radoslav bucik (mps) in collaboration with davina e. innes ... · radoslav bucik (mps) in...

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-

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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

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• 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


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• 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


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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

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• 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

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• 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

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Reames et al. ApJ 292, 1985

REPEATED IMPULSIVE EVENTS

Rarely identified

but multiple

electron events

frequently

occurred in data.

? ?

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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.


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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


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Wang et al. ApJ 639, 2006

Wang et al. ApJ 639, 2006

1.2 day of injections

jet times

195Å flares white-light ejections


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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?


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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

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AR1246

Bucik et al. ApJ 786, 2014 15

AR1244

3He 4He CIR

B7.6 B4.1


AR1244

B4.1 B7.6

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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

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Impulsive event in ‘old’ AR

preceded by new flux

emergence !


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

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+ 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)


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STB

ACE

ACE

STA


AR 1244 AR 1246


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)


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• 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)


Bucik et al. in Proc. 33rd ICRC, 2013

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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

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STEREO-A

D.E. Innes

G.M. Mason

STEREO-A ACE


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

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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


AR11045 out of the Earth view

Li et al. A&A 539, 2012

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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?


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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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• 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)

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Thanks !

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