USGS Geomagnetism Program

Video - Hazards: Geomagnetic Storms

View "Hazards: Geomagnetic Storms" - a 7-minute introductory video

Latest Magnetic Disturbance Event

Event: 2015-06-23

Maximum Dst Amplitude -195 nT

A “severe” storm occurred on June 21-23, 2015. This storm arose in response to variable solar-wind conditions that the Space Weather Prediction Center of the National Oceanic and Atmospheric Administration (SWPC, NOAA) associated with active region 2371 on the Sun. A series of 3 coronal mass ejections (CMEs) originated from this active region. These were subsequently recorded by NASA’s Advanced Composition Explorer (ACE) satellite, located on the Sun-Earth line at a distance approximately 1% of the distance from the Earth to the Sun, as abrupt enhancements in solar-wind velocity and density. With the arrival of the CMEs at the Earth on about June 21 16:45 UT, June 22 05:45 UT, and June 22 18:30 UT, concomitant increases in solar-wind ram pressure abruptly compressed the Earth’s magnetosphere. These generated eastward-flowing magnetopause electric currents and positive perturbations in the horizontal component of the geomagnetic field recorded at low-latitude magnetic observatories around the world, including at USGS observatories in Guam, Honolulu, and San Juan.