Lecture 3: The Earth, Magnetosphere and Ionosphere.
Sun Earth system Magnetospheric Physics Heliophysics Ionospheric Physics
Spacecraft
Heating of Solar Corona Convection cells Charged particles are moving Current and Magnetic Field Photo from UiO:Department of Physics movie
Solar Wind Solar wind (stream of charged particles or plasma) Velocity ~ 400-750 km/s, Temperature ~ 1000000 C In 2.5 days it reaches our planet Photo from UiO:Department of Physics movie
Mars Mars doesn t have a dynamo magnetic field It is constantly bombarded by the Solar wind NASA Viz: Mars' Lost Atmosphere
Comets and their coma Hubble image of Comet ISON shortly before perihelion. "Hubble's Last Look at Comet ISON Before Perihelion". ESA/Hubble Press Release. Retrieved 20 November 2013. Comet is an icy small Solar System body When passing close to the Sun, heats up and begins to outgas Solar radiation and the solar wind act upon the nucleus of the comet It creates a comet s atmosphere=coma The coma is generally made of H 2 O and dust, with water making up to 90%
Comet Tail The streams of dust and gas each form their own distinct tail, pointing in slightly different directions. The tail of dust is left behind in the comet's orbit; forms a curved tail called dust tail The ion tail, made of gases, always points directly away from the Sun because this gas is more strongly affected by the solar wind, following magnetic field lines rather than an orbital trajectory. http://solarsystem.nasa.gov/multimedia/gallery/comet_parts.jpg
Comets and their coma The ion tail of Encke's Comet was completely severed while the comet passed through a coronal mass ejection (April 2007) [STEREO space probe].
Parker Spiral Interplanetary Magnetic Field The Sun s corona is emitting a solar wind Solar wind consists of electrons, protons, αparticles = plasma Frozen-in, plasma carries magnetic filed Rotation + radial emission = ballerina skirt Parker spiral Smith, E. J., B. T. Tsurutani, and R. L. Rosenberg, Observations of the interplanetary sector structure up to heliographic latitudes of 16 : Pioneer 11, J. Geophys. Res., 83, 717, 1978.
Simulation of Earth s Geomagnetic Field Computer simulation of the Earth's field in a period of normal polarity between reversals. The lines represent magnetic field lines, blue when the field points towards the center and yellow when away. The rotation axis of the Earth is centered and vertical. The dense clusters of lines are within the Earth's core. generated by a geodynamo Glatzmaier, Gary A.; Roberts, Paul H. (1995). "A three-dimensional self-consistent computer simulation of a geomagnetic field reversal". Nature 377 (6546): 203 209. Bibcode:1995Natur.377..203G. doi:10.1038/377203a0.
Solar wind How does the Earth protect itself?
How does the Earth protect itself? Bow shock Tail
Van Allen Radiation Belt https://upload.wikimedia.org/wikipedia/comm ons/2/21/van_allen_belts.ogv This image was created using data from the Relativistic Electron-Proton Telescopes on NASA's twin Van Allen Probes. Image Credit: APL, NASA
Magnetic Bottle http://www.physics.byu.edu/faculty/christensen/physics%20220/fti/29%20magnetic%20fields/29.20%20motion%20of%20a%20charged%20p article%20in%20a%20magne tic%20bottle.htm
Radiation Belt Visualizations by Tom Bridgman on November 26, 2014
IMF How does the Earth protect itself?
Magnetic Reconnection
Charged particles Photo from UiO:Department of Physics movie
Charged particles Day Night Photo from UiO:Department of Physics movie
Photo from UiO:Department of Physics movie
Photo from UiO:Department of Physics movie Day Night
NASA - Magnetic Reconnection
Where on the Earth can we see Aurora? Aurora Borealis Aurora Australis Photo from UiO:Department of Physics movie
Ionosphere = Radiation Intensity Neutral density Ionosphere O +, NO +, O 2 +
Ionization: Photo photon neutral ion electron
Ionization: Precipitation particle neutral ion electron
What causes the light emission in aurora? Particle Nucleus Charged particles Light Photon
From grad.level lecture [AERO650_Hampton]
From grad.level lecture [AERO650_Hampton]
Why is it possible to see the aurora close to equator? 1859 Solar storm, the aurora was seen in Caribbean, Cuba and Hawaii
Colors of the Aurora Photo by Jan Curtis Oxygen Oxygen Oxygen 300 km Nitrogen 100 km O +, O 2 + NO +, O 2 +
Why it looks so different on different pictures? Photo by D. Lummerzheim 100 km
Why should we study plasmas? Fundamental understanding of the universe Modern infrastructure relies on the regions where plasma dominates: - Global communications - Weather forecasting - GPS navigation
How can we study plasmas? Build a large vacuum chamber in lab: $$$$$$$$$$$$$$ Build and fly spacecraft: $$$$$$$$$$$$$$ Observe from the ground (cameras) or probe (radars): $$ Model it: Find a graduate student
Poker Flat Incoherent Scatter Radar 4096 individual radar elements in a phased array Electron density electron temperature Ion temperature Velocity of ions Frequency of collisions
All-Sky Camera
From grad.level lecture [AERO650_Hampton]
Sounding Rocket Measurements Poker Flat Research Range is a University-owned Rocket Facility Onboard Payloads (data returned to ground antennas in real time) Electron & ion sensors, Electric field booms, Magnetometers, Cameras/photometers
2015 Rocket Launch PF
Laser Radar - Lidar Laser shots 20 pulses per second of green light into the sky. Echoes are recorded each time laser fires. Each pulse is half a Joule of energy ( 500 g falling through 8 inches on your toe). We count individual photons in the echoes coming from the sky. Echoes added up to reveal air, dust and clouds overhead.
How to take a picture of the Aurora? Almost any camera either digital or film will work for photographing the aurora, as long as you can adjust it manually to take time exposures of 10-30 seconds or longer. A wide-angle lens would be a much better choice lens be as 'fast' as possible (i.e., have a small f/ratio like f/2.8, f/2 or smaller) Never use a filter on your lens when photographing the aurora. This is not the time to use a flimsy tripod. It should be strong enough to hold the camera steady for long exposures. an electronic remote control is necessary to prevent vibrating the camera when pressing the shutter The key to aurora photography is a fast ISO setting for your camera. ISO 800 or 1600 (or higher) work well for aurora shots Time exposures: