In the magnetosphere, a region of current that flows in a disk-shaped region near the geomagnetic equator in the outer of the Van Allen radiation belts. The current is produced by the gradient and curvature drift of trapped charged particles. The ring current is greatly augmented during magnetic storms because of the hot plasma injected from the ma [..]

Five terms are often used to describe the activity (see x-ray solar flare class): Very low —- x-ray events less than C-solar flare class.

A geomagnetic index describing the auroral electrojet.

A mean, 3-hourly “equivalent amplitude” of magnetic activity based on K index data from a planetary of 11 Northern and 2 Southern Hemisphere magnetic observatories between the geomagnetic latitudes of 46 and 63 degrees. ap values are given in units of 2 nT.

A daily index determined from eight ap index values.

A sporadic, faint visual phenomena associated with geomagnetic activity that occurs mainly in the high-latitude night sky. Auroras occur within a band of latitudes known as the auroral oval, the location of which is dependent on geomagnetic activity. Auroras are a result of collisions between atmospheric gases and precipitating charged particles (m [..]

A current that flows in the ionosphere in the auroral zone.

The serial number assigned to 27-day rotation periods of solar and geophysical parameters. Rotation 1 in this sequence was assigned arbitrarily by Bartels to begin in January 1833, and the count has continued by 27-day intervals to present. (For example, rotation 2195 began on April 17, 1994). The 27-day period was selected empirically from the obs [..]

A collisional shock wave in front of the magnetosphere arising from the interaction of the supersonic solar wind with earth’s magnetic field.

An extended region in the corona, exceptionally low in density and associated with unipolar magnetic photospheric regions having “open” magnetic field topology. Coronal holes are largest and most stable at or near the solar poles, and a source of high-speed solar wind. Coronal holes are visible in several wavelengths but most notably in solar x-ray [..]