Plasma Vortices in Planetary Wakes (original) (raw)
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Nonlinear Processes in Geophysics, 2009
The Earth's magnetosphere and solar wind environment is a laboratory of excellence for the study of the physics of collisionless magnetic reconnection. At low latitude magnetopause, magnetic reconnection develops as a secondary instability due to the stretching of magnetic field lines advected by large scale Kelvin-Helmholtz vortices. In particular, reconnection takes place in the sheared magnetic layer that forms between adjacent vortices during vortex pairing. The process generates magnetic islands with typical size of the order of the ion inertial length, much smaller than the MHD scale of the vortices and much larger than the electron inertial length. The process of reconnection and island formation sets up spontaneously, without any need for special boundary conditions or initial conditions, and independently of the initial in-plane magnetic field topology, whether homogeneous or sheared.
Solar Wind and Interplanetary Magnetic Field: A Tutorial
The convection layer completes the transport of energy from the nuclear furnace at the center of the sun to its radiation into space by the photosphere, but most importantly for the solar wind it sets the temporal and spatial scales for the structure of the coronal magnetic field that in turn controls the properties of the solar wind. In this tutorial review we examine the properties of the fields and particles that constitute the solar wind and ultimately affect space weather and the underlying physical processes. In particular we discuss the role of the coronal magnetic field; the effect of the rotation of the sun; and the properties of the principal solar wind disturbance at 1 Astronomical Unit, the interplanetary coronal mass ejection.
Plasma and Magnetic Fields in the Solar System
Journal of Geophysical Research, 1959
I am planning to talk about the interplanetary gas in the inner part of the solar system, in which we live. I should like to discuss the circumstances that we shall find when we send up suitable instruments to investigate that gas.
Space Science Reviews, 2005
Observational evidence for a continuous stream of plasma filling interplanetary space was deduced from the properties of cometary tails by Biermann (1951). Parker (1958) demonstrated that solutions of the fluid equations describing the solar atmosphere necessitated the existence of a continuous supersonic wind. The first in situ measurements of this wind were made by Gringauz et al. (1960), and Snyder and Neugebauer (1966). At 1 Astronomical Unit (AU) the solar wind is a tenuous ionised gas that carries with it magnetic fields reaching back into the solar atmosphere. The density of this gas at 1 AU is typically about 5 particles cm −3. In composition it is about 95% protons, 5% He, with a small fraction of heavy ions. (Although we will not discuss the heavy ions further here, they are of profound importance to studies of the solar atmosphere and composition of the Sun.) The embedded magnetic field has a typical value (at 1 AU) of 5 nT. The wind flows at speeds ranging from a couple of hundred km s −1 to 1000 km s −1 , or more. The speed of sound in this plasma is about 40 km s −1. In addition, the speed of the most characteristic plasma wave, i.e., Alfvén waves (discussed below), is also about 40 km s −1 at 1 AU. Consequently, the flow is both supersonic and super-Alfvénic with a plasma β ∼ 1 where β is the ratio of thermal to magnetic pressure 2µ 0 nk B T /B 2 and k B is Boltzmann's constant.
Astronomy and Astrophysics, 2010
Vortex-type motions have been measured by tracking bright points in high-resolution observations of the solar photosphere. These small-scale motions are thought to be determinant in the evolution of magnetic footpoints and their interaction with plasma and therefore likely to play a role in heating the upper solar atmosphere by twisting magnetic flux tubes. We report the observation of magnetic concentrations being dragged towards the center of a convective vortex motion in the solar photosphere from high-resolution ground-based and space-borne data. We describe this event by analyzing a series of images at different solar atmospheric layers. By computing horizontal proper motions, we detect a vortex whose center appears to be the draining point for the magnetic concentrations detected in magnetograms and well-correlated with the locations of bright points seen in G-band and CN images.
Interaction of the Solar Wind with Unmagnetized Planets
The results of a one-dimensional electromagnetic hybrid simulation of the interaction between the ionospheres of Venus and Mars and the solar wind are presented. Finite electron inertia is retained, allowing for the analysis of the lower hybrid waves propagating along an oblique but fixed angle to the shocked solar-wind magnetic field. The waves are excited by a relative drift between a cold electron beam, created by E 3 B pickup, and the planetary oxygen ions. The free energy source for instability is in the solar-wind proton flow supporting electron drift through the convective electric field. The waves generate a collective friction between the shocked solar-wind flow and planetary ions. PACS numbers: 96.50.Ek, Because Venus and Mars do not possess a significant intrinsic magnetic field, the ionosphere is the main, however weak, obstacle to the solar-wind flow, and the planetary bow shocks are located quite close to the planets. The ionospheres of both planets are directly exposed to the streaming shocked solar wind. Data from the particle and wave instruments onboard the Pioneer Venus Orbiter (PVO) and Phobos-2 spacecraft show the existence of a thin D ϳ 100 km turbulent transition region between the shocked solar wind and the ionospheres of Venus and Mars, referred to as the plasma mantle [1]. In the mantle, plasmas of both solar wind and ionospheric origin are present in comparable densities n 10 2 cm 23 , but with very different temperatures. The solar-wind proton (electron) temperature is approximately 100 (30) eV, and the drift velocity is close to the proton thermal velocity. The planetary oxygen and electron temperature is close to 1 eV. There is also experimental evidence for the presence of superthermal oxygen [2] and electron populations at Mars and Venus. Large tailward escape of planetary ions, most probably originating from the dayside mantle, was also observed at Mars .
Solar wind control of the terrestrial magnetotail as seen by STEREO
At the beginning of 2007 the twin STEREO spacecraft provided a unique opportunity to study the global solar wind control of the terrestrial magnetotail under typical solar activity minimum conditions. The STEREO-B (STB) spacecraft flew in the vicinity of the far terrestrial magnetotail, while the STEREO-A (STA) spacecraft was located in front of the Earth performing measurements in the undisturbed solar wind. In February, the STB spacecraft was located in the magnetosheath most of the time but experienced several incursions into the distant magnetotail. Comparison of STA and STB observations determines unambiguously whether solar wind events such as energetic particle enhancements observed by STB are of pure solar origin or due to the influence of the terrestrial magnetosphere. During this time period in 2007, there were solar minimum conditions with alternating fast and slow solar wind streams that formed corotating interaction regions, which were the dominating source of magnetospheric disturbances encountering the Earth almost every week. Under these conditions, STB experienced multiple bow shock and magnetopause crossings due to the induced highly dynamic behavior of the terrestrial magnetotail and detected bursts of tailward directed energetic ions in the range of 110-2200 keV accompanied by suprathermal electrons of~700-1500 eV, which were not seen in the undisturbed solar wind by STA. The corotating interaction regions triggered these energetic particle enhancements, and we demonstrate their magnetosphere-related origin. Even after leaving the magnetosheath in March 2007, STB continued to observe antisunward directed energetic ion bursts until May up to a distance of~800 R E behind Earth, the largest distance to which solar wind and magnetospheric interaction has been observed. These results show that Earth is a very significant source of energetic particles in its local interplanetary environment.