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A severe geomagnetic storm occurred from June 21-23, 2015; the storm arose in response to variable solar-wind conditions emanating from the Sun. The storm is now over, but USGS experts say the geomagnetic conditions on Earth may remain somewhat disturbed for the next couple days.

Impacts and Effects

Geomagnetic storms can interfere with radio communications, GPS systems, satellites and directional drilling for oil and gas. Large magnetic storms can even interfere with the operations of electric power grids, causing blackouts. For these reasons, magnetic storms are considered hazardous for both the economy and national security.

What Happened?

The origin of this storm can be traced to a series of large concentrations of solar wind ejected from a sunspot. There were three such instances occurring on June 21 at 16:45 UT, June 22 at 5:45 UT and June 22 at 18:30 UT.

When these concentrations of solar wind arrived at Earth, they injected electrically charged particles into the Earth’s magnetosphere (a bubble-shaped region of space formed by the extent of Earth’s magnetic field). Complex geomagnetic disturbance around the world was driven by the interaction of the solar wind with the magnetosphere.

All of this activity was recorded by ground-based magnetic observatories, including those operated by the USGS.

By standard measures, this magnetic storm was the second largest of the present solar cycle. Solar cycles are defined by the waxing and waning of sunspots every 11 years or so. Right now, the number of sunspots is diminishing, but we can expect a few more intense magnetic storms over the next 2 or 3 years.

As is typical for magnetic storms, activity was particularly intense at high latitudes. At the USGS Barrow observatory in northern Alaska, for example, the direction of the Earth’s magnetic field fluctuated by almost 10 degrees in less than an hour. You could actually measure the effect of this storm on a simple compass.  Aurora borealis—or northern lights—were seen across Alaska, Canada and in many states in the lower continental United States as far south as North Carolina, Georgia and Texas.

 

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Solstice Storm: A Special Sight

Magnetic storms are most likely to be seen during or around the equinoxes, so this one during the solstice is slightly special. The equinoxes correspond to the time of the year when the Sun’s position in the sky crosses the equator, and we have equal amounts of daylight and night. The solstices correspond to the time of the year when the Sun is at its northernmost or southernmost position in the sky, and we have the greatest and least amount of sunlight.

Research as to why solar storms are more common and severe around the equinoxes is still ongoing, but it most likely has to do with the way the Earth’s position relative to the Sun changes.

Start with USGS Science

USGS scientists provide a unique role in exploring space weather by monitoring activity on the ground. The USGS Geomagnetism Program monitors variations in the Earth’s magnetic field through a network of 14 ground-based observatories around the United States and its territories. The USGS observatory data are used to calculate magnetic storm intensity.

USGS scientists conduct research into the physical causes of magnetic storms, and they develop products useful for real-time situational awareness and to assess the hazardous effects of magnetic storms. The USGS is also involved with making maps of magnetic activity, which are derived from data we acquire from ground-based observatories. In addition, USGS scientists are mapping the nature of the Earth's lithosphere to construct maps of geomagnetic hazards.

The USGS magnetic observatory network is itself part of the global INTERMAGNET network. USGS observatory data are used by NOAA’s Space Weather Prediction Center and the U.S. Air Force Weather Agency for issuing geomagnetic warnings and forecasts. The USGS works cooperatively with government partners within the U.S. National Space Weather Program and with private entities that are affected by space weather and geomagnetic activity, including electric-power grid companies and the oil and gas drilling industries.

Watch our Video to Learn More

Watch a video with USGS scientists to learn more about solar storms and relevant research underway.