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Sample records for order ionospheric effects

  1. Higher Order Ionospheric Effects on P-Band SAR Data

    NASA Astrophysics Data System (ADS)

    Zhang, Haizhen; Zeng, Qiming; Jiao, Jian; Li, Yingbing

    2014-11-01

    Future Synthetic Aperture Radar (SAR) spaceborne systems such as the European Space Agency (ESA) BIOMASS candidate mission will operate in P-band. To overcome the constraints of full polarimetric SAR, the compact mode is proposed where the transmit polarization is circular. At such a low frequency, the higher order ionospheric (HOI) effects may become seriously problematic and cannot be negligible. This study is focusing on the HOI terms especially HOI phase shift for the compact circularly polarimetric mode which is always ignored in L-band and even P-band SAR signal. The Faraday Rotation (FR) for the linearly polarised signal caused by the HOI terms has also been discussed in detail.

  2. Ionospheric Modelling using GPS to Calibrate the MWA. I: Comparison of First Order Ionospheric Effects between GPS Models and MWA Observations

    NASA Astrophysics Data System (ADS)

    Arora, B. S.; Morgan, J.; Ord, S. M.; Tingay, S. J.; Hurley-Walker, N.; Bell, M.; Bernardi, G.; Bhat, N. D. 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.; Kapińska, 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.

    2015-08-01

    We compare first-order (refractive) ionospheric effects seen by the MWA with the ionosphere as inferred from 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 CODE. However, 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 DCBs. The receiver DCBs need to be estimated for any non-CODE GPS station used for ionosphere modelling. In this work, single GPS station-based ionospheric modelling is performed at a time resolution of 10 min. Also the receiver DCBs are estimated for selected Geoscience Australia GPS receivers, located at Murchison Radio Observatory, Yarragadee, Mount Magnet and Wiluna. The ionospheric gradients estimated from GPS are compared with that inferred from MWA. The ionospheric gradients at all the GPS stations show a correlation with the gradients observed with the MWA. The ionosphere estimates obtained using GPS measurements show promise in terms of providing calibration information for the MWA.

  3. Higher-Order Ionospheric Effects on the GPS Reference Frame and GPS velocities

    NASA Astrophysics Data System (ADS)

    Petrie, E. J.; King, M. A.; Moore, P.; Lavallée, D. A.

    2009-04-01

    We present time series over the period of a complete solar cycle (1995 - 2008) showing the influence of the second and third order ionospheric terms on the GPS reference frame. We include a comparison of the differences found when using either a tilted dipole model or the International Geomagnetic Reference Field (IGRF) for the magnetic field component of the second order term. We examine reference frame translation, rotation, and scale change and velocity effects. We find relatively small differences between the dipole and IGRF solutions, reaching their maximum at ionospheric maximum. For both approaches the reference frame effect is most significant in the Z-translation, where it varies from < 1mm at solar minimum up to 10-15mm at times of peak ionospheric activity. The impact on the other reference frame parameters is much less significant. The mathematical formulation is as outlined in Fritsche et al. (2005). The GPS processing was performed using a modified version of the GAMIT software using a global network of stations, and includes recent developments such as improved tropospheric mapping functions and antenna phase centre corrections. The Total Electron Content (TEC) was obtained from IONEX files. Finally, we present preliminary data showing the effects on the above of including a simple model of ionospheric bending of GPS signals, as suggested by Hoque & Jakowski(2008).

  4. Effects on noise properties of GPS time series caused by higher-order ionospheric corrections

    NASA Astrophysics Data System (ADS)

    Jiang, Weiping; Deng, Liansheng; Li, Zhao; Zhou, Xiaohui; Liu, Hongfei

    2014-04-01

    Higher-order ionospheric (HOI) effects are one of the principal technique-specific error sources in precise global positioning system (GPS) analysis. These effects also influence the non-linear characteristics of GPS coordinate time series. In this paper, we investigate these effects on coordinate time series in terms of seasonal variations and noise amplitudes. Both power spectral techniques and maximum likelihood estimators (MLE) are used to evaluate these effects quantitatively and qualitatively. Our results show an overall improvement for the analysis of global sites if HOI effects are considered. We note that the noise spectral index that is used for the determination of the optimal noise models in our analysis ranged between -1 and 0 both with and without HOI corrections, implying that the coloured noise cannot be removed by these corrections. However, the corrections were found to have improved noise properties for global sites. After the corrections were applied, the noise amplitudes at most sites decreased, among which the white noise amplitudes decreased remarkably. The white noise amplitudes of up to 81.8% of the selected sites decreased in the up component, and the flicker noise of 67.5% of the sites decreased in the north component. Stacked periodogram results show that, no matter whether the HOI effects are considered or not, a common fundamental period of 1.04 cycles per year (cpy), together with the expected annual and semi-annual signals, can explain all peaks of the north and up components well. For the east component, however, reasonable results can be obtained only based on HOI corrections. HOI corrections are useful for better detecting the periodic signals in GPS coordinate time series. Moreover, the corrections contributed partly to the seasonal variations of the selected sites, especially for the up component. Statistically, HOI corrections reduced more than 50% and more than 65% of the annual and semi-annual amplitudes respectively at the selected sites.

  5. Higher-order ionosphere modeling for CODE's next reprocessing activities

    NASA Astrophysics Data System (ADS)

    Lutz, S.; Schaer, S.; Meindl, M.; Dach, R.; Steigenberger, P.

    2009-12-01

    CODE (the Center for Orbit Determination in Europe) is a joint venture between the Astronomical Institute of the University of Bern (AIUB, Bern, Switzerland), the Federal Office of Topography (swisstopo, Wabern, Switzerland), the Federal Agency for Cartography and Geodesy (BKG, Frankfurt am Main, Germany), and the Institut für Astronomische und Phsyikalische Geodäsie of the Technische Universität München (IAPG/TUM, Munich, Germany). It acts as one of the global analysis centers of the International GNSS Service (IGS) and participates in the first IGS reprocessing campaign, a full reanalysis of GPS data collected since 1994. For a future reanalyis of the IGS data it is planned to consider not only first-order but also higher-order ionosphere terms in the space geodetic observations. There are several works (e.g. Fritsche et al. 2005), which showed a significant and systematic influence of these effects on the analysis results. The development version of the Bernese Software used at CODE is expanded by the ability to assign additional (scaling) parameters to each considered higher-order ionosphere term. By this, each correction term can be switched on and off on normal-equation level and, moreover, the significance of each correction term may be verified on observation level for different ionosphere conditions.

  6. 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.

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

    NASA Astrophysics Data System (ADS)

    Jakowski, Norbert; Danielides, Michael; Mayer, Christoph; Borries, Claudia

    Space weather effects are closely related to complex perturbation processes in the magnetosphere-ionosphere-thermosphere systems, initiated by enhanced solar energy input. To understand and model complex space weather processes, different views on the same subject are helpful. One of the ionosphere key parameters is the Total Electron Content (TEC) which provides a first or-der approximation of the ionospheric range error in Global Navigation Satellite System (GNSS) applications. Additionally, horizontal gradients and time rate of change of TEC are important for estimating the perturbation degree of the ionosphere. TEC maps can effectively be gener-ated using ground based GNSS measurements from global receiver networks. Whereas ground based GNSS measurements provide good horizontal resolution, space based radio occultation measurements can complete the view by providing information on the vertical plasma density distribution. The combination of ground based TEC and vertical sounding measurements pro-vide essential information on the shape of the vertical electron density profile by computing the equivalent slab thickness at the ionosonde station site. Since radio beacon measurements at 150/400 MHz are well suited to trace the horizontal structure of Travelling Ionospheric Dis-turbances (TIDs), these data products essentially complete GNSS based TEC mapping results. Radio scintillation data products, characterising small scale irregularities in the ionosphere, are useful to estimate the continuity and availability of transionospheric radio signals. The different data products are addressed while discussing severe space weather events in the ionosphere e.g. events in October/November 2003. The complementary view of different near real time service data products is helpful to better understand the complex dynamics of ionospheric perturbation processes and to forecast the development of parameters customers are interested in.

  8. Assessments of higher-order ionospheric effects on GPS coordinate time series: A case study of CMONOC with longer time series

    NASA Astrophysics Data System (ADS)

    Jiang, Weiping; Deng, Liansheng; Zhou, Xiaohui; Ma, Yifang

    2014-05-01

    Higher-order ionospheric (HIO) corrections are proposed to become a standard part for precise GPS data analysis. For this study, we deeply investigate the impacts of the HIO corrections on the coordinate time series by implementing re-processing of the GPS data from Crustal Movement Observation Network of China (CMONOC). Nearly 13 year data are used in our three processing runs: (a) run NO, without HOI corrections, (b) run IG, both second- and third-order corrections are modeled using the International Geomagnetic Reference Field 11 (IGRF11) to model the magnetic field, (c) run ID, the same with IG but dipole magnetic model are applied. Both spectral analysis and noise analysis are adopted to investigate these effects. Results show that for CMONOC stations, HIO corrections are found to have brought an overall improvement. After the corrections are applied, the noise amplitudes decrease, with the white noise amplitudes showing a more remarkable variation. Low-latitude sites are more affected. For different coordinate components, the impacts vary. The results of an analysis of stacked periodograms show that there is a good match between the seasonal amplitudes and the HOI corrections, and the observed variations in the coordinate time series are related to HOI effects. HOI delays partially explain the seasonal amplitudes in the coordinate time series, especially for the U component. The annual amplitudes for all components are decreased for over one-half of the selected CMONOC sites. Additionally, the semi-annual amplitudes for the sites are much more strongly affected by the corrections. However, when diplole model is used, the results are not as optimistic as IGRF model. Analysis of dipole model indicate that HIO delay lead to the increase of noise amplitudes, and that HIO delays with dipole model can generate false periodic signals. When dipole model are used in modeling HIO terms, larger residual and noise are brought in rather than the effective improvements.

  9. Ionospheric effects of Birkeland currents.

    NASA Technical Reports Server (NTRS)

    Cloutier, P. A.

    1971-01-01

    Since Birkeland's observations of high-latitude magnetic perturbations led him to postulate the existence of geomagnetically aligned electric currents, theoretical studies have led to a general understanding of the mechanisms that are capable of driving such currents, and of the processes associated with formation and control of current configurations. Recent advances in experimental techniques have yielded information on the spatial and temporal behavior of such field-aligned Birkeland currents and have established their association to an individual auroral arc and energetic precipitating particles. This paper gives a brief summary of ionospheric effects related to production, maintenance, and control of Birkeland current systems. Available experimental data are discussed in relation to some of these effects.

  10. A review of ionospheric effects on Earth-space propagation

    NASA Technical Reports Server (NTRS)

    Klobuchar, J. A.

    1984-01-01

    A short description is given of each ionospheric total electron content (TEC) effect upon radio waves, along with a representative value of the magnitude of each of these effects under normal ionospheric conditions. A discussion is given of the important characteristics of average ionospheric TEC behavior and the temporal and spatial variability of TEC. Radio waves undergo several effects when they pass through the Earth's ionosphere. One of the most important of these effects is a retardation, or group delay, on the modulation or information carried on the radio wave that is due to its encounter with the free, thermal electrons in the Earth's ionosphere. Other effects the ionosphere has on radio waves include: radio frequency (RF) carrier phase advance; Doppler shift of the RF carrier of the radio wave; Faraday rotation of the plane of polarization of linearly polarized waves; angular refraction or bending of the radio wave path as it travels through the ionosphere; and amplitude and phase scintillations.

  11. Ionospheric Scintillation Effects on GPS

    NASA Astrophysics Data System (ADS)

    Steenburgh, R. A.; Smithtro, C.; Groves, K.

    2007-12-01

    . Ionospheric scintillation of Global Positioning System (GPS) signals threatens navigation and military operations by degrading performance or making GPS unavailable. Scintillation is particularly active, although not limited to, a belt encircling the earth within 20 degrees of the geomagnetic equator. As GPS applications and users increases, so does the potential for detrimental impacts from scintillation. We examined amplitude scintillation data spanning seven years from Ascension Island, U.K.; Ancon, Peru; and Antofagasta, Chile in the Atlantic/Americas longitudinal sector at as well as data from Parepare, Indonesia; Marak Parak, Malaysia; Pontianak, Indonesia; Guam; and Diego Garcia, U.K.; in the Pacific longitudinal sector. From these data, we calculate percent probability of occurrence of scintillation at various intensities described by the S4 index. Additionally, we determine Dilution of Precision at one minute resolution. We examine diurnal, seasonal and solar cycle characteristics and make spatial comparisons. In general, activity was greatest during the equinoxes and solar maximum, although scintillation at Antofagasta, Chile was higher during 1998 rather than at solar maximum.

  12. Ionospheric Effects on Spaceborne Synthetic Aperture Radar and a New Capability of Imaging the Ionosphere From Space

    NASA Astrophysics Data System (ADS)

    Pi, Xiaoqing

    2015-11-01

    This article reviews research activities and results in a new field, where ionospheric effects on spaceborne synthetic aperture radar have been investigated and techniques of imaging the ionosphere using the same radar are also explored. The research was originally to minimize ionospheric-induced distortions and contaminations in Earth remote sensing observations. As a product, the radar-based high-resolution ionospheric imaging from a low Earth orbit satellite can also benefit studies of space weather effects on the ionospheric density distribution in essentially all latitude regions, which would provide useful information to studies of coupling of the magnetosphere, ionosphere, and thermosphere.

  13. Equatorial ionosphere 'fountain- effect' above imminent earthquake epicenter

    NASA Astrophysics Data System (ADS)

    Ruzhin, Yu.; Depueva, A. H.; Devi, M.

    2003-04-01

    Existence of lithosphere-ionosphere interaction is known for a long time, but it does not mean that the ionospheric morphology above areas of earthquakes preparation is investigated sufficiently well. It was shown that seismo-precursor variations of the atmosphere electricity cause appropriate electric field at the ionospheric heights, which being added to existing natural field may both increase or decrease its action on the ionospheric plasma characteristics: drifts, aeronomy, plasma chemistry, ion composition etc. Anomalous variations appear inside whole ionosphere volume from the lowest boundary of Earth's plasma shell (100 km) up to 1000km and higher. Under fortunate coincidence seismo-precursor electric field can generate natural ionosphere phenomena, 'fountain- effect', leading to Appleton anomaly in the equatorial ionosphere over future earthquake position. Our basic idea is to take into account dependence of the observable effects on a geographical position of the earthquake epicenter. As for low latitudes it is proved by specificity of formation and dynamics of equatorial ionosphere (seismogenic ""fountain" effect , first of all), and also by features of earth crust structure close to the equator (mainly meridionally alongated tectonic faults). Ionospheric effects of low-latitude earthquakes were not investigated separately so far though rather semo-active zones are located namely at low latitudes: India, Peru, Oceania. We used the data of topside sounding of ALOUETTE-1 and ISS-b satellites, and also data of ground-based vertical sounding stationary stations Kodaikanal, Huancayo, Djibouti etc. and records of the total electron content (TEC).

  14. 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.

  15. On a possible seismomagnetic effect in the topside ionosphere

    NASA Astrophysics Data System (ADS)

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

    2015-10-01

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

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

    NASA Astrophysics Data System (ADS)

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

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

  17. Effects of tropospheric and ionospheric refraction errors in the utilization of GEOS-C altimeter data

    NASA Technical Reports Server (NTRS)

    Goad, C. C.

    1977-01-01

    The effects of tropospheric and ionospheric refraction errors are analyzed for the GEOS-C altimeter project in terms of their resultant effects on C-band orbits and the altimeter measurement itself. Operational procedures using surface meteorological measurements at ground stations and monthly means for ocean surface conditions are assumed, with no corrections made for ionospheric effects. Effects on the orbit height due to tropospheric errors are approximately 15 cm for single pass short arcs (such as for calibration) and 10 cm for global orbits of one revolution. Orbit height errors due to neglect of the ionosphere have an amplitude of approximately 40 cm when the orbits are determined from C-band range data with predominantly daylight tracking. Altimeter measurement errors are approximately 10 cm due to residual tropospheric refraction correction errors. Ionospheric effects on the altimeter range measurement are also on the order of 10 cm during the GEOS-C launch and early operation period.

  18. Ionospheric effects on synthetic aperture radar at VHF

    SciTech Connect

    Fitzgerald, T.J.

    1997-02-01

    Synthetic aperture radars (SAR) operated from airplanes have been used at VHF because of their enhanced foliage and ground penetration compared to radars operated at UHF. A satellite-borne VHF SAR would have considerable utility but in order to operate with high resolution it would have to use both a large relative bandwidth and a large aperture. The presence of the ionosphere in the propagation path of the radar will cause a deterioration of the imaging because of dispersion over the bandwidth and group path changes in the imaged area over the collection aperture. In this paper we present calculations of the effects of a deterministic ionosphere on SAR imaging for a radar operated with a 100 MHz bandwidth centered at 250 MHz and over an angular aperture of 23{degrees}. The ionosphere induces a point spread function with an approximate half-width of 150 m in the slant-range direction and of 25 m in the cross-range direction compared to the nominal resolution of 1.5 m in both directions.

  19. 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.

  20. Study of the March 31, 2001 magnetic storm effects on the ionosphere using GPS data

    NASA Astrophysics Data System (ADS)

    Fedrizzi, M.; de Paula, E. R.; Langley, R. B.; Komjathy, A.; Batista, I. S.; Kantor, I. J.

    Despite the fact that much has been learned about the Sun-Earth relationship during disturbed conditions, understanding the effects of magnetic storms on the neutral and ionized upper atmosphere is still one of the most challenging topics remaining in the physics of this atmospheric region. In order to investigate the magnetospheric and ionospheric-thermospheric coupling processes, many researchers are taking advantage of the dispersive nature of the ionosphere to compute total electron content (TEC) from global positioning system (GPS) dual-frequency data. Even though there are currently a large number of GPS receivers in continuous operation, they are unevenly distributed for ionosphere study purposes, being situated mostly in the Northern Hemisphere. The relatively smaller number of GPS receivers located in the Southern Hemisphere and, consequently, the reduced number of available TEC measurements, cause ionospheric modelling to be less accurate in this region. In the work discussed in this paper, the University of New Brunswick Ionospheric Modelling Technique (UNB-IMT) has been used to describe the local time and geomagnetic latitude dependence of the TEC during the March 31, 2001 magnetic storm with an emphasis on the effects in the Southern Hemisphere. Data collected from several GPS networks worldwide, including the Brazilian network for continuous monitoring, have been used along with ionosonde measurements to investigate the global ionospheric response to this severe storm. Data analysis revealed interesting ionospheric effects, which are shown to be dependent on the local time at the storm commencement and the magnetic conditions previous to and during the storm period. The southward turning of the interplanetary magnetic field during the recovery phase of the storm began a process of substorm activity and development and intensification of electrojet activity over broad regions. Observed effects on the ionosphere during that storm are analysed and the mechanisms that gave rise to the ionospheric behaviour are discussed.

  1. Equatorial and Low Latitude Ionospheric Effects During Sudden Stratospheric Warming Events. Ionospheric Effects During SSW Events

    NASA Astrophysics Data System (ADS)

    Chau, Jorge L.; Goncharenko, Larisa P.; Fejer, Bela G.; Liu, Han-Li

    2012-06-01

    There are several external sources of ionospheric forcing, including these are solar wind-magnetospheric processes and lower atmospheric winds and waves. In this work we review the observed ion-neutral coupling effects at equatorial and low latitudes during large meteorological events called sudden stratospheric warming (SSW). Research in this direction has been accelerated in recent years mainly due to: (1) extensive observing campaigns, and (2) solar minimum conditions. The former has been instrumental to capture the events before, during, and after the peak SSW temperatures and wind perturbations. The latter has permitted a reduced forcing contribution from solar wind-magnetospheric processes. The main ionospheric effects are clearly observed in the zonal electric fields (or vertical E B drifts), total electron content, and electron and neutral densities. We include results from different ground- and satellite-based observations, covering different longitudes and years. We also present and discuss the modeling efforts that support most of the observations. Given that SSW can be forecasted with a few days in advance, there is potential for using the connection with the ionosphere for forecasting the occurrence and evolution of electrodynamic perturbations at low latitudes, and sometimes also mid latitudes, during arctic winter warmings.

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

    NASA Astrophysics Data System (ADS)

    Prez-de-Tejada, H.

    2008-11-01

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

  3. 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.

  4. Planetary wave effect on ionospheric absorption

    NASA Astrophysics Data System (ADS)

    Abraham, Saji; Dhaka, S. K.; Praveen, K. D.; Nath, N.; Nagpal, O. P.; Baluja, K. L.

    1998-03-01

    A relationship is examined between quasi-periodic fluctuations in absorption data at ionospheric altitudes and wave perturbations in wind data at tropospheric, stratospheric and lower mesospheric heights at Indian latitudes. The spectral analyses using Maximum Entropy Method (MEM) reveal almost the same band of periodicities in both the parameters. The important band of frequencies of 6-8 days and between 20-25 days in wind data are found to propagate up to mesospheric heights and are well reflected in absorption data. These fluctuations in absorption data are thought to be due to the vertical propagation of Rossby waves on different time scales. The correlation coefficient between absorption and wind data are found to be of the order of 0.5 to 0.75 at 95% confidence level in most of the cases at a lag of 1 to 5 days with lower stratospheric zonal winds. The lag reduces considerably when the correlation coefficient was computed at 60 km altitude using rocket data. Another important finding is that when the QBO is in the easterly phase the long-period band preferably shows a predominance of 20-25 days, while during the westerly phase of the QBO, this band of periods extends to 30-45 days, which is consistently observed in quasi-periodic fluctuations of both absorption and wind data. This may have possible implications of coupling between the stratosphere and mesosphere through the QBO.

  5. 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.

  6. Ionospheric Effects of Underground Nuclear Explosions

    NASA Astrophysics Data System (ADS)

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

    2010-12-01

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

  7. Method for Canceling Ionospheric Doppler Effect

    NASA Technical Reports Server (NTRS)

    Vessot, R. F. C.

    1982-01-01

    Unified transponder system with hydrogen-maser oscillators at both stations can compensate for both motional and ionospheric components of Doppler shift. Appropriate choices of frequency shift in output of mixer m3. System exploits proportionality between dispersive component of frequency shift and reciprocal of frequency to achieve cancellation of dispersive component at output.

  8. Study of magnetic storm effects on the ionosphere using GPS data

    NASA Astrophysics Data System (ADS)

    Fedrizzi, M.; de Paula, E. R.; Kantor, I. J.; Batista, I. S.; Langley, R. B.; Komjathy, A.

    Despite the fact that much has been learned about Sun-Earth relationship during disturbed conditions, understanding the effects of magnetic storms on the neutral and ionized upper atmosphere is still one of the most challenging topics remaining in the physics of this atmospheric region. In order to investigate the magnetospheric and ionospheric-thermospheric coupling processes, many researchers are taking advantage of the dispersive nature of the ionosphere to compute total electron content (TEC) from Global Positioning System (GPS) dual-frequency data. Even though there are currently a large number of GPS receivers in continuous operation, they are unevenly distributed for ionosphere study purposes, being situated mostly in the Northern Hemisphere. The relatively smaller number of GPS receivers located in the Southern Hemisphere and, consequently, the reduced number of available TEC measurements, cause ionospheric modelling to be less accurate in this region. In this work, the University of New Brunswick (UNB) Ionospheric Modelling Technique, which applies a spatial linear approximation of the vertical TEC above each station using stochastic parameters in a Kalman filter estimation, has been used to describe the local time and geomagnetic latitude dependence of the TEC. Data collected from several GPS networks worldwide, including the Brazilian Network for Continuous Monitoring (RBMC), have been used along with ionosonde measurements to investigate the ionospheric response to a severe magnetic storm occurred on March 31, 2001. Data analysis revealed distinct ionospheric effects, which are shown to be dependent on the season, local time and magnetic conditions previous and during the storm period. During the March 31, 2001 storm, the global ionosphere showed a distinct behaviour over Australian/Asian and American regions, which are located at approximately opposite longitude sectors. The southward turning of the interplanetary magnetic field during the recovery phase of the storm began a process of substorm activity and development and intensification of electrojet activity over broad regions. Observed effects on the ionosphere during both storms are analysed and the mechanisms that gave rise to the ionospheric behaviour are discussed.

  9. Effects of Saturn's magnetospheric dynamics on Titan's ionosphere

    NASA Astrophysics Data System (ADS)

    Edberg, N. J. T.; Andrews, D. J.; Bertucci, C.; Gurnett, D. A.; Holmberg, M. K. G.; Jackman, C. M.; Kurth, W. S.; Menietti, J. D.; Opgenoorth, H. J.; Shebanits, O.; Vigren, E.; Wahlund, J.-E.

    2015-10-01

    We use the Cassini Radio and Plasma Wave Science/Langmuir probe measurements of the electron density from the first 110 flybys of Titan to study how Saturn's magnetosphere influences Titan's ionosphere. The data is first corrected for biased sampling due to varying solar zenith angle and solar energy flux (solar cycle effects). We then present results showing that the electron density in Titan's ionosphere, in the altitude range 1600-2400 km, is increased by about a factor of 2.5 when Titan is located on the nightside of Saturn (Saturn local time (SLT) 21-03 h) compared to when on the dayside (SLT 09-15 h). For lower altitudes (1100-1600 km) the main dividing factor for the ionospheric density is the ambient magnetospheric conditions. When Titan is located in the magnetospheric current sheet, the electron density in Titan's ionosphere is about a factor of 1.4 higher compared to when Titan is located in the magnetospheric lobes. The factor of 1.4 increase in between sheet and lobe flybys is interpreted as an effect of increased particle impact ionization from 200 eV sheet electrons. The factor of 2.5 increase in electron density between flybys on Saturn's nightside and dayside is suggested to be an effect of the pressure balance between thermal plus magnetic pressure in Titan's ionosphere against the dynamic pressure and energetic particle pressure in Saturn's magnetosphere.

  10. Solar and lunar ionospheric electrodynamic effects during stratospheric sudden warmings

    NASA Astrophysics Data System (ADS)

    Yamazaki, Yosuke

    2014-11-01

    Both solar and lunar atmospheric tides are believed to drive ionospheric electrodynamic effects during stratospheric sudden warmings (SSWs), but their relative importance is not well understood. In this study, long-term records (1958-2007) of the geomagnetic field are analyzed to determine the average solar (S) and lunar (L) ionospheric current systems for SSW and non-SSW periods. It is found that the L current intensity is enhanced during SSWs approximately by 75%, while the relative change in the S current intensity is much smaller (~10%). Nonetheless, absolute changes are comparable in the S and L current intensities. At the magnetic equator, semidiurnal perturbations produced by S and L currents reinforce or cancel each other depending on the phase of the moon, creating lunar-dependent recurrent onset in the total effect. These results indicate that both S and L contributions need to be considered to understand ionospheric variability during SSWs.

  11. Maps of average ionospheric vorticity ordered by relationship with the open-closed magnetic field line boundary

    NASA Astrophysics Data System (ADS)

    Chisham, Gareth

    2015-04-01

    Spatiotemporal variations of ionospheric vorticity are a measure of the dynamical coupling of the magnetosphere to the ionosphere via magnetic field-aligned currents (FACs). Indeed, ionospheric vorticity measurements have often been used as proxy measurements for FACs. Previously, we have determined statistical models of ionospheric vorticity using 6 years of ionospheric convection velocity measurements made by the SuperDARN HF radar network in the northern hemisphere ionosphere and shown that the spatial variation of these probability distributions is well organised according to the well-established large-scale FAC structure in the polar ionosphere. However, to date, these statistical models have been parameterised solely by the state of the interplanetary magnetic field (IMF), and as such do not account for the range of polar cap sizes that occur for a single IMF state. This leads to a distortion of the shape of the resulting statistical maps that makes features in the statistical variations appear smoother than those in instantaneous/short-time averaged measurements. This is because the averaging process does not consider the variable size of the polar cap, by which spatial features in the ionospheric vorticity variation are ordered. Using open-closed magnetic field line boundary measurements determined from FUV imager data from the IMAGE spacecraft, we investigate the parameterisation of the statistical ionospheric vorticity models with polar cap size in addition to the state of the IMF. The results of this analysis have implications for other statistical models determined in this way, such as those for FACs and ionospheric convection.

  12. Ionospheric effects of the extreme solar activity of February 1986

    NASA Technical Reports Server (NTRS)

    Boska, J.; Pancheva, D.

    1989-01-01

    During February 1986, near the minimum of the 11 year Solar sunspot cycle, after a long period of totally quiet solar activity (R sub z = 0 on most days in January) a period of a suddenly enhanced solar activity occurred in the minimum between solar cycles 21 and 22. Two proton flares were observed during this period. A few other flares, various phenomena accompanying proton flares, an extremely severe geomagnetic storm and strong disturbances in the Earth's ionosphere were observed in this period of enhanced solar activity. Two active regions appeared on the solar disc. The flares in both active regions were associated with enhancement of solar high energy proton flux which started on 4 February of 0900 UT. Associated with the flares, the magnetic storm with sudden commencement had its onset on 6 February 1312 UT and attained its maximum on 8 February (Kp = 9). The sudden enhancement in solar activity in February 1986 was accompanied by strong disturbances in the Earth's ionosphere, SIDs and ionospheric storm. These events and their effects on the ionosphere are discussed.

  13. 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.

  14. Some ionospheric storm effects at an antarctic station

    NASA Astrophysics Data System (ADS)

    Mansilla, Gustavo A.; Zossi, Marta M.

    2016-03-01

    In this paper, the ionospheric response of a high latitude station to some intense geomagnetic storms occurred in 2000 and 2001 is analyzed. For that, data of the critical frequency of the F2-layer foF2 and the virtual height h‧F measured at Base Gral. San Martín (68°08‧S; 67°06‧W) during the storms of April 6, 2000; May 23, 2000; March 31, 2001 and April 11, 2001 (high solar activity) are considered. In order to obtain the features of the disturbances, a comparison of the foF2 data with the outputs of the IRI-2001 model during quiet conditions is made. The results show in general negative storm effects (decreases of foF2 with respect to quiet conditions) following the storm commencement irrespective of the local time. Also, increases in foF2 prior to intense storms are sometimes observed. The h‧F data show increases in association with the negative storm effects. The role of some physical mechanisms acting during the phases of the storms is analyzed.

  15. 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.

  16. Effect of horizontal gradients on ionospherically reflected or transionospheric paths using a precise homing-in method

    NASA Astrophysics Data System (ADS)

    Strangeways, H. J.

    2000-10-01

    A homing-in method is presented for determining ionospheric reflected or transionospheric paths between fixed transmitter and receiver locations in the presence of ionospheric gradients or ripples. Both initial elevation and azimuth are automatically adjusted to find the path that arrives exactly at the receiver. The method can be used for any 3D ionospheric model to find precise ray paths and phase and group delays for both magneto-ionic modes. The method takes full account of path location, geomagnetic field orientation and the bending of the ray path resulting from horizontal as well as vertical gradients of electron density. It can also find multiple paths e.g. low and high angle, 1- and 2-hops for both ordinary and extraordinary modes. Examples of its use are given for both terrestrial HF links and Earth to Satellite paths. For paths reflected from the ionosphere, the effect of gradients of both critical frequency and height of maximum electron density are determined and the comparative effect of gradients on high and low angle and 1- and 2-hops paths for both magneto-ionic modes investigated. Path variation with frequency for a fixed link is also studied and the bandwidth of the ionospheric background channel (dispersive bandwidth) and its reciprocal (the pulse rise time), important for wideband digital HF broadcasting or spread spectrum HF communications, is estimated for a range of frequencies, for high- and low-angle rays and 1- and 2-hop paths. For Earth-satellite paths, the effect of the ionosphere and horizontal ionospheric gradients is determined for a range of frequencies and elevation angles. It is shown that the method can also enable the determination of second-order errors in satellite navigation methods, such as GPS, due to ionospheric gradients and the effect of the geomagnetic field.

  17. Effects of Small Electrostatic Fields on the Ionospheric Density Profile

    NASA Astrophysics Data System (ADS)

    Salem, M. A.; Liu, N.; Rassoul, H.

    2014-12-01

    It is well known that short-lived strong electric fields produced by natural lightning activities in tropospheric altitudes can significantly affect the upper atmosphere. This effect is directly evidenced by the production of transient luminous events (TLEs), such as sprites, jets, and elves. It has also been demonstrated that thunderstorms can modify ionospheric densities on a longer time scale, during which TLEs may or may not occur [e.g., Cheng and Cummer, GRL, 32, L08804, 2005; Han and Cummer, JGR, 115, A09323, 2010; Shao et al., Nat. Geosci., doi: 10.1038/NGEO1668, 2012]. In particular, according to Shao et al. [2012], the electron density at 75-80 km altitudes may be reduced by about 2-3 orders of magnitude. In this talk, we study the modification of the ionospheric density profile by small electrostatic fields that may exist in the upper atmosphere during a thunderstorm. A simplified ion chemistry model described by Liu [JGR, 117, A03308, 2012] has been used to conduct this study. The model is based on the one developed by Lehtinen and Inan [GRL, 34, L08804, 2007], which is in turn an improved version of the GPI model discussed in Glukhov et al. [JGR, 97, 16971, 1992]. According to this model, the charged particles can be grouped into five species: electrons, light negative ions, cluster negative ions, light positive ions, and cluster positive ions. In this chemistry model, the three-body electron attachment is the only process whose rate constant depends on the electric field, when it is below about one third of the conventional breakdown threshold field. We have compared various sources of the three-body attachment rate constant. The result shows that the rate constant increases linearly with the reduced electric field in the range of 0 to 0.1 Td, while decreases exponentially from 0.1 Td to about one third of the conventional breakdown threshold field. With this dependence, our modeling results indicate that under the steady-state condition, the nighttime electron density profile can be reduced by about 40% or enhanced by a factor of about 6 when the electric field varies in the aforementioned range.

  18. Global ionospheric effects of the October 1989 geomagnetic storm

    NASA Astrophysics Data System (ADS)

    Yeh, K. C.; Ma, S. Y.; Lin, K. H.; Conkright, R. O.

    1994-04-01

    Based on a large data base from 40 ionosonde stations distributed worldwide and 12 total electron content stations, a case study is made on the global behavior of ionospheric responses to the great magnetic storm of October 1989. The magnetic storm was triggered by a solar flare with the largest class of X13/4B and started with a sudden storm commencement (ssc) at 0917 UT on October 20. After the initial phase the storm underwent two periods of maximum activities in the following 2 days. Low-latitude auroras were sighted and reported in widely separated areas in both northern and southern hemispheres. In response to these magnetic and auroral activities the ionosphere showed remarkable effects. Depending on the local time of ssc occurrence, the ionospheric response differed appreciably. Impressive changes were long-lasting, large-scale effects, such as the severe depressions of foF2 at higher latitudes, the temporary suppression of the equatorial anomaly and large horizontal gradients at certain latitudes. Also observed were positive storm effects of short duration during the post-sunset period in response to the onset of both ssc and main phase of the magnetic storm. These two positive storm effects showed different patterns suggesting different causal mechanisms. In addition, global propagation of large-scale traveling ionospheric disturbances (TIDs) was seen during 2 nights, identified by dramatic rises of h'F with periodic fluctuations. The equatorward propagation velocities of the TIDs varied between 330 m/s and 680 m/s for the east Asia region.

  19. The Effect of Ionospheric Models on Electromagnetic Pulse Locations

    SciTech Connect

    Fenimore, Edward E.; Triplett, Laurie A.

    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.

  20. Influence of geomagnetic storms of September 26-30, 2011, on the ionosphere and HF radiowave propagation. I. Ionospheric effects

    NASA Astrophysics Data System (ADS)

    Klimenko, M. V.; Klimenko, V. V.; Bessarab, F. S.; Ratovsky, K. G.; Zakharenkova, I. E.; Nosikov, I. A.; Stepanov, A. E.; Kotova, D. S.; Vorobjev, V. G.; Yagodkina, O. I.

    2015-11-01

    Geomagnetic storm ionospheric effects observed at different latitudes and longitudes on September 26 and 28-30, 2011, are interpreted with the GSM TIP model. It has been justified that the results of this model can subsequently be used to calculate the HF radiowave ray tracing under quiet conditions and for the selected dates in September 2011. The model calculations are compared with observations of the ionospheric parameters performed by different radiophysical methods. The presented results confirm the classical mechanisms by which positive and negative ionospheric storms are formed during the main phase of a geomagnetic storm. At high latitudes, the electron density is mainly disturbed due to changes in the neutral composition of the thermosphere, resulting in an increase in the chemical loss rates, and the electromagnetic drift, which results in a substantial reconstruction of the high-latitude ionosphere owing to the horizontal plasma transfer. During the storm recovery phase at midlatitudes, electron density positive disturbances are formed in the daytime due to an increase in the n(O)/ n(N2) ratio; at the same time, negative effects in the electron density are formed at night as a result of plasma tube devastation. Comparison with the observations indicates that the presented model calculation results can be used to describe a medium for solving problems of radiowave propagation in the ionosphere during the storm main phase on September 26 and during the recovery phase on September 28-30, 2011.

  1. Improved Ionospheric Correction for DGPS by taking into account the Horizontal Gradient Effect over the Equatorial Region

    NASA Astrophysics Data System (ADS)

    Nagarajoo, Karthigesu

    Improved Ionospheric Correction for DGPS by taking into account the Horizontal Gradient Effect over the Equatorial Region K Nagarajoo Universiti Tun Hussein Onn Malaysia 86400 Parit Raja Johor Darul Takzim Email: karthi@uthm.edu.my DGPS is a system where the range error at a reference station will be eliminated from the range measurement at the user, which `view' the same satellite, presuming that the satellite's path to both the reference station and the user experience common errors due to the ionosphere, clock errors, multipath etc. In this assumption, the error due to the ionospheric refraction is assumed to be the same for the two closely spaced paths (such as a baseline length between reference station and the user is 10km) and thus the presence of ionospheric horizontal gradient is ignored. If a user's path is exposed to a drastically large ionosphere gradient (i.e., over the equatorial region), the large difference of ionosphere delays between the reference station and the user can result in significant position error for the user. Apart from that, the difference in the elevation angle at the reference and the user that `view' the same satellite to get the range measurement does also introduce some millimetre to centimetre of range difference. The neglect of the effect due to the presence of an ionospheric horizontal gradient and the elevation angle's difference (at both ends of the baseline) will cause a significant amount of error in the final DGPS user positioning. In this work, those two effects have been investigated in order to obtain a more accurate ionospheric correction for DGPS and have been found to be roughly comparable showing that they are both important. By performing ray-tracing calculations (using Jones 3-D Ray Tracing program) with and without a linear horizontal ionosphere gradient, the effects of elevation angle and horizontal gradient have been separated and a final positioning improvement of about 8cm has been shown at the user of a DGPS system over the equatorial region. Empirical models have been introduced to model these variations based on the ray tracing results. This is quite a good positioning improvement at the user location which really needs to be considered in applications such as geophysics, surveying and navigation. The geometric dilution of precision or GDOP factor also has been taken into account to get the best formation (geometry) of stocktickerGPS satellites in order to do the DGPS positional improvement at the user station. Keywords : Ionospheric correction, DGPS, horizontal gradient, GDOP, user positioning improvement

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

    NASA Astrophysics Data System (ADS)

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

    2009-12-01

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

  3. The effect of large-scale tropospheric storms on the ionospheres of giant planets

    NASA Astrophysics Data System (ADS)

    Matcheva, Katia

    2015-11-01

    It is well recognized that large-scale storms in the Earth troposphere can leave observable signatures in the structure of the ionosphere in terms of local electron density distribution. Terrestrial numerical models indicate that thunderstorms can change the electron density by more than an order of magnitude (Shao et al. 2012). The atmospheres of Jupiter and Saturn are riddled by atmospheric storms of all scales. Lightning has been successfully detected in optical images in the tropospheres of both planets. Our work presents a theoretical study of the dynamical and electromagnetic effects of large thunderstorms on the vertical plasma distribution in the ionospheres of Jupiter and Saturn and compares the predicted signatures with the available electron density profiles from the Galileo and the Cassini missions.

  4. 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.

  5. Effects of ionospheric turbulence on SPS pilot signal

    NASA Technical Reports Server (NTRS)

    Clynch, J. R.

    1981-01-01

    The spatial variation of the electron density was studied by monitoring the differential Doppler on radio beacons aboard the Navy navigation satellites. The radio frequency heater was used to deposit energy in the F-region ionosphere with the heating frequency above peak plasma frequency. The effects of the solar power satellite power beam on the pilot signal were simulated. It was found that a small depletion was formed in the beam and that there was turbulence in the elctron density up the magnetic field line from the beam. It is suggested that the depletion will not seriously affect the power or pilot beams of the solar power satellite.

  6. 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

  7. Studing Solar Flare Effects on Ionosphere Using AWESOME Receiver

    NASA Astrophysics Data System (ADS)

    Mustafa, Famil; Babayev, Elchin; Alekperov, Ilgar

    2015-08-01

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

  8. 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.

  9. Investigation of solar-flare effects by the oblique sounding of the ionosphere

    NASA Astrophysics Data System (ADS)

    Blagoveshchenskaia, N. F.; Bubnov, V. A.; Ustinovich, V. T.

    1989-01-01

    The paper examines results of an investigation of solar-flare effects by the oblique sounding of the ionosphere on a subauroral path about 9000 km long during 1981-1982. Oblique sounding data are compared with investigations of SWF, SPA, SEA, and SFD sudden ionospheric disturbances, as well as with solar-radio emission parameters in the 650-15,000 MHz range.

  10. Investigations of solar flares effects by oblique-sounder ionosphere method.

    NASA Astrophysics Data System (ADS)

    Blagoveshchenskaya, N. F.; Bubnov, V. A.; Ustinovich, V. T.

    1989-01-01

    Results of investigations of solar flares effects by oblique-sounder ionosphere method in a subauroral line 9000 km long during 1981 - 82 are considered. Comparison is made between results of oblique-sounder ionosphere disturbances of type SWF, SPA, SEA, SFD and also sun radio-burst parameters in the band of 650 - 15000 MHz.

  11. Broadband Electron Precipitation in Global MHD Simulation and its Effect on the Ionosphere

    NASA Astrophysics Data System (ADS)

    Zhang, B.; Lotko, W.; Brambles, O. J.; Wiltberger, M. J.

    2010-12-01

    A broadband electron (BBE) precipitation model is implemented and analyzed in the MI coupling module of the Lyon-Fedder-Mobarry MHD simulation. Both number flux and energy flux of precipitating BBEs are regulated by MHD variables calculated near the low-altitude boundary of the LFM simulation. An empirical relation deduced from results of Keiling et al. (2003) is used to relate the AC Poynting flux to the energy flux precipitating BBEs in the simulation. We are investigating two different ways of regulating the number flux of BBE precipitation, one using an empirical relation between AC Poynting flux and number flux (Strangeway, unpublished) and another by constraining the intensity and cut-off energy of a fixed-pitch angle distribution of BBEs in terms of MHD simulation variables. The contributions to ionospheric conductance from BBE precipitation are evaluated using empirical relations derived by Robinson et al. (1987). The BBE-induced-conductance is added to the “standard” auroral contribution to conductance derived from monoenergetic and diffuse electron precipitation in the existing LFM precipitation model. The simulation is driven by ideal SW/IMF conditions with Vsw=400 km/s, Nsw=5/cc and Bz=-5 nT. The simulated time-average AC Poynting flux pattern resembles statistical patterns from Polar data (Keiling et al. 2003), and the simulated statistical pattern of BBE number flux resembles the statistical maps derived from DMSP data (Newell et al. 2009) on the nightside with a similar dawn-dusk asymmetry. The ionospheric Pedersen and Hall conductances are enhanced about 20% by the BBE precipitation. The number flux produced by BBEs is the same order of magnitude as that of monoenergetic and diffuse electrons. We thus expect BBE precipitation to have a moderate effect on the E-region ionosphere and a more significant influence on the density distribution of the F-region ionosphere.

  12. Modeling the Earth-ionosphere cavity. Effects of hypothetical earthquake precursors over the Schumann resonance

    NASA Astrophysics Data System (ADS)

    Toledo-Redondo, Sergio; Salinas, Alfonso; Fornieles, Jesús; Portí, Jorge

    2013-04-01

    Schumann resonances (SR) are global phenomena which occur within the Earth-ionosphere cavity. They are the result of waves propagating several turns around the Earth. Due to the dimensions of the cavity, SR belong to the ELF spectra. The main source of excitation is lightning, and several natural processes do modify the geometry of the cavity and its parameters, like for instance seismo-electromagnetic activity, atmospheric aerosols, solar radiation, etc. Therefore, SR are a promising tool for monitoring (and even forecasting) these natural events. Although several measurements seem to confirm the link between electromagnetic activity and earthquake precursors, the physical mechanisms which produce them are still not clear, and several possibilities have been proposed, like for instance piezoelectric effects on the rocks in the lithosphere, emanation of ionizing gasses like radon, or acoustic gravity waves modifying the properties of the ionosphere in the earthquake preparation zone. However, further measurements combined with analytical models and/or numerical simulations are required in order to better understand the seismo-electromagnetic activity. In this work, the whole Earth-ionosphere electromagnetic cavity has been modeled with 10 km accuracy, by means of Transmission-Line Modeling (TLM) method. Since Schumann resonance parameters depend primarily on the geometry of such cavity, electromagnetic changes produced by earthquake precursors can modify the properties of SR. There is not much quantitative information available about the changes produced by the precursors, either in the lithosphere, atmosphere, or ionosphere. Therefore, different models of the precursors are proposed and their consequences over the SR are evaluated. The so-called Chi-Chi earthquake is employed as a case of study.

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

    NASA Astrophysics Data System (ADS)

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

    2007-02-01

    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 day in the occurrence of riometer absorption, 0.056 MHz in the minimum frequency of reflection of the F layer, and 2.6 and 6.7 km, in the change of the minimum height of reflection and height of reflection from the region with maximum electron density of the ionospheric F layer, respectively. The lunar tide action changes the ionospheric conductivity and, thus, influences the current systems of the magnetosphere. Through changes of magnetospheric currents, the Moon phase effect is exhibited in the Ap and Dst indices and is 4.3 and 4.25 nT, respectively.

  14. Effects of geographic-geomagnetic pole offset on ionospheric outflow: Can the ionosphere wag the magnetospheric tail?

    NASA Astrophysics Data System (ADS)

    Barakat, Abdallah R.; Eccles, J. Vincent; Schunk, Robert W.

    2015-10-01

    The generalized polar wind model was used to simulate the polar ionosphere during the September/October 2002 storm. The solar terminator moved across the polar caps in a diurnal oscillation during this equinox period. The main conclusions of this study are the following: (1) the terminator oscillation generates a diurnal oscillation in the total hemispheric fluxes of the polar wind from the ionosphere into the magnetosphere; (2) the diurnal oscillation of outflow in the Northern Hemisphere is 12 h out of phase with the Southern Hemisphere; (3) the H+ outflow flux is near its limiting value, so the oscillation is larger than the nonperiodic contributions (e.g., geomagnetic activity); and (4) the O+ flux is less than its limiting value, hence the diurnal oscillation is comparable to the non-periodic effects. The simulation suggests that the hemispherical asymmetry and periodicity of the total ion outflow could "wag the magnetospheric tail" and perhaps contribute to substorm triggering.

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

    NASA Astrophysics Data System (ADS)

    Narvaez, C. L.; Mendillo, M.

    2009-12-01

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

  16. Ionospheric physics

    SciTech Connect

    Sojka, J.J. )

    1991-01-01

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

  17. 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.

  18. Lightning Interaction with the Lower Ionosphere: Effects of Mesospheric Ions and Geomagnetic Field

    NASA Astrophysics Data System (ADS)

    Marshall, R. A.; Inan, U. S.

    2011-12-01

    The interaction between the lightning electromagnetic pulse (EMP) and quasi-electrostatic (QE) fields and the D-region ionosphere has been observed optically in the past 20 years through sprites, elves, and gigantic jets. Very-low-frequency (VLF) measurements have been used to measure direct ionospheric modification, which may comprise electron density changes and/or heating. In the same time period, a number of models have been used to study the lightning-ionosphere interaction. Here, we present new time-domain 2D and 3D models of the lightning-ionosphere interaction, including EMP and QE effects. These spherical-coordinate models include effects of Earth's magnetic field; effects of mesospheric and ionospheric electron and ion densities; and responses to arbitrary lightning amplitudes, waveforms, and orientations. In this paper, we use the new models to investigate the response of the ionosphere under varying conditions. First, we focus on the effects of different mesospheric ion density profiles. Mesospheric ions, for which measurements are nearly nonexistent, serve to reduce the amplitude of the electromagnetic pulse as it propagates towards the ionosphere; high ion densities will reduce the wave electric field enough that it does not exceed the breakdown field in the ionosphere. We demonstrate the relationship between the lightning parameters, ion density profile, and observed elve intensity, and show that elves are suppressed when the ion density is high. Second, we investigate the effects of the geomagnetic field magnitude and orientation on wave propagation in and through the ionosphere. We compare these simulation results with known global lightning distributions and compare to the observed whistler distributions onboard satellites.

