The Geophysical Alert Message
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Geophysical Alert Message Description
Sample Messages
- The messages begin with 6 standard header lines. On NWS systems, this product is called the "Three-hourly Space Weather Conditions and Forecast" and their header contains two additional lines.
- The first paragraph: the dates have leading zeros. The mid-latitude A- and K-indices are normally from Boulder magnetometer, but alternate stations are used when necessary.
- The second and third paragraphs express observed and predicted condition in term of the NOAA Space Weather Scales. See description below.
:Product: Geophysical Alert Message wwv.txt :Issued: 2007 Nov 21 2105 UTC # Prepared by the US Dept. of Commerce, NOAA, Space Weather Prediction Center # # Geophysical Alert Message # Solar-terrestrial indices for 21 November follow. Solar flux 69 and estimated mid-latitude A-Index 12. The mid-latitude K-index at 2100 UTC on 21 November was 1 (5 nT). No space weather storms were observed for the past 24 hours. No space weather storms are predicted for the next 24 hours.
:Product: Geophysical Alert Message wwv.txt :Issued: 2002 Feb 06 2105 UTC # Prepared by the US Dept. of Commerce, NOAA, Space Environment Center # # Geophysical Alert Message # Solar-terrestrial indices for 06 February follow. Solar flux 203 and estimated mid-latitude A-Index 16. The mid-latitude K-index at 2100 UTC on 06 February was 3 (21 nT). Space weather for the past 24 hours has been moderate. Geomagnetic storms reaching the G2 level occurred. Solar radiation storms reaching the S2 level occurred. Radio blackouts reaching the R1 level occurred. Space weather for the next 24 hours is predicted to be minor. Geomagnetic storms reaching the G1 level are likely/expected.
:Product: Geophysical Alert Message wwv.txt :Issued: 2002 Feb 06 0005 UTC # Prepared by the US Dept. of Commerce, NOAA, Space Environment Center
# # Geophysical Alert Message # Solar-terrestrial indices for 05 February follow. Solar flux 221 and mid-latitude A-Index 17. The mid-latitude K-index at 0000 UTC on 06 February was 3 (36 nT). Space weather for the past 24 hours has been moderate. Geomagnetic storms reaching the G2 level occurred. Solar radiation storms reaching the S2 level occurred. Radio blackouts reaching the R1 level occurred. Space weather for the next 24 hours is predicted to be extreme. Geomagnetic storms reaching the G1 level are likely/expected. Solar radiation storms reaching the S3 level are likely/expected. Radio blackouts reaching the R5 level are likely/expected
Geophysical Alert Message Description
The National Oceanic and Atmospheric Administration (NOAA) uses WWV and WWVH to broadcast geophysical alert messages that provide information about solar terrestrial conditions. Geophysical alerts are broadcast from WWV at 18 minutes after the hour and from WWVH at 45 minutes after the hour. The messages are less than 45 seconds in length and are routinely updated every 3 hours beginning at 0000 UT. Updates are more frequent when activity warrants.
The geophysical alerts provide information about the current and predicted solar terrestrial conditions found useful for long distance HF radio communications and other applications. The alerts use a standardized format and terminology that requires some explanation. The terms used in the announcements are defined below:
Solar flux is a measurement of the intensity of solar radio emissions with a wavelength of 10.7 cm (a frequency of about 2800 MHz). The daily solar flux measurement is recorded at 2000 UTC by the Dominion Radio Astrophysical Observatory of the Canadian National Research Council located at Penticton, B.C., Canada. The value broadcast is in solar flux units that range from a theoretical minimum of about 50 to numbers larger than 300. During the early part of the 11-year sunspot cycle, the flux numbers are low; but they rise and fall as the cycle proceeds. The numbers will remain high for extended periods around sunspot maximum.
The A and K indices are a measurement of the behavior of the magnetic field in and around the Earth. The K index uses a scale from 0 to 9 to measure the change in the horizontal component of the geomagnetic field. A new K index is determined and added to the broadcast every 3 hours based on magnetometer measurements made at the Table Mountain Observatory, north of Boulder, Colorado, or an alternate middle latitude observatory. The A index is a daily value on a scale from 0 to 400 to express the range of disturbance of the geomagnetic field. It is obtained by converting and averaging the eight, 3-hour K index values. An estimate of the A index is first announced at 2100 UTC, based on 7 measurements and 1 estimated value. At 0000 UTC, the announced A index consists entirely of known measurements, and the word "estimated" is dropped from the announcement.
