26 minutes ago, linkedwinters said:

Can a coronal hole have entirely north bz? Is it possible that this chhss will not dip into the negative or is that unlikely? This coronal hole will be earth facing during my time in Tromso next month, which is why I'm concerned

Yes, the source of the IMF itself is mostly irrelevant in relation to its orientation. There's work being done to better predict what direction the magnetic field could be orientated but it's mostly related to CME's. It's difficult to impossible for us to know until the source arrives at L1 and remains consistent. SoLO might provide a few days notice in advance but that depends on its orbit in the next month. My advice would be prepared for it's initial arrival, the impact is what generally causes biggest shock to the magnetosphere. If you time it right your chances to see aurora go up quite a bit. After that you'll just have to take your chances and wait to see if it maintains a north or south orientation.

On 11/2/2024 at 2:42 AM, libmar96 said:

I'll ask here, because I can't find a proper answer anywhere. What's the X-ray saturation limit for working GOES satellites? Can the current technology (GOES 16, 18, 19) precisely measure >X20 flares, what couldn't be done in SC23?

I would love to know this also. Not a really big deal but I only know from other sources that our first x ray satellite Solrad allegedly saturated at about X -5 because we knew so little about the sun’s activity despite years of observations in the 1960s

Vela was up there looking for the characteristic double flash of a thermonuclear detonation but not specifically for solar stuff.

A rough guess might be X 17 plus the correction factor of 40 percent. Perhaps @Jesterface23 or @Philalethes might know

Edited February 24Feb 24 by hamateur 1953
Vela

2 hours ago, linkedwinters said:

Can a coronal hole have entirely north bz? Is it possible that this chhss will not dip into the negative or is that unlikely? This coronal hole will be earth facing during my time in Tromso next month, which is why I'm concerned

Typically not entirely, at least not during the initial turbulent SIR, but generally speaking a CH is carrying out the magnetic field at the source, so for CHs in positive fields the phi-angle will generally be "away" (directed radially outward from the solar surface, i.e. a negative Bx) and for those in negative fields the angle will tend to be "towards" (directed radially inwards towards the solar surface); these two designations can be seen in the plot of the phi-angle here.

However, due to the Parker spiral, the magnetic field lines don't just extend radially, but are generally bent clockwise when looking at the Solar System from above (i.e. looking down at the north poles), which means that when the field is "away" it also tends to get a positive By (and vice versa for "towards", a negative By). For the same reason it gets this, it can also tend to get a Bz of a specific direction due to how this aligns with the axial tilt of Earth, which forms the basis for the so-called Russell-McPherron (R-M) effect. Here you can see an illustration of how that works:

So long story short, it means that when you get closer to the March equinox CHs situated within a negative polarity will tend to be more geoeffective, whereas closer to the September equinox the CHs with a positive polarity will tend to be more geoeffective.

That being said this is just one contributing factor. At the equinoctes you have another separate effect occurring, the so-called equinoctial effect, which has to do with the component of the solar wind speed perpendicular to the geomagnetic field, and this is particularly noticeable for CHs given the fast solar wind of HSSs.

Both of these effects are why activity, especially that from CHs, tends to be noticeably higher around the equinoctes; and in your specific case you'll be hoping more for CHs situated within negative field, which during those times can cause prolonged negative Bz conditions.

Edited February 24Feb 24 by Philalethes
typo, remembering which way a clock turns

15 minutes ago, Philalethes said:

Typically not entirely, at least not during the initial turbulent SIR, but generally speaking a CH is carrying out the magnetic field at the source, so for CHs in positive fields the phi-angle will generally be "away" (directed radially outward from the solar surface, i.e. a negative Bx) and for those in negative fields the angle will tend to be "towards" (directed radially inwards towards the solar surface); these two designations can be seen in the plot of the phi-angle here.

However, due to the Parker spiral, the magnetic field lines don't just extend radially, but are generally bent counterclockwise when looking at the Solar System from above (i.e. looking down at the north poles), which means that when the field is "away" it also tends to get a positive By (and vice versa for "towards", a negative By). For the same reason it gets this, it can also tend to get a Bz of a specific direction due to how this aligns with the axial tilt of Earth, which forms the basis for the so-called Russell-McPherron (R-M) effect. Here you can see an illustration of how that works:

So long story short, it means that when you get closer to the March equinox CHs situated within a negative polarity will tend to be more geoeffective, whereas closer to the September equinox the CHs with a positive polarity will tend to be more geoeffective.

