U13A-0034
The Energetic Particle, Composition, and Thermal Plasma Instrument Suite on the Radiation Belt Storm Probes Mission: Instrument Overview and Science Investigation Summary
We provide an overview of the instruments and a summary of the science goals of the Energetic particle, Composition, and Thermal plasma (ECT) Suite, a comprehensive, coordinated science investigation in development for NASAs Radiation Belt Storm Probes (RBSP) mission. RBSP-ECT comprises six instruments on each of the two RBSP spacecraft and provides collectively five of the six charged particle measurements required to achieve RBSP mission success. The ECT suite science goals centrally address the top-level RBSP science objective: to provide understanding, ideally to the point of predictability, of how populations of relativistic electrons and penetrating ions in space form or change in response to variable inputs of energy from the Sun. Three ECT sensor types provide measurements of not only the core radiation belt electrons and ions, but also of the lower energy charged particles in the inner magnetosphere that control the processes that accelerate, transport, and lead to the loss of radiation belt particles. The Helium-Oxygen- Proton-Electron (HOPE) sensor measures the lowest energy populations. The Magnetic Electron Ion Spectrometer (MagEIS) sensor (comprised of four instruments) measures medium energy to relativistic electron populations as well as medium energy bulk ions. The Relativistic Electron Proton Telescope (REPT) measures ultra-relativistic electrons and high energetic protons. An ECT Science Operations Center (SOC) and Science Data Center (SDC) unify the ensemble HOPE, MagEIS, and REPT measurements into a single data set in order to deconvolve the complex, coupled drivers required to understand radiation belt dynamics. A diverse, collaborative, and integrated group of scientists from 11 institutions make up the ECT Suite science team, and provide the experimental, data processing and analysis, modeling, theory, and space weather application experience required to meet ECT and RBSP science objectives. We present a status report on ECT suite instrument and SOC/SDC development; we discuss how ECT measurements will enable science closure on RBSP mission objectives; and we describe data and analysis products that will be available to the broad scientific community to accomplish that science. The RBSP mission is currently slated for launch in late 2011.
U13A-0035
The Electric Field and Waves (EFW) Instrument on the NASA Radiation Belt Storm Probes (RBSP) Mission: Investigating the Physical Mechanisms of Energetic Particle Acceleration in the Inner Magnetosphere
Measurement of the DC and low-frequency electric field in the inner magnetosphere is a crucial element of any attempt to determine the physical mechanisms of energization, transport, and loss of energetic particles in the terrestrial radiation belts. Each of the two satellites in the NASA Radiation Belt Storm Probes (RBSP) mission will be equipped with a three-axis E-field instrument, the Electric Fields and Waves (EFW) instrument (J. R. Wygant, PI). This instrument provides direct waveform, spectral, and interferometric measurements of DC and low-frequency electric fields and fluctuations, as well as supports coordinated measurements of waveform and spectral data of both the electric and magnetic fields through collaboration with the Electric and Magnetic Field Instrument Suite with Integrated Science (EMFISIS) instrument. The requirements and capabilities of the EFW instrument will be described and compared against previous suites of field instruments flow in the inner magnetosphere, and the application of those measurements to salient unresolved aspects of energetic particle dynamics in the inner magnetosphere and terrestrial radiation belts will be explored.
U13A-0036
Wave Science with the Electric and Magnetic Field Instrument Suite with Integrated Science (EMFISIS) on the Radiation Belt Storm Probes
The physics of the creation and loss of radiation belt particles is intimately connected to the electric and magnetic fields of waves which mediate these processes. A large range of field regimes are involved in this physics from ring current magnetic fields to microscopic kinetic interactions such as whistler-mode chorus waves with energetic electrons. To measure these key field interactions, NASA has selected the Electric and Magnetic Field Instrument Suite and Integrated Science (EMFISIS) on the Radiation Belt Storm Probes (RBSP). EMFISIS is an integrated set of instruments consisting of a tri-axial fluxgate magnetometer (MAG) and a Waves instrument which includes a tri-axial search coil magnetometer and measures AC electric and magnetic fields from 10 Hz to 400 kHz. The broad frequency range of the Waves instrument enables the identification of resonances and cutoffs from Waves to achieve high cadence, accurate plasma density measurements that are essential to RBSP theory and modeling efforts. In combination with the selected double probe electric field and particle investigations on RBSP, EMFISIS will provide the essential measurements necessary to open the frontier of predictive capability for the Earth's highly variable radiation belts. We discuss of the key scientific goals of the EMFISIS investigation with particular attention to the wave physics of the radiation belts.
