12,455 research outputs found

    Delayed Babcock-Leighton dynamos in the diffusion-dominated regime

    Full text link
    Context. Solar dynamo models of Babcock-Leighton type typically assume the rise of magnetic flux tubes to be instantaneous. Solutions with high-magnetic-diffusivity have too short periods and a wrong migration of their active belts. Only the low-diffusivity regime with advective meridional flows is usually considered. Aims. In the present paper we discuss these assumptions and applied a time delay in the source term of the azimuthally averaged induction equation. This delay is set to be the rise time of magnetic flux tubes which supposedly form at the tachocline. We study the effect of the delay, which adds to the spacial non-locality a non-linear temporal one, in the advective but particularly in the diffusive regime. Methods. Fournier et al. (2017) obtained the rise time according to stellar parameters such as rotation, and the magnetic field strength at the bottom of the convection zone. These results allowed us to constrain the delay in the mean-field model used in a parameter study. Results. We identify an unknown family of solutions. These solutions self-quench, and exhibit longer periods than their non-delayed counterparts. Additionally, we demonstrate that the non-linear delay is responsible for the recover of the equatorward migration of the active belts at high turbulent diffusivities. Conclusions. By introducing a non-linear temporal non-locality (the delay) in a Babcock-Leighton dynamo model, we could obtain solutions quantitatively comparable to the solar butterfly diagram in the diffusion-dominated regime.Comment: 11 pages, 10 Figure

    Pinsker estimators for local helioseismology

    Full text link
    A major goal of helioseismology is the three-dimensional reconstruction of the three velocity components of convective flows in the solar interior from sets of wave travel-time measurements. For small amplitude flows, the forward problem is described in good approximation by a large system of convolution equations. The input observations are highly noisy random vectors with a known dense covariance matrix. This leads to a large statistical linear inverse problem. Whereas for deterministic linear inverse problems several computationally efficient minimax optimal regularization methods exist, only one minimax-optimal linear estimator exists for statistical linear inverse problems: the Pinsker estimator. However, it is often computationally inefficient because it requires a singular value decomposition of the forward operator or it is not applicable because of an unknown noise covariance matrix, so it is rarely used for real-world problems. These limitations do not apply in helioseismology. We present a simplified proof of the optimality properties of the Pinsker estimator and show that it yields significantly better reconstructions than traditional inversion methods used in helioseismology, i.e.\ Regularized Least Squares (Tikhonov regularization) and SOLA (approximate inverse) methods. Moreover, we discuss the incorporation of the mass conservation constraint in the Pinsker scheme using staggered grids. With this improvement we can reconstruct not only horizontal, but also vertical velocity components that are much smaller in amplitude

    Field-dependent diamagnetic transition in magnetic superconductor Sm1.85Ce0.15CuO4ySm_{1.85} Ce_{0.15} Cu O_{4-y}

    Full text link
    The magnetic penetration depth of single crystal Sm1.85Ce0.15CuO4y\rm{Sm_{1.85}Ce_{0.15}CuO_{4-y}} was measured down to 0.4 K in dc fields up to 7 kOe. For insulating Sm2CuO4\rm{Sm_2CuO_4}, Sm3+^{3+} spins order at the N\'{e}el temperature, TN=6T_N = 6 K, independent of the applied field. Superconducting Sm1.85Ce0.15CuO4y\rm{Sm_{1.85}Ce_{0.15}CuO_{4-y}} (Tc23T_c \approx 23 K) shows a sharp increase in diamagnetic screening below T(H)T^{\ast}(H) which varied from 4.0 K (H=0H = 0) to 0.5 K (H=H = 7 kOe) for a field along the c-axis. If the field was aligned parallel to the conducting planes, TT^{\ast} remained unchanged. The unusual field dependence of TT^{\ast} indicates a spin freezing transition that dramatically increases the superfluid density.Comment: 4 pages, RevTex

    Discrimination of the light CP-odd scalars between in the NMSSM and in the SLHM

    Full text link
    The presence of the light CP-odd scalar boson predicted in the next-to-minimal supersymmetric model (NMSSM) and the simplest little Higgs model (SLHM) dramatically changes the phenomenology of the Higgs sector. We suggest a practical strategy to discriminate the underlying model of the CP-odd scalar boson produced in the decay of the standard model-like Higgs boson. We define the decay rate of "the non bb-tagged jet pair" with which we compute the ratio of decay rates into lepton and jets. They show much different behaviors between the NMSSM and the SLHM.Comment: 5 pages, 2 figures (5 figure files

    Alien Registration- Fournier, Rose D. (Lewiston, Androscoggin County)

    Get PDF
    https://digitalmaine.com/alien_docs/29751/thumbnail.jp

    Alien Registration- Fournier, Fred D. (Van Buren, Aroostook County)

    Get PDF
    https://digitalmaine.com/alien_docs/33298/thumbnail.jp

    Alien Registration- Fournier, Elizabeth D. (Brunswick, Cumberland County)

    Get PDF
    https://digitalmaine.com/alien_docs/31474/thumbnail.jp
    corecore