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Sample records for order ionospheric effects

  1. Higher order ionospheric propagation effects on GPS radio occultation signals

    NASA Astrophysics Data System (ADS)

    Hoque, M. Mainul; Jakowski, N.

    2010-07-01

    With the increasing number of remote sensing satellites using the GPS radio occultation technique for atmospheric sounding, the estimation of higher order ionospheric effects and their mitigation have become relevant and important. Due to long ionospheric limb paths, GPS signals are strongly affected by ionospheric refraction during radio occultation. Standard dual-frequency GPS measurements may be used to estimate the first order term of the refractive index. However, non-linear terms such as the second and third order ionospheric terms and ray path bending effects are not considered in occultation measurements so far. Analysing selected CHAMP-GPS occultation events different higher order ionospheric terms are estimated and their effects on dual-frequency range estimation and total electron content (TEC) estimation are discussed. We have found that the separation between the GPS L1 and L2 ray paths exceeds the kilometer level during occultation for a vertical TEC level of more than 160 TEC units. Corresponding errors in the GPS dual-frequency range estimation and TEC estimation are found to exceed the meter and 10 TEC units level, respectively.

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

    E-print Network

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

    2015-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-08-01

    We compare first-order (refractive) ionospheric effects seen by the MWA with the ionosphere as inferred from GPS data. The first-order ionosphere manifests itself as a bulk position shift of the observed sources across an MWA field of view. These effects can be computed from global ionosphere maps provided by GPS analysis centres, namely the CODE. However, for precision radio astronomy applications, data from local GPS networks needs to be incorporated into ionospheric modelling. For GPS observations, the ionospheric parameters are biased by GPS receiver instrument delays, among other effects, also known as receiver DCBs. The receiver DCBs need to be estimated for any non-CODE GPS station used for ionosphere modelling. In this work, single GPS station-based ionospheric modelling is performed at a time resolution of 10 min. Also the receiver DCBs are estimated for selected Geoscience Australia GPS receivers, located at Murchison Radio Observatory, Yarragadee, Mount Magnet and Wiluna. The ionospheric gradients estimated from GPS are compared with that inferred from MWA. The ionospheric gradients at all the GPS stations show a correlation with the gradients observed with the MWA. The ionosphere estimates obtained using GPS measurements show promise in terms of providing calibration information for the MWA.

  4. Second-order ionospheric effects on satellite radio occultation observations and their impact on atmospheric studies

    NASA Astrophysics Data System (ADS)

    Vergados, Panagiotis

    This dissertation describes the development of first-of-a-kind mathematical models that both quantify higher-order ionospheric effects and their impact on Global Positioning System radio occultation (GPS/RO) data products. We develop new and innovative models to: a) remove the second-order ionospheric effect from Total Electron Content (TEC) estimations; b) quantify the second-order ionospheric delay in GPS/RO signal propagation using the Faraday phenomenon; c) quantify the vertical distribution of the first- and second-order ionospheric residual effects on GPS/RO data products; and d) retrieve improved atmospheric water vapour profiles. For the first time we combine GPS/RO measurements with space-based gravity missions to characterize the response of the GPS/RO-derived atmospheric parameters to the Earth's gravity anomalies. Independently, we implement these mathematical models in a new GPS/RO processing software package to investigate, for the first time, the impact of higher-order ionospheric residual effects on ionospheric and atmospheric products. We observe that under low solar activity, the second-order ionospheric residual effect introduces: a) slowly varying positive systematic biases of ˜1-3 TECU on TEC estimations as function of occultation time; b) maximum negative systematic biases of ˜0.35 N-units on atmospheric refractivity close to the Earth's surface; c) negative systematic biases of ˜0.5 K close to the Earth's surface, which decrease with altitude and above 26 km become positive, peaking at ˜2.0 K at 50 km and d) negative systematic biases of ˜0.08 mbar on the water vapour pressure. Further studies reveal that the second-order ionospheric residual effect increases non-linearly with solar variability, oscillating between +/-3 mm (at Rz12=2) and +/-15 mm (at Rz12=114), whereas its value increases with increasing latitude. The first-order ionospheric residual effect arising from the geometrical splitting of the dual-frequency GPS radiowave signals is ˜2-3 orders of magnitude smaller than the second-order ionospheric residual effect, with the potential of increasing in magnitude at high solar activity. A series of sensitivity studies show that the LEO velocity uncertainties affect the GPS/RO bending angle accuracy more than the Doppler shift uncertainties. Finally, we find that the Earth's gravity anomalies can introduce negative systematic biases on the atmospheric temperature profiles of up to ˜0.5 K close to the Earth's surface. This dissertation demonstrates the simplicity, innovation, effectiveness and importance of our proposed mathematical models on the future of GPS/RO atmospheric remote sensing.

  5. Effects of modelling higher-order ionospheric terms on global GPS solutions

    NASA Astrophysics Data System (ADS)

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

    2010-12-01

    Higher order ionospheric effects arise both from the expansion of the refractive index of the ionosphere as a series and from signal bending due to gradients in refractive index. There is an approximately eleven year variation in the electron content of the ionosphere due to the solar cycle. This means that systematic errors with a trend over several years are possible. Presented here are comparisons of the effects on the GPS reference frame and/or coordinates from modeling variations of the second and third order ionospheric refractive index terms. Results from an experimental implementation of the higher-order bending terms are also outlined. In particular, we perform periodic analysis and noise analysis of differenced coordinate time series and find that that higher-order ionospheric effects do not appear to contribute to the power-law noise typically seen in GPS coordinate time series. However, neglecting higher order ionospheric terms may bias station velocities and also tropospheric zenith delays at low latitudes.

  6. Higher order ionospheric effects in GNSS positioning in the European region

    NASA Astrophysics Data System (ADS)

    Elmas, Z. G.; Aquino, M.; Marques, H. A.; Monico, J. F. G.

    2011-08-01

    After removal of the Selective Availability in 2000, the ionosphere became the dominant error source for Global Navigation Satellite Systems (GNSS), especially for the high-accuracy (cm-mm) demanding applications like the Precise Point Positioning (PPP) and Real Time Kinematic (RTK) positioning. The common practice of eliminating the ionospheric error, e.g. by the ionosphere free (IF) observable, which is a linear combination of observables on two frequencies such as GPS L1 and L2, accounts for about 99 % of the total ionospheric effect, known as the first order ionospheric effect (Ion1). The remaining 1 % residual range errors (RREs) in the IF observable are due to the higher - second and third, order ionospheric effects, Ion2 and Ion3, respectively. Both terms are related with the electron content along the signal path; moreover Ion2 term is associated with the influence of the geomagnetic field on the ionospheric refractive index and Ion3 with the ray bending effect of the ionosphere, which can cause significant deviation in the ray trajectory (due to strong electron density gradients in the ionosphere) such that the error contribution of Ion3 can exceed that of Ion2 (Kim and Tinin, 2007). The higher order error terms do not cancel out in the (first order) ionospherically corrected observable and as such, when not accounted for, they can degrade the accuracy of GNSS positioning, depending on the level of the solar activity and geomagnetic and ionospheric conditions (Hoque and Jakowski, 2007). Simulation results from early 1990s show that Ion2 and Ion3 would contribute to the ionospheric error budget by less than 1 % of the Ion1 term at GPS frequencies (Datta-Barua et al., 2008). Although the IF observable may provide sufficient accuracy for most GNSS applications, Ion2 and Ion3 need to be considered for higher accuracy demanding applications especially at times of higher solar activity. This paper investigates the higher order ionospheric effects (Ion2 and Ion3, however excluding the ray bending effects associated with Ion3) in the European region in the GNSS positioning considering the precise point positioning (PPP) method. For this purpose observations from four European stations were considered. These observations were taken in four time intervals corresponding to various geophysical conditions: the active and quiet periods of the solar cycle, 2001 and 2006, respectively, excluding the effects of disturbances in the geomagnetic field (i.e. geomagnetic storms), as well as the years of 2001 and 2003, this time including the impact of geomagnetic disturbances. The program RINEX_HO (Marques et al., 2011) was used to calculate the magnitudes of Ion2 and Ion3 on the range measurements as well as the total electron content (TEC) observed on each receiver-satellite link. The program also corrects the GPS observation files for Ion2 and Ion3; thereafter it is possible to perform PPP with both the original and corrected GPS observation files to analyze the impact of the higher order ionospheric error terms excluding the ray bending effect which may become significant especially at low elevation angles (Ioannides and Strangeways, 2002) on the estimated station coordinates.

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

    NASA Astrophysics Data System (ADS)

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

    2009-04-01

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

  8. Higher-order ionospheric effects on the GPS observables and means of modeling them

    NASA Technical Reports Server (NTRS)

    Bassiri, Sassan; Hajj, George A.

    1993-01-01

    Based on relaistic modeling of the electron density of the ionosphere and using a dipole moment approximation for the earth magnetic field, we are able to estimate the effect of the ionosphere on the Global Positioning Systems (GPS) signal for a ground user. The lowest-order (1/f(exp 2)) effect, which is of the order of .1 - 30 meters of zenith group delay, is subtracted out by forming a linear combination of the dual frequencies of the GPS signal. One is left with second- (1/f(exp 3)) and third-order (1/f(exp 4)) effects which are estimated typically to be approximately 0 - 2 cm, and approximately 0 - 2 mm at zenith respectively, depending on the time of day, 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, we derive an approximation to the second-order term which is accurate to approximately 90% 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 are examined for two ground receivers located at equatorial and mid-latitude regions tracking several GPS satellites.

  9. Distribution and mitigation of higher-order ionospheric effects on precise GNSS processing

    NASA Astrophysics Data System (ADS)

    Hernández-Pajares, Manuel; Aragón-Ángel, Àngela; Defraigne, Pascale; Bergeot, Nicolas; Prieto-Cerdeira, Roberto; García-Rigo, Alberto

    2014-04-01

    Higher-order ionospheric effects (I2+) are one of the main limiting factors in very precise Global Navigation Satellite Systems (GNSS) processing, for applications where millimeter accuracy is demanded. This paper summarizes a comprehensive study of the I2+ effects in range and in GNSS precise products such as receiver position and clock, tropospheric delay, geocenter offset, and GNSS satellite position and clock. All the relevant higher-order contributions are considered: second and third orders, geometric bending, and slant total electron content (dSTEC) bending (i.e., the difference between the STEC for straight and bent paths). Using a realistic simulation with representative solar maximum conditions on GPS signals, both the effects and mitigation errors are analyzed. The usage of the combination of multifrequency L band observations has to be rejected due to its increased noise level. The results of the study show that the main two effects in range are the second-order ionospheric and dSTEC terms, with peak values up to 2 cm. Their combined impacts on the precise GNSS satellite products affects the satellite Z coordinates (up to +1 cm) and satellite clocks (more than ±20 ps). Other precise products are affected at the millimeter level. After correction the impact on all the precise GNSS products is reduced below 5 mm. We finally show that the I2+ impact on a Precise Point Positioning (PPP) user is lower than the current uncertainties of the PPP solutions, after applying consistently the precise products (satellite orbits and clocks) obtained under I2+ correction.

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

    NASA Astrophysics Data System (ADS)

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

    2011-05-01

    Higher order ionospheric effects are increasingly relevant as precision requirements on GPS data and products increase. The refractive index of the ionosphere is affected by its electron content and the magnetic field of the Earth, so the carrier phase of the GPS L1 and L2 signals is advanced and the modulated code delayed. Due to system design the polarisation is unaffected. Most of the effect is removed by expanding the refractive index as a series and eliminating the first term with a linear combination of the two signals. However, the higher order terms remain. Furthermore, transiting gradients in refractive index at a non-perpendicular angle causes signal bending. In addition to the initial geometric bending term, another term allows for the difference that the curvature makes in electron content along each signal. Varying approximations have been made for practical implementation, mainly to avoid the need for a vertical profile of electron density. The magnetic field may be modelled as a tilted co-centric dipole, or using more realistic models such as the International Geomagnetic Reference Field. The largest effect is from the second term in the expansion of the refractive index. Up to several cm on L2, it particularly affects z-translation, and satellite orbits and clocks in a global network of GPS stations. The third term is at the level of the errors in modelling the second order term, while the bending terms appear to be absorbed by tropospheric parameters. Modelling improvements are possible, and three frequency transmissions will allow new possibilities.

  11. Estimate of higher order ionospheric errors in GNSS positioning

    NASA Astrophysics Data System (ADS)

    Hoque, M. Mainul; Jakowski, N.

    2008-10-01

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

  12. 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.

  13. Effect of Ionospheric Scintillations on GNSS A White Paper

    E-print Network

    Boneh, Dan

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

  14. Higher-order ionospheric error at Arecibo, Millstone, and Jicamarca

    NASA Astrophysics Data System (ADS)

    Matteo, N. A.; Morton, Y. T.

    2010-12-01

    The ionosphere is a dominant source of Global Positioning System receiver range measurement error. Although dual-frequency receivers can eliminate the first-order ionospheric error, most second- and third-order errors remain in the range measurements. Higher-order ionospheric error is a function of both electron density distribution and the magnetic field vector along the GPS signal propagation path. This paper expands previous efforts by combining incoherent scatter radar (ISR) electron density measurements, the International Reference Ionosphere model, exponential decay extensions of electron densities, the International Geomagnetic Reference Field, and total electron content maps to compute higher-order error at ISRs in Arecibo, Puerto Rico; Jicamarca, Peru; and Millstone Hill, Massachusetts. Diurnal patterns, dependency on signal direction, seasonal variation, and geomagnetic activity dependency are analyzed. Higher-order error is largest at Arecibo with code phase maxima circa 7 cm for low-elevation southern signals. The maximum variation of the error over all angles of arrival is circa 8 cm.

  15. A new unequal-weighted triple-frequency first order ionosphere correction algorithm and its application in COMPASS

    NASA Astrophysics Data System (ADS)

    Liu, WenXiang; Mou, WeiHua; Wang, FeiXue

    2012-03-01

    As the introduction of triple-frequency signals in GNSS, the multi-frequency ionosphere correction technology has been fast developing. References indicate that the triple-frequency second order ionosphere correction is worse than the dual-frequency first order ionosphere correction because of the larger noise amplification factor. On the assumption that the variances of three frequency pseudoranges were equal, other references presented the triple-frequency first order ionosphere correction, which proved worse or better than the dual-frequency first order correction in different situations. In practice, the PN code rate, carrier-to-noise ratio, parameters of DLL and multipath effect of each frequency are not the same, so three frequency pseudorange variances are unequal. Under this consideration, a new unequal-weighted triple-frequency first order ionosphere correction algorithm, which minimizes the variance of the pseudorange ionosphere-free combination, is proposed in this paper. It is found that conventional dual-frequency first-order correction algorithms and the equal-weighted triple-frequency first order correction algorithm are special cases of the new algorithm. A new pseudorange variance estimation method based on the three carrier combination is also introduced. Theoretical analysis shows that the new algorithm is optimal. The experiment with COMPASS G3 satellite observations demonstrates that the ionosphere-free pseudorange combination variance of the new algorithm is smaller than traditional multi-frequency correction algorithms.

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

    E-print Network

    Stanford University

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

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

    E-print Network

    Stanford University

    Bounding Higher Order Ionosphere Errors for the Dual Frequency GPS User Seebany Datta-Barua, Todd through the ionosphere is the largest and most variable source of positioning error. Dual-frequency users take advantage of the dispersive nature of the ionosphere, combining the GPS observables to eliminate

  18. 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.

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

    NASA Astrophysics Data System (ADS)

    Hu, Yaogai; Zhao, Zhengyu; Zhang, Yuannong

    2011-07-01

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

  20. On a possible seismomagnetic effect in the topside ionosphere

    NASA Astrophysics Data System (ADS)

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

    2015-10-01

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

  1. 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.

  2. 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.

  3. 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.

  4. 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.

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

    NASA Astrophysics Data System (ADS)

    Zehentner, Norbert; Mayer-Gürr, Torsten

    2015-04-01

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

  6. Ionospheric effects on a large radio telescope.

    NASA Astrophysics Data System (ADS)

    Zhang, Xizhen; Han, Wenjun; Zheng, Yijia

    1996-12-01

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

  7. Effects of the ultra-fast Kelvin waves on the Brazilian equatorial ionosphere

    NASA Astrophysics Data System (ADS)

    Onohara, Amelia; Takahashi, Hisao; Batista, Inez S.; Prado Batista, Paulo; Clemesha, Barclay; Lima, Lourivaldo

    In this work we investigated the effects of an ultra-fast Kelvin wave (an equatorial planetary wave with period of almost 3 days) on the ionospheric parameters over the Brazilian equatorial region. For this purpose, the meteor wind data from São João do Cariri (7.4° S, 36.5° W) a a and ionospheric data from digissonde installed at Fortaleza (3.9° S, 38.4° W) for the year 2005 were used. Zonal and meridional winds, h'F and foF2 were submitted to a wavelet analysis in order to find the oscillation appeared in the temporal series. The study was conducted for the time intervals in which the ultra-fast Kelvin wave signature was present in both mesospheric and ionospheric parameters. For each of these intervals, the amplitude and phase of the prop-agating wave were calculated from the wind data. The effect of the ultra-fast Kelvin waves on the ionospheric parameters was tested using an ionospheric model that solves the coupled electrodynamics of the equatorial ionosphere and calculates the electrostatic potential for the E region and the F region vertical and horizontal plasma drifts. Some relevant results obtained from the comparison between observation and model results will be discussed.

  8. Effect of Ionospheric Scintillations on GNSS Summary of a White Paper

    E-print Network

    Boneh, Dan

    1 Effect of Ionospheric Scintillations on GNSS ­ Summary of a White Paper SBAS Ionospheric Working frequency eliminates the major limitation on today's use of GNSS caused by ionospheric delays. These new signals will enable the use of GNSS in parts of the world where concern over significant ionospheric

  9. Modeling the effects of solar flares on the ionosphere of Mars

    E-print Network

    Withers, Paul

    Modeling the effects of solar flares on the ionosphere of Mars Paul Withers, Joei Wroten, Michael:00 EGU Meeting 2007, Vienna, Austria #12;A Typical Mars Ionospheric Profile Outline of talk: Observations of Mars ionosphere during a solar flare Model description Models of Mars ionosphere during a solar flare

  10. Ionospheric Effect on a GNSS Radio Occultation Climate Data Record

    NASA Astrophysics Data System (ADS)

    Rocken, C.; Schreiner, W.; Sokolovskiy, S.; Hunt, D.

    2008-12-01

    Radio occultation (RO) is widely considered to be an observation technique that is particularly well suited for establishing a long-term stable global climate record of density, temperature and bending angle profiles in the 8-30 km height range of the atmosphere. To measure profiles in this height range the ionospheric effect on the RO signals must be eliminated. This ionospheric correction is not perfect and is the most challenging noise source affecting GPS radio occultation temperature profiles in the upper stratosphere. The ionosphere introduces random noise on individual temperature profiles that can affect weather forecasting applications. More serious for climate monitoring are systematic bending angle and resulting temperature biases that change with the solar cycle. We have found a strong correlation between these bending angle biases and F10.7 solar flux values. We have also found a diurnal signal which shows stronger bending angle biases during the day than at night. While the ionosphere is expected to be the main source of these diurnal effects, additional neutral atmospheric influence due to tides cannot be ruled out and needs further investigation. With different GNSS signals and improving receiver technology ionospheric correction in RO processing will evolve in the future. We will also investigate if tracking of the stronger L2C GPS signal could introduce a bias between past and future GNSS observations. This presentation will discuss ways to quantify and limit the ionospheric effect on the RO climate record.

  11. The effect of rocket launches on the ionosphere

    NASA Technical Reports Server (NTRS)

    Mendillo, M.

    1981-01-01

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

  12. Global characteristics of the second-order ionospheric delay error using inversion of electron density profiles from COSMIC occultation data

    NASA Astrophysics Data System (ADS)

    Wang, Hu; Wang, Cheng; Wang, JieXian; Dang, YaMing; Bai, GuiXia; Wang, QianXin

    2014-01-01

    It is a well known fact that ionospheric delay error is a predominant factor which influences the positioning accuarcy of GNSS. Although the main part of the first-order ionospheric delay error can be removed by the frequency-dependent behaviors of the ionosphere, the second-order ionospheric delay error must be eliminated to achieve millimetre-scale positioning accuracy. Due to COSMIC occultation providing electron density profiles on the global scale, the paper presents the first-order and the second-order ionospheric delay error analysis on the global scale using the inversion of electron density profiles from COSMIC occultation data during 2009-2011. Firstly, because of the special geographical location of three ISR (incoherent scatter radar), the first-order and the second-order ionospheric delay errors are calculated and discussed; the paper also shows and analyzes the diurnal, seasonal, semi-annual variation of ionospheric delay error with respect to signal direction. Results show that for the L1 signal path, the first-order ionospheric delay error is the largest near the equator, which is circa 7 m; the maximum second-order ionospheric delay error are circa 0.6 cm, 0.8 cm and 0.6 cm respectively for L1 signals coming from the zenith, the north and the south at 10 degree elevation angles. The second-order ionospheric delay error on the L1 signal path from zenith are the symmetry between 15° and ˜15° with respect to magnetic equator, and are nearly zero at the magnetic equator. For the first time, the second-order ionospheric delay error on the global scale is presented, so this research will greatly contribute to analysing the higher-order ionospheric delay error characteristics on the global scale.

  13. 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.

  14. Ionospheric effects upon a satellite navigation system at Mars

    NASA Astrophysics Data System (ADS)

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

    2004-04-01

    Trans-ionospheric radio propagation effects resulting in ranging errors are examined for a potential orbital network of communications and navigational satellites at Mars. Using recent results from the radio science experiment on board the Mars Global Surveyor (MGS) spacecraft and a photochemical model of Mars' ionosphere, we study the total electron content (TEC) at Mars to investigate how its latitude, local time, and solar cycle patterns would contribute to errors in positioning on the planet. In addition, we examine the relationship between TEC and peak density (Nmax) and find that their ratio, called the equivalent slab thickness, shows that integral preserving distortions of the Ne(h) profile can be rather substantial, implying that neutral atmosphere dynamics can have strong effects upon Mars' photochemical ionosphere. We use MGS observations to validate modeling results and determine the extreme cases for TEC at Mars (i.e., when the planet is at perihelion during solar maximum years and at aphelion during solar minimum years). If a proposed Mars Communication and Navigation (MC&N) System used UHF/L-band (1-2 GHz) transmission frequencies similar to those used for the terrestrial Global Positioning System (GPS) satellites, upper limits to the magnitude and variability of the martian ionosphere (TEC < ~few × 1016 el m-2, with ? ~ 10%) would not be of concern unless extremely precise positional information were required (<1 m). The impact of the ionosphere would be greater along slanted ray paths, and especially if lower frequency UHF beacon frequencies (e.g., 400 MHz) were selected for use. Indeed, such effects could be used as a diagnostic for the global structure of Mars' ionosphere, much in the same way as GPS measurements are used in terrestrial ionospheric physics.

  15. Magnetosphere-ionosphere coupling currents in Jupiter's middle magnetosphere: effect of magnetosphere-ionosphere decoupling by field-aligned auroral voltages

    NASA Astrophysics Data System (ADS)

    Nichols, J. D.; Cowley, S. W. H.

    2005-03-01

    We consider the effect of field-aligned voltages on the magnetosphere-ionosphere coupling current system associated with the breakdown of rigid corotation of equatorial plasma in Jupiter's middle magnetosphere. Previous analyses have assumed perfect mapping of the electric field and flow along equipotential field lines between the equatorial plane and the ionosphere, whereas it has been shown that substantial field-aligned voltages must exist to drive the field-aligned currents associated with the main auroral oval. The effect of these field-aligned voltages is to decouple the flow of the equatorial and ionospheric plasma, such that their angular velocities are in general different from each other. In this paper we self-consistently include the field-aligned voltages in computing the plasma flows and currents in the system. A third order differential equation is derived for the ionospheric plasma angular velocity, and a power series solution obtained which reduces to previous solutions in the limit that the field-aligned voltage is small. Results are obtained to second order in the power series, and are compared to the original zeroth order results with no parallel voltage. We find that for system parameters appropriate to Jupiter the effect of the field-aligned voltages on the solutions is small, thus validating the results of previously-published analyses.

  16. Thermodynamic effect of the ion sound instability in the ionosphere

    NASA Technical Reports Server (NTRS)

    Khazanov, G. V.; Gombosi, T. I.; Gorbachev, O. A.; Trukhan, A. A.; Miller, R. H.

    1994-01-01

    During geomagnetic disturbances when the ring current interacts intensely with the plasmasphere, the plasma of this region undergoes a strong heating due to an ion cyclotron instability. This is followed by the transfer of heat along geomagnetic field lines from the heating region to the ionosphere. One of the results of this process is the formation of non-isothermal region (in which T(sub e) greater than 3.4 T(sub i) at ionospheric heights) caused by a rapid cooling the H(+) ions due to their resonant charge exchange with neutral hydrogen. Heat transfer from the top of the flux tube to the ionosphere is investigated using a hydrodynamic model for the ionosphere-plasmasphere coupling. Field-aligned currents, present in the topside ionosphere, are often accompanied by ion sound turbulence. The turbulence scatters electrons, increasing the total electron collision frequency through wave-particle effects. The influence of wave-particle interactions introduces an anomalous component to the total collision frequency, which modifies substantially the heat conduction coefficient of the plasma. As a result, the plasma is heated more intensely above than below this region of ion sound turbulence.

  17. Irregularities in ionospheric plasma clouds: Their evolution and effect on radio communication

    NASA Astrophysics Data System (ADS)

    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.

  18. Numerical simulation of the effects of a solar energetic particle event on the ionosphere of Mars

    E-print Network

    Withers, Paul

    Numerical simulation of the effects of a solar energetic particle event on the ionosphere of Mars. [1] We investigate the ionospheric effects of a solar energetic particle (SEP) event at Mars, specifically the 29 September 1989 event. We use its energy spectrum and a steady state ionospheric model

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

    E-print Network

    Stanford University

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

  20. Modeling of multiple effects of atmospheric tides on the ionosphere: An examination of possible coupling

    E-print Network

    California at Berkeley, University of

    Click Here for Full Article Modeling of multiple effects of atmospheric tides on the ionosphere ionosphere S. L. England,1 T. J. Immel,1 J. D. Huba,2 M. E. Hagan,3 A. Maute,3 and R. DeMajistre4 Received 10 in the thermosphere and the electron density structure of the ionosphere. The most commonly proposed mechanism

  1. Verification of Low Latitude Ionosphere Effects on WAAS During October 2003 Geomagnetic

    E-print Network

    Stanford University

    Verification of Low Latitude Ionosphere Effects on WAAS During October 2003 Geomagnetic Storm S one of the strongest geomagnetic and ionospheric storms of the solar cycle. WAAS user integrity density region was as much as 60 TECU (about 10 m delay at L1) higher than the surrounding ionosphere

  2. Ionospheric effects of sudden stratospheric warmings in eastern Siberia region

    NASA Astrophysics Data System (ADS)

    Polyakova, A. S.; Chernigovskaya, M. A.; Perevalova, N. P.

    2014-12-01

    Ionospheric effects observed in Russia's Asia region during sudden stratospheric warmings (SSWs) in the winters 2008/2009 and 2012/2013 corresponding to both extreme solar minimum and moderate solar maximum conditions have been examined. To detect the ionospheric effects which must have been induced by the SSWs, we have carried out a joint analysis of total electron content (TEC) global ionospheric maps (GIM), MLS (Microwave Limb Sounder, EOS Aura) measurements of vertical temperature profiles, as well as NCEP/NCAR and UKMO Reanalysis data. It has been revealed for the first time that during strong SSWs the amplitude of diurnal variation of TEC decreases nearly by half in the mid-latitude ionosphere. Besides, the intensity of TEC deviations from the background level increases during SSWs. It has also revealed that during SSW peak the midday TEC maximum considerably decreases, and the night/morning TEC increases compared to quiet days. The pattern of TEC response to SSW is shown to be identical for both quiet and disturbed geophysical conditions.

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

    NASA Astrophysics Data System (ADS)

    Maruyama, Takashi; Jin, Hidekatsu

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

  4. 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.

  5. Simulation of PPEF effects in dayside low-latitude ionosphere for the October 30, 2003, Superstorm

    NASA Astrophysics Data System (ADS)

    Verkhoglyadova, Olga P.; Tsurutani, Bruce T.; Mannucci, Anthony J.; Saito, Akinori; Araki, Tohru; Anderson, David; Abdu, M.; Sobral, J. H. A.

    One of the important signatures during strong magnetic storms is prompt penetrating electric fields (PPEFs) into the ionosphere, which causes the dayside ionospheric superfountain (DIS). Interplanetary-ionosphere coupling for the October 30, 2003, superstorm is analyzed by using ACE and ground-based measurements. The relationships between the interplanetary magnetic field Bz component, ionospheric vertical velocities above Jicamarca, and horizontal magnetic field components measured at Huancayo are presented. DIS is associated with uplift, displacement, and enhancement of the equatorial ionospheric anomalies. We apply an extended SAMI-2 ionospheric model to simulate DIS effects above Jicamarca for this superstorm. An agreement between our results and observed ƒ0F2 during the main phase of the storm is reported. It is shown that the PPEF approach and corresponding modeling results capture the main physics of the dayside low-latitude ionospheric response during the first couple hours of the magnetic superstorm.

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

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

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

  7. On the principal factors that determine ionospheric superstorms effects

    NASA Astrophysics Data System (ADS)

    Astafyeva, E.; Tatarinov, P.

    2009-04-01

    Ionosphere response to geomagnetic storms, known as ionospheric storms, is a very interesting geophysical event. The most prominent effects produced by intense geomagnetic storms at middle and low-latitudes is dayside ionosphere uplift with concurrent movements of the equatorial ionization anomaly (EIA) crests and anomalously strong TEC increase within the crests of the EIA. However, such significant dayside ionosphere changes were observed during only a few geomagnetic storms for the previous solar cycle. In connection with that, a very interesting question has been opened: what are the most important reasons for the drastic ionosphere changes to be developed and whether there is a "preferred" geographic longitude for the formation and occurrence of ionosphere superstorm effects? It is known that the primary cause of geomagnetic storms and the dayside ionosphere uplift are dawn-to-dusk electric fields associated with the passage of southward directed IMF Bz. Generally speaking, the electric field is composed of two factors: the solar wind velocity and the southward IMF. It has been empirically shown that intense storms with a peak Dst<-100 nT are primarily caused by large Bz<-10 nT with duration greater than 3 hours (Gonzalez and Tsurutani, Planetary and Space Science, 35, 9, 1987). In addition, the electric fields seem to be modulated by the solar wind ram pressure, so that solar wind density, besides Bz IMF and solar wind velocity, plays an important role in the ring current intensification. For this study, from geomagnetic storms that occurred in 2000-2005, we selected those with sharp decrease of IMF Bz below -12-15 nT of duration about 3 hours and with the consequent drop of Dst index to no more than -120-150 nT. The selected 18 events vary in season by their occurrence and in time by a storm onset, so we can analyze seasonal and longitudinal features of TEC response to geomagnetic storms and discuss possible reasons for the observed difference in TEC response to geomagnetic storms. We used data of the CHAMP and SAC-C satellites along with data of satellite altimeters TOPEX and Jason-1. As a result, we obtained 3-dimensional visualization of the ionosphere plasma redistribution during strong geomagnetic storms and good possibility to study in detail the dayside "super-fountain effect" (SFE). We observed severe enhancements of the equatorial TEC (up to 50-60%) with concurrent traveling of the EIA crests for a distance up to 15° of latitude during the "Halloween storms" of 29-31 October 2003 and during intense geomagnetic storms of 21 October 2001, 6 November 2001, 7-8 September 2002 and 20 November 2003. These events were accompanied by increase of TEC above 715 km 2-3 times compared to quiet-time TEC level. Large enhancements in the equatorial and mid-latitude TEC were observed also during events of 30-31 March 2001, 19-20 April 2002 and 7-8 November 2004. However, TEC response to the other of the selected events was not so well pronounced: generally, we observed formation of the dual-peak EIA structure with concurrent increase of the near-equatorial TEC up to 80 TECU. However, the peaks did not travel far from each other, i.e. were located within their normal position.

  8. 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.

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

    PubMed

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

    2006-02-24

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

  10. 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.

  11. Studing Solar Flare Effects on Ionosphere Using AWESOME Receiver

    NASA Astrophysics Data System (ADS)

    Mustafa, Famil; Babayev, Elchin; Alekperov, Ilgar

    2015-08-01

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

  12. Effect of Ionospheric Electron Density on the Amplitude of Field Line Resonances

    NASA Astrophysics Data System (ADS)

    Menk, F. W.; Sciffer, M. D.; Dupont, M.; Townsend, C.

