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Spaceweather Forecast using IMPACT/PLASTIC


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The following presentation on IMPACT/PLASTIC review may be new info to some readers. (I'm grateful to to Vancanneyt Sander of the spaceweatherlive crew for alerting me to the IMPACT resource.)

IMPACT/PLASTIC is a solar wind monitor located on STEREO-A. DSCOVR/ACE are solar wind monitors in-line with earth, roughly the same distance from the sun as IMPACT.  Solar wind (or other solar activity) can take 3 days (+/- 1 day) to arrive at IMPACT or ACE (from the sun). Solar activity recorded at IMPACT, if it continues, will arrive at ACE/DSCOVR ~6 days later (and at earth shortly thereafter), as that is the approximate time for the the sun to rotate an active position earthward after facing STEREO-A.

Here are the positions of STEREO-A, approximately one solar rotation ago, and now:


We observe that STEREO-A is just a bit 'advanced' now than it was on Aug. 25, which means the time-lag between IMPACT and ACE one rotation ago--being ~6 days then--will not be much different than what it is today.  This explanation will become clearer after looking at the IMPACT data.

Below is the IMPACT data (plotted in Red) from one rotation ago, where we see the following sequence of events (in 7-day plots), starting on Aug. 25 recorded at IMPACT:

  1. bump in Bx to >10nT;
  2. drop in By to -10nT;
  3. rapid swings in Bz from +10nT to -10nT;
  4. bump in total B to +15nT;
  5. a rise of Np to ~13/cm^3, then it fell in sequence with...
  6. a rapid rise of V to over 600 km/s, sustained at that level for over 1.5 days.



The chart on the above right, shows a response in activity recorded on ACE (plotted in Brown) starting on Aug. 31, roughly six days after what was recorded on IMPACT.  We see a similar sequence of events listed above, with just some slight differences.  For example, the Velocity ramps a little slower, but it registers a higher magnitude (eventually reaching over 800 km/sec) than what was recorded by IMPACT six days earlier. 


(to be continued)

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So now, one rotation later (than the data discussed above), here is the current IMPACT recording (showing a 3-day plot and 7-day plot):


Quite conspicuously, the sequence of activity recorded by IMPACT (plotted in Red) starting on Sept. 21, listed below, is very similar to what was observed in the data one rotation ago, with only slight differences:

  1. bump in Bx to 10nT;
  2. drop in By exceeding -10nT;
  3. rapid swings in Bz from >+10nT to >-10nT;
  4. bump in total B to almost +15nT;
  5. a rise of Np to ~13/cm^3, then it fell in sequence with...
  6. a ramp of V to over 600 km/s (eventually reaching ~700 km/s) and sustaining these elevated levels for over 1.5 days. 


If the pattern repeats, we expect a similar response mirrored in the ACE data (i.e., earthward), ~6 days later, starting on Sept. 26-27.

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We can begin a close inspection of the incoming (to arrive in ~three days), as we see a pickup in the solar wind starting this morning, next figure:



As yet, it does not appear as strong as the blast that picked up in intensity on 08-28-19 (one rotation ago, producing earth geomagnetic disturbance on 8-31-19), next figure:



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As we await the spaceweather storm that should arrive by the end of today or tomorrow, here are some things to consider in assessing its potential strength in geomagnetic disturbance.  In the last rotation, there were actually two events first picked up at STEREO-A, as seen in the left figure below (circled in blue); the responses recorded by ACE, ~6 days later, are in the right figure:


Notice that the Total B at STEREO-A was larger for EVENT 1 than for EVENT 2, although the Total B recorded at ACE was about the same for both events.  The Velocity for EVENT 2 was larger than the Velocity for EVENT 1 as recorded on both STEREO-A and ACE, although the difference in Velocity between the two events was much greater on ACE.

The geomagnetic disturbance resulting from each event is circled in the figure below:87754253_Georesponses.thumb.jpg.394fe193020d3541d7de4c7079fc0f67.jpg

Clearly, EVENT 2 resulted in a much bigger geomatic disturbance than EVENT 1.

At this point, it may be easy to conclude that the Velocity difference between the events must have accounted for the extreme difference in geomagnetic disturbance between the events. However, it behooves us to look at the magnetic responses in both events more closely, particularly in all three orthogonal axis.

