Search

We study the broadband emission of Mrk 501 using multiwavelength observations from 2017 to 2020 performed with a multitude of instruments, involving, among others, MAGIC, Fermi's Large Area Telescope (LAT), NuSTAR, Swift, GASP-WEBT, and the Owens Valley Radio Observatory. Mrk 501 showed an extremely low broadband activity, which may help to unravel its baseline emission. Nonetheless, significant flux variations are detected at all wave bands, with the highest occurring at X-rays and very-high-energy (VHE) γ -rays. A significant correlation (>3 σ ) between X-rays and VHE γ -rays is measured, supporting leptonic scenarios to explain the variable parts of the emission, also during low activity. This is further supported when we extend our data from 2008 to 2020, and identify, for the first time, significant correlations between the Swift X-Ray Telescope and Fermi-LAT. We additionally find correlations between high-energy γ -rays and radio, with the radio lagging by more than 100 days, placing the γ -ray emission zone upstream of the radio-bright regions in the jet. Furthermore, Mrk 501 showed a historically low activity in X-rays and VHE γ -rays from mid-2017 to mid-2019 with a stable VHE flux (>0.2 TeV) of 5% the emission of the Crab Nebula. The broadband spectral energy distribution (SED) of this 2 yr long low state, the potential baseline emission of Mrk 501, can be characterized with one-zone leptonic models, and with (lepto)-hadronic models fulfilling neutrino flux constraints from IceCube. We explore the time evolution of the SED toward the low state, revealing that the stable baseline emission may be ascribed to a standing shock, and the variable emission to an additional expanding or traveling shock.

Two phytoplankton succession events (September-October 1993 and March 1994) in the Ría de Vigo were studied in relation to their hydrodynamic context. By means of a circulation box model we calculated horizontal and vertical residual fluxes as well as budgets of phytoplankton associated with them. This allowed us to assess the importance of the two factors involved in the selection processes: one hydrodynamic (dependent upon physical dispersion) and one biogeochemical (involving all other processes such as growth, mortality and grazing). The first period was characterised by a downwelling event which produced a reversal of the estuarine circulation pattern (horizontal velocity = 4 km d-1 and downward velocities up to 9 m d-1). This provided suitable conditions for the blooming of Gymnodinium catenatum favoured by its capacity to swim, while the diatom community almost disappeared. The second period corresponded to an upwelling Æ relaxation sequence. During upwelling (horizontal velocity = 6 km d-1; upward velocities up to 12 m d-1), Thalassiosira spp. was dominant. It is suggested that the less energetic conditions associated with the relaxation event (horizontal velocity=1 km d-1; upward velocities < 1 m d-1) favoured the selection of Chatoceros spp. due to its lower sinking rate.

The European Research Council (ERC) marks a new approach to investing in frontier research in Europe. Since its establishment, the ERC has taken numerous actions to tackle imbalances and monitors data from each call. The aim of this paper is to review descriptive statistics of men and women participating in ERC calls in the geosciences. The share of women applying for Starting Grants is on average around 30 %, whereas for Consolidator Grants and Advanced Grants the share is around 25 % and 11 % respectively. Success rate analysis shows no significant gender disparities. The paper provides an overview of the ERC peer-review system, discusses results specific to the geosciences compared to national funding and SHE Figures, and concludes with a review of past actions and future goals.

Using the wave model SWAN (simulating waves nearshore), high waves on the southwestern Atlantic generated by extra-tropical cyclones are simulated from 2000 to 2010, and their impact on the Rio Grande do Sul (RS) coast is studied. The modeled waves are compared with buoy data and good agreement is found. The six extreme events in the period that presented significant wave heights above 5 m, on a particular point of interest, are investigated in detail. It is found that the cyclogenetic pattern between the latitudes 31.5 and 34° S is the most favorable for developing high waves. Hovmöller diagrams for deep water show that the region between the south of Rio Grande do Sul up to a latitude of 31.5° S is the most energetic during a cyclone's passage, although the event of May 2008 indicates that the location of this region can vary, depending on the cyclone's displacement. On the other hand, the Hovmöller diagrams for shallow water show that the different shoreface morphologies were responsible for focusing or dissipating the waves' energy; the regions found are in agreement with the observations of erosion and progradation regions. It can be concluded that some of the urban areas of the beaches of Hermenegildo, Cidreira, Pinhal, Tramandaí, Imbé and Torres have been more exposed during the extreme wave events on the Rio Grande do Sul coast, and are more vulnerable to this natural hazard.

The problem of optimization of analytical and numerical approximations of Hasselmann's nonlinear kinetic integral is discussed in general form. Considering the general expression for the kinetic integral, a principle to obtain the optimal approximation is formulated. From this consideration it follows that the most well-accepted approximations, such as Discrete Interaction Approximation (DIA) (Hasselmann et al., 1985), Reduced Integration Approximation (RIA) (Lin and Perry, 1999), and the Diffusion Approximation proposed recently in Zakharov and Pushkarev (1999) (ZPA), have the same roots. The only difference among them is, essentially, the choice of the 4-wave configuration for the interacting waves. To evaluate a quality of any approximation for the 2-D nonlinear energy transfer, a mathematical measure of relative error is constructed and the meaning of approximation efficiency is postulated. By the use of these features it is shown that DIA has better accuracy and efficiency than ZPA. Following to the general idea of optimal approximation and by using the measures introduced, more efficient and faster versions of DIA are proposed.