What does this data represent?

This graph represents 1 minute data provided by the ground based USGS magnetometer located in Boulder, Colorado. A magnetometer is used to detect sudden changes in Earth's magnetic field at ground level. Magnetometer values are the average of 60 1-second samples. The H component (Red) is directed along magnetic north, which is currently about 10 degrees east of geographic north. The D component (Blue) is pointing 90 degrees clockwise relative to H. A sudden and rapid flucuation detected by a magnetometer is known as a geomagnetic sudden impulse. These sudden impulses are measured in units called nanoteslas (nT).

Example of a sudden impulse detected by the magnetometer

Geomagnetic Sudden Impulse

A sudden magnetic impulse represents a rapid momentary fluctuation of the geomagnetic field over a period of only a few minutes. It is generally associated with interplanetary shockwaves produced by energetic solar events and can (but need not always) be followed by increased geomagnetic activity.

Sudden Storm Commencement (SSC)

An SSC is the magnetic signature of an interplanetary shockwave most often produced by solar flares. It is always a precursor to increased geomagnetic activity, most often followed within 3 to 8 hours by a Minor to Major geomagnetic storm. It appears on the H (horizontal) trace of magnetometers. This phenomenon is detectable at almost all magnetic observatories world-wide within 4 minutes of eachother.