A personal note for the ESWW in Toulouse regarding:
“Twenty Years Since the ”Halloween Storm” of 2003:
Our Present Understanding of Space Weather Effects Caused by Extreme Solar and Geomagnetic Storms, and Outlook on Remaining Open Questions and Issues”.
Hermann J. Opgenoorth
Department of Physics, Umeå University, Umeå, Sweden and
Department of Physics and Astronomy, University of Leicester, Leicester, UK
Dear colleagues and friends
Please let me express my sincere apologies for not being in Toulouse with you today.
I was very proud about the kind invitation to present this morning’s keynote lecture.
It was supposed to be about the Halloween Storms of 2003 and the fascinating progress of space weather knowledge ever since.
Unfortunately, a nasty cancer forbids me to travel during the next half year or so, but the doctors tell me that I will be cured and will survive – albeit with the help of a heavy Chemotherapy.
So, in my present state I am obviously not able to deliver a full-scale lecture with bells and whistles, but I would like to share with you a few personal thoughts about the progress of space weather research and predictions over the last 20 years.
The Program Committee has kindly offered me to do this remotely and less formal.
To begin with, I will have to share an important anecdote with you – one that I am not particularly proud of – and never have been – but which does illustrate the beginning of my work with – and for – space weather at the first European Space Weather Week at ESTEC in 2004 – about 20 years ago.
Just one year before, in 2003, I had been appointed Head of Solar and Solar-Terrestrial Missions at ESA, and in that same year we created an inter-agency collaboration initiative between NASA, ESA, CSA, Roskosmos, and Jaxa – a few years later even China joined us:
It was called International Living With a Star (ILWS)
I was elected to chair the ILWS for the first years. We aimed to facilitate the necessary coordinated science missions and other endeavors to create some first foundations for a future global space weather program, which should be truly operational rather than scientific.
Jean Lilensten and others had invited me to co-organize the 1st European Space Weather Week at ESTEC in 2004, and I delivered a lecture on the purpose and mission of the ILWS.
In the well formulated Mission Statement of the ILWS we proposed to identify and study the GOVERNING plasma processes, which are of particular relevance for SWx, and not just any “esoteric” space plasma physics processes…
I was young, ambitious, and proud – which often is not a good combination – and I strongly believed (and did express in my talk) that a lot of new and basic science still had to be done before one could dare to make reliable space weather predictions. I was not very fond of premature attempts of early SWx predictions at the time.
When I sat down after my lecture, I noticed that Risto Pellinen was sitting just behind me.
He was the Chairman of the ESA Science Program Committee at the time and an old friend.
He leaned forward and said: “Hermann, that was the most boring and uninspiring lecture I’ve seen you give during your entire career!”
I was quite stunned by his frank remark, but he was probably right.
All I could do was to reply in a very cheeky – and maybe even somewhat arrogant manner:
“You know Risto, I do grow with my audience…”
I must admit that these silly words have been ringing in my ears for 20 years now, and I have never been particularly proud about that cheeky remark, but I will have opportunity and reason to come back to those same words at the end of my short presentation – please bear with me that long…
But let’s now come to the topic of today:
When I think and speak about space weather impacts on the terrestrial system, I regularly refer to the multitude of SWx impacts related to Coronal Mass Ejections (CMEs).
They contain not only the most violent, but also the widest range of any space weather.
In contrast, the rather direct effect of Solar Flares is relatively straightforward to understand, impacting mainly on the global dayside ionospheric plasma density, while CMEs are truly complex features, affecting the entire near-Earth space environment.
A CME is THE one SWx event that potentially can cause the broadest set of SWx impacts of all solar disturbances:
Everything from radiation to increased ionisation, enhanced convection, and current flow.
It creates a large variety of impacts on human infrastructure, like power-cuts through GICs, satellite malfunctions via drag and radiation, and even GNSS disturbances via ionospheric irregularities.
But over the years we have come to the insight that the ideal case of a single CME, nicely ejected from the Sun, ploughing through an undisturbed solar wind, hitting Earth head-on with a homogeneous plasma structure, imbedded in a perfect flux rope…
is probably never going to happen
– even if the early ENLIL movies of CME propagation made us believe in that picture.
What we have learned from the very complicated Halloween Storms 20 years ago
– and other major storms since then – is the simple fact that
“When you have seen one storm, then you actually have only seen one storm!”.
The reason for that is actually quite simple.
Considering observational facts, starting at the Sun, it becomes obvious that the history of one or more ejected CME’s is always preceded by a period of other solar activity, which has produced an active and disturbed solar wind for several days.
This activity has filled the space between Sun and Earth with all kinds of plasma structures, including Corotating Interaction Regions, CIRs, and High-Speed Streams, HSSs.
Moving on into the Heliosphere, the eventually ejected CME must plough through, and eventually interact with all previously created solar wind structures on its faster propagation towards Earth.
Therefore, the exact history of the solar activity during the previous few days does matter a lot for its propagation and its arrival time at 1 AU.
