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In support of a multiagency project for assessing induction hazards, we present maps of extreme-value geoelectric amplitudes over about half of the continental United States. These maps are constructed using a parameterization of induction: estimates of Earth surface impedance, obtained at discrete geographic sites from magnetotelluric survey data, are convolved with latitude-dependent statistical maps of extreme-value geomagnetic activity, obtained from decades of magnetic observatory data. Geoelectric amplitudes are estimated for geomagnetic waveforms having 240 s sinusoidal period and amplitudes over 10 min that exceed a once-per-century threshold. As a result of the combination of geographic differences in geomagnetic activity and Earth surface impedance, once-per-century geoelectric amplitudes span more than 2 orders of magnitude and are an intricate function of location. For north-south induction, once-per-century geoelectric amplitudes across large parts of the United States have a median value of 0.26 Vkm; for east-west geomagnetic variation the median value is 0.23 Vkm. At some locations,once-per-century geoelectric amplitudes exceed 3 Vkm.

On 21 January 2005, a moderate magnetic storm produced a number of anomalous features, some seen more typically during superstorms. The aim of this study is to establish the differences in the space environment from what we expect (and normally observe) for a storm of this intensity, which make it behave in some ways like a superstorm. The storm was driven by one of the fastest interplanetary coronal mass ejections in solar cycle 23, containing a piece of the dense erupting solar filament material. The momentum of the massive solar filament caused it to push its way through the flux rope as the interplanetary coronal mass ejection decelerated moving toward 1 AU creating the appearance of an eroded flux rope (see companion paper by Manchester et al. (2014)) and, in this case, limiting the intensity of the resulting geomagnetic storm. On impact, the solar filament further disrupted the partial ring current shielding in existence at the time, creating a brief superfountain in the equatorial ionosphere—an unusual occurrence for a moderate storm. Within 1 h after impact, a cold dense plasma sheet (CDPS) formed out of the filament material. As the interplanetary magnetic field (IMF) rotated from obliquely to more purely northward, the magnetotail transformed from an open to a closed configuration and the CDPS evolved from warmer to cooler temperatures. Plasma sheet densities reached tens per cubic centimeter along the flanks—high enough to inflate the magnetotail in the simulation under northward IMF conditions despite the cool temperatures. Observational evidence for this stretching was provided by a corresponding expansion and intensification of both the auroral oval and ring current precipitation zones linked to magnetotail stretching by field line curvature scattering. Strong Joule heating in the cusps, a by-product of the CDPS formation process, contributed to an equatorward neutral wind surge that reached low latitudes within 1–2 h and intensified the equatorial ionization anomaly. Understanding the geospace consequences of extremes in density and pressure is important because some of the largest and most damaging space weather events ever observed contained similar intervals of dense solar material.

We examine a three-dimensional (3-D) numerical magnetohydrodynamic (MHD) simulation describing a very fast interplanetary coronal mass ejection (ICME) propagating from the solar corona to 1 AU. In conjunction with its high speed, the ICME evolves in ways that give it a unique appearance at 1 AU that does not resemble a typical ICME. First, as the ICME decelerates far from the Sun in the solar wind, filament material at the back of the flux rope pushes its way forward through the flux rope. Second, diverging nonradial flows in front of the filament transport poloidal flux of the rope to the sides of the ICME. Third, the magnetic flux rope reconnects with the interplanetary magnetic field (IMF). As a consequence of these processes, the flux rope partially unravels and appears to evolve to an entirely unbalanced configuration. At the same time, filament material at the base of the flux rope moves forward and comes in direct contact with the shocked plasma in the CME sheath. We find evidence that such remarkable behavior has actually occurred when we examine a very fast CME that erupted from the Sun on 2005 January 20. In situ observations of this event near 1 AU show very dense cold material impacting the Earth following immediately behind the CME sheath. Charge state analysis shows this dense plasma is filament material. Consistent with the simulation, we find the poloidal flux (Bz) to be entirely unbalanced, giving the appearance that the flux rope has eroded. The dense solar filament material and unbalanced positive IMF Bz produced a number of anomalous features in a moderate magnetic storm already underway, which are described in a companion paper by Kozyra et al. (2014).

A new scenario is presented for the cause of magnetospheric relativistic electron decreases (REDs) and potential effects in the atmosphere and on climate. High density solar wind heliospheric plasmasheet (HPS) events impinge onto the magnetosphere, compressing it along with remnant noon-sector outer-zone magnetospheric ~10-100 keV protons. The betatron accelerated protons generate coherent EMIC waves through a temperature anisotropy (T┴/T|| > 1) instability. The waves in turn interact with relativistic electrons and cause the rapid loss of these particles to a small region of the atmosphere. A peak total energy deposition of ~3 x 1020 ergs is derived for the precipitating electrons. Maximum energy deposition and creation of electron-ion pairs at 30-50 km and at

Several two-phase decay magnetic storms are examined using a kinetic transport model to find the spatial and temporal distribution of the perpendicular and field-aligned currents in the inner magnetosphere. The global morphology of these currents in the calculational domain (inside of geosynchronous orbit) is discussed as a function of storm epoch, obtaining good comparison between the numerically derived features and observed values of stormtime currents in this region. The model results are also consistent with quiet time plasma observations showing an increasing pressure in to L = 3 or 4, including a pressure maximum near midnight for the generation of region 2 Birkeland currents in the proper direction. A detailed analysis of the characteristic features of these currents is also presented and discussed. It is found that most of the ring current (>90%) during the main phase and early recovery phase is partial rather than symmetric, closing mostly (up to 90%) through field-aligned currents into the ionosphere. Conversely, the quiet time ring current is largely (>60%) symmetric, with most of the asymmetry produced by minor injections of near-Earth plasma sheet material. In general, the peak asymmetric current (which occurs during the main phase) is 2-3 times larger than the peak symmetric current (which occurs during the recovery phase) for any particular two-phase decay event. This is the case for all of the events studied, regardless of storm size, solar wind parameters, or solar cycle. The maximum azimuthal current (integrated over a local time slice) reaches 5 to 20 MA, compared with

During the rise to the maximum phase of solar cycle 23, several periods of extreme solar wind conditions have occurred. During such an example on May 4, 1998, the solar wind monitors observed a period of strong southward interplanetary magnetic field (IMF) accompanied by a solar wind dynamic pressure that was 30 times higher than average. During this period the Polar spacecraft crossed the magnetopause and bow shock and experienced its first solar wind encounter. This case provides a rare opportunity to study the magnetopause, low-latitude boundary layer, magnetosheath, and bow shock and to test our ability to model the dynamic behavior of these boundary regions under extreme and highly variable solar wind conditions. In this study we use the gas dynamic convected field model to predict the time-dependent magnetic field and plasma properties upstream from the magnetopause and the location of the Polar spacecraft relative to the magnetopause and bow shock during the event. To test the accuracy of the prediction, model magnetic field characteristics are compared to the fields observed along the satellite track by the magnetometer on Polar. The predicted model plasma characteristics (density, velocity, and temperature) are compared to moments derived from TIDE observations, extrapolated to account for the higher energy portion of the magnetosheath distributions. Where ambiguities occur in identifying the satellite location, plasma distribution functions from two additional ion detectors (TIMAS and HYDRA) are used to resolve the observed location of Polar relative to the boundaries. With this procedure, carried out separately for ACE and Wind and for two different magnetopause models, observed features at Polar can be traced back to drivers in the solar wind, providing a unique opportunity to assess the evolution of the solar wind and its predictability from the solar wind monitors to the magnetopause. When the Polar apogee drifts to low latitudes in the future, it will provide more and more observations in this region. Therefore what we learn from this case can be indicative of what we will see in the future in Polar operations. The high-level correlation between the predictions and in situ measurements indicates that the solar wind monitors often provide adequate and useful solar wind conditions near the Earth. The tests indicate that in this event the vacuum dipole field magnetosphere model predicts a significantly larger magnetosphere than observed. While the empirical magnetopause model predictions are more consistent with the observations, they overpredict the response of the magnetosphere to transient southward turnings of the IMF, indicating that the magnetosphere does not respond to the southward IMF turnings on small timescales. Sometimes, there are significant differences at relatively small time scales between the measurements from the two solar wind monitors. It is possible for the solar wind conditions near the Earth to be different from the measurements made by at least one of the solar wind monitors. Cautions should be taken when interpreting near-Earth observations if the observations are inconsistent at small timescales with the predictions based on one solar wind monitor.

