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| Titel |
Extended power laws for heliospheric KeV ions due to injection from the ACR- ion population |
| VerfasserIn |
H. J. Fahr  , Igor V. Chashei, Daniel Verscharen |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250031172
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| Zusammenfassung |
| Though pick-up ions are well known in the inner heliosphere, their phase-space distribution
nevertheless is a theoretically unsettled problem till now. Especially the question why pick-up
ions form suprathermal tails, extending to far above their primary injection energy, is
not satifactorily answered. Fermi-2 velocity diffusion theories indicate that such
tails to some degree should become populated, but cannot explain observations
showing power-laws with an indicated velocity index of ”-5”. First we show that such
power-laws cannot result from a quasi-equilibrium state between suprathermal ions and
magnetohydrodynamic turbulences in mutual energy exchange. The required equilibrium if
established near the shock, would require too high pick-up ion pressures enforcing a
shock-free deceleration of the solar wind. Fermi-2 type energy diffusion is too
ineffective in the outer heliosphere for the generation of power law shapes of the ion
distribution function. As we can show, however, power-laws ranging to far above
the injection threshold can be established, if the injection takes place at higher
energies of the order of 100 KeV. Such an injection is in fact connected with the
modulated anomalous cosmic ray (ACR) particles at the lower end of their spectrum
where they again start being convected outwards with the solar wind. A quantitative
calculation of the pick-up ion spectrum resulting under such conditions in fact delivers
power-laws, however, with a velocity power index of ”-4” and astonishingly enough fairly
distance-independent spectral intensities. These results seem to be observationally well
supported by VOYAGER-1 measurements in the lowest energy channels, i.e. 50-100
KeV. |
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