# Presentation: 119284

## Compositional Characteristics of SEP Events

***Focus on Fe/O:***
***Fe has a much different A/Q value (3-5) than lighter ions (2-2.6)***
***Fe can arise from a broader distribution of charge states: Q ~6-26***
***QFe can change significantly during acceleration in high-density regions***
***Fe is a probe for both BOTH rigidity-dependent acceleration & transport AND characteristics of the source region***
***Examine:***
***Time-dependence of Fe/O (Wednesday PM, Reames)***
***Energy-dependence of Event-Integrated Fe/O***
***Composition & spectral characteristics are closerly related***

***WG2 Question #2:  Can compositional characteristics of large SEP events be related to specific features of the solar source?***

- A.J. Tylka/NRL, LWS/CDAW on SEPs, WG2

- 23 July 2002

## Heavy-Ion Spectral Variability in Large SEP Events

***From ACE News #58 by Tylka, Cohen, Dietrich, Maclennan, Ng, & Reames***

- A.J. Tylka/NRL, LWS/CDAW on SEPs, WG2

- 23 July 2002

## Fe/O vs. Time --  These plots are available on the CDAW Event Matrix

***Fe/O vs. Time ******--  These plots are available on the CDAW Event Matrix***

***14 July 2000***

***14 July 2000***

***16 August 2001***

- A.J. Tylka/NRL, LWS/CDAW on SEPs, WG2

- 23 July 2002

## Energy-Dependence of Event-Integrated Fe/O-- also available on the CDAW Event Matrix

***Largest GLE of Cycle 23***

- A.J. Tylka/NRL, LWS/CDAW on SEPs, WG2

- 23 July 2002

## Event-to-Event Variability in Energy-Dependent Fe/O:Can we find feature(s) of the solar sources that explain this variability?

- A.J. Tylka/NRL, LWS/CDAW on SEPs, WG2

- 23 July 2002

## Events with highly-suppressed Fe/O at high energies

***Events with highly-suppressed Fe/O at high energies***

- A.J. Tylka/NRL, LWS/CDAW on SEPs, WG2

- 23 July 2002

## Spectral Origin of Highly Suppressed Fe/O at High Energies

***Spectral Origin of Highly Suppressed Fe/O at High Energies***

***Fits to Ellison-Ramaty Form:  F******x******(E) ~ E******-************ ******exp(-E/E******0x******)***

***Event-Integrated O & Fe Energy Spectra:  24 September 2001 Event***

- A.J. Tylka/NRL, LWS/CDAW on SEPs, WG2

- 23 July 2002

## Event-Integrated O & Fe Energy Spectra

*08 November 2000*

*20  April 1998*

***Both O & Fe are reasonably well fit by E-R form ******except < 0.5 MeV/nuc***
***But Fe has a smaller e-folding energy, correspnding to QFe ~10.***

- A.J. Tylka/NRL, LWS/CDAW on SEPs, WG2

- 23 July 2002

## More Event-Integrated Oxygen Spectra

*14 July 2000*

*04 November 2001*

*22 November 2001*

***Reasonably well-fit to Ellison-Ramaty Form***
***Morphologically similar to the previous events***

- A.J. Tylka/NRL, LWS/CDAW on SEPs, WG2

- 23 July 2002

## But ...very different energy dependence in Fe/O

- A.J. Tylka/NRL, LWS/CDAW on SEPs, WG2

- 23 July 2002

## Event-Integrated Iron Spectra

*14 July 2000*

*04 November 2001*

*22 November 2001*

***Not well-fit to Ellison-Ramaty Form***

- A.J. Tylka/NRL, LWS/CDAW on SEPs, WG2

- 23 July 2002

## Q:  Why is Fe/O different in these events, even though oxygen spectra are similar?

***95%***
***SW ST***

***Tylka et al,  Ap. J. Letters, 558, L69-L63, (2001)***

***5%***
***Rem. Flare ST***

***A:   Fe are accelerated out of  a broader distribution of charge states in these events, e.g.******    ******remnant flare suprathermals in the source population.***

***Bastille Day 2000 Event***

- A.J. Tylka/NRL, LWS/CDAW on SEPs, WG2

- 23 July 2002

## Implication:  Energy-Dependent Charge States

**Consistent with Bastille Day  <Q****Fe****> from SEPICA**** ****and SAMPEX.**** **
**Compare with <Q****Fe****> from other events:**
**1992 event remarkably similar to Bastille Day event.**** **
**1997 November 6 has very strong energy dependence below ~2 MeV/nuc.**
**Probably cannot be reproduced by this model. **
** ****Due to stripping in low corona.  ****(Reames et al 1999; Barghouty & Mewaldt 1999, 2000; Stovpyuk & Ostryakov 2001).**
**Another calculation: dashed curve:**
**Same source mixture **
**But 10x larger e-folding energies.**
**     ****(e.g. Sept 1989 – Lovell et al.  1998)**
**Agrees with 1989 Q****Fe**** measurements **
**     **

