Ussuriysk Astrophysical Observatory

Primorsky Krai, Russia

Ussuriysk Astrophysical Observatory

Primorsky Krai, Russia
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Cano Z.,University of Iceland | De Ugarte Postigo A.,Institute Astrofisica Of Andalucia Iaa | De Ugarte Postigo A.,Niels Bohr Institute | Pozanenko A.,Space Research Institute | And 67 more authors.
Astronomy and Astrophysics | Year: 2014

We present optical and near-infrared (NIR) photometry for three gamma-ray burst supernovae (GRB-SNe): GRB 120729A, GRB 130215A/SN 2013ez, and GRB 130831A/SN 2013fu. For GRB 130215A/SN 2013ez, we also present optical spectroscopy at t - t0 = 16.1 d, which covers rest-frame 3000-6250 Å. Based on Fe ii λ5169 and Si ii λ6355, our spectrum indicates an unusually low expansion velocity of ~4000-6350 km s-1, the lowest ever measured for a GRB-SN. Additionally, we determined the brightness and shape of each accompanying SN relative to a template supernova (SN 1998bw), which were used to estimate the amount of nickel produced via nucleosynthesis during each explosion. We find that our derived nickel masses are typical of other GRB-SNe, and greater than those of SNe Ibc that are not associated with GRBs. For GRB 130831A/SN 2013fu, we used our well-sampled R-band light curve (LC) to estimate the amount of ejecta mass and the kinetic energy of the SN, finding that these too are similar to other GRB-SNe. For GRB 130215A, we took advantage of contemporaneous optical/NIR observations to construct an optical/NIR bolometric LC of the afterglow. We fit the bolometric LC with the millisecond magnetar model of Zhang & Mészáros (2001, ApJ, 552, L35), which considers dipole radiation as a source of energy injection to the forward shock powering the optical/NIR afterglow. Using this model we derive an initial spin period of P = 12 ms and a magnetic field of B = 1.1 × 1015 G, which are commensurate with those found for proposed magnetar central engines of other long-duration GRBs. © ESO, 2014.

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.

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.

Mordvinov A.V.,Russian Academy of Sciences | Grigoryev V.M.,Russian Academy of Sciences | Erofeev D.V.,Ussuriysk Astrophysical Observatory
Advances in Space Research | Year: 2015

A spatiotemporal analysis of the Sun's magnetic field was carried out to study the polar-field inversion in the current cycle in relation to sunspot activity. The causal relationship between these phenomena was demonstrated in a time-latitude aspect. After decay of long-lived activity complexes their magnetic fields were redistributed into the surrounding photosphere and formed unipolar magnetic regions which were transported to high latitudes. Zones of intense sunspot activity during 2011/2012 produced unipolar magnetic regions of the following polarities, whose poleward drift led to the inversion of the Sun's polar fields at the North and South Poles. At the North Pole the polar field reversal was completed by May 2013. It was demonstrated that mixed magnetic polarities near the North Pole resulted from violations of Joy's law at lower latitudes. Later sunspot activity in the southern hemisphere has led to a delay in magnetic polarity reversal at the South Pole. Thus, the north-south asymmetry of sunspot activity resulted in asynchronous polar field reversal in the current cycle. © 2015 COSPAR.

Kramynin A.P.,Ussuriysk Astrophysical Observatory | Mikhalina F.A.,Ussuriysk Astrophysical Observatory
Geomagnetism and Aeronomy | Year: 2015

Features of the dynamics and relationship between the parameters of 11-year solar cycles, which were found from different characteristic points of an 11-year cycle, are discussed. The cycle period is determined from the time of the appearance of the first sunspot of a new cycle, which makes it possible to exclude the contributions of cycle overlapping and asymmetry effects to variations in the cycle repetition interval, to reveal the dependence of the 11-year cycle repetition period on the secular cycle, and to ascertain a longer length of an even cycle as compared to an odd one. A change in the length of a 22-year cycle found by this technique is evidence of the presence of lags near secular cycle minima. A strong correlation between the length of the physical cycle decay and the interval between neighboring cycles is revealed. It is found that the dependence of the amplitude of an 11-year cycle on the length of the ascending branch depends on the secular cycle phase. © 2015, Pleiades Publishing, Ltd.

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 | Uralov A.M.,Russian Academy of Sciences | Kochanov A.A.,Russian Academy of Sciences | Kuzmenko I.V.,Ussuriysk Astrophysical Observatory | And 4 more authors.
Solar Physics | Year: 2016

A solar eruptive event SOL2010-06-13 observed with the Atmospheric Imaging Assembly (AIA) of the Solar Dynamics Observatory (SDO) has been extensively discussed in the contexts of the CME development and an associated extreme-ultraviolet (EUV) wave-like transient in terms of a shock driven by the apparent CME rim. Continuing the analysis of this event, we have revealed an erupting flux rope, studied its properties, and detected wave signatures inside the developing CME. These findings have allowed us to establish new features in the genesis of the CME and associated EUV wave and to reconcile all of the episodes into a single causally related sequence. i) A hot 11 MK flux rope developed from the structures initially associated with a compact filament system. The flux rope expanded with an acceleration of up to 3 km s−2 one minute before a hard X-ray burst and earlier than any other structures, reached a velocity of 420 km s−1, and then decelerated to about 50 km s−1. ii) The CME development was driven by the expanding flux rope. Closed coronal structures above the rope got sequentially involved in the expansion from below upwards, came closer together, and apparently disappeared to reveal their common envelope, the visible rim, which became the outer boundary of the cavity. The rim was probably associated with the separatrix surface of a magnetic domain, which contained the pre-eruptive filament. iii) The rim formation was associated with a successive compression of the upper active-region structures into the CME frontal structure (FS). When the rim was formed, it resembled a piston. iv) The disturbance responsible for the consecutive CME formation episodes was excited by the flux rope inside the rim, and then propagated outward. EUV structures arranged at different heights started to accelerate, when their trajectories in the distance–time diagram were crossed by that of the fast front of this disturbance. v) Outside the rim and FS, the disturbance propagated like a blast wave, manifesting in a type II radio burst and a leading part of the EUV transient. Its main, trailing part was the FS, which consisted of swept-up 2 MK coronal loops enveloping the expanding rim. The wave decelerated and decayed into a weak disturbance soon afterwards, being not driven by the trailing piston, which slowed down. © 2016 Springer Science+Business Media Dordrecht

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