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Sample records for latitude ionospheric effects

  1. Low-latitude ionospheric effects on SBAS

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1991-01-01

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

  3. Ionospheric storm effects at subauroral latitudes: A case study

    SciTech Connect

    Proelss, G.W. ); Brace, L.H.; Mayr, H.G. ); Carignan, G.R.; Killeen, T.L. ); Klobuchar, J.A. )

    1991-02-01

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

  4. Common origin of positive ionospheric storms at middle latitudes and the geomagnetic activity effect at low latitudes

    SciTech Connect

    Proelss, G.W. )

    1993-04-01

    The author looks for a correlation between two different atmospheric effects. They are a positive atmospheric storm (an anomalous increase in the F2 region ionization density), observed at middle latitudes, and the geomagnetic activity effect (the anomalous changes of temperature and gas density seen in the thermosphere), observed at low latitudes. A temporal correlation is sought to test the argument that both of these effects are the result of travelling atmospheric disturbances (TAD). A TAD is a pulselike atmospheric wave thought to be generated by substorm activity, and to propagate with high velocity (600 m/s) from polar latitudes toward equatorial latitudes. The author looks at data from five separate events correlating magnetic, ionospheric, and neutral atmospheric measurements. The conclusion is that there is a positive correlation between magnetic substorm activity at high latitudes, and positive ionospheric storms at middle latitudes and geomagnetic activity at low latitudes. The time correlations are consistent with high propagation speeds between these events. The author also presents arguments which indicate that the middle latitude positive ionospheric storms are not the result of electric field effects.

  5. 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.

  6. HF Radar Observations of Space Weather Effects in the Low and Mid-latitude Ionosphere

    NASA Astrophysics Data System (ADS)

    Menk, F. W.

    2015-12-01

    The ionosphere is dynamically coupled to the magnetosphere and hence diurnal and seasonal processes in the ionosphere are strongly influenced by space weather effects. These may vary the electron density distribution and cause changes in the reflection and absorption of HF radio signals. Other consequences include the formation of enhanced convective flows and irregularity features which may contribute to Doppler clutter. While there has been much discussion on the ionospheric signatures of magnetic storms at high latitudes, this presentation focuses on effects detected using mid- and low-latitude HF radars which examine field lines mapping to the vicinity of the ring current. Characteristic features include travelling ionospheric disturbances, high velocity flows and sustained irregular and quasi-sinusoidal 5 - 20 mHz waves recorded near the plasmapause. Such observations provide new insight on complex M-I coupling dynamics.

  7. 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.

  8. 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.

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

    NASA Technical Reports Server (NTRS)

    Burns, Alan; Killeen, Timothy

    1993-01-01

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

  10. Effects of Solar Activity Variation on the Low Latitude Topside Nighttime Ionosphere

    NASA Astrophysics Data System (ADS)

    Min, K. W.; Kim, H.; Park, J.; Park, S.; Lee, J.; Lee, E.

    2006-05-01

    We investigate the effects of solar activity variation on the topside nighttime ionosphere of the low latitude region using the DMSP F15 data taken at 840 km altitude as well as the KOMPSAT-1 data taken at 685 km altitude. The change of the ionospheric parameters shows a good correlation with F 10.7 variations, in accordance with 27-day solar rotations. The correlation is especially good when a time delay of 1 to 2 days is incorporated and when the F 10.7 variation is large. Vertical drift velocities and the oxygen ion fractions, observed by DMSP F15, are also seen to have good correlations with F 10.7 with similar time delays. We suspect the delayed correlation of the ionospheric response is closely related to the neutral density changes affected by the solar activity as it has been reported that changes in the solar soft X-rays and the neutral density are well correlated with a delay of approximately 1.5 days. We also compare the ionospheric response for the solar maximum period with that of the declining phase using the data for the period 2000 through 2004 during which average F 10.7 varied from over 200 to around 100. The density does not seem to saturate at high F 10.7 values even during the solar maximum phase, in contrast to the daytime ionospheric response reported previously. The density during the low solar activity cycle is observed to be lower than that of the high solar activity for the same F 10.7 values, implying the long term dependence of the ionosphere in addition to the prompt response of 1 to 2 days.

  11. The ionospheric storm effects at low latitudes and equatorial regions during the 2015 St. Patrick's Day storm

    NASA Astrophysics Data System (ADS)

    Kuai, Jiawei; Liu, Libo

    2016-04-01

    Ionospheric storms manifest an extreme state of the ionosphere caused by geomagnetic storms, and the complicated ionospheric storm effects are always a research focus for the ionospheric community. The geomagnetic storm occurring on 17-20 March 2015, which is characterized by the minimum SYM-H value -233 nT, is an extremely event of space weather in the current 24th solar cycle. In this report, multiple observations including GPS total electron content (TEC), ionospheric parameters from ionosondes, and magnetometer data are used to investigate the profound ionospheric disturbances at low latitudes and equatorial regions during this geomagnetic storm. Through observation and analysis, the disturbed electric fields, which comprise penetration electric fields (PEFs) and disturbance dynamo electric fields (DDEFs), are closely related to the ionospheric storm effects at low latitudes and equatorial regions during this event. The decisive role of electrodynamics at equatorial regions are focused in view of these observations to understand the complete process of the low-latitude and equatorial ionospheric response during the great geomagnetic storm.

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

    NASA Astrophysics Data System (ADS)

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

    2016-07-01

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

  13. 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.

  14. Characteristics of High Latitude Ionosphere Scintillations

    NASA Astrophysics Data System (ADS)

    Morton, Y.

    2012-12-01

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

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

    NASA Astrophysics Data System (ADS)

    Veenadhari, B.; Alex, S.

    2006-11-01

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

  16. The effect of gravity and pressure in the electrodynamics of the low-latitude ionosphere

    NASA Astrophysics Data System (ADS)

    Eccles, J. Vincent

    2004-05-01

    The source of the plasma drift structure in the low-latitude ionosphere during magnetically quiet times is generally understood. Nearly all the quiet time electric field structure has been attributed to divergences in the neutral wind current dynamo. However, there are other current drivers active in the low latitude ionosphere: a gravity-driven current (g × B drift of O+) and a gradient-pressure current (∇P × B drift of e and O+). The gravity-driven current is important in the development of the Rayleigh-Taylor instability and equatorial spread F (ESF) but is ignored in global dynamo electric field models. The gradient pressure and gravity terms in the ionosphere momentum equation normally oppose each other. This paper examines the magnitude of the large-scale electric fields generated by divergences in these lesser currents in a coupled ionosphere-electrodynamics model. The low-latitude electric fields generated by the neutral wind dynamo are altered only slightly by these additional terms. The resulting vertical electric fields (zonal plasma drifts) do not change significantly but the vertical plasma drifts are affected by ˜10 to 15 m/s in the hours before sunrise and after sunset. These low-latitude plasma drift differences are due entirely to the inclusion of the gravity-driven current. The gravity current term produces a downward drift after sunset, which reduces the evening prereversal enhancement. Additionally, the positive vertical drift before sunrise is sometimes large enough to cause a predawn vertical enhancement. The gradient pressure terms can be ignored for large and medium scale ionosphere features.

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

    SciTech Connect

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

    1993-05-01

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

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

    NASA Astrophysics Data System (ADS)

    Cherniakov, Sergey

    2016-07-01

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

  19. Ionospheric effects at low latitudes during the March 22, 1979, geomagnetic storm

    SciTech Connect

    Fesen, C.G. ); Crowley, G.; Roble, R.G. )

    1989-05-01

    This paper investigates the response of the equatorial ionosphere to the neutral atmosphere perturbations produced by the magnetic storm of March 22, 1979. A numerical model of the equatorial ionosphere is used to calculate the maximum electron densities and F layer heights associated with a storm-perturbed neutral atmosphere and circulation model. Possible electric field perturbations due to the storm are ignored. The neutral atmosphere and dynamics are simulated by the National Center for Atmospheric Research thermospheric general circulation model (TGCM) for the storm day of March 22, 1979, and the preceding quiet day. The most striking feature of the TGCM storm day simulations is the presence of waves in the neutral composition, wind, and temperature fields which propagate from high latitudes to the equator. The TGCM-calculated fields for the two days are input into a low-latitude ionosphere model which calculates n{sub max} and h{sub max} between {plus minus}20{degree}dip latitude. The calculated nighttime 6300-{angstrom} airglow emission and the altitude profiles of electron concentration are also highly perturbed by the storm. Examination of ionosonde data for March 22, 1979, shows remarkable agreement between the measured and predicted changes in f{sub 0}F{sub 2} and h{sub max} near 140{degree}W. Poorer agreement near 70{degree}W may be due to the neglect of electric field perturbations and the approximations inherent in the modeling. The results of these simulations indicate that the major factor influencing the storm time ionospheric behavior in this case is the neutral wind.

  20. The effects on the ionosphere of inertia in the high latitude neutral thermosphere. Final report, April 1989-April 1993

    SciTech Connect

    Burns, A.; Killeen, T.

    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 has been studied under this grant.

  1. Ionospheric effects of the March 13, 1989, magnetic storm at low and equatorial latitudes

    SciTech Connect

    Batista, I.S.; De Paula, E.R.; Abdu, M.A.; Trivedi, N.B. ); Greenspan, M.E. )

    1991-08-01

    The great geomagnetic storm of March 13, 1989 caused severely anomalous behavior in the equatorial and low latitude ionosphere in the Brazilian longitude sector. The ionograms over Fortaleza indicated F region upward plasma drifts exceeding 200 m s{sup {minus}1} at 1,830 LT as compared to normal values of 40 m s{sup {minus}1} for this epoch. Large negative phases were observed in foF2 over Fortaleza and Cachoeira Paulista and in total electron content measured over Sao Jose dos Campos. The equatorial ionization anomaly was totally absent either because of its anomalous expansion to higher latitudes or because of inhibition of its development on the two nights following the storm. Many anomalous variations in F region peak density and height, occurring simultaneously with sharp variations on H component of magnetic field over Fortaleza and with auroral substorms, give strong evidence of penetration of magnetospheric electric fields to equatorial and low latitudes. Auroral type sporadic E and night E layers are observed after 1,830 LT over Cachoeira Paulista, the latter showing peak electron density of about 6 {times} 10{sup 4} el cm{sup {minus}3}, therefore comparable to the E layer peak density in the morning hours at that station. The Fortaleza ionograms show the presence of the F1 layer at night, a phenomenon that has never been observed over our two stations before. The role played by electric fields penetrating from high to low latitudes, particle precipitation, and composition changes in explaining the observations is discussed.

  2. 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.

  3. 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

  4. Climatology of GNSS ionospheric scintillation at high latitudes

    NASA Astrophysics Data System (ADS)

    Spogli, L.; Alfonsi, L.; de Franceschi, G.; Romano, V.; Aquino, M.; Dodson, A.; Mitchell, C. N.

    2009-12-01

    Under perturbed conditions caused by intense solar wind magnetosphere coupling, the ionosphere may become highly turbulent and irregularities, typically enhancements or depletions of the electron density embedded in the ambient ionosphere, can form. Such irregularities cause diffraction effects, mainly due to the random fluctuations of the refractive index of the ionosphere, on the satellites signals passing through them and consequent perturbations may cause GNSS navigation errors and outages, abruptly corrupting its performance. Due to the morphology of the geomagnetic field, whose lines are almost vertical at high latitude, polar areas are characterized by the presence of significant ionospheric irregularities having scale sizes ranging from hundreds of kilometers down to a few centimeters and with highly dynamic structures. The understanding of the effect of such phenomena is important, not only in preparation for the next solar cycle (24), whose maximum is expected in 2012, but also for a deeper comprehension of the dynamics of the high-latitude ionosphere. We analyze the fluctuations in the carrier frequency of the radio waves received on the ground, commonly referred to as ionospheric amplitude and phase scintillations, to investigate the physical processes causing them. The phase scintillations on GNSS signals are likely caused by ionospheric irregularities of scale size of hundreds of meters to few kilometers. The amplitude scintillations on GNSS signals are caused by ionospheric irregularities of scale size smaller than the Fresnel radius, which is of the order of hundreds of meters for GNSS signals, typically embedded into the patches. The Istituto Nazionale di Geofisica e Vulcanologia (INGV) and the Institute of Engineering Surveying and Space Geodesy (IESSG) of the University of Nottingham manage the same kind of GISTM (GPS Ionospheric Scintillation and TEC Monitor) receivers over the European high and mid latitude regions and over Antarctica. The

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

    NASA Astrophysics Data System (ADS)

    Tracy, Brian D.

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

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

    NASA Astrophysics Data System (ADS)

    Dashora, Nirvikar; Suresh, Sunanda

    2016-07-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

  8. Electrodynamics of ionospheric weather over low latitudes

    NASA Astrophysics Data System (ADS)

    Abdu, Mangalathayil Ali

    2016-12-01

    The dynamic state of the ionosphere at low latitudes is largely controlled by electric fields originating from dynamo actions by atmospheric waves propagating from below and the solar wind-magnetosphere interaction from above. These electric fields cause structuring of the ionosphere in wide ranging spatial and temporal scales that impact on space-based communication and navigation systems constituting an important segment of our technology-based day-to-day lives. The largest of the ionosphere structures, the equatorial ionization anomaly, with global maximum of plasma densities can cause propagation delays on the GNSS signals. The sunset electrodynamics is responsible for the generation of plasma bubble wide spectrum irregularities that can cause scintillation or even disruptions of satellite communication/navigation signals. Driven basically by upward propagating tides, these electric fields can suffer significant modulations from perturbation winds due to gravity waves, planetary/Kelvin waves, and non-migrating tides, as recent observational and modeling results have demonstrated. The changing state of the plasma distribution arising from these highly variable electric fields constitutes an important component of the ionospheric weather disturbances. Another, often dominating, component arises from solar disturbances when coronal mass ejection (CME) interaction with the earth's magnetosphere results in energy transport to low latitudes in the form of storm time prompt penetration electric fields and thermospheric disturbance winds. As a result, drastic modifications can occur in the form of layer restructuring (Es-, F3 layers etc.), large total electron content (TEC) enhancements, equatorial ionization anomaly (EIA) latitudinal expansion/contraction, anomalous polarization electric fields/vertical drifts, enhanced growth/suppression of plasma structuring, etc. A brief review of our current understanding of the ionospheric weather variations and the

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

    NASA Astrophysics Data System (ADS)

    Kumar, Abhikesh; Kumar, Sushil

    2014-12-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1994-01-01

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

  11. Ionosphere Scintillation at Low and High Latitudes (Modelling vs Measurement)

    NASA Astrophysics Data System (ADS)

    Béniguel, Yannick

    2016-04-01

    This paper will address the problem of scintillations characteristics, focusing on the parameters of interest for a navigation system. Those parameters are the probabilities of occurrence of simultaneous fading, the bubbles surface at IPP level, the cycle slips and the fades duration statistics. The scintillation characteristics obtained at low and high latitudes will be compared. These results correspond to the data analysis performed after the ESA Monitor ionosphere measurement campaign [1], [2]. A second aspect of the presentation will be the modelling aspect. It has been observed that the phase scintillation dominates at high latitudes while the intensity scintillation dominates at low latitudes. The way it can be reproduced and implemented in a propagation model (e.g. GISM model [3]) will be presented. Comparisons of measurements with results obtained by modelling will be presented on some typical scenarios. References [1] R. Prieto Cerdeira, Y. Beniguel, "The MONITOR project: architecture, data and products", Ionospheric Effects Symposium, Alexandria (Va), May 2011 [2] Y. Béniguel, R Orus-Perez , R. Prieto-Cerdeira , S. Schlueter , S. Scortan, A. Grosu "MONITOR 2: ionospheric monitoring network in support to SBAS and other GNSS and scientific purposes", IES Conference, Alexandria (Va), May 2015-05-22 [3] Y. Béniguel, P. Hamel, "A Global Ionosphere Scintillation Propagation Model for Equatorial Regions", Journal of Space Weather Space Climate, 1, (2011), doi: 10.1051/swsc/2011004

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

    NASA Astrophysics Data System (ADS)

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

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

  13. Interhemispheric differences and solar cycle effects of the high-latitude ionospheric convection patterns deduced from Cluster EDI observations

    NASA Astrophysics Data System (ADS)

    Förster, Matthias; Haaland, Stein

    2015-04-01

    Here, we present a study of ionospheric convection at high latitudes that is based on satellite measurements of the Electron Drift Instrument (EDI) on-board the Cluster satellites, which were obtained over a full solar cycle (2001-2013). The mapped drift measurements are covering both hemispheres and a variety of different solar wind and interplanetary magnetic field (IMF) conditions. The large amount of data allows us to perform more detailed statistical studies. We show that flow patterns and polar cap potentials can differ between the two hemispheres on statistical average for a given IMF orientation. In particular, during southward directed IMF conditions, and thus enhanced energy input from the solar wind, we find that the southern polar cap has a higher cross polar cap potential. We also find persistent north-south asymmetries which cannot be explained by external drivers alone. Much of these asymmetries can probably be explained by significant differences in the strength and configuration of the geomagnetic field between the Northern and Southern Hemisphere. Since the ionosphere is magnetically connected to the magnetosphere, this difference will also be reflected in the magnetosphere in the form of different feedback from the two hemispheres. Consequently, local ionospheric conditions and the geomagnetic field configuration are important for north-south asymmetries in large regions of geospace. The average convection is higher during periods with high solar activity. Although local ionospheric conditions may play a role, we mainly attribute this to higher geomagnetic activity due to enhanced solar wind - magnetosphere interactions.

  14. Equatorial and Low-Latitudes Ionospheric Reaction to Solar Flares

    NASA Astrophysics Data System (ADS)

    Nicoli Candido, C. M.; Becker-Guedes, F.; Paula, E. R.; Takahashi, H.

    2015-12-01

    Solar X-ray and extreme ultraviolet (EUV) photons are responsible for ionizing the terrestrial atmosphere and create the ionosphere. During solar flares, a fast increase in the electron density at different altitude regions takes place due to the abrupt enhance of the X-ray and EUV fluxes reaching Earth. With these changes in the ionosphere, radio communication and navigation can be drastically affected. The magnitudes of these Space Weather events can be related to the X-ray peak brightness and duration, which drive the intensity of the ionosphere response when the associated electromagnetic wave hit the sunlit side of the Earth's atmosphere. Other aspects defining these changes in a particular region are the local time, the solar zenith angle, and the position of the flare in the solar disc for each event. In order to improve the understand of radio signal degradation and loss in the Brazilian sector due to solar abrupt electromagnetic emissions, total electron content (TEC) data obtained by a GPS network formed by tents of dual-frequency receivers spread all over Brazilian territory were analyzed. It was observed different ionospheric local changes during several X-ray events identified by GOES satellite regarding the 0.1-0.8 nm range, and some case studies were ponder for a more detailed analysis of these effects. Considering the results, we have made an estimation of the ionospheric disturbances range for a particular event with great chance to affect space based communications in the equatorial and low-latitude regions.

  15. 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.

  16. Statistical study of possible pre-, co- (coeval to) and post- earthquake effects in the near-equatorial, low and mid latitude ionosphere

    NASA Astrophysics Data System (ADS)

    Gousheva, Mariyana; Danov, Dimitar; Hristov, Plamen; Georgieva, Katya

    This paper presents the quasi-static electric field disturbances in the upper ionosphere observed from the satellite INTERCOSMOS-BULGARIA-1300 over earthquakes' source regions at different latitudes. The earthquake data were obtained from United State Geological Survey (USGS) website. In the present paper, an attempt of a statistical stady of ionospheric effects during seismic activity in August- November 1981 is presented. Present study focuses on four main areas- (i) satellite and seismic data selection, (ii) data processing and observations of some most important experimental results, (iii) comparison of observational new data with the results in our previous studies, (iiii) statistical study of possible pre-, co- (coeval to) and postearthquake effects in the near-equatorial, low and mid latitude ionosphere. After review of observational results we analyze an increase of about 5-10-15 mV/m in the vertical component of the quasi-static electric field observed by INTERCOSMOS-BULGARIA-1300 in the upper ionosphere above earthquakes sources during seismic activity. The obtained results strengthen our previous studies (Gousheva et al., 2005a, b; 2006a, b; 2007a, b).The paper discusses the observed effects. The main goal of this study is to generalize our results of possible connection between anomalous vertical electric fields penetrating from the earthquake zone into the ionosphere, and seismic activity. An additional goal of this study is to evaluate some morphological peculiarities of quasi-static electric field disturbances such as their appearance time before and after the main shock, sensitivity, amplitude and time duration.

  17. Ionospheric studies using a low-latitude ionospheric model (LION-model) and ground-based ionosonde observations.

    NASA Astrophysics Data System (ADS)

    Pillat, V. G.; Bittencourt, J. A.; Fagundes, P. R.

    Ionospheric observations made with ionosondes of the type CADI at S a o Jos e dos Campos 23 2 o S 45 9 o W dip latitude 17 6 o S and at Palmas 10 2 S 48 2 W dip latitude 5 7 S Brazil under conditions of high and low solar activity are presented and compared with ionospheric results obtained from a realistic fully time-dependent Low-Latitude Ionosphere Model denominated LION model which simulates the dynamic behavior of the low-latitude ionosphere In the LION model the time evolution and spatial distribution of the ionospheric particle densities and velocities are computed by numerically solving the time-dependent coupled nonlinear system of continuity and momentum equations for the ions O O 2 NO N 2 and N taking into account photoionization of the atmospheric species by the solar extreme ultraviolet radiation chemical and ionic production and loss reactions and plasma transport processes including the ionospheric effects of thermospheric neutral winds plasma diffusion and electromagnetic E x B plasma drift The Earth s magnetic field is represented by a tilted centered magnetic dipole This set of coupled nonlinear equations is solved along a given magnetic field line in a frame of reference moving vertically in the magnetic meridian plane with the electromagnetic plasma drift velocity The model results reproduce adequately the main characteristics and dynamic behavior of the low-latitude ionosphere under quiet

  18. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2010-12-01

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

  20. High-latitude upgrade to the Wideband ionospheric scintillation model

    NASA Astrophysics Data System (ADS)

    Secan, J. A.; Bussey, R. M.; Fremouw, E. J.; Basu, S.

    1997-07-01

    The high-latitude sections of the Wideband ionospheric scintillation model (WBMOD) have been upgraded extensively, based on analysis of scintillation data from the Defense Nuclear Agency Wideband, HiLat, and Polar BEAR satellite-beacon experiments. Data collected at Sondre Stromfjord, Greenland; Tromso, Norway; Fort Churchill, Canada; and Bellevue, Washington (United States) over a 4-year period were analyzed, and the results of these analyses were used to construct a completely new model for the behavior of the height-integrated irregularity-strength parameter (CkL) at high latitudes. The new high-latitude CkL model includes variations with sunspot number, geomagnetic activity (Kp), latitude, local time, longitude, and season. The new WBMOD CkL models (equatorial and high-latitude) have been implemented in a more versatile code, denoted SCINTMOD, which has the capability to generate a wide range of user-controlled maps of scintillation effects over large spatial areas. Examples of the types of graphical output that SCINTMOD can generate are presented.

  1. Recent Advances in Mid-latitude Ionosphere/Thermosphere Science

    NASA Astrophysics Data System (ADS)

    Kelley, Michael

    One of the original reasons for building a National Ionospheric Observatory (now the National Astronomy and Ionospheric Center or NAIC) near Arecibo, Puerto Rico was the location, which is in the best behaved region of the ionosphere. At 30° magnetic latitude and 19° geographic latitude, it is well equatorward of the auroral and sub-auroral zones and poleward of the equatorial anomalies most of the time. The island thus has some of the best weather and space weather on the planet. However, similar to an occasional hurricane striking the island, the ionosphere overhead has occasional ionospheric and thermospheric disturbances. Some of these space weather phenomena, e.g., mesoscale TIDs and unstable sporadic E layers, are endemic to the region and, prior to the advent of airglow imagers and GPS networks, were difficult to visualize using radiowave data alone. Other weather events are caused by infringement on this zone from processes in more active weather regions. For example, neutral waves launched from the auroral oval (large scale TIDs) pass through the region; electric fields penetrate from the solar wind and create both plasma uplifts, causing positive ionospheric storms, and stormenhanced density plumes, coursing through the region. From the south, convective equatorial ionospheric storms create plasma bubbles that can reach mid-latitudes. Examples of data obtained during these phenomena, and possibly more, will be presented and discussed in light of our present understanding.

  2. Anomalous ionospheric conductivities caused by plasma turbulence in high-latitude E-region ionosphere

    NASA Astrophysics Data System (ADS)

    Dimant, Yakov; Oppenheim, Meers

    2015-11-01

    During periods of intense geomagnetic activity, electric fields penetrating from the Earth's magnetosphere to the high-latitude E-region ionosphere drive strong currents named electrojets and excite there plasma instabilities. These instabilities give rise to plasma turbulence that induces nonlinear currents and strong anomalous electron heating. This increases the ionospheric conductances and modifies the global energy flow, affecting behavior of the entire near-Earth plasma. A quantitative understanding of anomalous conductance and global energy transfer is important for accurate modeling of the geomagnetic storm/substorm evolution. Our theoretical analysis, supported by recent 3D fully kinetic particle-in-cell simulations, shows that during strong geomagnetic storms the inclusion of anomalous conductivity can more than double the total Pedersen conductance - the crucial factor responsible for magnetosphere-ionosphere coupling through the current closure. We have started incorporating the effects of anomalous heating and nonlinear conductivity into existing global magnetosphere-ionosphere-thermosphere codes developed for predictive modeling of Space. In our presentation, we will report on the latest progress in this modeling. Work supported by NASA Heliophysics GCR Grant NNX14AI13G.

  3. Low- and mid-latitude ionospheric electric fields during the January 1984 GISMOS campaign

    NASA Technical Reports Server (NTRS)

    Fejer, B. G.; Kelley, M. C.; Senior, C.; De La Beaujardiere, O.; Lepping, R.

    1990-01-01

    The electrical coupling between the high-, middle-, and low-latitude ionospheres during January 17-19, 1984 is examined, using interplanetary and high-latitude magnetic field data together with F region plasma drift measurements from the EISCAT, Sondre Stromfjord, Millstone Hill, Saint-Santin, Arecibo, and Jicamarca incoherent scatter radars. The penetration both the zonal and meridional electric field components of high-latitude origin into the low-latitude and the equatorial ionospheres are studied. The observations in the postmidnight sector are used to compare the longitudinal variations of the zonal perturbation electric field with predictions made from global convection models. The results show that the meridional electric field perturbations are considerably more attenuated with decreasing latitude than the zonal fluctuations. It is concluded that variations in the meridional electric field at low latitudes are largely due to dynamo effects.

  4. Latitudinal TEC gradients over polar ionosphere using high latitude GPS measurements

    NASA Astrophysics Data System (ADS)

    Shagimuratov, Irk; Cherniak, Iurii; Zakharenkova, Irina; Tepenitsyna, Nadezhda; Yakimova, Galina; Ephishov, I. I.

    The GPS observations of Greenland network were used to analyze the latitudinal variations of TEC at the high-latitudes ionosphere. This network provides unique opportunity to monitor TEC variability in polar ionosphere on a regular base. GPS stations are arranged along the latitude over the range 60-83°N (65°-87° Corrected Geomagnetic Latitude) near of 30°-40° longitudes. More than 20 GPS stations are located closely with one another along latitude. The distance between stations is about 1°-2°.Such spatial resolution provides the possibility to analyze the detailed structure of latitudinal TEC profiles. The standard procedure of processing GPS observations was used for TEC estimation. On this base it was obtained the diurnal TEC variations over all Greenland stations. The TEC data is used to form latitudinal profiles (TEC section) covered subauroral, auroral and polar ionosphere. In the report the observations of TEC for quiet and disturbed ionosphere during several geomagnetic storms occurred in September 2011 are presented. During quiet conditions in the night-time TEC profiles demonstrated invariable values about of 4-6 TECU in latitudinal region of 60°-75°N; then it presented THE increase towards the higher latitude and reached the value of 10 TECU near 80°N. The daytime profiles revealed TEC decrease toward high latitude in keeping with 0.8 TECU/degree. During storm the structure of latitudinal TEC profiles was essentially changed with agreement to the development of geomagnetic storm. The positive effect was observed at subauroral and auroral latitudes, negative effect was prevailed at the polar region. During the night time the ionospheric trough can be observed. In the report features of the behavior of latitudinal profiles at high-latitude ionosphere for September 2011 events were discussed.

  5. Ionospheric effects of the simultaneous occurrence of a solar proton event and relativistic electron precipitation as recorded by ground-based instruments at different latitudes

    NASA Astrophysics Data System (ADS)

    Shirochkov, A. V.; Makarova, L. N.; Sokolov, S. N.; Sheldon, W. R.

    2004-08-01

    The intense event of highly relativistic electron (HRE) precipitation of May 1992 has been analyzed using data from ground-based observations (riometers and VLF phase measurements). Special attention was given to some features of this event observed at high and very high geomagnetic latitudes, since this aspect of the event was not well documented in previous studies. A remarkable feature of the HRE event of May 1992 was the simultaneous occurrence of a strong solar proton event (SPE), although reliable evidence shows that the simultaneous appearance of SPE and HRE events is not unique. It was demonstrated that a meridian chain of riometers with high latitudinal resolution is an effective and low-cost (as compared with satellite observations) tool to separate the effects of solar proton and relativistic electrons in the lower ionosphere. A significant conclusion is that the polar cap area is free from relativistic electron precipitation. Other interesting aspects of this complex geophysical phenomenon are also discussed.

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

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

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

  7. Mid-latitude Ionospheric HF Channel Reciprocity: Evidence from the Ionospheric Oblique Incidence Sounding Experiments

    NASA Astrophysics Data System (ADS)

    Zhou, Chen; Zhao, Zhengyu; Zhang, Yuannong

    The mid-latitude ionospheric HF channel reciprocity is studied in this paper through theoret-ical considerations and ionospheric oblique incidence sounding experiments. The reciprocity of ionospheric HF channel experiments were carried out by using two identical Wuhan Iono-spheric Oblique Incidence Sounding Systems (WIOISS) located in Wuhan (30° 32N, 114° 21E) and Wanning (18° 58N, 110° 31E) respectively. The comparisons of group distance and Doppler shift between Wuhan-Wanning and Wanning-Wuhan HF ionospheric propagation paths show that the reciprocity of ionospheric HF channel is satisfied to some extent. The group dis-tances of two paths are calculated by a 3-D ray tracing simulation as well. The theoretical and experimental results could be widely used for HF communication systems and sky wave over-the-horizon radar.

  8. The role of superthermal electrons in high latitude ionospheric outflows

    NASA Astrophysics Data System (ADS)

    Glocer, A.; Khazanov, G. V.; Liemohn, M. W.; Toth, G.; Gombosi, T. I.

    2014-12-01

    It is well accepted that the ionosphere is a critical source of plasma for the magnetosphere, providing O+, H+, and He+ which can have wide ranging consequences for the space environment system. Changing ion composition affects magnetic reconnection in the magnetosphere, the ring current, and the wave environment which is important for high energy radiation belt electrons. Of the myriad of mechanisms that are important in determining the ionospheric outflow solution at high latitudes, we focus on the role of superthermal electron populations. It has been demonstrated in multiple studies that even small concentrations of superthermal electrons can have a dramatic effect on the outflow solution. In this presentation, we present simulation results using our Polar Wind Outflow Model (PWOM) and our SuperThermal Electron Transport (STET) code. We describe recent results on superthermal electrons role in defining the quiet time solar wind solution with comparisons to observations. We also discuss preliminary results that combine the PWOM and STET codes for a more comprehensive treatment of the impact of superthermal electrons.

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

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

    Neutral flywheel effects are investigated in NCAR-TIGCM simulation of geomagnetic storms that occurred in November 23, 1982 and December 7-8, 1982. Theoretical calculations from the latter storm are compared with measurements of currents form instruments on the Dynamics Explorer 2 satellite. It is concluded that neutral flywheel effects can make a contribution to high latitude electrodynamics for a few hours after the main phase of a geomagnetic storm. The Hall currents that are driven by neutral winds during B(Z) northward conditions are generally in the opposite direction to those that occur during B(Z) southward conditions, when they are driven primarily by ion winds. The morphology of the field-aligned current system calculated by the NCAR-TIGCM during southward B(Z) conditions is in general agreement with observations.

  10. Analytical model of ionospheric convection at subauroral latitudes

    NASA Astrophysics Data System (ADS)

    Deminov, M. G.; Kim, V. P.; Shubin, V. N.; Khegai, V. V.

    An analytical model of plasma convection in the subauroral ionosphere is developed, assuming that the electric shielding of the inner magnetosphere is controlled by polarization of the hot ion zone situated behind the inner boundary of the plasma sheet. It is shown that, at subauroral latitudes at night, the plasma drifts eastward, while during the day it shifts westward. Thus, in the predmidnight sector, the direction of convection in the subauroral ionosphere is opposite to that of auroral convection. In general, the electric field, with a strength of 10 mV/m, has a meridional direction.

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

    NASA Astrophysics Data System (ADS)

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

    2016-07-01

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

  12. Comparative study of high-latitude, mid-latitude and low-latitude ionosphere on basis of local empirical models

    NASA Astrophysics Data System (ADS)

    Ratovsky, K. G.; Shi, J. K.; Oinats, A. V.; Romanova, E. B.

    2014-08-01

    The analysis of the regular features of the high-, mid- and low-latitude ionosphere characteristics has been carried out using local empirical models. The local empirical models were derived from the manual scaled ionogram data recorded by DPS-4 Digisondes located at Norilsk (69 N, 88E), Irkutsk (52 N, 104E) and Hainan (19 N, 109E) for a 6-year period from December, 2002 to December, 2008. The technique used to build the local empirical model is described. Primary focuses are diurnal, seasonal and solar cycle variations of the peak electron density and the peak height under low solar activity and their changes with increasing solar activity. The main objective of the paper is to reveal both common and specific features of high-, mid- and low-latitude ionosphere. Based on earlier comparisons with the International Reference Ionosphere model, we analyze how the common and specific features are reproduced by this model.

  13. The Low-latitude Ionospheric Sensor Network: The Initial Campaigns

    NASA Astrophysics Data System (ADS)

    Doherty, P. H.; Valladares, C. E.; Carrano, C.

    2009-05-01

    The Low-latitude Ionospheric Sensor Network (LISN) is a distributed observatory designed to provide regional coverage in South America and high-temporal resolution measurements to diagnose the initiation and development of plasma structures and the state and dynamics of the low latitude ionosphere. It combines inexpensive GPS receivers and state-of-the-art radars such as the Vertical Incidence Pulsed Ionospheric Radar (VIPIR) ionosondes and magnetometers. This paper describes the characteristics of the LISN distributed observatory and discusses the results of the first two campaigns. LISN will be comprised of nearly 70 GPS receivers with the capability to measure Total Electron Content (TEC), amplitude and phase scintillation and Traveling Ionospheric Disturbances (TIDs). LISN will also include 5 ionosondes able to measure nighttime E-region densities and 5 collocated magnetometers that will be placed along the same magnetic meridian. The first campaign was dedicated to detect medium-scale (~100 km) TIDs and was conducted at Huancayo, Peru in July 2008 using 3 GPS receivers spaced by 4-5 km arranged in a triangular configuration. TEC data corresponding to 3 consecutive days indicate that the TIDs phase velocity was close to 120 m/s and directed northward during the early evening hours. The second campaign was conducted in February 2009 using 3 GPS receivers installed near Ancon and coordinated with the VIPIR ionosonde running in an interferometer mode. We will discuss the implications of these new results within the frame of the current theories of plasma bubble onset.

  14. Comparing ionospheric models with mid-latitude ionosonde observations

    NASA Astrophysics Data System (ADS)

    Al-Ubaidi, Najat M. R.

