3000F2, which is related to the F2 peak height, are introduced as new options. For high latitudes the model will benefit from the introduction of auroral oval boundaries and their variation with magnetic activity. Regarding the electron temperature, IRI-2010 now models variations with solar activity.

  20. Parametric Instabilities and Ionospheric Modification

    Microsoft Academic Search

    F. W. Perkins; C. Oberman; E. J. Valeo

    1974-01-01

    Parametric instabilities, excited in the ionosphere by high-power HF transmitters with a frequency below the maximum ionospheric plasma frequency, produce nonlinear energy absorption and enhanced scattering of electromagnetic radiation, which has been detected by the Arecibo Thomson scatter radar. This paper reviews and extends both the linear and nonlinear saturation theory of parametric instabilities within the ionospheric context. The new

  1. Experimental evidence of electromagnetic pollution of ionosphere

    NASA Astrophysics Data System (ADS)

    Pronenko, Vira; Korepanov, Valery; Dudkin, Denis

    The Earth’s ionosphere responds to external perturbations originated mainly in the Sun, which is the primary driver of the space weather (SW). But solar activity influences on the ionosphere and the Earth's atmosphere (i.e., the energy transfer in the direction of the Sun-magnetosphere-ionosphere-atmosphere-surface of the Earth), though important, is not a unique factor affecting its state - there is also a significant impact of the powerful natural and anthropogenic processes, which occur on the Earth’s surface and propagating in opposite direction along the Earth’s surface-atmosphere-ionosphere-magnetosphere chain. Numerous experimental data confirm that the powerful sources and consumers of electrical energy (radio transmitters, power plants, power lines and industrial objects) cause different ionospheric phenomena, for example, changes of the electromagnetic (EM) field and plasma in the ionosphere, and affect on the state of the Earth atmosphere. Anthropogenic EM effects in the ionosphere are already observed by the scientific satellites and the consequences of their impact on the ionosphere are not currently known. Therefore, it is very important and urgent task to conduct the statistically significant research of the ionospheric parameters variations due to the influence of the powerful man-made factors, primarily owing to substantial increase of the EM energy production. Naturally, the satellite monitoring of the ionosphere and magnetosphere in the frequency range from tens of hertz to tens of MHz with wide ground support offers the best opportunity to observe the EM energy release, both in the global and local scales. Parasitic EM radiation from the power supply lines, when entering the ionosphere-magnetosphere system, might have an impact on the electron population in the radiation belt. Its interaction with trapped particles will change their energy and pitch angles; as a result particle precipitations might occur. Observations of EM emission by multiple low orbiting satellites have confirmed a significant increase in their intensity over the populated areas of Europe and Asia. Recently, there are many experimental evidences of the existence of power line harmonic radiation (PLHR) in the ionosphere. Their spectra consist of succession of 50 (60) Hz harmonics which is accompanied by a set of lines separated by 50 (60) or 100 (120) Hz - the central frequency of which is shifted to high frequency. These lines cover rather wide band - according to the available experimental data, their central frequencies are observed from ~1.5 - 3 kHz up to 15 kHz, and recently the main mains frequencies are also observed. The examples of power line harmonic radiation, which were detected by “Sich-1M”, “Chibis-M” and “Demeter” satellites, have been presented and discussed. The available experimental data, as well as theoretical estimations, allow us with a high degree of certainty to say that the permanent satellite monitoring of the ionospheric and magnetospheric anthropogenic EM perturbations is necessary for: a) objective assessment and prediction of the space weather conditions; b) evaluation of the daily or seasonal changes in the level of energy consumption; c) construction of a map for estimation of near space EM pollution. This study is partially supported by SSAU contract N 4-03/13.

  2. Ionospheric sources for molecular ion outflow

    NASA Astrophysics Data System (ADS)

    Zettergren, M. D.; Peterson, W. K.; Blelly, P. F.; Alcayde, D.; Semeter, J. L.

    2012-12-01

    Mass-resolved satellite observations have established the presence of molecular ions in the low-altitude magnetosphere, outer magnetosphere, and ring current. Associated molecular outflows originate from the auroral zone F-region ionosphere and, while normally several orders of magnitude less intense than the well-known O+ outflow, are perhaps more closely tied to intense geomagnetic disturbances. Molecular outflow is also fundamentally different from O+ outflow, since molecular ions must first be generated in large quantities in the F-region, and then are subject to very short recombination lifetimes as they escape. Owing to observational difficulties, very little detailed information exists on the generation, energization, and upward transport of molecular ions. Furthermore, the basic geographic and geomagnetic activity dependence of the ionospheric source and higher altitude outflow are only loosely constrained. This research synthesizes both observations and models to gain a better understanding of molecular ion generation and upflow, and the basic characteristics of the ionospheric molecular source during geomagnetic storms. To illustrate ionospheric dynamics associated with published satellite observations of molecular upflow, a 2D ionospheric model is driven by boundary conditions consistent with observed field-aligned currents. These simulations provide detailed information about expected species-dependent ion densities, temperatures, fluxes, and associated transients. Similar model results are also compared against PFISR radar estimates of molecular ions generated by auroral arc activity. A detailed case study of the 24-25 Sept. 1998 geomagnetic storm is presented in which the EISCAT ESR and Tromso radars suggested enhancements in F-region molecular ions and Polar satellite simultaneously observed moleculars in the magnetosphere. Finally, data from Sondrestrom and EISCAT radars during multiple storms are combined in an attempt to build a statistical picture of the latitude and magnetic local time dependence of the ionospheric molecular source. Connections of this source with satellite observations of molecular outflow are also discussed.

  3. Titan ionospheric conductivities from Cassini measurements

    NASA Astrophysics Data System (ADS)

    Rosenqvist, L.; Wahlund, J.-E.; Ågren, K.; Modolo, R.; Opgenoorth, H. J.; Strobel, D.; Müller-Wodarg, I.; Garnier, P.; Bertucci, C.

    2009-12-01

    We present the first results of ionospheric conductivities at Titan based on measurements during 17 Titan flybys from the Cassini spacecraft. We identify an ionospheric region ranging from 1450±95km (approximately the location of the exobase) to approximately 1000 km where electrical currents perpendicular to the magnetic field may become important. In this region the ionosphere is highly conductive with peak Pedersen conductivities of 0.002-0.05 S/m and peak Hall conductivities of 0.01-0.3 S/m depending on Solar illumination and magnetospheric conditions. Ionospheric conductivities are found to be typically higher on the sunlit side of Titan. However, Hall and Pedersen conductivities depend strongly on the magnetic field magnitude which is highly variable, both in altitude and with respect to the draping configuration of Saturn's magnetic field around Titan. Furthermore, a consistent double peak nature is found in the altitude profile of the Pedersen conductivity. A high altitude peak is found to be located between 1300 and 1400 km. A second and typically more conductive region is observed below 1000 km, where the magnetic field strength drops sharply while the electron density still remains high. This nature of the Pedersen conductivity profile may give rise to complicated ionospheric-atmospheric dynamics and may be expected also at other unmagnetized objects with a substantial atmosphere, such as e.g. Mars and Venus. Estimates of the total Pedersen conductance are found to range between 1300 and 22,000 S. The Pedersen conductance is always higher than the local Alfvén conductance but the difference varies by two orders of magnitude (from a factor 4 to 100). Thus, the conditions for reflection or absorption of Alfvén waves in Titans ionosphere are highly variable and depends strongly on the magnetic field strength.

  4. Ionospheric tomography using the FORTE satellite

    SciTech Connect

    Murphy, T.C.

    1993-08-01

    The possibility of obtaining ionospheric profile data via tomographic techniques has elicited considerable interest in recent years. The input data for the method is a set of total electron content measurements along intersecting lines of sight which form a grid. This can conveniently be provided by a fast-moving satellite with a VHF beacon which will generate the multiple paths needed for effective tomography. Los Alamos and Sandia National Laboratories will launch and operate the FORTE satellite for the US Department of Energy, with launch scheduled in 1995. FORTE will provide such a beacon. Additionally, wideband VHF receivers aboard the satellite will allow corraborative measurements of ionospheric profile parameters in some cases.

  5. Kinetic Framework for the Magnetosphere-Ionosphere-Plasmasphere-Polar Wind System: Modeling Ion Outflow

    NASA Astrophysics Data System (ADS)

    Schunk, R. W.; Barakat, A. R.; Eccles, V.; Karimabadi, H.; Omelchenko, Y.; Khazanov, G. V.; Glocer, A.; Kistler, L. M.

    2014-12-01

    A Kinetic Framework for the Magnetosphere-Ionosphere-Plasmasphere-Polar Wind System is being developed in order to provide a rigorous approach to modeling the interaction of hot and cold particle interactions. The framework will include ion and electron kinetic species in the ionosphere, plasmasphere and polar wind, and kinetic ion, super-thermal electron and fluid electron species in the magnetosphere. The framework is ideally suited to modeling ion outflow from the ionosphere and plasmasphere, where a wide range for fluid and kinetic processes are important. These include escaping ion interactions with (1) photoelectrons, (2) cusp/auroral waves, double layers, and field-aligned currents, (3) double layers in the polar cap due to the interaction of cold ionospheric and hot magnetospheric electrons, (4) counter-streaming ions, and (5) electromagnetic wave turbulence. The kinetic ion interactions are particularly strong during geomagnetic storms and substorms. The presentation will provide a brief description of the models involved and discuss the effect that kinetic processes have on the ion outflow.

  6. Effects of low concentrations of O2 and CO on the ion-clustering reactions in the lower ionosphere of Mars

    NASA Technical Reports Server (NTRS)

    Sieck, L. W.; Gorden, R., Jr.; Ausloos, P.

    1973-01-01

    It is demonstrated that under conditions which approximate those of the Martian ionosphere traces of CO and O2 can be effectively incorporated in ion clusters via ion-molecule reaction schemes initiated by the CO2(+) ion. For example, when 0.3% CO is added to CO2, (CO)2(+), and /(CO)2CO2/(+) appear as the major cations (584 A radiation, 300 K). In mixtures containing O2 in addition to CO, (CO2,O2+) and /(CO2)2O2/(+) are important species. A recently proposed mechanism to account for the low abundance of CO and O2 in the Martian atmosphere is discussed in the light of these observations.

  7. The great magnetic storms of October 29-30, 2003 and their ionospheric effects observed at the equatorial ionization anomaly region

    NASA Astrophysics Data System (ADS)

    Saroso, S.; Liu, J. Y.; Chen, C. H.; Asnawi, M.

    The solar winds ejected from the coronal holes or the coronal mass ejection CME during solar flares form magnetic clouds and high speed streams which may hit magnetosphere and ionosphere of the Earth and induce many complex phenomena including geomagnetic storms The huge injected energy accompanied with the geomagnetic storms will result in thermospheric and ionospheric storms The ionosphere during the storms will change in complex ways and the electron densities The electron densities may increase or decrease and the height of the ionosphere may change too Due to the complexity of ionospheric storms some storms are different from the other especially at equatorial ionization anomaly region The ionospheric storms are far from being fully understood so case studies are still crucial to the understanding of ionospheric storms The 29-30 October 2003 Halloween storms event have been an object of a close attention of the scientific community The various aspects of this event have been well documented by a large number of observations Thus complex studies based on very different measuring techniques and instruments will contribute to an improved understanding of solar-terrestrial relationships These studies are of great practical importance because severe storms may degrade radio communications cause power blackouts We will present the ionospheric response to the storms using the ionosonde and GPS observation at Indonesia and Taiwan which are located in the north and south equatorial ionization anomaly region

  8. A Review of VHF Ionospheric Propagation

    Microsoft Academic Search

    M. G. Morgan

    1953-01-01

    Although the very high frequencies (vhf,30-300 mc) are allocated for utilization almost entirely upon the premise that propagation will be tropospheric, there are very definite ionospheric effects with which one must reckon. These are: (1) regular F2 ionization, (2) sporadic E ionization, (3) scattering from regular ionization, (4) auroral ionization, (5) meteoric ionization. The first of these is predictable with

  9. Ionospheric manifestations of earthquakes and tsunamis in a dynamic atmosphere

    NASA Astrophysics Data System (ADS)

    Godin, Oleg A.; Zabotin, Nikolay A.; Zabotina, Liudmila

    2015-04-01

    Observations of the ionosphere provide a new, promising modality for characterizing large-scale physical processes that occur on land and in the ocean. There is a large and rapidly growing body of evidence that a number of natural hazards, including large earthquakes, strong tsunamis, and powerful tornadoes, have pronounced ionospheric manifestations, which are reliably detected by ground-based and satellite-borne instruments. As the focus shifts from detecting the ionospheric features associated with the natural hazards to characterizing the hazards for the purposes of improving early warning systems and contributing to disaster recovery, it becomes imperative to relate quantitatively characteristics of the observed ionospheric disturbances and the underlying natural hazard. The relation between perturbations at the ground level and their ionospheric manifestations is strongly affected by parameters of the intervening atmosphere. In this paper, we employ the ray theory to model propagation of acoustic-gravity waves in three-dimensionally inhomogeneous atmosphere. Huygens' wavefront-tracing and Hamiltonian ray-tracing algorithms are used to simulate propagation of body waves from an earthquake hypocenter through the earth's crust and ocean to the upper atmosphere. We quantify the influence of temperature stratification and winds, including their seasonal variability, and air viscosity and thermal conductivity on the geometry and amplitude of ionospheric disturbances that are generated by seismic surface waves and tsunamis. Modeling results are verified by comparing observations of the velocity fluctuations at altitudes of 150-160 km by a coastal Dynasonde HF radar system with theoretical predictions of ionospheric manifestations of background infragravity waves in the ocean. Dynasonde radar systems are shown to be a promising means for monitoring acoustic-gravity wave activity and observing ionospheric perturbations due to earthquakes and tsunamis. We will discuss the effects of the background ionospheric disturbances and uncertainty in atmospheric parameters on the feasibility and accuracy of retrieval of the open-ocean tsunami heights from observations of the ionosphere.

  10. 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.

  11. Impact of the dipole tilt angle on the ionospheric plasma in the outer plasmasphere

    NASA Astrophysics Data System (ADS)

    Marchaudon, Aurelie; Blelly, Pierre-Louis

    2015-04-01

    We have developed a new interhemispheric 16-moment based ionosphere model. This model describes the field-aligned transport of the multi-species ionospheric plasma (6 ions) from one hemisphere to the other, taking into account source processes at low altitudes (photoionization, chemistry) and coupling with suprathermal electrons. We simulate the convection and corotation transport of closed flux tubes in the outer plasmasphere for tilted/eccentric dipolar magnetic field configuration. We ran the model in solstice and equinox conditions and for two plasmapause boundary conditions: one corresponding to standard conditions with a stagnation point at 4.5 Earth radii (RE) and 15h Magnetic Local Time (MLT) and one corresponding to very quiet conditions with a stagnation point at 6 RE and 15h MLT. For each season/stagnation simulation, the model is run for 30 days before the equinox/solstice date in order to eliminate the transients. The goal is to study the combined effect of the tilt of the magnetic field and the rotation axis on the field-aligned dynamics and overall equilibrium of the subauroral ionosphere. In the classical representation of the plasmasphere, the ionosphere only depends on angular MLT sector. We will show that due to the tilt effect, this view is erroneous and no real dynamic equilibrium is reached, in particular close to the stagnation point where we can observe large day-to-day variations in the ionospheric parameters. Finally, we will present the temperatures anisotropy development along the flux tube for different positions of the stagnation point.

  12. Solitons and ionospheric heating

    NASA Technical Reports Server (NTRS)

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

    1982-01-01

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

  13. Global ionospheric weather

    SciTech Connect

    Decker, D.T.; Doherty, P.H.

    1994-02-28

    In the last year, the authors have studied several issues that are critical for understanding ionospheric weather. Work on global F-region modeling has consisted of testing the Phillips Laboratory Global Theoretical Ionosphere Model. Comparisons with both data and other theoretical models have been successfully conducted and are ongoing. GPS observations, as well as data analysis, are also ongoing. Data have been collected for a study on the limitations in making absolute ionospheric measurements using GPS. Another study on ionospheric variability is the first of its kind using GPS data. The observed seasonal total electron content behavior is consistent with that determined from the Faraday rotation technique. Work on the FAA's Phase 1 Wide Area Differential GPS (WADGPS) Satellite Navigation Testbed Experiment also continues. Initial results indicate that stations using operational WADGPS should be located no greater than 430 km apart. Work comparing the authors electron-proton-H atom model to both observations and other models has been generally successful. They have successfully modeled the creation of high-latitude large-scale plasma structures using two separate mechanisms (time-varying global convection and meso-scale convection events).

  14. The ionospheric disturbance dynamo

    Microsoft Academic Search

    M. Blanc; A. D. Richmond

    1980-01-01

    The purpose of the present work is to develop a theory of the ionospheric disturbance dynamo and to examine, on the basis of theoretically predicted features, its relevance to the understanding of certain observations. A longitudinally symmetric, time-dependent numerical model of the thermospheric disturbance winds driven by an auroral heating event and the associated electric fields and currents derived for

  15. Solar flares induced D-region ionospheric and geomagnetic perturbations

    NASA Astrophysics Data System (ADS)

    Selvakumaran, R.; Maurya, Ajeet K.; Gokani, Sneha A.; Veenadhari, B.; Kumar, Sushil; Venkatesham, K.; Phanikumar, D. V.; Singh, Abhay K.; Siingh, Devendraa; Singh, Rajesh

    2015-02-01

    The D-region ionospheric perturbations caused by solar flares which occurred during January 2010-February 2011, a low solar activity period of current solar cycle 24, have been examined on NWC transmitter signal (19.8 kHz) recorded at an Indian low latitude station, Allahabad (Geographic lat. 25.75°N, long. 81.85°E). A total of 41 solar flares, including 21 C-class, 19 M-class and 01 X-class, occurred during the daylight part of the NWC-Allahabad transmitter receiver great circle path. The local time dependence of solar flare effects on the change in the VLF amplitude, time delay between VLF peak amplitude and X-ray flux peak have been studied during morning, noon and evening periods of local daytime. Using the Long Wave Propagation Capability code V 2.1 the D-region reference height (H/) and sharpness factor (?) for each class of solar flare (C, M and X) have been estimated. It is found that D-region ionospheric parameters (H/, ?) strongly depend on the local time of flare's occurrence and their classes. The flare time electron density estimated by using H/ and ? shows maximum increase in the electron density of the order of ~80 times as compared to the normal day values. The electron density was found to increase exponentially with increase in the solar flux intensity. The solar flare effect on horizontal component (H) of the Earth's magnetic field over an equatorial station, Tirunelveli (Geographic lat., 8.7°N, long., 77.8°E, dip lat., 0.4°N), shows a maximum increase in H of ~8.5% for M class solar flares. The increase in H is due to the additional magnetic field produced by the ionospheric electrojet over the equatorial station.

  16. Model of Jovian F region ionosphere (Jovian ionosphere model in offset dipole approximation)

    NASA Technical Reports Server (NTRS)

    Tan, A.

    1990-01-01

    The geomagnetic control of the Earth's atmosphere is well understood. In the F-region and the topside ionosphere, non-electrical forces transport plasma along the magnetic field lines only. In consequence, the worldwide distribution of ionization is strongly dependent on the dip angle. For example, the equatorial anomaly is roughly symmetrical about the dipole equator rather than the geographic. The same appears to be the case in the Jovian ionosphere (Mahajan, 1981). The influence of the magnetic field of Jupiter on its ionization pattern is one of several outstanding topics which need to be studied. Tan (1986) investigated the formation of the equatorial anomaly in the Jovian ionosphere under a centered dipole model. Tan (1988) further studied the effect of the tilt of the Jovian dipole. The results were in broad agreement with those of a diffusive equilibrium model (Tan and Wu, 1981). An off-centered dipole model is constructed and its effects on the ionization pattern are investigated.

  17. Acoustic and gravity waves in the neutral atmosphere and the ionosphere, generated by severe storms

    NASA Technical Reports Server (NTRS)

    Balachandran, N. K.

    1983-01-01

    Gravity waves in the neutral atmosphere and their propagation in the ionosphere and the study of infrasonic signals from thunder were investigated. Doppler shifts of the order of 0.1 Hz are determined and they provide high-resolution measurements of the movements in the ionosphere. By using an array of transmitters with different frequencies and at different locations, the horizontal and vertical propagation vectors of disturbances propagating through the ionosphere are determined.

  18. 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…

  19. Seismic source characterization by ionospheric sounding from Gound Positioning System data

    NASA Astrophysics Data System (ADS)

    Rolland, L.; Lognonné, P.; Kherani, A. E.; Crespon, F.; Murakami, M.

    2007-12-01

    Imaging the terrestrial ionosphere is becoming possible since the installation of dense GPS networks, with a temporal and spatial resolution allowing the detection of ionospheric seismic waves. Since the 1960s, ionospheric seismic waves are detectable almost punctually after large shallow earthquakes, with current minimum magnitude of 6.5. Most recently, the use of dense networks gave the way to a global visualization of the horizontal propagation of co-seismic ionospheric disturbances. Such a use of a Global Positioning System array, and the sounding capability of the method above the ocean, prove the potential of this method as a complement to more traditional techniques used in seismology. From now on, after imaging seismic waves in the ionosphere, the challenge is the characterization of the seismic source, whose rupture involves coupling mechanisms between the moving solid earth and its surrounding atmosphere. The study presented here is based on the Total Electronic Content variations mapped close to the source and shortly after the Tokachi-Oki earthquake (M=8.3) that occurred on September, 25, 2003, in Japan. The first fundamental source parameters derived from 1 Hz sampled data will be reminded here. The rupture process is then pre-modelled in reference to the co-seismic displacements estimated by other techniques. Therefore, a modelling of the horizontal propagation of acoustic waves generated by three aligned separated sources is developed. The preliminary results of the subsequent GPS data inversion tests will be presented. Finally, for physical modelling of the vertical propagation, we used ray tracing in the atmosphere, in order to study the effects of the near-field pulse spreading in acoustic domain as well as the redistribution of the charged particles under geomagnetic dependency.

  20. Inductive-dynamic magnetosphere-ionosphere coupling via MHD waves

    NASA Astrophysics Data System (ADS)

    Tu, Jiannan; Song, Paul; Vasyli?nas, Vytenis M.

    2014-01-01

    In the present study, we investigate magnetosphere-ionosphere/thermosphere (M-IT) coupling via MHD waves by numerically solving time-dependent continuity, momentum, and energy equations for ions and neutrals, together with Maxwell's equations (Ampère's and Faraday's laws) and with photochemistry included. This inductive-dynamic approach we use is fundamentally different from those in previous magnetosphere-ionosphere (M-I) coupling models: all MHD wave modes are retained, and energy and momentum exchange between waves and plasma are incorporated into the governing equations, allowing a self-consistent examination of dynamic M-I coupling. Simulations, using an implicit numerical scheme, of the 1-D ionosphere/thermosphere system responding to an imposed convection velocity at the top boundary are presented to show how magnetosphere and ionosphere are coupled through Alfvén waves during the transient stage when the IT system changes from one quasi steady state to another. Wave reflection from the low-altitude ionosphere plays an essential role, causing overshoots and oscillations of ionospheric perturbations, and the dynamical Hall effect is an inherent aspect of the M-I coupling. The simulations demonstrate that the ionosphere/thermosphere responds to magnetospheric driving forces as a damped oscillator.

  1. Planetary waves in rotating ionosphere

    SciTech Connect

    Khantadze, A. G.; Jandieri, V. G. [Tbilisi State University (Georgia); Jandieri, G. V. [Georgian Technical University (Georgia)

    2008-06-15

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

  2. New SuperDARN Radar Capabilities for Observing Ionospheric Plasma Convection and ITM Coupling in the Mid-Latitude Ionosphere

    NASA Astrophysics Data System (ADS)

    Ruohoniemi, J. M.; Baker, J. B.; Greenwald, R. A.; Clausen, L. B.; Shepherd, S. G.; Bristow, W. A.; Talaat, E. R.; Barnes, R. J.

    2010-12-01

    Within the past year the first pair of SuperDARN radars funded under the NSF MSI program has become operational at a site near Hays, Kansas. The fields of view of the co-located radars are oriented to provide common-volume observations with two existing radars in Virginia (Wallops, Blackstone) and two MSI radars under construction in Oregon (Christmas Valley). The emerging mid-latitude radar chain will complement the existing SuperDARN coverage at polar cap and auroral latitudes within North America. The mid-latitude radars observe the expansion of auroral effects during disturbed periods, subauroral polarization streams, and small-scale ionospheric irregularities on the nightside that open a window on the plasma drifts and electric fields of the quiet-time subauroral ionosphere. They also measure neutral winds at mesospheric heights and the propagation of ionospheric disturbances due to the passage of atmospheric gravity waves. The new radar capabilities provide unprecedented views of ITM processes in the subauroral ionosphere with applications to studies of ionospheric electric fields, ion-neutral coupling, atmospheric tides and planetary waves, ionospheric plasma structuring and plasma instability. In this talk we describe the new capabilities and the potential for providing large-scale context for related ITM measurements over North America. We present the first high-resolution two-dimensional maps of ionospheric plasma convection at mid-latitudes as generated from common-volume observations with the Hays and Blackstone radars.

  3. Ionospheric refraction corrections in the GTDS for satellite-to-satellite tracking data

    Microsoft Academic Search

    G. Nesterczuk; J. K. Kozelsky

    1976-01-01

    In satellite-to-satellite tracking (SST) geographic as well as diurnal ionospheric effects must be contended with, for the line of sight between satellites can cross a day-night interface or lie within the equatorial ionosphere. These various effects were examined and a method of computing ionospheric refraction corrections to range and range rate measurements with sufficient accuracy were devised to be used

  4. Reconstruction of the ionospheric electron density by geostatistical inversion

    NASA Astrophysics Data System (ADS)

    Minkwitz, David; van den Boogaart, Karl Gerald; Hoque, Mainul; Gerzen, Tatjana

    2015-04-01

    The ionosphere is the upper part of the atmosphere where sufficient free electrons exist to affect the propagation of radio waves. Typically, the ionosphere extends from about 50 - 1000 km and its morphology is mainly driven by solar radiation, particle precipitation and charge exchange. Due to the strong ionospheric impact on many applications dealing with trans-ionospheric signals such as Global Navigation Satellite Systems (GNSS) positioning, navigation and remote sensing, the demand for a highly accurate reconstruction of the electron density is ever increasing. Within the Helmholtz Alliance project "Remote Sensing and Earth System Dynamics" (EDA) the utilization of the upcoming radar mission TanDEM-L and its related products are prepared. The TanDEM-L mission will operate in L-band with a wavelength of approximately 24 cm and aims at an improved understanding of environmental processes and ecosystem change, e.g. earthquakes, volcanos, glaciers, soil moisture and carbon cycle. Since its lower frequency compared to the X-band (3 cm) and C-band (5 cm) radar missions, the influence of the ionosphere will increase and might lead to a significant degradation of the radar image quality if no correction is applied. Consequently, our interest is the reconstruction of the ionospheric electron density in order to mitigate the ionospheric delay. Following the ionosphere's behaviour we establish a non-stationary and anisotropic spatial covariance model of the electron density separated into a vertical and horizontal component. In order to estimate the model's parameters we chose a maximum likelihood approach. This approach incorporates GNSS total electron content measurements, representing integral measurements of the electron density between satellite to receiver ray paths, and the NeQuick model as a non-stationary trend. Based on a multivariate normal distribution the spatial covariance model parameters are optimized and afterwards the 3D electron density can be calculated by kriging for arbitrary points or grids of interest.

