The heliosphere, The visible solar corona structure and dynamics • Solar corona, structure and evolution • The heliosphere, structure and dynamics • Solar wind (heliospheric) magnetic field • Corotating interaction regions • Interplanetary shock waves • The outer heliosphere and LISM Eclipse 11.8.1999 Electron density in the corona Heliospheric temperatures + Current Halo (4%) sheet and streamer belt, closed Electrons Core (96%) • Polar coronal Tp ≤ Te hole, open magnetically Protons Heliocentric distance / Rs Guhathakurta and Sittler, McComas 1999, Ap.J., 523, 812 Skylab coronagraph/Ulysses in-situ Ulysses et al., 1998 Rotation of the sun and corona Heliospheric current sheet Stack plot of Carrington rotations from 1983 to 1994, showing the location of the heliospheric current sheet (HCS) on the source surface at 2.5 Rs Negative polarity, dark Neutral line, bold Hoeksema, Space Sci. Rev., 72, 137, 1995 1 Coronal magnetic field and density Solar wind stream structure and heliospheric current sheet Dipolar, Polar field: quadrupolar, B = 12 G current sheet contributions Current sheet is a symmetric disc anchored Parker, 1963 at high latitudes ! Banaszkiewicz et al., 1998; LASCO C1/C2 Schwenn et al., images 1997 (SOHO) Alfven, 1977 Solar wind fast and slow streams Stream interaction region Helios 1976 Dynamic processes in inter- planetary space • Wave amplitude steepening (n~ r-2) • Compression and rarefaction • Velocity shear • Nonlinearity by advection (V•∇)V • Shock formation (co-rotating) Alfvén waves and small-scale structures Marsch, 1991 Stream interaction region (Helios) Solar wind stream interactions Forward Corotating interaction shock FS region (CIR) Reverse shock RS Stream interface SI, tangential discintinuity with T jump Schwenn, 1990 Hundhausen, 1973; Pizzo, 1978 2 Model of coronal-heliospheric field (Parker) spiral interplanetary magnetic field rot(E) = rot(VXB) = 0 Fisk Parker Fisk, JGR, 1996 Heliospheric magnetic field direction Latitudinal variation of the 2 heliospheric magnetic field BR = Bs (Rs/R) Parker spiral -1 BT = BR Ω(θ)R/V cosθ ϕp = tan (BT/BR) BN = 0 (Rs = 700000 km) Field Ω(θ) = 3.101 - 0.464 sin(θ)2 - 0.328 sin(θ)4 [µrad/s ] polarity Ulysses Alfvén waves Balogh and Forsyth, 1998 Forsyth et al., A&A 316, 287, 1996 Heliospheric magnetic field Conservation of radial magnetic flux At 1 AU: Ulysses: BR ≈ 3.1 nT Helios: BR ≈ 3.3 nT Magnetic semi-monopole Ulysses SWOOPS Smith et al., Adv. Space McComas et al., 1998 Res. 20, 47, 1997 3 Solar wind speed and density Current sheet crossings Polar Dense diagram B outward Less Helium V Speeds equal Ecliptic Density Slow n R2 Temperatures B inward Cold close McComas et al., GRL, 25, Borrini et al., JGR, 1981 1, 1998 Polar diagram of solar wind Polar plot of density and He/H ratio SWICS Ulysses Proton density Ecliptic 2 nα/np np(r/1AU) Near solar maximum: Slow wind at - 65° ! Woch, 2000 McComas et al., 1998; Geiss et al., 1998 Ulysses SWOOPS/SWICS Polar plot of mass/momentum flux Heliosphere and local interstellar medium Particle Ram V = 25 km/s flux pressure Bow shock Heliopause Hydrogen wall 2 2 2 Heliospheric np/mpV(r/1AU) np/mpV (r/1AU) SW shock 3 McComas et al., 1998 Ulysses SWOOPS/SWICS (red) - 0.3 > log(ne/cm ) > - 3.7 (blue) Kausch, 1998 4 Structure of the heliosphere Heliospheric termination shock 2-3 kHz radio emission generated at the heliopause (compression region); radiation is trapped in heliospheric cavity; source: largest CMEs of solar activity maximum in 1983 and 1993 Shock at 100 AU? • Basic plasma motions in the restframe of the Sun Stone, 1999; Kurth, 1999 • Principal surfaces (wavy lines indicate disturbances) The outer frontier The interstellar neighbourhood Termination schock at about 100 AU and Voyager at 80 AU Frisch, Space Sci. Rev. 86, 107, 1998 Changing corona and solar wind Solar wind types I 1. Fast wind in high-speed streams High speed 400 - 800 kms-1 Low density 3 cm-3 Low particle flux 2 x 108 cm-2 s-1 Helium content 3.6 %, stationary Source coronal holes Signatures stationary for long times (weeks!) 