    2009-06-01

    The purpose of this research work is to validate the ionospheric models (IRI and CHIU) to assess its suitability and usefulness as an operational tool. The ionospheric model is a computer model designed to predict the state of the global ionosphere for 24 h. The scope was limited to conduct comparisons between the predicted F2 layer critical frequencies (f0F2) against observed ionosonde data. The ionospheric prediction model (IPM) was designed to predict by using monthly median sunspot number, while the observation data are taken from two digital ionospheric sounding stations (Okinawa, 26.28N, 127.8E and Wakkanai, 45.38N, 141.66E) which lies within the mid-latitude region of the globe. Analysis of the f0F2 data from stations for year (2001) with high solar activity and year (2004) with low solar activity, four months (March, June, September and December) chosen based primarily on data availability. From results it seen that the ratio between monthly median predicted and observed f0F2 values for each model used in this research work and for the chosen months was nonlinear with local time, so the empirical formula for applying correction factors were determined, these formula can be used to correct the error occurred in predicted f0F2 value.

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

    NASA Astrophysics Data System (ADS)

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

    2016-02-01

    In this article, we presented ionospheric F2 responses to total solar eclipses on the basis of the data obtained from five (5) equatorial/low-latitude and twenty-seven (27) mid-latitude ionosonde stations, which are within the obscuration percentage of 50-100% of the path of the total solar eclipses progression. Statistically, the diurnal changes in the F2 layer peak height hmF2 and electron density NmF2, as well as the latitudinal and hemispheric dependence and the contribution of both magnetic and solar activities during the eclipse window were investigated. The estimation of the solar ionizing radiation that remains unmasked during the eclipse window was as well carried out. Plasma diffusion processes dominate the F2 region plasma, and determine the height at which the F2 peak formed at mid-latitude. The electron density decreased during the eclipse window, closely following the variation in the local solar radiation at the mid-latitude. However, at equatorial/low-latitude, the plasma distribution during total solar eclipse depends on combine effect of solar radiation and the background nighttime ionospheric irregularities mechanism. The uncertainty level of the estimated solar ionizing radiation was <±0.3 at mid-latitude and greater±0.3 at equatorial/low-latitude. Their correlation ranges from (0.42-0.99). The ionospheric F2 layer eclipse effect is latitudinal and hemispheric dependent. The effect is largest at mid-latitude and relatively small at equatorial/low-latitudes. It is more pronounced at the equator, and decreases toward the equatorial ionospheric anomaly (EIA) region. The better correlation of 0.5840 and 0.6435 between geographic latitude and E(t) and electron density justifies the latitudinal relationship. The increase in percentage deviation of electron density increases with latitude and delay time (∆T) in the northern hemisphere of the mid-latitude. Conversely, in the southern hemisphere the percentage deviation decreases with an increase in

  16. The Ionospheric Mid-Latitude Summer Nighttime Anomaly

    NASA Astrophysics Data System (ADS)

    Lin, C.; Chen, C.; Hsu, M.; Liu, C. H.; Liu, J. G.; Burns, A. G.; Wang, W.

    2009-12-01

    This paper presents monthly variations of the mid-latitude summer nighttime anomaly (MSNA) of the ionosphere for the first time by using global observations of the FORMOSAT-3/COSMIC (F3/C), NASA TIMED-GUVI, ground-based radars and GPS receiver network. The MSNA is characterized by greater nighttime (19:00 LT - 24:00 LT, or period of larger solar zenith angles) ionospheric electron density than that during daytime (08:00 - 18:00 LT, or period of smaller solar zenith angles) at middle latitudes during solstices. The anomaly shown in the southern hemisphere during December solstice was previously known as the Weddell Sea Anomaly (WSA) occurring around the Antarctica and the nearby Pacific Ocean, while a WSA-like electron density structure also occurs in the northern hemisphere around June solstice. This study demonstrates that the anomalies occurred in both the northern and southern hemispheres share similar character of greater nighttime density. Moreover, the latitude-altitude cross-section plots of the electron density structure show very similar time-varying electron density evolutions of the MSNA. In both hemispheres, the anomalies with similar electron density characteristics and variations caused by the similar mechanism prompts us to name this phenomenon the mid-latitude summer nighttime anomaly.

  17. Radar-satellite studies of the high-latitude ionosphere. Annual progress report no. 2, Aug 90-Aug 91

    SciTech Connect

    Foster, J.C.

    1991-10-09

    During the second year of this research program, work has continued on multi-instrument experiments investigating the effects of the large-scale convection electric field in the auroral and mid-latitude ionosphere. A radar-satellite study of electric field latitude structure during the February 8-9, 1986 great magnetic storm was completed and has provided an excellent example of the application of multi-instrument techniques to the investigation of magnetosphere-ionosphere coupling problems. Studies of the high-latitude boundary between auroral and polar cap latitudes have emphasized convection and ionospheric plasma structure near the dayside cusp and the transport of ionospheric plasma into the polar cap during storms. Mesoscale resolution electric field structure was addressed in a multi-instrument study involving the Canadian BARS radar facility and the Millstone Hill incoherent scatter radar.

  18. Probing high latitude ionospheric irregularities by GPS: Results and analysis

    NASA Astrophysics Data System (ADS)

    Krankowski, Andrzej; Shagimuratov, Irk; Ephishov, I. I.; Sieradzki, Rafal

    The GPS measurements of IGS network were used to study the occurrence of TEC fluctuations at northern and southern high latitude ionosphere during severe geomagnetic disturbances of 22-28 July 2004. For the northern hemisphere we selected 20 GPS stations located higher than 55 degrees of Corrected Geomagnetic Latitude. For the southern hemisphere, Antarctic permanent GPS stations were used. Dual-frequency GPS measurements along individual satellite passes served as row data. As a measure a fluctuation activity the rate of TEC (ROT) was used, and fluctuation intensity was evaluated using ROTI index. Using daily GPS measurements from all the selected stations, the images of spatial and temporal behavior of TEC fluctuations (in Corrected Geomagnetic Coordinate and local geomagnetic time) were formed. Similarly to the auroral oval the images demonstrate an irregularities oval. The occurrence of irregularities oval relates with the auroral oval and polar caps. During the storm, TEC fluctuation activity and intensity essentially increased. The irregularities oval expands equatorward with increasing magnetic activity. As a whole, the dynamics of the irregularities ovals in both hemispheres are similar during the storm time, however we found some difference in development of TEC fluctuations between northern and southern ionosphere. They may be caused by seasonal features of excitation of irregularities at high latitude ionosphere. Daily pattern of the irregularities oval was controlled by the motion of the station location into auroral oval. Maximal intensity of TEC fluctuations took place over polar stations. The strong TEC fluctuations were associated with the polar patches. Their study showed that the existing high-latitude GPS stations can provide a permanent monitoring of the irregularities oval in near real-time.

  19. Climatological response of Indian low-latitude ionosphere to geomagnetic storms

    NASA Astrophysics Data System (ADS)

    Suresh, Sunanda; Dashora, N.

    2016-05-01

    A climatological response of low-latitude ionosphere to geomagnetic storms is presented using long-term global ionospheric maps data from June 1998 to June 2015 covering two solar cycles 23 and 24. The results are presented for daytime forenoon and afternoon sectors under minor, moderate, and major ionospheric storm categories based on minimum Dst index criterion. For the first time the effectiveness of storms is identified using monthly standard deviation as an indicator of the day to day variability in equatorial and low-latitude ionosphere. Thus, results on climatology are definitive and form a database that would be comparable to statistical results from any other longitude and time. Seasonal statistics for total storms, effective positive and negative storms, and amplitude of mean seasonal perturbation in total electron content are obtained. Total and effective storms are found to be higher in solar cycle 23 than in 24 and only a couple of effective storms occurred during low solar activity 2007-2009 that too in minor category. Afternoon sector is found to be favorable for occurrence of maximum number of effective positive storms. A latitudinal preference is found for a given storm to be effective in either time sectors. Equinoctial asymmetry in ionospheric response both in terms of occurrence and perturbation amplitude is found. September equinoxes are found to bear maximum total, effective positive and negative storms. Winters are found more prone to negative storms, whereas summers have recorded minimum number of either of storms and minimum perturbation amplitudes.

  20. Ionospheric vertical drift response at a mid-latitude station

    NASA Astrophysics Data System (ADS)

    Kouba, Daniel; Koucká Knížová, Petra

    2016-07-01

    Vertical plasma drift data measured at a mid-latitude ionospheric station Pruhonice (50.0 ° N, 14.6 ° E) were collected and analysed for the year 2006, a year of low solar and geomagnetic activity. Hence these data provide insight into the drift behaviour during quiet conditions. The following typical diurnal trend is evident: a significant decay to negative values (downward peak) at dawn; generally less pronounced downward peak at dusk hours. Magnitude of the downward drift varies during the year. Typically it reaches values about 20 ms-1 at dawn hours and 10 ms-1 at dusk hours. Maximum dawn magnitude of about 40 ms-1 has been detected in August. During daytime the vertical drifts increases from the initial small downward drifts to zero drift around noon and to small upward drifts in the afternoon. Night-time drift values display large variability around a near zero vertical drift average. There is a significant trend to larger downward drift values near dawn and a less pronounced decrease of the afternoon upward vertical drifts near sunset. Two regular downward peaks of the drift associated with the dawn and dusk are general characteristics of the analysed data throughout the year 2006. Their seasonal course corresponds to the seasonal course of the sunrise and sunset. The duration of prevailing negative drift velocities forming these peaks and thus the influence of the dawn/dusk on the drift velocity is mostly 1.5-3 h. The dawn effect on vertical drift tends to be larger than the effect of the dusk. The observed magnitude of the sunrise and sunset peaks show significant annual course. The highest variability of the magnitude is seen during winter. High variability is detected till March equinox and again after September equinox. Around solstice, both peaks reaches lowest values. After that, the magnitudes of the drift velocity increase smoothly till maxima in summer (August). The vertical drift velocity course is smooth between June solstice and September

  1. Low-latitude Ionospheric Heating during Solar Flares

    NASA Astrophysics Data System (ADS)

    Klenzing, J.; Chamberlin, P. C.; Qian, L.; Haaser, R. A.; Burrell, A. G.; Earle, G. D.; Heelis, R. A.; Simoes, F. A.

    2013-12-01

    The advent of the Solar Dynamics Observatory (SDO) represents a leap forward in our capability to measure rapidly changing transient events on the sun. SDO measurements are paired with the comprehensive low latitude measurements of the ionosphere and thermosphere provided by the Communication/Navigation Outage Forecast System (C/NOFS) satellite and state-of-the-art general circulation models to discuss the coupling between the terrestrial upper atmosphere and solar radiation. Here we discuss ionospheric heating as detected by the Coupled Ion-Neutral Dynamics Investigation (CINDI) instrument suite on the C/NOFS satellite during solar flares. Also discusses is the necessity of decoupling the heating due to increased EUV irradiance and that due to geomagnetic storms, which sometimes occur with flares. Increases in both the ion temperature and ion density in the subsolar topside ionosphere are detected within 77 minutes of the 23 Jan 2012 M-class flare, and the observed results are compared with the Thermosphere-Ionosphere-Mesosphere-Electrodynamics General Circulation Model (TIME-GCM) using the Flare Irradiance Spectral Model (FISM) as an input.

  2. The effects of modification of a high-latitude ionosphere by high-power HF radio waves. Part 1. Results of multi-instrument ground-based observations

    NASA Astrophysics Data System (ADS)

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

    2011-02-01

    We present the results of multi-instrument experiments related to studying the phenomena in the high-latitude ionosphere affected by high-power radio waves using the EISCAT technical facilities. It was found for the first time that strong small-scale artificial field-aligned irregularities (AFAIs) are excited when the ionospheric F region is heated by a high-power HF radio wave with X-mode polarization near the altitude at which the critical frequency {f_{x{F_2}}} of the F 2 layer is equal to the frequency f H of the heating accompanied by an up to 50% increase in the electron temperature. The spatial structure of the artificially perturbed ionospheric F region is examined in detail using an incoherent scatter radar operated in the regime of scanning over elevation angles from 92° to 74° with a 2° step. It is shown that the spatial size of the heated patch strongly depends on the angle of the HF pumping relative to the Earth's magnetic field. The phenomena occurring in the artificially modified ionospheric F region heated at frequencies near the third electron gyroharmonic, i.e., at f H = 3 f ce = f UH, where f UH is the upper-hybrid frequency, are explored on the basis of multi-instrument observation data.

  3. LION: A dynamic computer model for the low-latitude ionosphere

    NASA Astrophysics Data System (ADS)

    Bittencourt, J. A.; Pillat, V. G.; Fagundes, P. R.; Sahai, Y.; Pimenta, A. A.

    2007-11-01

    A realistic fully time-dependent computer model, denominated LION (Low-latitude Ionospheric) model, that simulates the dynamic behavior of the low-latitude ionosphere is presented. The time evolution and spatial distribution of the ionospheric particle densities and velocities are computed by numerically solving the time-dependent, coupled, nonlinear system of continuity and momentum equations for the ions O+, O2+, NO+, N2+ and N+, taking into account photoionization of the atmospheric species by the solar extreme ultraviolet radiation, chemical and ionic production and loss reactions, and plasma transport processes, including the ionospheric effects of thermospheric neutral winds, plasma diffusion and electromagnetic E×B plasma drifts. The Earth's magnetic field is represented by a tilted centered magnetic dipole. This set of coupled nonlinear equations is solved along a given magnetic field line in a Lagrangian frame of reference moving vertically, in the magnetic meridian plane, with the electromagnetic E×B plasma drift velocity. The spatial and time distribution of the thermospheric neutral wind velocities and the pattern of the electromagnetic drifts are taken as known quantities, given through specified analytical or empirical models. The model simulation results are presented in the form of computer-generated color maps and reproduce the typical ionization distribution and time evolution normally observed in the low-latitude ionosphere, including details of the equatorial Appleton anomaly dynamics. The specific effects on the ionosphere due to changes in the thermospheric neutral winds and the electromagnetic plasma drifts can be investigated using different wind and drift models, including the important longitudinal effects associated with magnetic declination dependence and latitudinal separation between geographic and geomagnetic equators. The model runs in a normal personal computer (PC) and generates color maps illustrating the typical behavior of the

  4. 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.

  5. Study of the low latitude ionospheric turbulence observed by DEMETER

    NASA Astrophysics Data System (ADS)

    Li, F.; Lefeuvre, F.; Parrot, M.

    Following previous works from Molchanov et al 2002a 2002b 2004a 2004b and Hobara et al 2005 data bases dedicated to the systematic analysis of the power and spectral indices of the electric field have been elaborated Two data bases are considered one for the survey mode and the other for the burst mode For the survey mode estimations of the turbulence parameters are performed from the 8 first Fourier components of the averaged power spectra 0-150 Hz frequency band A single slope power law model f - alpha is assumed A quality factor allows to test that hypothesis For the burst mode the power spectra are derived from the waveforms One and two slope models are systematically tested Results are presented and the possibility to use these data bases for correlation with seismic activity is discussed Y Hobara F Lefeuvre M Parrot and O A Molchanov Low-latitude ionospheric turbulence observed by Aureol-3 satellite Annales Geophysicae 23 1259--1270 2005 Molchanov O A Hayakawa M Afonin V V Akentieva O A and Mareev E A Possible influence of seismicity by gravity waves on ionospheric equatorial anomaly from data of IK-24 satellite 1 Search for idea of seismo-ionosphere coupling Seismo Electromagnetics Lithosphere-Atmosphere-Ionosphere Coupling edited by Hayakawa M and Molchanov O A TERRAPUB Tokyo 275--285 2002a Molchanov O A Hayakawa M Afonin V V Akentieva O A Mareev E A and Trakhtengerts V Yu Possible influence of seismicity by gravity waves on ionospheric

  6. A multi-technique study of the 29-31 October 2003 geomagnetic storm effect on low latitude ionosphere over Indian region with magnetometer, ionosonde, and GPS observations

    NASA Astrophysics Data System (ADS)

    Panda, Sampad Kumar; Gedam, Shirish S.; Rajaram, Girija; Sripathi, S.; Pant, Tarun Kumar; Das, Rupesh M.

    2014-12-01

    The present study demonstrates the ionospheric response to the extreme geomagnetic storms during 29-31 Oct 2003 (the Halloween storm), in the low latitude anomaly Indian region, based on multi-instrument measurements namely magnetometer, ionosonde, and GPS observations. Unlike earlier reports, we have suitably chosen the best quiet days (CQ-Days) amongst 10 international quiet days (Q-Days), on the basis of equatorial electrojet strength and pattern, that drives the distribution of plasma over the low latitude. We stress that arbitrarily selecting the Control/Q-Days may lead to erroneous interpretations and will not yield a clearer understanding of the equatorial electrodynamics. Our analysis confirms the anomalous increase in TEC at all stations on 29 Oct 2003 and suppressed TEC across anomaly crest latitudes during 30-31 Oct 2003. The sharp transition in h'F is noticed during the progressive period of the storm, though it was relatively lower at the equator. The respective foF2 remained subordinate at Trivandrum. However, we did not notice such foF2 changes at Delhi. Observations at various latitudes confirm the maximum positive deviation of TEC at mid-latitude POL2 (140 %), followed by the low latitude Jodhpur (108 %), and the rest of the stations showing relatively lower enhancements with deviations ranging between 60-90 %. However, at Ahmedabad, the lowest divergence from the mean CQ-Days, attribute the typical quiet day formation of crest at this latitude. Although the results are well agreeing with earlier reports, miniature differences is noticeable due to our way of choosing the best reference days in the analysis.

  7. High-Latitude Ionospheric Dynamics During Conditions of Northward IMF

    NASA Technical Reports Server (NTRS)

    Sharber, J. R.

    1996-01-01

    In order to better understand the physical processes operating during conditions of northward interplanetary magnetic field (IMF), in situ measurements from the Dynamics Explorer-2 (low altitude) polar satellite and simultaneous observations from the auroral imager on the Dynamics Explorer-1 (high altitude) satellite were used to investigate the relationships between optical emissions, particle precipitation, and convective flows in the high-latitude ionosphere. Field aligned current and convective flow patterns during IMF north include polar cap arcs, the theta aurora or transpolar arc, and the 'horse-collar' aurora. The initial part of the study concentrated on the electrodynamics of auroral features in the horse-collar aurora, a contracted but thickened emission region in which the dawn and dusk portions can spread to very high latitudes, while the latter part focused on the evolution of one type of IMF north auroral pattern to another, specifically the quiet-time horse-collar pattern to a theta aurora.

  8. GPS derived ionospheric TEC response to geomagnetic storm on 24 August 2005 at Indian low latitude stations

    NASA Astrophysics Data System (ADS)

    Kumar, Sanjay; Singh, A. K.

    2011-02-01

    Results pertaining to the response of the low latitude ionosphere to a major geomagnetic storm that occurred on 24 August 2005 are presented. The dual frequency GPS data have been analyzed to retrieve vertical total electron content at two Indian low latitude stations (IGS stations) Hyderabad (Geographic latitude 17°20‧N, Geographic longitude 78°30‧E, Geomagnetic latitude 8.65°N) and Bangalore (Geographic latitude 12°58‧N, Geographic longitude 77°33‧E, Geomagnetic latitude 4.58°N). These results show variation of GPS derived total electron content (TEC) due to geomagnetic storm effect, local low latitude electrodynamics response to penetration of high latitude convection electric field and effect of modified fountain effect on GPS-TEC in low latitude zone.

  9. Effects of magnetospheric electric fields and neutral winds on the low-middle latitude ionosphere during the March 20-21, 1990, Storm

    SciTech Connect

    Buonsanto, M.J.; Foster, J.C.

    1993-11-01

    During the geomagnetic storm of March 20-21, 1990, substorm activity is clearly evident in magnetometer data collected during the night at the middle- and low-latitude stations Fredericksburg (38.2{degrees}N, 282.6{degrees}E) and San Juan (18.1{degrees}N, 293.8{degrees}E). At the same time, incoherent scatter radars at Millstone Hill (42.6{degrees}N, 288.5{degrees}E) and Arecibo (18.3{degrees}N, 293.25{degrees}E) observed ionospheric storm effects, which included the penetration of magnetospheric electric fields and disturbance neutral winds to the latitude of Arecibo. The eastward electric fields associated with the substorm disturbances result in increases in the F2 peak height (hmF2) at Arecibo. Decreases in hmF2 follow as a result of increased downward diffusion and/or the effects of an ion drag induced poleward wind. During the intervals between the electric field penetration events, equatorward surges in the neutral wind result in westward electric fields by the disturbance dynamo mechanism. At these times the horizontal ionization drifts are not as strong as the neutral winds, apparently because of a partial shorting out of the dynamo electric fields as a result of some E region conductivity. The anticorrelation between the components of ion drift parallel (V{sub {parallel}}) and perpendicular to the magnetic field in the northward direction (V{sub {perpendicular}}N) results in approximately horizontal (constant altitude) ion drift motion throughout the interval. Calculations of spatial gradients in the electron density and in the components of the ion velocity are carried out using the multi-directional incoherent scatter observations at Arecibo. The results show that the variations in electron density during the disturbed interval follow closely the motion term in the F2 region continuity equation, with both advection of spatial gradients and divergence of the ion flow important at times. 28 refs., 8 figs.

  10. Impact of Solar Proton Events on High Latitude Ionospheric Conditions

    NASA Astrophysics Data System (ADS)

    Aslam, A. M.; Gwal, Ashok Kumar; Mansoori, Azad Ahmad

    2016-07-01

    We investigate the ionospheric response to the solar protons which are accelerated to different energies (MeV-GeV) and thought to be originated at the solar atmosphere during the various energetic phenomena knows as solar transients viz. Solar Flares, Coronal Mass Ejections (CMEs). These transients are believed to be a manifestation of same energy release processes from a highly complex condition in the magnetic field configuration on the solar surface. We have taken six solar proton events (SPE) of solar cycle 23rd for analysis in the various energy bands of the protons. In order to find the ionospheric responses to these incoming solar protons ionospheric total electron content (TEC) is taken as the characteristic parameter. We have taken the data observed by GOES satellites which provides the data for different energy channels (0.8-4 MeV, 4-9 MeV, 9-15 MeV, 15-40 MeV, 40-80 MeV, 80-165 MeV, and 165-500 MeV). The enhancement in peak TEC (∆TEC) was then obtained for the high latitude station Davis (Lat-68.35, Lon 77.58). To find the association of this enhancement with proton flux characteristics we derived the correspondence between spectral indices and ∆TEC. We obtained a strong correlation (0.84) to exist between the spectral indices and ∆TEC.

  11. Simultaneous observations of ionospheric irregularities in the African low-latitude region

    NASA Astrophysics Data System (ADS)

    Ngwira, Chigomezyo M.; Seemala, Gopi K.; Bosco Habarulema, John

    2013-05-01

    Ionospheric storms represent large global disturbances of the ionospheric F-region electron density in response to geomagnetic storms. This study investigates the ionospheric response during a minor geomagnetic storm that occurred on 13-15 September 2004. In particular, we use total electron content (TEC) measurements (rate of TEC change, ROT) to examine the presence of ionospheric irregularities over four low-latitude stations in the African sector, a region that has been less studied. Ionospheric irregularities are known to cause fading and phase fluctuation of L-band radio navigation signals such as those used by the Global Navigation Satellite Systems (GNSS), and are a common feature in the equatorial and low-latitude ionosphere. In the present study, the storm began with a sudden commencement at approximately 20:00 UT on 13 September, while the peak of the main phase occurred on 14 September with an SYM-H index value around -59 nT. On 13 September, the storm did not appear to hinder the development of irregularities as they were observed over all the stations. In contrast, irregularities were rarely observed at two of the 4 stations under study and were absent over the other two stations on 14 September. The DSMP F15 satellite post-sunset flight over the African region observed deep density depletions on 13 September that can be associated with the presence of ionospheric plasma bubble irregularities. Furthermore, an analysis of ΔH (horizontal geomagnetic component corrected for ring current effects) shows that there was a strong positive ΔH perturbation observed in the post-sunset hours on 13 September, which suggests the presence of an eastward penetration electric field, while a negative perturbation of ΔH, which is associated with the equatorial counter-electrojet, was observed on 14 September.

  12. Ionospheric signatures of cusp latitude Pc 3 pulsations

    NASA Technical Reports Server (NTRS)

    Engebretson, M. J.; Anderson, B. J.; Cahill, L. J., Jr.; Arnoldy, R. L.; Rosenberg, T. J.

    1990-01-01

    Search coil magnetometer, riometer, photometer, and ELF-VLF receiver data obtained at South Pole Station and McMurdo, Antarctica during selected days in March and April 1986 are compared. Narrow-band magnetic pulsations in the Pc 3 period range are observed simultaneously at both stations in the dayside sector during times of low IMF cone angle, but are considerably stronger at South Pole, which is located at a latitude near the nominal foot point of the dayside cusp/cleft region. Pulsations in auroral light at 427.8 nm wavelength are often observed with magnetic pulsations at South Pole, but such optical pulsations are not observed at McMurdo. The observations suggest that precipitating magnetosheathlike electrons at nominal dayside cleft latitudes are at times modulated with frequencies similar to those of upstream waves. These particles may play an important role, via modification of ionospheric currents and conductivities, in the transmission of upstream wave signals into the magnetosphere and in the generation of dayside high-latitude Pc 3 pulsations.

  13. Importance of E-F Region Coupling on Low and Mid-Latitude Ionospheric Irregularities

    NASA Astrophysics Data System (ADS)

    Yokoyama, T.

    2014-12-01

    It is well known that ionospheric conductivity has a strong anisotropy so that even a relatively small-scale electrostatic polarization electric field can be easily mapped along geomagnetic field lines. As well as the conjugate characteristics between the northern and southern henmispheres, the electrodynamical coupling between the E and F region plays an important role in the formation of the ionospheric irregularities in low and mid-latitude: equatorial plasma bubbles (EPBs) and medium-scale traveling ionospheric disturbances (MSTIDs). Although they are characterized as the F-region plasma density irregularities, they are substantially controlled by the E-region effect such as the conductivity gradient in the evening and patchy sporadic-E layers. Recent observations and numerical studies of EPBs and MSTIDs will be presented.

  14. A mathematical model of the middle and high latitude ionosphere

    NASA Technical Reports Server (NTRS)

    Schunk, R. W.

    1988-01-01

    A time-dependent three-dimensional model of the middle and high latitude ionosphere is described. The density distributions of six ion species NO(+), O(2+), N(2+), O(+), N(+), He(+), and the electron and ion temperatures are obtained from a numerical solution of the appropriate continuity, momentum, and energy equations. The equations are solved as a function of height for an inclined magnetic field at E and F region altitudes. The three-dimensional nature of the model is obtained by following flux tubes of plasma as they convect or corotate through a moving neutral atmosphere. The model takes account of field-aligned diffusion, cross-field electrodynamic drifts, thermospheric winds, polar wind escape, energy-dependent chemical reactions, neutral composition changes, ion production due to solar EUV radiation and auroral precipitation, thermal conduction, diffusion-thermal heat flow and local heating and cooling processes. The model also takes account of the offset between the geomagnetic and geographic poles.

  15. Optimal interpolation analysis of high-latitude ionospheric Hall and Pedersen conductivities: Application to assimilative ionospheric electrodynamics reconstruction

    NASA Astrophysics Data System (ADS)

    McGranaghan, Ryan; Knipp, Delores J.; Matsuo, Tomoko; Cousins, Ellen

    2016-05-01

    We have developed a new optimal interpolation (OI) technique to estimate complete high-latitude ionospheric conductance distributions from Defense Meteorological Satellite Program particle data. The technique combines particle precipitation-based calculations of ionospheric conductances and their errors with a background model and its error covariance (modeled with empirical orthogonal functions) to infer complete distributions of the high-latitude ionospheric conductances. We demonstrate this technique for the 26 November through 2 December 2011 period and analyze a moderate geomagnetic storm event on 30 November 2011. Quantitatively and qualitatively, this new technique provides better ionospheric conductance specification than past statistical models, especially during heightened geomagnetic activity. We provide initial evidence that auroral images from the Defense Meteorological Satellite Program Special Sensor Ultraviolet Spectrographic Imager instrument can be used to further improve the OI conductance maps. Our OI conductance patterns allow assimilative mapping of ionospheric electrodynamics reconstructions driven separately by radar and satellite magnetometer observations to be in closer agreement than when other, commonly used, conductance models are applied. This work (1) supports better use of the diverse observations available for high-latitude ionospheric electrodynamics specification and (2) supports the Cousins et al. (2015b) assertion that more accurate models of the ionospheric conductance are needed to robustly assimilate ground- and space-based observations of ionospheric electrodynamics. We find that the OI conductance distributions better capture the dynamics and locations of discrete electron precipitation that modulate the coupling of the magnetosphere-ionosphere-thermosphere system.

  16. Large Scale High-Latitude Ionospheric Electrodynamic Fields and Currents

    NASA Astrophysics Data System (ADS)

    Lu, Gang

    2016-07-01

    This paper provides an overview as well as the application of the Assimilative Mapping of Ionospheric Electrodynamics (AMIE) procedure. AMIE synthesizes observations from various ground-based and space-born instruments to derive global patterns of ionospheric conductance, electric fields, ionospheric equivalent current, horizontal currents, field-aligned currents, and other related electrodynamic fields simultaneously. Examples are presented to illustrate the effects of the different data inputs on the AMIE outputs. The AMIE patterns derived from ground magnetometer data are generally similar to those derived from satellite magnetometer data. But ground magnetometer data yield a cross-polar potential drop that is about 15-45 % smaller than that derived from satellite magnetometer data. Ground magnetometers also grossly underestimate the magnetic perturbations in space when compared with the in situ satellite magnetometer data. However, when satellite magnetometer data are employed, AMIE is able to replicate the observed magnetic perturbations along the satellite tracks with a mean root-mean-square (RMS) error of 17-21 %. In addition to derive snapshots of ionospheric electrodynamic fields, the utility of AMIE can be easily expanded to obtain the average distributions of these fields along with their associated variability. Such information should be valuable to the analysis and interpretation of the Swarm observations.

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

    NASA Astrophysics Data System (ADS)

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

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

  18. Ion temperature of low-latitude and mid-latitude topside ionosphere for high solar activity

    NASA Astrophysics Data System (ADS)

    Cai, Lei; Zhang, Donghe; Hao, Yongqiang; Xiao, Zuo

    The International Reference Ionosphere (IRI) describes the day and night latitudinal variation of ion temperature at 430 km with two functions using AEROS satellite measurements. The ion temperature at this height as one of the boundary parameters is used to make the ion temperature profile represented by a Booker-function. Since the low-latitude and mid-latitude topside ionospheric ion temperature has been measured with the Ionopsheric Plasma and Elec-trodynamics Instrument (IPEI) onboard Rocsat-1 satellite at about 600 km during the high solar activity years from 2000 to 2002, a new boundary at 600 km can be set for the ion temperature modeling. The latitudinal variation of ion temperature could be approximated by Epstein family of functions for different local time sectors. Furthermore, the longitudinal and seasonal variations are also taken into account to decide the fitting parameters. Only the magnetic quiet time data (Kp <3) are used for the statistical study. The results are compared with IRI-2007 model. In addition, events when Kp >4 are also analyzed to feature the ion temperature characteristic during the magnetic disturbance time condition. Combined with the IPEI field-aligned ion flow velocities and the plasma temperatures measured by the Special Sensors-Ions, Electrons, and Scintillation (SSIES) thermal plasma analysis package on board the DMSP F13 and F15 satellites, several feasible ion heating and heat loss mechanisms are summarized to interpret the ion temperature crests and toughs for different local time sectors, seasonal and longitudinal variations.

  19. Plasma dynamics in Saturn's middle-latitude ionosphere and implications for magnetosphere-ionosphere coupling

    NASA Astrophysics Data System (ADS)

    Sakai, Shotaro; Watanabe, Shigeto

    2016-08-01

    A multifluid model is used to investigate how Saturn's magnetosphere affects ionosphere. The model includes a magnetospheric plasma temperature of 2 eV as a boundary condition. The main results are: (1) H+ ions are accelerated along magnetic field lines by ambipolar electric fields and centrifugal force, and have an upward velocity of about 10 km/s at 8000 km; (2) the ionospheric plasma temperature is 10,000 K at 5000 km, and is significantly affected by magnetospheric heat flow at high altitudes; (3) modeled electron densities agree with densities from occultation observations if the maximum neutral temperature at a latitude of 54˚ is about 900 K or if electrons are heated near an altitude of 2500 km; (4) electron heating rates from photoelectrons (≈100 K/s) can also give agreement with observed electron densities when the maximum neutral temperature is lower than 700 K (note that Cassini observations give 520 K); and (5) the ion temperature is high at altitudes above 4000 km and is almost the same as the electron temperature. The ionospheric height-integrated Pedersen conductivity, which affects the magnetospheric plasma velocity, varies with local time with values between 0.4 and 10 S. We suggest that the sub-corotating ion velocity in the inner magnetosphere depends on the local time, because the conductivity generated by dust-plasma interactions in the inner magnetosphere is almost comparable to the ionospheric conductivity. This indicates that magnetosphere-ionosphere coupling is highly important in the Saturn system.

  20. High-Latitude Ionospheric Structuring at Kilometer Scales

    NASA Astrophysics Data System (ADS)

    Bust, G. S.; Datta-Barua, S.; Su, Y.; Deshpande, K.; Hampton, D.

    2014-12-01

    Ionospheric observations in the polar and auroral zones have been made regularly with radar chains and optical imaging at larger spatio-temporal cadence. However, the observation of kilometer scale variations at sub-second cadence has not been practically realizable until recently. Quantifying the irregularities at these sizes and scales is necessary for an understanding of the dynamics leading to fine scale phenomena in the high latitude environment. We present measurements of kilometer-scale plasma variations made at the northern auroral zone using an array of specialized Global Positioning System (GPS) receivers. These 6 CASES receivers (plus 1 from ASTRA, LLC) are sited at the Poker Flat Research Range, Alaska, and have been collecting data since late 2013. The array monitors for ionospheric scintillations, fluctuations in phase and amplitude of the GPS L-band signals received due to ionospheric variations. The array spans 2 km east-west and about 1 km north-south, with a variety of intermediate baseline lengths down to about 200 m. In addition to measuring amplitude and phase scintillation with the S4 and sigma_phi indices at 100-s cadence, these receivers also record 100 Hz raw power and phase measurements from GPS baseband signal processing. These low-rate data are publicly available for download through a web portal at http://apollo.tbc.iit.edu/~spaceweather/ with high rate available upon request. A detailed case study is presented from the December 8, 2013, 0300-0400 UT time period. During this period several interesting scintillation periods were observed. We use array cross-correlation processing methods to first estimate direct ground parameters of the array including a) estimate the 2D drift velocity on the ground; b) estimate a de-correlation (or turbulent) speed; and c) parameters of correlation elliptical coordinates (axial ratio and tilt angle). We then use these results and cross-correlation measurements to derive the ground 2D spatial spectrum of

  1. Structure of High Latitude Currents in Magnetosphere-Ionosphere Models

    NASA Astrophysics Data System (ADS)

    Wiltberger, M.; Rigler, E. J.; Merkin, V.; Lyon, J. G.

    2016-07-01

    Using three resolutions of the Lyon-Fedder-Mobarry global magnetosphere-ionosphere model (LFM) and the Weimer 2005 empirical model we examine the structure of the high latitude field-aligned current patterns. Each resolution was run for the entire Whole Heliosphere Interval which contained two high speed solar wind streams and modest interplanetary magnetic field strengths. Average states of the field-aligned current (FAC) patterns for 8 interplanetary magnetic field clock angle directions are computed using data from these runs. Generally speaking the patterns obtained agree well with results obtained from the Weimer 2005 computing using the solar wind and IMF conditions that correspond to each bin. As the simulation resolution increases the currents become more intense and narrow. A machine learning analysis of the FAC patterns shows that the ratio of Region 1 (R1) to Region 2 (R2) currents decreases as the simulation resolution increases. This brings the simulation results into better agreement with observational predictions and the Weimer 2005 model results. The increase in R2 current strengths also results in the cross polar cap potential (CPCP) pattern being concentrated in higher latitudes. Current-voltage relationships between the R1 and CPCP are quite similar at the higher resolution indicating the simulation is converging on a common solution. We conclude that LFM simulations are capable of reproducing the statistical features of FAC patterns.

