Effects of Re-connection in the Structuring of Plasma and Aurora in the Polar Cap

Abstract:

In Earths’ geomagnetic polar regions, the convergent magnetic field serves as a lens, projecting complex interactions between the solar wind, magnetosphere, and ionosphere into a confined latitudinal region. Magnetic reconnection plays an important role in establishing the density and thermal structure of the high-latitude ionosphere, thus becoming a magnetospheric process that can be studied by looking at its signatures utilizing ground-based and low earth orbit sensors. Areas of high plasma density inside the polar cap, also known as patches, are the perfect proxy for studying the plasma dynamics at higher latitudes as they follow a frozen-in-flux principle as they travel. A multi-sensor approach is taken for following and understanding the movement of high latitude plasma by utilizing Incoherent Scatter Radar (ISR), measurements from red-line images on site (OMTI), available satellite data from the Defense Meteorological Satellite Program (DMSP), and solar wind parameters during a day of Bz positive (and thus possible high latitude reconnection). By exploiting the 4-dimensional capabilities (3 dimensions + time) of the Resolute Bay Incoherent Scatter Radar (RISR) it is possible to study these signatures at higher latitudes and even track the plasma properties on its rest frame of reference (Lagrangian frame of reference). This is done by utilizing the plasma parameters that a phased array from the Advanced Modular Incoherent Scatter Radar (AMISR) provides (Ne, Te, Ti, Vlos) and interpolating them accordingly to create full 3D images of the ionospheric plasma. The results show a synchronous increase in electron temperature above 200km and plasma density below 250km (both hallmarks of soft precipitation) while simultaneously showing a negligible change in patch density over the duration of the event. Evidence indicates the existence of high latitude reconnection happening closer to dawn for this event due to two main reasons: patches exiting the polar cap closer to dawn and their sudden accelerations that coincide with changes in auroral brightness, and the existence of red line aurora most likely caused by the release of magnetic tension. Results show that the changes in the plasma state that are observed represent a co-mingling of transport and precipitation effects, rather than a causative link.