Black Cat Systems

Follow our tweets!

Lost Reg Code?
Online KiwiSDRs
macOS Software
Windows Software
Ham Radio iPhone/iPad
Linux Software
Update Policy

USB Icom CI-V Interface

Radio Hobbyist Products

  22m Programmable Beacon Kit
  22m Part 15 Beacon Kit
  CW Keyer For Beacons Kit
  Jellyfish Transformer
  Cyclops Antenna Transformer

General Interest Programs

  Atomic Mac/PC
  Audio Toolbox
  Black Cat Timer
  Diet Sleuth
  Graph Paper Maker
  Health Tracker
  Image Resizer
  Knitting Wizard
  Label Wizard
  Prog Audio Gen
  Sound Byte
  Synth 76477

Amateur Radio Programs
  AirSpyHF+ Server
  Black Cat Absolute ACARS
  Black Cat ACARS
  Black Cat ALE
  Black Cat ALE Vacuum Cleaner
  Black Cat NetFinder
  Black Cat GMDSS
  Black Cat HF Fax
  Black Cat SSTV
  Carrier Sleuth
  Cocoa 1090
  Cocoa RTL Server
  DGPS Decoding
  DX Toolbox
  eQSL Factory
  KiwiSDR Monitor
  KiwiSDR Sound Client
  Morse Mania
  RF Toolbox
  SDRuno Plugin
  SDRuno Equalizer Plugin

iPhone/iPad Apps
  Atoms To Go
  dB Calc
  Clik Trak
  DGPS Decoder
  Drill Calc
  DX Toolbox
  Elmer Extra
  Elmer General
  Elmer Tech
  Feld Hellschreiber
  Field Strength Calc
  Function Generator Pad
  HF Weather Fax
  Morse Mania
  Morse Pad
  Packet Pad
  PSK31 Pad
  SSTV Pad
  Photon Calc
  Rad Map Tracker
  RF Link Calc
  SelCall Tone Gen
  Sound Byte
  Sound Byte Control
  Spectrum Pad
  SWBC Schedules
  Synth 76477
  Synth Motion
  Transmission Line Calc
  Weather Calc
  Wire Calc

iPhone/iPad Bundles
  RF Calculator Apps
  Ham Radio Decoder Apps
  Audio Utility Apps
  Shortwave Weather Apps
  Ham Radio Exam Study Apps
  Shortwave Decoder Apps

Android Apps
  Audio Function Generator
Audio Spectrum Analyzer
DGPS Decoder
  HF Weather Fax
  Rad Map Tracker
  SelCall Tone Gen
  Sound Byte Control
  SWBC Schedules
  Wire Calc

About Black Cat Systems
Site Map
Our software for Mac OSX
Privacy Policy
Apple /// Emulator

Macintosh Links
Shortwave Radio
Pirate Radio
Spy Numbers Stations
Science and Electronics
Ham Radio Software


DX Toolbox gives you real time information on current HF radio conditions, alerts you to flares and geomagnetic storms, and helps you determine the best bands for any path under various conditions.

HF Shortwave Radio Propagation Information - Solar Flares

Solar Flares

Sometimes, especially during periods of high solar activity, the magnetic lines in the Sun can become so twisted that they eventually release a large amount of energy in the form of a solar flare. These flares produce a large amount of x-ray radiation. This radiation can strongly ionize the D layer in a short amount of time, a minute or less, resulting in a large amount of attenuation of radio waves passing through the affected region (that is, the side of the Earth facing the Sun). Large flares can cause ionization levels sufficient to completely stop all shortwave propagation, causing the infamous "HF Blackouts".

Several satellites in orbit around the Earth continuously monitor the x-ray levels from the Sun, and can detect solar flares as they occur.

Solar flares are categorized according to their strength, using letters and numbers. The letters range are A,B,C,M and X, and a number follows the letter, such as C4.5 or M8.2, etc. A flares are the weakest, and X flares the strongest. There is no upper limit. The strongest flare ever recorded was an X28, in November of 2003. It was possibly higher, some think as high as X40, but the sensors used to measure flares cannot go that high.

DX Toolbox gives you the current solar x-ray conditions, as well as graphs showing the past several days readings, and alerts you to solar flares immediately when they occur.

In addition to major solar flares, there is a constant background of x-ray radiation from the Sun. In general, the lower this background level, the better radio propagation conditions are.

Large solar flares can also eject bursts of charged particles, called Coronal Mass Ejections. These CMEs can strike the Earth if the flare occurs on a region of the Sun facing the Earth. If so, they can disrupt the Earth's magnetic fields, causing auroras (northern and southern lights) which can affect shortwave radio propagation. They can also cause generally higher noise levels, and weaker signals.

[Table of Contents]
Previous [Solar Flux]
Next [A Index and K Index]

Email your comments and questions to

Last modified July 26, 2004