That being said this is just one contributing factor. At the equinoctes you have another separate effect occurring, the so-called equinoctial effect, which has to do with the component of the solar wind speed perpendicular to the geomagnetic field, and this is particularly noticeable for CHs given the fast solar wind of HSSs.

Both of these effects are why activity, especially that from CHs, tends to be noticeably higher around the equinoctes; and in your specific case you'll be hoping more for CHs situated within negative field, which during those times can cause prolonged negative Bz conditions.

Thank you so much for the detailed response!!! I really appreciate it 🙏

1 hour ago, hamateur 1953 said:

I would love to know this also. Not a really big deal but I only know from other sources that our first x ray satellite Solrad allegedly saturated at about X -5 because we knew so little about the sun’s activity despite years of observations in the 1960s

Vela was up there looking for the characteristic double flash of a thermonuclear detonation but not specifically for solar stuff.

A rough guess might be X 17 plus the correction factor of 40 percent. Perhaps @Jesterface23 or @Philalethes might know

@Aten found the best information I've seen about that so far earlier in this thread, here and here (which you've liked, but maybe forgotten about since, heh).

Yeah. Absolutely correct me bucko. My age is showing physically too finally. Haha

@linkedwinters

I totally forgot that next month is the equinox, were you intentionally planning your trip around that? I apologize for being a bit misleading!

Edited February 24Feb 24 by Parabolic

3 hours ago, Parabolic said:

@linkedwinters

I totally forgot that next month is the equinox, were you intentionally planning your trip around that? I apologize for being a bit misleading!

I was! I don't know the mechanisms of the equinoxes but I'm aware that they exist. Are they over exaggerated? The last two equinoxes were relatively quiet when we were in Norway, which is why I'm very hopeful that this time it's different

so Whats with the earth line within the BZ BT density and solar wind components?

51 minutes ago, linkedwinters said:

I was! I don't know the mechanisms of the equinoxes but I'm aware that they exist. Are they over exaggerated? The last two equinoxes were relatively quiet when we were in Norway, which is why I'm very hopeful that this time it's different

It's nothing radical, just a slight increase in response to the solar wind the closer to the equinoxes. Some crazy storms of September and October were most probably intensified quite a bit by the proximity to the equinox. As far as I understood, the effect is quite pronounced already a month before and after.

41 minutes ago, oaooaiia9i98 said:

so Whats with the earth line within the BZ BT density and solar wind components?

Could you expand your question a bit? I am unsure if you are asking about coupling with Newell, or something else.

2 hours ago, linkedwinters said:

I was! I don't know the mechanisms of the equinoxes but I'm aware that they exist. Are they over exaggerated? The last two equinoxes were relatively quiet when we were in Norway, which is why I'm very hopeful that this time it's different

Personally I don't think it's exaggerated but a lot of things do have to line up fairly well for it to be easily distinguishable from average geomagnetic storms. I'm trying to remember the day a particular event was during last fall equinox because it was a great example of how effective By can be under the right circumstances. I recall that a few people were confused because bz hovered northward for the majority of the period but there was still G2-G3 conditions. That day By was around -20 to -30 for most of the storm.

14 hours ago, Philalethes said:

but generally speaking a CH is carrying out the magnetic field at the source, so for CHs in positive fields the phi-angle will generally be "away" (directed radially outward from the solar surface, i.e. a negative Bx) and for those in negative fields the angle will tend to be "towards" (directed radially inwards towards the solar surface)

14 hours ago, Philalethes said:

when the field is "away" it also tends to get a positive By (and vice versa for "towards", a negative By). For the same reason it gets this, it can also tend to get a Bz of a specific direction due to how this aligns with the axial tilt of Earth, which forms the basis for the so-called Russell-McPherron (R-M) effect.

14 hours ago, Philalethes said:

CHs situated within negative field, which during those times can cause prolonged negative Bz conditions.

