Questions about IMF polarity from ACE?

[oemSpace]

IMF Polarity Predictions:

Comparison of real-time ACE IMF polarity data (solid black line) with Wang-Sheeley-Arge model predictions (colored dots). The three sets of predictions (i.e., red, green, and blue dots) are based on data from, respectively, Wilcox (WSO), Mount Wilson (MWO) and SOLIS (NSO) solar observatories. The solid black line is the real-time (9-hour-averaged) ACE IMF values normalized to equal unit value. A positive (negative) polarity indicates that the IMF is directed radially outward (inward) from the Sun to the Earth. Each 9-hour interval of real-time ACE data corresponds to 9 individual (hourly averaged) values when there are no gaps in coverage. If two-thirds of the 9 values have positive (negative) sign, they are assigned a polarity of +1 (-1). If less than two-thirds are of a particular sign, that time interval is assigned a polarity of zero, implying mixed or indeterminate polarity. Source : http://www.swpc.noaa.gov/ws/predimf_3d.html

Referring to following image, based on data from Bz, 8 out of 9 numbers are positive polarity, but ACE shows negative polarity, I would like to confirm whether ACE IMF polarity come from data of Bz or not, does anyone have any suggestions?

Thanks in advance for any suggestions :>

I am so confusing ... :unsure:

[Vancanneyt Sander]

Read it all again. It is not confusing, your making it yourself too hard... we do our best to give you the right answers and always your doubting it. So your making it confusing for yourself.

Look, it was a forecast MODEL. Models are not 100% accurate and are based on measurements from the past and what we already know about Solar physics. So like ALL models, they can't be 100% accurate. It always gives an INDICATION of what you can expect.

If a model was 100% accurate, we wouldn't do predictions of what to expect. Look at the local weather, if the forecast says it will be sunny but you'll see clouds that's all the same!

[oemSpace]

Thanks you very much for your reply :>

Referring to the image, Blue, Red, Green lines are predicted results, but ACE (solid black line) is the real-time ACE IMF polarity data.

Based on the definition, when I compare this real-time ACE with Bz, data of ACE is negative, but Bz is positive (8 out of 9).

This make me very confusing on not knowing which one is correct for IMF polarity data.

Do you have any suggestions on what wrong it is?

Thanks you very much for any suggestions :>

IMF Polarity Predictions:

Comparison of real-time ACE IMF polarity data (solid black line) with Wang-Sheeley-Arge model predictions (colored dots). The three sets of predictions (i.e., red, green, and blue dots) are based on data from, respectively, Wilcox (WSO), Mount Wilson (MWO) and SOLIS (NSO) solar observatories. The solid black line is the real-time (9-hour-averaged) ACE IMF values normalized to equal unit value. A positive (negative) polarity indicates that the IMF is directed radially outward (inward) from the Sun to the Earth. Each 9-hour interval of real-time ACE data corresponds to 9 individual (hourly averaged) values when there are no gaps in coverage. If two-thirds of the 9 values have positive (negative) sign, they are assigned a polarity of +1 (-1). If less than two-thirds are of a particular sign, that time interval is assigned a polarity of zero, implying mixed or indeterminate polarity. Source : http://www.swpc.noaa.gov/ws/predimf_3d.html

Referring to linked image, it mentions "NOAA/SWPC, BOULDER, CO, USA", is the real-time data for ACE for the location BOULDER, CO, USA only or from ACE Satellite?

Does anyone have any suggestions?

Thanks in advance for any suggestions :>

[Vancanneyt Sander]

There is nothing wrong with it...

The red, green and blue lines are the three models that predict the direction of the IMF (NSO, SWO and GONG). The solid black line is the measured average of the direction from the Ace satellite.

Like we said earlier: THESE ARE MODELS

SO as with every model, it PREDICTS, so it can ALWAYS be that the measured direction is DIFFERENT than the model.

