Showing papers on "Space weather published in 2003"

Predicting interplanetary magnetic field (IMF) propagation delay times using the minimum variance technique

Abstract: [1] It has been known that the fluctuations in the interplanetary magnetic field (IMF) may be oriented in approximately planar structures that are tilted with respect to the solar wind propagation direction along the Sun-Earth line. This tilting causes the IMF propagating from a point of measurement to arrive at other locations with a timing that may be significantly different from what would be expected. The differences between expected and actual arrival times may exceed an hour, and the tilt angles and subsequent delays may have substantial changes in just a few minutes. A consequence of the tilting of phase planes is that predictions of the effects of the IMF at the Earth, on the basis of IMF measurements far upstream in the solar wind, will suffer from reduced accuracy in the timing of events. It has recently been shown how the tilt angles may be determined using multiple satellite measurements. However, since the multiple satellite technique cannot be used with real-time data from a single sentry satellite, then an alternative method is required to derive the phase front angles, which can then be used for more accurate predictions. In this paper we show that the minimum variance analysis (MVA) technique can be used to adequately determine the variable tilt of the plane of propagation. The number of points that is required to compute the variance matrix has been found to be much higher than expected, corresponding to a time period in the range of 7 to 30 min. The optimal parameters for the MVA were determined by a comparison of simultaneous IMF measurements from four satellites. With use of the optimized parameters it is shown that the MVA method performs reasonably well for predicting the actual time lags in the propagation between multiple spacecraft, as well as to the Earth. Application of this technique can correct for errors, on the order of 30 min or more, in the timing of predictions of geomagnetic effects on the ground.

Energetic particle acceleration and transport at coronal mass ejection–driven shocks

Abstract: [1] Evidence now exists which suggests that in large solar energetic particle (SEP) events, particles are often accelerated to ∼ MeV energies (and perhaps up to GeV energies) at shock waves driven by coronal mass ejections (CMEs). These energetic particles are of considerable importance to space weather studies since they serve as a precursor signal for possible disruptive events at the Earth. As a CME-driven shock propagates, expands and weakens, particles accelerated diffusively at the shock can escape upstream and downstream into the interplanetary medium. The escaping energized particles propagate along the interplanetary magnetic field, experiencing only weak scattering from fluctuations in the interplanetary magnetic field (IMF). In this work, we study the time-dependent transport of energetic particles accelerated at a propagating shock using a Monte-Carlo approach. This treatment, together with our previous work on particle acceleration at shocks, allows us to investigate the characteristics (intensity profiles, angular distribution, particle anisotropies) of high-energy particles arriving at various distances from the sun. Such an approach is both easy to implement and allows us to study the affect of interplanetary turbulence on particle transport in a systematic manner. These theoretical models form an excellent basis on which to interpret observations of high-energy particles made in situ at 1 AU by spacecraft such as ACE and WIND.

Multiple magnetic clouds: Several examples during March-April 2001

Abstract: [1] Multiple magnetic cloud (Multi-MC), which is formed by the overtaking of successive coronal mass ejections (CMEs), is a kind of complex structure in interplanetary space. Multi-MC is worthy of notice due to its special properties and potential geoeffectiveness. Using the data from the ACE spacecraft, we identify the three cases of Multi-MC in the period from March to April 2001. Some observational signatures of Multi-MC are concluded: (1) Multi-MC only consists of several magnetic clouds and interacting regions between them; (2) each subcloud in Multi-MC is primarily satisfied with the criteria of isolated magnetic cloud, except that the proton temperature is not as low as that in typical magnetic cloud due to the compression between the subclouds; (3) the speed of solar wind at the rear part of the front subcloud does not continuously decrease, rather increases because of the overtaking of the following subcloud; (4) inside the interacting region between the subclouds, the magnetic field becomes less regular and its strength decreases obviously, and (5) b value increases to a high level in the interacting region. We find out that two of three Multi-MCs are associated with the great geomagnetic storms (Dst �� 200 nT), which indicate a close relationship between the Multi-MCs and some intense geomagnetic storms. The observational results imply that theMulti-MC is possibly another type of the interplanetary origin of the large geomagnetic storm, though not all of them have geoeffectiveness. Based on the observations from Solar and Heliospheric Observatory (SOHO) and GOES, the solar sources (CMEs) of these Multi-MCs are identified. We suggest that such successive halo CMEs are not required to be originated from a single solar region. Furthermore, the relationship between Multi-MC and complex ejecta is analyzed, and some similarities and differences between them are discussed. INDEX TERMS: 2111 Interplanetary Physics: Ejecta, driver gases, and magnetic clouds; 1739 History of Geophysics: Solar/planetary relationships; 7513 Solar Physics, Astrophysics, and Astronomy: Coronal mass ejections; 2788 Magnetospheric Physics: Storms and substorms; KEYWORDS: multiple magnetic clouds, coronal mass ejections, geomagnetic storms, interaction, interplanetary space

