Growth of Cycle 25

[3gMike]

4 hours ago, Philalethes said:

I haven't looked into it enough to know much about what extent to which it's a good indicator of Solar activity, but it does clearly seem to match with the cyclic patterns.

Here is a link to how it is derived... https://www.sciencedirect.com/science/article/abs/pii/S1364682618301354#:~:text=Thermosphere Climate Indexes (TCI) represent,running averages of the F10.

[helios]

Here is the original paper on the description of the TCI: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4681456/

The TCI can be measured directly, or it can be derived from radio flux and AP/DST values with impressive accuracy.

So, the 10.7cm radio flux plays an important role on the calculation. But the radio flux does not heat the thermosphere, because the thermosphere is transparent to those frequencies.

Since the radio flux does correlate well with EUV flux, i would assume, that this is the reason for the heating. The F10.7 is a good indication for the amplitude of the cycle (and it is already used for this purpose 🙂)

 

 

[Philalethes]

2 hours ago, 3gMike said:

Here is a link to how it is derived... https://www.sciencedirect.com/science/article/abs/pii/S1364682618301354#:~:text=Thermosphere Climate Indexes (TCI) represent,running averages of the F10.

Very interesting, especially this:

Quote

The TCI are accurately expressed as linear combinations of the 60-day running averages of the F10.7, Ap, and Dst indexes, thus providing terrestrial context to the long record of solar and geomagnetic indexes.

If that's true then that's actually a fantastic index; I suppose it remains to be seen if this always remains true, but it does make sense given what it represents. It also indicates that the flux seems to be a more fundamental quantity with regards to effects here than sunspot number itself (not unexpectedly), although the two are typically quite intimately correlated as we've seen from other data. That explains why they'd feel so confident in extrapolating the current data so far back too, something I wondered about.

1 hour ago, helios said:

Here is the original paper on the description of the TCI: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4681456/

The TCI can be measured directly, or it can be derived from radio flux and AP/DST values with impressive accuracy.

So, the 10.7cm radio flux plays an important role on the calculation. But the radio flux does not heat the thermosphere, because the thermosphere is transparent to those frequencies.

Since the radio flux does correlate well with EUV flux, i would assume, that this is the reason for the heating. The F10.7 is a good indication for the amplitude of the cycle (and it is already used for this purpose 🙂)

Right, I just saw that fact mentioned above; that's a very cool empirical relationship! Hadn't come across that when briefly reading about it previously. And yeah, it must be due to the correlation of the F10.7 with spectral flux at higher wavelengths; I see that paper also provides the coefficients themselves, and from looking at them it seems like it doesn't play any minor role in the combined outcome either, so that relatively small overall increase those changes represent for the total Solar irradiance must clearly have a significant effect indeed.

Given all of this it's definitely an index I'll be paying attention to in the future; such simple empirical relationships are really the essence of physics.

[helios]

I applied a 13 month running average, similar to the 13-month smoothed sunspot number.

[Philalethes]

On 7/5/2023 at 7:32 PM, helios said:

I applied a 13 month running average, similar to the 13-month smoothed sunspot number.

Are you using monthly F10.7 data to smooth, or are you smoothing it daily over the equivalent interval of time? Just wondering, because using daily 365-day smoothing it looks like the SC25 flux just surpassed the SC24 peak quite recently:

Another thing to consider is where to start drawing each cycle; are you using the SSN minimum, or have you identified the minimum in the flux itself? Some similar questions arose when we were analyzing the data over in the other thread where we've been discussing it, and in this post in particular I went over some of my reasoning for identifying the flux minima.

EDIT: Some of the data below, and subsequently some of the reasoning, is faulty; a new post has been made here to clarify, apologies for the confusion.

