Space Weather Alerts Description and Criteria


Space Weather Alerts Description and Criteria

Space Weather Alert Service:

There are 4 types of Space Weather Alert Messages

  • Watchmessages, for Geomagnetic A-indices, are issued for long-lead geomagnetic activity predictions.
  • Warningmessages are issued when some condition is expected. The messages contain a warning period and other information of interest.
  • Alertmessages are issued when an event threshold is crossed and contain information that is available at the time of issue.
  • Summary messages are issued after the event ends, and contain additional information available at the time of issue.

Space Weather Alerts are issued for these categories. Alerting criteria and descriptions are given below:


X-ray Flux Alert and Event Summaries

ALERT: X-ray Flux exceeded M5
SUMMARY: X-ray Event exceeded M5
SUMMARY: X-ray Event exceeded X1
SUMMARY: X-ray Event exceeded X10
SUMMARY: X-ray Event exceeded X20
  • X-ray Flux ALERT: Issued in near-real-time, when flare x-ray flux exceeds the M5 (NOAA Scale R2 Moderate) level. Includes time of occurrence.
  • X-ray Event SUMMARY: Issued for all flares exceeding M5, after decrease to half-peak flux level. Includes event begin, maximum, and end times, optical class, location, the peak flux level (M5, X1, X10, or X20) and the appropriate NOAA Space Weather Scale (R2-R5).

These products provide information on Major Flares (with peak X-ray flux above M5). An initial ALERT is issued in near-real-time when the flux exceeds the M5 level on the primary GOES satellite. After the flux has reached a confirmed maximum and decreased to a half-peak flux level, a SUMMARY is issued with details of the event. The SUMMARY is coded by maximum flux value, so individual summaries are available for M5, X1, X10, and X20 flares. The thresholds correspond to the NOAA Radio Blackout (R-Scale) for categories R2 through R5.

Sequence of Space Weather Messages Issued for a Series of Major X-ray Events

Sequence of Space Weather Messages Issued for a Series of Major X-ray Events

NOAA Scale for
Radio Blackouts
X-ray flux
R5 – Extreme
X20 (2 x 10-3 W·m-2)
R4 – Severe
X10 (10-3 W·m-2)
R3 – Strong
X1 (10-4 W·m-2)
R2 – Moderate
M5 (5 x 10-5 W·m-2)
R1 – Minor
M1 (10-5 W·m-2)

Radio Burst Alerts and Summaries

ALERT: Type II Radio Emission
ALERT: Type IV Radio Emission
SUMMARY: 10cm Radio Burst

ALERTS are issued based on the confirmed onset of Type II and IV radio sweep observations.
SUMMARY will be issued for 10 cm Radio Bursts, upon receipt of a final observation report.

These products provide alerts and summaries of solar radio phenomena based on event begin time (and maximum and end times in the case of 10 cm). See the Sample Radio Alerts and Summaries for examples of these products.


Geomagnetic Sudden Impulse Warning and Summary

All SWPC Space Weather Alert Messages for geomagnetic phenomena are based primarily on real-time data from the Boulder-NOAA Magnetometer, which can be taken as a proxy for other mid-latitude locations, and as a general indicator of the trend in USAF “Planetary” values (based on a combined measure of several mid- and high-latitude magnetometer locations that are not available in real-time).

WARNING: Geomagnetic Sudden Impulse expected
SUMMARY: Geomagnetic Sudden Impulse

A Geomagnetic Sudden Impulse WARNING is issued based primarily on solar wind data available from the ACE satellite. These warnings are generally for short lead-time (30-60 minutes), high confidence indication of an expected Geomagnetic Sudden Impulse, and possible onset of subsequent geomagnetic storming. A Geomagnetic Sudden Impulse SUMMARY is issued upon its observation, and will generally be based on data from the primary Boulder-NOAA magnetometer, but may be based on a specified alternate magnetometer station if Boulder data is not available.


