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 Q Fe “ in Solar Wind Solar Wind Q Fe ≥ 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 Q Fe with high Q only at high E Substantially lower Q Fe at the low SEP energy end Stripping model indicates a 1-3 MK Source Temperature “Low Source Q Fe “ in Impulsive SEPs

Events with High Source Q During Used ACE SEPICA data, along with ACE ULEIS, SWICS and SOHO STOF Events with mean Q Fe > 14 are found during ACE SEPICA Moebius et al 1998

Ev. # Time PeriodSWICSSTOFSEPICA 0.08 –0.13 Mev/n 0.18 –0.25 Mev/n 0.25 –0.36 Mev/n 0.36 –0.54 Mev/n YearDOY Solar Wind kev/n Mev/n 1* ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ±1.27 5* ± ± ± ± ± ± ± ± ± ± ±0.71 Events with High Source Q During We found a total number of 6 events that qualified for our cretiria, having Q Fe >14 over entire SEPICA energy range -- consistent with solar wind findings -- indicating a source temperature of 2-6 MK

In 2 events Q Fe show impulsive stripping feature, but still has Q Fe >14 at lowest SEP energy, and Q Fe >13 in solar wind. In 4 events Q Fe show no energy dependence, and are randomly distributed around a mean of over 14. (“High-Q Fe events”) -- Searched for correlation with specific solar activities, no decisive feature can be found for all 6 events -- Flat Q Fe behavior excludes stripping in low corona: indicates acceleration in interplanetary space

Occurrence of He + in High Q Fe Events -- Typical He + /He 2+ = ~ in the solar wind -- Presence of He +: Indicates of acceleration in interplanetary space (Kucharek et al., 2003) Investigated Q He for the high- Q Fe events He + presence found in all 4 events, and can be analytically separated from He 2+ distribution Ev. # YearTime Period Fitted Counts He + /He 2+ He 2+ He

Occurrence of He + in High Q Fe Events Presence of He + can also be seen in the impulsive event #6, however, the distribution cannot be well fitted by a double gaussian # The Impulsive event may show some He + at low energies, but it’s depleted at E ≥0.35 MeV/nuc For the High Q Fe events, He + can be seen at all energy channels. He + He 2+

Occurrence of He + in High Q Fe Events To get better statistics -- Combine the 4 high Q Fe events, and 33 impulsive events (confirmed in DiFabio, 2008) -- Fit with double Gaussian using the same technique Every energy channel of the combined Q He 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 Q Fe Events No He + at above 0.35 MeV/nuc for impulsive events Consistently observed He + for the high Q Fe events Same acceleration mechanism for He + and Fe in high Q Fe events Plot temporal intensity profile of He and Fe for High Q Fe events He and Fe share a similar intensity profile for the core event

Conclusions 6 SEP Events are found to have Q Fe >14 even at <0.1 MeV/nuc during 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 Q Fe behavior, indicating no stripping has occurred, which suggests acceleration in interplanetary space All 4 events show presence of He + over 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

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2 “High Q” event is classified as impulsive (DiFabio, et al, 2008) 4 “High Q” events has no been associated with specific event, but Q Fe shows no energy dependence, i.e. no stripping involved  Acceleration far away from the Sun Occurrence of He + in the events  Shock acceleration in interplanetary space (Kucharek et al. 2003) However, enhancement of 3 He 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 association with shocks / compression regions for these events.

Consistent high Q Fe >14 over the entire SEPICA energy range is found for 6 out of 89 SEP events While high Q Fe is often found in SW from active regions, SEP events with high Q Fe 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 found No 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 Instrument Electrostatic Analyzer y ~ Q/E Proportional Counter: Specific energy loss ΔE =f(Z, E/A) Solid State Detector: E res Other system parameters E phd, Δ E Window, U defl, 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 regions 2. Impulsive events correlated preferential acceleration happened at flare site 3. Low energy part of such impulsive event gets little stripping and shows no energy dependence 4. 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 Q Fe 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 event.

New Observations Thereforth “Plateau” at lowest energy: - compatible with CME Q: 9-11 “Upturn” at higher energy -Q Fe rises up quickly within SEPICA energy range -Compatible with what’s used to be seen: a higher Q Fe Adding up to the mystery? Observation of Energy dependent Q Fe 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 Q Fe at MeV/n ranges Requires T ≈ K in Source Region Extension of ACE Q Fe energy range and its implication of source temperature R.DiFabio 2008 Si Iron trail crosses all other elements, and disentangles C O Ne Mg S Ca Fe N Si

“Low” starting Q Fe in impulsive SEPs VS High Q Fe in Solar Wind Solar Wind Q Fe ≥ 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 Mev/n. Approach 1: Q Fe from SEPICA Klecker 2007 Search for events with Q mean > 14 at MeV/n Analyze for high Q Fe at extended energy of MeV/n Exclude already identified impulsive events 2 events found 1998 DOY – DOY – Q mean =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 Q mean in 89 SEPICA events to corresponding daily Q mean in solar wind with ACE SWICS and at kev/n with SOHO STOF Approach 2: Combining data from SEPICA, SWICS and STOF Q Fe >13 as threshold to see if all 3 instruments show high mean Q Fe

STOF Q Fe are usually consistent with SWICS SW Q Fe SEPICA Q Fe either go with SWICS SW Q Fe, or much higher than it (Impulsive cases) 2 events found 1998 DOY DOY – Search for SEP Events with High Q at low Energy Approach 2: Combining data from SEPICA, SWICS and STOF