  2. Vertical coupling between troposphere and lower ionosphere by electric currents and fields at equatorial latitudes

    NASA Astrophysics Data System (ADS)

    Tonev, P. T.; Velinov, P. I. Y.

    2016-04-01

    Thunderstorms play significant role in the upward electrical coupling between the troposphere and lower ionosphere by quasi-static (QS) electric fields generated by quiet conditions (by slow variations of electric charges), as well as during lightning discharges when they can be strong enough to produce in the nighttime lower ionosphere sprites. Changes are caused in lower ionosphere by the QS electric fields before a sprite-producing lightning discharge which can play role in formation of the stronger sprite-driving transient QS electric fields due to lightning. These changes include electron heating, modifications of conductivity and electron density, etc. We demonstrate that such changes depend on the geomagnetic latitude determining the magnetic field lines inclination, and thus, the anisotropic conductivity. Our previous results show that the QS electric fields in the lower ionosphere above equatorial thunderstorms are much bigger and have larger horizontal extension than those generated at high and middle altitudes by otherwise same conditions. Now we estimate by modeling the electric currents and fields generated in lower ionosphere above equatorial thunderstorms of different horizontal dimensions during quiet periods and of their self-consistent effects to conductivity whose modifications can play role in formation of post-lightning sprite-producing electric fields. Specific electric currents configurations and distributions of related electric fields are estimated first by ambient conductivity. Then, these are evaluated self-consistently with conductivity modification. The electric currents are re-oriented above ~85 km and flow in a narrow horizontal layer where they dense. Respectively, the electric fields and their effect on conductivity have much larger horizontal scale than at middle latitudes (few hundred of kilometers). Horizontally large sources, such as mesoscale convective structures, cause enhancements of electric fields and their effects. These

  3. Hemispheric asymmetries in high-latitude ionospheric convection and upper atmosphere neutral wind circulation

    NASA Astrophysics Data System (ADS)

    Foerster, M.; Cnossen, I.; Haaland, S.

    2015-12-01

    Recent observations have shown that the ionospheric/thermospheric response to solar wind and IMF dependent processes in the magnetosphere can be very dissimilar in the Northern and Southern polar regions. We present statistical studies of both the high-latitude ionospheric convection and the upper thermospheric circulation patterns obtained over almost a full solar cycle during the first decade of this century by measurements of the electron drift instrument (EDI) on board the Cluster satellites and by the accelerometer on board the CHAMP spacecraft, respectively. The asymmetries are attributed to the non-dipolar portions of the Earth's magnetic field that constitute hemispheric differences in magnetic flux densities, different offsets of the invariant geomagnetic poles, and generally in different field configurations of both hemispheres. Seasonal and solar cycle effects of the asymmetries are considered and first trials to explain the effects by numerical modeling are presented.

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

    NASA Astrophysics Data System (ADS)

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

    2010-12-01

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

  5. Simulation of the low latitude ionosphere response to disturbed winds and electric fields: Brazilian region

    NASA Astrophysics Data System (ADS)

    Batista, Inez S.; Souza, Jonas; Bailey, Graham; Bravo, Manuel

    2016-07-01

    Modeling the ionosphere during disturbed periods is one of the most challenging tasks due to the complexity of the phenomena that affect the electric fields and the thermosphere environment as whole. It is well known that depending on the direction of the interplanetary magnetic field disturbance electric fields (undershielding or overshielding) can penetrate from high to low latitudes causing significant disturbances in the electron density distribution and in the equatorial ionization anomaly (EIA) development. Besides that, the large amount of energy deposited in the polar region during disturbed periods will be responsible for the generation of disturbed winds that will flow towards the equator where they produce a disturbance dynamo which also affects the EIA density distribution. The TIDs and TADs are also sources of disturbances that propagate at high velocity reaching the equator 2-3 hours after the beginning of the magnetic storm. In this work we use the Sheffield University Plasmasphere-Ionosphere Model at INPE (SUPIM-INPE), to simulate the drastic effects that were observed at the low latitude ionosphere in the Brazilian region during a very intense magnetic storm event. A few models are tested for the disturbed electric field and wind. The simulation results showed that the observations are better explained when considering a traveling waveform disturbance propagating from north to south at a velocity equal to 200 m/s.

  6. Long term changes in the ionosphere over Indian low latitudes: Impact of greenhouse gases

    NASA Astrophysics Data System (ADS)

    Sharma, Som; Chandra, H.; Beig, G.

    2015-06-01

    Increased concentration of greenhouse gases due to anthropogenic activities warm the troposphere and have a cooling effect in the middle and upper atmosphere. Ionospheric densities and heights are affected due to cooling. Carbon dioxide is one of the most dominant gases for the cause of long term ionospheric trends along with other radiatively active greenhouse gases. Regular ionospheric soundings are made over Ahmedabad (23.1°N, 72.7°E), since 1953. Long term changes in the ionosphere as a consequence of the cooling of the mesosphere and thermosphere due to the increased concentration of greenhouse gases have been studied. Ionospheric observations over Ahmedabad, a low latitude station in the anomaly crest region, for the years 1955-2003 are examined to study the long term changes in the critical frequencies of the various ionospheric layers and the height of the maximum ionization as characterized by hPF2. A decrease in foF2 (1.9 MHz for midday, 1.4 MHz for midnight) and hPF2 (18 km for midday, 17 km for midnight) during about five decades are noted. An increase is noted in foF1 (0.4 MHz). The foF2 data are also examined over an equatorial station Kodaikanal (10.2°N, 77.5°E), situated near the magnetic equator for the years 1960-1995 and a decrease of 0.5 MHz for midday and 0.7 MHz for midnight are noted in ~35 years.

  7. Climatological study of ionospheric irregularities over the European mid-latitude sector with GPS

    NASA Astrophysics Data System (ADS)

    Wautelet, Gilles; Warnant, René

    2014-03-01

    High-frequency variability of the ionosphere, or irregularities, constitutes the main threat for real-time precise positioning techniques based on Global Navigation Satellite Systems (GNSS) measurements. Indeed, during periods of enhanced ionospheric variability, GNSS users in the field—who cannot verify the integrity of their measurements—will experience positioning errors that can reach several decimeters, while the nominal accuracy of the technique is cm-level. In the frame of this paper, a climatological analysis of irregularities over the European mid-latitude region is presented. Based on a 10 years GPS dataset over Belgium, the work analyzes the occurrence rate (as a function of the solar cycle, season and local time) as well as the amplitude of ionospheric irregularities observed at a single GPS station. The study covers irregularities either due to space weather events (solar origin) or of terrestrial origin. If space weather irregularities are responsible for the largest effects in terms of ionospheric error, their occurrence rate highly depends on solar activity. Indeed, the occurrence rate of ionospheric irregularities is about 9 % during solar maximum, whereas it drops to about 0 % during medium or low solar activity periods. Medium-scale ionospheric disturbances (MSTIDs) occurring during daytime in autumn/winter are the most recurrent pattern of the time series, with yearly proportions slightly varying with the solar cycle and an amplitude of about 10 % of the TEC background. Another recurrent irregularity type, though less frequent than MSTIDs, is the noise-like variability in TEC observed during summer nighttime, under quiet geomagnetic conditions. These summer nighttime irregularities exhibit amplitudes ranging between 8 and 15 % of the TEC background.

  8. Statistical features of the high-latitude ionospheric convection structure associated with enhanced solar wind fluctuations

    NASA Astrophysics Data System (ADS)

    Kim, H.; Lyons, L. R.; Ruohoniemi, J. M.; Frissell, N. A.

    2012-12-01

    While the IMF and solar wind dynamic pressure almost certainly play larger roles under most conditions, evidence has been recently found that Ultra Low Frequency (ULF) wave power in the solar wind has an additional substantial effect on the strength of convection within the polar caps, and on the nightside within both the aurora ionosphere and the plasma sheet. An initial study shows that the convection flows under enhanced solar wind fluctuations often appear to be more structured, with localized strong vortical features, than the convection under steady solar wind conditions. In this work, we statistically examine characteristic features of the ionospheric convection structure in terms of vortex patterns and how they are related to the convection enhancements during periods of enhanced solar wind fluctuations. Specifically, we examine whether enhanced solar wind ULF power will drive localized turbulence within enhanced convection cells while it increases convection strength at the same time. The results of this study will provide evidence for how solar wind ULF fluctuations can contribute to the solar wind energy transfer to the magnetosphere-ionosphere system. To determine the features of 2-D convection structure, we analyze the large-scale global convection maps derived from the SuperDARN observations with extensive radar echo coverage over a large portion of the high latitude ionosphere. Wind and ACE data are used for examination of solar wind and IMF conditions.

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

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

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

  10. Anomalous ionospheric variations prior to major earthquakes during 2015 affecting Indian low latitude station Delhi

    NASA Astrophysics Data System (ADS)

    Gupta, Sumedha; Upadhayaya, Arun Kumar

    2016-07-01

    We have analyzed five major earthquakes (M>6) that occurred during the year 2015, affecting Indian ionosphere, using F2 layer critical frequency (foF2) data obtained using Digisonde from a low latitude station, Delhi (28.6°N, 77.2°E, 42.4°N dip). Normal day-to-day variability occurring in ionosphere is segregated by calculating F2 layer critical frequency variations (ΔfoF2) from the normal quiet time behavior apart from calculating interquartile range. We find that ionospheric F2 region across Delhi by and large shows some significant perturbations 3-4 days prior to these earthquake events. These observed perturbations indicate towards seismo-ionospheric coupling as solar and geomagnetic indices were normally quiet and stable during the period of these events. Further, it was also observed that the effect of earthquake was prominently observed even outside the earthquake preparation zone, calculated using Dobrovolsky et al. [1979].

  11. Response of the topside and bottomside ionosphere at low and middle latitudes to the October 2003 superstorms

    NASA Astrophysics Data System (ADS)

    Lei, Jiuhou; Zhu, Qingyu; Wang, Wenbin; Burns, Alan G.; Zhao, Biqiang; Luan, Xiaoli; Zhong, Jiahao; Dou, Xiankang

    2015-08-01

    Ionospheric observations from the ground-based GPS receiver network, CHAMP and GRACE satellites and ionosondes were used to examine topside and bottomside ionospheric variations at low and middle latitudes over the Pacific and American sectors during the October 2003 superstorms. The latitudinal variation and the storm time response of the ground-based GPS total electron content (TEC) were generally consistent with those of the CHAMP and GRACE up-looking TEC. The TECs at heights below the satellite altitudes during the main phases were comparable to, or even less than, the quiet time values. However, the storm time CHAMP and GRACE up-looking TECs showed profound increases at low and middle latitudes. The ground-based TEC and ionosonde data were also combined to study the TEC variations below and above the F2 peak height (hmF2). The topside TECs above hmF2 at low and middle latitudes showed significant increases during storm time; however, the bottomside TEC below hmF2 did not show so obvious changes. Consequently, the bottomside ionosphere made only a minor contribution to the ionospheric positive phase seen in the total TEC at low and middle latitudes. Moreover, at middle latitudes F2 peak electron densities during storm time did not have the obvious enhancements that were seen in both the ground-based and topside TECs, although they were accompanied by increases of hmF2. Therefore, storm time TEC changes are not necessarily related to changes in ionospheric peak densities. Our results suggest that TEC increases at low and middle latitudes are also associated with effective plasma scale height variations during storms.

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

    NASA Astrophysics Data System (ADS)

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

    2008-12-01

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

  13. GPS derived spatial ionospheric total electron content variation over South-Indian latitudes during intense geomagnetic storms

    NASA Astrophysics Data System (ADS)

    Panda, Sampad K.; Gedam, Shirishkumar S.

    2012-10-01

    The geomagnetic storms are turbulence in geomagnetic field when interplanetary magnetic field driven by solar wind move southward and continue for extended period of time. Although these occur less frequently, but may energize ionospheric electrons and particles adversely affecting ground- and space-based electronic systems. Ionosphere at higher latitude is more prone to geomagnetic storms. Over lower latitude region like Indian sub-continent, the effect is less prominent but still can exhibit many distinctive effects like scintillations, equatorial ionization anomaly, fountain effect and equatorial electrojets. The increased numbers of free electrons in ionosphere introduce delays in global positioning system (GPS) satellite signals resulting in errors during GPS positioning. In a dual frequency GPS receiver, the line integral of free electron density along the pathway of signal through the ionosphere (i.e., Total Electron Content, TEC) can be measured. In this present paper, GPS observation data of three low latitude GPS stations in India located at Bangalore, Hyderabad and Mumbai during four severe geomagnetic storms from 2003-2005, are processed to measure ionospheric TEC during the events. The measured TEC at each of the station is compared with quietest days of the months to investigate its abnormal changes in responses to severe geomagnetic storms. The consequences of TEC variation is analyzed and correlated with interplanetary magnetic field (IMF-Bz), geomagnetic Kp and Dst-indices to study its behavioral changes during the storms. Eventually the aim of the study is to estimate the influence of ionospheric condition on GPS positioning to devise suitable method for accurate position measurements in the low latitude Indian region.

  14. Ionospheric scintillation modeling for high- and mid-latitude using B-spline technique

    NASA Astrophysics Data System (ADS)

    Priyadarshi, S.

    2015-09-01

    Ionospheric scintillation is a significant component of space-weather studies and serves as an estimate for the level of perturbation in the satellite radio wave signal caused due to small-scale ionospheric irregularities. B-spline functions are used on the GPS ground based data collected during the year 2007-2012 for modeling high- and mid-latitude ionospheric scintillation. Proposed model is for Hornsund, Svalbard and Warsaw, Poland. The input data used in this model were recorded by GSV 4004b receivers. For validation, results of this model are compared with the observation and other existing models. Physical behavior of the ionospheric scintillation during different seasons and geomagnetic conditions are discussed well. Model is found in good coherence with the ionospheric scintillation theory as well as to the accepted scintillation mechanism for high- and mid-latitude.

  15. Comparison of high-latitude and mid-latitude ionospheric electric fields

    NASA Technical Reports Server (NTRS)

    Carpenter, L. A.; Kirchhoff, V. W. J. H.

    1975-01-01

    Simultaneous measurements of the F region electric field by the incoherent scatter technique have been made at Chatanika, Alaska (65.1 deg N, 147.5 deg W), and Millstone Hill, Massachusetts (42.6 deg N, 71.5 deg W), on July 18-19 and Aug. 7-8, 1973. Good correlation was observed in the time variation of the perpendicular electric field at the two stations. Magnetic conditions for these days were relatively quiet with some variations evident from the high-latitude magnetograms and the Chatanika radar, but no distinct effect appeared on the mid-latitude magnetograms. Since magnetospheric electric fields are thought to be the source of high-latitude electric fields such as those observed at Chatanika, the good correlation in the perpendicular electric field for the two stations indicates that the magnetospheric originated electric fields have an appreciable effect down to at least L equals 3.2.

  16. TEC disturbances during major Sudden Stratospheric Warmings in the mid-latitude ionosphere.

    NASA Astrophysics Data System (ADS)

    Polyakova, Anna; Voeykov, Sergey; Chernigovskaya, Marina; Perevalova, Natalia

    Using total electron content (TEC) global ionospheric maps, dual-frequency GPS receivers TEC data and MLS (Microwave Limb Sounder, EOS Aura) atmospheric temperature data the ionospheric disturbances during the strong sudden stratospheric warmings (SSWs) of 2008/2009 and 2012/2013 winters are investigated in Russia's Asia region. It is established that during the SSW maximum the midday TEC decrease and the night/morning TEC increase compared to quiet days are observed in the mid-latitude ionosphere. As a result it caused the decrease of the diurnal TEC variations amplitude of about two times in comparison with the undisturbed level. The analysis of TEC deviations from the background level during the SSWs has shown that deviations dynamics vary depending on the observation point position. Negative deviations of TEC are registered in the ionosphere above the region of maximum stratosphere heating (the region of the stratospheric circulation change) as well as above the anticyclone. On the contrary, TEC values increase compared to the quiet day's values above the stratosphere cyclone. It is shown that during maximum phase of a warming, and within several days after it the amplification of wave TEC variations intensity with periods of up to 60 min is registered in ionosphere. The indicated effects may be attributed to the vertical transfer of molecular gas from a stratospheric heating region to the thermosphere as well as to the increase in activity of planetary and gravity waves which is usually observed during strong SSWs. The study is supported by the RF President Grant of Public Support for RF Leading Scientific Schools (NSh-2942.2014.5), the RF President Grant No. MK-3771.2012.5 and RFBR Grant No. 12-05-00865_а.

  17. Superposed epoch analysis of the ionospheric convection evolution during substorms: onset latitude dependence

    NASA Astrophysics Data System (ADS)

    Grocott, A.; Wild, J. A.; Milan, S. E.; Yeoman, T. K.

    2008-12-01

    Using data from the Super Dual Auroral Radar Network (SuperDARN) we investigate the ionospheric convection response to magnetospheric substorms. Substorms were identified using the Far Ultraviolet (FUV) instrument on board the Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) spacecraft, and were then grouped according to the magnetic latitude of their onset. A superposed epoch analysis of the ionospheric convection patterns for each latitude group was then performed using radar data for the interval 60 minutes before onset to 90 minutes after. It is found that lower latitude onset substorms are associated with generally more enhanced convection than the higher latitude substorms, although they suffer from the most significant localised suppression of the flow in the midnight sector during the expansion phase. On the other hand, the higher-latitude events are associated with a significant and rapid increase in the nightside convection following substorm onset. These results suggest differences in the electrodynamics associated with substorms occurring at different latitudes.

  18. HF Doppler oscillations in the low-latitude ionosphere coherent with equatorial long-period geomagnetic field oscillations

    NASA Astrophysics Data System (ADS)

    Motoba, Tetsuo; Kikuchi, Takashi; Shibata, Takashi F.; Yumoto, Kiyohumi

    2004-06-01

    We present observations of HF Doppler (HFD) oscillations in the low-latitude ionosphere seen during global long-period (5˜15 min) geomagnetic field oscillation events, which occurred on 21 April 1993 and on 28 February 1998. In both events, daytime polar-equatorial magnetometer data on the ground indicated that the long-period geomagnetic field oscillations at the daytime dip equator were not only considerably enhanced but also highly correlated with those at afternoon high latitudes with no apparent time shift (within 10 s). This earlier finding [, 2002, 2003] strongly suggested that the long-period geomagnetic field oscillations at the daytime dip equator were produced by an extension of polar-originating ionospheric current system associated with high-latitude geomagnetic field oscillations. In the first event on 21 April 1993, the HFD measurement at the postmidnight low latitude detected frequency oscillations coherent with the geomagnetic field oscillations at the afternoon dip equator in the Pc5 range (˜6 min). However, there was no magnetic field change at low-latitude magnetometer stations adjacent to the reception site of the HFD. Therefore it is reasonable to consider that the HFD oscillations are not effects of directly incoming hydromagnetic waves on the nighttime low-latitude ionosphere. In the second event on 28 February 1998, both the low-latitude HFD and equatorial magnetometer measurements were located in the postsunrise terminator. Similar to the first event, HFD oscillations were well correlated with long-period geomagnetic field oscillations (˜14 min) at the daytime equator, although both variations were in antiphase. In the same local time sector the corresponding low-latitude magnetic field variations were predominant in the D component rather than the H component, suggesting that the meridional ionospheric currents originating in the polar region make a major contribution for the low-latitude magnetic field oscillations. The two case

  19. Middle- and low-latitude ionosphere response to 2015 St. Patrick's Day geomagnetic storm

    NASA Astrophysics Data System (ADS)

    Nava, B.; Rodríguez-Zuluaga, J.; Alazo-Cuartas, K.; Kashcheyev, A.; Migoya-Orué, Y.; Radicella, S. M.; Amory-Mazaudier, C.; Fleury, R.

    2016-04-01

    This paper presents a study of the St Patrick's Day storm of 2015, with its ionospheric response at middle and low latitudes. The effects of the storm in each longitudinal sector (Asian, African, American, and Pacific) are characterized using global and regional electron content. At the beginning of the storm, one or two ionospheric positive storm effects are observed depending on the longitudinal zones. After the main phase of the storm, a strong decrease in ionization is observed at all longitudes, lasting several days. The American region exhibits the most remarkable increase in vertical total electron content (vTEC), while in the Asian sector, the largest decrease in vTEC is observed. At low latitudes, using spectral analysis, we were able to separate the effects of the prompt penetration of the magnetospheric convection electric field (PPEF) and of the disturbance dynamo electric field (DDEF) on the basis of ground magnetic data. Concerning the PPEF, Earth's magnetic field oscillations occur simultaneously in the Asian, African, and American sectors, during southward magnetization of the Bz component of the interplanetary magnetic field. Concerning the DDEF, diurnal magnetic oscillations in the horizontal component H of the Earth's magnetic field exhibit a behavior that is opposed to the regular one. These diurnal oscillations are recognized to last several days in all longitudinal sectors. The observational data obtained by all sensors used in the present paper can be interpreted on the basis of existing theoretical models.

  20. Mid-Latitude Ionospheric Disturbances Due to Geomagnetic Storms at ISS Altitudes

    NASA Technical Reports Server (NTRS)

    Minow, Joseph I.; Willis, Emily M.; Neergaard Parker, Linda

    2014-01-01

    Spacecraft charging of the International Space Station (ISS) is dominated by interaction of the US high voltage solar arrays with the F2-region ionosphere plasma environment. ISS solar array charging is enhanced in a high electron density environment due to the increased thermal electron currents to the edges of the solar cells. High electron temperature environments suppress charging due to formation of barrier potentials on the charged solar cell cover glass that restrict the charging currents to the cell edge [Mandell et al., 2003]. Environments responsible for strong solar array charging are therefore characterized by high electron densities and low electron temperatures. In support of the ISS space environmental effects engineering community, we are working to understand a number of features of solar array charging and to determine how well future charging behavior can be predicted from in-situ plasma density and temperature measurements. One aspect of this work is a need to characterize the magnitude of electron density and temperature variations that occur at ISS orbital altitudes (approximately 400 km) over time scales of days, the latitudes over which significant variations occur, and the time periods over which the disturbances persist once they start. This presentation provides examples of mid-latitude electron density and temperature disturbances at altitudes relevant to ISS using data sets and tools developed for our ISS plasma environment study. "Mid-latitude" is defined as the extra-tropical region between approx. 30 degrees to approx. 60 degrees magnetic latitude sampled by ISS over its 51.6 degree inclination orbit. We focus on geomagnetic storm periods because storms are well known drivers for disturbances in the ionospheric plasma environment.

  1. Fractal and wavelet analysis evaluation of the mid latitude ionospheric disturbances associated with major geomagnetic storms

    NASA Astrophysics Data System (ADS)

    López-Montes, Rebeca; Pérez-Enríquez, Román; Araujo-Pradere, Eduardo A.; López Cruz-Abeyro, Jose Antonio

    2015-01-01

    Variations of the total electron content (TEC) of the ionosphere are mainly associated with major geomagnetic storms occurring with the arrival of coronal mass ejections (CMEs) to the Earth environment. The purpose of this paper is to show results of the analysis we made of the impact of all major geomagnetic storms (Dst < - 200 nT) on the ionosphere at mid latitudes, which have occurred since 2000. The analysis consists in the calculation of TEC of the ionosphere using data from several Mexican GPS stations, with the purpose of quantifying the impact into the ionosphere to these latitudes, through the variations in amplitude, Hurst index, that is roughness, and wavelet transform of the time series of TEC. Indeed, during the geomagnetic storms of April 7, 2000, July 16, 2000, October 30, 2003, November 20, 2003 and November 8, 2004, major ionospheric disturbances at mid latitudes took place with changes in amplitude of TEC going from 3.29 to 8.82 sigmas. These ionospheric disturbances were probably associated with prompt penetration electric fields (PPEFs) and equatorward neutral winds. On the other hand, during four geomagnetic storms (August 12, 2000, March 31, 2001, April 11, 2001 and May 15, 2005), there were negative ionospheric storms that pushed the TEC to significantly lower values. This has been interpreted as the presence of regions in which the neutral composition is changed. Also, in some cases during the disturbed days, the Hurst values were smaller than during the undisturbed days, i.e. during these geomagnetic storms, the roughness of the time series of TEC increased. The wavelet analysis showed a strong influence of the diurnal variation on TEC values (periodicities of 12 h), and periodicities characteristics of ionospheric disturbances of 1-8 h. It is found that large geomagnetic storms produce significant ionospheric disturbances at mid latitudes, as shown by the wavelet analysis and, in some cases, changes in the roughness of the time series of

  2. Theoretically Modeling the Ionospheric Response at Low Latitudes to the Great Storms in October, 2003

    NASA Astrophysics Data System (ADS)

    Anderson, D. N.; Anghel, A.; Eccles, V.; Valladares, C.; Chau, J.; Veliz, O.

    2004-05-01

    In the low latitude, ionospheric F region, the primary transport mechanism that determines the electron and ion density distributions is the magnitude of the daytime, upward ExB drift velocity. During the geomagnetic storms on Oct. 29 and 30, 2003, we have inferred these upward ExB drift velocities from ground-based magnetometer observations at Jicamarca and Piura, Peru as a function of local time (0700 - 1700LT). On both days these ExB drifts exceeded 80 m/sec which is about four times greater than the normal, quiet time value of 20 m/sec. We study the ionospheric response in the Peruvian longitude sector to these large upward drifts by theoretically-calculating electron and ion densities as a function of altitude, latitude and local time using the time-dependent Low-Latitude Ionospheric Sector model (LLIONS). This is a single sector ionosphere model capable of incorporating data-determined drivers. Initial results indicate that the large, upward ExB drift velocities on Oct. 29 produce equatorial anomaly crests in ionization at +/- 22° dip latitude rather than the usual +/- 16° dip latitude. We compare the theoretically-calculated results with a variety of ground-based and satellite observations for Oct. 28, 29, 30 and 31 and discuss the implications of these comparisons as they relate to the capabilities of current theoretical models and our ability to infer ionospheric drivers such as ExB drifts.

  3. Ionospheric TEC variations at mid-latitudes obsereved using SBAS L1/L5 signals.

    NASA Astrophysics Data System (ADS)

    Padokhin, A. M.; Kunitsyn, V.; Kurbatov, G.; Yasyukevich, Y.

    2014-12-01

    With the development of Satellite based augmentation systems (SBAS) the dual frequency L1/L5 observations from a number of geostationary satellites are now available. It provides the possibility to retrieve ionospheric total electron content (TEC) from these observations using the same approach as for dual frequency GPS/GLONASS observations. In this work we study L1/L5 signals of Indian GAGAN geostationary satellites observed with geodetic GNSS receivers at several stations at mid-latitudes and estimate corresponding geostationary TEC and errors of such estimations. TEC RMS was found to reach up to 1.5 TECU with typical values of 0.25-0.5 TECU which is several times greater than for common GPS/GLONASS observations. TEC RMS also manifests UT-dynamics which is specific for the chosen geostationary satellite and not relevant to the receiver site and signal paths. SBAS TEC was found to be in good agreement with the data of nearest ionosondes taking into account low elevation angles of SBAS satellites already at mid-latitudes and spatial gradients of electron density along the ray paths. We also present the wavelet analysis of geostationary TEC, providing typical periods of observed variations at different time scales (from tens of minutes to tens of days) and discuss the capabilities of SBAS TEC observations in connection with ionospheric effects of solar flares.

  4. The structure of mid- and high-latitude ionosphere during September 1999 storm event obtained from GPS observations

    NASA Astrophysics Data System (ADS)

    Shagimuratov, I. I.; Baran, L. W.; Wielgosz, P.; Yakimova, G. A.

    2002-05-01

    TEC data, obtained from over 60 GPS stations, were used to study the ionospheric effects of the 12 16 September 1999 magnetic storm over Europe. The spatial and temporal changes of the ionosphere were analysed as a time series of TEC maps, which present 15 min averages of TEC. The data set consisting of GPS observations, collected by a dense network of European stations, with sampling rate of 30 s, enable the creation of TEC maps with high spatial and temporal resolution. The storm included the positive as well as the negative phase. The positive phase took place during the first storm day of 12 September 1999. The short-lived daytime TEC enhancement was observed at all latitudes. The maximal enhancement reached a factor of 1.3 1.5. On the second and third days, the negative phase of the storm developed. The TEC decrease was registered regardless of time of the day. The TEC depression exceeded 70% relative to quiet days. On the following days (15 and 16 September), a significant daytime enhancement of TEC was observed once again. The complex occurrence of the ionospheric storm was probably related to the features of development of the magnetic storm. We found out that during the storm the large and medium-scale irregularities developed in the high-latitude ionosphere. The multi-stations technique, employed to create TEC maps, was particularly successful while studying the mid-latitude ionospheric trough. We found out that the essential changes of TEC during the storm, which were registered at the auroral and sub-auroral ionosphere, were connected with the effect of the trough and its dynamics, which depends on geomagnetic activity.

  5. Longitudinal Variations of Low-Latitude Gravity Waves and Their Impacts on the Ionosphere

    NASA Astrophysics Data System (ADS)

    Cullens, C. Y.; England, S.; Immel, T. J.

    2014-12-01

    The lower atmospheric forcing has important roles in the ionospheric variability. However, influences of lower atmospheric gravity waves on the ionospheric variability are still not clear due to the simplified gravity wave parameterizations and the limited knowledge of gravity wave distributions. In this study, we aim to study the longitudinal variations of gravity waves and their impacts of longitudinal variations of low-latitude gravity waves on the ionospheric variability. Our SABER results show that longitudinal variations of gravity waves at the lower boundary of TIME-GCM are the largest in June-August and January-February. We have implemented these low-latitude gravity wave variations from SABER instrument into TIME-GCM model. TIME-GCM simulation results of ionospheric responses to longitudinal variations of gravity waves and physical mechanisms will be discussed.

  6. The high latitudes in the International Reference Ionosphere; Meeting C4 of Commission C, COSPAR Scientific Assembly, 30th, Hamburg, Germany, July 11-21, 1994

    NASA Technical Reports Server (NTRS)

    Rawer, K.; Bilitza, D.; Singer, W.

    1995-01-01

    An international conference on high-latitude ionospheric modeling produced 27 papers in the areas of ionospheric mapping, electron density and distribution, ion density and distribution, ionospheric storems, ionospheric composition, and ionospheric sounding techniques. Upgrades to the International Reference Ionosphere (IRI) model were proposed in several papers.

  7. Characterization of different magnetospheric and ionospheric contributions at mid-latitude magnetic observatories

    NASA Astrophysics Data System (ADS)

    Castillo, Yvelice; Pais, Maria Alexandra; Fernandes, João; Ribeiro, Paulo; Morozova, Anna; Pinheiro, Fernando J. G.

    2016-04-01

    The main goal of space weather (SW) research is to produce reliable forecasts and nowcasts of the space environment and to evaluate the risks for technological infrastructures and human safety. Most of SW studies concern high and equatorial latitudes, because of well-known and significant effects of field-aligned currents and the equatorial electrojet at those latitudes. Less studies are made at mid-latitudes, resulting in an incomplete understanding of the local effect of magnetospheric and ionospheric currents. We compare the performance of global indices of geomagnetic activity such as Kp and Dst with simulations of the Tsyganenko semi-empirical model of storm-time geomagnetic field, in predicting the irregular geomagnetic activity observed at the Coimbra magnetic observatory (40.22 N, 351.58 E). At first we use principal component analysis to efficiently separate the geomagnetic daily variation. Then we identify the effect of different magnetospheric current systems and estimate their contributions. Finally, we discuss how ground observatory observations can benefit from semi-empirical models, but also contribute to improve their parameterization.

  8. HF Doppler oscillations in the low-latitude ionosphere coherent with equatorial long-period geomagnetic field oscillations

    NASA Astrophysics Data System (ADS)

    Motoba, T.; Kikuchi, T.; Shibata, T.; Yumoto, K.

    2004-12-01

    We present observations of HF Doppler (HFD) oscillations in the low-latitude ionosphere seen during global long-period (5-15 min) geomagnetic field oscillation events, which occurred on 21 April 1993 and on 28 February 1998. In both events, daytime polar-equatorial magnetometer data on the ground indicated that the long-period geomagnetic field oscillations at the daytime dip equator were not only considerably enhanced but also highly correlated with those at afternoon high latitudes with no apparent time shift. This earlier finding [Motoba et al., 2002, 2003] strongly suggested that the long-period geomagnetic field oscillations at the daytime dip equator were produced by an extension of polar-originating ionospheric current system associated with high-latitude geomagnetic field oscillations. In the first event on 21 April 1993, the HFD measurement at the post-midnight low latitude detected frequency oscillations coherent with the geomagnetic field oscillations at the afternoon dip equator in the Pc5 range. However, there was no magnetic field change at low-latitude magnetometer stations adjacent to the reception site of the HFD. Therefore, it is reasonable to consider that the HFD oscillations are not effects of directly incoming hydromagnetic waves on the nighttime low-latitude ionosphere. In the second event on 28 February 1998, both the low-latitude HFD and equatorial magnetometer measurements were located in the post sunrise-terminator. Similar to the first event, HFD oscillations were well correlated with long-period geomagnetic field oscillations at the daytime equator, although both variations were in anti-phase. In the same local time sector the corresponding low-latitude magnetic field variations were predominant in the D component rather than the H component, suggesting that the meridional ionospheric currents originating in the polar region make a major contribution for the low-latitude magnetic field oscillations. The two case studies presented here

  9. An equinoctial asymmetry in the high-latitude thermosphere and ionosphere

    NASA Astrophysics Data System (ADS)

    Aruliah, A. L.; Farmer, A. D.; Fuller-Rowell, T. J.; Wild, M. N.; Hapgood, M.; Rees, D.

    1996-07-01

    A large equinoctial asymmetry has been observed in thermospheric winds and ion velocities at high latitude sites in northern Scandinavia. Throughout the solar cycle, average nighttime thermospheric meridional winds are larger in spring than autumn despite similar levels of solar insolation. The average ion velocities are also larger in spring than autumn at solar maximum, but at solar minimum this position is reversed. Numerical simulations of the thermosphere and ionosphere have not predicted such asymmetries because they generally assume forcing functions that are symmetric about the solstices. The proposed explanation lies in the annual and diurnal variation in solar wind-magnetosphere coupling caused by changes in the orientation of the geomagnetic pole, and hence the magnetosphere, with respect to the average orientation of the IMF (the Russell-McPherron effect). This causes a 12-hour phase difference between the times of maximum solar wind-magnetosphere coupling at the two equinoxes. In addition, the orientation of the geomagnetic axis with respect to the average IMF is such that >0 for the March equinox and <0 for September. This results in a further source of asymmetry of forcing of the high-latitude ionosphere as the result of electric fields associated with the four sign combinations of By and Bz. Several predictions arise from the explanation given: for example, a high-latitude station measuring thermospheric neutral winds in Alaska, 180° in longitude from Kiruna, might be expected to see nighttime thermospheric winds that are larger in the autumn than in the spring.

  10. First results on climatological response of Indian low latitude ionosphere to geomagnetic storms during solar cycle 23 and 24

    NASA Astrophysics Data System (ADS)

    Suresh, Sunanda; Dashora, Nirvikar

    2016-07-01

    For the first time, a climatological response of low latitude ionosphere to geomagnetic storms is presented using long term global ionospheric maps (GIM) data from June 1998 to June 2015 covering two solar cycles 23 and 24. The results are not only the first from Indian region but also the first around the globe to bring latitudinal character of daytime ionospheric storms with use of newly defined criteria. The results are presented for daytime forenoon and afternoon sectors under minor, moderate and major ionospheric storm categories based on minimum Dst index criterion. For the first time the effectiveness of storms is identified using monthly standard deviation as an indicator of the day-to-day variability in equatorial and low latitude ionosphere. Thus results on climatology are definitive and form a data base that would be comparable to statistical results from any other longitude and time. Seasonal statistics for total storms, effective positive and negative storms, and amplitude of mean seasonal perturbation in total electron content are obtained. Total and effective storms are found to be higher in solar cycle 23 than in 24 and only couple of effective storms occurred during low solar activity 2007-2009 that also in minor category. Afternoon sector is found to be favourable for occurrence of maximum number of effective positive storms. A latitudinal preference is found for a given storm to be effective in either time sectors. Equinoctial asymmetry in ionospheric response both in terms of occurrence and perturbation amplitude is found. September equinoxes are found to bear maximum total, effective positive and negative storms. Winters are found more prone to negative storms whereas summers have recorded minimum number of either of storms and minimum perturbation amplitudes.

