outside pressure of the ISM at any given location. In particular, the effect of the 11-year solar cycle, which sees a distinct maximum and minimum of solar wind activity, is thought to be significant. On a broader scale, the motion of the heliosphere through the fluid medium of the ISM results in an overall comet-like shape. The solar wind plasma which is moving roughly "upstream" (in the same direction as the Sun's motion through the galaxy) is compressed into a nearly-spherical form, whereas the plasma moving "downstream" (opposite the Sun's motion) flows out for a much greater distance before giving way to the ISM, defining the long, trailing shape of the heliotail. The limited data available and the unexplored nature of these structures have resulted in many theories as to their form. In 2020, Merav Opher led the team of researchers who determined that the shape of the heliosphere is a crescent that can be described as a deflated croissant. Solar wind The solar wind consists of particles (ionized atoms from the solar corona) and fields like the magnetic field that are produced from the Sun and stream out into space. Because the Sun rotates once approximately every 25 days, the heliospheric magnetic field transported by the solar wind gets wrapped into a spiral. The solar wind affects many other systems in the Solar System; for example, variations in the Sun's own magnetic field are carried outward by the solar wind, producing geomagnetic storms in the Earth's magnetosphere. Heliospheric current sheet The heliospheric current sheet is a ripple in the heliosphere created by the rotating magnetic field of the Sun. It marks the boundary between heliospheric magnetic field regions of opposite polarity. Extending throughout the heliosphere, the heliospheric current sheet could be considered the largest structure in the Solar System and is said to resemble a "ballerina's skirt". Edge structure The outer structure of the heliosphere is determined by the interactions between the solar wind and the winds of interstellar space. The solar wind streams away from the Sun in all directions at speeds of several hundred km/s in the Earth's vicinity. At some distance from the Sun, well beyond the orbit of Neptune, this supersonic wind must slow down to meet the gases in the interstellar medium. This takes place in several stages: The solar wind is traveling at supersonic speeds within the Solar System. At the termination shock,