Bibliography

Evolution and slow decay of an unusual narrow ring of relativistic electrons near L ~ 3.2 following the September 2012 magnetic storm

A quantitative analysis is performed on the decay of an unusual ring of relativistic electrons between 3 and 3.5 RE, which was observed by the Relativistic Electron Proton Telescope instrument on the Van Allen probes. The ring formed on 3 September 2012 during the main phase of a magnetic storm due to the partial depletion of the outer radiation belt for L > 3.5, and this remnant belt of relativistic electrons persisted at energies above 2 MeV, exhibiting only slow decay, until it was finally destroyed during another magnetic storm on 1 October. This long-term stability of the relativistic electron ring was associated with the rapid outward migration and maintenance of the plasmapause to distances greater than L = 4. The remnant ring was thus immune from the dynamic process, which caused rapid rebuilding of the outer radiation belt at L > 4, and was only subject to slow decay due to pitch angle scattering by plasmaspheric hiss on timescales exceeding 10\textendash20 days for electron energies above 3 MeV. At lower energies, the decay is much more rapid, consistent with the absence of a long-duration electron ring at energies below 2 MeV.

Thorne, R.; Li, W.; Ni, B.; Ma, Q.; Bortnik, J.; Baker, D.; Spence, H.; Reeves, G.; Henderson, M.; Kletzing, C.; Kurth, W.; Hospodarsky, G.; Turner, D.; Angelopoulos, V.;

Published by: Geophysical Research Letters      Published on: 06/2013

YEAR: 2013     DOI: 10.1002/grl.50627

RBSP; Van Allen Probes

A novel technique for rapid L* calculation: algorithm and implementation

Computing the magnetic drift invariant, L*, rapidly and accurately has always been a challenge to magnetospheric modelers, especially given the im- portance of this quantity in the radiation belt community. Min et al. (2013) proposed a new method of calculating L* using the principle of energy con- servation. Continuing with the approach outlined therein, the present pa- per focuses on the technical details of the algorithm to outline the implemen- tation, systematic analysis of accuracy, and verification of the speed of the new method. We also show new improvements which enable near real-time computation of L*. The relative error is on the order of 10-3 when \~ 0.1 RE grid resolution is used and the calculation speed is about two seconds per particle in the popular Tsyganenko and Sitnov 05 model (TS05). Based on the application examples, we suggest that this method could be an added resource for the radiation belt community.

Min, Kyungguk; Bortnik, J.; Lee, Jeongwoo;

Published by: Journal of Geophysical Research      Published on: 05/2013

YEAR: 2013     DOI: 10.1002/jgra.50250

calculating L*; rapid L* calculation; RBSP; Van Allen Probes

A novel technique for rapid L* calculation using UBK coordinates

[1] The magnetic drift invariant (L*) is an important quantity used for tracking and organizing particle dynamics in the radiation belts, but its accurate calculation has been computationally expensive in the past, thus making it difficult to employ this quantity in real-time space weather applications. In this paper, we propose a new, efficient method to calculate L* using the principle of energy conservation. This method uses Whipple\textquoterights (U, B, K) coordinates to quickly and accurately determine trajectories of particles at the magnetic mirror point from two-dimensional isoenergy contours. The method works for any magnetic field configuration and is able to accommodate constant electric potential along field lines. We compare the result of this method with those of International Radiation Belt Environment Modeling library (IRBEM-LIB) to demonstrate the performance of this new method. The method requires a preparation step, and thus may not be the optimal method for a single trajectory calculation; however, it presents a huge performance gain when adiabatically propagating a large population of particles in a given magnetic field configuration.

