SAMPEX -- Solar Anomalous and Magnetospheric Particle Explorer

MISSION REQUIREMENTS

The following overview was taken from the SAMPEX Requirements Document:

The primary scientific objectives are to measure the elemental and isotopic composition of solar energetic particles, anomalous cosmic rays, and galactic cosmic rays over the energy range from ~1 to several hundred MeV per nucleon. By determining the dependence of the fluxes on geomagnetic cutoff rigidity over the polar orbit, the ionization state of the anomalous component will be determined, along with the mean ionization state of solar energetic particles. The dependence of these fluxes on the solar activity cycle will be measured by carrying out continuous observations over an extended (3 year) portion of the current activity cycle. A further primary objective is to determine flux levels and local time dependence of relativistic precipitating magnetospheric electrons during a period of declining solar activity.

Secondary objectives include providing support data and undertaking correlative studies with other groups concerning, for example, (a) examination of fluxes, composition, and spectra in gamma-ray line flares, in collaboration with SMM, GRO, Solar-A, and balloon experiments such as those in the MAX '91 program; (b) comparison of precipitating electron observations with LANL experiments on geostationary satellites and CRRES; comparison with atmospheric ozone measurements by the SAGE II sensor system (LaRC, NASA) and UARS, and with balloon and rocket data, and ground based riometer and Schumann resonance monitoring stations; (c) modulation studies of galactic cosmic rays, done in collaboration with Pioneer, Voyager, Ulysses, and Galileo; and (d) studies of the acceleration and propagation of impulsive solar particles, in collaboration with Type III radio burst studies, and deep space observations taken on Ulysses and Galileo.

On-Orbit Science Observations

Target Characteristics

Energetic particles with origins on the Sun, in the Local Interstellar Medium, and electrons within the earth's magnetosphere are being observed on this mission. The energetic particles are deflected by the earth's magnetic field and their trajectory measured by the HILT, LEICA, and MAST instruments. Knowledge of the spacecraft location within the earth's magnetic field and the spacecraft attitude with respect to an inertial reference frame is needed to determine (post flight) the origin of the measured particles. The majority of the charged particles measured will be observed at magnetic latitudes greater than 60 degrees.

Principal Observations

The majority (~90%) of the mission science data will be acquired when the instruments are looking along the magnetic field line in the general zenith direction while overflying the earth's magnetic poles. The remaining science data is taken at lower magnetic latitudes with the instruments viewing at elevations that vary between local horizontal and zenith. Precipitating electron measurements will be made at these lower magnetic latitudes by the PET instrument.

Science Results and Publications

(as of June 21, 1994)

SAMPEX -- major discoveries published in refereed journals

• Anomalous Cosmic Rays
  • Discovery of the precise location of trapped anomalous cosmic rays in the magnetosphere.
  • Measurement of the elemental composition of trapped ACR, including C, N, 0, and Ne.
  • "Early" return of the anomalous cosmic ray component in the 1992 solar minimum period, well before the relativistic ions. LI>Discovery that trapped anomalous cosmic rays are the dominant component of high energy (>10 MeV/nuc) ions heavier than He in the magnetosphere.
• Solar Energetic Particles
  • Determination of "normal" solar system isotopic abundances for Ne and Mg in the large solar particle events of October/November 1993.
  • Excesses (factor 4) of neutron rich isotopes of Ne and Mg in 3He-rich solar particle events.
• Magnetospheric Physics
  • Discovery that magnetospheric electrons are globally accelerated in association with the impact of high speed solar wind streams.
• Other
  • Demonstration that NASA can develop, test, and launch a successful scientific satellite within a period of three years.

SAMPEX--major discoveries reported at scientific meetings but not yet published in refereed journals

