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Multipoint Observations of 3 He-rich SEP Events Since the Launch of STEREO PowerPoint PPT Presentation


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Multipoint Observations of 3 He-rich SEP Events Since the Launch of STEREO. M.E. Wiedenbeck, JPL/Caltech Thanks to: the ACE/ULEIS &SIS Teams and the STEREO/LET, SIT, & SEPT Teams. Longitudinal Spread of SEPs from 3 He-rich Events

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Multipoint Observations of 3 He-rich SEP Events Since the Launch of STEREO

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Multipoint observations of 3 he rich sep events since the launch of stereo

Multipoint Observations of 3He-rich SEP Events Since the Launch of STEREO

M.E. Wiedenbeck, JPL/Caltech

Thanks to:

the ACE/ULEIS &SIS Teams and

the STEREO/LET, SIT, & SEPT Teams

ACE/SOHO/STEREO/Wind Workshop


Multipoint observations of 3 he rich sep events since the launch of stereo

  • Longitudinal Spread of SEPs from 3He-rich Events

  • single spacecraft studies looked at longitudinal difference between point of SEP observation and site of the flare from which the particles were thought to have been released

  • complicated by the fact that 3He-rich events are often associated with small x-ray flares, so making the association is sometimes difficult

  • one of the goals of STEREO is to investigate the characteristics of individual SEP events from multiple points of observation

Number of Events

Reames 1999

2σ ~ 40°

Longitude

ACE/SOHO/STEREO/Wind Workshop


Multipoint observations of 3 he rich sep events since the launch of stereo

  • Fraction of Time with 3He Present Near 1 AU – Solar Cycle Variation

  • the first several years of the STEREO mission have characterized by very low solar activity

  • the number of 3He-rich events available for study has been small, but the chance of confusing different events is significantly reduced

  • 3He-rich SEP activity has sharply increased in the past 6 months

STEREO Launch

ACE ULEIS & SIS

points: individual Bartels rotation curve: 7-rotation averages

ACE/SOHO/STEREO/Wind Workshop


Multipoint observations of 3 he rich sep events since the launch of stereo

  • 3He Observed with ACE: Solar Minimum--Solar Maximum Comparison

  • at solar maximum there are lots of 3He-rich events

  • at solar minimum 3He-rich events are rare—provides a better opportunity to correlate events between different spacecraft without (much) confusion

Solar Minimum

Solar Maximum

small 3He-rich event

ACE/SOHO/STEREO/Wind Workshop


Multipoint observations of 3 he rich sep events since the launch of stereo

3He rich Events at ACE, STEREO-Ahead, and STEREO-Behind

ticks indicate days with 3He-rich SEPs present

AHEAD

±20°

ACE

  • Data sources:

  • STEREO-A & -B: LET, 2.3-3.8 MeV/nuc

  • ACE: ULEIS, 0.2-1 MeV/nuc

BEHIND

ACE/SOHO/STEREO/Wind Workshop


Multipoint observations of 3 he rich sep events since the launch of stereo

  • 3He rich Events at ACE, STEREO-Ahead, and STEREO-Behind

  • an event observed on both STEREO spacecraft and on ACE

AHEAD

±20°

ACE

BEHIND

ACE/SOHO/STEREO/Wind Workshop


Multipoint observations of 3 he rich sep events since the launch of stereo

Event Observed over a Wide Range of Heliographic Longitudes

  • 3-4 Nov 2008 event

  • the STEREOs were located ±41° from ACE

  • electrons were observed at all three spacecraft using STEREO/SEPT and ACE/EPAM

  • 3He and heavy ions with enhanced Fe/O were observed at STEREO-B and ACE

  • the lack of an ion detection at STEREO-A might be due to sensitivity limitations

  • results discussed in Wiedenbeck et al. 2010, SW12 Proceedings

ACE/SOHO/STEREO/Wind Workshop


Multipoint observations of 3 he rich sep events since the launch of stereo

  • 3He rich Events at ACE, STEREO-Ahead, and STEREO-Behind

  • events in the first quarter of 2010

AHEAD

±20°

ACE

BEHIND

ACE/SOHO/STEREO/Wind Workshop


Multipoint observations of 3 he rich sep events since the launch of stereo

  • Increased Rate of 3He-rich Events in Early 2010

  • see numerous events, some of which overlap in time

  • In some cases there are approximate time coincidences (e.g., Feb 13-15), but often there are not

  • these 3He-rich events have very low intensity compared to some events observed near solar maximum; with larger events, establishing that different spacecraft are observing the same event should be easier

ACE/SOHO/STEREO/Wind Workshop


Multipoint observations of 3 he rich sep events since the launch of stereo

  • Improving Reliability of Event Associations between Different Spacecraft

  • A variety of event characteristics can be compared to improve confidence in associations between events detected at different spacecraft:

  • timing of onset

  • timing of release from the Sun (onset time corrected for transit time based on velocity dispersion)

  • fluence

  • details of time-intensity profile

  • energy spectra

  • anisotropy

  • associated impulsive electron events

  • ion composition (3He/4He, Fe/O, etc.)

  • Useful comparisons with solar context:

  • jets associated with the flare event

  • longitudinal spread of open field from active region from PFSS model

  • Larger events are needed to take advantage of many of these comparisons.

ACE/SOHO/STEREO/Wind Workshop


Multipoint observations of 3 he rich sep events since the launch of stereo

  • STEREO/LET Observations of

  • 3He-rich SEPs at Solar Minimum

  • search for events in low energy (2.3-3.8 MeV/nuc) interval to improve ratio of He signal to background from ACRs & CIRs.

  • events are typically very small

  • to confirm event identification, look for 1) 3He spectrum that falls with increasing energy, 2) anisotropy, 3) velocity dispersion, and/or 4) coincident electron event

to Sun

STEREO-A SEPT electron measurements

ACE/SOHO/STEREO/Wind Workshop


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