Solar Flare, March 29 2001

We are approximately at the peak of the 11-year solar activity cycle, and solar flares have been in the news. A major event was recorded on March 29 2001, and described in the reports of the National Oceanic and Atmospheric Administration (NOAA):


2001 March 29 at 10:07 a.m. MST (2001 March 29 1707 UT)


Space weather increased to strong levels due to a major solar flare eruption. A category R3 (strong) radio blackout occurred today at 3:15 a.m. MST (2001 March 29 1015 UTC). The blackout was caused by a major solar flare eruption from a very large, complex sunspot group, referred to by NOAA space weather forecasters as Region 9393. Category R3 radio blackouts adversely affect high-frequency radio communications and low-frequency navigation signals on the sunlit side of Earth. As a result this morning's flare, a category S1 (minor) solar radiation storm began at 9:35 a.m. MST (2001 March 29 1635 UTC). Category S1 solar radiation storms will adversely affect high frequency radio communications in the polar regions. Forecasters also expect geomagnetic storms reaching category G1 (minor) to G2 (moderate) to occur during March 30 - April 1 as a result of recent Earth-directed coronal mass ejections. Power systems, spacecraft operations, and high-frequency radio communications are adversely affected by geomagnetic storms. In addition, aurora may be visible along the northern tier of the U.S. this weekend. NOAA forecasters expect that Region 9393 will produce more major flares before it rotates to the far side of the Sun on April 5.

The NOAA website, under "Solar Weather Now" provides a thorough description and presents summaries of the data in excellent graphical displays. Here are two images from their library that show very clear effects of this event in terms of proton flux and x-ray flux. Both graphs show three days, with March 29 in the center.

Solar Flare, March 29 
2001 proton flux

Solar Flare, March 29 
2001 xray flux

The EGG data

To see whether these major bombardments of the earth with unusual amounts of energy flux might affect the GCP/EGG network, the data from the 29th were treated in the usual manner, resulting in the following plot of cumulative deviation of Z² from chance expectation. The moment of the most extreme flare is marked. By inspection, it is apparent that the data show normal variation, and there is no obvious correlation with the solar flare data shown in the previous graphs.

Solar Flare, March 29 

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