Apatity, Russia
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Barabash V.,Lulea University of Technology | Osepian A.,Polar Geophysical Institute | Dalin P.,Swedish Institute of Space Physics | Kirkwood S.,Swedish Institute of Space Physics
Annales Geophysicae | Year: 2012

The theoretical PGI (Polar Geophysical Institute) model for the quiet lower ionosphere has been applied for computing the ionization rate and electron density profiles in the summer and winter D-region at solar zenith angles less than 80° and larger than 99° under steady state conditions. In order to minimize possible errors in estimation of ionization rates provided by solar electromagnetic radiation and to obtain the most exact values of electron density, each wavelength range of the solar spectrum has been divided into several intervals and the relations between the solar radiation intensity at these wavelengths and the solar activity index F10.7 have been incorporated into the model. Influence of minor neutral species (NO, H2O, O, O3) concentrations on the electron number density at different altitudes of the sunlit quiet D-region has been examined. The results demonstrate that at altitudes above 70 km, the modeled electron density is most sensitive to variations of nitric oxide concentration. Changes of water vapor concentration in the whole altitude range of the mesosphere influence the electron density only in the narrow height interval 73-85 km. The effect of the change of atomic oxygen and ozone concentration is the least significant and takes place only below 70 km.

Model responses to changes of the solar zenith angle, solar activity (low-high) and season (summer-winter) have been considered. Modeled electron density profiles have been evaluated by comparison with experimental profiles available from the rocket measurements for the same conditions. It is demonstrated that the theoretical model for the quiet lower ionosphere is quite effective in describing variations in ionization rate, electron number density and effective recombination coefficient as functions of solar zenith angle, solar activity and season. The model may be used for solving inverse tasks, in particular, for estimations of nitric oxide concentration in the mesosphere. © Author(s) 2012. CC Attribution 3.0 License.

Barabash V.,Lulea University of Technology | Osepian A.,Polar Geophysical Institute | Dalin P.,Swedish Institute of Space Physics
Annales Geophysicae | Year: 2014

Mesospheric water vapour concentration effects on the ion composition and electron density in the lower ionosphere under quiet geophysical conditions were examined. Water vapour is an important compound in the mesosphere and the lower thermosphere that affects ion composition due to hydrogen radical production and consequently modifies the electron number density. Recent lower-ionosphere investigations have primarily concentrated on the geomagnetic disturbance periods. Meanwhile, studies on the electron density under quiet conditions are quite rare. The goal of this study is to contribute to a better understanding of the ionospheric parameter responses to water vapour variability in the quiet lower ionosphere. By applying a numerical D region ion chemistry model, we evaluated efficiencies for the channels forming hydrated cluster ions from the NO+ and O2+ primary ions (i.e. NO+.H2O and O2+.H2O, respectively), and the channel forming H+(H2O)nproton hydrates from water clusters at different altitudes using profiles with low and high water vapour concentrations. Profiles for positive ions, effective recombination coefficients and electrons were modelled for three particular cases using electron density measurements obtained during rocket campaigns. It was found that the water vapour concentration variations in the mesosphere affect the position of both the Cl2+ proton hydrate layer upper border, comprising the NO+(H2O)nand O2+(H2O)nhydrated cluster ions, and the Cl1+ hydrate cluster layer lower border, comprising the H+(H2O)npure proton hydrates, as well as the numerical cluster densities. The water variations caused large changes in the effective recombination coefficient and electron density between altitudes of 75 and 87 km. However, the effective recombination coefficient, αeff, and electron number density did not respond even to large water vapour concentration variations occurring at other altitudes in the mesosphere. We determined the water vapour concentration upper limit at altitudes between 75 and 87 km, beyond which the water vapour concentration ceases to influence the numerical densities of Cl2+ and Cl1+, the effective recombination coefficient and the electron number density in the summer ionosphere. This water vapour concentration limit corresponds to values found in the H2O-1 profile that was observed in the summer mesosphere by the Upper Atmosphere Research Satellite (UARS). The electron density modelled using the H2O-1 profile agreed well with the electron density measured in the summer ionosphere when the measured profiles did not have sharp gradients. For sharp gradients in electron and positive ion number densities, a water profile that can reproduce the characteristic behaviour of the ionospheric parameters should have an inhomogeneous height distribution of water vapour.©Author(s) 2014.

