10 11 Current sheets are ubiquitous in the solar wind. They are a major source of the solar wind MHD turbulence intermittency. They may result from non-linear interactions of the solar wind MHD turbulence or are the boundaries of flux tubes that originate from the solar surface. Some current sheets appear in pairs and are the boundaries of transient structures such as magnetic holes and reconnection exhausts, or the edges of pulsed Alfvén waves. For an individual current sheet, discerning whether it is a flux tube boundary or due to non-linear interactions,or the boundary of a transient structure is difficult. In this work, using data from the Wind spacecraft, we identify two three-current-sheet events. Detailed examination of these two events suggest that they are best explained by the flux tube crossing scenario. Our study provides a convincing evidence supporting the scenario that the solar wind consists of flux tubes where distinct plasmas reside.
Aurora study is a key area in understanding the connection and interaction of the solar-terrestrial system. Auroral events are monitored on the global scale at the Far Ultraviolet (FUV) spectrum by satellite-based sensors. However, the existence of dayglow emission significantly limits scientists is the ability to determine the location and the size of auroral ovals. A dynamic methodology to remove day airglow emission from the LBHL band UVI images on the Polar satellite is presented in this paper. First, the methodology identifies the geomagnetic latitude bound of the night side auroral oval. Then, the maximum range of geomagnetic latitude bound of the auroral is inferred based on the domain knowledge. Using the non-auroral dayglow pixels, a multi-variable regression fit of the intensity as function of the cosine of the solar zenith angle and cosine of the satellite viewing zenith angle is obtained. The methodology then uses this fitting function to estimate the dayglow intensity and to remove its effect in the LBHL band FUV images. This methodology does not require an external source of input solar flux and the dayglow removal is solely based on individual images. Experiment results show that dayglow effect is removed significantly from the original LBHL FUV images.Using this methodology, the performance of auroral oval detection algorithms is significantly improved.
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