Three storms are examined to determine the contribution to the Dst* index from the symmetric and asymmetric (partial) components of the ring current. The storms (September 24–25, 1998, October 18–19, 1998, and May 14–15, 1997) all have a similar solar wind trigger (an initial shock followed by a coronal mass ejection with southward interplanetary magnetic field) and placement in the solar cycle (rising phase). The near-Earth ion distribution function is simulated for each storm using a kinetic transport model. The use of a McIlwain magnetospheric electric field description improves the simulation results over the Volland-Stern field used previously. It is found that most of the main phase magnetic field depression is due to the asymmetric component of the ring current (≥80% at the Dst* minimum for the three storms). Note that this is a minimum asymmetric ring current contribution, because the closed-trajectory ions may also be spatially asymmetric. Ions in the partial ring current make one pass through the inner magnetosphere on open drift paths that intersect the dayside magnetopause. Changes in the density of the inner plasma sheet are transmitted directly along these open drift paths. For a steady convection field, an increase in the source population produces a decrease (more intense perturbation) in Dst*, while a decrease produces a Dst* recovery. As the storm recovery proceeds, a decrease in the electric field results in a conversion of open to closed drift paths, forming a trapped, symmetric ring current that dominates Dst*. The mostly H+ composition of the ring current for all three storms rules out the possibility of differential charge exchange being the cause of the fast and slow decay timescales, confirming that outflow is the main loss of ring current-generated Dst* during the early phase decay. The slow decay timescale in the late recovery, however, is dominated by charge exchange with the hydrogen geocorona. The symmetric-asymmetric ring current is also placed in the context of the solar wind and plasma sheet drivers.

To quantify the energy input to the thermal electrons due to Coulomb collisional degradation of hot ions in the inner magnetosphere, the heating rate is calculated from the results of a time-dependent kinetic ring current model. The large June 4–7, 1991, storm during the last solar maximum, when the hot O+ content is maximal, is chosen for this study. Modeled electron heat fluxes into the topside ionosphere reach 1011 eV cm−2 s−1 on the dusk side, a large value that will certainly have an impact on the density, temperature, and composition of the upper ionosphere and thermosphere. Comparable maximum values of heat inputs to the inner magnetospheric thermal plasma are expected to arise again during storms of the present solar maximum. The calculated heating rates from the ring current simulations are compared directly with detailed ionospheric modeling results for the Millstone Hill field line (L = 3). It is seen that heating from the ring current is more than adequate to account for the nightside topside heat input necessary to obtain the observed electron temperatures during this storm, even taking into account the limitations of the comparison. The reason for this is the abundance of O+ in the ring current at energies of a few tens of keV deep in the inner magnetosphere.

The global evolution of an artificially injected relativistic electron beam is simulated and examined. The study focuses on injections originating in the upper ionosphere, magnetically mirroring above the lower atmosphere where significant energy loss occurs, and so a long-lived population arises in the inner magnetosphere from this particle source. This investigation is conducted by solving the bounce-averaged relativistic kinetic equation for the electron distribution function for various L shells. It is found that the beam quickly spreads in MLT due to differential drift rates, eventually morphing into a fairly uniform shell around the Earth. Wave interactions are comparable to collisional losses in reducing the beam content. It is also found that the beam total particle loss rate is a complicated function of L and, for the chosen conditions, the total beam particle counts are 73%, 77%, and 52% of the initial count at t=24 hours after injection for L=2, 3, and 4, respectively. The loss rates at this time are ∼1%/hour (of the remaining beam strength) and very slowly decreasing with time. These loss rates and other features of the beam evolution are discussed in detail. There are now four distinct stages recognized in the evolution of an injected relativistic beam: (1) the immediate loss of particles injected at pitch angles mapping to the lower thermosphere; (2) the initial loss of particles injected right next to the loss cone by collisional scattering; (3) the continuation of this collisional loss along with the spread of the beant to all local times by differential drift rates; and (4) the transformation of the beam into a fairly uniform shell covering all energies and all local times, with the loss rate mainly governed by wave scattering. Other stages may exist beyond the 1-day limit set on these simulations. While the study dwells on beam dynamics, it is also a general examination of the leading edge population next to the loss cone. This has implications for the physics of the naturally occurring radiation belt particles, as this region of phase space regulates the actual precipitation of these particles into the atmosphere. The applicability of this model for studying the natural radiation environment around the Earth is also pondered.

A time-dependent kinetic model is used to investigate the relative importance of various mechanisms in the early phase decay rate of the ring current. It is found that, for both the solar maximum storm of June 4–7, 1991 and especially the solar minimum storm of September 24–27, 1998, convective drift loss out the dayside magnetopause is the dominant process in removing ring current particles during the initial recovery. During the 1998 storm, dayside outflow losses outpaced charge exchange losses by a factor of ten.

A new time-dependent kinetic model is used to investigate the effects of self-consistency and hot plasma influences on plasmaspheric refilling. The model employs a direct solution of the kinetic equation with a Fokker-Planck Coulomb collision operator to obtain the phase space distribution function of the thermal protons along a field line. Of particular interest is the influence of several processes on the source cone distribution function formation. It is found that a self-consistent ion temperature in the collision term can increase or decrease the equatorial plane density, depending not only on the choice of ion temperature in the static-background calculations but also on the form of the nonlinear representation. The inclusion of a self-consistent polarization electric field increases the early stage equatorial plane density by a factor of 2. Investigations of the effects of anisotropic hot plasma populations on the refilling rates shows that, after a slight initial decrease in equatorial density from clearing out the initial distribution, there is a 10 to 30% increase after 4 hours due to these populations. This increase is due primarily to a slowing of the refilling streams near the equator from the reversed electric field.

Relativistic electron beam injection simulation results are presented from a new interhemispheric transport model, with a spatial domain reaching from 90 km to 90 km in the conjugate ionospheres. A single beam pulse is injected upward at 700 km during the first time step (10 -4 s) and allowed to scatter and decay through collisional interactions with neu- tral particles and the core plasma. The maximum pulse dura- tion for collisional processes to prevail over the wave-beam instabilities is estimated, and the assumed pulse length is well within this limit. For an L=2 field line, the e-folding time of a 5 MeV beam is 265 s, which is much bigger than the bounce period (0.19 s) and comparable to drift period around the Earth.

