FG: Radiation Belts and Wave Modeling

2013 Tentative Agenda [1]

Chairs: Yuri Shprits, Scot Elkington, Jacob Bortnik, and Craig Kletzing

1. Topic description

Relativistic electrons may cause a variety of types of damage to spacecraft systems: deep dielectric charge build up, which in turn may lead to electrical discharges in a satellite’s insulating materials; direct damage to semi-conductor materials as energetic radiation belt particles traverse these materials; and transient signals induced by these particles which can cause single event upsets. Any of these interactions can leed to satellite failures. This focus group dedicated to the investigation of physical processes active within the radiation belts, with the goal of providing quantitative descriptions of the dynamics of the trapped radiation environment within the framework of first-principles physical models and in situ observations. This Radiation Belt and Wave Modeling Focus Group (RBWM) will concern itself with identifying and quantifying the contributions and effects of various sources of heating, transport, and loss of radiation belt ions and electrons, and developing global and local models of the radiation belts. Such models will require the development of physical models of the excitation, propagation, and distribution of the plasma waves that are known to affect the radiation belts. These wave models will be used to develop a quantitative description of the dynamics of the trapped radiation environment within the framework of first-principles physical models.

2. Timeliness of the focus group

These efforts will complement the existing NASA Radiation Belt Storm Probes (RBSP) mission planned for launch in May of 2012. The GEM RBWM will provide context for understanding RBSP observations, and will leverage new results from the RBSP mission in terms of advancing radiation belt modeling capabilities by quantifying input conditions, validating model results, and identifying missing physical processes. Other missions that are directly relevant to this FG that are due for launch within the next 2 years are the Air Force's DSX mission, Canadian ORBITALS mission, and Japanese ERG mission.

3. Relation to existing GEM focus groups

Radiation belt dynamics and its underlying magnetospheric plasma wave environment affects nearly every aspect of the space environment, and impacts broadly on several existing focus groups. The RBWM will leverage results and progress from other FGs, and will actively contribute to the following GEM Research Areas:

Space Radiation Climatology. This focus group endeavors to investigate the radiation belts from an empirical/observational point of view. The RBWM will work with the radiation climatology focus group using associated observational efforts to validate and constrain physics-based models developed under the RBWM, and in return will provide a global context and physical understanding for the empirical efforts of the climatology group.

Near Earth Magnetosphere: Plasma, Fields and Coupling. The results of this focus group will be used for modeling electric and magnetic fields which have a significant effect on the dynamics of the radiation belt particles. Understanding the processes governing the acceleration and transport of the seed populations required for producing the radiation belts, and the plasma waves resulting from the free energy provided by injected plasmasheet particles, is critical for the models produced by the RBWM.

Diffuse Auroral Precipitation. The scattering mechanisms associated with diffuse auroral precipitation originate in wave-particle interactions that will be studied in the RBWM, and many of the same processes simultaneously affect the high energy radiation belt electrons, e.g. whistler-mode chorus. The RBWM will work with the diffuse aurora focus group, applying advances in understanding the morphology and effect of these waves on charged particles to the acceleration, transport, and loss of radiation belt particles.

Plasmasphere-Magnetosphere Interactions. The cold plasma distribution in the inner magnetosphere has a profound effect on the wave growth, propagation, and distribution of several wave types that are critical for radiation belt and ring current dynamics. The RBWM will apply advances in understanding the dynamics of the plasmasphere to modeling the wave environment, and quantify the subsequent effects on radiation belt particles.

Modes of Solar Wind-Magnetosphere Energy Transfer. Particle injections via substorm, SMC, and sawtooth events often provide seed populations for subsequent acceleration to MeV energies in the radiation belts, as well as producing temperature anisotropies associated with waves driven by plasma instabilities. These efforts may be applied by the RBWM for determining the associated wave characteristics and initial and boundary conditions for inclusion in radiation belt models.

4. Goals and deliverables

The goal of this focus group is a fundamental physical understanding of the coupled dynamics of the high energy electrons and ions in the radiation belts and the plasma waves which produce these changes in the near-Earth environment. This focus group will develop models of the radiation belts and models of waves responsible for the dynamic variability of the radiation belt particles. We aim to advance physical models of the radiation belts and making them available for the analysis of results from the upcoming NASA’s RBSP mission. The efforts of this group will focus on modeling the energy, pitch-angle, and particle transport. We also seek an understanding of the wave excitation, propagation, and attenuation, specifically of those waves that impact the radiation-belt environment (e.g., chorus, EMIC, hiss, magnetosonic, lightning, and ECH waves), and a specification of the inner magnetospheric wave environment as a function of space (e.g., L, MLT, and latitude), and time (relative to storm or substorm phase). We will also involve a wide range of observations, including ground observations of waves, balloon observations of precipitating particles, and in-situ observations of ULF/VLF/ELF waves and energetic electron and ion fluxes. International researchers from France, the UK, Canada, China, Italy, and Russia will be strongly encouraged to participate.

