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Sample records for order ionospheric effects

  1. A semi-analytical estimation of the effect of second-order ionospheric correction on the GPS positioning

    NASA Astrophysics Data System (ADS)

    Munekane, H.

    2005-10-01

    We developed a semi-analytical method to evaluate the effect of the second-order ionospheric correction on GPS positioning. This method is based on the semi-analytical positioning error simulation method developed by Geiger and Santerre in which, assuming the continuous distribution of the satellites, a normal equation is formed to estimate the positioning error taking all the contributions of the ranging error by the visible satellites into account. Our method successfully reproduced the averaged time-series of three IGS sites which is comparable to the rigorous simulation. We then evaluated the effect of the ionospheric error on the determination of the reference frame. We evaluated the additional Helmert parameters that are required for the ionospheric effect. We found that the ionospheric effect can lead to annual scale changes of 0.1 ppb, with an offset of 1.8 mm and a semi-annual oscillation of 1 mm in the z-direction. However, these values are too small to explain the current deviations between the GPS-derived reference frame and the ITRF reference frame. Next, we estimated the apparent scale changes due to the ionospheric error in the GEONET coordinate time-series in Japan. We could qualitatively reproduce the observed semi-annual scale changes peaking at the equinoxes and having asymmetrical amplitudes between the vernal and autumnal equinoxes.

  2. 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

  3. A semi-analytic evaluation of the effect of second-order ionosphere term on GPS positioning

    NASA Astrophysics Data System (ADS)

    Munekane, H.

    2005-05-01

    We developed a method to evaluate the effect of the second-order ionosphere term on GPS positioning. The method is based on the semi-analytic positioning error simulation method developed by Geiger (1988), which assumes the continuous distribution of the GPS satellites and maps the ranging error to the positioning error using the normal equation. We expanded the method to incorporate the satellite positioning error due to the second-order ionospheric term, which is estimated in a similar manner as the site positioning error, assuming the continuous distribution of the ground tracking stations instead of the continuous satellite distribution in the case of the site positioning error estimation. The method is first applied to simulate the positioning errors on three IGS sites (BAHR, COCO, GALA) which were investigated in Kedar et al. (2002) by analyzing the observed GPS data using the GIPSY software with the correction for second-order ionospheric term. We considered three cases, namely, 1) without satellite positioning error, 2) with satellite positioning error, and 3) with satellite positioning error whose spatial average of each component is corrected for. The third case corresponds to the situation where there are other observations available such as SLR and the center of the mass of the GPS satellite network is corrected properly. For the first case, we found that our method reproduced the positioning errors observed at these stations as well as Kedar et al. (2002). For the second case, however, we found that the positioning error is almost canceled. For the third case, we found that the error is reproduced as well as in the first case, though the spatial distribution of the error is different. These results indicate that 1) the semi-analytic method developed in this paper is accurate enough to simulate the position error due to the second-order ionospheric term, and 2) the satellite positioning error due to the second-order ionospheric term may have significant

  4. 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.

  5. Low-latitude ionospheric effects on SBAS

    NASA Astrophysics Data System (ADS)

    Arenas, J.; Sardón, E.; Sainz, A.; Ochoa, B.; Magdaleno, S.

    2016-06-01

    Satellite-based augmentation systems (SBAS) provide augmentation to Global Navigation Satellite Systems (GNSS) users in three areas: (1) broadcasting accurate corrections to GNSS satellite ephemeris, (2) providing a real-time empirical ionospheric model in the service area, and (3) providing integrity information in the form of estimates of the confidence of the ephemeris corrections and ionospheric delays. Ionospheric effects on SBAS are twofold: (a) the input data used by the SBAS will be affected by ionospheric effects, and (b) the more perturbed the ionosphere is, the more difficult it will be to provide accurate and reliable ionospheric information to the users. The ionosphere at low latitudes presents larger variability and more intense phenomena than at midlatitudes. Therefore, SBAS providing service to low-latitude regions will be more affected than those at other latitudes. From the different low-latitude ionospheric effects, this paper will focus on those having the largest impact on SBAS, which are total electron content temporal and spatial gradients, ionospheric scintillations, and depletions. This paper will present the impact of these effects on EGNOS (European Global Navigation Overlay System), the European SBAS. Although EGNOS can be considered as a midlatitude SBAS, it has to provide coverage down to rather low latitudes, so sometimes low-latitude ionospheric effects are observed in the EGNOS data. It will be shown how EGNOS performs under nominal conditions and how its performance is degraded when low-latitude ionospheric phenomena occur. Real EGNOS data affected by low-latitude ionospheric phenomena will be used.

  6. Mitigation of Second-Order Ionospheric Error for Real-Time PPP Users in Europe

    NASA Astrophysics Data System (ADS)

    Abdelazeem, Mohamed

    2016-07-01

    Currently, the international global navigation satellite system (GNSS) real-time service (IGS-RTS) products are used extensively for real-time precise point positioning and ionosphere modeling applications. The major challenge of the dual frequency real-time precise point positioning (RT-PPP) is that the solution requires relatively long time to converge to the centimeter-level accuracy. This relatively long convergence time results essentially from the un-modeled high-order ionospheric errors. To overcome this challenge, a method for the second-order ionospheric delay mitigation, which represents the bulk of the high-order ionospheric errors, is proposed for RT-PPP users in Europe. A real-time regional ionospheric model (RT-RIM) over Europe is developed using the IGS-RTS precise satellite orbit and clock products. GPS observations from a regional network consisting of 60 IGS and EUREF reference stations are processed using the Bernese 5.2 software package in order to extract the real-time vertical total electron content (RT-VTEC). The proposed RT-RIM has spatial and temporal resolution of 1º×1º and 15 minutes, respectively. In order to investigate the effect of the second-order ionospheric delay on the RT-PPP solution, new GPS data sets from another reference stations are used. The examined stations are selected to represent different latitudes. The GPS observations are corrected from the second-order ionospheric errors using the extracted RT-VTEC values. In addition, the IGS-RTS precise orbit and clock products are used to account for the satellite orbit and clock errors, respectively. It is shown that the RT-PPP convergence time and positioning accuracy are improved when the second-order ionospheric delay is accounted for.

  7. 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.

  8. 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.

  9. The composition of Mars' topside ionosphere: Effects of hydrogen

    NASA Astrophysics Data System (ADS)

    Matta, Majd; Withers, Paul; Mendillo, Michael

    2013-05-01

    one-dimensional model of the Martian ionosphere is used to explore the importance of atomic and molecular hydrogen chemistry in the upper atmosphere and ionosphere. Neutral and ionized H and H2 undergo chemical reactions that lead to the production of the hydrogenated ions: H+, H2+, H3+, OH+, HCO+, ArH+, N2H+, HCO2+, and HOC+. Simulations are conducted for the cases of photochemistry only and photochemistry coupled with transport in order to asses the separate effects of plasma diffusion in the topside ionosphere. For both of these cases, the sensitivity of the ionosphere is tested for (1) molecular hydrogen abundance and (2) reaction rate, k1, for the charge exchange between H+ and H2. Results are reported for midday solar minimum conditions. We find that the ionospheric composition of Mars is sensitive to H2 abundance, but relatively insensitive to the reaction rate, k1. Depending on the conditions simulated, the topside ionosphere can contain appreciable amounts of hydrogenated species such as H3+, OH+, and HCO+. Comparisons are made with Viking ion density measurements as well as with results of other published Mars ionospheric models. Future comparisons with more extensive ion composition will be available when the Mars Atmosphere and Volatile Evolution mission arrives at Mars.

  10. Assessment of second- and third-order ionospheric effects on regional networks: case study in China with longer CMONOC GPS coordinate time series

    NASA Astrophysics Data System (ADS)

    Deng, Liansheng; Jiang, Weiping; Li, Zhao; Chen, Hua; Wang, Kaihua; Ma, Yifang

    2016-09-01

    Higher-order ionospheric (HOI) delays are one of the principal technique-specific error sources in precise global positioning system analysis and have been proposed to become a standard part of precise GPS data processing. In this research, we apply HOI delay corrections to the Crustal Movement Observation Network of China's (CMONOC) data processing (from January 2000 to December 2013) and furnish quantitative results for the effects of HOI on CMONOC coordinate time series. The results for both a regional reference frame and global reference frame are analyzed and compared to clarify the HOI effects on the CMONOC network. We find that HOI corrections can effectively reduce the semi-annual signals in the northern and vertical components. For sites with lower semi-annual amplitudes, the average decrease in magnitude can reach 30 and 10 % for the northern and vertical components, respectively. The noise amplitudes with HOI corrections and those without HOI corrections are not significantly different. Generally, the HOI effects on CMONOC networks in a global reference frame are less obvious than the results in the regional reference frame, probably because the HOI-induced errors are smaller in comparison to the higher noise levels seen when using a global reference frame. Furthermore, we investigate the combined contributions of environmental loading and HOI effects on the CMONOC stations. The largest loading effects on the vertical displacement are found in the mid- to high-latitude areas. The weighted root mean square differences between the corrected and original weekly GPS height time series of the loading model indicate that the mass loading adequately reduced the scatter on the CMONOC height time series, whereas the results in the global reference frame showed better agreements between the GPS coordinate time series and the environmental loading. When combining the effects of environmental loading and HOI corrections, the results with the HOI corrections reduced

  11. Ionospheric effects on modern electronic systems

    NASA Astrophysics Data System (ADS)

    Goodman, John M.; Aarons, Jules

    1990-03-01

    A basic overview of ionospheric phenomenology is provided. Some of the modern electronic systems of interest and the extent to which the ionosphere may place limits on design and operation are discussed. The effects of importance to electronic systems are defined, and the effects are discussed by frequency regime: the ELF (less than 3 kHz), VLF (3-30 kHz), and LF (30-300 kHz) bands. Shortwave and earth-space propagation are considered. Special attention is given to systems for which propagation factors are predominantly deleterious; these include satellite communication and navigation systems that operate in the earth-space regime. Special note is made of the fact that the solar maximum is to be reached in 1990-1991 and that maximum ionospheric effects are anticipated during this period, which is predicted to be one of the most active epochs of the last 200 years.

  12. Ionospheric effects of solar x-rays

    NASA Astrophysics Data System (ADS)

    Danskin, Donald

    2016-07-01

    The ionospheric absorption of radio waves caused by solar x-ray bursts is measured directly by Riometers from the Canada Riometer Array. The absorption is found to be proportional to the square root of the flux intensity of the X-ray burst with time delays of 18-20 seconds between the peak X-ray emission and absorption in the ionosphere. A detailed analysis showed that some X-ray flares during 2011-2014 are more effective at producing absorption than others. Solar longitude of X-ray burst for several X-class flares shows no consistent pattern of enhancement in the absorption.

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

    NASA Astrophysics Data System (ADS)

    Elias, Ana G.

    2014-12-01

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

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

    NASA Technical Reports Server (NTRS)

    Klobuchar, J. A.

    1984-01-01

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

  15. 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.

  16. Effects of the different times of sunrise at different altitudes in the ionosphere

    NASA Astrophysics Data System (ADS)

    Verhulst, Tobias; Stankov, Stan

    2016-07-01

    It is well established that the sunrise and sunset periods are of particular importance to ionospheric research and modeling because of the rapid changes in the ionospheric plasma density, temperature, and dynamics. In particular, the sharp increase in the ionisation following sunrise results in a quick increase in the ionospheric peak density, N_mF_2, and a decrease in the peak height, h_mF_2. Changes in plasma temperature, scale height and transport processes add further complexity which makes it difficult to investigate and model the ionospheric behaviour during this transitional period from night to day. One of the aspects contributing to this difficulty is that not all ionospheric altitudes are exposed to the first sunlight of the day at the same time. During sunrise, the upper part of the ionosphere is illuminated prior to the lower part which is still in the dark. The boundary between sunlit and dark regions moves downwards until it reaches the surface of the Earth, which is commonly taken as the moment of sunrise at certain geographical coordinates. This means that the ``traditional'' sunrise does not occur until after the entire ionosphere has been illuminated. During sunset, the same process happens in reverse order. In this presentation, we will address the issue and report on our study of some of the effects of this altitude-dependent time of sunrise on the diurnal variations in the ionospheric characteristics.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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

  2. Bounding higher-order ionosphere errors for the dual-frequency GPS user

    NASA Astrophysics Data System (ADS)

    Datta-Barua, S.; Walter, T.; Blanch, J.; Enge, P.

    2008-10-01

    Civil signals at L2 and L5 frequencies herald a new phase of Global Positioning System (GPS) performance. Dual-frequency users typically assume a first-order approximation of the ionosphere index of refraction, combining the GPS observables to eliminate most of the ranging delay, on the order of meters, introduced into the pseudoranges. This paper estimates the higher-order group and phase errors that occur from assuming the ordinary first-order dual-frequency ionosphere model using data from the Federal Aviation Administration's Wide Area Augmentation System (WAAS) network on a solar maximum quiet day and an extremely stormy day postsolar maximum. We find that during active periods, when ionospheric storms may introduce slant range delays at L1 as high as 100 m, the higher-order group errors in the L1-L2 or L1-L5 dual-frequency combination can be tens of centimeters. The group and phase errors are no longer equal and opposite, so these errors accumulate in carrier smoothing of the dual-frequency code observable. We show the errors in the carrier-smoothed code are due to higher-order group errors and, to a lesser extent, to higher-order phase rate errors. For many applications, this residual error is sufficiently small as to be neglected. However, such errors can impact geodetic applications as well as the error budgets of GPS Augmentation Systems providing Category III precision approach.

  3. Ionospheric criticial frequencies and solar cycle effects

    NASA Astrophysics Data System (ADS)

    Kilcik, Ali; Ozguc, Atila; Rozelot, Jean Pierre; Yiǧit, Erdal; Elias, Ana; Donmez, Burcin; Yurchyshyn, Vasyl

    2016-07-01

    The long term solar activity dependencies of ionospheric F1 and F2 regions critical frequencies (foF1 and foF2) are investigated observationally for the last four solar cycles (1976-2015). We here show that the ionospheric F1 and F2 regions have different solar activity dependencies in terms of the sunspot group (SG) numbers: F1 region critical frequency (foF1) peaks at the same time with small SG numbers, while the foF2 reaches its maximum at the same time with the large SG numbers especially during the solar cycle 23. Thus, we may conclude that the sensitivities of ionospheric F1 and F2 region critical frequencies to sunspot group (SG) numbers are associated with different physical processes that are yet to be investigated in detail. Such new results provide further evidence that the two ionospheric regions have different responses to the solar activity. We also analyzed short term oscillatory behavior of ionospheric critical frequencies and found some solar signatures.

  4. Ionospheric Geo-effectiveness of Magnetic Clouds

    NASA Astrophysics Data System (ADS)

    Bronder, T. J.; Knipp, D. J.; Lynch, B.; Zurbuchen, T.; McHarg, M. G.; Chun, F. K.

    2002-12-01

    We present an analysis of the geo-effectiveness of magnetic clouds and the disturbed solar wind surrounding them. Estimates of the ionospheric Joule heating rates based on two ground magnetic indices and estimates of auroral zone particle heating from polar satellites will be combined to provide a summary of the total geomagnetic heating during magnetic cloud passage. Preliminary estimates suggest that intervals of magnetic cloud passage experience about 50 percent greater heating rates than intervals associated with the more general class of interplanetary coronal mass ejection. Heating rates for magnetic clouds are about four times greater than heating rates estimated for intervals of background slow solar wind flow. Preliminary work also indicates that magnetic clouds lying in the ecliptic plane (leading or trailing fields oriented N-S or S-N) have heating rates about 50 percent greater than clouds with leading or trailing fields perpendicular to the ecliptic plane. We will provide hourly heating profiles for more than 50 magnetic clouds passing the earth during the rise and peak of solar cycle 23.

  5. Effects of UGTs on the ionosphere

    SciTech Connect

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

    1992-10-01

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

  6. Effects of UGTs on the ionosphere

    SciTech Connect

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

    1992-01-01

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

  7. Effect of Ionosphere on Geostationary Communication Satellite Signals

    NASA Astrophysics Data System (ADS)

    Erdem, Esra; Arikan, Feza; Gulgonul, Senol

    2016-07-01

    Geostationary orbit (GEO) communications satellites allow radio, television, and telephone transmissions to be sent live anywhere in the world. They are extremely important in daily life and also for military applications. Since, satellite communication is an expensive technology addressing crowd of people, it is critical to improve the performance of this technology. GEO satellites are at 35,786 kilometres from Earth's surface situated directly over the equator. A satellite in a geostationary orbit (GEO) appears to stand still in the sky, in a fixed position with respect to an observer on the earth, because the satellite's orbital period is the same as the rotation rate of the Earth. The advantage of this orbit is that ground antennas can be fixed to point towards to satellite without their having to track the satellite's motion. Radio frequency ranges used in satellite communications are C, X, Ku, Ka and even EHG and V-band. Satellite signals are disturbed by atmospheric effects on the path between the satellite and the receiver antenna. These effects are mostly rain, cloud and gaseous attenuation. It is expected that ionosphere has a minor effect on the satellite signals when the ionosphere is quiet. But there are anomalies and perturbations on the structure of ionosphere with respect to geomagnetic field and solar activity and these conditions may cause further affects on the satellite signals. In this study IONOLAB-RAY algorithm is adopted to examine the effect of ionosphere on satellite signals. IONOLAB-RAY is developed to calculate propagation path and characteristics of high frequency signals. The algorithm does not have any frequency limitation and models the plasmasphere up to 20,200 km altitude, so that propagation between a GEO satellite and antenna on Earth can be simulated. The algorithm models inhomogeneous, anisotropic and time dependent structure of the ionosphere with a 3-D spherical grid geometry and calculates physical parameters of the

  8. 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.

  9. 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

  10. The Effect of Diurnal Variations on Ionospheric Radio Occultations

    NASA Astrophysics Data System (ADS)

    Yelle, Roger V.; Koskinen, Tommi; Withers, Paul; Schinder, Paul J.; Moses, Julianne I.; Mueller-Wodarg, Ingo

    2016-10-01

    Radio occultations are a powerful technique for the study of atmospheres and ionospheres by planetary spacecraft. For missions to the outer solar system, the occultations always probe the terminator region of the planet. The analysis of radio occultations typically assumes symmetry along the ray path in the horizontal direction about the tangent point. While this is an excellent assumption for the neutral atmosphere where the scale length of horizontal gradients is large, it is suspect for the ionosphere where electron densities decrease rapidly from day to night. Diurnal variations in peak electron density are often several orders of magnitude and may occur over a region of a few degrees. We investigate the consequences of diurnal variations on ionospheric occultations with a ray tracing calculation for the angular deflection and frequency residual of the radio wave. The calculations are based on photochemical/diffusion models for the ionospheres of Saturn and Titan. Differences from analysis based on the assumption of horizontal symmetry are most pronounced in the bottom side ionosphere where chemical time constants are short.

  11. 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.

  12. Ionospheric Effects from the superbolid exploded over the Chelyabinsk area

    NASA Astrophysics Data System (ADS)

    Ruzhin, Yuri; Smirnov, Vladimir; Kuznetsov, Vladimir; Smirnova, Elena

    The Chelyabinsk meteorite fall is undoubtedly the most documented in history. Its passage through the atmosphere was recorded by video and photographers, visual observers, infrasonic microphones, seismographs on the ground, and by satellites in orbit. The data of transionospheric sounding by signals from the GPS cluster satellites carried out in the zone of explosion of the Chelyabinsk meteoroid have been analyzed. The analysis has shown that the explosion had a very weak effect on the ionosphere. The observed ionospheric disturbances were asymmetric with respect to the explosion epicenter. The signals obtained were compared both in shape and in amplitude with the known surface explosions for which the diagnostics of the ionospheric effects had been made by radio techniques. Ionospheric effects in the form of acoustic-gravity waves (AGW) produced by 500-600 tons TNT explosions on the ground are detected with confidence both by vertical sounding and by GPS techniques. This allows us to suggest that the reported equivalent of the meteoroid explosion was obviously overestimated. The experiments on the injection of barium vapor (3.3 kg) carried out under similar conditions in the terminator zone revealed the response of the ionosphere in variations of the critical frequencies of the layer at a distance of 1500-2000 km (AGW with a period of 5-10 min). The absence of such ionospheric effects in the remote zone at 1500-1700 km from the epicenter of the bolide explosion in the case under discussion also makes us feel doubtful about the estimated explosion equivalent.

  13. Irregularities in ionospheric plasma clouds: their evolution and effect on radio communication. Technical report

    SciTech Connect

    Vesecky, J.F.; Chamberlain, J.W.; Cornwall, J.M.; Hammer, D.A.; Perkins, F.W.

    1980-09-01

    Both satellite radio communications, which travel through the Earth's ionosphere, and high frequency (HF) sky wave circuits, which use the ionosphere as a refracting medium, can be strongly affected by radio wave scintillation. High altitude nuclear explosions cause scintillation (by strongly disturbing the ionosphere) and thus severely degrade satellite radio communications over a large region. Since further atmospheric nuclear tests are banned, a thorough understanding of the physics involved in both the disturbed ionosphere and its interaction with radio waves is necessary in order to design radio communications systems which will operate satisfactorily in a nuclear environment. During the 1980 JASON Summer Study we addressed some aspects of the evolution of ionospheric irregularities following a high altitude nuclear explosion--the radio wave propagation theory being apparently well understood for the satellite link case. In particular, we have worked on irregularity evolution at late times (approx. hours) after an explosion and the impact of early time irregularity structure on late time evolution. We also raise the question of scintillation effects on HF sky wave communications.

  14. The effect of solar energetic particles on the Martian ionosphere

    NASA Astrophysics Data System (ADS)

    Darwish, Omar Hussain Al; Lillis, Robert; Fillingim, Matthew; Lee, Christina

    2016-10-01

    The precipitation of Solar Energetic Particles (SEP) into the Martian atmosphere causes several effects, one of the most important of which is ionization. However, the importance of this process to the global structure and dynamics for the Martian ionosphere is currently not well understood. The MAVEN spacecraft carries instrumentation which allow us to examine this process. The Neutral Gas and Ion Mass Spectrometer (NGIMS) measures the densities of planetary ions in the Mars ionosphere (O+,CO2+ and O2+). The Solar Energetic Particle (SEP) detector measures the fluxes of energetic protons and electrons. In this project, we examine the degree to which the density of ions in the Martian ionosphere is affected by the precipitation of energetic particles, under conditions of different SEP ion and electron fluxes and at various solar zenith angles. We will present statistical as well as case studies.

  15. 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.

  16. Effects of ionizing energetic electrons and plasma transport in the ionosphere during the initial phase of the December 2006 magnetic storm

    NASA Astrophysics Data System (ADS)

    Suvorova, A. V.; Huang, C.-M.; Dmitriev, A. V.; Kunitsyn, V. E.; Andreeva, E. S.; Nesterov, I. A.; Klimenko, M. V.; Klimenko, V. V.; Tumanova, Yu. S.

    2016-06-01

    The initial phase of a major geomagnetic storm on 14 December 2006 was selected in order to investigate the ionizing effect of energetic electrons in the ionosphere. The global network of GPS receivers was used to analyze the total electron content (TEC). A strong positive ionospheric storm of ~20 TEC units (TECU) with ~6 h duration was observed on the dayside during the interval of northward interplanetary magnetic field. At the same time, the NOAA/POES satellites observed long-lasting intense fluxes of >30 keV electrons in the topside ionosphere at middle and low latitudes, including a near-equatorial forbidden zone outside of the South Atlantic Anomaly (SAA). We found that the TEC increases overlapped well with the enhancements of energetic electrons. Modeling of the ionospheric response by using a Global Self-consistent Model of the Thermosphere, Ionosphere, and Protonosphere, based on the standard mechanisms of plasma transport, could only partially explain the ionospheric response and was unable to predict the long-duration increase of TEC. For the energetic electrons, we estimated the ionizing effect of ~45 TECU and ~23 TECU in the topside ionosphere, respectively, inside and outside of SAA. The ionizing effect contributed from 50% to 100% of TEC increases and provided the long duration and wide latitudinal extension of the positive ionospheric storm. This finding is a very important argument in supporting significant ionizing effect of energetic electrons in the storm time ionosphere both at middle and low latitudes.

  17. Ionospheric scintillation effects on single frequency GPS

    NASA Astrophysics Data System (ADS)

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

    2008-04-01

    Ionospheric scintillation of Global Positioning System (GPS) signals threatens navigation and military operations by degrading performance or making GPS unavailable. Scintillation is particularly active within, although not limited to, a belt encircling the Earth within 20 degrees of the geomagnetic equator. As GPS applications and users increase, so does the potential for degraded precision and availability from scintillation. We examined amplitude scintillation data spanning 7 years from Ascension Island, U.K.; Ancon, Peru; and Antofagasta, Chile in the Atlantic/American longitudinal sector 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 1 min 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.

  18. Ionospheric storm effects at subauroral latitudes - A case study

    NASA Technical Reports Server (NTRS)

    Proelss, G. W.; Brace, L. H.; Mayr, H. G.; Carignan, G. R.; Killeen, T. L.

    1991-01-01

    An attempt is made to classify ionospheric storm effects at subauroral latitudes according to their presumed origin. The storm of December 7/8, 1982, serves as an example. It is investigated using ionosonde, electron content, and DE 2 satellite data. The following effects are distinguished: (1) positive storm effects caused by traveling atmospheric disturbances, (2) positive storm effects caused by changes in the large-scale thermospheric wind circulation, (3) positive storm effects caused by the expansion of the polar ionization enhancement, (4) negative storm effects caused by perturbations of the neutral gas composition, and (5) negative storm effects caused by the equatorward displacement of the trough 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. Ionospheric Disturbance Effects on IPS signals from MEXART

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

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

  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

  2. Methods of alleviation of ionospheric scintillation effects on digital communications

    NASA Technical Reports Server (NTRS)

    Massey, J. L.

    1974-01-01

    The degradation of the performance of digital communication systems because of ionospheric scintillation effects can be reduced either by diversity techniques or by coding. The effectiveness of traditional space-diversity, frequency-diversity and time-diversity techniques is reviewed and design considerations isolated. Time-diversity signaling is then treated as an extremely simple form of coding. More advanced coding methods, such as diffuse threshold decoding and burst-trapping decoding, which appear attractive in combatting scintillation effects are discussed and design considerations noted. Finally, adaptive coding techniques appropriate when the general state of the channel is known are discussed.

  3. 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.

  4. 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.

  5. Ionospheric theory. [effect of vertically propagating waves on NO densities in the ionosphere

    NASA Technical Reports Server (NTRS)

    1981-01-01

    The effects of the atmospheric dynamics on the ionosphere and neutral chemistry of the stratosphere, mesosphere, and thermosphere were studied. Effects of vertically propagating planetary waves on NO densities in the 70 to 120 km altitude region were investigated. A time dependent model was developed to calculate the transport of NO due to planetary wave induced winds. These transports are sensitive to the planetary wave forcing used at the lower boundary, as well as to the structure of the zonal mean basic state. Fluxes and transport of NO are calculated for the months of January and February, using a separate basic state and boundary forcing for each month. The zonal mean wind profile for the months of January and February were inferred from NMC data. A major stratospheric warming occurred near the end of the month of February. The large planetary wave amplitude and reduction in zonal mean wind velocities due to this warming are reflected in the February average boundary forcing and zonal mean state.

  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.

  7. 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.

  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. 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.

  10. PolInSAR at Low Frequency and Ionospheric Effects

    NASA Astrophysics Data System (ADS)

    Dubois-Fernandez, P.; Angelliaume, S.; Truong-Loi, M.-L.; Freeman, A.; Pottier, E.

    2009-04-01

    Global warning is now known to be the major environmental issue mankind will have to face in the next decade. Monitoring of vegetation and biomass is clearly an essential piece of information required at all levels ranging from the scientific studies to understand and forecast, to the political actors and government leaders responsible for drafting remediation policies and evaluating their impact. Microwave remote sensing with the low-frequency SAR technique can provide a useful characterization of forest (spatial coverage, species, density, height...) at a global scale, relying on the all-weather imaging capabilities of SAR linked with the significant penetration of the low-frequency EM wave in the canopy. The published techniques for forest characterization from low frequency SAR data include radiometry inversion, polarimetric inversion based on the anisotropy parameters and PolInSAR Random Volume Over Ground inversion [1]. In this paper, we will more specifically concentrate on the PolInSAR technique and the impact of ionospheric effect on this inversion. PolInSAR at low frequency can be envisioned with two radar platforms flying in formation or as a repeat pass mission. The second alternative is more plausible given the cost and the size of a low frequency SAR instrument. However the two cases will be discussed in the paper. Among the challenges, the following questions need to be addressed: · What is the impact of ionosphere and Faraday rotation on the PolInSAR inversion results? · Is it necessary to correct the data prior to applying the inversion and what is the highest Faraday rotation for which a correction is not necessary? · What is the effect of loss of interferometric coherence and could this be compensated for? · Can the technique provide an estimation of the Faraday rotation or the differential Faraday rotation? · How does ionospheric and calibration effects interact? · What are the implications on a compact polarimetry mode of operation?

  11. High-order stimulated ionospheric diffuse plasma resonances: Significance for magnetospheric emissions

    SciTech Connect

    Benson, R.F. ); Osherovich, V.A. )

    1992-12-01

    The sequence nature of the diffuse ionospheric resonances D[sub n] stimulated by topside sounders was discovered by Oya (1970) with n ranging from 1 to 4. Osherovich (1987) organized these observations using his earlier theory which predicted a nonequidistant spectrum with frequencies proportional to n[sup [1/2

  12. Investigation of ionospheric effects on SAR Interferometry (InSAR): A case study of Hong Kong

    NASA Astrophysics Data System (ADS)

    Zhu, Wu; Ding, Xiao-Li; Jung, Hyung-Sup; Zhang, Qin; Zhang, Bo-Chen; Qu, Wei

    2016-08-01

    Synthetic Aperture Radar Interferometry (InSAR) has demonstrated its potential for high-density spatial mapping of ground displacement associated with earthquakes, volcanoes, and other geologic processes. However, this technique may be affected by the ionosphere, which can result in the distortions of Synthetic Aperture Radar (SAR) images, phases, and polarization. Moreover, ionospheric effect has become and is becoming further significant with the increasing interest in low-frequency SAR systems, limiting the further development of InSAR technique. Although some research has been carried out, thorough analysis of ionospheric influence on true SAR imagery is still limited. Based on this background, this study performs a thorough investigation of ionospheric effect on InSAR through processing L-band ALOS-1/PALSAR-1 images and dual-frequency Global Positioning System (GPS) data over Hong Kong, where the phenomenon of ionospheric irregularities often occurs. The result shows that the small-scale ionospheric irregularities can cause the azimuth pixel shifts and phase advance errors on interferograms. Meanwhile, it is found that these two effects result in the stripe-shaped features in InSAR images. The direction of the stripe-shaped effects keep approximately constant in space for our InSAR dataset. Moreover, the GPS-derived rate of total electron content change index (ROTI), an index to reflect the level of ionospheric disturbances, may be a useful indicator for predicting the ionospheric effect for SAR images. This finding can help us evaluate the quality of SAR images when considering the ionospheric effect.

  13. Effective recombination coefficients in the high-latitude lower ionosphere from solar eclipse observations

    NASA Astrophysics Data System (ADS)

    Cherniakov, Sergey

    2016-07-01

    The photochemistry of processes in the lower ionosphere is rather difficult and up to the end is not developed: it is necessary to specify photochemical schemes, there is big uncertainty in coefficients of separate reactions and concentration of small neutral components. Therefore introduction of the effective coefficients determining the total speed of several reactions was widely adopted when modeling the lower ionosphere, especially the D-region. Experimental opportunities of obtaining of effective recombination coefficients are rather limited. One of the methods allows to define effective recombination coefficients is based on the phenomenon of a solar eclipse and the changes of electron concentration in the ionosphere connected with it. During a solar eclipse there is a short-term and controlled change of solar ionizing radiation intensity that allows to research photochemical processes at known input parameters. The time delay between the eclipse maximum (the sunlight minimum) and the electron concentration minimum at the chosen height during the "short night" is defined as the "sluggishness" [Appleton E.V., 1953] and "relaxation time" [Mitra A., 1974]. The received time delay from observations at the considered ionosphere height with the known electron concentration value gives possibility to calculate the effective recombination coefficient for this height. During solar eclipses on 1 August 2008, on 1 June 2011 and on 20 March 2015 at the partial reflection facility of the observatory "Tumanny" (69° N, 35.7 E) observations of the lower ionosphere behavior were made. On the basis of the obtained data the electron concentration profiles at the heights of the lower ionosphere were received. Calculation of relaxation times allowed to define effective recombination coefficients at some heights of D region of the ionosphere. Appleton, E. V. A note on the "sluggishness" of the ionosphere // J. Atmos. Terr. Phys. - 1953. - Vol. 3, N 5. - P. 282-284. Mitra, A. P

  14. 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.

  15. The study of the effect of solar eclipses on the ionosphere based on satellite beacon observations

    NASA Astrophysics Data System (ADS)

    Cohen, E. A.

    1984-06-01

    The ionospheric effect of a solar eclipse was first noticed in 1927 during an English eclipse. In studies of the effects of solar eclipses on the ionosphere by ionosondes during the next 30 years, the obtained results were difficult to interpret. Results obtained after the introduction of additional techniques indicate that the redistribution of ionization due to temperature changes is important, as is recombination. More recently, a more detailed study of the eclipse effects throughout the ionosphere was made possible as a result of the addition of the satellite beacon observations. The present investigation provides a review of the study of eclipse effects on the ionosphere based on satellite beacon observations. Attention is given to early observations, and total and partial solar eclipses over North America, Africa, Australia, and India.

  16. 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.

  17. 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.

  18. Effects of X-ray flares on the aeronomy of Mars: Simultaneous measurements of ionospheric effects of X-ray flares on Earth and Mars

    NASA Astrophysics Data System (ADS)

    Haider, Syed A.; Machado Santos, Angela; Abdu, Mangalathayil A.; Batista, Inez S.; Shah, Siddhi Y.; Thirupathaiah, P.

    2016-07-01

    MIRI: Validation and Testing Requirements We have studied X-ray aeronomy in the ionospheric E region of Mars during six X-ray flares that occurred on 28 March and 6 April, 2001; 17,18 March and 21 April, 2003 and 19 February, 2005 respectively. These flares were responded by the corresponding electron density profiles of Mars Global Surveyor (MGS). The time series of photoionization rate, photoelectron impact ionization rate, photoelectron flux, ion density, electron density and total Electron Content (TEC) are predicted for each flare day. The estimated production rate, flux and densities are increased by 1-2 orders of magnitude due to effects of these flares in the E region ionosphere of Mars. The normalized estimated TEC are compared with the normalized measured TEC of MGS profiles. At the peak flare time the normalized estimated and normalized measured TEC were enhanced by a factor of 5-10 and 2 respectively. The effects of these flares were also registered in the D region equatorial ionosphere of Earth at Fortaleza observatory. The flares of 6 April, 2001, 17 March and 21 April, 2003 also produced electron density enhancement in the E region ionosphere of Earth at College AK and Cachoeira Paulista observatories. The minimum frequency fmin, recorded in ionogram, increased by 100% (due to D region absorption) while the foE increased by 20%, in the Earth's ionosphere.

  19. Solar Energetic Particle Precipitation Effects on the ionosphere of Mars

    NASA Astrophysics Data System (ADS)

    Lillis, Robert; Larson, Davin; Luhmann, Janet; Lee, Christina; Jakosky, Bruce

    2016-10-01

    Solar Energetic Particles (SEPs) are an important, if irregular, source of ionization and energy input to the Martian atmosphere. As is the case for much-studied Polar Cap precipitation events on the earth, when SEPs precipitate into the Mars atmosphere, they cause heating, ionization, excitation and dissociation, leading to altitude-dependent changes in chemistry. We present a study of the effects of SEP ionization in the Martian atmosphere using data from the Mars Atmosphere and Volatile Evolution (MAVEN) mission. Specifically, we will correlate altitude profiles of thermal planetary ions (O+, CO2+ and O2+) and electrons measured by the Neutral Gas and Ion Mass Spectrometer (NGIMS) and Langmuir Probe on the MAVEN spacecraft with fluxes of energetic protons and electrons measured by the Solar Energetic Particle (SEP) detector. First, we will present case studies of this correlation, before and during SEP events to examine short-term effects of SEP ionization. We will also examine SEP ionization under different heliospheric conditions, leading to different SEP shadowing geometries and ionization rates. Second, we will present a statistical study showing the degree to which ionospheric densities are affected by the presence of energetic particles, as a function of altitude, SEP spectrum flux and solar zenith angle. This work will provide a better understanding of this important source of ionization in the Martian upper atmosphere and hence, how more frequent and more intense SEP events in Mars' past may have affected the structure of the Martian upper atmosphere and hence atmospheric escape.

  20. Effect of dust storms on the D region of the Martian ionosphere: Atmospheric electricity

    NASA Astrophysics Data System (ADS)

    Haider, S. A.; Sheel, V.; Smith, M. D.; Maguire, W. C.; Molina-Cuberos, G. J.

