Solar particle events and their impact on stratospheric composition Miriam Sinnhuber Institut für Umweltphysik, Universität Bremen

Solar particle events and their impact on stratospheric composition Origin of particle events Atmospheric impacts Model predictions Miriam Sinnhuber Institut für Umweltphysik, Universität Bremen

Extraterrestrical charged particles: Protons, electrons, heavier ions from: - galactic cosmic raysoutside solar system - energetic electronssolar flares, magnetosphere - solar proton eventssolar coronal mass ejections, solar flares

Solar proton events and the solar cycle Sunspot number courtesy of NOAA GOES daily averaged particle flux

From the homepage of the Ulysses instrument (

 22 year solar magnetic cycle

Evolution of a CME at the point where magnetic polarities change Low and Zhang, in: Solar variability and its effect on climate

Solar coronal mass ejections: November 2000 Pictures from several instruments onboard the SOHO satellite

Polar cap: open magnetic field lines

Auroral ovals: impact of particles from the radiation belts

solar wind thermosphere magnetospheric particles thermosphere solar energetic particles mesosphere and stratosphere galactic cosmic rays lower stratosphere / surface

Proton fluxes measured by GOES- 10 instrument Modelled ion pair production rate based on GOES, Northern polar cap Proton fluxes and atmospheric ionisation, October `03 Ionisation rates courtesy of May-Britt Kallenrode, University of Osnabrück

Impact on the atmosphere: Ionisation and radical formation N 2 + p,e N 2 +,N + O 2 + p,e O2+O2+ lots of ion reactions H2OH2O O N,NO H,OH chemically inert radicals

Impact on the atmosphere: Ion chemistry Positive ion chemistry scheme from the Sodynkylä ion chemistry model, E. Turunen

Impact on the atmosphere: NOx production HALOE measurement during July 2000 event HALOE/UARS at ~68°N NO + NO 2, ppb

Impact on the atmosphere: Ozone destruction Katalytic ozone destruction: Odd hydrogen HO x =H+OH+HO 2 OH + O H + O 3 OH + O 2 H + O 2 Odd nitrogen NO x =N+NO+NO 2 NO + O 3 NO 2 + ONO + O 2 NO 2 + O 2 > 40 km < 40 km

Impact on the atmosphere: Ozone destruction HALOE measurement during July 2000 event HALOE/UARS at ~68°N Ozone change %

Impact on the atmosphere: Ozone destruction SCIAMACHY measurement during Oct 2003 event

POAM measurement of NO 2 at 850 K, 65°S-88°S, Inside vortex Adapted from Randall et al., GRL, 2001 Long-term impact: Downward transport of NOx

A test of our understanding: Model / measurement comparisons 2 D / 1 D global chemistry and transport model of the atmosphere NOx / HOx production parameterised

MIPAS / ENVISAT, October 2003, NH ozone 2 D / 1 D model MIPAS Data from Lopez- Puertas et al, JGR, 2005

MIPAS 2 D / 1 D model MIPAS / ENVISAT, October 2003, NH NOx

Outside vortex POAM measurement of NO 2 at 850 K, 65°S-88°S, Inside vortex POAM data adapted from Randall et al., GRL, 2001 Long-term impact: Downward transport of NOx

MIPAS / ENVISAT, October 2003, NH N2O5 MIPAS 2 D / 1 D model

MIPAS / ENVISAT, October 2003, NH HNO3 MIPAS 2 D / 1 D model

HNO3 formation pathways Neutral chemistry: OH + NO 2  HNO 3

HNO3 formation pathways Neutral chemistry: OH + NO 2  HNO 3 Ion chemistry: Water cluster ion chain (Kawa et al, 1995) N 2 O 5 + X + (H 2 O) n  X + (H 2 O) n-1 (HNO 3 ) + HNO 3 X + (H 2 O) n-1 (HNO 3 ) + H 2 O  HNO 3 + X + (H 2 O) n Net: N 2 O 5 + H 2 O  2 HNO 3

A very simple model approach N 2 O 5 + X + (H 2 O) n  X + (H 2 O) n-1 (HNO 3 ) + HNO 3 X + (H 2 O) n-1 (HNO 3 ) + H 2 O  HNO 3 + X + (H 2 O) n Net: N 2 O 5 + H 2 O  2 HNO 3 Ion densities from equilibrium of ionisation rates and recombination Protonized ion density = total ion density Reaction rate of net reaction = rate of N 2 O 5 + X + (H 2 O) n

HNO 3 production by H + (H 2 O) n cycles Base run Run with H + (H 2 O) n cycles

N 2 O 5 production, H + (H 2 O) n cycles Base run Run with H + (H 2 O) n cycles

Conclusions Solar proton events derive from solar coronal mass ejections or solar flares during solar maximum During solar proton events, the composition of the middle atmosphere is strongly disturbed, with large ozone losses and NOx production This disturbance can continue for weeks or month after the events, especially in polar night NOx production and ozone loss during and after events are well reproduced by models  these processes appear to be well understood Changes of other species – HNO3, N2O5 – are not reproduced at all  these are not well understood yet

Model results: July 2000 SPE ozone HALOE at ~ 68° North Model at 68° North

Model results: July 2000 SPE NO+NO 2 HALOE at ~ 68° North Model at 68° North

Solar proton events: July 2000 HALOE at ~68°N NO + NO 2 change ppb HALOE at ~68°N Ozone change %

The last 400 years of Solar Proton Events: McCracken et al., JGR, „Space age“

SOHO image of a coronal mass ejection

The sun‘s corona during an eclipse (1966) From: Kivelson and Russell, Introduction to Space Physics