  5. Summary of Sessions: Ionosphere - Thermosphere - Mesosphere Working Group

    NASA Technical Reports Server (NTRS)

    Spann, J. F.; Bhattacharyya, A.

    2006-01-01

    The topics covered by the sessions under the working group on Ionosphere-Thermosphere-Mesosphere dealt with various aspects of the response of the ionosphere-thermosphere coupled system and the middle atmosphere to solar variability. There were four plenary talks related to the theme of this working group, thirteen oral presentations in three sessions and six poster presentations. A number of issues related to effects of solar variability on the ionosphere-thermosphere, observed using satellite and ground-based data including ground magnetometer observations, radio beacon studies of equatorial spread F, and modeling of some of these effects, were discussed. Radar observations of the mesosphere-lower thermosphere region and a future mission to study the coupling of thunderstorm processes to this region, the ionosphere, and magnetosphere were also presented.

  6. Effects of time ordering in quantum nonlinear optics

    NASA Astrophysics Data System (ADS)

    Quesada, Nicolás; Sipe, J. E.

    2014-12-01

    We study time-ordering corrections to the description of spontaneous parametric down-conversion (SPDC), four-wave mixing (SFWM), and frequency conversion using the Magnus expansion. Analytic approximations to the evolution operator that are unitary are obtained. They are Gaussian preserving, and allow us to understand order-by-order the effects of time ordering. We show that the corrections due to time ordering vanish exactly if the phase-matching function is sufficiently broad. The calculation of the effects of time ordering on the joint spectral amplitude of the photons generated in SPDC and SFWM are reduced to quadrature.

  7. Test order effects in simultaneous protocols.

    PubMed

    Imam, Abdulrazaq A; Warner, Timothy A

    2014-03-01

    Simultaneous protocols typically yield poorer stimulus equivalence outcomes than do other protocols commonly used in equivalence research. Two independent groups of three 3-member equivalence sets of stimuli were used in conditional discrimination procedures in two conditions, one using the standard simultaneous protocol and the other using a hybrid simultaneous training and simple-to-complex testing. Participants completed the two conditions in one long session in Experiment 1, but in separate sessions in Experiment 2. The same stimulus sets used in Experiment 1 were randomized for the two conditions in Experiment 2. Overall, accuracy was better with the hybrid than with the standard protocol in both experiments. The equivalence yield was also better under the hybrid than under the standard protocol in each experiment. The results suggest that the order of testing for emergent relations may account for the difficulty often encountered with the standard simultaneous protocol. PMID:24272620

  8. 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, Valery V.; Hegai, Lidiya P.

    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.

  9. Predictions of the effects of Mars's encounter with comet C/2013 A1 (Siding Spring) upon metal species in its ionosphere

    NASA Astrophysics Data System (ADS)

    Withers, Paul

    2014-10-01

    The infall of dust from the coma of comet C/2013 A1 (Siding Spring) and its subsequent ablation in the atmosphere of Mars has the potential to affect the abundances of metal species in the atmosphere and ionosphere. We develop relationships between properties of the dust population in the coma and densities of metal species in the atmosphere and ionosphere. These can be used to predict the abundances of metal species in the atmosphere and ionosphere during the encounter. Given postencounter observations of the atmosphere and ionosphere, they can also be used to infer relevant cometary properties. Although current predictions suggest that the influx of cometary dust will be comparable to the sporadic background, the higher entry speed involved, which leads to a greater production rate of ions during ablation, means that metal ion abundances may be enhanced during and after the encounter.

  10. Vertical ionospheric sounding measurements

    Microsoft Academic Search

    W. F. Utlaut; T. N. Gautier

    1964-01-01

    This report presents data on the ionospheric perturbations resulting from the five 1962 high-altitude nuclear detonations, Star Fish, Check Mate, Blue Gill, King Fish, and Tight Rope, as obtained with sweep-frequency vertical-incidence ionosondes operated at the Islands of Maui, Tern (French Frigate Shoals), Midway, Wake (Star Fish only), Canton, Tutuila (American Samoa), and Tongatapu. The ionosondes at Midway and Tongataupu

  11. Variability of the ionosphere

    Microsoft Academic Search

    Jeffrey M. Forbes; Scott E. Palo; Xiaoli Zhang

    2000-01-01

    Hourly foF2 data from over 100 ionosonde stations during 1967–89 are examined to quantify F-region ionospheric variability, and to assess to what degree the observed variability may be attributed to various sources, i.e., solar ionizing flux, meteorological influences, and changing solar wind conditions. Our findings are as follows. Under quiet geomagnetic conditions (Kp<1), the 1-? (? is the standard deviation)

  12. Variability of the ionosphere

    Microsoft Academic Search

    J. M. Forbes; S. E. Palo; X. Zhang

    2000-01-01

    Hourly foF2 data from over 100 ionosonde stations during 1967-89 are examined to quantify F-region ionospheric variability, and to assess to what degree the observed variability may be attributed to various sources, i.e., solar ionizing flux, meteorological influences, and changing solar wind conditions. Our findings are as follows. Under quiet geomagnetic conditions (Kp<1), the \\/1-sigma (\\/sigma is the standard deviation)

  13. Nighttime behavior of the equatorial topside ionosphere

    NASA Astrophysics Data System (ADS)

    Venkatraman, Sarita

    The high altitude region of the ionosphere above the F2 peak is called the topside ionosphere. In this region, the effects of diffusion are comparable to production and loss processes. The behavior of this region is dominated by transport and chemical processes which help determine the relative amounts of O+ and H+ which are the dominant ions in the topside. In order to understand the dynamics and energetics of this region, it is also necessary to understand the roles of E × B drifts and F region neutral winds. This region of the ionosphere has been studied for the last 30 years using in- situ measurements from instruments on spacecraft, ground-based radars, mathematical and computational methods, etc. In our study we use data from the Defense Meteorological Satellite Program (DMSP) F10 satellite which orbits in a sun- synchronous polar orbit with an orbital inclination of about 98°. We have examined latitude profiles of ion temperatures and densities at 2100 hours LT and at an altitude of 800 km to discover the influence of field- aligned plasma transport induced by F region neutral winds. Such dependencies are readily seen by contrasting observations at different seasons, longitudes, and magnetic declinations. Our initial study involves examination of the temperature and density variations in 1991 under high solar activity levels. Data show strong evidence for adiabatic heating effects produced by interhemispheric plasma transport. This heating manifests itself as a local temperature maximum that appears in the winter hemisphere during solstices and is generally absent during equinox. A longitudinal variation in the appearance of this maximum is consistent with the roles of meridional and zonal winds in modulating the field-aligned plasma velocities. The data also show a local temperature minimum near the dip equator. However, it is not so easy to attribute this minimum to adiabatic cooling. This initial study is followed by a further study involving solar activity dependencies in the topside. A study of plasma temperatures under moderate solar activity conditions in 1992 indicates features similar to those in 1991, except that overall temperatures are lower. Evidence for ion cooling and heating by adiabatic expansion and compression seen in 1991 are also seen in 1992, and are attributed to interhemispheric transport of plasma. In this case, temperature and density data in 1992 are examined and compared with similar data set in 1991. It is found that the adiabatic effects are strongly dependent on the location of the transition height. In contrast to high solar activity levels, both, the temperature maximum and the temperature minimum manifest themselves much closer to the dip equator under moderate levels of solar activity. Note that, for both years O+ is the dominant ion at latitudes where the heating effect is seen.

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

    SciTech Connect

    Singh, Rohtash; Sharma, A. K.; Tripathi, V. K. [Department of Physics, Indian Institute of Technology Delhi, New Delhi-110016 (India)

    2011-11-15

    The formation of a volume grating in the near-equator regions of ionosphere due to a high power radio wave is investigated. The radio wave, launched from a ground based transmitter, forms a standing wave pattern below the critical layer, heating the electrons in a space periodic manner. The thermal conduction along the magnetic lines of force inhibits the rise in electron temperature, limiting the efficacy of heating to within a latitude of few degrees around the equator. The space periodic electron partial pressure leads to ambipolar diffusion creating a space periodic density ripple with wave vector along the vertical. Such a volume grating is effective to cause strong reflection of radio waves at a frequency one order of magnitude higher than the maximum plasma frequency in the ionosphere. Linearly mode converted plasma wave could scatter even higher frequency radio waves.

  15. 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.

  16. Effect of third-order dispersion on dark solitons

    NASA Astrophysics Data System (ADS)

    Afanasjev, Vsevolod V.; Kivshar, Yuri S.; Menyuk, Curtis R.

    1996-12-01

    Third-order dispersion has a detrimental effect on dark solitons, leading to resonant generation of growing soliton tails and soliton decay. This effect is shown to be much stronger than that for bright solitons.

  17. Vlasov Simulations of Ionospheric Heating Near Upper HybridResonance

    NASA Astrophysics Data System (ADS)

    Najmi, A. C.; Eliasson, B. E.; Shao, X.; Milikh, G. M.; Papadopoulos, K.

    2014-12-01

    It is well-known that high-frequency (HF) heating of the ionosphere can excite field- aligneddensity striations (FAS) in the ionospheric plasma. Furthermore, in the neighborhood of variousresonances, the pump wave can undergo parametric instabilities to produce a variety of electrostaticand electromagnetic waves. We have used a Vlasov simulation with 1-spatial dimension, 2-velocitydimensions, and 2-components of fields, to study the effects of ionospheric heating when the pumpfrequency is in the vicinity of the upper hybrid resonance, employing parameterscurrently available at ionospheric heaters such as HAARP. We have found that by seeding theplasma with a FAS of width ~20% of the simulation domain, ~10% depletion, and byapplying a spatially uniform HF dipole pump electric field, the pump wave gives rise to a broadspectrum of density fluctuations as well as to upper hybrid and lower hybrid oscillating electricfields. We also observe collisionless bulk-heating of the electrons that varies non-linearly with theamplitude of the pump field.

  18. Low-latitude ionosphere dynamics as deduced from meridional ionosonde chain: Ionospheric ceiling

    NASA Astrophysics Data System (ADS)

    Maruyama, Takashi; Uemoto, Junpei; Tsugawa, Takuya; Supnithi, Pornchai; Ishii, Mamoru; Komolmis, Tharadol

    Interest in the equatorial anomaly in the ionosphere has been focused mostly on f_oF_2, and not much attention was paid to h_mF_2 except for the time rate of change of it in connection with the vertical plasma drift velocity. There have been few climatological studies on h_mF_2 variations associated with development of the equatorial anomaly. In this paper, we revisit the equatorial anomaly in terms of height variations. For this purpose, we analyzed scaled ionogram parameters from three stations located along the magnetic meridian that is a primary component of Southeast Asia low-latitude ionospheric network (SEALION); one at the magnetic equator and the others at conjugate off-equatorial latitudes near 10 degrees magnetic latitude. The daytime h_mF_2 was investigated for each season during the solar minimum period, 2006-2007 and 2009. The peak height increased for approximately 3 hr after sunrise at all locations, as expected from the daytime upward E×B drift. The apparent upward drift ceased before noon at the magnetic equator, while the layer continued to increase at the off-equatorial latitudes, reaching altitudes higher than the equatorial height around noon. The noon time restricted layer height at the magnetic equator did not depend much on the season, while the maximum peak height at the off-equatorial latitudes largely varied with season. The daytime specific limiting height of the equatorial ionosphere was termed ionospheric ceiling. Numerical modeling using the SAMI2 code reproduced the features of the ionospheric ceiling quite well. Dynamic parameters provided by the SAMI2 modeling were investigated and it was shown that the ionospheric ceiling is another aspect of the fountain effect, in which increased diffusion of plasma at higher altitudes has a leading role.

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

  20. Ionospheres of the terrestrial planets

    Microsoft Academic Search

    R. W. Schunk; A. F. Nagy

    1980-01-01

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

  1. Two Anomalies in the Ionosphere

    Microsoft Academic Search

    Edward V. Appleton

    1946-01-01

    DURING the War, many new ionospheric stations were instituted in different parts of the world to serve the operational requirements of the Allied Forces. As a result., there have become available, for the first time, sufficient data to provide a rough general morphological picture of the F2 layer of the ionosphere. A study of these data has disclosed the remarkable

  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. Results from a coupled model of the thermosphere, ionosphere and plasmasphere (CTIPM)

    Microsoft Academic Search

    R. J. Moffett; G. H. Millward; S. Quegan; A. D. Aylward; T. J. Fuller-Rowell

    1996-01-01

    The Sheffield\\/UCL\\/SEL coupled model of the thermosphere and ionosphere has been extended to include a plasmasphere and equatorial ionosphere. Model results are presented for field-aligned ion fluxes in the topside ionosphere. Results are also given for global NmF2, showing a semi-annual effect at Stanley (52° S). While showing a winter anomaly comparable to that observed, Slough (52° N) results disagree

  4. Results from a coupled model of the thermosphere, ionosphere and plasmasphere (CTIPM)

    Microsoft Academic Search

    R. J. Moffett; G. H. Millward; S. Quegan; A. D. Aylward; T. J. Fuller-Rowell

    1996-01-01

    The Sheffield\\/UCL\\/SEL coupled model of the thermosphere and ionosphere has been extended to include a plasmasphere and equatorial ionosphere. Model results are presented for field-aligned ion fluxes in the topside ionosphere. Results are also given for global NmF2, showing a semi-annual effect at Stanley (52 deg S). While showing a winter anomaly comparable to that observed, Slough (52 deg N)

  5. Response-Order Effects in Likert-Type Scales.

    ERIC Educational Resources Information Center

    Chan, Jason C.

    1991-01-01

    A study involving 102 high school students (49 males and 53 females) from Taiwan revealed that the order of response scale labels had a primacy effect on subjects' choices of the alternatives in Likert-type attitude scales. Practical implications of the response-order effects for measurement are discussed. (SLD)

  6. Morphology of the dayside ionosphere of Venus: Implications for ion outflows

    Microsoft Academic Search

    J. L. Fox

    2008-01-01

    The nightside ionosphere of Venus is formed mostly by day-to-night transport of ions below the ionopause, with a small contribution from precipitation of energetic electrons from the wake. This nightward flux of ions should result in dayside ionospheres that are characterized by smaller electron density scale heights at high altitudes than those that are characteristic of diffusive equilibrium. In order

  7. Modeling of Ionospheric Responses to the Solar Flux Change Based on Millstone Hill Incoherent Scatter Radar

    Microsoft Academic Search

    S. Zhang; J. M. Holt

    2002-01-01

    In order to develop ionospheric empirical models of electron density Ne, plasma temperatures (Te and Ti) and ion drifts based on Millstone Hill incoherent scatter radar observations, we investigate an important issue of ionospheric responses to the solar flux changes that have to be quantitatively represented. The representation is associated with selecting a mathematical function where a suitable solar flux

  8. Solar radiation-induced changes in ionospheric height and the Schumann resonance waveguide on different timescales

    Microsoft Academic Search

    E. R. Williams; G. Sátori

    2007-01-01

    This study draws together the available observations in the Schumann resonance frequency range to examine the general issue of sensitivity of ionospheric height variations to changes in ionizing radiation from the Sun on different timescales. Ionospheric height can be formally defined, and two characteristic heights are recognized in the Schumann resonance frequency range. In general, order of magnitude changes in

  9. Ionospheric Estimation and Integrity Threat Detection

    E-print Network

    Stanford University

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

  10. Feedback instability of the ionospheric resonant cavity

    Microsoft Academic Search

    Robert L. Lysak

    1991-01-01

    The exponential increase of the Alfven speed in the topside ionosphere leads to the formation of a resonant cavity (Lysak, 1988) which has been termed the ionospheric Alfven resonator by Trakhtengertz and Feldstein (1984). These authors primarily considered the situation where the ionospheric Pedersen conductivity is low, while Lysak (1988) considered the opposite limit of the infinite ionospheric conductivity. These

  11. Ionosphere around equinoxes during low solar activity

    Microsoft Academic Search

    Libo Liu; Maosheng He; Xin'an Yue; Baiqi Ning; Weixing Wan

    2010-01-01

    The seasonal behaviors of the ionosphere have been investigated for several decades, but the differences of the ionosphere between the March and September equinoxes are still an open question. In this analysis we utilize the data of ionospheric electron density (Ne) profiles from Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) mission radio occultation measurements, total electron density (TEC)

  12. Towards the azimuthal characteristics of ionospheric and seismic effects of "Chelyabinsk" meteorite fall according to the data from coherent radar, GPS and seismic networks

    E-print Network

    Berngardt, O I; Kutelev, K A; Zherebtsov, G A; Dobrynina, A A; Shestakov, N V; Zagretdinov, R V; Bakhtiyarov, V F; Kusonsky, O A

    2015-01-01

    We present the results of a study of the azimuthal characteristics of ionospheric and seismic effects of the meteorite 'Chelyabinsk', based on the data from the network of GPS receivers, coherent decameter radar EKB SuperDARN and network of seismic stations. It is shown, that 6-14 minutes after the bolide explosion, GPS network observed the cone-shaped wavefront of TIDs that is interpreted as a ballistic acoustic wave. The typical TIDs propagation velocity were observed 661+/-256m/s, which corresponds to the expected acoustic wave speed for 240km height. 14 minutes after the bolide explosion, at distances of 200km we observed the emergence and propagation of a TID with spherical wavefront, that is interpreted as gravitational mode of internal acoustic waves. The propagation velocity of this TID was 337+/-89m/s which corresponds to the propagation velocity of these waves in similar situations. At EKB SuperDARN radar, we observed TIDs in the sector of azimuthal angles close to the perpendicular to the meteorite...

  13. Auroral and photoelectron fluxes in cometary ionospheres

    SciTech Connect

    Bhardwaj, A.; Haider, S.A.; Singhal, R.P. (Banaras Hindu Univ., Varanasi (India))

    1990-05-01

    The analytical yield spectrum method has been used to ascertain photoelectron and auroral electron fluxes in cometary ionospheres, with a view to determining the effects of cometocentric distances, solar zenith angle, and solar minimum and maximum conditions. Auroral electron fluxes are thus calculated for monoenergetic and observed primary electron spectra; auroral electrons are found to make a larger contribution to the observed electron spectrum than EUV-generated photoelectrons. Good agreement is established with extant theoretical works. 55 refs.

  14. Intense Vibrations of the Martian Ionosphere Observed by MARSIS Active Sounding during a Sun--Earth--Mars Conjunction

    NASA Astrophysics Data System (ADS)

    Morgan, D. D.; Dieval, C.; Gurnett, D. A.; Lester, M.

    2014-12-01

    The ISSI Working Group on The Induced Magnetosphere of Mars: Physical Processes and Consquences has covered three conjunction campaigns, in which the Sun, Earth,and Mars are lined up radially. During these campaigns data taken on the Sun, at Earth, and from spacecraft in solar orbit such as STEREO can be applied to events occurring in the Martian ionosphere to gauge the response to events in the solar wind more precisely than at other times when solar wind data cannot be accurately projected to Mars. In this presentation, we apply data from all of these sources as well as the Mars Express spacecraft in order to characterize a few events in which MARSIS Active Ionospheric Sounding, the topside sounder on board the Mars Express spacecraft, detects intense vibrations of period about 10 s in both locally detected electron density and magnetic field strength and remotely sensed electron density profiles near the ionospheric peak. That these vibrations appear both locally and in the remote sensing indicates the global nature of this phenomenon. The vibrations are seen to occur as the effect of one or more ICME impacts on the Martian ionosphere.

  15. Solitons and ionospheric modification

    NASA Technical Reports Server (NTRS)

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

    1982-01-01

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

  16. Ionospheric wave spectrum measurements

    NASA Technical Reports Server (NTRS)

    Harker, K. J.; Ilic, D. B.; Crawford, F. W.

    1979-01-01

    The local spectrum S(k, omega) of either potential or electron-density fluctuations can be used to determine macroscopic-plasma characteristics such as the local density and temperature, transport coefficients, and drift current. This local spectrum can be determined by measuring the cross-power spectrum. The paper examines the practicality of using the cross-power spectrum analyzer on the Space Shuttle to measure ionospheric parameters. Particular attention is given to investigating the integration time required to measure the cross-power spectral density to a desired accuracy.

  17. Microbiological studies on the radiation environment of the ionosphere and stratosphere.

    PubMed

    Petras, E; Bisa, K

    1968-01-01

    Rocket, balloon and laboratory experiments have been performed in order to study the survival chances of microorganisms, which exist under the environmental conditions of ionosphere and stratosphere. The main results are: 1. Not only near the earth, but also in the stratosphere and even in the ionosphere, microorganisms are endangered primarily by UV- and EUV-light irradiation. 2. The observed effect of more penetrating kinds of radiation was relatively unimportant. High-vacuum and temperature effects have not been observed at all. Even membrane filters and thin protein layers protected the exposed spores of Bacillus subtilis var. niger (= Bac. globigii) in a clear-cut manner. 3. UV-light with a wavelength between 200 and 300 nm reduces the number of cells able to divide much quicker, than EUV-light of the same energy level does, but damages caused by EUV-light can not be reversed by photoreactivation. 4. Microbes which have been damaged by solar radiation, can be photoreactivated to a degree. Photoreactivation is high after exposure near the Earth and significant after exposure within the stratosphere. 5. After exposure to ionospheric irradiations no changes in the antigenic behavior of E. coli cells could be detected. PMID:11982026

  18. On the equatorial transport of Saturn's ionosphere as driven by a dust-ring current system

    NASA Technical Reports Server (NTRS)

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

    1983-01-01

    The diurnal modulation of the dust ring current of Saturn's D-ring causes field-aligned Birkeland currents to flow near the dawn and dusk terminators and close across the midlatitude ionosphere. One consequence of this current system is the establishment of a global convection pattern in the equatorial outer ionosphere. Outward motion of the dayside ionospheric plasma as well as the corresponding absorption effect of the inner ring system might be one physical cause of the depletion of the ionospheric content of Saturn.

  19. 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.

  20. Waterhole - An auroral-ionosphere perturbation experiment

    NASA Astrophysics Data System (ADS)

    Whalen, B. A.; Yau, A. W.; Creutzberg, F.; Pongratz, M. B.

    Preliminary results of the effect of the detonation of 100 kg of high explosives into the field lines of an auroral arc are presented. The payload was rocket-borne to an altitude of 300 km, and caused a depletion of the local ionospheric F region. The explosives were a mixture of the nitromethane and ammonium nitrate, and were housed in the front of the rocket while an instrument package trailed behind. The launch vehicle was a Black Brant X, and created an expanding cloud 40 km in diam. For 130 sec, a hole was cut in the electron precipitation field, and energetic electron precipitation in the hole dropped to background levels. The luminosity of the auroral arc observed by a ground-based scanning photometer decreased by a factor of two, and the ionospheric E region density below the hole decayed at a rate implying a reduction in particle precipitation.

  1. Physics-based formula representations of high-latitude ionospheric outflows: H+ and O+ densities and flow velocities vs. precipitation, wave-heating, and solar zenith angle effects

    NASA Astrophysics Data System (ADS)

    Horwitz, J. L.; Zeng, W.

    2007-12-01

    For many current global magnetospheric modeling efforts, it is highly desirable to try to incorporate realistic compact representations of the ionospheric outflow bulk parameters and their relationships to putative drivers. Recent satellite data analyses by Strangeway et al. [2005] and Zheng et al.[2005] have obtained formula fits for the measurement-based relationships of the outflow levels to parameterizations for electron precipitation and Poynting fluxes, which are expected to be among the principal drivers, or closely related to them, for the ionospheric outflows. In this presentation, we shall use the results of an extensive set of systematic simulation runs with our Dynamic Fluid Kinetic (DyFK) simulation code for ionospheric plasma field-aligned transport to obtain O+ and H+ densities and flow velocities at altitudes corresponding to typical inner boundary levels for prominent current global magnetospheric models which are moving toward multi-fluid treatments. These O+ and H+ densities and parallel flow velocities are parameterized versus precipitation electron energy flux levels, characteristic energy levels of the precipitating electron, the peak spectral wave densities for BBELF waves which transversely heat ionospheric ions, and solar zenith angle. Strangeway, R. J., R. E. Ergun, Y.-J. Su, C. W. Carlson, and R. C. Elphic, Factors controlling ionospheric outflows as observed at intermediate altitudes, J. Geophys. Res., 110, A03221, doi:10.1029/2004JA010829, 2005. Zheng, Y., T. E. Moore, F. S. Mozer, C. T. Russell, and R. J. Strangeway, Polar study of ionospheric ion outflow versus energy input, J. Geophys. Res., 110, A07210, doi:10.1029/2004JA010995, 2005.

  2. Nonlinear effects on the early stage of phase ordering kinetics

    SciTech Connect

    Copetti, M.I.M. [LANA, Departamento de Matematica, Universidade Federal de Santa Maria, 97119-900, Santa Maria, RS (Brazil); Krein, G.; Marques de Carvalho, R.S. [Instituto de Fisica Teorica, Universidade Estadual Paulista, Rua Pamplona, 145, 01405-900, Sao Paulo, SP (Brazil); Machado, J.M. [Instituto de Biociencias, Letras e Ciencias Exatas, Universidade Estadual Paulista, Rua Cristovao Colombo, 2265, 15054, Sao Jose do Rio Preto, SP (Brazil)

    2004-12-02

    Nonlinear effects on the early stage of phase ordering of a non conserved order parameter are studied using Adomian's decomposition method for the Ginzburg-Landau equation. In this method, the solution is systematically calculated in the form of a polynomial expansion for the order parameter. The method is very accurate for short times, which allows to incorporate the short-time dynamics of the nonlinear terms in a analytical and controllable way.

