Space Weather Lab
Education-first dashboards for amateur radio operators (UTC)
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)
5
as of 2026-03-21T05:18:00
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
102
as of 2026-03-20T22:00:00
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 / G2
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 Mar 21 0030 UTC Obs date: 2026 Mar 20
| Region | Location | Area | Extent | McIntosh | Spots | Mag |
|---|---|---|---|---|---|---|
| 4392 | S16W40 | 130 | 5 | CSO | 5 | B |
| 4397 | N18E42 | 30 | 5 | CAO | 3 | 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.
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 Mar 21 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 7 (NOAA Scale
G3).
The greatest expected 3 hr Kp for Mar 21-Mar 23 2026 is 6.67 (NOAA Scale
G3).
NOAA Kp index breakdown Mar 21-Mar 23 2026
Mar 21 Mar 22 Mar 23
00-03UT 6.67 (G3) 4.67 (G1) 3.33
03-06UT 6.33 (G2) 5.00 (G1) 4.33
06-09UT 5.67 (G2) 4.33 3.00
09-12UT 5.00 (G1) 4.00 3.00
12-15UT 3.33 2.67 2.00
15-18UT 4.00 3.33 2.00
18-21UT 4.67 (G1) 4.33 3.33
21-00UT 4.33 4.33 3.00
Rationale: G1-G3 (Minor-Strong) geomagnetic storm conditions are
expected on 21 Mar with G1 (Minor) conditions likely on 22 Mar due to
persistent CME effects followed by HSS activity.
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 Mar 21-Mar 23 2026
Mar 21 Mar 22 Mar 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
No radio blackouts were observed over the past 24 hours.
Radio Blackout Forecast for Mar 21-Mar 23 2026
Mar 21 Mar 22 Mar 23
R1-R2 10% 10% 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.
:Product: 27-day Space Weather Outlook Table 27DO.txt
:Issued: 2026 Mar 16 0302 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 2026-03-16
#
# UTC Radio Flux Planetary Largest
# Date 10.7 cm A Index Kp Index
2026 Mar 16 108 15 4
2026 Mar 17 108 10 3
2026 Mar 18 105 8 3
2026 Mar 19 105 5 2
2026 Mar 20 105 10 3
2026 Mar 21 100 35 5
2026 Mar 22 102 25 5
2026 Mar 23 105 15 4
2026 Mar 24 110 15 4
2026 Mar 25 100 18 5
2026 Mar 26 110 10 3
2026 Mar 27 120 8 3
2026 Mar 28 125 5 2
2026 Mar 29 125 5 2
2026 Mar 30 125 15 4
2026 Mar 31 125 10 3
2026 Apr 01 130 5 2
2026 Apr 02 135 5 2
2026 Apr 03 140 18 5
2026 Apr 04 135 20 5
2026 Apr 05 135 8 3
2026 Apr 06 130 15 4
2026 Apr 07 135 8 3
2026 Apr 08 130 5 2
2026 Apr 09 125 25 5
2026 Apr 10 120 40 6
2026 Apr 11 115 20 5
Source: NOAA/SWPC. Interpretation on this site is educational; always cross-check with SWPC directly.
Alerts (recent/active)
- 2026-03-21 05:17:35.590 — Space Weather Message Code: WARK06 Serial Number: 646 Issue Time: 2026 Mar 21 0517 UTC EXTENDED WARNING: Geomagnetic K-Index of 6 expected Extension to Serial Number: 645 Valid From: 2026 Mar 20 2020 UTC Now Valid Until: 2026 Mar 21 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 55 degrees Geomagnetic Latitude. Induced Currents - Power grid fluctuations can occur. High-latitude power systems may experience voltage alarms. Spacecraft - Satellite orientation irregularities may occur; increased drag on low Earth-orbit satellites is possible. Radio - HF (high frequency) radio propagation can fade at higher latitudes. Aurora - Aurora may be seen as low as New York to Wisconsin to Washington state.
- 2026-03-21 05:17:35.583 — Space Weather Message Code: ALTK06 Serial Number: 703 Issue Time: 2026 Mar 21 0517 UTC ALERT: Geomagnetic K-index of 6 Threshold Reached: 2026 Mar 21 0514 UTC Synoptic Period: 0300-0600 UTC Active Warning: Yes NOAA Scale: G2 - Moderate NOAA Space Weather Scale descriptions can be found at www.swpc.noaa.gov/noaa-scales-explanation Potential Impacts: Area of impact primarily poleward of 55 degrees Geomagnetic Latitude. Induced Currents - Power grid fluctuations can occur. High-latitude power systems may experience voltage alarms. Spacecraft - Satellite orientation irregularities may occur; increased drag on low Earth-orbit satellites is possible. Radio - HF (high frequency) radio propagation can fade at higher latitudes. Aurora - Aurora may be seen as low as New York to Wisconsin to Washington state.
- 2026-03-21 05:17:35.570 — Space Weather Message Code: WARK05 Serial Number: 2209 Issue Time: 2026 Mar 21 0517 UTC EXTENDED WARNING: Geomagnetic K-index of 5 expected Extension to Serial Number: 2208 Valid From: 2026 Mar 20 1930 UTC Now Valid Until: 2026 Mar 21 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 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.