Forecasting solar wind structures and shock arrival times using an ensemble of models

Abstract: [1] Forecasting the time of arrival at Earth of interplanetary shocks following solar metric type II activity is an important first step in the establishment of an operational space weather prediction system. The quality of the forecasts is of utmost importance. The performances of the shock time of arrival (STOA) and interplanetary shock propagation models (ISPM) were previously evaluated by Smith et al. [2000] for 36 solar events. Here we use 173 solar events between February 1997 and October 2000 to set thresholds for the Hakamada–Akasofu–Fry version 2 (HAFv.2) model and then present the results of a comparison of the performance of this model to the STOA and ISPM solar wind models. Each model predicts shock arrival time (SAT) at the Earth using real-time metric type II radio frequency drifts and coincident X-ray and optical data for input and L1 satellite observations for verification. Our evaluation of input parameters to the models showed that the accuracy of the solar metric type II radio burst observations as a measure of the initial shock velocity was compromised for those events at greater than 20° solar longitude from central meridian. The HAF model also calculates the interplanetary shock propagation imbedded in a realistic solar wind structure through which the shocks travel and interact. Standard meteorological forecast metrics are used. A variety of statistical comparisons among the three models show them to be practically equivalent in forecasting SAT. Although the HAF kinematic model performance compares favorably with ISPM and STOA, it appears to be no better at predicting SAT than ISPM or STOA. HAFv.2 takes the inhomogeneous, ambient solar wind structure into account and thereby provides a means of sorting event-driven shock arrivals from corotating interaction region (CIR) passage.

The first coordinated ground- and space-based optical observations of equatorial plasma bubbles

Abstract: [1] We report on ionospheric optical emissions detected by the GUVI instrument on the TIMED satellite. As the satellite crosses the equatorial zone the bright Appleton Anomaly region is imaged. Often these bright zones are interrupted by regions slanted from west to east as the equator is approached forming a backwards ‘C’-shape in the image. To explain this feature we use simultaneous ground-based observations looking equatorward from Hawaii using the 777.4-nm emission. We also compare these optical observations to inverted electron density maps, as well as to those made by radar and to numerical simulations of the Rayleigh-Taylor instability. The characteristic shape is a result of a shear in the eastward plasma flow velocity, which peaks near the F peak at the equator and decreases both above and below that height. The ability to detect these unstable and usually turbulent ionospheric regions from orbit provides a powerful global remote sensing capability for an important space weather process.

Periodicities in solar coronal mass ejections

Abstract: Mid-term quasi-periodicities in solar coronal mass ejections (CMEs) during the mostrecent solar maximum cycle 23 are reported here for the first time using the four-year data (February 5, 1999 to February 10, 2003) of the Large Angle SpectrometricCoronagraph (LASCO) onboard the Solar and Heliospheric Observatory (SOHO). Inparallel, mid-term quasi-periodicities in solar X-ray flares (class >M5.0) from theGeosynchronous Operational Environment Satellites (GOES) and in daily averages ofAp index for geomagnetic disturbances from the World Data Center (WDC) at theInternationalAssociation for Geomagnetism andAeronomy (IAGA)are alsoexaminedfor the same four-year time span. By Fourier power spectral analyses, the CME dataappears to contain significant power peaks at periods of ∼ 358 ± 38, ∼ 272 ± 26,∼ 196±13 days and so forth, while except for the ∼ 259±24-day period, X-ray solarflares of class >∼ M5.0 show the familiar Rieger-type quasi-periods at ∼ 157 ± 11,∼ 122± 5, ∼ 98±3 days and shorter ones until ∼ 34±0.5 days. In the data of dailyaverages of Ap index, the two significant peaks at periods ∼ 273±26 and ∼ 187±12days (the latter is most prominent) could imply that CMEs (periods at ∼ 272±26and∼ 196 ± 13 days) may be proportionally correlated with quasi-periodic geomagneticstorm disturbances; at the speculative level, the ∼ 138 ± 6-day period might implythat X-ray flares of class >∼ M5.0 (period at ∼ 157±11 days) may drive certain typesof geomagnetic disturbances; and the ∼ 28±0.2-day periodicity is most likely causedby recurrent high-speed solar winds at the Earth’s magnetosphere. For the same threedata sets, we further perform Morlet wavelet analysis to derive period-time contoursand identify wavelet power peaks and timescales at the 99 percent confidence level forcomparisons. Several conceptual aspects of possible equatorially trapped Rossby-typewaves at and beneath the solar photosphere are discussed.Key words: oscillations — space weather — Sun: activities — corona — coronalmass ejections — magnetic fields