  3. Modeling of Ionosphere Effects of Geomagnetic Storm Sequence on September 9-14, 2005 in View of Solar Flares and Dependence of Model Input Parameters from AE-and Kp-indices

    NASA Astrophysics Data System (ADS)

    Klimenko, Maxim; Klimenko, Vladimir; Ratovsky, Konstantin; Goncharenko, Larisa

    Earlier by Klimenko et al., 2009 under carrying out the calculations of the ionospheric effects of storm sequence on September 9-14, 2005 the model input parameters (potential difference through polar caps, field-aligned currents of the second region and particle precipitation fluxes and energy) were set as function of Kp-index of geomagnetic activity. The analyses of obtained results show that the reasons of quantitative distinctions of calculation results and observations can be: the use of 3 hour Kp-index at the setting of time dependence of model input parameters; the dipole approach of geomagnetic field; the absence in model calculations the effects of the solar flares, which were taken place during the considered period. In the given study the model input parameters were set as function of AE-and Kp-indices of geomagnetic activity according to different empirical models and morphological representations Feshchenko and Maltsev, 2003; Cheng et al., 2008; Zhang and Paxton, 2008. At that, we taken into account the shift of field-aligned currents of the second region to the lower latitudes as by Sojka et al., 1994 and 30 min. time delay of variations of the field-aligned currents of second region relative to the variations of the potential difference through polar caps at the storm sudden commencement phase. Also we taken into account the ionospheric effects of solar flares. Calculation of ionospheric effects of storm sequence has been carried out with use of the Global Self-Consistent Model of the Thermosphere, Ionosphere and Protonosphere (GSM TIP) developed in WD IZMIRAN (Nam-galadze et al., 1988). We carried out the comparison of calculation results with experimental data. This study is supported by RFBR grant 08-05-00274. References Cheng Z.W., Shi J.K., Zhang T.L., Dunlop M. and Liu Z.X. Relationship between FAC at plasma sheet boundary layers and AE index during storms from August to October, 2001. Sci. China Ser. E-Tech. Sci., 2008, Vol. 51, No. 7, 842-848. Feshchenko E.Yu., Maltsev Yu.P. Relations of the polar cap voltage to the geophysical activity. Physics of Auroral Phenomena: XXVI Annual Seminar (February 25-28, 2003): Proc./PGI KSC RAS. Apatity, 2003, 59-61. Klimenko M.V., Klimenko V.V., Ratovsky K.G., and Goncharenko L.P. Numerical modeling of ionospheric parameters during sequence of geomagnetic storms on September 9-14, 2005. Physics of Auroral Phenomena: XXXII Annual Seminar (March 3-6, 2009): Proc./PGI KSC RAS. Apatity, 2009, 162-165. Namgaladze A.A., Korenkov Yu.N., Klimenko V.V., Karpov I.V., Bessarab F.S., Surotkin V.A., Glushenko T.A., Naumova N.M. Global model of the thermosphere-ionosphere-protonosphere system. Pure and Applied Geophysics (PAGEOPH), 1988, Vol. 127, No. 2/3, 219-254. Sojka J.J., Schunk R.W., Denig W.F. Ionospheric response to the sustained high geomagnetic activity during the March '89 great storm. J. Geophys. Res., 1994, Vol. 99, No. A11, 21341-21352. Zhang Y., Paxton L.J. An empirical Kp-dependent global auroral model based on TIMED/GUVI FUV data. J. Atmos. Solar-Terr. Phys., 2008, Vol. 70, 1231-1242.

  4. Ionospheric responses to two large geomagnetic storms over Japanese and Indian longitude sectors

    NASA Astrophysics Data System (ADS)

    Uma, G.; Brahmanandam, P. S.; Kakinami, Yoshihiro; Dmitriev, A.; Latha Devi, N. S. M. P.; Uday Kiran, K.; Prasad, D. S. V. V. D.; Rama Rao, P. V. S.; Niranjan, K.; Seshu Babu, Ch.; Chu, Y. H.

    2012-01-01

    The physical processes including the prompt penetration electric field, disturbance dynamo originated electric field, disturbed thermospheric winds and composition changes can play a significant role in restructuring the equatorial, low, mid and high-latitude ionosphere during storm-time. However, it has not yet been revealed that the contribution of individual physical processes, their interactions and impacts on that restructuring (Maruyama et al., 2005) is primarily due to the lack of continuous observational facilities. In this present research, the electric field (measured indirectly) and thermospheric wind (derived from an empirical disturbance wind model) components are effectively utilized as alternate database to ascertain the individual role of physical processes by studying the ionospheric response over Japanese and Indian longitude sectors during two geomagnetic storms occurring on 31 March, 2001 and 20 November, 2003 using ground (ionospheric parameters scaled from ionosondes and global ionospheric maps of total electron content measured by the ground-based GPS receivers) and satellite-borne (in-situ electron density data measured by the Planar Longmuir Probe onboard CHAMP satellite) measurements. It has been found that the equatorial ionization anomaly is expanded and intensified during the main phase of these two storms, which is believed to be caused by the prompt penetration electric field according to the current theory. In addition, the storm associated thermospheric wind is propagating equatorward (with an average velocity of ˜230 m/s) during the recovery phase of these two storms that is responsible for a height rise in the virtual height of the F-layer (h'F) starting from mid to low and equatorial latitudes with a consistent time delay. The empirical model derived winds corroborate the equatorward propagation, suggesting that this wind model data could be used as an alternate database particularly during the space weather events in order to discuss the global dynamical state of the ionosphere. Further, an important observation is that the ionospheric irregularities are found in the electron densities in the form of depletions nearly at anomaly crest region (˜23°N) as measured by the CHAMP satellite over the Japanese longitude sector during the main phase of the 20 November, 2003 storm during the pre mid night period that correspond to the time of rapid decrease (˜-30-35 nT/h) in Sym-H index due to prompt penetration of eastward electric fields into the low latitudes.

  5. The effective cosmological constant in higher order gravity theories

    E-print Network

    S. Capozziello; R. de Ritis; A. A. Marino

    1998-06-09

    An effective time--dependent cosmological constant can be recovered for higher--order theories of gravity by extending to these ones the no--hair conjecture. The results are applied to some specific cosmological models.

  6. Effects of the geomagnetic asymmetry of flux-tube integrated neutral winds to the Rayleigh-Taylor instability in equatorial ionosphere

    NASA Astrophysics Data System (ADS)

    Luo, Weihua; Xu, Jisheng; Tian, Mao

    Neutral winds play an important role in the develop-ment of Rayleigh-Taylor instability which is very associated with the occurrence of irregularities in the equatorial and low-latitude regions. For example, eastward winds would make for the development of R-T instability and meridional winds suppress the development of R-T insta-bility. In this work, we investigate effects of the geomagnetic asymmetry of neutral winds to the flux-tube integrated R-T instability in equatorial ionosphere. The flux-tube integrated lin-ear growth rate of R-T instability were estimated and considering the ambient electric fields and asymmetry of neutral winds between North-South hemispheres, and the integrated growth rates were compared which were get with and without the neutral wind, including the zonal and meridional wind. Effects of the longitudinal distribution of the meridional winds on the inte-grated growth rate are investigated also. It is shown that the zonal and meridional wind could significantly affect the growth rates and the meridional winds could decrease the integrated growth rate, respectively. The longitudinal variation of occurrence of irregularities would be related with the global distribution of meridional wind. Reference: Sultan, P.J., Linear theory and modeling of the Rayleigh-Taylor instability leading to the occurrence of equatorial spread F, J. Geophys. Res., 1996, 101(A12), 26875-26891 Basu, B., On the linear theory of equato-rial plasma instability: Comparison of different descriptions, J. Geophys. Res., 2002, 107(A8), 1199, doi: 10.1029/2001JA000317

  7. Three-dimensional multifluid simulations of ionospheric loss at Mars from nominal solar wind conditions to magnetic cloud events

    Microsoft Academic Search

    E. M. Harnett; R. M. Winglee

    2006-01-01

    conditions. Ionospheric losses on the order of 1025 O2 + ions per second are found for quiet solar wind conditions. This is of the same order as that estimated from Phobos 2 measurements. Varying the orientation of Mars' magnetic anomalies relative to the incident solar wind direction leads to only minor variation in the ionospheric loss rates of O2 +

  8. F-region Magnetospheric ULF Generation by Modulated Ionospheric Heating

    NASA Astrophysics Data System (ADS)

    Papadopoulos, K.; Tesfaye, B.; Shroff, H.; Shao, X.; Milikh, G.; Chang, C.; Wallace, T.; Inan, U.; Piddyachiy, D.

    2007-12-01

    Current modulation of D/E region ionospheric currents at ULF frequencies results in generation of Shear Alfven Waves injected upwards and guided by the magnetic field lines towards the conjugate ionosphere. Under particular ionospheric conditions frequencies in the PC1 range (.2-6Hz) are reflected by the gradient in the Alfven velocity above the F-region resulting in the well-known Ionospheric Alfven Resonator (IAR) structure. Ground detection of ULF waves due to current modulation on the ground is thus limited to the vicinity of the heated spot since at these frequencies the coupling to the earth ionosphere waveguide is evanescent. Propagation of ULF waves at significant lateral distances requires generation of magnetosonic waves since they are the only mode that propagates isotropically and can thus couple efficiently in the Alfvenic duct. In this paper we present a completely new mechanism to generate magnetosonic waves by modulated ionospheric heating that does not require the presence of electrojet currents. The process relies in anomalous electron heating near the F-region peak by preferably using O-mode upper hybrid heating modulated at ULF Pc-1 frequencies. The modulation in the electron pressure drives a Bxgrad(p) oscillatory current. The resultant field aligned magnetic moment generates predominantly magnetosonic waves that are injected laterally into the Alfvenic duct and can also detected above the F-peak by over-flying satellites over distances larger than spanned by the field lines connecting to heated area. In addition to the concept and analytic results the paper will present simulations results using the ZEUS-MP MHD. Non-uniform grids are used to adapt to non-uniform ionospheric plasma density and thin layer of heating source. The effective heating region is placed at about 200-300 km in altitude (F-layer ionosphere). The modulated heating source is modeled as a source with perturbed density, temperature and magnetic field and it transmits modulated-HF electromagnetic waves into a stable ionosphere. Ratios of perturbed magnetic field and density to their background values are extracted from simulations. Different radiation patterns from different polarization component of magnetic field perturbation are investigated. Effects of different profiles of non-uniform ionospheric plasma density on ULF wave propagation are also studied through simulation. Preliminary experimental evidence of the process will also be presented. This work was sponsored by ONR MURI Grant 5-28828

  9. Plasma Instability Growth Rates in the F-Region Cusp Ionosphere

    NASA Astrophysics Data System (ADS)

    Moen, J. I.; Daabakk, Y.; Oksavik, K.; Clausen, L.; Bekkeng, T. A.; Abe, T.; Saito, Y.; Baddeley, L. J.; Lorentzen, D. A.; Sigernes, F.; Yeoman, T. K.

    2014-12-01

    There are at least two different micro-instability processes that applies to the F-region cusp/polar cap ionosphere. These are the Gradient Drift Instability (GDI) and the Kelvin Helmholtz Instability (KHI). Due to space weather effects on radio communication and satellite signals it is of practical interest to assess the relative importance of these two instability modes and to quantify their growth rates. The Investigation of Cusp Irregularities (ICI) rocket program has been developed to investigate these plasma instabilities and formation scintillation irregularities. High resolution measurements are critical to get realistic quantities on the growth rates. The results achieved so far demonstrates that cusp ionosphere precipitation can give rise to km scale plasma structures on which grow rates are down to a few tens of seconds compared to earlier measures of ten minutes based on ground observations. This has to do with the spatial resolution required for these measurements. Growth rates for the KHI instability is found to be of the same order, which is consistent with growth rates calculated from the EISCAT Svalbard Radar. I.e. both instability modes can be highly efficient in the cusp ionosphere.

  10. Seismo-ionospheric coupling appearing as equatorial electron density enhancements observed via DEMETER electron density measurements

    NASA Astrophysics Data System (ADS)

    Ryu, K.; Lee, E.; Chae, J. S.; Parrot, M.; Pulinets, S.

    2014-10-01

    We report the processes and results of statistical analysis on the ionospheric electron density data measured by the Detection of Electro-Magnetic Emissions Transmitted from Earthquake Regions (DEMETER) satellite over a period of 6 years (2005-2010), in order to investigate the correlation between seismic activity and equatorial plasma density variations. To simplify the analysis, three equatorial regions with frequent earthquakes were selected and then one-dimensional time series analysis between the daily seismic activity indices and the equatorial ionization anomaly (EIA) intensity indices, which represent relative equatorial electron density increase, were performed for each region. The statistically significant values of the lagged cross-correlation function, particularly in the region with minimal effects of longitudinal asymmetry, indicate that some of the very large earthquakes with M > 5.0 in the low-latitude region can accompany observable precursory and concurrent EIA enhancements, even though the seismic activity is not the most significant driver of the equatorial ionospheric evolution. The physical mechanisms of the seismo-ionospheric coupling is consistent with our observation, and the possibility of earthquake prediction using the EIA intensity variation is discussed.

  11. Study of the effect of magnetic ordering on order-disorder transitions in binary alloys

    NASA Astrophysics Data System (ADS)

    Jena, Ambika Prasad; Sanyal, Biplab; Mookerjee, Abhijit

    2014-06-01

    We set up a mean-field approximation in a random Ising model characterized by two order parameters: the local sublattice magnetization and a mean-field occupation variable which act as an order parameter for the order-disorder transition. In the effective model Hamiltonian the two order-parameters are coupled. We solve the coupled equations arising from this to describe the total phase diagram. The exchange energies for FeCo alloys have then been accurately obtained from first-principles based on the technique of orbital peeling and a Monte Carlo analysis using a coupled Metropolis-Kawasaki updating has been carried out. Our results reasonably successfully agree with earlier experimental data.

  12. IONOSPHERIC POWER-SPECTRUM TOMOGRAPHY IN RADIO INTERFEROMETRY

    SciTech Connect

    Koopmans, L. V. E., E-mail: koopmans@astro.rug.n [Kapteyn Astronomical Institute, University of Groningen, P.O. Box 800, 9700 AV Groningen (Netherlands)

    2010-08-01

    A tomographic method is described to quantify the three-dimensional power spectrum of the ionospheric electron-density fluctuations based on radio-interferometric observations by a two-dimensional planar array. The method is valid for the first-order Born approximation and might be applicable in correcting observed visibilities for phase variations due to the imprint of the full three-dimensional ionosphere. It is shown that the ionospheric electron-density distribution is not the primary structure to model in interferometry, but rather its autocorrelation function or equivalently its power spectrum. An exact mathematical expression is derived that provides the three-dimensional power spectrum of the ionospheric electron-density fluctuations directly from a rescaled scattered intensity field and an incident intensity field convolved with a complex unit phasor that depends on the w-term and is defined on the full sky pupil plane. In the limit of a small field of view, the method reduces to the single phase-screen approximation. Tomographic self-calibration can become important in high-dynamic range observations at low radio frequencies with wide-field antenna interferometers because a three-dimensional ionosphere causes a spatially varying convolution of the sky, whereas a single phase screen results in a spatially invariant convolution. A thick ionosphere can therefore not be approximated by a single phase screen without introducing errors in the calibration process. By applying a Radon projection and the Fourier projection-slice theorem, it is shown that the phase-screen approach in three dimensions is identical to the tomographic method. Finally, we suggest that residual speckle can cause a diffuse intensity halo around sources due to uncorrectable ionospheric phase fluctuations in the short integrations, which could pose a fundamental limit on the dynamic range in long-integration images.

  13. Experimentally investigate ionospheric depletion chemicals in artificially created ionosphere

    SciTech Connect

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

    2012-09-15

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

  14. Time Variability of Titan's Ionosphere Revisited

    NASA Astrophysics Data System (ADS)

    Hsu, Jen-Kai; Ip, Wing-Huen; Perryman, Rebecca; Waite, Hunter

    2015-04-01

    Since the Saturn Orbital Insertion in 2004, the Ion Neutral Mass Spectrometer (INMS) experiment aboard the Cassini-Huygens spacecraft has acquired an extensive data set. The decadal coverage of the measurements during numerous close encounters with Titan allows the study of spatial and temporal variations of Titan's nitrogen-rich atmosphere above 1000-km altitude. Titan's ionosphere is quite different to that of Earth's ionosphere. Due to Titan's thick (hundreds of kilometers) and dense atmosphere, the measurable ion density of Titan's nightside ionosphere extends well beyond the terminator. The diurnal variation of the ion density profiles and compositional changes are the result of photoionization and magnetospheric electron ionization (important at the night side). The different time evolutions of the light and heavy species from day to night could be indicative of the effects of flow dynamics and ion-molecule chemistry. From the observations, we can determine the ion content in Titan's night-side and the asymmetry between the dawn and dusk ion density profiles. We have also found in the long term data base the signature of the equatorial expansion of Titan's atmosphere during solar maximum. In addition the global distributions of the major compound N2 and minor species like CH4 and H2 all exhibit significant changes over a solar cycle as the closest approach points of Cassini moved from the northern hemisphere to the southern hemisphere. In this work, we will first compare the diurnal variations between different ion species and simulate the ion densities to study the possible contributing factors. Then we will compare the results of our analysis to those reported by other groups to construct a comprehensive model of Titan's neutral atmosphere and ionosphere under different solar conditions.

  15. Sounding rockets explore the ionosphere

    SciTech Connect

    Mendillo, M. (Boston Univ., MA (USA))

    1990-08-01

    It is suggested that small, expendable, solid-fuel rockets used to explore ionospheric plasma can offer insight into all the processes and complexities common to space plasma. NASA's sounding rocket program for ionospheric research focuses on the flight of instruments to measure parameters governing the natural state of the ionosphere. Parameters include input functions, such as photons, particles, and composition of the neutral atmosphere; resultant structures, such as electron and ion densities, temperatures and drifts; and emerging signals such as photons and electric and magnetic fields. Systematic study of the aurora is also conducted by these rockets, allowing sampling at relatively high spatial and temporal rates as well as investigation of parameters, such as energetic particle fluxes, not accessible to ground based systems. Recent active experiments in the ionosphere are discussed, and future sounding rocket missions are cited.

  16. Assimilative modeling of low latitude ionosphere

    NASA Technical Reports Server (NTRS)

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

    2004-01-01

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

  17. Ionospheric correction of space radar data

    E-print Network

    Hapgood, Mike

    2009-01-01

    Radar is a critical tool for maintaining knowledge of the many ob-jects in low Earth orbit and thus for maintaining confidence that societies around the world are secure against a variety of space-based threats. It is therefore important to raise awareness that LEO objects are embedded in the envelope of relatively dense plasma that co-rotates with the Earth (ionosphere-plasmasphere system) and thus accurate tracking must cor-rect for the group delay and refraction caused by that system. This paper seeks to promote that awareness by reviewing those effects and high-lighting key issues: the need to customise correction to the altitude of the tracked object and prevailing space weather conditions, that ionospheric correction may be particularly important as an object approaches re-entry. The paper outlines research approaches that should lead to better techniques for ionospheric correction and shows how these might be pur-sued in the context of the EURIPOS initiative.

  18. A quantum probability account of order effects in inference.

    PubMed

    Trueblood, Jennifer S; Busemeyer, Jerome R

    2011-01-01

    Order of information plays a crucial role in the process of updating beliefs across time. In fact, the presence of order effects makes a classical or Bayesian approach to inference difficult. As a result, the existing models of inference, such as the belief-adjustment model, merely provide an ad hoc explanation for these effects. We postulate a quantum inference model for order effects based on the axiomatic principles of quantum probability theory. The quantum inference model explains order effects by transforming a state vector with different sequences of operators for different orderings of information. We demonstrate this process by fitting the quantum model to data collected in a medical diagnostic task and a jury decision-making task. To further test the quantum inference model, a new jury decision-making experiment is developed. Using the results of this experiment, we compare the quantum inference model with two versions of the belief-adjustment model, the adding model and the averaging model. We show that both the quantum model and the adding model provide good fits to the data. To distinguish the quantum model from the adding model, we develop a new experiment involving extreme evidence. The results from this new experiment suggest that the adding model faces limitations when accounting for tasks involving extreme evidence, whereas the quantum inference model does not. Ultimately, we argue that the quantum model provides a more coherent account for order effects that was not possible before. PMID:21951058

  19. A physical mechanism of positive ionospheric storms at low latitudes and midlatitudes

    Microsoft Academic Search

    N. Balan; K. Shiokawa; Y. Otsuka; T. Kikuchi; D. Vijaya Lekshmi; S. Kawamura; M. Yamamoto; G. J. Bailey

    2010-01-01

    A physical mechanism of the positive ionospheric storms at low latitudes and midlatitudes is presented through multi-instrument observations, theoretical modeling, and basic principles. According to the mechanism, an equatorward neutral wind is required to produce positive ionospheric storms. The mechanical effects of the wind (1) reduce (or stop) the downward diffusion of plasma along the geomagnetic field lines, (2) raise

  20. Test of GPS for permanent ionospheric TEC monitoring at high latitudes

    Microsoft Academic Search

    N. Zarraoa; E. Sardón

    1996-01-01

    The Global Positioning System (GPS) observables are affected by the ionosphere. The dispersive nature of this effect and the use of two frequencies in the GPS observations make possible to measure the ionospheric total electron content (TEC) from dual frequency GPS data. In this work we test the concept of permanent monitoring of TEC using a network of GPS receivers

  1. Ionospheric F-region Drift Measurements, First Results for Winter 2006

    E-print Network

    Santolik, Ondrej

    of the ionosphere is intimately linked with fluctuations in the electromagnetic and corpuscular radiations from effects due to electromagnetic fields, winds and waves in the neutral atmosphere. Vertical ionospheric sounding The classical ionosonde transmits vertically an upward propagating pulse of radio wave

  2. Time variations of the ionosphere at the northern tropical crest of ionization at Phu Thuy, Vietnam

    Microsoft Academic Search

    H. Pham Thi Thu; C. Amory-Mazaudier; M. Le Huy

    2011-01-01

    This study is the first which gives the climatology of the ionosphere at the northern tropical crest of ionization in the Asian sector. We use the data from Phu Thuy station, in Vietnam, through three solar cycles (20, 21 and 22), showing the complete morphology of ionosphere parameters by analyzing long term variation, solar cycle variation and geomagnetic activity effects,

  3. Variation of ionospheric total electron contents near the equatorial anomaly region during the solar minimum

    Microsoft Academic Search

    Abhay Kumar Singh; Sanjay Kumar; Francisco Azpilicueta

    2008-01-01

    The ionospheric total electron content (TEC), derived by analyzing dual frequency signals from the Global Positioning System (GPS) recorded near the equatorial anomaly region, Varanasi (geomag. lat. 14 degree 55 minute N, geomag. long.154 degree E) is studied. Specifically, we studied monthly seasonal and annual variations as well as solar and geomagnetic effects on the equatorial ionospheric anomaly (EIA) during

  4. Effects of the solar wind electric field and ionospheric conductance on the cross polar cap potential: Results of global MHD modeling

    Microsoft Academic Search

    V. G. Merkine; K. Papadopoulos; G. Milikh; A. S. Sharma; X. Shao; J. Lyon; C. Goodrich

    2003-01-01

    The behavior of the cross polar cap potential, ?PC, under strong solar wind conditions is studied using global MHD simulations. Simulations using two typical values of the ionospheric Pedersen conductance in agreement with others show that the cross polar cap potential is reduced compared to the corresponding potential in the solar wind due to the stagnation of the magnetosheath flow

  5. International Ionospheric Effects Symposium, May 7-9, 2002, ed. J.M. Goodman, 364-371 1 Improved polar HF propagation

    E-print Network

    Michigan, University of

    Cameron, United Air Lines, Palo Alto, CA George Davenport, ARINC, Colorado Springs, CO John Goodman, Radio of the nowcast/forecast plasma drift velocities from the DICM electric circuit model. The electron densities- ties and incident charged particle fluxes significantly change ionospheric electron density distribu

  6. Ionospheric chemistry of NO(+)

    NASA Technical Reports Server (NTRS)

    Breig, E. L.; Hanson, W. B.; Hoffman, J. H.

    1984-01-01

    An investigation is described of the behavior of NO(+) in the daytime F region, with basic ion concentration measurements from the Atmosphere Explorer C satellite. The data set was acquired along select orbits at low latitudes and exhibits substantial variations in the NO(+) concentration, both along and between nearby orbits. An excellent consistency is demonstrated between these observations and current chemical equilibrium theory, in contrast to differences that have been reported for the related N2(+) ion. Large variations in the concurrently observed electron temperature permit a relevant comparison between different laboratory determinations of the dissociative recombination rate coefficient. Contributions to the NO(+) production from several secondary sources are also evaluated. Results strengthen the basis for the current theoretical ionospheric chemistry of NO(+) and establish important constraints on resolution of the difficulties with N2(+).

  7. 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.

  8. Formation and evolution of the ionospheric plasma density shoulder and its relationship to the superfountain effects investigated during the 6 November 2001 great storm

    NASA Astrophysics Data System (ADS)

    Horvath, Ildiko; Lovell, Brian C.

    2008-12-01

    This study investigates the 6 November 2001 great storm's impact on the topside ionosphere utilizing data from the onboard TOPEX/Poseidon-NASA altimeter, Defense Meteorological Satellite Program-Special Sensor Ions, Electrons and Scintillation instruments and ACE interplanetary observatory. A set of field-aligned profiles demonstrate the storm evolution, caused by the precursor and promptly penetrating interplanetary eastward electric (E) fields, and strong equatorward winds reducing chemical loss, during the long-duration negative BZ events. At daytime-evening, the forward fountain experienced repeated strengthening, as the net eastward E field suddenly increased. The resultant symmetrical equatorial anomaly exhibited a continuous increase, while the energy inputs at both auroral regions were similar. In both hemispheres, by progressing poleward, a midlatitude shoulder exhibiting increased plasma densities, a plasma-density dropoff (steep gradient) and a plasma depletion appeared. These features were maintained while the reverse fountain operated. At the dropoff, elevated temperatures indicated the plasmapause. Consequently, the plasma depletion was the signature of plasmaspheric erosion. In each hemisphere, an isolated plasma flow, supplying the minimum plasma, was detected at the shoulder. Plasmaspheric compression, due to the enhanced E fields, could trigger this plasma flow. Exhibiting strong longitudinal variation at evening-nighttime, the shoulder increased 306% over the southeastern Pacific, where the nighttime Weddell Sea Anomaly (WSA) appeared before the storm. There, the shoulder indicated the storm-enhanced equatorward section of the quiet time WSA. Owing to the substantial equatorward plasmapause movement, a larger poleward section of the quiet time WSA eroded away, leaving a large depletion behind. This study reports first these (northern, southern) plasma flows and dramatic storm effects on a nighttime WSA.

  9. Response of the Ionosphere-Plasmasphere System to Periodic Forcing

    NASA Astrophysics Data System (ADS)

    Pedatella, Nicholas M.

    The role of different mechanisms for generating periodic variability in the ionosphere and plasmasphere is studied in this dissertation. The impact of vertically propagating waves of lower atmospheric origin on introducing periodic spatial and temporal variability in the ionosphere and plasmasphere is first investigated. This is comprised of several different aspects. Initial focus is on the seasonal, local time, and altitude dependence of longitude variations due to nonmigrating tides in the F-region and topside ionosphere/plasmasphere using a combination of observations and numerical models. This is facilitated by the development of a new method for mitigating the effect of multipath on low-Earth orbit (LEO) satellite Global Positioning System (GPS) observations. The impact of large-scale changes in tropospheric convection due to the El-Nino Southern Oscillation on the ionosphere is also explored observationally. The influence of nonmigrating tides on the global ionosphere is revealed through study of the longitude variations in the solar quiet current system. Periodic temporal variability in the ionosphere due to planetary waves originating in the lower atmosphere is also investigated. The response of the global ionosphere to the quasi-16 day planetary wave is first presented. This is followed by observational evidence demonstrating that the nonlinear interaction between planetary waves and tides is the primary mechanism responsible for low-latitude ionospheric variability during sudden stratospheric warmings. Periodic temporal variability in the ionosphere and plasmasphere of solar origin is also studied. During the declining phase of solar cycle 23, near-Earth geospace was routinely disturbed due to high-speed solar wind streams emanating from solar coronal holes. The nature of the coronal holes was such that the Earth's upper atmosphere exhibited periodic behavior due to recurrent geomagnetic activity. A study of the latitude and local time response of the ionosphere to recurrent geomagnetic activity is performed herein. A method for estimating the location of the plasmapause from LEO GPS observations is also developed and applied to study periodic oscillations in the plasmapause.

