Estimation and testing for spatially indexed curves with application to ionospheric and magnetic field trends

We develop methodology for the estimation of the functional mean and the functional principal components when the functions form a spatial process. The data consist of curves $X(\mathbf{s}_k;t),t\in[0,T],$ observed at spatial locations $\mathbf{s}_1,\mathbf{s}_2,...,\mathbf{s}_N$. We propose several methods, and evaluate them by means of a simulation study. Next, we develop a significance test for the correlation of two such functional spatial fields. After validating the finite sample performance of this test by means of a simulation study, we apply it to determine if there is correlation between long-term trends in the so-called critical ionospheric frequency and decadal changes in the direction of the internal magnetic field of the Earth. The test provides conclusive evidence for correlation, thus solving a long-standing space physics conjecture. This conclusion is not apparent if the spatial dependence of the curves is neglected.Comment: Published in at http://dx.doi.org/10.1214/11-AOAS524 the Annals of Applied Statistics (http://www.imstat.org/aoas/) by the Institute of Mathematical Statistics (http://www.imstat.org

Ionospheric Induced Scintillation: A Space Weather Enigma

The effect of scintillation on radio signals whose propagation path involves the Earth’s ionosphere is analogous to the allies of World War II receiving radio messages that had passed through the Enigma machine. In both these cases, man-made information has been encrypted and transmitted via radio. The two encryption methods are shown in Figure 1. The right panel shows a World War II Enigma machine used extensively by German U-boats to convey encrypted messages transmitted by radio [Perera, 2010]. The left panel gives an extreme example of a mapping of ionospheric irregularities at 3 m, which creates very severe scintillation on radio communications through this ionospheric region [Fejer, 1996]. In addition, the task of formally deciphering the encrypted signal is a monumental task as time is of the essence and old information quickly becomes redundant

Development of a Cubesat Pico-Satellite

The CubeSat Project was developed by California Polytechnic State University (CalPoly) and Stanford University in order to provide launch opportunities to universities previously unable to afford access to space. Today, it provides low-cost launch opportunities to students, government, and business. The CubeSat program is able to provide these low-cost launch opportunities by defining a common form factor and design guidelines. All satellites conforming to the regulations are able to be deployed from a standard, flight-proven deployment system called a PPOD. by adhering to the prescribed form factor and safety requirements, necessary documents and export licenses and more easily obtained. CalPoly coordinates launch opportunities and facilitates the export and licensing of completed satellites

Microgravity Experiments for the ISS

The Get Away Special (GAS) team is a microgravity research team know for leading Utah State University to impressive distinction of flying more experiments in space than any other university in the world. The following experiments were designed by the GAS team after receiving the opportunity to develop and experiment to be performed by a Space Flight Participant aboard the International Space Station (ISS)

Theoretical Study of the High-Latitude Ionosphere’s Response to Multicell Convection Patterns

It is well known that convection electric fields have an important effect on the ionosphere at high latitudes and that a quantitative understanding of their effect requires a knowledge of the plasma convection pattern. When the interplanetary magnetic field (IMF) is southward, plasma convection at F region altitudes displays a two-cell pattern with antisunward flow over the polar cap and return flow at lower latitudes. However, when the IMF is northward, multiple convection cells can exist, with both sunward flow and auroral precipitation (theta aurora) in the polar cap. The characteristic ionospheric signatures associated with multicell convection patterns were studied with the aid of a three-dimensional time-dependent ionospheric model. Two-, three-, and four-cell patterns were considered and the ionosphere’s response was calculated for the same cross-tail potential and for solar maximum and winter conditions in the northern hemisphere. As expected, there are major distinguishing ionospheric features associated with the different convection patterns, particularly in the polar cap. For two-cell convection the antisunward flow of plasma from the dayside into the polar cap acts to maintain the densities in this region in winter. For four-cell convection, on the other hand, the two additional convection cells in the polar cap are in darkness most of the time, and the resulting O+ decay acts to produce twin polar holes that are separated by a sun-aligned ridge of enhanced ionization due to theta aurora precipitation. For three-cell convection, only one polar hole forms in the total electron density, but in contrast to the four-cell case, an additional O+ depletion region develops near noon owing to large electric fields causing an increased O+ + N2 loss rate. These general distinguishing features do not display a marked universal time variation in winter

Model‐Based Properties of the Dayside Open/Closed Boundary: Is There a UT‐Dependent Variation?

