Subsiding geomagnetic and solar radiation storms

Subsiding geomagnetic and solar radiation storms

Geomagnetic storm sparked by a combination of CMEs from last couple of days is now subsiding. We might still see uptick today but it will most likely remain below G1 levels.

At 10:57 UTC on April 20, a 24 nT geomagnetic sudden impulse (interplanetary shockwave passage) was recorded at the Boulder magnetometer. Geomagnetic activity subsequently reached active levels at 12:35 UTC and minor storm (G1) levels by 13:01 UTC.  The relatively benign behavior of Bz kept the activity from exceeding minor storm levels.  

According to SWPC, minor (G1) storm conditions may persist into the first synoptic period of April 21 with an overnight sub-storm before diminishing to unsettled to active levels on April 22. A return to quiet to unsettled levels are expected on April 22

"The 10 Mev greater than 10 pfu proton event (S1-minor) which began on April 18 at 15:25 UTC reached a maximum of 58 pfu at 01:05 UTC on April 19 before beginning to decline. The decline was interrupted when an interplanetary (IP) shock passage was detected at ACE at 10:57 UTC on April 20. 10 MeV flux briefly rose from 15 pfu to near 30 pfu before plummeting below the 10 pfu threshold at 11:55 UTC on April 20, signaling the end of the proton event.

The greater than 2 MeV electron flux at geosynchronous orbit is expected to be at normal to moderate levels during the rest of the day. The greater than 10 MeV proton flux at geosynchronous orbit is expected to be elevated, but below the 10 pfu threshold.  It should gradually return to nominal levels over the next three days with a slight chance for another event on April 21 and 22." (SWPC) 

Image credit: NOAA / SWPC

Solar activity has been at low levels during past 24 hours. Only three low level C-class solar flares have been observed by 11:00 UTC on April 21.

There are currently 9 numbered sunspot regions on the Earth side of the Sun. Most regions were stable or decaying during last 34 hours.  The three largest regions, 2034 (N04W66, Eko/beta-gamma), 2035 (S16W43, Eai/beta-gamma), and 2036 (S17E68, Dac/beta-gamma) decreased in areal extent from yesterday but retained their beta-gamma magnetic complexity. This large complex regions will exit around the west limb and start their farside rotation over the next couple of days.

Sunspots on April 21, 2014. Image credit: NASA SDO / HMI

2033 N11W84   264  0060 Hsx  02   01 Alpha
2034 N04W66   246  0270 Eko  11   16 Beta-Gamma
2035 S16W43   223  0200 Eai  13   30 Beta-Gamma
2036 S17W68   248  0180 Dac  10   20 Beta-Gamma
2037 S10W67   247  0040 Cao  09   04 Beta
2038 S11W05   185  0080 Dai  06   12 Beta
2042 N19E15   165  0170 Cso  09   04 Beta
2044 S20E37   143  0030 Dro  09   11 Beta
2045 S22E62   118  0050 Cao  03   04 Beta

SWPC forecasters estimate 55% chance of M-class, and 10% chance of X-class solar flares in next three days.

Featured image: NOAA / SWPC - Enlil Solar Wind Prediction model

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