There are two more types of solar wind!
3. Low speed wind of "maximum" type
Similar characteristics as (2), except for
Helium content 4%, highly variable Source above active regions, at activity maximum, Signatures very variable, Lectures at the shock waves often International Max-Planck-Research School imbedded, Oktober 2002 by Rainer Schwenn, MPAe Lindau 4. Ejecta following interplanetary shocks
6. Variations on all time scales High speed 400-2000 kms-1 • The ballerina dances through the solar cycle Helium content often up to 30% • The modulation of Galactic Cosmic Rays: How? Other constituents often Fel6+ ions, in rare • Irradiance variations cases He+ • Biological record for past solar activity! • Butterflies on the Sun? Magnetic clouds in about 30% of cases • The Sun affects climate on Earth Sources erupting prominences • What causes global warming: The Sun or mankind?
The ballerina Sun right before activity minimum
Bpolarity SW type
In this solar rotation in early 1975 (1996) we found all four types of solar wind! The Sun as a “ballerina”, according to Alfvén, 1977.
Coronal hole evolution through the solar cycle The ballerina dancing through the solar cycle
Maximum
Minimum With increasing solar activity, the long- lived large polar cap coronal holes dissolve. At activity maximum, the They are replaced by several short-lived ballerina skirt flips over, smaller coronal holes distributed all over Minimum and the magnetic polarity the Sun. is then reversed at next Towards minimum, the small holes merge to minimum. The magnetic reform large polar holes, but now with cycle of the opposite magnetic polarity. sun (the “Hale-cycle”) takes 22 years!
Maximum Minimum
1 Butterfly diagram for magnetic flux The solar wind stream structure, observed by the Helios and IMP spacecraft from activity minimum in polar field reversal 1975/76 onward.
ecurring use of the r Note: the ca e treams is th high speed s uiet Sun, q imum activity min right before
With increasing solar activity (in 1978), many transient events destroyed any regular solar wind structure The magnetic cycle of the Sun , the „Hale-Cycle“, takes 22 years
7yearsofdata, arranged by solar rotations:
•IPMagnetic field, • Coronal holes, • Solar wind speed, • Geomagnetic index
ers in the s in all paramet egular pattern 75. Note the r y minimum in 19 With increasing solar activity (in 1978, 2000), many around activit upper half, i.e., transient events destroyed any regular solar wind structure
„Galactic Cosmic Radiation“ through the solar cycle The modulation of
Minimum Maximum Minimum Minimum GCR spectra
Sunspots
Maximum
The modulation of Neutron flux at Earth galactic cosmic rays The active sun keeps the (GCRs) affects particles galactic cosmic rays (GCRs) with less than 2 GeV. away from the Earth much Their fluxes are highest! better than the inactive Galactic cosmic rays Sun. That might have impact on our terrestrial weather. question is: The d the solar win Solar cosmic rays how does The modulator must be the uch strong accomplish s solar wind, but how? ion ? GCR modulat 1974 1986
2 The solar wind through the solar cycle Solar wind properties as functions of heliomagnetic latitude, observed by Helios1/2 and IMP
Flow speed (km s-1) 1976 Note in particular:
Proton density • the slow wind “belt” is only 30 deg wide, (cm-3) 1977 The solar cycle variation of • it is asymmetric w.r.t. the ecliptic, solar wind parameters, as • it widens with increasing activity, Proton flux density observed by the Helios • the momentum flux density is invariant, (cm-2s-1) solar probes. • the total energy flux density is invariant
magnetic - kinetic - thermal Each point denotes an energy density Energy flux density average over a full solar (10-7 W cm-2) rotation. momentum flux density r not to iations appea Helium abundance These var cing (%) t for produ total energy sufficien flux density be ion ! GCR modulat
How does the Sun manage to modulate the GCR influx?
With increasing activity: Ulysses found slow solar wind at all latitudes!
In t he ecliptic plane, the solar wind modula tion is small, but at h igh latitudes it is substantial! Note t hat the influx of GCRs from polar latitudes is much easie r because of the more radial field lines (N ot true any more!) The model by Wang & Sheeley, to explain solar wind speeds in terms of their „field expansion factor“ measured near the photosphere
CMEs and shocks during 2 solar cycles Ejected plasma clouds in space
CMEs The daily rate of all CMEs
• Between minimum and Mag maximum, the rates of netic clou ds imply scale r large- both: shocks and CMEs otations ma of the vary by a factor of 10. gnetic fi eld vector • The ratio between CME and shock rates is 10. • There is a clear maximum of CME occurrence at shocks maximum acticivty. They are rather effective in • The shock rate shows a shielding off the GCRs! double peak: maximum occurrence before and after the maximum.
