In May, the Earth experienced its most powerful geomagnetic storm in over two decades, resulting in dazzling displays of the Northern Lights visible as far south as Florida and Mexico. With solar activity continuing to escalate at an unprecedented rate, could a similar spectacle be in store for September? While there are no guarantees, there are compelling reasons to believe that the period surrounding this month’s autumn equinox (September 22nd) might witness more intense geomagnetic storms than usual, potentially ushering in a brief aurora season.
This heightened possibility stems from the Russell-McPherron Effect, a phenomenon that explains why the equinoxes (March and September) often see the most vibrant auroral displays. A research paper published in 1973 suggested that auroras appear more frequently during these periods due to a temporary alignment between Earth’s magnetic field and the solar wind. The solar wind, a continuous stream of charged particles emanating from the sun, becomes significantly more intense following solar flares and coronal mass ejections (CMEs) — powerful bursts of radiation and solar material.
The sun’s magnetic activity operates on an 11-year cycle, currently nearing its peak. While this cyclical peak contributes to heightened solar activity, it’s not the primary reason for a potential aurora season in September. Auroras are born when charged particles from the solar wind interact with Earth’s magnetic field, colliding with oxygen and nitrogen molecules in the atmosphere. This collision excites the molecules, causing them to release light in a mesmerizing array of colors.
Usually, Earth’s magnetic field and the solar wind’s magnetic field are misaligned. However, the Russell-McPherron Effect comes into play during the equinoxes, as Earth’s magnetic poles tilt, making it easier for charged particles to enter our atmosphere. During this time, the southward-pointing magnetic fields within the solar wind counteract Earth’s northward-pointing magnetic field, creating openings in Earth’s magnetosphere. These openings allow the solar wind to flow more easily along the magnetic field lines, facilitating the entry of charged particles.
This specific geometry is particularly favorable for the Northern Hemisphere during the September equinox, when 12 hours of darkness follow 12 hours of daylight. This means that there’s not only a higher likelihood of intense auroral displays but also a greater chance of witnessing them under the cloak of a dark sky, a luxury we haven’t enjoyed throughout the brighter summer months.
