Solar wind origin of terrestrial water

The origin of the Earth water reserves during the evolution of the planet is one of the big miracles in geophysics. Common explanations are storage of water in the Earth mantle at a time when the crust had not yet formed and depositing of water by comets during the time of late heavy bombardement. Both explanations have different problems - especially when comparing with the evolution of Mars and Venus. Here we discuss the possible role of hydrogen collected from the solar wind by the early Earth magnetosphere. While the water production by solar wind capture is very small today it may have been significant during the first billion years after planetary formation because solar wind was much stronger at that time and Earth magnetospheric configuration may have been different. We estimate that the contribution of solar wind hydrogen to the Earth water reserves can be up to 10% when we assume a that the Earth dipole acted as a collector and early solar wind was 1000 times stronger than today. We can not even exclude that solar wind hydrogen was the main contributor to Earth water reserves

Détermination des précipitations extrêmes et des crues extrêmes en Suisse à l'aide de la méthode PMP-PMF

Les barrages alpins en Suisse doivent être dimensionnés pour résister à des crues extrêmes avec un temps de retour d’au moins 10'000 ans. La méthode PMP-PMF a été appliquée pour estimer des pluies et des crues extrêmes avec un temps de retour aussi élevé. Les PMP ont été calculées avec un modèle atmosphérique et un modèle de pluie pour plusieurs durées avec une résolution horizontale de 2 km. Ces modèles permettent de reproduire de manière satisfaisante ces PMP pour l’ensemble du pays lorsqu’on les compare avec les précipitations extrêmes estimées pour un temps de retour de 500 ans à partir de méthodes statistiques. Les PMP calculées par les modèles sont toutefois trop élevées sur plusieurs sommets alpins et trop basses au Sud des Alpes. Malgré ces approximations, elles peuvent être utilisées pour calculer avec un modèle hydrologique approprié des crues de sécurité avec un temps de retour d’au moins 10'000 ans pour les bassins versants en Suisse ayant une surface inférieure à 230 km2

Test particle comparison of heavy atomic and molecular ion distributions at Mars

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/106919/1/jgra50899.pd

Three spacecraft observations of solar wind discontinuities

Observations of solar wind magnetic field discontinuities using 3 spacecraft allow their orientations to be estimated. During 5 days when Geotail, Wind and IMP 8 were between 6 × 104 and 4 × 105 km apart, 35 events identified using the Tsurutani‐Smith method were detected in all 3 magnetic field data sets. Normals estimated from inter‐spacecraft timings showed that very few were unambiguous rotational discontinuities, with 77% likely to be tangential, with < 20% of the magnetic field at the discontinuity threading the normal plane. However, previous single spacecraft studies using minimum variance suggest that most discontinuities are rotational. Minimum variance analysis resulted in many normal estimates lying far from the timing‐derived normals. While some of this discrepancy is likely to be due to random errors in minimum variance vectors, there appears to be a class of events with small field magnitude changes where the minimum variance directions and discontinuity normals are approximately perpendicular, probably due to surface waves on the discontinuities

Martian Proton Aurora Brightening Reveals Atmospheric Ion Loss Intensifying

Abstract The Martian proton aurora is a distinct aurora phenomenon resulting from the direct deposition of solar wind energy into Mars' dayside atmosphere. What solar wind parameters influence the aurora activity in the short term is yet unknown, as are the associated repercussions in the Martian atmospheric ion loss. Here we present observational evidence of synchronized proton aurora brightening and atmospheric ion loss intensifying on Mars, controlled by solar wind dynamic pressure, using observations by the Mars Atmosphere and Volatile Evolution spacecraft. The solar wind dynamic pressure possibly has a saturation effect on brightening proton aurora. Significant erosion of the Martian ionosphere during periods of high dynamic pressure indicates at least five-to-tenfold increase in atmospheric ion loss. An empirical relationship between ion escape rate and auroral emission enhancement is established, providing a new proxy of Mars' atmospheric ion loss with optical imaging that may be used remotely and with greater flexibility. Key Points &nbsp; Synchronized proton aurora brightening and atmospheric ion loss intensifying on Mars, both controlled by solar wind dynamic pressure The solar wind dynamic pressure possibly has a saturation effect on brightening proton aurora An empirical power law model between ion escape rate and proton auroral emission enhancement is established &nbsp; Plain Language Summary Ion loss during solar events early in Mars history may have been the major cause to the long-term evolution of the Mars atmosphere. Restricted by observation data, the relationship between ion loss and solar wind is still in debate. We have shown observational evidence for synchronized dayside proton aurora brightening and atmospheric ion loss intensifying on Mars, controlled by solar wind dynamic pressure using comprehensive observations by the NASA's MAVEN spacecraft. A power law model between ion escape rate and proton auroral emission enhancement is established for the first time, providing a new proxy of Mars' atmospheric loss with optical imaging that may be used remotely and with greater flexibility. The results presented in this study shed light on the direct control of dynamic pressure on interactions of the solar wind with Mars and other objects in solar system (e.g., Venus and Titan), and presumably stellar wind with exoplanets. &nbsp;</p