space weather: overview and beginnings 10 september 2011 william j. burke air force research...

Space Weather: Overview and Beginnings

10 September 2011

William J. Burke

Air Force Research Laboratory/Space Vehicles Directorate

Boston College Institute for Scientific Research

DMSPC/NOFS

CRESS

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Space Weather Overview

Near-Earth space is the environment in which the AF conducts expensive operations to advance both national security and scientific understanding about the Earth, our star and the cosmos.

• Like severe terrestrial weather the space variety comes and goes

• Solar sources of space climatology and weather:

– Extreme ultraviolet radiation maintains & disrupts the ionosphere

– Solar wind and interplanetary magnetic field couple to Earth’s magnetic field

– Energy storage and transport in the magnetosphere

– Geomagnetic storms and Substorms

• Space weather impacts from an Air Force perspective

– Satellite and debris lost in space during magnetic storms

– Ionospheric irregularities disrupt communications and navigation

– Radiation damage to spacecraft components

Google

Actual Position

Predicted Position

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Space Weather Course Overview

• Lecture 1: Overview and Beginnings

• Lecture 2: Basic Physics (painlessly administered)

• Lecture 3: The Main Players

• Lecture 4: Solar Wind Interactions with the Earth’s Magnetic Field

• Lecture 5: Magnetosphere – Ionosphere Interactions

• Lecture 6: The Aurorae

• Lecture 7: Solar Induced Disruptions

• Lecture 8: Magnetic Storms and Substorms

• Lecture 9The Satellite Drag Problem

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

Wollen Sie Deutch Sprechen?)

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Space WeatherHistorical Roots

Early Auroral Reports

• Aristotle: Meterorologia (ca 340 BCE)

• Galileo (1610) sunspots, (1619) Aurora borealis

• Capt. James Cook: (1770) Aurora australis from Endeavor

• Herman Fritz: (1881) Aurorae occur most commonly ~23° from magnetic poles

Early Geomagnetic Disturbance Reports

• William Gilbert: (1600) de Magnete

• Edmund Halley: (1716) magnetic disturbances connected to aurora displays.

• Anders Celsius & Olaf Hiorter: (1741) Magnetic needle experiments

• Carl Friedrich Gauss: (1834) Göttingen Magnetic Union, (1839) Algemeine Theorie des Erdmagnetismus

Aurorae and Geomagnetic Disturbances

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• The remainder of this discussion concerns the seminal contributions of two Norwegians to present under-standing auroral electrodynamics

Kristian Birkeland (1867 – 1917)

Prof. of Physics, Royal Frederiks U. of Kristiania

Carl Størmer (1874 – 1957)Prof. of Mathematics, Royal Frederiks U. of Kristiania

Royal Frederiks University of Kristiania- Founded: 1811- Astrophysical Observatory: 1832- Domus Media: 1851- Blindern Campus: 1934

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• 1867: born in Kristiania

• 1880 - 1890: High school and university education

• 1893 - 1895: Postgraduate Research in France & Germany - published 1st generalized solution of Maxwell equations - characterized electric sparks (telegraphic applications) - began cathode ray experiments (Röntgenstrahlen)

• 1897: elected member of The Norwegian Academy

• 1898: appointed Professor of Physics (by King Oscar II of Sweden)

• 1917: died in Tokyo

• 88 scientific papers (more than 50 in Comptes Rendus) 3 books describing his arctic expeditions60 patents (electromagnetic cannon/artificial fertilizer)

Kristian Olaf Bernhard Birkeland

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– Concept:

– Experimental Results:

– Birkeland’s Interpretation:Energetic electrons (cathode rays ) fromthe Sun are “sucked” into Earth’s magnetic field and reach the upper atmosphere where they excite optical emissions.

–

Birkeland’s Terrella Simulations:

• Cathode rays fired at a magnetized sphere

• Light emissions surround magnetic pole like aurorae

Does interpretation make sense?

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• 1897 Campaign to Kåfjord

• Total disaster in surprise early autumn blizzard, T => -25° C; student severely injured

• 1899-1900 Campaign to Kåfjord– Constructed 2 auroral observatories at tops of Mts. Haldde and Talvik,

separated by 2.7 km but connected via telephone line

– Measured magnetic perturbations associated with overhead aurora

– Separation too small to estimate heights of aurorae by parallax

– Student Elisar Boye killed in an avalanche

Norwegian Polar Expeditions

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• 1902 – 1903 Campaign: 4 Stations:

– Supplies, sled dogs and coal

– Kåfjord, Norway

– Dyrafjord, Iceland

– Axeløen, Svalbard

– Matotchkin, Novaya Zemlya

• All stations equipped with:

– Magnetometers and calibration sensors

– Electrometers to measure atmospheric conductivity and Earth currents

– Meteorological sensors to measure P, T and V

– All personnel had to have experienced wintering over in the Arctic


Inter-station separation of about 1000 km

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• 1902 – 1903 Campaign Results:

– Analyzed magnetometer and auroral optical datademonstrated that disturbances span wide regionsof the globe and identified characteristics of magnetic storms and substorms.

– NAPE volumes 1 and 2 published in 1908 and 1913801 pages in English

– Birkeland calculated that millions of Amperes flow in the upper atmosphere during disturbances.

– Argued that such large currents must be driven by Sun and transmitted via field-aligned currents.

– After decades of hot debate field-aligned currents first observed by TRIAD satellites in 1967


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• 1874: born in Skien

• 1887 - 1897: High school and university education (1st publication in HS)

• 1898 - 1900: Postgraduate Research in France & Germany - published about 10 paper in pure mathematics

• 1902: elected member of The Norwegian Academy

• 1903: appointed Professor of Pure Mathematics

• 1904: begins particle trajectory in magnetic dipole calculations

• 1910, 1913: auroral expeditions to Bossekop

• 1957: died in Oslo

• ~ 300 scientific papers (more than 50 in Comptes Rendus) Auroral Atlas (1930, 1934, 1951) and The Polar Aurora (1953)4 nominations for Nobel Prize in Physics with Kr. Birkeland

Fredrik Carl Mülertz Størmer

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• Calculated trajectories allowed energetic charged particles in dipole representation of Earth’s magnetic field

• Enticed by Birkeland’s terrella experiments (1904)

• Solved trajectories of all possible particles numerically

• Demonstrated forbidden and allowed regions

• Cosmic ray access to Earth

• Van Allen radiation belts

• Predicted ring current during magnetic storms

Størmer's Contributions to Auroral Physics:

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• Determined auroral heights classes and locations

– With Krogness developed first camera to photograph aurorae

– Conducted auroral expeditions to Bossekop in 1910 and 1913

– Developed physical /analytical tools to conduct parallactic measurements of auroral features

– Established auroral network in southern Norway

• Aurorae do not penetrate below 90 km, can reach 1,000 km

• Align in the magnetic east-west direction

• Normally near magnetic latitudes of 67° but in storms move to about 57°

Størmer's Contributions to Auroral Physics:

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• Decades before entry into space European scientist were investigating

phenomena that occur in the atmosphere above 100 km that reflect the

variability of our space environment

• Birkeland’s field-aligned current model first suggested how energy from

the Sun electrically couples to Earth’s upper atmosphere.

• Størmer's analysis of allowed particle trajectories anticipated properties

cosmic rays and the radiation belts discovered decades later.

• Størmer's parallactic photography provided the first systematic basis for

understanding the structure of the upper atmosphere.

Some Conclusions

space weather: overview and beginnings 10 september 2011 william j. burke air force research...

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