That being said, as we found out eventually some of the data I'd been using was not reliable from ~2018 and onward (which I've since corrected with the right data, including the above), and I've also concluded that using 5-year smoothing to find the minima might pull the minima back a bit too far due to the generally asymmetric nature of the cycles. I've ended up compromising between 365-day (1-year) smoothing, where as seen below the minima get misplaced in my view, and 5-year smoothing by using 2-year smoothing instead. Here you can see the placement of the different flux minima of the last cycles overlaid on the 365-day smoothed flux:

Hopefully it's apparent here how the 365-day smoothed minima don't seem to capture the overall troughs due to the curve not being smooth enough; it should hopefully also illustrate how the 2-year smoothed minima seem to fall closer to the 5-year smoothed ones, but correct for the places where the latter seems to be pulled back too much (like e.g. the minimum between SC20 and SC21, presumably caused by including the drop before the anomalous spike on the descent around 1972, which is when we got a huge superstorm).

So, using these minima to do a similar comparison as I did in that post (and using the right data), and as you've done above, this is the end result when looking at the past few cycles:

This seems to be starting quite nicely at the appropriate part of the minima. And only SC24 and SC25:

To me it's interesting how SC25 so closely mimicked SC24 during the rise, but then continued to grow. If I were a pessimistic person, maybe I'd conclude something like Patrick seems to have, that the cycle is actually going to fizzle out and that we just got the peak earlier rather than later. But on the other hand, the flux still seems to be rising as steeply as SC20, and even SC23, soon going to surpass the peak of the former too if we continue like this for a bit longer (given the flux values we've seen recently, that actually seem quite likely at this point).

So best keep in mind that this is only a small sample size of cycles, and that while earlier and steeper rises seem to be associated with the overall strength it's not always clear-cut.

Edited July 6, 2023 by Philalethes
warning

[Patrick P.A. Geryl]

The highest flux was in January… since then it fizzled out..

[helios]

@Philalethes Thank you for your analysis!

I was using the monthly flux numbers, including June 2023. And I used the cycle start date from wikipedia (December 2008 for cycle 24 and December 2019 for cycle 25).

[Philalethes]

3 hours ago, Patrick P.A. Geryl said:

The highest flux was in January… since then it fizzled out..

There was definitely a peak there, but there was also a significant rebound after the biggest drop. On average it looks like it's continuing to grow for now, but it's of course hard to say conclusively whether it will keep growing or whether we're really at a peak. Zooming out and looking at the 81-day smoothed flux like in the image from Solen above but for SC24 and SC25 both, it looks like this:

Looking at this you can't really tell whether we're e.g. seeing something like in ~2011, where it dropped down but then rose much higher, or whether it's more like the larger peaks followed by drops. As discussed previously I think there are indications that we're still not yet at max, but only time will tell.

1 hour ago, helios said:

@Philalethes Thank you for your analysis!

I was using the monthly flux numbers, including June 2023. And I used the cycle start date from wikipedia (December 2008 for cycle 24 and December 2019 for cycle 25).

Yeah, that's what I thought. Not to invalidate that at all, looking at the flux with respect to the sunspot minima as you did there is also probably a good idea.

Edited July 6, 2023 by Philalethes
clarification

[hamateur 1953]

Just to chime in here a bit.  Yes we hit 234 sfi In January. However our sun most definitely has not finished with us, not by a long shot kids!  Fizzled out? Just resting a bit.  He will be back this winter.  I’d bet on it.  haha. 

[Philalethes]

After staring at some of the above plots for a while because something didn't seem quite right with how the cycles lined up with the minima, especially in the comparison between only SC24 and SC25, I found a couple of bugs in the code I used to produce them; that's what I get for trying to use old code without checking it thoroughly I guess.

The bugs were a misplacement of the minima given a certain period of smoothing, and that the cycles when plotted started half a year after the minimum due to not accounting for the smoothing; the former was the biggest problem, and what led some of my reasoning astray in the first place, whereas the latter is not as important, but still nice to fix so the whole cycles are visible.

I considered editing the above post with the plots, but as will promptly be seen it actually changes a lot, including my reasoning about it, so I opted to just let it stand as a monument to how trying to reason about erroneous data is problematic. That's not to say that everything about the presented data was wrong at all, but from the following I hope it's clear what's good and what's bad.

