Exploring the Global Response of the Sun-Heliosphere-Magnetosphere-Ionosphere-Atmosphere System III Posters
Presiding: S M Bailey, University of Alaska; R R Heelis, Center for Space Sciences, University of Texas at Dallas
SA13A-01 1330h
An Investigation of the Effect of Particle Ionization on the Earth's Middle Atmosphere Using a Two-dimensional Model
The amount of NO transported to the stratosphere is determined by mesospheric processes where uncertainties in the production, loss and transport of odd nitrogen exist. We have used the NRL 2 Dimensional model of atmospheric chemistry and dynamics to investigate aspects of the transport of odd nitrogen from the mesopause region to the upper stratosphere. An important aspect of the NOx transport problem is determining the influence of time varying middle energy electron ionization rates on the flux of odd nitrogen into the lower atmosphere. This problem is investigated with the two dimensional model employing a time dependent ionization source scaled to the measured particle energy incident on the atmosphere. The model results are guided by comparisons to HALOE measurements of mesospheric and stratospheric odd nitrogen. In particular we will use the data to provide information on the interannual and seasonal variability of odd nitrogen in the upper stratosphere/mesosphere. These data will be compared over several years with the model results employing the time dependent energy measurements to calculate the flux of odd nitrogen into the lower atmosphere. The effect of the enhanced odd nitrogen on upper stratospheric ozone will be discussed.
SA13A-02 1330h
Thermospheric neutral wind response to geomagnetic storms
The CISM Coupled Magnetosphere-Ionosphere-Thermosphere (CMIT) model, which includes two-way coupling between the Thermosphere/Ionosphere Nested Grid (TING) Model and the Lyon-Fedder-Mobarry (LFM) global magnetosphere MHD code, is run to investigate the near Earth space weather response to the 12-15 May 1997 geomagnetic storm. In this paper we will focus on the high and middle latitudes thermospheric wind variations during the storm. Two major processes change the storm time neutral wind circulation: an enhanced ion drag effect that forces the neutrals to follow the expanded ion convective drift, and an intensified Joule heating effect that increases the high latitude pressure gradient and thus changes the global wind pattern. We will discuss temporal and spatial evolutions of neutral wind changes after the storm commencement, and the time cadence of neutral wind recovery after the storm. Of particular interest to this study is a jet of neutral winds that occurs in the middle latitudes during the storm.
SA13A-03 1330h
High Latitude Thermospheric Winds A Multi-Year Study
Based on multi-year Fabry-Perot interferometer O 6300 A emission thermosphere neutral wind observations from high latitude stations: Thule (76.4 N) and Resolute (74.9 N), we examine the long-term inter-annual variations of the thermosphere neutral winds in the northern high latitude region. We have noticed that thermosphere neutral winds tend to flow anti-sunward, which is consistent with earlier observations. However, the magnitude of the neutral winds varies from year to year. Solar, IMF, and geomagnetic activities are believed to be the contributing factors. We will compare the neutral wind data from Thule of 1987/88 and 1988/89 to Resolute data from 2003/04 and 2004/05. Strong amplitude of neutral winds was observed at Thule during the 1987/88 winter season, so far the neutral winds observed at Resolute have been smaller in general. Comparisons with model and further analysis are planned.
SA13A-04 1330h
On the possible correlation of impulsive polar nitrate enhancements and solar energetic particle events
It is known that energetic solar proton events can penetrate deep into the Earth's polar atmosphere, dissociating O3 and N2 and leading to the formation of odd nitrogen compounds (or generically referred to as NOy). Several recent works have examined ice core nitrate data and observed impulsive nitrate enhancements within weeks of large known solar proton events. It has been suggested that the nitrate molecules produced by large solar proton events can precipitate downward rapidly and be deposited by snowfall into polar regions. In the past few years, advancements in ice core analysis techniques have allowed for the production of much higher-resolution data than previously available. In this paper we present the results of a comparison between extremely high-resolution ice core measurements and space-based cosmic ray data. The nitrate data are the highest-resolution available today, are accurately dated, and come from multiple cores. We will address the question of whether the previously observed correlation, which was based on a limited number of events, is reproducible.
