heliospheric transients and the imprint of their solar sources
TRANSCRIPT
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Heliospheric Transientsand the Imprint of Their Solar Sources
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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
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Suprathermal electronsas sensors of magnetic topology
Closed fields in ICMEs
True solar polarity Sector
boundaries Field
inversions
Disconnected fields
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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 fieldsin magnetic clouds
Shodhan et al., 2000
Crooker et al., 2004
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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
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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
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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°
Diff
ere
ntia
l Flu
x
Search for Disconnected Flux
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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
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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
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Other Transient Outflows
CMEs
smallersteadier
quietloops
plasmaparcels
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Quiet Loops
Active region expanding loops [Uchida et al., 1992] Sometimes apparent on successive solar rotations
CR 1890CR 1891CR 1892
Yohkoh images provided by Nariaki Nitta
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Sector Boundary with no Field Reversal
Field Reversal with no Sector Boundary
Quiet Loop Signature in Solar Wind?
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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
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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 withQuiet Loop Gives Mismatch Signature
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Relationship to CMEs
Eight inversions Scale sizes
comparable SB location
consistent A few have
ICME signatures
Most appear to be quiet loops
Dec 18, 1994 24 ?
Jan 16, 1995 16 no
Feb 8, 1995 53 yes
Feb 25, 1995 16 no
Apr 5, 1995 16 ??
Apr 21, 1995 15 ??
May 29, 1995 21 no
Jul 11, 1995 22 no
inversion SB date duration (h) ICME?
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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
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Synoptic Height-Time Trajectories
Curved paths indicate ~four events per day
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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]
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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)
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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
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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]
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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
TruePolarity
toward
away
Counterstreaming electronsSource-surface toward sectorsField inversions
27-day plotsISEE 3 data
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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
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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
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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
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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]
Cloud Axis vs. Neutral Line Tilts:Direct Test
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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
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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)
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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]
Mo
de
l im
plic
atio
ns
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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
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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
+
-
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satellite trajectory
map mismatch intervals
magnetic cloud interval
Sector Structure ContextElectron pitch angle spectrogram comparison with PFSS prediction
toward fields
away fields
TOWARD
AWAY
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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
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Additional Clues
No counterstreaming implies cloud is open Away polarity of open fields implies interchange
reconnection in negative leg
cloud
Webb et al. [2000]
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Interchange reconnection in negative island
Need open positive field lines.Where are they?
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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 leg opens
Interchange reconnection in asymmetric “breakout” model
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1997 Yohkoh SXT images from ~ 25-hour interval (12 May 0114 – 13 May 0241)
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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.
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Filament-arcade relationship Reflects cross-scale
pattern Connects predictions
from filament properties to predictions from HCS properties
S. Martin
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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
ACE data, 00 – 12 UT, 27 Feb 1998modeled by Qiang Hu