Space Weather Lab

An education-first dashboard for amateur radio operators (UTC time)

Sunspots — what they are, why they matter, and what to do about it

Sunspots are dark regions on the solar photosphere where the magnetic field is unusually strong. They’re not just "interesting astronomy": sunspots mark active regions that can produce solar flares and coronal mass ejections (CMEs), which are the events most likely to disrupt HF propagation.

Right now (ham-relevant quick context)

Planetary Kp (1-minute)
0
as of 2026-02-04T04:35:00
What does this mean to me?
Kp is a summary of geomagnetic disturbance. A rising Kp often means polar HF paths degrade first (flutter, fades, absorption), while VHF aurora modes may become possible.
F10.7 cm Solar Flux
173
as of 2026-02-03T22:00:00
What does this mean to me?
F10.7 is a "baseline ionization" proxy: higher usually supports higher MUF (more frequent 15m/10m openings). Sunspots and active regions often correlate with higher F10.7, but the relationship is not one-to-one.
NOAA scales (now)
R0 / S0 / G0
at-a-glance severity categories
What does this mean to me?
R events are the "instant HF fadeout" category (flare-driven). G events are the geomagnetic storm category (CME/solar-wind driven). S events matter most for polar paths and satellites.

Visual: the Sun right now

These are SWPC-provided "latest" imagery tiles. Click any image to enlarge.

SDO/HMI intensity image (sunspots)
White-light sunspots
GOES-R SUVI 195Å image (false color)
EUV active regions

What are sunspots, physically?

A sunspot is a region where magnetic field lines concentrate and inhibit normal convective heat transport. Less heat reaches the surface locally, so the spot looks darker (cooler) compared to surrounding photosphere. Typical spot fields are on the order of thousands of gauss, far stronger than Earth's surface field.

What does this mean to me?
Sunspots themselves don’t "block" your signal. The practical reason hams care is that sunspots identify magnetically active regions. Those regions are the real estate where flares and CMEs happen — and those events can strongly affect propagation.

How sunspots form (the short, honest version)

  • Solar dynamo: the Sun’s rotating, convecting plasma generates magnetic fields.
  • Flux emergence: buoyant magnetic flux tubes rise and pierce the photosphere as bipolar regions (pairs/groups of spots).
  • Complexity matters: twisted/sheared fields store free magnetic energy; that energy can be released as flares/CMEs.

A useful operator translation: more/larger/complex spot groups generally imply a higher probability of flare activity.

How sunspots are measured (and what those numbers mean)

  • Sunspot Number (SSN): a standardized count-like index used to track solar-cycle activity.
  • F10.7 flux: a radio measurement that tracks solar EUV fairly well; often correlates with SSN.
  • Active-region classification: systems like Mount Wilson and McIntosh describe magnetic/structural complexity (a flare risk clue).
What does this mean to me?
If you want one "baseline" number for high-band HF odds, use F10.7 (and the Solar Cycle page). If you want "today’s risk of sudden HF fadeout", watch the R scale and D‑RAP. If you want "storm risk over the next few days", watch solar wind/geomagnetics (Kp/G scale).

Active-region classification (McIntosh + Mount Wilson) — a practical operator view

Two widely used descriptors appear in daily region summaries: the Mount Wilson magnetic class (how the polarities are arranged) and the McIntosh class (a compact code describing group structure). You don’t need to memorize every nuance — you just need to recognize when a region is “simple” vs “complex and flare-capable.”

System Common Values Operator Translation Why You Care
Mount Wilson Alpha, Beta, Beta-Gamma, Beta-Gamma-Delta Alpha/Beta = simpler. Beta-Gamma/Delta = more complex, mixed polarities. More complex magnetic structure generally implies higher probability of M/X flares (R events).
McIntosh 3-character codes (e.g., “Eki”, “Fkc”) Bigger/more developed groups + compact structure can be more flare-capable. It’s a quick “shape + complexity” label that helps identify which region(s) to watch.
What does this mean to me?
Think in timelines: flares can degrade HF immediately on the sunlit side (minutes), while CMEs drive storms later (days). When region complexity is high, it’s a cue to keep an eye on the R scale and D‑RAP during your operating window, and to expect more “surprise” absorption events.

The Solar Region Summary table below shows these codes for today’s active regions.

Solar Region Summary (current active regions)

This is the daily SWPC region list: NOAA active-region number, heliographic location, area/extent, and the two “complexity shorthand” codes. If this table is blank, it usually means the server cannot reach SWPC right now (see the Status page).