The open‐closed boundary (OCB) defines a region of significant transformation in Earth\u27s protective magnetic shield. Principle among these changes is the transition of magnetic field lines from having two foot points, one in each hemisphere, to one foot point at Earth, the other mapping to the solar wind. Charged particles in the solar wind are able to follow these open field lines into Earth\u27s upper atmosphere. The OCB also defines the polar cap boundary. Being able to identify and track the OCB allows study of several components of the geomagnetic system. Among them are the electrodynamics of the geomagnetic field and the reconnection balance between the dayside and nightside of the geomagnetic field. Furthermore, the OCB can provide insights into the precipitation of energetic protons into the ionosphere. Using the Tsyganenko model of the geomagnetic field (T96), we demonstrate a diurnal fluctuation which we call the Universal Time (UT) effect of the OCB. This UT effect is independent of all other inputs. We anticipate this UT effect to have important consequences in modeling the OCB and other polar cap‐associated structures, especially polar cap absorption events that adversely affect high‐frequency radio wave propagation in polar regions

A Theoretical \u3ci\u3eF\u3c/i\u3e Region Study of Ion Compositional and Temperature Variations in Response to Magnetospheric Storm Inputs

The response of the polar ionosphere to magnetospheric storm inputs was modeled. During the “storm,” the spatial extent of the auroral oval, the intensity of the precipitating auroral electron energy flux, and the plasma convection pattern were varied with time. The convection pattern changed from a symmetric two-cell pattern with a 20-kV cross-tail potential to an asymmetric two-cell pattern with enhanced plasma flow in the dusk sector and a total cross-tail potential of 90 kV. During the storm there were significant changes in the ion temperature, ion composition, and molecular/atomic ion transition height. The storm time asymmetric convection pattern produced an ion temperature hot spot at the location of the dusk convection cell owing to increased ion-neutral frictional heating. In this hot spot there were significantly enhanced NO+ densities and hence molecular/atomic ion transition heights. During the storm recovery phase, the decay of the enhanced NO+ densities closely followed the decrease in the plasma convection speed. During the storm, elevated ion temperatures also appeared at high altitudes in the midnight-dawn auroral oval region. These elevated ion temperatures were a consequence of the storm-enhanced topside O+ densities, which provided better thermal coupling to the hot electrons. This region also contained reduced molecular/atomic ion transition heights. These elevated ion temperatures and reduced transition heights persisted for several hours after the storm main phase ended

A Theoretical Study of the Global \u3ci\u3eF\u3c/i\u3e Region for June Solstice, Summer Maximum, and Low Magnetic Activity

We constructed a time-dependent, three-dimensional, multi-ion numerical model of the global ionosphere at F region altitudes. The model takes account of all the processes included in the existing regional models of the ionosphere. The inputs needed for our global model are the neutral temperature, composition, and wind; the magnetospheric and equatorial electric field distributions; the auroral precipitation pattern; the solar EUV spectrum; and a magnetic field model. The model produces ion (NO+, O2+, N2+, N+, O+, He+) density distributions as a function of time. For our first global study, we selected solar maximum, low geomagnetic activity, and June solstice conditions. From this study we found the following: (1) The global ionosphere exhibits an appreciable UT variation, with the largest variation occurring in the southern winter hemisphere; (2) At a given time, NmF2 varies by almost three orders of magnitude over the globe, with the largest densities (5 × 106 cm-3) occurring in the equatorial region and the lowest (7 × 103 cm-3) in the southern hemisphere mid-latitude trough; (3) Our Appleton peak characteristics differ slightly from those obtained in previous model studies owing to our adopted equatorial electric field distribution, but the existing data are not sufficient to resolve the differences between the models; (4) Interhemispheric flow has an appreciable effect on the F region below about 25° magnetic latitude; (5) In the southern winter hemisphere, the mid-latitude trough nearly circles the globe. The dayside trough forms because there is a latitudinal gap of several degrees between the terminator and the dayside oval. In this gap, there is no strong ion production source, and the ionosphere decays; (6) For low geomagnetic activity, the effect of the auroral oval on the densities is not very apparent in the summer hemisphere, but is clearly evident in the winter hemisphere; (7) The densities in both the northern and southern polar caps exhibit a complex temporal variation owing to the competition between the various photochemical and transport processes