Radoslav Bucik (MPS) in collaboration with Davina E. Innes (MPS

-MPS SGS 2014 Oct 14-
MPS PRESS RELEASE
STEREO & ACE
SCIENCE HIGHLIGHTS
nominated to
NASA HELIOPHYSICS
GPRAMA ITEM
Radoslav Bucik (MPS) in collaboration with
Davina E. Innes (MPS) & Glenn M. Mason (JHU)
1
OUTLINE
 Solar Energetic Ions
 Motivation
 Repeated Impulsive Events
 Features of Two Long-Lasting Sources
 Solar Source Identification
 Other Long-Lasting Sources
 What Drives Ion Production in Long-Lasting Sources?
 Summary & New Implications
2
SOLAR ENERGETIC IONS -- IMPULSIVE EVENTS
HXR
HXR
HXR
Shimojo & Shibata ApJ 542, 2000
• this mechanism for solar electron events
‘independently’ seen in hard X-ray images as 3
foot-point bremsstrahlung source (e.g., Krucker et
al. ApJ 742, 2011)
• ion acceleration in solar
flares or in impulsive SEP
events not clear at all
• association with EUV/X-ray
jets (Wang et al. ApJ 639,
2006; Nitta et al. ApJL 675,
2008) or fast & narrow
CMEs (Kahler et al. ApJ
562, 2001; Nitta et al. ApJ
650, 2006) has suggested
the interchange
reconnection (Shibata et al.
PASJ 44, 1992; where
emerging loop annihilates
with overlying open field) as
a primary energy source
3
2-10 MeV/n 3He-rich events \ corona abund.
SOLAR ENERGETIC IONS -- IMPULSIVE EVENTS
• keV electrons often accompany
these events although
enhanced f. <104 !
acceleration sites are likely
different (Hurford et al. ApJL
644, 2006)
• type III radio bursts better
associated with these events
than their parent electrons (Nitta
et al. ApJ 650, 2006)
enhanced f. 10
enhanced f. 2-3
unenhanced
(3 MK)
Reames & Ng ApJ 610, 2004
• abundance observations
suggest that mechanism must
be highly selective – enormously
enhances 3He & ultra heavies
but not H, 4He, C, N, O; most
theories involve resonant
interaction with waves (e.g.;
Temerin & Roth ApJL 391, 1992)
or turbulence (e.g.; Miller SSRv
4
86, 1998)
SOLAR ENERGETIC IONS -- IMPULSIVE EVENTS
• none of the current theories explains all the observed features of
impulsive events
• they do not include charge stripping effects or address
enhancements of UH nuclei
• no consistent theory explaining simultaneous enrichment of both 3He
and heavy ions
• one reason why small impulsive events are not well understood the acceleration has not been studied in-situ
• even Solar orbiter or Solar probe+ missions will likely not reach
the acceleration sites: 0.5-1 Rs above the photosphere (e.g.;
DiFabio et al. ApJ 687, 2008; Wang et al. ApJ 759, 2012) based on
ionic charge states & solar electron observations
5
SOLAR ENERGETIC IONS -- A NOTE ON GRADUAL EVENTS
Desai et al. ApJ 611, 2004
Reames SSRs 90, 1999
• acceleration in gradual events better understood – CME shocks with particle
acceleration can be observed in-situ
• in addition, the shock acceleration has been studied in-situ in other sites – CIRs,
the Earth’s bow shock or even the Termination shock
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MOTIVATION
• successive events from the same AR observed by a single s/c only
during about 1 day (Reames & Stone ApJ 308, 1986; Mason et al.
ApJL 525, 1999; Mason et al. ApJL 545, 2000; Wang et al. ApJ 639,
2006)
• successive events have suggested more steady production/release of
energetic ions from solar source regions (Pick et al. ApJ 648, 2006)
• how long these ion injections continue in an AR?
• difficult to answer with single s/c observations – because of Sun
rotation we could be connected to the AR only for a limited time
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MOTIVATION
• other (indirect) evidence for more steady ion production – (rare) long
duration (< 0.4 day) solar γ-ray line/neutron emissions (e.g., Ryan
SSRv 93, 2000; Feldman et al. JGR 115, 2010) explained by ion
trapping in AR magnetic loops (Mandzhevidze & Ramaty ApJ 396,
1992; Hudson et al. ApJL 698, 2009) or continuous acceleration
(Rank et al. A&A 378, 2001; Ajello et al. ApJ 789, 2014) or maybe due
to multiple events (?)