  10. Evaluation of higher-order effective potentials with dimensional regularization

    Microsoft Academic Search

    S. Y. Lee; Alain M. Sciaccaluga

    1975-01-01

    A new and simple method for evaluating high-order effective potentials is presented. It is based on the renormalization procedure of 't Hooft and Veltman used in conjunction with the scheme of dimensional regularization. Explicit calculations of the effective potential of a scalar field in two-loop approximation are carried out.

  11. The high order relativistic effects in millisecond pulsar timing

    Microsoft Academic Search

    Jia-Qiu Liu; Chong-Ming Xu

    1989-01-01

    The second order relativistic effects of the sun and the earth in deriving the precise equation of transformation between proper atomic time on earth and the PPN time in the solar system are considered. The time arrival formula is obtained from the null geodesic equation, and various relativistic effects are estimated. The results improve Hellings' to 10 to the -14th

  12. First and Higher Order Effects on Zero Order Radiative Transfer Model

    NASA Astrophysics Data System (ADS)

    Neelam, M.; Mohanty, B.

    2014-12-01

    Microwave radiative transfer model are valuable tool in understanding the complex land surface interactions. Past literature has largely focused on local sensitivity analysis for factor priotization and ignoring the interactions between the variables and uncertainties around them. Since land surface interactions are largely nonlinear, there always exist uncertainties, heterogeneities and interactions thus it is important to quantify them to draw accurate conclusions. In this effort, we used global sensitivity analysis to address the issues of variable uncertainty, higher order interactions, factor priotization and factor fixing for zero-order radiative transfer (ZRT) model. With the to-be-launched Soil Moisture Active Passive (SMAP) mission of NASA, it is very important to have a complete understanding of ZRT for soil moisture retrieval to direct future research and cal/val field campaigns. This is a first attempt to use GSA technique to quantify first order and higher order effects on brightness temperature from ZRT model. Our analyses reflect conditions observed during the growing agricultural season for corn and soybeans in two different regions in - Iowa, U.S.A and Winnipeg, Canada. We found that for corn fields in Iowa, there exist significant second order interactions between soil moisture, surface roughness parameters (RMS height and correlation length) and vegetation parameters (vegetation water content, structure and scattering albedo), whereas in Winnipeg, second order interactions are mainly due to soil moisture and vegetation parameters. But for soybean fields in both Iowa and Winnipeg, we found significant interactions only to exist between soil moisture and surface roughness parameters.

  13. Application of nonlinear methods to the study of ionospheric plasma

    NASA Astrophysics Data System (ADS)

    Chernyshov, A. A.; Mogilevsky, M. M.; Kozelov, B. V.

    2015-01-01

    Most of the processes taking place in the auroral region of Earth's ionosphere are reflected in a variety of dynamic forms of the aurora borealis. In order to study these processes it is necessary to consider temporary and spatial variations of the characteristics of ionospheric plasma. Most traditional methods of classical physics are applicable mainly for stationary or quasi-stationary phenomena, but dynamic regimes, transients, fluctuations, selfsimilar scaling could be considered using the methods of nonlinear dynamics. Special interest is the development of the methods for describing the spatial structure and the temporal dynamics of auroral ionosphere based on the ideas of percolation theory and fractal geometry. The fractal characteristics (the Hausdorff fractal dimension and the index of connectivity) of Hall and Pedersen conductivities are used to the description of fractal patterns in the ionosphere. To obtain the self-consistent estimates of the parameters the Hausdorff fractal dimension and the index of connectivity in the auroral zone, an additional relation describing universal behavior of the fractal geometry of percolation at the critical threshold is applied. Also, it is shown that Tsallis statistics can be used to study auroral ionosphere

  14. Dynamics of the Venus ionosphere revisited

    SciTech Connect

    Mccormick, P.T.; Whitten, R.C.; Knudsen, W.C.

    1987-06-01

    The Whitten et al. (1984) dynamical model of the Venus ionosphere is presently modified in order to obtain a better match between observations and predictions. It is found that the nighttime ion densities are comparatively insensitive to the height of the ionopause above a value of 450 km. The density increases by only about 25 percent when the ionopause is raised to 800 km, but is noted to be very sensitive to the choice of a neutral model atmosphere, and to the ion and electron temperatures that influence both plasma scale height and ion diffusivity. 12 references.

  15. Extended ionospheric amplitude scintillation model for GPS receivers

    NASA Astrophysics Data System (ADS)

    Oliveira Moraes, Alison; Costa, Emanoel; Paula, Eurico Rodrigues; Perrella, Waldecir João.; Monico, João. Francisco Galera

    2014-05-01

    Ionospheric scintillation is a phenomenon that occurs after sunset, especially in the low-latitude region, affecting radio signals that propagate through the ionosphere. Depending on geophysical conditions, ionospheric scintillation may cause availability and precision problems to Global Navigation Satellite System users. The present work is concerned with the development of an extended model for describing the effects of the amplitude ionospheric scintillation on GPS receivers. Using the ?-? probabilistic model, introduced by previous authors in different contexts, the variance of GPS receiver tracking loop error may be estimated more realistically. The proposed model is developed with basis on the ?-? parameters and also considering correlation between amplitude and phase scintillation. Its results are interpreted to explain how a receiver may experience different error values under the influence of ionospheric conditions leading to a fixed scintillation level S4. The model is applied to a large experimental data set obtained at São José dos Campos, Brazil, near the peak of the equatorial anomaly during high solar flux conditions, between December 2001 and January 2002. The results from the proposed model show that depending on the ?-? pair, moderate scintillation (0.5 ? S4 ? 0.7) may be an issue for the receiver performance. When S4 > 0.7, the results indicate that the effects of scintillation are serious, leading to a reduction in the receiver availability for providing positioning solutions in approximately 50% of the cases.

  16. Ionospheric Refraction Corrections in the GTDS for Satellite-To-Satellite Tracking Data

    NASA Technical Reports Server (NTRS)

    Nesterczuk, G.; Kozelsky, J. K.

    1976-01-01

    In satellite-to-satellite tracking (SST) geographic as well as diurnal ionospheric effects must be contended with, for the line of sight between satellites can cross a day-night interface or lie within the equatorial ionosphere. These various effects were examined and a method of computing ionospheric refraction corrections to range and range rate measurements with sufficient accuracy were devised to be used in orbit determinations. The Bent Ionospheric Model is used for SST refraction corrections. Making use of this model a method of computing corrections through large ionospheric gradients was devised and implemented into the Goddard Trajectory Determination System. The various considerations taken in designing and implementing this SST refraction correction algorithm are reported.

  17. Model of superthermal ions in the Venus ionosphere

    NASA Astrophysics Data System (ADS)

    Kramer, L.; Cloutier, P. A.; Taylor, H. A.

    1993-03-01

    A model is presented that simulates the behavior of superthermal ions previously reported in the dayside ionosphere of Venus. The model considers effects of ExB and gradient drifts, charge exchange and collisions with the ambient neutral atmosphere and the possible effects of a wave-particle (anomalous) scattering process. Results indicate that scattering processes are required if superthermal ions are the explanation for the observed 'missing pressure' component in the day-side Venus ionosphere. The scattering scale length required to match the 'missing pressure' distribution is similar to the scale length previously predicted for growth of a lower hybrid beam instability.

  18. Rocket vehicle targeting for the PLACES ionospheric plasma test series

    NASA Astrophysics Data System (ADS)

    Rollstin, L. R.

    1984-02-01

    The PLACES (Position Location And Communication Effects Simulations) test program, conducted in December 1980 at Eglin Gulf Test Range, involved a series of ionospheric releases of barium/barium-nitrate vapor. The Defense Nuclear Agency sponsored program investigated effects of a structured ionospheric plasma (similar to that produced by a high-altitude nuclear explosion) on satellite navigation systems and provided in situ measurement of plasma structure. Terrier-Tomahawk rocket systems boosted the barium payloads, beacon payloads (plasma occultation experiment), and probe payloads (plasma in situ measurement). Drifting plasma tracking procedures, beacon- and probe-vehicle targeting procedures, and vehicle flight test results are presented.

  19. Scale Height variations with solar cycle in the ionosphere of Mars

    NASA Astrophysics Data System (ADS)

    Sanchez-Cano, Beatriz; Lester, Mark; Witasse, Olivier; Milan, Stephen E.; Hall, Benjamin E. S.; Cartacci, Marco; Radicella, Sandro M.; Blelly, Pierre-Louis

    2015-04-01

    The Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) on board the Mars Express spacecraft has been probing the topside of the ionosphere of Mars since June 2005, covering currently almost one solar cycle. A good knowledge of the behaviour of the ionospheric variability for a whole solar period is essential since the ionosphere is strongly dependent on solar activity. Using part of this dataset, covering the years 2005 - 2012, differences in the shape of the topside electron density profiles have been observed. These variations seem to be linked to changes in the ionospheric temperature due to the solar cycle variation. In particular, Mars' ionospheric response to the extreme solar minimum between end-2007 and end-2009 followed a similar pattern to the response observed in the Earth's ionosphere, despite the large differences related to internal origin of the magnetic field between both planets. Plasma parameters such as the scale height as a function of altitude, the main peak characteristics (altitude, density), the total electron content (TEC), the temperatures, and the ionospheric thermal pressures show variations related to the solar cycle. The main changes in the topside ionosphere are detected during the period of very low solar minimum, when ionospheric cooling occurs. The effect on the scale height is analysed in detail. In contrast, a clear increase of the scale height is observed during the high solar activity period due to enhanced ionospheric heating. The scale height variation during the solar cycle has been empirically modelled. The results have been compared with other datasets such as radio-occultation and retarding potential analyser data from old missions, especially in low solar activity periods (e.g. Mariner 4, Viking 1 and 2 landers), as well as with numerical modelling.

  20. F region electron density profile inversion from backscatter ionogram based on international reference ionosphere

    NASA Astrophysics Data System (ADS)

    Zhu, Peng; Zhou, Chen; Zhang, Yuannong; Yang, Guobin; Jiang, Chunhua; Sun, Hengqing; Cui, Xiao

    2015-07-01

    Ionospheric backscatter sounding transmits HF (3-30 MHz) radio wave obliquely into ionosphere and receives echoes backscattered from remote ground. Due to the focusing effect, the echoes form leading edge on the swept frequency backscatter ionogram (BSI). This kind of backscatter ionogram contains plentiful ionospheric information, such as electron density, radio wave propagation modes and maximum usage frequency (MUF). By inversion algorithm, the backscatter ionogram can provide two-dimensional electron density profile (EDP) down range. In this paper, we propose an ionospheric F2 region EDP inversion algorithm. By utilizing the F2 bottomside electron density profile represented by the International Reference Ionosphere (IRI) model and ray tracing techniques, this approach inverts the leading edge of the backscatter ionogram to two dimensional F region EDP. Results of validation experiments demonstrate that the inverted ionospheric EDPs show good agreement with the results of vertical ionosonde and provide reliable information of ionosphere. Thus the proposed inversion algorithm provide an effective and accurate method for achieving large scale and remote ionospheric electron density structure.

  1. DyFK-simulation-based formulaic representation of the effects of wave-driven ion heating and electron precipitation on ionospheric outflows

    NASA Astrophysics Data System (ADS)

    Horwitz, J. L.; Zeng, W.

    2006-12-01

    There is great interest in the magnetospheric community in obtaining compact representations of the ionospheric outflow fluxes and their relationships to putative drivers. Recently, analyses of measurements by FAST [Strangeway et al., 2005] and POLAR [Zheng et al., 2005] has led to best fit formulas for the measurement-based relationships of the outflows levels to parameterizations for electron precipitation and Poynting fluxes, which are expected to be among the principal drivers, or closely related to them, for the ionospheric outflows. In this presentation, we shall use the results of an extensive set of systematic simulation runs with our Dynamic Fluid Kinetic (DyFK) simulation code for ionospheric plasma field-aligned transport to obtain O+ outflow flux levels versus precipitation electron energy flux levels and the peak spectral wave densities for BBELF waves which transversely heat ionospheric ions. We shall present spectrograms of the relationship of the ion outflow values to these electron energy flux and BBELF wave levels. A preliminary approximate formulaic representation at this time is: FluxO+ = 5*(3.0x10^9 + 0.02x1013 f_e^{1.4})(tanh(8Dwave)+0.2Dwave^{0.6}) where FluxO+ is the O+ number flux in m-2s-1 at 3R_E mapped to 1000 km altitude, f_e is the electron precipitation energy flux in ergs cm-2 s-1, and Dwave is the wave spectrum density at 6.5 Hz in (mV)2 m-2 Hz-1. Strangeway, R. J., R. E. Ergun, Y.-J. Su, C. W. Carlson, and R. C. Elphic, Factors controlling ionospheric outflows as observed at intermediate altitudes, J. Geophys. Res., 110, A03221, doi:10.1029/2004JA010829, 2005. Zheng, Y., T. E. Moore, F. S. Mozer, C. T. Russell, and R. J. Strangeway, Polar study of ionospheric ion outflow versus energy input, J. Geophys. Res., 110, A07210, doi:10.1029/2004JA010995, 2005.

  2. Light filaments with higher-order Kerr effect.

    PubMed

    Wang, Haitao; Fan, Chengyu; Zhang, Pengfei; Qiao, Chunhong; Zhang, Jinghui; Ma, Huimin

    2010-11-01

    The influence mechanism of higher-order Kerr effect on the propagation of laser beam is investigated by a modified model, which indicates that a collapsing wave will transform into a universe blowup profile. The analysis of higher-order terms of the nonlinear refractive index shows that the filamentation process can be induced by Kerr self-focusing without the occurrence of the ionization effect. The determining role of the combination of self-focusing and spontaneous defocusing and the energy reservoir in formation of lengthy filament is confirmed visually. PMID:21164776

  3. Saturation spectrum of the parametric decay instability in the presence of an external magnetic field. [geomagnetic effect in ionospheric heating

    NASA Technical Reports Server (NTRS)

    Chen, H. C.; Fejer, J. A.

    1975-01-01

    The effects of an external magnetic field on the saturation spectrum of parametric decay instabilities is examined by means of a modification of the Kuo and Fejer (1972) analysis. The main effect of the magnetic field is shown to be a decrease of the wavenumber with increasing angle between the wave vector and the magnetic field, particularly when the pump frequency is near the second harmonic of the cyclotron frequency. The spread of the phase velocities as measured in the direction of the magnetic field is significantly greater in the saturation spectrum when the pump frequency is near the second harmonic of the cyclotron frequency, facilitating the acceleration of tail electrons to energies of a few electron volts. It is suggested that this effect accounts for the greatly enhanced airglow observed (Haslett and Megill, 1974) under these conditions.

  4. 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.

  5. Quantifying and modeling birth order effects in autism.

    PubMed

    Turner, Tychele; Pihur, Vasyl; Chakravarti, Aravinda

    2011-01-01

    Autism is a complex genetic disorder with multiple etiologies whose molecular genetic basis is not fully understood. Although a number of rare mutations and dosage abnormalities are specific to autism, these explain no more than 10% of all cases. The high heritability of autism and low recurrence risk suggests multifactorial inheritance from numerous loci but other factors also intervene to modulate risk. In this study, we examine the effect of birth rank on disease risk which is not expected for purely hereditary genetic models. We analyzed the data from three publicly available autism family collections in the USA for potential birth order effects and studied the statistical properties of three tests to show that adequate power to detect these effects exist. We detect statistically significant, yet varying, patterns of birth order effects across these collections. In multiplex families, we identify V-shaped effects where middle births are at high risk; in simplex families, we demonstrate linear effects where risk increases with each additional birth. Moreover, the birth order effect is gender-dependent in the simplex collection. It is currently unknown whether these patterns arise from ascertainment biases or biological factors. Nevertheless, further investigation of parental age-dependent risks yields patterns similar to those observed and could potentially explain part of the increased risk. A search for genes considering these patterns is likely to increase statistical power and uncover novel molecular etiologies. PMID:22039484

  6. Quantifying and Modeling Birth Order Effects in Autism

    PubMed Central

    Turner, Tychele; Pihur, Vasyl; Chakravarti, Aravinda

    2011-01-01

    Autism is a complex genetic disorder with multiple etiologies whose molecular genetic basis is not fully understood. Although a number of rare mutations and dosage abnormalities are specific to autism, these explain no more than 10% of all cases. The high heritability of autism and low recurrence risk suggests multifactorial inheritance from numerous loci but other factors also intervene to modulate risk. In this study, we examine the effect of birth rank on disease risk which is not expected for purely hereditary genetic models. We analyzed the data from three publicly available autism family collections in the USA for potential birth order effects and studied the statistical properties of three tests to show that adequate power to detect these effects exist. We detect statistically significant, yet varying, patterns of birth order effects across these collections. In multiplex families, we identify V-shaped effects where middle births are at high risk; in simplex families, we demonstrate linear effects where risk increases with each additional birth. Moreover, the birth order effect is gender-dependent in the simplex collection. It is currently unknown whether these patterns arise from ascertainment biases or biological factors. Nevertheless, further investigation of parental age-dependent risks yields patterns similar to those observed and could potentially explain part of the increased risk. A search for genes considering these patterns is likely to increase statistical power and uncover novel molecular etiologies. PMID:22039484

  7. The effects of nitric oxide cooling and the photodissociation of molecular oxygen on the thermosphere/ionosphere system

    E-print Network

    Boyer, Edmond

    The effects of nitric oxide cooling and the photodissociation of molecular oxygen of thermospheric cooling by 5.3 m nitric oxide has been neglected and the photo- dissociation of O2 and heating photodissociation rate, in the model. Seasonally dependent 5.3 m nitric oxide cooling is also included

  8. Model of Jovian F region ionosphere (Jovian ionosphere model in offset dipole approximation). Annual report No. 2

    SciTech Connect

    Tan, A.

    1990-10-01

    The geomagnetic control of the Earth's atmosphere is well understood. In the F-region and the topside ionosphere, non-electrical forces transport plasma along the magnetic field lines only. In consequence, the worldwide distribution of ionization is strongly dependent on the dip angle. For example, the equatorial anomaly is roughly symmetrical about the dipole equator rather than the geographic. The same appears to be the case in the Jovian ionosphere (Mahajan, 1981). The influence of the magnetic field of Jupiter on its ionization pattern is one of several outstanding topics which need to be studied. Tan (1986) investigated the formation of the equatorial anomaly in the Jovian ionosphere under a centered dipole model. Tan (1988) further studied the effect of the tilt of the Jovian dipole. The results were in broad agreement with those of a diffusive equilibrium model (Tan and Wu, 1981). An off-centered dipole model is constructed and its effects on the ionization pattern are investigated.

  9. Remote sensing of the Ionosphere over the Murchison Radio Observatory, Western Australia, Leading to an Understanding of Fine Scale Behaviour

    NASA Astrophysics Data System (ADS)

    Herne, D. E.; Lynch, M. J.; Coster, A. J.; Oberoi, D.; Carrano, C. S.; Williams, J.; Kennewell, J.; Groves, K. M.

    2010-12-01

    The Murchison Radio Observatory (MRO) is the home of radio astronomy in Australia. Projects currently under development at the MRO include a low-frequency instrument, the Murchison Widefield Array (MWA). The MWA is an aperture synthesis, imaging array that when complete will comprise approximately 8,000 dipole antennas operating in the frequency range, 80 to 300 MHz. Signals in this frequency range are subject to distortions caused by the ionosphere. The effects of scintillation and faraday rotation degrade image quality. In order to ‘unwind’ faraday rotation, the distribution of the electron content in the ionosphere must be determined. Knowledge of the absolute total electron content (TEC) provides information about this distribution. This step is necessary in order to study processes in space involving magnetism. Over a period of two years, TEC measurements have been made over the MRO using high-precision, dual-frequency, GPS systems. Continuous measurements were performed for 12 months and campaign-based measurements at other times, due to the remote location of the MRO. The determination of the GPS receiver biases used to calculate TEC were studied with respect to changing temperatures. TEC measurements are compared to the results of modelling conducted previously (Kennewell et. al. 2005) as part of Australia’s bid to host the Square Kilometre Array radio telescope (SKA). Further, due to the fine grained nature of measurements (on the order of 0.01-0.03 TEC units), fine-scale structure can be resolved in the behaviour of the ionosphere in both temporal and spatial domains and is discussed. This work too, is laying a foundation for the accurate characterisation of the ionosphere over the MRO which is also the possible future site of the SKA. Plans to extend this work and the implementation of useful new measurement regimes are discussed, enabled by facilities currently being established as part of Australia’s ongoing commitment to radio astronomy on the MRO.

  10. How Uncertainties in the Neutral Wind Affect Ionospheric Modeling

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

    An ionospheric model relies on a number of input fields that are climatological in nature, being based on the statistical averaging of observations that have been classified or binned according to parameters such as season, solar activity level, geomagnetic activity level, and so on. One of the most important input fields for an ionospheric model, especially at mid-latitudes, is the neutral wind. The primary mechanism by which the neutral wind affects ionospheric densities is an induced upward or downward ion drift along the magnetic field lines. The magnitude of this effect depends upon the dip angle of the magnetic field; for this reason, the impact of the neutral wind is less in polar regions than at mid-latitudes. The quality of a model's output cannot be expected to be better than the quality of its inputs. It is unfortunate that observations of the neutral wind are relatively scarce, as compared for example with observations of the earth's electric field or auroral precipitation, and that the existing climatological models of the neutral wind are thus sharply limited in their accuracy. In this work, using Utah State University's Time Dependent Ionospheric Model (TDIM), we bring to light the degree to which a model's ability to simulate or forecast the ionosphere is hampered by an uncertain representation of the neutral wind.

  11. Ionospheric anomalous disturbance during the tropospheric strong convective weather

    NASA Astrophysics Data System (ADS)

    Cang, Zhongya; Cheng, Guangguang; Cheng, Guosheng

    2015-07-01

    Based on TBB data from Chinese FY-2 geostationary satellite, NCEP Reanalysis data and GPS-TEC data provided by IGS, by using sliding mean method, ionospheric anomalous disturbance during a typical convective weather was investigated. Results show that this severe convective weather was caused by a high-altitude cold eddy and a strong squall line. The ionospheric total electron content increased abnormally when convection occurred. The maximum increase of tested point was more than 6 TECU mainly at 8-12 UT of the day, and the peak time of the day lagged about 2 h than usual. Ionospheric anomalous region reached about 20 longitudes and 10 latitudes, and anomalous center was on the west side of the convective cloud, which may be related to the topographic effect of the Tibetan Plateau. Series of Case Studies further determine that convective weather can influence the ionospheric state. Furthermore, tropospheric vertical velocity was also analyzed to discuss the possible mechanisms of troposphere-ionosphere coupling.

  12. Coupling Tsunamis with the Ionosphere: A New Modeling Approach

    NASA Astrophysics Data System (ADS)

    Meng, X.; Komjathy, A.; Yang, Y. M.; Verkhoglyadova, O. P.; Mannucci, A. J.

    2014-12-01

    Tsunamis can generate gravity waves propagating upward through the atmosphere and induce total electron content (TEC) disturbances in the ionosphere. The wave propagation has been captured by waveform models, which are effective but lack physical consistency. For the first time, we have implemented tsunami-generated gravity waves into the Global Ionosphere-Thermosphere Model (GITM) to develop a fully physics-based three-dimensional model describing the upper atmosphere under the influence of tsunamis. The model takes tsunami wave characteristics, including the wave heights, wavelengths and propagation velocities at the ocean surface as input parameters and characterizes the ionosphere-thermosphere between altitudes 100km and 600km. The computational region and grid resolution in the horizontal direction can be specifically adjusted according to applications.As an initial application and test case, we simulate the ionosphere-thermosphere above the US west coastal region where the tsunamis caused by the 2011 Tokohu earthquake arrived and caused disturbances in the ionosphere. To validate our modeling approach, the GITM-simulated TEC disturbances are compared with GPS-derived TEC measurements at multiple geographic locations. We envision that modeled and measured TEC perturbations could play a critical role in detecting and imaging the upper atmospheric signatures of natural hazards including earthquakes, tsunamis, and volcanic eruptions.

  13. Maternal age, birth order, and race: differential effects on birthweight

    PubMed Central

    Swamy, Geeta K; Edwards, Sharon; Gelfand, Alan; James, Sherman A; Miranda, Marie Lynn

    2014-01-01

    Background Studies examining the influence of maternal age and birth order on birthweight have not effectively disentangled the relative contributions of each factor to birthweight, especially as they may differ by race. Methods A population-based, cross-sectional study of North Carolina births from 1999 to 2003 was performed. Analysis was restricted to 510 288 singleton births from 28 to 42 weeks’ gestation with no congenital anomalies. Multivariable linear regression was used to model maternal age and birth order on birthweight, adjusting for infant sex, education, marital status, tobacco use and race. Results Mean birthweight was lower for non-Hispanic black individuals (NHB, 3166 g) compared with non-Hispanic white individuals (NHW, 3409 g) and Hispanic individuals (3348 g). Controlling for covariates, birthweight increased with maternal age until the early 30s. Race-specific modelling showed that the upper extremes of maternal age had a significant depressive effect on birthweight for NHW and NHB (35+ years, p<0.001), but only age less than 25 years was a significant contributor to lower birthweights for Hispanic individuals, p<0.0001. Among all racial subgroups, birth order had a greater influence on birthweight than maternal age, with the largest incremental increase from first to second births. Among NHB, birth order accounted for a smaller increment in birthweight than for NHW and Hispanic women. Conclusion Birth order exerts a greater influence on birthweight than maternal age, with signficantly different effects across racial subgroups. PMID:21081308

  14. The calculation of ionospheric ray paths 

    E-print Network

    Koehler, Buford Ray

    1967-01-01

    Parabolic ionospheric layer of electrons, altitude versus electron density Page 1- 2 Sample ray paths with constant angle of propagation and increasing frequency, parabolic ionosphere of electrons assumed, earth's magnetic field neglected 1- 3 Sample... ray paths with constant frequency and variable angle of propagation and range, parabolic ionosphere of electrons assumed, earth's magnetic field neglected 2- 1 The vertical and lateral deviations of a radio wave propagated in a plane ionosphere...

