STEREO / SECCHI
The Sun in 3D
SECCHI (Sun Earth Connection Coronal and Heliospheric Investigation) is a component of the STEREO mission (Solar Terrestrial Relations Observatory). STEREO will observe the Sun with two almost identical spacecrafts and reveal the 3D structure of the solar corona. The launch of STEREO is planed for 2006. The spacecrafts have different orbits due to Swing-by at moon. The two STEREO spacecrafts separate about 44 degree every year.
The primary goal of the mission is to undertake a major step towards a better
understanding of the 3D structure of the solar corona.
Key questions of the mission are related to the origin and evolution of
CMEs (Coronal Mass Ejections), in particularly:
- What configurations of the corona lead to a CME?
- What initiates a CME?
- What accelerates CMEs?
- How does a CME interact with the heliosphere?
- How do CMEs cause space weather disturbances?
SECCHI on STEREO contains two white light coronagraphs
(COR1 and COR2), an EUV imager (EUVI) and a Heliospheric Imager (HI).
COR1 and COR2 will observe the inner (1.1-3 Rsun) and outer (2-15 Rsun)
EUVI will provide full Sun coverage with twice the spatial resolution
as SOHO/EIT. HI is an externally occulted coronagraph
and will observe the heliosphere from the Sun to the Earth (12-318 Rsun).
The SECCHI-STEREO 3D software package contains the Tomography code FETOC,
a stereoscopy program and
the magnetic modelling tool LINFF for the 3D reconstruction of
the solar corona.
FETOC is a finite element tomography code for the inversion of
coronagraph data. The tomographic inversion procedure uses coronal magnetic field
models for regularization. A stereoscopic reconstruction of magnetic loops from
two viewpoints is not unique. We use more than two viewpoints with help of tomography
or magnetic field models as additional constrains. The magnetic field tool LINFF
uses different coronal magnetic field models (Laplace field, linear and non-linear
force-free fields, MHD-equilibria) and reconstructs the 3D coronal magnetic field
from photospheric measurements (from Line-of-sight magnetographs or vector magnetographs).