atmospheric transport and chemistry lecture i.introduction ii.fundamental concepts in atmospheric...
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Atmospheric transport and chemistry lecture
I. Introduction
II. Fundamental concepts in atmospheric dynamics: Brewer-Dobson circulation and waves
III. Radiative transfer, heating and vertical transport
IV. Stratospheric ozone chemistry
V. The tropical tropopause
VI. Climate gases
VII. Solar variability
I. The sun
II. Solar radiation changes and ozone
III. Solar particles and the middle atmosphere
The sun seen in the visible (by MDI on the SOHO satellite)
The sun seen in the visible (by MDI on the SOHO satellite)
The sun seen in the visible (by MDI on the SOHO satellite)
Planck‘s function (black-body radiation)
deviation from Planck‘s function
some structure
Internal structure of the sun
The (assumed) zones within the sun:
core
radiative zone
convective zone
atmosphere
The core of the sun
All energy is produced in the solar core, by nuclear reactions (fusion reactions of H)
Inner core: composed of 4He, no nuclear reactions
Core edge: nuclear reactions of H, producing 4He
Nuclear reactions at the core edge
Proton-proton fusion chain to form 4He
Nuclear reactions at the core edge
Proton-proton fusion chain to form 4He
Proton-carbon fusion chain to form 4He
Relative abundances of species in the sun
Relative abundances of species in the sun ... and in the solar system
Relative abundances of species in the sun ... and in the solar system
the sun is formed of the debris of dead stars
Nuclear reactions at the core edge
Energy is released in the form of radiation ( - rays)
....
and kinetic energy of the products
The (assumed) zones within the sun:
core
radiative zone
convective zone
atmosphere
Radiative zone
Temperature and density are not large enough for nuclear reactions
Radiation is transmitted from the core through the radiative zone – on it‘s way, it is absorbed and emitted many times, and loses energy
Convective zone
Formation of convection zells – cooled by updraft of ‚hot‘ plasma parcels
moving plasma produces a strong magnetic field (‚dynamo effect‘), similar to the formation of the terrestrial magnetic field
The solar atmosphere
Photosphere: ~ 1000 km small, forms the visible surface of the sun
Chromosphere: several 1000 km
Corona: several solar radii
The solar spectrum – the spectrum of the solar atmosphere
Temperature and density of the solar atmosphere
Solar spectrum: black-body radiation of the photosphere
Spectrum of the solar atmosphere: black body radiation, emission and absorption at different T and p
Low T: only ground-state of atoms is occupied
absorption
Spectrum of the solar atmosphere: black body radiation, emission and absorption at different T and p
Low T: only ground-state of atoms is occupied
absorption
High T: excited-states are occupied
emission
Spectrum of the solar atmosphere: black body radiation, emission and absorption at different T and p
Low p: clearly defined lines
High p: pressure broadening smears out lines
Spectrum of the solar atmosphere: black body radiation, emission and absorption at different T and p
Clearly defined emission lines: hot, low density
broad absorption feature: cold, high density
Temperature and density of the solar atmosphere
Density is constant within the corona !Clearly defined emission lines: hot, low density
broad absorption feature: cold, high density
Spectrum of the solar atmosphere: black body radiation, emission and absorption in the solar atmosphere
Fraunhofer lines in the far UV: emission from the chromosphere and corona
Spectrum of the solar atmosphere: black body radiation, emission and absorption in the solar atmosphere
in the near-UV: absorption in the photosphere
Fraunhofer lines in the far UV: emission from the chromosphere and corona
The photosphere – the visible surface of the sun
granules across the solar surface: top of convection zells
The photosphere – the visible surface of the sun
Quiet sun Active sun
dark sunspots in active regions
The photosphere – the visible surface of the sun
Quiet sun Active sun
dark sunspots in active regions light
faculae around active regions
Sunspots and the solar 11-year (22-year) cycle
Dark sunspots: cooler than the surrounding plasma
Sunspots and the solar 11-year (22-year) cycle
Sunspots and the solar 11-year (22-year) cycle
Sunspots are
• colder than the surrounding plasma
• associated with the solar magnetic field
• extend into the chromosphere and corona as brighter areas
Sunspots and the solar 11-year (22-year) cycle
Sunspots are
• colder than the surrounding plasma convection below sunspots is prohibited by the strong field
• extend into the chromosphere and corona as brighter areas plasma is trapped within the strong outer field
The 11 – year sunspot cycle: the last 400 years
Maunder minimum
Solar minimum: low sunspot numbers, low solar activity
Solar maximum: high sunspot numbers, high solar activity
periodicity of 9 - 13 years
Distribution of sunspots across the solar disk: the butterfly diagramm
From the homepage of the Ulysses instrument (http://www.sp.ph.ic.ac.uk/~forsyth/reversals)
From the homepage of the Ulysses instrument (http://www.sp.ph.ic.ac.uk/~forsyth/reversals)
From the homepage of the Ulysses instrument (http://www.sp.ph.ic.ac.uk/~forsyth/reversals)
From the homepage of the Ulysses instrument (http://www.sp.ph.ic.ac.uk/~forsyth/reversals)
the 11-year solar cycle is a 22 year solar magnetic cycle !
at the approach to solar max
the form of the corona changes
the brightness of the chromosphere increases
the surface of the chromosphere gets patchy
The sun‘s corona during an eclipse (1966): solar magnetic field and the brightness of the corona
From: Kivelson and Russell, Introduction to Space Physics
Solar min: even surface Solar max: bright loops and dark patches across surface
Loops: plasma trapped in closed magnetic field lines
Closed loops in the solar magnetic field of the corona: prominences
Closed loops in the solar magnetic field of the corona: prominences
The final fate of a prominence: eruption
Breaking and reconnection of the magnetic field lines above sunspots: solar coronal mass ejections
flare associated with the CME
large plasma bubble is hurled into space
Breaking and reconnection of the magnetic field lines above sunspots: solar coronal mass ejections
flare
plasma bulb
Evolution of a CME at the point where magnetic polarities change
Low and Zhang, in: Solar variability and its effect on climate
Internal structure of the sun
SOHO image of a coronal mass ejection
The last 400 years of Solar Proton Events:
McCracken et al., JGR, 2000
1989
18591893-1896
„Space age“