Storm Of October Research Articles

Relative importance of ring and tail currents to Dst under extremely disturbed conditions

Relative ring current (RC) and tail current (TC) contributions to Dst were investigated on the basis of the statistical study of 70 magnetic storms of different intensities. Special attention was paid to the extremely disturbed conditions during magnetic storms in October–November 2003. Variations of the magnetic field produced by magnetospheric currents on the Earth's surface were calculated using paraboloid model of the magnetosphere A2000 [Alexeev, I.I., Belenkaya, E.S., Kalegaev, V.V., Feldstein, Y.I., Grafe, A., 1996. Journal of Geophysical Research 101,7737; Alexeev, I.I., Kalegaev, V.V., Belenkaya, E.S., Bobrovnikov, S.Yu., Feldstein, Ya.I., Gromova, L.I., 2001. Journal of Geophysical Research 106, 25683], taking into account the effect of terrestrial induced currents. For each magnetic storm we calculated Dst and contributions produced by large-scale magnetospheric current systems. The relative RC and TC contributions for each event at the storm maximum were examined in relationship to the peak pressure-corrected Dst value. Analysis of Dst sources confirms the conclusions of Kalegaev and Ganushkina [2005. In: Pulkkinen, T., Tsyganenko, N.A., Friedel, R.H.W. (Eds.), Physics and Modeling of the Inner Magnetosphere, AGU Geophysical Monograph 155. AGU, Washington, DC, p. 293] and Kalegaev and Makarenkov [2006. Geomagnetism and Aeronomy 46, 570] about saturation of the TC effect under extremely disturbed conditions. The RC becomes the dominant Dst source during severe magnetic storms, but during moderate storms its contribution to Dst is comparable with TC's contribution. The RC injection amplitude increases with the growth of magnetospheric disturbance level.

Total Lightning Signatures of Thunderstorm Intensity over North Texas. Part II: Mesoscale Convective Systems

Abstract Total lightning data from the Lightning Detection and Ranging (LDAR II) research network in addition to cloud-to-ground flash data from the National Lightning Detection Network (NLDN) and data from the Dallas–Fort Worth, Texas, Weather Surveillance Radar-1988 Doppler (WSR-88D) station (KFWS) were examined from individual cells within mesoscale convective systems that crossed the Dallas–Fort Worth region on 13 October 2001, 27 May 2002, and 16 June 2002. LDAR II source density contours were comma shaped, in association with severe wind events within mesoscale convective systems (MCSs) on 13 October 2001 and 27 May 2002. This signature is similar to the radar reflectivity bow echo. The source density comma shape was apparent 15 min prior to a severe wind report and lasted more than 20 min during the 13 October storm. Consistent relationships between severe straight-line winds, radar, and lightning storm cell characteristics (e.g., lightning heights) were not found for cells within MCSs as was the case for severe weather in supercells in Part I of this study. Cell interactions within MCSs are believed to weaken these relationships as reflectivity and lightning from nearby storms contaminate the cells of interest. Another hypothesis for these weak relations is that system, not individual cell, processes are responsible for severe straight-line winds at the surface. Analysis of the total lightning structure of the 13 October 2001 MCS showed downward-sloping source density contours behind the main convective line into the stratiform region. This further supports a charge advection mechanism in developing the stratiform charge structure. Bimodal vertical source density distributions were observed within MCS convection close to the center of the LDAR II network, while the lower mode was not detected at increasing range.

Recent advances in observations and modeling of the solar ultraviolet and X-ray spectral irradiance

There have been significant, recent advances in understanding the solar ultraviolet (UV) and X-ray spectral irradiance from several different satellite missions and from new efforts in modeling the variations of the solar spectral irradiance. The recent satellite missions with solar UV and X-ray spectral irradiance observations include the X-ray Sensor (XRS) aboard the series of NOAA GOES spacecraft, the Upper Atmosphere Research Satellite (UARS), the SOHO Solar EUV Monitor (SEM), the Solar XUV Photometers (SXP) on the Student Nitric Oxide Explorer (SNOE), the Solar EUV Experiment (SEE) aboard the Thermosphere, Ionosphere, Mesosphere, Dynamics, and Energetics (TIMED) satellite, and the Solar Radiation and Climate Experiment (SORCE) satellite. The combination of these measurements is providing new results on the variability of the solar ultraviolet irradiance throughout the ultraviolet range shortward of 200 nm and over a wide range of time scales ranging from years to seconds. The solar UV variations of flares are especially important for space weather applications and upper atmosphere research, and the period of intense solar storms in October–November 2003 has provided a wealth of new information about solar flares. The new efforts in modeling these solar UV spectral irradiance variations range from simple empirical models that use solar proxies to more complicated physics-based models that use emission measure techniques. These new models provide better understanding and insight into why the solar UV irradiance varies, and they can be used at times when solar observations are not available for atmospheric studies.

