The sunspot cycle and “auroral”Flayer irregularities
Aarons, J.; Kersley, L.; Rodger, A.S.. 1995 The sunspot cycle and “auroral”Flayer irregularities. Radio Science, 30 (3). 631-638. https://doi.org/10.1029/94RS03191
Full text not available from this repository. (Request a copy)Abstract/Summary
The use of the word “aurora” for many different observations at high latitudes has limited the concepts involved; this is particularly true for F region irregularities. Observations setting the position of the auroral oval (Starkov and Fel'dshtein, 1970) were made using primarily the 555.7-nm green line, which is emitted predominantly at E layer heights. These observations have shown that the change in position of the auroral oval for low values of Kp as a function of sunspot cycle is of the order of 1° to 2° between sunspot maximum and sunspot minimum. However, irregularities in the F region show much larger solar cycle variations in the locations of the equatorward boundary, typically 10°. A review of scintillation data indicates that at a given auroral latitude, the scintillation activity increases with sunspot number. In addition, for a constant scintillation intensity, the equatorward boundary moves to lower latitudes as sunspot maximum is approached. We review existing spread F studies and show that for quiet geomagnetic conditions, there is lower occurrence during years of low sunspot numbers than during years of high sunspot numbers. However, the spread F index, related to Δ ƒ/ƒ0F2, is higher during years of low sunspot number than during years of high sunspot number. We demonstrate that this apparent dichotomy can be reconciled by using a new method of normalizing the spread F index by the maximum electron concentration of the F layer. We briefly discuss the possible explanations for the observed solar cycle variations of irregularity occurrence in terms of the absolute values and gradients of electron concentration and the E region conductivity.
Item Type: | Publication - Article |
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Digital Object Identifier (DOI): | https://doi.org/10.1029/94RS03191 |
Programmes: | BAS Programmes > Pre 2000 programme |
ISSN: | 00486604 |
Date made live: | 06 Dec 2016 11:33 +0 (UTC) |
URI: | https://nora.nerc.ac.uk/id/eprint/515391 |
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