Long-Lasting 3He-Rich Solar Energetic Particle Sources

R. Bučík, D. E. Innes, U. Mall, A. Korth (MPS)

G. M. Mason (JHU)

R. Gómez-Herrero (UAH)

STEREO SEP meeting - JHU/APL - 2014 September 25

see Bučík et al. 2014, ApJ 786; Bučík et al. 2013, in Proc. 33rd ICRC, paper 0552

3He-rich SEPs : some features

• abundances arise from resonant wave-particle interaction in flare sites (e.g. Temerin & Roth 1992; Miller 1998)

• different waves/mechanisms for 3He and heavier ions

• association with type III radio bursts - better than with energetic electrons (Nitta et al. 2006)

• association with EUV jets & minor X-ray flares (Nitta et al. 2006, 2008; Wang et al., 2006)

Reames & Ng (2004)

2-1

0 M

eV

/n 3

He

-ric

h e

vent

s \ c

oro

na

ab

und

.

(3 MK)

unenhanced

enhanced f. 2-3

enhanced f. 10

enhanced f. <104 !

2

3He-rich SEPs : multiple events

Wang et al. (2006) Wang et al. (2006)

jet times

195 Å C2

• multiple events from the same AR observed by a single s/c (Reames & Stone 1986; Mason et al. 1999, 2000; Wang et al. 2006) – injections seen during about 1 day!

• these recurrent events have suggested more steady production of 3He-rich SEPs (Pick et al. 2006) 3

~1.2 day of injections

4

• but how long these injections continue in a single AR?

• difficult to answer this with single s/c observations – because of Sun rotation we could be connected to a single AR only for a limited time

• multiday 3He-rich SEP periods have been observed where oftenmultiple injections were not obvious (Reames et al. 1985; Wiedenbeck et al. 2003; Kocharov et al. 2006; Mason 2007) – not clear if continuous emission is going on since other effects (e.g.; IP propagation, re-acceleration by CMEs) may be important

• multiple injections might be closely spaced in time and therefore hardly resolved

• therefore we do a multipoint study of recurrent events

Motivation

2011 July 1-7 & July 9-16 3He-rich recurrent events

(ACE)

7.1 daysco-rotation

7.5 daysco-rotation

• s/c position in July 2011 during the recurrent events

• delay between events on different s/c corresponds to a co-rotation time

• July 1-7 events consecutively observed on STEREO-B and ACE

• July 9-16 events consecutively observed on ACE & STEREO-A 5

STEREO-B 3He-rich event (2011 July 1)

• SIT (0.3-0.9 MeV/n) mass histogram reveals clear 3He peak

• LET (2.3-8 MeV/n) shows no 3He increase

• 3He-rich SEPs preceded by an electron event; associated with B4.1 X-ray flare in AR1244 (NOAA SWPC), located at W97° from STB view6

3He 4He

CIR

0.3-0.9 MeV/n

Solar Source Identification

1AU

*flare

s/c

Schatten et al. (1969) 7

with similar approach as in prior studies (Wang et al. 2006; Nitta et al. 2006; Klein et al. 2008; Rust et al. 2008)

• Identified connection region on the Sun (e.g., Neugebauer et al. 1988)

• Parker spiral - determines the s/c foot-point longitude on imaginary source surface

• PFSS model of corona with 6 hr resolution (based on SDO magnetograms - Schrijver & DeRosa 2003) determines location on the Sun

• consistency check with in-situ magnetic polarity

• examined SDO/STEREO EUV images for temporal coincidence with type III bursts around expected ion injection time

Solar Source Identification

8

• improved source identification 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

• whole Sun surface in view with STEREO and SDO since Feb 2011 – leads to a further improvement in the source identification; but STEREO-A connection regions not covered by SDO magnetogram observations making the PFSS extrapolations less reliable

Carrington Longitude (deg)

