A raytracing program is used to reproduce with a computer the image of a three-dimensional object as seen by an imaging device, like the eye, a photographic camera or a telescope. The three-dimensional object can be either a solid object or a diffuse object. The Solar corona is a diffuse object: it is made of a plasma of electrons and particules of dust. These electrons and dusts scatter the light coming from the photosphere. In our software we intend to simulate the Thomson scattering of the electrons of the corona. This component of the solar corona is called the K corona. This is in this component that we observe the most structured and transcient phenomenons, like streamers and Coronal Mass Ejections (CMEs). The K corona is optically thin and its optical index is uniform and constant: the line of sights (LOS) are then simple straight lines.

The solar corona is observed during total eclipses or with an instrument called a coronagraph. Eclipses are only available roughly once a year while coronagraphs can record images of the solar corona all year long. Spacial coronagraphs like LASCO aboard the SOHO spacecraft, is positionned at the lagrangian point L1 between Sun and Earth, so that it can even record images of the corona without interruptions due to the night and day cycle we have on earth.

The K corona structures we observe are linked to the solar magnetic field. Loops and streamers are the main structures we observe. They are related respectively to closed and open field lines. An other coronal structures that are the most studied are Coronal Mass Ejections (CMEs). They are, as their name indicate, transcient ejections of plasma from the nearby solar surface to the open space. Some of them can travel toward Earth. They can generate magnetic and particule storms. The main manifestation we can see on earth are aurora borealis. They can also have more dramatic consequences as they can damage orbiting satelites or irradiate astronauts. Understanding their mechanism is then of a particular interest for both science and space weather forcasts.

The main goal of the raytracing software is to reproduce by numerical simulation coronagraphic observations. These simulations are important to test different model and compare the simulated image with the true data. It can be useful to infer some of the model parameters too, like a CME electron density for example. The software is also useful when designing new instruments to simulate the future observations.

The engine of the software and the models are written in C++ for efficiency purposes. The software can be run via an IDL command line and a graphic user interface (GUI) front-end. Facilities are available for interactive, 3-D visualization of electron density models. Particularly useful is the ability to position models by using a simple click-and-drag interface with rendered 3-D models.