  15. The Schumann resonance eigenmodes in the Earth's ionosphere observed by Chibis-M microsatellite

    NASA Astrophysics Data System (ADS)

    Dudkin, Denys

    2014-05-01

    The Schumann resonance (SR) occurs due to the global thunderstorm activity in the Earth-ionosphere cavity. The first five eigenmodes of the SR are 7.8, 14.3, 20.8, 27.3 and 33.8 Hz. This effect is well observed from ground-based electromagnetic (EM) sensors. However, the results of published numerical simulations show that the penetration depth into the ionosphere of EM fields, related to SR, is limited to 50-70 km for electric field and 120-240 km for magnetic field. From this follows, that SR can hardly ever be detected by the low Earth orbiting satellites. In spite of this fact, SR has been found for the first time in data collected by the Communications/Navigation Outage Forecasting System (C/NOFS) satellite [Simoes et al., 2011]. C/NOFS observed SR signals in the altitude range 400-850 km at local night time, from three orthogonal pairs of 20 m tip-to-tip electric field double probes. The SR spectral density is about 0.3 (?V/m)/Hz1/2, which is almost 3 orders of magnitudes lower than usually observed on the Earth's surface. As well, the SR harmonics were observed by Russian Chibis-M microsatellite in 2013, also at local night time. The Chibis-M satellite has mass ~40kg and was launched on January 24, 2012, at 23:14 UTC from the cargo ship 'Progress M-13M' to circular orbit with altitude ~500 km and inclination ~52° . One of the mission goals is to study the plasma wave processes related to solar-magnetosphere-ionosphere-atmosphere connections in ULF-VLF range. The Chibis-M EM field sensors were developed and designed in Lviv Centre of Institute for Space Research, Ukraine. The electric field antenna of Chibis-M has very short base, ~0.42 m, nevertheless the SR eigenfrequencies were reliably detected. The measured spectral density of first SR peak is about 0.5 (?V/m)/Hz1/2, which is very close to value, obtained by C/NOFS satellite. The fact of SR registration in the ionosphere suggests that the Earth-ionosphere waveguide should be described as a leaky cavity for ELF wave propagation. Perhaps the SR detection in ionosphere at local night can be explained by decreasing of plasma density in shadow zone. Thus, at study of ELF waves propagation, the model of the Earth-ionosphere structure should be refined. Simoes, F. A., R. F. Pfaff, H. T. Freudenreich, Satellite observations of Schumann resonances in the Earth's ionosphere, Geophys. Res. Lett., 38, L22101, doi:10.1029/2011GL049668, 2011.

  16. The effects of neutral inertia on ionospheric currents in the high-latitude thermosphere following a geomagnetic storm

    NASA Technical Reports Server (NTRS)

    Deng, W.; Killeen, T. L.; Burns, A. G.; Roble, R. G.; Slavin, J. A.; Wharton, L. E.

    1993-01-01

    Neutral flywheel effects are investigated in NCAR-TIGCM simulation of geomagnetic storms that occurred in November 23, 1982 and December 7-8, 1982. Theoretical calculations from the latter storm are compared with measurements of currents form instruments on the Dynamics Explorer 2 satellite. It is concluded that neutral flywheel effects can make a contribution to high latitude electrodynamics for a few hours after the main phase of a geomagnetic storm. The Hall currents that are driven by neutral winds during B(Z) northward conditions are generally in the opposite direction to those that occur during B(Z) southward conditions, when they are driven primarily by ion winds. The morphology of the field-aligned current system calculated by the NCAR-TIGCM during southward B(Z) conditions is in general agreement with observations.

  17. Second-order wave effects on TLP tendon tension responses

    SciTech Connect

    Xue, H.; Mercier, R.S. [Shell E and P Technology Co., Houston, TX (United States). Offshore Structures

    1996-12-31

    This paper presents a general procedure for analyzing the second-order wave effects on the tendon tension responses of a TLP. The approach solves both first- and second-order equation of motions for a TLP system in frequency domain. Viscous effects are included in the form of statistically linearized damping coefficients. An efficient algorithm has been devised for reducing the burden of second-order wave diffraction analysis, which selects the interacting frequency pairs according to springing frequency of interest to minimize the cost of computing quadratic transfer functions (QTFs) and allow accurate interpolation of QTFs. Moment statistics of the tension process are computed through an eigenvalue analysis. The developed method is applied to analyze the tendon tension responses of a TLP design in water depth of 3,000 ft.

  18. Solar Flux Effect on the Reproducibility of Global\\/Local-Time Variations of Ion Density Structure at Low-Latitude Ionosphere

    Microsoft Academic Search

    Shin-Yi Su

    2008-01-01

    Longitudinal\\/seasonal (l\\/s) variations of ion density structures at the 600-km low-latitude ionosphere observed by ROCSAT-1 between two similar solar activity years of 2000 and 2002 are examined at four different local-time (LT) regions. The gross feature of l\\/s density structure is almost identical to each other at the four LT regions examined. A complete reproducibility of density structure can be

  19. Birth-Order Effects in the Academically Talented.

    ERIC Educational Resources Information Center

    Parker, Wayne D.

    1998-01-01

    Birth-order position was studied among 828 academically talented sixth-grade students. When compared to census data, the sample was disproportionately composed of first-born students. However, this effect was largely explained by the covariate of family size, with small families over represented among the gifted. Other findings indicated no…

  20. The effect of granularity and order in XML element retrieval

    Microsoft Academic Search

    Nils Pharo

    2008-01-01

    The article presents an analysis of the effect of granularity and order in an XML encoded collection of full text journal articles. Two-hundred and eighteen sessions of searchers performing simulated work tasks in the collection have been analysed. The results show that searchers prefer to use smaller sections of the article as their source of information. In interaction sessions during

  1. Smearing formula for higher-order effective classical potentials

    Microsoft Academic Search

    Hagen Kleinert; Axel Pelster

    1998-01-01

    In the variational approach to quantum statistics, a smearing formula efficiently describes the consequences of quantum fluctuations upon an interaction potential. The result is an effective classical potential from which the partition function can be obtained by a simple integral. In this work, the smearing formula is extended to higher orders in the variational perturbation theory. An application to the

  2. The ionospheric impact on GPS performance in southern polar region

    USGS Publications Warehouse

    Hong, C.-K.; Grejner-Brzezinska, D. A.; Arslan, N.; Willis, M.; Hothem, L.

    2006-01-01

    The primary objective of this paper is to present the results of the study of the effects of varying ionospheric conditions on the GPS signal tracking in the southern polar region. In the first stage of this study, the data collected by the OSU/USGS team in October-November 2003 within the TAMDEF (Transantarctic Mountains Deformation) network were used together with some IGS Antarctic stations to study the effect of severe ionospheric storms on GPS hardware. Note that TAMDEF is a joint USGS/OSU project with the primary objective of measuring crustal motion in the Transantarctic Mountains of Southern Victoria Land using GPS techniques. This study included ten Antarctic stations equipped with different dual-frequency GPS hardware, and the data were evaluated for two 24-hour periods of severe ionospheric storm (2003/10/29) and moderate ionospheric conditions (minor storm of 2003/11/11). The results of this study were presented at the LAG Assembly in Cairns, Australia (Grejner-Brzezinska et al., 2005). Additional tests, in a more controlled environment, were carried out at the US Antarctic station, McMurdo, between January 10 and February 6, 2006, under varying ionospheric conditions, where several different types of receivers were connected to the same antenna located on the rooftop of the Crary Laboratory (the primary test site). In this scenario, each antenna was subject to identical ionospheric effects during each day of the test, and no spatial decorrelation effects were present, as seen in the previous study, due to the spatial separation of the receivers tested. It should be noted, however, that no moderate or severe ionospheric storms occurred during the experiment, so, unfortunately, this type of conditions was not tested here. The test was repeated with different receivers connected to different antenna types; a total of four 5-day sessions were carried out. The following receiver types were used at the primary site: Trimble 5700, Ashtech Z-Surveyor, JNS Euro-80 and Novatel DL-4, with the following antennas: Trimble Zephyr Geodetic, Ashtech D/M and Ashtech E/M chokering. In addition, data collected by the MCM4 IGS station, MCMD UNAVCO station, and CRAR USGS station, all located within 300 m from the primary test site, were used in the analyses. These stations were equipped with the following receiver/antenna combinations: ADA SNR-12/AOAD/MJT chokering (MCM4), Trimble NETRS/AOAD/MJT chokering (MCMD), and TPS ODYSEY_E/JPSREGANT_DD_E (CRAR). The UNAVCO TEQC software was used to carry out the analyses. Depending on the data sampling rate and the mask angle, the expected numbers of observations per receiver/satellite were compared to the actual number of measurements collected during the ionospheric events, with a special emphasis on L2 data. A total number of cycle slips and losses of lock were computed and compared among the hardware types. The results presented here indicate that there is no significant effects on the GPS receivers during minor ionospheric storms (Kp<5). However, the results reported in ibid, indicate significant differences in the hardware performance under severe ionospheric storms. Thus, careful hardware selection is needed to assure data quality/continuity when observations may be affected by severe ionospheric disturbances, while under calm to minor ionospheric activity level there is no significant difference in performance among the hardware tested here.

  3. Extraordinary induction heating effect near the first order Curie transition

    NASA Astrophysics Data System (ADS)

    Barati, M. R.; Selomulya, C.; Sandeman, K. G.; Suzuki, K.

    2014-10-01

    While materials with a 1st order Curie transition (TC) are known for the magnetic cooling effect due to the reversibility of their large entropy change, they also have a great potential as a candidate material for induction heating where a large loss power is required under a limited alternating magnetic field. We have carried out a proof-of-concept study on the induction heating effect in 1st order ferromagnetic materials where the temperature is self-regulated at TC. LaFe11.57Si1.43H1.75, a well-known magnetocaloric material, was employed in this study because TC of this compound (319 K) resides in the ideal temperature range for hyperthermia treatment of cancerous cells. It is found that the hysteresis loss of LaFe11.57Si1.43H1.75 increases dramatically near TC due to the magnetic phase coexistence associated with the 1st order magnetic transition. The spontaneous magnetization (Ms) shows a very abrupt decrease from 110 Am2kg-1 at 316 K to zero at 319 K. This large Ms immediately below TC along with the enhanced irreversibility of the hysteresis curve result in a specific absorption rate as large as 0.5 kWg-1 under a field of 8.8 kAm-1 at 279 kHz. This value is nearly an order of magnitude larger than that observed under the same condition for conventional iron oxide-based materials. Moreover, the large heating effect is self-regulated at the 1st order TC (319 K). This proof-of-concept study shows that the extraordinary heating effect near the 1st order Curie point opens up a novel alloy design strategy for large, self-regulated induction heating.

  4. Introduction to the Ionosphere Alan Aylward

    E-print Network

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

  5. Radar Soundings of the Ionosphere of Mars

    E-print Network

    Gurnett, Donald A.

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

  6. LWA Ionospheric Workshop Christopher Watts1

    E-print Network

    Ellingson, Steven W.

    LWA Ionospheric Workshop Christopher Watts1 and Kenneth Dymond2 with: Ronald Caton5 , Clayton Coker The LWA Ionospheric Workshop was held in parallel with the CEDAR workshop at the Eldorado Hotel on Sunday June 28, 2009. The purpose of the workshop was to bring together the ionospheric and astronomy

  7. Automated Ionospheric Front Velocity Estimation Algorithm for

    E-print Network

    Stanford University

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

  8. Equatorial ionosphere semiannual oscillation investigated from Schumann resonance measurements on board the C/NOFS satellite

    NASA Astrophysics Data System (ADS)

    Simões, Fernando; Pfaff, Robert; Freudenreich, Henry; Klenzing, Jeffrey; Rowland, Douglas; Bromund, Kenneth; Kepko, Larry; Le, Guan; Liebrecht, Maria Carmen; Martin, Steven; Uribe, Paulo

    2013-11-01

    of Schumann resonance signatures in the equatorial ionosphere offers remote sensing capabilities for the investigation of tropospheric and space weather effects in the ionosphere. Schumann resonances are electromagnetic oscillations in the earth-ionosphere cavity produced by lightning activity. Analysis of AC electric field measurements gathered by the Communications/Navigation Outage Forecasting System satellite reveals a semiannual pattern in Schumann resonance data recorded during nighttime in the equatorial ionosphere. This pattern observed in the Schumann resonance amplitude is expected to help validate—or at least constrain—potential mechanisms proposed to explain the semiannual oscillation observed in different geophysical records, such as those reported in a variety of tropospheric, ionospheric/thermospheric, and magnetospheric observations.

  9. Low-latitude ionospheric height variation as observed by meridional ionosonde chain: Formation of ionospheric ceiling over the magnetic equator

    NASA Astrophysics Data System (ADS)

    Maruyama, Takashi; Uemoto, Jyunpei; Ishii, Mamoru; Tsugawa, Takuya; Supnithi, Pornchai; Komolmis, Taradol

    2014-12-01

    A multipoint ionosonde observation campaign was conducted along the magnetic meridional plane in Southeast Asia to study ionosphere-thermosphere coupling. One station was near the magnetic equator and two of the other stations were at off-equatorial latitudes (˜10° magnetic latitude). The daytime ionospheric peak height (hmF2) was analyzed for each season during the solar minimum years, 2006-2007 and 2009. The peak height increased for ˜3 h after sunrise at the magnetic equator and off-equatorial latitudes, as expected from the daytime upward E × B drift. The apparent upward drift at the magnetic equator ceased before noon, while the drift at the off-equatorial latitudes continued upward and the layer height exceeded the equatorial height around noon. The noontime limited layer peak height at the magnetic equator, which was termed the ionospheric ceiling, did not depend on the season, while the maximum peak height at the off-equatorial latitudes largely varied with each season. Numerical modeling using the SAMI2 code was conducted and the features of the ionospheric ceiling were reproduced quite well. The dynamical parameters provided by the SAMI2 modeling runs showed that the ionospheric ceiling is formed by the field-aligned plasma diffusion, which is a part of the fountain effect.

  10. A general statistical instrument theory of atmospheric and ionospheric radars

    SciTech Connect

    Woodman, R.F. (Instituto Geofisico del Peru, Lima (Peru))

    1991-05-01

    Some basic functional relationships between the statistics of the signals received in a radar and the statistics of the density fluctuations of a scattering medium are derived. They vary in their degree of generality, but they are all very general in scope. They include monostatic and bistatic radars scattering from either atmospheric, ionospheric, or meteorological media. They are valid for refractive and slightly dispersive media, so they can also be used for HF ionospheric radars. They include the effects of filtering, including receiver filtering, pulse compression coding and decoding schemes, and coherent integration, or any alternative linear digital filtering scheme. Functional relationships to include cross-correlation schemes, such as Faraday rotation experiments and interferometers, are included. Some simplified expressions are derived for frequently encountered situations, where different approximations can be made. These simplified expressions cover a large number of radar techniques currently in use for atmospheric and ionospheric applications.

  11. Electrodynamics of solar wind-magnetosphere-ionosphere interactions

    NASA Technical Reports Server (NTRS)

    Kan, Joseph R.; Akasofu, Syun-Ichi

    1989-01-01

    The paper presents a coherent picture of fundamental physical processes in three basic elements of the solar-wind/magnetosphere/ionosphere coupling system: (1) the field-aligned potential structure which leads to the formation of auroral arcs, (2) the magnetosphere-ionosphere coupling which leads to the onset of magnetospheric substorms, and (3) the solar-wind/magnetosphere dynamo which supplies the power driving various magnetospheric processes. Process (1) is forced into existence by the loss-cone constriction effect when the upward field-aligned current density exceeds the loss-cone thermal flux limit. Substorm onset occurs when the ionosphere responds fully to the enhanced magnetospheric convection driven by the solar wind. Energy is transferred from the solar wind to the magnetosphere by a dynamo process, primarily on open field lines.

  12. New Ethanol Ordering Process Effective March 11, 2013, Ethanol must be ordered through an Ethanol Form in the

    E-print Network

    Sibille, Etienne

    New Ethanol Ordering Process Effective March 11, 2013, Ethanol must be ordered through an Ethanol Services will accept faxed orders for Ethanol. · Monday, March 11, 2013 is the first day the PantherExpress System will accept orders for Ethanol. Requirements · Your PantherExpress System account must be properly

  13. Macroscopic effects in noncollinear high-order harmonic generation.

    PubMed

    Heyl, C M; Rudawski, P; Brizuela, F; Bengtsson, S N; Mauritsson, J; L'Huillier, A

    2014-04-11

    We study two-color high-order harmonic generation using an intense driving field and its weak second harmonic, crossed under a small angle in the focus. Employing sum- and difference-frequency generation processes, such a noncollinear scheme can be used to measure and control macroscopic phase matching effects by utilizing a geometrical phase mismatch component, which depends on the noncollinear angle. We further show how spatial phase effects in the generation volume are mapped out into the far field allowing a direct analogy with temporal carrier envelope effects in attosecond pulse generation. PMID:24765964

  14. Macroscopic Effects in Noncollinear High-Order Harmonic Generation

    NASA Astrophysics Data System (ADS)

    Heyl, C. M.; Rudawski, P.; Brizuela, F.; Bengtsson, S. N.; Mauritsson, J.; L'Huillier, A.

    2014-04-01

    We study two-color high-order harmonic generation using an intense driving field and its weak second harmonic, crossed under a small angle in the focus. Employing sum- and difference-frequency generation processes, such a noncollinear scheme can be used to measure and control macroscopic phase matching effects by utilizing a geometrical phase mismatch component, which depends on the noncollinear angle. We further show how spatial phase effects in the generation volume are mapped out into the far field allowing a direct analogy with temporal carrier envelope effects in attosecond pulse generation.

  15. SUNDIAL - A world-wide-study of interactive ionospheric processes and their roles in the transfer of energy and mass in the sun-earth system

    Microsoft Academic Search

    E. P. Szuszczewicz; B. Fejer; E. Roelof; R. Schunk; R. Wolf

    1988-01-01

    Solar-terrestrial observations have been obtained in the SUNDIAL program during the October 5-13, 1984 period in order to explore cause and effect relationships controlling the global-scale ionosphere. It is suggested that the increased solar wind velocities noted are the result of a corotating high-speed stream coupled to a transequatorial solar coronal hole. The results are consistent with a step-wise coupling

  16. Total ionospheric electron content observation and ETS-V beacon experiment for studying GHz-band scintillation in the equatorial zone

    Microsoft Academic Search

    K. Igarashi; M. Nagayama; A. Ohtani; N. Hamamoto; Y. Hashimoto; T. Ide; H. Wakana; T. Ikegami; S. Taira; S. Yamamoto; E. Morikawa; K. Tanaka; Utoro Sastrokusumo; M. W Sutopo; Narong Hemmakorn; Apinan Manyanon; G. H Bryant; Kevin Maitava

    1997-01-01

    A L-band CW-beacon experiment using ETS-V satellite for mobile satellite communications experiments was made with the small satellite ground stations installed at Fiji, Indonesia, Papua New Guinea, Thailand and Japan in order to study propagation effects on satellite-to-ground-links in the equatorial zone. GPS observations of total ionospheric electron content and monitoring of geomagnetic variations were started at the same ground

  17. Higher order and asymmetry effects on saturation of magnetic islands

    SciTech Connect

    Smolyakov, A. I. [Department of Physics and Engineering Physics, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E2 (Canada) [Department of Physics and Engineering Physics, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E2 (Canada); International Institute for Fusion Science, UMR7345, Aix Marseille Université, CNRS, IIFS-PIIM, Marseille 13397 (France); NRC “Kurchatov Institute,” 1 Kurchatov Sqr., Moscow 123182 (Russian Federation); Poye, A.; Agullo, O.; Benkadda, S. [International Institute for Fusion Science, UMR7345, Aix Marseille Université, CNRS, IIFS-PIIM, Marseille 13397 (France)] [International Institute for Fusion Science, UMR7345, Aix Marseille Université, CNRS, IIFS-PIIM, Marseille 13397 (France); Garbet, X. [CEA, IRFM, F-13108 Saint Paul Lez Durance (France)] [CEA, IRFM, F-13108 Saint Paul Lez Durance (France)

    2013-06-15

    Higher order asymptotic matching procedure is developed to derive the nonlinear equation for saturated magnetic island with the symmetric profile of the equilibrium current. The theory extends the previous results to include higher order effects such as nonlinear modification of the equilibrium current and asymmetry in the boundary conditions in the outer region. It is shown that due to a finite width of the nonlinear region, the magnitude of the magnetic flux at the rational surface is different from the asymptotic value found from the outer solution, resulting in the suppression of the island growth for higher values of ?{sup ?} parameter.

  18. Ionospheric disturbances detected by MEXART

    NASA Astrophysics Data System (ADS)

    Carrillo-Vargas, A.; Pérez-Enríquez, R.; Rodríguez-Martínez, Mario; López-Montes, R.; Casillas-Pérez, G. A.; Araujo-Pradere, E. A.

    2012-06-01

    The radio telescope MEXART was developed to make observations of interplanetary scintillation (IPS) produced by large scale disturbances associated with solar events. In this work it is shown that on occasion there are disturbances in the ionosphere that are related with these events and which cannot only contaminate the IPS but actually be the main contribution to the observed oscillations. This was the case of the event of 15 December 2006 observed by MEXART, which presented clear scintillation. The total electron content (TEC) of the ionosphere above Mexico was calculated for the same period. It was found that the variations in TEC were associated with the scintillations detected by MEXART.

  19. The upper ionosphere of Titan

    NASA Technical Reports Server (NTRS)

    Whitten, R. C.; Capone, L. A.; Mcculley, L.; Michelson, P. F.

    1977-01-01

    Photoionization of the upper atmosphere of Titan by sunlight is expected to produce a substantial ionospheric layer. One-dimensional forms of the mass, momentum, and energy conservation equations for ions and electrons have been solved along with electron number densities of about 1000/cu cm, using various model atmospheres. The significant ions in a CH4-H2 atmosphere are H(+), H3(+), CH5(+), CH3(+), and C2H5(+). Electron temperatures may be as high as 1000 K, depending on the abundance of hydrogen in the high atmosphere. Interaction of the solar wind with the ionosphere is also discussed.

  20. 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

  1. 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.

  2. Polar Kerr effect from chiral-nematic charge order

    NASA Astrophysics Data System (ADS)

    Wang, Yuxuan; Chubukov, Andrey; Nandkishore, Rahul

    2014-11-01

    We analyze the polar Kerr effect in an itinerant electron system on a square lattice in the presence of a composite charge order proposed for the pseudogap state in underdoped cuprates. This composite charge order preserves discrete translational symmetries, and is "chiral nematic" in the sense that it breaks time-reversal symmetry, mirror symmetries in x and y directions, and C4 lattice rotation symmetry. The Kerr angle ?K in C4-symmetric system is proportional to the antisymmetric component of the anomalous Hall conductivity ?x y-?y x . We show that this result holds when C4 symmetry is broken. We show that in order for ?x y and ?y x to be nonzero the mirror symmetries in x and y directions have to be broken, and that for ?x y-?y x to be nonzero time-reversal symmetry has to be broken. The chiral-nematic charge order satisfies all these conditions, such that a nonzero signal in a polar Kerr effect experiment is symmetry allowed. We further show that to get a nonzero ?K in a one-band spin-fluctuation scenario, in the absence of disorder, one has to extend the spin-mediated interaction to momenta away from (? ,? ) and has to include particle-hole asymmetry. Alternatively, in the presence of disorder, one can get a nonzero ?K from impurity scattering: either due to skew scattering (with non-Gaussian disorder) or due to particle-hole asymmetry in case of Gaussian disorder. The impurity analysis in our case is similar to that in earlier works on Kerr effect in px+i py superconductors, however, in our case, the magnitude of ?K is enhanced by the flattening of the Fermi surface in the "hot" regions, which mostly contribute to charge order.

  3. Deuteron Matrix Elements in Chiral Effective Theory at Leading Order

    E-print Network

    L. Platter; D. R. Phillips

    2006-05-12

    We consider matrix elements of two-nucleon operators that arise in chiral effective theories of the two-nucleon system. Generically, the short-distance piece of these operators scales as 1/r^n, with r the relative separation of the two nucleons. We show that, when evaluated between the leading-order wave functions obtained in this effective theory, these two-nucleon operators are independent of the cutoff used to renormalize the two-body problem for n=1 and 2. However, for n greater than or equal to 3 general arguments about the short-distance behavior of the leading-order deuteron wave function show that the matrix element will diverge.

  4. Review of critical velocity experiments in the ionosphere

    NASA Astrophysics Data System (ADS)

    Torbert, R. B.

    Observations relevant to Alfven's Critical Velocity Effect, of the several shaped-charge releases in the ionosphere are compared with three generations of a macroscopic model of these releases. Good agreement is found with experiments which have reported a low ion yield, but major discrepancies remain with the Porcupine experiment which has the largest yield yet reported.

  5. Review of critical velocity experiments in the ionosphere

    NASA Technical Reports Server (NTRS)

    Torbert, R. B.

    1990-01-01

    Observations relevant to Alfven's Critical Velocity Effect, of the several shaped-charge releases in the ionosphere are compared with three generations of a macroscopic model of these releases. Good agreement is found with experiments which have reported a low ion yield, but major discrepancies remain with the Porcupine experiment which has the largest yield yet reported.

  6. Ionospheric heating with oblique HF waves

    SciTech Connect

    Field, E.C.; Bloom, R.M.

    1990-10-01

    This paper presents calculations of ionospheric electron density perturbations and ground-level signal changes produced by intense oblique high-frequency (HF) transmitters. Our analysis takes into account radio field focusing at caustics, the consequent joule-heating of the surrounding plasma, heat conduction, diffusion, and recombination processes--these being the effects of a powerful oblique modifying, wave. It neglects whatever plasma instabilities might occur. We then seek effects on a secondary 'test wave that is propagated along the same path as the first. Our calculations predict ground-level field-strength reductions of several dB in the test wave for modifying waves having ERP in the 85-to-90 dBW range. These field-strength changes are similar in sign, magnitude, and location to ones measured in Soviet experiments. Our results are sensitive to the the model ionosphere assumed, so future experiments should employ the widest possible range of frequencies and propagation conditions. An effective power of 90 dBW seems to be a sort of threshold that, if exceeded, results in substantial rather than small signal changes. Our conclusions are based solely on joule-heating and subsequent defocusing of waves passing through caustic regions.

  7. Theory of the First-Order Raman Effect in Crystals

    Microsoft Academic Search

    R. Loudon

    1963-01-01

    The theory of the first-order lattice vibration Raman effect is given with particular reference to semiconductors. It is shown that the most important Raman scattering mechanism is always one in which the radiation interacts indirectly with the lattice via the electrons. The electron-lattice interaction is treated by the deformation potential approximation, and the additional long-range electrical interaction is included for

  8. One-dimensional multi-species MHD model of the ionospheres of Venus and Mars

    SciTech Connect

    Shinagawa, H.

    1987-01-01

    The behavior of the ionospheric magnetic fields and ionospheric plasma of the dayside ionospheres of Venus and Mars was studied using a one-dimensional multi-species MHD model. The coupled continuity, momentum, and Maxwell's equations were solved simultaneously for the major ions and for the magnetic field. In the ionosphere of Venus, the calculated magnetic-filed profiles were in good agreement with observations obtained by the Pioneer Venus Orbiter magnetometer at all altitudes. Good agreement was also obtained between the calculated and observed plasma densities for altitudes below 250 km, including the electron density ledge near 190 km in magnetized ionospheres. It was found that the magnetic field in the lower ionosphere is maintained by the magnetic flux transported from the magnetic barrier region by the downward plasma motion. The model was also applied to the ionosphere of Mars in order to study the solar wind-Mars interaction and to estimate the magnitude of a possible intrinsic magnetic field on Mars. The calculation showed that even a small intrinsic magnetic field (B approx. = 30 nT) results in considerably larger electron densities at high altitudes than the densities measured by the retarding potential analyzers on Viking 1 and 2.

