James J. Connell
Cosmic Ray Physics
Joint Appointment Department of Physics
Ph.D., Washington University
My principal research interest is measuring energetic particle radiation in space. This includes Galactic cosmic rays which fill the Galaxy and are probably accelerated by supernovae shocks; Solar energetic particles which are accelerated by events on the Sun and by shocks in interplanetary space; and the anomalous cosmic rays, which are believed to be interstellar neutral atoms that drift into the Solar System, become ionized and are carried by the Solar wind out to the termination shock (a shock formed where the Solar wind becomes sub-sonic) where they undergo acceleration.
As recently announced (press release and Spheres article), I am the principal investigator for the High Energy Particle Sensor (HEPS) for the National Polar-orbiting Operational Environmental Satellite System (NPOESS). HEPS was to be part of the Space Environmental Sensor Suite (SESS). An ADIS (see below) based instrument, HEPS was to measure protons from 10 MeV to ~320 MeV and heavy ions through Ni at corresponding energies (AGU poster). Owing to major cost overruns on other parts of NPOESS, HEPS is presently de-scoped. Recently, a very similar instrument was selected as the Energetic Heavy Ion Sensor (EHIS) for the Geostationary Operational Environmental Satellite (GOES-R) Program (press release). My colleague Cliff Lopate is principal investigator and I a co-investigator.
Much of my research involves the development of new and innovative instrumentation. The exigencies of space flight mean that instruments have to be very low in mass and power usage, and be extremely reliable. During graduate school, I worked on scintillating optical fibers for detecting cosmic rays with Bob Binns and Marty Israel at Washington University. Fibers of this kind have now been flown in the Cosmic Ray Ion Spectrometer (CRIS) on the Advanced Composition Explorer (ACE) spacecraft. New instrument concepts include my Angle Detecting Inclined Sensors (ADIS) system. ADIS has now been tested with an accelerator and proven successful (poster paper).
Scientifically, most of my work has been detailed measurements of the isotopic and elemental composition of Galactic cosmic rays using data from our High Energy Telescope (HET), on the Ulysses spacecraft. This involves the origins of cosmic rays and the chemical evolution of the Galaxy (nucleosynthesis) together with cosmic ray propagation in the Galaxy. As cosmic rays propagate through the Galaxy, some undergo nuclear collisions with material in the interstellar medium producing "secondary" cosmic rays. We study the propagation of cosmic rays by measuring these secondary cosmic rays. For example, some secondary cosmic ray nuclei are unstable (that is, they decay to other isotopes). From the longer lived unstable secondary isotopes, we can estimate how long cosmic rays are confined to the Galaxy. From our measurements of 10Be, 26Al and 36Cl we know cosmic rays spend a few tens of millions of years in the Galaxy.
I have also been involved in the study of cosmic ray modulation by the Solar wind, particularly the three dimensional structure of the Heliosphere, again mainly using data from Ulysses. Ulysses is a joint ESA/NASA mission to explore the polar regions of the Sun. Launched in Oct. 1990, Ulysses was sent to Jupiter to get a gravitational sling-shot into a high inclination Solar orbit. It passed first over the south and then the north poles of the Sun, becoming the first (and so far, only) spacecraft to reach such high Solar latitudes (> 80 degrees). It has now completed its second set of polar passes and we hope (pending funding) to complete a third set. That would permit us to observe the Sun during Solar minimum (first set of polar passes), Solar maximum (second set of passes) and again at minimum, but after the Sun's magnetic field has reversed (third set).