A conductivity model for the Brazilian equatorial e-region: initial results

Denardini, Clezio Marcos

doi:10.1590/s0102-261x2007000600011

Cited by 10 publications

(7 citation statements)

References 15 publications

(8 reference statements)

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“…After obtaining E z , we used the conductivity model to calculate the Hall ( σ H ) and Pedersen ( σ P ) conductivities along the magnetic meridian overhead the RESCO radar site with grid resolution of 1 km in both up‐down and magnetic north‐south directions. Thereafter, we used the magnetic field model to obtain the field line coordinates, as described in Denardini [], and the E y are derived as follows:

E_{y} = \frac{\int_{- θ}^{+ θ} \begin{array}{c} center & σ_{P} & boldr \cdot normald boldθ \end{array}}{\int_{- θ}^{+ θ} \begin{array}{c} center & σ_{H} & boldr \cdot normald boldθ \end{array}} \cdot E_{z} \Rightarrow E_{y} = \frac{{normalΣ}_{P}}{{normalΣ}_{H}} \cdot E_{z} .

…”

Section: Methodsmentioning

confidence: 99%

“…In order to provide the physical plasma parameter (e.g., collision frequencies, cyclotron frequency, densities, and conductivities) and the geomagnetic field at the E region height to allow the computations of the zonal component of the electric field, a magnetic field‐aligned‐integrated conductivity model was developed for proving the conductivities using the IRI‐2007, the MSIS‐2000, and the IGRF‐11 models as input parameters for ionosphere, neutral atmosphere, and Earth magnetic field, respectively. This model was originally developed by Denardini [], and several other updates have being applied since then, like the ion‐neutron collision frequencies of all the species to be combined through the momentum transfer collision frequency equation.…”

Section: Methodsmentioning

confidence: 99%

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E region electric field dependence of the solar activity

et al. 2015

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We have being studying the zonal and vertical E region electric field components inferred from the Doppler shifts of type 2 echoes (gradient drift irregularities) detected with the 50 MHz backscatter coherent radar set at São Luis, Brazil (SLZ, 2.3°S, 44.2°W) during the solar cycle 24. In this report we present the dependence of the vertical and zonal components of this electric field with the solar activity, based on the solar flux F10.7. For this study we consider the geomagnetically quiet days only (Kp ≤ 3+). A magnetic field‐aligned‐integrated conductivity model was developed for proving the conductivities, using the IRI‐2007, the MISIS‐2000, and the IGRF‐11 models as input parameters for ionosphere, neutral atmosphere, and Earth magnetic field, respectively. The ion‐neutron collision frequencies of all the species are combined through the momentum transfer collision frequency equation. The mean zonal component of the electric field, which normally ranged from 0.19 to 0.35 mV/m between the 8 and 18 h (LT) in the Brazilian sector, show a small dependency with the solar activity. Whereas the mean vertical component of the electric field, which normally ranges from 4.65 to 10.12 mV/m, highlights the more pronounced dependency of the solar flux.

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E_{y} = \frac{\int_{- θ}^{+ θ} \begin{array}{c} center & σ_{P} & boldr \cdot normald boldθ \end{array}}{\int_{- θ}^{+ θ} \begin{array}{c} center & σ_{H} & boldr \cdot normald boldθ \end{array}} \cdot E_{z} \Rightarrow E_{y} = \frac{{normalΣ}_{P}}{{normalΣ}_{H}} \cdot E_{z} .

…”

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

E region electric field dependence of the solar activity

et al. 2015

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“…The zonal electric field component, E y , is calculated from E z and a magnetic field line‐integrated conductivity model developed by Denardini [] and recently updated by Moro et al [] to include more realistic atmospheric parameters. The model is essentially composed by (a) neutral densities and temperature provided by the Mass Spectrometer and Incoherent Scatter Model (NRLMSISE‐00, hereafter written as MSIS), (b) electron density and ion composition in the momentum transfer collision frequency equation provided by the International Reference Ionosphere (IRI–2007) model, (c) adjustments to the mean electron density obtained from the E region ordinary frequency ( f o E ) obtained by ionosondes at three stations across the magnetic equator to compensate the IRI underestimation of the E region peak density in the Brazilian sector [ Abdu et al , ], and (d) geomagnetic field strength and its horizontal component provided by the International Geomagnetic Reference Field (IGRF–11) model.…”

