Determining the Location of Open Magnetic Field Areas in Active Regions and their Potential as Sources of the Slow Solar Wind J. L. Culhane 1, S.J. Edwards.

Determining the Location of Open Magnetic Field Areas in Active Regions and their

Potential as Sources of the Slow Solar Wind

J. L. Culhane1, S.J. Edwards2,3, C.E. Parnell2, L.K. Harra1, D.H. Brooks4,5

1University College London, Mullard Space Science Laboratory, Dorking, UK2University of St Andrews, School of Mathematics and Statistics, North Haugh, St Andrews, UK

3Currently at University of Durham, UK 4George Mason University, Fairfax, VA 22030, USA

5Hinode Team, ISAS/JAXA, Sagamihara, Kanagawa 252-5210, Japan

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Hinode XRT/EIS Discovery of Persistent AR Upflows

• EIS observed upflows of ~ 50 km/s (Harra et al., 2008) in the region of upflow seen by XRT (Sakao et. al., 2007)

- persistent upflows at AR peripheries with temperatures: 1 MK ≤ Te ≤ 2.5 MK (Doschek et al., 2008) - morphology differs from fan-loops where plasma downflowing with Te ~ 0.6 MK (Warren et al., 2011) - upflows mainly originate at sites of Quasi-Separatrix Layers (QSLs) (Baker et al., 2009)

• Comment by Sakao et al that AR upflows could contribute ~ 25% to Slow Solar Wind led to significant interest in the topic but authors did not suggest any outflow paths

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AR Plasma Outflow Paths (van Driel-Gesztelyi et al., 2012)

• AR1/AR2 observed by Hinode/EIS in Fe XII emission (a) with significant NE upflow at AR1 (b) - LFFF extrapolation (c) shows QSL footprints and long, possibly open, field lines from QSL and upflow region

• LFFF model shows null at 102 Mm height between AR1 and AR2; supported by potential field model (d) - these models only describe the AR1/AR2 neighbourhood

• Global PFSS model addresses full-Sun (b) and shows AR1 fully covered by streamer (yellow)

• AR2 is not covered (a); null point and its spine field line extends to PFSS source surface at 2.5 Rʘ

- provides pathway for upflow plasma to heliosphere - related AR-composition plasma was later detected by ACE spacecraft

AR 2

AR 1

NULL

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• Back-mapped ACE data shown relative to a) ST-B EUVI 195 Å synoptic map for CR 2064

• Data include: b) vp c) He/p, d) O+7/O+6 and C+6/C+5, e) Fe/O, f) Bradial, g) Babs

- red line indicates change in Bradial polarity seen at ACE which shows HCS crossing

• Increases in O+7/O+6 , C+6/C+5 and Fe/O (FIP-bias) are present from West of the HCS crossing

- active region material in a slow solar wind flow

• Fast solar wind parameters are evident before and after the HCS transition - fast wind from the two adjacent CHs E and W of AR 10978

b)

c)

d)

e)

f)

g)

a)

30 Nov, 200727 Dec, 2007

Plasma Outflow from a Fully Enclosed AR (Culhane et al., 2014)• EIS measurements of upflowing plasma E and W of AR 10978 show Te, ne and fFIP (FIP-bias) values characteristic of closed AR structures

• Single AR bisected by HCS and completely covered by closed streamer structures

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N1

Possible Mechanism for Plasma Escape from AR 10978

N1

• AR loops (blue) reconnect with large scale network fields (red) at the Eastern QSL - reconnection driven by AR expansion (green arrows) puts AR plasma into long low density network loops

• These large scale loops reconnect with the open field lines (pink) at N1 that are associated with the Northern CH

• Mandrini et al., (2014) analysed the global magnetic topology - located four high altitude magnetic null points within ± 200 longitude of AR 10978 - only one of these (N1) has associated open field lines

