Heliospheric Transients and the Imprint of Their Solar Sources

Sensing change in magnetic connections Suprathermal electron tool CMEs Disconnected flux Other transient outflows Imprint of solar magnetic field on ICMEs Review quantitative results Implications for CME models Application to May 1997 event New constraints on May ’97 event from deduced magnetic connections Topics

Suprathermal electrons as sensors of magnetic topology Closed fields in ICMEs True solar polarity Sector boundaries Field inversions Disconnected fields

Range from completely open to completely closed On average, clouds are nearly half open Within each cloud, open fields mingle randomly with closed fields Clouds at 5 AU are nearly as closed as those at 1 AU Closed fields in magnetic clouds Shodhan et al., 2000 Crooker et al., 2004

Conceptual Explanation Gosling, Birn, and Hesse [1995] explain how a coherent flux rope can have open and closed fields through remote reconnection at the Sun a.Partial disconnection (closed-closed) creates flux rope coil b.Interchange reconnection (closed-open) opens coil

Implications for Models, Flux Budget CME models must open fields in ICMEs initially by about 40% completely over the long term, to balance heliospheric magnetic flux budget otherwise closed fields would lead to a continual flux build- up, which is not observed [Gosling, 1975] alternatively, ICMEs could remain half-closed, and flux could disconnect elsewhere little evidence of disconnection in suprathermal electron data interchange reconnection disconnection

Heat-flux dropout (HFD) [McComas et al., 1989] Disconnection eliminates strahl Problems Lin and Kahler [1992] and Fitzenreiter and Ogilvie [1992] find higher-energy electrons still streaming from Sun in McComas HFDs Scattering also can eliminate strahl Can differentiate between pure scattering and disconnection by testing for drop in integrated flux 0° Pitch angle 180° Differential Flux Search for Disconnected Flux

Search for Disconnected Flux [Pagel et al., 2004, 2005] Heat flux is controlled independently by anisotropy A and integrated flux F Drop in A and F required for disconnection (Case 2) Drop in A alone signals pitch angle scattering (Case 3) Application to 4 yrs of data 419 HFDs 240 candidates tested for higher-energy electron streaming Only 2 pass test Conclusions Disconnection is rare (timescales > 30 min) HFDs are highly unreliable signatures of disconnection 1 2 3

HFD Postscript Gosling et al. [2005] identify rare case of in situ reconnection between open field lines across HCS using standard plasma signatures Yields 4-min interval of known disconnected fields (no impact on flux budget) Electron distributions show expected strahl dropout and remaining halo Confirms HFD is necessary signature of disconnection Pagel et al. [2005] establish that it is far from sufficient

Other Transient Outflows CMEs smaller steadier quiet loops plasma parcels

Quiet Loops Active region expanding loops [Uchida et al., 1992] Sometimes apparent on successive solar rotations CR 1890 CR 1891 CR 1892 Yohkoh images provided by Nariaki Nitta

Sector Boundary with no Field Reversal Field Reversal with no Sector Boundary Quiet Loop Signature in Solar Wind?

Mismatches in day recurrence plots of magnetic longitude angle  4-sector structure True sector boundaries marked in red Mismatches with  marked in yellow Not uncommon (~1 out of 4) Quasi-recurrent     

Loop emerges with leg polarity matching sector structure Open field line from above or below approaches leg with opposite polarity Interchange reconnection creates field inversion changes loop to open field line with toward polarity Sector boundary separates from HCS Interchange Reconnection with Quiet Loop Gives Mismatch Signature

Relationship to CMEs Eight inversions Scale sizes comparable SB location consistent A few have ICME signatures Most appear to be quiet loops Dec 18, ? Jan 16, no Feb 8, yes Feb 25, no Apr 5, ?? Apr 21, ?? May 29, no Jul 11, no inversion SB date duration (h) ICME?

Small plasma parcel outflows Sheeley, Wang et al. [ ] document “blobs” “Time-lapse sequences… indicate that streamers are far more dynamic than was previously thought, with material continually being ejected at their cusps and accelerating outward along their stalks.” Difference image indicates outward movement Synoptic maps can be built from sequential radial strips

Synoptic Height-Time Trajectories Curved paths indicate ~four events per day

Parcel Release by Interchange Reconnection Wang et al. [1998] propose interchange reconnection as release mechanism parcels as transient source of heliospheric plasma sheet Crooker et al. [2004] document transient nature of plasma sheets concur with Wang et al. [1998] suggest interchange reconnection creates field inversions, consistent with local current sheets found in most plasma sheets adapted from Wang et al. [1998], modified by Crooker et al.[2004]

Heliospheric plasma sheet What’s wrong with this picture? Sector boundary precedes well- defined plasma sheet Local current sheets in high-beta region (High beta creates HFD mistakenly interpreted as disconnection)

Observations of the full spectrum of transient outflows suggest that Interchange reconnection at the Sun is ubiquitous Magnetic fields rarely disconnect from the Sun Observations bear upon two competing models of how the heliospheric magnetic field reverses at solar maximum Fisk model fully consistent Interchange reconnection is means of continuous flux transport No disconnection required to reverse solar magnetic field Wang-Sheeley model faces challenge Interchange reconnection essential at coronal hole boundaries Comparable disconnection required for field reversal Both models highly successful in explaining other phenomena Synthesis view will require incorporation of dynamics into potential field model of Wang-Sheeley realistic solar fields into Fisk model understanding of solar dynamo Implications for Models of the Heliospheric Magnetic Field Reversal

Solar Magnetic Field Imprint on CMEs ICME leg polarity and sector structure [Zhao, Crooker, Kahler] ICME axis and neutral line/filament orientation [Marubashi, Zhao, Mulligan, Blanco] ICME leading field and solar dipole orientation [Bothmer, Mulligan, Martin, McAllister] ICME handedness and source hemisphere [Martin, Bothmer, Rust, McAllister]