  19. 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.

  20. Effect of Space Weather on Ionospheric Total Electron Content Variation during the 23rd Solar Cycle.

    NASA Astrophysics Data System (ADS)

    Bergeot, N.; Tsagouri, I.; Bruyninx, C.; Legrand, J.; Chevalier, J.-M.; Defraigne, P.; Baire, Q.; Pottiaux, E.

    2012-04-01

    One of the future challenges of the Space Weather community is to predict the Earth's ionospheric state in response to variations of the Solar activity, especially during stormy events. The beginning of the 23rd Solar cycle coincided with the start of the catalogue of global ionospheric Total Electron Content (TEC) maps based on GNSS data. Consequently, the 23rd Solar cycle (1996-2008) is the first full Solar cycle ever having both GNSS-based TEC measurements as well as observed Solar parameters. This study takes advantage of this new double dataset (1) to develop an empirical ionospheric climatological model to predict the Mean Daily Ionospheric Total Electron Content (MDITEC, i.e. the mean value of the TEC over a day at a given latitude) taking Solar parameters as input and (2) to analyze the variation of the MDITEC during identified ionospheric storm events. In this paper, several Solar parameters (e.g. daily Sunspot Number, F10.7 flux and derived F10.7P) are tested as input and different parameterizations are considered to estimate, i.e. to model, the MDITEC for a given day and at a given latitude. The residuals between the models and the observed MDITEC are minimized by a least-squares adjustment. The best model is obtained using (1) a combination of linear, annual and semi-annual terms between the MDITEC and F10.7P; (2) a discretization w.r.t. the phases of the Solar cycle. Our preferred ionospheric climatological model is tested in terms of yearly median absolute error (1.4±0.9 TECu) and median relative error (11.5±2.9 %). The relative error remains constant during the entire 23rd Solar cycle which comforts us in the robustness of our climatological model with no degradation during the different phases of the Solar activity. Finally, differences greater than 15 TECu between the observed and modeled MDITEC are concordant with 70 intense ionospheric storm events occurred during the period 1998-2005. The onset of these events was identified from the analysis of interplanetary magnetic field (IMF) observations provided by NASA ACE spacecraft from the vantage L1 point. The storms affect significantly the MDITEC mainly in polar regions, with a loss of ionization with respect to our climatological model and a peak one day after the onset. The mean difference between the observed and modeled MDITEC (absolute error) is -3.2±1.5 TECu one day after the onset and becomes negligible again 2-3 days after the onset. Concerning the relative errors, they are of the order of -19.6±15.0% one day after the onset and normal values can be seen again 3-4 days after the onset. These results show a global picture of the effect of extreme Space Weather events on the Earth's upper atmosphere.

  1. Space Weather Topics at Ionospheric Effects Symposium 2008

    NASA Astrophysics Data System (ADS)

    Goodman, John

    2008-08-01

    The ionosphere has captured the interest of scientists and communications specialists for many years. Research has been intrinsically applications oriented since Guglielmo Marconi identified an ionized region within the upper atmosphere that acted like a high-altitude mirror reflecting radio waves so that long-distance communication could be achieved. His successful transatlantic radio transmissions early in the twentieth century heralded the beginning of an era of wireless communications. Eager to capitalize on this, civilian and military industries sponsored research to better understand the ionosphere. These endeavors established that the ionosphere exhibits considerable variability, with significant changes associated with ionospheric storms that are driven by solar disturbances. This variability, now termed space weather, also introduces changes in radio propagation conditions that can disrupt various radio systems, such as high-frequency and satellite communications, the Global Positioning System, radar, and specialized surveillance methods.

  2. Characteristics of second-order residual ionospheric error in GNSS radio occultation and its impact on inversion of neutral atmospheric parameters

    NASA Astrophysics Data System (ADS)

    Qu, Xiaochuan; Li, Zhenghang; An, Jiachun; Ding, Wenwu

    2015-08-01

    In Global Navigation Satellite Systems (GNSS) radio occultation (RO), one of the most significant error sources is the ionospheric error, which is largely eliminated by dual-frequency linear combination. However, second-order residual ionospheric error (RIE) in excess phase still remains and affects the retrievals of neutral atmospheric parameters in RO. Second-order RIE varies with RO azimuth in a sinusoidal pattern for a set of simulated RO events occurring in the same location at different azimuths. The amplitude of the sinusoidal curve below 60 km is at the order of sub-centimeter under moderate solar activity level. The retrieval biases of the neutral atmospheric parameters induced by second-order RIE also have sinusoidal features with RO azimuth, but have opposite variation trends to that of the second-order RIE. The RO azimuths of the maximum positive and negative retrieval biases correspond approximately to the azimuths of maximum negative and positive second-order RIEs, respectively. The order of the maximum bending angle bias induced by the second-order RIE is about 10-8 rad under moderate solar activity level. However, the retrieval errors at low latitude are larger than those at high and middle latitudes, and the maximum temperature bias at low latitude could be 0.35 K at 40 km. Based on the sinusoidal variation of second-order RIE, it is shown that even at the same RO point and under the same solar activity level, the second-order RIEs at different RO azimuths still have different effects on the retrieval precision of atmospheric parameters. This should be considered carefully when many RO profiles are averaged for climate trend detection, especially at low latitude.

  3. The effect of longitudinal conductance variations on the ionospheric prompt penetration electric fields

    NASA Astrophysics Data System (ADS)

    Sazykin, S.; Wolf, R.; Spiro, R.; Fejer, B.

    Ionospheric prompt penetration electric fields of magnetospheric origin, together with the atmospheric disturbance dynamo, represent the most important parameters controlling the storm-time dynamics of the low and mid-latitude ionosphere. These prompt penetration fields result from the disruption of region-2 field-aligned shielding currents during geomagnetically disturbed conditions. Penetration electric fields con- trol, to a large extent, the generation and development of equatorial spread-F plasma instabilities as well as other dynamic space weather phenomena in the ionosphere equatorward of the auroral zone. While modeling studies typically agree with average patterns of prompt penetration fields, experimental results suggest that longitudinal variations of the ionospheric con- ductivities play a non-negligible role in controlling spread-F phenomena, an effect that has not previously been modeled. We present first results of modeling prompt pene- tration electric fields using a version of the Rice Convection Model (RCM) that allows for longitudinal variations in the ionospheric conductance tensor. The RCM is a first- principles numerical ionosphere-magnetosphere coupling model that solves for the electric fields, field-aligned currents, and particle distributions in the ionosphere and inner/middle magnetosphere. We compare these new theoretical results with electric field observations.

  4. Long-duration positive ionospheric storm during the December 2006 geomagnetic storm: Ionizing effect of forbidden electrons

    NASA Astrophysics Data System (ADS)

    Suvorova, A. V.; Huang, C.-M.; Tsai, L.-C.; Dmitriev, A. V.; Ratovsky, K. G.

    2015-11-01

    The magnetosphere-ionosphere coupling at low latitudes was studied during the major geomagnetic storm on 14-16 December 2006. Data from NOAA/POES satellites were used to identify the enhancements of forbidden energetic electrons (FEE). Global Ionospheric Maps and COSMIC/FORMOSAT-3 radio occultation measurements were used for studying positive ionospheric storm phases. We found that long-lasting positive ionospheric storms were concomitant with FEE enhancements. We discussed relative contributions of the FEE ionizing effect as well as other general mechanisms to the positive ionospheric storm at different phases of the geomagnetic storm.

  5. 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.

  6. Monitoring the ionospheric storm effect with multiple instruments in North China: July15-16, 2012 magnetic storm event.

    NASA Astrophysics Data System (ADS)

    Wang, Min

    2014-05-01

    A major geomagnetic storm occurred on July 15-16, 2012, which is characterized by a long-lasting southward turning of interplanetary geomagnetic field (IMF) for ~30 hours below -10 nT. Prominent large-scale ionospheric disturbances were observed in North China during this extreme space weather event. This study reveals the possibility of using the newly built China seismo-ionospheric ground-based monitoring network (CSGMN) to investigate the ionospheric storm effect during different phase of the storm. As a main part of the CSGMN, the oblique and vertical sounding systems and global position system (GPS) network all observed a moderate and a strong positive storm effects around the noon and the sunset sector on 15 July. The maximum enhancement of parameter peak electron density (NmF2) increased 100% and TEC 60%. The positive phase then is followed by an intense negative storm effect during the entire day on July 16 with NmF2 and TEC fell below 40% of the previous quiet day values. Also, the electron density profiles retrieved from the COSMIC radio occultation measurements were examined and validated with the ground measurements in order to estimate the possibility of its use as an additional data source to study altitude distribution of ionospheric storms. Good agreement has been reached between the ground and satellite occultation measurements even if they are not close. The result here shows that CSGMN can be a very powerful network not only for the seismo-ionospheric study but also in monitoring space weather.

  7. Monitoring the ionospheric storm effect with multiple instruments in North China: July 15-16, 2012 magnetic storm event

    NASA Astrophysics Data System (ADS)

    Wang, Min; Lou, Wenyu; Li, Peng; Shen, Xuhui; Li, Qiang

    2013-09-01

    A major geomagnetic storm occurred on July 15-16, 2012, which is characterized by a long-lasting southward turning of interplanetary geomagnetic field (IMF) for ∼30 h below -10 nT. Prominent large-scale ionospheric disturbances were observed in North China during this extreme space weather event. This study reveals the possibility of using the newly built China seismo-ionospheric ground-based monitoring network (CSGMN) to investigate the ionospheric storm effect during different phase of the storm. As a main part of the CSGMN, the oblique and vertical sounding systems and global position system (GPS) network all observed a moderate and a strong positive storm effects around the noon and the sunset sector on 15 July. The maximum enhancement of parameter peak electron density (NmF2) increased 100% and TEC 60%. The positive phase then is followed by an intense negative storm effect during the entire day on July 16 with NmF2 and TEC fell below 40% of the previous quiet day values. Also, the electron density profiles retrieved from the COSMIC radio occultation measurements were examined and validated with the ground measurements in order to estimate the possibility of its use as an additional data source to study altitude distribution of ionospheric storms. Good agreement has been reached between the ground and satellite occultation measurements even if they are not close. The result here shows that CSGMN can be a very powerful network not only for the seismo-ionospheric study but also in monitoring space weather.

  8. Lightning effect on the lower ionosphere deduced from MF recordings

    NASA Astrophysics Data System (ADS)

    Farges, T.; Blanc, E.; Tanguy, M.

    2006-12-01

    Previous studies of direct lightning effect on the ionosphere have been done using VLF signals. These studies shown that the quasi-electrostatic field theory explain most of the observed `early/fast' VLF perturbations. However, some recent results showed that the EMP, produced by the lightning, could also perturb the VLF propagation. This property is even used to monitor the lower ionosphere. During the summer 2004, in the frame of the 2004 Eurosprite campaign, the CEA installed in the centre of France a station to measure the vertical electric field with dipole whip antenna. The measurement is not continuous but triggered when the electric field exceeds a threshold of 3 V/m. The data are dated with GPS. The electric field is digitalised in two bands from few kHz to 1 MHz and from 500 kHz to 10 MHz. Lightning appear on spectrograms of the MF-HF component as a vertical line; furthermore during the night, the numerous radio carriers are horizontal lines. We observe on the spectrograms the fading, and even sometimes the disappearance, of some of the MF radio carriers during several milliseconds a millisecond after lightning. About 4000 cloud to ground lightning, during two months, triggered our system. All these lightning have been associated to lightning localised by Meteorage (the French lightning detection network). All the signals have been digitally filtered around several selected carrier signals from 900 to 1600 kHz. For each of lightning detected and each selected carrier frequency, the characteristics of the fading waveform have been measured: attenuation, duration of this attenuation, onset time, time where the signal is at the most attenuated and recovery time. Using these data, we make statistics and plot the impact map of the fading. Lightning of peak current higher than 60 kA may perturb a zone of a radius larger than 300 km. The shape of the attenuation in function of the distance (from the lightning to the crossing point of the radio carrier path and the ionosphere at 80-90 km) is similar to the shape of the ionisation produced by a lightning by the EMP, in other words with a maximum at 80-90 km of the lightning. The fading of a radio carrier is mainly a function of the electron density and the collision frequency. The collision frequency is directly related to the electron temperature. Previous studies showed that the electron density recovery time to the level before the lightning is 10-100 s while the electron temperature recovery time is 0.1-1 s. The mean duration of the attenuation being ~5 ms, the observed fading is thus mainly controlled by the collision frequency change.

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

    NASA Technical Reports Server (NTRS)

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

    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 Facility (FDF), the ionospheric refraction effects on the tracking measurements are modeled in the Goddard Trajectory Determination System (GTDS) using the Bent ionospheric model. While GTDS has the capability of incorporating the ionospheric refraction effects for measurements involving ground-to-spacecraft tracking links, such as those generated by the Ground Spaceflight Tracking and Data Network (GSTDN), it does not have the capability to incorporate the refraction effects for spacecraft-to-spacecraft tracking links for measurements generated by the Tracking and Data Relay Satellite System (TDRSS). The lack of this particular capability in GTDS raised some concern about the achievable accuracy of the estimated orbit for certain classes of spacecraft missions that require high-precision orbits. Using an enhanced research version of GTDS, some efforts have already been made to assess the importance of the spacecraft-to-spacecraft ionospheric refraction corrections in an orbit determination process. While these studies were performed using simulated data or real tracking data in definitive orbit determination modes, the study results presented here were obtained by means of covariance analysis simulating the weighted least-squares method used in orbit determination.

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

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

  11. Modeling the pre-earthquake electrostatic effect on the F region ionosphere

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

    This paper presents the results of modeling the ionospheric effect of the seismogenic electrostatic field (SEF) seen at the earth's surface as a perturbation of the vertical atmospheric electrostatic field in the earthquake preparation zone. The SEF distribution at ionospheric altitudes is obtained as an analytical solution of the continuity equation for the electric current density. It is shown that at night, the horizontally large scale SEF can efficiently penetrate into the ionosphere and produce noticeable changes in the horizontal distribution of the F region electron density. The results suggest that the seismogenic electrostatic field could be a possible source for the ionospheric variations observed over Taiwan before the strong Chi Chi earthquake of September 21, 1999.

  12. Effects of the equatorial ionosphere anomaly on the interhemispheric circulation in the thermosphere

    NASA Astrophysics Data System (ADS)

    Qian, Liying; Burns, Alan G.; Wang, Wenbin; Solomon, Stanley C.; Zhang, Yongliang; Hsu, V.

    2016-03-01

    We investigate the interhemispheric circulation at the solstices, in order to understand why O/N2 is larger in the northern hemisphere winter than in the southern hemisphere winter. Our studies reveal that the equatorial ionosphere anomaly (EIA) significantly impacts the summer-to-winter wind through plasma-neutral collisional heating, which changes the summer-to-winter pressure gradient, and ion drag. Consequently, the wind is suppressed in the summer hemisphere as it encounters the EIA but accelerates after it passes the EIA in the winter hemisphere. The wind then converges due to an opposing pressure gradient driven by Joule heating in auroral regions and produces large O/N2 at subauroral latitudes. This EIA effect is stronger near the December solstice than near the June solstice because the ionospheric annual asymmetry creates greater meridional wind convergence near the December solstice, which in turn produces larger O/N2 in the northern hemisphere winter than in the southern hemisphere winter.

  13. Effects of Geomagnetic effect on Sub-ionospheric VLF-LF Signals Propagation

    NASA Astrophysics Data System (ADS)

    Sondhiya, Deepak Kumar; Gwal, Ashok Kumar; Verma, Shivali; Kasde, Satish Kumar; Sonakia, Anjana

    Abstract: To investigate the effect of geomagnetic storm on subionospheric VLF-LF signal propagation, we analyze the variation in amplitude of VLF-LF signal using advanced complex continuous wavelet transform techniques. We analyze the VLF signal transmitted form ICV (20.27 kHz) located at Isola di Tavolara (40.55o N, 9.430 E), Italy and DH038 (23.40 kHz) Rhauderfehn (53.040 N, 7.340 E) Germany and one LF signal transmitted form NRK (37.50 kHz) transmitter located at Grindavik (63.510 N, 22.280 E), Iceland. We observed significant absorption in amplitude of these signals during the geomagnetic storm compared to their ambient values for the same period during the adjacent 7 days. The signal strength along their propagation paths was controlled by the storm associated decrease in ionization in the D-region of the ionosphere. Waveguide mode theory calculations show that the elevation of the height of lower ionosphere boundary of Earth-ionosphere waveguide was significantly decreased during this period. Key words: Subionospheric VLF-LF propagation, Complex Wavelet Transform, Geomagnetic activity and Earth-ionosphere waveguide

  14. 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.

  15. Effect of solar Coronal Mass Ejections on the ionosphere

    NASA Astrophysics Data System (ADS)

    Sheiner, Olga; Fridman, Vladimir; Rakhlin, Alexander; Pershin, Alexsander; Vybornov, Feodor

    The influence of solar processes on the state of near-earth space is constantly the object of serious study. First of all the solar radiation affects the parameters of the ionosphere and ionizing processes in it. The basic level indicator of the ionized particles is the critical frequency f0F2 of the reflection of radio signal during sounding of ionosphere. Understanding of the role of Coronal Mass Ejections (CME) in global solar-terrestrial processes allow us to put up the problem about their possible influence on near Earth’ processes and ionosphere behavior. Earlier the authors proposed the procedure of the detection the influence of CMEs on the differential parameters of the upper ionosphere Deltaf0F2 as more sensitive in comparison with the traditional methods. First results were based on the data of regular observations of critical frequency f0F2 during the cycle of solar activity (1975-1986). To verify the relationship discovered we used in the proposed study the data of critical frequency f0F2, determined from uniform ionograms obtained with the modern digital Ionosonde CADI. This ionosonde is installed at the landfill NIRFI "Vasilsursk" (near Nizhny Novgorod), and working program of regular observations allowed to obtain ionograms at least once in 1 minutes. The accuracy of determining the critical frequency was less than ± 50 kHz. There are many examples of time coincidence between the periods of CMEs existence and negative deflection in Deltaf0F2 behaviour.

  16. 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.

  17. 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.

  18. 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.

  19. Electric fields and conductivity in the nighttime E-region - A new magnetosphere-ionosphere-atmosphere coupling effect

    NASA Technical Reports Server (NTRS)

    Banks, P. M.; Yasuhara, F.

    1978-01-01

    Calculations have been made of the effects of intense poleward-directed electric fields upon the nighttime ionospheric E-region. The results show the Pedersen and Hall conductivities are substantially changed, thereby decreasing the ionospheric electrical load seen by magnetospheric sources. It appears that relatively large electric fields can exist in the absence of accompanying large field-aligned currents, as long as the underlying ionosphere remains in darkness and/or energetic particle precipitation is absent.

  20. 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.

  1. 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.

  2. Effect of small ionospheric irregularities on radio wave absorption

    NASA Technical Reports Server (NTRS)

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

    1975-01-01

    The ionospheric absorption of a radio wave caused by small-scale irregularities with a gaussian autocorrelation function is calculated for various values of the linear scale height, the radio frequency, the scale size of the irregularities, and the mean-square fractional electron density fluctuations. The absorption is due to scattering of the radio wave into plasma oscillations by the irregularities. It is concluded that the absorption due to such irregularities with a mean-square fractional electron density deviation greater than about 0.000001 exceeds the normal collisional height-integrated absorption. Absorption of this type could play a significant part in heating experiments or in an ionosphere containing naturally occurring irregularities.

  3. The worldwide ionospheric data base

    NASA Technical Reports Server (NTRS)

    Bilitza, Dieter

    1989-01-01

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

  4. Anomalous electron heating effects on the E region ionosphere in TIEGCM

    NASA Astrophysics Data System (ADS)

    Liu, Jing; Wang, Wenbin; Oppenheim, Meers; Dimant, Yakov; Wiltberger, Michael; Merkin, Slava

    2016-03-01

    We have recently implemented a new module that includes both the anomalous electron heating and the electron-neutral cooling rate correction associated with the Farley-Buneman Instability (FBI) in the thermosphere-ionosphere electrodynamics global circulation model (TIEGCM). This implementation provides, for the first time, a modeling capability to describe macroscopic effects of the FBI on the ionosphere and thermosphere in the context of a first-principle, self-consistent model. The added heating sources primarily operate between 100 and 130 km altitude, and their magnitudes often exceed auroral precipitation heating in the TIEGCM. The induced changes in E region electron temperature in the auroral oval and polar cap by the FBI are remarkable with a maximum Te approaching 2200 K. This is about 4 times larger than the TIEGCM run without FBI heating. This investigation demonstrates how researchers can add the important effects of the FBI to magnetosphere-ionosphere-thermosphere models and simulators.

  5. Speed-dependent collision effects on radar back-scattering from the ionosphere

    NASA Technical Reports Server (NTRS)

    Theimer, O.

    1981-01-01

    A computer code to accurately compute the fluctuation spectrum for linearly speed dependent collision frequencies was developed. The effect of ignoring the speed dependence on the estimates of ionospheric parameters was determined. It is shown that disagreements between the rocket and the incoherent scatter estimates could be partially resolved if the correct speed dependence of the i-n collision frequency is not ignored. This problem is also relevant to the study of ionospheric irregularities in the auroral E-region and their effects on the radio communication with satellites.

  6. Quantifying ionospheric effects on time-domain astrophysics with the Murchison Widefield Array

    NASA Astrophysics Data System (ADS)

    Loi, Shyeh Tjing; Murphy, Tara; Bell, Martin E.; Kaplan, David L.; Lenc, Emil; Offringa, André R.; Hurley-Walker, Natasha; Bernardi, G.; Bowman, J. D.; Briggs, F.; Cappallo, R. J.; Corey, B. E.; Deshpande, A. A.; Emrich, D.; Gaensler, B. M.; Goeke, R.; Greenhill, L. J.; Hazelton, B. J.; Johnston-Hollitt, M.; Kasper, J. C.; Kratzenberg, E.; Lonsdale, C. J.; Lynch, M. J.; McWhirter, S. R.; Mitchell, D. A.; Morales, M. F.; Morgan, E.; Oberoi, D.; Ord, S. M.; Prabu, T.; Rogers, A. E. E.; Roshi, A.; Shankar, N. Udaya; Srivani, K. S.; Subrahmanyan, R.; Tingay, S. J.; Waterson, M.; Wayth, R. B.; Webster, R. L.; Whitney, A. R.; Williams, A.; Williams, C. L.

    2015-11-01

    Refraction and diffraction of incoming radio waves by the ionosphere induce time variability in the angular positions, peak amplitudes and shapes of radio sources, potentially complicating the automated cross-matching and identification of transient and variable radio sources. In this work, we empirically assess the effects of the ionosphere on data taken by the Murchison Widefield Array (MWA) radio telescope. We directly examine 51 h of data observed over 10 nights under quiet geomagnetic conditions (global storm index Kp < 2), analysing the behaviour of short-time-scale angular position and peak flux density variations of around ten thousand unresolved sources. We find that while much of the variation in angular position can be attributed to ionospheric refraction, the characteristic displacements (10-20 arcsec) at 154 MHz are small enough that search radii of 1-2 arcmin should be sufficient for cross-matching under typical conditions. By examining bulk trends in amplitude variability, we place upper limits on the modulation index associated with ionospheric scintillation of 1-3 per cent for the various nights. For sources fainter than ˜1 Jy, this variation is below the image noise at typical MWA sensitivities. Our results demonstrate that the ionosphere is not a significant impediment to the goals of time-domain science with the MWA at 154 MHz.

  7. 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.

  8. Meteorological effects observed by SuperDARN Hokkaido radar in the ionosphere

    NASA Astrophysics Data System (ADS)

    Oinats, Alexey; Chernigovskaya, Marina; Kurkin, Vladimir; Nishitani, Nozomu

    2012-07-01

    An analysis of the groundscatter data obtained by SuperDARN Hokkaido radar in September 2008 and 2009 is presented in the report. The main goal is to find ionospheric effects concerned with different meteorological events in the lower atmosphere. Among these events are tropospheric storms such as strong tropical cyclones that occur in the Northwest Pacific (Super Typhoon). Super Typhoon might result in the appearance of traveling ionosphere disturbances (TID) of the different scales that propagate from the location of Typhoon and registered by SuperDARN Hokkaido radar as variations of the different parameters of the received groundscatter signal.

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

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

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

  10. Towards estimation of atmospheric tidal effects on the ionosphere via data assimilation

    NASA Astrophysics Data System (ADS)

    Solomentsev, Dmitry; Cherniak, Yakov; Titov, Anton; Khattatov, Boris; Khattatov, Vyacheslav

    2015-11-01

    The impact of atmospheric tides on the night time ionosphere is now being a subject of the extensive research within the scientific community. The plausible effect has been observed using the multiple space-borne instruments (e.g. COSMIC/FORMOSAT-3 constellation, TIMED GUVI and NASA IMAGE). Along with the observations, several modelling attempts has been undertaken to prove or refute the interrelation between the atmospheric tides and the wave-four longitudinal night time ionosphere structure. The scope of the current article is to assess the data assimilation ionosphere model capabilities in representing the longitudinal effect in the night time ionosphere induced by the DE3 atmospheric tide. Along with this, the core physics-based model capabilities in estimating the same effect are presented and discussed. For the current research, two periods were taken into consideration: the autumn equinox of the years 2006 and 2012. In the current article the data assimilation and physics-based models calculation results are presented and discussed along with the models' error estimation and analysis.

  11. Effects of Lightning Return Stroke Parameters on Radiated Fields, on the Ground and in the Ionosphere

    NASA Astrophysics Data System (ADS)

    Marshall, R. A.

    2012-12-01

    We present numerical simulations of lightning return stroke currents and the fields radiated in the Earth-ionosphere waveguide and into the lower ionosphere. Where previous lightning-ionosphere interaction models approximate the return stroke current as constant over the altitude range of the return stroke, we implement a modified transmission line model of the return stroke, with either linear (MTLL) or exponential (MTLE) current decay with altitude. Using this model we investigate the effects of the return stroke rise time τr, fall time τf, propagation speed vrs, and terminal altitude h on both the electrostatic and radiated fields. These parameters affect the field amplitudes and waveforms both as measured along the ground and in the lower ionosphere, the latter having implications for sprite initiation, D-region ionization and elve luminosity. In addition, these parameters affect the interpretation of temporal signatures of elves. We present results that demonstrate the effects of each of the four parameters on fields, ionization, and elve luminosity and temporal signature. We further investigate the effects of these parameters on the relationship between peak current Ik and E100, the electric field measured at 100 km range on the ground.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. Ionospheric effects of the missile destruction on December 9, 2009

    NASA Astrophysics Data System (ADS)

    Kozlovsky, Alexander; Shalimov, Sergey; Lukianova, Renata

    2014-05-01

    We report on ionosonde and meteor radar observations made in Sodankyla Geophysical Observatory (SGO, 67N, 27E, Finland) on December 9, 2009 during a test launch of the Russian solid propellant military missile. Because of the technical problem the missile was self-destroyed around 07 UT at ionospheric height (170-260 km) over the Kola Peninsula (Russia), at a distance about 500 km to east from the observatory. Products of the explosion, including long-lived ionized aluminum oxides, were spread into the large area and reached the region of SGO meteor radar observations in about 2 hours (around 09 UT). After about 3 hours (around 10 UT) a sporadic E layer presumably composed of the remains was observed close to the zenith of the SGO ionosonde. We present the data and discuss possible mechanisms accounting for both vertical and horizontal transport of the remains. Theoretical estimations suggest that the observed transport could be likely due to thermospheric turbulence.

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

    NASA Astrophysics Data System (ADS)

    Mostafa, Md. Golam; Haralambous, Haris

    2015-06-01

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

  18. Review of radio-frequency, non-linear effects on the ionosphere

    NASA Astrophysics Data System (ADS)

    Gordon, William E.; Duncan, Lewis M.

    1988-06-01

    The nonlinear effects of powerful radio waves on the ionosphere are reviewed. The history of such effects beginning in the early 1930s are retold, highlighting important events up to the late 1960s. A phenomenological treatment is then given to ohmic heating, parametric instabilities, self-focusing, and kilometric-scale irregularities, meter-scale irregularities, and a collection of recently discovered effects. The benefits that international cooperation would provide for this research are discussed, giving a list of future research challenges.

  19. Effect of self-absorption on attenuation of lightning and transmitter signals in the lower ionosphere

    NASA Astrophysics Data System (ADS)

    Marshall, R. A.

    2014-05-01

    The attenuation of VLF signals from lightning and ground-based VLF transmitters during transionospheric propagation has been the subject of recent interest, as discrepancies have been found between satellite data and model calculations. Previous modeling efforts, however, have not considered the self-absorption effect due to nonlinear heating and ionization in the lower ionosphere. A self-consistent model of ionospheric heating is presented here using a time-domain model of VLF wave propagation through the ionosphere. The model is able to estimate the attenuation of signals due to heating below ˜100 km altitude. In this model, the ionospheric state is updated as the fields propagate, leading to changes in collision frequency and electron density, which in turn affect the wave propagation. We use this model for ground-based VLF transmitters at different frequencies, amplitudes, and latitudes (i.e., magnetic dip angle), and for lightning-generated sferics with different amplitudes, at different latitudes, and using a variety of ionospheric density profiles. We find that the inclusion of self-consistent heating causes a change in the transionospherically propagating wave amplitude that varies considerably with the source amplitude and other parameters. Typical values for the heating contribution to wave attenuation are 1-2 dB for VLF transmitters, but greater than 10 dB for large amplitude lightning discharges. An interesting effect is observed for VLF transmitters and low-amplitude lightning, where the signal is actually enhanced due to heating, rather than attenuated, in the direction propagating across the Earth's magnetic field.

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

    NASA Astrophysics Data System (ADS)

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

    2015-09-01

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

  1. Optimization of satellite coverage in observing cause and effect changes in the ionosphere, magnetosphere, and solar wind. Master's thesis

    SciTech Connect

    Loveless, M.J.

    1993-06-01

    Disturbances in the ionosphere sometimes cause adverse effects to communications systems, power grids, etc. on the earth. Currently, very little, if any, lead time is given to warn of an impending problem. If a forecast could be made of ionospheric occurrences, some lead time may be given to appropriate agencies and equipment may be saved. Most changes that occur in the ionosphere are a result of interaction of energy, currents, etc. between the magnetosphere and/or solar wind. Before a forecast can be made, however, improvement of ionospheric models currently in use need to be made. The models currently depict features in various regions of the ionosphere but not always where these features are actually observed. So an improvement to the model is needed to create an accurate baseline condition, or in other words an accurate depiction of the current ionosphere. Models could be improved by inputting real-time data from the ionosphere into the model. This data would come from satellites and/or ground-based stations.

  2. Analyses of solar activity effects on the low-latitude ionosphere

    NASA Astrophysics Data System (ADS)

    Wolven, B. C.; Talaat, E. R.; Yee, J.; Demajistre, R.; Paxton, L. J.; Christensen, A.; Sotirelis, T.; Smith, D. C.; Bilitza, D.; Azeem, I.

    2006-12-01

    Long-term measurement datasets have recently become available from several satellite missions. The TOPEX and JASON satellites obtain the total electron content (TEC) from ~1200 km orbit and the DMSP satellites measure the in-situ ion densities at ~800 km, while the GUVI instrument onboard the TIMED satellite retrieves the electron density profile below ~550 km altitude. TOPEX, JASON, and TIMED are slowly precessing satellites that are able to obtain complete local time coverage approximately every two months. The DMSP satellites are sun-synchronous and in situ sample the ionosphere at 4 or more discrete local times. In addition, the SSUSI instrument onboard DMSP F16 obtains profiles of electron density below ~840 km. This rich dataset allows us to examine the solar activity effects on the low-latitude ionosphere on different timescales including solar flare, rotational, and 11-year solar cycle effects. In this paper we describe the effects of solar activity on the low-latitude ionosphere as observed by three different sets of measurements, including the maximum electron number density, the peak height, the latitudinal separation of the equatorial arcs, and the asymmetry of the peak densities. We also compare these results with those from the IRI model and a first-principles general circulation model, the TIE-GCM. The characterization and analysis of the observed effects are essential for understanding low-latitude electrodynamics.

  3. Impact and Mitigation of Ionospheric Space Weather Effects on GNSS Receiver Performance (Invited)

    NASA Astrophysics Data System (ADS)

    Vadakke Veettil, S.; Aquino, M. H.

    2013-12-01

    The Earth's ionosphere is considered to be the single largest source of space weather effects on Global Navigation Satellite System (GNSS) signals and positioning accuracy. Most of the space weather effects leading to ionospheric perturbations on the GNSS signals are either due to dispersion or to scintillation caused by plasma density irregularities. This paper presents some significant results related to the impact and mitigation of ionospheric space weather effects on GNSS receiver performance. The correlation of scintillation occurrence with changes in the solar and interplanetary conditions with the consequential impact on GNSS receiver tracking performance at high latitudes is analysed. Further, an assessment of the GNSS receiver tracking performance under scintillation is presented and the construction of the receiver Phase Locked Loop (PLL) jitter variance maps is proposed. These maps can offer a potentially useful tool to provide users with the prevailing tracking conditions under scintillation over a certain area. They can also be used to help mitigate the effects of scintillation on GNSS positioning. This can be done in association with a strategy that involves using the tracking errors to improve the stochastic model of the observations in the position estimation. Validation strategies and practical aspects as well as limitations in the use of these maps are also discussed in this paper.

  4. Absorption of radio waves and the effective electron collision frequency in the midlatitude ionosphere

    NASA Astrophysics Data System (ADS)

    Vodolazkin, V. I.; Denisenko, P. F.; Rzhanitsyn, V. P.; Sotskij, V. V.; Faer, Yu. N.

    1993-06-01

    An empirical model of the effective electron collision frequency is presented for the 100-200-km height range in the midlatitude ionosphere. The model is based on multifrequency measurements of the absorption of ordinary and extraordinary radio waves as studied via vertical sounding near Rostov (47 deg 13 min N, 39 deg 14 min E). The model reflects seasonal variations for daytime periods and two levels of solar activity.

  5. 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.

  6. Effect of interhemispheric currents on equivalent ionospheric currents in two hemispheres: Simulation results

    NASA Astrophysics Data System (ADS)

    Lyatskaya, Sonya; Lyatsky, Wladislaw; Zesta, Eftyhia

    2016-02-01

    In this research, we used numerical simulation to study the effect of interhemispheric field-aligned currents (IHCs), going between two conjugate ionospheres in two hemispheres, on the equivalent ionospheric currents (EICs). We computed the maps of these EICs in two hemispheres during summer-winter conditions, when the effect of the IHCs is especially significant. The main results may be summarized as follows. (1) In winter hemisphere, the IHCs may significantly exceed and be a substitute for the local R1 currents, and they may strongly affect the magnitude, location, and direction of the EICs in the nightside winter auroral ionosphere. (2) While in summer polar cap the EICs tend to flow sunward, and in winter polar cap the EICs turn toward dawn due to the effect of the IHCs. (3) The well-known reversal in the direction of the EICs in the vicinity of the midnight meridian, in winter hemisphere, is observed not at the polar caps boundary (as usually expected) but equatorward of this boundary in the region of the IHCs location. (4) The IHCs in winter hemisphere may be, in fact, not only a substitute for the R1 currents but also the major source of the Westward Auroral Electrojet, observed in both hemispheres during substorm activity.

  7. 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.

  8. Propagation of ULF waves (0.1-1Hz) through the ionosphere including dip angle effect

    NASA Astrophysics Data System (ADS)

    Shi, Run; Zhao, Zhengyu; Zhang, Beichen

    An analytic model for the propagation of ultra low frequency (ULF) waves in the Pc1 range (0.1-1Hz) within oblique background magnetic field is developed. By taking a Carte-sian coordinate system, we stratify the area of ULF wave propagation into three regions: the magnetosphere, the thin sheet ionosphere (lies in XY plane) and the insulated atmosphere. The variation of the Alfven speed with height (Z direction) is considered in the present study. The reflection coefficient, wave mode conversion coefficient are derived and the ky (the perpen-dicular wave number for an oblique background magnetic field, B0 in the XZ plane) effect is emphasized. The results show that variation in dip angle can effectively modify the resonant frequency and the growth rate of the Ionospheric Alfven Resonator (IAR) and consequently alter the reflection and transition properties of the Alfven waves. By taking into account the effects of ky, the model also shows that ky plays an important role in affecting the ULF wave propagation and the ratio between ky and kx is important for the wave reflection and ground magnetic signal. Key words: Pc1; dip angle; Ionospheric Alfven Resonator (IAR)

  9. Measurements of possible D- and E-region telecommunications effects during ionospheric heating. Final report

    SciTech Connect

    Showen, R L

    1980-02-01

    For this research project, measurements were made of the effects that heating the ionosphere might have on the passage of radiowaves through the D- and E-regions. The purpose of this work was to simulate the effects of the proposed Solar Power Satellite microwave power beam on the lower ionosphere. The increased electron temperatures produced by the Platteville, Colorado, HF ionospheric heater caused cross-modulation on certain radiowaves when the heater was rapidly modulated (the Luxembourg effect). Small amounts of cross-modulation were detected at four frequencies between 60 kHz and 5 MHz. Attempts were made to detect phase path changes - indicative of electron number density changes - while the heater was slowly cycled on and off. No phase path changes could be seen for radiowaves of frequency 10.2 or 60 kHz. If these results are extrapolated to the powers and frequency of the Solar Power Satellite power beam, then no significant impact from D- and E-region modification on telecommunications services are expected.

  10. Saturn ionosphere - Theoretical interpretation

    NASA Astrophysics Data System (ADS)

    Atreya, S. K.; Waite, J. H.

    1981-08-01

    Voyager 1 high latitude and Pioneer 11 equatorial ionospheric structure indicate a solar EUV-controlled ionosphere with a possible molecular ion in the topside. Vibrationally excited H2 in the high latitudes may be an important loss mechanism. Dynamical effects are expected to be important for determining the peak density and its location.

  11. 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.

  12. Modeling the ionospheric impact of tsunami-driven gravity waves with SAMI3: Conjugate effects

    NASA Astrophysics Data System (ADS)

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

    2015-07-01

    The Naval Research Laboratory first-principles ionosphere model SAMI3 is used to study the ionospheric effects associated with tsunami-driven gravity waves. Specifically, the Tohoku-Oki tsunami of 11 March 2011 is modeled. It is shown that gravity wave-induced variations in the neutral wind lead to plasma velocity variations both perpendicular and parallel to the geomagnetic field. Moreover, the electric field induced by the neutral wind perturbations can map to the conjugate hemisphere. Thus, electron density variations can be generated in both hemispheres which impact the total electron content (TEC) and 6300 Šairglow emission. It is found that the TEC exhibits variations of ≲ ±0.1 total electron content unit (1 TECU = 1016 el m-2) and the 6300 Šairglow emission variation is up to ˜±2.5% relative to the unperturbed background airglow.

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

    SciTech Connect

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

    1980-10-01

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

  14. High-latitude ionospheric drivers and their effects on wind patterns in the thermosphere

    NASA Astrophysics Data System (ADS)

    Liuzzo, L. R.; Ridley, A. J.; Conde, M.; Hampton, D. L.; Bristow, W. A.; Nicolls, M. J.; Mitchell, E. J.

    2013-12-01

    Winds in the thermosphere are highly important for transporting mass, momentum and energy over the globe. It has been moderately difficult to validate how well models reproduce the winds because of a lack of data. In the high latitude region, the ions and neutrals are strongly coupled when the aurora is present, whereas the coupling is weaker when there is no aurora. In this study, we investigate the ability of the Global Ionosphere Thermosphere Model (GITM) to simulate the meso-scale wind structure over Alaska before and during a substorm. Ten distinct numerical simulations of a substorm event that occurred between 02:00 and 17:00 universal time on November 24, 2012 have been preformed. Using GITM, we are able to highlight both subtle and drastic differences in model results affected by various high-latitude ionospheric drivers. Distinct ionospheric inputs considered as drivers include the Weimer potential patterns using IMF solar wind data coupled with the Fuller-Rowell and Evans auroral patterns, SuperDARN fitted potential pattern data, and changes in ionospheric currents measured by the Auroral Electrojet index. We also consider the effects of the boundary between the neutral wind dynamo calculation and the high-latitude imposed electric potential. Neutral wind velocities measured from Scanning Doppler Imager instruments located at three locations in Alaska are then compared to GITM simulated winds for every distinct run. Each component of the wind is compared individually, as they are driven by different forcing terms. Further, electron densities at 240km as a function of location and time are compared with data from the Poker Flat Incoherent Scatter Radar instrument. We have found that differences in the type of input used to model the substorm can lead to significantly disparate results among each individual run. This points to the need to have accurate specifications of the electric potential and auroral precipitation if the wind is to be fully understood.

  15. Testing Ionospheric Faraday Rotation Corrections in CASA

    NASA Astrophysics Data System (ADS)

    Kooi, Jason E.; Moellenbrock, George

    2015-04-01

    The Earth’s ionosphere introduces direction- and time-dependent effects over a range of physical and temporal scales and so is a major source for unmodeled phase offsets for low frequency radioastronomical observations. Ionospheric effects are often the limiting factor to making sensitive radioastronomical measurements to probe the solar corona or coronal mass ejections at low frequencies (< 5 GHz). It has become common practice to use global ionospheric models derived from the Global Positioning System (GPS) to provide a means of externally calibrating low frequency data. We have developed a new calibration algorithm in the Common Astronomy Software Applications (CASA) package. CASA, which was developed to meet the data post-processing needs of next generation telescopes such as the Karl G. Jansky Very Large Array (VLA), did not previously have the capability to mitigate ionospheric effects. This algorithm uses GPS-based global ionosphere maps to mitigate the first and second order ionospheric effects (dispersion delay and Faraday rotation, respectively). We investigated several data centers as potential sources for global ionospheric models and chose the International Global Navigation Satellite System Service data product because data from other sources are generally too sparse to use without additional interpolation schemes. This implementation of ionospheric corrections in CASA has been tested on several sets of VLA observations and all of them showed a significant reduction of the dispersion delay. In order to rigorously test CASA’s ability to mitigate ionospheric Faraday rotation, we made VLA full-polarization observations of the standard VLA phase calibrators J0359+5057 and J0423+4150 in August 2014, using L band (1 - 2 GHz), S band (2 - 4 GHz), and C band (4 - 6 GHz) frequencies in the D array configuration. The observations were 4 hours in duration, beginning near local sunrise. In this paper, we give a general description of how these corrections are implemented as well as discussion of the code’s ability to mitigate the ionospheric effects present in these test observations over a range of times and elevation angles. This work was supported at the University of Iowa by grant ATM09-56901.

  16. Post-flare effects in the lower ionosphere of middle latitudes

    NASA Technical Reports Server (NTRS)

    Krivsky, L.

    1989-01-01

    Beginning in the 1960s, records were made of noise from the region around the Polar Star on 29 MHz (Krivsky and Tlamicha, 1960) at the Ondrejov Observatory near Prague. Since the aerial characteristic was not too narrow, radio bursts were received of solar origin (of flares) at the noise level, SCNA effects (sudden cosmic noise absorption) at the time of intensive flare X-emission and in some rare cases, after large proton flares, small absorption effects of a few hours duration (Krivsky, 1969). These post-flare absorption effects in cosmic noise are evidently analogous with PCA effects (polar cap absorption) and are connected with ionospheric absorption of radio cosmic noise, caused by fast particles of subcosmic radiation. The recording of long term absorption effects after large particle flares at European midlatitudes was reported at the beginning of the 1960s. It was then usual to record radio cosmic noise with riometers at frequencies of about 18 MHz in the polar or subpolar regions in an effort to record PCA effects of subcosmic radiation (Hakura, 1968). An attempt was made to record the complex of emissions mentioned as well as the effects in a new frequency range (30 MHz), which did not agree with the ideas of the contemporaneous representatives of the Ionospheric Department of the Geophysical Institute in Prague. In recent years radio cosmic noise has been recorded at the Upice Observatory. These long term after flare effects of cosmic radio noise absorption (AF-CNA) at middle latitudes are reported to the geophysical and ionospheric community for the first time.

  17. 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.

  18. Simulations of the effects of vertical transport on the thermosphere and ionosphere using two coupled models

    NASA Astrophysics Data System (ADS)

    Drob, Douglas; Siskind, David; Dymond, Kenneth; McCormack, John

    2014-05-01

    We have explored the sensitivity of the thermosphere and ionosphere to dynamical forcing from altitudes near the mesopause (˜ 95 km) as recently described by Siskind et al., (2014). We show results from five simulations, all for the year 2009, with the NCAR/Thermosphere Ionosphere Electrodynamics General Circulation Model (TIEGCM). Two simulations were driven with the NCAR Global Scale Wind Model (GSWM) and three used output from the Advanced Level Physics High Altitude (ALPHA) version of the Navy's Operational Global Atmospheric Prediction System (NOGAPS). Use of NOGAPS-ALPHA allows for realistic meteorological variability from the lower atmosphere to propogate up into the TIEGCM, including a rich spectrum of non-migrating tides. We find that the additional vertical transport from these tides causes a significant reduction in the calculated peak electron density of the ionospheric F2 layer (NmF2). The mechanism for this effect is the enhanced downward transport of atomic oxygen to the base of the thermosphere. In turn, this yields a greater relative abundance of N2 and hence, enhanced recombination of ions and electrons. To get improved agreement with observed electron densities, we must reduce (Kzz) by a factor of 5. However, even with lower Kzz, our calculation still underestimates the NmF2 compared with radio occultation observations by the Constellation Observing System for Meterology, Ionosphere and Climate (COSMIC) satellite system. This underestimate of NmF2 may be linked to an overestimate of the non-migrating tides in the coupled TIEGCM-NOGAPS calculations or to uncertainties in the bottom boundary for atomic oxygen in the TIEGCM. We are currently exploring the second hypothesis by actively constraining the bottom boundary of the TIEGCM to observed atomic oxygen values from the NASA TIMED/SABER instrument. Siskind et al., (2014) Simulations of the effects of vertical transport on the thermosphere and ionosphere using two coupled models, J. Geophys. Res., DOI:10.1002/2013JA019116. This work sponsored by the Office of Naval Research.

  19. The energetics of Titan's ionosphere

    NASA Technical Reports Server (NTRS)

    Roboz, A.; Nagy, A. F.

    1994-01-01

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

  20. The energetics of Titan's ionosphere

    NASA Astrophysics Data System (ADS)

    Roboz, A.; Nagy, A. F.

    1994-02-01

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

  1. 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.

  2. Effect of ionospheric self-conditioning and preconditioning on the broad upshifted maximum component of stimulated electromagnetic emission

    NASA Astrophysics Data System (ADS)

    Wagner, L. S.; Berhnardt, P. A.; Goldstein, J. A.; Selcher, C. A.; Frolov, V. L.; Sergeev, E. N.

    1999-02-01

    Stimulated electromagnetic emissions (SEE) are high-frequency radio emissions that are generated during high-power, high-frequency, ordinary mode (O-mode), radiowave heating of the ionosphere. These emissions are particularly useful in ionospheric heating experiments because they provide a way of monitoring space plasma processes remotely and passively. In order to utilize these emissions for diagnostic purposes, it is necessary to understand the space plasma processes involved in their generation. The purpose of these experiments was to observe the responses of a particular component of the SEE, the broad upshifted maximum (BUM), to a variety of heating stimuli in an effort to understand the factors involved in its development. Heating experiments were conducted at the Radiophysical Research Institute SURA Ionospheric Modification Facility in Russia. Experiments consisted of single-pump, two-pump, and single-pump power-stepping experiments. The single-pump and two-pump transmissions were organized into groups of pulses of varying widths and spacings to facilitate the investigation of self-conditioning, preconditioning, and two-pump-interaction conditioning effects. The major findings of these experiments are that the action of a pump can have a conditioning effect on the medium that affects the time development of the BUM. The result of the conditioning process is the formation of an overshoot in the temporal development of the BUM. A residual conditioning effect is sustained after the end of a pump pulse for a period of time (~30 s). The residual conditioning acts as preconditioning for the BUM of a subsequent pump pulse. A second O-mode pump (pump2), at a frequency a few hundred kilohertz above that of the first pump (pump1), is observed to cause additional suppression of the pump1 BUM, implying an enhanced conditioning effect. Time constants for the buildup and decay of the conditioning effects are estimated. During power-stepping experiments, the BUM spectrum was observed to evolve from a weak, narrow spectrum at an effective radiated power (ERP) of ~5 MW, to a strong, broad spectrum with a ramp-like spectral tail at an ERP of ~150 MW. Other features noted during power stepping include (1) strong BUM transients at pump power level transitions, (2) BUM amplitude asymmetry between power-up and power-down sides of a power stepping cycle, (3) reduction of the BUM spectral peak offset from the pump frequency with increasing pump power, and (4) power law dependence of BUM power on pump power (exponent ~2). Results of these experiments are used in an attempt to assess the relevance of small-scale irregularity generation and electron heating mechanisms to the observed conditioning effects.

