962 research outputs found
Evolution of Kadhis Courts in Zanzibar
Zanzibar, is an Island on the east coast of Africa in Tanzania. The region is mostly populated by Muslims. This region had long time relationship in international trade with the people of near and far-east. The relationship however resulted in the islamization of the island. The early contact had ever lasting impact on the peoples of the region, yet the Islamic Legal System has been treated with a step mother affection since the colonial era. However, in recent times Muslims in the region including the island are asserting for a change of the status of administration of justice system in the region to make it in accordance to Islamic Law. Keywords: Islamic Law, Kadhis Courts, Islamic Legal System and Zanzibar
Solar polarimetry through the K I lines at 770 nm
We characterize the K I D1 & D2 lines in order to determine whether they
could complement the 850 nm window, containing the Ca II infrared triplet lines
and several Zeeman sensitive photospheric lines, that was studied previously.
We investigate the effect of partial redistribution on the intensity profiles,
their sensitivity to changes in different atmospheric parameters, and the
spatial distribution of Zeeman polarization signals employing a realistic
magnetohydrodynamic simulation. The results show that these lines form in the
upper photosphere at around 500 km and that they are sensitive to the line of
sight velocity and magnetic field strength at heights where neither the
photospheric lines nor the Ca II infrared lines are. However, at the same time,
we found that their sensitivity to the temperature essentially comes from the
photosphere. Then, we conclude that the K I lines provide a complement to the
lines in the 850 nm window for the determination of atmospheric parameters in
the upper photosphere, especially for the line of sight velocity and the
magnetic field.Comment: 10 pages, 9 figures, main journal publicatio
Study of the polarization produced by the Zeeman effect in the solar Mg I b lines
The next generation of solar observatories aim to understand the magnetism of
the solar chromosphere. Therefore, it is crucial to understand the polarimetric
signatures of chromospheric spectral lines. For this purpose, we here examine
the suitability of the three Fraunhofer Mg I b1, b2, and b4 lines at 5183.6,
5172.7, and 5167.3 A, respectively. We start by describing a simplified atomic
model of only 6 levels and 3 line transitions for computing the atomic
populations of the 3p-4s (multiplet number 2) levels involved in the Mg I b
line transitions assuming non-local thermodynamic conditions and considering
only the Zeeman effect using the field-free approximation. We test this
simplified atom against more complex ones finding that, although there are
differences in the computed profiles, they are small compared with the
advantages provided by the simple atom in terms of speed and robustness. After
comparing the three Mg I lines, we conclude that the most capable one is the b2
line as b1 forms at similar heights and always show weaker polarization signals
while b4 is severely blended with photospheric lines. We also compare Mg I b2
with the K I D1 and Ca II 8542 A lines finding that the former is sensitive to
the atmospheric parameters at heights that are in between those covered by the
latter two lines. This makes Mg I b2 an excellent candidate for future
multi-line observations that aim to seamlessly infer the thermal and magnetic
properties of different features in the lower solar atmosphere.Comment: 14 pages, 11 figures, and 5 table
Chromospheric polarimetry through multi-line observations of the 850 nm spectral region II: A magnetic flux tube scenario
In this publication we continue the work started in Quintero Noda et al.