Type II Solar Radio Bursts: Theory and Space Weather Implications

Abstract: Recent data and theory for type II solar radio bursts are reviewed, focusing on a recent analytic quantitative theory for interplanetary type II bursts. The theory addresses electron reflection and acceleration at the type II shock, formation of electron beams in the foreshock, and generation of Langmuir waves and the type II radiation there. The theory's predictions as functions of the shock and plasma parameters are summarized and discussed in terms of space weather events. The theory is consistent with available data, has explanations for radio-loud/quiet coronal mass ejections (CMEs) and why type IIs are bursty, and can account for empirical correlations between type IIs, CMEs, and interplanetary disturbances.

April 2000 geomagnetic storm: ionospheric drivers of large geomagnetically induced currents

Abstract: . Geomagnetically induced currents (GIC) flowing in technological systems on the ground are a direct manifestation of space weather. Due to the proximity of very dynamic ionospheric current systems, GIC are of special interest at high latitudes, where they have been known to cause problems, for example, for normal operation of power transmission systems and buried pipelines. The basic physics underlying GIC, i.e. the magnetosphere – ionosphere interaction and electromagnetic induction in the ground, is already quite well known. However, no detailed study of the drivers of GIC has been carried out and little is known about the relative importance of different types of ionospheric current systems in terms of large GIC. In this study, the geomagnetic storm of 6–7 April 2000 is investigated. During this event, large GIC were measured in technological systems, both in Finland and in Great Britain. Therefore, this provides a basis for a detailed GIC study over a relatively large regional scale. By using GIC data and corresponding geomagnetic data from north European magnetometer networks, the ionospheric drivers of large GIC during the event were identified and analysed. Although most of the peak GIC during the storm were clearly related to substorm intensifications, there were no common characteristics discernible in substorm behaviour that could be associated with all the GIC peaks. For example, both very localized ionospheric currents structures, as well as relatively large-scale propagating structures were observed during the peaks in GIC. Only during the storm sudden commencement at the beginning of the event were large-scale GIC evident across northern Europe with coherent behaviour. The typical duration of peaks in GIC was also quite short, varying between 2–15 min. Key words. Geomagnetism and paleo-magnetism (geomagnetic induction) – Ionosphere (ionospheric disturbances) – Magnetospheric physics (storms and substorms)

A new model of solar EUV irradiance variability 2. Comparisons with empirical models and observations and implications for space weather

