Mauro Messerotti

Analysis of the polarization of pulsating structures at m-dm wavelengths

We performed an analysis of the polarization of 60 pulsating radio events identified in type IV bursts recorded in the m-dm band during the Solar Cycle XXI at the Trieste Astronomical Observatory.Two major points summarize the results of such an analysis: (i) the emission is totally polarized at the source and the source itself is unique; (ii) the emission occurs in the ordinary magneto-ionic mode for most of the samples, if one accepts the leading-spot hypothesis.The first point confirms what was derived by other authors who anyhow considered a more limited set of samples: highly-polarized events are the most frequent, intense and long-lasting. The intermediate and low polarization observed in other cases are to be attributed to propagation effects, which are effective along the path after the emission, and this interpretation is supported by different observed features such as shorter duration and lower intensity of the events.Our second point differs from a previous work which claims the extraordinary mode, but this discrepancy can be justified by: (a) the small number of events analyzed in that work, which gives poorer statistics; (b) a quite different observing frequency range; (c) the different selection criterion. However, in spite of the relative richness of our data set we cannot give a final answer to the emission mode problem as the leading-spot hypothesis is questionable and we report critical arguments against it based on experimental results.The polarization degree of pulsations looks generally constant during the whole lifetime. As a general trend the selected events show the same polarization features both for the pulsations and the background. A different polarization degree of the continuum is probably the signature of the contemporaneous presence of more than one source.

Simulation of the geomagnetic field experienced by the International Space Station in its revolution around the Earth: effects on psychophysiological responses to affective picture viewing.

There is evidence suggesting that exposure to an abnormal magnetic environment may produce psychophysiological effects related to abnormalities in responses to stress. This may be of relevance for space medicine where astronauts are exposed to a magnetic field different from that exerted by the Earth. Aim of this study was to assess how the exposure of the head to a magnetic field simulating the one encountered by the International Space Station (ISS) during a single orbit (90 min) around the Earth affects the cardiovascular and psychophysiological parameters. Twenty-four human volunteers were studied double blindly in random order under sham and magnetic exposure. During exposure, the persons were shown a set of pictures of different emotional content while subjective self-rating, skin conductance (SC), blood pressure (BP), and heart rate (HR) were measured. In addition, BP, HR, and tooth pain threshold were assessed before and after exposure. While subjects were under magnetic exposure, skin conductance was strongly differentiated (F(2,36)=22.927; p=0.0001), being high during emotionally involving (positive and negative) pictures and low during neutral pictures. Conversely, when subjects were under sham exposure, no significant differences were observed. There was, however, a trend for higher heart rate during picture viewing under magnetic exposure as compared to sham exposure. No effects were found for the other variables. These results suggest that an abnormal magnetic field that simulates the one encountered by ISS orbiting around the Earth may enhance autonomic response to emotional stimuli.

Renewed Support Dawns in Europe: An Action to Develop Space Weather Products and Services

The effects of space weather span a range of sectors. They can cause radio communications problems; can disrupt synthetic aperture radar systems, the Global Positioning System (GPS), and the future European Galileo systems; and can increase radiation risks for aircraft crew and passengers. Electric power network disturbances and enhanced corrosion effects observed in long-distance fuel supply pipelines are other well-known effects of unfavorable space weather. In severe cases, large-scale power outages have also been traced to space weather phenomena (Figure 1). Research efforts in various countries—including the U.S. multiagency National Space Weather Program (http:// www.nswp.gov), the International Space Environment Service (ISES; http://www.ises-spaceweather.org/), and several European initiatives sponsored by the European Space Agency (ESA) and the European Commission (EC)—have demonstrated that adverse space weather poses a tangible threat to humans and modern technological systems and assets on the ground, in the air, and in space. Although methods to model some aspects of space weather have been developed by these agencies, all agree that their performance needs to be improved—in many cases, prediction accuracy is inadequate to allow the transition from models to reliable operational services. Further targeted research and development is needed. Funding for coordinated space weather science and applications effects in Europe has so far been on a project-by-project basis. Systematic national contributions to a pan-European space weather program are not yet in place, leading to fragmentation of European space weather initiatives. A certain level of

Investigations of a simulated geomagnetic field experienced by the international space station on attentional performance

We have previously reported that the exposure to an abnormal magnetic field simulating the one encountered by the International Space Station (ISS) orbiting around the Earth may enhance autonomic response to emotional stimuli. Here we report the results of the second part of that study which tested whether this field also affects cognitive functions. Twenty-four volunteers participated in the study, 12 exposed to the natural geomagnetic field and 12 to the magnetic field encountered by ISS. The test protocol consisted of a set of eight tests chosen from a computerized test battery for the assessment of attentional performance. The duration of exposure was 90 min. No effect of exposure to ISS magnetic field was observed on attentional performance.

Radio Emission Processes as Tracers of Heliospheric Weather: An Ontological Approach

The heliosphere is a complex physical system composed of a set of coupled plasma sub-systems typically in a state of marginal stability. Hence a variety of perturbations can be triggered by instabilities occurring from large to small spatial and temporal scales. This characterizes the heliospheric weather, i.e. the physical state of the heliosphere on short- to mid-timescale, which is a key aspect for the study of space weather and space climate. Interacting plasmas in the heliosphere originate a variety of radio emissions according to processes that, in turn, are signatures of kinetic and magnetohydrodynamic plasma processes occurring at different scales. Space- and ground-based observations of such radio emissions represent a fundamental tool for deriving the associated emission processes and, therefore, the underpinning plasma processes that are tracers of the plasma state, i.e. of the heliospheric weather. In this work, by means of an ontological approach, we illustrate the present observational and interpretative scenario of the heliospheric radio emission processes and we highlight the expected improvements by the forthcoming next generation instruments.

Observing, modeling and predicting the effects of solar radio bursts on radio communications

The Sun is a source of broadband radio noise, which can reach significantly high levels during outbursts associated with the time evolution of the activity cycle. The statistics point out that the maximum occurrence frequency and intensity of solar radio bursts (SRBs) are observed in the proximity of the activity maximum, but relevant phenomena can occur also in the raising and declining phases of the cycle. Both theoretical estimations based on extensive statistical analyses carried out in recent years and direct observations performed in the past solar activity cycle indicate that solar radio bursts can interfere wireless communications as well as Global Navigation Satellite Systems (GNSS). In this work, we briefly review the theoretical basis and the experimental evidences to date and we show the effectiveness of fast multichannel solar radiopolarimeters, like the Trieste Solar Radio System, in monitoring and predicting solar radio noise increase in the framework of Space Weather applications.

Radio science for space weather

Radio emissions in the solar and planetary environments are originated by a series of plasma processes whose nature is related to the physical state of plasmas at the source. Hence, Radio Weather is an effective diagnostics of space plasmas that can be exploited only via diachronic observations.

Cellular Automata Models for Convection

We present here three models for convection. The models make use of the concept of cellular automata (CA). CA are discrete systems. The advantages of CA are their simple and parallel structure. The simplest of the presented models simulates two-dimensional Boussinesq convection. The two other models are extensions to compressible fluids and three-dimensional convection, respectively. We derive the model equations for the simplest model and present some of our results.