Energetic Particles in the Atmosphere

J.M. Wissing and M.-B. Kallenrode

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Motivation

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Motivation: Ozone depletion by precipitating particles

altitude O3 depletion duration

>50 km 35-40% ~2 days

42 km 25 % ~2 days

38 km 10% >6 days

35 km 5% >6 days

Bastille day event July 14, 2000

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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?

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Particle precipitation in general

Main questions

Modeling particle precipitation

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Where do the Particles come from?

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Where do the Particles come from?

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magnetospheric solar

Where do these particles precipitate into the atmosphere?

(Wissing and Kallenrode 2009)

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Primary effects

What happens to the energetic particles in the atmosphere?

Exitation (e.g. aurora) Ionization! Secondaries Bremsstrahlung Cosmogenic isotopes

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Primary effects

What happens to the energetic particles in the atmosphere?

(Quack, 2005)

Bragg peak Exitation (e.g. aurora) Ionization! Secondaries Bremsstrahlung Cosmogenic isotopes

interaction → vertical pattern!

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Particle energy and it's main deposition altitude

Entering the atmosphere

(Wissing and Kallenrode 2009)

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Atmospheric ionization at different places

quiet event

(Wissing and Kallenrode, 2009)

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Atmospheric follow-ups due to ionization by precipitating particles

Secondary effects

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

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ionization of most abundant species (N2, O2, NO, O) forms radicals: NOx (N, NO) and HOx (H, HO) (Crutzen et al. 1975)

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Production of NOx and HOx

Secondary effect: Ozone depletion

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.“

NOx and HOx catalytically destroy Ozone

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Rohen et al., 2005

same forcing but effect depends

on hemisphere

Secondary effect: Ozone depletion – single event

winter (NH): NOx is transported down into the Ozone layer. other seasons/regions: NOx stays at high altitudes and is destroyed by

sunlight

North

South

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variation during solar cycle comparable in size with impact of UV-variation

Sinnhuber et al., 2005

Secondary effect: Ozone depletion – solar cycle

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Marsh & Svensmark, 2000

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)

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thunderstorms as dynamo ionosphere/ground highly conductive atmospheric ionization determines

conductivity between ionosphere and ground

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Global electric curcuit

Secondary effect: Global electrical curcuit

(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

(e.g. Singh, Singh and Kamra, 2004)

→ Impact on lightning frequency? suggested by Schlegel et al. (2001)

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Tertiary effects

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!

Impact on radiation budget

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above the atmosphere by satellite measurements

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Determine particle flux

How does a particle precipitation model work?

Combine to energy deposition

Calculate energy deposition for single particles

of the full spectra

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model particle source

particle species and energy

precipitation pattern used satellites

internal mechanism

resolution

area fix or variable

Hardy et al.(1989)

magnetospheric

p+ (30 eV–30 keV) global dynamic,dependingon Kp

DMSP

Callis (1997, 1998, ...andLambeth 1998)

magnetospheric

e- (4.25–1050 keV) NH &SHauroralovals

POES-6,later8 & 12

Walt etal.(1968)

Jackman et al.(2001, 2005)

solar p+ (1–300 MeV) polarcap(>60)

static GOES-11and before

range energyrelation

1 h

Schröter et al.(2006)

solar e- (0.5–5 MeV)p+ (0.29–440 MeV)

polarcap

static IMP/GOES MonteCarlo(GEANT4)

Fang et al.(2007)

magnetospheric

p+ (30–240 keV) global dynamic POES-15/16

AIMOS solar &magnetospheric

e- (154eV–5MeV)p+(154eV–500MeV)alpha (4–500MeV)

global dynamic,dependingon Kp

POES-15/16GOES-10or 11

MonteCarlo(GEANT4)

2 h

Models for atmospheric particle precipitation (without GCRs)

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Main challenge in modeling global particle precipitation

(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)

missingdata

coverage

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polar cap (dots):

good satellite coverage

→ good agreement (factor 1) auroral oval:

interpolation → less accurate (mean underestimation: factor 0.5)

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Setup

(Wissing et al. 2011)

How accurate are recent models for particle precipitation?

electron density derived from AIMOS ionizations and the GCM HAMMONIA

in comparison to: radar measurements

night time

Results

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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

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Do we really need precipitating particles in atmospheric modeling?

(Wissing et al. 2011)

without particles

with particles

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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

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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...

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Modeling ionization

Summary

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