# Presentation: 865407

## Aurora, Substorms, and THEMIS

- D. G. Sibeck
- NASA/GSFC
- THEMIS Project Scientist

## Outline

- What do aurora look like?
- Where do aurora occur?
- When do aurora occur?
- Why do aurora occur?
- How will THEMIS help us understand aurora?
- Where can I find out more information?

## Quartz Lake State Park, AlaskaSeptember 6, 1996

## January 6, 1998

## Aurora in Alaska

## March 11, 1998

## Aurora in Lapland

## Loomis Auroral Chart, 1860

- You are
- here

**North**
**Pole**

- Elias Loomis
- Professor,
- Yale

## % Nights With Aurora

- You can also see
- aurora in
- Antarctica!

- You are still
- here- you have
- a small but
- finite chance
- of seeing
- aurora

## Aurora over the Eastern U.S.

- You  are here

- Sometimes the
- auroral oval
- brightens and
- expands over
- the continguous
- United States

## Good news: Auroras come furthest equatorward here on the East CoastBad news: only during severe geomagnetic storms

**X**

## Ground Magnetograms

- Example

- Summary:
- One Year of
- Kp index

- Sudden Commencement
- Compression

- Storm
- Disturbance

- 27 Day Solar Rotation

## When Should One Look?

- Spring

- Fall

- At or just before
- midnight,
- Spring or
- Fall

## SOHO: Solar Flares and Ejecta

- Our story
- begins at
- the Sun

## Solar Wind Model: Streams and Blast Waves

## Earth’s Magnetic Field

## Our Magnetic Shield

## Solar Wind Buffetting: Model

- Aurora

## Reconnection

## Cause of Aurora

- 120 km

- 60 km

## Reconnection Model

## Current Disruption

## THEMIS

- Science:
- Identify when and where substorms (building blocks of storms) begin
- Distinguish between competing models
- Understand substorm physics
- Impact on Society
- Predict when and where substorms occur
- Understand and guard against substorm-related increases in radiation belt particle flux, communication disruptions, and current surges in power/pipelines

## THEMIS Launch

## Orbital Information

- Launched at Sunset, February 17, 2007
- Presently: all 5 s/c on almost identical orbits:
- 1.1 x 14.7 RE with inclination 14.4°, period 31 hours, separated by 100’s to 1000’s km
- Apogees between the Sun and the Earth, studying radiation belts and the outer boundary of the Earth’s magnetic field
- Future...each has its own special orbit to help pinpoint when and where substorm onset occurs

## THEMIS

- (**T****ime ****H****istory of ****E****vents and ****M****acroscale ****I****nteractions during ****S****ubstorms)**
- distinguishes amongst competing substorm models

- Careful positioning of
- 5 well-instrumented
- probes and dedicated array
- of ground observatories
- Allows us to impartially
- test two competing models
- and determine the cause of
- substorms

## SPACECRAFT AND INSTRUMENTS

- _FIVE IDENTICALLY-INSTRUMENTED_
- _SPACECRAFT (128 kg), EACH CARRYING:_
- ESA: 	Electrostatic analyzer measures
- 	0.003-30 keV ions/electrons (UCB)
- SST: 	Solid state telescopes measures
- 	0.03-6 MeV ions and electrons (UCB)
- FGM: 	Fluxgate magnetometer measures 		magnetic field to 128 Hz (Germany)
- SCM: 	Search coil magnetometer measures 	0.001 - 4 kHz magnetic field (France)
- EFI: 	Electric field instrument on wires and
- 	axial booms 0.0003 - 400 kHz (UCB)

## 5 THEMISS/C Line Up in Tail Once/4 Days

- Sun

## Timing a Substorm

- TH-GBOs: High resolution & sensitivity
- Onset: 11:12:51UT, Intensification: 11:18:30UT

- First on THD

- Last on THE

- 2nd on THB

- 3rd on THA

- Magnetic Field

- THE
- THA
- THB
- THD
- THC

- Sun

- March 23, 2007

## Dedicated Array ofUS/Canadian Ground ObservatoriesProvide Daily Auroral Movies

## First Auroral Mosaic MovieFebruary 14, 2007

- Dedicated Array of US and Canadian Ground Stations

## FOR MORE INFORMATION

- Principle Investigator: Vassilis Angelopoulos (NASA/JPL)
- Project Scientist: David Sibeck (NASA/GSFC)
- NASA SITE _WWW.NASA.GOV/THEMIS_
- SCIENCE SITE: _themis.ssl.berkeley.edu_
- EPO SITE: http://ds9.ssl.berkeley.edu/themis/no_flash.html