    2012-12-01

    Ultra-low frequency (ULF) field line resonances are recorded on the ground because shear Alfvén mode waves are reflected at the ionosphere, allowing the formation of standing field line eigenoscillations. For detection at the ground, ULF wave energy must also pass through the ionosphere and atmosphere. We may expect that the ionospheric conductance affects the propagation of ULF waves and hence the amplitude of field line resonances at the ground. However, few studies of this effect have been reported. Here we describe a combined theoretical and observational study of the effect of ionospheric electron density on FLR amplitude at the ground. We use the one-dimensional model of ULF wave propagation through the ionosphere by Sciffer et al. (2005) to determine wave amplitude and phase and conductance profiles for a range of conditions (time, season, latitude, solar F10.7 flux) incorporating input data from the empirical IRI, MSIS and IGRF ionospheric, atmospheric and magnetic field models. We also examine ground magnetometer and ionospheric electron density data from a range of locations, and compare the observed variation in electron density in the ionospheric F and E regions with the FLR amplitude for specific days and on a statistical basis. We find that high electron densities in the F region, and in particular in the E region, for example associated with sporadic E, reduce the amplitude of the FLR amplitude on the ground as a result of the enhanced ionospheric conductance.

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

    E-print Network

    Withers, Paul

    Space weather effects on the Mars ionosphere due to solar flares and meteors P. Withers (1), M observed two aspects of space weather at Mars. Following solar flares of both moderate to strong magnitude the simultaneous responses of the ionospheres of Earth and Mars to solar flares, highlighting the importance

  14. Ionospheric effects upon a satellite navigation system at Mars Michael Mendillo,1

    E-print Network

    Mendillo, Michael

    modeling results and determine the extreme cases for TEC at Mars (i.e., when the planet is at perihelion Planetology: Solar System Objects: Mars; 5435 Planetology: Solid Surface Planets: Ionospheres (2459); 5494Ionospheric effects upon a satellite navigation system at Mars Michael Mendillo,1 Xiaoqing Pi,2

  15. On the effect of near-equatorial thunderstorms on the global distribution of ionospheric potential

    E-print Network

    Michigan, University of

    On the effect of near-equatorial thunderstorms on the global distribution of ionospheric potential examination of the hypothesis that electric currents flowing up from thunderstorms to the ionosphere (also thunderstorm regions over equatorial Asia/Oceania, Africa and the Americas. We compare the local time variation

  16. Stability of a cometary ionosphere/ionopause including pressure effects

    SciTech Connect

    Mckenzie, J.F.; Axford, W.I.; Ershkovich, A.I. Tel Aviv Univ. )

    1990-09-01

    The stability analysis by Ershkovich, McKenzie, and Axford of a cometary ionosphere/ionopause determined by ion-neutral friction is extended to include the effects of finite plasma pressure. It is shown that, from a formal viewpoint, the inclusion of pressure effects leaves intact the sufficient condition for instability. Application of the results to Comet Halley demonstrates that plasma pressure reduces the instability growth rate of the cavity and therefore that the boundary should not be expected to exhibit any significant mixing arising from overturning. The generalization to include plasma pressure is applicable to a wider range of physical parameters than is available at Halley and is of interest to other comets, particularly during periods of high solar activity. 12 refs.

  17. A first look at the effects of ionospheric signal bending on a globally processed GPS network

    NASA Astrophysics Data System (ADS)

    Petrie, Elizabeth J.; King, Matt A.; Moore, Philip; Lavallée, David A.

    2010-08-01

    This study provides a first attempt at quantifying potential signal bending effects on the GPS reference frame, coordinates and zenith tropospheric delays (ZTDs). To do this, we homogeneously reanalysed data from a global network of GPS sites spanning 14 years (1995.0-2009.0). Satellite, Earth orientation, tropospheric and ground station coordinate parameters were all estimated. We tested the effect of geometric bending and dTEC bending corrections, which were modelled at the observation level based, in part, on parameters from the International Reference Ionosphere 2007 model. Combined, the two bending corrections appear to have a minimal effect on site coordinates and ZTDs except for low latitude sites. Considering five days (DOY 301-305, 28 October-1 November 2001) near ionospheric maximum in detail, they affect mean ZTDs by up to ~1.7 mm at low latitudes, reducing to negligible levels at high latitudes. Examining the effect on coordinates in terms of power-spectra revealed the difference to be almost entirely white noise, with noise amplitude ranging from 0.3 mm (high latitudes) to 2.4 mm (low latitudes). The limited effect on station coordinates is probably due to the similarity in the elevation dependence of the bending term with that of tropospheric mapping functions. The smoothed z-translation from the GPS reference frame to ITRF2005 changes by less than 2 mm, though the effect combines positively with that from the second order ionospheric refractive index term. We conclude that, at the present time, and for most practical purposes, the geometric and dTEC bending corrections are probably negligible at current GPS/reference frame precisions.

  18. Comparison of space weather effects and tectonic activity effects on the ionosphere and levels of their predictability.

    NASA Astrophysics Data System (ADS)

    Pulinets, Sergey; Davidenko, Dmitry

    2014-05-01

    Space weather produces profound effects on the ionosphere at the all levels (from D-region up to the palsmasphere). Except the electron concentration redistribution (what is most often discussed in the literature) we deal with the changes of ion composition, heating of the ionosphere what leads to the scale height vertical profile modification. Serious problems of these effects which have many space and terrestrial technological systems put forward the problem of space weather effects predictability the quality of which in the present moment is not high in different models. Recent years presented the reliable proofs that tectonic activity may produce the local effects within the ionosphere, but their order of magnitude can be the same as during geomagnetic storms, and sometimes even higher. It means that technological systems are prone to the degradation of their quality during disturbed periods. This paper tries to present the comparison of both types of disturbances in terms of their temporal, spatial and dynamic characteristics and to analyze the probability of their forecast.

  19. Swarm Modelling studies of the magnetic effect of low-latitude ionospheric F region currents

    NASA Astrophysics Data System (ADS)

    Stolle, C.; Lühr, H.; Förster, M.; Aylward, A.; Spain, T.; Aruliah, A.; Haagmans, R.; Plank, G.

    2009-04-01

    High-resolution magnetic field measurements of the CHAMP satellite have provided evidence that there are considerable currents flowing at F region altitude even during the night when Hall and Pedersen conductivities are very small. The plasma pressure gradient (Lühr et al., 2003) and the Earth's gravity (Maus and Lühr, 2006) have been suggested as dominant forces driving these currents. In order to assess the impact of such currents at low and mid latitudes on Swarm magnetic field measurements, an ESA-sponsored model study was performed. With the help of the Coupled Thermosphere-Ionosphere-Plasmasphere (CTIP) model representative ionospheric conditions were simulated. Based on this "simulated world" environment the distribution of the various current types was calculated and the magnetic effects along representative Swarm orbits estimated. The results are largely consistent with the propositions derived from CHAMP observations. For the first time, the spatial and local time distribution of the F region currents has been made visible on global scale. On the night side, strongest currents are found in the height range 300 to 600 km. Under solar maximum conditions magnetic effects of the order of 5 nT are obtained. With the help of the simulated environment it is possible to investigate the different current components independently. A very promising result is that the magnetic effect of the plasma pressure gradient currents can effectively be corrected by the approach proposed by Lühr et al. (2003).

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

    NASA Astrophysics Data System (ADS)

    Benson, Robert F.; Osherovich, Vladimir A.

    1992-12-01

    The paper presents Alouette 2/ISIS 1 data which furnish evidence for the stimulation of high-order D(n) resonances (n greater than 4) by topside sounders, confirming the prediction of Osherovich (1990) based on an analogy with naturally occurring narrowband magnetospheric emissions. The results indicate that observations of stimulated ionospheric emissions and naturally occurring magnetospheric emissions can be used as complementary data sets to address such fundamental questions as the nature of the excitation mechanism for these emissions and the nature of the waves (i.e., whether the waves predominantly electrostatic or with a significant magnetic component present), and the question of the dominance among the Dn, Dn(+), and Dn(-) resonances and the conditions required for all three to be present at the same time.

  1. Ionosphere Effects for Wideband GNSS Signals Grace Xingxin Gao, Seebany Datta-Barua, Todd Walter, and Per Enge

    E-print Network

    Gao, Grace Xingxin

    Ionosphere Effects for Wideband GNSS Signals Grace Xingxin Gao, Seebany Datta-Barua, Todd Walter to 1215 MHz, over 25 times the two-sided bandwidth of the GPS C/A code. However, because the ionosphere the upper atmosphere. Signal delay due to refraction through the ionosphere is the largest and most variable

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

    E-print Network

    California at Berkeley, University of

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-10-01

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

  4. Finite Larmor Radius Effects on the Ionosphere Interchange Instabilities: A Gyrofluid Approach

    NASA Astrophysics Data System (ADS)

    Despain, K. M.; Huba, J. D.

    2012-12-01

    Ionospheric irregularities responsible for the scintillation of radio waves and radar backscatter have scale lengths in the range of 10s-100s of m. At these scales, finite Larmor radius (FLR) effects can become important and affect the evolution of ionospheric instabilities. Standard electrostatic models with FLR effects are only valid down to scale lengths approaching the ion gyroradius. To extend our investigation to smaller scales, we use a gyrofluid model appropriate for ionospheric conditions. We will present nonlinear simulation results from both models which highlight these effects.

  5. 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.

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

    NASA Technical Reports Server (NTRS)

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

    1984-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2012-04-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

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

  9. 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.

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

    NASA Astrophysics Data System (ADS)

    Moses, Ronald W., Jr.

    2004-05-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  12. Stochastic modelling considering ionospheric scintillation effects on GNSS relative and point positioning

    NASA Astrophysics Data System (ADS)

    da Silva, Heloísa Alves; de Oliveira Camargo, Paulo; Galera Monico, João Francisco; Aquino, Marcio; Marques, Haroldo Antonio; de Franceschi, Giorgiana; Dodson, Alan

    2010-05-01

    Global Navigation Satellite Systems (GNSS), in particular the Global Positioning System (GPS), have been widely used for high accuracy geodetic positioning. The Least Squares functional models related to the GNSS observables have been more extensively studied than the corresponding stochastic models, given that the development of the latter is significantly more complex. As a result, a simplified stochastic model is often used in GNSS positioning, which assumes that all the GNSS observables are statistically independent and of the same quality, i.e. a similar variance is assigned indiscriminately to all of the measurements. However, the definition of the stochastic model may be approached from a more detailed perspective, considering specific effects affecting each observable individually, as for example the effects of ionospheric scintillation. These effects relate to phase and amplitude fluctuations in the satellites signals that occur due to diffraction on electron density irregularities in the ionosphere and are particularly relevant at equatorial and high latitude regions, especially during periods of high solar activity. As a consequence, degraded measurement quality and poorer positioning accuracy may result. This paper takes advantage of the availability of specially designed GNSS receivers that provide parameters indicating the level of phase and amplitude scintillation on the signals, which therefore can be used to mitigate these effects through suitable improvements in the least squares stochastic model. The stochastic model considering ionospheric scintillation effects has been implemented following the approach described in Aquino et al. (2009), which is based on the computation of weights derived from the scintillation sensitive receiver tacking models of Conker et al. (2003). The methodology and algorithms to account for these effects in the stochastic model are described and results of experiments where GPS data were processed in both a relative and a point positioning mode are presented and discussed. Two programs have been developed to enable the analyses: GPSeq (currently under development at the FCT/UNESP Sao Paulo State University - Brazil) and PP_Sc (developed in a collaborative project between FCT/UNESP and Nottingham University - UK). The point positioning approach is based on an epoch by epoch solution, whereas the relative positioning on an accumulated solution using a Kalman Filter and the LAMBDA method to solve the Double Differences ambiguities. Additionally to the use of an improved stochastic model, all data processing in this paper were performed using an option implemented in both programs, to estimate, for each observable, an individual ionospheric parameter modelled as a stochastic process, using either the white noise or the random walk correlation models. Data from a network of GPS Ionospheric Scintillation and TEC Monitor (GISTM) receivers set up in Northern Europe as part of the ISACCO project (De Franceschi et al., 2006) were used in the experiments. The point positioning results have shown improvements of the order of 45% in height accuracy when the proposed stochastic model is applied. In the static relative positioning, improvements of the order of 50%, also in height accuracy, have been reached under moderate to strong scintillation conditions. These and further results are discussed in this paper.

  13. Effects of prolonged southward interplanetary magnetic field on low-latitude ionospheric electron density

    NASA Astrophysics Data System (ADS)

    Bagiya, Mala S.; Hazarika, Rumajyoti; Laskar, Fazlul I.; Sunda, Surendra; Gurubaran, S.; Chakrabarty, D.; Bhuyan, P. K.; Sridharan, R.; Veenadhari, B.; Pallamraju, D.

    2014-07-01

    The present work describes the low-latitude ionospheric variability during an unusually prolonged (~33 h) geomagnetically disturbed condition that prevailed during 15-16 July 2012. The low-latitude electron density in summer hemisphere, investigated using ground- and satellite-based observations, responded to this by generating strong negative ionospheric storm on 16 July. The maximum electron density on 16 July over Indian low latitudes was reduced by more than 50% compared to that on a geomagnetically quiet day (14 July 2012). In contrast to the extreme reduction in total electron content (TEC) in the Northern Hemisphere, TEC from a winter hemispheric station revealed substantial (~23 total electron content unit, 1 TECU = 1016 el m-2) enhancements on the same day. This contrasting hemispherical response in TEC is suggested to be due to the combined effects of strong interhemispheric and solar-driven day-night winds. Further, very weak equatorial electrojet (EEJ) strength on 16 July indicated that the westward electric field perturbations in the low-latitude ionosphere were possibly due to the disturbance dynamo effect associated with meridional circulation from polar to equatorial latitudes. Interestingly, despite reduction in the integrated EEJ strength on 15 July, the low-latitude electron density showed substantial enhancement, highlighting the significant effect of the positive ionospheric storm on the low-latitude ionosphere. The roles of electrodynamical/neutral-dynamical and compositional disturbances are discussed in view of these observations to understand low-latitude ionospheric response when geomagnetic disturbance persists for longer duration.

  14. 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.

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

    NASA Technical Reports Server (NTRS)

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

    1978-01-01

    Ionospheric range and range rate corrections in satellite-to-satellite tracking were investigated and the magnitude of errors that have to be considered for communications between satellites and related experiments was defined. The major causes of the sudden and sometimes large variations apparent in the ionospheric range and range rate corrections along the satellite arc are the geometric effects of the raypath and the curved ionosphere, and the localized perturbations in electron density along the satellite-to-satellite line of sight. Ionospheric tracking errors are greatly effected by the following parameters, whose influence was thoroughly investigated: satellite height, height of maximum electron density, localized ionospheric perturbations and gradients, and electron density variations with diurnal, day-to-day, seasonal, and solar cycle patterns. The results point to the need of using a sophisticated modeling approach incorporating daily solar data, and where possible actual ionospheric measurements as update information. Simulations were performed for satellites at various heights: Apollo, Geos, and Nimbus tracked by ATS-6; and in two different geometric configurations: coplanar and perpendicular orbits.

  16. 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.

  17. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

  20. 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.

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

    NASA Astrophysics Data System (ADS)

    Ruzhin, Yuri

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

  2. 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.

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

    E-print Network

    Loi, Shyeh Tjing; Bell, Martin E; Kaplan, David L; Lenc, Emil; Offringa, Andre 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

    2015-01-01

    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 hours of data observed over 10 nights under quiet geomagnetic conditions (global storm index Kp < 2), analysing the behaviour of short-timescale 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 ...

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

    E-print Network

    California at Berkeley, University of

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

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

    NASA Astrophysics Data System (ADS)

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

    2012-07-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

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

    NASA Astrophysics Data System (ADS)

    Burns, Alan; Killeen, Timothy

    1993-02-01

    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.

  8. Effect of atmospheric tides on the morphology of the quiet time, postsunset equatorial ionospheric anomaly

    E-print Network

    Mende, Stephen B.

    Effect of atmospheric tides on the morphology of the quiet time, postsunset equatorial ionospheric,it isshownthatthepredictedmodulationofthedaysidethermosphericwindsandtemperaturesat E region altitudes created by non-migrating diurnal tides can explain the modulation understanding of atmospheric tides on a global scale. Citation: England, S. L., T. J. Immel, E. Sagawa, S. B

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

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

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

  10. Ionospheric disturbance overview

    NASA Technical Reports Server (NTRS)

    Rush, C. M.

    1980-01-01

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

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

    E-print Network

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

  13. Disturbance Effects Seen in the Midlatitude Ionosphere with SuperDARN

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  14. 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.

  15. Interplanetary magnetic field effects on high latitude ionospheric convection

    NASA Technical Reports Server (NTRS)

    Heelis, R. A.

    1985-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2010-08-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-09-01

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

  18. 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.

  19. Magnetic zenith effect in the ionospheric modification by an X-mode HF heater wave

    NASA Astrophysics Data System (ADS)

    Blagoveshchenskaya, N. F.; Borisova, T. D.; Haggstrom, I.; Rietveld, M. T.; Yeoman, T. K.

    2013-12-01

    We report experimental results aimed at an investigation of the magnetic zenith effect in the high latitude ionosphere F region from ionospheric modification by powerful HF heater wave with X-polarization. The ionospheric modification was produced by the HF heating facility at Tromsø (Norway) using the phased array with a narrow beam with of 6 degrees. Effective radiated power was varied between 450 and 1000 MW. The HF pump wave radiated in different directions relative to the magnetic field from 90 degrees (vertical) to 78 degrees (magnetic zenith) at frequencies near or above the ordinary-mode critical frequency. The response of the ionosphere plasma to the HF pump wave impact was checked by the UHF incoherent scatter radar located in the immediate vicinity of the HF heater. UHF radar was probing the plasma parameters, such as electron density and temperature (Ne and Te), HF-induced plasma and ion lines in the altitude range from 90 to 600 km. It was running in a scanning mode when UHF radar look angles were changed from 74 to 90 degrees by 1 or 2 degree step. It was clearly demonstrated that the strongest heater-induced effects took place in the magnetic field-aligned direction when HF pointing was also to the magnetic zenith. It was found that strong Ne enhancement of up to 80 % along magnetic field (artificial density ducts) were excited only under HF pumping towards magnetic zenith. The width of the artificial ducts comes to only 2 degrees. The Ne increases were accompanied by the Te enhancements of up to about 50 %. Less pronounced Te increases were also observed in the directions of 84 and 90 degrees. Strong Ne enhancements can be accompanied by excitation of strong HF-induced plasma and ion lines. Thus experimental results obtained points to the strong magnetic zenith effect due to self-focusing powerful HF radio wave with X-mode polarization.

  20. Effect of H2 on the Martian ionosphere: Implications for atmospheric evolution

    NASA Astrophysics Data System (ADS)

    Fox, J. L.

    2003-06-01

    Because H2 reacts efficiently with O+, CO2+, CO+, and N2+, the molecular hydrogen abundance assumed in models of the Martian ionosphere greatly affects the high altitude density profiles of these ions. We have found that models of the low solar activity Martian ionosphere exhibit much smaller O+ densities than the measured values if the adopted H2 abundance is of the order of 40 ppm, the value proposed in a 1998 model of the Martian atmosphere. For a model based on the recently measured H2 abundance of 15 ppm [, 2001a, 2001b], the O+ densities are closer to, but still somewhat less than the Viking densities. The O+ peak densities of ˜600-750 cm-3 measured by the retarding potential analyzers on Vikings 1 and 2 [, 1977] are best reproduced with H2 abundances less than ˜4 ppm. We have investigated the effect of various H2 mixing ratios at the lower boundary of our model, and we find that the high altitude densities of O+, CO2+, CO+, and N2+ ions decrease as the H2 abundance increases, and are much less for H2 mixing ratios greater than 4 ppm than previous models have shown. Moreover, the photochemical escape rates of heavy atoms, such as C and N that are due to reactions of these ions, are also reduced. The Martian atmosphere was probably more reducing in past epochs, and therefore consisted of a larger fraction of H2. As the abundance of H2 increases, the composition of the exosphere will also be altered, and the altitude of the exobase will rise. At very large mixing ratios, H and H2 could potentially dominate the absorption of EUV radiation. Thus the escape of species by other photochemical mechanisms such as photodissociation and photodissociative ionization could also be reduced. If so, the nonthermal escape rates of heavy atoms in past epochs may have been much lower than previous estimates in which it is assumed that the oxidation state of the Martian atmosphere has remained constant over time.

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

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

    NASA Technical Reports Server (NTRS)

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

    2001-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  4. Implementation of Inductive Magnetosphere-Ionosphere Coupling and its Effects on Global MHD Magnetospheric Simulations

    NASA Astrophysics Data System (ADS)

    Xi, S.; Lotko, W.; Zhang, B.; Brambles, O.; Wiltberger, M. J.; Lyon, J.; Merkin, V. G.

    2010-12-01

    In global modeling, magnetosphere-ionosphere (MI) coupling physically connects a global magnetospheric (GM) model and a global ionospheric-thermospheric (GIT) model. The field-aligned current from the GM model and the conductance distributions from the GIT model are used in a Poisson equation derived from the ionospheric Ohm's law combined with current continuity to determine the electrostatic potential in the ionosphere. In current GM models, this electrostatic potential is mapped to the inner boundary of the GM simulation to determine electrostatic boundary conditions on the electric field and MHD velocity there. Inductive effects and the finite Alfven transit time between the low-altitude GM boundary and the high-altitude GIT boundary (MI gap region) are neglected in this formulation of MI coupling. Using fields and currents derived from Lyon-Fedder-Mobarry GM simulations, and conductance distributions derived from its standalone empirical conductance model in the MI coupling Poisson equation, we have computed the fast Fourier transform of the electrostatic field at the low-altitude LFM simulation boundary as described above, and the FFT of the inductive electric field at the boundary under the assumption that ? 0 ? P vA ? 1, where ? P is the ionospheric Pedersen conductance and vA is the smallest value of the Alfven speed in the MI gap region. In this regime, the complete electric field at the low-altitude simulation boundary includes the usual mapped electrostatic field with an inductive addition for which the finite Alfven transit time and the diversion of field-aligned into polarization currents in the gap region are negligible (Lotko, 2004). By comparing the boundary-averaged spectra of the electrostatic and so-determined inductive fields, we confirm that the purely electrostatic formulation of MI coupling is valid when the MHD state varies on times scales exceeding about 200 s. For faster MHD time variations, the inductive electric field is shown to be larger than the electrostatic field at the low-altitude boundary and is thus non-negligible. For example, inductive corrections are expected to be important for sudden impulse events and substorm-related Pi2 fluctuations. We are currently implementing the inductive MI coupling algorithm of Lotko (2004) in the LFM global simulation. Lotko, W. (2004), Inductive magnetosphere-ionosphere coupling, JASTP 66, 1443-1456.

  5. The effect of 20 May 2012 annular solar eclipse on the ionosphere

    NASA Astrophysics Data System (ADS)

    Lo, C.; Liu, J. G.

    2012-12-01

    The 20 May 2012 annular solar eclipse crossed the mid-latitude ionosphere of Southeast China, Taiwan, Japan, and America West. The total electron content (TEC) derived from ground-based GPS receivers and frequency shifts recorded by Doppler sounding systems in Taiwan are employed to monitor the eclipse signatures. We compare the two observations on the eclipse day and those recorded 1-5 days before to find the associated eclipse effects. Results show that Doppler shifts yield negative values after the first contact but positive values after the third contact. The TECs variations and their time rate of changes are used to observe simultaneous responses of the ionosphere plasma density and soft Doppler during the annular solar eclipse.

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

    NASA Astrophysics Data System (ADS)

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

    2015-07-01

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

  7. 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.

  8. A re-analysis of the atmospheric and ionospheric effects of the Flixborough explosion

    NASA Astrophysics Data System (ADS)

    Krasnov, V. M.; Drobzheva, Ya. V.; Venart, J. E. S.; Lastovicka, J.

    2003-07-01

    The ionospheric record of the 1974 cyclohexane vapour cloud explosion (VCE) accident near Flixborough is re-examined in light of a new theory used to describe the acoustic field in the atmosphere and ionosphere caused by explosions on the ground. The reconstructed oblique Doppler sounding records from six radio traces agree remarkably well with experimental results when a ground source explosion yield of 283+/-38tons of TNT is utilized. This result, when compared to the detonation of large hydrocarbon fuel-drop-air clouds, suggests that only 14+/-2tons of cyclohexane was involved in the explosion. Additionally the time of the explosion determined from the model, 15:52:08+/-6, agrees, within the mutual uncertainty, with that determined seismically, 15:52:15.5+/-2 UT. The precision in the value of the yield and accuracy of the time of the explosion validates the model used to describe the propagation of acoustic waves by taking into account expansion, absorption, and non-linear and inhomogeneous effects in the atmosphere and ionosphere.

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

    SciTech Connect

    Siddiqui, M. U.; Gayetsky, L. E.; Mella, M. R.; Lynch, K. A.; Lessard, M. R.

    2011-09-15

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

  10. Testing Ionospheric Faraday Rotation Corrections in CASA

    NASA Astrophysics Data System (ADS)

    Kooi, Jason E.; Moellenbrock, George

    2015-04-01

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

  11. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-05-01

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

  13. Influence of ionospheric perturbations in GPS time and frequency transfer

    E-print Network

    Pireaux, Sophie; Wauters, Laurence; Bergeot, Nicolas; Baire, Quentin; Bruyninx, Carine; 10.1016/j.asr.2009.07.011

    2009-01-01

    The stability of GPS time and frequency transfer is limited by the fact that GPS signals travel through the ionosphere. In high precision geodetic time transfer (i.e. based on precise modeling of code and carrier phase GPS data), the so-called ionosphere-free combination of the code and carrier phase measurements made on the two frequencies is used to remove the first-order ionospheric effect. In this paper, we investigate the impact of residual second- and third-order ionospheric effects on geodetic time transfer solutions i.e. remote atomic clock comparisons based on GPS measurements, using the ATOMIUM software developed at the Royal Observatory of Belgium (ROB). The impact of third-order ionospheric effects was shown to be negligible, while for second-order effects, the tests performed on different time links and at different epochs show a small impact of the order of some picoseconds, on a quiet day, and up to more than 10 picoseconds in case of high ionospheric activity. The geomagnetic storm of the 30th...

  14. Statistical investigation of the saturation effect in the ionospheric foF2 versus sunspot, solar radio noise, and solar EUV radiation

    E-print Network

    Chen, Yuh-Ing

    radio noise, and solar EUV radiation J. Y. Liu Institute of Space Science and Center for Space are important for the saturation features. INDEX TERMS: 2479 Ionosphere: Solar radiation and cosmic ray effects: Solar radiation and cosmic ray effects; KEYWORDS: saturation effect, ionospheric foF2, sunspot number

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

    E-print Network

    Boneh, Dan

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

  16. 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.

  17. 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..

  18. 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.

  19. The Effects of Large Ionospheric Gradients on Single Frequency Airborne

    E-print Network

    Stanford University

    , the error can be significantly larger than the multipath errors the smoothing is intended to mitigate. Figu WAAS and LAAS receivers use carrier-smoothing filters to reduce the effects of multipath and thermal noise at the aircraft. For the majority of users this reduces the magnitude of the errors and leads

  20. The effect of ionospheric reflected noise on the performance of an orbital-debris radar system

    NASA Technical Reports Server (NTRS)

    Bishop, Dennis F.

    1991-01-01

    An orbital-debris radar system was designed to detect the presence of small objects in low earth orbit by reflecting radio waves off the objects. The author provides a rigorous derivation of the ionospheric reflected noise power and provides an integration over the complete pulse period. Free electrons and ions contained in the ionosphere cause incoherent scatter of the radar signal. This ionospheric reflection tends to increase the noise at the terrestrial radar receiver. A parameter called the ionospheric scattering cross section per unit volume, which is a function of altitude, is useful for computing the power of the ionospheric reflection signal. The Doppler frequency speed of the ionospheric reflected signal is a function of altitude also. The ionospheric noise of a 9-GHz orbital-debris radar receiver is computed using these concepts. Annual and diurnal variations of the noise are included.

  1. Effect of double layers on magnetosphere-ionosphere coupling

    NASA Technical Reports Server (NTRS)

    Lysak, Robert L.; Hudson, Mary K.

    1987-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  3. The effects of ionospheric outflow on ICME and SIR driven sawtooth events

    NASA Astrophysics Data System (ADS)

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

    2013-10-01

    Magnetosphere sawtooth oscillations have been observed during interplanetary coronal mass ejection (ICME) events, when the solar wind conditions are relatively steady, and during periods when the interplanetary magnetic field (IMF) fluctuates between northward and southward, as during interplanetary stream interaction regions (SIR). The impact of ionospheric outflow on the ICME-driven 18 April 2002 and SIR-driven 24 October 2002 sawtooth events is investigated using a multifluid adaptation of the Lyon-Fedder-Mobarry global simulation. The mechanisms that generate the sawtooth oscillations are investigated by comparing a baseline simulation without outflow and a simulation that includes an O+ outflow model. The ionospheric outflow is regulated by a statistical relationship between Alfvénic Poynting flux and O+ ion outflow flux. In the baseline simulation for the 18 April 2002 ICME-driven event, one substorm is observed that is generated by the southward turning of the IMF, after which the magnetosphere-ionosphere system settles into a quasi-steady convection mode. When outflow is included, quasi-periodic substorms are observed suggesting that the sawtooth oscillations are generated internally by the effects of the O+ ions. In contrast, during the 24 October 2002 SIR-driven event, quasi-periodic substorms are generated regardless of whether outflow is included or not. For this event, the generation and triggering of the substorms is controlled by the external driving of the solar wind. For both events, when outflow is included, the signatures of the substorms are more intense and are more noticeable across a wider range of local times than in the baseline simulations.

  4. Realtime Monitoring of Traveling Ionospheric Disturbances Caused by Tsunamis

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  5. 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.

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

    SciTech Connect

    Kang Cheng; Yinnnien Huang; Senwen Chen )

    1992-01-01

    The ionospheric responses to the solar eclipse of September 23, 1987, in the equatorial anomaly crest region have been investigated by using ionospheric vertical sounding, VLF propagation delay time, and differential Doppler shift data observed at Chungli, which is located near the northern equatorial anomaly crest region. It has been found that temporal variations of the F{sub 1} layer and D region are mainly controlled by local solar radiation. Quantitative analysis of the variations of the F{sub 1} layer critical frequency, F{sub o} F{sub 1}, shows that electrons are removed from the F{sub 1} layer through ionic recombination. However, the temporal variations of f{sub o}F{sub 2} and electron density above 200 km show that the variations o the F{sub 2} layer around the equatorial anomaly region are controlled not by local solar radiation but by solar radiation at the equator. The fountain effect plays an important role even during the solar eclipse. The VLF propagation time delay is controlled by the variations of average path obscuration. Atmospheric gravity waves produced by the moving bow wave front of the solar eclipse are found with a period around 17-23 min and wavelength about 293 km.

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1980-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-08-01

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

  11. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-09-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1991-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-08-01

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

  15. 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.

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

    E-print Network

    Withers, Paul

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

  17. Ionosphere Weighted GPS Cycle Ambiguity Resolution1

    E-print Network

    Calgary, University of

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

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

    SciTech Connect

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

    1981-01-01

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

  19. Ionosphere research

    NASA Technical Reports Server (NTRS)

    1976-01-01

    A report is presented on on-going research projects in ionospheric studies. The topics discussed are planetary atmospheres, E and F region, D region, mass spectrometer measurements, direct measurements and atmospheric reactions.

  20. Ionospheric research

    NASA Technical Reports Server (NTRS)

    1975-01-01

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

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

    E-print Network

    Michigan, University of

    in 10th International Ionospheric Effects Symposium, May 7-9, 2002, ed. J.M. Goodman, 364-371 1 1 Cameron, United Air Lines, Palo Alto, CA George Davenport, ARINC, Colorado Springs, CO John Goodman, Radio

  2. Ionosphere of Mars as seen by Mars Express. Effect of crustal fields

    NASA Astrophysics Data System (ADS)

    Dubinin, E.; Fraenz, M.; Andrews, D.; Witasse, O.; Barabash, S.

    2015-10-01

    The Martian ionosphere is studied using the local electron number densities and total electron content (TEC) derived from the observations onboard Mars Express. The data are complemented by the ASPER A-3 observations which provide us with the information about upward/downward velocity of the low-energy ions and electron precipitation. We consider 5 years of Mars Express observations at different solar cycle intervals. Different factors which influence the ionosphere dynamics are analyzed. The focus is made on a role of the crustal magnetic field on the Martian ionosphere.

