NASA's experiments are divided into four areas:
Magnetic and solar storms inject plasma into the magnetosphere. The reaction of the natural magnetosphere to these injections is important to understanding energy and particle transport. Injections of barium ions will simulate natural plasma injections in a precisely controlled manner. These four injections will be at different altitudes and magnetic field strengths to understand how different regions of space react to the artificial cloud plasmas.
The late Neil Brice proposed in 1970 that injections of artificial ion clouds in the Van Allen radiation belts would cause the high-energy charged particles to "unstick" from the magnetic field and crash into the atmosphere.
This theory will be tested by injecting an artificial lithium plasma in a region of high-energy, trapped electrons. Observers with optical instruments and radars will closely monitor the footprint of the magnetic field line where it enters the atmosphere in Canada and South America to search for artificial auroras created by these particles.
High-energy protons dominate the pre-midnight sector of the high-altitude magnetosphere. Some of these "leak out" of stable trapped orbits and precipitate into the atmosphere to cause a weak aurora. This experiment will inject an artificial lithium plasma cloud into this proton region and measure any increased proton precipitation.
Essentially this experiment has the same objectives as the previous one, except the particles of interest are protons rather than electrons. The enhanced precipitation will be detected by optical instruments at the base of the magnetic field line, as these protons will produce light in the distinct wavelengths of the hydrogen atom. The instruments on CRRES will monitor the state of the magnetosphere and will aid in determining the best time for the release.
The release of tracer lithium ions will be tracked by instruments aboard the NASA Dynamics Explorer 1, CRRES, SCATHA and the Japanese AKEBONO satellites. The previous two lithium releases also can be used for this experiment, but this release will be made when the relative positions of these satellites are especially favorable for observing the artificial tracer ions.
Space plasmas often become highly irregular and structured. Electric and magnetic fields are known to be important to this process, but less is known about the effects of gravity. For the light protons in the magnetosphere, it is safe to assume that the effect of gravity is negligible compared to electric and magnetic forces. For the heavier ions, such as oxygen and nitrogen, this assumption is questionable. This release will create a heavy barium plasma along a magnetic field line, and the distortions due to the action of gravity will be studied with optical instruments and the radar at Jicamarca, Peru.
The CRRES satellite releases gas at orbital velocity, and the ion clouds that form are moving very rapidly (8 to 10 kilometers per second) relative to the natural ionosphere. This state is common in nature, occurring when beams of electrons enter the auroral zone or when material is pulled into a star. The beams eventually slow down, but not through physical collisions between particles, as is the case with neutral gases. Instead, the physics of beam-plasma interactions are dominated by the long-range electrical and magnetic forces that act on the charged particles. The exact mechanisms of these interactions are not well understood
In this experiment, barium will be released over an extensive network of ground and aircraft observatories in the Caribbean, while instruments on CRRES will measure the electric and magnetic fields resulting from the interactions.
Sometimes during a magnetospheric substorm a very large number of charged particles reach the atmosphere together, causing a very bright aurora.
This experiment will attempt to create a substorm by injecting an artificial barium plasma at the precise moment which the magnetosphere is unstable, "pushing the magnetosphere over the edge." Since barium ions can be seen glowing in sunlight (the particles normally there cannot), scientists will be able to obtain a clear visual picture of the magnetic substorm creation and its behavior.
As the release of barium ions flows along magnetic field lines, it will be affected by electric fields as well. By tracking the details of the ions' motion, these electric fields can be measured. Such electric fields are important in controlling inter- hemispheric flows of electrons and ions.
The releases over the Caribbean will fill the entire magnetic field line over the equator and down to the other end in South America. Observations from ground and aircraft observatories in the Caribbean and South America will pinpoint the details of the ion motions.
The objective of these releases is to investigate the critical ionization velocity phenomenon, first proposed by Alfven to explain mass differentiation in planetary formation -- why the inner planets are made of heavy material and the outer planets are mostly hydrogen.
The critical ionization velocity model states that if the relative velocity of electrically neutral chemical species and a magnetized plasma is large enough, ionization of the neutral gas will take place even though the energy available is less than that required for ionization.
Barium, calcium and strontium will be released in these experiments. These materials have a range of critical ionization velocities, allowing study of the effect over a wide range of this parameter.
In addition to the releases from the CRRES spacecraft, the CRRES program includes chemical-release experiments from several sounding rockets. Two sounding-rocket campaigns are planned, one from Kwajalein in the Marshall Islands in July and August 1990 and the other from Puerto Rico in June and July 1991:
The reflection of high-frequency (HF) radio waves by a smooth, conducting ionosphere allows reception of AM radio, long-range HF communications and over-the-horizon surveillance radar. When stressed, the ionosphere "fractures" along the direction of the magnetic field and acts like a picket fence to scatter radio waves.
This experiment and a companion, AA-7, will stimulate this plasma fracturing process with large barium releases in the F and E regions of the lower ionosphere over the Arecibo, Puerto Rico, radar site. The radar will diagnose the details of the structuring while airborne instruments monitor fading and disruption of satellite radio signals. Comparing these observations to theoretical predictions will provide an acid test of present understanding of principles of plasma physics with far-reaching implications.
The Arecibo High-Frequency Radio Ionospheric Heater can beam powerful radio waves into the ionosphere. These radio waves, with millions of watts of effective power, can "push the ionosphere around" and create significant perturbations and structures.
In this experiment, a heavy barium plasma will replace the natural light ionosphere plasma (normally hydrogen and oxygen) in the beam of the radio wave heater. The heater beam will be turned on the heavy plasma and scientists can see its response to the perturbations and compare the results to heater experiments with the natural ionosphere.