    2010-12-01

    We have used dust opacity values observed by the Thermal Emission Imaging System onboard Mars Odyssey to estimate the effect of dust aerosols in the D region of the Martian ionosphere. An ion-dust aerosol model has been developed to calculate ion concentrations and conductivity at midlatitudes during a dust storm in the Southern Hemisphere. We report that the concentration of the water cluster ions H+(H2O)n, NO2-(H2O)n, and CO3-(H2O)n are reduced by 2 orders of magnitude in the presence of dust aerosols. This indicates that during a dust storm, when the optical depth changes considerably, a large hole in the ion concentrations may appear until this anomalous condition returns to the normal condition after a period of about a few days. During such dust storms, the total ion conductivity is reduced by an order of magnitude.

  1. 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.

  2. Precise Point Positioning with Ionosphere Estimation and application of Regional Ionospheric Maps

    NASA Astrophysics Data System (ADS)

    Galera Monico, J. F.; Marques, H. A.; Rocha, G. D. D. C.

    2015-12-01

    The ionosphere is one of most difficult source of errors to be modelled in the GPS positioning, mainly when applying data collected by single frequency receivers. Considering Precise Point Positioning (PPP) with single frequency data the options available include, for example, the use of Klobuchar model or applying Global Ionosphere Maps (GIM). The GIM contains Vertical Electron Content (VTEC) values that are commonly estimated considering a global network with poor covering in certain regions. For this reason Regional Ionosphere Maps (RIM) have been developed considering local GNSS network, for instance, the La Plata Ionospheric Model (LPIM) developed inside the context of SIRGAS (Geocentric Reference System for Americas). The South American RIM are produced with data from nearly 50 GPS ground receivers and considering these maps are generated for each hour with spatial resolution of one degree it is expected to provide better accuracy in GPS positioning for such region. Another possibility to correct for ionosphere effects in the PPP is to apply the ionosphere estimation technique based on Kalman filter. In this case, the ionosphere can be treated as a stochastic process and a good initial guess is necessary what can be obtained from an ionospheric map. In this paper we present the methodology involved with ionosphere estimation by using Kalman filter and also the application of global and regional ionospheric maps in the PPP as first guess. The ionosphere estimation strategy was implemented in the house software called RT_PPP that is capable of accomplishing PPP either for single or dual frequency data. GPS data from Brazilian station near equatorial region were processed and results with regional maps were compared with those by using global maps. Improvements of the order 15% were observed. In case of ionosphere estimation, the estimated coordinates were compared with ionosphere free solution and after PPP convergence the results reached centimeter accuracy.

  3. 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.

  4. Physics of planetary ionospheres

    NASA Technical Reports Server (NTRS)

    Bauer, S. J.

    1973-01-01

    The fundamental physical and chemical processes in an idealized planetary ionosphere are considered as a general abstraction, with actual planetary ionospheres representing special cases. After describing the structure of the neutral atmospheres (the barosphere, the thermosphere, and the exosphere) and noting the principal ionizing radiations responsible for the formation of planetary ionospheres, a detailed study is made of the thermal structure of these ionospheres and of the chemical processes and plasma-transport processes occurring in them. The features of equilibrium and realistic models of planetary ionospheres are discussed, and an attempt is made to determine the extent of these ionospheres. Considering the ionosphere as a plasma, a plasma kinetic approach is developed for determining the effects of interactions between individual particles and waves in this plasma. The use of remote-sensing radio techniques and direct measurement or in situ techniques is discussed. Finally, the observed properties of the ionospheres of the Earth, Mars, Venus, and Jupiter are reviewed.

  5. The effect of large-scale ionospheric gradients on backscatter ionograms

    NASA Astrophysics Data System (ADS)

    Russell, C. J.; Dyson, P. L.; Houminer, Z.; Bennett, J. A.; Li, L.

    1997-09-01

    This paper presents the results of the synthesis of a range of backscatter ionograms using ray tracing through model ionospheres. The backscatter ionograms were obtained by the Jindalee over-the-horizon radar facility at Alice Springs in northern Australia. Sample ionograms obtained during 1990 were used, and the study concentrated on reproducing effects due to sunrise-sunset gradients and the equatorial anomaly. Backscatter ionograms were synthesized using both analytical and numerical ray tracing through ionospheric models based on FAIM (fully analytic ionospheric model). To make the synthesis realistic, signal strength was calculated taking account of ray divergence, ionospheric absorption, and antenna patterns. Analytical ray tracing produced quite realistic results when horizontal gradients were small but did not reproduce prominent features observed during sunrise-sunset or when propagation occurred through the equatorial anomaly region. Since the analytical ray tracing was restricted to a single vertical profile which could be tilted, this result shows that gradients in ionospheric electron density, rather than simple tilts, are most significant in determining propagation characteristics. Numerical ray tracing through ionospheric models based on the FAIM model reproduced dominant features of backscatter ionograms for those situations when analytical ray tracing proved inadequate. Major seasonal variations were also reproduced. Overall, the results of this initial study show that many premier features on backscatter ionograms, including the power variation of the backscattered signals, can be realistically modeled using ray tracing and ionospheric models. Further work is required before all the detailed structure of backscatter ionogram traces can be synthesized and accurately interpreted in terms of ionospheric structure.

  6. Effects of Soft Electron Precipitation on the Coupled Magnetosphere-Ionosphere-Thermosphere

    NASA Astrophysics Data System (ADS)

    Zhang, B.; Lotko, W.; Brambles, O.; Wiltberger, M. J.; Wang, W.; Schmitt, P. J.; Lyon, J.

    2011-12-01

    Global simulations play an important role in understanding the coupled magnetosphere-ionosphere-thermosphere (MIT) system. The MIT interaction involves both electrodynamic and plasma transport processes, and it is influenced by precipitating particles that deposit both thermal and kinetic energy from the magnetosphere in the ionosphere-thermosphere. Currently, global simulation codes do not include soft electron precipitation, which can significantly influence the thermospheric and ionospheric structure. In this study, two types of causally specified soft electron precipitation, direct-entry cusp and broadband electron precipitation, are implemented in the Coupled Magnetosphere-Ionosphere-Thermosphere (CMIT) model. The direct entry cusp electron precipitation is modeled by specifying the electron thermal flux and temperature in a dynamically determined cusp area. The broadband electron precipitation is regulated by the downward Alfvenic Poynting flux based on empirical relations from Polar and FAST satellite data. Simulation results show that while both types of soft electron precipitation have only minor effects on the ionospheric conductance, they can significantly modify the plasma distribution in the F-region ionosphere and the neutral density in the thermosphere.

  7. Symposium on the Effect of the Ionosphere on Radiowave Systems, Washington, DC, April 14-16, 1981, Preprints

    NASA Astrophysics Data System (ADS)

    1981-12-01

    Topics related to ionospheric modification are examined, taking into account the ionospheric effects of rocket exhaust products, the ionospheric depletion response to booster rocket exhaust perturbations, in situ active experiment techniques to study the ionosphere, the stimulation of ULF magnetic pulsations by rapid change in ionospheric conductivity, and ionospheric modification by high-power radio waves. Equatorial scintillation studies are discussed, giving attention to scintillation of satellite signals at Guam for two elevation angles and two frequencies, ionospheric scintillation measurements at C-band, the microwave equatorial scintillation intensity during solar maximum, daytime scintillations due to F-region irregularities, VHF scintillation near the equatorial anomaly crest in the Indian sector, and the global distribution of equatorial spread-F in the topside ionosphere during equinoctial periods. Other subjects considered are related to HF propagation/remote sensing, high latitude scintillation studies, sub-HF propagation/radar and systems effects, and ionospheric/propagation models. A radar network for studying the large-scale structure and dynamics of ionospheric electric fields is described in connection with a review of future plans and programs.

  8. Ionization effects due to solar flare on terrestrial ionosphere

    NASA Technical Reports Server (NTRS)

    Wu, S. T.; Tan, A.

    1976-01-01

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

  9. 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.

  10. Investigation of the Ionospheric Fluctuations Caused by Space Weather Effects Using GNSS TEC Measurements

    NASA Astrophysics Data System (ADS)

    Shagimuratov, Irk; Krankowski, Andrzej; Cherniak, Iurii; Ephishov, Ivan; Zakharenkova, Irina; Yakimova, Galina

    2013-04-01

    It is known that GPS radio signals passing through the ionosphere suffer varying degrees of rapid variations of their amplitude and phase - signal scintillations. The scintillations are caused by the presence of wide range of scale size irregularities in the ionosphere. It is very important to estimate scintillation and phase fluctuation effects on GNSS navigation system (GPS/GLONASS) performance and consequently on the precession of the obtained position. Effects of the ionospheric irregularities on the GPS signals can be evaluated by measurements of the differential phase time rate of dual frequency GPS signals. GPS observations carried out at the Arctic IGS (International GNSS Service) stations were used to study the development of TEC fluctuations in the high latitude ionosphere. Standard GPS measurements with 30s sampling rate allow the detection of middle- and large-scale ionospheric irregularities. For detection of ionospheric fluctuations the rate of TEC (ROT, in the unit of TECU/min) at 1 min interval was used. The temporal occurrence of TEC fluctuations is clearly observed in time variations in the dual frequency carrier phase along satellite passes. As a measure of the fluctuation activity level the Rate of TEC Index (ROTI) based on standard deviation of ROT was also used. ROTI was estimated in 10-minute interval. These techniques and IGS data were used to study the occurrence of TEC fluctuations at the northern latitude ionosphere for selected geomagnetic storms occurred at the end of 23rd and beginning of new 24th solar cycles. Results demonstrate that fluctuation activity of GPS signals in the high latitude ionosphere is depended on geomagnetic conditions. Intensity of fluctuations essentially increases during geomagnetic storms. The strongest TEC fluctuations occurred as short time rate of TEC enhancements of a factor of 2-5 relative to the quiet time. During geomagnetic disturbed conditions strong phase fluctuations can register at latitudes low

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

    NASA Technical Reports Server (NTRS)

    Lastovicka, J.

    1984-01-01

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

  12. 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.

  13. 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.

  14. Low and Midlatitude Ionospheric Plasma Density Irregularities and Their Effects on Geomagnetic Field

    NASA Astrophysics Data System (ADS)

    Yokoyama, Tatsuhiro; Stolle, Claudia

    2016-10-01

    Earth's magnetic field results from various internal and external sources. The electric currents in the ionosphere are major external sources of the magnetic field in the daytime. High-resolution magnetometers onboard low-Earth-orbit satellites such as CHAMP and Swarm can detect small-scale currents in the nighttime ionosphere, where plasma density gradients often become unstable and form irregular density structures. The magnetic field variations caused by the ionospheric irregularities are comparable to that of the lithospheric contribution. Two phenomena in the nighttime ionosphere that contribute to the magnetic field variation are presented: equatorial plasma bubble (EPB) and medium-scale traveling ionospheric disturbance (MSTID). EPB is formed by the generalized Rayleigh-Taylor instability over the dip equator and grows nonlinearly to as high as 2000 km apex altitude. It is characterized by deep plasma density depletions along magnetic flux tubes, where the diamagnetic effect produced by a pressure-gradient-driven current enhances the main field intensity. MSTID is a few hundred kilometer-scale disturbance in the midlatitude ionosphere generated by the coupled electrodynamics between the ionospheric E and F regions. The field-aligned currents associated with EPBs and MSTIDs also have significant signatures in the magnetic field perpendicular to the main field direction. The empirical discovery of the variations in the magnetic field due to plasma irregularities has motivated the inclusion of electrodynamics in the physical modeling of these irregularities. Through an effective comparison between the model results and observations, the physical process involved has been largely understood. The prediction of magnetic signatures due to plasma irregularities has been advanced by modeling studies, and will be helpful in interpreting magnetic field observations from satellites.

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  16. Ionospheric effects in active retrodirective array and mitigating system design

    NASA Technical Reports Server (NTRS)

    Nandi, A. K.; Tomita, C. Y.

    1980-01-01

    The operation of an active retrodirective array (ARA) in an ionospheric environment (that is either stationary or slowly-varying) was examined. The restrictions imposed on the pilot signal structure as a result of such operation were analyzed. A 3 tone pilot beam system was defined which first estimates the total electron content along paths of interest and then utilizes this information to aid the phase conjugator so that correct beam pointing can be achieved.

  17. Ppp Analisys with GPS and Glonass Integration in Periods Under Ionospheric Scintillation Effects

    NASA Astrophysics Data System (ADS)

    Marques, H. A. S.

    2015-12-01

    The GNSS is widely used nowadays either for geodetic positioning or scientific purposes. The GNSS currently includes GPS, GLONASS, Galileo among other emerging systems. The GPS and GLONASS are currently operational with a full satellite constellation. The GPS is still the most used nowadays and both GPS and GLONASS are under a modernization process. The geodetic positioning by using data from multi-constellation can provide better accuracy in positioning and also more reliability. The PPP is benefited once the satellite geometry is crucial in this method, mainly for kinematic scenarios. The satellite geometry can change suddenly for data collected in urban areas or in conditions of strong atmospheric effects such as Ionospheric Scintillation (IS) that causes weakening of signals with cycle slips and even loss of lock. The IS is caused by small irregularities in the ionosphere layer and is characterized by rapid change in amplitude and phase of the signal being stronger in equatorial and high latitudes regions. In this work the PPP is evaluated with GPS and GLONASS data collected by monitoring receivers from Brazilian CIGALA/CALIBRA network under IS conditions. The PPP processing was accomplished by using the GPSPPP software provided by Natural Resources Canadian (NRCAN). The IS effects were analyzed taking account the S4 and PHI60 indices. Considering periods with moderate IS effects, the use of only GPS data in the PPP presented several peaks in the coordinate time series due to cycle slips and loos of lock. In cycle slip conditions the ambiguity parameter are reinitialized by GPSPPP and considering loss of lock few satellites can be available in some epochs affecting the positioning geometry and consequently decreasing accuracy. In such situations, the PPP using GPS and GLONASS data presented improvements in positioning accuracy of the order to 70% in height component when compared with PPP using only GPS data. Analyses of GDOP and ambiguities parameters were

  18. 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.

  19. Mitigation of Ionospheric Effects on DGPS and WADGPS Operations

    NASA Astrophysics Data System (ADS)

    Skone, S.

    2007-12-01

    Under high levels of ionospheric activity, significant degradations in differential GPS (DGPS) and wide area DGPS (WADGPS) positioning accuracies can occur. DGPS and WADGPS methods are employed for many applications and millions of users. Examples include marine DGPS services, land applications (such as transportation monitoring, fleet management and emergency response) and commercial aviation. In previous studies for the North American sector, DGPS and WADGPS positioning errors were observed to increase by factors of 10-30 under increased ionospheric activity. In particular, gradients of up to 50 ppm are associated with a feature known as storm enhanced density (SED). This feature is a localized enhancement of total electron content (TEC) extending northwest through the mid-latitudes. Positioning errors of 20 m or more have persisted for hours during such events. Specific WADGPS services include the Satellite-Based Augmentation Systems (SBAS) WAAS and EGNOS. The WAAS has been designed for commercial aviation in the United States; EGNOS operates in a similar manner for the European sector. In this presentation, DGPS, WAAS and EGNOS capabilities are assessed under severe ionosphere events. The horizontal and vertical positioning accuracies are determined throughout North America and Europe during such events using available data from existing GPS networks (IGS and CORS). All DGPS baselines of length 100-200 km are processed; one station of the baseline is designated as reference and the other as remote user. Differential corrections are computed for the reference and applied at the remote user location. DGPS positioning solutions are generated for hundreds of baselines simultaneously in this manner to derive full spatial statistics of positioning accuracies. WADGPS positioning solutions are also generated for the same set of remote user stations using archived WAAS and EGNOS messages, and computing and applying localized corrections. An extensive study is conducted

  20. 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.

  1. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

    The Multi-Instrument Data Analysis System (MIDAS) algorithm is based on the oceanographic imaging techniques first applied to do the imaging of 2D slices of the ionosphere. The first version of MIDAS (version 1.0) was able to deal with any line-integral data such as GPS-ground or GPS-LEO differential-phase data or inverted ionograms. The current version extends tomography into four dimensional (lat, long, height and time) spatial-temporal mapping that combines all observations simultaneously in a single inversion with the minimum of a priori assumptions about the form of the ionospheric electron-concentration distribution. This work is an attempt to investigate the Radio Occultation (RO) data assimilation into MIDAS by assessing the ionospheric asymmetry and its impact on RO data inversion, when the Onion-peeling algorithm is used. Ionospheric RO data from COSMIC mission, specifically data collected during 24 September 2011 storm over mid-latitudes, has been used for the data assimilation. Using output electron density data from Midas (with/without RO assimilation) and ideal RO geometries, we tried to assess ionospheric asymmetry. It has been observed that the level of asymmetry was significantly increased when the storm was active. This was due to the increased ionization, which in turn produced large gradients along occulted ray path in the ionosphere. The presence of larger gradients was better observed when Midas was used with RO assimilated data. A very good correlation has been found between the evaluated asymmetry and errors related to the inversion products, when the inversion is performed considering standard techniques based on the assumption of spherical symmetry of the ionosphere. Errors are evaluated considering the peak electron density (NmF2) estimate and the Vertical TEC (VTEC) evaluation. This work highlights the importance of having a tool which should be able to state the effectiveness of Radio Occultation data inversion considering standard

  3. Saturn's ionosphere and plasmasphere

    NASA Astrophysics Data System (ADS)

    Moore, Luke Edward

    2008-01-01

    A number of puzzling phenomena were revealed when the Voyager spacecraft flew past Saturn in 1981 to measure the ionized portions (ionosphere) of its upper atmosphere (thermosphere). Most of these issues have remained unexplained in the intervening 25 years due to a lack of conclusive observational data. With the arrival of Cassini at Saturn in July 2004, however, a new era of observations began, providing the promise of fresh evidence and demanding the development of a contemporary theoretical framework in order to re-examine old mysteries and understand new discoveries. This dissertation presents studies of Saturn's ionosphere and inner plasmasphere based on new time-dependent photochemical and diffusive transport models that solve the ion equations of continuity in one dimension. Calculations are conducted within the overall framework of a self-consistent, three-dimensional general circulation model (GCM) of Saturn's thermosphere, and the results of these studies are combined with GCM results to provide the building blocks of a new comprehensive model, the Saturn-Thermosphere- Ionosphere-Model (STIM). The one-dimensional model calculations are used to constrain and investigate a number of unresolved issues and to make testable predictions based on those investigations. Five primary topics are addressed: (1) the additional loss processes required to bring predicted electron densities into agreement with observations, (2) the discrepancy between theory and observations regarding the diurnal variation of peak electron density, (3) the effects of shadowing by Saturn's rings on its ionosphere, (4) the yet unknown electron and ion temperatures at Saturn, and (5) the ionospheric contribution to Saturn's plasmasphere. The models show that a steady influx of water into Saturn's atmosphere--from its rings or icy satellites--is required to explain observed electron densities. Additionally, the time-variability of the water source may be the cause of frequently observed

  4. Effects of Crustal Fields on the Ionosphere of Mars as seen by MAVEN

    NASA Astrophysics Data System (ADS)

    Vogt, Marissa F.; Withers, Paul; Flynn, Casey L.; Andersson, Laila; Brain, David; Mitchell, David; Connerney, Jack; Espley, Jared R.

    2016-10-01

    Mars lacks a global intrinsic magnetic field but possesses regions of strong crustal magnetic field that are concentrated in the southern hemisphere. Previous studies have used Mars Global Surveyor or Mars Express data to show that these crustal fields influence the electron densities in the Martian ionosphere. However, many of these studies relied on remote radio occultation or radar sounding measurements and therefore relied on models to infer the crustal magnetic field strength and direction. In fall 2015 the MAVEN spacecraft passed through these crustal field regions at low altitudes, on the day side, and collected comprehensive measurements of the local plasma and magnetic field properties. The MAVEN observations therefore provide an excellent dataset with which to examine the effects of crustal fields on the ionosphere. We report on the MAVEN electron density measurements in the southern crustal field regions and discuss the influence of the magnetic field direction and topology on the dayside Martian ionosphere.

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

    NASA Technical Reports Server (NTRS)

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

    2011-01-01

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

  6. VLF Radio Observations and Modeling of the Ionospheric Effects of SGR 1550-5418

    NASA Astrophysics Data System (ADS)

    Carlson, B. E.; Lehtinen, N. G.; Cohen, M.; Fishman, G. J.; Kouveliotou, C.; van der Horst, A.; Chaplan, V.; Inan, U. S.

    2010-12-01

    Cosmic gamma-ray bursts ionize the upper atmosphere, affecting sub-ionospheric propagation of very-low-frequency (VLF) radio waves. Perturbations of VLF radio signals can therefore be used to study gamma-ray burst effects on the ionosphere. We present observations of VLF radio signal perturbations coincident with bursts observed by the Fermi satellite to be produced by soft gamma-ray repeater (SGR) 1550-5418 on January 22, 2009. Massive VLF signal amplitude perturbations as large as 15 dB are seen coincident with the gamma-ray events. Models of gamma-ray ionization and chemical recovery of the upper atmosphere are then used to drive simulations of VLF radio propagation. Simulation results are compared to the observed radio data and to Fermi gamma-ray observations and are used to constrain the properties of the ionosphere and the gamma-ray events.

  7. Effect of TADs on the F-region of Low midlatitude ionosphere during intense geomagnetic storm.

    NASA Astrophysics Data System (ADS)

    Upadhayaya, Arun Kumar; Joshi, Shivani; Singh Dabas, Raj; Das, Rupesh M.; Yadav, Sneha

    Effect of TAD's on the F region ionosphere of low-mid latitude ionosphere during three intense storms of20 th Nov,2003(-422nT),30 th Oct 2003(-383nT),07Nov,2004(-373nT)respectively are studued using ionosonde data of Delhi(28ø N 77øE).It has been seen that the electon density profile in the F1 region are greatly influenced by the TAD's presence. Further the pre-existing F1 cusp become better devloped during the passage of TAD's.

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  9. The effects on the ionosphere of inertia in the high latitude neutral thermosphere

    NASA Technical Reports Server (NTRS)

    Burns, Alan; Killeen, Timothy

    1993-01-01

    High-latitude ionospheric currents, plasma temperatures, densities, and composition are all affected by the time-dependent response of the neutral thermosphere to ion drag and Joule heating through a variety of complex feedback processes. These processes can best be studied numerically using the appropriate nonlinear numerical modeling techniques in conjunction with experimental case studies. In particular, the basic physics of these processes can be understood using a model, and these concepts can then be applied to more complex realistic situations by developing the appropriate simulations of real events. Finally, these model results can be compared with satellite-derived data from the thermosphere. We used numerical simulations from the National Center of Atmospheric Research Thermosphere/Ionosphere General Circulation Model (NCAR TIGCM) and data from the Dynamic Explorer 2 (DE 2) satellite to study the time-dependent effects of the inertia of the neutral thermosphere on ionospheric currents, plasma temperatures, densities, and composition. One particular case of these inertial effects is the so-called 'fly-wheel effect'. This effect occurs when the neutral gas, that has been spun-up by the large ionospheric winds associated with a geomagnetic storm, moves faster than the ions in the period after the end of the main phase of the storm. In these circumstances, the neutral gas can drag the ions along with them. It is this last effect, which is described in the next section, that we have studied under this grant.

  10. 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.

  11. 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.

  12. Polarization effects of the finite-size low-altitude ionosphere

    NASA Astrophysics Data System (ADS)

    Nenovski, P.

    2001-01-01

    We use two-fluid or Hall effect MHD description of weakly-ionized stratified atmosphere to describe several polarization features of the MHD disturbance penetration. We employ a pair of functions for the electric and magnetic field components ratio which can be treated analytically. As an example we derive an approximation to the case of the MHD waves in the Earth's Hall ionosphere and demonstrate its different polarization responses (ellipticity and rotation) for Alfvén and fast magnetosonic modes depending on the Hall region thickness. Neglecting the Hall thickness effect we derive previously obtained, well-known results for the rotation of the polarization plane of the MHD waves (Dungey, 1963; Nishida, 1964; Inoue, 1973; Hughes, 1974; Hughes and Southwood, 1976). The ionospheric effects are more essential for the polarization of the fast magnetosonic waves. The polarization changes of the magnetosonic waves are expressed as a function of i) the ratio (R) of the height-integrated Hall (Σ_H) and Pedersen (Σ_p) conductivities (conductances) in the Hall region (85-125 km) and ii) a wave/magnetospheric parameter (A_m) and the ratio A_m/Σ_p. The wave/magnetospheric parameter A_m depends on the wave frequency and the horizontal scale of the ULF waves. Using standard models IRI 90 and MSIS 86, responses of ULF magnetosonic waves to seasonal/diurnal ionospheric variations at subauroral/middle latitudes are illustrated for arbitrary, but reasonable values of the wave/magnetospheric parameter A_m. The polarization plane rotation for the ULF compressional waves ranges between 0 and π/2 and reaches the classical π/2 degree only for special cases. Along with the rotation effect an ellipticity effect has also local time course. These findings suggest a new dissipative mechanism (non-resonant) of transformation of magnetosonic waves into Alfvén modes in the ionosphere. In addition we suggest a physical insight for the MHD wave transformation effects by the ionosphere

  13. Impacts of Space Weather Effects on the Ionospheric Vertical Total Electron Content

    NASA Astrophysics Data System (ADS)

    Hinrichs, Johannes; Bothmer, Volker; Mrotzek, Niclas; Venzmer, Malte; Erdogan, Eren; Dettmering, Denise; Limberger, Marco; Schmidt, Michael; Seitz, Florian; Börger, Klaus; Brandert, Sylvia; Görres, Barbara; Kersten, Wilhelm F.

    2016-04-01

    Space weather effects on the terrestrial ionospheric vertical total electron content (VTEC) are caused by solar EUV- and X-Ray emissions, solar wind streams and coronal mass ejections (CMEs), amongst other processes. They can lead to major disturbances of telecommunication and navigation systems. Accurately predicting the global VTEC distribution is thus of utmost importance for our societal infrastructure. Here we present results obtained within the German space situational awareness project OPTIMAP (OPerational Tool for Ionosphere Mapping And Prediction) through analyzing the solar effects on the global and regional distribution as well as on the temporal variation of the ionospheric VTEC. For the state-of-the-art analysis in the OPTIMAP project, key data from the GOES, SDO, ACE, SOHO, Proba2 and STEREO missions are analysed together with ground based parameters such as the F10.7 index. The ionospheric data are taken from global VTEC-maps provided by the International GNSS Service (IGS). The results will be used as input for the development of an improved operational VTEC forecast service providing forecasts up to five days in advance.

  14. 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.

  15. Tropical cyclone effects on the equatorial ionosphere: First result from the Indian sector

    NASA Astrophysics Data System (ADS)

    Guha, Anirban; Paul, Bapan; Chakraborty, Monti; De, Barin Kumar

    2016-06-01

    Ionospheric response to the effects of tropical cyclone (TC) "Mahasen" in 2013 and Hudhud in 2014 is studied on the equatorial ionosphere over the Indian sector for the first time using Global Positioning System-derived total electron content (TEC) data. We observed an anomalous decrease of 3.8 TEC unit (1 TECU = 1016 el m-2) in vertical TEC (VTEC) value from the monthly mean for TC Mahasen and 2.1 TECU for TC Hudhud on the day of the landfall. We have also observed similar VTEC depletion of 1.5, 1.9, and 2.1 TECU for three different receivers on the landfall day for TC Vongfong over Japan. This anomalous decrease is observed over a wide zone around the trajectory of the cyclone during the active cyclonic storm stage. This observed anomaly might be the result of combined effect of TC-inspired gravity waves, ejection of neutral particles from the terminator of a TC, and lightning electric fields which redistribute the chemical constituents of the ionosphere by increasing the number of neutral particles at different ionospheric heights, thus decreasing the TEC over the satellite-receiver path.

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

    SciTech Connect

    Sastri, J.H.

    1985-01-01

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

  17. 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.

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

    NASA Astrophysics Data System (ADS)

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

    1982-09-01

    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.

  19. 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.

  20. 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.

  1. Ionospheric research opportunity

    NASA Astrophysics Data System (ADS)

    Rickel, Dwight

    1985-05-01

    Ground-based explosions have been exploited successfully in the past as a relatively controlled source for producing ionospheric disturbances. On June 25, the Defense Nuclear Agency will conduct a high explosives test on the northern section of the White Sands Missile Range. Approximately 4,800 tons of ammonium nitrate and fuel oil (ANFO) will be detonated at ground level, producing an acoustic shock wave with a surface pressure change of approximately 20 mbar at a 6 km range. This shock front will have sufficient strength to propagate into the ionosphere with at least a 10% change in the ambient pressure across the disturbance front in the lower F region. Such an ionospheric perturbation will give ionospheric researchers an excellent opportunity to investigate acoustic propagation at ionospheric heights, shock dissipation effect, the ion-neutral coupling process, acoustic-gravity wave (traveling ionospheric disturbance) generation mechanisms, and associated RF phenomena.

  2. 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.

  3. Hemispheric Asymmetry and Universal Time Effects in Ionospheric Total Electron Content and Outflow Rates

    NASA Astrophysics Data System (ADS)

    Perlongo, N. J.; Welling, D. T.; Ridley, A. J.; Glocer, A.; Immel, T. J.; Katus, R. M.; Liemohn, M. W.

    2014-12-01

    Recent studies have suggested that the strength of the ionospheric response to a geomagnetic storm may be a function of Universal Time (UT), with storms that peak in the post-noon UT having the strongest reaction. The strength of the ring current has also been observed to depend on the UT of the storm peak. A recent superposed epoch analysis found that storm intensity is enhanced when the storm peak occurs near 0 UT compared to 12 UT. Ionospheric outflow has been shown to be a significant contributor to magnetospheric dynamics, especially during storm time. It is possible that the changes in the ring current resulting from outflow significantly contribute to the subsequent UT effect. The Polar Wind Outflow Model (PWOM) and the Global Ionosphere-Thermosphere Model (GITM) are used to investigate this dependence by simulating particular storms shifted both to each of the seasons, and in time during the day. The system response is analyzed and compared for both hemispheres using an unshifted base simulation for each storm. The total electron content, electron and ion temperatures, total ionospheric outflow fluence at different altitudes, as well as the magnitude and spatial distributions of outflow are investigated.

  4. Ionospheric effects of magnetospheric and thermospheric disturbances on March 17-19, 2015

    NASA Astrophysics Data System (ADS)

    Polekh, N. M.; Zolotukhina, N. A.; Romanova, E. B.; Ponomarchuk, S. N.; Kurkin, V. I.; Podlesnyi, A. V.

    2016-09-01

    Using vertical and oblique radio-sounding data, we analyze the ionospheric and thermospheric disturbances during the magnetic storm that occurred in northeastern Russia on March 17-19, 2015. We consider the heliospheric sources that induced the magnetic storm. During the main and early recovery phases, the midlatitude stations are characterized by extremely low values of electron density at the F2 layer maximum. Using oblique sounding data, we recorded signals that propagated outside the great circle arc. In evening and night hours, no radio signals were found to pass along the Norilsk-Irkutsk and Magadan-Irkutsk paths. The observed ionospheric effects are shown to be caused by a sharp shift of the boundaries of the main ionospheric trough to the invariant latitude 46° N during the main phase of the magnetic storm. The negative ionospheric disturbance during the recovery phase of the storm, which was associated with significant variations in the composition of the neutral atmosphere, led to a change in the mode composition of received radio signals and a decline in observed maximal frequencies in daytime hours of March 18, 2015 by more than 2 times.

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

    NASA Astrophysics Data System (ADS)

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

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

  6. Stratospheric Sudden Warming Effects on the Ionospheric Migrating Tides during 2008-2010 observed by FORMOSAT-3/COSMIC

    NASA Astrophysics Data System (ADS)

    Lin, J.; Lin, C.; Chang, L. C.; Liu, H.; Chen, W.; Chen, C.; Liu, J. G.

    2013-12-01

    In this paper, ionospheric electron densities obtained from radio occultation soundings of FORMOSAT-3/COSMIC are decomposed into their various constituent tidal components for studying the stratospheric sudden warming (SSW) effects on the ionosphere during 2008-2010. The tidal analysis indicates that the amplitudes of the zonal mean and major migrating tidal components (DW1, SW2 and TW3) decrease around the time of the SSW, with phase/time shifts in the daily time of maximum around EIA and middle latitudes. Meanwhile consistent enhancements of the SW2 and nonmigrating SW1 tides are seen after the stratospheric temperature increase. In addition to the amplitude changes of the tidal components, well matched phase shifts of the ionospheric migrating tides and the stratospheric temperatures are found for the three SSW events, suggesting a good indicator of the ionospheric response. Although the conditions of the planetary waves and the mean winds in the middle atmosphere region during the 2008-2010 SSW events may be different, similar variations of the ionospheric tidal components and their associated phase shifts are found. Futher, these ionospheric responses will be compared with realistic simulations of Thermosphere-Ionosphere-Mesophere-Electrodynamics General Circulation Model (TIME-GCM) by nudging Modern-Era Retrospective analysis for Research and Applications (MERRA) data.

  7. 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.

  8. Effect of the solar activity variation on the Global Ionosphere Thermosphere Model (GITM)

    NASA Astrophysics Data System (ADS)

    Masutti, Davide; March, Günther; Ridley, Aaron J.; Thoemel, Jan

    2016-09-01

    The accuracy of global atmospheric models used to predict the middle/lower thermosphere characteristics is still an open topic. Uncertainties in the prediction of the gas properties in the thermosphere lead to inaccurate computations of the drag force on space objects (i.e. satellites or debris). Currently the lifetime of space objects and therefore the population of debris in low Earth orbit (LEO) cannot be quantified with a satisfactory degree of accuracy. In this paper, the Global Ionosphere Thermosphere Model (GITM) developed at the University of Michigan has been validated in order to provide detailed simulations of the thermosphere. First, a sensitivity analysis has been performed to investigate the effect of the boundary conditions on the final simulations results. Then, results of simulations have been compared with flight measurements from the CHallenging Minisatellite Payload (CHAMP) and Gravity Recovery and Climate Experiment (GRACE) satellites and with existing semi-empirical atmospheric models (IRI and MSIS). The comparison shows a linear dependency of the neutral density values with respect to the solar activity. In particular, GITM shows an over-predicting or under-predicting behaviour under high or low solar activity respectively. The reasons for such behaviour can be attributed to a wrong implementation of the chemical processes or the gas transport properties in the model.

  9. Modeling the effects of ionospheric scintillation on GPS/Satellite-Based Augmentation System availability

    NASA Astrophysics Data System (ADS)

    Conker, Robert S.; El-Arini, M. Bakry; Hegarty, Christopher J.; Hsiao, Thomas

    2003-02-01

    Ionospheric scintillation is a rapid change in the phase and/or amplitude of a radio signal as it passes through small-scale plasma density irregularities in the ionosphere. These scintillations not only can reduce the accuracy of GPS/Satellite-Based Augmentation System (SBAS) receiver pseudorange and carrier phase measurements but also can result in a complete loss of lock on a satellite. In a worst case scenario, loss of lock on enough satellites could result in lost positioning service. Scintillation has not had a major effect on midlatitude regions (e.g., the continental United States) since most severe scintillation occurs in a band approximately 20° on either side of the magnetic equator and to a lesser extent in the polar and auroral regions. Most scintillation occurs for a few hours after sunset during the peak years of the solar cycle. Typical delay locked loop/phase locked loop designs of GPS/SBAS receivers enable them to handle moderate amounts of scintillation. Consequently, any attempt to determine the effects of scintillation on GPS/SBAS must consider both predictions of scintillation activity in the ionosphere and the residual effect of this activity after processing by a receiver. This paper estimates the effects of scintillation on the availability of GPS and SBAS for L1 C/A and L2 semicodeless receivers. These effects are described in terms of loss of lock and degradation of accuracy and are related to different times, ionospheric conditions, and positions on the Earth. Sample results are presented using WAAS in the western hemisphere.

  10. On differences of magnetic storm effects on ionosphere above neighbouring locations

    NASA Astrophysics Data System (ADS)

    Buresova, Dalia; Bosco Habarulema, John; Thobeka Katamzi, ama; Lastovicka, Jan; Chum, Jaroslav; Sindelarova, Tereza; Mosna, Zbysek; Urbar, Jaroslav; Kouba, Daniel

    2016-04-01

    The paper is focused on cases of different ionospheric reaction above a few neighbouring European and South African locations to disturbances induced by CIR/HSS-related storms. Most of storms involved in the analysis occurred within the 23rd and 24th solar cycle. We analysed variability of the F2 layer critical frequency foF2, peak height hmF2 and GPS TEC values for the entire storm period. Both positive and negative deviations of foF2, hmF2 and TEC have been obtained independently on season. Observed differences in ionospheric effects (mainly in positive effects) for the individual events and neighbouring locations are well pronounced both in foF2 and hmF2. We considered an impact of several factors (e.g. intensity of geomagnetic storm, local geomagnetic situation, and season, difference between geographic and geomagnetic coordinates etc.) with aim to identify the "main players".

  11. The spectral effect of the ionospheric irregularities on the scintillation of transionospheric signals

    SciTech Connect

    Lyle, R.; Kuo, S.P.; Huang, J.

