09/12/2014 15:26:00 UTC

Comments

An X1.6 flare and wave near Sun Center and a nearly symmetric halo CME on Sept. 10. The ICME at L1 on 12-13 Sept., following two IP shocks, mostly had strong northward field in the putative flux rope (several models produced). The southward fields, which drove the early storm activity, were in the sheaths trailing two IP shocks, the second one being the strongest. The ICME north field rapidly shut down the auroral and storm activity.

A STEREO SWx Group event. B. Jackson at UCSD runs a real time forecast site, and have included the Rosetta comet mission in the forecasts, currently using IPS data. A density response at Rosetta due to the Sept. 10 event was predicted for IPS and modeled using the ENLIL 3D-MHD code. We are looking for Rosetta solar wind data to confirm an ICME there.

Solar Data

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• GOES X-ray plot showing the X1.6 peak level flare.

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• Tracking program on CME based on realtime data listed in the CORIMP "Weekly CME detections (past 7 days)" online here:
  

http://alshamess.ifa.hawaii.edu/CORIMP
[From Jason Bryne]

Heliospheric Data

• Link to GSFC SWRC Enlil prediction run on Sept. 10 at 11:58 pm.
  

http://iswa.gsfc.nasa.gov/ENSEMBLE/2014-09-10_ncmes1_sims18_LIHUE079/20140910_181800_ncmes1_sims18_LIHUE079_anim_tim-den.gif

• This and other CMEs on 9-10 Sept. were tracked out to the Rosetta S/C using IPS-driven 3D tomography and ENLIL modeling as discussed by McKenna-Lawlor et al. (EM&P, subm, 2015).

In-Situ Data

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• ACE plasma and magnetic field plots are Sept. 9-15, 2014 showing two shocks at 11, 22:56 UT and 12, 15:26 UT. Southward field in the shock sheaths drives some storminess but Bz in the long duration ICME following the second shock is entirely northward, shutting down the storm activity.

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• Nitta's plot of ACE RTSW data in the style of K. Marubashi (http://www.lmsal.com/nitta/outgoing/nrt/plot_sw_mag_ace_rtsw_201409110900_201409142100.gif). The bottom panel suggests that the closest MC type is WNE (RH) in reference to Mulligan, Russell and Luhmann (1999) (http://www.lmsal.com/nitta/outgoing/nrt/mc_mulligan_20140912.png.) For this event people predicted either WSE or SEN with Bz<0, and LH. [Plot from Nariki Nitta on Sept. 15, 2014]

• THE "FORBUSH REBOUND": Radiation levels in the stratosphere are back to normal following a mid-September dip caused by one of the strongest solar storms in years. The story begins three weeks ago. On Sept. 12th a CME hit Earth head-on, sparking a G3-class geomagnetic storm. Using a helium balloon, the students of Earth to Sky Calculus launched a radiation sensor into the storm, expecting to measure an increase in energetic particles. Instead of more, however, they measured less. The CME had swept away many of the cosmic rays around Earth and so radiation levels in the stratosphere dropped.

The CME was long gone on Sept. 28th when they repeated the experiment and found radiation levels returning to pre-storm values. The drop in radiation is called a "Forbush Decrease" after the 20th century physicist Scott Forbush who first described it. This would make the bounce-back a "Forbush Rebound." According to the data, the rebound took less than two weeks and possibly only a few days. The next time a CME hits, the students plan to launch balloons with a faster cadence to better measure the stratosphere's response time. The group uses a Space Weather Buoy--an insulated capsule containing an X-ray/gamma-ray detector (10 keV - 20 MeV), multiple video cameras, GPS trackers, and other sensors. The payload went to 108,700 feet above the Death Valley National Park.
From Spaceweather.com, issue 3 Oct. 2014.

References

- McKenna-Lawlor et al. EM&P, subm, 2015