Abstract: [1] Motivated by the need for reliable specification of the Sun's electromagnetic radiation in the extreme ultraviolet (EUV) spectrum, we have developed a new model of solar EUV irradiance variability at wavelengths from 50 to 1200 A. Solar images are used to quantify changes in the sources of EUV irradiance during the solar cycle. Optically thin EUV emission line fluxes are estimated from differential emission measures (DEMs) that characterize the properties of the solar atmosphere in the source regions, while fluxes for optically thick lines are modeled directly by specifying the source region contrasts. We compare the new model, NRLEUV, with three different empirical models of solar EUV irradiance since 1975. For solar cycles 21 and 22, NRLEUV predicts overall lower EUV irradiances and smaller solar cycle variability than the empirical models. The average total EUV energy at wavelengths from 50 to 1050 A is 2.9 mW m−2, smaller than the HFG, EUVAC, and SOLAR2000 models for which average energies are 3.7, 4.3, and 5.6 mW m−2, respectively. These differences have distinct wavelength dependencies. The solar cycle variation in total EUV energy is 1.9 for NRLEUV compared with 2.7, 2.9, and 2.3 for HFG, EUVAC, and SOLAR2000. Here, too, the differences are wavelength dependent. We compare both the NRLEUV and the empirically modeled EUV irradiances with selected wavelength bands and emission lines measured during 4 years in cycle 21 by Atmospheric Explorer-E (AE-E) and two broad bands at 170–200 and 260–340 A measured in cycle 23 by the Solar X-Ray Photometer (SXP) on the Student Nitric Oxide Experiment (SNOE) and the Solar EUV Monitor (SEM) on the Solar and Heliospheric Observatory (SOHO), respectively. The NRLEUV model reproduces the variations observed during solar rotation better than, or as well as, the empirical models. Comparisons of solar cycle variations are more ambiguous because undetected instrumental drifts can cause spurious trends in the observations over these longer timescales. Drifts in the AE-E instruments may explain why the HFG and EUVAC models, which are based on parameterizations of these data, have larger solar cycle variations than NRLEUV. We assess the implications for space weather of the significant differences among the modeled EUV irradiances by using the Atmospheric Ultraviolet Radiance Integrated Code (AURIC) to quantify corresponding differences in upper atmosphere energy deposition and photoionization rates.

Statistical Relationships between Solar, Interplanetary, and Geomagnetic Disturbances, 1976-2000: 2

Abstract: In this paper we continue the analysis of the influence of solar and interplanetary events on magnetospheric storms that was started in [1]. Two data sets are additionally analyzed in the present study: solar flares of importance M5 and greater in 1976–2000 and halo CMEs observed by the SOHO spacecraft during the period of 1996–2000. It is demonstrated that the statistical characteristics of the new set of flares and of that analyzed before in [1] differ little, while the geoeffectiveness of the halo CMEs turned out to be much less than that of the previously published CMEs.

MHD tomography using interplanetary scintillation measurement

Abstract: [1] The MHD tomography analysis, an advanced version of the computer-assisted tomography (CAT) analysis for interplanetary scintillation (IPS) observational data, is presented. When combined with a MHD simulation, the CAT analysis can reconstruct the MHD-based three-dimensional solar wind structure within 1 AU from the IPS line-of-sight integrated velocity data. At the same time, the MHD code can simulate the actual conditions in the heliosphere beyond 1 AU by utilizing the results of the MHD tomography analysis and extrapolate to r ≥ 1 AU. The present MHD tomography aims to reconstruct the global structure of corotating solar wind, under the assumption that the global solar wind does not vary significantly in time during one Carrington rotation. The reconstructed three-dimensional solar wind variables including interplanetary magnetic field (IMF) are compared with the in situ measurement data made at the Ulysses spacecraft and nearby Earth, and good correlations are obtained. We anticipate that the combination of MHD simulation and the IPS tomography will enhance solar wind research and space weather prediction algorithms.

Geomagnetic Induction During Highly Disturbed Space Weather Conditions: Studies of Ground Effects

Abstract: The thesis work tackles the end of the space weather chain. By means of both theoretical and data-based investigations the thesis provides new tools and physical understanding of the processes related to geomagnetic induction and its effects on technological systems on the ground during highly disturbed geomagnetic conditions. In other words, the thesis focuses on geomagnetically induced currents (GIC). Noteworthy is also that GIC research is a practical interface between the solid Earth and space physics domains. It is shown that GIC can be modeled accurately with rather simple mathematical tools requiring that the topology and the electrical parameters of the conductor system, the ground conductivity structure and either the ionospheric source current or the ground magnetic field variations are known. Data-based investigations revealed that from the geophysical viewpoint, the character of GIC events is twofold. On one hand, large GIC can be observed at the same time instant throughout the entire auroral region. On the other hand, spatial and temporal scales related to these events are rather small making the detailed behavior of individual GIC events relatively local. It was observed that although substorms are statistically the most important drivers of large GIC in the auroral region, there are a number of different magnetospheric mechanisms capable to such dynamic changes that produce large GIC. Publishing unit Geophysical Research Classification (UDC)

