NORTHERN LIGHTS (AURORA BOREALIS): WHAT THEY ARE & HOW TO SEE THEM?

             The Northern Lights are an atmospheric phenomenon that's regarded as the holy grail of the sky watching.

Image Credits: Freepik

            The Northern Lights, or the aurora borealis, are beautiful dancing waves of lights that have captivated people for millennia. But for all its beauty, this spectacular light show is a rather violent event.

            Energized particles from the sun slam into Earth's upper atmosphere at speeds of up to 45 million mph (72 million kph), but our planet's magnetic field protects us from the onslaught.

           As Earth's magnetic field redirects the particles towards the poles -- there are southern lights, too, which you can read about below -- the dramatic process transforms into a cinematic atmosphere phenomenon that dazzles and fascinates scientist and sky watches alike.

            

THE HISTORY OF THE NORTHERN LIGHTS

            Though it was Italian astronomer Galileo Galilei who coined the name "aurora borealis" in 1619 -- after the Roman Goddess of down, Aurora, and the Greek god of the north wind Breas -- the earliest suspected record of the northern lights in a 30,000-years old cave painting in France.

            Since that time, civilizations around the world have marveled at the celestial phenomenon, ascribing all sorts or origin myths to the dancing lights. One North American Inuit legend suggests that the northern lights are spirits playing balls with a Walrus head, while the Viking thought the  phenomenon was light reflecting off the Armor of the Valkyrie, the super natural maiden who brought the warriors into the afterlife.

            Early astronomer also mentioned the Northern Lights in their records. A royal astronomer under Babylon's king Nebuchadnezzar ll inscribed his report of the phenomenon on a tablet dated to 567 B.C., for example, while a Chinese report from 193 B.C. also notes the aurora, according to NASA.

            The science behind the Northern Light wasn't theorized until the turn of the 20th century. Norwegian scientist Kristian Birkland proposed that electrons emitted from sunspots produced the atmospheric lights after being guided towards the poles by Earth's magnetic field. The theory would eventually prove correct, but not until long after Birkland's 1917 death.

            A lime-green aurora glows above Earth's city lights in this view from the International Space Station. At the this photo was taken, the Space Station was orbiting about 258 miles (415 kilometers) above Russia and the Ukraine. A portion of the space station's solar array is visible in the top left corner of the image. (Image Credit: NASA)

WHAT ARE THE NORTHERN LIGHTS?

            At any given moment, the sun is ejecting charged particles from its corona, or upper atmosphere, creating what's called the solar wind. when that wind slams into Earth's ionosphere, or upper atmosphere, the aurora is born. In the Northern Hemisphere, the phenomenon is called the northern lights (aurora borealis), while in the Southern Hemisphere, it's called  the southern lights (aurora australis).

            "These particles are deflected towards the poles of the Earth by our planet's magnetic field and interact with our atmosphere, depositing energy and causing the atmosphere to fluoresce, "said astronomer Billy Teets, the director of Dyer Observatory at Vanderbilt University in Nashville, Tennessee. 

            The bright colors of the northern lights are dictated by the chemical composition of Earth's atmosphere.

            "Every type of atom molecule, whether it's atomic hydrogen or a molecule like carbon dioxide, absorbs and radiates its own unique set of colors, which is analogous to how every human being has a unique set of fingerprints, "Teets told Space.com. "Some of the dominant color seen in aurorae at red, a hue produced by the nitrogen molecules, and green, which is produced by oxygen molecules".

            While solar wind is constant, the sun's emission go through a roughly 11-years cycle of activity. Sometimes there's a lull, but other times, there are vast storms that bombard Earth with extreme amount of energy. This is when the Northern Lights are at their brightest and most frequent. The last Solar maximum, or period of peak activity, occurred in 2014, according to the U.S National Oceanic and Atmospheric Administration (NOAA), placing the next one in approximately 2025.

            Despite plenty of advances in heliophysics and atmospheric science, much about the northern lights remains a mystery. For example, researches weren't entirely sure how the energized particles in the solar wind get accelerated to their extraordinary speeds (45 million mph) until June 2021, when a study published in the journal Nature Communications confirmed that a phenomenon called Alfven waves gave the particles a boost. Alfven waves are low-frequency yet powerful undulations that occurs in plasma due to electromagnetic forces; that electrons that create the northern lights "surf" along these waves in Earth's atmosphere, accelerating rapidly.

            NASA is also on the hunt for clues about how the Northern Lights work. In 2018, the space agency launched the Parker Solar Probe, which is currently orbiting the Sun and eventually get close enough to "touch" the corona. While there, the spacecraft will collect information that could reveal more about the Northern Lights.

Image Credits: Parker Solar Probe - Wikipedia

NORTHERN LIGHTS, SOUTHERN LIGHTS AND STEVE

            On Earth, the northern lights counterpart in the Southern Hemisphere is the southern lights - they are physically the same and differ only in their location. As such, scientists expect them to occur simultaneously during the solar storm, but sometimes the onset of one lags behind the other.

            "One of the more challenging aspects of nightside aurorae involves the comparison of the aurora borealis with the aurora australis", said Steven Petrina, a physicist at the aerospace company Lockheed Martin who specializes in magnetospheric and heliosphere physics.

            While some auroral emissions occur in both hemispheres at the same magnetic local time, other emissions appear in opposing sectors in the two hemispheres at different times - for example, pre-midnights in the Hemisphere and post-midnight in the Southern Hemisphere, "Petrinec told Space.com

            The hemispheric asymmetry of the aurora is due in part to the sun's magnetic field interfering with Earth's magnetic field, but research into the phenomenon is ongoing.

