Measures of the solar spectral irradiance between 1200 and 3000 A

Tabulated data on solar flux measurements are presented. The measurements, taken from balloons, rockets and satellites, are not new data, but have been critically re-evaluated. The eleven year sunspot cycle is discussed. Also discussed is the brightness temperature. The effect of solar radiation at various wavelengths, on the photochemistry of stratospheric ozone is briefly discussed

Using ICT to support public and private community memories: case studies and lessons learned

Information communication technologies (ICTs) enable the development of memories across a variety of communities. We identify a spectrum of deployment from private through to open public spaces. As we move along this spectrum key variables change including mechanisms of trust and accountability and the definition of ownership, authorship and readership. Some challenges however, remain constant such as designing for sustainability and the need to align research and community goals. Private spaces can be created to enhance existing interactions, develop bonding capital and build shared memory. Such spaces allow a defined membership the opportunity to explore new ideas away from the public gaze, using language which may not be intelligible to outsiders. ICTs may be used to bridge internal and external audiences, repurposing content for a wider public. The original content may require alternative presentation, organisation or navigation methods to support its effective use by an external audience. Increasingly, community memories are being developed using social software within the public sphere, however this raises issues of authority, reputation management, and conflict resolution. Unexpected innovation may occur, and issues of sustainability must be addressed. In our analysis we will draw on three ICT initiatives in which we have participated: Bletchley Park Guides’ Forum, Bletchley Park Text and Milton Keynes Open Guide

Environments and Morphologies of Red Sequence Galaxies with Residual Star Formation in Massive Clusters

We present a photometric investigation into recent star formation in galaxy clusters at z ~ 0.1. We use spectral energy distribution templates to quantify recent star formation in large X-ray selected clusters from the LARCS survey using matched GALEX NUV photometry. These clusters all have signs of red sequence galaxy recent star formation (as indicated by blue NUV-R colour), regardless of cluster morphology and size. A trend in environment is found for these galaxies, such that they prefer to occupy low density, high cluster radius environments. The morphology of these UV bright galaxies suggests that they are in fact red spirals, which we confirm with light curves and Galaxy Zoo voting percentages as morphological proxies. These UV bright galaxies are therefore seen to be either truncated spiral galaxies, caught by ram pressure in falling into the cluster, or high mass spirals, with the photometry dominated by the older stellar population.Comment: Accepted for publication in MNRAS, 11 pages, 11 figure

Sums and differences of four k-th powers

We prove an upper bound for the number of representations of a positive integer $N$ as the sum of four $k$-th powers of integers of size at most $B$, using a new version of the Determinant method developed by Heath-Brown, along with recent results by Salberger on the density of integral points on affine surfaces. More generally we consider representations by any integral diagonal form. The upper bound has the form $O_{N}(B^{c/\sqrt{k}})$, whereas earlier versions of the Determinant method would produce an exponent for $B$ of order $k^{-1/3}$ in this case. Furthermore, we prove that the number of representations of a positive integer $N$ as a sum of four $k$-th powers of non-negative integers is at most $O_{\epsilon}(N^{1/k+2/k^{3/2}+\epsilon})$ for $k \geq 3$, improving upon bounds by Wisdom.Comment: 18 pages. Mistake corrected in the statement of Theorem 1.2. To appear in Monatsh. Mat

Influence of a solar proton event on stratospheric ozone

Ozone depletion in the stratosphere associated with the solar proton event of August 4, 1972, was observed with the backscattered ultraviolet experiment on the Nimbus 4 satellite. An abrupt ozone decrease in the 75-80 deg N zone of about 0.002 atm-cm above 4 mb was observed to persist throughout the month of August. A decrease was noted in the 55-65 deg N zone on days 219 and 220, but recovery occurred on day 221. Thereafter, a more gradual decrease was observed. The equatorial zone also showed gradual decrease after day 218, but these were not uniquely distinguished from seasonal variations. The observed change in total ozone following the event was -0.003 atm-cm for the 75-80 deg N zone, corresponding to a 1.3 percent reduction in the 0.305 atm-cm zonal average, but within the 0.019 atm-cm standard deviation. Above the 10 mb surface in the 75-80 deg N zone however, a decrease of 0.004 atm-cm may be compared with a standard deviation of 0.001 atm-cm

NIMBUS-7 SBUV (Solar Backscatter Ultraviolet) observations of solar UV spectral irradiance variations caused by solar rotation and active-region evolution for the period November 7, 1978 - November 1, 1980

Observations of temporal variations of the solar UV spectral irradiance over several days to a few weeks in the 160-400 nm wavelength range are presented. Larger 28-day variations and a second episode of 13-day variations occurred during the second year of measurements. The thirteen day periodicity is not a harmonic of the 28-day periodicity. The 13-day periodicity dominates certain episodes of solar activity while others are dominated by 28-day periods accompanied by a week 14-day harmonic. Techniques for removing noise and long-term trends are described. Time series analysis results are presented for the Si II lines near 182 nm, the Al I continuum in the 190 nm to 205 nm range, the Mg I continuum in the 210 nm to 250 nm range, the MgII H & K lines at 280 nm, the Mg I line at 285 nm, and the Ca II K & H lines at 393 and 397 nm