Space Weather with SOHO and MEUDON Observations

Violent events occuring on the Sun, such as solar flares, eruptive prominences and coronal mass ejections (CMEs), produce tremendously energetic particles. These charged particles, after a long travel through space, arrive to the Earth and then interact with the atmosphere. They have a large influence on communications and atmospheric environment around the Earth. Especially, during solar maximum years, they can often cause and drive disastrous electric disturbances around the Earth. The aim in studying solar flares, filaments and CMEs is to find the relations between them, and understand the physical mechanisms. We especially focus here on the close relationship with filament eruptions.

With the former solar mission SMM (Solar Maximum Mission), CMEs have been mainly related to flares. With the SOHO satellite which was launched on December 1995, period of minimum activity it was discovered that the rate of CMEs was in fact as high during the minimum or maximum of solar activity. To predict the disturbances produced around the Earth, it is useful to have a comprehensive view of the origin and the mechanism of CMEs.

In recent papers a class of CMEs has been linked to filament eruptions. Brigitte Schmieder, from Paris Observatory, and her collaborators show an interesting example of spatial and temporal related events : filament eruption and a CME launch on the North West limb of the Sun. On its front, the CME has a projected circular shape (bright loop) which can be either a sphere or a torus ; there is then a dimmed region and following, the prominence material observed in emission since it is heated (see figures). The filament before eruption undergoes violent twists ; such a twist is maintained in the CME and studies have shown that the helicity of the filament is the same as the one of the magnetic cloud which reaches the Earth in 78 hours.

This study was possible due to multiwavelength instrument observations obtained during an international campaign organized by B. Schmieder ; thanks to the ground based instruments (Meudon spectroheliograph, heliograph, see BASS2000, MSDP spectrograph on the Pic du Midi telescope) and SOHO instruments (spectrometers : CDS and SUMER, imager EIT, coronographs : LASCO C1 and C2). A team from the DASOP department of Paris-Meudon Observatory (Malherbe J-M., Pick M., Schmieder B., van Driel L.) develops a space weather program with the help of ESA and Alcatel, to investigate on a large basis the relationship between CMEs, solar events and magnetic clouds.

Figure 1

L’évolution du filament observé le 31 mai 1997 qui a été associé à une EMC observée avec les coronographes de SOHO/LASCO. En haut : gaz ionisé à une température de 10 000K, observé dans la raie de Halpha (à 6562 angströms) avec le spectroheliographe de Meudon. Au milieu : SOHO EIT a observé l’éruption de filament à 304 angströms (gaz à une température de 80 000 K) et En bas : le manque d’émission à 195 angströms (un million de degrés K).

Figure 2

L’image en lumière blanche de LASCO C2 de l’EMC associée à l’éruption de protubérance

Publication
Schmieder, B., Delannée, C., Yong, Deng Yuan, Vial, J. C., Madjarska, M. : 2000, ``Multi-wavelength study of the slow ``disparition brusque" of a filament observed with SOHO’’, Astron. and Astrophys., 358, 728

Contact : B. Schmieder (DASOP, Observatoire de Paris, UMR 8645 du CNRS)
 

Dernière modification le 4 mars 2013