ELF polar chorus and magnetic storms

The data of continuous observations of ELF emissions (polar chorus) at South Pole Antarctic observatory (Φ = −74.02°) for 1997–1999 and during the superstrong magnetic storms of October and November 2003 are analyzed. It has been established that an increase in polar chorus is as a rule observed during the initial and recovery phases of a magnetic storm at positive values of the IMF vertical component (IMF B z > 0). Under such conditions, South Pole is located in the region of closed field lines. It has been found that the generation of polar chorus at South Pole abruptly ceases during the storm main phase after the IMF B z southward turning and beginning of an intense substorm in the nightside auroral zone, probably, because this observatory appears in the region of projection of the open magnetosphere due to the expansion of the polar cap.

Monitoring global traveling ionospheric disturbances using the worldwide GPS network during the October 2003 storms

AbstractThe global traveling ionospheric disturbances (TIDs) during the drastic magnetic storms of October 29–31, 2003 were analyzed using the Global Position System (GPS) total electron content (TEC) data observed in the Asian-Australian, European and North American sectors. We collected the most comprehensive set of the TEC data from more than 900 GPS stations on the International GNSS Services (IGS) website and introduce here a strategy that combines polynomial fitting and multi-channel maximum entropy spectral analysis to obtain TID parameters. The results of our study are summarized as follows: (1) large-scale TIDs (LSTIDs) and medium-scale TIDs (MSTIDs) were detected in all three sectors after the sudden commencement (SC) of the magnetic storm, and their features showed longitudinal and latitudinal dependences. The duration of TIDs was longer at higher latitudes than at middle latitudes, with a maximum of about 16 h. The TEC variation amplitude of LSTIDs was larger in the North American sector than in the two other sectors. At the lower latitudes, the ionospheric perturbations were more complicated, and their duration and amplitude were relatively longer and larger. (2) The periods and phase speeds of TIDs were different in these three sectors. In Europe, the TIDs propagated southward; in North America and Asia, the TIDs propagated southwestward; in the near-equator region, the disturbances propagated with the azimuth (the angle of the propagation direction of the LSTIDs measured clockwise from due north with 0°) of 210° showing the influence of Coriolis force; in the Southern Hemisphere, the LSTIDs propagated conjugatedly northwestward. Both the southwestward and northeastward propagating LSTIDs are found in the equator region. These results mean that the Coriolis effect cannot be ignored for the wave propagation of LSTIDs and that the propagation direction is correlated with polar magnetic activity.

Regional response of the mesosphere–lower thermosphere dynamics over Scandinavia to solar proton events and geomagnetic storms in late October 2003

The short-term regional responses of the mesosphere–lower thermosphere (MLT) dynamics over Scandinavia to the exceptionally strong solar storms with their accompanying solar proton fluxes on the Earth in late October 2003 have been investigated using radar measurements at Andenes (69°N, 16°E) and Esrange (68°N, 21°E). Several solar activity storms resulted in solar proton events (SPEs) at this time, but a particularly active period of high proton fluxes occurred between 28 and 31 October 2003. The significant temperature drop (∼25 K), detected by the meteor radar at Andenes at altitude ∼90 km, was in line with the enhancement of the proton fluxes and was caused by the dramatic reduction of the ozone in the high-latitude middle atmosphere monitored by satellite measurements. This exceptionally strong phenomenon in late October 2003 was composed of three geomagnetic storms, with the first one occurring in the daytime of 29 October and the other two storms in the nighttime of 29 and 30 October, respectively. The responses of the prevailing wind and the main tides (24- and 12-h tides) were studied in detail. It was found that the response of the MLT dynamics to the first geomagnetic storm occurring in the daytime and accompanied by solar proton fluxes is very different from those to the second and third geomagnetic storms with onsets during the nighttime. Some physical mechanisms have been suggested in order to explain the observed short-term variability of the MLT dynamics. This case study revealed the impact of the SPEs observed in late October 2003 and the timing of the geomagnetic storms on the MLT neutral wind responses observed over Scandinavia.

