solar radio emission
Solar radio emission consists of emissions of the Sun at radio wavelengths from centimeters to decameters, under both quiet and disturbed conditions, of which several types are recognized. Type I is a noise storm composed of many short, narrowband bursts in the metric range (50 to 300 mehahertz). Type II is narrowband emission that begins in the meter range (300 MHz) and sweeps slowly (over tens of minutes) toward decameter wavelengths (10 MHz). Type II emissions occur in loose association with major flares and are indicative of a shock wave moving through the solar atmosphere. Type III are narrowband bursts that sweep rapidly (in a matter of seconds) from decimeter to decameter wavelengths (0.5 to 500 MHz). This type often occurs in groups and is an occasional feature of complex solar active region. Type IV is a smooth continuum of broadband bursts primarily in the meter range (30–300 MHz). These bursts are associated with some major flare events beginning 10 to 20 min after the flare maximum, and can last for hours.