5. Co-chairs

Yuri Shprits, UCLA (yshprits@atmos.ucla.edu)

Scot Elkington, LASP (Scot.Elkington@lasp.colorado.edu)

Jacob Bortnik, UCLA (jbortnik@atmos.ucla.edu)

Craig Kletzing, U. Iowa (craig-kletzing@uiowa.edu)

6. The Research Area with which it will be associated

IMS: Inner Magnetosphere and Storms

7. Term of effort

5 years: 2010-2014

8. Expected activities, questions, and challenges

The specific questions, challenges and themes of our focus group include:

8.1 What are the quantitative effects of various waves on radiation belt acceleration and loss? This question will be addressed through efforts to develop statistical models of the most important plasma waves using in-situ observations of waves, and by quantifying scattering rates induced by different types of waves. Results of model simulations will be compared with in-situ observations of precipitating and trapped fluxes, and balloon and ground observations of precipitating particles.

8.2 What are the physical processes responsible for wave excitation? That is, how are waves generated from an unstable distribution of particles? Is it possible to predict characteristics such as frequency bandwidth of excited waves, spatial location and distribution of the waves, saturation amplitudes, and other characteristics of the waves, e.g., frequency rise-time of chorus elements?

8.3 What is the wave distribution and what are its spatiotemporal characteristics? How is wave power distributed in the inner magnetosphere as a function of space (L, MLT, latitude), and time (relative to storm/substorm phase)? How are various wave modes correlated spatially and temporally across the inner magnetosphere? How is wave power distributed in frequency and wave-normal angle? (i.e., k-space), and can we describe the phenomenology of wave characteristics? e.g., chorus subpackets, formation in minimum-B pockets, EMIC wave structure, etc.

8.4 What is the role of non-diffusive processes? What role do nonlinear processes play in radiation-belt acceleration and loss? i.e., quantifying the effect of large-amplitude waves on energetic particles. What are the nonlinear processes that control wave amplitude saturation, and can these be quantitatively described? i.e., effect of particles on waves. What nonresonant processes are associated with these waves, and what role do they play? In addition prompt injection of MeV particles during storm sudden commencement can have a profound impact on the belts; injection of keV particles during substorms can provide source populations for acceleration to radiation belt energies. This work will contrast these effects with diffusive acceleration of particles.

8.5 What are the quantitative effects of transport via interaction with ULF waves? Activities relating to this question will include particle tracing and diffusive simulations of the radiation belts, with the aim of properly quantifying diffusive transport of MeV particles. Analysis of ground-based and in situ observation of ULF waves will be undertaken in this effort, as well as modeling the excitation of ULF waves due to solar wind driving and inner-magnetospheric plasma instabilities.

8.6 What role do seed populations play in the dynamics of the radiation belts? This work will examine the role of keV seed populations on the evolution of the wave environment and radiation belts, and will involve in situ and modeling studies of the access of these particles to the inner magnetosphere and their subsequent acceleration.

8.7 Why do some storms produce increases in the radiation belt fluxes while others produce no net change? This effort will combine quantitative insight from efforts described above into working models of the waves and radiation belts. Coupling existing codes to account for the range of different physics and validation studies for selected events will be a key part of this work.

9.1 Session 2010

Tues PM 1: RBWM 1 -- Development, verification, validation (Scot Elkington and Yuri Shprits)

Tues PM 2: RBWM 2 -- Preparing Radiation Belt models for RBSP data (Scot Elkington and Yuri Shprits)

Wed AM 2: RBWM 3 -- Particle scattering and transport (Scot Elkington and Yuri Shprits)

Wed PM 1: RBWM 4 -- ULF Waves (Jacob Bortnik and Craig Kletzing)

Wed PM 2: RBWM 5 -- VLF Waves (Jacob Bortnik and Craig Kletzing)

Thur AM 2: RBWM 6 -- Planning session (Jacob Bortnik, Scot Elkington, Craig Kletzing, and Yuri Shprits)

9.2 Session 2011

[GEM-RBW Schedule 2011]

[Link] to RBW GEM 2011 Schedule and Presentation Title Form

Monday, June 27, 2011 - 1:30 - 3:30pm: Eldorado Zia: GEM Challenge Presentations (Jacob Bortnik, Scot Elkington, and Craig Kletzing)

Monday, June 27, 2011 - 4:00 - 6:00pm: Eldorado Zia: Dynamical Evolution of the Radiation Belts (Yuri Shprits and Scot Elkington)

Thursday, June 30, 2011 - 10:00am - 12:00pm: CC Coronado+De Vargas: Joint with CEDAR: Remote Sensing the Inner Magnetosphere (Yuri Shprits and Roman Makarevich)

Thursday, June 30, 2011 - 4:00 - 6:00pm: Eldorado Sunset: Wave-particle Interactions (Yuri Shprits and Scot Elkington)

Friday, July 1, 2011 - 10:15am - 12:15pm: Eldorado Sunset: Observations and Modeling of Waves (Jacob Bortnik and Craig Kletzing)

10. Presentation

[Presentation]