    1995-12-31

    The effect of the spectral width {Delta}k of the ionospheric density irregularity an scintillation of the transionospheric signal is examined. The results show that the Scinti1lation Index S{sub 4} depends strongly on {Delta}/k which can enhance or reduce S{sub 4} value depending on the wave length of the irregularity. However, a 10% spectral width reduces S{sub 4} to a negligibly small value almost independent of the scale length of the irregularity.

  12. An instrument for probe diagnostic of ionospheric plasma with compensation for spacecraft-charge effect

    SciTech Connect

    Ivanitskii, A.S.; Kashirin, A.I.; Chasovitin, Yu.K.; Chkalov, V.G.

    1994-10-01

    A device to probe ionospheric plasma that includes a simple circuit to eliminate the spacecraft-charge effect on the probe potential is described. It can record the current-voltage curves of the probe at particle currents of 15 nA-60 {mu}A over voltages of -2.5...+3.5 V when the voltage on the spacecraft surface with respect to the ambient potential is -3.5...+2.5 V.

  13. Effects of high power R.F. fields in the atmosphere and the ionosphere

    NASA Astrophysics Data System (ADS)

    Ganguly, Suman

    1990-04-01

    The effects of high-power RF fields generated in the context of a strategic defense system on the atmosphere and ionosphere are discussed. The significance of density perturbations, electron accelerations, IR emissions, optical emissions, UV emissions, generation of RF noise field, and air breakdown due to the fields are discussed. The impact of these physical changes on communication, jamming, surveillance, and tracking are noted.

  14. Effect of finite blob size on the current convective instability in the auroral ionosphere. Memorandum report

    SciTech Connect

    Huba, J.D.; Chaturvedi, P.K.

    1986-04-11

    It has been suggested that the current convective instability may be responsible for the structuring, i.e., generation of density irregularities, of density enhancements (known as blobs) in the auroral ionosphere. However, previous theories have neglected the finite extent of the blob along the geomagnetic field. In this paper, a nonlocal theory of the current convective instability is developed, which considers the finite extent of an ionospheric blob parallel to the geomagnetic field. It was found that the growth rate of the instability can be substantially reduced in the finite-sized blob case from the value obtained in the local approximation for an infinitely long blob. For auroral ionosphere parameters, the reduction in the growth rate for medium scale irregularities (1-10 km) can be one to two orders of magnitude for the typical observed values of blob sizes (approx. a few hundred km). Thus, it appears that the current convective instability is not a viable mechanism to generate scintillation causing irregularities, i.e., 1-10 km irregularities.

  15. 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.

  16. 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.

  17. 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.

  18. Thermospheric Wind Effects on the Evolution of Dayside Ionospheric Total Electron Content (TEC)

    NASA Astrophysics Data System (ADS)

    Boyd, E. C.; Zou, S.

    2015-12-01

    The ionospheric electron density is a highly varying quantity and significantly affects the propagation of radio signals that pass through or are reflected by the ionosphere. During moments of enhanced geomagnetic activity, in particular geomagnetic storms, Ionospheric total electron content (TEC) anomalies can form that have very severe spatial and temporal gradients. Occasionally, these anomalies can be large enough to reduce the accuracy of positioning and timing service from GPS causing serious problems for planes and other systems. This research targets on a particular TEC structure, named TEC plumes, a region of high TEC extending from the mid-latitudes to the higher latitudes and polar areas in the north hemisphere. It has been found recently that the growth and decay of the plumes can be affected by the interplanetary conditions through convection as well as the thermospheric winds. In particular, this research focuses on thermospheric wind effects on plume evolution in terms of longitudinal and hemispheric asymmetries. We use the International Geomagnetic Reference Field (IGRF) model to specify the geomagnetic field lines as well as idealized thermospheric wind pattern to identify the wind effects at different longitudes. We found that the thermospheric wind would be most effective in changing TEC at two longitudinal sectors in the Northern Hemisphere, i.e. near Alaska and East Europe, and one longitudinal sector in the Southern Hemisphere, i.e. near Antarctic Peninsula. We also compare the results to TEC data through event and statistical analysis and to ionosphere-thermosphere simulation results. Preliminary results show that the TEC value dips are coincident with these longitudinal sectors.

  19. Longitudinal effects of ionospheric responses to substorms at middle and lower latitudes: a case study

    NASA Astrophysics Data System (ADS)

    Pi, Xiaoqing; Mendillo, Michael; Spalla, Paolo; Anderson, David N.

    1995-08-01

    An ionospheric model is used to simulate total electron content (TEC) disturbance events observed at middle and lower latitude sites near 75°W and 7°E longitudes. Within this longitudinal range, daytime TEC disturbances show patterns that are correlated with substrom activity seen in both auroral electrojet and ring current behavior. In modeling studies of the observed ionospheric effects, both electric field and neutral wind perturbations are examined as possible mechanisms. The morphological features of the required electric field perturbations near drawn and dusk are compared with those at other times to examine the local time characteristics of magnetospheric influence. Large-scale traveling atmospheric disturbances (TADs), an alternative candidate for the disturbance source, are also characterized and compared with known thermospheric behavior.

  20. Spatial effects of HF multiple scattering in the ionosphere: Experimental observations

    NASA Astrophysics Data System (ADS)

    Zabotin, Nikolay; Bullett, Terence

    2011-08-01

    The theory of multiple scattering of MF/HF radio waves by intermediate-scale (0.1-5 km) ionospheric irregularities predicts a very distinctive distribution of the relative integral intensity of a signal reflected from the ionosphere in the vicinity of a ground-based transmitter. It is significantly reduced within a distance of about several tens of kilometers. A ring of enhancement occurs at a greater distance. At still larger distances from the transmitter, effects of multiple scattering are weakened and the integral intensity returns to its undisturbed value. While there are experimental confirmations of the "anomalous attenuation" effect near the transmitter location, no attempt has yet been made to track the intensity features at the larger distances. This paper presents results of the first experimental campaign of this kind that was conducted in September-November 2009 in and around Boulder, CO. The results obtained confirm that significant deviations from the predictions of geometrical optics occur, and these deviations are in general agreement with the theory of multiple scattering in the ionosphere.

  1. The 20 March 2015 total solar eclipse: effects in the high-latitude lower ionosphere

    NASA Astrophysics Data System (ADS)

    Cherniakov, Sergey; Tereshchenko, Valentina; Ogloblina, Olga; Vasiliev, Evgeny; Gomonov, Alexander

    2016-07-01

    The medium-wave facility of partial reflections of the Polar Geophysical Institute (observatory "Tumanny", 69 N, 35.7 E) has observed behavior of the lower high-latitude ionosphere during the 20 March 2015 total solar eclipse. There were several effects during the eclipse. Generally on the heights of the lower ionosphere the "short night" effect had shown, but at some heights local enhanced electron concentration were revealed and the behavior of the electron concentration had the wave-like form. It had seen also at the behavior of the total electron content of the lower ionosphere. The periods and behavior of the wave are considered. It can be explained by influence of acoustic-gravity waves which originated after cooling of the atmosphere by the lunar shadow during its supersonic movement along the earth surface. The periods and behavior of waves during the eclipse were also received using riometer data at the observatory "Tumanny" and the magnetometer at the observatory "Loparskaya" (68.63 N, 33.38 E).

  2. 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.

  3. The effects of neutral inertia on ionospheric currents in the high-latitude thermosphere following a geomagnetic storm

    SciTech Connect

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

    1993-05-01

    The authors extend previous work with a National Center for Atmospheric Research (NCAR) thermosphere/ionosphere general circulation model (TIGCM), to study dynamo effects in the high latitude thermosphere. Ionospheric convection can drive neutral currents in much the same pattern by means of ion drag reactions. It has been observed that ion currents established during magnetic storms can induce neutral currents which persist for hours after the end of the storm. Model results have shown that such currents can account for up to 80 percent of the Hall currents in the period immediately following storms. Here this previous work is extended and compared with experimental observations. The authors simulate time dependent Hall currents, field-aligned currents, and electrical power fluxes coupling the magnetosphere and ionosphere. They discuss their results in terms of a loaded magnetosphere, which accounts for the fact that the neutral currents can also induce currents and electric fields in the ionosphere.

  4. 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

  5. Thermospheric tidal effects on the ionospheric midlatitude summer nighttime anomaly using SAMI3 and TIEGCM

    NASA Astrophysics Data System (ADS)

    Chen, C. H.; Lin, C. H.; Chang, L. C.; Huba, J. D.; Lin, J. T.; Saito, A.; Liu, J. Y.

    2013-06-01

    This paper is the first study to employ a three-dimensional physics-based ionosphere model, SAMI3, coupled with the National Center for Atmospheric Research Thermosphere Ionosphere Electrodynamics General Circulation Model (TIEGCM) and Global Scale Wave Model to simulate the mesospheric and lower thermospheric tidal effects on the development of midlatitude summer nighttime anomaly (MSNA). Using this coupled model, the diurnal variation of MSNA electron densities at 300 km altitude is simulated on both June solstice (day of year (DOY) 167) and December solstice (DOY 350) in 2007. Results show successful reproduction of the southern hemisphere MSNA structure including the eastward drift feature of the southern MSNA, which is not reproduced by the default SAMI3 runs using the neutral winds provided by the empirical Horizontal Wind Model 93 neutral wind model. A linear least squares algorithm for extracting tidal components is utilized to examine the major tidal component affecting the variation of southern MSNA. Results show that the standing diurnal oscillation component dominates the vertical neutral wind manifesting as a diurnal eastward wave-1 drift of the southern MSNA in the local time frame. We also find that the stationary planetary wave-1 component of vertical neutral wind can cause diurnal variation of the summer nighttime electron density enhancement around the midlatitude ionosphere.

  6. 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.

  7. Active plasma antenna in the Earth's ionosphere

    NASA Astrophysics Data System (ADS)

    Chugunov, Yu. V.; Markov, G. A.

    2001-11-01

    We discuss a new method for controlled stimulation of global perturbations in the Earth's ionosphere and magnetosphere and new possibilities of diagnostics of the wave-particle interaction in the ionospheric and magnetospheric plasma. The method is based on the excitation of an RF plasma-wave discharge in the electromagnetic field of a rocket-borne dipole antenna in the lower oblique-resonance frequency band. The evolution of the discharge leads to the creation of strong local disturbances at ionospheric altitudes in the form of magnetic-field-aligned plasma irregularities with controllable properties. The method was verified in 6 rocket flights at middle and polar latitudes. We review the results of these experiments, focusing considerable attention on those which show significant plasma disturbances in the magnetic flux tube where the rocket is located and which demonstrate the diversity of capabilities of this method. In particular, it is shown that a deep (by an order of magnitude) modulation of energetic (>=40keV) precipitating electrons is available. We have demonstrated that a modulated discharge in the ionosphere can operate as an active plasma antenna. A generation of ``echo'' signals at the discharge modulation frequency and an excitation of the ionospheric Alfvén resonator in the PC band have also been observed. Along with numerous scientific advantages, the method has appeared to be energy-effective and low-cost, which makes it very promising for ionospheric and magnetospheric studies as well as for various practical applications.

  8. 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.

  9. 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.

  10. 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

  11. Order effects in dynamic semantics.

    PubMed

    Graben, Peter Beim

    2014-01-01

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

  12. Investigating the effect of geomagnetic storm and equatorial electrojet on equatorial ionospheric irregularity over East African sector

    NASA Astrophysics Data System (ADS)

    Seba, Ephrem Beshir; Nigussie, Melessew

    2016-11-01

    The variability of the equatorial ionosphere is still a big challenge for ionospheric dependent radio wave technology users. To mitigate the effect of equatorial ionospheric irregularity on trans-ionospheric radio waves considerable efforts are being done to understand and model the equatorial electrodynamics and its connection to the creation of ionospheric irregularity. However, the effect of the East-African ionospheric electrodynamics on ionospheric irregularity is not yet well studied due to lack of multiple ground based instruments. But, as a result of International Heliophysical Year (IHY) initiative, which was launched in 2007, some facilities are being deployed in Africa since then. Therefore, recently deployed instruments, in the Ethiopian sector, such as SCINDA-GPS receiver (2.64°N dip angle) for TEC and amplitude scintillation index (S4) data and two magnetometers, which are deployed on and off the magnetic equator, data collected in the March equinoctial months of the years 2011, 2012, and 2015 have been used for this study in conjunction with geomagnetic storm data obtained from high resolution OMNI WEB data center. We have investigated the triggering and inhibition mechanisms for ionospheric irregularities using, scintillation index (S4), equatorial electrojet (EEJ), interplanetary electric field (IEFy), symH index, AE index and interplanetary magnetic field (IMF) Bz on five selected storm and two storm free days. We have found that when the eastward EEJ fluctuates in magnitude due to storm time induced electric fields at around noontime, the post-sunset scintillation is inhibited. All observed post-sunset scintillations in equinox season are resulted when the daytime EEJ is non fluctuating. The strength of noontime EEJ magnitude has shown direct relation with the strength of the post-sunset scintillations. This indicates that non-fluctuating EEJ stronger than 20 nT, can be precursor for the occurrence of the evening time ionospheric irregularities

  13. Effects of the magnetic storm in April 2000 in the low latitude ionosphere near longitude 120E

    NASA Astrophysics Data System (ADS)

    Liu, L.; Wan, W.; Lee, C.

    A halo-CME induced interplanetary shock wave that passed the Earth around 1648 UT on April 6, 2000 triggered a geomagnetic storm with a minimum value of about -300 nT in Dst index. In this paper, digisonde data from ionospheric stations at Chungli, Wuhan, and Kokubunji are included to investigate the ionospheric responses of low latitudes near longitude 120 E to this storm. At three low latitudes near longitude 120 E during this storm, the significant ionospheric responses was an anomalous rapid and large increase in the ionospheric heights occurred around the beginning of the main phase, and the lifts in h'F and hmF2 lasted for about 2 hours. The nearsimultaneous ionosphere increase was also observed at Chungli, Taiwan. And a wave like disturbance appeared on daytime of the second day. The near simultaneity of the ionospheric lifts at these stations in the nighttime ionospheric heights after the SSC suggested that an ExB plasma drift due to the storm related perturbed east-west electric fields. The empirical models of storm time equatorial zonal electric fields (Fejer and Scherliess, 1997) attributed those rapid and large lifts to the effect of solar wind-magnetosphere dynamo origin, which penetrate to low latitudes and equatorial regions. The following wave like disturbance was suggested to be caused by storm induced Travelling atmospheric disturbances (TADs). A method developed by Liu et al. (2002) and Luan et al. (2002) was used to derive the vertical effective winds from ionospheric measurements. It also shows that there was a significantly downward and upward vertical drift during the storm, which verifies the existence of the storm related perturbed east-west electric fields. Finally, the ionospheric storm time derivation from its monthly median level at these stations was also used to validate the predication ability of STORM, a storm empirical model of Araujo-Pradere et al. (2001), which is now included in the international reference ionosphere model IRI

  14. 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.

  15. The Effects of the Ionosphere on Ground-based Detection of the Global 21 cm Signal from the Cosmic Dawn and the Dark Ages

    NASA Astrophysics Data System (ADS)

    Datta, Abhirup; Bradley, Richard; Burns, Jack O.; Harker, Geraint; Komjathy, Attila; Lazio, T. Joseph W.

    2016-11-01

    Detection of the global H i 21 cm signal from the Cosmic Dawn and the Epoch of Reionization is the key science driver for several ongoing ground-based and future ground-/space-based experiments. The crucial spectral features in the global 21 cm signal (turning points) occur at low radio frequencies ≲ 100 {{MHz}}. In addition to the human-generated radio frequency interference, Earth’s ionosphere drastically corrupts low-frequency radio observations from the ground. In this paper, we examine the effects of time-varying ionospheric refraction, absorption, and thermal emission at these low radio frequencies and their combined effect on any ground-based global 21 cm experiment. It should be noted that this is the first study of the effect of a dynamic ionosphere on global 21 cm experiments. The fluctuations in the ionosphere are influenced by solar activity with flicker noise characteristics. The same characteristics are reflected in the ionospheric corruption to any radio signal passing through the ionosphere. As a result, any ground-based observations of the faint global 21 cm signal are corrupted by flicker noise (or 1/f noise, where f is the dynamical frequency) which scales as {ν }-2 (where ν is the frequency of radio observation) in the presence of a bright galactic foreground (\\propto {ν }-s, where s is the radio spectral index). Hence, the calibration of the ionosphere for any such experiment is critical. Any attempt to calibrate the ionospheric effects will be subject to the inaccuracies in the current ionospheric measurements using Global Positioning System (GPS) ionospheric measurements, riometer measurements, ionospheric soundings, etc. Even considering an optimistic improvement in the accuracy of GPS–total electron content measurements, we conclude that Earth’s ionosphere poses a significant challenge in the absolute detection of the global 21 cm signal below 100 MHz.

  16. Ionospheric irregularity physics modelling

    SciTech Connect

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

    1982-01-01

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

  17. Upward Propagating Tidal Effects Across the E- and F-Regions of the Ionosphere

    NASA Astrophysics Data System (ADS)

    Immel, T. J.; England, S. L.; Forbes, J. M.; Demajistre, R.; Mende, S. B.; Russell, J. M.; Mlynczak, M. G.

    2006-12-01

    The dayside ionospheric dynamo is driven largely by tidal winds in the E-region. These tides vary significantly during the year, but are highly structured during equinox, with a dominant non-migrating wave-4 signature at low latitudes. These tidal components originate in the troposphere with the release of latent heat and absorption of IR radiation in persistent tropical rainstorms. Recent observations by NASA TIMED and IMAGE satellites have reported the finding of the effects of these tides in the density and morphology of the equatorial ionospheric anomaly (EIA), reasonably attributed to the modulation of the E-region dynamo electric field in daytime by the tidal winds. However, significant day-to-day variability in the zonal wave-4 signature of the brightness and separation of the bands of the EIA is found. Here, we seek to understand this variability, whether it is tied to variations in the strength of the upward-propagating tides, or to some other effect that diminishes and/or overrides the effect of the tides on the EIA development. This study relies on global observations from the TIMED-SABER instrument that measures the temperature variations in the mesosphere and lower thermosphere (MLT) associated with the upward-propagating tides. F-region density measurements are made concurrent to the MLT temperature retrievals by both the TIMED-GUVI and IMAGE-FUV instruments. This initial study focuses on the March-April period in 2002 and on times of low magnetic activity where penetrating electric fields from high latitudes do not complicate the ionospheric observations.

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

    NASA Astrophysics Data System (ADS)

    Berngardt, Oleg; Kurkin, Vladimir; Zherebtsov, Gelii; Grigorieva, Svetlana; Kusonski, Oleg

    In this paper, we analyzed the ionospheric effects within the 100-1500 km ranges from the Chelyabinsk meteorite explosion site from the ISTP SB RAS EKB radar data, and from the IG UB RAS PARUS ionosonde data. Both instruments are located at the Arti Observatory, approximately 200 km north of the supposed explosion location. The ionospheric disturbance caused by the meteorite flyby, explosion, and impact had high dynamics and amplitude. Essential effects, however, were observed at more than 100-200 km from the explosion site, and farther, up to 1500 km. Almost simultaneously with the explosion and for 3 minutes (03:20-03:23 UT), there was a motion away from the radar 400 km southwest of the latter (and approximately 200 km west of the explosion site) at the E-layer height with the characteristic velocities 200 m/s and high spectral width. A short delay of the detected effect at a significant distance from the explosion site also testifies to the hypothesis of a large short-living irregularity formations at the heights of the lower E-layer, with the transversal size of several hundreds of kilometers. The first disturbance in the F-layer was observed 15 minutes after the explosion, and it propagated away from the radar almost radially. The radial disturbances were observed up to about 80-100 minutes. The main disturbances in the F-layer were nearly radial waves with the center close to the explosion site. Analyzing the experimental data allowed us to determine the equivalent ionospheric velocities for individual travel mode. The work was done under financial support of RFBR grant #14-05-00514-a.

  19. 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.

  20. 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.

  1. Solar Illumination of the Polar Ionosphere and Its Effects on Cold Ion Outflow.

    NASA Astrophysics Data System (ADS)

    Maes, L.; Maggiolo, R.; Haaland, S.; Li, K.; Andre, M.; Eriksson, A. I.

    2015-12-01

    Solar illumination is the most important form of energy driving the outflow of cold ionospheric ions in the polar regions, called the polar wind. Due to the offset of the magnetic poles from the rotation axis and Earth's rotational and orbital motion, the part of the magnetic polar cap being illuminated and the part being in the dark, will vary throughout the day and the seasons. Therefore the outflowing ion flux from the whole polar cap will vary accordingly. Moreover, the offset in the Northern hemisphere is different from the one in the Southern hemisphere. Thus the flux from both polar caps will also be different. With a very simple model we will explore the effects of this on the outflowing flux, which will affect the atmospheric erosion as well as the supply of ionospheric ions to the plasma sheet. In recent observations with the Cluster satellites, the heavier O⁺ ions have been shown to be affected more strongly by solar illumination than H⁺ ions. So this may lead to an alteration of the mass density in the plasma sheet on a periodic basis. This study will also look for signatures of the effects predicted by this model in data of cold ion outflow. The Cluster extensive data set from André et al. [2015] seems best suited for this. It uses the technique detecting the wake formed behind a charged spacecraft in a low density and low energy plasma environment. This technique will generally only observe ions with an energy too low to overcome the spacecraft potential (i.e. ~< 40 eV). The measurements are made in the magnetospheric lobes, up to altitudes of 20 RE, between 2001 and 2010. This long period of observations creates the possibility to study the seasonal variation of cold ion outflow from the polar ionosphere and look for possible differences between both hemispheres.

  2. Investigations into the properties, conditions, and effects of the ionosphere. Final report 4 Dec 86-31 Dec 89

    SciTech Connect

    Fremouw, E.J.; Reinisch, B.W.; Szuszczewica, E.P.

    1990-01-15

    The contractor and its subcontractors supported GL/AFSC research in ionospheric physics and its systems effects. Support was provided in the following six categories; laboratory measurements; field measurements, aircraft measurements; rocket, satellite, and Shuttle measurements; analytical and theoretical investigations; and engineering analysis. This report summarizes results on 15 specific topics. These topics included ionospheric characteristics central to operation of HF systems, such as OTH radars; engineering studies of meteor/scatter communication links; effects on transionospheric radio propagation controlled by the total electron content (path integral of electron density) of the ionosphere and its fine structure (which produces radiowave scintillation); optical and ultraviolet effects of the aurora and airglow, as well as laboratory uv studies; and feasibility studies on modifying radio blackout and measuring electron density in the D region..

  3. Changes in the ionosphere prior to weak earthquakes in the Irkutsk region

    NASA Astrophysics Data System (ADS)

    Korsunova, L. P.; Chistuakova, L. V.; Khegai, V. V.

    2016-07-01

    Data from 15-minute measurements at the vertical ionospheric sounding station in Irkutsk during the summer months of 2008-2011 are analyzed in order to detect in the ionosphere effects of preparation of weak earthquakes of the K = 10-12 energy class. The method of revealing disturbances in ionospheric parameters by simultaneous observations of the sporadic E layer and regular F2 layer, which was previously applied by the authors in the case of stronger earthquakes, was used. The efficiency of using this method to detect ionospheric disturbances preceding earthquakes also in the case of weak earthquakes is demonstrated. Possible ionospheric precursors of the selected series of earthquakes are identified. For them, an empirical dependence relating the time of advance of the shock moment by the probable ionospheric precursor on the energy class of the earthquake and the epicenter distance to the observation point is found.

  4. Dynamical effects of geomagnetic storms and substorms in the middle-latitude ionosphere: An observational campaign

    NASA Astrophysics Data System (ADS)

    Pi, Xiaoqing; Mendillo, Michael; Hughes, W. Jeffrey; Buonsanto, Michael J.; Sipler, Dwight P.; Kelly, John; Zhou, Qihou; Lu, Gang; Hughes, Terrence J.

    2000-04-01

    An observational campaign was conducted in October 1992 for ~36 hours, at three high- to low-latitude sites near 75°W longitude (Sondre Stromfjord, Millstone Hill, and Arecibo). Vector plasma drift velocities are obtained using the incoherent scatter radar technique at each site. Neutral winds were measured using a Fabry-Perot interferometer, and 6300 Å airglow structures were imaged at the midlatitude site. Electric fields and meridional winds for the period were perturbed when magnetic storms and substorms occurred on the day and night of the campaign. The penetration of magnetospheric electric field and the following interplays between ionospheric electrodynamics and thermospheric wind perturbations in the midlatitude ionosphere are assessed using the multidiagnostic measurements. Evidence for traveling atmospheric disturbances (TADs) and large-scale gravity waves induced by auroral heating effects upon the thermosphere is identified. Diffuse aurora and a stable aurora red (SAR) arc were observed from Millstone Hill during the night of the campaign. The SAR arc moved southward when there were westward electric field perturbations, indicating plasmasphere compression in the postmidnight sector under substorm conditions. The SAR arc location was used to infer the motion of the magnetospheric shielding layer past the Millstone Hill site. Ionospheric F region disturbances in hmF2, NmF2, and total electron content were driven by the observed dynamics, exhibiting a complex mix of wind and electric field perturbations. While standard model episodes of penetration and shielding/overshielding occurred during the daytime event, such unambiguous clarifications were far less obvious during the nighttime event. This is perhaps due to the prolonged period of moderate geomagnetic activity that served as the background conditions for the substorms that occurred during the campaign.

  5. Study of potential ionospheric effects on space-based radars. Report for 7 July 1987-28 February 1988

    SciTech Connect

    Fremouw, E.J.; Secan, J.A.

    1988-02-28

    The Air Force and the Navy have considered development of space-based radars for purposes of defense surveillance. System configurations considered include sufficiently low frequencies and grazing angles and sufficiently large apertures (synthetic or otherwise) to require consideration of the effects of the ionosphere on the radar propagation path. Toward this end, the Air Force Geophysics Laboratory hosted a Workshop in which engineering organizations responsible for system design were brought together with research organizations active in identifying and characterizing ionospheric effects to assess the need for and state of relevant knowledge. This report summarizes an assessment of the suitability and limitations of information presented at the Workshop and available from related studies. Dispersive phase, Ionosphere, Radar clutter, Radiowave scintillation, Space-based radar, Synthetic-aperture radar, TEC, Defense surveillance, Total electron content.

  6. 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.

  7. Effects of TADs on the F region of the mid-latitude ionosphere during an intense geomagnetic storm

    NASA Astrophysics Data System (ADS)

    Yuan, Zhigang; Ning, Baiqi; Deng, Xiaohua

    2009-11-01

    Based on observations of two ionosondes at Wuhan and Kokubunji, this paper presents effects of TADs on the daytime mid-latitude ionosphere during the intense geomagnetic storm on March 31, 2001. During a positive ionospheric storm, the start of the enhancement of the foF2 (F2 peak plasma frequency) at Wuhan lags that at Kokubunji by 15 min, which corresponds to the time interval of traveling atmospheric disturbances (TADs') propagation from Kokubunji to Wuhan. Associated with the uplifting of the hmF2 (height of F2 peak) caused by TADs, it is observed by the two ionosondes that the F1 cusp becomes better developed. Therefore, during a geomagnetic storm, TADs originating from the auroral oval may have a strong influence on the shape of the electron density profile in the F1 region ionosphere at middle latitudes. It is highly likely that TADs are responsible for the evolution of the F1 cusp.

  8. Effects of TADs on the F region of the mid-latitude ionosphere during geomagnetic storms: A case study

    NASA Astrophysics Data System (ADS)

    Yuan, Zhigang; Ning, Baiqi; Deng, Xiaohua

    Based on observations of two ionosondes at Wuhan and Kokubunji, this paper presents effects of an intense geomagnetic storm on the daytime mid-latitude ionosphere on March 31, 2001. During a positive ionospheric storm, the start of the enhancement of the foF2 (F2 peak plasma frequency) at Wuhan lags that at Kokubunji by 15 min, which corresponds to the time interval of traveling atmospheric disturbances (TADs)' propagation from Kokubunji to Wuhan. Associated with the uplifting of the hmF2 (height of F2 peak), it is observed by the two ionosondes that the F1 cusp becomes better developed. Therefore, during a geomagnetic storm, TADs originating from the auroral oval may have a strong influence on the shape of the electron density profile in the F1 region ionosphere at middle latitudes. It is highly likely that TADs are responsible for the evolution of the F1 cusp.

  9. Ion Upflow Dependence on Ionospheric Density and Solar Photoionization

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

    Wahlund et al. [1992] first categorized the upflow of ionospheric ions into two types: that driven by ion frictional heating and that caused by auroral precipitation. 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 (MICA) 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, 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 (IPY) 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.

  10. Multi-GNSS for Ionospheric Scintillation Studies

    NASA Astrophysics Data System (ADS)

    Morton, Y.

    2015-12-01

    GNSS have been widely used for ionospheric monitoring. We anticipate over 160 GNSS satellites broadcasting 400 signals by 2023, nearly double the number today. With their well-defined signal structures, high spatial density and spectral diversity, GNSS offers low cost and distributed passive sensing of ionosphere effects. There are, however, many challenges to utilize GNSS resources to characterize and forecast ionospheric scintillation. Originally intended for navigation purposes, GNSS receivers are designed to filter out nuisance effects due to ionosphere effects. GNSS measurements are plagued with errors from multipath, oscillator jitters, processing artifacts, and neutral atmosphere effects. Strong scintillation events are often characterized by turbulent structures in ionosphere, causing simultaneous deep amplitude fading and abrupt carrier phase changes. The combined weak signal and high carrier dynamics imposes conflicting requirements for GNSS receiver design. Therefore, GNSS receivers often experience cycle slips and loss of lock of signals during strong scintillation events. High quality, raw GNSS signals bearing space weather signatures and robust receiver algorithms designed to capture these signatures are needed in order for GNSS to be a reliable and useful agent for scintillation monitoring and forecasting. Our event-driven, reconfigurable data collection system is designed to achieve this purpose. To date, our global network has collected ~150TB of raw GNSS data during space weather events. A suite of novel receiver processing algorithms has been developed by exploitating GNSS spatial, frequency, temporal, and constellation diversity to process signals experiencing challenging scintillation impact. The algorithms and data have advanced our understanding of scintillation impact on GNSS, lead to more robust receiver technologies, and enabled high spatial and temporal resolution depiction of ionosphere responses to solar and geomagnetic conditions. This

  11. Cyclotron Harmonic Effects on Stimulated Electromagnetic Emission in the Ionosphere: a Theoretical Study

    NASA Astrophysics Data System (ADS)

    Huang, Joe

    The dissertation studies parametric instabilities and nonlinear scattering processes that explain the electron cyclotron harmonic effects on the spectral features of stimulated electromagnetic emission (SEE) spectrum observed in ionospheric modification experiments. Four topics are explored. A thermal oscillating two stream instability as the generation mechanism of electron Bernstein/upper hybrid waves by the o-mode HF heater wave is first investigated. Analysis shows that the instability zone of upper hybrid waves below the upper hybrid resonance layer becomes small when the heater frequency f_0 is operated near 3f_ c, where f_ c is the local electron cyclotron frequency. This result is used to explain the quenching of downshifted maximum (DM). Parametric decay of an upper hybrid/electron Bernstein pump wave into an upper hybrid/electron Bernstein sideband wave and a lower hybrid decay wave is next examined. When appropriate nonlinear scattering processes are taken into account, this instability process along with its cascading is proposed as a generation mechanism for the observed DM, 2DM, 3DM ... etc. as well as upshifted maximum (UM). A modulational instability of the electron Bernstein wave is also studied. This process involves the decay of a pump electron Bernstein wave into both Stokes and anti-Stokes electron Bernstein sidebands together with a lower hybrid decay mode. It is proposed that scattering of the anti-Stokes and Stokes sidebands of this modulational instability off field-aligned density irregularities produces the frequency upshifted and downshifted sidebands constituting the broad symmetric structure (BSS). The last instability studied is a second order, four wave interaction process involving two pump photons, an upper hybrid plasmon and an electron Bernstein plasmon along with driven lower hybrid fluctuations. It is suggested that (1) frequency upshifted upper hybrid waves excited by this process scatter off field-aligned density

  12. 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.

  13. 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…

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

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

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

  15. 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.

  16. A comparison of the effects of initializing different thermosphere-ionosphere model fields on storm time plasma density forecasts

    NASA Astrophysics Data System (ADS)

    Chartier, Alex T.; Jackson, David R.; Mitchell, Cathryn N.

    2013-11-01

    assimilation has been used successfully for real-time ionospheric specification, but it has not yet proved advantageous for forecasting. The most challenging and important ionospheric events to forecast are storms. The work presented here examines the effectiveness of data assimilation in a storm situation, where the initial conditions are known and the model is considered to be correct but the external solar and geomagnetic drivers are poorly specified. The aim is to determine whether data assimilation could be used to improve storm time forecast accuracy. The results show that, in the case of the storm of Halloween 2003, changes made to the model's initial thermospheric conditions improve electron density forecasts by at least 10% for 18 h, while changes to ionospheric fields alone result in >10% forecast accuracy improvement for less than 4 h. Further examination shows that the neutral composition is especially important to the accuracy of ionospheric electron density forecasts. Updating the neutral composition gives almost all the benefits of updating the complete thermospheric state. A comparison with real, globally distributed observations of vertical total electron content confirms that updating the thermospheric composition can improve forecast accuracy.

  17. 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.

  18. F-region ionosphere effects on the mapping accuracy of SuperDARN HF radar echoes

    NASA Astrophysics Data System (ADS)

    Chen, Xiangcai; Lorentzen, Dag; Moen, Jøran; Oksavik, Kjellmar; Baddeley, Lisa; Lester, Mark

    2016-04-01

    Structured particle precipitation in the cusp is an important source for the generation of F -region ionospheric irregularities. The equatorward boundaries of broad Doppler spectral width in Super Dual Auroral Radar Network (SuperDARN) data and the concurrent OI 630.0 nm auroral emission are good empirical proxies for the dayside open-closed field line boundary (OCB). However, SuperDARN currently employs a simple virtual model to determine the location of its echoes, instead of a direct calculation of the radio wave path. The varying ionospheric conditions could influence the final mapping accuracy of SuperDARN echoes. A statistical comparison of the offsets between the SuperDARN Finland radar spectral width boundary (SWB) and the OI 630.0 nm auroral emission boundary (AEB) from a meridian-scanning photometer (MSP) in Longyearbyen from December 1995 to January 2014 in wintertime is performed. By restricting the location of the OI 630.0 nm data to be near local zenith, where the MSP has the highest spatial resolution, the mapping errors were significantly reduced for the AEB. The variation of the SWB - AEB offset confirms that there is a close relationship between the mapping accuracy of the HF radar echoes and solar activity. The asymmetric variation of the SWB - AEB offset versus magnetic local time suggests that the intake of high density solar extreme ultraviolet ionized plasma from post-noon at sub-auroral latitudes could result in a stronger refraction of the HF radar signals in the noon sector. The changing HF radar operating frequency also has a refraction effect that contributes to the final location of the HF radar echoes.

  19. F region ionosphere effects on the mapping accuracy of SuperDARN HF radar echoes

    NASA Astrophysics Data System (ADS)

    Chen, X.-C.; Lorentzen, D. A.; Moen, J. I.; Oksavik, K.; Baddeley, L. J.; Lester, M.

    2016-05-01

    Structured particle precipitation in the cusp is an important source for the generation of F region ionospheric irregularities. The equatorward boundaries of broad Doppler spectral width in Super Dual Auroral Radar Network (SuperDARN) data and the concurrent OI 630.0 nm auroral emission are good empirical proxies for the dayside open-closed field line boundary. However, SuperDARN currently employs a simple virtual model to determine the location of its echoes, instead of a direct calculation of the radio wave path. The varying ionospheric conditions could influence the final mapping accuracy of SuperDARN echoes. A statistical comparison of the offsets between the SuperDARN Finland radar spectral width boundary (SWB) and the OI 630.0 nm auroral emission boundary (AEB) from a meridian-scanning photometer (MSP) on Svalbard is performed in this paper. By restricting the location of the 630.0 nm data to be near local zenith where the MSP has the highest spatial resolution, the optical mapping errors were significantly reduced. The variation of the SWB-AEB offset confirms that there is a close relationship between the mapping accuracy of the HF radar echoes and solar activity. The asymmetric variation of the SWB-AEB offset versus magnetic local time suggests that the intake of high-density solar extreme ultraviolet ionized plasma from postnoon at subauroral latitudes could result in a stronger refraction of the HF radar signals in the noon sector, while changing the HF radar operating frequency also has a refraction effect that contributes to the final location of the HF radar echoes.

  20. 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.

  1. 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

  2. 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.

  3. Ionospheric storms on Mars

    NASA Astrophysics Data System (ADS)

    Dubinin, E.; Fraenz, M.; Woch, J.; Duru, F.; Gurnett, D.; Modolo, R.; Barabash, S.; Lundin, R.

    2009-04-01

    Measurements made by the ASPERA-3 and MARSIS experiments on Mars Express have shown that space weather effects related to the impact of a dense and high pressure solar wind on Mars cause strong perturbations in the martian induced magnetosphere and ionosphere. The magnetic barrier formed by pile-up of the draped interplanetary magnetic field ceases to be a shield for the incoming solar wind. Large blobs of solar wind plasma penetrate to the magnetosphere and sweep out dense plasma from the ionosphere. The topside martian ionosphere becomes very fragmented consisting of intermittent cold/low energy and energized plasmas. The scavenging effect caused by the intrusions of solar wind plasma clouds enhances significantly the losses of volatile material from Mars.

