3rd RSIH&SWA Workshop – Morelia, Mexico – 20 October 2015

IPS Cross-Analyses

M.M. Bisi (Mario.Bisi@stfc.ac.uk) (1), E. Aguilar-Rodriguez (2),

and The world-wide IPS community..

(1) RAL Space, Science and Technology Facilities Council, Rutherford Appleton Laboratory, Harwell Oxford, Didcot,

Oxfordshire, OX11 0QX, England, UK

(2) Instituto de Geofisica, Unidad Michoacan, UNAM, Mexico

Outline

Why?

Original Plan

Ad-hoc Modified Plan

Where are we?

Open Discussions

Why?

Why (1) IPS is a powerful tool for investigating coronal and heliospheric

outflow; this includes ambient, co-rotating, and transient flows.

There are multiple active IPS analysis suites in use world wide

with different methodologies in getting to, and in presenting, the

end data products such as velocity(ies), g-levels, non-radial flow

angles, relative densities, etc…

There are both single-station and multi-station analyses methods

where the results from the two are not always the same.

There are formal fitting methods as well as geometrical methods

to be able to get to the end results.

Why (2)

IPS is hugely under-exploited by the greater Heliophysics

community and part of that is people’s lack of understanding of

the data products, and how they are obtained, that IPS is able to

provide to them.

Some great example of exploitation thus far include multi-

technique studies (visible-light combined with IPS), driving

MHD models (including comparisons with the outer

heliosphere), tomographic methods, and studies using IPS from

different frequencies and different systems to track features right

through the inner heliosphere (at least to the Earth and Mars);

but much more could be achieved.

Why (3) For multi-site methods, two or more observing sites are used to

simultaneously observe the same radio source where the

geometry is sufficient to have the parallel baseline roughly

aligned to that of the plasma outflow.

There is typically a cross-correlation analyses undertaken where

velocity estimates are given based on the peak position in time

lag of the cross-correlation function and the parallel baseline

length.

Additional formal fitting to multiple spectra have been used in

the past to be able to obtain more fundamental parameter values

such as the axial ratio, alpha, density ratios, etc…

Why (4) For single-site analyses, there are several different approaches

based around the fitting of the IPS power spectrum where the

position of the Fresnel knee gives an indication of the outflow

velocity.

However, there are not uniform methods to produce power

spectra (as became evident at the Nagoya 2013 meeting) and

also no uniform method (although based in principle on solving

the same IPS equation, but with so many different parameter

assumptions in different cases by different observatories) to

obtain velocity values.

Producing g-level values also seems to have differences.

Why (5)

End result is often different values of parameters for very

similar/identical plasma regimes with no complete understanding

of how, where, or why these differences came about – hence the

need for some form of cross-analyses of methods and perhaps

some cross-calibration of results (certainly from single- to multi-

site approaches); tomographic methods where multiple data

sources are subsumed into one single tomographic output

account for some of the discrepancies due to best-fitting of the

data to a model, but not for all…

Original Plan

Original Plan (1) Share well-known (to the observer) IPS time-series data for

several good IPS sources over a few days (perhaps five sources

over three days of observing – needn’t be consecutive).

A description of how the time series is formatted (e.g. time-

series sampled at 100Hz for 15 minutes of data observing

J0318+164 using XXXXX observatory/station with an arbitrary

amplitude scale in YYYYY binary format including ZZZZZ

lines of header, etc…).

Each active analyses suite would then be used on each of the

different data sets to produce power spectra, velocity/g-level

values, cross-correlation functions, etc…, accordingly.

Original Plan (2)

A DropBox was set up for sharing the data and data descriptions

and then for sharing all the analyses on each of the sets of data.

Then a comparison at this workshop (today) would be

undertaken in looking at the differences/similarities in how the

power spectra are ‘looking’, and also in how the results compare

– at least for velocity as a starting point (with g-level also

considered for sites and analyses tools where this is a capability).

All of this would be undertaken for each INDIVIDUAL

observation in the hope of forming a larger picture of where

things stand between the different observing methods.

Ad-hoc Modified Plan

Modifications

A time period of May 2013 was taken as something to work on.

Concentration of observations with 3C48 was suggested.

Not all sites have data from that period of that radio source

during that period – and so not all sites have participated due to

the above thinking.

Where are we?

Where are we? (1) From looking at the DropBox (Sunday 18 October 2015) only

BSA (Pushchino) and MEXART made data available in the

expected format with a readme, STELab also supplied much data

but no explanation of the data, and ORT (Ooty) and KSWC

provided data in different formats with no explanation for the

latter.

There were no good/well-studies data available from EISCAT for

3C48 during May 2013, and no LOFAR data at all for 3C48

during May 2013 (although some unstudied observations from

April 2013 still).

UTR-2 and China data availabilities are unknown.

Where are we? (2) Do we need some time here now to concentrate on this

study/project and is it something really of interest to the world-

wide IPS community?

If so, then all is not lost and we should ensure that today and

throughout this workshop we plan accordingly to ensure this

activity is completed effectively, and we can then learn from

each other the differences/similarities and perhaps the good and

bad ways to go about providing end data products to each other

as well as to the wider Heliophysics community.

This study is important to the IPSCDFv1.0 and to its usefulness/

reliability for the non-IPS end user/scientist as well as in the

validation of IPS for use in space-weather-related activities.

Open Discussions

Over to you all…

Open Discussions