- 2026-03-21 05:17:35.560 — Space Weather Message Code: WARK04 Serial Number: 5291 Issue Time: 2026 Mar 21 0517 UTC EXTENDED WARNING: Geomagnetic K-index of 4 expected Extension to Serial Number: 5290 Valid From: 2026 Mar 20 0719 UTC Now Valid Until: 2026 Mar 21 2359 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.
- 2026-03-21 03:32:05.153 — Space Weather Message Code: ALTK05 Serial Number: 1982 Issue Time: 2026 Mar 21 0332 UTC ALERT: Geomagnetic K-index of 5 Threshold Reached: 2026 Mar 21 0331 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.
- 2026-03-21 01:54:56.203 — Space Weather Message Code: ALTK07 Serial Number: 213 Issue Time: 2026 Mar 21 0154 UTC ALERT: Geomagnetic K-index of 7 Threshold Reached: 2026 Mar 21 0154 UTC Synoptic Period: 0000-0300 UTC Active Warning: Yes NOAA Scale: G3 - Strong NOAA Space Weather Scale descriptions can be found at www.swpc.noaa.gov/noaa-scales-explanation Potential Impacts: Area of impact primarily poleward of 50 degrees Geomagnetic Latitude. Induced Currents - Power system voltage irregularities possible, false alarms may be triggered on some protection devices. Spacecraft - Systems may experience surface charging; increased drag on low Earth-orbit satellites and orientation problems may occur. Navigation - Intermittent satellite navigation (GPS) problems, including loss-of-lock and increased range error may occur. Radio - HF (high frequency) radio may be intermittent. Aurora - Aurora may be seen as low as Pennsylvania to Iowa to Oregon.
- 2026-03-21 01:41:52.367 — Space Weather Message Code: ALTK06 Serial Number: 702 Issue Time: 2026 Mar 21 0141 UTC ALERT: Geomagnetic K-index of 6 Threshold Reached: 2026 Mar 21 0141 UTC Synoptic Period: 0000-0300 UTC Active Warning: Yes NOAA Scale: G2 - Moderate NOAA Space Weather Scale descriptions can be found at www.swpc.noaa.gov/noaa-scales-explanation Potential Impacts: Area of impact primarily poleward of 55 degrees Geomagnetic Latitude. Induced Currents - Power grid fluctuations can occur. High-latitude power systems may experience voltage alarms. Spacecraft - Satellite orientation irregularities may occur; increased drag on low Earth-orbit satellites is possible. Radio - HF (high frequency) radio propagation can fade at higher latitudes. Aurora - Aurora may be seen as low as New York to Wisconsin to Washington state.
- 2026-03-21 00:34:35.307 — Space Weather Message Code: ALTK05 Serial Number: 1981 Issue Time: 2026 Mar 21 0034 UTC ALERT: Geomagnetic K-index of 5 Threshold Reached: 2026 Mar 21 0033 UTC Synoptic Period: 0000-0300 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.
- 2026-03-20 23:29:12.240 — Space Weather Message Code: ALTK07 Serial Number: 212 Issue Time: 2026 Mar 20 2329 UTC ALERT: Geomagnetic K-index of 7 Threshold Reached: 2026 Mar 20 2328 UTC Synoptic Period: 2100-2400 UTC Active Warning: Yes NOAA Scale: G3 - Strong NOAA Space Weather Scale descriptions can be found at www.swpc.noaa.gov/noaa-scales-explanation Potential Impacts: Area of impact primarily poleward of 50 degrees Geomagnetic Latitude. Induced Currents - Power system voltage irregularities possible, false alarms may be triggered on some protection devices. Spacecraft - Systems may experience surface charging; increased drag on low Earth-orbit satellites and orientation problems may occur. Navigation - Intermittent satellite navigation (GPS) problems, including loss-of-lock and increased range error may occur. Radio - HF (high frequency) radio may be intermittent. Aurora - Aurora may be seen as low as Pennsylvania to Iowa to Oregon.
- 2026-03-20 23:05:56.793 — Space Weather Message Code: WARK07 Serial Number: 145 Issue Time: 2026 Mar 20 2305 UTC WARNING: Geomagnetic K-index of 7 or greater expected Valid From: 2026 Mar 20 2305 UTC Valid To: 2026 Mar 21 0600 UTC Warning Condition: Onset NOAA Scale: G3 or greater NOAA Space Weather Scale descriptions can be found at www.swpc.noaa.gov/noaa-scales-explanation Potential Impacts: Area of impact primarily poleward of 50 degrees Geomagnetic Latitude. Induced Currents - Power system voltage irregularities possible, false alarms may be triggered on some protection devices. Spacecraft - Systems may experience surface charging; increased drag on low Earth-orbit satellites and orientation problems may occur. Navigation - Intermittent satellite navigation (GPS) problems, including loss-of-lock and increased range error may occur. Radio - HF (high frequency) radio may be intermittent. Aurora - Aurora may be seen as low as Pennsylvania to Iowa to Oregon.
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