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Spectral Properties of Heavy Ions Spectral Properties of Heavy Ions Associated with Interplanetary Shocks Associated with Interplanetary Shocks

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SHINE 2004SHINE 2004Big Sky, Montana Big Sky, Montana

M. I. Desai M. I. Desai University of Maryland, College Park, MD 20742, USAUniversity of Maryland, College Park, MD 20742, USA

Co-Authors: Co-Authors: G. M. Mason: University of MarylandG. M. Mason: University of Maryland

C.M.S.Cohen & M. E. Wiedenbeck: SRL, Caltech, CA C.M.S.Cohen & M. E. Wiedenbeck: SRL, Caltech, CA J. E. Mazur: Aerospace CorpJ. E. Mazur: Aerospace Corp

J. R. Dwyer: Florida Institute of TechnologyJ. R. Dwyer: Florida Institute of TechnologyR.E. Gold & S. M. Krimigis: JHU/APLR.E. Gold & S. M. Krimigis: JHU/APL

C.W.Smith: University of New HampshireC.W.Smith: University of New HampshireQ. Hu: IGPP, UC Riverside, CAQ. Hu: IGPP, UC Riverside, CA

R. M. Skoug: Los Alamos National LaboratoryR. M. Skoug: Los Alamos National Laboratory

Spectral Properties of Heavy Ions Spectral Properties of Heavy Ions Associated with Interplanetary Shocks Associated with Interplanetary Shocks

at 1 AUat 1 AU

SHINE 2004SHINE 2004Big Sky, Montana Big Sky, Montana

M. I. Desai M. I. Desai University of Maryland, College Park, MD 20742, USAUniversity of Maryland, College Park, MD 20742, USA

Co-Authors: Co-Authors: G. M. Mason: University of MarylandG. M. Mason: University of Maryland

C.M.S.Cohen & M. E. Wiedenbeck: SRL, Caltech, CA C.M.S.Cohen & M. E. Wiedenbeck: SRL, Caltech, CA J. E. Mazur: Aerospace CorpJ. E. Mazur: Aerospace Corp

J. R. Dwyer: Florida Institute of TechnologyJ. R. Dwyer: Florida Institute of TechnologyR.E. Gold & S. M. Krimigis: JHU/APLR.E. Gold & S. M. Krimigis: JHU/APL

C.W.Smith: University of New HampshireC.W.Smith: University of New HampshireQ. Hu: IGPP, UC Riverside, CAQ. Hu: IGPP, UC Riverside, CA

R. M. Skoug: Los Alamos National LaboratoryR. M. Skoug: Los Alamos National Laboratory

CME-driven Interplanetary ShocksCME-driven Interplanetary Shocks

“Ambient”

(Desai et al. 2001, ApJ 553, L89 & 2003, ApJ, 588, 1149).

• Surveyed 72 shocks

between Oct. 1997-Oct.

2002

• 3He ions accelerated in

45 IP shocks

Pre-shock intervals provide a “proxy” for ambient particles in the IP medium

Intensity-time profiles Intensity-time profiles for an IP shockfor an IP shock

Ambient and SEP Ambient and SEP Abundances Abundances

Ambient and SEP Ambient and SEP Abundances Abundances

Ambient Ambient

material material

comprises comprises

~30% from ~30% from

impulsive impulsive

flares, and flares, and

~70% from ~70% from

large gradual large gradual

SEPsSEPs

Gradual SEPs

Impulsive SEPs

Upstream Material

10-2

10-1

100

C N O Ne MgSi S Ca Fe

12 1416 20 24 2832 40 56

Mass (AMU)

(Desai et al. 2003 ApJ, 588, 1149).

IP Shock compared with solar wind IP Shock compared with solar wind abundancesabundances

0

1

2

3

4

1 2 3 4 5 6Mass/Charge (AMU e-1)

m = 1.22 ± 0.23

c = 0.40 ± 0.22

cu

2 =3.34; =1.45 10P x-3

= 0.43; =0.13r p

4He C

Mg

Ne

N

O

Si

S

Fe

GI = + *[c m MIQO/MOQI]

(Desai et al. 2003 ApJ, 588, 1149).