This experiment has two sets of objectives. The first is to release a small tracer amount of barium into an ionospheric region that has been heated and disturbed by the Arecibo transmitter, making the heater-induced perturbations visible. This experiment complements the previous barium plasma heating experiment and enlarges the area under study.
The second objective is a study of multi-ion expansion processes. Since ions are electrically charged, they interact through long-range electrical forces, not just by physical collisions. Many natural processes, such as the population of the magnetosphere with upward flowing ions from the ionosphere and the expansion of the atmospheres of stars, involve ions of more than one type or mass. The presence of one type of ion can have a strong influence on another.
Canisters of lithium (a light ion, mass = 7) and barium (a heavy ion, mass = 137) will be released. As the expanding ion clouds sweep past the rocket, on-board instruments will study the details of the clouds and their complex interactions.
The ionosphere bends radio waves just like a lens or prism bends light. A chemical release will create a spherical lens in the ionosphere focusing waves from a high-power ground transmitter into a powerful beam travelling upward. The power density input level is expected to be 10 to 100 times the level it would be without focusing.
The Arecibo radar and instruments will study how the ionosphere is changed by this focused radio beam. This will be important to the understand of how the ionosphere responds to natural energy inputs from magnetic storms and solar flares.
The ionosphere near the Equator, where the magnetic field is horizontal, suffers from natural perturbations known as Spread-F. The normally smooth ionosphere breaks up and radio wave signals are distorted.
These experiments will release sulfur hexafluoride, which will start a "bubble" at the bottom of the ionosphere and trigger artificial Spread-F. This will allow study of the growth and decay of this effect with a controlled experiment. In these experiments, one rocket will deploy the ionospheric depletion chemical, and a second will carry instruments to diagnose the release effects.
The ionosphere is divided into layers, designated D, E and F (from lowest to highest). The layers are connected by magnetic field lines, which allow particles to travel between regions.
A large barium release in the F-region will be placed so the connected E-region is directly over the Arecibo radar. The artificial cloud in the F-region will create an image in the E- region that can be mapped by the radar, allowing scientists to study the strength and speed of inter-region ionospheric coupling.
More than 50 DOD scientific instruments will be operating aboard CRRES, including a microelectronics package, experimental high-efficiency solar panels and instruments to investigate the effects of solar flares and cosmic rays on the Earth's magnetosphere and radiation belts. Instruments to support the perigee observations include two pulsed plasma probes (a very low frequency wave analyzer with two electric field antennas), a magnetic field loop antenna and a quadrupole ion mass spectrometer.
Some DOD scientific instruments on CRRES will complement the CRRES chemical science mission, measuring the effects of the releases at close range. For some of the releases, the instruments will measure the state of particles and waves in the magnetosphere and assess if a large magnetic storm is imminent. This will help scientists determine the best time to conduct a release. The five main DOD experiments:
CRRES Program Experiments
Release Release
Experiment no. Chemical Location Altitude Period
____________________________________________________________________________________
SATELLITE EXPERIMENTS
Critical Velocity
Critical Velocity G-13 Strontium Am. Samoa 270-360 mi. Sept. 1990
Ionization Barium
G-14 Calcium Am. Samoa 270-360 mi. Sept. 1990
Barium
High-Altitude Magnetospheric
Diagmagnetic Cavity, G-1 Barium N. America 1.3 Re* Jan-Feb 1991
Plasma Coupling G-2 Barium N. America 1.8 Re Jan-Feb 1991
G-3 Barium N. America 3.5 Jan-Feb 1991
G-4 Barium N. America 5.5 Jan-Feb 1991
Stimulated Electron/ G-5 Lithium N. America >6.0 Re Jan-Feb 1991
Aurora Production
Stimulated Ion- G-6 Lithium N.America >6.0 Re Jan-Feb 1991
Cyclotron Waves
and Ion Precip.
Ion Tracing G-7 Lithium N. America >6.0 Re Jan-Feb 1991
and Acceleration
Velocity Distribution G-9 Barium Caribbean June-July 1991
Relaxation
Caribbean Perigee
Grav. Instability G-8 Barium Caribbean 270-480 mi. June-July 1991
Field Equipotentiality
Field Line G-10 Barium Caribbean 270-480 mi June-July 1991
Tracing and G-11 Barium Caribbean 270-480 mi June-July 1991
Equipotentiality G-11A Barium Caribbean 270-480 mi June-July 1991
G-12 Barium Caribbean 270-480 mi June-July 1991
G-12A Barium Caribbean 270-480 mi June-July 1991
*Re=Earth radii
CRRES PROGRAM EXPERIMENTS
Release Release
Experiment no. Chemical Location Altitude Period
__________________________________________________________________________________
SOUNDING ROCKET EXPERIMENTS
Kwajalein
Equatorial AA-5 SF6* Kwajalein 240 mi Jul.-Aug. 1990
Instability Seeding AA-6A SF6 Kwajalein 150 mi Jul.-Aug. 1990
AA-6B SF6 Kwajalein 150 mi Jul.-Aug. 1990
Puerto Rican Rockets
F-Region AA-1 Barium Puerto Rico 150 mi June-July 1991
Irregularity Evolution
HF Ionospheric AA-2 Barium Puerto Rico 150 mi June-July 1991
Modification of
a Barium Plasma
E-Region AA-7 Barium Puerto Rico 150 mi June-July 1991
Image Formation
HF-Induced Ion AA-3 Barium Puerto Rico 90-240 mi June-July 1991
Striation/Differential Barium Puerto Rico 90-240 mi June-July 1991
Ion Expansion Barium Puerto Rico 90-240 mi June-July 1991
SF6 Puerto Rico 90-240 mi June-July 1991
Ionospeheric AA-4 SF6 Puerto Rico 210-240 mi June-July 1991
Focused Heating
*SF6=Sulfur hexafluoride
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