Issued: 2026 Feb 04 0030 UTC    Obs date: 2026 Feb 03

Region Location Area Extent McIntosh Spots Mag
4358 N16W30 30 4 CRO 5 B
4362 S16E06 40 5 CAO 7 BG
4366 N14E07 1100 16 FKC 42 BGD
4367 N09E38 50 8 CAO 10 B
4368 S10E38 40 2 HSX 1 A
4369 S03E43 40 2 HSX 1 A
4370 S18E50 30 1 CRO 1 B
4371 S22E60 40 9 DAO 8 B
4372 S24W39 15 4 BXO 6 B
How do I interpret these codes?
McIntosh is a 3-letter morphology code (development + penumbra + compactness). Mag is a compressed magnetic-class code (A, B, BG, BGD). In general, more complex regions have a higher flare probability. Use this as a “what to watch” list, then check R scale + D‑RAP for real-time HF impacts.

Solar Cycle (predicted smoothed SSN range)

This is a long-term trend indicator (months/years). For day-to-day operations, disturbances dominate.

12562.3-0.53201920402022202520282031203420372040

More detail is in Solar Cycle.

Solar wind: what it is

The solar wind is a continuous outflow of charged particles (mostly protons/electrons) carrying the Sun’s magnetic field (the IMF). When fast streams or CME-driven plasma reach Earth, they can drive geomagnetic storms.

  • Bz south (negative): magnetic reconnection becomes efficient → storm potential rises.
  • Speed/density up: more energy coupled into Earth’s system.
  • Outcome: aurora expansion, polar absorption, HF instability, and sometimes VHF aurora.

Live context: solar wind & geomagnetic response

ACE magnetometer and solar wind (24 hour)
Watch for sustained negative Bz plus fast wind for geomagnetic storm potential.
Geospace geomagnetic activity plot (3 day)
A quick context plot: did a storm hit, and is it recovering?

On-air impacts: the chain from sunspots → flares/CMEs → ionosphere

  • Flares (minutes to hours): increase X‑ray/EUV, boosting D‑region ionization on the dayside → more absorption → sudden HF fadeouts (R events).
  • CMEs (1–4 days): disturb Earth’s magnetosphere → geomagnetic storms (G events) → polar HF degradation, fading/flutter, and aurora.
  • High baseline activity: often raises MUF (good), but increases the probability of disruptive events (bad).
D-RAP global HF absorption map
D‑RAP shows where HF absorption is strongest right now.

How to protect your station and electronics

Most station damage risk comes from lightning and power transients. Severe geomagnetic storms can also drive long-conductor currents (grid/pipelines), but at the amateur-station scale your best ROI is disciplined grounding, bonding, and surge control.

  • Single-point ground/bonding: bond radio, power supply, coax protectors, and ground bar together to avoid dangerous potential differences.
  • Coax surge protection: use quality lightning arrestors and bond them properly; route coax to an entry panel.
  • AC surge protection: use whole-house or shack-level surge protection and keep safety grounding intact.
  • Unplug when needed: for thunderstorms or severe alerts, physically disconnect antennas and power (no protector is perfect).
  • Antenna considerations: avoid long, unbonded control lines; bond towers/masts; keep ground leads short and wide.
What does this mean to me?
Space weather is mostly a propagation problem — but your station safety plan should be built for lightning and power surges. If you build for those correctly, you’re also well-positioned for most geomagnetic-related nuisance effects.

SWPC forecast text (for context)