  3. Nighttime ionospheric saturation effect estimation in the African equatorial anomaly trough: A comparison of two approaches

    NASA Astrophysics Data System (ADS)

    Ikubanni, Stephen O.; Adeniyi, Jacob O.

    2016-02-01

    Using the two-segmented and the quadratic regression analyses methods, the existence of saturation effect in the ionospheric electron content has been established in published literatures. With data set that spans an 11 year period (one solar cycle) from an African low-latitude station—Ouagadougou, Burkina Faso (Geographical coordinates 12oN, 1.8oW, dip ~3oN)—and adopting the quadratic and the two-segmented regression methods, we have studied nighttime saturation effect on the critical frequency of ionospheric F2 layer (foF2) around the magnetic dip. Both methods revealed that saturation effect in foF2 cuts across all seasons during nighttime. This phenomenon was least at the peak of the prereversal enhancement (PRE) period and increases significantly beyond midnight. Either of the two approaches can be adopted for saturation effect studies. The advantage of the two-segmented over the quadratic is that the change point (breakpoint), which is the solar flux level where saturation effects first become observable, can be determined. The effect seen around the PRE period may be attributed to the E × B drift while the effect beyond the PRE period is masked by other mechanisms.

  4. Ionospheric observations during the geomagnetic storm events on 24-27 July 2004: Long-duration positive storm effects

    NASA Astrophysics Data System (ADS)

    Ngwira, Chigomezyo M.; McKinnell, Lee-Anne; Cilliers, Pierre J.; Coster, Anthea J.

    2012-01-01

    Ionospheric storms represent large global disturbances of the ionospheric F region electron density in response to geomagnetic storms. In this study, we use a combination of ionospheric total electron content (TEC) global maps and data from in-situ satellite measurements, such as solar wind data from the Advanced Composition Explorer (ACE), the Defense Meteorological Satellite Program (DMSP), and TOPographic EXplorer (TOPEX) and JASON-1 satellites, to investigate the ionospheric response during the geomagnetic storm event on 24-27 July 2004. A chain of ground-based Global Positioning System (GPS) stations and ionosonde measurements across South Africa have been used to give a comprehensive coverage over this midlatitude location. The most pronounced ionospheric effects of the storm occurred at low- and midlatitudes in the Southern hemisphere, with the most significant enhancements, observed on 25 and 27 July, presented here. The DMSP F15 satellite observed a sharp density enhancement over the midlatitudes. Over South Africa, the enhancement on 25 July was about twice as large as that observed on 27 July. The positive storm enhancements on 25 and 27 July both lasted over 7 hours, and can be classified as long-duration positive storm effects. Also, IMF Bz had southward orientation for an extended number of hours (exceeding 9 hours) and could have been the means by which energy was continuously fed into the magnetosphere and ionosphere. In addition, the F region critical frequency (foF2) values observed at two ionosonde stations showed marked positive responses that were associated with an increase in the ionospheric peak height (hmF2).

  5. Environmental assessment for the Satellite Power System: concept development and evaluation program - effects of ionospheric heating on telecommunications

    SciTech Connect

    Not Available

    1980-08-01

    The microwave power beam that is associated with the operation of the Satellite Power System (SPS) will provide a continuous source of power density into the earth's ionosphere. As currently conceptualized, the power density at the center of the beam would be 23 mW/cm/sup 2/. This power density may be of sufficient magnitude to give rise to changes in the structure of the ionosphere and to increases in the electron temperature in the ionosphere. The work described in this report was undertaken to assess the degree to which the ionosphere and ionospheric-dependent telecommunication systems would be impacted by the passage of the Satellite Power System microwave power beam. The program of study utilized resources from Government, industry, and universities in order to conduct theoretical and experimental investigations that relate to the operational scenario surrounding the Satellite Power System concept. The results of the numerous investigations that were undertaken are summarized in this document and areas in which further study is required are pointed out.

  6. 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).

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

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

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

  8. Geomagnetic activity effect on the global ionosphere during the 2007-2009 deep solar minimum

    NASA Astrophysics Data System (ADS)

    Chen, Yiding; Liu, Libo; Le, Huijun; Wan, Weixing

    2014-05-01

    In this paper the significant effect of weaker geomagnetic activity during the 2007-2009 deep solar minimum on ionospheric variability on the shorter-term time scales of several days was highlighted via investigating the response of daily mean global electron content (GEC, the global area integral of total electron content derived from ground-based GPS measurements) to geomagnetic activity index Ap. Based on a case during the deep solar minimum, the effect of the recurrent weaker geomagnetic disturbances on the ionosphere was evident. Statistical analyses indicate that the effect of weaker geomagnetic activity on GEC variations on shorter-term time scales was significant during 2007-2009 even under relatively quiet geomagnetic activity condition; daily mean GEC was positively correlated with geomagnetic activity. However, GEC variations on shorter-term time scales were poorly correlated with geomagnetic activity during the solar cycle descending phase of 2003-2005 except under strong geomagnetic disturbance condition. Statistically, the effects of solar EUV irradiance, geomagnetic activity, and other factors (e.g., meteorological sources) on GEC variations on shorter-term time scales were basically equivalent during the 2007-2009 solar minimum.

  9. Effect of double layers on magnetosphere-ionosphere coupling

    NASA Technical Reports Server (NTRS)

    Lysak, Robert L.; Hudson, Mary K.

    1987-01-01

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

  10. Atmospheric Tidal Effects on the Zonal Mean Thermal and Dynamical Structure of the Ionosphere-Thermosphere System

    NASA Astrophysics Data System (ADS)

    Jones, M., Jr.; Forbes, J. M.; Hagan, M. E.

    2014-12-01

    The influences that vertically-propagating tides of lower atmosphere origin have on the dynamics, temperature, composition, and plasma structure of the ionosphere-thermosphere (IT) system continue to be revealed. Specifically, it is now recognized that dissipating tides exert significant changes in the mean state of the IT system with respect to latitude, season and solar cycle. However, the mechanisms and pathways through which this happens are not fully understood. Therefore, we utilize the National Center for Atmospheric Research Thermosphere-Ionosphere-Electrodynamics General Circulation Model (TIE-GCM), forced with observationally-based tides at the model lower boundary from the Climatological Tidal Model of the Thermosphere (CTMT, from Oberheide et al. [2011]), to evaluate the different terms in the thermodynamic energy and momentum equations in order to elucidate how tidal dissipation acts to alter the mean thermal and dynamical structure of the IT. Numerical experiments are performed for all months of the year and for solar minimum, medium, and maximum conditions so as to quantify the seasonal and solar cycle variability associated with the different terms in the thermodynamic energy and momentum equations. Implications for more completely understanding prior results from Jones Jr. et al. [2014a, 2014b] concerning tidal effects on the mean neutral composition and electron density distributions are also assessed. Only select highlights of this work will be presented. References: Jones, M., Jr., J. M. Forbes, M. E. Hagan, and A. Maute (2014a), Impacts of vertically propagating tides on the mean state of the ionosphere-thermosphere system, J. Geophys. Res. Space Physics, 119, 2197-2213, doi:10.1002/2013JA019744. Jones, M., Jr., J. M. Forbes, and M. E. Hagan (2014b), Tidal-induced net transport effects on the oxygen distribution in the thermosphere, Geophys. Res. Lett., 41, doi:10.1002/2014GL060698. Oberheide, J., J. M. Forbes, X. Zhang, and S. L. Bruinsma (2011), Climatology of upward propagating diurnal and semidiurnal tides in the thermosphere, J. Geophys. Res., 116, A11306, doi:10.1029/2011JA016784.

  11. Effects of the ionosphere and solar activity on radio occultation signals: Application to CHAllenging Minisatellite Payload satellite observations

    NASA Astrophysics Data System (ADS)

    Pavelyev, A. G.; Liou, Y. A.; Wickert, J.; Schmidt, T.; Pavelyev, A. A.; Liu, S. F.

    2007-06-01

    We analyze the ionospheric effect on the phase and amplitude of radio occultation (RO) signal. The introduced theoretical model predicts a correlation between the phase acceleration and intensity variations of RO signal and opens a way to locate layered structures in the propagation medium, in particular, in trans-ionospheric satellite-to-satellite links. For considered CHAllenging Minisatellite Payload (CHAMP) RO events, the locations of the inclined plasma layers in the lower ionosphere are estimated, and the electron density distribution is retrieved. By analysis of the CHAMP RO data, we reveal the dependence of the intensity variations of RO signal on sharp changes in the DST index and on the local time. Maps of the seasonal, geographical, and temporal distributions of the CHAMP RO events with amplitude scintillations, having high S4 index values, and observed during the years 2001-2004 indicate dependence on solar activity. As follows from this analysis, the GPS signals in the trans-ionospheric links can be used for investigating the location and parameters of inclined plasma layers and monitoring the influence of solar activity on the ionosphere with global coverage.

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

    SciTech Connect

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

    1992-10-22

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

  13. Effect of mesoscale atmospheric vortex processes on the upper atmosphere and ionosphere of the Earth

    NASA Astrophysics Data System (ADS)

    Bondur, V. G.; Pulinets, S. A.

    2012-12-01

    The mechanisms of incipience and intensification of dangerous atmospheric vortex processes such as tropical cyclones (TCs) and their interaction with the Earth's ionosphere are considered. Different models of TCs are analyzed, including models taking into account the ionization processes. The mechanisms taking into account the spiral field of velocities during TC formation are analyzed, as are the physical mechanism that explains the statistical correlation between short-term variations in galactic cosmic rays (Forbush decreases) and the frequency of incipience and the intensification of TCs. It is shown that such an effect is conditioned by a decrease in the ion-production rate during Forbush decreases against the tropopause and, hence, a decrease in the temperature upon the top of the ionosphere altitude because of a decrease in the latent heat release due to water-vapor condensation on the newly formed ions. This process leads to an increase in the temperature difference between the ocean surface and the top level of TCs and, respectively, to the intensification of vertical convection, which results in cyclone intensification. It is concluded that the study of these mesoscale vortex processes requires taking into account not only the hydrodynamical features of these formations, but also their thermodynamical and electrodynamical properties. The results are important for the organization of studying and monitoring TCs with the use of spaceborne techniques.

  14. Magnetic field effects on the accuracy of ionospheric mirror models for geolocation

    NASA Astrophysics Data System (ADS)

    Dao, Eugene V.; McNamara, Leo F.; Colman, Jonah J.

    2016-04-01

    The geolocation of an uncooperative HF emitter is based on observations of the azimuth and elevation (angle of arrival; AoA) of its signals as they arrive at a surveillance site, along with a model of the propagation medium. The simplest propagation model that provides an estimate of the location of the emitter is based on the use of a horizontal mirror placed at the appropriate altitude. If there are large-scale horizontal ionospheric gradients or traveling ionospheric disturbances present, tilts derived from a suitable ionosonde or from the AoA of convenient known emitters (check targets) may be applied to the mirror before geolocation is performed. However, the methodology of this approach to geolocation completely ignores the Earth's magnetic field, producing errors that can reach 25% of range for a short range (less than 100 km) low-latitude target. The errors are generally smaller at midlatitudes. This paper investigates and characterizes these errors in terms of wave polarization, magnetic dip, circuit length, and azimuth relative to the direction of the magnetic field. The magnetic field also affects the procedure of using tilts derived from check-target AoA because the field effects can masquerade as tilts of unknown magnitude.

  15. Estimation of Ionospheric Conductivity Based on the Measurements by Superdarn

    NASA Astrophysics Data System (ADS)

    Lee, Eun-Ah; An, Byung-Ho; Yi, Yu

    2002-06-01

    The ionosphere plays an important role in the electrodynamics of space environment. In particular, the information on the ionospheric conductivity distribution is indispensable in understanding the electrodynamics of the magnetosphere and ionosphere coupling study. To meet such a requirement, several attempts have been made to estimate the conductivity distribution over the polar ionosphere. As one of such attempts we compare the ionospheric plasma convection patterns obtained from the Super Dual Auroral Radar Network (SuperDARN), from which the electric field distribution is estimated, and the simultaneously measured ground magnetic disturbance. Specifically, the electric field measured from the Goose Bay and Stokkseyri radars and magnetic disturbance data obtained from the west coast chain of Greenland are compared. In order to estimate ionospheric conductivity distribution with these information, the overhead infinite sheet current approximation is employed. As expected, the Hall conductance, height-integrated conductivity, shows a wide enhancement along the center of the auroral electrojet. However, Pedersen conductance shows negative values over a wide portion of the auroral oval region, a physically unacceptable situation. To alleviate this problem, the effect of the field-aligned current is taken into account. As a result, the region with negative Pedersen conductance disappears significantly, suggesting that the effect of the field-aligned current should be taken into account, when one wants to estimate ionospheric conductance based on ground magnetic disturbance and electric field measurements by radars.

  16. Realtime Monitoring of Traveling Ionospheric Disturbances Caused by Tsunamis

    NASA Astrophysics Data System (ADS)

    McBride, P. J.; Crowley, G.; Reynolds, A.; Azeem, I.; Makela, J. J.; Vadas, S.

    2014-12-01

    The ocean-ionosphere coupling associated with tsunamis was predicted as early as the 1970s and had been observed previously by various radio frequency techniques, including arrays of ground-based Global Positioning System (GPS) receivers. Much work is still needed in order to fully understand the coupling mechanism and allow for the development of effective tsunami detection/warning systems. These challenges include the need for additional observations of the tsunami ionospheric signature to provide new scientific insight into the geophysical source phenomenology and wave propagation physics, and to better constrain the conditions under which ocean-atmospheric coupling is effective. One of the ionospheric signatures of tsunamis is a Traveling Ionospheric Disturbance (TID). ASTRA has developed a realtime TID Mapping System based on HF radio sounding. We will provide examples of TIDs associated with various tsunamis, including the propagation characteristics of the TIDs. We are deploying an expanded ground-based observation network using strategically placed optical imaging systems together with ASTRA's TID Mapping Systems, to obtain new information about the ionospheric waves associated with tsunamis. We will also use a published and validated gravity wave ray trace model to perform studies of the propagation of tsunami-generated gravity waves through the atmosphere and into the thermosphere/ionosphere system. This work will also enhance our understanding of upward coupling caused by all gravity wave sources in the lower atmosphere (not just tsunamis) and how this coupling can generate ionospheric irregularities that affect navigation, communications and surveillance systems.

  17. 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.

  18. The investigation of man-made modifications of the ionosphere. [effects of detonations and rocket exhaust

    NASA Technical Reports Server (NTRS)

    Bernhardt, P. A.; Darosa, A. V.; Price, K. M.

    1980-01-01

    Topics covered include: (1) the application of ionosphere modifications models to the simulation of results obtained when rocket-borne explosives were detonated in the ionosphere; (2) the problem of hypersonic vapor releases from orbiting vehicles; (3) measuring the electron content reduction resulting from the firing of a Centaur rocket in the ionosphere; and (4) the preliminary design of the critical frequency tracker which displays the value of electron concentration at the peak of the F 2 region, in real time.

  19. 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.

  20. Effect of powerful oblique HF waves on ionospheric D-layer absorption

    NASA Astrophysics Data System (ADS)

    Bloom, R. M.

    1993-04-01

    A simple model of D-layer ionospheric heating in the presence of strong, high frequency (HF) radio waves is used to predict the anomalous, nonlinear wave absorption due to collisional and recombination effects induced by the indirect signal. It is found that little anomalous absorption occurs until effective radiated power (ERP) approaches 100 dBW; further increases in power of several dB beyond this 100 dBW threshold are frustrated by a comparable increase in self-induced, one-way absorption. This trend of increasing absorption with increasing transmitter ERP has considerable implications for design of communication or radar systems that use ultra-powerful, high-gain HF transmitters.

  1. Global ionospheric effects of geomagnetic storm on May 2-3, 2010 and their influence on HF radio wave propagation

    NASA Astrophysics Data System (ADS)

    Kotova, Daria; Klimenko, Maxim; Klimenko, Vladimir; Zakharov, Veniamin

    2013-04-01

    In this work we have investigated the global ionospheric response to geomagnetic storm on May 2-3, 2010 using GSM TIP (Global Self-consistent Model of the Thermosphere, Ionosphere and Protonosphere) simulation results. In the GSM TIP storm time model runs, several input parameters such as cross-polar cap potential difference and R2 FAC (Region 2 Field-Aligned Currents) varied as a function of the geomagnetic activity AE-index. Current simulation also uses the empirical model of high-energy particle precipitation by Zhang and Paxton. In this model, the energy and energy flux of precipitating electrons depend on a 3 hour Kp-index. We also have included the 30 min time delay of R2 FAC variations with respect to the variations of cross-polar cap potential difference. In addition, we use the ground-based ionosonde data for comparison our model results with observations. We present an analysis of the physical mechanisms responsible for the ionospheric effects of geomagnetic storms. The obtained simulation results are used by us as a medium for HF radio wave propagation at different latitudes in quiet conditions, and during main and recovery phase of a geomagnetic storm. To solve the problem of the radio wave propagation we used Zakharov's (I. Kant BFU) model based on geometric optics. In this model the solution of the eikonal equation for each of the two normal modes is reduced using the method of characteristics to the integration of the six ray equation system for the coordinates and momentum. All model equations of this system are solved in spherical geomagnetic coordinate system by the Runge-Kutta method. This model was tested for a plane wave in a parabolic layer. In this study, the complex refractive indices of the ordinary and extraordinary waves at ionospheric heights was calculated for the first time using the global first-principal model of the thermosphere-ionosphere system that describes the parameters of an inhomogeneous anisotropic medium during a geomagnetic storm. A comparison of the ordinary and extraordinary modes of HF radio ray paths in quiet and disturbed conditions has been done. We considered in more detail the features of the radio ray paths in the presence of F3 layer in the equatorial ionosphere, the main ionospheric trough and tongue of ionization at high latitudes. It is shown that the results obtained with use of radio propagation and GSM TIP models adequately describe HF radio ray paths in the Earth's ionosphere and can be used in applications. These investigations were carried out at financial support of Russian Foundation for Basic Research (RFBR) - Grant # 12-05-31217 and RAS Program 22.

  2. The contribution to IHY from the COST296 Action MIERS: Mitigation of Ionospheric Effects on Radio Systems

    NASA Astrophysics Data System (ADS)

    de Franceschi, Giorgiana; Alfonsi, Lucilla; Altadill, David; Bencze, Pal; Bourdillon, Alain; Buresova, Dalia; Cander, Ljiljana R.; de La Morena, Benito; Economou, Lefteris; Herraiz, Miguel; Kauristie, Kirsti; Lastovicka, Jan; Pau, Silvia; Rodriguez, Gracia; Stamper, Richard; Stanislawska, Iwona

    2009-04-01

    The objective of the COST296 Action MIERS (Mitigation of Ionospheric Effects on Radio Systems) is to develop an increased knowledge of the effects imposed by the ionosphere on practical radio systems, and for the development and implementation of techniques to mitigate the deleterious effects of the ionosphere on such systems ( http://www.cost296.rl.ac.uk ). The COST296 Community contributes to the international efforts of IHY with scientific and outreach activities as well. After the realization of a web site hosted by Istituto Nazionale di Geofisica e Vulcanologia (INGV), developed also to promote the ionospheric physics to the open public, the COST296 Community supported an initiative addressed to the pupils of the primary school of several European Countries: the realization of a school-calendar dedicated to the Sun and to the Sun-Earth connections.

  3. 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

  4. 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…

  5. The ionosphere of Neptune

    SciTech Connect

    Shinagawa, H.; Waite, J.H. Jr.

    1989-08-01

    Limited knowledge of ionospheric processes of the outer planets and practically no information on the upper atmosphere of Neptune result in a range of possible ionospheres of Neptune. Various cases are investigated in order to establish a theoretical framework of the ionospheric structure against which the radio occultation measurements can be evaluated. The peak electron densities could range from 10{sup 3} cm{sup {minus}3} to 10{sup 6} cm{sup {minus}3} depending on ion loss processes and particle ionization processes. The scale height could also range from 300 km to 2000 km depending on the exospheric temperature. Although various assumptions must be made, the authors predict that an auroral ionosphere with large electron densities ({approximately}10{sup 5} cm{sup {minus}3}) and a large scale height ({approximately}2000 km) will be observed by the ingress radio occultation measurement, and that a compressed ionosphere with small electron densities (order of 10{sup 3} cm{sup {minus}3}) will be seen during the egress measurement.

  6. Exposed high-voltage source effect on the potential of an ionospheric satellite

    NASA Technical Reports Server (NTRS)

    Tribble, A. C.; D'Angelo, N.; Murphy, G. B.; Pickett, J. S.; Steinberg, J. T.

    1988-01-01

    A pulsed, high-voltage source, which is able to draw a current from the surrounding plasma, is seen to induce large changes in the potential of an ionospheric satellite (the Iowa Plasma Diagnostics Package flown on Space Shuttle flight STS-51F). This, in turn, may affect the operation of other instruments that use the chassis of the satellite as a ground for electrical circuits. The magnitude of the change in satellite potential is dependent upon both the orientation of the high-voltage source, relative to the plasma flow, and the characteristics of the high-voltage source. When the satellite is grounded to the Shuttle Orbiter, this effect is sufficient to change the potential of the Orbiter by a small, but noticeable, amount.

  7. Effect of the ionosphere on the interaction between ULF waves and radiation belt electrons

    NASA Astrophysics Data System (ADS)

    Shah, Asif; Waters, C. L.; Sciffer, M. D.; Menk, F. W.; Lysak, R. L.

    2015-10-01

    The diffusion and energization of electrons in the equatorial plane of Earth's magnetosphere by ULF waves under different ionosphere boundary conditions are examined. Using test-particle simulations and considering intervals of weak geomagnetic activity, we find that the highest energization and minimum diffusion rates correspond to nightside ionosphere conditions. Conversely, the highest diffusion rates and minimum energization are seen for a perfectly reflecting ionosphere boundary. The maximum energies gained under dayside conditions, when Hall conductivity is included, are slightly greater than the maximum energy for similar conditions without Hall conductivity. The diffusion rates for dayside ionosphere conditions with only Pedersen conductivity are greater than the diffusion rates when Hall conductivity is included. These findings show that ULF wave-particle interactions in Earth's magnetosphere depend on the ionosphere conductance.

  8. 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…

  9. 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.

  10. 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.

  11. Ionospheric modeling

    NASA Astrophysics Data System (ADS)

    Dandekar, B. S.

    1982-01-01

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

  12. 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

  13. Modification of the lower ionospheric conductivity by thunderstorm electrostatic fields

    NASA Astrophysics Data System (ADS)

    Salem, Mohammad A.; Liu, Ningyu; Rassoul, Hamid K.

    2016-01-01

    This paper reports a modeling study of the modifications of the nighttime lower ionospheric conductivity by electrostatic fields produced by underlying thunderstorms. The model used combines Ohm's law with a simplified lower ionospheric ion chemistry model to self-consistently calculate the steady state nighttime conductivity above a thunderstorm. The results indicate that although the electron density is generally increased, the lower ionospheric conductivity can be reduced by up to 1-2 orders of magnitude because electron mobility is significantly reduced due to the electron heating effect. For a typical ionospheric density profile, the resulting changes in the reflection heights of extremely low frequency and very low frequency waves are 5 and 2 km, respectively.

  14. Thunderstorm coupling to the magnetosphere and associated ionospheric effects. Semiannual Report, 1 November 1991-30 April 1992

    SciTech Connect

    Inan, U.S.

    1992-01-01

    This project deals with the coupling of electromagnetic energy released during a thunderstorm to the magnetosphere and the ionosphere. Both the effects of an individual lightning event as well the aggregate of all the lightning events during a thunderstorm are considered. Energy in the very low frequency (VLF) band can play a variety of roles in the magnetospheric and ionospheric physics: generation of plasmaspheric hiss believed to be responsible for the slot region in the radiation belts, generation of lower hybrid waves that can heat ions in the auroral and subauroral regions, precipitation of energetic electrons, ionospheric heating etc. While these phenomena have been identified, and characterized to some extent, the influence and role of thunderstorm energy on the magnetosphere and ionosphere at a global scale is not known. Only recently, simultaneous high resolution (temporal and spatial) data sets from ground based lightning detectors and space and ground based VLF detectors have become available, and thus it has become possible to raise a question of the kind mentioned above and try to answer it quantitatively. Work on the correlation between individual lightning discharges in a thunderstorm as detected by the lightning network and the whistlers observed on the DE-1 satellite continued during this period. Results are summarized.

  15. The effect of including field-aligned potentials in the coupling between Jupiter's thermosphere, ionosphere, and magnetosphere

    NASA Astrophysics Data System (ADS)

    Ray, L. C.; Achilleos, N. A.; Yates, J. N.

    2015-08-01

    Jupiter's magnetosphere-ionosphere-thermosphere system drives the brightest, steadiest aurora in our solar system. This emission is the result of an electrical current system, which couples the magnetosphere to the planetary atmosphere in an attempt to enforce the corotation of the middle magnetospheric plasma. Field-aligned currents transfer angular momentum from the atmosphere to the magnetosphere. In the equatorial plane, the field-aligned currents diverge into radially outward currents, which exert a torque on the plasma due to the J × B forces. Equatorward ionospheric currents exert an opposite torque on the ionosphere, which interacts with the thermosphere via ion-neutral collisions. The upward field-aligned currents result in auroral electron precipitation, depositing energy into the high-latitude atmosphere. This energy input is a possible candidate for explaining the large thermospheric temperature measured by the Galileo probe at equatorial latitudes; however, previous atmospheric circulation models have shown that the bulk of the energy is transported poleward, rather than equatorward. We present numerical results of Jupiter's coupled magnetosphere-ionosphere-thermosphere system including, for the first time, field-aligned potentials. The model is compared with three previously published works. We find that the rotational decoupling of the magnetospheric and thermospheric angular velocities in the presence of field-aligned potentials tempers the thermospheric response to the outward transport of magnetospheric plasma, but this is a secondary effect to variations in the Pedersen conductance.

  16. A case study of lightning, whistlers, and associated ionospheric effects during a substorm particle injection event

    SciTech Connect

    Rodriguez, J.V.; Inan, U.S. ); Li, Y.Q.; Holzworth, R.H. ); Smith, A.J. , Cambridge ); Orville, R.E. ); Rosenberg, T.J. )

    1992-01-01

    Simultaneous ground-based observations of narrowband and broadband VLF radio waves and of cloud-to-ground lightning were made at widely spaced locations during the 1987 Wave-Induced Particle Precipitation (WIPP) campaign, conducted from Wallops Island, Virginia. Based on these observations, the first case study has been made of the relationships among located cloud-to-ground (CG) lightning flashes, whistlers, and associated ionospheric effects during a substorm particle injection event. This event took place 2 days after the strongest geomagnetic storm of 1987, during a reintensification in geomagnetic activity that did not affect the high rate of whistlers observed at Faraday Station, Antarctica. At the time of the injection event, several intense nighttime thunderstorms were located over Long Island and the coast of New England, between 400 km northwest and 600 km north of the region geomagnetically conjugate to Faraday. About two thirds of the CG flashes that were detected in these thunderstorms during the hour following the injection event onset were found to be causatively associated with whistlers received at Faraday. During the same period the amplitude of the 24.0-kHz signal from the NAA transmitter in Cutler, Maine, propagating over the thunderstorm centers toward Wallops Island was repeatedly perturbed in a manner characteristic of previously reported VLF signatures of transient and localized ionization enhancements at D region altitudes. Though such enhancements may have been caused by whistler-induced bursts electron precipitation from the magnetosphere, the data in this case are insufficient to establish a clear connection between the NAA amplitude perturbations and the Faraday Station whistlers. In view of the proximity of the NAA great circle path to the storm center, having the lower ionosphere by intense radiation from lightning may also have played a role in the observed VLF perturbations.

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

    NASA Astrophysics Data System (ADS)

    Liu, Jing; Liu, Libo; Nakamura, Takuji; Zhao, Biqiang; Ning, Baiqi; Yoshikawa, A.

    2014-09-01

    Multiple instrumental observations including GPS total electron content (TEC), foF2 and hmF2 from ionosondes, vertical ion drift measurements from Communication/Navigation Outage Forecasting System, magnetometer data, and far ultraviolet airglow measured by Thermosphere, Ionosphere, Mesosphere Energetics and Dynamics/Global Ultraviolet Imager (TIMED/GUVI) are used to investigate the profound ionospheric disturbances at midlatitude and low latitude during the 14-17 July 2012 geomagnetic storm event, which was featured by prolonged southward interplanetary geomagnetic field component for about 30 h 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 TIMED/GUVI O/N2 measurements and long-lasting daytime westward DDEF inferred from the equatorial electrojet 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 plume in the initial phase. In addition, multiple short-lived prompt penetration electric fields appeared during stable southward interplanetary magnetic field (IMF) Bz in the recovery phase and were responsible for enhanced the EIA and equatorial ionospheric uplift around sunset.

  18. Ionospheric refraction effects on TOPEX orbit determination accuracy using the Tracking and Data Relay Satellite System (TDRSS)

    NASA Technical Reports Server (NTRS)

    Radomski, M. S.; Doll, C. E.

    1991-01-01

    This investigation concerns the effects on Ocean Topography Experiment (TOPEX) spacecraft operational orbit determination of ionospheric refraction error affecting tracking measurements from the Tracking and Data Relay Satellite System (TDRSS). Although tracking error from this source is mitigated by the high frequencies (K-band) used for the space-to-ground links and by the high altitudes for the space-to-space links, these effects are of concern for the relatively high-altitude (1334 kilometers) TOPEX mission. This concern is due to the accuracy required for operational orbit-determination by the Goddard Space Flight Center (GSFC) and to the expectation that solar activity will still be relatively high at TOPEX launch in mid-1992. The ionospheric refraction error on S-band space-to-space links was calculated by a prototype observation-correction algorithm using the Bent model of ionosphere electron densities implemented in the context of the Goddard Trajectory Determination System (GTDS). Orbit determination error was evaluated by comparing parallel TOPEX orbit solutions, applying and omitting the correction, using the same simulated TDRSS tracking observations. The tracking scenarios simulated those planned for the observation phase of the TOPEX mission, with a preponderance of one-way return-link Doppler measurements. The results of the analysis showed most TOPEX operational accuracy requirements to be little affected by space-to-space ionospheric error. The determination of along-track velocity changes after ground-track adjustment maneuvers, however, is significantly affected when compared with the stringent 0.1-millimeter-per-second accuracy requirements, assuming uncoupled premaneuver and postmaneuver orbit determination. Space-to-space ionospheric refraction on the 24-hour postmaneuver arc alone causes 0.2 millimeter-per-second errors in along-track delta-v determination using uncoupled solutions. Coupling the premaneuver and postmaneuver solutions, however, appears likely to reduce this figure substantially. Plans and recommendations for response to these findings are presented.

  19. Statistical investigation of the noise added to a model of the effect of solar activities on the plasma of the ionosphere using DEMETER satellite data

    NASA Astrophysics Data System (ADS)

    Sharzehei, Mahmoud; Masnadi-Shirazi, M. A.; Golbahar-Haghighi, Sh.

    2015-08-01

    Although a relation between ionospheric anomalies and occurrence of strong earthquake has been studied for several decades, the issue of finding anomalies in ionospheric parameter before earthquakes has been always a matter of controversy among scientific community. In this way, the study of the ionosphere by satellite observers plays a significant role in assessing the feasibility of finding anomalies in ionospheric parameters as short-term precursors of earthquakes. Regardless of whether this assertion about ionospheric precursor is true or false, the ionosphere has been shown to be affected more by solar activities than other events such as seismic activities; thus, the modeling of ionospheric variation caused by solar activities is valuable in assessing the possibility of ionospheric precursors. One of the most famous satellites launched to investigate the ionospheric plasma perturbation associated with solar and seismic activities is the DEMETER, the French micro-satellite. To carry on such investigation, one of its payloads, the onboard IAP experiment, allows for the measurement of important plasma parameters including ion composition densities and their temperature. The current work presents a statistical distribution for the noise added to the proposed model describing the regular effect of solar activities on the ionospheric plasma above Iran during one half-orbit time of the DEMETER (~35 min) in the absence of an earthquake and a quiet time condition. The results of this study show that the proposed modeling noise statistically agrees with the Gaussian distribution; however, its variance may vary from one day to another. In other words, the noise is a non-stationary random process. The proposed model is then evaluated by a set of experimental data. The results of this evaluation show that the measured data follow the proposed model.

  20. A case study of lightning, whistlers, and associated ionospheric effects during a substorm particle injection event

    NASA Technical Reports Server (NTRS)

    Rodriguez, J. V.; Inan, U. S.; Li, Y. Q.; Holzworth, R. H.; Smith, A. J.; Orville, R. E.; Rosenberg, T. J.

    1992-01-01

    The relationships among cloud-to-ground (CG) lightning, sferics, whistlers, VLF amplitude perturbations, and other ionospheric phenomena occurring during substorm events were investigated using data from simultaneous ground-based observations of narrow-band and broad-band VLF radio waves and of CG lightning made during the 1987 Wave-Induced Particle Precipitation campaign conducted from Wallops Island (Virginia). Results suggest that the data collected on ionospheric phenomena during this event may represent new evidence of direct coupling of lightning energy to the lower ionosphere, either in conjunction with or in the absence of gyroresonant interactions between whistler mode waves and electrons in the magnetosphere.

  1. Effect of the quasi-biennial oscillation on radio-wave absorption variations in the lower ionosphere

    NASA Astrophysics Data System (ADS)

    Lastovicka, J.; Kniazev, A. K.

    1990-08-01

    An analysis of a 19-year series of regular variations on radio-wave absorption in Central Europe demonstrates that the quasi-biennial oscillation (QBO) has a significant effect on the amplitude of the semiannual harmonic in the lower-ionospheric absorption. This amplitude is higher for the western phase of the QBO than for the eastern phase. The effect of the QBO on the semiannual wave is primarily connected with variations of the difference between the spring and summer absorption levels.

  2. Lunar tidal effects in the electrodynamics of the low-latitude ionosphere

    NASA Astrophysics Data System (ADS)

    Tracy, Brian D.

    We used extensive measurements made by the Jicamarca Unattended Long-Term Investigations of the Ionosphere and Atmosphere (JULIA) and Incoherent Scatter Radar (ISR) systems at Jicamarca, Peru during geomagnetic quiet conditions to determine the climatologies of lunar tidal effects on equatorial vertical plasma drifts. We use, for the first time, the expectation maximization (EM) algorithm to derive the amplitudes and phases of the semimonthly and monthly lunar tidal perturbations. Our results indicate, as expected, lunar tidal effects can significantly modulate the equatorial plasma drifts. The local time and seasonal dependent phase progression has been studied in much more detail than previously and has shown to have significant variations from the average value. The semimonthly drift amplitudes are largest during December solstice and smallest during June solstice during the day, and almost season independent at night. The monthly lunar tidal amplitudes are season independent during the day, while nighttime monthly amplitudes are largest and smallest in December solstice and autumnal equinox, respectively. The monthly and semimonthly amplitudes decrease from early morning to afternoon and evening to morning with moderate to large increases near dusk and dawn. We also examined these perturbation drifts during periods of sudden stratospheric warmings (SSWs). Our results show, for the first time, the enhancements of the lunar semimonthly tidal effects associated with SSWs to occur at night, as well as during the day. Our results also indicate during SSWs, monthly tidal effects are not enhanced as strongly as the semimonthly effects.

  3. Effect of scattering on the dispersion distortions of signals and the diffraction of finite beams in the case of partial reflection from the ionosphere

    NASA Astrophysics Data System (ADS)

    Gusev, V. D.; Zhidovlenko, I. Iu.; Prikhod'Ko, L. I.

    1987-11-01

    An analysis is made of distortions of pulsed signals and finite radio-wave beams of different shape and duration in a triangular ionospheric layer with small-scale irregularities. The effects of the regular ionospheric gradient and of small-scale irregularities on the distortions are examined. The problem is solved using the method of statistical tests with modeling of the random permittivity of the ionosphere. It is shown that the spreading of the beams due to reflection and scattering significantly exceeds their diffraction divergence.

  4. Effect of diffusion-thermal processes on the high-latitude topside ionosphere

    NASA Technical Reports Server (NTRS)

    Schunk, R. W.; Raitt, W. J.; Nagy, A. F.

    1978-01-01

    The extent to which diffusion-thermal heat flow affects H(+) temperatures in the high-latitude topside ionosphere is studied. Such a heat flow occurs whenever there are H(+)-O(+) relative drifts. From our study we have found that at high-latitudes, where H(+) flows up and out of the topside ionosphere, diffusion-thermal heat flow acts to reduce H(+) temperatures by 500-600 K at altitudes above about 900 km.

  5. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-11-01

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

  7. 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

  8. Effects of convection electric field on upwelling and escape of ionospheric O(+)

    NASA Technical Reports Server (NTRS)

    Cladis, J. B.; Chiu, Yam T.; Peterson, William K.

    1992-01-01

    A Monte Carlo code is used to explore the full effects of the convection electric field on distributions of upflowing O(+) ions from the cusp/cleft ionosphere. Trajectories of individual ions/neutrals are computed as they undergo multiple charge-exchange collisions. In the ion state, the trajectories are computed in realistic models of the magnetic field and the convection, corotation, and ambipolar electric fields. The effects of ion-ion collisions are included, and the trajectories are computed with and without simultaneous stochastic heating perpendicular to the magnetic field by a realistic model of broadband, low frequency waves. In the neutral state, ballistic trajectories in the gravitational field are computed. The initial conditions of the ions, in addition to ambipolar electric field and the number densities and temperatures of O(+), H(+), and electrons as a function of height in the cusp/cleft region were obtained from the results of Gombosi and Killeen (1987), who used a hydrodynamic code to simulate the time-dependent frictional-heating effects in a magnetic tube during its motion though the convection throat. The distribution of the ion fluxes as a function of height are constructed from the case histories.

  9. Effects of plasmaspheric ion heating due to ionospheric and magnetospheric sources

    NASA Technical Reports Server (NTRS)

    Comfort, Richard H.

    1996-01-01

    In an initial study, the He(+) observations from the Retarding Ion Mass Spectrometer on Dynamics Explorer 1 (RIMS/DE 1) was examined for more than 120 transits of the plasmasphere in the fall of 1981. The He(+) to H(+) ratio was determined as it varied spatially over portions of the DE 1 orbit, and its variation with solar and magnetic activities and with local time, focusing specifically on the inner plasmasphere. These variations were compared along the L = 2 field line with calculations made by the Field Line Interhemispheric Plasma (FLIP) code. In a recently submitted paper, the He(+) to H(+) density ratio was examined for all the available data from 1981 to 1984 from the RIMS on DE 1. There are two basic characteristics of the ratio: one is that the ratio decreases with radial distance in the plasmasphere, and the other is the strong dependence of the density ratio on solar activity. In addition to the He(+)/H(+) ratio research, a phenomenon has been studied in the topside ionosphere which relates to the thermal coupling of the ionosphere to the plasmasphere. There is little or no correlation with magnetic and solar activity here. Another study has been directed toward the relation of plasma properties to the density gradients forming the plasmapause. The study has followed a two-pronged approach. First, the observations have been analyzed to determine what happens to the plasma properties across these boundary layers (density gradients). Second, comparisons were made with FLIP model calculations to determine how well the model is able to treat these conditions. Among the significant lessons learned in these studies are two that bear directly on the direction of future investigations in this area. First, composition cannot be viewed independently of thermal structure. Second, solar and magnetic activity effects are real; but the causal relationship between activity and effects is frequently quite complicated because several different processes appear to be operating in different ways and on different time scales. Under these circumstances, large correlation coefficients should not be expected and are not generally found.

  10. Ionospheric chemical releases

    NASA Technical Reports Server (NTRS)

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

    1990-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Cole, K. D.

    1993-03-01

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

  12. 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.

  13. Ion upflow dependence on ionospheric density and solar photoionization

    NASA Astrophysics Data System (ADS)

    Cohen, I. J.; Lessard, M. R.; Varney, R. H.; Oksavik, K.; Zettergren, M.; Lynch, K. A.

    2015-11-01

    Motivated by rocket observations showing a variety of different ionospheric responses to precipitation, this paper explores the influence of the background ionospheric density on upflow resulting from auroral precipitation. Simulations of upflow driven by auroral precipitation were conducted using a version of the Varney et al. (2014) model driven by precipitation characterized by observations made during the 2012 Magnetosphere-Ionosphere Coupling in the Alfvén resonator rocket mission and using a variety of different initial electron density profiles. The simulation results show that increased initial density before the onset of precipitation leads to smaller electron temperature increases, longer ionospheric heating timescales, weaker ambipolar electric fields, lower upflow speeds, and longer upflow timescales but larger upflow fluxes. The upflow flux can increase even when the ambipolar electric field strength decreases due to the larger number of ions that are accelerated. Long-term observations from the European Incoherent Scatter (EISCAT) Svalbard radar taken during the International Polar Year support the effects seen in the simulations. This correlation between ionospheric density and ion upflows emphasizes the important role of photoionization from solar ultraviolet radiation, which the EISCAT observations show can increase ionospheric density by as much as an order of magnitude during the summer months.

  14. Ionospheric Data Assimilation

    NASA Astrophysics Data System (ADS)

    Schunk, R.; Scherliess, L.; Sojka, J.; Thompson, D.

    2003-04-01

    Ionospheric weather disturbances can have detrimental effects on a variety of civilian and military systems and operations. They can affect over-the-horizon (OTH) radars, HF communications, surveying and navigation systems, surveillance, spacecraft charging, power grids, pipelines, and the FAA's Wide-Area Augmentation System (WAAS). In an effort to mitigate the adverse effects of the ionosphere on these systems/operations, there is a strong emphasis on developing specification and forecast models. One of the models under development is the Global Assimilation of Ionospheric Measurements (GAIM) model. GAIM uses a physics-based ionosphere-plasmasphere-polar wind model and a Kalman filter as a basis for assimilating a diverse set of real-time (or near real-time) measurements. Some of the data that are assimilated include in situ electron density measurements from the DMSP satellites, bottomside electron density profiles from the Air Force network of digisondes, GPS-TEC data from a network of more than 100 stations, and occultation data. GAIM provides specifications and forecasts on a spatial grid that can be global, regional, or local (25 x 25 km). The primary GAIM output is in the form of 3-dimensional electron density distributions from 90 km to the geosynchronous altitude (35,000 km). GAIM also provides auxiliary parameters (N_mF_2, h_mF_2, N_mE, h_mE, slant and vertical TEC) and global distributions of the self-consistent ionospheric drivers (neutral winds and densities, magnetospheric and dynamo electric fields, and particle precipitation patterns). In its specification mode, GAIM provides quantitative estimates for the accuracy of the reconstructed ionospheric densities. An outline of the GAIM model will be presented and then the presentation will focus on data issues, including the availability of real-time data sources, data quality problems, and the need to have realistic errors attached to all of the real-time data.

  15. 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 μW/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 ( β) 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.

  16. Using Remote Sensing as a Plasma Diagnostic: A Discussion of Techniques Being Used to Probe the Ionosphere in Order to Determine the Energy and Spectral Characteristics of Precipitating Electrons and Protons

    NASA Technical Reports Server (NTRS)

    Spann, J.; Parks, G.; Brittnacher, M.; Germany, G.; Mende, S.; Frey, H.; Chenette, D.; Schulz, M.; Petrinec, S.

    1999-01-01

    Spectrally resolved global images of the Earth from recent (and planned) missions are being (and will be) used to probe the ionosphere in order to determine the energy characteristics of precipitating electrons and protons. We describe the techniques that are being used, discuss the extent to which they are successful, and envision the approach that future space experiments should take in order to improve on current techniques.

  17. 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.

  18. 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.

  19. 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 fields (PPEF) appeared during stable southward IMF Bz in the recovery phase and were responsible for enhanced the EIA and equatorial ionospheric uplift around sunset.

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

    SciTech Connect

    Merkin, V. G.

    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.

  1. Effects of the Large June 1975 Meteoroid Storm on Earth's Ionosphere.

    PubMed

    Kaufmann, P; Kuntz, V L; Leme, N M; Piazza, L R; Boas, J W; Brecher, K; Crouchley, J

    1989-11-10

    The June 1975 meteoroid storm detected on the moon by the Apollo seismometers was the largest ever observed. Reexamination of radio data taken at that time showed that the storm also produced pronounced disturbances on Earth, which were recorded as unique phase anomalies on very low frequency (VLF) radio propagation paths in the low terrestrial ionosphere. Persistent effects were observed for the major storm period (20 to 30 June 1975), including reductions in the diurnal phase variation, advances in the nighttime and daytime phase levels, and reductions in the sunset phase delay rate. Large nighttime phase advances, lasting a few hours, were detected on some days at all VLF transmissions, and for the shorter propagation path they were comparable to solar Lyman alpha daytime ionization. Ion production rates attributable to the meteor storm were estimated to be about 0.6 to 3.0 ions per centimeter cubed per second at the E and D regions, respectively. The storm was a sporadic one with a radiant (that is, the point of apparent origin in the sky) located in the Southern Hemisphere, with a right ascension 1 to 2 hours larger than the sun's right ascension. PMID:17748704

  2. 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.

  3. Observation of Vertical Acoustic Resonance Effect on the Ground and in the Ionosphere During July 22 Total Eclipse

    NASA Astrophysics Data System (ADS)

    Iyemori, T.; Chiba, R.; Han, D.; Iguchi, M.; Kanda, W.; Matsumura, M.; Mori, J. J.; Nishioka, M.; Nose, M.; Odagi, Y.; Oshiman, N.; Saito, A.; Sanoo, Y.; Shinagawa, H.; Taira, K.; Takemura, A.; Tanaka, Y.; Toh, H.; Tomizawa, I.; Takeda, M.; Utsugi, M.; Yang, D.; Gong, Y.; Li, Q.

    2009-12-01

    The vertical acoustic resonance which can couple the ground, lower atmosphere and thermosphere (ionosphere) has been observed, for example, for the Mt. Pinatubo eruption in 1991 (Kanamori and Mori, 1992) and the great 2004 Sumatra earthquake (Iyemori et al., 2005). In the Mt. Pinatubo case, it was assumed that the acoustic wave (i.e., pressure variation) caused a very low frequency oscillation of the ground observed worldwide. However, a volcanic eruption or earthquake can also cause the ground oscillation directly. The ground oscillation may cause atmospheric oscillations but with a complicated causality. In the case of the Sumatra earthquake, the acoustic wave (i.e., vertical wind in the ionosphere) is assumed to be the cause of magnetic pulsations observed in Thailand. However, in this case, we have no atmospheric pressure and no appropriate ionospheric observation to validate it. When a total eclipse occurs, the rapid pressure variations over a wide area caused by the rapid decrease of temperature may also generate the acoustic resonance, however, in this case, the situation is expected to be simpler than for volcanic eruptions. This situation provides better conditions for quantitative modeling of the acoustic resonance effects. On July 22, 2009, a total eclipse was observed along a band from China, Iwo Island, and through the Tokara Islands, south of Japan. We conducted barometric, geomagnetic, temperature, GPS-TEC and HF Doppler observations at several points along the eclipse path. Because of the turbulent weather and occurrence of a magnetic storm, it is difficult to see very clear indications of the acoustic resonance in the raw pressure and magnetic field data. However, in the frequency domain, we can identify the acoustic resonance. The HF-Doppler observation also shows ionospheric oscillations in the total eclipse region. In this paper, we show the results of our observations.

  4. Predictions of electron temperatures in the Mars ionosphere and their effects on electron densities

    NASA Astrophysics Data System (ADS)

    Withers, Paul; Fallows, Kathryn; Matta, Majd

    2014-04-01

    Observations of peak electron densities in the Mars ionosphere are well fit by a simplistic theory that assumes the electron temperature, Te, at the peak remains constant as solar zenith angle, χ, changes. However, Te ought to vary with both altitude and χ. Here we use an existing numerical model of ionospheric energetics, which includes both vertical and diurnal variations in temperatures, to predict that Te at the ionospheric peak is relatively independent of χ. This model accurately predicts the observed dependence of peak electron density on χ, whereas predictions using Viking-based electron temperatures that are held constant with time do not. A simplified analytic model is developed to interpret these results further. It predicts that the difference between electron and neutral temperatures is proportional to the ratio of electron heating rate to electron production rate and proportional to the square root of solar irradiance.

