We investigate the possibility of measuring and using the phase delay of radio frequency transmissions in the amateur satellite band as a method to determine the distribution of currents systems in the ionosphere. The amateur satellite transmissions at 7MHz, 14M Hz, and 144M Hz are low enough for Faraday rotation to cause a significant phase delay on the propagating signals in addition to the phase delay produced by the total electron content (TEC) in the ionosphere. The ionosphere in the E and F regions is modeled as an equivalent thin planar shell of collision free cold plasma 100 km in thickness located in an altitude range of 100 � 200 km. The earth's magnetic field is superposed with a weaker magnetic field due to a narrow Gaussian strip of current representing an ionospheric electrojet. The prole of the current system is obtained by numerically optimizing the Appleton-Hartree dispersion relation for rays of simulated radio frequency (RF) signals that propagate through the ionosphere shell. The optimization procedure is performed with a differential evolution algorithm. From the optimization procedure, we obtain the ionosphere total electron content (TEC) and the strength, prole, and orientation of the ionospheric current system.

The Earth's equatorial ionosphere most often shows the occurrence of large plasma density and velocity fluctuations with a broad range of scale sizes and amplitudes. These night time ionospheric irregularities in the F-region are commonly referred to as equatorial spread F (ESF) or plasma bubbles (EPBs). This dissertation focuses on analysis of ground-based optical and radar measurements to investigate the development and dynamics of ESF, which can significantly disrupt radio communication and GPS navigation systems. OI (630.0 nm) airglow image data were obtained by the Utah State University all-sky CCD camera, primarily during the equinox period, from three different longitudinal sectors under similar solar flux conditions: Christmas Island in the Central Pacific Ocean, Ascension Island in South Atlantic, and Brasilia and Cariri in Brazil. Well-defined magnetic field-aligned depletions were observed from each of these sites enabling detailed measurements of their morphology and dynamics. These data have also been used to investigate day-to-day and longitudinal variations in the evolution and distribution of the plasma bubbles, and their nocturnal zonal drift velocities. In particular, comparative optical measurements at different longitudinal sectors illustrated interesting findings. During the post midnight period, the data from Christmas Island consistently showed nearly constant eastward bubble velocity at a much higher value (~80 m/s) than expected, while data from Ascension Island exhibited a most unusual shear motion of the bubble structure, up to 55 m/s, on one occasion with westward drift at low latitude and eastward at higher latitudes, evident within the field of view of the camera. In addition, long-term radar observations during 1996-2006 from Jicamarca, Peru have been used to study the climatology of post-sunset ESF irregularities. Results showed that the spread F onset times did not change much with solar flux and that their onset heights increased linearly from solar minimum to solar maximum. On average, radar plume onset occurred earlier with increasing solar flux, and plume onset and peak altitudes increased with solar activity. The F-region upward drift velocities that precede spread F onset increased from solar minimum to solar maximum, and were approximately proportional to the maximum prereversal drift peak velocities.

<p>This thesis deals with energetic oxygen ions (i.e. single-charged atomic oxygen ions, O+) at altitudes higher than 5 Earth radii (RE) and at latitudes above 75 (toward 90) degrees invariant latitude (deg ILAT) in the dayside polar magnetosphere observed by Cluster. The instrument used in this study is CIS (Cluster Ion Spectrometry experiment) / CODIF (a time-of-flight ion COmposition and DIstribution Function analyser), which covers an energy range from »10 eV up to 38 keV. Cluster detected O+ with energies more than 1 keV (hereafter termed “keV O+”), indicating that energization and/or acceleration process(es) take place in the dayside high-altitude (inside magnetopause) and high-latitude region. These O+ are outflowing (precisely, upward-going along the geomagnetic field lines), and these outflowing keV O+ show a heated (or energized) signature in the velocity distribution as well.</p><p>First, outflowing O+ are observed at the poleward cusp and/or the mantle formed a partial shell-like configuration seen in the velocity distribution. Second, the latitudinal distribution of outflowing O+ (most of them have energies less than 1 keV statistically) observed below 7 RE is consistent with velocity filter effect by the polar convection, while the latitudinal distribution of outflowing keV O+ observed above 7 RE cannot be explained by velocity filter effect only, i.e. this indicates that additional energization and/or acceleration takes place at higher altitudes in the dayside polar region. Thirdly, a tendency to observe outflowing keV O+ for during different geomagnetic conditions is studied. The keV O+ above 9 RE is more often for K p¸5 rather than for K p•3. However the energy of O+ is not dependent on ASY /SYM indices.</p><p>Finally, the dependence on the solar wind conditions is also studied. The energization and/or acceleration of outflowing O+ is controlled by both solar wind moments (except solar wind electric field) and strong southward interplanetary magnetic field (IMF) at the time scale of tens of minutes at only higher altitudes. Further examination shows that solar wind dependence is different at three regions: one is the poleward cusp, another is the low-altitude polar cap, and finally the high-altitude polar cap, combining all the results. There is (a) new energization and/or acceleration process(es) at the high-altitude polar cap. On the other hand, flux enhancement of O+ observed above 5 RE is also controlled by solar wind moments (e.g. solar wind electric field) and strong southward IMF, however the ionospheric changes play a more important role on the flux enhancement of O+.</p>

"November 15, 1962." "Submitted to the Department of Electrical Engineering, M.I.T., January 15, 1962, in partial fulfillment of the requirements for the degree of Master of Science." / Bibliography: p. 75-76. / Army Signal Corps Contract No. DA 36-039-sc-78108. Dept. of the Army Project No. 3-99-20-001 Project 3-99-00-000. Army Signal Corps Contract No. DA-SIG-36-039-61-G14.