Dynamics of the radiation belt formed by solar protons during magnetic storms

Experimental proofs of the existence of the formation and destruction mechanisms of solar proton belts in the inner magnetosphere at a rapid change in the penetration boundary of solar protons are presented. An analysis of the measurements of solar protons and alpha-particles on board the Coronas-F low-altitude polar satellite during the magnetic storms in October–November 2003 is performed. During this period, formation and destruction of the belts of solar cosmic rays was observed several times. The compression of the magnetosphere during a storm makes possible the direct penetration of solar protons deep into the inner magnetosphere. The proton trajectories outside the penetration boundary are open, and the preliminary captured particles can easily leave the magnetosphere. During the recovery of the magnetospheric configuration, when the penetration boundary goes away from the Earth, the solar protons and alpha-particles with relatively low velocity of the magnetic drift remain stably captured, whereas the particles of higher energies follow the motion of the penetration boundary. That is why the energy range of the captured protons is limited from above in contrast to the effect of injection during ineffective SC in the low-energy region.

Recent Space Data

This paper summarises the workshop session on recent space data. Most presentations addressed the intense solar storm in October–November 2003. Large perturbations of atmospheric trace gas concentrations, notably NO2 and HNO3, were found over extended areas around the magnetic poles in the mesosphere and stratosphere, extending over many weeks in the stratosphere. The impact on total ozone seems to be very limited although some more subtle investigations are still to be done. Several new space instruments with many innovative data products have been introduced. Very good coverage in vertically resolved observations of many chemical species is reached for stratospheric chemistry and dynamics research. Data have already been used to improve stratospheric models. Data continuity is an issue. However, the greatest concern is the lack of any suitable future space instrumentation for tropospheric research (air quality and climate forcing/carbon cycle) as well as UTLS problems (climate/chemistry interaction, stratosphere/troposphere exchange).

Low-energy ion precipitation during the Halloween storm

During the Halloween storm of October 29–31, 2003, four defense meteorological satellite program (DMSP) satellites detected fluxes of low-energy ions precipitating well equatorward of auroral electrons in the dawn/morning magnetic local time sector during the main phase. There were three southward turnings of the interplanetary magnetic field (IMF), leading to three intensifications of the ring current to DST values of −125, −310 and −350 nT. In each case the ion fluxes weakened dramatically and/or vanished during DST recoveries. DMSP only encountered short-lived episodes of subauroral ion precipitation in the dusk/evening sector. A brief survey of the DMSP database reveals that near-dawn, ion precipitation is a main-phase characteristic of all large magnetic storms. DMSP satellites also detected similar ion precipitation during the main phase of the March 1991 magnetic storm. During an outbound pass of the combined release radiation effect satellite (CRRES) through the inner magnetosphere it detected low energy (<1 keV) ion fluxes that were collocated with, but spectrally separated in energy from the ring current “nose structure”. As CRRES moved toward perigee in the dawn sector, it crossed similar low-energy (⩽500 eV) ions embedded in a broad ion population, located earthward of plasma sheet electrons. Simultaneously the DMSP F8 satellite detected spectrally similar low-energy ions precipitating at subauroral latitudes near dawn at the same invariant latitudes. To reconcile DMSP/CRRES observations with elementary concepts of allowed ion drift paths, the data suggest two source populations. The lowest-energy ions, of ionospheric origin, were initially energized earthward of the plasma sheet electron boundary in the evening local-time sector then co-rotated eastward. Higher-energy ions originated in the plasma sheet and drifted close to the Earth under the combined influences of time-varying convective electric fields and azimuthal gradients in the Earth's magnetic field generated by the stormtime ring current [Tsyganenko, N.A., Singer, H. J., Kasper, J. C., 2003. Storm-time distortion of the inner magnetosphere: how severe can it get? Journal of Geophysical Research, 108 (A5), 1209].

