Earth Space Plasma Research Articles

Linear unstable whistler eigenmodes excited by a finite electron beam

Electron beam-generated whistler waves are widely found in the Earth's space plasma environment and are intricately involved in a number of phenomena. Here, we study the linear growth of whistler eigenmodes excited by a finite gyrating electron beam, to facilitate the interpretation of relevant experiments on beam-generated whistler waves in the Large Plasma Device at UCLA. A linear instability analysis for an infinite gyrating beam is first performed. It is shown that the whistler waves are excited through a combination of cyclotron resonance, Landau resonance, and anomalous cyclotron resonance, consistent with our experimental results. By matching the whistler eigenmodes inside and outside the beam at the boundary, a linear growth rate is obtained for each wave mode and the corresponding mode structure is constructed. These eigenmodes peak near the beam boundary, leak out of the beam region, and decay to zero far away from the beam.

Assimilation of GIRO data into a real‐time IRI

Increasingly accurate and detailed global 3‐D specification of the Earth's space plasma environment is required to further understand its intricate organization and behavior. For a long time space physics and aeronomy research has been data starved due to the great variety of natural time scales involved in the plasma phenomenology. We have started developing a new approach to the global ionospheric specification called Real‐Time Assimilative Mapping (RTAM). The IRI‐RTAM will use data from the Global Ionospheric Radio Observatory (GIRO) to smoothly transform IRI's background empirical maps of the ionospheric characteristics to match the observations. Such empirical assimilative modeling will provide a high‐resolution, global picture of the ionospheric response to various short‐term events observed during periods of storm activity or the impact of gravity waves coupling the ionosphere to the lower atmosphere, including timelines of the vertical restructuring of the plasma distribution. It will also contribute to the challenging task of providing a rapid insight into the temporal and spatial space weather development using the real‐time GIRO data streams. The new assimilation technique “updates” the IRI electron density distribution while preserving the overall integrity of IRI's typical ionospheric feature representations. The technique adjusts the coefficients of the spherical/diurnal expansions used by the CCIR and URSI‐88 model to obtain the global subpeak electron density distribution. The set of global corrected coefficients can be generated as frequently as every 15 min and easily disseminated using a single real‐time RTAM server operated by GIRO.

Near Earth space plasma monitoring under COST 296

This review paper presents the main achievements of the near Earth space plasma monitoring under COST 296 Action. The outputs of the COST 296 community making data, historical and real-time, standardized and avail- able to the ionospheric community for their research, applications and modeling purposes are presented. The con- tribution of COST 296 with the added value of the validated data made possible a trusted ionospheric monitoring for research and modeling purposes, and it served for testing and improving the algorithms producing real-time data and providing data users measurement uncertainties. These value added data also served for calibration and validation of space-borne sensors. New techniques and parameters have been developed for monitoring the near Earth space plasma, as time dependent 2D maps of vertical total electron content (vTEC), other key ionospheric parameters and activity indices for distinguishing disturbed ionospheric conditions, as well as a technique for im- proving the discrepancies of different mapping services. The dissemination of the above products has been devel- oped by COST 296 participants throughout the websites making them available on-line for real-time applications.

Space weather explorer – The KuaFu mission

The KuaFu mission is designed to explore the physical processes that are responsible for space weather, complementing planned in situ and ground-based programs, and also to make an essential contribution to the space weather application. KuaFu encompasses three spacecraft. KuaFu-A will be located at the L1 libration point and have instruments to observe solar extreme ultraviolet (EUV) and far ultraviolet (FUV) emissions and white-light coronal mass ejections (CMEs), and to measure radio waves, the local plasma and magnetic field, and high-energy particles. KuaFu-B1 and KuaFu-B2 will be in elliptical polar orbits chosen to facilitate continuous (24 h per day 7 days per week) observation of the northern polar aurora oval and the inner magnetosphere. The KuaFu mission is designed to observe globally the complete chain of disturbances from the solar atmosphere to geospace, including solar flares, CMEs, interplanetary clouds, shock waves, and their geo-effects, with a particular focus on dramatic space weather events such as magnetospheric substorms and magnetic storms. The mission start is targeted for the next solar maximum with launch hoped for in 2012. The initial mission lifetime will be 3 years. The overall mission design, instrument complement, and incorporation of recent technologies will advance our understanding of the physical processes underlying space weather, solve several key outstanding questions including solar CME initiation, Earth magnetic storm and substorm mechanisms, and advance our understanding of multi-scale interactions in and system-level behavior of our Sun–Earth space plasma system.