N1N1

Long. 00 Longitude 450 E

• Open field lines bend towards ecliptic and deliver upflowing plasma from East of the AR to the Sun – ACE line before HCS passage i.e. from North-West

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Study of Additional Active Regions

Example # 1: AR 11271 on 21-AUG-2011

• Located at ~ 170 N; observed at age ~ 25 days

• EIS Fe XII profiles show peripheral upflow regions - 3 regions E and W of AR were analysed

No Log Te Log ne Log EM FIP-bias 1 6.25 8.57 27.63 2.0 2 6.20 8.46 27.37 1.6 3 6.20 8.47 27.48 1.8

a)

• Following detailed studies of two ARs from Dec 2007/Jan 2208, we report preliminary analysis of a further seven ARs

- different locations and life cycle stages - range of magnetic configurarions

• Measured - locations of associated upflows- Te, ne and fFIP (FIP-bias) values- PFSS models to identify possible outflows

b) c)

a) AIA 193 Å image. b) EIS 195 Å image. c) EIS Doppler map

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Potential-Field-Source-Surface (PFSS) Models

• Global PFSS models (Van Ballegooijen et al., 1998, Mackay & Yeates, 2012) were constructed for the seven ARs considered; model for 21-AUG-2011 shown

Closed field

Open field

Heliospheric current sheet curtains.

• Lower boundary condition set from a synoptic HMI magnetogram - upper boundary fixed radial above 2.0 Rʘ

• Thick green lines show HCS null lines - thin green lines show the separatrix surface (HCS curtains)

• Blue/red lines show intersection of separatrix surfaces from negative/positive null points with the photosphere

• Wine lines show closed field; Yellow lines: open

• For AR 11271 on 21-AUG-2011 open field comes from the negative active region polarity

PFSS Model for AR 11271 on 21-AUG-2011

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a) b)

a) EIS 195 Å image. b) EIS Doppler velocity map. c) Maximum height reached by PFSS field lines

c)

Height above Photosphere Reached by Upflowing Plasma • AR surrounded by upflow regions - pink and blue lines on velocity map (b) show intersection of separatrix surfaces with photosphere - green line shows HCS curtain intersection with photosphere

• Contour map (c) shows upflow region to the West of AR 11271 where open field reaches the source surface at h = 2.0 Rʘ - site is adjacent to a Coronal Hole (CH)

- this plasma could contribute to the Slow Solar Wind: would be recognised at ACE with fFIP = 1.8 - although there are significant upflows to the East, there is no open field and plasma is contained in long loops ≥ 300 Mm

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Active Region with no Open Magnetic Field

a)

AR 11419

b) c) d)

a) AIA 193 Å image for AR 11419

b) EIS 195 Å image. c) EIS Doppler velocity map. d) Maximum height reached by PFSS field lines

Example # 2: AR 11419 on 17-FEB-2012

• Located at ~ 280 N; observed at age ~ 25 days

• EIS Fe XII profiles show peripheral upflow regions (c) : 3 were analysed

• B-field height contour map (d) shows no field lines at h > 1.4Rʘ

• EIS upflow plasma parameters are given in the table

• B-field contour map (d) shows no outflow paths to the source surface

No Log Te Log ne Log EM FIP-bias 1 6.20 8.94 27.77 1.5 2 6.25 8.81 27.86 1.6 3 6.20 8.81 27.82 1.8

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PFSS Model for 17-FEB-2012• Global PFSS model for AR 11419 observation (a) - small set of open field lines (yellow) SE of AR do not overlap with EIS raster - upflowing plasma (SW) in long closed structures and not on open field lines - closed loop structures reach ≤ 450 Mm

• Separatrix surface running through strongest outflow region in SW (box 2) supports high QSL reconnection as cause of upflows

• No outflow paths exist to source surface and heliosphere

a)

Closed field

Heliospheric current sheet curtains.

