Pre-storm electron density enhancements at middle latitudes

• Published in: Journal of atmospheric and solar-terrestrial physics Vol. 70; no. 15; pp. 1848 - 1855
• Main Authors: Buresova, D., Lastovicka, J.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.12.2008
• Subjects: Electron density; Ionosphere; Pre-storm enhancement; Asia; USA; Europe; Pre-storm enhancement; Electron density; Ionosphere
• ISSN: 1364-6826; 1879-1824
• DOI: 10.1016/j.jastp.2008.01.014

Substantial increases of the F2 region peak electron density several hours to a day before the geomagnetic storm onset, the so-called pre-storm enhancements, belong to still not clear and hardly predictable features of the ionospheric disturbances. This paper presents analysis of the pre-storm enhancements observed at middle latitudes for 15 storms out of 65 strong-to-severe geomagnetic storms of the period 1995–2005. All 15 events were accompanied by significant (>20%) increases of foF2 before the storm onset over European area. We focus on the longitudinal extent and height profile of the pre-storm enhancements, particularly on their effects on the F1 and E regions of the ionosphere. Possible origin of such enhancements is also partly discussed. We observe no systematic effect of pre-storm enhancements of foF2 in electron density profiles in the F1 region. The E region (foE) appears to be insensitive to pre-storm enhancements. We find the pre-storm enhancements to be confined to the F2 region. The longitudinal extent of the pre-storm enhancements seems to be 120–240° based on comparison of simultaneous foF2 measurements in Europe, northern USA, and Eastern Asia.