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)
2
as of 2026-02-06T08:59:00
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
166
as of 2026-02-05T22:00:00
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.
White-light sunspots
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 06 0030 UTC Obs date: 2026 Feb 05
| Region | Location | Area | Extent | McIntosh | Spots | Mag |
|---|---|---|---|---|---|---|
| 4358 | N17W57 | 30 | 5 | BXO | 3 | B |
| 4362 | S17W22 | 40 | 4 | CAO | 8 | B |
| 4366 | N14W19 | 1100 | 18 | FKC | 25 | BGD |
| 4367 | N09E12 | 50 | 8 | CAO | 5 | B |
| 4368 | S10E12 | 40 | 2 | HSX | 1 | A |
| 4369 | S03E17 | 40 | 2 | HSX | 1 | A |
| 4370 | S19E25 | 10 | 1 | AXX | 2 | A |
| 4371 | S23E34 | 120 | 8 | DKI | 14 | BD |
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.
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
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).
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 06 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 5 (NOAA Scale
G1).
The greatest expected 3 hr Kp for Feb 06-Feb 08 2026 is 4.67 (NOAA Scale
G1).
NOAA Kp index breakdown Feb 06-Feb 08 2026
Feb 06 Feb 07 Feb 08
00-03UT 4.67 (G1) 4.00 4.67 (G1)
03-06UT 4.00 2.67 3.67
06-09UT 3.33 1.67 3.33
09-12UT 2.67 1.67 3.33
12-15UT 2.67 2.33 2.00
15-18UT 3.00 2.67 3.33
18-21UT 3.33 3.33 3.33
21-00UT 3.67 4.00 3.67
Rationale: G1 (Minor) geomagnetic storms are likely on 06 and 08 Feb due
to the anticipated arrival of two CMEs glancing impacts near Earth.
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 06-Feb 08 2026
Feb 06 Feb 07 Feb 08
S1 or greater 25% 25% 25%
Rationale: There is a chance for a S1 (Minor) solar radiation storms on
06-08 Feb due to the magnetic complexity and dynamic of the active
regions on the visible disk.
C. NOAA Radio Blackout Activity and Forecast
Radio blackouts reaching the R1 levels were observed over the past 24
hours. The largest was at Feb 05 2026 0436 UTC.
Radio Blackout Forecast for Feb 06-Feb 08 2026
Feb 06 Feb 07 Feb 08
R1-R2 80% 80% 80%
R3 or greater 35% 35% 35%
Rationale: R1-R2 (Minor-Moderate) radio blackouts are expected, with a
chance for R3 (Strong) or greater levels on 06-08 Feb due to the
magnetic complexity and dynamic of the active regions on the visible
disk.
: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)
- 2026-02-05 15:51:31.013 — Space Weather Message Code: WATA20 Serial Number: 1094 Issue Time: 2026 Feb 05 1551 UTC WATCH: Geomagnetic Storm Category G1 Predicted Highest Storm Level Predicted by Day: Feb 06: G1 (Minor) Feb 07: None (Below G1) Feb 08: 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.
- 2026-02-05 08:54:59.493 — Space Weather Message Code: WARK04 Serial Number: 5246 Issue Time: 2026 Feb 05 0854 UTC EXTENDED WARNING: Geomagnetic K-index of 4 expected Extension to Serial Number: 5245 Valid From: 2026 Feb 04 1515 UTC Now Valid Until: 2026 Feb 05 1800 UTC Warning Condition: Persistence NOAA Space Weather Scale descriptions can be found at www.swpc.noaa.gov/noaa-scales-explanation Potential Impacts: Area of impact primarily poleward of 65 degrees Geomagnetic Latitude. Induced Currents - Weak power grid fluctuations can occur. Aurora - Aurora may be visible at high latitudes such as Canada and Alaska.
- 2026-02-05 08:54:38.777 — Space Weather Message Code: WARK05 Serial Number: 2187 Issue Time: 2026 Feb 05 0854 UTC EXTENDED WARNING: Geomagnetic K-index of 5 expected Extension to Serial Number: 2186 Valid From: 2026 Feb 05 0300 UTC Now Valid Until: 2026 Feb 05 1500 UTC Warning Condition: Persistence 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.
