A 'double punch' of solar storms could smash into Earth and spark widespread auroras this week

By Robert Lea
published 1 day ago

NASA watched the sun throw out a coronal mass ejection "double punch" that could strike our planet before the weekend.

An illustration shows the sun as it throws out a coronal mass ejection that can contain millions of tons of stellar material. (Image credit: NASA)

While the U.S. celebrated Independence Day on July 4, the sun held its own, more powerful firework display.

The stellar fireworks came in the form of two solar storms, or coronal mass ejections (CMEs), that are partly directed at Earth and were observed by NASA's Solar and Heliospheric Observatory (SOHO) that orbits our star. CMEs can contain as much as a billion tons of plasma made up of charged particles and thus carry with them their own magnetic fields.

NASA has projected that the massive ejection of ionized gas called plasma will impact Earth by Friday (July 7). When the charged particles within CMEs strike the magnetic field of our planet, the magnetosphere, they can give rise to large disturbances called geomagnetic storms.

Space Weather physicist Tamitha Skov shared footage of both CMEs recorded by the SOHO's Large Angle and Spectrometric Coronagraph Experiment (LASCO) on her Twitter feed. Skov wrote: "Our #Sun celebrates #July4 with its own special fireworks! We have two partly Earth-directed #solarstorms (aka CMEs) on their way. The second storm will catch up to the first giving us a 1,2-punch. Model predictions show impact likely July 7. I'll post NASA model runs next"

As promised, the space weather expert shared models of both CMEs, created by NASA's Chris Stubenrauch, describing the outflows of stellar matter as a "double punch" of solar storms.

The first tweet showed the initial CME, which NASA predicted is slower and will arrive before 8 am (EDT) on Friday and will head mostly to the northeast.

Screenshot 2023-07-06 at 16.38.04.png
Dr. Tamitha Skov, @tamithaskov, 4 July 2023

The second CME is hurtling through space more rapidly and will result in what Skov described as more of a "direct hit" on Earth, with it veering slightly southward. It should arrive in the early hours of July 7.

She added that the CMEs have the possibility of triggering a G-1 level geomagnetic storm, defined by the National Oceanic and Atmospheric Administration (NOAA) as minor events that can, nonetheless, give rise to power grid fluctuations and impact spacecraft operations.

While the fireworks of Independence Day are long over, the CMEs could also result in another spectacular light show, this time high in the atmosphere over Earth. When charged particles travel down the magnetic field lines in Earth's magnetosphere, they create bright, colorful displays called auroras. These are usually only visible at high latitudes on Earth near the poles, but these powerful CMEs could give rise to auroras that are visible at lower mid-latitudes.

The NOAA adds that auroras connected to G-1 geomagnetic storms can often be seen in the U.S. as far south as Michigan and Maine.

See: https://www.space.com/sun-coronal-m...-468C-8CFD-3658D1201A8D&utm_source=SmartBrief

Coronal Mass Ejections (CMEs) are large expulsions of plasma and magnetic field from the Sun’s corona. They can eject billions of tons of coronal material and carry an embedded magnetic field (frozen in flux) that is stronger than the background solar wind interplanetary magnetic field (IMF) strength. CMEs travel outward from the Sun at speeds ranging from slower than 250 kilometers per second (km/s) to as fast as near 3000 km/s. The fastest Earth-directed CMEs can reach our planet in as little as 15-18 hours. Slower CMEs can take several days to arrive. They expand in size as they propagate away from the Sun and larger CMEs can reach a size comprising nearly a quarter of the space between Earth and the Sun by the time it reaches our planet.

The more explosive CMEs generally begin when highly twisted magnetic field structures (flux ropes) contained in the Sun’s lower corona become too stressed and realign into a less tense configuration – a process called magnetic reconnection. This can result in the sudden release of electromagnetic energy in the form of a solar flare; which typically accompanies the explosive acceleration of plasma away from the Sun – the CME, or a Coronal Mass Ejection.

These types of CMEs usually take place from areas of the Sun with localized fields of strong and stressed magnetic flux; such as active regions associated with sunspot groups. CMEs can also occur from locations where relatively cool and denser plasma is trapped and suspended by magnetic flux extending up to the inner corona - filaments and prominences. When these flux ropes reconfigure, the denser filament or prominence can collapse back to the solar surface and be quietly reabsorbed, or a CME may result. CMEs travelling faster than the background solar wind speed can generate a shock wave. These shock waves can accelerate charged particles ahead of them – causing increased radiation storm potential or intensity.

Important CME parameters used in analysis are size, speed, and direction. These properties are inferred from orbital satellites’ coronagraph imagery by SWPC forecasters to determine any Earth-impact likelihood. The NASA Solar and Heliospheric Observatory (SOHO) carries a coronagraph – known as the Large Angle and Spectrometric Coronagraph (LASCO). This instrument has two ranges for optical imaging of the Sun’s corona: C2 (covers distance range of 1.5 to 6 solar radii) and C3 (range of 3 to 32 solar radii). The LASCO instrument is currently the primary means used by forecasters to analyze and categorize CMEs; however another coronagraph is on the NASA STEREO-A spacecraft as an additional source.

Imminent CME arrival is first observed by the Deep Space Climate Observatory (DSCOVR) satellite, located at the L1 orbital area. Sudden increases in density, total interplanetary magnetic field (IMF) strength, and solar wind speed at the DSCOVR spacecraft indicate arrival of the CME-associated interplanetary shock ahead of the magnetic cloud. This can often provide 15 to 60 minutes advanced warning of shock arrival at Earth – and any possible sudden impulse or sudden storm commencement; as registered by Earth-based magnetometers.

Important aspects of an arriving CME and its likelihood for causing more intense geomagnetic storming include the strength and direction of the IMF beginning with shock arrival, followed by arrival and passage of the plasma cloud and frozen-in-flux magnetic field. More intense levels of geomagnetic storming are favored when the CME enhanced IMF becomes more pronounced and prolonged in a south-directed orientation. Some CMEs show predominantly one direction of the magnetic field during its passage, while most exhibit changing field directions as the CME passes over Earth. Generally, CMEs that impact Earth’s magnetosphere will at some point have an IMF orientation that favors generation of geomagnetic storming. Geomagnetic storms are classified using a five-level NOAA Space Weather Scale. SWPC forecasters discuss analysis and geomagnetic storm potential of CMEs in the forecast discussion and predict levels of geomagnetic storming in the 3-day forecast.

See: https://www.swpc.noaa.gov/phenomena/coronal-mass-ejections

Coronal Mass Ejections can occur during solar flares unleashing a giant cloud of solar wind particles into space. The Cactus software autonomously detects CMEs in image sequences from the LASCO instrument on board SOHO. When they strike the Earth's magnetosphere, they can reduce, interrupt or eliminate radio communications across large parts of the Earth's surface. And, they result in those glowing Northern Lights, often seen closer to the poles, but may be clearly observed farther south from the polar north or north of Antarctica.