chromosphere

e–: X- and γ-ray bremsstrahlung

ions: excited nuclei → prompt γ-ray line radiation

escape to space

neutrons →capture on H → 2.223 MeV γ-ray line

delayed γ-ray line emission

radioactive nuclei →e+ → γ511

π → γ (decay, e± bremsstrahlung, γ511)

coronae, p, 3He, α, C, N, O, ...

reactionproducts

X-, γ-ray and NeutronProduction in Solar Flares

R. J. Murphy, J. M. Ryan, M. Pesce-Rollins & G. H. Share

0.010.001 0.1 1 10 100

thermalbremsstrahlung

non-thermalbremsstrahlung

non-thermalbremsstrahlung

nuclear deex-citation lines

pion-decay

neutron-capture line

GOES 1–8 Å band

positron-annihilation line

1000Photon energy (MeV)

10-8

10-6

10-4

10-2

1

102

104

106Ph

oton

s M

eV–1

• What are the accelerated-ion and ambient compositions? What is the association between flare-accelerated ions and 3He-rich SEP event ions? Is FIP fractionation taking place at the chromospheric densities where flare ions are interacting?

• What is the angular distribution of interacting flare ions? What can be learned about accelerated-ion transport?

• What is the shape of the 511 keV positron annihilation-line and what can it reveal about flare conditions at the Sun?

• Can long-lived radioactive isotope deexcitation lines be observed? Can they reveal small-scale or continuous ion acceleration? What do they say about atmospheric mixing?

• What is the association of Fermi high-energy emission and SEPs? What improv-ment in PSF at 100’s of MeV will help resolve the issue?

• What unique information do observations of flare-produced neutrons provide?

• How efficient and how fast is primary flare electron acceleration? To what energies are electrons accelerated?

0 2 4

12C 16O

20Ne, 24Mg, 28Si, 56Fe

12C 16O

20Ne, 24Mg, 28Si, 56Fe

6 8Photon energy (MeV)

senil daorBsenil worraN

10 -5

10 -4

10 -3

10 -2

10 -1

Phot

ons

MeV

–1

0 2 4 6 8Photon energy (MeV)

10 -5

10 -4

10 -3

10 -2

10 -1

Phot

ons

MeV

–1

Ambient and Accelerated-Ion Composition

Interactions of flare-accelerated ions with the solar atmosphere produce gamma-ray deexcitation lines.

12C + 4He → 12C*4.439H

p + 12C → 12C*4.439α3He

Narrow line ratios are proportional to the relative abundances of the chromosphere where the ions interact

Broad line ratios are proportional to the relative abundances of the accelerated ions

Ambient Composition

Earlier analyses (Ramaty et al. 1995) found:

The ambient composition is similar to that of the corona (FIP effect).

The Ne abundance appears to be elevated (Ne/O = 0.25 vs. 0.15)

But more recent analyses (Share priv. comm.) found:

The ambient composition is consistent with the photosphere.

The Ne abundance is not elevated.

C N O Ne Mg Si Fe

Element

1

2

3

4

5Corona

6

Abun

danc

e / P

hoto

sphe

ric a

bund

ance April 27

Murphy, Ramaty, Kozlovsky & Reames 1991

Accelerated-Ion Composition

Gradual SEP(associated with shocks)

footpoint

footpoint

open field lines

chromosphere

energyrelease

SunCME

acceleratedions

Flare/CME initiated at the Sun

CME-driven shock

Ambient coronal suprathermals

Shock + Suprathermals → SEPs

Reames 2002

3He-rich impulsive SEP(associated with flares)

Gradual SEP (corona)3He-rich events

Element

0

5

10

15

20

25

30

35

Abun

danc

e re

lativ

e to

pho

tosp

here

([O

] = 1

)

C N O Ne Mg Si FeReames 1995

Reames 1994

[3He/4He]corona ≅ 4 × 10–4

Solar Energetic Particle Events

Accelerated-Ion Composition (cont.)

RHESSI spectrum of the 2005 January 20 flare(24220.000 - 25220.000 sec UT)

1000

n-capture (2.223 MeV)

e– bremsstralung

π-decayradiation

broad deex-citation lines

narrow deex-citation lines

e+ annihilation (511 keV)

10000Energy (keV)

10-5

10-4

10-3

10-2Co

unts

cm

-2s-1

keV

-1

Fitting calculated broad-line spectra to measured spectra directly determines the heavy accelerated-ion composition

Accelerated-Ion Composition (cont.)

C N O Ne Mg Si Fe

Element

0

2

4

6

8

10

Abun

danc

e (re

lativ

e to

car

bon)

April 27

Large SEP (coronal)

3He-richEarlier analyses (Murphy et al. 1991) found:

The accelerated-ion composition may resem-ble 3He-rich SEP composition.