  5. 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.

  6. Effect of an MLT dependent electron loss rate on the magnetosphere-ionosphere coupling

    NASA Astrophysics Data System (ADS)

    Gkioulidou, Matina; Wang, Chih-Ping; Wing, Simon; Lyons, Larry R.; Wolf, Richard A.; Hsu, Tung-Shin

    2012-11-01

    As plasma sheet electrons drift earthward, they get scattered into the loss cone due to wave-particle interactions and the resulting precipitation produces auroral conductance. Realistic electron loss is thus important for modeling the magnetosphere - ionosphere (M-I) coupling and the degree of plasma sheet electron penetration into the inner magnetosphere. In order to evaluate the significance of electron loss, we used the Rice Convection Model (RCM) coupled with a force-balanced magnetic field to simulate plasma sheet transport under different electron loss rates and under self-consistent electric and magnetic field. We used different magnitudes of i) strong pitch angle diffusion everywhere electron loss rate (strong rate) and ii) a more realistic loss rate with its MLT dependence determined by wave activity (MLT rate). We found that electron pressure under the MLT rate is larger compared to the strong rate inside L ∼ 12 RE. The dawn-dusk asymmetry in the precipitating electron energy flux under the MLT rate, with much higher energy flux at dawn than at dusk, agrees better with statistical DMSP observations. High-energy electrons inside L ∼ 8 RE can remain there for many hours under the MLT rate, while those under the strong rate get lost within minutes. Under the MLT rate, the remaining electrons cause higher conductance at lower latitudes; thus after a convection enhancement, the shielding of the convection electric field is less efficient, and as a result, the ion plasma sheet penetrates further earthward into the inner magnetosphere than under the strong rate.

  7. Hf propagation through actively modified ionospheres

    SciTech Connect

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

    1990-01-01

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

  8. Geomagnetic storm effects in the ionospheric E- and F-regions

    NASA Astrophysics Data System (ADS)

    Gordienko, G. I.; Vodyannikov, V. V.; Yakovets, A. F.

    2011-08-01

    Ground-based ionosonde data obtained at Alma-Ata station [φ=43.25°N, λ=76.92°E, Φ=33.47°N, L=1.44) were analysed to study the ionospheric responses of nine intense (Kp≥8, Dst<-100 nT) geomagnetic storms with storm sudden commencement (ssc). The collected data show that the ionospheric responses to the geomagnetic storms are highly complex and variable; however, negative ionospheric disturbances are a common feature of the responses. The occurrence of normal night E2-, E-, F1- and auroral type r (retardation) sporadic Es-layers, which are unusual for Alma-Ata, was observed during most active phase in the Dst index. Employing the International Reference Ionosphere (IRI), the night-time E region electron density Ne was estimated for “quiet” conditions on the epochs of the storm time periods. A direct comparison of the “quiet” and “storm” electron density in the 110-200 km altitude range shows a significant storm-induced increase in Ne that reaches a factor of approximately 10 at the 110 km altitude. The interaction of precipitating energetic neutralised ring current particles with the upper atmosphere during geomagnetic disturbances is assumed to be a possible explanation for the observed night events at this latitude sector.

  9. Electron densities and temperatures in the Venus ionosphere Effects of solar EUV, solar wind pressure and magnetic field

    NASA Technical Reports Server (NTRS)

    Elphic, R. C.; Russell, C. T.; Brace, L. H.

    1985-01-01

    The Venus ionosphere is influenced by variations in both solar EUV flux and solar wind conditions. On the dayside the location of the topside of the ionosphere, the ionopause, is controlled by solar wind dynamic pressure. Within the dayside ionosphere, however, electron density is affected mainly by solar EUV variations, and is relatively unaffected by solar wind variations and associated magnetic fields induced within the ionosphere. The existence of a substantial nightside ionosphere of Venus is thought to be due to the rapid nightward transport of dayside ionospheric plasma across the terminator. Typical solar wind conditions do not strongly affect this transport and consequently have little direct influence on nightside ionospheric conditions, except on occasions of extremely high solar wind dynamic pressure. However, both nightside electron density and temperature are affected by the presence of magnetic field, as in the case of ionospheric holes.

  10. 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.

  11. 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…

  12. Meteorological effects in the lower ionosphere as based on VLF/LF signal observations

    NASA Astrophysics Data System (ADS)

    Rozhnoi, A.; Solovieva, M.; Levin, B.; Hayakawa, M.; Fedun, V.

    2014-04-01

    Very low and low frequency (VLF/LF) data recorded in the Far Eastern stations Petropavlovsk-Kamchatsky (158.92° E, 53.15° N), Yuzhno-Sakhalinsk (142.75° E, 46.95° N) and Yuzhno-Kurilsk (145.861° E, 44.03° N) are investigated to study the meteorological effects in the lower ionosphere. The results demonstrate the sensitivity of the VLF/LF signals to the variations of atmospheric pressure, humidity, wind velocity and temperature, and the VLF/LF record at the station of Yuzhno-Kurilsk is found to be most sensitive to those variations of atmospheric parameters. The region under consideration is characterized by high winter cyclonic activity in midlatitudes and strong summer and autumn typhoon activity in low latitudes. VLF/LF signal variations during 8 tropical cyclones (TCs) with different intensity are considered. Negative nighttime anomalies in the signal amplitude that are most probably caused by TC activity are found for 6 events. Those anomalies are observed during 1-2 days when TCs move inside the sensitivity zones of the subionospheric paths. Perturbations of the VLF signal observed during 2 TCs can be caused by both the TC influence and seismic activity, but no correlation between TC intensity and magnitude of the signal anomalies is found. Spectral analysis of the typhoon-induced disturbed signals revealed the fluctuations with time periods in the range of 7-16 and 15-55 min that corresponds to the range of internal gravity waves periods.

  13. Meteorological effects in the lower ionosphere as based on VLF/LF signal observations

    NASA Astrophysics Data System (ADS)

    Rozhnoi, A.; Solovieva, M.; Levin, B.; Hayakawa, M.; Fedun, V.

    2014-10-01

    Very low and low frequency (VLF/LF) data recorded in the Far Eastern stations Petropavlovsk-Kamchatsky (158.92° E, 53.15° N), Yuzhno-Sakhalinsk (142.75° E, 46.95° N) and Yuzhno-Kurilsk (145.861° E, 44.03° N) are investigated to study the meteorological effects in the lower ionosphere. The results demonstrate the sensitivity of the VLF/LF signals to the variations of atmospheric pressure, humidity, wind velocity and temperature, and the VLF/LF record at the station of Yuzhno-Kurilsk is found to be most sensitive to those variations of atmospheric parameters. The region under consideration is characterized by high winter cyclonic activity in mid-latitudes and strong summer and autumn typhoon activity in low latitudes. VLF/LF signal variations during eight tropical cyclones (TCs) with different intensity are considered. Negative nighttime anomalies in the signal amplitude that are most probably caused by TC activity are found for six events. Those anomalies are observed during 1-2 days when TCs move inside the sensitivity zones of the subionospheric paths. Perturbations of the VLF signal observed during two TCs can be caused by both the TC influence and seismic activity, but no correlation between TC intensity and magnitude of the signal anomalies is found. Spectral analysis of the typhoon-induced disturbed signals revealed the fluctuations with time periods in the range of 7-16 and 15-55 min that corresponds to the range of internal gravity waves periods.

  14. Multi-PLL with two-stage fusion to mitigate ionospheric scintillation effects on GPS receivers

    NASA Astrophysics Data System (ADS)

    Xu, Rui; Liu, Zhizhao; Chen, Wu

    2015-07-01

    Ionospheric scintillation poses a great threat to the reliability and accuracy of Global Positioning System (GPS) in various applications. It can increase tracking errors of the phase-locked loop (PLL) in a GPS receiver and even cause the PLL loss of lock under severe scintillations. To mitigate the effect of scintillation on GPS receivers, especially to reduce the occurrence of loss of lock, a multi-PLL with two-stage fusion (i.e., tracking fusion and output fusion) is proposed in this paper. This algorithm integrates several parallel sub-PLLs with different loop parameters into one channel to track one GPS satellite's signal. Every sub-PLL has its own discriminator, loop filter, carrier numerical controlled oscillator, and a tracking fusion (i.e., the first stage fusion). The tracking fusion of each sub-PLL integrates the Doppler frequency measurements from all other sub-PLLs to detect the state of its own sub-PLL and feeds back reliable Doppler frequency measurements. Simultaneously, the tracking fusion outputs the Doppler frequency measurements to the second stage fusion (i.e., output fusion), which integrates the outputs from all tracking fusions to provide continuous and accurate Doppler frequency measurements for the following positioning/navigation estimator. Performances of the proposed algorithm are tested using real-world GPS data with different levels of scintillations and compared with results from single-PLLs. For three real-world scintillation cases (S4 = 0.26-1.1, σϕ = 0.05-1.49 rad, and average C/N0 = 41.2-45.7 dB Hz), the multi-PLL algorithm performs more robustly than the single-PLLs and is able to keep tracking in all scintillation cases.

  15. High-latitude ionospheric drivers and their effects on wind patterns in the thermosphere

    NASA Astrophysics Data System (ADS)

    Liuzzo, L. R.; Ridley, A. J.; Perlongo, N. J.; Mitchell, E. J.; Conde, M.; Hampton, D. L.; Bristow, W. A.; Nicolls, M. J.

    2015-01-01

    Winds in the thermosphere are highly important for transporting mass, momentum, and energy over the globe. In the high-latitude region, observations show that ion and neutral motions are strongly coupled when the aurora is present but the coupling is less evident when there is no aurora. In this study, we investigate the ability of the Global Ionosphere-Thermosphere Model (GITM) to simulate the mesoscale wind structure over Alaska during a substorm. Thirteen distinct numerical simulations of a substorm event that occurred between 02:00 and 17:00 Universal Time on 24 November 2012 have been performed. Distinct drivers considered include the Weimer and SuperDARN potential patterns and the OVATION Prime and OVATION-SME auroral models. The effects of the boundary between the neutral wind dynamo calculation and the high-latitude imposed electric potential were also considered. Neutral wind velocities and thermospheric temperatures measured by the Scanning Doppler Imager instruments located at three locations in Alaska were compared to GITM simulation results, and electron densities within GITM were compared to data from the Poker Flat Incoherent Scatter Radar. It was found that the different drivers used between multiple simulations lead to various amounts of momentum coupling within the simulation, affecting the accuracy of the modeled neutral and ion flow patterns and the strength of electron precipitation at high latitudes. This affirms that better observations of auroral precipitation and electric fields are required to accurately understand and consistently reproduce the mesoscale neutral wind flow patterns and temperature structure in the high-latitude thermosphere.

  16. 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-.

  17. Initial results from the operation of two argon ion generators in the auroral ionosphere

    NASA Technical Reports Server (NTRS)

    Erlandson, R. E.; Cahill, L. J., Jr.; Pollock, C. J.; Arnoldy, R. L.; Scales, W. A.

    1987-01-01

    Two argon ion generators have been lofted by sounding rockets in order to investigate ion beam dynamics and beam effects on the ionosphere, and auroral electrodynamics during rocket passage over auroral arcs. The ion generators were on a subpayload that was separated from the main payload early in the flight. The main payload conducted the diagnostic measurements during ion beam operations. Evidence of heating of the ionosphere around the subpayload during each ion beam emission is noted.

  18. 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.

  19. Monitoring the ionospheric positioning error with a GNSS dense network

    NASA Astrophysics Data System (ADS)

    Wautelet, Gilles; Lejeune, Sandrine; Warnant, Ren

    2010-05-01

    Local variability in the ionospheric Total Electron Content (TEC) can seriously affect the accuracy of GNSS real-time applications. In relative positioning, users have to compute the vector (called baseline) linking their receiver to a reference station for which the position is accurately known. As long as the ionosphere remains quiet (i.e. a background ionosphere with no local disturbance), the accuracy of relative positioning using phase measurements is of a few cm. The SoDIPE-RTK software developed at the Royal Meteorological Institute of Belgium allows to compute the part of the positioning error only due to the ionosphere (referred later as "ionospheric error") for a given baseline. In practice, baselines considered in this paper are not larger than 40km in order to ensure a successful ambiguity resolution process for both L1 and L2 carriers. More precisely, data analysed in the frame of this work are baselines belonging to the Belgian GPS dense network called Active Geodetic Network (AGN). SoDIPE-RTK has been applied on the whole network during typical ionospheric conditions: quiet, active and stormy. Active conditions refer to disturbed ionosphere due to the occurrence of Traveling Ionospheric Disturbances (TID's) while stormy conditions are relative to extremely disturbed plasma during the occurrence of powerful geomagnetic storms. From this dataset, we extract some descriptive statistics like average, standard deviation, extrema... of the ionospheric error. As expected, this term is centimeter-level during quiet conditions while maximum values are reached during stormy conditions. For a 10km baseline, one can observe ionospheric errors of about 15cm during the occurrence of a winter medium-scale TID (MSTID) and up to 1m during geomagnetic storms. Moreover, the availability of a dense network allows to study the influence of baseline orientation on ionospheric error magnitude. We have analysed two specific cases of moving ionospheric structures: a winter MSTID and an "ionospheric wall" (TEC depletion) caused by an extreme geomagnetic storm. In both cases, equatorwards direction of propagation was clearly visible on polar plots. Indeed, baselines oriented parallel to the direction of propagation of disturbances are more affected by TEC gradients than others. SoDIPE-RTK is therefore a tool which allows not only to assess the effect of ionospheric disturbances on relative positioning but also to monitor propagation patterns of such disturbances while run through a GPS dense network. Finally, we propose a service dedicated to GNSS relative positioning users based on SoDIPE-RTK. Every 15 minutes, each AGN baseline is mapped in a given color ranging from green (quiet conditions) to red (extreme conditions). This easy-to-use application allows registered users to access to local information about current ionospheric conditions on the field.

  20. Characteristics of Pi2 Electric Pulsations at the Ionosphere

    NASA Astrophysics Data System (ADS)

    Ikeda, A.; Yumoto, K.; Shinohara, M.; Nozaki, K.; Yoshikawa, A.; Uozumi, T.; Tokunaga, T.; Hirayama, Y.

    2007-12-01

    At the onset of magnetospheric substorms, impulsive hydromagnetic oscillations occur with period range from 40 to 150 seconds. They are called Pi2 magnetic pulsations and occur globally in the magnetosphere. Pi2 has been studied with arrays of magnetometers on the ground and with in-situ observation by satellites. However Pi2 electric pulsation in the low-latitude ionosphere is not yet clarified sufficiently. Therefore we have focused on measuring Pi2 electric pulsations by an FM-CW radar. In order to detect the ionospheric electric fields we have built an FM-CW (HF) radar at Sasaguri, Fukuoka, Japan (Magnetic Latitude: 23.2 degree, Magnetic Longitude: 199.6 degree). The radar provides us Doppler information of the ionosphere by high-time resolution of 10 sec. When the eastward electric field penetrates into the low- latitude ionosphere, it drifts upward owing to the frozen-in effects of the F-region. In contrast to the penetration of the eastward electric field, the ionosphere drifts downward when the westward electric field penetrates. Thus we can measure the east-west ionospheric electric fields. From our ionospheric radar observation, Pi2 electric pulsation of about 0.2 mV/m amplitude can be identified in nightside at Nov.6, 2003. We also compared the Pi2 with geomagnetic field data obtained from Circum-pan Pacific Magnetic Network (CPMN) stations. As a result, we found a phase lag between the Pi2 electric pulsation and mightside magnetic Pi2 pulsation at Kujyu (KUJ; M. Lat. 23.6 degree, M. Lon. 203.2 degree).

  1. The effect of time ordering revisited

    SciTech Connect

    Rosato, J.; Boland, D.; Capes, H.; Marandet, Y.; Stamm, R.

    2008-10-22

    The effects of time ordering on line shapes are investigated for the dynamic ionic broadening of the Lyman alpha line in hydrogen plasmas. The difference between calculations with and without time ordering is calculated for an electric field created by a single particle, and for a thermal average over plasma configurations with moderate temperature and density.

  2. The effect of magnetospheric erosion on mid- and high-latitude ionospheric flows

    NASA Astrophysics Data System (ADS)

    Freeman, M. P.; Southwood, D. J.

    1988-05-01

    Simple quasi-global models of ionospheric flow are described, with the aim of elucidating the potential signatures of magnetopause erosion and allied phenomena at ionospheric heights. Erosion implies the addition of flux to the polar cap and consequently a reduction in the latitude of the polar cap boundary. The possibility of localized erosion over part of the dayside is considered. Systematic turning of the midlatitude flow can result to the west and east of the erosion region. After erosion, the boundary must eventually return poleward as stress is released on the nightside. The pattern associated with polar cap boundary reconfiguration is examined. This can give rise to substantial equatorward and tailward flows on closed field lines. Data from the SABRE radar system during a period in which spacecraft measurements have shown erosion is occurring are presented. Various features shown in the present models are seen.

  3. The Effects of Magnetic Anomalies Discovered at Mars on the Structure of the Martian Ionosphere and the Solar Wind Interaction as Follows from Radio Occultation Experiments

    NASA Technical Reports Server (NTRS)

    Ness, N. F.; Acuna, M. H.; Connerney, J. E. P.; Cloutier, P.; Kliore, A. J.; Breus, T. K.; Krymskii, A. M.; Bauer, S. J.

    1999-01-01

    The electron density distribution in the ionosphere of nonmagnetic (or weakly magnetized) planet depends not only on the solar ultraviolet intensity, but also on the nature of the SW interaction with this planet. Two scenarios previously have been developed based on the observations of the bow shock crossings and on the electron density distribution within the ionosphere. According to one of them Mars has an intrinsic magnetosphere produced by a dipole magnetic field and the Martian ionosphere is protected from the SW flow except during "overpressure conditions, when the planetary magnetic field can not balance the SW dynamic pressure. In the second scenario the Martian intrinsic magnetic dipole field is so weak that Mars has mainly an induced magnetosphere and a Venus-like SW/ionosphere interaction. Today the possible existence of a sufficiently strong global magnetic field that participates in the SW/Mars interaction can no longer be supported. The results obtained by the Mars-Global-Surveyor (MGS) space-craft show the existence of highly variable, but also very localized magnetic fields of crustal origin at Mars as high as 400-1500 nT. The absence of the large-scale global magnetic field at Mars makes it similar to Venus, except for possible effects of the magnetic anomalies associated with the remnant crustal magnetization. However the previous results on the Martian ionosphere obtained mainly by the radio occultation methods show that there appears to be a permanent existence of a global horizontal magnetic field in the Martian ionosphere. Moreover the global induced magnetic field in the Venus ionosphere is not typical at the solar zenith angles explored by the radio occultation methods. Additional information is contained in the original extended abstract.

  4. 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.

  5. Comparison of Ionospheric and Thermospheric Effects During Two High Speed Stream Events

    NASA Astrophysics Data System (ADS)

    Verkhoglyadova, O. P.; Tsurutani, B.; Mannucci, A. J.; Paxton, L.; Mlynczak, M. G.; Hunt, L. A.; Echer, E.

    2013-12-01

    We analyze two CIR-HSS events during ascending phase of the current solar cycle. The first event occurred on 8-12 May 2012 and was characterized by a large CIR and intense High Intensity Long Duration Continuous Auroral Activity (HILDCAA). Long-duration moderate geomagnetic storm (Dst ~ -50 nT) occurred during this event. The second event on 29 April - 4 May 2011 had a large CIR and extended HSS, but weaker geomagnetic activity. We focus on understanding differences and similarities of the magnetosphere-ionosphere-thermosphere coupling during these two events. We will use a suite of ground-based and satellite measurements to create a comprehensive picture of the events. Evolution of the polar cap convection pattern is analyzed based on SuperDARN data. DMSP/SSUSI far ultraviolet measurements provide information on airglow intensity and characteristics of the F-region of the dusktime ionosphere. The GPS total electron content (TEC) database and JPL's Global Ionospheric Maps (GIM) are used to study vertical TEC (VTEC) for different local times and latitude ranges. We discuss dynamics of VTEC above individual ground GPS sites with respect to local time and latitude ranges. We analyze the TIMED/SABER zonal flux of nitric oxide (NO) infrared cooling radiation and auroral heating throughout the events. Global dynamics of the column density ratio ΣO/N2 is studied based on TIMED/GUVI measurements. Our results will advance understanding of the ionosphere-thermosphere response to external forcing and help future forecasting efforts.

  6. A review of vertical coupling in the Atmosphere-Ionosphere system: Effects of waves, sudden stratospheric warmings, space weather, and of solar activity

    NASA Astrophysics Data System (ADS)

    Yiğit, Erdal; Koucká Knížová, Petra; Georgieva, Katya; Ward, William

    2016-04-01

    This brief introductory review of some recent developments in atmosphere-ionosphere science is written for the "Vertical Coupling Special Issue" that is motivated by the 5th IAGA/ICMA/SCOSTEP Workshop on Vertical Coupling in the Atmosphere-Ionosphere System. Basic processes of vertical coupling in the atmosphere-ionosphere system are discussed, focusing on the effects of internal waves, such as gravity waves and solar tides, sudden stratospheric warmings (SSWs), and of solar activity on the structure of the atmosphere. Internal waves play a crucial role in the current state and evolution of the upper atmosphere-ionosphere system. SSW effects extend into the upper atmosphere, producing changes in the thermospheric circulation and ionospheric disturbances. Sun, the dominant energy source for the atmosphere, directly impacts the upper atmosphere and modulates wave-induced coupling. The emphasis is laid on the most recent developments in the field, while giving credits to older works where necessary. Various international activities in atmospheric vertical coupling, such as SCOSTEP's ROSMIC project, and a brief contextual discussion of the papers published in the special issue are presented.

  7. Ionospheric and Thermospheric Effects During the Initial Radiative Phase of the Bastille Day Event

    NASA Astrophysics Data System (ADS)

    Meier, R. R.; Drob, D. P.; Nicholas, A. C.; Bishop, J.; Picone, J. M.; Thonnard, S. E.; Dymond, K. F.; Budzien, S. A.; Lean, J.; Mariska, J. T.; Huba, J. D.; Joyce, G.; Warren, H. P.; Judge, D. L.

    2001-05-01

    Increases in the solar EUV and X-ray irradiance during a solar flare can produce enhanced ionization and heating in the terrestrial ionosphere. The resulting energetic photoelectrons in turn cause increases in the far ultraviolet (FUV) dayglow (100 - 150 nm). Enhancements of some 50 per cent had previously been detected in OGO-4 nadir-viewing data [C B Opal, Space Research XIII, 797, 1973]. Similar enhancements have now been seen in the FUV limb-viewing dayglow observations from the ARGOS satellite during the Bastille Day flare (July 14, 2000). Because extinction of the FUV dayglow by O2 prevents seeing below 140 km tangent altitude on the limb, increases in the dayglow above that altitude must be caused by the component of the flare spectral irradiance which is deposited there, namely at wavelengths greater than 20 nm. This conclusion is corroborated by the observation of the flare at 30.3 nm made by the SEM instrument on the SOHO satellite. We study this solar-ionospheric connection using a modified version of the NRL solar spectrum as input to the SAMI2 ionospheric model, and also calculate thermospheric heating rates for this event.

  8. 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.

  9. Effects of Energetic Solar Emissions on the Earth-Ionosphere Cavity of Schumann Resonances

    NASA Astrophysics Data System (ADS)

    Sátori, Gabriella; Williams, Earle; Price, Colin; Boldi, Robert; Koloskov, Alexander; Yampolski, Yuri; Guha, Anirban; Barta, Veronika

    2016-03-01

    Schumann resonances (SR) are the electromagnetic oscillations of the spherical cavity bounded by the electrically conductive Earth and the conductive but dissipative lower ionosphere (Schumann in Z Naturforsch A 7:6627-6628, 1952). Energetic emissions from the Sun can exert a varied influence on the various parameters of the Earth's SR: modal frequencies, amplitudes and dissipation parameters. The SR response at multiple receiving stations is considered for two extraordinary solar events from Solar Cycle 23: the Bastille Day event (July 14, 2000) and the Halloween event (October/November 2003). Distinct differences are noted in the ionospheric depths of penetration for X-radiation and solar protons with correspondingly distinct signs of the frequency response. The preferential impact of the protons in the magnetically unshielded polar regions leads to a marked anisotropic frequency response in the two magnetic field components. The general immunity of SR amplitudes to these extreme external perturbations serves to remind us that the amplitude parameter is largely controlled by lightning activity within the Earth-ionosphere cavity.

  10. The effect of downward electron heat flow and electron cooling processes in the high-latitude ionosphere

    NASA Astrophysics Data System (ADS)

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

    2011-10-01

    The electron energy balance in the ionosphere is affected by numerous local heating and cooling processes, as well as by transport processes. The thermal electrons gain energy from photoelectrons, auroral electrons, hot thermal ions, and a downward flow of heat from high altitudes. The thermal electrons lose energy in elastic collisions with ions and neutrals (N2, O2, O, He, H) and in inelastic collisions with neutrals, including rotational excitation of N2 and O2, vibrational excitation of N2 and O2, excitation of the fine structure levels of atomic oxygen, and electronic excitation of atomic oxygen, e.g., O(1S) and O(1D). The transport processes include thermal conduction and thermoelectric heat flow. Recently, new electron cooling rates have been calculated that are substantially different from those in current use, which are more than thirty years old. Therefore, model simulations were conducted that show the impact that these new cooling rates have on the electron temperatures and ion densities in the mid- and high-latitude ionosphere. It was found that, while several of the new cooling rates differ significantly from the old rates, collectively these differences largely cancel each other, with the result that the impact of the new rates on the ionospheric temperatures and densities is small. Also, a possible important source of heat for the thermal electrons in the polar cap is the downward flow of heat that results from the interaction of the escaping polar wind electrons with the relatively hot polar rain, squall, and drizzle. This electron heat source has typically been ignored in the past due to a lack of measurements, but recent work based on satellite measurements has made it possible to estimate values of the downward electron heat flow in the polar cap. Therefore, model simulations were also conducted to determine the effect of a downward electron heat flow on the high-latitude ionosphere. We found that in many cases the addition of a heat flow does have a large impact on the F-region temperatures and densities, sometimes increasing the total electron content (TEC) by 50% or more; topside densities may be increased by a factor of 5. The effects of the new cooling rates and downward heat flow were determined for a wide range of geophysical conditions.

  11. 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.

  12. Calculating Second-Order Effects in MOSFET's

    NASA Technical Reports Server (NTRS)

    Benumof, Reuben; Zoutendyk, John A.; Coss, James R.

    1990-01-01

    Collection of mathematical models includes second-order effects in n-channel, enhancement-mode, metal-oxide-semiconductor field-effect transistors (MOSFET's). When dimensions of circuit elements relatively large, effects neglected safely. However, as very-large-scale integration of microelectronic circuits leads to MOSFET's shorter or narrower than 2 micrometer, effects become significant in design and operation. Such computer programs as widely-used "Simulation Program With Integrated Circuit Emphasis, Version 2" (SPICE 2) include many of these effects. In second-order models of n-channel, enhancement-mode MOSFET, first-order gate-depletion region diminished by triangular-cross-section deletions on end and augmented by circular-wedge-cross-section bulges on sides.

  13. 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.

  14. Effects of a solar wind pressure pulse in the magnetosphere and in the ionosphere

    NASA Astrophysics Data System (ADS)

    Juusola, Liisa; Andreeova, Katerina; Palmroth, Minna; Amm, Olaf

    2010-05-01

    On 17 July 2005, an earthward bound north-south oriented magnetic cloud and its sheath were observed by the Advanced Composition Explorer (ACE), the Solar and Heliospheric Observatory (SoHO), and the Wind solar wind monitors. A steplike increase of the solar wind dynamic pressure was related to the leading edge of the sheath. A timing analysis between the three spacecraft revealed that this front was not aligned with GSE y axis, but tilted by an angle of about 55 towards the x axis. Hence, the first contact with the magnetosphere occured on the dawnside rather than at the subsolar point. Fortunately, Cluster, Double Star 1, and Geotail happened to be distributed close to the magnetopause in this region, which made it possible to closely monitor the motion of the magnetopause. When the pressure pulse impacted the magnetosphere, the magnetopause was perceived first to move inward and then immediatelly correct the overshoot by slightly expanding again such that it ended up between the Cluster constellation with Double Star 1 inside the magnetosphere and Geotail in the magnetosheath. In the ionosphere, the AE index showed a relatively weak enhancement with a peak of less than 200 nT. This enhancement lasted for about 10 minutes and coincided with the inward and subsequent outward motion of the magnetopause observed by the magnetospheric spacecraft. The ground-based International Monitor for Auroral Geomagnetic Effects (IMAGE) magnetometer network was also located on the dawn side during the arrival of the pressure pulse. The 1-D equivalent currents showed a peak of eastward current in the region covered by IMAGE, where the westward electrojet generally dominates at that time. After 10 minutes, the region of weakening eastward current was divided in two by the recovering westward electrojet. The 2-D equivalent currents further revealed that while the region of eastward current expanded from the east, the recovery of the westward electrojet began from the western edge of IMAGE field-of-view. We suggest that these observations could be interpreted as a temporary and local reversal of the direction of the plasma sheet convection due to the compression of the magnetosphere.

  15. Artificial defocusing lens in ionosphere

    NASA Astrophysics Data System (ADS)

    Boyko, G. N.; Vaskov, V. V.; Golyan, S. F.; Gurevich, A. V.; Dimant, Y. S.; Zyuzkin, V. A.; Kim, V. Y.; Komrakov, G. P.; Lobacheviskiy, L. A.; Migulin, V. V.

    1984-10-01

    Strong defocusing of perturbing radio waves is detected, indicating the creation of an effective defocusing lens in the ionosphere. Modess in which there is not anomalous absorption are employed in order to isolate the defocusing effects unambiguously. The experimental setup incorporates a 300 MW SURG heating system with a narrow radiation pattern. The concentration perturbations are diagnosed in the vertical sounding mode at 8 frequencies by means of a Doppler system. The experimental results were obtained during May and July 1983 under daytime conditions. The amplitude and Doppler frequency shift behavior of the probe wave is analyzed, and the defocusing coefficient is computed as a function of the frequency of the probe wave and power of the heating wave. The artificial lens detected results in significant attenuation of radio waves passing through it.

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

    PubMed

    Coates, Andrew J

    2009-02-28

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

  17. Ionospheric imaging in Africa

    NASA Astrophysics Data System (ADS)

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

    2014-01-01

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

  18. 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)

  19. The Maunder Minimum Ionosphere

    NASA Astrophysics Data System (ADS)

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

    2004-12-01

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

  20. Effect of meteoroid ablation in the chemistry of the martian ionosphere

    NASA Astrophysics Data System (ADS)

    Pandya, B.; Haider, S.

    2014-07-01

    Comets release streams of dust particles at their perihelion distance due to the normal process of gas ejection. These particles of micron-size or larger are called micro-meteoroids and the meteoroids leave the comet nucleus at a speed of less than the orbital speed of the comets. When the planet Mars passes through such a meteoroid dust stream periodically, the meteoroids and micrometeoroids enter the martian atmosphere and encounter a suitable density of atmospheric gases, such as O_2, CO_2, CO, O, O_3, NO, N_2, to ablaze. This ablation produces ionization in the lower ionosphere at an altitude between 60-120 km. We use a coupled chemical model to calculate the density of abundant meteoric ions Mg, Fe, and Si with their neutrals and their compositions with atmospheric gases. We have observed that comets P/2003 WC7 (LINEAR Catalina) and 10P/ Tempel 2 intersected the orbit of Mars on 18 April 2004 and 11 May 2005, respectively. The meteoroids of fluxes 4.0×10^{-15} and 8.3×10^{-16} cm^{-2} s^{-1} and of masses 4.5×10^{-7} g and 1.0×10^{-3} g have produced a third ionospheric layer of electron densities, in good agreement with the electron density profiles observed by Mars Express and Mars Global Surveyor on April 18, 2004 and 11 May 11, 2005, respectively. The densities of 21 ions (CO_2+, O_2+, CO+, O+, NO+, N_2+, Mg+, Fe+, Si+, MgO+, FeO+, SiO+, MgCO_2+, MgO_2+, FeCO_2+, FeO_2+, SiCO_2+, SiO_2+, MgN_2+, FeN_2+, and SiN_2+) have been computed self-consistently for both days. It is observed that the lower ionosphere of Mars is strongly dependent on the incoming velocity, mass, and flux of the meteoroids. We have calculated a total ion production rate and a total ion density for meteoroids of with sizes from 10 g to 10^{-12} g entering the martian atmosphere with initial speeds of 10 km/s and 18 km/s. Micro-meteoroids with an incoming speed of 18 km/sec and mass between 10^{-5} g to 10^{-12} g ablaze and produce a significantly high total ion density between ˜0.5×10^6 cm^{-3} to ˜6×10^6 cm^{-3}. If the incoming speed of the meteoroid decreases to 10 km/s, the total ion density is between 5×10^{5} cm^{-3} to 2×10^6 cm^{-3}, which indicates that the ion deposition in the Martian ionosphere depends upon the incoming speed of the meteoroids. The total ion density calculated for the meteoroids of mass between 10^{-4} g to 10 g is 2×10^1 cm^{-3} - 0.5×10^6 cm^{-3} for both incoming speeds. We have combined the chemistry of the impact of the meteoroids and the solar X-ray and EUV radiation in our model which is predicting three plasma layers in the martian ionosphere. Our effort is to balance our theoretical model of the meteoric chemistry with the observed ionospheric electron density.

  1. Model study of the effects of gravity wave dissipation on the thermosphere and ionosphere from deep convection worldwide

    NASA Astrophysics Data System (ADS)

    Vadas, Sharon; Liu, Hanli

    In this paper, we discuss the methods and results of a global modeling study for the effect of deep convection on the thermosphere and ionosphere through the dissipation of atmospheric gravity waves (GWs). The selected time periods are 15-27 June 2009, during the recent extreme solar minimum, and 15-27 June 2000, during the recent solar maximum. The convective plumes which overshot the tropopause are identified from IR images obtained by 5 satellites covering the Earth during each period. We model the excitation of GWs from these plumes, and ray trace them into the thermosphere using our ray trace model which has been upgraded to span the Earth. We then calculate the forcings/heatings/coolings which result when and where these GWs dissipate in the thermosphere. We input these forcings/heatings/coolings into the global TIME-GCM, and re-run the model. In this paper, we discuss these methods and models in detail. We then discuss how the thermosphere and ionosphere responded to the dissipation of these convectively-generated GWs worldwide. We show that the responses propagate westward due to wind filtering by tides in the lower thermosphere. We also show that the neutral temperature and wind perturbations are larger during extreme solar minimum than during solar maximum.

  2. 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.

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

    SciTech Connect

    Basak, Tamal; Pal, S.; Chakrabarti, S. K.

    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.

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

    NASA Astrophysics Data System (ADS)

    Basak, Tamal; Chakrabarti, S. K.; Pal, S.

    2010-10-01

    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°23', Longitude 77°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.

  5. Effects of modeled ionospheric conductance and electron loss on self-consistent ring current simulations during the 5-7 April 2010 storm

    NASA Astrophysics Data System (ADS)

    Chen, Margaret W.; Lemon, Colby L.; Guild, Timothy B.; Keesee, Amy M.; Lui, Anthony; Goldstein, Jerry; Rodriguez, Juan V.; Anderson, Phillip C.

    2015-07-01

    We investigate the effects of different ionospheric conductance and electron loss models on ring current dynamics during the large magnetic storm of 5-7 April 2010 using the magnetically and electrically self-consistent Rice Convection Model-Equilibrium (RCM-E). The time-varying RCM-E proton distribution boundary conditions are specified using a combination of TWINS 1 and 2 ion temperature maps and in situ THEMIS and GOES spectral measurements in the plasma sheet. With strong electron pitch-angle diffusion, the simulated equatorial ring current electron pressure is weak with (1) uniform conductance or (2) conductance based on parameters from the International Reference Ionosphere 2007 and the feedback of simulated precipitating electrons. With the Chen and Schulz electron loss model that includes strong diffusion in the plasma sheet and weak diffusion in the plasmasphere, the stormtime equatorial RCM-E electron pressure is enhanced in the inner magnetosphere from midnight through dawn to the dayside. The enhancement extends to lower geocentric distance with uniform conductance than with the more realistic ionospheric conductance model due to electric field shielding effects. Electron losses affect not only the simulated electron pressures, but through magnetospheric-ionospheric coupling, the redistributed electric and magnetic fields affect the ring current proton transport. The simulations reproduced features observed by in situ magnetic field and proton flux data, and TWINS global ENA observations. The simulated stormtime ring current energization can vary significantly depending on the ionospheric conductance and electron loss model used. Thus, it is important to incorporate realistic descriptions of ionospheric conductance and electron losses in inner magnetospheric models.

  6. Electron Impact Dissociative Excitation of Ionospheric Ions: Rate Coefficients and Implications for Ionospheric Studies.

    NASA Astrophysics Data System (ADS)

    Sheehan, C. H.; St.-Maurice, J.

    2004-05-01

    A survey of the literature indicates that dissociative recombination is seemingly the only interaction between molecular ions and electrons that is considered in ionospheric studies. Dissociative recombination begins with a collision between an electron and a molecular ion in which the ion captures the electron, resulting in the formation of an unstable neutral molecule that subsequently stabilizes by dissociating. In the dissociative recombination of an arbitrary molecular ion AB+; AB+ + e yields A* + B. Being effectively the only electron loss mechanism in planetary ionospheres, dissociative recombination is a very significant process. Owing to the typically high reaction rates, dissociative recombination in general is the most important interaction between molecular ions and electrons in planetary ionospheres. We discuss at length the dissociative recombination of ionospheric ions in a topical review paper (2003ja010132) that will appear in the near future in JGR: Space Physics. Dissociative recombination is, however, not the only possible interaction. In recent years, molecular physicists have made considerable progress in the study of a variety of molecular ion-electron processes both theoretically and experimentally. One of these processes in particular, electron impact dissociative excitation, is potentially of considerable significance for ionospheric studies. In the dissociative excitation of an arbitrary molecular ion AB+; AB+ + e yields A* + B+ + e. Experiments have consistently shown that as collision energy increases, dissociative excitation cross sections begin to dominate over dissociative recombination cross sections. Like dissociative recombination, dissociative excitation is a source of excited atoms and so both processes will contribute to emissions. Unlike dissociative recombination, dissociative excitation is a source of atomic ions and after a dissociative excitation interaction there is still a free electron. These differences have potential implications for a variety of studies, including those which involve ionospheric composition, and those which involve electron cooling rates. Using published experimental electron impact dissociative excitation cross sections for NO+, O2+, and N2+ we have calculated both temperature dependent and energy dependent reaction rates for the dissociative excitation of these species of ions. These calculations, in conjunction with our previous work on the dissociative recombination of ionospheric ions, have allowed us to estimate dissociative excitation to dissociative recombination branching ratios for these species of ions for both ground state and vibrationally excited ions. We have found that as collision energies increase, dissociative excitation rates can dominate dissociative recombination rates by up to two orders of magnitude. We will present the results of our reaction rate and branching ratio calculations as well as a discussion of possible implications.

  7. Role of ionospheric conductance in magnetosphere-ionosphere coupling

    NASA Astrophysics Data System (ADS)

    Bhattacharya, Tapas

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

  8. Presentation order effects in product taste tests.

    PubMed

    Dean, M L

    1980-05-01

    Presentation order in paired-comparison testing was varied to measure the impact of primacy versus recency effects on consumer product evaluations. Overall preference and product rating scores were gathered for 1196 male and female Ss aged 13--49 years in two consumer research studies covering 11 taste tests. 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. PMID:7381797

  9. MLT Asymmetries in the Magnetospheric Wave Distribution and Their Effect on Ionospheric Conductivity and Global Transport

    NASA Astrophysics Data System (ADS)

    Thorne, R. M.; Li, W.; Bortnik, J.; Ni, B.; Jordanova, V.; Kletzing, C.; Kurth, W. S.; Hospodarsky, G. B.; Angelopoulos, V.

    2014-12-01

    Diffuse auroral precipitation is the major source of ionospheric conductivity at high latitudes, and the resulting global distribution of enhanced conductivity affects the penetration of magnetospheric electric fields and plasma transport into the inner magnetosphere. Recent work has demonstrated that diffuse auroral precipitation is caused by resonant scattering of plasma sheet electrons due to a combination of both electrostatic electron cyclotron harmonic waves and electromagnetic whistler mode chorus emissions. Each class of wave is excited, predominantly on the dawn side of the magnetosphere, following the convective injection and gradient drifting of plasma sheet electrons into the inner magnetosphere. During geomagnetically active periods, the resultant electron scattering can approach the limit of strong diffusion, and the timescale for scattering loss into the atmosphere becomes shorter than the time for transport of plasma to the dayside. This leads to a pronounced day/night asymmetry in the diffuse auroral precipitation and a localized enhancement in conductivity in the post midnight sector. Quantifying the rate of diffuse auroral scattering by each class of wave is therefore imperative for understanding the global distribution of enhanced ionospheric conductivity and its non-linear feedback on plasma transport in the inner magnetosphere. Recent attempts to model the observed global distribution of waves and the associated pattern of electron precipitation will be discussed.

  10. 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).

  11. 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.

  12. Topside Ionospheric Sounder for CubeSats

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  13. Effect of dust on the ionosphere of 67P/Churyumov-Gerasimenko

    NASA Astrophysics Data System (ADS)

    Vigren, E.; Galand, M.; Lavvas, P.; Wahlund, J.-E.; Eriksson, A. I.

    2014-04-01

    The ESA Rosetta mission is a unique cometary mission consisting both of an orbiter and a lander. The orbiter will follow comet 67P/Churyumov- Gerasimenko (67P) closely from August 2014 to the end of the nominal mission in December 2015. The comet passes perihelion in August 2015, at heliocentric distance of ~1.3 AU. At that stage 67P is expected to be actively outgassing. The gas, dominated by H2O, carries with it dust particles to the coma and for 67P, near perihelion, the dust-to-gas mass emission ratio is anticipated to exceed 1. The well-developed coma/ionosphere, will be probed in situ e.g. by the dual Langmuir probe (LAP) [1] and the Mutual Impedance Probe (MIP) [2], which are parts of the Rosetta Plasma Consortium (RPC) [3], and by the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA) [4], providing e.g., electron and ion number densities down to cometocentric distances of ~5-20 km. We present a model of the ionization balance in the diamagnetic cavity of 67P near perihelion. The model builds upon an earlier presented pure gasphase model [5]. The updated model takes into account gas-dust interactions. We aim in particular to qualitatively address the potential role of grains in the ionization balance and discuss the possibility of a significant level of electron depletion due to electron attachment to grains of different sizes. The study is in part motivated by the discovery of a pronounced level of electron depletion in the plume of Enceladus, which has been attributed to nanograin charging [6,7]. On the one hand we argue that grains with radii of ~ 100 nm and more are unlikely to significantly affect the overall ionospheric particle balance of 67P at least for cometocentric distances >10 km. On the other hand, our simulations suggest that if nanograins with radii in the 1-3 nm range are as ubiquitous (~1% with respect to the gas in terms of mass) in the coma of 67P as in the Enceladus plume a pronounced level of electron depletion can prevail up to cometocentric distances of several tens of km, possibly throughout the diamagnetic cavity. The results of our simulations may prove useful in the interpretation of scientific data returned from individual instruments of the Rosetta orbiter as well as in inter-instrumental data comparisons. At the same time, in situ measurements will be used for driving the model after which model-observation comparisons will serve as a good test of our understanding of the key processes affecting the ionospheric particle balance of 67P in the near nucleus surrounding.

  14. Influence of water vapour on the height distribution of positive ions, effective recombination coefficient and ionisation balance in the quiet lower ionosphere

    NASA Astrophysics Data System (ADS)

    Barabash, V.; Osepian, A.; Dalin, P.

    2014-03-01

    Mesospheric water vapour concentration effects on the ion composition and electron density in the lower ionosphere under quiet geophysical conditions were examined. Water vapour is an important compound in the mesosphere and the lower thermosphere that affects ion composition due to hydrogen radical production and consequently modifies the electron number density. Recent lower-ionosphere investigations have primarily concentrated on the geomagnetic disturbance periods. Meanwhile, studies on the electron density under quiet conditions are quite rare. The goal of this study is to contribute to a better understanding of the ionospheric parameter responses to water vapour variability in the quiet lower ionosphere. By applying a numerical D region ion chemistry model, we evaluated efficiencies for the channels forming hydrated cluster ions from the NO+ and O2+ primary ions (i.e. NO+.H2O and O2+.H2O, respectively), and the channel forming H+(H2O)n proton hydrates from water clusters at different altitudes using profiles with low and high water vapour concentrations. Profiles for positive ions, effective recombination coefficients and electrons were modelled for three particular cases using electron density measurements obtained during rocket campaigns. It was found that the water vapour concentration variations in the mesosphere affect the position of both the Cl2+ proton hydrate layer upper border, comprising the NO+(H2O)n and O2+(H2O)n hydrated cluster ions, and the Cl1+ hydrate cluster layer lower border, comprising the H+(H2O)n pure proton hydrates, as well as the numerical cluster densities. The water variations caused large changes in the effective recombination coefficient and electron density between altitudes of 75 and 87 km. However, the effective recombination coefficient, ?eff, and electron number density did not respond even to large water vapour concentration variations occurring at other altitudes in the mesosphere. We determined the water vapour concentration upper limit at altitudes between 75 and 87 km, beyond which the water vapour concentration ceases to influence the numerical densities of Cl2+ and Cl1+, the effective recombination coefficient and the electron number density in the summer ionosphere. This water vapour concentration limit corresponds to values found in the H2O-1 profile that was observed in the summer mesosphere by the Upper Atmosphere Research Satellite (UARS). The electron density modelled using the H2O-1 profile agreed well with the electron density measured in the summer ionosphere when the measured profiles did not have sharp gradients. For sharp gradients in electron and positive ion number densities, a water profile that can reproduce the characteristic behaviour of the ionospheric parameters should have an inhomogeneous height distribution of water vapour.

  15. Investigations into the properties, conditions, and effects of the ionosphere. Technical report, 4 December 1986-3 December 1987

    SciTech Connect

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

    1988-01-15

    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.

  16. Ionospheric Data Assimilation from a Data Provider's Perspective

    NASA Astrophysics Data System (ADS)

    Schaefer, R. K.; Paxton, L. J.; Bust, G.; Zhang, Y.; Romeo, G.; Comberiate, J.; Gelinas, L. J.

    2014-12-01

    The Ionosphere/Thermosphere system is a very dynamic and complex medium to model. Given sufficient data and proper data handling, assimilative models can give a good representation of this system. One good dataset for this purpose comes from UV imagers on spacecraft. In particular, the Oxygen recombination emission (135.6 nm) and the Nitrogen Lyman-Birge Hopfield band (both 140-150 nm and 165-180 nm) are being collected by instruments on the NASA TIMED/GUVI and DMSP/SSUSI instruments. Similar UV data will also be available in the future from the ICON and GOLD missions. Currently, the Air Force is using the oxygen emission to infer ionospheric electron densities in the USU GAIM model for ionospheric forecasts. We have also been integrating data for the IDA4D model assimilation (Bust et al, 2007). As the data product designer for these UV products, we have an unique perspective on issues related to assimilating this data. These issues concern model resolution scales (Schunk, et al, 2011), filtering of noisy data, and handling of second order effects. We will discuss our experience with these issues and point out some future directions for assimilation of UV data. Bust, G., Crowley, G., Curtis, N., Reynolds, A., Paxton, L., Coker, C., Bernhardt, P. "IDA4D - a new ionospheric imaging algorithm using non-linear ground-based and spaced- based data sources", American Geophysical Union, Fall Meeting 2007, abstract #SA11B-06. Schunk, R.W., Scherliess, L., and Thompson, D.C., 2011 "Ionospheric Data Assimilation: Problems Associated with Missing Physics", Aeronomy of the Earth's Atmosphere and Ionosphere. IAGA Special Sopron Book Series Volume 2, pp 437-442.