Sin

e of

Hel

iola

titud

eSTEREO-B 3He-rich event: Solar Source

B4.1

4-min difference image around X-ray flare onset

• in-situ polarity suggests connection to both ARs 1243 & 1244

• but B4.1 flare originated in AR 1244

• marked brightening in AR 1244 at the time of B4.1 flare/type III burst, but no activity in AR 1243

STB

PFSS coronal field lines open to ecliptic

ACE 3He-rich events (2011 July 7 & July 9)

10

• dispersive onset• associated with multiple

electron events, type III bursts and B-class flares presumably in AR 1244

• enrichments seen in SIS (4.5-16.3 MeV/n)

July 7 3He-rich SEPs

July 9 3He-rich SEPs

• dispersionless onset• no electron event or X-ray

flare associated• presumably associated

with jets & type III bursts in newly emerging AR 1246

• no obvious event in SIS

jet

LEMS120

ACE July 7 3He-rich event: Solar Source

Carrington Longitude (deg)

Sin

e of

Hel

iola

titud

e

B7.6

B6.4

1244

1244• ACE connected to AR 1244• X-ray flares/type III coincident with

EUV brightening in AR 1244• source AR checked also with

STEREO-A EUVI images

• same AR produced energetic electrons & 3He-rich SEPs after almost 7 days

• this is 1st ever example of such long lasting source

4-min diff. images around X-ray flares

11

ACE

ACE July 9 3He-rich event: Solar SourceS

ine

of H

elio

latit

ude

Carrington Longitude (deg)

1246

1246

• In-situ polarity suggests connection to AR1246 / low-latitude coronal hole

• but no assoc. X-ray flare or solar electrons + event dispersionless → time of SEPs release on the Sun unknown

• examined whole Sun for EUV brightenings coincident with (the event preceding) type III bursts

emergence of AR 1246 at coronal hole

ACE

12hrs later

ACE July 9 3He-rich event: Solar Source

1246

jet time

• type III burst at 16:25 UT, ~8 hrs prior to the event start, coincides with the jet in newly emerging AR 1246

• another prominent type III burst at 11:37 UT also coincides with brightening in AR 1246

13

1246 1246

STEREO-A 3He-rich event (2011 July 16)

14

• dispersionless onset

• no solar electrons associated

• event presumably associated with EUV brightenings & type III bursts in AR 1246

• LET shows 3He

increase in 2.3-3.3 MeV/n but not above 4.3 MeV/n

brightening/jet

0.3-0.9 MeV/n

STEREO-A 3He-rich event: Solar SourceS

ine

of H

elio

latit

ude

Carrington Longitude (deg)

1246

• STEREO-A connected to the same coronal hole / AR 1246

• time of SEPs release on the Sun unknown

• new regions A1, A2 appeared nearby coronal hole (open field region) but notably active is only AR 1246

15

STA

1246

1246open field region

ordinary image

difference image

jet

STEREO-A 3He-rich event: Solar Source

• 3 prominent type III bursts coincide with brightenings in AR 1246

• these bursts occurred >14 hrs prior to event

• what could retain these ions in IP space?

16

1246 1246 1246

STEREO-A

17

STEREO-A 3He-rich event: association with the CIR

SEPT Sunward sensor

Anti-sunward sensor

Stream interface

• the event occurred within CIR with well defined stream interface & trailing boundary

• 3He intensities start at the stream interface and show a maximum in the vicinity of CIR trailing edge – commonly observed in CIR events

• SEPs confinement in CIRs simulated by Kocharov et al. 2003, 2006, 2008

Summary & Further investigations

• the first report of multiple 3He-rich SEPs outbursts in single active regions for relatively long time periods, lasting at least a quarter of a solar rotation

• the physical processes responsible for particle acceleration and escape from the Sun appear to be more continuous than previously thought

• other recurrent 3He-rich SEP events are being examined

• what (conditions) in the solar sources cause re-appearance of 3He-rich SEP emission?

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