  9. The ionospheric focused heating experiment

    SciTech Connect

    Bernhardt, P.A.; Siefring, C.L.; Rodriguez, P. [Naval Research Lab., Washington, DC (United States)] [and others] [Naval Research Lab., Washington, DC (United States); and others

    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.

  10. Ionospheric mapping computer contouring techniques

    SciTech Connect

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

    1993-09-01

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

  11. Ionospheric observations in southern Norway

    Microsoft Academic Search

    N. Kjørsvik; O. Øvstedal; B. R. Pettersen; J. G. G. Svendsen

    2003-01-01

    A permanent GPS reference receiver is established in station AK06 at the campus of NLH, Norway. The monumentation, hardware, software and network connection is according to IGS practice. In this poster the first application of dual frequency GPS observations from this station is presented. Carrier phase and pseudorange observations at 1 Hz are used to monitor ionospheric TEC values. The

  12. Ionospheric imaging using computerized tomography

    Microsoft Academic Search

    Jeffrey R. Austen; Steven J. Franke; C. H. Liu

    1988-01-01

    Computerized tomography (CT) techniques can be used to produce a two-dimensional image of the electron density in the ionosphere. The CT problem requires that the measured data be the line integral through the medium of the unknown parameter; transionospheric satellite beacon total electron content data recorded simultaneously at multiple ground stations fulfill this requirement. In this paper the CT problem

  13. Global morphology of ionospheric scintillations

    Microsoft Academic Search

    J. Aarons

    1982-01-01

    A radio wave traversing the upper and lower atmosphere of the earth suffers a distortion of phase and amplitude. When it traverses drifting ionospheric irregularities, the radio wave experiences fading and phase fluctuation which vary widely with frequency, magnetic and solar activity, time of day, season, and latitude. This review has the objective to organize the experimental and theoretical studies

  14. Electrodynamics of the Low-Latitude Ionosphere.

    NASA Astrophysics Data System (ADS)

    Riley, Peter

    We have undertaken a study of the low and mid latitude ionospheric electric field pattern, during both magnetospherically quiet and active periods. Our analysis can be conveniently split into two parts. i.In an effort to study the penetration of magnetospheric electric fields to low latitudes, we have compared Jicamarca F-region vertical drifts for 10 radar-observation periods with the auroral boundary index (ABI). The ABI is the latitude of the equatorward edge of the diffuse aurora at local midnight, as estimated from precipitating-electron fluxes measured from DMSP spacecraft. The periods occurred in the interval January 1984 to June 1991 inclusive and each lasted between 2 and 5 days. We focus on periods that occurred in September 1986, March 1990, and June 1991. In the post-midnight sector, where we expect the penetration to be strongest, we found many examples of correlation; specifically, associated with an ionospheric updraft (implying an eastward electric field) is a strong poleward motion of the auroral boundary. However, we also found a significant number of cases where there was little or no correlation. We conclude that there is only mediocre agreement between the observed Sudden Postmidnight Ionospheric Events (SPIEs) and the ABI. These SPIEs have also been compared with other magnetospheric parameters, namely D_ {rm st} IMF B_{z } and the polar cap potential. D_ {rm st} showed significantly better correlation with the SPIEs. We summarize the proposed models for SPIEs and compare their predictions with the data, concluding that no single model can account for all events. While it is clear that some of these SPIEs can be explained in terms of direct penetration of magnetospheric electric fields, we suggest that the remainder may be due to magnetospherically-generated neutral wind effects. ii. We have constructed a model of the low- and mid-latitude potential distribution, applicable for both quiet and active times. We use the Mass-Spectrometer-Incoherent -Scatter (MSIS) model to input the number densities and temperature of the neutral species, and the International reference Ionosphere (IRI) model to input the electron/ion densities and temperatures. As our wind input we use the Horizontal Wind Model (HWM). We find that our model can reproduce the all of the main features of the low latitude ionosphere during quiet times, and supports some of our ideas about magnetospheric penetration during active periods. We use the model to probe the dependency of the low latitude penetration pattern on solar conditions and season and found that the inferred equatorial drifts are relatively insensitive to either. Thus we conclude that ionospheric pre-conditioning is unlikely to play a significant role. On the other hand, the low latitude penetration pattern is strongly dependent on the assumed poleward boundary.

  15. Fluid-Kinetic simulation study of the evolution of a penetrating electron beam measured at the top of the ionosphere and its effect on the ISR

    NASA Astrophysics Data System (ADS)

    Diaz, M.; Zettergren, M. D.; Abarca, A.; Lynch, K. A.; Semeter, J. L.; Oppenheim, M. M.

    2012-12-01

    A penetrating electron beam measured during the SERSIO campaign at the top of the ionosphere is evolved by using TRANSCAR to obtain the change in the velocity distribution at different altitudes. The velocity distribution at different altitudes is used as starting point of an Electrostatic Parallel Particle-In-Cell (EPPIC) code where the impact of the beam on the Incoherent Scatter Radar (ISR) spectrum is analyzed. Simulations of the ISR spectra around 500 MHz are compared with Eiscat Svalbard Radar (ESR) observations, which was operated during the SERSIO campaign. During the SERSIO campaign, ESR detected Natural Enhanced Ion Acoustic Waves (NEIALs) between 200 to 400 km of altitude.

  16. A comprehensive method for GNSS data quality determination to improve ionospheric data analysis.

    PubMed

    Kim, Minchan; Seo, Jiwon; Lee, Jiyun

    2014-01-01

    Global Navigation Satellite Systems (GNSS) are now recognized as cost-effective tools for ionospheric studies by providing the global coverage through worldwide networks of GNSS stations. While GNSS networks continue to expand to improve the observability of the ionosphere, the amount of poor quality GNSS observation data is also increasing and the use of poor-quality GNSS data degrades the accuracy of ionospheric measurements. This paper develops a comprehensive method to determine the quality of GNSS observations for the purpose of ionospheric studies. The algorithms are designed especially to compute key GNSS data quality parameters which affect the quality of ionospheric product. The quality of data collected from the Continuously Operating Reference Stations (CORS) network in the conterminous United States (CONUS) is analyzed. The resulting quality varies widely, depending on each station and the data quality of individual stations persists for an extended time period. When compared to conventional methods, the quality parameters obtained from the proposed method have a stronger correlation with the quality of ionospheric data. The results suggest that a set of data quality parameters when used in combination can effectively select stations with high-quality GNSS data and improve the performance of ionospheric data analysis. PMID:25196005

  17. A Comprehensive Method for GNSS Data Quality Determination to Improve Ionospheric Data Analysis

    PubMed Central

    Kim, Minchan; Seo, Jiwon; Lee, Jiyun

    2014-01-01

    Global Navigation Satellite Systems (GNSS) are now recognized as cost-effective tools for ionospheric studies by providing the global coverage through worldwide networks of GNSS stations. While GNSS networks continue to expand to improve the observability of the ionosphere, the amount of poor quality GNSS observation data is also increasing and the use of poor-quality GNSS data degrades the accuracy of ionospheric measurements. This paper develops a comprehensive method to determine the quality of GNSS observations for the purpose of ionospheric studies. The algorithms are designed especially to compute key GNSS data quality parameters which affect the quality of ionospheric product. The quality of data collected from the Continuously Operating Reference Stations (CORS) network in the conterminous United States (CONUS) is analyzed. The resulting quality varies widely, depending on each station and the data quality of individual stations persists for an extended time period. When compared to conventional methods, the quality parameters obtained from the proposed method have a stronger correlation with the quality of ionospheric data. The results suggest that a set of data quality parameters when used in combination can effectively select stations with high-quality GNSS data and improve the performance of ionospheric data analysis. PMID:25196005

  18. Initial results on ionosphere sounding based on GOLPE

    NASA Astrophysics Data System (ADS)

    Rios, V.; Soria, F.; de Haro, B.

    After SAC-C has been successfully launched on 16 November 2000, the GPS flight receiver tracks up to 8 satellites simultaneously for precision orbit determination by GPS O ccultation and Passive Reflection Experiment (GOLPE) . Since these navigation data are measured with a sampling rate of 10s, the dual frequency GPS signals provide valuable information on the ionisation state of the topside ionosphere. Combining differential carrier and code phases, absolute values of the total electron content (TEC) along the numerous radio links are estimated after calibrating the instrumental biases of each SAC-C receiver - GPS transmitter combination in a separate way. The calibration is carried out by applying a model assisted technique under nighttime ionospheric conditions that promises a low ionization level and therefore small calibration errors. The calibrated TEC data derived for a full SAC-C revolution are then assimilated into the Parameterized Ionospheric Model (PIM). The assimilation technique and preliminary results that provide a 2D-reconstruction of the ionosphere electron density in the SAC-C orbit plane from the SAC -C altitude up to GPS orbit heights will be discussed. First order validation checks will be presented using electron density in situ measurements by the Digisonde 256 of Tucumán for selected coincidence cases.

  19. Upper limits to the nightside ionosphere of Mars

    NASA Astrophysics Data System (ADS)

    Fox, J. L.; Brannon, J. F.; Porter, H. S.

    1993-07-01

    The nightside ionosphere of Mars could be produced by electron precipitation or by plasma transport from the dayside, by analogy to the Venus, but few measurements are available. We report here model calculations of upper limits to the nightside ion densities on Mars that would be produced by both mechanisms. For the auroral model, we have adopted the downward traveling portions of the electron spectra measured by the HARP instrument on the Soviet Phobos spacecraft in the Martian plasma sheet and in the magnetotail lobes. For the plasma transport case, we have imposed on a model of the nightside thermosphere, downward fluxes of O(+), C(+), N(+), NO(+) and O2(+) that are near the maximum upward fluxes that can be sustained by the dayside ionosphere. The computed electron density peaks are in the range (1.3 - 1.9) x 10 exp 4/cu cm at altitudes of 159 to 179 kin. The major ion for all the models is O2(+), but significant differences in the composition of the minor ions are found for the ionospheres produced by auroral precipitation and by plasma transport. The calculations reported here provide a guide to the data that should be acquired during a future aeronomy mission to Mars, in order to determine the sources of the nightside ionosphere.

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

    PubMed

    Pérez-De-Tejada

    1999-11-01

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

  1. A comprehensive magnetohydrodynamic model of the Venus ionosphere

    SciTech Connect

    Shinagawa, H. (NASA Marshall Space Flight Center, Huntsville, AL (USA)); Kim, J.; Nagy, A.F. (Univ. of Michigan, Ann Arbor (USA)); Cravens, T.E. (Univ. of Kansas, Lawrence (USA))

    1991-07-01

    The MHD Venus ionospheric model developed by Shinagawa and Cravens (1988) has been improved by including the energy equations for ions and electrons in a self-consistent manner. This new model reproduces observed electron density and magnetic field profiles very well, and the basic MHD processes of the Venus ionosphere, as described by Shinagawa and Cravens (1988), remain virtually unchanged. The results indicate that including energetics does not significantly alter the density and magnetic field profiles. Under unmagnetized conditions, it is necessary to impose heat fluxes for both ions and electrons in order to reproduce the observed plasma temperature profiles, which are consistent with the studies by Cravens et al. (1979, 1980) and Kim et al. (1990). In the magnetized ionosphere, it is likely that a heat source for the ions is present at higher altitudes. On the other hand, the observed very high electron temperatures can be reproduced with a reduced conductivity or with a heat source at high altitudes. It is also found that heating processes do not play a significant role in the dynamics at low altitudes. Thus a nearly supersonic downward velocity layer in the lower ionosphere of Venus, proposed by Cloutuer at al. (1987), is unlikely, suggesting that their flow/field model is not applicable to the solar wind-Venus interaction and other unmagnetized bodies in magnetized plasma flows.

  2. Upper limits to the nightside ionosphere of Mars

    NASA Technical Reports Server (NTRS)

    Fox, J. L.; Brannon, J. F.; Porter, H. S.

    1993-01-01

    The nightside ionosphere of Mars could be produced by electron precipitation or by plasma transport from the dayside, by analogy to the Venus, but few measurements are available. We report here model calculations of upper limits to the nightside ion densities on Mars that would be produced by both mechanisms. For the auroral model, we have adopted the downward traveling portions of the electron spectra measured by the HARP instrument on the Soviet Phobos spacecraft in the Martian plasma sheet and in the magnetotail lobes. For the plasma transport case, we have imposed on a model of the nightside thermosphere, downward fluxes of O(+), C(+), N(+), NO(+) and O2(+) that are near the maximum upward fluxes that can be sustained by the dayside ionosphere. The computed electron density peaks are in the range (1.3 - 1.9) x 10 exp 4/cu cm at altitudes of 159 to 179 kin. The major ion for all the models is O2(+), but significant differences in the composition of the minor ions are found for the ionospheres produced by auroral precipitation and by plasma transport. The calculations reported here provide a guide to the data that should be acquired during a future aeronomy mission to Mars, in order to determine the sources of the nightside ionosphere.

  3. Experimental observations of the spatial structure of wave-like disturbances generated in midlatitude ionosphere by high power radio waves

    NASA Astrophysics Data System (ADS)

    Kunitsyn, V.; Andreeva, E.; Padokhin, A. M.; Nazarenko, M.; Frolov, V.; Komrakov, G.; Bolotin, I.

    2012-12-01

    We present the results of the experiments carried out in 2009-2012 on the Sura heating facility (Radio Physical Research Institute, N. Novgorod, Russia) on modification of the midlatitude ionosphere by powerful HF radiowaves. The experiments were conducted using O-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. The variations in the slant total electron content (TEC), which are proportional to the reduced phase of navigational signals, were studied for the satellite passes for which ionospheric penetration points crossed the disturbed area during HF heating. The variations in TEC caused by HF heating are identified in a number of examples. It is shown that the GNSS TEC spectra 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. Different behavior of TEC variations was observed during nighttime and daytime heating experiments. In daytime conditions the pump wave switched ON causes the increase of TEC while in the nighttime it causes a decrease in TEC. This can be explained by the different contribution of the processes responsible for the increase and decrease of TEC in daytime in nighttime conditions. In this work we also present the first time radiotomographic reconstructions of the spatial structure of the wave-like disturbances, generated in the ionosphere by high-power radio waves radiated by the Sura heater with a square wave modulation of the ERP at a frequency lower than or of the order of the Brunt-Vaisala frequency of the neutral atmosphere. The observed wavelike structures, which are possibly AGWs, diverge from the heated area of the ionosphere (observed like a narrow trough with dimensions corresponding to the diagram pattern of the Sura heater), the spatial period of these disturbances is 200-250 km and they are easily traced up to a distance of 700-800 km from the heated region. These observations are in good agreement with complimentary GPS/GLONASS data. We also present the examples of amplitude scintillations of the signals of low-orbital radio beacons corresponding to small-scale field-aligned irregularities in the heated area of ionosphere. 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 are grateful to the staff of the Sura facility for their help in conducting the experiments and acknowledge the support of the Russian Foundation for Basic Research (grants 10-05-01126, 11-02-00374, 11-05-01157, 12-02-31839, 12-05-33065, 12-05-10068), grant of the President of Russian Federation MK-2544.2012.5 and Lomonosov Moscow State University Program of Development.

  4. Transient growth of IGW in the ionosphere with non-uniform shear winds

    NASA Astrophysics Data System (ADS)

    Chargazia, Khatuna; Kharshiladze, Oleg

    2015-04-01

    Linear mechanism of intensification and transient growth of internal gravity waves (IGW) at smoothly stratified dissipative ionosphere at interaction with non-uniform zonal winds (shear flows) is studied. It is shown that amplification of IGW with respect to time is not flowing exponentially, but in algebraic power law manner. Frequency and wave number of the generated IGW modes are functions of time. So, in the ionosphere with shear flows due to linear mechanism, when the nonlinear and turbulent effects are absent, the wide spectra of wave perturbations will generate. Effectiveness of the IGW amplification mechanism is analyzed at interaction with the zonal winds. It is shown, that at the initial stage of evolution IGW perturbations effectively extract energy from the shear flows sufficiently increasing own amplitude and energy (almost by an order). Energy exchange process between the shear flows and the wave perturbations is based on the "lift-up" mechanism, according to which the perturbations carry the liquid from the high velocity region to the lower ones and vise versa. Energy exchange between the spatial Fourier harmonics as intensive, as faster moves the liquid particle along the shear flow. The value of the threshold velocities for compressible and incompressible wave perturbations is estimated. Numerical simulations are carried out and phenomenon of the mutual transformation of the wave modes is revealed.

  5. Investigation of ionospheric disturbances and associated diagnostic techniques. Final report, 1 January 1992-31 December 1994

    Microsoft Academic Search

    1995-01-01

    The objectives of this research and development program were to conduct simulation modeling of the generation and propagation of atmospheric acoustic signals associated with surface and subsurface ground disturbances; to construct an experimental measurement system for exploratory research studies of acoustic generated ionospheric disturbances; to model high power radio wave propagation through the ionosphere, including nonlinear wave plasma interaction effects;

  6. Variation of ionospheric total electron content in Indian low latitude region of the equatorial anomaly during May 2007–April 2008

    Microsoft Academic Search

    Sanjay Kumar; A. K. Singh

    2009-01-01

    The ionospheric total electron content (TEC), derived by analyzing dual frequency signals from the Global Positioning System (GPS) recorded near the Indian equatorial anomaly region, Varanasi (geomagnetic latitude 14°, 55?N, geomagnetic longitude 154°E) is studied. Specifically, we studied monthly, seasonal and annual variations as well as solar and geomagnetic effects on the equatorial ionospheric anomaly (EIA) during the solar minimum

  7. Nighttime ionospheric D region: Equatorial and nonequatorial

    NASA Astrophysics Data System (ADS)

    Thomson, Neil R.; McRae, Wayne M.

    2009-08-01

    Nighttime ionospheric D region parameters are found to be generally well modeled by the traditional H? and ? as used by Wait and by the U.S. Navy in their Earth-ionosphere VLF radio waveguide programs. New comparisons with nonequatorial, mainly all-sea VLF path observations reported over several decades are shown to be consistent with the previously determined height H? ˜ 85.0 km and sharpness ? ˜ 0.63 km-1. These paths include NPM (Hawaii) to Washington, D. C., Omega Hawaii and NLK (Seattle) to Japan, NWC (N.W. Australia) to Madagascar, and NBA (Panama) to Colorado. In marked contrast, transequatorial path observations (even when nearly all-sea) are found to be often not well modeled: for example, for Omega Japan and JJI (Japan) to Dunedin, New Zealand, the observed amplitudes are markedly lower than those which would be expected from H? ˜ 85.0 km and ? ˜ 0.63 km-1, or any other realistic values of H? and ?. Other transequatorial observations compared with modeling include NWC to Japan, Omega Hawaii to Dunedin, and NPM (Hawaii) to Dunedin. It is suggested that the effects of irregularities in the equatorial electrojet may extend down into the nighttime D region and so account for the observed equatorial VLF perturbations through scattering or mode conversion.

  8. Ionospheric magnetic fields at Venus and Mars

    NASA Astrophysics Data System (ADS)

    Dubinin, E.; Fraenz, M.; Zhang, T. L.; Woch, J.; Wei, Y.

    2014-04-01

    Mars Global Surveyor (MGS) and Venus Express(VEX) spacecraft have provided us a wealth of insitu observations of characteristics of induced magnetospheres of Mars and Venus at low altitudes during the periods of solar minimum. At such conditions the interplanetary magnetic field (IMF) penetrates deeply inside the ionosphere while the solar wind is terminated at higher altitudes. We present the measurements made by MGS and VEX in the ionospheres of both planets which reveal similar features of the magnetization. The arising magnetic field pattern occurs strongly asymmetrical with respect to the direction of the cross-flow component of the IMF revealing either a sudden straightening of the field lines with a release of the magnetic field stresses or a sudden rotation of the magnetic field vector with a reversal of the sign of the cross-flow component. Such an asymmetrical response is observed at altitudes where the motion of ions and electrons is decoupled and collisional effects become important for generation of the electric currents Asymmetry in the field topology significantly modifies a plasma transport to the night side.

  9. Principles and Problems of Data Assimilation for High-Latitude Ionospheric Electrodynamics

    NASA Astrophysics Data System (ADS)

    Richmond, A. D.; Matsuo, T.; Cousins, E. D. P.; Knipp, D. J.; Lu, G.; Marsal, S.

    2014-12-01

    Knowledge of the time-varying distributions of high-latitude ionospheric ionospheric electric fields and currents is needed for modeling the physics of the ionosphere and thermosphere. The patterns can also be used to investigate magnetospheric processes. The Assimilative Mapping of Ionospheric Electrodynamics (AMIE) procedure was developed to estimate the distributions of electrodynamic parameters from combinations of observations of ionospheric drifts, ground- and satellite-based magnetic perturbations, and quantities related to ionospheric electrical conductivities, together with prior information about climatology and covariance of the parameters. AMIE uses optimal estimation theory to build on previous statistical studies and on an earlier mapping procedure that used only ground magnetometer data. Many of the improvements made to AMIE have been the addition of new data sets and procedures for semi-automatically processing the data. Theoretical developments have included improvements to the organization of the data in realistic magnetic coordinates, and dynamic estimation of the covariance matrices based on the data available at any given time. More recently, it has been shown that most of the large-scale variability can be represented with a relatively small number of empirical orthogonal basis functions derived from statistical analysis of large data sets. A key remaining limitation of AMIE-type estimations is the limited knowledge of auroral ionospheric conductivities, including limited understanding of nonlinear conductivities when electric fields are very strong. Neutral winds have heretofore been neglected, but they can sometimes have significant effects on the electrodynamics.

  10. Thermospheric Wind Impacts on Ionospheric Upflow and Outflow

    NASA Astrophysics Data System (ADS)

    Burleigh, M.; Zettergren, M. D.

    2014-12-01

    Significant amounts of thermal ionospheric plasma can be transported to high altitudes in response to magnetospheric and atmospheric forcing. Soft electron precipitation serves as a heat source for the ambient F-region ionospheric electrons, which enhances the ambipolar electric field and induces upflowing ions. Frictional heating of ions from fast convection through the neutral atmosphere creates pressure-driven ion upflows. Finally, large neutral winds along the geomagnetic field may effectively lift or lower the F-region density peak. At regions above where ion upflows are typically initiated, transverse ion acceleration is thought to give upflowing ions sufficient energy to escape to the magnetosphere. This study examines how low-altitude upflow processes affect ion outflow, focusing particularly on the impacts of neutral winds. A new multi-fluid ionospheric model, which solves conservation equations for mass, momentum, and parallel and perpendicular energy is developed for this study. These fluid equations are solved for all species relevant to the E, F, and topside ionospheric regions and the system is closed through an electrostatic treatment of the auroral currents. This model is driven by the specification of field-aligned currents and a resonant transverse heating term. The model therefore encapsulates the basic ionospheric upflow processes and provides a simple way to approximate the effects of transverse heating and ion outflow. Using this model, individual species responses to electron precipitation, frictional heating, neutral winds, and transverse heating are examined to determine the effects of these low-altitude upflow processes on ion outflow. Results suggest that upflows, including those induced by neutral winds, can have a significant impact on the types and amounts of outflowing ions.

  11. Satellite Radiotomography of Ionospheric Responces to Extra-Terrestrial Forcing

    NASA Astrophysics Data System (ADS)

    Kunitsyn, Viacheslav; Padokhin, Artem; Andreeva, Elena; Tereshchenko, Evgeny; Nesterov, Ivan; Vorontsov, Artem

    Our work addresses the study of the response of the atmosphere and ionosphere to a variety of external forcing such as solar flares and particle precipitation. Particle precipitation plays important role in the system of magnetosphere-ionosphere- atmosphere coupling during geomagnetic storms. Using radio tomographic imaging of the ionosphere based on navigational satellite systems (Parus/Transit and GPS/GLONASS) we present and discuss the examples illustrating ionospheric effects caused by particle precipitations detected by DMSP satellites. It is shown that the spatial structure of corpuscular ionization in the tomographic images is qualitatively close to latitudinal distribution of the precipitating particles. The distributions of ionospheric plasma observed during strong geomagnetic disturbances and particle precipitations have multiple extrema and wave-like structures with a spatial scale ranging from a few dozens to a few hundreds of kilometers; the characteristic sizes of latitudinal variations in the corresponding corpuscular flows widely vary from a few degrees to a few dozens degrees latitude. The obtained experimental results are in good agreement with the results of the numeric modelling of the AGW generation by volumetric sources. We also present the comparison of the effects of ionization of the ionosphere by a series of intense X-class solar flares during the 23rd and 24th solar cycles based on the data of satellite navigation and augumentation systems (GPS/GLONASS and SBAS). The analysis shows that the intensity of the ionospheric effects estimated from the variations in total electron content is barely related to the intensity of the X-ray flare for the X-class events. The amplitude of variations in the ionization of the upper atmosphere is mainly controlled by the intensity of variations in solar EUV radiation, which is not always correlated to the X-Ray radiation during flares. 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.

  12. Tomographic estimation of the ionosphere using terrestrial GPS sensors

    NASA Astrophysics Data System (ADS)

    Hansen, Andrew Jakob

    2002-09-01

    The ionosphere is a region of partially ionized plasma in Earth's upper atmosphere distributed in layers of varying free electron density. The free electrons change the local index of refraction causing radio waves propagating in the ionosphere to be delayed and bent. Trans-ionospheric propagation of GPS radio signals transmitted from satellites provides observations, in a tomographic sense, of the electron density field by measuring the amount of delay and/or bending. Tomographic estimation of the ionosphere is attractive for two reasons: one, the number of measurements grows as the product of the number of transmitters and receivers whereas for in situ techniques the number grows linearly in the number of sensors; two, the smoothing function of the integral operator makes the measurements most sensitive to large scale structure. A three-dimensional tomographic inversion algorithm is implemented as a real time process ingesting live measurements from a network of dual frequency GPS reference receivers. The tomographic inversion technique is based on a state space model encompassing ionospheric parameters as well as certain measurement biases in the GPS satellite transmitters and reference receivers. Three different state space models were constructed using discrete spectra, separable lattice wavelets, and a hybrid of separable and non-separable two-dimensional wavelets. The primary purpose of the real-time estimator is to provide an ionospheric model for correcting range delay errors on GPS measurements to differentially improve the position solution for aviation applications. Specifically, the Federal Aviation Administration is developing the Wide Area Augmentation System (WAAS) for GPS where positioning accuracy on the order of ones of meters is coupled with a six second time to alarm in the aircraft. In this application the real-time estimator ingests measurements from the GPS reference receiver network, applies the tomographic inversion to form an ionospheric model and transmits that model through a low bandwidth broadcast data link to the aircraft. Further, the estimator must provide a confidence interval for each and every correction to protect the navigation solution. Indeed this latter function is the most ambitious and critical in safety of life operations such as precision approach.

