National Astronomy Meeting Poster Exhibition

The solar wind is a stream of charged particles originating from the Sun to the interstellar medium. Regular interactions of solar wind with the Earth’s magnetosphere and ionosphere gives rise to Auroras. Any alterations in the solar wind affects Earth’s magnetic field and can cause geomagnetic storms. Thus, understanding the formation and acceleration of the solar wind is critical towards investigating the Sun-Earth connection and predicting space weather. It is of the consensus that the solar wind originates in the lower solar atmosphere and along coronal holes (regions of open magnetic fields).

The solar chromosphere serves as a bridging region between the photosphere and the corona. This dynamic layer is filled with a plethora of features that vary in time and space. In this project we focus on plasma dynamics of jets observed along the coronal hole boundary. The interaction of these events with the neighboring plasma can influence the energy and mass flow across the solar atmosphere and influence the solar wind.

We will aim to address the questions:

A.1) What physical processes create upward propagating jets on the boundary of the coronal hole?

A.2) What physical processes are responsible for the acceleration and create turbulence in the jets?

I present a statistical study of oscillations associated with jets formed along the coronal hole boundaries. Since the coronal hole region has open field lines, jets can transfer mass and energy along open field lines and reach the solar wind. We will investigate oscillations of different motions using CRISP instrument on-board Swedish Solar Telescope (SST). We will classify these oscillations as high-frequency (>5 mHz) and low frequency (5 mHz) and low frequency (5 mHz) regions, and then investigate different waves that flow around the jets. I will then show whether such jets are observed in IRIS and SDO channels that probe the higher solar atmospheric regions. We will show how the morphology of the jets vary as we travel across the solar atmosphere and in future work, we will show how plasma properties change, in order to quantify their role as mass and energy channels that could accelerate the solar wind.

The transition of the martian climate from the wet Noachian era to the dry Hesperian (4.1-3.0 Gya) likely resulted in saline surface waters that were rich in sulfur species. Terrestrial analogue environments that possess a similar chemistry to these proposed waters can be used to develop an understanding of the diversity of microorganisms that could have persisted on Mars under such conditions. Here, we report on the chemistry and microbial community of the highly reducing sediment of Colour Peak springs, a sulfidic and saline spring system located within the Canadian High Arctic. DNA and cDNA 16S rRNA gene profiling demonstrated that the microbial community was dominated by sulfur oxidising bacteria, suggesting that primary production in the sediment was driven by chemolithoautotrophic sulfur oxidation. It is possible that the sulfur oxidising bacteria also supported the persistence of the additional taxa. Gibbs energy values calculated for the brines, based on the chemistry of Gale crater, suggested that the oxidation of reduced sulfur species was an energetically viable metabolism for life on early Mars.

According to observation, the number of flares on different stars almost does not change from dwarf to hot stars. As it is known from the Sun observations, the flares may be followed by the coronal mass ejection events (CME). The estimates of a magnetic field strength in tubes in photospheres of O-M stars were made. We use simple formulas with a clear physical meaning, which give results for the Sun that differ by no more than a factor of 2–3 from the observed ones. The main motivation for such approach is as follows: our knowledge of the stars’ medium is at approximately the same level as our knowledge of the Sun in the 1950s. Moreover, such simple models allow a complete picture of the processes in the system to be obtained without knowing any details of the stellar activity. Basing on the obtained values and parameters of different objects we made estimates of flare energies and estimates of CME’s masses and made some assumptions on the minimum and maximum limits for different types of stars and compare them with flares energies, stars luminosities and temperatures.

Gravitational waves from compact binaries measured by the LIGO and Virgo detectors are routinely analyzed using Markov Chain Monte Carlo sampling algorithms. Because the evaluation of the likelihood function requires evaluating millions of waveform models that link between signal shapes and the source parameters, running Markov chains until convergence is typically expensive and requires days of computation. In this work, we provide a proof of concept that demonstrates how the latest advances in neural simulation-based inference can speed up the inference time by up to three orders of magnitude -- from days to minutes -- without impairing the performance. Our approach is based on a convolutional neural network modeling the likelihood-to-evidence ratio and entirely amortizes the computation of the posterior. We find that our model correctly estimates credible intervals for the parameters of simulated gravitational waves.

We analyze the coronal elemental abundances during a small flare using Hinode/EIS observations. Compared to the preflare elemental abundances, we observed a strong increase in coronal abundance of Ca xiv 193.84 Å, an emission line with low first ionization potential (FIP 10 eV), as quantified by the ratio Ca/Ar during the flare. This is in contrast to the unchanged abundance ratio observed using Si x 258.38 Å/S x 264.23 Å. We propose two different mechanisms to explain the different composition results. First, the small flare-induced heating could have ionized S, but not the noble gas Ar, so that the flare-driven Alfvén waves brought up Si, S, and Ca in tandem via the ponderomotive force which acts on ions. Second, the location of the flare in strong magnetic fields between two sunspots may suggest fractionation occurred in the low chromosphere, where the background gas is neutral H. In this region, high-FIP S could behave more like a low-FIP than a high-FIP element. The physical interpretations proposed generate new insights into the evolution of plasma abundances in the solar atmosphere during flaring, and suggests that current models must be updated to reflect dynamic rather than just static scenarios.

