Scientists Sheds Light on Turbulence in Astrophysical Plasmas

The theoretical analysis uncovers new mechanisms in plasma turbulence.

Scientists Sheds Light on Turbulence in Astrophysical Plasmas
Magnetic reconnection is a complicated phenomenon that Nuno Loureiro, an associate professor of nuclear science and engineering and of physics at MIT, has been studying in detail for more than a decade. To explain the process, he gives a well-studied example: “If you watch a video of a solar flare” as it arches outward and then collapses back onto the sun’s surface, “that’s magnetic reconnection in action. It’s something that happens on the surface of the sun that leads to explosive releases of energy.” Loureiro’s understanding of this process of magnetic reconnection has provided the basis for the new analysis that can now explain some aspects of turbulence in plasmas. Image: Pixabay

Almost 99 percent of the visible matter in the universe is actually originated from plasma. A large portion of these plasmas, including the sun-powered breeze that always streams out from the sun and breadths through the nearby planetary group, exist in a turbulent state.

But how this turbulence actually works is still remains a mystery. This mysterious topic is one of the most dynamic research areas in plasma physics.

Focusing on it, 2 scientists at the MIT university have proposed a new model to explain these dynamic turbulent processes.

Nuno Loureiro, an associate professor of nuclear science and engineering and of physics at MIT said, “Naturally occurring plasmas in space and astrophysical environments are threaded by magnetic fields and exist in a turbulent state. That is, their structure is highly disordered at all scales: If you zoom in to look more and more closely at the wisps and eddies that make up these materials, you’ll see similar signs of the disordered structure at every size level.”

While the turbulence is most widely studied, but the turbulence occurs in plasma is more difficult to predict. It’s because of additional factors such as electrical currents and magnetic fields. In particular, Magnetized plasma turbulence is fascinatingly complex and remarkably challenging.

Magnetic reconnection must play a crucial role in the dynamics of plasma turbulence. It could fundamentally change the understanding of the dynamics and properties of space and astrophysical plasmas.

Loureiro said, “It is indeed a conceptual shift in how one thinks about turbulence.”

He along with Stanislav Boldyrev, a professor of physics at the University of Wisconsin at Madison explained, “we can fix this by essentially merging the existing theoretical descriptions of turbulence and magnetic reconnection. Thus, the picture of turbulence will conceptually modify and leads to results that more closely match what has been observed by satellites that monitor the solar wind, and many numerical simulations.”

Loureiro said, “The theory is quite universal, which increases the possibilities for direct tests. For instance, there is some expectation that another NASA mission, the Parker Solar Probe, which is gotten ready for dispatch one year from now and will watch the sun’s crown (the hot ring of plasma around the sun that is just unmistakable from Earth amid an aggregate overshadowing), could give the required confirmation. That test, Loureiro says, will go nearer to the sun than any past rocket, and it ought to give the most precise information on turbulence in the crown up until now.”

The study is a critical advance forward toward a more profound physical comprehension of polarized plasma turbulence. By clarifying profound associations and collaborations between two pervasive and crucial plasma forms — magnetohydrodynamic turbulence and magnetic reconnection — this examination change our hypothetical picture of how the vitality of turbulent plasma movements falls from expansive down to little scales.

Loureiro said, “This work builds on a previous pioneering study published by these authors earlier this year and extends it into a broader realm of collisionless plasmas. This makes the resulting theory directly applicable to more realistic plasma environments found in nature.”

“At the same time, this paper leads to new tantalizing questions about plasma turbulence and reconnection and thus opens new directions of research, hence stimulating future research efforts in space physics and plasma astrophysics.”