SM13A-1636
Bulk Acceleration of Outflowing Ionospheric Thermal Plasma in Multi-Fluid MHD
We present an analysis of the forces that accelerate outflowing ionospheric O+ in MHD plasma. The acceleration of outflowing O+ from the high-altitude polar cap region has been examined observationally from analysis of satellite data and theoretically from tracing particle trajectories (e.g. Nilsson et al., Cully et al.). An increasing interest in the role of O+ in magnetospheric dynamics and the need to globally quantify the dynamics and effects of outflowing O+ has led to the use of MHD models to simulate the behavior of outflowing plasma. However, an understanding of the relevant forces that act to accelerate the outflow within these models is still lacking. We analyze results from the Multi-Fluid Lyon-Fedder-Mobarry (MFLFM) MHD model, including thermal O+ outflow from an empirical model derived from Akebono data. We present an assessment of the relevant field-aligned acceleration terms in the MFLFM. Our results show that for low- velocity thermal outflow, the pressure gradient, rather than the centrifugal force, is the dominant term that accelerates MHD plasma above the high-altitude polar cap.
SM13A-1637
High-latitude ionospheric outflows characterized through analytic formulas
Recent advances involving multi-fluid treatments have begun to allow the prospect of global magnetospheric models to simulate the dynamics of multiple ion species, such as various ion species originating from sources in the solar wind and terrestrial ionosphere. Such opportunities for the dynamic treatment of ionospheric ions within the magnetosphere portend a need for realistic accessible methods of estimating ionospheric outflows as linked plasma sources for these global models. Toward this end, in this presentation, the results of numerous physics-based simulations of ionospheric plasma outflows under varied driving agents are distilled in terms of relatively compact analytic expressions. The simulations are conducted with the UT Arlington Dynamic Fluid (DyFK) ionospheric plasma transport code. These analytic expressions for O+ and H+ densities, temperatures and flow velocities are obtained at the 3 RE altitudes corresponding to typical inner boundary levels for certain current global magnetospheric models. These O+ and H+ parameters are expressed as functions of precipitation electron energy flux levels, characteristic energy levels of the precipitating electrons, the peak spectral wave densities for low-frequency electrostatic waves which transversely heat ionospheric ions, and solar zenith angle.
SM13A-1638
Ionospheric Outflows and Geomagnetic and Solar Activity
We present studies of long-term variations of ionospheric outflows over 11-year solar cycle between 1996 and 2008. Using measurements of cold ions of Polar/TIDE instrument, we calculated monthly averages of the fluxes of the ionospheric outflows at altitudes of 0.8-3 Re for dayside and nightside polar cap regions and correlated with solar EUV F10.7 index, sunspot numbers and geomagnetic Dst index. We found a good correlation between the Solar EUV or sunspot numbers and the flux of ionospheric outflows in the dayside polar cap region over the solar cycle. The correlation coefficients are ~0.6 for the dayside polar cap region compared with ~0.4 in the nightside. The changes in the monthly average fluxes of the outflows are about a factor of 10 from solar minimum to solar maximum. On the other hand, ionospheric outflows are not correlated well with the Dst index over the 11-year solar cycle. Although the Dst index is somewhat more variables during the periods of the solar maximum, the correlation between the outflows and Dst was reduced in the monthly-average data set. This indicates that the periodicities of the variations the Dst mostly occur in a time scale smaller than a month. Spectral analysis of the ionospheric outflows indicates annual and seasonal variations on top of the 11-year solar cycle trend. The amplitudes of these variations are comparable or even larger than the minimum-to-maximum value of the solar cycle trend. This indicates the importance of the influence of solar wind-magnetosphere-ionosphere interaction on the ionospheric outflows at short time scales in addition to the 11-year solar cycle trend caused by the more direct energization of the ionospheric ions by the solar EUV flux.
SM13A-1639
Proton Auroral Emissions without Electron Auroral Emissions in Long-lasting Complex Substorms
The SI-12 and WIC FUV instruments aboard the IMAGE satellite provide a unique ability to compare LBH and proton auroral emissions. The auroral power allows for the examination of the relationship of proton and electron emissions. In the past, measurements in the LBH band have been used to identify substorms. There are, however, cases where there is significant proton auroral emission while there is little to no electron emission in the LBH band. During intense, long-lasting complex substorms it is possible that while the WIC images show a decreasing intensity and entry into a more recovered state. At the same time, images from the SI-12 camera show increased intensities and possibly further substorms seen only in the proton emissions. An example of this can be seen in the events of November 15, 2001 from 1700-2200 UT. An investigation of this event will be presented and possible explanations of these events will be put forth.
SM13A-1640
Multispacecraft observations of broadband electrons during geomagnetic storms
During a large geomagnetic storm occurred on 15 May 2005, the FAST satellite encountered a local onset of substorm identified by the far ultraviolet (FUV) imager onboard the IMAGE satellite. At this time, FAST observed Broad-Band Electrons (BBEs), which were electron flux enhancements over a broad energy range (50 eV-30 keV) at the lower latitude side of the auroral oval (-58°--65° ILAT in this BBE event). Ground-based magnetograms measured a geomagnetic H-bay and Pi2 pulsations started around the post-midnight sector at ~0655 UT. At the same time, energetic particle injections were observed by the geosynchronous LANL satellite. The auroral intensification identified by IMAGE-FUV started at 0655 UT at a magnetic local time (MLT) of ~3 h. From 3 min after the onset, FAST observed the BBEs at 0658-0703 UT, 3 MLT, and -58°--65° ILAT (footprint of -54°--60°MLAT) above the auroral emission region. These data clearly show that the BBEs occur at the auroral brightening region at the onset of a storm-time substorm. The auroral emission region due to the precipitation of the BBEs lasted for ~10 min at ~-50°--60° MLAT and ~3-6 MLT. In this presentation, we also report spatial relationships between BBEs and the plasmapause in order to investigate the source region of the BBEs for 8 events selected from the BBE event list created in previous multi-event studies using the data from the Plasma Wave and Sounder (PWS) experiments on board the Akebono satellite.
