From audrey.schillings@umu.se Tue Dec 17 17:24:47 2024
Date: Tue, 17 Dec 2024 16:24:45 +0000
From: Audrey Schillings <audrey.schillings@umu.se>
To: Maria.Hamrin <Maria.Hamrin@space.umu.se>
Subject: Re: Questions about equivalent currents

Hej Maria, 

Sorry for my very late answer. I didn't want to answer "quickly" so it turns up
not answering in one week 😕

Great that the student decided on doing that project!
For the equivalent currents it is quite difficult to compute from scratch a
ready to use code should probably be used, especially for a student or a
database. 

From previous email yes there are 2 EQCs types depending if the
divergence-free or curl-free the  method is used, one referring to the Hall &
Pedersen (horizontal) and the other to the FAC currents. In my analysis I only
use the Horizontal current to see how the electroject is moving and enhancing
which is also related to the convection pattern. Also the Hall current are the
one mostly related to signatures that could be described by the dB/dt. 
Amm  & Viljanen (1997) described that in this paper
 https://earth-planets-space.springeropen.com/articles/10.1186/BF03352247

Another thing is that for computing the EQCs the magnetometer station be well
spreaded that is why it is possible on Fenno-scandia and in Canada/US (but not
really on Greenland for example). 

For the data for the St Patrick storm paper, Max Van KAmp (FMI) computed the
differential EQCs for Laurianne and so I had a start and end time for the On/Off
Hall loop and therefore I could reproduce them with the FMI website and playing
with the baseline of EQCs on the website itself. Without the start and end time
it would be impossible to do, and no the website does not compute the
differential EQCs. 

Liisa Juusola indeed has a code for the EQCs and the internal/external currents.
So she could definitely help with that. It does exist Python code from Greg
Lucas as well from what I know but I never used it really. 

I don't know the database you are talking about from Weygand but it looks like
they have ready to go plot, so not really able to change the time and these the
EQCs not the differential as I understood. 

I hope that helps. 
Have a nice evening. 
/Audrey 

________________________________________________________________________________
From: Maria Hamrin <Maria.Hamrin@space.umu.se>
Sent: Saturday, December 14, 2024 12:21 PM
To: Audrey Schillings <audrey.schillings@umu.se>
Subject: Fwd: Questions about equivalent currents  

Hi Audrey,

I hope you are fine and that you are looking forward to Christmas.

The student that wanted to do the master project about non-stormy spikes and
investigating the currents systems similar to your St Patrick's article has a
been a bit hesitant (students are often quite "volatile", going here and there
and changing their minds), but as of yesterday he decided that he wants to do
this project anyway.

He will start in mid/end-January.

I think that he should, among other things, compute and study differential
equivalent currents and I'm a bit unsure how to do those. Did you compute them
yourself or did you use any prepared tool from Juusola or anyone else? It seems
that the IMAGE network doesn't allow you to download the data to compute the
difference yourself.

I'm also thinking about using the Weygand data sets for equivalent currents.
What do you know about them? See also my questions below.

Merry Christmas!

/Maria

-----------------------------------------------------------------
Maria Hamrin                     Email: maria.hamrin@space.umu.se
Associate Professor              Phone: +46 (0)70 325 80 38
Docent in space physics
Department of Physics
Umeå University
Linnaeus väg 24, 901 87 Umeå, Sweden
https://www.umu.se/personal/maria-hamrin/
https://www.umu.se/en/research/groups/space-plasma-physics-group/
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-------- Forwarded Message --------
Subject:
Questions about equivalent currents
Date:
Sat, 7 Dec 2024 11:04:15 +0100
From:
Maria Hamrin <Maria.Hamrin@space.umu.se>
To:
Audrey Schillings <audrey.schillings@umu.se>

Hej Audrey,

How are you and how are your family in these difficult times? Are you still on a
leave from work.

If not, perhaps you can answer a few questions about equivalent currents. I got
some ideas on ESWW24 which I'm no trying to merge into a master project. I have
a good student who reached out to me this week.

The plan is that he will go through several events of quite strong spikes but
during stormy-times. He will do similar studies as in you Sy Patrick study and
lock on equivalent currents, all-sky cameras and space craft, depending on
availability. And if/when this become a paper, you will of course become a
co-author.

My questions:

 *  For the differential currents that you used, did you compute them yourself?
    Did you use the online IMAGE tools or do you have your own tool or did you
    get help from Liisa Juusola or someone else for this?

 *  I've also looked into the availability for equivalent currents in North
    America and I found a data base by James Weygand (I also have been in
    contact with him the other week since I found some errors in his data base -
    the wrong dates):https://spdf.gsfc.nasa.gov/pub/data/aaa_special-purpose-datasets/spherical-elem
    entary-and-equivalent-ionospheric-currents-weygand/Quicklook/
    In his README file he mentions: "...The SECS are the current amplitudes are
    a proxy for the field aligned current
    and are derived for an altitude of 100 km above the surface of the Earth.
    ... The Equivalent Ionospheric Currents (EICs) data set
    contains horizontal ionospheric current data..."
    I didn't know that there are field-aligned equivalent currents too but I
    guess you knew. But it doesn't seem like IMAGE computes the field-aligned
    currents. Do you have any information on these currents? Can the
    field-aligned currents be trusted as much as the horizontal? Is there any
    possibility that you know about to calculate Jpara also  for IMAGE?
    The README file is here:https://spdf.gsfc.nasa.gov/pub/data/aaa_special-purpose-datasets/spherical-elem
    entary-and-equivalent-ionospheric-currents-weygand/Weygand_readme.txt

 *  And do you know any other data bases for equivalent currents in North
    America? I sounded from Hermann that there might be (I spoke with him over
    the phone the other day and he seems muck beter)

I wish you the best for you and your family.

And let me know if there is anything you need help with concerning ESWW25.

Have a nice week-end.


-- 
/Maria

-----------------------------------------------------------------
Maria Hamrin                     Email: maria.hamrin@space.umu.se
Associate Professor              Phone: +46 (0)70 325 80 38
Docent in space physics
Department of Physics
Umeå University
Linnaeus väg 24, 901 87 Umeå, Sweden
https://www.umu.se/personal/maria-hamrin/
https://www.umu.se/en/research/groups/space-plasma-physics-group/
-----------------------------------------------------------------