Min, Kyungguk; Bortnik, J.; Lee, Jeongwoo;

Published by: Journal of Geophysical Research      Published on: 01/2013

YEAR: 2013     DOI: 10.1029/2012JA018177

Generalized L value; L star; RBSP; Van Allen Probes

Radiation Belt Storm Probe Spacecraft and Impact of Environment on Spacecraft Design

NASA\textquoterights Radiation Belt Storm Probe (RBSP) is an Earth-orbiting mission scheduled to launch in September 2012 and is the next science mission in NASA\textquoterights Living with a Star Program. The RBSP mission will investigate, characterize and understand the physical dynamics of the radiation belts, and the influence of the sun on the earth\textquoterights environment, by measuring particles, electric and magnetic fields and waves that comprise the geospace. The mission is composed of two identically instrumented spinning spacecraft in an elliptical orbit around earth from 600 km perigee to 30,000 km apogee at 10 degree inclination to provide full sampling of the Van Allen radiation belts. The twin spacecraft will follow slightly different orbits and will lap each other 4 times per year; this offers simultaneous measurements over a range of spacecraft separation distances. A description of the spacecraft environment is provided along with spacecraft and subsystem key characteristics and accommodations that protect sensitive spacecraft electronics and support operations in the harsh radiation belt environment.

Kirby, Karen; Bushman, Stewart; Butler, Michael; Conde, Rich; Fretz, Kristen; Herrmann, Carl; Hill, Adrian; Maurer, Richard; Nichols, Richard; Ottman, Geffrey; Reid, Mark; Rogers, Gabe; Srinivasan, Dipak; Troll, John; Williams, Bruce;

Published by:       Published on: 03/2012

YEAR: 2012     DOI: 10.1109/AERO.2012.6187020

RBSP; Van Allen Probes

Radiation Belt Storm Probe Spacecraft and Impact of Environment on Spacecraft Design

NASA\textquoterights Radiation Belt Storm Probe (RBSP) is an Earth-orbiting mission scheduled to launch in September 2012 and is the next science mission in NASA\textquoterights Living with a Star Program. The RBSP mission will investigate, characterize and understand the physical dynamics of the radiation belts, and the influence of the sun on the earth\textquoterights environment, by measuring particles, electric and magnetic fields and waves that comprise the geospace. The mission is composed of two identically instrumented spinning spacecraft in an elliptical orbit around earth from 600 km perigee to 30,000 km apogee at 10 degree inclination to provide full sampling of the Van Allen radiation belts. The twin spacecraft will follow slightly different orbits and will lap each other 4 times per year; this offers simultaneous measurements over a range of spacecraft separation distances. A description of the spacecraft environment is provided along with spacecraft and subsystem key characteristics and accommodations that protect sensitive spacecraft electronics and support operations in the harsh radiation belt environment.

Kirby, Karen; Bushman, Stewart; Butler, Michael; Conde, Rich; Fretz, Kristen; Herrmann, Carl; Hill, Adrian; Maurer, Richard; Nichols, Richard; Ottman, Geffrey; Reid, Mark; Rogers, Gabe; Srinivasan, Dipak; Troll, John; Williams, Bruce;

Published by:       Published on: 03/2012

YEAR: 2012     DOI: 10.1109/AERO.2012.6187020

RBSP; Van Allen Probes

On the loss of relativistic electrons at geosynchronous altitude: Its dependence on magnetic configurations and external conditions

[1] The present study statistically examines 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 it 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 interplanetary magnetic field 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.

Ohtani, S.; Miyoshi, Y.; Singer, H.; Weygand, J.;

Published by: Journal of Geophysical Research      Published on: 01/2009

YEAR: 2009     DOI: 10.1029/2008JA013391

Magnetopause Losses

Timescales for radiation belt electron acceleration and loss due to resonant wave-particle interactions: 1. Theory

