Ernest F. Hollings Ernest F. Hollings Undergraduate Scholarship ProgramUndergraduate Scholarship Program

http://www.orau.gov/noaa/HollingsScholarship/http://www.orau.gov/noaa/HollingsScholarship/

Where Have All the Where Have All the Electrons Gone?Electrons Gone?

Testing mechanisms proposed Testing mechanisms proposed to explain the loss of high to explain the loss of high

energy electrons from Earth's energy electrons from Earth's magnetospheremagnetosphere

Christina HaigChristina Haig

Space Environment CenterSpace Environment Center July 29, 2005July 29, 2005

• Monitors and forecasts Earth's space environmentMonitors and forecasts Earth's space environment• Provides accurate, reliable, and useful solar-terrestrial Provides accurate, reliable, and useful solar-terrestrial

informationinformation• Conducts and leads research and development programsConducts and leads research and development programs• Nation's official source of space weather alerts and Nation's official source of space weather alerts and

warnings. warnings.

Science & Technology Science & Technology Infusion BranchInfusion Branch

• Solar Terrestrial Models and TheorySolar Terrestrial Models and Theory

• Solar Terrestrial Instrumentation and DataSolar Terrestrial Instrumentation and Data

• Responsibilities for Data and InformationResponsibilities for Data and Information– SatellitesSatellites– Rapid Prototyping Center Rapid Prototyping Center – Cooperative Science ProgramsCooperative Science Programs– PublicationsPublications

Introduction and Research OutlineIntroduction and Research Outline

• Introduction to the Earth’s magnetosphereIntroduction to the Earth’s magnetosphere

• Introduction to the Earth’s radiation belts Introduction to the Earth’s radiation belts and our reasons for interestand our reasons for interest

• Introduction to the potential mechanisms of Introduction to the potential mechanisms of electron losselectron loss

• Testing of the currently applied explanationTesting of the currently applied explanation

• Conclusions about the theoryConclusions about the theory

Studying the MagnetosphereStudying the Magnetosphere

Magnetosphere

Solar Wind

Magnetopause

Solar Wind and Magnetic Field Lines

Inner (Proton) Zone

Outer (Electron) Zone

Earth’s Radiation BeltsEarth’s Radiation Belts

The electron belt is particularly important to satellites that reside in geosynchronous orbit (around 5.6 RREE)

• The Inner belt is around 1.5-3 Earth radii, The Inner belt is around 1.5-3 Earth radii, Outer belt around 3-10 ROuter belt around 3-10 REE

• Radiation belt electrons are relativistic Radiation belt electrons are relativistic (travel near the speed of light)(travel near the speed of light)

Motions of Radiation Belt ParticlesMotions of Radiation Belt Particles

Inner (Proton) Zone

Outer (Electron) Zone

Inner (Proton) Zone

Outer (Electron) Zone Drift motion Drift motion around Eartharound Earth

• Gyro motion Gyro motion around magnetic around magnetic field linesfield lines

• Bounce motion Bounce motion between polesbetween poles

The Challenge to ModelersThe Challenge to Modelers• Relativistic electron flux is extremely variable.Relativistic electron flux is extremely variable.• Flux may increase or decrease on rapid Flux may increase or decrease on rapid

timescales of less than one day.timescales of less than one day.

Day of Year

elec

tron

flu

x

>2 MeV Electron Flux at Geosynchronous

Electron Radiation Belt Hazards

Telestar Failure

>1.

5 M

eV E

lec

tro

n d

os

e

• High energy electrons can penetrate through shielding causing internal electrical charge to build up.

• A sudden discharge may cause minor problems, temporarily disabling satellites due to flipped program bits.

• More cataclysmic situations can permanently disable satellites due to damaged electronics, as in the loss of the Telestar satellite.

Magnetopause LossMagnetopause Loss• Adiabatic motion can lead to real loss if electrons move out far enough to encounter the magnetopause.

• Kim and Chan [1997] examined one storm and based on theoretical calculations concluded that electrons at geosynchronous could be pushed out to the magnetopause.

• Currently, there is no observational support in favor of this loss mechanism.

Earth

Magnetopause

e

Magnetopause

Testing Magnetopause LossTesting Magnetopause LossUsing the Geotail satellite data to build a Using the Geotail satellite data to build a statistical picture of the magnetopause:statistical picture of the magnetopause:

Testing Magnetopause LossTesting Magnetopause LossLooking at electron flux during times of Looking at electron flux during times of

known magnetic field at the magnetopause:known magnetic field at the magnetopause:Geotail Crossing:Geotail Crossing:

17-Feb-2002 13:01:38 48.198 nT17-Feb-2002 13:01:38 48.198 nT

Median Field Outside: 47.81 nTMedian Field Inside: 62.58 nT

4 day period surround magnetopause crossing of Geotail

MagnetopauseField

Magnetic Field at GOES 10

Electron Counts at GOES 10

Testing Magnetopause LossTesting Magnetopause LossLooking at electron flux during times of Looking at electron flux during times of

known magnetic field at the magnetopause:known magnetic field at the magnetopause:Geotail Crossing:

06-Nov-1999 23:23:00 58.702 nT

Median Field Outside: 11.18 nTMedian Field Inside: 75.25 nT

4 day period surround magnetopause crossing of Geotail

MagnetopauseField

Magnetic Field at GOES 10

Electron Counts at GOES 10

Testing Magnetopause LossTesting Magnetopause LossLooking at dependency of electron flux on the Looking at dependency of electron flux on the

pitch angle:pitch angle:

Testing Magnetopause LossTesting Magnetopause LossLooking at dependency of electron flux on the Looking at dependency of electron flux on the

pitch angle:pitch angle:

ConclusionsConclusions• The characteristics of the magnetopause are The characteristics of the magnetopause are

highly variablehighly variable

• The explanation of electron flux dropouts The explanation of electron flux dropouts through the magnetopause does not fit well with through the magnetopause does not fit well with observationsobservations

• The pitch angle data suggest another The pitch angle data suggest another mechanism that preferentially loses electrons mechanism that preferentially loses electrons with pitch angles far from 90 degreeswith pitch angles far from 90 degrees

• The theory of electron loss into the atmosphere The theory of electron loss into the atmosphere fits better to the observed flux dropsfits better to the observed flux drops

AcknowledgementsAcknowledgements

Special Thanks to:Special Thanks to:

Janet Green (Mentor)Janet Green (Mentor)

Terry OnsagerTerry Onsager

Ann NewmanAnn Newman

Jorgeann HiebertJorgeann Hiebert

Satellite Data Provided by:T. Onsager – NOAA SECH. Singer – NOAA SEC

S. Kokubun – STELAB, Nagoya University