  3. Order effects in dynamic semantics.

    PubMed

    Graben, Peter Beim

    2014-01-01

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

  4. 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

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. Magnetic declination and zonal wind effects on longitudinal differences of ionospheric electron density at midlatitudes

    NASA Astrophysics Data System (ADS)

    Zhang, Shun-Rong; Foster, John C.; Holt, John M.; Erickson, Philip J.; Coster, Anthea J.

    2012-08-01

    A prominent ionospheric longitudinal variation at midlatitudes, in particular, over the continental US, was found recently. This variation is characterized as a higher east-side electron density in the evening and a higher west-side electron density in the morning, and with clear seasonal and solar activity dependencies. A combined effect of geomagnetic declination and changing zonal winds was proposed to explain it. This paper represents a comprehensive investigation of this effect by examining climatology for both electron density longitudinal differences and the nighttime zonal winds in the eastern US. Electron density is from incoherent scatter radar extra-wide coverage experiments during 1978-2011 over Millstone Hill for which the spatial separation of the data can be up to 50° in longitude. The thermospheric zonal wind is from the on-site Fabry-Perot interferometer measurements during 1989-2001. The observed zonal wind climatology is found to be perfectly consistent with the expectation based on the east-west electron density differences in terms of local time, seasonal, and solar cycle dependencies. The correlation between the zonal wind and the east-west differential ratio is extremely high with an overall correlation coefficient of 0.93. The observed time delay of ˜3 hours in the response of electron density differences to zonal winds is a marked feature. Thus these results confirm positively the declination-zonal wind mechanism and provide new insight into longitudinal variations at midlatitudes for other geographic sectors.

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

    NASA Astrophysics Data System (ADS)

    Nina, A.; ?adež, V.; Šuli?, D.; Sre?kovi?, V.; Žigman, V.

    2012-05-01

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

  11. Solar effect on the Ionosphere/Thermosphere system obtained from the GAIM-Physics-Based Data Assimilation Model (GAIM-FP)

    NASA Astrophysics Data System (ADS)

    Scherliess, Ludger; Lomidze, Levan; Schunk, Robert

    Our ability to specify and forecast ionospheric dynamics and weather at low and mid latitudes is strongly limited by our current understanding of solar variability, the coupling processes in the ionosphere-thermosphere system and the coupling between the high and low latitude regions. Furthermore only a limited number of observations are available for a specification of ionospheric dynamics and weather at these latitudes. As shown by meteorologists and oceanographers, the best specification and weather models are physics-based data assimilation models that combine the observational data with our understanding of the physics of the environment. Therefore, we have developed and continue to develop four data assimilation models; two for the ionosphere, one for the high-latitude ionosphere dynamics, and one for the thermosphere. One of these models is the Global Assimilation of Ionospheric Measurements Full-Physics model (GAIM-FP). The model is based on an Ensemble Kalman filter technique and a physics-based model of the ionosphere/plasmasphere (IPM), which covers the altitude range from 90 to 20,000 km, includes six ion species, is based on the International Geomagnetic Reference Field (IGRF), and allows for inter-hemisphere flow. The model can assimilate bottom-side Ne profiles from ionosondes, slant TEC from ground-based GPS stations, in situ Ne from the DMSP satellites, occultation data from several satellites, and line-of-sight UV emissions measured by satellites. As an output the assimilation model provides the 3-dimensional density distribution throughout the ionosphere and information about the physical drivers, including the neutral winds, composition and electric fields. In the current application of the model we have assimilated a multitude of ground- and space-based ionospheric observations during the last solar minimum to specify the effects of solar variability on the low- and mid-latitude ionosphere/thermosphere. The model was used to determine the 3-dimensional ionospheric morphology and the various driving forces. We will present examples of the ionosphere weather and driver specifications obtained from our model runs with an emphasis on its relationship with solar variability.

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

    NASA Astrophysics Data System (ADS)

    Liu, J., Sr.

    2014-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

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

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

    SciTech Connect

    Merkin, V. G.

    2011-01-04

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

  15. Contribution of ionospheric irregularities to the error of dual-frequency GNSS positioning

    NASA Astrophysics Data System (ADS)

    Kim, B. C.; Tinin, M. V.

    2007-03-01

    This paper investigates the third-order residual range error in the dual-frequency correction of ionospheric effects on satellite navigation. We solve the two-point trajectory problem using the perturbation method to derive second-approximation formulas for the phase path of the wave propagating through an inhomogeneous ionosphere. It is shown that these formulas are consistent with the results derived from applying perturbation theory directly to the eikonal equation. The resulting expression for the phase path is used in calculating the residual range error of dual-frequency global positioning system (GPS) observations, in view of second- and third-order terms. The third-order correction includes not only the quadratic correction of the refractive index but also the correction for ray bending in an inhomogeneous ionosphere. Our calculations took into consideration that the ionosphere has regular large-scale irregularities, as well as smaller-scale random irregularities. Numerical examples show that geomagnetic field effects, which constitute a second-order correction, typically exceed the effects of the quadratic correction and the regular ionospheric inhomogeneity. The contribution from random irregularities can compare with or exceed that made by the second-order correction. Therefore, random ionospheric irregularities can make a significant (sometimes dominant) contribution to the residual range error.

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

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1977-01-01

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

  18. Hf propagation through actively modified ionospheres

    SciTech Connect

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

    1990-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Watkins, Brenton; Fallen, Christopher; Secan, James

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

  20. Effects of a magnetic cloud simultaneously observed on the equatorial ionosphere in midday and midnight sectors

    NASA Astrophysics Data System (ADS)

    Rastogi, R. G.; Chandra, H.; Das, A. C.; Sridharan, R.; Reinisch, B. W.; Ahmed, Khurshid

    2012-04-01

    An impact of a magnetic cloud on the Earth's magnetosphere occurred at 1636 UT on 25 June, 1998, associated with a sudden increase of the solar wind density and velocity, as well as a sudden increase of the zenithal component of the interplanetary magnetic field (IMF- B z). Following the impact of the magnetic cloud, IMF- B z was northward (10 nT) and remained steadily strong (about 15 nT) for the next six hours. IMF- B z turned southward at 2330 UT on 25 June, 1998, and remained strongly southward (-15 nT) for the next four hours. During the positive phase of IMF- B z, both the Auroral index and ring current index SYM/H remained steadily low indicating complete isolation of the Earth's magnetosphere from the solar wind and no significant changes were observed in the equatorial ionosphere. After the southward turning, the steady southward IMF- B z permitted solar wind energy to penetrate the magnetosphere and caused the generation of a magnetic storm associated with strong auroral electrojet activity ( A E index). Strong southward IMF- B z corresponds to the dawn-dusk interplanetary electric field (eastward on the dayside and westward on the night side). The ionograms at Jicamarca (night side) showed strong spread- F and at Thumba (dayside) showed an absence of equatorial type of sporadic- E, indicating a dusk-to-dawn electric field. Thus, the observations point to an electric field opposite in direction to that expected by the prompt penetration of the interplanetary electric field. An abnormally-large Auroral index ( A E) associated with the start of the storm suggests that the cause of the equatorial electric field changes is due to the disturbance dynamo effect.

  1. 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, ?? = 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.

  2. 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.

  3. 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.

  4. 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.

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

    NASA Astrophysics Data System (ADS)

    Wautelet, Gilles; Lejeune, Sandrine; Warnant, René

    2010-05-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1999-01-01

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

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

    PubMed

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

    2006-11-10

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

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

  9. Modeling the effect of sudden stratospheric warming within the thermosphere-ionosphere system

    NASA Astrophysics Data System (ADS)

    Bessarab, F. S.; Korenkov, Yu. N.; Klimenko, M. V.; Klimenko, V. V.; Karpov, I. V.; Ratovsky, K. G.; Chernigovskaya, M. A.

    2012-12-01

    This paper presents an investigation of thermospheric and ionospheric response to the sudden stratospheric warming (SSW) event, which took place in January 2009. This period was characterized by low solar and geomagnetic activity. Analysis was carried out within the Global Self-consistent Model of Thermosphere, Ionosphere and Protonosphere (GSM TIP). The experimental data of the atmospheric temperatures obtained by Aura satellite above Irkutsk and ionosonde data over Yakutsk and Irkutsk were utilized as well. SSW event was modeled by specifying the temperature and density perturbations at the lower boundary of the GSM TIP model (80 km altitude). It was shown that by setting disturbances in the form of a stationary planetary perturbation s=1 at the lower boundary of the thermosphere, one could reproduce the negative electron density disturbances in the F region of ionosphere during SSW events. Our scenario for the 2009 SSW event in the GSM TIP allowed to obtain results which are in a qualitative agreement with the observation data.

  10. Assessment and Mitigation of Ionospheric Residual Errors in GPS Radio Occultation Retrievals

    NASA Astrophysics Data System (ADS)

    Ao, C. O.; Mannucci, A.; Pi, X.; Iijima, B. A.

    2009-12-01

    Atmospheric soundings derived from Global Positioning System radio occultations (GPSRO) have the potential to be global climate benchmark observations of significant value to the global climate observing system. Past studies comparing refractivity and temperature retrievals from different GPSRO satellite platforms have demonstrated the very high precision of the measurements. However, such studies do not provide an upper bound on any systematic errors that might exist in the retrievals. One possibly significant error source for stratospheric retrievals comes from the Earth’s ionosphere. To remove the ionospheric contribution to the GPSRO measurements, a linear combination of the bending angles from the two GPS frequencies is typically used. However, due to raypath separation from the two GPS signals as well as higher-order frequency dependency of the refractive index, not all the ionospheric effects will be eliminated with this procedure. Uncorrected ionospheric diurnal- and solar-cycle variability could have an undesirable impact on the interpretation of stratospheric trends inferred from GPSRO. In this talk, we will provide an assessment of the ionospheric residual errors using three-dimensional raytracing through the USC/JPL Global Assimilative Ionosphere Model (GAIM) and discuss a new approach towards mitigating the ionospheric residual errors.

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

    PubMed Central

    Cundiff, Patrick R.

    2014-01-01

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

  12. Ionospheric bending correction for GNSS radio occultation signals

    NASA Astrophysics Data System (ADS)

    Hoque, M. M.; Jakowski, N.

    2011-12-01

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

  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. PMID:19073464

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

    E-print Network

    Withers, Paul

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

  15. 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.

  16. 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.

  17. 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.

  18. Seismo-ionospheric effects associated with 'Chelyabinsk' meteorite during the first 25 minutes after its fall

    E-print Network

    Berngardt, Oleg I

    2014-01-01

    This paper presents the properties of ionospheric irregularities elongated with Earth magnetic field during the first 25 minutes after the fall of the meteorite 'Chelyabinsk' experimentally observed with EKB radar of Russian segment of the SuperDARN. It is shown that 40 minutes before meteor fall the EKB radar started to observe powerful scattering from irregularities elongated with the Earth magnetic field in the F-layer. Scattering was observed for 80 minutes and stopped 40 minutes after the meteorite fall. During 9-15 minutes after the meteorite fall at ranges 400-1200 km from the explosion site a changes were observed in the spectral and amplitude characteristics of the scattered signal. This features were the sharp increase in the Doppler frequency shift of the scattered signal corresponding to the Doppler velocities about 600 m/s and the sharp increase of the scattered signal amplitude. This allows us to conclude that we detected the growth of small-scale ionospheric irregularities elongated with the Ea...

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

    E-print Network

    Stanford University

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

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

    NASA Astrophysics Data System (ADS)

    Rycroft, M. J.; Odzimek, A.

    2010-06-01

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

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

    NASA Astrophysics Data System (ADS)

    Rycroft, Michael J.; Odzimek, Anna

    2010-05-01

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

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

    NASA Astrophysics Data System (ADS)

    Rycroft, M. J.; Odzimek, A.

    2010-06-01

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

  4. Solitons versus parametric instabilities during ionospheric heating

    NASA Technical Reports Server (NTRS)

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

    1984-01-01

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

  5. The Ptolemaic Approach to Ionospheric Electrodynamics

    NASA Astrophysics Data System (ADS)

    Vasyliunas, V. M.

    2010-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

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

  7. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2013-02-01

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

  9. Topside Ionospheric Sounder for CubeSats

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  10. Lunar atmospheric tidal effects in the plasma drifts observed by the Low-Latitude Ionospheric Sensor Network

    NASA Astrophysics Data System (ADS)

    Eccles, Vince; Rice, Donald D.; Sojka, Jan J.; Valladares, Cesar E.; Bullett, Terence; Chau, Jorge L.

    2011-07-01

    Data from the Low-Latitude Ionospheric Sensor Network are used to examine ionospheric electrodynamics during quiet, low solar conditions from September to November 2009. The ground-based magnetometers and the Jicamarca Vertical Incidence Pulsed Ionospheric Radar ionosonde in the Peruvian Sector are used to identify the neutral winds and plasma drifts that control the large-scale plasma structure of the ionosphere. It is observed that the solar- and lunar-driven semidiurnal tides have a significant influence on the background electrodynamics during this period of extreme solar minimum. The lunar tidal influence of the ionosphere electrodynamics is a large component of the variation of the vertical drift during the geophysically quiet study period. A significant portion, though not all, of the variation through the lunar month can be attributed to the lunar semidiurnal tide.

  11. 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.

  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 converted to ionospheric phase screens from which phase power spectra are calculated. We introduce the concept of the error model and provide examples of global error maps calculated for the NISAR mission. We also propagate ionospheric phase errors to errors in line-of-site deformation estimates assuming simple multi-temporal stacking algorithms.

  13. A Model of Callisto's Ionosphere

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  14. 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…

  15. 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.

  16. Planetary atmospheres and ionospheres...

    E-print Network

    Withers, Paul

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

  17. Ionospheric Correction Using Tomography

    E-print Network

    Stanford University

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

  18. Roughness in Lattice Ordered Effect Algebras

    PubMed Central

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

    2014-01-01

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

  19. 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.

  20. Earthquake-Ionosphere Coupling Processes

    NASA Astrophysics Data System (ADS)

    Kamogawa, Masashi

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

  1. Numerical modeling of the global ionospheric effects of storm sequence on September 9-14, 2005—comparison with IRI model

    NASA Astrophysics Data System (ADS)

    Klimenko, M. V.; Klimenko, V. V.; Ratovsky, K. G.; Goncharenko, L. P.

    2012-06-01

    This study presents the modeling of ionospheric response to geomagnetic storms of September 9-14, 2005. We examine the performance of the Global Self-Consistent Model of Thermosphere, Ionosphere and Protonosphere (GSM TIP) and International Reference Ionosphere-2000 (IRI-2000), and compare the modeling predictions with the ionosonde and incoherent scatter radar observations over Yakutsk, Irkutsk, Millstone Hill and Arecibo stations. IRI-2000 predicted well all negative f o F 2 disturbances. In comparison with IRI-2000, the GSM TIP better reproduced the positive phase observed during the disturbed times. We discuss the possible reasons of the differences between the GSM TIP model calculations, IRI predictions, and the observations.

  2. GUMICS-3 A Global Ionosphere-Magnetosphere Coupling Simulation with High Ionospheric Resolution

    NASA Astrophysics Data System (ADS)

    Janhunen, Pekka

    1996-12-01

    The prediction of satellite charging and other harmful effects can not be successful unless we can model and predict substorms and other kinds of auroral breakups. For this we need a high-resolution global simulation system whose only essential input consists of measured solar-wind data. GUMICS-2 ("Grand Unified Ionosphere-Magnetosphere Coupling Simulation, version 2") is a simulation system, which integrates a three-dimensional global magnetohydrodynamic (MHD) simulation box with a high-resolution model of ionospheric electrodynamics. We use a hierarchical rectangular grid, which is recursively refined according to a specified density function. The density function is such that the grid resolution is high in the near-Earth region, at the magnetopause and in the tail current sheet, while the solar wind, far tail and lobe regions have a lower resolution. The finite volume method is used in the MHD equations. The ionospheric conductivities depend on the electron precipitation, along with a dayside enhancement due to solar radiation. A model for field-aligned potential drop (current-voltage relationship) can also be defined. The most important difference between GUMICS-2 and other similar programs is the use of a locally varying time step. In the near-Earth region the Alfven speed is very high, which makes it necessary to use a very small time step, sometimes less than 10 ms. In conventional simulation methods the same time step must be used throughout the grid, but in our version of MHD the time step is locally adaptive. This results in significant reduction (at least one order of magnitude) of computing time, making it possible to use a previously unavailable resolution in the near-Earth region and in the ionosphere without increasing the computer requirements. The grid spacing in the auroral ionospheric is less than 100 km in the supercomputer versions of the model. We will present the GUMICS-2 model and show some examples of simulated events where solar wind data has been available. Comparisons with observations will be included. The problems of how to translate the MHD and ionospheric variables produced by GUMICS-2 into useful information about high-energy particle fluxes at geostationary orbit and elsewhere will also be briefly discussed. The GUMICS-3 Home Page

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

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2009-03-01

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

  5. 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

  6. 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

  7. Conversion of ionospheric heater HF waves into electron acoustic waves in warm ionospheric plasma

    NASA Astrophysics Data System (ADS)

    Lehtinen, N. G.; Inan, U. S.; Bunch, N. L.

    2012-12-01

    The Stanford full-wave method (StanfordFWM) was developed in order to calculate generation and propagation of electromagnetic waves in cold magnetized stratified plasmas. We generalize it by including the effects of electron temperature, by following a procedure analogous to that of [Budden and Jones, 1987, doi:10.1098/rspa.1987.0077]. The advantage of StanfordFWM is that it is intrinsically numerically stable against ``swamping'' by evanescent waves while in the method of Budden and Jones [1987] ``the problem of numerical swamping is severe ...'' The new method is used to calculate mode conversion between electron acoustic (Langmuir) and electromagnetic modes for propagation in a warm ionospheric plasma with a gradient of electron density and an arbitrary direction of the background geomagnetic field, in the vicinity of density corresponding to the plasma resonance. As a numerical check, we demonstrate good agreement with previous calculations of Budden and Jones [1987] obtained by a numerically-unstable full-wave method scheme; Mjolhus [1990, doi:10.1029/RS025i006p01321] obtained by the method of contour integration in the complex n-plane; and Kim et al [2008, doi:10.1063/1.2994719] using a numerical electron fluid simulation code. We demonstrate that under certain conditions the linear conversion of the ordinary HF electromagnetic waves radiated by an ionospheric heater into electron acoustic waves may be very efficient, with implications for the HF heating of the F-region of ionosphere.

  8. Characterization of the Ionosphere Over the Murchison Radio Observatory

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

    The Murchison Radio Observatory (MRO), home of radio astronomy in Australia, is located in mid-latitude Western Australia. Projects currently under development at the MRO include a low-frequency instrument, the Murchison Widefield Array (MWA). The MWA is an aperture synthesis, imaging array operating over the frequency range 80 to 300 MHz. Signals in this range are subject to distortions caused by the ionosphere. The effects of scintillation and Faraday rotation degrade image quality. Historical measurements and models have long shown that the mid-latitude ionosphere has very low scintillation activity. TEC measurements we have made of the ionosphere over the MRO using high-precision, dual-frequency, GPS systems support this belief. Fine grained measurements (of the order 0.01-0.03 TEC units) have permitted fine-scale ionospheric structure to be resolved. These findings are reported and discussed. We review plans to extend this work with the implementation of mobile solar-powered instrumentation that will permit deployment of various GPS configurations that will collect TEC data during the forthcoming period of expected higher solar activity.

  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 use of ionospheric estimators such as the TEC (Total Electron Content) fluctuations, I95 index and scintillation parameters (such as S4 and ??), observed positioning degradation has been correlated with ionospheric disturbances in order to characterise the impact. The ultimate objective is to quantify how residual errors remaining in both the double differenced and undifferenced GNSS observables are driven by ionospheric related phenomena. Two different scale GNSS networks have been used in this study. One is a large scale sparse network (Brazilian wide), which is a specialized ionospheric monitoring network, built by the CIGALA project (http://cigala.galileoic.org/); the other is a regional (state of São Paulo) network, which can provide case study data and also ground truth. The outcome of the above characterization study will be discussed in this paper. It will enable and facilitate the development of the mitigation algorithms, which include the screening of contaminated observations, observation de-weighting, enhanced network interpolation and ambiguity fixing strategy.

  10. Ionosphere. [of Jupiter

    NASA Technical Reports Server (NTRS)

    Strobel, D. F.; Atreya, S. K.

    1983-01-01

    The original interest in an ionosphere on Jupiter was generated by the discovery of strong radio-frequency emissions at approximately 20 MHz which were thought to be plasma frequencies associated with Jupiter's ionosphere. The ionosphere of Jupiter provides a means to couple the magnetosphere to the atmosphere by virtue of its high conductivity and collisional interaction with the neutral atmosphere. The Pioneer and Voyager have provided direct measurements of profiles of electron concentration at selected locations on Jupiter. Attention is given to basic principles regarding the characteristics of the Jovian ionosphere, the ionization sources, aspects of ion recombination, ion chemistry, observations of Jupiter's ionosphere, the structure of Jupiter's upper atmosphere, and questions of ionospheric modeling. On the basis of the Pioneer and Voyager observations it appears that Jupiter's ionosphere and thermosphere undergo significant solar cycle changes.

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

    NASA Astrophysics Data System (ADS)

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

    2012-03-01

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

  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 (Dsteffect of the observed variation in ionospheric storm response on the measured strength of the terrestrial ring current, possibly connected through UT-dependent modulation of ion outflow. PMID:26167429

  13. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2007-10-01

    Ionospheric responses to the major magnetic storm disturbances of October 2003 are investigated using database selected in the Brazilian and Japanese-Asian longitude sectors. Data obtained from latitudinally spaced digisondes in the equatorial and low-latitude sites in Brazil and from the Asian and Japanese ionosonde network, the total electron content data from the extensive Japanese GPS receiver chain, and magnetometer data from the Pacific equatorial electrojet stations are analyzed during the period 28-31 October. Prompt penetrating (PP) dawn-dusk polar cap electric fields produce large F region plasma uplift on the dayside and eveningside, while the associated westward electric field on the nightside produces large downdraft of the F region plasma, and causes development of westward electrojet current, observed for the first time. Episodes of PP electric field effects appear to be of larger intensity over Brazil than over Asian longitudes. Equatorial anomaly, development due to undershielding as well as overshielding electric fields, was observed in the Brazilian and in the Asian sectors. Disturbance dynamo electric field causes large nighttime F layer uplifts that are modulated by strong meridional winds in both sectors. The disturbance electric field local time variation patterns are compared with the results of recent global model (MTIEGCM) simulation by Richmond et al. (2003) and validated in some cases. Transients of transequatorial winds, flipping direction from southward to northward, in the widely separated longitude sectors, were diagnosed to be present toward the final recovery phase of the storm. These results are presented and discussed in this paper.

  15. 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

  16. 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.

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

    NASA Astrophysics Data System (ADS)

    Gao, Shan

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

  18. 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.

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

    NASA Astrophysics Data System (ADS)

    Wezka, K.; Galas, R.

    2013-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

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

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

    NASA Technical Reports Server (NTRS)

    Keskinen, M. J.; Satyanarayana, P.

    1993-01-01

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

  2. Space weather. Ionospheric control of magnetotail reconnection.

    PubMed

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

    2014-07-11

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

  3. 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.

  4. 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.

  5. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

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

  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. Ionospheric convection driven by NBZ currents

    NASA Technical Reports Server (NTRS)

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

    1987-01-01

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

  9. Effect of Mutation Order on Myeloproliferative Neoplasms

    PubMed Central

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

    2015-01-01

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

  10. South Atlantic magnetic anomaly ionization: A review and a new focus on electrodynamic effects in the equatorial ionosphere

    NASA Astrophysics Data System (ADS)

    Abdu, M. A.; Batista, I. S.; Carrasco, A. J.; Brum, C. G. M.

    2005-12-01

    Satellite observations of enhanced energetic particle fluxes in the South Atlantic Magnetic Anomaly (SAMA) region have been supported by ground-based observations of enhanced ionization induced by particle precipitation in the ionosphere over this region. Past observations using a variety of instruments such as vertical sounding ionosondes, riometers and VLF receivers have provided evidences of the enhanced ionization due to energetic particle precipitation in the ionosphere over Brazil. The extra ionization at E-layer heights could produce enhanced ionospheric conductivity within and around the SAMA region. The energetic particle ionization source that is operative even under “quiet” conditions can undergo significant enhancements during magnetospheric storm disturbances, when the geographic region of enhanced ionospheric conductivity can extend to magnetic latitudes closer to the equator where the magnetic field line coupling of the E and F regions plays a key role in the electrodynamics of the equatorial ionosphere. Of particular interest are the sunset electrodynamic processes responsible for equatorial spread F/plasma bubble irregularity generation and related dynamics (zonal and vertical drifts, etc.). The SAMA represents a source of significant longitudinal variability in the global description of the equatorial spread F irregularity phenomenon. Recent results from digital ionosondes operated at Fortaleza and Cachoeira Paulista have provided evidence that enhanced ionization due to particle precipitation associated with magnetic disturbances, in the SAMA region, can indeed significantly influence the equatorial electrodynamic processes leading to plasma irregularity generation and dynamics. Disturbance magnetospheric electric fields that penetrate the equatorial latitudes during storm events seem to be intensified in the SAMA region based on ground-based and satellite-borne measurements. This paper will review our current understanding of the influence of SAMA on the equatorial electrodynamic processes from the perspective outlined above.

  11. Exploring the ionosphere of Mars

    E-print Network

    Withers, Paul

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

  12. Wenchuan Earthquake Ionospheric Precursors: Modeling and Experiment

    NASA Astrophysics Data System (ADS)

    Klimenko, Maxim; Klimenko, Vladimir; Zhao, Biqiang; Pulinets, Sergej; Zakharenkova, Irina; Bryukhanov, Valerij

    Early it was shown, that for strong middle-latitude earthquakes the effects in Total Electron Content (TEC) and in critical frequency of F2-layer (foF2) look like local changes in electron concentration which maxima are located in immediate proximity from epicenter area. Pre-cursory effects of strong near-equatorial earthquakes might be in the form of deepening and widening of electron concentration minimum over the magnetic equator and displacement of equatorial ionization anomaly crests. The problems of physical explanation of possible forma-tion mechanisms of the seismo-ionospheric effects are under discussion now. In Namgaladze et al., 2009 it has been come out with the assumption, that the most probable formation mech-anism of TEC disturbed areas, observable prior strong earthquakes, is the vertical transport of the F2-region ionospheric plasma under the zonal electric field action. The geomagnetic conjugacy of the earthquake ionospheric precursors and effects in equatorial anomaly which development is controlled by zonal electric field are strong arguments in favor of this hypoth-esis. Besides, the analysis of model calculation results with use of the Global Self-consistent Model of the Thermosphere, Ionosphere, Protonosphere (GSM TIP) in Namgaladze et al., 2009 testifies in favor of this hypothesis. There is a question how such electric fields can arise in the ionosphere prior to earthquakes? Now it is not answer to this question. Therefore, for understanding of formation mechanisms of earthquake ionospheric precursors it is necessary to understand the physics of lithosphere-atmosphere-ionosphere coupling prior to earthquake. Many researchers tried to solve this problem. However, until now there is not common opinion concerning to the lithosphere-atmosphere-ionosphere coupling prior to earthquake. Some ba-sic hypotheses for the explanation of this mechanism have been offered: the Internal Gravity Waves (IGWs) of seismogenic origin with the period 1-3 hours, the IGWs with the period from several minutes up to tens minutes, the seismogenic electric field with amplitude from units up to tens mV/m, the abnormal electromagnetic fields and emissions. However, the appearance of local large-scale seismo-ionospheric anomalies in TEC and foF2 it is possible to explain only by two of the mentioned mechanisms: an atmospheric electric field and/or small-scale IGWs. In this study, we present the numerical calculation results for reproduction of observed changes in the ionosphere prior to strong Wenchuan earthquake. This earthquake has been fixed on 12 May 2008. The geomagnetic activity indices for the period on 1-13 May were low. The calcu-lations of Wenchuan earthquake ionospheric precursors were carried out with use of the GSM TIP model. In calculations, the small-scale IGWs and/or the penetration of vertical electric field are considered as the formation mechanisms of earthquake ionospheric precursors. It was carried out the comparison of calculation results with experimental data of TEC and foF2 at various stations, located in China and nearby areas. The obtained results confirm the proposed mechanisms of seismo-ionospheric effect formation by small-scale IGWs and the penetration of the seismogenic vertical electric field from the atmosphere into the ionosphere. References Namgaladze A.A., Klimenko M.V., Klimenko V.V. and Zakharenkova I.E. Physical Mechanism and Mathematical Simulation of Ionosphere Earthquake Precursors Observed in Total Electron Content. Geomagnetism and Aeronomy, 2009, Vol. 49, 252-262.

  13. Study of ionospheric models for satellite orbit determination

    NASA Technical Reports Server (NTRS)

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

    1988-01-01

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

  14. Meteorological effects observed in the D-region of the equatorial ionosphere

    SciTech Connect

    Gupta, S.P.; Narayan, A.

    1984-01-01

    Electron density values were measured during morning hours over Thumba. The results show that electron density in mesosphere is more during summer than during winter for some solar zenith angle. The temperature measurements carried out on the same day during night hours show that mesosphere is hotter in winter and cooler in summer over Thumba. The electron density and temperature are anti-correlated. The results are explained in terms of temperature effects and other meteorological effects.

  15. Saturn's ionosphere: Inferred electron densities

    NASA Technical Reports Server (NTRS)

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

    1983-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Namgaladze, A. A.

    2013-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2008-07-01

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

  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 instead of the typically used climatologically derived one, we assert that this technique improves geolocation accuracy.

  19. 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.

  20. Ionospheric convection driven by NBZ currents

    SciTech Connect

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

    1987-05-01

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

  1. 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.

  2. 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.

  3. 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.

  4. The ESPERIA satellite project for detecting seismo-associated effects in the topside ionosphere. First instrumental tests in space

    NASA Astrophysics Data System (ADS)

    Sgrigna, V.; Buzzi, A.; Conti, L.; Picozza, P.; Stagni, C.; Zilpimiani, D.

    2008-05-01

    In recent times, ionospheric and magnetospheric perturbations constituted by radiation belt particle precipitations, variations of temperature and density of ionic and electronic components of ionospheric plasma as well as electric and magnetic field fluctuations have been detected on board of the LEO satellites and associated with earthquake preparation and occurrence. Several mechanisms have been suggested as justifying the seismoelectromagnetic phenomena observed in the upper lithosphere and in the topside ionosphere before, during and after an earthquake. Their propagation in these media has also been investigated, but physical knowledge of such processes is below standard. Consequently, coordinated space and ground-based observations based on data gathered simultaneously in space and at the Earth's surface are needed to investigate seismo-associated phenomena. To this end, the ESPERIA space mission project has been designed for the Italian Space Agency (ASI). To date, a few instruments of its payload have been built and tested in space. This paper reports on the justification, science background, and characteristics of the ESPERIA mission project as well as the description and testing of ESPERIA Instruments (ARINA and LAZIO-EGLE) in space.

  5. 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

  6. 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

  7. 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.

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

    E-print Network

    Stanford University

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

  9. Impact of lightning on the lower ionosphere of Saturn and possible generation of halos and sprites

    E-print Network

    Ebert, Ute

    Impact of lightning on the lower ionosphere of Saturn and possible generation of halos and sprites 2014 Accepted 24 June 2014 Available online 3 July 2014 Keywords: Saturn Lightning Ionospheres a b s t r a c t We study the effect of lightning on the lower ionosphere of Saturn. A self-consistent one

  10. 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.

  11. 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

  12. Global Ionosphere Radio Observatory

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  13. 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.

  14. 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-.

  15. 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-?.

  16. LEISA: CubeSat for Ionospheric Characterization

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

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

  17. Characterisation of residual ionospheric errors in bending angles using GNSS RO end-to-end simulations

    NASA Astrophysics Data System (ADS)

    Liu, C. L.; Kirchengast, G.; Zhang, K. F.; Norman, R.; Li, Y.; Zhang, S. C.; Carter, B.; Fritzer, J.; Schwaerz, M.; Choy, S. L.; Wu, S. Q.; Tan, Z. X.

