Physics – Plasma Physics
Scientific paper
Dec 2009
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009agufmsa31a1402r&link_type=abstract
American Geophysical Union, Fall Meeting 2009, abstract #SA31A-1402
Physics
Plasma Physics
[6929] Radio Science / Ionospheric Physics, [6994] Radio Science / Instruments And Techniques, [7800] Space Plasma Physics, [7900] Space Weather
Scientific paper
The spatial and temporal variability of E-region densities and conductivities play a role in different types of instabilities, especially in the interchange instabilities that lead to the development of equatorial spread F (ESF) irregularities near the geomagnetic equator. It has been suggested that global E-region profiles could be estimated from GPS radio occultation (RO) measurements [e.g. Kelley et al., 2004] and that these measurements could be used assess the effects of the E region on ESF variability. However, large horizontal density gradients at F-region heights, especially near sunset, make accurate estimates of E-region densities more challenging than initially expected. A new methodology for estimating E-region profiles from radio occultation measurements assisted by an assimilative ionospheric model has been recently developed [Nicolls et al., 2009]. This new approach was applied to COSMIC RO measurements using IDA4D (Ionospheric Data Assimilation Four Dimensional) results. Comparisons of estimated E-region profiles against independent, nearly coincident E-region radar measurements suggest an accuracy of about 2x1010 electrons/m3. We use the new methodology to produce global estimates of E-region density profiles over different seasons. COSMIC RO measurements and IDA4D F-region results are used in this study. IRI is used as an initial background model for IDA4D. Neutral parameters from MSIS and geomagnetic parameters from IGRF are used to estimate vertical profiles of Pedersen and Hall conductivities. Results of our global estimates of E-region densities and conductivities are presented. The climatological variability of the low-latitude E-region are investigated and the implications for ESF are discussed.
Bust Gary S.
Nicolls Michael J.
Rodrigues Fabiano S.
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