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Titel |
Survey of upper band chorus and ECH waves: Implications for the diffuse aurora |
VerfasserIn |
Nigel Meredith, Richard Horne, Richard Thorne, Roger Anderson |
Konferenz |
EGU General Assembly 2010
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Medientyp |
Artikel
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Sprache |
Englisch
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Digitales Dokument |
PDF |
Erschienen |
In: GRA - Volume 12 (2010) |
Datensatznummer |
250038286
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Zusammenfassung |
The origin of the diffuse aurora has been a source of controversy for many years. More
recently the question has taken a new significance in view of the associated changes in
atmospheric chemistry which may affect the middle atmosphere. Here we use CRRES data to
assess the importance of upper band chorus and electron cyclotron harmonic (ECH) waves in
the production of the diffuse aurora. Both wave modes increase with increasing
geomagnetic activity, suggesting they are related to periods of enhanced convection and/or
substorm activity. They are confined to the near-equatorial region which excludes
the pre-noon sector from the wave survey. During active conditions intense ECH
waves and upper band chorus, with amplitudes exceeding 1 mVm-1, are observed in
the region 4 < L < 7 from 2100 to 0600 MLT approximately 20% and 6% of the
time respectively. This suggests that both wave modes can put electrons on strong
diffusion, but only during active conditions and not at all local times. Scattering rates
fall below the strong diffusion limit at other times when the wave amplitudes are
weaker. Fluxes of low energy electrons (100 eV < E < 30 keV) also increase with
increasing geomagnetic activity in approximately the same region of geospace
as the waves, suggesting that these electrons are responsible for the generation
of the waves. The patterns of the upper band chorus, ECH waves and low energy
electrons are similar to the global morphology of the diffuse aurora, suggesting that
both wave modes play significant roles in the production of the diffuse aurora. |
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