• Shock abundances are

poorly correlated with

solar wind abundances

• No clear dependence on

M/Q

• Difficult to understand in

terms of rigidity-

dependent acceleration of

solar wind ions

IP Shock compared with ambient suprathermal IP Shock compared with ambient suprathermal abundancesabundances

0.2

0.4

0.6

0.8

2.0

1.0

1 2 3 4 5 6Mass/Charge (AMU e-1)

m = -0.64 ± 0.05

c = 0.63 ± 0.04

=4.39;P=2.56x10-5

r = -0.92; p=7.8x10-5

cu

2

(logGI) = + *[c m MIQO/MOQI]

4He N

CO

Ne

MgSi

S

Ca Fe

(Desai et al. 2003 ApJ, 588, 1149).

• Shock abundances are

well correlated with

ambient suprathermal

abundances

• Exhibit a M/Q-dependent

depletion

• Consistent with rigidity-

dependent shock

acceleration of ambient

suprathermals

(Desai et al. To appear in ApJ.Aug. 20, 2004 issue)

10-4

10-3

10-2

10-1

100

101

102

103

10-2

10-1

100

101

22 23 24 25 26 27 28 29

1999 June (UT)

10-1

100

101

ACE/ULEIS C, O, Fe Intensities

ACE/ULEIS C/O ratio

ACE/ULEIS Fe/O ratio

S2

0.16-0.23 MeV n-1 (x10)

0.91-1.28 MeV n-1

OCFe

0.2 MeV n-1

1.0 MeV n-1

0.2 MeV n-1

1.0 MeV n-1

Ambient

(a)

(b)

(c)

Shock

Fe/O at IP shocks is Fe/O at IP shocks is

depleted relative to depleted relative to

ambient values ambient values

Larger decrease at Larger decrease at

higher energy higher energy

Energy Spectra during an IP Energy Spectra during an IP shock: shock:

All Spectra fitted by All Spectra fitted by j = jj = j00EE--

exp(-E/Eexp(-E/E00))

Parameter Carbon Oxygen Iron

No. of Points 8 10 8

j0 4.64 0.87 9.32 1.21 3.17 1.49

1.36 0.11 1.33 0.09 1.08 0.27

E0 0.69 0.09 0.72 0.06 0.35 0.06

2 0.87 0.91 0.88

10-1 100 101

Energy (MeV n-1)

10-3

10-2

10-1

100

101

102

103 2001, day 98::0426-1719 UT

Carbon

Oxygen

IronACE/ULEIS

however and E0 are coupled; Use only 0.1-0.5 MeV n-1 to obtain the power-law indices


Spectral indices of C, O, & Fe Spectral indices of C, O, & Fe Spectral indices of C, O, & Fe Spectral indices of C, O, & Fe

ACE/ULEIS: 0.1-0.5 MeV n-1

N = 72; r = 0.98;p ~ 0% N = 72; r = 0.79;p = 4.4 x10 -14%

0

1

2

3

4

0 1 2 3 4

O Spectral Index

0

1

2

3

4

0 1 2 3 4

O Spectral Index

(a) (b)

ACE/ULEIS: 0.1-0.5 MeV n-1

Differences in Fe and O indices are at odds Differences in Fe and O indices are at odds with injection of a mono-energetic seed with injection of a mono-energetic seed populationpopulation


O e-folding energy vs. shock O e-folding energy vs. shock parameters parameters

O e-folding energy vs. shock O e-folding energy vs. shock parameters parameters

0.1

1.0

10

0.1

1.0

10

0 15 30 45 60 75 90

Shock Normal Angle [deg.]qBn

( ) [ Shock speed upstream km s-1]VS

10 100 1000

( )a ( )b

= 57; = -0.04; = 76%N r p = 51; = 0.09; = 52%N r p

E-folding energy is independent of local shock E-folding energy is independent of local shock parametersparameters


0 1 2 3 4 50

1

2

3

4

5

(M+2)/(2M-2)

N = 60; r ~ 0.09; p ~ 51%

ACE/ULEIS 0.1-0.5 MeV n-1

Spectral index is poorly correlated with compression ratio, M

Results are at odds with predictions of simple steady-state models

2-hr. av. O spectral index vs. 2-hr. av. O spectral index vs. (M+2)/(2M-2) (M+2)/(2M-2)

