Radio tomographic imaging of the northern high‐latitude ionosphere on a wide geographic scale

Abstract

[1] Several chains of receivers, measuring total electron content (TEC) during passes of satellites in the U.S. Navy Ionospheric Measuring System (NIMS), are operated at northern high latitudes by members of the International Ionospheric Tomography Community (IITC). Results are presented here of nearly simultaneous latitude-altitude images of the ionosphere over Scandinavia, Greenland, and Alaska, generated from IITC data obtained on 20 September 2001 and interpreted in the context of an IMF-dependent convection model. The images are compared with output from a coupled thermosphere-ionosphere-plasmasphere model and also with maps of high-latitude TEC generated from GPS measurements. With B z and B y both weakly negative, the images and map reveal plasma features of a two-cell convection pattern rotated slightly to earlier local magnetic times. The tomographic images provide details of map features such as a tongue of ionization created by solar EUV radiation on the dayside and entrained by convection into the polar cap from the western Russian sector. Combining latitude versus altitude tomographic images generated in different longitudinal sectors from polar-orbiting beacon satellites such as those of NIMS with TEC maps from GPS offers an emerging opportunity for polar aeronomic studies, especially if further related to synoptic convection measurements. The results also demonstrate the potential role of wide-scale radio tomography in the verification of ionospheric models.Citation: Kersley, L., S. E. Pryse, M. H. Denton, G. Bust, E. Fremouw, J. Secan, N. Jakowski, and G. J. Bailey (2005), Radio tomographic imaging of the northern high-latitude ionosphere on a wide geographic scale, Radio Sci., 40, RS5003,

The dayside high-latitude trough under quiet geomagnetic conditions: Radio tomography and the CTIP model

“…In the longer term, the effect of precipitation input in the model needs to be addressed, although in the first instance the existence of other disparities need to be established at different geomagnetic activity levels, universal times and geographic locations, so that any changes to the model are considered within the global framework rather than tuning the model to this data set alone (Schoendorf et al, 1996). Radio tomography offers the potential for such comparisons, with long term observations being made in the European sector and also by the recently established International Ionospheric Tomography Community with receivers in the high-latitude sector in Alaska, Greenland, and Europe (Kersley et al, 2005).…”

Observing the north polar ionosphere on 30 October 2003 by GPS imaging and IS radars

“…Sojka et al, 1993Sojka et al, , 1994. Recently, experimental evidence of different large-scale TOI events could be monitored across the polar cap from their electron content traces based on navigational measurements (Kersley et al, 2005;Stolle et al, 2005a) and together with plasma drift data .…”

Evidence for the tongue of ionization under northward interplanetary magnetic field conditions

“…A tongue of photoionization from the dayside has been identified in both modeling [Sojka et al, 1993] and observations [Valladares et al, 1994], entering the cross polar antisunward flow in the polar cap when B z is negative (southward). A tongue of ionization was also revealed in the dayside polar ionosphere under B z < 0 conditions in a study by Kersley et al [2005]. The study used radio tomography measurements from three different longitude sectors and compared the observations to the spatial distribution of Total Electron Content measured using GPS signals, which has very wide geographic coverage but limited spatial resolution in comparison to the radio tomographic reconstructions.…”

“…Tomographic inversion of the TEC yields an image of the spatial distribution of the electron density in a height-versus-latitude plane of the ionosphere in the region of interest. The International Ionospheric Tomography Community (IITC) has brought together several groups with interests in the field to apply the technique to ionospheric imaging, where routine observations by several chains in different longitude sectors are used to provide information on the plasma distribution over a wide geographic region [Kersley et al, 2005]. The present study employs images from tomography chains in Europe [Kersley et al, 1997] and Greenland [Coker et al, 2001] in a study of the large-scale spatial distribution of the ionospheric plasma in the magnetic postnoon sector in winter, under stable conditions of quiet geomagnetic activity (Kp $ 1) and positive B z .…”