Effects of fieldline topology on energy propagation in the corona

We study the effect of photospheric footpoint motions on magnetic field structures containing magnetic nulls. The footpoint motions are prescribed on the photospheric boundary as a velocity field which entangles the magnetic field. We investigate the propagation of the injected energy, the conversion of energy, emergence of current layers and other consequences of the non-trivial magnetic field topology in this situation. These boundary motions lead initially to an increase in magnetic and kinetic energy. Following this, the energy input from the photosphere is partially dissipated and partially transported out of the domain through the Poynting flux. The presence of separatrix layers and magnetic null-points fundamentally alters the propagation behavior of disturbances from the photosphere into the corona. Depending on the field line topology close to the photosphere, the energy is either trapped or free to propagate into the corona.Comment: 14 pages, 15 figure

Satellite vehicle tracking aiming to increase traffic safety within the Serbian Armed Forces

The purpose of this work is to show how to affect the most important factor of traffic safety - an individual, by using some technical solutions of satellite tracking of vehicles. By using units of the Land Forces as an example, a brief analysis of traffic safety for vehicles less than 5 years old has been performed. It is noticed that the number of traffic accidents with these vehicles involved has increased, so we tried to use one software package commercially available in order to show all advantages and disadvantages which could be noticed during this kind of vehicle tracking. The conclusion is that preventive vehicle tracking can improve traffic safety, but that a techno-economic analysis has to be done as well, in order to create all the necessary conditions for the introduction of this system in the units of the Serbian Armed Forces

Chromospheric Heating due to Cancellation of Quiet Sun Internetwork Fields

The heating of the solar chromosphere remains one of the most important questions in solar physics. Our current understanding is that small-scale internetwork (IN) magnetic fields play an important role as a heating agent. Indeed, cancellations of IN magnetic elements in the photosphere can produce transient brightenings in the chromosphere and transition region. These bright structures might be the signature of energy release and plasma heating, probably driven by the magnetic reconnection of IN field lines. Although single events are not expected to release large amounts of energy, their global contribution to the chromosphere may be significant due to their ubiquitous presence in quiet Sun regions. In this paper, we study cancellations of IN elements and analyze their impact on the energetics and dynamics of the quiet Sun atmosphere. We use high-resolution, multiwavelength, coordinated observations obtained with the Interface Region Imaging Spectrograph and the Swedish 1 m Solar Telescope (SST) to identify cancellations of IN magnetic flux patches and follow their evolution. We find that, on average, these events live for ∼3 minutes in the photosphere and ∼12 minutes in the chromosphere and/or transition region. Employing multi-line inversions of the Mg ii h and k lines, we show that cancellations produce clear signatures of heating in the upper atmospheric layers. However, at the resolution and sensitivity accessible to the SST, their number density still seems to be one order of magnitude too low to explain the global chromospheric heating.© 2018. The American Astronomical Society. All rights reserved.RIS is a NASA small explorer mission developed and operated by LMSAL with mission operations executed at NASA Ames Research center and major contributions to downlink communications funded by ESA and the Norwegian Space Centre. M.G. was supported by NASA grant NNX16AC34G. J.dl.C.R. is supported by grants from the Swedish Research Council (2015-03994), the Swedish National Space Board (128/15), and the Swedish Civil Contingencies Agency (MSB). This project has received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (SUNMAG, grant agreement 759548). B.D.P. was supported by NASA grant NNX11AN98G and NASA contracts NNG09FA40C (IRIS). The work of L.B.R. and S.E.P. was supported by the Spanish Ministerio de Economia and Competitividad through grants ESP2013-47349-C6-1-R and ESP2016-77548-C5-1-R, including a percentage from European FEDER funds. Image reconstruction was performed at IAA-CSIC supercomputing facilities. The Swedish 1 m Solar Telescope is operated by the Institute for Solar Physics of Stockholm University in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias. M.C. was supported by the Research Council of Norway through its Centres of Excellence scheme, project number 262622, and through grants of computing time from the Programme for Supercomputing. This research has made use of NASA's Astrophysics Data System

