RESEARCH TO UNDERSTAND THE PLASMA PROPERTIES AROUND SATURN MAY HELP SPACE MISSIONS

Prof. Ioannis Kourakis

University Professor Mathematics

Ioannis Kourakis, Professor of Mathematics at Khalifa University and Theme Leader for magnetospheric modeling at Khalifa University’s Space and Planetary Research Group, along with colleagues carried out a research entitled “Significance of Kappa Distributed Electrons on Electrostatic Solitary Waves in Saturn’s Magnetosphere” with the ambition to understand the statistical properties of electron populations in space plasmas, and the role of kappa distributions, which helps in the study of phenomena like the solar wind, planetary magnetospheres and astrophysical jets, among others. The findings might offer space missions such as the UAE Asteroid mission more information on the plasma environment around stellar bodies to better enhance spacecraft instruments, design, and more.

Over the past few decades, a range of theoretical models and experiments have provided ample evidence for the occurrence of kappa distributions in various space plasma environments. Among various planetary magnetospheres, Saturn’s magnetosphere, for one, makes an excellent testing ground for the investigation of kappa-distributed electrons.

The Cassini spacecraft Mission detected suprathermal electrons around Saturn. Such nonthermal populations are efficiently described by the Kappa distribution function. Motivated by this fact and by observations of electrostatic solitary waves (ESWs) in planetary magnetospheres, Kourakis and his colleagues formulated a theoretical model to explore the significance of the electron parameters in the evolution and the characteristics of ESWs occurring in Saturn’s magnetosphere.

The method provides an efficient tool for understanding ESWs and their dependence on electron statistics, which may be vital in characterizing the microphysics of Saturn’s magnetosphere.

Kappa-distributed electrons

Kappa-distributed electrons refer to a type of particle distribution commonly observed in space plasmas. As Kourakis explains, “In simple terms, a «kappa distribution» in this context describes how the electrons’ speed values are spread, statistically speaking, in a particular environment, such as plasma in space. The term «kappa distribution» comes from the mathematical formula used to describe how these electrons are distributed in velocity space. The kappa distribution function is a way to model the behavior of electrons in plasma based on certain parameters. In essence, kappa distributed electrons have a distribution that deviates from the more familiar Gaussian (bell-shaped curve) distribution, that boasts numerous applications in statistical physics or in financial (stock market) dynamics, for instance.”

He adds, “A kappa distribution has a long tail, meaning that there are more electrons at high energies compared to what a Gaussian distribution would predict. This type of distribution is often observed in space plasmas, where various factors like turbulence, magnetic fields, and particle interactions can affect how electrons are distributed and energized”.

Importance of studying Kappa distributed electrons on Saturn

Matter in the regions surrounding planets in our solar system usually consists of ionized gases, formed by numerous particles that are electrically charged. These are either electrons or ionized atoms. This type of ionized gas environment is called plasma.

Kourakis explains, “It is believed that 99% of the matter in the Universe is in plasma state, often referred to as the 4th fundamental state of matter, alongside solid, liquid and gas. Given that Saturn›s magnetosphere itself is a complex environment influenced by various factors including the solar wind, the planet’s strong magnetic field, and of course the plasma characteristics in that region, investigating the behavior of electrons with kappa distributions on electrostatic waves helps scientists understand energetic particle dynamics within this magnetosphere, including how energy is transferred and distributed among different plasma constituents.”

In addition, electrostatic waves play significant role in energizing and scattering charged particles within the magnetosphere, and thus studying the interaction between kappa-distributed electrons and these waves, allows researchers to learn more about how wave-particle interactions affect particle acceleration, transport, and loss processes in Saturn›s magnetosphere.

The Innovative Finding

This research, unlike others carried out before, is the first ever comprehensive work to predict the possibility for the existence of certain non-conventional solitary wave (pulse) structures such as the so-called super solitary waves and also flat-top solitary waves in Saturn’s magnetosphere.

Kourakis comments, “From a wider perspective, our methodology is not only relevant with modeling plasma behavior in a planet’s surroundings, but it may also inspire works in other fields, in Physics, and even trigger fundamental mathematical work on the foundations of these “exotic” solitary waves (localized waves) predicted in our work. We still have a long way to go, until the formation and behavior of such waves has been thoroughly elucidated.”

Effect on Space studies and exploration

While this specific research covered the role of kappa-distributed electrons on electrostatic waves in Saturn’s magnetosphere, the same methodology adopted in this study could be extended to similar environments on other planets.

Kourakis states, “Our research can provide valuable insight into the fundamental physics governing solitary waves occurring in a variety of space plasma environments, for instance in planetary magnetospheres and in the solar wind. This may help improve space weather prediction and may thus assist in optimizing the design of future space missions.”

Plasma waves and their interactions with different electron populations play a significant role in shaping the magnetosphere environment. Understanding the role of kappa distributed electrons can enhance the ability to predict and mitigate potential hazards for spacecraft and astronauts operating in Space.

This research can also lead to more accurate simulations of the dynamics of plasma waves in planetary magnetospheres, inside the solar system, improving the prediction of what one might expect to encounter in these environments, in the context of future space exploration.

Finally, the knowhow gained from studying the role of kappadistributed electrons can help optimize the design and planning of future space missions to Saturn and to other planets. Kourakis adds, “Understanding space plasma better can help in optimizing spacecraft trajectories, instrument configurations, and data analysis techniques. Some knowledge of plasma environments surrounding planets may be crucial for assessing the habitability of planets or their moons.”

Findings of research

This research relies on a sophisticated mathematical technique. By adopting a pseudopotential methodology and a multi-ion/ multi-electron plasma-fluid model as a starting point. The analysis established a pseudo-mechanical energy balance equation in terms of the electrostatic potential associated with electric field pulses in the magnetosphere. Nonlinear solutions were thus obtained numerically, in order to understand the salient features of electrostatic solitary waves in Saturn’s magnetosphere.

Thorough analysis has revealed that an increase in the nonthermal electron component results in the formation of larger amplitude solitary structures. The model was compared with real observations of electrostatic solitary waves and the theoretically predicted values came out to match the characteristics of the observed waveforms to a highly satisfactory extent.

Potential Benefits to the UAE Mission to the Asteroid Belt

Although Kourakis has no specific formal association with the Emirates Mission to the Asteroid Belt (EMA) at the moment, space missions in general may benefit from research carried out by him and his collaborators, as their results will allow the science team behind the mission design to better understand the plasma environment around a stellar body, be it a planet or an asteroid.

Kourakis states, “Insights gained from this research can inform the design of spacecraft instrumentation necessary for monitoring plasma waves. It can also be crucial for future missions, including the design of spacecraft systems that can operate effectively in such environments.”

Kourakis believes that better understanding of how energetic electrons affect plasma waves can contribute to improving spacecraft navigation and maneuvering strategies, by optimizing navigation routes and avoiding potential hazards.

He adds, “Not less importantly, electrostatic plasma waves can also interfere with communication systems onboard spacecraft. Research in this area can help in developing robust communication systems that are resilient to disruptions caused by plasma waves, ensuring reliable communication between the spacecraft and Earth-based control centers.”