Affiliation

Kiepeneheuer-Institute for Solar Physics

Main category

Natural Sciences (Astrophysics and Astrononmy)

Abstract

Context: Our Sun is an unique high-energy plasma physics laboratory, which can be studied with exceptional spatial and temporal resolution. Using dedicated telescopes, it is possible to verify and enhance our knowledge about aspects of modern physics unaccessible to any experiments on earth. State of the art magneto-hydrodynamic simulations of the solar photosphere have a spatial resolution of 6km at a wavelength $\lambda$ = 500nm and model the dynamics of solar pores, sunspots and coronal mass ejections. The theoretical models have to be evaluated in different atmospheric heights with highly resolving spectro-polarimetric observations. Therefore, the international solar community started to build a 4 m-class telescope. Furthermore an imaging spectro-polarimeter for visible light is developed. This is an unique tool to access highly dynamical, small scale processes on the solar photosphere and chromosphere for ground breaking scientific research. Method: Since a similar, yet smaller instrument is operated at the Vacuum-Tower- Telescope on the Canarian Island Tenerife, it was used as a test bed to characterize realistic instrumental induced errors. This defined the relevant parameters of the filter instrument for scientific research which were modelled: the etalons surface micro roughness, a varying reflectivity, plate figure errors, the photon noise, the relative aperture and the distance of the individual etalons to a defined focal plane of the telescope. Micro roughness, reflectivity and plate figure errors will shift and broaden the observed line profiles. Thus an instrumental error is induced in calculated Doppler velocity and full width half maximum maps of the solar surface. Additionally, the magnetic measurement sensitivity is limited by noise . Therefore, simulated observations of the quiet Sun were performed for two instrument configurations to study their measurement capabilities. One instrument is simulated with three etalons and a spectral bandwidth of $\delta\ambda$ = 3.8pm and the other with two etalons and $\delta\ambda$ = 6.1pm (spectral bandwidth is given for wavelength $\lambda$=630 nm). To study the effect of a defocused mounting of the etalons on the optical axis, the simulations were carried out for the instruments theoretical in a focal plane and at specified distances.

Conference

KIS.Colloquium

Link this presentation

https://science-media.org/presentation/179