C. P. McLeod

Solar p-mode frequencies and their dependence on solar-activity - recent results from the BISON network

We present here high-accuracy determinations of the frequencies of low-l solar p-modes and their solar-cycle dependence. The data were obtained using the Birmingham network of solar spectrometers (BISON). The precision of the measurements is discussed. Our previously published results of a significant frequency shift between solar minimum and solar maximum, apparently independent of l and similar to that found by other workers for intermediate-l modes, is confirmed and extended. This suggests that at most only a small fraction of the variation is due to the solar core. Sets of frequencies at high and low solar activity, and an average corrected for solar-activity effects, are presented. There is now evidence that the solar-activity dependence of the frequencies varies across the 5 minute spectrum.

K+p elastic scattering between 432 and 939 MeV/c and phase shift analysis

Abstract Measurements of K + p elastic scattering have been carried out at 13 momenta between 432 MeV/ c and 939 MeV/ c using spark chambers. The data establish unambiguously the constructive interference of the Coulomb and nuclear amplitudes at 432 MeV/ c . The elastic cross section is found to be independent of momentum through the range covered. The phase shifts for S, P, D and F waves are obtained in an energy dependent analysis in which higher waves are held at theoretical values. The initial behaviour ofthe P, D and F amplitudes is quite close to that predicted by the calculation of the peripheral partial waves. Only the P3 and D5 amplitudes become strikingly different with increasing momentum.

K+n elastic and charge-exchange scattering between 430 and 940 MeV/c

Abstract Elastic and charge-exchange K+n differential cross sections have been measured from K+d interactions from 430 to 940 MeV/c using spark chambers and scintillation counters. The data have been compared with existing results and in an accompanying paper have been included with other measurements in a phase-shift analysis.

The 160 minute solar oscillation - an artifact?

Analysis of data obtained over the years 1980-1985 are analyzed to show that the period of the 160-minute signal is indeed 160.00 minutes. It is demonstrated that this signal may be simulated by a slightly distorted diurnal sine wave such as that occasioned by differential atmospheric extinction. 15 refs.

The radial velocity of the sun as a star and the solar cycle

Abstract Radial velocity measurements of the sun as a star using a resonant scattering spectrometer have been obtained at Izana (Tenerife) during long observing seasons from 1976 to 1985. Its analysis shows that except for the global oscillations with periods shorter than one day there are stable signals with longer periods: at ∼13 days with mean amplitude of ∼ 3 m/s (it changes with the solar cycle) and another one of ∼ 15 m/s amplitude which shows a temporal variation of various years related to the solar cycle. The first signal has a partial explanation as an effect produced by the passage of active regions through the visible surface of the sun but it does not completely explain the observed signal. The second one, related to the limb shift, is probably due to changes in the convection zone in connection with the solar cycle.

Structure of the 5-minute solar oscillations 1976–1980

The discrete structure in the 5 min velocity oscillations of the solar surface has been confirmed by a re-analysis of data obtained between 1976 and 1979, and in addition a preliminary analysis of 1980 data show excellent consistency of the determined frequencies over the five year period. It is further shown that atmospheric transparency, as measured by the power in the solar intensity fluctuations, shows no correlation with the measured amplitude of the velocity fluctuations, over 2 orders of magnitude.

Measurement of K−p elastic differential cross sections between 610 and 943 MeV/c

Measurements of K−p elastic scattering have been carried out at 14 momenta between 610 MeV/c and 943 MeV/c over the angular range −0.9 < cos θ < 0.9. The results agree well with the best existing data and have significantly smaller errors.

An automatic spark chamber system with sonic and magnetostrictive read-out

Abstract A spark chamber system with sonic read-out operating as a magnetic spectrometer is described. Operational and design information is given and the choice of type of read-out and spark chamber gas is discussed. Magnetostrictive beam chambers are included in the system and an account is given of our experiences in reading out from the high voltage wire planes and of the problems associated with long sensitive times. Performance data for both types of spark chamber are presented.

K−n elastic scattering between 610 and 840 MeV/c

Abstract Elastik K−n (I = 1) differential cross sections have been measured at 14 momenta between 610 and 940 MeV/c, over the c.m. angular range −0.7 cos θ ∗ . The results, which cover the c.m. energy range 1610–1765 MeV, have been fitted with Legendre polynomials and compared with some existing predictions from a partial-wave analysis.

Comparison of Solar Oscillation Data Obtained from a Study of the Na and K Fraunhoffer Absorption Lines

Two independent resonant scattering spectrometers one using a sodium and the other a potassium vapour cell, were operated simultaneously at the same site. Due to the differing abundances of ground state atoms of these two elements different depths of the photosphere are sampled. An intercomparison of solar p modes obtained with these spectrometers is given.