  17. Plasma effects of active ion beam injections in the ionosphere at rocket altitudes

    NASA Technical Reports Server (NTRS)

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

    1992-01-01

    Data from ARCS rocket ion beam injection experiments are primarily discussed. There are three results from this series of active experiments that are of particular interest in space plasma physics. These are the transverse acceleration of ambient ions in the large beam volume, the scattering of beam ions near the release payload, and the possible acceleration of electrons very close to the plasma generator which produce intense high frequency waves. The ability of 100 ma ion beam injections into the upper E and F regions of the ionosphere to produce these phenomena appear to be related solely to the process by which the plasma release payload and the ion beam are neutralized. Since the electrons in the plasma release do not convect with the plasma ions, the neutralization of both the payload and beam must be accomplished by large field-aligned currents (milliamperes/square meter) which are very unstable to wave growth of various modes.

  18. The effect of the solar cycle on the maintenance of the nightside ionosphere of Venus

    NASA Technical Reports Server (NTRS)

    Kliore, Arvydas J.; Luhmann, Janet G.; Zhang, Martina H. G.

    1991-01-01

    The behavior of the Venus nightside ionosphere at solar maximum and solar minimum is discussed based on Pioneer Venus radio occultation measurements. Although some solar maximum measurements are similar to those observed at minimum, which have an average peak density of about 7000/cu cm, others show much higher peak densities, reaching values of about 40,000/cu cm. These elevated peak densities also occur at higher altitudes. The integrated electron column densities for these measurements indicate the presence of substantial ionization above the main peak. The magnitudes of both the peak density and the integrated content above the peak are anticorrelated with the solar wind dynamic pressure, indicating that these enhancements during solar maximum are due to transterminator transport of O(+) ions from the dayside. The resulting ionization peak can be many times the concentration produced by energetic electron fluxes impacting the neutral atmosphere on the nightside.

  19. 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.

  20. 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.

  1. 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.

  2. Ionospheric data assimilation and forecasting during storms

    NASA Astrophysics Data System (ADS)

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

    2016-01-01

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

  3. LETTER: Effects of mobility on ordering dynamics

    NASA Astrophysics Data System (ADS)

    Baronchelli, Andrea; Pastor-Satorras, Romualdo

    2009-11-01

    Models of ordering dynamics allow us to understand natural systems in which an initially disordered population homogenizes some traits via local interactions. The simplest of these models, with wide applications ranging from evolutionary to social dynamics, are the Voter and Moran processes, usually defined in terms of static or randomly mixed individuals that interact with a neighbor to copy or modify a discrete trait. Here we study the effects of diffusion in Voter/Moran processes by proposing a generalization of ordering dynamics in a metapopulation framework, in which individuals are endowed with mobility and diffuse through a spatial structure represented as a graph of patches upon which interactions take place. We show that diffusion dramatically affects the time to reach the homogeneous state, independently of the underlying network's topology, while the final consensus emerges through different local/global mechanisms, depending on the mobility strength. Our results highlight the crucial role played by mobility in ordering processes and set up a general framework that allows its effect to be studied on a large class of models, with implications in the understanding of evolutionary and social phenomena.

  4. Developing an Error Model for Ionospheric Phase Distortions in L-Band SAR and InSAR Data

    NASA Astrophysics Data System (ADS)

    Meyer, F. J.; Agram, P. S.

    2014-12-01

    Many of the recent and upcoming spaceborne SAR systems are operating in the L-band frequency range. The choice of L-band has a number of advantages especially for InSAR applications. These include deeper penetration into vegetation, higher coherence, and higher sensitivity to soil moisture. While L-band SARs are undoubtedly beneficial for a number of earth science disciplines, their signals are susceptive to path delay effects in the ionosphere. Many recent publications indicate that the ionosphere can have detrimental effects on InSAR coherence and phase. It has also been shown that the magnitude of these effects strongly depends on the time of day and geographic location of the image acquisition as well as on the coincident solar activity. Hence, in order to provide realistic error estimates for geodetic measurements derived from L-band InSAR, an error model needs to be developed that is capable of describing ionospheric noise. With this paper, we present a global ionospheric error model that is currently being developed in support of NASA's future L-band SAR mission NISAR. The system is based on a combination of empirical data analysis and modeling input from the ionospheric model WBMOD, and is capable of predicting ionosphere-induced phase noise as a function of space and time. The error model parameterizes ionospheric noise using a power spectrum model and provides the parameters of this model in a global 1x1 degree raster. From the power law model, ionospheric errors in deformation estimates can be calculated. In Polar Regions, our error model relies on a statistical analysis of ionospheric-phase noise in a large number of SAR data from previous L-band SAR missions such as ALOS PALSAR and JERS-1. The focus on empirical analyses is due to limitations of WBMOD in high latitude areas. Outside of the Polar Regions, the ionospheric model WBMOD is used to derive ionospheric structure parameters for as a function of solar activity. The structure parameters are converted to ionospheric phase screens from which phase power spectra are calculated. We introduce the concept of the error model and provide examples of global error maps calculated for the NISAR mission. We also propagate ionospheric phase errors to errors in line-of-site deformation estimates assuming simple multi-temporal stacking algorithms.

  5. Effects of solar wind high-speed streams on the high-latitude ionosphere: Superposed epoch study

    NASA Astrophysics Data System (ADS)

    Grandin, M.; Aikio, A. T.; Kozlovsky, A.; Ulich, T.; Raita, T.

    2015-12-01

    Solar wind high-speed streams (HSSs) are the most important source of geomagnetic disturbances during the declining phase of the solar cycle. Their ionospheric response, especially at high latitudes, is not fully understood yet. We carried out a phase-locked superposed epoch analysis to study the effects of HSSs on the high-latitude ionospheric F region, using data from the Sodankylä ionosonde (L = 5.25) during 2006-2008. We found that the F layer critical frequency foF2 decreases between 12 and 23 magnetic local time (MLT) in summer and around equinoxes for several days. Our interpretation, supported by numerical estimations, is that increased electric fields in the evening sector of the auroral and subauroral regions create ion-neutral frictional heating. Frictional heating will increase the loss rate of O+ due to two reasons. The first one is neutral heating producing thermal expansion of the atmosphere and enhancing N2 and O2 contents at the F region peak. The second one is ion heating which may occur under strong enough electric fields (about 50-60 mV/m), leading to enhancement of the reaction coefficients. An increase in foF2 is observed in two different MLT sectors. First, a short-lived foF2 increase is visible during all seasons near noon on the first day after the arrival of the HSS, possibly triggered by the compressed solar wind plasma pressure pulse, which may produce particle precipitation from the dayside central plasma sheet. Second, foF2 is enhanced for several days in the morning sector during equinoxes and in winter. We suggest that this is caused by the low-energy tail of particle precipitation.

  6. Earthquake-Ionosphere Coupling Processes

    NASA Astrophysics Data System (ADS)

    Kamogawa, Masashi

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

  7. Effect of Mutation Order on Myeloproliferative Neoplasms

    PubMed Central

    Nangalia, Jyoti; Silber, Yvonne; Wedge, David C.; Grinfeld, Jacob; Baxter, E. Joanna; Massie, Charles E.; Papaemmanuil, Elli; Menon, Suraj; Godfrey, Anna L.; Dimitropoulou, Danai; Guglielmelli, Paola; Bellosillo, Beatriz; Besses, Carles; Döhner, Konstanze; Harrison, Claire N.; Vassiliou, George S.; Vannucchi, Alessandro; Campbell, Peter J.; Green, Anthony R.

    2015-01-01

    BACKGROUND Cancers result from the accumulation of somatic mutations, and their properties are thought to reflect the sum of these mutations. However, little is known about the effect of the order in which mutations are acquired. METHODS We determined mutation order in patients with myeloproliferative neoplasms by genotyping hematopoietic colonies or by means of next-generation sequencing. Stem cells and progenitor cells were isolated to study the effect of mutation order on mature and immature hematopoietic cells. RESULTS The age at which a patient presented with a myeloproliferative neoplasm, acquisition of JAK2 V617F homozygosity, and the balance of immature progenitors were all influenced by mutation order. As compared with patients in whom the TET2 mutation was acquired first (hereafter referred to as “TET2-first patients”), patients in whom the Janus kinase 2 (JAK2) mutation was acquired first (“JAK2-first patients”) had a greater likelihood of presenting with polycythemia vera than with essential thrombocythemia, an increased risk of thrombosis, and an increased sensitivity of JAK2-mutant progenitors to ruxolitinib in vitro. Mutation order influenced the proliferative response to JAK2 V617F and the capacity of double-mutant hematopoietic cells and progenitor cells to generate colony-forming cells. Moreover, the hematopoietic stem-and-progenitor-cell compartment was dominated by TET2 single-mutant cells in TET2-first patients but by JAK2–TET2 double-mutant cells in JAK2-first patients. Prior mutation of TET2 altered the transcriptional consequences of JAK2 V617F in a cell-intrinsic manner and prevented JAK2 V617F from up-regulating genes associated with proliferation. CONCLUSIONS The order in which JAK2 and TET2 mutations were acquired influenced clinical features, the response to targeted therapy, the biology of stem and progenitor cells, and clonal evolution in patients with myeloproliferative neoplasms. (Funded by Leukemia and Lymphoma Research and others.) PMID:25671252

  8. Ray trace calculation of ionospheric propagation at lower frequencies

    NASA Astrophysics Data System (ADS)

    Reilly, Michael H.

    2006-10-01

    The Raytrace/Ionospheric Conductivity and Electron Density-Bent-Gallagher model has been revised to make it applicable to ionospheric propagation at low radio frequencies (0.5-5.0 MHz), where the ionosphere and magnetic anisotropy drastically alter propagation paths and provide a severe test of propagation model algorithms. The necessary revisions are discussed, and the model is applied to the problem of ionospheric penetration from a source below the ionosphere to a receiver above the ionosphere. It is necessary to include the electron collision frequency in the Appleton-Hartree index of refraction in order to permit ionospheric penetration for radio frequencies below the maximum plasma frequency (e.g., whistler modes). The associated reformulation of the ray trace equations for a complex index of refraction is straightforward. Difficulties with numerical methods are cited for the lowest frequencies, and future improvements are indicated.

  9. Auroral absorption in the artificially heated ionospheric volume

    NASA Astrophysics Data System (ADS)

    Pashin, A. B.; Kotitov, A. L.; Pudovkin, M. I.

    2003-04-01

    Observations of cosmic noise absorption are widely used to study energetic electron precipitation. However, auroral absorption depends not only on electron density in the ionospheric D-region and in the lower part of the E region but also on electron temperature. Natural variations of the electron temperature are not so significant and are usually ignored during interpretation of riometer data. This parameter can be changed by an order of magnitude during an active modification of the ionosphere by a powerful ground-based HF transmitter. Therefore, it is of importance to estimate the effect of electron heating on auroral absorption. Numerical modilling of auroral absorption in the case without the heating and the case of disturbed electron temperature shows that in the developed D-region the cosmic noise power is decreased by about 0.5 dB due to increasing temperature of ionospheric electrons. This effect is not more than 0.2 dB for the quiet ionosphere. Absorption measurements along with operation of a heating transmitter can be used for more accurate reconstruction of an electron density profile below 90 km, where incoherent scatter measurements give not precise values.

  10. Investigating ionosphere-thermosphere space weather using ensemble based modeling

    NASA Astrophysics Data System (ADS)

    Pawlowski, D. J.; Ridley, A. J.; Flegal, J.

    2013-12-01

    In order to be able to predict ionosphere-thermosphere space weather using numerical models, it is necessary to understand the sources of uncertainty within the model. A major source of uncertainty arises due to inaccurate specification of the external drivers of the ionosphere-thermosphere system. In addition, uncertainties within the ionosphere-thermosphere models themselves, due to the myriad of parameterizations that are utilized, results in further uncertainty in the prediction. One way to help quantify the uncertainty when attempting to predict space weather is to use ensembles of model simulations to better understand the effects of these different sources of uncertainty on the system. This is done in the lower atmospheric community where, for example, ensembles of model runs are used to predict the percent chance that there will be a thunderstorm tomorrow. In this presentation, we examine the effect that uncertainty in the high-latitude drivers has on the upper atmosphere using ensembles of simulations of the Global Ionosphere-thermosphere model. The ensembles are created using results from an analysis of solar wind data from the past 15 years.

  11. Ionospheric modification by rocket effluents. Final report

    SciTech Connect

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

    1980-06-01

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

  12. Chemical releases in the ionosphere

    NASA Technical Reports Server (NTRS)

    Davis, T. N.

    1979-01-01

    The study of the interaction between the atmosphere, ionosphere and magnetosphere is identified as a major task worthy of pursuit. The present review demonstrates the major contributions to this complex problem already made by active experiments involving the injection of chemicals and energetic electron beams into the atmosphere, ionosphere and magnetosphere. Through the use of chemical releases, it has been possible to investigate a number of quantities including high-altitude winds and electric fields, the detailed configurations of the geomagnetic field within the ionosphere and the magnetosphere, as well as the propagation of energetic particle beams and their interaction with natural neutral and ionized constituents of the high atmosphere. So far, virtually all of this effort has been accomplished using rockets. In the future, it is obvious that satellite platforms will play a greater role, both in making injections and in observing their effects.

  13. Effects of a strong ICME on the Martian ionosphere as detected by Mars Express and Mars Odyssey

    NASA Astrophysics Data System (ADS)

    Morgan, D. D.; Diéval, C.; Gurnett, D. A.; Duru, F.; Dubinin, E. M.; Fränz, M.; Andrews, D. J.; Opgenoorth, H. J.; Uluşen, D.; Mitrofanov, I.; Plaut, J. J.

    2014-07-01

    We present evidence of a substantial ionospheric response to a strong interplanetary coronal mass ejection (ICME) detected by the Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) on board the Mars Express (MEX) spacecraft. A powerful ICME impacted the Martian ionosphere beginning on 5 June 2011, peaking on 6 June, and trailing off over about a week. This event caused a strong response in the charged particle detector of the High-Energy Neutron Detector (HEND) on board the Odyssey spacecraft. The ion mass spectrometer of the Analyzer of Space Plasmas and Energetic Atoms instrument on MEX detected an increase in background counts, simultaneous with the increase seen by HEND, due to the flux of solar energetic particles (SEPs) associated with the ICME. Local densities and magnetic field strengths measured by MARSIS and enhancements of 100 eV electrons denote the passing of an intense space weather event. Local density and magnetosheath electron measurements and remote soundings show compression of ionospheric plasma to lower altitudes due to increased solar wind dynamic pressure. MARSIS topside sounding of the ionosphere indicates that it is extended well beyond the terminator, to about 116° solar zenith angle, in a highly disturbed state. This extension may be due to increased ionization due to SEPs and magnetosheath electrons or to plasma transport across the terminator. The surface reflection from both ionospheric sounding and subsurface modes of the MARSIS radar was attenuated, indicating increased electron content in the Mars ionosphere at low altitudes, where the atmosphere is dense.

  14. Effect of Grid Definition and Data Distribution on Accuracy of Ionospheric Imaging

    NASA Astrophysics Data System (ADS)

    Burston, R.

    2011-12-01

    In tomography, the region to be imaged is divided into a grid and knowledge of the values of a parameter as measured along known paths through the region is used to reconstruct the interior of the region by assigning a value to each voxel of the grid. In the ionospheric case, slant Total Electron Content (sTEC) values for rays passing through the ionosphere can be used. The principle source of such data is recordings from Global Positioning System (GPS) ground receiver stations. Each ray is broken down into pieces, according to the path length within each voxel traversed. Each voxel is assigned an unknown value of electron concentration. A set of simultaneous equations in electron concentration and path length can then be constructed for each ray. In ideal circumstances enough rays from sufficient broadcast points to different receiver points exist so that a unique solution to the set of simultaneous equations can be determined. In practice the solution with the minimum error (usually in a least-squares sense) is found because there is always some error in the input measurements. In the case of the ionosphere and the set of broadcasting GPS satellites and ground based receivers, it is in principle impossible to determine a unique solution even in terms of a minimum error. The geometry is such that the set of simultaneous equations has more unknowns than equations. Hence it is necessary to constrain the solution by some additional method or methods [Bust and Mitchell, 2008]. The solution to this inverse problem is re-calculated for each epoch of interest. The Multi-Instrument Data Assimilation System algorithm developed at the University of Bath, UK, and used at the University of New Brunswick under licence uses empirical Orthogonal Functions (EOFs) to constrain the vertical dimension and spherical harmonics to constrain the locally horizontal dimensions. Two different grid boundaries are tested, using MIDAS. The larger of the two includes two ground receiver stations within it that are excluded from the smaller. (The larger there-by including all northern-hemisphere International Global Navigation Satellite System Service (IGS) permanent stations operating at the time.) It is not clear without testing whether the extra voxels necessary to include these two extra stations offset the benefits of their extra input-data or not, when the MIDAS reconstruction is made. For each grid boundary, runs with 2x2, 3x3 and 4x4, latitude x longitude (in degrees), divisions of the grid are compared with Incoherent Scatter Radar (ISR) data the NmF2 parameter. The results shown demonstrate that in each case tested the extra data improves the results despite the increase in number of grid voxels. Further results show that accuracy in the vertical dimension is worse affected than in the locally horizontal dimensions.

  15. Effective medium theory of ordering in alloys

    SciTech Connect

    Xi, Z.

    1993-12-31

    This thesis presents the first study of alloy phase stability based on the effective medium theory (EMT) of intermetallic interaction. The systems under study are the noble metal alloys of Cu and Au. EMT theory is applied to Cu-Au system to study the Cu-Au configurational ordering phase diagram and to study the kinetics of Cu{sub 3}Au order-disorder transition. Monte Carlo simulations and mean field theory are the statistical techniques used in the study. The agreements with experimental results are broad, the three stoichiometric composition structures, their order-disorder transition temperatures, the lattice constant, the cohesive energy, the superlattice structure in Cu{sub 50}Cu{sub 50}, the Cu-Au phase diagram, and the anisotropy in structure factor in domain growth in Cu{sub 3}Au. This work also compares EMT with Ising model and results of other methods. The author concludes that EMT is a proper theory for interatomic interactions in intermetallic alloys.

  16. The Nightside Ionosphere of Venus Under Varying Levels of Solar EUV Flux

    NASA Technical Reports Server (NTRS)

    Ho, C. M.; Stangeway, R. J.; Russell, C. T.; Luhmann, J. G.; Brace, L. H.

    1993-01-01

    Solar activity varied widely over the 14 year lifetime of the Pioneer Venus Orbiter, and these variations directly affected the properties of the nightside ionosphere. At solar maximum, when solar EUV was largest, the Venus ionosphere was found to extend to highest altitudes and nightward ion transport was the main source of the nightside ionosphere. At solar minimum, nightward ion transport was reduced, and electron precipitation was thought to be the main source. In this study, we have attempted a separation of spatial variations from temporal variations by examining the altitude profiles of the magnetic field, and electron density and temperature for three different solar EUV flux ranges. In the upper ionosphere and near-planet magnetotail (h greater than 1800 km), the solar EUV effects are significant. The electron density decreases about an order of magnitude from high to low EUV flux, while the electron temperature at least doubles. The magnetic field also increases 2 - 3 nT. In the lower ionosphere (200 - 600 km), lower EUV fluxes are associated with slightly reduced density, and higher temperature. These results are in accord with recent entry phase observations, where the electron density measured above the ionospheric density peak is lower than that observed at solar maximum during the early Pioneer Venus mission.

  17. The nightside ionosphere of Venus under varying levels of solar EUV flux

    NASA Technical Reports Server (NTRS)

    Ho, C. M.; Strangeway, R. J.; Russell, C. T.; Luhmann, J. G.; Brace, L. H.

    1993-01-01

    Solar activity varied widely over the 14 year lifetime of the Pioneer Venus Orbiter (PVO), and these variations directly affected the properties of the nightside ionosphere. At solar maximum, when solar EUV was largest, the Venus ionosphere was found to extend to highest altitudes and nightward ion transport was the main source of the nightside ionosphere. At solar minimum, nightward ion transport was reduced, and electron precipitation was thought to be the main source. In this study, we have attempted a separation of spatial variations from temporal variations by examining the altitude profiles of the magnetic field, and electron density and temperature for three different solar EUV flux ranges. In the upper ionosphere and near-planet magnetotail (h greater than 1800 km), the solar EUV flux effects are significant. The electron density decreases about an order of magnitude from high to low EUV flux, while the electron temperature at least doubles. The magnetic field also increases 2 - 3 nT. In the lower ionosphere (200 - 600 km), lower EUV fluxes are associated with slightly reduced density, and higher temperature. These results are in accord with recent entry phase observations, where the electron density measured above the ionospheric density peak is lower than that observed at solar maximum during the early Pioneer Venus mission.

  18. Effects of a solar wind dynamic pressure increase in the magnetosphere and in the ionosphere

    NASA Astrophysics Data System (ADS)

    Juusola, L.; Andréeová, K.; Amm, O.; Kauristie, K.; Milan, S. E.; Palmroth, M.; Partamies, N.

    2010-10-01

    On 17 July 2005, an earthward bound north-south oriented magnetic cloud and its sheath were observed by the ACE, SoHO, and Wind solar wind monitors. A steplike increase of the solar wind dynamic pressure during northward interplanetary magnetic field conditions was related to the leading edge of the sheath. A timing analysis between the three spacecraft revealed that this front was not aligned with the GSE y-axis, but had a normal (-0.58,0.82,0). Hence, the first contact with the magnetosphere occurred on the dawnside rather than at the subsolar point. Fortunately, Cluster, Double Star 1, and Geotail happened to be distributed close to the magnetopause in this region, which made it possible to closely monitor the motion of the magnetopause. After the pressure front had impacted the magnetosphere, the magnetopause was perceived first to move inward and then immediately to correct the overshoot by slightly expanding again such that it ended up between the Cluster constellation with Double Star 1 inside the magnetosphere and Geotail in the magnetosheath. Coinciding with the inward and subsequent outward motion, the ground-based magnetic field at low latitudes was observed to first strengthen and then weaken. As the magnetopause position stabilised, so did the ground-based magnetic field intensity, settling at a level slightly higher than before the pressure increase. Altogether the magnetopause was moving for about 15 min after its first contact with the front. The high latitude ionospheric signature consisted of two parts: a shorter (few minutes) and less intense preliminary part comprised a decrease of AL and a negative variation of PC. A longer (about ten minutes) and more intense main part of the signature comprised an increase of AU and a positive variation of PC. Measurements from several ground-based magnetometer networks (210 MM CPMN, CANMOS, CARISMA, GIMA, IMAGE, MACCS, SuperMAG, THEMIS, TGO) were used to obtain information on the ionospheric E×B drift. Before the pressure increase, a configuration typical for the prevailing northward IMF conditions was observed at high latitudes. The preliminary signature coincided with a pair of reverse convection vortices, whereas during the main signature, mainly westward convection was observed at all local time sectors. Afterwards, the configuration preceding the pressure increase was recovered, but with slightly enhanced convection. Based on the timing analysis, the existence of the preliminary signature coincided with the passage of the oblique pressure front, whereas during the main signature the front was already well past Earth. The main signature existed during the time the magnetopause was observed to move. As the position stabilised, also the signature disappeared.

  19. Effects of geomagnetic storm on low latitude ionospheric total electron content: A case study from Indian sector

    NASA Astrophysics Data System (ADS)

    Chakraborty, Monti; Kumar, Sanjay; De, Barin Kumar; Guha, Anirban

    2015-07-01

    The effect of geomagnetic storms on low latitude ionosphere has been investigated with the help of Global Positioning System Total Electron Content (GPS-TEC) data. The investigation has been done with the aid of TEC data from the Indian equatorial region, Port Blair (PBR) and equatorial ionization anomaly region, Agartala (AGR). During the geomagnetic storms on 24th April and 15th July 2012, significant enhancement up to 150% and depression up to 72% in VTEC is observed in comparison to the normal day variation. The variations in VTEC observed from equatorial to EIA latitudes during the storm period have been explained with the help of electro-dynamic effects (prompt penetration electric field (PPEF) and disturbance dynamo electric field (DDEF)) as well as mechanical effects (storm-induced equatorward neutral wind effect and thermospheric composition changes). The current study points to the fact that the electro-dynamic effect of geomagnetic storms around EIA region is more effective than at the lower latitude region. Drastic difference has been observed over equatorial region (positive storm impact) and EIA region (negative storm impact) around same longitude sector, during storm period on 24th April. This drastic change as observed in GPS-TEC on 24th April has been further confirmed by using the O/N2 ratio data from GUVI (Global Ultraviolet Imager) as well as VTEC map constructed from IGS data. The results presented in the paper are important for the application of satellite-based communication and navigational system.

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

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

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

  1. Transient Solar Wind Features and Their Effects on the Magnetosphere and the Ionosphere (Invited)

    NASA Astrophysics Data System (ADS)

    Sibeck, D. G.; Omidi, N.

    2009-12-01

    Solar wind parameters are constantly varying. On time scales of 1-10 min, dynamic pressure variations are relatively infrequent, but variations in the interplanetary magnetic field orientation are relatively common. The pressures associated with suprathermal particles within the foreshock excavate density and magnetic field strength cavities on bundles of magnetic field lines connected to the bow shock, piling up density and magnetic field strength enhancements on neighboring magnetic field lines. Within the foreshock, the interaction of parallel propagating sinusoidal waves with highly oblique fast magnetosonic waves generates cavitons marked by depressions in the density and magnetic field strength. The pressure variations associated with both intrinsic solar wind and foreshock-generated density structures are transmitted through the magnetosheath and batter the magnetosphere, driving substantial magnetopause motion, triggering reconnection, and generating transient field-aligned currents that result in traveling convection vortices in the high latitude ionosphere. This talk reviews recent progress in understanding the interaction of solar wind pressure pulses with the magnetosphere and outlines future objectives.

  2. The effect of the solar cycle on the maintenance of the nightside ionosphere of Venus

    SciTech Connect

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

    1991-07-01

    Pioneer Venus radio occultation measurements of the nightside ionosphere of Venus collected from 1979 to 1986 have made it possible to study its behavior at times of both solar maximum and solar minimum. Although some solar maximum measurements are similar in nature to those observed at solar minimum, which have an average peak density of about 7 {times} 10{sup 3} cm{sup {minus}3}, others show much higher peak densities, reaching values of about 4 {times} 10{sup 4} cm{sup {minus}3}. These elevated peak densities also occur at higher altitudes. The integrated electron column densities for these measurements are also much higher, indicating the presence of substantial ionization above the main peak. The magnitudes of both the peak density and the integrated content above the peak are anticorrelated with the solar wind dynamic pressure, leading to the interpretation that these enhancements during solar maximum are due to transterminator transport of O{sup +} ions from the dayside when the solar wind dynamic pressure is low enough to permit a sufficiently high dayside ionopause. The resulting ionization peak can be many times the concentration produced by energetic electron fluxes impacting the neutral atmosphere on the nightside, which apparently form the remaining source of the nightside peak at such times during solar maximum, when transterminator flow is cut off by high solar wind pressure depressing the dayside ionopause, and during solar minimum, when the ionopause is always depressed.

  3. Ionospheric Correction Based on Ingestion of Global Ionospheric Maps into the NeQuick 2 Model

    PubMed Central

    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

  4. 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.

  5. A GPS/GNSS dense network used to monitor ionospheric positioning error

    NASA Astrophysics Data System (ADS)

    Wautelet, G.; Lejeune, S.; Warnant, R.

    2010-12-01

    GPS/GNSS networks are, for the last few years, quickly expanding their density all over the surface of the globe. The present idea is to use this density in order to assess the effect of ionospheric disturbances on relative positioning but also to monitor their propagation patterns. Local variability in the ionospheric electron density can dramaticaly affect the reliability of GPS/GNSS real time applications. In particular, Traveling Ionospheric Disturbances (TID's) or plasma instability due to geomagnetic storms can induce strong disturbances in relative positioning. It is therefore useful to develop an integrity monitoring service based on a GPS/GNSS dense network. To assess the effects of ionospheric activity on relative positioning, the SoDIPE-RTK software (Software for Determining the Ionospheric Positionning Error on RTK) has been developed at the Royal Meteorological Institute of Belgium. The approach consists in computing the positioning error due to the ionosphere and has been applied, as a proof of concept, on the Belgian dense network. This network called Active Geodetic Network (AGN) is composed of 66 GPS (dual-frequency) stations. In order to ensure a successful ambiguity resolution for both L1 and L2 carriers, baselines larger than 40 km are not taken into account in the analysis. In a first step, we assess the nominal RTK precision for each baseline during quiet ionospheric conditions (i.e. a background of low Total Electron Content (TEC) variability). The observed positioning accuracy is ~1 cm and depends mainly on baseline length and satellite geometry at the two considered stations. In a second step, the impact of two ionospheric events on positioning error (a medium scale TID and a powerful geomagnetic storm) is evaluated. As expected, the study demonstrates that the largest effects are observed during the occurrence of the geomagnetic storm with an ionospheric positioning error reaching 0.9 m. The maximal positioning error observed during the TID is around 0.15 m, depending on baseline orientation. This is due to the fact that the sharpest TEC gradients are observed for baselines oriented parallel to the direction of disturbance propagation. Finally, we propose a web service dedicated to GPS/GNSS relative positioning users based on SoDIPE-RTK. Every 15 minutes, a thematic map is produced showing each AGN baseline in a given color ranging from green (quiet conditions) to red (extreme conditions). This user-friendly application allows registered users to access and visualize current ionospheric conditions in the area covered by the whole network. This service based on the AGN is therefore an useful application of a GPS/GNSS dense network and will be extended to other networks in a near future.

  6. Numerical Study of Alfven Wave Absorption in the Ionosphere

    NASA Astrophysics Data System (ADS)

    Sydorenko, D.; Rankin, R.

    2011-12-01

    Previously, Lessard and Knudsen [2001] showed that reflection of a shear Alfven wave with sub-kilometer transverse wavelength from the ionosphere is negligible. In the present paper, we study the effect of the transverse wavelength on interaction between an Alfven wave and the ionosphere using a two-dimensional multi-fluid numerical model of low-altitude auroral flux-tubes. We focus on the role of dissipation due to the intense parallel electric currents and parallel electric fields which are generated in the ionosphere by the waves with short tranverse spatial scale. The parallel electric field is obtained from the condition of divergence-free electric current in order to maintain quasineutrality. The electromagnetic solver of the model combines the quasineutrality equation with the Maxwell equations. The ionosphere is described realistically, similar to [Schunk, 1988], and includes a detailed chemistry model, collisions between charged particles, and neutral winds. Lessard, M.R. and D. J. Knudsen (2001), Geophys. Res. Lett., 28, 3573. Schunk, R. W. (1988), PAGEOPH, 127, 255.

  7. Effects observed in the ionospheric F region in the east Asian sector during the intense geomagnetic disturbances in the early part of November 2004

    NASA Astrophysics Data System (ADS)

    Sahai, Y.; Becker-Guedes, F.; Fagundes, P. R.; de Jesus, R.; de Abreu, A. J.; Otsuka, Y.; Shiokawa, K.; Igarashi, K.; Yumoto, K.; Huang, C.-S.; Lan, H. T.; Saito, A.; Guarnieri, F. L.; Pillat, V. G.; Bittencourt, J. A.

    2009-03-01

    The Sun was very active in the early part of November 2004. During the period of 8-10 November 2004, intense geomagnetic disturbances with two superstorms were observed. In a companion paper (hereinafter referred to as paper 1), the effects observed in the F region during the intense geomagnetic disturbances in the early part of November 2004 in the Latin American sector were presented. In the present paper, we investigate the effects observed in the F region during the intense geomagnetic disturbances in the early part of November 2004 in the east Asian sector. We have used the ionospheric sounding observations at Ho Chi Minh City (Vietnam) and Okinawa, Yamagawa, Kokubunji, and Wakkanai (Japan) in the present investigations. Also, GPS observations in the east Asian sector (several longitude zones) have been used to study the effect in the F region during the intense geomagnetic disturbances. The ion density versus latitudinal variations obtained by the DMSP F15 satellite orbiting at about 800 km altitude in the east Asian sector and the magnetic field data obtained at several stations in the Japanese meridian are also presented. Several important features from these observations in both the sectors during this extended period of intense geomagnetic disturbances are presented. The east Asian sector showed very pronounced effects during the second superstorm, which was preceded by two storm enhancements. It should be mentioned that around the beginning of the night on 10 November, ionospheric irregularities propagating from higher midlatitude region to low-latitude region were observed in the Japanese sector. The most intense geomagnetic field H component in that sector was observed on 10 November at L = 2.8, indicating that the auroral oval and the heating got further to low latitudes and the ionospheric irregularities observed in the Japanese sector on this night are midlatitude ionospheric disturbances associated with the second superstorm. The absence of ionospheric irregularities in the Japanese sector during the 8 November superstorm suggests that the magnetosphere-ionosphere system was possibly preconditioned (primed) when the second interplanetary structure impacted the magnetosphere.

  8. 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 σΦ), 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.

  9. 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.

  10. Effect of the self-induced variations of radio signals in the lower layers of the ionosphere on the directivity characteristics of radio antennas

    NASA Astrophysics Data System (ADS)

    Karlov, V. D.; Kadykov, V. B.; Mozhaev, A. A.; Trubaev, S. I.

    1989-04-01

    An analysis is made of the effect of the self-induced nonlinear variations of high-power radio signals propagating through the lower layers of the ionosphere on the directivity characteristics of radio antennas whose carrier frequencies are lower than the effective frequency of collisions between electrons and neutral particles. The dynamics of the propagation of a pulsed signal in the ionosphere is analyzed by solving equations describing changes in the signal field amplitude and electron temperature in the signal field. It is shown that the self-induced variations of radio signals lead to the broadening of the main lobe of the normalized directivity characteristic, an increase in sidelobe level, and a decrease in directivity.

  11. Compensation for the effect of the ionosphere on Doppler measurements in the experiments of the satellite-to-satellite tracking type

    NASA Astrophysics Data System (ADS)

    Latka, J. K.

    The effect of the ionosphere on satellite-to-satellite tracking experiment measurements is analyzed, and a method for the elimination of the ionospheric effect by measuring specific signals at different frequencies is described. While the existing NNSS TRANSIT system, which employs the emission of two coherent signals on the satellite-to-terrestrial receiver path, yields results similar to the present method, its application to satellite-to-satellite tracking requires a greater number of transmitters, thereby increasing technical difficulties and cost. This is especially true in the case of a three-frequency measurement system. The main disadvantage of the method proposed is the greater likelihood of failure, since a main satellite transmitter malfunction will abort the entire experiment. This weakness may be addressed by the use of redundant systems.

  12. 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.

  13. Birth order effects on autism symptom domains.

    PubMed

    Reichenberg, Abraham; Smith, Christopher; Schmeidler, James; Silverman, Jeremy M

    2007-03-30

    Autism is predominantly genetically determined. Evidence supports familiality of the main sets of behavioral characteristics that define the syndrome of autism; however, possible non-genetic effects have also been suggested. The present study compared levels of autism symptom domains, as measured by the Autism Diagnostic Interview, and useful phrase speech scores between 106 pairs of first- and second-born siblings from multiply affected families. In addition, the intercorrelations between the measures were compared between siblings. The overall mean repetitive behavior total score was significantly higher (worse) in first-born than in second-born siblings. In contrast, first-born siblings had significantly lower (better) useful phrase speech than their younger siblings. Autism social and non-verbal communication scores were significantly correlated in first- and in second-born siblings. However, there was a significant difference in the coefficients between first- and second-born siblings. Performance on the non-verbal communication domain was also significantly and positively correlated with useful phrase speech score in both first- and second-born siblings. It is unclear at this time whether these results are of biologic origin. Nevertheless, the findings suggest that genetic studies in autism using specific levels of familial autism traits as phenotypes should take into account their intercorrelations and birth order effects embedded in the instrument. PMID:17289158

  14. 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.

  15. Global Assimilation of Ionospheric Measurements (GAIM)

    NASA Astrophysics Data System (ADS)

    Schunk, Robert W.; Scherliess, Ludger; Sojka, Jan J.; Thompson, Donald C.; Anderson, David N.; Codrescu, Mihail; Minter, Cliff; Fuller-Rowell, Timothy J.; Heelis, Roderick A.; Hairston, Marc; Howe, Bruce M.

    2004-02-01

    The ionosphere is a highly dynamic medium that exhibits weather disturbances at all latitudes, longitudes, and altitudes, and these disturbances can have detrimental effects on both military and civilian systems. In an effort to mitigate the adverse effects, we are developing a physics-based data assimilation model of the ionosphere and neutral atmosphere called the Global Assimilation of Ionospheric Measurements (GAIM). GAIM will use a physics-based ionosphere-plasmasphere model and a Kalman filter as a basis for assimilating a diverse set of real-time (or near real-time) measurements. Some of the data to be assimilated include in situ density measurements from satellites, ionosonde electron density profiles, occultation data, ground-based GPS total electron contents (TECs), two-dimensional ionospheric density distributions from tomography chains, and line-of-sight UV emissions from selected satellites. When completed, GAIM will provide specifications and forecasts on a spatial grid that can be global, regional, or local. The primary output of GAIM will be a continuous reconstruction of the three-dimensional electron density distribution from 90 km to geosynchronous altitude (35,000 km). GAIM also outputs auxiliary parameters, including NmF2, hmF2, NmE, hmE, and slant and vertical TEC. Furthermore, GAIM provides global distributions for the ionospheric drivers (neutral winds and densities, magnetospheric and equatorial electric fields, and electron precipitation patterns). In its specification mode, GAIM yields quantitative estimates for the accuracy of the reconstructed ionospheric densities.

  16. Ionospherically reflected proton whistlers

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  17. 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.

  18. 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.

  19. Historical overview of HF ionospheric modification research

    NASA Astrophysics Data System (ADS)

    Gordon, William E.; Duncan, Lewis M.

    1990-10-01

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

  20. On the feasibility of detecting the ionospheric effects of solar energetic particle events at Mars using spacecraft-spacecraft radio links

    NASA Astrophysics Data System (ADS)

    Withers, Paul

    2016-04-01

    Indirect evidence and theoretical modeling suggests that the effects of solar energetic particle (SEP) events on the ionosphere of Mars are substantial, but observations have not yet provided quantitative information on the magnitude or vertical distribution of the plasma produced below 100 km by SEP events. Strong radio wave absorption is anticipated during a SEP event due to the production of plasma at low altitudes where the neutral atmosphere is relatively dense. Here we test the feasibility of measuring the ionospheric effects of SEP events using power losses in spacecraft-spacecraft UHF radio links. Both lander-orbiter and orbiter-orbiter cases are considered for the UHF radio frequency of 400 MHz. A large SEP event should cause an ionospheric power loss at 400 MHz of 1.5 dB in lander-orbiter communications and, due to the longer path length, a larger power loss of 35 dB in orbiter-orbiter communications. Multiple SEP events occur each year that can cause a lander-orbiter power loss of 0.1 dB, which is shown to be theoretically detectable by current instrumentation, and an orbiter-orbiter power loss of 2 dB. The vertical profile of electron density at low altitudes can be determined from orbiter-orbiter power losses.

  1. Effects of solar X-ray flares in the E region ionosphere of Mars: First model results

    NASA Astrophysics Data System (ADS)

    Haider, S. A.; McKenna-Lawlor, S. M. P.; Fry, C. D.; Jain, Rajmal; Joshipura, K. N.

    2012-05-01

    We have used radio occultation data obtained from Mars Global Surveyor (MGS) at high latitudes (65.3°-65.6°N, 69.3°-69.6°N and 76.4°-77.5°N) to study the effects of X-ray flares and CMEs on Total Electron Content (TEC) in the E region of the Martian ionosphere in response to solar events that occurred on 29 and 31 May 2003 and on 17 January and 13 May 2005. Modeling of flare induced solar X-ray fluxes, ion production rates, electron densities and TEC are carried out, in each case based on GOES data. The estimated TEC values are compared with the in situ MGS observations. It is found that solar flare caused enhancements in the TEC of Mars by a factor of ˜5. Also, a 3D kinetic solar wind model (Hakamada-Akasofu-Fry Version 2/HAFv.2) is used to predict the arrivals of CME shocks at Mars associated with the flare event of May 2005. These predicted shock arrivals were associated with in situ enhancements in TEC by a factor of ˜2.

  2. Ionosphere monitoring using NOAA's CORS network

    NASA Astrophysics Data System (ADS)

    Smith, D.

    NOAA's National Geodetic Survey is currently engaged in research to use the CORS (Continuously Operating GPS Reference Stations) network to model the ionosphere over the conterminous United States and surrounding areas. The CORS network consists of over 700 stations that continuously collect data from all GPS satellite vehicles in view; these data are available free of charge for (predominantly) positioning applications. However, the nature of the network makes it an excellent tool for continuously monitoring the nature of the ionosphere over and near the conterminous United States. From the standpoint of geodesy, the ionosphere effect is generally considered a nuisance parameter: that should be modeled and removed so that the ambiguity in dual frequency GPS carrier-phase signals may be resolved and accurate positions determined. As such, the initial direction of this research is toward modeling the ionosphere for geodetic use, using a single-layer "shell model". The results presented here show the first steps toward accurately modeling the ionosphere through the CORS network, in terms of absolute (non-differential) Total Electron Content Units (TECUs) through an innovative cross-over adjustment of "tracks". Each track is made by the intersection of a satellite/receiver vector with the ionosphere shell as the satellite moves overhead. Results of the initial research in applying the modeled ionosphere toward ambiguity resolution will be discussed. Limitations of using the one-dimensional shell will also be presented. Future plans for creating a time-stream of the ionosphere, increasing the complexity beyond the shell model, and applications toward nowcast and forecast of the ionosphere, will also be discussed.

  3. 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.

  4. Registration of ionospheric effect of 20 March 2015 solar eclipse from GPS data in single-frequency mode

    NASA Astrophysics Data System (ADS)

    Kolmogorov, Andrey; Ivanov, Vsevolod; Gorbachev, Oleg

    2015-12-01

    This article is devoted to the influence of solar eclipse of 20 March 2015 on the total electron content (TEC) of the ionosphere with using data from satellite navigation system GPS. In addition to considering TEC variations, one of the main aims was to show the possibility of using the data of the single-frequency receivers for the diagnostics of the ionosphere. Data from the single-frequency receivers were compared with dual-frequency receivers GPS. As a result, the possibility of using of the low-cost and mobile single-frequency devices for diagnostics of the ionosphere has been demonstrated. It should be noted that the data from the single-frequency receivers, as expected, showed a more noisy result, compared with the phase measurement on two-frequencies. However, after filtering high frequency harmonics result was very similar.

  5. Solar cycle effects on the structure of the electron density profiles in the dayside ionosphere of Venus

    NASA Technical Reports Server (NTRS)

    Kliore, Arvydas J.; Luhmann, Janet G.

    1991-01-01

    Results are presented of observations from the changes in the electron density structure of the dayside ionosphere of Venus that were brought about by changing solar activity. The ionopause height is generally low for values of the solar zenith angle below about 50 deg regardless of the phase in the solar cycle. At solar maximum, and at times of intermediate solar activity, the ionopause height for solar zenith angles greater than about 50 deg is highly variable, ranging from a minimum of about 200 km to a maximum of more than 1000 km. At times of solar minimum the great majority of all ionopause heights for all solar zenith angles are uniformly low, lying between 200 and 300 km. It is argued that the compressed nature of the Venus atmosphere at solar minimum is produced by permeation of the ionosphere by the solar wind magnetic field, which occurs when the solar wind dynamic pressure exceeds the ionospheric plasma pressure.

  6. Investigations into the properties, conditions, and effects of the ionosphere. Report No. 9, 16 December 1987-31 December 1988

    SciTech Connect

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

    1989-01-15

    Northwest Research Associates (NWRA), as prime contractor, and its two team subcontractors, Science Applications International Corp. (SAIC) and the University of Lowell Center for Atmospheric Research (ULCAR), provide members of their technical staffs to conduct and support scientific and engineering investigations of the ionosphere. 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. This report provides a summary of the work performed during the period 16 December 1987 through 31 December 1988.

  7. The use of subionospheric VLF/LF propagation for the study of lower ionospheric perturbations associated with earthquakes

    SciTech Connect

    Hayakawa, M.

    2010-10-20

    It is recently recognized that the ionosphere is very sensitive to seismic effects, and the detection of ionospheric perturbations associated with earthquakes (EQs), attracts a lot of attention as a very promising candidate for short-term EQ prediction. In this review we propose a possible use of VLF/LF (very low frequency (3-30 kHz)/low frequency (30-300 kHz)) radio sounding of seismo-ionospheric perturbations. We first present the first convincing evidence on the presence of ionospheric perturbations for the disastrous Kobe EQ in 1995. The significant shift in terminator times in the VLF/LF diurnal variation, is successfully interpreted in terms of lowering of the lower ionosphere prior to the EQ, which is the confirmation of seismo-ionospheric perturbations. In order to avoid the overlapping with my own previous reviews [1, 2], we try to present the latest results including the statistical evidence on the correlation between the VLF/LF propagation anomalies (ionospheric perturbations) and EQs (especially with large magnitude and with shallow depth), a case study on the Indonesia Sumatra EQ (wavelike structures in the VLF/LF data), medium-distance (6{approx}8 Mm) propagation anomalies, the fluctuation spectra of subionospheric VLF/LF data (atmospheric gravity waves effect, the effect of Earth's tides etc.), and the mechanism of lithosphere - atmosphere - ionosphere coupling. Finally, we indicate the present situation of this kind of VLF/LF activities going on in different parts of the globe and we suggest the importance of international collaboration in this seismo-electromagnetics study.

  8. Ionospheric calibration for single frequency altimeter measurements

    NASA Technical Reports Server (NTRS)

    Schreiner, William S.; Born, George H.

    1993-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2012-03-01

    We present an observational study of magnetospheric and ionospheric disturbances during the December 2006 intense magnetic storm associated with the 4В/Х3.4 class solar flare. To perform the study we utilize the ground data from North-East Asian ionospheric and magnetic observatories (60-72°N, 88-152°E) and in situ measurements from LANL, GOES, Geotail and ACE satellites. The comparative analysis of ionospheric, magnetospheric and heliospheric disturbances shows that the interaction of the magnetosphere with heavily compressed solar wind and interplanetary magnetic field caused the initial phase of the magnetic storm. It was accompanied by the intense sporadic E and F2 layers and the total black-out in the nocturnal subauroral ionosphere. During the storm main phase, LANL-97A, LANL 1994_084, LANL 1989-046 and GOES_11 satellites registered a compression of the dayside magnetosphere up to their orbits. In the morning-noon sector the compression was accompanied by an absence of reflections from ionosphere over subauroral ionospheric station Zhigansk (66.8°N, 123.3°E), and a drastic decrease in the F2 layer critical frequency (foF2) up to 54% of the quite one over subauroral Yakutsk station (62°N, 129.7°E). At the end of the main phase, these stations registered a sharp foF2 increase in the afternoon sector. At Yakutsk the peak foF2 was 1.9 time higher than the undisturbed one. The mentioned ionospheric disturbances occurred simultaneously with changes in the temperature, density and temperature anisotropy of particles at geosynchronous orbit, registered by the LANL-97A satellite nearby the meridian of ionospheric and magnetic measurements. The whole complex of disturbances may be caused by radial displacement of the main magnetospheric domains (magnetopause, cusp/cleft, plasma sheet) with respect to the observation points, caused by changes in the solar wind dynamic pressure, the field of magnetospheric convection, and rotation of the Earth.

  10. International reference ionosphere 1990

    NASA Technical Reports Server (NTRS)

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

    1990-01-01

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

  11. Dynamic Agents of Magnetosphere-Ionosphere Coupling

    NASA Technical Reports Server (NTRS)

    Khazanov, George V.; Rowland, Douglas E.; Moore, Thomas E.; Collier, Michael

    2011-01-01

    VISIONS sounding rocket mission (VISualizing Ion Outflow via Neutral atom imaging during a Substorm) has been awarded to NASA/GSFC (PI Rowland) in order to provide the first combined remote sensing and in situ measurements of the regions where ion acceleration to above 5 e V is occurring, and of the sources of free energy and acceleration mechanisms that accelerate the ions. The key science question of VISIONS is how, when, and where, are ions accelerated to escape velocities in the auroral zone below 1000 km, following substorm onset? Sources of free energy that power this ion acceleration process include (but not limited) electron precipitation, field-aligned currents, velocity shears, and Alfvenic Poynting flux. The combine effect of all these processes on ionospheric ion outflows will be investigated in a framework of the kinetic model that has been developed by Khazanov et al. in order to study the polar wind transport in the presence of photoelectrons.

  12. Comparative study of Mars and Venus ionospheres using ionospheric photoelectron measurements by Mars and Venus Express

    NASA Astrophysics Data System (ADS)

    Molaverdikhani, K.; Brain, D. A.