SM13A-1641
The efficacy of automated examination methods of conjugate substorms seen from space
Conjugate studies of high-latitude geomagnetic activity provide understanding of the global magnetospheric reaction to external perturbations and the role of the ionosphere in modulating and coupling with the magnetosphere. Interhemispheric asymmetries as manifested in auroral emissions have been observed for over 40 years. Until recently, the nature of the problem limited the type and extent of studies that can be performed to either conjugate ground based observations or comparison of space based images from all-sky cameras. With the availability of multiple space-based observing platforms, observations of conjugate aurora have been performed, primarily on an event basis. Recent investigations have used automated processing techniques to perform statistical comparisons of conjugate auroras seen by Polar/UVI and IMAGE/FUV between 2001 and 2003. The automated methods enable access to a very large data set of potential events, for example, over 900 potential conjugate periods were examined in previous studies. This paper will examine the relative merits and shortcomings of the automated techniques previously used. Interactive analysis of selected conjugate events will be used as a standard against which automated analysis will be compared.
SM13A-1642
Auroral Asymmetries in the Conjugate Hemispheres During Strong IMF Bx
Simultaneous UV images of the conjugate aurora, taken from the IMAGE and Polar spacecraft reveal prominent differences between the two hemispheres. During a period of 1.5 hours of continuous measurements, we observe: 1) An intense arc in the dusk sector which extends further towards midnight in the southern hemisphere than in the northern hemisphere, 2) A much more severe poleward expansion in the southern hemisphere during a substorm growth phase, and 3) An asymmetric intensity distribution, with the most intense aurora at dusk in the southern hemisphere, and at dawn in the northern hemisphere. Throughout this period, the IMF was stable, with Bz negative (≈-4 nT), By slowly increasing from ≈-2 to ≈ 2 nT, and Bx positive (≈ 10 nT). Previous studies suggest that penetration of positive IMF Bx into the magnetosphere may explain at least part of the observations presented here.
SM13A-1643
Sub-keV Electron Signatures Within Pulsating Aurora
The Rocket Observations of Pulsating Aurora (ROPA) sounding rocket was launched on February 12, 2007 at 12:45:04UT from Poker Flat Research Range, AK into a region of pulsating aurora. One hour beforehand, the REIMEI satellite passed through the same pulsating aurora event, within the field - of - view of the Poker Flat all sky camera. Previous measurements of electron precipitation associated with pulsating aurora have varied with many showing high energy, tens to hundreds of keV, modulated populations. Collocated with the pulsating aurora, REIMEI and ROPA ESA data from Feb 12, 2007 show low energy (<1 keV) inverted - v type structures within a region of widespread, diffuse plasma sheet precipitation, suggesting the presence of a local electric field, which seem to correspond with optical pulsations. Poker Flat Incoherent Scatter Radar (PFISR) observations of this event show intermittent ionospheric electron density enhancements at high altitudes which may be the signature of these inverted - v type features. These observations are consistent with those of Sato et. al. (2002, 2004) who suggest a near - Earth modulation source for the pulsating aurora, as opposed to modulated cyclotron resonance interactions in the equatorial magnetosphere. The focus of this presentation will be the relationship, if any, between these low energy structures and the pulsating aurora, which at present remains unclear.
SM13A-1644
Intensity, Duration and Motion of Auroral Arcs: Case Studies and Survey
Auroral arcs are investigated in the two dominant visible wavelengths (5581 Å and 6304 Å) using images from the all-sky camera in Gillam, Canada part of the NORSTAR array. With the use of cross sections drawn across the arcs, both the brightness and latitudinal movement are plotted over time with a time resolution of 10 seconds. First, the actual meridional velocities of the arcs are evaluated by converting pixel coordinates in the fisheye perspective of the camera to true latitudinal coordinates. From the mapping of arc movements, examples of almost non-moving arcs with lifetimes of more than 10 minutes have been given in support of the Stationary Inertial Alfvén Wave Model [Knudsen, SSR 2001] which could explain some auroral structures. Second, a statistical survey suggests that the brightness of arcs is directly proportional to their duration. The stronger brightness is directly related to higher precipitating-electron energy flux that in turn depends on the magnetotail configuration. We will report on the variation of the auroral intensity as a function of magnetotail configuration (stretched or dipolar) based on a comparison with magnetic field measurements provided by NOAA's Geosynchronous Operational Environmental Satellite (GOES-12).
SM13A-1645
South Pole all-sky imager observations of dayside aurora activity induced by a solar wind dynamic pressure enhancement
Ground observations of the optical aurora in the dayside cusp region have the distinct advantages of continuity of coverage and sufficient temporal-spatial sensitivity to monitor dayside signatures of solar wind/magnetosphere/ionosphere interaction mechanisms. The South Pole Station (SP, geomagnetic latitude (GMLat) = -74.3 degs, magnetic local time = UT-3.5 h) in Antarctica is a unique place for dayside aurora observations during austral winter season. We present the detailed features of enhancements of dayside aurora activity induced by a sudden increase in the solar wind dynamic pressure (Psw), using a ground-based all-sky imager (ASI) at SP. The interplanetary magnetic field (IMF) was northward during the Psw enhancement. Just after the arrival of the Psw enhancement on the Earthfs magnetosphere, the 557.7 nm aurora activity on the dayside is suddenly intensified almost in the whole field of view of ASI. Further a few minutes later, the intensity of the auroral emissions shows a maximum, and then decays within about 5 minutes. Even after decay of the transient aurora activity at lower latitudes, the newly formed auroral emissions from the dayside cusp to the polar cap (GMLat -76 to -80 degs) develop during the Psw enhancement lasting about an hour. The polar aurora intensifications seem to be associated with lobe reconnection under the northward IMF conditions as well as the Psw enhancement. In this talk, two cases have been studied and the possible generation mechanisms will be discussed by comparing the ASI data at SP with other instruments.