            Another aurora-like occurrence on Earth is STEVE ("Strong Thermal Emission Velocity Enhancement"). Like the northern and southern lights, STEVE is a glowing atmospheric phenomenon, but it looks slightly different from its undulating auroral counterparts. "These emissions appear as a narrow and distinct arc, are typically purple in color and often include a green picket-fence structure that slowly moves westward, "Petrinec said.

            STEVE is also visible from lower latitudes, closer to the equator, than the auroras.

            A 2019 study published in the journal Geophysics Research  Letters discovered that STEVE is the result of two mechanisms: The mauve streaks are caused by the heating of charged particles in the upper atmosphere, while the picket-fence structure results from electrons falling into the atmosphere. The latter process is the same driver of the aurora, making STEVE a special kind of aurora hybrid.

AURORAS ON OTHER WORLDS

            Auroras are in other planets, too - all that's required to make an aurora is an atmosphere and a magnetic field.

            "Auroras have been seen in the atmospheres of all the gas giant planets, which is not surprising, since these planets all have robust magnetic fields, "said Jeff Register, an instructor of physics and astronomy at High Point University in North Carolina. "More surprisingly, auroras have also been discovered on both Venus and Mars, both of which have very week magnetic fields".

            Indeed, scientists have catalogued three different types of Martian auroras. One occurs only on the planet's dayside, another is a widespread nigh-time feature fueled by strong solar storms and another is a much patchier nightside phenomenon.

            The Hope Mars Orbiter, the United Arab Emirates' first ever interplanetary mission, managed to capture the discrete nocturnal aurora shortly after arriving at the red planet in early 2021. The probe's observations could help scientist better understand this mysterious phenomenon.

            Jupiter magnetic field is 20,000 times stronger than that of Earth, so the giant planet's auroras are far brighter than the once that blaze in our skies. And the Jupiter lights aren't just by the solar wind: Most of the particles that cause the planet's auroras are blasted into space by its close-orbiting moon lo, the most volcanic body in the solar system.

            Astronomers have even caught glimpses of apparent auroral activity in other solar systems. For example, two October 2021 studies reported the detection of radio waves emitted by multiple red dwarfs, stars smaller and dimmer than our own sun.

            These radio waves are likely associated with a sort of "backward" aurora, one that flares up near stars and is driven by particles released by close-orbiting planets, researchers said.

            "Our model for this radio emission from our stars is a scaled-up version of Jupiter and lO, with a planet enveloped in the magnetic field of a star, feeding material into vast currents that similarly power bright aurorae, "Joseph Callingham, a radio astronomer at Leiden University in the Netherlands and the Dutch National Observatory ASTRON and co-author on both new studies, said in a statement. "It's a spectacle that has attracted our attention from light-years away".

            These feeder planets remain hypothetical at the moment; nobody has yet discovered any circling the red dwarfs that the team studied. But if Callingham and his colleagues are right, astronomers may have powerful new planet-hunting technique at their disposal.

             Auroras are expected to be relatively common in the skies of exoplanets as well. But we'll have to get better looks at these faraway worlds to see their light shows directly.

New Insight into How Sun's Powerful Magnetic Field Affects Earth

Image Credits: The Week

WHERE AND WHEN TO SEE THE NORTHERN LIGHTS

            Seeing the northern lights with your own eyes is a bucket-list item for astronomy lovers and travelers alike. Fortunately, they occur frequently.

            "The northern lights are happening 24 hours a day, seven days a week, 365 days a year," said photographer Chad Blakely, owner of the northern lights tour company Lights Over Lapland. But that doesn't mean they're easy to spot; you need to be at the right place at the right time.

          The best place to see the northern light is any destinations in the "auroral zone", the area within an approximately 1,550-mile (2500 kilometers) radius of the north pole, according to the Tromso Geophysical Observatory in Norway. That's where the aurora most frequently occurs, though the phenomenon can creep farther south during particularly strong solar storms.

Related: Where to see the northern lights: 2022 aurora borealis guide.

            In March 1989, for example, a powerful solar eruption made the northern lights visible, albeit briefly, to people as far south as Honduras. (There were some negative consequences as well, however: The geomagnetic storm that supercharged the aurora also temporarily knocked out electricity across the entire Canadian province of Quebec).

            Within the auroral zone, it's best to be as far away from city lights as possible to maximize visibility. But it's pretty tricky to get into the middle of the arctic wilderness, even with a a guide, so it's best to base yourself in a destination with solid infrastructure, like Fairbanks, Alaska, Yellowknife, Canada, Svalbard, Norway, Abisko National Park, in Sweden, Rovaniemi, Finland and pretty much anywhere in Iceland.

            The best time of year to see the northern lights is between September and April, when the sky gets dark enough to see the aurora. (Far northern locals experience the midnight sun, or 24 hours of daylight in the summer). The most action usually happens between 9 p.m. and 3 a.m., according to the Geophysics Institute of the University of Alaska Fairbanks. Keep the moon phases in mind, as a bright full moon might fill the night sky with light. Check local weather forecast as well, because you won't be able to spot the aurora through the clouds.

Image Credits: World Atlas          

              You can also monitor the aurora forecasts from the University of Alaska Fairbanks' Geophysical Institute and NOAA, which offers both three-days and 30-minutes forecasts.