U13A-0037
Proton Spectrometer Belt Research (PSBR)
The National Reconnaissance Office (NRO), NASA, the Air Force Research Laboratory (AFRL), the Aerospace Corporation, the Los Alamos National Laboratory (LANL) and the Naval Research Laboratory (NRL) have jointly formed the Proton Spectrometer Belt Research (PSBR) program to meet two primary objectives: to measure the high-energy proton spectrum by placing the Relativistic Proton Spectrometer (RPS) instrument on board the Radiation Belt Storm Probes (RBSP) spacecraft to measure the inner Van Allen belt protons with energies from 50 MeV to 2 GeV, and to produce the next generation radiation belt models. Presently, the intensity of trapped protons with energies beyond about 150 MeV is not well known and thought to be underestimated in existing specification models. Such protons are known to pose a number of hazards to astronauts and spacecraft; including total ionizing dose, displacement damage, single event effects, and nuclear activation. The RPS addresses a priority highly ranked by the scientific and technical community and will extend the measurement capability of the RBSP mission to a range beyond that originally planned. The PSBR program will use the RPS data, coupled with other data sets, to upgrade existing radiation belt models, significantly improving the radiation hazards specified by increasing the spectral and spatial coverage, and the time-correlated probability of occurrence statistics, quantifying the model accuracy and uncertainty.
U13A-0038
Balloon Array for RBSP Relativistic Electron Losses (BARREL) Piggyback Test Flight
BARREL is a multiple long duration balloon (LDB) project that will study radiation belt electron losses during the RBSP mission. Each balloon payload will include a three-inch by three-inch NaI scintillator that measures bremsstrahlung X-rays produced by electrons as they interact with neutrals in Earth's atmosphere. This instrument design has proven effective in characterizing MeV precipitation during previous balloon campaigns such as the MINIS campaign in January 2005. Each payload will also carry a commercial DC magnetometer. A series of test flights have been scheduled prior to the 2012 and 2013 BARREL campaigns to assess various subsystem performances and collect science data. The first of these test flights is a NASA Columbia Scientific Balloon Facility (CSBF) piggyback launch from McMurdo, Antarctica in December 2008/January 2009. This test payload will include a new solar power system, designed to reduce the weight and increase the lifetime of each BARREL payload. The power supply voltage ranges, instrument temperatures, and science instrument measurements will be screened during this winter's piggyback flight. We present an overview of the BARREL project science goals and plans for the piggyback flight this winter.
U13A-0039
Proton Spectra in the Inner Magnetosphere: Measurements from the TSX-5, HEO-1, HEO- 3 and ICO Satellites
Measurements of energetic protons made by the Compact Environment Anomaly Sensor (CEASE) on the TSX-5 satellite in low-Earth orbit from Jun 2000 to Jul 2006 and by dosimeters on the HEO-1, HEO-3 and ICO satellites flying in the medium-Earth orbit regime from May 1994 to Jul 2007, Nov 1997 to Jul 2007, and Jan 2001 to Dec 2007, respectively, provide a long term picture of proton dynamics in the inner magnetosphere. Given that each of these detectors has a relatively small number of channels with broad integral energy response, spectral inversion algorithms are needed to extract information about the differential flux at a level of detail sufficient for the development of empirical radiation belt models. Assuming a power law spectra between 10 and 100 MeV with variable index and amplitude attached to an exponential with a fixed e-folding rate at higher energies, algorithms have been developed to determine the best-fit spectral parameters and variances for each measurement (5 to 15 sec time resolution) for all of the missions. Details of the algorithms will be presented and snapshots of the resultant spectra from each satellite data set will be shown for different phases of the solar cycle.