  4. 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

  5. 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.

  6. The ionospheric effects of a weak intrinsic magnetic field at Mars

    NASA Technical Reports Server (NTRS)

    Shinagawa, H.; Cravens, T. E.

    1992-01-01

    An improved model of the Martian ionosphere which allows the magnetic field to have any direction in the horizontal plane is presented, as well as results of calculations for several different intrinsic magnetic field strengths and directions. When the solar wind dynamic pressure exceeds the Martian ionospheric thermal pressure, the plasma motion is weakly downward throughout the ionosphere for the case of no intrinsic magnetic field, but when the intrinsic and induced fields are in opposite directions, the plasma flow tends to converge toward the current sheet. As a consequence of this convergence, the plasma density is somewhat enhanced near the current sheet, which is located near an altitude of 170 km. The ionosphere above an altitude of about 190 km is not significantly affected by the existence of an intrinsic field as weak as 60 nT.

  7. Statistical Analysis of the Ionosphere based on Singular Value Decomposition

    NASA Astrophysics Data System (ADS)

    Demir, Uygar; Arikan, Feza; Necat Deviren, M.; Toker, Cenk

    2016-07-01

    Ionosphere is made up of a spatio-temporally varying trend structure and secondary variations due to solar, geomagnetic, gravitational and seismic activities. Hence, it is important to monitor the ionosphere and acquire up-to-date information about its state in order both to better understand the physical phenomena that cause the variability and also to predict the effect of the ionosphere on HF and satellite communications, and satellite-based positioning systems. To charaterise the behaviour of the ionosphere, we propose to apply Singular Value Decomposition (SVD) to Total Electron Content (TEC) maps obtained from the TNPGN-Active (Turkish National Permanent GPS Network) CORS network. TNPGN-Active network consists of 146 GNSS receivers spread over Turkey. IONOLAB-TEC values estimated from each station are spatio-temporally interpolated using a Universal Kriging based algorithm with linear trend, namely IONOLAB-MAP, with very high spatial resolution. It is observed that the dominant singular value of TEC maps is an indicator of the trend structure of the ionosphere. The diurnal, seasonal and annual variability of the most dominant value is the representation of solar effect on ionosphere in midlatitude range. Secondary and smaller singular values are indicators of secondary variation which can have significance especially during geomagnetic storms or seismic disturbances. The dominant singular values are related to the physical basis vectors where ionosphere can be fully reconstructed using these vectors. Therefore, the proposed method can be used both for the monitoring of the current state of a region and also for the prediction and tracking of future states of ionosphere using singular values and singular basis vectors. This study is supported by by TUBITAK 115E915 and Joint TUBITAK 114E092 and AS CR14/001 projects.

  8. 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.

  9. 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.

  10. HF ground scatter from the polar cap: Ionospheric propagation and ground surface effects

    NASA Astrophysics Data System (ADS)

    Ponomarenko, P. V.; St. Maurice, J.-P.; Hussey, G. C.; Koustov, A. V.

    2010-10-01

    In addition to being scattered by the ionospheric field-aligned irregularities, HF radar signals can be reflected by the ionosphere toward the Earth and then scattered back to the radar by the rugged ground surface. These ground scatter (GS) echoes are responsible for a substantial part of the returns observed by HF radars making up the Super Dual Auroral Radar Network (SuperDARN). While a GS component is conventionally used in studying ionosphere dynamics (e.g., traveling ionospheric disturbances, ULF waves), its potential in monitoring the state of the scattering surface remains largely unexploited. To fill this gap, we investigated diurnal and seasonal variation of the ground echo occurrence and location from a poleward-looking SuperDARN radar at Rankin Inlet, Canada. Using colocated ionosonde information, we have shown that seasonal and diurnal changes in the high-latitude ionosphere periodically modulate the overall echo occurrence rate and spatial coverage. In addition, characteristics of GS from a particular geographic location are strongly affected by the state of the underlying ground surface. We have shown that (1) ice sheets rarely produce detectable backscatter, (2) mountain ranges are the major source of GS as they can produce echoes at all seasons of the year, and (3) sea surface becomes a significant source of GS once the Arctic sea ice has melted away. Finally, we discuss how the obtained results can expand SuperDARN abilities in monitoring both the ionosphere and ground surface.

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

    NASA Technical Reports Server (NTRS)

    Cole, Keith D.

    1993-01-01

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

  12. Radiotomography and HF ray tracing of the artificially disturbed ionosphere above the Sura heating facility

    NASA Astrophysics Data System (ADS)

    Andreeva, E. S.; Frolov, V. L.; Kunitsyn, V. E.; Kryukovskii, A. S.; Lukin, D. S.; Nazarenko, M. O.; Padokhin, A. M.

    2016-06-01

    We present the results of the radiotomographic imaging of the artificial ionospheric disturbances obtained in the recent experiments on the modification of the midlatitude ionosphere by powerful HF radiowaves carried out at the Sura heater. Radio transmissions from low orbital PARUS beacon satellites recorded at the specially installed network of three receiving sites were used for the remote sensing of the heated ionosphere. We discuss the possibility to generate acoustic-gravity waves (AGWs) with special regimes of ionospheric heating (with the square wave modulation of the effective radiated power at the frequency lower than or of the order of the Brunt-Vaisala frequency of the neutral atmosphere at ionospheric heights during several hours) and present radiotomographic images of the spatial structure of the disturbed volume of the ionosphere corresponding to the directivity pattern of the heater, as well as the spatial structure of the wave-like disturbances, which are possibly heating-induced AGWs, diverging from the heated area of the ionosphere. We also studied the HF propagation of the pumping wave through the reconstructed disturbed ionosphere above the Sura heater, showing the presence of heater-created, field-aligned irregularities that effectively serve as "artificial radio windows."

  13. foF2 seismo-ionospheric effect analysis: actual data and numerical simulations

    NASA Astrophysics Data System (ADS)

    Liperovskaya, E. V.; Biagi, P.-F.; Meister, C.-V.; Rodkin, M. V.

    2008-12-01

    On the background of seasonal and helio-geomagnetic disturbances, disturbances of the ionization density near noon connected to earthquakes are investigated. The study is performed for some tens of earthquakes with magnitudes M>5 and depths h<70 km, which occur at distances from the vertical sounding stations "Tokyo", "Akita", and "Yamagawa" not larger than R=exp(M)+150 km. The analysis is performed using data registered by the three sounding stations every hour during 30 years. Especially methods of the statistical analysis are applied to search for regularities in the lithospheric-ionospheric links before and after earthquakes. The growth of the mean ionization density N at the F-layer electron density maximum Fof2 five-three days before earthquakes, and the decrease of N approaching the eruption and during a few days after the earthquake is investigated in dependence on both the magnitude of the earthquake M and the ionization density N near the F-layer maximum. It is found that some days before earthquakes the decrease of the ionization density ΔN is proportional to the values of M and N. After the earthquakes, ΔN depends much weaker on the magnitude M, and it is not influenced by the ionization density N. The variations of the ionization density three days before earthquakes do not depend on N and M (within the same order of approximation).

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

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

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

  15. 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.

  16. 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

  17. Effect of the Crustal Magnetic Field on the Day-to-night Plasma Transport in the Martian Nightside Ionosphere

    NASA Astrophysics Data System (ADS)

    Zhang, S.; Cui, J.

    2015-12-01

    Day-to-night plasma transport and electron precipitation from the solar wind (SW) are two most likely sources for the Martian nightside ionosphere. Although Mars does not have a large-scale intrinsic magnetic field, the existence of the crustal magnetic field and the induced field associated with the SW/Mars interaction can affect the morphology and ion-dynamics of the Martian ionosphere considerably. As revealed from the magnetometer/electron reflectometer (MAG/ER), the most intense crustal magnetic fields at Mars are located in the Terra Sirenum region. Mini-magnetospheres can be formed by the crustal magnetic anomalies, which can shield the Martian ionosphere from the upstream solar wind flow. Strong horizontal magnetic field may favor the day-to-night plasma transport and hinder the electron precipitation and the vertical plasma diffusion. In the cusp-like regions where the magnetic field line is nearly vertical, the connection with interplanetary magnetic field can permit the precipitation of the SW and the energetic particles.Here, we use the MARSIS subsurface total electron content (TEC) data to study the role of day-to-night plasma transport in the Martian nightside ionosphere. As an extended work of Cui et al. (2015), we will study the effect of different crustal magnetic components on the transport process in the Time in Darkness (TD) domain. The Bx component points to the local north, By points to the local east, and Bz points to the nadir. It is supposed that eastward By term will enhance the day-to-night plasma transport, and vice verse for the westward By term. Constraining the observations in the strong crustal magnetic region of the southern hemisphere, we find that TEC generally maintains a higher value for By > 100 nT compared with By < -100 nT as the ionosphere is turning into the night. The opposite is found for the Bz component, and it may indicate that large vertical B-field can make the plasma diffuse up or down according to the direction of

  18. 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

  19. Perturbation effect of the electronic induction drag on the orbital elements of a charged satellite moving in an ionosphere

    NASA Astrophysics Data System (ADS)

    Li, Lin-Sen

    The influence of the electronic induction drag on the variation of the orbital elements of a charged satellite moving in a magnetic-field-free ionosphere are studied. The theoretical result show that the induction drag results in both the secular and periodic variations of the semi-major axis, however the eccentricity, the argument of perigee and the mean longitude of epoch exhibits no secular variation, but only periodic variation. The inclination and the ascending node remain no variation. As example, the secular effect of the induction drag on the orbital semi-major axis at a supposed satellite is calculated. It can be shown that the semi-major axis is contracted due to the induction drag, if this satellite carries many charges in an ionosphere.

  20. 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.

  1. 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.

  2. The simulation of electromagnetically driven strong Langmuir turbulence effect on the backscatter radiation from ionosphere

    NASA Astrophysics Data System (ADS)

    Kochetov, Andrey

    2016-07-01

    Numerical simulations of the dynamics of electromagnetic fields in a smoothly inhomogeneous nonlinear plasma layer in frameworks of the nonlinear Schrödinger equation with boundary conditions responsible for the pumping of the field in the layer by an incident wave and the inverse radiation losses supplemented the volume field dissipation due to the electromagnetic excitation of Langmuir turbulence are carried out. The effects of the threshold of non-linearity and it's evolution, of the threshold and saturation levels of dissipation in the vicinity of the wave reflection point on the features of the dynamics of reflection and absorption indexes are investigated. We consider the hard drive damping depending on the local field amplitude and hysteresis losses with different in several times "on" and "off" absorption thresholds as well. The dependence of the thresholds of the steady-state, periodic and chaotic regimes of plasma-wave interaction on the scenario of turbulence evolution is demonstrated. The results are compared with the experimental observations of Langmuir stage ionospheric modification.

  3. Modeling ionospheric electron precipitation due to wave particle scattering in the magnetosphere and the feedback effect on the magnetospheric dynamics

    NASA Astrophysics Data System (ADS)

    Yu, Y.; Jordanova, V.; Ridley, A. J.; Albert, J.; Horne, R. B.; Jeffery, C. A.

    2015-12-01

    Electron precipitation down to the atmosphere caused by wave-particle scattering in the magnetosphere contribute significantly to the enhancement of auroral ionospheric conductivity. Global MHD models that are incapable of capturing kinetic physics in the inner magnetosphere usually adopt MHD parameters to specify the precipitation flux to estimate auroral conductivity, hence losing self-consistency in the global circulation of the magnetosphere-ionosphere system. In this study we improve the coupling structure in global models by connecting the physics-based (wave-particle scattering) electron precipitation with the ionospheric electrodynamics and investigate the feedback effect on the magnetospheric dynamics. We use BATS-R-US coupled with a kinetic ring current model RAM-SCB that solves pitch angle dependent particle distributions to study the global circulation dynamics during the Jan 25-26, 2013 storm event. Following tail injections, we found enhanced precipitation number and energy fluxes of tens of keV electrons being scattered into loss cone due to interactions with enhanced chorus and hiss waves in the magnetosphere. This results in a more profound auroral conductance and larger electric field imposing on the plasma transport in the magnetosphere. We also compared our results with previous methods in specifying the auroral conductance, such as empirical relation used in Ridley et al. (2004). It is found that our physics-based method develops a larger convection electric field in the near-Earth region and therefore leads to a more intense ring current.

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

    NASA Technical Reports Server (NTRS)

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

    1975-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

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

  7. GNSS station characterisation for ionospheric scintillation applications

    NASA Astrophysics Data System (ADS)

    Romano, Vincenzo; Spogli, Luca; Aquino, Marcio; Dodson, Alan; Hancock, Craig; Forte, Biagio

    2013-10-01

    Ionospheric scintillations are fluctuations in the phase and amplitude of the signals from GNSS (Global Navigation Satellite Systems) occurring when they cross regions of electron density irregularities in the ionosphere. Such disturbances can cause serious degradation of several aspects of GNSS system performance, including integrity, accuracy and availability. The two indices adopted worldwide to characterise ionospheric scintillations are: the amplitude scintillation index, S4, which is the standard deviation of the received power normalised by its mean value, and the phase scintillation index, σΦ, which is the standard deviation of the de-trended carrier phase. Collaborative work between NGI and INGV supports a permanent network of GISTM (GPS Ionospheric Scintillation and TEC Monitor) receivers that covers a wide range of latitudes in the northern European sector. Data from this network has contributed significantly to several papers during the past few years (see e.g. De Franceschi et al., 2008; Aquino et al., 2009; Spogli et al., 2009, 2010; Alfonsi et al., 2011). In these investigations multipath effects and noise that contaminate the scintillation measurements are largely filtered by applying an elevation angle threshold. A deeper analysis of the data quality and the development of a more complex filtering technique can improve the results obtained so far. The structures in the environment of each receiver in the network which contaminate scintillation measurements should be identified in order to improve the quality of the scintillation and TEC data by removing error sources due to the local environment. The analysis in this paper considers a data set characterised by quiet ionospheric conditions of the mid-latitude station located in Nottingham (UK), followed by a case study of the severe geomagnetic storm, which occurred in late 2003, known generally as the "Halloween Storm".

  8. Fluctuations in the Venusian Ionosphere and Their Effect on Venus Express Lightning Detection Rates

    NASA Astrophysics Data System (ADS)

    Hart, R. A.; Russell, C. T.; Zhang, T.

    2015-12-01

    Venus Express completed its nearly 9 year campaign at Earth's sister planet in late 2014. During this period the onboard fluxgate magnetometer collected data up to 64 Hz in frequency near periapsis. This is the expected frequency range for lightning-generated whistler-mode waves at Venus, between the local electron (~100 Hz) and ion gyrofrequencies (~1 Hz). These waves are right-hand circularly polarized and are guided by the local magnetic field. When the Venusian ionopause is low enough to reside in the collisional region, the interplanetary magnetic field can get carried down with the ions and magnetize the lower ionosphere. As the field travels towards terminator it gains a radial component, enabling whistlers to reach higher altitudes and be detected by the spacecraft. The mission covered almost an entire solar cycle and frequently observed a magnetized ionosphere during the solar minimum phase when the ionosphere was weak due to reduced incident EUV. In addition, the detection rate of whistler-mode signals varied with the solar cycle. Here, we examine the changes in the ionospheric properties associated with the evolution of the solar cycle and the rate of detection of these lightning-generated signals.

  9. Solar Cycle Effects on Equatorial Electrojet Strength and Low Latitude Ionospheric Variability (P10)

    NASA Astrophysics Data System (ADS)

    Veenadhari, B.; Alex, S.

    2006-11-01

    veena_iig@yahoo.co.in The most obvious indicators of the activity of a solar cycle are sunspots, flares, plages, and soon. These are intimately linked to the solar magnetic fields, heliospheric processes which exhibit complex but systematic variations. The changes in geomagnetic activity, as observed in the ground magnetic records follow systematic correspondence with the solar activity conditions. Thus the transient variations in the magnetic field get modified by differing solar conditions. Also the solar cycle influences the Earth causing changes in geomagnetic activity, the magnetosphere and the ionosphere. Daily variations in the ground magnetic field are produced by different current systems in the earth’s space environment flowing in the ionosphere and magnetosphere which has a strong dependence on latitude and longitude of the location. The north-south (Horizontal) configuration of the earth’s magnetic field over the equator is responsible for the narrow band of current system over the equatorial latitudes and is called the Equatorial electrojet (EEJ) and is a primary driver for Equatorial Ionization anomaly (EIA). Equatorial electric fields and plasma drifts play the fundamental roles on the morphology of the low latitude ionosphere and strongly vary during geomagnetically quiet and disturbed periods. Quantitative study is done to illustrate the development process of EEJ and its influence on ionospheric parameters. An attempt is also made to examine and discuss the response of the equatorial electrojet parameters to the fast varying conditions of solar wind and interplanetary parameters.

  10. Effects of different convection models upon the high-latitude ionosphere

    NASA Technical Reports Server (NTRS)

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

    1986-01-01

    The plasma convection models of Volland (1975) and Heelis (1982) are utilized to study the ionosphere. The parameters for the two models are evaluated. The two-cell convection models have similar total cross tail electric potential, diameter of the polar cap, and potential falloff rate outside the polar cap; however, they differ in maximum potential, and the electric field in the polar cap. The input parameters for the high-latitude ionospheric model are described. Two high-latitude ionospheric model runs were conducted and the data are compared in terms of electron density at and above the F 2 peak, attitude of the F 2 peak, ion temperature, and molecular-atomic ion transition height. The altitude dependence of electron density is analyzed using coherent scatter radar data. The data reveal differences between the two models in the height of the F 2 peak and in the ion temperature. The altitude values of the Heelis model are higher than the Volland model in the region where plasma is transported into the polar cap and lower in the region plasma is transported out of the polar cap; the Heelis model also produces an increase in ion temperature. It is noted that the ionosphere has a limited dependence upon the details of the convection models.

  11. 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

  12. Effect of high-latitude ionospheric convection on Sun-aligned polar caps

    NASA Technical Reports Server (NTRS)

    Sojka, J. J.; Zhu, L.; Crain, D. J.; Schunk, R. W.

    1994-01-01

    A coupled magnetospheric-ionospheric (M-I) magnetohydrodynamic (MHD) model has been used to simulate the formation of Sun-aligned polar cap arcs for a variety of interplanetary magnetic field (IMF) dependent polar cap convection fields. The formation process involves launching an Alfven shear wave from the magnetosphere to the ionosphere where the ionospheric conductance can react self-consistently to changes in the upward currents. We assume that the initial Alfven shear wave is the result of solar wind-magnetosphere interactions. The simulations show how the E region density is affected by the changes in the electron precipitation that are associated with the upward currents. These changes in conductance lead to both a modified Alfven wave reflection at the ionosphere and the generation of secondary Alfven waves in the ionosphere. The ensuing bouncing of the Alfven waves between the ionosphere and magnetosphere is followed until an asymptotic solution is obtained. At the magnetosphere the Alfven waves reflect at a fixed boundary. The coupled M-I Sun-aligned polar cap arc model of Zhu et al.(1993a) is used to carry out the simulations. This study focuses on the dependence of the polar cap arc formation on the background (global) convection pattern. Since the polar cap arcs occur for northward and strong B(sub y) IMF conditions, a variety of background convection patterns can exist when the arcs are present. The study shows that polar cap arcs can be formed for all these convection patterns; however, the arc features are dramatically different for the different patterns. For weak sunward convection a relatively confined single pair of current sheets is associated with the imposed Alfven shear wave structure. However, when the electric field exceeds a threshold, the arc structure intensifies, and the conductance increases as does the local Joule heating rate. These increases are faster than a linear dependence on the background electric field strength. Furthermore

  13. Study of the mid-latitude ionospheric response to geomagnetic storms in the European region

    NASA Astrophysics Data System (ADS)

    Berényi, Kitti Alexandra; Barta, Veronika; Kis, Arpad

    2016-07-01

    Geomagnetic storms affect the ionospheric regions of the terrestrial upper atmosphere through different physical and atmospheric processes. The phenomena that can be regarded as a result of these processes, generally is named as "ionospheric storm". The processes depend on altitude, segment of the day, the geomagnetic latitude and longitude, strength of solar activity and the type of the geomagnetic storm. We examine the data of ground-based radio wave ionosphere sounding measurements of European ionospheric stations (mainly the data of Nagycenk Geophysical Observatory) in order to determine how and to what extent a geomagnetic disturbance of a certain strength affects the mid-latitude ionospheric regions in winter and in summer. For our analysis we used disturbed time periods between November 2012 and June 2015. Our results show significant changing of the ionospheric F2 layer parameters on strongly disturbed days compared to quiet ones. We show that the critical frequencies (foF2) increase compared to their quiet day value when the ionospheric storm was positive. On the other hand, the critical frequencies become lower, when the storm was negative. In our analysis we determined the magnitude of these changes on the chosen days. For a more complete analysis we compare also the evolution of the F2 layer parameters of the European ionosonde stations on a North-South geographic longitude during a full storm duration. The results present the evolution of an ionospheric storm over a geographic meridian. Furthermore, we compared the two type of geomagnetic storms, namely the CME caused geomagnetic storm - the so-called Sudden impulse (Si) storms- and the HSS (High Speed Solar Wind Streams) caused geomagnetic storms -the so-called Gradual storms (Gs)- impact on the ionospheric F2-layer (foF2 parameter). The results show a significant difference between the effect of Si and of the Gs storms on the ionospheric F2-layer.

  14. 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.

  15. The "SABEIS" Project: Warning systems based on earthquake and tsunamis-induced ionospheric effects.

    NASA Astrophysics Data System (ADS)

    Rodriguez-Bouza, Marta; Sánchez-Dulcet, Francisco; Herraiz, Miguel; Rodríguez-Caderot, Gracia; Altadill, David; Blanch, Estefania; Santoyo, Miguel Angel

    2016-04-01

    The study of a possible lithosphere-atmosphere-ionosphere coupling (LAI) is mainly focused on the analysis and comprehension of atmospheric and ionospheric anomalies caused by extreme lithospheric events. In this context, earthquakes are considered as possible sources of atmosphere-ionosphere anomalies. The goal of the two-year long project SABEIS (Sistemas de Alerta Basados en Efectos de terremotos y tsunamis en la IonoSfera) granted by the Spanish Ministry of Economy and Competitiveness, is to analyze the disturbances caused by earthquakes and tsunamis and their possible contribution to warning systems. These topics are receiving increased attention in the scientific community and their correct understanding can meaningfully contribute to the protection of people and economic assets in areas subject to seismic threat. The project is based on the analysis of Total Electron Content (TEC) obtained from signals of Global Navigation Satellite Systems (GNSS) and anomalies of the ionospheric F2 layer observed in ionograms. This methodology was partially applied in a previous study of the Mw6.1 earthquake in Greece occurred on January 26, 2014. In that case two TEC disturbances were detected the days prior the earthquake. The first one, four days before, was registered by the majority of the stations analyzed over Europe and after studying its temporal variation, was considered unrelated to the earthquake. The second one occurred the day before the earthquake. This anomaly appeared only at stations close to the epicenter and their temporal proximity to the earthquake point to a possible connection with the earthquake preparation process. In the SABEIS project possible anomalies caused by earthquakes in Mexico and Peru with magnitude ranging from 5.5 to 8.2, will be studied. If the results confirm the influence of seismic events on the ionosphere, the possibility of incorporating this type of analysis in a seismic alert network for the Gulf of Cadiz (southern Iberian

  16. Storm-time Magnetospheric Effects on Electric Fields in the Subauroral Ionosphere

    NASA Astrophysics Data System (ADS)

    Wolf, R. A.; Garner, T. W.; Goldstein, J.; Sazykin, S.; Spiro, R. W.

    2001-12-01

    Although the inner edge of the plasma sheet tends to shield the mid- and low-latitude ionosphere from the full force of magnetospheric convection, the shielding is particularly ineffective during magnetic storms. This talk will review several effects that represent quick responses to magnetospheric drivers, specifically the following: 1. Overshielding and undershielding. The overshielding electric fields, which occur during convection decreases, were predicted theoretically and observed in the post-midnight sector more than twenty years ago. The predicted patterns have been largely confirmed by statistical analysis of radar observations, although it has been necessary to modify the original overshielding idea somewhat to be consistent with the observed strength and duration. Overshielding has also been seen in plasmaspheric observations, most recently by the IMAGE spacecraft. Simulations of the main phase of a large storm predict the sustained presence of an undershielding (direct penetration) eastward electric field in the post-dusk sector, possibly triggering scintillations there. 2. Polarization jets. Simulations indicate that strong ring current injection is accompanied by a several-degree-wide westward-moving jet of plasma in the dusk-midnight quadrant, just equatorward of the auroral zone. These have been observed in recent years from CRRES and Millstone Hill. 3. Interchange-associated electric-field eddies. These are predicted by recent Rice Convection Model simulations and have not, as far as we know, been reported observationally. We predict their occurrence in the early recovery phase of a magnetic storm whose main phase terminates with a strong and sustained northward turning of the interplanetary magnetic field. They should occur in a band roughly 5 degrees wide, just equatorward of the auroral zone, in the dusk-midnight sector.

  17. 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.

  18. 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.

  19. 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-.

  20. 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…

  1. 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.

  2. Observed and modelled effects of auroral precipitation on the thermal ionospheric plasma: comparing the MICA and Cascades2 sounding rocket events

    NASA Astrophysics Data System (ADS)

    Lynch, K. A.; Gayetsky, L.; Fernandes, P. A.; Zettergren, M. D.; Lessard, M.; Cohen, I. J.; Hampton, D. L.; Ahrns, J.; Hysell, D. L.; Powell, S.; Miceli, R. J.; Moen, J. I.; Bekkeng, T.

    2012-12-01

    Auroral precipitation can modify the ionospheric thermal plasma through a variety of processes. We examine and compare the events seen by two recent auroral sounding rockets carrying in situ thermal plasma instrumentation. The Cascades2 sounding rocket (March 2009, Poker Flat Research Range) traversed a pre-midnight poleward boundary intensification (PBI) event distinguished by a stationary Alfvenic curtain of field-aligned precipitation. The MICA sounding rocket (February 2012, Poker Flat Research Range) traveled through irregular precipitation following the passage of a strong westward-travelling surge. Previous modelling of the ionospheric effects of auroral precipitation used a one-dimensional model, TRANSCAR, which had a simplified treatment of electric fields and did not have the benefit of in situ thermal plasma data. This new study uses a new two-dimensional model which self-consistently calculates electric fields to explore both spatial and temporal effects, and compares to thermal plasma observations. A rigorous understanding of the ambient thermal plasma parameters and their effects on the local spacecraft sheath and charging, is required for quantitative interpretation of in situ thermal plasma observations. To complement this TRANSCAR analysis we therefore require a reliable means of interpreting in situ thermal plasma observation. This interpretation depends upon a rigorous plasma sheath model since the ambient ion energy is on the order of the spacecraft's sheath energy. A self-consistent PIC model is used to model the spacecraft sheath, and a test-particle approach then predicts the detector response for a given plasma environment. The model parameters are then modified until agreement is found with the in situ data. We find that for some situations, the thermal plasma parameters are strongly driven by the precipitation at the observation time. For other situations, the previous history of the precipitation at that position can have a stronger

  3. A multiple receiver - multiple transmitter VLF high-order differential analysis evaluation network for near real-time detection and discrimination of seismic-ionospheric precursor phenomena

    NASA Astrophysics Data System (ADS)

    Skeberis, Christos; Zaharis, Zaharias; Xenos, Thomas; Spatalas, Spyridon; Stratakis, Dimitrios; Maggipinto, Tommaso; Biagi, Pier francesco

    2016-04-01

    This study provides an evaluation of the application of high-order differential analysis on VLF signals on a multiple-receiver multiple-transmitter network. This application provides a method for near-real-time detection of disturbances that can be attributed to seismic-ionospheric precursor phenomena and can discriminate disturbances that could be classified as false positives and thus should be attributed to other geomagnetic influences. VLF data acquired in Thessaloniki, Greece (40.59N, 22,78E) Herakleion, Greece (35.31N, 25.10E), Nicosia, Cyprus (35.17N, 33.35E), Italy (42.42N, 13.08E) and transmitted by the VLF station in Tavolara, Italy (ICV station 40.923N, 9.731E) and the station in Keflavik, Iceland (ICE 64.02N, 22.57W) from January 2015 to January 2016 were used for the purpose of this paper. The receivers have been developed by Elettronika Srl and are part of the International Network for Frontier Research on Earthquake Precursors (INFREP). The process applied for this study has been further developed and is based on differential analysis. The signals undergo transformation using an enhanced version of the Hilbert Huang Transform, and relevant spectra are produced. On the product of this process, differential analysis is applied. Finally, the method produces the correlation coefficient of signals that are on the same path over an earthquake epicenter in order to highlight disturbances, and on the opposite can make comparisons with unrelated transmitted signals of different paths to eliminate disturbances that are not localized to the area of interest. This improvement provides a simple method of noise cancellation to signals that would otherwise be considered as false positives. A further evaluation of the method is provided with the presentation and discussion of sample results. The method seems to be a robust tool of analysis of VLF signals and also an automatic detection tool with built-in noise cancellation of outside disturbances.

  4. Development of an ionosphere-atmosphere coupled model for space weather forecast

    NASA Astrophysics Data System (ADS)

    Shinagawa, Hiroyuki; Jin, Hidekatsu; Miyoshi, Yasunobu; Fujiwara, Hitoshi; Fujita, Shigeru; Tanaka, Takashi; Terada, Naoki; Terada, Kaori

    The solar-terrestrial system consists of the solar atmosphere, the solar wind, the magneto-sphere, the ionosphere, and the neutral atmosphere. Those regions have different physical characteristics with different temporal and spatial scales. In particular, the magnetosphere, the ionosphere, and the neutral atmosphere are strongly coupled with each other, and inter-action between the regions is nonlinear and extremely complicated. Even within each region, there are strong interactions between different physical processes. Furthermore, the geospace environment significantly varies as electromagnetic energy and particles from the sun vary. In order to quantitatively understand such a complicated system, it is necessary to model the entire region by including all fundamental processes self-consistently. Various types of global numerical models of the geospace have been constructed by many institutions in the world, and used to study and predict geospace disturbances. At the National Institute of Information and Communications Technology (NICT), real-time solar wind, magnetosphere, and ionosphere-thermosphere models have been developed and used for daily space weather forecast. However, recent observations of the ionosphere and the thermosphere have revealed that atmospheric waves generated in the lower atmosphere significantly influence the upper atmosphere, the ionosphere, and possibly the magnetosphere. In order to quantitatively study the effects of the lower atmosphere on the ionosphere, we have developed an ionosphere-atmosphere coupled model, which includes the whole neutral atmosphere and the ionosphere. It is planned that the model is coupled with our magnetosphere and solar MHD models, which will be used for space weather forecast. We will report the status and future plan of our ionosphere-atmosphere coupled modeling.

  5. Full 3-D TLM simulations of the Earth-ionosphere cavity: Effect of conductivity on the Schumann resonances

    NASA Astrophysics Data System (ADS)

    Toledo-Redondo, S.; Salinas, A.; Fornieles, J.; Portí, J.; Lichtenegger, H. I. M.

    2016-06-01

    Schumann resonances can be found in planetary atmospheres, inside the cavity formed by the conducting surface of the planet and the lower ionosphere. They are a powerful tool to investigate both the electric processes that occur in the atmosphere and the characteristics of the surface and the lower ionosphere. Results from a full 3-D model of the Earth-ionosphere electromagnetic cavity based on the Transmission-Line Modeling (TLM) method are presented. A Cartesian scheme with homogeneous cell size of 10 km is used to minimize numerical dispersion present in spherical schemes. Time and frequency domain results have been obtained to study the resonance phenomenon. The effect of conductivity on the Schumann resonances in the cavity is investigated by means of numerical simulations, studying the transition from resonant to nonresonant response and setting the conductivity limit for the resonances to develop inside the cavity. It is found that the transition from resonant to nonresonant behavior occurs for conductivity values above roughly 10-9 S/m. For large losses in the cavity, the resonances are damped, but, in addition, the peak frequencies change according to the local distance to the source and with the particular electromagnetic field component. These spatial variations present steep variations around each mode's nodal position, covering distances around 1/4 of the mode wavelength, the higher modes being more sensitive to this effect than the lower ones. The dependence of the measured frequency on the distance to the source and particular component of the electric field offers information on the source generating these resonances.

  6. 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.

  7. 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

  8. On diurnal dependence and spatial scales of seismo-ionospheric effects in the E-layer

    NASA Astrophysics Data System (ADS)

    Liperovskaya, E. V.; Meister, C.-V.; Hoffmann, D. H. H.; Silina, A. S.

    In the present work, disturbances of the fbEs -frequency of the sporadic E-layer of the ionosphere are investigated in connection with earthquakes. The fbEs -frequency is proportional to the square root of the maximum ionisation density of the sporadic E-layer. In this work, it is shown that two days before a seismic shock with magnitude M > 5.5 , and during the shock, an increase of the fbEs -frequency is obtained around midnight at distances from the epicentre R < expM + 100 km in the case that the focus of the shock was situated at depths smaller than 60 km. Data obtained by the three ionospheric sounding stations "Kokubunji", "Akita" and "Yamagawa" are analysed, which were recorded during a total time of 42 years. The superimposed epoches method is applied for a few tens of earthquakes.

  9. Electron Gyroharmonic Effects in Ionization and Electron Acceleration during High-Frequency Pumping in the Ionosphere

    SciTech Connect

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

    2006-11-10

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

  10. Magnetosphere--Ionosphere Coupling: Effects of Plasma Alfven Wave Relative Motion

    NASA Astrophysics Data System (ADS)

    Christiansen, P. J.; Dum, C. T.

    1989-06-01

    The introduction of relative perpendicular motion between a flux-tube supporting shear Alfven wave activity and the background plasma is studied in the context of the coupling of a wave generating region with a distant ionosphere. The results of a representative simulation, using an extended version of the code developed by Lysak & Dum (J. geophys. Res. 88, 365 (1983)), are used as a basis for interpreting some aspects of recent satellite observations.

  11. Magnetosphere-ionosphere coupling: effects of plasma Alfvén wave relative motion.

    NASA Astrophysics Data System (ADS)

    Christiansen, P. J.; Dum, C. T.

    The introduction of relative perpendicular motion between a flux-tube supporting shear Alfvén wave activity and the background plasma is studied in the context of the coupling of a wave generating region with a distant ionosphere. The results of a representative simulation, using an extended version of the code developed by Lysak & Dum, are used as a basis for interpreting some aspects of recent satellite observations.

  12. 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

  13. 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.

  14. 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.

  15. Influence of the ionospheric model on DCB computation and added value of LEO satellites

    NASA Astrophysics Data System (ADS)

    Wautelet, Gilles; Lestarquit, Laurent; Loyer, Sylvain; Mercier, Flavien; Perosanz, Félix

    2016-04-01

    In order to compute inter-frequency Differential Code Biases (DCBs), the Geometry-Free combination of a GNSS signal pair needs to be corrected from the ionospheric refraction effect. Such information is obtained using either Global Ionospheric Maps (GIMs) or local models. In this work we investigate the influence of GIMs on the final value and precision of DCB solution. The study covers different ionospheric conditions, ranging from very quiet ionospheric background up to a severe ionospheric storm. In a first step, the Slant Total Electron Content (STEC) between GIMs is assessed as a function of receiver latitude, elevation mask and ionospheric conditions. Then, daily DCBs are estimated using these different GIMs, receiver and satellite contributions being separated using a zero-mean constraint. If the precision of satellite DCBs is clearly dependent on ionospheric conditions and of the observing network, the choice of the GIM seems also to have a non negligible impact. At last, an independent estimation of DCBs is performed using Low Earth Orbit (LEO) observations (such as JASON's GPS data). This solution is compared with our ground network solution and with DCBs coming from the International GNSS Service.

  16. Ionospheric variability over Japan

    NASA Astrophysics Data System (ADS)

    Ezquer, R. G.; Mosert, M.; Corbella, R.; Erazu, M.; de La Zerda, L.

    The understanding of ionospheric variability is important for the user of ionospheric models. A satellite designer or operator needs to know not only monthly average conditions but also the expected deviations from these mean values. In order to contribute to the studies on ionospheric variability, in this paper values of critical frequencies of F2, F1 and E regions and M(3000)F2 factor measured at 4 Japanese stations are used. Data correspond to equinoxes, solstices, high and low solar activity. Quartiles and median values are used to specify variability, because they have the advantage of being less affected by large deviations that can occur during magnetic storms. The results are similar for the considered stations and show that the highest variability correspond to foF2. For March high solar activity the variability of fof2 decreases during hours of maximum ionisation. The M3000F2 factor, in general, shown low variability. Akita (39.72° N, 140.13° E) showed the highest variability for the three frequencies. Moreover, it can be seen that quartiles are not equidistant from the median value.

  17. 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

    2016-07-01

    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.

  18. 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.