2-hr. av. O spectral index vs. 2-hr. av. O spectral index vs. (M+2)/(2M-2) (M+2)/(2M-2)


22 23 24 25 26 27

2001 November (UT)

10-7

10-6

10-5

10-4

10-3

10-2

10-1

100

101

102

103

0.14

0.27

0.55

1.09

2.19

4.37

8.55

14.35

25.20

51.35

ACE ULEIS + SIS Oxygen Intensities

MeV n-1

S

S15W34

Ambient

IP shock event measured by ULEIS & IP shock event measured by ULEIS & SISSIS

IP shock event measured by ULEIS & IP shock event measured by ULEIS & SISSIS


Energy spectra measured by ULEIS & Energy spectra measured by ULEIS & SISSIS

Energy spectra measured by ULEIS & Energy spectra measured by ULEIS & SISSIS

10-1

101

103

105

107

10-2

10-1

100

101

10-1 100 101 102

Kinetic Energy (MeV n-1)

10-1 100 101 102


solid symbols = ULEISopen symbols = SIS

solid symbols = ULEISopen symbols = SIS

event #61 event #61

(a) (b)

O

C

Fe

C/O

Fe/O


10-1 100 101


10-5

10-3

10-1

100

103

10-2

10-1

100

101

10-5

10-3

10-1

100

103

10-5

10-3

10-1

100

103

10-1 100 101

Kinetic Energy (MeV n-1)10-1 100 101


10-1 100 101




10-2

10-1

100

101

10-2

10-1

100

101

C

O

Fe

CO

FeC

O

Fe

(a) (b) (c)

(d) (e) (f)

event #13

event #13

event #18

event #18

event #37

event #37

C/O

Fe/O

C/O

Fe/O

C/O

Fe/O

3 Classes of Fe/O energy-dependence 3 Classes of Fe/O energy-dependence 3 Classes of Fe/O energy-dependence 3 Classes of Fe/O energy-dependence


Energy-dependence of Fe/OEnergy-dependence of Fe/O Energy-dependence of Fe/OEnergy-dependence of Fe/O

0.01 0.1 1.0

Fe/O (0.22 MeV n-1)

0.01

0.1

1.0

0.01

0.1

1.0

0.01 0.1 1.0

Fe/O (0.22 MeV n-1)

0.01 0.1 1.0

Fe/O (0.22 MeV n-1)

0.01

0.1

1.0

N = 68 N = 33 N = 12

ACE/ULEIS ACE/ULEIS ACE/ULEIS & ACE/SIS

(a) (b) (c)

Fe = Fe/O (0.62 MeV/n.)

Fe/O (0.22 MeV/n.)

(Adapted from Desai et al. 2004, To appear in ApJ. Aug. 20, 2004)

FeFe vs. vs. 33He/He/44He ratio; He ratio; 33He/He/44He ratio vs. He ratio vs. BnBn

Extreme Events Only Extreme Events OnlyFeFe vs. vs. 33He/He/44He ratio; He ratio; 33He/He/44He ratio vs. He ratio vs. BnBn

Extreme Events Only Extreme Events Only


10-3

10-2

10-1

100

0 30 60 90

Shock Normal Angle, qBn [ .]deg

10 -3 10 -2 10 -1 1003 /He 4 He ratio

( )b( )a

3He/4He > 2%

N= 43;r= 0.08; p = 63.7%

3He/4He > 2%

N= 43;r= 0.56; p = 1.2x10-2%

m = 0.19 ± 0.06

c = 2.05 ± 0.41

1.0

0.2

0.4

0.6

0.8

2.0

3.0

4.0


All events All events


All events All events

33He/He/44He ratio vs. Injection Threshold Speed, VHe ratio vs. Injection Threshold Speed, Vinjinj = = VVSS*sec(*sec(BnBn))

33He/He/44He ratio vs. Injection Threshold Speed, VHe ratio vs. Injection Threshold Speed, Vinjinj = = VVSS*sec(*sec(BnBn))