Conclusion: It is NOT confusing

[oemSpace]

I understand that the solid black line is measured average of the direction from the Ace satellite based on following definition, referring to the linked image, I have highlight the raw data from ACE, if I manually calculate the average value for polarity, it should be +1, because 8 values of Bz are positive and only 1 value of Bz is negative, so two-thirds of the 9 values have positive signs, then it should assigned a polarity of +1, but on the solid black line it shows -1 instead of +1, this is the point making me so confusing, do you get this point for understanding my issue on ACE polarity?

Do you have any suggestions?

 

Thanks you very much for any suggestions :>

 

IMF Polarity Predictions:
If two-thirds of the 9 values have positive (negative) sign, they are assigned a polarity of +1 (-1). If less than two-thirds are of a particular sign, that time interval is assigned a polarity of zero, implying mixed or indeterminate polarity. Source : http://www.swpc.noaa.gov/ws/predimf_3d.html

 

[Vancanneyt Sander]

You got a point there. Now you where more clear of what you tried to say.

I can't give you a reason why it's different on the graph, it can be that some more factors are used but the explanation on the site didn't mention them because visitors would be freaked if they see a full scientific calculation method on how they derive the numbers ;-). If you really want to know, e-mail NOAA and ask for a clarification. The science team of ACE will probably know that.

[Guest Terry Tedor]

Doesn't the "Predicted Interplanetary Magnetic Field (IMF) Polarity at Earth" chart indicate the predicted Phi angle of the IMF and is not directly related to Bz?

[Guest Terry Tedor]

Perhaps this will help oem7110:

 

http://pluto.space.swri.edu/image/glossary/IMF.html

"

The interplanetary magnetic field (IMF) is a part of the Sun's magnetic field that is carried into interplanetary space by the solar wind. The interplanetary magnetic field lines are said to be "frozen in" to the solar wind plasma. Because of the Sun's rotation, the IMF, like the solar wind, travels outward in a spiral pattern that is often compared to the pattern of water sprayed from a rotating lawn sprinkler. The IMF originates in regions on the Sun where the magnetic field is "open"--that is, where field lines emerging from one region do not return to a conjugate region but extend virtually indefinitely into space. The direction (polarity, sense) of the field in the Sun's northern hemisphere is opposite that of the field in the southern hemisphere. (The polarities reverse with each solar cycle.)

The heliospheric current sheet

 

Along the plane of the Sun's magnetic equator, the oppositely directed open field lines run parallel to each other and are separated by a thin current sheet known as the "interplanetary current sheet" or "heliospheric current sheet" (see the figure above). The current sheet is tilted (because of an offset between the Sun's rotational and magnetic axes) and warped (because of a quadrupole moment in the solar magnetic field) and thus has a wavy, "ballerina skirt"-like structure as it extends into interplanetary space (see the figure on the left). Because the Earth is located sometimes above and sometimes below the rotating current sheet, it experiences regular, periodic changes in the polarity of the IMF. These periods of alternating positive (away from the Sun) and negative (toward the Sun) polarity are known as magnetic sectors.

IMF Bz

The IMF is a vector quantity with three directional components, two of which (Bx and By) are oriented parallel to the ecliptic. The third component--Bz--is perpendicular to the ecliptic and is created by waves and other disturbances in the solar wind. When the IMF and geomagnetic field lines are oriented opposite or "antiparallel" to each other, they can "merge" or "reconnect," resulting in the transfer of energy, mass, and momentum from the solar wind flow to magnetosphere The strongest coupling --with the most dramatic magnetospheric effects-- occurs when the Bz component is oriented southward.

The IMF is a weak field, varying in strength near the Earth from 1 to 37 nT, with an average value of ~6 nT. "

[Guest Harry Twinotter]

I agree with Terry Tedor.

 

The IMF polarity indicates if the solar wind magnetic field points towards the earth, or away from the earth.

 

In the NOAA Space Weather Discussion, they use it to see when a solar sector boundary crossing occurs. 

[oemSpace]

You got a point there. Now you where more clear of what you tried to say.