Section: Data and Analysismentioning

confidence: 99%

Equatorial E region electric fields at the dip equator: 2. Seasonal variabilities and effects over Brazil due to the secular variation of the magnetic equator

et al. 2016

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In this work, the seasonal dependency of the E region electric field (EEF) at the dip equator is examined. The eastward zonal (Ey) and the daytime vertical (Ez) electric fields are responsible for the overall phenomenology of the equatorial and low‐latitude ionosphere, including the equatorial electrojet (EEJ) and its plasma instability. The electric field components are studied based on long‐term backscatter radars soundings (348 days for both systems) collected during geomagnetic quiet days (Kp ≤ 3+), from 2001 to 2010, at the São Luís Space Observatory (SLZ), Brazil (2.33°S, 44.20°W), and at the Jicamarca Radio Observatory (JRO), Peru (11.95°S, 76.87°W). Among the results, we observe, for the first time, a seasonal difference between the EEF in these two sectors in South America based on coherent radar measurements. The EEF is more intense in summer at SLZ, in equinox at JRO, and has been highly variable with season in the Brazilian sector compared to the Peruvian sector. In addition, the secular variation on the geomagnetic field and its effect on the EEJ over Brazil resulted that as much farther away is the magnetic equator from SLZ, later more the EEJ is observed (10 h LT) and sooner it ends (16 h LT). Moreover, the time interval of type II occurrence decreased significantly after the year 2004, which is a clear indication that SLZ is no longer an equatorial station due to the secular variation of the geomagnetic field.

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“…The magnetic field-line-integrated conductivity model was developed by Denardini (2007). It is essentially composed of: (a) neutral densities and temperature provided by the MSIS model; (b) electron density and ions compositions in the momentum transfer collision frequency equation provided by the IRI model; (c) adjustments to the mean electron density obtained from f 0 E at three stations across the magnetic equator to compensate the IRI underestimation of the E-region peak density in the Brazilian sector ; and (d) geomagnetic field strength and its horizontal component provided by the IGRF model.…”

Section: Magnetic Field-line-integrated Ionospheric Conductivity Modelmentioning

confidence: 99%

Influence of uncertainties of the empirical models for inferring the E-region electric fields at the dip equator

et al. 2016

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Daytime E-region electric fields play a crucial role in the ionospheric dynamics at the geomagnetic dip latitudes. Due to their importance, there is an interest in accurately measuring and modeling the electric fields for both climatological and near real-time studies. In this work, we present the daytime vertical (Ez) and eastward (Ey) electric fields for a reference quiet day (February 7, 2001) at the São Luís Space Observatory, Brazil (SLZ, 2.31°S, 44.16°W). The component Ez is inferred from Doppler shifts of type II echoes (gradient drift instability) and the anisotropic factor, which is computed from ion and electron gyro frequencies as well as ion and electron collision frequencies with neutral molecules. The component Ey depends on the ratio of Hall and Pedersen conductivities and Ez. A magnetic field-line-integrated conductivity model is used to obtain the anisotropic factor for calculating Ez and the ionospheric conductivities for calculating Ey. This model uses the NRLMSISE-00, IRI-2007, and IGRF-11 empirical models as input parameters for neutral atmosphere, ionosphere, and geomagnetic field, respectively. Consequently, it is worth determining the uncertainties (or errors) in Ey and Ez associated with these empirical model outputs in order to precisely define the confidence limit for the estimated electric field components. For this purpose, errors of ±10 % were artificially introduced in the magnitude of each empirical model output before estimating Ey and Ez. The corresponding uncertainties in the ionospheric conductivity and electric field are evaluated considering the individual and cumulative contribution of the artificial errors. The results show that the neutral densities and temperature may be responsible for the largest changes in Ey and Ez, followed by changes in the geomagnetic field intensity and electron and ions compositions.

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A conductivity model for the Brazilian equatorial e-region: initial results

Cited by 10 publications

References 15 publications

E region electric field dependence of the solar activity

E region electric field dependence of the solar activity

Equatorial E region electric fields at the dip equator: 2. Seasonal variabilities and effects over Brazil due to the secular variation of the magnetic equator

Influence of uncertainties of the empirical models for inferring the E-region electric fields at the dip equator

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