The growth and recovery of the November 2–6, 1993 magnetic storm was simulated using a drift-loss ring current model that was driven by dynamic fluxes at geosynchronous orbit as an outer boundary condition. During the storm main phase, a high-density plasma sheet was observed by the Los Alamos National Laboratory geosynchronous satellites to move into and flow around the inner magnetosphere over a period of ∼12 hours [Borovsky et al., 1997; this issue] during the storm main phase. Densities at the leading edge of this structure reached 3 cm−3 as compared with more typical values

The possible role of precipitation losses in eroding stormtime ring current is subject to debate. To explore this controversy, the recovery phase of the February 6–10, 1986, great magnetic storm is examined, when intense ion precipitation was observed at midlatitudes by NOAA-6 and DMSP satellites. This storm period is particularly interesting because the ring current exhibits distinctive two-phase decay as seen in the Dst index, the early rapid timescale decay corresponding to the intense ion precipitation period described above. Hamilton et al. [1988] concluded, from close agreement between the observed timescale for ring current decay and the theoretical timescale for O+ charge exchange loss, that rapid early recovery phase of this storm resulted from the charge exchange loss of high energy O+; the second and longer decay phase was equated with H+ charge exchange loss. A model of the ring current evolution during this great magnetic storm [Fok et al., 1995] failed to reproduce the observed ring current decay rates, a puzzling result because charge exchange losses were well represented in the ring current model and initial and boundary conditions were taken from the same data set used in the Hamilton et al. [1988] study. A simple energy balance calculation for the global ring current is carried out using (1) either an energy input predicted from upstream solar wind parameters or one calculated from the drift-loss model output, (2) collisional loss timescales extracted from the drift-loss model, and (3) precipitation losses estimated from NOAA-6 and DMSP observations. The energy balance model replicates the evolution of the ring current energy content derived from Active Magnetospheric Particle Tracer Explorers/Charge Composition Explorer (AMPTE/CCE) observations when ion precipitation losses are included and model energy input function is reduced to agree with predictions based upon upstream solar wind parameters. The O+ charge exchange losses and observed global precipitation losses were of equal magnitude in early recovery of the ring current during this great magnetic storm. Later longer decay timescales in the model resulted from a combination of O+ and H+ charge exchange losses; O+ charge exchange losses remained important throughout the model time interval. The present model produces agreement with the AMPTE/CCE estimates of ring current kinetic energy content versus time. Disagreement between the Dst* inferred from the AMPTE/CCE particle measurements and the observed Dst* is an interesting issue needing further explanation.

Under the proper conditions, guided plasmaspheric hiss is shown to be more efficient than Coulomb collisions at scattering electrons in the superthermal energy range of 50 to 500 eV. Broadband, whistler mode hiss becomes guided by plasma density gradients, intensifying the wave energy densities and focusing the wave normal angles. These waves are shown to interact through Cherenkov (Landau) resonance with electrons below 500 eV, and the presented equatorial plane timescales for pitch angle, energy, and mixed diffusion are shown to be faster than Coulomb collision timescales for typical values at the inner edge of the plasmapause and in detached plasma regions. In the latter case, energy diffusion timescales of less than 100 s for small pitch angle electrons between 250 and 500 eV indicate that these waves have the potential to dramatically change the distribution function.

Our numerical model of the ring current-atmosphere coupling (RAM) is further developed in order to include wave-particle interaction processes. The model calculates the time evolution of the phase space distribution function in the region from 2 RE to 6.5 RE, considering losses due to charge exchange, Coulomb collisions, and plasma wave scattering along ion drift paths. The spatial regions of ion cyclotron wave instability are determined by calculating the convective growth rates for electromagnetic ion cyclotron (EMIC) waves, integrating them along wave paths, and selecting regions of maximum wave amplification. The source regions are located on the duskside in agreement with the predominant occurrence of EMIC waves. A spectral power density of 1 nT2/Hz is adopted within the unstable regions. According to quasi-linear theory, the fluctuating fields are regarded as imposed on the system, and the losses due to wave-particle interactions are described with diffusive processes. The effects of the presence of heavy ion components on the quasi-linear diffusion coefficients are also considered. Resonance with ion cyclotron waves reduce the anisotropy of the proton population and the unstable regions disappear with time. Global patterns of precipitating ion fluxes are obtained and compared with observations.

Ion composition measurements provided by recent satellite missions have confirmed the presence of heavy ions in the terrestrial magnetosphere. In order to describe the resonance of energetic ring current particles with electromagnetic ion cyclotron (EMIC) waves in a more realistic terrestrial environment, general expressions are derived that provide quasi-linear diffusion coefficients in a cold plasma containing heavy ions. Cold plasma theory is used as a first approximation. In such plasma, EMIC waves do not propagate in the frequency range between the ion gyrofrequency and the cutoff frequency for each ion component but form multiple stop bands. No interactions occur within the stop bands and the diffusion coefficients are zero over the corresponding frequency intervals. For most of the wave frequencies of interest, the particles in a multicomponent plasma resonate at lower parallel energies than particles in an electron-proton plasma for a given harmonic value. Therefore resonance with a fixed frequency wave occurs at larger pitch angles (lower parallel energies) in a multi-ion than in a proton-electron plasma. As a direct consequence, pitch angle diffusion coefficients for a given energy decrease at small pitch angles and increase at large pitch angles as heavy ions are added to the plasma. The energy and mixed diffusion coefficients change correspondingly. Also, higher harmonics need to be included in the calculations for resonances at higher energies. The pitch angle diffusion lifetimes are calculated for given plasmaspheric and wave parameters corresponding to conditions at a radial distance L=4. The values of the diffusion lifetimes decrease at low energies and increase at high energies in a multi-ion as compared to an electron-proton plasma. As a result, the resonances at lower energies (∼ approximately tens of keV) will contribute to the ion precipitation losses from the ring current during geomagnetic storms.

The time evolution of the ring current population during the recovery phase of a typical moderate magnetic storm is studied, using a newly developed kinetic model for H+, He+ and O+ ions which includes nonequatorially mirroring particles. The bounce-averaged distribution function is defined for variables that are accessible to direct measurement, and some useful formulas for calculating the total energy and number density of the ring current are derived. The bounce-averaged kinetic equation is solved, including losses due to charge exchange with neutral hydrogen and Coulomb collisions with thermal plasma along ion drift paths. Time-dependent magnetospheric electric fields and anisotropic initial pitch angle distributions are considered. The generation of ion precipitating fluxes is addressed, a process that is still not completely understood. It is shown that both the decrease of the distribution function due to charge exchange losses and the buildup of a low-energy population caused by Coulomb collisions proceed faster for particles with smaller pitch angles. The maximum of the equatorial precipitating fluxes occurs on the nightside during the early recovery phase and is found to be of the order of 104–105 cm−2sr−1s−1keV−1. The mechanisms considered in this paper indicate that magnetospheric convection plays the predominant role in causing ion precipitation; Coulomb scattering contributes significantly to the low-energy ion precipitation inside the plasmasphere.

[1] Frequency-banded electromagnetic VLF waves up to 2000 Hz are observed concurrently with warm (10 s to 10,000 s of eV) energy-banded ions in the low latitude auroral and sub-auroral zones during every large geomagnetic storm encountered by the FAST and DEMETER satellites. The banded ions and waves persist for several FAST or DEMETER orbits, lasting up to 12 h, in both dawn and dusk sectors, in both the northern and southern hemispheres. If the waves are generated at harmonics of the proton gyrofrequency, the inferred source region would be ∼4000 km altitude. Previous investigations have shown that such waves can propagate from this source region to the locations of both spacecraft. An investigation into the growth of waves at harmonics of fci in the inferred source region suggests that these emissions could be generated by ion bands similar to those observed at the same time as the waves. Magnetospheric waves such as these play a role in energy transfer between distinct particle populations and may contribute to ion heating and ion outflow as well as electron energization. All of these phenomena occur during the strongest magnetic storms. The appearance of the banded ions and associated wave activity suggests that there may be distinct changes in the geospace system that characterize large magnetic storms.

