Space Weather Observations, Alerts, and Forecast

3-day Solar-Geophysical Forecast

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Product: 3-Day Forecast - Issued: 2021 Apr 21 0030 UTC
Prepared by the U.S. Dept. of Commerce, NOAA, Space Weather Prediction Center.

Geomagnetic Activity Observation and Forecast

The greatest observed 3 hr Kp over the past 24 hours was 3 (below NOAA Scale levels). The greatest expected 3 hr Kp for Apr 21-Apr 23 2021 is 3 (below NOAA Scale levels).

NOAA Kp index breakdown Apr 21-Apr 23 2021

	Apr 21	Apr 22	Apr 23
00-03UT	2	2	2
03-06UT	3	2	2
06-09UT	3	2	2
09-12UT	2	1	2
12-15UT	2	1	2
15-18UT	2	1	2
18-21UT	2	1	2
21-00UT	2	1	3

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

Solar Radiation Activity Observation and Forecast

Solar radiation, as observed by NOAA GOES-16 over the past 24 hours, was below S-scale storm level thresholds.

Solar Radiation Storm Forecast for Apr 21-Apr 23 2021

	Apr 21	Apr 22	Apr 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.

Radio Blackout Activity and Forecast

No radio blackouts were observed over the past 24 hours.

Radio Blackout Forecast for Apr 21-Apr 23 2021

	Apr 21	Apr 22	Apr 23
R1-R2	15%	15%	10%
R3 or greater	1%	1%	1%

Rationale: No R1 (Minor) or greater radio blackouts are expected. No significant active region flare activity is forecast.

Current Space Weather Overview

Real Time Images of the Sun

SOHO EIT 171	SOHO EIT 195	SOHO EIT 284	SOHO EIT 304
SDO/HMI Continuum	SDO/HMI Magnetogram	LASCO C2	LASCO C3

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 Wind

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

WSA-Enlil Solar Wind Prediction

WSA-Enlil is a large-scale, physics-based prediction model of the heliosphere, used by the Space Weather Forecast Office to provide 1-4 day advance warning of solar wind structures and Earth-directed coronal mass ejections (CMEs) that cause geomagnetic storms. Solar disturbances have long been known to disrupt communications, wreak havoc with geomagnetic systems, and to pose dangers for satellite operations.

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, 2019, and the sun entered solar cycle 25 at that time.

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.

Radio Communications Impact

D-Region Absorption

D-Region Absorption Prediction

The D-Region Absorption Product addresses the operational impact of the solar X-ray flux and SEP events on HF radio communication. Long-range communications using high frequency (HF) radio waves (3 - 30 MHz) depend on reflection of the signals in the ionosphere. Radio waves are typically reflected near the peak of the F2 layer (~300 km altitude), but along the path to the F2 peak and back the radio wave signal suffers attenuation due to absorption by the intervening ionosphere. The D-Region Absorption Prediction model is used as guidance to understand the HF radio degradation and blackouts this can cause.

VHF and HF Band Conditions

Credits:

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additions by Martin of Hebrides Weather and Ken True of Saratoga Weather
with 3-day Solar-Geophysical Forecast text formatting by Jeremy Dyde of Jerbils Weather