Real-Time Space Weather
--assembled by David Rosenthal, N6TST
March 2007
Scroll-free near-real time conditions! Click here to go directly to the text of the latest Geophysical Alert Broadcast from the SEC.

Currently, three primary web-based solar-terrestrial information sources exist, one in the U.S., one in Canada, and one in Australia, each with its own unique as well as shared characteristics. Listed below is a summary of each location's offerings that should be of greatest interest to the HF user. I've set up this page to provide rapid, direct access to some of each site's most operationally useful information. But I've also chosen from the available data products those that will give the HF user an understandable overview of the solar-terrestrial conditions that impact communications. Utilizing some of the services available will provide a surprising amount of knowledge and operational capability.

Linked text is underlined.

All three of the sites listed contain substantial amounts of additional information and, once familiar with how the sites are laid out, the user can explore at will.

NOAA Space Environment Center (Boulder, CO, USA)
The U.S. "Space Weather Bureau," the SEC provides regular bulletins and forecasts as well as solar images and scientific data.

The following information can be accessed from the SEC Radio Users Page:

The latest Geophysical Alert Message text --broadcast via WWV and WWVH at 18 and 45 minutes past the hour, respectively. Updated every three hours, this provides an excellent "snapshot" of current solar-terrestrial conditions.

Report of Solar and Geomagnetic Activity --issued daily at 2200Z. Summarizes solar and geomagnetic conditions for the past 24 hours and provides forecasts for the next three days. Contains that day's Solar Flux value and A-index, plus forecasts for the next three. This link also enables you to view a long list of past reports.

D-region Absorption Prediction --updated once a minute, this color-coded world map graphic depicts the current position of the sun and how a solar flare might have caused an HF fade. Graphical software provides a picture of the impacted regions, highest frequency affected, as well as an estimated recovery time.

Another page of interest is Today's Space Weather --includes a full-disk H-Alpha solar image, 3-day Solar Geophysical Forecast (brief textual forecast of conditions), and a continuously updated (every 5 minutes) plot of solar X-ray flux. This latter plot enables you to review the last three days of solar X-ray activity.

NOAA Space Weather Scales --introduced in 2000, these letter-number classifiers are included in SEC Space Weather data products to communicate to the general public possible effects on people and systems (HF communications, power systems, etc.). They describe environmental disturbances for three event types: geomagnetic storms, solar radiation storms, and radio blackouts and you'll encounter them in the links I've included. This link takes you to directly to the tables that explain them.

Solar-Terrestrial Dispatch (University of Lethbridge, Stirling, Alberta, Canada)
Canada's Space Weather center, the STD focuses great emphasis upon HF communications. They offer their own HF prediction software package and use it to produce the charts available on their pages. They also provide hourly solar flux measurements and easy-to-access A- and K-indices.

The Ham Radio Page contains text data and regularly updated HF propagation-related maps. The most useful might be:

Current Solar & Geophysical indices --Current solar flux value (updated every 30 minutes), Boulder and planetary K-indices (computed each 3 hours) for the current UTC day, running estimated 24-hour planetary A-index, plus K- and A-indices for the previous UTC day. Handy.

10.7cm Solar Radio Flux --the current and previous 10 days' morning, noon, and afternoon solar flux values as measured at the Penticton, BC solar observatory.

The following contour charts are updated every five minutes using actual conditions. The maps also depict the position of the sun above the earth's surface, the day-night terminator, the twilight region (where HF propagation can be enhanced), and the position of the auroral oval:

Maximum Usable Frequency Maps --World map showing predicted MUFs along 3000 km (single F-hop) HF paths. Determine the midpoint of your communication path and choose an operating frequency at or below that position's depicted value.

Critical F2-Layer Freq. Maps --World map showing the highest vertically directed frequency being returned from the ionosphere. This chart can be used directly to determine frequencies usable for Near-Vertical Incidence Skywave (NVIS) communications within several hundred miles of your station.

