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Proceedings ArticleDOI

Investigation of The Atmosphere and Ionosphere by The Radiophysical Measuring Complex of The “Mikhnevo” Geophysical Observatory

01 Jul 2019-Vol. 2019, pp 171-174
TL;DR: In this paper, a study of appearance and spatio-temporal dynamics of disturbances of the atmosphere, the upper and lower ionosphere, require of integrated investigations of interrelated processes at different altitudes and in different geophysical conditions.
Abstract: A study of appearance and spatio-temporal dynamics of disturbances of the atmosphere, the upper and lower ionosphere, require of integrated investigations of interrelated processes at different altitudes and in different geophysical conditions. In the observatory of IDG RAS "Mikhnevo" created the unique radiophysical complex, allowing to carry out of coordinated measurements of variations of the geomagnetic field, propagation of SW, LW and VLF radio signals, variations of electric fields and atmospheric currents. Analysis of the data of measurements of the total electron content of the ionosphere with phase and amplitude of the signals of LF-VLF range on global and regional routes allows to obtain data on the features of the structure and dynamics of the ionospheric plasma in the mid-latitude zone of the European part of the Russian Federation. The coordinated analysis of GNSS and VLF signals makes it possible to study the mechanisms of the relationship between the perturbations of the upper and lower ionosphere and the dynamics of the ionosphere in the horizontal and vertical directions.
References
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Journal ArticleDOI
TL;DR: In this article, a quantitative model of the relaxation of transient lower ionospheric (D region) disturbances caused by lightning-induced electron precipitation is developed, taking advantage of known particular features of the lightning induced disturbances, such as the fact that they are produced in typically <1 s and decay over 10-100 s.
Abstract: A quantitative model of the relaxation of transient lower ionospheric (D region) disturbances caused by lightning-induced electron precipitation is developed, taking advantage of known particular features of the lightning-induced disturbances, such as the fact that they are produced in typically <1 s and decay over 10–100 s. The model represents the nighttime D region as consisting of only four kinds of charged particles (electrons, positive ions, negative ions, and positive cluster ions) and is particularly suited for description of the detailed behavior of the electron density. Application of the model to some previously modeled disturbances indicates that some of the least known chemical reaction rates in the nighttime D region altitudes may be measurable using subionospheric VLF data. In the production of secondary ionization by precipitating electron bursts, the model calculations indicate the presence of a saturation effect such that the number density of the secondary electrons is not simply equal to the ion pair production rate times the burst duration. In some cases involving precipitation of ∼1-MeV electrons, the model predicts the formation of new layers of ionization at 50–70 km altitude that represent a different attachment-detachment quasi-equilibrium value from that of the unperturbed ambient. Such new layers may exist for up to ∼105 s following electron precipitation bursts.

113 citations


"Investigation of The Atmosphere and..." refers methods in this paper

  • ...These models include two versions of widely accepted Glukhov-Pasko-Inan model (GPI) [11], two versions of our own 5-component model....

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Journal ArticleDOI
TL;DR: In this article, the authors present WACCM-D, a variant of the Whole Atmosphere Community Climate Model, which includes a set of lower ionosphere (D-region) chemistry: 307 reactions of 20 positive ions and 21 negative ions.
Abstract: Energetic particle precipitation (EPP) and ion chemistry affect the neutral composition of the polar middle atmosphere. For example, production of odd nitrogen and odd hydrogen during strong events can decrease ozone by tens of percent. However, the standard ion chemistry parameterization used in atmospheric models neglects the effects on some important species, such as nitric acid. We present WACCM-D, a variant of the Whole Atmosphere Community Climate Model, which includes a set of lower ionosphere (D-region) chemistry: 307 reactions of 20 positive ions and 21 negative ions. We consider realistic ionization scenarios and compare the WACCM-D results to those from the Sodankyla Ion and Neutral Chemistry (SIC), a state-of-the-art 1-D model of the D-region chemistry. We show that WACCM-D produces well the main characteristics of the D-region ionosphere, as well as the overall proportion of important ion groups, in agreement with SIC. Comparison of ion concentrations shows that the WACCM-D bias is typically within ±10% or less below 70 km. At 70–90 km, when strong altitude gradients in ionization rates and/or ion concentrations exist, the bias can be larger for some groups but is still within tens of percent. Based on the good agreement overall and the fact that part of the differences are caused by different model setups, WACCM-D provides a state-of-the-art global representation of D-region ion chemistry and is therefore expected to improve EPP modeling considerably. These improvements are demonstrated in a companion paper by Andersson et al.