    2013-09-01

    Global Navigation Satellite System (GNSS) radio occultation (RO) is an innovative meteorological remote sensing technique for measuring atmospheric parameters such as refractivity, temperature, water vapour and pressure for the improvement of numerical weather prediction (NWP) and global climate monitoring (GCM). GNSS RO has many unique characteristics including global coverage, long-term stability of observations, as well as high accuracy and high vertical resolution of the derived atmospheric profiles. One of the main error sources in GNSS RO observations that significantly affect the accuracy of the derived atmospheric parameters in the stratosphere is the ionospheric error. In order to mitigate the effect of this error, the linear ionospheric correction approach for dual-frequency GNSS RO observations is commonly used. However, the residual ionospheric errors (RIEs) can be still significant, especially when large ionospheric disturbances occur and prevail such as during the periods of active space weather. In this study, the RIEs were investigated under different local time, propagation direction and solar activity conditions and their effects on RO bending angles are characterised using end-to-end simulations. A three-step simulation study was designed to investigate the characteristics of the RIEs through comparing the bending angles with and without the effects of the RIEs. This research forms an important step forward in improving the accuracy of the atmospheric profiles derived from the GNSS RO technique.

  18. 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.

  19. 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.

  20. Characteristics of High Latitude Ionosphere Scintillations

    NASA Astrophysics Data System (ADS)

    Morton, Y.

    2012-12-01

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

  1. Imaging the Ionosphere Submitted by

    E-print Network

    Kassie, Endawoke Yizengaw

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

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

    PubMed

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

    2015-01-01

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

  3. 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

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

    NASA Astrophysics Data System (ADS)

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

    2015-08-01

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

  5. Evaluation of Inversion Methods Applied to Ionospheric ro Observations

    NASA Astrophysics Data System (ADS)

    Rios Caceres, Arq. Estela Alejandra; Rios, Victor Hugo; Guyot, Elia

    The new technique of radio-occultation can be used to study the Earth's ionosphere. The retrieval processes of ionospheric profiling from radio occultation observations usually assume spherical symmetry of electron density distribution at the locality of occultation and use the Abel integral transform to invert the measured total electron content (TEC) values. This pa-per presents a set of ionospheric profiles obtained from SAC-C satellite with the Abel inversion technique. The effects of the ionosphere on the GPS signal during occultation, such as bending and scintillation, are examined. Electron density profiles are obtained using the Abel inversion technique. Ionospheric radio occultations are validated using vertical profiles of electron con-centration from inverted ionograms , obtained from ionosonde sounding in the vicinity of the occultation. Results indicate that the Abel transform works well in the mid-latitudes during the daytime, but is less accurate during the night-time.

  6. Beacon satellite receiver for ionospheric tomography

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  7. Rocket studies of the lower ionosphere

    NASA Technical Reports Server (NTRS)

    Bowhill, Sidney A.

    1990-01-01

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

  8. Ionospheric tomography using the FORTE satellite

    SciTech Connect

    Murphy, T.C.

    1993-08-01

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

  9. 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.

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

    NASA Astrophysics Data System (ADS)

    Jiao, Yu; Morton, Yu T.

    2015-09-01

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

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

    NASA Astrophysics Data System (ADS)

    Hoang, Thai Lan

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

  13. 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.

  14. GNSS data filtering optimization for ionospheric observation

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

  15. Evaluation of ionospheric profilers using topside sounding data

    NASA Astrophysics Data System (ADS)

    Verhulst, T.; Stankov, S. M.

    2014-03-01

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

  16. 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.

  17. Solitons and ionospheric heating

    NASA Technical Reports Server (NTRS)

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

    1982-01-01

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

  18. Formation and detection of high latitude ionospheric irregularities

    NASA Technical Reports Server (NTRS)

    Lee, M. C.; Buchau, J.; Carlson, H. C., Jr.; Klobuchar, J. A.; Weber, E. J.

    1985-01-01

    Measurements of Total Electron Content (TEC) and airglow variations show that large scale plasma patches appearing in the high-latitude ionsophere have irregular structures evidenced by the satellite phase and amplitude scintillations. Whistler waves, intense quasi-DC electric field, and atmospheric gravity waves can become potential sources of various plamsa instabilities. The role of thermal effects in generating ionospheric irregularities by these sources is discussed. Meter-scale irregularities in the ionospheric E and F regions can be excited parametrically with lower hybrid waves by intense whistler waves. Ohmic dissipation of Pedersen current in the electron gas is able to create ionospheric F region irregularities in plasma blobs or plasma patches (i.e., high ambient plasma density environment) with broad scale lengths ranging from tens of meters to a few kilometers. Through the neutral-charged particle collisions, gravity waves can excite large-scale (less than tens of kilometers) ionospheric irregularities simultaneously with forced ion acoustic modes in the E region. The large-scale ionospheric density fluctuations produced in the E region can extend subsequently alogn the earth's magnetic field to the F region and the topside ionospheric regions. These mechanisms characterized by various thermal effects can contribute additively with other processes to the formation of ionospheric irregularities in the high latitude region.

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

    NASA Astrophysics Data System (ADS)

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

    2015-02-01

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

  20. Effect of shear on order-disorder and order-order transitions in block copolymers

    SciTech Connect

    Chien-Yueh Huang; Muthukumar, M.

    1996-12-31

    We have solved numerically the self-consistent equation for composition fluctuations in diblock and triblock copolymer systems under shear. Our results are in good agreement with known experimental data and analytical perturbation calculations. The controversy involving an apparent discrepancy between experimental data and predictions from perturbation theories is resolved. When a simple shear is applied to a chemically mismatched block copolymer melt, the composition fluctuations in the melt are distorted and suppressed; also the formation of mesophases may be induced by the hydrodynamic force. Theoretical explanations of this were given by Cates and Milner and Marques and Cates who also predicted that the shift in the shear-induced order-disorder transition (ODT) temperature increases quadratically with low shear rates ({gamma}), {delta}T{sub ODT} = T{sub ODT}{gamma} {minus} T{sub ODT}({gamma} = 0) {approximately} {gamma}{sup 2}, and saturates at high shear rates so that T{sub ODT}({gamma} {r_arrow} {integral}) will approach the prediction of the mean field theory. Recently, Nakatani et al. analyzed their experimental results together with others and constructed a master curve characterizing the common features of the shift of the transition temperatures due to shear ordering. This curve exhibits a rapid increase at low to intermediate shear rates and saturates at high shear rates and looks very different from the earlier theoretical predictions.

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

    NASA Technical Reports Server (NTRS)

    Balachandran, N. K.

    1983-01-01

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

  2. 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…

  3. 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.

  4. Satellite measurement of ionospheric-induced vhf distortion

    SciTech Connect

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

    1992-09-01

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

  5. Pressure-driven and ionosphere-driven modes of magnetospheric interchange instability

    NASA Astrophysics Data System (ADS)

    Miura, Akira

    2009-02-01

    A general stability criterion for magnetospheric interchange instability, which includes an ionospheric destabilizing contribution, is derived for an arbitrary finite-? magnetospheric model satisfying the magnetohydrostatic force balance. The derivation is based on the magnetospheric energy principle. Unperturbed field-aligned currents in finite-? nonaxisymmetric magnetospheric models are assumed to close via diamagnetic currents in the magnetosphere or in the ionosphere. By exploiting the limit of a very large perpendicular wave number and the eikonal representation for the perpendicular plasma displacement, the magnetospheric interchange mode is shown to be compressible. In this limit the kink mode makes no contribution to the change in the magnetospheric potential energy. By using magnetospheric flux coordinates, the explicit form of the magnetospheric potential energy change is calculated for interchange perturbations, which do not bend magnetospheric magnetic fields. For a nonaxisymmetric finite-? magnetospheric model, a combined effect of the pressure gradient and field line curvature, not only in the meridional plane but also in the plane parallel to the longitudinal direction, is responsible for pressure-driven interchange instability. For an axisymmetric, north-south symmetric and low-? magnetospheric model, in which the magnetic field is approximated by a dipole field, the m = 1 or m = 2 ionosphere-driven mode, where m is the azimuthal mode number, has an upper critical equatorial ? value for instability in the order of 1. Thus a substantial region of the inner magnetosphere or the near-Earth magnetosphere may be unstable against ionosphere-driven interchange instability caused by a horizontal plasma displacement on the spherical ionospheric surface.

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

    NASA Astrophysics Data System (ADS)

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

    2015-06-01

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

  7. Effect of sudden impulses on currents in the auroral ionosphere under northward interplanetary magnetic field conditions: A case study

    SciTech Connect

    Russell, C.T.; Ginskey, M.; Angelopoulos, V.

    1994-09-01

    The authors examine the response of auroral magnetic records to the passage of an interplanetary shock at a time when the interplanetary magnetic field was northward. They restrict their attention solely to the sector within 3 hours of local magnetic midnight for a single case selected when a bursty bulk flow event was recorded in the near tail by ISEE 2. Over most of the nightside at high latitudes only a weak disturbance if any is seen. At lower latitudes a plateau is seen in the H component, coincident with the bursty bulk flow event. At 65{degrees} latitude from about midnight to 3:00 LT a weak pair of negative bays is observed, also coincident with the bursty bulk flow event. The authors conclude that the tail and the auroral ionosphere were closely coupled during this sudden impulse, but the auroral zone disturbance appears to be mainly the brief activation of a section of the auroral electrojet rather than a classic substorm. No expansion or motion of the electrojet was observed, and the activation was no longer than that of the bursty bulk flow in the tail. 10 refs., 9 figs., 1 tab.

  8. Test order effects in simultaneous protocols.

    PubMed

    Imam, Abdulrazaq A; Warner, Timothy A

    2014-03-01

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

  9. Ionospheric Alfvén resonator response to remote earthquakes

    NASA Astrophysics Data System (ADS)

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

    2010-05-01

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

  10. Broadband Ionospheric Scintillation Measurements from Space

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  11. Planetary waves in rotating ionosphere

    SciTech Connect

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

    2008-06-15

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

  12. Reconstruction of the ionospheric electron density by geostatistical inversion

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

  13. Rocket exhaust expansion at high altitudes and ionospheric holes

    NASA Astrophysics Data System (ADS)

    Reilly, M. H.

    The introduction of rocket exhaust molecules at high altitudes during the launch of space systems produces a number of extraordinary ionospheric effects. The Skylab effect, as investigated by Mendillo et al. (1975), is a case in point. In this study Faraday rotation data for times including the Skylab launch were used to characterize the induced electron depletion region (i.e., ionospheric 'hole') and to help identify the essential chemical mechanisms responsible for it. The launch of the HEAO-C from Cape Kennedy on September 20, 1979, provided another opportunity for the study of ionospheric holes. The considered investigation is concerned with the development of a mathematical model for the description of the ionospheric hole dynamics. The investigation follows partly an approach reported by Bernhardt (1979). His relations are reformulated in terms of a different collisional relaxation model.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

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

    NASA Astrophysics Data System (ADS)

    Wang, Zhen; Wang, Na; Ping, Jinsong

    2015-04-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2012-10-01

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

  1. Coupled Magnetotail-Ionosphere Asymmetries from Ionospheric Hall Conduction

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  2. 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.

  3. 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…

  4. Effect of third-order dispersion on dark solitons

    NASA Astrophysics Data System (ADS)

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

    1996-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

  7. Far-field coseismic ionospheric disturbances of Tohoku earthquake

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

  8. Artificial ionospheric mirrors for radar applications

    NASA Astrophysics Data System (ADS)

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

    1990-10-01

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

  9. Mass spectrometry in ionospheric research.

    PubMed

    Ferguson, Eldon E

    2007-01-01

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

  10. Midlatitude Ionospheric Dynamics and Disturbances

    NASA Astrophysics Data System (ADS)

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

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

  12. (abstract) Application of the GPS Worldwide Network in the Study of Global Ionospheric Storms

    NASA Technical Reports Server (NTRS)

    Ho, C. M.; Mannucci, A. J.; Lindqwister, U. J.; Pi, X.; Sparks, L. C.; Rao, A. M.; Wilsion, B. D.; Yuan, D. N.; Reyes, M.

    1997-01-01

    Ionospheric storm dynamics as a response to the geomagnetic storms is a very complicated global process involving many different mechanisms. Studying ionospheric storms will help us to understand the energy coupling process between the Sun and Earth and possibly also to effectively forecast space weather changes. Such a study requires a worldwide monitoring system. The worldwide GPS network, for the first time, makes near real-time global ionospheric TEC measurements a possibility.

  13. Modeling seasonal variations of auroral particle precipitation in a global-scale magnetosphere-ionosphere simulation

    E-print Network

    Lotko, William

    Modeling seasonal variations of auroral particle precipitation in a global-scale magnetosphere shown strong seasonal variations in a vast array of magnetosphere-ionosphere parameters, including field of the coupled solar wind-magnetosphere-ionosphere system. In order to account for changes in the solar wind

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

    E-print Network

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

    2015-01-01

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

  15. Ionospheric Estimation and Integrity Threat Detection

    E-print Network

    Stanford University

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

  16. 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.

  17. Solitons and ionospheric modification

    NASA Technical Reports Server (NTRS)

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

    1982-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

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

  19. 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.

  20. Effective Hamiltonian with position-dependent mass and ordering problem

    NASA Astrophysics Data System (ADS)

    Tkachuk, V. M.; Voznyak, O.

    2015-08-01

    We derive the effective low-energy Hamiltonian for the tight-binding model with the hopping integral slowly varying along the chain. The effective Hamiltonian contains the kinetic energy with position-dependent mass, which is inverse to the hopping integral, and effective potential energy. Changing of ordering in the kinetic energy leads to change of the effective potential energy and leaves the Hamiltonian the same one. Therefore, we can choose arbitrary von Roos ordering parameters in the kinetic energy without changing the Hamiltonian. Moreover, we propose a more general form for the kinetic energy than that of von Roos, which nevertheless together with the effective potential energy represent the same Hamiltonian.

  1. Effective Hamiltonian with position dependent mass and ordering problem

    E-print Network

    V. M. Tkachuk; O. Voznyak

    2015-04-30

    We derive the effective low energy Hamiltonian for the tight-binding model with the hopping integral slowly varying along the chain. The effective Hamiltonian contains the kinetic energy with position dependent mass, which is inverse to the hopping integral, and effective potential energy. Changing of ordering in the kinetic energy leads to change of the effective potential energy and leaves the Hamiltonian the same one. Therefore, we can choose arbitrary von Roos ordering parameters in the kinetic energy without changing the Hamiltonian. Moreover, we propose a more general form for the kinetic energy than that of von Roos, which nevertheless together with the effective potential energy represent the same Hamiltonian.

  2. The Effect of N2 Photoabsorption Cross Section Resolution on C2H6 Production in Titan’s Ionosphere

    NASA Astrophysics Data System (ADS)

    Luspay-Kuti, Adrienn; Mandt, Kathleen E.; Plessis, Sylvain; Greathouse, Thomas K.

    2014-11-01

    Titan’s rich organic chemistry begins with the photochemistry of only two molecules: N2 and CH4. The details on how higher-order hydrocarbons and nitriles are formed from these molecules have key implications for both the structure and evolution of Titan’s atmosphere, and for its surface-atmosphere interactions. Of high importance is the production of C2H6, which is a sink for CH4, and a main component in the polar lakes. Results of photochemical models, though, may be sensitive to the choice of input parameters, such as the N2 photoabsorption cross section resolution, as previously shown for nitrogen (Liang et al. (2007) ApJL 664, 115-118), and CH4 (Lavvas et al. (2011) Icarus 213, 233-251). Here we investigate the possibility of the same effect on the production rates of C2H6. We modeled production and loss rates, as well as mixing ratio and density profiles between an altitude of 600 and 1600 km for low and high resolution N2 cross sections via a coupled ion-neutral-thermal model (De La Haye et al. (2008) Icarus 197, 110-136; Mandt et al. (2012) JGR 117, E10006). Our results show a clear impact of photoabsorption cross section resolution used on all neutral and ion species contributing to C2H6 production. The magnitude of the influence varies amongst species. Ethane production profiles exhibit a significant increase with better resolution; a factor of 1.2 between 750 and 950 km, and a factor of 1.1 in the total column-integrated production rate. These values are lower limits, as additional reactions involving C2H5 not included in the model may also contribute to the production rates. The clear effect on C2H6 (which is not a parent molecule, nor does it bear nitrogen) may have important implications for other molecules in Titan’s atmosphere as well. The possible non-negligible impact of an isotope of nitrogen may argue for the inclusion of isotopes in photochemical models. For future analysis, development of a more efficient and streamlined model called Planet-INC is underway. This open source model is a high-performance probabilistic planetary model that includes detailed uncertainty analysis capabilities.

  3. The ionosphere of Triton

    NASA Technical Reports Server (NTRS)

    Majeed, T.; Mcconnell, J. C.; Strobel, D. F.; Summers, M. E.

    1990-01-01

    A model of the atmospheric temperature structure and composition inferred from the Voyager (UVS) solar occultations was used together with a one-dimensional chemical diffusive model to interpret the Voyager Radio Science Spectrometer (RSS) ingress measurements of Triton's electron density. Although N2(+) is the major ion created, N(+) produced by dissociative ionization is the dominant ion. Reaction of thermospheric H2, produced by Lyman-alpha dissociation of CH4 in the lower atmosphere, is the major loss for N(+) ions and maintains these ions in PCSS below 600 km. Solar EUV ionization cannot generate electron densities at the magnitude measured by the RSS experiment and an additional ionization source about 3 x 10 to the 8th ions/sq cm per sec is required. The ionosphere may undergo a transition from PCSS to diffusive control if the N(+) ion production rates were greater than the H2 flux derived from CH4. In this case, the upward flowing H2 is totally converted to H by reaction with N(+) and the remaining N(+) ions recombine radiatively to create an ionosphere under diffusive control above the peak.

  4. 77 FR 58587 - Mr. James Chaisson; Confirmatory Order (Effective Immediately)

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-09-21

    ...IA-12-009; NRC-2012-0216] Mr. James Chaisson; Confirmatory Order (Effective Immediately) I Mr. James P. Chaisson was employed from April 10...conditions agreed upon in principle by Mr. James P. Chaisson, a former area...

  5. 10 CFR 221.34 - Effect of order.

    Code of Federal Regulations, 2010 CFR

    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...

  6. Present state of ionospheric time delay prediction

    NASA Astrophysics Data System (ADS)

    Klobuchar, J. A.

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

  7. The Ionosphere and Ocean Altimetry

    NASA Technical Reports Server (NTRS)

    Lindqwister, Ulf J.

    1999-01-01

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

  8. A quantitative study of ionospheric disturbance characteristics during solar flare events using the SuperDARN Hokkaido radar and solar radiation data

    NASA Astrophysics Data System (ADS)

    Watanabe, D.; Nishitani, N.; Imada, S.

    2013-12-01

    Ionospheric disturbances during solar flare events have been studied by various kinds of observation instrument in the last few decades. Kikuchi et al. (1985) reported on the positive Doppler shift in the HF Doppler system data during solar flare events, and indicated that there are two possible factors of Doppler shift, i.e., (1) apparent ray path decrease by changing refraction index due to increasing electron densities in the D-region ionosphere, and (2) ray path decrease due to descending reflection point associated with increasing electron density in the F-region ionosphere. In this study, we use the SuperDARN Hokkaido Radar to investigate the detailed characteristics of solar flare effects on ionospheric disturbances. We focus on the positive Doppler shift of ground / sea scatter echoes just before sudden fade-out of echoes. Davies et al. (1962) showed that if the factor (1) is dominant, the Doppler shift should have positive correlation with slant range and negative correlation with elevation angle and frequency. On the other hand, if the factor (2) is dominant, the Doppler shift should have negative correlation with slant range and positive correlation with elevation angle and frequency. While Kikuchi et al. (1985) studied solar flare events and mainly discussed frequency dependence of Doppler shift, we study mainly slant range and elevation angle dependence, for the first time to the best of our knowledge. We found that the factor (1), in other words, increase of electron densities at D-region ionosphere, is dominant during solar flare events. This result is consistent with that of Kikuchi et al. In order to study characteristics of ionospheric disturbance in more detail, we are studying relationship between timing / amplitude of ionospheric disturbance and that of the solar irradiation changes, by comparing the HF radar data with high wavelength resolution irradiation data for X-ray and EUV from RHESSI and SDO satellites. Generally, X-ray radiation becomes more important for the changes in the D-region during solar flare events. Therefore we investigate relationship between X-ray flux changes and electron density variation in the D-region ionosphere intensively. Further, we estimated electron density changes in the ionsosphere by analyzing elevation angle dependence of Doppler shift in radar echoes quantitatively. We are estimating electron density by considering chemical reaction and photoreaction caused by solar radiation. We will compare the two electron density changes deduced from different two ways and evaluate the amplitude of ionospheric disturbance observed by the HF radar. More detailed analysis result will be reported.

  9. Preseismic Lithosphere-Atmosphere-Ionosphere Coupling

    NASA Astrophysics Data System (ADS)

    Kamogawa, Masashi

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

  10. Analog ionospheric forecasts: Space weather forecasts by analogy with previous events

    NASA Astrophysics Data System (ADS)

    McNamara, Leo F.; Bishop, Gregory J.; Welsh, Judith A.

    2011-02-01

    Operational systems that take advantage of the ionosphere or for which the ionosphere is a major inconvenience require that deleterious changes to the ionosphere during geomagnetically disturbed intervals be forecast up to several days in advance, in order to allow mitigation procedures to be instituted. However, the reliability of current space weather models of the Sun, solar wind, magnetosphere and ionosphere is such that the consequential ionospheric forecasts depend too much on the uncertainties of the various models. It is no secret that the level of success of space weather forecasts is currently still a decade or two behind that achieved by the tropospheric weather forecasting community. As an interim solution to forecasting the low and midlatitude ionosphere, we propose the use of analog forecasts in which we look to the past to see what happened to the ionosphere during a historical interval for which the forecast geomagnetic conditions also applied. In order to investigate the concept of analog forecasts, we have analyzed Australian ionosonde values of NmF2 for ˜200 disturbed intervals. While we do not expect analog forecasts to match the details of individual storms, we do expect them to provide users with the essential nature of a forecast ionospheric storm. The reliability of analog forecasts should increase as we gain experience and thus provide a standard of reliability that will eventually be reached by fully coupled space weather forecasts.

  11. Examining the effects of birth order on personality.

    PubMed

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

    2015-11-17

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

  12. Characteristics of the global ionospheric electron density during the extreme solar minimum condition

    NASA Astrophysics Data System (ADS)

    Jee, G.

    2010-12-01

    The last solar minimum period between the cycles 23 and 24 was anomalously low and lasted long compared with previous solar minimums. The resulting solar irradiance received in the Earth’s upper atmosphere was extremely low and therefore it can readily be expected that the upper atmosphere should be greatly affected by this low solar activity. There were several studies on this effect but many of them was on the thermosphere (Solomon et al., 2010; Emmert et al., 2010). According to these studies, the thermospheric temperature was cooler and the density was lower than the previous solar minimum periods. The low solar irradiance during the last solar minimum should also affect the ionosphere, not only via the lower ion-electron production due to the lower EUV radiation but also through the interactions with the thermosphere that was already influenced by the low solar irradiance. In this study, we utilized the measurements of total electron content (TEC) from the TOPEX and JASON satellites during the periods of 1992 to 2010, which includes the last two solar minimums, in order to investigate the differences between the ionospheric behaviors during the two minimum conditions. Initially the levels of the global ionization will be examined during these minimum periods and then further discussions will be continued on the details of the ionospheric behavior such as the seasonal and storm-time variations.

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

    NASA Astrophysics Data System (ADS)

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

    2014-10-01

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

  14. Experimentally investigate ionospheric depletion chemicals in artificially created ionosphere

    SciTech Connect

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

    2012-09-15

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

  15. IONOSPHERIC POWER-SPECTRUM TOMOGRAPHY IN RADIO INTERFEROMETRY

    SciTech Connect

    Koopmans, L. V. E.

    2010-08-01

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

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

    PubMed

    Trueblood, Jennifer S; Busemeyer, Jerome R

    2011-01-01

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

  17. Solar Flare Impacts on Ionospheric Electrodynamics

    NASA Technical Reports Server (NTRS)

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

    2012-01-01

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

  18. Assimilative modeling of low latitude ionosphere

    NASA Technical Reports Server (NTRS)

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

    2004-01-01

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

  19. 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.

  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. Ionospheric F region effects observed in the American and African sectors during the intense geomagnetic storm of September-October 2012

    NASA Astrophysics Data System (ADS)

    De Jesus, Rodolfo; Gende, Mauricio; Fagundes, Paulo Roberto; Coster, Anthea; Bolaji, Segun; Kavutarapu, Venkatesh; De Abreu, Alessandro; Sobral, J. H. A.; Pillat, Valdir Gil; Batista, Inez S.

    This study presents an investigation of geomagnetic disturbance effects on the equatorial, low- and mid-latitude ionospheric F region over the American and African sectors during the intense geomagnetic storm (maximum Kp index of 6.7) that occurred on 30th September, 2012 and 1st October, 2012. In this study digital ionosonde and Global Positioning System (GPS) data are simultaneously utilized from 30th September to 3rd October 2012. The diurnal variability over this four day period observed from both the digital ionosonde and from ground based GPS units can be characterized as quiet, slightly disturbed, and strongly disturbed periods. This time period includes the sudden commencement of the storm (SCS), the main phase (MPS), and the recovery phase of the storm (RPS). During the period of investigation, ionospheric parameters F-region critical frequency (foF2) and minimum F-region virtual height ('hF) were obtained at Jicamarca, São Luís, Fortaleza, Palmas and Port Stanley at the following geographical coordinates, respectively: 12.0ºS 76.8ºW, 2.6ºS 44.2ºW, 3.8ºS 38ºW, 10.2ºS 48.8ºW and 51.6ºS 57.9ºW. In this study, we also used observations of 20 GPS stations located at Greenbelt (39.0ºN, 76.8ºW), Cambridge (38.6ºN, 76.1ºW), Virgin Islands (17.6ºN, 64.6ºW), Eusebio (03.9ºS, 38.4ºW), Iquitos (03.8ºS, 73.3 ºW), Arequipa (16.5ºS, 71.5ºW), Cachoeira Paulista (22.7ºS, 45.0ºW), Copiapo (27.4ºS, 70.4ºW), La Plata (34.9ºS, 57.9ºW), Concepcion (36.8ºS, 73.0ºW), Rio Grande (53.8ºS, 67.8ºW), Dakar (14.7ºN, 17.4ºW), Addis (09.0ºN, 38.8ºE), Cotonou (06.4ºN, 02.5ºE), Libreville (00.4ºN, 09.7ºE), Mbarara (00.6ºS, 30.7ºE), Lusaka (15.4ºS, 28.3ºE), Windhoek (22.6ºS, 17.1ºE), Springbok (29.7ºS, 17.9ºE) and Sutherland (32.4ºS, 20.8ºE). Vertical Total Electron Content (VTEC) and TEC fluctuations (ROT, rate of change of TEC) are calculated from GPS data using the measured Slant Total Electron Content (STEC) records from the 20 GPS receiving stations mentioned above in the American and African sectors. Measurements of scintillations (S4, amplitude scintillation index) are also used in this investigation to study the formation of irregularities. Salient features including the observed aforementioned characteristics will be presented and discussed.

  2. Global ionospheric response to the 2009 sudden stratospheric warming event using Ionospheric Data Assimilation Four-Dimensional (IDA4D) algorithm

    NASA Astrophysics Data System (ADS)

    Azeem, I.; Crowley, G.; Honniball, C.

    2015-05-01

    A data assimilation algorithm is used to delineate the time-dependent three-dimensional ionospheric response to the 2009 sudden stratospheric warming (SSW) event. We use the Ionospheric Data Assimilation Four-Dimensional (IDA4D) algorithm to study the global ionospheric response to the 2009 SSW. This is the first study to utilize global ionospheric measurements in a data assimilation framework to unambiguously characterize atmosphere-ionosphere coupling via tidal modifications during the 2009 SSW event. Model results reveal that the dominant mode of ionospheric variability during the 2009 SSW is driven by the enhancements in westward propagating semidiurnal tide with zonal wave number 1. The IDA4D results completely characterize the tidal perturbation during the 2009 SSW for the first time and show the global 3-D structure of the tide in total electron content (TEC) and electron density. The largest ionospheric responses were seen at low latitudes, where ionospheric plasma is extremely sensitive to the zonal electric field and susceptible to modifications by tidal winds in the lower thermosphere. The ionospheric response to the warming was characterized by an increase in TEC in the morning/early afternoon sector and a decrease during the late afternoon/evening period. The effects of coupling between the stratosphere and ionosphere were strongest between 220 km and 380 km. The IDA4D results also show a reversal of asymmetry in the equatorial ionization anomaly crests occurring several days after the peak of the 2009 SSW event. We suggest that this could be a result of the equatorial fountain effect being further modified by the summer-to-winter meridional neutral winds.

  3. 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

  4. 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.

  5. Spatial variability in the ionosphere measured with GNSS networks

    NASA Astrophysics Data System (ADS)

    Emardson, Ragne; Jarlemark, Per; Johansson, Jan; Schäfer, Sebastian

    2013-09-01

    Traveling ionospheric disturbances (TIDs) appear as medium-scale TIDs at midlatitudes and as polar cap patches at high latitudes. Both can have a negative impact on Global Navigation Satellite Systems (GNSS) measurements, although the amplitude is of tenths of a total electron content unit (TECU), 1 TECU = 1016 el m-2. Due to their spatial extension, they affect GNSS measurements using receivers separated with distances up to ~1000 km. We present statistical measures of the ionospheric spatial variability as functions of time in solar cycle, annual season, and time of day for different geographical locations in Europe. In order to perform this spatial characterization of the ionosphere, we have used archived GPS data from a 13 year period, 1999-2011, covering a complete solar cycle. We find that the ionospheric spatial variability is larger for the northern areas than for the southern areas. This is especially pronounced at solar maximum. For the more northern areas, the ionospheric variability is greater during nighttime than during daytime, while for central Europe, the variability is larger during daytime. At solar maximum, the variability is larger during the months October and November and smaller in June and July.

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

    NASA Astrophysics Data System (ADS)

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

    2012-01-01

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

  7. Localized lower hybrid acceleration of ionospheric plasma

    NASA Technical Reports Server (NTRS)

    Kintner, P. M.; Vago, J.; Chesney, S.; Arnoldy, R. L.; Lynch, K. A.; Pollock, C. J.; Moore, T. E.

    1992-01-01

    Observations of the transverse acceleration of ions in localized regions of intense lower hybrid waves at altitudes near 1000 km in the auroral ionosphere are reported. The acceleration regions are thin filaments with dimensions across geomagnetic field lines of about 50-100 m corresponding to 5-10 thermal ion gyroradii or one hot ion gyroradius. Within the acceleration region lower hybrid waves reach peak-to-peak amplitudes of 100-300 mV/m and ions are accelerated transversely with characteristic energies of the order of 10 eV. These observations are consistent with theories of lower hybrid wave collapse.

  8. Physical Model of Earthquake Ionospheric Precursors (Invited)

    NASA Astrophysics Data System (ADS)

    Namgaladze, A. A.

    2010-12-01

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

  9. Estimates of Horizontal Ionospheric Currents on the Dayside of Mars

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

    How the solar wind interacts with a planetary object depends upon the object's properties such as the presence of a magnetic field or an atmosphere. An unmagnetized object cannot stand-off the solar wind unless it possess a substantial atmosphere which can be ionized by solar radiation creating a conductive ionosphere. Currents can then be induced in the ionosphere; these currents act to cancel out the external solar wind magnetic field preventing it from reaching the surface. Here we present simple analytical calculations of such induced currents in the ionosphere of Mars. We consider currents in the ionospheric dynamo region which can be driven by thermospheric winds as well as currents driven by electric fields (i.e., plasma motion through the neutrals). We include in these estimates the effects of "equatorial-type" electrojets due to vertical conductivity gradients in the presence of horizontal magnetic fields. The direction of the external driver is important. Vertical neutral winds (or plasma motion) give rise to electrojets whereas horizontal winds (or plasma motion) lead to no net current. These results can give us insights into how external magnetic fields are effectively screened out by induced currents and how these induced currents can influence ionospheric dynamics around unmagnetized objects.

  10. Currents and Electrojets in the Ionosphere of Mars

    NASA Astrophysics Data System (ADS)

    Fillingim, Matthew O.; Lillis, Robert; Brain, D. A.

