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| Titel |
Empirical Determination of Solar Proton Access to the Polar Atmosphere |
| VerfasserIn |
Jason Neal, Craig Rodger, Janet Green, Ian Whittaker |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250088420
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| Publikation (Nr.) |
 EGU/EGU2014-2522.pdf |
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| Zusammenfassung |
| Violent expulsions on the Sun’s surface release high energy solar protons that ultimately
affect ionization levels and the local chemical composition in the upper atmosphere as well as
High Frequency (HF) communication used by aircraft. The geomagnetic field screens the low
altitude equatorial region, but these protons can access the atmosphere over the
poles. The latitudes over which the solar protons can reach vary with geomagnetic
indices such as Kp and Dst. In this study we use observations from Low Earth Orbit
to determine the atmospheric access of solar protons and hence the flights paths
most likely to be affected. Observations taken by up to six polar orbiting satellites
during 15 solar proton events are analyzed. From this we determine 16,850 proton
rigidity cutoff estimates across 3 energy channels. Empirical fits are undertaken
to estimate the most likely behavior of the cutoff dependence with geomagnetic
activity.
We provide simple equations by which the geomagnetic latitude (spatial extent) at which the
protons impact the atmosphere can be determined from a given Kp or Dst value. The
variation found in the cutoff with Kp is similar to that used in existing operational models,
although the changing Kp value is found to lead the variation in the cutoffs by
~3 hours .We also suggest a ~1-2° equatorward shift in latitude would provide
greater accuracy. This solar proton access can be used as an input into coupled
chemistry climate models and give the likely polar regions to be effected by Polar Cap
Absorption (PCA) which causes HF radio “blackout zones”. We find that a Kp predictive
model can provide additional warning to the variation in proton cutoffs. Hence a
prediction of the cutoff latitudes can be made ~3 hours to as much as 7 hours into the
future, meeting suggested minimum planning times required by the aviation industry. |
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