Solar Wind-Magnetosphere Interactions II Posters
Presiding: P D Craven, NASA Marshall Space Flight Center; R J Strangeway, Institute of Geophysics and Planetary Physics, University of California, Los Angeles
SM51A-01 0830h
The aurora and particle fluxes during the large January 21, 2005 geomagnetic storm
The geomagnetic storm on January 21, 2005 was special and different from other storms that an unusual large amount of ions were precipitated into the upper atmosphere. The proton aurora imager SI-12 on the NASA IMAGE spacecraft observed the strongest proton aurora signal since the beginning of the mission in May 2000. The storm started at 17:12 when a large solar wind dynamic pressure pulse must have hit the magnetopause thereby creating a subauroral proton flash. Within 2 minutes the whole southern auroral oval increased in brightness and rapidly expanded into the previously empty polar cap. The cusp signature is consistent with a southward IMF at the beginning of the storm. After a perigee pass IMAGE-FUV observed the later stage of the storm after 23:00 with a strong cusp signal during northward IMF. At the same time the FAST satellite observed unusually large fluxes of precipitating ions in the cusp, while the NOAA satellites detected large fluxes of ion and electron precipitation on the dayside and unusual energies on the nightside. The presentation will describe the auroral morphology and compare the auroral brightness with the low altitude in-situ measurements of partiucle fluxes. We will also compare the temporal evolution with other geomagnetic storms during the IMAGE mission.
SM51A-02 0830h
Cusp-Region Ion Outflows Observed During January 21, 2005 Storm Period
The FAST spacecraft observed intense ion outflows following the initiation of a geomagnetic storm on January 21, 2005. These outflows occur in conjunction with both magnetosheath electron precipitation and large-scale field-aligned currents. The detailed structure of the outflows appears to better correlated with the electron precipitation; a conclusion consistent with an earlier study of FAST data comparing cusp-region ion outflows to Poynting flux and electron precipitation. On comparing the observed ion fluxes to the soft electron precipitation using scaling laws derived from the earlier study we find the fluxes to be somewhat lower than predicted. This may be a consequence of the FAST observations being at lower altitudes than in the earlier study. At these lower altitudes the ions have not been accelerated to sufficiently high energy to overcome the energy cut-off of the detector. In addition the observed fluxes may be reduced since the spacecraft is moving upwards at ~ 1 km/s. It is also of interest to note that the velocity-dispersed ion precipitation signatures can appear to contradict the convection pattern inferred from the field-aligned current signatures. In particular while the field-aligned currents indicate convection to higher latitudes within the cusp-region, the velocity-dispersed ions can, on occasion, suggest convection to lower latitudes. This may be a manifestation of temporal effects, or it could be caused by complicated reconnection geometry at the magnetopause.
SM51A-03 0830h
Magnetospheric response to extreme solar events of January 2005, as observed by the Cluster and Double Star spacecraft
Extreme solar events can drive extraordinary responses of the terrestrial magnetosphere, characterised by strong deformations of the magnetic field and the plasma populations. Magnetospheric changes following extreme solar events of January 2005 have been analysed using particle data obtained with the Cluster and Double Star missions. The 17 January 2005 event was characterised by the arrival of an interplanetary cloud of solar energetic particles at the Earth orbit. The Double Star (TC - 1) spacecraft was situated in the Magnetosheath and detected a sudden Magnetosheath compression (increased density and temperature), whereas the Cluster spacecraft constellation, situated in the Solar wind, recorded a substantial increase of the particle flux at all energy ranges, characteristic of background provoked by the presence of penetrating particles. Four days later, on the 21 of January, Cluster and Double Star were both situated in the afternoon sector when they recorded the huge increase of solar wind pressure. At about 17:10 TU, Cluster, situated in the solar wind region, recorded an important increase (factor of ~4) of the proton density (CIS data), while the velocity jumped from ~ 500 to ~ 900 km.s-1. The Double Star TC-1 spacecraft, situated at the same time in the Magnetosheath on the inbound trajectory (R ~ 9 RE) crossed the bow shock at 18:53 UT and stayed in the solar wind for 14 minutes, due to the sudden compression before re-entering in the Magnetosheath (R < 8.5 RE). An analysis of the Magnetospheric modifications induced by these solar events, as recorded by the Cluster and Double Star spacecraft, will be presented.
