Ultra low frequency waves at Venus: Observations by the Venus Express spacecraft

Autor(es)

Fraenz, M. ^[1] ; Echer, E. ^[2] ; Marques de Souza, A. ^[2] ; Dubinin, E. ^[1] ; Zhang, T. L. ^[3]

Afiliação do(s) autor(es)

^[1] Max Planck Inst Sonnensyst Forsch, D-37077 Gottingen - Germany

^[2] Natl Inst Space Res, Sao Jose Dos Campos, SP - Brazil

^[3] Austrian Acad Sci, Space Res Inst, Graz - Austria

• Tipo de documento: Artigo Científico
• Fonte: Planetary and Space Science; v. 146, p. 55-65, OCT 15 2017.
• Citações Web of Science: 4

Resumo

The generation of waves with low frequencies (below 100 mHz) has been observed in the environment of most bodies in the solar system and well studied at Earth. These waves can be generated either upstream of the body in the solar wind by ionization of planetary exospheres or ions reflected from a bow shock or in the magnetosheath closer to the magnetic barrier. For Mars and Venus the waves may have special importance since they can contribute to the erosion of the ionopause and by that enhance atmospheric escape. While over the past years many case studies on wave phenomena observed at Venus have been published most statistical studies have been based on magnetic observations only. On the other hand the generation mechanisms and transport of these waves through the magnetosphere can only be quantified using both magnetic and particle observations. We use the long time observations of Venus Express (2006-2014) to determine the predominant processes and transport parameters. First we demonstrate the analysis methods in four case studies, then we present a statistical analysis by determining transport ratios from the complete Venus Express dataset. We find that Alfvenic waves are very dominant (>80%) in the solar wind and in the core magnetosheath. Fast waves are observed mainly at the bow shock (around 40%) but also at the magnetic barrier where they may be most important for the energy transfer into the ionosphere. Their occurrence in the magnetotail may be an artifact of the detection of individual plasma jets in this region. Slow mode waves are rarely dominating but occur with probability of about 10% at the bow shock and in the pile-up-region. Mirror mode waves have probability <20% in the magnetosheath slightly increasing towards the pile-up-boundary. (AU)

• Processo FAPESP: 16/10794-2 - Estudo da oscilação de elétrons na bainha magnética de marte
• Beneficiário: Adriane Marques de Souza Franco
• Modalidade de apoio: Bolsas no Brasil - Doutorado
• Processo FAPESP: 17/00516-8 - Estudo da oscilação de elétrons na bainha magnética de marte com observações da sonda mars express
• Beneficiário: Adriane Marques de Souza Franco
• Modalidade de apoio: Bolsas no Exterior - Estágio de Pesquisa - Doutorado