SM13A-1646
Ground-based Observations of Diffuse Auroral Structures During Reimei Overpasses
Conjunctive studies using in situ and ground-based auroral measurements provide insight into the acceleration processes associated with different types of auroral structures. We present results from such observations of diffuse aurora that took place during the winters of 2006, 2007 and 2008 from Poker Flat, Alaska. We combine all-sky camera data recorded at 30 frames per second and full pitch angle ion and electron spectra during Reimei overpasses. The optical and in situ particle data can be examined at similar time resolution, allowing the investigation of small scale and/or rapidly time-varying auroral structures. We have several examples of passes through stationary diffuse auroral structures, that will be studied in detail in order to identify the in situ signatures that correspond to them.
SM13A-1647
The Behaviour of Shear Alfven Waves along the Auroral Geomagnetic Field
Observational evidence is accumulating which demonstrates the importance of shear Alfvén waves (SAW) for auroral electron acceleration, especially in active regions of the magnetosphere, such as near the cusp and at auroral latitudes in the midnight sector. It has been shown through theory, numerical experiment and laboratory experiment that SAW with short perpendicular scale lengths carry parallel electric fields which may explain the resulting auroral electron acceleration in the Earth's magnetosphere. However, many details regarding the interaction of SAW with electrons are still not well understood, despite decades of research. The location of electron acceleration due to SAW in the magnetosphere is unclear, and we have yet to fully reconcile the range of electron energies possible through this acceleration process with the energy ranges required to deliver the observed auroral displays. As shear Alfvén waves travel from the magnetosphere towards the ionosphere, they leave regions of sparse, hot plasma and travel towards the ionosphere, where the plasma becomes denser and colder. The waves also experience an increase in magnetic field strength as they approach the ionosphere. These gradients in the plasma environment result in changes in the characteristics of the SAW, especially in the sign and strength of the accompanying parallel electric field. We present results from a self-consistent kinetic simulation code (DK1D: Watt and Rankin, Plasma Physics and Controlled Fusion, 50, 074008, [2008]) to demonstrate how the characteristics of the wave, and the resulting wave-particle interactions, change as SAW propagate through an inhomogeneous plasma. We compare the results with those predicted from local two-fluid theory, and show which locations along an auroral field line may be most conducive to auroral electron acceleration by SAW.
SM13A-1648
Alfven Waves and Electron Energization and Their Interaction with Auroral Ionospheric Plasma Transport
When inertial Alfvén waves propagate along auroral field lines, they involve parallel electric fields which can accelerate auroral electrons. Here, we simulate the propagation of Alfvén waves through O+ and H+ auroral ionosphere-magnetosphere density profiles obtained from the UT Arlington Dynamic Fluid- Kinetic (DyFK) ionospheric plasma transport model. A linear one dimensional gyrofluid code [Jones and Parker, 2003] is used for the Alfvén wave description, incorporating electron inertia, electron pressure gradient and finite ion gyroradius effects. Then, the test particle approach of Su et al. [2004] is used to simulate the response of a distribution of electrons to these Alfvén wave electric fields. These electrons are incorporated into the DyFK model to produce a partially-self-consistent approach to producing the associated ionization and thermal electron heating within the ionosphere-magnetosphere system. Jones, S. T., and S. E. Parker (2003), Including electron inertia without advancing electron flow, J. Comput. Phys., 191, 322. Su, Y.-J., S. T. Jones, R. E. Ergun, and S. E. Parker (2004), Modeling of field-aligned electron bursts by dispersive Alfvén waves in the dayside auroral region, J. Geophys. Res., 109, A11201, doi:10.1029/2003JA010344.
SM13A-1649
Transversely localized shear Alfven waves in resonance cones
Using fully electromagnetic 2.5-D particle-in-cell (2DPIC) simulations, we study the scattering of shear Alfven waves (SAWs) having long perpendicular wavelengths from multiple localized density cavities. We show that the scattered fields are radiated in conical wave structures, which are the inertial Alfven wave (IAW) cones with apexes at the cavities and half-cone angle approximately determined by the cold plasma theory. The waves within the cones obey the basic dispersion relation of IAWs. The scattered fields have relatively short transverse length scale lengths and are confined within the cones, which are embedded in the large-scale incident SAW. The resulting wave structures and their Fourier spectral behaviour found in the simulations are compared with observations on transversely localized IAWs from Freja, FAST and Polar. We highlight the fine structures in the parallel electric fields within the cones and in the associated parallel and transverse currents. The current closure consisting of the parallel and transverse currents forming loops inside the cone is seen. We demonstrate parallel acceleration of the electrons forming energetic tails and bulk transverse heating of ions in the scattered fields. The scattering mechanism discussed here provides a linear mechanism for converting large-scale SAW into the solitary structures of small-scale IAWs.