Geomagnetic K-index Warnings and Alerts

All SWPC Space Weather Alert Messages for geomagnetic phenomena are based primarily on real-time data from the Boulder-NOAA Magnetometer, which can be taken as a proxy for other mid-latitude locations, and as a general indicator of the trend in USAF “Planetary” values (based on a combined measure of several mid- and high-latitude magnetometer locations that are not available in real-time). Planetary K-index values of 5 through 9 correspond to the NOAA Geomagnetic Storm (G-Scale) for categories G1 through G5.

WARNING: Geomagnetic K-index of 4 expected
WARNING: Geomagnetic K-index of 5 expected
WARNING: Geomagnetic K-index of 6 expected
WARNING: Geomagnetic K-index of 7 or greater expected
Extended Warning
Extended Warning
Extended Warning
Extended Warning
ALERT: Geomagnetic K-index of 4
ALERT: Geomagnetic K-index of 5
ALERT: Geomagnetic K-index of 6
ALERT: Geomagnetic K-index of 7
ALERT: Geomagnetic K-index of 8
ALERT: Geomagnetic K-index of 9
 
  • WARNING:Issued and/or extended for any period with expected values of K= 4, 5, 6, or >= 7. Higher index warnings supersede lower ones.
  • K4, K5 ALERT: Issued near-real-time, only for first occurrence in any period covered by K=4 or K=5 WARNINGS.
  • K6, K7, K8, K9 ALERT: Issued near-realtime, for each occurrence within any 3-hr period, irrespective of WARNINGS.
  • A 12-hour dynamic plot of the Boulder-NOAA Magnetometer and end-of-period Boulder K and estimated Planetary K indices are on the SWPC Website.

K-index WARNINGS are issued by SWPC under two conditions: Warning of expected ONSET of geomagnetic activity, and/or, warning of expected PERSISTENCE of geomagnetic activity. A more detailed description can be found here.

K-index WARNINGS include a specific indication of what condition – Onset or Persistence – applies to the WARNING (or EXTENDED WARNING, when required). The WARNING period is expressed in terms of “Valid From” and “Valid To” times. EXTENDED WARNINGS always have the same “Valid From” time as the original WARNING, with a revised “Now Valid Until” time specified in the message. WARNINGS (and EXTENDED WARNINGS, when needed) are issued for K-index thresholds of 4, 5, 6, and 7 or greater. The appropriate NOAA Space Weather Scale is also appended to the warning.

K-index ALERTS for values of 4 through 9 are issued on a near-realtime criteria, based on thresholds of deflection from quiet-day curve values for geomagnetic field components over synoptic, 3-hour periods (the formal definition of a K-index is the maximum such deflection for the entire 3-hour period). K-index ALERTS are issued based on a near-realtime calculation of cumulative deflection values occurring within the current synoptic period. The message will also contain the magnetometer Station name which provided the data for the alert (in most cases this will be Boulder). End-of period values for Boulder (and estimated Planetary) K indices are available on the NOAA-SWPC Alerts Website

Lower-value K-index ALERTS (4 and 5) are only issued contingent on whether an active WARNING for that threshold is in effect. Given an active WARNING period for K = 4 or 5, only one such ALERT will be issued for the first occurrence within the valid WARNING time. Otherwise, K = 4 or 5 ALERTS will be issued once for each occurrence within a given synoptic period. To indicate the criteria in effect, K-index ALERT message formats include an Active Warning keyword (Yes/No), as well as a Synoptic Period keyword value for the period involved. See Sample K-index Alerts and Warnings.

In the case of higher value K-indices (deflections equaling a K-index of 6, 7, 8, or 9),one such ALERT will be issued for each and every synoptic period in which they occur, regardless of whether an active warning for those thresholds is presently in effect.

The diagrams below give an example of a severe geomagnetic storm period, indicating the K-index products that would likely be issued under these conditions. Also note the effect of active Warnings on the issuance of lower-value (K = 4 and 5) Alerts.

