Spencer Mark Hatch, UiB:

E3D-BRITE: EISCAT_3D-based reconstruction of ionosphere-thermosphere electrodynamics

In many experimental studies of ionosphere-thermosphere (IT) coupling and ionospheric electrodynamics, the limitations of existing observational data sets require one to represent the three-dimensional IT system as an infinitely thin, two-dimensional sheet. This 2D representation of the coupled IT system cannot however represent some of its most basic properties, such as the existence of different ionospheric layers. On the other hand, observing systems such as sounding rockets and ionosondes that are capable of probing the altitudinal structure of relevant quantities typically only provide information within a very narrow volume or along a 1D trajectory. This limitation requires one to assume that these quantities have no horizontal gradients. Measurements from the upcoming EISCAT_3D incoherent scatter radar therefore present an unprecedented opportunity to probe the 3D IT system in three dimensions and on relatively short time scales (of order minutes). Here we present a new data assimilation technique for estimation of all three components of the ionospheric current density and their uncertainties. We illustrate the technique using synthetic EISCAT_3D measurements of the plasma density and ion drift. We describe how the E3D-BRITE technique may also be used to simultaneously estimate the neutral wind and the perpendicular electric field.

Katie Herlingshaw, UNIS

What are Fragmented Aurora-like Emissions?

A strange type of aurora-like feature has been spotted over Svalbard. Most ionospheric emissions seen during the dark skies either fit into the categories of ‘aurora’ or ‘airglow’, where the former is caused by magnetospheric particles precipitating into the atmosphere and the latter by chemical processes. The newly discovered green features are puzzling as they do not fit neatly into either category.

The features are called Fragmented Aurora-like Emissions (FAE) or simply ‘fragments’. They appear as small splinters of green light and typically last for under a minute. Sometimes long chains of fragments form with regular spacing, typically close to auroral arcs, and other times the fragments are individual and move more unpredictably.

We want to figure out what causes fragments and if they are part of a bigger system that is connected to the nearby aurora. We will outline our research plan, including first results and how we will work towards our goal using a combination of scientific cameras, EISCAT radars, and citizen scientist photographers.

Yaqi Jin, UiO

High-latitude ionospheric irregularities and scintillations seen from ground and space

Our modern society relies on the Global Navigation Satellite System (GNSS) service that utilize trans-ionospheric radio waves. However, the GNSS applications can be severely affected by ionospheric scintillations. During strong scintillation event, the GNSS service can be heavily degraded. With an increasing human activity in the polar regions, there is a high demand to investigate and model ionospheric irregularities and scintillations in the Arctic. Ionospheric irregularities can be studied using in-situ observations from low Earth Orbiting satellites as well as remote sensing using ground-based instruments. In this study, we present some key characteristics of high-latitude irregularities using Swarm satellites and ground-based GNSS receivers. We first use the in-situ electron density data to calculate the rate of change of density index and electron density gradients. The climatological maps in magnetic latitude/magnetic local time coordinates show predominant plasma irregularities near the dayside cusp, polar cap, and nightside auroral zone. This feature is similar to the statistical studies of ionospheric scintillations. Ground-based instruments are another important aspect to study ionospheric irregularities. For example, GNSS scintillation receivers are often used to study the scintillation effect caused by small-scale ionospheric structures. Ionospheric scintillations are particularity severe during major geomagnetic storms. We report severe GNSS amplitude and phase scintillations, as well as losses of signal lock during the major storm on 17 March 2015. This event was observed near the edges of a high-density total electron content blob. The European Incoherent scatter ultra-high frequency radar observed significant enhancement of electron density in the F2 region, while the E region was only slightly enhanced. The losses of lock in the GPS L2 band were caused by both the power fade and rapid carrier phase fluctuations.