Solar 27-day signatures in standard phase height measurements above central Europe
<p>We report on the effect of solar variability at the 27-day and the 11-year timescales on standard phase height measurements in the ionospheric D region carried out in central Europe. Standard phase height corresponds to the reflection height of radio waves (for constant solar zenith distanc...
| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2019-02-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://www.atmos-chem-phys.net/19/2079/2019/acp-19-2079-2019.pdf |
| Summary: | <p>We report on the effect of solar variability at the 27-day and the 11-year
timescales on standard phase height measurements in the ionospheric D region
carried out in central Europe. Standard phase height corresponds to the
reflection height of radio waves (for constant solar zenith distance) in the
ionosphere near 80 km altitude, where NO is ionized by solar Lyman-<span class="inline-formula"><i>α</i></span>
radiation. Using the superposed epoch analysis (SEA) method, we extract
statistically highly significant solar 27-day signatures in standard phase
heights. The 27-day signatures are roughly inversely correlated to solar
proxies, such as the F10.7 cm radio flux or the Lyman-<span class="inline-formula"><i>α</i></span> flux. The
sensitivity of standard phase height change to solar forcing at the 27-day
timescale is found to be in good agreement with the sensitivity for the
11-year solar cycle, suggesting similar underlying mechanisms. The amplitude
of the 27-day signature in standard phase height is larger during solar
minimum than during solar maximum, indicating that the signature is not only
driven by photoionization of NO. We identified statistical evidence for an
influence of ultra-long planetary waves on the quasi 27-day signature of
standard phase height in winters of solar minimum periods.</p> |
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| ISSN: | 1680-7316 1680-7324 |