Kozelov B.V.,Polar Geophysical Institute | Golovchanskaya I.V.,Polar Geophysical Institute
Journal of Geophysical Research: Space Physics | Year: 2010

In the study of scaling properties of auroral luminosity variations by ground-based imaging observations, a problem arises that the actual scaling characteristics are distorted because of contributions to images from extension of auroral structures along the geomagnetic field. The field-aligned trends come into play for whatever small deviations from the magnetic zenith, making questionable the appropriateness of ground imaging data for investigation of turbulence signatures in aurora. In order to clear up how to correct for this effect, we have modeled the distortions, stemming from aspect angle broadening, for synthesized self-similar fluctuations with known scaling characteristics in the plane perpendicular to the magnetic field. Both narrow and wide field-aligned profiles of luminosity were considered. Three estimators for deriving scaling parameters were applied, including the wavelet estimator, dyadic filter estimator, and standard deviation statistical estimator, of which the wavelet estimator is shown to be most robust. The formulas are presented that relate the observed scaling characteristics with the true ones for the case of aurora being observed near magnetic zenith. Copyright 2010 by the American Geophysical Union.

Golovchanskaya I.V.,Polar Geophysical Institute | Kozelov B.V.,Polar Geophysical Institute
Journal of Geophysical Research: Space Physics | Year: 2010

We compare scaling properties of electric fields measured by the low-altitude polar-orbiting Dynamics Explorer 2 satellite in the auroral zone and the polar cap under interplanetary magnetic field (IMF) southward conditions. The techniques of logscale diagrams (LDs) and probability density function (PDF) are applied to demonstrate the scale-free structure of electric fluctuations on scales from 0.5 km to 256 km in both regions. It is shown that while the amplitudes of electric field fluctuations are much smaller in the polar cap than in the auroral zone, the scaling characteristics of the fluctuations in the two domains are basically the same. To examine the possibility that electric turbulence in the polar cap may be driven directly by turbulent solar wind variations, we searched for the relationship between the RMS values of the electric fluctuations in the polar cap and solar wind variability and did not find a clear relationship. We also demonstrate that the Poynting flux associated with electric and magnetic fluctuations in the polar cap tends to subside from the flanks toward the center of the polar cap. These findings are more consistent with plasma shear flow on open field lines being the driver of turbulence in the polar cap ionosphere. Copyright 2010 by the American Geophysical Union.

Kornilova T.A.,Polar Geophysical Institute | Kornilov I.A.,Polar Geophysical Institute
Journal of Geophysical Research: Space Physics | Year: 2012

Using of high-quality keograms constructed by filtered and averaged images from the Lovozero all-sky imager (ASI) station and THEMIS all-sky imager array allowed us to investigate in detail optical signatures of poleward forms propagating equatorward and getting involved in the auroral pattern in the course of substorm expansion. We found that weak, nearly east-west oriented auroral arcs often penetrate into poleward expanding regions of active auroras from preceding breakup activations in the south. In total, 40 such events have been analyzed. The major point that we aimed to clarify is whether these weak forms fade, disperse, or keep moving equatorward in such occasions. We were able to trace their fate and demonstrate that they keep their equatorward motion against the background of bright, poleward expanding auroras, forming a counterstreaming auroral pattern at substorm expansion. Copyright 2012 by the American Geophysical Union.

The paper presents a model of the kinetics of electronically excited O 2(c 1Σ u -,v), O 2(A′ 3Δ u,v), O 2(A 3Σ u +,v) molecules at heights of the lower thermosphere and mesosphere with allowance for electronic excitation transfer processes during molecular collisions. The model is used to calculate the relative O 2(A 3Σ u +,v) and O 2(A′ 3Δ u,v) populations at heights of 80-110 km. The calculated populations are compared with the available literature results on experimental estimates, and good agreement is obtained. It is shown how the increase in the quenching rates of the considered states by oxygen atoms affects the calculation results. © 2012 Pleiades Publishing, Ltd.

Kozelov B.V.,Polar Geophysical Institute | Golovchanskaya I.V.,Polar Geophysical Institute | Mingalev O.V.,Polar Geophysical Institute
Annales Geophysicae | Year: 2011

We investigate time evolution of scaling index alpha;A that characterizes auroral luminosity fluctuations at the beginning of substorm expansion. With the use of UVI images from the Polar satellite, it is shown that alpha;A typically varies from values less than unity to ∼1.5, increasing with breakup progress. Similar scaling features were previously reported for fluctuations at smaller scales from all-sky TV observations. If this signature is interpreted in terms of non-linear interactions between scales, it means that the power of small-scale fluctuations is transferred with time to larger scales, a kind of the inverse cascade. Scaling behavior in the aurora during substorm activity is compared with that in the field-aligned currents simulated numerically in the model of non-linear interactions of Alfvénic coherent structures, according to the Chang et al. (2004) scenario. This scenario also suggests an inverse cascade, manifesting in clustering of small-scale field-aligned current filaments of the same polarity and formation of "coarse-grained" structures of field-aligned currents. © Author(s) 2011.