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Active Region (AR) Doppler Regions Underlying B-Field Coronal Separatrix No. Flow FIP Hole Surfaces

•AR 11271 1 Up (large loops) 2.0 Closed (low) No Near(21-AUG-2011) 2 Up (base) 1.6 Closed (low) Yes Yes

3 Up (base) 1.8 Open Yes Near________________________________________________________________________________________

•AR 11419 1 Up(?) 1.5 Closed (low) No Yes(17-FEB-2012) 2 Up (base + loops) 1.6 Closed (high) No Yes 3 Mixed (short loops?) 1.8 Closed (mid) No Yes________________________________________________________________________________________ AR 11427 1 Up (large loops?) 1.6 Closed (low) No Yes(2-MAR-2102) 2 Mixed (?) 2.1 Narrow Open? No Yes

3 Up (base) 1.8 Narrow Open No Yes________________________________________________________________________________________AR 11445 1 Up (base large loops) 2.2 Closed (low) No Yes(28-MAR-2012) 2 Up (base large loops) 1.9 Narrow Open? No Yes________________________________________________________________________________________AR 11553 1 Mixed (short loops?) 3.7 Open No Yes(29-AUG-2012) 2 Up (large loops? ) 1.9 Open No Yes

3 Up (large loops) 1.6 Closed (mid) No No ________________________________________________________________________________________AR 11569 1 Up (base large loops) 2.4 Closed (low) Yes Yes(15-SEP-2012) 2 Down (base) 2.2 Open Yes Yes________________________________________________________________________________________AR 11575 1 Up (?) 1.7 Closed (low) No Yes(23-SEP-2012) 2 Up (base) 2.0 Closed (low) No Near

3 Up (base?) 1.7 Closed (mid) No ? 4 Up (base+large loops) .9 Narrow Open No Yes• examined in detail

Summary of Features for the Seven ARs

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SUMMARY

• Persistent upflows from AR peripheries found by EIS have 1 MK ≤ Te ≤ 2.5 MK - morphology differs from fan-loops where plasma is downflowing with Te ~ 0.6 MK - upflows mainly originate at sites of Quasi-Separatrix layers (QSLs)

• Detailed magnetic topology study of two ARs showed: - null point between an AR pair provided upflow plasma pathway to heliosphere with later detection at L1/ACE - for a single AR completely enclosed by streamers, upflow plasma was created in a long loop connecting to a null that is NW of the AR - at this site a second reconnection transferred AR plasma to open field that provides a pathway to L1/ACE

• Seven ARs with associated upflows from a range of on-disc locations studied by PFSS modelling - EIS also measured Te, ne and fFIP (FIP-bias) in addition to flow velocities

• Initial assessment of the upflows indicates: - only AR 11271 has an upflow region aligned with open field that reaches 2.0 Rʘ

- FIP-bias of 1.8 likely to register as Slow Solar Wind at ACE

- three regions: AR 11427, 11445, 11575 have narrow open channels that could be associated with upflows - AR 11419 has completely closed field but upflows align with separatrix surfaces - AR 11553 had open field regions East and West that did not align with the upflow regions - AR 11569 had open field to the West but the corresponding flows were downwards

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CONCLUSIONS• Assessment of ACE observations not yet made - upflow plasma has 1.6 ≤ fFIP ≤ 3.7 and would be recognized as Slow Solar Wind at ACE

• Upflows mainly associated with separatrix surfaces and high-lying field lines - supports Baker et al., 2009 suggestion that upflows are driven by reconnection at QSLs

• Only one upflow region, West of AR 11271, put plasma on open field lines that reached the heliosphere - this region is a likely contributor to the Slow Solar Wind, though the ACE response has not yet been checked

• For the remaining six regions, upflowing plasma in extended magnetic structures could through further reconnections transfer plasma to open field lines at nulls remote from the AR (Culhane et al., 2014, Mandrini et al., 2014) - identifying any such topologies would require further detailed magnetic modelling