Search Publications
Improved constraints on lepton asymmetry from the cosmic microwave background
Schwarz, Dominik J.; Oldengott, Isabel M.
A cosmic lepton asymmetry η\text{l}=(n\text{l}-n\bar{\text{l}})/nγ affects the primordial helium abundance and the expansion rate of the early Universe. Both of these effects have an impact on the anisotropies of the cosmic microwave background (CMB). We derive constraints on the neutrino chemical potent…
Multipoint observation of anisotropy and intermittency in solar-wind turbulence
Perri, S.; Carbone, V.; Sorriso-Valvo, L. +1 more
Using high-resolution magnetic-field Cluster observations, we have investigated the magnetic-field anisotropy via the second- and fourth-order structure functions over a wide range of scales reaching below the subproton scale. The magnetic-field increments have been computed from single- and two-spacecraft measurements. The two-satellite technique…
Observational evidence for travelling wave modes bearing distance proportional shifts
Guruprasad, V.
Discrepancies of range between the Space Surveillance Network radars and the Deep Space Network in tracking the 1998 Earth flyby of NEAR, and between ESA's Doppler and range data in Rosetta's 2009 flyby, reveal a consistent excess delay, or lag, equal to instantaneous one-way travel time in the telemetry signals. These lags readily explain all det…
Acceleration of solar wind ions to 1 MeV by electromagnetic structures upstream of the Earth's bow shock
Yamauchi, M.; Stasiewicz, K.; Markidis, S. +2 more
We present measurements from the ESA/NASA Cluster mission that show in situ acceleration of ions to energies of 1 MeV outside the bow shock. The observed heating can be associated with the presence of electromagnetic structures with strong spatial gradients of the electric field that lead to ion gyro-phase breaking and to the onset of chaos in ion…
Implications of the Planck bispectrum constraints for the primordial trispectrum
Byrnes, Christian T.; Nurmi, Sami; Tasinato, Gianmassimo +1 more
The new Planck constraints on the local bispectrum parameter f_NL are about 105 times tighter than the current constraints on the trispectrum parameter g_NL , which means that the allowed numerical values of the second-and third-order terms in the perturbative expansion of the curvature perturbation are comparable. We show that a conseq…
Double mid-latitude dynamical reconnection at the magnetopause: An efficient mechanism allowing solar wind to enter the Earth's magnetosphere
Califano, F.; Pegoraro, F.; Faganello, M. +1 more
Three-dimensional simulations of the Kelvin-Helmholtz (KH) instability in a magnetic configuration reproducing typical conditions at the flank Earth's magnetosphere during northward periods show the system's ability to generate favorable conditions for magnetic reconnection to occur at mid-latitude. Once these conditions are established, magnetic …
Detection of X-ray galaxy clusters based on the Kolmogorov method
Durret, F.; Gurzadyan, V. G.; Kashin, A. L. +3 more
The detection of clusters of galaxies in large surveys plays an important part in extragalactic astronomy, and particularly in cosmology, since cluster counts can give strong constraints on cosmological parameters. X-ray imaging is, in particular, a reliable means to discover new clusters, and large X-ray surveys are now available. Considering XMM…
On the scaling properties of anisotropy of interplanetary magnetic turbulent fluctuations
Carbone, V.; Sorriso-Valvo, L.; Yordanova, E.
The anisotropic character of interplanetary magnetic-field turbulence has been studied through the analysis of Cluster data. The full tensor of the mixed second-order structure functions has been used to quatitatively measure the degree of anisotropy and its effect on small-scale turbulence. Three different regions of the near-Earth space have bee…
Low-dimensional dynamics outside the laboratory: The case of roAp stars
Boyd, P. T.; Mindlin, G. B.; Merener, N.
In this work, we build a nonlinear model to account for the time variable energy flux of a class of pulsating stars which is simple and robust, and test it against recent observations made with the Hubble Space Telescope. By the construction of a standard global normal form for the model, we not only check that the model has solutions qualitativel…