Radiation hazard in space

Abstract: Preface 1: Introduction and Brief History 11 Space Radiation Environment 12 Identification of Radiation Hazard 13 Multilevel Nature of the Problem 14 Recent Developments 15 General Picture of Radiation Disturbance 2: Radiation Conditions in Space 21 Character of Radiation Influence 22 Main Concepts, Definitions and Terms 23 Objects of Radiation Impact 24 Dynamics of Radiation Dose 25 Extreme Radiation Conditions 26 Super-Events in the Heliosphere 3: Physical Conditions in Space 31 Solar Activity and Heliomagnetosphere 32 Properties of Interplanetary Medium 33 Motion of Energetic Particles in Space 34 Regular Geomagnetic Field and Anomalies 35 Disturbances of the Earth's Radiation Environment 36 Space Weather Systems and Standards 4: Radiation Belts of the Earth 41 Radiation Characteristics of Trapped Particles 42 Peculiarities of the Radiation Belts Formation 43 Spatial Distribution of Charged Particles 44 Model description of radiation impact 45 Temporal variations in the solar activity cycle 5: Dynamics of Galactic Cosmic Rays 51 Element Composition and Energy Spectrum 52 Anomalous Component and Long-Term Modulation 53 Model description of particle spectrum 54 Modeling Galactic Cosmic Ray Background 55 Cosmic Radiation Dose to Aircrews and Avionics 6: Cosmic Rays of Solar Origin 61 Modern Concept of Solar Proton Events 62 Classification Systems 63 Solar Event Databases 64 Energy Spectrum, and Occurrence Rate 65 Variations of Particle Intensity in Solar Cycle 7: Prediction and Modeling Radiation Hazard 71 Methodical Approaches and Constraints 72 Prediction of Solar Particle Flux 73 Prediction Heavy Ion Fluxes and Anomalous Events 74 Relativistic Protons in Prediction Schemes 75 Probability Techniques and Models 76 Models of Proton Fluence at Large Time Scale 8: Summary: Problems and Prospects 81 Shock Acceleration and Radiation Prediction 82 Radiation Hazard at Different Heliospheric Distances 83 New Model for Solar Cosmic Rays 84 Scenarios of Future Interplanetary Missions 85 Space Experiments on Radiation Effects 86 Radiation Conditions on Board the International Space Station 87 Matters Arising and Concluding Remarks Bibliography Appendices: A1 Definitions A2 Quantities and Units A3 Acronyms A4 Cosmic Rays in the Earth's Atmosphere

International standard model of the earth's inosphere and plasmasphere

Abstract: The standard plasmasphere-ionosphere model of the International Standardization Organization is aimed at providing the distributions of the electron density, total electron content, temperature and effective collision frequency of electrons at altitudes of 65-20000 km (or to the plasmapause) over the Earth, geodetic latitudes of 80 N to 80 S, any longitude, day of the year, and indices of solar and geomagnetic activity. It includes the International Reference Ionosphere developed by the Union Radio-Scientifique Internationale and the Committee on Space Research, and the Russian standard model of the ionosphere. Two modes of operation are envisaged: the climatological monthly average prediction and dynamic short-term forecast of space weather parameters. The reliability of results is improved on input of pre-history of observable solar and geophysical parameters. The software of the standard model is available via the Internet.

1.6 M Solar Telescope in Big Bear -- The NST

Abstract: New Jersey Institute of Technology (NJIT), in collaboration with the University of Hawaii (UH), is upgrading Big Bear Solar Observatory (BBSO) by replacing its principal, 65 cm aperture telescope with a modern, off-axis 1.6 m clear aperture instrument from a 1.7 m blank. The new telescope offers a significant incremental improvement in ground-based infrared and high angular resolution capabilities, and enhances our continuing program to understand photospheric magneto-convection and chromospheric dynamics. These are the drivers for what is broadly called space weather - an important problem, which impacts human technologies and life on earth. This New Solar Telescope (NST) will use the existing BBSO pedestal, pier and observatory building, which will be modified to accept the larger open telescope structure. It will be operated together with our 10 inch (for larger field-of-view vector magnetograms, Ca II K and Ha observations) and Singer-Link (full disk H, Ca II K and white light) synoptic telescopes. The NST optical and software control design will be similar to the existing SOLARC (UH) and the planned Advanced Technology Solar Telescope (ATST) facility led by the National Solar Observatory (NSO) - all three are off-axis designs. The NST will be available to guest observers and will continue BBSO`s open data policy. The polishing of the primary will be done in partnership with the University of Arizona Mirror Lab, where their proof-of-concept for figuring 8 m pieces of 20 m nighttime telescopes will be the NST`s primary mirror. We plan for the NST`s first light in late 2005. This new telescope will be the largest aperture solar telescope, and the largest aperture off-axis telescope, located in one of the best observing sites. It will enable new, cutting edge science. The scientific results will be extremely important to space weather and global climate change research.

