The Solar Energetic Particles (SEP) Package consists of four separate instruments that cover the full solar energetic particle energy, flux and composition ranges needed to meet the STEREO science goals. The SEP instruments include

• Solar Electron Proton Telescope (SEPT)
• Suprathermal Ion Telescope (SIT)
• Low Energy Telescope (LET)
• High Energy Telescope (HET)

Together, the SEP instruments will measure electrons, protons, and heavier ions from several tens of keV to ~100 MeV (or MeV/nucleon).

SIT, LET and HET are packaged together with a SEP-CPU in the main SEP package on the spacecraft body, with SEPT east-west and north-south telescopes located in separate small boxes located to clear their fields of view. The SEP instrument fields of view generally contain the Parker-Spiral interplanetary magnetic field direction, with some also including the anti-spiral. SEPT north-south is designed to measure the particles that come along the highly inclined interplanetary fields that occur during passage of a disturbance resulting from a coronal mass ejection.

Click on the active areas on the image below for instrument descriptions for the IMPACT SEP package.

[HET] [LET] [SEPT] [SIT]

SEP Package Science Goals

• Use comparisons of SEP flux time series and energy spectra at the STEREO sites to confirm the global picture of SEP populations
• Use composition information to sort out flare and interplanetary origins across ICME structures, with the help of flare images
• Use 3D information deduced from SWAVES and modeling of the ICME to globally model the SEP acceleration
• Test schemes for SEP prediction and use of SEP to forecast ICME impact

SEP Measurments

IMPACT coverage of the solar energetic proton spectrum. Ion composition and SEP electron coverage are indicated at the bottom

SEP Time Profile Dependence on Ion Composition

Figure adapted from Ng, Reames and Tylka, GRL, 1999, and Reames, Ng and Tylka, ApJ Lett, 2000

TOP: time profiles for different SEP ion species
BOTTOM: time profiles of ion abundance ratios

SEP Time Profile Dependence on Location

Figure from Reames, Kahler and Ng, ApJ Lett, 1997

TOP: time profiles for different SEP ion species depending on location
BOTTOM: energy spectra at different times

Flare Intensity v. Ion Composition (similar to SIT/LET)

Flux and Ion Composition from GOES & WIND (similar to SIT/LET)

Diagram of Proton Events (similar to HET/SEPT)

SWEA | STE | MAG | SEPT | SIT | LET | HET
Boom Suite | SEP Package