:Product: 3-Day Forecast :Issued: 2026 Feb 04 0030 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 2 (below NOAA Scale levels). The greatest expected 3 hr Kp for Feb 04-Feb 06 2026 is 5.00 (NOAA Scale G1). NOAA Kp index breakdown Feb 04-Feb 06 2026 Feb 04 Feb 05 Feb 06 00-03UT 1.67 2.00 4.67 (G1) 03-06UT 1.67 2.00 4.00 06-09UT 1.33 1.67 3.67 09-12UT 1.33 1.33 3.67 12-15UT 1.33 1.33 3.67 15-18UT 1.33 3.00 4.00 18-21UT 1.33 4.33 4.00 21-00UT 1.67 5.00 (G1) 4.00 Rationale: G1 (Minor) storming is likely on 05-06 Feb due to the arrival of the CME associated with the 01/2357 UTC X8.1 flare from Region 4366. 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 Feb 04-Feb 06 2026 Feb 04 Feb 05 Feb 06 S1 or greater 30% 30% 30% Rationale: The greater than 10 MeV proton flux has a chance to exceed S1 (Minor) levels over 04-06 Feb due to the high eruptive potential of Region 4366. The risk of a proton event will increase as the region moves into a more favorable magnetic connection point in the Suns western hemisphere. C. NOAA Radio Blackout Activity and Forecast Radio blackouts reaching the R3 levels were observed over the past 24 hours. The largest was at Feb 03 2026 1408 UTC. Radio Blackout Forecast for Feb 04-Feb 06 2026 Feb 04 Feb 05 Feb 06 R1-R2 80% 80% 80% R3 or greater 40% 40% 40% Rationale: Moderate to high solar activity is expected due to M-class flaring (R1-R2, Minor-Moderate) for the next three days with a high chance for X-class flares (R3-Strong or greater) due to expected further activity from AR 4366.
:Product: 27-day Space Weather Outlook Table 27DO.txt :Issued: 2026 Feb 02 0938 UTC # Prepared by the US Dept. of Commerce, NOAA, Space Weather Prediction Center # Product description and SWPC contact on the Web # https://www.swpc.noaa.gov/content/subscription-services # # 27-day Space Weather Outlook Table # Issued 2026-02-02 # # UTC Radio Flux Planetary Largest # Date 10.7 cm A Index Kp Index 2026 Feb 02 160 5 2 2026 Feb 03 155 5 2 2026 Feb 04 155 5 2 2026 Feb 05 145 5 2 2026 Feb 06 120 8 3 2026 Feb 07 125 8 3 2026 Feb 08 130 8 3 2026 Feb 09 135 10 3 2026 Feb 10 140 8 3 2026 Feb 11 135 8 3 2026 Feb 12 140 5 2 2026 Feb 13 145 20 5 2026 Feb 14 145 15 4 2026 Feb 15 155 15 4 2026 Feb 16 160 15 4 2026 Feb 17 170 15 4 2026 Feb 18 180 15 4 2026 Feb 19 175 15 4 2026 Feb 20 170 15 4 2026 Feb 21 160 15 4 2026 Feb 22 150 8 3 2026 Feb 23 140 8 3 2026 Feb 24 135 20 4 2026 Feb 25 130 20 4 2026 Feb 26 130 8 3 2026 Feb 27 140 5 2 2026 Feb 28 160 5 2

Source: NOAA/SWPC. Interpretation on this site is educational; always cross-check with SWPC directly.

Alerts (recent/active)