• Anomalous Cosmic Rays
  • Determination that ACR nitrogen, oxygen, and neon are singly charged.
  • Determination that the upper limit of ACR O2+ is less than 10% of the total ACR oxygen, thus limiting acceleration time scales in the heliosphere.
  • Discovery that the interplanetary spectrum of anomalous oxygen extends to at least 100 MeV/nucleon, implying that the ACR acceleration mechanism (termination shock?) accelerates particles to at least 1.6 GeV.
  • Discovery (in collaboration with Voyager, Ulysses, and Pioneer spacecraft) that the intensity of ACR oxygen ions increases with heliolatitude during the 1993 approach to solar minimum, in contrast to the opposite behavior observed at the previous solar minimum; this confirms predictions of one class of particle transport theories which include particle drift.
  • Demonstration (in collaboration with Voyager, Ulysses, and Pioneer spacecraft) that the radial gradients of ACR are much smaller in the current solar minimum than during the previous solar minimum in 1987.
• Solar Energetic Particles
  • Demonstration that high-energy (> 25 MeV/nucleon) Si and Fe ions in the large solar particle events of late 1992 were in partially ionized charge states, similar to those reported previously for energies near 1 MeV/nucleon.
• Magnetospheric Physics
  • Evidence for deep dielectric charging as a likely cause of the January 1994 Anik spacecraft anomalies.
  • Discovery that remnants of relativistic electron belt generated by the 24 March 1991 interplanetary shock persisted until 1993.
  • Discovery of a radiation belt at L=1.2 composed of roughly equal amounts of 3He and 4He.
  • Discovery of high-energy (>50 MeV/nucleon) deuterium trapped in the magnetosphere.
  • Discovery that relativistic electron precipitation routinely has temporal structure at the bounce period.
• Middle Atmosphere
  • Discovery that electron flux variations at SAMPEX altitudes are well correlated with solar wind variations, providing a solar-magnetosphere-middle atmosphere coupling.
  • Demonstration that the primary relativistic electron flux inputs into the middle atmosphere occur in the range 3.5Discovery that relativistic electron energy inputs into the middle atmosphere are asymmetric between the northern and southern hemispheres, with the largest inputs occurring in the southern hemisphere. Within each hemisphere, there are preferred longitudes for the energy inputs.
  • Indication that relativistic precipitating electrons provide a significant source of odd nitrogen to the middle atmosphere and can impact middle atmospheric ozone.
• Galactic Cosmic Rays
  • Improved demonstration that the isotopic composition galactic cosmic rays and anomalous component differ significantly.

SAMPEX--Refereed Journal Articles and Conference Proceedings

1990 Conference Proceedings

1. Mason, G.M., D.N. Baker, J.B. Blake, L.B. Callis, D.C. Hamilton, D. Hovestadt, B. Klecker, R.A. Mewaldt, M. Scholer, E.C. Stone, and T.T. von Rosenvinge. SAMPEX Mission Overview. in Particle Astrophysics: the NASA Cosmic Ray Program for the 1990s and Beyond. 1990. New York: American Institute of Physics. 1990. AlP Conference Proceedings #203: p.44-47.

1993 Refereed Journal Publications

1. Baker, D.N., G.M. Mason, 0. Figueroa, G. Colon, J.G. Watzin, and R.M. Aleman, An Overview of the Solar, Anomalous, and Magnetospheric Particle Explorer (SAMPEX) Mission. IEEE Trans. Geosci. & Remote Sens., 1993. 31: p. 531-541.

2. Cook, W.R., A.C. Cummings, J.R. Cummings, T.L. Garrard, B. Kecman, R.A. Mewaldt, R.S. Selesnick, E.C. Stone, D.N. Baker, T.T. von Rosenvinge, J.B. Blake, and L.B. Callis, PET: A Proton/Electron Telescope for Studies of Magnetospheric, Solar, and Galactic Particles. IEEE Trans. Geosci. and Remote Sens., 1993. 31: p. 565-571.

3. Cook, W.R., A.C. Cummings, J.R. Cummings, T.L. Garrard, B. Kecman, R.A. Mewaldt, R.S. Sdesnick, E.C. Stone, and T.T. von Rosenvinge, MAST: A Mass Spectrometer Telescope for Studies of the Isotopic Composition of Solar, Anomalous, and Galactic Cosmic Ray Nuclei. IEEE Trans. Geosi, and Remote Sens., 1993. 31: p. 557-564.

4. Cummings, J.R., A.C. Cummings, R.A. Mewaldt, R.S. Selesnick, E.C. Stone, and T.T. von Rosenvinge, New evidence for anomalous cosmic rays trapped in the magnetosphere. Geophys. Res. Letters, 1993. 20: p. 2003-2006.

5. Klecker, B., D. Hovestadt, M. Scholer, H. Arbinger, M. ErtI, H. Kaestle, E. Kuenneth, P. Laeverenz, E. Seidenschwang, J.B. Blake, N. Katz, and D.J. Mabry, HILT: A Heavy Ion Large Area Proportional Counter Telescope for Solar and Anomalous Cosmic Rays. IEEE Trans. Geosci. and Remote Sens, 1993. 31: p. 542-548.

