High Latitude Ionospheric Impact of the January 1997 Coronal Mass Ejection

On January 6-7, 1997, scientists from NASA's ISTP (International Solar Terrestrial Physics) program observed a large coronal mass ejection (CME). The matter from this event and the associated disturbances in the interplanetary magnetic field propagated in the solar wind to the earth several days later and continued through the magnetosphere and into the earth's ionosphere. This page presents ground based measurements of ionospheric activity associated with the coronal mass ejection. All data on this page were taken with the Sondrestrom incoherent scatter radar and the Sondrestrom allsky imager. For a comprehensive survey of data from all NASA instruments that observed this event, see http://www-istp.gsfc.nasa.gov/istp/cloud_jan97/event.html.

Preliminary Results

The radar data presented below are the result of a preliminary analysis. They were derived using standard processing procedures that assume isotropic Maxwellian velocity distributions. These assumptions may not be valid during periods of high electric fields shown in the data. An analysis that estimates the effects of non-Maxwellian velocity distributions is currently in progress.

Three plots presenting data from the radar and movies of allsky imager data in quicktime format are presented below

• Electron density time line
• Measurements of electron density, electron and ion temperatures, and derived electric field along the earth's magnetic field
• Electrodynamic properties

• Video data files from the Sondrestrom Allsky Imager

Time Line of Electron Density

The following shows the electron density as a function of altitude and time as measured with the Sondrestrom Radar in Kangerlussuaq, Greenland.

Electron Density, Electron and Ion Temperatures, and the derived Electric Field measured along the earth's magnetic field

Preliminary interpretation

• Ionospheric density enhancements observed from 00 to 09 UT (universal time) on January 10 were followed by a two hour period of very rarefied ionosphere (upper left panel)
• A sudden enhancement in all ionospheric quantities was observed at 12 UT following a period of very bright aurora
• Ions were heated to temperatures in excess of 4000° K (lower left panel) as they were subjected to an unusually strong electric field of approximately 200 mV/m (yellow trace in the lower right panel) that generated ionospheric winds of about 4 km/s

Electrodynamic Properties

Preliminary interpretation

• Strong frictional heating rates (upper panel) in the ionosphere were measured at the time of the maximum enhancement of the electric currents over western Greenland at approximately 08 UT
• An intense electric field combined with a highly electrically conductive ionosphere (lower panels) accounts for large heating rates
• The intense electric field continued to generate high frictional heating after 11 UT

Video data files from the Sondrestrom Allsky Imager

The following QuickTime video files include sequences of Sondrestrom Allsky images of auroral activity as recorded in 630.0 nm "red-line" emission on 09-10 Jan 1997 following the detection of a solar coronal mass ejection event by the SOHO and WIND satellites. The images are oriented such that the top pixel of the central column in each frame is at 5 degrees geographic azimuth. These images are presented in the normal allsky orientation with East counterclockwise from North. The magnetic meridian, therefore, is at the 2 O'clock position. The time on each image is in UT.

**To view these files, your browser must support QuickTime video.

21:08UT 09 Jan to 11:38UT 10 Jan : Entire night's Allsky data : 8.4 megabyte QuickTime video file with a JPEG codec

00:58UT to 05:58UT 10 Jan : 5-hour period following the arrival of the solar wind shock, the IMF fluctuations and the magnetic cloud associated with the coronal mass ejection : 2.2 megabyte QuickTime video file with a JPEG codec

05:59UT to 09:59UT 10 Jan : 4 hours during a period of extraordinary ionospheric Joule heating associated with the main phase of the storm produced by the solar coronal mass ejection : 1.6 megabyte QuickTime video file with a JPEG codec