A bounced-averaged ring current kinetic model for arbitrary pitch angle, including losses due to charge exchange and Coulomb collisions along ion drift paths, is developed and solved numerically. Results from simplifield model runs, intended to illustrate the effects of adiabatic drifts and collisional losses on the proton population, are presented. The processes of: (1) particle acceleration under the conditions of time-independent magnetospheric electric fields; (2) a predominant loss of particles with small pitch angles due to charge exchange; and (3) a buildup of a low-energy population caused by the Coulomb drag energy degradation, are discussed.

[1] Inner magnetospheric numerical simulations of the 17 April 2002 storm are conducted to explore the importance of transient spikes in the driving parameters at controlling the strength of the storm time ring current. The two main factors considered in this study are convection electric field strength and nightside plasma boundary condition. These quantities were smoothed and/or despiked across intervals of 20–180 min. It is found that the spikes contribute linearly to the ring current total energy content. Exceptions to this finding include too much resulting ring current after despiking or smoothing (relative to a linear response). This indicates that at best the relationship is linear and, if the timing of transient spikes in one driving parameter is not coincident with high values in the other main driving parameter, then the response is sublinear (that is, the transient spikes could be less effective than long-time duration increases in the input parameters).

The decay of the major ion species which constitute the ring current is studied by solving the time evolution of their distribution functions during the recovery phase of a moderate geomagnetic storm. In this work, only equatorially mirroring particles are considered. Particles are assumed to move subject to E x B and gradient drifts. They also experience loses along their drift paths. Two loss mechanisms are considered: charge exchange with neutral hydrogen atoms and Coulomb collisions with thermal plasma in the plasmasphere. Thermal plasma densities are calculated with a plasmaspheric model employing a time-dependent convection electric field model. The drift-loss model successfully reproduces a number of important and observable features in the distribution function. Charge exchange is found to be the major loss mechanism for the ring current ions; however the important effects of Coulomb collisions on both the ring current and thermal populations are also presented. The model predicts the formation of a low-energy (less than 500 eV) ion population as a result of energy degradation caused by Coulomb collision of the ring current ions with the plasmaspheric electrons; this population may be one source of the low-energy ions observed during active and quiet periods in the inner magnetosphere. The energy transferred to plasmaspheric electrons through Coulomb collisions with ring current ions is believed to be the energy source for the electron temperature enhancement and the associated 6300 A (stable auroral red (SAR) arc) emission in the subauroral region. The calculated energy deposition rate is sufficient to produce a subauroral electron temperature enhancement and SAR arc emissions that are consistent with observations of these quantities during moderate magnetic activity levels.

[1] The Analyzer of Space Plasmas and Energetic Atoms (ASPERA-4) instrument on Venus Express is used to determine bow shock position at Venus using ion data alone, using data recorded during a solar minimum from the Ion Mass Analyzer (IMA) which is part of the ASPERA-4 package. Previous models constructed from solar minimum data using Venus Express, Pioneer Venus Orbiter (PVO) and Venera 9 and 10 are also compared to the current fit. An important feature of this new fit is a statistical accuracy introduced in the form of a probability weighting function for the data points, based on the time spent in particular locations. The bow shock curve is then compared to two-dimensional ion maps. These verify the accuracy of this and previous solar minimum fit curves based on PVO and Venus Express magnetic data. Comparing all bow shock models to the 2D ion maps shows that a combination of models produces the best fit. Since all the fitted curves show differences in position they are investigated relative to the solar conditions pertaining at the times when the individual data sets were measured. The sub solar point and terminator distance were thus found to vary linearly with sunspot number and hence with solar activity. This relationship, which was already known to exist between solar maximum and solar minimum, is now shown to exist between different solar minima and even within the same minimum. This indicates a need for the mechanisms for bow shock maintenance and variance to be more closely modeled.

coronal holes lingered even as the sunspots disappeared. Consequently, for the months surrounding the WHI campaign, strong, long, and recurring high-speed streams in the solar wind intercepted the Earth in contrast to the weaker and more sporadic streams that occurred around the time of last cycle’s WSM campaign. In response, geospace and upper atmospheric parameters continued to ring with the periodicities of the solar wind in a manner that was absent last cycle minimum, and the flux of relativistic electrons in the Earth’s outer radiation belt was elevated to levels more than three times higher in WHI than in WSM. Such behavior could not have been predicted using sunspot numbers alone, indicating the importance of considering variation within and between solar minima in analyzing and predicting space weather responses at the Earth during solar quiet intervals, as well as in interpreting the Sun’s past behavior as preserved in geological and historical records.

[1] A low-dimensional, plasma physics-based, nonlinear dynamical model of the coupled magnetosphere-ionosphere system, called Real-Time Solar Wind Magnetosphere-Ionosphere System (WINDMI), is used to predict AL and Dst values approximately 1 h before geomagnetic substorm and storm event. Subsequently, every 10 min ground-based measurements compiled by World Data Center, Kyoto, are compared with model predictions (http://orion.ph.utexas.edu/� windmi/realtime/). WINDMI model runs are also available at the Community Coordinated Modeling Center (http://ccmc.gsfc.nasa.gov/). The performance of the Real-Time WINDMI model is quantitatively evaluated for 22 storm/substorm event predictions from February 2006 to August 2008. Three possible input solar wind-magnetosphere coupling functions are considered: the standard rectified coupling function, a function due to Siscoe, and a recent function due to Newell. Model AL and Dst predictions are validated using the average relative variance (ARV), correlation coefficient (COR), and root mean squared error (RMSE). The Newell input function yielded the best model AL predictions by all three measures (mean ARV, COR, and RMSE), followed by the rectified, then Siscoe input functions. Model AL predictions correlate at least 1 standard deviation better with the AL index data than a direct correlation between the input coupling functions and the AL index. The mean Dst ARV results show better prediction performance for the rectified input than the Siscoe and Newell inputs. The mean Dst COR and RMSE measures do not readily distinguish between the three input coupling functions.

We analyze in detail the February 2004 Global Ozone Monitoring by Occultation of Stars (GOMOS) NO2 observations in the northern polar latitudes during the springtime descent of NOx from the mesosphere into the stratosphere. We combine GOMOS observations with SABER-observed NO 5.3 mu m radiated power and an AARDDVARK-derived radio wave index (RWI) to describe the impact of the 11 February geomagnetic storm. Energetic electron precipitation generated some additional NOx, supplementing the original amounts that were already descending. At altitudes of 50-70 km, GOMOS observations of NO2 showed a delayed response to the geomagnetic storm, with NO2 being generated 3 days after the start of the storm. The delayed response and duration of NO2 production was found to be consistent with the increase in the flux of relativistic electrons measured by GOES at geostationary orbit and by POES through relativistic electron contamination of the >16 MeV proton channel. Using the Sodankyla Ion and Neutral Chemistry model (SIC), we found that a good fit to the observed NO2 mixing ratios at the peak of the geomagnetic storm effect was produced by a monoenergetic 1.25 MeV electron beam with a flux of similar to 0.3 x10(6) el cm(-2) sr(-1) s(-1) keV(-1) or with a "hard'' electron spectra taken from Gaines et al. (1995) but with fluxes enhanced by a factor of 15, i.e., 8 x 10(4) el cm(-2) sr(-1) s(-1) for 2-6 MeV. Prior to the storm the descending NO2 had average mixing ratio values of similar to 150 ppbv. The geomagnetic storm-induced relativistic electron precipitation event doubled the amount of NOx descending into the stratosphere to similar to 300 ppbv after the storm.

