Cometary Aurora

Comet 67P/Churyumov-Gerasimenko. Credit: NASA/JPL.

September 25, 2020

It has been awhile since the latest report about comet 67P/Churyumov-Gerasimenko. The Rosetta spacecraft crashed into it on September 30, 2016.

Aurorae on Earth are cause by charged particles from the Sun. As previously written, the U.S. Navy satellite, TRIAD, recorded electromagnetic disturbances as it passed over Earth’s poles and through the Van Allen Radiation Belts in 1966. Those vertical electric currents that flow to Earth from the solar wind were named, “Birkeland currents” by Alex Dessler. The solar wind is captured in the magnetosphere, where it is collected in a plasma sheet within the magnetotail, and held together by Earth’s magnetic field.

Electromagnetic instabilities also occur in bright aurorae. Norwegian scientist, Kristian Birkeland camped-out on the Arctic ice in the early 20th Century. Along with a research team, he discovered that electric charge from the Aurora Borealis flowed parallel to the auroral formation. Since electricity must flow in a circuit, and since the auroral glow seemed to be caused by events in space, Birkeland proposed that it came down from space at one end of the auroral arc and back out to space at the other. A clue to 67P’s aurora are probably couched in similar events.

What does it mean when atoms are excited? When charged particles from the Sun strike atoms in atmospheric gases, electrons jump to higher-energy orbits, farther from the nucleus. When those electrons return to lower-energy orbits, they emit light. The aurorae are like neon lights in that regard: electricity excites gas within the glass tubes of neon signs.

The MAVEN mission to Mars also found aurorae in the South Polar region. Mars has no intrinsic magnetic field, but it does possess bands of crustal magnetism in its lower latitudes. Astrophysicists do not know what caused the peculiar magnetized stripes that seem to focus on a specific point in the south, or why the auroral events should be associated with them.

Non-thermal radiation readings (evidence for lightning discharges), independent of the surface temperature, and during one of the giant dust storms, were gathered by MAVEN’s Langmuir Probe and Waves (LPW) instrument. To the surprise of the mission team, a dust cloud in the Martian atmosphere at around 150 kilometers above the surface was found to be electrically charged.

Synchrotron radiation is electromagnetic radiation emitted when charged particles travel in curved paths. In most accelerator experiments, particle trajectories are bent by magnetic fields. The emitted spectrum can include microwaves to X-rays. The radiation is vertically collimated and polarized, and can manifest as extreme ultraviolet light. Comet 67P was found to be a highly charged object interacting with the solar wind.

In an Electric Universe, cometary ion tails always point away from the Sun, because comets are affected by electrical discharges in a radial solar electric field. Their electric charges become increasingly negative with respect to the solar plasma as comets gradually move closer to the Sun. Comets lose mass in the form of extremely fine dust and negatively charged ions through a process called cathode sputtering, so their disturbance in the solar plasma is far greater than can be explained by inert objects. Negative charge in the comets and in their tails attract nearby solar wind protons, decelerating them in the vicinity and causing an overall deceleration of the solar wind.

Since the negative charge on cometary nuclei is discharged by solar wind protons, it is not surprising that low level electromagnetic fields are found there, including aurorae.

Stephen Smith

The Thunderbolts Picture of the Day is generously supported by the Mainwaring Archive Foundation.

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