Advancing information technology at AGU

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95405/1/eost9018.pd

Polar UVI images to study steady magnetospheric convection events: Initial results

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/94804/1/grl20687.pd

Characterizing the 18 April 2002 storm‐time sawtooth events using ground magnetic data

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95189/1/jgra17938.pd

Origin of the interhemispheric potential mismatch of merging cells for interplanetary magnetic field B Y ‐dominated periods

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95141/1/jgra18727.pd

A statistical investigation of traveling convection vortices observed by the west coast Greenland magnetometer chain

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95409/1/jgra16162.pd

Interpretation of Automated Forward Modeling Parameters for Sawtooth Events and Substorms

Automated Forward Modeling (AFM) is an inversion technique based on magnetic data alone, which can indicate physical parameters associated with electrojets. From perturbations along a meridian, the total electric current crossing the meridian may be determined, as well as the latitudes between which it flowed. The technique is based on nonlinear optimization of the parameters of a forward model. It is possible to compare model output to the original input to ensure that the routine has functioned well and that output parameters are reliable and presumably have physical meaning. Characteristic behaviors of substorms are readily seen in modeling output: the current strengthens rapidly and considerably at an expansive phase onset, following a growth phase during which the electrojet borders move equatorward, usually with some strengthening of current. At onset the poleward border is often seen to move poleward rapidly. Poleward border activity may be noted then and also at other times. After an onset, the recovery phase is often marked by a retreat of the equatorward border, indicating the well-known shrinkage of the auroral oval then. These complete cycles of activity are absent in sawtooth events. Our output parameters can be diagnostic of onsets and useful in determining their location and role in sawtooth events. These have many of the characteristics of expansive phase onsets, but maximum poleward expansion of the poleward border is followed by equatorward movement reminiscent of a growth phase. Since this is correlated with the interplanetary magnetic field remaining southward, the difference from common expansive phase phenomenology may simply be the lack of a recovery phase

Model-Driven Image Analysis to Augment Databases

In this paper we consider how information may be obtained from images. To search large image collections we need to search on secondary parameters. We may look for images containing certain types of objects, for images where the objects are of a certain size or shape, or for images having certain features. Since we now have techniques to rapidly acquire and store many images, we need techniques for automatic image analysis to generate such parameters. This paper describes a promising category of image analysis, namely model-driven methods. Two examples, operating in very different domains, are presented. 1. Introduction To be able to retrieve images stored in databases we must associate identifying parameters with each of the images. It is through these parameters that we can select stored images for display, comparison, and further analysis. Primary parameters are produced when the images are obtained, and describe the imaging event and its process. For satellite images of earth we ..

The Role of Solar Wind Density in Cross Polar Cap Potential Saturation Under Northward Interplanetary Magnetic Field

©2017. American Geophysical Union. All Rights Reserved. The role of solar wind density in the cross polar cap potential (CPCP) response under northward interplanetary magnetic field is investigated with observation-based global simulations. A rare event was reported by Clauer et al. (2016) during which the ionospheric electric field E ISP does not saturate under extreme interplanetary electric field (IEF) of â¼15 mV/m. While commonly utilized coupling functions based on IEF fail to provide an unambiguous explanation for the linear response, the Lyon-Fedder-Mobarry-Magnetosphere-Ionosphere Coupler/Solver model is used to explore the mechanisms in this study. The model first reproduces the observed linear feat ures of the E ISP . The simulated CPCP also responds linearly to IEF variations. A controlled simulation is designed with solar wind density artificially reduced to 10% of the observed value while all other parameters such as the IEF are kept the same. The controlled simulation shows saturation of the E ISP as well as the CPCP. Further analysis shows the difference in the magnetosheath plasma β, implying the distinct dominant forces between the two simulations. The Lopez magnetosheath force balance theory is used to explain the CPCP responses under different solar wind densities. This comparison study highlights the role of solar wind density in determining the magnetosphere-ionosphere response to extreme interplanetary drivings.Link_to_subscribed_fulltex