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Space Weather Final
Terms from Intro to Space Weather chpt 3-5
67
Astronomy
Undergraduate 1
05/05/2013

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Term
Archimedean Spiral
Definition
Sun's rotation rate basically constant, angle of spiral due to solar wind speed. Faster wind means smaller angle
Term
Closed-field Regions
Definition
Regions of diploe-like field with a loop of plasma coming out of the rim. Near sun's equatorial plane. Solar wind moves slower from these than open mgf regions.
Term
Open-field Regions
Definition
Near the poles where a "ray" of plasma flows along a field line not looping back to the surface, also called coronal holes.
Term
Shape of IMF
Definition
Has Archimedean spiral structure in N-S direction because magnetic equator of sun not aligned with earth's spin axis, causes waviness of IMF.
Term
Heliospheric Current Sheet
Definition
Plasma that came from sun's magnetic equator that divides IMF pointing away from sun from IMF pointing towards sun.
Term
CME
Definition
When reconfigurations of the solar mgf cause large portion of the corona to blast away from the sun and out into the heliopshere. Large-scale magnetic structures that can contain over 10^12 kg of hot coronal material. Often have a shock and a high-density "plug" of plasma in front of them due to slower solar wind plasma being "swept up".
Term
Shock Wave
Definition
Formed when speed of an object exceeds the sound speed of the background material.
Term
Sound Speed
Definition
Dependent on a material's density and temperature. Shockwave in interplanetary space is a good particle accelerator.
Term
Flux Ropes
Definition
Distinctive, loop-like mgf structures common in CME's. In CME's, called magnetic clouds.
Term
Geomagnetic Storms
Definition
Fast CME's are leading cause of these. A world-wide disturbance in the magnetic field at Earth caused by an enhancement of the ring current in the magnetosphere.
Term
Outer Heliosphere
Definition
Region well beyond the orbit of Pluto where the solar wind interacts directly with interstellar space.
Term
Heliopause
Definition
Boundary between heliosphere and interstellar medium (ISM). About 100 AU away.
Term
Termination Shock
Definition
Formed between supersonic flow of the solar wind and ISM. 90 AU from the sun.
Term
Interstellar Medium
Definition
ISM, mix of electrically neutral atoms and magnetized plasma.
Term
Shape of Heliosphere
Definition
Tear-drop shape caused by velocity different between heliosphere and ISM, with a termination shock inside the heliopause.
Term
How Long it Takes to Orbit Galaxy
Definition
~250,000,000 years. In 4.5 billion years, Earth's orbited galaxy 18 times.
Term
Alpha Centauri
Definition
Closest star, about 4 light years (1 lightyear= 10 trillion km) away.
Term
Cosmic Rays
Definition
Highly ionized atoms and other subatomic particles Nearly speed of light, mostly nuclei, electrons, positrons, MeV or GeV. Can't trace because galactic mgf's deflect charged particles.
Term
Galactic Cosmic Rays
Definition
1 of 2 sources of particles in Cosmic Rays, with particles that originate outside our heliosphere. Originate in super novae.
Term
Solar Energetic Particles
Definition
Particles that originate from our sun (part of cosmic rays)
Term
Electron-Volt
Definition
Energy unit equal to energy gained by an electron accelerated through a one-volt potential electric field or 1.6x10^-19 J.
Term
Super Novae
Definition
One per 50 years in a galaxy like the Milky Way.
Term
Death of a Star
Definition
After a star uses all its thermonuclear fusion, outer layers collapse with a huge explosion that expels stellar material into space and causes shock waves to form. Explosion and shock waves produce particles w/ very high energy.
Term
Progenitor Star
Definition
Dying star. Shock waves continue leaving star and acceleration particles for years after initial explosion.
Term
Pions
Definition
Unusual subatomic particles created by high energy cosmic ray particles hitting atmospheric particles and creating showers of secondary particles. Decay quickly to produce muons, neutrinos and gamma rays. Muons decay to positrons and electrons. About 1000 particles per min passing through our bodies. Can kill/damage astronauts/satellites in space.
Term
Mechanics
Definition
Study of moving objects or bodies
Term
Motion
Definition
Change in position of a body with respect to another body or some reference frame.
Term
Intertial Reference Frame
Definition
Fixed reference frame. Good to define so observers and describe motion of an object.
Term
Laws of Physics
Definition
Valid and identical in all reference frames, principle of physics.
Term
Coordinate systems
Definition
Set of rules that describes quantitatively where an object is located from a specific point, called the origin.
Term
Plane
Definition
2D region that can be describes by 2 coordinates
Term
Rene Descartes
Definition
French mathematician who developed the Cartesian plane/coordinate system.
