Tracking of polar cap ionospheric patches using data assimilation

Abstract

Ionospheric F‐region patches are 2–10 larger than background electron densities in the polar ionosphere. The EISCAT Svalbard incoherent radar (ESR) observed a sequence of patches between 2000–2200 UT on 12 December 2001. In this paper the source of these structures is investigated using several other data sets, together with a convection‐driven trajectory analysis. The data are assimilated into Ionospheric Data Assimilation Three Dimensional (IDA3D). The background model used is the National Center for Atmospheric Research‐Thermosphere Ionosphere Mesosphere Electrodynamics General Circulation Model (NCAR TIMEGCM). The trajectory analysis is based on maps of ionospheric convection obtained from the Assimilative Mapping of Ionospheric Electrodynamics (AMIE). In addition to patches, a tongue of ionization (TOI) is investigated. It is shown that patches formed part of the TOI. It is tempting to conclude the TOI and the patches originate at midlatitudes. However, the IDA3D and trajectory analysis suggest that they were transported toward noon from the morning and afternoon sectors near 62° geographic latitude. Thus for this case the TOI and patches did not originate at midlatitudes. This work represents advances in the field of patch research. A new capability to perform an analysis of patch origin and fate, using three‐dimensional (3‐D) ionospheric assimilation and 2‐D trajectory analysis codes, is demonstrated for a sequence of patches observed 12 December 2001. The current resolution of the technique is not able to identify detailed patch formation mechanisms. However, by it can track the plasma back in time to locations and times where patch formation mechanisms operate.

Global Ionospheric Processes

“…We analyzed optical images from Qaanaaq, Greenland, in the central polar cap to determine the location, extent, and motion of the patches, and then used global convection velocities from the SuperDARN network to drive a physics-based model accounting for recombination and other processes. By running the model in reverse, we were able to match the observed patches with incoherent scatter radar measurements from Sondrestrom and determine the origin of the patches to be in the afternoon sector, contrary to the findings of other recent studies suggesting that patch plasma originates from precipitation in the morning sector [MacDougall and Jayachandran, 2007;Bust and Crowley, 2007]. Another study from the active period during the autumn of 2003 was the October 30-31 "Halloween" storm.…”

First storm‐time plasma velocity estimates from high‐resolution ionospheric data assimilation

“…[8] Beginning from the top left of Figure 2, the International Reference Ionosphere (IRI) [Bilitza et al, 2003] is used as a background model and GPS data are used as measurements to be assimilated by Ionospheric Data Assimilation Four-Dimensional (IDA4D). IDA4D, described in 2.1, uses three-dimensional variational data assimilation to routinely produce mappings of the ionospheric densities globally .…”

Studies of the Origin and Evolution of Ionospheric Irregularities and Their Effects on AF Systems

“…No calculation of the ionospheric density within the flux tube is conducted. Bust and Crowley [2007] used a trajectory analysis based on maps of ionospheric convection, obtained from the assimilative Mapping of Ionospheric Electrodynamics (AMIE), to indicate that some of the patches detected by the EISCAT Svalbard radar on 12 December 2001 formed part of the TOI. Bust and Crowley's trajectory analysis demonstrated that the patches originated in several different locations either in the momingside or afternoon sectors at geographic latitudes near 60-70°.…”

“…More recently, MacDougall and Jayachandran, [2007] used foF 2 values from several stations located in the Canadian Arctic to propose a mechanism for patch generation in which density enhancements were produced by low-energy electron precipitation as the plasma returns from midnight around the dawn convection cell. Bust and Crowley [2007] also concluded that a sequence of patches observed at Svalbard on December 12, 2001 had been transported toward noon from the morning and afternoon sectors. These authors introduced a trajectory analysis method and an assimilation scheme to demonstrate that the origin of the patch densities was at 62° geographic latitude.…”

“…These authors introduced a trajectory analysis method and an assimilation scheme to demonstrate that the origin of the patch densities was at 62° geographic latitude. Bust and Crowley [2007] also indicated the need to use first-principles numerical models to associate ionospheric measurements conducted at separate locations to investigate the patch origin, and to forecast the decay of the large-scale enhanced densities.…”