Ejecta from compact binary mergers (CBM) emit transient signals known as kilonovae (KN), being one of the electromagnetic counterparts of related gravitational-wave (GW) events. The combined detection of GW170817 and KN transient AT2017gfo has provided observational evidence to rank CBM among the major r-process nucleosynthesis sites, thus making the study of KN a novel challenge for nuclear astrophysics in the multi-messenger astronomy era. Theoretical models, trying to reproduce observed KN light curves, depend on several physical conditions: dynamics, r-process yields, and opacity of the ejecta. In particular, the study of radiative transport in KN is crucial for correct modelling and robust predictions. However, due to the lack of an atomic database, models often oversimplify opacity calculations, causing possible gaps between observations and theory. To bridge this gap, we have recently proposed an experimental setup to measure plasma optical properties in compact magnetic traps in some astrophysical conditions typical of early-stage CBM ejecta. A numerical study in the framework of the PANDORA project has shown that ejecta, at the blue-KN emission stage, reach plasma densities and temperatures around 1012 cm-3 and 1-to-few-eV, respectively. In this work, we report about first tests on the Flexible Plasma Trap at INFN-LNS: plasmas from gaseous elements have been generated via electron cyclotron resonance and explored at different experimental conditions. Reproducible and stable plasma configurations were obtained up to pressures of 10-2 mbar and microwave powers of 400 W, with preliminary measured densities (1011÷1012cm-3) and temperatures (5÷25 eV) promising for the feasibility of the astrophysical task. Plasma parameters were monitored via optical emission spectroscopy and interfero-polarimetric measurements. First attempts of optical properties measurements have been done in hydrogen and argon plasmas reacting to an external white light source, useful for future in-laboratory plasma opacity measurements of metallic plasma species relevant for KN light curve studies.

We present an analysis of the shape of the decay phase of solar flares as seen in Sun-as-a-star SDO/AIA data. It was inspired by the study of white light flares on an M4 dwarf, presented by Davenport et al. (2014). We limited our study to the solar flare with a classical shape of decay phase consisting of a slow, continuous and smooth decay phase observed in 304, 1600 and 1700 Angstroms. We limited our study to those with a classical flare shape consisting of a slow, continuous and smooth decay phase observed in 304, 1600 and 1700 Angstroms. This left us with a sample of over 100 flares in 304 and 1600 Angstroms, and 53 flares in 1700 Angstrom data. The amplitudes and timescales of these flares were normalized, allowing us to construct average flare profiles for each channel, which were fitted with analytical templates. As was found for the M dwarf, the decay profiles were best described by a model containing two exponents. However, the time ranges used to best fit the data were different from those found for the M dwarf. We speculate that this was because of the impact of chromospheric plasma evaporation. We also found that the average solar flare profiles decayed more slowly than the average profile of the M dwarf flares, which potentially indicates that the M dwarf white light emission comes from a higher density layer than the solar emission considered here.

Turbulent magnetic relaxation is an important candidate mechanism for coronal heating and some types of solar flare. By developing turbulence that reconnects the magnetic field throughout a large volume, magnetic fields can spontaneously self-organize into simpler lower-energy configurations. We are using resistive MHD simulations to probe this relaxation process, in particular to test whether a linear force-free equilibrium is reached. Such an end state would be predicted if one assumes the classic Taylor hypothesis: that the only constraints on the relaxation come from conservation of total magnetic flux and helicity. In fact, a linear force-free state is not reached in our simulations, despite the conservation of these total quantities. Instead, the end state is better characterised as a state of (locally) uniform field-line helicity.

We present the results of a fossil record technique study using MaNGA and CALIFA galaxies showing the chemical enrichment history (ChEH) as well as how the mass-metallicity relation (MZR) has changed.
In order to analyze how the evolution of these relations correlates with the properties of the galaxy we separate the sample into mass, morphology and star-forming status bins, finding a strong dependence on the mass and the morphology, and dependence on the star-forming status that is more subtle after accounting for the correlation between morphology and star-forming status. We also measure the ChEH and MZR at different galactocentric radii, finding the effects of local downsizing as well as an inversion of the metallicity gradient for low mass galaxies.

Studies of extragalactic transients often use their offsets from, and locations on, their host galaxies to help infer the nature of their progenitors. In this work, we examine the spatial distribution of neutron stars in the Milky Way, as observed from an extragalactic distance and face-on orientation. Motivated by the association of fast radio bursts with the Galactic magnetar SGR1935, we compare the offset, host-normalised offset, enclosed flux and fraction of light distributions of Milky Way magnetars to FRBs on their hosts. We extend this to other Galactic neutron star populations, including X-ray binaries and pulsars, comparing to a range of extragalactic transients. We find that the fraction of light statistic should be carefully used when making comparisons between transients with different host morphologies, and in different redshift ranges. Our primary result is that Galactic neutron stars are distributed on the Milky Way's light in a manner consistent with FRBs on their host galaxies. While we cannot distinguish which specific population of neutron stars is the best match, the overall results further strengthen the FRB-neutron star connection.