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Space Weather Midterm
Terms and History in first 2 chapters of Intro to Space Weather
59
Astronomy
Undergraduate 1
02/25/2013

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Term
Galileo
Definition
Used sunspots to estimate sun's rotation rate.
Term
Carrington
Definition
Showed that the sun rotates differentially (different speeds at different solar latitudes).
Term
Tycho Brahe
Definition
Recorded the occurrence of aurora between 1582 and 1598 from his observatory in Denmark. Found that the number of aurora varies from year to year.
Term
Pierre Gassendi
Definition
Noted that the aurora must occur high in Earth's atmosphere because observes at distance locations could see the same thing.
Term
Henry Cavendish
Definition
Correctly estimated the auroral height to be between 80 to 112 km.
Term
Captain James Cook
Definition
First European to observe the souther lights while in the Indian Ocean in 1773. Called them aurora australis (southern lights)
Term
William Gilbert
Definition
Demonstrated that the Earth's magnetic field behaves like a magnet, led to systematic study of magnetic field orientation as a function of position on earth.
Term
Samuel Schwabe
Definition
Recognized existence of an 11 year solar cycle in 1844.
Term
Edmond Halley
Definition
Noted that an aurora over London seemed to have rays converging toward Earth that were similar to the Earth's magnetic field lines. Drew the magnetic field lines outside Earth by extrapolating from the shape that iron filings make around a magnet.
Term
Johann Wilke
Definition
Confirmed the alignment of auroral rays with Earth's magnetic field in 1770.
Term
Graham
Definition
Observed slight magnetic fluctuations with his compass in 1722.
Term
Anders Celsius and Olaf Hiorter
Definition
Observed magnetic fluctuations correlated with observations of aurorae in 1747.
Term
Edward Sabine and Rudolf Wolf
Definition
Independently first to publish results showing correlation between sunspots and geomagnetic activity.
Term
Space weather
Definition
An emerging field within space sciences that studies how the sun influences the Earth's space environment and the technological and societal impacts of that interaction.
Term
Climate
Definition
long-term weather trends.
Term
Meteorology
Definition
Science of understanding weather.
Term
Coronal Mass Ejection (CME)
Definition
A large part of the solar atmosphere streaming away from the sun at high speeds after erupting from the surface.
Term
Pauses
Definition
Boundaries between spheres.
Term
Geomagnetic Storms
Definition
Many degrees of magnetic needle fluctuation in several minutes. Large geomagnetic disturbances.
Term
Ionosphere
Definition
Region of the upper atmosphere associated with current flow and the aurorae.
Term
Solar nebula
Definition
Giant cloud of gas and dust of which sun was formed.
Term
Accretion
Definition
When denser area of solar nebula gathers material to itself because of its gravitational pull. Self-sustaining process.
Term
Density
Definition
Amount of material in a given volume.
Term
Hydrostatic equilibrium
Definition
The balance between force of gravity pulling material into sun and the force due to pressure of the gas pushing out.
Term
Electromagnetic radiation
Definition
Energy created by thermonuclear reactions in the core that fuse protons together to form helium nuclei, some is liberated and escapes into space as EMR.
Term
Conduction
Definition
Transfer of heat in absence of fluid motions.
Term
Convection
Definition
Transfer of heat by fluid motions.
Term
Radiation
Definition
Transfer of heat through EMR.
Term
Helioseismology
Definition
Using sound waves to study the interior of the sun.
Term
Luminosity
Definition
Total amount of energy emitted by the sun each second.
Term
Nuclear fusion
Definition
Light nuclei are fused to heavier nuclei. High temps mean mostly protons in the core, when they collide forms a proton-proton chain which leads to 1 helium nucleus. Some energy escapes.
Term
Sunspots
Definition
Regions of strong magnetic field. Darker because sightly cooler. Can last for weeks.
Term
Granules
Definition
Dark and light regions on photosphere, proves solar convection because bright areas show Doppler shift up to blue while dark areas show Doppler shift down to red.
Term
H-Alpha
Definition
Specific electronic transition within hydrogen. Unique wavelength of visible light with a reddish hue.
Term
Spicules
Definition
Hot jets of gas.
Term
Prominences
Definition
Loop-like filaments observed above the limb of the sun.
Term
Plages
Definition
Light filaments
Term
Corona
Definition
Outer atmosphere of the sun, visible during solar eclipses, expands out supersonically.
Term
Zeeman Effect
Definition
In presence of magnetic field, a gas' spectral lines split into 2 or more components. Frequency of lines depends on strength of magnetic field. Used to measure solar surface magnetic field.
Term
Solar Cycle
Definition
11 year cycle of waxing and waning number of sunspots.
Term
Period (T)
Definition
Time it takes 1 density perturbation cycle to pass.
Term
Frequency (f or v)
Definition
Number of events in a given time interval in Hertz.
Term
Amplitude
Definition
Amount of displacement, measure of size of a wave.
Term
Wavelength
Definition
Distance between troughs or crests of waves.
Term
Doppler Effect
Definition
Shift in frequency of a wave due to relative motion of the sound emitter and observer.
Term
Photoelectric Effect
Definition
Produced when light energy is above a certain threshold level, demonstrates the particle nature of light.
Term
Blackbody Radiation
Definition
Amount of EMR and its peak frequency depend on the temperature of an object. The amount of radiation at any frequency is based only on temperature.
Term
Wein's Law
Definition
Relates peak wavelength to temperature (Blackbody radiation). Wavelength(peak)T = 2.898x10^-3 m K
Term
Plasma
Definition
Ionized gas.
Term
Heliosphere
Definition
The region of interplanetary space where the solar wind is flowing supersonically.
Term
Comet tail
Definition
Made up of cometary material that has been heated by sunlight as it gets close to the sun and escaped from the nucleus.
Term
Coma
Definition
Glowing cloud of neutral and ionized gas and dust around the nucleus. "Blown back" away from the sun by solar wind.
Term
Solar wind
Definition
Plasma composed of mostly protons, helium nuclei and electrons that moves supersonically away from the sun and carries with it the sun's magnetic field.
Term
Corona
Definition
Sunlight scattered by electrons in Sun's outer atmosphere, not spherically symmetric or equally bright. More emission near equator because of structure of sun's magnetic field.
Term
Coronagraphs
Definition
Telescopes that routinely observe the corona without solar eclipse by using an occulting disk to block out photospheric light.
Term
Sun's escape velocity
Definition
The speed at which a particle needs to be moving away from the sun for it to never slow down, turn around and fall onto the sun. 618 km/s.
Term
Coronal particles
Definition
Mostly protons, helium nuclei and electrons that move supersonically away from the sun and carry with them the sun's magnetic field. Temperature of over 1 million kelvin therefore many have velocities great enough to escape sun. Make up solar wind, so solar wind is ionized plasma.
Term
Interplanetary Magnetic Field (IMF)
Definition
Part of the sun's magnetic field that is pulled out into the heliosphere by solar wind.
Term
Archimedean Spiral
Definition
The shape of the IMF, cause because of the sun's rotation causing the magnetized solar wind expands radially/directly away from the sun pulling solar magnetic field with it.
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