Space Weather Observations, Alerts, and Forecast

3-day Solar-Geophysical Forecast

:Product: 3-Day Forecast
:Issued: 2025 May 21 1230 UTC
# Prepared by the U.S. Dept. of Commerce, NOAA, Space Weather Prediction Center
#
A. NOAA Geomagnetic Activity Observation and Forecast

The greatest observed 3 hr Kp over the past 24 hours was 4 (below NOAA
Scale levels).
The greatest expected 3 hr Kp for May 21-May 23 2025 is 4.00 (below NOAA
Scale levels).

NOAA Kp index breakdown May 21-May 23 2025

             May 21       May 22       May 23
00-03UT       4.00         2.67         2.00     
03-06UT       3.00         2.00         2.00     
06-09UT       3.00         2.33         1.67     
09-12UT       3.00         2.33         2.67     
12-15UT       3.33         2.33         2.67     
15-18UT       3.00         2.33         4.00     
18-21UT       1.67         2.33         2.67     
21-00UT       2.00         2.67         2.67     

Rationale: No G1 (Minor) or greater geomagnetic storms are expected.  No
significant transient or recurrent solar wind features are forecast.

B. NOAA Solar Radiation Activity Observation and Forecast

Solar radiation, as observed by NOAA GOES-18 over the past 24 hours, was
below S-scale storm level thresholds.

Solar Radiation Storm Forecast for May 21-May 23 2025

              May 21  May 22  May 23
S1 or greater    1%      1%      1%

Rationale: No S1 (Minor) or greater solar radiation storms are expected.
No significant active region activity favorable for radiation storm
production is forecast.

C. NOAA Radio Blackout Activity and Forecast

Radio blackouts reaching the R1 levels were observed over the past 24
hours. The largest was at May 21 2025 0008 UTC.

Radio Blackout Forecast for May 21-May 23 2025

              May 21        May 22        May 23
R1-R2           35%           35%           35%
R3 or greater    5%            5%            5%

Rationale: Solar flare activity is expected to remain low as most
regions on the disk are fairly simple in their magnetic complexities.
There remains a 35% chance for R1-R2 (Minor-Moderate) and a 5% chance
for R3 (Strong) activity through 23 May.

Real Time Images of the Sun

SOHO EIT 304

SOHO EIT 284

The sun is constantly monitored for sun spots and coronal mass ejections. EIT (Extreme ultraviolet Imaging Telescope) images the solar atmosphere at several wavelengths, and therefore, shows solar material at different temperatures. In the images taken at 304 Angstrom the bright material is at 60,000 to 80,000 degrees Kelvin. In those taken at 171 Angstrom, at 1 million degrees. 195 Angstrom images correspond to about 1.5 million Kelvin, 284 Angstrom to 2 million degrees. The hotter the temperature, the higher you look in the solar atmosphere.

Real Time Solar X-ray and Solar Wind

Latest LASCO Solar Corona Large Angle and Spectrometric Coronagraph (LASCO).

Real-Time Solar Wind Real-Time Solar Wind data broadcast from NASA's ACE satellite.

Solar X-ray Flux This plot shows 3-days of 5-minute solar x-ray flux values measured on the SWPC primary and secondary GOES satellites.

Satellite Environment Plot The Satellite Environment Plot combines satellite and ground-based data to provide an overview of the current geosynchronous satellite environment.

Space Weather Overview

Solar Cycle

Sun Spot Number Progression This plot shows the Solar Cycle Sun Spot Number Progression.

F10.7cm Radio Flux Progression This plot shows the F10.7cm Radio Flux Progression.

The Solar Cycle is observed by counting the frequency and placement of sunspots visible on the Sun. Solar minimum occurred in December, 2008.
Solar maximum was expected to occur in May, 2013.

Auroral Activity Extrapolated from NOAA POES

Northern Hemi Auroral Map

Southern Hemi Auroral Map

Instruments on board the NOAA Polar-orbiting Operational Environmental Satellite (POES) continually monitor the power flux carried by the protons and electrons that produce aurora in the atmosphere. SWPC has developed a technique that uses the power flux observations obtained during a single pass of the satellite over a polar region (which takes about 25 minutes) to estimate the total power deposited in an entire polar region by these auroral particles. The power input estimate is converted to an auroral activity index that ranges from 1 to 10.

VHF and HF Band Conditions

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