The northern lights, or aurora borealis, one of nature's most spectacular visual shows, can be elusive. Conventional wisdom says that to see them, we need to travel to northern Canada or Alaska. However, in the past two years, New Englanders have been seeing these colorful atmospheric displays on a few occasions - including this week - from the comfort of their backyards, as auroras have been visible in central and southern New England and beyond. These unusual auroral events have been driven by increased space weather activity, a phenomenon studied by a team of MIT Haystack Observatory scientists.
Auroral events are generated when particles in space are energized by complicated processes in the near-Earth environment, following which they interact with gases high up in the atmosphere. Space weather events such as coronal mass ejections, in which large amounts of material are ejected from our sun, along with geomagnetic storms, greatly increase energy input into those space regions near Earth. These inputs then trigger other processes that cause an increase in energetic particles entering our atmosphere.
The result is variable colorful lights when the newly energized particles crash into atoms and molecules high above Earth's surface. Recent significant geomagnetic storm events have triggered these auroral displays at latitudes lower than normal - including sightings across New England and other locations across North America.
New England has been enjoying more of these spectacular light shows, such as this week's displays and those during the intense geomagnetic solar storms in May and October 2024, because of increased space weather activity.
Research has determined that auroral displays occur when selected atoms and molecules high in the upper atmosphere are excited by incoming charged particles, which are boosted in energy by intense solar activity. The most common auroral display colors are pink/red and green, with colors varying according to the altitude at which these reactions occur. Red auroras come from lower-energy particles exciting neutral oxygen and cause emissions at altitudes above 150 miles. Green auroras come from higher-energy particles exciting neutral oxygen and cause emissions at altitudes below 150 miles. Rare purple and blue aurora come from excited molecular nitrogen ions and occur during the most intense events.
Scientists measure the magnitude of geomagnetic activity driving auroras in several different ways. One of these uses sensitive magnetic field-measuring equipment at stations around the planet to obtain a geomagnetic storm measurement known as Kp, on a scale from 1 (least activity) to 9 (greatest activity), in three-hour intervals. Higher Kp values indicate the possibility - not a guarantee - of greater auroral sightings as the location of auroral displays move to lower latitudes. Typically, when the Kp index reaches a range of 6 or higher, this indicates that aurora viewings are more likely outside the usual northern ranges. The geomagnetic storm events of this week reached a Kp value of 9, indicating very strong activity in the sun-Earth system.
At MIT Haystack Observatory in Westford, Massachusetts, geospace and atmospheric physics scientists study the atmosphere and its aurora year-round by combining observations from many different instruments. These include ground-based sensors - including large upper-atmosphere radars that bounce signals off particles in the ionosphere - as well as data from space satellites. These tools provide key information, such as density, temperature, and velocity, on conditions and disturbances in the upper atmosphere: basic information that helps researchers at MIT and elsewhere understand the weather in space.
Haystack geospace research is primarily funded through science funding by U.S. federal agencies such as the National Science Foundation (NSF) and NASA. This work is crucial for our increasingly spacefaring civilization, which requires continual expansion of our understanding of how space weather affects life on Earth, including vital navigation systems such as GPS, worldwide communication infrastructure, and the safety of our power grids. Research in this area is especially important in modern times, as humans increasingly use low Earth orbit for commercial satellite constellations and other systems, and as civilization further progresses into space.
Studies of the variations in our atmosphere and its charged component, known as the ionosphere, have revealed the strong influence of the sun. Beyond the normal white light that we experience each day, the sun also emits many other wavelengths of light, from infrared to extreme ultraviolet. Of particular interest are the extreme ultraviolet portions of solar output, which have enough energy to ionize atoms in the upper atmosphere. Unlike its white light component, the sun's output at these very short wavelengths has many different short- and long-term variations, but the most well known is the approximately 11-year solar cycle, in which the sun goes from minimum to maximum output.
Scientists have determined that the most recent peak in activity, known as solar maximum, occurred within the past 12 months. This is good news for auroral watchers, as the most active period for severe geomagnetic storms that drive auroral displays at New England latitudes occurs during the three-year period following solar maximum.
Despite intensive research to date, we still have a great deal more to learn about space weather and its effects on the near-Earth environment. MIT Haystack Observatory continues to advance knowledge in this area.
Larisa Goncharenko, lead geospace scientist and assistant director at Haystack, states, "In general, understanding space weather well enough to forecast it is considerably more challenging than even normal weather forecasting near the ground, due to the vast distances involved in space weather forces. Another important factor comes from the combined variation of Earth's neutral atmosphere, affected by gravity and pressure, and from the charged particle portion of the atmosphere, created by solar radiation and additionally influenced by the geometry of our planet's magnetic field. The complex interplay between these elements provides rich complexity and a sustained, truly exciting scientific opportunity to improve our understanding of basic physics in this vital part of our home in the solar system, for the benefit of civilization."
For up-to-date space weather forecasts and predictions of possible aurora events, visit SpaceWeather.com or NOAA's Aurora Viewline site .
