Earth’s O+ Outflow and Escape during Various Solar Wind Conditions

• Ion outflow at Earth is studied since several decades and is important for the global atmospheric evolution. Over the years, spacecraft and technology improved leading to new studies and breakthrough in the field. With different mechanisms to gain energy and velocity such as field-aligned acceleration, centrifugal acceleration and transversal heating, a large amount of ions becomes gravitationally untrapped above the ionosphere. While some of these ions may enter the plasma sheet and partially be redirected towards Earth, majority of these ions reaches the high-latitude boundary region, such as the plasma mantle and are lost into the solar wind. We examined this phenomenon using Cluster European Spacecraft that covers these high-latitude regions. Here, we studied the influence of solar wind conditions on O+ outflow and escape during 7 years of observations (2001 to 2007). We found that O+ outflow is exponentially correlated with enhanced geomagnetic activity (Kp index) as well as with solar wind dynamic pressure and IMF. Under undisturbed magnetospheric conditions, the O+ outflow is typically 1012.5 m-2s-1 while it reaches 1014 m-2s-1 during major geomagnetic storms. Additionally, tracing (forward in time) about 25000 O+ ions initially observed in the plasma mantle showed that 98% of these ions escape directly through the magnetopause whereas only a few escape through the distant tail. In summary, the more disturbed the magnetosphere is, the more ion outflow and escape is observed.

Ämnesord

TEKNIK OCH TEKNOLOGIER  -- Maskinteknik -- Strömningsmekanik och akustik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Mechanical Engineering -- Fluid Mechanics and Acoustics (hsv//eng)

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Strömningslära

Fluid Mechanics

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