1. Extremely Intense (SML ≤ -2500 nT) Supersubstorms (SSS)
B. T. Tsurutani1, R. Hajra2, E. Echer2 W.D. Gonzalez2 and J. Gjerloev3,4 
1Jet Propulsion Laboratory, CalTech, Pasadena, CA
2INPE, Sao Jose dos Campos, Brazil
3Johns Hopkins Applied Physics Laboratory, Laurel, MD
4University of Bergen, Norway

2. Royal Academy of Engineering report (2013), “Extreme space weather impacts on engineered systems and infrastructure”, London UK.
Space Weather engineering reports always attribute
power outages to “magnetic storms”, but these are simply
enhanced ring current intervals. Is there something else?

3. Substorm Ionospheric Currents
> 106 Amperes in auroral electrojets
Flow at ~100 km altitude associated with auroral displays
The auroral electrojet induces currents on the ground and causes overheating of conductors such as power line transformers.
Therefore we decided to investigate supersubstorms (SSSs).

4. Questions to Ask Yourself:
Do SSSs only occur during super magnetic storms where Dst ≤ -250 nT?
And do SSSs occur during magnetic storm peaks or do they occur stochastically throughout the storm main phase?
Could SSSs be externally triggered?
And what is the energy source for supersubstorms?

5. Interplanetary FF Shocks Can Trigger Intense Substorms
ΔPram = ~4.0
~2000 nT
A very large
substorm!
Zhou and Tsurutani, JGR 2001

6. Shock occurs here Nightside intense substorm JGR, 2001
Dayside aurora: shock compression,
involving nonadiabatic processes (discussed
on Tuesday).
Shock occurs here
JGR, 2001
Nightside intense substorm

7. A Study of SSS Occurrence Properties
SML < nT
~3 ½ solar cycles
74 events
Hajra et al., 2016

8. Supersubstorm onsets superstorm November 24, 2001 What is this?
Two FF shocks
November 24, 2001
What is this?
ICME Loop
superstorm
Tsurutani et al. Ann. Geo. 2015

9. The Magnetic Perturbations at the Ground During the Two Supersubstorms

10. Two More Supersubstorms Also Triggered by
Interplanetary Pressure Pulses
24 August 2005
Intense storm
(-250 nT ≤ Dst ≤-100 nT)
Tsurutani et al. 2015

11. Major Parts of Coronal Mass Ejections (CMEs)
August 18, 1980
Outer loop
Filament
Courtesy of A.Hundhausen
Dark region (MC)
We need to know more about high densities within MCs. Can one see these at the Sun
with coronagraphs? Do they maintain themselves as the propagate to 1 AU?

12. SSS Solar Cycle Phase Dependence
(1981 to 2012)
SSS events
Intense storms
superstorms

13. Summary of SSS Solar Cycle Dependence
3.8 SSS/yr in SC descending phase
3.1 SSS/yr events in SC maximum
1.5 SSS/yr in SC ascending phase
0.9 SSS/yr in SC mininimum

14. SSS Seasonal Dependences: Equinoxes
However a SSS dominance in spring in SC22 and fall in SC23. No Russell-McPherron
effect, in agreement with Mursula et al. GRL 2011.

15. SSS Storm Phase Dependences
Although this shows SSSs occurring most probably near peak of storm, one
has to be careful. Not all storms last 10 hrs.

16. Do SSSs Occur Only During Superstorms (Dst ≤-250 nT)?
For 74 SSS events:
49% were associated with superstorms
46% were associated with intense storms
1% were associated with moderate storms
5% were associated with geomagnetic quiet
Answer: No
Asked the other way, do all superstorms have SSS events?
63% had at least one associated SSS event

17. Superposed Epoch Analysis of SC23
Isolated SSS Events
Precurser IMF Bz
Hajra et al. 2016
Start of SSS events

18. Joule heating EJ/Eε (%)
Lead Time for Precurser Energy
1 hr best fit
1 h
1.5 h
2 h
Total energy
Magnetosphere Eε (1016 J)
4.0±2.9 (3.2)
5.7±4.3 (4.1)
7.4±5.8 (4.7)
Joule heating EJ (1016 J)
2.2±1.5 (1.3)
3.1±2.5 (1.8)
4.0±2.6 (2.3)
Ring current ER (1016 J)
0.09±0.07 (0.08)
0.13±0.1 (0.11)
0.17±0.1 (0.14)
Energy dissipation rate
Joule heating EJ/Eε (%)
46.4±24.2 (46.1)
48.5±29.1 (38.9)
47.3±28.1 (37.8)
Ring current ER/Eε (%)
3.6±2.3 (3.8)
3.5±2.1 (3.9)
3.4±2.2 (3.4)

19. Loading/Unloading, Directly Driven or Both?
We estimated the precursor magnetospheric energy before the SSS onset, during the SSS event, and total SSS energy dissipation.
In ~29% of cases, the precursor energy was less than the SSS energy.
In ~12% of the cases, the solar wind energy input during the SSS event was not sufficient for the SSS events.
Our conclusion appears to be that the energy for SSSs are both: precursor energy/triggering and directly driven.

20. Are SSS Events Externally Triggered?
77% of SSSs were triggered by/associated with high density solar wind plasma parcels (PPs).
Could satellite detection at L1 libration point be used to give warnings? .

21. Should One Focus on Extreme Storms Like the Dst < -3500 nT Maximum Discussed on Tuesday?
The source of energy for both SSSs and storms is the same: IMF Bsouth and high Vsw. When extreme storms occur, the aurora will be at lower magnetic latitudes exposing major power grids. Thus these SSSs will be more Geoeffective in causing GICs. Answer: Yes, but…..

22. Should One Also Look Outside Extreme Magnetic Storms?
SSS events can occur during any phase of the solar cycle both during storms and during quiet. Huttunen et al. (2008) have shown with the Mäntsälä pipeline (~56° to 58°) data, there was only a loose correlation between GICs and magnetic storms during SC23. Were these GICs due to intense substorms? Answer to main question: yes

23. Other Questions
Are supersubstorms somehow different than regular substorms?
Why don’t people use shock-triggered and PP-triggered substorms to study magnetospheric/magnetotail energy storage and onset mechanisms? The timing should be sharp.
Where is the energy being stored?
What are the solar wind pressure pulses inside MCs?

24. Thank you for your attention