Credit: Vincent Ledvina, theauroraguy.com Phenomena called “Steve” and “picket fence” are masquerading as auroras, graduate student argues.The shimmering green, red, and purple drapes of the northern and southern lights– the auroras– may be the best-known phenomena lighting up the nighttime sky, however the most mystical are the mauve and white streaks called Steve and their regular buddy, a radiant green “picket fence. Due to the fact that all these transient luminous phenomena are activated by solar storms and coronal mass ejections from the sun, the approaching solar maximum is a perfect time to study rare occasions like Steve and the picket fence.Understanding the Picket Fence PhenomenonGasque explained the physics behind the picket fence in a paper published last month in the journal Geophysical Research Letters and will go over the outcomes on Dec. 14 in a welcomed talk at the American Geophysical Union conference in San Francisco.She determined that in an area of the upper atmosphere further south than that in which auroras form, electrical fields parallel to Earths magnetic field could produce the color spectrum of the picket fence. Steve and the picket fence also occur at lower latitudes than the aurora, possibly even as far south as the equator.Some researchers proposed that Steve is triggered by ion streams in the upper environment, referred to as subauroral ion drift, or SAID, though theres no well accepted physical explanation for how SAID might create the vibrant emissions.Gasques interest was triggered by tips that the picket fences emissions could be generated by low-altitude electrical fields parallel to Earths magnetic field, a scenario believed to be difficult because any electric field lined up with the magnetic field ought to quickly short out and disappear.Using a common physical model of the ionosphere, Gasque consequently revealed that a moderate parallel electric field– around 100 millivolts per meter– at a height of about 110 km might accelerate electrons to an energy that would delight oxygen and nitrogen and create the spectrum of light observed from the picket fence. Their estimations likewise forecast the type of ultraviolet emissions that this procedure would produce, which can be examined to validate the new hypothesis about the picket fence.Though Gasques calculations dont directly resolve the on-off radiance that makes the phenomenon look like a picket fence, its most likely due to wavelike variations in the electric field, she said. And while the particles that are accelerated by the electric field are most likely not from the sun, the rushing of the atmosphere by solar storms probably activates Steve and the picket fence, as it does the typical aurora.Enhanced Auroras Exhibit a Picket Fence-Like GlowThe next action, Harding stated, is to launch a rocket from Alaska through these phenomena and measure the strength and instructions of the electric and magnetic fields.
Credit: Vincent Ledvina, theauroraguy.com Phenomena called “Steve” and “picket fence” are masquerading as auroras, graduate trainee argues.The glittering green, red, and purple drapes of the southern and northern lights– the auroras– might be the best-known phenomena lighting up the nighttime sky, but the most mystical are the mauve and white streaks called Steve and their frequent companion, a radiant green “picket fence. Due to the fact that all these short-term luminous phenomena are activated by solar storms and coronal mass ejections from the sun, the approaching solar maximum is an ideal time to study unusual events like Steve and the picket fence.Understanding the Picket Fence PhenomenonGasque described the physics behind the picket fence in a paper released last month in the journal Geophysical Research Letters and will go over the results on Dec. 14 in an invited talk at the American Geophysical Union conference in San Francisco.She calculated that in a region of the upper atmosphere farther south than that in which auroras form, electrical fields parallel to Earths magnetic field might produce the color spectrum of the picket fence. Steve and the picket fence likewise happen at lower latitudes than the aurora, potentially even as far south as the equator.Some scientists proposed that Steve is caused by ion flows in the upper atmosphere, referred to as subauroral ion drift, or SAID, though theres no well accepted physical description for how SAID could generate the colorful emissions.Gasques interest was stimulated by suggestions that the picket fences emissions might be generated by low-altitude electric fields parallel to Earths magnetic field, a scenario believed to be difficult because any electric field lined up with the magnetic field should quickly short out and disappear.Using a common physical design of the ionosphere, Gasque subsequently showed that a moderate parallel electrical field– around 100 millivolts per meter– at a height of about 110 km could accelerate electrons to an energy that would delight oxygen and nitrogen and create the spectrum of light observed from the picket fence.
