18 research outputs found
Sunspot waves and flare energy release
We address a possibility of the flare process initiation and further
maintenance of its energy release due to a transformation of sunspot
longitudinal waves into transverse magnetic loop oscillations with initiation
of reconnection. This leads to heating maintaining after the energy release
peak and formation of a flat stage on the X-ray profile. We applied the
time-distance plots and pixel wavelet filtration (PWF) methods to obtain
spatio-temporal distribution of wave power variations in SDO/AIA data. To find
magnetic waveguides, we used magnetic field extrapolation of SDO/HMI
magnetograms. The propagation velocity of wave fronts was measured from their
spatial locations at specific times. In correlation curves of the 17 GHz (NoRH)
radio emission we found a monotonous energy amplification of 3-min waves in the
sunspot umbra before the 2012 June 7 flare. This dynamics agrees with an
increase in the wave-train length in coronal loops (SDO/AIA, 171 {\AA})
reaching the maximum 30 minutes prior to the flare onset. A peculiarity of this
flare time profile in soft X-rays (RHESSI, 3-25 keV) is maintaining the
constant level of the flare emission for 10 minutes after the short impulse
phase, which indicates at the energy release continuation. Throughout this
time, we found 30-sec period transverse oscillations of the flare loop in the
radio-frequency range (NoRH, 17 GHz). This periodicity is apparently related to
the transformation of propagating longitudinal 3-min waves from the sunspot
into the loop transverse oscillations. The magnetic field extrapolation showed
the existence of the magnetic waveguide (loop) connecting the sunspot with the
energy release region. A flare loop heating can be caused by the interaction
(reconnections) of this transversally oscillating waveguide with the underlying
twisted loops.Comment: 7 pages, 9 figure
Eruptions of Magnetic Ropes in Two Homologous Solar Events on 2002 June 1 and 2: a Key to Understanding of an Enigmatic Flare
The goal of this paper is to understand the drivers, configurations, and
scenarios of two similar eruptive events, which occurred in the same solar
active region 9973 on 2002 June 1 and 2. The June 2 event was previously
studied by Sui, Holman, and Dennis (2006, 2008), who concluded that it was
challenging for popular flare models. Using multi-spectral data, we analyze a
combination of the two events. Each of the events exhibited an evolving
cusp-like feature. We have revealed that these apparent ``cusps'' were most
likely mimicked by twisted magnetic flux ropes, but unlikely to be related to
the inverted Y-like magnetic configuration in the standard flare model. The
ropes originated inside a funnel-like magnetic domain whose base was bounded by
an EUV ring structure, and the top was associated with a coronal null point.
The ropes appear to be the major drivers for the events, but their rise was not
triggered by reconnection in the coronal null point. We propose a scenario and
a three-dimensional scheme for these events in which the filament eruptions and
flares were caused by interaction of the ropes.Comment: 22 pages, 11 figure
Response of optical hydrogen lines to beam heating: I. Electron beams
We investigate the role of non-thermal electrons in the formation regions of
Halpha, Hbeta, and Hgamma lines in order to unfold their influence on the
formation of these lines. We concentrate on pulse-beam heating varying on a
subsecond timescale. Furthermore, we theoretically explore possibility that a
new diagnostic tool exists indicating the presence of non-thermal electrons in
the flaring chromosphere based on observations of optical hydrogen lines. To
model the evolution of the flaring atmosphere and the time-dependent hydrogen
excitation and ionisation, we used a 1-D radiative hydrodynamic code combined
with a test-particle code that simulates the propagation, scattering, and
thermalisation of a power-law electron beam in order to obtain the flare
heating and the non-thermal collisional rates due to the interaction of the
beam with the hydrogen atoms. All calculated models have shown a
time-correlated response of the modelled Balmer line intensities on a subsecond
timescale, with a subsecond timelag behind the beam flux. Depending on the beam
parameters, both line centres and wings can show pronounced intensity
variations. The non-thermal collisional rates generally result in an increased
emission from a secondary region formed in the chromosphere.Comment: 13 pages, 11 figures, accepted to Astronomy and Astrophysic
An Extreme Solar Event of 20 January 2005: Properties of the Flare and the Origin of Energetic Particles
The extreme solar and SEP event of 20 January 2005 is analyzed from two
perspectives. Firstly, we study features of the main phase of the flare, when
the strongest emissions from microwaves up to 200 MeV gamma-rays were observed.
Secondly, we relate our results to a long-standing controversy on the origin of
SEPs arriving at Earth, i.e., acceleration in flares, or shocks ahead of CMEs.
All emissions from microwaves up to 2.22 MeV line gamma-rays during the main
flare phase originated within a compact structure located just above sunspot
umbrae. A huge radio burst with a frequency maximum at 30 GHz was observed,
indicating the presence of a large number of energetic electrons in strong
magnetic fields. Thus, protons and electrons responsible for flare emissions
during its main phase were accelerated within the magnetic field of the active
region. The leading, impulsive parts of the GLE, and highest-energy gamma-rays
identified with pi^0-decay emission, are similar and correspond in time. The
origin of the pi^0-decay gamma-rays is argued to be the same as that of lower
energy emissions. We estimate the sky-plane speed of the CME to be 2000-2600
km/s, i.e., high, but of the same order as preceding non-GLE-related CMEs from
the same active region. Hence, the flare itself rather than the CME appears to
determine the extreme nature of this event. We conclude that the acceleration,
at least, to sub-relativistic energies, of electrons and protons, responsible
for both the flare emissions and the leading spike of SEP/GLE by 07 UT, are
likely to have occurred simultaneously within the flare region. We do not rule
out a probable contribution from particles accelerated in the CME-driven shock
for the leading GLE spike, which seemed to dominate later on.Comment: 34 pages, 14 Postscript figures. Solar Physics, accepted. A typo
corrected. The original publication is available at
http://www.springerlink.co
Aminoglycosides ototoxicity molecular mechanisms
Aminoglycosides are a group of antibiotics which are currently widespread in clinical practice due to their relatively low price. However, aminoglycosides have several side effects that complicate their application. One of the most severe is ototoxicity that is related to destruction of hair cells. In the current literature review molecular mechanisms of aminoglycosides’ interaction with hair cells are described as so as clinical effects which were described during researches in vivo.Аминогликозиды являются антибиотиками, широко используемыми в клинической практике из-за своей относительно недорогой цены. Однако у аминогликозидов существует ряд побочных эффектов, которые усложняют их применение. Одним из самых значительных является ототоксичность, которая связана с поражением волосковых клеток. В данном литературном обзоре описываются молекулярные механизмы воздействия аминогликозидов на волосковые клетки и их выявленные in vivo клинические проявления
DETERMINATION OF THE BASE COMPOSITION OF SIDERITE BY WDXRF
WDXRF spectrometry was used to determine the concentration of Fe and other elements in a sample of siderite mineral. The reference materials (RMs) were produced by analytes sorption from solutions with known concentration. Control of RMs composition was performed by ICP-MS method, analyzing solutions before and after sorption process. The statistical data processing and metrological parameters evaluation were carried out