Yahnin A.G.,Polar Geophysical Institute | Yahnina T.A.,Polar Geophysical Institute | Frey H.,University of California at Berkeley | Pierrard V.,Belgian Institute for Space Aeronomy
Journal of Atmospheric and Solar-Terrestrial Physics | Year: 2013

Sub-oval proton auroras discovered by the IMAGE spacecraft correlate with EMIC waves (geomagnetic pulsations of the Pc1 range). This means that a common source of the waves and proton precipitation is the ion-cyclotron (IC) instability developing in the vicinity of the equatorial plane. Different forms of the proton auroras reflect different regimes of the IC instability and different conditions in the near-Earth equatorial magnetosphere. To understand what are the conditions for the generation of the sub-oval proton aurora one may map the aurora onto the equatorial plane and compare the projection with some important magnetospheric boundaries. In this report we compare the projection of so-called "proton aurora spots" with the location of the plasmapause. The latter is determined by the plasmapause formation model based on the quasi-interchange instability mechanism. The comparison shows that often the proton aurora spot source is located in the vicinity of the plasmapause or in the cold plasma gradient inside the plasmapause. In some events, the proton aurora spots map well outside the plasmapause. We assume that in the latter case the IC instability develops when westward drifting energetic protons interact with the cold plasma that was earlier detached from the plasmasphere. © 2012 Elsevier Ltd.

Vorobjev V.G.,Polar Geophysical Institute | Yagodkina O.I.,Polar Geophysical Institute | Katkalov Y.,Polar Geophysical Institute
Journal of Atmospheric and Solar-Terrestrial Physics | Year: 2013

Based on statistical treatment of DMSP F6 and F7 spacecraft observations, an interactive Auroral Precipitation Model (APM) parameterized by magnetic activity has been created (available at http://apm.pgia.ru/). For a given level of magnetic activity the model yields a global distribution of electron precipitation and planetary patterns of both average electron energy and electron energy flux in different precipitation zones. Outputs of the model were used to determine the basic variables of the magnetosphere, such as boundary location and the area of the polar cap, magnetic flux transferred from the dayside magnetosphere into the tail, global precipitation power realized by different types of precipitation and others. The model predicts an increase in the polar cap area from about 6.3×106km2 to 2.0×107km2, in the magnetic flux from 390MWb to 1200MWb, and in the global precipitation power from 3.4GW to 188.0GW, when the magnetic activity changes from silence (null AL and Dst) to significant disturbance (AL=-1000nT, Dst=-200nT). The use of dayside auroral observations as an input for APM provides an opportunity for continuous monitoring of magnetospheric conditions. Two time intervals on Dec. 27, 2000, and Dec. 12, 2004, of dayside auroral observations with the meridian scanning photometer at Barentsburg (Spitsbergen) were selected to demonstrate derivation of magnetospheric variables with APM. It is shown that the values of the AL index derived from optical observation appear in a reasonable agreement with those published by WDC. © 2013 Elsevier Ltd.

Golovchanskaya I.V.,Polar Geophysical Institute | Kozelov B.V.,Polar Geophysical Institute | Mingalev O.V.,Polar Geophysical Institute | Fedorenko Y.V.,Polar Geophysical Institute | Melnik M.N.,Polar Geophysical Institute
Geophysical Research Letters | Year: 2011

Magnetic perturbations in the topside auroral ionosphere observed by the FAST satellite in the events of broadband extra low frequency (BB ELF) turbulence are investigated at frequencies 0.5-8 Hz (scales from 14 km down to 0.9 km). The power-law scaling and peculiar polarization patterns of the perturbations are highlighted. By comparing with the magnetic fields simulated according to the Chang et al. (2004) scenario of coarse-graining process development, we demonstrate that the magnetic perturbations observed in the events of the BB ELF turbulence can be reasonably understood in terms of non-linearly interacting multiscale field-aligned currents traversed by the spacecraft. Copyright 2011 by the American Geophysical Union.

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