Solar-terrestrial Space Research Articles

Development of the Chinese Meridian Project

The Meridian Project is a ground-based network program to monitor Solar-Terrestrial space environment, which consists of a chain of ground-based observatories with multiple instruments including magnetometers, ionosondes, HF and VHF radars, Lidars, IPS monitors, sounding rockets etc. The chain is mainly located in the neighborhood of 120$^\circ$E meridian, and is thus named the Meridian Project. The Meridian Project has officially been approved and supported by the Chinese government and will be finished by the end of 2010. This report gives an overview of the Meridian Project, and reports the recent development since 2008.

Space Weather Model Descriptions: Which Should Be Published?

Since the launch of Space Weather, a number of space weather models of all types have been reported in the journal. One of the more uncertain (and at times controversial) aspects of numerical simulations of the entire Sun-to-Earth environment is for authors (and editors) to determine when such “global” models and their results are deserving of consideration for publication. Models of solar-terrestrial processes are essential for successful predictions of these processes and of their effects on technological systems. Models can take many forms, from simple empirical expressions of the relationships among two or more physical variables to more detailed physics-based codes of subsets of the solar-terrestrial environment. Numerical simulations of the entire environment—from the Sun to Earth's ionosphere and surface—now exist. Such simulations generally incorporate modules for the several subsystems of the environment, with each module containing the relevant physics (and chemistry in appropriate cases) that is required. Many codes are in various states of testing, validation, and use in the joint U.S. National Science Foundation/NASA Community Coordinated Modeling Center. Numerical simulations must be considered and evaluated in the context of actual physical measurements. Models can be essential in deriving physical understanding from obtained data. At the same time, data are essential in validating and calibrating models. Therefore, computational simulations considered for publication should ideally report their success, or lack of success, in explaining observations. In particular, reports of failures permit a modeling group and interested outside research groups to better understand limitations of a numerical code and its modules, and thereby spur new modeling insights and developments. Often it appears that modeling teams concentrate on studying some of the largest solar-terrestrial events, especially those that involve the release of coronal mass ejections and their transit to Earth. This concentration is natural in that large events are those that can most affect technological systems. While models often do not fully explain all of the data in such large-event studies, these attempts nevertheless illuminate important limitations in the codes and their modules, and therefore point the way to new directions. But which models deserve consideration for publication? The perception of some modelers that Space Weather and its applications-oriented readers favor modeling papers that address extreme events is not in actuality the case. The journal is quite interested in publishing modeling papers that address less severely disturbed solar-terrestrial conditions, but ones that still involve perturbations of the Earth's environment that can produce effects on technical systems. One condition that requires more modeling analysis under numerical simulation is the case where enhanced relativistic electrons are produced at geosynchronous orbit when Earth is hit by an interplanetary corotating interaction region. In such a case, the enhanced relativistic electrons can produce charging of dielectric materials such as shielded electronics and coaxial cables deep inside spacecraft bodies. Modeling, beginning at the Sun and continuing to geosynchronous orbit, is of prime interest for this problem. I invite modelers to consider possible papers on this and other less disturbed but important solar-terrestrial space weather topics. Louis J. Lanzerotti is editor of Space Weather, a distinguished research professor at the New Jersey Institute of Technology, and a consultant at Alcatel-Lucent Technologies’ Bell Laboratories.

The COMPASS-2 satellite and the ground-based LOIS vector sensing radar facility as novel tools for ionospheric plasma diagnostics

To give a more detailed and complete understanding of physical plasma processes that govern the solar–terrestrial space, and to develop qualitative and quantitative models of the magnetosphere–ionosphere–thermosphere coupling, it is necessary to design and build the next generation of instruments for space diagnostics and monitoring. Novel ground-based wide-area sensor networks, such as the LOFAR Outrigger In Scandinavia (LOIS, LOFAR: Low Frequency Array) radar facility, comprising wide band, and vector-sensing radio receivers with full three-dimensional polarization coverage, and multi-spacecraft plasma diagnostics should help solve outstanding problems of space physics and describe long-term environmental changes. The new digital radio frequency analyzer (RFA) on board the low-orbiting COMPASS-2 satellite was designed to monitor and investigate the ionospheric plasma properties. This two-point ground-based and topside ionosphere-located space plasma diagnostic can be a useful new tool for monitoring and diagnosing turbulent plasma properties. The RFA on board the COMPASS-2 satellite is the first in a series of experiments which is planned to be launched into the near-Earth environment. The main purpose of this presentation is to describe new advanced diagnostic techniques of the near-Earth space plasma and point out the scientific challenges of the COMPASS-2 and LOIS experiments.