This thesis deals with energetic oxygen ions (i.e. single-charged atomic oxygen ions, O+) at altitudes higher than 5 Earth radii (RE) and at latitudes above 75 (toward 90) degrees invariant latitude (deg ILAT) in the dayside polar magnetosphere observed by Cluster. The instrument used in this study is CIS (Cluster Ion Spectrometry experiment) / CODIF (a time-of-flight ion COmposition and DIstribution Function analyser), which covers an energy range from »10 eV up to 38 keV. Cluster detected O+ with energies more than 1 keV (hereafter termed “keV O+”), indicating that energization and/or acceleration process(es) take place in the dayside high-altitude (inside magnetopause) and high-latitude region. These O+ are outflowing (precisely, upward-going along the geomagnetic field lines), and these outflowing keV O+ show a heated (or energized) signature in the velocity distribution as well. First, outflowing O+ are observed at the poleward cusp and/or the mantle formed a partial shell-like configuration seen in the velocity distribution. Second, the latitudinal distribution of outflowing O+ (most of them have energies less than 1 keV statistically) observed below 7 RE is consistent with velocity filter effect by the polar convection, while the latitudinal distribution of outflowing keV O+ observed above 7 RE cannot be explained by velocity filter effect only, i.e. this indicates that additional energization and/or acceleration takes place at higher altitudes in the dayside polar region. Thirdly, a tendency to observe outflowing keV O+ for during different geomagnetic conditions is studied. The keV O+ above 9 RE is more often for K p¸5 rather than for K p•3. However the energy of O+ is not dependent on ASY /SYM indices. Finally, the dependence on the solar wind conditions is also studied. The energization and/or acceleration of outflowing O+ is controlled by both solar wind moments (except solar wind electric field) and strong southward interplanetary magnetic field (IMF) at the time scale of tens of minutes at only higher altitudes. Further examination shows that solar wind dependence is different at three regions: one is the poleward cusp, another is the low-altitude polar cap, and finally the high-altitude polar cap, combining all the results. There is (a) new energization and/or acceleration process(es) at the high-altitude polar cap. On the other hand, flux enhancement of O+ observed above 5 RE is also controlled by solar wind moments (e.g. solar wind electric field) and strong southward IMF, however the ionospheric changes play a more important role on the flux enhancement of O+.

Observations of modifications of the electron temperature in the F-region produced by powerful high-frequency waves transmitted in X-mode are presented. The experiments were performed during quiet nighttime conditions with low ionospheric densities so no reflections occurred. Nevertheless temperature enhancements of the order of 300-400K were obtained. The modifications found can be well described by the theory of Ohmic heating by the pump wave and both temporal and spatial changes are reproduced.  A brief overview of several different experimental campaigns at EISCAT facilities in the period from October 2006 to February 2008 are also given pointing out some interesting features from the different experiments. The main focus is then on the campaign during October 2006 and modifications of the electron temperature in the F-region.

This thesis is focused on the role of Alfvén waves in the energy transformation and transport in the magnetosphere. Different aspects of Alfvén wave generation, propagation and dissipation are considered. The study involves analysis of experimental data from the Freja, Polar and Cluster spacecraft, as well as theoretical development. An overview of the linear theory of Alfvén waves is presented, including the effects of fnite parallel electron inertia and fnite ion gyroradius, and nonlinear theory is developed for large amplitude Alfvén solitons and structures. The methodology is presented for experimental identification of dispersive Alfvén waves in a frame moving with respect to the plasma, which facilitates the resolution of the space-time ambiguity in such measurements. Dispersive Alfvén waves are identified on field lines from the topside ionosphere up to the magnetopause and it is suggested they play an important role in magnetospheric physics. One of the processes where Alfvén waves are important is the establishment of the field aligned current system, which transports the energy from the reconnection regions at the magnetopause to the ionosphere, where a part of the energy is dissipated. The main mechanism for the dissipation in the top-side ionosphere is related to wave-particle interactions leading to particle energization/heating. An observed signature of such a process is the presence of parallel energetic electron bursts associated with dispersive Alfvén waves. The accelerated electrons (electron beams) are unstable with respect to the generation of high frequency plasma wave modes. Therefore this thesis also demonstrates an indirect coupling between low frequency Alfvén wave and high frequency oscillations.