  19. Modeling of sub-ionospheric VLF signal anomalies associated with precursory effects of the latest earthquakes in Nepal

    NASA Astrophysics Data System (ADS)

    Sasmal, Sudipta; Chakrabarti, Sandip Kumar; Palit, Sourav; Chakraborty, Suman; Ghosh, Soujan; Ray, Suman

    2016-07-01

    We present the nature of perturbations in the propagation characteristics of Very Low Frequency (VLF) signals received at Ionospheric & Earthquake Research Centre (IERC) (Lat. 22.50 ^{o}N, Long. 87.48 ^{o}E) during and prior to the latest strong earthquakes in Nepal on 12 May 2015 at 12:50 pm local time (07:05 UTC) with a magnitude of 7.3 and depth 18 km at southeast of Kodari. The VLF signal emitted from JJI transmitter (22.2kHz) in Japan (Lat. 32.08 ^{o}N, Long. 130.83 ^{o}E) shows strong shifts in sunrise and sunset terminator times towards nighttime beginning three to four days prior to the earthquake. The shift in terminator times is numerically simulated using Long Wavelength Propagation Capability (LWPC) code. Electron density variation as a function of height is calculated for seismically quiet days using the Wait's exponential profile and it matches with the IRI model. The perturbed electron density is calculated using the effective reflection height (h') and sharpness parameter (β) and the rate of ionization due to earthquake is being obtained by the equation of continuity for ionospheric D-layer. We compute the ion production and recombination profiles during seismic and non-seismic conditions incorporating D-region ion chemistry processes and calculate the unperturbed and perturbed electron density profile and ionization rate at different heights which matches with the exponential profile. During the seismic condition, for both the cases, the rate of ionization and the electron density profile differ significantly from the normal values. We interpret this to be due to the seismo-ionospheric coupling processes.

  20. Pre-Storm effect at the equatorial, low and Mid-latitude Ionosphere and their possible causes

    NASA Astrophysics Data System (ADS)

    Joshua, B. W.

    2015-12-01

    The occurrence and the possible causes of pre storm effect at the equatorial, low latitude and mid latitude have been investigated using some geomagnetic storm parameters and Electron density of the Ionospheric F2 layer. The data used is for 2010 t0 2012. The pre storm effects appeared as either NmF2 depletions or enhancements or even both, when the Dst and Kp indicates a geomagnetically quiet condition (i.e. Dst > -10 nT, Kp < 3). Our results reveal a simultaneous response of the Ionospheric F2 layer and the auroral indices, e.g. AL, AU and AE indices. This suggest their connection to sub storms and a possibility of penetration of the aurora electric field to the mid and low latitudes, leading to the modification of the zonal electric field which in turn affects the drift of electrons from these regions. This and other observations from this study have further shown that Dst and Kp which are indices that have been most widely used in academic research to describe the behavior of geomagnetic storms, are not sufficient for storm time analysis in the equatorial and low latitude. Therefore, it is suggested that AU, AL and AE indices should always be used alongside Dst and Kp or Ap indices for proper and effective storm analysis.

  1. Ionospheric research for space weather service support

    NASA Astrophysics Data System (ADS)

    Stanislawska, Iwona; Gulyaeva, Tamara; Dziak-Jankowska, Beata

    2016-07-01

    Knowledge of the behavior of the ionosphere is very important for space weather services. A wide variety of ground based and satellite existing and future systems (communications, radar, surveillance, intelligence gathering, satellite operation, etc) is affected by the ionosphere. There are the needs for reliable and efficient support for such systems against natural hazard and minimalization of the risk failure. The joint research Project on the 'Ionospheric Weather' of IZMIRAN and SRC PAS is aimed to provide on-line the ionospheric parameters characterizing the space weather in the ionosphere. It is devoted to science, techniques and to more application oriented areas of ionospheric investigation in order to support space weather services. The studies based on data mining philosophy increasing the knowledge of ionospheric physical properties, modelling capabilities and gain applications of various procedures in ionospheric monitoring and forecasting were concerned. In the framework of the joint Project the novel techniques for data analysis, the original system of the ionospheric disturbance indices and their implementation for the ionosphere and the ionospheric radio wave propagation are developed since 1997. Data of ionosonde measurements and results of their forecasting for the ionospheric observatories network, the regional maps and global ionospheric maps of total electron content from the navigational satellite system (GNSS) observations, the global maps of the F2 layer peak parameters (foF2, hmF2) and W-index of the ionospheric variability are provided at the web pages of SRC PAS and IZMIRAN. The data processing systems include analysis and forecast of geomagnetic indices ap and kp and new eta index applied for the ionosphere forecasting. For the first time in the world the new products of the W-index maps analysis are provided in Catalogues of the ionospheric storms and sub-storms and their association with the global geomagnetic Dst storms is

  2. Geomagnetic Storm Main Phase effect on the Equatorial Ionosphere as measured from GPS observations at Ile-Ife

    NASA Astrophysics Data System (ADS)

    Olabode, Ayomide; Ariyibi, Emmanuel

    2016-07-01

    The effect of the main phase of two intense geomagnetic storm events which occurred on August 5-6 and September 26-27, 2011 on the equatorial ionosphere have been investigated using Global Positioning System (GPS) data obtained from an Ile-Ife station (geomagnetic lat. 9.84°N, long. 77.25°E). The WinTEC-P and GPS-TEC analysis software programs were used to process the GPS data to obtain Total Electron Content (TEC) and Scintillation Index (S4). TEC profiles during the main phase of the two geomagnetically disturbed days were compared with quiet time average profiles to examine the response of the equatorial ionosphere. International Reference Ionosphere (IRI) 2012 TEC model was also obtained from Virtual Ionosphere, Thermosphere, Mesosphere Observatory (VITMO) and the extents of deviation from measured GPS-derived TEC were examined for the main phase of the storm events. The results showed that the intensity of both storm events during the main phase which occurred at night-time correlated well with a strong southward direction of the z-component of the Interplanetary Magnetic Field (IMF-Bz) and Solar Wind Speed (Vsw), with the Disturbance storm time (Dst) profile showing multiple step development. TEC depletion was observed during the main phase of the August 5-6, 2011 storm event with TEC recording a maximum value of 9.31 TECU. A maximum TEC value of 55.8 TECU was recorded during the main phase of the September 26-27, 2011 storm event depicting TEC enhancement. Significant scintillation index value of 0.57 was observed when the main phase started on August 5-6, 2011 followed by a prolonged suppression while there was less significant scintillation impact on September 26-27, 2011 with a maximum value of 0.33. The study concluded that the intensification of the ring current during the main phase of geomagnetic storm events was responsible for the intensity of the storm events causing large variations in TEC and significant scintillation phenomenon.

  3. 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.

  4. Response of Ionosphere to the Tropospheric disturbances

    NASA Astrophysics Data System (ADS)

    Maurya, A. K.; Dube, A.; Singh, R.; Cohen, M.

    2015-12-01

    The aim of the present work is to find out response of the ionosphere to the various cases of tropical cyclones. The main process involved is suggested through Atmospheric Gravity waves (AGWs) originating from strong convective systems, propagating upward upto the ionospheric heights and perturbing ionospheric parameters (Bishop et al., 2006). We have used ground and satellite data to extract cyclone induced perturbations at different ionospheric heights along with the various parameters of AGWs during cyclones and associated thunderstorm. The initial results suggest that there is increase in total electron content of the ionosphere with wave like signatures in ionosphere. The satellite observation in optical band shows presence of concentric gravity wave pattern associated with troposphere disturbances with horizontal wavelength of ~50-200km and periods ranging from hours to days. The ground based Very Low Frequency (VLF) measurement shows fluctuations in VLF navigational transmitter signal passing over the region of disturbance. The lightning data from GLD360 lightning network shows intense activity associated with cyclones and increase in lightning peak current and energy during main phase of cyclones which seems to be sufficient enough to derive ionospheric disturbances in the ionosphere. This multi-instrument analysis provide detail information of the three dimensional structure of cyclone and their effect at different altitudes of the ionosphere in the Indian subcontinent.

  5. 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)

  6. GBAS Ionospheric Anomaly Monitoring Based on a Two-Step Approach.

    PubMed

    Zhao, Lin; Yang, Fuxin; Li, Liang; Ding, Jicheng; Zhao, Yuxin

    2016-01-01

    As one significant component of space environmental weather, the ionosphere has to be monitored using Global Positioning System (GPS) receivers for the Ground-Based Augmentation System (GBAS). This is because an ionospheric anomaly can pose a potential threat for GBAS to support safety-critical services. The traditional code-carrier divergence (CCD) methods, which have been widely used to detect the variants of the ionospheric gradient for GBAS, adopt a linear time-invariant low-pass filter to suppress the effect of high frequency noise on the detection of the ionospheric anomaly. However, there is a counterbalance between response time and estimation accuracy due to the fixed time constants. In order to release the limitation, a two-step approach (TSA) is proposed by integrating the cascaded linear time-invariant low-pass filters with the adaptive Kalman filter to detect the ionospheric gradient anomaly. The performance of the proposed method is tested by using simulated and real-world data, respectively. The simulation results show that the TSA can detect ionospheric gradient anomalies quickly, even when the noise is severer. Compared to the traditional CCD methods, the experiments from real-world GPS data indicate that the average estimation accuracy of the ionospheric gradient improves by more than 31.3%, and the average response time to the ionospheric gradient at a rate of 0.018 m/s improves by more than 59.3%, which demonstrates the ability of TSA to detect a small ionospheric gradient more rapidly. PMID:27240367

  7. GBAS Ionospheric Anomaly Monitoring Based on a Two-Step Approach

    PubMed Central

    Zhao, Lin; Yang, Fuxin; Li, Liang; Ding, Jicheng; Zhao, Yuxin

    2016-01-01

    As one significant component of space environmental weather, the ionosphere has to be monitored using Global Positioning System (GPS) receivers for the Ground-Based Augmentation System (GBAS). This is because an ionospheric anomaly can pose a potential threat for GBAS to support safety-critical services. The traditional code-carrier divergence (CCD) methods, which have been widely used to detect the variants of the ionospheric gradient for GBAS, adopt a linear time-invariant low-pass filter to suppress the effect of high frequency noise on the detection of the ionospheric anomaly. However, there is a counterbalance between response time and estimation accuracy due to the fixed time constants. In order to release the limitation, a two-step approach (TSA) is proposed by integrating the cascaded linear time-invariant low-pass filters with the adaptive Kalman filter to detect the ionospheric gradient anomaly. The performance of the proposed method is tested by using simulated and real-world data, respectively. The simulation results show that the TSA can detect ionospheric gradient anomalies quickly, even when the noise is severer. Compared to the traditional CCD methods, the experiments from real-world GPS data indicate that the average estimation accuracy of the ionospheric gradient improves by more than 31.3%, and the average response time to the ionospheric gradient at a rate of 0.018 m/s improves by more than 59.3%, which demonstrates the ability of TSA to detect a small ionospheric gradient more rapidly. PMID:27240367

  8. Modelling ionospheric density structures

    NASA Technical Reports Server (NTRS)

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

    1989-01-01

    Large-scale density structures are a common feature in the high-latitude ionsphere. The structures were observed in the dayside cusp, polar cap, and nocturnal auroral region over a range of altitudes, including the E-region, F-region and topside ionosphere. The origins, lifetimes and transport characteristics of large-scale density structures were studied with the aid of a three-dimensional, time-dependent ionospheric model. Blob creation due to particle precipitation, the effect that structured electric fields have on the ionosphere, and the lifetimes and transport characteristics of density structures for different seasonal, solar cycle, and interplanetary magnetic field (IMF) conditions were studied. The main conclusions drawn are: (1) the observed precipitation energy fluxes are sufficient for blob creation if the plasma is exposed to the precipitation for 5 to 10 minutes; (2) structured electric fields produce structured electron densities, ion temperatures, and ion composition; (3) the lifetime of an F-region density structure depends on several factors, including the initial location where it was formed, the magnitude of the perturbation, season, solar cycle and IMF; and (4) depending on the IMF, horizontal plasma convection can cause an initial structure to break up into multiple structures of various sizes, remain as a single distorted structure, or become stretched into elongated segments.

  9. Ionospheric disturbance dynamo

    SciTech Connect

    Blanc, M.; Richmond, A.D.

    1980-04-01

    A numerical simulation study of the thermospheric winds produced by auroral heating during magnetic storms, and of their global dynamo effects, establishes the main features of the ionospheric disturbanc dynamo. Driven by auroral heating, a Hadley cell is created with equatorward winds blowing above about 120 km at mid-latitudes. The transport of angular momentum by these winds produces a subrotation of the midlatitude thermosphere, or westward motion with respect to the earth. The westward winds in turn drive equatorward Pedersen currents which accumulate charge toward the equator, resulting in the generation of a poleward electric field, a westward E x B drift, and an eastward current. When realistic local time conductivity variations are simulated, the eastward mid-latitude current is found to close partly via lower latitudes, resulting in an 'anti-Sq' type of current vortex. Both electric field and current at low latitudes thus vary in opposition to their normal quiet-day behavior. This total pattern of distrubance winds, electric fields, and currents is superimposed upon the background quiet-day pattern. When the neutral winds are artificially confined on the nightside, the basic pattern of predominantly westward E x B plasma drifts still prevails on the nightside but no longer extends into the dayside. Considerable observational evidence exists, suggesting that the ionospheric disturbance dynamo has an appreciable influence on storm-time ionospheric electric fields at middle and low latitudes.

  10. 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

  11. Study of the effects of solar activities on the ionosphere as observed by VLF signals recorded at TNU station, Vietnam

    NASA Astrophysics Data System (ADS)

    Tan, L. M.

    2015-12-01

    A SuperSID monitor installed at Tay Nguyen University (TNU), Vietnam is used to detect the temporal variations of Very Low Frequency (VLF) signals during 2013 and 2014 to understand the responses of the ionosphere to sunset/sunrise transitions and solar flares. Two VLF station signals are tracked, JJI/22.2 kHz in Japan and NWC/19.8 kHz in Australia. Results show that the effects of sunrise, sunset and solar flares on the NWC signal are more significantly different than those on the JJI signal. Sunset and sunrise spikes only occur on the JJI-TNU path because of longitudinal differences between the receiver and transmitter. Two sunset dips and three sunrise dips appear on the NWC signal during summer season. During intense solar flares, the dips occur after the maximum disturbance of the VLF signals for the North-South path. The appearance of these dips is explained by modal interference patterns. Observing temporal variations of sunrise and sunset dips or spikes of VLF signals during different seasons enhances the understanding of the behavior of the ionosphere.

  12. 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.

  13. 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.

  14. 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.

  15. Ionospheric observations in southern Norway

    NASA Astrophysics Data System (ADS)

    Kjørsvik, N.; Øvstedal, O.; Pettersen, B. R.; Svendsen, J. G. G.

    2003-04-01

    A permanent GPS reference receiver is established in station AK06 at the campus of NLH, Norway. The monumentation, hardware, software and network connection is according to IGS practice. In this poster the first application of dual frequency GPS observations from this station is presented. Carrier phase and pseudorange observations at 1 Hz are used to monitor ionospheric TEC values. The processing is carried out in near real time. Observation files containing one hour of observations are added to moving observation files containing 24 hours of data. Differential Code Biases (DCB) in the satellites are taken from the IONEX (IONosphere Exchange format) computed by the ionosphere working group of the International GPS Services. The IGS estimate daily Global Ionospheric Models with DCBs and ionospheric Total Electron Content (TEC) parameters. Daily estimates for the receiver DCB are estimated using dual frequency pseudorange observations and satellite DCBs and TEC values from IGS. Final TEC values are estimated using undifferenced carrier phase observations leveled to pseudorange. Hourly snap shots as well as animations are presented on a web-page. GPS-observations from other stations will be added in order to extend the area of coverage.

  16. The Ptolemaic Approach to Ionospheric Electrodynamics

    NASA Astrophysics Data System (ADS)

    Vasyliunas, V. M.

    2010-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2010-11-01

    The Multifluid-Lyon-Fedder-Mobarry (MFLFM) global simulation model incorporating an ionospheric cusp O+ outflow model based on an empirical relation between downward DC Poynting flux and O+ outflow flux regulated by the precipitating electron number flux (Fen) is used to simulate the 31 August 2005 storm. A baseline run incorporating the original solar wind data is contrasted against a case where the solar wind dynamic pressure (Pdyn) is artificially adjusted to see what effects this variable has on the O+ fluence generated in the model. Consistent with data, it is found that both the fluence and O+ outflow flux have a positive correlation with the solar wind dynamic pressure. Additionally, changes in Pdyn affect the downward Poynting flux only marginally and regulates both outflow flux and cusp outflow area via Fen. Increases in Pdyn lead to increased cusp electron precipitation, which has the physical effect of enhancing the upwelling O+ population available for outflow.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. The effect of the induced magnetic field on the electron density vertical profile of the Mars' ionosphere: A Mars Express MARSIS radar data analysis and interpretation, a case study

    NASA Astrophysics Data System (ADS)

    Ramírez-Nicolás, M.; Sánchez-Cano, B.; Witasse, O.; Blelly, P.-L.; Vázquez, L.; Lester, M.

    2016-07-01

    We report the indirect detection of an induced magnetic field in the ionosphere of Mars and its effects on the electron density behaviour. The observations were made by the Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) aboard Mars Express, in its Active Ionospheric Sounding mode. During several orbits on June 2006, the ionosphere showed an unusual behaviour, characterised by a compression of the plasma above the main ionospheric peak as observed by the topside total electron content, the plasma scale height, and the local plasma in the Mars Express surroundings. The compression was most likely due to an induced magnetic field originating from the solar wind and measured by the MARSIS antennas, which was able to penetrate into the ionosphere. In particular, for several profiles, the density distribution can be clearly defined by two different plasma scale heights, which indicates a transition region between both of them. From the balance of magnetic and thermal plasma pressures and from a comparison with a numerical model of the Martian ionosphere, the hypothesis of a penetrating induced magnetic field down to a transition altitude around 150 km is confirmed. This compressed ionosphere has also been compared with data from other orbits in the same location and at the same time period, i.e. 18.5 days of difference between first and last orbits, where there is no measured induced magnetic field, and the orbits show a clearly different behaviour.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. The effects of interplanetary magnetic field orientation on dayside high-latitude ionospheric convection

    NASA Technical Reports Server (NTRS)

    Heelis, R. A.

    1984-01-01

    The Atmosphere Explorer C data base of Northern Hemisphere ionospheric convection signatures at high latitudes is examined during times when the interplanetary magnetic field orientation is relatively stable. It is found that when the interplanetary magnetic field (IMF) has its expected garden hose orientation, the center of a region where the ion flow rotates from sunward to antisunward is displaced from local noon toward dawn irrespective of the sign of By. Poleward of this rotation region, called the cleft, the ion convection is directed toward dawn or dusk depending on whether By is positive or negative, respectively. The observed flow geometry can be explained in terms of a magnetosphere solar wind interaction in which merging is favored in either the prenoon Northern Hemisphere or the prenoon Southern Hemisphere when the IMF has a normal sector structure that is toward or away, respectively.

  8. Electrodynamics of the Nighttime Equatorial Ionosphere: the Effects of Winds and Waves

    NASA Astrophysics Data System (ADS)

    Gelinas, L. J.; Kelley, M. C.; Clemmons, J.; Larsen, M.; Makela, J.

    2004-12-01

    In this paper we present initial results from two sounding rockets designed to study the coupling bewteen neutral winds and electric fields in the equatorial ionosphere. The combined instrumented and chemical release payloads were launched from Kwajalein in September 2004. The rockets carried instruments measuring electric fields, plasma densities, neutral densities, and was accompanied by a TMA release to profile neutral winds. Ground based airglow imagers and were used to determine mesospheric conditions; specifically, the presence of gravity waves. The goal of the experiment was to investigate correlations between the gravity wave wind structure and local electric fields. This coupling is expected to be appreciable at the equator, where the magnetic field is nearly horizontal. Here we present initial results and discuss plans for data analysis.

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

    NASA Technical Reports Server (NTRS)

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

    1982-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2003-04-01

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

  11. Earthquake-Ionosphere Coupling Processes

    NASA Astrophysics Data System (ADS)

    Kamogawa, Masashi

    an ionospheric phenomenon attributed to tsunami, termed tsunamigenic ionospheric hole (TIH) [Kakinami and Kamogwa et al., GRL, 2012]. After the TEC depression accompanying a monoperiodic variation with approximately 4-minute period as an acoustic resonance between the ionosphere and the solid earth, the TIH gradually recovered. In addition, geomagnetic pulsations with the periods of 150, 180 and 210 seconds were observed on the ground in Japan approximately 5 minutes after the mainshock. Since the variation with the period of 180 seconds was simultaneously detected at the magnetic conjugate of points of Japan, namely Australia, field aligned currents along the magnetic field line were excited. The field aligned currents might be excited due to E and F region dynamo current caused by acoustic waves originating from the tsunami. This result implies that a large earthquake generates seismogenic field aligned currents. Furthermore, monoperiodical geomagnetic oscillation pointing to the epicenter of which velocity corresponds to Rayleigh waves occurs. This may occur due to seismogenic arc-current in E region. Removing such magnetic oscillations from the observed data, clear tsunami dynamo effect was found. This result implies that a large EQ generates seismogenic field aligned currents, seismogenic arc-current and tsunami dynamo current which disturb geomagnetic field. Thus, we found the complex coupling process between a large EQ and an ionosphere from the results of Tohoku EQ.

  12. 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

  13. Ionospheric modification by rocket effluents. Final report

    SciTech Connect

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

    1980-06-01

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

  14. 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.

  15. 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.

  16. Ionospheric plasma dynamics and instability causedby upward currents above thunderstorms

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

    Thunderstorms are electric generators, which drive currents upwardly into the ionosphere. In thispaper, we examine the effects of thunderstorm upward current on the ionosphere. We use a thunderstormmodel to calculate the three-dimensional current flows in the atmosphere and to simulate the upward currentabove the thunderstormwith the tripole-charge structure. The upward current flows into the ionosphere, whilethe associated electric field causes the plasma E × B motion. The caused plasma motion redistributes theplasma density, leading to ionospheric density variations. In the nighttime ionosphere, the E × B motion mayalso cause the formation of plasma bubbles.

  17. 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.

  18. 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.

  19. A new coupled model of the ionosphere-magnetosphere interhemispheric dynamics

    NASA Astrophysics Data System (ADS)

    Amaya, J.; Marchaudon, A.; Peymirat, C.; Blelly, P.-L.

    2012-04-01

    The ionosphere is known to play a key role in the electrodynamics of the magnetosphere, but the interhemispheric asymmetries and the connexions between the two hemispheres along the closed magnetic field lines introduce a new feature, the interhemispheric dynamics, which may have a significant contribution to the overall equilibrium. In order to access this dynamics, we have built a new interhemispheric model of the ionosphere, issued from the TRANSCAR family of ionospheric models (Blelly et al., 2005) and based on a 16-moment approximation. This new code has the ability to be used at all latitudes, and as it was the case for the previous generation, it accounts for the magnetosphere electrodynamics in transport of the ionospheric species along the field lines. However, the core of the new model is the dynamical and consistent coupling of the ionospheric transport to the magnetospheric transport through the development of an interface with the magnetosphere model IMM (Hurtaud et al. 2007), which accounts for the interhemispheric asymmetries in the ionospheric electrodynamics. The TRANSCAR-IMM retroactive coupled system is a pseudo 3D ionosphere-magnetosphere model, coupling a 1D approach along the magnetic field lines (TRANSCAR) and a 2D approach in the magnetic equatorial plane (IMM). It has been ported to a parallel architecture based on the Message Passing Interface (MPI) that allows for the simulation of large computational domains. The system is used to study the seasonal asymmetries between the northern and southern hemispheres, the resulting transport and energy transfer and the coupled effects between the ionosphere and the magnetosphere for many different latitudes and solar illumination conditions. We will present this new model and the initial results we obtain on the interhemispheric dynamics in condition of asymmetries between the two hemispheres.

  20. 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

  1. Ionospheric Challenges for GNSS Based Augmentation Systems

    NASA Astrophysics Data System (ADS)

    Doherty, P.; Valladares, C. E.

    2007-12-01

    The ionosphere is a highly dynamic physical phenomenon that presents a variable source of error for Global Navigation Satellite System (GNSS) signals and GNSS based operational systems. The Federal Aviation Administration's (FAA) Wide-Area Augmentation System (WAAS) was designed to enhance the GNSS standard positioning service by providing additional accuracy, availability and integrity that is sufficient for use in commercial aviation. It is the first of a number of planned regional Satellite Based Augmentation Systems (SBAS). Other systems in development include the European EGNOS system, the MSAS system in Japan and the GAGAN system in India. In addition, the South American countries are investigating the feasibility of operating an SBAS system in this region. Much of the WAAS ionospheric research and development focused on defining and mitigating ionospheric challenges characteristic of the mid-latitude regions, where the ionosphere is well studied and relatively quiescent. The EGNOS and MSAS systems will primarily operate under a similarly quiescent mid-latitude ionosphere. SBAS system development in South America, India and other low-latitude regions, however, will have to contend with much more extreme conditions. These conditions include strong spatial and temporal gradients, plasma depletions and scintillation. All of these conditions have a potential to limit SBAS performance in the low latitude regions. This presentation will review the effects that the ionosphere has on the mid-latitude WAAS system. It will present the techniques that are used to mitigate ionospheric disturbances induced on the system during severe geomagnetic activity and it will quantify the effect that this activity has on system performance. The presentation will then present data from the South American Low-latitude Ionospheric Sensor Network (LISN) that can be used to infer the ionospheric effects on SBAS performance in the most challenging low-latitude ionospheric environment

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

    PubMed

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

    2015-01-01

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

  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. 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

  5. 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

  6. 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

  7. 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.

  8. 4D computerized ionospheric tomography by using GPS measurements and IRI-Plas model

    NASA Astrophysics Data System (ADS)

    Tuna, Hakan; Arikan, Feza; Arikan, Orhan

    2016-07-01

    Ionospheric imaging is an important subject in ionospheric studies. GPS based TEC measurements provide very accurate information about the electron density values in the ionosphere. However, since the measurements are generally very sparse and non-uniformly distributed, computation of 3D electron density estimation from measurements alone is an ill-defined problem. Model based 3D electron density estimations provide physically feasible distributions. However, they are not generally compliant with the TEC measurements obtained from GPS receivers. In this study, GPS based TEC measurements and an ionosphere model known as International Reference Ionosphere Extended to Plasmasphere (IRI-Plas) are employed together in order to obtain a physically accurate 3D electron density distribution which is compliant with the real measurements obtained from a GPS satellite - receiver network. Ionospheric parameters input to the IRI-Plas model are perturbed in the region of interest by using parametric perturbation models such that the synthetic TEC measurements calculated from the resultant 3D electron density distribution fit to the real TEC measurements. The problem is considered as an optimization problem where the optimization parameters are the parameters of the parametric perturbation models. Proposed technique is applied over Turkey, on both calm and storm days of the ionosphere. Results show that the proposed technique produces 3D electron density distributions which are compliant with IRI-Plas model, GPS TEC measurements and ionosonde measurements. The effect of the GPS receiver station number on the performance of the proposed technique is investigated. Results showed that 7 GPS receiver stations in a region as large as Turkey is sufficient for both calm and storm days of the ionosphere. Since the ionization levels in the ionosphere are highly correlated in time, the proposed technique is extended to the time domain by applying Kalman based tracking and smoothing

  9. 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

  10. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2010-10-01

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

  12. On the effect of BUM generation enhancement revealed using the scheme of additional heating of ionospheric plasma

    NASA Astrophysics Data System (ADS)

    Frolov, V. L.; Erukhimov, L. M.; Komrakov, G. P.; Sergeev, E. N.; Thidé, B.; Bernhardt, P. A.; Wagner, L. S.; Goldstein, J. A.; Selcher, G.

    1997-05-01

    We present measured characteristics of the artificial ionospheric radio emission (AIRE), which were obtained experimentally using additional heating of the ionospheric F-region by O-polarized waves. It is shown that the observed enhancement of intensity of the broad upshifted maximum (BUM) of the AIRE can result from the influence of electrons accelerated in the plasma: esonance region on its generation. An empirical model of the phenomenon observed is developed. It is concluded from experimental results that the BUM has a complex structure and only one of its components produces the above emission enhancement. We show the possibility of using the AIRE in additional heating of ionospheric plasma for diagnostics of artificial ionospheric turbulence and investigation of the features of perturbation propagation along the geomagnetic field lines.

  13. Investigation of Tsunami-Ionospheric Coupling Efficiency

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  14. Empirical model of the Martian dayside ionosphere: Effects of crustal magnetic fields and solar ionizing flux at higher altitudes

    NASA Astrophysics Data System (ADS)

    Němec, F.; Morgan, D. D.; Gurnett, D. A.; Andrews, D. J.

    2016-02-01

    We use electron density profiles measured by the Mars Advanced Radar for Subsurface and Ionosphere Sounding instrument on board the Mars Express spacecraft to investigate the effects of possible controlling parameters unconsidered in the empirical model of Němec et al. (2011, hereafter N11). Specifically, we focus on the effects of crustal magnetic fields and F10.7 proxy of the solar ionizing flux at higher altitudes. It is shown that while peak electron densities are nearly unaffected by crustal magnetic fields, electron densities at higher altitudes are significantly increased in areas of stronger magnetic fields. The magnetic field inclination appears to have only a marginal effect. Moreover, while the N11 empirical model accounted for the variable solar ionizing flux at low altitudes, the high-altitude diffusive region was parameterized only by the solar zenith angle and the altitude. It is shown that this can lead to considerable inaccuracies. A simple correction of the N11 model, which takes into account both the crustal magnetic field magnitude and the effect of F10.7 at higher altitudes, is suggested.

  15. 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.

  16. 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.

  17. Ionospheric irregularity physics modelling. Memorandum report

    SciTech Connect

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

    1982-02-09

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

  18. Coupling of Earth's Atmosphere and Ionosphere

    NASA Astrophysics Data System (ADS)

    Singh, A. K.

    2012-12-01

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

  19. Lowest-order average effect of turbulence on atmospheric profiles derived from radio occultation

    NASA Technical Reports Server (NTRS)

    Eshleman, V. R.; Haugstad, B. S.

    1977-01-01

    Turbulence in planetary atmospheres and ionospheres causes changes in angles of refraction of radio waves used in occultation experiments. Atmospheric temperature and pressure profiles, and ionospheric electron concentration profiles, derived from radio occultation measurements of Doppler frequency contain errors due to such angular offsets. The lowest-order average errors are derived from a geometrical-optics treatment of the radio-wave phase advance caused by the addition of uniform turbulence to an initially homogeneous medium. It is concluded that the average profile errors are small and that precise Doppler frequency measurements at two or more wavelengths could be used to help determine characteristics of the turbulence, as well as accuracy limits and possible correction terms for the profiles. However, a more detailed study of both frequency and intensity characteristics in radio and optical occultation measurements of turbulent planetary atmospheres and ionospheres is required to realize the full potential of such measurements.

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

    NASA Astrophysics Data System (ADS)

    Liu, Ningyu; Dwyer, Joseph; Rassoul, Hamid

    2013-04-01

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

  1. 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.

  2. Parallel Density-Based Clustering for Discovery of Ionospheric Phenomena

    NASA Astrophysics Data System (ADS)

    Pankratius, V.; Gowanlock, M.; Blair, D. M.

    2015-12-01

    Ionospheric total electron content maps derived from global networks of dual-frequency GPS receivers can reveal a plethora of ionospheric features in real-time and are key to space weather studies and natural hazard monitoring. However, growing data volumes from expanding sensor networks are making manual exploratory studies challenging. As the community is heading towards Big Data ionospheric science, automation and Computer-Aided Discovery become indispensable tools for scientists. One problem of machine learning methods is that they require domain-specific adaptations in order to be effective and useful for scientists. Addressing this problem, our Computer-Aided Discovery approach allows scientists to express various physical models as well as perturbation ranges for parameters. The search space is explored through an automated system and parallel processing of batched workloads, which finds corresponding matches and similarities in empirical data. We discuss density-based clustering as a particular method we employ in this process. Specifically, we adapt Density-Based Spatial Clustering of Applications with Noise (DBSCAN). This algorithm groups geospatial data points based on density. Clusters of points can be of arbitrary shape, and the number of clusters is not predetermined by the algorithm; only two input parameters need to be specified: (1) a distance threshold, (2) a minimum number of points within that threshold. We discuss an implementation of DBSCAN for batched workloads that is amenable to parallelization on manycore architectures such as Intel's Xeon Phi accelerator with 60+ general-purpose cores. This manycore parallelization can cluster large volumes of ionospheric total electronic content data quickly. Potential applications for cluster detection include the visualization, tracing, and examination of traveling ionospheric disturbances or other propagating phenomena. Acknowledgments. We acknowledge support from NSF ACI-1442997 (PI V. Pankratius).

  3. Non-LTE Effects on the H3+ Rovibrational Population in the Jovian Ionsophere rK Planets: Jupiter, Ionosphere: Modeling

    NASA Astrophysics Data System (ADS)

    Kim, Yong Ha

    2012-04-01

    We investigate non-LTE effects on the hrp\\ level populations to help the analysis of the observed 2 and 3.5 micron hrp\\ emissions from the Jovian ionosphere. We begin by constructing a simple three-level model, in order to compute the intensity ratio of the R(3,4) line in the hot band to the Q(1,0) line in the fundamental band, which have been observed in the Jovian auroral regions. We find that non-LTE effects produce only small changes in the intensity ratios for ambient hto\\ densities less than or equal to 5×1011 cm-3. We then construct two comprehensive models by including all the collisional and radiative transitions between pairs of more than a thousand known hrp\\ rovibrational levels with energies less than 10000 cm-1. By employing these models, we find that the intensity ratios of the lines in the hot and fundamental bands are affected greatly by non-LTE effects, but the details depend sensitively on the number of collisional and radiative transitions included in the models. Non-LTE effects on the rovibrational population become evident at about the same ambient hto\\ densities in the comprehensive models as in the three-level model. However, the models show that rotational temperatures derived from the intensities of rotational lines in the ν_2 and 2ν_2 bands may differ significantly from the ambient temperatures in the non-LTE regime. We find that significant non-LTE effects appear near and above the hrp\\ peak, and that the kinetic temperatures in the Jovian thermospheric temperatures derived from the observed line ratios in the 2 and 3.5 micron hrp\\ emissions are highly model dependent.

  4. Geomagnetic storm effect on the occurrence of ionospheric irregularities over African equatorial sector using GPS-TEC

    NASA Astrophysics Data System (ADS)

    Amaechi, Paul; Oyeyemi, Elijah; Akala, Andrew

    2016-07-01

    Total electron content (TEC) derived from Global Navigation Satellite Systems (GNSS) measurements provided by the International GNSS Service (IGS) network have been used to study the occurrence of large scale ionospheric irregularities over the African equatorial sector. The rate of change of TEC (ROT) as well as its standard deviation over five minutes (ROTI) were used to monitor the level of irregularities over 3 stations distributed across the three longitudinal sectors of Africa (eastern, central and western longitudinal sectors). The storm effect on irregularities occurrence has been studied in conjunction with the disturbance storm time (Dst) and the z component of the Interplanetary magnetic field (IMFBz) indices during four intense storms which were classified according to their season of occurrence during the year 2015. Irregularities were associated with GPS-TEC fluctuations as seen in the increased ROT and ROTI values especially in the post sunset period. Irregularities were inhibited over all the stations during the storm of March plausibly as a result of electric field conditioned by the southward turning of IMFBz during the pre and post midnight periods. The triggering of irregularities over the western and central stations and their inhibition over the eastern station during the storm of June was controlled by the ring current. The storm effect on irregularities was not evident over the western and central stations but inhibition of irregularities was observed over the eastern station during the storm of September.

  5. Climatology of low latitude ionosphere under effect of varying solar flux during solar cycle 23 and 24

    NASA Astrophysics Data System (ADS)

    Dashora, Nirvikar; Suresh, Sunanda

    2016-07-01

    The characteristics of quiet time equatorial and low latitude total electron content (TEC) over the Indian sector using GIM data (1998-2014) is obtained. For the first time the analysis is carried filtering out the solar flare and storm effects and time series of quiet time VTEC data from three locations namely dip equator and two low latitude conjugate locations in Indian sector are obtained. It is well known that a complex interplay among drivers of equatorial electrodynamics like Solar flux, dynamo electric field and meridional winds determine the daytime ionization and distribution in equatorial ionization anomaly zone. In this study, we have critically examined the role of varying solar flux and response of low latitude ionosphere with new and standardized definitions. The results are examined and interpreted in the context of large number of previous studies. The newly found features from this study are as follows. Marked difference in nature of equinoctial asymmetry is noted between solar cycle 23 and 24. Long absence of winter anomaly both during low and high solar activity (HSA) in LL (low latitude) regions is found. Climatology of the diurnal cycle is provided in four categories using new criteria for demarcation of solar activity levels. Highest correlation (~77%) between GIM ionospheric electron content (IEC) and PI (solar EUV proxy index) is noted over equator in contrast to previous studies. The minimum positive contribution of PI in variation of IEC requires minimum of 2 years of data and if more than 7-8 years of data is used, it saturates. RMS (root mean square) width of PI can be used to define the HSA. Strong QBO (quasi biennial oscillations) in IEC is noted in tune with the one in PI over both the LL location but QBO remains surprisingly subdued over equator. The semi-annual oscillations in GIM-IEC are found to be stronger at all locations during high solar activity and weaker between 2005 and 2011, whereas, the annual oscillations are found to

  6. 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.