SA13A-05 1330h
Thermosphere Density and Wind Responses During Severe Magnetic Storms from CHAMP and GRACE Accelerometer Measurements
Measurements of atmospheric density and winds near 410 km from the STAR accelerometer on the CHAMP satellite and near 490 km from the STAR accelerometers on the GRACE satellites are used to illustrate the spatial-temporal dependence of the thermospheric response to solar/geomagnetic storms. The storm studied here is the Oct/Nov 2003 severe storm events. This interval includes periods of elevated magnetic activity with kP values of 5-9. Measurements made by the CHAMP satellite are available from -87° to +87° latitude during both night and day at local times near 01:00 and 13:00 hours, while measurements made by the GRACE satellites are available from -89° to +89° latitude at local times near 04:00 and 16:00. During times of geomagnetic activity, density measurements exhibit enhancements of 200-300%. Northern hemisphere day-time responses are much larger than in the Southern hemisphere; the origins of this effect are unknown. Night-time density disturbances more readily propagate to equatorial latitudes at night, possibly facilitated by the predominant equator-ward flow in both hemispheres due to the diurnal tides driven by in-situ EUV heating. The CHAMP density measurements are compared with density predictions from the NRL-MSISe-00 empirical density model, and demonstrate some model shortcomings. Measurements of cross-track accelerations also provide the opportunity to estimate zonal winds from the equator to about ± 60° latitude, transitioning to a measure of purely meridional winds at the turning point of the orbit near ± 87° and ± 89° latitude for the CHAMP and GRACE missions, respectively. These horizontal components are compared to the thermospheric Horizontal Wind Model (HWM-93). The GRACE satellites also provide radial axis accelerometry which can be used to estimate vertical winds.
http://suttonek.000k2.com
SA13A-06 1330h
Specifying the Upper Atmospheric Drivers Using an Ensemble Kalman Filter
A data assimilation system for specifying the thermospheric composition and density in near real time has been developed over the last several years. Although it is possible to describe the physics of the upper atmospheric forcing, quantifying the time-dependent drivers still remains difficult - particularly during geomagnetic storm conditions. Incorporating the high latitude forcing into the data assimilation system requires knowledge of the spatial and temporal variations of the convection electric field and the auroral precipitation. Innaccurate knowledge of these drivers in data assimilation systems for space weather applications is the current limitation in improving the specification further. Compared with the solar wind parameters that force the magnetosphere, the drivers of the upper atmosphere, although well understood, remain poorly quantified. At best, the globally averaged Joule heating rate at a given time is only known to within a factor of two. At a given location, this uncertainty can rise to a factor of ten. This research endeavors to better quantify the balance between solar and magnetospheric forcing over the range of solar and geomagnetic activity through the implementation of an ensemble Kalman filter. This research plans to use recent advances in meteorology which use the ensemble Kalman filter to specify the drivers for the troposphere. Since the solar heating at low latitudes and the magnetospheric sources at high latitudes control the magnitude and spatial distribution of the global circulation, these drivers strongly affect the neutral composition and density structure, and as a result, the ensemble Kalman filter approach for specifying the drivers may be even better suited for the thermosphere. Further, the improved driver specification, in turn, improves the composition and density specification in the data assimilation system.
SA13A-07 1330h
Forecasting GPS Scintillations For Low Latitude Stations, in Brazil, using Real-Time Space Weather Data.
The Global Positioning System (GPS) is a useful constellation of satellites for navigation. In low latitudes, however, the signals from these satellites are plagued with ionospheric scintillations, due to the presence of plasma irregularities in the ionosphere, between sunset and sunrise. This phenomenon occurs during approximately six months of the year, although many nights may present less scintillations or no scintillations at all. To help in finding out, in advance, which nights will be `calm', in terms of scintillations, we propose a method for predicting how frequent strong scintillations will be for a given night. To do this, firstly, we need to have at hand real time indices of space weather, which can be found at NOAA/SEC, in Boulder, Colorado or, more specifically, in their summary `Space Weather Alerts and Warnings Timeline.' Secondly, we need a measurement of the amount of scintillations, for each night, that we take to be the average scintillation index for all scintillations on all observed satellites, for that night. The scintillation index is similar to the statistical dispersion, applied to the time-series that represents the satellites signal. From all the data supplied in the NOOA/SEC timeline, we choose to use only the alerts and warnings concerning geomagnetic data, and mostly the ones related to the Kp index. The reason for choosing geomagnetic data is that the earth's magnetic field shows the effects of solar charged particles on earth, which can be measured by geo-synchronous satellites (e.g., GOES.) With these two ingredients (previous scintillation data and space-weather indices,) we show that during magnetic storms the ionosphere is quieter, with regards to scintillation on GPS signals. Then, it is possible to do the opposite: by looking at the space weather warnings, we can predict the amount of scintillation at a given night. The scintillation data used to support this method ranges from 2003 through 2005. In this work, emphasis is given to the period October-November, 2003, which contains three days used by other authors, to support an argument that is opposite to ours. Our data has been collected at a station at Natal, Brazil, located at 5.84° S and 35.20° W. The magnetic declination is 21° W and the magnetic dip is 20°.