SM51A-04 0830h
Prediction of Auroral Electrojet AL Index
We studied the possibility for improving the prediction of the auroral electrojet AL index that shows substorm activity. We used 15-min and hourly data for 1995 when high-resolution data for the solar wind and AL indices are available. For prediction of AL indices we used the Akasofu coupling function averaged for a previous time interval and corrected for non-linearity, and season/UT variations of the AL index. For 15-min mean AL indices our method is able to account for ~ 88% of variance (R 0.94) in AL index for 15-min prediction and for ~ 77.5% of variance (R 0.88) for 30-min prediction. For hourly AL indices and one-hour prediction, our method is able to account for up to 79% of the variance (R 0.89) in AL index. These results are higher than earlier results for predicted AL and AE indices. Main causes for high correlation between predicted and actual AL indices are accounting for both previous solar wind history and strong seasonal/UT variations.
SM51A-05 0830h
Contributions from Different Sources to Semiannual Variation of Geomagnetic Activity
Historically, the three possible causes for semiannual variation of geomagnetic activity were proposed: 1) an inclination of the ecliptic plane to the solar equatorial plane (while moving around the Sun, the Earth attains its highest heliospheric latitudes, where solar wind speed increases, in equinoctial months); 2) the semiannual variation of the angle between the Earth's axis and the y-axis in the solar-ecliptic (SE) coordinate system (this angle attains its minimum in equinoctial months that results in increasing the contribution from IMF By in the SE coordinate system to IMF Bz in the solar-magnetospheric coordinate system, which is responsible for geomagnetic activity; this effect is known as the Russell-McPherron effect); and 3) the semiannual variation of solar luminosity of high-latitude conjugate ionospheres (in summer-winter months one of the polar caps is in sunlit conditions while in equinoxes both nightside high-latitude ionospheres are in darkness that is favor for the generation of substorm activity). The last mechanism is not dependent on solar wind conditions while two first mechanisms are dependent. This allowed us to estimate the contributions from these two possible mechanisms to the semiannual variation of geomagnetic activity. For this purpose we investigated the semiannual variation of the Dst index for ten years, 1995-2004. We found that after exclusion of the first mechanism, the amplitude decreases by less than 10%, after excluding the second mechanisms (the Russell-McPherron effect) the amplitude of the semiannual variation decreases by ~ 20%. Although both dependence of solar wind speed on heliospheric latitude and the Russell-McPherron effect are evidently seen in the data, our study showed that these effects contribute in total to the semiannual variation of Dst index not more than 30%.
SM51A-06 0830h
The Phase Structure of Pc3 Geomagnetic Pulsations at Low Latitudes
The use of ground based magnetometer arrays has proved to be one of the most successful methods of studying the spatial structure of hydromagnetic waves in the earth's magnetosphere. The spatial and temporal variations observed in wave polarization and signal phase are vitally important since they provide evidence which can be directly related to wave generation mechanisms both inside and external to the magnetosphere and propagation modes inside the magnetosphere. An array of four low latitude induction coil magnetometer stations (L =1.7-2.8) has been used to study longitudinal and latitudinal variations in Pc3 pulsation interstation phase and polarization characteristics. Studies on ten days of data indicate an east-west phase pattern which shows left-hand polarization associated with westward propagation in the afternoon. Similar polarization is seen on latitudinal station pair but propagation is always from north to south away from the equator. Low latitude wave sources are discussed and these results are considered to be consistent with a field line resonance situated at L >3.
SM51A-07 0830h
A Study of the Characteristics and Behavior of the Low Energy Plasma in the Magnetospheric Lobal Wind
The results of a survey of the characteristics of the low energy plasma flowing along the field lines in the low latitude lobes of the magnetosphere, the lobal wind, are presented. Data from the TIDE instrument on the Polar satellite are used to derive the characteristics (density, temperature, and flow speed) of the lobal wind. The behavior of these characteristics with changes in the ambient magnetic field, solar wind, and other parameters representing controlling factors are examined.
