[SFDXA] SUMMARY: Geomagnetic Sudden Impulse

[Bill]

/For those who know what this causes...:/

Space Weather Message Code: SUMSUD
Serial Number: 237
Issue Time: 2022 Jun 06 1059 UTC

SUMMARY: Geomagnetic Sudden Impulse
Observed: 2022 Jun 06 1041 UTC
Deviation: 13 nT
Station: Fredericksburg

NOAA Space Weather Scale descriptions can be found at
www.swpc.noaa.gov/noaa-scales-explanation

///I had to look this one up. Here is WikipediA's description./


  Geomagnetic jerk

 From Wikipedia, the free encyclopedia

In geophysics <https://en.wikipedia.org/wiki/Geophysics>, a *geomagnetic 
jerk* or *secular geomagnetic variation impulse* is a relatively sudden 
change in the second derivative 
<https://en.wikipedia.org/wiki/Derivative_(mathematics)> of the Earth's 
magnetic field <https://en.wikipedia.org/wiki/Geomagnetic_field> with 
respect to time.^[1] 
<https://en.wikipedia.org/wiki/Geomagnetic_jerk#cite_note-michelis-1>

These events were noted by Vincent Courtillot 
<https://en.wikipedia.org/wiki/Vincent_Courtillot> and Jean-Louis Le 
Mouël in 1976.^[2] 
<https://en.wikipedia.org/wiki/Geomagnetic_jerk#cite_note-2> ^[3] 
<https://en.wikipedia.org/wiki/Geomagnetic_jerk#cite_note-3> The 
clearest ones, observed all over the world, happened in 1969, 1978, 
1991, and 1999. Data before 1969 is scarcer, but there is evidence of 
other global jerks in 1901, 1913, and 1925. Other events in 1932, 1949, 
1958, 1986, and 2003 were detected only in some parts of the world.^[1] 
<https://en.wikipedia.org/wiki/Geomagnetic_jerk#cite_note-michelis-1> 
^[4] <https://en.wikipedia.org/wiki/Geomagnetic_jerk#cite_note-mioara-4> 
^[5] <https://en.wikipedia.org/wiki/Geomagnetic_jerk#cite_note-olsen-5> 
These events are believed to originate in the interior of the Earth 
<https://en.wikipedia.org/wiki/Interior_of_the_Earth> (rather than being 
due to external phenomena such as the solar wind 
<https://en.wikipedia.org/wiki/Solar_wind>); but their precise cause is 
still a matter of research.^[5] 
<https://en.wikipedia.org/wiki/Geomagnetic_jerk#cite_note-olsen-5>

The name "jerk" <https://en.wikipedia.org/wiki/Jerk_(physics)> was 
borrowed from kinematics <https://en.wikipedia.org/wiki/Kinematics>, 
where it means the rate of change of the acceleration 
<https://en.wikipedia.org/wiki/Jerk_(physics)> of a body, that is, the 
third derivative of its position with respect to time (the acceleration 
<https://en.wikipedia.org/wiki/Acceleration> being the second 
derivative); or, more specifically, a sudden and momentary spike (or 
dip) <https://en.wikipedia.org/wiki/Impulse_function> in that rate.


    Description

Jerks seem to occur in irregular intervals, on average about once every 
10 years. In the period between jerks, each component of the field at a 
specific location changes with time /t/ approximately as a fixed 
polynomial <https://en.wikipedia.org/wiki/Polynomial> of the second 
degree, /A/ /t/^2 + /B/ /t/ + /C/. Each jerk is a relatively sudden 
change (spread over a period of a few months to a couple of years) in 
the /A/ coefficient <https://en.wikipedia.org/wiki/Coefficient> of this 
formula, which determines the second derivative; and usually in /B/ and 
/C/ coefficients as well.

The strength of each jerk varies from location to location, and some 
jerks are observed only in some regions. For example, the 1949 jerk was 
clearly observed at Tucson <https://en.wikipedia.org/wiki/Tucson> (North 
America <https://en.wikipedia.org/wiki/North_America>, long. 
<https://en.wikipedia.org/wiki/Longitude> 110.93°), but not at Chambon 
la Forêt 
<https://en.wikipedia.org/w/index.php?title=Chambon_la_For%C3%AAt&action=edit&redlink=1> 
(Europe <https://en.wikipedia.org/wiki/Europe>, long. 2.27°). Moreover, 
the global jerks seem to occur at slightly different times in different 
regions; often earlier in the Northern hemisphere than in the Southern 
hemisphere.^[1] 
<https://en.wikipedia.org/wiki/Geomagnetic_jerk#cite_note-michelis-1>


    Theories

These events are believed to be caused by changes in the flow patterns 
of the liquid outer core of the Earth 
<https://en.wikipedia.org/wiki/Earth%27s_outer_core>,^[4] 
<https://en.wikipedia.org/wiki/Geomagnetic_jerk#cite_note-mioara-4> as 
for instance carried by hydromagnetic waves such as torsional 
oscillations.^[1] 
<https://en.wikipedia.org/wiki/Geomagnetic_jerk#cite_note-michelis-1> 
^[6] <https://en.wikipedia.org/wiki/Geomagnetic_jerk#cite_note-6> 
Numerical simulations of core dynamics have successfully reproduced the 
characteristics of well documented jerks.^[7] 
<https://en.wikipedia.org/wiki/Geomagnetic_jerk#cite_note-7> In these 
simulations, jerks are caused by Alfvén waves 
<https://en.wikipedia.org/wiki/Alfv%C3%A9n_wave> emitted inside the 
outer core <https://en.wikipedia.org/wiki/Earth%27s_outer_core> and 
focusing at the core surface. Prior to these explanations there had also 
been claims that geomagnetic jerks were connected to strong 
earthquakes.^[8] 
<https://en.wikipedia.org/wiki/Geomagnetic_jerk#cite_note-8>

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