and Alfv6n velocity fluctuations, respectively. For small amplitude Alfv6n waves the fluctuation variable •Z + simply relates to outward propagation and •Z-to an inward sense of propagation, if the ambient magnetic field Bo is directed inward. The frequency range analysed in this paper is 6 x 10 -6 Hz to 6 x 10 -3 Hz. It is found that (1) the autocorrelation length for $Z-is much larger than for/SZ + in both the high-speed and low-speed wind. (2) The power spectra of •Z-, especially in high-wind speed, are steeper in the low-frequency range and flatten in the high-frequency range. (3) In the low-frequency range, the power spectra for the components of •Z + tend to be isotropic with respect to the three polarization directions, while the spectra of •Z-are dominated by the radial component. In the high-frequency domain, the spectra of both •Z + and •Z-are dominated by the transverse component in high-speed wind and are more isotropic in low-speed wind. (4) The spectra related to the residual energy or the cross-correlation in low-speed flows have a power law with the slope near to -5/3. However, in high-speed flows the corresponding data are widely distributed in a cloud of points with an upper envelope near to the spectrum of •Z-. The origin of all these spectra and their importance for the solar wind physics have also been discussed. Several generation mechanisms are suggested as candidates. In the flat part of e-spectrum, the fluctuations may be generated by non-local (in wave number space) interactions with the low-frequency part of the e + spectrum, or just by parametric decay of the high-frequency part of the e + spectrum. The steep part of e-(f) may be related to small-scale stream tubes, or be influenced by pressure waves, nonlinear cascading, and the interaction with the outgoing Alfv6n waves. wave description are entirely in contradiction. To get out of this dilemma,'Dobrowolny et al. [1980a, b] proposed a model known as "dynamic alignment," in which the fluctuations are conceived as the final state of a turbulent relaxation of cross-helicity, resulting in a disappearance of nonlinear interactions. Instead of considering only local interactions in k space, Matthaeus et al. [1983] suggested that outward propagating fluctuations might even be generated outside the Alfv•nic critical point by nonlocal interactions in wave number space. However, the recent observations did not support these conjectures [Roberts et al., 1987a, b; Luttrell and Richter, 1988], and the problem how to describe the solar wind fluctuations remained unsolved. The observational findings of Denskat and Neubauer [1982] and Bavassano et al. [1982a, b] that the slope of the spectrum in the low-frequency range of Alfv•nic fluctuations becomes steeper with increasing heliospheric distance cannot be explained by the WKB theory of pure Alfv•n waves. This evidence strongly suggests that nonlinear interactions in fact occur between the fluctuations that still preserve some properties of Alfv•n waves. The nonlinear interactions couple the primord...

The DARWIN observatory is a proposed nextgeneration experiment to search for particle dark matter and for the neutrinoless double beta decay of 136 Xe. Out of its 50 t total natural xenon inventory, 40 t will be the active target of a time projection chamber which thus contains about 3.6 t of 136 Xe. Here, we show that its projected half-life sensitivity is 2.4 × 10 27 years, using a fiducial volume of 5 t of natural xenon and 10 years of operation with a background rate of less than 0.2 events/(t • year) in the energy region of interest. This sensitivity is based on a detailed Monte Carlo simulation study of the background and event topologies in the large, homogeneous target. DARWIN will be comparable in its science reach to dedicated double beta decay experiments using xenon enriched in 136 Xe.

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Mean temperature gradients of solar wind electrons between 0.3 and 1 AU are determined from Helios observations. Electrons are found to cool more slowly than adiabatically, with flattest temperature profiles in high‐speed streams. These in situ observations are used to estimate the radial gradients of Te inside 0.3 AU under the constraint of matching coronal temperatures. Electrons in high‐speed streams are inferred to cool more strongly closer to the Sun than within the Helios orbital range. For low‐speed wind, no significant breaks in the temperature profiles have been found, while for intermediate‐speed structures the results are somewhat ambiguous. These results are discussed in the context of solar wind generation and modeling.

We detail the sensitivity of the proposed liquid xenon DARWIN observatory to solar neutrinos via elastic electron scattering. We find that DARWIN will have the potential to measure the fluxes of five solar neutrino components: pp, $$^7$$ 7 Be, $$^{13}$$ 13 N, $$^{15}$$ 15 O and pep. The precision of the $$^{13}$$ 13 N, $$^{15}$$ 15 O and pep components is hindered by the double-beta decay of $$^{136}$$ 136 Xe and, thus, would benefit from a depleted target. A high-statistics observation of pp neutrinos would allow us to infer the values of the electroweak mixing angle, $$\sin ^2\theta _w$$ sin 2 θ w , and the electron-type neutrino survival probability, $$P_{ee}$$ P ee , in the electron recoil energy region from a few keV up to 200 keV for the first time, with relative precision of 5% and 4%, respectively, with 10 live years of data and a 30 tonne fiducial volume. An observation of pp and $$^7$$ 7 Be neutrinos would constrain the neutrino-inferred solar luminosity down to 0.2%. A combination of all flux measurements would distinguish between the high- (GS98) and low-metallicity (AGS09) solar models with 2.1–2.5$$\sigma $$ σ significance, independent of external measurements from other experiments or a measurement of $$^8$$ 8 B neutrinos through coherent elastic neutrino-nucleus scattering in DARWIN. Finally, we demonstrate that with a depleted target DARWIN may be sensitive to the neutrino capture process of $$^{131}$$ 131 Xe.