Viewing archive of Saturday, 21 April 2018
Solar activity report
Any mentioned solar flare in this report has a scaling factor applied by the Space Weather Prediction Center (SWPC). Because of the SWPC scaling factor, solar flares are reported as 42% smaller than for the science quality data. The scaling factor has been removed from our archived solar flare data to reflect the true physical units.
Report of Solar-Geophysical Activity 2018 Apr 21 2200 UTCPrepared by the NOAA © SWPC and processed by SpaceWeatherLive.com
Joint USAF/NOAA Report of Solar and Geophysical Activity
SDF Number 111 Issued at 2200Z on 21 Apr 2018IA. Analysis of Solar Active Regions and Activity from 20-2100Z to 21-2100Z Solar activity has been at very low levels for the past 24
hours. There are currently 2 numbered sunspot regions on the disk.
IB. Solar Activity Forecast
Solar activity is expected to be very low
with a chance for a C-class flares on days one, two, and three (22 Apr,
23 Apr, 24 Apr).
IIA. Geophysical Activity Summary 20-2100Z to 21-2100Z
The geomagnetic
field has been at quiet to unsettled levels for the past 24 hours. Solar
wind speed reached a peak of 630 km/s at 20/2357Z. Total IMF reached 6
nT at 21/0701Z. The maximum southward component of Bz reached -5 nT at
20/2308Z. Electrons greater than 2 MeV at geosynchronous orbit reached a
peak level of 21310 pfu.
IIB. Geophysical Activity Forecast
The geomagnetic field is expected
to be at quiet to unsettled levels on day one (22 Apr) and quiet levels
on days two and three (23 Apr, 24 Apr).
III. Event Probabilities 22 Apr to 24 Apr
| Class M | 01% | 01% | 01% |
| Class X | 01% | 01% | 01% |
| Proton | 01% | 01% | 01% |
| PCAF | green | ||
IV. Penticton 10.7 cm Flux
Observed 21 Apr 077 Predicted 22 Apr-24 Apr 078/078/078 90 Day Mean 21 Apr 070
V. Geomagnetic A Indices
Observed Afr/Ap 20 Apr 029/038 Estimated Afr/Ap 21 Apr 011/012 Predicted Afr/Ap 22 Apr-24 Apr 010/010-005/005-006/005
VI. Geomagnetic Activity Probabilities 22 Apr to 24 Apr
| A. Middle Latitudes | |||
|---|---|---|---|
| Active | 30% | 10% | 10% |
| Minor storm | 10% | 01% | 01% |
| Major-severe storm | 01% | 01% | 01% |
| B. High Latitudes | |||
|---|---|---|---|
| Active | 20% | 20% | 20% |
| Minor storm | 30% | 20% | 20% |
| Major-severe storm | 35% | 10% | 10% |
All times in UTC
Latest news
Sunday, 7 December 2025
M8.1 solar flare with earth-directed CME
Monday, 1 December 2025
X1.9 solar flare, Coronal hole faces Earth
Friday, 14 November 2025
X4.0 solar flare
Latest forum messages
AR4294 / 4296 / 4298 390AR4299 M8.1 CME 2025/12/06 87AR 4299 115New paper on the Gannon Storm 10-11 May 2024 2Electron event 10
More topicsSupport SpaceWeatherLive.com!
A lot of people come to SpaceWeatherLive to follow the Solar activity or if there is a chance to see the aurora, but with more traffic comes higher costs to keep the servers online. If you like SpaceWeatherLive and want to support the project you can choose a subscription for an ad-free site or consider a donation. With your help we can keep SpaceWeatherLive online!
Space weather facts
| Last X-flare | 2025/12/08 | X1.1 |
| Last M-flare | 2025/12/08 | M1.8 |
| Last geomagnetic storm | 2025/12/04 | Kp5 (G1) |
| Spotless days | |
|---|---|
| Last spotless day | 2022/06/08 |
| Monthly mean Sunspot Number | |
|---|---|
| November 2025 | 91.8 -22.8 |
| December 2025 | 162.7 +70.9 |
| Last 30 days | 108 +13.3 |