http://agu2005.ponta-negra.com
SA13A-08 1330h
Auroral Undulations During Magnetic Storms: TIMED/GUVI Observations
Giant undulations on the equatorward edge of the diffuse aurora have been identified in TIMED/GUVI auroral images in the far ultraviolet wavelengths. Some new features have been observed: (1) The GUVI 121.6nm auroral images provide direct optical evidence that the undulations occur in the proton aurora, (2) Undulations are not limited to the dusk sector, they can occur in all local time sectors, (3) Both large ionospheric ion drift velocity (1000 m/s and above) and strong velocity shear (> 0.1 1/s) appear to be a necessary condition for the undulation to occur, (4) While almost all of the undulation events are observed during magnetic storms (Dst < -60 nT), one exceptional case shows undulation in the dayside associated with a positive Dst (30 nT), a large solar wind speed and a high solar wind dynamic pressure. The undulations can be explained by the K-H instability.
SA13A-09 1330h
Ion Outflow Response to the ICME on 29 October-03 November 2004 and the ICME on 07-13 November 2004
We examine the flux of ions outflowing from the polar ionosphere into the magnetosphere in response to two different Interplanetary Coronal Mass Ejections (ICMEs). We discuss differences in the solar wind conditions and then compare and contrast different outflow responses. We examine the outflowing thermal ions that flow away from the Earth along magnetic field lines. Previous simulation studies indicate that such outflowing ions can travel to the plasma sheet and ring current. Most of the field-aligned outward moving ions we observe during these storms appears to be O+. The flux of O+ outflowing ions has been shown to increase linearly with increasing solar wind pressure. However, much of the previous work was done over a limited range of solar wind dynamic pressures. We look at these ICMEs, which have large solar wind pressures, to determine if the outflow response is linear at higher pressures. We use ion measurements from the Thermal Ion Dynamics Experiment (TIDE) on the Polar spacecraft and solar wind measurements from the Solar Wind Electron Proton Alpha Monitor (SWEPAM) on the ACE spacecraft.
SA13A-10 1330h
What Determines the Properties of the Prompt Penetration Electric Fields? -- A Case Study of April 17, 2002, Storm Event
During geomagnetic storms, the prompt penetration to lower latitudes of the convection electric fields has often been observed. The mechanism involves interactions of the solar wind, magnetosphere, and ionosphere. One of the major causes is a sudden change in the cross polar cap potential drop, which represents a change in the region-1 field-aligned currents and is controlled by the interaction between the solar wind and magnetosphere. The pressure in the plasma sheet is redistributed by the convection electric field. Another contribution is from the reconfiguration of the storm-time magnetic fields. The resultant pressure gradients from inner edge of the plasma sheet generate the region-2 field-aligned currents which tend to shield the region earthward of it from the convection electric fields. The typical time scale of the penetration electric field is less than one hour, before shielding is established. During some time periods, a strong correlation has been observed between the interplanetary electric field and the penetration fields in the equatorial ionosphere [e.g., Nishida, 1968; Kelley et al., 2003]. The main goal of our study is to explore the impact of the various solar wind and IMF parameters on the correlation between the interplanetary and equatorial ionospheric electric fields, such as reported in Kelley et al. [2003]. Utilizing the Rice Convection Model (RCM) and altering the various input parameters, we investigate the temporal variation of the penetration electric field. Our previous results demonstrate that the penetration electric field can modify the ionospheric dynamo by changing the conductivity and neutral wind, preferentially at night. We will address the feedback of the time-dependent conductivity and neutral wind on the penetration electric field. Furthermore, we will discuss our results in relation to global latitudinal-chain observations of the ionospheric electric field during the April 17, 2002, storm event.