So, here I will present the corrected version of the three last plots, and my reasoning; first the minima:

Due to the error the 365-day (1-year) smoothed minima had been misplaced, which was particularly prominent in the minimum between SC24 and SC25; this is what led me to try to "fix" this by using a longer smoothing period for the minima, but now that I see the correctly placed minima and after thinking about it for a while, I believe that was a fundamental error in my reasoning. After all, this is already looking at smoothed data, so this was essentially an attempt at finding the right period to place the minima where I thought it seemed like they "should" be instead of acknowledging that the data had already been smoothed. In my defense this happened primarily because of that single horribly misplaced minimum arising from my erroneous code.

With all that in mind, and looking at the actual 365-day smoothed minima as seen above, I think it's rather correct to use that after all. In fact, this actually seems to give a much more accurate relationship between rise time and cycle strength, but without the misplaced SC25 that I thought was there previously.

Looking at the second plot with the corrected data:

This seems reasonable, as it places SC25 in a way that I think is more closely matching what I expect from it; I could be biased of course, but now it matches SC20 very well, and doesn't match SC24 as closely at all. Also worth noting is how SC22 actually seems a bit stronger than SC21 in terms of flux, which is reflected in the thermosphere climate index (TCI) that we discussed above. That's curious given how the SSN puts SC21 as the slightly stronger one. Maybe SC22 had fewer and larger/stronger sunspots, or something similar in terms of general activity?

And the last plot, now with the correct label for SC24 too:

This is also more similar to what Helios found above by using the SSN minima. It's now more or less the same reasoning as is used for the SSN, so if there is a similar relationship I would consider this at least some indication that we will indeed be seeing a cycle that's at least somewhat stronger than SC24, as we're already seeing indications of.

Apologies for any confusion. I've now looked closely at the minima and cycles and ensured that they match up as they should, so hopefully the data itself should be correct now. Needless to say, that doesn't mean that this is necessarily the correct way to reason about it anyway, but I think that makes more sense personally at least (edit: I actually had to correct another small bug for SC25, since it's separate to the others due to not being complete yet, but now there should be no more errors).

Any critique is always welcome if you think there might be a problem with the reasoning or the data.

Edited July 6, 2023 by Philalethes
fixed another small bug pertaining to SC25 only, added note about SC21 vs. SC22

[hamateur 1953]

Very interesting, indeed @Philalethes

I wonder if it will continue to follow SC 20  with its nearly constant sfi 1968-1971.   That was what I found so unusual among the other distinguishing characteristics of SC 20. 

[Archmonoth]

57 minutes ago, hamateur 1953 said:

Very interesting, indeed @Philalethes

I wonder if it will continue to follow SC 20  with its nearly constant sfi 1968-1971.   That was what I found so unusual among the other distinguishing characteristics of SC 20. 

I still have my fictional money on it being equal to, or near sc23 strength. 

Edited July 6, 2023 by Archmonoth

[Philalethes]

1 minute ago, hamateur 1953 said:

Very interesting, indeed @Philalethes

I wonder if it will continue to follow SC 20  with its nearly constant sfi 1968-1971.   That was what I found so unusual among the other distinguishing characteristics of SC 20. 

Just now, Archmonoth said:

I still have my fictional money on it being equal to, or near sc23 strength. 

I just made an edit where I fixed what I think was the last remaining bug, because I was still placing the minimum for SC25 based on unsmoothed values, should finally all be correct, since all the others are checked already.

This does place SC25 eerily close to SC20, and whether or not it might follow the same pattern and remain flat will be interesting to see. It's not really far from the trajectory of SC23 either, so I definitely agree that it's within the realm of possibility to match that if it keeps rising instead, but SC25 is certainly still a bit lacking in the SSN department relative to that so far.

The next 6-12 months will definitely be interesting to see, as we'll get at least some idea what kind of trajectory it will be relative to those two other cycles.

[Sam Warfel]

3 hours ago, hamateur 1953 said:

Just to chime in here a bit.  Yes we hit 234 sfi In January. However our sun most definitely has not finished with us, not by a long shot kids!  Fizzled out? Just resting a bit.  He will be back this winter.  I’d bet on it.  haha. 