    2013-12-01

    The Analyser of Space Plasmas and Energetic Atoms (ASPERA-4) instrument package on Venus Express (VEX) has a nearly identical counterpart on Mars Express, called ASPERA-3, which provides a unique opportunity to study the Venus and Mars ionospheres with minimal instrumental interpretation side effects. Previously we used the Electron Spectrometer (ELS) on ASPERA-4 to study the structure and variability of the Venus ionosphere, which is of interest for both plasma escape and the dynamics of the neutral upper atmosphere. We discovered a dawn-dusk asymmetry in the Venus ionosphere, uncorrelated with Interplanetary Magnetic Field strength or direction. Here, we have adapted an automatic algorithm (filter) from this previous work to detect the presence of photoelectrons near Mars in ASPERA-3 ELS data. With information about ionospheric photoelectrons at both Venus (> 6 years of data) and Mars (~9 years of data), we are able to directly compare the ionospheres of the two planets. The filter has identified approximately 200,000 and 3 million measurements at Venus and Mars, respectively, that contain significant photoelectron peaks in the range of 20-30 eV. We find that the Martian ionosphere is more extended vertically in comparison to the Venus ionosphere, relative to the planet's radius. Relative to Venus, the Mars ionosphere is denser in sunlight, less abundant in eclipse, and has a larger tailward extent. The Mars ionosphere also responds to external drivers, such as solar EUV intensity, differently than the Venus ionosphere. We present some plausible ideas to explain these differences based on photoionization and plasma transport mechanisms, and differences in external conditions at the two planets.

  13. Integrity monitoring in real-time precise point positioning in the presence of ionospheric disturbances

    NASA Astrophysics Data System (ADS)

    Wezka, K.; Galas, R.

    2013-12-01

    Ionospheric disturbances are characterized as fast and random variability in the ionosphere. Those phenomena are difficult to predict, detect and model. Occurrence of some strong ionospheric disturbances can cause, inter alia degradation and interruption of GNSS signals. Therefore they are especially harmful for real-time applications, as for example Precise Point Positioning (PPP) in real time, where one of the most important requirements is to ensure the high level of reliability. In such applications verification and confirmation of a high trust degree towards the estimated coordinates is a very critical issue. In one of the previous papers (K. Wezka, 2012 -Identification of system performance parameters and their usability) two sets of parameters have been proposed for enhance reliability of the PPP. The first one for data quality control (QC) of the raw GNSS observations and the second one for examination of the quality, robustness and performance of various processing approaches (strategies). To the second group the following parameters has been proposed: accuracy, precision, availability, integrity and convergence time. In consideration of perturbation of GNSS signal resulting from sudden ionospheric disturbances, one of the most important demands is effective autonomous integrity monitoring. The poster presents first preliminary results of the applicability of the proposed parameters in order to ensure the high level of reliability/integrity of GNSS observations and positioning results under the presence of strong ionospheric anomalies. The data-set from continuously operated GNSS station located at high latitude, where ionospheric disturbances occur more frequently, were used for the analysis. Various selected Receiver Autonomous Integrity Monitoring (RAIM) approaches for quality control of the GNSS observables are applied to the data sets recorded under different (low/quite and high) ionospheric activities. Based on those analyses the usability of the proposed parameters is verified.

  14. Mitigating satellite motion in GPS monitoring of traveling ionospheric disturbances

    NASA Astrophysics Data System (ADS)

    Penney, R. W.; Jackson-Booth, N. K.

    2015-11-01

    We discuss the impact of satellite motion on the use of compact arrays of GPS receivers for estimating the velocity of traveling ionospheric disturbances (TIDs). It is shown that satellite motion has subtle effects upon standard techniques of waveform cross correlation, or time difference of arrival, which can easily lead to spurious TID velocity estimates. We present some improved techniques for cross-correlating TID waveforms while taking account of the Doppler shifts created by satellite motion. In addition, we discuss some improved techniques for separating TID waveforms from background ionospheric trends, such as diurnal variation, based on high-order polynomial fitting with well-defined frequency selectivity. The application of these techniques to a sensor array in the UK is discussed.

  15. 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

  16. 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.

  17. Lightning location and lower-ionospheric height determination from two-station magnetic field measurements

    NASA Technical Reports Server (NTRS)

    Mcdonald, T. B., III; Uman, M. A.; Tiller, J. A.; Beasley, W. H.

    1979-01-01

    Wide band magnetic direction finding from two stations is used to determine lightning locations and ionospheric height during two nocturnal maritime thunderstorms near Florida. A comparison of calculated lightning locations with radar reflectivity data of the two storms indicates systematic direction-finding errors to be on the order of 1 deg. From the lightning locations and measured arrival times of the first and second sky waves, ionospheric reflecting heights for both sky waves were determined. The effective heights for the first and second sky waves may differ, leading to large errors in single-station determinations of ionospheric height, such as in the method described by Kinzer (1974). The distribution of peak electric fields for the strokes studied is shown to be in reasonable agreement with other determinations, indicating the reliability of the present measurements.

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

    NASA Technical Reports Server (NTRS)

    Keskinen, M. J.; Satyanarayana, P.

    1993-01-01

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

  19. Ionosphere effects of tropical cyclones over the Asian region of Russia according to oblique radio-sounding data

    NASA Astrophysics Data System (ADS)

    Chernigovskaya, Marina A.; Kurkin, Vladimir I.; Oinats, Alexey V.; Poddelsky, Igor N.

    2014-11-01

    The possibility of manifestation of tropical cyclones in variations of ionospheric parameters in the zone far removed from the disturbance source region has been studied. The data from frequency analysis by maximal observed frequencies (MOF) for the oblique sounding (OS) signals were used. We revealed 1-5 h time intervals with higher oscillation energetics along the Norilsk-Irkutsk, Magadan-Irkutsk, and Khabarovsk-Irkutsk paths (Eastern Siberia and the Far East of Russia) during equinoctial periods (March, September 2005-2011), in November, 2005 and in summer 2010-2011 for different periods of the solar cycle. These time intervals may be interpreted as a manifestation of large-scale traveling ionospheric disturbances (TIDs) whose sources are atmospheric internal gravity waves. By jointly analyzing ionospheric, heliomagnetic, atmospheric, and satellite data on tropical cyclones (TCs), we attempted to associate the series of the revealed TIDs with ionospheric responses to TCs over the Western North Pacific Ocean during the above periods. A significant increase in wave disturbances on OS paths was established to be noted during active tropical cyclogenesis periods in autumn months. For spring equinox (March, 2005-2011), we also note TID manifestations in MOF time variations under quiet heliomagnetic conditions and in TC absence, but the intensity of these wave disturbances was significantly lower, than that of autumn seasons for various years. We estimated the wavelike disturbance propagation velocity by the delay time of TID passing the medium points of the spaced OS paths.

  20. 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.

  1. A case study on effect of the magnetic storm of 20 November 2003 on GPS ionospheric scintillation at Vanimo station

    NASA Astrophysics Data System (ADS)

    Yang, Shenggao; Fang, HanXian; Weng, Libin; Luo, Jie; Zhou, Xiaoke

    2015-11-01

    The magnetic storm of November 20-21, 2003 was a super storm with minimum Dst -438 nT. Using the GPS ionospheric scintillation data recorded at Vanimo station near the magnetic equator, we investigate the behaviors of the ionospheric scintillations during the storm. The amplitude ionospheric scintillations were enhanced evidently at 19:00-20:00 LT on November 20 2003, corresponding to the sudden increased solar wind speed, steep increase and reorientation in IMF components, intensification of AE and decreased Dst (Sym-H). Severe density depletion region over Vanimo station, and density enhanced areas adjacent to its northern and southern directions were observed simultaneously. It is the prompt penetration of eastward electric field associated with the southward turning of the IMF and intensification of AE that elevate the ionospheric plasma to certain height through the E × B mechanism, then the plasma drifts along the magnetic lines to low latitude, thus forming the great north-south gradient of electron density. Therefore, the sudden change of the electron density during the period may be responsible for the storm-induced scintillation enhancements at Vanimo station.

  2. Effect of a plasma-wave discharge on the radiation of a dipole antenna stimulating this discharge in the lower ionosphere

    NASA Astrophysics Data System (ADS)

    Markov, G. A.; Dejneko, V. N.; Ivanov, V. N.; Martinson, A. A.; Pokhun'kov, A. A.; Chugunov, Yu. V.

    1993-04-01

    A rocket experiment on the excitation of a plasma-wave discharge in the lower ionosphere at midlatitudes is described. A 480-kHz signal was received at the earth surface from the onboard dipole antenna, in the near field of which a discharge was initiated at a distance of about 1000 km from the rocket launch site. The time structure of the signal correlated with the evolution of the discharge during the flight and indicates the strong effect of the discharge plasma on the antenna radiation characteristics: the effective dipole moment and the radiation pattern.

  3. Resonance between coherent whistler mode waves and electrons in the topside ionosphere

    SciTech Connect

    Neubert, T.; Bell, T.F.; Storey, L.R.O. )

    1987-01-01

    Landau resonance and cyclotron resonance of coherent whistler mode waves and energetic electrons are explored for magnetoplasmas with appreciable gradients in the plasma density and magnetic field strength. It is shown that in the topside ionosphere of the earth near the ion transition height the gradients in plasma density and magnetic field strength along a magnetic field line may match in a way which enhances both Landau and cyclotron interactions between waves and electrons at the loss cone pitch angle. The pitch angle scattering induced by a signal from a ground-based VLF transmitter in the ionosphere above the transmitter has been estimated and compared to the pitch angle scattering induced by naturally occurring ELF hiss through cyclotron resonance. It is found that the expected scattering due to plasmaspheric hiss is an order of magnitude larger than that due to Landau resonance in the topside ionosphere. Pitch angle scattering due to cyclotron resonance in the topside ionosphere, however, may be larger by a factor of 2. The authors suggest that the fast Trimpi effect may be caused by a cyclotron resonance interaction in the topside ionosphere.

  4. Resonance between coherent whistler mode waves and electrons in the topside ionosphere

    NASA Technical Reports Server (NTRS)

    Neubert, T.; Bell, T. F.; Storey, L. R. O.

    1987-01-01

    Landau resonance and cyclotron resonance of coherent whistler mode waves and energetic electrons are explored for magnetoplasmas with appreciable gradients in the plasma density and magnetic field strength. It is shown that in the topside ionosphere of the earth near the ion transition height the gradients in plasma density and magnetic field strength along a magnetic field line may match in a way which enhances both Landau and cyclotron interactions between waves and electrons at the loss cone pitch angle. The pitch angle scattering induced by a signal from a ground-based VLF transmitter in the ionosphere above the transmitter has been estimated and compared to the pitch angle scattering induced by naturally occurring ELF hiss through cyclotron resonance. It is found that the expected scattering due to plasmapheric hiss is an order of magnitude larger than that due to Landau resonance in the topside ionosphere. Pitch angle scattering due to cyclotron resonance in the topside ionosphere, however, may be larger by a factor of 2. It is suggested that the 'fast Trimpi' effect may be caused by a cyclotron resonance interaction in the topside ionosphere.

  5. Effects of VLF heating of ionosphere on the transmission cone of MF waves propagating from ground to space

    NASA Astrophysics Data System (ADS)

    Lefeuvre, F.; Pincon, J.; Parrot, M.

    2012-12-01

    Global maps of VLF-MF waves observed by the low-altitude (~700 km) DEMETER satellite (Parrot et al., 2009) have pointed out localized enhancements of wave energy above the most powerful VLF transmitters and their conjugate regions, both in the 18-25 kHz frequency range (VLF transmitters) and in the 2.-2.5 MHz frequency range (emissions associated with lightning discharges). Under hypothesis made for the computation of the refractive index by the Appleton-Hartree formula, simulations are conducted to estimate the effect of VLF heating on the transmission cone of MF waves propagating from ground to space. The method used consists in the computation of the vertical variations of the Real part of the refractive index n and of the ? attenuation factor (? = ?. Imag(n)/c), with an IRI electron density profile derived from the geophysical parameters of a DEMETER orbit and an hybrid collision frequency model taking into account of theoretical and experimental data. Half-angles of the transmission cone are estimated: first, at the X=1 (X=fpe2/f2) low altitude boundary (where Ordinary mode waves may be converted into Extraordinary mode waves), and second, at the high-altitude X=1 boundary (where Extraordinary mode waves may be converted into Ordinary mode waves). It is shown that enhancements in the collision frequencies, produced by VLF heating at altitudes where the product of the collision frequency ? by the electronic density Ne is maximum (i.e. at altitudes including the low-altitude and the high-altitude X=1 boundaries), open the half angle of the transmission cones for MF waves which cross the ionosphere, and so explain enhancements of wave energy observed in the 2. - 2.5 MHz band above the powerful VLF transmitters and their conjugate regions.

  6. 10 CFR 1003.10 - Effective date of orders.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... terms, unless and until it is stayed, modified, suspended, or rescinded. An order is deemed to be issued on the date, as specified in the order, on which it is signed by the Director of the OHA or his... Provisions § 1003.10 Effective date of orders. Any order issued by the OHA under this part is effective...

  7. The Effects of Presentation Order in Multitrial Free Recall.

    ERIC Educational Resources Information Center

    Maitland, Anthony J.

    The experiment tested the effects of presentation word orders in a multitrial free-recall task. Three types of presentation were used: (1) randomized; (2) constant order; and (3) maintained order (maintenance of subjects order of recall on the subsequent presentation). In addition, the effects of number of recalls per presentation (1 or 3) were…

  8. Recent Advances in Ionospheric Modeling for Mars Exploration using Ground Penetrating Radars

    NASA Astrophysics Data System (ADS)

    Restano, Marco; Picardi, Giovanni; Seu, Roberto

    2013-04-01

    Orbiting ground penetrating radars (GPRs) as the Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) and the Shallow Radar (SHARAD) currently operating on Mars need a fine ionospheric correction in order to deliver products useful for geological investigations. Ionosphere influence can be assessed using a new approach based on the finite-difference time-domain (FDTD) method. The proposed work aims to underline the errors introduced by a not perfect knowledge of the ionosphere electron density profile on the transmitted chirp signal. Such effect has a great impact on the data inversion process that aims to estimate the permittivity of the subsurface detected interfaces. Data inversion is accomplished by evaluating, via a two channels approach, quantities related to crust attenuation, surface/subsurface geometry and power scattered by the detected interfaces. The final product delivered after SAR processing is highly dependent on the ionosphere compensation. Ionosphere phase related distortions have been theoretically modelled using the Chapman density function. They introduce an S/N and a side lobe level (SLL) degradation after matched filtering along with a delay and a pulse shape distortion. Since several data acquired over smooth surfaces do not present a pulse shape verifying the backscattering models introduced for MARSIS and SHARAD and based on Kirchhoff approximation it is important to provide a different approach for the ionosphere compensation in order to obtain more reliable products. Not perfectly compensated data would provide erroneous power levels and a wrong geometric interpretation jeopardizing the entire data inversion process. The finite-difference time-domain (FDTD) method can be used to study the propagation of a MARSIS/SHARAD chirp signal into a plasma modelled according to a desired electron density profile adding a new important benefit to the simulation methods available to understand GPR signals in this context. A 1D-FDTD code is enough to model both plasma and collision frequencies. Using the simulator some recently proposed Martian multi-peak electron density profiles similar to Chapman's one have been synthetized. The Chapman model is then used during matched filtering, as on MARSIS/SHARAD data, to compensate the distortions introduced by the ionosphere underlining the eventual presence of uncompensated residuals quantified in terms of S/N loss, SLL degradation and pulse shape distortion. Such work will be highly useful to produce new ionosphere compensation schemes providing more reliable data to be employed in the data inversion procedure.

  9. Saturn's ionosphere: Inferred electron densities

    NASA Technical Reports Server (NTRS)

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

    1983-01-01

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

  10. Saturn's ionosphere: inferred electron densities

    SciTech Connect

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

    1983-12-01

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

  11. Ionospheric redistribution during geomagnetic storms

    PubMed Central

    Immel, T J; Mannucci, A J

    2013-01-01

    [1]The abundance of plasma in the daytime ionosphere is often seen to grow greatly during geomagnetic storms. Recent reports suggest that the magnitude of the plasma density enhancement depends on the UT of storm onset. This possibility is investigated over a 7year period using global maps of ionospheric total electron content (TEC) produced at the Jet Propulsion Laboratory. The analysis confirms that the American sector exhibits, on average, larger storm time enhancement in ionospheric plasma content, up to 50% in the afternoon middle-latitude region and 30% in the vicinity of the high-latitude auroral cusp, with largest effect in the Southern Hemisphere. We investigate whether this effect is related to the magnitude of the causative magnetic storms. Using the same advanced Dst index employed to sort the TEC maps into quiet and active (Dst<−100 nT) sets, we find variation in storm strength that corresponds closely to the TEC variation but follows it by 3–6h. For this and other reasons detailed in this report, we conclude that the UT-dependent peak in storm time TEC is likely not related to the magnitude of external storm time forcing but more likely attributable to phenomena such as the low magnetic field in the South American region. The large Dst variation suggests a possible system-level effect of the observed variation in ionospheric storm response on the measured strength of the terrestrial ring current, possibly connected through UT-dependent modulation of ion outflow. PMID:26167429

  12. 42 CFR 2.61 - Legal effect of order.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 42 Public Health 1 2011-10-01 2011-10-01 false Legal effect of order. 2.61 Section 2.61 Public Health PUBLIC HEALTH SERVICE, DEPARTMENT OF HEALTH AND HUMAN SERVICES GENERAL PROVISIONS CONFIDENTIALITY... effect of order. (a) Effect. An order of a court of competent jurisdiction entered under this subpart...

  13. 10 CFR 205.10 - Effective date of orders.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 10 Energy 3 2010-01-01 2010-01-01 false Effective date of orders. 205.10 Section 205.10 Energy DEPARTMENT OF ENERGY OIL ADMINISTRATIVE PROCEDURES AND SANCTIONS General Provisions § 205.10 Effective date of orders. Any order issued by the DOE or a State Office under this chapter is effective as...

  14. 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.

  15. Topside ionospheric effective scale heights (HT) derived with ROCSAT-1 and ground-based ionosonde observations at equatorial and midlatitude stations

    NASA Astrophysics Data System (ADS)

    Tulasi Ram, S.; Su, S.-Y.; Liu, C. H.; Reinisch, B. W.; McKinnell, Lee-Anne

    2009-10-01

    In this study we propose the assimilation of topside in situ electron density data from the Republic of China Satellite (ROCSAT-1) along with the ionosonde measurements for accurate determination of topside ionospheric effective scale heights (H T ) using an ?-Chapman function. The reconstructed topside electron density profiles using these scale heights exhibit an excellent similitude with Jicamarca incoherent scatter radar (ISR) profiles and are much better representations than the existing methods of Reinisch-Huang method and/or the empirical International Reference Ionosphere-2007 model. The main advantage with this method is that it allows the precise determination of the effective scale height (H T ) and the topside electron density profiles at a dense network of ionosonde/Digisonde stations where no ISR facilities are available. The demonstration of the method is applied by investigating the diurnal, seasonal, and solar activity variations of H T over the dip-equatorial station Jicamarca and the midlatitude station Grahamstown. The diurnal variation of scale heights over Jicamarca consistently exhibits a morning time descent followed by a minimum around 0700-0800 LT and a pronounced maximum at noon during all the seasons of both high and moderate solar activity periods. Further, the scale heights exhibit a secondary maximum during the postsunset hours of equinoctial and summer months, whereas the postsunset peak is absent during the winter months. These typical features are further investigated using the topside ion properties obtained by ROCSAT-1 as well as Sami2 is Another Model of the Ionosphere (SAMI2) model simulations. The results consistently indicate that the diurnal variation of the effective scale height (H T ) does not closely follow the plasma temperature variation and at equatorial latitudes is largely controlled by the vertical E B drift.

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

    NASA Astrophysics Data System (ADS)

    Berngardt, O. I.; Perevalova, N. P.; Dobrynina, A. A.; Kutelev, K. A.; Shestakov, N. V.; Bakhtiarov, V. F.; Kusonsky, O. A.; Zagretdinov, R. V.; Zherebtsov, G. A.

    2015-12-01

    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, and network of seismic stations, located near the meteorite fall trajectory. It is shown that 6-14 min after the bolide explosion, GPS network observed the cone-shaped wavefront of traveling ionospheric disturbances (TIDs) that is interpreted as a ballistic acoustic wave. The typical TIDs propagation velocity were observed 661 ± 256 m/s, which corresponds to the expected acoustic wave speed for 240 km height. Fourteen minutes after the bolide explosion, at distances of 200 km, we observed the emergence and propagation of a TID with annular wavefront that is interpreted as gravitational mode of internal atmospheric waves. The propagation velocity of this TID was 337 ± 89 m/s which corresponds to the propagation velocity of these waves in similar situations. At EKB radar, we observed TIDs in the sector of azimuthal angles close to the perpendicular to the meteorite trajectory. The observed TID velocity (400 m/s) and azimuthal properties correlate well with the model of ballistic wave propagating at 120-140 km altitude. It is shown that the azimuthal distribution of the amplitude of vertical seismic oscillations with periods 3-60 s can be described qualitatively by the model of vertical strike-slip rupture, propagating at 1 km/s along the meteorite fall trajectory to distance of about 40 km. These parameters correspond to the direction and velocity of propagation of the ballistic wave peak by the ground. It is shown that the model of ballistic wave caused by supersonic motion and burning of the meteorite in the upper atmosphere can satisfactorily explain the various azimuthal ionospheric effects, observed by the coherent decameter radar EKB, GPS receivers network, and the azimuthal characteristics of seismic waves at large distances.

  18. Solar wind-magnetosphere-ionosphere coupling at Jupiter

    NASA Astrophysics Data System (ADS)

    Bunce, E. J.

    A fundamental property of planetary magnetospheres, which varies from planet to planet, is the dynamical influence of either the solar wind and its embedded interplanetary magnetic field (IMF) or of the rotation of the planet. Jovian magnetospheric dynamics are mainly dominated by the combination of rapid planetary rotation and the outflow of material originating from the moon Io, orbiting deep within the magnetospheric cavity. The outward radial transport of this plasma results in the breakdown of corotation at all local times, which in turn sets up a large-scale magnetosphere-ionosphere coupling current system. The main auroral oval in Jupiter's polar ionosphere appears fixed with respect to the planet, an indication of planetary control, and is understood to be associated with this large-scale magnetosphere-ionosphere coupling, and the transfer of angular momentum from the ionosphere to the middle magnetosphere plasma. Jupiter's polar auroral emissions, however, which include all auroral emission lying poleward of the main auroral oval, are ordered by magnetic local time, indicating external control by the solar wind interaction with the jovian magnetosphere. We have recently considered the flows present in Jupiter's ionosphere in terms of three different flow regimes: the sub-corotational flows associated with the main auroral oval, the Vasyliunas cycle associated with the down-tail loss of plasmoids (predominantly a feature of the dusk-side magnetosphere), and the Dungey-cycle flows which are associated with the interaction of the solar wind and embedded interplanetary magnetic field with the magnetosphere, principally via reconnection. Motivated by this picture, we consider from a theoretical standpoint what the effects of pulsed dayside magnetic reconnection will be at Jupiter. This will generate a twin-vortical flow pattern in the ionosphere across the open-closed field line boundary, associated with a bi-polar (i.e. upward and downward) field-aligned current pair. Here we discuss the conditions under which such currents may be carried in either magnetospheric or cusp plasmas, and consider the consequences for auroral emissions at UV and X-ray wavelengths.

  19. 10 CFR 205.10 - Effective date of orders.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... it is stayed, modified, suspended, or rescinded. An order is deemed to be issued on the date, as specified in the order, on which it is signed by an authorized representative of the DOE or a State Office... of orders. Any order issued by the DOE or a State Office under this chapter is effective as...

  20. Ionospheric Storms in Equatorial Region: Digisonde Observations

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

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

  1. Ionospheric Variability and Storms on Mars

    NASA Technical Reports Server (NTRS)

    Mendillo, Michael

    2004-01-01

    The goal of this grant was to conduct the first-ever study of ionospheric variability on Mars. To do so, we used data from the Radio Science (RS) experiment onboard the Mars Global Surveyor (MGS) satellite. Dr. David Hinson of the RS team at Stanford University was a most helpful and valuable colleague throughout the studies we conducted. For the initial RS datasets available from the MGS mission, there were no severe storms caused by solar wind activity, so we concentrated on day-to-day effects. This turned out to be a wise approach since understanding "normal variability" had to be done before any claim could be made about "space weather" effects. Our approach was three-fold: (1) select a good dataset for characterization of ionosphere variability at Mars, one for which excellent terrestrial data were also available. This turned out to be the period 9-27 March 1999; (2) once the variability at Mars was described, develop and use a new photochemical model of the martian ionosphere to find the extent to which solar variability on those days caused or contributed to the observed patterns; (3) use the results from the above, together with additional datasets from the MGS/RS experiment, to describe some practical consequences that the martian ionosphere would have upon NASA s proposed navigation and communications systems for Mars. The results of these studies showed that: (a) solar variability is the dominant source of ionospheric variability at Mars (during periods of quiet solar wind), (b) that current models do a good job in portraying such effects at the height of the ionospheric peak electron density, and (c) that ionospheric structure on Mars can affect attempts at precise position-fixing at Mars should relatively high (GPS-like) frequencies not be used in a Mars communications and navigation system.

  2. Role of Ionospheric Plasmas in Earth's Magnetotail

    NASA Technical Reports Server (NTRS)

    Moore, Thomas E.

    2007-01-01

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

  3. 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.

  4. Dayside Ionospheric Superfountain

    NASA Technical Reports Server (NTRS)

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

    2010-01-01

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

  5. Use of IRI to Model the Effect of Ionosphere Emission on Earth Remote Sensing at L-Band

    NASA Technical Reports Server (NTRS)

    Abraham, Saji; LeVine, David M.

    2004-01-01

    Microwave remote sensing in the window at 1.413 GHz (L-band) set aside for passive use only is important for monitoring sea surface salinity and soil moisture. These parameters are important for understanding ocean dynamics and energy exchange between the surface and atmosphere, and both NASA and ESA plan to launch satellite sensors to monitor these parameters at L-band (Aquarius, Hydros and SMOS). The ionosphere is an important source of error for passive remote sensing at this frequency. In addition to Faraday rotation, emission from the ionosphere is also a potential source of error at L-band. As an aid for correcting for emission, a regression model is presented that relates ionosphere emission to the integrated electron density (TEC). The goal is to use TEC from sources such as TOPEX, JASON or GPS to obtain estimates of emission over the oceans where the electron density profiles needed to compute emission are not available. In addition, data will also be presented to evaluate the use of the IRI for computing emission over the ocean.

  6. 38 CFR 1.490 - Legal effect of order.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... exercise discretion pursuant to 38 U.S.C. 5701(b)(5) and 38 CFR 1.511 to disclose such records. It does not... 38 Pensions, Bonuses, and Veterans' Relief 1 2014-07-01 2014-07-01 false Legal effect of order. 1... PROVISIONS Court Orders Authorizing Disclosures and Use § 1.490 Legal effect of order. The records to...

  7. 38 CFR 1.490 - Legal effect of order.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... exercise discretion pursuant to 38 U.S.C. 5701(b)(5) and 38 CFR 1.511 to disclose such records. It does not... 38 Pensions, Bonuses, and Veterans' Relief 1 2013-07-01 2013-07-01 false Legal effect of order. 1... PROVISIONS Court Orders Authorizing Disclosures and Use § 1.490 Legal effect of order. The records to...

  8. 38 CFR 1.490 - Legal effect of order.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... exercise discretion pursuant to 38 U.S.C. 5701(b)(5) and 38 CFR 1.511 to disclose such records. It does not... 38 Pensions, Bonuses, and Veterans' Relief 1 2010-07-01 2010-07-01 false Legal effect of order. 1... PROVISIONS Court Orders Authorizing Disclosures and Use § 1.490 Legal effect of order. The records to...

  9. 38 CFR 1.490 - Legal effect of order.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... exercise discretion pursuant to 38 U.S.C. 5701(b)(5) and 38 CFR 1.511 to disclose such records. It does not... 38 Pensions, Bonuses, and Veterans' Relief 1 2011-07-01 2011-07-01 false Legal effect of order. 1... PROVISIONS Court Orders Authorizing Disclosures and Use § 1.490 Legal effect of order. The records to...

  10. 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.

  11. Effect of auroral substorms on the ionospheric range spread-F enhancements at high southern midlatitudes using real time vertical-sounding ionograms

    NASA Astrophysics Data System (ADS)

    Hajkowicz, Lech A.

    2016-03-01

    A comprehensive study has been undertaken on the effect of magnetic substorm onsets (as deduced from the auroral hourly electrojet AE-index) on the occurrence of high midlatitude (or sub-auroral latitude) ionospheric range spread-F (Sr). Unlike the previous reports real-time ionograms were used in this analysis thus eliminating ambiguities stemming from the correlating secondary evidence of spread-F with auroral substorms. The Australian southernmost ionosonde station Hobart (51.6°S geom.) proved to be uniquely suitable for the task as being sufficiently close to the southern auroral zone. Sr was assigned in km to each hourly nighttime ionogram at two sounding frequencies: Sr1 (at 2 MHz) and Sr2 (at 6 MHz) for four months in 2002: January and June (representing southern summer and winter solstices), and March and September (representing autumn and vernal equinoxes). It is evident that the southern winter solstitial period (June) is associated with high endemic midlatitude spread-F activity. All other seasons are closely linked with temporal sequences of enhanced spread-F activity following substorm onsets. For the first time it was possible not only find a simultaneous occurrence pattern of these diverse phenomena but to deduce numerical characteristics of the response of midlatitude ionosphere to the global auroral stimulus. Excellent case events, hitherto unpublished, are shown illustrating the presence of the AE peaks (in nT) being ahead of Sr peaks (in km) by a time shift ∆t (in h). Sr1 magnitude showed a significant correlation with the magnitudes of the preceding AE with a correlation coefficient (r) of 0.51 (probability of the occurrence by chance less than 0.01). Sr2 peaks were more sensitive to auroral disturbances but were not correlated with the AE magnitude variations. The time shift (∆t) was on average 4 h with a standard deviation of 3 h. The general pattern in the occurrence of magnetic substorms and spread-F is very similar. A number of corresponding peaks of the AE-index and Sr fluctuations were identified. The sub-auroral ionosphere response tends to last longer than the initiating auroral disturbance (hysteresis effect). The simultaneous quiescent periods in the auroral and sub-auroral ionospheres have been encountered on at least 14 days.

  12. Upper atmospheric effects of the hf active auroral research program ionospheric research instrument (HAARP IRI)

    SciTech Connect

    Eccles, V.; Armstrong, R.

    1993-05-01

    The earth's ozone layer occurs in the stratosphere, primarily between 10 and 30 miles altitude. The amount of ozone, O3, present is the result of a balance between production and destruction processes. Experiments have shown that natural processes such as auroras create molecules that destroy O. One family of such molecules is called odd nitrogen of which nitric oxide (NO) is an example. Because the HAARP (HF Active Auroral Research Program) facility is designed to mimic and investigate certain natural processes, a study of possible effects of HAARP on the ozone layer was conducted. The study used a detailed model of the thermal and chemical effects of the high power HF beam, which interacts with free electrons in the upper atmosphere above 50 miles altitude. It was found only a small fraction of the beam energy goes into the production of odd nitrogen molecules, whereas odd nitrogen is efficiently produced by auroras. Since the total energy emitted by HAARP in the year is some 200,000 times less than the energy deposited in the upper atmosphere by auroras, the study demonstrates that HAARP HF beam experiments will cause no measurable depletion of the earth's ozone layer.... Ozone, Ozone depletion, Ozone layer, Odd nitrogen, Nitric oxide, HAARP Emitter characteristics.

  13. Comparison of ionospheric drift and magnetic deflections on the ground

    NASA Astrophysics Data System (ADS)

    Bahcivan, Hasan; Chen, Steven; Cosgrove, Russell

    2013-12-01

    Resolute Bay, Canada, with an almost vertical geomagnetic field and the associated simplicity of ionospheric current system, is an optimal location to determine the relationship between the ionospheric electric field and the magnetic deflections on the ground. Considering uniform current sheets in a plane geometry, the magnetic deflection direction on the ground is expected to be (1) the same as the ionospheric electric field direction for the Hall current only or (2) lag the electric field direction 0-to-90° in the clockwise sense looking down when the Pedersen current is included. However, our analysis of Resolute incoherent scatter radar and magnetometer data shows that the magnetic deflection angle is leading in a range 30-70° depending on the magnetic local time. Additional magnetometers at Thule and Cambridge Bay observatories were used to investigate the effect of auroral zone currents, however, a simple deconvolution using these stations did not change the results significantly. Furthermore, inclusion of the neutral winds only slightly changed the offset angle. We conclude that a sunward magnetic contribution on the order of 50 nT caused by magnetospheric currents is needed to explain the offset.

  14. On the Convergence of Ionospheric Constrained Precise Point Positioning (IC-PPP) Based on Undifferential Uncombined Raw GNSS Observations

    PubMed Central

    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

  15. Ionospheric and geomagnetic radiowave interference. (Latest citations from the INSPEC database). Published Search

    SciTech Connect

    1996-04-01

    The bibliography contains citations concerning ionospheric radiowave propagation and scattering, atmospheric radio noise, radiofrequency interference, and ionospheric electron density profile. Radio signal attenuation and interference, mechanisms of ionospheric propagation, magnetospheric phenomena, seasonal and phase variations, and multipath effects are also presented. (Contains 50-250 citations and includes a subject term index and title list.) (Copyright NERAC, Inc. 1995)

  16. Ionospheric and geomagnetic radiowave interference. (Latest citations from the INSPEC database). Published Search

    SciTech Connect

    1995-01-01

    The bibliography contains citations concerning ionospheric radiowave propagation and scattering, atmospheric radio noise, radiofrequency interference, and ionospheric electron density profile. Radio signal attenuation and interference, mechanisms of ionospheric propagation, magnetospheric phenomena, seasonal and phase variations, and multipath effects are also presented. (Contains a minimum of 124 citations and includes a subject term index and title list.)

  17. 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.

  18. 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-.

  19. TOPEX ionospheric height correction precision estimated from prelaunch test results

    SciTech Connect

    Monaldo, F. )

    1993-03-01

    Free electrons in the ionosphere will lengthen the electromagnetic path between the TOPEX/Poseidon altimeters and the ocean surface. The path delay is proportional to the total electron content of the ionosphere along the line-of-sight between the altimeter and the surface. Since these ionosphere delays are also inversely proportional to frequency squared, the nearly simultaneous use of both Ku-band (13.6 GHz) and C-band (5.3 GHz) TOPEX altimeters permits a first-order correction for ionospheric delays. Using results from prelaunch ground testing of the TOPEX satellite altimeters, the author presents here the residual height tracking noise after application of the ionosphere correction algorithm. Results are presented as function of ocean significant wave height and for both the 320 MHz and 100 MHz bandwidth of the C-band altimeter.

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

    NASA Astrophysics Data System (ADS)

    Kurkin, Vladimir; Laryunin, Oleg; Podlesnyi, Alexey

    Data from vertical (quasi-vertical) sounding are traditionally used for determining a number of ionospheric parameters such as critical frequencies of E and F layers, peaks of these layers, and for reconstructing electron density profiles. In this respect, radio sounding is not used to its full capacity. Modern ionosondes provide additional information encoded in ionospheric echoes, including information on reflected-signal amplitude. The time dependence of the amplitude-frequency characteristic of reflected signal has been named "amplitude chart" (A-chart). Ionosondes used by the ISTP SB RAS Geophysical Observatory for constructing A-charts employ the frequency-modulated continuous-wave (FMCW) signal in a range 1.3-15 MHz. One-minute sounding interval allows a more detailed study of dynamic processes in the ionosphere. The ionosonde has a direct digital synthesizer and direct sampling receiver without automatic gain control (AGC). The absence of AGC and the high dynamic range enable determination of the relative field strength at a receiving point and registration of relative long-term variations in reflected-signal amplitude over the entire range of operating frequencies of the ionosonde. We have revealed that the passage of travelling ionospheric disturbances (TID) along with height-frequency distortion modulates amplitude characteristics of signal. The characteristic depth of the modulation reaches 40 dB. The pronounced alternate vertical stripes typical for A-charts are likely to be associated with focusing properties of TID. In order to examine the space-time structure of TID able to induce such a focusing of the radio waves, we performed ray tracing simulations. We used geometrical-optics approximation, took magneto-ionic effects into account and prescribed electron density to be a stratified electron density profile on which an undulating disturbance was superimposed. This work was supported by the RFBR grant №14-05-00259-а.

  1. Time-dependent calculations of Jupiter's ionosphere

    NASA Technical Reports Server (NTRS)

    Chen, R. H.

    1982-01-01

    Time-dependent calculations of the vertical distribution of protons in Jupiter's ionosphere show that the accumulation of protons in the topside ionosphere produced from solar ionizing radiation overwhelms the loss to vibrationally excited molecular hydrogen at vibrational temperatures as high at 1600 K. At 2500 K the ionization is decreased over the entire planet with little diurnal variation. For Voyager 1 then, unless the H2 vibrational temperature is as high as thousands of degrees and the topside density of H2 is asymmetric and larger by orders of magnitude, dynamical processes are more likely causes of the low electron densities seen in the nightside upper ionosphere. A calculation of the H3(+) density profile showed that the distribution above the turbopause is controlled by diffusion.

  2. Total electron content measurements in ionospheric physics

    NASA Astrophysics Data System (ADS)

    Garner, T. W.; Gaussiran, T. L., II; Tolman, B. W.; Harris, R. B.; Calfas, R. S.; Gallagher, H.

    2008-08-01

    With the advent of modern global networks of dual-frequency Global Positioning System (GPS), total electron content (TEC) measurements along slant paths connecting GPS receivers and satellites at 22,000 km have become the largest data set available to ionospheric scientists. The TEC can be calculated from the time and phase delay in the GPS signal using the GPS Toolkit, but an unknown bias will remain. In addition, UHF/VHF radio beacons on board low-Earth-orbiting satellites can also be used to measure the electron content. However, the TEC measurements are obtained by integrating TEC differences between slant paths, but also contain biases. It is often necessary to use data assimilative algorithms like the Ionospheric Data Assimilation Three-Dimensional (IDA3D), and to treat both GPS- and LEO-beacon TEC measurements as relative data in order to conduct ionospheric studies.

  3. LEISA: CubeSat for Ionospheric Characterization

    NASA Astrophysics Data System (ADS)

    Suddarth, S. C.; Vera, A.; Pollard, H.; Burgett, T.; King, B.; Hulem, D.; MacGillivray, J.; Montoya, M.; Stanton, W.; Trujillo, B.; Wilson, S.; Heileman, G.

    2012-12-01

    The University of New Mexico / Configurable Space Microsystems Innovation and Applications Center (COSMIAC) is designing a highly affordable research satellite called LEISA (Low Earth Ionospheric Spectrum Analyzer) to characterize Ionospheric properties that affect electromagnetic wave propagation. By measuring spectral distortion of both natural and man-made impulses LEISA will measure Total Electron Content (TEC), magnetic field strength, refractive effects, plasma properties, and higher-order electron density profile effects. Additionally, LEISA may shed light on the relationships between lightning effects and thunderstorm weather in the troposphere and the potential relationship between the acoustic/seismic events around thunderstorms and Ionospheric weather. The LEISA design effort has led to a number of innovations that may be relevant to other small science spacecraft. The design is particularly challenging because of the need to implement broadband RF reception from 20-200 MHz as well as to capture and process the resulting signals within a 1u spacecraft (10cm x 10cm x 10cm) with less than 2 watts of average available power. One particular challenge is the deployable electrically small biconic wideband UHF antenna that deploys to approximately 1.5m in length and .5 m in width. The resulting antenna system deploys from a diminutive 500 cubic centimeter volume. The remaining electronics must fit within the remaining 500 cubic centimeters, leading the team to develop a system-on-a-chip (SoC) design using a Xilinx Spartan 6 FPGA. The resulting circuit handles the spectrogram capture as well as all command and data handling functions within an average power footprint of approximately 200mW, reserving energy for analog-to-digital conversion (ADC) during capture events. LEISA builds upon prior work by Los Alamos National Laboratory with FORTE and Cibola Flight Experiment. In addition to being much more affordable, LEISA offers the potential of geo-locating events to within approximately 1km, which is useful for inverting the key scientific findings from collected data. The project provides rich research opportunities for undergraduates including FPGA design, deployable systems, RF design, data analysis, antenna design, digital signal processing, filter design, power reduction techniques, and networking and communications.

  4. Effect of homopolymer molecular weight on order-order transition in block copolymer and homopolymer blends.

    PubMed

    Lee, Sang-In; Zin, Wang-Cheol; Ahn, Jong-Hyun

    2009-12-01

    The order-order transition temperature (T(OOT)) in blends of poly(styrene-b-isoprene-b-styrene) (S-I-S) triblock copolymer and polyisoprene (PI) homopolymer was investigated by using synchrotron small-angle X-ray scattering (SAXS). Pure triblock copolymer undergoes an order-order transition (OOT) from hexagonally ordered cylinder (HEX) to body centered cubic (BCC) phases. In order to investigate the effect of the molecular weight of the added homopolymer on T(OOT) of the triblock copolymer, various low-molecular-weight PI homopolymers were studied. The results revealed that T(OOT) was affected by the PI molecular weight. T(OOT) was reduced for blends having low-molecular-weight PI. PMID:19908817

  5. Effects of multiple scatter on the propagation and absorption of electromagnetic waves in a field-aligned-striated cold magneto-plasma: implications for ionospheric modification experiments

    NASA Astrophysics Data System (ADS)

    Robinson, T. R.

    2002-01-01

    A new theory of the propagation of low power electromagnetic test waves through the upper-hybrid resonance layer in the presence of magnetic field-aligned plasma density striations, which includes the effects of multiple scatter, is presented. The case of sinusoidal striations in a cold magnetoplasma is treated rigorously and then extended, in an approximate manner, to the broad-band striation spectrum and warm plasma cases. In contrast to previous, single scatter theories, it is found that the interaction layer is much broader than the wavelength of the test wave. This is due to the combined electric fields of the scattered waves becoming localised on the contour of a fixed plasma density, which corresponds to a constant value for the local upper-hybrid resonance frequency over the whole interaction region. The results are applied to the calculation of the refractive index of an ordinary mode test wave during modification experiments in the ionospheric F-region. Although strong anomalous absorption arises, no new cutoffs occur at the upper-hybrid resonance, so that in contrast to the predictions of previous single scatter theories, no additional reflections occur there. These results are consistent with observations made during ionospheric modification experiments at Tromsø, Norway.

  6. Model study of the effects of gravity wave dissipation on the thermosphere and ionosphere from deep convection worldwide 15-27 June 2009

    NASA Astrophysics Data System (ADS)

    Vadas, S.; Liu, H.

    2013-12-01

    In this paper, we discuss the methods and results of a global modeling study for the effect of deep convection on the thermosphere and ionosphere through the dissipation of atmospheric gravity waves (GWs). The selected time period is 15-27 June 2009, during the recent extreme solar minimum. The convective plumes which overshot the tropopause are identified from IR images obtained by the instruments on 5 satellites covering Earth (from west to east: GOES11, GOES12, M9, M7, and MTS). We model the excitation of GWs from these plumes, and ray trace them into the thermosphere using our ray trace model which has been upgraded to span the Earth. We then calculate the forcings/heatings/coolings which result when and where these GWs dissipate in the thermosphere. We input these forcings/heatings/coolings into the global TIME-GCM, and re-run the model. In this paper, we discuss these methods and models in detail. We then discuss how the thermosphere and ionosphere responded to the dissipation of these convectively-generated GWs worldwide.

  7. 42 CFR 2.61 - Legal effect of order.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 42 Public Health 1 2014-10-01 2014-10-01 false Legal effect of order. 2.61 Section 2.61 Public... OF ALCOHOL AND DRUG ABUSE PATIENT RECORDS Court Orders Authorizing Disclosure and Use § 2.61 Legal.... Such an order does not compel disclosure. A subpoena or a similar legal mandate must be issued in...

  8. 42 CFR 2.61 - Legal effect of order.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 42 Public Health 1 2010-10-01 2010-10-01 false Legal effect of order. 2.61 Section 2.61 Public... OF ALCOHOL AND DRUG ABUSE PATIENT RECORDS Court Orders Authorizing Disclosure and Use § 2.61 Legal.... Such an order does not compel disclosure. A subpoena or a similar legal mandate must be issued in...

  9. 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.

  10. Photolysis of methane and the ionosphere of Uranus

    NASA Astrophysics Data System (ADS)

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

    1983-08-01

    Photochemical calculations for Uranus predict an extensive region of condensation of acetylene, ethane and methane in the vicinity of the temperature inversion layer. This could explain why ethane was not detected on Uranus, unlike Neptune which has a much warmer inversion layer. Subsequent snow-out of the condensibles is expected to result in reduced visibility in the troposphere. Ionospheric calculations for the equatorial region to be probed by Voyager, indicate peak electron concentrations on the order of 5×103 cm-3, if dynamical effects are important. Upper limit to the electron peak is 3×104 cm-3. Exospheric temperatures as high as 200-250K are conceivable.

  11. 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.

  12. 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.

  13. Ionospheric Specifications for SAR Interferometry (ISSI)

    NASA Technical Reports Server (NTRS)

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

    2013-01-01

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

  14. 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.

  15. Ray trajectories in an absorbing ionosphere

    NASA Astrophysics Data System (ADS)

    Sonnenschein, Elazar; Censor, Dan; Rutkevich, Igor; Bennett, John A.

    1997-11-01

    The present paper deals with the simulation of electromagnetic ray propagation in a cold collisional ionosphere in the presence of the Earth's magnetic field. This subject has been extensively studied in the past. The novel aspect here is our attempt to assess the effect of absorption on the ray trajectories, not merely the field intensity. In addition to the theoretical interest in this problem, practical questions, such as target location by means of Over The Horizon Radar (OTHR) systems, in the presence of high losses, provide the motivation. The analytical investigation of such problems is limited by the complexity of the wave propagation field problem and the physics of the ionosphere, which combine to yield a complex dispersion relation, and the restricted capability of available computers and mathematical software packages for handling the ray tracing model. The present model is based on the familiar Appelton-Hartree, sometimes called the Appelton-Lassen, dispersion equation for the cold, collisional, magnetized ionosphere. The way that the ray tracing is performed (ray tracing being an approximation) and the model chosen by the researcher predetermines the resultant ray trajectories. Thus, in the presence of losses, certain decisions regarding the use of the Hamiltonian ray tracing model have to be made. Unlike some studies which first compute the lossless trajectories, and then add on a posteriori the attenuation along these trajectories, as a perturbation of the lossless solution, here the Hamiltonian ray tracing formalism is extended in order to include the absorption effects in the formalism a priori. For small absorption all models yield more or less the same results; therefore, in the present study high losses are considered in order to emphasize the effects. However, the present study contributes to our understanding of the basic problem of ray propagation in the presence of arbitrary losses. The extended Hamiltonian ray tracing formalism used here assumes complex space, and an additional constraint that guarantees real space and time subspace for the ray trajectories, as well as for the group velocity, whereas the propagation vector and the frequency may be complex. Other formulations for the ray equations formalism exist too. At this time it remains an open problem whether ray trajectories computed by those models will agree with the results obtained here or not. Furthermore, in the absence of sufficient direct ray trajectories empirical data, where high absorption cases are compared to lossless cases, the question as to which model better describes the physical reality must remain open. The variation of the ray paths with frequency, launching angle, collision frequency, electron density profile and other variables, are examined for Chapman type E and F layers. By using typical F layer parameters, it is found that, in certain cases, a high collision frequency affects the ray path by as much as 500 km. This result is important for sub-ionospheric propagation and for target location tracking.

  16. 10 CFR 221.34 - Effect of order.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 10 Energy 3 2010-01-01 2010-01-01 false Effect of order. 221.34 Section 221.34 Energy DEPARTMENT OF ENERGY OIL PRIORITY SUPPLY OF CRUDE OIL AND PETROLEUM PRODUCTS TO THE DEPARTMENT OF DEFENSE UNDER THE DEFENSE PRODUCTION ACT Administrative Procedures and Sanctions § 221.34 Effect of order....

  17. 10 CFR 221.34 - Effect of order.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 10 Energy 3 2014-01-01 2014-01-01 false Effect of order. 221.34 Section 221.34 Energy DEPARTMENT OF ENERGY OIL PRIORITY SUPPLY OF CRUDE OIL AND PETROLEUM PRODUCTS TO THE DEPARTMENT OF DEFENSE UNDER THE DEFENSE PRODUCTION ACT Administrative Procedures and Sanctions § 221.34 Effect of order....

