Medium-scale traveling ionospheric disturbances by three-dimensional ionospheric GPS tomography 3. Space science

In this study, we develop a three-dimensional ionospheric tomography with the ground-based global position system (GPS) total electron content observations. Because of the geometric limitation of GPS observation path, it is difficult to solve the ill-posed inverse problem for the ionospheric electron density. Different from methods given by pervious studies, we consider an algorithm combining the least-square method with a constraint condition, in which the gradient of electron density tends to be smooth in the horizontal direction and steep in the vicinity of the ionospheric F2 peak. This algorithm is designed to be independent of any ionospheric or plasmaspheric electron density models as the initial condition. An observation system simulation experiment method is applied to evaluate the performance of the GPS ionospheric tomography in detecting ionospheric electron density perturbation at the scale size of around 200 km in wavelength, such as the medium-scale traveling ionospheric disturbances

Investigating the Relationship between IPDPs and Pi1B Waves

IPDPs (intervals of pulsations with diminishing periods) are a subset of EMIC waves. Pi1Bs (pulsations irregular 1Hz bursts) are ULF waves closely correlated with substorm onset. Prior research has indicated there may be a relationship between the two, but this relationship has not yet been fully fleshed out. In this presentation, we investigate the relationship between evening sector IPDPs and Pi1B. To do so we utilize searchcoil magnetometer, fluxgate magnetometer, riometer, and imaging riometer data from a collection of Antarctic ground stations (Halley Research Station, Neumayer, Maitri, Syowa, and Mawson) that span 10 degrees in CGM latitude, 4 hours in MLT, and L shells 4 through 9. We also utilize magnetometer data from satellites in conjunction including SWARM, which reveals a local unidentified ULF signature equatorward of the ground instrumentation (more work is required to fully understand this). From the ground instrumentation, we observe Pi1B in the late evening MLT region crossing over into the early dawn region, and IPDPs in the early evening MLT region. Despite the 4 hour range in MLT, we observe these events near simultaneously with only a ~15 minute delay between the start of the Pi1B and the start of the IPDP. We observe correlated cosmic noise absorption (CNA) that occurs simultaneously with and encompasses the full duration of these events. The ULF activity we observe aligns well with what we expect from previous work done on the subject-- IPDPs appear at lower geomagnetic latitudes (60-65 degrees) than Pi bursts, which are more prominent at ~70 degrees-- but the CNA we observe has less precedence in prior research. In this presentation, we describe our observations in detail as well as possible mechanisms that might link the Pi1B and IPDP waves, as well as the CNA