National Astronomy Meeting Poster Exhibition

The Space Weather Instrumentation, Measurement, Modelling and Risk: Thermosphere (SWIMMR-T) programme aims to improve the UK’s ability to specify and forecast the thermosphere. AENeAS (Advanced Ensemble electron density [Ne] Assimilation System) is a physics-based, thermosphere-ionosphere, coupled, assimilative model, which makes possible thermospheric forecasts. Currently AENeAS uses the Heelis and Weimer electric field spacecraft climatology models but it is possible a more recent electric field model will improve its functionality. The new models include three statistical models for ionospheric convection using line-of-sight velocity measurements from the Super Dual Auroral Radar Network (SuperDARN): Thomas and Shepherd (TS18), the Time-Variable Ionospheric Electric Field model (TiVIE) and the empirical orthogonal functions (BAS EOF) model. Before implementation in AENeAS, we first compare the new SuperDARN-based models to the established spacecraft climatology models.

Here we present quantitative comparison of the electric-field models across a variety of geophysical conditions, including during storm times. To allow for fair comparison between models we explore methods of standardizing the input parameters using pre-existing equations. Once standardized, each model’s ionospheric convection patterns can be compared for varying solar wind and interplanetary magnetic field (IMF) conditions. We explore the relationships between the IMF conditions and model output parameters such as the polar cap transpolar voltage and size. During storms we compare the parameterized model output time series from the different electric field models, including the commonly used SuperDARN Map Potential Model. At peak storm times we find the calculated electric potential magnitude to be much greater from the spacecraft-based models. We will discuss the similarities and differences found using each method.

Total eclipses provide a unique opportunity to observe the solar corona over a short period of minutes. A white-light optical system designed and built by a team from Aberystwyth University was used to make polarized brightness (pB) observations of the corona during the Argentinian total solar eclipse of December 2020. The pB images enable the separation of the light produced by dust (the F-corona) from the light emitted by electrons in the plasma of the corona (the K-corona). The K-corona observations allow us to determine the density of the plasma, which is central to understanding the balance of forces in the solar atmosphere. The instrument was called the “Coronal Imaging Polariser” (CIP: in Welsh “cip” means a quick look). Due to Covid-19, and the poor weather in South America at the time, the Aberystwyth team were lucky to gather successful scientific observations during this eclipse. CIP works by automatically rotating a polarizer to six polarization angles (0, 30, 60, 90, 120, and 150 degrees) and takes five different exposures at each angle (0.001s, 0.01s, 0.1s, 1s, and 3s), enabling a precise measurement of the polarization of the strong light from the lower corona, as well as the fainter outer corona. I will present a brief description of the calibration and image processing methods, present some preliminary results, and summarize what we hope to achieve with this data.

Recent observations have shown that current sheets in the solar wind can have systematic spatial asymmetries in their particle density and temperature while the pressure remains constant. For one-dimensional current sheets the magnetic field has to be force-free, but known self-consistent equilibrium particle distribution functions for force-free current sheets usually lead to spatial density and temperature structures that are either constant or vary symmetrically in space. Using a specific ad hoc example, Neukirch et al. (2020) showed that it is possible to introduce spatial asymmetries into the density and temperature profiles without changing the magnetic field structure.

In this contribution, a systematic method will be presented that can in principle be used to construct particle distribution functions leading to density and temperature asymmetries of the form given in Neukirch et al. (2020). We will show how it explains why the known examples work and present some results of our attempts to find new examples.

We use the magnetic field measurements from the FIELDS fluxgate and search-coil magnetometers onboard Parker Solar Probe (PSP) during its first solar encounter to probe the nature of Alfvénic turbulence at small scales in the near-Sun solar wind. These high-resolution, low-noise measurements provide a rare opportunity to be able to investigate the spectral properties of magnetic field fluctuations to scales smaller than the proton gyro-radius. After accounting for sampling effects arising from the unique nature of PSP’s orbit, we analyse a 12-hour interval during perihelion where the spacecraft encountered a highly Alfvénic slow wind stream. By comparing our results with a model spectrum of linear Alfvén waves, we find that the spacecraft observations are consistent with a transition from an Alfvénic to kinetic Alfvén turbulent cascade approaching the proton gyro-radius, as previously reported in simulations and elsewhere in the heliosphere. In addition, we find evidence for a possible second transition in the turbulence at even smaller scales, as suggested by a subsequent decrease in the amplitude of the coherent magnetic helicity signature toward zero from a peak close to the proton gyro-radius. A decrease in the helicity at these scales is seen by other spacecraft in the solar wind, but these data are often contaminated by an increasing contribution of noise to the physical signal toward smaller scales. After a detailed characterisation of the different sources of spacecraft and instrument noise throughout our interval, we conclude that the observed decrease in helicity observed by PSP is physical and extends over a larger range of scales compared to previous studies. We discuss the possible physical interpretations of this transition to a state of zero magnetic helicity and the potential implications for sub-ion scale turbulence in the solar wind.

