Solar Terrestrial Activity Report

Last major update issued on February 27, 2025 at 04:40 UT.

Recent activity

The geomagnetic field was at quiet to unsettled levels on February 26 under the influence of effects from CH1272. Solar wind speed at SOHO ranged between 348 and 665 km/sec, averaging 460 km/sec (+85 km/sec compared to the previous day). The high latitude magnetometer at Andenes recorded quiet to minor storm levels. The above 10 MeV proton flux 0.8 pfu at the end of the day.

Solar flux density measured at 20h UT on 2.8 GHz was 180.2 - decreasing 3.5 over the previous solar rotation. (Centered 1 year average SF at 1 AU - 183 days ago: 193.61. In comparison SC24 peaked on June 28, 2014 at 145.50 while SC23 peaked on February 23, 2002 at 198.15. Current SC25 peak: 193.61 on August 28, 2024 (subtracting a baseline solar flux level of 65, this is +59.76% compared to the SC24 peak and -3.41% compared to the SC23 peak). The Potsdam WDC planetary A index was 13 (STAR Ap - based on the mean of three hour interval ap indices: 12.9). Three hour interval K indices: 33323332 (planetary), 23333432 (Boulder), 54223443 (Andenes).

The background x-ray flux is at the class C1 level (GOES 18).

At the time of counting spots (see image time), spots were observed in 15 active regions using 2K resolution (SN: 269) and in 12 active regions using 1K resolution (SN: 167) SDO/HMI images.

AR 13998 [S12W67] decayed slowly and produced low level C flares. C1 flares: C1.9 @ 10:00 UT
AR 14000 [N14W63] decayed further and was mostly quiet.
AR 14002 [N13W34] decayed slowly and quietly.
AR 14003 [N10W02] decayed slowly and quietly.
AR 14004 [S12E21] decayed slowly and produced a few C flares. C1 flares: C1.9 @ 10:53 UT
AR 14006 [N18E19] decayed slowly and was mostly quiet.
AR 14008 [N05E53] decayed slowly and quietly.

Spotted regions not observed (or interpreted differently) by SWPC/USAF:
S10826 [N27W73] was quiet and stable.
S10830 [N19E41] was quiet and stable.
New region S10831 [N27E27] emerged with tiny spots.
New region S10832 [N24E57] emerged with tiny spots.
New region S10833 [N07E74] rotated into view with tiny spots.
New region S10834 [N20W22] emerged with tiny spots.
New region S10835 [S15W16] emerged with a tiny spot.

C2+ flares

Coronal mass ejections (CMEs)

February 24, 26: No obviously Earth directed CMEs.
February 25: A CME was observed after the M3 flare in AR 13998. While the main part of the ejecta is not headed towards Earth, there is a chance of a solar wind shock on February 28.

Coronal holes

[Coronal hole history (since October 2002)]
[Compare today's report to the situation one solar rotation ago: 28 days ago 27 days ago 26 days ago]

A positive polarity southern hemisphere coronal hole (CH1272) rotated across the central meridian on February 22-27. A recurrent trans equatorial positive polarity coronal hole (CH1271) was Earth facing on February 25-26.

Propagation

Long distance low and medium frequency (below 2 MHz) propagation along paths north of due west over upper middle and high latitudes is poor. Propagation on long distance northeast-southwest paths is poor.

Forecast

The geomagnetic field is expected to be at quiet to active levels on February 27 due to effects from CH1272. Quiet to minor storm levels are likely on February 28 - March 1 due to effects from CH1271 and CH1272.

1) Effects from a coronal hole could reach Earth within the next 5 days. When the high speed stream has arrived the color changes to green.
2) Effects from a CME are likely to be observed at Earth within 96 hours.
3) There is a possibility of either M or X class flares within the next 48 hours.

Green: 0-30% probability, Yellow: 30-70% probability, Red: 70-100% probability.

Active solar regions

(Click on image for 2K resolution). 4K resolution. Compare to the previous day's image. 0.5K image

When available the active region map has a coronal hole polarity overlay where red (pink) is negative and blue is positive.

Data for all officially numbered solar regions according to the Solar Region Summary provided by NOAA/SWPC, all other regions are numbered sequentially as they emerge using the STAR spot number. Comments are my own, as is the STAR spot count (spots observed at or inside a few hours before midnight) and data for regions not numbered by SWPC or where SWPC has observed no spots. SWPC active region numbers in the table below and in the active region map above are the historic SWPC/USAF numbers. SWPC data considered to be not sufficiently precise (location, area, classification) are colored red.

Monthly solar cycle data

1) Running average based on the daily 20:00 UTC observed solar flux value at 2800 MHz and any corrections applied to that measurement.
2A) Current impact on the monthly sunspot number based on the Boulder (NOAA/SWPC) sunspot number (accumulated daily sunspots / month days).
2B) Boulder SN current month average to date.
2C) STAR SDO 1K Wolf number 27 day average.
3) Running average based on the quicklook and definitive Potsdam WDC ap indices. Values in red are based on the definitive international GFZ Potsdam WDC ap indices.
4) Source: WDC-SILSO, Royal Observatory Of Belgium, Brussels

Solar cycles 24-25

Update on the progress of solar cycle 25 as of February 10, 2025

Sunspot activity has been on a slowly decreasing trend since September 2024 (using the mean solar flux over 3 solar rotations as a proxy). The 365 days average ISN has a peak on July 8, 2024, but is still expected to peak in October 2024 due to low sunspot numbers in March and the first half of April 2024. Unless there is an uptick in sunspot activity over the next couple of months, the 365 days average solar flux is likely to peak 1-2% below the peak of solar cycle 23. While the 365d average solar flux peaks of SC23 and SC25 are similar, sunspot numbers will peak significantly lower for SC25 compared to SC23.

--------------------------------------------------------------------------------------

This report has been prepared by Jan Alvestad. It is based on the analysis of data from whatever sources are available at the time the report is prepared. All time references are to Universal Time. Comments and suggestions are always welcome.

SDO images are courtesy of NASA/SDO and the AIA, EVE, and HMI science teams.