SM13A-1650
Localized electromagnetic waves and currents observed by Cluster in the magnetosphere -- result of magnetosphere-ionosphere interactions at high latitudes
We present results from a numerical study of ultra-low-frequency electromagnetic waves and magnetic field- aligned currents observed by Cluster satellites in the high-latitude magnetosphere. Usually, these waves are registered on the boundaries between downward and upward large-scale magnetic field-aligned current channels or inside the downward current channel. The goal of this study is to explain spatial structure (in particular, perpendicular wavelength of the order of 12-14 km at 100 km altitude) and frequency (10-20 mHz) of small-scale electromagnetic waves observed by Cluster satellites inside two neighboring downward current channels in the auroral magnetosphere at the radial distance of 5 RE. The main hypothesis investigated in this study is that these waves are generated by the interaction between large-scale magnetic field-aligned currents and the ionosphere. The numerical model used to investigate these interactions is based on a nonlinear system of partial differential equations representing reduced, two-fluid MHD. This model includes effect of the active ionospheric feedback on structure and amplitude of magnetic field-aligned currents interacting with the ionosphere and it is implemented numerically in the realistic dipole magnetic field geometry. Simulations confirm that localized electromagnetic waves with parameters close to ones observed by Cluster indeed can be generated by a large-scale, slowly evolving current system interacting with the ionosphere when certain geophysical conditions are satisfied.
SM13A-1651
Extended Region Magnetosphere-Ionosphere Coupling Model
Magnetospheric and ionospheric MHD models have been used to study their respective regions for some time. This Magnetosphere-Ionosphere coupling model aims to bridge these two regions and study their interactions. The model is a 3-fluid MHD model with Ohm's Law and parametrized collisions. By applying low altitude (high density) approximations we can resolve heights down to approximately 60 Km. This allows simulations with the entire Ionosphere. Previously time step considerations required that the lower boundary occur in the E-region of the Ionosphere which is less than ideal.
SM13A-1652
Production and Effects of Secondary Electrons in Global Simulations of the Magnetosphere-Ionosphere Interaction
The effects of primary electron precipitation are included in global simulation models of the magnetosphere-ionosphere interaction, with the basic properties of the precipitation usually derived from MHD variables characterizing the magnetospheric plasma. In this study, the electron precipitation model is extended to include secondary and degraded primary electrons as well as the usual primary electron population. The spectrum of the secondaries and degraded primaries is modeled following Evans (1974). We have implemented this model in the Lyon-Fedder-Mobarry (LFM) global model. Simulation results show that the precipitating number flux is increased dramatically by secondary electrons. Other ionosphere variables such as electron average energy, Peterson and Hall conductances are influenced by secondary electron precipitation as well, with polar cap potential and field-aligned current less affected. Although these extensions to the electron precipitation model have a minor effect on the electrodynamics of the magnetosphere-ionosphere interaction in the standalone LFM model, they are expected to modify the state of the F-region ionosphere more significantly, e.g., when the LFM model is coupled to a thermosphere-ionosphere general circulation model such as the NCAR TIEGCM. Evans, D. S., Precipitating electron fluxes formed by a magnetic field-aligned potential difference, J. Geophys. Res, 79, 19, 2853, 1974
SM13A-1653
Relationships between field-aligned currents and particle precipitation
Both the field-aligned currents and particle precipitation play important roles in the magnetosphere- ionosphere coupling. The polarities and densities of large scale field-aligned currents from the DMSP magnetometer data 1983-2005 were determined using an automated algorithm. The particle precipitations often have characteristics that reflect their source regions in the magnetosphere, which led to the development of the automatic region identification schemes. The particle precipitation regions from the DMSP SSJ4 particle data were also determined from 1983-2005. The relationships between the field-aligned currents and the particle precipitation regions on the dayside were explored and identified. The ion westward and electron eastward drifts may contribute to the prenoon-postnoon asymmetry of the regions. The solar wind-magnetosphere coupling issues were investigated.
SM13A-1654
Multi-Resonator Dynamics in Regions of Downward Field-Aligned Current
The interaction of field-aligned current with the auroral ionosphere is investigated using a 2-d (no azimuthal variation), non-linear, reduced-MHD model for a low-β plasma in dipole coordinates. It is shown that a magnetosphere-ionosphere resonant cavity (MIAR), similar in nature to the well-studied ionospheric Alfven resonator (IAR), exists at auroral latitudes. To characterize the role of parallel inhomogeneities in supporting an MIAR, the profile of the parallel wave conductivity, ΣA=1/μ0vA, which is proportional to the Alfven wave refractive index, is examined. At low-altitude, the negative gradient in ΣA defines the upper boundary of the IAR, whereas, the upper boundary of the MIAR is defined by a weaker, positive gradient at geocentric distances of about 7 RE. Excitation of the MIAR by ionospheric feedback instability resembles that of the IAR; however, the characteristic resonances of the MIAR are quite different. Numerically simulated oscillations of the simultaneously excited resonators are shown to originate from standing quarter-wavelength modes. The driven MIAR oscillates in the Pi2 range at a frequency much lower than that of the quarter-wave mode, and its threshold for instability is lower than that of the IAR. Perturbation analysis of a simple dispersion model is used to the explain this frequency shift. It is shown that the downshift in frequency occurs when the upper boundary of the resonator is formed by an upward gradient in ΣA. In contrast, the negative gradient in ΣA in the topside ionosphere gives rise to an upshift in frequency of the IAR oscillation relative to the quarter-wave mode. These characteristics may be understood in terms of the non-ideal boundary conditions on the standing wave modes at the ionospheric end of the field line.