The Epoch of Reionization is this era in cosmic history when the neutral Hydrogen in the intergalactic medium turned into its ionized state due to the ionizing fronts produced by the newborn stars, galaxies, black holes, among others. Its progression is directly linked to the UV photons' sources, particularly the first galaxies. This work focuses on the properties of high redshift galaxies, their star formation rate, the feedback of this process with the intergalactic medium, and other observational constraints. Using high-resolution hydrodynamical simulations, we characterize the evolution of these galaxies towards the tail of Reionization and their relation with the dark matter halos, its interaction with the environment, and the self-consistent chemical enrichment. The most remarkable finding of this work is that the budget of ionizing photons to conclude the Reionization era comes from faint galaxies below the resolution of current instruments. However, the upcoming JWST will confirm this assumption by measuring the faint end of the galaxy luminosity function out to z ~ 10 and will extend our understanding of the first stages of the evolution of the cosmic structures.

Wide-field sub-millimetre surveys have driven many major advances in galaxy evolution in the past decade, but without extensive follow-ups the coarse angular resolution of these surveys limits the science exploitation. This has driven many deconvolution efforts. Generative Adversarial Networks have already been used to attempt deconvolutions on optical data. In this talk I will present an autoencoder with a novel loss function to overcome this problem at submm wavelengths. This approach is successfully demonstrated on Herschel SPIRE COSMOS data, with the super-resolving target being the JCMT SCUBA-2 observations of the same field. We reproduce the JCMT SCUBA-2 images with surprisingly high fidelity, and quantify the point source flux constraints using this autoencoder.

This poster details Outreach work from before and during lockdown, and gives some information about a post-lockdown project in the works.

Penumbral transient brightening events have been attributed to magnetic reconnection episodes occurring in the low corona. We investigated the trigger mechanism of these events in active region NOAA 12546 by using
multiwavelength observations obtained with IBIS@DS, the space-born IRIS and the XRT@Hinode instruments. We studied three brightening events detected from the chromosphere to the corona related to two small-scale emerging flux regions. The brightening events had one of the footpoints embedded in the penumbra and seemed to result from the distinctive interplay between the preexisting penumbral
fields, MMFs, and the EFRs. The IRIS spectra measured therein reveal enhanced temperature and asymmetries in spectral lines, suggestive of event triggering at different heights in the atmosphere. Specifically, the blue asymmetry noted in C II and Mg II h&k lines suggests the occurrence of chromospheric evaporation at the footpoint located in the penumbra as a consequence of the magnetic reconnection process at higher atmospheric heights.

Two-minute science is a science communication project initiated and supported by early-career Greek astrophysicists. With this endeavor, which started in December 2020, we try to bridge the gap between the scientific community and the public. This project is based on the simple idea of writing short articles with an approximate reading time of two minutes. These articles cover several topics and their difficulty scales to cover a broad audience range, from young students to experienced adults. We support the idea of “ask an expert” in Astrophysics in Greece, where any reader can pose a question. We offer the appropriate answer either by writing it ourselves or by contacting the field experts from the Greek astronomical society. Furthermore, our previous science communication experience leads us to design educational activities for students and/or adults based on pedagogical means. A successful one was an “escape-zoom” titled “Escape to Other Worlds”, a digital version of an escape room. Further activities are Astronomy workshops for teenagers, online talks to schools, and our participation in a scientific podcast to trigger the public interest in Astrophysics. We communicate this work through social media, where several thousands of people already follow our work.

Gravitational waves (GWs) can be used to measure the Hubble parameter. The optimal technique, a "Standard Siren", requires the identification of the electromagnetic (E/M) counterpart of the GW source. However, a significant fraction of GWs will not have E/M counterparts. Such "Dark Sirens" can still help constrain the Hubble parameter by statistical techniques. In this work we investigate the power of this method using high-resolution, cosmological simulations that include realistic clustering effects. In addition, we quantify the role of catalogue incompleteness, i.e. the lack of certain galaxies from our catalogues due to observational limitations, when applying this technique.