Brane Space: Why Space Weather Is Still "Something of a Black Box"

A CME impacts Earth's magnetosphere in this artist's illustration

The recent (June 10, p. 12) TIME essay 'What's Going On With Storms On The Sun?' noted that space weather (that form which produces aurora, coronal mass ejections, etc.) is "still something of a black box for researchers." Adding:

"Even if we could predict it as reliably as we can predict terrestrial weather, the U.S. power grid is so sprawling and regionalized that it's hard to put protocols in place to protect everything."

But let's be clear that predicting a space weather event - say a massive CME erupting from the solar meridian - is not the same as correctly forecasting its effects on one particular part of a hodge-podge power grid. In other words, you can't hold space physicists responsible for failing to forecast that field line currents generated by a powerful solar storm (like the one that clobbered Ottawa in 1989) wiped out part of a Texas power grid that was disconnected from the rest of the U.S. to begin with.

As those auroral currents wax and wane from minute to minute they induce enormous voltages in the conducting surface of Earth. That induced voltage can be as large as 1V/ km or 0.6V/mile. The anomalous outside voltage can be enough to 'trip' a section of the power grid especially if it is isolated from a larger, more protected grid.

There are currently, in the lower 48, three major interconnected systems that comprise the power grid — one covering everything east of the Rocky Mountains (the Eastern Interconnection), one for everything west of the Rocky Mountains (the Western Interconnection), and one for Texas- governed by ERCOT. The power system that serves 95 percent of the state is intentionally isolated from the rest of the country. This has been deliberate given a severely deregulated energy system is incongruent with regulated ones. In this case Texas features a competitive wholesale power market but which offers scant incentives for investment in backup power. Therefore also, scant protection in the event a major CME strikes. (One likely forecast with a 2 day ''head start" but which Texas was ill-equipped to protect against.)

Is this a failure of space weather researchers? Nope. It's a failure of Texas to protect its citizens by intentionally isolating its grid from the larger grid. Therefore in case of a massive CME triggering huge induced currents that knock out its grid there is no provision for backup power. Texans in that case had better have their own generators.

My own research had focused on the origin of sudden ionospheric disturbances (SIDs ) from a specific type of flare identifiable from its soft x-ray signature. This led me to postulate, in early 1984, sudden ionospheric disturbance-generating (SID) flares, with the release attendant on a change in initial free magnetic energy (E _m = B²/2m ) given more completely by:

¶ / ¶ t {ò_v B²/2m dV} = 1/m ò_v div[(v X B) X B] dV

- ò_v {h_an | J_ms |² }dV

where the first term on the right side embodies (loop) footpoint motion, and the second, joule dissipation, but with J_ms the current density at marginal stability – since the marginal stability hypothesis is required for a driven process, and h_an is the anomalous resistivity. Much of this was published in a paper (‘Limitations of Empirical-Statistical Methods of Solar Flare Prognostication’ ) appearing in The Proceedings of The Meudon Solar -Terrestrial Predictions Workshop

Even with greatly enhanced resolution and the acquisition of other critical data, moving beyond statistical models to wholly physical ones (yielding their own self-consistent aspects) will not be easy.

In the case of CMEs,a theoretical, quantitative strategy would revolve around obtaining the rate of increase of the poloidal magnetic flux (Φp) associated with a specific flux rope (e.g. that shows kink or other instability) e.g.

dΦp(t )/dt

Then, for a predictive basis one would require the related function be adjusted for each potential CME (dependent on its current heliographic location) that best fits the total observed data. This function would normally be given in terms of the electromotive force associated with the active region so that:

E(t ) ≡ −(1/c)dΦp(t )/dt

Where the preceding would constitute a forecast from the theory for each CME trajectory. This would be called a "theoretical forecast" say compared to an empirical forecast, i.e. based on analyzing the frequency and intensity of fluctuating microwave bursts over time (say several Carrington rotations). In the above case we see that rapid changes in the poloidal magnetic field, B p , can throw off theoretical model forecasts. Hence, the more we can learn about the genesis and maintenance of such localized fields the more the models (and forecasts) can be improved.

Then there is the influence of the much larger scale solar magnetic field. Beyond all the above considerations, space weather forecasting requires understanding what happens when the Earth’s magnetic field meets the Sun’s in space. When their field lines make contact, for example, they can suddenly link up and explosively realign. Like a snapping rubber band, the field lines rebound, sparking geomagnetic storms and sending dangerous radiation toward Earth that can damage satellites and threaten power grids.

However, some conditions are more conducive to this process, called magnetic reconnection. Particularly important is the orientation of the Sun’s magnetic field. Although the Earth’s magnetic field is fixed about its North and South poles, the Sun’s magnetic field is warped throughout space, and the Earth may find itself in a part of the field pointing in a different direction at any given time. The best conditions for magnetic reconnection are when the Sun’s magnetic field is aligned southward, antiparallel to Earth’s.

Recent studies have shown that the direction of the Sun’s field can shift by the time it reaches Earth’s magnetic field, apparently twisting after passing those satellites. This could lead to inaccurate space weather forecasts. To determine why this happens, Turc et al. analyzed archival data for 82 solar storms caused by approaching magnetic clouds ejected by the Sun. The team compared solar wind measurements with data from closer satellites orbiting in and around Earth’s magnetic field and used a model to reconstruct the conditions in between. Their work zeroed in on two factors.

1) The bow shock that the Earth creates in the solar wind. Like a ship plowing through water, the Earth creates a shock wave in the solar wind as it flows past, which the Sun’s field lines must traverse. Turc et al's analysis showed that depending on their relative orientations, the shock could alter the direction of the field.

2) After crossing the bow shock, the solar field lines encounter the Earth’s magnetic field. They don’t simply meet it head-on, but instead overlap the Earth’s field, and are warped in the process.

The authors reported that these two factors combined to shift the direction of the field, which could alter the probability of magnetic reconnection and the timing of a space weather event. In some cases, it even reversed a benign northward field into a reconnection-prone southward field, and vice versa. These reversals spanned roughly 20% of the Earth–Sun magnetic field boundary and lasted over half an hour, making them significant enough to potentially throw off forecasts of geomagnetic storms.

In terms of here and now solutions, the TIME article highlights a piece of hardware known as a geomagnetically induced current (GIC) blocker. This could be installed on power plant transformers to protect them from destructive pulses of energy via induced mega-currents. The problem is that when you shut down the adverse induced current from a solar storm in one area, it double in another.

At least protecting satellites is much easier, since it merely entails managing "phantom commands" arising from the incoming solar particles. The solution is just to send repeated 'spam' commands to the affected satellites (like Elon Musk's Starlink system) reminding them over and over to continue functioning as they are supposed to.

In the case of SIDs and CMEs the space weather forecasting difficulties are even more formidable. But I am still confident that the Parker Solar Probe will finally put us on the path to genuine space weather forecasts for all phenomena that affect the near Earth space environment.

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