James van Allen and his namesake NASA mission

Abstract In many ways, James A. Van Allen defined and “invented” modern space research. His example showed the way for government-university partners to pursue basic research that also served important national and international goals. He was a tireless advocate for space exploration and for the role of space science in the spectrum of national priorities

Jovian, Solar, and other Possible Sources of Radiation Belt Particles

It is well known that electrons, protons, and heavier ions can be accelerated to high energies (≳1 MeV) throughout the solar system by a variety of mechanisms. We review several of the sources of energetic ions and electrons that can produce enhanced fluxes of particles near the Earth's orbit. Solar energetic particles and particles accelerated at interplanetary shock waves are considered. We also review the properties and potential terrestrial influence of Jovian electrons. Recent measurements from the SAMPEX spacecraft in low-Earth orbit are examined to look for extraterrestrial sources of electrons and ions. We find clear evidence of both solar and Jovian electrons at high latitudes and at high altitudes around the Earth, but the durably trapped outer zone electron population seems best and most completely explained by an internal acceleration mechanism

Modulation of Jovian electrons at 1 AU during solar cycles 22-23

We report here, on the observation of Jovian electrons during the time period 1992 to 2002, using instruments on board SAMPEX and IMP8 at 1 AU. The Jovian electron flux diminished greatly from early 1996 to the end of 1997 and recovered subsequently and was observed till the end of 2001. The decrease in the Jovian flux was seen in three distinct instruments lasting for about two Jovian synodic periods. Such a dramatic and persistent decrease has not been observed before. The observed decrease could be due to changes at the source or variations in interplanetary conditions affecting transport of these particles. The latter may be solar cycle dependent as in the heliospheric modulation of cosmic rays. Long-term measurements from IMP8 suggest that solar cycle related propagation effects may not be responsible for the observed decrease. We suggest that either a change in the Jovian source strength or a softening of the Jovian electron energy spectrum produced the observed attenuation

Science Objectives and Rationale for the Radiation Belt Storm Probes Mission

The NASA Radiation Belt Storm Probes (RBSP) mission addresses how populationsof high energy charged particles are created, vary, and evolve in space environments,and specifically within Earths magnetically trapped radiation belts. RBSP, with a nominallaunch date of August 2012, comprises two spacecraft making in situ measurements for atleast 2 years in nearly the same highly elliptical, low inclination orbits (1.1 5.8 RE, 10).The orbits are slightly different so that 1 spacecraft laps the other spacecraft about every2.5 months, allowing separation of spatial from temporal effects over spatial scales rangingfrom 0.1 to 5 RE. The uniquely comprehensive suite of instruments, identical on the twospacecraft, measures all of the particle (electrons, ions, ion composition), fields (E and B),and wave distributions (dE and dB) that are needed to resolve the most critical science questions.Here we summarize the high level science objectives for the RBSP mission, providehistorical background on studies of Earth and planetary radiation belts, present examples ofthe most compelling scientific mysteries of the radiation belts, present the mission design ofthe RBSP mission that targets these mysteries and objectives, present the observation andmeasurement requirements for the mission, and introduce the instrumentation that will deliverthese measurements. This paper references and is followed by a number of companionpapers that describe the details of the RBSP mission, spacecraft, and instruments

Recurrent geomagnetic storms and relativistic electron enhancements in the outer magnetosphere: ISTP coordinated measurements

New, coordinated measurements from the International Solar-Terrestrial Physics (ISTP) constellation of spacecraft are presented to show the causes and effects of recurrent geomagnetic activity during recent solar minimum conditions. It is found using WIND and POLAR data that even for modest geomagnetic storms, relativistic electron fluxes are strongly and rapidly enhanced within the outer radiation zone of the Earth\u27s magnetosphere. Solar wind data are utilized to identify the drivers of magnetospheric acceleration processes. Yohkoh solar soft X-ray data are also used to identify the solar coronal holes that produce the high-speed solar wind streams which, in turn, cause the recurrent geomagnetic activity. It is concluded that even during extremely quiet solar conditions (sunspot minimum) there are discernible coronal holes and resultant solar wind streams which can produce intense magnetospheric particle acceleration. As a practical consequence of this Sun-Earth connection, it is noted that a long-lasting E\u3e1MeV electron event in late March 1996 appears to have contributed significantly to a major spacecraft (Anik E1) operational failure

Radiation belt electron acceleration by chorus waves during the 17 March 2013 storm

Abstract Local acceleration driven by whistler-mode chorus waves is fundamentally important for accelerating seed electron populations to highly relativistic energies in the outer radiation belt. In this study, we quantitatively evaluate chorus-driven electron acceleration during the 17 March 2013 storm, when the Van Allen Probes observed very rapid electron acceleration up to several MeV within ~12 hours. A clear radial peak in electron phase space density (PSD) observed near L* ~4 indicates that an internal local acceleration process was operating. We construct the global distribution of chorus wave intensity from the low-altitude electron measurements made by multiple Polar Orbiting Environmental Satellites (POES) satellites over a broad region, which is ultimately used to simulate the radiation belt electron dynamics driven by chorus waves. Our simulation results show remarkable agreement in magnitude, timing, energy dependence, and pitch angle distribution with the observed electron PSD near its peak location. However, radial diffusion and other loss processes may be required to explain the differences between the observation and simulation at other locations away from the PSD peak. Our simulation results, together with previous studies, suggest that local acceleration by chorus waves is a robust and ubiquitous process and plays a critical role in accelerating injected seed electrons with convective energies (~100 keV) to highly relativistic energies (several MeV)