Fall, I'm hoping. August/September and then on

15 minutes ago, Archmonoth said:

I still have my fictional money on it being equal to, or near sc23 strength. 

I'll add my fictional money to yours if it makes it more likely 😉

[helios]

An alternative metric was presented by Keith Strong in his latest youtube video (link). The total sunspot area (combined area of all spots).

But it has yet to be compared with other cycles and it appears to be a bit cumbersome to collect the data.

[Delz86]

I have a question (I hope this is the right topic).

Why are there so many eruptions in this cycle? I often look at the "solar cycle" page, and I see that, for example, if we continue at this rate, the year 2023 will contain more M-Class and C-Class eruptions than the year 2003, for example.

The ratio of eruptions to sunspots seems to me to be particularly high (already for the year 2022 it was the case I think, I don't know if anyone has already calculated this ratio over the different years).

Is there an explanation for this?

The coming months are going to be interesting in any case

Thanks to this site and this forum, even if I don't contribute much, I've been consulting it every day for several years now

[Philalethes]

11 hours ago, helios said:

An alternative metric was presented by Keith Strong in his latest youtube video (link). The total sunspot area (combined area of all spots).

But it has yet to be compared with other cycles and it appears to be a bit cumbersome to collect the data.

Sunspot area is definitely another metric I think will be useful to keep track of. There's been a fair amount of papers on it dating a couple of decades back at least, including this one from 2006 suggesting to use it as an index. There is however indeed a lack of easily accessible and reliable data for it, like with many other metrics that aren't sunspot number. Would certainly be interesting to see e.g. a comparison between SC21 and SC22 and see if the latter did actually have larger sunspots and more total area to compensate for slightly fewer sunspots.

Hopefully it'll be tracked well from now on for future reference.

10 hours ago, Delz86 said:

I have a question (I hope this is the right topic).

Why are there so many eruptions in this cycle? I often look at the "solar cycle" page, and I see that, for example, if we continue at this rate, the year 2023 will contain more M-Class and C-Class eruptions than the year 2003, for example.

The ratio of eruptions to sunspots seems to me to be particularly high (already for the year 2022 it was the case I think, I don't know if anyone has already calculated this ratio over the different years).

Is there an explanation for this?

The coming months are going to be interesting in any case

Thanks to this site and this forum, even if I don't contribute much, I've been consulting it every day for several years now

The more, the merrier!

I would say your question is definitely relevant to this topic, and if I recall correctly I saw someone ask something similar towards the end of last year, particularly about why there seemed to be so many flares in 2022 relative to the sunspot number, when previous years seemed to have a somewhat stable relationship there.

I don't really know why that is, but then again the data is only for a couple of cycles back, so maybe that relationship doesn't really always hold that well; or maybe it's yet another indication of a stronger cycle than expected.

As for comparisons to 2003 that's not necessarily the most appropriate, given that the two are at quite different parts of the cycle, but it's certainly interesting considering how 2003 brought the infamous Halloween superstorm, one of the largest in recent times. That being said, I believe activity tends to be more energetic on the descent like in 2003 than on the ascent like now; there's certainly a big difference between impulsive low-level M-flares and the more eruptive high-levels ones, and while I haven't checked I would suspect that the flares of 2003 were likely more eruptive than what we're seeing now. I could definitely be wrong about that, but at least it feels like there have been a ton of impulsive M-flares lately that haven't been eruptive at all. The data should definitely be consulted on that.

Edited July 7, 2023 by Philalethes
typo

[Drax Spacex]

11 hours ago, Delz86 said:

Why are there so many eruptions in this cycle? I often look at the "solar cycle" page, and I see that, for example, if we continue at this rate, the year 2023 will contain more M-Class and C-Class eruptions than the year 2003, for example.

The ratio of eruptions to sunspots seems to me to be particularly high (already for the year 2022 it was the case I think, I don't know if anyone has already calculated this ratio over the different years).

Is there an explanation for this?