Term
Solar Ecliptic Frame of Reference
Definition
Center of sun is the origin, x axis is line connecting center of sun with center of earth, z axis is perpendicular to x-line and plane that contains earth's yearly orbit around the sun.
Term
Speed
Definition
(x2-x1)/(t2-t1) or delta x over delta t in m/s. It is a scalar.
Term
Velocity
Definition
An object's speed and direction of motion. It is a vector.
Term
Vector
Definition
Mathematical quantity with both magnitude (speed) and direction.
Term
Scalar
Definition
Parameter with magnitude but no direction.
Term
Accelerating
Definition
if object is slowing down/speeding up/changing direction over time. Changing velocity over time. Vector. a= (v2-v1)/(t2-t1) or delta v over delta t
Term
Force
Definition
Action that causes an object to change its velocity or acceleration. F= mass x acceleration.
Term
Sir Isaac Newton
Definition
Developed laws of motion that accurately describe the motion of almost everything. (Einstein's special relativity accounts for the almost).
Term
Gravitational Acceleration
Definition
Is 9.8 m s^-2 near Earth's surface.
Term
Weight
Definition
The mass of Earth pulling us down to the surface.
Term
Magnetosphere
Definition
The region around an astronomical object in which phenomena are dominated or organized by its magnetic field.
Term
100 km above Earth's surface
Definition
The amount of ionized gas becomes appreciable.
Term
Magnetic fields
Definition
force fields around magnets, electric currents, or moving charged particles that exert a force on other magnets.
Term
Earth's magnetic field
Definition
Relatively strong due to motion of molten iron inside Earth. Emerges from one hemisphere with a certain direction and points towards the opposite hemisphere. Usually north pole is where mgf points outward.
Term
Dipole
Definition
A mgf where there are two magnetic poles, such as Earth. Field is two times stronger at the poles than at the equator and falls off very quickly with distance.
Term
Magnetic Pole
Definition
Points where the magnetic field emerges straight out of or into the Earth.
Term
Weight
Definition
The mass of Earth pulling us down to the surface.
Term
Inner magnetosphere
Definition
Dipole region of Earth's magnetosphere.
Term
100 km above Earth's surface
Definition
The amount of ionized gas becomes appreciable.
Term
Magnetic fields
Definition
force fields around magnets, electric currents, or moving charged particles that exert a force on other magnets.
Term
Earth's magnetic field
Definition
Relatively strong due to motion of molten iron inside Earth. Emerges from one hemisphere with a certain direction and points towards the opposite hemisphere. Usually north pole is where mgf points outward.
Term
Dipole
Definition
A mgf where there are two magnetic poles, such as Earth. Field is two times stronger at the poles than at the equator and falls off very quickly with distance.
Term
Magnetic Pole
Definition
Points where the magnetic field emerges straight out of or into the Earth.
Term
Strength of mgf at equator
Definition
|B| = C/r^3, were C = a constant that depends on latitude and r = distance
Term
Outer magnetosphere
Definition
Non-dipolae regions of Earth's magnetosphere.
Term
Geosynchronous Orbit
Definition
6.6 Earth radii (rE) from the center of Earth
Term
Plasmasphere
Definition
Region of cold, dense plasma that essentially co-rotates with, and immediately surrounds, Earth. Dominated entirely by the geomagnetic field. consists mostly of hydrogen and helium w/ appreciable amt of oxygen atoms that have just enough energy to escape from Earth’s ionosphere.
Term
eV
Definition
Electron-volt. Measure of kinetic energy. For a proton, 1 eV corresponds to a velocity of about 14 km s^-1
Term
Latitude
Definition
Position above or below the equator, measured in degrees
Term
Longitude
Definition
Position marked by degrees, starting with 0 meridian, and extending Eastward around the globe.
Term
plasmapause
Definition
very sharp outer boundary to the dense plasmasphere
Term
Plasma density
Definition
frequently drops an order of magnitude within a very short radial distance (less than 0.5 rE)
Term
Van Allen radiation belts and
Definition
Often overlapping with the plasmasphere, characterized by high-energy particles that are trapped inEarth's magnetosphere. belts are particles w/ energies extending into relativistic regime.
Term
Relativistic particles
Definition
have velocities near the seed of light and carry tremendous amounts of kinetic energy.
Term
the ring current
Definition
Often overlapping with the plasmasphere, characterized by high-energy particles that are trapped inEarth's magnetosphere. Ring current is made of particles w/ a peak energy of about 200 KeV. Charged particles produce an electric current that encircles Earth.
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