***Tylka et al,  Ap. J. Letters, 558, L69-L63, (2001)***

- A.J. Tylka/NRL, LWS/CDAW on SEPs, WG2

- 23 July 2002

## There are 48 events on the CDAW Event List.So far, we’ve looked at 6.  Why these 6?

| CDAW # | Date | Rank by >30 MeV Event-Integrated Proton Fluence | Rank by >10 MeV Peak Proton Flux |
| --- | --- | --- | --- |
| 15 | 2000 Jul 14 | 1 | 2 |
| 43 | 2001 Nov 04 | 2 | 1 |
| 22 | 2000 Nov 08 | 3 | 4 |
| 39 | 2001 Sep 24 | 4 | 5 |
| 45 | 2001 Nov 22 | 5 | 3 |
| 3 | 1998 Apr 20 | 6 | 7 |

***There are 48 events on the CDAW Event List.******So far, we’ve looked at 6.  ******Why these 6?***

- A.J. Tylka/NRL, LWS/CDAW on SEPs, WG2

- 23 July 2002

## Another Problem:  What’s going on in this event?

- A.J. Tylka/NRL, LWS/CDAW on SEPs, WG2

- 23 July 2002

## Complicated behavior not due to multiple injections!

***Complicated behavior not due to multiple injections!***

***Hourly Profiles: 2001 15 April 0600 UT -18 Apr 1200 UT ***

- A.J. Tylka/NRL, LWS/CDAW on SEPs, WG2

- 23 July 2002

## Many events show similar behavior:

***Seen in 25 -50%  of large SEP event. ***
***Appears over a wide range of event sizes***
***Appears over a wide range of longitudes***

- A.J. Tylka/NRL, LWS/CDAW on SEPs, WG2

- 23 July 2002

## Event-Integrated Energy Spectra in the 15 April 2001 Event

***Event-Integrated Energy Spectra in the 15 April 2001 Event***

- A.J. Tylka/NRL, LWS/CDAW on SEPs, WG2

- 23 July 2002

## A Clue: Energy-Dependent Fe Charge States ?

***SAMPEX Charge State Measurements:***
***MAST:  Labrador et al., Spring 2002 AGU***
***LICA:  Mazur et al, Fall 2001 AGU***

***A Clue: Energy-Dependent Fe Charge States ?***

***( Limited ) geomagnetic measurements from SAMPEX***
***Indirect measurements from Time-to-Maximum Analysis  (Dietrich & Tylka, 2002)***

- A.J. Tylka/NRL, LWS/CDAW on SEPs, WG2

- 23 July 2002

## Not all events show dramatic energy-dependence in Fe/O...

***Not all events show dramatic energy-dependence in Fe/O...***

***(Biggest Flare in the CDAW List)***

***(Distant Backside Source?)***

- A.J. Tylka/NRL, LWS/CDAW on SEPs, WG2

- 23 July 2002

## Hypothesis:  Two types of large SEP Events, --based on spectral, compositional, and QFe characteristics:

***Type A  (eg., 20Apr98, 14Jul00)***
***Ellison-Ramaty spectra, except for transport-distortions at low energies***
***Fe/O generally falls with increasing energy***
***“******Trivial” energy dependence in QFe , indicating acceleration occurred only in low-density regions.***
***The largest events fall in this category.***

***Type B: (e.g., 15Apr01)***
***Power-law spectra, apart from transport-distortions at low energies.***
***“******knees” presumably at event higher energies***
***Fe/O rises with increasing energy, due to harder Fe spectrum***
***Strong energy dependence in QFe, perhaps due to stripping during acceleration in a high-density region***

***(WG1) Are there observable differences in the characteristics of the solar sources? ***
***For example, in timing, indicating acceleration beginning at different coronal altitudes?***
***(WG2) What physics factors govern the spectral/size characteristics?***

- A.J. Tylka/NRL, LWS/CDAW on SEPs, WG2

- 23 July 2002

## Detour: What about flare-accelerated (a.k.a. “impulsive”) events?

***~10% in 14Apr01 Event, ****** <2% (upper limit) in others***

***Detour: What about flare-accelerated (a.k.a. “impulsive”) events?***

***14 April 2001:  The Largest Impulsive Event of Cycle 23 (?)***

- A.J. Tylka/NRL, LWS/CDAW on SEPs, WG2

- 23 July 2002

## The 14 April 2001 Flare-Accelerated SEP Event

***Inferred Charge State: <QFe> = 25.8 ***_***+***_*** 2.3***

***The 14 April 2001 Flare-Accelerated SEP Event***

***Fe & O spectra nearly identical over entire energy range***
***Fe/O strongly enhanced at ~12x coronal***
***Time–to-Maximum independent of species:  all fully-ionized.***

- A.J. Tylka/NRL, LWS/CDAW on SEPs, WG2

- 23 July 2002