Launching Rockets from the Top of the World 🚀
Over the next 14 months, our scientists will join a group of international researchers to explore a special region — Earth’s northern polar cusp, one of just two places on our planet where particles from the Sun have direct access to our atmosphere.
Earth is surrounded by a giant magnetic bubble known as a magnetosphere, which protects our planet from the hot, electrically charged stream of particles from the Sun known as the solar wind. The northern and southern polar cusps are two holes in this protection — here, Earth’s magnetic field lines funnel the solar wind downwards, concentrating its energy before injecting it into Earth’s atmosphere, where it mixes and collides with particles of Earthly origin.
The cusp is the only place where dayside auroras are found — a special version of northern and southern lights, visible when the Sun is out and formed by a different process than the more familiar nighttime aurora. That’s what makes this region so interesting for scientists to study: The more we learn about auroras, the more we understand about the fundamental processes that drive near-Earth space — including those processes that disrupt our technology and endanger our astronauts.
Photo credit: Violaene Kaeser
The teams working on the Grand Challenge Initiative — Cusp will fly sounding rockets from two Norwegian rocket ranges that fall under the cusp for a short time each day. Sounding rockets are sub-orbital rockets that shoot up into space for a few minutes before falling back to Earth, giving them access to Earth’s atmosphere between 30 and 800 miles above the surface. Cheaper and faster to develop than large satellite missions, sounding rockets often carry the latest scientific instruments on their first-ever flights, allowing for unmatched speed in the turnaround from design to implementation.
Each sounding rocket mission will study a different aspect of Earth’s upper atmosphere and its connection to the Sun and particles in space. Here’s a look at the nine missions coming up.
1. VISIONS-2 (Visualizing Ion Outflow via Neutral Atom Sensing-2) — December 2018
The cusp isn’t just the inroad into our atmosphere — it’s a two-way street. Counteracting the influx of particles from the Sun is a process called atmospheric escape, in which Earthly particles acquire enough energy to escape into space. Of all the particles that escape Earth’s atmosphere, there’s one that presents a particular mystery: oxygen.
At 16 times the mass of hydrogen, oxygen should be too heavy to escape Earth’s gravity. But scientists have found singly ionized oxygen in near-Earth space, which suggests that it came from Earth. The two VISIONS-2 rockets, led by NASA’s Goddard Space Flight Center in Greenbelt, Maryland, will create maps of the oxygen outflow in the cusp, tracking where these heavy ions are and how they’re moving to provide a hint at how they escape.
2. TRICE-2 (Twin Rockets to Investigate Cusp Electrodynamics 2) — December 2018
If the cusp is like a funnel, then magnetic reconnection is what turns on the faucet. When the solar wind collides with Earth’s magnetic field, magnetic reconnection breaks open the previously closed magnetic field lines, allowing some solar wind particles to stream into Earth’s atmosphere through the cusp.
But researchers have noticed that the stream of particles coming in isn’t smooth: instead, it has abrupt breaks in it. Is magnetic reconnection turning on and off? Or is the solar wind shooting in from different locations? TRICE-2, led by the University of Iowa in Iowa City, will fly two separate rockets through a single magnetic field line in the cusp, to help distinguish these possibilities. If reconnection sputters on and off over time, then the two rockets should get quite different measurements, like noting how it feels to run your finger back and forth under a faucet that is being turned on and off. If instead reconnection happens consistently in multiple locations — like having ten different faucets, all running constantly — then the two rockets should have similar measurements whenever they pass through the same locations.
Magnetic reconnection is a process by which magnetic field lines explosively realign
3. CAPER-2 (Cusp Alfvén and Plasma Electrodynamics Rocket) — January 2019
The CAPER-2 rocket, led by Dartmouth College in Hanover, New Hampshire, will examine how fast-moving electrons — particles that can trigger aurora — get up to such high speeds. The team will zero in on the role that Alfvén waves, a special kind of low-frequency wave that oscillates along magnetic field lines, play in accelerating auroral electrons.
An illustration of rippling Alfvén waves
4. G-CHASER (Grand Challenge Student Rocket) — January 2019
G-CHASER is made up entirely of student researchers from universities in the United States, Norway and Japan, many of whom are flying their experiments for the first time. The mission, led by the Colorado Space Grant Consortium at the University of Colorado Boulder, is a collaboration between seven different student-led missions, providing a unique opportunity for students to design, test and ultimately fly their experiment from start to finish. The students involved in the mission — mostly undergraduates but including some graduate teams — are responsible for all aspects of the mission, from developing the initial idea, to securing the funding, to making sure it passes all the tests before flight.
5 & 6. AZURE (Auroral Zone Upwelling Rocket Experiment) and CHI (Cusp Heating Investigation) — April & November/December 2019
When the aurora shine, they don’t just emit light — they also release thermal and kinetic energy into the atmosphere. Some of this energy escapes back into space, but some of it stays with us. Which way this balance tips depends, in part, on the winds in the cusp. AZURE, led by Clemson University in South Carolina, will measure the vertical winds that swish energy and particles around within the auroral oval, the larger ring around the pole where the aurora are most common.
Later that year, the same team will launch the CHI mission, using a methodology similar to AZURE to measure the flow of charged and neutral gases inside the cusp. The goal is to better understand how particles, flowing in horizontal and vertical directions, interact with each other to produce heating and acceleration.
7. C-REX-2 (Cusp-Region Experiment) — November 2019
The cusp is a place where strange physics happens, producing some anomalies in the physical structure of the atmosphere that can make our technology go haywire. For satellites that pass through the cusp, density increases act like potholes, shaking up their orbits. Scientists don’t currently understand what causes these density increases, but they have some clues. C-REX-2, led by the University of Alaska Fairbanks, aims to figure out which variables — wind, temperature or ion velocity — are responsible.
8. ICI-5 (Investigation of Cusp Irregularities-5) — December 2019
Recent research has uncovered mysterious hot patches of turbulent plasma inside the auroral region that rain energetic particles towards Earth. GPS signals become garbled as they pass through these turbulent plasma patches, affecting so many of today’s technologies that depend on them. ICI-5, led by the University of Oslo, will launch into the cusp to take measurements from inside these hot patches. To measure their structure as several scales, the rocket will eject 12 daughter payloads in concentric squares which will achieve a variety of different separations.
9. JAXA’s SS-520-3 mission — January 2020
Exploring the phenomenon of atmospheric escape, the Japan Aerospace Exploration Agency’s SS-520-3 mission will fly 500 miles high over the cusp to take measurements of the electrostatic waves that heat ions up and get them moving fast enough to escape Earth.
For updates on the Grand Challenge Initiative and other sounding rocket flights, visit nasa.gov/soundingrockets or follow along with NASA Wallops and NASA heliophysics on Twitter and Facebook.
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