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Questions concerning the Sun’s Magnetic Connections

Questions concerning the Sun’s Magnetic Connections. and prospects for the near future. Karel Schrijver SHINE 2006. “The real voyage of discovery consists not in seeking new landscapes, but in having new eyes.” Marcel Proust (1871-1927).

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Questions concerning the Sun’s Magnetic Connections

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  1. Questions concerning the Sun’sMagnetic Connections and prospects for the near future. Karel Schrijver SHINE 2006 “The real voyage of discovery consists not in seeking new landscapes, but in having new eyes.” Marcel Proust (1871-1927) “The human understanding is moved by those things most which strike and enter the mind simultaneously and suddenly, and so fill the imagination.” Sir Francis Bacon (1561-1626)

  2. Questions related to connections • AR “anchoring” • ER “production” • Field dispersal, retraction, ejection • Role(s) of atmospheric reconnection: • Heating • Flares and mass ejections • Dynamo action • Coronal hole formation and evolution • … • …

  3. New instrumentation: 2006-2008 • GBO: SST, DOT, GONG, SOLIS, … • STEREO (Aug.[?] 2006): stereoscopic measurements of the dynyamic corona and inner heliosphere • Solar-B (23 Sep. 2006): high-resolution vector-magnetometry, and atmospheric spectrocopy and imaging • SDO (Aug. 2008): the global Sun, from deep interior to high corona, and Sun-as-a-star spectroscopy • Virtual Solar Observatory?

  4. 4-6 kK 2 3 40 kK 0.1 4 0.9 8 1.2 12 Instrument capabilities: solar atmosphere • Data rates to increase >1,000x; e.g., • EIT: 1024x1024 / 1000s (average) • AIA: 4096x4096 / 1s; >1TB/d (compressed) Temperature Coverage (MK) AIA 10 TRACE Images per minute 1 SOLAR B XRT STEREO SECCHI SOHO EIT 0.1 Moss Layer Granulation AR Loop Length Filaments CMEs Pore Solar Diameter Sunspot Diameter Chromospheric Thickness 1 10 100 1000 Spatial range (arcsec)

  5. STEREO/SECCHI-EUVI (3.5”) AIA&HMI (0.6”) XRT (1”) TRACE (0.5”) SOT/NFI (0.08) SOT/SP (0.16”) FOV and resolution Transitioning: from 1k x 1k to 2k x 2k, 2k x 4k, and 4k x 4k; • from frames/ksec to frames/sec; • from one to many channels.

  6. Example of AIA (&HMI) resolution

  7. AR scale: Obs: m ~10-60 Instab. scale: Models: m ~1-2 By A. Nordlund Active region emergence •  Fernando Moreno-Insertis • How does emerging flux interact with pre-existing (deep and near-surface) field? • Does “Joy’s law” require deep connections for active regions? Magnetogram movies

  8. Mature active regions • Emerging flux connects to pre-existing field within hours to a day, • within AR nests [TRACE movies] • to adjacent ARs [e.g., Longcope et al. 2005: 7-24h] • to ARs on opposite hemisphere[e.g., Pevtsov 2000 (ApJ 531 553)] • Active Regions remain in a “plage state” prior to sudden decay/dispersal with characteristic <>100G. [Schrijver and Harvey 1994 (SPh 150,1)] • Flare-related electrical currents decay on a time scale of ~1d [Pevtsov et al. 1994 (ApJL 425, 117); Schrijver et al. 2005 (ApJ 628, 501)], although filament-related systems may survive for weeks or more [?]. TRACE movie Studied by Longcope et al. 2005 (ApJ 630, 596) [movie: 2001/08/10:07UT - 08/12:00UT] Studied by Schrijver et al. 2005 (ApJ 628, 501)

  9. Decay and dispersal of ARs • Long-term decay of ARs is influenced by neighboring ARs and by internal flux emergence(s)  statistical modeling only • Surface-dispersal models: flux behaves essentially as a signed scalar advected in differential rotation and meridional flow, subject to supergranular random walk and magnetoconvective coupling. On time scales up to months • no deep field ‘anchoring’? [e.g., Schrijver &Title 1999 (SPh 188, 331); Schuessler & Rempel 2005 (A&A 337, 346); but Longcope & Choudhuri 2002 (SPh 205, 63)] • no effects of near-surface shear (1 part in 25) • no apparent response to ‘AR inflows’ (up to 50 m/s)

  10. Flux retraction / expulsion • Flux appears to retract upon cancellation: • Relative timing in EUV/chrom.B/phot.B: Harvey et al. 1999 (SPh 190, 35); • Surface vector-B: Chae et al. 2004 (ApJL 602, 65) • Simulations: Stein and Nordlund 2006 (ApJ 624, 1246) Harvey et al. 1999 (SPh 190, 35) Stein and Nordlund 2006 (ApJ 624, 1246)

  11. AR-ER spectrum / Local dynamo? • Ephemeral regions: • Decay products of active regions? If so, on many-year time scale. • (Partially) Generated by a locally-operating dynamo? If so, what does stellar ‘basal’ activity tell us; how to reconcile with 3D flows [e.g. Stein & Nordlund]? • Generated in a single global dynamo process? • Does the ER spectrum or frequency depend on magnetic environment (e.g, CH, QS, AR)? [e.g., Abramenko et al. 2006 (ApJL 641, 65); Zhang et al. (2006?)] ? From Hagenaar et al., 2003 (ApJ 584, 1107)

  12. Carpets, braids, and twists, … • Flux is continually replaced (and thereby forced to reconnect): • granular scale: R  5-10 min. in quiet Sun; loop reconnection time scale: < (<<?) 5-10 min. [Consequences for loop atmospheres and their modeling!] • supergranular scale: R  10-20 h in quiet Sun, up to ~5 d in unipolar regions [magnetic carpet, e.g., Schrijver et al. 1997 (ApJ 487, 424)] • global scales: months to a decade[e.g., Wang & Sheeley …; Schrijver and Harvey 1994 (SPh 150,1)] 1 2 3 4

  13. How important is the small stuff? • A “magnetic canopy” was thought to separate the strong network field from essentially field-free regions around the network in a closed-vault geometry. But then: • “Weak field” away from the network discovered in the mid 70s • Maybe “weak field,” but lots of flux: ~5  50 Mx/cm2 , on average ~20 Mx/cm2 • Maybe not “weak,” but merely “small”: 1016-17Mx compared to 1018-19Mx?

  14. Photosphere-corona connection • The “intranetwork field” steals flux from the network, so that • the field geometry is inconsistent with the classical canopy concept, while • the connectivity into corona & heliosphere changes on minute-to-hours time scale! Potential field above unipolar network and mixed-polarity intranetwork; side and top view

  15. Opportunities (near-term) • Solar-B+[TRACE or SDO]: very high resolution vector field; spectroscopy. • SDO: • Continuous high-res. (vector)B and seismology • Continuous comprehensive coronal imaging • STEREO+[TRACE or Solar-B or SDO]: multiple viewing angles of the corona and its coupling to the inner heliosphere. Multicolor corona Contact the teams!

  16. Opportunities (long-term; past 2008) • To be defined by the research community … soon!

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