Shear Rate Determination of Flow Near Magnetopause

Shear rate of flow near magnetopause is related to the degree of energy transfer near magnetopause. Many numerical simulations near magnetopause have to use shear rate of flow as an important input parameter. However, up to now it is still hypothetical and not realistic. By simultaneous multipoint observations of Cluster, using methods of linear interpolation and barycentric coordinates, we have determined shear rate of flow near magnetopause, an observational spatial parameter that can not be obtained until Cluster. Observational spatial distribution of shear rate of flow at dawn side and dusk side of magnetopause, magnetosphere and magnetosheath nearby has been analysed. Data analysis demonstrates that shear rate of flow as large as velocity difference of 330\,km/s over the distance of 100 km can exist near magnetopause sometimes even under quiet solar wind and geomagnetic conditions. Under many circumstances shear rate of flow near magnetopause is small, with the spatial velocity difference of dozens of km/s over the distance of 1000 km. The method we have adopted here can be used widely to determine shear rate of flow at any location.