Program of telluric lines monitoring

A new observational program of telluric lines monitoring was introduced at Belgrade Astronomical Observatory. The ultimate goal of this program is to investigate the properties of Earth’s atmosphere through modeling the observed profiles of telluric lines. The program is intend to observe infrared molecular oxygen lines that were selected according to spectral sensitivity of the available CCD camera. In this paper we give the initial and the final selection criteria for spectral lines included in the program the description of equipment and procedures used for observations and reduction, a review of preliminary observational results with the estimated precision, and a short discussion on the comparison of the theoretical predictions and the measurements

Emergence of Internetwork Magnetic Fields through the Solar Atmosphere

Internetwork (IN) magnetic fields are highly dynamic, short-lived magnetic structures that populate the interior of supergranular cells. Since they emerge all over the Sun, these small-scale fields bring a substantial amount of flux, and therefore energy, to the solar surface. Because of this, IN fields are crucial for understanding the quiet Sun (QS) magnetism. However, they are weak and produce very small polarization signals, which is the reason why their properties and impact on the energetics and dynamics of the solar atmosphere are poorly known. Here we use coordinated, high-resolution, multiwavelength observations obtained with the Swedish 1 m Solar Telescope and the Interface Region Imaging Spectrograph (IRIS) to follow the evolution of IN magnetic loops as they emerge into the photosphere and reach the chromosphere and transition region. We studied in this paper three flux emergence events having total unsigned magnetic fluxes of 1.9 × 1018, 2.5 × 1018, and 5.3 × 1018 Mx. The footpoints of the emerging IN bipoles are clearly seen to appear in the photosphere and to rise up through the solar atmosphere, as observed in Fe I 6173 A and Mg I b2 5173 A magnetograms, respectively. For the first time, our polarimetric measurements taken in the chromospheric Ca II 8542 A line provide direct observational evidence that IN fields are capable of reaching the chromosphere. Moreover, using IRIS data, we study the effects of these weak fields on the heating of the chromosphere and transition region. © 2021 Institute of Physics Publishing. All rights reserved.IRIS is a NASA Small Explorer Mission developed and operated by LMSAL with mission operations executed at NASA Ames Research Center and major contributions to downlink communications funded by the ESA and the Norwegian Space Centre. M.G., B.D.P., and A.S.D. are supported by NASA contract NNG09FA40C (IRIS). The work of L.B.R. and S.E.P. was supported by the Spanish Ministerio de Economia and Competitividad through grants ESP201347349-C6-1-R and ESP2016-77548-C5-1-R, including a percentage from European Regional Development Fund (FEDER) funds. L.B.R. acknowledges financial support from the State Agency for Research of the Spanish Ministerio de Ciencia e Innovacion through project RTI2018-096886-B-C5 (including FEDER funds) and through the "Center of Excellence Severo Ochoa" award to the Instituto de Astrofisica de Andalucia (SEV-2017-0709). The Swedish 1 m Solar Telescope is operated on the island of La Palma by the Institute for Solar Physics of Stockholm University in the Spanish Observatory del Roque de los Muchachos of the Instituto de Astrofisica de Canarias. The Institute for Solar Physics is supported by a grant for research infrastructures of national importance from the Swedish Research Council (registration No. 2017-00625). This research has made use of NASA's Astrophysics Data System.Peer reviewe

Erratum: Supergranular turbulence in the quiet Sun: Lagrangian coherent structures

This is an erratum to the paper ‘Supergranular turbulence in the quiet Sun: Lagrangian coherent structures’ that was published in MNRAS, 488, 3076–3088 (2019). In the original version of stz1909, there were several instances where the author's corrections had not been implemented during the proofing stages. These have now been corrected as follows: i. Page 3077: in the second paragraph, the reference ‘G16 G17’ has been corrected to ‘Gošić et al. 2014, 2016’. ii. Page 3079: in section 3.1, the reference ‘G20’ has been corrected to ‘Haller (2015)’. iii. Page 3087: the article ID ‘eeau2307’ has been added to reference ‘Hotta H., Iijima H., Kusano K., 2019, Sci. Adv., 5’. The publisher apologises for these errors