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Primorsky Krai, Russia

Grechnev V.V.,Russian Academy of Sciences | Uralov A.M.,Russian Academy of Sciences | Kuzmenko I.V.,Ussuriysk Astrophysical Observatory | Kochanov A.A.,Russian Academy of Sciences | And 2 more authors.
Solar Physics | Year: 2014

Multi-instrument observations of two filament eruptions on 24 February and 11 May 2011 suggest the following updated scenario for eruptive flare, coronal mass ejection (CME), and shock wave evolution. An initial destabilization of a filament results in stretching out of the magnetic threads belonging to its body that are rooted in the photosphere along the inversion line. Their reconnection leads to i) heating of parts of the filament or its environment, ii) an initial development of the flare cusp, arcade, and ribbons, iii) an increasing similarity of the filament to a curved flux rope, and iv) to its acceleration. Then the pre-eruption arcade enveloping the filament becomes involved in reconnection according to the standard model and continues to form the flare arcade and ribbons. The poloidal magnetic flux in the curved rope developing from the filament progressively increases and forces its toroidal expansion. This flux rope impulsively expands and produces a magnetohydrodynamical disturbance, which rapidly steepens into a shock. The shock passes through the arcade that expands above the filament and then freely propagates for some time ahead of the CME like a decelerating blast wave. If the CME is slow, then the shock eventually decays. Otherwise, the frontal part of the shock changes into the bow-shock regime. This was observed for the first time in the 24 February 2011 event. When reconnection ceases, the flux rope relaxes and constitutes the CME core–cavity system. The expanding arcade develops into the CME frontal structure. We also found that reconnection in the current sheet of a remote streamer forced by the shock passage results in a running flare-like process within the streamer responsible for a type II burst. The development of dimming and various associated phenomena are discussed. © 2014, Springer Science+Business Media Dordrecht.


Grechnev V.V.,Russian Academy of Sciences | Kuzmenko I.V.,Ussuriysk Astrophysical Observatory | Uralov A.M.,Russian Academy of Sciences | Chertok I.M.,RAS Institute of Radio Engineering and Electronics | Kochanov A.A.,Russian Academy of Sciences
Publications of the Astronomical Society of Japan | Year: 2013

Low-temperature plasma ejected in solar eruptions can screen active regions as well as quiet solar areas. Absorption phenomena can be observed in microwaves as "negative bursts" and in various spectral domains. We analyze two very different recent events with such phenomena, and present an updated systematic view of solar events associated with negative bursts. Related filament eruptions can be normal, without essential changes of shape and magnetic configuration, and "anomalous." The latter are characterized by disintegration of an eruptive filament and dispersal of its remnants as a cloud over a large part of the solar disk. Such phenomena can be observed as giant depressions in the He II 304 ?A line. One of possible scenarios for an anomalous eruption is proposed in terms of reconnection of the filament's internal magnetic fields with an external large-scale coronal surrounding. © 2013. Astronomical Society of Japan.


Grechnev V.V.,Russian Academy of Sciences | Uralov A.M.,Russian Academy of Sciences | Chertok I.M.,RAS Institute of Radio Engineering and Electronics | Kuzmenko I.V.,Ussuriysk Astrophysical Observatory | And 4 more authors.
Solar Physics | Year: 2011

We show examples of the excitation of coronal waves by flare-related abrupt eruptions of magnetic rope structures. The waves presumably rapidly steepened into shocks and freely propagated afterwards like decelerating blast waves that showed up as Moreton waves and EUV waves. We propose a simple quantitative description for such shock waves to reconcile their observed propagation with drift rates of metric type II bursts and kinematics of leading edges of coronal mass ejections (CMEs). Taking account of different plasma density falloffs for propagation of a wave up and along the solar surface, we demonstrate a close correspondence between drift rates of type II bursts and speeds of EUV waves, Moreton waves, and CMEs observed in a few previously studied events. © 2011 Springer Science+Business Media B.V.


Erofeev D.V.,Ussuriysk Astrophysical Observatory
Geomagnetism and Aeronomy | Year: 2015

The ratio of regular and stochastic components in the behavior of the longitudinal-temporal distribution of solar activity is studied with the use of correlation and spectral analysis of data on sunspot groups for 12 solar cycles. It was found that data samples of about 10 years in length often (in 50% of cases) show the presence of regular structures in the longitudinal distribution of sunspot groups. However, these structures are nonstationary; their characteristic scales and rotation periods vary when changing from one 10-year interval to another. The behavior of the longitudinal structure of sunspot activity is mainly stochastic on a long time scale (50–100 years); it is characterized by a wide spectrum of spatial scales and a continuous spectrum of rotation periods, which takes a period from 25.6 to 28.5 days. © 2015, Pleiades Publishing, Ltd.


Grechnev V.V.,Russian Academy of Sciences | Kuzmenko I.V.,Ussuriysk Astrophysical Observatory | Chertok I.M.,RAS Institute of Radio Engineering and Electronics | Uralov A.M.,Russian Academy of Sciences
Astronomy Reports | Year: 2011

Plasma with a temperature close to the chromospheric one is ejected in solar eruptions. Such plasma can occult some part of emission of compact sources in active regions as well as quiet solar areas. Absorption phenomena can be observed in the microwave range as the so-called "negative bursts" and also in the He II 304 Å line. The paper considers three eruptive events associated with rather powerful flares. Parameters of absorbing material of an eruption are estimated from multi-frequency records of a "negative burst" in one event. "Destruction" of an eruptive filament and its dispersion like a cloud over a huge area observed as a giant depression of the 304 Å line emission has been revealed in a few events. One of the three currently known events is considered in this paper. One more of the events considered here is a possible candidate for such events. © 2011 Pleiades Publishing, Ltd.

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