SA13A-11 1330h
High speed solar wind streams with and without magnetic storms at Earth
We show two high speed solar wind streams in April 2002 carrying solar energy flux that with high probability, couple to the Earth's magnetosphere and cause enhanced magnetospheric fluctuations. Many aspects of the two streams are similar and with similar effects at Earth. However there are also significant differences that allow us to differentiate cause and effect in some cases. For the first stream the IMF is primarily northward and Dst at Earth is modest. The second stream has strong southward IMF and large Dst. The first high speed stream is not associated with a large magnetic storm, but strong Pc5 pulsations are observed just inside the magnetopause (dawn, noon, and dusk), in the magnetotail, and at geostationary orbit. The second high speed stream shows strong magnetospheric pulsations and is associated with a large magnetic storm. Enhanced fluxes of energetic particles are observed for both streams, but the second stream with the geomagnetic storm shows fluxes extending across a larger L-shell range. Wind observations, 70-80 RE upstream from Earth, show significant, sustained power at Pc5 frequencies intrinsic to the high speed stream for both cases. The enhanced power is evident in dynamic pressure fluctuations and to a lesser extent in compressional magnetic field fluctuations. In the Earth's magnetosphere the wave mode depends on the location that the waves are observed. Polodial mode waves are commonly seen on the dawn and dusk flanks of the magnetosphere, but at the nose the compressional component is frequently dominant. In the magnetotail, there are both polodial and torodial modes, but the torodial mode is usually dominant.
SA13A-12 1330h
Kp forecast models
Magnetically active times, e.g., Kp > 5, are notoriously difficult to predict, precisely the times when such predictions are crucial to the space weather users. Taking advantage of the routinely available solar wind measurements at Langrangian point (L1) and nowcast Kps, Kp forecast models based on neural networks were developed with the focus on improving the forecast for active times. To satisfy different needs and operational constraints, three models were developed: (1) a model that inputs nowcast Kp and solar wind parameters and predicts Kp 1 hr ahead; (2) a model with the same input as model 1 and predicts Kp 4 hr ahead; and (3) a model that inputs only solar wind parameters and predicts Kp 1 hr ahead (the exact prediction lead time depends on the solar wind speed and the location of the solar wind monitor.) Extensive evaluations of these models and other major operational Kp forecast models show that, while the new models can predict Kps more accurately for all activities, the most dramatic improvements occur for moderate and active times. Information dynamics analysis of Kp, suggests that geospace is more dominated by internal dynamics near solar minimum than near solar maximum, when it is more directly driven by external inputs, namely solar wind and interplanetary magnetic field (IMF).
SA13A-13 1330h
A Geomagnetic Cutoff Rigidity Interpolation Tool: A Discussion of its Application to Space Weather
We have developed a fast and accurate geomagnetic vertical cutoff interpolation tool that has general space weather applications. The interpolation aid is based on cutoff rigidity values determined from world grids of geomagnetic cutoff rigidities obtained by tracing cosmic ray trajectories through the Tsyganenko magnetospheric field model combined with the International Geomagnetic Reference Field. Calculations were done for a 450 km satellite altitude for all magnetic conditions represented by Kp indices ranging from super quiet to extremely disturbed. The interpolation tool extrapolates these results to other positions or altitudes. We demonstrate the accuracy of this vertical geomagnetic cutoff interpolation tool by comparing our predicted cutoff latitudes with those measured by the SAMPEX spacecraft. In general our predicted cutoff latitudes are within about one degree of the observed cutoff latitudes for low levels of geomagnetic activity and within several degrees at high levels of geomagnetic activity.
SA13A-14 1330h
Simulation of the Halloween 2003 and April 2002 Magnetic Storms
We examine two large magnetic storms, the events of Halloween 2003 and the April 2002, through numerical simulation. We have performed high resolution simulations of these events using the Lyon-Fedder-Mobarry (LFM) global MHD code. ACE solar wind field and plasma observations will be used for the simulations. However, the Halloween 2003 event will be driven using our synthesis of the ACE and GEOTAIL plasma data, which was shown in the last meeting to best agree with the magnetospheric observations. We will compare the activity of the storms in the simulations, focusing on strongly driven periods in which sawtooth activity has been observed. We will examine closely the plasma and magnetic field configurations in the inner magnetosphere to identify the possible presence of such sawtooth activity in the simulations, comparing our results with the available magnetospheric and ionospheric observations. We plan to compare these results with those from the CMIT model, in which the ionosphere of the LFM is replaced by the NCAR Thermosphere Ionosphere Nested Grid (TING). [This work is supported by NSF grant ATM-0120950].