THEMIS SRR 1 UCB/SSL, July 8-9,2003

THEMIS Science Requirements

Dr. Vassilis Angelopoulos

Principal Investigator

Space Sciences Laboratory

University of California, Berkeley

THEMIS SRR 2 UCB/SSL, July 8-9,2003

THEMIS primary objectives

AuroraAurora

Understand substorm onset and evolution (baseline mission, primary objective)

As a minimum: Where does substorm eruption start? (ionosphere, CD, Rx ?).

MAGNETOSPHERESO

LAR

WIN

D

EQUATORIAL PLANE

Themis overcomes:Meridional onset confinement (GBOs)

Mapping distortions (in situ probes)Global timing (GBOs-probes)

THEMIS SRR 3 UCB/SSL, July 8-9,2003

Events that comprise the substorm

CurrentDisruption

AuroralEruption

Reconnection

THEMIS SRR 4 UCB/SSL, July 8-9,2003

Flows

Primary Objectives, Goals and Means

Onset and evolution of substorms

Time History of Events (Onset)…

– Delineate cause and effect

• Measure WhenWhere

… and Macroscale Interactionsduring Substorms (Evolution)

– Coupling in the magnetosphere

• Measure plasma flows and waves

– Coupling to the ionosphere

• Measure currents and structures

Distinguishes among competing models: impartially answers a well-posed question…

Current Disruption Model

time Event

0 sec Current Disruption

30 sec Auroral Eruption

60 sec Reconnection

Reconnection Model

time Event

0 sec Reconnection

90 sec Current Disruption

120 sec Auroral Eruption

?

?Rarefaction wave

?

P1P2P3P4P5

GBO

…as implied by Themis,goddess of impartial justice

THEMIS SRR 5 UCB/SSL, July 8-9,2003

Mission elements

Probe conjunctions along Sun-Earth line recur once per 4 days over North America.

Ground based observatories completely cover North American sector; determine

auroral breakup within 1-3s …

… while THEMIS’s space-based probes determine onset of Current Disruption and

Reconnection each within <10s.

: Ground Based Observatory

THEMIS SRR 6 UCB/SSL, July 8-9,2003

First bonus: What producesstorm-time “killer” MeV electrons?

Affect satellites and humans in space

Source:

– Radially inward diffusion?

– Wave acceleration at radiation belt?

THEMIS:

–Tracks radial motion of electrons

•Measures source and diffusion

•Frequent crossings

–Measures E, B waves locally

ANIK telecommunicationsatellites lost for days to weeks

during space storm

THEMIS SRR 7 UCB/SSL, July 8-9,2003

Second bonus: What controls efficiencyof solar wind – magnetosphere coupling?

Important for solar wind energy transfer in Geospace

Need to determine how:– Localized pristine solar wind features…

– …interact with magnetosphere

THEMIS:

– Alignments track evolution of solar wind

– Inner probes determine entry type/size

THEMIS SRR 8 UCB/SSL, July 8-9,2003

Mission Science Objectives in a Nutshell

Minimummission

CSR, Table E-1

THEMIS SRR 9 UCB/SSL, July 8-9,2003

Ground Rules

Mission Level Science Adherence to requirement

Minimum mission Primary Performance floor

Primary Design driverAncillary (HF modes) Design goal

Baseline mission Secondary (Rad Belt) Design goalTertiary (Dayside) Design goal

Extended mission 3rd year baseline orbits At negligible impact if on target

Phase F mission 4th, 5th year shock/pause At negligible impact if on target

ExplicitlyincludedIn Level1Req’s