  7. Simulation of the Mars Ionosphere Radio Occultation Experiments

    NASA Astrophysics Data System (ADS)

    Hu, X.; Wu, X. C.; Gong, X. Y.; Wang, X.; Xu, Q. C.

    2009-07-01

    The Mars ionosphere radio occultation experiment between the Chinese YH-1 spacecraft and the Russian Phobos-Grunt spacecraft orbiting Mars will be the first satellite to satellite radio occultation experiment in history, which will achieve high quality ionospheric electron density profiles. The technique used in this experiment is analyzed and introduced. Simulations of the radio occultation have been completed. Forward calculations of the radio wave observable for the ionospheric radio occultation events have been done with the 3D ray tracing method and a simple Chapman ionosphere background model. The backward inversion with the forward calculated radio occultation observation data gives reliable and consistent ionospheric electron density profiles, which show the reliability of the simulation algorithms. With the simulation method, the effects of errors from the radio signal phase measurement and the orbit determination of the satellite on the inversion are analyzed in cases. Results show that phase errors of 5% circle have a negligible effect on the daytime ionosphere radio occultation, and lead to an absolute error of less than 4×;10^8 m3 for nighttime electron density profiles. Orbit errors of the satellite mainly pose a systematic rising or descending to the ionosphere height. The above results show that Sino-Russian cooperative Mars ionosphere radio occultation experiments is expected to achieve high quality Mars ionosphere profiles. Their technique regime can be used for the lunar ionosphere exploring.

  8. Ionospheric calibration for single frequency altimeter measurements

    NASA Astrophysics Data System (ADS)

    Schreiner, William S.; Born, George H.

    1993-08-01

    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. Ionospheric calibration for single frequency altimeter measurements

    NASA Technical Reports Server (NTRS)

    Schreiner, William S.; Born, George H.

    1993-01-01

    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.

  10. Topside ionospheric effects of the annular solar eclipse of 15th January 2010 as observed by DEMETER satellite

    NASA Astrophysics Data System (ADS)

    Pal, Sujay; Chakrabarti, Sandip Kumar; Kanta Maji, Surya; Chakraborty, Suman; Sanki, Dipak

    2016-07-01

    We present effects of the annular solar eclipse of 15th January 2010 on the topside ionosphere using the DEMETER satellite data. Measurements of the electron-ion density and electron temperature by the ISL (Instrument Sonde de Langmuir) and IAP (Instrument Analyseur de Plasma) instruments on board the DEMETER satellite during the eclipse time over the low latitude (±40) Indian ocean area are presented. We found decrease in electron density by about 25% and decrease in ion density by about 33% from the reference orbits at the altitude of the satellite (~ 660 km). Electron and ion temperatures were also found to have decreased by 200-300 K at the same altitude. Instead of simple decrease as in ion density, electron temperature showed a complex wave-like oscillation as solar eclipse progressed. Electron density decreased to a minimum value before the maximum obscuration and again starts to increase before passing through another minimum at the time of maximum obscuration. Both the minima are located at the ±10 degree geomagnetic latitude. Variations of electron and ion densities were found to follow the average solar illumination experienced by the real and conjugate paths at satellite altitude, while the electron temperature showed no such correlation.

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

    NASA Technical Reports Server (NTRS)

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

    1976-01-01

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

  12. 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.

  13. The ionospheric signature of flux transfer events

    NASA Technical Reports Server (NTRS)

    Cowley, S. W. H.; Freeman, M. P.; Lockwood, Mike; Smith, M. F.

    1991-01-01

    The effects at ionospheric heights which take place when transient reconnection events (i.e., Flux Tranfer Events (FTEs)) occur at the dayside magnetopause are considered. The nature of the FTE related ionospheric flows, the associated current systems, and the plasma precipitation, are discussed. In particular, the nature of the time dependent cusp precipitation which occurs on this case is outlined and expectations are compared with those based on steady magnetopause reconnection.

  14. 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.

  15. Venus' nighttime horizontal plasma flow, 'magnetic congestion', and ionospheric hole production

    NASA Technical Reports Server (NTRS)

    Grebowsky, J. M.; Mayr, H. G.; Curtis, S. A.; Taylor, H. A., Jr.

    1983-01-01

    A simple rectilinear, two-dimensional MHD model is used to investigate the effects of field-aligned plasma loss and cooling on a dense plasma convecting across a weak magnetic field, in order to illumine the Venus nighttime phenomena of horizontal plasma flow, magnetic congestion and ionospheric hole production. By parameterizing field-aligned variations and explicitly solving for cross magnetic field variations, it is shown that the abrupt horizontal enhancements of the vertical magnetic field, as well as sudden decreases of the plasma density to very low values (which are characteristic of ionospheric holes), can be produced in the presence of field-aligned losses.

  16. 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.

  17. 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.

  18. 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.

  19. Improved geodetic earthquake source modelling through correction of ionospheric disturbances in L-band InSAR data

    NASA Astrophysics Data System (ADS)

    Sudhaus, Henriette; Gomba, Giorgio; Eineder, Michael

    2016-04-01

    The use of L-band InSAR data for observing the surface displacements caused by earthquakes can be very beneficial. The retrieved signal is generally more stable against temporal phase decorrelation with respect to C-band and X-band InSAR data, such that fault movements also in vegetated areas can be observed. Also, due to the longer wavelength, larger displacement gradients that occur close to the ruptures can be measured. A serious draw back of L-band data on the other hand is that it more strongly reacts to heterogeneities in the ionosphere. The spatial variability of the electron content causes spatially long wavelength trends in the interferometric phase, distorts the surface deformation signal therefore impacts on the earthquake source analysis. A well-known example of the long-wavelength distortions are the ALOS-1 InSAR observations of the 2008 Wenchuan earthquake. To mitigate the effect of ionospheric phase in the geodetic modelling of earthquake sources, a common procedure is to remove any obvious linear or quadratic trend in the surface displacement data that may have been caused by ionospheric phase delays. Additionally, remaining trends may be accounted for by including so-called ambiguity (or nuisance) parameters in the modelling. The introduced ionospheric distortion, however, is only approximated arbitrarily by such simple ramp functions with the true ionospheric phase screen unknown. As a consequence, either a remaining ionospheric signal may be mistaken for surface displacement or, the other way around, long-wavelength surface displacement may be attributed to ionospheric distortion and is removed. The bias introduced to the source modelling results by the assumption of linear or quadratic ionospheric effects is therefore unknown as well. We present a more informed and physics-based correction of the surface displacement data in earthquake source modelling by using a split-spectrum method to estimate the ionospheric phase screen superimposed to the

  20. Magnetic Fluctuations in the Martian Ionosphere

    NASA Technical Reports Server (NTRS)

    Espley, Jared

    2010-01-01

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

  1. 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

  2. Magnetosphere-ionosphere coupling during plasmoid evolution - First results

    NASA Technical Reports Server (NTRS)

    Hesse, Michael; Birn, Joachim

    1991-01-01

    The influence of magnetosphere-ionosphere coupling on the dynamic evolution of the magnetotail is investigated by a three-dimensional resistive MHD code that includes the effects of the closure of field-aligned currents in a simple resistive model ionosphere. Particular emphasis is on the role of this coupling during substorm evolution and the modification of the latter by the convection driven by the ionospheric electric fields. For comparison, results are presented from a simulation which uses an infinitely conducting ionosphere but is otherwise identical. Comparison of the two simulations shows that the major impact of magnetosphere-ionospheric communication is an acceleration of magnetotail evolution. Otherwise, phenomena in the two models are qualitatively similar. It is concluded that ionospheric effects do not significantly affect substorm associated magnetotail dynamics.

  3. 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.

  4. Ionospheric Modelling using GPS to Calibrate the MWA. II: Regional Ionospheric Modelling using GPS and GLONASS to Estimate Ionospheric Gradients

    NASA Astrophysics Data System (ADS)

    Arora, B. S.; Morgan, J.; Ord, S. M.; Tingay, S. J.; Bell, M.; Callingham, J. R.; Dwarakanath, K. S.; For, B.-Q.; Hancock, P.; Hindson, L.; Hurley-Walker, N.; Johnston-Hollitt, M.; Kapińska, A. D.; Lenc, E.; McKinley, B.; Offringa, A. R.; Procopio, P.; Staveley-Smith, L.; Wayth, R. B.; Wu, C.; Zheng, Q.

    2016-07-01

    We estimate spatial gradients in the ionosphere using the Global Positioning System and GLONASS (Russian global navigation system) observations, utilising data from multiple Global Positioning System stations in the vicinity of Murchison Radio-astronomy Observatory. In previous work, the ionosphere was characterised using a single-station to model the ionosphere as a single layer of fixed height and this was compared with ionospheric data derived from radio astronomy observations obtained from the Murchison Widefield Array. Having made improvements to our data quality (via cycle slip detection and repair) and incorporating data from the GLONASS system, we now present a multi-station approach. These two developments significantly improve our modelling of the ionosphere. We also explore the effects of a variable-height model. We conclude that modelling the small-scale features in the ionosphere that have been observed with the MWA will require a much denser network of Global Navigation Satellite System stations than is currently available at the Murchison Radio-astronomy Observatory.

  5. Characterization of Ionospheric Scintillation Using Simultaneous Formosat-3/COSMIC Radio Occultation Observations and AFRL SCINDA Ground Scintillation Measurements

    NASA Astrophysics Data System (ADS)

    Starks, M. J.; Lin, C. S.; Groves, K. M.; Pedersen, T. R.; Basu, S.; Syndergaard, S.; Rocken, C.

    2007-05-01

    Ionospheric scintillation at low latitudes has been studied using ionospheric radio occultation (RO) measurements by the FORMOSAT-3/COSMIC micro-satellites in conjunction with ground-based data from the Scintillation Network Decision Aid (SCINDA) station at Kwajalein Atoll. The Air Force Research Laboratory has developed the SCINDA network for monitoring low-latitude ionospheric total electron content (TEC) and scintillation associated with equatorial spread F. The network currently consists of sixteen stations distributed around the globe and the data have been used to conduct numerous studies on the characteristics and climatology of equatorial scintillation. The present study focuses on COSMIC RO and SCINDA data during the three COSMIC campaigns in 2006. Radio occultation events are selected by requiring that ionospheric scintillation was detected by the SCINDA VHF scintillation monitor at Kwajalein, and that the occultation ray path intersected the Kwajalein longitude below the satellite altitude, which varied from 500 to 800 km for the six FORMOSAT-3 satellites. In order to exclude tropospheric effects, only GPS signal amplitudes from FORMOSAT-3 with ray path tangent altitudes above 100 km are considered. Locations of ionospheric scintillation are estimated by triangulation using the satellites and the SCINDA ground station. Airglow images at Kwajalein are also used to confirm occurrence of equatorial ionospheric scintillations. For the selected events, large amplitude L1 and L2 scintillations tend to occur at altitudes below 200 km at frequencies around 0.5 Hz. The results are discussed as a potential path toward better specifying the occurrence of equatorial scintillations.

  6. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2013-05-01

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

  8. A comparison of ionospheric model predictions with MITHRAS observations

    NASA Astrophysics Data System (ADS)

    Schunk, Robert W.

    1987-01-01

    MITHRAS is a coordinated multiradar program to study the interactions between the magnetosphere, ionosphere, and thermosphere, as well as the phenomena that result from these interactions. The program is based on a data set acquired by the Chatanika, Millstone Hill, and Eiscat incoherent scatter radars. A large portion of the data is unique in that it was the only time when the radars, well separated in local and magnetic time, simultaneously probed the high latitude ionosphere. Our effect concerned model data comparisons. Specifically, we compared the predictions of our three-dimensional, time dependent model of the high latitude ionosphere with MITHRAS data sets. Of particular interest were the variations of the ionosphere with altitude, latitude, longitude, universal time, season, and magnetic activity. Model data comparisons enabled us to determine the adequacy of our current understanding of high latitude ionosphere dynamics as well as certain magnetosphere ionosphere atmosphere coupling processes.

  9. 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.

  10. The lower ionosphere at high latitudes

    NASA Astrophysics Data System (ADS)

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

    The lower ionosphere is a particularly difficult region to both observe and model. Although radars and rockets have probed this region for more than two decades, our overall understanding of the interplay between radiative, chemical, dynamical, and electrodynamical processes in the lower ionosphere is relatively poor in comparison to the other regions of the solar-terrestrial system. Part of the problem is that the various radar and rocket campaigns have focused on different scientific issues, have been of limited duration, or have been restricted to specific geographical locations. However, the lower ionosphere is a complex region, being acted upon by magnetospheric processes from above and stratospheric processes from below. Within the lower ionosphere are chemical reactions involving negative, positive, and cluster ions; transport processes that sometimes involve ordinary diffusion, turbulence, and wave-particle interactions due to plasma instabilities; radiative processes that could involve multiple scattering effects; and energetics that could result in non-Maxwellian ion velocity distribution functions. A further complication arises in that the processes acting on and within the lower ionosphere do so on widely different spatial and temporal scales, and these scales are directly reproduced in the medium. An overview of our current knowledge of the lower ionosphere is presented in this brief review, with the emphasis on the high latitude region.

  11. Multifractal behaviour of the ionospheric scintillation index time series over an Indian low latitude station Surat

    NASA Astrophysics Data System (ADS)

    Tanna, H. J.; Pathak, K. N.

    2014-03-01

    The amplitude scintillation information recorded by the GSV4004B GISTM (Global Ionospheric Scintillation TEC Monitor) GPS receiver at an Indian low latitude station Surat (21.16°N, 72.78°E) for 48 months during the years 2009, 2010, 2011 and 2012 are utilized in the present work. Multifractal detrended fluctuation analysis (MF-DFA) have been carried out along with computation of q-order fluctuation function, q-order Hurst exponent, q-order mass exponent and multifractal spectrums for each monthly post-sunset S4 index time series. The non-linear dependence of mass exponent and dependence of q-order Hurst exponent on q-values reflect the existence of nonlinear interaction between different scales and multifractal structure in the system, respectively. The comparison of broadness and shape of spectra with the occurrence of scintillation activities registered in the same period reveal the existence of multifractality/complexity in the turbulent ionosphere, which is influenced by the small-scale intermittency and solar flux indices. The truncation of the spectrum is the evidence of manifestation of small-scale intermittency of the turbulent ionosphere. The higher values of the Hölder exponent α0, calculated from the spectrum, imply the irregular nature of the underlying process. The present study suggests that, MF-DFA may act as an important non-linear technique for identifying the effect of large and small-scale fluctuations in complex and turbulent ionosphere.

  12. 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

  13. 21 CFR 12.38 - Effective date of an order.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... Commissioner will— (1) Publish a final order denying or withdrawing approval of an NDA, NADA, device premarket... effective date of the order; and (2) If the order involves withdrawal of approval of an NADA,...

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

    NASA Astrophysics Data System (ADS)

    Schmitter, E. D.

    2013-09-01

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

  15. 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 α attenuation factor (α = ω. 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 ν 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.

  16. 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…

  17. Modeling Ionospheric Electrodynamics (Invited)

    NASA Astrophysics Data System (ADS)

    Huba, J. D.

    2009-12-01

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

  18. Trans-Ionospheric High Frequency Signal Ray Tracing

    NASA Astrophysics Data System (ADS)

    Wright, S.; Gillespie, R. J.

    2012-09-01

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

  19. 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.

  20. 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.

  1. 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.

  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. 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...

  4. Ionospheric Cubeswarm Concept Study: using low-resource instrumentation for truly multipoint in situ ionospheric observations

    NASA Astrophysics Data System (ADS)

    Hampton, D.; Lynch, K. A.; Earle, G. D.; Mannucci, A. J.; Clayton, R.; Fisher, L. E.; Fernandes, P. A.; Roberts, M.; Zettergren, M. D.

    2015-12-01

    Magnetosphere-ionosphere coupling currents close in the nightside lower ionosphere. These spatially inhomogeneous and time varying volume currents are difficult to capture with in situ observations. Our understanding of M-I coupling systems is limited by our understanding of the actual structure of ionospheric current closure. A path forward includes assimilation of a variety of data sets into increasingly capable ionospheric models. While each data set provides only a piece of the picture, the assimilation process allows optimal use of each piece.An important development for the necessary in situ observations involves making them truly multi-point, and therefore, low-resource. For thermal particle observations, the high densities of the lower ionosphere allow the use of low-gain (current-sensing rather than particle-counting) particle sensors. One observational goal is the definition of the actual structure of ionospheric closure currents. This can be approached with a number of different measurement techniques, in tandem with an ionospheric model, since the closure currents need to follow the rules of electrodynamics and current continuity. Low resource thermal plasma sensors such as retarding potential analyzers and drift meters can provide valuable measurements of plasma parameters, including density and plasma flow, without the need for high voltages or deployable boom systems. These low-resource measurements, which can be reproduced on arrays of in situ observation platforms, used in tandem with proper plasma physics interpretation of their signatures in the disturbed observing environment, and as part of an assimilated data set into an ionospheric model, can allow us to progress in our understanding of ionospheric structuring and its effects on auroral coupling. Now, with increasingly capable multipoint arrays of spacecraft, and quantitative 2D-with-time context from cameras and imagery, we are moving toward truly multipoint studies of the system

  5. Array-based GNSS Ionospheric Sensing: Estimability and Precision Analyses

    NASA Astrophysics Data System (ADS)

    Teunissen, Peter

    2016-04-01

    Array-based GNSS Ionospheric Sensing: Estimability and Precision Analyses PJG Teunissen1,2, A Khodabandeh1 and B Zhang1 1GNSS Research Centre, Curtin University, Perth, Australia 2Geoscience and Remote Sensing, Delft University of Technology, The Netherlands Introduction: The Global Navigation Satellite Systems (GNSS) have proved to be an effective means of measuring the Earth's ionosphere. The well-known geometry-free linear combinations of the GNSS data serve as the input of an external ionospheric model to capture both the spatial and temporal characteristics of the ionosphere. Next to the slant ionospheric delays experienced by the GNSS antennas, the geometry-free combinations also contain additional unknown delays that are caused by the presence of the carrier-phase ambiguous cycles and/or the code instrumental delays. That the geometry-free combinations, without an external ionospheric model, cannot unbiasedly determine the slant ionospheric delays reveals the lack of information content in the GNSS data. Motivation and objectives: With the advent of modernized multi-frequency signals, one is confronted with many different combinations of the GNSS data that are capable of sensing the ionosphere. Owing to such diversity and the lack of information content in the GNSS data, various estimable ionospheric delays of different interpretations (and of different precision) can therefore be formed. How such estimable ionospheric delays should be interpreted and the extent to which they contribute to the precision of the unbiased slant ionosphere are the topics of this contribution. Approach and results: In this contribution, we apply S-system theory to study the estimability and precision of the estimable slant ionospheric delays that are measured by the multi-frequency GNSS data. Two different S-systems are presented, leading to two different estimable parameters of different precision: 1) the phase-driven ionospheric delays and 2) the code-driven ionospheric delays

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

    PubMed

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

    2013-01-01

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

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

    PubMed

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

    2013-11-18

    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.

  8. 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

  9. 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.

  10. 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

  11. Preface: C/NOFS Results and Equatorial Ionospheric Dynamics

    NASA Technical Reports Server (NTRS)

    Klenzing, J.; de La Beaujardiere, O.; Gentile, L. C.; Retterer, J.; Rodrigues, F. S.; Stoneback, R. A.

    2014-01-01

    The Communication/Navigation Outage Forecasting System (C/NOFS) satellite was launched into orbit in April 2008 as part of an ongoing effort to understand and identify plasma irregularities that adversely impact the propagation of radio waves in the upper atmosphere. Combined with recent improvements in radar, airglow, and ground-based studies, as well as state-of-the-art modeling techniques, the C/NOFS mission has led to new insights into equatorial ionospheric electrodynamics. In order to document these advances, the C/NOFS Results and Equatorial Dynamics Technical Interchange Meeting was held in Albuquerque, New Mexico from 12 to 14 March 2013. The meeting was a great success with 55 talks and 22 posters, and covered topics including the numerical simulations of plasma irregularities, the effects of atmospheric tides, stratospheric phenomena, and magnetic storms on the upper atmosphere, causes and predictions of scintillation-causing ionospheric irregularities, current and future instrumentation efforts in the equatorial region. The talks were broken into the following three topical sessions: A. Ambient Ionosphere and Thermosphere B. Transient Phenomena in the Low-Latitude Ionosphere C. New Missions, New Sensors, New Science and Engineering Issues. The following special issue was planned as a follow-up to the meeting. We would like to thank Mike Pinnock, the editors and staff of Copernicus, and our reviewers for their work in bringing this special issue to the scientific community. Our thanks also go to Patricia Doherty and the meeting organizing committee for arranging the C/NOFS Technical Interchange Meeting.

  12. 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.

  13. 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.

  14. 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

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

    NASA Technical Reports Server (NTRS)

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

    1983-01-01

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

  16. 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...

  17. 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...

  18. 37 CFR 251.57 - Effective date of order.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 37 Patents, Trademarks, and Copyrights 1 2011-07-01 2011-07-01 false Effective date of order. 251.57 Section 251.57 Patents, Trademarks, and Copyrights COPYRIGHT OFFICE, LIBRARY OF CONGRESS COPYRIGHT... Procedures of Copyright Arbitration Royalty Panels § 251.57 Effective date of order. An order...

  19. Scrambled Order--Scrambled Brains: The Effects of Presenting Test Items in Sequential Versus Random Order.

    ERIC Educational Resources Information Center

    Sander, Angelle M.; And Others

    The effects of presenting test items in random order or in a sequence parallel to the order of presentation were studied by testing 92 undergraduates in an introductory psychology course at Emporia State University (Kansas). Two test forms, sequential (S) and random (R), of multiple-choice questions were prepared for four 1-hour examinations…

  20. Modeling of the Storm time Electric Fields and the Response of the Ionosphere- Plasmasphere-Thermosphere

    NASA Astrophysics Data System (ADS)

    Maruyama, N.; Fuller-Rowell, T.; Codrescu, M.; Anderson, D.; Richmond, A.; Maute, A.; Sazykin, S.; Toffoletto, F.; Spiro, R.; Wolf, R.; Millward, G.

    2008-12-01

    We have developed a self-consistent first-principles model of the coupled inner magnetosphere- thermosphere- ionosphere- plasmasphere system in order to understand the storm time electrodynamic coupling of the magnetosphere and ionosphere and its consequences for the ionosphere, plasmasphere, and thermosphere. The model involves electrodynamic coupling of the Rice Convection Model (RCM) and the Coupled Thermosphere Ionosphere Plasmasphere electrodynamics (CTIPe) model: RCM provides the region 2 field aligned currents resulting from pressure gradients in the inner magnetosphere, which are important for modeling electric-field penetration and the shielding processes, while CTIPe provides time-dependent conductivity and neutral wind fields that are key to modeling the disturbance dynamo. A newly developed potential solver takes into account all these inputs to derive the global pattern of ionospheric electric fields. We found that the storm time vertical ExB drifts from the coupled model provided a better agreement with those from the observations for the March 2001 storm as compared to the predictions from the stand-alone RCM and CTIPe. Our simulation results suggest that the temporal variation of the magnetospheric magnetic field plays a significant role in the storm time variation of the drifts, especially for super storms such as March 2001 and November 2004 storm events. As responses of the ionosphere, plasmasphere and thermosphere to the storm time disturbance drifts, we found that daytime and evening upward enhancement of the ExB drift caused by the penetration electric field modifies the electron density and zonal neutral wind, leading to the zonal drift disturbances near the terminator through the F-region dynamo process. In this paper, we will address the role of the combined effect of the vertical and zonal drift disturbances as possible drivers to reproduce the massive restructuring of TEC.

  1. 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-.

  2. 37 CFR 251.57 - Effective date of order.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... ARBITRATION ROYALTY PANEL RULES AND PROCEDURES COPYRIGHT ARBITRATION ROYALTY PANEL RULES OF PROCEDURE Procedures of Copyright Arbitration Royalty Panels § 251.57 Effective date of order. An order...

  3. 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.

  4. 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.

  5. Assessment of ionospheric threat modeling techniques over Marmara Region

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

    It is generally known that extreme ionospheric density associated with severe magnetic storm degrades the Global Navigation satellite Systems (GNSS) measurements also at mid - to high latitudes. Strong solar activity can cause large local spatial and temporal gradients in the delays induced on the GNSS signals by the ionosphere. The local nature of gradients can result in significant decorrelation between Ground Based Augmentation System (GBAS) Ground Stations and the GNSS receiver on board the aircraft. For the mitigation of this effect either a special functional architecture is established to monitor the ionosphere on the basis of so called Extended GBAS or ionospheric threat models can be constructed for a certain region. In this work two different techniques have been evaluated for the estimation of ionospheric threat model parameters consisting of width, slope and velocity of the ionospheric wave front by using real ground-based observations from both GPS and GLONASS in the Marmara Region. The data collected between 2012 and 2015 also containing high ionospheric activities are pre-processed to extract ionospheric gradients. Ionospheric delays at each ionospheric piercing point are determined by applying a local ionospheric Total Electron Content (TEC) modeling and filtering techniques on the basis of raw carrier-phase observations. The ionospheric fronts are searched by looking at high ionospheric gradients which result from ionospheric delay differences between ionospheric piercing points. The first technique of the threat model evaluation is based on the propagation of an ideal plane wave as a wave front, velocity of which is estimated on the basis of a Gauss Markov Model using an ordinary least square estimation procedure. The remaining parameters namely slope and width are calculated afterwards using rate of change gradients and the duration of the wave front in context with the estimated front velocity. In the second technique both the magnitude of the

  6. 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.

  7. 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.

  8. 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

  9. Ionospheric calibration for single frequency altimeter measurements

    NASA Astrophysics Data System (ADS)

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

    1994-03-01

    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

  10. 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

  11. 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.

  12. Characterizing Extreme Ionospheric Storms

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

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

  13. Analysis of Ionospheric Delay Estimates from GNSS Carrier Phase Measurements

    NASA Astrophysics Data System (ADS)

    Gao, Yang

    2016-07-01

    There is an increased demand for more precise ionospheric information such as ionospheric augmentation for fast ambiguity convergence and resolution in real-time kinematic (RTK) and precise point positioning (PPP). More precise ionospheric information is also highly desired to improve the understanding of the space weather dynamics and its impacts on various applications such as aviation and communication systems. Carrier phase measurements from GNSS offer the best precision for precise applications. Current ionospheric models, however, are mostly derived from code or carrier-smoothed code measurements. Ionopsheric models based on carrier phase measurements are expected to provide improved accuracy and should be investigated. In this contribution, various data analyses will be conducted on ionospheric estimates from carrier phase measurements. Since carrier phase measurements are ambiguous and they are also affected by fractional biases, proper observation model is necessary and will be developed. With proper observation model, the analysis results are used to investigate the differences and characteristics of the ionospheric estimates between the code and carrier phase derived estimates and subsequently to help develop methods for precise estimation of the biases in carrier phase measurements and the recovery of the ionospheric effects. Data acquired at different geographic locations and under different ionospheric conditions will be processed for numerical analysis.

  14. 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.

  15. Photoinduced ultrafast charge-order melting: Charge-order inversion and nonthermal effects

    NASA Astrophysics Data System (ADS)

    van Veenendaal, Michel

    2016-09-01

    The effect of photoexcitation is studied for a system with checkerboard charge order induced by displacements of ligands around a metal site. The motion of the ligands is treated classically and the electronic charges are simplified to two-level molecular bond charges. The calculations are done for a checkerboard charge-ordered system with about 100 000 ligand oscillators coupled to a fixed-temperature bath. The initial photoexcitation is followed by a rapid decrease in the charge-order parameter within 50-100 femtoseconds while leaving the correlation length almost unchanged. Depending on the fluence, a complete melting of the charge order occurs in less than a picosecond. While for low fluences, the system returns to its original state, for full melting, it recovers to its broken-symmetry state leading to an inversion of the charge order. For small long-range interactions, recovery can be slow due to domain formation.

  16. Local ionospheric corrections derived from GNSS - A case study with TerraSAR-X

    NASA Astrophysics Data System (ADS)

    Gisinger, Christoph; Balss, Ulrich; Cong, Xiao Ying; Steigenberger, Peter; Eineder, Michael; Pail, Roland; Hugentobler, Urs

    2013-04-01

    Germany's synthetic aperture radar (SAR) satellites TerraSAR-X and TanDEM-X belong to the latest generation of radar satellites which have moved radar remote sensing to a new level. Besides being an all weather and all day imaging system, radar remote sensing offers various advanced methods like SAR interferometry or persistent scatterer interferometry that exploit magnitude and phase information of the radar signal. In order to achieve centimeter to millimeter accuracy with these advanced methods, all occurring error contributions (internal signal delay, orbit, troposphere, ionosphere, solid earth tides, loading effects, ...) have to be taken into account by applying appropriate corrections. Within the project DLR@Uni funded by the German Helmholtz Association HGF, an experimental framework at Wettzell station has been set up to perform a detailed analysis of all the corrections required for high resolution radar satellites and to achieve the goal of a 1cm precision level for absolute radar coordinates. This framework involves a 1.5 meter corner reflector (CR), a 1.5 year series of data takes from TerraSAR-X, and it makes use of the multi-sensor environment of Wettzell station. Besides Satellite Laser Ranging (SLR) for orbit assessment and the local geodetic network to control the CR reference coordinates, the Wettzell GNSS receivers are used for generating tropospheric and ionospheric corrections. By comparing the reference radar times (range and azimuth) available from geodetic survey with those from the TerraSAR-X data takes, the quality of the corrections can be investigated. Although often being considered negligible for X-band observations, the conducted experiment has clearly shown the necessity for ionospheric corrections, if the capabilities of current SAR satellites are to be fully exploited. For every TerraSAR-X data take, the ionospheric impact was derived from the geometry-free linear combination of the GNSS measurements and modeled in terms of

  17. 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.

  18. 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

  19. 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

    2015-08-12

    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.

  20. 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.

  1. Using DORIS measurements for ionosphere modeling

    NASA Astrophysics Data System (ADS)

    Dettmering, Denise; Schmidt, Michael; Limberger, Marco

    2013-04-01

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

  2. 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.

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

    ERIC Educational Resources Information Center

    Chan, Jason C.

    1991-01-01

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

  4. Response-Order Effect in Likert-Type Scales.

    ERIC Educational Resources Information Center

    Chan, Jason C.

    The importance of the presentation order of items on Likert-type scales was studied. It was proposed that subjects tend to choose the first alternative acceptable to them from among the response categories, so that a primacy effect can be predicted. The effects of reversing the order of the response scale on the latent factor structure underlying…

  5. 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....

  6. 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....

  7. GNSS data filtering optimization for ionospheric observation

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

  8. 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

    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.

  9. Ionospheric Scintillation Explorer (ISX)

    NASA Astrophysics Data System (ADS)

    Iuliano, J.; Bahcivan, H.

    2015-12-01

    NSF has recently selected Ionospheric Scintillation Explorer (ISX), a 3U Cubesat mission to explore the three-dimensional structure of scintillation-scale ionospheric irregularities associated with Equatorial Spread F (ESF). ISX is a collaborative effort between SRI International and Cal Poly. This project addresses the science question: To what distance along a flux tube does an irregularity of certain transverse-scale extend? It has been difficult to measure the magnetic field-alignment of scintillation-scale turbulent structures because of the difficulty of sampling a flux tube at multiple locations within a short time. This measurement is now possible due to the worldwide transition to DTV, which presents unique signals of opportunity for remote sensing of ionospheric irregularities from numerous vantage points. DTV spectra, in various formats, contain phase-stable, narrowband pilot carrier components that are transmitted simultaneously. A 4-channel radar receiver will simultaneously record up to 4 spatially separated transmissions from the ground. Correlations of amplitude and phase scintillation patterns corresponding to multiple points on the same flux tube will be a measure of the spatial extent of the structures along the magnetic field. A subset of geometries where two or more transmitters are aligned with the orbital path will be used to infer the temporal development of the structures. ISX has the following broad impact. Scintillation of space-based radio signals is a space weather problem that is intensively studied. ISX is a step toward a CubeSat constellation to monitor worldwide TEC variations and radio wave distortions on thousands of ionospheric paths. Furthermore, the rapid sampling along spacecraft orbits provides a unique dataset to deterministically reconstruct ionospheric irregularities at scintillation-scale resolution using diffraction radio tomography, a technique that enables prediction of scintillations at other radio frequencies, and

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

    NASA Astrophysics Data System (ADS)

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

    2014-08-01

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

  11. 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.

  12. Ionosphere-thermosphere space weather issues.

    NASA Astrophysics Data System (ADS)

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

    1996-10-01

    Weather disturbances in the ionosphere-thermosphere system can have a detrimental effect on both ground-based and space-based systems. Because of this impact and because this field has matured, it is now appropriate to develop specification and forecast models, with the aim of eventually predicting the occurrence, duration, and intensity of weather effects. As part of the new National Space Weather Program, the CEDAR community will focus on science issues concerning space weather, and this tutorial/review is an expanded version of a tutorial presentation given at the recent CEDAR annual meeting. The tutorial/review provides a brief discussion of weather disturbances and features, the causes of weather, and the status of weather modeling. The features and disturbances discussed include plasma patches, boundary and auroral blobs, Sun-aligned polar cap arcs, the effects of traveling convection vortices and SAID events, the lifetime of density structures, sporadic-E and intermediate layers, spread F and equatorial plasma bubbles, geomagnetic storms and substorms, traveling ionospheric disturbances (TIDs), and the effects of tides and gravity waves propagating from the lower atmosphere. The tutorial/review is only intended to provide an overview of some of the important scientific issues concerning ionospheric-thermospheric weather, with the emphasis on the ionosphere. Tutorials on thermospheric and magnetospheric weather issues are given in companion papers.

  13. Response of migrating tides to the stratospheric sudden warming in 2009 and their effects on the ionosphere studied by a whole atmosphere-ionosphere model GAIA with COSMIC and TIMED/SABER observations

    NASA Astrophysics Data System (ADS)

    Jin, H.; Miyoshi, Y.; Pancheva, D.; Mukhtarov, P.; Fujiwara, H.; Shinagawa, H.

    2012-10-01

    This paper compares results from a whole atmosphere-ionosphere coupled model, GAIA, with the COSMIC and TIMED/SABER observations during the 2008/2009 northern winter season. The GAIA model has assimilated meteorological reanalysis data by a nudging method. The comparison shows general agreement in the major features from the stratosphere to the ionosphere including the growth and decay of the major stratospheric sudden warming (SSW) event in 2009. During this period, a pronounced semidiurnal variation in the F region electron density and its local-time phase shift similar to the previous observations are reproduced by the model and COSMIC observation. The model suggests that the electron density variation is caused by an enhanced semidiurnal variation in the E × B drift, which is probably related to an amplified semidiurnal migrating tide (SW2) in the lower thermosphere. The model and TIMED/SABER observation show that the SW2 tide amplifies at low latitudes from the stratosphere to the thermosphere as well as the phase variation. Possible mechanisms for the SW2 variability in the low latitude stratosphere could be the change of its propagation condition, especially the (2, 2) mode, due to changing zonal background wind and meridional temperature gradient, and/or an enhancement of its source due to redistribution of stratospheric ozone. Present results also show a prominent long-term variation of the terdiurnal migrating component (TW3) in the ionosphere and atmosphere.

  14. 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.

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

    NASA Technical Reports Server (NTRS)

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

    1973-01-01

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

  16. Phase perturbation measurements through a heated ionosphere

    NASA Technical Reports Server (NTRS)

    Frey, A.; Gordon, W. E.

    1982-01-01

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

  17. Moving of the High-Speed Plasma jet Through the Ionosphere of the Different Density: Optical and Radiation Effects

    NASA Astrophysics Data System (ADS)

    Zetzer, J. I.; Erlandson, R. E.; Gavrilov, B. G.; Kiselev, Y. N.; Lynch, K. A.; Meng, C. I.; Pfaff, R. F.; Poklad, Y. V.; Rybakov, V. A.; Stenbaek-Nielsen, H.

    2003-12-01

    The investigation of the high-speed plasma jet dynamics in the geomagnetic field has important implications to the basic magnetospheric and ionospheric physics and to the applied problems. The new results of the active geophysical rocket experiment (AGRE) "North Star" (1999) are represented. The high-speed plasma jet was injected on the altitudes 360 and 280 km perpendicular to the geomagnetic field. During first injection plasma jet was injected in the artificial air cloud with the density ~ 10-12 g/cm3, during second one - in the free space with the density ~ 10-15 g/cm3. The design and characteristics of the plasma jet generator, the radiation dynamics of the plasma cloud and dynamics of the charged particles takes place during of the process of the interaction of the plasma jet with environment are discussed.

  18. 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.

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

    NASA Astrophysics Data System (ADS)

    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 March 8-18, 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)-type 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 F2 layer, f0F2, 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.

