Application of Autoregressive Moving Average Linear Prediction Filters to the Characterization of Solar Wind-Magnetosphere Coupling

Linear prediction filtering techniques have been used in studying the coupling processes between the solar wind and magnetosphere. The magnetosphere is a complex, dynamic system with at least two independent coupling methods for energy input, driven and unloading. Linear models were built and tested on the Bargatze data set, consisting of over 70 days of geomagnetic indices and solar wind data ordered in 34 intervals of increasing geomagnetic activity. Linear filtering techniques employing single-and multiple-input, autoregressive models predicted values of the magnetic index AL from solar wind data. The impulse response curves of the AL-coupling function groups showed amplitude peaks at 25 and 70 minutes, confirming results in previous studies. The separate peaks indicate responses corresponding to the driven and unloading time scales. The average correlation coefficients generated between predicted AL values and the measured values of AL were 0.665, 0.738, and 0.793 for single, dual, and triple input models, respectively

Life Cycle Analysis of Convective Cells through Image Processing and Data Fusion

Nykyaikana numeeriset säänennustusmallit pystyvät ennustamaan suuren skaalan sääilmiöitä merkittävällä tarkkuudella. Nämä mallit ovat kuitenkin liian karkeita pienen skaalan sääilmiöille, kuten paikallisille ukkosmyrskyille. Paikallinen, lyhyen ajan säänennustaminen eli lähihetkiennustaminen on haastava meteorologinen ongelma. Tämä vaatii erityisesti ajallisesti ja paikallisesti tarkkojen modernien kaukokartoitusinstrumenttien sekä tietokonenäköön perustuvien menetelmien soveltamista. Tämä diplomityö käsittelee paikallisten ukkosmyrskyjen eli konvektiosolujen lähihetkiennustamista. Erityisesti tarkastelemme oliopohjaista konvektiosolun jäljitystä, joka on yleisesti käytetty lähestymistapa ukkosen lähihetkiennustamisessa. Perinteisesti konvektiosolun lähihetkiennustamiseen sovelletaan säätutkadataa. Työ esittelee uuden konvektiosolujen jäljitysmenetelmän, joka hyödyntää sekä säätutka- että salamainformaatiota. Koska salamadata antaa tärkeää lisäinformaatiota ukkosmyrskyjen paikasta ja liikkeestä, uusi datafuusiopohjainen menetelmä parantaa algoritmin toimintavarmuutta. Työssä testataan algoritmin toimintaa useiden esimerkkitapausten avulla. Suunniteltu jäljitysmenetelmä tarjoaa tärkeän apuvälineen moniin käytännön tarkoituksiin. Ensisijainen sovelluskohde on vaarallisten konvektiosolujen monitorointi sekä liikkeen ennustaminen. Lisäksi menetelmää voidaan soveltaa ukkosen elinkaaren ja ominaisuuksien analysointiin. Tämä työ tarkastelee ukkossolun tilastollisia ominaisuuksia uuden jäljitysmenetelmän avulla. Menetelmällä tuotettua informaatiota sovelletaan myös solun salamoinnin ja erilaisten tutkaparametrien välisen yhteyden analysointiin. Lisäksi työssä suunnitellaan probabilistiseen päättelyyn perustuva malli, jonka avulla voidaan tarkastella yksittäisen konvektiosolun salamariskiä. Työssä suunnitellaan myös uusi sumeaan logiikkaan perustuva automaattinen asiantuntijamalli, jonka avulla voidaan antaa informaatiota konvektiosolun elinvaiheista. Mallin päätehtävä on analysoida asiantuntijan tavoin konvektiosolun voimistumista tai heikkenemistä.Today numerical weather models can predict large scale weather phenomena with a reasonable accuracy. Still, these models are too coarse for small scale rapidly changing weather phenomena, such as thunderstorms. Therefore, doing short term local forecasts, i.e. nowcasting, is a challenging task for the contemporary weather forecasting. State-of-the-art remote sensing instruments and computer vision techniques are the key to this challenging task. This thesis discusses nowcasting of thunderstorms, i.e. convective cells, through different computer vision techniques that are applied to spatially and temporally accurate weather radar and lightning data. Emphasis is on object-oriented convective cell tracking, which is widely accepted as an important concept regarding the nowcasting of convective cells. Conventionally, the nowcasting of convective cells is performed through weather radar data. In this thesis, we propose a novel cell tracking method, which fuses both weather radar and important lightning information. The aim of the data fusion is to consolidate the tracking, as more information is incorporated in the procedure. The functioning of the algorithm is tested with several case studies. The proposed tracking algorithm provides an important tool for several applications. Primarily, convective cell tracking is applied to monitoring and predicting movement of hazardous thunderstorms. It can also be used for analyzing cell properties and life cycle. Therefore, this thesis examines also convective cell properties and derives descriptive statistic of the convective cell by means of the proposed tracking algorithm. The results are based on tests, which are carried out through an extensive case material provided by the Finnish Meteorological Institute. The thesis elaborates also on the lightning properties of the convective cell. The information extracted by the tracking algorithm is applied to analyze the relationship between lightning and different radar parameters within the cell. In addition, probabilistic reasoning is applied to determine possible lightning hazard of individual cells. Finally, this thesis proposes a new fuzzy logics model for analyzing cell life cycle phases. The model provides an automated method, which mimics expert made reasoning and infer whether the cell is intensifying or dissipating