The space around Earth, confined in the terrestrial magnetosphere, is to some extent shielded from the Sun's solar wind plasma and magnetic field. During certain conditions, however, strong interaction can occur between the solar wind and the magnetosphere, resulting in magnetospheric activity of several forms, among which substorms and storms are the most prominent. A general framework for how these processes work have been outlayed through the history of research, however, there still remain questions to be answered. The most striking example regards the onset of substorms, where both the onset cause and location in the magnetosphere/ionosphere are still debated. These are clearly not easily solved problems, since a substorm is a global process, ideally requiring simultaneous measurements in the magnetotail and ionosphere. Investigated in this work are temporal and spatial scales for substorm and convection processes in the Earth's magnetosphere and ionosphere. This is performed by combining observations from a number of both ground-based and spacecraft-borne instruments. The observations indicate that the magnetotail's cross-section is involved to a larger spatial extent than previously considered in the substorm process. Furthermore, convection changes result in topological changes of the magnetosphere on a fast time scale. The results show that the magnetosphere is, on a global magnetospheric scale, highly dynamic during convection changes and ensuing substorms.

We investigate the possibility of measuring and using the phase delay of radio frequency transmissions in the amateur satellite band as a method to determine the distribution of currents systems in the ionosphere. The amateur satellite transmissions at 7MHz, 14M Hz, and 144M Hz are low enough for Faraday rotation to cause a significant phase delay on the propagating signals in addition to the phase delay produced by the total electron content (TEC) in the ionosphere. The ionosphere in the E and F regions is modeled as an equivalent thin planar shell of collision free cold plasma 100 km in thickness located in an altitude range of 100 􀀀 200 km. The earth's magnetic field is superposed with a weaker magnetic field due to a narrow Gaussian strip of current representing an ionospheric electrojet. The prole of the current system is obtained by numerically optimizing the Appleton-Hartree dispersion relation for rays of simulated radio frequency (RF) signals that propagate through the ionosphere shell. The optimization procedure is performed with a differential evolution algorithm. From the optimization procedure, we obtain the ionosphere total electron content (TEC) and the strength, prole, and orientation of the ionospheric current system.

The original objectives of this thesis were to use the new PolarDARN radars to study the convection patterns at high latitudes and to attempt to explain them in terms of reconnection. Because the IMF is important in reconnection, studies of the Interplanetary Magnetic Field (IMF) components Bx, By and Bz were done. The study showed that <|Bz|> was lower by 21.5% than <|By|> from Jan. 2006 to Dec. 2008, so By was expected to play an important role in reconnection. The IMF, spiral angle, and the amount of warping of the solar magnetic field in interplanetary space decreased slightly during this 36-month period. The decrease in IMF was a more sensitive indicator of the solar minimum than the decrease in the 10.7 cm solar microwave flux.<p> A solar magnetic sector boundary study from the Jan 1, 2007 Dec 31, 2008 interval showed the occurrence of four or two sectors in a synodic solar rotation cycle. A sector boundary crossing frequently takes place in less than 3 hours. The transition from four sectors to two sectors is surprisingly smooth, in that no interruption in the 27-day synodic period occurs. A superposed epoch analysis of solar wind speed near sector boundary crossings showed a speed minimum about half a day before the crossing, and a maximum about two days after the crossing. The standard deviation reached a minimum at about the same time as the velocity. The sector boundary study also showed that, since Dec. 2007, there were six roughly 27-day synodic solar rotation cycles near spring equinox when away field dominated, and that the following seven 27-day cycles close to the autumnal equinox were dominated by toward field. This is consistent with the quasi-sinusoidal annual magnetic sector polarity oscillations that occur for about three years during solar minimum. These oscillations are due to the mainly dipolar magnetic field which is roughly aligned with the Suns axis, tilted 7.25° from the normal to the ecliptic plane. The three-year oscillation for the present minimum between Solar Cycles 23 and 24 appeared to begin in Dec. 2007. For the past four solar minima, an El Nino event has occurred during the last of the three oscillations, and the El Nino and sinusoidal magnetic oscillation ended together. The new solar cycle began about 6 months before that. During the past eight years, a new 3D topological null-separator formulation of magnetic reconnection and its effect on convection has been led by Dr. M. Watanabe in ISAS at the University of Saskatchewan. This formulation includes two types of interchange reconnection (Russell and Tanaka) as well as the traditional Dungey reconnection. For conditions when the IMF clock angle was within 30° of a Bz+ dominant convection, the new reconnection model shows that the convection can be driven strictly by the two types of interchange reconnection. The model predicts the existence of a reciprocal cell on closed field lines and an interchange merging cell surrounding an interior lobe cell. The construction of the PolarDARN radars at Rankin Inlet and Inuvik, completed in December, 2007, allowed polar cap convection to be measured for predominantly Bz+ conditions. The existence of the two predicted features was confirmed. This also required that satellite data be analyzed to determine the location of the open-closed-field-line-boundary (OCFLB). Several PolarDARN studies are represented to show convection for different IMF clock angles and seasons.