We examine time series of the daily global power (W) radiated by carbon dioxide (at 15 microns) and by nitric oxide (at 5.3 microns) from the Earth s thermosphere between 100 km and 200 km altitude. Also examined is a time series of the daily absorbed solar ultraviolet power in the same altitude region in the wavelength span 0 to 175 nm. The infrared data are derived from the SABER instrument and the solar data are derived from the SEE instrument, both on the NASA TIMED satellite. The time series cover nearly 5 years from 2002 through 2006. The infrared and solar time series exhibit a decrease in radiated and absorbed power consistent with the declining phase of the current 11-year solar cycle. The infrared time series also exhibits high frequency variations that are not evident in the solar power time series. Spectral analysis shows a statistically significant 9-day periodicity in the infrared data but not in the solar data. A very strong 9-day periodicity is also found to exist in the time series of daily A(sub p) and K(sub p) geomagnetic indexes. These 9-day periodicities are linked to the recurrence of coronal holes on the Sun. These results demonstrate a direct coupling between the upper atmosphere of the Sun and the infrared energy budget of the thermosphere.

[1] We report a newly created highly parallelized global test particle model for resolving the pickup oxygen ion distribution around Mars. The background magnetic and convection electric fields are calculated using a three-dimensional multispecies magnetohydrodynamic model, which includes the effect of the Martian crustal magnetic field. In addition to photo-ionization, charge exchange collisions and solar wind electron impact ionization are included for the pickup ion generation. The most novel feature of our model is that more than one billion test particles are launched in the simulation domain in total. This corresponds to a profound enhancement by at least 3 orders of magnitude in the total number, compared to all existing test particle models. This substantial improvement enables an unprecedented examination of the pickup ion flux distribution in velocity space, which is not achievable in previous simulation studies due to the insufficient statistics arising from the limited number of test particles. Using the velocity space distribution of pickup O + ions as a tool, the Mars-solar wind interaction can be investigated in a unique way. It is shown that the velocity space distribution is highly non-Maxwellian, exhibiting non-gyrotropic and non-symmetric distributions, including many beam-like features. In the tail region, pickup ions have a prominent outflowing component in the whole energy range. The energy examination of particles traveling across the tail region shows that the acceleration highly depends on the source region where the particles originate. The strong convection electric field in the magnetosheath region is favorable to the pickup ion acceleration.

The complex interplanetary structures during 7 to 8 Nov 2004 are analyzed to identify their properties as well as resultant geomagnetic effects and the solar origins. Three fast forward shocks, three directional discontinuities and two reverse waves were detected and analyzed in detail. The three fast forward shocks 'pump' up the interplanetary magnetic field from a value of approx.4 nT to ~44 nT. However, the fields after the shocks were northward, and magnetic storms did not result. The three ram pressure increases were associated with major sudden impulses (SI + s) at Earth. A magnetic cloud followed the third forward shock and the southward Bz associated with the latter was responsible for the superstorm. Two reverse waves were detected, one at the edge and one near the center of the magnetic cloud (MC). It is suspected that these 'waves' were once reverse shocks which were becoming evanescent when they propagated into the low plasma beta MC. The second reverse wave caused a decrease in the southward component of the IMF and initiated the storm recovery phase. It is determined that flares located at large longitudinal distances from the subsolar point were the most likely causes of the first two shocks without associated magnetic clouds. It is thus unlikely that the shocks were 'blast waves' or that magnetic reconnection eroded away the two associated MCs. This interplanetary/solar event is an example of the extremely complex magnetic storms which can occur in the post-solar maximum phase.

[1] Plasma measurements at geosynchronous orbit are examined via superposed epoch analysis for various storm categories to assess whether superstorms have an unusually altered source population for the storm-time ring current. It is found that certain characteristics of this near-Earth plasma distribution during superstorms are similar to those of moderate or intense storms, or extensions of the trends seen in these lesser storms. These similarities include the dawn sector development of cold, dense plasma. However, other characteristics are unique to superstorms, such as the existence of cold, dense plasma at dusk and midnight. It is concluded that the ring current source during superstorms is a combination of the usual storm-time characteristics as well as an unusually altered component.

[1] Magnetohydrodynamic (MHD) simulations of the Mars magnetic field topology are presented for the auroral observations reported from the Mars Express SPICAM instrument. It is found that the field lines closest to the assumed emission location are open. That is, they are connected to the interplanetary magnetic field, thus allowing access for solar wind electrons to bombard the upper atmosphere and create a auroral-like emission. The most likely population responsible for the creation of the emissions recorded by SPICAM is magnetosheath electrons. It is found that numerous closed magnetic field lines, connected to two strong crustal field regions, can straddle the terminator, leaving open the speculation that atmospheric photoelectrons could be responsible for nightside auroral-like emissions. However, for the particular case of the initially reported SPICAM auroral observations, the MHD results do not produce such terminator-crossing field lines near the emission region.

[1] It is well-known that the effects of electromagnetic ion cyclotron (EMIC) waves on ring current (RC) ion and radiation belt (RB) electron dynamics strongly depend on such particle/wave characteristics as the phase-space distribution function, frequency, wave-normal angle, wave energy, and the form of wave spectral energy density. The consequence is that accurate modeling of EMIC wave spatialtemporal-spectral distributions and RC particles requires robust inclusion of the interdependent dynamics of wave growth/damping and wave propagation/refraction/reflection, along with wave tunneling and mode conversion and particles. Such a self-consistent RC-EMIC wave model is being progressively developed by Khazanov et al. [2002, 2003a, 2006, 2007]. This model is based on a system of coupled kinetic equations for the RC and EMIC wave power spectral density with explicit inclusion of the ray tracing equations. [2] The theoretical formalism for RC ions and RB electrons is well established and is based on gyroaveraged and bounce-averaged kinetic equations that have been developed over the years and systemized in the book by Khazanov [1979]. The application of this formalism to RC ions was continued by Khazanov and Kozyra at the University of Michigan during 1991–1994 and formed a large part of the Ph.D. dissertation work of Fok [1993] and of Jordanova [1995]. Khazanov et al. also applied this formalism to the study of ionosphere-plasmasphere transport of suprathermal electrons [Khazanov et al., 1992, 1994], and global photo [Khazanov et al., 1996; Khazanov and Liemohn, 2002] and plasma sheet [Khazanov et al., 1998] electron transport. This formalism was also generalized to study relativistic electron transport [Khazanov et al., 1999, 2000], as well as different aspects of RC and RB electron formation using various magnetospheric electric and magnetic field topologies [Khazanov et al., 2003b, 2004b, 2004c]. All these above-mentioned studies are the heritage of our RC-EMIC wave model that was presented by Khazanov et al. [2006]. [3] Thorne and Horne [2007, hereinafter referred to as TH2007] call the Khazanov et al. [2002, 2006] results into question in their Comment. The points in contention can be summarized as follows. TH2007 claim that (1) important damping of waves by thermal heavy ions is treated incorrectly in our model, and Landau damping during resonant interaction with thermal electrons is not included; (2) EMIC wave damping due to RC O is not included in our simulation of the 2–7 May 1998 storm; (3) nonlinear processes limiting EMIC wave amplitude are not included in our model; (4) growth of the background electromagnetic fluctuations to a physically significant amplitude must ‘‘occur during a single transit of the unstable region’’ with subsequent damping in the vicinity of the bi-ion latitude, and consequently the bounce-averagedwave kinetic equation employed in the code is not valid. Our reply will address each of these points as well as other criticisms mentioned in the Comment. [4] TH2007 is focused on two of our papers that are separated by 4 years. Significant progress in the selfconsistent treatment of the RC-EMIC wave system has been achieved during those years. The paper by Khazanov et al. [2006] presents the latest version of our model, and in this Reply we refer mostly to this paper.