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

    NASA Astrophysics Data System (ADS)

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

    2015-01-01

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

  14. Quantifying residual ionospheric errors in GNSS radio occultation bending angles based on ensembles of profiles from end-to-end simulations

    NASA Astrophysics Data System (ADS)

    Liu, C. L.; Kirchengast, G.; Zhang, K.; Norman, R.; Li, Y.; Zhang, S. C.; Fritzer, J.; Schwaerz, M.; Wu, S. Q.; Tan, Z. X.

    2015-01-01

    The radio occultation (RO) technique using signals from the Global Navigation Satellite System (GNSS), in particular from the Global Positioning System (GPS) so far, is meanwhile widely used to observe the atmosphere for applications such as numerical weather prediction and global climate monitoring. The ionosphere is a major error source in RO measurements at stratospheric altitudes and a linear ionospheric correction of dual-frequency RO bending angles is commonly used to remove the first-order ionospheric effect. However, the residual ionopheric error (RIE) can still be significant so that it needs to be further mitigated for high accuracy applications, especially above about 30 km altitude where the RIE is most relevant compared to the magnitude of the neutral atmospheric bending angle. Quantification and careful analyses for better understanding of the RIE is therefore important towards enabling benchmark-quality stratospheric RO retrievals. Here we present such an analysis of bending angle RIEs covering the stratosphere and mesosphere, using quasi-realistic end-to-end simulations for a full-day ensemble of RO events. Based on the ensemble simulations we assessed the variation of bending angle RIEs, both biases and SDs, with solar activity, latitudinal region, and with or without the assumption of ionospheric spherical symmetry and of co-existing observing system errors. We find that the bending angle RIE biases in the upper stratosphere and mesosphere, and in all latitudinal zones from low- to high-latitudes, have a clear negative tendency and a magnitude increasing with solar activity, in line with recent empirical studies based on real RO data. The maximum RIE biases are found at low latitudes during daytime, where they amount to with in -0.03 to -0.05 ?rad, the smallest at high latitudes (0 to -0.01 ?rad; quiet space weather and winter conditions). Ionospheric spherical symmetry or asymmetries about the RO event location have only a minor influence on RIE biases. The RIE SDs are markedly increased both by ionospheric asymmetries and increasing solar activity and amount to about 0.3 to 0.7 ?rad in the upper stratosphere and mesosphere. Taking into account also realistic observation errors of a modern RO receiving system, amounting globally to about 0.4 ?rad (un-biased; SD), shows that the random RIEs are typically comparable to the total observing system error. The results help to inform future RIE mitigation schemes that will improve upon the use of the linear ionospheric correction of bending angles and that will also provide explicit uncertainty estimates.

  15. Parameterized ionospheric model: A global ionospheric parameterization based on first principles models

    Microsoft Academic Search

    R. E. Daniell; L. D. Brown; D. N. Anderson; M. W. Fox; P. H. Doherty; D. T. Decker; J. J. Sojka; R. W. Schunk

    1995-01-01

    We describe a parameterized ionospheric model (PIM), a global model of theoretical ionospheric climatology based on diurnally reproducible runs of four physics based numerical models of the ionosphere. The four numerical models, taken together, cover the E and F layers for all latitudes, longitudes, and local times. PIM consists of a semianalytic representation of dimally reproducible runs of these models

  16. Day-to-night transport in the Martian ionosphere

    NASA Astrophysics Data System (ADS)

    Cui, Jun; Galand, Marina; Yelle, Roger; Wei, Yong

    2015-04-01

    The nightisde Martian ionosphere is thought to be contributed by day-to-night transport and electron precipitation, of which the former has not been well studied. In this work, we evaluate the role of day-to-night transport based on the total electron content (TEC) measurements made by the Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) onboard Mars Express (MEx). This is accomplished by an examination of the variation of nightside TEC in the time domain rather than the traditional solar zenith angle (SZA) domain. Our analyses here, being constrained to the northern hemisphere where the effects of crustal magnetic fields can be neglected, reveal that day-to-night transport serves as the dominant source for the nightside Martian ionosphere from terminator crossing up to time in darkness, TD, of ˜ 5.3 × 103 s, beyond which it is surpassed by electron precipitation. We also compare the observations with predictions from a simplified time-dependent ionosphere model. We conclude that the solid body rotation of Mars is insufficient to account for the observed depletion of nightside TEC but the data could be reasonably reproduced by the zonal transport model with a zonal electron flow velocity of ˜ 1.9 km s-1. Such a velocity corresponds to a day-to-night electron transport rate of ˜ 2.6 × 1025 s-1, of which the driving force is unclear.

  17. The Role of Superthermal Electrons in Ionospheric Outflow

    NASA Astrophysics Data System (ADS)

    Glocer, Alex; Khazanov, George

    2013-04-01

    Superthermal Electrons (SEs), play an important role in the outflow of ions from the Earth's ionosphere through two physical mechanisms: the development of a self-consistent parallel electric field as well as Coulomb collisions with thermal electrons that raises the electron temperature and hence the scale height of the ions. The sources of these electrons are photoionization of the neutral atmosphere (photoelectrons), precipitating electrons of magnetospheric origin (primary electrons), or by the resulting impact ionization (secondary electrons). We explore the role of Superthermal Electrons (SEs) in the ionospheric outflow solution using two theoretical modeling techniques: A field-aligned multi-fluid model that solves the gyrotropic transport equations, and a Fokker-Planck Kinetic Model of the SE populations. First, we present the results of our recent study describing the effect of photoelectrons in the geomagnetically quiet polar wind, comparing with statistical data from Akebono and ESR. We find that photoelectrons play an important role in explaining the observed solar zenith angle dependence. Second, we present results our other recent study describing how SEs regulate the energy interplay between the ionosphere and plasmasphere and how this process controls ionospheric outflow on closed field-lines, i.e. plasmaspheric refilling.

  18. The ionospheric disturbance dynamo investigated with CHAMP observations

    NASA Astrophysics Data System (ADS)

    Xiong, Chao; Lühr, Hermann; Fejer, Bela G.

    2015-04-01

    The energy and momentum input from the magnetosphere is most efficiently coupled into the high latitude Ionosphere-Thermosphere (IT) system. During disturbance periods the direct penetration electric field and the ionospheric disturbance dynamo are the two important coupling mechanisms from high latitudes to low latitude regions. The disturbance dynamo has been postulated many decades ago. But due to the sparseness of thermospheric wind measurements details of the phenomena could not be studied. In this study we focus on the ionospheric disturbance dynamo as observed by CHAMP during 2001 to 2005. During quiet times the zonal wind at equatorial regions exhibits a typical diurnal variation blowing westward at daytime and changing sign to eastward around 1500 LT. On a global scale the wind is deflected westward when propagating equatorward under the influence of the Coriolis force during magnetically disturbed periods. At high and subauroral latitudes, the westward zonal wind is strongly enhanced, and an enhancement of westward zonal wind (about 40 m/s) can be found at low latitudes between 00 to 06 local time (LT). At middle latitudes the westward enhancement occurs already around evening to early night hours. By applying a superposed epoch analysis it is shown that the disturbance dynamo needs 3-4 h to reach the equator. Based on CHAMP observations we try to illustrate the whole chain of processes from the solar wind driving to the ionospheric effects at lower latitudes.

  19. 29 CFR 2700.21 - Effect of filing notice of contest of citation or order.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...Effect of filing notice of contest of citation or order. 2700.21 Section 2700...COMMISSION PROCEDURAL RULES Contests of Citations and Orders § 2700.21 Effect of filing notice of contest of citation or order. (a) The filing of...

  20. 29 CFR 2700.21 - Effect of filing notice of contest of citation or order.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...Effect of filing notice of contest of citation or order. 2700.21 Section 2700...COMMISSION PROCEDURAL RULES Contests of Citations and Orders § 2700.21 Effect of filing notice of contest of citation or order. (a) The filing of...

  1. 29 CFR 2700.21 - Effect of filing notice of contest of citation or order.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...Effect of filing notice of contest of citation or order. 2700.21 Section 2700...COMMISSION PROCEDURAL RULES Contests of Citations and Orders § 2700.21 Effect of filing notice of contest of citation or order. (a) The filing of...

  2. 29 CFR 2700.21 - Effect of filing notice of contest of citation or order.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...Effect of filing notice of contest of citation or order. 2700.21 Section 2700...COMMISSION PROCEDURAL RULES Contests of Citations and Orders § 2700.21 Effect of filing notice of contest of citation or order. (a) The filing of...

  3. 29 CFR 2700.21 - Effect of filing notice of contest of citation or order.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...Effect of filing notice of contest of citation or order. 2700.21 Section 2700...COMMISSION PROCEDURAL RULES Contests of Citations and Orders § 2700.21 Effect of filing notice of contest of citation or order. (a) The filing of...

  4. Expert Knowledge and Multivariate Emulation: The Thermosphere-Ionosphere Electrodynamics

    E-print Network

    Oakley, Jeremy

    Expert Knowledge and Multivariate Emulation: The Thermosphere-Ionosphere Electrodynamics General the Thermosphere-Ionosphere Electrodynamics General Circulation Model (TIE-GCM)', by the same authors. 1 #12

  5. Scale Dependence of Medium-Scale Traveling Ionospheric Disturbances: Perkins Instability and Es Layer Seeding

    NASA Astrophysics Data System (ADS)

    Yokoyama, T.

    2014-12-01

    Plasma density structures and associated irregularities in the nighttime midlatitude ionosphere are frequently observed as frontal structures elongated from northwest to southeast (NW-SE) in the Northern Hemisphere with a wavelength of 100-200 km, also known as medium-scale traveling ionospheric disturbances (MSTIDs). The MSTIDs and the coupling process between the E and F regions are studied with a midlatitude ionosphere electrodynamics coupling (MIECO) model which can simulate two instability mechanisms: Perkins instability in the F region and sporadic-E (Es)-layer instability in the E region. Using the MIECO model, MSTID structure is reproduced from random perturbation on an Es layer in a wide horizontal coverage. A typical wavelength of ~150 km, larger amplitude, and smaller MSTID's tilt angles at lower latitudes are consistent with observations. It is shown that the polarization process in the E region driven by neutral winds is essentially important for the full development of MSTIDs as well as the seeding of NW-SE perturbation in the F region. The upgraded version of MIECO model comprises both hemispheres where electric field is solved by integrating conductivities in both hemispheres, and all other parameters such as plasma density and neutral wind are independent. In order to study the scale dependence of MSTIDs, the initial perturbation scale on the Es layer is given from 20 km to 320 km range. The results show that shorter scale perturbation tends to saturate faster both at the E and F regions, whereas the Es-layer instability does not work effectively at very long wavelength mode. As a result, the typical wavelength of MSTIDs (100-200 km) can be spontaneously generated without scale-dependent forcing.

  6. Self-organization of IGW structures in an inhomogeneous ionosphere: 2. Nonlinear vortex structures

    NASA Astrophysics Data System (ADS)

    Aburjania, G. D.; Kharshiladze, O. A.; Chargazia, Kh. Z.

    2013-11-01

    The generation and further nonlinear dynamics of internal gravity wave (IGW) structures in a dissipative ionosphere in the presence of an inhomogeneous zonal wind (shear flow) have been studied. The effectiveness of the IGW amplification mechanism during the interaction with an inhomogeneous zonal wind is analyzed based on the corresponding model system of nonlinear dynamic equations constructed in (Aburjania et al., 2013). It has been indicated that IGWs effectively obtain the shear flow energy at the initial linear evolution stage and substantially (by an order of magnitude) increase their amplitude and, correspondingly, energy. The nonlinear self-localization mechanism starts operating with increasing amplitude, and the process terminates with the self-organization of nonlinear solitary strongly localized vortex structures. A new degree of system freedom and the disturbance evolution trend in a medium with a shear flow appear in such a way. Nonlinear IGW structures can be a purely monopoly vortex, a transverse vortex chain, and/or a longitudinal vortex path against the background of an inhomogeneous zonal wind, depending on the shear flow velocity profile. The accumulation of such vortices in the ionospheric medium can generate a strongly turbulent state.

  7. 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.

  8. GPS Occultation Sensor Observations of the Ionospheric E-Region

    NASA Astrophysics Data System (ADS)

    Straus, P. R.; Hajj, G. A.; Anderson, P. C.; Crowley, G.

    2003-12-01

    GPS occultation sensor measurements of the GPS L1 (1575 MHz) and L2 (1227 MHz) signal phase can be used to derive line-of-sight total electron content (TEC). The GPS TEC values are highly precise in a relative sense, with noise levels on the order of ~0.01 TECu. Limb-viewing occultation profiles of vertical TEC may be converted into electron density profiles by means of the Abel transform. The high relative TEC accuracy potentially leads to very precise profiles, resulting in an ability to remotely sense density features below the 10E4/cc level. Thus one would expect GPS occultations to provide a new means for observing E-region features. This is particular true because the E-region often has significant vertical refractivity gradients, to which the occultation technique is particularly sensitive. However, the absolute accuracy of these retrievals can be compromised by the presence of F-region gradients, which violate the Abel assumption of spherical symmetry. We present an initial analysis of the gradient effects on E-region retrievals and discuss methods to mitigate the effects of asymmetry. Examples from simulations and actual observations from the Ionospheric Occultation Experiment (IOX) will be presented to illustrate our results. The utility of low-density E-region measurements will be discussed in the context of validation of models predicting the evolution of the structure of the post-sunset equatorial anomaly region.

  9. Ionospheric Imaging from Geostationary Orbit

    Microsoft Academic Search

    R. P. McCoy; K. S. Wood; K. F. Dymond; S. E. Thonnard

    2001-01-01

    An ultraviolet imager is under development to image the ionosphere and thermosphere from geostationary orbit. The instrument will consist of two telescopes, one with a filter wheel to measure the atomic oxygen airglow emission at 130.4 nm and 135.6 nm and molecular nitrogen Lyman-Birge-Hopfield bands near 142.5 nm. The second telescope will image the atomic oxygen ion resonance multiplet at

  10. 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.

  11. Topside high latitude ionospheric structures

    NASA Astrophysics Data System (ADS)

    Rothkaehl, Hanna; Przepióka, 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.

  12. 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.

  13. A statistical model of ionospheric signals in low-frequency SAR data

    Microsoft Academic Search

    F. J. Meyer; B. Watkins

    2011-01-01

    This paper focuses on deriving a realistic statistical model for ionospheric effects in low-frequency Synthetic Aperture Radar (SAR) data. The approach used to develop this statistical model is based on the assumption that, for a certain range of scales, ionospheric plasma turbulence can be considered a scale-invariant process that can be described by power-law functions or fractal statistics. Based on

  14. On the control of magnetospheric convection by the spatial distribution of ionospheric conductivities

    Microsoft Academic Search

    Catherine Senior; Michel Blanc

    1984-01-01

    Using the linear approximation of the motions of the magnetospheric ring current inner edge, a self-consistent, semianalytical model is developed of its coupling to the ionosphere via field-aligned currents, its reaction to an externally imposed dawn-to-dusk potential drop across the magnetospheric cavity, and its effect on the shielding of convection electric field from midlatitudes. The spatial distribution of ionospheric conductivities

  15. 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.

  16. The Effect of Birth Order on Roommate Compatibility

    ERIC Educational Resources Information Center

    Schuh, John H.; Williams, Ondre J.

    1977-01-01

    A group of students were matched on the basis of compatible birth order; another was matched on the basis of conflicting birth order. After a month's experience in a residence hall their compatibility was examined. Students with conflicting birth order were more compatible than those with the same birth order. (Author)

  17. Present and Future IGS Ionospheric Products

    NASA Astrophysics Data System (ADS)

    Krankowski, Andrzej; Wielgosz, Pawel; Hernández-Pajares, Manuel; García-Rigo, Alberto

    2010-05-01

    The purpose of this paper is, on one hand, to show the present performance of the combined final and rapid IGS global ionosphere maps (GIMs), and on the other hand to inform the geodetic community on new product - predicted IGS GIMs. In addition, information on future development of IGS ionospheric products will be also presented. Nowadays, the Ionosphere Working Group of IGS generates three types of ionospheric products: final, rapid and predicted, respectively. There are currently four IGS Associate Analysis Centres (IAACs) for the ionospheric products: CODE (Center for Orbit Determination in Europe, University of Berne, Switzerland), ESA/ESOC (European Space Operations Center of ESA, Darmstadt, Germany), JPL (Jet Propulsion Laboratory, Pasadena, U.S.A) and gAGE/UPC (Technical University of Catalonia, Barcelona, Spain). These centres provide ionosphere maps computed with different approaches. Their maps are uploaded to IGS Ionosphere Product Coordinator, who computes official IGS combined products. Since January 2008, this coordination is carried out by the GRL/UWM (Geodynamics Research Laboratory of the University of Warmia and Mazury in Olsztyn, Poland). The IGS GIMs are provided in Ionosphere Exchange (IONEX) format with spatial resolution of 5.0 degrees in longitude and 2.5 degrees in latitude, and temporal resolution of 2 hours. Latency of the final and rapid GIMs is 10 days and 1 day, respectively. In November 2009, the IGS Iono WG started to generate predicted ionospheric products 1 and 2 days in advance (requested for ESA's SMOS mission). These new IGS products are currently based on predicted ionosphere maps prepared by UPC and ESA. During period of more than 10 years of continuous IGS ionosphere operation, the techniques used by the IAACs and the strategies of combination have improved in such a way that the combined IGS GIMs are now significantly more accurate and robust. Future plans include, among others, increasing temporal resolution to 1 hour and studies on taking advantage of COSMIC occultation data.

  18. High-frequency beam wave propagation in a stratified random ionosphere

    NASA Astrophysics Data System (ADS)

    Lin, Jyh-Chang; Kiang, Yean-Woei

    1988-08-01

    High-frequency (HF) beam wave propagation in a turbulent stratified ionosphere is investigated. At oblique incidence the beam wave is refracted in the ionosphere with its amplitude and phase calculated by geometrical optics approximation. The diffraction from the bottom of the ionosphere down to the ground is taken into account by solving a parabolic equation. Under appropriate assumptions, numerical results for the two-frequency mutual coherence function and the mean field are obtained. It turns out that the random medium does have effects on the beam wave propagation. As the turbulence strength increases, the coherence bandwidth of the wave is greatly reduced. Thus the width of a pulsed wave will be broadened if it propagates in the random ionosphere.

  19. Impact of geomagnetic storm on fine and global structures of the ionosphere

    NASA Astrophysics Data System (ADS)

    Przepiorka, D.; Gromadzki, M.; Grzesiak, M.; Slominska, E.; Rothkaehl, H.; Space Plasma Group

    2011-12-01

    We have analyzed Demeter micro-satellite data, in particular from ISL, IAP and ICE experiments to study 3 magnetic storm events on January 2005: 7-8, 17-19 and 21-22. The most direct impact on ionosphere is situated at auroral zone but it also affects the dynamics of the ionosphere-thermosphere system at lower latitudes. In effect one can observe changes in the plasma parameters on the global scale. In this study we have analyzed plasma processes related to magnetic storm events and their impact on large scale ionospheric structures such as ionospheric trough. The aim of this study was to establish relation between large scale plasma inhomogeneities and small scale processes. We have produced diurnal global maps for electron density and temperature, ion temperature and ion concentrations. We also analyzed dynamics of the electric field distribution at ULF, ELF, VLF frequency ranges.

  20. Correction of the ionospheric distortion on the MARSIS surface sounding echoes

    NASA Astrophysics Data System (ADS)

    Mouginot, J.; Kofman, W.; Safaeinili, A.; Herique, A.

    2008-05-01

    Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) on the Mars Express (MEX) spacecraft has made numerous measurements of the Martian surface and subsurface. However, all of these measurements are distorted by the ionosphere and must be compensated before any analysis. We have developed a technique to compensate for the ionospheric distortions. This technique provides a powerful tool to derive the total electron content (TEC) and other higher-order terms of the limited expansion of the plasma dispersion function that are related to overall shape of the electron column profile. The derived parameters are fitted by using a Chapman model to derive ionospheric parameters like n0, electron density primary peak (maximum for solar zenith angle (SZA) equal 0), and the neutral height scale H. Our estimated ionospheric parameters are in good agreement with Mars Global Surveyor (MGS) radio-occultation data. However, since MARSIS does not have the observation geometry limitations of the radio occultation measurements, our derived parameters extend over a large range of SZA for each MEX orbit. The first results from our technique have been discussed by Safaeinili et al. [2007, Estimation of the total electron content of the Martian ionosphere using radar sounder surface echoes. Geophys. Res. Lett. 34, L23204, doi:10.1029/2007GL032154].

  1. Monitoring and forecasting Regional Ionospheric perturbations over Australia based on GNSS techniques.

    NASA Astrophysics Data System (ADS)

    Bouya, Zahra; Terkildsen, Michael; Francis, Matthew

    2013-04-01

    Ionospheric storms have the capability to cause serious propagation errors in modern radio systems such as Global Navigation Satellite Systems (GNSS). Thus near real time detection and forecasting of ionospheric storms is helpful to estimate potential degradation of the performance of these systems. In this paper, a new Australian Regional Ionospheric Disturbance Index (AusRDI) is introduced based on a regional dynamic approach. The Spherical Cap Harmonic Analysis (SCHA) method was firstly used to estimate Total Electron Content (TEC) at evenly distributed grid points from GPS data collected from the Australian Regional GPS Network (ARGN). The SCHA model is based on longitudinal expansion in Fourier series and fractional Legendre co-latitudinal functions over a spherical cap-like region including the Australian continent. This harmonic expansion requires fewer coefficients to represent the fine structure of regional ionospheric features and may be adapted to take advantage of regions of densely distributed observations in order to observe and model ionospheric dynamics over Australia on a range of spatial scales. Principal Component Analysis (PCA) was then used to decompose the TEC dataset into a series of orthogonal Eigenfunctions (EOF base functions) and associated coefficients. PCA is non parametric and as such does not utilize deviation from a previously described average to determine perturbations. The new disturbance index provides an objective measure of ionospheric perturbation processes. Furthermore the index is predictable using early space weather information. Keywords: GNSS, Space Weather, Disturbance , Regional, Forecast, SCHA, PCA.

  2. Regional GPS-based ionospheric TEC model over Australia using Spherical Cap Harmonic Analysis

    NASA Astrophysics Data System (ADS)

    Bouya, Zahra; Terkildsen, Michael; Neudegg, Dave

    This paper proposes an approach to regional Total Electron Content (TEC) representation using Spherical Cap Harmonic Analysis (SCHA) [Haines,1988] which, when applied to the whole sphere, is the usual method referred to as ordinary Spherical Harmonic Analysis (SHA). The model is based on longitudinal expansion in Fourier series and fractional Legendre colatitudinal functions over a spherical cap-like region including the Australian continent. The SCHA has been applied to values of the ionospheric TEC parameter as observed by the Australian Regional GPS Network (ARGN). This harmonic expansion requires less coefficients to represent the fine structure of regional ionospheric features than global SHA. Slant TEC values along the GPS signal path from the ARGN GPS receivers are converted to vertical TEC. The SCHA coefficients are estimated from the vertical TEC at the Ionospheric Pierce Points (IPPs). TEC maps were interpolated on a 2x0.5 longitude/latitude grid using the estimated spherical harmonic coefficients. The TEC maps produced over the region are promising and reveal a marginally small rms error. It has been found that for the regional modeling of TEC over the Australian continent, the model well represents basic ionospheric features in the sample space and behaves reasonably within regions where no experimental data are available. The obtained results confirm the usefulness of SCHA for near real time regional TEC mapping and the potential for its application to the modeling of other ionospheric parameters. Also, the SCHA parameters may be adapted to take advantage of regions of densely distributed observations in order to observe and model ionospheric dynamics over Australia on a range of spatial scales, as well as investigate TEC variations under quiet and disturbed ionospheric conditions. KEYWORDS: SCHA, TEC, GPS, IONOSPHERE, AUSTRALIA

  3. Topside ionosphere irregularities in He+ density: statistical study

    NASA Astrophysics Data System (ADS)

    Sidorova, L.; Filippov, S.

    Topside ionosphere He density irregularities as depletions were firstly revealed from OGO-4 data and then from OGO-6 ISIS-2 Oreol-2 data He density depletions subtroughs were seen as well-pronounced structures with He density drop from several times to two orders of magnitude in narrow latitude belt 5 r to 10 r at equatorial and low latitudes mostly However they were distinctly observed in common in several tens of cases only According to ISS-b data He density subtroughs are revealed in sim 440 cases in sim 4000 ISS-b passes over equatorial and low-latitudinal regions L sim 1 3-3 of the topside ionosphere sim 1100 km The available ISS-b data cover high and maximal solar activity period 1978-1979 The present study deals with the He density subtrough statistics The subtrough occurrence probability as function of local time season longitude and Kp activity is obtained and discussed

  4. Ion dynamics in the Venus ionosphere

    NASA Astrophysics Data System (ADS)

    Miller, K. L.; Whitten, R. C.

    1991-02-01

    Measurement data on the ion velocity in the Venus ionosphere (mainly from the Pioneer Venus Orbiter Retarding Potential Analyzer) are summarized, and theoretical models developed to explain them are reviewed. Data and theoretical predictions are compared in extensive graphs and diagrams and discussed in detail. It is shown that the predominant flow is away from the subsolar point, at up to 3 km/sec in the terminator region. A model of axisymmetric flow based on momentum, energy, and mass conservation laws is found to reproduce the observed ion velocities at solar zenith angles less than about 140 deg, but not the high velocities and chaotic behavior seen near the antisolar point. Also discussed are significant differences between the flow above and below about 400 km and the effects of changes in the dynamic pressure of the solar wind.

  5. VLF/LF (very low frequency/low frequency) reflection properties of the low-latitude ionosphere. Interim technical report

    SciTech Connect

    Klemetti, W.I.; Kossey, P.A.; Rasmussen, J.E.; Sueli Da Silveira Macedo Moura, M.

    1988-02-04

    Low-latitude observations of VLF/LF pulse reflections from the lower ionosphere obtained at nine locations to the east and west of a transmitter in southeastern Brazil are described. The data provide a variety of information on the reflection properties of the ionosphere below about 90-km altitude. Aspects of the data are presented in quasi-dimensional formats useful for identifying ionosphere structure and variability, and detailed analyses of portions of the data provided, which characterize the effective heights of the reflection coefficients of the ionosphere at noon and midnight, over a frequency range from 15 to 65 kHz. Electron-density models of the ionosphere, derived from VLF/LF reflection data are also discussed.

  6. Using SDO-EVE Satellite Data to Model for the First Time how Large Solar Flares Influence the Earths Ionosphere

    NASA Astrophysics Data System (ADS)

    Jensen, Joseph; Sojka, Jan; Schunk, Robert; David, Michael; Woods, Tom; Eparvier, Frank

    2012-10-01

    The earth's ionosphere is very important in our everyday life. During large solar flares the ionosphere expands to the point of disrupting communications from GPS, military, and commercial communications satellites, and even radio blackouts can occur. The EVE instrument on the SDO satellite has given unprecedented spectral resolution for the Extreme Ultraviolet(EUV) spectrum with a time cadence of 10 seconds. This has made it possible to analyze flare spectra as never before. Using the Time Dependent Ionospheric Model (TDIM) we have input this new spectral data for large solar flares and analyzed the effect on the ionosphere. We take as a test case the X1.6 flare on March 9, 2011. Even this minor X-class provides insight into how the ionospheric layers respond differently to solar flares.

