Strong Pressure Pulses from the Solar Wind to the Magnetosheath

High temporal resolution data from Magnetospheric Multiscale Spacecraft (MMS) has revealed fine structures in the terrestrial magnetosheath. In addition to the more well-known dynamic pressure pulses, there is another kind of pressure enhancement in the magnetosheath. During these events, the total of the magnetic and plasma thermal pressure can increase to over four times the background value around a thin central current sheet. Among the enhanced pressures, magnetic field contributes the most. These pulses last about one minute and are located just outside the magnetopause. In addition, the plasma properties are quite different between the two sides of the central current sheet, which accompanies the peak of magnetic field. These properties are similar to a phenomenon seen previously in the solar wind called the interplanetary field enhancement (IFE) that has been attributed to dust produced by colliding meteoroids.

With data from MMS, Cluster, ACE, Wind, Geotail and ARTEMIS, we confirm that these pressure pulses come from the solar wind. Not only are their field structures similar to the IFEs, which also have a cusp-shaped field increase collocated in a thin current sheet, but they also join two different plasma populations at the current sheet as do the magnetosheath pressure pulses. In contrast, IFEs are rarer and generally last about 30 minutes. We suggest that the difference in rate and duration is because the IFEs are seen during their slow acceleration while the magnetosheath pressure pulses are seen in their rapid deceleration near the magnetopause. In this paper, a systematic comparison study is performed between the IFEs and the magnetosheath pressure pulses. Numerical simulations are also used to obtain a quantitative relation between the pressure pulses and the amount of charged dust entering the magnetosheath.