Linear mixing model applied to coarse resolution satellite data

A linear mixing model typically applied to high resolution data such as Airborne Visible/Infrared Imaging Spectrometer, Thematic Mapper, and Multispectral Scanner System is applied to the NOAA Advanced Very High Resolution Radiometer coarse resolution satellite data. The reflective portion extracted from the middle IR channel 3 (3.55 - 3.93 microns) is used with channels 1 (0.58 - 0.68 microns) and 2 (0.725 - 1.1 microns) to run the Constrained Least Squares model to generate fraction images for an area in the west central region of Brazil. The derived fraction images are compared with an unsupervised classification and the fraction images derived from Landsat TM data acquired in the same day. In addition, the relationship betweeen these fraction images and the well known NDVI images are presented. The results show the great potential of the unmixing techniques for applying to coarse resolution data for global studies

F-region Dusk Ion Temperature Spikes at the Equatorward Edge of the High Latitude Convection Region

By examining continuous data from the Poker Flat Incoherent Scatter Radar (PFISR) in Poker Flat, Alaska, short-lived enhancements in the F-region ion temperature, or "Tᵢ spikes", were discovered in the evening while the radar was on the equatorward edge of the high latitude convection region. These enhancements were several hundred Kelvin above the background temperature, would last less than 15 minutes and were preceded by sharp depletions in plasma density (of roughly one half). Though they were mostly detected in the summer, 25 events throughout a whole year of data were identi ed in which the spike occurred within 1.5 hours of the density drop. By examining the location of PFISR at the time of the enhancements, as well as the conditions under which these spikes occurred, it was concluded that these enhancements were the result of electric elds increasing the frictional heating between ions and neutrals. By then examining geophysical data, it was found that these events were temporal and related to changes in magnetic indices. One possible explanation for the observations is that the electric eld is at its strongest near the plasmapause during substorms. Another more likely possibility is that during substorms the region of sunward ion convection expands into a region in the evening side where the neutral gas moves in a direction opposite to the ions, thereby enhancing the frictional heating rate

Absolute Positioning Using the Earth\u27s Magnetic Anomaly Field

Achieving worldwide alternatives to GPS is a challenging engineering problem. Current GPS alternatives often suffer from limitations such as where and when the systems can operate. Navigation using the Earth\u27s magnetic anomaly field, which is globally available at all times, shows promise to overcome many of these limitations. We present a navigation filter which uses the Earth\u27s magnetic anomaly field as a navigation signal to aid an inertial navigation system (INS) in an aircraft. The filter utilizes highly-accurate optically pumped cesium (OPC) magnetometers to make scalar measurements of the Earth\u27s magnetic field and compare them to a map using a marginalized particle filter approach. We demonstrate navigation accuracy of 13 meters DRMS with a high quality magnetic anomaly map at low altitudes with real flight data. We conduct a simulation over the continental United States to predict accuracies with respect to variables like location and altitude. Finally, we address the problem of map availability by presenting a method for a self-building magnetic anomaly model

