Polar mesosphere summer echo strength in relation to solar variability and geomagnetic activity during 1997–2009
This paper is based on measurements of Polar Mesosphere Summer Echoes (PMSE) with the 52 MHz radar ESRAD, located near Kiruna, in Northern Sweden, during the summers of 1997–2009. Here, a new independent calibration method allowing estimation of possible changes in antenna feed losses and transm...
| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2011-03-01
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| Series: | Annales Geophysicae |
| Online Access: | https://www.ann-geophys.net/29/563/2011/angeo-29-563-2011.pdf |
| Summary: | This paper is based on measurements of Polar Mesosphere Summer Echoes (PMSE)
with the 52 MHz radar ESRAD, located near Kiruna, in Northern Sweden, during
the summers of 1997–2009. Here, a new independent calibration method
allowing estimation of possible changes in antenna feed losses and
transmitter output is described and implemented for accurate calculation of
year-to-year variations of PMSE strength (expressed in absolute units –
radar volume reflectivity η). The method is based on radar-radiosonde
comparisons in the upper troposphere/lower stratosphere region
simultaneously with PMSE observations. Inter-annual variations of PMSE
volume reflectivity are found to be strongly positively correlated with the
local geomagnetic K-index, both when averaged over all times of the day, and
when considering 3-h UT intervals separately. Increased electron density
due to energetic particle precipitation from the magnetosphere is suggested
as one of the possible reasons for such a correlation. Enhanced ionospheric
electric field may be another reason but this requires further study.
Multi-regression analysis of inter-annual variations of PMSE η shows also an
anti-correlation with solar 10.7 cm flux and the absence of any
statistically significant trend in PMSE strength over the interval
considered (13-years). Variations related to solar flux and K-index account
for 86% of the year-to-year variations in radar volume reflectivity. |
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| ISSN: | 0992-7689 1432-0576 |