Most IP shocks including the 3 with rising Fe/O ratios have Vinj<2*Vsw

3He/4He ratio and Fe are

poorly correlated with Vinj

Vinj > 600 km s-1

3He/4He > 2%

Conclusion: Injection Conclusion: Injection threshold speeds do not threshold speeds do not appear to play a appear to play a significant role in the significant role in the energy-dependent energy-dependent behavior of Fe/Obehavior of Fe/O


FeFe vs. O spectral index & O fluence vs. O spectral index & O fluenceFeFe vs. O spectral index & O fluence vs. O spectral index & O fluence

0 1 2 3 4

Oxygen Spectral Index(0.1-0.5 MeV n-1)

101 102 103 104 105 106 107

Oxygen Fluence (#/cm2 sr MeV n-1)(0.5-2.0 MeV n-1)

1.0

0.2

0.4

0.6

0.8

2.0

3.0

4.0

1.0

0.2

0.4

0.6

0.8

2.0

3.0

4.0

N= 68;r=0.58; p = 2.4 x10-5%

m = 0.39 ± 0.05

c =-0.94 ± 0.26

N= 61;r=-0.46; p =2.0 x10-2%

m = -0.09 ± 0.02

c = 1.81 ± 0.78

(a) (b)

Fe/O at IP shocks vs. ambientFe/O at IP shocks vs. ambientFe/O at IP shocks vs. ambientFe/O at IP shocks vs. ambient

10-2

10-1

100

Fe/O (Upstream)10-2 10-1 100

log(Fe/OShock) = c + m*log(Fe/OUpstream)

cu2 =0.53; =1.0P

=62; =0.51; =1.0 10N r p x -5

= 0.40 m ± 0.02 = 0.26 c ± 0.05

#29event

(Desai et al. 2003 ApJ, 588, 1149).

Fe/O ratios at IP Fe/O ratios at IP

shocks and ambient shocks and ambient

are well correlatedare well correlated


Shock C/O & Fe/O normalized to ambient Shock C/O & Fe/O normalized to ambient values values

Shock C/O & Fe/O normalized to ambient Shock C/O & Fe/O normalized to ambient values values

• Fe/O ratios are depleted by ~30% relative to ambient values

• Energy-dependence of Fe/O is diminished when compared with ambient Fe/O - not expected from mono-energetic injection


O Spectral index & Fe/O O Spectral index & Fe/O dependence at IP shocks vs. dependence at IP shocks vs.

Ambient Ambient

O Spectral index & Fe/O O Spectral index & Fe/O dependence at IP shocks vs. dependence at IP shocks vs.

Ambient Ambient

SummarySummarySummarySummary

• Spectral parameters and energy-dependence of Fe/O are independent of local shock parameters

• 5 out of 72 events (~7%) have rising Fe/O with energy; Fe/O in other events are constant or decrease with energy

• Fe/O at IP shocks are typically ~30% lower than in the ambient population

• The O spectra and energy-dependence of Fe/O are similar at IP shocks and in the ambient population


Sketch of Re-acceleration of Seed spectra at IP Sketch of Re-acceleration of Seed spectra at IP shocks shocks

Sketch of Re-acceleration of Seed spectra at IP Sketch of Re-acceleration of Seed spectra at IP shocks shocks

10-1 100 101

Kinetic Energy (MeV n -1)

10-5

10-3

10-1

100

103

OFe

Seed SpectraShock Spectra

ConclusionConclusionConclusionConclusion

IP shocks accelerate seed spectra composed of

suprathermal ions from gradual and impulsive SEP

events by a systematic rigidity-dependent mechanism

where ions with higher M/Q are accelerated less

efficiently than those with lower M/Q

Relevant IssuesRelevant IssuesRelevant IssuesRelevant Issues

• How common are IP shock events with rising Fe/O ratios? ~7% of events have rising Fe/O with energy

• What are the key differences between IP shocks with rising and decreasing Fe/O ratios? No appreciable differences in shock properties

• Does any particular local shock parameter play a role in determining the energy-dependent behavior of Fe/O? Cannot rule this out completely, but no

evidence that local shock properties are important

• The primary cause of rising Fe/O in IP shocks Re-acceleration of energetic ion seed spectra

that themselves have rising Fe/O with energy