  11. Theoretically modeling the low-latitude, ionospheric response to large geomagnetic storms

    NASA Astrophysics Data System (ADS)

    Anderson, D.; Anghel, A.; Araujo, E.; Eccles, V.; Valladares, C.; Lin, C.

    2006-10-01

    In the low-latitude, ionospheric F region, the primary transport mechanism that determines the electron and ion density distributions is the magnitude of the daytime, upward E × B drift velocity. During large geomagnetic storms, penetration of high-latitude electric fields to low latitudes can often produce daytime, vertical E × B drift velocities in excess of 50 m/s. Employing a recently developed technique, we can infer these daytime, upward E × B drift velocities from ground-based magnetometer observations at Jicamarca and Piura, Peru, as a function of local time (0700-1700 LT). We study the ionospheric response in the Peruvian longitude sector to these large upward drifts by theoretically calculating electron and ion densities as a function of altitude, latitude, and local time using the time-dependent Low-Latitude Ionospheric Sector (LLIONS) model. This is a single-sector ionosphere model capable of incorporating data-determined drivers, such as E × B drift velocities. For this study, we choose three large storms in 2003 (29 and 30 October and 20 November) when daytime E × B drift velocities approached or exceeded 50 m/s. Initial results indicate that the large, upward E × B drift velocities on 29 October produced equatorial anomaly crests in ionization at ±20° dip latitude rather than the usual ±16° dip latitude. We compare the theoretically calculated results with a variety of ground-based and satellite observations for these three periods and discuss the implications of these comparisons as they relate to the capabilities of current theoretical models and our ability to infer ionospheric drivers such as E × B drifts (Anderson et al., 2002).

  12. Review of Ionospheric Scintillation Models and proposing a Novel Model for Characterizing High Latitude Irregularities

    NASA Astrophysics Data System (ADS)

    Deshpande, K.; Bust, G. S.; Clauer, C. R.

    2013-12-01

    The study of ionospheric scintillations of radio signal involves a problem of electromagnetic (EM) wave propagation in random media and has been a subject of interest for more than last 5 decades. Some of the representative works are by Booker et. al (1950), Ratcliffe (1956), Wernik and Liu (1975), Yeh and Liu (1982), Secan et. al (1995), Costa and Basu (2002), Rino and Carrano (2011). Many of the scintillation models employ a phase screen model introduced by Rino (1979). Beniguel and Hamel (2011) implemented a global ionospheric scintillation model for equatorial regions showing a good agreement of the model with measurements. Implementing these models in the study of ionospheric scintillations of radio signals at high latitudes could be challenging since the path of satellite signal to ground has a variable angle of incidence, in addition to the complicated geometry of magnetic field lines at high latitude and polar regions, and complex magnetosphere-ionosphere coupling mechanisms creating the irregularities. We have developed a high fidelity 3-dimensional Global Positioning System Ionospheric Scintillation Model (3D-GPSISM) which is a full 3D EM wave propagation model to simulate GPS scintillations in high latitude ionosphere. The results from this model can form a basic framework on the use of inverse method to understand the physics of high latitude irregularities using GPS scintillations. We are using our model and an inverse method for selected scintillation observations during 2010 - 2013 from GPS receivers at South Pole, McMurdo and remote stations on Antarctica in conjunction with ancillary observations from SuperDARN, magnetometers, All Sky Imagers etc. We believe that such inverse method can be used to derive certain characteristics of the irregularity causing the scintillations and further achieve an improved understanding of the physics of high latitude irregularities.

  13. Impact of X-class solar flares on the ionospheric Total Electron Content over low latitude stations in India

    NASA Astrophysics Data System (ADS)

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

    X-rays, UV radiation and Coronal mass emitted during solar flares can affect the Earth's ionosphere and disrupt long-range radio communications. The present study investigates the effects of solar flares on the ionospheric Total Electron Content (TEC) with the help of global positioning system (GPS) data from low latitude stations in India located within the EIA region. Two X-class solar flares on 05th and 08th November 2013 have been selected for the present study. A significant enhancement in TEC is observed at regions around the EIA crest region during the flare and this enhancement is attributed to (a) the flare related EUV flux enhancement and consequent increased production of ionization, and (b) flare induced changes in the equatorial electrodynamics which in turn modifies ionospheric altitude profile of plasma via E × B drift mechanism. The supporting data from COSMIC electron density profile is also used to confirm the flare time enhancement.

  14. Characterization of ionospheric variability in TEC using EOF and wavelets over low-latitude GNSS stations

    NASA Astrophysics Data System (ADS)

    Dabbakuti, J. R. K. Kumar; Venkata Ratnam, D.

    2016-06-01

    Investigation of ionospheric variability is essential for improving the daily ionospheric modeling and forecasting services of Global Navigation Satellite System (GNSS) applications. As India is a low-latitude region, more care has to be taken here to characterize the ionosphere due to irregularities and Equatorial Ionization Anomaly (EIA) conditions. Therefore, an appropriate method is required to diagnose the ionospheric variations during geomagnetic, solar and other disturbances. In this paper, the temporal ionospheric time delay variations were studied based on the Empirical Orthogonal Function (EOF) analysis and wavelet transforms (WT).These analyses were carried out with Total Electron Content (TEC) datasets obtained from three GNSS stations located in low-latitude regions. EOF analysis was performed on the TEC datasets, which were decomposed into a time series of orthogonal eigen values (or base functions) and associated coefficients. EOF base functions and their associated coefficients signify the hourly time variations and the day of the year variations. The results reveal that the first few EOFs represented the majority of TEC variability pertaining to the physical processes of the ionosphere. The accuracy of the EOF model was validated by the evaluation of observational TEC data with International Reference Ionosphere (IRI) 2012 models. The EOF model coefficients for each GNSS station showed a strong correlation with the IRI models and also described the correlation between the impacts of the level of geomagnetic activity on the ionosphere. The correlation coefficients for the first three EOFs were more than 0.95. The phase relationship of ionospheric TEC anomalies, with respect to the geomagnetic indices (Dst), were analyzed by wavelet transforms.

  15. Goose Bay radar observations of earth-reflected atmospheric gravity waves in the high-latitude ionosphere

    SciTech Connect

    Ruohoniemi, J.M.; Greenwald, R.A.; Baker, K.B.; Samson, J.C.

    1990-05-03

    An HF backscatter radar at Goose Bay, Labrador made it possible to observe irregularities in the distribution of ionospheric ionization at E and F region altitudes (100 - 600 km) in the high-latitude (65 - 85 deg Lambda) ionosphere. Recently it has been established that the passage of atmospheric gravity waves perturbs the ionosphere in ways that are readily detected in returns that reflect off the ionospheric layers. The particular strength of the technique lies in the nearly instantaneous measurement of gravity wave effects over large areas ( 1 million sq. km). With this information the propagation of gravity waves can be accurately modelled. Generally gravity waves are observed during daylight hours propagating away from the auroral electrojets. The propagation mode involves penetration of wave energy through the lower atmosphere and subsequent reflection by the earth's surface. The frequencies associated with the waves lie in the 0.4 - 0.6 mHz range and the wavelengths vary from 300 to 500 km. The excitation sources appear to lie in the vicinity of the high-latitude electrojets. In this paper we outline the analysis of gravity wave effects on HF propagation and present an example of a modelled gravity wave event.

  16. Investigation of Ionospheric response to Geomagnetic Storms over a Low Latitude Station, Ile-Ife, Nigeria

    NASA Astrophysics Data System (ADS)

    Jimoh, Oluwaseyi E.; Yesufu, Thomas K.; Ariyibi, Emmanuel A.

    2016-05-01

    Due to several complexities associated with the equatorial ionosphere, and the significant role which the total electron content (TEC) variability plays in GPS signal transmission, there is the need to monitor irregularities in TEC during storm events. The GPS SCINDA receiver data at Ile-Ife, Nigeria, was analysed with a view to characterizing the ionospheric response to geomagnetic storms on 9 March and 1 October 2012. Presently, positive storm effects, peaks in TEC which were associated with prompt penetration of electric fields and changes in neutral gas composition were observed for the storms. The maximum percentage deviation in TEC of about 120 and 45% were observed for 9 March and 1 October 2012, respectively. An obvious negative percentage TEC deviation subsequent to sudden storm commencement (SSC) was observed and besides a geomagnetic storm does not necessarily suggest a high scintillation intensity (S4) index. The present results show that magnetic storm events at low latitude regions may have an adverse effect on navigation and communication systems.

  17. The domination of Saturn's low-latitude ionosphere by ring 'rain'.

    PubMed

    O'Donoghue, J; Stallard, T S; Melin, H; Jones, G H; Cowley, S W H; Miller, S; Baines, K H; Blake, J S D

    2013-04-11

    Saturn's ionosphere is produced when the otherwise neutral atmosphere is exposed to a flow of energetic charged particles or solar radiation. At low latitudes the solar radiation should result in a weak planet-wide glow in the infrared, corresponding to the planet's uniform illumination by the Sun. The observed electron density of the low-latitude ionosphere, however, is lower and its temperature higher than predicted by models. A planet-to-ring magnetic connection has been previously suggested, in which an influx of water from the rings could explain the lower-than-expected electron densities in Saturn's atmosphere. Here we report the detection of a pattern of features, extending across a broad latitude band from 25 to 60 degrees, that is superposed on the lower-latitude background glow, with peaks in emission that map along the planet's magnetic field lines to gaps in Saturn's rings. This pattern implies the transfer of charged species derived from water from the ring-plane to the ionosphere, an influx on a global scale, flooding between 30 to 43 per cent of the surface of Saturn's upper atmosphere. This ring 'rain' is important in modulating ionospheric emissions and suppressing electron densities. PMID:23579676

  18. Modeling study of the mid-latitude ionospheric nighttime electron density enhancement by SAMI3

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

    The mid-latitude summer nighttime anomaly (MSNA) is a feature that the nighttime electron density is larger than in the daytime around the mid-latitude ionosphere. This anomaly was first detected in the southern hemisphere five decades ago and reported in the northern hemisphere recently. Previous studies presented the electron density structure of MSNA by satellite observation data and found that MSNA is clearly seen at 300 km altitude during local summer around South American, European, and Northeast Asian regions. A three-dimensional self-consistent model, SAMI3 (Sami3 is Also a Model of the Ionosphere), with inputting neutral wind data from TIEGCM (Thermosphere Ionosphere Electrodynamics General Circulation Model) model is used to simulate the MSNA feature and further discuss its mechanisms. The comparisons between observation data and the model simulation results suggest that the equatorial neutral winds play the most important role in the formation of MSNA.

  19. On the coupled interactions between ring current intensity and high-latitude ionospheric electron density variations

    NASA Astrophysics Data System (ADS)

    Yadav, Sneha; Pallamraju, Duggirala

    2015-04-01

    Investigations on the magnetospheric-ionospheric processes form an important element of research in the understanding of the solar-terrestrial interactions. In this work, we have investigated the linkage between the ring current intensity and the high-latitude ionospheric plasma density variations during different geomagnetic conditions. The Global Positioning System (GPS) derived Vertical Total Electron Content (VTEC) during 2011-2013 over high- and low-latitude stations in both the hemispheres and the symmetric ring current index (SYM-H) have been used in this study. A cross-correlation analysis performed between the variations of these two parameters during a wide range of geomagnetic conditions reveal that there is a seasonal, latitudinal and hemispherical dependence in the interrelationship between SYM-H and VTEC. The best cross-correlation between SYM-H and VTEC over both the hemispheres is obtained during equinoctial months which can be attributed to the semiannual variation of the solar wind-magnetospheric-ionospheric coupling. Summer time VTEC over southern hemisphere exhibits a better correlation with SYM-H index in comparison to that of the northern hemisphere. These results have been explained in the light of relative contributions from seasonal and hemispherical variation that exists in the ionospheric plasma. The results are striking as the correlation is found between the variation in two independent processes occurring at widely separated regions in space, namely, the ring current intensity and the behavior of ionospheric densities at high-latitudes. Season-dependent high- and low-latitude coupling of the ionospheric VTEC is observed during the disturbed geomagnetic conditions.

  20. Short-term prediction of the foF2 critical frequency in the high latitude ionosphere for DIAS extending services

    NASA Astrophysics Data System (ADS)

    Tsagouri, Ioanna; Belehaki, Anna

    2013-04-01

    Ionospheric forecasting products and services for Europe are provided routinely by the European Digital upper Atmosphere Server, DIAS (http://dias.space.noa.gr). These include alerts and warnings for upcoming ionospheric storm time disturbances as well as single station and regional ionospheric forecasts up to 24 hours ahead for the middle latitude European region. However, in order to meet the users' requirements, it is planned within the Space Situational Awareness Programme of the European Space Agency the extension of the DIAS forecasting services to cover the whole European region, including Scandinavia. To this effect, the Solar Wind driven autoregression model for Ionospheric short-term Forecast (SWIF) will be applied. In the operational mode, SWIF combines historical and real-time ionospheric observations with solar wind parameters obtained in real time at L1 point from ACE spacecraft through the cooperation of an autoregression forecasting algorithm, namely TSAR with an empirical ionospheric storm time model, namely STIM that is triggered by solar wind disturbances detected by STIM's alert detection algorithm. The ionospheric storm time response is then empirically formulated taken into account the latitude and the local time of the observation point at the storm onset. SWIF's prediction efficiency was recently fully documented for the middle latitude ionosphere. As a first step towards the operational implementation of the SWIF for high latitude ionospheric forecasts, the work presented here includes the evaluation of the SWIF's performance over high latitude locations and under disturbed geophysical conditions based on historical data. For this purpose, all available high latitude foF2 observations obtained during a significant number of selected storm events occurred in the previous as well as the current solar cycle are analyzed in respect with the foF2 reference level and the model's predictions. The results verify the validity of STIM's storm alert

  1. Monitoring, mapping and prediction of ionospheric scintillation over the Brazilian equatorial and low latitude regions

    NASA Astrophysics Data System (ADS)

    Becker-Guedes, Fabio; de Paula, E. R.; de Rezende, L. F. C.; Stephany, S.; Kantor, I. J.; Muella, M. T. A. H.; Siqueira, P. M.; Correa, K. S.; Dutra, A. P.; Guedes, C.; Takahashi, H.; Silva, J. D. S.

    It is well known, today, that equatorial ionospheric scintillations affect performance of GPS receivers. Scintillation occurs when a radio wave crosses the ionosphere and suffers distortion in phase and amplitude. It also contributes to loss of lock of GPS receivers, resulting decrease of the number of available satellites and consequently yielding poor satellite geometry. Therefore, the required accuracy and positioning precision for aerial navigation are affected. Among other activities, EMBRACE, the space weather program of INPE, is monitoring and mapping the ionospheric scintillation over the South American equatorial and low latitude region in real time. This mapping is available in the internet by means of computer programs that retrieve data from a network of GPS receivers distributed in Brazil. These data are also being used to survey and predict the occurrence of ionospheric scintillation through data mining techniques.

  2. Observations of the High-Latitude Ionospheric Response to the Onset of the April 2002 Storm

    NASA Astrophysics Data System (ADS)

    Thayer, J. P.; Heinselman, C. J.; Tsunoda, R. T.; van Eyken, A. P.; Stromme, A.; McCready, M. A.

    2002-12-01

    The high-latitude incoherent scatter radars at Sondrestrom, Greenland, and Longyearbyen, Svalbard, observed detailed ionospheric behavior during the initial shock, occurring near 11:00 UT on April 17, and the onset of the geomagnetic storm. During this period, the Sondrestrom radar observed extreme electric field enhancements in excess of 120 mV/m. The direction of the electric field at Sondrestrom indicates the measurements are located in the sunward convection region of the dawn and pre-noon sector. These large electric fields subsequently produced very high levels of Joule heating rates (greater than 80 mW/m2), extreme ion heating events (in excess of 3500 K), aurorally enhanced electron temperatures and current-driven instabilities leading to extreme electron temperatures in the lower E region (in excess of 2000 K). Additionally the F-region meridional neutral wind response and E region neutral winds are inferred. Concurrent observations on Svalbard, in the post-noon and dusk sector, also indicate enhanced F- and E-region ion and electron temperatures. Though the ionospheric response observed by the radars are determined locally, electric field enhancements estimated by AMIE runs during this period of the storm suggest that these effects may, in fact, occur over a much larger region.

  3. Mid-Latitude Ionospheric Disturbances Due to Geomagnetic Storms at ISS Altitudes

    NASA Technical Reports Server (NTRS)

    Minow, Joseph I.; Willis, Emily M.; Parker, Linda Neergaard

    2014-01-01

    Spacecraft charging of the International Space Station (ISS) is dominated by the interaction of the high voltage US solar arrays with the F2-region ionospheric plasma environment. We are working to fully understand the charging behavior of the ISS solar arrays and determine how well future charging behavior can be predicted from in-situ measurements of plasma density and temperature. One aspect of this work is a need to characterize the magnitude of electron density and temperature variations that may be encountered at ISS orbital altitudes (approximately 400 km), the latitudes over which they occur, and the time periods for which the disturbances persist. We will present preliminary results from a study of ionospheric disturbances in the "mid-latitude" region defined as the approximately 30 - 60 degree extra-equatorial magnetic latitudes sampled by ISS. The study is focused on geomagnetic storm periods because they are well known drivers for disturbances in the high-latitude and mid-latitude ionospheric plasma. Changes in the F2 peak electron density obtained from ground based ionosonde records are compared to in-situ electron density and temperature measurements from the CHAMP and ISS spacecraft at altitudes near, or above, the F2 peak. Results from a number of geomagnetic storms will be presented and their potential impact on ISS charging will be discussed.

  4. Observing the mid- and low-latitude ionosphere - global UV remote sensing

    NASA Astrophysics Data System (ADS)

    Paxton, L. J.; Kil, H.; Miller, E. S.; Comberiate, J.; Schaefer, R. K.; Zhang, Y.; GUVI Team

    2013-05-01

    Understanding the global-, meso- and small-scale structure of the ionosphere. We need more observations to reallly test whether we have correctly captured not only the physics but the parameterizations of the sub-grid scale processes in the upper atmosphere. In this talk we present results from APL UV experiments that enable us to characterize TEC on a global basis. In addition, we can determine the topside scale height, peak density and altitude of the peak. In the auroral region we obtain maps of the E-region parameters (HmE, NmE) and conductivity profiles. Global UV remote sensing of the ionosphere, especially tomographic imaging, is a technique that is now readily implemented on even small spacecraft. The sensors are small, compact and flexible. In this talk we will show results of our extended climatology of the characteristics of the mid- and low-latitude ionosphere. In particular, we have completed converting our extensive GUVI database into 3D "datacubes" of low-latitude F-region ionospheric profiles. These 3D profiles, besides giving you the familiar electron density profiles (including topside scale height) also exhibit the action of the ExB drift as the separation of the arcs and the influence of the meridional component of the neutral wind as the hemispheric assymetry and the influence of lower atmosphere forcing in the longitudinal amplitude of the ionosphere.

  5. Ionospheric fluctuation study over mid-latitude during one large magnetic storm based on GPS observatio

    NASA Astrophysics Data System (ADS)

    Zhang, D.; Li, Q.; Xiao, Z.

    Form Nov 5 to Nov 10 2004 a large number of solar events occurred that triggered many solar flares and CMEs These CMEs caused two large geomagnetic storms and continuous energy proton event During this period one large positive ionospheric storm happened over the East-Asian region on Nov 08 2004 On Nov 10 2004 a strong spread-F was observed by the ionosonda located in the mid-latitude region of East china and Japan and the ionospheric fluctuation over the ionosonda station derived from GPS observation was also obvious In this report the characteristics of the spatial distribution of the ionosphere fluctuation and its temporal evolution using the parameter of ROT derived from dual-frequency GPS measurement are studied It is found that the ionosphere over the mid-latitude region in southern and northern hemisphere between the longitude of 100 E and 180 E behaves strong fluctuating activity during the magnetic storm period on Nov 10 2004 a regular movement of the disturbing region is observed in the end the reason of the ionospheric fluctuation during this magnetic storm is analyzed

  6. Response of ionospheric electric fields at mid-low latitudes during geomagnetic sudden commencements

    NASA Astrophysics Data System (ADS)

    Takahashi, N.; Kasaba, Y.; Shinbori, A.; Nishimura, Y.; Kikuchi, T.; Ebihara, Y.; Nagatsuma, T.

    2014-12-01

    Geomagnetic sudden commencements (SCs) are known as one of the distinct magnetospheric disturbance phenomena triggered by solar wind disturbances. Many previous studies have focused on the generation mechanism of SCs by using in-situ observations and simulations. However, the global evolution of ionospheric electric fields has primarily been estimated from the ionospheric current. Although a few studies utilized electric field data from radar observations, the coverage is limited in time, and limited component of the electric field is obtained. In this study, we investigated the response and local time dependence of the ionospheric electric field at mid-low latitudes associated with 203 SCs occurred from 1999 to 2004 by the in-situ observation of the ROCSAT-1 spacecraft. We found that the ionospheric electric field associated with SCs instantaneously responds to geomagnetic fields regardless of spacecraft local time. Our statistical analysis also showed the instantaneous response of the electric field, which indicates the global instant transmission of the electric field from polar region. In contrast, peak times in the preliminary impulse (PI) and main impulse (MI) phases were different between the ionospheric electric field and equatorial geomagnetic field (20 sec in the PI phase). Based on a comparison to the ground-ionosphere waveguide model by Kikuchi [2014], this time lag is suggested to be due to the latitudinal difference of the ionospheric conductivity. After constructing the local time distribution of the SC amplitude, we found that the dayside feature was seen at 18-22 h even the ionospheric conductivity is lower than that at dayside. We performed a magnetohydrodynamic (MHD) simulation for an ideal SC. The result of the simulation showed that the electric potential distribution is asymmetric with respect to the noon-midnight meridian, which is similar to our observational result. It appears to result from the divergence of the Hall current under the non

  7. Phenomena in the high latitude ionosphere induced by an X-mode HF heater wave

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

    New experimental results are presented from high power ionospheric modification experiments with the EISCAT/Heating HF facility at Tromsø, Norway. The experiments were conducted in the course of Russian EISCAT HF heating campaigns in 2009 - 2011 using the following diagnostic tools: the EISCAT UHF incoherent scatter radar at Tromsø, the CUTLASS (SuperDARN) HF coherent radar, bi-static HF Doppler radio scatter and the EISCAT ionosonde (dynasonde). The effects on the high-latitude F region of the ionosphere by X-mode powerful HF radio waves injected towards the magnetic zenith (MZ) are analysed. We present the first experimental evidence for strong plasma modifications induced by the X-mode powerful HF radio waves. The distinctive feature of modification experiments is that the heater frequency is choosen by a special way, namely, it is above the ordinary-mode critical frequency but comparable with the extraordinary-mode critical frequency. The results show that the X-mode HF pump wave can generate very strong small-scale artificial field aligned irregularities (AFAIs) in the F-region of the high-latitude ionosphere. These irregularities, with spatial scales across the geomagnetic field of the order of 8 - 15 m, appeared 10 s - 4 min after the heater is turned on. They had the unusually long decay time which varied in a wide range between 3 and 30 min. The generation of the X-mode AFAIs was accompanied by electron temperature (Te) enhancements up to 50 % above the background level and an increase in the electron density (Ne) by up to 30 %. Such electron density enhancements can be attributed to HF-induced ionization production rather than the change of the density distribution due to the thermal diffusion. The analysis of the incoherent backscatter spectra obtained with the EISCAT UHF radar during X-mode HF pumping demonstrated the strongly enhanced ion line shoulders (upshifted and downshifted spectral peaks) observed during the whole 10 min heater-on period

  8. Day-to-day changes in ionospheric electron content at low latitudes

    NASA Astrophysics Data System (ADS)

    Dabas, R. S.; Bhuyan, P. K.; Tyagi, T. R.; Bhardwaj, R. K.; Lal, J. B.

    1984-06-01

    For a number of years, the ionospheric electron content (IEC) over the Indian subcontinent has been determined on the basis of the Faraday rotation of satellite radio beacon transmissions. In these determinations, use was made of the orbiting satellites BE-B and BE-C, and, for a limited period, of the geostationary satellite ATS 6. A large variability in day-to-day values of IEC was reported, and it was tried to correlate this phenomenon with magnetic activity, solar flux, or the effect of neutral winds. Tyagi (1978) observed that the day-to-day changes in IEC occur in the form of single day abnormality, and alternate day abnormality. Long-term fluctuations were found with a periodicity of about 45 days. The present investigation is concerned with a more detailed study of the observed variations. An analysis is conducted of IEC data recorded during the low phase of the solar cycle, taking into account data from six low-latitude stations covering a latitude range from approximately 15.0 deg N to 30.0 deg N.

  9. Analysis of local ionospheric variability based on SVD and MDS at low-latitude GNSS stations

    NASA Astrophysics Data System (ADS)

    Dabbakuti, J. R. K. Kumar; Devanaboyina, Venkata Ratnam; Kanchumarthi, S. Ramesh

    2016-06-01

    Investigation of ionospheric anomalies during equatorial and low latitude is of major concern for modeling and global navigation satellite system (GNSS) applications. Total electron content (TEC) varies with the ionospheric conditions, which will lead to the errors in the global positioning system (GPS) measurements. It is therefore a method that is necessary to characterize the ionospheric anomalies for satellite-based navigation systems. In this study, characterization of ionospheric variations based on the singular value decomposition (SVD) and classical multidimensional scaling (MDS) methods was studied. The yearly and daily variations are decomposed from the GPS-TEC, international reference ionosphere (IRI) 2007 and IRI 2012 models TEC over the three low-latitude GNSS stations located at Koneru Lakshmaiah University (KLU-Guntur), Hyderabad and Bangalore, respectively. From the results, it is found that there is a strong correlation between GPS-TEC and IRI models. The correlation coefficient for the first three singular values is more than 0.86. From this, it is possible to reconstruct more than 85 % of the variability contained in global GPS-derived VTEC data (for year 2013) by using only the first three modes. The semiannual variation has maximum value during March-April and September-October and has minimum value during June-July. It is observed that the annual variations have maximum value in summer and minimum value in winter, and the amplitudes decrease with increasing latitude. Further, opposite latitudinal asymmetry among annual and semiannual variations for three GNSS stations is noticed. SVD and MDS methods clearly show time-varying characteristics and the absence of the winter anomaly at low-latitude GNSS stations.

  10. Comparison of measured and calculated low latitude ionospheric properties

    NASA Technical Reports Server (NTRS)

    Chandler, M. O.; Behnke, R. A.; Nagy, A. F.; Fontheim, E. G.; Richards, P. G.; Torr, D. G.

    1983-01-01

    Measurements of ionospheric parameters above Arecibo, Puerto Rico, have been compared with a computer simulation for a variety of conditions. Agreement was found between the measured and calculated electron concentration during geomagnetically quiet conditions. Comparisons for more active conditions indicate a significant upward flow of ionization during the mid-afternoon. Calculated electron temperatures were found to be consistently lower than measured temperatures during the daytime. Calculated values of NmF2 and h(max) agreed with measured results except during the post-midnight period. Calculated values of the ion flux indicate a 24-hour net flow of ionization from the northern to the Southern Hemisphere amounting to 12 percent and 6 percent of the equilibrium flux tube content above 1000 km for the winter solstice and equinox cases, respectively.

  11. Magnetospheric convection and the high-latitude F2 ionosphere

    NASA Technical Reports Server (NTRS)

    Knudsen, W. C.

    1974-01-01

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

  12. Superposed epoch analysis of the ionospheric convection evolution during substorms: onset latitude dependence

    NASA Astrophysics Data System (ADS)

    Grocott, A.; Wild, J. A.; Milan, S. E.; Yeoman, T. K.

    2009-02-01

    Using data from the Super Dual Auroral Radar Network (SuperDARN) we investigate the ionospheric convection response to magnetospheric substorms. Substorms were identified using the Far Ultraviolet (FUV) instrument on board the Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) spacecraft, and were then binned according to the magnetic latitude of their onset. A superposed epoch analysis of the ionospheric convection patterns for each onset-latitude bin was then performed using radar data for the interval 60 min before onset to 90 min after. It is found that lower onset-latitude substorms are associated with generally more enhanced convection than the higher latitude substorms, although they suffer from a significant localised reduction of the flow in the midnight sector during the expansion phase. Higher-latitude substorms are associated with a significant and rapid increase in the nightside convection following substorm onset, with all onset-latitude bins showing an enhancement over onset values by ~60 min into the expansion phase. A rudimentary inspection of the concurrent auroral evolution suggests that the duration of the flow reduction following substorm onset is dependent on the strength and duration of the expansion phase aurora and its associated conductivity enhancement.

  13. Ionospheric signatures of cusp-latitude Pc 3 pulsations

    SciTech Connect

    Engebretson, M.J. ); Cahill, L.J. Jr. ); Arnoldy, R.L. )

    1988-01-01

    It has been well established that many of the disturbances in the Earth's magnetosphere, such as auroral substorms, are a response to variations in the solar wind that continually sweeps from the Sun past the Earth and other planets. Studies over the past several years, most recently reviewed by Odera (1986) and Arnoldy at el. (1988), have shown that Pc 3 pulsations, a class of ultra-low-frequency waves in the Earth's magnetic field with periods between 15 and 40 seconds, are also directly related to activity in the solar wind just upstream of the Earth. The authors present in this report new observations from South Pole Station, Antarctica, which during certain hours every day is located under the nominal position of the magnetospheric cleft/cusp region. There has been ample evidence that plasmas from interplanetary space can penetrate to ionospheric altitudes in the cusp region. Two earlier papers based on South Pole data noted that large-amplitude, narrowband Pc 3 magnetic pulsations occurred at South Pole Station near local magnetic noon when the interplanetary magnetic field was aligned near the Earth-Sun direction (low interplanetary magnetic field cone angle). They have now found evidence of these pulsations in data from other South Pole instruments as well.

  14. The Ionospheric Model Adaptation to the Auroral Latitudes With UHF EISCAT Radar and Tromso Magnetometer Data

    NASA Astrophysics Data System (ADS)

    Nikolaeva, Vera; Gordeev, Evgeny; Kotikov, Andrey

    E-layer Auroral Ionosphere Model (E-AIM) developed in Arctic and Antarctic Research Institute can provide temporal and spatial distribution of the main ionosphere parameters: ion and electron density distribution in the altitude range from 90 to 150 km. The statistical study of E-layer electron density dependence on substorm activity was made to improve model results in high latitudes. About fifty substorms were included to the data analysis. Particular attention was paid to the dynamics of magnetic disturbances and ionospheric parameters measured by the radar. Correlation of electron density values measured by the UHF EISCAT incoherent scattering radar with geomagnetic indices was determined. Applicability of geomagnetic indices as input parameters of the local E-AIM model was estimated.

  15. a Study of Ionospheric Low Latitude Velocity and Density Irregularity Correlations during Solar Minimum

    NASA Astrophysics Data System (ADS)

    Haaser, R. A.; Earle, G. D.; Heelis, R. A.; Klenzing, J. H.; Coley, W. R.; Stoneback, R. A.; Burrell, A. B.

    2010-12-01

    The C/NOFS satellite has measured ionospheric plasma density irregularities at low latitudes on scales larger than 10 km over a full set of seasons. The focus of this study is on data from the Ion Velocity Meter (IVM) from Jan-Dec 2009 for pre-midnight and post-midnight times when the data are most reliable. Correlations between the normalized changes in density and velocity (dni/n and dv-horz,vert) during spread-F events (plasma bubbles through the f-peak) and localized plasma enhancements associated with those events are analyzed and compared to investigate seasonal, spatial, and temporal properties during the 2009 solar minimum conditions. The correlations presented and their relationship to the unusually quiescent background conditions in this epoch challenge our understanding and add significantly to our knowledge of ionospheric irregularity events and distribution statistics at low latitudes during solar minimum.

  16. Trends of ionospheric irregularities over African low latitude region during quiet geomagnetic conditions

    NASA Astrophysics Data System (ADS)

    Mungufeni, Patrick; Habarulema, John Bosco; Jurua, Edward

    2016-02-01

    The occurrence patterns of ionospheric irregularities during quiet geomagnetic conditions over the African low latitude region were analysed. GNSS-derived Total Electron Content of the ionosphere data during the period 2001-2012 were used. The data were obtained from Libreville, Gabon (0.35°N, 9.68°E, geographic, 8.05°S, magnetic), Mbarara, Uganda (0.60°S, 30.74°E, geographic, 10.22°S, magnetic), and Malindi, Kenya (2.99°S, 40.19°E, geographic, 12.42°S, magnetic). The rate of change of total electron content index greater than 0.5 TECU/Min were considered as severe ionospheric irregularities. For most of the time, the strength of ionospheric irregularities in March equinox were greater than those during September equinox over East Africa and an opposite observation was made over West Africa. These asymmetries might be due to the direction of the meridional winds during equinoxes over the different stations. Severity of ionospheric irregularity reduced from west towards the east. This might have been related to the decreasing geomagnetic field strength from east towards the west. This is the first study that reveals the equinoctial asymmetry is different in the West and East African sectors. Moreover, the importance of this study lies in the fact that it has used extensive data to examine the isolated and un-explained earlier observations of equinoctial asymmetry and longitudinal variation of ionospheric irregularities over the African low latitude region.

  17. Study of TEC variations induced by powerful HF-heating in mid-latitude dayside ionosphere

    NASA Astrophysics Data System (ADS)

    Kunitsyn, Viacheslav; Padokhin, Artem; Frolov, Vladimir L.; Komrakov, G. P.

    In this work we report on the experimental evidences for the influence of the heating-induced electron density perturbations in the dayside mid-latitude ionosphere on the GNSS signals. We analyze the spectral characteristics of the observed perturbations for different heating regimes. The experiments were carried out at the Sura heating facility (Radio Physical Research Insti-tute, N. Novgorod). The inospheric heating was scheduled in such a way to provide crossing of the heated area by the ionospheric penetration points of several GPS-satellites during the ses-sions of heating with different time modulations of the effective radiated power of the O-mode pumping wave. Based on the studying of the variations in TEC (total electron content propor-tional to the reduced phases of the navigational signals), we show that in case of square-wave modulation of the effective radiated power (with periods of 1, 6, 10, and 15 minutes) of the heating wave, perturbations with periods of the main modulation of heating and its harmonics appear in the wavelet spectrum of TEC variations. Examples are presented of identification of the heating-induced variations in TEC, including the determination of amplitudes and time characteristics of these variations and estimation of electron density perturbations at the height of the heating wave reflection. The work was supported by the Russian Foundation for Basic Research (grants nos. 08-02-00171, 08-05-00676 and 10-05-01126). The authors are grateful to the staff of the Sura facility for their help in the experiments.

  18. Coordinated observations of high-latitude ionospheric turbulence

    SciTech Connect

    Basu, S.; Basu, S.; Valladares, C.E.; Weber, E.J.; Buchau, J.

    1988-01-01

    A coordinated data set comprised of scintillation, ionosonde, incoherent scatter radar and optical measurements obtained on two nights during the CEDAR/WITS campaign of February, 1988 was selected for the study of two distinct classes of high latitude plasma turbulence. Under IMP Bz northward conditions, the polar cap arc detected by the all-sky imaging photometer (ASIP) in this phase of low solar activity (SSN=40) was found to be associated with a total electron content enhancement of only 2x10 to the 16th power/sq. m and weak amplitude scintillations (S sub 4 about = 0.35) at 250 MHz. The photometer and scintillation measurements indicated that in addition to the dawn to dusk motion of 200/ms in the inertial frame, there existed enhanced plasma motion of about 400/ms along the arc. The second data set conforming to IMF Bz southward condition showed the existence of ionization patches in the polar cap and their anti-sunward motion towards the auroral oval. The polar cap patches detected deep within the polar cap with electron contents as large as 10x10 to the 16th power/sq. m caused 15 dB scintillations at 250 MHz. These patches detected close to the auroral oval also caused strong scintillations which indicated that the patches get continually structured during their convection through the winter polar cap.