[1] NOAA Polar Orbiting Environmental Satellites 30–240 keV proton precipitation measurements in the 17–18 April 2002 geomagnetic storms are used with a Monte Carlo ion transport model to obtain ionization and heating rates that are subsequently fed into the Global Ionosphere Thermosphere Model to investigate the proton impact on the ionosphere and thermosphere. Simulation results show that after the addition of proton precipitation in a moderate geomagnetic storm (specifically, the one during mid-April 2002), there are places at low altitudes (100–120 km) on the nightside undergoing significant increases in electron and nitric oxide (NO) densities. The enhancement can be as large as several factors or even by an order of magnitude. Moreover, the temporal profiles of the enhancement in ionospheric electron densities demonstrate a direct correlation with proton precipitation imposed on the topside boundary, and there is no integral effect. This is in contrast with a continuous buildup process illustrated in the time variation of the thermospheric NO density enhancement because NO at these altitudes has a long lifetime. In addition, by including high-energy precipitating protons in a global ionosphere thermosphere coupled model, significant changes take place in the ion convection (locally around ±20%) and in the neutral winds (locally around ±40%). This study represents the first attempt to understand the global influence of proton precipitation on the ionosphere and thermosphere using in situ observational data.

[1] The question of how much interplanetary shock (IP) events contribute to the geoeffectiveness of solar wind drivers is assessed through numerical experiments using the WINDMI model, a physics-based model of the solar wind-driven magnetosphere-ionosphere system. Analytic fits to solar wind input parameters (B⊥IMF, usw, nsw) allowed shocks and associated shock-sheath plasma to be removed while leaving other features of the solar wind driver undisturbed. Percent changes in WINDMI-derived AL and Dst indices between runs with and without the observed shock and sheath signatures were taken as a measure of its relative contribution to the geoeffectiveness. The major magnetic storms during 15–24 April 2002 and 3–6 October 2000 were selected for this experiment. In both cases, the IP shock and sheath features contributed significantly to the geoeffectiveness of the solar wind driver. The magnetic field compressional jump is important to producing the changes in the AL during these two storm intervals.

[1] Global 30–240 keV proton precipitation patterns during the 17–18 April 2002 magnetic storm events were generated using newly developed 3-hour data products of the medium energy proton and electron detector (MEPED) on board the NOAA-15 and -16 satellites. The observational data set was sorted in 1-degree corrected magnetic latitude (CML) and 8-min magnetic local time (MLT) bins. To achieve global coverage, the missing MLT data were filled by interpolation techniques in each 1-degree CML interval. The resulting global 30–240 keV proton precipitation maps, available on a 3-hour cadence, provide new information on the development and variability in the structure of incident high-energy protons on a timescale commensurate with the growth and decay of the plasma sheet and ring current. The change of energetic proton precipitation patterns in the April 2002 storms is quantified in terms of three aspects: hemispheric integrated total particle energy input, midnight proton oval equatorward boundary, and position of proton precipitation peak. In a general sense, as magnetospheric activity intensified, the midnight equatorward boundary tended to move to the lower latitude, while the precipitation peak moved equatorward and westward away from midnight, in agreement with ring current motion. It is well illustrated that energetic proton precipitation patterns can serve as a valuable diagnostic tool for investigating the inner magnetospheric activity.

[1] We investigate the global Pedersen and Hall conductance distribution during the 17–18 April 2002 geomagnetic storms by combining NOAA/POES 30–240 keV proton precipitation measurements with three-dimensional (3-D) particle transport modeling. Significant conductances are generated due to energetic proton precipitation in the selected storms, with peak values up to ∼10 S in the dusk sector. The effect of horizontal beam spread on the conductances, which is a unique feature of ion precipitation, is first assessed in this paper. It is found that with the neglect of the beam spread, an overestimation (up to 10%) occurs at the center of the major proton precipitation region. At the edge (particularly at the equatorward edge), a severe underestimation (around −50% or worse) is induced. Moreover, 3-D scattering extends the equatorward edge of the high conductance region down to around 55° magnetic latitude in the storms. A significance domain (up to 4.4°) exists equatorward of the peak proton precipitation region, in which significant conductances would be seriously underestimated without the beam spreading effect. It is also found that the beam spreading effect is more significant for the Pedersen conductances than for the Hall conductances because of the altitude dependence of both the conductivity profiles and the spreading. The findings emphasize the role of proton precipitation as well as its associated beam spreading, especially at the equatorward edge of the precipitation zone in the evening sector, where proton precipitation-produced conductivity can influence storm-time phenomena, such as subauroral polarization streams, ionospheric storm enhanced density structures, and inner magnetospheric plasma dynamics (i.e., the ring current and plasmasphere).

location of the plasmapause gradient. The strongest fluxes of about 4 � 10 6 (cm 2 s sr) � 1 are observed during the main and early recovery phases of the storm. The very interesting and probably more important finding is that in a number of cases the most intense precipitating fluxes are not connected to the most intense waves in simple manner. The characteristics of the wave power spectral density distribution over the wave normal angle are extremely crucial for the effectiveness of the ring current ion scattering. Second, comparison of the global proton precipitating patterns with the results from RAM (Kozyra et al., 1997a) reveals that although we observe a qualitative agreement between the localizations of the wave induced precipitations in the models, there is no quantitative agreement between the magnitudes of the fluxes. The quantitative differences are mainly due to a qualitative difference between the characteristics of the wave power spectral density distributions over the wave normal angle in RAM and in our model. Third, the heat fluxes to plasmaspheric electrons caused by Landau resonate energy absorption from electromagnetic ion cyclotron waves are observed in the postnoon-premidnight MLT sector and can reach the magnitude of 10 11 eV/(cm 2 s). The Coulomb energy degradation of the RC H + and O + ions maximizes at about 10 11 eV/(cm 2 s) and typically leads to electron energy deposition rates of about 2 � 10 10 eV/(cm 2 s) which are observed during two periods, 32–48 hours and 76–86 hours after 1 May, 0000 UT. The theoretically derived spatial structure of the thermal electron heating caused by interaction of the ring current with the plasmasphere is strongly supported by concurrent and conjugate plasma measurements from the plasmasphere, ring current, and topside ionosphere (Gurgiolo et al., 2005). Finally, the wave induced intense electron heating has a structure of the spot-like patches along the most enhanced density gradients in the plasmasphere boundary layer and can be a possible driver of the observed but still not explained smallscale structures of enhanced emissions in the stable auroral red arcs.

[1] A computationally optimized low-dimensional nonlinear dynamical model of the magnetosphere-ionosphere system called WINDMI is used to analyze two large geomagnetic storm events, 3–7 October 2000 and 15–24 April 2002. These two important storms share common features such as the passage of magnetic clouds, shock events from coronal mass ejections, triggered substorms, and intervals of sawtooth oscillations. The sawtooth oscillations resemble periodic substorms but occur in association with strong or building ring current populations and have injection regions that are unusually close to the Earth and unusually wide in magnetic local times (Henderson et al., 2006; Borovsky et al., 2007). The April 2002 event includes one of the best examples of sawtooth events ever observed. On 18 April 2002, sawtooth oscillations were clearly visible when solar wind conditions (IMF Bz, density, pressure) were relatively steady with a slowly varying Dst. In this study, WINDMI is used to model the 3–7 October 2000 and 15–24 April 2002 geomagnetic activity. WINDMI results are evaluated focusing on the sawtooth intervals and the overall prediction of the westward auroral electrojet (AL) index and Dst index. The input to the model is the dynamo driving voltage derived from the fluctuating solar wind plasma and the interplanetary magnetic field measured by the ACE satellite. The output of the model is a field-aligned current proportional to the AL index and the energy stored in the ring current which is proportional to the Dst index. The model parameters are optimized using a genetic algorithm (GA) to obtain solutions that simultaneously have least mean square fit to the AL and Dst indices and also exhibit substorms of period 2–4 hours. The GA optimization results show that the model is able to predict the Dst index reliably and captures the timing and periodicity of the sawtooth signatures in the AL index reasonably well for both storm events.