Conclusion based primarily on the Mg and Fe results.

But more recent analyses (Share priv. comm.) found:

The accelerated-ion composition may be more consistent with a coronal composition, but with the heavy/proton ratio larger by a factor of ~2.

10.1 10 100Projectile energy (MeV nucleon–1)

1

10

100

1000

Cro

ss s

ectio

n (m

b)

solid: 14N(p,pʹ)14N*dotted: 14N(α,αʹ)14N*dot-dot-dashed: 14N(3He,3Heʹ)14N*solid green: 16O(3He,3p2n)14N*

dot-dashed: 12C(α,“d”)14N*dotted grn: 16O(p,x)14N*dashed grn: 16O(α,x)14N*

Eγ = 2.313 MeV

solid red: 12C(3He,p)14N*

2 4 6 8 10

0.1

1

10

φ6.129 / φ1.634 ratio 00.010.11

3He/α

Ion power-law Index

Rat

io

2 4 6 8 10Ion power-law Index

Rat

io

0.1

1

10

φ2.3 / φ4.4 ratio

3He/α = 0

3He/α = 0.01

3He/α = 0.1

3He/α = 1

s = 4, 3He/α = 1, Np(>30 MeV) = 1

2.0 2.2 2.4 2.6

29Si 31P 28Si20Ne13C

32S (2.229)14N

24Mg

2.8

neutron-capture (2.223)

3.0Photon energy (MeV)

10-5

10-4

10-3

10-2

Phot

ons/

MeV

black: total

red: proton & alpha onlygreen: 3He only

Accelerated-Ion Composition (cont.)

2.313 MeV line of 14N

Direct determination of the accelerated 3He abundance via 3He deexcitation lines

Sunheliocentric angle θobs

isotropicdownward beam θobs = 0º

0.000

0.001

0.002

0.003

0.004

Phot

ons

MeV

–1

4.439 MeV 12C line

4.0 4.2

θobs = 73º

4.4

isotropicdownward beam

RHESSI rear GeSMM/GRS NaI

4.6 4.8Photon energy (MeV)

0.000

0.001

0.002

0.003

0.004

0.005

Phot

ons

MeV

–1

Interacting Accelerated-Ion Angular Distribution

Provides information about ion trans-port in the flare magnetic loop

Interacting Accelerated-Ion Angular Distribution (cont.)

-1.0 1.0-0.5 0.0 0.5µ

δ0.000.100.20

0.00

0.05

0.10

0.15

0.20

dN/d

Ω (s

r−1 )

0.00

0.05

0.10

0.15

0.20

dN/d

Ω (s

r−1 )

PASnoneλ = 300saturated

θ

µ = cos(θ)µ > 0 ⇒ upwardµ < 0 ⇒ downward

no PAS

(δ = 0.2)

4.364.34

4.38

4.40

4.42

4.44

4.46

4.48s = 4

6.00

6.05

6.10

6.15

6.20

16O (6.129 MeV)

12C (4.439 MeV)

1.60

1.59–0.2 0.0 0.2 0.4 0.6 0.8 1.0

1.61

1.62

1.63

1.64

1.65

20Ne (1.634 MeV)

Ener

gy (M

eV)

cos θobs

downward isotropic

isotropic

downward isotropic

isotropic

downward isotropic

isotropic

SMM observations (Share, priv. comm.)

Positron Production and Annihilation

p + p p + αp + 12C → 11C + X α → π+ → µ+ + ν

e+ + ν + ν

τ (sec)

Radioactive positron emitters

Positron Production

Positron Annihilation

Pions

16O 9.6 × 10–11 11C 1800τ (sec)

π+ 3.8 × 10–8 µ+ 2.1 × 10–6

τ

τπ

τµ11B + ν + e+

Two possible Ps spin configurations1Ps → 2 511keV photons (a line) 3Ps → 3 <511 keV photons (continuum)

1. Direct annihilation with free electrons (daf) or bound electrons (dab) yields two 0.511 MeV photons in rest frame producing a line

2. Positronium (Ps) formation via radiative combination with free electrons (rc) or charge exchange with H and He (ce)

Positron Production and Annihilation

e+of

1 MeV

radiative combination

charge exchange

Ps13Ps

direct annihilation with free electrons

direct annihilation with bound electrons

energy loss∗

thermalization

in-flight

spin

flip2γ

3γ 2γ

2γ

break up

>~

∗ energy loss via Coulomb interaction with ambient electrons and via excitation and ionization of ambient atoms

Positron Production and Annihilation (cont.)