U13A-0040
New Measurements of Trapped Anomalous Cosmic Rays and Other Heavy Ions in the Inner Magnetosphere
Anomalous cosmic rays (ACR) are a sample of the local interstellar medium that originate as neutral atoms with first ionization potential greater than that of hydrogen. Once the atoms become singly ionized by solar ultraviolet radiation or charge exchange with the solar wind, they convect to the outer heliosphere, become accelerated to greater than 10 MeV/nucleon at the termination shock, and propagate back in to the inner heliosphere. The Earth's magnetosphere becomes a reservoir for ACR ions after the ions become further stripped in collisions with the upper atmosphere and are stably trapped near L=2 with long lifetimes. During the last solar cycle, observations from low-Earth orbit with SAMPEX and other satellites mapped the abundances and time dependence of the trapped ACR. Those observations revealed insights into the ACR acceleration process, the trapping process, as well as other elements (Mg-S and Fe) that might have originated as pickup ions from dust grains in the inner heliosphere. Radial diffusion of solar energetic particles into low L is also a potential source for trapped heavies near L=2. This paper reports new measurements of the trapped heavy ion abundances, energy spectra, and pitch angle distributions in the inner (L<3) magnetosphere made with the High Linear Energy Transfer (HiLET) sensor in highly elliptical Earth orbit. HiLET uses arrays of silicon detectors in multiple coincidence with high thresholds to eliminate backgrounds from penetrating protons and electrons. The energy range is ~3 to 30 MeV/nucleon (Z=8). Our measurement database begins in the spring of 2008, and therefore we are observing solar minimum conditions when the ACR and trapped ACR intensities are at their highest. Compared to the LEO measurements from the last solar cycle, HiLET has the advantage of sampling the heavy-ion environment in the inner magnetosphere near the magnetic equator where the trapped heavy ions have maximum intensity. We will report on the new findings and preliminary comparisons with previous LEO measurements and a model of the ACR trapping process.
U13A-0041
Quantifying the Role of Non-Adiabatic Processes in the Creation of the Outer Radiation Belt
We have reported (Fox et al., 2006) strong evidence that non-adiabatic (first invariant breaking) energization is required to explain the generation of Earth's outer electron radiation belt during intense storm events and also during more typical outer belt conditions. This evidence relies on the most conservative of assumptions that maximize the phase space densities of particle distributions adiabatically displaced in our models from the measured source population within the near-Earth magnetotail to the inner magnetospheric regions using initially only first adiabatic invariant transport, and subsequently first and second adiabatic invariant transport. Importantly, the phase space densities measured within the outer belt electron populations exceed the phase space densities of these adiabatically maximized source population distributions at energies > 1 MeV. By including the 2nd adiabatic invariant, we show that the angular distributions are strongly scattered during the transport and energization process. The scattering was so strong that we found it advisable to find another invariant in place of the combination of the 1st and 2nd. In this paper, we consider the isotropic invariant (Schulz, 1998). We compare the results of adiabatic transport followed by scattering against isotropic invariant transport. We find that this new approach demonstrates an even greater need for non- adiabatic processes with energies > 0.5 MeV profoundly affected. Below ~0.5 MeV the observed intensities are substantially below the adiabatic transport expectations. We test here the hypothesis that the lower-energy spectral intensities are constrained by Kennel-Petschek-type limits (Kennel and Petschek, 1966). The energization that electrons can acquire via non-adiabatic radial transport under these new constraints is determined using data from ISEE, and CRRES. Fox, N. J., B. H. Mauk, and J. B. Blake (2006), Role of non-adiabatic processes in the creation of the outer radiation belts, Geophys. Res. Lett., 33, L18108, doi:10.1029/2006GL026598. Kennel C. F. and Petschek H. E. Limit of stably trapped particle fluxes, J. Geophys. Res., 71, 1, 1-28, 1966. Schulz, M. (1998), Particle drift and loss rates under strong pitch angle diffusion in Dungey's model magnetosphere, J. Geophys. Res., 103, A1, 61-68
U13A-0042
Detailed Observations of the outer radiation belt with LANL GPS instruments
Los Alamos has been flying energetic particle detectors on the GPS constellation for two solar cycles. The
current instrument (CXD, Combined X-ray Dosimeter) has now been deployed on 9 GPS spacecraft and this
constellation is returning unprecedented high spatial resolution data of the outer radiation belts from L=4
outward, for energies > 100keV. We present here combined data from this constellation covering every 0.2
L-bin from L=4 to L=8 with a time resolution of better than 30 min.
