He+ Increase in SEP Events with a High Source Temperature

and Implication for Acceleration Site

ICRC, 2011, Beijing

Z. Guo; E. Moebius; M. Popecki

Space Science Center & Department of Physics

University of New Hampshire

B. Klecker

Max-Planck Institut für extraterrestrische Physik

G. Mason

Applied Physics Laboratory, Johns Hopkins University

Versus “High QFe“ in Solar Wind

• Solar Wind QFe ≥ 16 from Active Regions consistently observed by ACE SWICS

If material from Active Region SW is accelerated

It should show high Q at low E of SEP energy

(Lepri et al., 2004)

• Systematic study of impulsive events shows an E-dependent QFe with high Q only at high E

• Substantially lower QFe at the low SEP energy end

• Stripping model indicates a 1-3 MK Source Temperature

“Low Source QFe“ in Impulsive SEPs

Events with High Source Q During 1998-2000

Used ACE SEPICA data, along with ACE ULEIS, SWICS and SOHO STOF

Events with mean QFe > 14 are found during 1998-2000

ACE SEPICAMoebius et al 1998

Ev.#

Time Period SWICS STOF SEPICA

0.08 –0.13Mev/n

0.18 –0.25Mev/n

0.25 –0.36

Mev/n

0.36 –0.54Mev/nYear DOY

Solar Wind

10-100kev/n

0.18-0.54Mev/n

1* 1997311.17-

314.00

15.43

±1.78

14.71

±1.78

14.16

±1.78

15.47

±1.78

16.99

±1.78

2 1998101.90 -103.50

16.60

±0.98

16.61

± 1.16

15.91

±0.83

15.63

±1.02

17.73

±0.81

3 1998124.25-

125.2913.60

13.33

±0.12

14.59

±0.26

14.19

±0.22

13.83

±0.27

16.09

±0.30

4 1998158.25-

160.50

15.39

±1.03

14.43

±0.67

14.29

±1.69

14.66

±1.91

16.33

±1.27

5* 2000144.80-

145.9014.00

13.43

± 0.50

15.95

±0.42

14.70

±0.44

16.80

±0.38

16.80

±0.38

16.80

±0.38

6 2000225.75-

226.1013.90

13.21

± 0.56

18.22

±0.72

16.62

±0.74

17.86

±0.74

19.29

±0.71

Events with High Source Q During 1998-2000

We found a total number of 6 events that qualified for our cretiria, having QFe>14 over entire SEPICA energy range

-- consistent with solar wind findings-- indicating a source temperature of 2-6 MK

• In 2 events QFe show impulsive stripping feature, but still has QFe>14 at lowest SEP energy, and QFe>13 in solar wind.

• In 4 events QFe show no energy dependence, and are randomly distributed around a mean of over 14. (“High-QFe events”)

-- Searched for correlation with specific solar activities, no decisive feature can be found for all 6 events

-- Flat QFe behavior excludes stripping in low corona: indicates acceleration in interplanetary space

Occurrence of He+ in High QFe Events

-- Typical He+/He2+ = ~5.10-5 in the solar wind

-- Presence of He+: Indicates of acceleration in interplanetary space

(Kucharek et al., 2003)

Investigated QHe for the high- QFe events

He+ presence found in all 4 events, and can be analytically separated from He2+ distribution

Ev.#

Year Time Period

Fitted Counts

He+/He2+

He2+ He+

2 1998 101.90 -103.50 441.63 48.27 0.11

3 1998 124.25-125.29 17218.88 164.09 0.0095

4 1998 158.25-160.50 180.88 17.63 0.097

5 2000 144.80-145.90 3903.71 40.45 0.010

Occurrence of He+ in High QFe Events

Presence of He+ can also be seen in the impulsive event #6, however, the distribution cannot be well fitted by a double gaussian

#6 2000 225-226The Impulsive event may show some He+ at low energies, but it’s depleted at E ≥0.35 MeV/nuc

For the High QFe events, He+ can be seen at all energy channels.

He+He2+

Occurrence of He+ in High QFe Events

To get better statistics

-- Combine the 4 high QFe events, and 33 impulsive events (confirmed in DiFabio, 2008)-- Fit with double Gaussian using the same technique

Every energy channel of the combined QHe can be reliably fitted

Width of fitted He+ and He2+ population increase with energy--- consistent with instrumental spread of single charge

Occurrence of He+ in High QFe Events

No He+ at above 0.35 MeV/nuc for impulsive eventsConsistently observed He+ for the high QFe events

Same acceleration mechanism for He+ and Fe in high QFe events

Plot temporal intensity profile of He and Fe for High QFe events

He and Fe share a similar intensity profile for the core event

Conclusions

• 6 SEP Events are found to have QFe>14 even at <0.1 MeV/nuc during 1998-2000

• No consistent association of specific solar event or single acceleration mechanism for all these events can be found

• 4 of these events show a flat QFe behavior, indicating no stripping has occurred, which suggests acceleration in interplanetary space

• All 4 events show presence of He+ over 0.25-0.8 MeV/nuc, stems from interplanetary pick up He+. This supports acceleration in the interplanetary space

• These events are likely accelerated in interplanetary space out of high temperature source material from active regions that also contains remnant impulsive material

Thank you

2 “High Q” event is classified as impulsive (DiFabio, et al, 2008)

4 “High Q” events has no been associated with specific event, but

QFe shows no energy dependence, i.e. no stripping involved Acceleration far away from the SunOccurrence of He+ in the events Shock acceleration in interplanetary space (Kucharek et al. 2003)

However, enhancement of 3He and heavy elements: Observed also in gradual events that involve remnant of impulsive material (Desai, et al. 2006)

Consistent with Klecker et al 2010 with data from STOF that observed a similar event in 2002

We have not found consistent associationwith shocks / compression regions for these events.