  19. Model of the mid-latitude ionospheric trough on the base of Cosmos-900 and Intercosmos-19 satellites data

    NASA Astrophysics Data System (ADS)

    Karpachev, A. T.; Deminov, M. G.; Afonin, V. V.

    1996-01-01

    A new model of the mid-latitude ionospheric trough is developed on the base of Intercosmos-19 and Cosmos-900 satellites data (over 1500 orbits). It is valid for the nighttime (18 to 06 MLT), winter and equinox, K_p-indices from 0 to 8. It covers the topside ionosphere up to 1000 km and describes the trough minimum position Lambda_T depending on longitude lambda, altitudeh , local magnetic time MLT and K_p-index. Model is presented in the analytical form, as well as a nomogram versus MLT and K_p and a nighttime segment of a circle (in the polar coordinate system) with the radius depending on the K_p-index. The effective K_p-index taken for preceding 4.4 hours is used in the model. Agreement between the model and other data on the trough and the equatorial boundary of the auroral oval is discussed.

  20. Observations of ionospheric convection from the Wallops SuperDARN radar at middle latitudes

    NASA Astrophysics Data System (ADS)

    Baker, J. B. H.; Greenwald, R. A.; Ruohoniemi, J. M.; Oksavik, K.; Gjerloev, J. W.; Paxton, L. J.; Hairston, M. R.

    2007-01-01

    During geomagnetic storms the ability of the Super Dual Auroral Radar Network (SuperDARN) to measure ionospheric convection becomes limited when the radars suffer from absorption and the auroral disturbance expands equatorward of the radar sites. To overcome these shortcomings, it was decided to construct a SuperDARN radar at middle latitudes on the grounds of the NASA Wallops Flight Facility. This paper presents the first comprehensive analysis of Doppler measurements from the Wallops radar, which commenced operations in May 2005. Wallops measurements are compared with the Goose Bay radar during the onset of a geomagnetic storm on 31 August 2005: Goose Bay measured the onset of geomagnetic activity at high latitude while Wallops monitored the expansion of convection to middle latitudes. Average convection patterns binned by the Kp geomagnetic index are also presented. During weak-moderate geomagnetic activity (Kp ≤ 3) the Wallops radar observes ionospheric irregularities between 50° and 60° magnetic latitude drifting westward across much of the nightside. When these measurements are incorporated into the calculation of an average SuperDARN convection pattern, the streamlines of polar cap outflow on the nightside become kinked in a manner reminiscent of the Harang discontinuity. This morphology arises quite naturally when the two-cell convection at high latitudes merges with the prevailing westward convection at middle latitudes. During increased geomagnetic activity (Kp ≥ 3), Wallops is able to measure the expansion of auroral electric fields to middle latitudes and the average SuperDARN cross-polar cap potential is increased by 25%.

  1. Mid-latitude magnetically conjugate ionospheric F2-layer during magnetic storm periods. Ph.D. Thesis

    SciTech Connect

    Wu, H.Y.

    1993-01-01

    Thermospheric winds and penetrating electric fields play important roles in the complex phenomenon of F2-layer magnetic storms. The combined effect of both on the ionosphere can be inferred using a method based on the nonlinear relationship between the neutral winds and the height of the F2-layer. The F2-layer peak electron density depletion on the storm day generally became more pronounced than quiet-time median values during nighttime. The high to low latitude F2-layer electron density depletion is particularly evident at both hemispheres. A simultaneous enhancement of the eastward electric fields at all latitudes suggests an intimate relationship between the peak electron density depletion and the penetrating electric fields during an onset of storm. The behavior of meridional neutral winds during magnetic storm periods at all latitudes has been shown to differ from their quiet-time patterns. Meridional neutral winds during quiet-time for the months considered are usually equatorward during day and night in the summer season, poleward during the day, and slightly equatorward at night during the winter season for both hemispheres. Meridional neutral winds during storm periods generally become equatorward of quiet time values at night and reach their maximum deviation from the quiet time medians near local midnight. Electric fields can be separated from the effects of neutral air dynamics during the onset of magnetic storms. Simultaneous changes from the quiet-time values of hmF2 occurring at one or more pairs of conjugate stations indicate the penetration of zonal electric fields. Different local times of storm onset were examined to show that the penetration of electric fields to mid-latitudes normally occurs near midnight periods. This may be correlated with the currents flowing into the high latitude ionosphere in the evening sector.

  2. Use of radio occultation to probe the high-latitude ionosphere

    NASA Astrophysics Data System (ADS)

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

    2015-07-01

    We have explored the use of COSMIC data to provide valuable scientific information on the ionospheric impacts of energetic particle precipitation during geomagnetic storms. Ionospheric electron density in the E region, and hence ionospheric conductivity, is significantly altered by precipitating particles from the magnetosphere. This has global impacts on the thermosphere-ionosphere because of the important role of conductivity on high-latitude Joule heating. Two high-speed stream (HSS) and two coronal mass ejection (CME) storms are examined with the COSMIC data. We find clear correlation between geomagnetic activity and electron density retrievals from COSMIC. At nighttime local times, the number of profiles with maximum electron densities in the E layer (below 200 km altitude) is well correlated with geomagnetic activity. We interpret this to mean that electron density increases due to precipitation are captured by the COSMIC profiles. These "E-layer-dominant ionosphere" (ELDI) profiles have geomagnetic latitudes that are consistent with climatological models of the auroral location. For the two HSS storms that occurred in May of 2011 and 2012, a strong hemispheric asymmetry is observed, with nearly all the ELDI profiles found in the Southern, less sunlit, Hemisphere. Stronger aurora and precipitation have been observed before in winter hemispheres, but the degree of asymmetry deserves further study. For the two CME storms, occurring in July and November of 2012, large increases in the number of ELDI profiles are found starting in the storm's main phase but continuing for several days into the recovery phase. Analysis of the COSMIC profiles was extended to all local times for the July 2012 CME storm by relaxing the ELDI criterion and instead visually inspecting all profiles above 50° magnetic latitude for signatures of precipitation in the E region. For 9 days during the July 2012 period, we find a signature of precipitation occurs nearly uniformly in local time

  3. Mid-latitude ionospheric perturbation associated with the Spacelab-2 plasma depletion experiment at Millstone Hill

    NASA Astrophysics Data System (ADS)

    Foster, J. C.; Holt, J. M.; Lanzerotti, L. J.

    2000-01-01

    Elevation scans across geomagnetic mid latitudes by the incoherent scatter radar at Millstone Hill captured the ionospheric response to the firing of the Space Shuttle Challenger OMS thrusters near the peak of the F layer on July 30, 1985. Details of the excitation of airglow and the formation of an ionospheric hole during this event have been reported in an earlier paper by Mendillo et al.. The depletion (factor sim2) near the 320 km Shuttle orbital altitude persisted for sim35 min and then recovered to near normal levels, while at 265 km the density was reduced by a factor of sim6; this significant reduction in the bottomside F-region density persisted for more than 3 hours. Total electron content in the vicinity of the hole was reduced by more than a factor of 2, and an oscillation of the F-region densities with 40-min period ensued and persisted for several hours. Plasma vertical Doppler velocity varied quasi-periodically with a sim80-min period, while magnetic field variations observed on the field line through the Shuttle-burn position exhibited a similar sim80-min periodicity. An interval of magnetic field variations at hydromagnetic frequencies (sim95 s period) accompanied the ionospheric perturbations on this field line. Radar observations revealed a downward phase progression of the 40-min period density enhancements of -1.12° km-1, corresponding to a 320-km vertical wavelength. An auroral-latitude geomagnetic disturbance began near the time of the Spacelab-2 experiment and was associated with the imposition of a strong southward IMF Bz across the magnetosphere. This created an additional complication in the interpretation of the active ionospheric experiment. It cannot be determined uniquely whether the ionospheric oscillations, which followed the Spacelab-2 experiment, were related to the active experiment or were the result of a propagating ionospheric disturbance (TID) launched by the enhanced auroral activity. The most reasonable conclusion is that

  4. A forward propagation model of GPS scintillations to characterize high latitude ionospheric irregularities

    NASA Astrophysics Data System (ADS)

    Deshpande, K.; Bust, G. S.; Clauer, C. R.

    2012-12-01

    Complex magnetosphere-ionosphere coupling mechanisms result in high latitude irregularities that are difficult to characterize using only GPS scintillation measurements. GPS observations combined with physical parameters such as width, height of the irregularity etc. derived from modeling can be used to study the physics of these irregularities. We have recently developed a full 3D EM wave propagation model to simulate GPS scintillations in ionosphere. The model is applicable to high latitudes as it accounts for a more complicated geometry of magnetic field lines in high latitude regions. In this work, we present a parametric study to determine the sensitivity of the model towards different input parameters such as spectral index of the irregularity spectrum, outer scale of the irregularity, height, thickness and drift velocity of the irregularity etc. The parameters to which this model is most sensitive are determined from this study, and are focused on during our preliminary comparison with GPS scintillation data from 24 January 2012 storm from CASES GPS receiver on an AAL-PIP station at the South Pole, Antarctica. As a following step, we used our model and an inverse method for GPS scintillation observations from CASES and Novatel receivers at the South Pole in conjunction with ancillary observations from other instruments such as SuperDARN. We believe that such inverse method can be used to derive certain characteristics of the irregularity causing the scintillations and further achieve an improved understanding of the physics of these high latitude irregularities.

  5. Mid-latitude field-aligned ionospheric irregularities and its impact on GPS

    NASA Astrophysics Data System (ADS)

    Yasyukevich, Yury; Afraimovich, Edward; Ishin, Artem; Tinin, Mikhail

    2010-05-01

    Strong scintillations of amplitude and phase of transionospheric radio signals occur due to signal scattering on intensive small scale irregularities. Scintillation can have an adverse effect on GPS signals and cause a GPS receiver to lose lock on the signal in some extreme cases. Although the plasma bubble is a common phenomenon and it has been studied for years, precise observed data of ionospheric scintillations and loss of lock to GPS receivers due to plasma bubble at mid-latitude are still limited. In most papers there are no data regarding the space geometry of field-aligned irregularities. For the first time, we propose a GPS method to detect mid-latitude field-aligned irregularities (FAIs) by line-of-sight angular scanning regarding the local magnetic field vector. We show that total GPS L2 phase slips over Japan during the recovery phase of the 12 February, 2000 geomagnetic storm (Ma and Maruyama, 2006, doi:10.1029/2006GL027512) were caused by GPS signal scattering on FAIs for the line-of-sight of both aligned to magnetic field line (the field of aligned scattering, FALS), and across it or at large angles to magnetic field line (the field of across scattering, FACS). Our FALS results confirm well with data of investigation of magnetic field orientation control of GPS occultation observations of equatorial scintillation during detailed LEO CHAMP, SAC-C and PICOSat measurements, realized by Anderson and Strauss (2005, doi:10.1029/2005GL023781). The role of large-angle scattering almost along the normal to the magnetic field line in GPS scintillation is determined by attenuation of the irregularity anisotropy factor as compared with the other factors. The work was supported by the Fundamental Research Program of RAS Physical Science Department (Project IV.12 "Modern problems of radiophysics").

  6. Statistical maps of small-scale electric field variability in the high-latitude ionosphere

    NASA Astrophysics Data System (ADS)

    Cousins, E. D. P.; Shepherd, S. G.

    2012-12-01

    Statistical maps of small-scale electric field variability in the high-latitude ionosphere are derived for the Northern and Southern Hemispheres using 48 months of data from the Super Dual Auroral Radar Network (SuperDARN). Maps of variability magnitude (from scales of 45-450 km and 2-20 min) are derived for a range of interplanetary magnetic field (IMF) orientations and dipole tilt angles (the angle between the best fit dipole axis and the plane perpendicular to the Sun-Earth line). It is found that the observed spatial distribution of average variability is significantly modified as the IMF and dipole tilt conditions change. Under negative (winter-like) and neutral (equinox-like) dipole tilt angles, variability is concentrated in the auroral and dayside cusp regions, and the spatial distributions of variability appear to be correlated to those of large- and small-scale field-aligned currents (FACs). Additionally, variability on the nightside is found to be more enhanced in the downward FAC region than it is in the upward FAC region. Under positive (summer-like) dipole tilt angles, the average variability magnitudes across the high-latitude regions are smaller than those observed under negative dipole tilt angles, and the spatial distributions are more uniform. These dipole tilt effects suggest that scale-size- and conductivity-dependent field-aligned potential drops and conductivity-dependent changes in the processes that generate variability are possible factors that impact the observed small-scale electric field variability. In general, Southern Hemisphere maps appear very similar to Northern Hemisphere maps, although some minor differences are observed that may result from interhemispheric asymmetries in the geomagnetic field.

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

    NASA Astrophysics Data System (ADS)

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

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

  8. Solar cosmic ray effects in the lower ionosphere

    NASA Technical Reports Server (NTRS)

    Shirochkov, A. V.

    1989-01-01

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

  9. Mapping high-latitude ionospheric electrodynamics with SuperDARN and AMPERE

    NASA Astrophysics Data System (ADS)

    Cousins, E. D. P.; Matsuo, Tomoko; Richmond, A. D.

    2015-07-01

    An assimilative procedure for mapping high-latitude ionospheric electrodynamics is developed for use with plasma drift observations from the Super Dural Auroral Radar Network (SuperDARN) and magnetic perturbation observations from the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE). This procedure incorporates the observations and their errors, as well as two background models and their error covariances (estimated through empirical orthogonal function analysis) to infer complete distributions of electrostatic potential and vector magnetic potential in the high-latitude ionosphere. The assimilative technique also enables objective error analysis of the results. Various methods of specifying height-integrated ionospheric conductivity, which is required by the procedure, are implemented and evaluated quantitatively. The benefits of using both SuperDARN and AMPERE data to solve for both electrostatic and vector magnetic potentials, rather than using the data sets independently or solving for just electrostatic potential, are demonstrated. Specifically, solving for vector magnetic potential improves the specification of field-aligned currents (FACs), and using both data sets together improves the specification of features in regions lacking one type of data (SuperDARN or AMPERE). Additionally, using the data sets together results in a better correspondence between large-scale features in the electrostatic potential distribution and those in the FAC distribution, as compared to using SuperDARN data alone to infer electrostatic potential and AMPERE data alone to infer FACs. Finally, the estimated uncertainty in the results decreases by typically ˜20% when both data sets rather than just one are included.

  10. High-Latitude Ionospheric Imaging using Canadian High Arctic Ionospheric Network (CHAIN)

    NASA Astrophysics Data System (ADS)

    Meziane, K.; Jayachandran, P. T.; Hamza, A. M.; MacDougall, J. W.

    2013-12-01

    Understanding the polar cap dynamics is a fundamental problem in solar-terrestrial physics; any breakthroughs would have to take into account the interactions that take place at the interfaces between the Solar Wind and the Magnetosphere and between the latter and the ionosphere, respectively. Over the past decade a significant number of ground-based GPS receivers and digital ionosondes have been deployed in the polar cap and auroral region. This deployment has allowed the harvest of much needed data, otherwise not available, which in turn helps understand the dynamics of the polar ionospheric regions. A technique, used consistently by researchers in the field, consists of inverting the Total Electron Content (TEC) along the ray path obtained from a system of GPS receivers. In the present study, a combination of tomography and ionosonde data from the CHAIN network is used to examine the dynamics of polar cap patches. First, the TEC derived from GPS receivers through tomographic reconstruction is directly compared with ionosonde data. The comparison includes periods of quite and disturbed geomagnetic activity. We then use the vertical density profiles derived from the CHAIN ionosondes as initial seeds for the reconstruction of the tomographic images of the polar cap regions. Precise electron density peaks obtained through the tomographic reconstruction fall within a range that is consistent with direct CHAIN measurements when certain conditions are met. An assessment of the performance of the resulting combination of GPS and ionosonde data is performed, and conclusions are presented.

  11. A Unified Fluid Model for Low-latitude Ionosphere Turbulence Causes Radiowave Scintillations

    NASA Astrophysics Data System (ADS)

    Hassan, E.; Horton, W.

    2012-12-01

    Nonlinear dynamics of the low latitudes E-layer simulated with a systems of differential equations describing the neutral wind driven Farley-Buneman instability and the density-gradient-drift instability as rising bubbles and falling higher electron density spikes. The simulations extent earlier nonlinear studies by using empirical models for the atmosphere and ionosphere backgrounds to give realistic local time-altitude parameters within a Python wrapped F90 simulations. New equations that keep both the compressional and rotational ion flows that apply in the lower F layer are analyzed to describe plumes extending to the peak of the F layer. A ray-tracing technique is used to describe the small angle scattering at high frequency [Gigahertz] GNSS signals treated as rays in the turbulent ionospheric plasma.

  12. Experimental investigation of mechanisms of mid-latitude ionosphere and geophysical fields perturbation

    NASA Astrophysics Data System (ADS)

    Gavrilov, Boris; Zetzer, Julius; Egorov, Dmitry

    The investigations are carried out to study mechanisms and channels of the mid-latitude ionosphere, near-Earth electric field and current perturbations, and their connection to high-latitude and magnetospheric events. The basis of these investigations is a measurement of the geophysical fields in the Geophysical Observatory Mikhnevo (54.9 N, 37,8 E) of the Institute of Geospheres Dynamics RAS situated at 80 km to the south from Moscow. The observatory includes a set of measuring complexes for radiophysics, magnetic, electrical, optic, infrasound, seismic, and other investigations. All of them are controlled by the united computer centre in the common scale of time. Our approach bases on well known conception that the main reasons of the mid-latitude perturbations are the processes in the auroral regions. But auroral phenomena impact on mid-latitudes by means of different physical mechanisms and agents of disturbances. Fortunately, they differ from each other in the time of their generation and velocities of their propagation. For example, the typical velocity of propagation of thermosphere winds is about 100 m/s, the acoustic gravity wave propagate with a velocity of about 400 m/s, and a prompt penetration of the magnetospheric electric field affects the mid-latitude practically instantly. If we can determine a time lag between the action of the perturbation source and mid-latitude ionosphere response, we can determine the velocity of perturbation propagation and recognize the dominating mechanisms and channels of disturbances. The important requirements for the organization of such investigation is a positioning of different measuring facilities in one place and organization of coordinated and synchronous registration of the ionosphere parameters and geophysical fields variations with high temporal resolution. The Mikhnevo observatory gives us such ability. As an indicator and marker of high latitude events (magnetic storms and substorms) we use AE-index. The

  13. A Comprehensive Assessment of Radio Occultation Ionospheric Measurements at Mid-Latitudes

    NASA Astrophysics Data System (ADS)

    Keele, C.; Brum, C. G. M.; Rodrigues, F. S.; Aponte, N.; Sulzer, M. P.

    2015-12-01

    The GPS radio occultation (RO) has become a widely used technique for global measurements of the ionospheric electron density (Ne). To advance our understanding of the accuracy of the RO profiles at mid latitudes, we performed a comprehensive comparison of RO measurements made by the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) satellites and observations of Ne profiles made by the Arecibo Observatory incoherent scatter radar (ISR). COSMIC is formed by six satellites in circular, 800 km altitude low-Earth orbit (LEO) at 72° inclination. The satellites orbit in their own plane, approximately 24° apart in ascending node. The satellites are equipped with dual-frequency GPS receivers capable of making measurements of the total electron content (TEC) along the signal path and, therefore, RO observations. The Arecibo ISR, located at(18.35°N, 66.75°W; ˜28.25°N dip latitude), operates at a frequency of 430 MHz with a maximum bandwidth of about 1 MHz. The large collecting area provided by the 300 m dish antenna combined with high peak power transmitters (2.0-2.5 MW) allows the radar to make accurate Ne measurements throughout the entire ionospheric F-region and topside heights. We analyzed 74 and 89 days of line feed and Gregorian data, respectively, collected between 2006 and 2014. There were 638 RO profiles measured within 10° of latitude and 20° of longitude from Arecibo Observatory and within ±10 minutes of the radar measurements. Preliminary analyses of the observations show patterns in the relationship between densities measured by the Arecibo ISR and densities estimated from the COSMIC ROs. We will present and discuss the behavior of the patterns. We will also present results of a numerical model representing the patterns and discuss the possibility of using this model to improve RO estimates of density profiles.

  14. Evolution of high latitude ionospheric convection associated with substorms: Multiple radar observations

    NASA Astrophysics Data System (ADS)

    Zou, Shasha

    The work presented in this dissertation concerns evolution of the high latitude ionospheric convection and the relevant current systems associated with substorms, with emphasize on these features near the nightside Harang reversal region. Three different types of radars, including the Super Dual Auroral Radar Network (SuperDARN) coherent-scatter radars, the new advanced modular incoherent-scatter radar at Poker Flat (PFISR), and the Sondrestrom incoherent-scatter radar (ISR), have been utilized. Observations from those radars, together with those from complementary instruments, including satellites and other ground-based instruments, have revealed fundamental new understand of the ionospheric electrodynamic properties associated with substorms. By using the SuperDARN and the PFISR radars, we found that the auroral activity at substorm onset is located in the center of the Harang reversal, which represents a key region in the magnetospheric and ionospheric convection and is part of the Region 2 system. We have also shown that nightside convection flows exhibit repeatable, distinct variations at different locations relative to the substorm-related auroral activity. Taking advantage of the simultaneous flow and ionization measurements from PFISR, a current closure relation has been found between the Region 2 and the substorm field-aligned current systems. These observations demonstrate a strong coupling between the Region 2 system and the substorm dynamics. This study sheds new light on the substorm-related magnetosphere-ionosphere coupling and contributes to the building of a holistic picture of the substorm dynamics. The third radar has been used to study the dayside ionospheric convection response to the external soar wind and IMF driving and its role in substorm dynamics. The results have been applied to study substorm triggering and in the future could be used to study the relation between the external driving and the formation of the Harang reversal.

  15. Theoretical study of the electron temperature in the high-latitude ionosphere for solar maximum and winter conditions

    NASA Technical Reports Server (NTRS)

    Schunk, R. W.; Sojka, J. J.; Bowline, M. D.

    1986-01-01

    The T(e) variation in the high-latitude ionosphere at altitudes between 120 and 800 km has been modeled for solar maximum, winter solstice, and strong magnetic activity conditions. The calculated electron temperatures are consistent with the plasma densities and ion temperatures computed from a time-dependent ionospheric model. Heating rates for both solar EUV and auroral precipitation were included. In general, the predicted UT variation of the electron temperature that results from the displacement between the magnetic and geographic poles is only a few hundred degrees. However, in sunlit trough regions, T(e) hot spots develop, and these hot spots show a marked UT variation, by as much as 2500 K. The dominant parameter controlling the T(e) variation above 200 km is the magnetospheric heat flux into the ionosphere, which is essentially unknown. For realistic values of the magnetospheric heat flux, the maximum electron temperature ranges from 5000 to 10,000 K at 800 km. A magnetospheric heat flux is particularly effective in enhancing trough electron temperatures. In general, the electron heat flux at high altitudes is uniquely related to the electron temperature and gradient, except on auroral field lines where thermoelectric heat flow is important.

  16. A Statistical study of the Doppler spectral width of high-latitude ionospheric F-region echoes recorded with SuperDARN coherent HF radars

    NASA Astrophysics Data System (ADS)

    Villain, J.-P.; André, R.; Pinnock, M.; Greenwald, R. A.; Hanuise, C.

    2002-11-01

    The HF radars of the Super Dual Auroral Radar Network (SuperDARN) provide measurements of the E × B drift of ionospheric plasma over extended regions of the high-latitude ionosphere. We have conducted a statistical study of the associated Doppler spectral width of ionospheric F-region echoes. The study has been conducted with all available radars from the Northern Hemisphere for 2 specific periods of time. Period 1 corresponds to the winter months of 1994, while period 2 covers October 1996 to March 1997. The distributions of data points and average spectral width are presented as a function of Magnetic Latitude and Magnetic Local Time. The databases are very consistent and exhibit the same features. The most stringent features are: a region of very high spectral width, collocated with the ionospheric LLBL/cusp/mantle region; an oval shaped region of high spectral width, whose equator-ward boundary matches the poleward limit of the Holzworth and Meng auroral oval. A simulation has been conducted to evaluate the geometrical and instrumental effects on the spectral width. It shows that these effects cannot account for the observed spectral features. It is then concluded that these specific spectral width characteristics are the signature of ionospheric/magnetospheric coupling phenomena.

  17. The middle and high latitude winter ionosphere at the Ariel 4 satellite altitude

    NASA Technical Reports Server (NTRS)

    Tulunay, Y. K.; Grebowsky, J. M.

    1983-01-01

    The electron (0+) density variations over the northern and southern winter high latitude ionosphere are comprehensively analyzed using the technique of Brinton et al. (1978). Two-hour Magnetic Local Time (MLT) arithmetic means of electron densities are studied in terms of invariant magnetic latitude and in terms of magnetic activity as classified by the three-hour planetary magnetic activity index. It is found that the southern hemisphere densities are significantly lower than those in the northern hemisphere. Further, the maximum electron densities observed in the northern hemisphere are located in a MLT range symmetrical about the 14-02 MLT meridian, whereas in the southern hemisphere the maxima are observed about the noon midnight magnetic meridian. A deep localized ionization hole on the nightside of the polar cap is not observed although the polar cavity is apparent.

  18. Modelling the probability of ionospheric irregularity occurrence over African low latitude region

    NASA Astrophysics Data System (ADS)

    Mungufeni, Patrick; Jurua, Edward; Bosco Habarulema, John; Anguma Katrini, Simon

    2015-06-01

    This study presents models of geomagnetically quiet time probability of occurrence of ionospheric irregularities over the African low latitude region. GNSS-derived ionospheric total electron content data from Mbarara, Uganda (0.60°S, 30.74°E, geographic, 10.22°S, magnetic) and Libreville, Gabon (0.35°N, 9.68°E, geographic, 8.05°S, magnetic) during the period 2001-2012 were used. First, we established the rate of change of total electron content index (ROTI) value associated with background ionospheric irregularity over the region. This was done by analysing GNSS carrier-phases at L-band frequencies L1 and L2 with the aim of identifying cycle slip events associated with ionospheric irregularities. We identified at both stations a total of 699 events of cycle slips. The corresponding median ROTI value at the epochs of the cycle slip events was 0.54 TECU/min. The probability of occurrence of ionospheric irregularities associated with ROTI ≥ 0.5 TECU / min was then modelled by fitting cubic B-splines to the data. The aspects the model captured included diurnal, seasonal, and solar flux dependence patterns of the probability of occurrence of ionospheric irregularities. The model developed over Mbarara was validated with data over Mt. Baker, Uganda (0.35°N, 29.90°E, geographic, 9.25°S, magnetic), Kigali, Rwanda (1.94°S, 30.09°E, geographic, 11.62°S, magnetic), and Kampala, Uganda (0.34°N, 32.60°E, geographic, 9.29°S, magnetic). For the period validated at Mt. Baker (approximately, 137.64 km, north west), Kigali (approximately, 162.42 km, south west), and Kampala (approximately, 237.61 km, north east) the percentages of the number of errors (difference between the observed and the modelled probability of occurrence of ionospheric irregularity) less than 0.05 are 97.3, 89.4, and 81.3, respectively.

  19. Simultaneous observations of large-scale traveling ionospheric disturbances on the nightside and dayside middle latitude

    NASA Astrophysics Data System (ADS)

    Cai, H. T.; Yin, F.; Ma, S. Y.; Xu, J. S.; Liu, Y. W.

    2012-12-01

    In this paper, we present further observational evidence for the transpolar propagation of large-scale traveling ionospheric disturbances (LSTIDs) from their nightside source region to the dayside reported by Cai et al. (2011). Slant total electron content (STEC) observed by longitudinally aligned GPS receiver chains in North American and European sectors was analyzed to demonstrate presences of LSTIDs at both nightside and dayside mid-latitude. Signatures of TID were inferred from phase difference in time series of STEC perturbations (TECP) derived from measurements of ground-based GPS receivers, which are separated by hundreds of kilometers longitudinally. Periods of the daytime and nighttime ionospheric disturbances were estimated to be around 128 min, being in good agreement with that of the transpolar AGW (atmospheric gravity wave) recorded by EISCAT (European Incoherent Scatter Scientific Association)/ESR (EISCAT Svalbard Radar) radars. On the dayside, the LSTID moved equatorward with an average phase speed of ~440 m s-1. In North American sector, however, southward speed of the nighttime LSTID was much slower, being around 160 m s-1. We suggest that the observed daytime and nighttime mid-latitude LSTIDs are likely to have the same source region, being located somewhere at nighttime auroral latitude. Having been launched on the nightside, the waves propagate simultaneously equatorward and poleward. The equatorward-moving waves are recorded by GPS receiver chain in North American sector. The poleward-moving waves, however, cross the polar cap from nightside to dayside and then are detected consecutively at high and mid-latitudes by EISCAT/ESR radars and GPS receiver chains, respectively.

  20. Ionospheric Studies From Low to Sub-Auroral Latitudes Using Geomagnetic Conjugate All-Sky Imagers and Satellite Data

    NASA Astrophysics Data System (ADS)

    Martinis, C. R.; Macinnis, R.; Sullivan, C.; Baumgardner, J. L.; Pfaff, R. F., Jr.; Hairston, M. R.; Mendillo, M.; Taylor, M. J.; Moffat-Griffin, T.; Heelis, R. A.; Wroten, J.; Hickey, D.

    2014-12-01

    Magnetically conjugate all-sky imagers (ASIs) from low to sub-auroral latitudes are used to investigate inter-hemispheric coupling of ionospheric processes including medium scale travelling ionospheric disturbances (MSTIDs) and, at higher latitudes, stable auroral red (SAR) arcs. The chain of imagers operated by Boston University in the American sector provide thermosphere/ionosphere information through the observation of brightness patterns in 630.0 nm airglow simultaneously at both hemispheres. Complementary information was obtained from space-based satellite data (C/NOFS, DMSP, GPS and RBSP). This study aims to present a comprehensive analysis of thermosphere/ionosphere processes and their coupling mechanisms covering L-shell values from ~ 1.1 to ~3.

  1. Response of the low-latitude D region ionosphere to extreme space weather event of 14-16 December 2006

    NASA Astrophysics Data System (ADS)

    Kumar, Sushil; Kumar, Abhikesh; Menk, Frederick; Maurya, Ajeet K.; Singh, Rajesh; Veenadhari, B.

    2015-01-01

    response of the D region low-latitude ionosphere has been examined for extreme space weather event of 14-16 December 2006 associated with a X1.5 solar flare and an intense geomagnetic storm (Dst = -146 nT) using VLF signals from Northwest Cape, Australia (NWC) (19.8 kHz) and Lualualei, Hawaii (callsign NPM) (21.4 kHz) transmitters monitored at Suva (Geographic Coordinates, 18.10°S, 178.40°E), Fiji. Modeling of flare associated amplitude and phase enhancements of NWC (3.6 dB, 223°) and NPM (5 dB, 153°) using Long-Wave Propagation Capability code shows reduction in the D region reflection height (H') by 11.1 km and 9.4 km, and enhancement in ionization gradients described by increases in the exponential sharpness factor (β) by 0.122 and 0.126 km-1, for the NWC and NPM paths, respectively. During the storm the daytime signal strengths of the NWC and NPM signals were reduced by 3.2 dB on 15 and 16 December (for about 46 h) and recovered by 17 December. Modeling for the NWC path shows that storm time values of H' and β were reduced by 1.2 km and 0.06 km-1, respectively. Morlet wavelet analysis of signal amplitudes shows no clearly strong signatures of gravity wave propagation to low latitudes during the main and recovery phases. The reduction in VLF signal strength is due to increased signal attenuation and absorption by the Earth-ionosphere waveguide due to storm-induced D region ionization changes and hence changes in D region parameters. The long duration of the storm effect results from the slow diffusion of changed composition/ionization at D region altitudes compared with higher altitudes in the ionosphere.

  2. A quantitative deconstruction of the morphology of high-latitude ionospheric convection

    NASA Astrophysics Data System (ADS)

    Grocott, A.; Milan, S. E.; Imber, S. M.; Lester, M.; Yeoman, T. K.

    2012-05-01

    We present an analysis of ionospheric convection data derived from velocity measurements made by the Super Dual Auroral Radar Network (SuperDARN). Our analysis uses an established technique for combining the network data to produce maps of large-scale convection by fitting a spherical harmonic expansion of the ionospheric electric potential to the radar measurements. We discuss how the basis functions of the spherical harmonic expansion describe different characteristic elements of the ionospheric convection pattern and show how their associated coefficients can be used to quantify the morphology of the convection, much like the total transpolar voltage is used to quantify its strength, in relation to upstream interplanetary magnetic field conditions and associated magnetospheric activity. We find that ˜2/3 of the voltage associated with the typical convection pattern is described by a simple twin vortex basis function. The magnitude of the twin vortex is strongly dependent on IMF BZ and the degree of its (typically westward) rotation is weakly dependent on IMF BY. The remaining ˜1/3 of the total voltage is associated with deviations from the basic twin vortex pattern, introduced by the addition of other basis functions, such as IMF BY associated dusk-dawn asymmetries, nightside convection features associated with tail activity, and “reverse” high-latitude convection cells associated with intervals of IMF BZ > 0.

  3. Characterization of the Ionospheric Scintillations at High Latitude using GPS Signal

    NASA Astrophysics Data System (ADS)

    Mezaoui, H.; Hamza, A. M.; Jayachandran, P. T.

    2013-12-01

    Transionospheric radio signals experience both amplitude and phase variations as a result of propagation through a turbulent ionosphere; this phenomenon is known as ionospheric scintillations. As a result of these fluctuations, Global Positioning System (GPS) receivers lose track of signals and consequently induce position and navigational errors. Therefore, there is a need to study these scintillations and their causes in order to not only resolve the navigational problem but in addition develop analytical and numerical radio propagation models. In order to quantify and qualify these scintillations, we analyze the probability distribution functions (PDFs) of L1 GPS signals at 50 Hz sampling rate using the Canadian High arctic Ionospheric Network (CHAIN) measurements. The raw GPS signal is detrended using a wavelet-based technique and the detrended amplitude and phase of the signal are used to construct probability distribution functions (PDFs) of the scintillating signal. The resulting PDFs are non-Gaussian. From the PDF functional fits, the moments are estimated. The results reveal a general non-trivial parabolic relationship between the normalized fourth and third moments for both the phase and amplitude of the signal. The calculated higher-order moments of the amplitude and phase distribution functions will help quantify some of the scintillation characteristics and in the process provide a base for forecasting, i.e. develop a scintillation climatology model. This statistical analysis, including power spectra, along with a numerical simulation will constitute the backbone of a high latitude scintillation model.

  4. Prediction of Geomagnetic Activity and Key Parameters in High-Latitude Ionosphere-Basic Elements

    NASA Technical Reports Server (NTRS)

    Lyatsky, W.; Khazanov, G. V.

    2007-01-01

    Prediction of geomagnetic activity and related events in the Earth's magnetosphere and ionosphere is an important task of the Space Weather program. Prediction reliability is dependent on the prediction method and elements included in the prediction scheme. Two main elements are a suitable geomagnetic activity index and coupling function -- the combination of solar wind parameters providing the best correlation between upstream solar wind data and geomagnetic activity. The appropriate choice of these two elements is imperative for any reliable prediction model. The purpose of this work was to elaborate on these two elements -- the appropriate geomagnetic activity index and the coupling function -- and investigate the opportunity to improve the reliability of the prediction of geomagnetic activity and other events in the Earth's magnetosphere. The new polar magnetic index of geomagnetic activity and the new version of the coupling function lead to a significant increase in the reliability of predicting the geomagnetic activity and some key parameters, such as cross-polar cap voltage and total Joule heating in high-latitude ionosphere, which play a very important role in the development of geomagnetic and other activity in the Earth s magnetosphere, and are widely used as key input parameters in modeling magnetospheric, ionospheric, and thermospheric processes.

