Earth’s Radiation BeltEarth’s Radiation Belt

Xi ShaoXi Shao

Department of Astronomy, Department of Astronomy, University Of Maryland, College Park, MD 20742University Of Maryland, College Park, MD 20742

OutlineOutline History and importance of studying Earth’s History and importance of studying Earth’s radiation beltradiation belt Dynamics of Earth’s radiation belt: Dynamics of Earth’s radiation belt: ObservationsObservations Origin of Earth’s radiation belt: Geomagnetic Origin of Earth’s radiation belt: Geomagnetic Storms and Substorms.Storms and Substorms. Modeling formation of Earth’s radiation belt.Modeling formation of Earth’s radiation belt. Slot Region formation.Slot Region formation.

• The Radiation Belt is a energetic torus of energetic charged particles (plasma) around Earth, held in place by Earth's magnetic field • Historic discovery in 1958 by the Explorer I in 1958, and Explorer III missions, under Dr.James Van Allen at the University of Iowa. • The trapped radiation was first mapped out by Sputnik 3, Explorer IV, Pioneer III and Luna 1. • Energetic electrons form two distinct radiation belts, while protons form a single belt.

Radiation Belts: The Big Picture

Explorer I

The Radiation Belts Today: a Dynamic Space Weather Environment

Space Weather Applications:• Astronauts safety• Hardware integrity• Mission performance

• Satellite solar cell panel degradation• Single Event Upset (SEU)

The Radiation Belts Today: a Dynamic Space Weather Environment

Why Trapped?Why Trapped?

Electron Orbit Proton Orbit

NOAA POES Observations-Dynamical View Orbit Altitude: ~ 800 kmInclination: ~ 98 degreeOrbit Period:~100 mins

MEPED Detector Energy Channels used in this poster:Proton: >80 MeV(Omni-Detector)Electron: > 300 keV(Omni-Directional flux derived from 2 telescopes)NOAA POES Data obtained from

http://poes.ngdc.noaa.gov

NOAA POES Satellite OribitNOAA POES Satellite Oribit

Electron (> 300 keV) Belt Dynamics(1979-1991)

Mar. 1989Mar. 1991

Feb. 1986

Outer BeltWeakens

Inner belt Enhanced

Apr. 1981Jul. 1982

Electron (> 300 keV) Belt Dynamics(1992-2004)

NOAA-15 changes telescope pointing direction and data is still in processing for L < 2.

Oct-Nov, 2003Outer BeltWeakens

Inner belt Re-Enhanced

Radiation Belt Dynamics and Geomagnetic Storms

Proton (> 80 MeV) Belt Dynamics(1979-1991) Mar. 1991

Mar. 1989Feb. 1986

Proton (> 80 MeV) Belt Dynamics(1992-2004) Oct-Nov, 2003

Radiation Belt inside the Earth’s Magnetosphere: Its Origin.

Earth’s Magnetosphere

Modeling Solar Wind Interaction with Earth’s Magnetosphere

MHD Equations Solved on a 3D Stretched Spherical Mesh

Magnetospheric Storms/SubstormsMagnetospheric Storms/Substorms

Vortices During 2002-03-29 EventVortices During 2002-03-29 Event

Complex Vortices Structure inside Complex Vortices Structure inside MagnetosphereMagnetosphere

Magnetospheric Substorm

t= 00:-07:-48

t= 00:51:05

t= 01:01:07

t= 00:47:20

t= 00:56:06

t= 01:06:08

Mid-Tail Reconnection

Development of Bursty Bulk Flow

1:00 UT

Ring Current DevelopmentRing Current Development

3D Particle Tracing Code (Full Motion forProtons, and Guiding Center for electrons)

Initial Test Particle Distribution

3D Electric-Magnetic field from LFM Global

MHD Model of Earth’s Magnetosphere

RB energetic particle distribution

Physical Modeling of Radiation Belt

e

p

Radiation Belt Electron DynamicsRadiation Belt Electron Dynamics

Radiation Belt Protons DynamicsRadiation Belt Protons Dynamics

A snapshot of electron location and energy in 3D 10 mins later

Initial Configuration of 5keV electrons

Energization of Radiation Belt Electrons

Formation of Slot Region in Electron Formation of Slot Region in Electron Radiation BeltRadiation Belt

Whistler Waves in the Plasmasphere

Slot Region

Quick Time Movie

Solar Cycle Shifting of Safe-ZoneSolar Cycle Shifting of Safe-Zone

SummarySummary

Review History and Importance of Review History and Importance of Radiation BeltRadiation Belt Radiation Belt StructureRadiation Belt Structure Origin of Radiation BeltOrigin of Radiation Belt Radiation Belt Slot regionRadiation Belt Slot region Safe-zone Solar-Cycle Shifting.Safe-zone Solar-Cycle Shifting.

Outstanding science questionsAcceleration mechanisms; their relative significance Solar wind-inner magnetosphere coupling Loss mechanisms

User needs a Model: Accurate flux models L shell specificity Forensic evaluation Nowcasting