  7. Discrimination of Earthquake Precursors using Radio-Tomography of the Ionosphere

    NASA Astrophysics Data System (ADS)

    Rekenthaler, Douglas; Currie, Douglas; Kunitsyn, Vyacheslav; Gribkov, Dmitrii; Andreeva, Elena; Nesterov, Ivan

    2014-05-01

    This program relates to addresses lithospheric-ionospheric coupling during strong earthquakes (EQ). We discuss both the ionospheric implications of EQs, and the ionospheric precursors to EQ. the data are analyzed using the methods of satellite radio tomography (RT). Signals from both low-orbiting beacons ("LORT": Transit, Parus, Tsikada, etc.) and high orbiting global navigational satellite systems ("HORT": the GNSS satellites: GPS, GLONASS, Beidot, ....)are used for tomographic reconstructions. Our resulting 2D and 3D tomographic images and their time flow (4-D RT) allow us to map spatio-temporal changes due to ionospheric perturbations induced by EQs and EQ precursors. Low-orbital RT (LORT) provides near "instantaneous" mappings, with a time span of 5-8 minutes, and 2-D graphics of the electron density over the seismically active region of interest. LORT supports 2D imaging of various anomalies, including wave structures such as ionospheric manifestations of acoustic-gravity waves (AGW), wave-like disturbances, and solitary waves with the gaps between images, depending on the number of operating satellites (currently, 30-100 minutes). High-orbital RT (HORT) provides imaging of 4D distributions of ionospheric plasma (resulting in 3D snapshots every 20-30 minutes). Using this approach, one can reconstruct RT images of ionospheric irregularities, wave structures, and perturbations such as solitary waves. In regions with a sufficient number of GNSS receivers (California, Japan), 4-D RT images can be generated every 2-4 minutes. The spatial resolution of LORT and HORT systems is on the order of 20-40 km, and 100 km, respectively. We present the results of a long-term study using HORT and LORT techniques for study of the ionosphere over California, Alaska, and Southeast Asia (Taiwan region). In particular, we established a ground station array extending from Washington to California, which we operated from 2011 to 2013 on a 24/7 basis. Reconstructions of the ionosphere using those data showed evidence of earthquake precursory processes from hours to days prior to earthquakes along the US West Coast. The system proved to be approximately 80% successful in discriminating unique signatures which correlated well with the eventual events in terms of geo-location of the eventual epicenters. Additionally, ionospheric waves arriving over the US West Coast as a result of Japan's Tohoku event were recorded, arriving well ahead of the ocean waves, suggesting use of the ionospheric tomography technique for timely tsunami early warning and determination of wave heights.

  8. Overview of ionospheric modification from space platforms

    Microsoft Academic Search

    Peter M. Banks

    1990-01-01

    Spaceborne, nonelectromagnetic methods of modifying the E- and F-regions of the terrestrial ionosphere are discussed. Of these methods, the most well-understood is the direct injection of chemical vapors into the ambient medium. The first injection of barium clouds into the upper atmosphere over two decades ago has led to evolution of understanding of complex electrodynamic processes acting in the ionosphere

  9. Microwave heating of the lower ionosphere

    NASA Technical Reports Server (NTRS)

    Meltz, G.; Nighan, W. L.

    1980-01-01

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

  10. Global aspects of solar wind ionosphere interactions

    Microsoft Academic Search

    T. E. Moore; M.-C. Fok; D. C. Delcourt; S. P. Slinker; J. A. Fedder

    2007-01-01

    Recent observations have quantified the auroral wind O+ outflow in response to magnetospheric inputs to the ionosphere, notably Poynting energy flux and precipitating electron density. For moderate to high activity periods, ionospheric O+ is observed to become a significant or dominant component of plasma pressure in the inner plasma sheet and ring current regions. Using a global circulation model of

  11. Ionospheric Alfvén resonator revisited: Feedback instability

    Microsoft Academic Search

    Oleg A. Pokhotelov; V. Khruschev; M. Parrot; S. Senchenkov; V. P. Pavlenko

    2001-01-01

    The theory of ionospheric Alfvén resonator (IAR) and IAR feedback instability is reconsidered. Using a simplified model of the topside ionosphere, we have reanalyzed the physical properties of the IAR interaction with magnetospheric convective flow. It is found that in the absence of the convective flow the IAR eigenmodes exhibit a strong damping due to the leakage of the wave

  12. Modeling longitudinal variations the low latitude ionosphere

    Microsoft Academic Search

    S. L. England; T. J. Immel; J. D. Huba; S. B. Mende

    2006-01-01

    A new large-scale longitudinal structure has recently been discovered in the equatorial ionosphere. The peak plasma density and separation of the two bands of the post-sunset equatorial ionospheric anomaly (EIA) observed by the FUV instruments onboard the NASA IMAGE and TIMED satellites were found to vary significantly, with maxima in 4 sectors around the planet during equinox. It has been

  13. The structure of the Venus ionosphere

    Microsoft Academic Search

    L. H. Brace; A. J. Kliore

    1991-01-01

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

  14. Plasma Temperatures in the Ionosphere of Saturn

    Microsoft Academic Search

    Luke Moore; M. Galand; M. Mendillo; I. Müller-Wodarg

    2007-01-01

    Using a one-dimensional version of the Saturn Thermosphere Ionosphere Model (STIM), we perform calculations of the ion and electron temperatures in the ionosphere of Saturn. There are no direct measurements of plasma temperatures in Saturn's atmosphere published to date, but they are often estimated from the topside plasma scale heights of radio occultation measurements of electron density. Based on Pioneer,

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

    E-print Network

    Schuh, Harald

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

  16. The ionospheric responses to the 11 August 1999 solar eclipse: observations and modeling

    NASA Astrophysics Data System (ADS)

    Le, H.; Liu, L.; Yue, X.; Wan, W.

    2008-02-01

    A total eclipse occurred on 11 August 1999 with its path of totality passing over central Europe in the latitude range 40°-50° N. The ionospheric responses to this eclipse were measured by a wide ionosonde network. On the basis of the measurements of foE, foF1, and foF2 at sixteen ionosonde stations in Europe, we statistically analyze the variations of these parameters with a function of eclipse magnitude. To model the eclipse effects more accurately, a revised eclipse factor, FR, is constructed to describe the variations of solar radiation during the solar eclipse. Then we simulate the effect of this eclipse on the ionosphere with a mid- and low-latitude ionosphere theoretical model by using the revised eclipse factor during this eclipse. Simulations are highly consistent with the observations for the response in the E-region and F1-region. Both of them show that the maximum response of the mid-latitude ionosphere to the eclipse is found in the F1-region. Except the obvious ionospheric response at low altitudes below 500 km, calculations show that there is also a small response at high altitudes up to about 2000 km. In addition, calculations show that when the eclipse takes place in the Northern Hemisphere, a small ionospheric disturbance also appeared in the conjugate hemisphere.

  17. Ionospheric differential error determination using ray tracing for a short baseline

    NASA Astrophysics Data System (ADS)

    Abdullah, M.; Strangeways, H. J.; Zulkifli, S. S. N.

    2010-11-01

    Since the United States government discontinued Selective Availability (SA) on 1 May 2000, ionospheric effects have been responsible for the largest errors in GPS systems. The standard Differential GPS (DGPS) method is incapable of completely eliminating the ionospheric error. This paper describes a new approach to determine the differential ionospheric error between geographically distributed receiver stations. The ray paths of GPS signals were simulated using a modified Jones 3D ray tracing programme that includes the effect of the geomagnetic field. A Nelder-Mead optimisation algorithm was embedded in the program to precisely determine the satellite-to-station path. A realistic ionospheric model is essential for accurate ray tracing results and for estimates of differential error that are accurate on sub-centimetre scales. Here, the ionospheric model used in the ray tracing programme was developed by fitting realistic ionosphere profiles with a number of exponential functions. Results were compared to the theoretical approach. Results show that the differential delay is about 1-5 cm at low elevation angles for a short baseline of 10 km, as reported in other literature. This delay is often neglected in DGPS application. The differential delay also shows a pattern similar to that predicted by the Klobuchar model. The method proposed here can be used to improve future GPS applications.

  18. GPS based method of ionospheric study

    NASA Astrophysics Data System (ADS)

    Gwal, A. K.; Sarkar, S.; Malhotra, K.

    The GPS ionospheric sounding is a powerful tool for remote sensing of the ionosphere. The GPS signals have provided an unique opportunity to study the short scale length variations in TEC (Total Electron Content) along the signal path in the presence of ionospheric irregularities and scintillations caused by these irregularities. GPS based ionospheric measurement can measure TEC variations smaller than 10-2 TEC unit. This paper presents the observations of real time TEC and scintillation obtained with dual frequency GPS receiver GSV4004A at Bhopal. The receiver is specially configured to measure amplitude and phase scintillation from the L1 frequency GPS signals and ionospheric TEC from the L1 (1575 MHz) and L2 (1227 MHz) frequency GPS signals. The data for TEC and scintillation have been analyzed and the results for the crest of anomaly region (Bhopal) have been discussed.

  19. On a method computing transient wave propagation in ionospheric regions

    NASA Technical Reports Server (NTRS)

    Gray, K. G.; Bowhill, S. A.

    1978-01-01

    A consequence of an exoatmospheric nuclear burst is an electromagnetic pulse (EMP) radiated from it. In a region far enough away from the burst, where nonlinear effects can be ignored, the EMP can be represented by a large-amplitude narrow-time-width plane-wave pulse. If the ionosphere intervenes the origin and destination of the EMP, frequency dispersion can cause significant changes in the original pulse upon reception. A method of computing these dispersive effects of transient wave propagation is summarized. The method described is different from the standard transform techniques and provides physical insight into the transient wave process. The method, although exact, can be used in approximating the early-time transient response of an ionospheric region by a simple integration with only explicit knowledge of the electron density, electron collision frequency, and electron gyrofrequency required. As an illustration of the method, it is applied to a simple example and contrasted with the corresponding transform solution.

  20. Non-migrating tides in the ionosphere-thermosphere: In situ versus tropospheric sources

    NASA Astrophysics Data System (ADS)

    Jones, M.; Forbes, J. M.; Hagan, M. E.; Maute, A.

    2013-05-01

    In this paper we demonstrate how magnetic control of ion-neutral interactions in the ionosphere-thermosphere (IT) system effectively produces source terms for non-migrating solar tides in the neutral momentum equations for the thermosphere. The National Center for Atmospheric Research (NCAR) Thermosphere-Ionosphere-Mesosphere-Electrodynamics General Circulation Model (TIME-GCM) is utilized to quantify these tides, and to assess their importance relative to those that propagate upward from lower atmospheric regions. The primary diurnal tides excited in situ by the above mechanism include DE1, D0 and DW2, with zonal wind amplitudes on the order of 20 m s-1 (5-10 m s-1) at ˜500 km (˜350 km) under solar maximum (minimum) conditions. Smaller amplitude semidiurnal non-migrating tides, mainly SE1, S0, SW1, and SW3, are also generated under solar maximum conditions. The aggregate effect of these tidal components is to produce extrema ranging from -110 to +140 m s-1 in a typical illustration of latitude versus longitude at a constant local time. The associated wind circulations include vertical wind perturbations that drive temperature perturbations through adiabatic heating and cooling effects. At high latitudes, hydromagnetic coupling effects generate non-migrating tidal components including DE1, D0, DW2, SE1, S0, and SW1, which show interhemispheric differences in both amplitude and latitudinal structure due to interhemispheric differences in the offset between the geographic and geomagnetic poles. Our computational results show that the in situ generated non-migrating tidal components dominate some parts of the tidal spectrum at high levels of solar activity and suggest that in situ generated non-migrating tides must be taken into account in order to reconcile differences in data-model comparisons.

  1. Application of computerized tomography to the investigation of ionospheric structures

    Microsoft Academic Search

    T. D. Raymund; J. R. Austen; S.J. Franke; J. A. Klobuchar; J. Stalker

    1990-01-01

    Ionospheric total electron content (TEC) measurements, obtained simultaneously at several locations, can be processed using computerized tomography (CT) algorithms to obtain two-dimensional images of ionospheric electron density. Using TEC data computerized ionospheric tomography (CIT) reconstructs an image of the electron density structures in a vertical slice above the receiving stations. We successfully applied this technique to realistic simulations of ionospheric

  2. An Ionosphere Estimation Algorithm for WAAS Based on Kriging

    E-print Network

    Stanford University

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

  3. Assessment of Nominal Ionosphere Spatial Decorrelation for LAAS

    E-print Network

    Stanford University

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

  4. Ionospheric Alfvén resonator excitation due to nearby thunderstorms

    Microsoft Academic Search

    V. V. Surkov; M. Hayakawa; A. Y. Schekotov; E. N. Fedorov; O. A. Molchanov

    2006-01-01

    A theory of midlatitude Ionospheric Alfvén Resonator (IAR) excitation due to random cloud-to-ground lightning discharges is developed. Electromagnetic wave radiated from the lightning discharges penetrates into the ionosphere, thereby exciting the shear Alfvén and magnetosonic waves in the F region of ionosphere. The IAR arises due to wave reflection from the Alfvén velocity gradients in the topside ionosphere. Typically, the

  5. Assessing the effectiveness of a computerized blood order "consultation" system.

    PubMed

    Lepage, E F; Gardner, R M; Laub, R M; Jacobson, J T

    1991-01-01

    To optimize blood ordering and accurately assess transfusion practice, in 1987, an "on line" computerized, knowledge-based, blood order critiquing system was integrated into the HELP Hospital Information System (HIS) at LDS Hospital. Evaluations of the computerized ordering system demonstrated its benefits and limitations on transfusion practice. Based on this experience, a second generation blood ordering system using a consultation mode was developed. A pilot test of this blood order consultant system, using historical data in the HELP system's database, was performed. This pilot test demonstrated that the consultation system provided accurate recommendations for red blood cell (RBC) and platelet orders. Comparing the appropriateness of blood orders with the recommendations made by the director of the blood bank, the orders recommended by the computer "consultant" agreed 95.5% of the time. The computer consultation system also recommended fewer RBC units for transfusion. Preliminary results obtained using the consultant approach suggest that we may be able to simplify blood ordering practice and also reduce the number of units of blood products ordered. Based on these findings we are now preparing to compare the "critiquing" and "consultation" approaches using a clinical trial. PMID:1807617

  6. Solar activity variations of nighttime ionospheric peak electron density

    Microsoft Academic Search

    Yiding Chen; Libo Liu; Huijun Le

    2008-01-01

    Monthly median NmF2 (maximum electron density of the F2-layer) data at Okinawa, Yamagawa, Kokubunji, and Wakkanai have been collected to investigate the solar activity dependence of the nighttime ionosphere. The result shows that there are seasonal and latitudinal differences of the solar activity variation of nighttime NmF2. The main seasonal effects are as follows: nighttime NmF2 increases with F107 linearly

  7. Aerosol growth in Titan's ionosphere.

    PubMed

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

    2013-02-19

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

  8. Ion temperature anisotropy effects on threshold conditions of a shear-modified current driven electrostatic ion-acoustic instability in the topside auroral ionosphere

    NASA Astrophysics Data System (ADS)

    Perron, P. J. G.; Noël, J.-M. A.; Kabin, K.; St-Maurice, J.-P.

    2013-03-01

    Temperature anisotropies may be encountered in space plasmas when there is a preferred direction, for instance, a strong magnetic or electric field. In this paper, we study how ion temperature anisotropy can affect the threshold conditions of a shear-modified current driven electrostatic ion-acoustic (CDEIA) instability. In particular, this communication focuses on instabilities in the context of topside auroral F-region situations and in the limit where finite Larmor radius corrections are small. We derived a new fluid-like expression for the critical drift which depends explicitly on ion anisotropy. More importantly, for ion to electron temperature ratios typical of F-region, solutions of the kinetic dispersion relation show that ion temperature anisotropy may significantly lower the drift threshold required for instability. In some cases, a perpendicular to parallel ion temperature ratio of 2 and may reduce the relative drift required for the onset of instability by a factor of approximately 30, assuming the ion-acoustic speed of the medium remains constant. Therefore, the ion temperature anisotropy should be considered in future studies of ion-acoustic waves and instabilities in the high-latitude ionospheric F-region.

  9. Ordering Effects In Self-Organized Quantum-Dot Stacks

    NASA Astrophysics Data System (ADS)

    Kunert, R.; Schöll, E.; Pohl, U. W.

    2011-12-01

    Deviations from ideal ordering in quantum-dot stacks observed in experiment are compared to growth simulations based on a kinetic Monte Carlo model. Anticorrelated vertical alignment with a weak specificity is only found if the first layer is well ordered. Randomly distributed dots in the first layer lead to correlated vertical alignment preferentially for thin spacers and increased temperature, with gradually improving ordering regarding sizes and arrangement.

  10. Ground and Space-Based Measurement of Rocket Engine Burns in the Ionosphere

    NASA Technical Reports Server (NTRS)

    Bernhardt, P. A.; Ballenthin, J. O.; Baumgardner, J. L.; Bhatt, A.; Boyd, I. D.; Burt, J. M.; Caton, R. G.; Coster, A.; Erickson, P. J.; Huba, J. D.; Earle, G. D.; Kaplan, C. R.; Foster, J. C.; Groves, K. M.; Haaser, R. A.; Heelis, R. A.; Hunton, D. E.; Hysell, D. L.; Klenzing, J. H.; Larsen, M. F.; Lind, F. D.; Pedersen, T. R.; Pfaff, R. F.; Stoneback, R. A.; Roddy, P. A.; Rodriguez, S. P.; San Antonio, G. S.; Schuck, P. W.; Siefring, C. L.; Selcher, C. A.; Smith, S. M.; Talaat, E. R.; Thomason, J. F.; Tsunoda, R. T.; Varney, R. H.

    2013-01-01

    On-orbit firings of both liquid and solid rocket motors provide localized disturbances to the plasma in the upper atmosphere. Large amounts of energy are deposited to ionosphere in the form of expanding exhaust vapors which change the composition and flow velocity. Charge exchange between the neutral exhaust molecules and the background ions (mainly O+) yields energetic ion beams. The rapidly moving pickup ions excite plasma instabilities and yield optical emissions after dissociative recombination with ambient electrons. Line-of-sight techniques for remote measurements rocket burn effects include direct observation of plume optical emissions with ground and satellite cameras, and plume scatter with UHF and higher frequency radars. Long range detection with HF radars is possible if the burns occur in the dense part of the ionosphere. The exhaust vapors initiate plasma turbulence in the ionosphere that can scatter HF radar waves launched from ground transmitters. Solid rocket motors provide particulates that become charged in the ionosphere and may excite dusty plasma instabilities. Hypersonic exhaust flow impacting the ionospheric plasma launches a low-frequency, electromagnetic pulse that is detectable using satellites with electric field booms. If the exhaust cloud itself passes over a satellite, in situ detectors measure increased ion-acoustic wave turbulence, enhanced neutral and plasma densities, elevated ion temperatures, and magnetic field perturbations. All of these techniques can be used for long range observations of plumes in the ionosphere. To demonstrate such long range measurements, several experiments were conducted by the Naval Research Laboratory including the Charged Aerosol Release Experiment, the Shuttle Ionospheric Modification with Pulsed Localized Exhaust experiments, and the Shuttle Exhaust Ionospheric Turbulence Experiments.

  11. 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.

  12. Modelling the ionospheric perturbations excited by large earthquakes for source characterization

    NASA Astrophysics Data System (ADS)

    Rolland, Lucie; Lognonné, Philippe; Occhipinti, Giovanni; Kherani, Alam; Crespon, François; Murakami, Makoto

    The local state of the ionosphere is now routinely mapped just after strong and shallow earthquakes instrumented by dense Ground Positioning System networks. Actually, for most of these events, ionospheric disturbances are registered in the Total Electronic Content a dozen minutes after the source rupture. In some favourable configurations - that will be reminded here - an integrated "seismo-ionospheric" radiative pattern is visualized. Thus, a dozen minutes after the Hokka¨ - 2003, September 25th - and Honshu - 2007, July 16th - earthquakes, different in ?do term of magnitudes (8.1 and 6.6 and respectively) and in term of source mechanisms, the two patterns present the same attenuation in the northern part. This directivity was first pointed out by (Calais et al., 1998) and the geomagnetic field was invoked as a possible cause, posing the problem geometry. In our model, we assimilate the observed radiative pattern to a combination of concentric waves, taking into account that the electrons are redistributed under the effect of the acoustic pressure waves, themselves excited by the seismic vertical ground displacements. In other words, we describe how the ionosphere interacts with an acoustic pulse propagating in the atmosphere up to the ionosphere, with a special highlight on the influence of the geomagnetic field. A 3-dimensional model is developed according to the ionospheric coupling model of E.A. Kherani et al., 2008. The geometry of the acoustic pulse is modelled with a ray tracing method and the horizontal component of the propagation provides an explication to the attenuation. A final inversion allows us to derive the parameters of the source. [E. Calais et al., 1998] Ionospheric signature of surface mine blasts from Global Positioning System measurements, Geophys. J. Int., vol. 132, pp.191-202 [E. A. Kherani et al., submitted] "Response of the Ionosphere to the seismic triggered acoustic waves: electron density and electromagnetic fluctuations," Geophys. J. Int.

  13. Photochemistry of Titan's Atmosphere and Ionosphere

    NASA Astrophysics Data System (ADS)

    Krasnopolsky, Vladimir A.

    2008-09-01

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

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

    E-print Network

    Larson, Kristine

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

  15. The large-scale isolated disturbances dynamics in the main peak of electronic concentration of ionosphere

    NASA Astrophysics Data System (ADS)

    Kalinin, U. K.; Romanchuk, A. A.; Sergeenko, N. P.; Shubin, V. N.

    2003-07-01

    The vertical sounding data at chains of ionosphere stations are used to obtain relative variations of electron concentration in the F2 ionosphere region. Specific isolated traveling large-scale irregularities are distinguished in the diurnal succession of the fcF2 relative variations records. The temporal shifts of the irregularities at the station chains determine their motion velocity (of the order of speed of sound) and spatial scale (of order of 3000-5000km, the trajectory length being up to 10000km). The motion trajectories of large-scale isolated irregularities which had preceded the earthquakes are reconstructed.

  16. Study of the ionosphere of Mars: application and limitations of the Chapman-layer model

    NASA Astrophysics Data System (ADS)

    Sanchez-Cano, B.; Herraiz, M.; Rodriguez-Caderot, G.; Radicella, S. M.

    2011-11-01

    The study of data from Viking, Mars Global Surveyor and Mars Express missions is enabling a rapid progress in the knowledge of ionosphere of Mars. Although the Earth's ionosphere is a reference is necessary to note that Mars doesn't have a global magnetic field to form a magnetosphere and the composition of his atmosphere is very different from the case of the Earth. Therefore, the effect of solar wind on the atmosphere, chemical reactions and ionization processes are very different in the two planets. For this reason there may be doubts about the applicability of terrestrial ionospheric models to the ionosphere of Mars. In a first step in this line of study we have applied the Chapman layer model to a significant number of radio-occultation data obtained by the Mars Global Surveyor mission to check the validity range for the fit of the electron density profiles. We also analyze the status of the ionosphere under different conditions of latitude, longitude, time of observation, Martian seasons and solar activity to compare these results with the characteristics and variations in the Earth's ionosphere.

  17. Simple instruments used in monitoring ionospheric perturbations and some observational results showing the ionospheric responses to the perturbations mainly from the lower atmosphere

    NASA Astrophysics Data System (ADS)

    Xiao, Zuo; Hao, Yongqiang; Zhang, Donghe; Xiao, Sai-Guan; Huang, Weiquan

    Ionospheric disturbances such as SID and acoustic gravity waves in different scales are well known and commonly discussed topics. Some simple ground equipment was designed and used for monitoring continuously the effects of these disturbances, especially, SWF, SFD. Besides SIDs, They also reflect clearly the acoustic gravity waves in different scale and Spread-F and these data are important supplementary to the traditional ionosonde records. It is of signifi-cance in understanding physical essentials of the ionospheric disturbances and applications in SID warning. In this paper, the designing of the instruments is given and results are discussed in detail. Some case studies were introduced as example which showed very clearly not only immediate effects of solar flare, but also the phenomena of ionospheric responses to large scale gravity waves from lower atmosphere such as typhoon, great earthquake and volcano erup-tion. Particularlyresults showed that acoustic gravity waves play significant role in seeding ionospheric Spread-F. These examples give evidence that lower atmospheric activities strongly influence the ionosphere.

  18. Towards order-by-order calculations of the nuclear and neutron matter equations of state in chiral effective field theory

    E-print Network

    F. Sammarruca; L. Coraggio; J. W. Holt; N. Itaco; R. Machleidt; L. E. Marcucci

    2015-04-18

    We calculate the nuclear and neutron matter equations of state from microscopic nuclear forces at different orders in chiral effective field theory and with varying momentum-space cutoff scales. We focus attention on how the order-by-order convergence depends on the choice of resolution scale and the implications for theoretical uncertainty estimates on the isospin asymmetry energy. Specifically we study the equations of state using consistent NLO and N2LO (next-to-next-to-leading order) chiral potentials where the low-energy constants cD and cE associated with contact vertices in the N2LO chiral three-nucleon force are fitted to reproduce the binding energies of 3H and 3He as well as the beta-decay lifetime of 3H. At these low orders in the chiral expansion there is little sign of convergence, while an exploratory study employing the N3LO two-nucleon force together with the N2LO three-nucleon force give first indications for (slow) convergence with low-cutoff potentials and poor convergence with higher-cutoff potentials. The consistent NLO and N2LO potentials described in the present work provide the basis for estimating theoretical uncertainties associated with the order-by-order convergence of nuclear many-body calculations in chiral effective field theory.

  19. Study of stratospheric-ionospheric coupling during thunderstorms and tornadoes

    NASA Technical Reports Server (NTRS)

    Hung, R. J.; Smith, R. E.

    1977-01-01

    A continuous-wave-spectrum high-frequency Doppler sounder array with three transmitters at each of three sites was used to observe the dynamics of the coupling of energy between the stratosphere and the ionosphere. During times of severe weather activity wavelike disturbances have been detected on ground-based ionospheric sounding records as perturbations in electron densities. Infrasonic waves with wave periods of 3-7 min and with horizontal phase velocities of 600-800 m/s were observed when there was thunderstorm activity; gravity waves with wave periods of 10-15 min and horizontal phase velocities of 100-200 m/s were detected when there was tornado activity. Both triangulations from the cross correlation functions of the Doppler records based on an assumption of no background wind shear and ray-tracing computations including an assumed background wind shear indicate that the waves originated in the vicinity of the thunderstorms and tornadoes. A comparison of the wavelengths of the infrasonic and gravity waves observed at ionospheric heights and those in cloud-top pictures from satellites show that they are all of the order of 100-300 km.

  20. Ionospheric modification research at HIPAS

    SciTech Connect

    Brandt, R.G.

    1990-10-01

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