Heliospheric Transients

1. Heliospheric Transients and the Imprint of Their Solar Sources

2. Topics • 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

3. Suprathermal electronsas sensors of magnetic topology • Closed fields in ICMEs • True solar polarity • Sector boundaries • Field inversions • Disconnected fields

4. Closed fieldsin magnetic clouds • 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 Shodhan et al., 2000 Crooker et al., 2004

5. Partial disconnection(closed-closed) creates flux rope coil • Interchange reconnection(closed-open) opens coil 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

6. interchange reconnection disconnection 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

7. Search for Disconnected Flux • 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 Differential Flux 0° Pitch angle 180°

8. 2 1 3 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

9. 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

10. CMEs smaller steadier quietloops plasmaparcels Other Transient Outflows

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

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

13.  Mismatches in 1995  • 27-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   

14. Interchange Reconnection withQuiet Loop Gives Mismatch Signature • 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

15. Relationship to CMEs • Eight inversions • Scale sizes comparable • SB location consistent • A few have ICME signatures • Most appear to be quiet loops inversion SB date duration (h) ICME?

16. Small plasma parcel outflows • Sheeley, Wang et al. [1997-2000] 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

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

18. 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]

19. 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)

20. Implications for Models of the Heliospheric Magnetic Field Reversal • 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

21. 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]

22. 27-day plots ISEE 3 data Counterstreaming electrons Source-surface toward sectors Field inversions TruePolarity toward away ICMEs blend into sector structure • 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

23. 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

24. 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 Bz on cloud axis tilt yields Bz prediction from filament tilt

25. Cloud Axis vs. Neutral Line Tilts:Indirect Test • 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

26. Cloud Axis vs. Neutral Line Tilts:Direct 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 0.57 • 74% (56%) differ by less than 45° (30°) Blanco, Rodriguez-Pacheco, and Crooker [2005]

27. phase shift Sunspot # 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 • from Mulligan et al. [1998] • Unipolar dominates bipolar near solar max • Shift from SN to NS confirmed • Phase shift confirmed

28. Kitt Peak Magnetogram Post-max CME source with pre-max polarity (12 Sep 2000) 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

29. Model implications 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]

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

31. + - 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

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

33. Implications for Models • 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?

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

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

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

37. 1997 Yohkoh SXT images from ~ 25-hour interval (12 May 0114 – 13 May 0241)

38. 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.

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

41. Closed loops at sector boundaries • Small, closed(?) flux rope (3.5 hrs, 2 x 106 km) • No depression in T[cf. Moldwin et al., 1995, 2000] • Rise in O7+/O6+ • Model fit to Wind data matches ACE data modeled by Qiang Hu ACE data, 00 – 12 UT, 27 Feb 1998