These data show fast, global changes of the outer radiation belt with loss events as fast as out data time
resolution, across all observed L and all observed energies, even during relatively quiet time periods. These
observations are not consistent with current ideas on energetic electron loss (EMIC scattering,
magnetopause shadowing, outward diffusion).
Combining our observations with predicted plasmapause location further shows evidence of particle
acceleration in regions inside the plasmapause, which conflicts with current ideas of energization by whistler
mode waves - which occur outside the plasmapause.
U13A-0043
NOAA POES Observations of Relativistic Electron Precipitation during a Radiation Belt Depletion Event
We present POES observations of relativistic electron precipitation during an electron depletion event observed by GOES and GPS. On January 19, 2000 NOAA-15 passed very near the MAXIS balloon payload (L=4.7) which detected an intense duskside precipitation event (Millan et al., 2007). Recent work has shown that the NOAA MEPED proton detector responds to electrons above ~700 keV. We combine data from this high energy channel with data from the MEPED electron detector to examine the energy distribution and spatial extent of precipitation during this period. The results are compared with the MAXIS balloon observations.
U13A-0044
On the Loss of Relativistic Electrons at Geosynchronous Altitude: Its Dependence on Magnetic Configurations and External Conditions
In the present study we statistically examined geosynchronous magnetic configurations and external conditions that characterize the loss of geosynchronous MeV electrons. The loss of MeV electrons often takes place during magnetospheric storms, but a considerable fraction of loss events also takes place without any clear storm activity. It is found that irrespective of storm activity, the day-night asymmetry of the geosynchronous H (north-south) magnetic component is pronounced during electron loss events. For the loss process, the magnitude, rather than the duration, of the magnetic distortion appears to be important, and its effective duration can be as short as ~ 30 min. The solar wind dynamic pressure tends to be high and IMF BZ tends to be southward during electron loss events. Under such external conditions the dayside magnetopause moves closer to Earth, and the day-night magnetic asymmetry is enhanced. As a consequence the area of closed drift orbits shrinks. The magnetic field at the subsolar magnetopause, which is estimated from force balance with the solar wind dynamic pressure, is usually stronger than the nightside geosynchronous magnetic field during electron loss events. It is therefore suggested that geosynchronous MeV electrons on the night side are very often on open drift paths when geosynchronous MeV electrons are lost. Whereas the present result does not preclude the widely accepted idea that MeV electrons are lost to the atmosphere by wave-particle interaction, it suggests that magnetopause shadowing is another plausible loss process of geosynchronous MeV electrons.
U13A-0045
Magnetospheric Configurations During Relativistic Electron Dropout Events
We characterize how relativistic electrons are lost from the magnetosphere using global observations and models in order to better understand the dynamic variability of the radiation belts. We focus on relativistic electron dropout events during non-storm intervals like those identified by Onsager et al. [2007], because the magnetospheric response is much less complex than during storm times. Multi-spacecraft measurements, e.g., GOES and THEMIS satellites, provide simultaneous magnetic field and particle data at various radial distances and local times which improves our understanding of the variability of the inner magnetosphere on a global scale. We compare the magnetic field data and a magnetospheric model to characterize the field configurations and particle drift paths at the equatorial plane before and after intervals when measured electron fluxes are rapidly decreased. By integrating the particle data with the magnetospheric configurations, we quantify the temporal and spatial variations of the relativistic electrons during dropout events. Finally, we follow the trajectories of relativistic electrons to characterize their transport and loss under different solar wind conditions through changing field configurations and possible magnetopause shadowing effects.
