Physics Dept Seminar
April 7, Thursday (*SPECIAL DAY*)
The Role of Sun to Earth Coupling in Ionospheric Electric Field and Plasma Density Structures
Dr. Lindsay Goodwin
(Solar & Terrestrial Physics)
*SPECIAL TIME: 2:45 pm - 3:45 pm with 2:30 pm teatime
Room: ECE 202
The earth's high-latitude ionosphere is replete with electric field structures and plasma density variations. The dominant driver of both of these is coupling from the sun to the earth, and characterizing this driving is critically important in our understanding of space weather and the cascade of energy from the sun to the earth. This presentation begins by showcasing a selection of studies that focus on how this coupling creates electric field and plasma density structures. First, the occurrence of narrow electric field structures coincident with plasma density depletions, and their relevance in understanding "STEVE" (Strong Thermal Emission Velocity Enhancement, the latest high-latitude optical phenomenon), is discussed. Next, the first in situ spacecraft observations that track the creation, structuring, and evolution of high-latitude plasma density variations as they travel due to magnetospheric-ionospheric coupling is presented. Then, spacecraft and ground-based imager data are displayed that shows magnetospheric driving of localized electric field and precipitation systems associated with plasma density variations. Next, this presentation highlights statistical studies examining the scale-width of plasma density variations for a variety of solar and geophysical conditions. These are computed using novel radar techniques that generate observations at a higher spatiotemporal resolution than has been previously possible with ionospheric radars. Here, it is found that irregularities 50 km and less become more prevalent in the absence of solar radiation, which is dominating plasma density structuring.
The second part of this presentation will focus on how strong electric fields, that would be generated through sun-earth coupling, impact the behavior of plasma. Namely, how under strong electric field conditions at high latitudes the ion velocity distribution of weakly ionized plasma distorts from a Maxwellian shape. Here, an advanced Monte Carlo simulation is employed to derive ion velocity distributions for a range of electric fields, aspect angles, and ion-neutral collisions. Then, hypothetical radar spectra are developed that show how distortions from the Maxwellian shape can substantially change our interpretation of instrument data.