Australian Space Forecast Centre (Haymarket, NSW, Australia)
Known as "IPS" (Ionospheric Prediction Service), Australia's center puts an emphasis on applying real-time solar-terrestrial conditions and predicting HF propagation paths. Links provide extensive, practical access to their available ASAPS predictive software package and the amateur can utilize its extensive capabilities free of charge.

IPS Real-Time Space Weather Status Panel --Real-time red/green clickable icons depicting current solar, HF, ionospheric, and geomagnetic conditions. Ionospheric Conditions icons bring up color-coded maps for North America, Europe, and Australasia showing regions of enhanced, normal, or depressed propagation, based on the IPS "T-index", which is related to the sunspot number. The Recent X-Ray Flare List is the fastest way I've yet found to get nearly instantaneous data on flare activity that might have taken place during the recent past; use this in conjunction with the SEC's X-ray Flux (last 3 days) plot described above.

Online Prediction Tools-- A handy and powerful assortment of methods to determine and predict HF propagation paths, using real-time as well as forecast information. All free:

GRAFEX Point to Point HF prediction. Provides frequencies and times for HF communication paths between two user-entered points anywhere in the world. GRAFEX predictions employ the IPS ASAPS predictive propagation software enhanced with input based upon actual recent conditions. The GRAFEX prediction screen provides a surprisingly large amount of useful information. This is one of the best online means to determine when and whether a global path should exist.

Min Max HAP Charts (Hourly Area Prediction). On a world map, click your location, enter up to ten operating frequencies, the desired UTC hour, and then use the mouse to drag out a target region. Choose either real-time or forecast ionospheric conditions and receive a color-coded coverage map for all frequencies plus individual maps for each chosen frequency. Use with the GRAFEX plot to see a regional coverage snapshot. Powerful. Also HAP Prediction Display using the same inputs to get predictions for an entire day in 6-hour blocks.

URSL--Upper, Recommended, Secondary, and Lower HF frequency Prediction uses constantly updated ionospheric condition data to enable a user to determine the best HF frequencies between two points.

Real-Time HAP Charts (Hourly Area Prediction) use current data to predict frequencies usable from mobile stations to the base stations named in each chart. Links on this page take users to North American charts but IPS provides the same products for locations in the rest of the world as well. Also links to IPS' Real-Time Map that shows current propagation conditions for North America based on ionosonde foF2 data. Use color-coded contours directly for choosing NVIS frequencies. Also available for Australasia, Japan, Europe, and the North Atlantic.

Additional Links to Related Items

Radio Netherlands' Solar Guide by David Rosenthal: an overview of how Space Weather affects the Earth and HF radio propagation as well as easy-to-follow instructions on getting the most from the Space Environment Center's "Geophysical Alert Broadcasts" on WWV at 18 minutes past the hour (and on WWVH at 45 past).

NOAA's On-Line Glossary of Solar-Terrestrial Terms: an extremely well-produced collection of definitions with linked keywords.

Articles on HF communication: From IPS Australia, these are .pdf documents with excellent descriptions of how short wave radio signals propagate, transequatorial propagation, and an FAQ on their T-index.

Primer on the Space Environment: Overview of the sun's effects on the earth. Well- presented with excellent, colorful images and even an MPEG movie.

A Short Glossary of Solar-Terrestrial Terms

A index: A daily index of geomagnetic activity derived as the average of the eight 3-hourly a- indices in a UTC day.

Active: A descriptive word specifically meaning
(1) a probability of >50% for an M-class x-ray flare in a sunspot region;
(2) disturbed geomagnetic levels such that 15 < A index < 30.

D region: A daytime region of the ionosphere ranging in height from approximately 30-50 miles. Radio wave absorption in this region can significantly increase in response to increased ionization associated with changes in solar electromagnetic emissions, e.g., x-ray flares. Under normal conditions, D region absorption drops off dramatically above about 9 MHz but, following an x-ray flare, signals up to and beyond 30 MHz can be significantly degraded. The D region is the lowest region of the ionosphere.

E region: A daytime region of the ionosphere, forming roughly between heights of 70 and 100 miles. Ionization in the E region is caused mainly by x-rays. Other sources of E region ionization include trails from incoming meteors and electrically charged sub-atomic particles from the sun. Transient patches of ionization in the E-region, known as "sporadic E" or Es, can often refract HF and VHF signals over great distances (500-1500 miles).