Sample Severe Geomagnetic Storm Period on Boulder-NOAA Magnetometer
Sample Severe Geomagnetic Storm Period on Boulder-NOAA Magnetometer

Boulder-NOAA Magnetometer, H & D component trace data, from 2001 March 30 1200 UTC until 2001 April 1, 1200 UTC, with approximated Quiet Day Curve. Boulder K-indices were issued at the end of each 3-hour synoptic period (e.g. 0000 – 0300 UTC, etc.)

Sample K-index Warning Periods and K-index Messages Issued for the Boulder-NOAA Magnetometer Condition Show Above

Sample K-index Warning Periods and K-index Messages Issued

Magnetometer Data, showing cumulative value of nT deflections for each 3-hour period, and corresponding Alerts that would be issued. Note the effect of Active Warnings on K=4 and K=5 Alerts.

NOAA Scale for
Geomagnetic Storms
Kp index
G5 – Extreme
Kp = 9
G4 – Severe
Kp = 8 and 9 minus
G3 – Strong
Kp = 7
G2 – Moderate
Kp = 6
G1 – Minor
Kp = 5

Geomagnetic A-Index Watches

All SWPC Space Weather Watches Messages for geomagnetic phenomena are based on Fredericksburg, Virginia (mid-latitude) magnetometer.

WATCH: Geomagnetic A-index of 20 or greater predicted
WATCH: Geomagnetic A-index of 30 or greater predicted
WATCH: Geomagnetic A-index of 50 or greater predicted
WATCH: Geomagnetic A-index of 100 or greater predicted

A-index WATCHES are issued for valid times corresponding to entire calendar days, based upon the daily analyses and forecasts produced by SWPC. They serve as a long lead-time prediction of the expected trend in geomagnetic activity, within the limits of what the 24-hour A-index value can describe.

Geomagnetic activity WARNINGS and ALERTS are available only in terms of the K-index products (described above), however a running 24-hour value of the A-index (updated every 3 hours) is available on SWPC’s Alerts website.


Electron Flux Alert

ALERT: Electron 2MeV Integral Flux exceeded 1000pfu Continued Alert

Electron Events can persist for days, but the flux values observed at geosynchronous orbit follow a strong diurnal cycle due to the geometry of the Earth’s magnetic field. Maximum values generally occur near local noon locations on the daytime side of the Earth. ALERTS for Electron Events are therefore issued once per “satellite day” based on data from SWPC’s primary GOES satellite, when electron fluxes have exceeded the event threshold (1000 pfu). The “satellite day” for GOES East, SWPC’s current primary Electron satellite, is approximately 0500 to 0500 UTC; for GOES West, the secondary GOES Electron satellite, its approximately 0900 to 0900 UTC. On subsequent “days”, an additional Electron ALERT is issued upon a new threshold crossing, and include the prior day’s maximum flux time and value observed (if it occurred). No Electron ALERTS are issued on “days” when the threshold is not exceeded. As with any Electron Event, users should consider the locations of the satellite platforms of interest vs. the location of GOES, with regard to the specific timing of enhanced electron exposures that may occur. GOES East satellites are at approximates 75 degrees west longitude and GOES West at approximately 135 degrees west longitude. The satellite used is identified in the “Station” keyword, e.g. Station: GOES12 See GOES Satellite Location.


Proton 10MeV and 100 MeV Warnings, Event Alerts, and Event Summaries

WARNING: Proton 10MeV Integral Flux above 10pfu expected
Extended Warning
ALERT: Proton Event 10MeV Integral Flux exceeded 10pfu
ALERT: Proton Event 10MeV Integral Flux exceeded 100pfu
ALERT: Proton Event 10MeV Integral Flux exceeded 1000pfu
ALERT: Proton Event 10MeV Integral Flux exceeded 10000pfu
ALERT: Proton Event 10MeV Integral Flux exceeded 100000pfu
 