• homologous hard X-ray flares (e.g.; Sui et al. ApJ 612, 2004 reports
multiple HXRs in 1.5 day period)
• impulsive events associated with minor soft X-ray flares (e.g.,
Reames et al. ApJ 327, 1988) - these events should be quite frequent
in an AR
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REPEATED IMPULSIVE EVENTS
?
?
Reames et al. ApJ 292, 1985
Rarely identified
but multiple
electron events
frequently
occurred in data.
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REPEATED IMPULSIVE EVENTS
1.3-1.6 MeV/n
The 1st
observation of
repeated
events.
0.6 day of injection
W44°
W69°
gradual SEP events from the same AR
Reames & Stone ApJ 308, 1986
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REPEATED IMPULSIVE EVENTS
1.5 day of injection
He I 10830Å
new connection
loss of the connection
Mason et al. ApJL 545, 2000
Fe I 8688Å
Wang et al. ApJ 639, 2006
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REPEATED IMPULSIVE EVENTS
1.2 day of injections
380 keV/n
195Å flares
white-light ejections
jet times
Wang et al. ApJ 639, 2006
Wang et al. ApJ 639, 2006 12
REPEATED IMPULSIVE EVENTS
• periods of continuous 3Herich SEP presence are
observed (e.g., Wiedenbeck
et al. AIP Conf. Proc. 679,
2003)
270 keV/n
• not clear if single solar
sources are responsible
Mason SSRv 130, 2007
• not clear how these multiday periods are formed –
unresolved injections
closely spaced in time? IP
propagation effects masking
the injections? confinement
of ions in large scale
structures in solar wind
(Kocharov et al. ApJS 176,
2008)? no consecutive
injections but steady
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escape?
FEATURES OF TWO LONG-LASTING SOURCES
• identified several
long-lasting sources;
examined in
detail/published two
when STEREOs
were near the
greatest elongation
FEATURES
AR 1244
AR 1246
Y
Y
age
newly emerging
newly emerging
spatial size
relatively large
small/spot-like
soft X-ray flare
several B-class
N
Hα flare
Y
N
EUV jets
no obvious
numerous recurrent
material eruption
surge-like
no obvious
sunspot
photospheric field irregularly distributed
compact shape
• reported long-lasting
sources AR 11244 &
AR 11246 do not
show any unusual
features!
• Any active region
could be a long
lasting energetic ion
source (?)
14
AR1246
Bucik et al.
ApJ 786, 2014
15
AR1244
3He
4He
CIR
B4.1
Bucik et al.
ApJ 786, 2014
B7.6
16
AR1244
B4.1
B7.6
17
FEATURES OF TWO LONG-LASTING SOURCES
AR 1244 in SDO HMI 720s magnetograms
220 x 170 arcsecs; 1hr step
60 x 60 arcsecs; 0.5hr
6 Jul 15:00 – 7 Jul 05:20
prior to 2nd impulsive event
Impulsive event in ‘old’ AR
preceded by new flux
emergence !
29 June 21:00 – 1 July 13:00 (~1.7d)
from emergence till 1st impulsive event
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FEATURES OF TWO LONG-LASTING SOURCES
AR 1246 in SDO HMI 720s magnetograms
160 x 160 arcsecs; 0.5hr step
60 x 100 arcsecs; 0.5hr
10 Jul 19:00 – 11 Jul 18:20
2nd emergence
+ several other re-emergences
when out of the Earth’s view
7 July 16:00 – 8 July 15:22 (~1d)
from emergence till 1st impulsive event
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SOLAR SOURCE IDENTIFICATION
• key task for this study; 1 of the 3 focused science topics in LWS program for 2014
• similar approach as in prior studies (Wang et al. ApJ 639, 2006; Nitta et al. ApJ
650, 2006; Klein et al. A&A 486, 2008; Rust et al. ApJ 687, 2008)
• identify connection region on the Sun (e.g.,
Neugebauer et al. JGR 103, 1998)
• Parker spiral - determines s/c foot-point
longitude on the model’s source
surface
• PFSS model of corona (with 6 hr
resolution - Schrijver & DeRosa SoPh
212, 2003) determines location on the
Sun tracking open field lines
• consistency check with in-situ magnetic
polarity
• examine EUV images for temporal
coincidence with type III bursts around
expected ion injection time
flare
*
s/c
1AU
Schatten et al. SoPh 6,1969
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SOLAR SOURCE IDENTIFICATION
• improved with SDO because of (1) – full solar disk EUV images with
unprecedented high temporal resolution (2) – new 94 and 131 Å
