Space Weather: Verbindung/Synthèse

28 November 2011

William J. Burke

Air Force Research Laboratory/Space Vehicles Directorate

Boston College Institute for Scientific Research

DMSPC/NOFS

CRESS

2

Space Weather Course Overview

• Lecture 1: Overview and Beginnings

• Lecture 2: The Aurorae

• Lecture 3: Basic Physics (painlessly administered)

• Lecture 4: The Main Players

• Lecture 5: Solar Wind Interactions with the Earth’s Magnetic Field

• Lecture 6: Magnetic Storms

• Lecture 7: Magnetic Substorms

• Lecture 8: Magnetosphere – Ionosphere Coupling

• Lecture 9 The Satellite Drag Problem

• Lecture 10: Verbindung (to help make up for your rash decision not to take

Wollen Sie Deutch Sprechen?)

3

Space Weather Verbindung

• Today’s objective is to review Space Weather as a comprehensible whole.

• Take away #1: All near Earth space weather is caused either directly or indirectly by the Sun.

• Take away #2: Atmosphere’s structure (up to 1000 km) is controlled by the absorption of solar radiation and consequent thermodynamics.

• Take away #3: Dynamics of the magnetosphere-ionosphere system are responses to the variability of solar wind and embedded magnetic field.

• Take away #4: Effectiveness the of solar wind coupling to M-I system is mediated by the polarity of the IMF’s north-south component.

• Take away #5: Maxwell’s equations as applied to magnetized plasmas critical for understanding and predicting space weather.

• Take away #6: Space weather affects modern communications, spacecraft operations, human activities, electric power grid safety.

Overview

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Space WeatherVerbindung

Take away #1: Solar Dominance

• We live about 100 million miles from a run-of-the-mill main sequence star.• 1610: Galileo discovered sunspots• 1843: Schwabe identified sun-spot cycle• L1 imagery shows sun spots are sources of CMEs and thus the largest magnetic storms

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Space Weather Verbindung

Take-away #2: Atmospheric Structure

• EUV from solar corona responsible for heating of thermosphere and creation of ionosphere.• UV light from chromosphere heats stratosphere via ozone absorption• Visible and infra-red light from photosphere heats the troposphere in which we live.

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Space Weather Verbindung

Take away #3: M-I Dynamics

• An ionized supersonic solar wind continually propagates outward from the solar corona carrying with it a weak (few nT) interplanetary magnetic field.

• Solar wind interacts strongly with Earth’s magnetic field• Stand-off bow shock and sub-sonic magnetosheath flow (like air flow past a supersonic jet plane)• Earth’s magnetic field distorts into a long cylinder called the magnetosphere to which solar wind has limited access.• Solar wind has direct access to ionosphere through the two dayside cusps. • Nightside field lines connected on both ends to Earth host the plasma sheet and radiation belts.

• Solar wind interactions alone cannot explain dynamics observed in the magnetosphere or the magnetically conjugate high-latitude ionosphere.

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Space Weather Verbindung

Take away #4: IMF BZ Control

SunEarth

Clo

sed

Fie

ld li

nes

Interp

lanetary F

ield lin

es

Open Field lines

Open Field lines

Magnetic merging at dayside magnetopause

Magnetopause current sheet

Solar Wind

Three Magnetic Topologies- IMF: two feet in solar wind- Closed: two feet on Earth- Open: one foot on Earth and one in the solar wind

The single most importantconcept in space physics

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Space Weather Verbindung

Take away #5: Rules for Magnetized Plasmas

Name

Differential form

Gauss's law

Gauss's law for magnetism

Maxwell–Faraday equation(Faraday's law of induction)

Ampère's circuital law(with Maxwell's correction)

James Clerk Maxwell (1831 – 1879)

• More than 99% of universe made up of plasma. • We are the exception to the rule. • What little we have allows space weather to happen.

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Space Weather Verbindung

Take away #6.1: Space Weather Effects

NOAA Group 1: Geomagnetic Storms

• Five Levels == Extreme to minor Ranked by Kp index (9 to 5)

• Effects: == Spacecraft charging, navigation errors Upsets to outage of power grid systems

• Causes: === Coronal mass ejections (solar max) High speed streams in solar wind (solar min)

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Space Weather Verbindung

Take away #6.2: Space Weather Effects

NOAA Group 2: Solar Radiation Storms

• Five Levels == Extreme to minor Ranked by > 10 Mev ion flux level

• Effects: == Biological hazards for human activity in space and transpolar air flights. Damage to onboard computation capabilities

• Causes: === Solar energetic particles from coronal flares

N.B. Not all flares and CME events produce high SEP fluxes

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Space Weather Verbindung

Take away #6: Space Weather Effects

NOAA Group 3: Radio Blackouts

• Five Levels == Extreme to minor Ranked by X-ray flux level observed by GOES

• Effects: == Dayside HF radio transmission on impossible

to degraded for hours. Significant GPS navigation errors.

• Causes: == Solar coronal X-ray flares

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Space Weather Verbindung

Summary and Conclusions

• While in grade school I looked forward to the Sunday comics and the adventures of Buck Rogers fighting against inter-galactic malefactors.

• The little boy in me was a bit disappointed when Prof Olbert lectured on Størmer cosmic-ray trajectories in Space Physics 8-48.

• The physics was messier than undergraduate text books that never mentioned the trial-and-error accompanying human progress.

• Over time I came to see the job of a space physicist as more akin to an explorer in a new world or a detective sifting through clues that often seem to point in contradictory directions.

• I hope that over the course of ten weeks each of you has come to see something more of the subtlety and beauty of forces that combine to make the 21st century world. Für alles deine Geduld, viele Danke!