Science Seminars

Space Weather at Earth and Mars: How Bad Can it Get?

Speaker: Jim Green (NASA Chief Scientist)
Date: Wednesday, Nov 28, 2018
Time: 2:00 PM
Location: SPSC W120

Seminar Abstract:

The great geomagnetic storm of August 28 through September 3, 1859 on Earth is, arguably, the greatest and most famous space weather event in the last two hundred years. It is believed that the Solar storm consisted of two coronal mass ejections (CME) occurring about two days apart with the first clearing a path for the second one to reach the Earth in ~17 hours. A significant portion of the world’s 120,000 km of telegraph lines were adversely affected, many of which were unusable for 8 hours or more which had a real economic impact. At its height, the aurora was described as a blood or deep crimson red that was so bright that one ‘‘could read a newspaper by.’’ At its peak, the red aurora lasted for several hours and was observed to reach extremely low geomagnetic latitudes on August 28–29 (~25o) and on September 2–3 (~18o). Auroral forms of all types and colors were observed below 50o latitude for ~24 hours on August 28–29 and ~42 hours on September 2–3. Because Mars was on the other side of the Sun this storm missed the planet Mars. Another enormous solar storm CME with solar wind speeds of ~2500 km/sec occurred on July 23, 2012 but both the Earth and the planet Mars were on the same side of the Sun and opposite the CME. These are fantastic events with some evidence that they may occur on a regular basis in the past, but what evidence do we have that these are the most intense space weather events that the Sun can produce? By looking at the variation in the light from several thousand G2 (Sun-like) stars from the Kepler mission an activity index can be created. Since solar observations from a SOHO mission imager are near the same wavelength we can create a similar activity index for the Sun and compare that with the G2 stars observed by Kepler. The result is that two-thirds of the Kepler G2 stars are more active. Although many of them are younger than our Sun these results indicate intense solar storms will continue which should produce significant space weather effects at Earth and Mars. To investigate the potential effects of these types of events we will present the magnetohydrodynamic (MHD) simulation results of a hypothetical “Carrington-type” space weather event at both Earth and Mars.