  20. Major magnetic storm of March 13-14, 1989 and associated ionosphere effects. (Reannouncement with new availability information)

    SciTech Connect

    Rich, F.J.; Denig, W.F.

    1993-06-30

    The geomagnetic storm of March 1989 was the largest geomagnetic storm of the decade and one of the largest of the century. The authors review many of the `high-latitude` ionospheric observations that were made during this storm. Most of the data presented here comes from the polar-orbiting satellites of the Defense Meteorological Satellite Program (DMSP) series. A review of the DMSP data shows that most of the high-latitude, top-side ionospheric disturbance occurred on March 13 and 14. The magnitudes of the particle energy flux (ergs cm 2) (1 erg = 10{minus}7 J) and Joule heating were not unusually large for a storm, but the area of the energy deposition, and thus the total energy deposition, was extremely large. At the peak of the storm (minimum in D(st) (disturbance with storm time) and midnight boundary indices) the auroral particle precipitation extended down to magnetic latitudes of 40.1 deg or L = 1.71 while the polar edge of the auroral zone expanded poleward only slightly. The storm was also a period of intense, hemispherically symmetric polar rain fluxes. The auroral electric field was clearly observed down to magnetic latitude of 35 deg. This is consistent with the auroral electrojet (AE) current density and the AE index having a saturation level beyond which the index will increase slowly or not at all as more energy is transferred from the solar wind to the magnetosphere, but the cross polar-cap potential during this storm shows no evidence of saturation. There are only two visible light images from DMSP available near the peak of the storm.

  1. Incoherent radar spectra in the auroral ionosphere in the presence of a large electric field: The effect of O+-O+ Coulomb collisions

    NASA Astrophysics Data System (ADS)

    Barghouthi, I. A.

    2005-06-01

    We have used Monte Carlo simulations of O+ velocity distributions in the high latitude F- region to improve the calculation of incoherent radar spectra in auroral ionosphere. The Monte Carlo simulation includes ionneutral, O+-O collisions (resonant charge exchange and polarization interaction) as well as O+-O+ Coulomb self-collisions. At high altitudes, atomic oxygen O and atomic oxygen ion O+ dominate the composition of the auroral ionosphere and consequently, the influence of O+-O+ Coulomb collisions becomes significant. In this study we consider the effect of O+-O+ Coulomb collisions on the incoherent radar spectra in the presence of large electric field (100 mVm-1). As altitude increases (i.e. the ion-to-neutral density ratio increases) the role of O+-O+ Coulomb self-collisions becomes significant, therefore, the one-dimensional, 1-D, O+ ion velocity distribution function becomes more Maxwellian and the features of the radar spectrum corresponding to non-Maxwellian ion velocity distribution (e.g. baby bottle and triple hump shapes) evolve to Maxwellian ion velocity distribution (single and double hump shapes). Therefore, O+-O+ Coulomb self-collisions act to isotropize the 1-D O+ velocity distribution by transferring thermal energy from the perpendicular direction to the parallel direction, however the convection electric field acts to drive the O+ ions away from equilibrium and consequently, non-Maxwellian O+ ion velocity distributions appeared. Therefore, neglecting O+-O+ Coulomb self-collisions overestimates the effect of convection electric field.

  2. 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 Health PUBLIC HEALTH SERVICE, DEPARTMENT OF HEALTH AND HUMAN SERVICES GENERAL PROVISIONS CONFIDENTIALITY OF ALCOHOL AND DRUG ABUSE PATIENT RECORDS Court Orders Authorizing Disclosure and Use § 2.61...

  3. 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 OF ALCOHOL AND DRUG ABUSE PATIENT RECORDS Court Orders Authorizing Disclosure and Use § 2.61...

  4. 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 Health PUBLIC HEALTH SERVICE, DEPARTMENT OF HEALTH AND HUMAN SERVICES GENERAL PROVISIONS CONFIDENTIALITY OF ALCOHOL AND DRUG ABUSE PATIENT RECORDS Court Orders Authorizing Disclosure and Use § 2.61...

  5. 42 CFR 2.61 - Legal effect of order.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 42 Public Health 1 2012-10-01 2012-10-01 false Legal effect of order. 2.61 Section 2.61 Public Health PUBLIC HEALTH SERVICE, DEPARTMENT OF HEALTH AND HUMAN SERVICES GENERAL PROVISIONS CONFIDENTIALITY OF ALCOHOL AND DRUG ABUSE PATIENT RECORDS Court Orders Authorizing Disclosure and Use § 2.61...

  6. 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…

  7. 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.

  8. 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.

  9. 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

  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. 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.

  12. 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.

  13. An improved ionospheric model for the Wide Area Augmentation System

    NASA Astrophysics Data System (ADS)

    Cormier, D.; Altshuler, E.

    2004-02-01

    We provide an enhanced model of the errors induced by deviations of ionospheric delays from those estimated by the planar model used by the GPS-based Wide Area Augmentation System (WAAS). To a first approximation the nominal ionospheric spatial decorrelation of vertical equivalent signal delays, σdecorrnom, is roughly constant over the whole of the WAAS service volume. However, significant gains may be achieved by including a more detailed description of σdecorrnom as a function of various metrics such as geomagnetic latitude, time of day, as well as the quality of the planar fit as characterized by the radius, relative centroid of the fit, and the density of delay data. We take the first step in the development of this more sophisticated model by determining which of these parameters is best suited for use as a metric for determining σdecorrnom. This allows us to construct a first-order model of the ionospheric decorrelation which depends on the local density of ionospheric pierce points. Our preliminary study indicates that this first-order model will result in a better than 20% reduction in the values of broadcast grid ionospheric vertical errors (GIVEs) within the coterminous United States. We also observe a better than 50% reduction in trips of the ionospheric irregularity detector in the Alaska region, which will lead to significant improvements to continuity, although this comes at the cost of a roughly 20% increase in the median GIVE in the Alaska region.

  14. Comparison between the effect of two geomagnetic storms with the same seasonal and daily characteristics and different intensity on the European ionosphere.

    NASA Astrophysics Data System (ADS)

    Rodriguez-Bouza, Marta; Herraiz, Miguel; Rodríguez-Caderot, Gracía; Paparini, Claudia; Otero, Xurxo; Radicella, Sandro M.

    2016-04-01

    This work presents an analysis of the ionospheric disturbance caused by two geomagnetic storms occurred on the same day, 17th March, but one in 2013 and other in 2015. The greatest intensity of both storms occurs after sunset when geomagnetic indexes (Dst index, Kp and Ap) reached the peak values. Both geomagnetic storms can be classified as intense according to the Dst index criteria. The storm of March 17, 2015, ("St Patricḱs storm"), can be considered even "severe" because the Dst index dropped off -200nT. The solar origins of both geomagnetic storms were magnetic filament eruptions followed by Coronal Mass Ejections, CME. The ionospheric behavior has been studied through the total electron content, TEC. This parameter is obtained from RINEX files processed using the calibration technique developed by Prof. Luigi Ciraolo. RINEX files from selected GNSS stations on Europe belonging to International GPS Service, IGS, and EUREF Permanent Network, have been used. The calibration technique assumes the ionospheric thin shell model to obtain vertical total electron content (vTEC) from slant total electron content (sTEC) at the Ionospheric Pierce Point. The data were obtained in periods of the geomagnetic storms and during quite days surrounding the storms days, at 1 minute sampling. The behavior of the ionosphere during the two geomagnetic storms was similar. In both cases, a positive ionospheric storm, defined as an increase on the TEC, occurred during the main phase of the geomagnetic storms on 17th of March. These increases were followed by a negative ionospheric storm, a decreasing of TEC, in the recuperation phase. However, in the event of 2015, the positive ionospheric storm of the main phase had more intensity but the same duration than that of 2013 and for the negative ionospheric storm both, intensity and duration, were largest in 2015 than in 2013.

  15. 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

  16. Observations and simulations of the ionospheric lunar tide: Seasonal variability

    NASA Astrophysics Data System (ADS)

    Pedatella, N. M.

    2014-07-01

    The seasonal variability of the ionospheric lunar tide is investigated using a combination of Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) observations and thermosphere-ionosphere-mesosphere electrodynamics general circulation model (TIME-GCM) simulations. The present study focuses on the seasonal variability of the lunar tide in the ionosphere and its potential connection to the occurrence of stratosphere sudden warmings (SSWs). COSMIC maximum F region electron density (NmF2) and total electron content observations reveal a primarily annual variation of the ionospheric lunar tide, with maximum amplitudes occurring at low latitudes during December-February. Simulations of the lunar tide climatology in TIME-GCM display a similar annual variability as the COSMIC observations. This leads to the conclusion that the annual variability of the lunar tide in the ionosphere is not solely due to the occurrence of SSWs. Rather, the annual variability of the lunar tide in the ionosphere is generated by the seasonal variability of the lunar tide at E region altitudes. However, compared to the observations, the ionospheric lunar tide annual variability is weaker in the climatological simulations which is attributed to the occurrence of SSWs during the majority of the years included in the observations. Introducing a SSW into the TIME-GCM simulation leads to an additional enhancement of the lunar tide during Northern Hemisphere winter, increasing the lunar tide annual variability and resulting in an annual variability that is more consistent with the observations. The occurrence of SSWs can therefore potentially bias lunar tide climatologies, and it is important to consider these effects in studies of the lunar tide in the atmosphere and ionosphere.

  17. Film and Text: Order Effects in Recall and Social Inferences.

    ERIC Educational Resources Information Center

    Cowen, Paul S.

    1984-01-01

    Describes a study which compared film and written material with regard to effects produced by order in which conflicting information is presented. Results indicate film is more influential and better recalled than conflicting written information: conflicting paragraphs produce a primacy effect, whereas analogous film segments produce no order…

  18. 49 CFR 511.57 - Effective date of order.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 49 Transportation 6 2011-10-01 2011-10-01 false Effective date of order. 511.57 Section 511.57 Transportation Other Regulations Relating to Transportation (Continued) NATIONAL HIGHWAY TRAFFIC SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION ADJUDICATIVE PROCEDURES Decision § 511.57 Effective date of...

  19. 49 CFR 511.57 - Effective date of order.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 49 Transportation 6 2010-10-01 2010-10-01 false Effective date of order. 511.57 Section 511.57 Transportation Other Regulations Relating to Transportation (Continued) NATIONAL HIGHWAY TRAFFIC SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION ADJUDICATIVE PROCEDURES Decision § 511.57 Effective date of...

  20. 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.

  1. 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.

  2. 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.

  3. Ionosphere-Thermosphere Coupling in Jupiter's Low Latitudes

    NASA Astrophysics Data System (ADS)

    Stallard, T.; Melin, H.; Johnson, R.; O'Donoghue, J.; Moore, L.; Miller, S.; Tao, C.; Achilleos, N. A.; Smith, C.; Ray, L. C.; Yates, J. N.

    2015-12-01

    One of the leading problems in our understanding of Jupiter's atmosphere, known colloquially as the 'energy crisis', is that the upper atmosphere has global temperatures far in excess of that predicted by solar heating. Unlike the Earth, solar heating has only a small effect on the thermosphere, varying little in temperature with local time, and with equatorial neutrals co-rotating with the planet due to meridional advection. Within the auroral region, ionosphere-thermosphere coupling produces strong flows and results in huge Joule Heating from auroral currents. In this region, the temperature excess can be explained, but Jupiter's fast rotation means that Coriolis forces prevent energy in the poles from transferring equatorward, so there remains no explanation of why low latitudes are overheated by a factor of 3-5 over that predicted by solar heating alone.Despite this anomaly, although the past twenty years has seen a wealth of new data and results in Jupiter's auroral region, studies of the equatorial region have been somewhat limited. This lack of investigation comes partly from the apparent uniform nature of the equatorial region, and partly from the difficulty in observing this region. It is only in the past three years that observers begun to re-examine this region, revealing evidence of complex interactions between the thermosphere and ionosphere, including what appears to be thermospheric weather patterns at a fixed planetary longitudes, stable over two decades; perhaps caused by continuous flows from the auroral region. Here, we introduce our recent research, in order to compare and contrast what has been observed at Jupiter with the more well understood interactions between Earth's ionosphere and thermosphere. We hope that this will open a discussion between the communities that will improve our understanding of the underlying physical processes, as they occur at both planets.

  4. Three-dimensional structure of the Martian nightside Ionosphere

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

    The night side ionosphere of Mars is known to be highly variable: essentially nonexistent in certain regions, while occasionally nearly as strong as the photoionization-produced dayside ionosphere in others. Using a kinetic approach called MarMCET (Mars Monte Carlo Electron Transport) [3], we model the dynamics of precipitating electrons on the nightside of Mars to study the effects of magnetic field geometry and electron precipitation on ionospheric structure over the geographic region with the strongest crustal magnetic field (140°-220°E, 20°-70°S). As input, we use nightside precipitating electron energy spectra and pitch angle distributions from the Mars Global Surveyor (MGS) Magnetometer & Electron Reflectometer (MAG/ER), as well as a vector sum of a typical external tail-lobe magnetic field and crustal magnetic field model. We thus calculate ionization rate in 3 dimensions, both for specific observations and average cases. We find that magnetic topology (via pitch angle distributions) plays an important part in determining peak ionization rates. Also, we see large geographic differences in average precipitating electron spectra, likely due to the dynamical coupling of the rotating planet-fixed crustal field with the draped interplanetary magnetic field. This leads to differences in peak ionization rates of more than 4 orders of magnitude across this region of the Martian nightside (see figure 1). We also see a strong dependence of peak ionization rate on magnetic elevation angle measured at MGS mapping orbit altitude of 400 km, as precipitating fluxes are generally lower in regions of closed magnetic topology where magnetic field is generally horizontal at this altitude.

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

    NASA Technical Reports Server (NTRS)

    Spann, J. F.; Bhattacharyya, A.

    2006-01-01

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

  6. 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.

  7. Performance of ionospheric maps in support of long baseline GNSS kinematic positioning at low latitudes

    NASA Astrophysics Data System (ADS)

    Park, J.; Sreeja, V.; Aquino, M.; Cesaroni, C.; Spogli, L.; Dodson, A.; De Franceschi, G.

    2016-05-01

    Ionospheric scintillation occurs mainly at high and low latitude regions of the Earth and may impose serious degradation on GNSS (Global Navigation Satellite System) functionality. The Brazilian territory sits on one of the most affected areas of the globe, where the ionosphere behaves very unpredictably, with strong scintillation frequently occurring in the local postsunset hours. The correlation between scintillation occurrence and sharp variations in the ionospheric total electron content (TEC) in Brazil is demonstrated in Spogli et al. (2013). The compounded effect of these associated ionospheric disturbances on long baseline GNSS kinematic positioning is studied in this paper, in particular when ionospheric maps are used to aid the positioning solution. The experiments have been conducted using data from GNSS reference stations in Brazil. The use of a regional TEC map generated under the CALIBRA (Countering GNSS high-Accuracy applications Limitations due to Ionospheric disturbances in BRAzil) project, referred to as CALIBRA TEC map (CTM), was compared to the use of the Global Ionosphere Map (GIM), provided by the International GNSS Service (IGS). Results show that the use of the CTM greatly improves the kinematic positioning solution as compared with that using the GIM, especially under disturbed ionospheric conditions. Additionally, different hypotheses were tested regarding the precision of the TEC values obtained from ionospheric maps, and its effect on the long baseline kinematic solution evaluated. Finally, this study compares two interpolation methods for ionospheric maps, namely, the Inverse Distance Weight and the Natural Neighbor.

  8. 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.

  9. 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.

  10. Introducing a disturbance ionosphere index

    NASA Astrophysics Data System (ADS)

    Jakowski, N.; Borries, C.; Wilken, V.

    2012-01-01

    Although ionospheric perturbations such as traveling ionospheric disturbances have a strong impact on Global Navigation Satellite Systems (GNSS) and other space-based radio systems, the description of individual perturbations is difficult. To overcome this problem, it is suggested to use a disturbance ionosphere index (DIX) that describes the perturbation degree of the ionosphere in a less specific form as a proxy. Although such an index does not describe the exact propagation conditions at the measurement site, the estimated index number indicates the probability of a potential impact on radio systems used in communication, navigation, and remote sensing. The definition of such a DIX must take into account the following major requirements: relevance to practical needs, objective measure of ionospheric conditions, easy and reproducible computation, and availability of a reliable database. Since the total electron content has been shown in many publications to act as an outstanding parameter for quantifying the range error and also the strength of ionospheric perturbations, we propose a DIX that is based on GNSS measurements. To illustrate the use of the index, recent storms monitored in 2011 and the Halloween storm are discussed. The proposed index is a robust and objective measure of the ionospheric state, applicable to radio systems which are impacted by a highly variable perturbed ionosphere.

  11. Variable methods to estimate the ionospheric horizontal gradient

    NASA Astrophysics Data System (ADS)

    Nagarajoo, Karthigesu

    2016-06-01

    DGPS or differential Global Positioning System is a system where the range error at a reference station (after eliminating the error due to its’ clock, hardware delay and multipath) will be eliminated from the range measurement at the user, which view the same satellite, presuming that the satellites path to both the reference station and the user experience common errors due to the ionosphere, clock errors 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 of 10km as used in simulations throughout this paper, unless otherwise stated) and thus the presence of ionospheric horizontal gradient is ignored. If a user's path is exposed to a drastically large ionosphere gradient, the large difference of ionosphere delays between the reference station and the user can result in significant position error for the user. Several examples of extremely large ionosphere gradients that could cause the significant user errors have been observed. The ionospheric horizontal gradient could be obtained instead from the gradient of the Total Electron Content, TEC observed from a number of received GPS satellites at one or more reference stations or based on empirical models updated with real time data. To investigate the former, in this work, the dual frequency method has been used to obtain both South-North and East-West gradients by using four different receiving stations separated in those directions. In addition, observation data from Navy Ionospheric Monitoring System (NIMS) receivers and the TEC contour map from Rutherford Appleton Laboratory (RAL) UK have also been used in order to define the magnitude and direction of the gradient.

  12. Ionosphere-thermosphere perturbations due to lower atmospheric waves

    NASA Astrophysics Data System (ADS)

    Schunk, Robert; Gardner, Larry; Scherliess, Ludger; Thompson, Donald; Sojka, Jan

    We are developing a thermosphere-ionosphere-plasmasphere data assimilation model that will be used as an upper atmospheric component for an ocean-atmosphere model. This data assimilation model is based on a physics model of the ionosphere-plasmasphere system that covers the E-region, F-region, topside ionosphere, and plasmasphere (90 - 30,000 km). The model is capable of assimilating data from a variety of sources, including bottomside Ne profiles from ionosondes, slant GPS/TEC from a network of stations, in situ Ne from DMSP satellites, lineof-sight UV emissions measured by satellites, and occultation data. The data are assimilated via an ensemble Kalman filter technique. The thermosphere data assimilation model has been constructed from a physics-based, global, thermosphere model using an ensemble Kalman filter technique. This model will eventually be able to assimilate UV radiances from the SSUSI and SSULI instruments, in situ winds and densities along satellite tracks, and satellite drag data. The coupled data assimilation model will be used for studies of the effect that troposphere weather disturbances have on the upper atmosphere. Preliminary simulations have been conducted with the physics-based ionosphere-thermosphere model of the effect that upward propagating tides (diurnal, semi-diurnal, terdiurnal), sound waves, and gravity waves have on the ionosphere-thermosphere system at middle and low latitudes. The status of this modeling effort will be reviewed. The wave effects will also be compared with thermosphere disturbances generated by the ionosphere.

  13. 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

  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. 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.

  16. 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.

  17. Ionospheric wave spectrum measurements

    NASA Technical Reports Server (NTRS)

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

    1979-01-01

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

  18. The effect of enactment on memory for order.

    PubMed

    Olofsson, U

    1996-01-01

    The effect of enactment on memory for serial order was investigated in two experiments. In both experiments a reconstruction task was used to separate order from item information. In Experiment 1 enactment and test information was manipulated between groups. For subjects who had not been informed about the reconstruction test, performance of verbal and motor groups was similar with regard to both serial-position curves and overall performance. For subjects who knew beforehand that they would be tested for memory of the order of the action events, performance in the verbal condition was significantly better than in the motor condition. In Experiment 2, the reversed enactment effect for test-informed subjects was replicated with a within-subjects design. The results agree with Engelkamp and Zimmer's (1984, 1994) position that enactment serves exclusively to enhance item information, and indicate that subjects have less control over the encoding processes when they are enacting than during verbal encoding (cf. Cohen, 1981).

  19. 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.

  20. SU(2) Higher-order effective quark interactions from polarization

    NASA Astrophysics Data System (ADS)

    Braghin, Fábio L.

    2016-10-01

    Higher order quark effective interactions are found for SU(2) flavor by departing from a non-local quark-quark interaction. By integrating out a component of the quark field, the determinant is expanded in chirally symmetric and symmetry breaking effective interactions up to the fifth order in the quark bilinears. The resulting coupling constants are resolved in the leading order of the longwavelength limit and exact numerical ratios between several of these coupling constants are obtained in the large quark mass limit. In this level, chiral invariant interactions only show up in even powers of the quark bilinears, i.e. O(ψ bar ψ) 2 n (n = 1 , 2 , 3 , . .), whereas (explicit) chiral symmetry breaking terms emerge as O(ψ bar ψ) n being always proportional to some power of the Lagrangian quark mass.

  1. Numerical simulation of the interaction between two high-energy plasma bunches in the ionosphere

    NASA Astrophysics Data System (ADS)

    Motorin, A. A.; Stupitsky, E. L.; Kholodov, A. S.

    2016-07-01

    The 3D MHD algorithm developed by us has been adapted to modeling the interaction between two plasma bunches in the ionosphere, mainly in order to sufficiently correctly describe the physics of the interaction between two plasma regions with regard to the ionospheric inhomogeneity and the geomagnetic field action. Modeling has been performed for several versions of location of the plasma region centers.

  2. Extraordinary induction heating effect near the first order Curie transition

    NASA Astrophysics Data System (ADS)

    Barati, M. R.; Selomulya, C.; Sandeman, K. G.; Suzuki, K.

    2014-10-01

    While materials with a 1st order Curie transition (TC) are known for the magnetic cooling effect due to the reversibility of their large entropy change, they also have a great potential as a candidate material for induction heating where a large loss power is required under a limited alternating magnetic field. We have carried out a proof-of-concept study on the induction heating effect in 1st order ferromagnetic materials where the temperature is self-regulated at TC. LaFe11.57Si1.43H1.75, a well-known magnetocaloric material, was employed in this study because TC of this compound (319 K) resides in the ideal temperature range for hyperthermia treatment of cancerous cells. It is found that the hysteresis loss of LaFe11.57Si1.43H1.75 increases dramatically near TC due to the magnetic phase coexistence associated with the 1st order magnetic transition. The spontaneous magnetization (Ms) shows a very abrupt decrease from 110 Am2kg-1 at 316 K to zero at 319 K. This large Ms immediately below TC along with the enhanced irreversibility of the hysteresis curve result in a specific absorption rate as large as 0.5 kWg-1 under a field of 8.8 kAm-1 at 279 kHz. This value is nearly an order of magnitude larger than that observed under the same condition for conventional iron oxide-based materials. Moreover, the large heating effect is self-regulated at the 1st order TC (319 K). This proof-of-concept study shows that the extraordinary heating effect near the 1st order Curie point opens up a novel alloy design strategy for large, self-regulated induction heating.

  3. 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…

  4. 21 CFR 12.38 - Effective date of an order.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 1 2014-04-01 2014-04-01 false Effective date of an order. 12.38 Section 12.38 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES GENERAL FORMAL... approval application, or biologics license, in whole or in part, or revoking a device product...

  5. 21 CFR 12.38 - Effective date of an order.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 1 2013-04-01 2013-04-01 false Effective date of an order. 12.38 Section 12.38 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES GENERAL FORMAL... approval application, or biologics license, in whole or in part, or revoking a device product...

  6. 21 CFR 12.38 - Effective date of an order.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 1 2012-04-01 2012-04-01 false Effective date of an order. 12.38 Section 12.38 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES GENERAL FORMAL... approval application, or biologics license, in whole or in part, or revoking a device product...

  7. Order Effects in Belief Updating: The Belief-Adjustment Model.

    ERIC Educational Resources Information Center

    Hogarth, Robin M.; Einhorn, Hillel J.

    1992-01-01

    A theory of the updating of beliefs over time is presented that explicitly accounts for order-effect phenomena as arising from the interaction of information-processing strategies and task characteristics. The belief-adjustment model is supported by 5 experiments involving 192 adult subjects. (SLD)

  8. Pecuniary Effects, Second-Order Conditions, and the LRAC Curve.

    ERIC Educational Resources Information Center

    Comolli, Paul M.

    2000-01-01

    Explores the importance of second-order conditions in the cost-minimization problem confronting the monopsonistic employer of factor inputs. Describes an alternative approach to the presence of pecuniary effects that does not depend on the assumption that firms are monopsonistic in factor markets. (CMK)

  9. High-order primordial perturbations with quantum gravitational effects

    NASA Astrophysics Data System (ADS)

    Zhu, Tao; Wang, Anzhong; Kirsten, Klaus; Cleaver, Gerald; Sheng, Qin

    2016-06-01

    In this paper, we provide a systematic investigation of high-order primordial perturbations with nonlinear dispersion relations due to quantum gravitational effects in the framework of uniform asymptotic approximations. Because of these effects, the equation of motion of the mode function in general has multiple turning points. After obtaining analytically approximated solutions to any order in different regions, associated with different types of turning points, we match them to the third one. To this order the errors are less than 0.15%. General expressions of the power spectra of the primordial tensor and scalar perturbations are derived explicitly. We also investigate effects of backreactions of the quantum gravitational corrections, and make sure that inflation lasts long enough in order to solve the underlying problems, such as flatness, horizon, and monopole. Then we study various features of the spectra that are observationally relevant. In particular, under a moderate assumption about the energy scale of the underlying theory of quantum gravity, we have shown that the quantum gravitational effects may alter significantly the ratio between the tensor and scalar power spectra, thereby providing a natural mechanism to alleviate the tension between observations and certain inflationary models, including the one with a quadratic potential.

  10. Calibration of precise satellite altimetry for the ionosphere and wet troposphere

    NASA Astrophysics Data System (ADS)

    Benada, J. R.; Callahan, P. S.

    1984-08-01

    Ionospheric variability; dual frequency altimeter measurement of ionospheric error; and determination of wet tropospheric error from a three frequency microwave radiometer are discussed. Temporal and/or spatial extrapolations of the ionosphere are likely to result in errors of 20% to 30% of the total ionospheric effect which is 2 to 20 cm at 13.7 GHz. The TOPEX dual frequency system can measure the effect to 1.3 cm. The TOPEX 3 frequency microwave radiometer can meet the TOPEX requirement of a 1.2 cm wet troposphere calibration, if the correction algorithm is calibrated with data from a variety of humid conditions.

  11. Ionospheric disturbances during the magnetic storm of 15 July 2000: Role of the fountain effect and plasma bubbles for the formation of large equatorial plasma density depletions

    NASA Astrophysics Data System (ADS)

    Kil, Hyosub; Paxton, Larry J.

    2006-12-01

    We investigate the role of the fountain effect and plasma bubbles for the formation of the large equatorial plasma depletions during the geomagnetic storm of 15 July 2000. The large equatorial plasma depletions are detected in the Atlantic sector on the night of the 15th by the Defense Meteorological Satellite Program (DMSP) F15 and the first Republic of China Satellite (ROCSAT-1). The observations show discontinuous drop of the plasma density at the walls of the depletions, flat plasma density inside the depletions, and persistence or growth of the depletions over night. These properties are not consistent with the trough morphology induced by the fountain effect. The coincident ionospheric observations of DMSP F15 and ROCSAT-1 demonstrate that the large depletions are created in the longitude regions where plasma bubbles are present. The occurrence of the large depletions after sunset, elongation in the north-south direction, formation of steep walls, and colocation with plasma bubbles at lower altitudes or earlier times suggest that the large depletions are closely associated with plasma bubbles.

  12. 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.

  13. Placing order in space: the SNARC effect in serial learning.

    PubMed

    Previtali, Paola; de Hevia, Maria Dolores; Girelli, Luisa

    2010-03-01

    The SNARC effect, consisting of a systematic association between numbers and lateralized response, reflects the mental representation of magnitude along a left-to-right mental number line (Dehaene et al. in J Exp Psychol 122:371-396, 1993). Critically, this effect has been reported in the classification of overlearned non-numerical sequences such as letters, days and months (Gevers et al. in Cognition 87:B87-B95, 2003 and Cortex 40:171-172, 2004) suggesting that ordinal, rather than magnitude information, is critical for spatial coding. This study tests the hypothesis of an oriented spatial representation as the privileged way of mentally organizing serial information, by looking for stimulus-response compatibility effects in the processing of a newly acquired arbitrary sequence. Here we report an association between ordinal position of the items and spatial response preference for both order-relevant and order-irrelevant tasks. These results suggest that any ordered information, even when order is not intrinsically relevant to it, is spontaneously mapped in the representational space. This spatial representation is likely to acquire a left-to-right orientation, at least in western cultures.

  14. Generality of a congruity effect in judgements of relative order.

    PubMed

    Liu, Yang S; Chan, Michelle; Caplan, Jeremy B

    2014-10-01

    The judgement of relative order (JOR) procedure is used to investigate serial-order memory. Measuring response times, the wording of the instructions (whether the earlier or the later item was designated as the target) reversed the direction of search in subspan lists (Chan, Ross, Earle, & Caplan Psychonomic Bulletin & Review, 16(5), 945-951, 2009). If a similar congruity effect applied to above-span lists and, furthermore, with error rate as the measure, this could suggest how to model order memory across scales. Participants performed JORs on lists of nouns (Experiment 1: list lengths = 4, 6, 8, 10) or consonants (Experiment 2: list lengths = 4, 8). In addition to the usual distance, primacy, and recency effects, instructions interacted with serial position of the later probe in both experiments, not only in response time, but also in error rate, suggesting that availability, not just accessibility, is affected by instructions. The congruity effect challenges current memory models. We fitted Hacker's (Journal of Experimental Psychology: Human Learning and Memory, 6(6), 651-675, 1980) self-terminating search model to our data and found that a switch in search direction could explain the congruity effect for short lists, but not longer lists. This suggests that JORs may need to be understood via direct-access models, adapted to produce a congruity effect, or a mix of mechanisms.

  15. 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.

  16. 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.

  17. A new algorithm and results of ionospheric delay correction for satellite-based augmentation system

    NASA Astrophysics Data System (ADS)

    Huang, Z.; Yuan, H.

    Ionospheric delay resulted from radio signals traveling ionosphere is the largest source of errors for single-frequency users of the Global Positioning System GPS In order to improve users position accuracy augmentation systems based on satellite have been developed to provide accurate calibration since the nineties A famous one is Wide Area Augmentation System WAAS which is aimed to the efficiency of navigation over the conterminous United States and has been operating successfully so far The main idea of ionospheric correction algorithm for WAAS is to establish ionospheric grid model i e ionosphere is discretized into a set of regularly-spaced intervals in latitude and longitude at an altitude of 350km above the earth surface The users calculate their pseudoranges by interpolating estimates of vertical ionospheric delay modeled at ionospheric grid points The Chinese crust deformation monitoring network has been established since the eighties and now it is in good operation with 25 permanent GPS stations which provide feasibility to construct similar satellite-based augmentation system SBAS in China For the west region of China the distribution of stations is relatively sparse not to ensure sufficient data If we follow the ionospheric grid correction algorithm some grid points can t obtain their estimate and lost availability Consequently ionospheric correction measurement on the users situated in that region is inestimable which constitute a fatal threat to navigation users In this paper we presented a new algorithm that

  18. TEC Fluctuations Map - pilot phase of the new IGS Ionospheric Product

    NASA Astrophysics Data System (ADS)

    Sieradzki, Rafal; Krankowski, Andrzej

    2013-04-01

    Since 1998 Ionospheric Working Group of the International GNSS Service has been creating the reliable global VTEC maps. Currently the ionospheric maps are generated with 2 hour time resolution and show the mean state of the Total Electron Content for this period.They cannot demonstrate the whole dynamic of the electron concentration especially during the storm-time periods for the equatorial region and at high latitudes. However, in the last few years the number of the permanent GNSS station around North Geomagnetic Pole increased systematically and nowadays it is possible to create the map of ionospheric variability for this region. Importance of this topic has turned up in the latest IGS Ionosphere Working Group resolution passed during the International GNSS Service Workshop 2012. At the beginning 2013 the IGS is planning to start the pilot phase of the new ionospheric product - TEC Fluctuations map, which are generated at GRL/UWM Center in Olsztyn. The maps are created based on phase observations from over 150 permanent GNSS stations belong to IGS/EPN, PBO and POLENET Networks located over 45th degree of the north geomagnetic latitude. In order to estimate the level of the ionospheric variability ROT Index is used. The presentation shows the applied algorithm, the example maps for different ionospheric conditions and plans. In the future other IGS Ionosphere Associate Analysis Centers will also create maps of ionospheric variability for routine generation IGS combined product.

  19. Ionospheric data assimilation with thermosphere-ionosphere-electrodynamics general circulation model and GPS-TEC during geomagnetic storm conditions

    NASA Astrophysics Data System (ADS)

    Chen, C. H.; Lin, C. H.; Matsuo, T.; Chen, W. H.; Lee, I. T.; Liu, J. Y.; Lin, J. T.; Hsu, C. T.

    2016-06-01

    The main purpose of this paper is to investigate the effects of rapid assimilation-forecast cycling on the performance of ionospheric data assimilation during geomagnetic storm conditions. An ensemble Kalman filter software developed by the National Center for Atmospheric Research (NCAR), called Data Assimilation Research Testbed, is applied to assimilate ground-based GPS total electron content (TEC) observations into a theoretical numerical model of the thermosphere and ionosphere (NCAR thermosphere-ionosphere-electrodynamics general circulation model) during the 26 September 2011 geomagnetic storm period. Effects of various assimilation-forecast cycle lengths: 60, 30, and 10 min on the ionospheric forecast are examined by using the global root-mean-squared observation-minus-forecast (OmF) TEC residuals. Substantial reduction in the global OmF for the 10 min assimilation-forecast cycling suggests that a rapid cycling ionospheric data assimilation system can greatly improve the quality of the model forecast during geomagnetic storm conditions. Furthermore, updating the thermospheric state variables in the coupled thermosphere-ionosphere forecast model in the assimilation step is an important factor in improving the trajectory of model forecasting. The shorter assimilation-forecast cycling (10 min in this paper) helps to restrain unrealistic model error growth during the forecast step due to the imbalance among model state variables resulting from an inadequate state update, which in turn leads to a greater forecast accuracy.

  20. 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.

  1. Ionospheric hot spot at high latitudes

    NASA Technical Reports Server (NTRS)

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

    1982-01-01

    Schunk and Raitt (1980) and Sojka et al. (1981) have developed a model of the convecting high-latitude ionosphere in order to determine the extent to which various chemical and transport processes affect the ion composition and electron density at F-region altitudes. The numerical model produces time-dependent, three-dimensional ion density distributions for the ions NO(+), O2(+), N2(+), O(+), N(+), and He(+). Recently, the high-latitude ionospheric model has been improved by including thermal conduction and diffusion-thermal heat flow terms. Schunk and Sojka (1982) have studied the ion temperature variations in the daytime high-latitude F-region. In the present study, a time-dependent three-dimensional ion temperature distribution is obtained for the high-latitude ionosphere for an asymmetric convection electric field pattern with enhanced flow in the dusk sector of the polar region. It is shown that such a convection pattern produces a hot spot in the ion temperature distribution which coincides with the location of the strong convection cell.

  2. Low Altitude Initiation of Ionospheric Upflow and Outflow

    NASA Astrophysics Data System (ADS)

    Burleigh, M.; Zettergren, M. D.; Rowland, D. E.; Klenzing, J.

    2015-12-01

    Significant amounts of ionospheric plasma can be transported to high altitudes (above 1000 km) in response to a variety of plasma heating and uplifting processes. Soft electron precipitation heats ambient, F-region ionospheric electrons creating electron pressure increases and upflows. Strong DC electric fields frictionally heat the ion population also resulting in ion upflows. Lastly, field-aligned thermospheric winds can contribute to ion motion at lower altitudes, while geomagnetically perpendicular winds may affect frictional heating. Once ions have been lifted to high altitudes, transverse ion acceleration by broadband ELF waves can give the upflowing ions sufficient energy to escape into the magnetosphere (ionospheric outflow). This study examines the thermospheric wind regulation of ionospheric upflow and outflow with a focus on how lower ionosphere dynamics feed source populations for transverse energization and determine the types, and amounts, of outflowing ions. The model used here for this study is a 2D ionospheric model based on a modified 16-moment transport description. It solves conservation of mass, momentum, and parallel and perpendicular energy for all relevant ionospheric species. This model encapsulates ionospheric upflow and outflow processes through the inclusion of DC electric fields, and empirical descriptions of heating by soft electron precipitation and BBELF waves. This model is used to conduct a parametric study of neutral wind effects on upflow and outflow and highlights how low-altitude processes affect ion outflow through the regulation of source plasma available to higher altitudes. This model is also used to construct a case study of ion outflows at the nightside polar cap boundary using data from the VISIONS sounding rocket campaign.