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4 hours ago, theartist said:

However, it behooves us to look at the magnetic responses in both events more closely, particularly in all three orthogonal axis.

On both STEREO-A and later on ACE, the magnetic disturbance was as follows:

  • EVENT 1:  Bx went largely NEGATIVE, By went largely POSITIVE, Bz had rapid cyclic change between POSITIVE and NEGATIVE (i.e., net magnitude contribution to Bt was ~zero);
  • EVENT 2:  Bx went largely POSITIVE, By went largely NEGATIVE, Bz had rapid cyclic change between POSITIVE and NEGATIVE (i.e., net magnitude contribution to Bt was ~zero).


We might better understand that the magnetic response in all three orthogonal axis factors greatly into the resulting intensity of earth's geomagnetic disturbance by looking at another event; consider the responses on ACE (plotted in Brown color) from the following geomagnetic disturbance event on 2-Oct-2013 (likely due to a Coronal Mass Ejection that took place prior on 30-Sept-2013, although multiple CME's occurred around this time):


The Velocity for this event barely went above 600 km/s, yet the resulting geomagnetic disturbance was a G4 storm, per the following:


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As for the current go-around...so it begins!:



The Np spike happened before the perturbation in magnetic activity last time.  Happening in conjunction with the magnetic disturbance, and at the same or greater magnitude as last time, could possibly result in an increase in geomagnetic disturbance effects.


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Below is an update to the storm:


Although the magnetic polarities are following a similar pattern to last time, the magnetic magnitudes, in all of the orthogonal axis, are not as great this time. The rate of velocity increase was greater this time.

Keep in mind the data considered is ahead of (before impacting) earth's magnetosphere (although the magnetosphere interaction might possibly affect the observed magnetic magnitudes), and there has been some change in orientation of the 'earthen magnet' since last time:

EarthOrbit.png.cbb6e63daac3a6faaafb1636ba985ba3.png (image source).



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I just came across a tidbit on the deeper science ("Hinode" satellite reveals the origin of the solar wind) that might be of interest to some readers.  It would be nice to have a better english translation:

  • High speed solar wind has the same elemental composition ratio as the photosphere from the polar region.
  • Slow solar wind erupts from the equatorial region at the same elemental composition ratio as the corona.


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  • 2 weeks later...

Folks, this go-around, it is not "on".  Some aurora chasers might be disappointed.  If interested in this topic, continue reading.

The method discussed in this thread is one of the few techniques that actually allow the citizen scientists themselves to look ahead several days in advance for the possibility of an approaching geomagnetic storm.  Aurora chasers, for example, could take this knowledge into account if planning a trip.  

The previous few months has presented an opportunity during solar minimum where the solar wind, unencumbered by flare activity, has presented a highly repeatable pattern, first revealed in IMPACT, and then ~6.5 days later in ACE.  (The planetary positions will likely also factor into the repeatability, and for the past few months, we have not had transit interaction from Mercury or other apparent planetary effects which could potentially cause disruption.  Obviously, there is a lot more that could be discussed regarding the subtleties of using this technique.) 

Readers following this blog are aware of the persistent solar structure that has repeatedly created geomagnetic disturbance over the past few months.  But the solar wind velocity dropped off on the last rotation, as well as the magnetic strength of the influence.  We discussed this earlier in this thread.

And now, the return of the 'persistent magnetic structure' is upon us.  Have things changed over this solar rotation?  If so, how?

Suffice to say, "it" is not "on" this time.  Yes there is a minor disturbance coming on ~Oct. 24, per IMPACT, but so far it is revealed this disturbance will only be a shell of its former self.  The pertinent data is presented below.  Do you see it?  


BTW, as before, again this time we have a smaller event to look forward to, prior to the real action.  The smaller event occurred on Oct 15 at IMPACT, so we first expect a minor disturbance on ~Oct. 21-22.

4 hours ago, theartist said:

Some aurora chasers might be disappointed.  

Now obviously, this point is being directed at folks hoping for a big dip down into the mid-latitudes, and doesn't apply to those that live way up in Norway, or other very high latitudes where aurora are frequent even without significant geomagnetic disturbance.

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