For some reason this never clicked in my head even though I've brought up By in a few posts a little while back. I know negative polarity CH's are more geoeffective without fully understanding why. Just to make sure I'm understanding this: During the fall equinox, a negative polarity CH with a negative phi-angle, a negative By, has an increased chance for southward Bz?

What’s causing the high energy protons to rise?

19 minutes ago, stargazer007 said:

What’s causing the high energy protons to rise?

Long duration event from the western limb. Probablyfrom old AR3990.

So no CME incoming? Can the goes proton flux be used like the ACE epam?

Edited February 25Feb 25 by stargazer007

1 hour ago, stargazer007 said:

So no CME incoming? Can the goes proton flux be used like the ACE epam?

It's probably going to be too far west to reach earth. As for the protons, in a way yes, although using higher energetic protons for detecting weaker solar storms isn't as useful as low energetic protons.

5 hours ago, Parabolic said:

Just to make sure I'm understanding this: During the fall equinox, a negative polarity CH with a negative phi-angle, a negative By, has an increased chance for southward Bz?

Well, whether it's the fall or spring equinox depends on which hemisphere you're in! But of course, I naturally assume you're referring specifically to the NH fall equinox here, i.e. the September equinox. In that case it's the other way around: during the September equinox it's positive-polarity CHs which will tend to have a negative Bz and thus be more geoeffective, and vice versa for the March equinox (where negative-polarity CHs will tend to be more geoeffective); the former will be associated with a positive By ("away"), the latter with a negative By ("towards"), although it should be made clear that the By itself isn't contributing to the activity in those cases, just a concomitant factor due to the field orientation at those times.

If you picture how the Earth is tilted at the solstices and how it orbits counterclockwise, it should be fairly quick to get a mental image of how it's tilted at the two equinoctes, and then you can get a better intuitive feel for whether or not the Parker spiral is directed against the tilt (more chance of negative Bz) or with the tilt (higher chance of positive Bz). In passing it also bears mentioning that the solar axial tilt also is part of the consideration when calculating the peaks of that effect, but that tilt is relatively small and coincides well enough with the equinoctes that the R-M effect peaks occur just a couple of weeks after them.

Here you can see an applet which shows the angle in question over the year (the so-called P-angle), which reaches a maximum of around ~26.3° in either direction at the peaks in the beginning of April and October. If you've played around with SunPy you can also use this function from its library to get the angle for any date.

As mentioned this is just one factor on top of others though, so it's far from the whole picture; you can of course still get good activity from opposite-polarity CHs too if things go right. But it's something worthy of consideration for sure.

4 minutes ago, Philalethes said:

Here you can see an applet which shows the angle in question over the year (the so-called P-angle), which reaches a maximum of around ~26.3° in either direction at the peaks in the beginning of April and October. If you've played around with SunPy you can also use this function from its library to get the angle for any date.

I've struggled to visual things like GSM and GSE coordinates on a globe in my mind. This seems like it will really help me better understanding the ecliptic by being able to interact with it instead of putting together single mental images. I always appreciate the resources you provide.

5 minutes ago, Parabolic said:

I've struggled to visual things like GSM and GSE coordinates on a globe in my mind. This seems like it will really help me better understanding the ecliptic by being able to interact with it instead of putting together single mental images. I always appreciate the resources you provide.

Yeah, coordinate systems can definitely be tricky. GSE coordinates are luckily among the easier, since it's all neatly defined with respect to Earth's orbit. In this case the trickiest part when it comes to coordinates would be the GSEQ (geocentric solar equatorial) coordinate system, i.e. the smaller and not that crucial contribution from the solar axial tilt; as the paper the above graphic is from reads:

[...] the R-M effect holds that the angle between Z axis in geocentric solar magnetospheric (GSM) coordinate system and Y axis in geocentric solar equatorial (GSEQ) coordinate system plays an important role.

That applet should hopefully help in visualizing how that angle varies over time.

Apart from that, and disregarding that angle entirely, to illustrate just the effect from Earth's tilt I drew this rough sketch, heh:

It should hopefully be possible to see more clearly how the different directions of the field are along or against the tilt in the two cases.