  18. 10 CFR 221.34 - Effect of order.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 10 Energy 3 2011-01-01 2011-01-01 false Effect of order. 221.34 Section 221.34 Energy DEPARTMENT OF ENERGY OIL PRIORITY SUPPLY OF CRUDE OIL AND PETROLEUM PRODUCTS TO THE DEPARTMENT OF DEFENSE UNDER THE DEFENSE PRODUCTION ACT Administrative Procedures and Sanctions § 221.34 Effect of order....

  19. 10 CFR 221.34 - Effect of order.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 10 Energy 3 2012-01-01 2012-01-01 false Effect of order. 221.34 Section 221.34 Energy DEPARTMENT OF ENERGY OIL PRIORITY SUPPLY OF CRUDE OIL AND PETROLEUM PRODUCTS TO THE DEPARTMENT OF DEFENSE UNDER THE DEFENSE PRODUCTION ACT Administrative Procedures and Sanctions § 221.34 Effect of order....

  20. 10 CFR 221.34 - Effect of order.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 10 Energy 3 2013-01-01 2013-01-01 false Effect of order. 221.34 Section 221.34 Energy DEPARTMENT OF ENERGY OIL PRIORITY SUPPLY OF CRUDE OIL AND PETROLEUM PRODUCTS TO THE DEPARTMENT OF DEFENSE UNDER THE DEFENSE PRODUCTION ACT Administrative Procedures and Sanctions § 221.34 Effect of order....

  1. 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.

  2. 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.

  3. 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.

  4. Ionospheric calibration for single frequency altimeter measurements

    NASA Technical Reports Server (NTRS)

    Schreiner, William S.; Born, George H.; Markin, Robert E.

    1994-01-01

    This study is a preliminary analysis of the effectiveness (in terms of altimeter calibration accuracy) of various ionosphere models and the Global Positioning System (GPS) to calibrate single frequency altimeter height measurements for ionospheric path delay. In particular, the research focused on ingesting GPS Total Electron Content (TEC) data into the physical Parameterized Real-Time Ionospheric Specification Model (PRISM), which estimates the composition of the ionosphere using independent empirical and physical models and has the capability of adjusting to additional ionospheric measurements. Two types of GPS data were used to adjust the PRISM model: GPS receiver station data mapped from line-of-sight observations to the vertical at the point of interest and a grid map (generated at the Jet Propulsion Laboratory) of GPS derived TEC in a sun-fixed longitude frame. The adjusted PRISM TEC values, as well as predictions by the International Reference Ionosphere (IRI-90), a climatological (monthly mean) model of the ionosphere, were compared to TOPEX dual-frequency TEC measurements (considered as truth) for a number of TOPEX sub-satellite tracks. For a 13.6 GHz altimeter, a Total Electron Content (TEC) of 1 TECU 10(exp 16) electrons/sq m corresponds to approximately 0.218 centimeters of range delay. A maximum expected TEC (at solar maximum or during solar storms) of 10(exp 18) electrons/sq m will create 22 centimeters of range delay. Compared with the TOPEX data, the PRISM predictions were generally accurate within the TECU when the sub-satellite track of interest passed within 300 to 400 km of the GPS TEC data or when the track passed through a night-time ionosphere. If neither was the case, in particular if the track passed through a local noon ionosphere, the PRISM values differed by more than 10 TECU and by as much as 40 TECU. The IRI-90 model, with no current ability to unseat GPS data, predicted TEC to a slightly higher error of 12 TECU. The performance of PRISM is very promising for predicting TEC and will prove useful for calibrating single frequency altimeter height measurements for ionospheric path delay. When adjusted to the GPS line-of-sight data the PRISM URSI empirical model predicted TEC over a day's period to within a global error of 8.60 TECU rms during a nighttime ionosphere and 9.74 TECU rms during the day. When adjusted to the GPS derived TEC grid, the PRISM parametrized model predicted TEC to within an error of 8.47 TECU rms for a nighttime ionosphere and 12.83 TECU rms during the day. However, the grid cannot be considered globally due to the lack of sufficient numbers of GPS stations and large latitude gaps in GPS data. It is the opinion of the authors that using the PRISM model and adjusting to the global sun-fixed TEC grid regenerated with a localized weighted interpolation offers the best possibility of meeting the 10 TECU global rms (or 2 cm at 13.6 GHz) ionosphere range correction accuracy requirement of TOPEX/Poseidon and should be the subject of further study. However, it is clear that the anticipated requirement of 34 TECU global rms for TOPEX/Poseidon Follow-On (corresponding to the TOPEX/Poseidon performance) can not be met with any realizable combination of existing models and data assimilation schemes.

  5. Ionospheric topside sounding.

    PubMed

    Calvert, W

    1966-10-14

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

  6. Beacon satellite receiver for ionospheric tomography

    NASA Astrophysics Data System (ADS)

    Vierinen, J.; Norberg, J.; Lehtinen, M. S.; Amm, O.; Roininen, L.; Väänänen, A.; Erickson, P. J.; McKay-Bukowski, D.

    2014-12-01

    We introduce a new coherent dual-channel beacon satellite receiver intended for ionospheric tomography. The measurement equation includes neutral atmosphere and ionosphere propagation effects, relative errors in satellite and receiver clocks, and residual Doppler shifts caused by errors in the satellite ephemeris. We also investigate the distribution of errors for phase curve measurements and the use of phase curve measurements for limited angle tomography using the framework of statistical linear inverse problems. We describe the design of our beacon satellite receiver software and present one possible hardware configuration. Finally, we present results obtained using a network of four newly developed receivers and compare the results with those of an existing ionospheric tomography network at Sodankylä Geophysical Observatory.

  7. Rocket studies of the lower ionosphere

    NASA Technical Reports Server (NTRS)

    Bowhill, Sidney A.

    1990-01-01

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

  8. The effect of induction emf on the parameters of an ion screen around a low-frequency cylindrical antenna in the ionosphere

    NASA Astrophysics Data System (ADS)

    Aksenov, V. I.; Modestov, L. P.; Khatskevich, I. G.

    1981-05-01

    Induction emf can arise in a low-frequency cylindrical satellite antenna in the ionosphere as a result of the motion of the satellite in the geomagnetic field. This paper presents a theoretical study of the effect of this induction emf on the parameters of the ion screen formed around the antenna. Simple analytical expressions are obtained for the capacitance and active admittance of the ion screen, with allowance for the induction emf. Computational results agree well with experimental data obtained on Copernicus 500 by means of a low-frequency impedance probe. The value of induction emf was determined by an analysis of the triaxial orientation of the satellite. It is shown that the experimentally observed modulation of antenna parameters during the motion of the satellite about its center of mass can be explained by the effect of induction emf.

  9. Tomographic reconstruction of ionospheric electron density during the storm of 5-6 August 2011 using multi-source data.

    PubMed

    Tang, Jun; Yao, Yibin; Zhang, Liang; Kong, Jian

    2015-01-01

    The insufficiency of data is the essential reason for ill-posed problem existed in computerized ionospheric tomography (CIT) technique. Therefore, the method of integrating multi-source data is proposed. Currently, the multiple satellite navigation systems and various ionospheric observing instruments provide abundant data which can be employed to reconstruct ionospheric electron density (IED). In order to improve the vertical resolution of IED, we do research on IED reconstruction by integration of ground-based GPS data, occultation data from the LEO satellite, satellite altimetry data from Jason-1 and Jason-2 and ionosonde data. We used the CIT results to compare with incoherent scatter radar (ISR) observations, and found that the multi-source data fusion was effective and reliable to reconstruct electron density, showing its superiority than CIT with GPS data alone. PMID:26266764

  10. Tomographic reconstruction of ionospheric electron density during the storm of 5-6 August 2011 using multi-source data

    PubMed Central

    Tang, Jun; Yao, Yibin; Zhang, Liang; Kong, Jian

    2015-01-01

    The insufficiency of data is the essential reason for ill-posed problem existed in computerized ionospheric tomography (CIT) technique. Therefore, the method of integrating multi-source data is proposed. Currently, the multiple satellite navigation systems and various ionospheric observing instruments provide abundant data which can be employed to reconstruct ionospheric electron density (IED). In order to improve the vertical resolution of IED, we do research on IED reconstruction by integration of ground-based GPS data, occultation data from the LEO satellite, satellite altimetry data from Jason-1 and Jason-2 and ionosonde data. We used the CIT results to compare with incoherent scatter radar (ISR) observations, and found that the multi-source data fusion was effective and reliable to reconstruct electron density, showing its superiority than CIT with GPS data alone. PMID:26266764

  11. Tomographic reconstruction of ionospheric electron density during the storm of 5-6 August 2011 using multi-source data

    NASA Astrophysics Data System (ADS)

    Tang, Jun; Yao, Yibin; Zhang, Liang; Kong, Jian

    2015-08-01

    The insufficiency of data is the essential reason for ill-posed problem existed in computerized ionospheric tomography (CIT) technique. Therefore, the method of integrating multi-source data is proposed. Currently, the multiple satellite navigation systems and various ionospheric observing instruments provide abundant data which can be employed to reconstruct ionospheric electron density (IED). In order to improve the vertical resolution of IED, we do research on IED reconstruction by integration of ground-based GPS data, occultation data from the LEO satellite, satellite altimetry data from Jason-1 and Jason-2 and ionosonde data. We used the CIT results to compare with incoherent scatter radar (ISR) observations, and found that the multi-source data fusion was effective and reliable to reconstruct electron density, showing its superiority than CIT with GPS data alone.

  12. 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.

  13. Theory of imperfect magnetosphere-ionosphere coupling

    SciTech Connect

    Kan, J.R.; Lee, L.C.

    1980-09-01

    A theory of magnetosphere-ionosphere coupling in the presence of field-aligned potential drops is formulated within the framework of magnetohydrodynamic equations. Our formulation allows the magnetosphere as well as the ionosphere to respond self-consistently to the parallel potential drop along auroral field lines. Equipotential contours are distorted into a V-shaped structure near the convection reversal boundary and S-shaped on the equatorward side, each gives rise to an inverted V precipitation band. The loading effect of the imperfect coupling results in a valley in the electric field profile which occurs equatorward of the convection reversal boundary.

  14. 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.

  15. Topside ionospheric response to solar EUV variability

    NASA Astrophysics Data System (ADS)

    Anderson, Phillip C.; Hawkins, Jessica M.

    2016-02-01

    We present an analysis of 23 years of thermal plasma measurements in the topside ionosphere from the Defense Meteorological Satellite Program (DMSP) spacecraft. The H+/O+ ratio and density vary dramatically with the solar cycle; cross-correlation coefficients between E10.7 and the daily averaged densities are greater than 0.85. The ionospheric parameters also vary dramatically with season, particularly at latitudes away from the equator where the solar zenith angle varies greatly with season. There are also 27 day solar rotation periodicities in the density, associated with periodicities in the directly measured solar EUV flux. Empirical orthogonal function analysis captures over 95% of the variation in the density in the first two principal components. The first principal component (PC1) is clearly associated with the solar EUV while the second principal component (PC2) is clearly associated with the solar zenith angle variation. The magnitude of the variation of the response of the topside ionosphere to solar EUV variability is shown to be closely related to the ionospheric composition. This is interpreted as the result of the effect of composition on the scale height in the topside ionosphere and the "pivot effect" in which the variation in density near the F2 peak is amplified by a factor of e at an altitude a scale height above the F2 peak. When the topside ionosphere is H+ dominated during solar minimum, DMSP may be much less than a scale height above the F2 peak while during solar maximum, when it is O+ dominated, DMSP may be several scale heights above the F2 peak.

  16. COSMIC-2: A Platform for Advanced Ionospheric Observations

    NASA Astrophysics Data System (ADS)

    Straus, P. R.; Betz, D. A.

    2013-12-01

    The equatorial component of the COSMIC-2 program will consist of 6 satellites to be flown in a 24 degree inclination/520 km altitude orbit. In addition to the primary GNSS radio occultation (RO) payload, to be provided by JPL, the USAF plans to fly a pair of space weather sensors: a multi-frequency radio beacon and the Velocity, Ion Density and Irregularities (VIDI) in-situ plasma sensor package. Together, these three instruments will provide data to address key issues related to the specification and forecast of ionospheric densities and the instabilities/irregularities associated with ionospheric scintillation. The TriG GNSS receiver will provide a substantial increase in the number of daily ionospheric observations relative to COSMIC-1, both in the RO limb-viewing and overhead geometries. These data will provide a significant improvement of assimilative model capabilities for providing accurate ionospheric specifications in the important equatorial region. In addition, TriG will make routine measurements of ionospheric scintillation at L-band frequencies, as pioneered by the CORISS instrument on C/NOFS. The radio beacon, together with a network of ground receivers, will enable direct measurement of scintillation effects on trans-ionospheric signal propagation across the UHF to S-band frequency spectrum. The VIDI sensors will measure the in-situ density depletions associated with scintillation-producing irregularities. Together, the beacon, TriG, and VIDI will provide an unprecedented ability to map equatorial ionospheric instabilities and their effects. The in-situ package will also provide observations of plasma drifts from which electric fields, the most important physical driver for equatorial ionospheric structure, can be inferred. This will enable advancements in ionospheric models to further improve specifications and forecasts. In addition to discussing ionospheric science and operational support aspects of the COSMIC-2 mission, this presentation will also discuss high level COSMIC-2 programmatic status and plans, particular with respect to the mission sensors.

  17. Ionospheric plasma dynamics and instability caused by upward currents above thunderstorms

    NASA Astrophysics Data System (ADS)

    Kuo, C. L.; Lee, L. C.

    2015-04-01

    Thunderstorms are electric generators, which drive currents upwardly into the ionosphere. In this paper, we examine the effects of thunderstorm upward current on the ionosphere. We use a thunderstorm model to calculate the three-dimensional current flows in the atmosphere and to simulate the upward current above the thunderstorm with the tripole-charge structure. The upward current flows into the ionosphere, while the associated electric field causes the plasma E × B motion. The caused plasma motion redistributes the plasma density, leading to ionospheric density variations. In the nighttime ionosphere, the E × B motion may also cause the formation of plasma bubbles.

  18. Characteristics of ionospheric storms in East Asia

    NASA Astrophysics Data System (ADS)

    Wang, Xiao; Wang, Guojun; Shi, Jiankui

       The ionosphere experiences intense response during the geomagnetic storm and it varies with latitude and longitude. The DPS-4 digisonde measurements and GPS-TEC data of ionospheric stations located at different latitudes in the longitudinal sector of 90-130E during 2002 to 2012 were analyzed to investigate the ionospheric effects in the different latitude of East Asia during geomagnetic storm. About 70 geomagnetic storms are selected according to the Dst index and observed data and they are in different seasons and different solar activity levels. A few quiet days’ averages of data before geomagnetic storm were used as the undisturbed level. Results show that for the middle and high latitude, the short-lived positive disturbance associated with the initial phase of the every storm was observed in each season and then the disturbances were negative till the termination of storm. At the low latitude, storm-time disturbances of foF2 have obvious diurnal, seasonal and solar cycle characteristics. Generally, geomagnetic activity will cause foF2 to increase at daytime and decrease at nighttime except for the summer in low solar activity period. The intensity of response of foF2 is stronger at nighttime than that at daytime. The negative ionospheric storm effect is the strongest in summer and the positive ionospheric storm effect is the strongest in winter. In high solar activity period, the diurnal variation of the response of foF2 is very pronounced in each season, and the strong ionospheric response can last several days. In low solar activity period, ionospheric response has very pronounced diurnal variation in winter only. It’s notable that geomagnetic activities occurred at local time nighttime can cause stronger and longer responses of foF2 at the low latitude. All in all, the obvious negative phase ionospheric storms often occurred at the low latitude. Moreover a notable phenomenon was observed for the low latitude, there are the intensive oscillations of foF2 occurring during the main storm phase of enhanced storm in Hainan, and it occurred in the morning generally. For the TEC data, strong disturbances can be observed simultaneously from high latitude to low latitude during the main phase of some storms. Generally strong/weak storms can cause the negative/positive phase storms of TEC in the low latitude and which are obvious in the daytime for the summer and winter and in the period from noon to midnight for the equinox. The differences of the responses of foF2 and TEC are also investigated.

  19. Ionospheric monitoring by the Global Navigation Satellite System (GNSS)

    NASA Astrophysics Data System (ADS)

    Park, Jihye

    The ionosphere reacts to geophysical events, such as earthquakes, tsunamis, surface explosions, underground nuclear explosions (UNE), etc. The Global Navigation Satellite System (GNSS) remote sensing (RS) enables monitoring of the ionospheric disturbances excited by these events. The purpose of this dissertation is to use GNSS RS to detect, discriminate, model and monitor ionospheric disturbances induced by earthquakes and UNEs. Ionospheric delay, which can be derived from dual frequency GNSS signals, is converted to the total electron contents (TEC) along the signal path. After eliminating the main trend of TEC by taking the numerical third order horizontal 3-point derivatives, the traveling ionospheric disturbances (TIDs) are isolated. Since a TID can be generated due to various events, the source of TID must be verified. In this dissertation, the characteristics of the TID waves induced by an earthquake and an UNE are examined. The case studies are: (1) M9.0 2011 Tohoku, Japan earthquake, (2) 2006 North Korean UNE, and (3) 2009 North Korean UNE. From these experiments, the TIDs resulting from different types of events were characterized and discriminated due to the different waveform properties. In addition, the epicenter of the point source can be determined by TID observations. In experiment (2), the 2009 North Korean UNE was examined, using data from eleven nearby GNSS stations. Within a few hours from the explosion, the GNSS stations detected the TIDs, whose arrival time for each station formulated the linear model with respect to the distance to the station. TIDs were observed to propagate with speeds of roughly 150 - 400 m/s at stations about 365 km to 1330 km from the explosion site. Considering the wind effect, the wind-adjusted TIDs located the UNE to within about 2.7 km of its seismically determined epicenter. Through the case studies, the distinctive signatures of different events were demonstrated, which suggests the uniqueness of TIDs excited by different types of events. The major contributions of this dissertation is a demonstration of the applicability of GNSS RS to detect and discriminate geophysical events causing TIDs, and its ability to determine the epicenter of the point source.

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

    SciTech Connect

    Copetti, M.I.M.; Krein, G.; Marques de Carvalho, R.S.; Machado, J.M.

    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.

  1. 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.

  2. 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.

  3. Comparison of the effect of high-latitude and equatorial ionospheric scintillation on GPS signals during the maximum of solar cycle 24

    NASA Astrophysics Data System (ADS)

    Jiao, Yu; Morton, Yu T.

    2015-09-01

    Radio signal scintillation caused by electron density irregularities in the ionosphere affects the accuracy and integrity of Global Navigation Satellite Systems, especially in the equatorial and high-latitude regions during solar maxima. Scintillation in these two regions, nevertheless, is usually influenced by different factors and thus has different characteristics that cause different effects on GNSS signals. This paper compares the characteristics of high-latitude and equatorial scintillation using multifrequency GPS scintillation data collected at Gakona, Alaska, Jicamarca, Peru, and Ascension Island during the 24th solar maximum. Several statistical distributions are established based on the data to characterize the intensity, duration, and occurrence frequency of scintillation. Results show that scintillation in the equatorial region is generally more severe and longer lasting, while high-latitude scintillation is, in general, more moderate and usually dominated by phase fluctuations. Results also reveal the different impacts of solar activity, geomagnetic activity, and seasons on scintillation in different geographic locations.

  4. GNSS data filtering optimization for ionospheric observation

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

  5. Responses of the equatorial ionosphere of Vietnam to the solar flare of April 3, 2010

    NASA Astrophysics Data System (ADS)

    Hoang, Thai Lan

    This report presents the results of ionospheric responses to the solar flare of April 3, 2010 observed over Ho Chi Minh city during period from April 3 to April 9, 2010. The results shows that the magnetic storm created enhancement of foF2 and TEC mainly, i.e.negative storm. The positive phase appeared weakly and only in nighttime. The positive phase of the ionospheric storm appears after 4 hours as a response to the magnetic storm. The most dominant effect on the disturbances during this event is the ionospheric dynamo. During the recovery phase, there is a positive phase at 12 UT on April 9, the foF2 values dropped and h’F2 values increased suddenly, but the TEC values not decreased respectively. It suggests that the efforts must be concentrated on the magnetic-ionospheric disturbance dynamo signature at equatorial region in order to better understand the circulation of the various currents generated during this type of long period geomagnetic storms.

  6. 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.

  7. Evaluation of ionospheric profilers using topside sounding data

    NASA Astrophysics Data System (ADS)

    Verhulst, T.; Stankov, S. M.

    2014-03-01

    An operational system for deducing and imaging the vertical distribution of the electron density in the local ionosphere has been recently developed. The electron density profile is deduced from combined ground-based measurements of the total electron content, ionospheric vertical incidence soundings, and empirically obtained values of the O+-H+ ion transition height. The topside profile is permitted to take one of several forms: Exponential, Chapman, or Epstein. An evaluation of the above mentioned ionospheric profilers is needed in order to determine which one of them provides the best representation of the current ionospheric conditions. For this purpose, we use electron density profiles obtained from ionograms recorded by the topside sounders onboard the Alouette and ISIS satellites. Every profile has been fitted with each of the above mentioned theoretical ionospheric profilers and the corresponding approximation errors calculated. The results have been analyzed with respect to local time, geomagnetic latitude, season, magnetic and solar activity, ion transition height, and the ionospheric density peak characteristics. It has been found that, in the majority of cases, the best fit is provided by the exponential profiler, followed by the Chapman profiler. Also, while some influence of the underlying physical drivers on the topside electron density profile is detected, it is the use of ionospheric characteristics that offers more reliable selection criteria for the most appropriate profiler.

  8. Sputnik 1 and the First Satellite Ionospheric Experiment

    NASA Astrophysics Data System (ADS)

    Sinelnikov, Vyacheslav; Kuznetsov, Vladimir; Alpert, Svetlana

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

  9. Radiative transfer modeling of the OI 135.6 nm emission in the nighttime ionosphere

    NASA Astrophysics Data System (ADS)

    Qin, Jianqi; Makela, Jonathan J.; Kamalabadi, Farzad; Meier, R. R.

    2015-11-01

    Remote sensing of the nighttime OI 135.6 nm emissions has been a widely used method for measuring the F region ionospheric plasma densities. In this work, we first develop a comprehensive radiative transfer model from first principles to investigate the effects of different physical processes on the production and transport of the 135.6 nm photons in the ionosphere and then propose a new approach for estimating electron densities from the nightglow. The forward modeling investigation indicates that under certain conditions mutual neutralization can contribute up to ˜38% of the total production of the nighttime 135.6 nm emissions. Moreover, depending on the ionospheric conditions, resonant scattering by atomic oxygen and pure absorption by oxygen molecules can reduce the limb brightness observed by satellite-borne instruments by up to ˜40% while enhancing the brightness viewing in the nadir direction by typically ˜25%. Further analysis shows that without properly addressing these effects in the inversion process, the peak electron density in the F region (NmF2) obtained using limb observations can be overestimated by up to ˜24%. For accurate estimation of the ionospheric electron density, we develop a new type of inverse model that accounts for the effects of mutual neutralization, resonant scattering, and pure absorption. This inversion method requires the knowledge of O and O2 densities in order to solve the radiative transfer equations. Application of the inverse model to the nighttime ionosphere in the noiseless cases demonstrates that the electron density can be accurately quantified with only ˜1% error in NmF2 and hmF2.

  10. Examining the effects of birth order on personality

    PubMed Central

    Rohrer, Julia M.; Egloff, Boris; Schmukle, Stefan C.

    2015-01-01

    This study examined the long-standing question of whether a person’s position among siblings has a lasting impact on that person’s life course. Empirical research on the relation between birth order and intelligence has convincingly documented that performances on psychometric intelligence tests decline slightly from firstborns to later-borns. By contrast, the search for birth-order effects on personality has not yet resulted in conclusive findings. We used data from three large national panels from the United States (n = 5,240), Great Britain (n = 4,489), and Germany (n = 10,457) to resolve this open research question. This database allowed us to identify even very small effects of birth order on personality with sufficiently high statistical power and to investigate whether effects emerge across different samples. We furthermore used two different analytical strategies by comparing siblings with different birth-order positions (i) within the same family (within-family design) and (ii) between different families (between-family design). In our analyses, we confirmed the expected birth-order effect on intelligence. We also observed a significant decline of a 10th of a SD in self-reported intellect with increasing birth-order position, and this effect persisted after controlling for objectively measured intelligence. Most important, however, we consistently found no birth-order effects on extraversion, emotional stability, agreeableness, conscientiousness, or imagination. On the basis of the high statistical power and the consistent results across samples and analytical designs, we must conclude that birth order does not have a lasting effect on broad personality traits outside of the intellectual domain. PMID:26483461

  11. Examining the effects of birth order on personality.

    PubMed

    Rohrer, Julia M; Egloff, Boris; Schmukle, Stefan C

    2015-11-17

    This study examined the long-standing question of whether a person's position among siblings has a lasting impact on that person's life course. Empirical research on the relation between birth order and intelligence has convincingly documented that performances on psychometric intelligence tests decline slightly from firstborns to later-borns. By contrast, the search for birth-order effects on personality has not yet resulted in conclusive findings. We used data from three large national panels from the United States (n = 5,240), Great Britain (n = 4,489), and Germany (n = 10,457) to resolve this open research question. This database allowed us to identify even very small effects of birth order on personality with sufficiently high statistical power and to investigate whether effects emerge across different samples. We furthermore used two different analytical strategies by comparing siblings with different birth-order positions (i) within the same family (within-family design) and (ii) between different families (between-family design). In our analyses, we confirmed the expected birth-order effect on intelligence. We also observed a significant decline of a 10th of a SD in self-reported intellect with increasing birth-order position, and this effect persisted after controlling for objectively measured intelligence. Most important, however, we consistently found no birth-order effects on extraversion, emotional stability, agreeableness, conscientiousness, or imagination. On the basis of the high statistical power and the consistent results across samples and analytical designs, we must conclude that birth order does not have a lasting effect on broad personality traits outside of the intellectual domain. PMID:26483461

  12. Phase perturbation measurements through a heated ionosphere

    NASA Technical Reports Server (NTRS)

    Frey, A.; Gordon, W. E.

    1982-01-01

    High frequency radiowaves incident on an overdense (i.e., HF-frequency penetration frequency) ionosphere produce electron density irregularities. The effect of such ionospheric irregularities on the phase of UHF-radiowaves was determined. For that purpose the phase of radiowaves originating from celestial radio sources was observed with two antennas. The radiosources were chosen such that the line of sight to at least one of the antennas (usually both) passed through the modified volume of the ionosphere. Observations at 430 MHz and at 2380 MHz indicate that natural irregularities have a much stronger effect on the UHF phase fluctuations than the HF-induced irregularities for presently achieved HF-power densities of 20-80 uW/sq m. It is not clear whether some of the effects observed are the result of HF-modification of the ionosphere. Upper limits on the phase perturbations produced by HF-modification are 10 deg at 2380 MHz and 80 deg at 430 MHz.

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

    SciTech Connect

    Yinn-Nien Huang; Kang, Cheng )

    1991-08-01

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

  14. Penetration of magnetospheric electric fields to the equator and their effects on the low-latitude ionosphere during intense geomagnetic storms

    NASA Astrophysics Data System (ADS)

    Veenadhari, B.; Alex, S.; Kikuchi, T.; Shinbori, A.; Singh, Rajesh; Chandrasekhar, E.

    2010-03-01

    The penetration of magnetospheric electric fields to the magnetic equator has been investigated for two intense magnetic storms that occurred on 31 March 2001 and 6 November 2001. The digital ground magnetic data from equatorial station Tirunelveli (TIR, 0.17°S geomagnetic latitude (GML)) and low-latitude station Alibag (ABG, 10.17°N GML) have been used to identify the storm time electrojet index, EEJ(Dis), which is the difference of the magnetic field variations between TIR and ABG after removing the quiet day variations. The appearance of enhanced DP 2 currents and counterelectrojets (CEJ) during the main and recovery phases of the magnetic storms is possibly due to prompt penetration of electric fields from the high latitudes. These signatures can be interpreted as a clear indicator of the eastward and westward electric fields at the equator. The observed results suggest that the magnitude of the equatorial ionospheric currents driven by the penetrating electric fields is very sensitive to ionospheric conductivity (which depends on local time). Moreover, the intensity of the DP 2 currents started decreasing during the end of the main phase of the storm despite the large negative southward IMF Bz, indicating the dominance of a well-developed shielding electric field for 1 h. As an effect of penetrating electric fields at the equator, the equatorial ionization anomaly is enhanced during the main phase (because of strong eastward electric field) and is inhibited or reduced due to the strong CEJ (because of westward electric field) during the recovery phase.

  15. 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.

  16. Ionospheric Features Diagnosed by Radio Tomography during Strong Geomagnetic Disturbances

    NASA Astrophysics Data System (ADS)

    Andreeva, Elena S.; Kunitsyn, Vyacheslav E.; Tereshchenko, Evgeniy D.; Kozharin, Maksim A.; Nazarenko, Marina O.

    2013-04-01

    During the periods of geomagnetic storms, the ionosphere has a particularly complicated and rapidly changing structure. Each storm is marked by its own set of specific manifestations, which reflect rearrangement of the dynamical pattern of the ionosphere and strong perturbations in its parameters. The complexity and global scale of the ionospheric processes that occur during the storms call for the nonlocal methods for diagnosing the spatiotemporal structure of the ionospheric disturbances. Here, we present the results of studying the ionospheric structure by the methods of low orbital radio tomography (RT). The ionospheric radio tomography is rapidly developing during the last two decades. Due to the sufficiently high satellite velocity (~7.9 km/s) and, correspondingly, quite fast (compared to the characteristic times of the ionospheric processes) passage of the satellite through the ionospheric region under study, the radio tomographic approach is suitable for making nearly instantaneous (covering an interval of 5-10 min) 2D snapshots of the ionosphere in the altitude-latitude plane. The vertical and horizontal resolution of RT is 30-40 km and 20-30 km, respectively. We consider the ionospheric manifestations of strong geomagnetic storms (1991-2012) in different regions worldwide including the European part of Russia and North America. We note that during the geomagnetic disturbances, the ionosondes frequently show unstable operation. In contrast to the ionosondes that use HF radio waves, the RT methods are suitable for imaging the ionosphere even during severe solar and geophysical disturbances. During the periods of strong perturbations, RT detected various wavelike structures, travelling ionospheric disturbances, and different manifestations of acoustic gravity waves in the ionosphere. Using the RT methods, the wave effects of particle precipitation were analyzed, and plasma flows were estimated. Radio tomographic imaging of the ionosphere during severe disturbances reveals multiextremal spotty patterns with steep wall-like gradients in electron density in the north. Thin enhancements of electron concentration that are elongated by hundreds of kilometers along the magnetic field lines and attain dozens of kilometers in the transversal direction are identified. The complexly structured ionospheric trough with a tilted polar wall shifted towards the equator is revealed. Many RT reconstructions show the ionospheric trough to split. For example, the RT imaging of the storm of March 24-28, 1991 indicates that the ionospheric structures that are normally typical of the subauroral and auroral ionosphere (the troughs and anomalous ionization in the F-region) reached middle latitudes at that time. During the strongest geomagnetic storm on October 30-31, 2003, the ionosphere over the European part of Russia was marked by anomalously high electron concentration; the distribution of electron density in the region of increased ionization was extremely complicated in space and highly variable in time. We are grateful to the North-West Research Associates (NWRA) for providing the experimental data on relative TEC measured at the RT system in Alaska. The work was supported by the Russian Foundation for Basic Research (grants 11-05-01157 and 13-05-01122).

  17. 75 FR 77675 - AREVA NP, Inc.; Confirmatory Order (Effective Immediately)

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-12-13

    ... be filed in accordance with the NRC E-Filing rule (72 FR 49139, August 28, 2007). The E-Filing... COMMISSION AREVA NP, Inc.; Confirmatory Order (Effective Immediately) I AREVA NP, Inc. (AREVA or Licensee) is.... SNM-1227, effective April 24, 2009. The license authorizes the operation of the AREVA NP facility...

  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. Higher order spin effects in inspiralling compact objects binaries

    NASA Astrophysics Data System (ADS)

    Marsat, Sylvain

    2015-04-01

    We present recent progress on higher order spin effects in the post-Newtonian dynamics of compact objects binaries. We present first an extension of a Lagrangian formalism for point particle with spins, where finite size effects are represented by an additional multipolar structure. When applied to the case of a spin-induced octupole, the formalism allows for the computation of the cubic-in-spin effects that enter at the order 3.5PN. We also report on results obtained for quadratic-in-spin effects at the next-to-leading order 3PN. In both cases, we recover existing results for the dynamics, and derive for the first time the gravitational wave energy flux and orbital phasing. These results will be useful for the data analysis of the upcoming generation of advanced detectors of gravitational waves. NASA Grant 11-ATP-046.

  20. Characterization of the Ionosphere Above the HAARP HF Heater Using DEMETER Satellite Data

    NASA Astrophysics Data System (ADS)

    Piddyachiy, D.; Inan, U. S.; Bell, T. F.; Parrot, M.

    2008-12-01

    One of the goals of the High Frequency Active Auroral Research Program (HAARP) is to study the properties of the ionosphere and the overlying plasma, especially those which can be modified and controlled by electromagnetic waves [Kennedy and Kossey, 2002]. For this purpose, a phased array of HF transmitters (3.6 MW, 2.8 - 10 MHz) is used to radiate intense electromagnetic waves up into the ionosphere. There are many possible applications of HF transmitter operation, and one of the most important is generation of ELF waves via modulation of the auroral electrojet current [Stubbe and Kopka, 1977]. All these applications depend on the natural parameters of the ionosphere during an experiment and on the change of the parameters produced by the HAARP transmitter on its own. In this work we present measurements of ionospheric parameters carried out during many passes of the DEMETER satellite over HAARP, both when HAARP is transmitting and when not. DEMETER is a low-earth orbit satellite (660 km) capable of simultaneous measurements of electron and ion densities, electron and ion temperatures, and electromagnetic waves in different frequency bands from 0 to 3.3 MHz. It should be noted that the use of the upper band of the receiver enables observation of the HAARP HF signal which directly reaches the spacecraft in some cases of close passes and favorable ionospheric conditions. The purpose of this work is to differentiate the effects naturally existing over HAARP and those created by HAARP. One such effect considered in detail is the depletion of ionospheric densities and formation of a duct for ELF/VLF waves. The first results of direct satellite observations suggested that depletion of electron and ion densities up to one order of magnitude and corresponding increase in electron temperatures can occur during HAARP heating experiments. However, a thorough analysis of a number of DEMETER passes revealed that such depletions also exists over HAARP when the transmitter is not operating. Further correlation of the position of this depletion region with Kp indices suggested that this depletion is in fact an ionospheric trough [Rodgers et al.,1992]. Even though such depletion is not created by HAARP it can substantially affect the propagation of ELF/VLF generated by HAARP and also influences on other experiments conducted with HAARP.

  1. 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.

  2. HF modulated ionospheric currents

    NASA Astrophysics Data System (ADS)

    Payne, J. A.; Inan, U. S.; Foust, F. R.; Chevalier, T. W.; Bell, T. F.

    2007-12-01

    The HAARP HF facility is used to modulate the components of the auroral electrojet that flow in the D-region of the ionosphere, creating ELF/VLF radiation which is then measured at a receiver co-located with the HAARP HF antenna. An HF heating model is coupled to a full wave plasma interaction FDTD code to determine the ELF/VLF response of the ionospheric plasma to the modulated HF stimulation. The predicted FDTD fields on the ground are found to be in remarkable agreement with those measured at a receiver co-located with HAARP. The FDTD code also predicts an upwardly propagating whistler mode that is tightly bound to the magnetic field lines.

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

    NASA Astrophysics Data System (ADS)

    Tu, Jiannan; Song, Paul; Vasyliūnas, 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.

  4. Satellite measurement of ionospheric-induced vhf distortion

    SciTech Connect

    Armstrong, W.T.; Murphy, T.; Roussel-Dupre, R.; Carter, M.J.; Blevins, B.

    1992-09-01

    BLACKBEARD is a satellite RF experiment designed to study distortion and interference effects on transient transionospheric VHF signals. RF distortion will be characterized by a frequency-coherence bandwidth for different ionospheric conditions. Limitations of broad-band measurements from the frequency-coherence bandwidth of the ionosphere and broadcast interference signals will be established through these studies. Distinction between multi-path distortion resulting from large scale, coherent perturbations and small scale, random perturbations to the ionosphere will be emphasized. Ionospheric transfer function models, trans-ionospheric signal predictions, and coherence bandwidth predictions will be tested and optimized with these measurements. A global data base for both broadcast and lightning interference will also derive from these studies. This database will form the basis for interference feature extraction, signal typing, and possible neural network cataloging. The specific missions of the BLACKBEARD experiment include: perform broad-band VHF measurements of transient signals originating from a controlled pulsed ground beacon, to characterize broad-band ionospheric distortion, perform narrow-band VHF measurements of cw signals from a multi-chord interferometry ground beacon array, to characterize ionospheric structure contributing to transmission distortion, and survey power envelopes of lightning and man-made interference in selectable VHF bands, for background rejection purposes. BLACKBEARD is part of the ALEMS soft x-ray measurement satellite, a small satellite system designed for a PEGASUS launch into a 70{degrees} inclination, low earth orbit in late 1992.

  5. Satellite measurement of ionospheric-induced vhf distortion

    SciTech Connect

    Armstrong, W.T.; Murphy, T.; Roussel-Dupre, R.; Carter, M.J.; Blevins, B.

    1992-01-01

    BLACKBEARD is a satellite RF experiment designed to study distortion and interference effects on transient transionospheric VHF signals. RF distortion will be characterized by a frequency-coherence bandwidth for different ionospheric conditions. Limitations of broad-band measurements from the frequency-coherence bandwidth of the ionosphere and broadcast interference signals will be established through these studies. Distinction between multi-path distortion resulting from large scale, coherent perturbations and small scale, random perturbations to the ionosphere will be emphasized. Ionospheric transfer function models, trans-ionospheric signal predictions, and coherence bandwidth predictions will be tested and optimized with these measurements. A global data base for both broadcast and lightning interference will also derive from these studies. This database will form the basis for interference feature extraction, signal typing, and possible neural network cataloging. The specific missions of the BLACKBEARD experiment include: perform broad-band VHF measurements of transient signals originating from a controlled pulsed ground beacon, to characterize broad-band ionospheric distortion, perform narrow-band VHF measurements of cw signals from a multi-chord interferometry ground beacon array, to characterize ionospheric structure contributing to transmission distortion, and survey power envelopes of lightning and man-made interference in selectable VHF bands, for background rejection purposes. BLACKBEARD is part of the ALEMS soft x-ray measurement satellite, a small satellite system designed for a PEGASUS launch into a 70{degrees} inclination, low earth orbit in late 1992.

  6. Observations of Ionospheric Currents at Mars and Venus

    NASA Astrophysics Data System (ADS)

    Fillingim, M. O.; Lillis, R. J.; Brain, D. A.

    2013-12-01

    How the solar wind interacts with a planetary object depends upon the object's properties, such as the presence of a magnetic field or an atmosphere. An unmagnetized object cannot stand-off the solar wind unless it possess a substantial atmosphere. Currents can be induced in the ionosphere which act to cancel out the external solar wind magnetic field preventing it from reaching the surface. Here we present observations of such induced currents in the ionospheres of Mars and Venus. During aerobraking maneuvers, Mars Global Surveyor made several passes through the ionosphere of Mars in the unmagnetized northern hemisphere. Likewise, Pioneer Venus Orbiter and Venus Express have passed through the ionosphere of Venus. From the observed changes in the local magnetic field, we calculate vertical profiles of (predominantly) horizontal ionospheric currents. Given an atmospheric model, we also calculate the ionospheric conductivity and the ionospheric electric fields associated with these currents. These results can give us insights into how external magnetic fields are effectively screened out by induced currents and how induced magnetospheres form around unmagnetized objects.

  7. Robust GPS carrier tracking under ionospheric scintillation

    NASA Astrophysics Data System (ADS)

    Susi, M.; Andreotti, M.; Aquino, M. H.; Dodson, A.

    2013-12-01

    Small scale irregularities present in the ionosphere can induce fast and unpredictable fluctuations of Radio Frequency (RF) signal phase and amplitude. This phenomenon, known as scintillation, can degrade the performance of a GPS receiver leading to cycle slips, increasing the tracking error and also producing a complete loss of lock. In the most severe scenarios, if the tracking of multiple satellites links is prevented, outages in the GPS service can also occur. In order to render a GPS receiver more robust under scintillation, particular attention should be dedicated to the design of the carrier tracking stage, that is the receiver's part most sensitive to these types of phenomenon. This paper exploits the reconfigurability and flexibility of a GPS software receiver to develop a tracking algorithm that is more robust under ionospheric scintillation. For this purpose, first of all, the scintillation level is monitored in real time. Indeed the carrier phase and the post correlation terms obtained by the PLL (Phase Locked Loop) are used to estimate phi60 and S4 [1], the scintillation indices traditionally used to quantify the level of phase and amplitude scintillations, as well as p and T, the spectral parameters of the fluctuations PSD. The effectiveness of the scintillation parameter computation is confirmed by comparing the values obtained by the software receiver and the ones provided by a commercial scintillation monitoring, i.e. the Septentrio PolarxS receiver [2]. Then the above scintillation parameters and the signal carrier to noise density are exploited to tune the carrier tracking algorithm. In case of very weak signals the FLL (Frequency Locked Loop) scheme is selected in order to maintain the signal lock. Otherwise an adaptive bandwidth Phase Locked Loop (PLL) scheme is adopted. The optimum bandwidth for the specific scintillation scenario is evaluated in real time by exploiting the Conker formula [1] for the tracking jitter estimation. The performance of the proposed tracking scheme is assessed by using both simulated and real data. Real data have been collected in Vietnam by using a USRP (Universal Software Radio Peripheral) N210 front end connected to a rubidium oscillator. Selected events are exploited in order to challenge the algorithm with strong phase and amplitude variations. Moreover, simulated data have been collected by using the prototype of a digital front end developed by Novatel, namely the 'Firehose'. Since the latter includes a TCXO oscillator, the proposed tracking scheme is also opportunely modified to take in account the clock error contribution. References 1. R.S., Conker, M. B. El-Arini, C. J. Hegarty, and T. Hsiao, Modelling the effects of ionospheric scintillation on GPS/satellite-based augmentation system availability. Radio Sci., 38, 1, 1001, doi: 10.1029/2000RS002604, 2003. 2. B. Bougard et al, 'CIGALA: Challenging the Solar Maximum in Brazil with PolaRxS,' ION GNSS, Portland, Sept. 2011.

  8. Correcting ionospheric Faraday rotation for ASKAP

    NASA Astrophysics Data System (ADS)

    O'Sullivan, Shane; Gaensler, Bryan; Landecker, Tom L.; Willis, Tony

    2012-10-01

    Next-generation polarisation surveys, such as the POSSUM survey on ASKAP, aim to measure weak, statistical, cosmological effects associated with weak magnetic fields, and so will require unprecedented accuracy and stability for measuring polarisation vectors and their Faraday rotation measures (RMs). Ionospheric Faraday rotation (IFR) corrupts polarization observations and cannot be ignored at mid to low frequencies. In aperture-synthesis polarimetry IFR rotates individual visibilities and leads to a loss of coherence and accuracy of polarization angle determination. Through the POSSUM survey science team we have been involved in developing detailed ionospheric prediction software (POSSUM memos #10a,b) that will be used to correct the observed visibilities on ASKAP before imaging to obtain sufficiently accurate polarization and RM data. To provide a stringent test of this software, we propose a continuous 24 hr observing block using the 1.1-3.1 GHz band to monitor the variations caused by the time-variable ionosphere in the polarization angle and RM of a strongly polarized calibrator source, PKS B1903-802. We request a total of 96 hrs (4 x 24 hrs) to monitor the changes in the ionosphere every 3 to 6 months until BETA/ASKAP-12 is taking reliable polarization data.

  9. Broadband Ionospheric Scintillation Measurements from Space

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  10. Ray tracing technique for global 3-D modeling of ionospheric electron density using GNSS measurements

    NASA Astrophysics Data System (ADS)

    Alizadeh, Mohamad Mahdi; Schuh, Harald; Schmidt, Michael

    2015-06-01

    For space geodetic techniques, operating in microwave band, ionosphere is a dispersive medium; thus, signals traveling through this medium are in the first approximation, affected proportional to the inverse of the square of their frequencies. This effect allows gaining information about the parameters of the ionosphere in terms of total electron content (TEC) or the electron density (Ne). Making use of this phenomenon, space geodetic techniques have turned into a capable tool for studying the ionosphere in the last decades. Up to now, two-dimensional (2-D) models of Vertical TEC (VTEC) have been widely developed and used by different communities; however, due to the fact that these models provide information about the integral of the whole electron content along the vertical or slant raypath, these maps are not useful when information about the ionosphere at different altitude is required. This paper presents a recent study which aims at developing a global 3-D model of the electron density, using measurements from Global Navigation Satellite Systems and by applying the ray tracing technique to the upper atmosphere. The developed modeling approach represents the horizontal variations of the electron density, with two sets of spherical harmonic expansions of degree and order 15. The height dependency of the electron density is represented by a multilayered Chapman profile function for the bottomside and topside ionosphere, and an appropriate model for the plasmasphere. In addition to the geodetic applications of the developed models, within this study, the 3-D models of electron density can include geophysical parameters like maximum electron density and its corresponding height. High-resolution modeling of these parameters allows an improved geophysical interpretation, which is essential in all studies of the upper atmosphere, space weather, and for the solar-terrestrial environment.

  11. 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.

  12. Rotation of the ionospheric electric potential caused by spatial gradients of ionospheric conductivity

    NASA Astrophysics Data System (ADS)

    Nakamizo, A.; Yoshikawa, A.; Ohtani, S.; Ieda, A.; Seki, K.

    2013-12-01

    The present study focuses on the relationship between the inhomogeneity of the ionospheric conductivity and the rotation of the ionospheric potential. By applying a simplified version of the Hall-conjugate separation method [Yoshikawa, in preparation] to a global ionospheric potential solver, we analyze calculated potential structures separating them into the primary field and secondary field (the polarization field generated by the Hall effect). Calculations are performed with the following conditions for simplification. Here we call the diagonal and off-diagonal components of the conductivity tensor used in the potential solver SGTT/SGPP and SGTP, respectively, and we regard them as Pedersen and Hall conductivities for the high-latitude region. Besides, we call SGTP 'effective-Hall conductivity' based on its characteristics. (1) The input is a dawn-dusk and day-night symmetric R1-FAC. (2) The basic conductivity distribution is homogeneous in the longitudinal direction with only the latitudinal gradient by solar EUV and equatorial enhancement, no day-night difference and no auroral enhancement. (3) From the basic distribution, SGTP is changed with respect to the fixed SGTT/SGPP with the Hall-Pedersen ratio and offset that are applied globally. It is confirmed that the rotation angle (polarization field) is not so changed when we add only offsets but it becomes larger as the Hall-Pedersen ratio increases. This result is not only consistent with a theoretical prediction [Yoshikawa et al., 2013b] but also provides the fact that the ionospheric internal process, the primary-secondary fields generation process, does affect largely on the potential structure, and eventually on the magnetosphere-ionosphere processes. By combining the previously obtained and current results, we will clarify how the potential structure is actually described by the primary field and secondary field. The results can be applied to qualitatively/quantitatively identify the ionospheric causes of components of potential rotation/asymmetries that cannot be explained only by solar wind-magnetosphere effects.

  13. 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.

  14. 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

  15. Effect of the deformation of a regular ionospheric plasma profile on the anomalous absorption of a high-power radio wave in the resonance region

    NASA Astrophysics Data System (ADS)

    Vas'kov, V. V.; Dimant, Ia. S.

    1989-06-01

    It is shown that localized distortions of ionospheric plasma density profile due to the intense excitation of plasma oscillations near the upper-hybrid resonance of a high-power radio wave can lead to a change in the anomalous absorption of the disturbing wave. The profile deformation stabilizes the amplitude of a high-power radio wave reflected from the ionosphere and leads to an asymmetry in sounding waves with frequencies above and below that of the high-power wave.

  16. Study of Ionospheric Storms Using Global Assimilative Ionospheric Models

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  17. Coupled Magnetotail-Ionosphere Asymmetries from Ionospheric Hall Conduction

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  18. Ionospheric and thermospheric couplings: vertical, latitudinal and longitudinal

    NASA Astrophysics Data System (ADS)

    Wickwar, V. B.; Carlson, H. C.