  3. 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

  4. 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

  5. Day-To-Night Ionosphere Transport by Neutral Winds

    NASA Astrophysics Data System (ADS)

    Grebowsky, J. M.; Bougher, S. W.; Benna, M.

    2015-12-01

    Nightside low altitude nightside ionosphere production sources for the terrestrial planets are either transport from the dayside and production due to energetic particle impacts. The transport can be driven by ion coupling to the neutral atmosphere motions as part of the general atmospheric global circulation patterns and/or by ionosphere density gradients near the terminators produced as a result of a dayside source of ionization (photoionization) and a nightside sink (chemical losses). The day to night transport of ionization at high altitudes on Venus (during solar max and at Earth maintains the ionosphere throughout the night. This is not the case for Mars, where the dense ionosphere carried from the day does not extend much further than ~120 degrees solar zenith angle. Although predicted neutral wind speeds in the lower thermosphere of Mars are comparable to those on Earth and Venus, the winds at Mars can have larger impacts on horizontal transport since the planet's circumference is much smaller. One prominent effect of the winds is indicated by the observed rapid global dispersal of long-lived metal ions associated following the short, localized impact of the meteor storm associated with Comet Siding Spring . This paper will explore wind control of the low altitude Mars ionosphere ion composition measurements across the terminator from day into night, using the Neutral Gas Ion Mass Spectrometer instrument on MAVEN with the wind patterns predicted by the Mars Global Ionosphere-Thermosphere Model (M-GITM).

  6. Evaluation of six ionospheric models as predictors of TEC

    SciTech Connect

    Brown, L.D.; Daniell, R.E.; Fox, M.W.; Klobuchar, J.A.; Doherty, P.H.

    1990-05-03

    The authors have gathered TEC data from a wide range of latitudes and longitudes for a complete range of solar activity. This data was used to evaluate the performance of six ionospheric models as predictors of Total Electron Content (TFC). The TEC parameter is important in correcting modern DOD space systems, which propagate radio signals from the earth to satellites, for the time delay effects of the ionosphere. The TEC data were obtained from polarimeter receivers located in North America, the Pacific, and the East Coast of Asia. The ionospheric models evaluated are: (1) the International Reference Ionosphere (IRI); (2) the Bent model; (3) the Ionospheric Conductivity and Electron Density (ICED) model; (4) the Penn State model; (5) the Fully Analytic Ionospheric Model (FAIM, a modification of the Chiu model); and (6) the Damen-Hartranft model. They will present extensive comparisons between monthly mean TEC at all local times and model TEC obtained by integrating electron density profiles produced by the six models. These comparisons demonstrate that even thought most of the models do very well at representing f0F2, none of them do very well with TEC, probably because of inaccurate representation of the topside scale height. They suggest that one approach to obtaining better representations of TEC is the use of f0E2 from coefficients coupled with a new slab thickness developed at Boston University.

  7. Regional differences in climate change of the ionosphere

    NASA Astrophysics Data System (ADS)

    Lastovicka, Jan

    2016-07-01

    The increasing concentration of greenhouse gases, particularly carbon dioxide CO2, in the atmosphere affects not only the troposphere and surface climate, it affects the whole atmosphere-ionosphere system and it induces long-term trends and/or climate change in the ionosphere. The geographic distribution of CO2 in the upper atmosphere/ionosphere is relatively homogeneous and the long-term increase of CO2 concentration in the atmosphere is known to be stable. However, there are some other secondary drivers of long-term trends in the upper atmosphere/ionosphere, whose long-term behavior and/or effects either are not spatially homogeneous or are not stable in time (or both). Geomagnetic activity, solar activity, secular change of the Earth's magnetic field, long-term evolution of stratospheric ozone concentration and atmospheric wave activity are such trend drivers. They are responsible for regional differences in trends and also for their temporal non-stability. Regions of strong trends as a consequence of regional differences of trends represent a specific kind of risk from the point of view of space/ionospheric climate. These features of ionospheric trends will briefly be treated in this presentation.

  8. 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.

  9. Full-wave reflection of lightning long-wave radio pulses from the ionospheric D region: Numerical model

    NASA Astrophysics Data System (ADS)

    Jacobson, Abram R.; Shao, Xuan-Min; Holzworth, Robert

    2009-03-01

    A model is developed for calculating ionospheric reflection of electromagnetic pulses emitted by lightning, with most energy in the long-wave spectral region (f ~ 3-100 kHz). The building block of the calculation is a differential equation full-wave solution of Maxwell's equations for the complex reflection of individual plane waves incident from below, by the anisotropic, dissipative, diffuse dielectric profile of the lower ionosphere. This full-wave solution is then put into a summation over plane waves in an angular direct Fourier transform to obtain the reflection properties of curved wavefronts. This step models also the diffraction effects of long-wave ionospheric reflections observed at short or medium range (~200-500 km). The calculation can be done with any arbitrary but smooth dielectric profile versus altitude. For an initial test, this article uses the classic D region exponential profiles of electron density and collision rate given by Volland. With even these simple profiles, our model of full-wave reflection of curved wavefronts captures some of the basic attributes of observed reflected waveforms recorded with the Los Alamos Sferic Array. A follow-on article will present a detailed comparison with data in order to retrieve ionospheric parameters.

  10. Performance evaluation of selected ionospheric delay models during geomagnetic storm conditions in low-latitude region

    NASA Astrophysics Data System (ADS)

    Venkata Ratnam, D.; Sarma, A. D.; Satya Srinivas, V.; Sreelatha, P.

    2011-06-01

    Investigation of space weather effects on GPS satellite navigation systems is very crucial in high-precision positional applications such as aircraft landings and missile guidance, etc. The geomagnetic storms can drastically affect the total electron content (TEC) of the ionosphere even in low latitudes, especially for Indian region as it comes under low-latitude region. Hence, the performance of three prominent ionospheric models is investigated for adverse ionospheric conditions using 17 GPS TEC stations data. The models characterized the ionospheric disturbances due to two magnetic storms well.

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

    NASA Astrophysics Data System (ADS)

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

    1983-03-01

    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 mid-latitude 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.

  12. Shear flow energy redistribution stipulated by the internal-gravity wavy structures in the dissipative ionosphere

    NASA Astrophysics Data System (ADS)

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

    2013-07-01

    The linear mechanism of generation, intensification and further nonlinear dynamics of internal gravity waves (IGW) in stably stratified dissipative ionosphere with non-uniform zonal wind (shear flow) is studied. In case of the shear flows the operators of linear problem are non-selfadjoint, and the corresponding Eigen functions - nonorthogonal. Thus, canonical - modal approach is of less use studying such motions. Non-modal mathematical analysis becomes more adequate for such problems. On the basis of non-modal approach, the equations of dynamics and the energy transfer of IGW disturbances in the ionosphere with a shear flow is obtained. Exact analytical solutions of the linear as well as the nonlinear dynamic equations of the problem are built. The increment of shear instability of IGW is defined. It is revealed that the transient amplification of IGW disturbances due time does not flow exponentially, but in algebraic - power law manner. The effectiveness of the linear amplification mechanism of IGW at interaction with non-uniform zonal wind is analyzed. It is shown that at initial linear stage of evolution IGW effectively temporarily draws energy from the shear flow significantly increasing (by an order of magnitude) own amplitude and energy. With amplitude growth the nonlinear mechanism turns on and the process ends with self-organization of nonlinear solitary, strongly localized IGW vortex structures (the monopole vortex, the transverse vortex chain or the longitudinal vortex street). Accumulation of these vortices in the ionospheric medium can create the strongly turbulent state.

  13. 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.

  14. Models of Titan's Ionosphere

    NASA Astrophysics Data System (ADS)

    Robertson, I. P.; Cravens, T. E.; Waite, J. H.; Wahlund, J.; Yelle, R. V.; Vuitton, V.; Coates, A.; Magee, B.; Gell, D. A.

    2007-12-01

    During the TA and T18 encounters with Titan, in situ measurements were made of Titan's atmosphere and ionosphere by several instruments on board the Cassini Orbiter, including the Ion and Neutral Mass Spectrometer (INMS), the Langmuir probe on the Cassini Radio and Plasma Wave Experiment (RPWS), and the Cassini Plasma Spectrometer Subsystem (CAPS). Both of these encounters were on the day as well as the night side of Titan. The model uses neutral densities measured by the INMS instrument and the electron temperature was measured by the RPWS instrument. The model also includes energetic electron fluxes measured by the CAPS instrument, which act as an important source of ionization on the night side. The modeled ion densities are compared with densities measured by INMS in its Open Source mode.

  15. The October 28, 2003 extreme EUV solar flare and resultant extreme ionospheric effects: Comparison to other Halloween events and the Bastille Day event

    NASA Astrophysics Data System (ADS)

    Tsurutani, B. T.; Judge, D. L.; Guarnieri, F. L.; Gangopadhyay, P.; Jones, A. R.; Nuttall, J.; Zambon, G. A.; Didkovsky, L.; Mannucci, A. J.; Iijima, B.; Meier, R. R.; Immel, T. J.; Woods, T. N.; Prasad, S.; Floyd, L.; Huba, J.; Solomon, S. C.; Straus, P.; Viereck, R.

    2005-01-01

    Some of the most intense solar flares measured in 0.1 to 0.8 nm x-rays in recent history occurred near the end of 2003. The Nov 4 event is the largest in the NOAA records (X28) and the Oct 28 flare was the fourth most intense (X17). The Oct 29 flare was class X7. These flares are compared and contrasted to the July 14, 2000 Bastille Day (X10) event using the SOHO SEM 26.0 to 34.0 nm EUV and TIMED SEE 0.1-194 nm data. High time resolution, ~30s ground-base GPS data and the GUVI FUV dayglow data are used to examine the flare-ionosphere relationship. In the 26.0 to 34.0 nm wavelength range, the Oct 28 flare is found to have a peak intensity greater than twice that of the Nov 4 flare, indicating strong spectral variability from flare-to-flare. Solar absorption of the EUV portion of the Nov 4 limb event is a possible cause. The dayside ionosphere responds dramatically (~2.5 min 1/e rise time) to the x-ray and EUV input by an abrupt increase in total electron content (TEC). The Oct 28 TEC ionospheric peak enhancement at the subsolar point is ~25 TECU (25 × 1012 electrons/cm2) or 30% above background. In comparison, the Nov 4, Oct 29 and the Bastille Day events have ~5-7 TECU peak enhancements above background. The Oct 28 TEC enhancement lasts ~3 hrs, far longer than the flare duration. This latter ionospheric feature is consistent with increased electron production in the middle altitude ionosphere, where recombination rates are low. It is the EUV portion of the flare spectrum that is responsible for photoionization of this region. Further modeling will be necessary to fully understand the detailed physics and chemistry of flare-ionosphere coupling.

  16. Study of the Total Electron Content in Mars ionosphere from MARSIS data set

    NASA Astrophysics Data System (ADS)

    Bergeot, Nicolas; Witasse, Olivier; Kofman, Wlodek; Grima, Cyril; Mouginot, Jeremie; Peter, Kerstin; Pätzold, Martin; Dehant, Véronique

    2016-04-01

    Centimeter level accuracy on the signal delay will be required on X-band radio link for future Mars landers such as InSIGHT, aiming at better determining the interior structure of Mars. One of the main error sources in the estimated signal delay is directly linked to the Total Electron Content (TEC) values at Earth and Mars ionosphere level. While the Earth ionosphere is now well modeled and monitored at regional and global scales, this is not the case concerning the Mars' upper atmosphere. The present paper aims at establishing the basis to model the climatological behavior of the TEC on a global scale in the Mars' ionosphere. For that we analyzed ˜8.5 years of data (mid-2005 to 2014) of the vertical Total Electron Content (vTEC) expressed in TEC units (1 TECu = 1016e-.m-2) from the Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) radar. Our study takes advantage of the double data set of EUV solar index and Mars vTEC data to develop an empirical Model of Mars Ionosphere (MoMo). The finality of this model is to predict the vTEC at a given latitude, solar zenith angle and season taking only F10.7P solar index as input. To minimize the differences during the least-square adjustment between the modeled and observed vTEC, we considered (1) a 4th-order polynomial function to describe the vTEC diurnal behavior (2) a discretization with respect to Mars seasons (depending on Ls) and (3) two latitudinal sectors (North and South hemispheres). The mean of the differences between the model and the observations is 0.00±0.07 TECu with an error of the model around 0.1 TECu depending on the Solar Zenith Angle (SZA), season and hemisphere of interest (e.g. rms 0.12 TECu for SZA equal to 50°±5° in the Northern hemisphere during the spring season). Additionally, comparison with 250 Mars Express radio occultation data shows differences with MoMo predictions of 0.02±0.06 TECu for solar zenith angles below 50 degrees. Using the model we (1) highlighted

  17. The super-low frequency resonances at magnetospheric boundaries versus geostationary and ionospheric data

    NASA Astrophysics Data System (ADS)

    Savin, Sergey; Surjalal Sharma, A.; Pilipenko, Viacheslav; Marcucci, Maria Federica; Nemecek, Zdenek; Safrankova, Jana; Consolini, Giuseppe; Belakhovsky, Vladimir; Kozak, Ludmila; Blecki, Jan; Kronberg, Elena

    2016-07-01

    We do a multi-point study of the influence of the lowest frequency resonances (0.02-10 mHz) at the outer magnetospheric boundaries on the fluctuations inside the magnetosphere and ionosphere presented. The correlations of the dynamic pressure data from CLUSTER, DOUBLE STAR, GEOTAIL, ACE/ WIND, particle data from LANL, GOES with the magnetic data from polar ionospheric stations on March 27, 2005, show that: i) the waves generated by boundary resonances and their harmonics penetrate inside the magnetosphere and reach the ionosphere; ii) correlations between the dynamic pressure fluctuations at the magnetospheric boundaries and magnetospheric/ ionospheric disturbances, including indices such as AE and SYM-H, can exceed 80%; iii) the new resonance frequencies are lower by an order of magnitude compared with our previous studies, which are as low as 0.02 mHz. Furthermore, such resonances are characteristic also for the night-side geostationary/ionospheric data and for the middle tail, i.e., they are global magnetospheric features. Analysis of different types of correlations yields the unexpected result that in ~48% of the cases with pronounced maximum in the correlation function the geostationary/ ionospheric response is seen before the magnetosheath (MSH) response. We propose that some global magnetospheric resonances (e.g. membrane bow shock surface (0.2-0.5 mHz) and/or magnetopause (0.5-0.9 mHz) modes along with the cavity MHS/ cusp (3-10 mHz) and magnetospheric global modes (0.02-0.09mHz)) can account for the data presented. The multiple jets at the sampled MSH locations can be a consequence of the resonances, while an initial disturbance (e.g. through the interplanetary shocks, Hot Flow Anomalies, foreshock irregularities etc., were not observed by particular spacecraft in MSH because they were localized in the plane perpendicular to the Sun-Earth line. So, in the explorations of the solar wind - magnetosphere interactions one should take into account these

  18. Ionospheric forecasts for the European region for space weather applications

    NASA Astrophysics Data System (ADS)

    Tsagouri, Ioanna; Belehaki, Anna

    2015-04-01

    This paper discusses recent advances in the implementation and validation of the Solar Wind driven autoregression model for Ionospheric short-term Forecast (SWIF) that is running in the European Digital upper Atmosphere Server (DIAS) to release ionospheric forecasting products for the European region. The upgraded implementation plan expands SWIF's capabilities in the high latitude ionosphere while the extensive validation tests in the two solar cycles 23 and 24 allow the comprehensive analysis of the model's performance in all terms. Focusing on disturbed conditions, the results demonstrate that SWIF's alert detection algorithm forecasts the occurrence of ionospheric storm time disturbances with probability of detection up to 98% under intense geomagnetic storm conditions and up to 63% when storms of moderate intensity are also considered. The forecasts show relative improvement over climatology of about 30% in middle-to-low and high latitudes and 40% in middle-to-high latitudes. This indicates that SWIF is able to capture on average more than one third (35%) of the storm-associated ionospheric disturbances. Regarding the accuracy, the averaged mean relative error during storm conditions usually ranges around 20% in middle-to-low and high latitudes and 24% in the middle-to-high latitudes. Our analysis shows clearly that SWIF alert criteria were designed to effectively anticipate the ionospheric storm time effects that occurred under specific interplanetary conditions, e.g., cloud Interplanetary Coronal Mass Ejections (ICMEs) and/or associated sheaths. The results provide valuable input in advancing our ability in predicting the space weather effects in the ionosphere for future developments, and further work is proposed to enhance the model forecasting efficiency to support operational applications.

  19. Coseismic ionospheric and geomagnetic disturbances caused by great earthquakes

    NASA Astrophysics Data System (ADS)

    Hao, Yongqiang; Zhang, Donghe; Xiao, Zuo

    2016-04-01

    Despite primary energy disturbances from the Sun, oscillations of the Earth surface due to a large earthquake will couple with the atmosphere and therefore the ionosphere, then the so-called coseismic ionospheric disturbances (CIDs) can be detected in the ionosphere. Using a combination of techniques, total electron content, HF Doppler, and ground magnetometer, a new time-sequence of such effects propagation were developed on observational basis and ideas on explanation provided. In the cases of 2008 Wenchuan and 2011 Tohoku earthquakes, infrasonic waves accompanying the propagation of seismic Rayleigh waves were observed in the ionosphere by all the three kinds of techniques. This is the very first report to present CIDs recorded by different techniques at co-located sites and profiled with regard to changes of both ionospheric plasma and current (geomagnetic field) simultaneously. Comparison between the oceanic (2011 Tohoku) and inland (2008 Wenchuan) earthquakes revealed that the main directional lobe of latter case is more distinct which is perpendicular to the direction of the fault rupture. We argue that the different fault slip (inland or submarine) may affect the way of couplings of lithosphere with atmosphere. References Zhao, B., and Y. Hao (2015), Ionospheric and geomagnetic disturbances caused by the 2008 Wenchuan earthquake: A revisit, J. Geophys. Res. Space Physics, 120, doi:10.1002/2015JA021035. Hao, Y. Q., Z. Xiao, and D. H. Zhang (2013), Teleseismic magnetic effects (TMDs) of 2011 Tohoku earthquake, J. Geophys. Res. Space Physics, 118, 3914-3923, doi:10.1002/jgra.50326. Hao, Y. Q., Z. Xiao, and D. H. Zhang (2012), Multi-instrument observation on co-seismic ionospheric effects after great Tohoku earthquake, J. Geophys. Res., 117, A02305, doi:10.1029/2011JA017036.

  20. 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

  1. The ionospheric response to the Saint Patrick storm over South East Asia

    NASA Astrophysics Data System (ADS)

    Spogli, L.; Alfonsi, L.; Di Mauro, D.; Pezzopane, M.; Cesaroni, C.; Povero, G., Sr.; Pini, M., Sr.; Dovis, F., Sr.; Romero, R.; Linty, N.; Abadi, P.; Nuraeni, F.; Husin, A.; Huy Le, M.; La The, V.; Pillat, V. G.; Floury, N.

    2015-12-01

    ERICA, a project funded by the European Space Agency, aims at characterizing the ionospheric variability of the Equatorial Ionospheric Anomaly in the South East Asia. In particular, ERICA focuses on the variation of the plasma electron density in the southern and northern crests of the anomaly and over the dip equator identified by the Equatorial Ionospheric Trough. To achieve this goal, an ad hoc measurements campaign is on-going with ground-based instruments located in the footprints of the Equatorial Ionospheric Anomaly and of the Equatorial Ionospheric Trough in Vietnam and Indonesia.The campaign started on the 1st of March 2015, timing to monitor the Saint Patrick storm effects on the ionosphere by means of ionosondes, double frequency hardware and software defined radio GNSS receivers, ground based and spaceborne magnetometers and Langmuir probe. Such multi-instrumental and multi-parametric observations of the region enables an in-depth investigation of the ionospheric response to the largest geomagnetic storm of the current solar cycle. The observations record positive and negative ionospheric storms, sporadic E layer and spread F conditions, scintillations enhancement and inhibition, TEC gradients. The ancillary information on the local magnetic field allows to highlight the variety of ionospheric perturbations happened during the main and the long recovery phase of the storm.The paper presents the outcomes of the investigation evidencing the peculiarities of a region not yet extensively reported in the open literature.

  2. N site ordering effect on partially ordered Fe{sub 16}N{sub 2}

    SciTech Connect

    Ji Nian; Wang Jianping

    2011-02-28

    Partially ordered Fe{sub 16}N{sub 2} thin films have been fabricated on Fe (001)-buffered GaAs (001) single-crystal substrates by a facing target sputtering process. The saturation magnetization has been systematically investigated as a function of N site ordering in partially ordered Fe{sub 16}N{sub 2} thin films, which is found to be increased monotonically with the increase in the N site ordering parameter, reaching up to 2.68 T at high ordering case. A model discussion is provided based on the partial localization of 3d electron states in this material system, which successfully rationalizes the formation of the giant saturation magnetization in chemically ordered Fe{sub 16}N{sub 2}. We further demonstrate that the average magnetic moment of partially ordered Fe{sub 16}N{sub 2} sensitively depends on the special arrangement of Fe{sub 6}N clusters, which is the key to realize high magnetic moment in this material system.

  3. 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

  4. Recent Advances in Ionospheric Anomalies detection

    NASA Astrophysics Data System (ADS)

    Titov, Anton; Vyacheslav, Khattatov

    2016-07-01

    The variability of the parameters of the ionosphere and ionospheric anomalies are the subject of intensive research. It is widely known and studied in the literature ionospheric disturbances caused by solar activity, the passage of the terminator, artificial heating of high-latitude ionosphere, as well as seismic events. Each of the above types of anomalies is the subject of study and analysis. Analysis of these anomalies will provide an opportunity to improve our understanding of the mechanisms of ionospheric disturbances. To solve this problem are encouraged to develop a method of modeling the ionosphere, based on the assimilation of large amounts of observational data.

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  6. Observations and Modeling of the Nighttime Electron Density Enhancement in the Mid-latitude Ionosphere

    NASA Astrophysics Data System (ADS)

    Chen, C.; Saito, A.; Lin, C.; Huba, J. D.; Liu, J. G.

    2010-12-01

    In this study, we compare the observational data from FORMOSAT-3/COSMIC and theoretical model results performed by SAMI2 (Sami2 is Another Model of the Ionosphere) for studying the longitudinal structure of the Mid-latitude Summer Nighttime Anomaly (MSNA). In order to study the occurrence of the nighttime electron density enhancement, we defined MSNA index by the ratio of the difference of the nighttime and daytime electron densities. The observational results by the FORMOSAT-3/COSMIC satellites show that there are three obvious nighttime electron density enhancement areas around South American, European, and Northeast Asian regions during local summer. The SAMI2 model can also successfully reproduce the ionospheric MSNA structure during local summer on both hemispheres, except for Northeast Asian region. This difference between observation and model simulation may be caused by the difference between the neutral wind model and the real winds. The physical mechanisms for the longitudinal structure of the MSNA are investigated in the different model conditions. Results show that the equatorward meridional neutral winds can drive the electron density up to a higher altitude along the magnetic field lines and the longer plasma production rate by solar EUV at higher latitudes in the summer time can provide the electron density source in the nighttime ionosphere. We concluded that the combination effect by the neutral wind and the plasma production rate play the important role of the MSNA longitudinal structure.

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

    NASA Astrophysics Data System (ADS)

    Luo, Weihua; Xu, Jisheng; Tian, Mao

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

  8. Ionospheric Modulation of Venus Express Lightning Detection Rates

    NASA Astrophysics Data System (ADS)

    Hart, Richard A.; Russell, Christopher T.; Zhang, Tielong

    2015-11-01

    Venus Express completed its nearly 9 year campaign at Earth’s sister planet in late 2014. During this period the onboard fluxgate magnetometer collected data up to 64 Hz in frequency while near periapsis. This is the expected frequency range for lightning-generated whistler-mode waves at Venus, between the local electron and ion gyrofrequencies. These waves are right-hand circularly polarized and are guided by the local magnetic field. When the Venusian ionopause is low enough in altitude to reside in the collisional region, the interplanetary magnetic field can get carried down with the ions and magnetize the lower ionosphere. As the field travels towards the terminator it gains a radial component, enabling whistlers to reach higher altitudes and be detected by the spacecraft. The mission covered almost an entire solar cycle and frequently observed a magnetized ionosphere during the solar minimum phase when the ionosphere was weak due to reduced incident EUV. Detection was most common at 250 km altitude where the waves travel more slowly due to reduced ionospheric density. In response they increase in amplitude in order to conserve magnetic energy flux. Here, we examine the changes in the ionospheric properties associated with the evolution of the solar cycle and the rate of detection of these lightning-generated signals.

  9. Ionospheric scintillation studies. Final report, October 1984-September 1987

    SciTech Connect

    Livingston, R.C.

    1988-05-01

    Irregular structure in ionospheric plasma density can significantly affect DoD communications and radar systems that utilize transionospheric radiowave paths. Transport and dissipation of ionospheric structure is therefore of direct relevance. Such an understanding can aid the long-term goal of developing a predictive capability for global ionospheric structure. Experimental observation of the ionosphere over the past few years has concentrated on high latitudes. This is the most-complex portion of the global ionospheric system; the auroral zone, the polar cap, and the boundary between them can all be regions of highly dynamic and structured plasma. In the polar cap, very-large-scale plasma patches and sun-aligned arcs occur, and can convect rapidly from their source regions to the entire high-latitude region. Much of what has been learned about this extended regime of irregularity structure at high latitudes has been through the application of complementary diagnostics: Optics, ionosonde, incoherent scatter radar, in-situ satellite, and scintillation measurements. These various techniques allow the observation of structure over several orders of magnitude in spatial scale. The optics, ionosonde, and radar provide an overall view of large-scale production and dynamics; the satellites diagnose the inputs to the large- and medium-scale irregularities; from the scintillation data, the strength, shape, and motion of the kilometer-scale structure can be identified.

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

    NASA Astrophysics Data System (ADS)

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

    2015-01-01

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

  11. Quantifying Total Electron Content Forecasts during Ionospheric Storms

    NASA Astrophysics Data System (ADS)

    Meng, X.; Mannucci, A. J.; Verkhoglyadova, O. P.; Tsurutani, B.

    2015-12-01

    We make total electron content (TEC) predictions with the Global Ionosphere-Thermosphere Model (GITM), in order to explore the feasibility of ionospheric forecasts with the current generation of physics-based models. For a number of representative ionospheric storms, we perform GITM simulations in a forecast mode. The simulations are driven by solar wind conditions at 1 AU from either in-situ observations or predictions by one of the physics-based heliospheric models ENLIL, CORHEL, and SWMF. A TEC metric has been developed to quantify forecasted storm-time TEC disturbances. To evaluate the forecasts, we compare the simulation results with Global Positioning System satellite observations. We introduce methods to deduce the primary factors responsible for the forecasted TEC response. Statistical results are obtained and analyzed for different types of storms.

  12. Diffuse spreading of inhomogeneities in the ionospheric dusty plasma

    SciTech Connect

    Shalimov, S. L.; Kozlovsky, A.

    2015-08-15

    According to results of sounding of the lower ionosphere at altitudes of about 100 km, the duration of radio reflections from sufficiently dense ionized meteor trails, which characterizes their lifetime, can reach a few tens of seconds to several tens of minutes. This is much longer than the characteristic spreading time (on the order of fractions of a second to several seconds) typical in meteor radar measurements. The presence of dust in the lower ionosphere is shown to affect the ambipolar diffusion coefficient, which determines the spreading of plasma inhomogeneities. It is found that the diffusion coefficient depends substantially on the charge and size of dust grains, which allows one to explain the results of ionospheric sounding.

  13. Ionospheric and tropospheric scintillation as a form of noise

    NASA Technical Reports Server (NTRS)

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

    1975-01-01

    Recent tests of signals observed through the ionosphere, the solar wind, and a laboratory plasma have revealed a surprising consistency in parameters describing the first order statistics of a signal caused to scintillate by a randomly structured plasma. This paper describes a means for exploiting these new findings in a transionospheric communication channel model.

  14. Determining polar ionospheric electrojet currents from Swarm satellite constellation magnetic data

    NASA Astrophysics Data System (ADS)

    Aakjær, Cecilie Drost; Olsen, Nils; Finlay, Christopher C.

    2016-08-01

    We determine the strength and location of the ionospheric currents responsible for the polar electrojets from magnetic data collected by the Swarm satellite constellation on an orbit-by-orbit basis. The ionospheric currents are modelled using a simple, yet robust, method by a series of line currents at 110 km altitude (corresponding to the ionospheric E-layer) perpendicular to the satellite orbit, separated by 1° (about 113 km). We assess the reliability of our method, with the aim of a possible near-real-time application. A study of the effect of different regularization methods is therefore carried out. An L_1 model regularization of the second-order spatial differences, and robust treatment of the data (to account for non-Gaussian error distributions), yields the most encouraging results. We apply our approach to two three-weekly data periods in March 2014 (geomagnetic quiet conditions) and March 2015 (more disturbed conditions), respectively. Our orbit-by-orbit approach also allows the temporal evolution of the polar electrojets to be investigated. We find remarkable agreement of the ionospheric activity in Northern and Southern polar regions, with correlation exceeding 0.9 for periods longer than two days. Reliability of the approach is shown by three key results: (1) a common regularization parameter for all orbits with enough data coverage, (2) 0.95 squared coherence with the Auroral Electrojet index, and (3) 0.97 squared coherence is found between the side-by-side flying satellites, Alpha and Charlie, indicating a method invariant to small changes in data input. All these results indicate a possible automated near-real-time application.

  15. Simultaneous, dual-point, in situ measurements of ionospheric structures using space tethers: TSS-1R observations

    NASA Astrophysics Data System (ADS)

    Indiresan, R. S.; Gilchrist, B. E.; Basu, S.; Lebreton, J.-P.; Szuszczewicz, E. P.

    First ever simultaneous, dual-point, in situ measurements of natural ionospheric structures using widely spaced tethered sensors, flying in formation, were made during the reflight of the Tethered Satellite System (TSS-1R) mission. A “target-of-opportunity” observation provided a direct comparison of structured ionospheric irregularity features at two altitudes near the South American geomagnetic equator at approximately 2000 hours local time and at an altitude of ≈300 km. With the TSS-1R satellite and space shuttle separated by a vertical distance of 10 km, correlated plasma signatures detected by plasma instruments at each end indicated a strong eastward displacement in the irregularity features and possible growth of steepened features at the higher altitude. Observations made by a SUNDIAL ground station ionosonde located north of the flight path also indicated considerable spread-F activity at the time. A SUNDIAL corrected ionospheric model indicated that the shuttle was flying near the F-peak. Therefore, the strongly correlated in situ observations were most likely associated with irregularities in their early development or modulations near the F-peak due to equatorial spread-F (ESF). While the TSS-1R system was not optimized for dual-point in situ ionospheric measurements, and the tether break eliminated additional equatorial zone observations planned for later in the mission, the results reported here nevertheless indicate that vertically correlated plasma features can exist and can also have strong structural variations as a function of altitude. Such variations need closer examination in order to understand their effects on radiowave scintillation. These observations also demonstrated the feasibility of tethered sensors in the study of ionospheric irregularities using controlled vertical sampling.

  16. Electric fields in the ionosphere

    NASA Technical Reports Server (NTRS)

    Kirchhoff, V. W. J. H.

    1975-01-01

    F-region drift velocities, measured by incoherent-scatter radar were analyzed in terms of diurnal, seasonal, magnetic activity, and solar cycle effects. A comprehensive electric field model was developed that includes the effects of the E and F-region dynamos, magnetospheric sources, and ionospheric conductivities, for both the local and conjugate regions. The E-region dynamo dominates during the day but at night the F-region and convection are more important. This model provides much better agreement with observations of the F-region drifts than previous models. Results indicate that larger magnitudes occur at night, and that daily variation is dominated by the diurnal mode. Seasonal variations in conductivities and thermospheric winds indicate a reversal in direction in the early morning during winter from south to northward. On magnetic perturbed days and the drifts deviate rather strongly from the quiet days average, especially around 13 L.T. for the northward and 18 L.T. for the westward component.

  17. Toward Consistent Understanding Of The Coupling Between The Ionosphere And Plasmasphere

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

    The overarching objective of this study is to follow the transport and flow of plasma through the plasmasphere and ionosphere, and the exchange between them during geomagnetic storms. From the ionospheric point of view, storm time redistribution of plasma was observed in the GPS TEC [Mannuci et al 2005]. On the other hand in the plasmasphere, erosion, plumes and dynamic variation of the plasmapause were observed in the IMAGE EUV during the same Halloween storm period [Goldstein et al., 2005]. However, we do not have a good picture about how the plasma should be flowing between the ionosphere and plasmasphere during storms to explain both observations in a consistent manner. In order to address the coupling issues between the ionosphere and plasmasphere, we have developed the Ionosphere-Plasmasphere-Electrodynamics (IPE) model. It consists of a physics based model of an ionosphere and plasmasphere using the IGRF geomagnetic field configuration (APEX) with flexible spatial resolutions depending on the type of physical phenomena we would like to target. Furthermore, the global ionosphereic potential is solved self-consistently on the same grid to understand how fine structures of the ionospheric conductivity impact the electric potential, such as caused by Storm Enhanced Densities (SEDs). In this presentation, we will present TEC, a reconstruction of the IMAGE EUV, and the refilling flux along field lines obtained our model results.

  18. Multi-instrumental study of the ionosphere in European region

    NASA Astrophysics Data System (ADS)

    Zakharenkova, I.; Krankowski, A.; Cherniak, I.; Rothkaehl, H.

    2013-12-01

    We present the techniques for the investigation of the spatial-temporal structure of the mid-latitude ionosphere on the base of comprehensive analysis of multi-instrumental satellite and ground-based measurements and demonstrates their application at several case study results. For our analysis we used the ionospheric data provided by European ionosondes network (DIAS), as well as GNSS TEC observations. Manually scaled ionosondes' data are used as a benchmark in our study. Two-dimensional maps of vertical TEC over Europe are created using IGS and EUREF permanent networks. These maps have spatial resolution of 1 deg and temporal resolution of 1 h, for investigation of ionosphere response on special events (geomagnetic storms, solar eclipses, etc) there is possibility to create TEC maps with 5-10 min resolution. The high temporal resolution maps give the possibility to study of spatial gradients of electron density. Joint analysis of GPS TEC and FORMOSAT-3/COSMIC radio occultation data allows us to extract and estimate electron content corresponded to the ionosphere (its bottom and topside parts) and the plasmasphere (h>700 km) for different conditions. Several case-studies of geomagnetic storms were analyzed in order to estimate changes and redistribution of electron content between ionosphere and plasmasphere over Europe. The obtained results were compared with TEC, IEC and PEC estimates retrieved by IRI-Plas Model that has the plasmasphere extension up to 20,000 km (GPS orbit). As a new data source there will be new ionospheric sounding station, located in European mid-latitudes in Olsztyn, Poland, that will start its operation at the end of 2013. One of the possible user of ionospheric products is represented by LOFAR (LOw Frequency Array), a new fully digital radio telescope designed for frequencies between 30 MHz and 240 MHz. To the summer of 2015 three new LOFAR stations will be installed in Poland: Lazy (East of Krakow), Borowiec near Poznan and Baldy near

  19. Cubesat-Based Dtv Receiver Constellation for Ionospheric Tomography

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

    The Radio Aurora Explorer mission, funded by NSF's Space Weather and Atmospheric Research program, has demonstrated the utility of CubeSat-based radio receiver payloads for ionospheric research. RAX has primarily been an investigation of microphysics of meter-scale ionospheric structures; however, the data products are also suitable for research on ionospheric effects on radio propagation. To date, the spacecraft has acquired (1) ground-based UHF radar signals that are backscattered from meter-scale ionospheric irregularities, which have been used to measure the dispersion properties of meter-scale plasma waves and (2) ground-based signals, directly on the transmitter-spacecraft path, which have been used to measure radio propagation disturbances (scintillations). Herein we describe the application of a CubeSat constellation of UHF receivers to expand the latter research topic for global-scale ionospheric tomography. The enabling factor for this expansion is the worldwide availability of ground-based digital television (DTV) broadcast signals whose characteristics are optimal for scintillation analysis. A significant part of the populated world have transitioned, or soon to be transitioned, to DTV. The DTV signal has a standard format that contains a highly phase-stable pilot carrier that can be readily adapted for propagation diagnostics. A multi-frequency software-defined radar receiver, similar to the RAX payload, can measure these signals at a large number of pilot carrier frequencies to make radio ray and diffraction tomographic measurements of the ionosphere and the irregularities contained in it. A constellation of CubeSats, launched simultaneously, or in sequence over years, similar to DMSPs, can listen to the DTV stations, providing a vast and dense probing of the ionosphere. Each spacecraft can establish links to a preprogrammed list of DTV stations and cycle through them using time-division frequency multiplexing (TDFM) method. An on board program can

  20. Utilizing GPS to Determine Ionospheric Delay over the Ocean

    NASA Technical Reports Server (NTRS)

    Katzberg, Stephen J.; Garrison, James L., Jr.

    1996-01-01

    Several spaceborne altimeters have been built and flown, and others are being developed to