草榴社区

A graduate research assistant at 草榴社区 (UAH), a part of The University of Alabama system, has in the journal Astronomy and Astrophysics. that builds on an to help understand why the solar corona is so hot compared to the surface of the sun itself. To shed further light on this age-old mystery, Syed Ayaz, a Ph.D. candidate in the UAH Center for Space Plasma and Aeronomic Research (CSPAR), employed a statistical model known as a Kappa distribution to describe the velocity of particles in space plasmas, while incorporating the interaction of suprathermal particles with kinetic Alfv茅n waves (KAWs).

KAWs are oscillations of the charged particles and magnetic field as they move through the solar plasma, caused by motions in the photosphere, the sun's outer shell. The waves are a valuable tool for modeling various phenomena in the solar system, including particle acceleration and wave-particle interactions.

鈥淥ur earlier work focused on how KAWs contribute to the sun's mysterious ability to heat its corona to over a million degrees despite the much cooler surface,鈥� Ayaz explains. 鈥淯sing the Cairns distribution function, we explored magnetic energy conversion, plasma transport and particle acceleration mechanisms in the solar corona. However, the Cairns distribution, while insightful, lacks a strong statistical foundation. In this new paper, we build upon our earlier findings by employing the Kappa distribution, which offers a statistically robust framework widely recognized in space plasma research.鈥�

In heliophysics, a Kappa distribution is a statistical model that describes the velocity distribution of particles in space plasmas, particularly in the solar wind. 鈥淏y extending our work to this distribution,鈥� the researcher says, 鈥渨e uncover new and fascinating details about solar coronal heating, particularly how KAWs facilitate energy transfer and particle acceleration.鈥�

Syed Ayaz, a graduate research assistant in the Center for Space Plasma and Aeronomic Research (CSPAR).

Michael Mercier | UAH

鈥淔or the first time, Syed has provided a deep understanding of the role of energetic particles on the characteristics of kinetic Alfv茅n waves, yielding important insights into the dissipation, and hence heating, of the coronal plasma by these important waves,鈥� says Dr. Gary Zank, Aerojet/Rocketdyne Chair in Space Science and director of CSPAR. 鈥淜AWs represent the end point of energy transfer in a turbulent magnetized plasma and are a critical element in understanding how the corona reaches such high temperatures. This is an important step forward in understanding this longstanding problem about the sun鈥檚 atmosphere.鈥�

When charged particles interact with wave electric fields in a plasma, KAWs can transfer energy to the particles, leading to plasma heating over extended distances.

鈥淭his new approach strengthens our understanding of the interplay between waves and particles, the mechanisms driving the solar wind and the corona's extreme temperatures,鈥� Ayaz notes. 鈥淭he Kappa distribution allows us to incorporate the effects of suprathermal particles, which significantly influence wave-particle interactions and the dynamics of KAWs.鈥�

Suprathermal particles are charged ions and electrons found throughout interplanetary space that move at speeds up to hundreds of times faster than the thermal plasma of the solar wind.

鈥淥ur analysis highlights the influence of suprathermal particles alongside variations in the electron-to-ion temperature ratio and height relative to the solar radius of the sun,鈥� Ayaz says. 鈥淭his comprehensive approach reveals how these parameters affect wave-particle interactions and energy dynamics in the solar corona.鈥�

In addition, the researcher鈥檚 work complements the missions of both NASA鈥檚 Parker Solar Probe and the ESA鈥檚 Solar Orbiter.

鈥淥ne of the most significant findings is our ability to address the observational gap left by NASA's Parker Solar Probe (PSP) and ESA's Solar Orbiter, which struggle to investigate the critical region within 10 solar radii,鈥� Ayaz says. 鈥淲hile the PSP鈥檚 closest approach on December 24, 2024, partially explores this zone, our theoretical framework provides insights into Alfv茅n wave behavior and their heating contributions in the uncharted 0鈥�10 radii region.

鈥淏y bridging this gap, our study not only complements the observational data but also offers a predictive model for understanding wave dynamics and particle acceleration mechanisms in the solar corona, marking a significant step forward in solving the 鈥榗oronal heating problem.鈥欌��