磁気嵐に伴う極冠電離圏でのプラズマ密度構造に関する研究

The polar-cap ionosphere is directly coupled with the magnetosphere, which makes the region unique compared with the low- and mid-latitude ionosphere. Because of this coupling with the magnetosphere, the polar cap ionosphere is disturbed during magnetic storms. In this thesis, we examine ionospheric plasma density structures in the polar cap during magnetic storms. In Chapter 1, after reviewing the solarterrestrialenvironment in general, we present some important features of the polar upper atmosphere and ionosphere with special attention to magnetic storms. Following this general introduction, Chapters 2 and 3 are dedicated to specific researches. In Chapter 2, Steep plasma depletion in dayside polar cap during a CME-driven magnetic storm, we investigate a horizontal structure of dayside polar cap ionosphere during a magnetic storm. A series of steep plasma depletions was observed in the dayside polar cap during an interval of highly enhanced electron density on 14 October 2000 through EISCAT Svalbard Radar (ESR) field-aligned measurements and northward-directed low-elevation measurements. Each depletion started with a steep dropoff to as low as 10^11 m^-3 from the enhanced level of ～3×10^12 m^-3 at F2 region altitudes, and it continued for 10-15 min before returning to the enhanced level. These depletions moved poleward at a speed consistent with the observed ion drift velocity. DMSP spacecraft observations over an extended period of time which includes the interval of these events indicate that a region of high ion densities extended into the polar cap from the equatorward side of the cusp, i.e., a tongue of ionization existed, and that the ion densities were very low on its prenoon side. Solar wind observations show that a sharp change from IMF BY > 0 to BY < 0 is associated with each appearance of the ESR electron density dropoff. These facts present the first observational evidence for some of the previously speculated theories on patch formation. In addition, we propose a scenario that the series of plasma density depletions is a result of the poleward drift of the undulating boundary of the tongue of ionization; this undulating boundary is created in the cusp roughly 20 min before the ESR observation by the azimuthal intrusion, in response to the rapid prenoon shift of the footprint of the reconnection line, of the low-density plasmas originating in the morning sector. In Chapter 3, Storm-time enhancements of 630.0-nm airglow associated with polar cap patches, we study the vertical structures of both neutral and ionized gases in the polar cap. We examined the brightness of 630.0-nm airglow, I630, associated with polar cap patches observed during a magnetic storm that occurred on 22 January 2012. Brightness was measured using an all sky imager (ASI) located at Longyearbyen, Svalbard. The observed I630 was compared with the F-region electron density observed by the EISCAT Svalbard Radar (ESR). The I630 was positively correlated with the F2-layer peak electron density, NmF2, and inversely correlated with the altitude of the F2-layer peak electron density, hmF2, as expected from the known relationship between these parameters. To estimate the altitude of the peak emission of the airglow, we performed model alculations of the volume emission rate, V630, under quiet and disturbed conditions, using MSIS-modelled neutral gas profiles and the electron density profile obtained from the ESR data. In order to validate the V630 calculation, I630 was calculated by integrating the V630 along altitude, and then compared with the ASI-observed I630. During the observation periods the measured brightness frequently exceeded the calculated I630; we infer that, in most cases, low energy particle precipitation is responsible for the extra brightness. However, when there was less particle precipitation, the observed values were in good agreement with the calculated values. Under the magnetically disturbed conditions during our observations, the model calculation showed that the altitude of V630 peak increases, the thickness of the emission layer increases, and patch brightness increases. The results clearly show the previously unknown vertical structure of polar-patch airglow under magnetic storms.電気通信大学201

Exploring Magnetotail Structure and Dynamics with Magnetohydrodynamic Simulations

