Abro un inciso,
los rayos cósmicos son los precursores de la formación de cloro atmosférico, a partir de Ar36 (el Ar36 por interacción de los rayos cósmicos con Ar40),
vamos, que parece que los rayos cósmicos son también parte fundamental en este proceso, no solo la radiación solar,
¿otro equilibrio semiestable?
Efectivammente, "los solar proton events (SPEs)" pueden llegar a generar agujeros en la capa de ozono.
http://elib.suub.uni-bremen.de/diss/docs/00011076.pdfDe nuevo el sol está más presente en la atmósfera (en esta caso en la química) de lo que pensábamos.
10. Summary and conclusions
Different geomagnetic field configurations, of which some are realistic representations for reversal
situations, have been analysed with respect to their influence on atmospheric impacts of
several single solar proton events. Additionally, enabled by a simulated 200 year time series of
SPEs, impacts on longer time scales have been investigated. The simulations have shown that
geomagnetic field variations can have considerable effects on the ozone destructions caused by
solar proton events. In all magnetic shielding scenarios the ozone losses on longer time scales
are most pronounced in the polar regions which indicates the importance of global transport of
NOy and its subsidence into the ozone layer. The atmospheric impacts of single events depend
significantly on the season in which they occur. On average, the ozone destruction is in general
for all considered scenarios larger in the southern hemisphere than in the northern hemisphere.
This is due to hemispheric differences in the transport processes.
In case of the present-day high halogen load in the stratosphere, there is an interference between
halogen chemistry and SPE induced NOy perturbations especially during spring. This somewhat
weakens the immediate SPE impact on ozone, but the general effect is that the anthropogenically
burdened ozone layer is further negatively affected by large SPEs.
The ozone losses are found to increase with the magnetic polar cusp size and with its nearness to
the polar regions. In this sense, the current field configuration with its small tilt of geomagnetic
to geographic axis is almost a worst case situation for the present field strength. The same
cusp size in the tropics would cause much lower ozone destructions. The main reason for this
is the strong photochemical destruction of NOy in combination with the basically nonexistent
downward transport into the ozone layer at low latitudes. The very scenario of an equatorial
dipole of actual cusp size can be regarded as a snap-shot of a hypothetical geomagnetic reversal
with current field strength. As field reversals are very likely connected to field weakenings, they
rather correspond to the other investigated scenarios which lead to significantly enhanced ozone
depletions. For these geomagnetic field configurations, large events are able to cause considerable
ozone losses, especially in the polar regions. With increasing cusp size also mid-latitudes
become affected, but in general to a lesser extent than the polar regions.
For all investigated single SPEs, the total ozone reductions are found to be samller than due
to an ozone hole. Nevertheless, especially in case of a large polar cusps, considerable ozone
losses are found. In contrast to ozone holes, the impacts of SPEs on ozone are less restricted to
spring times and early summer but can last for several years provided that the proton fluences
are large. For exceptionally large SPEs, as they are included in the simulated time series, the
total ozone losses can be comparabel to ozone hole situations. Subsequently, harmful ultraviolet
radiation increases at ground level.
The absolute ozone losses due to SPEs are smaller at mid-latitudes and in the tropics but due to
smaller solar zenith angles the increasing erythemal weighted ultraviolet radiation might also be
of importance in these regions. These results gain importance by the time scales of geomagneticfield variations. For instance, in case of a full field reversal, for thousands of years the protecting
ozone layer at high latitudes would be reduced to a notable extend, and consequently, UV fluxes
would increase for the long time period of the reversal.
It has not been possible within the scope of this study to assess the possible biological impacts
of these increased UV fluxes over time periods of thousands of years. However, it appears as if
SPEs during field reversals are unlikely to directly cause (or have caused) mass-extinctions. On
the other hand, major events in combination with a reduced shielding by the geomagnetic field
have a negative effect on the surface UV burden which could impair living organisms, especially
those how already suffer from other impacts.
The modelled temperature changes which arise from the SPE caused perturbations of the atmosphere’s
chemistry are not very large. On average, the temperature tends to decrease in
the middle atmosphere. According to the largest ozone losses, the cooling is strongest in the
antarctic lower stratosphere. There the decreasing temperatures denote a negative feedback on
ozone as they facilitate the formation of polar stratospheric clouds which provide surfaces for
heterogeneous reactions which are important for ozone hole situations in spring times. In terms
of global temperature change, the effect of SPEs seems to be of minor importance, even during
a field reversal.