Reducing carbon dioxide emissions from UK road transport

Several cases of extreme local weather conditions since the storms of October 1987 have served as reminders of some of the possible consequences of global warming, recently more usually, although less precisely, referred to as ‘climate change’. Carbon dioxide emissions have been identified as the principal likely culprit and road traffic is the only major source from the UK which is increasing in amount. Local authorities may feel impotent to make a significant contribution to a solution, but example is a worthwhile motive. A local authority can contribute in several ways: implementation of improved vehicle technologies; adopting road speed limits and upholding them; promotion of driving styles which are more sensitive to their environmental effects and of improved vehicle maintenance; policies to change mode of travel and transport and to reduce the amount of travel by several means, including fuller use of vehicles. Many of the ways of reducing carbon dioxide discharges locally will have other environmental benefits. The implementation of cleaner travel lags behind the science to allow it; local authorities have an important role to play in reducing the gap. Average vehicle loadings are low, especially for personal travel; there is much scope for improved environmental performance, and for public transport there are issues relating to value for public spending. Reductions in the amount of travel can also contribute to several government policies relating to social exclusion, promotion of sustainable communities and supporting town centre activities.

Development of an unattended estuarine nutrient monitoring program using ferries as data-collection platforms

Water quality monitoring of estuarine ecosystems relies on measurement of biogeochemically important elements, including nitrogen (N), phosphorus (P), carbon (C), and silicon (Si) at a time-step relevant to the environmental conditions affecting the estuary. To improve the temporal resolution of sample collection from the Neuse River estuary, North Carolina, USA, a water sampling system was installed on a state-operated motor vehicle ferry. A gravity-filtration device consisting of a plastic cylinder (15 cm long, 4 cm wide) with a 0.7 μm pore size filter at the bottom was suspended inside the mouth of the collection bottle. Dissolved organic nitrogen (DON), orthophosphate, dissolved organic carbon (DOC), ammonium, and silica were analyzed from filtered water samples, whereas nitrate plus nitrite analysis required acidification of samples in addition to filtration. Refrigerated storage of samples for 7 days had minimal effect on nutrient concentrations. A daily sample collection scheme was employed during September and October 2005 in the Neuse River estuary. There were relatively minor changes in N, P, C, and Si nutrients during and after passage of Hurricane Ophelia in September, but high concentrations of ammonium, silica, and orthophosphate occurred at the onset of high riverine discharge during a separate storm in October. In contrast, DOC, nitrate plus nitrite, and DON reached highest values after the peak riverine discharge. This high temporal resolution sampling regimen was essential for examining estuarine response to brief meteorological and hydrologic perturbations and is applicable to many other estuaries worldwide.

Global thermosphere‐ionosphere response to onset of 20 November 2003 magnetic storm

There is great interest in understanding how the thermosphere‐ionosphere system responds to geomagnetic storms. New insights are possible using the new generation of fully coupled three‐dimensional models, together with extensive ionospheric databases. The period of postsolar maximum geomagnetic storms in October and November 2003 were some of the largest storms ever recorded. In this paper, we explore how the thermosphere‐ionosphere system responded to the onset of the 20 November 2003 geomagnetic storm, using the NCAR TIMEGCM. The model simulates dramatic changes in the thermospheric equatorward winds, O/N2, and corresponding ionospheric electron densities. The model is used as a framework to interpret an increase in the observed ionospheric total electron content, and F region electron density, in the European and North African sector, in terms of changes in the neutral gas. Corresponding compositional effects observed by the GUVI instrument on the TIMED satellite lend credence to the model results. We describe some of the important physical processes that will affect planning for the utilization of measurements from the Geospace investigations in NASA's Living With a Star Program. The study illustrates the value of measuring both the neutral and ionized gases, of obtaining quasi‐global views from imaging instruments, and the synergy between satellite data, ground‐based measurements, and models.

Large-scale disturbances of auroral origin during strong magnetic storms of October 29–31, 2003, and November 7–11, 2004, according to the data of the GPS network and ionosondes

The intensity of large-scale traveling ionospheric disturbances (LS TIDs), registered according to measurements of the total electron content (TEC) during the magnetic storms of October 29–31, 2003, and November 7–11, 2004, has been compared with that of local electron density disturbances. The data of TEC measurements at ground-based GPS receivers located near the ionospheric stations and the corresponding values of the critical frequency of the ionospheric F region (foF2) were used for this purpose. The variations in TEC and foF2 were similar for all events mentioned above. The previous assumption that the region of thickness 150–200 km in the vicinity of the ionospheric F region mainly contributes to TEC modulation was confirmed for the cases when the electron density disturbance at an F region maximum was not more than 50%. However, this region probably becomes more extensive in vertical when the electron density disturbance in the vicinity of the ionospheric F region is about 85%.