  • 2026-02-03 16:46:38.020 — Space Weather Message Code: WATA20 Serial Number: 1093 Issue Time: 2026 Feb 03 1646 UTC WATCH: Geomagnetic Storm Category G1 Predicted Highest Storm Level Predicted by Day: Feb 04: None (Below G1) Feb 05: G1 (Minor) Feb 06: G1 (Minor) THIS SUPERSEDES ANY/ALL PRIOR WATCHES IN EFFECT NOAA Space Weather Scale descriptions can be found at www.swpc.noaa.gov/noaa-scales-explanation Potential Impacts: Area of impact primarily poleward of 60 degrees Geomagnetic Latitude. Induced Currents - Weak power grid fluctuations can occur. Spacecraft - Minor impact on satellite operations possible. Aurora - Aurora may be visible at high latitudes, i.e., northern tier of the U.S. such as northern Michigan and Maine.
  • 2026-02-03 15:10:43.490 — Space Weather Message Code: SUMXM5 Serial Number: 310 Issue Time: 2026 Feb 03 1510 UTC SUMMARY: X-ray Event exceeded M5 Begin Time: 2026 Feb 03 1445 UTC Maximum Time: 2026 Feb 03 1456 UTC End Time: 2026 Feb 03 1503 UTC X-ray Class: M7.2 Location: N14E14 NOAA Scale: R2 - Moderate NOAA Space Weather Scale descriptions can be found at www.swpc.noaa.gov/noaa-scales-explanation Potential Impacts: Area of impact centered primarily on sub-solar point on the sunlit side of Earth. Radio - Limited blackout of HF (high frequency) radio communication for tens of minutes.
  • 2026-02-03 14:58:28.183 — Space Weather Message Code: ALTXMF Serial Number: 519 Issue Time: 2026 Feb 03 1458 UTC ALERT: X-Ray Flux exceeded M5 Threshold Reached: 2026 Feb 03 1455 UTC NOAA Scale: R2 - Moderate NOAA Space Weather Scale descriptions can be found at www.swpc.noaa.gov/noaa-scales-explanation Potential Impacts: Area of impact centered on sub-solar point on the sunlit side of Earth. Extent of blackout of HF (high frequency) radio communication dependent upon current X-ray Flux intensity. For real-time information on affected area and expected duration please see http://www.swpc.noaa.gov/products/d-region-absorption-predictions-d-rap.
  • 2026-02-03 14:28:00.830 — Space Weather Message Code: SUMX01 Serial Number: 210 Issue Time: 2026 Feb 03 1428 UTC SUMMARY: X-ray Event exceeded X1 Begin Time: 2026 Feb 03 1358 UTC Maximum Time: 2026 Feb 03 1408 UTC End Time: 2026 Feb 03 1418 UTC X-ray Class: X1.5 Location: N14E14 NOAA Scale: R3 - Strong NOAA Space Weather Scale descriptions can be found at www.swpc.noaa.gov/noaa-scales-explanation Potential Impacts: Area of impact consists of large portions of the sunlit side of Earth, strongest at the sub-solar point. Radio - Wide area blackout of HF (high frequency) radio communication for about an hour.
  • 2026-02-03 14:11:30.957 — Space Weather Message Code: ALTXMF Serial Number: 518 Issue Time: 2026 Feb 03 1411 UTC ALERT: X-Ray Flux exceeded M5 Threshold Reached: 2026 Feb 03 1407 UTC NOAA Scale: R2 - Moderate NOAA Space Weather Scale descriptions can be found at www.swpc.noaa.gov/noaa-scales-explanation Potential Impacts: Area of impact centered on sub-solar point on the sunlit side of Earth. Extent of blackout of HF (high frequency) radio communication dependent upon current X-ray Flux intensity. For real-time information on affected area and expected duration please see http://www.swpc.noaa.gov/products/d-region-absorption-predictions-d-rap.
  • 2026-02-03 07:25:39.580 — Space Weather Message Code: SUMXM5 Serial Number: 309 Issue Time: 2026 Feb 03 0725 UTC SUMMARY: X-ray Event exceeded M5 Begin Time: 2026 Feb 03 0643 UTC Maximum Time: 2026 Feb 03 0701 UTC End Time: 2026 Feb 03 0719 UTC X-ray Class: M7.2 Location: N14E17 NOAA Scale: R2 - Moderate NOAA Space Weather Scale descriptions can be found at www.swpc.noaa.gov/noaa-scales-explanation Potential Impacts: Area of impact centered primarily on sub-solar point on the sunlit side of Earth. Radio - Limited blackout of HF (high frequency) radio communication for tens of minutes.
  • 2026-02-03 07:02:06.397 — Space Weather Message Code: ALTXMF Serial Number: 517 Issue Time: 2026 Feb 03 0702 UTC ALERT: X-Ray Flux exceeded M5 Threshold Reached: 2026 Feb 03 0700 UTC NOAA Scale: R2 - Moderate NOAA Space Weather Scale descriptions can be found at www.swpc.noaa.gov/noaa-scales-explanation Potential Impacts: Area of impact centered on sub-solar point on the sunlit side of Earth. Extent of blackout of HF (high frequency) radio communication dependent upon current X-ray Flux intensity. For real-time information on affected area and expected duration please see http://www.swpc.noaa.gov/products/d-region-absorption-predictions-d-rap.
  • 2026-02-03 04:59:47.073 — Space Weather Message Code: ALTEF3 Serial Number: 3619 Issue Time: 2026 Feb 03 0459 UTC CONTINUED ALERT: Electron 2MeV Integral Flux exceeded 1000pfu Continuation of Serial Number: 3618 Begin Time: 2026 Jan 21 0950 UTC Yesterday Maximum 2MeV Flux: 7292 pfu Potential Impacts: Satellite systems may experience significant charging resulting in increased risk to satellite systems.
  • 2026-02-02 11:43:12.050 — Space Weather Message Code: SUMXM5 Serial Number: 308 Issue Time: 2026 Feb 02 1143 UTC SUMMARY: X-ray Event exceeded M5 Begin Time: 2026 Feb 02 1115 UTC Maximum Time: 2026 Feb 02 1124 UTC End Time: 2026 Feb 02 1131 UTC X-ray Class: M6.7 Location: N18E30 NOAA Scale: R2 - Moderate NOAA Space Weather Scale descriptions can be found at www.swpc.noaa.gov/noaa-scales-explanation Potential Impacts: Area of impact centered primarily on sub-solar point on the sunlit side of Earth. Radio - Limited blackout of HF (high frequency) radio communication for tens of minutes.
  • 2026-02-02 11:23:15.280 — Space Weather Message Code: ALTXMF Serial Number: 516 Issue Time: 2026 Feb 02 1123 UTC ALERT: X-Ray Flux exceeded M5 Threshold Reached: 2026 Feb 02 1121 UTC NOAA Scale: R2 - Moderate NOAA Space Weather Scale descriptions can be found at www.swpc.noaa.gov/noaa-scales-explanation Potential Impacts: Area of impact centered on sub-solar point on the sunlit side of Earth. Extent of blackout of HF (high frequency) radio communication dependent upon current X-ray Flux intensity. For real-time information on affected area and expected duration please see http://www.swpc.noaa.gov/products/d-region-absorption-predictions-d-rap.

Sources (recommended reading)

Data is cached and may lag real-time conditions. Always confirm on-air.