Magnetic Reconnection in the Space Sciences: Past, Present, and Future

Abstract

Magnetic reconnection converts, often explosively, stored magnetic energy to particle energy in space and in the laboratory. Through processes operating on length scales that are tiny, it facilitates energy conversion over dimensions of, in some cases, hundreds of Earth radii. In addition, it is the mechanism behind large current disruptions in fusion machines, and it can explain eruptive behavior in astrophysics. We have known about the importance of magnetic reconnection for quite some time based on space observations. Theory and modeling employed magnetized fluids, a very simplistic description. While successful at modeling the large‐scale consequences of reconnection, it is ill suited to describe the engine itself. This is because, at its heart, magnetic reconnection in space is kinetic, that is, governed by the intricate interaction of charged particles with the electromagnetic fields they create. This complex interaction occurs in very localized regions and involves very short temporal variations. Researching reconnection requires the ability to measure these processes as well as to express them in models vastly more complex than fluid approaches. Until very recently, neither of these capabilities existed. With the advent of NASA's Magnetospheric Multiscale mission and modern modeling advances, this has now changed, and we have now determined its small‐scale structure in exquisite detail. In this paper, we review recent research results to predict what will be achieved in the future. We discuss how reconnection contributes to the evolution of larger‐scale systems, and its societal impacts in the context of threatening space hazards, customarily referred to as “space weather.”

Coronal heating problem solution by means of axion origin photons

“…where sunspot area max ≈ 7.5 • 10 9 km 2 ≈ 2470 ppm, sunspot area min ≈ 9.0 • 10 8 km 2 ≈ 300 ppm of visible hemisphere is the sunspot area (over the visible hemisphere [123,124]) for the cycle 22 experimentally observed by the Japanese X-ray telescope Yohkoh (1991) (see [96]); R Sun = 6.96 × 10 5 km; P a→γ ≈ 1 at maximum of solar luminosity, and P a→γ ≈ 0.95 at minimum (see Eqs. (119) and (120) in [8]). The product of the total fraction of axions originating from the Sun core and the fraction of the sunspot area (see [123,124]) yields the total fraction of the corona luminosity, or more precisely, the fraction of photon luminosity of axion origin in the corona.…”

“…Let us recall the jocular but practically understandable words of M. Hesse and P. A. Cassak[120] about the essence of magnetic reconnection: "There is an imprecise -but useful -analogy to rubber bands that helps us picture magnetic reconnection. A loose rubber band cannot hold a pile of pencils in place, but a stretched rubber band can.…”

AME: A Cross-Scale Constellation of CubeSats to Explore Magnetic Reconnection in the Solar–Terrestrial Relation

“…It can further address the critical question of why reconnection operates in small bursts at times and in large eruptions at others. It will furthermore shed light on the puzzle of whether large eruptions are a collection of small bursts occurring together, or whether they are a different, organized, type of reconnection altogether [11]. Understanding when and how these disruptions occur is also critical to predict the harmful effects on the space environment, which are collectively referred to as "space weather" [12].…”

A New Look at the Electron Diffusion Region in Asymmetric Magnetic Reconnection

“…Magnetic reconnection is arguably the most important energy conversion and transport process in collisionless plasmas. Magnetic reconnection is believed to be a key driver in astrophysical plasmas (e.g., Uzdensky, 2011), the mechanism behind solar eruptions (e.g., Antiochos et al., 1999), and it facilitates both energy entry into the magnetosphere as well as energy dissipation inside the magnetosphere (e.g., M. Hesse and Cassak, 2020). For these reasons, magnetic reconnection is also the ultimate engine behind many of the deleterious effects associated with space weather.…”