    2015-04-01

    How the solar wind interacts with a planetary object depends upon the object's properties such as the presence of a magnetic field or an atmosphere. An unmagnetized object cannot stand-off the solar wind unless it possess a substantial atmosphere which can be ionized by solar radiation creating a conductive ionosphere. Currents can then be induced in the ionosphere; these currents act to cancel out the external solar wind magnetic field preventing it from reaching the surface. Here we present simple analytical calculations of such induced currents in the ionosphere of Mars. We consider currents in the ionospheric dynamo region which can be driven by thermospheric winds as well as currents driven by electric fields (i.e., plasma motion through the neutrals). We include in these estimates the effects of "equatorial-type" electrojets due to vertical conductivity gradients in the presence of horizontal magnetic fields. In addition, we consider "auroral-type" electrojets due to horizontal conductivity gradients resulting from particle precipitation and/or large variations in the magnetic field strength near vertical cusps in strong crustal field regions. The direction of the external driver is important. In some cases, the secondary current adds to the primary current creating electrojets. In other cases, the secondary current can cancel or nearly cancel the primary current resulting in very weak net currents. These results can give us insights into how external magnetic fields are effectively screened out by induced currents and how these induced currents can influence ionospheric dynamics around unmagnetized objects.

  11. 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.

  12. Cubesat-Based Dtv Receiver Constellation for Ionospheric Tomography

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

    The Radio Aurora Explorer mission, funded by NSF's Space Weather and Atmospheric Research program, has demonstrated the utility of CubeSat-based radio receiver payloads for ionospheric research. RAX has primarily been an investigation of microphysics of meter-scale ionospheric structures; however, the data products are also suitable for research on ionospheric effects on radio propagation. To date, the spacecraft has acquired (1) ground-based UHF radar signals that are backscattered from meter-scale ionospheric irregularities, which have been used to measure the dispersion properties of meter-scale plasma waves and (2) ground-based signals, directly on the transmitter-spacecraft path, which have been used to measure radio propagation disturbances (scintillations). Herein we describe the application of a CubeSat constellation of UHF receivers to expand the latter research topic for global-scale ionospheric tomography. The enabling factor for this expansion is the worldwide availability of ground-based digital television (DTV) broadcast signals whose characteristics are optimal for scintillation analysis. A significant part of the populated world have transitioned, or soon to be transitioned, to DTV. The DTV signal has a standard format that contains a highly phase-stable pilot carrier that can be readily adapted for propagation diagnostics. A multi-frequency software-defined radar receiver, similar to the RAX payload, can measure these signals at a large number of pilot carrier frequencies to make radio ray and diffraction tomographic measurements of the ionosphere and the irregularities contained in it. A constellation of CubeSats, launched simultaneously, or in sequence over years, similar to DMSPs, can listen to the DTV stations, providing a vast and dense probing of the ionosphere. Each spacecraft can establish links to a preprogrammed list of DTV stations and cycle through them using time-division frequency multiplexing (TDFM) method. An on board program can sort the frequencies and de-trend the phase variations due to spacecraft motion. For a single channel and a spacecraft-DTV transmitter path scan, TEC can be determined from the incremental phase variations for each channel. Determination of the absolute TEC requires knowledge of the absolute phase, i.e., including the number of 2? cycles. The absolute TEC can be determined in the case of multi-channel transmissions from a single tower (most towers house multiple television stations). A CubeSat constellation using DTV transmissions as signals of opportunity is a composite instrument for frontier ionospheric research. It is a novel application of CubeSats to understand the ionospheric response to solar, magnetospheric and upper atmospheric forcing. Combined tomographic measurements of ionospheric density can be used to study the global-scale ionospheric circulation and small-scale ionospheric structures that cause scintillation of trans-ionospheric signals. The data can support a wide range of studies, including Sub-auroral Polarization Streams (SAPS), low latitude plasma instabilities and the generation of equatorial spread F bubbles, and the role of atmospheric waves and layers and sudden stratospheric warming (SSW) events in traveling ionospheric disturbances (TID).

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

    NASA Astrophysics Data System (ADS)

    Horwitz, J. L.; Zeng, W.

    2006-12-01

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

  14. Superimposed disturbance in the ionosphere triggered by spacecraft launches in China

    NASA Astrophysics Data System (ADS)

    He, L. M.; Wu, L. X.; Liu, S. J.; Liu, S. N.

    2015-11-01

    Using GPS dual-frequency observations collected by continuously operating GPS tracking stations in China, superimposed disturbances caused by the integrated action of spacecraft's physical effect and chemical effect on ionosphere during the launches of the spacecrafts Tiangong-1 and Shenzhou-8 in China were firstly determined. The results show that the superimposed disturbance was composed of remarkable ionospheric waves and significant ionospheric depletion emerged after both launches. Meanwhile, we found for the first time that the ionospheric waves were made up of two periods of wave by wavelet analysis. The first period of ∼ 4 min shows one event in the near stations and two sub-events in the few far stations. The second period of ∼ 9 min shows only one event in all the observed stations. Finally, the time characteristics for ionospheric waves and depletions were examined.

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

    NASA Technical Reports Server (NTRS)

    Nesterczuk, G.; Kozelsky, J. K.

    1976-01-01

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

  16. 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 Olsztyn. From one side, operation of LOFAR requires calibration of the ionosphere which at low frequencies varies greatly. From the other hand, LOFAR measurements retrieved from several closely located stations can be used for ionosphere/plasmasphere research.

  17. Role of Hall conductivity in the ionospheric dynamo

    SciTech Connect

    Takeda, Masahiko )

    1991-06-01

    Effects of the Hall conductivity ({sigma}{sub 2}) on the ionospheric dynamo were examined. Simulations for the ionospheric dynamo by the (1,{minus}2) mode tidal winds were made for the cases with and without {sigma}{sub 2}. It was found that existence of {sigma}{sub 2} does not modify global morphology of the height-integrated ionospheric currents much, although it enhances the total currents measured by the intensity of the equivalent current vortex by 2.1 times and diminishes the total potential difference by 1.4 times. This can be understood by the extended Cowling mechanism in which {sigma}{sub 2} makes secondary polarization field and the field drives the Hall current which enhances the original Pedersen currents. It was also shown that the equatorial electrojet and an undulated latitudinal profile of the geomagnetic H field variation near the equatorial electrojet can be understood by the latitudinal variation of the extended Cowling effect.

  18. First demonstration of HF-driven ionospheric currents

    NASA Astrophysics Data System (ADS)

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

    2011-10-01

    The first experimental demonstration of HF driven currents in the ionosphere at low ELF/ULF frequencies without relying in the presence of electrojets is presented. The effect was predicted by theoretical/computational means in a recent letter and given the name Ionospheric Current Drive (ICD). The effect relies on modulated F-region HF heating to generate Magneto-Sonic (MS) waves that drive Hall currents when they reach the E-region. The Hall currents inject ELF waves into the Earth-Ionosphere waveguide and helicon and Shear Alfven (SA) waves in the magnetosphere. The proof-of-concept experiments were conducted using the HAARP heater in Alaska under the BRIOCHE program. Waves between 0.1-70 Hz were measured at both near and far sites. The letter discusses the differences between ICD generated waves and those relying on modulation of electrojets.

  19. A study of tomographically reconstructed ionospheric images during a solar eclipse

    NASA Astrophysics Data System (ADS)

    Huang, C. R.; Liu, C. H.; Yeh, K. C.; Lin, K. H.; Tsai, W. H.; Yeh, H. C.; Liu, J. Y.

    1999-01-01

    The low-latitude ionospheric tomography network (LITN) consists of a chain of six Naval Navigation Satellite System (NNSS) receiving stations established along 121°E longitude from a geographic latitude of 14.6°N to 31°N. It is specifically designed to observe large-scale ionospheric variations over the equatorial anomaly region by using tomographic imaging techniques. Recently, the network LITN was applied to observations of the October 24, 1995, solar eclipse. Two-dimensional images of ionospheric electron density during the eclipse period were reconstructed. These images and the corresponding results from a nearby ionosonde were compared with those for a reference day. It is shown that during the eclipse day the ionosphere experienced some large-scale changes. In particular, four episodes of electron density enhancement or depression have been identified. (1) The maximum enhancement occurred before the maximum phase of the solar eclipse at approximately 7°-10°N geomagnetic latitude at the 275-300 km ionospheric height. (2) The second enhancement appeared roughly 3 1/2 hours after the maximum obscuration at 15°-22°N geomagnetic latitude and 300-325 km ionospheric height. (3) The largest electron density depression occurred roughly 2 hours after the maximum obscuration at approximately 9°-15°N geomagnetic latitude and on both the bottom and topside ionosphere. (4) The second depression occurred about 4 hours after the maximum obscuration at approximately 5.5°N geomagnetic latitude and mainly on the topside ionosphere. More detailed study suggests that the two enhancements have their origins in the ionospheric day-to-day variations, the first depression is related to the combined photochemical and the equatorial fountain effects, and the second depression may have its origin in geomagnetic coupling between conjugate ionospheres. These observations are interpreted within the framework of ionospheric dynamics in the equatorial anomaly region.

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

  1. Systematic Residual Ionospheric Error in the Radio Occultation Data

    NASA Astrophysics Data System (ADS)

    Danzer, J.; Scherllin-Pirscher, B.; Foelsche, U.

    2012-04-01

    The Radio Occultation (RO) method is used to study the Earth's atmosphere in the troposphere and lower stratosphere. The path of a transmitted electromagnetic signal from a GPS satellite changes when passing through the ionosphere and neutral atmosphere. The altered signal is detected at a receiving Low Earth Orbit satellite and provides information about atmospheric parameters such as the refractivity of the Earth's atmosphere and in a further processing step, e.g., pressure or temperature. The processing of the RO data has been done at the Wegener Center for Climate and Global Change. Different corrections are applied on the data, such as a kinematic Doppler correction, induced by the moving satellites, and an ionospheric correction due to the ionosphere dispersive nature. The standard ionospheric correction enters via a series expansion, which is truncated after first order and the correction term is proportional to the inverse square of the carrier frequency. Due to this approximation we conjecture there to be still an ionospheric residual error in the RO data, which does not fully address the change of ionization in the day to night time, and at times of high and low solar activity. This residual ionospheric error is studied by analyzing the bending angle bias (and noise). It is obtained by comparing the bending angle profiles to Mass Spectrometer and Incoherent Scatter Radar (MSIS) climatology in an altitude between 65 km and 80 km. In order to detect the residual ionospheric induced error we investigate the bias over a time period from 2001 to 2010, using CHAMP and COSMIC RO data. The day to night time bias and noise are compared for different latitudinal zones. We focus on zones between 20°N to 60°N, 20°S to 20°N and 60°S to 20°S. Our analysis shows a difference between the day and night time bias. While the night time bias is roughly constant over time, the day time bias increases in the years of high solar activity, and decreases in the years of low solar activity. The aim of our analysis is to quantify this systematic residual error in order to perform an advanced ionospheric correction in the processing of the RO data.

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

    NASA Astrophysics Data System (ADS)

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

    2015-07-01

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

  3. Calibration of a cylindrical RF capacitance probe. [for ionospheric plasma effects on Radio Astronomy Explorer 1 antenna

    NASA Technical Reports Server (NTRS)

    Mosier, S. R.; Kaiser, M. L.

    1975-01-01

    Ambient electron concentrations derived from observations with the Radio Astronomy Explorer 1 antenna capacitance probe have been compared with upper hybrid resonance measurements from the same spacecraft. From this comparison an empirical correction factor for the capacitance probe measurements has been derived. The differences between the two types of measurements is attributed to sheath effects.

  4. Natural hazards monitoring and forecast using the GNSS and other technologies of the ionosphere monitoring

    NASA Astrophysics Data System (ADS)

    Pulinets, S. A.; Davidenko, D.

    2013-12-01

    It is well established now that Atmosphere-Ionosphere Coupling is provided through the local changes of the Global Electric Circuit parameters. Main agent - is column conductivity, modulated mainly at the altitudes of the Global Boundary Layer. We demonstrate the ionospheric effects for different types of natural hazards including volcano eruptions, dusty storms from Western Africa, ionospheric effects from tropical hurricanes, multiple earthquakes. We consider the important role of air ionization from natural (natural ground radioactivity and galactic cosmic rays) and artificial sources (nuclear weapon tests in atmosphere and underground, nuclear power stations and other nuclear enterprises emergencies). We rise also important question that such effects of the ionosphere variability are not taken into account by any ionospheric model and their correct recognition is important not only from the point of view the disasters monitoring but for navigation itself because the magnitude of the ionospheric effects sometimes exceeds the effects from strong magnetic storms and other severe space weather conditions. Some effects like ionospheric effects from tropical hurricanes have more complex physical nature including the formation of streams of neutral atmosphere over the hurricane eye and formation of the strong positive plasma concentration anomaly at the altitude near 1000 km. Some plasma anomalies registered over the tropical depressions before hurricane formation give hope on predictive capabilities of plasma observations over the tropical depressions.

  5. Storm-induced changes of the topside ionosphere as deduced from incoherent-scatter radars. Master's thesis

    SciTech Connect

    Lunn, K.J.

    1990-01-01

    Incoherent scatter radar observations from Millstone Hill, Saint Santin, and Arecibo are used to illustrate changes of the topside ionosphere during a geomagnetic storm. These observations consist of electron density, electron and ion temperatures, and ion velocity components parallel and perpendicular to the magnetic field. These parameters can further describe changes in ion composition, electric fields, and neutral winds. Attention is given to a specific storm during the Equinox Transition Study (ETS) of September 1984. In order to isolate the storm effects in the topside ionosphere, a comparison will be made between a disturbed and quiet day. A novel result from this study is the finding of correlated oscillations between parallel and perpendicular ion velocity components which are apparently storm induced. Previously, these oscillations have been observed primarily at night, but now it's noticed that during storm conditions there are prominent oscillations during the day.

  6. Low latitude ionosphere response to severe geomagnetic storms

    NASA Astrophysics Data System (ADS)

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

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

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

    NASA Astrophysics Data System (ADS)

    Horwitz, James; Zeng, Wen

    2006-10-01

    There is great interest in the magnetospheric community in obtaining compact representations of the ionospheric outflow fluxes and their relationships to putative drivers. Recently, analyses of measurements by FAST and POLAR have led to best fit formulas for the measurement-based relationships of the outflows levels to parameterizations for electron precipitation and Poynting fluxes, which are expected to be among the principal drivers, or closely related to them, for the ionospheric outflows. In this presentation, we shall use the results of an extensive set of systematic simulation runs with our Dynamic Fluid Kinetic (DyFK) simulation code for ionospheric plasma field-aligned transport to obtain O^+ outflow flux levels versus precipitation electron energy flux levels and the peak spectral wave densities for BBELF waves which transversely heat ionospheric ions. We shall present spectrograms of the relationship of the ion outflow values to these electron energy flux and BBELF wave levels. A preliminary approximate formulaic representation at this time is: FluxO+ = 5(3.0x10^9 + 0.02x10^13 fe ^1.4 tanh(8Dwave)+0.2Dwave^0.6 ) where FluxO+ is the O^+ number flux in m-2s-1 at 3RE mapped to 1000 km altitude, fe is the electron precipitation energy flux in ergs cm-2s-1, and Dwave is the wave spectrum density at 6.5 Hz in mV^2m-2 Hz-1. This work was completed under financial support by NASA grant NNG05GF67G and NSF grant ATM-0505918 to the University of Texas at Arlington.

  8. Global ionospheric dynamics and electrodynamics during geomagnetic storms (Invited)

    NASA Astrophysics Data System (ADS)

    Mannucci, A. J.; Tsurutani, B.; Verkhoglyadova, O. P.; Komjathy, A.; Butala, M. D.

    2013-12-01

    Globally distributed total electron content (TEC) data has become an important tool for exploring the consequences of storm-time electrodynamics. Magnetosphere-ionosphere coupling during the main phase is responsible for the largest ionospheric effects observed during geomagnetic storms, mediated by global scale electrodynamics. Recent research using case studies reveals a complex picture of M-I coupling and its relationship to interplanetary drivers such as the solar wind electric field. Periods of direct coupling exist where the solar wind electric field is strongly correlated with prompt penetration electric fields, observed as enhanced vertical plasma drifts or an enhanced electrojet in the daytime equatorial ionosphere. Periods of decoupling between low latitude electric fields and the solar wind electric field are also observed, but the factors distinguishing these two types of response have not been clearly identified. Recent studies during superstorms suggest a role for the transverse (y-component) of the interplanetary magnetic field, which affects magnetospheric current systems and therefore may affect M-I coupling, with significant ionospheric consequences. Observations of the global ionospheric response to a range of geomagnetic storm intensities are presented. Scientific understanding of the different factors that affect electrodynamic aspects of M-I coupling are discussed.

  9. Ionospheric anomalous disturbance during the tropospheric strong convective weather

    NASA Astrophysics Data System (ADS)

    Cang, Zhongya; Cheng, Guangguang; Cheng, Guosheng

    2015-07-01

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

  10. 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…

  11. 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.

  12. Simultaneous infrasonic, seismic, magnetic and ionospheric observations in an earthquake epicentre

    NASA Astrophysics Data System (ADS)

    Laštovi?ka, J.; Baše, J.; Hruška, F.; Chum, J.; Šindelá?ová, T.; Horálek, J.; Zedník, J.; Krasnov, V.

    2010-10-01

    Various pre-seismic and co-seismic effects have been reported in the literature in the solid Earth, hydrosphere, atmosphere, electric/magnetic field and in the ionosphere. Some of the effects observed above the surface, particularly some of the pre-seismic effects, are still a matter of debate. Here we analyze the co-seismic effects of a relatively weak earthquake of 28 October 2008, which was a part of an earthquake swarm in the westernmost region of the Czech Republic. Special attention is paid to unique measurements of infrasonic phenomena. As far as we know, these have been the first infrasonic measurements during earthquake in the epicentre zone. Infrasonic oscillations (˜1-12 Hz) in the epicentre region appear to be excited essentially by the vertical seismic oscillations. The observed oscillations are real epicentral infrasound not caused by seismic shaking of the instruments or by meteorological phenomena. Seismo-infrasonic oscillations observed 155 km apart from the epicentre were excited in situ by seismic waves. No earthquake-related infrasonic effects have been observed in the ionosphere. Necessity to make vibration tests of instruments is pointed out in order to be sure that observed effects are not effects of mechanical shaking of the instrument.

  13. The ionospheric impact on GPS performance in southern polar region

    USGS Publications Warehouse

    Hong, C.-K.; Grejner-Brzezinska, D. A.; Arslan, N.; Willis, M.; Hothem, L.

    2006-01-01

    The primary objective of this paper is to present the results of the study of the effects of varying ionospheric conditions on the GPS signal tracking in the southern polar region. In the first stage of this study, the data collected by the OSU/USGS team in October-November 2003 within the TAMDEF (Transantarctic Mountains Deformation) network were used together with some IGS Antarctic stations to study the effect of severe ionospheric storms on GPS hardware. Note that TAMDEF is a joint USGS/OSU project with the primary objective of measuring crustal motion in the Transantarctic Mountains of Southern Victoria Land using GPS techniques. This study included ten Antarctic stations equipped with different dual-frequency GPS hardware, and the data were evaluated for two 24-hour periods of severe ionospheric storm (2003/10/29) and moderate ionospheric conditions (minor storm of 2003/11/11). The results of this study were presented at the LAG Assembly in Cairns, Australia (Grejner-Brzezinska et al., 2005). Additional tests, in a more controlled environment, were carried out at the US Antarctic station, McMurdo, between January 10 and February 6, 2006, under varying ionospheric conditions, where several different types of receivers were connected to the same antenna located on the rooftop of the Crary Laboratory (the primary test site). In this scenario, each antenna was subject to identical ionospheric effects during each day of the test, and no spatial decorrelation effects were present, as seen in the previous study, due to the spatial separation of the receivers tested. It should be noted, however, that no moderate or severe ionospheric storms occurred during the experiment, so, unfortunately, this type of conditions was not tested here. The test was repeated with different receivers connected to different antenna types; a total of four 5-day sessions were carried out. The following receiver types were used at the primary site: Trimble 5700, Ashtech Z-Surveyor, JNS Euro-80 and Novatel DL-4, with the following antennas: Trimble Zephyr Geodetic, Ashtech D/M and Ashtech E/M chokering. In addition, data collected by the MCM4 IGS station, MCMD UNAVCO station, and CRAR USGS station, all located within 300 m from the primary test site, were used in the analyses. These stations were equipped with the following receiver/antenna combinations: ADA SNR-12/AOAD/MJT chokering (MCM4), Trimble NETRS/AOAD/MJT chokering (MCMD), and TPS ODYSEY_E/JPSREGANT_DD_E (CRAR). The UNAVCO TEQC software was used to carry out the analyses. Depending on the data sampling rate and the mask angle, the expected numbers of observations per receiver/satellite were compared to the actual number of measurements collected during the ionospheric events, with a special emphasis on L2 data. A total number of cycle slips and losses of lock were computed and compared among the hardware types. The results presented here indicate that there is no significant effects on the GPS receivers during minor ionospheric storms (Kp<5). However, the results reported in ibid, indicate significant differences in the hardware performance under severe ionospheric storms. Thus, careful hardware selection is needed to assure data quality/continuity when observations may be affected by severe ionospheric disturbances, while under calm to minor ionospheric activity level there is no significant difference in performance among the hardware tested here.

  14. The International Reference Ionosphere - Climatological Standard for the Ionosphere

    NASA Technical Reports Server (NTRS)

    Bilitza, Dieter

    2006-01-01

    The International Reference Ionosphere (IRI) a joint project of URSI and COSPAR is the defacto standard for a climatological specification of ionospheric parameters. IRI is based on a wide range of ground and space data and has been steadily improved since its inception in 1969 with the ever-increasing volume of ionospheric data and with better mathematical descriptions of the observed global and temporal variation patterns. The IRI model has been validated with a large amount of data including data from the most recent ionospheric satellites (KOMPSAT, ROCSAT and TIMED) and data from global network of ionosondes. Several IRI teams are working on specific aspects of the IRI modeling effort including an improved representation of the topside ionosphere with a seamless transition to the plasmasphere, a new effort to represent the global variation of F2 peak parameters using the Neural Network (NN) technique, and the inclusion of several additional parameters in IRI, e.g., spread-F probability and ionospheric variability. Annual IRI workshops are the forum for discussions of these efforts and for all science activities related to IRI as well as applications of the IRI model in engineering and education. In this paper I will present a status report about the IRI effort with special emphasis on the presentations and results from the most recent IRI Workshops (Paris, 2004; Tortosa, 2005) and on the most important ongoing IRI activities. I will discuss the latest version of the IRI model, IRI-2006, highlighting the most recent changes and additions. Finally, the talk will review some of the applications of the IRI model with special emphasis on the use for radiowave propagation studies and communication purposes.

  15. Automated Ionospheric Front Velocity Estimation Algorithm for

    E-print Network

    Stanford University

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

  16. Introduction to the Ionosphere Alan Aylward

    E-print Network

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

  17. LWA Ionospheric Workshop Christopher Watts1

    E-print Network

    Ellingson, Steven W.

    LWA Ionospheric Workshop Christopher Watts1 and Kenneth Dymond2 with: Ronald Caton5 , Clayton Coker The LWA Ionospheric Workshop was held in parallel with the CEDAR workshop at the Eldorado Hotel on Sunday June 28, 2009. The purpose of the workshop was to bring together the ionospheric and astronomy

  18. Radar Soundings of the Ionosphere of Mars

    E-print Network

    Gurnett, Donald A.

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

  19. Study of magnetic activity effects on the thermospheric winds in the low ionosphere. Master`s thesis

    SciTech Connect

    Davila, R.C.

    1994-09-01

    The purpose of this thesis is to examine the effects of magnetic activity on the low latitude F-region thermospheric winds. The F-region (120-1600 km) is a partially ionized medium where O+ and O are the major ion and neutral species, respectively. The thermospheric winds at these altitudes are driven primarily by pressure gradient forces resulting from the solar heating during the day and cooling at night. For this study, the author used measured Fabry-Perot Interferometer (FPI) winds at Arequipa (16.5 deg S, 71.5 deg W) and measured FPI and incoherent Scatter Radar (ISR) winds at Arecibo (18.6 deg N, 66.8 deg W).

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

    NASA Astrophysics Data System (ADS)

    Tuna, Hakan; Arikan, Orhan; Arikan, Feza

    2015-10-01

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

  1. Quantifying residual ionospheric errors in GNSS radio occultation bending angles based on ensembles of profiles from end-to-end simulations

    NASA Astrophysics Data System (ADS)

    Liu, C. L.; Kirchengast, G.; Zhang, K.; Norman, R.; Li, Y.; Zhang, S. C.; Fritzer, J.; Schwaerz, M.; Wu, S. Q.; Tan, Z. X.

    2015-07-01

    The radio occultation (RO) technique using signals from the Global Navigation Satellite System (GNSS), in particular from the Global Positioning System (GPS) so far, is currently widely used to observe the atmosphere for applications such as numerical weather prediction and global climate monitoring. The ionosphere is a major error source in RO measurements at stratospheric altitudes, and a linear ionospheric correction of dual-frequency RO bending angles is commonly used to remove the first-order ionospheric effect. However, the residual ionospheric error (RIE) can still be significant so that it needs to be further mitigated for high-accuracy applications, especially above about 30 km altitude where the RIE is most relevant compared to the magnitude of the neutral atmospheric bending angle. Quantification and careful analyses for better understanding of the RIE is therefore important for enabling benchmark-quality stratospheric RO retrievals. Here we present such an analysis of bending angle RIEs covering the stratosphere and mesosphere, using quasi-realistic end-to-end simulations for a full-day ensemble of RO events. Based on the ensemble simulations we assessed the variation of bending angle RIEs, both biases and standard deviations, with solar activity, latitudinal region and with or without the assumption of ionospheric spherical symmetry and co-existing observing system errors. We find that the bending angle RIE biases in the upper stratosphere and mesosphere, and in all latitudinal zones from low to high latitudes, have a clear negative tendency and a magnitude increasing with solar activity, which is in line with recent empirical studies based on real RO data although we find smaller bias magnitudes, deserving further study in the future. The maximum RIE biases are found at low latitudes during daytime, where they amount to within -0.03 to -0.05 ?rad, the smallest at high latitudes (0 to -0.01 ?rad; quiet space weather and winter conditions). Ionospheric spherical symmetry or asymmetries about the RO event location have only a minor influence on RIE biases. The RIE standard deviations are markedly increased both by ionospheric asymmetries and increasing solar activity and amount to about 0.3 to 0.7 ?rad in the upper stratosphere and mesosphere. Taking also into account the realistic observation errors of a modern RO receiving system, amounting globally to about 0.4 ?rad (unbiased; standard deviation), shows that the random RIEs are typically comparable to the total observing system error. The results help to inform future RIE mitigation schemes that will improve upon the use of the linear ionospheric correction of bending angles and also provide explicit uncertainty estimates.

  2. Estimation of parameters to monitor state of the ionosphere in a single station mode

    NASA Astrophysics Data System (ADS)

    Cokrlic, M.; Galas, R.

    2013-12-01

    Ionosphere is the dispersive medium and propagation of the electromagnetic waves depend on its frequency. In the Global Positioning System (GPS), after the Selected Availability (SA) has been turned off, ionospheric delay become one of the largest source of error. Relatively low cost of the GPS receivers makes it one of the cheapest tool for studying and monitoring of the ionosphere in a global scale. Especially because the GPS signals are carrying ionospheric characteristics that can be isolated and then studied. For real time applications, demanding high accuracy and availability, it is important to know variable, in time and space, state of the ionosphere in real-time. Ionospheric perturbations can degrade accuracy of the positioning for more than hundred meters and even make positioning impossible or false. Thus, information about state of the ionosphere must be available in real time to enhance availability and to improve navigation accuracy. The state of the ionosphere can be characterized by a couple of basic parameters such as: Total Electron Content (TEC), Rate of TEC (ROT), Rate of change of TEC (ROTI), amplitude scintillation (S4) and phase scintillation (?_?). This parameters can be estimated form GPS networks or from a single GPS station. We are developing software tools to measure those parameters in a very challenging single station mode. Some of the modules, like e.g. calculation of S4 and ROT, are validated and some others are still in the testing phase. The tools are needed in order to analyze ionospheric perturbation parameters in real- or near- real time and investigate if some new approaches for generation of corrections can be developed. Our main goal is provision of such corrections, or at least warnings about ionospheric perturbations, to single station PPP (Precise Point Positioning) users. In the poster the algorithms are described and preliminary results are presented.

  3. Pre-seismic Lithosphere, Atmosphere and Ionosphere Coupling

    NASA Astrophysics Data System (ADS)

    Kamogawa, M.

    2006-12-01

    Pre-seismic anomalous states in the atmosphere and ionosphere as well as those in the telluric currents and ultra-low frequency electromagnetic waves have been reported since the 1970s. These pre-seismic phenomena have not yet been universally accepted, partly because the low occurrence frequency of large earthquakes has hindered establishing their statistical significance. Recent achievements in this respect, however, seem to be highly encouraging for promoting further studies on the pre-seismic lithosphere-atmosphere-ionosphere (LAI) coupling. Liu et al. (JGR, 2006) constructed a set of quantitative definitions for ionospheric anomalies (depression of foF2) and examined the statistical correlation between thus defined ionospheric anomalies and all the Taiwan M>=5 earthquakes (184 in number) during the period 1994-1999. The results indicated that anomalies appeared within 5 days before the earthquakes. Examining the validity of the pre-seismic anomalous transmission of VHF electromagnetic waves beyond the line-of-sight, Fujiwara and Kamogawa et al. (GRL, 2004) statistically demonstrated the existence of atmospheric anomalies lasting for a few minutes to several hours before earthquakes. They found that the anomalies were significantly enhanced within 5 days before M>=4.8 earthquakes. If the pre-seismic atmospheric - ionospheric anomalies are real, some phenomena causing them should be detectable on the ground. If such causal phenomena are identified, the concept of lithosphere - atmosphere - ionosphere coupling (LAI coupling) will be greatly strengthened. Possible mechanisms for energy-transport channels from the lithosphere to the atmosphere-ionosphere are summarized as follows: First, the atmospheric electric field generated on/near the ground surface during the pre-seismic period may cause the ionospheric anomalies. Such an atmospheric electric field may be caused by ions generated from radon emissions. Actually, a number of reports have been published for pre-seismic radon emissions. However, such pre-seismic electric fields on the ground followed by pre-seismic ionospheric anomalies have not yet been observed. Alternatively, it has been proposed that atmospheric gravity waves propagate up to and disturbs the ionosphere before earthquakes. The proposed sources of the gravity waves are long-period ground oscillations or thermal anomalies. This proposed linkage is inferred from the observations of co-seismic ground vibrations and tsunami exciting atmospheric gravity waves which propagate into ionosphere. However, there is no report of pre-seismic long-period ground oscillations being detected, even by sensitive superconducting gravimeters. Although some reports claim the existence of pre-seismic rises of temperature, infrared radiation, and surface latent heat flux, it is difficult to explain how such anomalies disturb the ionosphere through the atmosphere. As discussed in this abstract, the cause and effect relationships may still be unestablished but pre-seismic atmospheric-ionospheric anomalies do exist and searching for the lithospheric connection remains an important research endeavor.

  4. Neutral winds and ionospheric electrodynamics during geomagnetic storms

    NASA Astrophysics Data System (ADS)

    Wang, Wenbin; Burns, Alan; Lei, Jiuhou; Solomon, Stan; Killeen, Tim; Wiltberger, Mike

    The Coupled Magnetosphere Ionosphere Thermosphere (CMIT) model is used to investigate the relative contributions of each electric field to the global changes of ionospheric F region electron densities during the Dec. 2006 storm. The CMIT model is capable of self-consistently simulating ionospheric electric fields that are of magnetospheric origin, and produced by the thermospheric neutral wind dynamo and penetration electric field. It is found that penetration electric fields were the primary driver of the electron density changes during the early phase of the geomagnetic storm. The neutral wind dynamo, however, contributed significantly to the global electric field and density changes during the main phase of the storm when Joule heating and ion drag enhanced significantly the global neutral wind circulation. Neutral wind dynamo became the dominant process during the recovery phase of the storm when the neutral wind fly-wheel effect still generated large dynamo field but the electric field of magnetospheric origin and penetration electric fields were very weak.

  5. Electrodynamics of solar wind-magnetosphere-ionosphere interactions

    NASA Technical Reports Server (NTRS)

    Kan, Joseph R.; Akasofu, Syun-Ichi

    1989-01-01

    The paper presents a coherent picture of fundamental physical processes in three basic elements of the solar-wind/magnetosphere/ionosphere coupling system: (1) the field-aligned potential structure which leads to the formation of auroral arcs, (2) the magnetosphere-ionosphere coupling which leads to the onset of magnetospheric substorms, and (3) the solar-wind/magnetosphere dynamo which supplies the power driving various magnetospheric processes. Process (1) is forced into existence by the loss-cone constriction effect when the upward field-aligned current density exceeds the loss-cone thermal flux limit. Substorm onset occurs when the ionosphere responds fully to the enhanced magnetospheric convection driven by the solar wind. Energy is transferred from the solar wind to the magnetosphere by a dynamo process, primarily on open field lines.

