Polar aurora effects associated with solar flares     

B.V. Rezhenov  V.G. Vorobjev 《Planetary and Space Science》1984,32(8):925-934

The behaviour of the polar auroras in the dark part of the auroral oval during the solar flares has been examined. For the analysis 29 solar flares during spring and autumn periods when a part of the polar cap was sunlit were selected. It has been found that a sharp decreasing of the auroral arc luminosity occurred just after the solar flare onsets. Auroral arcs broke up into patches and in most cases disappeared in 2–3 min. Bright discrete auroras appeared again as a rule close to the maximum phase of the solar flares. The duration of polar aurora effects was typically from 4 to 13 min with median value of about 8 min. These effects have been observed inside the interval 18.00-04.00 M.L.T. during periods both of magnetic quiet and disturbance.For the large set of data magnetic field variations in the sunlit polar cap after the solar flare onset have been investigated. A simple model of the auroral processes for the qualitative explanation of the observed phenomenon has been suggested.  相似文献   

Ion Pressure in Different Regions of the Dayside Auroral Precipitation     

Vorobjev  V. G.  Yagodkina  O. I.  Antonova  E. E. 《Geomagnetism and Aeronomy》2020,60(6):727-736

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   

Position of projections of the nightside auroral oval equatorward and poleward edges in the magnetosphere equatorial plane     

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 R_E, 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 R_E 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   

Response of the night aurora to a negative sudden impulse     

V. B. Belakhovsky  V. G. Vorobjev 《Geomagnetism and Aeronomy》2016,56(6):694-705

Data from the meridian scanning photometers of the NORSTAR network and all-sky cameras of the THEMIS network were used for a detailed study of the response of night auroras to the sharp decrease of the solar wind dynamic pressure on September 28, 2009. The decrease in dynamic pressure was accompanied by a corresponding depression of the magnetic field in the SYM-H index and the origin of a negative sudden impulse (SI) with a duration of 5–8 min and amplitude of 150–200 nT in the horizontal component of the magnetic field at stations of the night sector of the auroral zone. The magnetic impulse was preceded by a long calm magnetic period, although the IMF Bz-component was negative for ~1.5 hour before the SI ^–. The commencement of the SI ^–, which was determined by variations in the magnetic field at ~0650 UT, was accompanied by a sharp increase in the intensity of discrete forms of polar auroras in the midnight sector of the auroral zone and their fast propagation to the pole. Approximately 6–8 min after the SI ^–, the auroral intensity in the emissions, which were excited by the fluxes of precipitated electrons and protons, quickly began to decrease in the night sector. Analysis of the optical observations showed the two-stage character of the response of the night auroras to the SI ^– in the considered event: first, fast movement of the discrete aurora forms to the pole with a significant increase in their intensity, and a further fast decrease in auroral intensity with a delay of ~6–8 min relative to the SI ^–. The possible reasons for such aurora behavior are discussed.  相似文献   

Ground-based observations of auroras under the sunlit conditions     

A. V. Roldugin  V. G. Vorobjev  V. C. Roldugin  S. A. Chernouss 《Geomagnetism and Aeronomy》2010,50(1):34-40

The results of the ground-based optical observations of sunlit auroras, performed at Lovozero and Apatity observatories on April 10 (event 1) and April 27, 2007(event 2), are presented. The observations were performed in the (OI) 557.7 nm emission, using a new equipment based on a Fabry-Pérot interferometer connected to a PhotonMAX CCD camera. During event 1, the observations were performed in the Harang discontinuity region at a low magnetic disturbance. It has been indicated that an auroral arc was located in the polar part of the eastward electrojet, and the arc position coincides with the equatorward boundary of structured precipitation (b2e). During event 2, auroras were observed within the average statistical boundaries of the auroral oval and the region of structured precipitation under the conditions of rather high geomagnetic activity. However, during the period of low geomagnetic activity, discrete auroras were registered at a geomagnetic latitude of ~64° on that day, which is 3°—4° equatorward of the structured precipitation region. Such a low latitudinal position of auroras can be explained by the effect of a high solar wind velocity, which was ~580 km/s during the period of observations.  相似文献   

Response of dayside auroras to abrupt increases in the solar wind dynamic pressure at positive and negative polarity of the IMF <Emphasis Type="Italic">B</Emphasis><Subscript><Emphasis Type="Italic">z</Emphasis></Subscript> component     

V. G. Vorobjev  V. L. Zverev  O. I. Yagodkina 《Geomagnetism and Aeronomy》2009,49(6):712-721

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   

Dynamics of day and night aurora during substorms     

V.G. Vorobjev  G. Gustafsson  G.V. Starkov  Y.I. Feldstein  N.F. Shevnina 《Planetary and Space Science》1975,23(2):269-278

The motion of auroral forms on the day- and nightside of the Earth has been studied during different substorm phases by means of all-sky camera films. A substorm is characterized by a shift of the luminescence region towards the equator at noon and mainly towards the pole at midnight. However, individual forms drift predominantly toward the pole on the dayside and towards the equator on the nightside. The velocity of the poleward motion at noon is largest during the expansive phase of a substorm and amounts on the average to 330 $\text{m}\text{sec}$ but even during relatively quiet magnetic conditions a poleward motion is observed.  相似文献   

Planetary distribution of the intensity of Auroral luminosity obtained using a model of Aurora precipitation     

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   

Comparative characteristics of ion and electron precipitation in the dawn and dusk sectors     

V. G. Vorobjev  O. I. Yagodkina 《Geomagnetism and Aeronomy》2014,54(1):50-58

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   

Influence of geomagnetic storms of September 26–30, 2011, on the ionosphere and HF radiowave propagation. I. Ionospheric effects     

M. V. Klimenko  V. V. Klimenko  F. S. Bessarab  K. G. Ratovsky  I. E. Zakharenkova  I. A. Nosikov  A. E. Stepanov  D. S. Kotova  V. G. Vorobjev  O. I. Yagodkina 《Geomagnetism and Aeronomy》2015,55(6):744-762

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