Any CME may be
decelerated, by running into high density solar wind regions or
accelerated, if running into rarefaction regions in the wake of any previous CME(s).
When several CMEs are ejected in sequence, the faster ones will typically “cannibalize” on the preceding slower ones, creating sharper shocks and thus heavier impacts on the terrestrial space weather. The development of the magnetic field structure in combined CME’s and their interaction with each other is not yet fully understood.
Because of these unavoidable aspects of CME propagation, the present state-of-the-art prediction of CME arrival times at 1 AU is not better than about 6 hours, which means that we do not even know which continent will be hit by the day- and night-side consequences of a magnetic storm
– let alone that we could warn any particular national government about potential impacts on their specific infrastructure.
When the CME finally arrives at Earth, obviously it also makes a lot of difference whether the resulting solar wind structure at 1 AU does hit an unprepared, speak “normal magnetosphere” or not. “Normal” being a magnetosphere which is not compressed by earlier high-density solar wind structures and where no ring current has yet developed from earlier solar wind disturbances.
So, at Earth one needs to consider the history of not only a few days of solar activity
activities back up to a week matter for the resulting global response of the magnetosphere.
The exact impact of the CME density shock and its magnetic field direction makes a big difference in the first and original compression of the magnetosphere during a new storm, when strong Chapman-Ferraro magnetopause currents are set up to balance the increased solar wind pressure.
The infrastructure of many low-latitude countries will be strongly affected by the exact character of this the single initial magnetic pulse, called Sudden Storm Commencement.
Only later the high latitude regions will be strongly affected by the three-dimensional nightside current systems, which are built up by the increased magnetospheric convection and the electric current flows within it. Depending on the state of the magnetosphere at CME impact such nightside events can occur immediately or be delayed by up to an hour, again making predictions quite difficult.
In recent years we have become to realise that very short-lived sporadic and localised three-dimensional current systems – or current wedge-lets, often occurring in repetition – could be responsible for the most dangerous GIC events,
heavily impacting on human technological infrastructure.
Such ionospheric current spikes appear to be closely connected to Bursty Bulk Flows arriving at the very near-Earth inner edge of the plasma-sheet during storm conditions.
It is still unclear what causes bursty reconnection – instead of a smooth Dungey Cycle.
Special solar wind conditions or internal magnetospheric processes?
Some storms (or even parts of storms) just appear to be “spikier” than others.
The modelling of such dB/dt spikes is making a lot of progress recently, but their exact location and timing in the model sequence of a storm is not yet good enough to deliver predictions other than “there will be lightnings in that cloud”
– in an analogue prediction of terrestrial weather.
It appears that today’s space weather research is at the threshold of a paradigm shift.
We no longer study one sequential process of cause and action.
Instead, we have begun to see the Sun, the solar wind, and the Earth, with its magnetosphere, ionosphere, and atmosphere, as one coupled system.
Indeed, it is a “System of Systems” – if you so want.
There have been recent meetings in the US, led by Larry Kepko at NASA, and in Europe, led by Matt Taylor and Anja Strömme from ESA, discussing such new insights and looking into the future of Heliophysics (which is the Science of Space Weather).
The need for coordinated new space missions and supporting ground-based efforts is obvious, and these discussions will be carried into this European Space Weather Week.
Also, a new “SWx Coordination Mechanism” between COSPAR, WMO and ISES, initiated by the UN-COPUOS, has been kicked-off last week at a global SWx Summit in Geneve.
Final activities for a new updated COSPAR SWx Roadmap are under way within ISWAT, led by Masha Kuznetsova.
Any progress from last week’s meetings will be presented and further discussed at several splinter sessions during this SWx Week…
All this effectively means that solar, heliospheric, and magnetospheric physicists, including experts in data-handling, modelling, and prediction, will work even more closely together.
Looking back over the past 20 years of working for – and together with – the international space weather science and coordination efforts, I must say that I’m very proud to have been able to take part in the undeniable growth that we all have witnessed, ever since the Halloween storms in 2003.
It is more than fair to say that the Space Weather community – and its audience of analysts and end-users – has substantially matured and grown over the last 20 years.
In the end – and with facit at hand – my cheeky remark at the 1st European Space Weather Week may not have been so stupid and arrogant as I felt at the time.
I am proud that I could be an active part of this community,
which has grown in every aspect, not only by sheer numbers,
but both in breadth and in knowledge,
and last not least
in its importance for our human society
in times of an ongoing technological explosion into space,
and within a changing terrestrial environment.
I humbly admit that your collective growth has allowed me to grow a little myself, and thus, in a way it is now correct to say that I did, indeed, grow with my audience
at that 1st Space Weather Week at ESTEC in 2004.
Thank you all for that experience!
Let me end by wishing you all the best for this important meeting in Toulouse.
I truly hope to be able to join your/our efforts again in the not-too-distant future…
… maybe/hopefully at the 20th ESWW anniversary – a year from now!
Hermann J. Opgenoorth Uppsala, Sweden, November 16, 2023