wavelength channels better suited to identify high temperature EUV
emissions
• improved as whole Sun surface has been in view with STEREO and
SDO since Feb 2011; but STEREO-A connection regions not covered by
magnetogram observations making the PFSS extrapolations less reliable
• many recent publications have employed this two-step approach in
searching for solar wind sources (e.g.; Culhane et al., SoPh 289, 2014 &
references therein); the advantages in source identification for SEPs
compared to solar wind – type III bursts, EUV brightening & clear SEPs
intensity onsets (detected in-situ)
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SOLAR SOURCE IDENTIFICATION
AR 1244
AR 1246
ACE
STB
ACE
Bucik et al. ApJ 786, 2014
STA
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OTHER LONG-LASTING SOURCES : L1 – STEREO-A
• 32 impulsive events on STEREO-A in 20102012
•
3He
relative enrichment: 102 - 104 compared to
its thermal abundance
all corresponding
events observed
earlier at L1
events with
common source
AR marked by x
23
OTHER LONG-LASTING SOURCES : L1 – STEREO-A
Helium mass peaks for all 32 STEREO-A events (#4 - #35)
24
OTHER LONG-LASTING SOURCES : L1 – STEREO-A
Bucik et al. in Proc. 33rd ICRC, 2013
• isotopic ratios correlate for common solar sources
in relative 3He enrichment in the source AR
; it implies temporal stability
• previous studies do not show this for multiple events in short-sequences but our
result is not in contrast with this as we integrated abundances over whole event
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(i.e. over all injections in a short sequence when present)
WHAT DRIVES ION PRODUCTION/ESCAPE IN LONG-LASTING SOURCES?
AR11045 – long lasting (10 days) source
Feb 6 -7, Feb 8 3He onsets
2.8 MeV/n
Feb 6, 7
Feb 8
Feb 14, 16
3 s/c with favorable separation and angular
spread of escaping field lines allows
uninterrupted connection to AR 11045 for a
long-time at least with one s/c!
Wiedenbeck et al. ApJ 762, 2013
26
WHAT DRIVES ION PRODUCTION/ESCAPE IN LONG-LASTING SOURCES?
s/c connections Feb 13-16
STEREO-A
gradual SEPs
11045
STEREO-A
ACE
D.E. Innes
next impulsive event seen after 6 days
(on Feb 14) although we remained
connected; what happened with this AR?
G.M. Mason
27
WHAT DRIVES ION PRODUCTION/ESCAPE IN LONG-LASTING SOURCES?
STEREO-B, ACE impulsive events
AR 11045
AR11045 out of
the Earth view
STEREO-A event
day 14.3
Feb
Li et al. A&A 539, 2012
• energetic ions events initiated during emergence phase only; we do not see any
injections (although connected) in decay phase
• unknown magnetic flux evolution in AR for the STEREO-A event (no magnetometer
data)
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WHAT DRIVES ION PRODUCTION/ESCAPE IN LONG-LASTING SOURCES?
STEREO-A 304Å -- new emergence on AR11045 west edge?
2010 Feb 12 12:36
2010 Feb 13 12:36
STEREO-A impulsive SEP event on Feb 14.3 associated with new emergence?
2010 Feb 14 12:36
2010 Feb 15 12:36
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SUMMARY & NEW IMPLICATIONS (i)
• first evidence that energetic particles could be produced in solar
active regions on long time scales
• new results open question whether energetic ions are emitted into
IP space during whole active region lifetime (weeks)
• related Q: how frequent are these emissions in solar ARs (or are
they continuous)? There have been reports suggesting on-going
reconnection (e.g., Baker et al. ApJ 705, 2009) based on
observations of persistent AR plasma outflows (Sakao et al.
Science 318, 2007) - is this process able to produce also ion
outflows with speeds of 10 x solar wind?
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SUMMARY & NEW IMPLICATIONS (ii)
• the mechanism which accelerates these ions in flares must be
quite ordinary – i.e. conditions for ion production persist for a long
time or could be easily established
• is the magnetic flux emergence necessity for ion production on
open field lines? – conclusion similar to this has been drawn by
Nitta & Hudson, GRL 28, 2001 for recurrent CMEs in impulsive
homologous flares
Thanks !
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