Radiation belt electrons can interact with various modes of plasma wave in their drift orbits about the Earth, including whistler-mode chorus outside the plasmasphere, and both whistler-mode hiss and electromagnetic ion cyclotron waves inside the plasmasphere. Electrons undergo gyroresonant diffusion in their interactions with these waves. To determine the timescales for electron momentum diffusion and pitch angle diffusion, we develop bounce-averaged quasi-linear resonant diffusion coefficients for field-aligned electromagnetic waves in a hydrogen or multi-ion (H+, He+, O+) plasma. We assume that the Earth\textquoterights magnetic field is dipolar and that the wave frequency spectrum is Gaussian. Evaluation of the diffusion coefficients requires the solution of a sixth-order polynomial equation for the resonant wave frequencies in the case of a multi-ion (H+, He+, O+) plasma, compared to the solution of a fourth-order polynomial equation for a hydrogen plasma. In some cases, diffusion coefficients for field-aligned waves can provide a valuable approximation for diffusion rates for oblique waves calculated using higher-order resonances. Bounce-averaged diffusion coefficients for field-aligned waves can be evaluated generally in minimal CPU time and can therefore be profitably incorporated into comprehensive kinetic radiation belt codes.

Summers, D.; Ni, Binbin; Meredith, Nigel;

Published by: Journal of Geophysical Research      Published on: 04/2007

YEAR: 2007     DOI: 10.1029/2006JA011801

Local Acceleration due to Wave-Particle Interaction

Observation of two distinct, rapid loss mechanisms during the 20 November 2003 radiation belt dropout event

The relativistic electron dropout event on 20 November 2003 is studied using data from a number of satellites including SAMPEX, HEO, ACE, POES, and FAST. The observations suggest that the dropout may have been caused by two separate mechanisms that operate at high and low L-shells, respectively, with a separation at L \~ 5. At high L-shells (L > 5), the dropout is approximately independent of energy and consistent with losses to the magnetopause aided by the Dst effect and outward radial diffusion which can deplete relativistic electrons down to lower L-shells. At low L-shells (L < 5), the dropout is strongly energy-dependent, with the higher-energy electrons being affected most. Moreover, large precipitation bands of both relativistic electrons and energetic protons are observed at low L-shells which are consistent with intense pitch angle scattering driven by electromagnetic ion cyclotron (EMIC) waves and may result in a rapid loss of relativistic electrons near the plasmapause in the dusk sector or in plumes of enhanced density.

Bortnik, J.; Thorne, R.; O\textquoterightBrien, T.; Green, J.; Strangeway, R.; Shprits, Y; Baker, D.;

Published by: Journal of Geophysical Research      Published on: 12/2006

YEAR: 2006     DOI: 10.1029/2006JA011802

Local Loss due to VLF/ELF/EMIC Waves

Simultaneous Radial and Pitch Angle Diffusion in the Outer Electron Radiation Belt

A solution of the bimodal (radial and pitch angle) diffusion equation for the radiation belts is developed with special regard for the requirements of satellite radiation belt data analysis. In this paper, we use this solution to test the bimodal theory of outer electron belt diffusion by confronting it with satellite data. Satellite observations, usually over finite volumes of (L, t) space, are seldom sufficient in space-time duration to cover the relaxation to equilibrium of the entire radiation belt. Since time scales of continuous data coverage are often comparable to that of radiation belt disturbances, it is therefore inappropriate to apply impulsive semi-infinite time response solutions of diffusion theory to interpret data from a finite window of (L, t) space. Observational limitations indicate that appropriate solutions for the interpretation of satellite data are general solutions for a finite-volume boundary value problem in bimodal diffusion. Here we test such a solution as the prime candidate for comprehensive radiation belt dynamic modeling by applying the solution and developing a method of analysis to radiation belt electron data obtained by the SCATHA satellite at moderate geomagnetic activity. The results and the generality of our solution indicate its promise as a new approach to dynamic modeling of the radiation belts.

Chiu, Y.; Nightingale, R.; Rinaldi, M.;

Published by: Journal of Geophysical Research      Published on: 04/1988

YEAR: 1988     DOI: 10.1029/JA093iA04p02619

Radial Transport