Topic
TEC
About: TEC is a research topic. Over the lifetime, 5119 publications have been published within this topic receiving 84696 citations.
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TL;DR: In this article, the authors proposed a robust ionospheric disturbance index that is able to accurately characterize temporal and spatial ionosphere variations of small to medium scales, which is suitable as potential driver for an ionosphere space weather scale.
Abstract: Space weather can strongly affect trans-ionospheric radio signals depending on the used frequency. In order to assess the strength of a space weather event from its origin at the sun towards its impact on the ionosphere a number of physical quantities need to be derived from scientific measurements. These are for example the Wolf number sunspot index, the solar flux density F10.7, measurements of the interplanetary magnetic field, the proton density, the solar wind speed, the dynamical pressure, the geomagnetic indices Auroral Electrojet, Kp, Ap and Dst as well as the Total Electron Content (TEC), the Rate of TEC, the scintillation indices S4 and σ (ϕ ) and the Along-Arc TEC Rate index index. All these quantities provide in combination with an additional classification an orientation in a physical complex environment. Hence, they are used for brief communication of a simplified but appropriate space situation awareness. However, space weather driven ionospheric phenomena can affect many customers in the communication and navigation domain, which are still served inadequately by the existing indices. We present a new robust index, that is able to properly characterize temporal and spatial ionospheric variations of small to medium scales. The proposed ionospheric disturbance index can overcome several drawbacks of other ionospheric measures and might be suitable as potential driver for an ionospheric space weather scale.
29 citations
TL;DR: TEC are a source of cytokines and show that TEC respond to IL1 by producing cytokines with consequences on the thymic lymphoid population, which further emphasizes the importance and complexity of paracrine molecular interactions involved in intrathymic development.
29 citations
01 Apr 2013
TL;DR: In this paper, the ionosonde NmF2 data and the JPL TEC maps were collected to investigate the equinoctial asymmetries in ionospheric electron density and its variation with solar activity.
Abstract: Abstract. The ionosonde NmF2 data (covering several solar cycles) and the JPL TEC maps (from 1998 through 2009) were collected to investigate the equinoctial asymmetries in ionospheric electron density and its variation with solar activity. With solar activity increasing, the equinoctial asymmetry of noontime NmF2 increases at middle latitudes but decreases or changes little at low latitudes, while the equinoctial asymmetry of TEC increases at all latitudes. The latitudinal feature of the equinoctial asymmetry at high solar activity is different from that at low solar activity. The increases of NmF2 and TEC with the solar proxy P = (F10.7+F10.7A)/2 also show equinoctial asymmetries that depend on latitudes. The increase rate of NmF2 with P at March equinox (ME) is higher than that at September equinox (SE) at middle latitudes, but the latter is higher than the former at the EIA crest latitudes, and the difference between them is small at the EIA trough latitudes. The phenomenon of higher increase rate at SE than at ME does not appear in TEC. The increase rate of noontime TEC with P at ME is higher than that at SE at all latitudes, and the difference between them peaks at both sides of dip equator. It is mentionable that the equinoctial asymmetries of NmF2 and TEC increase rates present some longitudinal dependence at low latitude. The influences of equinoctial differences in the thermosphere and ionospheric dynamics processes on the equinoctial asymmetry of the electron density were briefly discussed.
29 citations
TL;DR: In this article, the authors derived the transfer function for a spherically symmetric ionosphere with an arbitrary radial electron density profile in the limit where the radio frequencies of interest are much larger than the plasma frequency pe 2 / 2 )i s carried out.
Abstract: The ionospheric transfer function is derived for a spherically symmetric ionosphere with an arbitrary radial electron density profile in the limit where the radio frequencies of interest are much larger than the plasma frequency pe .A n expansion of the transfer function to second order in the parameter X ( pe 2 / 2 )i s carried out. In this limit the dispersive properties of the ionosphere are manifested as a frequency-dependent time of arrival that includes quadratic, cubic, and quartic terms in 1/. The coefficients of these terms are related to the total electron content (TEC) along the slant path from transmitter to receiver, the product of TEC and the longitudinal magnetic field strength along the slant path, and refractive bending and higher-order electron density profile effects, respectively. By fitting the time of arrival versus frequency of a transionospheric signal to a polynomial in 1/ it is possible to extract the TEC, the longitudinal magnetic field strength, the peak electron density, and an effective thickness for the ionosphere. This exercise was carried out for a number of transionospheric pulses measured in the VHF by the FORTE satellite receiver and generated by the Los Alamos Portable Pulser. The results are compared with predictions derived from the International Reference Ionosphere and the United States Geological Survey geomagnetic field model.
29 citations
TL;DR: In this article, the authors compared the noise levels of geostationary satellite signals of augmentation systems such as the Indian GAGAN, the European EGNOS and the American WAAS, as well as the signals from the Chinese Beidou navigation system.
Abstract: With the development of receiver equipment and GNSS and SBAS constellations, the coherent dual-frequency L-band transmissions are now available from a number of geostationary satellites. These signals can be used for ionospheric total electron content (TEC) estimation. The quality of these data, i.e., the level of noise in such TEC estimation is of great interest and importance. We present results of comparisons of noise patterns in TEC estimation using signals of geostationary satellites of augmentation systems such as the Indian GAGAN, the European EGNOS and the American WAAS, as well as the signals from the Chinese Beidou navigation system. We used data from two receiving sites in the European part of Russia and the USA, which are equipped with JAVAD Delta receivers. We found out that the noise level in TEC estimation based on geostationary satellites of the Beidou system is one order smaller than that for SBAS and corresponds to those of GPS/GLONASS at the same elevation angles. Typically, the TEC RMS was about 0.05 TECU for GPS/GLONASS satellites at elevation range 5---15°, 0.06 TECU for Beidou geostationary satellites at elevation range 15---25°, 0.6 TECU for GAGAN at elevation range 15---25°, 0.7 TECU for WAAS at elevation 45°, and 5 TECU for EGNOS at elevation 20°. We also discuss the capabilities of geostationary TEC observations in connection with the recent G4 geomagnetic storm of March 2015 using six IGS MGEX stations in the American, Southeast Asian and Australian sectors. We demonstrate the hemispheric asymmetry in the ionospheric TEC response during this storm.
29 citations