HR: 15:30h
AN: SP14A-01    [Abstracts]
TI: HYDRAD: a Hydrodynamics Code for Time-Dependent Ionisation and Forward Modelling of EUV Emission from the Solar Atmosphere
AU: * Bradshaw, S J
EM: s.bradshaw@imperial.ac.uk
AF: Imperial College London, Space & Atmospheric Physics Group, Blackett Laboratory, Imperial College London, Prince Consort Road,, London, SW7 2BZ United Kingdom
AU: Cargill, P
EM: p.cargill@imperial.ac.uk
AF: Imperial College London, Space & Atmospheric Physics Group, Blackett Laboratory, Imperial College London, Prince Consort Road,, London, SW7 2BZ United Kingdom
AB: Observations in the Extreme Ultra-Violet have shown the solar atmosphere to be highly dynamic and time-dependent. The high-spatial resolution that these observations achieve has revealed the fundamental component of the solar atmosphere to be a loop-like structure: a tube of magnetic flux confining plasma which emits at EUV and X-ray wavelengths. The high-temporal cadence of these observations reveal activity time-scales for solar loops on the order of seconds. The emission spectrum of the solar atmosphere provides all of our information regarding the key physics that takes place. The properties of the individual spectral lines allow the calculation of plasma temperatures, densities and velocities. The spectral lines are critically dependent upon the population of emitting ions and in traditional hydrodynamic models these have been assumed to remain in equilibrium throughout the evolution of the plasma. However, the time-scale for ionisation in the solar atmosphere can be on the order of minutes. Thus, given activity time-scales on the order of seconds in solar loops, it is easy to see that the assumption of equilibrium ion populations may not be valid. This has extremely important consequences for the correct interpretation of observations, the accurate treatment of optically-thin radiation in numerical models and forward modelling studies derived from model results. The HYD(rodynamic) and RAD(iation) code (HYDRAD) has been developed specifically to handle non-equilibrium ion populations in the solar atmosphere and the consequences for optically-thin radiation, in a self-consistent way. The equations of hydrodynamics and ionisation balance are coupled together at each time-step during the evolution of the plasma. The HYDRAD package also provides tools for forward modelling and 3D visualisation. The results of some investigations carried out using HYDRAD will be presented and the specific consequences of a non-equilibrium ionisation balance will be discussed in each case.
DE: 7509 Corona
DE: 7519 Flares
DE: 7546 Transition region
DE: 7549 Ultraviolet emissions
SC: Solar Physics Division - AAS [SP]
MN: 2005 Joint Assembly