(1) Collisionless magnetic reconnection: Prof. Lee is responsible for the single greatest leap in the theory of collisionless magnetic reconnection (MR), a ubiquitous physical process in nature that underlies much of the space physics discipline spanning the sun to Earth’s ionosphere, and is an essential process in astrophysical plasmas. It was widely recognized that the occurrence of MR in highly conducting/collisionless space plasmas requires an effective “anomalous” resistivity. Determining the mechanism to create that resistivity was the single most challenging task facing the space science community until solved by Prof. Lee. Prof. Lee identified the off-diagonal terms of electron pressure tensor as the missing link to realize collisionless reconnection. Prof. James Dungey, who changed the course of space research with the suggestion that magnetic reconnection is a fundamental process for magnetospheric phenomena, was so excited in his work that he wrote a personal letter to Prof. Lee in 1995, stating “I think your paper marks the breakthrough”. Now, all numerical simulations on MR routinely calculate the electron pressure tensor for the effective resistivity.
(2) Theory of auroral kilometric radiation: In 1979, Prof. Lee solved one of the early outstanding science problems of the “space age”: that of “auroral kilometric radiation” (AKR). AKR is an intense emission discovered in 1974 from spacecraft. Prof. Lee’s deep physical insight led to the solution by invoking a novel form of non-thermal emission, that of a cyclotron maser amplification process, requiring relativistic Doppler resonance treatment (Astrophysical Journal, 230, 621, 1979). Prof. Lee’s work has become the “Standard Model” to explain the observed radio emissions from planets, the sun and ultracool dwarf stars.
(3) Formation of solar prominences: Prof. Lee is the first scientist to successfully explain solar prominences (Solar Physics, 138, 291, 1992). Prof. Lee’s successful theory showed that prominence mass is supplied by siphon-type flows induced by thermal instability. The original formation of the prominence is caused by footprint shear within a magnetic arcade in the solar chromosphere. The predictions of Prof. Lee’s theory: the formation of a prominence cavity and certain dynamic features, are well demonstrated. Professor Eugene Parker stated in a personal letter to Prof. Lee that Prof. Lee’s “study (dynamic formations of solar prominence) is a big step forward from the usual static models”.
(4) Theory of magnetic flux transfer events: Flux transfer events (FTEs) were among the most important discoveries made by the ISEE-I and ISEE-II spacecraft. The identification of magnetic flux transfer events has provided the first experimental evidence for the presence of intermittent magnetic reconnection at the dayside magnetopause. The basic signatures for FTEs are a bipolar variation of the magnetic field component normal to the magnetopause current layer and the mixture of magnetospheric and magnetosheath particle populations. In l985, Prof. Lee proposed a mechanism for the formation of FTEs in terms of a multiple X line reconnection (MXR) process, which leads to the formation of magnetic flux ropes. Prof. Lee's MXR model has been well tested by observations and simulations and recognized as the dominant reconnection process at the dayside magnetopause.
(5) Discovery of “gigantic jets” in the atmosphere: In 2003, Dr. Lee led a scientific team that discovered “gigantic jets” in the atmosphere (Nature, June 26, 2003). The observed gigantic jets establish a direct optical and electric link between a thundercloud (altitude ~ 16 km) and the ionosphere at a 90 km altitude confirming the prediction by C. T. R. Wilson (Nobel Laureat) in 1925.
(6) Theory of strong scintillations, interstellar turbulence spectrum and multiple scattering of coda waves: Prof. Lee achieved a significant breakthrough in the theory of strong scattering of pulsar radio waves by interstellar turbulent plasmas in 1975. Such scattering produces a wide variety of observed astrophysical phenomena such as intensity scintillations, angular broadening and pulse smearing. The significance of this work is that Prof. Lee developed a theoretical approach to strong scattering that is non-perturbative. The approach itself is so powerful, it has been applied to completely different geophysical sub-fields. For example, Prof. Lee’s multiple scattering theory has also been applied to seismic coda waves, in collaboration with Professor Keiiti Aki (Bull. Seim. Soc. Am., 73, 377, 1983).
