Sharp changes of solar wind ion flux and density within and outside current sheets - Physics > Space PhysicsReport as inadecuate

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Abstract: Analysis of the Interball-1 spacecraft data 1995-2000 has shown that thesolar wind ion flux sometimes increases or decreases abruptly by more than 20%over a time period of several seconds or minutes. Typically, the amplitude ofsuch sharp changes in the solar wind ion flux SCIFs is larger than 0.5x10^8cm^-2 s^-1. These sudden changes of the ion flux were also observed by theSolar Wind Experiment SWE, on board the WIND spacecraft, as the solar winddensity increases and decreases with negligible changes in the solar windvelocity. SCIFs occur irregularly at 1 AU, when plasma flows with specificproperties come to the Earth-s orbit. SCIFs are usually observed in slow,turbulent solar wind with increased density and interplanetary magnetic fieldstrength. The number of times SCIFs occur during a day is simulated using thesolar wind density, magnetic field, and their standard deviations as inputparameters for a period of 5 years. A correlation coefficient of ~0.7 isobtained between the modelled and the experimental data. It is found that SCIFsare not associated with coronal mass ejections CMEs, corotating interactionregions CIRs, or interplanetary shocks; however, 85% of the sector boundariesare surrounded by SCIFs. The properties of the solar wind plasma for days with5 or more SCIF observations are the same as those of the solar wind plasma atthe sector boundaries. One possible explanation for the occurrence of SCIFsnear sector boundaries is magnetic reconnection at the heliospheric currentsheet or local current sheets. Other probable causes of SCIFs inside sectorsare turbulent processes in the slow solar wind and at the crossings of fluxtubes.

Author: Olga Khabarova, Georgy Zastenker


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