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1.
V. A. Panchenko V. A. Telegin V. G. Vorob’ev G. A. Zhbankov O. I. Yagodkina V. I. Rozhdestvenskaya 《Geomagnetism and Aeronomy》2018,58(2):229-236
The results of studying spread F obtained from the DPS-4 ionosonde data at the observatory of the Pushkov Institute of Terrestrial Magnetism, Ionosphere, and Radio Wave Propagation (Moscow) are presented. The methodical questions that arise during the study of a spread F phenomenon in the ionosphere are considered; the current results of terrestrial observations are compared with previously published data and the results of sounding onboard an Earth-satellite vehicle. The automated algorithm for estimation of the intensity of frequency spread F, which was developed by the authors and was successfully verified via comparison of the data of the digisonde DPS-4 and the results of manual processing, is described. The algorithm makes it possible to quantify the intensity of spread F in megahertz (the dFs parameter) and in the number of points (0, 1, 2, 3). The strongest spread (3 points) is shown to be most likely around midnight, while the weakest spread (0 points) is highly likely to occur during the daytime. The diurnal distribution of a 1–2 point spread F in the winter indicates the presence of additional maxima at 0300–0600 UT and 1400–1700 UT, which may appear due to the terminator. Despite the large volume of processed data, we can not definitively state that the appearance of spread F depends on the magnetic activity indices Kp, Dst, and AL, although the values of the dFs frequency spread interval strongly increased both at day and night during the magnetic storm of March 17–22, 2015, especially in the phase of storm recovery on March 20–22. 相似文献
2.
N. A. Barkhatov V. G. Vorob’ev S. E. Revunov O. I. Yagodkina 《Geomagnetism and Aeronomy》2017,57(3):251-256
An algorithm for retrieving the AL index dynamics from the parameters of solar-wind plasma and the interplanetary magnetic field (IMF) has been developed. Along with other geoeffective parameters of the solar wind, an integral parameter in the form of the cumulative sum Σ[N*V 2] is used to determine the process of substorm formation. The algorithm is incorporated into a framework developed to retrieve the AL index of an Elman-type artificial neural network (ANN) containing an additional layer of neurons that provides an “internal memory” of the prehistory of the dynamical process to be retrieved. The ANN is trained on data of 70 eight-hour-long time intervals, including the periods of isolated magnetospheric substorms. The efficiency of this approach is demonstrated by numerical neural-network experiments on retrieving the dynamics of the AL index from the of solar wind and IMF parameters during substorms. 相似文献
3.
Geomagnetism and Aeronomy - The ion pressure in the regions of ionospheric projections of the plasma mantle, polar cusp, low-latitude boundary layer, and the region of structured precipitation of... 相似文献
4.
I. P. Kirpichev O. I. Yagodkina V. G. Vorobjev E. E. Antonova 《Geomagnetism and Aeronomy》2016,56(4):407-414
The position of the auroral oval poleward and equatorward boundary projections on the equatorial plane in the nightside MLT sector during magnetically quiet periods (|AL| < 200 nT, |Dst| < 10 nT) has been determined. The oval boundary positions were determined according to the precipitation model developed at Polar Geophysical Institute (http://apm.pgia.ru/). The isotropy of the averaged plasma pressure and the experimentally confirmed balance of pressures during the nighttime have been taken into account. The morphological mapping method has been used to map the oval poleward and equatorward edges without the use of any magnetic field model on the assumption that the condition of magnetostatic equilibrium is valid. Ion pressures at ionospheric altitudes and in the equatorial plane have been compared. It has been shown that the auroral oval equatorward boundary in the midnight sector is localized at geocentric distances of ~7 RE, which is in good agreement with the position of the energetic particle injection boundary in the equatorial plane. The oval poleward edge is localized at the ~10 RE geocentric distance, which is in good agreement with the position of the equatorward boundary of the region with a high turbulence level in the Earth’s magnetosphere plasma sheet. 相似文献
5.
The optical observations on Heiss Island (Φ′ = 75.0°) have been used to study the characteristics of auroras in the near-noon
MLT sector after abrupt increases in the solar wind dynamic pressure at negative and positive polarity of the IMF B
z
component. It has been found out that the 427.8 and 557.7 nm emission intensities considerably increased at B
z
< 0 both equatorward of the dayside red luminosity band and within this band. The value of the emission intensities at a
red luminosity maximum (I
6300/I
5577 ∼ 0.5) indicates that energetic electron precipitation is of the magnetospheric origin. At B
z
> 0, fluxes of harder (E > 1 keV) precipitating electrons were superimposed on the soft spectrum of precipitating particles in the equatorial part
of the red luminosity band. This red band part was hypothetically caused by the low-latitude boundary layer (LLBL) on closed
lines of the geomagnetic field, the estimated thickness of which is ∼3 R
e
. The 557.7 nm emission intensity increased during 3–5 min after SC/SI and was accompanied by the displacement of the red
band equatorward boundary toward lower latitudes. The displacement value was ∼150–200 km when the dynamic pressure abruptly
increased by a factor of 3–5. After SC/SI, the 630.0 nm emission intensity continued increasing during 16–18 min. It is assumed
that the time of an increase in the red line intensity corresponds to the time of saturation of the magnetospheric boundary
layers with magnetosheath particles after an abrupt increase in their density. 相似文献
6.