The daily rate of shocks seen by an in-situ observer
3 How does the Sun manage to modulate the GCR influx? How does the Sun manage to modulate the GCR influx? „Forbush decreases“ of GCRs are known since the 1940s At very large distances from the Sun, the „merged Interaction Regions“ (MIRs) and transient flows from CMEs (i.e. shocks and ejecta) form „global merged interaction regions“ (GMIRs).
These large-scale shells of turbulent plasma in GMIRs The GCRs are surround the whole Sun effectively shielded by and are rather efficient in magnetic clouds following shielding the heliosphere coronal mass ejections from GCRs. (CMEs) re hells are mo These s efficient at umerous and n imum activity max
How does the Sun manage to modulate the GCR influx? Solar cycles and Earth‘s climate variations
A sequence of global merged interaction regions caused a stepwise decrease in GCR flux.
solar explain the That might . tion of GCRs cycle modula The „butterfly“ diagram of sunspots
The solar activity cycle, seen in X-rays
Minimum X-rays Magnetic flux
The short-wave radiation varies strongly through the activity cycle: from a factor 2 in the UV (<100 nm) up to a factor 100 The „butterfly“ diagram of in X-rays. sunspots does also apply to flares and active regions, but NOT to Maximum Maximum prominences, filaments, CMEs
4 Solar spectral Solar irradiance measurements - irradiance in the the Sun as a star UV range
Note the strong solar cycle variation of the Sun‘s UV radiation: SEM (CELIAS): EUV disk The „hotter“ the line, the integrated flux from 1-500Å and in 260-340 Å (He II 304 Å) stronger the modulation
rth‘s outer VIRGO - Total solar irradiance heats the Ea y per mille! The UV flux ath“! ather than b d lets it „bre by factors, r mosphere an flux varies at Note: the UV
Solar activity from 14C data Solar cycles and Earth‘s climate variations
sunspots
Dalton
Maunder
Medieval maximum
Solar activity, cosmic rays, and tree rings Solar cycles and Earth‘s climate variations d peak is ften ignored: the secon plots like this one and o Not visible from o the inactive sun! ecurrent M-regions, i.e., t medieval maximum mainly due to r Days of strong storms Sunspots
Spörer minimum Maunder minimum A bio logical record of sola A uni r activ que ex ity hist ample! ory.
High solar activity causes: • better shielding of heliosphere against GCRs, • lower fluxes of GCRs on Earth‘s atmosphere, • less production of 14C isotopes in atmosphere, • less 14C inclusion in tree rings. The second peak in the storm occurrence allows to predict next cycle‘s maximum activity!
5 Overlap of solar cycles
Indeed, first signs of a new cycle appear at very high latitudes Sun-Earth chain, viewed years before the end backwards: of the previous one! • Next cycle maximum is indicated by M-regions, • M-regions are associated with high- speed streams, • High-speed streams come from polar Another nice coronal holes, exa mple for what Eart h observations can Conclusion: teach us about Next cycle‘s amplitude is pre-determined the Sun! by Sun‘s very high latitude properties years before the end of previous cycle!
Variations in the solar magnetic flux Solar cycle length and The solar magnetic flux has increased temperature on Earth, by a factor of 2.3 since 1901 A surprising correlation!
The estimated long term changes in TSI alone can account for: – 52% of the temperature rise between 1910-1960 Friis-Christensen & Lassen (1991) – 31% of the rise since 1970 Zykluslänge
Bodentemperatur Do GCRs cause increased Fligge & Solanki (2001) cloud formation by providing condensation nuclei?
Clouds on Earth and GCRs Variations of solar irradiance and temperatures on Earth High-altitude clouds
Do GCRs cause increased cloud formation by providing Low-altitude wet clouds condensation nuclei?
Note: from 1980 on another effect takes over: the man-made greenhouse effect!
6 Lectures at the International Max-Planck-Research School Oktober 2002 by Rainer Schwenn, MPAe Lindau
6. Variations on all time scales • The ballerina dances through the solar cycle • The modulation of Galactic Cosmic Rays: How? • Irradiance variations • Biological record for past solar activity! • Butterflies on the Sun? • The Sun affects climate on Earth • What causes global warming: The Sun or mankind?
7