Search Publications
Recovery of time evolution of Grad-Shafranov equilibria from single-spacecraft data: Benchmarking and application to a flux transfer event
Hasegawa, Hiroshi; Sonnerup, Bengt U. Ã. -.; Nakamura, Takuma K. M.
First results are presented of a method, developed by Sonnerup and Hasegawa (2010), for analyzing time evolution of magnetohydrostatic Grad-Shafranov (GS) equilibria, using data recorded by an observing probe as it traverses a quasi-static, two-dimensional (2D), magnetic-field/plasma structure. The method recovers spatial initial values used in th…
Energetic electron microsignatures as tracers of radial flows and dynamics in Saturn's innermost magnetosphere
Coates, A. J.; Krupp, N.; Roussos, E. +6 more
Signatures of energetic electron depletions from Saturn's inner moons (microsignatures) have been mainly utilized to infer properties of magnetospheric diffusion. The same data, however, indicate that microsignatures can be a much more powerful tool for magnetospheric studies. Here we introduce a new method where the energy structure of a microsig…
Harmonic growth of ion-cyclotron waves in Saturn's magnetosphere
Russell, C. T.; Dougherty, M. K.; Wilson, R. J. +3 more
Ion-cyclotron waves have been observed by the Cassini spacecraft in Saturn's middle magnetosphere. Waves have frequencies near the gyrofrequencies of water-group ions, they are left handed, and in most regions they propagate at small angles to the ambient magnetic field. Their origin is explained in terms of the ion-cyclotron instability generated…
On slowly evolving Grad-Shafranov equilibria
Hasegawa, Hiroshi; Sonnerup, Bengt U. Ã. -.
A method is developed for analyzing the slow, purely kinematic evolution of magnetohydrostatic Grad-Shafranov equilibria, recovered by reconstruction from data taken by a single spacecraft as it traverses a quasi-static, two-dimensional, magnetic field/plasma structure in space, such as a flux transfer event at the magnetopause. The evolution is c…
Hybrid simulations of the plasma environment around Enceladus
Russell, C. T.; Tokar, R. L.; Leisner, J. S. +1 more
The plasma environment around Enceladus is governed by the interaction between the corotating plasma with the body of the moon and the neutral gas associated with Saturn's extended cloud and plumes ejected from its southern polar region. To understand the nature of this interaction, we use 3-D electromagnetic hybrid simulations that treat ions kin…
Chorus wave generation near the dawnside magnetopause due to drift shell splitting of substorm-injected electrons
Keika, Kunihiro; Lee, Jeongwoo; Min, Kyungguk
We study the relationship between the electron injection and the chorus waves during a substorm event on 23 March 2007. The chorus waves were detected at high geomagnetic latitude (∼70°S) Antarctic observatories in the range of 0600-0900 h in magnetic local time (MLT). Electrons drifting from the injection event were measured by two LANL spacecraf…
An empirical relationship between coronal mass ejection initial speed and solar wind dynamic pressure
Cho, K. -S.; Kim, K. -H.; Moon, Y. -J. +3 more
Interplanetary shocks that precede coronal mass ejections (CMEs) are mainly responsible for sudden impulses, which are characterized by a simple step-like increase in the horizontal H component. Such a magnetic field change has been explained as a compression of the magnetosphere by the passage of a sudden increase in the solar wind dynamic pressu…
On the multispacecraft determination of periodic surface wave phase speeds and wavelengths
Farrugia, C. J.; Fazakerley, A. N.; Owen, C. J. +3 more
Observations of surface waves on the magnetopause indicate a wide range of phase velocities and wavelengths. Their multispacecraft analysis allows a more precise determination of wave characteristics than ever before and reveal shortcomings of approximations to the phase speed that take a predetermined fraction of the magnetosheath speed or the av…
Observations and simulations of a highly structured plasma sheet during northward IMF
El-Alaoui, Mostafa; Ashour-Abdalla, Maha; Walker, Raymond +2 more
We investigated a highly structured plasma sheet populated by counterstreaming beams observed by the Cluster and Double Star spacecraft on October 10, 2005, during an extended interval of northward interplanetary magnetic field (IMF). We used Wind spacecraft observations as input into our global magnetohydrodynamic (MHD) simulation of the event, a…
A series of plasma flow vortices in the tail plasma sheet associated with solar wind pressure enhancement
Shi, Q. Q.; Fu, S. Y.; Pu, Z. Y. +3 more
A series of earthward-moving (∼140 km/s) plasma flow vortices with anticlockwise (when viewed from above the ecliptic plane) rotation was detected in the dawnside tail plasma sheet between 1255 and 1400 UT on 6 July 2003. These flow vortices were observed under the condition of northward interplanetary magnetic field with an enhanced solar wind dy…