https://cdn.earthdata.nasa.gov/conduit/upload/5182/KeywordsCommunityGuide_Baseline_v1_SIGNED_FINAL.pdf 23.8 2026-04-29T10:52:37.449Z https://gcmd.earthdata.nasa.gov/KeywordViewer/scheme/sciencekeywords/882d9a10-713c-4b58-8c7b-d9af086115a3 GEOMAGNETIC FORECASTS The levels of geomagnetic field activity, or disturbance, currently used in thelong-term (up to 27 days) forecasts are labelled qualitatively for general usage. For each of the three major zones (subauroral, auroral, polar cap), the range of activity is divided into four classifications: quiet, unsettled, active, storm. The actual parameter used for reporting and forecasting magneticactivity is a daily index. It is known as DRX and is the average of the hourly ranges (maximum minus minimum during each hour) in the X (northward) component of the magnetic field intensity for a day (the UT [or GMT] day), i.e., DRX forthe zone is the mean of 24 values. Because this averaging process has the effect ofsmoothing (filtering) the more rapid fluctuations in the field, the qualitativedescriptors are defined rather differently than for the short-term forecasts. Units are nanoteslas (nT).