6 research outputs found
Determination of 3D Trajectories of Knots in Solar Prominences Using MSDP Data
In this paper we present a new method of restoration of the true
thee-dimensional trajectories of the prominence knots based on ground-based
observations taken with a single telescope, which is equipped with a
Multi-Channel Subtractive Double Pass imaging spectrograph. Our method allows
to evaluate true three-dimensional trajectories of the prominence knots without
any assumptions concerning the shape of the trajectories or dynamics of the
motion. The reconstructed trajectories of several knots observed in three
prominences are presented.Comment: 14 pages, 9 figures, accepted for publication in Solar Physic
ALMA as a prominence thermometer: First observations
We present first prominence observations obtained with ALMA in Band 3 at the
wavelength of 3 mm. High-resolution observations have been coaligned with the
MSDP H data from Wroclaw-Bialk\'{o}w large coronagraph at similar
spatial resolution. We analyze one particular co-temporal snapshot, first
calibrating both ALMA and MSDP data and then demonstrating a reasonable
correlation between both. In particular we can see quite similar fine-structure
patterns in both ALMA brightness temperature maps and MSDP maps of H
intensities. Using ALMA we intend to derive the prominence kinetic
temperatures. However, having current observations only in one band, we use an
independent diagnostic constraint which is the H line integrated
intensity. We develop an inversion code and show that it can provide realistic
temperatures for brighter parts of the prominence where one gets a unique
solution, while within faint structures such inversion is ill conditioned. In
brighter parts ALMA serves as a prominence thermometer, provided that the
optical thickness in Band 3 is large enough. In order to find a relation
between brightness and kinetic temperatures for a given observed H
intensity, we constructed an extended grid of non-LTE prominence models
covering a broad range of prominence parameters. We also show the effect of the
plane-of-sky filling factor on our results.Comment: 9 pages, 3 figures, accepted for publication in the The Astrophysical
Journal Letter
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Interferometric imaging of the type IIIb and U radio bursts observed with LOFAR on 22 August 2017
Context. The Sun is the source of different types of radio bursts that are associated with solar flares, for example. Among the most frequently observed phenomena are type III solar bursts. Their radio images at low frequencies (below 100 MHz) are relatively poorly studied due to the limitations of legacy radio telescopes. Aims. We study the general characteristics of types IIIb and U with stria structure solar radio bursts in the frequency range of 20-80 MHz, in particular the source size and evolution in different altitudes, as well as the velocity and energy of electron beams responsible for their generation. Methods. In this work types IIIb and U with stria structure radio bursts are analyzed using data from the LOFAR telescope including dynamic spectra and imaging observations, as well as data taken in the X-ray range (GOES and RHESSI satellites) and in the extreme ultraviolet (SDO satellite). Results. In this study we determined the source size limited by the actual shape of the contour at particular frequencies of type IIIb and U solar bursts in a relatively wide frequency band from 20 to 80 MHz. Two of the bursts seem to appear at roughly the same place in the studied active region and their source sizes are similar. It is different in the case of another burst, which seems to be related to another part of the magnetic field structure in this active region. The velocities of the electron beams responsible for the generation of the three bursts studied here were also found to be different
First high resolution interferometric observation of a solar prominence with ALMA
We present the first observation of a solar prominence at 84 − 116 GHz using the high resolution interferometric imaging of ALMA. Simultaneous observations in Hα from Białkaw Observatory and with SDO/AIA reveal similar prominence morphology to the ALMA observation. The contribution functions of 3 mm and Hα emission are shown to have significant overlap across a range of gas pressures. We estimate the maximum millimetre-continuum optical thickness to be τ3mm ≈ 2, and the brightness temperature from the observed Hα intensity. The brightness temperature measured by ALMA is ∼6000 − 7000 K in the prominence spine, which correlates well with the estimated brightness temperature for a kinetic temperature of 8000 K
Estimation of solar prominence magnetic fields based on the reconstructed 3D trajectories of prominence knots
We present an estimation of the lower limits of local magnetic fields in
quiescent, activated, and active (surges) promineces, based on reconstructed
3-dimensional (3D) trajectories of individual prominence knots. The 3D
trajectories, velocities, tangential and centripetal accelerations of the knots
were reconstructed using observational data collected with a single
ground-based telescope equipped with a Multi-channel Subtractive Double Pass
imaging spectrograph. Lower limits of magnetic fields channeling observed
plasma flows were estimated under assumption of the equipartition principle.
Assuming approximate electron densities of the plasma n_e = 5*10^{11} cm^{-3}
in surges and n_e = 5*10^{10} cm^{-3} in quiescent/activated prominences, we
found that the magnetic fields channeling two observed surges range from 16 to
40 Gauss, while in quiescent and activated prominences they were less than 10
Gauss. Our results are consistent with previous detections of weak local
magnetic fields in the solar prominences.Comment: 14 pages, 12 figures, 1 tabl