I can't give you a reason why it's different on the graph, it can be that some more factors are used but the explanation on the site didn't mention them because visitors would be freaked if they see a full scientific calculation method on how they derive the numbers ;-). If you really want to know, e-mail NOAA and ask for a clarification. The science team of ACE will probably know that.

 

Reply from them "Firstly, you are looking at the ACE data in GSM coordinates which means the Z direction is perpendicular (roughly) to the ecliptic plane and does not correspond to the polarity that is referred to in the Wang-Sheeley-Arge model.  The IMF polarity is not related to the Bz component in this coordinate system.  The IMF polarity is either pointing away or towards the Sun.  So you need to use the Bx and By components, not the Bz.  In GSM coordinates Bx is along the Earth-Sun line, so it is positive towards the Sun, a direction that is referred to as negative polarity.

 

So, if you want to determine the ACE IMF polarity from the text file and compare it to the plot, you need to use the negative of the observed Bx (NOT Bz) values in the table.  Your highlighted section has Bx values that are positive, which means the values you are interested in are negative...giving a negative polarity which agrees with the plot.  

 

I'm not sure where you got the idea that Bz is the IMF polarity, but I assure you it is not (in either GSM, GSE, or HSE coordinates)."

----------------------------------------------------------------------------------------------------

 

Bz value

A strong southward Bz value is the most important value if we want to see some aurora. A strong southward orientated IMF gives us nice aurora displays so how lower it goes the better. Source : http://www.spaceweatherlive.com/en/help/the-interplanetary-magnetic-field-imf

 

Referring to above definition of Bz, does anyone have any suggestions on what coordinate (GSM, GSE, or HSE ) is referring?  In addition, could anyone please clarify what those coordinates are about (GSM, GSE, or HSE ) ?

 

Does anyone have any suggestions?  

 

Thanks everyone very much for any suggestions :>  

 

[Vancanneyt Sander]

There are many kinds of coördinate systems ;-) the easiest is x,y,m(or z), her in Belgium we use Lambert 72A as a coördinate system. And in space we have also different ones like the GSM coördinates.

NOAA explains it in their post: Z direction perpendiucular on the ecliptic, so the other ones (x and y) are just in line of the ecliptic.

More info on coördination systems in space: http://spider.seds.org/spider/ScholarX/coords.html

[oemSpace]

Referring to following definition from spaceweatherlive website, I would like to know what kind of coordination is used and to confirm whether data using (Bz) could be used to monitor the possibility for "reconnection" between IMF and geomagnetic field lines or not.

Bz value

A strong southward Bz value is the most important value if we want to see some aurora. A strong southward orientated IMF gives us nice aurora displays so how lower it goes the better. Source : http://www.spaceweatherlive.com/en/help/the-interplanetary-magnetic-field-imf

There are many kinds of coördinate systems ;-) the easiest is x,y,m(or z), her in Belgium we use Lambert 72A as a coördinate system. And in space we have also different ones like the GSM coördinates.

NOAA explains it in their post: Z direction perpendiucular on the ecliptic, so the other ones (x and y) are just in line of the ecliptic.

More info on coördination systems in space: http://spider.seds.org/spider/ScholarX/coords.html

Referring to your suggested link, I find no description on explaining any terms of GSM, GSE, or HSE coordinates.

Based on your understanding, could you please briefly describes on what symbol is being used under different coordination (GSM, GSE, or HSE) to monitor the possibility for "reconnection" between IMF and geomagnetic field lines?

Does anyone have any suggestions?

IMF Bz

The IMF is a vector quantity with three directional components, two of which (Bx and By) are oriented parallel to the ecliptic. The third component--Bz--is perpendicular to the ecliptic and is created by waves and other disturbances in the solar wind. When the IMF and geomagnetic field lines are oriented opposite or "antiparallel" to each other, they can "merge" or "reconnect," resulting in the transfer of energy, mass, and momentum from the solar wind flow to magnetosphere The strongest coupling --with the most dramatic magnetospheric effects-- occurs when the Bz component is oriented southward.

http://pluto.space.swri.edu/image/glossary/IMF.html

[Guest Terry Tedor]

15aa593d4f94ab589e47bc16719347e5

[oemSpace]

"Bz (GSM coordinates) can be used to correlate reconnection events. When I say "reconnection" I am referring to reconnection in the magnetotail."

