Observations of solar flares by spacecraft at Mars, Venus and the Earth show that eruptions on the far side of the Sun may affect our "space weather" back on Earth.
In December 2006, a series of solar flares produced in a single active region were observed from three different points, each approximately 120 degrees apart. The results of these observations are now presented at the European Planetary Sciences Congress, Potsdam, on Thursday 23rd August by a team of scientists from the Swedish Institute of Space Physics.
Although solar flares and solar energetic particles (SEP) have been reported many times based on Earth-orbiting satellites or other planetary spacecraft, this time scientists achieved simultaneous plasma observations using instruments aboard Mars Express, Venus Express , the SOHO solar orbiter and a GOES environmental satellite, which is in geostationary orbit around the Earth.
"These observations indicate that flare activities on the far side of the Sun may affect terrestrial space weather as a result of travelling more than 90° in both azimuthal directions in the heliosphere", said Dr Yoshifumi Futaana, one of the investigators in this study.
Another important consequence of the analysis of SEP events is the insight they can provide into the process of planetary atmospheric evolution. During the December 2006 event, Mars Express observed an enhancement of ion (oxygen) outflow flux from the Martian atmosphere. This is the first observation of this kind and suggests that the solar extreme ultraviolet flux levels significantly affect the atmospheric loss from unmagnetized planets.
Dr Futaana explained, "This is of interest for planetary scientists because the ion outflow should play an important role on the evolution of planetary atmosphere if the flux is integrated over a geological time scale (billions of years)".
This violent solar flare event also gives us a hint to solve a mystery of missing water on Mars. Mars is believed to have possessed a large amount of water approximately 3.5-4.0 billion years ago. However, no one knows where the water has gone now. One plausible idea is that the water has escaped to space, in the evolution of the planet's atmosphere. One of the main scientific aims of Mars Express is to measure exactly how much of this water has been lost to space.
A series of images showing the evolution of the solar flares through the inner Solar System between 5th and 11th December 2006 is available at: http://www.europlanet-eu.org/index.php?option=com_content&task=view&id=105&I temid=32
Dr. Yoshifumi Futaana
Swedish Institute of Space Physics
Tel: +46 980 79025