The annihilation path depends on the ambient den-sity, temperature and ionization fraction

T = 1×106 KFWHM = 11.2 keV

T = 1×104 KFWHM = 1.1 keV

495 500 505

rc

daf

510 515 520 525Photon energy (keV)

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

Phot

ons

keV–1

495 500 505

nH = 1013 cm–3 ,100% ionized T = 5000 K, 100% neutral

510 515 520 5250.0

0.2

0.4

0.6

0.8

Phot

ons

keV–1

total

total

daf

rc3γ continuum

3γ continuum

495 500 505 510 515 520 5250.0

0.2

0.4

0.6

0.8

1.0nH = 1017 cm–3

FWHM = 1.6 keV

Photon energy (keV)

The line shape is NOT Gaussian!

Phot

ons

keV–1

495 500 505 510

ifce

dab (H)

515 520 5250.00

0.05

0.10

0.15nH = 109 cm–3

FWHM = 2.2 keV

Phot

ons

keV–1

total

total

ifce

2g-ifce

dab (He)thermal ce

dab (He)

3γ continuum

dab (H)

thermal ce

Positron Production and Annihilation (cont.)

500 505 510 515 520Energy (keV)

0.000

0.002

0.004

0.006

0.008

0.010

0.012

Cts

/sec

/keV

/cm

2

Solar

Bremss.Nuclear2.223 MeV

11/2/2003 – 62160.000 - 62760.000 sec UT

0.00

0.01

0.02

0.03

0.04

Cts

/sec

/keV

/cm

2

background

total

flare

Positron Production and Annihilation (cont.)

RHESSI observations

11:08:00 11:12:00 11:16:00 11:20:00 11:24:00 11:28:00 11:32:00

Time, UT on 28 Oct 2003

0.0

2.5

5.0

7.5

10.0

Wid

th, k

eV

Annihilation line width (FWHM)

0.000

0.005

0.010

0.015

0.020

0.025

0.030

Cou

nts

cm-2s-1

keV-1

Vernazza 6000KGaussian

FWHM ≅ 6.5 keV

500 505

5000K, 1015 cm–3, XH+ = 0.2Gaussian

510 515 520Energy (keV)

0.000

0.002

0.004

0.006

0.008

FWHM ≅ 1 keV

Positron Production and Annihilation (cont.)

Share et al. 2003; 2004

Broad line: dense, warm, ionizedNarrow line: cool, highly ionized

Neither are consistent with standard atmo-spheric models.

RHESSI observations

Long-lived Deexcitation Lines

0.511 MeV positron-annihilation line is strongest

Tatischeff et al. 2006

p + 12C → 11C → 11B + ν + e+ → γ511τ = 1800 s

p + 56Fe → 52Mn → 52Cr* → γ1434τ = 21 m

Radioactive X- and Gamma-Ray Line Emitters Ordered by Lifetime

Isotope Half-Life Photon Energy (keV ) and Intensity (%)

52Mnm ................ 21.1 m 1434 (99.8)60Cu................... 23.7 m 7.47 (2.5), 826.4 (21.7), 1332 (88.0), 1792 (45.4)34Clm.................. 32.00 m 146.4 (40.5), 1177 (14.1), 2127 (42.8), 3304 (12.3)63Zn ................... 38.47 m 8.04 (2.5)49Cr.................... 42.3 m 4.95 (2.5), 62.3 (16.4), 90.6 (53.2), 152.9 (30.3)56Mn ................ 2.5789 h 846.8 (98.9), 1811 (27.2), 2113 (14.3)45Ti ...................... 184.8 m 4.09 (2.3)61Cu.................. 3.333 h 7.47 (12.6), 283.0 (12.2), 656.0 (10.8)43Sc................... 3.891 h 372.9 (22.5)44Sc................... 3.97 h 1157 (99.9)52Fe................... 8.275 h 5.90 (11.2), 168.7 (99.2)58Com................ 9.04 h 6.92 (23.8)24Na ................... 14.9590 h 1369 (100), 2754 (99.9)55Co................... 17.53 h 6.40 (6.5), 477.2 (20.2), 931.1 (75.0), 1408 (16.9)57Ni.................... 35.60 h 6.92 (16.7), 127.2 (16.7), 1378 (81.7), 1920 (12.3)52Mng............... 5.591 d 5.41 (15.5), 744.2 (90.0), 935.5 (94.5), 1434 (100)48V..................... 15.9735 d 4.51 (8.6), 983.5 (100), 1312 (97.5)7Be..................... 53.22 d 477.6 (10.4)58Cog ................. 70.86 d 6.40 (23.0), 810.8 (99.4)56Co................... 77.233 d 6.40 (21.8), 846.8 (99.9), 1038 (14.2),

1238 (66.9), 1771 (15.5), 2598 (17.3)

Long-lived Deexcitation Lines (cont.)