  5. Features of the F3 layer in the low-latitude ionosphere at sunset

    NASA Astrophysics Data System (ADS)

    Zhao, Biqiang; Wan, Weixing; Reinisch, Bodo; Yue, Xinan; Le, Huijun; Liu, Jing; Xiong, Bo

    2011-01-01

    The F3 layer is a common feature within ±10° of the magnetic equatorial ionosphere in the daytime. According to Balan et al. (1998) the F3 layer occurs mainly during the morning-noon period due to the combined effect of the upward E × B drift and the neutral wind that provides upward plasma drifts at and above the F2 layer. The F3 layer occurrence rate is higher in summer and decreases with increasing solar activity. In this study, the characteristic of the sunset F3 layer is first investigated using a solar cycle of ionosonde data (1995-2010) from the magnetic equatorial station at Jicamarca, and compared with the features derived from the four subtropical stations at Sao Luis, Fortaleza, Kwajalein, and Vanimo. Evidence shows that the local time distribution of the occurrence of the F3 layer can extend to the postsunset time (1800-2100 local time). The sunset F3 layer has a strong seasonal dependence occurring mainly during the summertime. Unlike the daytime F3 layer, the occurrence of the sunset F3 layer clearly increases and the virtual height of the bottom side of the F3 layer statistically increases from 620 to 1000 km with increasing solar activity. In addition, the occurrence of the sunset F3 layer at the other stations is much less than that at Jicamarca. These features of the dependence on the season, solar activity, and latitude are clearly related to the geomagnetic control of the evening prereversal enhancement of the equatorial zonal electric field and geomagnetic configuration.

  6. Ionospheric Irregularities at High Latitudes During Geomagnetic Storms and Substorms: Simultaneous Observations of Magnetic Field Perturbations and GPS Scintillations

    NASA Astrophysics Data System (ADS)

    Kim, H.; Deshpande, K.; Clauer, C. R.; Bust, G. S.; Crowley, G.; Humphreys, T. E.; Kim, L.; Lessard, M.; Weatherwax, A. T.; Zachariah, T. P.

    2012-12-01

    Plasma instability in the ionosphere is often observed as disturbance and distortion of the amplitude and phase of radio signals, which are known as ionospheric scintillations. High-latitude ionospheric plasma, closely connected to solar wind and magnetospheric dynamics, produce very dynamic and short-lived GPS scintillations, making it challenging to characterize them. This study reports simultaneous observations of geomagnetic pulsations and GPS signal scintillations during geomagnetic storms and substorms using a newly designed Autonomous Adaptive Low-Power Instrument Platform (AAL-PIP) installed at the South Pole. A statistical investigation of the AAL-PIP data recorded from January through May 2012 is presented to study local time distribution of scintillation events and a correlation between GPS scintillation and magnetic field perturbations. This report discusses a possible connection between magnetic field perturbations associated with the ionospheric currents and the creation of plasma instability by examining relative contribution of storm/substorm activity to ionospheric irregularities.

  7. Relationship of the interplanetary electric field to the high-latitude ionospheric electric field and currents Observations and model simulation

    NASA Technical Reports Server (NTRS)

    Clauer, C. R.; Banks, P. M.

    1986-01-01

    The electrical coupling between the solar wind, magnetosphere, and ionosphere is studied. The coupling is analyzed using observations of high-latitude ion convection measured by the Sondre Stromfjord radar in Greenland and a computer simulation. The computer simulation calculates the ionospheric electric potential distribution for a given configuration of field-aligned currents and conductivity distribution. The technique for measuring F-region in velocities at high time resolution over a large range of latitudes is described. Variations in the currents on ionospheric plasma convection are examined using a model of field-aligned currents linking the solar wind with the dayside, high-latitude ionosphere. The data reveal that high-latitude ionospheric convection patterns, electric fields, and field-aligned currents are dependent on IMF orientation; it is observed that the electric field, which drives the F-region plasma curve, responds within about 14 minutes to IMF variations in the magnetopause. Comparisons of the simulated plasma convection with the ion velocity measurements reveal good correlation between the data.

  8. Modelling of ionospheric irregularities during geomagnetic storms over African low latitude region

    NASA Astrophysics Data System (ADS)

    Mungufeni, Patrick

    2016-07-01

    In this study, empirical models of occurrence of ionospheric irregularities over low latitude African region during geomagnetic storms have been developed. The geomagnetic storms considered consisted of Dst ≤ -50 nT. GNSS-derived ionospheric Total Electron Content (TEC) data over Libreville, Gabon (NKLG) (0.35° N, 9.68° E, geographic, 8.05° S, magnetic) and Malindi, Kenya (MAL2) (2.99° S, 40.19° E, geographic, 12.42° S, magnetic) during 2000 - 2014 were used. Ionospheric irregularities at scale- lengths of a few kilometers and ˜400 m were represented with the rate of change of TEC index (ROTI). The inputs for the models are the local time, solar flux index, Auroral Electrojet index, day of the year, and the Dst index, while the output is the median ROTI during these given conditions. To develop the models, the ROTI index values were binned based on the input parameters and cubic B splines were then fitted to the binned data. Developed models using data over NKLG and MAL2 were validated with independent data over stations within 510 km and 680 km radius, respectively. The models captured the enhancements and inhibitions of the occurrence of the ionospheric irregularities during the storm period. The models even emulated these patterns in the various seasons, during medium and high solar activity conditions. The correlation coefficients for the validations were statistically significant and ranged from 0.58 - 0.73, while the percentage of the variance in the observed data explained by the modelled data ranged from 34 - 53.

  9. F-region ionospheric perturbations in the low-latitude ionosphere during the geomagnetic storm of 25-27 August 1987

    NASA Astrophysics Data System (ADS)

    Pavlov, A.; Fukao, S.; Kawamura, S.

    2004-10-01

    We have presented a comparison between the modeled NmF2 and hmF2, and NmF2 and hmF2 which were observed at the equatorial anomaly crest and close to the geomagnetic equator simultaneously by the Akita, Kokubunji, Yamagawa, Okinawa, Manila, Vanimo, and Darwin ionospheric sounders and by the middle and upper atmosphere (MU) radar (34.85° N, 136.10° E) during the 25-27 August 1987 geomagnetically storm-time period at low solar activity near 201°, geomagnetic longitude. A comparison between the electron and ion temperatures measured by the MU radar and those produced by the model of the ionosphere and plasmasphere is presented. The corrections of the storm-time zonal electric field, EΛ, from 16:30 UT to 21:00 UT on 25 August bring the modeled and measured hmF2 into reasonable agreement. In both hemispheres, the meridional neutral wind, W, taken from the HWW90 wind model and the NRLMSISE-00 neutral temperature, Tn, and densities are corrected so that the model results agree with the ionospheric sounders and MU radar observations. The geomagnetic latitude variations in NmF2 on 26 August differ significantly from those on 25 and 27 August. The equatorial plasma fountain undergoes significant inhibition on 26 August. This suppression of the equatorial anomaly on 26 August is not due to a reduction in the meridional component of the plasma drift perpendicular to the geomagnetic field direction, but is due to the action of storm-time changes in neutral winds and densities on the plasma fountain process. The asymmetry in W determines most of the north-south asymmetry in hmF2 and NmF2 on 25 and 27 August between about 01:00-01:30 UT and about 14:00 UT when the equatorial anomaly exists in the ionosphere, while asymmetries in W, Tn, and neutral densities relative to the geomagnetic equator are responsible for the north-south asymmetry in NmF2 and hmF2 on 26 August. A theory of the primary mechanisms causing the morning and evening peaks in the electron temperature, Te, is

  10. Large-scale traveling ionospheric disturbances observed using GPS receivers over high-latitude and equatorial regions

    NASA Astrophysics Data System (ADS)

    Idrus, Intan Izafina; Abdullah, Mardina; Hasbi, Alina Marie; Husin, Asnawi; Yatim, Baharuddin

    2013-09-01

    This paper presents the first results of large-scale traveling ionospheric disturbances (LSTIDs) observation during two moderate magnetic storm events on 28 May 2011 (SYM-H∼ -94 nT and Dst∼-80 nT) and 6 August 2011 (SYM-H∼-126 nT and Dst∼-113 nT) over the high-latitude region in Russia, Sweden, Norway, Iceland and Greenland and equatorial region in the Peninsular Malaysia using vertical total electron content (VTEC) from the Global Positioning System (GPS) observations measurement. The propagation of the LSTID signatures in the GPS TEC measurements over Peninsular Malaysia was also investigated using VTEC map. The LSTIDs were found to propagate both equatorward and poleward directions during these two events. The results showed that the LSTIDs propagated faster at high-latitude region with an average phase velocity of 1074.91 m/s than Peninsular Malaysia with an average phase velocity of 604.84 m/s. The LSTIDs at the high-latitude region have average periods of 150 min whereas the ones observed over Peninsular Malaysia have average periods of 115 min. The occurrences of these LSTIDs were also found to be the subsequent effects of substorm activities in the auroral region. To our knowledge, this is the first result of observation of LSTIDs over Peninsular Malaysia during the 24th solar cycle.

  11. 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.

  12. Statistical Analysis of Ionospheric Storms on GPS TEC measurements between 2000 and 2014 in mid-latitude

    NASA Astrophysics Data System (ADS)

    Chung, J. K.

    2015-12-01

    The ionospheric storms that may generate the spatial/temporal gradient or irregularities of electron densities are very interest phenomena for two reasons. First, they occur by the increasing solar EUV/X-ray fluxes as well as by the equatorward or poleward plasma transportations by the global changes of the neutral winds and electric fields responded to geomagnetic storms. Second, they have been the practical interests in the satellite navigations and radio communications, especially in the mid-latitudes of the dense population regions in these days though ionosphere in mid-latitudes is quiet compared with high and low latitudes. In this presentation, the statistical analysis of the occurrences of the ionospheric storms in Korea are presented. They are examined from Korea GPS TEC dataset between 2000 and 2014 over the full-solar cycle coverage. We examine the two super geomagnetic storms cases of 29-31 October 2003 and 8-10 November 2004 to discuss the possible physical mechanisms for ionospheric storm of positive and negative phases and their affection on GPS positioning. The parameters to define the ionospheric storms are suggested to increase our understanding of their physical characteristic and then to apply the practical cases.

  13. Impact of the 15 January 2010 annular solar eclipse on the equatorial and low latitude ionosphere over the Indian region

    NASA Astrophysics Data System (ADS)

    Panda, S. K.; Gedam, S. S.; Rajaram, G.; Sripathi, S.; Bhaskar, A.

    2015-12-01

    The annular solar eclipse of 15 January 2010 over southern India was studied with a multi-instrument network consisting of magnetometer, ionosonde and GPS receivers. The presence of a counter electrojet (weakened or westward zonal electric field) during the eclipse and adjacent days suggests the strong gravitational tidal effect associated with the exceptional Sun-Moon-Earth alignment around the eclipse day. With a strong backup of magnetometer recordings on the day of eclipse, its adjacent days and the normal electrojet day, it is argued that the regular eastward electric field for the whole day at the equator was not just weakened, but actually was flipped for several hours by the influence of enhanced lunar tides. The effect of flipping the electric field was clearly seen in the equatorial ionosonde data and through the large array of GPS receivers that produced the total electron content (TEC) data. The main impact of flipping the electric field was poor feeding of equatorial ionization anomaly (EIA) due to the severely weakened fountain effect on the eclipse day, with the regular anomaly crest shifting towards the equator. The equatorial ionosonde profile was also showing an enhanced F2 region peak in spite of a reduced vertical TEC. While the plasma density depletion at the lower F region altitude over the equator was due to the temporary lack of photo-ionization, the reductions in high altitude plasma density beyond the equator were caused by the electrodynamics taking place around the eclipse. The important finding of this analysis is that the electrodynamical consequences on the low latitude ionosphere were mainly due to the combination of eclipse and lunar tides which were far more significant and influenced the EIA density rather than eclipse alone. Based on these findings, it is argued that the prevailing lunar tidal impact also needs to be taken into account while seeking to understand the electrodynamical impact of the solar eclipse on the low

  14. Characteristics of High-latitude and Equatorial Ionospheric Scintillation of GNSS Signals

    NASA Astrophysics Data System (ADS)

    Morton, Y.; Jiao, Y.

    2014-12-01

    In this paper, several years of multi-constellation global navigation satellite scintillation data collected at Alaska, Peru, and Ascension Island are analyzed to characterize scintillation features observed at high latitude and equatorial locations during the current solar maximum. Recognizing that strong scintillation data are often lost due to the lack of robustness in conventional GPS receivers used for ionosphere scintillation monitoring (ISM), an autonomous event driven scintillation data collection system using software-defined raw RF sampling devices have been developed deployed at a number of strategically selected high latitude and equatorial locations since 2009. This unique scintillation data recording system is triggered by indicators computed from a continuously operating ISM receiver and the raw RF data is post processed using advanced receiver signal processing algorithms designed to minimize carrier phase cycle slips and loss of lock of signals during strong scintillations. Based on scintillation events extracted from the raw data, several statistical distributions are established to characterize the intensity, duration and occurrence frequency of scintillation. Results confirm that scintillation at low latitudes is generally more intense and longer lasting, while high-latitude scintillation is milder and usually dominated by phase fluctuations. Results also reveal the impacts of solar activity, geomagnetic activity and seasons on scintillation in different areas. Combining measurements from a co-located geo-magnetometer and corresponding global geomagnetic activities, qualitative and quantitative correlations between scintillation and both local and global geomagnetic activities have been obtained. Results show that in Alaska, the occurrence frequency and intensity of scintillation, especially phase fluctuations, have strong correlations with geomagnetic field intensity disturbances, while in equatorial stations, the correlation is not obvious.

  15. Prediction of the level of ionospheric scintillation at equatorial latitudes in Brazil using a neural network

    NASA Astrophysics Data System (ADS)

    Lima, G. R. T.; Stephany, S.; Paula, E. R.; Batista, I. S.; Abdu, M. A.

    2015-08-01

    Electron density irregularity structures, often associated with ionospheric plasma bubbles, drive amplitude and phase fluctuations in radio signals that, in turn, create a phenomenon known as ionospheric scintillation. The phenomenon occurs frequently around the magnetic equator where plasma instability mechanisms generate postsunset plasma bubbles and density depletions. A previous correlation study suggested that scintillation at the magnetic equator may provide a forecast of subsequent scintillation at the equatorial ionization anomaly southern peak. In this work, it is proposed to predict the level of scintillation over São Luís (2.52°S, 44.3°W; dip latitude: ~2.5°S) near the magnetic equator with lead time of hours but without specifying the moment at which the scintillation starts or ends. A collection of extended databases relating scintillation to ionospheric variables for São Luís is employed to perform the training of an artificial neural network with a new architecture. Two classes are considered, not strong (null/weak/moderate) and strong scintillation. An innovative scheme preprocesses the data taking into account similarities of the values of the variables for the same class. A formerly proposed resampling heuristic is employed to provide a balanced number of tuples of each class in the training set. Tests were performed showing that the proposed neural network is able to predict the level of scintillation over the station on the evening ahead of the data sample considered between 17:30 and 19:00 LT.

  16. Probe experiment characterizing 30-MHz radio wave scatter in the high-latitude ionosphere

    NASA Astrophysics Data System (ADS)

    Nishino, M.; Gorokhov, N.; Tanaka, Y.; Yamagishi, H.; Hansen, T.

    1999-07-01

    A probe experiment, consisting of radio links between a common 30-MHz transmitter located at Murmansk, Russia, and two receivers used as the imaging riometer (two-dimensional 64 multiple-beam antenna) located at Ny Ålesund, Svalbard, and Tjornes, Iceland, was carried out to characterize wave scatter in the high-latitude ionosphere. They are nearly aligned with and perpendicular to the geomagnetic meridian, respectively. In experiments conducted in March-April 1994, the 30-MHz probe signals were identified at nighttime more frequently than during the day at both receiver stations during periods of increased geomagnetic activity near the path midpoints, indicating that a relationship between the propagation path and the location of the auroral oval controls signal identification. For the nighttime propagation paths within or crossing through the auroral oval, duty cycles of the probe signals were roughly correlated with increases in geomagnetic activity. Their arrival directions showed a spread with a dominant power on the low elevation and a normal distribution in azimuth. These results indicate that the probe signals are characterized as nonmeteoric "auroral E" scatter caused by irregular, large-scale profiles of electron density enhancements at the lower edge of the ionosphere. However, on 2 days of weak geomagnetic activity, strong probe signals with bursty behavior were identified by an extremely high duty cycle (˜98%) for the nighttime meridian path only, and their arrival directions showed an isotropic spread in azimuth. Such nonmeteoric probe signals are characterized as "coherent" scatter caused by small-scale (˜5 m) field-aligned irregularities in electron density in the E region ionosphere, related to "sporadic E" occurrence.

  17. Space Weather Studies Using the Low-Latitude Ionospheric Sensor Network (LISN)

    NASA Astrophysics Data System (ADS)

    Valladares, C. E.; Pacheco, E.

    2014-12-01

    LISN is an array of small instruments that operates as a real-time distributed observatory to understand the complex day-to-day variability and the extreme state of disturbance that occurs in the South American low-latitude ionosphere nearly every day after sunset. The LISN observatory aims to forecast the initiation and transport of plasma bubbles across the South American continent. The occurrence of this type of plasma structures and their embedded irregularities poses a prominent natural hazard to communication, navigation and high precision pointing systems. As commercial and military aviation is increasingly reliant on Global Navigation Satellite Systems (GNSS) any interruption due to ionospheric irregularities or errors due to large density gradients constitutes a serious threat to passengers and crew. Therefore, it is important to understand the conditions and sources that contribute to the formation of these irregularities. To achieve high quality regional nowcasts and forecasts, the LISN system was designed to include a dense coverage of the South American landmass with 47 GPS receivers, 5 flux-gate magnetometers distributed on 2 base lines and 3 Vertical Incidence Pulsed Ionospheric Radar (VIPIR) ionosondes deployed along the same magnetic meridian that intersects the magnetic equator at 68° W. This presentation will provide a summary of recent instrument installations and new processing techniques that have been developed under the LISN project. We will also present the results of recent efforts to detect TIDs and TEC plasma depletions on a near real-time basis. We will describe a method to estimate the zonal velocity and tilt of the plasma bubbles/depletions by combining observations of TEC depletions acquired with adjacent receivers, making it possible to predict precisely their future locations.

  18. Inverse procedure for high-latitude ionospheric electrodynamics: Analysis of satellite-borne magnetometer data

    NASA Astrophysics Data System (ADS)

    Matsuo, Tomoko; Knipp, Delores J.; Richmond, Arthur D.; Kilcommons, Liam; Anderson, Brian J.

    2015-06-01

    This paper presents an analysis of data from the magnetometers on board the Defense Meteorological Satellite Program (DMSP) F-15, F-16, F-17, and F-18 satellites and the Iridium satellite constellation, using an inverse procedure for high-latitude ionospheric electrodynamics, during the period of 29-30 May 2010. The Iridium magnetometer data are made available through the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE) program. The method presented here is built upon the assimilative mapping of ionospheric electrodynamics procedure but with a more complete treatment of the prior model uncertainty to facilitate an optimal inference of complete polar maps of electrodynamic variables from irregularly distributed observational data. The procedure can provide an objective measure of uncertainty associated with the analysis. The cross-validation analysis, in which the DMSP data are used as independent validation data sets, suggests that the procedure yields the spatial prediction of DMSP perturbation magnetic fields from AMPERE data alone with a median discrepancy of 30-50 nT. Discrepancies larger than 100 nT are seen in about 20% of total samples, whose location and magnitude are generally consistent with the previously identified discrepancy between DMSP and AMPERE data sets. Resulting field-aligned current (FAC) patterns exhibit more distinct spatial patterns without spurious high-frequency oscillatory features in comparison to the FAC products provided by AMPERE. Maps of the toroidal magnetic potential and FAC estimated from both AMPERE and DMSP data under four distinctive interplanetary magnetic field (IMF) conditions during a magnetic cloud event demonstrate the IMF control of high-latitude electrodynamics and the opportunity for future scientific investigation.

  19. Ground-satellite conjugate observations of low-latitude travelling ionospheric disturbances

    NASA Astrophysics Data System (ADS)

    Ceren Moral, Aysegul; Shiokawa, Kazuo; Otsuka, Yuichi; Suzuki, Shin; Liu, Huixin; Yatini, Clara

    2016-07-01

    Equatorial travelling ionospheric disturbances (TIDs) are studied by using three CHAMP satellite overpasses on ground-based 630-nm airglow images. The airglow images are obtained from Kototabang (KTB), Indonesia (geographic coordinates: 0.2S, 100.3E, geomagnetic latitude: 10.6S). From 7-year data from October 2002 to October 2009, April 30, 2006 (event 1), September 28, 2006 (event 2) and April 12, 2004 (event 3) are the only TID events found in both ground and satellite measurements. They show southward-moving structures in 630-nm airglow images. The events 1 and 2 are single pulse with horizontal scales of ~500-1000 km and event 3 show three wave fronts with horizontal scale sizes of 500-700 km. For events 1 and 3, the neutral density in CHAMP shows out-of-phase variations with the airglow intensity, while event 2 is in-phase. For event 1, the relation between electron density and airglow intensity is out of phase, while relationships of event 2 and 3 are unclear. These unclear relationships suggest that ionospheric plasma variation is not the cause of the TIDs. In the case if gravity waves in the thermosphere is the source of the observed TIDs, in-phase and out-of-phase relationships of neutral density and airglow intensity can be explained by different vertical wavelengths of the gravity wave. We estimate possible vertical wavelengths for those events using observed wave parameters and modeled neutral winds.

  20. High-latitude ionospheric irregularities: differences between ground- and space-based GPS measurements during the 2015 St. Patrick's Day storm

    NASA Astrophysics Data System (ADS)

    Cherniak, Iurii; Zakharenkova, Irina

    2016-07-01

    We present an analysis of ionospheric irregularities at high latitudes during the 2015 St. Patrick's Day storm. Our study used measurements from ~2700 ground-based GPS stations and GPS receivers onboard five low earth orbit (LEO) satellites—Swarm A, B and C, GRACE and TerraSAR-X—that had close orbit altitudes of ~500 km, and the Swarm in situ plasma densities. An analysis of the rate of TEC index (ROTI) derived from LEO-GPS data, together with Swarm in situ plasma probe data, allowed us to examine the topside ionospheric irregularities and to compare them to the main ionospheric storm effects observed in ground-based GPS data. We observed strong ionospheric irregularities in the topside ionosphere during the storm's main phase that were associated with storm-enhanced density (SED) formation at mid-latitudes and further evolution of the SED plume to the polar tongue of ionization (TOI). Daily ROTI maps derived from ground-based and LEO-GPS measurements show the pattern of irregularities oriented in the local noon-midnight direction, which is a signature of SED/TOI development across the polar cap region. Analysis of the Swarm in situ plasma measurements revealed that, during the storm's main phase, all events with extremely enhanced plasma densities (>106 el/cm3) in the polar cap were observed in the Southern Hemisphere. When Swarm satellites crossed these enhancements, degradation of GPS performance was observed, with a sudden decrease in the number of GPS satellites tracked. Our findings indicate that polar patches and TOI structures in the topside ionosphere were predominantly observed in the Southern Hemisphere, which had much higher plasma densities than the Northern Hemisphere, where SED/TOI structures have already been reported earlier. LEO-GPS data (ROTI and topside TEC) were consistent with these results.

  1. Goose Bay radar observations of Earth-reflected, atmospheric gravity waves in the high-latitude ionosphere

    SciTech Connect

    Samson, J.C.; Greenwald, R.A.; Ruohoniemi, J.M.; Frey, A.; Baker, K.B. )

    1990-06-01

    In the late fall and early winter, The Johns Hopkins University HF radar at Goose Bay, Labrador, observes the effects of atmospheric gravity waves on radar transmissions that are obliquely reflected from the ionosphere and subsequently backscattered from the Earth's surface. The waves exist under a wide variety of geomagnetic conditions; however, they are particularly noticeable under quiet conditions (O {le} Kp {le} 1 +). The clearest signatures of the waves are spatially localized enhancements in the backscattered power and quasi-periodic fluctuations in the backscatter powers, Doppler velocities, and reflection heights. The waves are generally observed during daylight hours and propagate equatorward from regions of high-latitude ionospheric backscatter that are located near the ionospheric convection reversal boundary. The gravity waves appear to be generated just equatorward of the dayside flow-reversal boundary in the vicinity of the auroral electrojet at altitudes of 115 to 135 km and propagate approximately perpendicular to the boundary along azimuths ranging from 156{degree} to 180{degree}. The waves propagate obliquely downward through the lower atmosphere until they are reflected by the Earth's surface back into the upper atmosphere. The frequencies associated with these gravity waves cover the range of 0.3 to 0.6 mHz, with wavelengths of 300 to 500 km, and with average phase velocities of 110 to 180 m/s. The maximum phase speeds are 270 to 300 m/s, which is slightly less than the speed of sound in the lower atmosphere. Poleward-propagating gravity waves are sometimes observed under disturbed conditions when the polar cap and convection reversal boundary have expanded equatorward.

  2. High-latitude currents and their energy exchange with the ionosphere-thermosphere system

    NASA Astrophysics Data System (ADS)

    Thayer, J. P.

    2000-10-01

    The transfer of electrical energy at high latitudes between the magnetosphere and ionosphere-thermosphere (IT) system is contained within the resulting currents and electric fields between the two systems. As such, the electrodynamic state of the IT system can influence how much of the electrical energy is transferred at any one time by modulating the currents that flow in the region. For this study, 1557 hours of detailed E region measurements by the Sondrestrom incoherent-scatter radar from 1993 through 1998 were collected, of which 95 hours were used to determine the local electromagnetic energy transfer rates within the IT system and evaluate the role of the IT system in modifying this energy transfer. The measurements have been organized into 59 periods of enhanced electrical energy transfer and cover all universal times but are local to the region above Sondrestrom at 74.2° magnetic latitude. In many of the events studied it was found that the IT system acted to reduce the net electromagnetic energy transferred from the magnetosphere owing to the presence of neutral winds. The dawn sector proved to have on average greater passive energy deposition rates than in the dusk sector. The reduction of this rate by neutral winds also proved stronger in the dawn sector. This enhanced modulation caused the dawn-dusk asymmetry in energy transfer to be less pronounced but still apparent in the electromagnetic energy transfer rate.

  3. Plasma and convection reversal boundary motions in the high-latitude ionosphere

    NASA Astrophysics Data System (ADS)

    Chen, Y.-J.; Heelis, R. A.; Cumnock, J. A.

    2016-06-01

    In this paper we present a statistical study of the high-latitude ionospheric plasma motion at the convection reversal boundary (CRB) and its dependence on the location of the CRB and the interplanetary magnetic field (IMF) orientation by using the Defense Meteorological Satellite Program (DMSP) F13 and F15 measurements over the period from 2000 to 2007. During periods of stable southward IMF, we find a smaller variability in plasma drifts across the CRB over a 4 h segment in magnetic local time (MLT) around dawn and dusk compared to that for variable IMF. Across these segments, the plasma motion at the CRB is directed poleward at local times closer to local noon and equatorward at local times closer to midnight on both the dawn and dusk sides with a total potential drop ~10 kV, suggesting that the CRB behaves much like an adiaroic line. For variable IMF with no stability constraint, we see a relatively narrow distribution of plasma drifts across the CRB only in the 6-7 h and 17-18 h MLT and equatorward/poleward motions of the CRB when the CRB is located at the highest/lowest latitudes. The smaller local time extent of the adiaroic line for variable IMF (~1 h) may be associated with rotation of the dayside merging gap in local time or local contractions and expansions of the polar cap boundary.

  4. Observations of very-high-latitude ionospheric irregularities with the Goose Bay HF (high frequency) radar

    SciTech Connect

    Greenwald, R.A.; Baker, K.B.

    1985-06-07

    The Goose Bay HF radar is a sophisticated instrument capable of providing detailed information on very-high-latitude E- and F-region ionospheric electron-density irregularities which act as a source of clutter on OTH radar systems. Through the use of two parallel phased-array antennas, this instrument is able to image the location of these irregularities within a three-dimensional volume covering much of northeastern Canada and Greenland. It is also capable of following the temporal variability of these irregularities as well as determining unambiguously the Doppler shift and broadening of radar signals scattered by them. This paper presents initial results with a single phased-array antenna, which represent typical examples of the spatial intensity distribution of these irregularities at different local times. Examples are presented of Doppler spectra of the irregularities at different local times. Data of this type are of appreciable value in ascertaining the techniques that must be utilized to improve clutter mitigation on high-latitude radar systems.

  5. C/NOFS Measurements of Magnetic Perturbations in the Low-Latitude Ionosphere During Magnetic Storms

    NASA Technical Reports Server (NTRS)

    Le, Guan; Burke, William J.; Pfaff, Robert F.; Freudenreich, Henry; Maus, Stefan; Luhr, Hermann

    2011-01-01

    The Vector Electric Field Investigation suite on the C/NOFS satellite includes a fluxgate magnetometer to monitor the Earth s magnetic fields in the low-latitude ionosphere. Measurements yield full magnetic vectors every second over the range of +/-45,000 nT with a one-bit resolution of 1.37 nT (16 bit A/D) in each component. The sensor s primary responsibility is to support calculations of both V x B and E x B with greater accuracy than can be obtained using standard magnetic field models. The data also contain information about large-scale current systems that, when analyzed in conjunction with electric field measurements, promise to significantly expand understanding of equatorial electrodynamics. We first compare in situ measurements with the POMME (Potsdam Magnetic Model of the Earth) model to establish in-flight sensor "calibrations" and to compute magnetic residuals. At low latitudes the residuals are predominately products of the storm time ring current. Since C/NOFS provides a complete coverage of all local times every 97 min, magnetic field data allow studies of the temporal evolution and local time variations of storm time ring current. The analysis demonstrates the feasibility of using instrumented spacecraft in low-inclination orbits to extract a timely proxy for the provisional Dst index and to specify the ring current s evolution.

  6. C/NOFS Measurements of Stormtime Magnetic Perturbations in the Low-latitude Ionosphere

    NASA Technical Reports Server (NTRS)

    Le, Guan; Burke, William J.; Pfaff, Robert F.; Freudenreich, Henry; Maus, Stefan; Luehr, Hermann

    2012-01-01

    The Vector Electric Field Investigation suite on the C/NOFS satellite includes a fluxgate magnetometer to monitor the Earth's magnetic fields in the low-latitude ionosphere. Measurements yield full magnetic vectors every second over the range of +/- 45,000 nT with a one-bit resolution of 1.37 nT (16 bit AID) in each component. The sensor's primary responsibility is to support calculations of both VxB and ExB with greater accuracy than can be obtained using standard magnetic field models. The data also contain information about large-scale current systems, that, when analyzed in conjunction with electric field measurements, promise to significantly expand understanding of equatorial electrodynamics. We first compare in situ measurements with the POMME (POtsdam Magnetic Model of the Earth) model to establish in-flight sensor "calibrations" and to compute magnetic residuals. At low latitudes the residuals are predominately products of the stormtime ring current. Since C/NOFS provides a complete coverage of all local times every 97 minutes, magnetic field data allow studies of the temporal evolution and local-time variations of stormtime ring current. The analysis demonstrates the feasibility of using instrumented spacecraft in low-inclination orbits to extract a timely proxy for the provisional Dst index and to specify the ring current's evolution.

  7. Ionospheric response to magnetic activity at low and mid-latitude stations

    NASA Astrophysics Data System (ADS)

    Adebiyi, Shola; Adimula, Isaac; Oladipo, Olusola; Joshua, Benjamin; Adebesin, Babatunde; Ikubanni, Stephen

    2014-08-01

    The F2-layer response to the moderate storm of 5-7 April 2010 was investigated using data from two equatorial stations (Ilorin: lat. 8.5°N, 4.5°E; Kwajalein: lat. 9°N, long. 167.2°E) and mid-latitude (San Vito: lat. 40.6°N, long. 17.8°E; Pruhonice: lat. 50°N, long. 14.6°E). Before storm commencement, enhancement, and depletion of NmF2 values were observed in the equatorial and mid-latitude stations, respectively, indicating the latitudinal dependence of the pre-storm event. All the stations with the exception of Kwajalein show positive phase in NmF2 response at the storm onset stage. Positive phase in NmF2 continues over Ilorin and appears on the daytime ionosphere of Kwajalein on 6 April, whereas negative phase suppressed the positive feature in Pruhonice and San Vito until the recovery condition. The differences in the response of F2-layer to the storm for the two equatorial stations were attributed to their longitudinal differences. On the average, both the AE and D st indices revealed poor correlation relationship. More studies are required to ascertain this finding.

  8. High-latitude topside ionospheric vertical electron density profile changes in response to large magnetic storms

    NASA Astrophysics Data System (ADS)

    Benson, Robert F.; Fainberg, Joseph; Osherovich, Vladimir A.; Truhlik, Vladimir; Wang, Yongli; Bilitza, Dieter; Fung, Shing F.

    2016-05-01

    Large magnetic-storm-induced changes were detected in high-latitude topside vertical electron density profiles Ne(h) in a database of profiles and digital topside ionograms, from the International Satellites for Ionospheric Studies (ISIS) program, that enabled Ne(h) profiles to be obtained in nearly the same region of space before, during, and after a major magnetic storm (Dst < -100 nT). Storms where Ne(h) profiles were available in the high-latitude Northern Hemisphere had better coverage of solar wind parameters than storms with available Ne(h) profiles in the high-latitude Southern Hemisphere. Large Ne(h) changes were observed during all storms, with enhancements and depletions sometimes near a factor of 10 and 0.1, respectively, but with substantial differences in the responses in the two hemispheres. Large spatial and/or temporal Ne(h) changes were often observed during Dst minimum and during the storm recovery phase. The storm-induced Ne(h) changes were the most pronounced and consistent in the Northern Hemisphere in that large enhancements were observed during winter nighttime and large depletions during winter and spring daytime. The limited available cases suggested that these Northern Hemisphere enhancements increased with increases of the time-shifted solar wind velocity v, magnetic field B, and with more negative values of the B components except for the highest common altitude (1100 km) of the profiles. There was also some evidence suggesting that the Northern Hemisphere depletions were related to changes in the solar wind parameters. Southern Hemisphere storm-induced enhancements and depletions were typically considerably less with depletions observed during summer nighttime conditions and enhancements during summer daytime and fall nighttime conditions.

  9. Two-dimensional ionospheric tomography over the low-latitude Indian region: An intercomparison of ART and MART algorithms

    NASA Astrophysics Data System (ADS)

    Das, Sukanta Kumar; Shukla, Ashish Kumar

    2011-04-01

    Single-frequency users of a satellite-based augmentation system (SBAS) rely on ionospheric models to mitigate the delay due to the ionosphere. The ionosphere is the major source of range and range rate errors for users of the Global Positioning System (GPS) who require high-accuracy positioning. The purpose of the present study is to develop a tomography model to reconstruct the total electron content (TEC) over the low-latitude Indian region which lies in the equatorial ionospheric anomaly belt. In the present study, the TEC data collected from the six TEC collection stations along a longitudinal belt of around 77 degrees are used. The main objective of the study is to find out optimum pixel size which supports a better reconstruction of the electron density and hence the TEC over the low-latitude Indian region. Performance of two reconstruction algorithms Algebraic Reconstruction Technique (ART) and Multiplicative Algebraic Reconstruction Technique (MART) is analyzed for different pixel sizes varying from 1 to 6 degrees in latitude. It is found from the analysis that the optimum pixel size is 5° × 50 km over the Indian region using both ART and MART algorithms.

  10. Investigation of natural and artificial stimulation of the ionospheric Alfvén resonator at high latitude

    NASA Astrophysics Data System (ADS)

    Yeoman, T. K.; Scoffield, H. C.; Wright, D. M.; Baddeley, L. J.; Vasilyev, A. N.; Semenova, N. V.