 

Do you use Bz to correlate reconnection events only for Night light aurora in the magnetotail?

 

What about Daylight aurora occur in the dayside of the Earth? Can we use Bz to correlate this reconnection events on day light aurora too?

 

 

 

 

Furthermore, do you have any suggestions on what kind of item to be monitored on forecasting reconnection Event (Magnetotail "Unloading") on above GOES Magnetometer image?

 

 

Referring to above image on the Wang-Sheeley-Arge model, in GSM coordinates Bx is along the Earth-Sun line, their replies mention that negative of the observed Bx (NOT Bz) values should be used to determine the ACE IMF polarity, since southward orientated IMF is important requirement to generated any geomagnetic disturbance on Earth, there is 2 different approaches (using -Bx and Bz in GSM coordinates) to determine the ACE IMF polarity, I am getting more confused now  

 

 

My main concern is what approach determines the IMF with southward polarity on forecasting any geomagnetic disturbance.

 

Does anyone have any suggestions on which approach is corrected one?

 

Thanks in advance for any suggestions :> :)

[Guest Terry Tedor]

"Do you use Bz to correlate reconnection events only for Night light aurora in the magnetotail?

 

What about Daylight aurora occur in the dayside of the Earth? Can we use Bz to correlate this reconnection events on day light aurora too?"

 

 

Yes, to your first question.

 

To your second question, I don't know, since I have no way to observe aurora on the dayside of Earth. Therefore, I have no desire/need to make any correlation between Bz and reconnection events.

 

"Can we use Bz to correlate this reconnection events on day light aurora too"

 

 

When you say "reconnection events on day light aurora too", are you referring to reconnection events in the magnetotail effecting day light aurora or reconnection events on the dayside? It is my understanding that reconnection occurs in the magnetosphere on both the day and night sides of Earth.

Try these, perhaps they will help you understand and answer some of your questions, but probably generate a lot more too! Which is good!

 

 

[oemSpace]

Thanks everyone very much for suggestions :>

 

Reconnection should be occurred on dayside and nightside, since crossing magnetic field lines exist on both sides, but I don't know the detailed processes among them.

 

 

I don't find much related materials defining IMF polarity on internet, will this topic be too advance to be discussed with any exisiting theory? since ACE satellite only launched since August 25, 1997

 

I think solar wind is a 3D object, when trying to define the IMF polarity based on 1 Dimension line Bx or Bz is difficult, does any expert know any interpretation on defining IMF polarity based on Bx, By, Bz all together? or at this moment, there is no theory related to this topic in Solar physics at all, and everyone uses his own subjective selection to define the IMF polarity.

 

At this moment, I only find a single source providing forecast on IMF polarity using -Bx viewpoints, not By or not Bz, so the best selection at this moment is -Bx, and I get no choice, and hope their selection are corrected ...

 

I just wonder whether the forecast on IMF Polarity ready base on -Bx to provide any alert on geomagnetic storm or not ...

 

 

 

Does anyone have any suggestions?

 

Thanks everyone very much for any suggestions :>

[Guest Terry Tedor]

"Reconnection should be occurred on dayside and nightside, since crossing magnetic field lines exist on both sides, but I don't know the detailed processes among them."

 

Yes, reconnection occurs on both the day and night sides. Unless you're looking for an academic or scholarly paper, I don't think you're going to find much information regarding detailed processes, but there is plenty of general information on the web discussing reconnection.

http://www.igpp.ucla.edu/public/THEMIS/SCI/Pubs/Nuggets/reconnection/tail_reconnection.HTML

 

http://astroengine.com/2008/07/24/auroral-substorm-themis-pinpoints-location-of-magnetic-reconnection-in-magnetotail/

 

http://www.nasa.gov/mission_pages/themis/auroras/themis_power.html

 

Along with the Youtube links I provided above.