Prediction Test for the Two Extremely Strong Solar Storms in October 2003

In late October and early November 2003, a series of space weather hazard events erupted in solar-terrestrial space. Aiming at two intense storm (shock) events on 28 and 29 October, this paper presents a Two-Step method, which combines synoptic analysis of space weather–`observing’ and quantitative prediction – ‘palpating’, and uses it to test predictions. In the first step, ‘observing’, on the basis of observations of the source surface magnetic field, interplanetary scintillation (IPS) and ACE spacecraft, we find that the propagation of the shock waves is asymmetric and northward relative to the normal direction of their solar sources due to the large-scale configuration of the coronal magnetic fields, and the Earth is located near the direction of the fastest speed and greatest energy of the shocks. Being two fast ejection shock events, the fast explosion of extremely high temperature and strong magnetic field, and background solar wind velocity as high as 600 and 1000 km s−1, are also helpful to their rapid propagation. According to the synoptic analysis, the shock travel times can be estimated as 21 and 20 h, which are close to the observational results of 19.97 and 19.63 h, respectively. In the second step, ‘palpating’, we adopt a new membership function of the fast shock events for the ISF method. The predicted results here show that for the onset time of the geomagnetic disturbance, the relative errors between the observational and the predicted results are 1.8 and 6.7%, which are consistent with the estimated results of the first step; and for the magnetic disturbance magnitude, the relative errors between the observational and the predicted results are 4.1 and 3.1%, respectively. Furthermore, the comparison among the predicted results of our Two-Step method with those of five other prevailing methods shows that the Two-Step method is advantageous in predicting such strong shock event. It can predict not only shock arrival time, but also the magnitude of magnetic disturbance. The results of the present paper tell us that understanding the physical features of shock propagation thoroughly is of great importance in improving the prediction efficiency.

Prospects of Russian participation in the international LWS program

This report describes current and future solar-terrestrial space missions of the Russian Federal Space Agency. They are discussed in the context of the International Living With a Star activity aimed at consolidation of efforts in developing a balanced cooperative program of solar-terrestrial and space weather oriented research. We provide information on several missions that are at different stages of realization: solar observing – CORONAS-F, CORONAS-PHOTON, and INTERHELIOPROBE; and magnetospheric – RESONANCE, ROY, and INTERBALL-PROGNOZ.

Prospects for High Angular Resolution at Low Frequencies

High angular resolution imaging at low frequencies (below ∼ 10 MHz) requires observations from above the ionosphere. A radio interferometer array in space will be able to open new vistas in solar, terrestrial, galactic, and extragalactic astrophysics. A space-based interferometer could image and track transient disturbances in the solar corona and interplanetary medium - a new capability which is crucial for understanding many aspects of solar-terrestrial interaction and space weather. It could also produce the first sensitive, high-angular-resolution radio surveys of the entire sky at low frequencies. The radio sky will look entirely different below 10-30 MHz because new emission and absorption processes become dominant at these frequencies. As a result, low frequency surveys from space will provide a fundamentally new view of the universe and an extraordinarily large and varied science return.

Propagation model of high-energy solar cosmic rays in interplanetary space and Green function

Based on main observational characteristics of solar flare particle transport in the coronal, a mathematical description of coronal transport is proposed. A model is presented for solar cosmic-ray propagation in solar-terrestrial space of infinite, homogeneous orthotropic medium. A Green function to the propagation equation with source is found. The integral solution to the propagation equation with the source, as well as the analytical solution to the equation for a pulse point source, is obtained by using the Green function in the medium.

Unusual solar disturbance

The solar flares, the speeds of shocks propagated in the solar-terrestrial space and driven by coronal mass ejections (CMEs), the heliographic longitudes and Carrington longitudes of source regions, and the geomagnetic storms, which are accompanied by the super solar proton events with a peak flux equal to or exceeding 10 000 pfu, have been studied by using the data of ground-based and space observations. The results show that the heliographic longitudes of source regions of super solar proton events distributed in the range from E30̊ to W75°. The Carrington longitudes of source regions of super solar proton events distributed in the two longitudinal belts, 130°∼220° and 260°∼320°, respectively. All super solar proton events were accompanied by major solar flares and fast CMEs. The averaged speeds of shocks propagated from the sun to the Earth were greater than 1 200 km/s. Eight super solar proton events were followed by major geomagnetic storms (Dst≤−100 nT), except that one super solar proton event was followed by a geomagnetic storm with the geomagnetic activity index Dst=−96 nT, a little smaller than that of major geomagnetic storms.