En-Sang Lee

In this paper we report plasma blob events (plasma density enhancements) that were observed from KOMPSAT‐1 (685‐km altitude, 2250 LT) and from DMSP F15 (840‐km altitude, 2130 LT) in the low‐latitude F region. The blobs were observed mostly along the ±15° magnetic latitudes. Their global distribution showed a seasonal‐longitudinal dependence similar to the distribution of the equatorial plasma bubbles. The blobs drifted upward relative to the ambient plasma, and the electron temperatures and H +

We investigated the global distribution of equatorial plasma bubbles (EPBs) using in situ plasma density measurements from Korea Multipurpose Satellite‐1 (KOMPSAT‐1) and Defense Meteorological Satellite Program (DMSP) F15 during the solar maximum period from June 2000 to August 2001. The results were generally consistent with those of previous studies. EPBs were observed at all longitudes around the magnetic dip equator in the equinoctial seasons with the peak occurrence in the American‐Atlantic

We study the two storm events of 1997: one in May that was accompanied by a relativistic electron event (REE) and the other in September, with a more profound Dst decrease, but with no significant flux increase of relativistic electrons. We find that a larger amount of seed electrons was present in the May event compared to that of the September storm, whereas the ULF (ultra low frequency) power was more enhanced and the particle spectrum was harder in the September event. Hence, we demonstrate

We investigated the properties of physical parameters during earthward flow burst (FB) events in the near‐Earth magnetic tail. For the investigation, we used the measurements made by two of the Cluster satellites, C1 and C4, from 2001 to 2003 and selected FB events based on a set of strict criteria. First, while we confirmed the well‐known fact that the FBs are characterized by generally having a lower density than that of their surrounding medium, we newly found that the maximum flow speed of F

[1] The radial diffusion process can play an important role in redistributing the radiation belt electron fluxes. In this work, we have performed 1-D radial diffusion simulations to examine the evolution of the phase space density (PSD) of the outer radiation belt electrons and to estimate the corresponding fluxes during the storm recovery phase. The key element that distinguishes our simulations from previous works is the initial condition for PSD, which is characterized by a steep radial gradi

Abstract We have studied the spectral properties of quiet‐time electromagnetic ion cyclotron (EMIC) waves following a steady quiet condition, which is defined with K p values ≤1 during 12 h, using GOES 10, 11, and 12 magnetometer data for solar minimum years 2007–2008. We identified 6584 steady quiet‐time EMIC wave samples using a semiautomated procedure. Approximately 82% of the samples were observed in the morning‐to‐early afternoon sector (0700–1500 magnetic local time) with a maximum occurre

Abstract Finite heat flux often exists in space and astrophysical plasmas, which can be a free energy source for heat flux instability. The solar wind is a well-known example of such plasmas and a number of previous studies have investigated the characteristics of heat flux instability in the context of solar wind. In the literature there exists some uncertainties regarding the properties of heat flux instability. While some linear theories predict the association of the heat flux instability wi

We have developed a 2.5-dimensional electromagnetic particle simulation code using the particle-in-cell (PIC) method to investigate electromagnetic phenomena that occur in space plasmas. Our code is based on the leap-frog method and the centered difference method for integration and differentiation of the governing equations. We adopted the relativistic Buneman-Boris method to solve the Lorentz force equation and the Esirkepov method to calculate the current density while maintaining charge cons

Three‐dimensional magnetic reconnection is studied using magnetohydrodynamic simulations. The initial configuration is based on the two‐dimensional Harris neutral sheet model that lies in the xz plane and is extended in the y direction. Localized anomalous resistivity is applied to the central region, and the subsequent evolution of spontaneous magnetic reconnection is observed. Special attention is given to the results with a finite B y superimposed on the Harris model. Significant changes are

In this paper we present analysis of current density when the Cluster spacecraft pass the nightside auroral region at about 4-5 RE from the center of Earth. The analysis is made when the inter-spacecraft separation is within 200 km, which allows all four spacecraft to be situated inside the same current sheet. On 22 February 2002, two field-aligned current (FAC) events were observed in both the southern and the northern hemispheres. The FACs were calculated with magnetic field data obtained by t

Magnetic decreases are often observed in various regions of interplanetary space. Many studies are devoted to reveal the physical nature and generation mechanism of the magnetic decreases, but still we do not fully understand magnetic decreases. In this study, we investigate the structure of a magnetic decrease observed in a corotating interaction region using multi-spacecraft measurements. We use three spacecraft, ACE, Cluster, and Wind, which were widely separated in the x- and y-directions in

Properties of plasmas that constitute the plasma sheet in the near-Earth magnetotail vary according to the solar wind conditions and location in the tail. In this case study, we present multi-spacecraft observations by Cluster that show a transition of plasma sheet from cold, dense to hot, tenuous state. The transition was associated with the passage of a spatial boundary that separates the plasma sheet into two regions with cold, dense and hot, tenuous plasmas. Ion phase space distributions sho

Magnetic decreases are often observed in various regions of interplanetary space. Many studies are devoted to reveal the physical nature and generation mechanism of the magnetic decreases, but still we do not fully understand magnetic decreases. In this study, we investigate the structure of a magnetic decrease observed in a corotating interaction region using multi-spacecraft measurements. We use three spacecraft, ACE, Cluster, and Wind, which were widely separated in the x- and y-directions in