SM13A-1655
FAST Spacecraft Observation of Ion Cyclotron Waves in the Auroral Zone
Ion cyclotron waves have been observed in many regions of the Earth's magnetosphere and by many spacecraft. Observations from the FAST spacecraft during auroral zone crossings have frequently shown ion cyclotron waves in conjunction with upward going ion beams, as well as solitary waves. The types of ion cyclotron waves available depend strongly on the heavy ion concentrations. Since radiation from the Sun ionizes most of the plasma in the ionosphere, the state of the ionosphere is dependent on the solar cycle. Furthermore, due to the fact that the upwelling from the ionosphere is the source of heavy ions such as oxygen in the Earth's magnetosphere, the ion composition of the magnetosphere changes dramatically during the solar cycle, with the number densities of heavier ions being much higher during the periods of maximum solar activity. We will present preliminary results from a study of FAST spacecraft observations of ion cyclotron waves including electric and magnetic field, and ion data along with comparisons to numerical dispersion relations. In this study we plan to correlate the ion cyclotron wave to the heavy ion concentration that is observed, as well as looking for correlation with the solar cycle.
SM13A-1656
Ground-based observation of MF auroral radio emissions in the polar cap and cusp regions
Recent ground-based observations have detected MF auroral radio emissions called MF burst and auroral roar. It is interpreted that origin of both emissions is upper hybrid waves generated in the ionosphere by auroral electrons. Some theoretical studies [e.g. Weatherwax et al., 2002] have proposed that MF burst which has a broad band spectrum is generated at an altitude of few hundred kilometers over a wide altitude range while auroral roar is excited in altitudes where a condition of fuh ~ nfce (n=2, 3) is met, which leads to its narrow band spectrum. The polarization spectrum observation at the Husafell observatory in Iceland, which started in 2005, revealed the polarization characteristics of 3fce roar and the relationship with energy of precipitating electrons [Sato et al., 2008]. However, occurrence rate is low because the observation site is located in the auroral zone. We install a new instrument for MF auroral radio emissions at Longyearbyen in Svalbard. The observation at Longyearbyen has several advantages: higher occurrence rate can be expected in the polar cap region, and simultaneous observations with EISCAT Svalbard Radar (ESR) and other ground-based observations can be easily obtained. The instrument consists of two types of observation systems. One is designed for the continuous observation of spectrum in a frequency range below 6 MHz. The other is designed to obtain waveform data in a frequency range below 4 MHz by an A/D converter with a sampling speed of 10MSPS. By using the wave form data, the arrival direction angle of a received radio wave can be estimated. In this presentation, we will introduce the purpose of the observation and the detail of the instrument, and report some initial results.
SM13A-1657
The first full-resolution measurements of Auroral Medium Frequency Burst Emissions
Auroral MF burst is a naturally occurring auroral radio emission which appears unstructured on resolution of previous measurements, is observed in the frequency range of 0.8-4.5 MHz, and has typical amplitudes of around 10-14 V2/m2Hz, and durations of a few minutes. The emission occurs at substorm onset. Since Sept 2006, Dartmouth has operated a broadband (0-5 MHz) interferometer at Toolik Lake, Alaska (68° 38' N, 149° 36' W, 68.51 deg. magnetic latitude), designed for the study of auroral MF burst emissions. Normal operation involves taking snapshots of waveforms from four spaced antennas from which wave spectral and directional information is obtained. However, the experiment can also be run in "continuous mode" whereby the signal from a selected antenna is sampled continuously at 10 M samples/second. A "continuous mode" campaign was run 0800-1200 UT (~2200-0200 MLT) daily from March 21 to April 19, 2008. During this campaign more than twenty auroral MF burst emissions were observed, including three extraordinarily intense examples lasting approximately two minutes each. These observations represent the highest time and frequency resolution data ever collected of MF burst emissions. These data allow us to better characterize the null near twice the electron gyrofrequency identified in previous experiments, since examples of this feature observed during this campaign display a strong null ~50 kHz in bandwidth, with sharp boundaries and occasionally coincident with 2 fce auroral roar. These data also allow us to search for frequency-time structures embedded in MF-burst. One prominent feature appears to be a strong single frequency emission which broadens down to lower frequencies over time, spreading to approximately 500 kHz in bandwidth over ~10 ms. Among other features observed are a diffuse and unstructured emission, as well as what could potentially be several separate emission sources, with multiple emissions occurring simultaneously, appearing as weaker "ghosts" behind the main MF burst emission. These data in will additionally allow us to search for the presence of sub-millisecond wave packets, sometimes quasi-periodic, reported by LaBelle et al. [1997, J. Geophys. Res. 102, 22221]. Finally, a search for frequency dispersion or absence thereof will provide a test of theories which speculate that different frequencies originate at different altitudes in the ionosphere.
SM13A-1658
Terrestrial AKR Growth Rates and Beaming: Implications for Extrasolar Planetary and Stellar Magnetospheric Radio Emission
Recent advances in our understanding of the electron cyclotron maser instability (CMI) in the Earth's magnetosphere are useful for predicting characteristics of low-frequency radio emission from extrasolar planets. In particular, the discovery that the CMI mechanism is likely driven by a shell-type velocity distribution rather than a loss-cone, and the narrow 'tangent-plane' angular beaming of the resulting radiation may have counterparts in Jovian-type planets both in our own solar system and in the many extrasolar planets discovered in the past 15 years. In addition, the recent discovery of periodic highly circularly polarized radiation from certain very late-type stars is most easily understood by a CMI mechanism which is narrowly beamed. I will discuss the plasma environmental conditions need to sustain the CMI mechanism and compare these constraints to what is presently known concerning extrasolar planetary and stellar magnetospheres.
