[Latinmag] Fwd: [Gpmag-l] MagNetZ July 29

[Claudia Gogorza]

---------- Mensaje reenviado ---------
De: Paterson, Greig <Greig.Paterson en liverpool.ac.uk>
Fecha: El sáb, 25 jul. 2020 a la(s) 09:40
Asunto: [Gpmag-l] MagNetZ July 29
Para: GPMAG List <gpmag-l en mailman.ucsd.edu>, EMRP List <emrp en gfz-potsdam.de>


Hi all,



Our next MagNetZ seminar is upcoming and we have a few changes in the works.



This time round we will be recording the seminars. These recordings will be
made available online via a video streaming platform such as YouTube or
similar (the exact platform has still to be decided as we are investigating
the possibility of making the seminars citable items). This is something
that a number of people have requested since we started MagNetZ and will
allow those in unable to attend to view the seminars at a later date;
particularly for those in different time zones and as easing restrictions
changes our “normal” schedules.



Our currently scheduled speakers are happy to have their work their
presentations disseminated like this and we encourage future speakers to
create content that they are happy to share fully online to help promote
our community.



*For attendees, please note that continued participation in a seminar after
recording beginnings constitutes agreement for the recording to be publicly
disseminated.* Some, but not all attendees may be visible in the recording.
So, we recommend muting your microphone and turning off your camera if you
do not want to be visible.



Note that the networking catchup at the end of the seminars * will not be
recorded*. We welcome all comments and feedback on this.





The next seminar is on Wednesday July 29 at 15:40 BST (GMT+1) and will be
given by Kathy Whaler from the University of Edinburgh. She will be
presenting “The 2016 Pacific jerk and core-mantle boundary flows obtained
purely from Swarm secular variation gradient information”. The abstract is
below.



As before, we will be emailing the meeting login details directly to
participants. So if you are interested please email us (
greig.paterson en liverpool.ac.uk) and we’ll add you to the list.



If you are already on the list from a previous seminar, there is no need to
get in touch.



And thanks to everyone who joined us last week and for support the seminar
series. We’re looking forward to seeing you all next week.



All the best



Greig Paterson, University of Liverpool (greig.paterson en liverpool.ac.uk)

Anita Di Chiara, INGV-Rome and SIO University of California, San Diego





Abstract:

The 2016 Pacific jerk and core-mantle boundary flows obtained purely from
Swarm secular variation gradient information

Kathy Whaler1, Magnus Hammer2, Chris Finlay2 and Nils Olsen2

1School of GeoSciences, University of Edinburgh, UK; 2DTU Space, Denmark



The Swarm constellation provides information on both along- and
across-track magnetic field gradients. Spatial changes of the magnetic
vector field elements are described by a magnetic field gradient tensor,
whose elements and their uncertainties can be estimated using the Virtual
Observatory (VO) concept, whereby data within a cylinder centred on the VO
with axis perpendicular to the Earth’s surface are reduced to a central
point at satellite altitude. Recent experiments have shown that analysing
data collected over a 4 month window provides the best compromise between
reducing bias from the way the satellite orbits sample each VO cylinder and
preserving information on temporal changes of the field, and that the data
provide spatial information sufficient to resolve 300 non-overlapping VOs.
We invert annual first differences of the 5 independent gradient tensor
elements (providing estimates of secular variation, SV, gradients) at these
300 VOs over the Swarm era for advective velocity at the core-mantle
boundary, forcing the flow to have minimal acceleration while providing an
adequate fit to the data. We obtain flows similar to those from previous SV
inversions but purely from the gradient information. The resolution of the
SV gradients is higher than that of the SV itself, resulting in a ~30%
increase in the number of effective flow parameters; this is thought to be
because the gradients are less affected by long period external signals
that are difficult to remove from the data, resulting in an improved signal
to noise ratio. Although very little temporal change in the flow is
required to reproduce even rapid changes in the magnetic field, we are able
to isolate some robust flow changes, in particular regarding changes in the
azimuthal flow acceleration, associated with the geomagnetic impulse in the
Pacific region in around 2016.

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