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Solar Radio Emissions at HF (go direct to HF Solar Radio) and VHF/UHF (go direct to e-CALLISTO)

We started monitoring solar activity in May 2009 not long after the end of sunspot cycle 23 (fall 2008). We presently operate two detection systems for solar emissions, one in the HF frequency band and another in the VHF/UHF frequency bands. Solar radio emissions generally are related to flare activity.

Many solar radio emission have similar characteristics and are classified on the basis of their frequency and time (spectral and temporal) characteristics into seven types, Type I through Type VII with Types I through Type V being basic types and Types VI and VII being extensions of Type III and Type V. See table below for a summary of spectral classifications.

Solar Radio Burst Spectral Classifications (see also table notes below)




Frequency Range (MHz)

Associated Phenomena


Short, narrow-bandwidth bursts. Usually occur in large numbers with underlying continuum

Single: ~1 second
Storm: hours days

80 200

Active regions, flares,
eruptive prominences


Slow frequency drift bursts. Usually accompanied by a second harmonic

3 30 minutes

20 150

Flares, proton emission, magneto-hydrodynamic shockwaves


Fast frequency drift bursts. Can occur singularly, in groups, or storms often with underlying continuum. Can be accompanied by a second harmonic

Single: 1 3 seconds
Group:  1 5 minutes
Storm: minutes hours

0.01 1000

Active regions, flares


Stationary Type IV:
Broadband continuum with fine structure

Hours days

20 2000

Flares, proton emission

Moving Type IV:
Broadband, slow frequency drift, smooth continuum

0.5 2 hours

20 400

Eruptive prominences,
magneto-hydrodynamic shockwaves

Flare Continua:
Broadband, smooth continuum

3 45 minutes

10 200

Flares, proton emission


Smooth, short-lived continuum. Follows some type III bursts. Never occurs in isolation

1 3 minutes

10 200

Same as type III bursts


Series of Type III bursts over a period of 10 minutes or more, with no period longer than 30 minutes without activity

> 10 minutes

See Type III

See Type III


Series of Type III and Type V bursts over a period of 10 minutes or more, with no period longer than 30 minutes without activity

> 10 minutes

See Type III and Type V

See Type III
and Type V

Table notes:
1. Drifting bursts almost always drift from high to low frequencies
2. Frequency range is the typical range in which the bursts appear and not their bandwidth
3. Sub-types of Type IV are not universally agreed upon


Seasonal Variations in Solar Radio Observations at Anchorage, Alaska USA

The diagram immediately below shows how the geometry of our observations varies from summer to winter.



High-frequency system operating in the approximate range of 3~30 MHz (primarily 15~32 MHz) called the HF System.

Click here for information and data for our HF System.

A block diagram is shown below.


Solar spectrometer operating in the range of 45~870 MHz called the e-CALLISTO system.

Click here to view information and data for our e-CALLISTO System.

We participate in the e-CALLISTO solar spectrometer network sponsored by the Swiss Institute of Technology, ETH Zurich. A block diagram is shown below.