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Mars Express and Venus Express multi-point observations of geoeffective solar flare events in December 2006 |
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| Authors: | Y Futaana S Barabash S McKenna-Lawlor JG Luhmann E Carlsson JD Winningham P Wurz H Gunell W Baumjohann JR Sharber H Andersson K Brinkfeldt K Asamura AJ Coates DO Kataria BR Sandel C Mazelle M Grande T Sales P Riihela N Krupp M Fränz S Orsini A Mura M Maggi P Brandt J Scherrer |
| Institution: | a Swedish Institute of Space Physics, Box 812, SE-981 28 Kiruna, Sweden b Space Technology Ireland, National University of Ireland, Maynooth, Co. Kildare, Ireland c Space Science Laboratory, University of California at Berkeley, Berkeley, CA 94720-7450, USA d Centre d’Etude Spatiale des Rayonnements, BP-4346, F-31028 Toulouse, France e Southwest Research Institute, San Antonio, TX 7228-0510, USA f Physikalisches Institut, University of Bern, CH-3012 Bern, Switzerland g Department of Physics, West Virginia University, Morgantown, WV 26506-6315, USA h Finnish Meteorological Institute, Box 503, FIN-00101 Helsinki, Finland i Space Research Institute, Austrian Academy of Sciences, Schmiedlstr. 6, 8042 Graz, Austria j University of Arizona, Tucson, AZ 85721, USA k Institute of Space and Astronautical Science, 3-1-1 Yoshinodai, Sagamichara, Japan l Mullard Space Science Laboratory, University College London, Surrey RH5 6NT, UK m Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire OX11 0QX, UK n Department of Physical Sciences, University of Helsinki, P.O. Box 64, 00014 Helsinki, Finland o Space Physics Research Laboratory, University of Michigan, Ann Arbor, MI 48109-2143, USA p Max-Planck-Institut für Sonnensystemforschung, D-37191 Katlenburg-Lindau, Germany q Instituto di Fisica dello Spazio Interplanetari, I-00133 Rome, Italy r Applied Physics Laboratory, Johns Hopkins University, Laurel, MD 20723-6099, USA s KFKI Research Institute for Particle and Nuclear Physics, H-1525, Box 49, Budapest, Hungary |
| Abstract: | In December 2006, a single active region produced a series of proton solar flares, with X-ray class up to the X9.0 level, starting on 5 December 2006 at 10:35 UT. A feature of this X9.0 flare is that associated MeV particles were observed at Venus and Mars by Venus Express (VEX) and Mars Express (MEX), which were ∼80° and ∼125° east of the flare site, respectively, in addition to the Earth, which was ∼79° west of the flare site. On December 5, 2006, the plasma instruments ASPERA-3 and ASPERA-4 on board MEX and VEX detected a large enhancement in their respective background count levels. This is a typical signature of solar energetic particle (SEP) events, i.e., intensive MeV particle fluxes. The timings of these enhancements were consistent with the estimated field-aligned travel time of particles associated with the X9.0 flare that followed the Parker spiral to reach Venus and Mars. Coronal mass ejection (CME) signatures that might be related to the proton flare were twice identified at Venus within <43 and <67 h after the flare. Although these CMEs did not necessarily originate from the X9.0 flare on December 5, 2006, they most likely originated from the same active region because these characteristics are very similar to flare-associated CMEs observed on the Earth. These observations indicate that CME and flare activities on the invisible side of the Sun may affect terrestrial space weather as a result of traveling more than 90° in both azimuthal directions in the heliosphere. We would also like to emphasize that during the SEP activity, MEX data indicate an approximately one-order of magnitude enhancement in the heavy ion outflow flux from the Martian atmosphere. This is the first observation of the increase of escaping ion flux from Martian atmosphere during an intensive SEP event. This suggests that the solar EUV flux levels significantly affect the atmospheric loss from unmagnetized planets. |
| Keywords: | Solar flare Space weather Ion escape Mars Venus SEP |
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