 

"I don't find much related materials defining IMF polarity on internet..."

 

What exactly are you looking for? It seems you've answered your own question several times over regarding this; it's either + or -. I think if you want a more detailed description, you need to investigate Phi angle.
 

"The IMF polarity is not related to the Bz component in this coordinate system.  The IMF polarity is either pointing away or towards the Sun.  So you need to use the Bx and By components, not the Bz.  In GSM coordinates Bx is along the Earth-Sun line, so it is positive towards the Sun, a direction that is referred to as negative polarity.

 

So, if you want to determine the ACE IMF polarity from the text file and compare it to the plot, you need to use the negative of the observed Bx (NOT Bz) values in the table.  Your highlighted section has Bx values that are positive, which means the values you are interested in are negative...giving a negative polarity which agrees with the plot."

 

 

"I think solar wind is a 3D object, when trying to define the IMF polarity based on 1 Dimension line Bx or Bz is difficult, does any expert know any interpretation on defining IMF polarity based on Bx, By, Bz all together? or at this moment, there is no theory related to this topic in Solar physics at all, and everyone uses his own subjective selection to define the IMF polarity.

 

At this moment, I only find a single source providing forecast on IMF polarity using -Bx viewpoints, not By or not Bz, so the best selection at this moment is -Bx, and I get no choice, and hope their selection are corrected ..."

 

Yes, of course the solar wind is a 3D object. Since the "line" is a line of a magnetic field, it contains more than 1 dimension. Bz yields the 3rd dimension but has no play in calculating the IMF polarity.

 

I thought we already established the fact that Bz has nothing to do with the polarity of the IMF? It is solely based on Bx & By as those 2 fields lie in the plane of the ecliptic. Isn't that what the folks at NOAA said in their response to your question?

 

I'm sorry, but I guess I don't understand why you want to go through this so many times. We've already established, several times over, that the IMF polarity is based on Bx & By; Bz has nothing to do with determining the polarity of the IMF.

 

You stated: "...everyone uses his own subjective selection to define the IMF polarity." No, it's established science and science is not subjective.

 

You stated: "...so the best selection at this moment is -Bx, and I get no choice...". Sorry, no, you don't have a "choice", because this is science and science doens't give you "choices", just facts.

 

Sorry, but there is no "...interpretation on defining IMF polarity based on Bx, By, Bz all together..." that's because, as we've already discussed, Bz has no bearing on IMF polarity, just Bx & By, so there does not need to be a "...theory related to this topic in Solar physics...".

 

"I just wonder whether the forecast on IMF Polarity ready base on -Bx to provide any alert on geomagnetic storm or not"

 

IMF polarity may contribute, but I don't think IMF polarity alone is sufficient to generate storms. There are too many other factors that need to be taken into account.

 

 

[oemSpace]

At this moment, it seems a perfect timing on analysing following GOES chart,

 

Do you have any suggestions on how to locate Reconnection Event at this present moment?

 

Thanks everyone very much for suggestions :>

 

 

[Guest Terry Tedor]

One possible event at approx. 0900UT 2013-09-09.

 

 

6 hours later there appear to be one, possibly two, more. One at 0900UT 2013-09-11 followed by a possible event around 1000UT 2013-09-11

[oemSpace]

Referring to following image, whenever red or blue lines rise sharply under yellow area, would the yellow area be the Reconnection Event (Magnetotail "Unloading") (Discharging)? and it is the best time (1, 2, 3, 4) for watching Aurora.

 

Do you have any suggestions on what kind of data (Bx, By, Bz) from GOES is used for Red and Blue lines? 

 

Thanks everyone very much for any suggestions :>

 

 

[Guest Harry Twinotter]

OEM7110.

 

A reconnection event happens on the nighttime side of the earth, I have never heard of one occuring on the daytime side.