SM51A-08 0830h
Solar Wind Entry and Plasma Sheet Formation in the Magnetosphere Using a Global Unstructured Hybrid Simulation Model
The transport of the solar wind energy and momentum into the inner magnetosphere, particularly the sheet region is investigated using a 2½/ dimensional hybrid model of particle ions and fluid electrons [1] % kazem on a finite element multi-resolution mesh. The model resolves to the magnetohydrodynamic limit by the inclusion of the finite ion larmor radius and inertial length. The model is first tested by initializing a dipole at equilibirum with a flow subjected to an incoming solar wind with either a northward or southward IMF. The test includes generation of the steady state shock by examining the density and temperature contour, shaded as well as one dimensional cuts in the equatorial plane. Further tests include observation of dayside reconnections from the magnetic vector potential plots when the incoming IMF points soutward; those are compared with the cases in which the incoming IMF points northward as a means to examine both the numerical dissipation impacts on the reconnection rates as well as impacts on particle trajectories and bulk flow motion in the vicinity of the reconnection regions. These empirical observations of the dayside reconnections are significant as no classical resistivity is employed in the hybrid model. After the initial tests, the trajectories of a certain percentage of the solar wind particles from hundreds of Earth radii upstream to hundreds downstream are followed by storing their time history. The time history reveals ions which can penetrate into the sheet region, and ions which get trapped in the closed field lines and subsequently reflect as well as ions which penetrate the polar cusp region and get deflected. The correlation of the particle velocities with the ambient flow and field fluctuations are used to determine locally the nature of the particle interaction with its ambient medium in their long paths. Throughout this work animations of the simulaions as well as other data will be presented.
SM51A-09 0830h
Geomagnetic Activity Forecasting Using Self-Learning Algorithms: Application in Space Weather Studies
The ability to forecast the geomagnetic activities is becoming more important as human activity in space becomes more prevalent. For example, early warning of geomagnetic storms could help mitigate their harmful effects on space electronics and on electrical power lines. Moreover, recently developed space weather algorithms that utilize physics-based models require future values of Kp as an input in order to forecast the ionospheric behavior. Computational learning theory and data-driven modeling techniques are new and rapidly expanding areas of research that aim at developing efficient learning algorithms. Here we compare self-learning algorithms regarding their abilities to forecast the level of geomagnetic activities, as represented by Kp. In particular, we consider the following algorithms: artificial neural networks, locally weighted projection regression, support vector machines, and relevance vector machines. Different parameters are considered such as: (1) length of forecasting time, (2) type and size of input data, and (3) training set size. These learning machines are compared regarding their generalization capabilities and structure reliabilities. The relative strengths and limitations of these algorithms will be presented.
SM51A-10 0830h
Equation free projective integration: A novel scheme for modeling multiscale processes in plasmas
We examine a novel simulation scheme called equation free projective integration1 which has the potential to allow global simulations of plasmas while still including the global effects of microscale physics. These simulation codes would be ideal for such multiscale problems as the Earth's magnetosphere, tokamaks, and the solar corona. In this method, the global plasma variables stepped forward in time are not time-integrated directly using dynamical differential equations, hence the name "equation free." Instead, these variables are represented on a microgrid using a kinetic simulation. This microsimulation is integrated forward long enough to determine the time derivatives of the global plasma variables, which are then used to integrate forward the global variables with much larger time steps. Results will be presented of the successful application of equation free to 1-D ion acoustic wave steepening. In addition, initial results of this technique applied to reconnection will also be discussed. 1 I. G. Kevrekidis et. al., "Equation-free multiscale computation: Enabling microscopic simulators to perform system-level tasks," arXiv:physics/0209043.
SM51A-11 0830h
Failure of Dst index fields to represent a ring current
Two geomagnetic storms were chosen for their size, isolation, seasonal difference, and global data availability. For these storm periods, records from all available stations, within the latitude range of Dst contributors, were collected to choose those pairs having similar longitude. Four-hour average fields centered at local noon and midnight were compared. The 1/Cos(theta) factor, used for the Dst derivation, was applied to the paired data to determine if a Ring Current adjustment was worthwhile. Results indicate that the local station measurements behave not like Ring Current fields, but more like those from other current sources, such as the ionosphere and field-aligned currents. The cosine factor, used to adjust station fields for the magnetospheric ring current effect, typically fails. I also verified the daytime ionospheric enhancement of the disturbance field at the magnetic dip equator. The lognormal form of the Dst, a result of multi-source Dst behavior, was verified. The Dst appellation "Equatorial Ring Current Index" is clearly a misnomer.