Space Weather describes the conditions in space that affect earth and its technological systems. Space weather is a consequence of the behavior of the sun, the nature of Earth&s magnetic field and atmosphere, and our location in the solar system.
Space Weather storms observed and predicted are characterized using the NOAA Space Weather scales. The abbreviated table below shows the levels of activity that are included in the announcements and the associated terminology. The descriptor used to identify observed or predicted conditions is the maximum level reached or predicted *. See NOAA Space Weather Scales for further description.
NOAA Space Weather Scales |
|||
Geomagnetic Storms |
Solar Radiation Storms |
Radio Blackouts |
Descriptor |
G5 |
S5 |
R5 |
Extreme |
G4 |
S4 |
R4 |
Severe |
G3 |
S3 |
R3 |
Strong |
G2 |
S2 |
R2 |
Moderate |
G1 |
S1 |
R1 |
Minor |
Geomagnetic storm levels are determined by the estimated 3-hourly Planetary K-indices which are that are derived in real time from a network of western hemisphere ground-based magnetometers.
Table 3.1 - Geomagnetic Storm levels | |
---|---|
Planetary K indices |
Geomagnetic storm level |
K = 5 |
G1 |
K = 6 |
G2 |
K = 7 |
G3 |
K = 8 |
G4 |
K= 9 |
G5 |
Solar Radiation storms levels are determined by the proton flux measurements made by the primary GOES satellite.
Table 3.2 - Solar Radiation Storm levels |
|
---|---|
Flux level of > 10 MeV particles |
Solar Radiation Storm level |
10 |
S1 |
102 |
S2 |
103 |
S3 |
104 |
S4 |
105 |
S5 |
Radio Blackouts are determined by the x-ray level measured by the primary GOES satellite.
Table 3.3 - Radio Blackouts |
|
---|---|
Peak x-ray level and flux |
Radio Blackout level |
M1 and (10-5) |
R1 |
M5 and (5 x 10-5) |
R2 |
X1 and (10-4) |
R3 |
X10 and (10-3) |
R4 |
X20 and (2 x 10-3) |
R5 |
Every geophysical alert consists of three parts as shown in tables 3.4 and 3.5. Table 3.4 describes the information contained in the geophysical alert. Table 3.5 provides example text from an actual message.
Section |
Table 3.4 - Information in Voice Message |
---|---|
1 |
The solar-terrestrial indices for the day: specifically the solar flux, the A index, and the K index. |
2 |
Space Weather storms observed during the previous 24 hours. Includes all observed geomagnetic storms, solar radiation storms (proton events) and Radio blackouts (class M1 and greater flares). |
3 |
Space Weather predicted during the following 24 hours. |
Section |
Table 3.5 - Example of Actual Geophysical Alert Message |
---|---|
1 |
Solar-terrestrial indices for 08 November follow. |
2 |
Space Weather for the past 24 hours has been severe. |
Alternate |
No Space Weather storms have been observed during the past 24 hours. |
3 |
Space Weather for the next 24 hours is predicted to be severe. |
Alternate |
No Space Weather storms are predicted during the next 24 hours. |
The announcements include the descriptor of the largest space weather event observed (2) or predicted (3) in the first line of each section. The remaining lines give the type of events and the level observed for each one. In the example above, no geomagnetic storm information is included because none was observed or is predicted during the period. In the case where none of the three types of events are observed or predicted, the announcement would contain section 1, plus alternate section 2 and alternate section 3.
* Maximum predicted
- Likely indicates >= 50% chance
- Expected indicates >= 70% chance
NOAA will always advise customers of the strongest storm level predicted. For example, if R2 storms are likely (>= 50%) and R1 storms are expected (>= 70%), then the Forecaster will choose R2 likely, implying a higher probability for R1 storming.
Last Update: April 2011