Space Weather: Its Effects and Predictability

Abstract: Terrestrial technology is now, and increasingly, sensitive to space weather Most space weather is caused by solar storms and the resulting changes to the Earth's radiation environment and the magnetosphere The Sun as the driver of space weather is under intense observation but remains to be adequately modelled Recent spacecraft measurements are greatly improving models of solar activity, the interaction of the solar wind with the magnetosphere, and models of the radiation belts In-situ data updates the basic magnetospheric model to provide specific details of high-energy electron flux at satellite orbits Shock wave effects at the magnetopause can also be coarsely predicted However, the specific geomagnetic effects at ground level depend on the calculation of magnetic and electric fields and further improvements are needed New work on physical models is showing promise of raising geomagnetic and ionospheric predictability above the synoptic climatological level

A class of TVD type combined numerical scheme for MHD equations with a survey about numerical methods in solar wind simulations

Abstract: It has been believed that three-dimensional, numerical, magnetohydrodynamic (MHD) modelling must play a crucial role in a seamless forecasting system. This system refers to space weather originating on the sun; propagation of disturbances through the solar wind and interplanetary magnetic field (IMF), and thence, transmission into the magnetosphere, ionosphere, and thermosphere. This role comes as no surprise to numerical modelers that participate in the numerical modelling of atmospheric environments as well as the meteorological conditions at Earth. Space scientists have paid great attention to operational numerical space weather prediction models. To this purpose practical progress has been made in the past years. Here first is reviewed the progress of the numerical methods in solar wind modelling. Then, based on our discussion, a new numerical scheme of total variation diminishing (TVD) type for magnetohydrodynamic equations in spherical coordinates is proposed by taking into account convergence, stability and resolution. This new MHD model is established by solving the fluid equations of MHD system with a modified Lax-Friedrichs scheme and the magnetic induction equations with MacCormack II scheme for the purpose of developing a combined scheme of quick convergence as well as of TVD property. To verify the validation of the scheme, the propagation of one-dimensional MHD fast and slow shock problem is discussed with the numerical results conforming to the existing results obtained by the piece-wise parabolic method (PPM). Finally, some conclusions are made.

Frequency agile solar radiotelescope

Abstract: The Frequency Agile Solar Radiotelescope (FASR) is a solar-dedicated, ground based, interferometric array optimized to perform broadband imaging spectroscopy from ~ 0.1-30+ GHz. It will do so with the angular, spectral, and temporal resolution required to exploit radio emission from the Sun as a diagnostic of the wide variety of astrophysical processes that occur there. FASR represents a major advance over existing radioheliographs, and is expected to remain the world's premier solar radio instrument for two decades or more after completion. FASR will be a versatile and powerful instrument, providing unique data to a broad users community. Solar, solar-terrestrial, and space physicists will exploit FASR to attack a broad science program, including problems of fundamental interest: coronal magnetography, solar flares and particle acceleration, drivers of space weather, and the thermal structure and dynamics of the solar atmosphere. A design study and implementation planning are underway. Recent progress is reviewed here.

New Insights on Geomagnetic Storms from Model Simulations Using Multi-Spacecraft Data

