SOLAR ACTIVITY AND SOLAR ACTIVITY AND CLIMATECLIMATE

The sun’s activity and the solar dynamo The sun’s activity and the solar dynamo Climate relationships Climate relationships

Grand Episodes and the recent Transition Grand Episodes and the recent Transition The next cycles The next cycles

C. de JagerC. de Jager

Gentle slopes on the Gentle slopes on the islandisland of of TexelTexel

Dominated by the ‘Hoge Dominated by the ‘Hoge Berg’ Berg’ (‘High mountain’; 15 m high; 18th (‘High mountain’; 15 m high; 18th century drawing)century drawing)

Part of chain of hills: the Part of chain of hills: the terminal moraine of glaciers, 135 terminal moraine of glaciers, 135

000 years BP000 years BP

Explanation of ice ages: Explanation of ice ages: Milankovitch theoryMilankovitch theory

The earth’s precessional and The earth’s precessional and orbital changesorbital changes

Solar irradiation variations as due to precessional Solar irradiation variations as due to precessional and orbital changes appear and orbital changes appear too small to explain ice too small to explain ice agesages. But . But ΔΔT is enhanced by T is enhanced by positive feedback positive feedback by by water vapourwater vapour

Feedback terminologyFeedback terminology

• Freedback strength defined by parameter Freedback strength defined by parameter dR/dq,dR/dq,

• where R is the global-average top-of-where R is the global-average top-of-atmosphere net radiative flux; atmosphere net radiative flux;

• q(x, y, z) is the amount of water vapor at a q(x, y, z) is the amount of water vapor at a particular latitude, longitude, and altitudeparticular latitude, longitude, and altitude

Actual feedback is dR/dq . (Actual feedback is dR/dq . (ΔΔq/T)q/T)

Sun with sunspot groupsSun with sunspot groups

ACTIVITY REGIONS, SUNSPOTS, ACTIVITY REGIONS, SUNSPOTS, FLARES, CORONAL MASS EJECTIONSFLARES, CORONAL MASS EJECTIONS

The equatorial component of solar activity.The equatorial component of solar activity.

Sunspot groups in Active Sunspot groups in Active RegionRegion

Active regions: seats of solar Active regions: seats of solar flaresflares

• Flare: due to Flare: due to reconnection between reconnection between current-carrying loopscurrent-carrying loops

• Currents of the order of Currents of the order of some 10some 101212 amps amps

• First phase: First phase: temperatures of order temperatures of order 50 – 70 million degrees 50 – 70 million degrees during some 10 s to one during some 10 s to one minuteminute

• Thereafter cooling down Thereafter cooling down

Active regions: seats of Coronal Mass Active regions: seats of Coronal Mass Ejections. Ejections. Total mass involved is some 10Total mass involved is some 101010 – 10 – 101212 kg. Speed kg. Speed from 500 – 2500 km/sfrom 500 – 2500 km/s

THE POLAR COMPONENTTHE POLAR COMPONENT

Not only equatorial activityNot only equatorial activity

Polar field dominated by polar Polar field dominated by polar bright points, coronal holes, etc. bright points, coronal holes, etc.

(X-ray picture)(X-ray picture)

Solar variability; the Solar variability; the tachoclinetachocline

Dynamo, regulating solar activity, is Dynamo, regulating solar activity, is source of equatorial and polar magnetic fields. source of equatorial and polar magnetic fields. These fields act in counterphase. Polar activity These fields act in counterphase. Polar activity

maximum ~5 years after equatorial maximum ~5 years after equatorial component. component.

A simplified description of the dynamo A simplified description of the dynamo (1)(1)

• Dynamo seated in Dynamo seated in tachoclinetachocline; layer of 30 000 ; layer of 30 000 km thick, located 200 000 km beneath solar km thick, located 200 000 km beneath solar surface: above lower boundary of convective surface: above lower boundary of convective regionregion

• Strong currents cause magnetic fields; these Strong currents cause magnetic fields; these increase in strength by differential solar rotationincrease in strength by differential solar rotation

• If fieldstrength ≈ 10If fieldstrength ≈ 1055 Gauss kink-instable parts Gauss kink-instable parts of that field detach and riseof that field detach and rise

• After After ~ one – three months they appear at the ~ one – three months they appear at the solar surface as sunspots. They draw weaker solar surface as sunspots. They draw weaker magnetic fields along upward: magnetic fields along upward: Active RegionsActive Regions originate, surrounding the spotsoriginate, surrounding the spots

A simplified decription of the dynamo A simplified decription of the dynamo (2)(2)

• Finally, most of the equatorial field component Finally, most of the equatorial field component disintegrates, whereupon weaker field disintegrates, whereupon weaker field components originate as closed loopscomponents originate as closed loops

• While rising they slowly rotate (Coriolis force), While rising they slowly rotate (Coriolis force), mainly moving parallel to solar rotation axis mainly moving parallel to solar rotation axis

• Thus, near poles a poloidal field originates; Thus, near poles a poloidal field originates; maximum strength occurs maximum strength occurs ~ ~ 5 years after that 5 years after that of equatorial toroidal field of equatorial toroidal field

• We are back at the beginning; We are back at the beginning; ~ 11 years later~ 11 years later

The result: the 11-years sunspot The result: the 11-years sunspot cyclecycle

Two comparable field Two comparable field componentscomponents

• The two main field components have The two main field components have comparable total magnetic comparable total magnetic