6. Mabry, D.J., S.J. Hansel, and J.B. Blake, The SAMPEX data Processing Unit (DPU). IEEE Trans. Geosci. and Remote Sens., 1993. 31: p. 572-574.

7. Mason, G.M., D.C. Hamilton, P.H. Walpole, K.F. Heuerman, T.L. James, M.H. Lennard, and J.E. Mazur, LEICA: A Low Energy Ion Composition Analyzer for the study of Solar and Magnetospheric Ions. IEEE Trans. Geosci. and Remote Sens., 1993. 31: p. 549-556.

8. Mewaldt, R.A., A.C. Cummings, J.R. Cummings, E.C. Stone, B. Klecker, D. Hovestadt, M. Scholer, G.M. Mason, J.E. Mazur, D.C. Hamilton, T.T. von Rosenvinge, and J.B. Blake, The return of the anomalous cosmic ray component to 1 in 1992. Geophys. Res. Letters, 1993. 20: p. 2263-2266.

9. Selesnick, R.S., A.C. Cummings, J.R. Cummings, R.A. Leske, R.A. Mewaldt, E.C. Stone, and T.T. von Rosenvinge, Coronal Abundances of Neon and Magnesium Isotopes from Solar Energetic Particles. Astrophys. J. (Letters), 1993. 418: p. L45-L48.

1993 Conference Proceedings

1. Cummings, J.R., A.C. Cummings, R.A. Mewaldt, R.S. Selesnick, E.C. Stone, and T.T. von Rosenvinge. New evidence for anomalous cosmic rays trapped in the magnetosphere. in Proc. 23rd Internat. Cosmic Ray Conf (Calgary). 1993. Calgary: 1993. 3: p. 428-431.

2. Leske, R.A., A.C. Cummings, J.R. Cummings, R.A. Mewaldt, R.S. Selesnick, E.C. Stone, and T.T. von Rosenvinge. Measurements of the Composition of Galactic Cosmic Rays on SAMPEX. in Proc. 23rd Internat. Cosmic Ray Conf (Calgary). 1993. 1993. 1: p. 551-554.

3. Mewaldt, R.A., A.C. Cummings, J.R. Cummings, E.C. Stone, and T.T. von Rosenvinge. The Return of the Anomalous Component in 1992. in Proc. 23rd Internat. Cosmic Ray Conf (Calgary). 1993. 1993. 3: p. 404-407.

4. Selesnick, R.S., A.C. Cummings, J.R. Cummings, R.A. Leske, R.A. Mewaldt, E.C. Stone, and T.T. von Rosenvinge. Isotopic Composition of Solar Energetic Particles Observed in the October/November, 1992 Solar Flares. in Proc. 23rd Internat. Cosmic Ray Conf (Calgary). 1993. 1993. 3: p.392-395.

1994 Refereed Journal Publications

1. Baker, D.N., J.B. Blake, L.B. Callis, J.R. Cummings, S. Kanekal, B. Klecker, R.A. Mewaldt, and R.D. Zwickl, Relativistic electron acceleration and decay time scales in the inner and outer radiation belts: SAMPEX. Geophys. Res. Letters, 1994. 21: p. 409-412.

2. Cummings, A.C., J.R. Cummings, R.A. Mewaldt, E.C. Stone, B. Blake, M. Fraenz, B. Klecker, D. Hovestadt, and W.R. Webber, Observations of anomalous cosmic rays in the heliosphere from the SAMPEX, Ulysses, Voyager, and Pioneer spacecraft. Adv. Space Res., 1994. 30th COSPAR Congress - June 1994.

3. Mason, G.M., J.E. Mazur, and D.C. Hamilton, Heavy ion isotopic anomalies in 3He-rich solar particle events. Astrophys. J., 1994. 425: p. 843-848.

4. Mewaldt, R.A., SAMPEX Observations of High-Energy Heavy Ions in the Magnetosphere. Adv. Space Res., 1994. 30th COSPAR Assembly June 1994.

5. Selesnick, R.S., A.C. Cummings, J.R. Cummings, R.A. Mewaldt, E.C. Stone, and T.T. von Rosenvinge, Geomagnetically Trapped Anomalous Cosmic Rays. J. Geophys. Res, 1994. submitted, May 1994.

OTHER MISSION INFORMATION

More mission info.

EnviroNET Radiation Survey of the SAMPEX mission.