    2008-09-01

    A brief review is provided of recent progress in understanding the ionospheric Alfvén resonator (IAR) at high latitude. Firstly, naturally occurring resonances of the IAR as detected by pulsation magnetometers in the auroral zone at Sodankylä and in the polar cap at Barentsburg are considered. The characteristics of the IAR in the two regions are broadly similar, although the effects of solar illumination are less clear at the higher latitudes. Secondly we review recent attempts to stimulate the IAR through high-power radio frequency experiments both in the auroral zone at Tromsø with the European Incoherent SCATter (EISCAT) heater, and within the polar cap at Longyearbyen with the Space Plasma Exploration by Active Radar (SPEAR) facility. In the auroral zone at, Tromsø the stimulated IAR has been observed by ground-based magnetometers, and through electron acceleration observed on the FAST spacecraft. At SPEAR in the polar cap, the stimulated IAR has been investigated, with ground magnetometers, with the first results indicative of a positive detection.

  11. Ionospheric Response to the 2009 Sudden Stratospheric Warming over the Equatorial, Low- and Mid-Latitudes in American Sector.

    NASA Astrophysics Data System (ADS)

    Fagundes, P. R.; Goncharenko, L. P.; de Abreu, A. J.; Gende, M.; de Jesus, R.; Pezzopane, M.; Kavutarapu, V.; Coster, A. J.; Pillat, V. G.

    2014-12-01

    The equatorial and low-latitude ionosphere/thermosphere system is predominantly disturbed by waves (MSTIDs, tides, and planetary waves), which are generated in the lower atmosphere or in-situ, as well as electric fields and TIDs produced by geomagnetic storm and UV, EUV, and X-ray solar radiation. For many years, it was thought that, during geomagnetic quiet conditions, the equatorial and low-latitude F-layer was mainly perturbed by waves that were generated not far away from the observed location or electric fields generated by the Equatorial Electroject (EEJ). On the contrary, during geomagnetic storms when the energy sources are in high latitudes the waves (TIDs) travel a very long distance from high latitude to equatorial region and electric fields can be mapped via magnetic field lines. However, in the recent times an unexpected coupling between high latitude, mid- latitude, and equatorial/low latitudes was discovered during sudden stratospheric warming (SSW) events. All aspects involved in this process must be explored in order to improve our knowledge about the Earth´s atmosphere. The present study investigates the consequences of vertical coupling from lower to the upper atmosphere in the equatorial and low-latitude ionosphere in Southern Hemisphere during a major SSW event, which took place during January-February 2009 in the Northern Hemisphere. Using seventeen ground-based dual-frequency GPS stations and two ionosonde stations spanning from latitude 2.8oN to 53.8oS and from longitude 36.7oW to 67.8oW over the South American sector, it has been observed that the ionosphere was significantly disturbed by the SSW event from Equator to the mid-latitudes. Using one GPS station located in mid-latitude (South America sector) it is reported for the first time that the mid-latitude in southern hemisphere (American Sector) was disturbed by the SSW event in the Northern hemisphere. The VTEC at all 17 GPS and two ionosonde stations show significant deviations

  12. Isis 1 observations of the high-latitude ionosphere during a geomagnetic storm.

    NASA Technical Reports Server (NTRS)

    Whitteker, J. H.; Hartz, T. R.; Brace, L. H.; Burrows, J. R.; Heikkila, W. J.; Sagalyn, R. C.; Thomas, D. M.

    1972-01-01

    The Isis 1 satellite has made measurements of several ionospheric and related parameters, and the results of the various measurements have been compared in detail for two north transpolar passes during the geomagnetic storm of February 3, 1969. Simultaneous measurements were made of local electron and ion densities and temperatures, electron density between the satellite and the peak of the F layer, radio noise, and particle fluxes over a wide energy range extending down to 10 eV. Several features of the ionosphere (in particular, enhancements of radio noise, scale height, and plasma temperatures) appear to be due to soft-particle (100 eV to 1 keV) precipitation, which is related to magnetospheric structure as delineated by the observation of more energetic particles. The magnetosheath particles precipitating on the dayside of the polar cap are particularly effective.

  13. A study on chaotic behaviour of equatorial/low latitude ionosphere over Indian subcontinent, using GPS-TEC time series

    NASA Astrophysics Data System (ADS)

    Unnikrishnan, K.; Ravindran, Sudha

    2010-09-01

    The deterministic chaotic behaviour of ionosphere, over Indian subcontinent falling under equatorial/low latitude region, -0.3 to 22.19°N (geomagnetic), was studied using GPS-TEC time series. The values of Lyapunov exponent are low at Thiruvananthapuram and Agatti (-0.30 and 2.38°N, geomagnetic, respectively), and thereafter increase through Bangalore and Hyderabad (4.14 and 8.54°N, geomagnetic, respectively), and attain maximum at Mumbai (10.09°N, geomagnetic), which is near/at the edge of an anomaly crest. The values of correlation dimension computed for TEC time series are in the range 3.1-3.6, which indicate that equatorial/low latitude ionosphere can be described with four variables. Entropy values estimated for TEC time series show no appreciable latitudinal variabilites. The values of non-linear prediction error exhibit a trough, around the latitude sector, 4.14-16.15°N (Geomagnetic). Based on the values of the above quantifiers, the features of chaotic behaviour of equatorial/low latitude ionosphere are briefly discussed.

  14. Equinoctial asymmetry in low latitude ionosphere as observed by SROSS-C2 satellite

    NASA Astrophysics Data System (ADS)

    Bardhan, Ananna; Aggarwal, Malini; Sharma, D. K.; Rai, J.

    2014-09-01

    The ionospheric plasma parameters (electron, ion temperatures and ion composition-Te, Ti, O+ and H+) measured by SROSS-C2 satellite at an average altitude of ~500 km has been investigated to study the behaviour of the ionosphere in equinoxes during half a solar cycle (year 1995-2000, F10.7 ~70-195). The region under study spans over 5-35°N geog. latitude and 65-95°E geog. longitude in the Indian sector. We found an equinoctial asymmetry in the diurnal behaviour of Te, Ti, O+ and H+ varying with increase in solar activity. The strength of equinoctial asymmetry in Te and Ti is strong during early morning and daytime and strength decreases with increase in solar activity whereas during night time no asymmetry/weaker is observed in low/high solar activity respectively. During the day time, a very strong equinoctial asymmetry in O+ is observed during solar minimum which diminishes with increase in solar activity. The similar diurnal behaviour of H+ as that of O+ is observed during low solar activity but no clear equinoctial asymmetry is observed during solar maximum, as H+ being highly dynamic. The transition height (O+/H+) is the lowest in early morning during solar minimum, which increases during local day-time. The rate of increase in transition height is different in both the equinoxes (higher in vernal than autumn) with respect to dependence on the solar activity, during daytime. Hence equinoctial asymmetry is stronger during solar minimum period than maximum, with higher/lower transition height in vernal during daytime/nighttime respectively.

  15. Coupling the Solar-Wind/IMF to the Ionosphere through the High Latitude Cusps

    NASA Technical Reports Server (NTRS)

    Maynard, Nelson C.

    2003-01-01

    Magnetic merging is a primary means for coupling energy from the solar wind into the magnetosphere-ionosphere system. The location and nature of the process remain as open questions. By correlating measurements form diverse locations and using large-scale MHD models to put the measurements in context, it is possible to constrain out interpretations of the global and meso-scale dynamics of magnetic merging. Recent evidence demonstrates that merging often occurs at high latitudes in the vicinity of the cusps. The location is in part controlled by the clock angle in the interplanetary magnetic field (IMF) Y-Z plane. In fact, B(sub Y) bifurcated the cusp relative to source regions. The newly opened field lines may couple to the ionosphere at MLT locations of as much as 3 hr away from local noon. On the other side of noon the cusp may be connected to merging sites in the opposite hemisphere. In face, the small convection cell is generally driven by opposite hemisphere merging. B(sub X) controls the timing of the interaction and merging sites in each hemisphere, which may respond to planar features in the IMF at different times. Correlation times are variable and are controlled by the dynamics of the tilt of the interplanetary electric field phase plane. The orientation of the phase plane may change significantly on time scales of tens of minutes. Merging is temporally variable and may be occurring at multiple sites simultaneously. Accelerated electrons from the merging process excite optical signatures at the foot of the newly opened field lines. All-sky photometer observations of 557.7 nm emissions in the cusp region provide a "television picture" of the merging process and may be used to infer the temporal and spatial variability of merging, tied to variations in the IMF.

  16. 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.

  17. Geomagnetic Dependence of Medium Scale Traveling Ionospheric Disturbances (MSTIDs) Observed by Mid- and High- Latitude SuperDARN Radars

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

    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. They are generally thought to be the ionospheric manifestation of Atmospheric Gravity Waves (AGWs). High-latitude MSTIDs have been studied using SuperDARN radars for many years, and have typically been attributed to auroral sources propagated by the Earth Reflected Wave (ERW) mode. Tropospheric sources and earthquakes are also known to be sources of MSTIDs. The goal of this study is to see if high- and mid- latitude MSTIDs share the same source region. Observations of MSTIDs using both mid- and high- latitude SuperDARN radars are presented. A case study using MSTIDs observed at the high latitude Goose Bay Radar (GBR) and the midlatitude Blackstone Radar (BKS) suggest that the auroral source is more likely for GBR than for BKS. BKS radar data from June 2010 - June 2011 were searched for signatures of MSTIDs. Statistics of propagation direction and wavelength for each event are used to suggest MSTID sources. Results show that MSTIDs are observed at BKS primarily in the fall/winter months, which is consistent with previously published results for high latitude stations. Distributions of MSTID occurrence organized by geomagnetic parameters Kp, SYM-H, and AE are presented to investigate MSTID dependence on geomagnetic activity at BKS. No correlation is found between these parameters and midlatitude MSTID occurrence, which suggests that high- and mid-latitude MSTIDs have different sources.

  18. Investigating Changes in the High-Latitude Topside Ionosphere During Large Magnetic Storms

    NASA Technical Reports Server (NTRS)

    Fainberg, Joseph; Benson, Robert F.; Osherovich, Vladimir; Truhlik, Vladimir; Wang, Yongli; Fung, Shing; Bilitza, Dieter

    2009-01-01

    A search was conducted to locate periods of nearly simultaneous solar-wind and high latitude topside-ionospheric data during magnetic storms. The focus was on the 20-yr interval from 1965 to 1985 when both solar-wind and Alouette/ISIS topside-sounder data are potentially available. The search yielded 125 large magnetic storms (minimum Dst less than 100) and 280 moderate magnetic storms (minimum Dst between -60 and -100). Solar wind data were available for most, but not all, of these storms. A search of the available high-latitude topside electron-density Ne(h) profiles available from the National Space Science Data Center (NSSDC), both from manual inspection of 35-mm film ionograms in the 1960s and more recent auto-processing of ISIS-2 topside digital ionograms using the TOPIST software, during 9-day intervals associated with the 125 large magnetic storm minimum Dst times yielded the following results: 31 intervals had 10 or more manual-scaled profiles (21 intervals had more than 100 profiles and 5 of these had more than 1,000 profiles), and 34 intervals had 10 or more TOPIST profiles (2 intervals had more than 100 profiles). In addition, a search of the available Alouette-2, ISIS-1 and ISIS-2 digital ionograms during the above periods has yielded encouraging initial results in that many ISIS-1 ionograms were found for the early time intervals. Future work will include the search for 35-mm film ionograms during selected intervals. This presentation will illustrate the results of this investigation to date.

  19. A Model for the Sounding Rocket Measurement on an Ionospheric E-F Valley at the Hainan Low Latitude Station

    NASA Astrophysics Data System (ADS)

    Wang, Zheng; Shi, Jiankui; Guan, Yibing; Liu, Chao; Zhu, Guangwu; Klaus, Torkar; Martin, Fredrich

    2014-04-01

    To understand the physics of an ionospheric E-F valley, a new overlapping three-Chapman-layer model is developed to interpret the sounding rocket measurement in the morning (sunrise) on May 7, 2011 at the Hainan low latitude ionospheric observation station (19.5°N, 109.1°E). From our model, the valley width, depth and height are 43.0 km, 62.9% and 121.0 km, respectively. From the sounding rocket observation, the valley width, depth and height are 42.2 km, 47.0% and 123.5 km, respectively. The model results are well consistent with the sounding rocket observation. The observed E-F valley at Hainan station is very wide and deep, and rapid development of the photochemical process in the ionosphere should be the underlying reason.

  20. Ionospheric plasma drift and structure studies at high and mid-latitudes. Volume 1. Final report, October 1990-October 1993

    SciTech Connect

    Reinisch, B.W.; Scali, J.L.; Dozois, C.; Crowley, G.

    1993-12-01

    Ground-based observations of the high latitude ionosphere with Digisonde sounders at Quaanaaq, Sondrestrom, Goose Bay, Argentina and Millstone Hill provide a description of the patch structure and the convection pattern in the polar cap. Correlation analysis of observed F-region plasma drifts with the orientation of the interplanetary magnetic field (measured by IMP8) lead to a new technique of deducing the signs of Bz and By from the measured drifts. Real time calculation of the plasma drift was successfully introduced at one of the Digisonde stations (Sondrestrom) providing the possibility of determining the IMF components in real time. Analysis of mid-latitude trough observation shows large westward velocities in the trough region. Digisonde data from Quaanaaq and DMSP F8 and F9 satellite data showed the development of the ionospheric polar hole.

  1. Ionospheric plasma bubbles observed concurrently by multi-instruments over low-latitude station Hainan

    NASA Astrophysics Data System (ADS)

    Wang, G. J.; Shi, J. K.; Reinisch, B. W.; Wang, X.; Wang, Z.

    2015-03-01

    Previous studies have shown that the ionospheric "strong range spread F" (SSF) closely correlates with the occurrence of scintillations caused by equatorial plasma bubbles. However, there is no report on concurrent observations of SSF and bubbles with in situ measurement. This paper discusses two cases of concurrent observations with a DPS4 Digisonde and a collocated scintillation monitor at the low-latitude station Hainan (19.5°N, 109.1°E), and with in situ ion density measurements made by the ROCSAT-1 satellite. Two case studies were made for 10 and 23 April 2004, respectively. In both cases, the SSF occurred before midnight and lasted more than 3.5 h. The scintillations were accompanied with strong range SF. Concurrently, the ROCSAT-1 satellite observed plasma bubbles over Hainan station. In the first case, two bubbles were observed by the satellite with east-west sizes of more than ~200 km over Hainan station. Two bubbles were also observed in the second case with east-west extensions of about 220 km and 35 km, respectively. For the first time, direct observational evidence is provided for the causal relationship between equatorial plasma bubbles with in situ measurement and the concurrent occurrence of SSF and strong scintillations.

  2. Ionospheric effects of supernova explosions

    NASA Astrophysics Data System (ADS)

    Edwards, P. J.

    Possible ionospheric effects of supernova explosions are considered, with special attention given to those of SN 1987a. Results are presented on the calculations of anticipated X-ray/UV flare parameters, including the shock temperature, the minimum flare duration, the average photon energy, and the shock-front travel time for a range of stellar radii bracketing SK 202-69, which was identified by White Malin (1987) as the progenitor star for SN 1987a. It is shown that the characteristics of the X-ray/UV flare are strongly influenced by the radius of the shock wave breakout, so that the flare from SN 1987a can be anticipated to have characteristics intermediate between those attributed to compact stars and stars with extended envelopes.

  3. Plasma modifications induced by an X-mode HF heater wave in the high latitude F region of the ionosphere

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

    We presented experimental results of strong plasma modifications induced by X-mode powerful HF radio waves injected towards the magnetic zenith into the high latitude F region of the ionosphere. The experiments were conducted in 2009-2011 using the EISCAT Heating facility, UHF incoherent scatter radar and the EISCAT ionosonde at Tromsø, Norway; and the CUTLASS SuperDARN HF coherent radar at Hankasalmi, Finland. The results showed that the X-mode HF pump wave can generate strong small-scale artificial field aligned irregularities (AFAIs) in the F region of the high-latitude ionosphere. These irregularities, with spatial scales across the geomagnetic field of the order of 9-15 m, were excited when the heater frequency (fH) was above the ordinary-mode critical frequency (foF2) by 0.1-1.2 MHz. It was found that the X-mode AFAIs appeared between 10 s and 4 min after the heater is turned on. Their decay time varied over a wide range between 3 min and 30 min. The excitation of X-mode AFAIs was accompanied by electron temperature (Te) enhancements and an increase in the electron density (Ne) depending on the effective radiated power (ERP). Under ERPs of about 75-180 MW the Te enhances up to 50% above the background level and an increase in Ne of up to 30% were observed. Dramatic changes in the Te and Ne behavior occurred at effective radiated powers of about 370-840 MW, when the Ne and Te values increased up to 100% above the background ones. It was found that AFAIs, Ne and Te enhancements occurred, when the extraordinary-mode critical frequency (fxF2) lied in the frequency range fH-fce/2≤fxF2≤fH+fce/2, where fce is the electron gyrofrequency. The strong Ne enhancements were observed only in the magnetic field-aligned direction in a wide altitude range up to the upper limit of the UHF radar measurements. In addition, the maximum value of Ne is about 50 km higher than the Te enhancement peak. Such electron density enhancements (artificial ducts) cannot be explained by

  4. The Upgraded European Digital Upper Atmosphere Server: new DIAS products for the high latitude ionosphere, the topside ionosphere and the plasmasphere

    NASA Astrophysics Data System (ADS)

    Belehaki, Anna; Kutiev, Ivan; Zolesi, Bruno; Tsagouri, Ioanna; Dialetis, Dimitris; Marinov, Pencho; Fidanova, Stefka; Cander, Lili; Pietrella, Marco; Tziotziou, Kostas; Lykiardopoulos, Angelos

    2013-04-01

    -time by the DIAS Digisondes. To further improve its accuracy, we adjust the modeled TEC parameter with the GNSS-TEC parameter calculated at the Digisondes location. This adjustment forces the model to correctly reproduce the topside scale height, even in cases when the scale height at hmF2 is not available. This adjustment is very important for the application of TaD in an operational environment. The second group of new products consists of long term prediction and of nowcasting maps of the foF2 parameter that cover the whole European region - including Scandinavia. Long term prediction maps have been extended to 80 deg N applying the CCIR coefficients for the region above 65 deg N, while from 32 to 60 deg N we continue to apply SIRM (Simplified Ionospheric Regional Model), as in the case of middle latitude maps that are released routinely by the DIAS system. Between 60 and 65 deg N there is a buffer zone where an interpolation routine is applied. Nowcasting maps are based on the SIRMUP (SIRM updated in real-time) concept, however, a different effective sunspot number (Reff) is estimated for each latitudinal zone, from which a synthetic Reff is calculated.

  5. Investigation of the morphology and Wait's parameter variations of the low-latitude D region ionosphere using the multiple harmonics of tweeks

    NASA Astrophysics Data System (ADS)

    Tan, Le Minh

    2016-06-01

    Recording the tweeks with a maximum up to eight harmonics using the receiver installed at Tay Nguyen University (12.65° N, 108.02° E) during 2013-2014, we investigated the morphology of the nighttime D-region ionosphere. Tweeks were recorded on 5 quiet nights per month. The results show that the mean reflection height in 2014 (Rz = 79.3) is lower by 3.3 km than that in 2013 (Rz = 64.9). The reflection height at low latitudes is higher than that at high latitudes. The mean reference height h‧ in 2013 is higher about 0.9 km than that in 2014 and the mean sharpness factor β in 2013 is higher by 0.07 km-1 than that in 2014. The short-term variation of reflection heights for tweeks with harmonics m = 1-3 and sunspot number have the negative correlation coefficients. However, the correlations between them are not clear. On some nights, from 19:00-21:00 LT, the reflection height temporal variability shows a moderate to strong negative correlation with the tweek occurrence. This suggests that the reflection height variation may be caused by QE fields generated by lightning discharges. The variations of tweek reflection heights observed during 2013-2014, at low latitudes could be significantly caused by the ionization effect by Lyman- α and Lyman- β coming from geocorona, variation of neutral density, particle precipitations, and by direct energy coupling between lightning and lower ionosphere.

  6. The response of the high-latitude ionosphere to the coronal mass ejection event of April 6, 2000: A practical demonstration of space weather nowcasting with the Super Dual Auroral Radar Network HF radars

    NASA Astrophysics Data System (ADS)

    Ruohoniemi, J. M.; Barnes, R. J.; Greenwald, R. A.; Shepherd, S. G.

    2001-12-01

    The ionosphere at high latitudes is the site of important effects in space weather. These include strong electrical currents that may disrupt power systems through induced currents and density irregularities that can degrade HF and satellite communication links. With the impetus provided by the National Space Weather Program, the radars of the Super Dual Auroral Radar Network have been applied to the real-time specification (``nowcasting'') of conditions in the high-latitude ionosphere. A map of the plasma convection in the northern high-latitude ionosphere is continually generated at the Johns Hopkins University Applied Physics Laboratory (JHU/APL) SuperDARN web site using data downloaded in real time from the radars via Internet connections. Other nowcast items include information on the conditions of HF propagation, the spatial extent of auroral effects, and the total cross polar cap potential variation. Time series of various parameters and an animated replay of the last 2 hours of convection patterns are also available for review. By comparing with simultaneous measurements from an upstream satellite, it is possible to infer the effective delay from the detection of changes in the solar wind at the satellite to the arrival of related effects in the high-latitude ionosphere. We discuss the space weather products available from the JHU/APL SuperDARN web site and their uses by simulating a nowcast of the ionosphere on April 6, 2000, during the arrival of a coronal mass ejection (CME) -related shock. The nowcast convection pattern in particular satisfies a critical need for timely, comprehensive information on ionospheric electric fields.

  7. Near-Simultaneous Polar and DMSP Measurements of Topside Ionosphere Field - Aligned Flows at High Latitudes

    NASA Technical Reports Server (NTRS)

    Zeng, W.; Horwitz, J.L.; Stevenson, B.A.; Wu, X.Y.; Su, Y.J.; Craven, P.D.; Rich, F.J.; Moore, T.E.

    2000-01-01

    Near-simultaneous observations of topside 0' parallel flows are presented for four periods of measurement by POLAR and DMSP satellites during April 1996. The POLAR measurements are from Southern perigee measurements near 5000 km altitude, while the DMSP measurements were from 840 km altitude. These observations provide a view of wide-spread upward/downward ionospheric O(+) flows over the broad polar region along extended and multiple distinct satellite tracks. In general, the velocities are upward toward expected cleft and auroral latitudes, typically about a 2-10 km/s at 5000 km altitude, and 0-2 km/s at 840 km altitudes. At the highest, polar cap latitudes, downward velocities are more frequent at both altitudes, but especially at the lower 840 km altitude. The downward velocities were typically a few hundred d s at 840 altitude, and 0-1 km/s at 5000 km altitude. In some instances, apparently downward velocities were observed at 840 km altitudes while upward 0' flows were observed at 5000 km altitude on the same flux tube. The O+ density were characteristically 1-10 O(+)/cu cm at 5000 km altitude and 10(exp 3) - 10(exp 40 O(+)/cu cm at 840 km altitude, while the O(+) flux were characteristically 1 10(exp 5) - 10(exp 7) O(+)+/sq cm -sec at 5000 km altitudes and characteristically 10(exp 7) - 10(exp 9) O(+)/sq cm -sec at 840 km altitude. We have also examined the dual altitude parameter measurements for a polar cap field line, the POLAR and DMSP measurements approximately 30 minutes apart, and compared them with results from a transport simulation in which a flux tube was subjected to a brief pulse of soft electron precipitation and topside transverse ion heating. The simulated density and velocity altitude profiles for 5 minutes later generally matched the observations, except that the observed downward velocities (500 - 600 m/s) at 840 km altitude were much larger than those simulated.

  8. Role of the Ionosphere in the Generation of Large-Amplitude Ulf Waves at High Latitudes

    NASA Astrophysics Data System (ADS)

    Tulegenov, B.; Guido, T.; Streltsov, A. V.

    2014-12-01

    We present results from the statistical study of ULF waves detected by the fluxgate magnetometer in Gakona, Alaska during several experimental campaigns conducted at the High Frequency Active Auroral Research Program (HAARP) facility in years 2011-2013. We analyzed frequencies of ULF waves recorded during 26 strongly disturbed geomagnetic events (substorms) and compared them with frequencies of ULF waves detected during magnetically quite times. Our analysis demonstrates that the frequency of the waves carrying most of the power almost in all these events is less than 1 mHz. We also analyzed data from the ACE satellite, measuring parameters of the solar wind in the L1 Lagrangian point between Earth and Sun, and found that in several occasions there is a strong correlation between oscillations of the magnetic field in the solar wind and oscillations detected on the ground. We also found several cases when there is no correlation between signals detected on ACE and on the ground. This finding suggests that these frequencies correspond to the fundamental eigenfrequency of the coupled magnetosphere-ionosphere system. The low frequency of the oscillations is explained by the effect of the ionosphere, where the current is carried by ions through highly collisional media. The amplitude of these waves can reach significant magnitude when the system is driven by the external driver (for example, the solar wind) with this particular frequency. When the frequency of the driver does not match the frequency of the system, the waves still are observed, but their amplitudes are much smaller.

  9. Numerical modeling of the ionospheric effects of substorms

    NASA Astrophysics Data System (ADS)

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

    2008-12-01

    the external ionosphere; to the penetration of magnetospheric convection electric field to the middle and low latitudes; to the effects in the equatorial ionosphere. This work was done under support of the Russian Foundation of Basic Research (Grant N08-05-00274).

  10. EUV/FUV remote sensing of the low-latitude ionosphere and thermosphere

    NASA Astrophysics Data System (ADS)

    Stephan, Andrew Ward

    2001-08-01

    The terrestrial environment is influenced continuously by energetic particles and radiation from the Sun that heat and ionize the gases of Earth's upper atmosphere. The absorption of solar energy by atmospheric oxygen leads to a temperature increase from the coldest point in the atmosphere near 90 km altitude, to the hot, nearly isothermal temperatures seen above 300 km. This region is called the thermosphere. Ionization of atmospheric species leads to the formation of a series of plasma layers in this same altitude range. Called the ionosphere, this minor population of charged particles controls much of the dynamics that occur at these altitudes because its principal motion is tied to the Earth's magnetic field lines. Understanding and predicting these interesting, but complex, solar- terrestrial interactions is important for the purpose of mitigating their sometimes hazardous effect on the technological infrastructure of our society. My research concerns the remote sensing of the ionosphere and thermosphere using the EUV/FUV emissions they produce through chemical and physical interactions. I built a suite of spectrographs on the TERRIERS satellite. My laboratory calibration tests for these instruments demonstrated a sensitivity 100-1000 times that of previously flown spectrographs. I have demonstrated the use of tomography, commonly applied to medical imaging problems, to three different remote sensing configurations: a low-altitude spinning satellite, a sensor that only scans near the horizon and limb of the Earth, and a high-altitude imager that obtains spectroscopic images of the full disk of the Earth. Finally, I have used the STP 78-1 and ARGOS satellites to make the first observations of EUV/FUV aurorae produced near the geomagnetic equator during both the daytime and nighttime. These emissions have been previously observed during the night, where the ambient airglow is small. I have combined data from many orbits to demonstrate that these equatorial

  11. Model of the high-latitude ionospheric convection pattern during southward interplanetary magnetic field using DE 2 data

    NASA Technical Reports Server (NTRS)

    Hairston, M. R.; Heelis, R. A.

    1990-01-01

    Data from the polar-orbiting satellite DE 2 are used to calculate one-dimensional electrostatic potential distributions across the polar cap region. Using passes that lie within + or - 3 hours MLT of the dawn-dusk line, various parameters of the polar potential distribution (location and magnitude of the maxima and minima, location of the zero potential point, etc.) are analyzed in relation to each other and to the IMF. The resulting dependences are used to derive a two-dimensional model of the distribution of the electrostatic potential in the high-latitude ionosphere during times of southward IMF. This model can be generated using as inputs either the ionospheric potential parameters or, based on the relationships analyzed here, the IMF conditions. The capabilities of the resulting mathematical model are illustrated, and the importance of retaining a flexibility in the model to accommodate individual observations is emphasized.

  12. Modification of the High-Latitude Ionospheric F Region By High-Power HF Radio Waves at Frequencies Near the fifth and Sixth Electron Gyroharmonics

    NASA Astrophysics Data System (ADS)

    Borisova, T. D.; Blagoveshchenskaya, N. F.; Kalishin, A. S.; Rietveld, M. T.; Yeoman, T. K.; Hägström, I.

    2016-01-01

    We study the modification effects of the high-latitude ionospheric F region induced by a highpower O-mode HF radio wave injected towards the magnetic zenith, at frequencies near the fifth and sixth electron gyroharmonics using the EISCAT/Heating facility. Multi-instrument diagnostics with the EISCAT incoherent scatter radar (930 MHz) at Tromsø, Norway, the CUTLASS coherent radar at Hankasalmi, Finland, and stimulated electromagnetic emission (SEE) receiver at Tromsø, has been used for analysis of the observed phenomena. The behavior of the ionospheric plasma parameters (electron's density and temperature), small-scale artificial field-aligned irregularities, plasma and ion-line spectra, and ionospheric SEE are analyzed in detail. Modification effects near the fifth and sixth electron gyroharmonics have been compared. The coexistence of the thermal (resonance) parametric instability, parametric decay (striction) instability, and/or oscillating two-stream instability was found at these frequencies. The excitation of instabilities occurred at altitudes close to the reflection altitude of the HF pump wave and at the altitudes of the upper-hybrid resonance.

  13. Electrodynamical response of the Indian low-mid latitude ionosphere to the very large solar flare of 28 October 2003 - a case study

    NASA Astrophysics Data System (ADS)

    Manju, G.; Pant, T. K.; Devasia, C. V.; Ravindran, S.; Sridharan, R.

    2009-10-01

    The electrodynamic effects on the low-mid latitude ionospheric region have been investigated using GPS (global positioning system) data, ionosonde data and ΔH values, during the very large solar flare (X17.2/4B) of 28 October 2003. The results bring out the flare induced unusual behaviour of the equatorial ionosphere on this day just prior to sunset. The important observations are i) Large and prolonged Ne enhancements observed from ionosonde data just after the flare-related peak enhancement in EUV flux. The observed enhancement in Ne is due to the increase in ionization production due to the enhanced EUV flux and the persistence of the enhancement is probably due to the prompt penetration related upliftment of the F layer (just prior to the flare peak phase) to higher altitudes, where recombination rates are lower. ii) A significant enhancement in total electron content (TEC) (~10 TEC units) at regions around the Equatorial Ionization Anomaly (EIA) crest region (Ahmedabad) during the flare in association with the flare related EUV flux enhancement. iii) Similar enhancements seen at stations of Jodhpur and Delhi in the mid latitude sector. iv)The flare related flux enhancements in different longitude sectors in the equatorial electrojet region have been shown to produce positive and negative variations in electrojet strength indicating the presence of current systems having positive and negative polarities in different longitude sectors. Thus the flare effect reveals the longitudinal variation of the counter electrojet events in the Equatorial Electrojet (EEJ) region.

  14. High-Latitude Topside Ionospheric Vertical Electron-Density-Profile Changes in Response to Large Magnetic Storms

    NASA Technical Reports Server (NTRS)

    Benson, Robert F.; Fainberg, Joseph; Osherovich, Vladimir A.; Truhlik, Vladimir; Wang, Yongli; Bilitza, Dieter; Fung, Shing F.

    2015-01-01

    Large magnetic-storm induced changes have been detected in high-latitude topside vertical electron-density profiles Ne(h). The investigation was based on the large database of topside Ne(h) profiles and digital topside ionograms from the International Satellites for Ionospheric Studies (ISIS) program available from the NASA Space Physics Data Facility (SPDF) at http://spdf.gsfc.nasa.gov/isis/isis-status.html. This large database enabled Ne(h) profiles to be obtained when an ISIS satellite passed through nearly the same region of space before, during, and after a major magnetic storm. A major goal was to relate the magnetic-storm induced high-latitude Ne(h) profile changes to solar-wind parameters. Thus an additional data constraint was to consider only storms where solar-wind data were available from the NASA/SPDF OMNIWeb database. Ten large magnetic storms (with Dst less than -100 nT) were identified that satisfied both the Ne(h) profile and the solar-wind data constraints. During five of these storms topside ionospheric Ne(h) profiles were available in the high-latitude northern hemisphere and during the other five storms similar ionospheric data were available in the southern hemisphere. Large Ne(h) changes were observed during each one of these storms. Our concentration in this paper is on the northern hemisphere. The data coverage was best for the northern-hemisphere winter. Here Ne(h) profile enhancements were always observed when the magnetic local time (MLT) was between 00 and 03 and Ne(h) profile depletions were always observed between 08 and 10 MLT. The observed Ne(h) deviations were compared with solar-wind parameters, with appropriate time shifts, for four storms.

  15. Study of the Ionospheric D Layer using Partial Reflections at the Middle Latitudes and in the Auroral Zone

    NASA Astrophysics Data System (ADS)

    Belikovich, V. V.; Vyakhirev, V. D.; Kalinina, E. E.; Tereshshenko, V. D.; Ogloblina, O. F.; Tereshshenko, V. A.

    2003-03-01

    Using the measuring facilities located in different latitudinal regions: in Vasil'sursk near Nizhny Novgorod (56.1° N and 46.1° E) and in Tumanny (Murmansk region, 69.0° N and 35.7° E), we study the ionospheric D layer by the partial-reflection technique. Quantitative estimates are obtained for the electron density in the polar and mid-latitude D layer, distinctions of these values are revealed, and the possible reasons for latitudinal variations in the electron density at the D-layer altitudes are discussed.

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

    NASA Astrophysics Data System (ADS)

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

    2011-04-01

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

  17. DC Electric Field measurement in the Mid-latitude Ionosphere during MSTID by S-520-27 Sounding Rocket Experiments

    NASA Astrophysics Data System (ADS)

    Ishisaka, K.; Yamamoto, M.; Yokoyama, T.; Tanaka, M.; Abe, T.; Kumamoto, A.

    2015-12-01

    In the middle latitude ionospheric F region, mainly in summer, wave structures of electron density that have wave length of 100-200 km and period of one hour are observed. This phenomena is called Medium Scale Traveling Ionosphiric Disturbance; MSTID. MSTID has been observed by GPS receiving network, and its characteristic were studied. In the past, MSTID was thought to be generated by the Perkins instability, but its growth ratio was too small to be effective so far smaller than the real. Recently coupling process between ionospheric E and F regions are studied by using two radars and by computer simulations. Through these studies, we now have hypothesis that MSTID is generated by the combination of E-F region coupling and Perkins instability. The S-520-27 sounding rocket experiment on E-layer and F-layer was planned in order to verify this hypothesis. S-520-27 sounding rocket was launched at 23:57 JST on 20th July, 2013 from JAXA Uchinoura Space Center. S-520-27 sounding rocket reached 316km height. The S-520-27 payload was equipped with Electric Field Detector (EFD) with a two set of orthogonal double probes to measure DC electric field in the spin plane of the payload. The electrodes of two double probe antennas were used to gather the potentials which were detected with high impedance pre-amplifier using the floating (unbiased) double probe technique. As a results of measurements of DC electric fields by the EFD, the natural electric field was about +/-5mV/m, and varied the direction from southeast to east. Then the electric field was mapped to the horizontal plane at 280km height along the geomagnetic field line. In this presentation, we show the detail result of DC electric field measurement by S-520-27 sounding rocket and then we discuss about the correlation between the natural electric field and TEC variation by using the GPS-TEC.

  18. Local and Global Studies of Ion Outflow From the High Latitude Ionosphere

    NASA Technical Reports Server (NTRS)

    Petersen, W. K.

    1997-01-01

    Ion outflow from the ionosphere plays a fundamental but poorly defined role in magnetospheric processes. The purpose of the research is to better understand the mass coupling between the Earth's ionosphere and Magnetosphere. The work performed under this grant falls in three areas: (1) event studies using archived data from the DE-1/2 satellites; (2) investigations using Data from the ISTP satellites; and (3) work supporting a Space Physics Educational Outreach (SPEO) grant supplement.

  19. Ionospheric total electron content behavior at a pair of mid-latitude conjugate stations

    NASA Astrophysics Data System (ADS)

    Essex, E. A.; Klobuchar, J. A.