  6. Global scale ionospheric irregularities associated with thunderstorm activity

    E-print Network

    Pulinets, S A

    2002-01-01

    The potential difference near 280 kV exists between ground and ionosphere. This potential difference is generated by thunderstorm discharges all over the world, and return current closes the circuit in the areas of fair weather (so-called fair weather current). The model calculations and experimental measurements clearly demonstrate non-uniform latitude-longitude distribution of electric field within the atmosphere. The recent calculations show that the strong large scale vertical atmospheric electric field can penetrate into the ionosphere and create large scale irregularities of the electron concentration. To check this the global distributions of thunderstorm activity obtained with the satellite monitoring for different seasons were compared with the global distributions of ionosphere critical frequency (which is equivalent to peak electron concentration) obtained with the help of satellite topside sounding. The similarity of the obtained global distributions clearly demonstrates the effects of thunderstor...

  7. Ionosphere and atmosphere of the moon in the geomagnetic tail

    NASA Technical Reports Server (NTRS)

    Daily, W. D.; Barker, W. A.; Parkin, C. W.; Clark, M.; Dyal, P.

    1977-01-01

    The paper presents calculations of the densities and energies of the various constituents of the lunar ionosphere during the time that the moon is in the geomagnetic tail; the surface concentrations of neon and argon are calculated from a theoretical model to be 3,900 and 1,700, respectively. It is found that a hydrostatic model of the ionospheric plasma is inadequate because the gravitational potential energy of the plasma is considerably smaller than its thermal energy. A hydrodynamic model, comparable to that used to describe the solar wind, is developed to obtain plasma densities and flow velocities as functions of altitude. The electromagnetic properties of the quiescent ionosphere are then investigated, and it is concluded that plasma effects on lunar induction can be neglected for quiescent conditions in the geomagnetic tail lobes.

  8. Titan's upper atmospheric structure and ionospheric composition

    NASA Astrophysics Data System (ADS)

    Westlake, Joseph H.

    This Dissertation investigates the density structure of the neutral upper atmosphere and the composition of the ionosphere of Titan through Cassini observations. The highly extended atmosphere of Titan consists primarily of N2, CH4, and H2. The focus is on data extracted from the Ion and Neutral Mass Spectrometer (INMS) and the Cassini Plasma Spectrometer (CAPS) instruments onboard Cassini. The INMS, which is fundamentally a quadrupole mass spectrometer, measures the abundance of neutral and ion components with masses of 1--8 and 12--99 Da. The CAPS instrument consists of three subsystems of which the Ion Beam Spectrometer (CAPS-IBS) is used in this study to derive mass spectra of thermal ions up to 400 Da. in mass in Titan's ionosphere. From measurements of molecular nitrogen in Titan's upper atmosphere an atmospheric scale height is derived implying an effective temperature. From an analysis of 29 targeted flybys of Titan we find that the thermosphere is isothermal from an altitude of 1050 km to the exobase height with an average effective temperature of 153 K. The scale height, and hence the effective temperature, is found to be highly variable. We assess this variability against the relevant geospatial, solar, and magnetospheric parameters to determine which are highly correlated to the effective temperatures. Titan's thermospheric temperature is found to be controlled by variations in the magnetospheric plasma environment. No correlation is found to exist with respect to geospatial parameters (i.e., latitude or longitude) and anti-correlation is found with solar parameters implying that Titan's nightside is hotter than its dayside. Furthermore, Titan's thermosphere is found to respond to plasma forcings on timescales less than one Titan day. To investigate the composition of Titan's ionosphere we present a 1D photochemical model of Titan's dayside ionosphere constrained by Cassini measurements. We show that the production of the primary products of photoionization match the INMS data to within 20%. The major ions, CH+5,C2H+ 5 , and HCNH+, are discussed at length and an investigation of the processes controlling their modeled densities is presented. We then present the ion density profiles for the major hydrocarbons in the C3--C6 groups and the major nitrogen-containing ions up to the C4 group. We find that significant chemistry in the nitrogen containing hydrocarbons is missing from previous models and suggest pathways for the growth of these molecules. We also find that the chemistry of Titan's ionosphere is not necessarily dominated by proton exchange processes and that significant molecular growth should be expected through associative ion-molecule reactions. The composition of the ions observed by the Ion Beam Spectrometer (CAPS-IBS) are analyzed with a specific emphasis on those larger than benzene (C 6H6). The CAPS-IBS mass spectra are found to have several peaks corresponding to ions having up to 14 carbon atoms with significant densities and masses up to 400 Da. Fits to the high mass ion spectra determine that each observed peak grouping must contain more than one ion of substantial density possibly indicating some degree of nitrogen incorporation. We compare the high mass ion spectra to various laboratory experiments which have produced large hydrocarbons or tholins through plasma processing of N2, CH4, and various simple hydrocarbons. We conclude from these comparisons that it is likely that Titan's ionospheric chemistry proceeds to higher mass through the reactions of C2 hydrocarbons and nitrogen containing hydrocarbons. Density profiles of the C8--C13 groups are presented from the CAPS-IBS data which show a region of initiation at altitudes above 1050 km and below 1200 km followed by a stagnation and drop-off at the lowest altitudes. We present modeled density profiles of the ions in the C6 and larger groups using an empirical model.

  9. Radar soundings of the ionosphere of Mars.

    PubMed

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

    2005-12-23

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

  10. Magnetospheres of Planets and Moons: Links to Their Ionospheres. (Invited)

    NASA Astrophysics Data System (ADS)

    Kivelson, M. G.

    2010-12-01

    The phrase “magnetosphere-ionosphere coupling” has become almost hackneyed in the terrestrial context, but plays an important role in the terrestrial system and must also be emphasized in the context of planetary- and moon-magnetospheres because the underlying principles are similar in all systems. This talk will introduce only two intriguing aspects of the coupling problem for planets and moons. In describing the first topic, we note that, especially for the gas giants Jupiter and Saturn, much of the evidence of magnetosphere-ionosphere coupling is obtained from auroral imaging. In images of Jupiter’s polar ionosphere, bright auroral spots are found to link magnetically to the moons Io, Europa and Ganymede. The spots give evidence of intense field-aligned currents generated near the equator in the interaction between the moons and the flowing plasma of Jupiter’s magnetosphere. The currents must penetrate through regions of impedance mismatch near the upper and lower boundaries of Jupiter’s equatorial plasma torus in order to close in the planetary ionosphere. There is some evidence that the signal propagates through the strong gradient of plasma density at the boundary of the plasma torus by converting into a striated structure that guides high frequency waves. As well, at Io, the interaction has been found to generate localized intense electron fluxes observed to flow along and antiparallel to the magnetic field near the equator. These bidirectional beams are probably accelerated by parallel electric fields near the ionospheric ends of the flux tube, but how the accelerated electrons reach the equator has not been explained. It seems likely that their presence there requires that the (parallel) electric fields in the Jovian ionosphere vary either temporally at high frequency or spatially on short transverse length scales. The full explanation has not yet been developed. As a second example of the role of magnetosphere-ionosphere coupling in planetary systems, we turn to an MHD simulation of the mini-magnetosphere of Ganymede carried out by X. Jia (2010). The significance of the ionosphere in the simulation is that, as the inner plasma boundary, it affects the flow and the dynamics of the entire system. The mathematical reason for the result is evident: differential equations have different solutions for different boundary conditions, but the dramatic changes that arise throughout the entire volume of the magnetosphere as the inner boundary condition is slightly modified may be both surprising and illuminating.

  11. Ionospheric parameter analysis techniques and anomaly identification in periods of ionospheric perturbations

    NASA Astrophysics Data System (ADS)

    Mandrikova, Oksana; Polozov, Yury; Fetisova Glushkova, Nadejda; Shevtsov, Boris

    In the present paper we suggest intellectual techniques intended for the analysis of ionospheric parameters. These techniques are directed at studying dynamic processes in the "magnetosphere-ionosphere" system during perturbations. Using the combination of the wavelet transform and neural networks, the authors have developed a technique of approximating the time variation of ionospheric parameters. This technique allows us to make data predictions and detect anomalies in the ionosphere. Multiscale component approximations of the critical frequency of the ionosphere layer F2 were constructed. These approximations can be presented in the following form: begin{center} c_{l,k+m} (t) = varphi_m(3) Bigl (sum_i omega(3_{mi}) varphi_i(2) Bigl (sum_j omega(2_{ij}) varphi_j(1) Bigl (sum_k omega(1_{jk}) c_{l,k} (t) Bigr ) Bigr ) Bigr ) , where c_{l,k} = bigl < f , Psi_{l,k} bigr > ; Psi_{l,k} (t) = 2(l/2) Psi (2(l) t - k) is the wavelet basis; omega(1_{jk}) are the weighting coefficients of the neuron j of the network input layer; omega(2_{ij}) are the weighting coefficients of the neuron i of the network hidden layer; omega(3_{mi}) are the weighting coefficients of the neuron m of the network output layer; varphi(1_j) (z) = varphi(2_i) (z) = (1)/(1+exp(-z))) ; varphi(3_m) (z) = x*z+y . The coefficients c_{l,k} can be found as a result of transforming the original function f into the space with the scale l . In order to obtain the approximations of the time variation of data, neural networks can be united in groups. In the paper we have suggested a multicomponent time variation model of ionospheric parameters, which makes it possible to perform the analysis of the ionospheric dynamic mode, receive predictions about parameter variations, and detect anomalies in periods of perturbations. The multicomponent model also allows us to fill missing values in critical frequency data taking into account diurnal and seasonal variations. Identification of the model is based on combining the wavelet transform with autoregressive integrated moving average methods. The general expression of the multicomponent model is f_0 (t) = sum_{mu = /line{1,M}} sum_{k = /line{1,N_1(mu}}) s_{l,k}(mu) (t) b_{l,k}(mu) (t) , where s_{l,k}(mu) (t) = sum_{q=1}(p_l(mu)) gamma_{l,q}(mu) w(mu_{l,k-q}) (t) - sum_{n=1}(h_l(mu)) theta_{l,n}(mu) alpha(mu_{l,k-n}) (t) is the estimated value of the mu -th component, p_l(mu) is the autoregressive model order of the mu -th component, gamma_{l,q}(mu) are the autoregressive parameters of the mu -th component, w_{l,k}(mu) (t) = nabla(nu(mu)) beta_{l,k}(mu) (t) , nu(mu) is the difference order of the mu -th component, beta_{l,k}(mu) are the decomposition coefficients of the mu -th component, h_l(mu) , theta_{l,k}(mu) are the model orders and moving average parameters of the mu -th component model, alpha(mu_{l,k}) are the residual errors of the mu -th component model, M is the number of characteristic components, N_l(mu) is the length of the mu -th component, b_{l,k}(mu) is the wavelet basis of the mu -th component, l is the scale. Using these techniques we have obtained the approximation of the ionospheric critical frequency time variation for regions located in Kamchatka and Magadan. The analysis of the quiet variation of the parameters was performed, the 5-hour prediction was made, and anomalies occurring in periods of increased solar activity and prior to strong earthquakes in Kamchatka were discovered in the ionosphere. The developed methods are useful for studying the properties of ionospheric perturbations, obtaining information about various parameters of ionospheric plasma irregularities and the dynamic mode of these parameters.

  12. Second-order nonlinear optical effects of spin currents

    NASA Astrophysics Data System (ADS)

    Wang, Jing; Liu, Ren-Bao; Zhu, Bang-Fen

    2011-12-01

    Pure spin currents, which carry information via spins in lieu of charges, are a key element in spintronics and signify the quantum spin Hall effect. However, they are hardly traceable as they bear neither net magnetization nor net charge currents, notwithstanding many "smoking-gun" evidences. We show that a pure spin current has measurable second-order nonlinear optical effects by symmetry analysis and microscopic calculations. These findings may be exploited for directly "seeing" spin currents in real-time and real-space with standard nonlinear optical spectroscopy.

  13. Effect of Disorder on First-Order Phase Transitions

    NASA Astrophysics Data System (ADS)

    Bellafard, Arash

    Disorder is an inevitable part of any condensed matter system and therefore its study has always been of great importance. The effect of quenched randomness on a system that exhibits a continuous phase transition in the absence of any impurity has been studied in the past and the results are relatively well understood. However, the effect of quenched randomness on first-order phase transitions is still not well understood. In this dissertation, we study the effect of quenched bond-randomness on the classical and quantum first-order phase transitions. In Chapter 2, we study the effect of the disordered three-color Ashkin-Teller model, whose pure version undergoes a first-order phase transition. We show that the rounding of the first-order transition of the pure model due to the impurities is manifested as a critical point. We conclusively rule out that the model belongs to the universality class of the two-dimensional Ising model. Furthermore, we find that the exponents beta and nu vary with disorder and the four-spin coupling strength. In Chapter 3, we extend our study of the disordered three-color Ashkin-Teller model. Utilizing extensive cluster Monte Carlo simulations on large lattice sizes of up to 128 x 128 spins, each of which is represented by three colors taking values +/-1, we show that the rounding of the first-order phase transition is an emergent criticality. We find that the critical exponents, nu and beta, change as the strength of disorder or the four-spin coupling varies, and we show that the correlation length critical exponent violates the lower bound 2/D ? nu, where D is the dimension of the system. In Chapter 4, we study the quantum three-color Ashkin--Teller model and show that the quantum critical point in (1+1) dimension is an unusual one, with activated scaling at the critical point and Griffiths-McCoy phase away from it. We find that the behavior is similar to the transverse random field Ising model, even though the pure system has a first-order transition in this case.

  14. The impact of large scale ionospheric structure on radio occultation retrievals

    NASA Astrophysics Data System (ADS)

    Mannucci, A. J.; Ao, C. O.; Pi, X.; Iijima, B. A.

    2011-12-01

    We study the impact of large-scale ionospheric structure on the accuracy of radio occultation (RO) retrievals. We use a climatological model of the ionosphere as well as an ionospheric data assimilation model to compare quiet and geomagnetically disturbed conditions. The presence of ionospheric electron density gradients during disturbed conditions increases the physical separation of the two GPS frequencies as the GPS signal traverses the ionosphere and atmosphere. We analyze this effect in detail using ray-tracing and a full geophysical retrieval system. During quiet conditions, our results are similar to previously published studies. The impact of a major ionospheric storm is analyzed using data from the 30 October 2003 "Halloween" superstorm period. At 40 km altitude, the refractivity bias under disturbed conditions is approximately three times larger than quiet time. These results suggest the need for ionospheric monitoring as part of an RO-based climate observation strategy. We find that even during quiet conditions, the magnitude of retrieval bias depends critically on assumed ionospheric electron density structure, which may explain variations in previously published bias estimates that use a variety of assumptions regarding large scale ionospheric structure. We quantify the impact of spacecraft orbit altitude on the magnitude of bending angle and retrieval error. Satellites in higher altitude orbits (700+ km) tend to have lower residual biases due to the tendency of the residual bending to cancel between the top and bottomside ionosphere. Another factor affecting accuracy is the commonly-used assumption that refractive index is unity at the receiver. We conclude with remarks on the implications of this study for long-term climate monitoring using RO.

  15. The impact of large scale ionospheric structure on radio occultation retrievals

    NASA Astrophysics Data System (ADS)

    Mannucci, A. J.; Ao, C. O.; Pi, X.; Iijima, B. A.

    2011-05-01

    We study the impact of large-scale ionospheric structure on the accuracy of radio occultation (RO) retrievals of atmospheric parameters such as refractivity and temperature. We use a climatological model of the ionosphere as well as an ionospheric data assimilation model to compare quiet and geomagnetically disturbed conditions. The largest contributor to ionospheric bias is physical separation of the two GPS frequencies as the GPS signal traverses the ionosphere and atmosphere. We analyze this effect in detail using ray-tracing and a full geophysical retrieval system. During quiet conditions, our results are similar to previously published studies. The impact of a major ionospheric storm is analyzed using data from the 30 October 2003 "Halloween" superstorm period. The temperature retrieval bias under disturbed conditions varies from 1 K to 2 K between 20 and 32 km altitude, compared to 0.2-0.3 K during quiet conditions. These results suggest the need for ionospheric monitoring as part of an RO-based climate observation strategy. We find that even during quiet conditions, the magnitude of retrieval bias depends critically on ionospheric conditions, which may explain variations in previously published bias estimates that use a variety of assumptions regarding large scale ionospheric structure. We quantify the impact of spacecraft orbit altitude on the magnitude of bending angle error. Satellites in higher altitude orbits (?700 km) tend to have lower biases due to the tendency of the residual bending to cancel between the top and bottomside ionosphere. We conclude with remarks on the implications of this study for long-term climate monitoring using RO.

  16. Wave Coupling in the Atmosphere-Ionosphere System (Invited)

    NASA Astrophysics Data System (ADS)

    Forbes, J. M.

    2013-12-01

    Within the last decade, a new realization has arrived on the scene of ionosphere-thermosphere (IT) science: terrestrial weather significantly influences space weather. The primary mechanism through which this occurs is the generation and propagation of waves of various spatial and temporal scales, including gravity waves, planetary waves and solar tides. Waves drive ionospheric variability through their influences on composition, the wind field, and through the generation of dynamo electric fields. Most of the relevant processes occur between about 100 and 200 km where observations are sparse. Outstanding questions include: How does the wave spectrum evolve with height, and what are the implications of wave-wave interactions and cross-scale coupling? How do waves of various scales dynamically interact with the ionospheric plasma? To what extent do waves determine the mean structure and circulation of the thermosphere? How do waves contribute to the transport of chemical constituents? How do magnetic disturbance and solar effects interact with responses to meteorological drivers? In this talk I will provide some further details on the above questions, and then outline observational strategies that will address them. The primary mechanism through which energy and momentum are transferred from the lower atmosphere to the upper atmosphere and ionosphere is through the generation and propagation of waves. In the ionosphere wind perturbations associated with the waves can redistribute ionospheric plasma, either through the electric fields generated via the dynamo mechanism, or directly by moving plasma along magnetic field lines. Modifications to neutral and ion chemistry by the waves are also possible.

  17. Numerical simulation of the effects of meteoroid ablation and solar EUV/X-ray radiation in the dayside ionosphere of Mars: MGS/MEX observations

    NASA Astrophysics Data System (ADS)

    Pandya, B. M.; Haider, S. A.

    2014-11-01

    We have developed a model which produces three plasma layers simultaneously due to the impact of the meteoroids, solar X-ray (0.5-9 nm), and EUV (9-102.6 nm) radiation at altitude range 75-85 km, 100-115 km, and 135-140 km, respectively, in the dayside ionosphere of Mars. The calculated results are compared with the radio occultation measurements made by Mars Express (MEX) and Mars Global Surveyor (MGS) on 18 April 2004 and 11 May 2005, when comets P/2003 WC7 (LINEAR Catalina) and 10P/Tempel 2 intersected the orbit of Mars, respectively. The densities of 21 ions (CO2+, O2+, CO+, O+, NO+, N2+, Mg+, Fe+, Si+, MgO+, FeO+, SiO+, MgCO2+, MgO2+, FeCO2+, FeO2+, SiCO2+, SiO2+, MgN2+, FeN2+, and SiN2+) and 10 neutral species (Mg, Fe, Si, MgO, FeO, SiO, MgCO3, FeCO3, MgO2, and FeO2) have been computed self-consistently for both days. The metallic ions are formed in the middle ionosphere due to the ablation of meteoroids. It is found that the middle ionosphere of Mars strongly depends on incoming mass and flux of the meteoroids. The meteoroids of fluxes 4.0 × 10-15 and 8.3 × 10-16 cm-2 s-1 for masses 4.5 × 10-7 g and 1.0 × 10-3 g have produced third layers, which are good in agreement with the observations made by MEX and MGS on 18 April 2004 and 11 May 2005, respectively.

  18. Atmospheric and ionospheric electrical parameter variations inferred from sub - ionospheric seismo - electromagnetic VLF/LF observations

    NASA Astrophysics Data System (ADS)

    Schwingenschuh, K.; Eichelberger, H. U.; Besser, B. P.; Prattes, G.; Boudjada, M. Y.; Stangl, G.; Wolbang, D.; Rozhnoi, A.; Solovieva, M.; Biagi, P. F.; Friedrich, M.; Biernat, H.; Hayakawa, M.

    2012-04-01

    Subionospheric VLF/LF radio links are an essential tool to investigate seismo - electromagnetic phenomena. The propagation of very low (VLF) and low frequency (LF) frequency radio waves is mainly controlled by the index of refraction and electrical conductivity in the waveguide between the surface and the ionosphere. These parameters can be disturbed during seismic active periods by the lithospheric - atmospheric - ionospheric coupling. The signals of various navigational and time service transmitters are received by a European network of VLF/LF receivers. Several methods have been developed to analyse the received VLF/LF amplitude and phase in order to get information on the seismic activity along the radio path. We present a simple model for the estimation of the VLF/LF radio wave propagation parameters using mainly the amplitude observations of receivers in Italy, Austria and Russia. The main emphasis is on the L'Aquila earthquake from April 2009 with a magnitude of 6.3. This event has been observed with ground based VLF/LF radio links as well as with satellite VLF receivers. The influence of the electrophysical parameters in the immediate vicinity of the active-seismic region on ionospheric parameters is a hot debated issue, where definite physical answers are still expected to be found. Its consequences for the VLF/LF propagation in the sub-ionospheric waveguide are theoretically not well understood up to now, although empirically the issue is well established. For the analysis of pre-seismic activity the systematic variation of the terminator time (TT) and the night time amplitude variations (residual method) seem to be an important indicator. Therefore we studied theoretically the propagation and the influence of ionospheric parameter changes on the VLF/LF mode conversion at the solar terminator and near the seismic region. Our method is based on analytical models of Ledinegg et al. (1982). In particular, we will present prelininary results of the influence of conductivity variations in the wave guide on the received VLF/LF amplitude. This is a first step in solving the inverse problem of VLF/LF seismo-electromagnetism.

  19. Meteoric layers in planetary ionospheres

    E-print Network

    Withers, Paul

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

  20. Magnetospheric-ionospheric Poynting flux

    NASA Technical Reports Server (NTRS)

    Thayer, Jeffrey P.

    1994-01-01

    Over the past three years of funding SRI, in collaboration with the University of Texas at Dallas, has been involved in determining the total electromagnetic energy flux into the upper atmosphere from DE-B electric and magnetic field measurements and modeling the electromagnetic energy flux at high latitudes, taking into account the coupled magnetosphere-ionosphere system. This effort has been very successful in establishing the DC Poynting flux as a fundamental quantity in describing the coupling of electromagnetic energy between the magnetosphere and ionosphere. The DE-B satellite electric and magnetic field measurements were carefully scrutinized to provide, for the first time, a large data set of DC, field-aligned, Poynting flux measurement. Investigations describing the field-aligned Poynting flux observations from DE-B orbits under specific geomagnetic conditions and from many orbits were conducted to provide a statistical average of the Poynting flux distribution over the polar cap. The theoretical modeling effort has provided insight into the observations by formulating the connection between Poynting's theorem and the electromagnetic energy conversion processes that occur in the ionosphere. Modeling and evaluation of these processes has helped interpret the satellite observations of the DC Poynting flux and improved our understanding of the coupling between the ionosphere and magnetosphere.

  1. Seismo-Ionospheric Coupling as Intensified EIA Observed by Satellite Electron Density and GPS-TEC Data

    NASA Astrophysics Data System (ADS)

    Ryu, K.; Jangsoo, C.; Kim, S. G.; Jeong, K. S.; Parrot, M.; Pulinets, S. A.; Oyama, K. I.

    2014-12-01

    Examples of intensified EIA features temporally and spatially related to large earthquakes observed by satellites and GPS-TEC are introduced. The precursory, concurrent, and ex-post enhancements of EIA represented by the equatorial electron density, which are thought to be related to the M8.7 Northern Sumatra earthquake of March 2005, the M8.0 Pisco earthquake of August 2007, and the M7.9 Wenchuan Earthquake of 12 May 2008, are shown with space weather condition. Based on the case studies, statistical analysis on the ionospheric electron density data measured by the Detection of Electro-Magnetic Emissions Transmitted from Earthquake Regions satellite (DEMETER) over a period of 2005-2010 was executed in order to investigate the correlation between seismic activity and equatorial plasma density variations. To simplify the analysis, three equatorial regions with frequent earthquakes were selected and then one-dimensional time series analysis between the daily seismic activity indices and the EIA intensity indices were performed for each region with excluding the possible effects from the geomagnetic and solar activity. The statistically significant values of the lagged cross-correlation function, particularly in the region with minimal effects of longitudinal asymmetry, indicate that some of the very large earthquakes with M > 7.0 in the low latitude region can accompany observable seismo-ionospheric coupling phenomena in the form of EIA enhancements, even though the seismic activity is not the most significant driver of the equatorial ionospheric evolution. The physical mechanisms of the seismo-ionospheric coupling to explain the observation and the possibility of earthquake prediction using the EIA intensity variation are discussed.

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

    SciTech Connect

    Georges, A.T.

    2002-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  4. A comprehensive method for GNSS data quality determination to improve ionospheric data analysis.

    PubMed

    Kim, Minchan; Seo, Jiwon; Lee, Jiyun

    2014-01-01

    Global Navigation Satellite Systems (GNSS) are now recognized as cost-effective tools for ionospheric studies by providing the global coverage through worldwide networks of GNSS stations. While GNSS networks continue to expand to improve the observability of the ionosphere, the amount of poor quality GNSS observation data is also increasing and the use of poor-quality GNSS data degrades the accuracy of ionospheric measurements. This paper develops a comprehensive method to determine the quality of GNSS observations for the purpose of ionospheric studies. The algorithms are designed especially to compute key GNSS data quality parameters which affect the quality of ionospheric product. The quality of data collected from the Continuously Operating Reference Stations (CORS) network in the conterminous United States (CONUS) is analyzed. The resulting quality varies widely, depending on each station and the data quality of individual stations persists for an extended time period. When compared to conventional methods, the quality parameters obtained from the proposed method have a stronger correlation with the quality of ionospheric data. The results suggest that a set of data quality parameters when used in combination can effectively select stations with high-quality GNSS data and improve the performance of ionospheric data analysis. PMID:25196005

  5. A Comprehensive Method for GNSS Data Quality Determination to Improve Ionospheric Data Analysis

    PubMed Central

    Kim, Minchan; Seo, Jiwon; Lee, Jiyun

    2014-01-01

    Global Navigation Satellite Systems (GNSS) are now recognized as cost-effective tools for ionospheric studies by providing the global coverage through worldwide networks of GNSS stations. While GNSS networks continue to expand to improve the observability of the ionosphere, the amount of poor quality GNSS observation data is also increasing and the use of poor-quality GNSS data degrades the accuracy of ionospheric measurements. This paper develops a comprehensive method to determine the quality of GNSS observations for the purpose of ionospheric studies. The algorithms are designed especially to compute key GNSS data quality parameters which affect the quality of ionospheric product. The quality of data collected from the Continuously Operating Reference Stations (CORS) network in the conterminous United States (CONUS) is analyzed. The resulting quality varies widely, depending on each station and the data quality of individual stations persists for an extended time period. When compared to conventional methods, the quality parameters obtained from the proposed method have a stronger correlation with the quality of ionospheric data. The results suggest that a set of data quality parameters when used in combination can effectively select stations with high-quality GNSS data and improve the performance of ionospheric data analysis. PMID:25196005

  6. Viscous Forces in Velocity Boundary Layers around Planetary Ionospheres.

    PubMed

    Pérez-De-Tejada

    1999-11-01

    A discussion is presented to examine the role of viscous forces in the transport of solar wind momentum to the ionospheric plasma of weakly magnetized planets (Venus and Mars). Observational data are used to make a comparison of the Reynolds and Maxwell stresses that are operative in the interaction of the solar wind with local plasma (planetary ionospheres). Measurements show the presence of a velocity boundary layer formed around the flanks of the ionosphere where the shocked solar wind has reached super-Alfvénic speeds. It is found that the Reynolds stresses in the solar wind at that region can be larger than the Maxwell stresses and thus are necessary in the local acceleration of the ionospheric plasma. From an order-of-magnitude calculation of the Reynolds stresses, it is possible to derive values of the kinematic viscosity and the Reynolds number that are suitable to the gyrotropic motion of the solar wind particles across the boundary layer. The value of the kinematic viscosity is comparable to those inferred from studies of the transport of solar wind momentum to the earth's magnetosphere and thus suggest a common property of the solar wind around planetary obstacles. Similar conditions could also be applicable to velocity boundary layers formed in other plasma interaction problems in astrophysics. PMID:10511515

  7. Traveling Ionospheric Disturbances Observed by Midlatitude SuperDARN Radars

    NASA Astrophysics Data System (ADS)

    Frissell, N. A.; Baker, J. B.; Ruohoniemi, J. M.; West, M. L.; Bristow, W. A.

    2012-12-01

    Medium Scale Traveling Ionospheric Disturbances (MSTIDs) are wave-like perturbations of the F-region ionosphere with horizontal wavelengths on the order of 100-250 km and periods between ~15 - 60 min, and are generally thought to be the ionospheric manifestation of Atmospheric Gravity Waves (AGWs). High-latitude MSTIDs have been studied using SuperDARN radars since 1989, and are typically attributed to auroral sources and propagated by the Earth Reflected Wave (ERW) mode. Tropospheric sources and earthquakes are also known to be sources of MSTIDs. Observations of MSTIDs using both mid- and high- latitude SuperDARN radars are presented. North American radar data from November 2010 - November 2011 were searched for signatures of MSTIDs. Initial results suggest that MSTIDs are observed at high latitudes primarily in the fall/winter months, which is consistent with published results. This search also reveals that mid-latitude MSTIDs often appear concurrently with high-latitude MSTIDs and share similar wave parameters. During the fall/winter months, SuperDARN mid-latitude MSTIDs appear more often than high-latitude MSTIDs, likely due to calmer ionospheric conditions at mid-latitudes. In the springtime, SuperDARN-observed MSTIDs are less likely to be seen at high-latitudes, but still appear at mid-latitudes. Selected events are analyzed for wave parameters using the Multiple Signal Classification (MUSIC) technique.

  8. Experimental observations of the spatial structure of wave-like disturbances generated in midlatitude ionosphere by high power radio waves

    NASA Astrophysics Data System (ADS)

    Kunitsyn, V.; Andreeva, E.; Padokhin, A. M.; Nazarenko, M.; Frolov, V.; Komrakov, G.; Bolotin, I.

    2012-12-01

    We present the results of the experiments carried out in 2009-2012 on the Sura heating facility (Radio Physical Research Institute, N. Novgorod, Russia) on modification of the midlatitude ionosphere by powerful HF radiowaves. The experiments were conducted using O-mode radiowaves at frequencies lower than critical frequency of the ionospheric F2 layer both in daytime and nighttime ionosphere. Various schemes of the radiation of the heating wave were used including square wave modulation of the effective radiated power (ERP) at various frequencies and power stepping. Radio transmissions of the low- (Parus/Tsikada) and high-orbital (GPS/GLONASS) navigational satellites received at the mobile network of receiving sites were used for the remote sensing of the heated area of the ionosphere. The variations in the slant total electron content (TEC), which are proportional to the reduced phase of navigational signals, were studied for the satellite passes for which ionospheric penetration points crossed the disturbed area during HF heating. The variations in TEC caused by HF heating are identified in a number of examples. It is shown that the GNSS TEC spectra contain frequency components corresponding to the modulation periods of the ERP of the heating wave. The manifestations of the heating-induced variations in TEC are most prominent in the area of magnetic zenith of the pumping wave. Different behavior of TEC variations was observed during nighttime and daytime heating experiments. In daytime conditions the pump wave switched ON causes the increase of TEC while in the nighttime it causes a decrease in TEC. This can be explained by the different contribution of the processes responsible for the increase and decrease of TEC in daytime in nighttime conditions. In this work we also present the first time radiotomographic reconstructions of the spatial structure of the wave-like disturbances, generated in the ionosphere by high-power radio waves radiated by the Sura heater with a square wave modulation of the ERP at a frequency lower than or of the order of the Brunt-Vaisala frequency of the neutral atmosphere. The observed wavelike structures, which are possibly AGWs, diverge from the heated area of the ionosphere (observed like a narrow trough with dimensions corresponding to the diagram pattern of the Sura heater), the spatial period of these disturbances is 200-250 km and they are easily traced up to a distance of 700-800 km from the heated region. These observations are in good agreement with complimentary GPS/GLONASS data. We also present the examples of amplitude scintillations of the signals of low-orbital radio beacons corresponding to small-scale field-aligned irregularities in the heated area of ionosphere. The possibility of generation of electromagnetic waves by moving wave-like structures in ionosphere (like AGWs induced by HF-heating observed in our experiments) is also addressed in this work. The authors are grateful to the staff of the Sura facility for their help in conducting the experiments and acknowledge the support of the Russian Foundation for Basic Research (grants 10-05-01126, 11-02-00374, 11-05-01157, 12-02-31839, 12-05-33065, 12-05-10068), grant of the President of Russian Federation MK-2544.2012.5 and Lomonosov Moscow State University Program of Development.