V. G. Vorobjev A. S. Kirillov Ju. V. Katkalov O. I. Yagodkina 《Geomagnetism and Aeronomy》2013,53(6):711-715
A model of auroral precipitation (AP) developed on the basis of statistical processing of DMSP F6 and F7 satellite data (Vorobjev and Yagodkina, 2005, 2007) was used for the calculation of the global distribution of the auroral luminosity in different spectral ranges. The algorithm for the calculation of the integral intensity in bands N2 LBH (170.0 nm), ING N 2 + (391.4 nm), 1PG N2 (669.0 nm), and (OI) 557.7-nm emission is shown in detail. The processes of formation of electronically excited atoms O(1S) as a result of the transport of excitation energy from metastable state N2(A3Σ u + ), excitation of O(3P) by primary and secondary electrons, and dissociative recombination were taken into account to calculate the intensity of emission at 557.7 nm. A high correlation between the model distribution of the auroral luminosity in the UV spectral range and the observations of the Polar satellite is demonstrated. 相似文献
7.
Characteristics of ion and electron precipitations in the dawn and dusk sectors are investigated by DMSP F6 and F7 satellite observations. It is shown that in the dusk sector the positions of electron and ion precipitation boundaries are nearly coincident for all levels of magnetic activity; however the latitudinal distribution of energy fluxes indicates that the positions of electron and ion precipitation maxima are spatially separated. Maximum energy fluxes of ions is observed at the equatorial precipitation boundary, while those of electrons at the poleward one. In the dawn sector, the electron precipitation region is 3°–4° wider than that of ions. The isotropy boundary in the dusk sector is located in the region of diffuse precipitation (DAZ) near its poleward boundary for all levels of magnetic activity, while in the dawn sector it falls in the region of structured precipitations (AOP). Electron precipitations are dominating in the dawn sector. Here in the region of diffuse precipitation (DAZ), the ion energy fluxes Fi make less than 5% as compared to the electron energy flux Fe. In the region of structured precipitations (AOP), the portion of Fi decreases with increasing magnetic activity from ~10–20% for AL ≈ -100 nT to <5% for AL ≈ -1000 nT. As for the dusk sector, in the AOP region, electron precipitations are dominating as well, while in the DAZ region the ion energy fluxes are significant. In the 1500–1800 MLT sector, the ratio Fi/Fe increases from ~0.7 to ~3.0 with AL changing from -100 nT to -1000 nT. 相似文献
8.
V.?G.?VorobjevEmail author O.?I.?Yagodkina V.?L.?Zverev 《Geomagnetism and Aeronomy》2016,56(6):682-693
Characteristics of isolated substorms selected by variations in the 1-min values of the AL index are analyzed. The substorms were divided into several types with respect to the behavior of the Bz component of the interplanetary magnetic field (IMF) during the expansion phase. The probability of observations of substorms associated with the northward turn of the Bz component of IMF was ~19%, while the substorms taking place at Bz < 0 were observed in 53% of cases. A substantial number of events in which no substorm magnetic activity was observed in the auroral zone after a long (>30 min) period of the southward IMF and a following sharp turn of the Bz component of IMF before the north was detected. The data suggest that a northward IMF turn is neither a necessary nor sufficient condition for generating substorms. It has been shown for substorms of the both types that the average duration of the southward IMF to moment T 0 and the average intensity of the magnetic perturbation in the maximum are approximately the same and amount to ~80 min and–650 nT, respectively. However, for substorms at Bz < 0, their mean duration, including the expansive and recovery phases, is on average 30 min longer than that at a northward turn of IMF. Correlations between the loading–unloading processes in the magnetosphere in the periods of magnetospheric substorms were investigated with different functions that determine the efficiency of the energy transfer from the solar wind to the magnetosphere. It has been shown that the highest correlation coefficient (r = 0.84) is observed when the function suggested by Newell et al. (2007) is used. It has been detected that a simple function VB S yields a high correlation coefficient (r = 0.75). 相似文献
9.
10.
The characteristics of dayside auroras during the large (16–24 nT) positive values of the IMF B
z
component, observed on January 14, 1988, during the interaction between the Earth’s magnetosphere and the body of the interplanetary
magnetic cloud, have been studied based on the optical observations on Heiss Island. A wide band of diffuse red luminosity
with an intensity of 1–2 kilorayleigh (kR) was observed during 6 h in the interval 1030–1630 MLT at latitudes higher than
75° CGL. Rayed auroral arcs, the brightness of which in the 557.7 nm emission sharply increased to 3–7 kR in the postnoon
sector immediately after the polarity reversal of the IMF B
y
component from positive to negative, were continuously registered within the band. Bright auroral arcs were observed at the
equatorward edge of red luminosity. It has been found out that the red auroral intensity increases and the band equatorward
boundary shifts to lower latitudes with increasing solar wind dynamic pressure. However, a direct proportional dependence
of the variations in the auroral features on the dynamic pressure variations has not been found. It has been concluded that
the source of bright discrete auroras is located in the region of the low-latitude boundary layer (LLBL) on closed geomagnetic
field lines. The estimated LLBL thickness is ∼3 R
e
. It has been concluded that the intensity of the dayside red band depends on the solar wind plasma density, whereas the position
of the position equatorward boundary depends on the dynamic pressure value and its variations. 相似文献