Questions concerning the Sun’s

Magnetic Connectionsand prospects for the near future.

Karel Schrijver

SHINE 2006

“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)

“The real voyage of discovery consists not in seeking new landscapes, but in having new eyes.”

Marcel Proust (1871-1927)

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 …

…

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?

Instrument capabilities: solar atmosphere

Data rates to increase >1,000x; e.g., EIT: 1024x1024 / 1000s (average) AIA: 4096x4096 / 1s; >1TB/d (compressed)

STEREO SECCHI

SOHO EIT

Spatial range (arcsec)1 10 100 1000

SOLAR B XRT

Images per minute

1

10

Solar Diameter

Granulation

Chromospheric Thickness

Moss Layer AR Loop Length

Sunspot DiameterPore

0.1Filaments

CMEs

AIA

TRACE

Temperature Coverage (MK)

12 8 0.9

40 kK 0.1

1.2

3 4

2 4-6 kK

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.

AIA&HMI (0.6”)

TRACE (0.5”)

XRT (1”)

SOT/NFI (0.08)SOT/SP (0.16”)

STEREO/SECCHI-EUVI (3.5”)

Example of AIA (&HMI) resolution

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?

By A. Nordlund

Instab. scale: Models: m ~1-2

AR scale: Obs: m ~10-60

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 [?].

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)

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)

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)

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)

?

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

How important is the small stuff?

“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?

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:

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

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.

Opportunities (long-term; past 2008)

To be defined by the research community … soon!