Leg polarity obtained from suprathermal electron signature [Kahler et al., 1999] 10 times more likely to match sector polarity than not Implies flux rope feet lie on opposite sides of neutral line Reflects strong imprint of solar dipolar field component ICMEs blend into sector structure True Polarity toward away Counterstreaming electrons Source-surface toward sectors Field inversions 27-day plots ISEE 3 data

Solar imprint on magnetic clouds Cloud axis Aligns with filament axis (low) and HCS (high) Directed along dipolar field distorted by differential rotation Leading field Aligns with skewed arcade (low) and coronal dipolar field (high) Handedness LH in NH, RH in SH Independent of solar cycle

Cloud Axis vs. Filament Axis Tilts 14 cases from Zhao and Hoeksema [1997] Drawn from Marubashi [1997], Rust [1994], and hemispheric rule of Martin et al. [1994] Linear correlation of 0.76 Additional dependencies of duration and intensity of B z on cloud axis tilt yields B z prediction from filament tilt

Axis alignment with HCS predicts bipolar (SN or NS) near minimum unipolar (N or S) near maximum Mulligan et al. [1998] analyze 63 clouds from PVO find suggestion of pattern with ~3-year lag Cloud Axis vs. Neutral Line Tilts: Indirect Test

On case-by-case basis, Blanco et al. [unpublished] compared axis tilts of 50 clouds modeled by Lepping to neutral line tilts on source- surface maps at corresponding predicted sector boundary crossings Linear correlation of % (56%) differ by less than 45° (30°) Blanco, Rodriguez-Pacheco, and Crooker [2005] Cloud Axis vs. Neutral Line Tilts: Direct Test

Leading Field from Bothmer and Rust [1997] SN (south leading) dominates from ~cycle 20 max to 21 max NS (north leading) dominates from ~cycle 21 max to 22 max phase changes after rather than at solar max Sunspot # phase shift from Mulligan et al. [1998] Unipolar dominates bipolar near solar max Shift from SN to NS confirmed Phase shift confirmed

Possible cause of phase shift After solar maximum, leading fields in low latitude arcades retain pre-maximum polarity Shift from SN to NS (or vice versa) may be delayed until polar fields dominate Kitt Peak Magnetogram Post-max CME source with pre-max polarity (12 Sep 2000)

Results of Imprint Tests on Clouds Cloud axis orientation, Fair 28/50 (56%) align within 30° of neutral line [Blanco et al., 2005] Handedness, Good (away from active regions) 65/73 (89%) quiescent filaments match hemispheric pattern [Martin et al., 1994] No pattern in 31 active-region filaments [cf. Leamon et al., 2004] 24/27 (89%) clouds match associated filament [Bothmer and Rust, 1997] Leading field, Good 33/41 (80%) match solar dipolar component with 2-3 year lag [Bothmer and Rust, 1997] 28/38 (74%) from PVO match [Mulligan et al., 1998] Leg polarity, Very Good 1/10 (90%) match solar dipolar component [Kahler et al., 1999] Model implications

Implications for CME Models Taken at face value, imprint of dipolar component on leading field and leg polarity favors streamer over breakout model by ~80%. STREAMER MODEL Dipolar fields reconnect Leading field matches dipolar component BREAKOUT MODEL Quadrupolar fields reconnect Leading field opposes dipolar component

Test Case: May 1997 Compare imprint predic- tions with parameters from Webb et al. [2000] Cloud axis tilt ~matches neutral line tilt orthogonal to filament tilt Left-handed matches NH source Leading field southward, matches solar dipolar component Leg polarity (away) opposite to sector polarity + -

satellite trajectory map mismatch intervals magnetic cloud interval Sector Structure Context Electron pitch angle spectrogram comparison with PFSS prediction toward fields away fields TOWARD AWAY

Quadrupolar field [courtesy Z. Mikic] Double dimming implies both feet above global NL consistent with island in field map leg polarity local eruption from quadrupolar structure Axis rotation to NL creates parallel fields overhead precludes breakout model? Implications for Models

Additional Clues No counterstreaming implies cloud is open Away polarity of open fields implies interchange reconnection in negative leg cloud Webb et al. [2000]

Interchange reconnection in negative island Need open positive field lines. Where are they?

Interchange reconnection with polar fields high in corona opens negative CME leg Freeing connection may facilitate axis rotation Similar to solar cycle magnetic field evolution in Wang and Sheeley [2003] Evidence in X ray images leg opens Interchange reconnection in asymmetric “breakout” model

1997 Yohkoh SXT images from ~ 25-hour interval (12 May 0114 – 13 May 0241)

Conclusions Knowledge of the true polarity of open field lines in ICMEs can provide important constraints on CME reconnection configurations. The solar imprint on magnetic clouds is significant and suggests that incorporation into empirical space weather models would improve predictions. Taken at face value, the solar imprint implies that 80% of ICMEs cannot arise from the breakout model configuration. On the other hand, the May 1997 ICME carried the imprint of the solar dipole yet seems to have arisen from an asymmetric “breakout” configuration. Observations of transient structures in the heliosphere supports ubiquitous interchange reconnection and rare disconnection.

Filament-arcade relationship Reflects cross-scale pattern Connects predictions from filament properties to predictions from HCS properties S. Martin

Closed loops at sector boundaries Small, closed(?) flux rope (3.5 hrs, 2 x 10 6 km) No depression in T [cf. Moldwin et al., 1995, 2000] Rise in O 7+ /O 6+ Model fit to Wind data matches ACE data ACE data, 00 – 12 UT, 27 Feb 1998 modeled by Qiang Hu