(2017) examining this time a numerical simulation of a magnetic flux tube
concentration. Our goal is to study if the physical phenomena that take place
in it, in particular, the magnetic pumping, leaves a specific imprint on the
examined spectral lines. We find that the profiles from the interior of the
flux tube are periodically dopplershifted following an oscillation pattern that
is also reflected in the amplitude of the circular polarization signals. In
addition, we analyse the properties of the Stokes profiles at the edges of the
flux tube discovering the presence of linear polarization signals for the Ca II
lines, although they are weak with an amplitude around 0.5% of the continuum
intensity. Finally, we compute the response functions to perturbations in the
longitudinal field and we estimate the field strength using the weak field
approximation. Our results indicate that the height of formation of the
spectral lines changes during the magnetic pumping process which makes the
interpretation of the inferred magnetic field strength and its evolution more
difficult. These results complement those from previous works demonstrating the
capabilities and limitations of the 850 nm spectrum for chromospheric Zeeman
polarimetry in a very dynamic and complex atmosphere.Comment: 12 pages, 12 figures, 0 tables, MNRAS main journal publicatio
Detection of interstellar hydrogen peroxide
The molecular species hydrogen peroxide, HOOH, is likely to be a key
ingredient in the oxygen and water chemistry in the interstellar medium. Our
aim with this investigation is to determine how abundant HOOH is in the cloud
core {\rho} Oph A. By observing several transitions of HOOH in the
(sub)millimeter regime we seek to identify the molecule and also to determine
the excitation conditions through a multilevel excitation analysis. We have
detected three spectral lines toward the SM1 position of {\rho} Oph A at
velocity-corrected frequencies that coincide very closely with those measured
from laboratory spectroscopy of HOOH. A fourth line was detected at the
4{\sigma} level. We also found through mapping observations that the HOOH
emission extends (about 0.05 pc) over the densest part of the {\rho} Oph A
cloud core. We derive an abundance of HOOH relative to that of H_2 in the SM1
core of about 1\times10^(-10). To our knowledge, this is the first reported
detection of HOOH in the interstellar medium.Comment: 5 pages, 4 figures, accepted for publication in Astronomy &
Astrophysics, new version corrects a typo in Table 1 (and consequently in Fig
4
Chromospheric polarimetry through multi-line observations of the 850 nm spectral region III: Chromospheric jets driven by twisted magnetic fields
We investigate the diagnostic potential of the spectral lines at 850 nm for
understanding the magnetism of the lower atmosphere. For that purpose, we use a
newly developed 3D simulation of a chromospheric jet to check the sensitivity
of the spectral lines to this phenomenon as well as our ability to infer the
atmospheric information through spectropolarimetric inversions of noisy
synthetic data. We start comparing the benefits of inverting the entire
spectrum at 850 nm versus only the Ca II 8542 A spectral line. We found a
better match of the input atmosphere for the former case, mainly at lower
heights. However, the results at higher layers were not accurate. After several
tests, we determined that we need to weight more the chromospheric lines than
the photospheric ones in the computation of the goodness of the fit. The new
inversion configuration allows us to obtain better fits and consequently more
accurate physical parameters. Therefore, to extract the most from multi-line
inversions, a proper set of weights needs to be estimated. Besides that, we
conclude again that the lines at 850 nm, or a similar arrangement with Ca II
8542 A plus Zeeman sensitive photospheric lines, poses the best observing
configuration for examining the thermal and magnetic properties of the lower
solar atmosphere.Comment: 14 pages, 11 figure
Detection of the hydroperoxyl radical HO2 toward \rho Oph A: Additional constraints on the water chemical network
Context: Hydrogen peroxide (HOOH) was recently detected toward \rho Oph A.
Subsequent astrochemical modeling that included reactions in the gas phase and
on the surface of dust grains was able to explain the observed abundance, and
highlighted the importance of grain chemistry in the formation of HOOH as an
intermediate product in water formation. This study also predicted that the
hydroperoxyl radical HO2, the precursor of HOOH, should be detectable. Aims: We
aim at detecting the hydroperoxyl radical HO2 in \rho Oph A. Methods: We used
the IRAM 30m and the APEX telescopes to target the brightest HO2 lines at about
130 and 260 GHz. Results: We detect five lines of HO2 (comprising seven
individual molecular transitions). The fractional abundance of HO2 is found to
be about 1e-10, a value similar to the abundance of HOOH. This observational
result is consistent with the prediction of the above mentioned astrochemical
model, and thereby validates our current understanding of the water formation
on dust grains. Conclusions: This detection, anticipated by a sophisticated
gas-grain chemical model, demonstrates that models of grain chemistry have
improved tremendously and that grain surface reactions now form a crucial part
of the overall astrochemical network.Comment: 5 pages, 4 figures, accepted for publication as a Letter to the
Editor in Astronomy and Astrophysic
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