Energetic Particles in the Atmosphere J.M. Wissing and M.-B. Kallenrode

1. Energetic Particles in the Atmosphere J.M. Wissing and M.-B. Kallenrode

2. Motivation

3. Motivation: Ozone depletion by precipitating particles • Bastille day event July 14, 2000 (Jackman et al, 2001) 3

4. Main questions Particle precipitation in general • Which particle sources affect the atmosphere? • Where do these particles enter the atmosphere? • How does a comparatively small energy content cause a significant atmospheric reaction? • Are there effects besides Ozone change? • What are the main challenges in modeling atmospheric particles precipitation? • Which (kind of) models exist? • Do we really need them? • How accurate are these models? Modeling particle precipitation 4

5. Where do the Particles come from?

6. Where do the Particles come from?

7. Where do these particles precipitate into the atmosphere? magnetospheric solar (Wissing and Kallenrode 2009) 7

8. What happens to the energetic particles in the atmosphere? Primary effects • Exitation (e.g. aurora) • Ionization! • Secondaries • Bremsstrahlung • Cosmogenic isotopes 8

9. What happens to the energetic particles in the atmosphere? Primary effects Bragg peak • Exitation (e.g. aurora) • Ionization! • Secondaries • Bremsstrahlung • Cosmogenic isotopes • interaction → vertical pattern! (Quack, 2005) 9

10. Entering the atmosphere Particle energy and it's main deposition altitude (Wissing and Kallenrode 2009) 10

11. Atmospheric ionization at different places quiet event (Wissing and Kallenrode, 2009) 11

12. Secondary effects Atmospheric follow-ups due to ionization by precipitating particles • chemical impacts due to ionization production of radicals (NOx, HOx) Ozone depletion production of condensation nuclei cloud formation • physical impact due to ionization higher conductivity 12

13. Secondary effect: Ozone depletion Production of NOx and HOx • ionization of most abundant species (N2, O2, NO, O) • forms radicals: NOx (N, NO) and HOx (H, HO) (Crutzen et al. 1975) NOx and HOx catalytically destroy Ozone • e.g. NO + 03 -> NO2 + O2 NO2 + O -> NO + 02 Crutzen (1970,1971) and JOHNSTON(1971) • „If you want to change the direction of a car the most energy-efficient solution is to tickle the driver.“ 13

14. Secondary effect: Ozone depletion – single event Rohen et al., 2005 North • same forcing • but effect depends on hemisphere South • winter (NH): NOx is transported down into the Ozone layer. • other seasons/regions: NOx stays at high altitudes and is destroyed by sunlight 14

15. Secondary effect: Ozone depletion – solar cycle variation during solar cycle comparable in size with impact of UV-variation Sinnhuber et al., 2005

16. Secondary effect: Cloud formation due to GCRs • observation: cloud coverage below 3.2 km correlates with GCR variations (Svensmark and Friis-Christensen, 1997) • process: still under debate, possible link: enhanced aerosol nucleation due to presence of ions • the CLOUD labratory experiments at CERN support this hypotheses (Duplissy et al., 2009) Marsh & Svensmark, 2000 16

17. Secondary effect: Global electrical curcuit Global electric curcuit • thunderstorms as dynamo • ionosphere/ground highly conductive • atmospheric ionization determines conductivity between ionosphere and ground (Markson, 1978) Conductivity (=current) variation with solar activity! • solar max: low GCR-ionization in low latitudes high SEP-ionization in high latitudes • solar min: vise versa → Impact on lightning frequency? suggested by Schlegel et al. (2001) (e.g. Singh, Singh and Kamra, 2004) 17

18. Tertiary effects Impact on radiation budget • Ozone is a radiation absorbing gas • Cloud coverage impacts the earth's radiation budget • different absorbtion: → e.g. UV radiation change on surface → impact on bisophere? → altitudinal temperature gradient changes! → impact on atmospheric circulation! 18

19. How does a particle precipitation model work? Determine particle flux • above the atmosphere by satellite measurements Combine to energy deposition • of the full spectra Calculate energy deposition • for single particles 19

20. Models for atmospheric particle precipitation (without GCRs) 20

21. Main challenge in modeling global particle precipitation missing data coverage ? (e.g. Wissing and Kallenrode, 2009) • No global ionization rates without intense interpolation! • e.g. cosine fits of actual measurements (Fang et al., 2007) • e.g. mean precipitation maps based on Kp-level (AIMOS model) 21

22. How accurate are recent models for particle precipitation? Setup • electron density derived from AIMOS ionizations and the GCM HAMMONIA • in comparison to: radar measurements • night time Results • polar cap (dots): good satellite coverage → good agreement (factor 1) • auroral oval: interpolation → less accurate (mean underestimation: factor 0.5) (Wissing et al. 2011) 22

23. Do we really need precipitating particles in atmospheric modeling? without particles • daytime: sunlight dominates ionization • in the high atmosphere: benefit of a factor of 100 to 1000 in electron density at night • ion-chemistry depends on electron density with particles (Wissing et al. 2011) 23

24. Unsolved questions in particle precipitation South Atlantic Anomaly More unsolved questions: • angular distribution of particle spectrum? (may cause shift in deposition altitude) • limitation of detectors: energy range, crosstalk (energy, species), degradation 24

25. Summary Modeling ionization • global and wide energy range possible • electron density benefits (factor 1000) • allows calculation of follow-ups • main problems: SAA, spatial data coverage, missing angular distribution of p. particles, quality of particle measurements... Effects on atmosphere • changes in electron density • conductivity, global electric curcuit • top-selling feature: Ozon depletion by catalytic reactions • in the stratosphere: few percents, but up to years • changes in cloud coverage? • changes in radiation budget → temperature gradients → circulation 25