95 citations

Journal ArticleDOI
TL;DR: In this article, the Earth-ionosphere waveguide mode interference pattern in the spectra of radio atmospherics (or sferics for short), which are the high-power, broadband, very low frequency (VLF, 3-30 kHz) signals launched by lightning discharges, was measured and applied to measure the local midlatitude daytime ionospheric D region electron density profile sharpness.
Abstract: [1] We described and applied a technique to measure the local midlatitude daytime ionospheric D region electron density profile sharpness from the Earth-ionosphere waveguide mode interference pattern in the spectra of radio atmospherics (or sferics for short), which are the high-power, broadband, very low frequency (VLF, 3–30 kHz) signals launched by lightning discharges. VLF propagation simulations are used to show that the upper VLF frequency spectral minima of sferics on several hundred kilometers long propagation paths depend critically on the effective D region sharpness while depending only weakly on the effective D region height. This enables the straightforward extraction of the sharpness parameter from measured VLF spectra, which generally exhibit well-defined minima at upper VLF frequencies. By applying this technique, we calculated the profile sharpness during morning, noontime, and afternoon periods in 3 different days using sferics from ∼660–800 km away. The measured sharpness showed a weak dependence on the solar zenith angle, with values between 0.35 and 0.45 km−1 for angles from 20° to 75°. This is different from the previous narrowband measurement since the sharpness derived from narrowband VLF signals highly depends on the solar zenith angle. To better understand this discrepancy, we also used simulations to calculate the equivalent exponential profiles for International Reference Ionosphere (IRI) profiles and the empirical FIRI model profiles. The equivalent exponential profiles can best duplicate the sferic spectral characteristics for IRI and FIRI models. We find that both the magnitudes and solar zenith angle variations of the sharpness for our broadband measurements, previous narrowband measurements, and both models are completely different. This suggests the daytime ionosphere, particularly at larger solar zenith angles, may not be well described by a simple two-parameter exponential model.

55 citations

Journal ArticleDOI
TL;DR: In this paper, the effects of solar flares on the propagation of subionospheric VLF signals from NWC and NLK transmitter stations monitored at a low-latitude station, Suva (18.2°S, 178.4°E), Fiji, between December 2006 and December 2010 (an unprecedented solar minimum of solar cycles 23 and 24) and between January 2012 and December 2013 (moderate solar activity at the peak of solar cycle 24) have been analyzed to find solar flare time D-region changes.
Abstract: The effects of solar flares on the propagation of subionospheric VLF signals from NWC and NLK transmitter stations monitored at a low-latitude station, Suva (18.2°S, 178.4°E), Fiji, between December 2006 and December 2010 (an unprecedented solar minimum of solar cycles 23 and 24) and between January 2012 and December 2013 (moderate solar activity at the peak of solar cycle 24) have been analyzed to find solar flare time D-region changes. The amplitude and phase enhancements associated with solar flares were observed in the signals from both stations which are due to an increase in the electron density of the D-region as a result of extra ionization caused by the solar flares. The solar flare-induced perturbations in both the amplitude and phase of VLF signals were used to determine D-region ionospheric parameters: H′ (the ionospheric reflection height) and β (rate of increase in electron density with height) using Long Wave Propagation Capability (LWPC) version 2.1 modeling. A comparative analysis of the ionospheric D-region parameter changes carried out for this location shows a greater increase in β and decrease in H′ during low-solar activity period than during moderate-solar activity period, for the same class of flares. Our results also show greater differences in the values of β and H′ for strong flares in comparison with weak flares under both low- and moderate-solar activity conditions.

33 citations


"Investigation of The Atmosphere and..." refers background in this paper

  • ...The complex provides comprehensive information on the state of the geophysical environment both in undisturbed conditions and during perturbations caused by natural and anthropogenic processes, such as solar eclipses [1], heating experiments [2], magnetic storms [3], solar flares [4]....

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Journal ArticleDOI

12 citations


"Investigation of The Atmosphere and..." refers background in this paper

  • ...The complex provides comprehensive information on the state of the geophysical environment both in undisturbed conditions and during perturbations caused by natural and anthropogenic processes, such as solar eclipses [1], heating experiments [2], magnetic storms [3], solar flares [4]....

    [...]