National Aeronautics and Space Administration

Living With A Star

Targeted Research and Technology

Determining the loss of outer radiation belt electrons: a high priority of LWS/RBSP

ROSES ID: NNH08ZDA001N      Selection Year: 2009      

Program Element: Independent Investigation

Principal Investigator: Xinlin Li

Affiliation(s): University of Colorado at Boulder

Project Member(s):
Selesnick, Richard S Collaborator AFRL/RVBXR
Looper, Mark Collaborator The Aerospace Corporation


Energetic electrons in the magnetosphere have been observed to exhibit

high variation in flux during geomagnetic storms. The electron flux

enhancements are known to be due to acceleration processes within the

Earth's magnetosphere, while the largest loss due to precipitation into

the atmosphere also occurs during magnetic storms. Thus the acceleration

mechanisms that replenish radiation belt electrons during storms

must be even more effective than they appear since they act in the

face of this enhanced loss. Without a quantitative knowledge of the loss,

a quantitative knowledge of the acceleration mechanisms cannot be obtained.

A high priority of the NASA/LWS/Radiation Belt Storm Probe program is to

differentiate among competing processes affecting the precipitation and

loss of radiation belt electrons.

We propose to investigate and quantify the loss rate of radiation

belt electrons due to precipitation. We will accomplish this by analyzing

SAMPEX data over a solar cycle. SAMPEX circles the Earth 15 times each day

in a high inclination orbit and has been providing the measurements of

radiation belt electrons at different since its launch in 1992. Because

of its low altitude and large geometric factors and the fast time

resolution of its detectors, SAMPEX data are ideally suited for determining

losses of electrons to the atmosphere. A simple Loss Index Method to

calculate the loss rate will be applied to a variety of storm events and over

different phases of solar cycle to quantify the electron loss rate as a

function of radial distance, magnetic local time, electron energy and relevant

geomagnetic indices. We will also adopt the Drift-Diffusion Model that includes

the effects of azimuthal drifts and pitch angle diffusion. The detailed

Drift-Diffusion Model method will be used to validate the loss rate results

from the Loss Index Method. And we will also apply the Drift-Diffusion Model

method to obtain complete information about the pitch angle diffusion rate

as functions of energy and pitch angle during indvidual storms.

The proposed research has the direct impact to the LWS goals

and is closely related to LWS/RBSP mission. RBSP measurements will be

taken near the equatorial plane and because of the limited angular

resolutions, the pitch angle distribution near and inside the loss

cone is difficult to be resolved. SAMPEX still has the best data to

address the precipitation loss. Our proposed study will help the mission

to ensure full science closure by having a better understanding of the

precipitation loss.


Performance YearReferenceInvestigation TypeActions
1Tu, Weichao; Selesnick, Richard; Li, Xinlin; Looper, ...
not set
1Zhao, H.; Li, X.; (2013), Inward shift of outer radiatio...
not set


Performance YearReferenceActions
1Tu, W.; Selesnick, R. S.; Li, X.; Looper, M. D.; (2...
1Tu, W.; Li, X.; Selesnick, R. S.; Looper, M. D.; (2...
1Blum, L. W.; Li, X.; (2012), Rapid Enhanced Precipitatio...
1Tu, W.; Reeves, G. D.; Cunningham, G.; Selesnick, R....
1Zhao, H.; Li, X.; (2012), Inward shift of outer radiatio...
1Blum, L. W.; Li, X.; (2013), Rapid enhanced precipitatio...
1Blum, L. W.; Schiller, Q.; Li, X.; Millan, R. M.; ...

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