SM13A-1659
Plasma Wave and Electron Density Structure Observed in the Cusp with a Dual-Rocket Experiment
The Twin Rockets to Investigate Cusp Electrodynamics (TRICE) were launched on December 10, 2007, from Andoya Research Range in Andenes, Norway, into the active cusp. Both payloads traveled north over Svalbard, with one payload reaching an apogee of ~1100 km, and the other reaching ~600 km. The payloads were separated by 100-400 km during the main portion of the flight. Both payloads included waveform receivers with 5 MHz bandwidth. These recorded several distinct types of auroral waves including whistler mode waves below ~1000 kHz and Langmuir-upper hybrid waves at 300-3000 kHz for several hundred km. Both payloads concurrently encountered a distinct period of Langmuir turbulence. Clearly defined wave cutoffs provide measurements of electron density and reveal significant density structure with density enhancements having amplitudes up to 100 percent and scale sizes from meters to tens of kilometers. Analysis of the inferred density profiles using windowed Fourier Transforms or Lomb-Scargle periodograms generates dynamic spectra of the density, which provide estimates of the spectral composition of the density irregularities for time intervals sufficiently short that the stationarity of the spectra can be investigated. The large-scale structures through which the two payloads propagated were measured by both the EISCAT and SuperDARN radars as well as by all-sky cameras operated at Longyearbyen and Ny-Alesund on Svalbard. Using this data when available, comparison of the density irregularity waveforms and spectra from the two flights is studied in relation to spatial and altitude variations of the turbulence. This examination of wave and density structures and the large scale formations with which they are associated will add to the understanding of the large scale electrodynamics of the cusp region.
SM13A-1660
Gap Region FACs Included in Calculating Ground Magnetic Perturbations in a Global MHD Model and Study of the Asymmetric of the Ring Current
In many previous studies that have compared ground-based magnetic perturbations to output from global MHD simulations of the magnetosphere, only the ionospheric Hall currents have been considered. This is problematic at low- and mid-latitudes, where a large percentage of the perturbation is due to currents in the magnetosphere. Inclusion of the currents within the magnetospheric domain is relatively easy, since the perturbations can simply be calculated in parallel and summed to give a total perturbation throughout the domain. But, there is a 'gap' region between the inner boundary of global magnetosphere models and ionospheric electrodynamics models, where it is difficult to solve the MHD equations numerically due to the high Alfven speed as well as the complex physical processes. Efforts have been made in solving the field- aligned currents (FACs) in this 'gap' region in three dimensions by tracing the dipole magnetic field lines starting from the ionosphere. This is done in the global magnetosphere model (BATSRUS) from University of Michigan. In addition to the currents from the global magnetosphere model and horizontal currents (Hall current, Pederson current) in the ionosphere, the newly solved FACs are also taken into account in calculating the ground magnetic perturbations through Biot-Savart integrals. Comparisons between the model results and the data for some real magnetometer stations will be presented. With high resolution, low- latitude perturbations (from both the simulation and the ground-based magnetometers), presented in MLT- UT plots will be shown to study the asymmetry of the ring current during quiet and storm times.
SM13A-1661
Statistical Wavelet Analysis and Index Development of the Magnetosphere-Ionosphere Current System Observed by Terrestrial Magnetometers
The current flowing in the magnetosphere-ionosphere (M-I) form a complicated multiscale geosystem that contains the temporal scales from seconds to days. Due to the nature of this current system, the magnetic effects recorded by the ground-based magnetometers are multi-scaled, impulsive, and asynchronous with non-stationary frequency spectra. Therefore, they are not amenable to traditional time domain or spectral (Fourier) analysis. This talk is to present the results and progresses of a project supported by the NSF Mathematics- Geoscience Joint Program, in which statistical study with the use of the wavelet analysis technique, which is especially suitable for analyzing the data that are impulsive and have time-dependent spectra, are performed upon a large database of ground-based magnetometer measurements to study the characteristics of the M-I current system. Specifically, the talk will cover 1) the development of a wavelet-based index of magnetic storm activity (WISA); 2) the strengths of the WISA over the Dst; 3) cross-wavelet analysis of the symmetric and asymmetric parts of the ring current; 4) an improved WISA that includes the day-to-day dynamic Sq variations. The statistical mathematical tools and the wavelet-based magnetic indices developed by this project will have a broad range of space weather applications and will be very useful for the space science community.
