Solar Terrestrial Activity Report

Last major update issued on February 25, 2025 at 05:55 UT.

Recent activity

The geomagnetic field was at quiet to active levels on February 24. Solar wind speed at SOHO ranged between 315 and 442 km/sec, averaging 365 km/sec (+40 km/sec compared to the previous day), probably under the influence of a co-rotating interaction region associated with CH1273. The high latitude magnetometer at Andenes recorded quiet to minor storm levels. The above 10 MeV proton flux was affected by two events during the course of the day. was very close to background levels all day. The first increase in proton levels was observed starting at 08:20 at GOES18 and peaked at 1.48 pfu at 13:15 UT and was likely associated with an event behind the northwest limb in AR 14001. The second increase was more significant and began at 23:00 UT, peaking at 37.1 pfu at 02:40 UT on February 25. The source of this event was behind the southwest limb. An impressive CME was observed as well after the last event.

Solar flux density measured at 20h UT on 2.8 GHz was 202.9 - increasing 31.4 over the previous solar rotation. (Centered 1 year average SF at 1 AU - 183 days ago: 193.53. In comparison SC24 peaked on June 28, 2014 at 145.50 while SC23 peaked on February 23, 2002 at 198.15. Current SC25 peak: 193.53 on August 26, 2024 (subtracting a baseline solar flux level of 65, this is +59.66% compared to the SC24 peak and -3.47% 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: 13.0). Three hour interval K indices: 31233243 (planetary), 31232232 (Boulder), 51022353 (Andenes).

The background x-ray flux is at the class C3 level (GOES 18).

At the time of counting spots (see image time), spots were observed in 13 active regions using 2K resolution (SN: 336) and in 12 active regions using 1K resolution (SN: 221) SDO/HMI images.

AR 13993 [N14W71] was quiet and stable.
AR 13996 [S15W61] decayed losing spots and area, all mature penumbra disappeared in the trailing spot section.
AR 13998 [S12W40] gained a tiny magnetic delta configuration in a small northern penumbra. M class flaring is possible.
AR 13999 [N09W60] developed slowly and quietly.
AR 14000 [N16W34] decayed losing spots and area. There is still a magnetic delta configuration in the central part of the region. M class flares are possible.
AR 14002 [N14W07] decayed slowly and quietly.
AR 14003 [N10E25] developed slowly and quietly.
AR 14004 [S12E47] decayed slowly and was mostly quiet. SWPC split off the northernmost spots into AR 14007. Currently there is no obvious reason for the split.
AR 14005 [S06E28] decayed slowly and quietly.
AR 14006 [N18E46] was mostly quiet and stable.

Spotted regions not observed (or interpreted differently) by SWPC/USAF:
S10820 [S07W07] developed slowly and quietly.
New region S10824 [N05E81] rotated into view.
New region S10825 [S19W17] was observed with tiny spots in an old plage area.

C2+ flares

Coronal mass ejections (CMEs)

February 22-24: No obviously Earth directed CMEs.

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 negative polarity northern hemisphere coronal hole (CH1273) rotated across the central meridian on February 21. A positive polarity southern hemisphere coronal hole (CH1272) may be too far to the south to cause a disturbance. CH1272 will rotate across the central meridian on February 22-26 having decayed in the western half on February 22. A recurrent trans equatorial positive polarity coronal hole (CH1271) will become 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 25 due to effects associated with CH1273. Quiet to unsettled levels are likely on February 26-27 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.

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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.