Two-stream instability in collisionless shocks and foreshock

Shocks play a key role in plasma thermalization and particle acceleration in the near Earth space plasma, in astrophysical plasma and in laser plasma interactions. An accurate understanding of the physics of plasma shocks is thus of immense importance. We give an overview over some recent developments in particle-in-cell simulations of plasma shocks and foreshock dynamics. We focus on ion reflection by shocks and on the two-stream instabilities these beams can drive, and these are placed in the context of experimental observations, e.g. by the Cluster mission. We discuss how we may expand the insight gained from the observation of proton beam driven instabilities at near Earth plasma shocks to better understand their astrophysical counterparts, such as ion beam instabilities triggered by internal and external shocks in the relativistic jets of gamma ray bursts, shocks in the accretion discs of micro-quasars and supernova remnant shocks. It is discussed how and why the peak energy that can be reached by particles that are accelerated by two-stream instabilities increases from keV energies to GeV energies and beyond, as we increase the streaming speed to relativistic values, and why the particle energy spectrum sometimes resembles power law distributions.

Evolution of Electron Phase-Space Holes in a 2D Magnetized Plasma

The nonlinear stage of the two-stream instability in a 2D magnetized plasma produces electron phase-space tubes, the counterpart of phase-space holes in a 1D plasma. These tubes align primarily perpendicular to the magnetic field ${\mathbf{B}}_{0}$ and have self-consistent bipolar electric fields parallel to ${\mathbf{B}}_{0}$. Such bipolar electric fields have recently been observed in four different regions of the Earth's space plasma environment. Massively parallel 2D kinetic simulations show the dynamics of tube formation, evolution, and breakup, accompanied by the generation of electrostatic whistler waves. We focus on the breakup of the tubes and describe a new numerical study of tube stability.

Studies of Large-Scale Earth Potentials Across Oceanic Distances

This paper describes some ongoing research to characterize and understand the large-scale (on the order of several thousand kilometers) geoelectric potentials that can be induced within the Earth by fluctuations of the geomagnetic field. An understanding of these induced potentials can be important for carrying out some geophysical investigations, as well as for solving numerous engineering problems related to the design and deployment of long, conducting installations on the Earth's surface. Such installations include the systems used to power long-distance cables, electrical power distribution networks, and pipeline corrosion-control systems. The magnitude of the induced potentials fluctuates significantly in time and in spatial extent. It reflects both the highly variable nature of the Earth's space plasma environment that produces the geomagnetic fluctuations and the heterogeneous nature of the geological structure of the Earth's surface and upper mantle. Present-day models of Earth's magnetic fluctuations are insufficient to predict the geopotentials reliably, particularly the extreme geopotentials that might be experienced on a specific long route. Thus, such geopotential measurements as those described in this paper on AT&T cables in the Atlantic and Pacific Oceans can contribute important knowledge of the Earth's geophysical environment, as well as new geopotential information for engineering design.

Earth Space Plasma Physics

A milestone in space research was reached in the early summer of 1985 when earth space plasma physicists and solar physicists came together at the European Space Agency (ESA) workshop on future missions in solar, heliospheric and space physics, held at Garmisch-Partenkirchen in West Germany. Until then, the fields of 'earth' and 'solar' plasma physics research, which have much in common, had developed independently.