SM13A-1662
Characteristics of 3-component Magnetic Fields of Equatorial Pi 2s - MAGDAS/CPMN Observations in Daytime and Nighttime -
At the onset of magnetospheric substorms, impulsive hydromagnetic oscillations with periods of 40-150 sec, so called Pi 2 magnetic pulsations, occur globally in the magnetosphere. Pi 2 pulsations have been researched for a long time. However, equatorial Pi 2 pulsations have not been analyzed sufficiently and in the most of past studies only H-component of equatorial Pi 2 pulsations were examined. In our previous study, we analyzed H-component magnetic data obtained from MAGDAS/CPMN stations, AAB(G.long.=38.77), LKW(99.78), CEB(123.91), DAV(125.40), YAP(138.08), ANC(-77.15) and EUS(-38.43) which are located near the dip equator. We found that enhancement of H-component wave amplitude of Pi 2 pulsations are occurred near the daytime dip equator. Furthermore, by comparing the data obtained from CEB, DAV and YAP, we also found that as the observation site is nearer to the dip equator, the Pi 2 amplitudes tended to become larger. This amplitude enhancement of Pi 2 pulsations was seen not only in daytime but also in nighttime. We could explain the enhancement in daytime as effect of equatorial electrojet, but we had no idea to explain the enhancement in nighttime. In the present study, we analyze H, D and Z-component wave amplitudes of equatorial Pi 2 pulsations obtained from CEB, DAV and ANC stations for the period of January 1-31, March 1~31 and Jun 1~30 2005. The following new results are obtained; (1) Amplitude ratio of H-component of equatorial Pi 2s at DAV (Dip Lat =-0.65) to CEB (2.73) is found to be almost 1.5 in nighttime, while that in daytime to show the equatorial enhancement and a monthly dependence. (2) Amplitude ratio of D-component to H-component of equatorial Pi 2 are found to be almost 0.3, in particularly to enhance to 0.5 at near local sunrise and sunset time, while H-component equatorial Pi 2 amplitude decrease at sunrise and sunset time. (3) Amplitude ratio of Z-component to H-component of equatorial Pi 2 are found to be 0.3 at CEB and ANC, and 0.1 at DAV respectively. The amplitude ratio of H-component Pi 2s at DAV to CEB is found to be almost 1.5 constantly in night in all season, indicating the CA effect of equatorial Pi 2. The enhancement of the ratio of D-component to H- component at around sunrise and sunset may be explained by the meridional ionospheric current of equatorial Pi 2, but more future study is needed. Acknowledgements We appreciate the following Co-investigators for their contribution to the MAGDAS/CPMN project; Dr. Baylie Damtie(Bahir Dar University, AAB), Dr. Ronald Woodman Pollitt and Dr. Jose Ishitsuka (Instituto Geofisico del Peru, ANC), Dr. Roland Emerito S. Otadoy(University of San Carlos, CEB), Fr. Daniel McNamara(Manila Observatory, DAV), Dr. Severino L. G. Dutra(Brazilian National Space Research Institute, EUS) and Dr. Mazlan Othman and Dr. Mohd Fairos (National Space Agency, LKW). We appreciate Dr. Shinichi Watari(National Institute of Information and Communications Technology) providing the magnetic field data of YAP.
SM13A-1663
The NJIT-UACNJ-PSU Collaborative: Magnetometer measurements from northwest New Jersey in collaboration with South Pole magnetometer measurements from the PENGUIn- AGO instrumentation
We present an overview of a new middle and upper atmospheric observatory located in northwest New Jersey; focusing specifically on magnetic field measurements obtained from a fluxgate magnetometer installed in spring 2008. These data, when used in conjunction with other fluxgate magnetometer data along the east coast and with PENGUIn-AGO fluxgate magnetometer data from across Antartica, lend interesting insight to the high-latitude impacts of co-rotating interaction regions.
SM13A-1664
Analysis on Ionospheric Electron Densities of Storm Events From FORMOSAT-3/COSMIC Observations
The FORMOSAT3/COSMIC mission is a Taiwan-US collaborative project jointly carried out by NSPO in
Taiwan and UCAR in the United States. This mission is composed of six identical micro-satellites launched on
April 14, 2006 in California and provides the first satellite constellation for monitoring global weather using
the Global Positioning System (GPS) radio occultation (RO) technique. The total electron content (TEC)
along the GPS raypath and the vertical profile of the electron density can be obtained. Nowadays there are
around 2000 electron density profiles acquired between 90 and 800 km per day covering a very wide range
of global distributions. Using these profiles, we have studied the correlation between the observed
ionospheric NmF2 and hmF2 and the geomagnetic indice Dst and Kp and found that the NmF2 is usually
enhanced at most local time and latitudes when the values of Kp increase and Dst decrease [Wang
et al., 2008]. In this study, we will present the results from the above analysis for TEC. Variations
of NmF2 and TEC of each storm event will also be investigated to differentiate the correlations at different
storm phases. This will enhance our understanding on the extent NmF2 and TEC can be estimated from a
given value of gomagnetic index as well as the ionospheric response to geomagnetic disturbances.
Reference
Wang, K., S. W. Y. Tam, J. H. Chen (2008), Correlation Study of Ionospheric Electron Densities and
Geomagnetic Indices Using Observational Data From FORMOSAT-3/COSMIC, Eos Trans.
AGU, 89(23), West. Pac. Geophys. Meet. Suppl., Abstract SP35A-03.
SM13A-1665
FORMOSAT-3/COSMIC Observations of the Ionospheric Response to Geomagnetic Activities Characterized by Global Indices
The ionospheric plasma usually responds drastically to severe space weather conditions, signified by strong magnetic field disturbances in the near-Earth environment. The level of disturbances is often well characterized by global indices such as Kp and Dst. Our statistical studies examine the ionospheric electron density under different levels of geomagnetic activities, as characterized by such indices. The studies are based on observations from the GPS occultation experiment (GOX) aboard the six satellites of the FORMOSAT-3/COSMIC mission, a Taiwan-US collaborative project that has been providing, among other data, observations of vertical electron density profiles of the ionosphere up to 800 km altitude since 2006. The focus of our studies is on the statistical change in the F2-layer peak density and its corresponding height, as well as the total electron content (TEC) at the various regions of the global ionosphere due to the effects of geomagnetic disturbances. We discuss the reasons for the spatial and temporal variations in those quantities associated with electron density.
SM13A-1666
PolarDARN/SuperDARN radar echo signatures of moving polar cap arcs
The OMTI all-sky camera at Resolute Bay, NWT (Canada) is located in the middle of the field of view of a newly installed SuperDARN radar pair, PolarDARN. The radars are located at Rankin Inlet and Inuvik and are capable of convection monitoring in significant portion of the northern polar cap. In this study we present several events with the polar cap arc-like forms crossing the Resolute Bay zenith. The forms show clear signatures in the HF echo parameters (both for the E and F region echoes) with the most dramatic effect in the Doppler velocity. The velocity changes polarity (plasma motion towards or away from the magnetic noon) right at the arc location. Local PolarDARN observations of plasma flows are compared with global-scale convection maps. Similarities/differences with published observations of theta-aurora are discussed.
