Spreading the Word, Protecting the Rights.

Bournemouth University and the Centre for Broadcasting History Research [CBHR] Archive collections have a unique flavour, at least in how projects linked to radio collections have come about. We should mention that there have been other projects linked to television as well, the TVTimes project also a partnership with the British Library, The This Week Project and BBC Panorama with the BBC. None of these projects, however, have actually involved digitising moving image. We have also recently acquired the giant IBA paper archive from Ofcom, dating back to the start of ITV. This paper, however, will focus on our sound radio archives, and in particular the creation of an online resource hosted by the BUFVC website, and funded by JISC, to preserve and provide access for students and academics in the UK, material from the LBC/Independent Radio News Archive

The Effect of Combined Magnetic Geometries on Thermally Driven Winds I: Interaction of Dipolar and Quadrupolar Fields

Cool stars with outer convective envelopes are observed to have magnetic fields with a variety of geometries, which on large scales are dominated by a combination of the lowest order fields such as the dipole, quadrupole and octupole modes. Magnetised stellar wind outflows are primarily responsible for the loss of angular momentum from these objects during the main sequence. Previous works have shown the reduced effectiveness of the stellar wind braking mechanism with increasingly complex, but singular, magnetic field geometries. In this paper, we quantify the impact of mixed dipolar and quadrupolar fields on the spin-down torque using 50 MHD simulations with mixed field, along with 10 of each pure geometries. The simulated winds include a wide range of magnetic field strength and reside in the slow-rotator regime. We find that the stellar wind braking torque from our combined geometry cases are well described by a broken power law behaviour, where the torque scaling with field strength can be predicted by the dipole component alone or the quadrupolar scaling utilising the total field strength. The simulation results can be scaled and apply to all main-sequence cool stars. For Solar parameters, the lowest order component of the field (dipole in this paper) is the most significant in determining the angular momentum loss.Comment: 15 pages + 9 figures (main), 3 pages + 1 figure (appendix), accepted for publication to Ap

The Effect of Magnetic Variability on Stellar Angular Momentum Loss II: The Sun, 61 Cygni A, ϵ\epsilon Eridani, ξ\xi Bootis A and τ\tau Bootis A

The magnetic fields of low-mass stars are observed to be variable on decadal timescales, ranging in behaviour from cyclic to stochastic. The changing strength and geometry of the magnetic field should modify the efficiency of angular momentum loss by stellar winds, but this has not been well quantified. In Finley et al. (2018) we investigated the variability of the Sun, and calculated the time-varying angular momentum loss rate in the solar wind. In this work, we focus on four low-mass stars that have all had their surface magnetic fields mapped for multiple epochs. Using mass loss rates determined from astrospheric Lyman-$\alpha$ absorption, in conjunction with scaling relations from the MHD simulations of Finley & Matt (2018), we calculate the torque applied to each star by their magnetised stellar winds. The variability of the braking torque can be significant. For example, the largest torque for $\epsilon$ Eri is twice its decadal averaged value. This variation is comparable to that observed in the solar wind, when sparsely sampled. On average, the torques in our sample range from 0.5-1.5 times their average value. We compare these results to the torques of Matt et al. (2015), which use observed stellar rotation rates to infer the long-time averaged torque on stars. We find that our stellar wind torques are systematically lower than the long-time average values, by a factor of ~3-30. Stellar wind variability appears unable to resolve this discrepancy, implying that there remain some problems with observed wind parameters, stellar wind models, or the long-term evolution models, which have yet to be understood.Comment: 15 pages + 8 figures, accepted for publication to Ap

New Calculations of Stellar Wind Torques

Using numerical simulations of magnetized stellar winds, we carry out a parameter study to find the dependence of the stellar wind torque on observable parameters. We find that the power-law dependencies of the torque on parameters is significantly different than what has been used in all spin evolution models to date.Comment: To appear in the proceedings for the 15th Cambridge Workshop on Cool Stars, Stellar Systems, and the Sun. 4 page poster contributio