The Earth's ionosphere is a region of plasma embedded within and on top of the Earth's atmosphere. As the Sun-Earth interaction medium closest to Earth, the ionosphere has many important implications for humankind. The ionosphere affects radio wave propagation, GPS performance, and both space- and ground-based asset response to space weather, to name just a few technological impacts. From a scientific perspective, there are a plethora of interesting and open plasma physics questions that can be studied in such a planetary-scale plasma laboratory. For this reason we strive to understand the ionosphere's properties and characteristics. In this dissertation, we specifically study the large-scale electrodynamics in the northern, polar region of the ionosphere. We also present developments in electric and magnetic field-sensing instruments that are necessary to obtain more accurate, sensitive, and cost-effective measurements of the ionosphere.
We begin by discussing measurements from a sounding rocket, TRICE-2, that observed multi-scale, large amplitude electric (E) and magnetic (B) field structures in the polar ionosphere. These structures indicated fast plasma convection speeds. At high latitudes, it is well established that ionospheric plasma convects in a two cell pattern, transporting plasma throughout the magnetosphere and informing on forcing from the Sun at the magnetopause. TRICE-2 made some of the first observations of very fast convection in the polar region of the ionosphere. Fast flows are associated with reconnection in the northern hemisphere of the magnetopause and lead to GPS scintillation. Meso- and small-scale E and B field structures are also expected to correlate and give a measure of the ionospheric conductance. Ionospheric conductance is crucial to studying how currents close in the ionosphere and how the magnetosphere is coupled to the ionosphere. TRICE-2 found many structures where the fields did not correlate, indicating that more careful treatment of in-situ calculations of conductance are required.
Next, we discuss an interesting and rarely studied electric probe phenomenon called sheath rectification. In this process, large amplitude waves of certain frequencies cause baseline shifts and very low frequency signatures that can be mistaken for geophysical processes. Identifying and characterizing these events is important in understanding how to prevent them from occurring and affecting data interpretation. TRICE-2 also observed hundreds of these events during its 20 minute flight. We discuss the characteristic signatures and how they were produced on TRICE-2 as well as potential design implementations that could minimize this in the future. Although there is no way to completely avoid rectification, we can design the instrument such that this occurs for higher frequency incident waves, whose amplitudes (and consequently rectification signatures) are significantly smaller.
Finally, we present a novel, space-based anisotropic magneto-resistive (AMR) magnetometer, named the MRM, utilizing small and cheap commercial off-the-shelf components to provide sensitive and scientifically useful B field measurements. Currently, the magnetometry field utilizes fluxgate and search coil magnetometers, which are comparatively larger in volume and cost more to manufacture, operate, and develop. Although those technologies are more sensitive, the AMR magnetometer is useful for measurements of larger amplitude phenomena and structures. For example the MRM would have been sensitive enough to detect the magnetic field structures observed by TRICE-2. Development culminated in two space flights, one on the sounding rocket, VIPER, and another on the CURIE cubesat. The VIPER flight proved the concept of the magnetometer but revealed some electrical engineering design flaws. CURIE has yet to receive radio communications and, consequently, has still not provided any MRM data. However, we expect careful design changes to lead to a viable space-flight rated magnetometer. As the space sciences field moves towards constellation and multi-point measurements of the magnetosphere, a small, cheap magnetometer like the MRM will prove useful.
We end with a summary of our results and potential future research. In presenting novel instrument developments and data analysis techniques we have furthered our knowledge of the near Earth ionosphere environment. Such analysis is important in understanding the Earth's connection to the interplanetary medium and its response to plasma events originating from the Sun. The knowledge obtained about these instruments is crucial to supporting data interpretation of future plasma missions such as TRACERS, which is scheduled to launch in March, 2025, and creating ever cheaper, smaller, and more sensitive instruments. Lastly, as all of the data utilized here comes from sounding rocket missions, this dissertation highlights that important science can be performed using quick and cheap missions. Sounding rockets provide an excellent platform to test new technologies and study rare or intermittent phenomena. Furthermore, their timelines are ideal for training future generations of scientists.