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

    NASA Technical Reports Server (NTRS)

    Yee, H. C.; Sjoegreen, B.; Mansour, Nagi (Technical Monitor)

    2001-01-01

    There has been much discussion on verification and validation processes for establishing the credibility of CFD simulations. Since the early 1990s, many of the aeronautical and mechanical engineering related reference journals mandated that any accepted articles in numerical simulations (without known solutions to compared with) need to perform a minimum of one level of grid refinement and time step reduction. Due to the difficulty in analysis, the effect of under-resolved grids and the nonlinear behavior of available spatial discretizations, are scarcely discussed in the literature. Here, an under-resolved numerical simulation is one where the grid spacing being used is too coarse to resolve the smallest physically relevant scales of the chosen continuum governing equations that are of interest to the numerical modeler. With the advent of new developments in fourth-order or higher spatial schemes, it has become common to regard high order schemes as more accurate, reliable and require less grid points. The danger comes when one tries to perform computations with the coarsest grid possible while still hoping to maintain numerical results sufficiently accurate for complex flows, and especially, data-limited problems. On one hand, high order methods when applies to highly coupled multidimensional complex nonlinear problems might have different stability, convergence and reliability behavior than their well studied low order counterparts, especially for nonlinear schemes such as TVD, MUSCL with limiters, ENO, WENO and discrete Galerkin. On the other hand, high order methods involve more operation counts and systematic grid convergence study can be time consuming and prohibitively expansive. At the same time it is difficult to fully understand or categorize the different nonlinear behavior of finite discretizations, especially at the limits of under-resolution when different types of bifurcation phenomena might occur, depending on the combination of grid spacings, time steps, initial conditions and numerical treatments of boundary conditions.

  10. The Role of Thermospheric Winds in Magnetosphere-Ionosphere Coupling

    NASA Astrophysics Data System (ADS)

    Richmond, A. D.

    2002-12-01

    Thermospheric winds are forced primarily by non-uniform solar heating, by atmospheric tides and other waves coming from below, and by ion drag and Joule heating associated with high-latitude convection. The high-latitude ion drag above 120 km altitude tends to drive winds in the direction of the ionospheric convection, although inertia of the air and other forces prevent a tight coupling of the ion and neutral motions. The tendency for high-latitude winds to move in the direction of ion motion tends to reduce the effective conductance of the ionosphere as felt by the magnetosphere, with consequences for magnetosphere-ionosphere coupling. The inertia of the air can cause delayed ``flywheel'' effects, which can potentially help maintain magnetospheric convection after a sudden reduction in the strength of solar-wind/magnetosphere coupling. At low latitudes, the ionospheric electric fields associated with magnetospheric disturbances can have complex temporal behavior. The electric field that penetrates to the equator directly from the polar cap tends to enhance the regular quiet-day equatorial east-west electric field. In contrast, the equatorial east-west electric field produced by the ``shielding'' region-2 currents tends to act oppositely to the directly penetrating field, but with a time delay of tens of minutes. Disturbance thermospheric winds have an ionospheric dynamo effect that also tends to act oppositely to the directly penetrating field, but with a time delay of a few hours. The combined effects can lead to electric-field disturbances of either sign, including long-lasting ``overshielding'' disturbances that can reduce or even reverse the normal quiet-day equatorial east-west electric field.

  11. Investigation of Ionospheric Precursors of 23 October 2011, Mw=7.2 Earthquake in Van, Turkey

    NASA Astrophysics Data System (ADS)

    Deviren, M. N.; Arikan, F.; Sezen, U.; Arikan, O.

    2012-04-01

    In recent years, a strong coupling between ionospheric disturbances and seismic activity has been observed through the increase of ion temperatures, critical frequencies of ionospheric layers and Total Electron Content (TEC) before high magnitude earthquakes. TEC is defined as total number of electrons over a ray path through the ionosphere. TEC can be estimated in a cost-effective way with dual-frequency Global Positioning Satellite (GPS) System receivers. The unit of TEC is given by TECU where 1 TECU = 1016 el/m2. In this study, the disturbances in daily TEC values before 23 October 2011, Mw=7.2 Earthquake in Van, Turkey are investigated using Turkish National Permanent GPS Network (TNPGN-Active). Earthquake Day Period (EDP) is chosen between October 1 and 31, 2011. Daily TEC values, for each station and each day, are estimated as IONOLAB-TEC (www.ionolab.org ) with 30 s time resolution. EDP-TEC values are compared with an Average Quiet Day TEC (AQDT) which is obtained by averaging the TEC values between 25 and 28 March, 2011. Statistical comparison is accomplished using Symmetric Kullback-Leibler Divergence (SKLD), which is also a method for measuring entropy of a system. It has been previously observed that SKLD is a better method for measuring the amount of disturbances compared to L2 norm and cross-correlation coefficient. AQDT is also compared with magnetically Quiet Day Period (QDP) from 25 to 28 April, 2011, during which Kp and Dst indices indicate a very quiet ionospheric and magnetospheric period. Also, in order to measure the variability between the consecutive days, TEC values for each day during EDP and QDP are compared with the TEC values of the following day. A third measure of W-index is also applied to identify the local disturbances in the ionosphere, where TEC of a given day is compared to the median of seven days prior to the day of investigation logarithmically. Since W-index is obtained for each epoch, the within-the-day variability can also be monitored. It has been observed that peak TEC values for all stations in TNPGN increase 10 to 15 TECU two days prior to the earthquake. The SKLD values for comparison of EDP and AQDT also peak on 21st of October, 2011, two days prior to the earthquake. Since ionospheric disturbance can be observed on all days prior to the earthquake, comparison of TEC for consecutive days for each station using SKLD does not provide extra information. The W-index values indicate that there may be small scale variability for stations closer to the earthquake epicenter. When compared with previous earthquakes that occurred in Turkey with magnitudes 4.5 and 5.2 on Richter scale, this 7.2 magnitude earthquake has been felt as an ionospheric disturbance for stations especially on Northern Anatolian Fault. The results also indicate the need for constant monitoring and statistical decision theory for detection of earthquake precursors. This study is supported by TUBITAK EEEAG Grant 109E055.

  12. Studies of VLF radio waves for sudden ionospheric disturbances (SID) in Kashmir region

    SciTech Connect

    Wani, M. R.; Iqbal, Naseer; Sasmal, Sudipta

    2010-10-20

    It is recognized that the ionosphere may be sensitive to seismic effects, and the detection of ionospheric perturbations associated with seismicity would be useful for short term prediction of seismic events. To observe this effect, Indian Centre for Space Physics has installed an antenna and receiver system at Kashmir University to monitor the variation of the VLF signal transmitted from VTX. We present the preliminary results from this station.

  13. The Space Weather Modeling System: An ESMF Compliant Solar Wind and Ionospheric Forecast System

    NASA Astrophysics Data System (ADS)

    Reich, J. P.; Fry, C. D.; Eccles, J. V.; Berman, L. M.; Sattler, M. P.

    2008-12-01

    Ionospheric storms can severely impact communications, navigation and surveillance systems. These ionospheric disturbances are driven by solar activity. A key challenge in space science is to understand the causes of the ionospheric response to solar forcing. Attempting to accurately forecast the time-dependent behavior of the ionosphere is the only way to truly test our understanding of the ionosphere. Space weather forecasters for the DoD face this challenge on a daily basis. The Air Force Weather Agency is meeting this challenge through the development of an operational Space Weather Modeling System (SWMS). The SWMS is a Battlespace Environments Institute (BEI) project that couples Earth system environmental models together under the Earth System Modeling Framework (ESMF). BEI is sponsored by the High Performance Computing (HPC) Modernization Office. The first two coupled components in SWMS are the Hakamada-Akasofu-Fry version 2 (HAFv2) solar wind model and the Global Assimilation of Ionospheric Measurements (GAIM) model. The HAFv2 model produces quantitative forecasts of solar wind parameters at Earth and elsewhere in the inner heliosphere. The Ionosphere Forecast Model (IFM) is the physics-based ionosphere model within GAIM. IFM provides highly representative specifications of plasma conditions in the global ionosphere. The one-way coupling of HAFv2 to IFM links the solar storm drivers to the ionospheric response. Predicted solar wind quantities are fed as inputs to IFM, which computes the solar wind energy deposition into the high latitude ionosphere, enabling GAIM to provide multi- day forecasts of ionospheric electron density, currents and upper atmosphere dynamics. The SWMS development is a structured project, moving from partial to full ESMF compliance. Bringing the HAFv2 and IFM models into the ESMF allows significant improvements in computational efficiency and data throughput. Modifying these computer codes for the HPC environment opens the door for other new capabilities. These include the ability to: 1) ingest diverse data sets at higher resolution and cadence; 2) use denser computational grids; and 3) perform ensemble forecasts. The HAFv2-IFM coupling provides the first operational, physics-based forecasts of the near-earth space environment that anticipate solar storm effects. The SWMS effort will shed light on our understanding of the underlying physics and ultimately lead to more accurate ionospheric forecasts to better support DoD missions

  14. Equatorial transport of Saturn's ionosphere as driven by a dust-ring current system

    SciTech Connect

    Ip, W.; Mendis, D.A.

    1983-03-01

    The diurnal modulation of the dust ring current of Saturn's D-ring causes field-aligned Birkeland currents ot 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 ionosheric 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.

  15. Kinetic response of ionospheric ions to onset of auroral electric fields

    NASA Technical Reports Server (NTRS)

    Chiu, Y. T.; Kan, J. R.

    1981-01-01

    Examination of the exact analytic solution of a kinetic model of collisional interaction of ionospheric fions with atmospheric neutrals in the Bhatnagar-Gross-Krook approximation, shows that the onset of intense auroral electric fields in the topside ionosphere can produce the following kinetic effects: (1) heat the bulk ionospheric ions to approximately 2 eV, thus driving them up to higher altitudes where they can be subjected to collisionless plasma processes; (2) produce a nonMaxwellian superthermal tail in the distribution function; and (3) cause the ion distribution function to be anisotropic with respect to the magnetic field with the perpendicular average thermal energy exceeding the parallel thermal energy.

  16. Kinetic response of ionospheric ions to onset of auroral electric fields

    NASA Technical Reports Server (NTRS)

    Chiu, Y. T.; Kan, J. R.

    1981-01-01

    By examining the exact analytic solution of a kinetic model of collisional interaction of ionospheric ions with atmospheric neutrals in the Bhatnagar-Gross-Krook approximation, we show that the onset of intense auroral electric fields in the topside ionosphere can produce the following kinetic effects: (1) heat the bulk ionospheric ions to approximately 2 eV, thus driving them up to higher altitudes where they can be subjected to collisionless plasma processes; (2) produce a non-Maxwellian superthermal tail in the distribution function; and (3) cause the ion distribution function to be anisotropic with respect to the magnetic field with the perpendicular average thermal energy exceeding the parallel thermal energy.

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

    SciTech Connect

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

    1989-09-01

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

  18. Ion-neutral collisions and dust grain charging in the presence of electromagnetic radiation in the Earth's Ionosphere

    NASA Astrophysics Data System (ADS)

    Kopnin, Sergey; Popel, Sergey; Morzhakova, Anastasia

    2010-05-01

    Ion-neutral collisions in dust particle charging process in the presence of electromagnetic radiation in Earth's "dusty" ionosphere are taken into account. These collisions can result in a charge exchange between a fast ion and a slow neutral. The slow neutrals become slow positively charged ions which interact effectively with positively charged dust grains. As a result a microscopic ion current on the dust grains decreases in comparison with the case when ion-neutral collisions are not taken into account in the dust grain charging process. The microscopic ion current on the positively charged dust grains is derived. A condition on neutral density is obtained for which the influence of ion-neutral collisions on dust particle charging process is important. It is shown that the effect of ion-neutral collisions should be taken into account when considering the charging of nano- and microsize dust grains in Noctilucent Clouds, Polar Mesosphere Summer Echoes, meteoritic dust, active geophysical rocket experiments such as Fluxus 1 and 2. We discuss also the effect of electrons with energies of the order of 1 eV which are produced as a result of photoelectric effect during the charging process, which can result in an increase of the electron temperature in plasmas. The most important effect resulting in cooling of such electrons is that of electron-ion collisions. We found a condition on the neutral density when the electron temperature in Earth's "dusty" ionosphere can become of the order of 1 eV. The importance of this effect for ionospheric plasmas is discussed. This work was supported by the Russian Foundation for Basic Research, project no. 06-05-64826-?. S.I.P. acknowledges financial support of the Dynasty Foundation.

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

    E-print Network

    Withers, Paul

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

  20. Nighttime ionospheric D region: Equatorial and nonequatorial

    NASA Astrophysics Data System (ADS)

    Thomson, Neil R.; McRae, Wayne M.

    2009-08-01

    Nighttime ionospheric D region parameters are found to be generally well modeled by the traditional H? and ? as used by Wait and by the U.S. Navy in their Earth-ionosphere VLF radio waveguide programs. New comparisons with nonequatorial, mainly all-sea VLF path observations reported over several decades are shown to be consistent with the previously determined height H? ˜ 85.0 km and sharpness ? ˜ 0.63 km-1. These paths include NPM (Hawaii) to Washington, D. C., Omega Hawaii and NLK (Seattle) to Japan, NWC (N.W. Australia) to Madagascar, and NBA (Panama) to Colorado. In marked contrast, transequatorial path observations (even when nearly all-sea) are found to be often not well modeled: for example, for Omega Japan and JJI (Japan) to Dunedin, New Zealand, the observed amplitudes are markedly lower than those which would be expected from H? ˜ 85.0 km and ? ˜ 0.63 km-1, or any other realistic values of H? and ?. Other transequatorial observations compared with modeling include NWC to Japan, Omega Hawaii to Dunedin, and NPM (Hawaii) to Dunedin. It is suggested that the effects of irregularities in the equatorial electrojet may extend down into the nighttime D region and so account for the observed equatorial VLF perturbations through scattering or mode conversion.

  1. Principles and Problems of Data Assimilation for High-Latitude Ionospheric Electrodynamics

    NASA Astrophysics Data System (ADS)

    Richmond, A. D.; Matsuo, T.; Cousins, E. D. P.; Knipp, D. J.; Lu, G.; Marsal, S.

    2014-12-01

    Knowledge of the time-varying distributions of high-latitude ionospheric ionospheric electric fields and currents is needed for modeling the physics of the ionosphere and thermosphere. The patterns can also be used to investigate magnetospheric processes. The Assimilative Mapping of Ionospheric Electrodynamics (AMIE) procedure was developed to estimate the distributions of electrodynamic parameters from combinations of observations of ionospheric drifts, ground- and satellite-based magnetic perturbations, and quantities related to ionospheric electrical conductivities, together with prior information about climatology and covariance of the parameters. AMIE uses optimal estimation theory to build on previous statistical studies and on an earlier mapping procedure that used only ground magnetometer data. Many of the improvements made to AMIE have been the addition of new data sets and procedures for semi-automatically processing the data. Theoretical developments have included improvements to the organization of the data in realistic magnetic coordinates, and dynamic estimation of the covariance matrices based on the data available at any given time. More recently, it has been shown that most of the large-scale variability can be represented with a relatively small number of empirical orthogonal basis functions derived from statistical analysis of large data sets. A key remaining limitation of AMIE-type estimations is the limited knowledge of auroral ionospheric conductivities, including limited understanding of nonlinear conductivities when electric fields are very strong. Neutral winds have heretofore been neglected, but they can sometimes have significant effects on the electrodynamics.

  2. Role of Excited Nitrogen In The Ionosphere

    SciTech Connect

    Campbell, L.; Brunger, M. J.; Cartwright, D. C.; Bolorizadeh, M. A.

    2006-12-01

    Sunlight photoionises atoms and molecules in the Earth's upper atmosphere, producing ions and photoelectrons. The photoelectrons then produce further ionisation by electron impact. These processes produce the ionosphere, which contains various positive ions, such as NO+, N+, and O+, and an equal density of free electrons. O+(4S) ions are long-lived and so the electron density is determined mainly by the density of O+(4S). This density is dependent on ambipolar diffusion and on loss processes, which are principally reactions with O2 and N2. The reaction with N2 is known to be strongly dependent on the vibrational state of N2 but the rate constants are not well determined for the ionosphere. Vibrational excitation of N2 is produced by direct excitation by thermal electrons and photoelectrons and by cascade from the excited states of N2 that are produced by photoelectron impact. It can also be produced by a chemical reaction and by vibrational-translational transitions. The vibrational excitation is lost by deexcitation by electron impact, by step-wise quenching in collisions with O atoms, and in the reaction with O+(4S). The distribution of vibrational levels is rearranged by vibrational-vibrational transitions, and by molecular diffusion vertically in the atmosphere. A computational model that includes these processes and predicts the electron density as a function of height in the ionosphere is described. This model is a combination of a ''statistical equilibrium'' calculation, which is used to predict the populations of the excited states of N2, and a time-step calculation of the atmospheric reactions and processes. The latter includes a calculation of photoionisation down through the atmosphere as a function of time of day and solar activity, and calculations at 0.1 s intervals of the changing densities of positive ions, electrons and N2 in the different vibrational levels. The validity of the model is tested by comparison of the predicted electron densities with the International Reference Ionosphere (IRI) of electron density measurements. The contribution of various input parameters can be investigated by their effect on the accuracy of the calculated electron densities. Here the effects of two different sets of rate constants for the reaction of vibrationally excited N2 with O+(4S) are investigated. For reference, predictions using the different sets are compared with laboratory measurements. Then the effect of using the different sets in the computational model of the ionosphere is investigated. It is shown that one set gives predictions of electron densities that are in reasonable agreement with the IRI, while the other set does not. Both sets result in underestimation of the electron density at the height of the peak electron density in the atmosphere, suggesting that either the amount of vibrational excitation or the rate constants may be overestimated. Our comparison is made for two cases with different conditions, to give an indication of the limitations of the atmospheric modeling and also insight into ways in which the sets of rate constants may be deficient.

  3. Satellite Radiotomography of Ionospheric Responces to Extra-Terrestrial Forcing

    NASA Astrophysics Data System (ADS)

    Kunitsyn, Viacheslav; Padokhin, Artem; Andreeva, Elena; Tereshchenko, Evgeny; Nesterov, Ivan; Vorontsov, Artem

    Our work addresses the study of the response of the atmosphere and ionosphere to a variety of external forcing such as solar flares and particle precipitation. Particle precipitation plays important role in the system of magnetosphere-ionosphere- atmosphere coupling during geomagnetic storms. Using radio tomographic imaging of the ionosphere based on navigational satellite systems (Parus/Transit and GPS/GLONASS) we present and discuss the examples illustrating ionospheric effects caused by particle precipitations detected by DMSP satellites. It is shown that the spatial structure of corpuscular ionization in the tomographic images is qualitatively close to latitudinal distribution of the precipitating particles. The distributions of ionospheric plasma observed during strong geomagnetic disturbances and particle precipitations have multiple extrema and wave-like structures with a spatial scale ranging from a few dozens to a few hundreds of kilometers; the characteristic sizes of latitudinal variations in the corresponding corpuscular flows widely vary from a few degrees to a few dozens degrees latitude. The obtained experimental results are in good agreement with the results of the numeric modelling of the AGW generation by volumetric sources. We also present the comparison of the effects of ionization of the ionosphere by a series of intense X-class solar flares during the 23rd and 24th solar cycles based on the data of satellite navigation and augumentation systems (GPS/GLONASS and SBAS). The analysis shows that the intensity of the ionospheric effects estimated from the variations in total electron content is barely related to the intensity of the X-ray flare for the X-class events. The amplitude of variations in the ionization of the upper atmosphere is mainly controlled by the intensity of variations in solar EUV radiation, which is not always correlated to the X-Ray radiation during flares. The authors acknowledge the support of the Russian Foundation for Basic Research (grants ? 13-05-01122, 14-05-31445, 14-05-00855, 14-05-10069), grants of the President of Russian Federation (MK-2670.2014.5) and Lomonosov Moscow State University Program of Development.

  4. High Resolution Ionospheric Mapping Using Spaceborne Synthetic Aperture Radars

    NASA Astrophysics Data System (ADS)

    Meyer, F. J.; Chotoo, K.; Roth, A. P.

    2012-12-01

    Spaceborne Synthetic Aperture Radars (SARs) are imaging radar systems that utilize the Doppler history of signals acquired during satellite flyby to produce high resolution images of the Earth. With modern sensors, operating at frequencies between about 1 GHz (L-band) and 10 GHz (X-band), radar images with resolutions in the meter to sub-meter range can be produced. The presence of the ionosphere is significantly affecting the propagation properties of the microwave signals transmitted by these systems, causing distortions of signal polarization and phase. These distortions can lead to a wide range of imaging artifacts including image range shifts, interferometric phase biases, loss of image focus, change of image geometry, and Faraday rotation. While these artifacts are particularly pronounced at L-band, they are still observable in data acquired at C- or even X-band. In recent years, a wealth of methods for measuring and correcting ionospheric influence were developed. These methods are self-calibration procedures that measure ionosphere-induced distortions to infer the two-dimensional TEC maps that affected the data. These TEC maps are then removed from the data to produce high performance SAR images. Besides being effective in correcting SAR observations, these self-calibration methods are producing high quality TEC information with sub-TECU sensitivity and sub-kilometer spatial resolution. The intent of this paper is to utilize SAR-derived ionospheric information and make the case for SAR as a data source for ionospheric research. After a short summary of ionosphere-induced distortions, the concept of TEC estimation from SAR is introduced. Here, the current state-of-the-art of ionospheric TEC estimation is presented, including Faraday rotation-based, interferometric, correlation-based, and autofocus-based techniques. For every approach, performance numbers are given that quantify the achievable TEC estimation accuracy as a function of system parameters, scene properties, and (if applicable) geographic location. Three case studies will be presented to highlight the type and quality of ionospheric information that can be retrieved: (1) The high spatial resolution of SAR-derived TEC maps is emphasized in a case study that focuses on high resolution mapping of aurora arcs in central Alaska. Here, TEC enhancements associated with aurora activity are mapped and compared to reference observations from sky cameras and GPS; (2) observations of mid-latitudal traveling ionospheric disturbances are shown to showcase the accuracy of SAR-derived TEC maps. Several SAR-based TEC mapping methods are compared to highlight their respective advantages and disadvantages regarding processing complexity and estimation accuracy; (3) a third example focuses on analyzing post-sunset scintillation phenomena in equatorial regions. SAR is used to assess the frequency of occurrence of scintillation and analyze their associated power spectra. To conclude the paper, the temporal and spatial sampling of the ionosphere provided by the fleet of current and future spaceborne SAR sensors is analyzed to provide an assessment of the global ionospheric mapping capabilities of SAR.

  5. Preface: International Reference Ionosphere - Progress in Ionospheric Modelling

    NASA Technical Reports Server (NTRS)

    Bilitza Dieter; Reinisch, Bodo

    2010-01-01

    The international reference ionosphere (lRI) is the internationally recommended empirical model for the specification of ionospheric parameters supported by the Committee on Space Research (COSPAR) and the International Union of Radio Science (URSI) and recognized by the International Standardization Organization (ISO). IRI is being continually improved by a team of international experts as new data become available and better models are being developed. This issue chronicles the latest phase of model updates as reported during two IRI-related meetings. The first was a special session during the Scientific Assembly of the Committee of Space Research (COSPAR) in Montreal, Canada in July 2008 and the second was an IRI Task Force Activity at the US Air Force Academy in Colorado Springs in May 2009. This work led to several improvements and additions of the model which will be included in the next version, IRI-201O. The issue is divided into three sections focusing on the improvements made in the topside ionosphere, the F-peak, and the lower ionosphere, respectively. This issue would not have been possible without the reviewing efforts of many individuals. Each paper was reviewed by two referees. We thankfully acknowledge the contribution to this issue made by the following reviewers: Jacob Adeniyi, David Altadill, Eduardo Araujo, Feza Arikan, Dieter Bilitza, Jilijana Cander, Bela Fejer, Tamara Gulyaeva, Manuel Hermindez-Pajares, Ivan Kutiev, John MacDougal, Leo McNamara, Bruno Nava, Olivier Obrou, Elijah Oyeyemi, Vadym Paznukhov, Bodo Reinisch, John Retterer, Phil Richards, Gary Sales, J.H. Sastri, Ludger Scherliess, Iwona Stanislavska, Stamir Stankov, Shin-Yi Su, Manlian Zhang, Y ongliang Zhang, and Irina Zakharenkova. We are grateful to Peggy Ann Shea for her final review and guidance as the editor-in-chief for special issues of Advances in Space Research. We thank the authors for their timely submission and their quick response to the reviewer comments and humbly apologize for any delays in the editing process.

  6. A Detection Study of the Ionospheric Total Electron Contents Variations Using GPS Network

    NASA Astrophysics Data System (ADS)

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

    2007-12-01

    We established a regional ionospheric model for investigating ionospheric TEC (Total Electron Contents) variations over the Korean Peninsula during major geomagnetic storms. In order to monitor the ionospheric TEC variations, we used nine permanent GPS reference stations uniformly distributed in South Korea operated by the Korea Astronomy and Space Science Institute (KASI). The cubic spline smoothing (CSS) interpolation method was used to analyze the characteristics of the ionospheric TEC variations. It has been found that variations of TEC over the Korean Peninsula increase when a major geomagnetic storm occurred on November 20, 2003. The TEC has increased about one and a half of those averaged quite days at the specific time during a geomagnetic storm . It has been indicated that the KASI GPS-derived TEC has a correlation with the geomagnetic storm indices (eq. Kp and Dst indices).

  7. A simulation study with a new residual ionospheric error model for GPS radio occultation climatologies

    NASA Astrophysics Data System (ADS)

    Danzer, J.; Healy, S. B.; Culverwell, I. D.

    2015-01-01

    In this study, a new model was explored, which corrects for higher order ionospheric residuals in global positioning system (GPS) radio occultation (RO) data. Recently, the theoretical basis of this new "residual ionospheric error model" has been outlined (Healy and Culverwell, 2015). The method was tested in simulations with a one-dimensional model ionosphere. The proposed new model for computing the residual ionospheric error is the product of two factors, one of which expresses its variation from profile-to-profile and from time-to-time in terms of measurable quantities (the L1 and L2 bending angles), the other of which describes the weak variation with altitude. A simple integral expression for the residual error (Vorob'ev and Krasil'nikova, 1994) has been shown to be in excellent numerical agreement with the exact value, for a simple Chapman layer ionosphere. In this case, the "altitudinal" element of the residual error varies (decreases) by no more than about 25% between ~10 and ~100 km for physically reasonable Chapman layer parameters. For other simple model ionospheres the integral can be evaluated exactly, and results are in reasonable agreement with those of an equivalent Chapman layer. In this follow-up study the overall objective was to explore the validity of the new residual ionospheric error model for more detailed simulations, based on modelling through a complex three-dimensional ionosphere. The simulation study was set up, simulating day and night GPS RO profiles for the period of a solar cycle with and without an ionosphere. The residual ionospheric error was studied, the new error model was tested, and temporal and spatial variations of the model were investigated. The model performed well in the simulation study, capturing the temporal variability of the ionospheric residual. Although, it was not possible, due to high noise of the simulated bending angle profiles at mid to high latitudes, to perform a thorough latitudinal investigation of the performance of the model, first positive and encouraging results were found at low latitudes. Furthermore, first application tests of the model on the data showed a reduction on temperature level of the ionospheric residual at 40 km from about -2.2 to -0.2 K.

  8. A simulation study with a new residual ionospheric error model for GPS radio occultation climatologies

    NASA Astrophysics Data System (ADS)

    Danzer, J.; Healy, S. B.; Culverwell, I. D.

    2015-08-01

    In this study, a new model was explored which corrects for higher order ionospheric residuals in Global Positioning System (GPS) radio occultation (RO) data. Recently, the theoretical basis of this new "residual ionospheric error model" has been outlined (Healy and Culverwell, 2015). The method was tested in simulations with a one-dimensional model ionosphere. The proposed new model for computing the residual ionospheric error is the product of two factors, one of which expresses its variation from profile to profile and from time to time in terms of measurable quantities (the L1 and L2 bending angles), while the other describes the weak variation with altitude. A simple integral expression for the residual error (Vorob'ev and Krasil'nikova, 1994) has been shown to be in excellent numerical agreement with the exact value, for a simple Chapman layer ionosphere. In this case, the "altitudinal" element of the residual error varies (decreases) by no more than about 25 % between ~10 and ~100 km for physically reasonable Chapman layer parameters. For other simple model ionospheres the integral can be evaluated exactly, and results are in reasonable agreement with those of an equivalent Chapman layer. In this follow-up study the overall objective was to explore the validity of the new residual ionospheric error model for more detailed simulations, based on modeling through a complex three-dimensional ionosphere. The simulation study was set up, simulating day and night GPS RO profiles for the period of a solar cycle with and without an ionosphere. The residual ionospheric error was studied, the new error model was tested, and temporal and spatial variations of the model were investigated. The model performed well in the simulation study, capturing the temporal variability of the ionospheric residual. Although it was not possible, due to high noise of the simulated bending-angle profiles at mid- to high latitudes, to perform a thorough latitudinal investigation of the performance of the model, first positive and encouraging results were found at low latitudes. Furthermore, first application tests of the model on the data showed a reduction in temperature level of the ionospheric residual at 40 km from about -2.2 to -0.2 K.

  9. Searching for seismo-ionospheric earthquakes precursors: Total Electron Content disturbances before 2005-2006 seismic events

    E-print Network

    Romanovskaya, Yu V; Zolotov, O V; Starikova, N A; Lopatiy, V Z

    2012-01-01

    During earthquakes preparation periods significant disturbances in the ionospheric plasma density are often observed. These anomalies are caused by lithosphere-atmosphere-ionosphere interaction, particularly by the seismic electric field penetrating from the ground surface into the ionosphere. The seismic electric field produces electromagnetic EB drift changing plasma density over the epicenter region and magnetically conjugated area. The paper is devoted to analysis of regular Global Positioning System observations and revelation of seismo-ionospheric precursors of earthquakes in Total Electron Content (TEC) of the ionosphere. Global and regional relative TEC disturbances maps (%) have been plotted for 2005-2006 M6, D<60 km seismic events and analyzed in order to determine general features of precursors. The obtained results agree with the recent published case-study investigations.

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

    E-print Network

    Carlson, Charles W.

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

  11. Quantifying residual ionospheric errors in GNSS radio occultation bending angles based on ensembles of profiles from end-to-end simulations

    NASA Astrophysics Data System (ADS)

    Liu, C. L.; Kirchengast, G.; Zhang, K.; Norman, R.; Li, Y.; Zhang, S. C.; Fritzer, J.; Schwaerz, M.; Wu, S. Q.; Tan, Z. X.

    2015-01-01

    The radio occultation (RO) technique using signals from the Global Navigation Satellite System (GNSS), in particular from the Global Positioning System (GPS) so far, is meanwhile widely used to observe the atmosphere for applications such as numerical weather prediction and global climate monitoring. The ionosphere is a major error source in RO measurements at stratospheric altitudes and a linear ionospheric correction of dual-frequency RO bending angles is commonly used to remove the first-order ionospheric effect. However, the residual ionopheric error (RIE) can still be significant so that it needs to be further mitigated for high accuracy applications, especially above about 30 km altitude where the RIE is most relevant compared to the magnitude of the neutral atmospheric bending angle. Quantification and careful analyses for better understanding of the RIE is therefore important towards enabling benchmark-quality stratospheric RO retrievals. Here we present such an analysis of bending angle RIEs covering the stratosphere and mesosphere, using quasi-realistic end-to-end simulations for a full-day ensemble of RO events. Based on the ensemble simulations we assessed the variation of bending angle RIEs, both biases and SDs, with solar activity, latitudinal region, and with or without the assumption of ionospheric spherical symmetry and of co-existing observing system errors. We find that the bending angle RIE biases in the upper stratosphere and mesosphere, and in all latitudinal zones from low- to high-latitudes, have a clear negative tendency and a magnitude increasing with solar activity, in line with recent empirical studies based on real RO data. The maximum RIE biases are found at low latitudes during daytime, where they amount to with in -0.03 to -0.05 ?rad, the smallest at high latitudes (0 to -0.01 ?rad; quiet space weather and winter conditions). Ionospheric spherical symmetry or asymmetries about the RO event location have only a minor influence on RIE biases. The RIE SDs are markedly increased both by ionospheric asymmetries and increasing solar activity and amount to about 0.3 to 0.7 ?rad in the upper stratosphere and mesosphere. Taking into account also realistic observation errors of a modern RO receiving system, amounting globally to about 0.4 ?rad (un-biased; SD), shows that the random RIEs are typically comparable to the total observing system error. The results help to inform future RIE mitigation schemes that will improve upon the use of the linear ionospheric correction of bending angles and that will also provide explicit uncertainty estimates.

