Solar Terrestrial Activity Report

Last major update issued on December 13, 2024 at 07:10 UT.
New SDO imagery is unavailable due to severe damage after flooding (broken pipe) at the processing facility on November 26, 2024. Reports from November 27 onwards will be updated when data becomes available sometime in 2025.

Recent activity

The geomagnetic field was at quiet levels on December 12. Solar wind speed at SOHO ranged between 322 and 393 km/sec, averaging 365 km/sec (-32 compared to the previous day). The high latitude magnetometer at Andenes recorded quiet to unsettled levels. The above 10 MeV proton flux was at background levels all day.

Solar flux density measured at 20h UT on 2.8 GHz was 160.9 - increasing 12.0 over the previous solar rotation. (Centered 1 year average SF at 1 AU - 183 days ago: 188.12. In comparison SC24 peaked on June 28, 2014 at 145.50 while SC23 peaked on February 23, 2002 at 198.15. Current SC25 peak: 188.12 on June 13, 2024 (given a base solar flux level of 65, this is +52.94% compared to SC24 peak and -7.53% compared to SC23 peak). The Potsdam WDC planetary A index was 5 (STAR Ap - based on the mean of three hour interval ap indices: 4.8). Three hour interval K indices: 22111121 (planetary), 22011221 (Boulder), 33000132 (Andenes).

C2+ flares

C1 flares: C1.3 @ 00:32, C1.3 @ 00:39, C1.4 @ 01:05, C1.3 @ 03:25, C1.9 @ 06:27, C1.9 @ 07:17, C1.3 @ 08:50, C1.4 @ 09:48, C1.3 @ 13:32, C1.7 @ 16:15, C1.5 @ 20:00, C1.5 @ 20:54 UT

Coronal mass ejections (CMEs)

December 11-12: No obviously Earth directed CMEs were observed.
December 10: A partial halo CME was associated with a major M6.4 flare in AR 13922. Weak effects from this CME are possible on December 13-14.

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 northern hemisphere coronal hole (CH1261) rotated across the central meridian on December 8-9, and may be too far to the north to cause a geomagnetic disturbance. A recurrent positive polarity northern hemisphere coronal hole (CH1262) was in an Earth facing position on December 11.

Propagation

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

Forecast

The geomagnetic field is expected to be quiet on December 13 with a chance of unsettled intervals should effects from CH1261 reach Earth. The December 10 CME could cause some unsettled and active intervals on December 13-14. A high speed stream associated with CH1262 could cause unsettled and active intervals on December 15-16.

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 30 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 December 10, 2024

Sunspot activity in November 2024 decreased compared to October and there is a trend towards lower levels since August 2024. The average solar flux for November was the fourth highest for a month during SC24. The above plot displays a projected peak for the ISN 365d smoothed sunspot numbers in October 15, 2024. All the other smoothed sunspot number have projected peaks either in late November or early December. Assuming that the average sunspot numbers in December 24 decreases significantly over the previous months, and then slowly until mid 2025, an earlier peak peak near July 9, 2024 becomes possible. Currently SC25 is tracking much closer to SC23 than to SC24.

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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.