• Consistent high QFe >14 over the entire SEPICA energy range is found for 6 out of 89 SEP events

• While high QFe is often found in SW from active regions,SEP events with high QFe are rare

• Only for 3 out of the 6 cases are the high SEP charge states observed simultaneously with high solar wind charge states

• Support for interplanetary acceleration is foundNo indication of stripping and substantial He+ contribution

• We are not able to find a consistent association of specific solar event or single acceleration mechanism for all these events

• These events are likely accelerated in interplanetary space out of high temperature source material from active regions that also contains remnant impulsive material

Summary

ACE SEPICA InstrumentElectrostatic Analyzer y ~ Q/E

Proportional Counter:Specific energy loss ΔE =f(Z, E/A)

Solid State Detector: Eres

Other system parametersEphd, Δ EWindow, Udefl, etc

Moebius et al 1998

y

E-dE plot from ACE SEPICA (Moebius et al 1998)

Enhancement of heavy ions

The Puzzle:

High Q

Moebius, 2000

First Results from SEPICA

• Furthermore, there’s a essential confliction between heavy ion enhancement and high charge state

Preferential heating / acceleration of certain species

M/Q acceleration:requires different M/Q’s

High Source Temperature

Fully stripped species up to Mg

Same M/Q = 2

• SEPICA also observed high Q with impulsive events and low Q with gradual events

• However there are events with charge states in between

1. High temperature source at flares / active regions2. Impulsive events correlated preferential acceleration happened

at flare site3. Low energy part of such impulsive event gets little stripping and

shows no energy dependence4. Remnant of such impulsive event gets re-accelerated in

interplanetary space, showing enhancement of He+ pick up ions

A possible picture of what happened:

Which event category is high QFe related to?

-- All conditions has to be met, and thus the event is rare.

-- “Clean” impulsive event that only satisfy condition 1 & 2 is also observed, as of 2000 225-226 event.

New Observations Thereforth

“Plateau” at lowest energy:- compatible with CME Q: 9-11

“Upturn” at higher energy-QFe rises up quickly within SEPICA energy range-Compatible with what’s used to be seen: a higher QFe

Adding up to the mystery?

Observation of Energy dependent QFe

2: Stripping process while particles getting out of Sun corona

– Or not

Propose of a 2 step mechanism:

1: Resonance heating/acceleration of heavy ions at lower corona

• Extension for 14 of the 33 Impulsive Events

• QFe at 0.087-0.13 MeV/nranges 10.5 - 15.5

• Requires T ≈ 1 -3.106 Kin Source Region

Extension of ACE QFe energy range and its implication of source temperature

R.DiFabio 2008

SiIron trail crosses all other elements, and disentangles

C

O

Ne

Mg

S

Ca

Fe

N

Si

“Low” starting QFe in impulsive SEPs VS

High QFe in Solar Wind

Solar Wind QFe ≥ 16 from Active Regions consistently observed by ACE SWICS

If material from Active Region SW is accelerated

It should show high Q at low E of SEP energy

(Lepri et al., 2004)

Search for SEP Events with High Q at low Energy

• Use a survey of 89 strong SEP Events observed between 1998 – 2000 by SEPICA

• Events are chosen based on their intensity of 0.23-0.33 Mev/n.

Approach 1: QFe from SEPICA

Klecker 2007

• Search for events with Qmean> 14 at 0.18-0.25 MeV/n

• Analyze for high QFe at extended energy of 0.09-0.13 MeV/n

• Exclude already identified impulsive events

2 events found

1998 DOY 101.9 – 103.51998 DOY 158.25 – 160.5 Qmean=14 as common threshold

between impulsive & gradual events

Search for SEP Events with High Q at low Energy

• Again use the survey of 89 strong SEP Events• Compare Qmean in 89 SEPICA events to corresponding daily

Qmean in solar wind with ACE SWICS and at 10-100 kev/n with SOHO STOF

Approach 2: Combining data from SEPICA, SWICS and STOF

QFe>13 as threshold to see if all 3 instruments show high mean QFe

• STOF QFe are usually consistent with SWICS SW QFe

• SEPICA QFe either go with SWICS SW QFe, or much higher than it (Impulsive cases)

2 events found

1998 DOY 124.25-125.292 2000 DOY 225.75 – 226.1

Search for SEP Events with High Q at low Energy

Approach 2: Combining data from SEPICA, SWICS and STOF