Influence of projection effects on the observed differential rotation rate in the UV corona

Following previous investigations by Giordano and Mancuso [1] and Mancuso and Giordano [2, 3] on the differential rotation of the solar corona as obtained through the analysis of the intensity time series of the O VI 1032 Ang. spectral line observed by the UVCS/SOHO telescope during solar cycle 23, we analysed the possible influence of projection effects of extended coronal structures on the observed differential rotation rate in the ultraviolet corona. Through a simple geometrical model, we found that, especially at higher latitudes, the differential rotation may be less rigid than observed, since features at higher latitudes could be actually linked to much lower coronal structures due to projection effects. At solar maximum, the latitudinal rigidity of the UV corona, with respect to the differential rotating photosphere, has thus to be considered as an upper limit of the possible rigidity. At solar minimum and near the equatorial region throughout the solar cycle, projection effects are negligible.Comment: In press on Journal of Advanced Researc

Plasma properties from the multi-wavelength analysis of the November 1st 2003 CME/shock event

The analysis of the spectral properties and dynamic evolution of a CME/shock event observed on November 1st 2003 in white-light by the LASCO coronagraph and in the ultraviolet by the UVCS instrument operating aboard SOHO, has been performed to compute the properties of some important plasma parameters in the middle corona below about 2 solar radii. Simultaneous observations obtained with the MLSO/Mk4 white-light coronagraph, providing both the early evolution of the CME expansion in the corona and the pre-shock electron density profile along the CME front, were also used to study this event. By combining the above information with the analysis of the metric type II radio emission detected by ground-based radio spectrographs, we finally derive estimates of the values of the local Alfv\'en speed and magnetic field strength in the solar corona.Comment: In press Journal of Advanced Research, Cairo University. Production and hosting by Elsevier B.

Coronal Rotation at Solar Minimum from UV Observations

UVCS/SOHO observations have been analyzed to reconstruct intensity time series of the O VI 1032 A and H 11216 A spectral lines at different coronal heliolatitudes from 1.5 to 3.0 solar radii from Sun center. Evidence was found for coronal differential rotation that differs significantly from that of the photospheric plasma. The study of the latitudinal variation shows that the UV corona decelerates toward the photospheric rates from the equator up to the poleward boundary 2 of the midlatitude streamers, reaching a peak of 28.16+/-0.20 days around +30 from the equator at 1.5 solar radii, while a less evident peak is observed in the northern hemisphere. This result suggests a real north-south rotational asymmetry as a consequence of different activity and weak coupling between the magnetic fields of the two hemispheres. The study of the radial rotation profiles shows that the corona is rotating almost rigidly with height

Household food waste from an international perspective

open2noThe food waste debate has flourished during the last years, leading to an impressive increase in the number of scientific publications. After FAO stated that about one-third of the total food produced at the global level goes wasted, the topic has been given increasing attention, and it became a specific sub-goal of the SDG 12 of Agenda 2030. The most recent study published by UNEP reported that globally around 931 million tons of food waste was generated in 2019, 61% of which came from households.openGiordano, C; Franco, S.Giordano, C; Franco, S

Probing Coronal Magnetic Fields with Sungrazing Comets: \hi\ Lyα\alpha from Pickup Ions

Observations of sungrazing comets can be used to probe the solar corona, to study the composition of the comets, and to investigate the plasma processes that govern the interaction between the coronal plasma and cometary gas. UVCS observations of the intensities and line profiles of \hi\ Ly$\alpha$ trace the density, temperature and outflow speed of the corona. Analysis of \hi\ Ly$\alpha$ observations of comet C/2002 S2 showed a surprising split in the comet's Ly$\alpha$ tail and an asymmetry of red-shifted and blue-shifted emission across the tail axis. It was suggested that the velocity structure might result from a population of neutrals produced by charge transfer between pickup ions and cometary neutrals. Here we present numerical simulations of the \hi\ Ly$\alpha$ intensity and velocity centroid for sungrazing comets under the assumption that the magnetic field and solar wind are radial. The models qualitatively reproduce the observations of Comet C/2002 S2 and potentially explain the split tail morphology that was seen in C/2002 S2 and also C/2001 C2. They also match the observed red- and blue-shifts, though the solar wind velocity needed to explain the blue-shift implies strong Doppler dimming and requires a higher outgassing rate to match the light curve. However, the models do not match the observations in detail, and we discuss the remaining discrepancies and the uncertainties in the model. We briefly discuss the implications for other UVCS comet observations and sungrazing comet observations with the Metis coronagraph.Comment: 15 pages, 9 figure

Probing the Solar Wind Acceleration Region with the Sun--Grazing Comet C/2002 S2

Comet C/2002 S2, a member of the Kreutz family of Sungrazing comets, was discovered in white light images of the SOHO/LASCO coronagraph on 2002 September 18 and observed in \hi\, \lya\, emission by the SOHO/UVCS instrument at four different heights as it approached the Sun. The \hi\, \lya\, line profiles detected by UVCS are analyzed to determine the spectral parameters: line intensity, width and Doppler shift with respect to the coronal background. Two dimensional comet images of these parameters are reconstructed at the different heights. A novel aspect of the observations of this sungrazing comet data is that, whereas the emission from the most of the tail is blue--shifted, that along one edge of the tail is red--shifted. We attribute these shifts to a combination of solar wind speed and interaction with the magnetic field. In order to use the comet to probe the density, temperature and speed of the corona and solar wind through which it passes, as well as to determine the outgassing rate of the comet, we develop a Monte Carlo simulation of the \hi\, \lya\, emission of a comet moving through a coronal plasma. From the outgassing rate, we estimate a nucleus diameter of about 9 meters. This rate steadily increases as the comet approaches the Sun while the optical brightness decreases by more than a factor of ten and suddenly recovers. This indicates that the optical brightness is determined by the lifetimes of the grains, sodium atoms and molecules produced by the comet.Comment: 17 pages, 17 figures. Accepted by Ap

Rational design of modular circuits for gene transcription: A test of the bottom-up approach

<p>Abstract</p> <p>Background</p> <p>Most of synthetic circuits developed so far have been designed by an ad hoc approach, using a small number of components (i.e. LacI, TetR) and a trial and error strategy. We are at the point where an increasing number of modular, inter-changeable and well-characterized components is needed to expand the construction of synthetic devices and to allow a rational approach to the design.</p> <p>Results</p> <p>We used interchangeable modular biological parts to create a set of novel synthetic devices for controlling gene transcription, and we developed a mathematical model of the modular circuits. Model parameters were identified by experimental measurements from a subset of modular combinations. The model revealed an unexpected feature of the lactose repressor system, i.e. a residual binding affinity for the operator site by induced lactose repressor molecules. Once this residual affinity was taken into account, the model properly reproduced the experimental data from the training set. The parameters identified in the training set allowed the prediction of the behavior of networks not included in the identification procedure.</p> <p>Conclusions</p> <p>This study provides new quantitative evidences that the use of independent and well-characterized biological parts and mathematical modeling, what is called a bottom-up approach to the construction of gene networks, can allow the design of new and different devices re-using the same modular parts.</p