2. Low-speed wind near activity minimum Low speed 250 - 400 km s-1 High density 10 cm-3 High particle flux 3.7 x 108 cm-2 s-1 Helium content below 2 %, highly variable 45 30 15 0 -15 -30 -45 Source helmet streamers near current sheet North Heliolatitude / degree South Signatures sector boundaries embedded McComas et al., 2000 LASCO/Ulysses 5 Speed profile of the slow solar wind Solar wind types II 3. Low speed wind near activity maximum Parker, 1963 Speed profile as determined Similar characteristics as 2., except for from plasma blobs in the wind Helium content 4%, highly variable Source related to active regions Signatures shock waves often imbedded 4. Ejecta following interplanetary shocks High speed 400 - 2000 kms-1 Helium content up to 30% Other constituents often Fel6+ ions; in rare cases He+ Outflow starts at about 3 RS Signatures of magnetic clouds in about 30% of cases 60 Radial distance / RS Sources erupting prominences Sheeley et al., Ap.J., 484, 472, 1998 Consistent with Helios data Coronal mass ejections Statistics of CME properties - longitudinal spreads? - origin and directions? - global distribution? Schwenn et al., 1998, 2000 LASCO on SOHO, helical CME About 1000 CMEs observed by SOLWIND Howard et al., 1985 Speeds of CMEs (1996 to 1998) Speed profile of balloon-type CMEs Histogram of expansion speeds of 640 CMEs LASCO/SOHO • Flare-associated fast CMEs with 0.3 ms-2 and initial V > 700 km/s • Eruptive slow CMEs with 0-50 ms-2 and initial V = 10-20 km/s St.Cyr et al., 2000 -2 Srivastava et al., 1999 Wide range of initial acceleration: 5-25 ms 6 Field variation in magnetic cloud Interplanetary CME • Rotation of field vector • Speed enhancement • Lower density • Higher Helium content • Cooler protons Magnetic loop or flux rope Burlaga, 1980 Philipps, 1997 Daily number of interplanetary Interplanetary shock waves shocks in a typical solar cycle Quasiparallel Quasiparallel 0 0 The daily (19 ) transient (12 ) corotating .... fast-mode shock fast-mode shock shock rate, based Sunspot on 400 shocks observed by the number Helios solar probes in 12 years. CME rates: 2-3/day (max) 0.2/day (min) Note the strong jumps in all Shock rate in the ecliptic plane is about 10 % of the parameters! total CME rate: every tenth CME shock hits the earth! Khalisi, 1995 Richter et al., 1986 Solar wind stream dynamics Solar wind streams and shocks Fast streams <-------> slow streams Coronal holes (open) - streamers (closed) Sharp transitions ≈ 20 - 80 (20 - 80) kms-1/degree Stream collisions <---> interaction regions advection <---> compression (V•∇) V = - ∇(p + B2/4π) • Colliding transient flows form corotating interaction regions (CIRs) • Compound streams: - two corotating streams - stream and transient ejection - two ejecta or clouds or shocks Schwenn, 1990 7 Corotating Corotating shocks interaction Schematic showing how the tilted streamer region CIR belt leads equatorward forward (FS) and poleward reverse (RS) shock propagation Ulysses shock statistics for northern (right) and southern (left) hemisphere Gosling & Pizzo, Space Sci. Rev. 89, 21, 1999 CIR simulation Merged stream interaction regions Tilted dipol geometry used at inner boundary In-situ MHD observation simulation at 1 AU at 2 AU White: fast, black: slow FS and RS pairs develop Stream MIRs coalescence Large-scale 3-D structure of CIRs is intimately linked --> pressure with slow/fast wind source pulse Pizzo, 1991; Pizzo Burlaga, 1995 & Gosling, 1994 geometry in solar corona Global merged interaction region Inventory of the heliosphere Voyager • Interplanetary magnetic field (sun) at 6.2 AU • Solar wind electrons and ions (corona) Merging • Solar energetic particles (solar atmosphere) wipes • Anomalous cosmic rays (planets, heliopause) out stream • Cosmic rays (galaxy) structure • Pick-up ions (solar wind, dust, surfaces) Helios at • Energetic neutrals (heliopause) 0.85 AU • Dust (interstaller medium, minor bodies) Burlaga, 1995 8 Gravitational focussing of interstellar Interstellar neutral gas gas He Stars in galactic plane View from Ulysses, in ecliptic Witte et al., Spac. Sci. Rev. 78, 289, 1996 coordinates: λ ≈ 225o, β ≈ 5o. 9.