- 2026-02-05 04:33:48.110 — Space Weather Message Code: ALTK05 Serial Number: 1963 Issue Time: 2026 Feb 05 0433 UTC ALERT: Geomagnetic K-index of 5 Threshold Reached: 2026 Feb 05 0426 UTC Synoptic Period: 0300-0600 UTC Active Warning: Yes NOAA Scale: G1 - Minor 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.
- 2026-02-05 02:59:21.917 — Space Weather Message Code: WARK05 Serial Number: 2186 Issue Time: 2026 Feb 05 0259 UTC WARNING: Geomagnetic K-index of 5 expected Valid From: 2026 Feb 05 0300 UTC Valid To: 2026 Feb 05 0900 UTC Warning Condition: Onset NOAA Scale: G1 - Minor 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.
- 2026-02-04 23:12:38.203 — Space Weather Message Code: WARK04 Serial Number: 5245 Issue Time: 2026 Feb 04 2312 UTC EXTENDED WARNING: Geomagnetic K-index of 4 expected Extension to Serial Number: 5244 Valid From: 2026 Feb 04 1515 UTC Now Valid Until: 2026 Feb 05 1200 UTC Warning Condition: Persistence NOAA Space Weather Scale descriptions can be found at www.swpc.noaa.gov/noaa-scales-explanation Potential Impacts: Area of impact primarily poleward of 65 degrees Geomagnetic Latitude. Induced Currents - Weak power grid fluctuations can occur. Aurora - Aurora may be visible at high latitudes such as Canada and Alaska.
- 2026-02-04 17:00:58.543 — Space Weather Message Code: ALTK04 Serial Number: 2627 Issue Time: 2026 Feb 04 1700 UTC ALERT: Geomagnetic K-index of 4 Threshold Reached: 2026 Feb 03 1700 UTC Synoptic Period: 1500-1800 UTC Active Warning: Yes NOAA Space Weather Scale descriptions can be found at www.swpc.noaa.gov/noaa-scales-explanation Potential Impacts: Area of impact primarily poleward of 65 degrees Geomagnetic Latitude. Induced Currents - Weak power grid fluctuations can occur. Aurora - Aurora may be visible at high latitudes such as Canada and Alaska.
- 2026-02-04 15:35:28.013 — Space Weather Message Code: SUMSUD Serial Number: 295 Issue Time: 2026 Feb 04 1535 UTC SUMMARY: Geomagnetic Sudden Impulse Observed: 2026 Feb 04 1506 UTC Deviation: 16 nT Station: BOU NOAA Space Weather Scale descriptions can be found at www.swpc.noaa.gov/noaa-scales-explanation
- 2026-02-04 15:08:25.473 — Space Weather Message Code: WARK04 Serial Number: 5244 Issue Time: 2026 Feb 04 1508 UTC WARNING: Geomagnetic K-index of 4 expected Valid From: 2026 Feb 04 1515 UTC Valid To: 2026 Feb 04 2359 UTC Warning Condition: Onset NOAA Space Weather Scale descriptions can be found at www.swpc.noaa.gov/noaa-scales-explanation Potential Impacts: Area of impact primarily poleward of 65 degrees Geomagnetic Latitude. Induced Currents - Weak power grid fluctuations can occur. Aurora - Aurora may be visible at high latitudes such as Canada and Alaska.
- 2026-02-04 14:33:09.777 — Space Weather Message Code: WARSUD Serial Number: 250 Issue Time: 2026 Feb 04 1433 UTC WARNING: Geomagnetic Sudden Impulse expected Valid From: 2026 Feb 04 1505 UTC Valid To: 2026 Feb 04 1535 UTC IP Shock Passage Observed: 2026 Feb 04 1421 UTC NOAA Space Weather Scale descriptions can be found at www.swpc.noaa.gov/noaa-scales-explanation
Sources (recommended reading)
- NOAA SWPC Products & Data: swpc.noaa.gov/products-and-data
- NOAA Space Weather Scales: swpc.noaa.gov/noaa-scales-explanation
- Solar Cycle Progression: swpc.noaa.gov/products/solar-cycle-progression
- SWPC Solar Region Summary: swpc.noaa.gov/products/solar-region-summary
- Sunspot Number (historical, WDC‑SILSO): sidc.be/SILSO