You're in the right place - and as you've found under Archive>Solar Cycle Progression at https://www.spaceweatherlive.com/en/solar-activity/solar-cycle.html there are several graphs in including Number of C, M, and X flares per year along with average sunspot number.

Indeed 2022 was a banner year for number of flares so early in the solar cycle.  From the bar chart for 2022 the total number of (C+M+X) flares (2036+178+7) was 2221, and the average sunspot number was 78, yielding an annualized ratio of 28.5 flares/average sunspot number.

 

Also in the Solar Cycle Progression page is the Butterfly Diagram.

Butterfly diagrams comparing SC24 and SC25 (to date) show a distinct difference in the latitude distribution of sunspots in the southern hemisphere.  SC25 sunspots in the southern hemisphere are more dispersed across a larger range of latitudes.  Thus far, the linear regression of the data for SC25 would appear flatter than SC24.  I don't know what the implications may be, just noting the difference.

Here is an overlay of butterfly diagrams of SC24 and SC25 (to date):
https://ibb.co/sydf3wG

Edited July 7, 2023 by Drax Spacex
Monarch migration

[3gMike]

2 hours ago, Drax Spacex said:

Here is an overlay of butterfly diagrams of SC24 and SC25 (to date):
https://ibb.co/sydf3wG

That is a nice plot, and it clearly demonstrates different behaviour between hemispheres.

On another thread 

we have been looking at the status of the polar fields. The WSO polar field data currently suggests that the Northern polar field has already reversed polarity, and is now negative. At the same time the southern polar field is still quite strongly negative, and has been more or less static for the last few months. On that basis it is not clear to me why the southern hemisphere should be showing a large number of spots generated nearer the equator whilst also producing more at higher latitudes.

My impression was that spots were generated at higher latitudes in both hemispheres when the 10.7cm flux surged towards the end of Nov / early Dec - almost like the cycle had 'reset' in some way. Apologies - that is not a particularly scientific analysis. The Sun continues to surprise us.

[hamateur 1953]

https://en.wikipedia.org/wiki/August_1972_solar_storms    Since @Philalethes Had brought this epic storm series up earlier, I thought a reposting of it might prove educational for anyone looking for Carrington class storms we have survived in the last sixty years or so.  It was reevaluated in 2018 to have been an outlier ( their words) to all previous storms.  I am hoping for a repeat this cycle!  If our moderator Sam feels im off-topic ( and I am ) fine to move this post. no problem. 

Edited July 8, 2023 by hamateur 1953

[Philalethes]

On 7/7/2023 at 10:59 PM, 3gMike said:

That is a nice plot, and it clearly demonstrates different behaviour between hemispheres.

On another thread we have been looking at the status of the polar fields. The WSO polar field data currently suggests that the Northern polar field has already reversed polarity, and is now negative. At the same time the southern polar field is still quite strongly negative, and has been more or less static for the last few months. On that basis it is not clear to me why the southern hemisphere should be showing a large number of spots generated nearer the equator whilst also producing more at higher latitudes.

My impression was that spots were generated at higher latitudes in both hemispheres when the 10.7cm flux surged towards the end of Nov / early Dec - almost like the cycle had 'reset' in some way. Apologies - that is not a particularly scientific analysis. The Sun continues to surprise us.

Something to note is what has been mentioned a few times over in that thread too, i.e. that WSO is measuring a specific polar cap (~55°+), and that this cap might turn out to not be as representative for the polar field as expected; if we use e.g. the HMI polar field data to compare the 50-60° band with the 60-70° one, we see this:

What I glean from this is that the 50-60° field itself flipped all the way back around June-July of 2022, whereas for the 60-70° the northern field has barely done so just recently, and the average field hasn't. To me that seems to indicate that of the entire cap that WSO measures, i.e. ~55°+, it's actually primarily the 55-60° band that's responsible for what we see in the WSO data, and not that representative of the entire polar field. Looking at the 60°+ cap from HMI now looks like this:

Still quite a bit left until it will flip, seemingly.

