Perhaps the most obvious feature of the sun is the sunspots that characterize the photosphere. The base temperature of the 300-km deep
photosphere is approximately 6400 °C whereas the sunspot regions are characterized with areas of relatively lower temperature (around 4800 °C
for the umbral regions and 5900 °C for the penumbral regions) and increased magnetic activity (up to 3000 times the average magnetic field of
the sun). Due to the differential rate of rotation of the solar disk (26 days at the equator and 36 days at the poles), there is a "twisting"
of the magnetic fields which surface to the photosphere producing sunspots. Typically, these spots and groups are found to lie + 30°
of the solar equator and can physically be many-fold times larger than our planet! As the images below indicate, sunspots are characterized
with a dark core, the "umbra", where the temperature is about 1600 °C less than the surrounding temperature of the photosphere whereas the
less darker envelope which typically encompasses the umbral region, the "penumbra", is about only 500 °C less than the surrounding
Studies have shown sunsplot activity to exhibit an eleven-yr cycle with virtually little sunspot activity during the minima of the cycle whereas frequent sunspots and associated groups dominate during the maximum of the same cycle, typically approximately 4.5 years after the minimum. During the solar maximum, we also have frequent filaments, flares and prominences (see here) which include ejected material from the sun's outermost "shell", the chromosphere, that reaches earth causing, for example, geomagnetic storms that produce the well-known and beautiful aurora borealis and australis.
Note: Who stole the sunspots?! Where have they gone?! As noted by Dr Phillips (SpaceWeather), "As of March 31st, there were no sunspots on 78 of the year's 90 days (87%)" and this a continuation of the lack of activity observed for 2008 where 266 days were characterized without any sunspot activity (same reference). The collage below is comprised of two images spaced precisely four years apart and which is a perfect representation of what is happening (actually NOT happening) with Sol at this moment. More specifically, one of the two component images in the collage below is from July 5th, 2005 and which documents the sample rich activity which is characteristic of the sun during non-minimum periods. The second component image in the collage is from July 5th, 2009 and is most characteristic of the blank sun and/or nominal activity which has become the norm and status quo.
Some research suggests this lack of sunspot activity impacts the levels of UV in our atmosphere and which in turn impact the development of clouds. Certainly winters have been unusually severe and it seems each and every winter manages to find a way to be worse than the previous one.
Please click on the image below to display in higher resolution (900 x 1200)
332,900 x Earth
Mean Eq Diameter:
109.1 x Earth
152 million km
RA / Dec:
06h 54m 44s /
+22° 50' 32"
0h 8m 27.3s
Jul 05, 2005 @ 13:27:27 UT+3
Jul 05, 2009 @ 13:35:26 UT+3
AP 160 f/7.5 StarFire EDF
Canon EOS 300D/350D
Baader ND-5 (full-aperture)
1 x (1/500 sec, 1/400 sec)
RAW image format
3456x2304 image size