Rehabilitation of a sea wall in Mandal, Norway

Gismerøy is a small island close to the city of Mandal on the south coast of Norway. The site has been selected for industrial development. An industrial estate was developed close to the sea with no particular attention to protection. The landfill and a factory building were nearly completely destroyed by two consecutive storms in May and October 2000. After the second storm, detailed studies and model tests were carried out to specify a reliable and safe design. The new design was based on a berm breakwater principle, but with some important local adaptations. It was also discovered that the wave runup due to a rock formation was so great that the rock would have to be removed. This work was especially challenging because there was a strong wish to preserve the infrastructure and investments that had already been laid down, and because the areas adjacent to the site are designated as natural recreational areas.

A lipid molecular marker assessment of sediments from the Northern Gulf of Mexico before and after the passage of Hurricane Lili

A characterization study of lipid molecular markers was undertaken to identify the provenance of organic matter in surface sediments from the Louisiana Shelf, west of the Atchafalaya River before and after the passage of Hurricane Lili (a category 2 storm) in October 2002. During both sampling periods, terrestrially derived organic matter, as revealed by long chain n-alkanes, terrestrial aquatic hydrocarbon ratio (TAR HC) and β-sitosterol, was a predominant component of the organic matter, supporting earlier studies. A petroleum derived unresolved complex mixture (UCM) was detected at each station during both sampling events and displayed no statistically significant difference between inshore and offshore stations. The absence of any relationship between the UCM and the bulk radiocarbon isotopic compositions suggests that petroleum derived organic matter does not significantly control the ages of the sedimentary organic carbon (>2000 years). In addition, sterols, linear, mono- and polyunsaturated fatty acids (FAs) from multiple organic matter sources, including diatoms, dinoflagellates and zooplankton, were also detected at each site. These compounds indicated the sources of organic matter for pre- and post-hurricane samples were similar overall. Surface area-normalized concentrations of n-alkanes and bacterially derived FAs for the pre- and post-hurricane sediments were statistically different between events whereas other parameters such as total sterol and FA concentrations were not.

Assessment of the levels of coastal marine pollution of Chennai city, Southern India

The levels of hydrological pollution of Chennai coastal zone in the southeastern part of India have been increased in the recent years by an uncontrolled disposal of wastewater and pollutants due to human activities. This study gave a special emphasis on the determination of the levels of pollution, the identification of vulnerable zones and providing some probable remedial measures for severely impacted coastal zone of Chennai city. During the period from September to November 2002, sampling was carried out along the shore in two traverses running in the seaside (surf zone) and landside (coastal aquifer). When sampling efforts took place the middle of the above period experienced a monsoonal storm over Chennai coast that significantly influenced large variations in the pollution level at both traverses in seaside and landside. Analysis of physical, chemical and biological parameter determinations indicated that the concentrations of dissolved oxygen (DO), biochemical oxygen demand (BOD), chemical oxygen demand (COD), nutrients (nitrate, nitrite and phosphate), turbidity, maximum probable number (MPN) and chlorophyll a (Chl a) reached notably high levels at all sample locations before monsoonal storm prevailed over these areas during October 2002, which resulted in large fresh water input to the coastal system reducing the levels of pollution to some extent. Analysis of water samples collected during November apparently indicated that the concentrations of above parameters attained abnormal level and often exceeded the permissible limit of international standards. The concentrations of trace/toxic metals such as manganese, copper, nickel, lead, cadmium and cobalt also reached very high levels as a result of their sub-aqueous disposal to these areas, leading to further habitat and ecological destruction. On the other hand, analysis of groundwater samples collected from coastal aquifer for determination of certain chemical parameters such as Ca2+/Mg2+, Cl−/(CO2−3+HCO3-) and the ratio of total alkalinity (TA) and total hardness (TH) revealed that coastal groundwater appeared to be severely contaminated by saltwater intrusion as a result of overexploitation and enormous pressure imposed by monsoonal storm of October. Higher concentrations of toxic elements, for example, lead, nickel, cobalt and cadmium from the influence of industrial wastes and contaminated coastal waters, were also found to deteriorate the quality of coastal aquifer system. Based on detailed examination, four sites including Cuvum estuary, Adyar estuary, Kannikoil and Bharathiyar nagar are identified as highly venerable zones because of receiving a large quantity of municipal and industrial wastes. To reduce severe pollution levels in these areas it is therefore necessary to design and construct the submarine pipeline system to transport and disperse such a large quantity of waste materials to the deep open ocean areas.