SUMMARY: Proton Event 10MeV Integral Flux exceeded 10pfu
SUMMARY: Proton Event 10MeV Integral Flux exceeded 100pfu
SUMMARY: Proton Event 10MeV Integral Flux exceeded 1000pfu
SUMMARY: Proton Event 10MeV Integral Flux exceeded 10000pfu
SUMMARY: Proton Event 10MeV Integral Flux exceeded 100000pfu
 

pfu = proton flux units = particles·s-1·ster-1·cm-2

  • 10 MeV Warning:Issued when flux levels above 10 pfu are predicted. The predicted level of activity is given in the NOAA Space Weather Scale categories.
  • 10 MeV ALERTS: Issued when flux level exceeding 10, 100, 1,000, 10,000, or 100,000 pfu confirmed.
  • 10 MeV Proton Event SUMMARY: Issued when 10 MeV flux levels make a confirmed drop below S-Scalethresholds. Includes date/times for begin, maximum, end, and applicable flux data.
  • The appropriate NOAA Space Weather Scale will be included on 10 MeV warning, alert and summary
    messages.
WARNING: Proton 100MeV Integral Flux above 1pfu expected
Extended Warning
ALERT: Proton Event 100MeV Integral Flux exceeded 1pfu  
SUMMARY: Proton Event 100MeV Integral Flux exceeded 1pfu  
  • 100 MeV Flux ALERT: Issued when flux level exceeding 1 pfu confirmed.
  • 100 MeV Proton Event SUMMARY: Issued when 100 MeV flux level makes confirmed drop below 1 pfu threshold. Includes date/times for begin, maximum, end, and applicable flux data.

Proton Event products are issued for several thresholds. The 10 MeV products match the NOAA Solar Radiation Storm (S-scale) thresholds, based upon values observed on the primary GOES satellite.

Proton Event WARNINGS are issued by SWPC under two conditions: Warning of expected ONSET of a Proton Event, and/or, warning of expected PERSISTENCE of a Proton Event.

The 10 MeV Integral Flux WARNING (and EXTENDED WARNING, when required) is issued based upon the expectation of exceeding flux levels above 10 pfu. The same applies for the 100 MeV Integral Flux WARNING, though for a threshold of 1 pfu. Proton Event WARNINGS include a specific indication of what condition – Onset or Persistence – applies to the WARNING (or EXTENDED WARNING, when required). The WARNING period is expressed in terms of “Valid From” and “Valid To” times. EXTENDED WARNINGS always have the same “Valid From” time as the original WARNING, with a revised “Now Valid Until” time specified in the message. The 10 MeV Integral Flux WARNING includes the predicted level of activity based on the NOAA S-scale.

Proton Event ALERTS are issued upon confirmation of 10 Mev or 100 MeV Integral Flux exceeding certain thresholds. Initial ALERTS for 10 MeV and 100 MeV are issued for integral flux exceeding 10 pfu and 1 pfu, respectively. Higher threshold 10 MeV ALERTS are also issued for threshold exceedences of 100, 1,000, 10,000, and 100,000 pfu, matching the thresholds described in the NOAA S-scale.

Once the Proton Flux has made a confirmed drop below a given threshold, a Proton Event SUMMARY is issued, specifying the start, maximum, end times, maximum flux observed for the event, and the corresponding NOAA S-scale. Because flux levels can drop slowly, the time of a “confirmed” drop below threshold can sometimes take several hours to determine.

Higher threshold products for 100 MeV flux levels, such as 100 pfu, are being considered for future implementation.

Sample High Energy Proton Event (July 2000) Showing Alert and Summary Messages To Be Issued

Sample High Energy Proton Event (July 2000) Showing Alert and Continuation Messages To Be Issued

NOAA Scale for
Solar Radiation Storms
Proton 10 MeV Integral Flux exceeds
S5 – Extreme
100,000 pfu
S4 – Severe
10,000 pfu
S3 – Strong
1,000 pfu
S2 – Moderate
100 pfu
S1 – Minor
10 pfu

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