Last major update issued on April 3, 2011 at 06:10 UTC.
[Solar and geomagnetic data - last month (updated
[Solar wind and electron fluence charts (updated daily)
[Solar cycles 21-24 (last update April 1, 2011)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22, 23 and 24 (last update April 1, 2011)]
[Graphical comparison of cycles 10, 12, 13, 14, 16 and 24 (last update April 1, 2011)]
[Historical solar and geomagnetic data charts 1954-2006 (last update April 5, 2007)]
[Archived reports since January 2003 (last update April 1, 2011)]
[POES auroral activity level charts since October
2009 - updated April 1, 2011]
Annotated geomagnetic activity charts - Carrington rotation 2106 [Jan.-Feb.2011] - 2107 [Feb.-March 2011]
The geomagnetic field was unsettled to active on April 2. Solar wind speed ranged between 349 and 706 km/s. Solar wind speed increased significantly after 07h UTC as a coronal hole high speed stream became the dominant solar wind factor. Wind speed had been fairly stable near 600 km/s until another sudden increase in speed occurred near 21h UTC as observed by SOHO/MTOF. As the IMF again became mostly southwards, an increase in geomagnetic activity was observed late in the day and early on April 3.
Solar flux estimated at 20h UTC on 2.8 GHz was 107.5 (decreasing 35.0 over the last solar rotation). The planetary A index was 20 (STAR Ap - based on the mean of three hour interval ap indices: 20.1). Three hour interval K indices: 43343334 (planetary), 43443234 (Boulder).
The background x-ray flux is at the class B2 level.
At midnight UTC the visible solar disk had 9 spotted regions.
Region 11176 decayed slowly and will be rotating over the southwest
Region 11178 was quiet and stable.
Region 11180 was quiet and stable.
Region 11183 decayed slowly losing penumbra on the trailing spots.
Region 11184 developed slowly and quietly.
Spotted regions not numbered by NOAA/SWPC:
[S922] reemerged on March 30 with a single tiny spot. Location at midnight: N24W69
[S924] reemerged on April 1 with a tiny spot. Location at midnight: N36W04
[S928] emerged with spots in an old plage field in the northeast quadrant on April 1. Location at midnight: N14E26
[S929] emerged in the southern hemisphere near the central meridian on April 1. Slow decay was observed on April 2. Location at midnight: S24W18
March 31 - April 2: No obviously Earth directed CMEs were observed in LASCO and STEREO imagery.
Coronal hole history (since late October
Compare today's report to the situation one solar rotation ago: 28 days ago 27 days ago 26 days ago
No obvious coronal holes are currently in or near Earth facing positions.
The darkest areas on the solar disk are likely coronal holes.
Long distance low and medium frequency (below 2 MHz) propagation along paths north of due west over high and upper middle latitudes is poor. Propagation on long distance northeast-southwest paths is fair.
The geomagnetic field is expected to be quiet to active on April 3, quiet to unsettled on April 4 and quiet on April 5-6.
|Coronal holes (1)||Coronal mass ejections (2)||M and X class flares (3)|
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
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: 0-20% probability, Yellow: 20-60% probability, Red: 60-100% probability.
(Click on image for higher resolution image) Compare to the previous day's image
When available the active region map has a coronal hole polarity overlay where red (pink) is negative and blue (blue-green) is positive.
Data for all numbered solar regions according to the Solar Region Summary provided by NOAA/SWPC. 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.
|Active region||Date numbered
|Spot count||Location at midnight||Area||Classification||SDO / HMI 4K continuum
image with polarity overlay
|Total spot count:||26||51|
|Month||Average measured solar flux||International sunspot number (SIDC)||Smoothed sunspot number||Average ap
|2008.07||65.7 (SF minimum)||0.5||2.8 (-0.4)|
|2010.02||84.7||18.8||10.6 (+1.3)||4.15 / 4.61|
|2010.03||83.4||15.4||12.3 (+1.7)||4.58 / 4.65|
|2010.04||75.9||8.0||14.0 (+1.7)||10.22 / 10.24|
|2010.05||73.8||8.7||15.5 (+1.5)||9.18 / 8.15|
|2010.06||72.5||13.6||16.4 (+0.9)||8.17 / 6.85|
|2010.07||79.8||16.1||16.8 (+0.4)||6.31 / 5.15|
|2010.08||79.2||19.6||17.4 (+0.6)||8.49 / 7.77|
|2010.09||81.1||25.2||19.6 (+2.2)||5.33 / 5.45|
|2010.10||81.6||23.5||(22.6 predicted, +3.0)||6.07 / 6.27|
|2010.11||82.5||21.6||(25.8 predicted, +3.2)||4.80 / 5.50|
|2010.12||84.2||14.5||(28.9 predicted, +3.1)||3.41 / 4.35|
|2011.01||83.6||19.1||(31.9 predicted, +3.0)||4.32|
|2011.02||94.6||29.4||(34.4 predicted, +2.5)||5.41|
|2011.03||115.0||56.2||(36.7 predicted, +2.3)||7.79|
|2011.04||108.2 (1)||4.3 (2A) / 64.0 (2B)||(39.2 predicted, +2.5)||(16.63)|
1) Running average based on the daily 20:00 UTC observed solar flux value at
2A) Current impact on the monthly sunspot number based on the Boulder (NOAA/SWPC) sunspot number (accumulated daily sunspots / month days). The official SIDC international sunspot number is typically 30-50% lower. 2B) Month average to date.
3) Running average based on the preliminary daily SWPC ap indices. Values in red are based on the official NGDC ap indices.
This report has been prepared by Jan Alvestad. It is based on analysis of data from whatever sources are available at the time the report is prepared. All time references are to the UTC day. Comments and suggestions are always welcome.
SDO images are courtesy of NASA/SDO and the AIA, EVE, and HMI science teams.