9 hours ago, linkedwinters said:

I was! I don't know the mechanisms of the equinoxes but I'm aware that they exist. Are they over exaggerated? The last two equinoxes were relatively quiet when we were in Norway, which is why I'm very hopeful that this time it's different

8 hours ago, MJOdorczuk said:

It's nothing radical, just a slight increase in response to the solar wind the closer to the equinoxes. Some crazy storms of September and October were most probably intensified quite a bit by the proximity to the equinox. As far as I understood, the effect is quite pronounced already a month before and after.

Yeah, I guess it's a bit subjective whether or not it's exaggerated, and it's certainly no guarantee of activity; the overall cycle also plays a large role, of course. The effects are at least quite demonstrable and quantifiable, as seen from e.g. this up-to-date chart of the Ap-index averaged across ~3 months, showing the clear fluctuations with the effects:

Also funny how you can see the distortion from the May storm of 2024; such powerful storms, while also exacerbated to some extent by the equinoctial effect, can easily overcome any such limitations and cause peaks in the "wrong" locations.

Hi,
I was looking at the HMI images captured yesterday and I noticed a significant amount of noise that appears as "speckles" (example here: 20250224_000000_1024_HMIBC.jpg (1024×1024)
I'm trying to understand what might be causing this! Could it be instrumental artefacts?

I'd appreciate any insights. Thank you 😀

11 hours ago, Philalethes said:

Yeah, coordinate systems can definitely be tricky. GSE coordinates are luckily among the easier, since it's all neatly defined with respect to Earth's orbit. In this case the trickiest part when it comes to coordinates would be the GSEQ (geocentric solar equatorial) coordinate system, i.e. the smaller and not that crucial contribution from the solar axial tilt; as the paper the above graphic is from reads:

That applet should hopefully help in visualizing how that angle varies over time.

Apart from that, and disregarding that angle entirely, to illustrate just the effect from Earth's tilt I drew this rough sketch, heh:

It should hopefully be possible to see more clearly how the different directions of the field are along or against the tilt in the two cases.

Yeah, I guess it's a bit subjective whether or not it's exaggerated, and it's certainly no guarantee of activity; the overall cycle also plays a large role, of course. The effects are at least quite demonstrable and quantifiable, as seen from e.g. this up-to-date chart of the Ap-index averaged across ~3 months, showing the clear fluctuations with the effects:

Also funny how you can see the distortion from the May storm of 2024; such powerful storms, while also exacerbated to some extent by the equinoctial effect, can easily overcome any such limitations and cause peaks in the "wrong" locations.

i said to my mom that spring starts 22nd of march but she doens't believe me but i bring up vernal equinox as proof

Can STEREO-A measure X-ray flux, if yes is there any way to access it?

Edited February 25Feb 25 by SpaceR
typo

23 minutes ago, SpaceR said:

Can STEREO-A measure X-ray flux, if yes is there any way to access it?

As far as I see in the instrument list, there is no x-ray detector. At best some EUV imagers.

1 hour ago, SpaceR said:

Can STEREO-A measure X-ray flux, if yes is there any way to access it?

54 minutes ago, MJOdorczuk said:

As far as I see in the instrument list, there is no x-ray detector. At best some EUV imagers.

There's indeed no instrument dedicated to it, but it is in principle possible to estimate it from EUVI data with some know-how and work, like Nitta did in this classic paper, where he among other things estimates the flare strength of the one associated with the 2012 ultrafast CME; surprisingly it was estimated at just ~X3.5 at most (~X2.5 in the paper, but that was before the removal of the correction factor for GOES-15 and earlier, so it must be multiplied by ~1.43). I did have an exchange with him a while back where he said it would still be possible to use this method, but that it would probably require some recalibration. He wrote:

The EUVI-GOES XRS relation may need more work as a result of EUVI instrument degradation (especially after 2016) and GOES re-calibration. I will have to address them when I try to update my paper.

On 2/24/2025 at 4:15 PM, stargazer007 said:

What’s causing the high energy protons to rise?

Cosmic yeast, from a plasma croissant.

Noticed the current coronal holes have shrunk quite a bit, is this a possible sign solar activity is on the rise?