Tatischeff et al. 2006

Tatischeff et al. 2006

Delayed X- and Gamma-Ray Line Fluxes at 3 Hours

Line Flux(photons cm 2 s 1)

Energy(keV) Parent Nucleus

511............. 18F, 11C, 55Co. . . 6.44 × 10 3

6.92............ 58Com, 57Ni 1.59 × 10 4

931.1.......... 55Co 1.07 × 10 4

1369........... 24Na 6.98 × 10 5

2754........... 24Na 6.97 × 10 5

846.8.......... 56Co, 56Mn 4.31 × 10 5

1434........... 52Mnm, 52Mng 2.97 × 10 5

477.2.......... 55Co 2.89 × 10 5

1408........... 55Co 2.42 × 10 5

1378........... 57Ni 2.20 × 10 5

6.40............ 55Co, 56Co, 58Cog 1.59 × 10 5

1238........... 56Co 1.51 × 10 5

935.5.......... 52Mng 1.40 × 10 5

744.2.......... 52Mng 1.33 × 10 5

7.47............ 61Cu, 60Cu 1.11 × 10 5

283............. 61Cu 1.06 × 10 5

f4.4+6.1 = 300 ph cm-2 s-1

s = 3.5

Fermi/LAT Observations

00:00 04:00 08:00 12:00 16:00 20:00 00:00 Time (Start at 06-Mar-12 23:00:00)

10-5

10-4

10-3

LAT >100 MeVINTEGRAL/SPI

(renormalized)

2012 March 7 flareAckermann, et al. 2014G. Share (priv. comm.)

00:00 00:30 01:00 01:30 02:00 02:30 03:00Time (Start at 07-Mar-12 00:00:00)

0.000

0.001

0.002

0.003

0.004

0.005

<> < >

B

C

M

X

Flux

, γ c

m-2

s-1

Flu

x, γ

cm

-2 s

-1

Ajello et al. 2014

Pion-decay emission from >300 MeV protons

Fermi/LAT pion-decay emission from a flare located beyond the solar limb. (Pesce-Rollins 2015)

Fermi/LAT Observations (cont.)

Cou

nts

s–1 c

m–2

MeV

–1

Energy (MeV)103

10–5

10–6

10–7

10–8

10–9

10–10102

bremsstrahlungpion-decay – PL (s = 3.5)pion-decay – PL/exponential (s = 2, E0 = 1.3 GeV)

10 102 103 10

s = 2

3

4

56

4 105

Photon energy (MeV)

10-10

10-9

10-8

10-7

10-6

10-5

10-4

10-3

Phot

ons

MeV

–1

RHESSI spectrum of the 2005 January 20 flare(24220.000 - 25220.000 sec UT)

1000

n-capture (2.223 MeV)

e– bremsstralung

π-decayradiation

broad deex-citation lines

narrow deex-citation lines

e+ annihilation (511 keV)

10000Energy (keV)

10-5

10-4

10-3

10-2

Coun

ts c

m-2

s-1ke

V-1

Observations up to only 20 MeV can provide the number of interacting >300 MeV protons but not the spectral shape

Provides both the shape of >300 protons and their number

Neutron Observations

1 10 100 1000 10000

O*6.13Ne*1.64

neutrons

Projectile Energy (MeV nucleon–1)

Production cross sections

1

10

100

1000

Cros

s se

ctio

n (m

b)

π +π 0

10-36

10-34

10-32

10-30

10-28

10-35

10-33

10-31

10-29

0.1 1 10 100 1000Neutron energy (MeV)

Neu

trons

MeV

–1 c

m–2

s = 4θobs = 0°n

Np(>30 MeV) = 1

Dn10 Rs

0.5 AU

1 AU

0 50 100 150

Dγ-ray = 1 AU

1 AU

20010-3

10-2

10-1

1

10

102

103

104

s = 2s = 4s = 6s = 8

Dn, distance to neutron detector (Rs)

R

θobs = θobs = 60°n 2.223

R =f1–10 neutrons(Dn)

f2.223 MeV(D=1 AU)

Electron Bremsstrahlung

10 102 103

Energy (MeV)

10-8

10-7

10-6

10-5

10-4

10-3

coun

ts s

-1 c

m-2

MeV

-1

24-Sep-2011 09:36:20.651 to 09:36:50.651

template pi_s75_b300_nh1e15template + 1pow

Performance parameter Goal valueField-of-view (FWHM, deg)

Angular resolution (FWHM)

~5 arc min~0.5 arc min for foot pts

~1°

Spectral resolution (∆E/E @ Energy) 1 – 2% at 5 MeV

Line sensitivity (@ Energy) (cm-2.s-1, 3 σ , 1 Ms) ~10-6 at 1 MeV

Timing performance ~1 ms

10% in 10 sPolarimetric capability (Minimum Polarization Fraction)