Of course the WSO data is its own domain, and still has clear connections to the Solar cycles (with flips occurring sometime around the maxima, within a few years typically), but I think it's definitely something to keep in mind. From looking at the butterfly diagram provided on the HMI polar field website, e.g. the last diagram in this post, you see the recognizable way in which the field progressively flips at higher and higher latitudes, so ultimately I would guess it's a matter of definition at which point exactly you should be considering the field to really have flipped, i.e. either what latitude/band should have flipped, or which latitude to delineate the cap that needs to have flipped; since in this case it's primarily the ~55-60° band that's responsible and outweighing the entire 60°+ cap in field strength, I'd at least be cautious to state whether or not the field can really be said to have flipped yet.

But by now I'm sure you're aware of many of these pitfalls anyway, and there's certainly nothing wrong with looking at and using the WSO data at all, it's just something I think is important to note and that others might be interested in too.

As for why there is an imbalance between where sunspots are produced, and why the southern hemisphere seems to have more both near the equator and farther from it, I'm not sure about the cause of that either. Could be that it has to do with the rapidity with which the field moves rather than or in addition to where the fields are in relation to each other, and that it's reflective of how the southern field (considering the HMI 60°+ plot above rather than WSO) was the first one to start moving towards the equator, and did so rather fast, whereas the northern field has been descending more slowly. Maybe it's even the acceleration of the movement and/or higher-order derivatives, i.e. times when the field starts to move more rapidly or when it stops. It's probably a lot more complex, but it would be great to find connections between the overall movement of the field and where sunspots appear and in what number, would probably improve the long-term predictive capabilities for space weather by quite a bit, but prima facie it sounds like there'd be a lot of chaotic dynamics to contend with, like when trying to forecast weather long-term here on Earth.

The "reset" you mention and accompanying surge in spots and flux is also definitely interesting. It seems to be reflected in the long-term data as when the southern field (again the 60°+ cap) suddenly stopped moving and "flattened" out, as the northern field also did recently, clearer in the long-term data:

Hard to say why exactly this happens, but it could lend credence to the idea that you see surges like that when the movement of the field accelerates (or decelerates as is a more apt term in this case, even though physically it's all acceleration anyway). It could also be why there's typically a lot of activity near the maxima, as the fields will tend to change their direction of movement back and forth a few times before continuing on their way. Considering this one would probably do well to monitor how the field is moving at a wide variety of latitudes and bands, including what WSO measures.

Just some data and speculations, I hope we'll eventually start to find some clearer connections between heliomagnetic field measurements in general regardless of source and where and to what extent sunspots form, as well as levels of activity in general.

18 hours ago, hamateur 1953 said:

https://en.wikipedia.org/wiki/August_1972_solar_storms    Since @Philalethes Had brought this epic storm series up earlier, I thought a reposting of it might prove educational for anyone looking for Carrington class storms we have survived in the last sixty years or so.  It was reevaluated in 2018 to have been an outlier ( their words) to all previous storms.  I am hoping for a repeat this cycle!  If our moderator Sam feels im off-topic ( and I am ) fine to move this post. no problem. 

Well, given how we've been comparing SC25 to SC20 for a while now I'd say it's at least marginally related, but it's of course up to the moderators. It's certainly not 100% on topic, but it does show what could potentially happen if we keep following the same growth trajectory.

It really shows that even cycles of this strength can potentially produce truly extreme events under the right circumstances, although there are probably still many variables we've yet to account for (i.e. there could have been something special going on around that time that we don't really know about). It would certainly be very cool to witness something like that, even though I would assume we got quite lucky with the circumstances when it happened.

Here's a paper I read through recently that also goes into the event in some depth, with the title itself describing the ejecta as "ultra-fast", heh; it was estimated to have been even faster than the Carrington event itself, after all. The abstract also mentions the detonation of the sea mines we've talked about:

Quote

There was an additional effect, long buried in the Vietnam War archives that add credence to the severity of the storm impact: a nearly instantaneous, unintended detonation of dozens of sea mines south of Hai Phong, North Vietnam on 4 August 1972. The U.S. Navy attributed the dramatic event to magnetic perturbations of solar storms.