U13A-0046
Relativistic electron loss; ULF waves and enhanced outward radial diffusion
In this study, observations from THEMIS and GOES are used to study the relationship between ULF waves and relativistic electron loss through the magnetopause. Around midnight UT on 25 June, 2008 the GOES satellites measured a two orders-of-magnitude drop in relativistic electron (> 1 MeV) fluxes over about 2.5 hours. The flux levels did not return to their previous levels for two and half days, suggesting an overall loss in MeV electrons. At the same time, THEMIS-A, D and E measured intense ULF waves starting at local dusk close to the magnetopause. Before midnight UT, THEMIS-A observed a sudden drop in hundreds of keV electrons close to the magnetopause and possibly due to the arrival of a pressure pulse. The drop-out in hundreds of keV electrons would result in a negative phase space density gradient for constant first adiabatic invariant, causing radiation belt electrons to diffuse outward. The observed ULF wave magnetic fields were strongly polarized in the radial and field-aligned directions, which corresponds to the poloidal wave mode. The ULF waves were also observed by ground-based magnetometers over North America and phase studies suggest low wave numbers. Eastward drifting electrons interact most strongly with poloidally polarized waves during drift resonance. Estimates of drift resonant energies using the low wave number ULF waves suggest the outward diffusing electrons, due to negative phase space density gradient, could strongly interact with the ULF waves. Commonly held theories for what causes relativistic electron losses are EMIC/VLF wave- particle interactions resulting in pitch-angle diffusion into the loss cone and/or magnetopause shadowing due to a compression of the magnetosphere. However, results here suggest that under certain conditions ULF wave-particle interactions may play an important role in relativistic electron loss from the outer radiation belt.
U13A-0047
A Monte Carlo Simulation of the NOAA POES MEPED Proton Detector
Experience with the NOAA POES satellites has shown that the SEM-2 MEPED proton channels respond to relativistic electron fluxes. The Geant4 code is employed to construct a Monte Carlo simulation of the detector, and computational results are used to derive a characteristic response. At electron energies greater than several hundred keV, all proton channels except the P4 and P5 channels are shown to respond to electrons. Moreover, because significant P6 channel counts are restricted to the domain of energetic electrons (>700 keV) and protons (>6,900 keV), an elevated P6 response may be employed in anti- coincidence with the P4 and P5 channel to identify relativistic electron precipitation. Finally, characterization of the incident electron spectrum may be attempted by examination of proton and electron channel ratios, and the resultant estimate used to correct reported fluxes or extend instrument capabilities.
U13A-0048
A New Product for Visualizing Energetic Particle Data from NOAA's POES Satellites
NOAA's Polar Orbiting Environmental Satellites monitor the energetic particle environment along their orbit
paths -- nominally 850 KM altitude, 98 degree inclination and a 100 minute period. Bi-directional detectors
allow these measurements to differentiate between particles that are trapped in the magnetic field and those
that are precipitating into the upper atmosphere. Archive files are prepared daily at NOAA's Space Weather
Prediction Center and submitted immediately to the National Geophysical Data Center where they have been
archived since their inception in 1978.
Our goal was to create a geographic presentation of the energetic particle data that balances spatial and
temporal resolution against the constraint that each product represents a complete global view. We found
that when accumulating the data into 2x2 degree bins that 210-260 orbits were needed to create a map of
this sort. A single satellite can generate such a map in around 15 days; however, by combining data from all
5 of the satellites in the current POES constellation only four days were needed to generate a complete
global map. Further, by using a sliding 4-day average we produced a daily product that always includes the
most recent UT day. Electron fluxes are displayed at three energy integrals of > 30, > 100, and >
300 keV. Proton fluxes are displayed at several discreet energy intervals between 30 keV and 6900 keV in
addition to a > 6900 keV integral. The resultant maps reveal the flux distribution of energetic electrons and
protons present in the South Atlantic Anomaly and the "horns" of the radiation belts. Animated sequences of
those maps clearly illustrate the dynamic evolution of those populations during event intervals.
http://www.ngdc.noaa.gov