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The dynamics of velocity fluctuations in the solar wind - I. Coronal mass ejections

Raga, A. C.; Lara, A.; de Gouveia Dal Pino, E. M. +3 more

In this paper we present a simple, analytic model for the dynamical evolution of supersonic velocity fluctuations at the base of the ambient solar wind. These fluctuations result in the formation of dense working surfaces that travel down the wind. It is shown how the initial parameters of the fluctuations (velocity, density and duration) are rela…

Plasma diagnostics of active-region evolution and implications for coronal heating

Mathioudakis, M.; Bloomfield, D. S.; Keenan, F. P. +2 more

A detailed study is presented of the decaying solar-active region NOAA 10103 observed with the Coronal Diagnostic Spectrometer (CDS), the Michelson Doppler Imager (MDI) and the Extreme-ultraviolet Imaging Telescope (EIT) onboard the Solar and Heliospheric Observatory (SOHO). Electron-density maps formed using SiX (356.03 Å/347.41 Å) show that the …

Noise characteristics of full-disc helioseismic observations made by resonant scattering spectrometers

Chaplin, W. J.; Elsworth, Y.; Isaak, G. R. +3 more

Resonant scattering spectrometers (RSSs) have been used to make high-precision full-disc helioseismic observations since the 1970s. They are capable of very high-precision determinations of line-shift, meaning that they are used to obtain precise velocity measurements, and, for suitably configured RSSs, the disc-averaged longitudinal magnetic fiel…

Photon scattering in the solar ultraviolet lines of HeI and HeII

Jordan, C.; Houdebine, E. R.; Smith, G. R.

Observations made with the Coronal Diagnostic Spectrometer (CDS) onboard the Solar and Heliospheric Observatory (SOHO) are used to investigate the behaviour of the intensities of the emission lines of HeI, HeII and OIII at the quiet Sun-centre and at θ= 60° towards the equatorial limb. The aim is to examine the possible effects of photon scatterin…