A significant mass density increase during a large magnetic storm in October 2003 obtained by ground-based ULF observations at L ≈ 1.4

Abstract During 28–31 October, 2003, a series of coronal mass ejections hit the magnetosphere and triggered two consecutive large storms. Three ground magnetometers at L = 1.32–1.41 recorded field-line resonances (FLRs) during this interval. The FLR frequencies decreased from 0600 LT on 31 October 2003 during the main phase of the second storm until 12 LT when the recovery phase of this storm began. After the decrease, the FLR frequencies returned to its pre-storm value (at 0600 LT on 31 Oct.) in a few hours. The measured decrease in the FLR frequency suggests a relative increase in mass density along the field lines during the magnetic storm. On the other hand, the total electron content (TEC) data suggest that the ionospheric plasma number density during this storm was similar to that during quiet times. A possible explanation for the increase in mass density would be an outflow of the heavy ions (e.g., O+) from the ionosphere to the plasmasphere.

The ionosphere of Europe and North America before the magnetic storm of October 28, 2003

The X17 solar flare occurred on October 28, 2003, and was followed by the X10 flare on October 29. These flares caused very strong geomagnetic storms (Halloween storms). The aim of the present study is to compare the variations in two main ionospheric parameters (foF2 and hmF2) at two chains of ionosondes located in Europe and North America for the period October 23–28, 2003. This interval began immediately before the storm of October 28 and includes its commencement. Another task of the work is to detect ionospheric precursors of the storm or substorm expansion phase. An analysis is based on SPIDR data. The main results are as follows. The positive peak of δfoF2 (where δ is the difference between disturbed and quiet values) is observed several hours before the magnetic storm or substorm commencement. This peak can serve as a disturbance precursor. The amplitude of δfoF2 values varies from 20 to 100% of the foF2 values. The elements of similarity in the variations in the δfoF2 values at two chains are as follows: (a) the above δfoF2 peak is as a rule observed simultaneously at two chains before the disturbance; (b) the δfoF2 variations are similar at all midlatitude (or, correspondingly, high-latitude) ionosondes of the chain. The differences in the δfoF2 values are as follows: (a) the effect of the main phase and the phase of strong storm recovery at one chain differs from such an effect at another chain; (b) the manifestation of disturbances at high-latitude stations of the chain differ from the manifestations at midlatitude stations. The δhmF2 variations are approximately opposite to the δfoF2 variations, and the δhmF2 values lie in the interval 15–25% of the hmF2 values. The performed study is useful and significant in studying the problems of the space weather, especially in a short-term prediction of ionospheric disturbances caused by magnetospheric storms or substorms.

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.

Modeling and prediction of the magnetospheric dynamics during intense geospace storms

The nonlinear dynamical models of the coupled solar wind‐magnetosphere system derived from observational data have been used to yield efficient forecasts of the magnetospheric conditions. These data‐derived models have the advantage of capturing the essential features inherent in the data and thus can be improved as larger and better databases become available. Current models are based largely on the data of periods when the magnetosphere is weakly driven. For example, the widely used Bargatze et al. (1985) data set corresponds to a declining phase of the solar cycle and contains only a few weak storms. A correlated database of solar wind and magnetospheric time series data for the last solar cycle near its peak (year 2001) is compiled and used to model the magnetospheric dynamics under strong driving. The solar wind variables are obtained from ACE spacecraft, while the magnetospheric response consists of geomagnetic indices as well as magnetic perturbations measured by ground magnetometers. The dynamical models of the magnetosphere during superstorms developed with this database are used to forecast the geospace storms of October–November 2003 and April 2002 and yields improved forecasts of the intense storms. A new technique is introduced for data‐derived modeling based on the distances of the nearest neighbors from the current state. In this technique the contributions of the nearest neighbors are weighted by factors inversely proportional to the distances in the reconstructed phase space. This yields better predictions, especially during the strongly driven periods. The comparison of the models based on the year 2001 and Bargatze et al. (1985) databases show the similarities and differences in the magnetospheric states during solar maximum and minimum periods.