The protective bubble of the Solar System, the heliosphere, would be shaped by the Universe

The magnetosphere, you’ve probably heard of it before. This is the name of the region that surrounds our Earth and protects it from solar wind in particular and cosmic rays in general. But maybe you know less about theheliosphere. This is the name that scientists give to a kind of magnetic bubble which protects all of our Solar system radiations in which interstellar space bathes. Researchers evoke a bubble that extends far beyond our little corner of Milky Way. However, they still don’t know the exact shape … and even the size.

The ambition of the Shield project – to Solar-wind with Hydrogen Ion Exchange and Large-scale Dynamics – is to combine theory, modelization and observations to create complete simulations of the heliosphere and its dynamics. A little over a year ago, using the data returned by the Voyager missions, researchers had thus concluded that this heliosphere must have a surprising shape of … deflated crescent. And a few months later, others had proposed a detailed 3D map based on a technique similar to that of sonar.

Today, still as part of the ambitious Shield project (in French shield), researchers – those who had previously presented the heliosphere with a deflated crescent shape – announce that they have made a discovery that may shed light on our understanding of how the interstellar medium shapes the heliosphere. According to them, the particles ofhydrogen Neutrals from outside our Solar System most likely play a crucial role in how our heliosphere takes shape.

Instability from elsewhere

This time, the researchers worked in particular on what they call heliospheric jets, jets of matter and D’energy which resemble other types of cosmic jets and which are emitted by the black holes and the stars. Including our Sun. And what intrigues astronomers, about these jets, it is their unstable character. Their irregular shape.

The astronomers involved in the Shield project have noticed that, when they erase neutral hydrogen from their models, these jets coming from our Sun, in fact, become extremely stable. To reproduce the real observations, it is imperative to let neutral hydrogen strike and even flow through our Solar system. To give rise to an instability which would disturb the solar wind and in fact, the jets which emanate from our Star.

The physicists know this phenomenon as Rayleigh-Taylor instability. It occurs when two materials of different densities collide. the material the lighter one pushes against the heavier material. The gravity then shapes surprisingly irregular shapes. In the case of cosmic jets, the drag between neutral hydrogen particles and charged ions creates an effect similar to gravity.

Until scientists find a way to observe the heliosphere directly, this model offers an explanation for the disruption of its shape in the northern and southern regions. And it could have consequences for how galactic cosmic rays penetrate our Earth and its immediate surroundings. With effects in particular on the threats that this radiation represents for life. Including for that of future space colonists.

Our heliosphere would be influenced by the interstellar medium

A sort of solar wind bubble, the heliosphere surrounds the solar system. The latest observations of the probe Interstellar Boundary Explorer (IBEX) surprised astrophysicists because for the moment they challenge theoretical models.

Article by Laurent Sacco published on 10/26/2009

Even between the stars, space is not empty. It is filled with gas, dust and cosmic rays. The interstellar medium is moreover a bit like theatmosphere and the magnetosphere of a planet for a galaxy, with a chemistry complex, rich and fascinating electrodynamics and hydrodynamics.

It is well known that our Sun generates a flow of particles, essentially made up of protons and D’electrons, in addition to photons released by thermonuclear reactions. This flow of charged particles is the solar wind. It traverses the entire solar system and interacts with the magnetic field clean of the Sun then with the magnetospheres of the Earth and of the other planets. It then produces auroras, as the images of Jupiter and Saturn taken by Hubble.

The blast of the solar wind repels gases from the interstellar medium to a certain extent and to some extent it shields us from interstellar cosmic rays just as the Earth’s magnetosphere does to the solar wind. A sort of bubble is therefore created surrounding the solar system and probably elongated in the direction opposite to the movement of the solar system around the galactic bulb of the Milky Way.

The shape and limits of this bubble, which is called the heliosphere, is the subject of study by astrophysicists. But as it does not emit light, it seems difficult to observe it other than using probes approaching its limits, theheliopause. At its level, a shock wave occurs, a sudden discontinuity in the state of the gas.

This is indeed what the probes found To travel in 2006 and 2007, at distances of the order of 14 to 15 billion kilometers from the Sun, when they reached the heliopause.

These occasional observations are insufficient to draw a map of the borders of the heliosphere. Yet this is what researchers from the Nasa using the probe Interstellar Boundary Explorer (IBEX) by using other data.

The strategy for doing this is simple. When protons and electrons from the solar wind join the interstellar medium at the border of the heliosphere, they can combine with the flow of ions from the interstellar medium to form atoms very energetic neutrals, speeding towards the center of the solar system. It suffices to measure this flux, more precisely the energies associated with these particles, to deduce information on the heliopause. By doing it well, we can then build a map of the characteristics of the boundaries of the heliosphere.

After a first observation campaign of 6 months, IBEX provided a first map which amazed the astrophysicists. While the theoretical models indicated, roughly, that an approximately round zone should appear, corresponding to the most energetic neutral atoms, it is a kind of ribbon that we observe!

This one is, moreover, not centered on the zone facing the displacement of the Sun. A close observation reveals areas richer in hydrogen atoms oroxygen with in addition different energies.

Astrophysicists are therefore puzzled for the moment. However, it appears that the ribbon is tied to lines of magnetic fields traversing the Galaxy, suggesting that interstellar magnetic fields have a much greater influence on the shape and structure of the heliosphere than previously thought. This is an important discovery because it means that there is a closer connection than previously imagined between the interior of the heliosphere and the conditions of the interstellar medium in the Milky Way.

Indeed, as we have said, the heliosphere somewhat plays the role of the Earth’s magnetosphere vis-à-vis interstellar cosmic rays, that is to say, it largely protects us from them. If this protection can be affected by what happens outside the heliosphere, we understand the interest in determining the mechanisms. This could be useful for common interplanetary flights and long durations during the colonization of the solar system for example. This would make the use of magnetic shields.

More details on the results of the IBEX mission can be obtained by reading the articles published by Science or, more simply, by looking at this video.