[1] With three components, global magnetosphere (GM), inner magnetosphere (IM), and ionospheric electrodynamics (IE), in the Space Weather Modeling Framework (SWMF), the moderate storm on 19 May 2002 is globally simulated over a 24-hour period that includes the sudden storm commencement (SSC), initial phase, and main phase of the storm. Simulation results are validated by comparison with in situ observations from Geotail, GOES 8, GOES 10, Polar, LANL MPA, and the Sym-H and Dst indices. It is shown that the SWMF is reaching a sophistication level for allowing quantitative comparison with the observations. Major storm characteristics at the SSC, in the initial phase, and in the main phase are successfully reproduced. The simulated plasma parameters exhibit obvious dawn-dusk asymmetries or symmetries in the ring current region: higher density near the dawn and higher temperature in the afternoon and premidnight sectors; the pressure is highest on the nightside and exhibits a near dawn-dusk symmetry. In addition, it is found in this global modeling that the upstream solar wind/ IMF conditions control the storm activity and an important plasma source of the ring current is in the solar wind. However, the ionospheric outflow can also affect the ring current development, especially in the main phase. Activity in the high-latitude ionosphere is also produced reasonably well. However, the modeled cross polar cap potential drop (CPCP) in the Southern Hemisphere is almost always significantly larger than that in the Northern Hemisphere during the May storm.

[1] The storm time inner magnetospheric electric field morphology and dynamics are assessed by comparing numerical modeling results of the plasmasphere and ring current with many in situ and remote sensing data sets. Two magnetic storms are analyzed, 22 April 2001 and 21–23 October 2001, which are the events selected for the Geospace Environment Modeling (GEM) Inner Magnetosphere/Storms (IM/S) Assessment Challenge (IMSAC). The IMSAC seeks to quantify the accuracy of inner magnetospheric models as well as synthesize our understanding of this region. For each storm, the ring current-atmosphere interaction model (RAM) and the dynamic global core plasma model (DGCPM) were run together with various settings for the large-scale convection electric field and the nightside ionospheric conductance, while keeping all other simulation settings the same. DGCPM plasmaspheric parameters were compared with IMAGE-EUV plasmapause extractions and LANL-MPA plume locations and velocities. RAM parameters were compared with Dst*, LANL-MPA fluxes and moments, IMAGE-MENA images, and IMAGE-HENA images. Both qualitative and quantitative comparisons were made to determine the electric field morphology that allows the model results to best fit the plasma data at various times during these events. The simulations with self-consistent electric fields were, in general, better than those with prescribed field choices. This indicates that the time-dependent modulation of the inner magnetospheric electric fields by the nightside ionosphere is quite significant for accurate determination of these fields (and their effects). It was determined that a shielded Volland-Stern field description driven by the 3-hour Kp index yields accurate results much of the time but can be quite inconsistent. The modified McIlwain field description clearly lagged in overall accuracy compared to the other fields, but matched some data sets (like Dst*) quite well. The rankings between the simulations varied depending on the storm and the individual data sets, indicating that each field description did well for some place, time, and energy range during the events, as well as doing less well in other places, times, and energies. Several unresolved issues regarding the storm time inner magnetospheric electric field are discussed.

The further development of a self-consistent theoretical model of interacting ring current ions and electromagnetic ion cyclotron waves (Khazanov et al., 2003) is presented In order to adequately take into account wave propagation and refraction in a multi-ion magnetosphere, we explicitly include the ray tracing equations in our previous self-consistent model and use the general form of the wave kinetic equation. This is a major new feature of the present model and, to the best of our knowledge, the ray tracing equations for the first time are explicitly employed on a global magnetospheric scale in order to self-consistently simulate the spatial, temporal, and spectral evolution of the ring current and of electromagnetic ion cyclotron waves To demonstrate the effects of EMIC wave propagation and refraction on the wave energy distribution and evolution, we simulate the May 1998 storm. The main findings of our simulation can be summarized as follows. First, owing to the density gradient at the plasmapause, the net wave refraction is suppressed, and He+-mode grows preferably at the plasmapause. This result is in total agreement with previous ray tracing studies and is very clearly found in presented B field spectrograms. Second, comparison of global wave distributions with the results from another ring current model (Kozyra et al., 1997) reveals that this new model provides more intense and more highly plasmapause-organized wave distributions during the May 1998 storm period Finally, it is found that He(+)-mode energy distributions are not Gaussian distributions and most important that wave energy can occupy not only the region of generation, i.e., the region of small wave normal angles, but all wave normal angles, including those to near 90 . The latter is extremely crucial for energy transfer to thermal plasmaspheric electrons by resonant Landau damping and subsequent downward heat transport and excitation of stable auroral red arcs.

[1] Measurements from the Atmospheric Chemistry Experiment show pronounced downward transport of NOx (NO+NO2) to the Arctic stratosphere in Feb–Mar 2006. NOx mixing ratios in the upper stratosphere were 3–6 times larger than observed previously in either the Arctic or Antarctic, aside from the extraordinary winter of 2003–2004. There was only minimal geomagnetic activity in late 2005 and early 2006, however, suggesting that NOx produced via energetic particle precipitation was not significantly elevated. On the other hand, the Arctic polar vortex at stratopause altitudes in Feb 2006 was exceptionally strong, implying greater confinement of air in the polar night. Carbon monoxide data also indicate enhanced confined descent of air from the mesosphere. These results confirm that impacts of EPP on the atmosphere are modulated by meteorological conditions; this has implications for understanding interannual variability and trends in stratospheric NOx and ozone.

[1] TIMED/GUVI detected anomalous FUV emissions from the nightside thermosphere over a wide latitude range, from the subauroral latitudes to the equatorial regions during each of three magnetic superstorms (29–31 October 2003, 20 November 2003, and 7–10 November 2004). We note that during the one case (7–10 November 2004) where there were coincident measurements of the flux of energetic particles as observed by IMAGE HENA, the FUV intensity (as seen in five bandpasses or “colors”: 121.6 nm, 130.4 nm, 135.6 nm, LBHS (140–150 nm) and LBHL (165–180 nm)) showed qualitative agreement with the behavior of the energetic neutral atoms (ENA). This suggests that the source of the FUV emissions is the ENA originating from the ring current. We also found that for all three storms we studied that the FUV intensities are well correlated with Dst. The intensity in all colors is observed to increase with latitude up to the auroral oval. Except for 121.6 nm, the observed intensities exhibit a sharp decrease near the magnetic equator region. The origin, location, and spatial extent of the FUV emissions is quite different from that of the traditional aurora, we find that this phenomena is consistent with neutral particle precipitation. We call this signature of the coupling of the ring current and the thermosphere the neutral particle aurora.