Abstract: The forecast of the terrestrial ring current as a major contributor to the stormtime Dst index and a predictor of geomagnetic storms is of central interest to ‘space weather’ programs We thus discuss the dynamical coupling of the solar wind to the Earth's magnetosphere during several geomagnetic storms using our ring current-atmosphere interactions model and coordinated space-borne data sets Our model calculates the temporal and spatial evolution of H+, O+, and He+ ion distribution functions considering time-dependent inflow from the magnetotail, adiabatic drifts, and outflow from the dayside magnetopause Losses due to charge exchange, Coulomb collisions, and scattering by EMIC waves are included as well As initial and boundary conditions we use complementary data sets from spacecraft located at key regions in the inner magnetosphere, Polar and the geosynchronous LANL satellites We present recent model simulations of the stormtime ring current energization due to the enhanced large-scale convection electric field, which show the transition from an asymmetric to a symmetric ring current during the storm and challenge the standard theories of (a) substorm-driven, and (b) symmetric ring current Near minimum Dst there is a factor of ∼ 10 variation in the intensity of the dominant ring current ion specie with magnetic local time, its energy density reaching maximum in the premidnight to postmidnight region We find that the O+ content of the ring current increases after interplanetary shocks and reaches largest values near Dst minimum; ∼ 60% of the total ring current energy was carried by O+ during the main phase of the 15 July 2000 storm The effects of magnetospheric convection and losses due to collisions and wave-particle interactions on the global ring current energy balance are calculated during different storm phases and intercompared

Operational impacts of space weather

Abstract: [1] Space weather events on the Sun, such as coronal mass ejections and solar flares, can lead to a worldwide disturbance of the geomagnetic field and associated ionospheric and thermospheric disturbances. These events can, and do, impact the performance and reliability of space-based and ground-based operational systems. This paper presents specific examples of the operational impact of space weather events on space surveillance systems. The paper concentrates on the 14 July 2000 event during which the solar-terrestrial environment experienced its largest disturbance in the past 11 years. We report on effects that were detected during the July storm with the Space-Based Visible (SBV) sensor, a visible-band electro-optical system that operates as a contributing sensor for the U. S. Space Surveillance Network. We also discuss the impact of this space weather event on the Global Positioning System (GPS) and on satellite tracking observations by ground-based radars.

On the estimates of the ring current injection and decay

Abstract: In the context of the space weather predictions, forecasting ring current strength (and of the Dst index) based on the solar wind upstream conditions is of specific interest for predicting the occurrence of geomagnetic storms In the present paper, we have studied separately its two components: the Dst injection and decay In particular, we have verified the validity of the Burton’s equation for estimating the ring current energy balance using the equatorial electric merging field instead of the original parameter V Bs (V is the solar wind speed and Bs is the southward component of the Interplanetary Magnetic Field, IMF) Then, based on this equation, we have used the phasespace method to determine the best-fit approximations for the ring current injection and decay as functions of the equatorial merging electric field (Em) Results indicate that the interplanetary injection is statistically higher than in previous estimations using V Bs Specifically, weak but not-null ring current injection can be observed even during northward IMF, when previous studies considered it to be always zero Moreover, results about the ring current decay indicate that the rate of Dst decay is faster than its predictions derived by using V Bs In addition, smaller quiet time ring current and solar wind pressure corrections are contributing to Dst estimates obtained by Em instead of V Bs These effects are compensated, so that the statistical Dst predictions using the equatorial electric merging field or using V Bs are about equivalent

The predictability of the magnetosphere and space weather

Abstract: Yogi Berra once observed, apparently paraphrasing Niels Bohr, “Prediction is difficult, especially about the future” Berra's and Bohr's backgrounds, respectively, in baseball and quantum mechanics, probably prejudiced them, since recent studies show that, at least in geophysics, not everything is as difficult to predict as the path of a knuckle ball or an electron through a double slit Large-scale magnetospheric activity we believe, is quite predictable, given solar wind conditions For example, in Figure 1 we show the long-term variation of radiation belt electrons and the Dst index for approximately the last solar cycle The long-term variation of radiation belt electrons and the Dst index provides evidence that radiation belt electrons and geomagnetic activity on average, have a systematic response to the solar wind

Some results of investigations on the space weather influence on functioning of several engineering–technical and communication systems and human health

Abstract: Some results of a complex study on the influence of such space weather factors as the effects of scintillation, solar and geomagnetic storms on human health and some engineering–technical systems both space borne and of ground-based origin are briefly described. The morphology and main characteristics of ionospheric scintillation, together with its impacts on navigation and communication systems, are developed to help space system designers who are involved in activities related to the development of systems in middle latitudes for microwave radio signals for the satellite-receiver path. A study of the effects of geomagnetic storms on electrical power generation and transmission network and equipment, that is the influence of the geomagnetically induced currents of selected magnetic storms and relevant power cuts has revealed that power line disturbances mainly occur when the geomagnetic field displays sharp changes. For the purposes of studying the possible influence of the solar and geomagnetic activity...