Author Topic: NASA Rocket, Satellite Tag-Team to View the Giant Electric Current in the Sky  (Read 607 times)

0 Members and 1 Guest are viewing this topic.

Offline Elderberry

  • TBR Contributor
  • *****
  • Posts: 24,274
NASA.gov 7/2/2021

Some 50 miles up, where Earth’s atmosphere blends into space, the air itself hums with an electric current. Scientists call it the atmospheric dynamo, an Earth-sized electric generator. It’s taken hundreds of years for scientists to lay the groundwork to understand it, but the principles that keep it running are only just now being revealed in detail.

Following up on its predecessor’s 2013 flight, the Dynamos, Winds, and Electric Fields in the Daytime Lower Ionosphere-2, or Dynamo-2, sounding rocket mission will soon pierce the atmospheric winds thought to keep the dynamo churning. With the sounding rocket’s launch timed as NASA’s Ionospheric Connection Explorer satellite passes nearby, these two space missions will combine their perspectives to advance our understanding of the giant electric circuit in the sky. See below for information on how to stream the launch and where it will be visible in person.

The Dynamo mission

The atmospheric dynamo is a pattern of electrical current swirling in continent-sized circuits high above our heads. Driven by the Sun, it migrates across the planet, centered wherever the Sun is directly overhead. It comes alive in Earth’s ionosphere, a layer of the atmosphere where the Sun’s intense radiation separates electrons from their atoms, allowing electricity to flow.


A map of the ionospheric currents at the time of Dynamo 1’s launch on July 4, 2013. Currents – whose intensity is marked by
red and blue coloring – travel in opposite directions on either side of the magnetic equator, marked with a pink line. The yellow
dots are magnetometer readings from the ground.

Most measurements of the dynamo come from magnetometers on the ground, which monitor how that current disturbs Earth’s magnetic field (think of them as souped-up compasses). Ground-based measurements have their advantages – they can monitor one location for long periods of time, for instance. But to really see what’s going on in detail, you have to make measurements from inside the ionosphere, right where the electric current flows.

“It’s a really tricky part of space to get measurements, because the air is much too thin for an aircraft, and yet it's still too dense to fly most spacecraft,” said Scott England, space physicist at Virginia Tech in Blacksburg and collaborator for the upcoming Dynamo-2 campaign. “So one way of making these measurements is to fly a rocket through it.”

Sounding rockets, named for the nautical term “to sound,” meaning to measure, launch to make brief measurements in space before falling back to Earth a few minutes later. They excel at reaching hard-to-access regions of space that are too low for satellites to measure and too high to reach with scientific balloons – and they’re ideal for comparing wind speeds at different altitudes, since they slice through the atmosphere near-vertically.

“While ground-based methods can provide large-scale, integrated measurements, sounding rockets give us local, fine-scale data on the ionospheric current,” said Takumi Abe, space physicist at the Japan Aerospace Exploration Agency, or JAXA, and collaborator for the Dynamo missions. “That's when we use sounding rockets – when we'd like to see the small-scale physics.”

The first Dynamo mission – comprising scientists from NASA, JAXA, and several U.S. universities – launched their rockets on the 4th of July, 2013, from NASA’s Wallops Flight Facility on Wallops Island, Virginia. The team divided their instruments between two rockets, the first measuring electric fields while the second, launched just 15 seconds later, traced the winds, leaving behind a cloudy plume that glistened red in the sunlight similar to those observed in firework shows.

Observing from the ground and from a NASA aircraft, the team watched the crimson clouds morph in the wind as simultaneous electric field measurements were beamed back to the ground.

The vapor trail teased about in the wind, twisting and curling into a spiraling zig-zag. The telltale shape meant the winds were changing direction along the rocket’s flight path.

“They moved first to the east, and then a few miles above, they're all moving to the west, and a few miles above, they're all moving back to the east,” England said.

The zig-zag confirmed one aspect of the theory of atmospheric tides, which create high-altitude winds thought to drive the atmospheric dynamo. Heat from the ground below radiates up in waves, forcing parts of the atmosphere to move back and forth like the ebb and flow of ocean waves as they hit the beach.

“The zig-zag is the signature of this huge wave moving through this region,” England added.

Though the winds were expected by theory, their strength was not.

Based on magnetometer readings from the ground at the time, the team expected a weak current and mild winds above. Indeed, things were calm below the ionosphere’s base. But right where the reddish cloud trail pierced the lower parts of the ionosphere, where the dynamo is strongest, it was rapidly smeared across the sky.

“Just in the dynamo region, the wind suddenly takes off and gets very fast, over 150 meters per second (335 miles per hour),” said Rob Pfaff, space physicist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and principal investigator for both Dynamo missions. “It’s much stronger than what's predicted.”

These oppositely directed, high-speed winds were too fine-grained to be detected from ground-based measurements.

“It might look from the ground like the wind is going east at a very low speed,” said England. “But it turns out that's a very high speed to the east and a slightly lower speed to the west, averaged together.”

More: https://www.nasa.gov/feature/goddard/2021/nasa-rocket-satellite-tag-team-to-view-the-giant-electric-current-in-the-sky