F region: The upper region of the ionosphere, above approximately 100 miles. F region ionization is highly variable, depending upon the local time, solar activity, season, and geomagnetic activity. The F region contains the F1 and F2 layers. The F2 layer, predominantly responsible for long-distance HF radio propagation, is more dense and peaks in ionization at altitudes between 125 and 375 miles. The F1 layer, which forms at lower altitudes in the daytime, usually possesses less ionization. On the night side of the earth, the F1 rises and the F2 falls to form a single region capable of refracting HF radio signals.

Flare: A sudden release of energy in the solar atmosphere, lasting from minutes to hours, from which radiation and particles are emitted.

Geomagnetic activity: Natural variations in the geomagnetic field, classified qualitatively into quiet, unsettled, active, and geomagnetic storm levels based on the A index and the range of K indices observed.

                      Range of

  Category            A index           Typical K indices

Quiet 0-7 Usually no Ks > 2 Unsettled 8-15 Usually no Ks > 3 Active 16-29 A few Ks of 4 and 5 Minor storm 30-49 Ks mostly of 4 and 5 Major storm 50-99 Some Ks of 6 or greater Severe storm 100-400 Some Ks of 7 or greater
Geomagnetic storm: A worldwide temporal disturbance of the earth's magnetic field. A storm is defined as occurring when the A index exceeds 29.

K index: a 3-hourly, quasi-logarithmic local index of geomagnetic activity relative to an assumed quiet-day condition. The K index ranges from 0 to 9.

Major solar flare: A class M5 or greater x-ray flare.

Quiet: a descriptive word specifically meaning (1) a probability of <50% for a C-Class x-ray flare in a sunspot region; (2) geomagnetic activity levels such that the A index is < 8.

Short wave fade (SWF): An abrupt decrease of HF radio signal strength, lasting form minutes to hours, caused by increased day-side ionization from solar flares, usually M or X x-ray class.

Solar activity: Transient perturbations of he solar atmosphere as measured by enhanced x-ray emissions, typically associated with flares. Five standard terms are used, based on the size and number of x-ray flares observed.

  Category                              Type of x-ray flare

Very Low Less than class C Low C-class Moderate Isolated (1-4) M-class High Several (>=5) M-class or Isolated (1-4) M5 or greater Very High Several (>=5) M5 or greater

Solar flux: A measurement of the intensity of solar radio emissions with a wavelength of 10.7 cm (frequency approx. 2800 MHz). 1 solar flux unit (sfu) = 1 x 10-22 Watts/(square meter * hertz) = 10,000 Jansky.

Ultraviolet (UV): That part of the electromagnetic spectrum with wavelengths between 5 and 400 nanometers (nm). Along with x-rays, solar radiation in these wavelengths produces the majority of ionization in the D, E, and F regions.

Unsettled: With regard to geomagnetic activity, a descriptive word defining conditions between quiet and active, specifically meaning that the A index is between 8 and 15.

X-ray: Electromagnetic radiation in the wavelength range of 0.1-10 nanometers (nm).

X-ray flare class: Ranking of a flare based on its x-ray output. Flares are classified according to the order of magnitude of the peak burst intensity (I) measured at the earth in watts/square meter in the 0.1-0.8 nm wavelength region.

  Class                         Peak, 0.1-0.8 nm band (watts/square meter)

B I < 10-6 C 10-6 <= I < 10-5 M 10-5 <= I < 10-4 X I >= 10-4

Note: A multiplier is used to indicate the level within each class. For example: An M6 flare is equal to 6x10-5 watts/square meter.

Compiled by D. Rosenthal, N6TST

E-mail: n6tst--then the "at" (Note: As a result of the unavoidable nuisance now posed by spammers and their automated Web page-scanning, e-mail address-collecting software, I can no longer use the conventional address format [humorously, that aforementioned e-mail address-collecting software will likely find my "" address example, harvest it, and try to send spam to it. Ha!]). March 2007