The magnetotail, the region of stretched magnetic field lines on the night side of the Earth, is important in a number of space weather processes, in particular geomagnetic storms and substorms. These processes can cause effects such as geomagnetically induced currents on the ground, spacecraft charging, and communications outages, which cause damage to infrastructure and disruption to human activities. Better understanding of the magnetotail and its properties can help to understand and perhaps predict these phenomena. The vast size of the magnetotail, and combined with a limited number of satellites traversing it, mean that models and simulations play an important role in providing insights into the magnetotail’s structure and its involvement in geospace processes. This dissertation consists of four studies aimed at improving understanding of the magnetotail using MHD simulations performed using the SWMF. The first of these is a validation study which showed that SWMF was able to reproduce important characteristics of the observed distributions of the Kp, Sym-H, and AL indices, as well as cross-polar cap potential. The model’s ability to reproduce these quantities indicates that it accurately represents many aspects of the magnetospheric current system. However, a tendency to under-predict the strength of the most negative diversions of AL was also noted. The second study explores the ion IB, a feature within the ionosphere as a result of pitch angle scattering in the magnetosphere. One of the processes that can cause this is called CSS (current sheet scattering), the strength of which is controlled by the paramter K = Rc/rg, the ratio of the field line radius of curvature to the particle gyroradius. The study estimates K using SWMF and using several empirical models for quiet conditions on 13 February 2009, when CSS was expected to be the operative mechanism for IB formation. After applying correction factors based on in situ satellite observations from the magnetotail, K was shown to be less than 10 in a majority of cases, supporting the hypothesis that the IB’s were formed by CSS. The third study extends the second into storm conditions on 4-6 April, 2010, in which wave-particle interaction as well as CSS is expected to play a role in IB formation. K estimates from SWMF and from empirical models were used to estimate the fraction of IB observations that might have been associated with CSS during this interval. Based on the assumption that the threshold for CSS could fall between K = 8 and K = 12, we found that between 20% and 69% of the IB observations might have been associated with CSS. We also found that K did not vary with local time, suggesting that CSS played a significant role in a majority of the IB’s observed. The fourth study explores the ability of MHD to predict magnetospheric substorms. A new procedure is introduced for combining lists of substorms identified using several different techniques, and this procedure is applied to both MHD output and observational data. It is shown that the procedure reduces false positive identifications and helps to address gaps in observational data, and that the resulting substorm list is consistent with certain known characteristics of substorms. The MHD output is shown to reproduce the observed distribution of substorm waiting times, and is shown to have statistically significant skill in predicting substorm onset times.PHDAtmospheric, Oceanic & Space ScienceUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/147633/1/jhaiduce_1.pd

Solar Modulation of the Cosmic Ray Intensity and the Measurement of the Cerenkov Reemission in NOvA’s Liquid Scintillator

The NOνA (NuMI Off-axis electron neutrino Appearance) experiment is a long baseline neutrino oscillation experiment at Fermi National Accelerator Laboratory. Its purpose is to observe the oscillation of νμ (muon neutrino) to νe (electron neutrino) and to investigate the neutrino mass hierarchy and CP violation in the neutrino sector. Two detectors have been built for this purpose, a Near Detector 300 feet underground at Fermilab, and a Far Detector, on the surface at Ash River, Minnesota. The completion of NOνA’s Far Detector in October 2014 enabled not only the recent measurement of neutrino oscillations, but an array of other physics studies. Coronal mass ejections cause an observable effect on the cosmic ray intensity measured at and around Earth, through the enhancement of the interplanetary magnetic field. Studying this phenomenon generally entails the measurement of the change in intensity of secondary neutrons from air showers, but it is of equal interest to observe the effects on secondary muons. Presented here is the study of the intensity modulation as measured in cosmic muon data from NOνA’s Far Detector in Ash River, MN. In addition, this thesis details the study of the non-linear energy response of NOνA’s liquid scintillator through the measurement of Cerenkov reemission, providing a needed correction to NOνA’s energy calibration