  12. The night when the auroral and equatorial ionospheres converged

    NASA Astrophysics Data System (ADS)

    Martinis, C.; Baumgardner, J.; Mendillo, M.; Wroten, J.; Coster, A.; Paxton, L.

    2015-09-01

    An all-sky imaging system at the McDonald Observatory (30.67°N, 104.02°W, 40° magnetic latitude) showed dramatic ionospheric effects during a moderate geomagnetic storm on 1 June 2013. The auroral zone expanded, leading to the observation of a stable auroral red (SAR) arc. Airglow depletions associated with equatorial spread F (ESF) were also seen for the first time at such high magnetic latitude. Total electron content measurements from a Global Positioning System (GPS) receiver exhibited ionospheric irregularities typically associated with ESF. We explore why this moderate geomagnetic disturbance leads to such dramatic ionospheric perturbations at midlatitudes. A corotating interaction region-like driver and a highly contracted plasmasphere caused the SAR arc to occur at L shell ~ 2.3. For ESF at L ~ 2.1, timing of the storm intensification, alignment of the sunset terminator with the central magnetic meridian, and sudden variations in the westward auroral electrojet all combined to trigger equatorial irregularities that reached altitudes of ~ 7000 km. The SAR arc and ESF signatures at the ionospheric foot points of inner magnetosphere L shells (L ~ 2) represent a dramatic convergence of pole to equator/equator to pole coupling at midlatitudes.

  13. Ionospheric total electron content response to solar eclipses

    NASA Astrophysics Data System (ADS)

    Tsai, H. F.; Liu, J. Y.

    1999-06-01

    On October 24, 1995, and March 9, 1997, two solar eclipse events occur. It is therefore of interest to investigate how the ionosphere responded to the eclipses. Five global positioning system (GPS) ground-based receivers are specifically designed to observe large-scale ionospheric variations over the geomagnetic equatorial, equatorial anomaly crest, and midlatitude regions. Two-dimensional images of ionospheric total electron content (TEC) during the two eclipse periods are constructed. The deviations in the TEC images on eclipse days from those on reference days show that during the eclipse days the ionosphere experienced some large-scale changes. Four features of the TEC deviations, pre-ascension (PA), major depression (MD), sunset ascension (SA), and secondary depression (SD) have been observed. A detailed study shows that in geomagnetic low latitudes, PAs are possibly related to the locations of the equatorial anomaly crest. The latitudinal location, amplitude, and occurrence time of MDs suggest that the fountain effect is essential. SAs and SDs occurring in geomagnetic equatorial and low latitudes and appearing respectively before/around and after local sunset indicate that the prereversal enhancement plays an important role.

  14. Kinetic modeling of the Saturn ring-ionosphere plasma environment

    NASA Technical Reports Server (NTRS)

    Wilson, G. R.; Waite, J. H., Jr.

    1989-01-01

    A time-independent kinetic plasma model was developed on the basis of the Li et al. (1988) semikinetic plasma model and was used to study the interaction of the Saturnian ionosphere and ring plasma. The model includes the gravitational magnetic mirror and centripetal and ambipolar electric forces, and the effect of the mixing of two plasma populations. The results obtained indicate that the density, temperature, and composition of plasma near the rings changing in the direction from the inner C ring to the outer A ring, due to the fact that the predominant source of plasma changes from the ionosphere to the rings. The model results also suggest that the outflow of hydrogen from the ionosphere to the rings may be shut off for field lines passing through the outer B and A ring, due to the ambipolar electric field set up by the warm ring plasma trapped near the ring plane by the centipetal force. In these regions, there will be a net flux of O(+) ions from the rings to the ionosphere.

  15. Characterizing the pre-Space Age ionosphere over Washington, DC

    NASA Astrophysics Data System (ADS)

    Rice, D. D.; Sojka, J. J.; Eccles, J. V.; Redmon, R.; Hunsucker, R. D.

    2014-08-01

    The study of long-term changes requires researchers to identify relevant historical measurements; quantifying and quality controlling these measurements becomes central to their utilization by broader communities. This pilot study reports on the evaluation of ionograms and their inversion from the decade prior to the Space Age. The ionograms were recorded on 35 mm film reels and archived at the National Geophysical Data Center World Data Center A in Boulder, Colorado. For this study, ionogram film from one of the earliest operational sites in North America, Fort Belvoir (near Washington, DC), is analyzed. This analysis generates two distinct products: a digital ionogram with virtual height and frequency coordinate registration, and scaled values including an electron density profile. Validation of the ionogram registration and its resolution are described. The scaling and inversion processing, including uncertainties for the parameters and quality assessment, are explained. This study demonstrates how the archived film ionograms can have extensive value as historic measurements of the ionosphere once they are digitized and coordinate registered. Furthermore, modern analysis of the ionograms shows that a complete bottomside ionospheric specification may be obtained at better time resolution than is typically available from original scaled data. This research has set the stage for an effective recovery of ionospheric information for almost a full solar cycle prior to International Geophysical Year. In addition, between Fort Belvoir and Wallops Island archives, an East Coast midlatitude ionospheric data set can be generated from the late 1940s through the present.

  16. Vlasov Simulations of Ionospheric Heating Near Upper Hybrid Resonance

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  17. Response of the ionosphere thermosphere system to magnetospheric processes

    NASA Astrophysics Data System (ADS)

    Schunk, R. W.; Zhu, L.

    2008-12-01

    The magnetosphere-ionosphere-thermosphere system at high latitudes is strongly coupled via electric fields, particle precipitation, plasma and neutral outflows, and field-aligned currents. Although the climatology of the coupled system is fairly well established, our understanding of the variability of the disturbed state (weather) is rudimentary. This variability is associated with magnetic storms and substorms, nonlinear processes that operate over a range of spatial scales, time delays, and feedback mechanisms between the different domains. The variability and resultant structure of the ionosphere can appear in the form of propagating plasma patches and polar wind jets, pulsing ion and neutral polar winds, auroral and boundary blobs, and ionization channels associated with polar cap arcs, discrete auroral arcs, and storm-enhanced densities (SEDs). The variability and structure of the thermosphere can appear in the form of propagating atmospheric holes, neutral gas fountains, neutral density patches, and transient neutral jets. In addition, during periods of enhanced plasma convection, the neutral winds can become supersonic in relatively narrow regions of the polar cap. The spatial structure in the ionosphere-thermosphere system not only affects the local environment, but the cumulative effect of multiple structures may affect the global circulation and energy balance. A focused topical review of recent results in our modeling the variability and structure of the high-latitude ionosphere-thermosphere system is presented. This review was given at the Greenland Space Science Symposium (May 2007).

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

    NASA Astrophysics Data System (ADS)

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

    2015-09-01

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

  19. The Response of the Thermosphere and Ionosphere to Magnetospheric Forcing

    NASA Astrophysics Data System (ADS)

    Rees, D.; Fuller-Rowell, T. J.

    1989-06-01

    During the past six years, rapid advances in three observational techniques (ground-based radars, optical interferometers and satellite-borne instruments) have provided a means of observing a wide range of spectacular interactions between the coupled magnetosphere, ionosphere and thermosphere system. Perhaps the most fundamental gain has come from the combined data-sets from the NASA Dynamics Explorer (DE) Satellites. These have unambiguously described the global nature of thermospheric flows, and their response to magnetospheric forcing. The DE spacecraft have also described, at the same time, the magnetospheric particle precipitation and convective electric fields which force the polar thermosphere and ionosphere. The response of the thermosphere to magnetospheric forcing is far more complex than merely the rare excitation of 1 km s-1 wind speeds and strong heating; the heating causes large-scale convection and advection within the thermosphere. These large winds grossly change the compositional structure of the upper thermosphere at high and middle latitudes during major geomagnetic disturbances. Some of the major seasonal and geomagnetic storm-related anomalies of the ionosphere are directly attributable to the gross wind-induced changes of thermospheric composition; the mid-latitude ionospheric storm `negative phase', however, is yet to be fully understood. The combination of very strong polar wind velocities and rapid plasma convection forced by magnetospheric electric fields strongly and rapidly modify F-region plasma distributions generated by the combination of local solar and auroral ionization sources. Until recently, however, it has been difficult to interpret the observed complex spatial and time-dependent structures and motions of the thermosphere and ionosphere because of their strong and nonlinear coupling. It has recently been possible to complete a numerical and computational merging of the University College London (UCL) global thermospheric model and the Sheffield University ionospheric model. This has produced a self-consistent coupled thermospheric--ionospheric model, which has become a valuable diagnostic tool for examining thermospheric--ionospheric interactions in the polar regions. In particular, it is possible to examine the effects of induced winds, ion transport, and the seasonal and diurnal U.T. variations of solar heating and photoionization within the polar regions. Polar and high-latitude plasma density structure at F-region altitudes can be seen to be strongly controlled by U.T., and by season, even for constant solar and geomagnetic activity. In the winter, the F-region polar plasma density is generally dominated by the effects of transport of plasma from the dayside (sunlit cusp). In the summer polar region, however, an increase in the proportion of molecular to atomic species, created by the global seasonal circulation and augmented by the geomagnetic forcing, controls the plasma composition and generally depresses plasma densities at all U.Ts. A number of these complex effects can be seen in data obtained from ground-based radars, Fabry--Perot interferometers and in the combined DE data-sets. Several of these observations will be used, in combination with simulations using the UCL--Sheffield coupled model, to illustrate the major features of large-scale thermosphere--ionosphere interactions in response to geomagnetic forcing. The past decade has seen a major improvement in the quality and quantity of experimental data available to study the thermosphere and ionosphere and their response to magnetospheric forcing. Earlier, large measured changes of individual parameters were difficult to place in a global or large-scale perspective. However, a clear picture of the distinction between the solar and geomagnetic forcing processes has emerged from the combined data-sets available from spacecraft such as the Dynamics Explorers, and from ground-based radar and optical observations of the polar thermosphere. A first experimental view of the strong coupling between the thermosphere and ionosp

  20. The evidence of ionosphere perturbation caused by Chelyabinsk event 15th February 2013

    NASA Astrophysics Data System (ADS)

    Losseva, Tatiana; Lyakhov, Andrey; Kuzmicheva, Marina; Kosarev, Igor

    The results of raw ionograms processing using A_{Sigma} carts technique prove the global effect of the impact of the Chelyabinsk meteoroid on February 15, 2013 on the midlatitude ionosphere. The impact caused wave-like ionospheric perturbations and significant range spread effects at distances up to 7000 km. Archive ionozonde data processing for the high altitude nuclear tests has been evaluated. It was shown that the behavior of the ionosphere significantly differs from the evidence obtained at high altitude nuclear tests with energetic equivalent similar to the estimations for the Chelyabinsk meteorite. We discuss some possible physical models that can explain the Chelyabinsk post-impact phenomena. Results of 3D gas-dynamics simulation and radiative transfer in atmosphere are presented. We acknowledge Global Ionospheric Radio Observatory (GIRO) and GIRO Principal Investigator B. W. Reinisch and Ivan Galkin of the University of Massachusetts Lowell for making ionogram data files available.

  1. Magnetospheric interaction with Triton's ionosphere

    NASA Technical Reports Server (NTRS)

    Strobel, Darrell F.; Cheng, Andrew F.; Summers, Michael E.; Strickland, Douglas J.

    1990-01-01

    The large electron densities measured by the Voyager radio occultation experiment are attributed to the precipitation of magnetospheric electrons with energy above 10 keV. Because the ionospheric electric Pedersen conductivity of Triton is about 10,000-20,000 mho and the Alfven conductance is about 3.5 mho, direct convective flow of plasma into the essentially infinitely conducting ionosphere is negligible. Magnetospheric electrons are transported to Triton's ionopause by curvature drift as a result of weak magnetic field line draping in a sub-Alfvenic plasma interaction with Triton. At the ionopause energetic electrons have a high probability of elastic and inelastic scattering and precipitate into the upper atmosphere. The average power dissipation is estimated to be about (2 - 3) x 10 to the 8th W.

  2. HAARP-Induced Ionospheric Ducts

    SciTech Connect

    Milikh, Gennady; Vartanyan, Aram

    2011-01-04

    It is well known that strong electron heating by a powerful HF-facility can lead to the formation of electron and ion density perturbations that stretch along the magnetic field line. Those density perturbations can serve as ducts for ELF waves, both of natural and artificial origin. This paper presents observations of the plasma density perturbations caused by the HF-heating of the ionosphere by the HAARP facility. The low orbit satellite DEMETER was used as a diagnostic tool to measure the electron and ion temperature and density along the satellite orbit overflying close to the magnetic zenith of the HF-heater. Those observations will be then checked against the theoretical model of duct formation due to HF-heating of the ionosphere. The model is based on the modified SAMI2 code, and is validated by comparison with well documented experiments.

  3. Sudden ionospheric disturbances in solar cycle 24

    NASA Astrophysics Data System (ADS)

    Bothmer, Volker; Bernert, Barbara

    2014-05-01

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

  4. Study of nighttime Medium Scale Travelling Ionospheric Disturbances (MSTID's) in the ionospheric F-region using all-sky imager and digisonde data

    NASA Astrophysics Data System (ADS)

    Stefanello, M. B.; Machado, C. S.; Pimenta, A. A.; Schuch, N. J.

    2013-05-01

    The plasma irregularities are characterized by an abrupt variation in the ionospheric plasma density at F-region. The ionospheric irregularities may manifest as Travelling Ionospheric Disturbances (TID's), Plasma Bubbles, Blobs and Brightness Waves. Some irregularities can affect the propagation of electromagnetic waves in the ionosphere, interfering in the transmission of radio signals used in telecommunications and positioning systems such as GPS and satellite navigation. This work presents a study of nighttime Medium Scale Travelling Ionospheric Disturbances (MSTID's) using all-sky images in the OI 630.0 nm emission obtained with an all-sky imager installed at the Southern Space Observatory (29.4° S, 53.8° W) in São Martinho da Serra, RS. Also, data of a digisonde installed at Cachoeira Paulista Observatory (22.7° S, 45.0° W) and other at Falkland Islands (51.4° S, 57.5° W), were used in the present study. In this work we present events of MSTID's and the effects of the ionization on its propagation in the nighttime ionosphere.

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

    SciTech Connect

    Kuo, Spencer P.

    2013-09-15

    Electron acceleration by upper hybrid waves under cyclotron harmonic resonance interaction is studied. Theory is formulated; the analytical solutions in the second and fourth harmonic cyclotron resonance cases are obtained, and in the third harmonic case, a first order differential equation governing the evolution of the electron energy is derived. The theory is applied for explaining the generation of artificial ionization layers observed in high-frequency (HF) ionospheric heating experiments. The upper hybrid waves are assumed to be excited parametrically by the O-mode HF heating wave. As the decay mode is the lower hybrid wave, the excited upper hybrid waves have wavelengths ranging from 0.25 to 0.5 m, which are short enough to effectively incorporate the finite Larmour radius effect for the harmonic cyclotron resonance interactions as well as have a frequency bandwidth of about 20 kHz, which provides an altitude region of about 10 km for continuous harmonic cyclotron resonance interaction between electrons and descending waves in the slightly inhomogeneous geomagnetic field. The numerical results on electron acceleration show that electron fluxes with energies larger than 14 eV are generated in the three harmonic cases. These energetic electrons cause impact ionizations, which are descending to form artificial ionization layers at the bottom of the ionospheric F region.

  6. Self-organization of IGW structures in an inhomogeneous ionosphere: 2. Nonlinear vortex structures

    NASA Astrophysics Data System (ADS)

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

    2013-11-01

    The generation and further nonlinear dynamics of internal gravity wave (IGW) structures in a dissipative ionosphere in the presence of an inhomogeneous zonal wind (shear flow) have been studied. The effectiveness of the IGW amplification mechanism during the interaction with an inhomogeneous zonal wind is analyzed based on the corresponding model system of nonlinear dynamic equations constructed in (Aburjania et al., 2013). It has been indicated that IGWs effectively obtain the shear flow energy at the initial linear evolution stage and substantially (by an order of magnitude) increase their amplitude and, correspondingly, energy. The nonlinear self-localization mechanism starts operating with increasing amplitude, and the process terminates with the self-organization of nonlinear solitary strongly localized vortex structures. A new degree of system freedom and the disturbance evolution trend in a medium with a shear flow appear in such a way. Nonlinear IGW structures can be a purely monopoly vortex, a transverse vortex chain, and/or a longitudinal vortex path against the background of an inhomogeneous zonal wind, depending on the shear flow velocity profile. The accumulation of such vortices in the ionospheric medium can generate a strongly turbulent state.

  7. Sources for Traveling Ionospheric Disturbances

    NASA Astrophysics Data System (ADS)

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

    2009-12-01

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

  8. Ionospheric very low frequency transmitter

    NASA Astrophysics Data System (ADS)

    Kuo, Spencer P.

    2015-02-01

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

  9. Lithosphere - Atmosphere - Ionosphere Circuit Model

    NASA Astrophysics Data System (ADS)

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

    2012-04-01

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

  10. Heat budget of ionospheric electrons

    NASA Technical Reports Server (NTRS)

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

    1976-01-01

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

  11. Relaxation of polar order in suspensions with Quincke effect

    NASA Astrophysics Data System (ADS)

    Belovs, M.; CÄ`bers, A.

    2014-05-01

    The Quincke effect—spontaneous rotation of dielectric particles in a liquid with low conductivity under the action of an electric field—is considered. The distribution functions for the orientation of particle rotation planes are introduced and a set of nonlinear kinetic equations is derived in the mean field approximation considering the dynamics of their orientation in the flow induced by rotating particles. As a result the nonequilibrium phase transition to the polar order, if the concentration of the particles is sufficiently high, is predicted and the condition of the synchronization of particle rotations is established. Two cases are considered: the layer of the Quincke suspension with one free boundary and the ensemble of the particles rolling on the solid wall under the action of a torque in an electric field. It is shown that in both cases the synchronization of particle rotations occurs due to the hydrodynamic interactions. In the limit of small spatial nonhomogeneity a set of nonlinear partial differential equations for the macroscopic variables—the concentration and the director of the polar order—is derived from the kinetic equation. Its properties are analyzed and compared with available recent experimental results.

  12. TRIO (Triplet Ionospheric Observatory) Mission

    NASA Astrophysics Data System (ADS)

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

    2009-12-01

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

  13. Mechanisms of Ionospheric Mass Escape

    NASA Technical Reports Server (NTRS)

    Moore, T. E.; Khazanov, G. V.

    2010-01-01

    The dependence of ionospheric O+ escape flux on electromagnetic energy flux and electron precipitation into the ionosphere is derived for a hypothetical ambipolar pick-up process, powered the relative motion of plasmas and neutral upper atmosphere, and by electron precipitation, at heights where the ions are magnetized but influenced by photo-ionization, collisions with gas atoms, ambipolar and centrifugal acceleration. Ion pick-up by the convection electric field produces "ring-beam" or toroidal velocity distributions, as inferred from direct plasma measurements, from observations of the associated waves, and from the spectra of incoherent radar echoes. Ring-beams are unstable to plasma wave growth, resulting in rapid relaxation via transverse velocity diffusion, into transversely accelerated ion populations. Ion escape is substantially facilitated by the ambipolar potential, but is only weakly affected by centrifugal acceleration. If, as cited simulations suggest, ion ring beams relax into non-thermal velocity distributions with characteristic speed equal to the local ion-neutral flow speed, a generalized "Jeans escape" calculation shows that the escape flux of ionospheric O+ increases with Poynting flux and with precipitating electron density in rough agreement with observations.

  14. 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.

  15. Dynamic processes in the ionosphere during the geospace storm on 30 May and solar eclipse on 31 May 2003

    NASA Astrophysics Data System (ADS)

    Grigorenko, Ye. I.; Paziura, S. A.; Puliaiev, V. A.; Taran, V. I.; Chernogor, L. F.

    Some results of the F region and topside ionosphere response to the 29-31 May 2003 severe geomagnetic storm (maximum index Kp=8) are presented. The observations are carried out with the Kharkov incoherent scatter radar. Considerable storm effects in the ionosphere were revealed. Among them were deep electron density N depletion, uplifting in the peak height zmF2, unusual heating of plasma, decrease of relative concentration of hydrogen ions in the main phase of the storm, infringement of processes of the ionosphere-magnetosphere interaction. The geospace storm was also accompanied by generation of wave-like ionosphere disturbances. Some features of the ionosphere response to the 73% solar eclipse on 31 May 2003 occurred after sunrise during the recovery phase of the geomagnetic storm are considered. It is shown that, during the eclipse, short-time (2-3 h) reforming the ionosphere to night conditions takes place. The effects of magnetic disturbance, solar flare and the peculiarities of ionosphere behaviour during sunrise period, that were being imposed on the ionosphere response to the soalr eclipse, are also discussed.

  16. Limb sounders tracking topographic gravity wave activity from the stratosphere to the ionosphere around midlatitude Andes

    NASA Astrophysics Data System (ADS)

    Alexander, P.; Torre, A.; Schmidt, T.; Llamedo, P.; Hierro, R.

    2015-10-01

    Several studies have shown that the surroundings of the highest Andes mountains at midlatitudes in the Southern Hemisphere exhibit gravity waves (GWs) generated by diverse sources which may traverse the troposphere and then penetrate the upper layers if conditions are favorable. There is a specific latitude band where that mountain range is nearly perfectly aligned with the north-south direction, which favors the generation of wavefronts parallel to this orientation. This fact may allow an optimization of procedures to identify topographic GW in some of the observations. We analyze data per season to the east and west of these Andes latitudes to find possible significant differences in GW activity between both sectors. GW effects generated by topography and convection are expected essentially on the eastern side. We use satellite data from two different limb sounding methods: the Global Positioning System radio occultation (RO) technique and the Sounding of the Atmosphere using Broadband Emission Radiometry instrument, which are complementary with respect to the height intervals, in order to study the effects of GW from the stratosphere to the ionosphere. Activity becomes quantified by the GW average potential energy in the stratosphere and mesosphere and by the electron density variance content in the ionosphere. Consistent larger GW activity on the eastern sector is observed from the stratosphere to the ionosphere (night values). However, this fact remains statistically significant at the 90% significance level only during winter, when GWs generated by topography dominate the eastern sector. On the contrary, it is usually assumed that orographic GWs have nearly zero horizontal phase speed and will therefore probably be filtered at some height in the neutral atmosphere. However, this scheme relies on the assumption that the wind is uniform and constant. Our results also suggest that it is advisable to separate night and day cases to study GWs in the ionosphere, as it is more difficult to find significant statistical differences during daytime. This may happen because perturbations induced by GWs during daytime are more likely to occur in a disturbed environment that may hinder the identification of the waves.

  17. Jovian Auroral Ionosphere-Thermosphere Model (J-AITM): Part 2. Benchmarks of the Ion Velocity Model (IVM) and the Electric Field Model (EFM)

    NASA Astrophysics Data System (ADS)

    Egert, A.; Waite, J. H., Jr.; Bell, J. M.; Goldstein, J.

    2014-12-01

    As part of the Jupiter Auroral Ionosphere-Thermosphere Model (J-AITM) construction in support of the Juno mission, we present benchmarks of the Electric Field Model (EFM) and the Ion Velocity Model (IVM). IVM uses the published results from Krupp et al., 2001, to constrain estimated velocities, and it is found that a modified Gaussian distribution gives a first-order approximation to the velocity flow profile. EFM calculates the magnetospheric electric fields using IVM and a magnetic field model, and then assumes magnetic flux conservation to map the electric fields into the ionosphere. These ionospheric electric fields are then used to estimate ionospheric drift velocities.

  18. A Campaign to Study Equatorial Ionospheric Phenomena over Guam

    NASA Astrophysics Data System (ADS)

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

    2007-05-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2012-03-01

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

  20. Radar signal propagation through the ionosphere of Europa

    NASA Astrophysics Data System (ADS)

    Grima, Cyril; Blankenship, Donald D.; Schroeder, Dustin M.

    2015-11-01

    We review the current state of knowledge of the Europan plasma environment, its effects on radio wave propagation, and its impact on the performance and design of future radar sounders for the exploration of Europa's ice crust. The Europan ionosphere is produced in two independently-rotating hemispheres by photo-ionization of the neutral exosphere and interaction with the Io plasma torus, respectively. This combination is responsible for temporal and longitudinal ionospheric heterogeneities not well constrained by observations. When Europa's ionosphere is active, the maximum cut-off frequency is 1 MHz at the surface. The main impacts on radar signal propagation are dispersive phase shift and Faraday rotation, both a function of the total electron content (up to 4×1015 m-2) and the Jovian magnetic field strength at Europa (~420 nT). The severity of these impacts decrease with increasing center frequency and increase with altitude, latitude, and bandwidth. The 9 MHz channels on the Radar for Icy Moons Exploration (RIME) and proposed Radar for Europa Assessment and Sounding: Ocean to Near-surface (REASON) will be sensitive to the Europan ionosphere. For these or similar radar sounders, the ionospheric signal distortion from dispersive phase shift can be corrected with existing techniques, which would also enable the estimation of the total electron content below the spacecraft. At 9 MHz, the Faraday fading is not expected to exceed 6 dB under the worst conditions. At lower frequencies, any active or passive radio probing of the ice shell exploration would be limited to frequencies above 1-8 MHz (depending on survey configuration) below which Faraday rotation angle would lead to signal fading and detection ambiguity. Radar instruments could be sensitive to neutrals and electrons added in the exosphere from any plume activity if present.

  1. Application of GPS Measurements for Ionospheric and Tropospheric Modelling

    NASA Astrophysics Data System (ADS)

    Rajendra Prasad, P.; Abdu, M. A.; Furlan, Benedito. M. P.; Koiti Kuga, Hélio

    military navigation. The DOD's primary purposes were to use the system in precision weapon delivery and providing a capability that would help reverse the proliferation of navigation systems in military. Subsequently, it was very quickly realized that civil use and scientific utility would far outstrip military use. A variety of scientific applications are uniquely suited to precise positioning capabilities. The relatively high precision, low cost, mobility and convenience of GPS receivers make positioning attractive. The other applications being precise time measurement, surveying and geodesy purposes apart from orbit and attitude determination along with many user services. The system operates by transmitting radio waves from satellites to receivers on the ground, aircraft, or other satellites. These signals are used to calculate location very accurately. Standard Positioning Services (SPS) which restricts access to Coarse/Access (C/A) code and carrier signals on the L1 frequency only. The accuracy thus provided by SPS fall short of most of the accuracy requirements of users. The upper atmosphere is ionized by the ultra violet radiation from the sun. The significant errors in positioning can result when the signals are refracted and slowed by ionospheric conditions, the parameter of the ionosphere that produces most effects on GPS signals is the total number of electrons in the ionospheric propagation path. This integrated number of electrons, called Total Electron Content (TEC) varies, not only from day to night, time of the year and solar flux cycle, but also with geomagnetic latitude and longitude. Being plasma the ionosphere affects the radio waves propagating through it. Effects of scintillation on GPS satellite navigation systems operating at L1 (1.5754 GHz), L2 (1.2276 GHz) frequencies have not been estimated accurately. It is generally recognized that GPS navigation systems are vulnerable in the polar and especially in the equatorial region during the solar maximum period. In the equatorial region the irregularity structures are highly elongated in the north-south direction and are discrete in the east-west direction with dimensions of several hundred km. With such spatial distribution of irregularities needs to determine how often the GPS receivers fails to provide navigation aid with the available constellation. The effects of scintillation on the performance of GPS navigation systems in the equatorial region can be analyzed through commissioning few ground receivers. Incidentally there are few GPS receivers near these latitudes. Despite the recent advances in the ionosphere and tropospheric delay modeling for geodetic applications of GPS, the models currently used are not very precise. The conventional and operational ionosphere models viz. Klobuchar, Bent, and IRI models have certain limitations in providing very precise accuracies at all latitudes. The troposphere delay modeling also suffers in accuracy. The advances made in both computing power and knowledge of the atmosphere leads to make an effort to upgrade some of these models for improving delay corrections in GPS navigation. The ionospheric group delay corrections for orbit determination can be minimized using duel frequency. However in single frequency measurements the group delay correction is an involved task. In this paper an investigation is carried out to estimate the model coefficients of ionosphere along with precise orbit determination modeling using GPS measurements. The locations of the ground-based receivers near equator are known very exactly. Measurements from these ground stations to a precisely known satellite carrying duel receiver is used for orbit determination. The ionosphere model parameters can be refined corresponding to spatially distributed GPS receivers spread over Brazil. The tropospheric delay effects are not significant for the satellites by choosing appropriate elevation angle. However it needs to be analyzed for user like aircraft for an effective use. In this paper brief description of GPS data utilization, Navigation

  2. High-midlatitude ionosphere response to major stratospheric warming

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

  3. Long-lasting disturbances in the equatorial ionospheric electric field simulated with a coupled magnetosphere-ionosphere-thermosphere model

    NASA Astrophysics Data System (ADS)

    Richmond, A. D.; Peymirat, C.; Roble, R. G.

    2003-03-01

    The Magnetosphere-Thermosphere-Ionosphere-Electrodynamics General Circulation model of [1998] is used to investigate ionospheric-wind-dynamo influences on low-latitude ionospheric electric fields during and after a magnetic storm. Simulations are performed with time-varying polar cap electric potentials and an expanding and contracting polar cap boundary. Three influences on equatorial electric fields can be of comparable importance: (1) global winds driven by solar heating; (2) direct penetration of polar cap electric fields to the equator that are partially shielded by the effects of Region-2 field-aligned currents; and (3) disturbance winds driven by high-latitude heating and ion-drag acceleration. The first two influences tend to have similar magnetic local time (MLT) variations in a steady state, while the disturbance-wind influence tends to have the opposite MLT variations. The nighttime disturbance winds at upper midlatitudes that affect the global ionospheric wind dynamo are predominantly westward after the simulated magnetic storm. The nighttime winds drive an equatorward dynamo current that tends to charge the low-latitude ionosphere positively around midnight, which can lead to reductions or reversals of the normal equatorial night-side east-west electric fields. The simulations partly support the theories of the so-called "disturbance dynamo" [, 1980] and "fossil wind" [, 1988], both of which predict long-lasting disturbances in the equatorial eastward electric field associated with magnetic storms. However, the simulations do not support the element of fossil wind theory that links the disturbance-wind influence on equatorial electric fields to polar cap contraction following the storm. The simulations show a stronger wind-produced enhancement of steady state shielding than predicted by the model of [1989], due to the fact that the disturbance winds extend well equatorward of the Region-2 currents.

  4. Topside ionosphere irregularities in He+ density: statistical study

    NASA Astrophysics Data System (ADS)

    Sidorova, L.; Filippov, S.

    Topside ionosphere He density irregularities as depletions were firstly revealed from OGO-4 data and then from OGO-6 ISIS-2 Oreol-2 data He density depletions subtroughs were seen as well-pronounced structures with He density drop from several times to two orders of magnitude in narrow latitude belt 5 r to 10 r at equatorial and low latitudes mostly However they were distinctly observed in common in several tens of cases only According to ISS-b data He density subtroughs are revealed in sim 440 cases in sim 4000 ISS-b passes over equatorial and low-latitudinal regions L sim 1 3-3 of the topside ionosphere sim 1100 km The available ISS-b data cover high and maximal solar activity period 1978-1979 The present study deals with the He density subtrough statistics The subtrough occurrence probability as function of local time season longitude and Kp activity is obtained and discussed

  5. Microwave heating of the lower ionosphere

    NASA Technical Reports Server (NTRS)

    Meltz, G.; Nighan, W. L.

    1980-01-01

    Changes in the properties of the lower ionosphere due to ohmic heating of the plasma by the solar power satellite (SPS) microwave power beam are considered. The development of a predictive model of the underdense interaction of an electromagnetic beam and the lower i