There is significant asymmetries in the heliosphere structure when compared to steady-state models, resulting in rippled surfaces oblique to the local interstellar medium in upwind directions.
The Solar System is our very own cosmic neighborhood, and home to the only planet in the universe that we know of that has life. We think of the solar system as the space between the Sun and the dwarf planet Pluto. However, there is more to it. In fact, the solar system’s boundaries stretch far beyond Pluto and the so-called Oort cloud. In terms of distance, our Solar System has a diameter of approximately 7,440,000,000 miles, 80 AU, or .00127 light years. This might sound small on cosmic scales, but it’s massive.
Now, scientists say that at the very edge of the solar system, there is a galactic kind of bubble that encompasses our cosmic oasis. And this bubble appears wrinkled at times. This is according to data gathered by a spacecraft orbiting Earth. It has found rippled structures that are located in the so-called termination shock and heliopause. In the Solar System, these are shifting regions that mark the boundary between outer interstellar space and inner.
A cosmic bubble
This boundary changes over time. And observations have shown that we are able to get a detailed picture of that distant region of space and observe its change over time. Understanding these changes is a big deal. This data will aid scientists in better understanding the region of space dubbed the heliosphere. Our Solar System’s planets are shielded from cosmic radiation by this region that extends from the Sun.
It is imperative to understand that the Sun affects space in a variety of ways. The solar wind is one of them, a continuous flow of plasma ionized at supersonic speeds. Eventually, it peters out in the vast emptiness between the stars, blowing past the planets and the Kuiper Belt. Science Alert describes the termination shock as the point when this flow falls below the speed at which sound waves can travel through the diffuse interstellar medium. In interstellar space, the heliopause is the point where it is no longer strong enough to push back against very slight pressure.
The heliosphere
We have gathered a plethora of data thanks to the Voyager probes. Both spacecraft crossed the heliopause. We will be able to measure the shifting boundary in situ as they cruise through interstellar space. However, we can also study this region from Earth. NASA’s Interstellar Boundary Explorer (IBEX) is another tool out orbiting Earth that has been helping scientists map the heliopause. This spacecraft has been doing science from orbit since it commenced operations in 2009.
Solar wind collides with the interstellar wind at the Solar System boundary, creating energized neutral atoms. IBEX measures these energized neutral atoms. In some cases, those atoms are catapulted forward into space, and in others, they are hurled back to Earth. Similar to cosmic echolocation, energized neutral particles that return to us can help us map the shape of the boundary depending on how strong the solar wind was, that had generated them.
Solar wind pressure and energetic neutral atom emission measurements have been used in the past to map the structure of the heliosphere, resulting in the smoothing of the boundary. A roughly 50 percent increase in solar wind dynamic pressure occurred in 2014 over a period of roughly six months. With the use of this shorter-scale event, Princeton University astronomer Eric Zirnstein was able to obtain a more detailed picture of the termination shock and heliopause. A time interval between Earth and the Sun equals one astronomical unit, so he found ripples as large as tens of astronomical units. You can find the research paper here.
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