SM13A-1667
ENA Emission from Low Altitude: A Survey of Medium Energy Neutral Atom (MENA) Observations from IMAGE
The precipitation of ring current ions into the upper atmosphere can provide a regionally important source of energy and ionization. The interaction of these ions with the upper atmosphere produces a non-isotropic Energetic Neutral Atom (ENA) emission that can be observed remotely by ENA imaging instrumentation on a suitably located spacecraft. We have recently developed a numerical algorithm for recognizing the signature of ENA emissions from low altitude in the IMAGE/MENA summary spectrograms. We use this algorithm to gather statistics on the observation of these emissions. We will present an overview of MENA observations of ENA emissions from low altitude throughout the IMAGE mission life, focusing on the spatial distributions of these emitted ENAs around Earth and the dependence of the emission on geomagnetic activity, especially the phase of the geomagnetic storm. Finally, we are working to extend our recognition algorithm to the TWINS data set and will provide a progress report on that activity.
SM13A-1668
Characteristics of a new type of SFE observed at CPMN dip-equator stations : SFE*
Solar flares are sometimes accompanied by temporal geomagnetic disturbances in the sunlit hemisphere. These disturbances are known as esolar flare effectsf(SFEs). The arrival of flare-electromagnetic radiations at the earth causes the ionospheric conductivity to drastically increase. Therefore, variations of SFEs are regarded as a simple enhancement of pre-flare ionospheric currents. Many scientists have demonstrated that SFEs show similar variation as the Sq in terms of the direction and magnitude [e.g. McNish, 1937; Nagata, 1952]. In this paper, wefll present a new type of SFE (we call eSFE*f) observed at Circum-pan Pacific Magnetometer Network (CPMN) [Yumoto et al, 2001] stations, in which geomagnetic response to an X-class flare showed negative (not positive) variations in the H component at the Dip-equator stations around local noon. The fact that these events occurred during the time period when the value of the local geomagnetic field was sufficiently above the night-time level suggests totally eastward-ionospheric current, while negative- direction changes (disturbances) of SFE* (H component) strongly suggests the enhancement of westward ionospheric currents. SFE*s may be reflected in complex height structure of the equatorial ionospheric current system. Thus an analysis of the SFE* events will result in an important contribution to the understanding of true picture of ionospheric current system.
SM13A-1669
A Search for Heavy Hydrogen Isotopes in Cosmic-Ray Atmospheric Albedo With SAMPEX/PET
Bidoli et al. (2003) reported observations of large abundances of deuterium and tritium relative to hydrogen below a few tens of MeV/nuc among the secondary particles escaping the atmosphere after the impact of primary cosmic rays. The SAMPEX satellite spent much of 1996-1998 spinning at 1 RPM, and since late 2007 it has been back in 1 RPM spin mode again; thus its sensors spend half their time looking downward, allowing atmospheric albedo particles to be observed directly. With the Proton/Electron Telescope (PET), hydrogen isotopes are measured in the energy range from about 18 MeV/nuc to 60 to 500 MeV/nuc depending on species. We have previously used PET to measure deuterium and tritium among the Earth's geomagnetically-trapped particle population; we will report here on the results of a search for these isotopes among atmospheric albedo during solar-activity minimum conditions.
SM13A-1670
3D, Multi-fluid, MHD Calculations Of Plasma Escape From Mars
We use our new multi-fluid, MHD model to calculate plasma escape from Mars. Our lower boundary is set at 100 km and we have a radial grid resolution of about 10 km in the ionosphere. We consider both photo and electron impact ionization, as well as charge exchange processes in calculating the escape fluxes, using a variety of solar and upstream conditions.
SM13A-1671
Bulk properties of ionospheric oxygen in the magnetosphere
Acceleration of ionospheric oxygen above the polar ionosphere and its further transport to the plasmasheet has been a matter of research for more than two decades. Guiding center particle tracing in external magnetic and electric field has demonstrated that oxygen ions are centrifugally accelerated, especially in regions of strong magnetic field curvature such as the cusps. Direct observations of the centrifugal acceleration are difficult but possible, and have shown that this term in the field-aligned motion of guiding centers may be significant. On the other hand, it is unclear how bulk properties of the oxygen fluid are influenced by centrifugal acceleration. Is the oxygen fluid accelerated as a whole or is it heated? Is the heating anisotropic? Do relaxation processes, e.g. wave-particle interactions, influence the parallel transport by isotropizing the distribution function? Whereas there have been observational studies that addressed these questions, we take a different approach and investigate the oxygen transport using a multi-fluid MHD model. The model implies a Maxwellian particle distribution function and therefore limits the possible physical scenarios to those where the role of relaxation processes is significant. We simulate a number of idealized configurations with constant southward interplanetary magnetic field and investigate the bulk magnetosphere properties of the oxygen fluid that originates in the ionosphere (bulk speeds, plasmasheet pressure and density, number flux into the plasmasheet) as a function of the strength of magnetospheric convection. The ion source is included by juxtaposing an empirical model of thermal ion population based on Akebono observations and more energetic dayside cusp outflow based on empirical relation between the incoming Pointing flux and the outflowing particle flux (the "Strangeway" formula). By qualitatively comparing our results with available observations, we attempt to shed the light on the questions posed above.