Erdfernerkundung - Numerische Physik: Modellierung

272 KAPITEL 5. DIE ERWEITERTE PERSPEKTIVE: CAWSES
Abbildung 5.39: Consequences
of the large October 1989 event
in the atmosphere at N75: HOx
production (top), NOx production
(middle) and ozone depletion
(bottom)
related to magnetic field reversals, variations of the terrestrial climate and variations of the
atmosphere, in particular its composition.
§ 906 These long-term questions can be analyzed with different scopes. For instance, we can
perform a single event analysis as described above only for modified boundary conditions.
This would be a suitable approach to understand ozone depletion in individual events during,
for instance, a magnetic field reversal or in a changing atmosphere. However, since magnetic
field reversals also are accompanied by climate change and mass extinction, we also might
ask wether ozone depletion might lead to climate change. Since large solar energetic particle
events are rather rare (a few per solar cycle), such speculation only can be reasonable if a
single event has a sufficiently long influence on the atmosphere and thus the effects from
events might overlap and amplify in time.
§ 907 Figure 5.39 shows atmospheric consequences following the large solar energetic particle
event in October 1989. The top panel shows vertical profiles of the HOx generation at 70 N,
the middle panel the same for NOx. Both species are highly reactive and lead to ozone
destruction. HOx is produced mainly at altitudes above 40 km. It is a short lived species and
is easily destroyed by photochemical reactions and during the ozone depletion reaction. Thus
HOx production during a solar energetic particle event certainly will not cause any longterm
effects. The situation is different in case of NOx: it is produced over a much broader
height range from about 20 km to the mesosphere, although the maximum production occurs
above about 40 km. The fundamental difference compared to HOx is the live-time: particle
precipitation is limited to a few days while high NOx levels persist for weeks to months. With
2. Juli 2008 c○ M.-B. Kallenrode