It might show up on the GOES satellite trace if the satellite is currently on the nighttime side of the earth. Look for the data dropping to zero or even lower, as per the description on the webpage http://www.swpc.noaa.gov/rt_plots/mag_3d.html

 

Other than that I think it is difficult to tell when a reconnection event occurs.
 

Please do not chop my answer up and use it to make up more questions, as you have done on other forums and in the comments of YouTube videos - this is spam.
 

[oemSpace]

OEM7110.

 

A reconnection event happens on the nighttime side of the earth, I have never heard of one occuring on the daytime side.

It might show up on the GOES satellite trace if the satellite is currently on the nighttime side of the earth. Look for the data dropping to zero or even lower, as per the description on the webpage http://www.swpc.noaa.gov/rt_plots/mag_3d.html

 

Other than that I think it is difficult to tell when a reconnection event occurs.

 

The most important point on GOES chart is to identify the pattern of charging and discharging, because it is so subjective, so I need to describe the situation more in details. For nighttime side of the earth, 1 and 4.

 

I don't understand this statement "6 hours later there appear to be one, possibly two, more." Could anyone please tell me when it is?

 

Thanks everyone very much for any suggestions :>

[Guest Terry Tedor]

Referring to following image, whenever red or blue lines rise sharply under yellow area, would the yellow area be the Reconnection Event (Magnetotail "Unloading") (Discharging)? and it is the best time (1, 2, 3, 4) for watching Aurora.

 

Do you have any suggestions on what kind of data (Bx, By, Bz) from GOES is used for Red and Blue lines? 

 

Thanks everyone very much for any suggestions :>

 

 

 

 

 

"Referring to following image, whenever red or blue lines rise sharply under yellow area, would the yellow area be the Reconnection Event (Magnetotail "Unloading") (Discharging)?"

 

Yes in 1 & 4. Reconnection events are when the lines come in very close proximity to one another or even touch. Loading occurs in the magnetotail when one line starts to diverge sharply from the other. The rapid rise in that same line is the unloading.

 

No in 2. This is normal day-to-day behavior, to the best of my knowledge and is visible in every GOES magnetometer graph I've ever seen.

 

Not sure about 3. This could be indicative of some event that has compressed the daytime side of the magnetosphere. There is a possibility that it is evidence of reconnection on the daytime side, but I'm not sure about that, just an assumption on my part.

 

"and it is the best time (1, 2, 3, 4) for watching Aurora."

 

Since I do not know your geographical location, I can not say. It depends on where you are and when you experience the hours of darkness at your location.

 

Where I live (Alaska) 1 & 4 occured during the hours of darkness, so they would be the best times.

 

"Do you have any suggestions on what kind of data (Bx, By, Bz) from GOES is used for Red and Blue lines?"

 

Bz is represented by the Red and Blue lines. From the GOES Magnetometer page at SWPC:

"The GOES Hp plot contains the 1-minute averaged parallel component of the magnetic field in nanoTeslas (nT), as measured at GOES-13 (W75) and GOES-15 (W89). The Hp component is perpendicular to the satellite orbit plane and Hp is essentially parallel to Earth's rotation axis."

[Guest Terry Tedor]

.

 

"I don't understand this statement "6 hours later there appear to be one, possibly two, more." Could anyone please tell me when it is?"

 

OK, you took my response and only quoted part of it, which I don't quite understand why...

The full quote:

"6 hours later there appear to be one, possibly two, more. One at 0900UT 2013-09-11 followed by a possible event around 1000UT 2013-09-11."

 

So, I told you, by time, 0900UT and 1000UT. Not quite sure why you asked again and then left the times out of the quote

[oemSpace]

The point I don't understand is "6 hours later", if the starting period is 0900UT 2013-09-09, then 6 hours later is 1500UT 2013-09-09.  But "6 hours later" starts from nowhere, so it makes me so confusing from my interpretation, but now I understand it refers to 0600UT 2013-09-11, which is very very minor question for discussion.

 

Thanks everyone very much for suggestions :>