[en] Solar surface rotation has been measured from sunspot drawings made in A.D. 1642-1644 and probable differences from present-day rates are found. The 17th century sunspots rotated faster near the equator by 3 or 4%, and the differential rotation between 0 and +-20⁰ latitude was enhanced by about a factor 3. These differences are consistent features in both spots and groups of spots and in both northern and southern hemispheres. It is presumed that this apparent change in surface rotation was related to the ensuing dearth of solar activity (the Maunder Minimum) which persisted until about 1715. (Auth.)

[en] Interplanetary magnetic field (IMF) sector structures, such as 'toward' the sun and 'away' from the sun on each day, have been objectivly estimated from daily and monthly mean values of the horizontal component of the geomagnetic variation field at Godhavn during the period 1926--1970. The agreement between this estimation and actual satellite observations of the sector structures of the interval 1964--1970 is 88, 79, and 58% in summer, equinox, and winter, respectively. A remarkable agreement (more than 95%) is obtained for the summers of 1964, 1969, and 1970. Various types of IMF sector behavior are examined by taking this seasonal factor into consideration. Approximately 27-day recurrences of the same structure are often found, and 5- to 14-day consecutive occurrences of the same sector are frequently noted. Furthermore, the total number of occurrences for each estimated sector in each year shows an apparently good correlation with smoothed sunspot numbers and geomagnetic aa index. After a brief introduction of the production mechanism of sector effects on polar geomagnetic fields the limitations and merits of IMF sector inference from geomagnetic data are emphasized

No abstract available

No abstract available

No abstract available

[en] New results for the neutron-deuteron analyzing power A_y(θ) at E_n=1.2 and 1.9 MeV and their comparison to proton-deuteron data reveal a sizeable and unexpected difference which increases with decreasing center-of-mass energy. This finding calls for the theoretical treatment of a subtle electromagnetic effect presently not incorporated in rigorous three-nucleon scattering calculations, before it is justified to invoke charge-dependent three-nucleon forces and/or other new physics

[en] The role of 3N forces in the 3N continuum is explored. The availability of rigorous 3N calculations, especially from the Bochum-Cracow group and the Pisa group allows accurate conclusions to be drawn from the comparison of experimental data and 3N calculations. For the first time n-p and n-n scattering lengths were simultaneously determined in a kinematically-complete n-d breakup FSI (final-state interaction) experiment. The associated data using rigorous 3N calculations and modern NN potentials models were analyzed. Neutrons of mean energy of 13 MeV and an energy spread of ±200keV were produced via the ²H(d,n)³He reaction in a deuterium gas cell. The neutrons are collimated and this beam interacts with the liquid scintillator C₆D₁₂ center detector, where recoil deuterons from n-d elastic scattering and protons from the n-d breakup reaction are detected. The n-n and n-p FSI measurements were done at four production angles (20.5^o 28.0^o 35.5^o and 43.0^o) of the n-n pair and n-p pair, respectively. The n-n and n-p scattering lengths determinations and their comparison to the existing NN and quasi NN results clearly show that 3N-force effects on the n-p and n-n FSI enhancements are considerable smaller than previously experimental and theoretical analyses. Refs. 14, figs. 4, tabs. 2 (nevyjel)

[en] Data for the neutron-neutron final-state-interaction cross section obtained recently in a kinematically complete neutron-deuteron breakup experiment have been reanalyzed using rigorous solutions of the three-nucleon Faddeev equations with realistic nucleon-nucleon interactions. A discrepancy was found with respect to a recent analysis based on the W-matrix approximation to the Paris potential. We also estimate theoretical uncertainties in extracting the neutron-neutron scattering length resulting from the use of different nucleon-nucleon interactions and the possible action of the two pion-exchange three-nucleon force. We find that there exists a certain production angle for the interacting neutron-neutron pair where the uncertainties become minimal. (author)

[en] Recent reanalysis of scattering data by the Nijmegen group has led to new values for the πNN coupling constants, g²_πdegree/4π and g²_π±/4π, about 6% smaller than the previously accepted values. The impact of this finding is far reaching. Since the neutron-proton A_y(θ) is dominated at low energies by the one-pion-exchange mechanism, accurate np data should provide unique information as to the magnitude of g²_π±/4π. Using a new experimental setup consisting of a shielded neutron source, a five-pair neutron detector array, a n-⁴He polarimeter, and an intense polarized source with fast spin-flipping capability, we have measured a 15 point angular distribution of the neutron-proton A_y(θ) at and incident neutron energy of 12 MeV to a statistical accuracy of 5x10^-4. We will discuss the data taking procedures, the analysis, and the corrections applied to the data. Preliminary results will be presented

[en] In this paper we present results for kinematically complete cross-section measurements of the space-star configuration in neutron-deuteron breakup for an incident neutron energy of 13.0 MeV. These data are a subset of the results obtained in a recent experiment in which cross sections for 46 configurations were measured simultaneously. The experimental techniques are described. These new data are in good agreement with previous n-d data but differ significantly from both rigorous n-d calculations and proton-deuteron breakup data. copyright 1995 American Institute of Physics