• But equatorial field is more But equatorial field is more conspicious because sunspots are well conspicious because sunspots are well visiblevisible

• Maximum of one at the time of Maximum of one at the time of minimum of the otherminimum of the other

• This is part of the exotic dance of the This is part of the exotic dance of the two field components two field components

The dance of the two The dance of the two components components Red: equatorial ; blue: polar (but Red: equatorial ; blue: polar (but note the curious behavior after 2000)note the curious behavior after 2000)

Magnetic fields only Magnetic fields only measured recentlymeasured recently

Equatorial fields since beginning Equatorial fields since beginning of 20th centuryof 20th century

Polar fields since about 40 yearsPolar fields since about 40 yearsWe need We need proxiesproxies for earlier data for earlier data

Proxy for equatorial magnetic Proxy for equatorial magnetic field: maximum sunspot number field: maximum sunspot number (Note the Maunder and Dalton Minima, centered around (Note the Maunder and Dalton Minima, centered around ~~1675 and 1675 and ~~ 1810 and the Grand Maximum centered around 1960. 1810 and the Grand Maximum centered around 1960.

Proxy for polar field component: minimum of Proxy for polar field component: minimum of geomagnetic geomagnetic aaaa index (Maximum index (Maximum ~~ 1975). Can we 1975). Can we

prove that?prove that?

Average terrestrial surface Average terrestrial surface temperature temperature

Is the variation of the earth’s Is the variation of the earth’s surface temperature correlated surface temperature correlated

with solar activity?with solar activity?If so, can it be explained? If so, can it be explained?

Empirical relation temperature with solar Empirical relation temperature with solar activity activity (De Jager, Duhau, Van Geel (2010). De Jager, Nieuwenhuijzen (De Jager, Duhau, Van Geel (2010). De Jager, Nieuwenhuijzen (2013)(2013)

Solar activity and earth’s Solar activity and earth’s temperaturestemperatures

Conclusions:Conclusions:

• Before ~ 1900: Long-term earth’s average Before ~ 1900: Long-term earth’s average ground temperature variations were due to ground temperature variations were due to solar variationsolar variation

• After ~ 1900: other (anthropic ?) After ~ 1900: other (anthropic ?) component becomes increasingly importantcomponent becomes increasingly important

• In addition: Unexplained gradual increase In addition: Unexplained gradual increase of ~ 0.051 degree per centuryof ~ 0.051 degree per century

• And: temperature stalled after ~ 2000 – And: temperature stalled after ~ 2000 – effect of recent solar Transition periodeffect of recent solar Transition period

No temperature increase after No temperature increase after 20002000

Temperature stalled after Temperature stalled after 2000 2000

Can these results be Can these results be explained?explained?

Equatorial component: yes Equatorial component: yes

Equatorial component: Total Solar Irradiance Equatorial component: Total Solar Irradiance increased due to increased UV radiation from increased due to increased UV radiation from faculae faculae (DOT image)(DOT image)

Total Solar Irradiance Total Solar Irradiance measured since 1976. measured since 1976. (ref.: Fröhlich)(ref.: Fröhlich)

Extrapolated down to 1610 on basis of Extrapolated down to 1610 on basis of good correlation with sunspot number good correlation with sunspot number (Lean, 2011)(Lean, 2011)

Average of recent TSI Average of recent TSI reconstructions reconstructions (Lean, Foucal, Solanki et al.)(Lean, Foucal, Solanki et al.)

• Conventional assumption: Conventional assumption: ΔΔT/T = (T/T = (ΔΔI/I) / 4 I/I) / 4 • Thus, one predicts an average gradient related Thus, one predicts an average gradient related

to equatorial field variations of 0.04 K/centuryto equatorial field variations of 0.04 K/century• This is half the observed increaseThis is half the observed increase• Positive feedback by water vapour etc. Positive feedback by water vapour etc.

explains the other halfexplains the other half• Hence: Hence: the T-variation corthe T-variation correlatedrelated with the with the

equatorial field can be explained by the equatorial field can be explained by the variation of total solar irradiancevariation of total solar irradiance

• Still open: variation related to polar field Still open: variation related to polar field

Future solar activityFuture solar activity

Grand Episodes, past and Grand Episodes, past and futurefuture

Next 11-years cycleNext 11-years cycle

Sun passed through several Grand Sun passed through several Grand

Episodes (Minima and Maxima)Episodes (Minima and Maxima) (Usoskin)(Usoskin)

The phase diagram – diagnostic The phase diagram – diagnostic tool; note the Transition Point tool; note the Transition Point (star)(star)

New Grand Episodes start after passage of curve New Grand Episodes start after passage of curve through or near to Transition Point (1924 and 2008, through or near to Transition Point (1924 and 2008, and also in 1620 and 1744) and also in 1620 and 1744)

Expected short-term Expected short-term variationvariation

We (Duhau and De Jager) studied We (Duhau and De Jager) studied solar variability over past few solar variability over past few

thousands of years and found it thousands of years and found it predictable (predictable (not yet publishednot yet published))

What about next Grand What about next Grand EpisodeEpisode• Coming solar Episode will last fot about Coming solar Episode will last fot about

a century. a century.

• Average maximum spotnumber of Average maximum spotnumber of these cycles will be smallthese cycles will be small

• But not as small as during Maunder But not as small as during Maunder MinimumMinimum

• It will partly compensate temperature It will partly compensate temperature increase during coming century. increase during coming century.

Thank you! Thank you!

This presentation can be This presentation can be consulted at consulted at

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