    1981-07-01

    A correlation study of the geomagnetic conjugate effects in the ionospheric total electron content carried out between Shemya, Alaska and Beveridge, Australia is discussed. In the study, the seasonal, diurnal, and magnetic activity dependence of the correlation is determined. It is found that for equinoxes during low magnetic activity the correlation is positive during local afternoon and negative during local night to local morning hours. For the early winter-summer conjugate study, the correlation is for the most part positive during the local daytime and negative during local nighttime. For later winter-summer, the correlation is for the most part low, oscillating about zero throughout the day. With higher magnetic activity, the correlation is generally positive throughout the day during equinoxes, dropping below zero for about 3 hours around local sunrise. A similar result is true for later winter-summer. However, early winter-summer shows significant positive correlation only during local afternoon hours. An investigation of equinoctial and winter-summer geomagnetically conjugate storm effects shows that while equinoctial storm effects can occur simultaneously in both hemispheres, the seasonal differences between winter and summer storms tend to dominate during solstice storms.

  20. Climatology of high-latitude ionospheric scintillation based on 38.2 MHz IRIS riometer measurements in Northern Finland

    NASA Astrophysics Data System (ADS)

    Szponarski, P.; Honary, F.; McKay-Bukowski, D.

    2015-12-01

    Dynamic electron density irregularities, ranging in scale sizes from hundreds of kilometres to a few centimetres, cause scintillation of radio-waves propagating through the ionosphere. They can significantly reduce performance of GNSS (Global Navigation Satellite System) receivers and other positioning systems of varying frequencies. The high latitude ionosphere becomes very disturbed during geomagnetic storms due to auroral precipitation and motion of polar patches. While the scintillation topic is researched heavily at GPS frequencies, relatively little work has been done at MHz frequencies. A rather unconventional approach has been taken, by using data from the IRIS riometer (Imaging Riometer for Ionospheric Studies), based in Kilspisjärvi, Finland (69.05° N 20.79° E). By observing the strong and homogeneous radio source Cassiopeia A, passing through multiple narrow beams, amplitude scintillations can be observed. The continuous dataset of approximately 14 years (1995 - 2009) was used to create climatological scintillation trends, presenting diurnal, seasonal and yearly variations of amplitude scintillation index, S­­­­4. The correlation between S4 index and geomagnetic indices (Kp, AE) was investigated and linear relationships were found.

  1. Comparative study on the ionospheric response to minor and major sudden stratospheric events in the Brazilian equatorial and low latitudes

    NASA Astrophysics Data System (ADS)

    Fagundes, Paulo Roberto; Kavutarapu, Venkatesh; Gil Pillat, Valdir; Vieira, Francisco

    2016-07-01

    The Total electron Content (TEC), derivate from GPS, becomes one of the most powerful techniques to study the space-time ionospheric (F-region) electrodynamics, during the quiet and disturbed periods. The number of GPS stations in Brazil increased significantly during the last few years; currently more than 100 GPS stations are in operation over the Brazilian region. The GPS-TEC values are derived using the differential delay technique from the dual frequency measurements at L1 and L2 frequencies over the considered locations at equatorial and low latitudes. The present study investigates the ionospheric total electron content (GPS-TEC) response in the Southern Hemisphere equatorial and low latitudes, due to major and minor sudden stratospheric warming (SSW) events, which took place during 2009 and 2012. During both the SSW events, the TEC values are depleted to the order of 20-30% all over the Brazil from equator to beyond Equatorial Ionization Anomaly (EIA) regions. In addition, the EIA were suppressed during the SSW events for several days. However, the TEC depletion and EIA suppression lasted for a longer period during SSW-2012 when compared with the SSW-2009; despite the SSW-2012 is considerd as a minor event.

  2. A multi-instrument case study of high-latitude ionospheric GNSS scintillation due to drifting plasma irregularities

    NASA Astrophysics Data System (ADS)

    van der Meeren, C.; Oksavik, K.; Moen, J. I.; Romano, V.

    2013-12-01

    For this study, GPS receiver scintillation and Total Electron Content (TEC) data from high-latitude locations on Svalbard have been combined with several other data sets, including the EISCAT Svalbard Radar (ESR) and allsky cameras, to perform a multi-instrument case study of high-latitude GPS ionospheric scintillations in relation to drifting plasma irregularities at night over Svalbard on 31 October 2011. Scintillations are rapid amplitude and phase fluctuations of electromagnetic signals. GNSS-based systems may be disturbed by ionospheric plasma irregularities and structures such as plasma patches (areas of enhanced electron density in the polar cap) and plasma gradients. When the GNSS radio signals propagate through such areas, in particular gradients, the signals experience scintillations that at best increases positioning errors and at worst may break the receiver's signal lock, potentially resulting in the GNSS receiver losing track of its position. Due to the importance of many GNSS applications, it is desirable to study the scintillation environment to understand the limitations of the GNSS systems. We find scintillation mainly localised to plasma gradients, with predominantly phase scintillation at the leading edge of patches and both phase and amplitude scintillation at the trailing edge. A single edge may also contain different scintillation types at different locations.

  3. A study of 3D structure of nighttime electron density enhancement in the mid-latitude ionosphere by GPS tomography

    NASA Astrophysics Data System (ADS)

    Chen, C.; Saito, A.

    2011-12-01

    The mid-latitude summer nighttime anomaly (MSNA) is a feature that the nighttime electron density larger than that in the daytime mid-latitude ionosphere. This anomaly was first detected in the southern hemisphere five decades ago and observed in the northern hemisphere recently by ionosondes and satellites. Previous studies presented the electron density structure of MSNA by using COSMIC occultation data and found that MSNA is clearly seen around 300 km altitude during local summer. However, due to lack of observation, the day-to-day variation of MSNA was not investigated. A GPS tomography method by SPEL of Kyoto University using the total electron content (TEC) data measured by the ground-based GPS receiver network is employed in this study. The wide coverage and continuous observation of GPS receivers are suitable for investigating the spatial and day-to-day variations of ionospheric electron densities. The algorithm of the GPS tomography developed by SPEL of Kyoto University use a constraint condition that the gradient of election density tends to be smooth in the horizontal direction and steep in the vicinity of the F2 peak, instead of inputting the initial conditions. Therefore, the algorithm is independent of any ionospheric and plasmaspheric electron density distribution models. The dense ground-based GPS receiver network around European region is used to study the three dimensional (3D) structure of MSNA with GPS tomography. Results show that the MSNA usually appear around the geomagnetic mid-latitude region during local summer nighttime. The feature of MSNA is most obvious at the ionospheric F2-peak altitudes. The result also shows a day-to-day variation in the formation of MSNA, in terms of the occurrence time, intensity, and spatial extent. The tomographic results are compared with the ionosondes, satellites, and radar measurements. A theoretical model simulation, SAMI2, is also used to further discuss the mechanism of MSNA. The comparison with other

  4. Simulation of low latitude ionospheric response to 2015 St. Patrick's Day super geomagnetic storm over Indian longitude sector

    NASA Astrophysics Data System (ADS)

    Mohan Joshi, Lalit; Sripathi, Samireddipelle; Singh, Ram

    2016-07-01

    We present low latitude ionospheric response over Indian longitude to the recent super geomagnetic storm of 17 March 2015, using the SAMI2 model which incorporates ionosonde derived vertical drift impacted by prompt penetration eastward electric field occurring during the evening Prereversal Enhancement (PRE) in the vertical drift. The importance of this storm is that (a) Dst reaches as low as -228 nT and (b) prompt penetration of eastward electric field coincided with evening hours PRE. The daytime vertical EXB drifts in the SAMI2 model are, however, considered based on Scherliess-Fejer model. The simulations indicate a significant enhancement in F layer height and equatorial ionization anomaly (EIA) in the post sunset hours on 17 March 2015 vis-a-vis quiet day. The model simulations during recovery phase, considering disturbance dynamo vertical EXB drift along with equatorward disturbance wind, indicates suppression of the daytime EIA. SAMI2 simulations considering the disturbance wind during the recovery phase suggests that equatorward wind enhances the ionospheric density in the low latitude, however, its role in the formation of the EIA depends on the polarity of the zonal electric field. Comparison of model derived total electron content (TEC) with the TEC from ground GPS receivers indicate that model does reproduce enhancement of the EIA during the main phase and suppression of the EIA during the recovery phase of the super storm. However, peculiarities pertaining to the ionospheric response to prompt penetration electric field in the Indian sector vis-a-vis earlier reports from American sector will be discussed.

  5. Mechanisms underlying the prereversal enhancement of the vertical plasma drift in the low-latitude ionosphere

    NASA Astrophysics Data System (ADS)

    Eccles, J. V.; St. Maurice, J. P.; Schunk, R. W.

    2015-06-01

    The evening prereversal enhancement (PRE) of the vertical plasma drift has important consequences for the Appleton density anomaly and the stability of the nighttime ionosphere. Simplified simulations were used to review the three competing theories of the PRE origin, to explore their relative importance, and to indentify their interdependence. The mechanisms involved in the generation and climatology of the PRE are, first, a curl-free electric field response to rapid changes in the vertical electric field associated with the nighttime F region dynamo; second, a divergence of Hall currents in the E region away from the magnetic equator; and, third, the moderating effect of the large Cowling conductivities in the equatorial E region. The simulations indicate that the equatorial Cowling conductivity creates an important current path that limits the other two mechanisms prior to equatorial sunset and releases them after equatorial sunset. The curl-free mechanism is the dominant mechanism when the terminator and magnetic meridian are aligned in part due to the accelerating F region zonal wind. When the solar terminator is not aligned with the magnetic meridian, there is an interaction involving all three mechanisms contributing to the magnitude and timing of the PRE. Finally, the altitude profile of the PRE decays more quickly with altitude when the curl-free mechanism dominates as compared to when the Hall current mechanism dominates.

  6. On the ionospheric impact of recent storm events on satellite-based augmentation systems in middle and low-latitude sectors

    NASA Technical Reports Server (NTRS)

    Komjathy, Attila; Sparks, Lawrence; Mannucci, Anthony J.; Pi, Xiaoqing

    2003-01-01

    The Ionospheric correction algorithms have been characterized extensively for the mid-latitude region of the ionosphere where benign conditions usually exist. The United States Federal Aviation Administration's (FAA) Wide Area Augmentation System (WAAS) for civil aircraft navigation is focused primarily on the Conterminous United States (CONUS). Other Satellite-based Augmentation Systems (SBAS) include the European Geostationary Navigation Overlay Service (EGNOS) and the Japanese Global Navigation Satellite System (MSAS). Researchers are facing a more serious challenge in addressing the ionospheric impact on navigation using SBAS in other parts of the world such as the South American region on India. At equatorial latitudes, geophysical conditions lead to the so-called Appleton-Hartree (equatorial) anomaly phenomenon, which results in significantly larger ionospheric range delays and range delay spatial gradients than is observed in the CONUS or European sectors. In this paper, we use GPS measurements of geomagnetic storm days to perform a quantitative assessment of WAAS-type ionospheric correction algorithms in other parts of the world such as the low-latitude Brazil and mid-latitude Europe. For the study, we access a world-wide network of 400+ dual frequency GPS receivers.

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

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

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

  8. Challenges for Future UV Imaging of the Earth's Ionosphere and High Latitude Regions

    NASA Technical Reports Server (NTRS)

    Spann, James

    2006-01-01

    Large scale imaging of Geospace has played a significant role in the recent advances in the comprehension of the coupled Solar-Terrestrial System. The Earth's ionospheric far ultraviolet emissions provide a rich tapestry of observations that play a key role in sorting out the dominant mechanisms and phenomena associated with the coupling of the ionosphere and magnetosphere (MI). The MI coupling is an integral part of the Solar-Terrestrial and as such, future observations in this region should focus on understanding the coupling and the impact of solar variability. This talk will focus on the outstanding problems associated with the coupled Solar-Terrestrial system that can be best addressed using far ultraviolet imaging of the Earthls ionosphere. Challenges of global scale imaging and high-resolution imaging will be discussed and how these are driven by unresolved compelling science questions of magnetospheric configuration, and auroral dynamics.

  9. 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.

  10. Ionospheric effects of solar x-rays

    NASA Astrophysics Data System (ADS)

    Danskin, Donald

    2016-07-01

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

  11. Ionospheric effects of the Chelyabinsk meteoroid

    NASA Astrophysics Data System (ADS)

    Chernogor, L. F.

    2015-05-01

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

  12. Study of Ionospheric TEC from GPS observations and comparisons with IRI and SPIM model predictions in the low latitude anomaly Indian subcontinental region

    NASA Astrophysics Data System (ADS)

    Panda, S. K.; Gedam, S. S.; Rajaram, G.

    2015-04-01

    The present study investigates variation of the ionospheric total electron content (TEC) in the low latitude Indian sub-continental region from the GPS observations and its comparison with the global ionosphere maps (GIMs), standard international reference ionosphere (IRI 2012), and the standard plasmasphere-ionosphere model (SPIM) for the period from November 2011 to October 2012 that corresponds to the progressive phase towards the midst of the solar cycle-24. Observations during quiet period show diurnal maximum of TEC occurring around 14:00-16:00 IST, with relatively broader and longer duration of local maximum at Bangalore and behave reversely towards Delhi. The secondary maximum of TEC was markedly noticeable at Bangalore during the months of March and September, and only in the month of September at Hyderabad and Mumbai. However, the relatively higher TEC during December month than the June is ascribed to the winter anomaly which is more prevalent during the high solar activity periods. The prevailing instability in latitudes of anomaly crest during January 2012 is possibly due to the seasonal variation of lunar tidal effects, modulating the EEJ strength at the equator. The studies covered the period of a strong geomagnetic storm during 6-11 March 2012 (SYM-H: -149 nT) which resulted in positive deviation of GPS-TEC at Bangalore (↑ 20%), Hyderabad (↑ 22%), and Lucknow (↑ 94%) compared to the mean quiet days level. The relatively large deviation of TEC at Lucknow could be attributed to the poleward shifting of the anomaly crest, manifested by enhanced fountain effect at the equator. Studies confirm excellent agreement (80-85%) of GPS-TEC with IGS-GIM at Bangalore and Hyderabad with the exception of the night-time hours (Deviations >50%). However relatively larger deviation of GPS-TEC from GIM-TEC at Delhi could be due to the unavailability of IGS stations in the proximity of the position. Predictions of the SPIM model (extension of IRI up to GPS

  13. Ionospheric variability over Indian low latitude linked with the 2009 sudden stratospheric warming

    NASA Astrophysics Data System (ADS)

    Patra, Amit; Alex, Sobhana; Samireddipalle, Sripathi; Peddapati, PavanChaitanya

    In this paper, we analyze radar observations of ExB drift and plasma irregularities, ionosonde observations of E- and F-layer parameters including spread F, and magnetic field observations made from Indian low latitudes linked with the 2009 sudden stratospheric warming (SSW) event. ExB drift variations presented here are the first of their kind from the Indian sector as far as the effect of SSW is concerned. Difference of magnetic fields observed from the equator and low latitude (∆H) and ExB drift show linear relation and both show remarkably large positive values in the morning and negative values in the afternoon exhibiting semidiurnal behavior. Remarkable changing patterns in the critical frequency of F2 layer (foF2) and F3 layer (foF3) were observed after the occurrence of SSW. Large variations with quasi-16-day periodicity were observed in ∆H, foF2 and foF3. Both semidiurnal and quasi-16-day wave modulation observed after the 2009 SSW event are consistent with those reported earlier. We also noted quasi-6 day variations in ∆H and foF2 soon after the SSW commencement, not much reported before. During the counter-electrojet events linked with the SSW event, while equatorial Es (Esq) disappeared as expected, there were no blanketing Es (Esb), a finding not reported and discussed earlier. Esb was also not formed at the off-equatorial location, indicating the absence of required vertical wind shear, but E region plasma irregularities were observed by the ionosonde and radar with a close relationship between the two. Weak F region irregularities were observed in the post-midnight hours and case studies suggest the possible role of SSW related background electric field in the manifestation of post-midnight F region irregularities.

  14. Ionospheric variability over Indian low latitude linked with the 2009 sudden stratospheric warming

    NASA Astrophysics Data System (ADS)

    Patra, A. K.; Pavan Chaitanya, P.; Sripathi, S.; Alex, S.

    2014-05-01

    In this paper, we analyze radar observations of E × B drift and plasma irregularities, ionosonde observations of E and F layer parameters including spread F, and magnetic field observations made from Indian low latitudes linked with the 2009 sudden stratospheric warming (SSW) event. E × B drift variations presented here are the first of their kind from the Indian sector as far as the effect of SSW is concerned. Difference of magnetic fields observed from the equator and low-latitude (∆H) and E × B drift show linear relation, and both show remarkably large positive values in the morning and negative values in the afternoon exhibiting semidiurnal behavior. Remarkable changing patterns in the critical frequency of F2 layer (foF2) and F3 layer (foF3) were observed after the occurrence of SSW. Large variations with quasi 16 day periodicity were observed in ∆H, foF2, and foF3. Both semidiurnal and quasi 16 day wave modulation observed after the 2009 SSW event are consistent with those reported earlier. We also noted quasi 6 day variations in ∆H and foF2 soon after the SSW commencement, not much reported before. During the counterelectrojet events linked with the SSW event, while equatorial Es (Esq) disappeared as expected, there were no blanketing Es (Esb), a finding not reported and discussed earlier. Esb was also not formed at the off-equatorial location, indicating the absence of required vertical wind shear, but E region plasma irregularities were observed by the ionosonde and radar with a close relationship between the two. Weak F region irregularities were observed in the postmidnight hours, and case studies suggest the possible role of SSW-related background electric field in the manifestation of postmidnight F region irregularities.

  15. Electron energy budget in the high-latitude ionosphere during Viking/EISCAT coordinated measurements

    SciTech Connect

    Lilensten, J.; Kofman, W.; Lathuillere, C. ); Fontaine, D. ); Eliasson, L. ); Oran, E.S. )

    1990-05-01

    The magnetospheric electron fluxes precipitating at the top of the auroral ionosphere contribute to the production of ionization, to the excitation of atmospheric constituents, and to the heating of the ambient electrons. This last process occurs essentially when the energy of the initial precipitated electrons and photoelectrons has been degraded to values lower than approximately 10 eV. The heated ambient electron gas loses this energy to the neutral gas and ambient ions. Finally, the temperature gradient produced in the ionospheric plasma induces a heat flux. In the absence of an electric field and for stationary conditions, the energy budget of ionospheric electrons results from the balance between these processes of heating, cooling, and heat conduction. The intensity of these different processes is quantitatively computed at each altitude in the ionosphere by combining simultaneous EISCAT and Viking in situ measurements, and by means of an electron transport model. The stationary electron flux, which leads to the heating rate, is computed, and remaining differences in the energy budget are discussed.

  16. Resonance cone measurements of non-thermal plasma properties in the mid-latitude ionosphere

    NASA Astrophysics Data System (ADS)

    Piel, A.; Oyama, K.-I.; Thiemann, H.; Morioka, A.

    Resonance cone data obtained during the Corex experiment on January 25, 1988, were used to evaluate the electron density and temperature in the midlatitude ionosphere. The electron temperature obtained from the resonance cone measurements was found to be close to gas temperature, while the thermal electron detector results resulted in much higher temperatures, indicating that actual distribution may be characterized by two characteristic temperatures.

  17. Multi-Resolution Assimilative Analysis of High-Latitude Ionospheric Convection in both Hemispheres

    NASA Astrophysics Data System (ADS)

    Thomas, Z. M.; Matsuo, T.; Nychka, D. W.; Cousins, E. D. P.; Wiltberger, M. J.

    2014-12-01

    Assimilative techniques for obtaining complete maps of ionospheric electric potential (and related parameters) from sparse radar and satellite observations greatly facilitates studies of magnetosphere/ionosphere coupling. While there is much scientific interest in studying interhemispheric asymmetry in ionospheric convection at both large and small scales, current mapping procedures rely on spherical harmonic expansion techniques, which produce inherently large-scale analyses. Due to the global nature of the spherical harmonics, such techniques are also subject to various instabilities arising from sparsity/error in the observations which can introduce non-physical patterns in the inferred convection. We present a novel technique for spatial mapping of ionospheric electric potential via a multi-resolution basis function expansion procedure, making use of compactly supported radial basis functions which are flexibly located over geodesic grids; the coefficients are modeled via a Markov random field construction. The technique is applied to radar observations from the Super Dual Auroral Radar Network (SuperDARN), whereupon careful comparison of interhemispheric differences in mapped potential is made at various scales.

  18. Relating OGO-5 H(+) Plasmapause Transitions to Mid-Latitude Topside-Ionospheric Signatures

    NASA Technical Reports Server (NTRS)

    Truhlik, Vladimir; Benson, Robert F.; Bilitza, Dieter; Grebowsky, Joseph M.; Wang, Yongli

    2009-01-01

    Plasmapause transitions, as seen in the H + and He+ density gradients measured by the Orbiting Geophysical Observatory 5 (OGO 5) ion spectrometer [Sharp, IEE Trans. in Geosci. Elect., 1969], have been investigated in an attempt to relate them to their topside ionospheric signatures as seen in the Alouette-1 & 2 and ISIS-1 data. The satellite data were obtained from the National Space Science Data Center (NSSDC). A search of the OGO-5 data revealed 54 sharp plasmapause crossings as evaluated from the H+ density. The ionospheric footprints (at 1400 km altitude) of the magnetic-field lines through the locations of these plasmapause crossings were then used to search for topside ionospheric electron-density profiles from the NSSDC. No profiles corresponding to these projections were identified. A similar search of the topside-sounder 35-mm ionogram-film database, however, identified 17 cases of candidate "conjunctions" involving Alouette l & 2 and ISIS 1. We will present samples of the plasmapause OGO-5 ion transitions and the related topside ionospheric signatures and discuss the observations in relation to the recent similar study based on Explorer-45 and ISIS-2 data [Grebowsky et al., JASTP, 2009].

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

    NASA Technical Reports Server (NTRS)

    Smith, Ernest K.; Flock, Warren L.

    1993-01-01

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

  20. Investigation of mid-latitude ionospheric currents by combined rocket techniques.

    NASA Technical Reports Server (NTRS)

    Rees, D.; Dorling, E. B.; Wrenn, G. L.; Aggson, T. L.; Burrows, K.; Haerendel, G.; Rieger, E.; Lloyd, K. H.; Wilson, J. W. G.

    1973-01-01

    A comprehensive range of neutral atmospheric and simultaneous ionospheric structure measurements were obtained from a Skylark rocket launched at Woomera during evening twilight on a quiet magnetic day. Above 150 km, good agreement was found between the results obtained from three different methods of electric field measurement despite the low field strength (about 1.5 mV/m). In the immediate vicinity of an intense sporadic E layer, the probe measurements indicated large excursions of the electrostatic field amounting to 6.5 mV/m at 105.3 km and 2.7 mV/m at 104.8 km. The calculated ionospheric current system in the vicinity of the rocket trajectory was of similar magnitude to that indicated by local ground-based magnetometers, but was diametrically opposed in direction.

  1. Plasma density undulations correlated with thermospheric neutral mass density in the daytime low-latitude to midlatitude topside ionosphere

    NASA Astrophysics Data System (ADS)

    Park, Jaeheung; Lühr, Hermann; Nishioka, Michi; Kwak, Young-Sil

    2015-08-01

    Plasma density undulations in the dayside low-latitude/midlatitude ionospheric F region were often attributed to thermospheric gravity waves (TGWs). However, the relationship between the former and the latter has been at best indirectly evidenced. In this study we investigate daytime fluctuations in neutral mass density (ρ) and plasma density (ne) measured onboard CHAMP from 2001 to 2010. A significant amount of daytime fluctuations in ne is strongly correlated with in situ fluctuations of ρ, which we term "TGW-related ne fluctuations." The TGW-related ne fluctuations are (1) stronger in the winter hemisphere than in the summer hemisphere and (2) strongest in the South American sector during June solstice months. These climatological features are in general agreement with those of TGWs reported previously, especially at midlatitudes. On the other hand, the relative amplitude of TGW-related ne fluctuations does not depend strongly on solar activity.

  2. Study of high-latitude ionosphere: One-year campaign over Husafell, Iceland

    NASA Astrophysics Data System (ADS)

    Bahari, S. A.; Abdullah, M.; Hasbi, A. M.; Yatim, B.; Suparta, W.; Kadokura, A.; Bjornsson, G.

    2016-07-01

    This paper reports on the effects of diurnal, seasonal, geomagnetic and solar activity on GPS Vertical Total Electron Content (VTEC) measurements at a high-latitude station in Husafell, Iceland (64.7°N, 21.0°W) from March 2009 to February 2010. According to the diurnal VTEC pattern, there was generally a build-up region at sunrise (0500-1000 LT), a daytime plateau in the afternoon (1200-1400 LT), and a decay region from evening to pre-dawn (1800-0400 LT). The month-to-month analysis showed high VTEC variability, particularly in February 2010, due to an increase in solar activity. The VTEC showed a high variability during both winter and the equinoxes, with the highest value being 90%, but showed a low variability in summer. Two abnormal peaks appeared at sunrise and sunset in winter and the equinoxes. These peaks were the result of steep density gradients caused by the onset and turnoff of solar radiation. The correlation analysis yielded almost no correlation between the VTEC and geomagnetic activity but showed a high correlation with solar activity for all the seasons, particularly at night-time.

  3. 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.

  4. Response of the equatorial and low-latitude ionosphere in the Indian sector to the geomagnetic storms of January 2005

    NASA Astrophysics Data System (ADS)

    Sreeja, V.; Devasia, C. V.; Ravindran, Sudha; Pant, Tarun Kumar; Sridharan, R.

    2009-06-01

    The equatorial and low-latitude ionospheric response to three moderate geomagnetic storms (17, 18, and 22 January) during the period from 16 to 23 January 2005 is investigated in the context of development/inhibition of the Equatorial Ionization Anomaly (EIA) and the subsequent occurrence/nonoccurrence of Equatorial Spread F (ESF) irregularities on these days. The study is carried out using the Total Electron Content (TEC) measured with the GPS receivers along the ˜80°E longitude sector and the F-layer bottom height obtained from the Ionosonde located over the dip equatorial location of Trivandrum (8.5°N, 77°E, dip latitude ˜0.5°N) in India. It is observed that, for the storms on days 17 and 22, the development of the anomaly was inhibited, probably due to the westward disturbance dynamo electric fields. Subsequently, the post sunset enhancement in the vertical drift of the equatorial F region was also inhibited significantly compared to the quiet day pattern and, as anticipated, no ESF was observed on these days. A large vertical drift of the equatorial F region followed by nearly simultaneous onset of weak ESF was observed on day 18. The late development of the EIA on this day could be due to the eastward prompt penetration electric field associated with the southward turning of the interplanetary magnetic field. Also, strong and distinct F3 layer appeared for a short time in the morning, reappeared later in the noon time, and then quickly ascended to the topside ionosphere during the main phase of the storm on day 18.

  5. Ionospheric and magnetic signatures of a high speed solar wind in low latitudes on 13 October 2012

    NASA Astrophysics Data System (ADS)

    Migoya-Orue, Y. O.; Azzouzi, I.; Coisson, P.; Amory Mazaudier, C.; Fleury, R.; Radicella, S. M.

    2016-03-01

    This paper presents the impact of a fast solar wind on the ionosphere, in low latitudes, on 13 October 2012. On that day, the high speed solar wind reached the Earth around 16:00UT, during the recovery phase of a geomagnetic storm which started around 00:00UT. The solar wind speed was determined to be 580km/s, on the same day, around 17:00UT. Its impact was observed in low and equatorial latitudes, in Africa and in Eastern South America, on the F layer and on the geomagnetic field variations. Through the analysis of magnetic indices, ionosonde characteristics and the horizontal component of the geomagnetic field, we found that the 13 October 2012 event exhibited a local impact, affecting the observatories situated in a longitude sector between 315°E and 45°E. Particularly, the F layer in Africa (observed by the ionosonde at Ascension Island) did not present any lift, and there was a delay for approximately two hours of the ascent of the F layer in America (the ionosonde at Fortaleza). In this case, there was an evident inhibition on the development of spread F at the time of the Pre Reversal Enhancement (PRE) in Africa and Eastern America, while the ionograms of the days before and after presented clear spread F traces. The disturbances of the ionospheric equivalent electric current (Diono) deduced from the variations of the geomagnetic field at M'Bour near Dakar (Africa) and at Kourou (Eastern America) exhibited on the dayside, an anti Sq current which is signature of the influence of the Disturbance Dynamo Electric Field (DDEF).

  6. Effect of the total solar eclipse of 20 March 2015 on the ELF propagation over high-latitude paths

    NASA Astrophysics Data System (ADS)

    Tereshchenko, E. D.; Sidorenko, A. E.; Tereshchenko, P. E.; Grigoriev, V. F.

    2015-09-01

    Propagation of the artificial electromagnetic waves with frequency of 82 Hz in the Earth-ionosphere waveguide was observed during the solar eclipse on both partially and totally obscured high-latitude paths with a length of 450-1200 km. Field excitation was monitored by the reference measurements in the near zone of the transmitter, which are free of the ionospheric influence. It is found that the amplitude of the field at the remote points varied depending on the solar illumination and solar elevation angle. We suppose that this effect was probably caused by the increase in the effective height of the ionospheric D layer, just as it was previously observed in VLF. The obtained results demonstrate the response of the propagating extremely low frequency (ELF, 3-300 Hz) wave to the change in the ionospheric boundary. This effect has been for the first time observed in this frequency range during a total solar eclipse.

  7. In-situ studies of plasma irregularities in high latitude ionosphere with the ICI-2 sounding rocket within the 4DSpace project

    NASA Astrophysics Data System (ADS)

    Miloch, Wojciech; Moen, Joran; Spicher, Andres

    Ionospheric plasma is often characterized by irregularities, instabilities, and turbulence. Two regions of the ionospheric F-layer are of particular interest: low-latitudes for the equatorial anomaly and electrojet, and high-latitude regions where the most dynamic phenomena occur due to magnetic field lines coupling to the magnetosphere and the solar wind. The spectra of plasma fluctuations in the low-latitude F-layer usually exhibit a power law with a steeper slope at high frequencies [1]. Until recently, there was no clear evidence of the corresponding double slope spectra for plasma fluctuations in the high latitude ionospheric F-layer, and this difference was not well understood. We report the first direct observations of the double slope power spectra for plasma irregularities in the F-layer of the polar ionosphere [2]. The ICI-2 sounding rocket, which intersected enhanced plasma density regions with decameter scale irregularities in the cusp region, measured the electron density with unprecedented high resolution. This allowed for a detailed study of the plasma irregularities down to kinetic scales. Spectral analysis reveals double slope power spectra for regions of enhanced fluctuations associated mainly with density gradients, with the steepening of the spectra occurring close to the oxygen gyro-frequency. The double slope spectra are further supported by the results from the ICI-3 sounding rocket. Double slope spectra were not resolved in previous works presumably due to limited resolution of instruments. The study is a part of the 4DSpace initiative for integrated studies of the ionospheric plasma turbulence with multi-point, multi-scale in-situ studies by sounding rockets and satellites, and numerical and analytical models. A brief overview of the 4DSpace initiative is given. [1] M.C. Kelley, The Earth’s Ionosphere Plasma Physics and Electrodynamics (Elsevier, Amsterdam 2009). [2] A. Spicher, W. J. Miloch, and J. I. Moen, Geophys. Res. Lett. 40, (in

  8. Response of low latitude D-region ionosphere to the Total Solar Eclipse of 22 July 2009, deduced from ELF/VLF analysis

    NASA Astrophysics Data System (ADS)

    Singh, A. K.; Singh, R.; Singh, A. K.

    2011-12-01

    Response of the D-region of the ionosphere to the total solar eclipse of 22 July 2009 at low latitude, Varanasi (geomagnetic lat = 140 55'N, longitude = 1540 E, dip. angle = 37.30) was investigated using ELF/VLF radio signal. The solar eclipse started at 05:30:04.4 hrs IST and lasted up to 07:27 hrs IST with totally from 6.25 IST to 6.27 IST.The changes in D-region ionospheric VLF reflection heights and electron density during eclipse have been estimated from tweek analysis. The reflection height increased from ~90 km from the first occurrence of tweek to about 93-94 km at the totality and then decreased to ~89 km at the end of the eclipse. The reflection heights are lower by 2-3 km as compared to the usual nighttime tweek reflection heights. The electron density is found to vary between 25-27 cm-3 at the reflection heights. The significant increase in tweek reflection height of about 15 km during the eclipse as compared to the daytime (morning) reflection heights of ~ 78 km is observed. Observations suggest that about 30-40% obscuration of solar disc can lead to the tweeks occurrence which otherwise occur only in the nighttime. A significant increase of 3dB in the strength of the amplitude of VLF signal is observed around the time of TSE as compared to a control day. These low latitude ionospheric perturbations on the eclipse day are discussed and compared with other normal days. During a solar eclipse, the decrease in solar flux due to moon's shadow causes sudden change in the D-region physical and chemical processes. During the totality due to blocking of Lyman-α 1215Å (major D-region ionizing radiation) by moon's umbral shadow, the electron density decreases drastically towards the nighttime values [Smith, 1972]. During the TSE, there was no production of ionization in the ionosphere and the ions and electrons in the lowest part of it recombined at a rapid rate resulting a depletion in the electron density in the 'D' region of the Ionosphere and hence an

  9. Studies on ionospheric scintillation using the S4 and ROT indices over Indian low latitude station during the year 2009 to 2012

    NASA Astrophysics Data System (ADS)

    Tanna, Hemali; Pathak, Kamlesh

    The dual frequency signals from the GPS satellites recorded at an Indian low latitude station Surat (21.16(°) N, 72.78(°) E), situated near the northern crest of the equatorial anomaly have been analysed to study the ionospheric scintillation in terms of amplitude scintillation S_{4} index and Total Electron Content (TEC) for the rising phase of solar activity period from the year 2009 to 2012. In this study we described the diurnal variation of scintillation along with TEC variation, solar activity dependence and effects of a space weather related event, a geomagnetic storms on scintillation. The diurnal variation of scintillation shows co-existence of F region irregularities with a scale length of few kilometers and 400 m as apparent from TEC depletion and ROT fluctuations, which occurred simultaneously during night-time ionospheric scintillation. The number of concurrently occurred scintillation activities with S _{4} _{}> 0.2 and enhancement of ROTI (ROTI>0.5) during different years are brought out. It is found that scintillation occurred with enhancement of ROTI at Surat is at its maximum during the year 2012, 2011 and 2010 followed by a minimum during the year 2009 showing positive correlation with solar activity. Scintillation variations during the geomagnetic storms registered during the period 2011-2012 with Dst <-100 nT are analysed. Scintillation inhibition and generation found the local time dependence of ring current strength measured by the Dst index showing good agreement with Aaron’s criteria.

  10. On the response of the equatorial and low latitude ionospheric regions in the Indian sector to the large magnetic disturbance of 29 October 2003

    NASA Astrophysics Data System (ADS)

    Manju, G.; Pant, T. Kumar; Ravindran, S.; Sridharan, R.

    2009-06-01

    The present paper investigates the response of the equatorial and low latitude ionosphere over the Indian longitudes to the events on 29 October 2003 using ionosonde data at Trivandrum (8.5° N (0.5° N geomagnetic), 77° E) and SHAR (13.7° N (5.7° N geomagnetic), 80.2° E), ground-based magnetometer data from Trivandrum and Total Electron Content (TEC) derived from GPS data at the locations of Ahmedabad (23° N (15° N geomagnetic), 72° E), Jodhpur (26.3° N (18.3° N geomagnetic), 73° E) and Delhi (28° N (20° N geomagnetic), 77° E). Following the storm sudden commencement, the TEC at all the three stations showed an overall enhancement in association with episodes of inter-planetary electric field penetration. Interestingly, real ionospheric height profiles derived using the ionosonde data at both Trivandrum and SHAR showed significant short-term excursions and recoveries. In the post noon sector, these features are more pronounced over SHAR, an off equatorial station, than those over Trivandrum indicating the increased effects of neutral winds.