Are impacts stronger in summer?

[MinYoongi]

Hey!

For awhile now I thought about something.

Since we're closer to the sun in Summer, do CME's etc. impact earth earlier resulting in stronger impacts? 🤔 This may be a stupid question because it's absolutely possible its such a small distance when you look at the gigantic rest of the solar system that it does make no difference at all 😅

I only know about the solstice related higher aurora activity. 

Have a nice day everyone 🙂

[Vancanneyt Sander]

Simple: no.

only around the equinox storms tend to have a bigger impact.

[Jesterface23]

That is interesting. There would definitely be a difference, but with our planets orbit the change would be hard to notice. I did check through my database some.

[Christopher S.]

Theoretically and to a small degree, the closer we are, the higher % of the ejecta of a CME that will arrive. So, yes, but the degree to which a single given CME impacts us at our closest(perihelion) vs. what the impact would have been at the furthest point(aphelion) is probably not very large. There's definitely an equation or two that you can use to make that determination after an impact, but as for the observable effects via our sensors on and around the planet there are still many variables. You may only be able to determine the net percentage received impact magnitude from a CME impact based on its departure from the median orbital distance(the equinox in layman's). As a rough example, a -3% weighted impact from a CME in May, or a +2% weighted impact in October.

In short, this data would only really be useful for studying the CMEs themselves, not their total global impacts. It may help to figure out trends when we're closer vs. when we're farther, but maybe not too much beyond that. Hope this helps

[Vancanneyt Sander]

See: https://www.sws.bom.gov.au/Educational/3/1/5

as you can see around the equinox the disturbances can be stronger  and definitely not in summer 

[helios]

We are actually further away from the sun during northern hemisphere summer.

Perihelion is in January, 146 million km.
Aphelion is in July, 153 million km.

[Drax Spacex]

Might this imply that Bz has south bias around equinoxes and north bias around solstices?

[Vancanneyt Sander]

2 uren geleden, Drax Spacex zei:

Might this imply that Bz has south bias around equinoxes and north bias around solstices?

no, for example when Bz is southward -10nT during equinox, the resulting geomagnetic activity is likely higher than during summer with the same conditions.

[Christopher S.]

4 hours ago, helios said:

We are actually further away from the sun during northern hemisphere summer.

Perihelion is in January, 146 million km.
Aphelion is in July, 153 million km.

Ah, wonderful point. I hadn't considered this at all.

[Newbie]

The affect of the sun on the earth has more to do with the orientation of the Earth's magnetic field at equinox. During autumn and spring equinox, this orientation enables a 'connection' to the sun thereby allowing solar wind to stream in, it is not the case at other times of the year.

I think there is so much more to learn about how and when the sun affects the earth in the way that it does. 

[Christopher S.]

1 hour ago, Newbie said:

The affect of the sun on the earth has more to do with the orientation of the Earth's magnetic field at equinox. During autumn and spring equinox, this orientation enables a 'connection' to the sun thereby allowing solar wind to stream in, it is not the case at other times of the year.

I think there is so much more to learn about how and when the sun affects the earth in the way that it does. 

What sources do you have for this? I remember a couple of courses and videos referencing this, but nothing concrete

[Newbie]

Dr Tony Phillips, (he was/is at NASA), spoke about this at least 10 years ago. There was a project called THEMIS. I thought they had established this research.

One thing that affects the magnetic field around the earth at any time of the year are CIR's or Co Rotating Interaction Regions These create compression regions between the slower ambient solar wind and fast moving streams of particles coming from coronal holes. This allows solar wind to stream in and produce geomagnetic storming. 

That's why sometimes bz goes down sharply and other markers like temp. and speed increase, for no apparent reason and auroras are visible.

But I'm sure you already know this.

[Drax Spacex]

The SWS bar graph above defines a geomagnetic disturbance event to be when the daily planetary Ap index exceeds a value of 25 (=Kp4).

The K (and derived Ap) index calculations are calculated using horizontal magnetic variation relative to "quiet day" baselines, and also use weighting factors applied to each individual station to equalize the rates of occurrence of K (and derived Ap) values from each station.

I would not discount the *possibility* that this seasonal variation could be an artifact of fluctuation introduced by the algorithms for K (and derived Ap) index and may not be a measurement of an actual physical phenomenon.  We saw recently how the observed DST calculation was not robust against bad or missing data.  A non-abrupt error or instability in an algorithm would be more difficult to detect.

For corroboration, the intensity and frequency of occurrence of aurora could be reviewed to check whether they exhibit the same seasonal variation.

[Vancanneyt Sander]

@Drax Spacexi’ve found an interesting paper about the whole thing, worth a read: https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2010JA016362

It’s about what they call the RMP effect. It explains that the semiannual geomagnetic activity originates from the variation of the angle between the cross-flow component of IMF and that of the Earth's magnetic dipole axis. Which seems its a logic explanation 

[Drax Spacex]

If the "magnetic connection" magnitude is positively correlated to the cross product of the Sun-to-Earth vector and the Earth's rotation vector (23.5 degress), then at the equinox, when the angle between those vectors is approximately 90 degrees (broadside not tilted towards or away), the magnitude would be maximized based on directional alignment.  |A X B| = |A| |B| sin(theta)

This I believe is the Equinoctial hypothesis referenced as [5] in the above paper.  The  Equinoctial hypothesis is a simpler, older, first order view.  The RMP effect appears to be the consensus modern theory to explain this seasonal variation. 

Edited July 6, 2021 by Drax Spacex
Equinoctial hypothesis (not horse-related)

[Newbie]

On 7/6/2021 at 6:47 AM, Drax Spacex said:

Equinoctial hypothesis (not horse-related)

Haha The word you would need then: equinal

Thanks for the above posts, everyone. It's amazing how the topic evolved, some really good information came out. 😁