Later they also mention how it indeed was an outlier even among extreme events:

Quote

Vaisberg and Zastenker (1976) and Cliver et al. (1990) estimated the average transit speed as 2,850 km/s. Freed and Russell (2014) reported the transit time was an outlier, even for the family of the extreme events they studied.

Now that is fast; I would assume that means it likely had an initial speed of over 3000 km/s, although I'm not sure exactly to which extent the Solar wind in front of it had already been cleared.

Even in the weaker SC24 there was the 2012 event that barely missed us, so maybe most cycles have at least one really strong event and that it really just boils down to whether or not it hits us or not.

Edited July 8, 2023 by Philalethes
typo

[hamateur 1953]

Indeed @Philalethes I was staggered also by the sheer duration of the time we remained at X Class levels! 16 hours has to exceed anything contemporary that I am aware of.  Magnetometers being off-scale high would indeed indicate the sheer power of that event.   Part of why I was so surprised that it ranked so low on the running Potsdam A index. Sam our moderator nailed it as a northward bz as I discussed awhile back.   cool stuff! 

[Philalethes]

4 hours ago, hamateur 1953 said:

Indeed @Philalethes I was staggered also by the sheer duration of the time we remained at X Class levels! 16 hours has to exceed anything contemporary that I am aware of.  Magnetometers being off-scale high would indeed indicate the sheer power of that event.   Part of why I was so surprised that it ranked so low on the running Potsdam A index. Sam our moderator nailed it as a northward bz as I discussed awhile back.   cool stuff! 

That's mind-boggling to think about; and here I am cheering for prolonged M-flares, heh.

And yeah, I did read that the Bz was mostly northwards, can only imagine what it'd have been like if it'd been southwards instead, would probably have gone down in space weather history as even more significant. That reminded me that I have a file with the OMNI data with IMF measurements dating back to the early 60s, although with a lot of missing data (particularly during extreme events like these), and for that storm it looks like this:

Quote

1972 217  6  -1.0   2.7
1972 217  7 -28.8  21.0
1972 217  8 -30.0  27.2
1972 217  9 999.9 999.9
1972 217 10 999.9 999.9
1972 217 11 999.9 999.9
1972 217 12 999.9 999.9
1972 217 13 999.9 999.9
1972 217 14 999.9 999.9
1972 217 15 999.9 999.9
1972 217 16 999.9 999.9
1972 217 17 999.9 999.9
1972 217 18 999.9 999.9
1972 217 19 999.9 999.9
1972 217 20 999.9 999.9
1972 217 21 999.9 999.9
1972 217 22 999.9 999.9
1972 217 23 999.9 999.9
1972 218  0   7.0  32.5
1972 218  1   1.8  30.7
1972 218  2  -1.4  30.7
1972 218  3  -0.7   9.2
1972 218  4  -0.5   2.2
1972 218  5  -3.6  36.0
1972 218  6  -6.6  33.8
1972 218  7  -6.6  22.8
1972 218  8  -2.4  14.7
1972 218  9  -0.4  14.9
1972 218 10   2.5   6.1
1972 218 11  -0.2   7.5
1972 218 12  -1.2   5.6

Day 217 is August 4 that year (day number is second column, third is hour), and the last column is the Bz; as you can see there's missing data right during the most interesting part, presumably due to malfunctions or measurement problems or similar issues, but for all the parts where the data is intact the Bz is indeed positive, quite strongly so for a lot of August 5 and for the very beginning on August 4 before the data is missing.

[hamateur 1953]

Thanks for the corroborative data @Philalethes much appreciated!  Mike   Just an additional note for the numerophiles among us.  The biggie was at the time  Mcmath 11976 facing us.  Notably it made five passes by us as well!  00486 in 2003 is one I unfortunately missed! 

Edited July 9, 2023 by hamateur 1953
memories of missed opportunities

[3gMike]

I just found this plot on Keith Strong's Twitter feed, relating to Sunspot Area. Since we are still only just over half way through year 4 the increase in total .area of sunspots over Cycle 24 appears to be very dramatic.