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Radoslav Bucik (MPS) in collaboration with
Davina E. Innes (MPS) & Glenn M. Mason (JHU)
MPS PRESS RELEASE
STEREO & ACE SCIENCE HIGHLIGHTS
nominated to NASA HELIOPHYSICS
GPRAMA ITEM
-MPS SGS 2014 Oct 14-
1
2
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
Shimojo & Shibata ApJ 542, 2000
• 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 • 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)
SOLAR ENERGETIC IONS -- IMPULSIVE EVENTS
HXR HXR HXR
3
• keV electrons often accompany
these events although
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)
• 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
86, 1998)
2-1
0 M
eV
/n 3
He-r
ich
eve
nts
\ c
oro
na
ab
un
d.
(3 MK)
unenhanced
enhanced f. 2-3
enhanced f. 10
enhanced f. <104 !
Reames & Ng ApJ 610, 2004
SOLAR ENERGETIC IONS -- IMPULSIVE EVENTS
4
• 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
SOLAR ENERGETIC IONS -- IMPULSIVE EVENTS
5
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
SOLAR ENERGETIC IONS -- A NOTE ON GRADUAL EVENTS
6
• 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
MOTIVATION
7
• 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
MOTIVATION
8
Reames et al. ApJ 292, 1985
REPEATED IMPULSIVE EVENTS
Rarely identified
but multiple
electron events
frequently
occurred in data.
? ?
9
W44° W69°
1.3
-1.6
MeV
/n
gradual SEP events from the same AR
0.6 day of injection
Reames & Stone ApJ 308, 1986
The 1st
observation of
repeated
events.
REPEATED IMPULSIVE EVENTS
10
Mason et al. ApJL 545, 2000
1.5 day of injection
loss of the connection new connection Wang et al. ApJ 639, 2006
He I 10830Å Fe I 8688Å
REPEATED IMPULSIVE EVENTS
11
Wang et al. ApJ 639, 2006
Wang et al. ApJ 639, 2006
1.2 day of injections
jet times
195Å flares white-light ejections
REPEATED IMPULSIVE EVENTS
12
380 keV/n
Mason SSRv 130, 2007
270 keV/n
• periods of continuous 3He-
rich SEP presence are
observed (e.g., Wiedenbeck
et al. AIP Conf. Proc. 679,
2003)
• not clear if single solar
sources are responsible
• not clear how these multi-
day 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
escape?
REPEATED IMPULSIVE EVENTS
13
FEATURES AR 1244 AR 1246
sunspot 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
photospheric field irregularly distributed compact shape
• identified several
long-lasting sources;
examined in
detail/published two
when STEREOs
were near the
greatest elongation
• 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 (?)
FEATURES OF TWO LONG-LASTING SOURCES
14
AR1246
Bucik et al. ApJ 786, 2014 15
AR1244
3He 4He CIR
B7.6 B4.1
Bucik et al. ApJ 786, 2014 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
29 June 21:00 – 1 July 13:00 (~1.7d)
from emergence till 1st impulsive event
60 x 60 arcsecs; 0.5hr
6 Jul 15:00 – 7 Jul 05:20
prior to 2nd impulsive event
18
Impulsive event in ‘old’ AR
preceded by new flux
emergence !
FEATURES OF TWO LONG-LASTING SOURCES
AR 1246 in SDO HMI 720s magnetograms
7 July 16:00 – 8 July 15:22 (~1d)
from emergence till 1st impulsive event
160 x 160 arcsecs; 0.5hr step 60 x 100 arcsecs; 0.5hr
10 Jul 19:00 – 11 Jul 18:20
2nd emergence
19
+ several other re-emergences
when out of the Earth’s view
SOLAR SOURCE IDENTIFICATION
1AU
* flare
s/c
Schatten et al. SoPh 6,1969
• 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 20
• 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)
SOLAR SOURCE IDENTIFICATION
21
STB
ACE
ACE
STA
SOLAR SOURCE IDENTIFICATION
AR 1244 AR 1246
Bucik et al. ApJ 786, 2014 22
OTHER LONG-LASTING SOURCES : L1 – STEREO-A
• 32 impulsive events on STEREO-A in 2010-
2012
• 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
Helium mass peaks for all 32 STEREO-A events (#4 - #35)
OTHER LONG-LASTING SOURCES : L1 – STEREO-A
24
• isotopic ratios correlate for common solar sources ; it implies temporal stability
in relative 3He enrichment in the source AR
• 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
(i.e. over all injections in a short sequence when present)
OTHER LONG-LASTING SOURCES : L1 – STEREO-A
Bucik et al. in Proc. 33rd ICRC, 2013
25
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!
WHAT DRIVES ION PRODUCTION/ESCAPE IN LONG-LASTING SOURCES?
AR11045 – long lasting (10 days) source
Wiedenbeck et al. ApJ 762, 2013
Feb 6 -7, Feb 8 3He onsets
2.8 MeV/n
Feb 6, 7 Feb 8 Feb 14, 16
26
STEREO-A
D.E. Innes
G.M. Mason
STEREO-A ACE
WHAT DRIVES ION PRODUCTION/ESCAPE IN LONG-LASTING SOURCES?
11045
next impulsive event seen after 6 days
(on Feb 14) although we remained
connected; what happened with this AR?
gradual SEPs
s/c connections Feb 13-16
27
STEREO-B, ACE impulsive events
• 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)
STEREO-A event day 14.3
AR 11045
WHAT DRIVES ION PRODUCTION/ESCAPE IN LONG-LASTING SOURCES?
AR11045 out of the Earth view
Li et al. A&A 539, 2012
28
Feb
STEREO-A 304Å -- new emergence on AR11045 west edge?
2010 Feb 12 12:36 2010 Feb 13 12:36
2010 Feb 14 12:36
2010 Feb 15 12:36
STEREO-A impulsive SEP event on Feb 14.3 associated with new emergence?
WHAT DRIVES ION PRODUCTION/ESCAPE IN LONG-LASTING SOURCES?
29
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?
30
• 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
SUMMARY & NEW IMPLICATIONS (ii)
31
Thanks !
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