    1999-01-01

    The ionosphere, embedded in and tightly coupled to the thermosphere, is strongly influenced by couplings to other geophysical regions. For example, above it, both the magnetosphere and plasmasphere greatly affect the ionosphere by the precipitation of soft and energetic particles, by heat conduction, and by fluxes of thermal particles. Below, the middle atmosphere affects it with upwardly propagating waves (gravity waves, tides, and planetary waves). All the while, polar and auroral regions greatly affect the mid-latitudes by the equatorward penetration of electric fields and winds, and by the equatorward propagation of waves (traveling ionospheric disturbances or TIDs). Exploring these couplings effectively furthers our understanding of at least the dominant processes and interactions that play such an important role in determining the character of this part of the Earths environment. Significant progress during the Solar-Terrestrial Energy Program (STEP) has demanded that the observational, analytical, and theoretical thrusts of the international scientific community be global in all senses. Observationally, this has led to coordinated measurements from many regions, from the poles to the equator, and from ground- and space-based instruments. It has also led to many different instruments, including new ones, measuring an extensive variety of (related) geophysical parameters. Depending on the instrument, measurements have been made continuously or at appropriate intervals to sample different geomagnetic conditions, and diurnal, seasonal, inter-annual, and solar-cycle variations. Extensive analyses have been carried out on these observations. New empirical models have been developed and old ones improved. Theoretical work has led to new and improved first-principles models that are being used to test our understanding of the observations. Our intent is to review this progress and suggest some future directions. Our approach is to illustrate the broad front of progress with representative examples, rather than to do an exhaustive review. We apologize from the start, to those whose good work we have not noted, in order to allow a broad balanced overview of areas advanced.

  19. A statistic study of ionospheric solar flare activity indicator

    NASA Astrophysics Data System (ADS)

    Xiong, Bo; Wan, Weixing; Ning, Baiqi; Ding, Feng; Hu, Lianhuan; Yu, You

    2014-01-01

    According to the Chapman ionization theory, an ionospheric solar flare activity indicator (ISFAI) is given by the solar zenith angle and the variation rate of ionospheric vertical total electron content, which is measured from a global network of dual-frequency GPS receivers. The ISFAI is utilized to statistically analyze the ionospheric responses to 1439 M-class and 126 X-class solar flares during solar cycle 23 (1996-2008). The statistical results show that the occurrence of ISFAI peak increases obviously at 3.2 total electron content unit (TECU)/h (1 TECU = 1016 el m-2) and reaches the maximum at 10 TECU/h during M-class flares and 10 TECU/h and 40 TECU/h for X-class flares. ISFAI is closely correlated with the 26-34 nm extreme ultraviolet flux but poorly related to the 0.1-0.8 nm X-ray flux. The central meridian distance (CMD) of flare location is an important reason for depressing relationship between ISFAI and X-ray Flux. Through the CMD effect modification, the ISFAI has a significant dependence on the X-ray flux with a correlation coefficient of 0.76. The ISFAI sensitivity enables to detect the extreme X-class flares, as well as the variations of one order of magnitude or even smaller (such as for C-class flares). Meanwhile, ISFAI is helpful to the calibration of the X-ray flux at 0.1-0.8 nm observed by GOES during some flares. In addition, the statistical results demonstrate that ISFAI can detect 80% of all M-class flares and 92% for all X-class ones during 1996-2008.

  20. A statistic study of ionospheric solar flare activity indicator

    NASA Astrophysics Data System (ADS)

    Xiong, Bo; Ding, Feng; Ning, Baiqi; Wan, Weixing; Yu, You; Hu, Lianhuan

    According to the Chapman ionization theory, an ionospheric solar flare activity indicator (ISFAI) is given by the solar zenith angle and the variation rate of ionospheric vertical total electron content, which is measured from a global network of dual-frequency GPS receivers. The ISFAI is utilized to statistically analyze the ionospheric responses to 1439 M-class and 126 X-class solar flares during solar cycle 23 (1996-2008). The statistical results show that the occurrence of ISFAI peak increases obviously at 3.2 total electron content unit (TECU)/h (1 TECU = 1016 elm-2) and reaches the maximum at 10 TECU/h during M-class flares and 10 TECU/h and 40 TECU/h for X-class flares. ISFAI is closely correlated with the 26-34 nm extreme ultraviolet flux but poorly related to the 0.1-0.8 nm X-ray flux. The central meridian distance (CMD) of flare location is an important reason for depressing relationship between ISFAI and X-ray Flux. Through the CMD effect modification, the ISFAI has a significant dependence on the X-ray flux with a correlation coefficient of 0.76. The ISFAI sensitivity enables to detect the extreme X-class flares, as well as the variations of one order of magnitude or even smaller (such as for C-class flares). Meanwhile, ISFAI is helpful to the calibration of the X-ray flux at 0.1-0.8 nm observed by GOES during some flares. In addition, statistical results demonstrate that ISFAI can detect 80% of all M-class flares and 92% for all X-class ones during 1996-2008. Owing to the high sensitivity and temporal resolution, ISFAI can be utilized as a solar flare detection parameter to monitor space weather.

  1. Ionospheric Flow and Escape of Ions from Titan and Venus

    NASA Technical Reports Server (NTRS)

    Hartle, R. E.; Intriligator, D. S.; Grebowsky, Joseph M.; Vondrak, Richard R. (Technical Monitor)

    2001-01-01

    Knowledge gained from measurements and models is used to study the high-speed plasmas interacting with the atmospheres and ionospheres of Titan and Venus. Considering the similarities of the interactions, comparative analysis is used to support the interpretations of observations made at each body. Ionospheric flow inferred to exist by analysis of measurements made from the Pioneer Venus Orbiter supports the interpretation of similar flow in the ionosphere of Titan. The concept that cold ions escape from the ionosphere of Venus is supported by the Voyager I observation that cold ions escape down the magnetic tail of Titan. Pickup O+ ion energy distributions observed at their source in the ionosheath of Venus are shown to be influenced by finite gyroradius effects. The signatures of such effects are expected to be retained as the ions move into the wakes of Titan and Venus.

  2. 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.

  3. A Review of Low Frequency Electromagnetic Wave Phenomena Related to Tropospheric-Ionospheric Coupling Mechanisms

    NASA Technical Reports Server (NTRS)

    Simoes, Fernando; Pfaff, Robert; Berthelier, Jean-Jacques; Klenzing, Jeffrey

    2012-01-01

    Investigation of coupling mechanisms between the troposphere and the ionosphere requires a multidisciplinary approach involving several branches of atmospheric sciences, from meteorology, atmospheric chemistry, and fulminology to aeronomy, plasma physics, and space weather. In this work, we review low frequency electromagnetic wave propagation in the Earth-ionosphere cavity from a troposphere-ionosphere coupling perspective. We discuss electromagnetic wave generation, propagation, and resonance phenomena, considering atmospheric, ionospheric and magnetospheric sources, from lightning and transient luminous events at low altitude to Alfven waves and particle precipitation related to solar and magnetospheric processes. We review in situ ionospheric processes as well as surface and space weather phenomena that drive troposphere-ionosphere dynamics. Effects of aerosols, water vapor distribution, thermodynamic parameters, and cloud charge separation and electrification processes on atmospheric electricity and electromagnetic waves are reviewed. We also briefly revisit ionospheric irregularities such as spread-F and explosive spread-F, sporadic-E, traveling ionospheric disturbances, Trimpi effect, and hiss and plasma turbulence. Regarding the role of the lower boundary of the cavity, we review transient surface phenomena, including seismic activity, earthquakes, volcanic processes and dust electrification. The role of surface and atmospheric gravity waves in ionospheric dynamics is also briefly addressed. We summarize analytical and numerical tools and techniques to model low frequency electromagnetic wave propagation and solving inverse problems and summarize in a final section a few challenging subjects that are important for a better understanding of tropospheric-ionospheric coupling mechanisms.

  4. Higher-order nonlinear effects in a Josephson parametric amplifier

    NASA Astrophysics Data System (ADS)

    Kochetov, Bogdan A.; Fedorov, Arkady

    2015-12-01

    Nonlinearity of the current-phase relationship of a Josephson junction is the key resource for a Josephson parametric amplifier (JPA) as well as for a Josephson traveling-wave parametric amplifier, the only devices in which the quantum limit for added noise has so far been approached at microwave frequencies. A standard approach to describe JPA takes into account only the lowest order (cubic) nonlinearity resulting in a Duffing-like oscillator equation of motion or in a Kerr-type nonlinearity term in the Hamiltonian. In this paper we derive the quantum expression for the gain of JPA including all orders of the Josephson junction nonlinearity in the linear response regime. We then analyze gain saturation effect for stronger signals within a semiclassical approach. Our results reveal nonlinear effects of higher orders and their implications for operation of a JPA.

  5. Research on the lunar ionosphere using dual-frequency radio occultation with a small VLBI antenna

    NASA Astrophysics Data System (ADS)

    Wang, Zhen; Wang, Na; Ping, Jinsong

    2015-04-01

    The Vstar in the Japanese lunar SELENE Radio Science experiment was occulted by virtue of the lunar ionosphere. Using the single sub-satellite and the S/X band coherent radio waves, dual-frequency measurements were acquired at a ground receiving station. In order to investigate the variation of ionospheric total electron content (TEC) surrounding the moon, the TEC, including the terrestrial ionosphere, the interplanetary plasma and lunar ionosphere, can be derived from the phase information of the observational data. We update the observation equation and algorithms, calculate the linear fitting trend of the lunar ionosphere from 60 to 30 km above the surface of the moon. The fitting trend is extended from 30 to 0 km above the surface of the moon. The lunar ionosphere is obtained by using the short time trend extrapolation method.

  6. 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…

  7. On the reliability of the Spatial Scintillation Index to detect earthquake precursors in the ionosphere

    NASA Astrophysics Data System (ADS)

    Masci, F.; Thomas, J. N.

    2015-08-01

    The scientific literature includes many reports of ionospheric phenomena that are retrospectively identified prior to seismic events. These disturbances of the Earth's ionosphere are considered to be possible precursors of the impending earthquakes. However, a causal relationship between ionospheric phenomena and earthquakes has never been definitively demonstrated, and attempts at identifying precursory effects in the ionosphere have been called into question by several studies. Among the candidate indicators of ionospheric precursors there is the Spatial Scintillation Index (SSI) proposed by Pulinets et al. (2007). The usefulness of this index in the search for precursory effects of earthquakes has been criticized by Thomas et al. (2012) and Masci (2013). In a recent report, Pulinets and Davidenko (2014) attempt to briefly respond to the remarks of these researchers. Here we cast doubt that Pulinets and Davidenko (2014) have shown that SSI is a reliable indicator of precursory effects of earthquakes in the ionosphere.

  8. Abnormally large magnetospheric electric field on 9 November 2004 and its effect on equatorial ionosphere around the world

    NASA Astrophysics Data System (ADS)

    Rastogi, R. G.; Chandra, H.; Condori, Louis; Abdu, M. A.; Reinisch, B.; Tsunoda, R. T.; Prasad, D. S. V. V. D.; Pant, T. K.; Maruyama, T.

    2012-10-01

    There was a solar event around 1850 UT on 9th November 2004, associated with an abnormally large solar wind flow pressure and large southward interplanetary magnetic field, causing an abnormally large prompt penetration electric field between 1850 and 2100 UT. Abnormally large vertical F-region drifts by Jicamarca backscatter radar were reported associated with the event. The F-region over Jicamarca, Peru (14-16 LT) and Sao Luis, Brazil (16-18 LT) was lifted upward, broken into two portions and the upper one was blown out of the range of the ionosonde. At Fortaleza, an off-equatorial station in Brazil, the F-region was also lifted up but later the foF2 increased due to the flow of ionization from upper layer blown up over the equatorial region. The F-region at Ascension Island (19-21 LT), an off-equatorial station, was lifted up without any deformations till 1915 LT but descended at 1930 LT due to reversal of electric field polarity. At Indian stations, Trivandrum and Waltair (00-02 LT), the F-region was pushed down and later disappeared as a consequence of enhanced westward ionospheric electric field in the night sector. The ionosonde did not receive any echo for a couple of hours till the next sunrise. The F-region at Kototaban (03-05 LT), Indonesia also disappeared after a rapid descend. At Kwajelien (06-08 LT) there was no equatorial type of sporadic-E at 07 to 09 LT due to the westward electric field.

  9. Transport from higher order g-jitter effects.

    PubMed

    Naumann, Robert J

    2002-10-01

    Large complex spacecraft, such as the International Space Station (ISS), will have a rich spectrum of vibrational modes that will be excited by crew activity as well as by on-board mechanical systems. The response of various experiments to this vibratory environment is not completely understood and has been a subject of concern to the users community. Since these vibrations arise for the most part from internal forces, the net acceleration must time-average to zero. Steady state periodic accelerations applied to a fluid in a completely filled container with an imposed density gradient will drive first-order flows that time-average to zero. Likewise, the resulting first-order thermal and solutal fluctuations time-average to zero. Over the range of frequencies in the vibrational environment expected on the ISS, the velocity oscillations tend to be nearly 90 degrees out of phase with the thermal and/or solutal fluctuations; consequently, little net transport occurs from the first-order effects. We must, therefore, examine possible higher-order effects that can lead to significant net transport. Second-order flows with non-zero time averages arise from the non-linear terms in the flow equations and from incomplete cancellation of first-order flows if the density gradient changes with time, or if the periodic acceleration has both axial and transverse components relative to the imposed density gradient. The time-average of such flows can be expressed in terms of the sum of the square of each periodic acceleration, weighted by the appropriate function of the frequency, taken over all frequencies; or as the weighted integral over the power spectral distribution (PSD) of the frequency spectrum. Approximate analytical solutions for these second-order flows, which agree closely with numerical computations, have been found using a perturbation analysis. These analytical models are then used to predict the effects of the anticipated vibratory environment on various classes of experiments planned for the ISS. Even though these second-order flows are much smaller than the first-order flows, it is shown that they can produce significant transport. PMID:12446311

  10. Tohoku earthquake shook the ionosphere

    NASA Astrophysics Data System (ADS)

    Balcerak, Ernie

    2011-08-01

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

  11. Towards a Pan-European network for the mitigation of ionospheric threats (Invited)

    NASA Astrophysics Data System (ADS)

    Jakowski, N.; Hlubek, N.; Sato, H.; Berdermann, J.; Aquino, M. H.

    2013-12-01

    Measurements of signals from Global Navigation Satellite Systems (GNSS) offer the possibility to analyze the spatial and temporal characteristics of the electron density structure in the ionosphere and plasmasphere. Dual frequency ground based measurements are well suited to observe horizontal structures of the electron density and their dynamics whereas space based GNSS measurements can effectively contribute to explore the vertical structure of the ionosphere-plasmasphere ionization. The current data base, covering more than one solar cycle, enabled the development of empirical models of ionospheric key parameters such as the total electron content (TEC), the peak density NmF2 and the corresponding peak density height hmF2. TEC models can directly be used as correction in single frequency GNSS applications. Utilizing well established geodetic networks such as that of the International GNSS Service (IGS), it is discussed how ground based GNSS measurements are used to derive regional and global maps of the vertical TEC in near real time. Actual TEC maps are used for correcting ionospheric range errors in operational single frequency applications, e.g. in space based augmentation systems (SBAS) like WAAS in US and EGNOS in Europe. However, severe space weather conditions lead to perturbations of the ionospheric plasma which in turn can affect the performance of GNSS. These perturbations come at a wide range of spatial and temporal scales and are observed as large scale ionization fronts, medium scale travelling ionospheric disturbances, plasma bubbles and small scale irregularities causing radio scintillations at the receiver level. These disturbances can strongly degrade the accuracy, reliability, integrity and availability of the GNSS. This is especially detrimental for space and ground based augmentation systems which have specific accuracy and availability requirements. Therefore an important use of the measurements of GNSS signals is to assess the threat that space weather can have on GNSS. One possible application is the estimation of the strongest possible influence of the ionosphere. This can then be used as a safety margin to fulfill the high safety requirements of aircrafts landing with GNSS and GBAS. GNSS receivers are a crucial component in countless modern systems, e.g. in telecommunication, navigation, remote sensing and precision timing. Additionally the demands on these systems with respect to accuracy, reliability and safety are permanently growing. Considering the fact that the ionospheric impact cannot be ignored enhanced research activities are required to improve current solutions for correcting or mitigating the ionospheric impact or at least to provide awareness of current threats. It is reported how the current EC funded research project TRANSMIT focuses on bringing together young researchers in this field in order to establish a Pan-European network for Ionospheric Perturbation Detection and Monitoring (IPDM) in the upcoming years. To highlight essential results of these researchers, a prototype solution is being prepared to be accessible via internet (http://swaciweb.dlr.de ).

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

    SciTech Connect

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

    2011-11-15

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

  13. Ion resonances and ELF wave production by an electron beam injected into the ionosphere - ECHO 6

    NASA Technical Reports Server (NTRS)

    Winckler, J. R.; Steffen, J. E.; Malcolm, P. R.; Erickson, K. N.; Abe, Y.; Swanson, R. L.

    1984-01-01

    Two effects observed with electron antennas ejected from a sounding rocket launched into the ionosphere in March 1983 carrying electron beam guns are discussed. The sensor packages were ejected and travelled parallel to the vehicle trajectory. Electric potentials were measured between the single probes and a plasma diagnostic package while the gun injected electrons into the ionosphere in perpendicular and parallel 1 kHz directions. Signal pulses over the dc-1250 kHz range were detected. A kHz gun frequency caused a signal that decreased by two orders of magnitude between 45-90 m from the beam field line. However, the signal was detectable at 1 mV/m at 120 m, supporting earlier data that indicated that pulsed electron beams can cause ELF waves in space. Beam injection parallel to the magnetic field produced an 840 Hz resonance that could be quenched by activation of a transverse beam.

  14. Response of the lower equatorial ionosphere to strong tropospheric disturbances

    NASA Astrophysics Data System (ADS)

    Vanina-Dart, L. B.; Pokrovskaya, I. V.; Sharkov, E. A.

    2008-04-01

    A morphological analysis of the results of sounding the lower equatorial ionosphere (the D region) in the region of action of strong tropospheric vortex disturbances (tropical cyclones, TC) is presented in this work. Based on the rocket sounding of the lower ionosphere at Thumba rocket site (8° N, 77° E) in May-June 1985 and on the satellite monitoring of TC in the northern Indian Ocean, it is demonstrated that a sharp depletion (by a factor of 2-4) of the electron concentration at altitudes of 60-80 km could be a response of the ionosphere during the TC active phase. In this case the lower boundary of the D region rose by several kilometers (not more than 5 km), and the temperature in the region of the stratopause slightly (by 2°-3°) increases. It is assumed that internal gravity waves (IGWs) generated by TC cause the effect on the lower ion-osphere.

  15. Robust detection of ionospheric scintillations using MF-DFA technique

    NASA Astrophysics Data System (ADS)

    Miriyala, Sridhar; Koppireddi, Padma Raju; Chanamallu, Srinivasa Rao

    2015-12-01

    The performance of Global Navigation Satellite System (GNSS) receivers is limited by the ionospheric scintillation effects that cause signal degradation due to refraction, reflection and scattering of the signals. Hence, there is a need to develop an ionospheric scintillation detection technique for robust GNSS receivers. In this paper, a new algorithm based on multifractal detrended fluctuation analysis (MF-DFA) is proposed for detecting the ionospheric irregularities. The ionospheric and scintillation GNSS data recorded at Koneru Lakshmaiah (KL) University, Guntur, India, was considered for the analysis. The carrier to noise ratio ( C/ N 0) time series data of GNSS satellite vehicles that are affected due to scintillations was decomposed using adaptive time-frequency methods like empirical mode decomposition (EMD), ensemble empirical mode decomposition (EEMD) and complementary ensemble empirical mode decomposition (CEEMD). It was observed that the CEEMD method combined with MF-DFA provides better results as compared to the EMD and EEMD techniques.

  16. Far-field coseismic ionospheric disturbances of Tohoku earthquake

    NASA Astrophysics Data System (ADS)

    Krasnov, V. M.; Drobzheva, Ya. V.; Chum, J.

    2015-12-01

    A computer code has been developed to simulate the generation of infrasonic waves by a strong earthquake at a distance of 9000 km from the epicenter, their propagation through the atmosphere and their effects in the ionosphere. We provide estimates of the perturbations in the ionosphere at the height (210-220 km) where radiowaves at the sounding frequency (3.595 MHz) of a continuous Doppler radar reflect. Ionospheric perturbations have a global character and amplitudes of 1.5-7.5% of ambient value. Perturbations exist for ~1 h. The form of calculated ionospheric disturbances coincides with the experimental results. The correlation coefficient between calculated and experimental forms was from 0.68 to 0.9.

  17. 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.

  18. VLF heating of the lower ionosphere: Variation with magnetic latitude and electron density profile

    SciTech Connect

    Barr, R. ); Stubbe, P. )

    1992-09-04

    The authors report the results of calculations of ionospheric absorption of VLF heating radiation, in comparison with HF heating. This work was motivated by recent observations of the effects of VLF heating, which indicate that it is much more efficient than HF heating, at least for certain ionospheric conditions. The authors assume an ionospheric model which is consistent with that observed during the previous heating experiments. Their results are in basic agreement with the experimental observations. They find that the enhancement in efficiency of VLF heating over HF heating is a feature of low latitudes, where ionospheric density profiles favor this effect. In the polar regions, HF heating is more efficient.

  19. A climatology of quiet/disturbed ionospheric conditions derived from 22 years of Westerbork interferometer observations.

    NASA Astrophysics Data System (ADS)

    Spoelstra, T. A. T.

    1996-08-01

    Knowledge of the quiet and disturbed conditions in the propagation medium is essential for quality control of trans-atmospheric radio signals. This holds equally for the troposphere and the ionosphere. This paper describes a climatology of ionospheric irregularities obtained from observations of celestial radio sources by radio interferometry, i.e. by the Westerbork Synthesis Radio Telescope (WSRT) in The Netherlands. This instrument is located at geomagnetic mid-latitude. All WSRT calibrator observations in the 22-year period 26 June 1970 - 31 December 1991 have been checked for manifestations of ionospheric effects. Although seasonal effects are clear, the occurrence and "strength" of ionospheric irregularities show no dependence on solar activity.

  20. Self-Consistent Magnetosphere-Ionosphere Coupling: Theoretical Studies

    NASA Technical Reports Server (NTRS)

    Khazanov, G. V.; Newman, T. S.; Liemohn, M. W.; Fok, M.-C.; Spiro, R. W.; Six, N. Frank (Technical Monitor)

    2002-01-01

    A self-consistent ring current (RC) model has been developed that couples electron and ion magnetospheric dynamics with the calculation of the electric field. Two new features were taken into account in order to close the self-consistent magnetosphere- ionosphere coupling loop. First, in addition to the RC ions, we solve an electron kinetic equation in our model. Second, using the relation of Galand and Richmond [2001], we calculate the height integrated ionospheric conductances as a function of the precipitated high energy magnetospheric electrons and ions that are produced by our code. To validate the results of our model we simulate the magnetic storm of May 2, 1986, a storm that has has been comprehensively studied, and compare our results with different theoretical approaches. The self-consistent inclusion of the hot electrons and, their effect on the conductance results in deeper penetration of the magnetospheric electric field. In addition, a slight westward rotation of the potential pattern (compared to previous self-consistent results) is evident in the inner magnetosphere. This changes the hot plasma distribution, especially by allowing increased access of plasma sheet ions and electrons to low L shells.

  1. Analysis of the blazing effect in second-order gratings

    SciTech Connect

    Matsumoto, Masauki )

    1992-10-01

    The validity of the blazing effect for improving the output-coupling efficiency of second-order gratings for use in grating-coupled surface-emitting lasers is examined. The Floquet-Bloch expansion method is used for the analysis of finite-length gratings with asymmetric tooth shapes operated in resonance condition. It is shown that for saw-tooth gratings the blazing effect is almost lost around the second-order Bragg wavelength because the reflected guide mode generated in the distributed Bragg reflector radiates preferentially into the substrate. By using a parallelogram grating with equal tooth and groove lengths, however, a high efficiency of radiation into the air is attainable even at the Bragg wavelength while the reflectivity is reduced. 32 refs.

  2. Steep Electron Density Gradients in the Midlatitude Nighttime Ionosphere: Current Understanding and Future Directions

    NASA Astrophysics Data System (ADS)

    Makela, J. J.; Kelley, M. C.; Mathews, J. D.; Kintner, P. M.; Aponte, N.; Ledvina, B. M.; Nicolls, M. J.; Seker, I.

    2004-12-01

    The midlatitude nighttime ionosphere is generally considered to be a fairly quiet system. Indeed, when compared to the highly active low- and high-latitudes, this seems to be a valid description. However, observations in the 1990s, notably those conducted as part of the multi-instrument Combined Ionospheric Campaigns (CICs) carried out periodically from 1997 to 1999, have shown that disturbances can indeed occur in this region. For example, a relatively common feature seen in allsky images taken at 630.0 nm are bands of depleted intensity aligned from the northwest to southeast that propagate to the southwest (in the northern hemisphere). The general characteristics of these bands are now fairly well documented, as is the basic understanding of their underlying physics. The effects of these medium-scale traveling ionospheric disturbances, or electrobouyancy waves, is to produce gradients in the electron density and F-layer height. During quiet magnetic periods, these gradients are fairly small, of the order of a few TEC units. However, these structures seem to be amplified by high geomagnetic activity at which times the gradients can be of the order of 10 to 20 TEC units over distances as small as several 10s of kilometers. Although much was learned about these structures during the CICs of the late 1990s, there are still several unexplained features that warrant further investigation, notably their genesis region, Kp dependence, and effects (if any) on trans-ionospheric radio signals. We suggest the need for a new set of campaigns in the Caribbean to address these questions, modeled on the CICs but extending their spatial coverage and including additional instrumentation not available during the initial campaigns. It is only through such a comprehensive, multi-technique investigation that we will make further headway on understanding these phenomena.

  3. Trapping of sensing radio waves in an artificial large-scale ionospheric cavity

    NASA Astrophysics Data System (ADS)

    Krasheninnikov, I. V.; Cherkashin, Yu. N.

    2016-03-01

    The results of phenomenological analysis of data from oblique chirp sounding of the ionosphere in a 2007 heating experiment with possible recording of the effect of trapping sounding-radiation in an artificial ionospheric cavity and spotlighting it in the near (over the Earth's surface) zone of the Sura facility are presented. The physical aspects of forming an additional trace on ionograms of oblique radio-sounding of the perturbed region of the ionosphere are discussed.

  4. Improved Ionospheric Electrodynamic Models and Application to Calculating Joule Heating Rates

    NASA Technical Reports Server (NTRS)

    Weimer, D. R.

    2004-01-01

    Improved techniques have been developed for empirical modeling of the high-latitude electric potentials and magnetic field aligned currents (FAC) as a function of the solar wind parameters. The FAC model is constructed using scalar magnetic Euler potentials, and functions as a twin to the electric potential model. The improved models have more accurate field values as well as more accurate boundary locations. Non-linear saturation effects in the solar wind-magnetosphere coupling are also better reproduced. The models are constructed using a hybrid technique, which has spherical harmonic functions only within a small area at the pole. At lower latitudes the potentials are constructed from multiple Fourier series functions of longitude, at discrete latitudinal steps. It is shown that the two models can be used together in order to calculate the total Poynting flux and Joule heating in the ionosphere. An additional model of the ionospheric conductivity is not required in order to obtain the ionospheric currents and Joule heating, as the conductivity variations as a function of the solar inclination are implicitly contained within the FAC model's data. The models outputs are shown for various input conditions, as well as compared with satellite measurements. The calculations of the total Joule heating are compared with results obtained by the inversion of ground-based magnetometer measurements. Like their predecessors, these empirical models should continue to be a useful research and forecast tools.

  5. Estimate of a D region ionospheric electron density profile from MF radio wave observations by the S-310-37 rocket

    NASA Astrophysics Data System (ADS)

    Ashihara, Y.; Ishisaka, K.; Miyake, T.

    2016-01-01

    The S-310-37 rocket, launched at 11:20 (JST) on 16 January 2007, was equipped with a radio receiver to observe the medium-frequency (MF) radio wave propagation characteristics in the ionosphere. The radio receiver measured the intensity and the waveform of the radio wave at 873 kHz from the NHK Kumamoto broadcasting station. The polarized mode waves' intensity characteristics were obtained by analyzing the observed waveform. In this study, the S-310-37 rocket-observed polarized mode waves' propagation characteristics are analyzed in order to estimate the electron density profile in the ionospheric D region. These observations become better measurement approach because the electron density profile in the ionospheric D region is difficult to be observed by other equipment such as a Langmuir probe. A Langmuir probe can measure in the ionospheric D region; however, the absolute values may be off by the influence of wake effects around the sounding rocket. It is demonstrated that the propagation characteristics of the polarized mode waves can be successfully used to derive the electron density profile in the ionospheric D region.

  6. Geometric modulation: A more effective method of steerable ELF/VLF wave generation with continuous HF heating of the lower ionosphere

    NASA Astrophysics Data System (ADS)

    Cohen, M. B.; Inan, U. S.; Golkowski, M. A.

    2008-06-01

    ELF/VLF radio waves (300 Hz-30 kHz) are difficult to generate with practical antennae, because of their extraordinarily long (10-1000 km) wavelengths, and the lossy nature of the Earth's surface at these frequencies. ELF/VLF waves have been successfully generated via amplitude modulated (AM) HF (2-10 MHz) heating of the lower ionosphere. Through the temperature-dependent conductivity of the lower ionospheric plasma, a patch of the ionospheric current becomes a large radiating `antenna'. We implement a new method of ELF/VLF wave generation, herein named `geometric modulation', involving scanning the HF heating beam in a geometric pattern without modulating its power. Utilizing results from the upgraded 3.6 MW radiated HAARP HF antenna array, we show that geometric modulation can enhance ELF/VLF wave generation by up to ~11 dB over the conventional AM method. Geometric modulation also allows directional launching of the signal into the Earth-ionosphere waveguide, forming an unprecedented steerable large-element ELF/VLF ionospheric phased array.

  7. 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.

  8. VLF/LF Radio Sounding of Ionospheric Perturbations Associated with Earthquakes

    PubMed Central

    Hayakawa, Masashi

    2007-01-01

    It is recently recognized that the ionosphere is very sensitive to seismic effects, and the detection of ionospheric perturbations associated with earthquakes, seems to be very promising for short-term earthquake prediction. We have proposed a possible use of VLF/LF (very low frequency (3-30 kHz) /low frequency (30-300 kHz)) radio sounding of the seismo-ionospheric perturbations. A brief history of the use of subionospheric VLF/LF propagation for the short-term earthquake prediction is given, followed by a significant finding of ionospheric perturbation for the Kobe earthquake in 1995. After showing previous VLF/LF results, we present the latest VLF/LF findings; One is the statistical correlation of the ionospheric perturbation with earthquakes and the second is a case study for the Sumatra earthquake in December, 2004, indicating the spatical scale and dynamics of ionospheric perturbation for this earthquake.

  9. HF Channel Availability under Ionospheric Disturbances: Model, Method and Measurements as Contributions

    NASA Astrophysics Data System (ADS)

    Tulunay, E.; Senalp, E. T.; Tulunay, Y.; Warrington, E. M.; Sari, M. O.

    2009-04-01

    A small group at METU has been developing data driven models in order to forecast some critical parameters, which affect the communication and navigation systems, since 1990. The background on the subjects supports new achievements in terms of theoretical and experimental basis contributing the COST 296 WG2 activities. This work mentions the representative contributions. (i) A method has been proposed for the assessment of HF Channel Availability under ionospheric disturbances. Signal to Noise Ratio (SNR), Doppler Spread and Modified Power Delay Spread were considered. The study relates the modem performance to ionospheric disturbances. Ionospheric disturbance was characterised by Disturbance Storm Type (DST) index. Radar data including Effective Multipath Spread, Composite Doppler Spread and SNR values were obtained from the experiment conducted between Leicester UK (52.63° N; 1.08° W) and Uppsala, Sweden (59.92° N; 17.63° E) in the year 2001. First, joint probability density function (PDF) of SNR, Doppler Spread, and Effective Multipath Spread versus DST were considered. It was demonstrated by determining the conditional PDFs, and by using Bayes' Theorem, that there were dependencies between DST and the above mentioned parameters [Sari, 2006]. Thus, it is concluded that the availability of the HF channel is a function of DST. As examples of modem characterizations, Military Standards were considered. Given a magnetic condition, the modem availability was calculated. The model developed represents the ionospheric HF channel, and it is based on a stochastic approach. Depending on the new experimental data, the conditional PDFs could be updated continuously. The HF channel availability under various ionospheric Space Weather (SW) conditions can be determined using the model. The proposed method is general and can include other indices as well. The method can also be applied to a variety of other processes. (ii) The effects of space weather conditions on the variation of group range and line-of-sight Doppler velocity of the HF Radar echo signal were investigated. HF radar system under ionospheric disturbances has been identified globally and some operational suggestions have been presented. It is possible for the HF radar operator to estimate the possible skip distance and possible single hop group ranges for the given frequencies of 11 MHz and 14 MHz [Buyukpabuscu, 2007]. (iii) The measurements over the HF band during the 29 March 2006 total solar eclipse in Antalya (36° N; 30° E) Turkey was conducted from the channel occupancy and atmospheric noise points of view. The whole HF band ranging from 1 to 30 MHz has been swept using 10 kHz peak and 200 Hz average detectors of a certified EMI receiver equipped with a calibrated active monopole antenna. The changes in the atmospheric noise during the eclipse were reported [Tulunay, 2006]. The model based, theoretical and experimental works mentioned are promising and have potential for future research and developments. References Buyukpabuscu S.O. (2007), System Identification with Particular Interest On The High Frequency Radar Under Ionospheric Disturbances, MS Thesis, Electrical and Electronics Eng., Middle East Technical Univ., Ankara, Turkey, February 2007. Sari M.O. (2006), A New Approach For The Assessment Of Hf Channel Availability Under Ionospheric Disturbances, MS Thesis, Electrical and Electronics Eng., Middle East Technical Univ., Ankara, Turkey, September 2006. Tulunay E., E. M. Warrington, Y. Tulunay, Y. Bahadırlar, A.S. Türk, R. Çaputçu, T. Yapıcı , E.T. Şenalp (2006), Propagation Related Measurements during Three Solar Eclipses in Turkey, IET 10th International Conference on Ionospheric Radio Systems & Techniques, IRST 2006, 18-21 July 2006, London, UK.

  10. Joint Correction of Ionospheric Artifact and Orbital Error in L-band SAR Interferometry

    NASA Astrophysics Data System (ADS)

    Jung, H.; Liu, Z.; Lu, Z.

    2012-12-01

    Synthetic aperture radar interferometry (InSAR) is a powerful technique to measure surface deformation. However, the accuracy of this technique for L-band synthetic aperture radar (SAR) system is largely compromised by ionospheric path delays on the radar signals. The ionospheric effect causes severe ionospheric distortion called azimuth streaking in SAR backscattering intensity images as well as long wavelength phase distortion similar to orbital ramp error. Effective detection and correction of ionospheric phase distortion from L-band InSAR images are necessary to measure and interpret surface displacement accurately. Recently Jung et al.(2012) proposed an efficient method to correct ionospheric phase distortions using the multiple aperture interferometry (MAI) interferogram. In this study, we extend this technique to correct the ionosphere effect in InSAR measurements of interseismic deformation. We present case studies in southern California using L-band ALOS PALSAR data and in-situ GPS measurements and show that the long wavelength noise can be removed by joint correction of the ionospheric artifact and the orbital error. Displacement maps created from 20070715-20091020 ALOS PALSAR pair: (a-b) before and after joint correction of ionospheric artifact and orbital error, and (c) after correction from 2D-polynomial fit Displacement maps created from 20071015-20091020 ALOS PALSAR pair: (a-b) before and after joint correction of ionospheric artifact and orbital error, and (c) after correction from 2D-polynomial fit

  11. Currents can be driven in the polar ionosphere

    NASA Astrophysics Data System (ADS)

    Balcerak, Ernie

    2011-08-01

    The study of ionospheric heaters that induce controlled modifications in the ionosphere allows better understanding of effects driven naturally by solar activity in the ionosphere and the radiation belts. Previous ionospheric heaters at the Earth's poles have generated ultralow-frequency, extremely low frequency, and very low frequency waves in the ionosphere's D and E regions by modulating the auroral electrojet, the strong horizontal currents that naturally flow in the D and E regions at high latitudes. Now Papadopoulos et al. present theoretical and computational results that indicate that using high-frequency heating, low-frequency ionospheric currents can also be generated at F region altitudes, independent of the presence or absence of electrojet currents. The new technique, whose validity has been confirmed tentatively in recent polar experiments, allows generation of low-frequency waves by midlatitude heaters, such as the one under construction in Arecibo, Puerto Rico, and their subsequent injection in the inner radiation belt. It will permit for the first time the study of the interaction of artificially generated low-frequency waves with multi-MeV protons trapped in the inner belt and their precipitation rates in the South Atlantic anomaly region. (Geophysical Research Letters, doi:10.1029/2011GL047368, 2011)

  12. New Method for Solving Inductive Electric Fields in the Ionosphere

    NASA Astrophysics Data System (ADS)

    Vanhamäki, H.

    2005-12-01

    We present a new method for calculating inductive electric fields in the ionosphere. It is well established that on large scales the ionospheric electric field is a potential field. This is understandable, since the temporal variations of large scale current systems are generally quite slow, in the timescales of several minutes, so inductive effects should be small. However, studies of Alfven wave reflection have indicated that in some situations inductive phenomena could well play a significant role in the reflection process, and thus modify the nature of ionosphere-magnetosphere coupling. The input to our calculation method are the time series of the potential part of the ionospheric electric field together with the Hall and Pedersen conductances. The output is the time series of the induced rotational part of the ionospheric electric field. The calculation method works in the time-domain and can be used with non-uniform, time-dependent conductances. In addition no particular symmetry requirements are imposed on the input potential electric field. The presented method makes use of special non-local vector basis functions called Cartesian Elementary Current Systems (CECS). This vector basis offers a convenient way of representing curl-free and divergence-free parts of 2-dimensional vector fields and makes it possible to solve the induction problem using simple linear algebra. The new calculation method is validated by comparing it with previously published results for Alfven wave reflection from uniformly conducting ionosphere.

  13. High-order multiphoton photoelectric effect at midinfrared laser wavelengths

    SciTech Connect

    Georges, A.T.

    2002-12-01

    A theoretical model that predicts the unexpectedly high photocurrents that were reported by Farkas et al. [J. Phys. B 31, L461 (1998)] for the photoelectric effect in gold at midinfrared laser wavelengths (12 {mu}m) is presented. It is shown that the observed effect, a nominally 46-photon process at threshold, is a stepwise and multiple-order process, which is strongly saturated at the moderate laser intensity of about {approx}10 MW/cm{sup 2}. The {approx_equal}30-photon-wide energy spectrum of the observed photoelectron current is due to above threshold photoemission. This relatively efficient above threshold effect is due to laser absorption in the long range Coulombic image surface potential.

  14. The Ionosphere and Ocean Altimetry

    NASA Technical Reports Server (NTRS)

    Lindqwister, Ulf J.

    1999-01-01

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

  15. Effect of Under-Resolved Grids on High Order Methods

    NASA Technical Reports Server (NTRS)

    Yee, H. C.; Sjoegreen, B.; Mansour, Nagi (Technical Monitor)

    2001-01-01

    There has been much discussion on verification and validation processes for establishing the credibility of CFD simulations. Since the early 1990s, many of the aeronautical and mechanical engineering related reference journals mandated that any accepted articles in numerical simulations (without known solutions to compared with) need to perform a minimum of one level of grid refinement and time step reduction. Due to the difficulty in analysis, the effect of under-resolved grids and the nonlinear behavior of available spatial discretizations, are scarcely discussed in the literature. Here, an under-resolved numerical simulation is one where the grid spacing being used is too coarse to resolve the smallest physically relevant scales of the chosen continuum governing equations that are of interest to the numerical modeler. With the advent of new developments in fourth-order or higher spatial schemes, it has become common to regard high order schemes as more accurate, reliable and require less grid points. The danger comes when one tries to perform computations with the coarsest grid possible while still hoping to maintain numerical results sufficiently accurate for complex flows, and especially, data-limited problems. On one hand, high order methods when applies to highly coupled multidimensional complex nonlinear problems might have different stability, convergence and reliability behavior than their well studied low order counterparts, especially for nonlinear schemes such as TVD, MUSCL with limiters, ENO, WENO and discrete Galerkin. On the other hand, high order methods involve more operation counts and systematic grid convergence study can be time consuming and prohibitively expansive. At the same time it is difficult to fully understand or categorize the different nonlinear behavior of finite discretizations, especially at the limits of under-resolution when different types of bifurcation phenomena might occur, depending on the combination of grid spacings, time steps, initial conditions and numerical treatments of boundary conditions.

  16. 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.

  17. Ionosphere of Venus - First observations of the dayside ion composition near dawn and dusk

    NASA Technical Reports Server (NTRS)

    Taylor, H. A., Jr.; Brinton, H. C.; Bauer, S. J.; Hartle, R. E.; Donahue, T. M.; Cloutier, P. A.; Michel, F. C.; Daniell, R. E., Jr.; Blackwell, B. H.

    1979-01-01

    Independent Bennett radio-frequency ion mass spectrometers on the Pioneer Venus bus and orbiter spacecraft obtained in situ measurements of the composition of the ionosphere of Venus. The spectrometer on the bus explored the dawn region while the spectrometer on the orbiter explored the duskside region. Information on the ion composition in the topside, the lower ionosphere, and the upper ionosphere is presented. Below the O(+) peak near 200 km, the ions are found to exhibit scale heights consistent with a neutral gas temperature of about 180 K near the terminator. In the upper ionosphere, scale heights of all species reflect the effects of plasma transport.

  18. 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

  19. Influence of layered structure of the lower ionosphere on nonmonotonic spectrum behavior of ELF atmospheric noise

    SciTech Connect

    Molchanov, O.A.; Nickolaenko, A.P.; Rafalsky, V.A.; Schecotov, A.Yu.; Hayakawa, M.

    1994-11-15

    The authors present studies related to resonance phenomena occurring between and within different layers in the ionosphere, and the effect these resonances can have on the amplitude of extremely low frequency (ELF) wave propagation through the ionosphere. They follow several model problems to illustrate the impact of theses effects.

  20. The Effect of N2 Photoabsorption Cross Section Resolution on C2H6 Production in Titan’s Ionosphere

    NASA Astrophysics Data System (ADS)

    Luspay-Kuti, Adrienn; Mandt, Kathleen E.; Plessis, Sylvain; Greathouse, Thomas K.

    2014-11-01

    Titan’s rich organic chemistry begins with the photochemistry of only two molecules: N2 and CH4. The details on how higher-order hydrocarbons and nitriles are formed from these molecules have key implications for both the structure and evolution of Titan’s atmosphere, and for its surface-atmosphere interactions. Of high importance is the production of C2H6, which is a sink for CH4, and a main component in the polar lakes. Results of photochemical models, though, may be sensitive to the choice of input parameters, such as the N2 photoabsorption cross section resolution, as previously shown for nitrogen (Liang et al. (2007) ApJL 664, 115-118), and CH4 (Lavvas et al. (2011) Icarus 213, 233-251). Here we investigate the possibility of the same effect on the production rates of C2H6. We modeled production and loss rates, as well as mixing ratio and density profiles between an altitude of 600 and 1600 km for low and high resolution N2 cross sections via a coupled ion-neutral-thermal model (De La Haye et al. (2008) Icarus 197, 110-136; Mandt et al. (2012) JGR 117, E10006). Our results show a clear impact of photoabsorption cross section resolution used on all neutral and ion species contributing to C2H6 production. The magnitude of the influence varies amongst species. Ethane production profiles exhibit a significant increase with better resolution; a factor of 1.2 between 750 and 950 km, and a factor of 1.1 in the total column-integrated production rate. These values are lower limits, as additional reactions involving C2H5 not included in the model may also contribute to the production rates. The clear effect on C2H6 (which is not a parent molecule, nor does it bear nitrogen) may have important implications for other molecules in Titan’s atmosphere as well. The possible non-negligible impact of an isotope of nitrogen may argue for the inclusion of isotopes in photochemical models. For future analysis, development of a more efficient and streamlined model called Planet-INC is underway. This open source model is a high-performance probabilistic planetary model that includes detailed uncertainty analysis capabilities.

  1. Studies of the high latitude ionospheric convection

    NASA Astrophysics Data System (ADS)

    Drake, Kelly Ann

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

  2. Anomalous ionospheric conductivities caused by plasma turbulence in high-latitude E-region ionosphere

    NASA Astrophysics Data System (ADS)

    Dimant, Yakov; Oppenheim, Meers

    2015-11-01

    During periods of intense geomagnetic activity, electric fields penetrating from the Earth's magnetosphere to the high-latitude E-region ionosphere drive strong currents named electrojets and excite there plasma instabilities. These instabilities give rise to plasma turbulence that induces nonlinear currents and strong anomalous electron heating. This increases the ionospheric conductances and modifies the global energy flow, affecting behavior of the entire near-Earth plasma. A quantitative understanding of anomalous conductance and global energy transfer is important for accurate modeling of the geomagnetic storm/substorm evolution. Our theoretical analysis, supported by recent 3D fully kinetic particle-in-cell simulations, shows that during strong geomagnetic storms the inclusion of anomalous conductivity can more than double the total Pedersen conductance - the crucial factor responsible for magnetosphere-ionosphere coupling through the current closure. We have started incorporating the effects of anomalous heating and nonlinear conductivity into existing global magnetosphere-ionosphere-thermosphere codes developed for predictive modeling of Space. In our presentation, we will report on the latest progress in this modeling. Work supported by NASA Heliophysics GCR Grant NNX14AI13G.

  3. Forecasting Space Weather in the Upper Atmosphere and Ionosphere (Invited)

    NASA Astrophysics Data System (ADS)

    Solomon, S. C.

    2013-12-01

    The feasibility of performing meaningful forecasts of the state of the thermosphere and ionosphere depends on the time scales of interest. Whether accomplished using empirical models derived from climatological information, or using numerical models describing the physics and dynamics of the coupled system, the reality of any forecast is dependent on the specification of the initial state, and the knowledge of the parameters that will impact it in the future. The zero-time forecast, or nowcast, is eminently possible, and basic systems have been implemented operationally using data assimilation techniques. This is considerably more advanced with respect to the ionosphere, because there are more ionospheric data currently available. But a fully coupled thermosphere is crucial for accomplishing accurate ionospheric specification and forecast, because the ionosphere responds strongly to thermospheric drivers, and because the effects of changing thermospheric dynamics are persistent. The prospects for short term (less than an hour) forecasts are also good. The 30 to 90 minute delay between measurements near the Sun-Earth L1 saddle point, and the arrival of solar wind and interplanetary field perturbations at the magnetopause, can be exploited to predict the effects of geomagnetic disturbances on the thermosphere-ionosphere. Lower atmosphere meteorology fields are sufficiently known and change slowly on these time scales, as do solar irradiance drivers (except during flares) so the boundary conditions to full-physics numerical models can be specified. The initial state of the system can be effectively characterized by data assimilation models. Sophisticated physical models using efficient parallel algorithms are available. Therefore, there are no fundamental obstacles to implementation of short-term thermosphere-ionosphere forecasting, only programmatic or technical ones. On longer time scales, magnetospheric forecasting is contingent on meaningful prediction of the solar wind and interplanetary magnetic field. Significant progress has been made on the former, but the latter remains extremely difficult, due to the lack of knowledge of solar magnetic field configuration during eruptive events. Therefore, forecasting thermosphere-ionosphere parameters when driven by magnetospheric storms, on time scales of one to several days, remains a speculative activity. In this paper, we will present simulations demonstrating the capabilities of a thermosphere-ionosphere model employed in a prognostic mode. Model initialization using fields obtained from data assimilation schemes will be demonstrated, and the interplay of their persistence with ionospheric dynamics described.

  4. Experimentally investigate ionospheric depletion chemicals in artificially created ionosphere

    SciTech Connect

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

    2012-09-15

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

  5. 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.

  6. 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.

  7. 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(+).

  8. Ionospheric research using digital ionosondes

    NASA Astrophysics Data System (ADS)

    Reinisch, B. W.; Bibl, K.

    1983-07-01

    New digital UF sounding techniques are used for the