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 Solar wind properties as functions of heliomagneticand IMP observed by Helios1/2 The solar wind through the solar cycle latitude, 1976 Note in particular: Flow speed (km s-1) • the slow wind “belt” is only 30 deg wide, 1977 • it is asymmetric w.r.t. the ecliptic, Proton density • it widens with increasing activity, (cm-3) The solar cycle variation of • the momentum flux density is invariant, solar wind parameters, as • the total energy flux density is invariant observed by the Helios Proton flux density solar probes. magnetic - kinetic - thermal (cm-2s-1) energy density Each point denotes an average over a full solar momentum Energy flux density rotation. flux density (10-7 W cm-2) not to ppear total energy iations a g hese var producin flux density T ent for Helium abundance suffici n ! (%) be dulatio GCR mo ? How does the Sun manage to modulate the GCR influx With increasing activity: Ulysses found slow solar wind at all latitudes! In the ecliptic plane, the solar wind modulation is small, but at high latitudes it is substantial! Note that the influx of GCRs from polar latitudes is much easier because of the more radial field lines (Not true any more!) The model by Wang & Sheeley, to explain solar wind speeds in terms of their „field expansion factor“ measured near the photosphere Ejected plasma clouds in space ng 2 solar cycles CMEs and shocks duri The daily rate of all CMEs CMEs Magnetic clouds imply large- scale • Between minimum and rotations of the mag maximum, the rates of netic field vector both: shocks and CMEs vary by a factor of 10. • The ratio between CME and shock rates is 10. • There is a clear maximum They are rather effective in of CME occurrence at shielding off the GCRs! maximum acticivty. shocks • The shock rate shows a 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? „Forbush decreases“ of GCRs are known since the 1940s How does the Sun manage to modulate the GCR influx ? 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). The GCRs are effectively shielded by These large-scale shells of magnetic clouds following turbulent plasma in GMIRs coronal mass ejections surround the whole Sun and are rather efficient in (CMEs) shielding the heliosphere from GCRs. These shells are more numerous and efficient at activity maximum How does the Sun manage to modulate the GCR influx ? Solar cycle s and Earth‘s cl imate variations A sequence of global merged interaction regions caused a stepwise decrease in GCR flux. That might explain the solar cycle modulation of GCRs. 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: The „butterfly“ diagram of from a factor 2 in sunspots does also apply to flares the UV (<100 nm) and active regions, but NOT to up to a factor 100 prominences, filaments, CMEs Maximum in X-rays. Maximum 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 cycles Overlap of solar Indeed, first signs of a new cycle appear at very high latitudes years before the end of the previous one! Sun-Earth chain, viewed backwards: • Next cycle maximum is indicated by M-regions, Another nice • M-regions are associated with high- example for what speed streams, Earth observations • High-speed streams come from polar can teach us about coronal holes, the Sun! Conclusion: Next cycle‘s amplitude is pre-determined by Sun‘s very high latitude properties years before the end of previous cycle! Solar cycle length and magnetic flux ions in the solar temperature on Earth, Variat A surprising correlation! The solar magnetic flux has increased by a factor of 2.3 since 1901 Friis-Christensen The estimated long term changes in TSI & Lassen (1991) alone can account for: – 52% of the temperature rise Zykluslänge between 1910-1960 – 31% of the rise since 1970 Bodentemperatur Fligge & Solanki (2001) Do GCRs cause increased cloud formation by providing condensation nuclei? Variations of solar irradiance and Clouds on Earth and GCRs temperatures on Earth High-altitude clouds Do GCRs cause increased cloud formation by Low-altitude wet clouds providing 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.