[1] Superposed epoch analyses of 549 storms are performed to make a comparison of solar wind features of geomagnetic storm events at solar minimum (July 1974 to June 1977; July 1984 to June 1987; July 1994 to June 1997) and solar maximum (January 1979 to December 1981; January 1989 to December 1991; July 1999 to June 2002). In this study, geomagnetic storms are defined by the pressure-corrected Dst (Dst*) and classified into moderate storms (−100 nT < Dst* ≤ −50 nT) and intense storms (Dst* ≤ −100 nT). The average values of interplanetary magnetic field (IMF), solar wind plasma, NOAA/POES hemispheric power, Kp, and Dst* are analyzed and compared among the different storm categories. During the main phase of storms in each category, the average solar wind plasma parameters and IMF components are disturbed and compressed by a relative high-speed plasma stream. It is shown that the peak of the average solar wind density leads the minimum Dst* (the zero epoch time) by 4.3–7.0 hours, which is longer than the peak time difference (0.3–1.0 hour) between the average IMF Bs and Dst*min. For intense storms at solar minimum, the average IMF By is greatly disturbed during both the main phase and the recovery phase. In addition, the average solar wind density is enhanced up to 28 cm−3, but the average solar wind bulk flow in this storm category is lower than those in all other categories. A significant finding is that the average interplanetary causes of intense storms at solar minimum are found to be against the well-known empirical criteria (Bs ≥ 10 nT or VBs ≥ 5.0 mV/m for ≥3 hours), having a long interval of average Bs = ∼10 nT with dual peaks separated by ∼4.0 hours. The interplanetary and solar origins of storms in the different storm categories are also discussed.

Hot-ion measurements at geosynchronous orbit from the Los Alamos Magnetospheric Plasma Analyzer (MPA) instrument during geomagnetic storms at solar maximum (July 1999–June 2002) and at solar minimum (July 1994–June 1997) are collected, categorized, and analyzed through the superposed epoch technique. To investigate this source of the storm-time ring current, the local time (LT) and universal time (UT) dependence of the average variations of hot-ion fluxes (at the energies of ∼30, ∼17, ∼8, and ∼1 keV), density, temperature, entropy, and temperature anisotropy are examined and compared among four storm categories, i.e., 44 intense storms and 120 moderate storms, defined by the pressure corrected Dst (Dst*), at the two solar extrema. All the hot-ion parameters are highly disturbed around Dst*min; they show distinct peaks or minima and display obvious increase or decrease regions, whose locations do not change much with levels of geomagnetic activity and solar activity. It is also found that intense storms at solar minimum always have the highest (lowest) average peak value (minimum) in each hot-ion parameter. Around Dst*min in each storm category, hot ions are clearly denser near dawn than those near dusk. On the nightside and in the afternoon sector, temperature and entropy during solar minimum storms are usually higher than those during solar maximum storms; there is actually no clear temperature and entropy enhancement during solar maximum storms. During each type of storm, hot ions are isotropic on the nightside but anisotropic (T per /T par > 1) close to noon.

We demonstrate extreme ionospheric response to the large interplanetary electric fields during the "Halloween" storms that occurred on October 29 and 30, 2003. Within a few (2 - 5) hours of the time when the enhanced interplanetary electric field impinged on the magnetopause, dayside total electron content increases of approx.40% and approx.250% are observed for the October 29 and 30 events, respectively. During the Oct 30 event, approx.900% increases in electron content above the CHAMP satellite (approx.400 km altitude) were observed at mid-latitudes (+/-30 degrees geomagnetic). The geomagnetic storm-time phenomenon of prompt penetration electric fields is a possible contributing cause of these electron content increases, producing dayside ionospheric uplift combined with equatorial plasma diffusion along magnetic field lines to higher latitudes, creating a "daytime super-fountain" effect.

The dramatic solar storm events of April 2002 deposited a large amount of energy into the Earth's upper atmosphere, substantially altering the thermal structure, the chemical composition, the dynam ...

[1] A new self-consistent version of a time-dependent magnetospheric paraboloid model is presented and tested on the 24–27 September 1998 magnetic storm interval (minimum Dst = −207 nT). The model uses DMSP satellite data to identify the location of the inner boundary of the magnetotail current sheet and the magnetic flux in the lobes and their variations with time. These inputs plus upstream solar wind dynamic pressure and IMF Bz values are used to iteratively model the Earth's field during the storm. Several interesting results with important consequences are obtained: (1) the model tail field strength at the Earth's surface (DT = −134 nT) is a significant fraction of the ring current value (DR = −167 nT); (2) the movement of the tail current sheet inward to L = 3.5–4.0 at storm maximum is consistent with geosynchronous magnetic field data; (3) at the Earth's surface the Chapman-Ferraro magnetopause current field (DCF = 117 nT) is almost equal at storm maximum to the value from the tail current, thus the fields from the two systems nearly cancel; (4) the magnetic flux from the polar cap in the course of the magnetic storm main phase approximately doubles in comparison with the magneto-quiet interval just before the storm onset; this fact shows that the driven processes prevail over dissipation processes throughout the storm main phase; (5) the large-scale internal currents in the magnetosphere (ring current, field-aligned currents, and magnetotail current) have significant influence on the shape and size of the magnetosphere; the location of the magnetopause subsolar point is different from that obtained by extrapolation of empirical results taken during high geomagnetic activity intervals and from magnetospheric models that do not include feedback from internal magnetospheric currents.

[1] Using the Dst value corrected for the effects of magnetopause currents (Dst*) and solar wind magnetic field and plasma data from 1 January 1998 to 30 April 2002, during elevated solar conditions, we have statistically examined the relationship of 271 storms (Dst* ≤ −30 nT) to 104 magnetic clouds. It is found that most of the magnetic clouds result in geomagnetic storms, but only about 30% of storms are due to magnetic clouds. A storm can be driven by a cloud's various regions or their combinations with dissimilar occurrence percentages. These percentages change as a function of geomagnetic activity levels as well. It is found that the leading field is the most geoeffective region and the sheath region is equally effective at causing magnetic storms during solar maximum (42%) compared to solar minimum (43%) as a percentage of magnetic cloud-induced storms. The occurrence percentage of intense storms caused by clouds is 72%, which is much higher than the ∼20% occurrence percentage of smaller storms caused by clouds. It is also found that “unipolar Bz” and “bipolar Bz” clouds have different geoeffectiveness percentages, depending on the Bz orientation. The long-known control of magnetic activity mainly by southward Bz is supported by the results of this study. It is also shown that multistep development storms can result not only from both the combinations of sheath and cloud fields but also from different fields within a cloud. A new name, quasi-cloud, is proposed for those cloud-like solar wind structures which show evidence of relatively organized field rotations.

[1] A comparison of how well three different electric field models can predict the storm time plasmapause shape is conducted. The magnetic storm of 17 April 2002 is selected for this event, and plasmapause locations are extracted from images from the EUV instrument on the Imager for Magnetopause-to-Aurora Geomagnetic Effects (IMAGE) satellite throughout the main phase and recovery phase of the event. The three electric field descriptions are as follows: the modified McIlwain E5D analytical formula, the Weimer statistical compilation from low-Earth orbit satellite data, and a self-consistent Poisson equation solution for the subauroral potential pattern. It is found that all of the models have certain strengths and weaknesses in predicting the plasmapause location during this storm. The modified McIlwain model did well on the nightside but not on the dayside because the electric fields near noon are too small (analogous to too large of a conductance in the subauroral dayside ionosphere). The Weimer model did well overall, but the resulting plasmapause is usually smaller than the observed one because the electric fields are a bit too strong in the inner magnetosphere (perhaps because of an ionosphere-magnetosphere mapping problem). The self-consistent model is also quite good in general, but the plasmapause in the postmidnight sector was always inward of the observed one. This is because of too low a conductance at the location of the field-aligned currents that close the partial ring current. It is concluded that the latter two models provide a sufficient description of the storm time development of the plasmaspheric morphology during this storm, with the self-consistent model being the best choice. Another conclusion is that plasmapause locations extracted from EUV images should be compared with peak density gradients from model results rather than with any one isocontour of the cold plasma density itself.